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Remotely triggered seismicity on the United States west coast following the Mw 7.9 Denali fault earthquake

January 1, 2004

The Mw 7.9 Denali fault earthquake in central Alaska of 3 November 2002 triggered earthquakes across western North America at epicentral distances of up to at least 3660 km. We describe the spatial and temporal development of triggered activity in California and the Pacific Northwest, focusing on Mount Rainier, the Geysers geothermal field, the Long Valley caldera, and the Coso geothermal field.

The onset of triggered seismicity at each of these areas began during the Love and Raleigh waves of the Mw 7.9 wave train, which had dominant periods of 15 to 40 sec, indicating that earthquakes were triggered locally by dynamic stress changes due to low-frequency surface wave arrivals. Swarms during the wave train continued for ∼4 min (Mount Rainier) to ∼40 min (the Geysers) after the surface wave arrivals and were characterized by spasmodic bursts of small (M ≤ 2.5) earthquakes. Dynamic stresses within the surface wave train at the time of the first triggered earthquakes ranged from 0.01 MPa (Coso) to 0.09 MPa (Mount Rainier). In addition to the swarms that began during the surface wave arrivals, Long Valley caldera and Mount Rainier experienced unusually large seismic swarms hours to days after the Denali fault earthquake. These swarms seem to represent a delayed response to the Denali fault earthquake. The occurrence of spatially and temporally distinct swarms of triggered seismicity at the same site suggests that earthquakes may be triggered by more than one physical process.

Publication Year 2004
Title Remotely triggered seismicity on the United States west coast following the Mw 7.9 Denali fault earthquake
DOI 10.1785/0120040610
Authors S. G. Prejean, D. P. Hill, E. E. Brodsky, S. E. Hough, M.J.S. Johnston, S. D. Malone, D. H. Oppenheimer, A. M. Pitt, K. B. Richards-Dinger
Publication Type Article
Publication Subtype Journal Article
Series Title Bulletin of the Seismological Society of America
Index ID 70026246
Record Source USGS Publications Warehouse
USGS Organization Alaska Science Center