Finding faults: Using ground roll reflections to image lateral discontinuities

Craig Hyslop, Robert R. Stewart, and Minyu Zhang


Determining lateral change in the subsurface is important for many scales of geophysical investigation: It is helpful in constraining models for tectonic behavior, structural mapping on a regional scale, characterizing reservoirs, and identifying faults for engineering applications. Surface-seismic survey geometries and reflection processing methods are well suited for imaging horizontal layers in the subsurface; however, illuminating and analyzing near-vertical features and lateral discontinuities may be more difficult. Processing surface waves directly can provide additional information about lateral change in the sub-surface. We have developed a processing flow for imaging faults using reflected surface waves. The method relies on VSP-type procedures as well as the undoing of dispersive effects. It provides a way to locate lateral change and the discontinuity depth using extracted surface-wave reflectivity. We apply the method to synthetic datasets generated from a buried fault model and find interpretable images of the fault. Next, we use surface-wave reflectivity for interpreting a near-surface fault in field data from the Hockley Fault system near Houston Texas. We note that a major fault breaks the surface (pavement) at 400m which is identified in the ground-roll image.

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