November 2015 – SAN FRANCISCO, CA – A total of 583 small earthquakes have shaken San Ramon, California, in the last three weeks or so – more than five times the record set 12 years ago, according to the latest US Geological Survey updates. “It’s the swarm with the largest number of total earthquakes in San Ramon,” said USGS scientist David Schwartz, who is more concerned about the size of quakes than he is the total number of them. Still, the number tops the previous record set in 2003, when 120 earthquakes hit over 31 days, with the largest clocking in at a magnitude of 4.2.
The largest magnitude earthquake in the current swarm, which began on Oct. 13, is a magnitude 3.6. In 1990, a total of 351 earthquakes struck in Alamo, about 30 miles east of San Francisco, over 42 days, with the largest recorded at a magnitude of 4.4. But Schwartz said those numbers might be inaccurate, as technology back then wasn’t as sophisticated. Despite the nearly 600 quakes that have hit San Ramon in the last month, no injuries or damage have been reported. And the USGS noted that activity has been relatively quiet for the last couple of days. –NBC Bay Area
In the past 24 hours, there have been 36 quakes. This map shows all earthquakes near the San Francisco Bay Area for the past 24 hours. The darker blue circle shows the range weʼre filtering for.