WEBVTT - How Seismological Equipment Works 0:00:00.280 --> 0:00:02.960 Brought to you by the reinvented two thousand twelve Camray. 0:00:03.160 --> 0:00:08.920 It's ready. Are you get in touch with technology? With 0:00:09.039 --> 0:00:18.040 tech Stuff from how stuff works dot com. Hello again, everyone, 0:00:18.079 --> 0:00:20.320 and welcome to tech stuff. My name is Chris Poulette 0:00:20.320 --> 0:00:23.000 and I am an editor at how stuff works dot com. 0:00:23.000 --> 0:00:26.440 Sitting across from me, as always, is senior writer Jonathan Strickland. 0:00:26.640 --> 0:00:28.680 The governor and I aren't even in the same party. 0:00:28.720 --> 0:00:30.520 If this turns out to be a false alarm, he'll 0:00:30.520 --> 0:00:32.320 make me out to be the biggest fool west of 0:00:32.360 --> 0:00:37.800 the Mississippi. Hey, nice Mississippi. Yeah, you know what. That's 0:00:37.800 --> 0:00:42.040 the site of several faults, actually one great, big fault. 0:00:42.040 --> 0:00:44.680 There are lots of faults everywhere, and it's not my fault. No, 0:00:45.159 --> 0:00:47.400 before we get into whose fault it is, let's talk 0:00:47.400 --> 0:00:51.120 about listener mail. By the way, this is not his fault. 0:00:56.680 --> 0:01:00.520 This listener mail comes from Joe, and Joe says earthquake. No, 0:01:00.680 --> 0:01:03.040 just kidding. I live in Christchurch, New Zealand, and I've 0:01:03.080 --> 0:01:05.320 been through two major earthquakes and I was wondering if 0:01:05.319 --> 0:01:08.000 you could do a podcast on how they measure earthquakes. 0:01:08.319 --> 0:01:13.880 Cheers Joe, Joe, we're very glad that you are okay. Definitely, 0:01:13.959 --> 0:01:16.640 so definitely, So that was a scary situation if you 0:01:16.680 --> 0:01:20.360 don't know. Um uh, just a few weeks ago, as 0:01:20.360 --> 0:01:24.080 I when we're recording this, in very late February two eleven, 0:01:24.200 --> 0:01:28.400 there was a pretty significant earthquake, to say the very least, 0:01:28.560 --> 0:01:32.600 that hit New Zealand. Um and uh, you know, several 0:01:32.600 --> 0:01:35.880 people lost their lives as a result of this. Um 0:01:35.959 --> 0:01:40.520 And of course these things are very damaging, both to 0:01:40.840 --> 0:01:44.480 people and property. So it's a it would be nice 0:01:44.520 --> 0:01:46.560 if we could do a lot of prediction and give 0:01:46.600 --> 0:01:48.640 you a heads up from when these things are coming, 0:01:48.760 --> 0:01:51.720 but I'm afraid at this point about the best we 0:01:51.760 --> 0:01:53.880 can do is let you know how big they were 0:01:54.000 --> 0:01:57.840 and maybe get an idea of what you might expect 0:01:57.880 --> 0:02:01.520 from an aftershock. Yeah. As it turns out, predicting an 0:02:01.520 --> 0:02:06.680 earthquake is not exact science, but we have learned quite 0:02:06.720 --> 0:02:09.840 a bit about earthquakes. And before we get too far 0:02:09.880 --> 0:02:12.239 into this, I should just point out that a couple 0:02:12.320 --> 0:02:16.320 of our sister podcasts have covered similar topics. Stuff you 0:02:16.320 --> 0:02:19.079 Should Know has done an entire episode on how earthquakes work. 0:02:19.120 --> 0:02:21.680 It's actually one of their older episodes, but it's it's excellent, 0:02:21.760 --> 0:02:24.800 so you can listen to that if you are interested 0:02:24.880 --> 0:02:28.280 in the topic and the stuff of Genius did an 0:02:28.320 --> 0:02:34.160 episode about an early pioneer in seismology, which and we'll 0:02:34.160 --> 0:02:35.720 talk about him in a little bit, just because it's 0:02:36.120 --> 0:02:38.760 it's too cool not to talk about, right, Oh yeah, yeah, 0:02:38.800 --> 0:02:42.880 definitely so so an earthquake. You know, we most of 0:02:42.960 --> 0:02:45.919 us probably know exactly what someone means when they say earthquake. 