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A Recent Triple-Threat - Earthquakes Shake New Zealand (GeoShort) · PlanetGeo: The Geology Podcast

• 0:03
  SPEAKER_00: Welcome to Planet Geo, the podcast where we talk about our amazing planet, how it works, and why it matters to you.
• 0:13
  SPEAKER_01: Hey Jesse, how are you doing today?
• 0:14
  SPEAKER_00: Chris, I'm doing great.
• 0:15
  SPEAKER_00: How about you?
• 0:16
  SPEAKER_01: I'm doing awesome.
• 0:18
  SPEAKER_01: I'm ready to roll today.
• 0:19
  SPEAKER_01: But before we begin, let's do some introductions.
• 0:21
  SPEAKER_01: You are Dr.
• 0:22
  SPEAKER_01: Jesse Rymink, one of my former students at Hudsonville, and now a professor of geoscience at Penn State University.
• 0:29
  SPEAKER_00: Yeah, that's right.
• 0:30
  SPEAKER_00: And you are Chris Bullheis.
• 0:31
  SPEAKER_00: You are a high school teacher extraordinaire from the great state of Michigan.
• 0:35
  SPEAKER_00: And uh you've been teaching for a long time now, 80 years, probably teaching high school kids, something like that.
• 0:42
  SPEAKER_00: No, at least since I was in high school, which is a bit longer ago than I'd like to admit.
• 0:46
  SPEAKER_00: And this is Planet Geo, a podcast where we talk about how cool our planet is, how important the geosciences are to everybody's everyday lives.
• 0:54
  SPEAKER_00: Right on.
• 0:54
  SPEAKER_01: I mean, we think it's important.
• 0:56
  SPEAKER_01: This planet is the only one we have, and so the more we know about it, the better we are equipped to take care of it.
• 1:02
  SPEAKER_00: That is right.
• 1:03
  SPEAKER_00: So, what are we talking about today?
• 1:05
  SPEAKER_00: I'm excited.
• 1:06
  SPEAKER_01: I am too.
• 1:07
  SPEAKER_01: Today, we're gonna talk about recent earthquakes that have occurred just north of New Zealand.
• 1:13
  SPEAKER_01: And these were big earthquakes, they made headlines, and so we thought this was like an appropriate thing because it's going on right now.
• 1:22
  SPEAKER_01: And also, we recorded an episode that's gonna come out in a few weeks on earthquakes, and so this was just timely.
• 1:30
  SPEAKER_00: Yeah, that's right.
• 1:31
  SPEAKER_00: And so, you know, you out there listening to this, this came out on March 11th of 2021.
• 1:36
  SPEAKER_00: And these earthquakes that we're talking about occurred last week, March 8, 2021.
• 1:41
  SPEAKER_00: And there are three earthquakes, they occurred off the northeast coast of New Zealand, and then further north than that, in between New Zealand and American Samoa, around Tonga.
• 1:52
  SPEAKER_00: And there were three pretty big earthquakes, right, Chris?
• 1:54
  SPEAKER_00: We had some sizable ones in here, and they occurred pretty close together in time.
• 1:58
  SPEAKER_01: That's right.
• 1:58
  SPEAKER_01: They occurred within about a six-hour time frame.
• 2:01
  SPEAKER_01: So the first one that happened was a 7.3 on the Richter scale.
• 2:05
  SPEAKER_01: And that's a that's considered to be a major earthquake.
• 2:08
  SPEAKER_01: Now, this 7.3 that happened, though, that's about 900 kilometers south of where these other big earthquakes happened.
• 2:17
  SPEAKER_01: So it's believed that we think, you know, it's still recent, so we're still learning, but it's not related to the other major earthquakes that happened just within a short period of time after that.
• 2:28
  SPEAKER_00: Yeah, that's right.
• 2:28
  SPEAKER_00: And so the other two, the second earthquake was a magnitude 7.4, so slightly bigger.
