Latest / PlanetGeo: The Geology Podcast / Discovering Ancient SuperQuakes: Why Large Earthquakes Occur and Where

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Discovering Ancient SuperQuakes: Why Large Earthquakes Occur and Where · PlanetGeo: The Geology Podcast

• 0:00
  SPEAKER_00: Before we get started, we want to highlight something really exciting that's happening next week.
• 0:04
  SPEAKER_00: Chris and I are doing a live podcast recording with Mappy Hour.
• 0:07
  SPEAKER_00: Mappy Hour, that's you know like happy hour but with maps, is a meetup event that's hosted several times a month, and we will be recording, that's Chris and I, we will be recording a live episode on the Geoscience of Glacier National Park in Montana, one of our favorite spots to go and a place that Chris goes every year.
• 0:25
  SPEAKER_00: We'll also be taking live questions as part of this event, and you can find all the details at mappyhour.org.
• 0:30
  SPEAKER_00: That's m-a-p-p-y-h-o-ur.org.
• 0:34
  SPEAKER_00: We are doing this live event on Tuesday, May 4th at 9 p.m.
• 0:37
  SPEAKER_00: Eastern, 6 p.m.
• 0:38
  SPEAKER_00: Pacific time.
• 0:39
  SPEAKER_00: And all the registration details are at mappyhour.org, or you can follow the links to the show notes for this episode.
• 0:46
  SPEAKER_00: So scroll down right now and you'll see some links where you can register.
• 0:50
  SPEAKER_00: So we hope to see you there.
• 0:52
  SPEAKER_00: Alright, let's get started.
• 0:54
  SPEAKER_00: All right, let's get into it.
• 0:56
  SPEAKER_00: Chris, how are you doing today?
• 0:57
  SPEAKER_00: Doing alright.
• 0:58
  SPEAKER_00: How are you doing, Jesse?
• 0:59
  SPEAKER_00: Hanging in there, hanging in there.
• 1:00
  SPEAKER_00: Things are kind of feeling a little bit normal every once in a while.
• 1:04
  SPEAKER_00: Get some sense of normalcy, so that's good.
• 1:06
  SPEAKER_00: Hey, before we get into it, let's uh give a little brief introduction.
• 1:10
  SPEAKER_00: You're Chris Bullheis.
• 1:11
  SPEAKER_00: You are a nationally recognized earth science teacher from the great state of Michigan, and we've known each other for kind of a long time, right?
• 1:18
  SPEAKER_01: It has been a long time.
• 1:19
  SPEAKER_01: Yeah, that's right.
• 1:20
  SPEAKER_01: You're Dr.
• 1:21
  SPEAKER_01: Jesse Rymink, one of my former students in high school.
• 1:24
  SPEAKER_01: I had you as uh ninth grader, as 11th grader, and then as a senior out of that field course.
• 1:28
  SPEAKER_01: And now you are a professor of geoscience at Penn State University.
• 1:32
  SPEAKER_00: And this is Planet Geo podcast where we hang out and talk about how amazing the Earth is and how important the geosciences are to society.
• 1:40
  SPEAKER_00: So on that note, what do we have today?
• 1:42
  SPEAKER_00: Something that's super fun, super interesting, and also very important to society.
• 1:47
  SPEAKER_01: Yeah, I think so.
• 1:48
  SPEAKER_01: Uh today we're gonna talk about earthquakes, and uh, we're gonna do this in you know, kind of four segments.
• 1:54
  SPEAKER_01: We're gonna first talk a little bit about some historical earthquakes.
• 1:57
  SPEAKER_01: And going through this and picking and choosing was kind of hard.
• 2:00
  SPEAKER_01: So, you know, we left some out.
• 2:01
  SPEAKER_01: It's a it's an impressive list.
• 2:03
  SPEAKER_00: It's a huge topic.
• 2:04
  SPEAKER_01: It is.
• 2:05
  SPEAKER_01: And then we're gonna talk about the scales of earthquakes, how we put numbers to this and numbers that you've all heard, and what that really means.
• 2:12
  SPEAKER_01: Well, that'll lead into all right, well, why do we get earthquakes?
• 2:15
  SPEAKER_01: Why do earthquakes occur?
• 2:17
  SPEAKER_01: And then finally, I think this is something that has always fascinated me and interested me, is talking about forecasting or predicting earthquakes and where we are with this.
• 2:27
  SPEAKER_00: That's right.
• 2:27
  SPEAKER_00: The list of earthquakes that are relevant to society in history is massive.
• 2:32
  SPEAKER_00: There are so many that you could talk about, and you know, we we could do a whole podcast episode on each one of these earthquakes.
• 2:38
  SPEAKER_00: But earthquakes have been a part of human history for forever, basically.
• 2:42
  SPEAKER_00: In medieval Europe, you know, places like Italy, Spain, Portugal, where they had a lot of earthquakes occurring, those people were very aware of the risks of earthquakes.
• 2:52
  SPEAKER_00: And in fact, they were kind of paying attention to them when they were laying out city planning, uh, when they were building their buildings back even in the 800s and 900s.
• 3:00
  SPEAKER_00: You could see that they were starting to build buildings thinking of earthquakes.
• 3:05
  SPEAKER_00: They had things like anchor plates.
• 3:06
  SPEAKER_01: Where is this specifically?
• 3:08
  SPEAKER_01: What part of Europe are we talking about?
• 3:09
  SPEAKER_00: Uh, this is in in medieval Europe and Italy and in some places in Spain where they have like extended buttresses and they have anchor plates in buildings, you know, timber and some iron in there.
• 3:20
  SPEAKER_00: They're actively thinking of building buildings to help during an earthquake, basically.
• 3:24
  SPEAKER_00: That is so cool.
• 3:25
  SPEAKER_00: Which is really impressive, yeah.
• 3:27
  SPEAKER_00: So we've been like kind of concerned about them for a long time.
• 3:30
  SPEAKER_00: I mean, I think earthquakes were acts of God, you know, back then a little bit too.
• 3:34
  SPEAKER_00: But yeah, so so they're really important and they've been important for a long time.
• 3:38
  SPEAKER_01: Yeah, right.
• 3:38
  SPEAKER_01: You know, you talk a little bit about looking back at earthquakes in antiquity, and uh, you can put different filters on this list that you get.
• 3:46
  SPEAKER_01: And if you put a filter on where let me only look at earthquakes that have caused a thousand or more deaths, and how long this list is going back a couple thousand years, is it's Jesse, it's crazy.
• 3:59
  SPEAKER_01: I mean, it is such a long list.
• 4:01
  SPEAKER_01: So, we're gonna talk about some specific earthquakes here coming up.
• 4:05
  SPEAKER_01: So, let's go ahead and get the ball started here, Jesse.
• 4:08
  SPEAKER_01: We're kind of gonna go in order, you know.
• 4:10
  SPEAKER_01: We're so I'm gonna start with an earthquake in that happened in 1700.
• 4:14
  SPEAKER_01: This is uh it's an earthquake that happened on what's called the Cascadia subduction zone.
• 4:19
  SPEAKER_01: And so this subduction zone is about like it's a 700-plus mile-long zone that goes from Northern California, Oregon, and the state of Washington.
• 4:28
  SPEAKER_00: And up into up into Canada.
• 4:31
  SPEAKER_00: Let's not forget about the Canadians in there.
• 4:33
  SPEAKER_01: You got it, yeah.
