Past oceanic plate motion based on seismological analysis

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K05533
• 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: The University of Tokyo
• Principal Investigator: ISSE Takehi 東京大学, 地震研究所, 助教 (60359180)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 海洋プレート構造

Outline of Final Research Achievements

We analyzed seismic waveform data recorded by land seismic stations and ocean bottom broadband seismometers in the Pacific Ocean, and obtained the upper mantle shear wave velocity structure in the Pacific region. Fast axis of the azimuthal anisotropic structure of shear wave was consistent with the direction of current plate motion in the deep part, but the shallow part structure is complicated. To estimate the past plate motion direction from the azimuthal anisotropic structure, it is necessary to remove the anomalous area that deviates from the plate growth in the analysis area. We performed analysis combining the velocity structure obtained and the temperature structure of the oceanic mantle, and clarified anomalous regions that can not be explained by the plate growth model.

Free Research Field

地球内部構造

Academic Significance and Societal Importance of the Research Achievements

太平洋地域の上部マントル地震波速度構造はこれまで陸上定常地震観測網のみから推定されており，推定された構造の空間解像度に限界があった．本研究は陸上観測網に加え，日本・アメリカの研究グループにより実施された臨時海底広帯域地震観測記録を用いて太平洋の海洋プレート構造を解析した最初の研究である．またプレート成長モデルで説明できない領域の解明は地球成長史の解明に寄与する知見である．