In response to the ongoing India-Eurasia collision in the late Cenozoic, the Tianshan orogenic belt was reactivated and experienced rapid uplift. Strong uplifted topography results in that the mountains propagate from the range front toward the foreland basin to form several fan-shaped foreland thrust belts both on its north and south sides. These foreland thrust belts accommodate the most north-south convergence strain and control the regional deformation pattern. However, in contrast to the well-studied foreland thrust belts, the kinematics and deformation rate of the transition area between different foreland thrust belts have not been well-documented. Therefore, it is still unclear how the crustal shortening in the foreland basins changes along the east-west direction. Further, the deformation characteristics and seismic hazard in this region are poorly understood because quantitative information on active deformation is lacking.

The Wensu foreland thrust belt is located in the Kalpin and Kuqa foreland thrust systems' transition areas. In contrast to the Kuqa and Kalpin foreland thrust belts at its east and west sides, the Wensu foreland thrust belt propagated approximately 20km toward the basin and only developed one row of active thrust fault-anticline belts, namely the North Wensu thrust fault-anticline belt. The North Wensu structural belt shows clear evidence of tectonic solid activity because the late Quaternary sediments and river terraces have been faulted. However, this structural belt's kinematics and late Quaternary deformation rate remain poorly constrained. This study quantifies its deformation mode based on field geological mapping across the anticline. Our results indicate that the North Wensu structural belt is a fault-bending fold. Based on interpretations of detailed high-resolution remote sensing images and field investigations, five levels of river terraces can be identified along the Kekeya River valley. By surveying of the displaced terraces with an unmanned drone, the crustal shortening values of ~20.7m、 ~35.3m and ~46.9m are determined for the T3, T4 and T5 terraces, respectively. Our optically stimulated luminescence(OSL)dating yields a depositional age of(9.02±0.55)ka for the T3 terrace, (24.23±1.58)ka for the T4 terrace, and(40.43±3.07)ka for the T5 terrace. Thus, we estimate a crustal shortening of ~1.31mm/a in the late Quaternary(since approximately 40ka), and approximately 2.29mm/a in the Holocene for the North Wensu structural belt. Our results indicate that the deformation rate of the North Wensu structural belt exhibits an obvious increase in the Holocene. This phenomenon indicates that the strong earthquake activity on the North Wensu thrust belt has increased significantly in the Holocene, implying an irregular activity habit of the strong earthquake recurrence cycle on this tectonic belt. The propagation deformation toward the basin of the Wensu foreland thrust belt is very limited. Therefore, we suggest that the foreland thrust belt is a thick-skinned nappe structure and is dominated by high-angle thrust faulting. The tectonic deformation in the Wensu region seems to be characterized by considered vertical growth. Although the deformation rate is small, the uplift amplitude is significant in this region.

Active block boundaries represent areas where significant crustal stress accumulates, leading to concentrated tectonic deformation and frequent seismic activity. These boundaries are crucial for understanding the patterns of strong earthquakes within mainland China. The China Seismic Experimental Site, located in the Sichuan-Yunnan region, is a key area of tectonic deformation caused by the collision and convergence of the Indian and Eurasian plates. This region plays a vital role in transferring tectonic stress between western China and adjacent plates.

This comprehensive study analyzes the integrity, three-dimensional characteristics, hierarchy, and tectonic activity of blocks within the Sichuan-Yunnan region, following established schemes and criteria for defining active block boundaries. After detailed research, the major active fault zones in the region have been divided into three primary active block boundary zones and sixteen secondary boundary zones.

A new reference scheme was developed by considering several factors, including the historical distribution of strong earthquakes, the hierarchical patterns of earthquake frequency and magnitude, spatial variations in present-day deformation as revealed by GNSS data, and deep crustal differences indicated by gravity data and velocity structures. The Jinshajiang-Honghe Fault, Ganzi-Yushu-Xianshuihe-Anninghe-Zemuhe-Xiaojiang Fault, and Longmenshan Fault are identified as the primary active block boundary zones, while faults such as the Lijiang-Xiaojinhe, Nantinghe, and Longriba faults are classified as secondary boundary zones.

Through an integrated analysis of seismic activity, current deformation patterns, fault sizes, deep crustal structures, and paleoseismic data, the study estimates that the primary boundary zones have the potential to generate earthquakes of magnitude 7.5 or greater, while the secondary boundary zones could produce earthquakes of magnitude 6.5 or greater.

The expansion of geophysical exploration, including shallow and deep earth data, has allowed for a transition in the study of active tectonics from surface-focused to depth-focused, from qualitative to quantitative, and from two-dimensional to three-dimensional analysis. By integrating multiple data sources, i.e. regional geology, geophysics, seismicity, and large-scale deformation measurements, this study presents a more refined delineation of active blocks in the Sichuan-Yunnan region.

The new delineation scheme provides a scientific basis for future mechanical simulations of interactions between active blocks in the Sichuan-Yunnan Experimental Site. It also offers a framework for assessing the probability of strong earthquakes and evaluating seismic hazards. The purpose of this study is to re-analyze and refine the delineation of active block boundaries using high-resolution, coordinated data while building on previous research.

In summary, the Sichuan-Yunnan region’s primary fault zones are divided into three primary and sixteen secondary active block boundary zones. The study concludes that primary boundary zones are capable of generating magnitude 7.5 or greater earthquakes, while secondary zones can produce magnitude 6.5 or greater earthquakes. While the current block delineation scheme offers a valuable foundation, further discussion and refinement of certain secondary boundary zones are needed as detection and observational data improve. This study provides an essential framework for analyzing the dynamic interactions between active blocks, identifying seismogenic environments, and assessing seismic risks in the Sichuan-Yunnan region.

The data of active fault structure and three-dimensional(3D)fault models is essential for seismic risk analysis. With more and more requirement for complex 3D fault models, the demand for data sharing and related research increases dramatically. A web-based display system for three-dimensional fault models would improve data sharing and user experience. Moreover, constructing such a web-based system is also an important issue for data sharing.

The 3D active fault models are built in a data modeling platform, while the web display system is constructed by the geographic information system(GIS)platform. Because the data structure, type, and content between data modeling and GIS platforms are different, the following questions are critical, for example, how to migrate 3D model data from the modeling platform to the GIS platform?and can the migrated data present the right attributions?In this paper we used the Web AppBuilder of ArcGIS 10.6 Enterprise Edition to build a Web prototype system to display 3D fault models of the China Earthquake Science Experimental Field(Sichuan-Yunnan region). The system implemented the basic functions of a 3D Web application and successfully tested the 3D scene display scheme, user interaction mode, and data migration scheme.

