I have been conducting a study of postseismic deformation following the 2016 Kumamoto earthquake using ALOS-2/PALSAR-2 acquired till 2018. I apply ionospheric correction to interferograms of ALOS-2/PALSAR-2. L-band SAR gives us high coherence enough to reveal surface deformation even in vegetated or mountainous area for pairs of images acquired more than 2 years. Postseismic deformation following the Kumamoto earthquake exceeds 10 cm during 2 years at some spots in and around Kumamoto city and Aso caldera. Westward motion of ~ 6 cm/year was dominant on the southeast side of the Hinagu fault, while westward shift was detected on both sides of the Futagawa fault. The area of latter deformation seems to have correlation with distribution of pyroclastic flow deposits. Significant uplift was found around the eastern Futagawa fault and on the southwestern frank of Aso caldera, whose rate reaches 4 cm/year. There are sharp changes across several coseismic surface ruptures such as Futagawa, Hinagu, and Idenokuchi faults. Rapid subsidence between Futagawa and Idenokuchi faults also found. It is confirmed that local subsidence continued along the Suizenji fault, which newly appeared during the mainshock in Kumamoto City. Subsidence with westward shift of up to 4 cm/year was also found in Aso caldera. Time constant of postseismic decay ranges from 1 month to 600 days at selected points, but that postseismic deformation during the first epochs or two is dominant at point in the Kumamoto Plain. This result suggests multiple source of deformation. Westward motion around the Hinagu fault may be explained with right lateral afterslip on the shallow part of this fault. Subsidence along the Suizenji fault can be attributed to normal faulting on dipping westward. Deformation around the Hinagu and Idenokuchi faults cannot be explained with right lateral afterslip of Futagawa fault, which requires other sources. Deformation in northern part of Aso caldera might be the result of right lateral afterslip on a possible buried fault.

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ALOS-2/PALSAR-2 检测到 2016 年熊本地震后的震后变形

我一直在使用直到 2018 年获得的 ALOS-2/PALSAR-2 对 2016 年熊本地震后的震后变形进行研究。我将电离层校正应用于 ALOS-2/PALSAR-2 的干涉图。L 波段 SAR 为我们提供了足够高的相干性，即使在植被或山区，对于获得超过 2 年的成对图像也能揭示表面变形。熊本市和阿苏火山口附近的一些地点，熊本地震后的震后变形在 2 年内超过 10 厘米。日奈古断层东南侧以每年~6 厘米的西移为主，而双川断层两侧则检测到西移。后者变形的面积似乎与火山碎屑流沉积物的分布有关。在东二川断层附近和阿苏火山口的西南弗兰克发现了显着的隆升，其上升速度达到了 4 厘米/年。在双川断层、日奈古断层和井田口断层等几个同震地表破裂上发生了剧烈的变化。还发现了二川断层和井田口断层之间的快速沉降。熊本市主震期间新出现的水前寺断层沿线继续发生局部沉降。在阿苏火山口也发现了向西偏移高达 4 厘米/年的沉降。在选定的点，震后衰减的时间常数从 1 个月到 600 天不等，但在熊本平原的点上，震后变形在前一两个纪元中占主导地位。这一结果表明变形的多种来源。围绕日那古断层的西向运动可以用该断层浅部的右侧后滑来解释。沿水前寺断层的沉降可归因于向西倾斜的正断层作用。日奈古断层和井田口断层周围的变形不能用双川断层的右侧后滑来解释，这需要其他来源。阿苏火山口北部的变形可能是可能的隐伏断层右侧后滑的结果。