• 2:34
  SPEAKER_00: And that occurred, as you said, Chris, about 900 kilometers northeast of the North Island of New Zealand.
• 2:39
  SPEAKER_00: And that was really quickly followed by a really big earthquake, an 8.1 magnitude earthquake.
• 2:46
  SPEAKER_00: So quake number two and quake number three were a little bit bigger and a lot bigger.
• 2:51
  SPEAKER_00: How much bigger was quake number three?
• 2:53
  SPEAKER_01: Yeah, well, Jesse, it seems like they're close, right?
• 2:56
  SPEAKER_01: A 7.4 and an 8.1.
• 2:57
  SPEAKER_01: That's really not that big of a difference.
• 3:00
  SPEAKER_00: Sounds sounds pretty small, right?
• 3:02
  SPEAKER_01: The 8.1 was about 11 times, almost 11 times larger than the 7.4.
• 3:07
  SPEAKER_00: Logarithmic scales always throw me off.
• 3:09
  SPEAKER_00: I must be, I'll admit that.
• 3:11
  SPEAKER_01: It's amazing though.
• 3:12
  SPEAKER_01: I mean, you know, you have the 7.4, which if this happened anywhere where people are largely concentrated, this is gonna be a major earthquake, right?
• 3:21
  SPEAKER_01: And this is just a foreshock to the 8.1.
• 3:24
  SPEAKER_00: Yeah, so these are a big deal.
• 3:26
  SPEAKER_00: I mean, you know, it occurs in the Pacific.
• 3:27
  SPEAKER_00: This is an area, we're gonna talk about the tectonics of that really briefly here.
• 3:31
  SPEAKER_00: But it occurred in an area in the middle of the ocean.
• 3:34
  SPEAKER_00: And the real danger here, because it was so far from land, the shaking on the ground was not considered to be a major threat, but tsunamis.
• 3:41
  SPEAKER_00: There was a bunch of tsunami warnings that went out all over New Zealand, many areas in the Pacific, and even to Chile and Samoa, Hawaii, and even places like Vancouver Island uh on the west coast of North America had some tsunami warnings as well.
• 3:55
  SPEAKER_00: No real big tsunamis ended up materializing, no big damaging ones, at least.
• 4:00
  SPEAKER_01: But right, but still pretty cool in terms of like what was witnessed and what was seen.
• 4:05
  SPEAKER_01: I mean, you and I both saw some footage or some some cool cell phone footage of you could see along these coastal areas the water receded from the beach very quickly, which is very typical with a tsunami that happens all the time.
• 4:18
  SPEAKER_01: And then you have this advancing wave coming right behind this.
• 4:22
  SPEAKER_01: That was really cool to see, you know.
• 4:24
  SPEAKER_01: Very cool.
• 4:24
  SPEAKER_00: Uh and it was cool to see that it wasn't, you know, super catastrophic either.
• 4:28
  SPEAKER_00: I mean, exactly.
• 4:29
  SPEAKER_00: It'd be terrible if this was a 10-foot tsunami or something.
• 4:32
  SPEAKER_01: But exactly, which which, Jesse, I want to you know, insert this right here.
• 4:35
  SPEAKER_01: You know, we're releasing this, and I think it's uh so appropriate to talk about right now.
• 4:39
  SPEAKER_01: We're releasing this on March 11, which is the 10-year anniversary of the March 11, 2011 tsunami in Japan.
• 4:46
  SPEAKER_01: And most of you listening to this will will remember this massive destruction and massive loss of life that happened as a result of this earthquake, which was on order of 30 times larger than what we're talking about here.
• 4:59
  SPEAKER_00: Yeah, no, exactly.
• 5:00
  SPEAKER_00: I mean, so so these are big earthquakes, they occur, you know, pretty frequently.
• 5:04
  SPEAKER_00: Let's get into why here a minute, Chris.
• 5:06
  SPEAKER_00: Like why are earthquakes here?
