Mexico earthquake: U-M experts available
Parts of Mexico and Guatemala were hit by the strongest earthquake recorded in nearly a century in the area. University of Michigan experts can discuss the natural disaster and the challenges recovery efforts might face as Mexico prepares for hurricanes Irma and Jose. Additional experts are available to discuss Hurricane Irma.
Rafael Meza, associate professor of epidemiology at the School of Public Health, is originally from Mexico. He can talk about the infrastructure and history of response to past earthquakes and hurricanes in the country, as well as potential public health challenges the country might face after being hit by back-to-back tropical storms as well as the earthquake.
“This is a very challenging situation, a triple whammy of storms and an earthquake,” he said. “The good news is that Mexicans have very good infrastructure to responding to disasters in part because of previous natural disasters, including the 1985 earthquake. There’s been a great effort to educate the population on how to to respond, there’s campaigns in schools, in coastal areas.
“The education the population has received should be helpful in terms of reducing the potential impact these disasters might have. Of course, if the storms are massive and there is a lot of damage, this will put a strain in the health systems.”
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Ben van der Pluijm is an earthquake geologist and professor in the Department of Earth and Environmental Sciences.
“Today’s M8.1 earthquake occurs in a geologic region known for large earthquakes,” he said. “The area represents the region where a tectonic plate (called Cocos) dives under Middle America, a process called subduction. The quake has a slightly unusual character, as it is not a thrust earthquake that is typical for subduction but likely a quake that reflects deformation in the subducting plate as it sinks. This is based on estimates of the quake’s 70+km focus depth (source area).
“The magnitude is large for this type of quake, but large earthquakes have occurred in the past, and will in the future. Today’s magnitude is similar to the 1985 Mexico M8 quake a few hundred kilometers to the northwest that was a thrust quake, which was much closer to Mexico City and slightly shallower. The 1985’s impact was greater, therefore, and before better building codes were adopted. Today’s quake hit a region with older buildings that often do not stand up well to earthshaking, such as brick buildings.
“The energy of this magnitude quake compares to our 1950s H-bomb test explosions.
There is no link between current hurricane activity in the Caribbean and this (or other) earthquakes.”
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Jeroen Ritsema is a professor of geophysics in the Department of Earth and Environmental Sciences. His research involves the analysis of seismic waves to image Earth’s interior.
“The earthquake today is further to the south than the 1985 earthquake, so at a larger distance from Mexico City,” he said. “It was also deeper at a depth of about 70 km than the 1985 earthquake. I expect the earthquake today to be less damaging because of its relatively large depth.
“The same tectonic plates are involved. Both earthquakes were within the zone of collision between the Cocos Plate (to the west) and the Caribbean Plate (to the east). However, the sliding orientations are different. The 1985 was shallow and involved sliding on the plate interface. Today’s earthquake was deeper and probably involved internal deformation of the Cocos plate as it is moving beneath the Caribbean Plate.
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Yihe Huang, assistant professor in the Department of Earth and Environmental Sciences, studies the physical mechanisms of earthquakes and faulting processes using both observational methods (e.g., seismic data analysis) and numerical tools (e.g., earthquake rupture simulation). Asked how the tsunami wave produced by today’s earthquake compares to the 2010 Chilean earthquake that triggered tsunami warnings in 53 countries, Huang said:
“Whether a large earthquake can generate large tsunami depends on the seafloor displacement. The faulting type is an important factor here. The M8.8 Chile earthquake is a megathrust earthquake that occurred between two plates (subducted plate and overriding plate). The relative motion between these two plates caused large seafloor displacement. But the Mexican earthquake is a normal earthquake and occurred inside the subducted plate, so the seafloor displacement is not that large. Besides, the Mexican earthquake is also deeper and smaller.”
Eric Hetland is a geophysicist and associate professor in the Department of Earth and Environmental Sciences. His work is broadly concerned with lithospheric deformation, principally the inference of the mechanical properties of the crust and upper mantle from observations.
“The earthquake occurred at a major subduction boundary along the west coast of Mexico and Central America,” he said. “The earthquake was fairly deep and was a normal mechanism, a mechanism typically associated with extensional settings. The depth and mechanism are in contrast to the 2011 M9 Japan earthquake, which was shallower and was a thrust mechanism, a mechanism which is typical of compressional settings such as subduction zones.
“The Mexico earthquake highlights that subduction zones, although compressional in nature, have deeper extension, in this case associated with the Cocoa plate located off of the west coast of southern Mexico, sinking down to greater depths in the Earth’s mantle.”
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Joseph Eisenberg, chair and professor of epidemiology in the School of Public Health, studies infectious disease epidemiology.
“Waterborne diseases are always a concern after any disaster that has the potential to displace large populations and impact water and sanitation infrastructure.”
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