Separation of Scattering Attenuation and Intrinsic Absorption using Multiple Lapse Time Window Analysis

Abstract

A large number of studies on the field of scattering caused by the heterogeneities in the earth are reported in literature. The study presented aims at determining the seismic wave attenuation factors namely, scattering attenuation and intrinsic absorption.Determination of the two factors require estimation of two parameters namely, seismic albedo and extinction length. The method of multiple lapse time window analysis is employed to estimate the two factors. Here, multiple finite lapse time windows of 0-15, 15-30 and 30-45 seconds are used for analysis. The mean square amplitudes of band pass filtered seismogram ( 1-2, 2-4, 4-8 Hz) data is averaged over the time windows to estimate the seismic energy. This energy is corrected for local site amplification and source effects. Coda normalization is employed for this purpose. The energy obtained is further corrected for geometrical spreading. Finally, the normalized energy is plotted with respect to the hypocentral distance. The synthetic energy distribution is obtained from Monte Carlo simulation.