Development of detect method of recent seismic slip in the fault zone of near-surface basement rocks

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K03991
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17030:Human geosciences-related
• Research Institution: Gifu University
• Principal Investigator: Ohtani Tomoyuki 岐阜大学, 工学部, 教授 (20356645)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 断層破砕帯 / 最新すべり面 / 根尾谷断層

Outline of Final Research Achievements

Analyses of fault gouges in the shallow zone of the Neodani Fault were performed using the borehole core drilled by the Nuclear Regulation Authority. Smectite and calcite are detected and Ca is well included in the whole zone of fault gouges. Latest slip plane, which is defined as a region with lower CT values, is Ca-poor relative to the neighboring fault gouges. SEM observation shows Ca-rich spots in the latest slip plane and mineralized veins with Ca in the neighboring fault gouges. This suggests that calcite filled cracks during ancient fault activity and no filling occurs recently and after the 1891 Nobi Earthquake.

Free Research Field

地質学

Academic Significance and Societal Importance of the Research Achievements

本研究の成果より浅部断層破砕帯における最新すべり面の特徴を根尾谷断層を例として明らかにした。これにより断層破砕帯の性状から最近の活動の手がかりを定性的に見いだすことが可能となった。学術的には地震性すべりに伴う浅部断層破砕帯の挙動をCT値や鉱物充填の観点から明らかにしたとともに、社会的には従来の手法では活動性評価が困難であった上載層を伴わない、あるいは地下浅部の活断層を対象として本研究成果を適用することにより定性的な評価が行えるようになることが期待される。