Notable Earthquake of the Week

Chalfant Valley, California, M6.2 and M6.6 Earthquake  

In During July 20-21, 1986, a strong double earthquake sequence rocked the east-central Sierra Nevada Mountains near Bishop, CA.

The sequence began at 7:29 am, July 20, with a particularly strong jolt measuring M6.2. The quake was centered along the northern portion of the Fish Slough fault zone about 6 miles north of Bishop, in Chalfant Valley. At 7:42 am the following morning, the region was rocked again by a very strong M6.6 earthquake in about the same location as the first temblor.

Minor surface ruptures were measured for over 6 miles with both vertical and horizontal displacements on the order of a few centimeters.

The town of Bishop and surrounding communities sustained minor damage with some structural damage; several injuries were reported but there were no deaths. Several local residents were frightened by the brief but intense shaking.

See the poster-sized map of California Nevada Earthquakes here.

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