Swarm of earthquakes - 4.6, 5.3, 4.9 - shake Brawley

U.S. Geological Survey

A screenshot of earthquake occurrences in the California Nevada region via the U.S. Geological Survey website. The red boxes indicate quakes that have rattled Brawley Sunday.

A series of strong earthquakes rolled through Imperial County this afternoon, with three of them measuring magnitude 4.6 or higher.

Most of the quakes shook the desert farming town of Brawley located on the southern tip of the Salton Sea. That area is located along the southern end of the 800-mile long San Andreas fault, and is one of the most seismically active regions in California.

A sheriff's dispatcher says there have been no reports of damage or injuries. But some buildings were evacuated in Brawley, a small farm town 115 miles east-northeast of San Diego.

"It's pretty bad. We had to evacuate the hotel just for safety," said Rowena Rapoza, office manager at the Best Western Hotel there.

The quake swarm began at sunrise, with the quakes growing in size as the morning wore on.

Paul Caruso with the U.S. Geological Survey says the first large quake, magnitude 3.9, struck at 10:02 a.m. Sunday about three miles north-northwest of Brawley.

It was followed by a 3.4 quake about 90 seconds later in the same area near the southern end of the Salton Sea about 16 miles north of El Centro. Magnitude 2.2 and 2.0 quakes followed minutes later.

The quake swarm hit a peak at 12:16 p.m. with a 4.0 quake, followed by a 4.6 quake four minutes later. At 12:31 p.m., the biggest quake in the series - at 5.3 - struck, with a 4.9 shaker following two minutes later.

The last of the large quakes - at 4.3 - hit at 12:40 p.m. Since then, dozens of smaller temblors have rumbled through the Brawley area.

"What we're seeing is a classic Brawley seismic swarm," USGS seismologist Lucy Jones told City News Service. "We haven't seen one of these since the 1970s, and there was another one back in the 1930s."

Jones said USGS seismographs and analysis computers were overwhelmed by the rash of rattling.

"Our system is choking on so many earthquakes," Jones said. "This area of California is deep soils, and we do not get as precise data as we do over the rest of the state, and that makes our data a little less precise."

Jones said the quake swarm was about midway between fault complex on the west side of the Imperial Valley, and the main branch of the San Andreas Fault, which runs from near Palm Springs to enter Mexico just west of Yuma.

"These don't seem to be related to earthquakes on the San Andreas itself, other than in a general way," she said. "It's pretty far away."

"Jones says she expected the quake swarm "to continue to bubble along, they're going to get a bunch of 4s and 5s."

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