Monday, February 4, 2013 11:55 AM PST (Monday, February 4, 2013 19:55 UTC)
Monitored CALIFORNIA VOLCANOES Current Volcano Alert Level: all NORMAL Current Aviation Color Code: all GREEN
Activity Update: All volcanoes monitored by CalVO's telemetered, real-time sensor networks exhibit normal levels of background seismicity and deformation. Real-time monitoring networks are in place at Mount Shasta, Medicine Lake Volcano, Clear Lake Volcanic Field, Lassen Volcanic Center, Long Valley Caldera and Mono-Inyo Chain.
Observations for January 1, 2013 (0000h PT) through January 31, 2013 (2359h PST): Mt Shasta: Three earthquakes, all M<2.0, were detected under the south flank of Mt Shasta. Medicine Lake: No earthquakes were detected at or above magnitude 1.0. Lassen Volcanic Center: Two earthquakes, both M<2.0, were detected within Lassen National Park. Clear Lake Volcanic Field: A short-lived swarm of low-magnitude earthquakes was detected under the south flank of Mt Konocti on Jan 8-9. The largest event was M=2.8. [Note: Typical high level of seismicity was observed under the Geysers steam field located at the western margin of CLVF. The largest event was a magnitude M=3.0]. Long Valley Caldera and Mono-Inyo Chain: One earthquake (M=1.2) was detected in the southern half of the Long Valley Caldera; Nine earthquakes (all M 2.0) were detected in the vicinity of Mono Lake; Four earthquakes (all M<2.0) were detected under Mammoth Mountain. [Note: The typical high level of seismicity was observed south of the caldera in the Sierra Nevada range. The largest event was M=2.6].
The U.S. Geological Survey will continue to monitor these volcanoes closely and will issue additional updates and changes in alert level as warranted. For a definition of alert levels see http://volcanoes.usgs.gov/activity/alertsystem/icons.php.
As part of the U.S. Geological Survey's Volcano Hazards Program, the California Volcano Observatory aims to advance scientific understanding of volcanic processes and lessen the harmful impacts of volcanic activity in the volcanically active areas of California and Nevada. For additional USGS CalVO volcano information, background, images, and other graphics visit http://volcano.wr.usgs.gov/vsc/observatories/calvo.html. For general information on the USGS Volcano Hazard Program http://volcanoes.usgs.gov. Statewide seismic information for California and Nevada can be found at http://earthquake.usgs.gov/earthquakes/recenteqscanv/.
CALIFORNIA VOLCANO OBSERVATORY MONTHLY UPDATE
Thursday, January 3, 2013 2:00 PM PST (Thursday, January 3, 2013 22:00 UTC)
Monitored CALIFORNIA VOLCANOES Current Volcano Alert Level: all NORMAL Current Aviation Color Code: all GREEN
Activity Update: All volcanoes monitored by CalVO's telemetered, real-time sensor networks exhibit normal levels of background seismicity and deformation. Real-time monitoring networks are in place at Mount Shasta, Medicine Lake Volcano, Clear Lake Volcanic Field, Lassen Volcanic Center, Long Valley Caldera and Mono-Inyo Chain.
Observations for December 1, 2012 (0000h PT) through December 31, 2012 (2359h PST): Mt Shasta: No earthquakes of magnitude 1.0 or above were detected. Medicine Lake: One M=1.0 earthquake was detected ~ 8 km N-NW of Medicine Lake caldera. Lassen Volcanic Center: One M=2.2 earthquake was detected ~ 5 km SW of Lassen Peak. Clear Lake Volcanic Field: Six earthquakes were detected south and west of the southern arm of Clear Lake. The largest event was M=1.8. [Note: Typical high level of seismicity was observed under the Geysers steam field located at the western margin of CLVF. The largest event was a magnitude M=3.1]. Long Valley Caldera and Mono-Inyo Chain: Fourteen earthquakes occurred in the southern half of the Long Valley Caldera (all M<2.0); No earthquakes at or above magnitude 1.0 were detected in the vicinity of Mono-Inyo craters; Two earthquakes (magnitude M=1.0 and 1.4) were detected under Mammoth Mountain. [Note: The typical high level of seismicity was observed south of the caldera in the Sierra Nevada range. The largest event was M=2.2]. The signal of modest inflation occurring within the caldera since 2011 (see previous updates) has dwindled to a level below detection by the CalVO continuous GPS network.
