Earthquake in Chiapas

 When a deadly magnitude-8.2 earthquake struck the coast of Mexico's Chiapas state on 7 September, the handful of scientists that study the region were stunned, but not altogether surprised. For more than a century, there had been little activity to study—precisely why they thought the area could be due for a big one. The epicenter of the quake, which struck just before midnight local time, was just southeast of the Tehuantepec gap, a 125-kilometer-long stretch of Mexico's Pacific coast that has been seismically silent since record-keeping began more than a century ago. Their first priority now is to figure out how much, if any, of the Tehuantepec gap slipped in last week's quake, which killed more than 90 people and destroyed or severely damaged the homes of 2.3 million more.

The region where the earthquake struck is one of the most active seismic zones in the country: this is where the Cocos Plate dives, or subducts, under the North American plate. “Earthquakes of this size are not uncommon at subduction zone boundaries,” notes Jascha Polet, a seismologist at California State Polytechnic University in Pomona.
But this quake was different: it occurred within the Cocos plate as it warped or bent, not at the boundary with the North American plate.

Mexico’s seismology agency has registered at least 337 aftershocks, with the strongest reaching a magnitude of 6.1.