| 00:06 | OK. The goal today is to how much amplitude you can reflect off |
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| 00:12 | a boundary. And again, I to introduce the velocity and density changes |
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| 00:21 | boundary. And that's going to introduce some relationships on how particles bounce near |
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| 00:29 | boundary. And I'm also going to again a little bit on the physical |
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| 00:38 | of the wavelengths, amplitude and velocity measurements during wave propagation or go over |
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| 01:05 | a couple slides. Remember what I you that a GEO phone, it's |
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| 01:12 | as the wave approaches it, it to know do you come from the |
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| 01:17 | or do you come from the top ? Which means this never happens. |
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| 01:23 | theoretically, if you hit the GFO , these are this one is a |
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| 01:32 | displacement GFO or vertical velocity. So does not record any current coming out |
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| 01:39 | it. If you hit it that is theoretically. But as you |
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| 01:44 | know, you hit it sideways, gonna go up and down too. |
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| 01:47 | gonna move some uh that is against hydrophone which sitting in the water, |
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| 01:57 | doesn't cure what direction you hit It's gonna record the same wavel any |
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| 02:03 | you approach it. Sometimes that's Sometimes it's bad. It does have |
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| 02:09 | advantages because we're able to separate the reflections from the downgoing surface reflectors going |
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| 02:19 | . So you can, you can energy get done, hit a |
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| 02:22 | come up, hit a hydrophone, the sea level and come back |
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| 02:26 | No, no, no, you want that. But if you happen |
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| 02:30 | have a GEO phone in the both at the same location, then |
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| 02:35 | can get rid of the energy that back down. That's, that's called |
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| 02:38 | ghost. We we can get rid those. The other little thing that |
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| 02:45 | learned was that the hydrophone, it's you uh that you have on it |
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| 02:56 | proportional to the Jetta phone particle velocity the acoustic impedes which is the density |
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| 03:06 | the wave velocity. Now all of sudden you have two velocities in that |
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| 03:13 | . One is how individual particle The other one is how the wave |
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| 03:20 | is the speed of sound inside a . No. How fast does the |
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| 03:32 | travel in that particular medium? This V right. Thunder cannot, can |
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| 03:40 | be changed when the properties of the through the wave it travels has |
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| 03:45 | Say another another way this wave propagation velocity is independent of time. So |
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| 03:53 | you're in water, it's 5000 ft second. I don't care. It's |
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| 03:57 | this side or that side, it's be 5000 ft per second. |
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| 04:01 | what about the particle motion? if so comes up to that |
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| 04:08 | All right, let's put a GE up to a geo filme. The |
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| 04:11 | is gonna start to move up and and push the geophones. Now, |
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| 04:16 | long as that particle is moving up down, the geophones will move and |
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| 04:21 | get a recording and the recording is velocity. It tells you how fast |
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| 04:28 | particle is going up and down. , as soon as that wave |
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| 04:33 | you don't get any particle motion You don't have any particle velocity. |
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| 04:40 | will see that again shortly. So thing to remember, wave velocity is |
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| 04:51 | of time. This depends upon time the earth moving back and forth due |
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| 04:57 | some wave coming in. What we to know is if you have energy |
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| 05:05 | a boundary, how much amplitude is be reflected if the amplitude coming down |
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| 05:14 | be known. Now, obviously, amount that we're gonna reflect off of |
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| 05:20 | boundary depends upon the two quantities shown acoustic impedes density times wave propagation velocity |
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| 05:29 | the first medium and the acoustic competes the second. And the East amplitude |
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| 05:37 | reflects right here going up is going be a ratio of how much came |
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| 05:43 | to how this goes up. So reflected particle velocity over the incident particle |
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| 05:50 | , normally we think of the incident having a value of one uh just |
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| 05:56 | , so what's the reflection coefficient, this ratio? You just kind of |
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| 06:00 | a value here. For instance, the amplitude going down as a value |
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| 06:11 | one is so near and this is pulse, if she rated here, |
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| 06:19 | it goes up right here, it'll the same shape, it'll have the |
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| 06:29 | shape a as the incident coming So that's the incident going down and |
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| 06:35 | up, it has the same Now, this is called quiz |
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| 06:41 | I'm gonna show off. OK. I want somebody here to show off |
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| 06:46 | me. If I'm going to folks the other side of the world, |
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| 06:53 | have people looking under their computer. don't know why, but I'm sorry |
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| 07:03 | we talk about having plus and minus of motion in order to have that |
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| 07:14 | have to have a reference and what we call? You have to have |
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| 07:19 | coordinate system. So a lot of we forget about that. So for |
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| 07:25 | example, here, I'm gonna put surface up here and there's the, |
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| 07:29 | is the spike of the GFO that in the ground and here's the |
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| 07:36 | Now, if I'm going down like , I'm going down and I say |
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| 07:43 | is my pulse. What I am , I have set up a corded |
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| 07:48 | where going down is positive and going is negative. You have to have |
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| 07:56 | cod to talking about plus or So I said this is positive going |
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| 08:02 | . Now, when I reflect and boundary here, I said it's a |
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| 08:08 | boundary. So the pulse that's going is gonna be reflected. So this |
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| 08:15 | is going up now that's opposite of downgoing pulse. And I consider the |
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| 08:22 | pulse to be positive. So this looking as reflected, looking, the |
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| 08:29 | reflected looking the same way as the , this must be negative when it |
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| 08:37 | the GEO oe because going down was . So what that means is even |
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| 08:46 | the pulse is going up has the shape and polarity as that going down |
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| 08:52 | it hits the GEO filme, you be careful because in reality, that |
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| 08:57 | really a negative sign. Now she , who cares? Well, when |
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| 09:04 | buy seismic data and you give there's something called the header and the |
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| 09:10 | is a little information that data processing tell you. And in that |
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| 09:17 | they're gonna tell you our standard for polarity. Is this in United |
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| 09:27 | It says if you come down and reflect off of a positive boundary and |
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| 09:33 | go back up at the top. United States says if it's a positive |
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| 09:40 | that's re that's on your seismic data we sent you. If it's a |
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| 09:45 | value, that means you reflect it of a positive boundary down here. |
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| 09:50 | reflection coefficient was positive. Now that's our standard. I mean that that's |
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| 09:59 | the US standard, but it's not right. The correct answer is if |
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| 10:06 | plus going down, you're going to negative, that's gonna hit a go |
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| 10:12 | it's gonna record negative, not Now, the English European standard is |
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| 10:21 | you see a trough on your seismic and you assume that you had a |
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| 10:31 | source going down, that means the was a plus and that it was |
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| 10:36 | increase of impede. So that difference not because somebody wants this to be |
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| 10:44 | . The English have it the correct . But we all grew up with |
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| 10:50 | peak on your seismic data is a reflection off of a boundary. |
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| 10:59 | Where it gets tricky as we start look at three dimensional reflections continuity of |
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| 11:08 | principles. Most geophysicists have this tattooed her forearm. And it says if |
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| 11:22 | assume my acoustic impedance going down my of the incident is one, then |
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| 11:30 | amplitude of the reflector, I'm gonna to this acoustic impedance right here. |
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| 11:36 | says my normal incidence and that's the . Although the reflected or the amplitude |
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| 11:45 | the incident, that's your normal It's the acoustic impedance difference between the |
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| 11:54 | and the upper two is the It's 12 down here. This equation |
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| 12:03 | can be approximately written as the difference density over the sum of the density |
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| 12:13 | the difference in P wave velocity over sum. Now the difference two minus |
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| 12:22 | is written as delta, a different . Delta is a different sign. |
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| 12:26 | the difference in density and the difference velocity is written with a delta. |
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| 12:36 | underneath notice that row here doesn't have one or two because here row means |
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| 12:48 | average. Now I am just explaining you what you're gonna see all types |
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| 12:56 | equation following this with this notation because we went to what we would call |
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| 13:03 | vo this became very essential shorthand that is gonna be the difference. So |
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| 13:14 | you see delta beta, what was again, what is it? Secondary |
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| 13:26 | ? Yeah, and what do we it secondary wave, the sheer |
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| 13:31 | And so that means what when you a boundary and you see a delta |
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| 13:41 | way, what does that mean difference what the lower and the upper survey |
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| 13:48 | ? And you then see in the a beta over here and that means |
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| 13:55 | average and that's share wave two plus wave one divided by two. Oh |
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| 14:04 | that's where this too comes in. see here you have the sum of |
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| 14:10 | two and here that was the So you gotta have two of those |
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| 14:16 | in order to get the sum road two plus density one. And then |
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| 14:24 | is to complicate, but it actually very good sense. And that is |
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| 14:32 | bring out our old calculus book. remember that you, it's probably used |
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| 14:36 | day in your work as a Yeah, Fred. And that is |
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| 14:43 | normal incidents. Reflection to fish can written as the difference of the natural |
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| 14:50 | of acoustic bes between the lower in upper medium. This does not make |
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| 15:00 | . Fred, we caught Fred Ginn to us. Why is that? |
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| 15:06 | , look, look up here, just tells you Fred's lying because here |
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| 15:12 | have a numerator and denominator. where'd it go? You don't have |
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| 15:20 | down here. How can you get and have a numerated? Numb and |
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| 15:25 | all of a sudden you do away the numb. Wow, something |
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| 15:31 | Here. Anybody got a clue. you remember your calculus? I |
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| 15:36 | I always go, go back to calculus book and look these things up |
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| 15:42 | you have natural log. What does mean? That means you have 0.5 |
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| 15:49 | this is the natural log of We've got alpha here of two divided |
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| 16:05 | the natural law of one. In words, when you have a division |
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| 16:13 | as this, here's the two natural of two mice and natural log, |
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| 16:18 | acoustic convenience of one. So that's the den denominator, the numerator is |
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| 16:26 | . Now, why would we like see this right here? Why do |
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| 16:32 | like that? Because I want to you a little visual quiz. I |
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| 16:40 | you to tell me how big of reflection you're gonna expect on your seismic |
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| 16:46 | now as geologists in some GS one two token geophysicists, it's your responsibility |
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| 16:55 | say what depositional environments am I gonna in this area? And with |
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| 17:03 | you now and then say, that helps me if I have a |
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| 17:07 | big reflection, it might be this or model and if I have a |
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| 17:12 | , it might be this. So examples. You just went into a |
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| 17:17 | area and you or ask immediately just if I have a gas in |
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| 17:24 | the shell, how big will my reflection be? Oh, how about |
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| 17:31 | coal bed beneath? Shall, how is my reflection coat gonna be? |
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| 17:38 | . Put a limestone beneath you, be but cool beneath the limestone all |
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| 17:43 | a sudden he got these four cases you, now you pull the seismic |
