Bedrock imaging using post-critical shallow seismic reflection data

Abstract

We acquired shallow seismic reflection data in an unusual range of offsets greater than critical distance, and examined the feasibility and consequences of processing these post-critical reflections using conventional seismic reflection procedures. The main motivations to develop this work were: (i) the reflections observed at larger offsets are sharper and stronger than at near offsets, and (ii) it is possible to select a broad optimum offset window, which will speed up the execution of a seismic reflection survey. In order to accomplish the proposed task, refraction data and elastic reflection modelling were integrated into processing of reflection data and their interpretation. The information from the refracted arrivals was used to image the shallower reflector (dry unconsolidated overburden), to estimate the interval velocity model above the bedrock, and to perform static correction. The elastic reflection modelling was decisive to perform the post-critical seismic reflection survey, and to check the reliability of our interpretation. The lithologic log information corroborated the feasibility of imaging subsurface structure from post-critical reflection data by conventional processing, provided additional velocity-depth information is integrated in the reflection processing.