• 4:34
  SPEAKER_01: Sorry, I didn't even think about that.
• 4:36
  SPEAKER_01: Um, this earthquake, like there's so much about it.
• 4:39
  SPEAKER_01: Oh, it's so fascinating.
• 4:40
  SPEAKER_01: Yeah, it's amazing.
• 4:41
  SPEAKER_01: I mean, so this is 1700, it's January 26th, and there's no written record in the United States for that goes back that far, right?
• 4:52
  SPEAKER_01: So, how do we know that this earthquake happened on January 26th?
• 4:55
  SPEAKER_01: And we even know what time it happened.
• 4:57
  SPEAKER_01: It happened at at roughly 9 p.m., which is crazy to me how this is all put together without a written record from the United States, anyway.
• 5:05
  SPEAKER_01: But there's a lot of interesting things about this.
• 5:08
  SPEAKER_01: This earthquake was an 8.7 to a 9.2 estimated moment magnitude scale.
• 5:15
  SPEAKER_00: Okay, before we get into the all the super interesting stuff about this earthquake, let's define this scale a little bit.
• 5:20
  SPEAKER_00: Let's talk about logarithmic scales because they're difficult.
• 5:23
  SPEAKER_00: They're not intuitive.
• 5:25
  SPEAKER_01: It's not intuitive at all, actually.
• 5:27
  SPEAKER_00: Yeah, so so what does that mean?
• 5:28
  SPEAKER_00: I mean, how big is 8.7 to 9.2?
• 5:31
  SPEAKER_00: I mean, is that a big number?
• 5:33
  SPEAKER_00: Is that a small number?
• 5:33
  SPEAKER_00: Let's let's talk about that a little bit.
• 5:35
  SPEAKER_01: Well, uh, first of all, it's huge, okay?
• 5:37
  SPEAKER_01: These earthquakes are very rare, and these they're very big.
• 5:41
  SPEAKER_01: You know, this all really started with what's called the Richter scale, and I think that's what something that almost everyone is familiar with.
• 5:47
  SPEAKER_01: This is an outdated scale now that's not really used.
• 5:50
  SPEAKER_01: It goes from one to ten, but there's really no upper limit on it.
• 5:55
  SPEAKER_01: That's just kind of an arbitrary limit that we put on this.
• 5:58
  SPEAKER_01: It's rather outdated because it really only measures two things.
• 6:02
  SPEAKER_01: It measures the amplitude of the waves, which is, you know, if you think about during an earthquake, the ground kind of wiggles or or the ground moves, you know, and and what we're talking about then is the maximum amount of movement that takes place.
• 6:15
  SPEAKER_01: That wave, the size of that wave.
• 6:18
  SPEAKER_01: So that's a part of it.
• 6:19
  SPEAKER_01: And then it also calculates in the distance that the waves have traveled.
• 6:23
  SPEAKER_01: That's the Richter scale, okay?
• 6:25
  SPEAKER_01: And in more recent times, then we've taken more things into account.
• 6:31
  SPEAKER_01: We still take into account the amplitude of the waves, we take into account the distance that the waves travel, but we also take into account like the amount that the fault actually moved.
• 6:42
  SPEAKER_01: You know, was it 10 feet of movement, was it 20 feet of movement, and then the amount of energy that's required to make that movement happen?
• 6:50
  SPEAKER_00: And this is movement where we're talking about rock breaking and then rebounding.
• 6:54
  SPEAKER_00: So it's movement of rock that's in the process of breaking.
• 6:57
  SPEAKER_00: How much does it break?
• 6:58
  SPEAKER_00: That's the movement we're talking about along a fault here.
• 7:01
  SPEAKER_00: So you alluded to the energy released here during and this this is a calibration to the amount of energy that's released.
• 7:08
  SPEAKER_00: So what is that, what does that look like?
• 7:10
  SPEAKER_00: What is a an eight or a nine on the moment magnitude scale look like?
• 7:14
  SPEAKER_01: Okay, so well, first of all, in terms of the amount of movement, one whole number up in the scale is a difference or on order of a magnitude of 10 difference.
• 7:24
  SPEAKER_01: So what I mean is if the size of the wave is one unit, let's say, of measurement, okay, then a seven would be ten times that amount.
• 7:35
  SPEAKER_01: That's in terms of ground movement.
• 7:37
  SPEAKER_01: But in terms of energy released, it varies by exponents of 30.
• 7:42
  SPEAKER_01: Actually, it varies by exponents of 31.6, but we usually just round down to 30.
• 7:48
  SPEAKER_01: That's close enough.
• 7:49
  SPEAKER_01: That's good enough for us.
• 7:50
  SPEAKER_01: So let me give you an analogy of this.
• 7:52
  SPEAKER_01: All right, and this is something that I use in class and I think it really works.
• 7:56
  SPEAKER_01: It's imagine an uncooked spaghetti noodle.
• 8:00
  SPEAKER_01: Okay, you got one of them, right?
• 8:01
  SPEAKER_01: And you know how they are.
• 8:03
  SPEAKER_01: They're long and they're skinny, but they're rather brittle, right?
• 8:06
  SPEAKER_01: And so let's say that I take that one spaghetti strand and I bend it until it breaks.
• 8:13
  SPEAKER_01: And let's equate that to a six on the Richter scale.
• 8:17
  SPEAKER_01: So that one spaghetti noodle is a six.
• 8:19
  SPEAKER_01: Well, what is a seven then?
• 8:21
  SPEAKER_01: A seven is gonna be thirty times that amount of energy.
• 8:24
  SPEAKER_01: So, in other words, that's the equivalent of taking 30 uncooked spaghetti noodles together and you bend them, and the amount of energy that you have to apply, and and therefore the energy released is 30 times that.
• 8:38
  SPEAKER_01: That's so that's a seven, 30 spaghetti noodles.
• 8:40
  SPEAKER_01: Well, what's an eight?
• 8:42
  SPEAKER_01: Well, it's 30 times that.
• 8:45
  SPEAKER_01: So now you have to have 900 spaghetti noodles all bundled together, and you gotta bend them to get them to break.
• 8:53
  SPEAKER_00: So you're one meal of spaghetti for you.
• 8:56
  SPEAKER_01: Maybe.
• 8:56
  SPEAKER_01: For me, too.
• 8:57
  SPEAKER_00: Is that what you meant?
• 8:58
  SPEAKER_00: All right, yeah.
• 8:59
  SPEAKER_01: So if we both hold on, hold on, let's let's go though, because you know, we talked about this Cascadia subduction zone as being an up to up a 9.2, right?
• 9:08
  SPEAKER_01: So a 9.2 would be 30 times that, which would be 27,000 spaghetti noodles bundled together, and the force that you would have to apply to bend that and get them to break, that's the energy released.
• 9:24
  SPEAKER_00: Right.
• 9:24
  SPEAKER_00: That's a ton.
• 9:25
  SPEAKER_01: That's a it's a lot, isn't it?
• 9:28
  SPEAKER_00: That's a lot.
• 9:28
  SPEAKER_00: I I just that analogy is awesome.
• 9:30
  SPEAKER_00: To put this in another analogy to think of it, the a magnitude one seismic wave releases as much energy as six ounces of TNT.
• 9:40
  SPEAKER_00: A whereas a magnitude eight earthquake releases the equivalent of six million tons of TNT in energy, which is you know, it's they're not even comparable, right?
