River terraces are primarily formed by the erosional action of river incision under the influence of vertical movements of the crust or changes in regional erosion base levels, resulting in layered landforms. As products of the long-term evolution of river systems, the formation, development, and evolution of terraces have always been a focal point in Quaternary research. Climate change and tectonic movements play crucial roles in the evolution of river terraces, providing important evidence for studying a region’s paleoclimate and tectonic history, while also indicating the geomorphic evolution of rivers. The ages and elevations of river terraces serve as a crucial window for understanding climate fluctuations and the intensity of tectonic uplift in a specific area. This role cannot be replaced by any other method. Therefore, accurately defining the incision and deposition ages of river terraces is essential for quantitatively reconstructing the development and evolution of rivers, making it a key data point in current research on surface processes and geomorphic evolution.

The study area is located at the southeastern margin of the Qinghai-Xizang Plateau, positioned in the main area of the Jinsha River suture zone at the southwestern edge of the Songpan-Ganzi orogenic belt and the eastern part of the Sanjiang orogenic belt. The regional tectonic setting is complex. Since the late Quaternary, the tectonic uplift at the southeastern margin of the Qinghai-Xizang Plateau has intensified, with accelerated plateau uplift in the post-Pleistocene era accompanied by significant tectonic activity. This has led to substantial incision of rivers in the region, forming multiple layers of overlapping terrace landforms on both sides of the river valleys. These landforms are crucial for quantitatively understanding the plateau uplift process and climate change.

The Jinsha River is one of the main large rivers in the western parts of Sichuan. The river terraces developed in the Jinsha River valley serve as an important evidence for studying the deformation of the plateau crust and climate change. However, there are few Holocene terraces developed in the valley, and their resolution is low. Therefore, current research on the Jinsha River terraces mainly focuses on the orbital time scale(from tens of thousands to millions of years)of climate change and the impact of tectonic uplift, with limited studies on the role of short-term time scales(thousands or hundreds of years)in climate change and tectonic uplift, and a lack of constraints on river incision rates since the late Quaternary. The formation and evolution of river landforms since the Holocene are currently the most important means of studying recent tectonic activities and predicting future climate fluctuations. Therefore, the Baqu River, as a major tributary of the Jinsha River, with the terraces preserved in its valley, has become crucial research material reflecting the climate change and tectonic uplift in the Jinsha River Basin since the Holocene.

The Batang segment of the Baqu River is situated in the midstream valley of the Jinsha River, characterized by a wide valley floor and gentle riverbed slope. Through drilling and shallow seismic exploration to investigate the valley stratigraphy, it was found that the valley sediments can be divided into four layers from top to bottom. The bottom layer consists of Permian strata mainly composed of weathered crystalline limestone, with a core exposure of 22m without reaching the bottom. The third layer is composed of Middle Pleistocene sediments, 68m thick, mainly consisting of large boulders, small gravel, and calcareous clay. The second layer comprises Late Pleistocene sediments, 30m thick, primarily consisting of large gravel and clay. The first layer is mainly composed of fine-grained clay with a small amount of sand and gravel blocks, 10m thick. This indicates that the valley has experienced at least two significant aggradation stages. Using Electron Spin Resonance dating methods, it was determined that these two aggradation events began at approximately 318ka and 143ka, corresponding to Marine Isotope Stages(MIS)10-9 and MIS 6-5, respectively, during glacial melting phases.

