Notable Earthquake of the Week
Eastern Sierra (Round Valley), California M 6.2 Earthquake

At a little past 10 a.m. on November 23, 1984, an earthquake registering M 6.2 struck the eastern side of the Sierra near Bishop, California. The quake occurred at 10:08 in the morning about 10 miles west of Bishop in Round Valley. The quake was not preceded by any foreshocks, but was followed by a robust aftershock sequence which consisted of thousands of events, including three in the M 5.0 range.

Vigorous shaking tossed items from tables and shelves, cracked walls and broke several windows. Many people were frightened by the temblor and thought it was one of the many quakes that had been occurring in the Mammoth Lakes region which is not far to the west. In fact, the media proclaimed that the Long Valley caldera was going to erupt but the U.S. Geological Survey disputed the reports, saying that the caldera was actually quite calm both during and after the Round Valley quake.

While there are numerous faults in the area, they are collectively referred to as the Round Valley Fault zone and the November 23 earthquake probably occurred along one of them as no surface fault ruptures were event found.


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