Abstract - Quantitative analysis of faults within a South Australian polygonal fault system, interpreted from a 3-D onshore seismic survey, provides a basis for establishing their growth and linkage. The geometric characteristics of faults are consistent with an origin arising from the gravitational instability of a low-density, overpressured, mobile layer. Fault size populations have scale-bound, non-power-law, properties that reflect the thickness of the underlying mobile layer and the strongly connected nature of the system. The spatial distributions of faults reflect the localisation of conjugate faults at the top of the mobile layer and the scale of polygons. Displacement variations on faults show marked decreases at or adjacent to the top of the mobile layer and attest to its active role in faulting. The wide range of fault strike directions provides numerous fault intersections with high intersection angles (³ 60° ) forming triple-junctions at which fault linkage and capture occurred. Fault linkage and capture is attributed to a simple model in which continued movement on faults which share a mutual footwall is favoured and hangingwall faults are deactivated. The model is attributed to thickening of the mobile layer within the footwalls of faults and thinning, and eventual grounding of the overlying sequence, within their hangingwalls.
In: Mobilisation, intrusion and faulting of subsurface sediments. (Edited by Van Rensbergen, P., Hillis, R., Maltman, A. & Morley, C.). Geological Society of London, Special Publication 216, 245-261, 2003.