HR: 0830h
AN: S11D-0325    [PDF]
TI: Preliminary Results From SILVVER '03 - Seismic Investigations of the Las Vegas Valley: Evaluating Risk
AU: * Snelson, C M
EM: csnelson@unlv.nevada.edu
AF: Department of Geoscience, University of Nevada Las Vegas, 4505 Maryland Pkwy, MS 4010, Las Vegas, NV 89154-4010 United States
AU: Sandru, J
AF: Department of Geoscience, University of Nevada Las Vegas, 4505 Maryland Pkwy, MS 4010, Las Vegas, NV 89154-4010 United States
AU: McEwan, D J
AF: Department of Geoscience, University of Nevada Las Vegas, 4505 Maryland Pkwy, MS 4010, Las Vegas, NV 89154-4010 United States
AU: Hirsch, A
AF: Department of Geology, St. John's /College of St. Benedict, Pengle Science Center, Box 745, Collegeville, MN 56321 United States
AU: Zaragoza, S A
AF: Department of Geoscience, University of Nevada Las Vegas, 4505 Maryland Pkwy, MS 4010, Las Vegas, NV 89154-4010 United States
AU: Draa, A
AF: Department of Geoscience, University of Nevada Las Vegas, 4505 Maryland Pkwy, MS 4010, Las Vegas, NV 89154-4010 United States
AU: Hanson, A D
AF: Department of Geoscience, University of Nevada Las Vegas, 4505 Maryland Pkwy, MS 4010, Las Vegas, NV 89154-4010 United States
AU: Kaip, G
AF: Department of Geological Sciences, University of Texas at El Paso, 500 University Ave., El Paso, TX 79968 United States
AU: Harder, S H
AF: Department of Geological Sciences, University of Texas at El Paso, 500 University Ave., El Paso, TX 79968 United States
AU: Azevedo, S
AF: IRIS PASSCAL Instrument Center, New Mexico Tech, 100 East Road, Socorro, NM 87801 United States
AU: McKibben, W
AF: IRIS PASSCAL Instrument Center, New Mexico Tech, 100 East Road, Socorro, NM 87801 United States
AU: Rodgers, A
AF: Seismology Group, Earth Science Division, Lawrence Livermore National Laboratory, L-205, Livermore, CA 94551 United States
AU: Lewis, J P
AF: Seismology Group, Earth Science Division, Lawrence Livermore National Laboratory, L-205, Livermore, CA 94551 United States
AU: Smith, D
AF: Seismology Group, Earth Science Division, Lawrence Livermore National Laboratory, L-205, Livermore, CA 94551 United States
AU: Rock, D
AF: Seismology Group, Earth Science Division, Lawrence Livermore National Laboratory, L-205, Livermore, CA 94551 United States
AU: McCallen, D
AF: Laser Science Engineering Division, Lawrence Livermore National Laboratory, Livermore, CA 94551 United States
AB: In August 2003, the University of Nevada Las Vegas (UNLV) with the assistance of the several other institutions acquired seismic refraction data and broadband data across the Las Vegas basin, NV. The SILVVER '03 (Seismic Investigations of the Las Vegas Valley: Evaluating Risk) project is in part a continuing effort to characterize the Las Vegas basin for strong ground motion. The objectives of this phase of the Las Vegas Valley Seismic Response (LVVSR) project were to acquire 3-D seismic data across the basin to define the geometry and structure in the sub-surface; to identify sub-basins, which can focus energy in the basin; and test the current basin model, which shows that the northeastern portion of the basin is as deep as 5 km of unconsolidated basin fill and has increased amplification. The experiment consisted of two seismic refraction profiles of about 55 km in length each. One profile extended from the northeast, across the Las Vegas Valley Shear Zone and the transition from the deep to shallow portions of the basin to the southwest. The second profile extended from the southeast from Frenchman Mountain to the northwest towards the Nevada Test Site along a corridor that is thought to focus energy into the Las Vegas Valley. Station spacing along the profile was nominally 100 to 200 m and shot point spacing was on the order of 10 km. There were 8 shots that were successfully recorded ranging in size from 50 to 1000 lb. The overall quality of the data is very high, especially since the majority of the instruments were deployed in the urban area. Initial results show that the basin can be characterized by an average velocity of 4 km/s while the transition into the crust indicates there is a dramatic velocity increase to 6 km/s at the basin/bedrock contact. The data from this experiment will be used to produce a 3-D tomographic velocity model of the Las Vegas basin. In addition to the seismic refraction profiles, we set out 6 broadband stations across the Valley in an effort to record the chemical blasts. These instruments are currently deployed and recording continuously. Only the larger shots were captured by the broadband array. These data will be used to further our understanding of the Las Vegas basin and the potential seismic hazards that the region faces. In addition, these newly acquired datasets will be integrated into a 3-D community model that is being developed by the working group that will identify areas in the Valley where there could be an increase of amplification due to strong ground motion.
UR: http://geoscience.unlv.edu/pub/snelson/SILVVER
DE: 7200 SEISMOLOGY
DE: 7223 Seismic hazard assessment and prediction
DE: 7230 Seismicity and seismotectonics
DE: 8107 Continental neotectonics
DE: 8180 Tomography
SC: Seismology [S]
MN: 2003 Fall Meeting