A new fault-valve model based on a geological approach

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K04046
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: National Institute of Advanced Industrial Science and Technology
• Principal Investigator: Otsubo Makoto 国立研究開発法人産業技術総合研究所, 地質調査総合センター, 研究グループ長 (70443174)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 南海トラフ / 地震 / 鉱物脈 / 亀裂 / 流体移動 / 流体圧 / スロー地震

Outline of Final Research Achievements

Using the poroelastic model of quartz veins filling extensional fractures in the Shimanto Belt, the formation of extensional fractures releases at most a few percent of the total pore pressure at depths of up to 8 km, indicating that the pore pressure near giant branch faults was close to lithostatic pressure throughout the entire earthquake cycle. The pore water pressure near the giant bifurcation fault was close to the static rock pressure throughout the entire earthquake cycle. A negative correlation was found between the amount of fluid pressure that exceeded the minimum principal stress and the spacing of mineral veins.

Free Research Field

地質学

Academic Significance and Societal Importance of the Research Achievements

研究成果は地震後の伸張性亀裂による間隙流体圧の低下が巨大分岐断層の断層強度を増加させるのにほとんど寄与せず，つまり，断層面付近は間隙流体圧が高い状態が維持されている可能性を示す．また，鉱物脈同士の間隔はスロー地震の発生サイクル内での間隙流体圧の過剰分の時間変化の結果である可能性があり，間隙流体圧の過剰分がスロー地震のサイズを規定する可能性がある．