HR: 1340h
AN: S23B-1376    [Abstracts]
TI: Synthetic finite-frequency tomography: The optimum coordinate system for traveltime and amplitude observations
AU: * Zhang, Z
EM: zzhang@gso.uri.edu
AF: Graduate School of Oceanography, University of Rhode Island, South Ferry Road, Narragansett, RI 02882, United States
AU: Shen, Y
EM: yshen@gso.uri.edu
AF: Graduate School of Oceanography, University of Rhode Island, South Ferry Road, Narragansett, RI 02882, United States
AU: Zhao, L
EM: zhaol@usc.edu
AF: Institute of Earth Sciences, Academia Sinica, 128 Academia Road Sec. 2. Nankang, Taipei, 115, Taiwan
AB: Recent advances in the finite-frequency seismic theory have provided more accurate representations of wave propagation. But how to harness the power of the new theories and fully extract the rich information about the earth from three-component broadband seismic records remain a challenge. In this study we carry out synthetic, 3D cross-well tomography using full waveforms simulated in elastic media with a staggered-grid finite-difference code. These controlled experiments allow us to compare the input and recovered structures and quantitatively assess the tomographic resolution in ways that cannot be done with a real data set for an earth structure. Our results show that the choice of the coordinate system in which travel times and amplitude anomalies are measured affects the Fréchet sensitivity kernels and results in significant differences in tomographic resolution. The radial, transverse, and vertical (RTZ) coordinate system has been widely used, because it reflects the intrinsic differences of P-SV and SH systems and therefore provides a direct way to separate the two wave fields. However, this and other fixed coordinate systems are not the optimum for resolving the structure in finite- frequency tomography. For example, in our 3D cross-well tomography experiments, the RTZ system may concentrate the energy of P waves on the radial direction and annihilate the energy on the transverse and vertical directions. In contrast, a variable and rotated coordinate system distribute the arrival evenly on the three components, making it possible to utilize the differences in the sensitivity kernels of the same arrival on the three components for tomography. Compared to a fixed RTZ system, the variable and rotated coordinate system yields much improved resolutions in our synthetic, 3D cross-well tomographic experiments.
DE: 7270 Tomography (6982, 8180)
DE: 8180 Tomography (6982, 7270)
SC: Seismology [S]
MN: 2007 Fall Meeting