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Impact of lower plate structure on upper plate deformation at the NW Sumatran convergent margin from seafloor morphology

David Graindorge 1, * Frauke Klingelhoefer 2 Jean-Claude Sibuet 2 Lisa Mcneill 3 Timothy J. Henstock 3 Simon Deanc 3 Marc-André Gutscher 1 Jean Xavier Dessa 4 Haryadi Permana 5 Satish C. Singh 6 Hélène Leau 7 Nicolas White 8 Hélène Carton 6 Jacques André Malod 1 Claude Rangin 9 Ketut G. Aryawan 10 Anil Kumar Chaubey 11 Ajay Chauhan 6 Dodi R. Galihe 5 Christopher James Greenroyd 12 Agus Laesanpura 13 Joko Prihantono 14 Gillian Royle 6 Uma Shankar 15
* Corresponding author
1 LDO - Domaines Océaniques
2 IFREMER Centre de Bretagne - Institut Français de Recherche pour l'Exploitation de la Mer - Brest
3 NOC - National Oceanography Centre [Southampton]
4 GEOAZUR 6526 - Géoazur
5 Earth Dynamics and Geological Disaster Division
6 IPGP - Institut de Physique du Globe de Paris
7 IPEV - L'Institut polaire français Paul-Emile Victor
8 Bullard Laboratories
9 CEREGE - Centre européen de recherche et d'enseignement des géosciences de l'environnement
10 Marine Geological Institute
11 NIO - National Institute of Oceanography [India]
12 Durham University
13 ITB
14 Marine and Fish Department
15 NGRI - National Geophysical Research Institute [Hyderabad]
Abstract : We present results from multibeam bathymetric data acquired during 2005 and 2006, in the region of maximum slip of the 26 Dec. 2004 earthquake (Mw 9.2). These data provide high-resolution images of seafloor morphology of the entire NW Sumatra forearc from the Sunda trench to the submarine volcanic arc just north of Sumatra. A slope gradient analysis of the combined dataset accurately highlights those portions of the seafloor shaped by active tectonic, depositional and/or erosional processes. The greatest slope gradients are located in the frontal 30 km of the forearc, at the toe of the accretionary wedge. This suggests that long-term deformation rates are highest here and that probably only minor amounts of slip are accommodated by other thrust faults further landward. Obvious N–S oriented lineaments observed on the incoming oceanic plate are aligned sub-parallel to the fracture zones associated with the Wharton fossil spreading center. Active strike-slip motion is suggested by recent deformation with up to 20–30 m of vertical offset. The intersection of these N–S elongated bathymetric scarps with the accretionary wedge partly controls the geometry of thrust anticlines and the location of erosional features (e.g. slide scars, canyons) at the wedge toe. Our interpretation suggests that these N–S lineaments have a significant impact on the oceanic plate, the toe of the wedge and further landward in the wedge. Finally, the bathymetric data indicate that folding at the front of the accretionary wedge occurs primarily along landward-vergent (seaward-dipping) thrusts, an unusual style in accretionary wedges worldwide. The N–S elongated lineaments locally act as boundaries between zones with predominant seaward versus landward vergence.
Keywords : subduction accretionary wedge seafloor morphology tectonic Sumatra
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CNRS | IPGP | OCA | GEOAZUR | UNICE | UPMC | UNIV-BREST | INSU | UNIV-PARIS7 | UNIV-AMU | CDF | USPC | OSU-INSTITUT-PYTHEAS | CEREGE | IRD | LGO | CMM | UNIV-COTEDAZUR | INRA | SORBONNE-UNIVERSITE | INRAE | UNIV-PARIS | AFRIQ | PSL | SU-TI

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David Graindorge, Frauke Klingelhoefer, Jean-Claude Sibuet, Lisa Mcneill, Timothy J. Henstock, et al.. Impact of lower plate structure on upper plate deformation at the NW Sumatran convergent margin from seafloor morphology. Earth and Planetary Science Letters, Elsevier, 2008, 275 (3-4), pp.201-210. ⟨10.1016/j.epsl.2008.04.053⟩. ⟨insu-00354708⟩

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