Northern Californians felt a series of quakes hitting near the Geysers geothermal field on Wednesday night, with the tremors rolling from Lakeport down to Sonoma and San Francisco, and even as far south as Santa Cruz, the Los Angeles Times reported.
The first quake was measured at 4.2 magnitude and struck about three miles northwest of the Geysers region, followed by aftershocks ranging in magnitudes of 4.0, 2.7, 2.7, 2.5 and 2.6.
More than 200 residents in surrounding areas had reported feeling the shakes within an hour after the string of quakes hit.
The Geysers area is located about 90 miles north of San Francisco and is considered to be one of the most seismically active regions in the U.S. Experts believe work associated with Geothermal plants operating near the epicenter of the quakes could trigger small quakes.
The U.S. Geological Survey explained that drilling in the area, to tap into steam for production of electric power, causes surrounding rock to contract and could induce earthquakes.
Over the years this has become a sore point for residents in Northern California already on edge about quakes.
The area, located near the town of Anderson Springs, has been the focus of engineers wanting to tap into its natural energy-generating capacity since the 1970s but as production levels have increased, so has the frequency of small tremblors, Scientific America reported.
Wednesday’s series of earthquakes hit a day after a magnitude 4.5 quake swept through parts of Southern California.
That quake occurred near the San Andreas fault zone, beneath the San Bernardino Mountains, The San Diego Tribune reported.
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