The U.S. Geological Survey will continue to monitor these volcanoes closely and will issue additional updates and changes in alert level as warranted. For a definition of alert levels see http://volcanoes.usgs.gov/activity/alertsystem/icons.php.
As part of the U.S. Geological Survey's Volcano Hazards Program, the California Volcano Observatory aims to advance scientific understanding of volcanic processes and lessen the harmful impacts of volcanic activity in the volcanically active areas of California and Nevada. For additional USGS CalVO volcano information, background, images, and other graphics visit http://volcano.wr.usgs.gov/vsc/observatories/calvo.html. For general information on the USGS Volcano Hazard Program http://volcanoes.usgs.gov. Statewide seismic information for California and Nevada can be found at http://earthquake.usgs.gov/earthquakes/recenteqscanv/.
CALIFORNIA VOLCANO OBSERVATORY MONTHLY UPDATE
Monday, December 17, 2012 4:05 PM PST (Tuesday, December 18, 2012 00:05 UTC)
Monitored CALIFORNIA VOLCANOES Current Volcano Alert Level: all NORMAL Current Aviation Color Code: all GREEN
Activity Update: All volcanoes monitored by CalVO's telemetered, real-time sensor networks exhibit normal levels of background seismicity and deformation. Real-time monitoring networks are in place at Mount Shasta, Medicine Lake Volcano, Clear Lake Volcanic Field, Lassen Volcanic Center, Long Valley Caldera and Mono-Inyo Chain.
Observations for November 1, 2012 (0000h PDT) through November 30, 2012 (2359h PST): Mt Shasta: One M=1.1 earthquake was detected under the southwest flank. Medicine Lake: One M=1.0 earthquake was detected near Caldwell Butte at the southern margin of Lava Beds National Monument. Lassen Volcanic Center: No earthquakes of magnitude M=1.0 or greater were detected. Clear Lake Volcanic Field: Six earthquakes were detected in the southern region of Clear Lake. The largest event was M=1.8. [Note: Typical high level of seismicity observed under the Geysers steam field located at the western margin of CLVF. The largest event was magnitude M=2.4]. Long Valley Caldera and Mono-Inyo Chain: Thirty-eight earthquakes occurred in the southern half of the Long Valley Caldera (all M<2.0); One earthquake was detected north of Long Valley Caldera in the Mono Basin east of Mono Lake (M=1.3); Four earthquakes of magnitude M=1.0 or greater (largest was M=1.4) were detected under Mammoth Mountain. [Note: Typical high level of seismicity observed south of the caldera in the Sierra Nevada range. Largest event was M=3.0]. Additionally, analysis of continuous GPS data over the last month shows that the persistent modest inflation occurring within the caldera over the past year may be leveling off (see previous updates).
The U.S. Geological Survey will continue to monitor these volcanoes closely and will issue additional updates and changes in alert level as warranted. For a definition of alert levels see http://volcanoes.usgs.gov/activity/alertsystem/icons.php.
As part of the U.S. Geological Survey's Volcano Hazards Program, the California Volcano Observatory aims to advance scientific understanding of volcanic processes and lessen the harmful impacts of volcanic activity in the volcanically active areas of California and Nevada. For additional USGS CalVO volcano information, background, images, and other graphics visit http://volcano.wr.usgs.gov/vsc/observatories/calvo.html. For general information on the USGS Volcano Hazard Program http://volcanoes.usgs.gov. Statewide seismic information for California and Nevada can be found at http://earthquake.usgs.gov/earthquakes/recenteqscanv/.
