Near Surface Characterization through Simultaneous Joint Inversion of Surface Waves and Refracted Waves

Near-surface characterization is an important part of seismic data processing, especially for land data. Conventional approaches rely on refracted waves and use of inversion techniques to estimate compression-wave velocity models from the first-break traveltimes. However, in a complex geologic setting in the shallow part of the subsurface, velocity inversions and hidden layers may reduce the reliability of the refraction solution, even with high-quality first breaks. Surface-wave inversion techniques provide shear-wave velocity models that can be integrated in the near-surface characterization workflow. The VP and VS models inferred from first-break traveltimes and Rayleigh waves have several synergies. Their integration can provide an effective solution for challenging geological situations. A robust way of integrating the two methods is simultaneous joint inversion: within this inversion scheme, the two measurements, together with some geological and/or petrophysical relationships linking the subsurface properties, are used in the computation of a unique cost function, which is to be minimized. The solution of the inverse problem results in a multiproperty model fitting data of both measurements and the linking relationship. Different portions of the model are resolved by the interacting contributions of complementary measurements. A field example from Kuwait is discussed to demonstrate the method.