Characterization of landslide displacements in an active fault zone in Northwest China

Abstract

AbstractLandslides can be caused by natural forcing and anthropogenic activities. Zhouqu County (China) on the eastern margin of Qinghai‐Tibet Plateau is set within the active Pingding‐Huama fault zone with evident fractures on the land surface. Frequent landslides and debris flows have occurred in this region due to river erosion, rainfall and deforestation. Here we quantified the slope movements using time‐series synthetic aperture radar interferometry (InSAR) based on the ascending and descending Sentinel‐1 satellite images acquired between October 2014 and August 2020. We observed distinct displacements in the highly fractured fault zone. The eastward and vertical displacement time series between February 2017 and July 2020 were constrained by the common‐day ascending and descending acquisitions. The eastward rates (461 mm/year) were greater than those in the vertical direction (−185 mm/year). We also note displacement discontinuities across the thrust faults beneath the Suoertou and Zhongpai landslides. Seasonal variations in the displacement time series suggest that the cyclic rainfall is the primary driver for the mass wasting processes rather than the tectonic loading. As a complement to in situ observations, our results demonstrate that InSAR is an effective tool to characterize the spatio‐temporal nature of landslide displacements in complicated geological environments.Plain Language SummaryZhouqu County in the Pingding‐Huama fault zone in the eastern margin of Qinghai‐Tibet Plateau is identified as a high priority site to research on clusters of landslides and debris flows in a mixed geodynamic setting of active tectonics, seasonal rainfall, river erosion and anthropogenic activities. However, our knowledge about landslide kinematics in this complicated region is still limited. We relied on remote sensing images from one ascending and one descending Sentinel‐1 satellite tracks to constrain the spatial–temporal displacement dynamics of active landslides from 2014 to 2020. The spatial patterns of displacements are determined by thrust faulting, river erosion, and anthropogenic activities. The temporal variations of landslide speed are mainly controlled by the seasonal rainfall rather than the tectonic loading.