Landslide protection and mitigation are critical issues in many regions worldwide, where lives and livelihoods depend on correctly determining landslide hazards. However, local differences in the response of landslide slopes to meteorological or seismic triggering factors can decrease the performance of landslide models and forecasts. Thus, recognising and understanding spatial patterns of landslide activity at a local scale should be one of the priorities of landslide research. In this study, we analyse the activity and triggering factors of two landslides in one mountain massif, <2 km apart, in the Western Carpathians, Poland. We analysed 61-year-long (1959–2019) records of the activity of study landslides, i.e. dendrochronological reconstruction based on ring eccentricity and compression wood dated in 65 specimens of European silver fir (). We compared the dendrochronological proxy of landslide activity at two study slopes with precipitation and earthquakes in the study area. Based on statistical correlations with 560 precipitation indicators, we found that the similarities between the two study landslides include only the direct triggers in June–July and March. The Wiśnia landslide, unlike Hajdowska, can also be triggered by precipitation in October. However, the main difference between the study landslides lies in the preparatory precipitation. Hajdowska shows significant dependence from precipitation of the previous December and current February, while at the Wiśnia study site, the preparatory precipitation is less important and covers the previous October–November and current January. Our results show that although study landslides could be reactivated at one time by similar direct triggers of spring or summer, such simultaneous reactivation would require preconditions of antecedent precipitation of the previous winter half-year (October–March) different for each landslide. Suppose, the requirements of antecedent precipitation are fulfilled only for one of the landslides during the winter half-year. In that case, the other will remain inactive despite the later occurrence of a shared direct trigger in spring or summer. The example of Hajdowska and Wiśnia shows that significant differences in landslide activity, hazard and triggering factors can exist even at the local scale. We argue that omitting even such subtle, unevident differences in the conditions of landslide activity leads to errors in landslide modelling and forecasting. For example, linking Hajdowska and Wiśnia landslides with one precipitation threshold or model of slope instability based on their adjacent location would not be effective in predicting reactivations. The precision of landslide modelling and forecasting depends on the accuracy of preceding analyses of landslide activity and triggering factors. We argue that in the case of the two adjacent landslides studied the divergent patterns of their activity and triggers would not be revealed without analysing long-term (> 60 years long) data sets.

中文翻译：

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单一山体局部范围内滑坡活动的不同模式和触发因素（贝斯基德岛，西喀尔巴阡山脉，波兰）

滑坡防护和缓解是全球许多地区的关键问题，这些地区的生命和生计取决于正确确定滑坡危害。然而，滑坡对气象或地震触发因素的响应的局部差异可能会降低滑坡模型和预报的性能。因此，认识和理解局部尺度滑坡活动的空间格局应该是滑坡研究的重点之一。在这项研究中，我们分析了波兰西喀尔巴阡山脉一个山体中相距 <2 公里的两次山体滑坡的活动和触发因素。我们分析了长达 61 年（1959 年至 2019 年）研究滑坡活动的记录，即基于 65 个欧洲银杉标本的环偏心率和压缩木进行的树木年代学重建。我们将两个研究斜坡滑坡活动的树木年代学代理与研究区域的降水和地震进行了比较。根据与560个降水指标的统计相关性，我们发现两次研究滑坡的相似之处仅包括6月至7月和3月的直接触发因素。与 Hajdowska 不同，Wiśnia 山体滑坡也可能由 10 月份的降水引发。然而，研究滑坡的主要区别在于预备降水。 Hajdowska 显示出对去年 12 月和当前 2 月降水的显着依赖，而在 Wiśnia 研究地点，预备降水不太重要，涵盖了去年 10 月至 11 月和当前 1 月。我们的结果表明，虽然研究的滑坡可以通过类似的春季或夏季直接触发因素同时重新激活，但这种同时重新激活需要前一个冬季半年（10月至3月）的前期降水的先决条件对于每个滑坡来说都是不同的。假设冬半年只有一场滑坡满足前期降水量的要求。在这种情况下，尽管稍后在春季或夏季发生共同的直接触发，另一个仍将保持不活跃状态。 Hajdowska 和 Wiśnia 的例子表明，即使在局部范围内，滑坡活动、灾害和触发因素也可能存在显着差异。我们认为，即使忽略滑坡活动条件中如此微妙、不明显的差异，也会导致滑坡建模和预测出现错误。例如，将 Hajdowska 和 Wiśnia 滑坡与一个降水阈值或基于其邻近位置的斜坡不稳定模型联系起来，并不能有效地预测再活动。滑坡建模和预报的精度取决于前期对滑坡活动和触发因素分析的准确性。我们认为，在研究两个相邻山体滑坡的情况下，如果不分析长期（> 60 年）数据集，就不会揭示其活动和触发因素的不同模式。