A modified energy flux model for lithospheric scattering of teleseismic body waves

Abstract

Energy flux models which have been proposed lately offer a unified concept of scattering attenuation and coda wave excitation. Here, an energy flux model for a plane wave propagating through a scattering layer above a homogeneous half‐space is developed. It takes into account the intrinsic attenuation of the layer as well as diffusion of coda energy out of the layer into the half‐space. All three parameters of the model—scattering attenuation, intrinsic attenuation and diffusion losses—can be determined from the coda strength relative to the direct arrival and the coda decay rate, if one makes some assumptions on the frequency dependence of intrinsic attenuation. The energy flux model has been tested with synthetic finite difference seismograms and has been found to give reliable results for both weak and strong scattering environments. It was then used for the analysis of short‐period data from deep events recorded at the Warramunga seismic array in central Australia. an average scattering Q of about 640 at 1 Hz was found for the lithosphere beneath the array with a strong increase of Q with frequency above 1 Hz. Intrinsic Q is much higher than scattering Q and most of the coda decay is caused by diffusion of coda energy into the half‐space below the scattering layer. Copyright © 1990, Wiley Blackwell. All rights reserved