The prototype system adopted a local scene, which can easily switch between the above-ground and underground viewing angles of the scene. The scene included 2D fault surface traces, 3D fault models, and earthquakes with or without focal depth. After data fusion, the 3D fault models were classified and displayed with active age, having a good visual fusion effect with 2D fault data. Earthquakes with or without focal depth were displayed in different colors. The earthquakes without focal depth were uniformly displayed at 17km depth according to the average focal depth of the earthquakes with focal depth. So the earthquakes without focal depth can be highly consistent with other elements in the 3D scene.

The user interface interaction mode in the 3D scene of the prototype system was consistent with the common interaction mode of 2D map applications in the following aspects: 1)map browsing; 2)Navigation menu; 3)Geographical inquiry; and 4)Functional interactive tools. The system interface was simple, clear, logical, and unified. Users were easily acquainted with the three-dimensional scene interface according to the two-dimensional map interaction experience. It conformed to the user interface interaction principles of simple, consistent, predictable, and easy feedback.

The prototype system had the basic functions of 3D scene browsing, zooming in and out, 3D object attribute viewing, geographic query, base map switching, layer control, legend, and distance measurement. However, the prototype system needed further development and more complex functions such as data attribute table browsing, space selection, and space query.

This paper presented a data migration scheme from the modeling platform to the GIS platform. The data migration of this scheme can be divided into four steps: data format conversion, coordinate system conversion, 2D and 3D attribute information mapping, and 3D data attribute table construction. After transforming the data format and coordination system from the modeling platform to the GIS platform, 2D and 3D data fusion should be carried out to make 3D data and 2D data have the same attribution. The format conversion and coordinate system conversion steps can be automatically completed in batches. Otherwise, mapping the 2D and 3D attribute information and building the 3D data attribute table need manual handling.

In summary, this paper presents a data migration scheme from the modeling platform to the GIS platform. Practice in reality shows that only after conversing data format and coordination system from the modeling platform, the 2D and 3D data fusion steps are caplable of ensuring a better visual integration of them. The Web-based prototype system of displaying 3D fault models of the China Seismic Experimental Site implements the basic functions of 3D scene application and tests the fused 2D and 3D data visualization. It is friendly and open to users, with a great demonstration significance.

In this paper, we relocated earthquakes occurred from April 2013 to July 2022 in Lushan seismic zone, inversed focal mechanism solution of the Lushan M_S6.1 earthquake on June 1, 2022 and discussed the seismogenic structure of the Lushan M_S6.1 earthquake and its relationship with the M_S7.0 earthquake in April 2013.

The results of the focal mechanism solution show that the Lushan M_S6.1 earthquake in 2022 is a thrust earthquake. The strike, dip and azimuth of nodal plane Ⅰ are 228°, 46° and 104° and for nodal plane Ⅱ are 28°, 46° and 76° respectively. The results of earthquake relocation show that the focal depth of the Lushan M_S6.1 earthquake sequence is shallow in the north and deep in the south, the fault length is about 10km. The focal depth is mainly concentrated between 10km to 19km. The fault dip is southeast with an angle of 60°. The initial rupture point of the main shock of the Lushan M_S6.1 earthquake is at a depth of 20km, located at the deepest part of the fault. The fault ruptured from deep to shallow. The Lushan M_S7.0 earthquake occurred on April 2013 strikes northeast and dips northwestward, but there exists a reverse fault in the aftershock sequence that has the same direction of strike but the opposite direction of dip. This reverse fault is consistent with the strike and dip of the M_S6.1 earthquake occurred in June 2022. It appears as two parallel faults in the profile. In addition to the reverse fault on the west side, the embryonic of another reverse fault seems to appear on the east side of the middle of earthquake sequence. These faults are about 10km away from the surface. The distribution of earthquakes in two northwest-oriented depth profiles shows that the dip angles of the main shock and the reverse fault of the M_S7.0 earthquake is different at different locations, and these faults are not simple straight planar sections. From one year after occurrence of the M_S7.0 earthquake to occurrence of the M_S6.1 earthquake, the seismic activity on the main fault decreased but the seismic activity on the reverse fault on the west side of the M_S7.0 earthquake sequence was more active during this period, most of the seismic activity occurred near the reverse fault that is parallel to the M_S6.1 earthquake fault.

By analyzing the seismogenic structure and seismic activity characteristics of the Lushan seismic zone, we concluded the Lushan M_S6.1 earthquake on June 1, 2022 is caused by a blind thrust fault with strike towards northeast and dip towards southeast, located 10km away from the surface. It has the opposite directions of strike and dip of the Longmenshan Fault. The epicenters of the Lushan M_S7.0 earthquake in April 2013 and the M_S6.1 earthquake in June 2022 are located near the surface exposure traces of the Shuangshi-Dachuan Fault and the Xiaoguanzi Fault, respectively. However, according to the analysis of the relocation aftershock depth in profile, the aftershock extension to the surface does not coincide with the surface exposure positions of the Shuangshi-Dachuan Fault and the Xiaoguanzi Fault. Therefore, the seismogenic faults of these two earthquakes are not the Shuangshi-Dachuan Fault and the Xiaoguanzi Fault, but two blind reverse faults. The Shuangshi-Dachuan Fault near the M_S6.1 earthquake sequence and the main shock fault of the 2013 M_S7.0 earthquake are thrust faults dipping northwest, while the Lushan M_S6.1 seismogenic fault has opposite direction of dip. The seismogenic fault of the Lushan M_S6.1 earthquake and the main thrust fault of the 2013 M_S7.0 earthquake, which strikes northeast and dips northwest with the reverse thrust fault of the hanging wall, which strikes northeast and dips southeast, together form a double layer Y-shaped structure. These faults are all blind thrust faults and belong to the Qianshan-Shanqian Fault system in the southern segment of the Longmenshan fault zone. The seismogenic structure in the Lushan seismic zone is a complex fault system composed of one main northeast strike fault with dipping northwest, and three faults dipping southeast.

From one year after occurrence of the Lushan M_S7.0 earthquake to the occurrence of the Lushan M_S6.1 earthquake, most of earthquakes in the Lushan seismic zone occurred near a reverse fault which is parallel to the Lushan M_S6.1 earthquake seismogenic fault. These earthquakes are located in the area where the coulomb stress change caused by the M_S7.0 earthquake acts as loading effect. The Lushan M_S6.1 earthquake sequence is mainly distributed in the area where the coulomb stress change plays an unloading role caused by the Lushan M_S7.0 earthquake. The research results showed that the coulomb rupture stress caused by the Lushan M_S7.0 earthquake on the seismic nodal plane of the M_S6.1 earthquake has a restraining effect on the M_S6.1 Lushan earthquake.

