Geology. The earthquake’s epicentre was unusually located, in central Mexico. Read our affiliate link policy. It occurred at the Cocos Plate rather than at the boundary with the North American plate. As you bend it, the skin stretches around the outside of your elbow, but relaxes on the inside as your forearm and bicep come together. The quake had a magnitude of 8.1 and struck about 60 miles, or 96 kilometers, southwest of Pijijiapan, … On Tuesday, a deadly quake reverberated along the boundary between the Cocos and the North American plate as the southern-most plate slid beneath its … All rights reserved. Whilst geophysicists continue to try and unravel the factors that drive these deep earthquakes inside tectonic plates, the key for people living in earthquake-prone areas is to prepare. Last modified on Thu 5 Oct 2017 11.52 EDT. Protecting people during earthquakes is all about minimizing surprises, so while they are always interesting, we want to limit the earthquakes that make you go "Huh.". As the Cocos plate plunges deeper into the bowels of our planet, fractures inside the slab bend and pull apart. The explanation here is that as the oceanic plate disappears beneath the continent, it sinks downward into the mantle. According to the U.S. Geological Survey, the epicenter of the earthquake took place in Raboso, Mexico—about 75 miles south of the capital city. The magnitude-8.0 quake occurred at 7:18 am.Many sources place the location of the epicentre in the state of Michoacán—approximately 200 miles (320 km) from Mexico City—in a region of tectonic tension between the North American Plate and the subducting Cocos Plate. The M=6.6 earthquake ruptured at 67 km (40 mi) deep along the plate boundary formed offshore of Central America on 1 February 2019. The two earthquakes occurred within just 11 days of each other and both were within the sinking Cocos plate. Similarly, faults moving because they’re being pulled apart on the outside of the bend should be clamped together on the inside of the bend. Scott K. Johnson - Oct 4, 2018 2:50 pm UTC And second, the sinking portion of the oceanic plate must be pulling downward pretty hard. We know very little about the geometry of these faults within plates, how they behave from one earthquake to another, and the frictional properties of the rocks that fracture. A magnitude 8.2 on September 8 just offshore the state of Chiapas was followed by a magnitude 7.1 on September 19—this time much closer to Mexico City, causing considerable destruction there. In this region, the Cocos Plate subducts beneath the North American Plate, creating a seismic and volcanic belt along the Pacific coast of Mexico. This process probably caused the magnitude 8.1 earthquake. Rescuers work in the rubble after a magnitude 7.1 earthquake struck on September 19, 2017 in Mexico City, Mexico ... of Mexico, and the North American tectonic plate. In this region, the oceanic Cocos plate dives beneath the North America and Caribbean plates to form the Middle America Trench, a subduction zone with a rich history of very large M>8 earthquakes (Ye et al., 2013). How Mexico City's 2017 "Bending" Earthquake Could Happen Again. (a) (b) (c) Figure 3. In this case the rupture took place inside a plate itself, not at the locked zone between plates. Join the Ars Orbital Transmission mailing list to get weekly updates delivered to your inbox. DOI: 10.1038/s41561-018-0229-y (About DOIs). The location of the 8.1 magnitude earthquake, 7 September. Ars may earn compensation on sales from links on this site. The shaking recorded at seismometers can be used to pinpoint the location of an earthquake, but more detail can be extracted if you have things like GPS sensors in the area detecting ground movement. Tectonic setting. That’s what Malgar and his colleagues did here, producing estimates of the portion of the fault plane that slipped and how much it moved. - Mexico City honors earthquake victims in Day of the Dead parade ... "It is not one single sharp plate boundary, but there are numerous fracture zones," Dahm explains. Mexico is adjacent to a plate tectonic boundary. A magnitude 8 earthquake that struck the city of Chillán in 1939 contributed to the deaths of nearly 30,000 people. Mexico’s most recent earthquakes did not directly involve two tectonic plates clashing, as is commonly the case. People from as far away as Mexico City felt the shaking from this deep quake, many of whom evacuated their buildings, spilling out into plazas and open space… A new study led by the University of Oregon’s Diego Malgar found something even weirder, though. Your California Privacy Rights | Do Not Sell My Personal Information CNMN Collection This earthquake occurred on the anniversary of the devastating 1985 M 8.0 Michoacan earthquake, which caused extensive damage to Mexico City and the surrounding region. 