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| 17:48 | up on your beautiful desktop screen and start looking at amplitudes. He |
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| 17:53 | uh that's kind of big, that's quarters of an inch and that's only |
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| 17:56 | quarter of an inch. Hm. the two possibilities of those two |
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| 18:02 | What, what could those Ortho So you'd like a way to visually |
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| 18:09 | this in your mind with ha having look at this equation over and over |
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| 18:15 | . Now you can compute and give a normal incidence value for each one |
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| 18:20 | those. But then you could have scenarios that make it difficult. So |
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| 18:25 | a little clue. Take the lithology make a scale and the scale is |
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| 18:36 | half the natural log of the particular . So here, limestone is the |
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| 18:44 | . So it has the largest natural of acoustic pieces and cool is way |
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| 18:50 | here even below a gas samp. I look at this equation down here |
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| 18:55 | it says, take the lower medium subtract from the upper and that's gonna |
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| 19:03 | you the natural log of acoustic at . So we'll do that. Who |
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| 19:09 | over here? And this says, about a gas sand beneath the |
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| 19:17 | So I'm gonna come over here and here's the shale and you wanna go |
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| 19:25 | the Gian. So we have this right here, the shale over the |
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| 19:38 | and you're gonna come down like I wanna know that normal incidence and |
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| 19:43 | way this chart is designed, it we're gonna satisfy this equation. I |
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| 19:49 | take this share value and I'm gonna down to that cast and this is |
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| 19:58 | normal incidence reflection coefficient that distance. Come on, Fred. That distance |
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| 20:03 | 1 ft. That's not normal Normal in it is uh uh |
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| 20:07 | no unit on it, right? what are we gonna do? We're |
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| 20:11 | compare this distance to this distance and , oops, this is a shale |
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| 20:20 | coal and I can tell my amplitude here on my seismic isn't that big |
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| 20:30 | here. So I think this most might be a shell over coal |
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| 20:35 | by the way, it's also negative this is a big negative. |
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| 20:40 | if I had a limestone beneath a , oops, it's Rhinestone. Uh |
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| 20:53 | it is cool beneath the limestone. I have the limestone and I go |
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| 20:59 | to the core, it's negative. a negative direction. So that's gonna |
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| 21:04 | a big negative amplitude sitting in No, you can see visually, |
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| 21:14 | can relate these two and it's uh what's, what's the back? |
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| 21:19 | am I comparing it to what you're it to is normally in your |
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| 21:24 | you're gonna have shale over a wet . So that distance right there is |
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| 21:32 | normal background. So you see an that looks kind of constant all over |
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| 21:37 | area and say, oh that must my shell over a wet sandstone. |
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| 21:42 | then you compare this to the other that you have. How much bigger |
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| 21:48 | I than the background amplitude? another benefit of this is what if |
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| 22:00 | get a new pathology? Well, keep these and you just put that |
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| 22:05 | lithology in salt and now immediately you start asking what if I have limestone |
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| 22:14 | on top of salt. Uh You're gonna get a big reflection, it's |
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| 22:20 | small and salt can almost look like , at least on the normal |
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| 22:32 | OK. That's, and this little, little spiel right here showed |
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| 22:43 | I went to my calculus book and up I what's this natural log |
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| 22:48 | What do we do with that? . Why is the mind show |
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| 23:00 | Why is the limestone? Why is the only one pointing out? And |
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| 23:10 | was a, a limestone beneath So I have chill on top and |
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| 23:23 | on the bottom and the limestone is , harder than shale. And if |
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| 23:36 | have shell over eight, yes. right here, the gas in has |
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| 23:46 | smaller acoustic be a, a smaller . OK. Now, here here |
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| 23:58 | that reflection coefficient equation again. And look at extremes. What if the |
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| 24:11 | medium? That's this one. What it is really, really a hard |
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| 24:18 | ? I mean, hard material, mean, really hard compared to the |
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| 24:22 | of. So we have cotton balls here on top of stainless steel. |
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| 24:29 | a hard boundary. So the reflection gonna be really, really big because |
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| 24:38 | medium acoustic competes much bigger. So two much, much bigger than L |
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| 24:44 | and yet I two or I two two is great big. This is |
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| 24:51 | . The cotton balls compared to the in that big number over big |
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| 24:57 | Throw away the small stuff, you one. Now you put the steel |
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| 25:03 | on top and put cotton on the here. No, your acoustic and |
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| 25:11 | of the upper medium is real So we could back up here. |
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| 25:16 | is big, this is insignificant. is big, this is insignificant. |
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| 25:22 | minus I over plus I one is be minus one. I know I |
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| 25:31 | have been looked on here. This insignificant, that's insignificant, given us |
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| 25:38 | two extremes. So the reflection goes plus one to minus one. An |
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| 25:49 | if I, if the reflection coefficient is related to the properties that you |
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| 25:57 | here, reflection coefficient, what's it equal to? It says the density |
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| 26:04 | the same. So I can factor the density. It doesn't matter at |
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| 26:09 | . But now say what about these ? Well, as it says, |
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| 26:16 | the lower minus the upper. So lower here is the 20 and the |
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| 26:26 | is 10 and that's over the sum should be 30. So what we |
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| 26:38 | is shown here a reflection coefficient of third. If the incident wave coming |
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| 26:51 | had a amplitude of three, then reflected is gonna be one third of |
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| 26:59 | incident which have a value of one here and it's positive now switch these |
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| 27:07 | around and your reflection coefficient is So when that is plotted, we |
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| 27:18 | its reverse polarity with respect to the wave. Oh That gives you another |
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| 27:28 | tool to remember if I have a coming up and hitting this boundary, |
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| 27:39 | going to reflect that. So what the reflection coefficient be at that boundary |
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| 27:49 | this wave coming up? It's gonna up and come down. What would |
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| 27:54 | reflection coefficient be negative? One third one third. This is, if |
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| 28:13 | hit it from the top, it out, it was plus one |
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| 28:18 | then if you turn around and hit from the boundary, it's just the |
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| 28:22 | polarity. Well, I'll be Do you know what that tells |
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| 28:28 | That tells me you see this sand there. I'm gonna go ahead and |
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| 28:36 | that sand right there and I have shell right up here and I have |
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| 28:44 | shell right underneath of it. And is plus one third and coming down |
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| 28:55 | this boundary is minus a third. , for the tricky question, what |
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| 29:09 | when this thickness becomes small? What happen to this combination of reflections? |
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| 29:19 | gonna reflect this off the top you're gonna reflect this of the bottom |
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| 29:32 | . Now, what do you These two reflections get added together but |
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| 29:39 | coming in almost at the same So what happens? The amplitude disappears |
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| 29:47 | you get thinner and thinner. If of a sudden the thickness of that |
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| 29:53 | bed right here, if it's only half of an inch, really |
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| 30:00 | you get a reflection from the top from the bottom essentially at the same |
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| 30:05 | . And so you have a pause the reflection coming right on top right |
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| 30:12 | a negative. But they get so together, you can just add their |
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| 30:17 | together giving you zero, you get response. So very, very thin |
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| 30:24 | is gonna be hard to see. gosh, Fred, wasn't that the |
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| 30:30 | that you asked on that one Yeah. Now we'll begin seeing how |
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| 30:36 | Mo White's article was. He had factor. His son, your amplitude |
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| 30:46 | a thin bed is equal to the incidence reflection coefficient times the thickness divided |
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| 30:55 | the wavelength of the pulse in that . And the core sense of physicists |
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| 31:03 | this times pi you're gonna have gonna the pilot. OK. Any comments |
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| 31:17 | questions and you all can see the significance of that. I hope we |
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| 31:35 | a problem here. Listen, we a problem. What's the problem? |
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| 31:42 | a formula that we can develop that the reflection coefficient was the transmitted coefficient |
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| 31:54 | equal to one. Now, what that mean? That means go back |
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| 32:01 | the previous slide and you had on previous slide that this reflection coefficient coming |
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| 32:11 | air was one third. So what going to be the amplitude of the |
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| 32:23 | that continues downward? Well, the says it's gonna be one minus the |
|
| 32:32 | coefficient. So this transmitted wave right , it should have an amplitude of |
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| 32:40 | thirds that will that will be the coefficient for the wave going through. |
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| 32:48 | that means if my initial wave had amplitude of three going down, then |
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| 32:56 | transmitted will be two thirds of that the value two sitting in here. |
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| 33:07 | Now I'm gonna show you how powerful am most people don't realize it but |
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| 33:13 | have this power over, over the world. Let me show you the |
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| 33:21 | that I have. If you reflect deep, real deep, you can |
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| 33:29 | a way of going up being So if I have a wave right |
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| 33:38 | and it has an amplitude of three before it hits his boundary. |
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| 33:44 | what's the reflection coefficient of this Remember this was normal incidence reflection coefficient |
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| 33:53 | a third. What's the reflection Now when I come from the bottom |
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| 33:58 | go like that, that reflection it's gonna be minus a third. |
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| 34:08 | just the opposite of the other. you come on the boundary this way |
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| 34:12 | down, going opposite the opposite, nonsense value. So that means the |
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| 34:21 | coefficient is gonna be one minus a one third or four thirds. So |
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| 34:36 | transmitting pulse going up through here is to be the value of four even |
|
| 34:45 | the incident was three. So what has showed you is that I can |
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| 34:55 | more energy when I go through a I can create amplitude. So the |
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| 35:03 | of laws, these energy in that don't hold for Fred you the common |
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| 35:10 | maybe but I can get away with . I just made an amplitude bigger |
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| 35:14 | the incident angle. How can I that? Anybody want to guess? |
|
| 35:38 | , these are particle motion and when talk about energy, you have to |
|
| 35:51 | some period of time. Energy is quote instantaneous. It requires some type |
|
| 35:59 | waveform to carry it. So here's exercise conservation of energy. Again, |
|
| 36:14 | small is a particle velocity and it's vector and it's positive going downward. |
|
| 36:23 | V is the propagation velocity. It's speed when you have a situation as |
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| 36:35 | shown here 22 20,000 or 11,000, particle velocity, that reflection is minus |
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| 36:50 | third. That's we agree with So now we're gonna make a cartoon |
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| 36:59 | of it. I have an area I have a length right in |
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| 37:09 | this propagation velocity in the upper that propagation velocity is 20,000 ft per |
|
| 37:20 | . So I have sitting here 20 and each layer is 1000 ft |
|
| 37:30 | And what that represents is the pulse I'm putting into the ground. I'm |
|
| 37:36 | send a pulse down and it's nothing a square wave and it's one second |
|
| 37:43 | . So if I send something that's second long, that's the time. |
|
| 37:52 | in space, what is it? one second times 20,000 ft per |
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| 37:57 | which is my propagation velocity. So is 20,000 ft long and it has |
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| 38:07 | area a which is arbitrary. But notice that this is the wave going |
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| 38:21 | when it reflects off of this boundary goes upward. What's the size of |
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| 38:31 | volume? Now, the volume is 20,000 ft long, it has the |
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| 38:38 | area. But how much is it ? That's what counts. How much |
|
| 38:45 | this volume shaking? Well, we're give this a particle velocity of |
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| 38:53 | So as that's going down, it's with a particle velocity of one, |
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| 38:59 | it's 20,000 ft long. Now, it reflects upward, it's gonna have |
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| 39:05 | particle velocity of minus one third. the reflection coefficient of this. |
