2017 Central Mexico earthquake
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Location of epicenter in Mexico and Puebla
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| Date | 19 September 2017 |
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| Origin time | 18:14:39 UTC |
| Duration | Strong shaking for about 20 seconds |
| Magnitude | 7.1 (Mw) |
| Depth | 51.0 km (32 mi) |
| Epicenter | 18°35′02″N 98°23′56″W / 18.584°N 98.399°WCoordinates: 18°35′02″N 98°23′56″W / 18.584°N 98.399°W |
| Type | Dip-slip (intraplate) |
| Max. intensity | VIII (Severe) |
| Casualties | 308 dead, 2,633 injured |
The 2017 Central Mexico earthquake struck at 13:14 CDT (18:14 UTC) on 19 September 2017 with a magnitude estimated to be Mw 7.1 and strong shaking for about 20 seconds, approximately 55 km (34 mi) south of the city of Puebla. It caused damage in the Mexican states of Puebla, Morelos and the Greater Mexico City area, including the collapse of more than forty buildings. Mexico's SASMEX earthquake warning system provided 20 seconds' warning in Mexico City. 308 people have been reported killed, 273 of which in Mexico City and surrounding areas, and more than 2,633 injured.
The quake occurred on the 32nd anniversary of the 1985 Mexico City earthquake, which killed about 10,000 people, commemorated with a national earthquake drill at 11 a.m. local time, two hours before this earthquake struck. There had been an even larger earthquake 650 km (400 mi) away off the coast of the state of Chiapas eleven days earlier.
Mexico is one of the world's most seismically active regions, sitting atop several intersecting tectonic plates. The border between the Cocos Plate and North American Plate, along the Pacific Coast of Mexico, creates a subduction zone that is able to generate large seismic events. Taken together with the activity along the edges of the Rivera and Caribbean plates, this causes the country to experience an average of 40 earthquakes a day.
Mexico City is built on a dry lakebed with soft soil made up of sand and clay that amplify the destruction caused by a major earthquake. Loose sediments near the surface have a decelerating effect on seismic shockwaves that is slowing them down from 1.5 miles per second to roughly 150 feet per second. This leads the waves' amplitude to increase, while deeper and denser soil layers cause shockwaves to endure in the valley longer, thereby extending the length of the earthquake.
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