The magnitude 6.5 quake was centered about 12 miles southwest of the city of Tehuacan, in the state of Puebla. It killed 17 people, damaged more than 1,000 schools, nine hospitals and more than 14,000 homes, displacing about 20,000 people. Some of the hospitals were forced to close just when they were most needed for surgeries and emergency services. A similar problem might exist within certain regions of the United States, such as the Midwest, where, because strong earthquakes are infrequent, the number of schools, other critical buildings and bridges with deficient seismic designs has increased over time, Ramirez says. The issue is more urgent in Mexico than it is in the United States, in part because builders there construct roofs with heavier materials than the more expensive steel joists and girders preferred by American builders.
Higher weight increases the forces exerted on buildings during earthquakes.
The buildings could often be strengthened with additional walls so that they better withstand earthquakes. In the case of one apartment building that collapsed, it is likely that just a few extra walls would have protected the building, Ramirez says. The findings were detailed in a report prepared by Ramirez, Purdue graduate student Santiago Pujol and civil engineer James Miller from Degenkolb Engineers in San Francisco. More than 20 other researchers were involved in preparing the report, which appeared in the September issue of a monthly newsletter published by the earthquake research institute. In addition to concerns about critical buildings, the report also concludes that design standards for low-income residential housing units need to be improved.