HR: 15:45h
AN: T23A-08    [Abstracts]
TI: Beam-formed Receiver Function Analysis From the Southern Sierra Nevada, CA: A Moho Hole??
AU: * Levandowski, W
EM: wlevando@princeton.edu
AF: Princeton University Dept of Geosciences, Guyot Hall, Princeton University, Princeton, NJ 08540, United States
AB: Single station receiver functions in the southern Sierra Nevada, California, USA show considerable variation in Moho conversion intensity. Specifically, in the range's western foothills, a region termed "the Moho Hole" (e.g. Zandt et al, 2004), the Moho appears to be completely absent on single station receiver functions. I explore the possibility that signal-generated reverberations have sufficiently obscured the seismograms to disguise a Moho P-S conversion. Using data from the 1997 Sierra Paradox Experiment, seismograms from 3 stations spaced ~20 km apart are slant-stacked to make the radial, transverse, and vertical components used in deconvolution. By stacking before deconvolution, signals from the Moho and intra-crustal discontinuities become more pronounced while reflections off of structure near individual receivers destructively interfere with one another. Receiver functions for these 3 station beams compare favorably with post-deconvolution stacking of the receiver functions calculation of their constituent stations. Of paramount interest is the use of this technique in the region interpreted as the "Moho Hole". Here, beam formed receiver functions better constrain the extent and geometry of the small amplitude Moho conversion than previous studies. In fact it seems that this region is part of a larger- scale (~100 km) west-northwestward trend of weakening P-S signal. This dimming is spatially correlated with a thickening crust, seen in increasing P to P-S lag times. I propose that the features are cogenetic: products of long-wavelength crutal down-flexure as the result of viscous coupling to downwelling delaminated lower lithosphere. Investigating this response is important to understanding the mechanism and kinematics of Sierran uplift and the response of upper crustal material to delamination events.
DE: 7205 Continental crust (1219)
DE: 7218 Lithosphere (1236)
DE: 9350 North America
SC: Tectonophysics [T]
MN: 2007 Joint Assembly