Sunday, May 25, 2014

Earthquake Bay Area science update

San Gregorio along the coast,
and San Andreas along San Mateo Peninsula
would mainly affect us in Pacifica
San Jose Mercury News/Science and Environment/Becky Bach, 5/23/14.  "Earthquake cluster likely to strike Bay Area, scientists say."

"The Bay Area's Big One will still be plenty big, but it might not be just one, according to a study released Monday by U.S. Geological Survey scientists.  A flurry of mid-sized quakes is more likely to strike the Bay Area rather than a giant 1906-esque rupture, said David Schwartz, a paleoseismologist at the USGS's Menlo Park office and the lead author of the study, which appeared in June's Bulletin of the Seismological Society of America.

The study marks the first comprehensive history of the Bay Area's seismicity dating to 1600. A quake cluster isn't necessarily good news, as it could keep communities constantly cleaning up the earthquake damage, several experts said." ....  Schwartz said he hopes to look back even farther than 1600 to more fully understand the Bay Area's seismic history--and its future."       Read article.

Related article - Wall Street Journal/Tamara Audi, 5/19/14. .... "Several Earthquakes are bigger threat to San Francisco Bay Area." "Scientists say the new information should shift the region's focus to preparing for the possibility of a potentially devastating quake on one fault followed by one on another fault within the same decade. A number of major faults in the Bay Area haven't seen large quakes in decades, so they haven't had a chance to catch up to the movements of the Earth's tectonic plates, the scientists behind the study said.  "So, as the region is recovering from one event, another event happens," said Mr. Schwartz, a geologist with the U.S. Geological Survey. "In a sense, it's a much more difficult hazard to deal with." ....  "It is an important study that has important data that needs to be incorporated into our thinking about earthquake forecasting," said Thomas Jordan, director of the Southern California Earthquake Center. The professor of geophysics at the University of Southern California said the data show that "earthquakes are not occurring randomly in time, but in fact are occurring in clustered sequences."

ReferenceUSGS/Earthquake Hazards Program.  "San Francisco Bay Area".  "The San Francisco Bay area has been identified in a recent report as a region where a magnitude 6.7 or greater earthquake is likely to occur before the year 2032. The USGS has installed a variety of instruments that measure strain changes and fault slip near the many active earthquake faults in the area. These measurements are made at least every 10 minutes and are transmitted to the USGS in Menlo Park, CA. Maps of San Francisco Bay area instrument locations and plots of the most recent measurements are available on these pages."

Note:  graphic from  City Data Forum.

Posted by Kathy Meeh

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