A study of the quadrature phase induction vector

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K04121
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: Tohoku University
• Principal Investigator: Ichiki Masahiro 東北大学, 理学研究科, 助教 (80359182)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: インダクションベクトル / 電磁誘導 / 海洋効果 / 海岸線効果

Outline of Final Research Achievements

This study revealed the following relationship between quadrature-phase induction arrow and the electrical resistivity distribution in the crust and uppermost mantle. In the two-dimensional settings, the quadrature-phase induction vector points seawards or a conductive body in the crust and uppermost mantle depending on the skin depth, and the quadrature-phase vector well indicates the ocean and the conductor in the earth. In the three-dimensional setting such as an isolated island surrounded by ocean, quadrature-phase induction vector points seawards in shorter periods, subparallel to coastline in middle periods, and inland in longer periods. The observed quadrature-phase induction vector in northeastern Japan in the period range 5000 to 10000 seconds, which points northwards, is likely ascribed to the resistive block rather than the conductive block in the uppermost mantle beneath the eastern part of Hokkaido.

Free Research Field

地球惑星内部電磁気学

Academic Significance and Societal Importance of the Research Achievements

地球内部の電磁誘導研究において虚部のインダクションベクトルの海洋効果、海岸線効果などの海陸境界、海底地形の影響をモデリングによって具体的特徴を明らかにしたことは地球内部の比抵抗構造を研究する上で学術的な意義は非常に大きい。作業仮説では実際の東北地方の虚部のインダクションベクトルの特徴は北海道西部の最上部マントルの高伝導体に原因があると考えていたが、実際は高抵抗の可能性が高いことが示唆されたことは、今後新しいマントルテクトニクスの解明に繋がる可能性がある。