Simultaneous estimation of the dip angles and slip distribution on the faults of the 2016 Kumamoto earthquake through a weak nonlinear inversion of InSAR data
Simultaneous estimation of the dip angles and slip distribution on the faults of the 2016 Kumamoto earthquake through a weak nonlinear inversion of InSAR data
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DOI：
10.1186/s40623-016-0580-4
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发表时间：
2016-12-19
影响因子：
3
通讯作者：
Hashimoto, Manabu
中科院分区：
文献类型：
--
作者：
Fukahata, Yukitoshi;Hashimoto, Manabu
在2016年熊本地震中，不仅在发生主要破裂的Futagawa断层沿线观测到地表破裂，而且在Hinagu断层沿线也观测到地表破裂。为了估计这些断层上的滑动分布，我们将非线性反演分析方法（Fukahata和Wright，地球物理学报，173:353-364,2008）扩展到双断层系统。Fukahata and Wright（2008）的方法基于赤池贝叶斯信息准则，将断层倾角作为一个超参数，可以同时确定断层的最佳倾角及其上的滑动分布。利用该方法反演InSAR数据，得到了二川断裂和日谷断裂的倾角分别为61°+/- 6°和74°+/- 12°。二川断层上的滑动以走滑为主。断层上最大的滑动在模型断层中心（经度130.9度）周围5 m以上，有明显的正滑分量。在与日谷断层相交的地方，二川断层的滑动迅速减小到零。另一方面，这次滑坡在阿索火山口内部有一个局部高峰，这将对该地区造成严重破坏。在与阿索火山口交点附近的较深处，反向断层滑动分量相对较大，这表明那里发生了一些复杂的事情。Hinagu断层上的滑动几乎是纯走滑，峰值约为2.4 m。当熊本地震这样的复杂断裂发生在偏远地区时，所开发的方法有助于明确滑动分布。
At the 2016 Kumamoto earthquake, surface ruptures were observed not only along the Futagawa fault, where main ruptures occurred, but also along the Hinagu fault. To estimate the slip distribution on these faults, we extend a method of nonlinear inversion analysis (Fukahata and Wright in Geophys J Int 173: 353-364, 2008) to a two-fault system. With the method of Fukahata and Wright (2008), we can simultaneously determine the optimal dip angle of a fault and the slip distribution on it, based on Akaike's Bayesian information criterion by regarding the dip angle as an hyperparameter. By inverting the InSAR data with the developed method, we obtain the dip angles of the Futagawa and Hinagu faults as 61 degrees +/- 6 degrees and 74 degrees +/- 12 degrees, respectively. The slip on the Futagawa fault is mainly strike slip. The largest slip on it is over 5 m around the center of the model fault (130.9 degrees in longitude) with a significant normal slip component. The slip on the Futagawa fault quickly decreases to zero beyond the intersection with the Hinagu fault. On the other hand, the slip has a local peak just inside Aso caldera, which would be a cause of severe damage in this area. A relatively larger reverse fault slip component on a deeper part around the intersection with Aso caldera suggests that something complicated happened there. The slip on the Hinagu fault is almost a pure strike slip with a peak of about 2.4 m. The developed method is useful in clarifying the slip distribution, when a complicated rupture like the Kumamoto earthquake happens in a remote area.