The Role of Tectonic Discontinuities in Triggering Large Seismic Landslides

Abstract

Abstract Rock landslides are generally controlled by a series of discontinuous interfaces formed by damage to complex structural rock masses that is related to folds, faults, and shear zones, which provide potential failure boundaries. Based on a detailed case study, the authors illustrate that structural damage not only affects the 3D boundaries of landslides but also significantly controls the initiation mode. In this paper, six large landslides triggered by the 2008 Wenchuan earthquake (Ms 8.0) in the carbonate strata within two wings of an anticline are selected as examples. A detailed geological engineering investigation, rock mass testing, and rock mass quality assessment are performed. The results of the research show that landslides near the core of the anticline may be closely related to the geological strength index, while landslides far away from the core of the anticline are more likely to be controlled by the preexisting weak zone within the slope. In addition, the combination of structural planes and weak zones further determines the initiation mode. A comparison of earthquake-induced landslides with gravity-induced landslides reveals that strong earthquakes accelerate the process of geomorphic erosion by reducing the geological strength index (GSI) values of landslides. Finally, this study proposes that the damage to rock masses in complex tectonic environments is of great importance to assess the location, initiation mechanism, and mode of potential large-scale landslides caused by strong earthquakes.