2017 earthquake off Mexico broke through an entire tectonic plate September 2017 saw a pair of weird earthquakes in Mexico. Both September earthquakes were the result of stretching, however, which is almost as much of a head-scratcher as finding that part of your car’s engine was pulled apart during a head-on crash. Tuesday’s earthquake took place on the anniversary of a devastating earthquake that killed thousands in Mexico City in 1985. Its depth was puzzling: only 50km down, but the faulting mechanism implied rupture inside a plate. Since the plates there seem to break rules followed by plate boundaries elsewhere around the world, the local rules need to be better understood. Let’s not pull on your wrist hard enough to stretch your elbow joint, but doing so would counteract the squeezing on the inside of your elbow as it bends. 370 people were killed by the earthquake and related building collapses, including 228 in Mexico City, and more than 6,00… Ad Choices. Beginning just south of Mexico City, the alignment of hills shifted, reflecting a zone where plate subduction flattened. Preliminary calculations show that because the earthquakes occurred more than 600km from each other, the first rupture would have only increased stress on Tuesday’s ruptured fault by a tiny amount. A magnitude 8.2 earthquake that struck southern Mexico on Sept. 7, 2017, not only occurred where existing earthquake modeling said it shouldn't happen, it also broke a tectonic plate… This quake in Chile occurred at a similar depth, with a similar faulting mechanism, and beneath a highly populated area in a sedimentary basin, similar to the two recent Mexico earthquakes. Mexico’s Huge 2017 Earthquake Split A Tectonic Plate In Two, Baffling Geologists. Although these types of earthquake are rare, the amount of damage caused by them is not globally unprecedented. Seismologist Dr Stephen Hicks explains, Dr Hicks is a postdoctoral research fellow in seismology at the University of Southampton. © 2021 Condé Nast. However, as this week’s events have shown, more work is still to be done in retro-fitting older buildings to bring them up to modern standards. The researchers say a couple additional factors must be at play. Scott K. Johnson In some ways, the region is primed for this activity because its two plates that are actively colliding. Mexico’s western coast is a tectonic plate boundary, where the oceanic plate collides with and dives beneath the continent. Based on previous scientific studies, the slab begins to behave as normal at shallow depths, but then it suddenly flattens for a distance of around 200 km, before again plunging into the deep Earth. with 25 posters participating, including story author. Second, the sinking plate pulls downward as it “hangs” from the part of the plate that is still up at the surface—another stretching force. This warping of the Cocos plate caused a large earthquake to occur close to Mexico city at a relatively shallow depth. The incident prompted a review of the system. Occasional earthquakes within this bending, sinking plate can reflect that stretching. We have seen such quakes striking Indonesia, Chile and Japan over the past 15 years. The 2017 Puebla earthquake struck at 13:14 CDT (18:14 UTC) on 19 September 2017 with an estimated magnitude of Mw7.1 and strong shaking for about 20 seconds. WIRED Media Group The magnitude-8.2 quake damaged buildings in Mexico City. subduction zone, Mexico City is subjected to both interplate (epicenter at plate boundary) and intraplate (epicenter inside the continental plate) earthquakes. The tectonic plate boundary known as a subduction zone, where an oceanic plate dives down beneath another plate. Due to the ongoing subduction of the Cocos plate, earthquakes of this nature in this location are common. Mexico, too, lies on the Ring of Fire and is no stranger to such quakes: the 1985 8.0 magnitude earthquake that devastated Mexico City was a fairly typical “thrust” earthquake that ruptured the shallow portion of the tectonic plate boundary. The world’s largest recorded earthquake, which struck Chile in 1960, was not the country’s most damaging earthquake. The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of Condé Nast. The Baja California peninsula lies near the boundary of the Pacific Plate and the North American Plate, while southern Mexico lies just north of the boundary between the North American Plate and the Cocos and Rivera tectonic plates. The epicentre of the quake was 120 km southeast of Mexico City, 12 km southeast of the city of Axochiapan, Morelos on the boundary between Puebla and Guerrero. Vertically, the portion of the fault that slipped starts at the top of the oceanic plate—about 15km below the Earth’s surface—and continues all the way down to a depth of about 80km, which is roughly the bottom of the plate. The system is widely reported to have detected the impending shaking near the epicenter and provided invaluable seconds to take appropriate actions in areas further afield. On 6 September, several earthquake alarms