The magnitude 7.1 Darfield earthquake on 4 September 2010 caused a 30-km-long surface rupture across the Canterbury plains in the South Island of New Zealand. The earthquake started on a steep, relatively small "blind" fault that ruptured into a fault intersection zone and triggered the rupture of the Greendale fault, which generated most of the energy of the earthquake. High-resolution (cm-scale) ground surface displacements in the area of the fault junction were determined by comparing pre- and post-earthquake LiDAR topographic surveys and property boundary surveys, supplemented by mapping of the fault scarp and earthquake-induced flooding. The study revealed exceptionally fine details of ground displacements, including subtle warping over hundreds of meters that was undetectable using traditional earthquake mapping techniques. The magnitude and direction of displacements were used to reconstruct how the faults surrounding the junction interacted with each other during the earthquake to create localized zones of extension and contraction. This study illustrates the value of multi-method investigations and provides a valuable real world example for comparison with dynamic simulations of rupture behavior on fault networks.
Development of extension-parallel corrugations in the Buckskin-Rawhide metamorphic core complex, west-central Arizona
John S. Singleton, Dept. of Atmospheric, Oceanic, and Earth Sciences, George Mason University, Fairfax, VA 22030. Posted online 21 Dec. 2012; http://dx.doi.org/10.1130/B30672.1.
Mountain ranges that have undergone large amounts of extension commonly form distinct ridges ("corrugations") that are parallel to the direction of maximum stretching. In western Arizona, these corrugated mountain ranges are as well defined as anywhere on Earth. Despite the significant amount of research that has been devoted to
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Geological Society of America