|
| 39:13 | here's where it comes interesting when you into the low, when this gets |
|
| 39:19 | the lower medium, what happens with area remains the same? But the |
|
| 39:27 | is not only 10,000 ft long because is 10,000 ft per second. That |
|
| 39:35 | that life 10,000 ft long. It's a second. You can't change |
|
| 39:42 | a wave when it propagates to the doesn't change side. It doesn't change |
|
| 39:47 | time lapse between peak and peak. does change is the wavelength think of |
|
| 39:55 | this way a traffic cop is chasing guy that violated the law and the |
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| 40:07 | happens to be about the one block . They are violator. So there |
|
| 40:22 | a period, you can say the time between the cop and that might |
|
| 40:29 | 60 seconds, one ball. That's . Five seconds, one block. |
|
| 40:36 | of a sudden they're traveling 60 miles hour, they come into a hospital |
|
| 40:43 | . So they have to slow Now, when they slow down, |
|
| 40:47 | still going by the speed limit, what happens. They get closer |
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| 40:55 | But it still takes five seconds for cop to reach the violator because they're |
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| 41:02 | traveling at the same speed. So happened is a wavelength that was one |
|
| 41:07 | long, now becomes only 400 ft . And then as soon as they |
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| 41:13 | out, it becomes a block between C and the speeder again, as |
|
| 41:19 | as they maintain the velocity of the . Now, that's the same that's |
|
| 41:26 | right here. This was 20,000 ft . But when I get in a |
|
| 41:31 | medium, it's only gonna be 10,000 long for that wavelength. So you |
|
| 41:37 | actually take a snapshot of the earth you could see up in the top |
|
| 41:42 | 20,000 ft was jiggling and you wait couple seconds and then down below the |
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| 41:49 | , only 10,000 ft was jiggling. there's a bigger volume, there's a |
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| 41:55 | volume that's jiggling then appear that you . And what that means is, |
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| 42:14 | did that come from? So here's summary of what the cartoon sets and |
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| 42:28 | it, we're not gonna meticulously go this. We have the conservation of |
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| 42:34 | energy. It says the kinetic energy must equal the kinetic energy after. |
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| 42:42 | I look at the incident kinetic That's this thing right in here. |
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| 42:48 | now V small V at your particle in one half mass times the velocity |
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| 42:58 | , that velocity is not your It's how much is your particle |
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| 43:03 | How much is your whole volume The volume comes into consideration when you |
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| 43:10 | the mass of the upper medium. now you're very long and that has |
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| 43:18 | equal after you gotta have kinetic energy this plus the kinetic energy in this |
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| 43:26 | to the original kinetic energy. Now the small is a vector but when |
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| 43:34 | square it forget about direction you can about. But now also when he |
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| 43:41 | over here, you find out that transmitted has a different vector. It's |
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| 43:51 | thirds, it's bigger. Your amp getting bigger. Now, the part |
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| 43:56 | kinetic energy it's OK. Then when go for conservation of momentum, you |
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| 44:04 | uh oh in order to do Freddie had to put an extra minus |
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| 44:09 | in there because now the particle velocity negative compared it was before. Since |
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| 44:20 | has a direction you see growing up going down have different directions. If |
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| 44:29 | want to conserve momentum, I gotta that into consideration. So if we |
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| 44:36 | ahead and we use a little cartoon this, we can show you have |
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| 44:43 | have a bigger transmitted wave. Then in order to conserve momentum and kinetic |
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| 44:55 | , it's not violated, it's actually . And where do we see that |
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| 45:05 | ? It's like a tsunami out in ocean. What's the wavelength a |
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| 45:13 | It's a mile long wavelength, maybe . But when it gets inside the |
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| 45:18 | . What's the wavelength? I don't . 100 ft. Yeah. |
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| 45:24 | what's that mean? Gotta get really out in the middle of the |
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| 45:28 | That's the problem for years. How heck do you detect a rise of |
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| 45:35 | inches? And then we, when storms come and the waves are there |
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| 45:42 | when you get in the bay? , that's 100 ft. Now, |
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| 45:45 | know how big that wave is. it? OK? If you folks |
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| 45:52 | don't know land, that's you folks there, I'm looking at you. |
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| 45:59 | , uh I have a question. was the particle velocity one coming down |
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| 46:07 | the incident wave? OK. Do just decide that? Now the part |
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| 46:14 | is a, this is a big and that volume is shaking up and |
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| 46:22 | the particle right at the front right . This particle right here. It's |
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| 46:27 | back and forth, back and back and forth as the whole volume |
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| 46:33 | downward. That's the particle velocity you're at your particle velocity is actually moving |
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| 46:43 | the wave. You might think it really, but it, in |
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| 46:48 | that's how I think of it. , it it's not moving downward. |
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| 46:53 | just has, it has a sign a uh here I said as far |
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| 47:04 | particle velocity is concerned, if you in that direction, you're positive, |
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| 47:09 | you move in that direction you're And so my transmitted wave, my |
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| 47:17 | wave rather I had all positive It's a positive value. But when |
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| 47:24 | reflected, I had to show opposite the particles move because it's negative |
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| 47:32 | If I have a particle right it's moving in this direction. This |
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| 47:39 | is moving in that direction. Zero right where the line of drawing you |
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| 47:45 | I reflect this particle here is moving that direction and that's moving in that |
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| 47:53 | with my reference line right there. turned the pulse upside down. When |
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| 48:01 | reflected from this weak boundary, it's a rope. When you snap a |
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| 48:11 | , it goes to a wall, gonna maintain the same positive signature. |
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| 48:17 | if you snap it and one ends , it's gonna reverse polarity as the |
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| 48:22 | comes back to you. That's the that I could think of. |
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| 48:39 | OK. I saw the first It's your turn to solve the next |
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| 48:46 | . OK. The seismic method will work. This has been a |
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| 48:56 | It's conducted in Hollywood studio productions. make those, all those seismic |
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| 49:02 | Yeah, that's what I'm gonna And I'll prove it. I'm going |
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| 49:08 | start with an amplitude of one. reflection coefficient on all these boundaries is |
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| 49:20 | no, the transmission coefficient is 0.91 0.1 is 0.9. So when I |
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| 49:31 | into the second medium, my amplitude is 0.9 then when that goes into |
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| 49:37 | next one, it's 0.9 times 0.9 and so forth and then it reflects |
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| 49:46 | down here and goes back up. I'm going to have 50 bounces at |
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| 49:56 | . So if I put an amplitude one going up, it has a |
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| 50:04 | 0.9. So you take that 0.9 you raise that multiply it by 50 |
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| 50:11 | . And that would be the amplitude down to this boundary and coming back |
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| 50:16 | . So you're looking at a number 4, 10 thousands of the original |
|
| 50:30 | . That's small. That's less than . That's less than a half of |
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| 50:37 | . That's like bio bionomics, Biden's plan. It's small, but we |
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| 50:46 | a solution that you're gonna give me after the break. Let's come back |
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| 50:52 | 930. You got quite a watch . Surprise you're strong enough to hold |
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| 51:14 | up. That's a big face. Yeah, I'll take a little |
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| 51:37 | appreciate you bringing that in. I to thank you. You too. |
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| 52:41 | I get out of here? I bring another follow up. Well, |
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| 52:50 | know, pay attention to me. Friday. Would it be possible for |
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| 54:57 | to take my Saturday quiz on Friday all three of them? Yeah. |
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| 55:03 | . Yeah. Ok. Ok. . I lost everybody. You |
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| 56:31 | you're gonna have to help me OK. Here's my, where I |
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| 56:39 | be. OK, maximize it and it. I can hear this, |
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| 56:45 | , the representative present. It, takes time it's loading. Ok. |
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| 56:53 | me too. You can tell yeah, let the window and the |
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| 56:58 | button at the same time. And was that you choose the no, |
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| 57:05 | , no choose the the zoom meeting right here. Just, just click |
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| 57:12 | zoom. You can, yeah, you can sh share. OK? |
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| 57:19 | when you present the slide zero, screen two will come out. So |
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| 57:23 | can this you have screen two and it. And then uh so tell |
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| 57:32 | that that's it. OK. Did touch up there? Because you, |
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| 57:38 | you didn't click the zoom meeting at first time. So it didn't |
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| 57:43 | but if you click the zoom this will show up directly. |
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| 57:51 | I think OK, folks can you me? You can't see me. |
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| 58:07 | can see. No, you can one person. I have a |
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| 58:13 | Well, or I don't know if a question though. I just trying |
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| 58:16 | know if I am understanding correctly. does that mean that every time if |
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| 58:23 | go back to your, it's like one that we were looking at, |
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| 58:28 | ? Yes, that one. So that mean if we start with one |
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| 58:33 | an amplitude of one and every time reaches or it passes through a layer |
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| 58:40 | going to lose some of that energy it's some of that energy is transmitted |
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| 58:46 | other is reflected right? And transmitted going to do the same. So |
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| 58:52 | reflected and other is transmitted. But it goes back like the bottom |
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| 59:00 | they transmitted this slide here. no, no, no. The |
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| 59:05 | slide. Yes, that one. when it reaches the bottom a second |
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| 59:12 | , let me get a little bit . Mhm When it reaches down |
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| 59:20 | yes, the transmitted energy or the that goes to this layer is around |
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| 59:29 | point 0.004 right. So that is same energy that needs to go |
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| 59:36 | This is no, when you, you reach here, I'm going to |
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| 59:41 | perfectly. The amplitude in this point refers to what it is when it |
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| 59:50 | the surface. So 0.004 is what the surface. Yes. OK. |
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| 60:01 | there's 25 layers on so going up down it's 50 layers. It says |
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| 60:09 | it's 0.9 to the 50th par if interfaces. And so that is the |
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| 60:21 | when you get up to there. so if you start with an amplitude |
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| 60:28 | one, we're saying by the time get to the surface, that's gonna |
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| 60:35 | 0.004 which is less than 0.5%. , but isn't it going through 100 |
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| 60:51 | because it went down through 50 then through 50 well 50 interfaces. In |
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| 61:03 | words, layer 123, so far go through 123 interfaces and I have |
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| 61:12 | layers. I'm going through 50 50 So that's, and that's, |
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| 61:21 | that's including just going down as 50 going down and up is 50 total |
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| 61:26 | down to 25 and it's 25 going up. Oh, ok. |
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| 61:31 | I was confused because it had the at that bottom layer on the bottom |
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| 61:36 | . Yeah. But there, there's , there's something wrong with my logic |
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| 61:43 | though and it, it's shown on next slide and the logic is |
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| 61:54 | my reflection coefficient is 0.1 going down I come up this way, what's |
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| 62:06 | reflection coefficient? It's not 0.1 it's 0.1. And the minus 0.1 means |
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| 62:16 | transmission coefficient is going to be now minus a minus 0.1 or it's gonna |
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| 62:26 | 1.1. My wave is gonna get as it goes back up and how |
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| 62:33 | bigger. Well, it's going to take that and uh one minus |
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| 62:41 | it's 0.9. No, it's not it's two way is 0.99 that's going |
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| 62:50 | , we're going back up. It's be 1.1 squared. And so when |
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| 62:55 | get that, I think it's got be like 0.6. So the |
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| 63:01 | the two, the two way travel one minus the reflection coefficient times one |
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| 63:08 | the reflection coefficient. And that's When you go down, the transmitted |
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| 63:16 | one minus the reflection coefficient. That's going up. It's one plus the |
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| 63:23 | coefficient. And that turned out it's , that's gonna be 1.1. |
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| 63:29 | so, so when it goes it kind of recovers some of that |
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| 63:36 | that it was lost when he, was going down. Well, |
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| 63:42 | you're not losing energy, it's the of the particle velocity, it's getting |
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| 63:49 | . Mm The, when I go this boundary here, I have 10,000 |
