For landslide assessment in a specific small area of interest, regional thresholds may not be applicable and the application of empirical-statistical methodologies could be limited due to a lack of required databases (landslide inventories and triggering rainfall events). Rainfall thresholds for landslides have been recently derived from the implementation of physically based methodologies that usually provide a power-law equation for the study area (e.g. region or a specific basin). In this work, a new methodology for defining rainfall intensity and duration thresholds using a physically based model (TRIGRS) is presented and implemented in a tropical mountain basin of the Colombian Andes. Multiple calculations of the factor of safety for different (synthetic) rainfall events permitted the fitting of power-law equations to the sets of critical intensity and duration conditions, causing failure in each grid cell. Maps of the equation parameters (scale and shape) and the range of applicability (initial and final duration) of the grid cell thresholds were analysed. The results show that the hydraulic and mechanical properties of the soil affected the threshold curve characteristics, comparing sandy soil with silty loam; the higher strength characteristics of sandy soil meant that most extreme rainfall conditions are required to reach their thresholds. This methodology could improve landslide early warning systems in terms of analysing the specific (local) areas that are highly susceptible to landslide occurrence.

中文翻译：

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基于物理和分布的浅层滑坡降雨强度和持续时间阈值

对于特定小范围内的滑坡评估，区域阈值可能不适用，并且由于缺乏所需的数据库（滑坡清单和触发降雨事件），经验统计方法的应用可能会受到限制。滑坡的降雨阈值最近是从基于物理的方法的实施中推导出来的，这些方法通常为研究区域（例如区域或特定盆地）提供幂律方程。在这项工作中，提出了一种使用基于物理的模型 (TRIGRS) 定义降雨强度和持续时间阈值的新方法，并在哥伦比亚安第斯山脉的热带山区盆地中实施。对不同（合成）降雨事件的安全系数的多次计算允许将幂律方程拟合到一组临界强度和持续时间条件，从而导致每个网格单元出现故障。分析了方程参数（比例和形状）和网格单元阈值的适用范围（初始和最终持续时间）的映射。结果表明，土壤的水力和力学性质影响了阈值曲线特征，比较了砂质土和粉质壤土；沙质土壤的较高强度特性意味着大多数极端降雨条件都需要达到其阈值。这种方法可以改进滑坡早期预警系统，以分析非常容易发生滑坡的特定（局部）区域。