In mountainous terrain, large earthquakes often cause widespread coseismic landsliding as well as hydrological and hydrogeological disturbances. A subsequent transient phase with high landslide rates has also been reported for several earthquakes. Separately, subsurface seismic velocities are frequently observed to drop coseismically and subsequently recover. Consistent with various laboratory work, we hypothesize that the seismic‐velocity changes track coseismic damage and progressive recovery of landscape substrate, which modulate landslide hazard and hydrogeological processes, on timescales of months to years. To test this, we analyze the near‐surface seismic‐velocity variations, obtained with single‐station high‐frequency (0.5–4 Hz) passive image interferometry, in the epicentral zones of four shallow earthquakes, for which constraints on landslide susceptibility through time exist. In the case of the 1999 Chi‐Chi earthquake, detailed landslide mapping allows us to accurately constrain an exponential recovery of landslide susceptibility with a relaxation timescale of about 1 yr, similar to the pattern of recovery of seismic velocities. The 2004 Niigata, 2008 Iwate, and 2015 Gorkha earthquakes have less‐resolved constraints on landsliding, but, assuming an exponential recovery, we also find matching relaxation timescales, from ∼0.1 to ∼0.6 yr⁠, for the landslide and seismic recoveries. These observations support our hypothesis and suggest that systematic monitoring of seismic velocities after large earthquakes may help constrain and manage the evolution of landslide hazard in epicentral areas. To achieve this goal, we end by discussing several ways to improve the link between seismic velocity and landscape mechanical properties, specifically by better constraining time‐dependent near‐surface strength and hydrogeological changes. Hillslopes displaying coseismic surface fissuring and displacement may be an important target for future geotechnical analysis and coupled to passive geophysical investigations.

中文翻译：

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使用地震干涉测量法量化地震后景观机械变化

在山区，大地震经常引起大范围的同震滑坡以及水文和水文地质扰动。一些地震也报告了随后的具有高滑坡率的瞬态阶段。另外，经常观察到地下地震速度同震下降并随后恢复。与各种实验室工作一致，我们假设地震速度的变化会在数月到数年的时间尺度上跟踪同震破坏和景观基质的逐步恢复，从而调节滑坡灾害和水文地质过程。为了测试这一点，我们分析了在四个浅层地震的震中带中使用单站高频（0.5-4 Hz）被动图像干涉测量法获得的近地表地震速度变化，存在滑坡敏感性随时间变化的限制。在 1999 年的 Chi-Chi 地震的情况下，详细的滑坡绘图使我们能够准确地限制滑坡敏感性的指数恢复，松弛时间尺度约为 1 年，类似于地震速度的恢复模式。2004 年新泻、2008 年岩手和 2015 年廓尔喀地震对滑坡的限制较少，但是，假设指数恢复，我们还发现了滑坡和地震恢复的匹配弛豫时间尺度，从 ~0.1 到 ~0.6 年。这些观察结果支持了我们的假设，并表明在大地震后系统地监测地震速度可能有助于限制和管理震中地区滑坡灾害的演变。为了实现这一目标，我们最后讨论了几种改善地震速度与景观力学特性之间联系的方法，特别是通过更好地约束时间相关的近地表强度和水文地质变化。显示同震表面裂缝和位移的山坡可能是未来岩土工程分析的重要目标，并与被动地球物理调查相结合。