Four levels of river terraces are developed within the valley, with T1-T3 being aggradational terraces and T4 being a bedrock terrace. T1 has a terrace height of 5~10m, T2 ranges from 15~25m, T3 ranges from 30~40m, and T4 has a terrace height of 120m. The terrace topography is generally parallel to the longitudinal profile of the modern riverbed, with only minor fluctuations, indicating a predominant overall uplift in the area after terrace formation, with consistent tectonic uplift rates and insignificant differential uplift. Combining Optically Stimulated Luminescence dating, Carbon-14 dating, and cosmogenic nuclide dating methods, it was determined that T1-T3 formed between 1~5ka, specifically 1~2ka, (3.1±0.2)ka, and(4.5±0.4)ka, respectively, while T4 formed around 62ka. A comparison of terrace ages with paleoclimate data revealed that the incision times of T1-T3 corresponded to transitions from cold to warm climates. Calculating the incision rates of terraces based on their ages and terrace heights and comparing them with incision rates in different sections of the Jinsha River, it was found that from the Late Pleistocene to the mid-Holocene, the Baqu River incision rate was(1.5±0.3)mm/a, consistent with other sections of the Jinsha River in western Sichuan. From the mid-Holocene to the present, the incision rate increased to(5.5±0.8)mm/a, approximately four times the incision rate during the Late Pleistocene. While there is a lack of quantified results on river incision rates since the Holocene in surrounding rivers, the enhanced incision rate aligns with the current vertical crustal deformation rates, indicating that intensified crustal uplift since the Holocene may be the primary driver of rapid river incision.

In the Cenozoic, under the influence of the collision of the India-Eurasia plate and the northward pushing after that, deformation occurred in the interior of the continent, and the crustal deformation is mainly absorbed by the thickening of the crust and the strike-slip movement of the fault. The GPS velocity field shows that the area north of Tianshan absorbs the shortening with a rate of~2mm/a. How the shortening with these rates is absorbed is a topic worthy of study. The West Junggar, located to the north of the Tianshan Mountains and developed with the inclined parallel strike-slip fault system is an important area of crustal shortening. The inclined parallel strike-slip fault system includes the east Tacheng Fault, Tuoli Fault and Daerbute Fault. Hence, the structural deformation of the Tuoli Fault in the late Quaternary is significant for understanding the structural deformation and crustal shortening absorption mode in the north of Tianshan Mountains.

In this study, two branches were found extending along the Tuoli Fault in the direction of NE based on remote sensing image interpretation. Field investigation to the two branch faults shows that many marker landforms were dislocated in the study area, including gullies and terrace riser. The two faults cross through the terraces developed in the Kapusheke River and the Tiesibahan River in this area, forming offset terrace riser. Because the terrace riser is in the retained bank of the river, the upper-layer terrace model is used to calculate the fault’s slip rate. The gullies are mainly distributed on the T3 terrace of the Kapushek River on the west branch fault. The horizontal dislocation of these gullies ranges from 10m to 37.5m, and the largest horizontal dislocation is located in the No. 8 gully, which is (37.5-4.1/+2.7)m. Since the actual value of the fault movement rate must be greater than the rate obtained by the sub-gully offset, we choose the maximum offset of the gully on the landform surface in calculating the slip rate. We used OSL(Optical Stimulated Luminescence)to date the age of the landform and used UAV(Unmanned Aerial Vehicle)photogrammetry technology to extract high-precision DEM of the study area. Then, we calculate the movement rate of the Tuoli Fault since the late Quaternary from the dislocations and the age of landmark landforms such as gullies and terraces. The results show that the Tuoli Fault comprises two branch faults in the east and the west, both of which are left-lateral horizontal strike-slip. The east branch fault produced a (89±31)m and (39±13)m horizontal dislocation on the T3 and T2 terrace of the Kapusheke River, respectively. Combined with the (52.9±5.1)ka of the T3 terrace age and (23.4±1.5)ka of the T2 terrace age, the horizontal slip-rate of (1.7±0.8)mm/a is calculated for the eastern branch fault. The western branch fault produced a horizontal dislocation of (34.0±6.8)m on the T2 terrace of the Tiesibahan River and 37.5⁽-4.1/+4.1)m of the gully on the T3 terrace of the Kapusheke River. Combined with (18.8±1.3)ka of the T2 terrace age, we obtained a sinistral slip rate of 1.8(+0.5/-1.3)mm/a for the western branch fault. The sinistral slip rate of two branch faults of the Tuoli Fault is similar to the sinistral slip rate of the east Tacheng Fault in the previous research results. This study result indicates that these parallel left-lateral strike-slip faults in the West Junggar area conform to the characteristics of the bookshelf faults structural model, and most of the compression shortening in the West Junggar area is absorbed by the parallel strike-slip movement of the fault system. So this fault system has played an important role in controlling the NS shortening of the crust in this region.

