June 14, 2005 California Earthquake

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Posting Date: June 15, 2005, 12:00:00 AM

A major earthquake struck off the coast of northern California on Tuesday, June 14, 2005, at 7:50 p.m. Pacific Standard Time, 2:50 UTC. The USGS has estimated the earthquake's magnitude at 7.0. The epicenter was located about 90 miles west southwest of Crescent City, California, and about 300 miles northwest of Sacramento, California, at an estimated depth of 6.2 miles. Residents of Crescent City and the northern California coast felt buildings shake during the earthquake, and the quake was felt as far inland as Sacramento. No major damage has been reported, though the earthquake triggered Crescent City's tsunami siren system at 8:14 p.m., prompting the evacuation of about 4,000 people from low-lying areas of the city. Emergency officials also issued a tsunami warning covering the entire west coast of the U.S., which was lifted shortly thereafter. Crescent City was the site of a deadly tsunami triggered by the 1964 Good Friday earthquake in Alaska. That tsunami killed 11 people and leveled 29 city blocks. Tuesday's event appears to have been a strike-slip earthquake, producing a horizontal motion rather than the vertical displacement that typically produces tsunamis. The event occurred within the Gorda plate, a microplate off the west coast of North America. The Gorda plate is at the southern end of the Juan de Fuca plate, which is composed of three micro-plates and subducts eastward at a rate of 30-35 mm/year under western North America in the Cascadia Subduction Zone system. The Gorda plate is undergoing significant internal deformation. Historic earthquakes have occurred not only along its boundaries, but also within the plate, where a series of northeast-southwest striking faults have developed under the intensive stress from the relative motion of the Pacific, Juan de Fuca and the North America plates. Yesterday's event occurred along one of the left-lateral strike-slip faults within the Gorda plate. The 1980 M7.3 Eureka earthquake, which was located further to the east in the coastal areas, was a similar event that ruptured one of the northeast striking faults. The 1980 Eureka tremor injured six people and caused $2 million in damage in 1980 dollars. Because this earthquake occurred well offshore, the AIR earthquake team does not expect any significant insured losses.

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Posting Date: June 15, 2005, 12:00:00 AM