HR: 14:25h
AN: S43C-04    [Abstracts]
TI: Shear Velocity Structure of the Las Vegas Basin, Nevada
AU: * McEwan, D J
EM: mcewand@unlv.nevada.edu
AF: University of Nevada Las Vegas, 4505 Maryland Parkway MS 4010, Las Vegas, NV 89120 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 89120 United States
AU: Rodgers, A
EM: rodgers7@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Avenue, L-205, Livermore, CA 94551 United States
AB: The Las Vegas Valley, Nevada is a northwest trending valley situated in the central Basin and Range province of western North America. It is recognized as being seismically active, containing at least eight tectonically active faults capable of producing mid-scale earthquakes in a highly populated region. In September 2002, Lawrence Livermore National Laboratory and the University of Nevada Las Vegas installed a semi-permanent array of three-component broadband seismometers, collectively known as the Las Vegas Valley Broadband array. The first deployment lasted for five months and consisted of twelve instruments. In July 2003, six of these instruments were redeployed for fourteen months. The array was located in the northern regions of the Valley to record ground motions in the area estimated to overlie the deepest portion of the basin. These data are used to better understand the correlation of strong ground motion and basin depth. Data consists of continuously recorded local, regional and global earthquakes. Three mid-scale regional earthquakes were used to calculate interstation group velocities along five paths located within the basin, criss-crossing northeast Las Vegas Valley. Interstation group velocities range from 0.25 km/s to 2.14 km/s over periods of 1.3 s to 4.0 s. These values were inverted for 1-D shear velocity profiles within the basin sediments. Shear velocity profiles reach depths up to 4 km with shear velocities ranging from 0.28 km/s to 2.85 km/s for the basin sediments. These velocities are associated with clays and mixed-gravels found in northeast Las Vegas Valley and comprising the shallow sub-basin. In this analysis, the basin-bedrock contact (~5 km) was not reached due to the small (2-10 km) interstation distances. However, the shallow shear velocities determined through this method correlate well with geotechnical surveys and offer greater depth of penetration making this method a non-invasive means for calculating shear velocity at the basin scale.
DE: 7200 SEISMOLOGY
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7255 Surface waves and free oscillations
SC: Seismology [S]
MN: Fall Meeting 2005