HR: 1330h
AN: S22B-0445    [PDF]
TI: 20-sec Rayleigh-Wave Attenuation Tomography for Central Asia
AU: * Yang, X
EM: xyang@lanl.gov
AF: Los Alamos National Laboratory, EES-11, MS D408, Los Alamos, NM 87545 United States
AU: Taylor, S R
EM: taylor@lanl.gov
AF: Los Alamos National Laboratory, EES-11, MS D408, Los Alamos, NM 87545 United States
AU: Patton, H J
EM: patton@lanl.gov
AF: Los Alamos National Laboratory, EES-11, MS D408, Los Alamos, NM 87545 United States
AB: Because of the complex crust and upper mantle structure in central Asia, lateral variations of the surface-wave attenuation are significant. To map out these variations, we construct tomographic attenuation models for 20-sec Rayleigh waves, which will be used to constrain 3-D shear-wave attenuation models of the region and to improve regional Ms measurements. In order to make reliable amplitude measurement, we use a phase-matched filter constructed from 2-D surface-wave group-velocity maps to isolate and enhance the primary surface-wave arrival. The filtering reduces the ambiguity due to multi-pathing and other noise in the data. We also use theoretical source radiation patterns and source spectra to guide our measurement and gauge the quality of the data. We take two steps in developing the attenuation model following a Bayesian approach. First, we invert two-station amplitude-ratio measurements, which are less affected by source-parameter error than single-station amplitude measurements, to obtain a 5-degree-cell model. This model is used as the a priori model in the final inversion of single-station measurements, which have much better path coverage, for a 2-degree-cell model. We found that results from two-station amplitude-ratio inversion exhibit general correlation between the model and geological provinces of the region. Single-station amplitude data collection and measurement are underway and we expect to present some tomography results at the conference.
DE: 7205 Continental crust (1242)
DE: 7218 Lithosphere and upper mantle
DE: 7255 Surface waves and free oscillations
SC: Seismology [S]
MN: 2003 Fall Meeting