The lower crust immediately below intraplate earthquake faults is weak? –A dense seismic observation in the northern part of the South Island in New Zealand-

2014 Fiscal Year Final Research Report

• Project/Area Number: 23253004
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 海外学術
• Research Field: Solid earth and planetary physics
• Research Institution: Kyoto University
• Principal Investigator: IIO YOSHIHISA 京都大学, 防災研究所, 教授 (50159547)
• Co-Investigator(Renkei-kenkyūsha): OKADA Tomomi 東北大学, 理学研究科, 准教授 (30281968) ; MATSUMOTO Satoshi 九州大学, 理学研究院, 准教授 (40221593) ; OHMI Shiro 京都大学, 防災研究所, 准教授 (50263158) ; FUKAHATA Yukitoshi 京都大学, 防災研究所, 准教授 (10313206) ; TAKADA Youichiro 京都大学, 防災研究所, 助教 (80466458) ; YAMADA Masumi 京都大学, 防災研究所, 助教 (60456829) ; KOSUGA Masahiro 弘前大学, 理工学研究科, 准教授 (90142835)
• Project Period (FY): 2011-04-01 – 2015-03-31
• Keywords: 内陸地震 / 活断層 / 下部地殻 / 地殻流体 / クライストチャーチ地震 / 地震発生過程 / 余震分布 / 地殻構造

Outline of Final Research Achievements

We conducted a dense seismic observation in the northern part of the South Island in New Zealand, and found anomalous seismic velocity structures immediately below intraplate earthquake faults, which is in accordance with the resistivity structures. This fact supports a model for the generating process of intraplate earthquakes, that the lower crust immediately below intraplate earthquake faults is weakened by water. Furthermore, we conducted an aftershock observation for the Christchurch earthquake, and estimated detailed aftershock distributions and velocity structures. It is suggested from the characteristic depth distributions of aftershock hypocenters that stress concentration occurred around the western end of the earthquake fault.

Free Research Field

固体地球惑星物理学