DI33A-4299:
Subslab seismic anisotropy and mantle flow in the western Pacific subduction zones
Wednesday, 17 December 2014
Cheng-Chien Peng, IONTU Institute of Oceanography National Taiwan University, Taipei, Taiwan, Ban-Yuan Kuo, Institute of Earth Sciences Academia Sinica, Taipei, Taiwan and Chin-Wu Chen, National Taiwan University, Taipei, Taiwan
Abstract:
We present source-side anisotropy for a few subduction zones in an attempt to map the mantle flow beneath the slab. Shear-wave splitting parameters of S were measured at stations towards the back of the subduction with the receiver-side anisotropy removed. We examined the observed fast directions against tilting/rotation of olivine fabric relative to the geometry of the subduction. We found that at the SW edge of the Ryukyu subduction zone the olivine fabric in the subslab mantle must rotate clockwise by 25 degrees from the slab subduction trajectory to explain the observed pattern of shear-wave splitting. This rotation echoes the deformation model of the slab when it is impinging against the Eurasian lithosphere. In the Vanuatu (New Hebrides) subduction zone, the olivine fabric may rotate dramatically to accommodate the rapid retreat of the trench and flipping of subduction polarity in the past a few Mys.