• 9:49
  SPEAKER_00: They're logarithmic scales, always kind of are are difficult to really grasp, but this is what we're dealing with.
• 9:54
  SPEAKER_01: You know, but you talk about okay, when they measure an earthquake and they say uh, you know, a 9.0, well, how much bigger than is a 9.2?
• 10:02
  SPEAKER_01: Well, most people would say, well, not a huge difference, right?
• 10:06
  SPEAKER_01: With this exponential scale, a difference of 0.2 means a doubling in the energy released.
• 10:13
  SPEAKER_00: Yeah, that's right.
• 10:13
  SPEAKER_00: And so when we are listing these numbers of earthquakes here, the scale matters, and the bigger it gets, it gets exponentially bigger.
• 10:20
  SPEAKER_00: So uh just kind of keep that in mind as we're going through here and talking about these.
• 10:24
  SPEAKER_00: Okay, so let's go back to the Cascadia subduction zone earthquake.
• 10:27
  SPEAKER_00: Let's talk about the 1700 event.
• 10:29
  SPEAKER_00: I mean, it's really interesting.
• 10:31
  SPEAKER_00: You know, there's a long history of evidence that points to the fact that there was a huge earthquake here.
• 10:37
  SPEAKER_00: And as you're saying, Chris, this is sort of there's a lot of uh new ideas about this or new evidence coming to light about the history of this earthquake.
• 10:44
  SPEAKER_00: Let's just go through a couple of the key pieces of evidence that there was an earthquake and the scale of devastation that this earthquake induced in this region.
• 10:53
  SPEAKER_01: Right.
• 10:53
  SPEAKER_01: Yeah, like I said, there hasn't been a you know a recorded earthquake that's significant along the Cascadia subduction zone in written human histories, you know, since the 1800s, right?
• 11:05
  SPEAKER_01: And so we didn't really know is this zone capable of knocking off major earthquakes until this guy comes along named Brian Atwell, Dr.
• 11:15
  SPEAKER_01: Brian Atwater.
• 11:16
  SPEAKER_01: This research is just it's fascinating and it's so cool how this was figured out.
• 11:22
  SPEAKER_01: But what he found are these what he calls ghost forests along the coastline of Oregon and Washington, you know, and and actually even down into California.
• 11:35
  SPEAKER_01: Here's what happens, right?
• 11:36
  SPEAKER_01: I'm gonna try to do my best to paint this picture, but imagine you have the subduction zone of the Wandafuca plate, which is the small plate just off the coast of the northwestern part of the United States, and that is jamming itself under that part of North America, okay.
• 11:52
  SPEAKER_01: I think I want to use an analogy keeping in line with the spaghetti.
• 11:57
  SPEAKER_01: Tell me if this makes sense, Jesse.
• 11:59
  SPEAKER_01: But you if you take one strand of spaghetti and you put it on a table, and let's say that half of that spaghetti is hanging off the edge of the table, okay?
• 12:09
  SPEAKER_01: Now you put your finger over top of the spaghetti that's on the table, okay, the end of it.
• 12:15
  SPEAKER_01: You put your finger on one end of it to hold it down.
• 12:18
  SPEAKER_01: All right, now that spaghetti strand represents the North American plate.
• 12:22
  SPEAKER_01: Okay, and the Juan de Fuca plate is subducting beneath that, okay.
• 12:27
  SPEAKER_01: So what it's gonna do to the spaghetti strand is the part that's off the table, you're bending that down.
• 12:33
  SPEAKER_01: You with me on that?
• 12:34
  SPEAKER_00: It's like a little weight hanging off the end of the uh of the spaghetti.
• 12:37
  SPEAKER_01: Yep.
• 12:38
  SPEAKER_01: But Jesse, let me ask you this then.
• 12:40
  SPEAKER_01: If you get it, what's happening to the overall spaghetti strand?
• 12:44
  SPEAKER_01: Because I'm only holding it down with my finger on part of the table.
• 12:47
  SPEAKER_01: It's getting pushed up a little bit.
• 12:48
  SPEAKER_01: Yeah, it's it's causing it to arch, right?
• 12:50
  SPEAKER_01: Does that make sense?
• 12:51
  SPEAKER_01: So I'm arching that spaghetti strand.
• 12:53
  SPEAKER_01: Now, then when the subducting slab jams down, there's a release of energy.
• 12:59
  SPEAKER_01: And that's so the spaghetti strand that I'm pulling down, the part that's hanging off the table, that part will snap back up, right?
• 13:06
  SPEAKER_01: And it takes the bend out of the whole spaghetti strand.
• 13:10
  SPEAKER_01: Okay, so two things happen there.
• 13:13
  SPEAKER_01: The coastline then of the North American plate along the Washington, Oregon, and California boundary, that coastline then is gonna lower very quickly.
• 13:22
  SPEAKER_00: Right.
• 13:22
  SPEAKER_00: The stuff that was being pushed up, the stuff that was being bent up above the table is suddenly dropped, it's relaxed and dropped back down.
• 13:28
  SPEAKER_01: It dropped back down, and the part of the spaghetti strand hanging off the table that snaps up.
• 13:35
  SPEAKER_01: Now that's in the ocean, and so that snapping back up, kind of in an elastic way, pushes the water, the column of water above it, and that's what generates a tsunami.
• 13:47
  SPEAKER_00: Yeah, it pushes it extremely quickly.
• 13:48
  SPEAKER_00: This is a very rapid rebound in most cases, and so generates a massive tsunami wave.
• 13:54
  SPEAKER_01: Yes.
• 13:55
  SPEAKER_01: And so this is what happened in 1700 on January 26.
• 14:01
  SPEAKER_01: And and how do we know this?
• 14:03
  SPEAKER_01: Well, what we had is we had this forest right along the coastline made up of red cedars and things like this, right?
• 14:10
  SPEAKER_01: Well, they were above the level of the ocean because of the the the bending of the rock.
• 14:17
  SPEAKER_01: It was bowed upward.
• 14:19
  SPEAKER_01: Well, then when it suddenly jammed in the subduction zone, you had this violent earthquake, that part of the coastline suddenly lowered, submerging it in salt water and therefore killing the trees.
• 14:31
  SPEAKER_00: Yeah.
• 14:32
  SPEAKER_00: So it go ahead.
• 14:33
  SPEAKER_00: Yeah, so it kills the forest, and you basically lose the trees that were there because they're now in saltwater.
• 14:38
  SPEAKER_00: That's one of the lines of evidence that point towards a major earthquake, and and this is one mechanism to kind of lower the ground in that area.
• 14:45
  SPEAKER_00: But you know, there's other mechanisms that could either raise sea level or drop the ground in that area that might not be related to an earthquake.
• 14:52
  SPEAKER_00: So the other key piece of evidence is the other part of the spaghetti straw, right?
• 14:56
  SPEAKER_00: Or that's the spaghetti strand is what's happening there.
• 14:59
  SPEAKER_01: Well, because that snapping up generated a tsunami, the tsunami slams into the coast, and that brings with it this layer of sand.
• 15:09
  SPEAKER_01: And so you have this forest floor that is like a knife-like contact where you have this layer of sand deposited right on top of it.
• 15:18
  SPEAKER_01: And so the layer of sand was brought in by the tsunami.
• 15:21
  SPEAKER_01: Because of the lowering, this place then after it returns to somewhat normal, it's in this tidal zone.
• 15:28
  SPEAKER_01: And so you get on top of the sand then just deposition of this mud.
