In 2018 Typhoon Mangkhut (locally known as Typhoon Ompong) triggered thousands of landslides in the Itogon region of the Philippines. A landslide inventory of the affected region is compiled for the first time, comprising 1101 landslides over a 570 km² area. The inventory is used to study the geomorphological characteristics and land cover more prone to landsliding as well as the hydrometeorological conditions that led to widespread failure. The results showed that landslides mostly occurred on grassland and wooded slopes of clay superficial geology, predominantly facing east-southeast. Rainfall (Integrated Multi-satellitE Retrievals for Global Precipitation Measurement, IMERG GPM) associated with Typhoon Mangkhut is compared with 33 high-intensity rainfall events that did not trigger regional landslide events in 2018. Results show that landslides occurred during high-intensity rainfall that coincided with the highest soil moisture values (estimated clays saturation point), according to Soil Moisture Active Passive level 4 (SMAP-L4) data. Our results demonstrate the potential of SMAP-L4 and GPM IMERG data for landslide hazard assessment and early warning where ground-based data are scarce. However, other rainfall events in the months leading up to Typhoon Mangkhut that had similar or higher rainfall intensities and also occurred when soils were saturated did not trigger widespread landsliding, highlighting the need for further research into the conditions that trigger landslides in typhoons.

中文翻译：

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地貌，降雨和土壤湿度在菲律宾2018年台风山竹引发的滑坡发生中的作用

在2018年的台风山竹（当地称为Ompong台风）在菲律宾的伊托贡地区引发了数千起山体滑坡。首次编制了受灾地区的滑坡清单，其中包括570 km ^2上的1101个滑坡 区域。该清单用于研究更容易发生滑坡的地貌特征和土地覆盖，以及导致广泛破坏的水文气象条件。结果表明，滑坡主要发生在草地和黏性表层地质的树木茂密的斜坡上，主要面向东南偏东。将与台风山竹相关的降雨（用于全球降水测量的多卫星综合反演，IMERG GPM）与2018年未触发区域滑坡事件的33次高强度降雨事件进行了比较。结果显示，在重合的高强度降雨期间发生了滑坡根据土壤水分主动被动等级4（SMAP-L4）数据，具有最高的土壤水分值（估计的粘土饱和点）。我们的结果证明了SMAP-L4和GPM IMERG数据在缺乏地面数据的情况下对滑坡灾害评估和预警的潜力。然而，在导致台风山竹的几个月内发生的其他降雨事件具有相似或更高的降雨强度，并且在土壤饱和时也发生了这些事件，这些事件并未引发大范围的滑坡，这凸显了需要对引发台风滑坡的条件进行进一步研究。