The 7.2-magnitude quake struck about 20 miles southeast of the border city of Mexicali, Mexico, according to the U.S. Geological Survey. Three aftershocks, of magnitudes 5.1, 4.5 and 4.3, followed within an hour.
"It sounds like it's felt by at least 20 million people at this point," USGS seismologist Lucy Jones said. "Most of Southern California felt this earthquake." The earthquake was felt the hardest in Mexicali, a commerce center along the border.
Alfredo Escobedo, civil protection director of Baja California state, said that a man was killed when his home collapsed just outside of Mexicali, and that there were reports of more people trapped in homes in the area. Rescue teams with dogs and digging equipment were rushing to the city from nearby Tijuana.
The parking garage at Mexicali's city hall also collapsed, he said, but no one there was hurt.
There was substantial damage on the other side of the border, in Calexico, Calif. Fire Chief Peter Mercado told KABC-TV of Los Angeles that there was structural damage and broken windows in an older section of town.