This paper focuses on the in-depth analysis of the aeromagnetic characteristics of the Dunhua-Mishan fault zone and its surrounding areas using wavelet multi-scale analysis. In order to analyze the anomalies of the crustal structure at different depths, wavelet multi-scale decomposition is used to separate the deep field from the shallow field sources, superimpose the aeromagnetic anomalies on different anomalies of different geological bodies, extract the required information, analyze the local field anomalies caused by the field sources, and invert and interpret the geological bodies. In this paper, wavelet multi-scale analysis is used to decompose the aeromagnetic data, separate the deep and shallow field sources of aeromagnetism in the study area, and obtain wavelet detail maps of order 1 to 4. The wavelet transform detail maps are a response to high frequency anomaly information, and also a reflection of local field aeromagnetic anomaly information, which can be used to infer information such as fault depth and basement depth of basin. The experimental results are used to analyze the anomaly characteristics at different depths, invert and analyze the characteristics of the aeromagnetic anomalies and crustal structure at different depths, explore the deep basement and fault tectonic features and the intersection relationship between the Dunhua-Mishan Fault and the surrounding faults, calculate the approximate field source depth by wavelet detail map and power spectrum method, and infer the fault cut-through depth. The results of the analysis can provide geophysical research information for the study of geotectonics and the evaluation and exploration of hydrocarbon resources.
Based on the original aeromagnetic anomaly map, aeromagnetic anomalies ranging from -494~2022nT can be obtained, with the highest anomaly located at about 50km from Baoqing County. The anomalies in the central part of the study area are high, while those in the eastern and western parts are low. The deposition of basal and ultramafic magmatic rocks in the Dunhua-Mishan area has caused massive high anomalies, while deep and large faults caused basement uplift or decline, shown as high and low anomaly zones. In the aeromagnetic shallow source field, the shallow surface and upper crustal media are more complex, and the Dunhua-Mishan fault zone shows multi-pearl-like small-scale anomalies, resulting mainly from the intrusion of basal or ultramafic magmatic rocks in the shallow part of the fault. In the deep source field, the magnetic anomalies in middle and lower crust are mainly caused by different magnetic properties of basin bedrock. The large fault zone presents as the dividing line of different trajectory feature zones, and the deep large fault cuts deeper and presents as the dividing line of different trajectory feature zones. The cut-through depth of the deep major faults is larger and affects the aeromagnetic characteristics of the deep tectonic zone. The paper further discusses the cut-through depth of the major faults of this region by analyzing the characteristics of the aeromagnetic anomalies at different depths and finds that there are the three deep major faults in the region, namely, the Dunhua-Mishan Fault, the Dahezhen Fault and the Yilan-Yitong Fault, while the Hulin River Fault, the Muling River Fault, the Fujin-Xiaojia River Fault and the Nanbeihe-Boli Fault only cut through the shallow crust; the Muling River Fault, the Dunhua-Mishan Fault, the Dahezhen Fault and the Fujin-Xiaojia River Fault only intersect in the shallow crust. The Parker method was used to invert the depth of the Curie points in the area, and the results show that the depth of the Curie points in the area ranges from 22.3~29.9km, with the deepest area in the south of Hulin County, which is a depressional basin formed by plate subduction and extrusion, and the Dunhua-Mishan fault zone has a controlling effect on the morphology of the Curie points. Seismic activity is low in the region as a whole, and earthquakes are densely distributed in the northwest of the study area along the Yilan-Yitong fault zone, and less distributed along the Dunhua-Mishan fault zone and the Dahezhen fault zone. In the vicinity of the Dunhua-Mishan fault zone, small earthquakes are mainly concentrated in the area south of the Mishan sub-uplift, and the northern section of the Dunhua-Mishan fault zone is generally more stable. The gravity field in this area has been studied in depth by previous authors. The area belongs to the Moho surface uplift zone in Heilongjiang Province, with the Moho depth of about 30~32.5km. The Yilan-Yitong rift zone is deep to the Moho surface, and the Moho surface often shows uplift in the seismically active area. The local deformation and uplift of the crust-mantle provides the possibility of stress concentration, while the existence of deep major faults provides a channel for material transport. The overall level of seismic activity in the region is low, and the areas with intense activity are mainly concentrated in the Yilan-Yitong fault zone, with small earthquakes also gathering near the Jixi area. Seismicity of Qitaihe-Jixi area is mainly influenced by the Mudanjiang Fault and the Nanbei River Fault. The Dunhua-Mishan Fault has a strong influence on the distribution of Curie points and also influences the formation of several major tectonic units. So, more attention should be paid to the crustal activity of areas around the faults and at the intersections of faults in the future.

The May 21, 2021 Yangbi M_S6.4 earthquake occurred at the western boundary of the Chuandian tectonic block in southeast Tibetan plateau. The structural background is complex, with multiple active faults distributed around the epicenter area. Focal mechanism and seismic waveform inversion reveal that this earthquake is right-lateral strike-slip type with a NW-trending rupture plane. This accords with the strike and motion directions of the Weixi-Qiaohou and Red River faults along the western boundary of the Chuandian block.
We made a careful field investigation along the Weixi-Qiaohou Fault and around the epicenter area, and did not find any obvious earthquake surface rupture. But we observed a NW-trending ground fissure zone near the epicenter area to the west of the Yangbi County. This zone is divided into two sections, the Yangkechang-Paoshuitian section in the northwest and the Xiquewo-Shahe section in the southwest. These sections have a length of 2.5~3km and 3~3.5km, respectively, and are separated by a ~6km gap. They are characterized by NW-trending ground fissures with a width of several meters to tens meters. The formation of these fissures is inferred to be related to the tectonic movement under the ground, and the fissures have the following features: 1)they are not affected by the topography and cut the slope and range upward; 2)they are continuous and concentrated in a zone with a strike of NW 310°~320°, which is consistent with the belt of aftershocks and differs from the gravity fissures that usually have no regular strikes; 3)they usually have a plane dipping towards upslope(southwest), opposite to the valley; 4)they present shear property, not tensional. This zone thus is interpreted to be the surficial expression of the seismogenic fault of the Yangbi M_S6.4 earthquake.
Moreover, satellite image and field observation suggest that a~30km long linear structure with a NW strike traverses the epicenter area, which may suggest an undiscovered fault. Relocation of small earthquakes shows that the aftershocks are concentrated in a NW-trending belt that is consistent with the linear structure. Furthermore, the fissure zone lies in the northeast side of the aftershock belt, which suggests that the earthquake fault dips SW. Such a dip direction coincides with that of the observed fissure plane, and also agrees with the results from the focal mechanism and InSAR inversion. Both the focal mechanism and the waveform inversion result suggest that the Yangbi earthquake is a right-lateral strike-slip type, which is consistent with the type of the observed ground fissures. No displacement is observed on the fissures, with is also consistent with the InSAR inversion results that suggest the rupture did not break the surface. In addition, there is no coseismic deformation observed along the Weixi-Qiaohou Fault, which may indicate this fault did not move during this earthquake.
Based on our field investigation, in combination with the focal mechanism, aftershock distribution, and InSAR and GNSS inversion results, the seismogenic fault for this Yangbi M_S6.4 earthquake is believed to be a NW-trending(310°~320°)fault with a length of~30km, named as the Yangkechang-Shahe Fault. According to the location, size, and motion of the fault, it is suggested that the Yangkechang-Shahe Fault is a secondary fault of the Weixi-Qiaohou fault system. This fault has a slightly SW-dipping plane, and is dominated by right-lateral strike-slip motion, which may be a younger fault developed during the westward expansion of the western boundary of the Chuandian block.

