Abstract

The geometries of extensional fault systems have been studied by use of experimental sand analogues and are compared with examples in the literature. Extensional faulting above a uniformly extending basement produces a domino-style fault array involving both planar rotational faults and listric faults. The faults evolve with time and may change from listric geometries (concave upward) through planar fault segments to convex-upward geometries. At high extensional strains early faults are cut by later high-angle planar extensional faults. Hanging-wall deformation above a simple listric extensional detachment is characterized by faults that nucleate and propagate into the hanging wall and produce crestal collapse grabens. Listric extensional faults with a ramp/flat geometry also produce hanging-wall crestal collapse grabens and local reverse faults. The experiments show that hanging-wall blocks in listric extensional fault systems must undergo significant internal strains in order to accommodate progressive deformation over nonplanar fault surfaces.

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