HR: 08:05h
AN: T51F-01 INVITED     [Abstracts]
TI: Attenuation of the Lg Phase in Central and East Asia
AU: * Phillips, S
EM: wsp@lanl.gov
AF: Los Alamos National Laboratory, MS D408, Los Alamos, NM 87545 United States
AU: Hartse, H
EM: hartse@lanl.gov
AF: Los Alamos National Laboratory, MS D408, Los Alamos, NM 87545 United States
AB: We obtain laterally varying, crustal attenuation (1/Q) by applying tomographic techniques to regional L_g amplitude ratios. The method assumes that source radiation is isotropic and that event-based amplitude ratios can be modeled by a two-dimensional Q map and relative site terms. Application to 2286, 1-Hz L_g amplitudes from 816 events recorded at 35 central and east Asia stations yields a misfit of 0.09 log₁₀ units, a variance reduction of 73%, relative to the uniform Q model that best fits the data, and laterally varying Q from 100 to 1000, with patterns closely following regional geology. The image is resolved, on average, to 2.5°, with resolution peaking at 1.5° in the best covered areas, which is remarkable given the sparse station geometry (10°) we employed. The high resolution is a consequence of the dense distribution of earthquake sources, which acts as a network of stations, in the reciprocal sense. Fine scale patterns are confirmed by independent, coda Q and amplitude tomography work in sub regions where dense network data are available. Comparison of Q-based predictions to coda-derived spectra in densely covered sub regions should further validate the attenuation results.
DE: 7205 Continental crust (1219)
DE: 7219 Seismic monitoring and test-ban treaty verification
DE: 7270 Tomography (6982, 8180)
SC: Tectonophysics [T]
MN: Fall Meeting 2005