The elevation evolution history of the southeastern Tibet Plateau is of great significance for examining the deformation mechanism of the plateau boundary and understanding the interior geodynamic mechanics. It provides an important window to inspect the uplift and deformation processes of the Tibet Plateau, and also an important way to test two controversial dynamic end-element models of the Plateau boundary. In recent years, some breakthroughs have been made in the study of paleoaltitudes in the southeastern Tibet Plateau, which allows us to have a clearer understanding of its evolution process and dynamic mechanism. By reviewing and recalculation of the latest achievements of paleo-altitude studies of the basins in the southeastern Tibet Plateau from north to south, including the Nangqian Basin, Gongjue Basin, Mangkang Basin, Liming-Jianchuan-Lanping Basin, Eryuan Basin, Nuhe Basin and Chake-Xiaolongtan Basin, we discuss the surface elevation evolution framework of the Cenozoic geomorphology and dynamics in the southeastern Tibet Plateau. The results show as follows:
(1)There was an early Eocene-Oligocene quasi plateau with an altitude of at least 2.5km from the north to middle of the southeastern Tibet Plateau(north of Dali), while the surface elevation in the south(south of Dali to Yunnan-Guizhou Plateau)was relatively low, even close to sea level. Until Miocene, the north to middle of the southeastern Tibet Plateau reached the present altitude, while the southern part of the Tibet Plateau showed a differential surface uplift trend, which established the present geomorphologic pattern. But it cannot be completely ruled out that this trend was probably caused by the accuracy of the calculation results.
(2)The quantitative constraints on the uplift process of the southeastern Tibet Plateau during Cenozoic provide certain constraints for the dynamic mechanism of geomorphic evolution in the southeastern Tibet Plateau. The northern and central parts of the southeastern Tibet Plateau can be well explained by the plate extrusion model. In this model, the collision and convergence between India and Eurasia plate or Qiangtang block and Songpan-Ganzi block resulted in the shortening and thickening of the upper crust in the region, and making the early stage(early Eocene)surface uplift. Subsequently, due to delamination or the continuous convergence between the Qiangtang block and the Songpan-Ganzi block resulting in the shortening and thickening of the crust, the plateau continued to grow northward and rose to its present altitude around Miocene. In the Eocene, the area from the south of the southeastern Tibetan plateau to the Yunnan-Guizhou Plateau mainly showed a low altitude. It seems that it may be in the peripheral area not affected by the shortening and thickening of the upper crust during the early stage India-Eurasia plate collision or plate extrusion and escape. In addition, as proposed by the lower crustal channel flow model, the lower crust material made the low-relief upland surface extending thousands of kilometers in the region uplift gradually towards the southeast, which seems to explain the low elevation landform of the region in the early stage, but it could not explain the whole uplift process of the southeastern Tibet Plateau. Therefore, a single dynamic model may not be able to perfectly explain the Cenozoic complex uplift process of the southeastern Tibet Plateau, and its process may be controlled by various dynamic processes.
(3)According to the paleoaltitude reconstruction results, if most areas of the ancient southeastern Tibet Plateau, especially the area to the north of Jianchuan Basin, had been uplifted in a certain scale and became part of the early plateau in the early Cenozoic, and reached to the current surface altitude around Miocene, the widely rapid surface erosion in this area since Miocene probably would be a continuous lag response to the finished surface uplift process, and the lag time may correspond to the sequential response process of surface uplift, the decline of river erosion base level and the gradual enhancement of river erosion capacity. Therefore, it is not proper to regard the rapid denudation and rapid river undercutting as the starting time of plateau uplift, as proposed in the previous thermochronological study.

The southeastern margin of the Ordos block is a key area for dynamic transformation from collision and compression in the western part of the Chinese mainland to extension in the east, and also is the junction of the NE-SW trending structure in the north and near the E-W trending structure in the south of the North China block. The tectonic activity in the southeastern margin of the Ordos block is intense. In this region, the Houma-Yuncheng section is a noteworthy area for medium- and long-term large earthquake risk determined by China Earthquake Administration, which involves three tectonic units: Linfen Basin, Yuncheng Basin and Emei Platform. The potential seismogenic faults include the Hancheng Fault, the southern margin fault of Emei Platform and the piedmont fault of Zhongtiao Mountains. Because the neotectonic movement in this region is mainly dominated by strong differential movement, it is important to estimate the fault kinematics parameters based on the high-resolution vertical crustal movement observation constraints.
Fault locking depth and slip rate are important indicators to judge the risk of future earthquakes. When the accumulation time of fault seismic moment and fault length are given, the larger fault locking depth and higher slip rate will cause the greater energy accumulation and stronger future earthquakes risk of the fault. Based on the traditional leveling and GPS data, previous studies found that the southeastern margin of the Ordos block is perhaps experiencing strong tectonic movement. However, the measuring point density of the above technical means is difficult to satisfy the quantitative study of the current activity characteristics of specific faults. Therefore, the interferogram stacking technique is used to obtain the spatial high-resolution InSAR average deformation rate field of the study area based on the Radarsat -2 wide-mode image in this paper firstly. At the same time, the three-component velocity of GPS continuous station in the study area is projected into the radar line of sight direction. After unifying the reference datum, comparative analysis was conducted to evaluate the accuracy and reliability of InSAR results. The results show that the standard deviation of the difference between the short-term InSAR and the long-term GPS observation values is 2.7mm. The annual crustal deformation field obtained by using the interferogram stacking technology in the study area has a high accuracy, which can reflect the characteristics of regional crustal movement. It also indicates that the regional crustal short-term deformation is consistent with the long-term deformation. Secondly, the dip-slip fault dislocation model and particle swarm optimization(PSO)were used to invert the main fault slip rate and locking depth, the inversion was repeated 1 000 times, and the optimum estimate of parameters was obtained by statistical analysis of results and uncertainty. The fault slip rate and locking depth data approximately obey the normal distribution, and the stability is good; the dip angles of faults are skewed but concentrated. The above results show that the fault movement parameters obtained from InSAR deformation field inversion are reliable and can be used for regional tectonic movement analysis. Finally, based on the data of regional geological structure, fault slip rate, fault locking depth and present seismic activity, this paper analyzes the variation characteristics of InSAR deformation field, and discusses the fault tectonic movement mode, future seismic risk and regional tectonic deformation pattern in the southeastern margin of Ordos. The results show that the tectonic and nontectonic deformations are superimposed on the southeastern margin of Ordos. Tectonic deformation mainly occurs near active faults, which is related to fault slip rate and closure depth. Nontectonic deformation mainly occurs in the Quaternary strata inside the basin, which is related to the thickness of the aquifer and the amount of groundwater extraction, and the maximum can reach 5cm/a. The slip rate of the fault at the northern foot of the Zhongtiao Mountains and the northern margin of the Emei Platform is 0.37mm/a and 0.74mm/a, and the blocking depth is 3.4km and 4.3km, which are relatively shallow. It may indicate that the fault was not completely closed after the last strong earthquake and is dominated by shallow seismic activity. The slip rate of the fault on the southern margin of the Emei Platform is 0.47mm/a, and the closure depth is 0.95km, indicating that the faults are mainly creepy. The counterclockwise rotation of the Ordos block and the eastward extrusion and escape of the Qinling Mountains formed a quasi-triple junction structural area on the southeastern margin of Ordos, characterized by strike-slip-extension transition.