In response to the ongoing far-field effects of the India-Eurasia collision, the Tianshan Mountains experience rapid NS convergence, and most of the present N-S shortening is absorbed along the southern and northern edges. The resultant frequent large earthquakes have inspired many scientists to explore the neotectonic activity of the Tianshan Mountains. The eastern Qiulitage anticlinal belt located in the Kuqa depression, on the southern piedmont of the Tianshan Mountains, is a typical blind fault-related fold. The Kuqa M7$\frac{1}{4}$ earthquake in 1949 as typical folding earthquake once occurred on the northern limb of the eastern segment of the Qiulitage anticline, and the epicenter was near the Village of Kang which is sparsely populated. This earthquake is a typical folding earthquake whose dominant fault did not thrust onto the earth surface. Although many tectonic-induced scarps and deformed Quaternary strata have been reported, there are still no direct evidences for the surface ruptures and corresponding causative faults of this earthquake at present. And systematic understanding of paleoseismic events in Qiulitage area is also limited by the lack of relevant chronological researches.
We conducted 1︰50 000 scale geological mapping in the Qiulitage anticline area. The local surface geological characteristics are investigated based on interpretation of Google Earth image and confirmation in the field. Together with interpreted subsurface structure by petroleum seismic reflection profiles, the relationship between the active faults thrust on the surface, low-dip-angle decollement faults in deep, and fold deformation are subsequently qualitatively analyzed. In this study, the active faults which have thrust to the surface and generated fault scarps are focused on.
Totally five trenches were chosen and cleared up, two of which are located on the southern limb of the eastern Qiulitage anticline and the others are on its northern limb. And all excavation sites are situated on fresh fault scarps. We carefully interpreted different characteristics of tectonic deformation and sedimentary process which are correlated with paleo-seismic events from trenches. According to the OSL(Optically Stimulated Luminescence)and ¹⁴C dating results, a reliable chronological framework for the deformed stratigraphic sequences was established. Based on the classic successive limiting method, six paleoseismic events were finally constrained.
Some of these interpreted paleo-seismic events produced surface ruptures on the breakthrough faults simultaneously on the southern and northern limbs of the Qiulitage anticline, and others only caused local surface ruptures on its northern limb. In a broad sense, the surface ruptures caused by these paleoseismic events have similar characteristics to those which are popular among the low-dip-angle thrust faults on the southern piedmont of the Tianshan Mountains. And the two common phenomena are that multiple ruptures may occur a single fault and multiple faults may rupture simultaneously. We speculate that only when the displacement of master faults at depth is big enough, multiple shallow secondary faults can be triggered at the same time. Conversely, only one fault is active at one time. In other words, constrained by the length and displacement of dominant faults, not all paloseismic events can cause surface ruptures on the northern and southern limbs of the Qiulitage anticline at the same time.
The revealed paleoearthquakes may have a clustering feature since ~7.4ka. They behaved as follows: 1)Three events occurred during 5.7~7.4ka. 2)one event occurred during 3.3~4.7ka. 3)the latest cluster of events may be marked by the 1949 M_W7$\frac{1}{4}$ Kuqa earthquake. Thus, the earthquake sequences have a recurrence period of about 2.5~4ka.
Significantly, the incompleteness of the paloseismic events recorded in trenches and the quality and intrinsic error of the OSL dating samples can mislead judgments. It is inevitable that the time of paloseismic event cannot be constrained strictly. In our research area, because of the lack of seismic events between event E5 and event E6(7.25~19.1ka), there is a gap in seismic event records for up to~11.85ka. However, our result offers a relatively systemic event sequence to fill the gap in studies on paleoseismicity in this area. Whether there will be a strong shock after the 1949 M_W7$\frac{1}{4}$ Kuqa earthquake remains to be further studied in detail.

