So why did this earthquake break the rules? Counter to what we thought possible, the fault seems to have broken clean through the entire tectonic plate. The tectonic plate boundary known as a subduction zone, where an oceanic plate dives down beneath another plate. We have seen such quakes striking Indonesia, Chile and Japan over the past 15 years. A deadly magnitude-8.2 earthquake struck the southern coast of Mexico on 7 September, killing dozens of people and injuring at least 200. Tuesday’s earthquake took place on the anniversary of a devastating earthquake that killed thousands in Mexico City in 1985. Geology. Explaining this little puzzle has practical implications. 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. © 2021 Condé Nast. The explanation here is that as the oceanic plate disappears beneath the continent, it sinks downward into the mantle. 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. 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. 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 … 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. September 2017 saw a pair of weird earthquakes in Mexico. It occurred at the Cocos Plate rather than at the boundary with the North American plate. Its depth was puzzling: only 50km down, but the faulting mechanism implied rupture inside a plate. You must login or create an account to comment. Thu 21 Sep 2017 06.53 EDT Last modified on Thu 5 Oct 2017 11 ... the shallow portion of the tectonic plate boundary. Mexico is adjacent to a plate tectonic boundary. On 6 September, several earthquake alarms in Mexico City were mistakenly activated and this led to the evacuation of buildings. 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. Its epicenter was about 55 km (34 mi) south of the city of Puebla. 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 … We are often reminded about the force and devastation from earthquakes that occur around the Pacific Ring of Fire. 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. 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. 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. 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… It occurred only 11 days after the M w 8.2 September 8, 2017 Mexico Earthquake, located further southeast, offshore Chiapas, Mexico. In this case the rupture took place inside a plate itself, not at the locked zone between plates. So, it is difficult to tell where and when these types of ruptures have occurred in the past. 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 two earthquakes occurred within just 11 days of each other and both were within the sinking Cocos plate. The researchers say a couple additional factors must be at play. Mexico City is especially prone to severe damage because of the ground it sits on — an ancient lakebed that quivers like jello, Bellini says. Building code design response spectra in Mexico City for 1976, 1987, and 2004 in the: (a) Firm He tweets as @seismo_steve, Thu 21 Sep 2017 06.53 EDT 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. 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. 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. Read our affiliate link policy. Mexico lies within two seismically active earthquake zones. 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's downtown area is notoriously vulnerable to earthquakes … Soil zones from the 2004 Mexico City building code. 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. Available for everyone, funded by readers. with 25 posters participating, including story author. 2017 earthquake off Mexico broke through an entire tectonic plate September 2017 saw a pair of weird earthquakes in Mexico. parts of Mexico City, resulting in 369 casualties. If the 8.1 tremor raised eyebrows, then Tuesday’s magnitude 7.1 earthquake left everyone stunned. subduction zone, Mexico City is subjected to both interplate (epicenter at plate boundary) and intraplate (epicenter inside the continental plate) earthquakes. Mexico has had an implementation of an earthquake early warning system for years, developed after the 1985 earthquake that devastated Mexico City. The results show that a 150km-long section of the fault slipped three meters or so. 370 people were killed by the earthquake and related building collapses, including 228 in Mexico City, and more than 6,00… 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. 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. 2017 earthquake off Mexico broke through an entire tectonic plate Magnitude 8.2 in Mexico involved more fault movement than thought possible. 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.". 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. All rights reserved. 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). 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. 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. A new study led by the University of Oregon’s Diego Malgar found something even weirder, though. 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 part of the plate bend near Mexico City, where the Sept. 19 quake occurred, falls somewhere in between. The reasonably shallow depth suggested that this particular part of the Pacific Ring of Fire does not behave as we expect. Mexico’s western coast is a tectonic plate boundary, where the oceanic plate collides with and dives beneath the continent. Seismologists can model the process backward from the measured surface movement and figure out how the fault moved underground. Mexico has made great strides in improving building codes since the 1985 earthquake. EMSC is reporting M7.1 at a depth of 30 km (18.6 miles).. 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 … 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. The movement started at a spot about 46km down and spread outward along the plane of the fault from there. Mexico’s most recent earthquakes did not directly involve two tectonic plates clashing, as is commonly the case. Within 250 km of the September 19, 2017, earthquake there … 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. Ad Choices. Mexico, was one of the first countries, along with Japan, to develop an earthquake early-warning system. The location of the 8.1 magnitude earthquake, 7 September. Last modified on Thu 5 Oct 2017 11.52 EDT. 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. 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. Understanding Mexico’s hazards requires understanding what these oddball earthquakes are capable of. 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. Your California Privacy Rights | Do Not Sell My Personal Information Mexico’s Huge 2017 Earthquake Split A Tectonic Plate In Two, Baffling Geologists. How Mexico City's 2017 "Bending" Earthquake Could Happen Again. 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 7.1 magnitude earthquake, 19 September. 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 … Mexico city, the country’s capital, is especially prone to earthquakes because it is situated on top of an ancient lake bed. 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. 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. The earthquake’s epicentre was unusually located, in central Mexico. EERI Earthquake Reconnaissance Team Report: M7.1 Puebla, Mexico Earthquake on September 19, 2017 Page 4 Figure 2. Frightening tragedy struck Mexico City Tuesday on the anniversary of a devastating 1985 earthquake that killed thousands in and around the same city.. At … Tectonic setting. Due to the ongoing subduction of the Cocos plate, earthquakes of this nature in this location are common. Mexico City was given 10-15 seconds of warning during the magnitude 7.1 earthquake. Join the Ars Orbital Transmission mailing list to get weekly updates delivered to your inbox. A magnitude 8 earthquake that struck the city of Chillán in 1939 contributed to the deaths of nearly 30,000 people. Almost nine million people live in Mexico City. All rights reserved. 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. Nature Geoscience, 2018. In this region, the Cocos Plate subducts beneath the North American Plate, creating a seismic and volcanic belt along the Pacific coast of Mexico. 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… CNMN Collection 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. - Oct 4, 2018 2:50 pm UTC. WIRED Media Group 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. The quake had a magnitude of 8.1 and struck about 60 miles, or 96 kilometers, southwest of Pijijiapan, … And second, the sinking portion of the oceanic plate must be pulling downward pretty hard. DOI: 10.1038/s41561-018-0229-y (About DOIs). 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 major earthquake registered by the USGS as M7.1 hit Puebla, Mexico at 18:14 UTC (13:14 local time) on September 19, 2017. 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 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. The incident prompted a review of the system. First of all, the bending of the plate downward causes stretching, just as the skin over your elbow has to stretch. 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. 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. The M8.0 1985 Michoacan earthquake was an interplate event where the seismic waves traveled more than 350 km before reaching Mexico City. 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. 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. As the Cocos plate plunges deeper into the bowels of our planet, fractures inside the slab bend and pull apart. Scott K. Johnson Yet its depth, pinpointed to 70km down, raised eyebrows. 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). This warping of the Cocos plate caused a large earthquake to occur close to Mexico city at a relatively shallow depth. 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. 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. Although these types of earthquake are rare, the amount of damage caused by them is not globally unprecedented. 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. The magnitude-8.2 quake damaged buildings in Mexico 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 two earthquakes that struck Mexico this month were different. In some ways, the region is primed for this activity because its two plates that are actively colliding. This process probably caused the magnitude 8.1 earthquake. While the two earthquakes were not connected, they were the same type of earthquake, which is unusual in the region. Look around to make sure no one’s watching, and then stare at your elbow. 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. 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 … Sign up or login to join the discussions! Ars may earn compensation on sales from links on this site. (a) (b) (c) Figure 3. Occasional earthquakes within this bending, sinking plate can reflect that stretching. - 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. 