The first, a 4.0-magnitude temblor, was centered one mile north of The Geysers and was recorded just after 8:30 a.m., as Lake County News reported midday Thursday.
The second, measuring 3.8, was reported at 4:54 p.m., according to the US Geological Survey.
Its epicenter was one mile north northwest of The Geysers, five miles west southwest of Cobb and seven miles west northwest of Anderson Springs, at a depth of 1.3 miles, the survey reported.
Cobb resident Roger Kinney, who shares earthquake reports with Lake County News, said he and his wife both felt the quake and saw the water in their swimming pool undulating as a result.
By 11 p.m. Thursday the US Geological Survey had received 12 shake reports from eight zip codes, including Kelseyville, Calistoga, Sebastopol, Cloverdale, San Pablo, Oakland, Port Costa and Creston, a small town located in San Luis Obispo County, approximately 424 miles away from the quake's epicenter.
So far this month there have been five earthquakes measuring 3.0 in magnitude or above, based on US Geological Survey records.
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