Displacement transfer between intersecting regional strike-slip and extensional fault systems

Abstract

Interaction and displacement transfer between active intersecting strike-slip (or transform) and extensional fault systems are examined. Outcrop data from a well-preserved strike-slip fault and rift intersection in New Zealand are compared to a global data set of 13 such intersections in both continental and oceanic crust. Displacement transfer between strike-slip and normal faults is typically accomplished by gradual changes of fault orientations and slip vectors close to the intersection zone. For two- and three-plate configurations, these changes result in sub-parallelism of the slip vectors of the component faults with their line of intersection. The dimensions of the area over which fault-strike and slip vectors change are principally controlled by the extent to which displacements on the dominant of the two intersecting fault systems are confined to a single slip surface or distributed across a zone. Where slip is spatially distributed, the region in which the two displacement fields are superimposed produces transtension and associated oblique slip. This distributed off-fault deformation facilitates the development of a quasi-stable configuration of the fault intersection region, maintaining both the regional geometry and kinematics of the intersection zone which, in many cases, would not be possible for rigid-block translations. The dimensions of the transition zone are larger for continental crust than for oceanic crust because oceanic crust is thinner, fault geometries in oceanic crust are simpler two-plate configurations and the slip vectors of the component intersecting fault systems are sub-parallel.