Interferograms pertaining to large earthquakes typically reveal the occurrence of elastic deformations caused by the earthquake along with several complex surface displacements. In this study, we identified displacement lineaments from interferograms; some of which occur on the shallow section of seismogenic faults. However, such displacements are typically located away from the hypocenter, and they are considered as triggered shallow slips. We found that the triggered shallow slips had a varied nature, as follows. (1) No evidence has yet been obtained regarding the generation of large seismic motion via triggered shallow slips; thus, their occurrence is seldom considered a cause of major earthquakes. However, we found that a movement of triggered shallow slip associated with an M 6-class earthquake occurred on an active fault that has previously caused an M 7-class earthquake. (2) At certain locations, several parallel displacement lineaments have been discovered. During the Kumamoto earthquake sequence in 2016, the strain created by the main shock and the motion of triggered shallow slips coincided at a specific location, resulting in the creation of parallel triggered shallow slips by the main shock. Conversely, at another location, the movements of the main shock and triggered shallow slips did not match, since the main shock was simply a trigger, whereas the latter parallel triggered shallow slips are likely a means for releasing previously accumulated strain. (3) The fault scaling law—which states that the length and displacement of a fault are proportional—does not hold true for triggered shallow slips. However, the parallel triggered shallow slips show a relationship between horizontal spacing and its displacement. This may be attributed to immobility in deep locations. These results lead to the following conclusions. Large earthquakes tend to trigger shallow slips on the pre-existing faults. Subsequently, these triggered shallow slips release accumulated strain by causing fault motions, which in turn result in displacement lineaments. The occurrence of such passive faulting creates weak, mobile fault planes that repeatedly move at the same location. These triggered shallow slips cause the diversity among active faults as a result.

中文翻译：

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使用 L 波段 SAR 干涉测量法检测由大地震引起的触发浅层滑动

与大地震有关的干涉图通常会显示由地震引起的弹性变形以及几个复杂的表面位移的发生。在这项研究中，我们从干涉图中确定了位移线；其中一些发生在发震断层的浅部。然而，这种位移通常远离震源，它们被认为是触发的浅层滑动。我们发现触发的浅滑移具有多种性质，如下所示。(1) 浅层滑移引发大地震运动的证据尚未得到证实；因此，它们的发生很少被认为是大地震的原因。然而，我们发现与 M 6 级地震相关的触发浅层滑动运动发生在先前引起 M 7 级地震的活动断层上。(2) 在某些位置，发现了多条平行位移线。在 2016 年熊本地震序列中，主震产生的应变与触发浅滑移的运动在特定位置重合，导致主震产生平行触发的浅滑移。相反，在另一个位置，主震和触发的浅滑移的运动不匹配，因为主震只是一个触发器，而后者平行触发的浅滑移可能是释放先前积累的应变的一种手段。(3) 断层缩放定律——断层的长度和位移是成比例的——不适用于触发的浅层滑动。然而，平行触发的浅滑移显示出水平间距与其位移之间的关系。这可能归因于在深部位置的不动。这些结果导致以下结论。大地震往往会在预先存在的断层上引发浅层滑动。随后，这些触发的浅层滑动通过引起断层运动释放累积应变，从而导致位移线状。这种被动断层的发生会产生在同一位置重复移动的弱移动断层平面。这些触发的浅层滑动导致活动断层之间的多样性。平行触发的浅层滑动显示了水平间距与其位移之间的关系。这可能归因于在深部位置的不动。这些结果导致以下结论。大地震往往会在预先存在的断层上引发浅层滑动。随后，这些触发的浅层滑动通过引起断层运动释放累积应变，从而导致位移线状。这种被动断层的发生会产生在同一位置重复移动的弱移动断层平面。这些触发的浅层滑动导致活动断层之间的多样性。平行触发的浅层滑动显示了水平间距与其位移之间的关系。这可能归因于在深部位置的不动。这些结果导致以下结论。大地震往往会在预先存在的断层上引发浅层滑动。随后，这些触发的浅层滑动通过引起断层运动释放累积应变，从而导致位移线状。这种被动断层的发生会产生在同一位置重复移动的弱移动断层平面。这些触发的浅层滑动导致活动断层之间的多样性。大地震往往会在预先存在的断层上引发浅层滑动。随后，这些触发的浅层滑动通过引起断层运动释放累积应变，从而导致位移线状。这种被动断层的发生会产生在同一位置重复移动的弱移动断层平面。这些触发的浅层滑动导致活动断层之间的多样性。大地震往往会在预先存在的断层上引发浅层滑动。随后，这些触发的浅层滑动通过引起断层运动释放累积应变，从而导致位移线状。这种被动断层的发生会产生在同一位置重复移动的弱移动断层平面。这些触发的浅层滑动导致活动断层之间的多样性。