• 15:32
  SPEAKER_01: And so you have this like instant lowering of the forest floor covered with a tsunami as indicated by the sand, and then this layer of mud on top of it.
• 15:43
  SPEAKER_01: And this is what Dr.
• 15:45
  SPEAKER_01: Atwater discovered.
• 15:48
  SPEAKER_00: Yeah, so this is the evidence on the North American continent.
• 15:51
  SPEAKER_00: And this isn't just one location that has these ghost forests in the tsunami wave deposit.
• 15:56
  SPEAKER_00: I mean, it's in many places on the west coast of North America.
• 16:00
  SPEAKER_00: And we can go back and look at this sort of record of ancient forests, then tsunami deposit, and then mud flat, and we can get some pretty good geochronology that dates that deposit and says, oh, it's close to 1700.
• 16:13
  SPEAKER_00: But when you introduce this earthquake, you gave a very specific date and in fact the time when this earthquake occurred.
• 16:18
  SPEAKER_00: And so the spaghetti straw bending back and creating a tsunami, that event allows us to date the exact time, exact day that this earthquake occurred.
• 16:29
  SPEAKER_00: So tell us that story, Chris.
• 16:30
  SPEAKER_00: How do we get from around about 1700 plus or minus like 10 years or something like that?
• 16:36
  SPEAKER_00: How do we get from there to the time of the event?
• 16:38
  SPEAKER_01: Right.
• 16:39
  SPEAKER_01: Well, this earthquake happened, and the tsunami not only hit the shoreline of Oregon and Washington and so on, it also traveled across the Pacific Ocean to the Western Pacific and hit Japan.
• 16:51
  SPEAKER_01: They have a written recorded history that goes back before 700 AD.
• 16:56
  SPEAKER_01: And so they wrote about this totally random tsunami.
• 17:02
  SPEAKER_01: They called it an orphan tsunami because this is the only tsunami in this time frame that they couldn't pinpoint to this came from this event.
• 17:10
  SPEAKER_00: I mean, in Japan, you know, much like ancient Italians or, you know, ancient Chileans, they had to worry about earthquakes a lot.
• 17:16
  SPEAKER_00: So there's a really intimate understanding or appreciation of earthquakes and the tsunamis that came along with them.
• 17:21
  SPEAKER_00: And in Japan, there's a lot of earthquakes as well.
• 17:23
  SPEAKER_00: So they would have earthquakes plus tsunamis, and then they would sometimes get a tsunami without the evidence for an earthquake or without feeling the earthquake, which probably had to travel all the way across the Pacific.
• 17:34
  SPEAKER_00: I mean, I just kind of find that amazing to try and picture being one of these people and writing about these giant random waves that just come in out of the middle of nowhere and no evidence.
• 17:43
  SPEAKER_00: It's one thing if the ground is shaking like crazy and then you get this wave, that that kind of makes sense, right?
• 17:49
  SPEAKER_00: But if it's just kind of coming from nowhere, that's a very much more potentially traumatic sort of thing to experience in a way.
• 17:57
  SPEAKER_00: I know, yeah.
• 17:57
  SPEAKER_01: It's um I agree.
• 17:59
  SPEAKER_01: I agree.
• 18:00
  SPEAKER_01: So that's how you know, because they wrote about it, and they wrote, you know, according to the time, and and we can then just you know extrapolate that back in terms of, well, okay, how long would it take for this wave to travel across the Pacific Ocean and slam into Japan?
• 18:15
  SPEAKER_01: So, because of their written record, we're able to really pinpoint not only the date, but the time that it happened uh in the evening, which is just fascinating.
• 18:24
  SPEAKER_00: It's such a cool example of a a big earthquake.
• 18:27
  SPEAKER_01: It really is.
• 18:28
  SPEAKER_01: Now, the one thing I want to say about this is that this Cascadia subduction zone knocks off major earthquakes, tsunami generating earthquakes every 500-ish years.
• 18:39
  SPEAKER_01: Now, of course, that's just a in a general sense.
• 18:42
  SPEAKER_01: I mean, it doesn't have to stick to 500, it can be less than that, it can be more than that.
• 18:46
  SPEAKER_01: But, you know, from a broad sense, that's roughly what we're looking at.
• 18:51
  SPEAKER_00: So it's a totally cool thing.
• 18:52
  SPEAKER_00: And these are what are called mega thrust earthquakes, which are the big ones, the big monsters that occur.
• 18:57
  SPEAKER_00: But there's many other examples of earthquakes that are not in this location and are equally impactful for humanity.
• 19:05
  SPEAKER_00: So, Chris, we didn't cover this, but have you ever been in an earthquake?
• 19:08
  SPEAKER_01: Um, I have been in an earthquake.
• 19:11
  SPEAKER_01: Um, and but I'm I'm ashamed.
• 19:13
  SPEAKER_01: Like, this is so I'm so dumb.
• 19:16
  SPEAKER_01: Okay, well, let's hear it.
• 19:18
  SPEAKER_01: Okay, I was I was in California and I'm in a hotel and I'm I'm with Jenny, and uh it was like a five-something earthquake, you know, and uh I I didn't realize what was going on.
• 19:29
  SPEAKER_01: I I thought, you know, you had this rumble, okay, things are rattling and so on.
• 19:33
  SPEAKER_01: I thought it was just a big move, like a truck going by the building outside, you know, and I'm it only lasted 10, 15 seconds, maybe, you know.
• 19:42
  SPEAKER_01: Then when it was done, I realized what had happened, and I and I'm like, oh no, do it again, you know.
• 19:48
  SPEAKER_01: I'm like, oh no, you are horrible.
• 19:51
  SPEAKER_01: You can't call yours turning your geology card right now.
• 19:54
  SPEAKER_01: You yeah, yeah, that's right.
• 19:55
  SPEAKER_01: That's right.
• 19:56
  SPEAKER_00: That's right.
• 19:56
  SPEAKER_00: That's funny.
• 19:57
  SPEAKER_00: So yeah, that's funny.
• 19:58
  SPEAKER_00: I mean, I've never been in an earthquake, but I'm just trying to imagine what shaking like this that lasts for four minutes and 38 seconds would be like.
• 20:06
  SPEAKER_00: I I mean, I'd be puking my guts out.
• 20:08
  SPEAKER_00: It'd be it'd be it'd be both amazing, impressive, and if you survived it, it'd be super cool, but it must be terrifying in the moment.
• 20:16
  SPEAKER_01: Well, that's the thing.
• 20:17
  SPEAKER_01: I'm telling you that the it's this kind of power that draws me into the field of geology.
• 20:23
  SPEAKER_01: It's this this kind of you know, trying to get this sense of the power that's involved in this.
• 20:29
  SPEAKER_00: Yeah.
• 20:30
  SPEAKER_00: I just love that.
• 20:31
  SPEAKER_01: That's it, gets me going.
• 20:32
  SPEAKER_00: I agree completely.
• 20:34
  SPEAKER_00: The scale of things in the geosciences and the the power, the the sheer force that's involved is really just incredible.
• 20:41
  SPEAKER_00: And earthquakes represent that really well.
• 20:43
  SPEAKER_00: Okay, so moving on, we have there's been some very catastrophic earthquakes as far as the human death toll in the last 20 years.
• 20:52
  SPEAKER_00: Sumatra earthquake in 2004, where well over 200,000 people passed away, and several more other ones that we'll highlight here.