The current and conventional fault-crossing short baseline measurement has a relatively high precision, but its measurement arrays usually fail to or cannot completely span major active fault zones due to the short length of the baselines, which are only tens to 100 meters. GNSS measurement has relatively low resolution on near-fault deformation and hence is not suitable for monitoring those faults with low motion and deformation rates, due to sparse stations and relatively low accuracy of the GNSS observation. We recently built up two experimental sites on the eastern boundary of the active Sichuan-Yunnan block, one crossing the Daqing section of the Zemuhe Fault and the other crossing the Longshu section of the Zhaotong Fault, aiming to test the measurement of near-fault motion and deformation by using fault-crossing arrays of one-kilometer-long baselines. In this paper, from a three-year-long data set we firstly introduce the selection of the sites and the methods of the measurement. We then calculate and analyze the near-field displacement and strain of the two sites by using three hypothetical models, the rigid body, elastic and composed models, proposed by previous researchers. In the rigid body model, we assume that an observed fault is located between two rigid blocks and the observed variances in baseline lengths result from the relative motion of the blocks. In the elastic model, we assume that a fault deforms uniformly within the fault zone over which a baseline array spans, and in the array baselines in different directions may play roles as strainmeters whose observations allow us to calculate three components of near-fault horizontal strain. In the composed model, we assume that both displacement and strain are accumulated within the fault zone that a baseline array spans, and both contribute to the observed variances in baseline lengths. Our results show that, from the rigid body model, variations in horizontal fault-parallel displacement component of the Zemuhe Fault at the Daqing site fluctuate within 3mm without obvious tendencies. The displacement variation in the fault-normal component keeps dropping in 2015 and 2016 with a cumulative decrease of 6mm, reflecting transverse horizontal compression, and it turns to rise slightly(suggesting extension)in 2017. From the elastic model, the variation in horizontal fault-normal strain component of the fault at Daqing shows mainly compression, with an annual variation close to 10^-5, and variations in the other two strain components are at the order of 10^-6. For the Longshu Fault, the rigid-body displacement of the fault varies totally within a few millimeters, but shows a dextral strike-slip tendency that is consistent with the fault motion known from geological investigation, and the observed dextral-slip rate is about 0.7mm/a on average. The fault-parallel strain component of the Longshu Fault is compressional within 2×10^-6, and the fault-normal strain component is mainly extensional. Restricted by the assumption of rigid-body model, we have to ignore homolateral deformation on either side of an observed fault and attribute such deformation to the fault displacement, resulting in an upper limit estimate of the fault displacement. The elastic model emphasizes more the deformation on an observed fault zone and may give us information about localizations of near-fault strain. The results of the two sites from the composed model suggest that it needs caution when using this model due to that big uncertainty would be introduced in solving relevant equations. Level surveying has also been carried out at the meantime at the two sites. The leveling series of the Daqing site fluctuates within 4mm and shows no tendency, meaning little vertical component of fault motion has been observed at this site; while, from the rigid-body model, the fault-normal motion shows transverse-horizontal compression of up to 6mm, indicating that the motion of the Zemuhe Fault at Daqing is dominantly horizontal. The leveling series of the Longshu site shows a variation with amplitude comparable with that observed from the baseline series here, suggesting a minor component of thrust faulting; while the baseline series of the same site do not present tendencies of fault-normal displacement. Since the steep-dip faults at the two sites are dominantly strike-slip in geological time scale, we ignore probable vertical movement temporarily. In addition, lengths of homolateral baselines on either side of the faults change somewhat over time, and this makes us consider the existence of minor faults on either side of the main faults. These probable minor faults may not reach to the surface and have not been identified through geological mapping; they might result in the observed variances in lengths of homolateral baselines, fortunately such variations are small relative to those in fault-crossing baselines. In summary, the fault-crossing measurement using arrays with one-kilometer-long baselines provides us information about near-fault movement and strain, and has a slightly higher resolution relative to current GNSS observation at similar time and space scales, and therefore this geodetic technology will be used until GNSS networks with dense near-fault stations are available in the future.

The northern margin of the Qinghai-Tibet Plateau is currently the leading edge of uplift and expansion of the plateau. Over the years, a lot of research has been carried out on the deformation and evolution of the northeastern margin of the Qinghai-Tibet Plateau, and many ideas have been put forward, but there are also many disputes. The Altyn Tagh Fault constitutes the northern boundary of the Qinghai-Tibet Plateau, and there are two active faults on the north side of the Altyn Tagh Fault, named Sanweishan Fault with NEE strike and Nanjieshan Fault with EW strike. Especially, studies on the geometric and kinematic parameters of Sanweishan Fault since the Late Quaternary, which is nearly parallel with the Altyn Tagn Fault, are of great significance for understanding the deformation transfer and distribution in the northwestward extension of the Qinghai-Tibet Plateau. Therefore, interpretation of the fault landforms and statistical analysis of the horizontal displacement on the Sanweishan Fault and its newly discovered western extension are carried out in this paper. We believe that the Sanweishan Fault is an important branch of the eastern section of the Altyn Tagh fault zone. It is located at the front edge of the northwestern Qinghai-Tibet Plateau and is a left-lateral strike-slip and thrust active fault. Based on the interpretation of satellite imagery and microgeomorphology field investigation of Sanweishan main fault and its western segments, it's been found that the Sanweishan main fault constitutes the contact boundary between the Sanweishan Mountain and the alluvial fans. In the bedrock interior and on the north side of the Mogao Grottoes, there are also some branch faults distributed nearly parallel to the main fault. The main fault is about 150km long, striking 65°, mainly dipping SE with dip angles from 50° to 70°. The main fault can be divided into three segments in the spatial geometric distribution:the western segment(Xizhuigou-Dongshuigou, I), which is about 35km long, the middle segment(Dongshuigou-Shigongkouzi, Ⅱ), about 65km long, and the east segment(Shigongkouzi-Shuangta, Ⅲ), about 50km long. The above three segments are arranged in the left or right stepovers.
In the west of Mingshashan, it's been found that the fault scarps are distributed near Danghe Reservoir and Yangguan Town in the west of Minshashan Mountain, and we thought those scarps are the westward extension of the main Sanweishan Fault. Along the main fault and its western extension, the different levels of water system(including gullies and rills)and ridges have been offset synchronously, forming a series of fault micro-geomorphology. The scale of the offset water system is proportional to the horizontal displacement. The frequency statistical analysis of the horizontal displacement shows that the displacement has obvious grouping characteristics, which are divided into 6 groups, and the corresponding peaks are 3.4m, 6.7m, 11.4m, 15m, 22m and 26m, respectively. Among them, 3.4m represents the coseismic displacement of the latest ancient earthquake event, and the larger displacement peak represents the accumulation of coseismic displacements of multi-paleoearthquake events. This kind of displacement characterized by approximately equal interval increase indicates that the Sanweishan Fault has experienced multiple characteristic earthquakes since the Late Quaternary and has the possibility of occurrence of earthquakes greater than magnitude 7. The distribution of displacement and structural transformation of the end of the fault indicate that Sanweishan Fault is an "Altyn Tagh Fault"in its infancy. The activities of Sanweishan Fault and its accompanying mountain uplift are the result of the transpression of the northern margin of the Qinghai-Tibet Plateau, representing one of the growth patterns of the northern margin of the plateau.

