日本地球惑星科学連合2016年大会

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ポスター発表

セッション記号 M (領域外・複数領域) » M-IS ジョイント

[M-IS34] 2016年熊本地震および関連する地殻活動

2016年5月25日(水) 17:15 〜 18:30 ポスター会場 (国際展示場 6ホール)

17:15 〜 18:30

[MIS34-P45] 2016年熊本地震に伴う地表地震断層

*白濱 吉起1吉見 雅行1粟田 泰夫1丸山 正1吾妻 崇1宮下 由香里1森 宏1今西 和俊1武田 直人1落 唯史1大坪 誠1朝比奈 大輔1宮川 歩夢1 (1.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)

キーワード:2016年熊本地震、布田川断層帯、日奈久断層帯、地表地震断層

The Kumamoto earthquake sequence that culminated in the Mj 7.3 event on April 16, 2016, produced the ca. 30 km long complex surface ruptures having a predominantly dextral with subordinately normal or reverse slip component along the eastern section of the Futagawa fault zone, the northern section of the Hinagu fault zone and previously unmapped faults including those across the Kiyama plain and across the western caldera rim of the Aso volcano, central Kyushu, Japan. Geological Survey of Japan, AIST, carried out urgent field investigation to explore and measure the surficial deformation associated with the Kumamoto earthquake during two weeks since the day of the mainshock. Our intensive field mapping revealed nature of the surface rupture in detail, including location, geometry, temporal growth and slip distribution of the complex ruptures. The remarkable features of the surface faulting were summarized as follows; i) the rupture zone is generally composed of a series of left-stepping en echelon array of discontinuous fault trace with various size; ii) the maximum dextral slip of ca. 2.2 m was measured at central part of the rupture zone, whose location and amount is consistent with InSAR analysis; iii) large slip (>1 m) occurred on the previously unrecognized fault traces that extend across the alluvial lowland; iv) slip is accommodated by complex rupture style, such as zigzag-shaped ruptures with ESE-trending dextral slip and NW-trending sinistral slip, slip partitioning that resolves oblique slip into dextral component and vertical component on sub-parallel traces, and widely developed grabens; v) accounts by eyewitnesses and repeated measurements show that part of the surface slip along the Hinagu fault has grown not only between the 14 April earthquake (Mj6.5) and mainshock (16 April) but also after the mainshock.