Hazard Notification System (HANS) for Volcanoes


U.S. Geological Survey
Tuesday, February 28, 2023, 9:39 AM PST (Tuesday, February 28, 2023, 17:39 UTC)

Current Volcano Alert Level: all NORMAL
Current Aviation Color Code: all GREEN

Activity Update: All volcanoes monitored by CalVO show normal background earthquake activity and ground movement. Monitored volcanoes include Mount Shasta, Medicine Lake Volcano, Lassen Volcanic Center, Clear Lake Volcanic Field, Long Valley Volcanic Region, Coso Volcanic Field, Ubehebe Craters, and Salton Buttes.

Past Week Observations for February 20, 2023 (0000h PST) through February 26, 2023 (2359h PST):

Five earthquakes greater than M1 were detected at the Clear Lake Volcanic Field, with the largest having a magnitude of M1.4. Typical seismicity was recorded at The Geysers geothermal field south of the Clear Lake Volcanic Field; 144 earthquakes greater than M1 were detected, with the largest having a magnitude of M2.9.

One earthquake greater than M1 was recored in Long Valley Caldera, with a magnitude of M2.9. Six earthquakes greater than M1 were recorded in the Sierra Nevada range south of Long Valley Caldera, with the largest having a magnitude of M2.4. These earthquakes occur within a regional fault zone and are related to tectonic movement not associated with the volcano. One earthquake greater than M1 was recorded at Mammoth Mountain, with a magnitude of M2.1.

One earthquake greater than M1 was recorded at Coso Volcanic Field, with a magnitude of 1.0.

CalVO's Weekly Update only highlights volcanoes which have experienced seismic activity or volcanic unrest. If there are no comments for a volcano, CalVO has detected no earthquakes with magnitudes greater than or equal to M1.0, or any other kind of unrest. Only earthquakes with magnitudes greater than M1.0 are reported here.

These earthquake counts are preliminary and subject to change as the earthquakes are reviewed by seismologists. 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 monitors the volcanoes of California and Nevada and advances scientific understanding of volcanic processes in order to reduce the harmful impacts of volcanic activity. For additional USGS CalVO volcano information, background, images, and other graphics visit http://volcanoes.usgs.gov/observatories/calvo/. For general information on the USGS Volcano Hazard Program visit http://volcanoes.usgs.gov. Statewide seismic information for California and Nevada can be found at https://earthquake.usgs.gov/earthquakes/map/.