Saturday, October 1, 2016

CALQUAKE: Small magnitude earthquakes near the Salton Sea earlier this week prompted state officials to issue an advisory on the possibility of similar or larger earthquakes in the near future.

Governor's Office of Emergency Services issues earthquake advisory for surrounding areas

Thursday Posted Sep 29, 2016 at 8:41 AM Updated Sep 29, 2016 at 4:35 PM

By Jose Quintero
Staff Writer

Small magnitude earthquakes near the Salton Sea earlier this week prompted state officials to issue an advisory on the possibility of similar or larger earthquakes in the near future.

“California is earthquake country. We must always be prepared and not let our guard down,” said Governor’s Office of Emergency Services Director Mark Ghilarducci in a statement. “The threat of an earthquake on the San Andreas Fault hasn’t gone away, so this is another important opportunity for us to revisit our emergency plans and learn what steps you need to take if a significant earthquake hits.”

Ghilarducci asked the California Earthquake Prediction Evaluation Council, which includes scientists from the California Geological Survey, University of California at San Diego, Southern California Earthquake Center at USC and the United States Geological Survey, to discuss and evaluate a sequence of small earthquakes that recently hit the Salton Sea area.

According to the Governor's Office of Emergency Services, the council “concluded that stresses associated with this recent earthquake swarm may slightly increase the probability between 0.03 percent and 1.0 percent of an additional earthquake as large, or larger, than the Sept. 26 magnitude 4.3” occurring until 9 a.m. on Oct. 4.

The Governor’s Office of Emergency Services has issued an earthquake advisory for the San Bernardino, Kern, Los Angeles, Riverside, Imperial, San Diego, Orange and Ventura counties based on the discussions.

“Local emergency management, government, schools and the public should review their earthquake preparedness plans, maintain awareness and be prepared to take action should the earthquake occur,” the Governor’s Office of Emergency Services said.

USGS Research Seismologist Robert Graves told the Daily Press that these types of advisories should serve as a reminder to residents to take precautionary measures.

“In general, advisories are not common. They have been issued in the past in situations like this where we see somewhat unusual behavior, particularly near our large active faults,” Graves said. “Living in Southern California we are in this together and have to acknowledge and recognize that earthquakes are a part of life.

"They are unpredictable in terms of when, where or how large. But past history has shown us you don’t go very long within a time span where you don't have a strong or major earthquake.”

The San Andreas Fault, which runs through the Cajon Pass, stretches 700 miles through California, and the southern end is estimated to be 50 to 100 years overdue for a large earthquake.

The San Andreas Fault suffered two major quakes in the 19th century — a 7.5 magnitude in 1812 and a 7.9 earthquake in 1857. The San Andreas Fault in Southern California has been quiet since and Southern California hasn’t had a true “Big One,” which is a quake greater than a 7.7 magnitude, since 1857.

Other nearby fault lines include the San Bernardino fault zone near Oak Hills, the Helendale Fault and a fault line that goes through Lenwood. Graves said most of the faults in the High Desert are active faults.

“The San Andreas Fault is a major player but it is not the only fault. But the rate in which (the other faults) have earthquakes is far lower than the San Andreas Fault,” Graves said. “In 1992, there was a large earthquake (magnitude 7.3) called the Landers Earthquake which ruptured north of Indio and east of Barstow. That quake ruptured on a series of faults that prior to that event, the previous earthquake was maybe 60 or 80 thousand years ago. So very infrequent, but obviously an active fault.

“Prediction in a precise sense is not and may never be possible, but with a fault like the San Andreas — (it's) had large earthquakes in the past and will have large earthquakes in the future.”