CALIFORNIA VOLCANO OBSERVATORY MONTHLY UPDATE
Wednesday, November 14, 2012 3:22 PM PST (Wednesday, November 14, 2012 23:22 UTC)
Monitored CALIFORNIA VOLCANOES Current Volcano Alert Level: all NORMAL Current Aviation Color Code: all GREEN
Activity Update: All volcanoes monitored by CalVO's telemetered, real-time sensor networks exhibit normal levels of background seismicity and deformation. Real-time monitoring networks are in place at Mount Shasta, Medicine Lake Volcano, Clear Lake Volcanic Field, Lassen Volcanic Center, Long Valley Caldera and Mono-Inyo Chain.
Observations for October 1, 2012 (0000h PDT) through October 31, 2012 (2359h PDT): Mt Shasta: No earthquakes were detected at or above M=1.0. Medicine Lake: No earthquakes were detected at or above M=1.0. Lassen Volcanic Center: No earthquakes of magnitude M=1.0 or greater were detected. Clear Lake Volcanic Field: Six earthquakes were detected with between M=1.0 and M=1.8. [Note: Typical high level of seismicity observed under the Geysers steam field located at the western margin of CLVF. The largest event was magnitude M=2.4]. Long Valley Caldera and Mono-Inyo Chain: Forty-four earthquakes occurred in the southern half of the Long Valley Caldera east of the town of Mammoth Lakes (the largest was M=2.6); Two earthquakes were located north of Long Valley Caldera, one east of Mono Lake in Mono Valley and another under Mono Craters due east of June Lake (both M<2.0); Eight earthquakes of magnitude M=1.0 or greater (largest was M=1.8) were detected under Mammoth Mountain. [Note: Typical high level of seismicity observed south of the caldera in the Sierra Nevada range. Largest event was M=2.6]. Additionally, analysis of continuous GPS data over the last several months show continued modest inflation within the caldera. Ground motion is directed upward and away from the caldera's center, with a maximum uplift rate between 2 and 3 cm/yr. Horizontal deformation is similar in magnitude, with a N/S extension rate across the caldera's center of about 3 cm/yr. These rates of deformation are comparable to those observed in 2002-2003, and well below the rates seen in the late 1990s.
The U.S. Geological Survey will continue to monitor these volcanoes closely and will issue additional updates and changes in alert level as warranted. For a definition of alert levels see http://volcanoes.usgs.gov/activity/alertsystem/icons.php.
As part of the U.S. Geological Survey's Volcano Hazards Program, the California Volcano Observatory aims to advance scientific understanding of volcanic processes and lessen the harmful impacts of volcanic activity in the volcanically active areas of California and Nevada. For additional USGS CalVO volcano information, background, images, and other graphics visit http://volcano.wr.usgs.gov/vsc/observatories/calvo.html. For general information on the USGS Volcano Hazard Program http://volcanoes.usgs.gov. Statewide seismic information for California and Nevada can be found at http://earthquake.usgs.gov/earthquakes/recenteqscanv/.
CALIFORNIA VOLCANO OBSERVATORY MONTHLY UPDATE
Monday, October 1, 2012 12:15 PM PDT (Monday, October 1, 2012 19:15 UTC)
Monitored CALIFORNIA VOLCANOES Current Volcano Alert Level: all NORMAL Current Aviation Color Code: all GREEN
Activity Update: All volcanoes monitored by CalVO's telemetered, real-time sensor networks exhibit normal levels of background seismicity and deformation. Real-time monitoring networks are in place at Mount Shasta, Medicine Lake Volcano, Clear Lake Volcanic Field, Lassen Volcanic Center, Long Valley Caldera and Mono-Inyo Chain.