The Xigaze fore-arc basin is adjacent to the Indian plate and Eurasia collision zone. Understanding the erosion history of the Xigaze fore-arc basin is significant for realizing the impact of the orogenic belt due to the collision between the Indian plate and the Eurasian plate. The different uplift patterns of the plateau will form different denudation characteristics. If all part of Tibet Plateau uplifted at the same time, the erosion rate of exterior Tibet Plateau will be much larger than the interior plateau due to the active tectonic action, relief, and outflow system at the edge. If the plateau grows from the inside to the outside or from the north to south sides, the strong erosion zone will gradually change along the tectonic active zone that expands to the outward, north, or south sides. Therefore, the different uplift patterns are likely to retain corresponding evidence on the erosion information. The Xigaze fore-arc basin is adjacent to the Yarlung Zangbo suture zone. Its burial, deformation and erosion history during or after the collision between the Indian plate and Eurasia are very important to understand the influence of plateau uplift on erosion.
In this study, we use the apatite fission track(AFT)ages and zircon and apatite(U-Th)/He(ZHe and AHe)ages, combined with the published low-temperature thermochronological age to explore the thermal evolution process of the Xigaze fore-arc basin. The samples' elevation is in the range of 3 860~4 070m. All zircon and apatite samples were dated by the external detector method, using low~U mica sheets as external detectors for fission track ages. A Zeiss Axioskop microscope(1 250×, dry)and FT Stage 4.04 system at the Fission Track Laboratory of the University of Waikato in New Zealand were used to carry out fission track counting. We crushed our samples finely, and then used standard heavy liquid and magnetic separation with additional handpicking methods to select zircon and apatite grains.
The new results show that the ZHe age of the sample M7-01 is(27.06±2.55)Ma(Table 2), and the corresponding AHe age is(9.25±0.76)Ma. The ZHe and AHe ages are significantly smaller than the stratigraphic age, indicating suffering from annealing reset(Table 3). The fission apatite fission track ages are between(74.1±7.8)Ma and(18.7±2.9)Ma, which are less than the corresponding stratigraphic age. The maximum AFT age is(74.1±7.8)Ma, and the minimum AFT age is(18.7±2.9)Ma. There is a significant north~south difference in the apatite fission track ages of the Xigaze fore-arc basin. The apatite fission track ages of the south part are 74~44Ma, the corresponding exhumation rate is 0.03~0.1km/Ma, and the denudation is less than 2km; the apatite fission track ages of the north part range from 27 to 15Ma and the ablation rate is 0.09~0.29km/Ma, but it lacks the exhumation information of the early Cenozoic. The apatite(U-Th)/He age indicates that the north~south Xigaze fore-arc basin has a consistent exhumation history after 15Ma.
The results of low temperature thermochronology show that exhumation histories are different between the northern and southern Xigaze fore-arc basin. From 70 to 60Ma, the southern Xigaze fore-arc basin has been maintained in the depth of 0~6km in the near surface, and has not been eroded or buried beyond this depth. The denudation is less than the north. The low-temperature thermochronological data of the northern part only record the exhumation history after 30Ma because of the young low-temperature thermochronological data. During early Early Miocene, the rapid erosion in the northern part of Xigaze fore-arc basin may be related to the river incision of the paleo-Yarlungzangbo River. The impact of Great Count Thrust on regional erosion is limited. The AHe data shows that the exhumation history of the north-south Xigaze fore-arc basin are consistent after 15Ma. In addition, the low-temperature thermochronological data of the northern Xigaze fore-arc basin constrains geographic range of the Kailas conglomerate during the late Oligocene~Miocene along the Yarlung Zangbo suture zone. The Kailas Basin only develops in the narrow, elongated zone between the fore-arc basin and the Gangdese orogenic belt.
The southern part of the Xigaze fore-arc basin has been uplifted from the sea level to the plateau at an altitude of 4.2km, despite the collision of the Indian plate with the Eurasian continent and the late fault activity, but the plateau has been slowly denuded since the early Cenozoic. The rise did not directly contribute to the accelerated erosion in the area, which is inconsistent with the assumption that rapid erosion means that the orogenic belt begins to rise.

The generation, abandonment and preservation of terraces formed in active tectonic areas are important to the analysis of the role of the tectonics and climate along the temporal variations, so it appears significant as how to use the effective quantitative methods to extract and accurately depict these terraces. The increasingly convenient acquisition of high-precision topographic data has greatly promoted the advancement of quantitative research in geoscience, making it possible to analyze mid-micro-geomorphic features on a large scale, especially by studying the temporal and spatial evolution of tectonic deformation through accurate capture of micro-geomorphic features. Over the past decade, the rapid development of LiDAR(Light Detection and Ranging)technology has provided unprecedented opportunity to access high-precision topographic data(up to centimeter in vertical and horizontal directions). However, its relatively high cost and relatively complex data processing techniques limit its widespread application in the field of earth sciences. In recent years, with the continuous innovation and advancement of topographic measurement technology, the three-dimensional structure of motion reconstruction technology(Structure from Motion, SfM)has gradually been introduced into the field of digital topographic photogrammetry due to its rapid advantage in providing quick, convenient and cost-effective methods for obtaining high-density geospatial point data. This method thus shows great potential for providing high resolution topographic data with comparable resolution and precision. Therefore, with the acquisition of more and more high-resolution terrain data in recent years, it is an important development trend to explore automated or semi-automated quantitative geomorphological analysis methods. R language, as an excellent programming language, has not been used in the geology and geomorphology, although is widely applied in medicine and meteorology based on its powerful capability of statistician and graphic visualization. In this paper, we focus on the Yellow River multi-terraces formed to the east of the Mijia Shan, which belongs to the Jingtai-Hasi Shan segment of the Haiyuan Fault. With the analysis and visualization of the high-resolution topographic data collected from the SfM in the environment of the R language, we implement the semiautomatic classification and mapping of the Yellow River multi-terraces. The method identifies 20 terraces with different elevation. Our results also imply that the younger terraces have better continuity and elongation, and the older terraces have more deformation, which can be demonstrated from their gradually notable semi-parabolic shape. Besides this, it also suggests the diverse evolution stages of the Yellow River terraces. Our study indicates that R language is expected to become an efficient tool of statistics and visualization of the high-resolution topographic data.

