Understanding landslide behavior over medium and long timescales is crucial for predicting landslide hazard and constructing accurate landscape evolution models. The behavior of landslides in soil that undergo periodic displacements, termed earthflows or compound soil slides, is especially difficult to forecast at these timescales. This is because velocities can increase by orders of magnitude over annual to decadal timescales, due to processes such as changing recharge conditions, erosion of the landslide toe, and retrogression of the landslide head. In this paper, we provide a detailed analysis of the Schlucher landslide, an unusual earthflow that is perched above the village of Malbun, Liechtenstein. This landslide had been displacing by 10 to 20 cm/year until 2015, when displacements on the order of 2 m/year occurred from 2016 to 2018. These large displacements damaged landslide mitigation measures, caused numerous surface deformation features, and threatened the local population downstream of the earthflow. This landslide has an unusually long monitoring record, with accurate displacement and climatic data available since 1983. We analyze this nearly 40-year monitoring time series to estimate recharge from snowmelt and rainfall, and its correlation with displacement. We also analyze recently collected, high-resolution surface and subsurface data in order to understand landslide response to recharge, landslide kinematics through time, and catastrophic failure potential. We find that interannual displacements can be explained with variations in recharge; however, periodic surges with recurrence times of tens of years must be explained by other mechanisms. In particular, recharge into the landslide during the recent acceleration (2016 to 2018) was not anomalously high. Instead, we argue that loss of internal strength is responsible for this recent acceleration period, and that this mechanism should be considered when forecasting the surge potential for certain earthflows and soil slides.

了解中长期的滑坡行为对于预测滑坡灾害和构建准确的景观演化模型至关重要。在这些时间尺度上，很难预测发生周期性位移的土壤滑坡的行为，称为泥石流或复合土壤滑坡。这是因为由于补给条件的变化，滑坡趾的腐蚀和滑坡头的倒退等过程，速度可能会在每年到十年的时间尺度上增加几个数量级。在本文中，我们对Schlucher滑坡进行了详细分析，Schlucher滑坡是一种异常的泥石流，位于列支敦士登的Malbun村上方。到2015年为止，该滑坡的位移量为10至20厘米/年，而从2016年至2018年，每年发生的位移量约为2 m。这些大位移破坏了滑坡缓解措施，造成了许多表面变形特征，并威胁了泥石流下游的当地居民。该滑坡具有异常长的监测记录，自1983年以来一直提供准确的位移和气候数据。我们分析了这近40年的监测时间序列，以估算融雪和降雨的补给量及其与位移的相关性。我们还分析了最近收集的高分辨率地表和地下数据，以了解滑坡对补给的响应，滑坡运动学随时间变化以及灾难性破坏的可能性。我们发现年际位移可以用补给的变化来解释。但是，必须通过其他机制来解释具有数十年复发时间的周期性电涌。尤其是，在最近的加速期间（2016年至2018年），滑坡补给量并非异常高。相反，我们认为内部强度的下降是最近加速期的原因，并且在预测某些泥石流和土层滑坡的涌浪潜力时应考虑采用这种机制。