408 Record Earthquake Swarm

San Ramon has experienced what is being called a record breaking 408 earthquake swarm (tinyurl.com/qxw2yko). Located to the east of San Francisco bay, San Ramon is a community of approximately 76, 000 people. The swarm began on Tuesday, October 13, 2015 and continued through today (October 27) with a couple of minor quakes registering 2.0 or larger per day. The largest registered at 3.9 on the Richter scale at 4:21 PM local time on October 19. The earthquakes in this swarm occurred 5 or so miles down along the “Calaveras Fault zone near the north end of the Pleasanton Fault.” They were strike-slip quake events. This general area has a history of earthquake swarms with 120 over 31 days in 2013 and 351 over 42 days in 1990 near Alamo, CA. Minor shaking will likely continue over the next several weeks. A larger event is “unlikely,” however, a 6.7 or greater earthquake is 8% likely to occur sometime in the next 30 years.

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