HR: 1340h
AN: S23B-1379    [Abstracts]
TI: Multi-scale Finite-Frequency Travel-time Tomography Applied to Imaging 3-D Velocity Structure of the Upper Mantle Beneath the Southwest United States
AU: * Yin, Y
EM: r95224203@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, Taipei, 106, Taiwan
AU: Hung, S
EM: shung@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, Taipei, 106, Taiwan
AB: Seismic tomographic imaging has played a key component to unravel the deep processes that caused the surface morphology and rift magmatism in the southwest United States. Several studies used teleseismic body- wave arrivals recorded by the La Ristra experiment, a dense broadband array of 950-km in length deployed during 1999-2001 and run through the Great Plains, the Rio Grande Rift, and the Colorado Plateau, to construct a 2-D tomographic image of the upper mantle structure beneath this linear array (e.g., Gao et al., 2004). However, because of the inevitable smoothing and damping imposed in the tomographic model, the resulting velocity contrast is too weak to explain distinct P and S waveform changes across the array (Song and Helmberger, 2007). In this study, we include all the data from the La Ristra and available nearby arrays and reexamine finite- frequency travel time delays measured by inter-station cross correlation of waveforms at both high- (0.3-2 Hz for P and 0.1-0.5 Hz for S) and low-frequencies (0.03-0.125 Hz for P and 0.03-0.1 Hz for S). Differing from the previous models that rely on classical ray theory and simple grid parameterization, our inversion considers more realistic 3-D sensitivity kernels for relative travel-time delays and a wavelet-based, multi-scale parameterization that enables to yield robust features with spatially-varying resolutions. Our preliminary P-wave model reveals a prominent low-velocity zone extending from near surface to the depth of 300 km beneath the Rio Grande Rift, while the upper mantle which underlies the Great Plains and the Colorado Plateau is seismically fast. We will demonstrate the difference and improvement of 3-D tomographic models through the use of finite-frequency kernels and multi-scale parameterization.
DE: 3260 Inverse theory
DE: 3280 Wavelet transform (3255, 4455)
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7270 Tomography (6982, 8180)
DE: 8109 Continental tectonics: extensional (0905)
SC: Seismology [S]
MN: 2007 Fall Meeting