Scattering and Intrinsic Attenuation of Short-Period S Waves in the Gyeongsang Basin, South Korea, Revealed from S-Wave Seismogram Envelopes Based on the Radiative Transfer Theory

摘要

Examining seismic envelopes for local earthquakes that occurred in the Gyeongsang Basin, South Korea, we estimated coda Q values in the crust and measured the total scattering coefficients for frequency bands 1-2, 2-4, 4-8, and 8-16 Hz using the Monte Carlo simulation method based on radiative transfer theory. In the seismic envelope synthesis, we assumed acoustic multiple isotropic scattering and adopted a depth-dependent S-wave velocity model that is slightly modified from a receiver function result in the middle of the study region. The estimated total scattering coefficients range from 3: 8 x 10(-3) to 4: 8 x 10(-3) km(-1) at 1-16 Hz, which agrees well with the average values in the crust. These values are corresponding to less than 0.5 of seismic albedo. This result represents that intrinsic absorption is a dominant contributor to the attenuation process for all frequency bands in the Gyeongsang Basin.