Full Waveform 2.5D Teleseismic Surface Wave Tomography with Application to the Tien Shan
Abstract
We adapt the 2.5D spectral domain finite difference waveform tomography algorithm of Roecker et al. (2010) to permit the analysis of teleseismically recorded surface waves. The teleseismic body wave technique of generating synthetic waveforms by specifying an analytic solution for a background wavefield in a 1D model and solving for a scattered field excited by this background is equally applicable to surface waves. We use the locked mode approach of Gomberg and Masters (1988) to calculate the background Greens functions at each point of the finite difference (FD) grid. Because of the much greater concentration of energy at the surface, we adopt the cell-based FD operators of Min et al. (2004) to calculate the free surface boundary conditions, and the generalized stretching function of Komatitch and Martin (2007) to improve the absorption in the PML. We use this algorithm to analyze broad band seismograms of events in Sumatra recorded by the MANAS array in the Tien Shan. Our results show that the upper mantle beneath much of the central Tien Shan has shear wavespeeds at least 10% lower than the lithosphere beneath the Tarim basin to the south or the Kazach shield to the north. At the same time, there appears to be a remnant lithospheric lid beneath the Kyrgyz range in the north, an observation consistent with previous receiver function studies in this area.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.S41A2163R
- Keywords:
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- 0560 COMPUTATIONAL GEOPHYSICS / Numerical solutions;
- 7270 SEISMOLOGY / Tomography;
- 7290 SEISMOLOGY / Computational seismology;
- 8102 TECTONOPHYSICS / Continental contractional orogenic belts and inversion tectonics