Integrating long- and short-wavelength statics with the generalized reciprocal method and the refraction convolution section

Abstract

Statics, the corrections for variations in the elevation of the ground surface and for the weathered layer, represent the major challenge to improving the resolution of land seismic reflection data. This study describes a simple approach to determining long- and short-wavelength refraction statics that are generally accurate to a few milliseconds with good quality data. The approach employs the generalized reciprocal method (GRM) and the refraction convolution section (RCS).The resolution achieved with the GRM and RCS is comparable to that achieved with the delay-time method (DTM) together with one application of residual statics. Furthermore, a comparison with a coincident set of data recorded with different acquisition parameters shows that there is a long-wavelength static error with the DTM but not the GRM.There is a limit in the lateral resolution of variations in the base of the weathering, which is demonstrated with triplications or ‘frowns’ in the shot records. However, the statics model also exhibits short-wavelength variations, which suggest a resolution considerably greater than that indicated to be possible by the ‘frowns’. This study proposes that the long-wavelength component represents the variations in the time model of the weathering, which are caused by gross variations in the thickness of the weathered layer, while the short-wavelength components represent the variations in the surface soil layers.With the data used in this study, variations of more than 10 ms in the time model of the weathering were observed over distances of 10 m. Such variations result in similar intra-array statics with receiver arrays over comparable distances. These intra-array statics are a major cause of reduced resolution of reflection data and poor signal-to-noise ratios with first-break refraction data, especially in arid regions. Poor quality refraction data are the major impediment to obtaining accurate refraction statics.