HR: 10:20h
AN: S42A-01    [Abstracts]
TI: Lateral Variations of 1 Hz Crustal Lg Q In Eastern Eurasia Mapped Using A Two-step Tomographic Procedure
AU: * Xie, J
AF: Air Force Research Laboratory/VSBYE, 29 Randolph Road, Hanscom AFB, MA 01731, United States
AB: More than 6,000 Lg spectra have been collected from 162 broad band seismic stations in Eastern Eurasia to map lateral variations of Q. To obtain Lg Q maps with high resolution while minimizing effects of the parameter trade-off with source spectra, we proposed a two-step tomographic procedure in January, 2003. In the first step, path-variable Q0 and eta (Lg Q at 1 Hz and its frequency dependence) are measured using the standard and reversed two-station methods. Reliable lower resolution maps of Q0 and eta are obtained in this step. In the second step of the procedure, spectra from individual events are used to simultaneously solve for the source spectrum and path-variable Q with a Bayesian method. Maps of Q0 and eta obtained in step 1 are used as a priori knowledge to constrain the source spectra. At the end of step 2 all path-variable Q measurements are brought together to obtain a tomographic map with a higher resolution. The first step of the inversion using the 6,000 plus spectra has been completed, resulting in long-wavelength maps of Q0 and eta (Xie et al., GRL 2006). We have since been conducting the second step of the inversion. We find that a reliable inversion of eta is difficult with our currently imprecise theoretical modeling of Lg spectra and the limited frequency range of the available data. Therefore we have focused on the inversion of Q0 only. Various numerical procedures have been implemented or fine-tuned for this inversion. The new high resolution Q0 map for eastern Eurasia, and its correlation with regional tectonics, will be presented.
DE: 7205 Continental crust (1219)
DE: 7219 Seismic monitoring and test-ban treaty verification
DE: 7270 Tomography (6982, 8180)
SC: Seismology [S]
MN: 2007 Fall Meeting