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Seismic Swarm Shaking Up Imperial Valley

Aired 3/5/12 on KPBS News.

A cluster of earthquakes has been rattling the Imperial Valley, centered at the southern tip of the Salton Sea.

Multiple earthquakes have shaken the earth and rattled the nerves of residents in the Imperial Valley recently.

Retired San Diego State Geology professor Pat Abbot says two things are going on. The region is still experiencing aftershocks from the Easter earthquake nearly two years ago. And, a seismic swarm is kicking in at the southeastern tip of the Salton Sea, an area known to seismologists as the Brawley Seismic Zone.

"It's an area where the geothermal power plants are, it's where there's magma relatively close below the surface and it's a very famous area for having swarms of earthquakes," Abbot said.

The good news, he said, is the earthquakes related to the Easter quake and the swarm are expected to be small-magnitude quakes.

He said the quakes the area is experiencing now are not on the San Andreas fault, which begins a little further north.

However, when that fault moves, it's going to be big.

"That section of the fault has not moved since around the year 1690. So when they do an analysis of where the next big one would be in California, that's the one that comes up number one, statistically speaking," Abbot said.

A quake on the south end of the San Andreas fault which begins at the Salton Sea, he said, will be in the range of a magnitude 7.8.