The bedrock scarps are believed to have recorded the continuous information on displacement accumulation and sequence of large earthquakes. The occurrence timing of large earthquakes is believed to be correlated positively with the exposure duration of bedrock fault surfaces. Accordingly, cosmogenic nuclides concentration determined for the bedrock footwall can offer their times, ages, and slip over long time. In general, multiple sites of fault scarps along one or even more faults are selected to carry out cosmogenic nuclide dating in an attempt to derive the temporal and spatial pattern of fault activity. This may contribute to explore whether earthquake occurrence exhibits any regularity and predict the timing and magnitude of strong earthquakes in the near future. Cosmogenic nuclide ³⁶ Cl dating is widely applied to fault scarp of limestone, and the height of fault scarp can reach as high as 15~20m. It is strongly suggested to make sure the bedrock scarp is exhumed by large earthquake events instead of geomorphic processes, based on field observation, and data acquired by terrestrial LiDAR and ground penetration radar (GPR). In addition, it is better for the fault surface to be straight and fresh with striations indicating recent fault movement. A series of bedrock samples are collected from the footwall in parallel to the direction of fault movement both above and below the colluvium, and each of them is~15cm long,~10cm wide, and~3cm thick. The concentrations of both cosmogenic nuclide ³⁶ Cl and REE-Y determined from these samples vary with the heights in parallel to fault scarps. Accordingly, we identify the times of past large earthquakes, model the profile of ³⁶ Cl concentration to seek the most realistic one, and determine the ages and slip of each earthquake event with the errors. In general, the errors for the numbers, ages, and slips of past earthquake events are ±1-2, no more than ±0.5-1.0ka, and ±0.25m, respectively.

On January 21 2016, an earthquake of M_S6.4 hit the Lenglongling fault zone(LLLFZ)in the NE Tibetan plateau, which has a contrary focal mechanism solution to the Ms 6.4 earthquake occurring in 1986. Fault behaviors of both earthquakes in 1986 and 2016 are also quite different from the left-lateral strike-slip pattern of the Lenglongling fault zone. In order to find out the seismogenic structure of both earthquakes and figure out relationships among the two earthquakes and the LLLFZ, InSAR co-seismic deformation map is constructed by Sentinel -1A data. Moreover, the geological map, remote sensing images, relocation of aftershocks and GPS data are also combined in the research. The InSAR results indicate that the co-seismic deformation fields are distributed on both sides of the branch fault(F₂)on the northwest of the Lenglongling main fault(F₁), where the Earth's surface uplifts like a tent during the 2016 earthquake. The 2016 and 1986 earthquakes occurred on the eastern and western bending segments of the F₂ respectively, where the two parts of the F₂ bend gradually and finally join with the F₁. The intersections between the F₁ and F₂ compose the right-order and left-order alignments in the planar geometry, which lead to the restraining bend and releasing bend because of the left-lateral strike-slip movement, respectively. Therefore, the thrust and normal faults are formed in the two bending positions. In consequence, the focal mechanism solutions of the 2016 and 1986 earthquakes mainly present the compression and tensional behaviors, respectively, both of which also behave as slight strike-slip motion. All results indicate that seismic activity and tectonic deformation of the LLLFZ play important parts in the Qilian-Haiyuan tectonic zone, as well as in the NE Tibetan plateau. The complicated tectonic deformation of NE Tibetan plateau results from the collisions from three different directions between the north Eurasian plate, the east Pacific plate and the southwest Indian plate. The intensive tectonic movement leads to a series of left-lateral strike-slip faults in this region and the tectonic deformation direction rotates clockwise gradually to the east along the Qilian-Haiyuan tectonic zone. The Menyuan earthquake makes it very important to reevaluate the earthquake risk of this region.

The Yingkou-Weifang fault zone (YWFZ) is the part of the Tanlu fault zone across the Bohai Sea, and is also an important part of the tectonics of the eastern Bohai Bay Basin. Many studies have been carried out on the neo-tectonics and activities of the YWFZ in recent years. In this paper, the neo-tectonics and activities of the YWFZ, and other related issues were studied again, based on our previous work and results of other researchers. The neo-tectonic movement in the Bohai Sea area began in the late Miocene (12~10Ma BP), which originated from the local crust horizontal movement, the tectonic stress field is characterized by NEE-SWW and near E-W horizontal compression. The neo-tectonics of the YWFZ is represented mainly by Neogene-Quaternary deformation, due to rejuvenation of Paleogene faults. Many faults have developed. The neo-tectonics and activities of YWFZ have characteristics of segmentation and weakening, because of the development of the NE-trending Northwest Miao Island-the Yellow River Estuary fault zone, which crosses the YWFZ. Earthquakes in the east of Bohai Sea are distributed along the Northwest Miao Island-the Yellow River Estuary fault zone, only few and small earthquakes along the Liaodong Bay and the Laizhou Bay section of the YWFZ. We made a preliminary analysis of the mechanics for this phenomenon.

To research the faults distribution and deep structures in the southern segment of Tan-Lu fault zone(TLFZ) and its adjacent area, this paper collects the Bouguer gravity data and makes separation by the multi-scale wavelet analysis method to analyze the crustal transverse structure of different depths. Meanwhile Moho interface is inversed by Parker variable density model. Research indicates that the southern segment of TLFZ behaves as a NNE-directed large-scale regional field gravity gradient zone, which separates the west North China-Dabie orogen block and the east Yangtze block, cutting the whole crust and lithosphere mantle. There are quite differences of density structures and tectonic features between both sides of this gradient belt. The sedimentary and upper crustal density structure is complex. The two east branches of TLFZ behave as linear gravity anomalous belt throughout the region, whereas the two west branches of TLFZ continue to extend after truncating the EW-trending gravity anomaly body. The lower crustal density structure is relatively simple. TLFZ behaves as a broad and gentle low abnormal belt, which reflects the Cretaceous-Paleogene extension environment caused graben structure. The two west branches of TLFZ, running through Hefei city, extend southward along the west margin of Feidong depression and pinch out in Shucheng area due to the high density trap occlusions in the south of Shucheng. The Feizhong Fault, Liu'an-Hefei Fault, and Feixi-Hanbaidu Fault intersect the two west branch faults of TLFZ without extending to the east. Recent epicenters are mainly located in conversion zones between the high-density and the low-density anomaly, especially in TLFZ and the junction of the faults, where earthquakes frequently occurred in the upper and middle crust. As strong earthquakes rarely occur in the southern segment of TLFZ, considering its deep feature of abrupt change of the Moho and intersections with many EW-trending faults, the hazard of strong earthquake cannot be ignored.

