Re-examination of the movement history of the Median Tectonic Line in Ina area

2017 Fiscal Year Final Research Report

• Project/Area Number: 15K05318
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Geology
• Research Institution: Waseda University
• Principal Investigator: Takagi Hideo 早稲田大学, 教育・総合科学学術院, 教授 (60154754)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Keywords: 中央構造線 / 断層ガウジ / K－Ar年代 / 活断層 / 伊豆孤の衝突

Outline of Final Research Achievements

From this research, the researcher got the following two results.
1. One of the faults along the Median Tectonic Line (MTL) transects a terrace deposit at Hiji Outcrop. We extracted volcanic glass shards from the deposit and determined bulk chemical composition of the glasses. The result is that the glasses are correlative with those from the Ontake tephra (On-Pm1), which was erupted at 100 Ka. Accordingly the MTL fault was reactivated as an active fault.
2. We collected fault gouges from several outcrops of the MTL and examined K-Ar ages and illite polytype component from four grain-size fractions divided. As a result, the fault gouges are formed by hydrothermal alteration associated with major fault movement at about 15 Ma , which is correlative with the beginning of the collision of Izu arc against the Honshu arc.

Free Research Field

構造地質学