17:15 〜 18:30
[SCG50-P07] 高精度余震分布より推定される2016年ニュージーランドカイコウラ地震の断層形状とプレート境界面
キーワード：ニュージーランドカイコウラ地震、高精度余震分布、断層形状、プレート境界
On 14 November 2016, in the northeast region of South Island, New Zealand, the Kaikoura earthquake (Mw 7.8) occurred. One of the main characteristics of this event, which is pointed out by previous studies, is the complexity of the rupture process involved with several faults. Our temporary observation group had installed more than 70 sites surrounding the target area before the mainshock and it has successfully recorded the mainshock and the aftershocks. In this study, we applied a double-difference relocation algorithm (Waldhauser and Ellsworth, 2000) to the dense observations and we determined fault geometries based on the high precision hypocenter distribution.
In order to evaluate the fault structure quantitatively, we employed multivariate analysis and a statistical method used in Yukutake and Iio (2017). As a result, we identified 11 fault planes in total. In particular, one of them is the fault where the rupture of the Kaikoura earthquake initiated, which is consistent with the structure shown by other studies and the nodal plane of the mainshock focal mechanism. Furthermore, the bottom of the aftershock distribution in the northern area reveals a curved surface deepening towards the northwest direction. The result is almost parallel to, but approximately 3 km above, the slab interface determined by Williams et al. (2013). We detected many aftershocks in reverse fault type above this interface, which showed similarity in dip angle of the events to the interface. We consider whether the curved surface could represent the top of the subducting slab, or another type of interface.
In order to evaluate the fault structure quantitatively, we employed multivariate analysis and a statistical method used in Yukutake and Iio (2017). As a result, we identified 11 fault planes in total. In particular, one of them is the fault where the rupture of the Kaikoura earthquake initiated, which is consistent with the structure shown by other studies and the nodal plane of the mainshock focal mechanism. Furthermore, the bottom of the aftershock distribution in the northern area reveals a curved surface deepening towards the northwest direction. The result is almost parallel to, but approximately 3 km above, the slab interface determined by Williams et al. (2013). We detected many aftershocks in reverse fault type above this interface, which showed similarity in dip angle of the events to the interface. We consider whether the curved surface could represent the top of the subducting slab, or another type of interface.