Quake swarm near Lassen Peak doesn't appear to be volcanic
Staff Reports
LASSEN PARK >> A hundred years ago the ground around Lassen Peak was shaking, as the volcano was in the midst of a year-long string of small eruptions that would culminate with an explosive eruption May 22, 1915.
The ground in that vicinity had been shaking again for the last week, although scientists don't think it's related to volcanic activity.
Since Nov. 8, there have been in excess of 150 densely-packed earthquakes just south of Lassen Volcanic National Park. Almost all the quakes have been tiny, with just a handful that could be felt even under favorable conditions. The largest was a 3.86 magnitude quake that happened just after midnight on Nov. 11.
The quake swarm has been concentrated in a band between Mill Creek and the North Fork of the Feather River, between Lassen Park and Childs Meadow. As of 5 p.m., there had been seven quakes on Friday, ranging from magnitude 2.7 to 1.6.
A call to the U.S. Geological Survey seeking comment was not returned by deadline, but the website of its California Volcanic Observatory indicated the swarm's cause doesn't appear to be volcanic activity. "Ground deformation indicative of volcanic unrest has not been detected by nearby GPS receivers," the website states.
Instead the quakes are likely fault motion along the Walker Lane Fault System, which runs near the California-Nevada border. No immediate threat is seen.
The Volcanic Observatory is in contact with Lassen Park, however, watching for any changes in the hydrothermal features there.
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