HR: 08:00h
AN: T31E-01    [Abstracts]
TI: Insights on Lithospheric Foundering from the Sierra Nevada Earthscope Project (SNEP)
AU: * Zandt, G
EM: gzandt@email.arizona.edu
AF: University of Arizona, Dept. of Geosciences, Tucson, AZ 85745, United States
AU: Gilbert, H
EM: hersh@purdue.edu
AF: Purdue University, Dept. of Earth and Atmospheric Sciences, West Lafayette, IN 47907, United States
AU: Frassetto, A
EM: andyf@email.arizona.edu
AF: University of Arizona, Dept. of Geosciences, Tucson, AZ 85745, United States
AU: Owens, T
EM: owens@seis.sc.edu
AF: University of South Carolina, Dept. of Geological Sciences, Columbia, SC 29208, United States
AU: Jones, C
EM: cjones@cires.colorado.edu
AF: University of Colorado, Dept. of Geological Sciences, Boulder, CO 80309,
AB: Interdisciplinary studies in the southern Sierra Nevada have documented an ongoing removal of the dense residual root from beneath the southern Sierra Nevada batholith. However, many questions remain concerning the timing, spatial extent, mechanism, and consequences of this lithospheric foundering event. The Sierra Nevada Earthscope Project (SNEP) is a scientific experiment designed to investigate these questions with a 2- phase (2 year) seismic deployment of 46 broadband Flex-Array stations embedded in the existing stations of the USArray Transportable Array (TA) in the region. In the 2 phases, approximately 80 sites have been occupied from the northern edge of Kings Canyon north to Honey Lake and from the Central Valley into the Great Basin. In this presentation, we will focus on the most recent common-conversion-point (CCP) stacks of the receiver functions that provide a 3D image of lithospheric layering beneath the central and northern Sierra Nevada. Examining sequential cross-sections reveals distinctive lithospheric "reflectivity" patterns that characterize different tectonic imprints. From phase 1 data, we observed that the westernmost Basin and Range exhibits strong layering with multiple low-velocity zones in the crust and uppermost mantle and a relatively flat and strong Moho varying slowly in depth between 30 and 35 km. In the south this Basin and Range character terminates on the eastern edge of the Sierra Nevada; however, north of Big Pine the Basin and Range character intrudes progressively farther into the range and ends up more than 50 km west of the eastern edge of the range. The lithosphere beneath the southern high Sierra Nevada is characterized by a relatively transparent (homogeneous) crust and sharp Moho that disappears westward beneath the adjacent foothills. The crustal thickness in this area is mostly between 30-35 km with localized welts of thicker crust. The phase 1 observations imply that the removal process appears to be actively affecting the crust northward through at least the central Sierra Nevada. The phase 2 deployment provides coverage to the northern limit of the Sierra Nevada to determine the extent of the affected region and the character of the batholith where root removal may or may not have occurred.
DE: 7200 SEISMOLOGY
DE: 7203 Body waves
DE: 7205 Continental crust (1219)
DE: 7218 Lithosphere (1236)
DE: 8100 TECTONOPHYSICS
SC: Tectonophysics [T]
MN: 2007 Fall Meeting