Observations for September 1, 2012 (0000h PDT) through September 30, 2012 (2359h PDT): Mt Shasta: No earthquakes were detected at or above M=1.0. Medicine Lake: No earthquakes were detected at or above M=1.0. Lassen Volcanic Center: Twelve earthquakes of magnitude M=1.0 or greater were detected. The largest was M=2.3. Clear Lake Volcanic Field: One earthquake magnitude M=1.0 was detected [Note: Typical high level of seismicity observed under the Geysers steam field located at the western margin of CLVF. The largest event was magnitude M=3.4 with 10 events of M=2.0 or greater]. Long Valley Caldera and Mono-Inyo Chain: Eight earthquakes occurred in the southern half of the Long Valley Caldera east of the town of Mammoth Lakes (largest events was M=1.9); Two earthquake were located east of Mono Lake in Mono Valley (M=1.95 and M=1.7); Six earthquakes of magnitude M=1.0 or greater (largest was M=1.4) were detected under Mammoth Mountain. [Note: Typical high level of seismicity observed south of the caldera in the Sierra Nevada range. Largest events were M=2.6 and M=3.0]. Additionally, analysis of continuous GPS data over the last several months show continued modest inflation within the caldera. Ground motion is directed upward and away from the caldera's center, with a maximum uplift rate between 2 and 3 cm/yr. Horizontal deformation is similar in magnitude, with a N/S extension rate across the caldera's center of about 3 cm/yr. These rates of deformation are comparable to those observed in 2002-2003, and well below the rates seen in the late 1990s.
The U.S. Geological Survey will continue to monitor these volcanoes closely and will issue additional updates and changes in alert level as warranted. For a definition of alert levels see http://volcanoes.usgs.gov/activity/alertsystem/icons.php.
As part of the U.S. Geological Survey's Volcano Hazards Program, the California Volcano Observatory aims to advance scientific understanding of volcanic processes and lessen the harmful impacts of volcanic activity in the volcanically active areas of California and Nevada. For additional USGS CalVO volcano information, background, images, and other graphics visit http://volcano.wr.usgs.gov/vsc/observatories/calvo.html. For general information on the USGS Volcano Hazard Program http://volcanoes.usgs.gov. Statewide seismic information for California and Nevada can be found at http://earthquake.usgs.gov/earthquakes/recenteqscanv/.
CALIFORNIA VOLCANO OBSERVATORY MONTHLY UPDATE
Thursday, September 6, 2012 11:55 AM PDT (Thursday, September 6, 2012 18:55 UTC)
Monitored CALIFORNIA VOLCANOES Current Volcano Alert Level: all NORMAL Current Aviation Color Code: all GREEN
Activity Update: All volcanoes monitored by CalVO's telemetered, real-time sensor networks exhibit normal levels of background seismicity and deformation. Real-time monitoring networks are in place at Mount Shasta, Medicine Lake Volcano, Clear Lake Volcanic Field, Lassen Volcanic Center, Long Valley Caldera and Mono-Inyo Chain.
Observations for August 1, 2012 (0000h PDT) through August 31, 2012 (2359h PDT): Mt Shasta: One earthquake of magnitude M=1.6 detected. Medicine Lake: No earthquakes were detected at or above M=1.0 Lassen Volcanic Center: Two earthquakes of magnitude M=1.0 or greater were detected. Clear Lake Volcanic Field: Three earthquakes magnitude M=1.0 or greater were detected [Note: Typical high level of seismicity observed under the Geysers steam field located at the western margin of CLVF. All events were below magnitude M=2.0]. Long Valley Caldera and Mono-Inyo Chain: Ten earthquakes occurred in the southern half of the Long Valley Caldera east of the town of Mammoth Lakes (largest events were M=2.4 and M=2.3); One earthquake was located east of Mono Lake in Mono Valley (M=1.3); One earthquake of magnitude M=1.2 was detected under Mammoth Mountain. [Note: Typical high level of seismicity observed south of the caldera in the Sierra Nevada range. Largest events were M=2.5 and M=3.0]. Additionally, analysis of continuous GPS data over the last several months show continued modest inflation within the caldera. Ground motion is directed upward and away from the caldera's center, with a maximum uplift rate between 2 and 3 cm/yr. Horizontal deformation is similar in magnitude, with a N/S extension rate across the caldera's center of about 3 cm/yr. These rates of deformation are comparable to those observed in 2002-2003, and well below the rates seen in the late 1990s.
