Propagation, interaction and linkage in normal fault systems

Abstract

Recent advances are reviewed in the understanding of the geometry and development of steep, planar normal faults with up to hundreds of meters throw in multilayered sedimentary rocks. This essential class of structures is of particular importance in basin formation and hydrocarbon development. The role of interaction and linkage between fault segments is emphasized. Such normal faults usually consist of complex zones of overstepping and linked segments, within which relay ramps are significant structures. Displacement is transferred between normal faults that overstep in map view and that dip in the same direction by tilting of beds to form a relay ramp and by the development of minor faults. Oversteps and bends also occur along normal faults in cross-section, these commonly being controlled by lithological variations. Damage zones are zones of fractures developed around faults as they initiate, propagate, link and build up displacement. Various models have been developed to account for the accumulation of slip and the finite displacement on faults. Recent models emphasize the importance of fault interaction and other mechanical effects in causing variations in the displacement characteristics of faults. A population of normal faults typically displays a linear length–displacement ratio and obeys a power–law-scaling relationship for displacement. It is likely, however, that complex networks of faults and reverse-reactivated normal faults do not obey simple scaling relationships, with the pattern and history of deformation changing with scale.