Major active faults and recent coseismic surface rupture characteristics of the Horba-Tsam Tso rift in southern Tibet

The Horba-Tsam Tso rift is one of the major rift systems in southern Tibet, with a general strike of N20°E and a total length of about 200 km, containing 20 parallel or oblique secondary fault zones and graben-half graben systems. The active faults and frequent earthquakes of the rift valley since the Neogene play an important role in understanding the uplift process and deformation mechanism of the Tibetan Plateau in the Late Cenozoic. In this paper, the development characteristics and spatial distribution of major normal faults and surface fractures in rifts were studied by means of remote sensing image interpretation, and then discussed their formation causes and deformation mechanisms. The main features of this region are the concentrated distribution of nearly north-south normal faults, which show the characteristics of high-density development of active faults in the Holocene. The development degree of faults in the rift valley shows a decreasing trend from east to west, and the number of faults and surface fractures decreases from north to south. The latest surface rupture in the rift valley developed at the eastern foot of the Lunggar Mountain, and the Holocene landform along the dislocation is closely related to the spatial distribution of the faults and the historical earthquakes. Based on the analysis of historical data, it is found that there is an earthquake gap in the northern section of the rift, which may cause strong earthquakes in the future.