• 5:07
  SPEAKER_00: This is a really earthquake-rich area uh of the world.
• 5:11
  SPEAKER_00: And so what's going on?
• 5:12
  SPEAKER_01: What we have here is what's called a convergent boundary, where two plates are converging on each other.
• 5:17
  SPEAKER_01: And if you recall back to the plate tectonics episode, both of these plates are oceanic, and so both of them are are rather thin, they're dense, but they're converging, they're colliding on a kind of a head-on collision.
• 5:30
  SPEAKER_01: And so we have one of these plates, the denser of the two that is converging, is subducting below uh the other plate.
• 5:40
  SPEAKER_00: Yeah, and so subducting, real quick, subducting, that that's the Pacific plate, which is to the east of this convergent boundary.
• 5:46
  SPEAKER_00: That's the denser one, and subducting, this is just basically diving down into the earth beneath the other one.
• 5:51
  SPEAKER_00: And so it's kind of diving down, the other one's the overriding plate, which is the Australian plate in this instance, is overriding it, is kind of hanging out on top.
• 6:00
  SPEAKER_00: So the Pacific plate is subducting or diving down beneath the Australian plate here.
• 6:05
  SPEAKER_01: Correct.
• 6:05
  SPEAKER_01: As this plate subducts or dives down below, the rock is locked in, and so it's still diving it, but it's not slipping.
• 6:13
  SPEAKER_01: And so what you have then are the rocks are bending each other.
• 6:17
  SPEAKER_01: And so this overriding plate is being bent down and dragged into the subduction zone, creating this deep trench.
• 6:26
  SPEAKER_01: And what happened then on March 8, this 8.1 earthquake, is the force of the subduction overcame the strength of the rocks, and they suddenly slipped.
• 6:37
  SPEAKER_00: The analogy I always kind of think of is if you have, you know, you got like a nut that you're putting on a bolt or something like that, and it's rusted and it's stuck there, right?
• 6:44
  SPEAKER_00: You really need to put a lot of force on that to break that bolt off, and then it'll kind of unwind really easily.
• 6:50
  SPEAKER_00: But when you're leaning on that thing a lot, you can sometimes put a lot of weight on your little wrench before that thing breaks.
• 6:56
  SPEAKER_00: And when it breaks, it breaks pretty big.
• 6:58
  SPEAKER_00: Like you, you know, you lose it pretty quickly.
• 7:00
  SPEAKER_00: That's it's kind of stuck.
• 7:01
  SPEAKER_00: These are rocks that are bound together, and then all of a sudden they break, and that's the earthquake, and that's the movement that's going on here.
• 7:08
  SPEAKER_01: Yeah, I gotta give you credit, Jesse.
• 7:10
  SPEAKER_01: That was a really good analogy, and I'm absolutely shocked that you came up with that analogy.
• 7:15
  SPEAKER_02: Most of my analogies are terrible, but that one, that one wasn't.
• 7:18
  SPEAKER_02: What the hell just happened there?
• 7:19
  SPEAKER_02: You came up with a really good analogy, a good teaching moment.
• 7:23
  SPEAKER_02: Did that just come off the top of your head right there?
• 7:25
  SPEAKER_02: Yeah, yeah, yeah.
• 7:26
  SPEAKER_02: No, did it really?
• 7:27
  SPEAKER_02: You just came up with that right now.
• 7:28
  SPEAKER_02: That could be in a textbook.
• 7:30
  SPEAKER_00: Chris, you know, I sometimes shock myself too, to be honest with you.
• 7:32
  SPEAKER_01: Well, you should, because that's not typical Jesse Randing, right?
• 7:36
  SPEAKER_00: That's true.
• 7:37
  SPEAKER_00: I'm putting it in my in my journal.
• 7:40
  SPEAKER_00: Chris gave me a compliment for the first time in all year.
• 7:44
  SPEAKER_01: It's a backhanded compliment because I'm really shocked that you came up with a good analogy.
