1986 Chalfant Valley earthquake
 Fallon
Sacramento
Oceanside
Las Vegas
Santa Cruz
Palm Springs
Death Valley
Coalinga
 |
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| Date | 21 July 1986 |
|---|---|
| Origin time | 14:42:28 UTC |
| Magnitude | 6.2 Mw |
| Depth | 10 km (6.2 mi) |
| Epicenter | 37°32′N 118°25′W / 37.54°N 118.42°WCoordinates: 37°32′N 118°25′W / 37.54°N 118.42°W |
| Type | Strike-slip |
| Areas affected |
Eastern California United States |
| Total damage | $2.7 million USD |
| Max. intensity | VI (Strong) |
| Peak acceleration | .46g |
| Foreshocks | 5.7 ML July 20 at 14:29 |
| Casualties | 2 injured |
The 1986 Chalfant Valley earthquake struck southern Mono County near Bishop and Chalfant, California at 07:42:28 Pacific Daylight Time on July 21. With a moment magnitude of 6.2 and a maximum Mercalli intensity of VI (Strong), the shock injured two people and caused property damage estimated at $2.7 million in the affected areas. There was a significant foreshock and aftershock sequence that included a few moderate events, and was the last in a series of three earthquakes that affected southern California and the northern Owens Valley in July 1986.
Strong motion stations at the Long Valley Dam and an instrumented building in Bishop captured light to moderate readings from the event. The faulting reached the surface of the ground, but the maximum amount of measurable slip was limited to about 11 centimeters (4.3 in) of strike-slip motion along the White Mountain Fault Zone. Other destructive and surface-rupturing earthquakes, as well as large volume volcanic eruptions, have occurred in the area. Although the series of shocks occurred within the White Mountain seismic gap, the region continues to have potential for a very large earthquake.
July 1986 was an unusually active month for moderate to strong earthquakes in California, with three events occurring in less than two weeks, each with mild to moderate effects. The first of these shocks came on July 8 with a M6.0 event on the Banning fault near Palm Springs and the second event occurred off the coast of Oceanside as a M5.8 shock on July 13. While the earthquake off the southern California coast occurred in an area thought to be capable of generating a tsunami, the earthquake near Palm Springs occurred on a portion of the southern San Andreas Fault system that has been designated a seismic gap, and is a likely location for a very large earthquake. The same seismic gap theory (regarding the potential for a future large earthquake) had also been presented for the White Mountains area near Chalfant.
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