Origin of the heterogeneity in the oceanic lithosphere

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K03807
• 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: Okayama University of Science (2020-2021); Kyushu University (2018-2019)
• Principal Investigator: Azusa Shito 岡山理科大学, 生物地球学部, 講師 (90376541)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 海洋リソスフェア

Outline of Final Research Achievements

Through the analysis of the Po/So waves propagating across the Atlantic Ocean, we found that the propagation efficiency of Po/So waves was remarkably low near the young Mid-Atlantic Ridge, while the Po/So waves propagating in the older Atlantic Northwest were highly efficient. Waveform modeling has shown that this feature can be explained by the thicker the ocean lithosphere increases as it ages, and the smaller the intrinsic attenuation. This result is consistent with the result in the Pacific. Furthermore, the correlation length and scattering intensity of the layered heterogeneous structure were also estimated to be the same as those in the Pacific Ocean. These results suggest, contrary to initial expectations, that the process of development of the heterogeneous structure in the ocean lithosphere does not depend on the spreading rate.

Free Research Field

地震学

Academic Significance and Societal Importance of the Research Achievements

本研究の結果は、アセノスフェアにはたらく剪断応力が海洋リソスフェアの拡大速度には関係しないことを示唆しており、プレート運動の原動力を考えるうえで重要な結果である。また、本研究において開発された、内部減衰と散乱減衰の三次元構造を推定するソフトウェアは、海洋リソスフェアの構造のみならず陸域の地殻構造においても適用可能であり、広範に応用可能な成果である。