The structure of the Sumatran Fault revealed by local seismicity

Weller, Owen and Lange, D. and Tilmann, F. and Natawidjaja, Danny Hilman and Rietbrock, Andreas and Collings, Rachel Elizabeth and Gregory, Laura (2012) The structure of the Sumatran Fault revealed by local seismicity. Geophysical Research Letters, 39 (1). L01306. ISSN 0094–8276 DOI https://doi.org/10.1029/2011GL050440

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Abstract

The combination of the Sunda megathrust and the (strike-slip) Sumatran Fault (SF) represents a type example of slip-partitioning. However, superimposed on the SF are geometrical irregularities that disrupt the local strain field. The largest such feature is in central Sumatra where the SF splits into two fault strands up to 35 km apart. A dense local network was installed along a 350 km section around this bifurcation, registering 1016 crustal events between April 2008 and February 2009. 528 of these events, with magnitudes between 1.1 and 6.0, were located using the double-difference relative location method. These relative hypocentre locations reveal several new features about the crustal structure of the SF. Northwest and southeast of the bifurcation, where the SF has only one fault strand, seismicity is strongly focused below the surface trace, indicating a vertical fault that is seismogenic to ~15 km depth. By contrast intense seismicity is observed within the bifurcation, displaying streaks in plan and cross-section that indicate a complex system of faults bisecting the bifurcation. In combination with analysis of topography and focal mechanisms, we propose that the bifurcation is a strike-slip duplex system with complex faulting between the two main fault branches.

Item Type:	Article
Uncontrolled Keywords:	2011AREP; IA63; Part III;
Subjects:	02 - Geodynamics, Geophysics and Tectonics
Divisions:	02 - Geodynamics, Geophysics and Tectonics 08 - Green Open Access
Journal or Publication Title:	Geophysical Research Letters
Volume:	39
Page Range:	L01306
Identification Number:	https://doi.org/10.1029/2011GL050440
Depositing User:	Sarah Humbert
Date Deposited:	23 Dec 2011 12:27
Last Modified:	29 Mar 2016 10:12
URI:	http://eprints.esc.cam.ac.uk/id/eprint/2321

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