HR: 1340h
AN: T13E-1631    [Abstracts]
TI: Modeling Lateral Sn Velocity, Gradient, and Anisotropic Variations in the Upper Mantle
AU: * Begnaud, M L
EM: mbegnaud@lanl.gov
AF: Los Alamos National Laboratory, PO Box 1663, MS F659, Los Alamos, NM 87544, United States
AU: Phillips, W
EM: wsp@lanl.gov
AF: Los Alamos National Laboratory, PO Box 1663, MS F659, Los Alamos, NM 87544, United States
AU: Rowe, C A
EM: char@lanl.gov
AF: Los Alamos National Laboratory, PO Box 1663, MS F659, Los Alamos, NM 87544, United States
AU: Steck, L K
EM: lsteck@lanl.gov
AF: Los Alamos National Laboratory, PO Box 1663, MS F659, Los Alamos, NM 87544, United States
AB: Various forms of Pn tomography have been developed to model the effect of two-dimensional (2-D) upper mantle variations on seismic travel times. The general abundance of Pn arrival times compared to Sn arrival times allows for higher resolution and more extensive path coverage. As seismic catalogs continue to increase in available data as well as pick quality, modeling upper mantle Sn velocity becomes more robust. Various researchers have modeled upper mantle velocity variations using Pn travel times. Phillips et al. (2007) also included solving for 2-D Pn gradient to the standard slowness solution. Based on the work of Zhao (1993) and Zhao and Xie (1993), the effect of upper mantle gradient on arrival times can be approximated by a simple term that can be extended to 2-D for tomographic studies. Pn gradient values matched those from previous studies for Tibet and North America. High gradients appeared to be associated with stable and convergent zones, low gradients with extensional zones. Recently, Pei et al. (2007) did a Pn and Sn seismic tomography study in China, also solving for velocity and anisotropy. Sn velocity variation was consistent with Pn variation, with overall variations consistent with tectonic activity. We merge arrivals from various local, regional, and global catalogs into one consistent, non-redundant catalog. Using the Bondár et al. (2004) ground truth (GT) criteria, we have ~22,000 GT25 and better events available for tomography in the Eurasia region. This data set includes ~3700 stations resulting in over 600,000 Sn arrivals. Using the tomography method from Phillips et al. (2007), we plan to continue the upper mantle 2-D modeling by solving for Sn slowness, gradient, and anistotropy in the Eurasia region.
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7218 Lithosphere (1236)
DE: 7270 Tomography (6982, 8180)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting