Magnitude 3.8 earthquake in Long Valley region is tectonic, and not volcanic, in origin

Release Date:

A magnitude 3.8 earthquake occurred on October 21, 2013 at 10:04 PDT 18 km (11 miles) SE of the town of Mammoth Lakes in eastern California.

Magnitude 3.8 earthquake (large purple dot) located about 18 km SE ...

Magnitude 3.8 earthquake (large purple dot) located about 18 km SE of Mammoth Lakes. Red shading is Long Valley Caldera.

(Public domain.)

It was weakly felt by some in Mammoth Lakes, Bishop, and nearby areas. This event occurred in area of persistently high seismicity beneath the Sierra Nevada mountains, and follows magnitude 3.3 and 3.4 events that occurred nearby on October 11. These earthquakes are occurring at a depth of about 8 km (5 miles) beneath the surface, and appear to related to regional tectonic stresses (combination of strike-slip and extensional faulting) rather than volcanic unrest in Long Valley caldera. For more information about the earthquake, visit the event webpage. Click image to right for mapped location and description.