California earthquake swarm raises risk of bigger quake

California earthquake swarm raises risk of bigger quake

“Risk of big earthquake on San Andreas fault rises after quake swarm at Salton Sea,” warns the LA Times. 
Since a big earthquake hits this area, on average, every 150 or 200 years, and since the southernmost stretch of the San Andreas fault has not ruptured in more than 300 years. experts think the region is long overdue for a major quake.

San Andreas Fault – Courtesy USGS

According to the USGS,  the earthquake swarm near Bombay Beach, California, started on Sept. 26, 2016, in the Brawley Seismic Zone, which lies near the southern terminus of the San Andreas Fault.

The swarm included 96 earthquakes above magnitude 2 (as of 12:00 pm on Sept. 30, 2016).  The largest of these events were two M4.3 earthquakes and a M4.1 earthquake on Sept. 26.

It marked only the third time since earthquake sensors were installed there in 1932 that the area had seen such a swarm, and this one had more earthquakes than the events of 2001 and 2009. says The LA Times,

What are the odds of this swarm triggering a “big one”?

Small. But possible.

According to the USGS,  the chances range from less than 1 in 10,000 up to 1 in 500 that a magnitude 7 or greater earthquake will be triggered on the Southern San Andreas Fault within the next seven days, with the likelihood decreasing over time.