Powerful Earthquake with Tsunami Threat hits MEXICO, GUATEMALA and EL SALVADOR !

[00:00:06]huge earthquake 7.4 initially now it's 7.3 shakes Mexico Guatemala El Salvador epicenter off the coast of Mexico and the aftershocks keep coming guys let's go through that first that is 6.0 5.3 5.2 5.1 5.1 5.1 5.1 5.1 5.0 zero. So I'll scroll down the list. You see many in the fives, many in the higher fours, and they keep coming. So this is big. So what actually happened and what's the damage? Epicenter is 58 km, that's roughly 36 miles off the coast of Chiapas near Puerto Mado. Uh shallow depth of approximately 15 km or 9 miles.

[00:00:51]and first aftershock less than 32 minutes later we had the magnitude 6.0 zero aftershock um that struck a little bit farther offshore and tsunami messages were immediately issued because you see the red line there that's a subduction zone and we're always worried with earthquakes like this along the Pacific Ring of Fire they can cause tsunamis so tsunami warning was issued for Mexico and Guatemala and buildings were shaking hundreds of kilometers or miles away people ran onto to the streets in Guatemala City. Um, the earthquake was felt across southern Mexico, Guatemala, and El Salvador, and reports of shaking reached as far as Mexico City. But the most revealing information came several hours later. I saw the earthquake this morning, but I decided to wait a little bit because I wanted to have more data for you to report on. um first detailed analysis of the earthquake's movement and that's interesting for us shows that this was a compressional earthquake. So the plate did not simply or the plates did not simply slide sideways. One side of the fault was forced upwards over the other.

[00:02:12]So what does that mean? That means this strong earthquake magnitude 7.3 was a reverse earthquake and most likely in my opinion a low angle thrust earthquake in the middle America subduction zone. So subduction zone that's the ones we need to worry about especially well of course we need to worry about strike slip faults like the San Andreas fault where there is unnerving new information that I'll put in the end screen because the San Andreas fault has moved silently it has slipped and what does that mean it has slipped without producing a large earthquake for us to noticed so does that increase the danger it's in the end screen the early reports that we about this earthquake thankfully remain quite a lot better than you would expect of an earthquake this large. Two people what were getting in were injured in southern Mexico. Uh one woman in Tapachula reportedly panicked and jumped approximately 4 m that is 13 ft from a building and suffered fractures. And do we blame her? No, we don't. because everyone knows what just happened in Venezuela, how these buildings were collapsing and there's lots of unreinforced old meme buildings um in Mexico as well. We've seen people jump out of buildings in Turkey only because of a magnitude 5 something earthquake because buildings there can collapse.

[00:03:40]So, she was worried. I don't blame her.

[00:03:43]Another person received minor injuries from broken glass. That's always if you run out of a high-rise with lots of glass, it can hit you. Um, in Guatemala, videos showed like dust rising from several apparent landslides in the mountain department of San Marcos. Uh, schools were closed in San Marcos. A lots of buildings, official buildings were closed. um while they were inspecting them and while the roads were inspected. Um so far um the current assessments can change um as emergency crews are still on their way to reach smaller coastal and mountain communities. We will receive more reports about potential damages. Um I the offshore location probably and let's hope so prevented a much worse disaster.

[00:04:37]Strongest shaking um occurred beneath our culprit the Pacific Ocean rather than directly below a densely populated city. But if an earthquake is strong enough that's even bad. I mean, think about Japan. 2011 Tohoko earthquake was not underneath Japan or a city was offshore, right? Um, so even though the earthquake was shallow enough to transmit powerful seismic waves into southern Mexico and Central America, and strangely, and that's the weird part here, Mexico has an early earthquake warning system, um, it did not activate across much of the region. And we've seen at the Venezuela earthquake that some earthquake warning systems at least gave people a few seconds. So Chiapas, for example, does not yet have complete coverage from the sensors that they use for this alert network. So I guess by the time that these waves have reached the sensors in Waksha, the initial energy detected there um reportedly did not exceed the threshold needed to trigger the public warning. Was that the right decision? Should they change the threshold?

