Abstract

The distortion effects of near-surface anomalies on the quality of the final (migrated) images have long been recognized as a source of risk for land exploration. These anomalies may be caused by inconsistent weathering, glacial scouring or deposition, fluvial drainage systems, aeolian erosion or deposition, tectonic deformations, etc. The proper accounting of these effects is absolutely necessary for an accurate subsurface image of the prospect to emerge. Near-surface anomalies express themselves in three main ways: (1) severely affecting the arrival times of the recorded seismic reflections and ultimately the clarity and positioning of the strata in the image; (2) affecting the type and magnitude of generated noise; and (3) distorting signal amplitudes. Due to their shallow occurrence in the seismic data, the static effects of these near-surface complexities are not suitably resolved by migration velocity analysis, so a plethora of techniques have been developed throughout the years to deal with them.

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