Quake Cluster Rattles Area Southeast of Mammoth Lakes

A flurry of moderately strong earthquakes, including a magnitude 5.1 and a 4.1, have struck an area 11 miles southeast of Mammoth Lakes, which was hit by a series of similar quakes last month.

The latest temblors, including five jolts in the magnitude 3 range, began with the 5.1 at 9:43 p.m. Tuesday and continued through a 3.3 at 1:35 p.m. Wednesday, according to the U.S. Geological Survey.

The only damage was scattered breakage of knickknacks, picture frames and other items in homes at Crowley Lake, near the epicenter. There were no injuries, law enforcement authorities said.

As with the quakes in June, the temblors were just outside the volcanic Long Valley caldera. The chief volcanic monitor for the survey, David Hill, said they were probably tectonic, reflecting normal earthquake processes, and not volcanic in origin.

The main shock was about a mile and a half south of the 5.1 quake of June 8 that initiated the series.

Hill said the quakes have been close to, but not on, the Hilton Creek fault, one of a series of faults that form the eastern face of the Sierra Nevada mountain range.

In light of the recent pattern, Hill said, more quakes in the magnitude 3 and 4 ranges will “almost certainly” occur, although there is less than a 10% chance of another 5 magnitude jolt in the next week.

A 3.7 quake took place inside the caldera, three miles east of Mammoth Lakes, at 11:50 p.m. Tuesday. But Hill characterized this as an isolated event.

Overall, seismicity in the Mammoth area is quite a bit less than it was last summer and fall, when thousands of volcanic quakes, which scientists said reflected subterranean movements of lava (magma), were taking place.

Hill said there are no signs of increased ground deformation--a possible sign of impending volcanic activity--associated with the latest series of quakes.

Recent monitoring of carbon dioxide gas emissions around 11,000-foot Mammoth Mountain, just west of Mammoth Lakes, shows that emissions have tailed off, dropping from 1,200 metric tons a day in 1995 to about 500 metric tons.

This so-called “degassing” is thought to be another sign of subterranean magmatic movements. The figures suggest considerably less degassing is occurring.