Shear-wave polarization anisotropy and subduction-induced flow in the mantle wedge of northeastern Japan

摘要: Abstract Shear-wave polarization anisotropy in the central part of northeastern (NE) Japan was investigated. We analyzed S phases 293 intermediate-depth earthquakes recorded at 77 stations and obtained 1286 splitting parameters. The results show systematic variation parameters across arc. leading shear-wave directions (fast direction) western side study area are oriented nearly E–W, which is sub-parallel to direction relative plate motion between Pacific North American/Okhotsk plate. In contrast, fast eastern approximately N–S. Stations have a larger average delay time compared those side. These variations suggest that nature quite different sides. Both experimental studies on deformation olivine numerical simulations plate-driven flow predict lattice-preferred orientation causes for conditions mantle wedge NE Japan. thus infer generated by flow-induced strain most likely candidate produces with E–W direction. Three possible considered: water-rich wedge, trench-parallel due along-strike dip slab crust slab. could not, however, determine dominant. Further required reveal cause