in Mexico City were mistakenly activated and this led to the evacuation of buildings. two earthquakes that struck Mexico this month. This earthquake comes just 12 days after major M8.1 quake near the coast of Chiapas, Mexico and on the anniversary of the devastating 1985 M8.0 … That means that earthquakes along that boundary are typically the result of compressive force that squeezes rock to slide up the plane of the fault. So why did this earthquake break the rules? EERI Earthquake Reconnaissance Team Report: M7.1 Puebla, Mexico Earthquake on September 19, 2017 Page 4 Figure 2. Not only do these earthquakes produce dangerous shaking, but if they occur close enough to the point on the seafloor where the two plates meet, they can push up seawater and create a tsunami wave. We are often reminded about the force and devastation from earthquakes that occur around the Pacific Ring of Fire. Mexico City was given 10-15 seconds of warning during the magnitude 7.1 earthquake. Its epicenter was about 55 km (34 mi) south of the city of Puebla. Mexico lies within two seismically active earthquake zones. Mexico City is especially prone to severe damage because of the ground it sits on — an ancient lakebed that quivers like jello, Bellini says. Mexico is located on one of Earth's subduction zones, where the ocean floor of the Cocos tectonic plate is forcing its way down ("subducting") beneath the continental edge of the North American plate. The first tremor, a magnitude 8.1 earthquake, had a fairly typical epicentre location – just offshore of the coastline. The titanic collision of two tectonic plates, which firmly lock together and accrue strain over tens to hundreds of years, eventually releases this pent-up energy as a large earthquake. Mexico has had an implementation of an earthquake early warning system for years, developed after the 1985 earthquake that devastated Mexico City. The part of the plate bend near Mexico City, where the Sept. 19 quake occurred, falls somewhere in between. You must login or create an account to comment. EMSC is reporting M7.1 at a depth of 30 km (18.6 miles).. The equations for the physics of all this tell us that the fault movement should have been restricted to the upper half of the oceanic plate. Mexico City’s potent 2017 earthquake was a rare ‘bending’ quake – and it could happen again March 12, 2018 10.34am EDT • Updated September 19, 2018 3.48pm EDT Soil zones from the 2004 Mexico City building code. The 1985 earthquake was the more typical great earthquake that breaks the boundary between the plates, and caused great devastation in Mexico City despite being more than 100 … Nature Geoscience, 2018. If building structures are improved, early warning systems continue to be implemented and the public is educated about what action to take to protect themselves when the warning sirens sound, then cities located in earthquake-prone areas will be making good progress to better protect their infrastructure and people during future quakes. So there is no immediate indication that these two quakes are directly linked. The 8.2 magnitude earthquake that brought devastation and 98 deaths to southern Mexico in September 2017 was even more extreme than initially thought — it split the tectonic plate … Mexico has made great strides in improving building codes since the 1985 earthquake. A powerful earthquake struck off the coast of Mexico early this morning and was felt as far away as Mexico City, reports said, the New York Times reports. Available for everyone, funded by readers. Following its head-on collision with the North American plate (to which Mexico belongs), the Cocos plate (a piece of crust beneath the Pacific Ocean) gradually sinks deeper into the earth under its own weight. parts of Mexico City, resulting in 369 casualties. Building code design response spectra in Mexico City for 1976, 1987, and 2004 in the: (a) Firm The 2017 earthquake likely was the result of “bending stresses occurring at the transition from flat-slab subduction to steeply dipping subduction,” the researchers concluded. These systems analyse recordings of the weak and faster-travelling seismic wave arrivals (P-waves) to try to estimate when the slower travelling, but more damaging waves (S-waves) will arrive and how strong they will be. The 1985 earthquake was the more typical great earthquake that breaks the boundary between the plates, and caused great devastation in Mexico City despite being more than 100 miles distant. Almost nine million people live in Mexico City. Mexico, was one of the first countries, along with Japan, to develop an earthquake early-warning system. Mexico city, the country’s capital, is especially prone to earthquakes because it is situated on top of an ancient lake bed. The results show that a 150km-long section of the fault slipped three meters or so. In June 1999, a M 7.0 at 70 km depth, just to the southeast of the September 19, 2017 earthquake, caused 14 