Integrating long and short wavelength time and amplitude statics

The single most important parameter for accurate statics corrections is an accurate time model of the weathering, when the replacement statics model is used. Representative seismic velocities in the weathering are generally adequate. The resolution achieved with the generalized reciprocal method (GRM) and the refraction convolution section (RCS) is comparable to that achieved with the delay time method (DTM) together with one application of residual statics. It is proposed that the long wavelength components of the statics represent gross variations in the thickness of the weathered layer, and that the short wavelength components represent variations in the surface soil layers. The head wave amplitudes are inverted to generate a model of the head coefficients. Like the time model, the head coefficient model is separated into a long wavelength component which is representative of the seismic parameters at the base of the weathering, and a short wavelength component representative of the surface soil layers. In the study area, the inhomogeneities in the surface soil layer produce static variations of ±3 ms and ±2 db. It is concluded that the surface soil layer is as important a source of intra-array statics as variations in topography and thickness of the weathered layer.