• 21:01
  SPEAKER_00: But earthquakes continue to be a very major feature in human life as a daily occurrence.
• 21:08
  SPEAKER_00: And we're always developing, trying to develop at least new detection techniques, early warning systems for tsunamis.
• 21:14
  SPEAKER_00: And there's one kind of recent example in 2009 in Italy, there was an earthquake that was somewhat small or modest, I would say.
• 21:21
  SPEAKER_00: It was a 5.8, and 300 people died, though, in the town of Laquila.
• 21:26
  SPEAKER_00: And this is kind of an interesting one from the geoscientist perspective because there's a little bit of a story about researchers and government officials who were talking about the risks involved in the lead up to this earthquake.
• 21:41
  SPEAKER_00: And actually, there was a seismologist who basically a month beforehand was predicting that there would be a big earthquake.
• 21:47
  SPEAKER_00: You know, as all predictions do, he was a little bit wrong.
• 21:50
  SPEAKER_00: And so he predicted there was gonna be an earthquake, there wasn't one, and then he got in trouble for wrongly predicting an earthquake and you know causing this fear in the population.
• 22:00
  SPEAKER_00: But then lo and behold, a month later the earthquake actually happened.
• 22:04
  SPEAKER_00: And 309, sorry, then 309 people died.
• 22:07
  SPEAKER_00: And then the Italian government put people on trial.
• 22:11
  SPEAKER_00: And so there were six scientists and one public official were eventually convicted of giving false or misleading statements that downplayed the risks of a earthquake to this particular city.
• 22:23
  SPEAKER_00: And this, I remember this was um this was right before I was in graduate school.
• 22:27
  SPEAKER_00: And you know, this was people were talking about this for a long time.
• 22:30
  SPEAKER_00: And every every time new news came out about this, uh, we were always paying attention to what was happening with those poor Italian volcanologists who were on trial for giving advice.
• 22:41
  SPEAKER_00: Well, they weren't really giving advice, but they're giving scientific forecasts that were wrong as all of them are.
• 22:48
  SPEAKER_00: Yeah, yeah.
• 22:49
  SPEAKER_00: You know, so you you kind of there's like a no-win situation here where you just can't predict these events.
• 22:54
  SPEAKER_00: And luckily, these verdicts were overturned later by the Italian Supreme Court.
• 22:59
  SPEAKER_01: Do you know when that was?
• 23:01
  SPEAKER_01: When was it overturned?
• 23:02
  SPEAKER_01: I think it was 2014.
• 23:04
  SPEAKER_01: Okay, I thought it was more recent than that, but okay.
• 23:07
  SPEAKER_01: It just seems that way in my mind.
• 23:09
  SPEAKER_00: Yeah, yeah.
• 23:10
  SPEAKER_00: But basically, every major scientific organization or outlet like roundly criticized the fact that these people were convicted of these so-called crimes.
• 23:18
  SPEAKER_00: Basically, that was not supported by any scientific community that they should be held accountable for really trying to predict an earthquake.
• 23:25
  SPEAKER_00: It's an impossible thing.
• 23:26
  SPEAKER_00: And we'll get we'll get to that a little bit more later at the end here.
• 23:29
  SPEAKER_01: All right, so one other earthquake that we want to highlight just a real briefly here is the 2011 Japan earthquake.
• 23:36
  SPEAKER_01: That was a 9.0 on the moment magnitude scale.
• 23:39
  SPEAKER_01: So, you know, roughly half the size of the you know 9.2 earthquake that we talked about earlier, the the Great Alaskan earthquake, right?
• 23:50
  SPEAKER_01: Because a 0.2 difference makes a big difference, right?
• 23:53
  SPEAKER_01: And this is something that all of you, the listeners, remember.
• 23:59
  SPEAKER_01: You have all seen the footage of the tsunami, you've seen the footage of the shaking of the buildings, and I mean, it you can't not just be amazed at what you see.
• 24:10
  SPEAKER_01: You know, it's horrifying and it's uh just so, so powerful.
• 24:14
  SPEAKER_01: I think this was perhaps the most publicly viewed event like this in maybe the history of mankind.
• 24:22
  SPEAKER_00: And this was the earthquake that led to the tsunami that shut down the Fukushima power reactor and created that catastrophic uh damage to the Fukushima Daichi uh nuclear power plant.
• 24:32
  SPEAKER_00: And this this earthquake was massive.
• 24:34
  SPEAKER_00: I mean, this is it's it's hard to overstate how big these earthquakes actually are.
• 24:39
  SPEAKER_00: And there's a couple of stats that it moved the main island of Japan like eight feet to the east, and these earthquakes can actually shift Earth's rotational axis a little bit because they're moving mass around and there's such a traumatic event that it influences the orbital dynamics of Earth.
• 24:53
  SPEAKER_00: They're they're just it's unbelievable the scale of these things, how powerful they are.
• 24:59
  SPEAKER_00: It's totally cool.
• 25:00
  SPEAKER_00: Yeah, and can be incredibly damaging.
• 25:03
  SPEAKER_01: So, Jesse, I think it's time to transition into why do earthquakes occur?
• 25:08
  SPEAKER_00: So, in order to do this, we really need to think back to our plate tectonics episode, which was episode number two of Planet Geo.
• 25:16
  SPEAKER_00: And we really need to understand that Earth's crust is broken up into different tectonic plates, which are moving independently and they're running into each other.
• 25:26
  SPEAKER_00: And so when these tectonic plates run into each other or break apart from one another or slide past one another, it's rock moving against rock, really.
• 25:35
  SPEAKER_00: And it that means that rock has to break.
• 25:37
  SPEAKER_00: So we're actually breaking rocks along these plate boundaries.
• 25:40
  SPEAKER_00: And we can think about this by kind of going back and thinking about the locations that we just mentioned where all these big earthquakes are occurring.
• 25:48
  SPEAKER_00: We have to think about the distribution of earthquakes.
• 25:50
  SPEAKER_00: Like where are they occurring?
• 25:51
  SPEAKER_00: Where are the big ones occurring?
• 25:53
  SPEAKER_00: And if you map that out on the surface of the earth, we can see that they correspond really nicely with tectonic plate boundaries.
• 26:02
  SPEAKER_00: And so if we use just use North America as an example, you know, all the earthquakes are occurring on the west coast of the United States on the west coast of North America for the most part.
• 26:11
  SPEAKER_00: And the same goes for Europe.
• 26:13
  SPEAKER_00: You know, there's a lot of earthquakes in Italy and in Spain.
• 26:16
  SPEAKER_00: There's not that many in France or in Germany or in the United Kingdom.
• 26:20
  SPEAKER_00: The ones that are there are pretty small.
• 26:22
  SPEAKER_01: So let's, Jesse, let's talk about the the different kinds of stress.
• 26:26
  SPEAKER_01: Okay, we talk about the force that's exerted on the rocks.
• 26:30
  SPEAKER_01: There's compression, there's tension, and then there's shearing.
• 26:34
  SPEAKER_01: Can you talk about those real quick?
• 26:36
  SPEAKER_00: Yeah, yeah, exactly.
• 26:37
  SPEAKER_00: So compression is just pushing the plates together, tension is pulling the plates apart, and shearing is them sliding past one another.
• 26:45
  SPEAKER_00: And those three different types of stress generate different types of earthquakes and earthquakes in different locations.
• 26:52
  SPEAKER_00: And so compression is the one that generates the big ones.
