Development of a controlled borehole seismic source and estimation of shallow S-wave velocity structure by use of tomography analysis

• Project/Area Number: 24310131
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Natural disaster science
• Research Institution: The University of Tokyo (2014); Nagoya University (2012-2013)
• Principal Investigator: WATANABE TOSHIKI 東京大学, 地震研究所, 教授 (50210935)
• Co-Investigator(Kenkyū-buntansha): KUNIMATSU Sunao 産業技術総合研究所, 地圏資源環境研究部門, 上級主任研究員 (70356921) ; YAMAOKA Koshun 名古屋大学, 環境学研究科, 教授 (70183118)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Project Status: Completed (Fiscal Year 2014)
• Budget Amount: ¥18,330,000 (Direct Cost: ¥14,100,000、Indirect Cost: ¥4,230,000); Fiscal Year 2014: ¥5,980,000 (Direct Cost: ¥4,600,000、Indirect Cost: ¥1,380,000); Fiscal Year 2013: ¥7,020,000 (Direct Cost: ¥5,400,000、Indirect Cost: ¥1,620,000); Fiscal Year 2012: ¥5,330,000 (Direct Cost: ¥4,100,000、Indirect Cost: ¥1,230,000)
• Keywords: 浅部構造 / 孔内振源 / 機器開発 / 制御震源 / S波速度 / 地盤構造 / 振源装置 / トモグラフィ

Outline of Final Research Achievements

We developed a borehole seismic source for shallow structure survey. The source generates seismic waves by rotating eccentric masses controlled by motors. The radius of the source is 80 millimeters so that we can use it in standard boreholes for engineering survey. From the result of the field experiment, we concluded that the source generates controlled signals up to 50 Hz, and that the signal is observed at the seismic stations loocated at 50-200 meters from the source with good S/N ratio. A linear vibration in horizontal direction is achieved by rotating two motors in opposite directions, resulting in verification that the efficient transmission of P-wave and S-wave is possible. On the other hand, we found some technical problems for further improvement. We developed a series of data processing flow from the continuous seismic signal observed at the seismic stations to the S-wave velocity structure using S-wave traveltime tomography.

Research Products

• [Presentation] 孔内用回転型精密制御振源の開発と性能試験 (2015)
  • Author(s): 渡辺俊樹, 国松 直, 山岡耕春, 太田賢治, 飯沼博幸, 葛尾拓也, 梶原 透
  • Organizer: 物理探査学会第132回(平成27年度春季)学術講演会
  • Place of Presentation: 早稲田大学西早稲田キャンパス（東京都新宿区）
  • Year and Date: 2015-05-11 – 2015-05-13