The 16 April 2016 Mw 7.0 Kumamoto earthquake caused prominent fault displacements and crustal deformation, not only around the main rupture faults but also around numerous secondary-ruptured faults. The physics and characteristics of such secondary faulting have not yet been studied in detail. We investigated a set of two secondary faults that appeared at the timing of the Mw 7.0 quake in the Aso Caldera by mainly using synthetic aperture radar interferometry and fault slip modeling. The two faults were found to be associated with surface displacement offsets of several centimeters or more, in the oblique sense of right-lateral and vertical motion. Fault slip inversions found that the slip was dominantly in normal sense with smaller contribution from the right-lateral component. The deeper limit of the slips was estimated to be around 1.3 km, which may coincide with the boundary between the superficial sediment layer and the basement rock. The shallowness of the slip and the difference in the dip angles of the main secondary fault and the Mw 7.0 seismogenic fault suggest separation of the two fault systems, although the fault strike and sense of motions were similar. The amount of slip on the two secondary faults was larger than that expected from the scaling law derived from seismogenic faults, which may indicate the difference in the physics of seismogenic and secondary faultings.

中文翻译：

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2016年7.0级熊本地震引发的阿苏火山口二次破裂断层特征

2016 年 4 月 16 日发生的 Mw 7.0 熊本地震不仅在主要破裂断层周围，而且在许多次要破裂断层周围引起了显着的断层位移和地壳变形。这种二次断层的物理性质和特征尚未得到详细研究。我们主要使用合成孔径雷达干涉测量法和断层滑动建模，研究了在阿苏火山口发生 Mw 7.0 地震时出现的一组两个次生断层。在右侧和垂直运动的倾斜意义上，发现这两个断层与几厘米或更多的地表位移偏移有关。断层滑动反演发现，正常意义上的滑动占主导地位，右侧分量的贡献较小。滑坡的更深极限估计约为 1.3 公里，这可能与表层沉积层和基岩之间的边界重合。尽管断层走向和运动感相似，但滑动的浅度以及主要次生断层和 Mw 7.0 发震断层的倾角差异表明两个断层系统是分离的。两条次生断层的滑动量大于由发震断层推导出的标度律所预期的滑动量，这可能表明发震断层和次生断层的物理差异。尽管断层走向和运动感相似。两条次生断层的滑动量大于由发震断层推导出的标度律所预期的滑动量，这可能表明发震断层和次生断层的物理差异。尽管断层走向和运动感相似。两条次生断层的滑动量大于由发震断层推导出的标度律所预期的滑动量，这可能表明发震断层和次生断层的物理差异。