• 26:54
  SPEAKER_00: Tension or spreading apart, this generates relatively small earthquakes, they're mostly relatively shallow.
• 27:01
  SPEAKER_00: Shearing also can generate big earthquakes.
• 27:03
  SPEAKER_00: It usually generates more damaging ones than more energetic ones, and they're shallow.
• 27:09
  SPEAKER_00: Because they're shallow and close to the surface.
• 27:11
  SPEAKER_00: So the San Andreas fault is a shear boundaries, um, whereas the big mega thrust earthquakes uh near on plate tectonic and subduction zone boundaries are compressional.
• 27:21
  SPEAKER_01: So then those three different types of stress, and stress we can think of as the force that's exerted on the rocks, caused by plate tectonics.
• 27:29
  SPEAKER_01: Okay.
• 27:30
  SPEAKER_01: Stress leads to strain.
• 27:32
  SPEAKER_01: And strain, so the force exerted on the rocks leads to strain, which we can think of as just deformation, the bending, the stretching, or the shearing of the rocks.
• 27:43
  SPEAKER_01: So they don't just slide past each other nicely, even if you're putting tension on rocks, and and that's pulling apart, okay?
• 27:51
  SPEAKER_01: And and like I think of tension as hey, you have one end of a rope, I've got the other.
• 27:56
  SPEAKER_01: Jesse, go ahead and put tension on that rope.
• 27:57
  SPEAKER_01: Ever you you know what to do.
• 27:59
  SPEAKER_01: You're gonna pull on it.
• 28:00
  SPEAKER_00: Well, I'm gonna pull, I'm gonna win the tug of war for sure.
• 28:03
  SPEAKER_00: But second of all, that's what tension is.
• 28:05
  SPEAKER_01: I you know, I I'm gonna tell you, I would love to see the world through your eyes just for one day.
• 28:10
  SPEAKER_00: It's pretty rosy.
• 28:11
  SPEAKER_00: It's pretty rosy over here.
• 28:12
  SPEAKER_01: It's nothing but oblivion, you know, and and so like let me live in my nice little world over here.
• 28:18
  SPEAKER_01: You are the definition of ignorance's bliss.
• 28:20
  SPEAKER_01: Anyway, um, yeah, they don't slide past each other.
• 28:23
  SPEAKER_01: They they're locked in.
• 28:25
  SPEAKER_01: If they're sliding past each other, they're locked, so the rocks are bending, bending, bending, bending, and then they snap.
• 28:32
  SPEAKER_01: Same thing as we talked about with the Cascadia subduction zone.
• 28:35
  SPEAKER_01: It's bending that piece of spaghetti down, down, down until a rupture happens and the spaghetti snaps back.
• 28:41
  SPEAKER_01: Or we pull rock apart.
• 28:43
  SPEAKER_01: And that it you can't just stretch rock.
• 28:46
  SPEAKER_01: I mean, it's rock for goodness sakes, right?
• 28:47
  SPEAKER_01: You can't just stretch it.
• 28:48
  SPEAKER_01: So it pulls, pulls, pulls, pulls, and then suddenly cracks.
• 28:52
  SPEAKER_01: Stress leads to strain, which is the deformation, and strain can lead to rupture.
• 28:58
  SPEAKER_00: And this rupture, as you described, you know, uh so nicely with the spaghetti, you know, hanging over the edge of the table, the rocks will bend.
• 29:06
  SPEAKER_00: They'll bend a little bit.
• 29:07
  SPEAKER_00: And when they break, they kind of snap back.
• 29:09
  SPEAKER_00: So they elastically snap back.
• 29:11
  SPEAKER_01: Okay, so Jesse, you said something about elastic and elasticity of rocks.
• 29:16
  SPEAKER_01: And, you know, that people don't think of elasticity or rocks being elastic.
• 29:22
  SPEAKER_01: But this is a really important point in geology or when earthquakes, in terms of why do earthquakes occur.
• 29:27
  SPEAKER_01: It's called the elastic rebound theory.
• 29:30
  SPEAKER_01: Walk us through this theory.
• 29:32
  SPEAKER_00: Yeah, so this is basically the ability of a material to return to its original position, basically.
• 29:38
  SPEAKER_00: So it's the snapping back after breaking component to this.
• 29:42
  SPEAKER_00: So they'll deform, they'll deform, and when it breaks, they return back to their initial state.
• 29:47
  SPEAKER_00: So if we go back to the spaghetti hanging over the edge of the table analogy, it's bending, it's bending, it's deforming, but then it's snapping back once it breaks.
• 29:58
  SPEAKER_00: Plasticity would be it bends and then it's just bent now.
• 30:01
  SPEAKER_00: So you just bent your metal wire and it's now bent.
• 30:04
  SPEAKER_00: With the piece of spaghetti, it's going to break and return back to being a straight, smaller piece of spaghetti.
• 30:09
  SPEAKER_00: And this is the way that rocks behave.
• 30:10
  SPEAKER_00: So they'll bend a little bit and then they'll break.
• 30:13
  SPEAKER_00: And when they break, they're not just bent rocks, they are returned back to their initial condition.
• 30:18
  SPEAKER_01: Okay, so now you have two pieces of rock that are now essentially pre-stress or straight.
• 30:25
  SPEAKER_00: With a break in between in between them.
• 30:26
  SPEAKER_00: So though the rocks will bend until they break.
• 30:29
  SPEAKER_00: And uh especially in places where earthquakes occur, rocks are breaking, and then there's a break in the rocks between two straight pieces.
• 30:36
  SPEAKER_00: Exactly.
• 30:36
  SPEAKER_00: Exactly.
• 30:37
  SPEAKER_01: And so they do this in an elastic way, right?
• 30:40
  SPEAKER_01: And they when they break, they rebound, which means they just simply vibrate back to a straight position, right?
• 30:47
  SPEAKER_01: They vibrate back and forth, come into rest as two pieces of wood or two spaghetti two pieces of spaghetti that are now straight.
• 30:56
  SPEAKER_01: And that vibration is what causes earthquakes.
• 31:01
  SPEAKER_00: Yes, exactly.
• 31:02
  SPEAKER_00: Exactly.
• 31:03
  SPEAKER_00: Um, and that vibration is also what causes uh that that return to normal, that elastic rebound is also what can cause tsunamis as well, uh, because that that return to normal will push what push water and create a big tsunami wave.
• 31:17
  SPEAKER_00: So the other thing that's important here about earthquakes, and in part the reason that they're useful, is that earthquakes are really good at mapping plate tectonic boundaries, and we use them all the time to understand the geometry of subduction zones, for instance, and where plates are moving in the earth is extremely well mapped out by earthquakes.
• 31:39
  SPEAKER_00: The location of earthquakes, the location in map view, and then also combined with the depth component, you can really see where subduction is going on, where plates are breaking apart, and you can see this in in three dimensions really nicely by using a map of earthquakes.
• 31:56
  SPEAKER_00: And there are some really, really deep earthquakes that occur 400 miles deep in the earth, and we don't quite understand how those form or why they form, because they shouldn't really be there.
• 32:06
  SPEAKER_00: The rock should behave plastically at that depth, but they occur.
• 32:11
  SPEAKER_00: So explaining it is a little bit more difficult, and there's some theories about that.
• 32:14
  SPEAKER_00: But they're really earthquakes are really great at mapping the earth.
