HR: 16:55h
AN: S12E-04    [PDF]
TI: Seismotectonics and Seismic Hazard of the Sierran Nevada Great Basin Boundary Zone and Yucca Mountain Region
AU: * Smith, K
EM: ken@seismo.unr.edu
AF: Nevada Seismological Laboratory, MS 174, University of Nevada Reno, Reno, NV 89557 United States
AU: von Seggern, D
EM: vonseg@seismo.unr.edu
AF: Nevada Seismological Laboratory, MS 174, University of Nevada Reno, Reno, NV 89557 United States
AU: Biasi, G P
EM: glenn@seismo.unr.edu
AF: Nevada Seismological Laboratory, MS 174, University of Nevada Reno, Reno, NV 89557 United States
AU: dePolo, D
EM: diane@seismo.unr.edu
AF: Nevada Seismological Laboratory, MS 174, University of Nevada Reno, Reno, NV 89557 United States
AB: Geodetic data indicate that the Sierra Nevada block is moving at about 14 mm/yr N40-450W relative to stable North America. This motion accounts for about 20-25% of the current western North American plate motion budget and is oblique to active faults along the Sierra Nevada-Great Basin boundary zone and Walker Lane belt in a transtensional deformation field. Faulting over the past few million years has been concentrated along faults of the Eastern California shear zone, and the Walker Lane belt. Linear strike-slip faults of the Eastern California shear zone terminate near the Long Valley Caldera region marking an abrupt transition in the deformational style between the southern and northern western Great Basin. These tectonic transitions are reflected in the distribution and character of the historical and instrumental seismicity. North of Long Valley, through going strike-slip faulting is concentrated outboard from the Sierran Range front in the Central Walker Lane belt, whereas normal faulting in a series of left-stepping range bounding faults exhibiting E-W extension characterizes the Sierra Great Basin Boundary region from Long Valley to about the latitude of Reno-Lake Tahoe. Seismicity in the Lake Tahoe region is primarily concentrated in the transition between left-stepping normal faults in zones of high-angle conjugate strike-slip faulting. These observations suggest potential shortening as a mechanism of slip transfer between normal fault systems along the range front. Also, these slip transition zones show different recurrence behavior, activity rates and maximum magnitudes than the adjacent primary normal fault systems. One important kinematic problem is how to reconcile extension directions observed from instrumental seismicity and Sierran motion in the central western Great Basin. An upgrade to a digital seismic network in southern Nevada under the DOE Yucca Mountain Project has increased the detection threshold by about 1 magnitude unit (the catalog is complete to about M -0.5 near Yucca Mountain) improving resolution of tectonic features near the potential high-level nuclear waste repository. Slip rates of Quaternary faults in the Yucca Mountain area are more than 2 orders of magnitude less than those of the Furnace Creek fault zone 75 km to the west. With the increase in the number of earthquakes that can now be located within the NTS regional network we propose that the observed distribution of seismicity in southern Nevada in the NTS area primarily reflects the remnant of a Miocene tectonic fabric consistent with low Quaternary strain rates. With increased urbanization of Las Vegas and the implications of significant seismic amplification in valley sediments, the understanding of the regional tectonics, fault slip rates and background seismicity becomes increasing important for seismic hazard assessment in southern Nevada.
DE: 7223 Seismic hazard assessment and prediction
DE: 7230 Seismicity and seismotectonics
DE: 8109 Continental tectonics--extensional (0905)
DE: 8123 Dynamics, seismotectonics
SC: Seismology [S]
MN: 2003 Fall Meeting