fatalities, around 200 injuries, and considerable damage in the city … A deadly magnitude-8.2 earthquake struck the southern coast of Mexico on 7 September, killing dozens of people and injuring at least 200. The M8.0 1985 Michoacan earthquake was an interplate event where the seismic waves traveled more than 350 km before reaching Mexico City. - Oct 4, 2018 2:50 pm UTC. Tuesday’s earthquake occurred near this interface along the tectonic plate boundary known as the Middle American Trench, just offshore at a shallow depth 13.7 miles (22.6 kilometers) according to SSN. A magnitude 8.2 on September 8 just offshore the state of Chiapas was followed by a magnitude 7.1 on September 19—this time much closer to Mexico City, causing considerable destruction there. Explaining this little puzzle has practical implications. The earthquake caused damage in the Mexican states of Puebla and Morelos and in the Greater Mexico City area, including the collapse of more than 40 buildings. All rights reserved. The two earthquakes that struck Mexico this month were different. Understanding Mexico’s hazards requires understanding what these oddball earthquakes are capable of. The reasonably shallow depth suggested that this particular part of the Pacific Ring of Fire does not behave as we expect. Use of and/or registration on any portion of this site constitutes acceptance of our User Agreement (updated 1/1/20) and Privacy Policy and Cookie Statement (updated 1/1/20) and Ars Technica Addendum (effective 8/21/2018). September 2017 saw a pair of weird earthquakes in Mexico. This is partly because hotter temperatures at greater depths make the rock less brittle and partly because the inside of the bend in the plate should be feeling squeezing rather than stretching. The Gulf of Tehuantepec lies above the convergent boundary where the Cocos Plate is being subducted below the North American Plate at a rate of 6.4 cm/yr (2.5 in/yr).. Background. Russell Pysklywec: An earthquake occurs when there's release of energy with slip or fracture of rock within the Earth, with the plate motions providing a massive amount of energy. If the 8.1 tremor raised eyebrows, then Tuesday’s magnitude 7.1 earthquake left everyone stunned. First, seawater percolating down into the cracks that formed as the oceanic plate first bent to head beneath the continent could have cooled the rock and reacted with minerals, making the rock more brittle than it would be otherwise. Thu 21 Sep 2017 06.53 EDT Last modified on Thu 5 Oct 2017 11 ... the shallow portion of the tectonic plate boundary. So, it is difficult to tell where and when these types of ruptures have occurred in the past. The combination of the earthquake’s location, radiated seismic energy, and the very foundations of Mexico City – thick, loose soils that behave like a bowl of jelly during earthquakes – created the conditions for devastation. Frightening tragedy struck Mexico City Tuesday on the anniversary of a devastating 1985 earthquake that killed thousands in and around the same city.. At … Look around to make sure no one’s watching, and then stare at your elbow. Seismologists can model the process backward from the measured surface movement and figure out how the fault moved underground. Mexico City's downtown area is notoriously vulnerable to earthquakes … While the two earthquakes were not connected, they were the same type of earthquake, which is unusual in the region. This final kink in the Cocos plate is located right where the 7.1 earthquake happened, and directly beneath the Valley of Mexico, in which Mexico City is located. Yet its depth, pinpointed to 70km down, raised eyebrows. The movement started at a spot about 46km down and spread outward along the plane of the fault from there. It occurred only 11 days after the M w 8.2 September 8, 2017 Mexico Earthquake, located further southeast, offshore Chiapas, Mexico. The agency is reporting a depth of 51 km (31.7 miles). First of all, the bending of the plate downward causes stretching, just as the skin over your elbow has to stretch. The 7.1 magnitude earthquake, 19 September. A major earthquake registered by the USGS as M7.1 hit Puebla, Mexico at 18:14 UTC (13:14 local time) on September 19, 2017. He tweets as @seismo_steve, Thu 21 Sep 2017 06.53 EDT 2017 earthquake off Mexico broke through an entire tectonic plate Magnitude 8.2 in Mexico involved more fault movement than thought possible. © 2021 Guardian News & Media Limited or its affiliated companies. Within 250 km of the September 19, 2017, earthquake there … Counter to what we thought possible, the fault seems to have broken clean through the entire tectonic plate. Our detailed earthquake records from instruments only go back a hundred years or so, and these deep quakes do not leave any noticeable imprint in the geological record from surface ruptures or large tsunamis. Sign up or login to join the discussions!

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