Along-strike growth of the Ostler fault, New Zealand: Consequences for drainage deflection above active thrusts

作者：Amos Colin B^*; Burbank Douglas W; Read Stuart A L

来源：Tectonics, 2010, 29: TC4021.

DOI：10.1029/2009TC002613

Rarely are geologic records available to constrain the spatial and temporal evolution of thrust-fault growth as slip accumulates during repeated earthquake events. Here, we utilize multiple generations of dated and deformed fluvial terraces to explore two key aspects of the along-strike kinematic development of the Ostler fault zone in southern New Zealand over the past similar to 100 k.y.: accumulation of fault slip through space and time and fixed-length thrust growth that results in patterns of drainage diversion suggestive of laterally propagating faults. Along the Ostler fault, surface deformation patterns revealed by topographic surveying of terrace profiles in nine transverse drainages define systematic variations in fault geometry and suggest deformation over both listric and planar thrust ramps. Kinematic modeling of folded terrace profiles and >100 fault-scarp surveys along major fault sections reveals remarkably similar slip distributions for multiple successions of geomorphic surfaces spanning similar to 100 k.y. Spatially abrupt and temporally sustained displacement gradients across zones of fault section overlap suggest that either persistent barriers to fault propagation or interference between overlapping faults dominate the interactions of fault tips from the scale of individual scarps to the entire fault zone. Deformed terrace surfaces dated using optically stimulated luminescence and cosmogenic radionuclides indicate steady, maximum rates of fault slip of similar to 1.9 mm/yr during the Late Quaternary. Slip data synthesized along the central Ostler fault zone imply that displacement accumulated at approximately constant fault lengths over the past similar to 100 k.y. A northward temporal progression of abandoned wind gaps along this section thus reflects lateral tilting in response to amplification of displacement, rather than simple fault lengthening or lateral propagation. Oscillations of climate at similar to 10(4)-yr time scales modulate the formation and incision of geomorphic surfaces during successive glacial stages. Superimposed on apparently steadier rates of fault slip, such climate-dependent surfaces contribute to a pattern of progressive drainage deflection along the central Ostler fault zone that is largely independent of fault propagation. Citation: Amos, C. B., D. W. Burbank, and S. A. L. Read (2010), Along-strike growth of the Ostler fault, New Zealand: Consequences for drainage deflection above active thrusts, Tectonics, 29, TC4021, doi:10.1029/2009TC002613.

• 出版日期2010-8-6