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The structure of the Sumatran Fault revealed by local seismicity
Author(s) -
Weller O.,
Lange D.,
Tilmann F.,
Natawidjaja D.,
Rietbrock A.,
Collings R.,
Gregory L.
Publication year - 2012
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2011gl050440
Subject(s) - geology , induced seismicity , seismology , fault trace , fault (geology) , slip (aerodynamics) , bifurcation , physics , nonlinear system , quantum mechanics , thermodynamics
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.