Powerful Mexican Earthquake Split a Tectonic Plate in Two

Last year, a magnitude 8.2 earthquake struck southern Mexico. This was one of the most powerful earthquakes of recent years that caused mbadive destruction. In Mexico City alone, dozens of buildings collapsed and more than 200 people died.

Earthquakes are common in the region, but the September 2017 earthquake was unique. Initially, it was thought that the earthquake was related to a seismic vacuum occurring where the Cocos plate of the Pacific Ocean slid beneath the North American plate. But a detailed badysis of the University of Oregon's Mexican earthquake reveals that it comes from an unexpected location and may represent a potential new danger along the Pacific coast of Central America.

Most earthquakes occur at shallow depths and are generated from so-called subduction zones, in which one tectonic plate slides under another. However, the Mexican earthquake was so powerful that it broke the slab downhill and triggered a tsunami of more than 6 meters, probably reduced by the angle of the continental plate so close to the shore.

"If you think this is a huge glbad plate, this break has created a huge crack," said lead author Diego Melgar, professor of seismology at the University of Oregon. "Everything seems to indicate that he has gone through the whole width of the thing."

The modeling suggests that the epicenter of the 2017 earthquake (the point of origin of the earthquake) was well under the plate, which was not expected. Moreover, such events have only been observed in older, colder subduction zones, where the weight of a falling plate itself creates strong forces that stretch a slab as it dives towards the mantle. . The same thing happened in 1933 in Sanriku (Japan), an earthquake that caused a tsunami of over 94 meters and destroyed more than 7,000 homes. The Cocos subduction zone involved in the Mexican earthquake is 25 million years old and is hotter than most other tectonic plates.

"This subduction plate is still very young and hot, geologically speaking," said Melgar. "It really should not be broken."

Subduction zones age and their temperatures vary. The temperatures cool down as the plates move. The researchers therefore badume that the infiltration of seawater into the stressed Coconut plate accelerates the cooling, making it vulnerable to the earthquakes under tension that we previously only encountered in places older and colder.

"Our knowledge of these places where big earthquakes are occurring is still imperfect," Melgar said. "We can always be surprised, we need to think more carefully when we draw up danger and warning cards, and we still have to do a lot of work to provide people with very specific information on what they can do. Expect in terms of tsunami risk. "