HR: 1340h
AN: T33A-1150    [Abstracts]
TI: Teleseismic Travel-Time Tomography of the Sierra Nevada and its Foundering Lithosphere
AU: * Reeg, H
EM: reegh@colorado.edu
AF: University of Colorado, Boulder, Geological Sciences 2200 Colorado Ave, Boulder, CO 80309, United States
AU: Jones, C H
EM: cjones@cires.colorado.edu
AF: University of Colorado, Boulder, Geological Sciences 2200 Colorado Ave, Boulder, CO 80309, United States
AU: Gilbert, H
EM: hersh@purdue.edu
AF: Purdue University, Department of Earth and Atmospheric Sciences 550 Stadium Mall Dr, West Lafayette, IN 47907, United States
AU: Owens, T
EM: owens@seis.sc.edu
AF: University of South Carolina, Department of Geological Sciences 701 Sumter St. Rm EWSC 617, Columbia, SC 29201, United States
AU: Zandt, G
EM: gzandt@email.arizona.edu
AF: University of Arizona, Department of Geosciences, Gould-Simpson Building #77 1040 E 4th St, Tucson, AZ 85721, United States
AB: Inferences of foundering lithosphere under the southern Sierra have mostly been based upon xenolith petrology and seismic tomography. To better evaluate the extent and geometry of any such unstable lithosphere, we timed teleseismic bodywave arrivals from approximately 500 teleseisms at 75 stations occupied for 1 or 2 years by the Sierra Nevada Earthscope Project (SNEP) and about 15 Earthscope Transportable Array (TA) stations in the region of the Sierra. With the SNEP footprint, stations are spaced about 25 km apart and extend roughly 400 km along the range and 150 km normal to the range. Additional TA stations extend the aperture of the array to about 600 km. Events were chosen to get the best signal-to-noise ratio while optimizing the backazimuthal coverage. P- wave arrival times were determined simultaneously across all stations for each event using a waveform correlation technique developed by G. Pavlis (dbxcor). Initial examination of the travel-time residuals indicates that no substantial lithospheric downwelling exists between the previously recognized "Isabella anomaly" at the southern end of the range and the approximate position of the south edge of the Gorda plate. Residuals in the Basin and Range are generally small but consistently late compared to stations to the west, but large differences in residuals (>1 s) in the western Sierran foothills can occur over short (~50 km) distances, suggesting substantial heterogeneity in the crust or uppermost mantle. Results of a 3-D isotropic inversion will be presented, and any systematic residual patterns remaining will be evaluated with an eye towards identifying any anisotropy.
DE: 6982 Tomography and imaging (7270, 8180)
DE: 7270 Tomography (6982, 8180)
DE: 8180 Tomography (6982, 7270)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting