Reactivation mechanism of old landslide triggered by coupling of fault creep and water infiltration: a case study from the east Tibetan Plateau

The platforms of old landslides triggered by historical earthquakes have often been important residential and agricultural places in active tectonic regions. In recent years, many old landslides have been reactivated due to various causes. Previous studies have shown that the hydrodynamic effect is an important triggering factor for landslide reactivation. However, as an old landslide has undergone a long consolidation period, the permeability of deposits is generally very low, and surface water can hardly infiltrate into deep zones of landslide deposits. Through field investigation, it is found that many old landslides are reactivated due to the coupled action of water infiltration and cracks in the east Tibetan Plateau. The cracks are controlled by fault creep in the initial formation process. In this paper, taking the Chashushan old landslide in the upstream of Jinsha River as a case study, field investigation, experimental study, numerical simulation, and PS-InSAR technique are performed to investigate the reactivation mechanism of the old landslide. The influences of cracks, rainfall, and canal leakage on old landslide reactivation are discussed. The cracks controlled by fault creep provide channels or media for the rapid infiltration of surface water, which is the triggering factor of landslide reactivation. The results in this paper can provide an important reference for research on the reactivation mechanism and risk control of old landslides in the east Tibetan Plateau and even in active tectonic areas around the world.