白龙江流域潜在滑坡InSAR识别与发育特征研究

Early identification and characteristics of potential landslides in the Bailong River Basin using InSAR technique

白龙江流域地处甘肃省东南部,位于青藏高原、黄土高原和四川盆地的交汇处。区内断裂构造发育、新构造运动活跃、地震频繁,加之多见的暴雨和持续降雨天气,使得流域内地质灾害频发,且分布范围广泛,其中以滑坡、泥石流灾害较为显著。本研究基于合成孔径雷达干涉测量技术,对白龙江流域进行区域尺度上的时序地表变形监测,得出2018年—2019年雷达视线方向的形变速率范围为-158—110 mm/a,并在人口分布集中的河谷区圈定出潜在滑坡点共计114处,并进行野外验证。统计发现研究区潜在滑坡多集中分布于两岸坡度20°—40°、坡向135°—270°、高差小于150 m、面积小于5×10^(4)m^(2)的千枚岩等软弱岩层中。牙豁口滑坡发生破坏前,滑坡中上部变形剧烈,变形速率达38 mm/a,于07-19在该区域剪出并不断向下推移,最终进入岷江。结合滑前的变形特征和滑坡地貌,将牙豁口滑坡分为搬运区、流通区和堆积区。该滑坡事件证明了InSAR技术在潜在滑坡早期识别中的有效性和可靠性。本研究可为白龙江流域的滑坡调查、综合治理和防灾减灾提供科学依据和参考。

The Bailong River Basin is located in the southeast of Gansu Province and situated at the intersection of the Qinghai–Tibet Plateau,the Loess Plateau,and the Sichuan Basin.Geohazards,such as landslides and debris flows,have high frequency and wide distribution due to the impact of rainfall,tectonic activity,and earthquakes.These phenomena pose a serious threat to the safety of life and property of the local people.Investigating a new method to detect potential landslide and study its characteristics is important to provide key supports for local disaster prevention and mitigation.In this study,an InSAR technique called Small Baseline Subset was selected to process60 Sentinel-1 A SAR images acquired from March 2018 to March 2019.Moreover,the study area was clipped into 8 blocks to improve the efficiency of data processing and minimize the errors caused by the complex terrain of the region.On the basis of the abovementioned method,the mean surface displacement rates ranging from-158 and 100 mm/year along the line-of-sight direction were detected during March 2018 and March 2019.A total of 114 potential landslides were investigated and identified in the Bailong River Basin based on optical image interpretation and field survey.Statistical analysis of their basic information shows that most of the potential landslides tend to develop in the S,SSW,and SSE-faced slope with a gradient of 20°—40°.The elevation difference of potential landslides is less than 150 m.The slope material is mostly composed of slope deposits and heavy weathered rocks,such as phyllite.The majority of potential landslides have an area less than 5×10^(4)m^(2).Yahuokou landslide,which was investigated as a potential landslide with displacement rates>38 mm/year,broke and ran into Min River from 19 July 2019.On the basis of the analysis of landslide pre-cursory deformation and geomorphology,the landslide was divided into three sections:source,propagation,and accumulation areas.The successful identification of potential landslide demonstrates the applicability and efficiency of InSAR technique in landslide investigation and identification.This research provides foundation and scientific support for landslide mapping and disaster prevention in Bailong River Basin.