What's behind the more than 130 small earthquakes hitting Northern California
Since Thursday, at least 131 earthquakes have been recorded — as small as magnitude 0.2 and as big as magnitude 4. The largest earthquake was recorded at 5:48 a.m. Thursday, with an epicenter 10 miles east of Cloverdale, 20 miles northwest of Calistoga and 26 miles north of Santa Rosa.
Small earthquakes are common in the Geysers geothermal steam field. The Geysers-Clear Lake area is one of California's eight volcanic areas, and the Geysers team field — on the southwest area of the volcanic field — is home to one of the world's most productive geothermal power facilities, according to the U.S. Geological Survey.
Power is produced using the steam generated from the volcanic field. (Despite its name, no geysers exist in the Geysers-Clear Lake area, the USGS says.) The Geysers provide electricity to Sonoma, Mendocino, Lake, Marin and Napa counties, the agency says, and power has been generated from the area since 1960.
Northern California's greatest seismic hazard are on faults, like the San Andreas and Healdsburg-Rodgers Creek faults, which are miles away from this geothermal field, according to the USGS.
'Activities associated with the withdrawal of steam for producing electric power cause or induce small quakes to occur in the field,' the agency says.
One possible reason for that, the USGS says, is that taking away steam and heat from the steam field can 'cause the surrounding rock to contract, which in turn can induce earthquakes as a result of the contractional stresses.'
Also, reclaimed cold water from Santa Rosa and Lake County is pumped to the Geysers, and it interacting with hot rock appears to be 'a significant factor in inducing the earthquakes,' the agency says.
The USGS says that the largest quake to hit the Geysers area was about a magnitude 4.5.
'It is possible that a magnitude 5 could occur, but larger earthquakes are thought to be unlikely. In order for a larger earthquake to occur, it is necessary that a large fault exist,' the USGS says, and 'at the Geysers, no such continuous fault is known to exist.'
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Los Angeles Times
2 days ago
- Los Angeles Times
What's behind the more than 130 small earthquakes hitting Northern California
A series of more than 100 earthquakes has hit Northern California, shaking up the Geysers geothermal steam field in Sonoma and Lake counties. Since Thursday, at least 131 earthquakes have been recorded — as small as magnitude 0.2 and as big as magnitude 4. The largest earthquake was recorded at 5:48 a.m. Thursday, with an epicenter 10 miles east of Cloverdale, 20 miles northwest of Calistoga and 26 miles north of Santa Rosa. Small earthquakes are common in the Geysers geothermal steam field. The Geysers-Clear Lake area is one of California's eight volcanic areas, and the Geysers team field — on the southwest area of the volcanic field — is home to one of the world's most productive geothermal power facilities, according to the U.S. Geological Survey. Power is produced using the steam generated from the volcanic field. (Despite its name, no geysers exist in the Geysers-Clear Lake area, the USGS says.) The Geysers provide electricity to Sonoma, Mendocino, Lake, Marin and Napa counties, the agency says, and power has been generated from the area since 1960. Northern California's greatest seismic hazard are on faults, like the San Andreas and Healdsburg-Rodgers Creek faults, which are miles away from this geothermal field, according to the USGS. 'Activities associated with the withdrawal of steam for producing electric power cause or induce small quakes to occur in the field,' the agency says. One possible reason for that, the USGS says, is that taking away steam and heat from the steam field can 'cause the surrounding rock to contract, which in turn can induce earthquakes as a result of the contractional stresses.' Also, reclaimed cold water from Santa Rosa and Lake County is pumped to the Geysers, and it interacting with hot rock appears to be 'a significant factor in inducing the earthquakes,' the agency says. The USGS says that the largest quake to hit the Geysers area was about a magnitude 4.5. 'It is possible that a magnitude 5 could occur, but larger earthquakes are thought to be unlikely. In order for a larger earthquake to occur, it is necessary that a large fault exist,' the USGS says, and 'at the Geysers, no such continuous fault is known to exist.'
CBS News
3 days ago
- CBS News
Why are there so many earthquakes at The Geysers Northern California geothermal field?
An earthquake swarm that rattled an area of Northern California early Thursday was another round of recurring temblors in a seismically active region that is home to the world's largest geothermal field. The Geysers Geothermal Field, located about 72 miles north of San Francisco, covers some 45 square miles among Lake, Mendocino and Sonoma counties. According to the U.S. Geological Survey, the activities associated with harnessing the steam to generate electricity cause frequent, minor earthquakes in the region. The quakes can be felt by those who work among the 18 geothermal power plants and by nearby residents. Seismologists offer several explanations for why earthquakes are induced at The Geysers. The withdrawal of steam and heat from the field causes the surrounding rock to contract, which can trigger quakes from the contractional stresses. Pumping reclaimed water back into the steam reservoirs is also a factor because of the thermal contrast between the cold returned water and the hot surrounding rock. In addition, the hydraulic pressure of the injected water may be finding its way into faults, facilitating fracturing due to increased fluid pressures, according to the USGS. No large continuous fault line is known to exist at The Geysers, but there are numerous small fractures in the rock located near the many steam and injection wells, the agency says. The activities cause local stress changes that, combined with regional tectonic stresses, induce the quakes on these small faults. Most of the major seismic hazards in Northern California are from large earthquakes that strike along regional faults miles away from The Geysers, such as the San Andreas and Healdsburg-Rodgers Creek faults. The largest quake recorded at The Geysers is approximately M4.5, and while it's possible that a magnitude 5 could occur, larger earthquakes are thought to be unlikely, the USGS said. The Calpine Corporation, which owns and operates 13 plants at The Geysers, says the field's current capacity is 725 megawatts of electricity around the clock, enough to power 725,000 homes. Energy generated at The Geysers totals about 25% of California's renewable energy and about 40% of all geothermal electricity generated in the U.S., according to the National Association of Regulatory Utility Commissioners.
Miami Herald
5 days ago
- Miami Herald
Small NC town sees 3 quakes over 4 days, USGS says. What's causing it?
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