Abstract - When viewed in sufficient detail individual faults are often seen to comprise an array of fault segments. Displacement transfer at segment boundaries is accommodated by relay zones which are generally characterized by relay ramps within layered sedimentary sequences. We present the kinematic analysis of a relay zone from South East Asia, the structural evolution of which is preserved within syn-faulting sediments imaged on high quality 3-D seismic data. Detailed mapping shows that the fault segments are linked at depth and displacement backstripping reveals that ramp length and strain are constant for each increment of ramp rotation. Our analysis indicates that the relay zone was established geologically instantaneously by upward bifurcation from an underlying single fault plane, with incremental ramp growth marked by displacement transfer and ramp rotation, without relay lengthening. Lower older horizons in the ramp have higher displacements and are characterised by associated ramp steepening and the formation of a cross-cutting breaching fault. It is envisaged that increased displacement will lead to upward propagation of this breaching fault, and the eventual formation of a through-going at progressively higher structural levels. Throughout its growth history the relay zone was geometrically and kinematically coherent providing an efficient means of transferring displacements.
Abstract of poster presented at:
Irish Geological Research Meeting, National University of Ireland, Galway, February 2011.