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| 64:04 | this is 20,000 and what happened is and this is gonna be feet per |
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| 64:16 | at the first boundary. Going, down to this next one, the |
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| 64:22 | of that little box is going to much bigger. But then the particle |
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| 64:32 | it gets smaller. I appear we when you go from fast to slow |
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| 64:56 | box gets smaller. But the amplitude bigger. OK? We're out in |
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| 65:10 | middle of the ocean and the tsunami 20,000 feet long, but it has |
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| 65:22 | amplitude of only a half of an as that tsunami. That tsunami comes |
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| 65:31 | a shallow bay. The length the goes from 20,000 ft to 100 |
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| 65:40 | And because it's only 100 ft long that shallow water, the amplitude becomes |
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| 65:49 | in order to have the same energy of energy. So you, you |
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| 65:57 | change the period, you can't change period, the wavelength will change period |
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| 66:03 | the same this out in the mid , that wave is traveling 20,000 ft |
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| 66:10 | second. But when he gets in bay, it's, you have to |
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| 66:16 | 100 ft per second. So what you do with all that water? |
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| 66:23 | was a half an inch high. , it's gonna be 10 ft 20 |
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| 66:28 | high. It's only 100 ft So when I come down here my |
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| 66:39 | pulse amplitude magnitude particle philosopher, it's smaller because the box is getting, |
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| 66:49 | are getting bigger and bigger. The getting bigger as we're going downward. |
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| 66:54 | therefore the particle velocity is smaller as go back up. What happens is |
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| 67:02 | length of my, the length of box that's going back and forth. |
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| 67:09 | getting smaller and smaller as I go the c uh as it gets smaller |
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| 67:14 | smaller, the magnitude that this is particle has to get bigger because it's |
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| 67:22 | whole mass of that box as it , it has to be considered. |
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| 67:29 | your mass here is becoming very small you need a big particle velocity in |
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| 67:38 | to have the same conservation of The, the thing that we did |
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| 67:44 | , what I did wrong is the coefficient is 0.1 going down, but |
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| 67:53 | up, reflection coefficient is minus And that enters in right over here |
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| 68:01 | the transmitted. So the transmitted now one minus a minus 0.1 meaning that's |
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| 68:10 | to 1.1. So when I go this boundary upward, whatever the, |
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| 68:18 | the amplitude was in this boundary down . It's gonna get bigger by this |
|
| 68:25 | because that's basically because the volume is . Are you a geologist? |
|
| 68:37 | Are you a geologist? No. Yes, John just, they don't |
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| 68:49 | anything. They just sit there. . Yeah. No, I'm just |
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| 68:54 | no, I'm not. Ok. continue onward. So uh oh |
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| 69:05 | no, no, I, I I'm good. So yeah, for |
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| 69:08 | two way then you do the one R which was the 0.9 and then |
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| 69:16 | one plus the one plus one, , you take the, take the |
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| 69:25 | value of the reflection coefficient and call R. So one minus R one |
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| 69:29 | R that's, that is, it give you the total two way. |
|
| 69:35 | other words, if I start with value one here, what's it going |
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| 69:39 | be when I go through it and up? It's gonna be 0.99 not |
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| 69:49 | . Is it, it's much bigger I'm sorry, I, I'm just |
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| 69:57 | all the math. Uh So one , so T two for the two |
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| 70:04 | time equals one minus one. Let's look at this one boundary, |
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| 70:15 | The upper one, this is the amplitude when you go through. |
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| 70:24 | Now, if I have an amplitude one right here going up, what's |
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| 70:31 | , what's the transmitted pulse piur gonna , it's gonna be one 0.1 because |
|
| 70:40 | is one minus a minus 0.1. the reflection coefficient here is 0.1 going |
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| 70:49 | way, but it's minus 0.1 if going that way, reflecting from the |
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| 70:57 | is opposite from reflecting from the right? So what is our in |
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| 71:04 | two way equation there? So the way equation here would be transmitted two |
|
| 71:13 | would be equal to this 0.9 times one you start with one here, |
|
| 71:28 | gonna get 1.1 on the other side 1.1. OK. OK. |
|
| 71:35 | Yup. Yup. And that's gonna 0.9 nine before it would have been |
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| 71:50 | the way we were computing it. , that makes sense. Thank you |
|
| 71:59 | going through that. OK. Here's a little cartoon that Mike Raw |
|
| 72:17 | and uh he's a better cartoonist than am. It shows over here the |
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| 72:24 | Model 8000 ft per 2nd 12. the way down here. It computes |
|
| 72:30 | reflection coefficient right beside it. And a cartoon wise shows you what the |
|
| 72:35 | coefficients are going from eight to the is a positive, going from 8 |
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| 72:40 | 16 is a little higher and, so forth. And this is |
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| 72:48 | this will be time going down that . So I take these and turn |
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| 72:53 | the other direction. So this right is really that and this one right |
|
| 73:00 | is really that one. So that's reflection coefficients. Then we're gonna put |
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| 73:09 | Wale on top every place that you a reflection we're going to add to |
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| 73:18 | the wavelet. So this wavel right is gonna be assigned to this two |
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| 73:26 | point two reflection coefficient. And so multiply this amplitude by 0.2. And |
|
| 73:33 | see that's this dot series right Now, when the wavelet propagating done |
|
| 73:41 | by this minus 0.2 that will be here that enters the summation chamber as |
|
| 73:51 | wavelength come on. OK. When it gets to the very big |
|
| 74:13 | amplitude here, 0.3 you have a bigger wavelet that's being added on. |
|
| 74:21 | , the lower one, it's a phase wavelength because you think of times |
|
| 74:28 | being right here, we we don't any seismic sources that are zero phase |
|
| 74:39 | you have action happening right here before zero. All our seismic wavelets are |
|
| 74:49 | minimum phase. When they start, , they have no motion until times |
|
| 74:56 | . And then most of the energy up front right there. Now, |
|
| 75:03 | we're going to do now is what does a seismic trace look |
|
| 75:08 | You will take this amplitude here and it to this amplitude and that will |
|
| 75:15 | us what the total sum would be this particular time, your dist adding |
|
| 75:22 | . And that is shown on this . So this light the blue dotted |
|
| 75:29 | dash line that is the summation of wages being involved with the reflectivity |
|
| 75:39 | The thing that's really interesting is that notice is that when you look at |
|
| 75:44 | zero phase, you see one, look at the peaks drop 23 individual |
|
| 75:55 | . And here on the seismic, were the reflections? 123 exactly. |
|
| 76:03 | they shown with a zero phase But a little less resolution, zero |
|
| 76:08 | wavelength has some bread. But on blue data find these three reflectors, |
|
| 76:16 | them on the blue outline. You find the three reflectors on the blue |
|
| 76:24 | for the zero face. So that why folks like to have zero phase |
|
| 76:32 | . When you get done, it better resolution, then if you keep |
|
| 76:38 | at minimum phase or any other again, you get to zero phase |
|
| 76:49 | seismic processing, that's where that is . And you validate its zero phase |
|
| 76:59 | making synthetic seismic grams with the zero wavelength on it. And you compare |
|
| 77:04 | to seismic data which we will do phase wavelets provide the maximum resolution over |
|
| 77:13 | wavelets with the same amplitude spectrum. somebody says here is the amplitude spectrum |
|
| 77:21 | this seismic data. And there's a spectrum that goes with that too in |
|
| 77:27 | to find a way to it. good lord, we're gonna need Mikey |
|
| 77:35 | Mike would say when your energy goes if theres a source, it goes |
|
| 77:40 | all types of physical mechanisms to get chance to beat on the poor seismic |
|
| 77:48 | . So it started off with a minimum phase wavelength by the time it |
|
| 77:53 | to the surface, it's looking pretty . It's lower in frequency and it's |
|
| 78:02 | any resolution. As Mike. Mike , this is where we go to |
|
| 78:07 | Jude's Processing Hospital. It's right off Saint James in Houston. Uh, |
|
| 78:13 | ever been Houston? Saint J, , uh, Saint Jude's and I |
|
| 78:18 | I just made that up my battery running. Do you know what I |
|
| 78:29 | discovered physical mechanism? You need to the battery in search? Oh, |
|
| 78:42 | surgeon. I solved it. my battery doesn't last long. I |
|
| 78:52 | at 830 oh hour and a Ok. Le le let's look at |
|
| 79:05 | things it could have been and if you take this type of a |
|
| 79:15 | and you think of involving it with spikes and then trying to find where |
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| 79:24 | spikes are in the reflection coefficients on final product. Wow, that is |
|
| 79:31 | be ugly compared to one that made phase. Oh, but it, |
|
| 79:37 | , as you're traveling, we already the transmission losses. How that affects |
|
| 79:45 | . And now because it was in open medium, the energy spreads |
|
| 79:54 | Would you like to say 3 to and 60 degrees? So it decays |
|
| 80:00 | one over the distance you travel. the amplitude at 10 ft there is |
|
| 80:06 | lot different than through to 20 It's twice as big at 10 ft |
|
| 80:11 | than it is 20 ft. So called the geometrical spreading loss. And |
|
| 80:20 | there's something called attenuation. And there's types of attenuation. The intrinsic means |
|
| 80:27 | property the ross, if you had that were filled with air bubbles in |
|
| 80:34 | pores, you probably get a lot beating down the amplitude, the |
|
| 80:43 | then there's Q filtering, that's just mechanism to bring that amplitude back up |
|
| 80:52 | at the bottom. Right here, might have a small structure and they |
|
| 80:57 | what's called a Fornell zone reflection. means that wave going down only reflects |
|
| 81:06 | of the small area. If you have a small area to reflect |
|
| 81:11 | you don't get a big wave coming . Now we get into the nasty |
|
| 81:18 | . Anybody that's dealing with data from Texas Birmingham invasion, Delaware man, |
|
| 81:29 | crap. So everything is still OK. Connect your film usually pops |
|
| 81:43 | . I lose the picture. These really bad news in certain areas, |
|
| 81:53 | Basin Australia, really bad. Any that you have Vapo deposits you're gonna |
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| 82:03 | into problems because shell to the terrible reflection really big. And once |
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| 82:14 | get underneath it, small reflections don't a chance because it's still ringing back |
|
| 82:20 | forth and we will look at OK. That's the end of |
|
| 82:30 | Any questions on that? OK. all the physical mes mechanisms to which |
|
| 82:39 | way it is subjective. How is possible that a synthetic, which we |
|
| 82:46 | the word of before will match the . So let's examine this pro process |
|
| 82:52 | well ties. I like to tie well to my seismic data and we |
|
| 82:59 | use really thick cord. OK. with that, I'll call my colleague |
|
| 83:07 | , who knows how to set this up. Do you know when I |
|
| 83:13 | a bring up a powerpoint? He to hit this computer 20 times to |
|
| 83:18 | it to you at least 20 times for an old man 44 buttons for |
|
| 83:24 | paying attention. Yes, I am section 1.5 section 1.5 pertains to. |
|
| 83:48 | you using two D data or are using 3D data? What kind of |
|
| 83:54 | do you look like in your 3d. Anybody looking at two D |
|
| 84:03 | ? OK. Can you help I put this into powerpoint? |
|
| 84:18 | it should be a nice window and window and T tab OK. Now |
|
| 84:25 | the window that I want zoom. to zoom. This is right |
|
| 84:30 | I choose the zoom window and you share screen and share the screen and |
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| 84:36 | the screen two and choose screen share it and then share it down |
|
| 84:43 | . Finished and I'm finished. Everybody to that. So next time he's |
|
| 84:49 | and you have to help me, better memorized it. OK. This |
|
| 84:58 | called a synthetic Seismo Gram. It's Cooper Basin. I would like to |
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| 85:16 | a show of hands from the people nowhere land. Raise your hand. |
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| 85:23 | you've ever used a synthetic seismic gram looked at one against seismic data. |
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| 85:28 | your hand. Is that a Je Jessica? No. Ok. |
|
| 85:37 | that? I got a, proceed raise their hand. And is your |
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| 85:48 | raise your hand button? Where? . Um You have a reaction side |
|
| 86:02 | the action. I have a chat I don't have a race and |
|
| 86:10 | We have different reactions. What's the that don't get touched? Just tell |
|
| 86:17 | here. Just more reaction. The , one, third. Very |
|
| 86:26 | Yeah. No. Uh you need go to see. Uh Yeah, |
|
| 86:34 | I got one and four. I Taylor and that's it. You |
|
| 86:43 | you can like Taylor and Taylor. I was just clapping for you because |
|
| 86:51 | got your hand raised. I I've used a synthetic. So all |
|
| 86:56 | OK. I'm we're gonna react in audience participation here. How may add |
|
| 87:01 | synthetic seismograms to match or to look you? Never even heard of it |
|
| 87:08 | you have. What do you think does? Does a geophysicist have that |
|
| 87:19 | to prove that they got something you have sort of like a well |
|
| 87:27 | Well, you look at seismic don't you? No, as a |
|
| 87:33 | , don't you look at seismic No. Who here does not look |
|
| 87:39 | seismic data anybody? 12. What you look at as a geologist? |
|
| 87:47 | ne Neuro theist. Oh I think , at work. Yes. What's |
|
| 88:00 | ? XRD? I have no idea that is on. What? |
|
| 88:08 | core analysis. OK. That I that word J is OK? You |
|
| 88:13 | look around. OK. Actually, you're looking for work and uh uh |
|
| 88:28 | find that. OK. For Dela to occidental and she doesn't work in |
|
| 88:43 | . OK. Oh, your She's management. She doesn't work with |
|
| 88:50 | . Uh she report OK. Nobody . Only tater would say he knows |
|
| 88:57 | about a synthetic or he just just not me. What's that? |
|
| 89:04 | me? I, I don't want seismograms. Just Prisa. OK. |
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| 89:15 | , that's seismic data. You're looking folks, this is seismic data and |
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| 89:24 | , this is a, well, was that, that data that was |
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| 89:29 | from a well. So when they a well, do they go ahead |
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| 89:36 | shoot seismic again around it? Where this come from? It disappears magically |
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| 89:47 | the seismic data. You just gotta near the, well and hold up |
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| 89:53 | camera or recorder and well, talk you. Well, that's what we're |
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| 89:59 | try to answer where it comes I forget how we get this back |
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| 90:22 | . OK. All right. Let's if we can do something with |
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| 90:30 | Let's look at a mathematical model. likes a mathematical model for local |
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| 90:36 | So I'm gonna start, here's a . I drill a well, |
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| 90:43 | do, do, do, I'm deeper. So the voice gets lower |
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| 90:46 | , do, do do do, . When I get done, I'm |
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| 90:51 | to log that well. And by , it means I'm gonna, I'm |
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| 90:57 | take a long piece of wire and it all the way to the |
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| 91:01 | And on that wire is a tool that tool does a particular action that |
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| 91:08 | talked about. There's a Sonic tool what the sonic tool does is to |
