A statistical approach to residual statics removal

David C. Henley

Images created from seismic data acquired on land are often significantly degraded by the influence of the weathered and non-uniform materials at or near the surface of the earth. Because of the relatively small-scale variations in these materials, seismic wavefronts arriving at the surface are distorted in space and time as they reach the detectors. In many cases, the bulk of the effect can be removed by the application of a discrete time shift to each trace recorded by a detector at the surface, applying a correction termed a "static shift". This is only an approximation, however, to the correction that should actually be applied, which is more properly represented as a distribution of shifts, unique to each trace.

This work explores an approach for removal of near-surface effects from seismic data in which the distribution of statics embedded in each trace is estimated, then removed by the application of an appropriate operator. This approach should automatically correct for such effects as multi-path arrivals on seismic traces; and it should be extensible to the non-stationary case where "statics" may vary with travel time due to local variations in rock velocity at depth. We demonstrate the general validity of the "statistical statics" approach by estimating and removing static distributions from the shot gathers of a set of field data; and we identify the main areas for further research.