Analysis of high-resolution lidar digital topographic data along the Marlborough Fault System: The Awatere and Clarence faults, South Island, New Zealand

Thursday, 18 December 2014
Robert Wayne Zinke1, James Francis Dolan1, Edward J Rhodes2, Russ Van Dissen3, Robert Langridge3, Jessica Grenader1, Chris P McGuire2 and Andrew Nicol3, (1)University of Southern California, Los Angeles, CA, United States, (2)University of California Los Angeles, Los Angeles, CA, United States, (3)GNS Science, Lower Hutt, New Zealand
We analyze newly acquired lidar high-resolution digital topographic data to measure offset geomorphic markers along the Awatere and Clarence faults in the Marlborough Fault System, northern South Island, New Zealand. With an average shot density of ≥ 12 shots/m2, these lidar data, which were acquired for us by the US National Center for Airborne Laser Mapping (NCALM) and New Zealand Aerial Mapping, offer a uniquely detailed view of the topography along ~90 km of the Awatere fault and ~160 km of the Clarence fault, allowing us to measure geomorphic offsets ranging in size from ~1 m to 100s of meters. In this specific study, we examine offset river terraces at the well-known Saxton River site on the Awatere fault, and at Tophouse Road on the Clarence fault. By constraining the ages of those river terraces using post-IR IRSL (225 °C) single-grain K-feldspar dating protocols, we determine latest Pleistocene to late-Holocene slip histories of the Awatere and Clarence faults at those locations. This project is part of a broader effort to generate incremental slip rates and paleoearthquake ages from the four main faults that comprise the Marlborough Fault System with the goal of further understanding how mechanically complementary faults work together to accommodate relative plate motions.