Notable Earthquake of the Week
Mexico City, M8.1 Earthquake

At 7:17 a.m. September 19, 1985, a powerful earthquake registering M8.1 rocked central Mexico. The quake was centered in the coastal mountains of the Michoacan Province and caused substantial damage throughout central Mexico, including in Mexico City - some 240 miles east of the epicenter.

Severe damage occurred to about 500 buildings in Mexico City with widespread light to moderate damage in other parts of the country. Although quake killed over 8,000 people, causalities would nave been much higher if the quake had occurred just a couple hours later when the schools and office buildings would have been full with people.

Mexico City has been rocked several times in the past. It is largely built upon soft, poorly consolidated lake sediments from the former Lake Texcoco, which was drained by the Spanish following their occupation of the region. Thick sequences of soft sediments like these tend to amplify seismic waves and cause the ground to shake much more vigorously than the surrounding bedrock.

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