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Earthquake Hazards Program

Tectonic Summary

2004 June 28 09:49:47 UTC

Preliminary Earthquake Report
U.S. Geological Survey, National Earthquake Information Center
World Data Center for Seismology, Denver

The June 28, 2004, earthquake occurred in the Queen Charlotte transform fault system, which accommodates the northwestward motion of the Pacific plate with respect to the North American plate at a long-term rate of 48 mm/yr. The earthquake occurred on a section of the fault system that had previously ruptured in the magnitude 8.1 earthquake of August 22, 1949. The elastic-wave radiation pattern is consistent with the earthquake occurring as the result of right-lateral strike-slip faulting on a northwest-striking fault -- as expected from the tectonic situation of the earthquake.


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