An inverse method to derive fault slip and geometry from seismically observed vertical stratigraphic displacements using elastic dislocation theory

This contribution describes the development of an inverse method to extract fault slip and fault geometry from subsurface horizons derived from seismic reflection datasets. The inversion process uses non-linear minimisation together with a forward model using elastic dislocation (ED) theory. The forward model calculates subsurface vertical displacements from fault parameters such as fault slip, dip, length and width for planar, listric or seismically observed fault geometries. Vertical subsurface displacements are measured at selected stratigraphic horizons from seismic depth sections, and act as observations for the inversion process. The non-linear inversion uses a standard procedure (Powell's method) to minimise an objective function (misfit parameter). The method has been tested using synthetic data generated by theoretical forward models. The inverse method can successfully recover slip distributions and non-planar, including listric, fault geometries. The method has also been applied to stratigraphic horizons derived from seismic reflection data. Fault slip and fault geometry derived from the inverse method are consistent with direct seismic interpretations, and are reproducible and geologically realistic. This inverse method provides a useful complement to conventional subjective seismic interpretations of fault slip and geometry. ED theory together with the retrieved fault parameters from the application of inverse theory may be used to determine strains for fracture prediction. (C) 2004 Published by Elsevier Ltd.