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| 91:15 | you the sonic tool has a source there that goes and then down here |
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| 91:23 | has a series of receivers in measures travel time it takes to go past |
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| 91:32 | four receivers. That'll allow it to the velocity that you assign for this |
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| 91:40 | . That's the medium velocity, the velocity 13,125 ft. But they don't |
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| 91:47 | philosophy, they give you delta How do you get your delta |
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| 91:53 | What's the magic number? A You take a million, you divide |
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| 91:58 | the sonic time? 125 microseconds per . Take that into a million, |
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| 92:07 | ft per second. They have a called a density tool. It shoots |
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| 92:17 | material and it looks for things to off of Adams Dudley. And by |
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| 92:23 | many bounces it gets, it sends back to the tools we count this |
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| 92:29 | gamma rays. Therefore, here's your . So we have a tool to |
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| 92:35 | velocity and density. Now we have tool that measures the radioactivity it's in |
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| 92:43 | borehole. And that gives us a tool. We can tell SAN from |
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| 92:52 | that type of talk. So here go ahead and I have velocity in |
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| 93:01 | . I take the product, I acoustic and beans. So I can |
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| 93:05 | a log as a function of depth acoustic and beads. Can you do |
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| 93:11 | ? Yes, but you gotta pay day for that. OK. And |
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| 93:17 | since you know the interval velocity you can take that and convert it |
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| 93:23 | a function of time. So now gonna display it in time rather in |
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| 93:28 | . Now, here's a hard We're gonna take that and repeat it |
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| 93:33 | here. Oops and just just repeat . Now at each interface, we're |
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| 93:46 | get a reflection coefficient. So I reflection coefficients. So now I kind |
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| 93:55 | know where all these boundaries are here these are those big reflection coefficients. |
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| 94:04 | I select a wavelet out of my and I start sticking, sticking it |
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| 94:12 | here. You know you, how you stick it on her? You |
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| 94:14 | draw the wavelet and your amplitude is amplitude of that reflection coefficient. And |
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| 94:24 | you slide it down a little bit you put another label on depending upon |
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| 94:29 | amplitude of that reflection to and then add horizontally and you come up with |
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| 94:36 | seismic trace. So we have what is the wave exactly like? |
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| 94:46 | you, where are you getting the . Ok. Great question. There |
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| 94:52 | various sources that we can use to and start the seismic process there. |
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| 95:03 | dynamite. And there's one called Vibber and Viber size is a big |
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| 95:09 | 60 ton truck that sits on the that's 4 ft by 4 ft. |
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| 95:18 | that paddock is done, hits the and lifts the truck up. So |
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| 95:24 | have £60,000 sitting on that four by path. Then that truck starts to |
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| 95:32 | , move up and down. that path is gonna move up and |
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| 95:37 | and it starts off. Hm. . And it increases in frequency. |
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| 95:43 | it goes for a very low maybe five cycles per second. And |
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| 95:50 | goes up to 100 cycles per So it goes up to in a |
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| 95:57 | of 20 seconds. So that thing for 20 seconds continuously changing frequency from |
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| 96:05 | to 100 Hertz. That pulse is seconds long. So you send a |
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| 96:12 | in here, that's 22nd long. you look at frequency versus amplitude, |
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| 96:22 | pulse was started five cycles and go to 100. But it doesn't |
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| 96:31 | a long time period, 20 But you can't use a 22nd pulse |
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| 96:40 | do expiration. It's gotta be So here's what the magic comes |
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| 96:46 | You take that low frequency pulse started and it keeps getting higher and higher |
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| 96:57 | and it goes from 5 to 100 and you take this in a processing |
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| 97:03 | and you do what's called a cross and what it does, it'll take |
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| 97:09 | that's 22nd long and convert it into that's only 20 milliseconds right here. |
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| 97:24 | you go from 20 seconds to 20 , you've collapsed it 1000 times. |
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| 97:34 | what have you done when you do cross correlation? It's a multiplication. |
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| 97:41 | take this pulse, you put it the seismic data, you cross multiply |
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| 97:46 | everything up as an output sample, it on one sample, do the |
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| 97:51 | multiplication and it collapses. It correlates the seismic data. So that becomes |
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| 98:01 | zero face pulse the times zero in middle. That's one way of doing |
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| 98:08 | Gideon. Another way as you commend seismic data and you look at your |
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| 98:17 | data right here and you say make a fourier transform convert this time sequence |
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| 98:25 | frequency. It's called a fourier And you use that in order to |
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| 98:31 | what the amplitude specter would be, we'll show a couple of those. |
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| 98:40 | , this process that you have you get a seismic trace, a |
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| 98:46 | seismic graph. That's this thing You have a wavelet in here. |
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| 98:52 | this right here. And you have coal visions or was that? And |
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| 98:59 | convolution is me taking this away but it down, putting all those ways |
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| 99:07 | there and then some horizontally. That's convolution. No, this is idealistic |
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| 99:19 | likely you're gonna get something that you this to be your idealistic. But |
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| 99:25 | that threat? Well, right there should be also a fate in |
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| 99:30 | right here, the way that remained same. But the reflection goldfish it |
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| 99:36 | uh oh, when I compute this coefficient, I'm not only gonna be |
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| 99:42 | at the vertical, up and down , I'm interested in what happens if |
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| 99:48 | have a very far offset angle So all of a sudden the reflection |
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| 99:56 | has the option of also being the of the incident angle. So that |
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| 100:02 | every spot on the earth can have normal incidence angle and then they can |
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| 100:11 | a source way out here that hits at a farther one. So that's |
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| 100:16 | angles and then they can have one the middle. So you can have |
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| 100:22 | different waves hitting this one spot. that would be this would be called |
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| 100:31 | . You have illuminated the same point three different times. Now we're getting |
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| 100:48 | goofy and tell you that seismic trace has a lot of things that has |
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| 100:57 | happen to him. We gotta do and I call here's more realistic, |
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| 101:03 | more realistic in that you have a component. And I have three of |
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| 101:08 | right here. And what are those components? This one right here? |
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| 101:16 | just didn't your waves spread out spherical it loses amplitude well in your |
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| 101:24 | you gotta compensate for that. Didn't have transmission effects? When you |
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| 101:31 | you got to compensate for that. . We'll do that. Well, |
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| 101:35 | about this thing? Right over remember that airplane that flew overhead? |
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| 101:41 | gotta compensate them that's sitting on the trace. Do you remember that great |
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| 101:47 | gully that you just went by? know, the seismic ways reflected off |
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| 101:53 | that gully, you gotta get rid that, it's on there. So |
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| 101:57 | have all kinds of noise that's You're shooting in West Texas. Did |
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| 102:03 | shut all the pumps down for you go across. Now in Russia, |
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| 102:08 | used to do that. I, was talking to some of the Russian |
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| 102:12 | business. He, oh he said God. When we shoot a |
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| 102:16 | the railroad stops, they stop the for us. When we go through |
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| 102:22 | , they stop the traffic. we're God and they're the mayor of |
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| 102:28 | city. Sometimes they're the mayor, the president of the university that's in |
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| 102:36 | city named Geophysics after geophysicists. So we have to do a lot of |
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| 102:46 | in order to get this one here we want, we wanna find the |
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| 102:53 | angle. We have to do a of corrections in processing and that is |
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| 103:01 | some of the seismic processing is, to make it look like the real |
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| 103:06 | this model here. So in you have to have a mathematical model |
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| 103:15 | order to process seismic data. Because you see these various noises on the |
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| 103:23 | , you have to say to is that adding or is that going |
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| 103:28 | the way because you can have multiples part of the wavelet and you gotta |
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| 103:38 | rid of it because this is where coming in and that's, that's a |
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| 103:43 | type of processing scheme. So the for communi communicating rock properties from the |
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| 103:57 | coefficients. And so which model should use? If you're shooting in |
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| 104:05 | if you're shooting in the Gulf coast in your way out in the |
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| 104:12 | there is no woods near you, no fences, fences carry electricity and |
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| 104:19 | it carries electricity, 60 Hertz. there's a fence and there's barbed wire |
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| 104:24 | it, you get a GIF phone that barbed wire, it's gonna have |
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| 104:30 | that's by coming from pools and they travel miles. All has to have |
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| 104:37 | telephone pole, car, electric car has to cross the fence somewhere and |
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| 104:45 | travel miles. Ok. So if in that type of an environment, |
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| 104:51 | have a good chance that you really have any contamination on your data. |
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| 104:58 | fairly clean, small reflection coefficients in gulf coast. Young rocks, |
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| 105:10 | no limestone, no hearts streak velocity as a function of depth or you |
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| 105:23 | have a wavelet that's time varying. what might that be? Well, |
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| 105:32 | you're in once again in the Gulf what could happen is some of your |
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| 105:40 | will attenuate the signal a bit and called intrinsic attenuation. We will identify |
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| 105:50 | . Now, you could be again the same area. And now not |
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| 105:56 | they have a little bit of intrinsic , this is something you want to |
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| 106:01 | . You want the far incident angle have a different reflection coefficient than the |
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| 106:11 | you need a better explanation. Remember of you when you're eight years |
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| 106:17 | where am I heading? When I seven or eight years old, what |
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| 106:19 | you a champion at? When you to the lake throwing stones? So |
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| 106:25 | threw the stone with your arm parallel the lake and it skipped, that |
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| 106:31 | 80 degree angle. Then you took stone and you try to kill a |
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| 106:37 | through that stone straight down. That's zero degree angle. So between zero |
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| 106:44 | and 80 degrees skipping stones, you different reflection coefficient artists. And then |
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| 106:54 | you're looking for the Austin shock, still in the Gulf coast, you |
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| 106:59 | be the first limestone that you You're gonna be looking for fractures and |
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| 107:05 | happen to be in the reflect reflection services is where they belong. |
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| 107:13 | The whole idea is to take your data and ask yourself what model do |
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| 107:20 | have. And that's going to tell how we're going to have to process |
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| 107:31 | processing goal, remove unwanted earth effects yield the idealistic model. And I |
|
| 107:39 | you say, I don't wanna hear math, but gosh, darn, |
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| 107:43 | the processing geophysicist doesn't understand a little of math, you need to talk |
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| 107:49 | somebody else because the algorithms they It's very important. He might, |
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| 107:56 | , that low frequency. I'm just filter that. No, you're |
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| 108:00 | you filter that you're gonna destroy the . So we need to find |
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| 108:08 | So, Fred, what's this definition a well type? I think there's |
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| 108:15 | very famous professor that used to be at the University of Houston called Bob |
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| 108:21 | . Anybody ever hear of Bob Sheriff ? The Sheriff lecture? Have |
|
| 108:28 | OK. Bob wrote a book. probably the best publication that the SCG |
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| 108:40 | put out. It's an encyclopedia all the Geophysical names he has definitions |
|
| 108:50 | . It's a thick book over years years. So any name Geophysical you're |
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| 108:58 | of, he has definitions and some terms. So in his encyclopedia |
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| 109:04 | a well typed seismic events on the synthetic that correlate with formations on low |
