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Mexico City Earthquake
AP Photo/Marco Ugarte
Picking up the pieces—again.
GRIM DÉJÀ VU

A 7.1-magnitude quake shook Mexico City on the anniversary of the deadliest tremor in its history

By Ana Campoy

This is a developing story.

Around lunchtime on Tuesday (Sept. 19), residents of Mexico City found themselves picking up the shattered pieces of their city after a deadly earthquake, just like they did 32 years ago.

Mexico’s capital and its surrounding areas were struck by a 7.1-magnitude earthquake that toppled several dozen buildings (link in Spanish) and killed more than 200 people. The quake happened on the anniversary of a 1985 tremor, the most devastating to rock Mexico City in recorded history.

It will take time to assess the full damage of today’s earthquake, which was felt through the neighboring states of Puebla, Morelos, and Guerrero. It hit as Mexico was still recovering from another powerful tremor in the southern part of the country on Sept. 7, and adds to the strain on Mexico’s emergency responders.

Mexico, whose territory is on the boundaries of five tectonic plates, is a hub of seismic activity. The National Seismology Service records 40 earthquakes (Spanish) a day on average.

The 1985 earthquake was measured at a magnitude of 8.1, according to Mexican authorities. However, magnitude is just one factor in determining the extent of the damage, says John Bellini, geophysicist at the US Geological Survey’s National Earthquake Information Center. “It would also depend on how close you are [to the epicenter], and how solid the ground is underneath you,” he says.

The 1985 quake’s epicenter was somewhere offshore in the Pacific Coast, relatively far from the populous interior of the country; Tuesday’s epicenter was near the town of Raboso, Puebla, roughly 120 kilometers (75 miles) southeast of Mexico City. The city was and remains particularly vulnerable because it sits in a former lakebed, which amplifies vibrations, says Bellini.

But this time around, Mexico City fared better in terms of another key variable: the soundness of its built environment. After the 1985 earthquake, which killed some 20,000 people (Spanish) and damaged nearly 3,000 buildings, the city upgraded its building codes. Seismic warning systems have also been installed. As a result, the city withstood the Sept. 7 earthquake largely unscathed.

Early reports already suggest Mexico City, where more than half the casualties have occurred, won’t be so lucky this time around, but likely, the toll also won’t be anywhere as bad as it was in 1985.

The story was updated at 3:12am ET on Sept. 20, 2017, to reflect a revised official toll.

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