CALIFORNIA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Tuesday, May 2, 2023, 9:29 AM PDT (Tuesday, May 2, 2023, 16:29 UTC)
Monitored CALIFORNIA VOLCANOES
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 April 24, 2023 (0000h PDT) through April 30, 2023 (2359h PDT):
One earthquake greater than M1 was recorded at Lassen Volcanic Center, with a magnitude of M1.8.
One earthquake greater than M1 was recorded at Clear Lake Volcanic Field, with a magnitude of M1.1. Typical seismicity was recorded at The Geysers geothermal field south of the Clear Lake Volcanic Field; 77 earthquakes greater than M1 were detected, with the largest having a magnitude of M2.3.
Two earthquakes greater than M1 were recorded at Long Valley Caldera, with the largest having a magnitude of M1.2. One earthquake greater than M1 was recorded in the Sierra Nevada range south of Long Valley Caldera, with a magnitude of M1.7. This earthquake occured within a regional fault zone, was related to tectonic movement, and was not associated with the volcano.
Five earthquakes greater than M1 were recorded at the Coso Volcanic Field, with the largest having a magnitude of M1.6.
51 earthquakes greater than M1 were recorded at the Salton Buttes, with the largest having a magnitude of M4.5. 46 of these earthquakes occurred as part of an aftershock sequence following the M4.5 earthquake on April 30, and are most likely related to regional tectonic movement.
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/.