Stratigraphic control of frontal décollement level and structural vergence and implications for tsunamigenic earthquake hazard in Sumatra, Indonesia
Author
Bradley, Kyle
Qin, Yanfang
Carton, Hélène
Hananto, Nugroho
Villanueva‐Robles, Fernando
Leclerc, Fréderique
Shengji, Wei
Tapponier, Paul
Sieh, Kerry
Singh, Satish
Date of Issue
2019School
Asian School of the Environment
Research Centre
Earth Observatory of Singapore
Version
Published version
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.
Subject
Subduction
Tsunami
DRNTU::Science::Geology
Tsunami
DRNTU::Science::Geology
Type
Journal Article
Series/Journal Title
Geochemistry, Geophysics, Geosystems
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.
Collections
http://dx.doi.org/10.1029/2018GC008025
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