• 7:48
  SPEAKER_01: So I wouldn't get too excited.
• 7:50
  SPEAKER_01: But that's good.
• 7:51
  SPEAKER_01: I like it.
• 7:51
  SPEAKER_01: And that's true.
• 7:53
  SPEAKER_00: So these plates are stuck, and and then all of a sudden they break, right?
• 7:56
  SPEAKER_00: And so the the rocks are moving.
• 7:57
  SPEAKER_00: This is rock breaking, this is like a catastrophic event, and this is what causes the earthquake.
• 8:03
  SPEAKER_00: But this is like a sizable area that moved, right?
• 8:06
  SPEAKER_00: There's a lot of movement.
• 8:07
  SPEAKER_00: I was shocked by this.
• 8:08
  SPEAKER_01: Yeah, no, it is shocking.
• 8:10
  SPEAKER_01: So it's estimated that the amount of slip was up to 30 feet.
• 8:16
  SPEAKER_01: That's a lot of movement.
• 8:17
  SPEAKER_00: That's 30 feet of like one rock moving past the other rock, right?
• 8:21
  SPEAKER_00: Yeah, yeah, okay.
• 8:22
  SPEAKER_01: In in an instant in time, right?
• 8:24
  SPEAKER_01: This is fast.
• 8:25
  SPEAKER_01: This is violent, right?
• 8:27
  SPEAKER_01: Also, though, Jesse, the size of the fault that actually broke.
• 8:31
  SPEAKER_01: This fault is much larger than what actually broke.
• 8:35
  SPEAKER_01: This is just a small section that broke, but this small section is what 175 kilometers long?
• 8:41
  SPEAKER_00: Yeah, it's crazy.
• 8:43
  SPEAKER_01: And 75 kilometers wide.
• 8:46
  SPEAKER_01: I mean, that's insane.
• 8:48
  SPEAKER_00: So that measurement, you know, long by wide, that kind of is hard to picture when you're thinking of a fault in a rock breaking.
• 8:55
  SPEAKER_00: Like how how does that how do we think about that of like a an area measurement that's breaking?
• 9:01
  SPEAKER_00: Or that's yeah.
• 9:02
  SPEAKER_01: So if you take a if you take a fault that's 2,000 miles or or to it doesn't matter, 2,000 kilometers long, okay.
• 9:11
  SPEAKER_01: We're saying that 175 miles of that section broke.
• 9:17
  SPEAKER_01: But then the width part, Jesse, what about the 75 miles wide?
• 9:22
  SPEAKER_01: What's that?
• 9:23
  SPEAKER_00: Yeah, so that's you we have to think of this not just in two dimensions, like we're looking at a map, looking down on a map, but we have to think in three dimensions because there's this plate that's diving down into the crust.
• 9:33
  SPEAKER_00: So think of it like you put your palms together, like take your two palms and put them together and you know, push them together, but push your left hand forward and pull your right hand back, right?
• 9:43
  SPEAKER_00: While you're pushing them together and putting friction there.
• 9:45
  SPEAKER_00: So that's the the movement.
• 9:47
  SPEAKER_00: You're moving your hand forward 30 feet, let's say, and we're talking about the area of your hands that are in contact with each other that are moving past each other.
• 9:56
  SPEAKER_00: So then the area measurement in this analogy, your hand would be 175 kilometers tall and 75 kilometers wide.
• 10:04
  SPEAKER_00: That's the area of the fault surface that is actually slipping or moving, because this plate is going down into the earth in three dimensions, so it's actually a a planar surface, not a line on a map.
• 10:17
  SPEAKER_01: And that planar surface is 75 kilometers wide.
• 10:20
  SPEAKER_00: Yeah, which is crazy.
• 10:22
  SPEAKER_00: I was shocked by that statistic.
• 10:23
  SPEAKER_00: That's uh that's a pretty crazy one.
