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Title: Stratigraphic control of frontal décollement level and structural vergence and implications for tsunamigenic earthquake hazard in Sumatra, Indonesia
Authors: Bradley, Kyle
Qin, Yanfang
Carton, Hélène
Hananto, Nugroho
Villanueva‐Robles, Fernando
Leclerc, Fréderique
Shengji, Wei
Tapponier, Paul
Sieh, Kerry
Singh, Satish
Keywords: Tsunami
Issue Date: 2019
Source: Bradley, K., Qin, Y., Carton, H., Hananto, N., Villanueva‐Robles, F., Leclerc, F., . . . Singh, S. (2019). Stratigraphic control of frontal décollement level and structural vergence and implications for tsunamigenic earthquake hazard in Sumatra, Indonesia. Geochemistry, Geophysics, Geosystems, 20(3), 1646-1664. doi:10.1029/2018GC008025
Series/Report no.: Geochemistry, Geophysics, Geosystems
Abstract: Propagation of fault rupture to the seafloor is a likely cause of enhanced tsunami generation during megathrust earthquakes. New, high‐resolution seismic reflection profiles and swath bathymetry collected across the northern limit of the Mw 7.8, 25 October 2010 Mentawai tsunami earthquake rupture reveal significant and systematic lateral variations in both the stratigraphic level of the frontal Sunda megathrust and the vergence of its frontal ramp faults. Where ramp faults are uniformly seaward vergent, the décollement resides on top of a strong reflector marking the inferred top of pelagic sediments. Where ramp faults are bivergent (both landward and seaward), the décollement is localized within the subducting clastic sequence, above a xseismically transparent unit inferred to be distal fan muds. Where ramp faults are uniformly landward vergent, the décollement is directly on top of the oceanic crust of the subducting Investigator Fracture Zone. Enhanced surface uplift and tsunamigenesis during the 2010 tsunamigenic earthquake appear to have coincided with propagation of rupture into frontal areas with well‐developed structural bivergence. Frontal bivergence is a geological signal of low basal traction during accrual of slip, and offshore of Sumatra this structural style may mark areas of enhanced tsunami hazard posed by small‐magnitude, shallow megathrust ruptures that propagate into the incoming terrigenous sequence at near‐trench levels.
DOI: 10.1029/2018GC008025
Rights: © 2019 The Authors. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.
Fulltext Permission: open
Fulltext Availability: With Fulltext
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