The Bolokonu-Aqikekuduke fault zone(Bo-A Fault)is the plate convergence boundary between the middle and the northern Tianshan. Bo-A Fault is an inherited right-lateral strike-slip active fault and obliquely cuts the Tianshan Mountains to the northwest. Accurately constrained fault activity and slip rate is crucial for understanding the tectonic deformation mechanism, strain rate distribution and regional seismic hazard. Based on the interpretation of satellite remote sensing images and topographic surveys, this paper divides the alluvial fans in the southeast of Jinghe River into four phases, Fan1, Fan2, Fan3 and Fan4 by geomorphological elevation, water density, depth of cut, etc. This paper interprets gullies and terrace scarps by high-resolution LiDAR topographic data. Right-laterally offset gullies, fault scarps and terrace scarps are distributed in Fan1, Fan2b and Fan3. We have identified a total of 30 right-laterally offset gullies and terrace scarps. Minimum right-lateral displacement is about 6m and the maximum right-lateral displacements are(414±10)m, (91±5)m and(39±1)m on Fan2b, Fan3a and Fan3b. The landform scarp dividing Fan2b and Fan3a is offset right-laterally by (212±11)m. Combining the work done by the predecessors in the northern foothills of the Tianshan Mountains with Guliya ice core climate curve, this paper concludes that the undercut age of alluvial fan are 56~64ka, 35~41ka, 10~14ka in the Tianshan Mountains. The slip rate of Bo-A Fault since the formation of the Fan2b, Fan3a and Fan3b of the alluvial-proluvial fan is 3.3~3.7mm/a, 2.2~2.6mm/a and 2.7~3.9mm/a. The right-lateral strike-slip rate since the late Pleistocene is obtained to be 3.1±0.3mm/a based on high-resolution LiDAR topographic data and Monte Carlo analysis.

As the most active intracontinental orogenic belt in the world, the Tianshan orogenic belt has complex and diverse internal structural deformation patterns, and among them, the particularly striking is the linear straight U-type valley landscapes which cut inside the mountains by multiple NW-SE and ENE-WSW strike-slip faults. Many of the modern strong earthquakes in Tianshan orogenic belt are closely related to these strike-slip faults. Therefore, it is important to elaborate the activity characteristics of these faults to understand the deformation process inside the Tianshan Mountains belt. This paper focuses on one of the NW-SE right-lateral strike-slip fault (the Kaiduhe Fault), which lies inside the southeastern Tianshan. Typical offset landforms and scarp lineaments on the western segment of the Kaiduhe Fault can be used to study the activity characteristics and strike-slip rate. In particular, the fault cuts through the late Quaternary alluvial fans and a series of river gullies were right-laterally faulted, producing dextral offsets ranging from 3 to 248m. A digital elevation model (DEM)with resolution of 0.25m was established by using multi-angle photogrammetry technique to stripe about 12km linear tectonic landforms along the Kaiduhe Fault. Geological and geomorphic mapping in DEM with 22 high-resolution dextral offset measurements reveals that the dextral offsets can be divide into four groups of 3.5m, 7.0m, 11.8m and 14.5m. It is presumed from the approximately uniformly-spaced offsets that the coseismic offset was 3~4m. In addition, the exposure age of an older alluvial fan surface was about 235.7ka by in situ ¹⁰Be terrestrial cosmogenic nuclide method. Combining the exposure ages and the maximum dextral offset of 248m, we found that the strike-slip rate of the Kaiduhe Fault is about 1mm/a. It is found by this study that the Kaiduhe Fault plays an important role in regulating SN compression deformation within Tianshan Mountains, and it should also be the main stress-strain accumulation area which has the risk of occurrence of strong earthquake.

