Imaging Offsets in the Moho: Synthetic Tests using Gaussian Beams with Teleseismic Waves |
| |
| Authors: | Robert L Nowack Wang-Ping Chen Ulrich Kruse Saptarshi Dasgupta |
| |
| Institution: | (1) Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, IN, 47907, U.S.A;(2) Department of Geology, University of Illinois, Urbana, IL, 61801, U.S.A;(3) Department of Physics, University of Illinois, Urbana, IL, 61801, U.S.A |
| |
| Abstract: | We carry out a sequence of numerical tests to understand conditions under which rapid changes in crustal thickness can be
reliably imaged by teleseismic body waves. Using the finite-difference method over a 2-D grid, we compute synthetic seismograms
resulting from a planar P-wavefield incident below the grid. We then image the Moho using a migration scheme based on the Gaussian beam representation
of the wavefield. The use of Gaussian beams for the downward propagation of the wavefield is particularly advantageous in
certain geologically critical cases such as overthrusting of continental lithosphere, resulting in the juxtaposition of high-velocity
mantle material over crustal rocks. In contrast to ray-based methods, Gaussian beam migration requires no special treatment
to handle such heterogeneities. Our results suggest that with adequate station spacing and signal-to-noise ratios, offsets
of the Moho, on the order of 10 km in height, can be reliably imaged beneath thickened crust at depths of about 50 km. Furthermore,
even sharp corners and edges are faithfully imaged when precise values of seismic wave speeds are available. Our tests also
demonstrate that flexibility in choices of different types of seismic phases is important, because any single phase has trade-offs
in issues such as spatial resolution, array aperture, and amplitude of signals. |
| |
| Keywords: | Seismic imaging receiver functions seismic inversion migration |
| 本文献已被 SpringerLink 等数据库收录！ |
|
