SEISMICITY AND EARTHQUAKE HAZARD ANALYSIS OF THE TETON-YELLOWSTONE REGION, WYOMING

The Teton-Yellowstone region reflects a region of high seismicity in the Intermountain west (U.S.A.) that is associated with intraplate extension of the Yellowstone hotspot and surrounding region including the Teton and Hebgen Lake faults. Seismicity and seismogenic structures were evaluated using a new earthquake catalog employing 3D seismic velocity models, followed by the estimation of the probabilistic seismic hazard (PSHA) incorporating Quat. fault slip and earthquake return rates. The P-wave velocity structure of the Teton-Yellowstone area was determined using data from the Jackson Lake seismic network, operated from 1986-2002, and from the Yellowstone seismic network that has operated since 1973. The resulting data for the Teton area revealed a seismically quiescent Teton fault, at ML>2.5, with diffuse seismicity in southern Jackson Hole but notable seismicity extending eastward into the Gros Ventre Range. Yellowstone earthquakes highlighted a dominant E-W zone of seismicity from the aftershock area of the 1959 moment magnitude MW 7.3 Hebgen Lake fault, MT, earthquake, along the north side of the 0.64Ma Yellowstone caldera. Yellowstone caldera seismicity is dominated by less frequent and shallow earthquake swarms along N-S zones sub-parallel to the post-caldera volcanic vents. Stress determinations from focal mechanisms and GPS data reveal E-W extension across the Teton fault rotating to NE-SW extension in southern Yellowstone to E-W extention across the Yellowstone caldera to N-S extension along the Hebgen Lake fault zone. Relocated hypocenters, unified magnitudes, and seismotectonic analysis help refine the seismicity as input for the PSHA that shows the highest seismic hazard is associated with the Teton fault compared to the highest hazard in Yellowstone on the Sheridan fault.