Model studies of shallow common‐offset seismic data

Abstract

For simplicity, optimum‐window common‐offset data‐acquisition procedures are frequently employed to collect near‐surface, high‐resolution, seismic reflection 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.