Mexico City was badly damaged in 1985 when a magnitude-8.0 earthquake killed at least 10,000 people. But experts say Tuesday's quake was smaller and released far less energy.
Mexico City was built on an ancient lakebed and its spongy soil amplifies seismic waves, and the damage they cause. The 1985 quake destroyed 400 buildings and damaged thousands more.
The latest jolt "wouldn't have been nearly as effective at generating those deep bass tones" that caused the damage seen in 1985, USGS seismologist Susan Hough said in an email.
Victor Hugo Espindola Castro of Mexico's national seismological service said another factor was improved building standards following the 1985 quake.
"Many of the buildings that were damaged in 1985 were poorly constructed and from that came the new building regulations, so that now buildings are stronger," he said.
In Mexico City, telephone service was down and some neighborhoods were without power, according to Mayor Marcelo Ebrard, who set up a hotline for people to report damage.
A pedestrian bridge collapsed on an empty transit bus.
About 40 passengers were stranded for a short time on the Mexico City airport air train, but later released. The airport closed briefly but officials said there was no runway damage and they resumed operations.
In the working-class neighborhood of Guerrero, pieces of concrete and plaster fell off some buildings and others had fresh cracks.
"I thought I was having a stroke at first. The earth danced. It was strong," said 42-year-old homemaker Marianela Jimenez. "But it looks like it will end up being some dust and a bad scare."
Groups of women hugged and cried at Mexico City's Angel of Independence monument, where hundreds of people evacuated from office buildings said they never had felt such a strong earthquake.
Samantha Rodriguez, a 37-year old environmental consultant, was evacuated from the 11th floor on the Angel Tower office building.
"I thought it was going to pass rapidly but the walls began to thunder and we decided to get out," she said.
