Unusual swarm of earthquakes shake Coachella Valley

A rash of moderate quakes shook the south end of theSalton Sea Sunday, and the largest quakes were felt from Orange County and SanDiego east into Arizona.

People throughout the Coachella valley reported feeling the ground move. Callers from Bermuda Dunes, Palm Desert, Indio, Salton Sea, and Coachella report feeling the earthquakes or aftershocks.

Ben Guitron of the Indio Police Department says one of the earlier big quakes was felt in Indio for about 30 seconds, as well as aftershocks. No damages or injuries in Indio.

“What we’re seeing is a classic Brawley seismic swarm,” USGSseismologist Lucy Jones told City News Service. “We haven’t seen one of thesesince the 1970s, and there was another one back in the 1930s.”

Some buildings were evacuated in Brawley, a small farm town 115 mileseast-northeast of San Diego. “It’s pretty bad, we had to evacuate the hoteljust for safety,” said Rowena Rapoza, office manager at the Best Western Hotelthere.

Jones said USGS seismographs and analysis computers were overwhelmed bythe rash of rattling that began at sunrise, and reached a crescendo with amagnitude 5.3 quake just after 12:30 p.m. It was followed by a 4.9 shakerwithin two minutes.

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

Preliminary computerized USGS reports had indicated that three quakeslarger than magnitude 5.3 had rattled out from Brawley at 12:30. That was laterresolved by seismologists to be two quakes, magnitude 5.3 and 4.9, Jones toldCNS.

The quakes were strongly felt at Borrego Springs, in San Diego Countyabout 25 miles west of the epicenter. “We’ve felt shaking for sure, butelectricity has not gone out,” said Gwenn Marie, owner of the Borrego ValleyInn.

The quakes were felt over all of San Diego, Riverside and Imperialcounties, and in Yuma and La Paz counties in Arizona, according to a USGSregistry.

However, there was no damage reported in Riverside County, according toMelody Hendrickson, spokeswoman for the Riverside County Fire Department. Adispatcher at the Riverside County Fire Department’s Office of EmergencyServices also reported no damage across the county.

The swarm forced an evacuation of patients from Pioneer’s Memorial Hospital in Brawley. The hospital announced an evacuation of all patients except those in its emergency room.

Some of those people were headed to John F. Kennedy Memorial Hospital in Indio. They included three Intensive Care Unit patients.

No major damage was reported to the Brawley hospital, but items were knocked off shelves and building inspectors were expected to enter the buildings Sunday evening to check on their integrity.

A representative for Indio’s JFK Memorial hospital said the medical center was able to accept more patients if requested. A representative for Eisenhower Medical Center in Rancho Mirage also said it could take patients from the earthquake zone if needed.

Southern California Edison declared an “unusual event” as the quakeswere felt in the control room of the San Onofre Nuclear Generating Station’stwin reactors. Both of those nuclear piles have been in secure shutdown modeall summer, while federal and state officials work with the utility to discoverwhy a recent upgrade and expansion caused parts of the boilers to shakeviolently.

SC Edison said the notification was a standard step requited by thefederal government.

The ground about 5 miles north-northwest of Brawley began to spasm atsunrise, and Brawley was rocked by a magnitude 3.9 quake at 10:02 a.m.,followed by a 3.4 quake about 90 seconds later.

In the three hours after the first earthquakes, an additional 11 quakesstruck the same approximate epicenter near the Salton Sea. Quakes withmagnitudes of 4.0, 4.0. 4.6 and 4.7 reportedly also hit during the noon hour.

The apparent quake cluster was centered 3 miles north-northwest ofBrawley, 16 miles north of El Centro and about 115 miles east-northeast of SanDiego. Some of the quakes may have been just east of Brawley.

Jones said the quake swarm was about midway between fault complex on thewest side of the Imperial Valley, and the main branch of the San AndreasFault, 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 Andreasitself, 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.”

By midafternoon, the automated USGS lists were lengthy with reports ofdozens of quakes echoing out from within 8 miles of Brawley. Jones hasemphasized that many of the reported quakes are duplicates or have unreliablemagnitudes, given the nature of the geology of the Brawley area.