A magnitude-5.8 earthquake in northern Baja California rocked the U.S.-Mexico border region Wednesday, causing buildings to sway more than 100 miles to the west in downtown San Diego and southwestern Arizona.
The main quake was centered about 20 miles southeast of the Mexican border city of Mexicali, according to the U.S. Geological Survey. It was followed quickly by a 4.9 quake and at least nine other aftershocks.
San Diego County sheriff's Lt. Anthony Ray said there were no immediate reports of damage or injury.
Busy phone circuits made it difficult to get information from Mexicali or authorities on the U.S. side of the border in Imperial County immediately after the quake.
In Calexico, on the U.S. side of the border from Mexicali, City Manager Victor Carrillo said were no injuries or significant property damage reported in the California city of 40,000 people.
"Basically it was a quick, shake-and-bake, jolt-type of thing that seemed to last 15, 20 seconds, 30 seconds at the max," said Carrillo, who was in a meeting at City Hall during the quake. "I have quite a few items on the shelves in my office and they're all intact."
City crews found no damage to bridges, buildings or roads during a preliminary inspections, Carrillo said.
The quake was centered in a desert valley near cities with low-rise buildings. Mexicali is a sprawling industrial city of about 750,000 people and the capital of Baja California state.
Two smaller quakes preceded the main shock, which was initially reported at magnitude-5.9 before being downgraded slightly. Citizen reports to the USGS indicated it was also felt in southern Nevada and metropolitan Los Angeles.
Julie Dutton, a geophysicist with the USGS, said the area is seismically active.
The quake occurred 4.3 miles deep and is considered shallow. Shallower quakes have the potential to cause more damage than deeper ones, Dutton said.
Residents of Mexicali and Calexico occasionally endure swarms of small, frequent tremors that rattle nerves but cause little damage. In February, a swarm had been under way for nearly two weeks when a magnitude-5.0 jolt rocked the region.
Wednesday's earthquake occurred in a region of Baja California where the Earth's crust is being pulled apart, resulting mostly in swarms.
'Very active area'
A quake the size of Wednesday's main shock rattles the region about every 10 years, said Kate Hutton, a seismologist at the California Institute of Technology.
"It's a very active area," Hutton said.
In Yuma, Ariz., Sally Zeller, a 31-year-old server at Brownie's cafe, said she and most everyone in her restaurant felt the quake for several seconds.
"It rumbled under our feet and the soup counter rumbled against my hip," Zeller said. "The chandeliers were swaying. It was like, 'Whoa!"'
She said many people stood up nervously during the quake and that she worried the building would collapse at first.
Yuma Fire Department spokesman Mike Erfert said there were no reports of damage to buildings.