The structural significance of seismic velocity reversals - an overview

Abstract

The basic property under investigation is the change of seismic velocity from one layer to the other. This paper looks into problems of velocity reversal, locations of low velocity zones, delineation methods, and presents case studies in the Niger Delta. This study therefore aims at delineating from the surface the subsurface distribution of velocity changes in the area of study. It has been recognised in the study area that seismic velocity contains important geological information. To be most effective determining these, however, it is necessary to have a thorough understanding of the rock properties under investigation. In areas with absence of structural uplift and lateral variation of lithology, iso-velocity surfaces are nearly horizontal planes. However, where structural uplift occurs, iso-velocity surfaces tend to follow structure but less relief than the structure. The study showed that seismic velocity increases with depth and age in some of the areas and deviation from this was observed within the geopressured shales. These low velocity zones constitute anomalies that are not only geophysically significant but have structural definition.

Keywords: seismic velocity reversals, Niger Delta

Nigeria Journal of Pure and Applied Physics Vol. 4(1) 2005: 75-81