Two strong earthquakes have rattled southern California in the past 10 days... Is this a sign that a bigger one is coming?

It's possible, but unlikely, according to CalTech seismologist Kate Hutton, who said that there's a "one in 20" chance that the two recent quakes would be precursors to a much larger quake.

It does, however, raise the danger for a while, said University of Washington seismologist John Vidale.

On average, the southern California area has about 10,000 earthquakes each year, according to the U.S. Geological Survey (USGS).. That's more than 27 a day.

"Most of them are so small that they are not felt," the USGS reports on its website. "Only several hundred are greater than magnitude 3.0, and only about 15-20 are greater than magnitude 4.0."

Southern California gets more earthquakes than any part of the contiguous U.S., Hutton reported, who noted that that both Alaska and the Big Island of Hawaii see more than California.

The Friday evening 5.1 earthquake was felt widely across the region. The USGS said the epicenter was 1 mile from Brea, located about 20 miles southeast of downtown Los Angeles.

"It's the biggest earthquake we've had in Los Angeles in a while," Vidale said, but added that it's still "a typical Los Angeles earthquake."

Friday's quake hit a week after a predawn magnitude-4.4 quake centered in the San Fernando Valley rattled the region. That jolt shook buildings and rattled nerves, but did not cause significant damage.

Neither quake was on the famed San Andreas fault, which Hutton said isn't unusual: "A lot of our small quakes are not on the San Andreas fault." Some of the areas bigger quakes, she said, are on the San Andreas.

Neither of the quakes caused any deaths.

Southern California has not experienced a damaging earthquake since the 1994 magnitude-6.7 Northridge quake killed dozens of people and caused $25 billion in damage.

Contributing: Bill Welch, USA TODAY; Associated Press

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