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| 109:16 | . That is a time. See peak right there. That is the |
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| 109:37 | of Wilcox C one sand. That's well T and this reflection is associated |
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| 109:47 | AC one Wilcox say that is a time. Now you're gonna hear about |
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| 109:53 | shot surveys and some of your folks your office are gonna use a check |
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| 109:57 | survey which gives you the time death and is gonna come in and try |
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| 110:03 | . No, no, no. of that C one according to my |
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| 110:06 | shot survey occurs at 2.04 seconds and put a little nick there and say |
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| 110:13 | the top of it. No, , no. Check out, |
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| 110:16 | we get you close. But the answer is with the synthetic, that's |
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| 110:22 | it remains because check shot did not a kicking a cop. All the |
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| 110:27 | surface effects. OK. Sorry for rude. Interrupted by Fred. I |
|
| 110:35 | have a question. So when, choosing the wavelength for the to generate |
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| 110:42 | synthetic size program, what would, would be better to pick a wavelength |
|
| 110:49 | is the phase or to extract the from the seismic? You got |
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| 110:58 | you, you, you hit it on it, you extract the wave |
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| 111:02 | from the seismic and you, if not zero face, you make it |
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| 111:06 | face. In other words, you a phase correction, you filter and |
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| 111:12 | can apply a phase correction and change to zero phase from the, the |
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| 111:18 | from the seismic. Yes. The that you get from the seismic, |
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| 111:24 | then go ahead and wanna make that phase. So now this is an |
|
| 111:35 | when you shoot a 3D and you it, you tell the processing company |
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| 111:43 | you want that to be final And the processing company should be responsible |
|
| 111:50 | take a synthetic extract wavelets and make correction. So those waves will become |
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| 111:59 | face the next time you try to the wavelet and their choice. |
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| 112:06 | some cat, they say no, want to be left in minimum |
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| 112:10 | bless their souls and fine as long you know what that phase is, |
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| 112:17 | you can search it and we'll, show methods of doing it. |
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| 112:23 | OK. Thanks the problem. If hy if the hydrocarbon target is a |
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| 112:38 | change, then the reflection coefficient reflectivity change spatially as the porosity changes |
|
| 112:48 | But what happens when the wavelength is varying and also change spatially due to |
|
| 112:58 | changes in acoustic and beams and shallower . This is difficult because you're asking |
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| 113:10 | process data and change it quickly as spatially go down the road. And |
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| 113:18 | , that is a difficult but very problem and that you can change it |
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| 113:27 | quickly and introduce a pseudo prosy So what you process, you gotta |
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| 113:35 | leery, what's there and now you're it, quantify time varying wavelets from |
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| 113:48 | well log curves and provide processors the parameters for decon Q. In version |
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| 113:57 | the specter mouth get back to high and analysis of statics. Wow and |
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| 114:05 | before processing starts try to go ahead make these predictions. You avoid interpretation |
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| 114:14 | . Later on. In some we show that the parameters that you |
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| 114:21 | for de convolution, which is right front can be totally wrong. Because |
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| 114:27 | didn't look at the wall law that had there looking at that. |
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| 114:32 | log before you can tell you how do decom, we will talk about |
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| 114:40 | near surface shapes. The wavel. we take a break? Five |
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| 114:50 | Ok. Let's, let's give you 10 minute break. We've been five |
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| 114:54 | before. So come back about 20 to 11, mid morning. |
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| 115:23 | uh, you know what? Do you know as you get |
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| 115:30 | you get to be here. You what dementia is? You lose your |
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| 115:38 | . Alzheimer's due to Alzheimer's disease. you most. As I know when |
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| 115:50 | get home, you sorry for your to remember. Yeah. How much |
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| 115:58 | brother beat me up? Ok. . So that means I have short |
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| 116:11 | memory, right? Do you know would help me? And probably other |
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| 116:18 | too as if you took the time wrote down the steps that you have |
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| 116:28 | the buttons you have to push in for me to visit them and they |
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| 116:34 | see the screen a proper way. that possible? No, you gotta |
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| 116:41 | what you're doing. I don't know I'm doing. That's why I asked |
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| 116:46 | . Can you do it? Think them? You don't have to give |
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| 116:55 | an answer. No, you might to tell me that because one day |
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| 117:00 | gonna have to tell your Children. , I wanna give a quiz purpose |
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| 118:38 | pop dump. So I'm gonna have show one. Sure. No, |
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| 118:49 | you have to drink. So is he what? Let me give you |
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| 118:58 | chance. So, so every time show the slide, you just go |
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| 119:05 | it first and share the. So you want your your students camera |
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| 119:17 | So you need to yeah, share screen. So it on the computer |
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| 119:23 | is a screen to. So you this one is your spring one and |
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| 119:28 | two. OK? Now you need like if you need to open, |
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| 119:35 | switch to zoom, you you can press the window and select zoom and |
|
| 119:43 | so go to so you have you need to find a share |
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| 119:50 | then the then you share share So only when you present your |
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| 119:56 | you will have screen too and then when you select your screen to to |
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| 120:02 | to share, you will see this instead of your screen. OK? |
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| 120:08 | that's it. No problem. And want to just and this whole part |
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| 120:16 | help you adjust the range of OK? Thank you this little bit |
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| 120:32 | the right because if you move to to the right, it was showed |
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| 120:40 | the screen to. So if you to close here, you will see |
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| 120:48 | will block, it will be OK? Yeah. Gotcha. Thank |
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| 120:57 | . You're welcome. You know what answer to that one is? Be |
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| 122:07 | Democrat. No, no, that's the fifth. No, but |
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| 122:54 | oh, you know, II I , I miss not having a news |
|
| 123:00 | . I could believe the political What they say, fuck me. |
|
| 123:05 | is terrible. Yeah, but you know, like they say now |
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| 123:32 | winning party is gonna be that party has the most money the at |
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| 124:26 | Answer the question, please. this is a, this is a |
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| 124:35 | believe one. Wow, you, got a dangerous situation with all those |
|
| 124:50 | . Think about electrocuting. They just that they have a new mechanism |
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| 124:55 | to kill you now. Nitrogen. my God. 20 minutes to die |
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| 125:01 | 25 minutes. I don't know what is to suffocate you. They put |
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| 125:09 | in your veins. I don't God, I'd just rather have a |
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| 125:17 | . Yeah. This, you don't to turn this one in, but |
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| 125:21 | gonna have one to turn in a . But what, what do you |
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| 125:24 | the answer is on it? Is there in the other world? Can |
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| 125:28 | hear me? No? Yes. . You hear me? Ok. |
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| 125:37 | you see the screen? Yeah. . And I tell you what number |
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| 125:44 | is not to be a democrat. not the answer to be a democrat |
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| 125:49 | not the answer to number five or or socialist. Number five is |
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| 126:00 | Yes, you got it. Right on the note. No. |
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| 126:04 | ? There isn't the number five It's very obvious everybody forgot about |
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| 126:11 | What is the obvious thing to be ? You got to get elected? |
|
| 126:22 | ? That's ok. Ok. I'm ready for the quiz now here's |
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| 126:31 | real quiz. No reply on your page. Put the numbers 12 and |
|
| 126:46 | . So you might think on your you're gonna have the numbers 12 and |
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| 126:53 | and besides 12 and three, you're have the letters T or F or |
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| 127:00 | or false? Mhm. Wow. . Start sending your emails in, |
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| 131:00 | . Anthony I Robbie and your name ? Ok. That's crazy. It |
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| 132:00 | . That's a what you want? . Ok. Ok. Everybody email |
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| 132:57 | . I'm noticing the time now. have, um, 10, 1048 |
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| 133:11 | . Any emails that can pass 1050 do not, I will not |
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| 133:17 | So we got about 30 seconds to it even. That's 1050 1050. |
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| 133:31 | . Dated. Ah, are we in from the audience here? |
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| 133:57 | Everybody down here. Ok. Time's audience there. 1050 if I'm not |
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| 134:04 | , I don't want them. Ok. Anybody have trouble with the |
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| 134:21 | ? No, so we're all together . Ok. Number one short |
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| 134:44 | Multiples make the seismic wave it Anybody want to take a guess on |
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| 134:49 | . Yeah. So it's 50% chance being correct. Just the opposite. |
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| 134:58 | make them longer short period, short period multiples are normally detected only |
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| 135:06 | the shallow reflection events. Just the once the short period multiples on it's |
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| 135:15 | on. So once, once it in there, you're, it's gonna |
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| 135:20 | forever. So they accumulate and you more deeper you go and the more |
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| 135:27 | you go, the lower the frequency it's making the wavelengths longer and |
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| 135:32 | Long as in long period, multiples to amplitude scale for the reflections. |
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| 135:40 | means opposite of short, you gotta a long distance before you hit a |
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| 135:48 | . That will be considered a bounce and forth. And we'll see long |
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| 135:54 | multiples create new events on the So the top of the Wilcox, |
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| 136:03 | be another event right beneath it. a multiple from up shallow short period |
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| 136:11 | distort the seismic wavelength make it fatter something we don't want. OK. |
|
| 136:26 | Does that mean that three is We're true. All, all three |
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| 136:32 | false. Nobody got the perfect So that might be everybody feels good |
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| 136:41 | . So if you, you got least one out of the three. |
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| 136:48 | , so the scores are gonna be or two. I can tell you |
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| 136:53 | we're guaranteed to get either a one a two. Uh at least for |
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| 136:57 | ones that I read so far. course, this audience might not represent |
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| 137:04 | real public. OK. Um Let's our second quiz off done right now |
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| 137:18 | . Oh And this oh Hold it might want to be reading, reading |
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| 137:22 | paper during lunchtime for the second So I won't, I won't do |
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| 137:28 | now. Ok, I stopped Ok, I hit that. |
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| 137:43 | And bringing me back. Ok. , I don't know what I'm doing |
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| 138:00 | the window windows and share the sweet . Share the sweet screen two sha |
|
| 138:36 | . People see me. Hear Good. Good, good, |
|
| 139:01 | Let's see what type of wavelets you put into the ground. So this |
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| 139:07 | an exercise sketch, what your ideal source wave? It looks like. |
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| 139:19 | you draw me a sketch of This, I've got something here. |
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| 139:28 | don't know why. So what, this for man in the back? |
|
| 139:33 | this one for? Oh It's for it's done. What's that? It's |
|
| 139:53 | . It's done. Yeah. I got that. Yeah. |
|
| 139:59 | I think it's, I think it might, if it falls |
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| 140:01 | I'll let you know. Can you ? Yes. OK. Remember there's |
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| 140:10 | energy source that creates a symmetric zero wavelet strictly in the field. Viber |
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| 140:18 | requires cross correlation processing to produce the phase wavelength. So this is not |
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| 140:26 | realistic wavel it because it says at particular time right here, I got |
|
| 140:33 | amplitude of this or an amplitude of or an amplitude of that at one |
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| 140:39 | , you cannot have three app because only can display one. So that's |
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| 140:44 | a realistic, go ahead and draw you think is a realistic seismic way |
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| 140:50 | you're proud of it. Hold it and let me take a look. |
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| 140:56 | me see yours. Jessica. You came online the seismic way to put |
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| 141:01 | in front of the camera, All right. No voice control and |
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| 141:10 | draw one. Anybody have one that want to put in front of |
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| 141:16 | in front of the uh screen. don't see any Carlos. I can't |
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| 141:24 | see you. OK. Kelly, have to hold it still. You |
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| 141:32 | move it back and forth. If can't see it on the camera on |
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| 141:36 | screen. I can't either. So, why, what are you |
