NUMERICAL-SIMULATION OF MULTIPARAMETER SEISMIC SCATTERING

Numerical simulations using viscoelastic wave equations allow investig ation of interactions between the effect of scattering by variations i n P velocity, S velocity, density, and intrinsic Q for both P and S wa ves. When variations are spatially correlated between the parameters i n a scattering medium, the amount of scattered energy increases. Thus, neglect of the the contribution of any parameter to scattering will r esult in biased estimates of the contributions by the other parameters ; this is especially true if interactions between intrinsic and appare nt Q are neglected. The presence of finite intrinsic Q values has two effects; the overall amplitudes of both the incident and scattered wav es are attenuated, and new scattering is introduced by the spatial var iation of Q. The energy in the coda is reduced substantially and shift ed to lower frequencies by attenuation in a viscoelastic medium. For a given scatterer size, the frequency at which the dominant scattering occurs is lower for S waves than for P waves.