The quake struck about 11 miles east of Cloverdale with a depth of 2.2 miles at 1:57 a.m., according to the USGS.
A series of at least eight aftershocks ranging from 1.0 to 2.5 in magnitude shook the region near or at The Geysers until 2:56 a.m.
The Geysers is the largest single geothermal field in the world, according to the U.S. Department of Energy.
The region experiences constant micro-seismic events -- earthquakes between 0.5 and 3.0 on the Richter scale -- related to deep-well injection that the Department of Energy says is necessary for the extended and sustained production of geothermal resources at the site.
There are 22 active geothermal plants in the region that produce roughly 950 megawatts of power, or enough for about 950,000 homes.
