TY  - JOUR
A1  - Collings, R.
A1  - Rietbrock, Andreas
A1  - Lange, Dietrich
A1  - Tilmann, F.
A1  - Nippress, Stuart
A1  - Natawidjaja, D.
T1  - Seismic anisotropy in the sumatra subduction zone
JF  - Journal of geophysical research : Solid earth
N2  - An important tool for understanding deformation occurring within a subduction zone is the measurement of seismic anisotropy through observations of shear wave splitting (SWS). In Sumatra, two temporary seismic networks were deployed between December 2007 and February 2009, covering the fore arc between the fore-arc islands to the back arc. We use SKS and local SWS measurements to determine the type, amount, and location of anisotropy. Local SWS measurements from the fore-arc islands exhibit trench-parallel fast directions which can be attributed to shape preferred orientation of cracks/fractures in the overriding sediments. In the Sumatran Fault region, the predominant fast direction is fault/trench parallel, while in the back-arc region it is trench perpendicular. The trench-perpendicular measurements exhibit a positive correlation between delay time and raypath length in the mantle wedge, while the fault-parallel measurements are similar to the fault-parallel fast directions observed for two crustal events at the Sumatran Fault. This suggests that there are two layers of anisotropy: one due to entrained flow within the mantle wedge and a second layer within the overriding crust due to the shear strain caused by the Sumatran Fault. SKS splitting results show a NNW-SSE fast direction with delay times of 0.8-3.0s. The fast directions are approximately parallel to the absolute plate motion of the subducting Indo-Australian Plate. The small delay times exhibited by the local SWS (0.05-0.45s), in combination with the large SKS delay times, suggest that the anisotropy generating the teleseismic SWS is dominated by entrained flow in the asthenosphere below the slab.
KW  - Sumatra
KW  - Anisotropy
KW  - Shear wave splitting
KW  - Subduction zone
KW  - Mantle rheology
Y1  - 2013
U6  - https://doi.org/10.1002/jgrb.50157
SN  - 2169-9313
SN  - 2169-9356
VL  - 118
IS  - 10
SP  - 5372
EP  - 5390
PB  - American Geophysical Union
CY  - Washington
ER  -