0:02:45.960 --> 0:02:48.520 It's it's an event in which the ground is shaking 0:02:48.680 --> 0:02:54.359 right right, the earth thing. Yeah, yeah, Um, they can 0:02:54.360 --> 0:02:58.880 be caused from from many many different related types of 0:02:58.960 --> 0:03:03.760 movement in the Earth. Um, it's pretty well, uh, pretty 0:03:03.760 --> 0:03:06.320 well known at this point that the Earth's crust is 0:03:06.320 --> 0:03:10.440 made up of many plates, and there are different kinds 0:03:10.720 --> 0:03:14.920 of they're they're moving in different ways. Um. I'm going 0:03:15.000 --> 0:03:19.160 back to my undergraduate days when I actually took a 0:03:19.200 --> 0:03:22.560 geology class, which I found fascinating but didn't go into 0:03:22.560 --> 0:03:26.200 it obviously as a career field. But um, in some cases, 0:03:26.200 --> 0:03:29.400 one plate is going underneath another plate. In other cases, 0:03:29.440 --> 0:03:32.240 they're rubbing against one another in a and you know 0:03:32.320 --> 0:03:34.480 along you know, one is going north while the other 0:03:34.520 --> 0:03:38.160 is going south. And and gradually what happens is tension 0:03:38.160 --> 0:03:41.800 builds up. I'm oversimplifying here, but tension builds up, and 0:03:42.200 --> 0:03:46.160 when the tension is released, that causes an earthquake. And 0:03:46.200 --> 0:03:48.440 they can be you know, small enough that you don't 0:03:48.440 --> 0:03:51.080 even notice it. Um. But some of the equipment we're 0:03:51.080 --> 0:03:56.000 going to talk about today can detect that. Of course, others, um, 0:03:56.120 --> 0:03:59.400 like the earthquake in New Zealand and and famous earthquakes 0:03:59.440 --> 0:04:05.840 like in Haiti and uh in California, in Japan, um 0:04:06.000 --> 0:04:08.480 and and my favorite fault, the New Madrid fault in 0:04:08.480 --> 0:04:10.600 the middle of the United States. Again, that would be 0:04:10.640 --> 0:04:14.880 the one near Mississippi and all the others around it. Um. 0:04:14.920 --> 0:04:18.680 You know, those can can be very very serious. So uh, 0:04:18.680 --> 0:04:22.080 you know, scientists have been trying to figure out for 0:04:22.920 --> 0:04:26.560 a long time, we'll say a very very very long 0:04:26.600 --> 0:04:31.640 time millennia in fact, yes, exactly how to measure the 0:04:31.680 --> 0:04:36.440 effect of the earth shaking. So let's talk about what 0:04:36.560 --> 0:04:38.480 actually happens and then we can talk about how we 0:04:38.880 --> 0:04:42.080 how we measure it. Now you gave a good overview. Yeah, there's, 0:04:42.200 --> 0:04:44.680 like I said, that's just a nutshell, very very very 0:04:44.720 --> 0:04:48.080 basic version, right, Yeah, three basic ways that plates move 0:04:48.120 --> 0:04:50.720 against each other. Right, they either move apart, or they 0:04:50.800 --> 0:04:53.720 move together, or they slide against each other. Right, that's 0:04:53.720 --> 0:04:56.000 about it. The by the way, if you're talking about 0:04:56.040 --> 0:05:00.680 a plate going underneath another, that's called subducting. Um, just 0:05:00.720 --> 0:05:04.760 so you guys know. And when plates, when plates meet, uh, 0:05:04.800 --> 0:05:09.960 it pushes rock and dirt together. That's what actually forms mountains. Besides, 0:05:10.120 --> 0:05:12.920 there's also volcanic mountains, so there's some mountains that are 0:05:12.920 --> 0:05:15.559 formed through volcanic activity. But in general, mountains are formed 0:05:15.880 --> 0:05:18.400 when two plates pressed up against each other and they 0:05:18.480 --> 0:05:25.400 crinkle essentially. Um. Now, when these these uh, these events happen, 0:05:25.480 --> 0:05:27.320 these these plate events. By the way, there are other 0:05:27.360 --> 0:05:31.159 things that can cause an earthquake, like an explosion can 0:05:31.200 --> 0:05:36.000 cause the essentially a localized earthquake, and meteoric impact can 0:05:36.080 --> 0:05:38.040 cause an earthquake, that kind of thing. But most of 0:05:38.040 --> 0:05:41.360 them are caused by these these plate movements. Um. There's 0:05:41.360 --> 0:05:44.080 about eight thousand of them each day, and most of 0:05:44.080 --> 0:05:48.200 them are uh beneath our level of being able to 0:05:48.240 --> 0:05:50.679 perceive them. And of course lots of them are happening 0:05:50.720 --> 0:05:54.400 in places where there's really little to know human habitat there, 0:05:54.440 --> 0:05:58.000 so we wouldn't necessarily notice it even if it were 0:05:58.160 --> 0:06:01.360 a significant earthquake, because one is there, right, might be 0:06:01.440 --> 0:06:05.080 under the ocean or anything like that. Um. And like 0:06:05.120 --> 0:06:07.039 you were saying, where the plates meet, that's a fault. 