Hydroacoustic observation and earthquake monitoring

2022 Fiscal Year Final Research Report

• Project/Area Number: 17K18948
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Research Field: Social systems engineering, Safety engineering, Disaster prevention engineering, and related fields
• Research Institution: The University of Tokyo
• Principal Investigator: Yamada Tomoaki 東京大学, 地震研究所, 助教 (40323654)
• Project Period (FY): 2017-06-30 – 2023-03-31
• Keywords: 水中音波 / 海中観測 / 海底観測 / 海中発破

Outline of Final Research Achievements

We investigate signal intensity and arrival directions based on hydroacoustic stations, which are operated by CTBTO, and ocean bottom seismometers and hydrophones. Hydroacoustic data show received signals over long distances across the Pacific Ocean, and comparison with 3D propagation simulations revealed that transmission losses due to seamounts on the path and diffraction effects explain the received signal reduction and delayed travel time based on a standard 1D structure. Furthermore, there are many reflected waves from marginal areas of the Pacific Rim and oceanic islands. The received signals on ocean bottom instruments varies greatly with location, especially with the depth of the installation.

Free Research Field

地震学

Academic Significance and Societal Importance of the Research Achievements

水中音波観測の有効な場所を示すと同時に、機動海底地震観測時に併用できる音波観測システムを開発した。また、本研究で利用した水中音波観測データは、包括的核実験条約機関準備委員会が、国際監視制度（IMS）の一つとして、海中における核実験監視のために整備を行い、取得されたものである。整備が進められて以降、公になっている海中での核実験は存在しないが、本研究では既知の海中発破データを用いることで、実データに基づく水中音波観測点の検知能力を示した。