Increased risk of major earthquake after series of small temblors

Dozens of earthquakes have struck the Salton Sea area along the San Andreas fault between Sep. 26-30, as seen on the Eyewitness News Quake Tracker graphic.

A flurry of small earthquakes near the Salton Sea prompted researchers at the U.S. Geological Survey to issue an earthquake advisory.

Ninety-six earthquakes above a magnitude 2 were observed between Sept. 26-30. Three of them were greater than 4.0.

The USGS initially estimated up to a 1 percent chance that a magnitude 7 or greater earthquake could be triggered along the Southern San Andreas fault within seven days. On Sept. 30, it was revised to a .2 percent chance (1 in 500) due to decreasing activity near the Salton Sea.

Gregg Wilkerson, a senior geologist with the Bureau of Land Management in Bakersfield, said the seismic activity in the area was significant because "75 percent of big earthquakes around the world have these swarms of smaller earthquakes before the big quake."

Whether or not the flurry is a precursor to a larger event, Wilkinson said such clusters are rare, and an advisory is not to be taken lightly.

"If you're in the business of earthquake prediction, you don't want to issue too many warnings, otherwise its like the boy who cried wolf," he said.

The advisory comes in the same week Gov. Jerry Brown signed a bill, giving $10 million to continue developing the state's early warning system.

While the early warning system cannot predict earthquakes before they happen, they can give people short notice if one triggers nearby.

Depending on the distance from the epicenter, this can afford people precious seconds or sometimes minutes to find safety.

Sen. Jerry Hill, D-San Mateo, said this could help fire stations "where the doors can come up before the shaking hits so we can make sure that they come up so the trucks and engines can get out."

It could also give warning for trains to slow down, heavy machinery to stop or enough time to get under a desk.

California already has around 570 earthquake sensors. The new funding will nearly double that. Once the sensors are installed, however, the other big challenge is connecting them to a central system and being able to quickly disseminate the warning information.

"Most people assume that they'll get the earthquake early warning on their cell phone. And that's certainly a goal," said Doug Given of the USGS. "But the system is currently not capable of delivering fast notifications to millions of people."

He estimates the system will be fully operational within two years.

Kern County's western edge sits right along what's known as the "big bend" section of the San Andreas fault. Wilkerson said the last big earthquake on that stretch was in 1857. Statistically, he said the fault has a major quake every 120 years, which means it is continuing to build up pressure.

He suggested everyone in Southern California be prepared at all times for a major quake. That not only includes having food, water and batteries, but knowing things like where to turn off the gas and where to meet if all communication channels are down.

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