Geersen, Jacob , Völker, David, Behrmann, Jan , Weinrebe, Wilhelm, Kläschen, Dirk , Krastel, Sebastian and Reichert, C. (2012) Segmentation of the 1960 Great Chile (Mw 9.5) and the 2010 Maule (Mw 8.8) earthquakes controlled by a giant submarine slope failure. [Talk] In: The Lübeck Retreat, Collaborative Research Centre SFB 574, Volatiles and Fluids in Subduction Zones: Climate Feedback and Trigger Mechanisms for Natural Disasters. , 23.05.-25.05.2012, Lübeck . The Lübeck Retreat - final colloquium of SFB 574, May 23-25, 2012: program & abstracts. ; p. 6 .

Abstract

About 1000 km of the South Chilean margin were ruptured in 1960 by the Mw 9.5 Great Chile
Earthquake. Early in 2010 the immediate area to the north was affected by the Mw 8.8 Maule
Earthquake. In the area of the rupture boundary three giant Pleistocene submarine slope failures are observed in bathymetric and reflection seismic data. The slope failures each shifted volumes between 253 km$ and 472 km$ of slope sediments, compacted accretionary wedge material and continental framework rock from the continental slope into the trench. Seismic reflection data image an undisturbed well layered sedimentary trench fill and a continuous décollement in the areas where no
slope failures are observed. However, at the exact locations of the slope failures, which coincide with the boundaries of the 1960 and 2010 ruptures, chaotic slide deposits compose the lower part of the trench-fill. At these locations no continuous décollement has developed. We speculate that the underthrusting of the highly inhomogeneous slide deposits prevents the development of a continuous
décollement and thus the buildup of a thin (few millimeters) slip zone that is continuous in space as necessary for earthquake rupture propagation. Thus the 1960 Great Chile – 2010 Maule earthquake rupture boundary seems to be controlled by the underthrusting of products of giant submarine slope failures which impeded further propagation of earthquake rupture during both events. Our results emphasize that upper plate mass wasting, if it impacts on the internal structure and composition of the
subduction channel rocks, can play a key role in defining seismotectonic segmentation at convergent plate boundaries.

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