The U.S. Geological Survey will continue to monitor these volcanoes closely and will issue additional updates and changes in alert level as warranted. For a definition of alert levels see http://volcanoes.usgs.gov/activity/alertsystem/icons.php.
As part of the U.S. Geological Survey's Volcano Hazards Program, the California Volcano Observatory aims to advance scientific understanding of volcanic processes and lessen the harmful impacts of volcanic activity in the volcanically active areas of California and Nevada. For additional USGS CalVO volcano information, background, images, and other graphics visit http://volcano.wr.usgs.gov/vsc/observatories/calvo.html. For general information on the USGS Volcano Hazard Program http://volcanoes.usgs.gov. Statewide seismic information for California and Nevada can be found at http://earthquake.usgs.gov/earthquakes/recenteqscanv/.
CALIFORNIA VOLCANO OBSERVATORY MONTHLY UPDATE
Monday, August 6, 2012 5:28 PM PDT (Tuesday, August 7, 2012 00:28 UTC)
Monitored CALIFORNIA VOLCANOES Current Volcano Alert Level: all NORMAL Current Aviation Color Code: all GREEN
Activity Update: All volcanoes monitored by CalVO's telemetered, real-time sensor networks exhibit normal levels of background seismicity and deformation. Real-time monitoring networks are in place at Mount Shasta, Medicine Lake Volcano, Clear Lake Volcanic Field, Lassen Volcanic Center, Long Valley Caldera and Mono-Inyo Chain.
Observations for July 1, 2012 (0000h PDT) through July 31, 2012 (2359h PDT): Mt Shasta: No earthquakes of magnitude M=1.0 or greater were detected. Medicine Lake: Two earthquakes were detected (both M<2.0). Lassen Volcanic Center: No earthquakes of magnitude M=1.0 or greater were detected. Clear Lake Volcanic Field: Four earthquakes were located in the southwest part of the volcanic field. All were below magnitude M=2.0 [Note: Typical high level of seismicity observed under the Geysers steam field located at the western margin of CLVF. The largest event was a magnitude 2.8]. Long Valley Caldera and Mono-Inyo Chain: Six earthquakes occurred in the southern half of the Long Valley Caldera east of the town of Mammoth Lakes (all M<2.0); Two earthquakes were located on the eastern end of Mono Lake (M<2.0); No earthquakes of magnitude M=1.0 or greater were detected under Mammoth Mountain. [Note: Typical high level of seismicity observed south of the caldera in the Sierra Nevada range. Largest event was M=2.4]. Additionally, analysis of continuous GPS data over the last several months show a modest inflationary pattern within the caldera. Ground motion is directed upward and away from the caldera's center, with a maximum uplift rate between 2 and 3 cm/yr. Horizontal deformation is similar in magnitude, with a N/S extension rate across the caldera's center of about 3 cm/yr. These rates of deformation are comparable to those observed in 2002-2003, and well below the rates seen in the late 1990s.
The U.S. Geological Survey will continue to monitor these volcanoes closely and will issue additional updates and changes in alert level as warranted. For a definition of alert levels see http://volcanoes.usgs.gov/activity/alertsystem/icons.php.
As part of the U.S. Geological Survey's Volcano Hazards Program, the California Volcano Observatory aims to advance scientific understanding of volcanic processes and lessen the harmful impacts of volcanic activity in the volcanically active areas of California and Nevada. For additional USGS CalVO volcano information, background, images, and other graphics visit http://volcano.wr.usgs.gov/vsc/observatories/calvo.html. For general information on the USGS Volcano Hazard Program http://volcanoes.usgs.gov. Statewide seismic information for California and Nevada can be found at http://earthquake.usgs.gov/earthquakes/recenteqscanv/.
CALIFORNIA VOLCANO OBSERVATORY MONTHLY UPDATE
Wednesday, July 4, 2012 1:01 PM PDT (Wednesday, July 4, 2012 20:01 UTC)
Monitored CALIFORNIA VOLCANOES Current Volcano Alert Level: all NORMAL Current Aviation Color Code: all GREEN
Activity Update: All volcanoes monitored by CalVO's telemetered, real-time sensor networks exhibit normal levels of background seismicity and deformation. Real-time monitoring networks are in place at Mount Shasta, Medicine Lake Volcano, Clear Lake Volcanic Field, Lassen Volcanic Center, Long Valley Caldera and Mono-Inyo Chain.
Observations for June 1, 2012 (0000h PDT) through June 30, 2012 (2359h PDT): Mt Shasta: Three earthquakes below magnitude 2.0 under the SE flank. Medicine Lake: No earthquakes were detected. Lassen Volcanic Center: Three earthquakes below magnitude 2.0 were detected south of Emerald Lake inside Lassen Volcanic National Park. Clear Lake Volcanic Field: Fourteen earthquakes were located in the southwest part of the volcanic field. The largest event was a magnitude 2.7; the others were below magnitude 2.0 [Note: Typical high level of seismicity observed under the Geysers steam field located at the western margin of CLVF. The largest event was a magnitude 2.3]. Long Valley Caldera and Mono-Inyo Chain: Six earthquakes occurred in the southern half of the Long Valley Caldera east of the town of Mammoth Lakes under the resurgent dome (all M<2.0); Two earthquakes were located on the eastern shores of Mono Lake (M<2.0); Thirteen earthquakes were located under the north flank of Mammoth Mountain (M<2.0). [Note: Typical high level of seismicity observed south of the caldera in the Sierra Nevada range. Largest event was M=2.4].
The U.S. Geological Survey will continue to monitor these volcanoes closely and will issue additional updates and changes in alert level as warranted. For a definition of alert levels see http://volcanoes.usgs.gov/activity/alertsystem/icons.php.
As part of the U.S. Geological Survey's Volcano Hazards Program, the California Volcano Observatory aims to advance scientific understanding of volcanic processes and lessen the harmful impacts of volcanic activity in the volcanically active areas of California and Nevada. For additional USGS CalVO volcano information, background, images, and other graphics visit http://volcano.wr.usgs.gov/vsc/observatories/calvo.html. For general information on the USGS Volcano Hazard Program http://volcanoes.usgs.gov. Statewide seismic information for California and Nevada can be found at http://earthquake.usgs.gov/earthquakes/recenteqscanv/.
CALIFORNIA VOLCANO OBSERVATORY MONTHLY UPDATE
Monday, June 4, 2012 4:08 PM PDT (Monday, June 4, 2012 23:08 UTC)
Monitored CALIFORNIA VOLCANOES Current Volcano Alert Level: all NORMAL Current Aviation Color Code: all GREEN
Activity Update: All volcanoes monitored by CalVO's telemetered, real-time sensor networks exhibit normal levels of background seismicity and deformation. Real-time monitoring networks are in place at Mount Shasta, Medicine Lake Volcano, Clear Lake Volcanic Field, Lassen Volcanic Center, Long Valley Caldera and Mono-Inyo Chain.
