Observations of scattering attenuation in the Earth and implications for Q

Abstract

Seismologists often attribute the attenuation of a transmitted seismic pulse to anelastic absorption or Q. Real data suggests a different dominant mechanism. The earth, particularly in sedimentary basins, is heterogeneous on all scales. This heterogeneity results in a transmitted pulse being attenuated by scattering at every boundary it encounters. Theoretical models proposed by Zien and Shapiro (1994) suggest that scattering attenuation is angle dependent, but not necessarily frequency dependent, at least for short propagation distances. In this paper we review the mechanisms for transmitted pulse attenuation both scattering- and absorption-based. We then analyze real data and compare the contributions of these mechanisms to the observed attenuation.