The Tian Shan Mountains is an active orogen in the continent. Previous studies on its tectonic deformation focus on the expanding fronts to basins on either side, while little work has been done on its interiors. This work studied the north-edge fault of the Yanqi Basin on the southeastern flank of Tian Shan. Typical offset landforms, and lineaments of scarps on the eastern segment of this fault were used to constrain the vertical displacement and shortening rates. Geological and geomorphic mapping in conjunction with high-resolution GPS differential measurement reveals that the vertical offsets can be divided into three groups of 1.9m, 2.4m and 3.0m, and the coseismic vertical offset was estimated as 0.5~0.6m. In situ ¹⁰Be terrestrial cosmogenic nuclide dating of three big boulders capping the regional geomorphic surface that preserved 3.0m vertical offset suggests that the surfaces were exposed at~5ka. Meanwhile, the lacustrine sediments from Bosten Lake within the Yanqi Basin suggest climate change during cooling-warming transitions was also at~5ka. The climate, therefore, controlled creation and abandonment of geomorphic surfaces in southern piedmont of Tian Shan. Combining the exposure ages and vertical offsets, we inferred that the east section of the north-edge fault in the Yanqi Basin has a dip slip rate 0.6~0.7mm/a,~0.5mm/a of vertical slip and~0.4mm/a of shortening since 5ka. Based on calculation of earthquake moment, we estimated that this fault is capable of generating M7.5 earthquakes in the future. This study provides new data for further understanding tectonic deformation of Tian Shan and is useful in seismic hazard assessment of this area.

With the development of the techniques acquiring high-resolution digital terrain data,the digital terrain data acquisition technology has been widespread applied to the geoscience research.A revolutionary,low-cost and simply operative SfM (Structure from Motion) technology will make obtain high-resolution DEM data more convenient for researches on active tectonics.This paper summarizes the basic principles and workflows of SfM technology and processes and selects the Hongshuiba River area along the northern margin of the Qilian Shan to conduct data collection.We use a series of digital pictures to produce a texture with geographic information,in which data resolution is 6.73cm/pix and average density of point cloud is 220.667 point/m².The coverage area is 0.286km².Further,in order to compare the accuracy between SfM data and differential GPS (DGPS) data in details,SfM data are vertically shifted and tilt-corrected.After optimizing corrections of SfM data,the absolute value of elevation difference between two data substantially concentrates around 20cm,roughly equivalent to 2-folds of data error only after the elevation error correction.Elevation difference between two data is 10~15cm in 90% confidence interval.The maximum error is about 30cm,but accounts for less than 10%.Along the direction of fault trace,the height of fault scarp extracted from SfM data shows that vertical displacement of the latest tectonic activity in the east bank of Hongshuiba River is about 1m,and some minimum scarps height may be 0.3m.The results show SfM technology with high vertical accuracy can be able to replace differential GPS in high-precision topographic survey.After correcting of SfM data,elevation difference still exists,which may be associated with methods of generating DEM and SfM data accuracy,which in turn is controlled by the number and distribution of Ground Control Points (GCPs),photos density and camera shooting height,but also related to surface features,Fodongmiao-Hongyazi Fault

