Last month’s temblor was atypical, because the epicenter was just 75 miles south of the city. Sections of the city’s south that had stood up well in 1985 bore the earthquake’s full force this time, and it was largely older buildings made of brittle concrete that collapsed, said H. Kit Miyamoto, a California seismic safety commissioner who visited Mexico after the recent quake.
The damage this time was limited because the earthquake was weaker than the 1985 quake and was quite deep, he said. But a closer, shallower temblor could cause 100 times more devastation.
“This is a warning not only to Mexico City, but a warning to L.A., San Francisco, San Diego, Tokyo, everywhere,” said Dr. Miyamoto, a structural engineer. In all of these cities, older structures of brittle concrete are vulnerable to a strong earthquake.
Los Angeles has moved toward mandatory retrofitting for the buildings most at risk — older concrete structures and those with a “soft story,” an open ground floor used for parking or a store front.
“L.A. is doing it right now as we speak,” Dr. Miyamoto said, estimating that 13,000 “soft-story” apartment buildings are affected by a recent city ordinance. “It’s definitely feasible to do this. It’s not as expensive as people think.”
“Businesses need to understand that seismic strengthening can be good business,” he added.
After the 1985 earthquake, Mexico City did retrofit schools, public buildings and a few of the largest private offices. Most of those buildings appear to have held up well this time, Dr. Alcocer said.