Earthquake swarm under Mammoth Mountain
February 06, 2014
An earthquake swarm under Mammoth Mountain (Mono County, CA), which started slowly on February 3, 2014 intensified in the early hours of February 5 with many small-magnitude earthquakes occurring in rapid succession, a phenomenon known as "spasmodic bursts." The largest earthquake over the ~ 4 hours of heightened activity, a magnitude 3.0, occurred shortly after 1am local time. The swarm is emanating from depths of about 5 km (~ 3 miles) below the surface. Most earthquakes in the swarm are too small to be felt, but the magnitude 3.0 earthquake was felt by a few people in the town of Mammoth Lakes. Presently, earthquake activity beneath the mountain remains above background levels. Earthquake swarms, including spasmodic bursts, occur periodically beneath Mammoth Mountain. The current swarm is notable, however, because it includes the largest magnitude event (M3.0) observed in ~15 years.
The attached plot
shows the numbers of earthquakes under Mammoth Mountain over the last three months.
CalVO deformation monitoring sensors at Mammoth Mountain show no significant change. In the adjacent Long Valley Caldera, the modest, quasi-steady inflation that has been observed for the last couple of years, also appears unchanged by the Mammoth Mountain swarm. CalVO scientists continue to closely monitor seismic, deformation, and gas emission signals.
Volcano Hazard Mitigation Included in California Multi-hazard Mitigation Plan
October 29, 2013
On October 6, 2013 the California Office of Emergency Services (CalOES) published its 2013 State of California Multi-Hazard Mitigation Plan
complete with a chapter from the USGS on volcano hazard mitigation. This document is the official statement of the State's hazard identification, vulnerability analysis, and hazard mitigation strategy. Volcanic eruptions occur in California about as frequently as the largest San Andreas Fault Zone earthquakes. Our State Geologist, John Parrish states, "California is the most geologically diverse state in the Nation. We are known for our earthquakes, landslides, and flood hazards. But our nearly forgotten hazard is our volcanoes." With as many as ten eruptions in the last 1,000 years, recognizing the potential for renewed volcanism in California is an essential first step in mitigating hazardous impacts.
You can see the full Mitigation Plan
on the CalOES website.