Seismic velocity structure of the crust and upper mantle estimated from S-wave polarization anisotropy

2015 Fiscal Year Final Research Report

• Project/Area Number: 25400454
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Solid earth and planetary physics
• Research Institution: Okayama University
• Principal Investigator: Oda Hitoshi 岡山大学, 自然科学研究科, 名誉教授 (50127552)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: S波偏向異方性 / Ps 変換波 / P波レシーバ関数 / 地殻 / マントルウエッジ

Outline of Final Research Achievements

We investigate the regional variation of the S-wave polarization anisotropy within the upper and lower crusts and the mantle wedge beneath southwest and northeast Japan from the Ps-converted waves which originate at the Conrad and Moho discontinuities and at the upper plane of subducting oceanic plates. Three similarities are found between the S-wave anisotropic structures estimated in southwest and northeast Japan. The first is that the anisotropic property is different between the upper and lower crusts, the second is that the upper crustal anisotropy is closely correlated to the tectonic stress fields acting on the Japan Islands, and the third is that the lower crustal anisotropy is significantly influenced by the subducting oceanic plates. Additionally, in the Tohoku district, the fast polarization directions show basically N-S and E-W direction trends in the fore-arc and back-arc sides of the mantle wedge, respectively.

Free Research Field

地震学