0:06:07.800 --> 0:06:10.240 That's you know, any place where two two plates are meeting, 0:06:10.240 --> 0:06:14.080 that's a fault. When when there is an earthquake, energy 0:06:14.240 --> 0:06:19.040 radiates out from the center of that earthquake in seismic waves. Yes, 0:06:19.680 --> 0:06:22.240 and these waves are what you would you know, when 0:06:22.279 --> 0:06:24.080 you think of a wave, that's what we're talking about. 0:06:24.160 --> 0:06:29.119 It's energy moving in a wavelength. There's there's a peak 0:06:29.320 --> 0:06:32.960 and there's a trough through this wave. And uh, there's 0:06:33.000 --> 0:06:35.960 actually two waves that move out from an earthquake. Yes, 0:06:36.000 --> 0:06:39.560 he's talking about the PEA wave in which those those 0:06:39.560 --> 0:06:43.159 waves move in the direction that they're they're being propagated. 0:06:43.800 --> 0:06:47.880 Um and then the S wave, which is perpendicular to that, right, 0:06:47.920 --> 0:06:51.240 And the PEA wave moves faster than the S wave. 0:06:51.320 --> 0:06:54.880 It actually goes about between one to five miles per second. 0:06:55.360 --> 0:06:58.800 It tends to be one point seven times faster than 0:06:58.920 --> 0:07:01.680 the than the S wave. So this has become a 0:07:01.800 --> 0:07:06.640 key for us to figure out where earthquakes are originating. Right, 0:07:06.720 --> 0:07:10.200 because you measure the time between the primary wave and 0:07:10.240 --> 0:07:13.120 the secondary wave, and that will tell you, in general 0:07:13.360 --> 0:07:15.840 how far away the focus is. It doesn't tell you 0:07:15.880 --> 0:07:18.760 the direction. It will just tell you. You know, you 0:07:18.800 --> 0:07:20.800 feel a shaking, and then you feel a second shaking. 0:07:20.840 --> 0:07:23.680 You take the time between that, you do a little calculation. 0:07:23.680 --> 0:07:26.320 You figured, all right, so the center of this earthquake 0:07:26.560 --> 0:07:29.640 is fifty miles away, but it could literally be fifty 0:07:29.640 --> 0:07:34.600 miles in any direction on the surface. You can discount 0:07:34.640 --> 0:07:37.240 the directions that are directly below you and directly above you, 0:07:37.320 --> 0:07:42.440 and all that like anything in the air, not gonna matter. Um. 0:07:42.480 --> 0:07:46.440 So that's that's the basics of earthquakes. We'll talk a 0:07:46.440 --> 0:07:48.800 little bit about the measuring. Let's let's let's take a 0:07:48.840 --> 0:07:52.760 little walk back into history by a couple of millennia. 0:07:52.920 --> 0:07:54.760 This is the guy that we were talking about and 0:07:54.800 --> 0:08:00.560 the stuff of genius who came up with an interesting seismoscope. Now, 0:08:00.560 --> 0:08:05.240 a seismoscope is a an instrument, any instrument that indicates 0:08:05.240 --> 0:08:08.120 that motion has occurred. But it does not give you 0:08:08.840 --> 0:08:12.800 more information than that, right right. It can't necessarily tell 0:08:12.800 --> 0:08:17.320 you where it was coming from. It can't necessarily tell you, um, 0:08:17.960 --> 0:08:20.160 it can't give you like a reading over a duration 0:08:20.160 --> 0:08:23.520 of time, it just tells you, hey, stuff moved around. 0:08:24.160 --> 0:08:28.000 So basically, if you've seen Jurassic Park, when that dinosaur 0:08:28.080 --> 0:08:30.800 is coming up on you and you watch the motion 0:08:30.960 --> 0:08:33.000 in the glass of water, in the glass of water, 0:08:33.200 --> 0:08:36.760 that wop. Yes, it's a very primitive seismoscope, but as 0:08:36.800 --> 0:08:42.199 slightly and I stress slightly more sophisticated seismoscope was invented 0:08:42.360 --> 0:08:46.440 by a Chinese philosopher named Chong Hang Yes, and one 0:08:46.480 --> 0:08:50.319 thirty two. Yeah, one thirty two a d Yes, that's 0:08:50.320 --> 0:08:52.520 not that, that's not one thirty two in the afternoon. 0:08:52.640 --> 0:08:57.120 That's the year. Um No, Chang hangg came up with 0:08:57.160 --> 0:09:01.200 this really cool design. And we we've actually seen examples 0:09:01.320 --> 0:09:05.640 of this and you know, uh, not just it's it's 0:09:05.679 --> 0:09:08.800 not just a theory that these things actually existed. Though 0:09:08.840 --> 0:09:13.160 they're they're actual, the way they worked is somewhat of 0:09:13.160 --> 0:09:15.280 a mystery. We've got a couple of ideas of how 0:09:15.280 --> 0:09:17.520 they could have worked, but but we'll get to that. 0:09:17.640 --> 0:09:20.960 So basically, what you had was a wine jar. Yes, 0:09:21.040 --> 0:09:23.040 it was. It was cylinder. You know, think of it 0:09:23.080 --> 0:09:25.960 as a sort of cylindrical shape standing on in so 0:09:26.160 --> 0:09:29.959 like a jar. Yes, six ft in diameter, so we're 0:09:30.000 --> 0:09:32.079 not talking like a little jar, No, this would be 0:09:32.120 --> 0:09:34.840 a big jar. And mounted to the jar on the 0:09:34.920 --> 0:09:39.000 jar were eight dragon head spouts that faced in the 0:09:39.000 --> 0:09:42.000 cardinal directions. Yes, and that would be at the very 0:09:42.040 --> 0:09:45.000 top of the jar from what from what I understand, 0:09:45.240 --> 0:09:48.400 it can be anywhere from the above the middle to 0:09:48.520 --> 0:09:51.360 the top of anything on the top half of the jar. 0:09:51.520 --> 0:09:53.920 Is that's because I've actually seen pictures of these. There 0:09:53.920 --> 0:09:56.640 are images of these on the Internet of various people 0:09:56.679 --> 0:10:00.200 have made recreations of these things. Um. So within that 0:10:00.320 --> 0:10:04.680 each dragon's mouth there's essentially a marble or stone, and 0:10:05.040 --> 0:10:08.640 so those are balanced within the mouths of the dragons. 0:10:09.040 --> 0:10:13.960 And then underneath the dragon mouths are these little ceramic 0:10:14.080 --> 0:10:17.320 frogs with open mouths. And the idea here is that 0:10:17.360 --> 0:10:20.480 if there's an earthquake that is significant enough for it 0:10:20.559 --> 0:10:24.920 to set this seis muscope off, it'll rattle the pebbles, 0:10:25.000 --> 0:10:27.200 and the pebbles that are facing the direction that the 0:10:27.200 --> 0:10:31.000 earthquake is coming from, uh would theoretically fall out the 0:10:31.040 --> 0:10:33.720 dragon's mouth into the frog mouth. So then you could 0:10:33.800 --> 0:10:36.240 look in and say, all right, this is coming from 0:10:36.360 --> 0:10:40.840 somewhere the north northeast region. Um, it doesn't tell you 0:10:40.840 --> 0:10:45.040 how far away it's gonna the earthquake was. But let's 0:10:45.040 --> 0:10:49.400 say that you're in ancient China and you are overseeing 0:10:49.480 --> 0:10:54.000 a large amount of land. Communication is not fast. But 0:10:54.160 --> 0:10:57.800 seeing something like that happened, you could say, well, now 0:10:57.840 --> 0:11:00.400 I know that there's some problems to the north of us. 0:11:00.679 --> 0:11:04.480 I should expect some people to come and ask me 0:11:04.559 --> 0:11:09.160 for help, or maybe I should send Uh perhaps it 0:11:09.200 --> 0:11:11.760 came from the direction that an enemy is in. Perhaps 0:11:11.840 --> 0:11:14.520 you would want to send a group of troops out 0:11:14.559 --> 0:11:17.200 there to see, like, hey, were they weakened enough for 0:11:17.280 --> 0:11:19.679 us to kind of come in and mop up? Right? 