Based on geological and geomorphologic characteristics of the surface faults acquired by field investigations and subsurface structure from petroleum seismic profiles, this paper analyzes the distribution, activity and formation mechanism of the surface faults in the east segment of Qiulitage anticline belt which lies east of the Yanshuigou River and consists of two sub-anticlines:Kuchetawu anticline and east Qiulitage anticline. The fault lying in the core of Kuchetawu anticline is an extension branch of the detachment fault developed in Paleogene salt layer, and evidence shows it is a late Pleistocene fault. The faults developed in the fold hinge in front of the Kuchetawu anticline in a parallel group and having a discontinuous distribution are fold-accommodation faults controlled by local compressive stress. However, trenching confirms that these fold-accommodation faults have been active since the late Holocene and have recorded part of paleoearthquakes in the active folding zone. The fault developed in the south limb near the core of eastern Qiulitage anticline is a low-angle thrust fault, likely a branch of the upper ramp which controls the development of the eastern Qiulitage anticline. The faults lying in the south limb of eastern Qiulitage anticline are shear-thrust faults, which are developed in the steeply dipping frontal limb of the fault-propagation folds, and also characterized by group occurrence and discontinuous distribution. Several fault outcrops are discovered near Gekuluke, in which the Holocene diluvial fans are dislocated by these faults, and trench shows they have recorded several paleoearthquakes. The surface anticlines of rapid growth and associated accommodation faults are the manifestations of the deep faults that experienced complex folding deformation and propagated upward to the near surface, serving as an indicator of faulting at depth. The fold-accommodation faults are merely local deformation during the folding process, which are indirectly related with the deep faults that control the growth of folds. The displacement and slip rate of these surface faults cannot match the kinematics parameters of the deeper fault, which controls the development of the active folding. However, these active fold-accommodation faults can partly record paleoearthquakes taking place in the active folding zone.

Fold-accommodation faults, secondary faults subordinated to the principal fold, are of much significance to accommodate strain variation in different parts of the rock during the evolution of folding. They are generally found in groups. And each of them has limited displacement and does not connect with the main detachment. After the geological survey in the East Qiulitage anticline zone, we find that the secondary faults accompanying fold scarps in this area are out-of-syncline thrusts and also give an instance of secondary faults occurring later than the folding. The fact that the secondary faults in fold scarps force the hanging wall to move upward relative to the footwall not only makes the terrace tilting and increases the slope of fold scarps, but also affects the authenticity in calculating regional shortening increment. The theoretical results show that if we do not consider the increased fold scarps height influenced by the secondary faults, the shortening increment is 51.42m. Otherwise, the value will be 45.23m and the difference between them is 6.19m. Because the deviation is 13.7% of the total shortening increment, the contributions of fold-accommodation faults to the calculation should not be ignored. The fold scarps in the northern and southern flanks of the East Qiultiage anticline depend on same bedrock type and formation mechanism. But three levels of fold scarps were found in the cross section of less than 300 meters in horizontal distance. This fact indicates that the active kink band of northern part is more closed because of higher compressive stress and faster lifting, which produce a large number of secondary faults in the fold scarps only in the northern flank. Therefore, the study of secondary faults is of significance in understanding of regional tectonic evolution and interaction between folds and faults. But there still exist many problems: 1)Limited by the observing scope, discontinuous distribution of secondary faults and variations of displacement along fault, we may underestimate the influence of secondary faults and the theoretical result should be the minimum. 2)What is the quantitative relationship among the increased height of fold scarps, the transfer slip and the dip of secondary faults?3)If secondary faults only grow in active kink band, how will they affect fold scarp?More examples of fold-accommodation faults are needed for further research.

How strain is distributed and partitioned on individual faults and folds on the margins of intermontane basins remains poorly understood. The Haermodun(Ha) anticline, located along the northern margin of the Yanqi Basin on the southeastern flank of the Tian Shan, preserves flights of passively deformed alluvial terraces. These terraces cross the active anticline and can be used to constrain local crustal shortening and uplift rates. Geologic and geomorphic mapping, in conjunction with high-resolution dGPS topographic surveys, reveal that the terrace surfaces are perpendicular to the fold's strike, and display increased rotation with age, implying that the anticline has grown by progressive limb rotation. We combine ¹⁰Be terrestrial cosmogenic nuclide(TCN) depth profile dating and optically stimulated luminescence(OSL) dating to develop a new chronology for the terraces along the Huangshui He since 550ka. Our in situ ¹⁰Be dating of fluvial gravels capping strath terraces suggests a relationship between the formation and abandonment of the terraces and glacial climate cycles since the middle-late Pleistocene. These data indicate that the formation of the four terraces occurred at ~550, ~430, ~350, and~60ka. We suggest that episodes of aggradation were facilitated by high sediment supply during glacial periods, followed by subsequent incision that led to abandonment of these terraces during deglaciation. Combining uplift and shortening distance with ages, we found the vertical uplift gradually decreased from 0.43 to 0.11mm/a, whereas the shortening rate was constant at ~0.3mm/a since the anticline began to grow. The shortening rates of the Ha anticline from geomorphology agree with current GPS measurements, and highlight the importance of determining slip rates for individual faults in order to resolve patterns of strain distribution across intermontane belts.

