HR: 08:00h
AN: S31E-01 INVITED    [Abstracts]
TI: Shear wave splitting intensity tomography beneath southwestern Japan and coupling with numerical flow models
AU: * Long, M D
EM: long@dtm.ciw.edu
AF: Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015, United States
AU: de Hoop, M V
EM: mdehoop@math.purdue.edu
AF: Center for Computational and Applied Mathematics, Purdue University, 150 N. University St., W. Lafayette, IN 47907, United States
AU: van der Hilst, R D
EM: hilst@mit.edu
AF: Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, United States
AU: Hager, B H
EM: brad@chandler.mit.edu
AF: Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, United States
AB: The inversion of shear wave splitting measurements for anisotropic structure is not often attempted due to the limitations imposed by sparse data and the difficulty of inverting for laterally varying general anisotropy. However, carefully constructed splitting data sets from dense broadband arrays can potentially illuminate regions of the upper mantle and facilitate a tomographic approach. In addition, the application of simplifying assumptions designed to study anisotropy in specific tectonic settings, such as a subduction zone, can reduce the complexity of the problem. We have developed a method for 2.5-D splitting intensity tomography that incorporates constraints from numerical models of geodynamical processes and applied this technique to study upper mantle anisotropy beneath southwestern Japan. We calculate wave-equation splitting intensity sensitivity kernels for the orientation and strength of anisotropy using the Born approximation. We focus on computing sensitivity kernels in heterogeneous, anisotropic starting models taken from a numerical modeling study of anisotropy development in a subduction zone mantle wedge. The calculation of such kernels in realistic heterogeneity is essential for true multi-scale, wave-equation splitting tomography. We use the results of the inversion to refine our flow models with control parameters that best fit the splitting observations, and further improve the models by using perturbed flow models as new starting models for the inversion. In this way, we identify tomographic models of upper mantle anisotropy beneath southwestern Japan that are consistent both with constraints from shear wave splitting observations and with constraints from geodynamics.
DE: 3285 Wave propagation (0689, 2487, 4275, 4455, 6934)
DE: 7260 Theory
DE: 7270 Tomography (6982, 8180)
DE: 8162 Rheology: mantle (8033)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Seismology [S]
MN: 2007 Fall Meeting