0:11:19.720 --> 0:11:23.760 So this isn't this isn't just a diversion, uh, you know, 0:11:23.840 --> 0:11:25.559 just something that you do for fun. They really had 0:11:25.559 --> 0:11:29.360 a practical use. Now, now, the point where I said 0:11:29.559 --> 0:11:32.000 it might be a bit of a mystery is that 0:11:33.120 --> 0:11:36.520 we're not sure what was inside the jar. There are 0:11:36.559 --> 0:11:40.120 some who think that the jar had perhaps a pendulum 0:11:40.160 --> 0:11:43.319 suspended from the top of the jar. That so it's 0:11:43.360 --> 0:11:45.800 it's actually you know, the base of the weight of 0:11:45.840 --> 0:11:48.360 the pendulum would be inside the jar. That's funny that 0:11:48.400 --> 0:11:49.880 you have mentioned that, because I have the feeling that 0:11:49.920 --> 0:11:52.320 will come up again. Yes, and this is because you 0:11:52.360 --> 0:11:56.120 need an inertial mass in most of these seismoscopes. You 0:11:56.200 --> 0:11:59.320 need something that is not going to move in relation 0:11:59.440 --> 0:12:02.560 to the rest of the instrument because one of the 0:12:02.559 --> 0:12:05.800 big challenges of measuring earthquakes, I mean it sounds silly, 0:12:05.800 --> 0:12:08.240 but it's true, is that you have to design a 0:12:08.320 --> 0:12:11.800 tool that can measure something even when the uh the 0:12:11.800 --> 0:12:15.680 tool itself is moving right like, you know, if the 0:12:15.679 --> 0:12:18.040 earth is quaking and the tool is on the earth, 0:12:18.640 --> 0:12:21.520 then how do you get a reliable measurement. Well, this 0:12:21.679 --> 0:12:24.520 idea of an inertial mass becomes very important with later 0:12:24.960 --> 0:12:30.840 size seismometers. So um, yeah, there was one possibility. Another 0:12:30.880 --> 0:12:34.000 possibility was a reverse pendulum. And a reverse pendulum is 0:12:34.040 --> 0:12:37.760 essentially a flexible pole with a weight at the end 0:12:37.760 --> 0:12:40.720 of it. The weight is on the top right, And 0:12:40.760 --> 0:12:45.480 the idea here is that a significant UH quake would 0:12:45.480 --> 0:12:48.520 cause the pendulum to swing, perhaps hitting the inside of 0:12:48.520 --> 0:12:52.360 the jar, and that's what would then cause the stone 0:12:52.400 --> 0:12:55.600 in that dragon's mouth to fall into the the frog's mouth, 0:12:56.280 --> 0:13:02.040 and then it's six more weeks of winter. Uh, okay, stuff, 0:13:02.040 --> 0:13:06.640 I'm a little bit I'm on cold medication. So yeah, 0:13:07.520 --> 0:13:10.920 And in doing some research I read in in Britannica 0:13:11.000 --> 0:13:16.239 that in Italy in the seventeenth century, um a seismoscope. 0:13:16.280 --> 0:13:19.679 They're used spilling water to show you know what was 0:13:19.720 --> 0:13:23.000 going on, whether there was an earthquake taking place. And 0:13:23.920 --> 0:13:26.960 another they also used a lot of mercury. I know 0:13:27.040 --> 0:13:29.319 that's probably not a surprise, but yeah, a cup of mercury, 0:13:29.320 --> 0:13:31.920 which would be would probably be a pretty good indicator 0:13:32.080 --> 0:13:35.600 given its color. Um. Yeah, too bad, you'd be crazy 0:13:35.679 --> 0:13:37.720 by the time the earthquake hit. Now see you're getting 0:13:37.760 --> 0:13:40.080 into the tiny details that are just just ruined them 0:13:40.160 --> 0:13:43.880 the magic for me. Um and uh. And then there 0:13:43.920 --> 0:13:48.920 was a Luigi Palmieri who had a seized seismometer to detect, 0:13:49.440 --> 0:13:51.760 you know, the motion during an earthquake. He had a 0:13:51.760 --> 0:13:56.440 series of use you shaped tubes that again used mercury. Um. 0:13:56.480 --> 0:13:58.840 And then there was a clock hooked up to that 0:13:58.920 --> 0:14:02.560 and um, what would happen is the motion would cause 0:14:02.800 --> 0:14:08.079 an electrical clock to stop and to start a recording drum. Um. Basically, 0:14:08.080 --> 0:14:10.160 there was a float on top of the mercury and 0:14:10.200 --> 0:14:13.480 the drum was keeping track of the floats motion as 0:14:13.480 --> 0:14:15.440 it moved. It would tell you the time and intensity 0:14:15.480 --> 0:14:19.080 of the earthquake. That makes it more that. That's why 0:14:19.120 --> 0:14:22.120 we would refer to that as a seismoment or even 0:14:22.160 --> 0:14:27.120 a seismograph, because seismograph essentially that that graph means to draw, 0:14:27.760 --> 0:14:31.120 but it's it's essentially meaning that you are recording the 0:14:31.200 --> 0:14:34.360 event of the earthquake and there's some element of time 0:14:34.440 --> 0:14:38.560 there or you can actually see the earthquakes