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| 141:40 | ? You're making me blind. I'm ready. Oh, ok. First |
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| 141:50 | zero. That's symmetrical. First time on the waver. Is it the |
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| 142:00 | on the far left? It starts . Ok. Yeah. Ok. |
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| 142:03 | , great. Anybody else? Kelly has a good way that she's |
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| 142:06 | best so far. Anybody else? . 0000, Taylor had a |
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| 142:14 | not bad at all except you got , you got the wave. |
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| 142:19 | sit sitting up in the air since wave it doesn't, amplitude doesn't come |
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| 142:23 | zero. That means the geophones is 10 inches above the ground. You |
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| 142:30 | bring it to the ground. Anybody ? Ah. Oh, good. |
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| 142:38 | pretty. Kelly took out. What you call that little dots? Gray |
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| 142:45 | junkie. The post it note. , the note. That's good. |
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| 142:50 | get one. Ok. In my here. Let's see. Oh you |
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| 142:57 | , if you can't see it on screen, you can't have zero |
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| 143:01 | I told you that I take your away from you. Now you, |
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| 143:05 | can't be symmetrical. Go ahead, he had on you. Oh That |
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| 143:13 | like that is good. Good We just, we're gonna go, |
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| 143:22 | gonna take a walk around the room to see how the audience here does |
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| 143:52 | Bill? Oh They get that out the possible. Oh You're very |
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| 143:59 | You by your side. Pyrosis. it's not a bad idea. This |
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| 144:05 | not a, that, well, How much? Mhm OK. |
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| 144:34 | Oh A OK. OK. Mhm . But it's not ideal. So |
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| 144:51 | an ideal fibrosis? Oh That's not . If you hit him, it's |
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| 144:58 | bad. Slice it. Bring it the very end though. Why would |
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| 145:04 | still love to grow? There you . Good human. OK. |
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| 145:44 | it was OK. OK. Correct. So that your limb |
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| 146:07 | I'm back. Do you miss No? OK. OK. Here's |
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| 146:16 | that's uh might be considered a nice . Seismic W and I think I've |
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| 146:24 | to you to this one before. is a seismic wave that where you |
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| 146:29 | energy into the ground before what's really times zero. See times zero on |
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| 146:37 | would be right here and this is hammer, putting a hammer as an |
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| 146:47 | source. Anybody ever see students put steel plate on the grind, take |
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| 146:54 | sledgehammer then hit that steel plate and that as the energy source. And |
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| 146:59 | , it looks something like this. is this though? What is |
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| 147:08 | I'm saying that you put energy into ground and yet it's before times |
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| 147:16 | How did you do that? Think how your body reacts when you're hitting |
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| 147:24 | steel plate. The guys especially, wanted to be the super shocked |
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| 147:32 | So they take that sledgehammer, they it over their head. They take |
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| 147:37 | deep breath and they start bringing that hammer down to hit the plate. |
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| 147:42 | as they do that, they get on their tippy toes. And as |
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| 147:47 | as they get up on their tippy , they've taken pressure off the |
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| 147:53 | And that's what you're seeing is the swinging, it is going up off |
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| 147:59 | toes, taking weight off the ground therefore putting energy into the ground before |
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| 148:06 | zero. The same used to be weight drop. They take a £6000 |
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| 148:16 | of concrete or metal and especially in Texas, the flat land that pulled |
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| 148:24 | 6 ft off the ground and then it. And when they hit the |
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| 148:29 | boom, that was their energy Same way as soon as you release |
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| 148:35 | , you took weight off the tires that put a pulse into the |
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| 148:42 | So estimate the way of spectrum. put this one on. I asked |
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| 148:47 | the question before. And just to folks I've taken and I put two |
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| 148:55 | pulses in here. I have this right here and this one right here |
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| 149:02 | then these have different amplitudes. And over here this is the same |
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| 149:09 | low frequency. And what, what notice is notice that the shape of |
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| 149:16 | pulse is the same as the one beside it. Except this one right |
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| 149:25 | is you take this pulse and you it on either side, making it |
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| 149:33 | , but essentially it has the same . No, let's see how this |
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| 149:39 | done here is the frequency spectrum, that and when you have pulses that |
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| 149:49 | the same amplitude right in here in frequency domain. And this is where |
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| 149:56 | describe the pulse that you want. not a flat spectrum. If you |
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| 150:02 | for a flat spectrum, your low pulse here is gonna be smaller then |
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| 150:09 | high frequency right here. So it sort of a little development what's happening |
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| 150:17 | . The other thing I said, high frequency is the same shape pulse |
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| 150:25 | the low. And how is that ? Take the 10 multiply it by |
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| 150:32 | 40 take the 30 multiply it by . They have the same bandwidth and |
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| 150:42 | . What's an octave? 5 to ? That's one octave, another octave |
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| 150:48 | to 40 another octave 2 to Oh wow, 248 16. |
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| 150:56 | you get two, 46, you three octaves and that low frequency. |
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| 151:05 | , this is why a warning processors a tendency of making quote the seismic |
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| 151:13 | look good bye. Applying a low filter. I mean, a low |
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| 151:22 | off filter, they get rid of low frequency and when they do |
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| 151:27 | they make it difficult to get 23 because you might not put 100 Hertz |
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| 151:37 | in the ground. People cut the off at 30 Hertz, nothing below |
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| 151:42 | Hertz, 3061 to Wow, you get two octaves. So what does |
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| 151:48 | mean? If you have a it's only one octave. Y save |
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| 151:55 | 10 to 20 Hertz. What is pulse gonna look like? 10 to |
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| 152:00 | Hertz? Ask it another way, ? OK. What if I put |
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| 152:06 | pulse in the ground that I said 15 Hertz. What was that? |
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| 152:11 | it just 15 Hertz? What would pulse look like? What does a |
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| 152:19 | Hertz pulse look like? Now we, we have those, you |
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| 152:25 | 60 Hertz on seismic data all the . And where does that come |
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| 152:32 | Getting by a fence? A wire ? And what does that p look |
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| 152:37 | on a seismic data? It's just Sinoa pick, pick, pick |
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| 152:43 | same amplitude top to bottom. There's resolution. If that reflects off of |
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| 152:51 | , a boundary, you can tell boundary it's on because area boundary has |
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| 152:56 | same continuous. So it says if go from 15 Hertz and it's infinitely |
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| 153:06 | . What, about 14 to 16 ? All right. That's not much |
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| 153:12 | than the 15 Hertz going to 14 16. Pretty much the same with |
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| 153:17 | to 16 Hertz. This same as , 13 to 17. Oh, |
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| 153:27 | we're gonna reach a goal. how will you keep telling me? |
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| 153:31 | the same. OK. 10 to Hertz between 10 to 20 Hertz is |
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| 153:38 | octave. 10 to 20 2 to is one octave. They both had |
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| 153:47 | same shape, wavelength except one squeezed , of the, of the |
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| 153:54 | So if you squeeze the 2 to Hertz, you're gonna end up looking |
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| 153:59 | a 20 to 40 Hertz, same only squeezed. My goal is to |
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| 154:11 | you never want anything. That's less two octaves. Never because it rings |
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| 154:18 | , as I say that you never less than two octaves. Think about |
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| 154:23 | processor quote that cleaned up your which is low frequency ground rule by |
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| 154:30 | all the low frequency. Just put filter. There's nothing, nothing in |
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| 154:34 | data below 30 hertz. And I've this, I'm dealing with it |
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| 154:39 | Nothing in there lower than 30 Well, one octave is 30 to |
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| 154:46 | . The source didn't put anything above . That means you got it. |
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| 154:50 | gonna be ringing just because it's 30 , right? That doesn't matter. |
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| 154:55 | what is the band was in? . Always strive no less than two |
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| 155:05 | . And what does that say? ? Don't you dare put a |
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| 155:10 | You get rid of all my low . That's what we strive for because |
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| 155:14 | gives you the shape of the Sharp 1941. He came in, |
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| 155:22 | said here is you're looking at maybe idea of pulse and before we actually |
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| 155:29 | sharps idea, wait, look, came from Buick Dick, professor uh |
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| 155:36 | out in California and here's what he . A wavelet has no DC |
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| 155:45 | What does DC value mean? Anybody hear of that? What would be |
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| 155:49 | DC value? Direct current? And what is direct current? It's |
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| 155:57 | , alternating current AC, right. what is direct current? One frequency |
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| 156:04 | Hertz flat. And what does that to this? Add all the amplitudes |
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| 156:12 | , add them all together and it add up to zero. If it |
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| 156:18 | , you got a, a non wavelength, it doesn't exist, it |
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| 156:25 | to have at least three lobes. anybody that stopped right there and didn't |
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| 156:30 | these that can't happen. You have have at least three in order to |
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| 156:36 | outward as a spherical wave. Other , the wave that should be minimum |
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| 156:44 | , all wavelets to propagate in the are minimum phase, even the fiber |
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| 156:50 | pulse that you put in the it's still minimum phase, that's all |
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| 156:57 | . It should be causal. In words, nothing should happen before time |
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| 157:03 | zero. So when you hit the , it's, it's a real |
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| 157:10 | but it's actually minimum phase. But have to adjust what times zero is |
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| 157:17 | the person is a big fat person a sledgehammer and when they get off |
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| 157:21 | ground, whoa, the ground pops and sets a Waba. So here's |
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| 157:31 | of the things that sharp said we a greater reflection amplitude if the charge |
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| 157:39 | in clay rather than in a limestone , speaking of a hole, this |
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| 157:46 | dynamite. Now you'll get a larger on the second shot in the same |
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| 157:56 | . Low frequency, here's one low reflections you'll get when you shoot in |
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| 158:02 | low velocity layer. What is the velocity layer has anybody in here than |
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| 158:09 | mechanics. What's the earth made Geologist? You're always talking about how |
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| 158:14 | , you know, the earth you make the GIF as as if, |
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| 158:18 | the thickness of the earth? What's name of the films that are 40 |
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| 158:22 | deep? And what's the next one that? I don't know. So |
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| 158:27 | the earth, what happens first, from the surface? Tell me a |
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| 158:33 | and tell me what you have in there. If you go |
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| 158:37 | go out up to Lufkin Texas and 60 ft. What are you gonna |
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| 158:41 | ? What are you gonna have per ft? What's that? You can |
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| 158:50 | clay? Anybody else? How rich gonna be? What kind of a |
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| 158:57 | ? Do you think it's gonna What type of velocity would you say |
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| 159:01 | 1st 60 ft? What's that? me a number for slow? But |
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| 159:11 | think you never, you went to , don't go negative or? |
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| 159:16 | or time 10? Ok. He 2000 ft per second. That's, |
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| 159:23 | a, that's a typical velocity. this should be called the weathering |
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| 159:28 | the weathered material. That's what normally like to find a, you can |
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| 159:34 | weathered clay. Ok? It's still be slow. A lot of |
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| 159:40 | There's no water table. If you a water table, your velocity starts |
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| 159:44 | go up. Now, after the zone, you get into the sub |
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| 159:51 | and then where would your velocity go the way? 2000 ft per second |
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| 159:56 | a typical velocity for uh Lufkin area I talked about. Then when you |
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| 160:02 | below 60 ft, you get into clay, the blue clay, what's |
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| 160:07 | velocity? Then it goes from 2000 6200 ft per second. Big big |
