著者

池田 倫治 柳田 誠 西坂 直樹

出版者

日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2012, no.36, pp.31-44, 2012

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The Mw 7.1 (GNS Science) earthquake (Darfield earthquake) occurred near Christchurch, New Zealand on 4 September 2010. The earthquake happened in the area where active faults had not recognized previously, produced the ground surface rupture (Greendale fault). We surveyed the mode of occurrences of the Greendale fault on 8 days after the Darfield earthquake. Measured dextral and vertical displacements along the fault are ~ 4.2 and ~ 1.5 m (predominantly southern parts up), respectively. The both slip components are distributed roughly symmetrically along the west fault segment. However, the maximum displacement points are perhaps different between dextral and vertical sense based on the survey results. The fault is roughly E–W strike, characterized by many Riedel fractures that show shapes of mole tracks accompanying main dextral displacements. Few active faults had recognized previously on Canterbury plain near Christchurch, whereas distribution of active faults and folds had cleared in the Pegasus Bay area where locates in the eastern part of the Christchurch. Moreover, there are records of a few paleoearthquakes (M>5) near Christchurch and in Pegasus Bay. These data would have been clues to forecast existence of blind active faults on Canterbury plain.