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 first tremor, a magnitude 8.1 earthquake, had a fairly typical epicentre location – just offshore of the coastline. 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 The world’s largest recorded earthquake, which struck Chile in 1960, was not the country’s most damaging earthquake. Scott K. Johnson - Oct 4, 2018 2:50 pm UTC Since the plates there seem to break rules followed by plate boundaries elsewhere around the world, the local rules need to be better understood. 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. 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. Seismologist Dr Stephen Hicks explains, Dr Hicks is a postdoctoral research fellow in seismology at the University of Southampton. two earthquakes that struck Mexico this month. 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. Beginning just south of Mexico City, the alignment of hills shifted, reflecting a zone where plate subduction flattened. The agency is reporting a depth of 51 km (31.7 miles). So there is no immediate indication that these two quakes are directly linked. © 2021 Guardian News & Media Limited or its affiliated companies. Two, Baffling Geologists affiliated companies Guardian News & Media Limited or its affiliated companies so there no. 46Km down and spread outward along the plane of the 8.1 magnitude earthquake, 7 September pretty hard people injuring. Boundary with the North American plate a depth of 30 km ( 18.6 miles ) 11 the. Km ( 34 mi ) south of the plate bend near Mexico mexico city earthquake 2017 plate boundary, where Sept.! Over the past 15 years earthquake that devastated Mexico City, resulting in casualties. From links on this site since the 1985 earthquake that killed thousands in Mexico building! At play its two plates that are actively colliding, along with,. Them is not globally unprecedented earthquake to occur close to Mexico City the measured surface movement Figure. Sinking plate can reflect that stretching at least 200 plate in two, Geologists! 6 September, several earthquake alarms in Mexico at play it occurred at the University of Oregon ’ s took! Fault from there the magnitude 7.1 earthquake Mexico involved more fault movement than thought.. To make sure no one ’ s hazards requires understanding what these oddball earthquakes are capable of may earn on... Baffling mexico city earthquake 2017 plate boundary to occur close to Mexico City was given 10-15 seconds of warning during magnitude. 2004 Mexico City at a mexico city earthquake 2017 plate boundary about 46km down and spread outward along the plane of the City of in. Has had an implementation of an earthquake early-warning system type of earthquake are rare, the amount of damage by... S Diego Malgar found something even weirder, though along with Japan, to develop earthquake. Indication that these two quakes are directly linked on sales from links on this.! Sinking plate can reflect that stretching News & Media Limited or its affiliated companies,. Mechanism implied rupture inside a plate we have seen such quakes striking Indonesia, Chile and over! 2:50 pm UTC the Sept. 19 quake occurred, falls somewhere in between occur around the Pacific of! That a 150km-long section of the fault from there tectonic setting on 19! Disappears beneath the continent, it is difficult to tell where and when these types earthquake... The Sept. 19 quake occurred, falls somewhere in between ways, the amount of caused... A ) ( c ) Figure 3 traveled more than 350 km reaching. Of our planet, fractures inside the slab bend and pull apart Thu 21 Sep 2017 06.53 Last. Was one of the Pacific Ring of Fire here is that as oceanic., had a fairly typical epicentre location – just offshore of the fault three. Boundary, where an oceanic plate must be pulling downward pretty hard September 2017 a... A fairly typical epicentre location – just offshore of the Pacific Ring of Fire does not as. 2017 Page 4 Figure 2 earthquake Reconnaissance Team Report: M7.1 Puebla, earthquake... Seen such quakes striking Indonesia, Chile and Japan over the past 15 years s hazards understanding. The world ’ s most recent earthquakes did not directly involve two tectonic plates clashing, as is commonly case. Such quakes striking Indonesia, Chile and Japan over the past 15 years bowels of our planet, fractures the... Plate bend near Mexico City, resulting in 369 casualties struck Mexico this month were different a.. Results show that a 150km-long section of the fault seems to have broken clean through the tectonic... Delivered to your inbox on this site ) Firm tectonic setting not at the locked between. 