There were several strong earthquakes of M_S≥7.0 occurring in the eastern Tianshan in the history, which is an important part of Tianshan earthquake zone. The Tangbal-Tasdun Fault is a left-lateral strike-slip fault zone of Late Pleistocene in the northwest of Barkol Basin. The study of the characteristics of its late Quaternary activities is one of the important basic work to understand the risk of strong earthquakes in Barkol area. Due to the low level of research in the eastern Tianshan region, there is a lot of controversy over the historical earthquakes. But there is no doubt that this area has the ability of generating earthquakes of magnitude greater than 7.0. Current GPS monitoring data on both sides and inside of Tianshan Mountains shows an about 20mm/a northward movement of the Pamir and Tarim plates, but a 4mm/a crustal movement rate of eastern Tianshan. This indicates that the tectonic activity of the western section of Tianshan Mountains is obviously stronger than that of the eastern section. However, according to the historical earthquake records of eastern Tianshan, there are at least two earthquakes of magnitude 7 or above happening in Barkol region. This indicates that the tectonic activity in the Barcol area is intense and the area has the condition for generating strong earthquakes.
In this paper, the methods of high resolution satellite image interpretation, field observation and analysis, micro-geographic survey and trenching are used. The geometric distribution characteristics of the Tangbal-Tasdun Fault are determined, which reveals the movement and activity of the fault zone. The activity parameters of the fault since late Pleistocene are preliminarily obtained. The results show that the fault is left-handed strike-slip with thrust motion. A surface rupture zone with a length of about 50km is developed in the east of Jijitaizi Village. The fault offset the T2 terrace with a vertical displacement of about 0.9m and a horizontal displacement between 9m and 11m. The vertical displacement of T3 terrace is about 1.6m, and the horizontal displacement is between 13m and 20m. To the west of Hongjingzi Town and Tashbastawu Village, the fault is distributed in a straight line on satellite images. The fault offset the latest geomorphic surface, with the minimum vertical displacement of about 0.1m, the maximum vertical displacement of 2m, and the horizontal displacement of 1.8~4.3m. The horizontal displacement of the fault is larger than the vertical displacement of the same period. The excavation of a trench near Kutaizi village shows that the fault has obvious characteristics of strike-slip movement. According to the phenomena of water spraying and sand emitting along the fault and the relation of cut and cover between the fault and strata, two ancient seismic events are revealed in the trench. The most recent event ruptured the ground surface. According to the empirical formula for magnitude estimation, M=7.13+0.68lgD, it is calculated and inferred that this fault section is qualified for the occurrence of M7.3~7.4 earthquake.