北京潮白河冲洪积扇地面沉降时空异质性特征及驱动因素分析

Spatio-Temporal Heterogeneity and Driving Factors of Land Subsidence in Middle-Lower Part of Chaobai River Alluvial Fan

为了研究地面沉降的时空分布模式、机理机制,选择北京典型沉降区——潮白河冲洪积扇为研究区,采用PS-InSAR技术、莫兰指数及地理探测器,分析了研究区地面沉降的空间异质性特征,探测了不同特征下的地面沉降的主要驱动因素。结果表明:2017-01—2019-01研究区内地面沉降时空分布特征以一般沉降为主,沉降速率为[-133,3] mm/a,最大累积沉降量为261 mm,呈北部轻微、中部较严重、南部较轻的分布状态,其中,严重、极严重等级地面沉降主要分布在中游顺义后沙峪东部等地区及中下游交界地带的潞城镇;不同地区地面沉降呈现不同的空间异质性特征,即不均匀地面沉降分布特征明显,中游、下游均表现为低—低集聚;不同分布特征下地面沉降主要驱动因素不同,中游地区主要驱动因素为第二承压水水位变化和可压缩层厚度,下游主要驱动因素为浅层地下水水位变化和第一承压水水位变化。莫兰指数能够有效分析地面沉降空间异质性,识别集聚特征;地理探测器可以探明沉降空间异质性成因,获得其主要驱动因素。

To study the spatio-temporal distribution pattern and mechanism of land subsidence, the Chaobai River alluvial fan, a typical subsidence area in Beijing, was selected as the study area, and the spatial heterogeneity and the driving factors of land subsidence were analyzed by using PS-InSAR, global and local moran indices, and geographic detectors. The results showed that the temporal and spatial distribution characteristics of land subsidence in the study area from January 2017 to January 2019 were mainly general subsidence, the subsidence rate was [-133,3] mm/a, and the maximum cumulative subsidence was 261 mm. It was slightly distributed in the north, more severe in the middle, and lighter in the south. The severe and extremely severe land subsidence mainly occurred in eastern Houshayu of Shunyi and Lucheng town at the junction of the middle and lower parts. The land subsidence in different areas presents different spatial heterogeneity, that is, the uneven distribution characteristics are obvious. The middle and lower parts show low-low agglomeration characteristics. Different driving factors of land subsidence are different under different distribution characteristics. The main driving factors in the middle part are the groundwater level change in the second confined aquifer and the thickness of the compressible layers, while the driving factors in the lower part are the groundwater level change in the shallow groundwater and the groundwater level change in the first confined aquifer. This study suggestes that Moran index can be used to effectively analyze the spatial heterogeneity of land subsidence and identify the characteristics of agglomeration, and the geographic detector can be used to find out the causes of spatial heterogeneity of land subsidence and obtain the main driving factors. This study also provides data support and reference for the prevention and control of land subsidence in different hydrogeological units.