Modeling and Inversion of Scattered Surface waves

Abstract

In this thesis, we present a modeling method based on a domain-type integral representation for waves propagating along the surface of the Earth which have been scattered in the vicinity of the source or the receivers. Using this model as starting point, we formulate an inversion scheme to estimate properties of scattering objects close to the surface of the Earth. The objectives of the resaerch are to develop an efficient and accurate modeling method for scattering of seismic waves by 3D near-surface heterogeneities close to the receivers or sources and to develop an inversion algorithm to reconstruct scattering-medium parameters from scattered surface waves. Model studies show that we accurately model near-surface scattering effects, which can seriously distort the wave fronts of upcoming reflections. Our method may therefore help in understanding this problem which is of particular interest for the oil industry as the upcoming wave fronts contain the primary information for making images of subsurface structure. For further validation, we compared our modeled data with experimental data collected with similar geometries at the Colorado School Mines (CSM). We have also applied our inversion algorithm to several synthetic data sets. We find that we can get a good estimate of the location and strength of contrasts up to a depth of about one Rayleigh wavelength.