Preliminary analysis of crustal anisotropy in the southernmost part of Simeulue Island

Abstract

The study location is in the southernmost region of Simeulue Island near the Indo-Australian subduction margin. The deformation and geodynamic evolution around the island have been studied through some geophysical and geological studies. However, information regarding crustal seismic anisotropy around this region is less investigated, which may be very useful in delineating the deformation process in this area. In this work, we conducted an initial crustal anisotropy study using shear wave splitting analysis for two seismic stations from two datasets. One seismic station is from temporary deployment data recording data between December 2005 and March 2006, and the other one is from IA permanent network data. The objective of using these two different datasets is to assess the splitting analysis’s consistency and constrain the dominant cause of crustal anisotropy around the study area. The anisotropy orientations at all seismic stations are parallel to the regional stress direction. This situation may imply that anisotropy around the study area is mainly due to stress-induced anisotropy. Furthermore, the delay time distribution with depth suggests that the anisotropic source is concentrated around 15-20 km depth of the crust. This indicates a strong influence from the interaction between the lower crust and the upper part of the subducting slab.