The characteristics of palaeo-earthquake landslides along Yushu faulted zone and their ages

After Yushu Ms7.1 earthquake in 2010, the authors first discovered 13 palaeo-earthquake landslides based on field geological survey. Studies show that the large-size palaeo-earthquake landslides are mainly distributed along with active faults within 5km on both sides accompanied by the surrounding palaeo-earthquake phenomenon, obviously controlled by Yushu active fault. An analysis of the characteristics of landslide surface morphology, scale and formation age as well as the superimposition relationship between ancient landslides and the surrounding strata shows that palaeo-earthquakes are characterized by large quantities, in-situ recurrence and multiperiodic activities. The authors further collected 14C dating samples from the main scarp of several typical palaeo-earthquake landslides, and AMS 14C dating results indicate that they were mainly formed in the middle-late Holocene and focused on five periods, consistent well with periods of paleoseismic events revealed by digging trenches. A comparison with the sizes of all palaeo-earthquake landslides further implies that the two largest paleo-earthquakes along Yushu faulted zone occurred in Mid-late Holocene The study also demonstrates that the relatively uniform age of massive palaeo-earthquake landslides might indicate the formation time of paleoseismic events, which is of important significance for the recovery and intensity study of paleo-seismic events.