[00:05:57]No, it's it's a thing, right? I mean tsunami can come, but that they can send out a warning later. um residents closest to the epicenter therefore felt the earthquake before receiving a normal earthquake alert. So to understand what broke um look at that red plate boundary line that is running parallel to the coast. I mean you already see in the blue ocean formation that there is something bigger going on. This is the middle America trench south of Mexico.

[00:06:30]The dense oceanic cocoos plate sounds so nice is moving northeast and sinking subducting beneath um the edge of North America and Central America and near Chiapas that's the interesting spot that convergence is approximately happening uh 76 millimeter or 3 in every year doesn't sound like much but that means the plates here are moving and they do not glide smoothly. um sections of the boundary become locked into friction, locked and loaded. And then the Koko's plate continues moving and stress builds across the contact that these plates have. And then the upper plate is slowly compressed and distorted and eventually a locked section can no longer hold the pressure and it breaks and we see the big earthquake. So the upper side of the fault then basically is surging upwards and towards the ocean while the Kokus plate moves beneath it. So that appears to be the mechanism behind today's earthquake. And I want you to have a close look at that beach ball diagram right now. So this circle is not a map of the ocean. I want to make that clear.

[00:07:45]It's basically a three-dimensional earthquake radiation pattern that is projected on a flat circle. And I'm trying to explain this a little bit more detail because some of you have asked me in the recent videos, well, can you explain what what are we looking at here with this beach ball? So, you see that light blue um shaded region? So it shows directions in which the first arriving Pwaves of the earthquake produced compression. If we look at the white region that shows directions where the initial motion was dilotational essentially pulling away from the source. So the boundary between blue and white forms these two curved lines.

[00:08:33]Those lines represent the two possible fault planes that are calculated from the seismic waves. So this beach ball alone cannot tell us which one physically ruptured. One represents the true fault. The other is the mathematically equivalent auxiliary plane. Aftershock locations, known plate geometry and later rupture modeling are definitely needed to choose between them. Um so the first possible plane if we look at this image had a strike of 286° a dip of 27° and a rake of 75°.

[00:09:15]If we want to translate that to plain English. So that means the fault runs approximately west northwest to eastsoutheast and it slopes gently beneath the coastline there. So a rake of 75° is close to the 90° movement expected from almost pure reverse falting. So because that plane dips only 27°, it would technically be called a thrust fault, a low angle reverse fault.

[00:09:47]So the second possible plane dips much more steeply at 64°. That is likely the auxiliary plane here. So the shallow 27 degree plane fits the known geometry of the Kokos plate that is descending subducting beneath southern Mexico. So it's currently the more logical candidate that we're dealing with. But still I want to describe it as likely rather than proven until we can map all aftershocks and calculate the full rupture surface. Um the principal axis reinforce that interpretation though the Paxis the main direction of compression is almost horizontal. The Taxis is steep plunging approximately 70°. So that is absolutely the classic pattern for a thrust earthquake. uh basically this horizontal compression that is combined horizontal compression that is combined with this vertical movement. Um and the letter T that is printed inside that blue region that you see there does not mean that blue represents tension. The P and the T symbols they show the orientation of the principal axis. So the blue and white areas show Pwave polarity. Those are two different layers of information. Um so USGS solution also says um 100% double couple.

[00:11:22]>> What does that mean? Um that means the seismic source is modeled as ordinary share movement across a fault line. So it does not resemble an explosion, underground collapse or unusual like a volcanic pressure event. This is what it tells us. It tells us this was a tectonic fault slip. So the thrust mechanism >> also explains why a tsunami warning was issued, right? A shallow offshore thrust earthquake can vertically lift or lower a broad section of the ocean floor of the seabed. And that is the dangerous thing. when the seafloor moves vertically um it can displace a lot of water above it and then it can launch these tsunami waves. So initial estimates that we have here suggested possible waves of between like 30 cm and one one meter that is 1 to 3 feet above normal tide levels along parts of Mexico and Guatemala. Um, Mexico's Navy later said the expected change would probably remain below half a meter, but advised people to stay away from the beaches while the monitoring continued. Of course, right now the tsunami alert has been cancelled. Um, instruments and coastal observations did not show changes that would have been large enough to represent a significant threat. So, that's a good thing. No tsunami, by the way, was initially also expected for like California, Oregon, Washington, Alaska, or Canada. Um, and and guys, I want to say if we're dealing with a thrust earthquake, that does not automatically produce a destructive tsunami as we've just seen today. Um, the magnitude is only one factor that contributes to that that tsunami creation. The outcome very much depends also on how much the fault slipped. How much did it slip? The size of the rupture area. Was it a long stretch or smaller? Um and also whether the movement was able to reach close to the seafloor and how much of the actual movement was actually vertical. The vertical I said it's the most important.

[00:13:38]So um today's earthquake had definitely the correct mechanism um to generate a tsunami but thankfully the actual ocean displacement was apparently too limited to produce a dangerous wave. So that at least is good. Um the aftershock sequence uh on the contrary is intense.

[00:14:00]We have to say that um at we're have so many aftershocks um in the higher magnitudes between 4.9 and 6.0 um we were reaching more than 100 aftershocks including several earthquakes I show you above magnitude 5 um and and that I want to point that out that first magnitude 6.0 zero aftershocks alone would have been capable of producing strong additional shaking near the coast and aftershocks are expected to continue um because the earthquake definitely has changed stress um in the surrounding areas of that section that has ruptured right now. So yes, parts of the fault were relieved from the 7.3, but neighboring sections uh have probably received additional stress because of that. Right? So now the crust must adjust to that new arrangement. So that does not mean that we have automatically a larger earthquake coming. Most aftershocks are smaller than the main shocks and their frequency normally decreases with time.

[00:15:10]I mean we have seen the 7.2 in Venezuela and 39 seconds later even bigger one 7.5 I don't expect this to happen here but another strong aftershock remains possible and already weakened slopes or buildings can be more vulnerable if we have a the next major shake. So, um, there's one crucial difference that I want to point out to you that came to my mind right away between today's earthquake and maybe you remember the devastating 2017 magnitude 8.2 Chiapas earthquake because there they already had one 2017 event was an intermediate depth normal fault earthquake inside the descending Kokus plate. So the slap was bending and breaking internally. Today's earthquake was a lot more shallow and it moved basically >> in the opposite sense compression and reverse falting. So its depth and mechanism are more consistent with movement on or very close to the actual contact between the plates not intraplate. So, but both earthquakes occurred in the same broad region. But I want to point that out. They represent different parts of the subduction system and they're failing or they were failing in completely different ways. So, this is not a repetition. Um, the next size of evidence will definitely come from the aftershocks. And if they form a shallow plane that is dipping gently beneath the coast, for example, that will support this rupture of the plate interface. But if they line up along the steeper plane, um we might instead be looking at a separate reverse fault cutting through one of the plates. So GPS stations and tide goss may also reveal whether parts of the coastline uh are permanently lifted through that or maybe lowered or maybe they have shifted sideways. We have seen that Venezuela has shifted quite significantly. I made a video about this. Kamchatka has shifted after the mega thrust earthquake last year. So, but what we already see that moment tensor that beach ball, it has a message that it gives us and it's a very serious message. The Kokos plate and that overriding margin did not pull apart.

[00:17:55]They compressed like a shallow section of this major subduction system has suddenly moved, created this earthquake with a mechanism capable of producing the region's largest earthquakes. So let's hope that today's main shock has ended, but we will see what the fault beneath Tiapas is doing while it is adjusting. I'll be on the pulse of this for you guys. Um, check out the videos here in the end screen. If you want to know what the San Andreas fault is doing, you really should watch that. And to my subscribers, if you haven't watched what's going on in Texas, you have to see this. It's absolutely crazy.

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