1986 North Palm Springs earthquake
 Oceanside
Los Angeles
Bishop
 |
|
| Date | July 8, 1986 |
|---|---|
| Origin time | 09:20:44 UTC |
| Magnitude | 6.0 Mw |
| Depth | 10 km (6.2 mi) |
| Epicenter | 34°01′N 116°46′W / 34.02°N 116.76°WCoordinates: 34°01′N 116°46′W / 34.02°N 116.76°W |
| Type | Strike-slip |
| Areas affected |
Coachella Valley Southern California United States |
| Total damage | $4.5–6 million |
| Max. intensity | VII (Very strong) |
| Peak acceleration | .778g |
| Casualties | 29–40 injured |
The 1986 North Palm Springs earthquake occurred on July 8 at 02:20:44 local time with a moment magnitude of 6.0 and a maximum Mercalli Intensity of VII (Very strong). The shock occurred in a complex setting along the San Andreas Fault Zone where it bisects San Gorgonio Mountain and San Jacinto Peak at the San Gorgonio Pass and was the first in a series of three earthquakes that affected southern California and the northern Owens Valley in July 1986. Between 29 and 40 people were injured, and financial losses were estimated to be in the range of $4.5 to 6 million.
July 1986 was an unusually active month for moderate to strong earthquakes in California, with three events occurring in less than two weeks. Each had mild to moderate effects and began on July 8 with the event near Palm Springs. The second event was a M5.8 shock that occurred off the coast of Oceanside 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 future earthquake. The Chalfant Valley earthquake occurred on July 21 along the White Mountains Fault Zone near Bishop.
The San Andreas Fault (SAF) spans nearly the length of California, where much of its length the fault is clearly identifiable, especially from San Francisco to near Cajon Pass. There, the fault splays into several branches. Several unusual characteristics are displayed further to the southeast in the area of the San Gorgonio Pass. There are no lateral stream offsets (that are associated with strike-slip faulting) near the pass like there are along other segments (one researcher indicated that thrust faulting was the dominant type of fault displacement at the pass). There are no great earthquakes that are known to have occurred at the pass, where the main trace of the SAF is marked by numerous sag ponds and north-facing scarps. The Banning Fault lies about two miles to the south of these features.
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