GPS/D-Acoustic survey using closely installed transponders

2018 Fiscal Year Final Research Report

• Project/Area Number: 17K18799
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Research Field: Earth and planetary science and related fields
• Research Institution: Tohoku University
• Principal Investigator: Kido Motoyuki 東北大学, 災害科学国際研究所, 教授 (10400235)
• Project Period (FY): 2017-06-30 – 2019-03-31
• Keywords: 海底測地 / 海底GPS / 海底間音響測距 / 海中音速 / 海溝型巨大地震 / 海底断層

Outline of Final Research Achievements

A new approach was proposed and verified that uses acoustic ranging from the sea surface at a site of localized strain of seafloor being expected, where traditional seafloor ranging has difficulty in acoustic paths not to be interfered by seafloor topography. During a sea trial at the reverse fault along the Japan trench, we confirmed that measured accuracy of strain is reasonable and the no significant strain was observed for the campaign period. On the contrary, during a sea trial off the Kii-peninsula, extremely complicated temperature perturbation was observed, which cannot adequately be corrected for. This indicated that the proposed approach is not always applicable to all the possible seafloor conditions and should be assessed beforehand.

Free Research Field

海底測地学

Academic Significance and Societal Importance of the Research Achievements

本研究では、従来の手法が適用困難な海底地形が急峻な場所でも局所変形の計測が可能となる新手法を提案し、実観測で実用性を検証するものである。考案した手法を適用した日本海溝の観測点では、理論的な予測に従った計測精度で変形のモニタリングに成功し、今後同様の場所に適用することで、海溝型巨大地震の予測に役立つことが分かった。一方で、海底付近の海水の擾乱の激しい箇所では必要な計測精度を達成できないことも判明し、事前に擾乱の度合いを把握した上で、適切に観測点を選択する重要性が明らかになった。