Abstract
In Taiwan, landslides pose serious threats to local residents and infrastructures each year due to high mountain relief and distinct seasonal precipitation distribution. Interferometric synthetic aperture (InSAR) provides a powerful tool to map terrain motion and characterize the failure mechanism of unstable slopes. However, it is challenging for the conventional InSAR technique to obtain reliable landslide information in mountainous regions because of insufficient coherent measurements and signal confusion caused by vegetation coverage and rugged terrain. In this study, we adopt an optimized multi-temporal InSAR (MTInSAR) approach to analyze the surface displacement of an artificial side slope along Freeway No. 3, where a catastrophic landslide failure occurred on 25 April 2010, in northern Taiwan. To increase the spatial extent of the deformation signal, we integrate information from both persistent scatterers (PSs) and distributed scatterers (DSs). Topographic residual and height-dependent atmospheric delays are corrected by a component-based method and joint model estimation, respectively. The results reveal the existence of slope movement with a rate of about −30 mm/year prior to the landslide failure. Further analysis shows that the temporal behaviors of downslope movement are correlated with local precipitation. The study demonstrates the need to continuously monitor and verify the stability of artificial slopes to prevent and minimize the probability of a similar landslide occurrence in the future.
Highlights
Landslides, as the result of gravitational force and geological instability, are one of the major types of geological disasters around the world [1,2]
Benefiting from the extensive archive of SAR acquisitions covering the same area, multi-temporal interferometric synthetic aperture radar (InSAR) (MTInSAR) have been developed in recent years to overcome the limitations associated with conventional InSAR techniques by exploiting time-series information of SAR acquisitions, all of which basically fall into two categories, namely persistent scatterer interferometry (PSI) [11,12,13,14] and short baseline subset (SBAS) [15,16,17,18]
An optimized MTInSAR approach based on the integrated use of persistent scatterers (PSs) and distributed scatterers (DSs) has been developed in this study
Summary
Landslides, as the result of gravitational force and geological instability, are one of the major types of geological disasters around the world [1,2]. PSI exploits phase information from point-like persistent scatterers (PSs) that keep high coherence in long observation period and usually correspond to man-made objects and large rock outcrops. This method uses N + 1 single-look SAR images to form N single-master interferograms with good performance in urban or peri-urban areas [19,20]. We modify the existing MTInSAR algorithm to process phase information from both PSs and DSs and thereby improve the spatial coverage in environments with low coherence. This study is expected to demonstrate the applicability of InSAR technique for safety inspections of geotechnical structures in mountainous areas
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