Land subsidence is recognized as one of the hazards that threaten Metro Manila, Philippines, and other major urban areas worldwide. It has become a significant global issue caused by excessive groundwater extraction, rapid urbanization, and natural sediment compaction, exacerbated by climate change through rising sea levels. This paper presents vertical ground motion rates in Philippine metropolitan cities using Sentinel-1 InSAR time series analysis from 2014 to 2020 through UK COMET’s LiCSAR products and the LiCSBAS package of Morishita et al. (2020). The results revealed a maximum subsidence rate of 109 mm/yr in Bulacan Province in Greater Manila. For the first time, this paper also presents ground motion estimates and the following maximum subsidence rates for other Philippine metropolitan cities: 11 mm/yr in Metro Cebu, 38 mm/yr in Metro Davao, 9 mm/yr in Metro Iloilo, and 29 mm/yr in Legazpi City. Areas with remarkably high subsidence rates are observed as circular to elliptical deformation features in vertical motion maps. Sinking areas mostly coincide with industrial and commercial complexes evident as a contiguous distribution of large and expansive man-made structures with distinct radar reflections. Monitoring this hazard is crucial as it increases the risk of floods, building and infrastructure damage, and economic loss, and exposes residents along the coast to worsening tidal incursions and storm surges due to climate change. InSAR is proposed here as a targeted, long-term deformation monitoring tool, especially related to groundwater usage.

中文翻译：

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2014 年至 2020 年菲律宾主要大城市的地面沉降


地面沉降被认为是威胁菲律宾马尼拉大都会和全球其他主要城市地区的危险之一。由于过度开采地下水、快速城市化和自然沉积物压实，它已成为一个重要的全球性问题，而气候变化导致海平面上升加剧了这些问题。本文通过英国 COMET 的 LiCSAR 产品和 Morishita 等人（2020 年）的 LiCSBAS 软件包，使用 Sentinel-1 InSAR 时间序列分析展示了 2014 年至 2020 年菲律宾大都市的垂直地震动速率。结果显示，大马尼拉布拉干省的最大沉降率为 109 毫米/年。本文还首次提出了其他菲律宾大城市的地震动估计值和以下最大沉降率：宿雾大都会区 11 毫米/年，达沃大都会区 38 毫米/年，伊洛伊洛大都会区 9 毫米/年，黎牙实比市 29 毫米/年。在垂直运动地图中，具有非常高沉降率的区域被观察为圆形到椭圆形的变形特征。下沉区域大多与工业和商业综合体重合，明显表现为具有明显雷达反射的大型和广阔的人造结构的连续分布。监测这种危害至关重要，因为它会增加洪水、建筑物和基础设施损坏以及经济损失的风险，并使沿海居民面临气候变化导致的日益恶化的潮汐入侵和风暴潮。这里提出 InSAR 作为一种有针对性的长期变形监测工具，特别是与地下水利用相关的工具。