Abstract

For simplicity, optimum-window common-offset data-acquisition procedures are frequently employed to collect near-surface, high-resolution, seismic reflec-tion data. However, because of large incidence angles, interpretations of the data often cannot be evaluated accurately using zero-offset simulations alone.Common-offset hammer seismic data collected in the central Appalachian plateau province of West Virginia are examined in this paper. Synthetic shot records using a minimum-phase wavelet estimated from the data and subsurface acoustic properties derived from full-waveform and other geophysical logs are used to simulate the offset seismic response of near-surface, coal-bearing Pennsylvanian aged rocks. Zoeppritz equations are used to model amplitudes.This study indicates that offset simulations may be required to determine the origins of events observed at a given offset. Offset simulations also help determine whether amplitude variations with offset have a significant effect on the appearance of events observed at the optimum offset. The offset seismic response is significantly different from the zero-offset response for reflections arising from depths less than about two-thirds of the offset distance; for greater depths, zero-offset simulations adequately approximate the offset response.

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