• 32:17
  SPEAKER_01: Okay, so earthquakes occur because rock is elastic, so it bends, then it breaks, and it vibrates and snaps back to its pre-bent position.
• 32:28
  SPEAKER_01: So Jesse, we need to turn to predicting earthquakes or forecasting earthquakes.
• 32:35
  SPEAKER_00: Yeah.
• 32:36
  SPEAKER_00: So there's two really different things there: forecasting and prediction.
• 32:40
  SPEAKER_00: And you know, prediction, I always think of it as a prediction needs to have a time or a date that's associated with it a little bit.
• 32:47
  SPEAKER_00: You're predicting that this earthquake will occur, you know, tomorrow at 2 p.m.
• 32:51
  SPEAKER_00: or something like that.
• 32:52
  SPEAKER_00: That's a little bit more of a prediction.
• 32:53
  SPEAKER_00: A forecast is a little bit more probabilistic in the sense of there is some probability, there's a lot of probability, there's little probability that an earthquake will occur in the next month, or an earthquake will occur this year.
• 33:06
  SPEAKER_00: That's forecasting.
• 33:07
  SPEAKER_00: So it's more general, it's less specific, and it's safer, if that makes sense, because we can't predict earthquakes, but we can forecast them.
• 33:16
  SPEAKER_00: We can give kind of probabilities in some way.
• 33:19
  SPEAKER_01: No matter what, whether you're talking about a short-term prediction, you know, minutes, days, or weeks, right?
• 33:26
  SPEAKER_01: Or a long-term prediction, which is decades to even longer.
• 33:30
  SPEAKER_01: Any prediction's got to say when, where, and how big it's gonna be.
• 33:33
  SPEAKER_01: Right.
• 33:34
  SPEAKER_01: Okay.
• 33:35
  SPEAKER_01: Short-term prediction.
• 33:37
  SPEAKER_01: Like, where are we with this?
• 33:39
  SPEAKER_00: I think we're a fair ways away from predicting when an earthquake might occur, giving the time, the place, the size.
• 33:47
  SPEAKER_00: We're getting better at forecasting.
• 33:49
  SPEAKER_00: Let's say we can do things like predicting uh if an earthquake occurs here, the tsunami might look like this.
• 33:54
  SPEAKER_00: If we know that there's an earthquake that occurs of some size in some location in Japan, we can predict where the tsunami will be and when it will be and what size it will be along the west coast of the Americas.
• 34:05
  SPEAKER_00: But as far as predicting where and when an earthquake might occur, we're we're kind of a long ways from that.
• 34:10
  SPEAKER_00: Although there is some cool, cool stuff with early warning systems.
• 34:14
  SPEAKER_01: There is cool research going on.
• 34:16
  SPEAKER_01: Uh, I will always remember this.
• 34:18
  SPEAKER_01: Uh, one of my capstone courses in geology, I did a uh seminar project on where I had to give a presentation and we get to pick our topic.
• 34:25
  SPEAKER_01: I chose earthquake prediction because it's always been something that's fascinating to me.
• 34:29
  SPEAKER_01: And I remember getting into this and I was so disappointed because it was all long-term, probabilistic.
• 34:37
  SPEAKER_01: Hey, this is you know what you can expect in the next 20 to 40 years, you know.
• 34:42
  SPEAKER_01: And I'm disappointed in that.
• 34:43
  SPEAKER_01: Like, wait, wait a second.
• 34:45
  SPEAKER_00: It's hard for them back in the day without computers, though, create what you to do.
• 34:50
  SPEAKER_01: You are a piece of work.
• 34:52
  SPEAKER_01: Okay, yeah.
• 34:53
  SPEAKER_01: You know, there's a little bit of truth to that.
• 34:55
  SPEAKER_01: There actually is.
• 34:57
  SPEAKER_01: There is, there is.
• 34:58
  SPEAKER_01: And and what about this?
• 34:59
  SPEAKER_01: In California, we we do this quite often.
• 35:01
  SPEAKER_01: Uh, radon emissions.
• 35:03
  SPEAKER_00: Yeah, so radon, this is actually one of the things that the Italian scientists got in trouble for was using or not using radon emissions.
• 35:10
  SPEAKER_00: But again, it goes back to this prediction thing.
• 35:12
  SPEAKER_00: Like, what is you it's really hard to predict the future?
• 35:16
  SPEAKER_00: Nobody knows what the future is going to hold.
• 35:19
  SPEAKER_00: And so, is there evidence that radon emissions occur in the lead up to an earthquake?
• 35:23
  SPEAKER_00: There very well could be.
• 35:25
  SPEAKER_00: Does it mean that any radon emissions precede a big earthquake?
• 35:30
  SPEAKER_00: Maybe or maybe not.
• 35:31
  SPEAKER_00: I mean, I think there's the the radon emissions are basically saying that the rocks are breaking, things are moving, we're we're getting close, though some of the minerals are are breaking before the rocks are and they're releasing radon.
• 35:41
  SPEAKER_00: Um, or you know, groundwater is moving about and releasing radon.
• 35:45
  SPEAKER_01: Yeah, so if I can give an analogy of that a second, like back to the stick, right?
• 35:49
  SPEAKER_01: If you think of a stick instead of rock, right?
• 35:52
  SPEAKER_01: So rock has uranium in it, and the uranium decays into radon.
• 35:57
  SPEAKER_01: And so that radon is trapped in this pore spaces between the air spaces between the mineral grains, right?
• 36:04
  SPEAKER_01: And so if you think about that as a stick, where you have radon trapped in the stick, and you bend it, bend it, bend it, that's the stick like breaking on a microscopic level.
• 36:15
  SPEAKER_01: And so it's gonna then release some of the gas, that radon.
• 36:20
  SPEAKER_01: And so if we can detect that in wells near the surface, then that's where the thought comes from that maybe radon can be used as a precursor to an erupt to uh an earthquake.
• 36:31
  SPEAKER_00: Yeah, and it and it makes it makes some sense.
• 36:33
  SPEAKER_00: That to me makes intuitive sense that it might be the lead up.
• 36:36
  SPEAKER_00: But does it mean that an earthquake is imminent?
• 36:38
  SPEAKER_00: Does it mean that it's gonna happen in one day in the future or one month in the future?
• 36:42
  SPEAKER_00: Or you know, it's hard to hard to put specific time periods on that.
• 36:46
  SPEAKER_01: So there's one other thing, this electromagnetic anomalies, that is really interesting, actually, and it's it's parallel to the radon emissions.
• 36:54
  SPEAKER_01: Except scientists are listening for these molecules, these bonds between molecules breaking.
• 37:01
  SPEAKER_01: And when that happens, electromagnetic radio waves are given off.
• 37:05
  SPEAKER_01: So if if they get this sudden flux of electromagnetic radiation within the Earth, that may signal kind of like the stick breaking again, except we're listening for something different, which is electromagnetic waves.
• 37:19
  SPEAKER_01: And so this is it's really an interesting field of study.
• 37:23
  SPEAKER_01: But the problem with all this, Jesse, is you know, science, we need lots of data.
• 37:29
  SPEAKER_01: Well, how many major earthquakes do we get, you know, a year?
• 37:33
  SPEAKER_01: We don't get many.
• 37:34
  SPEAKER_01: We don't get many major earthquakes a year.
• 37:36
  SPEAKER_01: So we love thousands of data points or tens of thousands of data points, and we're working with just a handful, right?
• 37:43
  SPEAKER_01: And so not all faults, not all earthquakes behave the same way.
