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. Thu 21 Sep 2017 06.53 EDT Last modified on Thu 5 Oct 2017 11 ... the shallow portion of the tectonic plate boundary. All rights reserved. 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. Since the plates there seem to break rules followed by plate boundaries elsewhere around the world, the local rules need to be better understood. The movement started at a spot about 46km down and spread outward along the plane of the fault from there. 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. © 2021 Condé Nast. Your California Privacy Rights | Do Not Sell My Personal Information So why did this earthquake break the rules? So, it is difficult to tell where and when these types of ruptures have occurred in the past. Nature Geoscience, 2018. 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. EMSC is reporting M7.1 at a depth of 30 km (18.6 miles).. 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. - 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. 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. The location of the 8.1 magnitude earthquake, 7 September. Mexico has made great strides in improving building codes since the 1985 earthquake. two earthquakes that struck Mexico this month. parts of Mexico City, resulting in 369 casualties. First of all, the bending of the plate downward causes stretching, just as the skin over your elbow has to stretch. Last modified on Thu 5 Oct 2017 11.52 EDT. 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 incident prompted a review of the system. The 7.1 magnitude earthquake, 19 September. 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. 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. In some ways, the region is primed for this activity because its two plates that are actively colliding. Mexico City is especially prone to severe damage because of the ground it sits on — an ancient lakebed that quivers like jello, Bellini says. 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. Mexico’s western coast is a tectonic plate boundary, where the oceanic plate collides with and dives beneath the continent. Seismologist Dr Stephen Hicks explains, Dr Hicks is a postdoctoral research fellow in seismology at the University of Southampton. Scott K. Johnson - Oct 4, 2018 2:50 pm UTC (a) (b) (c) Figure 3. 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 … Its epicenter was about 55 km (34 mi) south of the city of Puebla. The first tremor, a magnitude 8.1 earthquake, had a fairly typical epicentre location – just offshore of the coastline. Mexico City's downtown area is notoriously vulnerable to earthquakes … 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. Ars may earn compensation on sales from links on this site. Almost nine million people live in Mexico City. 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. Ad Choices. A deadly magnitude-8.2 earthquake struck the southern coast of Mexico on 7 September, killing dozens of people and injuring at least 200. - Oct 4, 2018 2:50 pm UTC. 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. And second, the sinking portion of the oceanic plate must be pulling downward pretty hard. DOI: 10.1038/s41561-018-0229-y (About DOIs). The part of the plate bend near Mexico City, where the Sept. 19 quake occurred, falls somewhere in between. He tweets as @seismo_steve, Thu 21 Sep 2017 06.53 EDT Mexico city, the country’s capital, is especially prone to earthquakes because it is situated on top of an ancient lake bed. The researchers say a couple additional factors must be at play. 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… 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. 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. 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 … 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. with 25 posters participating, including story author. Seismologists can model the process backward from the measured surface movement and figure out how the fault moved underground. © 2021 Guardian News & Media Limited or its affiliated companies. 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 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. The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of Condé Nast. Mexico is adjacent to a plate tectonic boundary. 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. This process probably caused the magnitude 8.1 earthquake. 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. Read our affiliate link policy. Mexico’s Huge 2017 Earthquake Split A Tectonic Plate In Two, Baffling Geologists. The world’s largest recorded earthquake, which struck Chile in 1960, was not the country’s most damaging earthquake. 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. 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 … Building code design response spectra in Mexico City for 1976, 1987, and 2004 in the: (a) Firm Due to the ongoing subduction of the Cocos plate, earthquakes of this nature in this location are common. The reasonably shallow depth suggested that this particular part of the Pacific Ring of Fire does not behave as we expect. 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. Within 250 km of the September 19, 2017, earthquake there … Mexico lies within two seismically active earthquake zones. Frightening tragedy struck Mexico City Tuesday on the anniversary of a devastating 1985 earthquake that killed thousands in and around the same city.. At … WIRED Media Group The magnitude-8.2 quake damaged buildings in Mexico City. 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. Occasional earthquakes within this bending, sinking plate can reflect that stretching. 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. We are often reminded about the force and devastation from earthquakes that occur around the Pacific Ring of Fire. 2017 earthquake off Mexico broke through an entire tectonic plate September 2017 saw a pair of weird earthquakes in Mexico. The two earthquakes occurred within just 11 days of each other and both were within the sinking Cocos plate. Scott K. Johnson This warping of the Cocos plate caused a large earthquake to occur close to Mexico city at a relatively shallow depth. Sign up or login to join the discussions! 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. 370 people were killed by the earthquake and related building collapses, including 228 in Mexico City, and more than 6,00… 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. The agency is reporting a depth of 51 km (31.7 miles). 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. 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… In this region, the Cocos Plate subducts beneath the North American Plate, creating a seismic and volcanic belt along the Pacific coast of Mexico. A new study led by the University of Oregon’s Diego Malgar found something even weirder, though. 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. A magnitude 8 earthquake that struck the city of Chillán in 1939 contributed to the deaths of nearly 30,000 people. Mexico has had an implementation of an earthquake early warning system for years, developed after the 1985 earthquake that devastated Mexico City.
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