HR: 0830h
AN: S11D-0322    [PDF]
TI: Comprehensive Analysis of Broadband Seismic Data in Las Vegas Valley
AU: * Tkalcic, H
EM: tkalcic1@llnl.gov
AF: Lawrence Livermore National Laboratory, Earth Science Division, P.O. Box 808, L-206, 8000 East Avenue, Livermore, CA 94551 United States
AU: Rodgers, A
EM: rodgers7@llnl.gov
AF: Lawrence Livermore National Laboratory, Earth Science Division, P.O. Box 808, L-206, 8000 East Avenue, Livermore, CA 94551 United States
AU: Snelson, C
EM: csnelson@unlv.edu
AF: University of Nevada, Las Vegas, Department of Geosciences, 4505 Maryland Parkway, Las Vegas, NV 89154 United States
AU: McEwan, D
EM: mcewand@unlv.edu
AF: University of Nevada, Las Vegas, Department of Geosciences, 4505 Maryland Parkway, Las Vegas, NV 89154 United States
AB: The city of Las Vegas is one of the fastest growing metropolitan areas in the world. Its urban area is located in a relatively broad sedimentary basin in the Basin and Range Province. Acknowledging that Las Vegas of 2003 is drastically different from Las Vegas of a decade ago, our objectives are to understand and predict ground motions and evaluate the effects of possible future earthquakes and nuclear tests at Nevada Test Site (NTS) on buildings in Las Vegas. A model of the basin depth was derived from gravity data in an independent study, while a model of compressional velocity structure of the basin was derived from seismic refraction studies. We are using strong motion accelerometers regional data, as well as newly acquired broadband teleseismic data to evaluate these models, and predict ground motions at the surface. Delay times of about a dozen analyzed teleseismic P-waves show variation of up to 0.5 seconds across relatively short distances (15 km or less), providing some valuable information on basin shape and thickness. Teleseismic P-waves have favorable signal-to-noise for low frequencies (0.1 to 1.0 Hz). This provides complementary site response measurements to those obtained from regional earthquakes and explosions. Our results indicate a clear difference in site response between hard-rock and basin stations, with amplification reaching factor 5 for the basin stations. The measured P and S wave energies for the recorded data also corelate well with the existing basin depth model, providing additional constraint in modeling the basin shape and structure. We use time domain deconvolution receiver functions to constrain the position of basin boundaries and main crustal discontinuities. Finally, we simulate low frequency (f $<$ 1 Hz) theoretical ground motion in Las Vegas Valley by an elastic finite difference code. Preliminary results show that we can predict relative amplification, as well as some of the complexity in the waveforms, even without invoking complex (and computationaly expensive) three-dimensional structural models. This work is in progress.
DE: 7203 Body wave propagation
DE: 7212 Earthquake ground motions and engineering
DE: 7219 Nuclear explosion seismology
DE: 7223 Seismic hazard assessment and prediction
SC: Seismology [S]
MN: 2003 Fall Meeting