The Kuqa depression is located in the middle segment of the southern Tianshan Mountains. There are four E-W extending rows of reverse fault and anticline zones in the depression. From the south Tianshan Mountains towards the Tarim basin, they are the mountain piedmont, the Kasangtuokai, the Qiulitag and the Yaken reverse fault and fold zones. After a month field working, we find the crustal shortening of the Kuqa depression in late Quaternary is almost caused by the Kasangtuokai, the Qiulitag and the Yaken reverse fault and fold zones. The reverse fault and anticline zones in the Kuqa depression are very different in tectonic feature. We accurately surveyed these tectonics with total station and differential GPS in order to get a new cognition of the deformation characteristic and the slip rate. Based on the deformation characteristics of conceptual fault-propagation fold and field investigation, we think the deformation of the fault-propagation fold in the Kuqa depression is caused by faulting rather than folding. The crustal shortening rate caused by the fault is approximately near to the actual rate. So we only surveyed the deformation near the fault. The Kasangtuokai anticline is a fault-propagation fold. From late Quaternary, the deformation of Kasangtuokai anticline is mainly caused by total-uplift of the hanging wall. The deformation rate is about 1.0～2.0mm/a. The deformation feature of the Dongqiulitag anticline is similar to that of the Kasangtuokai, while the crustal shortening rate is little more than that of Kasangtuokai, about 2.5mm/a. The Qiulitag anticline is a very complicated tectonic. It is a fault-bend fold. There are two reverse faults on the core and the north limb of the Qiulitag anticline. Its tectonic deformation includes two parts: the fold rise and the uplift of the hanging wall of the fault. By surveying and dating, we get the crustal shortening rate of the Qiulitag anticline limb of about 1.06～2.0mm/a. Considering the shortening of the core fault and southern limb, the total rate is possibly more than 3.0mm/a. The Yaken anticline is a blind thrust fault-anticline fold. Its shortening rate is 1.5～2.0mm/a. So the total crustal shortening rate of the Kuqa depression is more than 5.0～7.0mm/a from late Quaternary.

The distribution, tectonic style and new displacement and other features of the main active tectonics in Kuqa depression in the front of southern Tianshan were introduced in this paper. This depression is an “eye-shaped” tectonics in plane. It is composed of two fold zones in the south and north respectively. The northern one close to the main southern Tianshan Range is a southward thrusting fault-folding system. The most recent active fold in this system is the Kasangtuokai fold belt. The southern one close to the Tarim Basin is a northward thrust fault-fold system. The recent active folds in this system are the Qiulitage fault-fold belt and other young folds in its south, such as the Yaken fold. These two folding systems embrace the Baicheng Basin which likes an eyeball in the eyelids. The Kasangtuokai Fault with a length of 60km in the north and the Qiulitag Fault with the length over 200km in the south are the most important active faults in Kuqa depression. The younger and smaller folds in the south of Qiulitag anticline belt indicate the southward propagation of the thrust fault in Kuqa depression. The petroleum seismic profiles show that the folding and faulting processes are controlled by the detachment fault between the sediment cover and the basement of the basin. The depth of the detachment fault is around 10km and possibly defines the main seismogenic zone in the depression area.

The M_S 6.8 Bachu-Jiashi earthquake of Feb.24, 2003 occurred in the western Tarim Basin and is possibly the continuation of the Jiashi strong earthquake swarms in 1997-1998. However, its focal mechanism and rupture process are different from that of the Jiashi strong earthquake swarms, according to our preliminary study on its seismic tectonics with geomorphologic information from satellite images, the deep structures from the petroleum seismic exploration, the macro damage and isoseismic features from field investigation, the relocation of the epicenters of the aftershocks, and the regional seismic tectonics from both deep and surface tectonics. The occurrence of the M_S 6.8 Bachu-Jiashi earthquake is closely related with the revealed reverse fault on the Maigaiti slope belt between the Bachu uplift and Kashi depression in western Tarim Basin. The sites of the ground fissures found in the field fit with the revealed reverse fault. Isoseismal features are also corresponding to the rupture direction of the fault. These evidences indicate that the M_S 6.8 Bachu-Jiashi earthquake is the result of the southward rupturing from deep to shallow along a north-dipping reverse fault in Tarim Basin. This reverse fault is possibly the result of the propagation of the thrust fault-fold system named Kalpintag thrust belt in the front of Tianshan.