Diffraction and Broadening of Seismogram Envelopes

Abstract

The inhomogeneity of the earth’s lithosphere has a broad spectrum compared with the wavelength of regional seismic waves. We have presented models for wave propagation through inhomogeneous media, in which scattering by inhomogeneities of characteristic scales shorter than or equal to the wavelength dominates S-coda wave excitation. For the evaluation of scattering loss, as discussed in Chapter 5, subtraction of the travel-time fluctuation due to long-wavelength components of velocity inhomogeneities gave us a model that is consistent with measurement practice and in agreement with observed frequency characteristics. We will now present a model for wave propagation through media having long-wavelength components of velocity inhomogeneity, that is, we focus on diffraction and multiple forward-scattering effects.