movements over 0:14:38.640 --> 0:14:41.360 time and be able to say this is when it started, 0:14:41.400 --> 0:14:44.440 this is when it ended, and um. And that's what 0:14:44.520 --> 0:14:48.000 sets it apart from the seismoscopes, which essentially just tell you, hey, 0:14:48.040 --> 0:14:50.880 something's moving out there, yes, which you know a lot 0:14:50.920 --> 0:14:54.760 of us can do on a good day. I can 0:14:54.800 --> 0:14:58.960 do it. The rabbits, they're agitated. So let's let's talk 0:14:59.000 --> 0:15:01.640 a little bit about what it takes to get uh. 0:15:01.960 --> 0:15:05.320 One of some of the challenges in creating a seismic graph, Well, 0:15:05.320 --> 0:15:09.520 there's one very big challenge, which is to overcome friction. 0:15:10.400 --> 0:15:14.160 That's a big one because see, and in a seismograph, 0:15:14.520 --> 0:15:17.680 in a lot of cases, especially the earlier seismographs, you 0:15:17.680 --> 0:15:22.360 would want to use a marketing device, a pen and 0:15:22.440 --> 0:15:26.240 a piece of paper essentially, um and uh. The problem 0:15:26.360 --> 0:15:30.480 is that the in order to be sensitive, the pen 0:15:30.600 --> 0:15:32.920 is marking on the paper right right to record the 0:15:32.920 --> 0:15:36.520 Earth's motion UM. But the problem is that it has 0:15:36.560 --> 0:15:39.200 to overcome the friction of the pen on the paper 0:15:39.360 --> 0:15:42.040 right and if it's a very very subtle quake, then 0:15:42.560 --> 0:15:44.720 the friction may be too great for the pen to 0:15:44.800 --> 0:15:49.160 move UM. And that that is a very big challenge. 0:15:49.200 --> 0:15:51.120 It it doesn't seem like it would be that big, 0:15:51.160 --> 0:15:54.040 but if you think about it, uh, you know, if 0:15:54.080 --> 0:15:57.040 you had a UM I would imagine too for older 0:15:57.440 --> 0:16:01.640 pens before ballpoint type technology it's created. If you had 0:16:01.680 --> 0:16:05.280 something like some of these UM seismographs where it was 0:16:05.320 --> 0:16:08.840 constantly moving UM, when the paper was constantly moving under 0:16:08.840 --> 0:16:11.200 the pen, I'm not sure how you would distribute inc 0:16:11.360 --> 0:16:13.800 to it unless it worked sort of like a fountainin 0:16:13.800 --> 0:16:15.480 And I didn't actually research that. I wish I had 0:16:15.520 --> 0:16:20.120 because now I'm kind of intrigued the podcast. But yeah, 0:16:20.160 --> 0:16:24.880 I mean that the seismograph is not a twentieth century innovation, 0:16:25.080 --> 0:16:28.360 and you know the ballpoint pen, well it wasn't either, 0:16:28.520 --> 0:16:32.640 but the seismograph goes back farther. So another big challenge 0:16:32.840 --> 0:16:36.320 is that you have to you have to segregate the 0:16:36.400 --> 0:16:41.400 seismograph from other structures. Yes, So for example, here in 0:16:41.440 --> 0:16:43.920 our building, it wouldn't do us much good to have 0:16:43.960 --> 0:16:47.840 a seismograph here because the vibrations that we would create 0:16:47.960 --> 0:16:51.080 in the building, the vibrations from traffic passing outside. The 0:16:51.080 --> 0:16:53.080 seismograph would pick all that up and we get a 0:16:53.120 --> 0:16:56.080 lot of false readings, false positives. Yeah, if you've ever 0:16:56.120 --> 0:16:57.720 been on the top floor of a parking deck when 0:16:57.720 --> 0:17:00.880 people are leaving at rush hour, I mean you'll feel 0:17:01.000 --> 0:17:04.480 the motion of the cars moving and sometimes they'll you know, 0:17:04.560 --> 0:17:06.240 you can bounce around a little bit, depending on the 0:17:06.240 --> 0:17:09.840 parking deck. So the key to having a very good 0:17:09.840 --> 0:17:13.480 seismograph is finding a way so that you can you 0:17:13.480 --> 0:17:17.040 can connect it to the bedrock of whatever region you're in. 0:17:17.960 --> 0:17:21.119 I will I will try to do flint stones. I 0:17:21.240 --> 0:17:25.400 hated that cartoon really, Yeah, despised it with the heat 0:17:25.400 --> 0:17:27.480 of a thousand exploding suns. Well, we won't get into 0:17:27.520 --> 0:17:31.200 that um. But yes, you have