Splay faults imaged by fluid-driven aftershocks of the 2004 Mw 9.2 Sumatra-Andaman earthquake

LDEO Publication: 
Publication Type  Journal Article
Year of Publication  2012
Authors  Waldhauser, F.; Schaff, D. P.; Diehl, T.; Engdahl, E. R.
Journal Title  Geology
Volume  40
Issue  3
Pages  243-246

High-precision teleseismic double-difference locations and focal
mechanisms of aftershocks of the A.D. 2004 Mw 9.2 Sumatra-Andaman
earthquake illuminate an active imbricate fault system in the
accretionary prism offshore northern Sumatra. They reveal repeated
failure of a shallow northeast-dipping thrust fault above the megathrust,
which we interpret to be the reactivation of a splay fault that
rises from the megathrust at ~55 km depth and cuts through the
overriding Sunda plate. The projected intersection of the splay fault
with the seafl oor correlates with a recently active thrust fault seen in
postseismic bathymetry data west of the Aceh basin. A spatiotemporal
analysis of the streaky aftershock distribution indicates that ascending
fl uids released from the subducting oceanic crust along inherited
seafl oor fabric may control brittle fracture in the overriding plate. We
speculate that if the splay fault was active coseismically, it may have
led to amplifi ed vertical uplift of the forearc ridge and contributed to
generating the cataclysmic near-fi eld tsunami that struck the northwest
Sumatra coast following the 2004 rupture.

URL  http://www.ldeo.columbia.edu/~felixw/papers/Waldhauser_etal_GEOLOGY2012.pdf
DOI  doi:10.1130/G32420.1