2022 Fiscal Year Final Research Report

Elucidation of the Structure and Evolution of the Subduction Zone Using an Integrated Approach of High-Pressure Experiments and Seismic Wave Observations

Research Project

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Project/Area Number	19H02002
Research Category	Grant-in-Aid for Scientific Research (B)
Allocation Type	Single-year Grants
Section	一般
Review Section	Basic Section 17040:Solid earth sciences-related
Research Institution	Ehime University
Principal Investigator	Greaux Steeve 愛媛大学, 地球深部ダイナミクス研究センター, 講師 (90543166)
Co-Investigator(Kenkyū-buntansha)	肥後祐司公益財団法人高輝度光科学研究センター, 回折・散乱推進室, 主幹研究員 (10423435) 河合研志東京大学, 大学院理学系研究科(理学部), 准教授 (20432007) 佐藤友彦岡山理科大学, 基盤教育センター, 准教授 (80714831)
Project Period (FY)	2019-04-01 – 2023-03-31
Keywords	mantle composition / high pressure / ultrasonic measurement / seismological model / triplication
Outline of Final Research Achievements	In this research project, we conducted an investigation into the seismicity of regions with stagnating slabs, independently of global models. Our investigation was based on laboratory sound velocity measurements, geological records of the slab, and local seismological observations. Through the application of advanced ultrasonic interferometry and synchrotron X-ray techniques, we were able to perform experiments at the pressures and temperatures of the upper mantle (up to 2300 K at pressures of ~3-10 GPa), mantle transition zone (up to 2100 K at pressures of ~12-22 GPa), and uppermost lower mantle (up to 2100 K at pressures of ~24-27 GPa). These techniques were applied to investigate the sound velocities of pyrolite, Mid-Ocean Ridge Basalt (MORB), and harzburgite rock aggregates, as well as other relevant minerals and rock compositions. The results of our investigation have broad implications for the fields of Earth and planetary sciences.
Free Research Field	Solid Earth
Academic Significance and Societal Importance of the Research Achievements	The velocity models derived from our datasets enable us to constrain the local structure and composition of the mantle and subducted slabs, extending up to the uppermost lower mantle. This has implications for our understanding of Earth's internal dynamics and evolution throughout geological time.