A swarm of more than 60 mostly small magnitude earthquakes, the lion’s share smaller than 3.0 M events, occurred over the past week about 4 to 6 miles northwest of Pinnacles, California.  Pinnacles is situated along the San Andreas fault system in central California.  The events began on 22 August and continued through the morning of 28Pinnacles Swarm Aug 2011 August.  Nine events were in the 3.0 to about 3.6 Didyoufeelit 4-6range.  The largest event, which occurred just after midnight (PDT) on 27 August, was a 4.6 M event.   Shaking was light,  nonetheless more than 2000 people reported it to USGS’s “Did you feel it”. 

Mike Conway (28 August 2011)