High-resolution images of shallow aquifers—A challenge in near-surface seismology

A near-surface multifold high-resolution seismic reflection experiment was conducted in the vicinity of the waste management area of a potash mine in western Canada. A buried channel was identified in the data, and the stratigraphy of the Quaternary infill of this structure was mapped. The spatial extent of several prominent gravel-sandy aquifers, which represent the hydrogeologic framework of the region, was outlined by the survey. The seismic signatures also established the hydraulic independence of three major aquifers along the survey line. The complex heterogeneous lithology of the surface cover limited effective elastic-wave generation to surface sources. This geologic framework also caused propagation of strong diverse coherent-noise patterns which severely degraded reflected signal. The suppression of those overhelming interfering events required the design of noise-specific filters and their sequential multistep implementations. Results of forward modeling of background geologic information were crucial factors in the design of the data acquisition program and preliminary choices of the processing parameters, and (along with borehole data) were the primary guidance in the geologic interpretation of the final seismic section. Fundamental procedures were developed for mapping of glacial tills in theWestern Canadian Basin, techniques that can be applied in other regions with similar near surface glacial stratigraphy. The experiment revealed that even closely spaced borehole information could never duplicate the detail of the subsurface images of the seismic data.