Observations for May 1, 2012 (00:00 PDT) through May 31, 2012 (11:59 PDT): Mt Shasta: One magnitude 1.5 earthquake under the SE flank. Medicine Lake: One M=1.0 earthquake under western Glass Mountain. Lassen Volcanic Center: One magnitude 2.2 earthquake detected between Mt Dillar and Brokeoff Mountain inside Lassen Volcanic National Park. Clear Lake Volcanic Field: Two earthquakes within the southern arm of Clear Lake. Both events were below magnitude 2.0 [Note: Typical high level of seismicity observed under the Geysers steam field located at the western margin of CLVF. The largest events included magnitude 4.2 and 3.3 earthquakes on May 5 and a magnitude 3.9 on May 13]. Long Valley Caldera and Mono-Inyo Chain: Eleven earthquakes occurred in the southern half of the Long Valley Caldera east of the town of Mammoth Lakes (largest with M=2.2); One earthquake east of Mono Lake (M<2.0); One earthquake under Mammoth Mountain (M<2.0). [Note: Typical high level of seismicity observed south of the caldera in the Sierra Nevada range. Largest event was M=2.4].
The U.S. Geological Survey will continue to monitor these volcanoes closely and will issue additional updates and changes in alert level as warranted. For a definition of alert levels see http://volcanoes.usgs.gov/activity/alertsystem/icons.php.
As part of the U.S. Geological Survey's Volcano Hazards Program, the California Volcano Observatory aims to advance scientific understanding of volcanic processes and lessen the harmful impacts of volcanic activity in the volcanically active areas of California and Nevada. For additional USGS CalVO volcano information, background, images, and other graphics visit http://volcano.wr.usgs.gov/vsc/observatories/calvo.html. For general information on the USGS Volcano Hazard Program http://volcanoes.usgs.gov. Statewide seismic information for California and Nevada can be found at http://earthquake.usgs.gov/earthquakes/recenteqscanv/.
CALIFORNIA VOLCANO OBSERVATORY MONTHLY UPDATE
Sunday, May 6, 2012 2:38 PM PDT (Sunday, May 6, 2012 21:38 UTC)
Monitored CALIFORNIA VOLCANOES Current Volcano Alert Level: all NORMAL Current Aviation Color Code: all GREEN
Activity Update: All volcanoes monitored by CalVO's telemetered, real-time sensor networks exhibit normal levels of background seismicity and deformation. Real-time monitoring networks are in place at Mount Shasta, Medicine Lake Volcano, Clear Lake Volcanic Field, Lassen Volcanic Center, Long Valley Caldera and Mono-Inyo Chain.
Observations for April 1, 2012 (00:00 PDT) through April 30, 2012 (11:59 PDT): Mt Shasta: Two earthquakes under the SE flank; both M<2.0. Medicine Lake: Six M<2.0 earthquakes under the caldera. Lassen Volcanic Center: No earthquakes of M=1.0 or greater were detected. Clear Lake Volcanic Field: Five earthquakes within the southeast arm of Clear Lake. All events were below magnitude 2.0 [Note: Typical high level of seismicity observed under the Geysers steam field located outside the southwestern margin of CLVF. Largest event was M=2.8]. Long Valley Caldera and Mono-Inyo Chain: Twenty-one earthquakes occurred in Long Valley Caldera east of Mammoth Lakes near Lake Crowley (largest four with M=2.1 to 2.6); Two earthquakes east of Mono Lake (M<2.0); Two earthquakes under Mammoth Mountain (both M<2.0). [Note: Typical high level of seismicity observed south of the caldera in the Sierra Nevada range. Largest event was M=2.3].
The U.S. Geological Survey will continue to monitor these volcanoes closely and will issue additional updates and changes in alert level as warranted. For a definition of alert levels see http://volcanoes.usgs.gov/activity/alertsystem/icons.php.
As part of the U.S. Geological Survey's Volcano Hazards Program, the California Volcano Observatory aims to advance scientific understanding of volcanic processes and lessen the harmful impacts of volcanic activity in the volcanically active areas of California and Nevada. For additional USGS CalVO volcano information, background, images, and other graphics visit http://volcano.wr.usgs.gov/vsc/observatories/calvo.html. For general information on the USGS Volcano Hazard Program http://volcanoes.usgs.gov. Statewide seismic information for California and Nevada can be found at http://earthquake.usgs.gov/earthquakes/recenteqscanv/.