• 37:47
  SPEAKER_01: Sometimes if you bend a stick, it just breaks.
• 37:50
  SPEAKER_00: That's right, that's right.
• 37:50
  SPEAKER_00: Not that you don't always have the cracks, you might not have the radon released, exactly.
• 37:54
  SPEAKER_01: Yeah, you know how many times I've done this in class, I'm bending a ruler.
• 37:57
  SPEAKER_01: I'm like, all right, everybody quiet.
• 37:58
  SPEAKER_01: Tell me when it's gonna break.
• 38:00
  SPEAKER_01: And it just breaks, and it scares me every single time because I'm a wuss.
• 38:03
  SPEAKER_00: But yeah, yeah, you are a bit of a wuss.
• 38:05
  SPEAKER_00: No, but uh, it brings up a really interesting point about the the prediction versus forecasting, is that all you need is one earthquake, one massive earthquake that has no radon emissions beforehand to kind of disprove radon as a predictive tool, right?
• 38:18
  SPEAKER_00: Or one major earthquake that doesn't really have any foreshocks, and then it kind of disproves foreshocks as a 100% effective prediction tool.
• 38:26
  SPEAKER_00: So I think the forecasting is much more interesting because you're kind of building this probabilistic model of, you know, what are the odds that this earthquake might occur without radon or without foreshocks or with foreshocks.
• 38:38
  SPEAKER_00: And so the other thing that we use in the forecasting sense are gaps in earthquakes.
• 38:42
  SPEAKER_00: So if you know there's a fault, if you know there's a subduction zone, and you look along that and you say, oh, there was an earthquake that occurred here 10 years ago, here 20 years ago, up there, there's another one 10 years ago and 15 years ago, but there's this big gap in the middle where there hasn't been one for a long time.
• 38:56
  SPEAKER_00: Probabilistically, maybe that's a place that an earthquake is more likely to occur in the near future than somewhere where a recent earthquake has already occurred.
• 39:04
  SPEAKER_00: Because as we're as you said before, there's this buildup of strain in the rocks, and then they break and release that energy.
• 39:10
  SPEAKER_00: So we're kind of looking for places where there hasn't been a major earthquake in a while, and there maybe should be.
• 39:17
  SPEAKER_01: Right.
• 39:17
  SPEAKER_01: I mean, going back to the Cascadia subduction zone, you know, you can go back 3,000 years and you can radiocarbon date these ghost forests that it were buried by tsunamis where the coastline then sunk.
• 39:30
  SPEAKER_01: And it sinks down, you know, uh one to two meters.
• 39:33
  SPEAKER_01: That's you know, like three to six feet.
• 39:36
  SPEAKER_01: That's a lot.
• 39:37
  SPEAKER_01: And it shows that this subduction zone happened, it releases a major earthquake every 500-ish years.
• 39:45
  SPEAKER_00: Yeah, exactly.
• 39:46
  SPEAKER_00: And so there's just a couple examples.
• 39:47
  SPEAKER_00: I mean, between the North and South Islands of New Zealand, there is a pretty big, what are termed, seismic gap where earthquakes have not occurred in a while, and they maybe should.
• 39:56
  SPEAKER_00: And maybe one of the more famous ones was this earthquake in uh, was it 1989 that uh in San Francisco or near San Francisco that stopped?
• 40:05
  SPEAKER_00: Yeah, yeah, that stopped the World Series baseball game, right?
• 40:08
  SPEAKER_00: Or it occurred during the World Series baseball game.
• 40:10
  SPEAKER_00: And this was in one of these seismic gaps.
• 40:12
  SPEAKER_00: It's where an earthquake had not occurred for a while.
• 40:14
  SPEAKER_00: People had looked at it and thought, oh, this might be a high chance of an earthquake occurring here.
• 40:19
  SPEAKER_00: And then lo and behold, it did occur.
• 40:21
  SPEAKER_00: So again, difficult to predict, but helps us forecast more accurately.
• 40:26
  SPEAKER_00: Yeah, so I mean, earthquakes are just totally cool.
• 40:29
  SPEAKER_00: This has been a super fun conversation.
• 40:31
  SPEAKER_00: I uh I think it's they're totally fun things.
• 40:33
  SPEAKER_00: And as you said, Chris, these like really uh they're great examples of the real power that the Earth has.
• 40:40
  SPEAKER_01: Yeah, because they're you know, they're they're fun to think about and all this.
• 40:44
  SPEAKER_01: You know, the devastation that they you know unleash is not fun.
• 40:49
  SPEAKER_01: And I I want to be you know clear that we're not saying that, but like this is the this is the draw to geology.
• 40:56
  SPEAKER_01: And you know, these long-term forecasts that we're talking about, Jesse, this is what shapes, you know, building plan.
• 41:03
  SPEAKER_00: For sure.
• 41:03
  SPEAKER_00: I mean, there it's a hugely uh what you're saying is they're basically this huge economic and societal driver of we have to think about these things because they matter a lot to everyday lives, especially in places like uh where there's tectonic plates.
• 41:17
  SPEAKER_00: But it's all about plate tectonic.
• 41:19
  SPEAKER_00: That's the beauty of it.
• 41:19
  SPEAKER_00: It's all about plate tectonics.
• 41:21
  SPEAKER_01: I I do want to say, I want to plug this in that you know, maybe short-term predictions, maybe technology is gonna change this.
• 41:28
  SPEAKER_01: Uh, here's what I'm talking about.
• 41:30
  SPEAKER_01: The P waves travel way faster than the LAN waves do.
• 41:35
  SPEAKER_01: Okay, there are three types of waves.
• 41:36
  SPEAKER_01: We have P waves, S waves, and L waves.
• 41:38
  SPEAKER_01: The P waves travel much faster.
• 41:41
  SPEAKER_01: And so they're beginning this kind of warning system using smartphones.
• 41:47
  SPEAKER_01: And so if they detect this P wave, this these massive P waves, they know it's a big earthquake, they can send an alert out, which can give people an advance warning of depending on how close they are to the epicenter, it can give them advanced warning too of seconds and maybe even minutes, you know.
• 42:05
  SPEAKER_01: But those are important.
• 42:06
  SPEAKER_01: You know, if you have 10 seconds where you can shut something down, not get in an elevator, get your butt outside, you know, things like that.
• 42:17
  SPEAKER_01: So maybe prediction is gonna shift to something like this, which is something that we never would have thought of 15 years ago.
• 42:25
  SPEAKER_00: Yeah, exactly.
• 42:25
  SPEAKER_00: Everybody's got a little, effectively a little tiny seismometer in their phone that uh that we can use for these things.
• 42:31
  SPEAKER_00: Yeah, super cool stuff.
• 42:32
  SPEAKER_00: All right, well, that's a wrap on the episode.
• 42:34
  SPEAKER_00: If you liked this episode, we just asked that you share it with somebody.
• 42:38
  SPEAKER_00: You can also find us on Instagram, Facebook, and Twitter.
• 42:41
  SPEAKER_00: We are at Planet Geocast and our email is planetgeocast at gmail.com.
• 42:46
  SPEAKER_00: Let us know if you have any questions.
• 42:47
  SPEAKER_01: Yeah, absolutely.
• 42:48
  SPEAKER_01: Okay, man, that's a wrap, Jesse.
• 42:50
  SPEAKER_01: Good talk.
• 42:51
  SPEAKER_01: Take care.