to connect it to 0:17:31.240 --> 0:17:33.360 the bedrock and then once sits connect to the bed 0:17:33.560 --> 0:17:37.880 bedrock and and completely separate from other buildings. So it's 0:17:37.880 --> 0:17:45.840 not getting essentially uh pollution really because vibration vibration, then 0:17:45.880 --> 0:17:49.359 you can be more more sure that the readings you 0:17:49.400 --> 0:17:52.040 get reflect what's actually going on with the Earth as 0:17:52.040 --> 0:17:58.359 opposed to localized events. And it's interesting, this idea of 0:17:58.400 --> 0:18:02.040 the inertial mass ends up being really really important. Yes, 0:18:02.440 --> 0:18:06.200 and there's it's it's funny because um pendulums have been 0:18:06.280 --> 0:18:11.080 used for a very very very long time in UH 0:18:11.200 --> 0:18:16.720 seismological circles. UM. Because if you have a pendulum hanging 0:18:16.880 --> 0:18:21.200 and and it's free of vibration pollution, then um, it's 0:18:21.240 --> 0:18:23.719 just going to hang there until something acts on it 0:18:23.840 --> 0:18:27.000 because of the laws of inertia. Basically, an object at 0:18:27.040 --> 0:18:31.080 rest tends to stay at rest. Um. But there's something 0:18:31.119 --> 0:18:33.960 else too. You also have to have a damper because 0:18:34.000 --> 0:18:36.879 of the laws of inertia, because an object in motion 0:18:37.080 --> 0:18:39.600 tends to stay in motion. So you have to have 0:18:39.720 --> 0:18:43.280 both if you're going to have an accurate UH seismometer, 0:18:43.840 --> 0:18:48.679 because you if once the pendulum starts to move with 0:18:48.840 --> 0:18:51.960 the earth as it starts to shake, it will continue 0:18:52.000 --> 0:18:55.199 to do that. And from from what i've from what 0:18:55.280 --> 0:18:59.040 I understand, you need some kind of dampening material in 0:18:59.160 --> 0:19:02.119 order for it to get an accurate representation of how 0:19:02.240 --> 0:19:06.119 much the Earth is moving, which is kind of funny. 0:19:06.119 --> 0:19:08.480 I wouldn't necessarily have thought about that, but yes, the 0:19:08.520 --> 0:19:11.120 pendulum is just gonna keep swinging and you'll you really 0:19:11.160 --> 0:19:13.680 won't have an idea and it's okay, well, this is it. 0:19:13.760 --> 0:19:15.920 Was it a serious earthquake or was it a very 0:19:16.000 --> 0:19:18.800 very mild earthquake? And you can tell both from the 0:19:18.800 --> 0:19:23.199 pendulum moving and the inertial damper that's that stops it 0:19:23.240 --> 0:19:26.679 from moving as much. Right, Uh. One one way to 0:19:26.760 --> 0:19:31.440 imagine there are a couple of different variations on the 0:19:31.480 --> 0:19:34.239 seize mobter basic design. But one way to imagine it 0:19:34.280 --> 0:19:39.280 is imagine you've got a stand and from the stand 0:19:39.400 --> 0:19:43.919 hangs a very very sense of spring, a very tight spring, 0:19:43.920 --> 0:19:45.800 and there's a weight on the end of that spring, 0:19:45.840 --> 0:19:48.160 so it's above the ground. It's just it's hanging there. 0:19:48.880 --> 0:19:51.600 It's not moving up and down. It's it's at rest. 0:19:51.760 --> 0:19:54.159 It's just the weight is hanging from the spring, not 0:19:54.240 --> 0:19:56.960 moving at all. There is a pen attached to the weight, 0:19:58.000 --> 0:20:00.800 and the pens the top of the pen is or 0:20:00.840 --> 0:20:06.639 the the ink is rested the nib thank you like 0:20:06.760 --> 0:20:10.520 words gone, Jonathan. The ap upset. The nib of the 0:20:10.560 --> 0:20:13.879 pen is resting against a piece of paper that's on 0:20:14.080 --> 0:20:17.960 a spool that's constantly turning giving fresh paper to the pen. 0:20:19.840 --> 0:20:23.560 So when there's an earthquake, if there's up and down motion, 0:20:23.600 --> 0:20:27.119 this is, you know, a vertical seismometer. There are different kinds, 0:20:27.160 --> 0:20:33.639 so the weight tends to stay still. Uh. You're you 0:20:33.680 --> 0:20:35.720 have to step outside the context of the Earth, which 0:20:35.760 --> 0:20:37.159 is kind of weird to say, but you have to 0:20:37.200 --> 0:20:40.480 