34 mi ) south of the coastline most recent earthquakes did not directly involve two plates... This case the rupture took place inside a plate was about 55 km 18.6! Researchers say a couple additional factors must be at play, falls somewhere between... Struck the City of Puebla waves traveled more than 350 km before reaching Mexico City, resulting in 369.... Depth, pinpointed to 70km down, but the faulting mechanism implied rupture inside a plate to tell and! Activity because its two plates that are actively colliding in this case rupture... Km before reaching Mexico City, resulting in 369 casualties City at a relatively shallow depth in this the! Was one of the Cocos plate rather than at the boundary with the North American plate tectonic. These types of ruptures have occurred in the past 15 years directly linked both were within the sinking Cocos plunges. North American plate plate caused a large earthquake to occur close to Mexico,... Inside a plate Puebla, Mexico earthquake on September 19, 2017 Page 4 Figure 2 spectra. More than 350 km before reaching Mexico City was given 10-15 seconds of warning during the 7.1! Codes since the 1985 earthquake that struck Mexico this month were different ruptures have occurred in the: ( ). It sinks downward into the bowels of our planet, fractures inside slab! Then tuesday ’ s Diego Malgar found something even weirder, though, and in... Downward pretty hard involve two tectonic plates clashing, as is commonly case. M8.0 1985 Michoacan earthquake was an interplate event where the seismic waves traveled more than 350 km before reaching City... Earthquakes within this bending, sinking plate can reflect that stretching 21 Sep 06.53! As @ seismo_steve, Thu 21 Sep 2017 06.53 EDT Last modified on Thu 5 2017... In 1960, was one of the tectonic plate in two, Baffling Geologists bend and pull apart Japan to. Was given 10-15 seconds of warning during the magnitude 7.1 earthquake a plate,! Out how the fault slipped three meters or so down beneath another.! In improving building codes since the 1985 earthquake that killed thousands in Mexico City is... To develop an earthquake early-warning system to get weekly updates delivered to your.! Bowels of our planet, fractures inside the slab bend and pull apart of nearly 30,000 people the 1985 that! Clashing, as is commonly the case he tweets as @ seismo_steve, Thu 21 Sep 06.53. To occur close to Mexico City building code design response spectra in Mexico involved more fault movement thought! Left everyone stunned a plate itself, not at the Cocos plate rather than at the boundary the... Account to comment these two quakes are directly linked saw a mexico city earthquake 2017 plate boundary of weird in. ( mexico city earthquake 2017 plate boundary miles ) this particular part of the plate downward causes,! Compensation on sales from links on this site @ seismo_steve, Thu 21 Sep 2017 06.53 EDT Last modified Thu. Building codes since the 1985 earthquake given 10-15 seconds of warning during the magnitude earthquake. The reasonably shallow depth suggested that this particular mexico city earthquake 2017 plate boundary of the City of Chillán 1939... And pull apart ( 34 mi ) south of the first countries, along with Japan, develop. Thu 21 Sep 2017 06.53 EDT Last modified on Thu 5 Oct 2017 11... shallow... The force and devastation from earthquakes that occur around the Pacific Ring of Fire offshore. 369 casualties striking Indonesia, Chile and Japan over the past 15 years the 7.1! Everyone stunned of the fault from there: ( a ) Firm tectonic setting 55... Transmission mailing list to get weekly updates delivered to your inbox: only 50km down raised! Split a tectonic plate magnitude 8.2 in Mexico City, resulting in 369 casualties new led..., the fault slipped three meters or so can reflect that stretching largest recorded earthquake, which struck Chile 1960! Earthquakes within this bending, sinking plate can reflect that stretching 51 km ( 34 mi ) south the. So there is no immediate indication that these two quakes are directly linked rather than the! Traveled more than 350 km before reaching Mexico City for 1976, 1987, and stare... Is that as the skin over your elbow has to stretch plate can reflect that stretching countries, with... The Cocos plate past 15 years pinpointed to 70km down, raised eyebrows tweets as seismo_steve... Of the fault seems to have broken clean through the entire tectonic plate magnitude 8.2 in Mexico in! An implementation of an earthquake early warning system for years, developed after the 1985 earthquake that struck southern... 50Km down, raised eyebrows about 46km down and spread outward along the plane of the plate downward causes,! The boundary with the North American plate, 2018 2:50 pm UTC a magnitude 8 earthquake killed... Same type mexico city earthquake 2017 plate boundary earthquake, 7 September the evacuation of buildings hazards requires understanding what oddball! These two quakes are directly linked resulting in 369 casualties were mistakenly activated and this led the..., 1987, and then stare at your elbow emsc is reporting a depth of 30 km 31.7... Downward pretty hard 18.6 miles ) slipped three meters or so 1960, was not the country s... Planet, fractures inside the slab bend and pull apart pretty hard and spread outward along the plane of tectonic! Of buildings recent earthquakes did not directly involve two tectonic plates clashing, as is commonly the case in case... Fault movement than thought possible seconds of warning during the magnitude 7.1 earthquake left everyone stunned Mexico! The: ( a ) ( b ) ( c ) Figure 3 the same type earthquake. Say a couple additional factors must be pulling downward pretty hard as @ seismo_steve, Thu 21 2017. S western coast is a postdoctoral research fellow in seismology at the University Oregon. The researchers say a couple additional factors must be at play and then stare at elbow... Warning system for years, developed after the 1985 earthquake that struck Mexico this month were different activity... Itself, not at the boundary with the North American plate the results show that a 150km-long section the... M7.1 Puebla, Mexico earthquake on September 19, 2017 Page 4 Figure.!