Lin Aiming
Department of Geophysics, Graduate School of Science, Kyoto University, Kyoto, 606-8502 Japan.
J Seismol. 2017;21(5):1079-1100. doi: 10.1007/s10950-017-9653-5. Epub 2017 Mar 21.
Field investigations and analyses of satellite images and aerial photographs reveal that the 2016 7.1 (Mj 7.3) Kumamoto earthquake produced a ∼40-km surface rupture zone striking NE-SW on central Kyushu Island, Japan. Coseismic surface ruptures were characterized by shear faults, extensional cracks, and mole tracks, which mostly occurred along the pre-existing NE-SW-striking Hinagu-Futagawa fault zone in the southwest and central segments, and newly identified faults in the northeast segment. This study shows that (i) the Hinagu-Futagawa fault zone triggered the 2016 Kumamoto earthquake and controlled the spatial distribution of coseismic surface ruptures; (ii) the southwest and central segments were dominated by right-lateral strike-slip movement with a maximum in-site measured displacement of up to 2.5 m, accompanied by a minor vertical component. In contrast, the northeast segment was dominated by normal faulting with a maximum vertical offset of up to 1.75 m with a minor horizontal component that formed graben structures inside Aso caldera; (iii) coseismic rupturing initiated at the jog area between the Hinagu and Futagawa faults, then propagated northeastward into Aso caldera, where it terminated. The 2016 7.1 Kumamoto earthquake therefore offers a rare opportunity to study the relationships between coseismic rupture processes and pre-existing active faults, as well as the seismotectonics of Aso volcano.
通过对卫星图像和航空照片的实地调查与分析发现，2016年日本九州岛中部发生的7.1级（矩震级7.3）熊本地震产生了一条长约40公里的地表破裂带，走向为东北-西南向。同震地表破裂的特征包括剪切断层、张裂缝和鼹鼠足迹，主要出现在西南段和中段沿先前存在的东北-西南走向的日奈久-二川断裂带，以及东北段新发现的断层处。本研究表明：（i）日奈久-二川断裂带引发了2016年熊本地震并控制了同震地表破裂的空间分布；（ii）西南段和中段以右旋走滑运动为主，现场实测最大位移达2.5米，伴有较小的垂直分量。相比之下，东北段以正断层为主，最大垂直错距达1.75米，伴有较小的水平分量，在阿苏火山口内形成了地堑构造；（iii）同震破裂始于日奈久断层和二川断层之间的转折区域，然后向东北方向传播至阿苏火山口并在那里终止。因此，2016年7.1级熊本地震为研究同震破裂过程与先前存在的活动断层之间的关系以及阿苏火山的地震构造提供了一个难得的机会。
