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.

Purchase a poster-sized map of Earthquakes in the United States here.

Track weekly earthquake activity with the comprehensive Seismo-Watch Earthquake Reports.

• Global
• Northern California
• Southern California
• Western Basin and Range

You can also track local activity maps from

• Central California
• Eastern Sierra (Western Basin and Range)
• Mammoth Lakes
• Coachella Valley
• Pacific Northwest

Seismo-Watch EQ Flash! Alert Bulletins are a great way to be informed right away when significant earthquakes occurs.