HR: 1320h
AN: S43A-0978    [Abstracts]
TI: Shear Velocity Structure Beneath the Las Vegas Valley, Nevada From Regional and Teleseismic Events
AU: * McEwan, D J
EM: mcewand@unlv.nevada.edu
AF: University of Nevada Las Vegas, 4505 Maryland Parkway MS-4010, Las Vegas, NV 89154 United States
AU: Snelson, C M
EM: csnelson@unlv.nevada.edu
AF: University of Nevada Las Vegas, 4505 Maryland Parkway MS-4010, Las Vegas, NV 89154 United States
AU: Tkalcic, H
EM: hrvoje@gnem9.llnl.gov
AF: Lawrence Livermore National Laboratory, L-205, Livermore, CA 94551 United States
AU: Rodgers, A
EM: rodgers7@llnl.gov
AF: Lawrence Livermore National Laboratory, L-205, Livermore, CA 94551 United States
AB: The Las Vegas Valley (LVV), Nevada is located in the central Basin and Range province of western North America. The Valley sits atop a broad sedimentary basin and is susceptible to large earthquakes generated by local and regional faults. During ground motion events, the Las Vegas basin has been found to amplify seismic energy. In addition, the crustal and upper mantle structure of the Valley is poorly understood. Therefore, surface wave data have been used to create shear velocity profiles of the crust and upper mantle beneath LVV using regional and teleseismic events. This project is part of a larger collaborative study, which is characterizing the Las Vegas basin for test site readiness and seismic hazards. Although the frequency of large events is small, the risk associated with such an event is very high for the Valley. As a result, the Las Vegas Valley Broadband array (LVVBB) was deployed in late September 2002 by Lawrence Livermore National Laboratory and the University of Nevada Las Vegas. It consists of a mixture of twelve three-component broadband and short period seismometers deployed in a saw-tooth geometry oriented northeast-southwest across the northeastern and central LVV, above the area estimated to be the deepest portion of the basin. Data examined as part of this study include both regional and global earthquake events recorded within a five-month period on seven of the twelve stations. All seven broadband stations used a three-component Guralp CMG40T sensor with a 40 samples/second sampling rate. Group velocity dispersion curves from Rayleigh waves and Love waves were determined using a multiple filter technique. Rayleigh wave group velocities range from 2.7 to 3.5 km/s for periods from 10 to 30s. Love wave group velocities range from 3.1 to 4.0 km/s for periods from 10 to 100s. In addition, Rg and Lg were examined from local events. 1-D shear velocity profiles of the crust and upper mantle have been produced through inversion along regional source-receiver paths and two-station paths. Shear velocities at depths of 3-5 km have never been directly determined in the Valley; these values will be used to better understand the seismic hazards in the area as well as the tectonic development of southern Nevada in the Basin and Range province.
DE: 7255 Surface waves and free oscillations
DE: 7200 SEISMOLOGY
DE: 7218 Lithosphere and upper mantle
SC: Seismology [S]
MN: 2004 AGU Fall Meeting