HR: 0800h
AN: S41A-0973    [Abstracts]
TI: Integrated Passive and Active Source Seismic Investigation of the Northwestern Basin and Range Province
AU: * Gashawbeza, E
EM: ewenet1@stanford.edu
AF: Stanford university, 397 Panama Mall Mitchell Bldg., stanford, ca 94305 United States
AU: Lerch, D W
EM: lerch@pangea.Stanford.EDU
AF: Stanford university, 397 Panama Mall Mitchell Bldg., stanford, ca 94305 United States
AU: Wilson, C K
EM: wilsonck@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964-1000 United States
AU: Klemperer, S L
EM: sklemp@stanford.edu
AF: Stanford university, 397 Panama Mall Mitchell Bldg., stanford, ca 94305 United States
AU: Miller, E L
S41A-0973 AF: Stanford university, 397 Panama Mall Mitchell Bldg., stanford, ca 94305 United States
AB: We utilized teleseismic receiver function techniques and active-source refraction seismology to study the crustal structure and continental rift processes responsible for the development of the NW corner of the Basin and Range province (BRP). Despite relatively low extension measured at the surface, the crust in northwestern Nevada is thin, raising the possibility that the region underwent flow of a ductile middle or lower crust away from the area to more extended regions to the south. Our passive seismic array consisted of 29 short-period stations spanning about 70km from west to east and provided data on crustal anisotropy and thickness independent of the results of the active-source experiment. Combining data from the two experiments provides better constraints on Moho depth, Vp/Vs ratio, crustal structure and composition of the NW Basin and Range province. We analyzed eight months of data collected by short period digital stations that operated in NW Nevada, using standard teleseismic receiver-function techniques to investigate the central portion of the refraction line. These new data indicate Moho depths that vary from 29-35 km along the passive source array and Vp/Vs ratios ranging between 1.68 -1.78. Velocity modeling from the 300 km wide-angle refraction/reflection survey provides comparable Moho depths of 32-36 km under this same region. In addition to constraints on crustal thickness and structure, we may also be able to detect crustal anisotropy related to deformational fabrics in the lower crust. A preliminary investigation of the receiver function data at each individual station also showed back azimuthal variation as we compared events from northwest back azimuths with those from westerly back azimuths, which could possibly be due to the presence of anisotropy in the region.
DE: 0905 Continental structures (8109, 8110)
DE: 1219 Gravity anomalies and Earth structure (0920, 7205, 7240)
DE: 1734 Seismology
DE: 7205 Continental crust (1219)
SC: Seismology [S]
MN: Fall Meeting 2005