Amplified Ground Response Across the Western U.S. Interior from the M7.9 Denali Earthquake

It has been hypothesized that peak dynamic stresses from large earthquakes with large surface waves can trigger seismicity at great distances from the main shock. This effect has been observed earlier in the 1992 M7.4 Landers earthquake and the 1999 M7.1 Hector Mine earthquake. Unusually large surface waves of the M7.9 Denali earthquake triggered seismicity throughout the western U.S., especially in areas of hydrothermal activity These peak dynamic stresses are unusual in that they are so large at such great distances from the source. The known triggered earthquakes occurred at distances up to at least 3000 km away from the main shock and appeared to mostly effect areas of concentrated hydrothermal activity such as Yellowstone National Park and others, including Long Valley Caldera, The Geysers, CA, Mt. Rainer WA, and Coso Hot Springs, CA. Surface wave propagation effects, peak dynamic stresses (calculated from measurements of peak vector velocities) and peak displacements will be analyzed at localities throughout the western U.S. from both broadband and long period data. The data is primarily from the United States National Seismic Network (USNSN), the Advanced National Seismic System (ANSS), and regional seismograph arrays. The peak radiation values across the western U.S. will also be compared to areas of triggered seismicity. These data help to better understand how large earthquakes trigger seismicity at such large distances from the main shock and why areas of concentrated hydrothermal activity seem to be the most sensitive to such effects.