The Yanqi Basin is an important depression area of the Tianshan Mountains near the northeast margin of the Tarim Basin. The Hejing thrust-fold belt,a renascent thrust-fold belt with intense tectonic activity,is located on the north margin of the Yanqi Basin. We calculated the shortening and uplifting of the Hejing thrust-fold belt since Quaternary to analyze the tectonic activities of this region,then,made a preliminary estimation of the shortening and uplifting rate in the Yanqi Basin and compared the result with other areas to demonstrate the role of the Yanqi Basin in the tectonic deformation of Tianshan in late Cenozoic. With few seismic data but abundant attitude of stratum and fault,we restituted the geometry of the fold to calculate the shortening and uplifting of the fold and slip of the fault on the Hejing thrust-fold belt which has a simple and intact structural pattern,and obtained the shortening amount of 1.79km,0.88km and 26m,respectively since early Pleistocene(1.8Ma),middle Pleistocene(780ka) and late Pleistocene(80ka). The respective shortening rate is estimated as 0.99mm/yr,1.13mm/yr and 0.33mm/yr. The intensity of tectonic activity is not constant on the Hejing thrust-fold belt since the beginning of deformation. Compared with the result of crustal deformation,Yanqi Basin,as a major depression on southeastern Tianshan Mountains,absorbs most of crustal shortening of this area(86°～88°E)and exhibits strong deformation of the newborn thrust-fold belt on the northern margin of the basin.

Reverse fault-anticline is an important structure form in Tianshan area.The study on the syntagmatic relation and formation mechanism between active faults and anticline in reverse fault-anticline will help understand the structure system under extrusion stress.Haermodun anticline is a neogenic thrust-anticline in the north margin of the Yanqi Basin.It is the product of reverse fault extending to the inside of the basin.The main reverse fault of the anticline thrusts inwards the basin,with a dip angle of 30°.The present-day tectonic movement is intense along the fault.By interpreting aerial photos of the Haermodun anticline,measuring the scarp profiles and excavating trenches across the fault,we find that three different types of faults have been developed on the different levels of river terraces crossing the anticline,namely,the main reverse fault in front of the anticline forelimb(southern limb),the back thrust fault on the forelimb and the bending-moment normal fault on the top of the anticline,respectively.The main reverse fault has produced three scarps on T₁ terrace,with heights of 4m,0.8m and 1.8m,respectively,and a high scarp on T₂ terrace with a height of 16m.The back thrust fault has produced 2-4 reverse scarps,with the height up to 4m The bending-moment normal fault has produced about 10 scarps on all levels of terraces except T₁ on the top of anticline,and the height of a single scarp can reach 14.5m.The older the terrace,the higher the total height of scarp.Analysis on the geneses of the three faults reveals that the main reverse fault controls the growth of the Haermodun anticline.The back thrust faults help the main reverse fault release the compressive stress,and the part between the main reverse fault and the back thrust fault is extruded.The bending-moment normal fault is produced in the top of anticline.The top of the anticline is a tensional stress area.Back thrust fault and main reverse fault are synchronous.But the scale of back thrust fault is several times smaller than the main reverse fault.Bending-moment normal faults are synchronous with fold deformation.Accompanying the beginning of fold deformation,the bending-moment normal faults began to expand and grow gradually downwards from the top of anticline,synchronously.

