Letter abstract
Nature Geoscience 2, 648 - 652 (2009)
Published online: 16 August 2009 | doi:10.1038/ngeo609
Subject Categories: Seismology | Structural geology, tectonics and geodynamics
Origin and evolution of a splay fault in the Nankai accretionary wedge
Michael Strasser1, Gregory F. Moore2,3, Gaku Kimura3,4, Yujin Kitamura5, Achim J. Kopf1, Siegfried Lallemant6, Jin-Oh Park3,7, Elizabeth J. Screaton8, Xin Su9, Michael B. Underwood10 & Xixi Zhao11
Subduction zones are often characterized by wedge-shaped sedimentary complexes—called accretionary prisms—that form when sediments are scraped off the subducting plate and added to the overriding plate. Large, landward-dipping thrust faults can cut through such a prism: these faults, known as 'megasplay faults'1, 2, originate near the top of the subducting plate and terminate at the shallow, landward edge of the prism1, 3, 4, 5, 6. Megasplay faults have been the subject of numerous geological and geophysical studies4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, but their initiation and evolution through time remains poorly constrained. Here we combine seismic reflection data from the Nankai accretionary wedge with geological data collected by the Integrated Ocean Drilling Program (IODP) and find that the splay fault cutting this wedge initiated 
1.95 Million years (Myr) ago in the lower part of the prism as an out-of-sequence thrust (OOST). After an initial phase of high activity, the movement along the fault slowed down, but uplift and reactivation of the fault resumed about 1.55 Myr ago. The alternating periods of high and low activity along the splay fault that we document hint at episodic changes in the mechanical stability of accretionary prisms.
- MARUM, Centre for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
- Department of Geology and Geophysics, University of Hawaii, Honolulu, Hawaii 96822, USA
- Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science Technology, Kanazawa-ku, Yokohama, Kanagawa 2360001, Japan
- Department of Earth and Planetary Science, The University of Tokyo, Tokyo 113-0033, Japan
- IFM-GEOMAR, The Leibniz-Institute of Marine Sciences at University of Kiel, 24148 Kiel, Germany
- Geosiences & Environment Cergy, University of Cergy-Pontoise, 95031 Cergy-Pontoise, France
- Ocean Research Institute, The University of Tokyo, Tokyo 164-8639, Japan
- Department of Geology, University of Florida, Gainesville, Florida 32611, USA
- School of Marine Geosciences, China University of Geosciences, Beijing 100083, China
- Department of Geological Sciences, University of Missouri, Columbia, Missouri 65211, USA
- Department of Earth and Planetary Sciences, University of California, Santa Cruz, California 95064, USA
Correspondence to: Michael Strasser1 e-mail: mstrasser@marum.de
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