Abstract - Overlap zones between normal faults have
been studied using a variety of 2- and 3-D seismic reflection datasets.
The overlaps are of two types, (i) relay zones in which displacement is
transferred between the overlapping faults and (ii) non-relay overlaps
in which displacement is not transferred.Overlap zones are continually formed and destroyed during the growth of a fault system. Overlap zones are formed either by interference
between initially isolated faults or as a result of bifurcation of a single
fault. The mode of overlap formation is reflected in the 3-D geometry of
the overlapping faults which may be either unconnected or linked at a branch-line or branch-point. Seismic reflection data from regions of growth faulting, and also sandbox analogue data, allow analysis of fault development through time.
Reconstruction of the displacement distribution on some faults with sharp
bends and associated hangingwall splays, show that the bends originated
as overlap zones which were later breached to form through-going faults. Depending on the displacements of relay-bounding faults, the effect
of relay zones on hydrocarbon reservoirs may be to (a) provide structural
closure, (b) form gaps in otherwise sealing faults or (c) increase reservoir
connectivity.
Journal of the Geological Society, London 152,
535-549, 1995.