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- The epicenter of the Tehuantepec earthquake was deeper than expected in the tectonic plate.
- Earthquakes at this location usually occur only in much older, colder subduction plates.
- It is possible that the US West Coast is prone to similar earthquakes.
An earthquake of magnitude 8.2 that struck southern Mexico on September 7, 2017 is not only produced where existing seismic modeling indicated that this should not happen, but it also broken a tectonic plate, according to scientists.
The Tehuantepec earthquake hit the Pacific coast of the state of Chiapas, Mexico, on the border with Guatemala. Nearly 100 people were killed and hundreds of others were injured.
Geologists initially thought that the earthquake had occurred when the oceanic plate of Cocos had been replaced by a continental plate. Megaquakes generally occur near the top of the plate convergence, an area called the subduction zone.
The epicenter of the Tehuantepec earthquake, however, was much deeper – about 28 miles deep in the Cocos plate – than the earthquake models had said., according to a report from the journal Nature Geoscience.
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The study also showed that the Cocos plate was completely separate, Writes National Geographic. A huge amount of energy was released in seconds.
"If you think this is a huge glass plate, this breakup has created a huge crack," said Diego Melgar, lead author of the study. "Everything seems to indicate that he has gone through the whole width of the thing."
Earthquakes can occur far from the limits of a plate, but they usually only occur in older, colder subduction zonesaccording to a press release concerning the study. The 1933 earthquake in Sanriku, Japan, is an example. The tsunami killed 1,522 people and destroyed more than 7,000 homes.
"This subduction plate is still very young and hot, geologically, it really should not break," said Melgar, an assistant professor of seismology at the University of Oregon.
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The Melgar team suspects that seawater would have entered the Cocos plate and possibly accelerated the cooling, which would make it susceptible to earthquakes.
If it is possible, said Melgar, other areas – including the western coast of the United States and southern Guatemala in Central America – are exposed to earthquakes in areas of tension.
"Our knowledge of these places where big earthquakes are occurring is still imperfect," Melgar said. "We can still be surprised. We need to think more carefully when we draw hazard and warning cards. We still have a lot of work to do to provide people with very specific information on what to expect in terms of tremor and tsunami risk. "
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