Historic Earthquakes

Cape Mendocino, California Earthquakes
1992 04 25 18:06 UTC
Magnitude 7.2

1992 04 26 07:41 UTC
Magnitude 6.5

1992 04 26 11:18 UTC
Magnitude 6.7

On April 25 at 11:06 a.m. PDT, a major earthquake struck northern California. This magnitude 7.2 earthquake was located about 30 miles (50 km) south-southwest of Eureka. Ninety-five people were injured and considerable damage occurred in southwestern Humboldt County. The preliminary estimate of damage from this earthquake, and two strong aftershocks described below, is 66 million dollars. The observed maximum intensity, VIII, was experienced at Ferndale, Honeydew, Petrolia, Rio Dell, and Scotia. Landslides and rockfalls occurred in the Honeydew-Petrolia area. The quake was felt throughout much of northern California and as far south as San Francisco and southeast to Carson City and Reno, Nevada. It was also felt in many areas of southern Oregon. A tsunami was generated with maximum wave heights (peak-to-trough) of 1.1 meters at Crescent City and 0.2 meters at Point Arena, California, and 0.1 meters on Hawaii.

At 12:42 a.m. PDT on April 26, a magnitude 6.5 earthquake hit the same area causing some additional damage in the Ferndale, Petrolia, and Fortuna areas. A fire caused by a broken gas main destroyed much of the business district of Scotia. The quake was felt throughout much of northern California.

Less than 4 hours after the second quake, at 4:19 a.m. PDT, the same area experienced a third strong quake. This magnitude 6.7 earthquake caused additional damage in the area of Ferndale, Fortuna, and Petrolia. It was also felt thoughout much of northern California and southern Oregon and to the south as far as Salinas, Santa Cruz, and San Francisco. These earthquakes were accompanied by numerous aftershocks. Many of the aftershocks were in the magnitude 4.0 to 4.8 range. Some of them were strongly felt, but they caused very little damage.

Abridged from Earthquakes and Volcanoes, Volume 23, Number 5.

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