Geomorphological and geological characteristics reflecting the Holocene activity of the Dalangsonggou fault, eastern Tibetan Plateau

The Dalangsonggou (DLSG) fault is an internal fault within the Sichuan–Yunnan block, located on the southern side of the Garzê–Yushu fault. On the basis of geological and geomorphological surveys, we estimated the Holocene activity of the DLSG fault. We excavated two trenches and identified two paleoseismic events by analyzing the stratigraphic deformation and radiocarbon dating results of the faulted strata. The occurrence times of these events were determined to be 8420–8346 and 4612–5045 cal BP. The time elapsed since the latest earthquake, which exceeds 4500 years, indicates strong risk of occurrence of a large earthquake on the DLSG fault. Furthermore, the recurrence interval of large earthquakes on the DLSG fault is much longer than that of earthquakes on the Garzê–Yushu fault. Thus, the DLSG fault conducts only regulating effects in terms of regional tectonic deformation compared to the dominant impact of the Garzê–Yushu fault, which is a boundary fault of the block.