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| 160:14 | change said the note. The idea is there a saint is if you |
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| 160:21 | your shot in that low velocity which is your first one, it's |
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| 160:26 | to lose a lot of its And if you go to the sub |
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| 160:33 | , you get higher frequency, low shots bring more than sub weathering |
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| 160:42 | Larger charges have lower frequency. You keep adding charge the pond after pond |
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| 160:51 | ton, you're just not gonna have in 100 Hertz. You're gonna be |
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| 160:56 | to the five and six Hertz dominant because the explosion won't come back in |
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| 161:08 | velocity layer. You ever hear of ? Is there any other low velocity |
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| 161:14 | ? You know, nobody ever heard another? No, I, |
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| 161:22 | let's see. And you're your you say, huh? You're not |
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| 161:27 | . If you can't tell me real , where is the other low velocity |
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| 161:32 | ? I guess they don't teach plate anymore. Is it the moo? |
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| 161:39 | that? Is it the moo? , it's not the moo I don't |
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| 161:49 | it is. Anybody ever hear of stoere. What is it? That's |
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| 162:06 | . No. Uh well, something about it and plate tectonics, isn't |
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| 162:12 | a low velocity layer that the plates across? Isn't it called this the |
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| 162:22 | that plates above it? Am Am I wrong? Did they change |
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| 162:29 | ? Ok. In other words, got a low velocity layer. Anybody |
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| 162:40 | familiar, familiar with a term called submarine? Anybody heard the term |
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| 162:51 | Anybody ever hear of the sonar Anybody ever heard a low velocity layer |
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| 163:00 | water? What it is is the slowly increases with depth. Then all |
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| 163:08 | a sudden there is this big lower and then it continues again. If |
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| 163:17 | put a charge in this low velocity , what happens is the energy can't |
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| 163:26 | , it becomes trapped? Low velocity , trapped energy, it reaches critical |
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| 163:32 | reflections. It's like a bugle It just resonates. So what's the |
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| 163:43 | in that flip? If you take of dynamite and you go offshore Florida |
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| 163:51 | you put that dynamite at stay 400 and you detonated, you can go |
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| 164:06 | miles away, six miles away and barely hear it at £10 of |
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| 164:13 | If you take that £10 of dynamite you put it in the Sonar |
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| 164:19 | they will hear, hear it or in Miami, they'll hear it in |
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| 164:24 | . If they have a hydrophone in , they will hear that the energy |
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| 164:29 | trapped and this continues expanding our That's why the submarines have to be |
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| 164:37 | when they go through this. Absolutely sign whatsoever because it will go all |
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| 164:42 | way around the world. That's so that's one, any other low |
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| 164:50 | layers, any country folks here, raised in the country, anybody and |
|
| 165:04 | there raised in the country, I had a ranch which is outside |
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| 165:13 | town of Lexington. My nearest neighbor two miles away. So there wasn't |
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| 165:20 | lot of noise at night time. could sit outside every so often and |
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| 165:26 | could hear the neighbors talking two miles . What happens? There is a |
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| 165:35 | velocity layer that is right, could right by the nearest surface and as |
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| 165:40 | talk, you can hear it all way if the atmosphere and temperature are |
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| 165:46 | right. You get the sign in new low velocity it goes everywhere around |
|
| 165:53 | it's really spooky that you can hear music they're playing, you know, |
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| 165:57 | miles away that the, is there other low velocity layers? You can |
|
| 166:05 | of, think of big bombs going , think of atomic bombs. What |
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| 166:13 | the Las Vegas popular for in the fifties? Was it the entertainment? |
|
| 166:21 | do they sell in Las Vegas? sold atomic bombs being detonated. They |
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| 166:29 | initially they were published when the atomic are gonna be going off and they |
|
| 166:34 | all these tourists coming in to watch atomic bombs going off. Now, |
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| 166:43 | , they were asked when that first bomb went off, who should we |
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| 166:49 | people about? So the government put these ground stations from zero 40 miles |
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| 166:59 | or so and these were microphones and were set to try to listen and |
|
| 167:07 | listen for the atomic bomb when it off in Las Vegas is 8060 miles |
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| 167:16 | from uh atomic bomb explosions. And guarantee the people in Las Vegas that |
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| 167:31 | and her saying no problem. So 30 miles away can't hear us. |
|
| 167:37 | you're 60 miles away. There's no was it turned out there was a |
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| 167:43 | velocity layer and what happened was energy like this. It doesn't get out |
|
| 167:55 | here was 30 miles from where the went off right here, Las Vegas |
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| 168:04 | 60 miles away. So when that went off, the energy went |
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| 168:08 | came back down. Initially, it windows out of all the skyscrapers that |
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| 168:15 | just devastated them tremendous noise. And another low velocity layer. So we |
|
| 168:21 | low velocity layers all over the place energy gets trapped. Now, here's |
|
| 168:31 | problem, dig a hole or make a cavity detonated and tell me what |
|
| 168:40 | the seismic wave look like at a far away and go ahead and define |
|
| 168:48 | wave velocity, shear wave velocity and . That was 1941 sharp wasn't quite |
|
| 168:56 | uh variable, but it's good And since that time, many published |
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| 169:02 | P wave in sheer way both could in rather than just a ratio. |
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| 169:08 | here's the result I gave you the and, but we don't need the |
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| 169:14 | . The size of the dynamite charge off, the size of the cavity |
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| 169:19 | off. And here is some where shoot in the weather zone. In |
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| 169:25 | words, and left in there, put the dynamite at 30 ft rather |
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| 169:32 | below at 100 ft. Big 2000 ft per second. You look |
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| 169:42 | the spectrum in the spectrum right here a high amplitude at 25 Hertz right |
|
| 169:57 | . And this is the pulse. , this is the pulse of the |
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| 170:04 | outward at, I forget what distance at. And you'd say oh that's |
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| 170:08 | a bad looking false. Now, right here, you're gonna go up |
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| 170:14 | this value and then down and that's minimum phase wavelet. Now, let's |
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| 170:20 | ahead and put the shot in the weathering layer. Go down to, |
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| 170:27 | beneath the weathering zone. Now, at the spectrum there, that little |
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| 170:33 | is at 158 Hertz. It basically up to 100 Hertz, you got |
|
| 170:40 | flat spectrum. That's kind of Look at the wavel that you get |
|
| 170:46 | and three. So you go up you say, well, Fred, |
|
| 170:51 | not much different than this. But a look at the distance the |
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| 170:58 | That's five milliseconds, that's 50 that's very low frequency to put into your |
|
| 171:05 | data. It says 50 milliseconds between and to pigs. You know, |
|
| 171:14 | 20 Hertz data. You want something what's on the right hand side? |
|
| 171:25 | . Um What time do we normally ? We go to 12 or go |
|
| 171:32 | ? Well, I, I went 1130 last time but it's up to |
|
| 171:36 | . Should we go to uh 12 ? People say they don't care what |
|
| 171:46 | Jessica says 1230. The maid comes then. Ok. Does she cook |
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| 171:54 | for you too? Lunch. The . What does your maid cook? |
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| 172:01 | dinner? Me? Yeah, I have a maid but my husband does |
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| 172:07 | me dinner when I'm in class. . Does it really? Yes. |
|
| 172:11 | , uh, it's 630 over So it's about dinner time. Where's |
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| 172:16 | there again? Yeah. Well, , you're not a country girl, |
|
| 172:21 | you? Ok. Do you know I'm from California? Ok. |
|
| 172:26 | you said something about mills that tells you're not from the country. Can |
|
| 172:32 | know what it is? What did call? I said dinner and not |
|
| 172:41 | . Very good. Very good. is lunchtime. Supper is the evening |
|
| 172:48 | . Uh, and that is uh the country. Uh Speaking, who |
|
| 172:56 | ? Let me tell you about What does intrinsic mean? Anybody know |
|
| 173:01 | intrinsic means? I, I I have an idea means, doesn't |
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| 173:08 | anybody know what forensic means. Well, I, you should ask |
|
| 173:25 | , as I told you before, , I speak seven different languages. |
|
| 173:31 | outstanding, isn't it? Hm. one's understood though. I don't know |
|
| 173:41 | I have to look that up. look at Mobile did in the |
|
| 173:50 | This is a very difficult experiment to correct, really difficult trying to measure |
|
| 174:01 | in the field. And they went the Pierre shale and they drilled the |
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| 174:08 | down to 750 ft. So here 123456 holes that they drilled and they |
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| 174:17 | geophones clamped to the side of the and they had a shot went down |
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| 174:23 | 250 ft. All of these were close together within 40 ft. So |
|
| 174:32 | were looking at as the wave propagated . They're looking at measuring the vertical |
|
| 174:40 | attenuation. There were no boundaries, changes. It's a pure material. |
|
| 174:46 | pure show very thick homogeneous and so the shallow shot in the 350 |
|
| 174:55 | there's the pulse that they recorded at there's the pulse that they recorded. |
|
| 175:02 | , it may might look like these are the same. But that box |
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| 175:08 | that's in orange is the same width bo both of those. And notice |
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| 175:13 | left side is on the peak and left side is on the peak. |
|
| 175:17 | you could see the little small bit the pulse getting fatter on the deeper |
|
| 175:24 | right here. See here that left went right through the trough here. |
|
| 175:31 | left boundary to the waver, it's little lower frequency intrinsic attenuation. It's |
|
| 175:40 | of set up uh in a harmonic of thing. You might say amplitude |
|
| 175:48 | a distance next is equal to the at zero zero with Beaver who shot |
|
| 175:56 | with the source and it decays E the minus alpha of XX is the |
|
| 176:02 | you travel alpha is the attenuation So in this experiment, we could |
|
| 176:09 | each one of these amplitudes and also spectrum. But the thing is |
|
| 176:17 | this is not simple to be able put six different geophones at six different |
|
| 176:25 | and say their couplings are the same how do you test it? They're |
|
| 176:31 | same. Oh You can send a wave down or something like that, |
|
| 176:36 | it doesn't give you the coupling factor , really difficult. Now, when |
|
| 176:45 | take the natural log of this, see that the natural log of ace |
|
| 176:51 | X is the natural log of ace zero minus alpha X. Oh, |
|
| 177:01 | , doesn't that remind you of an Y is equal to the intercept, |
|
| 177:06 | slope times the distance travel. So distance traveled, you know what that |
|
| 177:11 | be? You can measure this distance it's 100 ft. This will be |
|
| 177:17 | ft difference. And the natural log X that's just measure the amplitude. |
|
| 177:24 | the natural al. So you're searching two parameters here, you're searching for |
|
| 177:33 | and M. So we'll go ahead plot the data and when we do |
|
| 177:41 | , you'll see this is an expression alpha and that E to the minus |
|
| 177:47 | equation. And this is an expression the frequency of the WAV, different |
|
| 177:58 | dance took these waves and a 48 so that they have amplitudes from them |
|
| 178:07 | to 205 100 Hertz. No, have the measurements they give here. |
|
| 178:18 | this is that slope right there. attenuation is in DB per 1000 |
|
| 178:27 | Decibels natural log ace of X over of zero ace of zero ace of |
|
| 178:34 | . And we go ahead and if know this line right here. We |
|
| 178:39 | went down to 25 Hertz and let's go ahead and find out what |
|
| 178:46 | slope is gonna be. And that's of given up with this equation. |
|
| 178:52 | there's another one alpha radar, we to express it in what's called Q |
|
| 179:02 | Q is what's normally given. When talk about the attenuation, they call |
|
| 179:08 | constant queue. The Q is the for all frequency. Now, here |
|
| 179:14 | where the biggie comes in. If look at that, what right here |
|
| 179:20 | plot, we see that alpha as function of frequency, that this line |
|
| 179:29 | alpha, the frequency, the first this other line in here is alpha |
|
| 179:38 | to the 1.1 it is not frequency . So this is the best |
|
| 179:44 | Why is this so important? Because this time, a gentleman from Exxon |
|
| 179:51 | Ricker Roman Ricker published his results on and his all said attenuation is a |
|
| 180:00 | of frequency squared. He was the of Geophysics at the time and he |
|
| 180:07 | two major articles in Geophysics. And was considering this is the best theoretical |
|
| 180:14 | results that we have Mobile contradicted all way it's its frequency to the first |
|
| 180:23 | , not the second Mobile did not this for publication. They held it |
|
| 180:29 | for two years until, until Norman was no longer the editor of the |
|
| 180:34 | Geophysics. Then they submitted it and got published it was quite the controversy |
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| 180:40 | the time I wasn't around but it no. Why do we have cues |
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| 180:49 | important? Because after mobile, the part, it says that constant Q |
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| 181:01 | it's independent of frequency, the Q . It's the first power Q is |
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| 181:09 | fir alpha is the first power relationship is a becomes constant then and it's |
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| 181:18 | much easier to deal with. So we hear in literature is constant |
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| 181:24 | we, we s say intrinsic attenuation constant. QE Thank you. |
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| 181:35 | if you have a cue that is we'll give you a physical example. |
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| 181:45 | that means? That means the wavelength 10% of its amplitude for every wavelength |
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| 181:54 | it travels. So if there's a that's 10 ft, you travel 20 |
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| 182:01 | , you decay 0.9 0.9 due to attenuation. Those who I want to |
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| 182:16 | , what are the key values here a, an approximation that a lot |
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| 182:23 | the processing geophysicists used in order to the high frequency back up, they |
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| 182:29 | assume Q is proportional to velocity squared by a million. That's an |
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| 182:39 | But it's one that was used by geophysicists. I'll tell you what I |
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| 182:53 | 20 to 12. Let's come back 20 to 1 because this is brand |
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| 182:58 | material that have to stop right in . So back at 20 to |
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| 183:04 | OK, Jessica, you might have call your maid to, to hold |
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| 183:10 | lunch, get right on |
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