The attenuation of surface waves due to scattering

Abstract

Surface wave attenuation is usually attributed to inelastic properties of the Earth, but a considerable part of the surface wave attenuation may be due to scattering by lateral heterogeneities. For body waves, the theory describing attenuation due to scattering is well known. In this paper, a similar theory is presented, which describes the attenuation of surface waves due to scattering. The Born approximation is used to derive the scattered wavefield, therefore only weak heterogeneities can be described. Some numerical experiments are performed for periods between 25 and 100 s. For realistic scatterers the conversions from the fundamental mode to the higher modes cannot be neglected. The Q−1 values computed for scattering media are of the same order of magnitude as measured Q−1 data. A whole range of attenuation curves as a function of frequency can be obtained by varying the parameters of the scattering experiment. This leads to believe that Q−1 data inversions to Q−1 depth models should be regarded with some suspicion, because the contribution of scattering to the attenuation cannot be neglected. Copyright © 1989, Wiley Blackwell. All rights reserved