THE LAS VEGAS VALLEY SEISMIC RESPONSE PROJECT
Recordings in Las Vegas of earthquakes and historical nuclear explosions at the Nevada Test Site (NTS) have provided valuable constraints on ground motion in the basin. Site response results show that ground motions in the basin can be amplified by factors of 20 or more relative to sites on Las Vegas Valleys periphery. Site response is strongly correlated with basin depth. Additional broadband data have been recorded to augment the coverage of earlier network data. Ground motions are being synthesized using an empirical convolution (transfer function) methodology. Geotechnical investigations of specific sites using ReMi and SASW are being performed to understand the relationship between ground motions and shallow seismic structure. In particular the presence of thick deposits of unconsolidated alluvial fill and strengthening effects of carbonate cementation. Seismic refraction studies are refining the basin depth model reported by Langenheim et al. (2001) based on gravity and seismic reflection. Preliminary results provide constraints on the fill velocities and are consistent with depth-to-basement model. All these results are being integrated into a community geophysical model of the region for use in finite-difference wave propagation calculations. Observed and simulated ground motions from scenario nuclear tests and earthquakes are being used to predict the response of structures in Las Vegas.
This work performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. UCRL-JC-153010.