2022 Fiscal Year Final Research Report
Development of the technique for the assessment of fault activity using the formation age of clay minerals in fault rocks
Project/Area Number |
17K01326
|
Research Category |
Grant-in-Aid for Scientific Research (C)
|
Allocation Type | Multi-year Fund |
Section | 一般 |
Research Field |
Natural disaster / Disaster prevention science
|
Research Institution | University of Yamanashi |
Principal Investigator |
|
Project Period (FY) |
2017-04-01 – 2023-03-31
|
Keywords | 活断層 / 糸魚川-静岡構造線 / 断層ガウジ / モンモリロナイト / カリ長石 / アンモニアラジカル / 熱水反応 / ESR年代測定 |
Outline of Final Research Achievements |
This study aims to develop a technique for the assessment of fault activity using the formation age of clay minerals in fault rocks. Experimental samples were collected from the Hakushu Fault, a part of the Itoigawa-Shizuoka Tectonic Line active fault system. ESR (electron spin resonance) and XRD (X-ray diffraction) analyses were carried out on the fault rocks, along with hydrothermal reaction experiments. The results show that the Mo quartet signals detected from smectite or thermally altered K-feldspar are attributed to the NH3+ radical. Hydrothermal reactions involving NH4+ ions may lead to the substitution of K+ and Na+ ions in smectite and K-feldspar with NH4+ ions, and natural radiation results in the knock-on of H atoms in NH4+ ions, leading to the generation of the NH3+ radical, that is, the Mo quartet signals. The Mo quartet signals are applicable not only to the ages of hydrothermal reactions associated with faulting, but also to the formation ages of clay minerals.
|
Free Research Field |
地球年代学,構造地質学
|
Academic Significance and Societal Importance of the Research Achievements |
原子力発電所直下に位置する断層の活動性評価は,日本のエネルギー政策を左右する重要な課題であるが,上載層が存在しない断層については活動性評価のための有効な手段が見当たらず,困難を極めている。断層活動性評価法の一つとして知られているESR年代測定法で最新活動年代を求めようとする場合,ESR信号のリセットが実現する地下深部から試料を採取しなければならないが,深部ボーリング掘削はコストが掛かり容易には実施できない。本研究手法では,地表の断層露頭から採取した断層岩試料をそのまま用いることができるので,コストを掛けずに活動性評価が実施できるのが利点である。
|