Frequency-dependent shear wave splitting beneath the Japan and Izu-Bonin subduction zones

Despite its importance for ourunderstandingof physical processes associatedwith subduction, the geometry of mantle flow in subduction zones remains poorly understood, particularly in the mantle wedge above subducting slabs. Constraints onmantle flowanddeformation canbeobtainedbymeasurements of shearwave splitting, a valuable tool used to characterize the geometry and strength of seismic anisotropy. A complete characterization of shear wave splitting is particularly important for understanding themantle wedge beneath Japan, which overlies multiple subduction zones with complex slab morphologies; previous studies indicate that the upper mantle beneath Japan exhibits complicated anisotropy that manifests itself in complex splitting patterns. To characterize better the geometry of mantle anisotropy beneath Japan, we analyzed direct S waves from local earthquakes originating in the subducting slabs for