FAULT SEGMENTATION, RELAY ZONES, AND GEOMETRICAL EVOLUTION OF FAULT LINKAGES IN SALT RELATED NORMAL FAULT SYSTEMS, EUGENE ISLAND SOUTH ADDITION, GULF OF MEXICO

The goal of this study is to test two hypotheses that explain the early stages of fault linkage. Hypothesis 1 describes initially isolated faults with varying orientations that propagate towards each other until their fault tips overlap, giving rise to relay ramps and eventually transfer faults that link these faults. Hypothesis 2 describes faults that nucleate along a narrow zone with a geometry that persists throughout the lifespan of the linked fault system. This hypothesis differs from hypothesis 1 in that it predicts that the relay ramp and transfer fault geometry is established early in the evolution of the fault.

These hypotheses are tested by analyzing a system of faults in the Gulf of Mexico using high-resolution 3D seismic data that it is approximately 1850 seismic survey acquired by Petroleum Geo-Services in 1995-1996. The seismic data was processed through Kirchhoff prestack time migration. The study area lies along the continental shelf edge, south of Louisiana, and is dominated by salt-related deformation.

Preliminary mapping shows that three types of relay zones are present (extensional, contractional and neutral relay zones). Faults and their footwall and hanging wall cutoffs are well imaged. The faults have preserved growth strata in their hanging walls, and therefore it is possible to determine their slip history, as well as the relative ages of adjacent faults. To test the predictions of the hypotheses above, I mapped faults and their growth strata. This mapping is used to construct fault network maps, displacement-length plots, and displacement histories.