SAN FRANCISCO (CBS SF) — The United States Geological Survey announced on its website Friday it was “closely tracking” a swarm of hundreds of earthquakes that began Thursday, located in Long Valley about 7 miles east of the Sierra Nevada resort town of Mammoth Lakes.
The region, known to geologists as the Long Valley Caldera, is the site of one of North America’s greatest pre-historic eruptions and is surrounded by a chain of recently-active volcanos. Earthquake swarms are fairly common in the area.
Geologists are careful to determine if the quakes indicate the movement of magma deep below the surface — possibly signaling another eruption — or if they are shallower, less-ominous quakes, sometimes called “tectonic quakes” or “brittle-failure earthquakes.”
The USGS California Volcano Observatory site states that these most-recent quakes “do not result from the underground movement of magma” and “pose no immediate hazard.”
Seismologist David Shelley told the Los Angeles Times the quakes may have been triggered by water pressure from area hot springs, heated by the magma far underground.
Shelly says at least 109 of the earthquakes reported since Thursday were magnitude 2.0 or greater and smaller quakes made up the bulk of the activity.
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Strong earthquakes with an epicenter off the coast can trigger tsunamis, depending on the size and type of the fault movement. The Pacific Tsunami Warning Center tracks earthquake data for the West Coast.
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