• 10:25
  SPEAKER_00: So there's a lot of movement, uh, a really big event, uh, obviously, with the amount of of uh of with the amount of energy that was released here, and uh, you know, created some concern for tsunamis kind of around the Pacific.
• 10:39
  SPEAKER_01: Right, just some interesting things that kind of surround this is that this was the biggest earthquake to hit in the world since uh August of 2018.
• 10:48
  SPEAKER_01: Wow, 8.1 in the world.
• 10:50
  SPEAKER_00: That's that's amazing.
• 10:52
  SPEAKER_01: And uh a lot of people got text messages and warning sirens were going off all over the place, warning people to get to higher ground.
• 11:01
  SPEAKER_01: Can you imagine getting a text?
• 11:03
  SPEAKER_01: Get out of your house, go to higher ground.
• 11:05
  SPEAKER_00: You know, that I find the technology around these earthquakes and earthquake detection, tsunami prediction, uh it's so interesting.
• 11:13
  SPEAKER_00: We we got to get somebody on here who can teach us about these things because it is so cool where they're going with this sort of early warning technology, amazing stuff.
• 11:21
  SPEAKER_01: So another interesting thing, Jesse, about this is that in the four-day period between March 6 and March 8, there were 123 earthquakes that were 5.0 to 8.1.
• 11:35
  SPEAKER_01: Wow.
• 11:36
  SPEAKER_01: In that's in this little region, right?
• 11:38
  SPEAKER_01: That that's not globally.
• 11:40
  SPEAKER_01: In a very small region.
• 11:41
  SPEAKER_01: So when you look at the map of this and they plot the earthquakes as dots, it totally filled in this area with earthquakes.
• 11:49
  SPEAKER_00: That's amazing.
• 11:50
  SPEAKER_00: So there's a lot of movement along this fault, uh, along this down.
• 11:54
  SPEAKER_00: Lots of foreshocks.
• 11:55
  SPEAKER_01: Yeah, lots of foreshocks, main event, lots of aftershocks.
• 11:59
  SPEAKER_01: You know, it's it is it's interesting because in my class every Thursday morning I have kids, my geology kids, uh group of four kids will come in and plot earthquakes, you know.
• 12:07
  SPEAKER_01: Oh, yeah.
• 12:08
  SPEAKER_01: My standard is 4.5 and above.
• 12:10
  SPEAKER_01: So they were they have been busy in a normal week.
• 12:13
  SPEAKER_01: They only plot like uh, you know, maybe 80, 85 earthquakes.
• 12:19
  SPEAKER_02: So wow, they're busy.
• 12:20
  SPEAKER_00: They're earning their kids.
• 12:21
  SPEAKER_02: They didn't get done, they had to come in the next day.
• 12:24
  SPEAKER_00: Oh, that's great.
• 12:25
  SPEAKER_00: All right, well, I think that's a wrap for this Geo Short.
• 12:28
  SPEAKER_00: So, you know, we've talked we've we have an episode on plate tectonics and how plate tectonics operate.
• 12:33
  SPEAKER_00: So if you got questions about that, you can go back and listen to previous episodes.
• 12:37
  SPEAKER_01: Hey, and we also have an upcoming episode on earthquakes, just earthquakes in general.
• 12:43
  SPEAKER_01: Yep.
• 12:43
  SPEAKER_01: What everybody should know.
• 12:44
  SPEAKER_00: Hit us up on Twitter, Instagram, Facebook, email.
• 12:47
  SPEAKER_00: We are at Planet Geocast, and our email is at planetgeocast at gmail.com.
• 12:53
  SPEAKER_00: And also, if you have any questions, you see something in the news you want explained, let us know.
• 12:58
  SPEAKER_00: We're happy to look into it and give you some explanations in a geo short or a longer episode.
• 13:03
  SPEAKER_00: All right, everybody, take care.
• 13:05
  SPEAKER_01: Take care, have a good week.