The Hejing reverse fault-fold zone locates on the northern margin of the Yanqi Basin which lies in the south Tianshan Mts.The zone has been growing since early-Quaternary till now.The Xiaermudeng and Haermodun anticlines in the western of Hejing reverse fault-fold are discussed in this paper.Based on the analysis of satellite images and DEM(digital elevation model)data with the spatial resolution of 25m as well as field observation,our results suggest that the Xiaermudeng and Haermodun anticlines have uplifted and propagated laterally during the late Quaternary.Stream-flow direction,topographic sections,decrease of elevation of wind gap and hypsometric analysis indicate that Xiaermudeng anticline uplifted preceding the Haermodun anticline.We also believe that the Xiaermudeng anticline grows laterally from middle to side and Haermodun anticline grows laterlally from west to east.The flows crossing the anticline have diverted eastward under the tectonic movement during the Quaternary,producing a series of wind gaps with straths lowering from west to east.In the Xiaermudeng anticline area,from middle to the side,the drainage density(Dd)is decreased(5.37km^-1 to 2.65km^-1 and 3.07km^-1),and the slope of catchment is increased.The anticline of Haermodun shows a main deformation pattern of uplift and lateral propagation from west to east.The drainage density is decreased(3.87km^-1 to 2.37km^-1),the catchment has steep slope(4° to 6°),the hypsometric curve is from concave-convex to concave-down and the hypsometric integral (∫) is increased(0.45 to 0.76),Moreover,11 topographical cross-sections transecting the anticlines also reveal the lateral propagation from west to east of the Hejing reverse fault-fold zone.

Using the aerial remote sensing photos and Google earth satellite images,we find seven terraces at the both sides along the Kuytun River in Dushanzi active anticline area,northern piedmont of Tianshan.Based on the field investigation,we find that all these terraces are pedestal terraces.The rock of pedestal is Pliocene mud rock,and on the top of each terrace pedestal are the stratums of sandy gravel or sandy clay with 2.5～15m in thickness.We collected samples from deposits of all terraces for OSL(optically stimulated luminescence)geological dating using the SMAR(single-multiple-aliquot-regeneration)method on fine grains.We also performed dating using the ¹⁴ C method to the samples from the deposit of terrace T₁ of the Kuytun River.The results show that the ages of all these deposits are the later phase of the Late Pleistocene.The accumulation time of the upper stratum for T₁,T₂,T₃,T₅,T₆and T₇ terraces is about 1.7ka,14.98ka,20.7～27.3ka,29.3～39.2ka,47～56ka and 103～118ka,respectively.Combining with late Quaternary climate change,we believe that the formation age for T₁～T₇ terraces of Kuytun River are 1.7ka,14ka,20ka,25ka,30ka,50ka and 100ka BP.Paleoearthquake data reveal that eight paleoearthquake events occurred on the Dushanzi-Anjihai reverse fault since about 25ka BP,respectively at 2ka,3.4ka,4.3ka,5.8ka,7.5ka,12.8ka,18ka and 24ka BP.Comparing the ages of paleoearthquakes and terraces,we find that the ages of the latest,the sixth,the seventh and the eighth paleoearthquake are roughly corresponding to the formation times of T₁,T₂,T₃and T₄ terraces,respectively.The other four paleoearthquake events occurred during the period after the formation of T₂and before the formation of T₁.In this time,no terraces developed along the Kuytun River,but the Kuytun River incised rapidly for 40m.We believe that the paleoearthquake events resulted in the fast uplift of Dushanzi active anticline on the hanging wall of Dushanzi-Anjihai Fault and the increase of riverbed slope and river incision ability,which led to the formation of river terraces or deep canyons.The terrace sequence in active anticline region may reflect the paleoearthquake sequence associated with fault or blind fault.