4.5 Quake at Mammoth Prompts Warning

A magnitude 4.5 earthquake shook the Eastern Sierra near Mammoth Lakes Monday afternoon, triggering issuance by the U.S. Geological Survey of a C status of “strong unrest” in the volcanic region.

David Hill, in charge of Mammoth geological monitoring for the agency, said the earthquake at 3:26 p.m. was located at a depth of six miles just outside the Long Valley caldera, which has been under close watch since four magnitude 6 quakes shook the area in 1980.

Hill said this was the strongest earthquake near Mammoth Lakes in nearly a year, but he said there does not appear to be cause for concern.

The C status is the third of five levels of warning, with the strongest, an A status, indicating that an eruption is likely within hours to days. The present status will last three days if nothing further happens.

Tracy Fuller, acting Mammoth Lakes town manager, said the quake, centered eight miles southeast, was felt distinctly in the town, but did not cause damage or injuries. About 30 aftershocks, none as strong as magnitude 3.0, followed within two hours.

There has been no volcanic activity in the Mammoth Lakes area for more than 200 years.