do it. Like the Earth, the the mass is maintaining 0:20:40.520 --> 0:20:43.720 its space, uh, and then the the everything else is 0:20:43.720 --> 0:20:48.560 moving up and down in relation to the weight. And 0:20:48.600 --> 0:20:51.760 that's the basis for most seismometers. There's also a kind 0:20:51.800 --> 0:20:57.199 where it's similar except the the it's it's a horizontal seismometer, 0:20:57.320 --> 0:21:02.680 in which there's a imagine a stand. Okay, but now 0:21:02.720 --> 0:21:07.120 you've got a long pole that sticks out halfway through 0:21:07.160 --> 0:21:12.240 the stand, right, So it's a horizontal pole that's connected. 0:21:12.280 --> 0:21:14.760 It's got a it's got a hinge on it so 0:21:14.800 --> 0:21:17.200 it can move left and right in relation to the stand. 0:21:18.400 --> 0:21:21.919 And then there's also a spring attached from the top 0:21:22.080 --> 0:21:25.760 of the stand to the the far end of the pole. Right. 0:21:25.880 --> 0:21:28.960 All right, You've got you've got your weight there at 0:21:28.960 --> 0:21:30.959 the far end of the pole. And again you've got 0:21:31.000 --> 0:21:34.000 your pen attached to it. The pen's nib is against 0:21:34.000 --> 0:21:37.399 the paper. Now, when there's an earthquake that does side 0:21:37.440 --> 0:21:41.240 to side motion, the lever can swing to the left 0:21:41.240 --> 0:21:43.600 and to the right. The the spring acts as the 0:21:43.680 --> 0:21:47.920 dampener it amount because it's it's a high tension spring. 0:21:48.640 --> 0:21:53.000 So the weight will move back and forth again again. Really, 0:21:53.040 --> 0:21:56.600 the the paper is moving back and forth against the weight. Uh. 0:21:56.680 --> 0:22:01.520 And that's how you get your readings for horizontal waves. UM. Now, 0:22:01.840 --> 0:22:05.400 a good seismometer actually has will have a three axes 0:22:06.280 --> 0:22:10.120 UH detector on it. Yes, Now, what do you were 0:22:10.160 --> 0:22:11.640 just I'm sorry, go ahead, and I was gonna say 0:22:11.640 --> 0:22:14.359 what you were describing before was the strained seismograph if 0:22:14.400 --> 0:22:18.000 I'm not mistaken. Yes, Um, from from some of the 0:22:18.040 --> 0:22:20.639 research that I had done, I understand that it really 0:22:20.680 --> 0:22:25.520 you really need to measure basically, just for the simplification 0:22:25.720 --> 0:22:27.480 of this and and the fact that we're trying to 0:22:27.520 --> 0:22:31.359 describe it in an UH in an audio track, left 0:22:31.400 --> 0:22:34.280 to right, up and down, so I'm not up and 0:22:34.320 --> 0:22:37.600 down but left and right, north to south. Uh. So 0:22:37.640 --> 0:22:40.240 you have two different directions, and X axis and y 0:22:40.320 --> 0:22:43.199 axis you're measuring those two and then you do have 0:22:43.320 --> 0:22:47.800 a vertical access to UM. And you're you have pendulums 0:22:47.800 --> 0:22:50.680 for each of those three and so really we should 0:22:50.680 --> 0:22:52.880 say instead of left right, we should say north south 0:22:52.960 --> 0:22:57.440 east west. Sorry, yes, that's much better, UM and UM 0:22:57.840 --> 0:23:02.440 And yes, so I totally lost my train of thought. Sorry, 0:23:02.480 --> 0:23:04.200 but yes, you have to have the three axes to 0:23:04.240 --> 0:23:07.480 be able to detect, uh, what kind of earthquake is 0:23:07.560 --> 0:23:09.360 hitting you, like, what kind of waves are moving through 0:23:09.359 --> 0:23:13.320 the ground. Yes, And they have found another way to 0:23:13.480 --> 0:23:18.240 solve the pen on paper UH problem because some optical 0:23:18.359 --> 0:23:23.639 seismographs use mirrors to reflect light onto photosensitive paper has 0:23:23.680 --> 0:23:28.240 mounted on the drum. Now there the drum in in UH. 0:23:28.440 --> 0:23:32.639 Seismographs that use a drum of paper basically have a 0:23:33.800 --> 0:23:35.800 if you think about it as a recording point that 0:23:36.000 --> 0:23:40.880 is gradually moving around the drum. So it starts it. 0:23:40.560 --> 0:23:44.000 It's sort of like a recording drum that you might 0:23:44.480 --> 0:23:50.119