Evolution of large normal faults: Evidence from seismic reflection data

Abstract

Recent advances have been made in understanding how extensional faults and basins develop as faults propagate and link. Evidence for these linkage patterns in seismic reflection data can be seen in data from East Africa. Early fault linkage patterns for boundary faults can follow three possible paths. Fault linkage and propagation occur either (1) prior to significant basin formation, (2) after minor faulting has created an extensive area of subsidence, or (3) during basin development. The data from East Africa show examples mainly of paths 1 and 2. Transverse anticlines (anticlines developed parallel to and in the hanging wall of the strike of faults) associated with boundary faults are common features. They represent either the sites of old synthetic transfer zones or a region of low fault displacement along the strike of a fault where two or more depocenters of different ages overlap. As fault activity decreases over time, displacement tends to be concentrated on progressively narrower parts of the fault. This pattern is developed particularly well in continental rifts and may help discriminate late synrift sedimentation from postrift sedimentation where strike lines across the hanging wall of the fault are observable.