Yishu Fault zone is the Shandong segment of Tan-Lu Fault zone, which is characterized by remarkable neotectonic activities and is one of the strong earthquake activity belts in North China. Wavelet multi-scale analysis method is applied to separate gravity fields effectively to study the features of crust structures and spatial distribution of faults with collected Bouguer gravity data of this area. Moho depths are inversed by using the variable density model. The following conclusions are concluded: (1)The gravity fields show that the Yishu Fault zone forms a large-scale NNE-striking gravity gradient zone, which separates the western Shandong block and eastern Shandong block as a major geophysical boundary in this area. (2)The local gravity fields show that the structure of mid and upper crust is complex. The gravity anomaly pattern of 1 horst trapped between 2 grabens appears in the Yishu Fault zone and 5 main faults distributed in the east and west grabens form a linear gradient zone. Many NW-striking active faults in Western Shandong block intersect with Yishu Fault zone in the deep part. The majority of these faults intersect to the west graben of Yishu Fault zone. Only Mengshan Fault and Cangni Fault traverse the Yishu Fault zone. The structure of lower crust is relative simple, fold structures are evident, and there is typical characteristics of large-scale high and low density anomalies alternating in the lower crust.(3)In the Moho depths image, the east part is high and the west is low. The Yishu Fault zone forms the Moho abrupt change zone, creating the separating pattern. Uplift of Moho occurs along the east Weifang-Juxian-Linyi regions, providing deep conditions for strong earthquake preparation.(4)Earthquake epicenters are mainly located in conversion zones between the high and the low-density anomaly, especially in the transitional area from the low-density to high-density anomaly. The occurrence of earthquake is closely related to activity of fault. The Yishu Fault zone sees the strongest seismic activity in this area, and the seismicity in east graben is higher than that in west graben.

Based on ALOS, ETM+images and field works, combining with the existing research results of the study area, using information enhancement and image fusion methods, we extracted the texture, color and water-bearing features and studied the spatial distribution and development of the southeastern piedmont faults of the Nyenchen Tonglha Mountains. Moreover, SL index and Hack profile were used to analyze and compare the regional tectonic activity. The results show that the main faults obviously present a three-stage distribution on remote sensing images. Fault movement has produced different surface topography, such as fault scarp, fault facet and surface rupture zone. Small pull-apart basin, rift lakes and swamps were found in the basin. Their distribution and development are obviously controlled by faults. Geomorphic evidences interpreted from images generally indicate the fault movement property as normal faulting with strike-slip component. Major rivers cross the southeastern piedmont faults of the Nyenchen Tonglha Mountains from northwest to southeast and flow into Dangxiong-Yangbajain rift basins. The rivers with length bigger than four kilometers are selected to calculate the tectonic geomorphology parameters. The Hack profiles of rivers present obvious convex uplift that represents strong tectonic differential uplifting. Rivers had no time to make adjustments in the process of development and the tectonic movement produced convex and concave shape on the river section traces. The area where standard stream length-gradient index is abnormal indicates strong tectonic movement. This abnormal changes not only verify the impact on river profile caused by fault movement, but also improve the fault location accuracy when interpreted combining with these abnormal features. The average SL/K value in this area tends to increase from F₁ to F₃. From the point of historical earthquakes distribution, a large amount of small earthquakes occurred mainly on F₃ and seldom on F₁ and F₂. This trend is similar to SL/K value change. It indicates that the fault activity increases accordingly from F₁ to F₃. The standard length-gradient index K represents the river erosion ability, which increases from F₁ to F₃. This feature shows that normal fault movement is strong on F₃ and tectonic uplift has a significant impact on river erosion. Movement on F₁ and F₂ show strong strike-slip and weak normal faulting, whereas normal faulting is stronger on F₃. Dislocation of rivers is more evident on the remote sensing image. The southeastern piedmont faults of Nyenchen Tonglha Mountains and Dangxiong-Yangbajain rift basins are important conversion and absorption zones in the central Tibetan plateau, where the seismic activity is still high and more attention should be paid.

A set of en-echelon quartz veins in the Ordovician sandstone in the Noushoushan was analyzed. The quart veins in the Niushoushan show both characteristics of those formed at the tip of mode-I parent faults and the ones in the tip zone of mode-II faults,which means that they took place by different mechanism from those extensional veins. The bridges between the veins were deformed not only by bending but also by some extent of ductile deformation. And to those early fabrics such as faults,joints and bedding surfaces in the bridges,the buckling may take place. The early fabric in the rocks was one of the important factors which control the late development of the en-echelon veins. These results show that the development of these veins may be controlled by the R' shear zones at the fault-tip damage zone of a strike-slip fault(Mode-Ⅱ),instead of minor en-echelon ones formed at the tip of a mode-I parent fault. The wedge-type fault damage zone at the tip of a major strike-slip fault was bounded by R and P minor shear zones derived from the major fault,and in the wedge region antithetic and synthetic shear veins or fractures will take place. This type of deformation is pervasive at the termination of the strike-slip fault,and it is an important way for the propagation of faults.

The activity of fault is one of the causes of earthquakes.The distribution of the velocity structure of small earthquakes on the fault structure can offer an accurate underground crust structure model for us to analyze the activity of fault.Using the seismic network monitoring data at the southern end of the Taihang Mountains and the small earthquake P wave travel time data,the paper reconstructs the three-dimensional velocity structure model for the southern end of the Taihang Mountains Fault zone by joint inversion of seismic source and velocity structure.The results show: on the west of Taihang Mountain piedmont fault zone,there exists a NNE-trending fault.Horizontal distribution shows a zonal distribution of low velocity zone along the fault zone.The thickness of the sedimentary layer in Taihangshan uplift has reduced gradually from approximately 8km to about 2km,while under the force from the western side,the crust thickens gradually.

Based on the remote sensing images interpretation,the spatial distribution of the Fei Huanghe(the ancient Yellow River)fault zone in Xuzhou area was studied and the intersection relationships between Fei Huanghe Fault and Shaolou Fault,and Tan-lu Fault were discussed in the paper.Besides,we researched the deep-seated geometric structure of Fei Huanghe Fault by studying the gravity-magnetic data,and discussed the intersection relationships with the west boundary of Tan-lu Fault. The cutting depth of Fei Huanghe Fault reflected by second order-wavelet transform detail of the Bouguer gravity anomalies is up to 7～8km.The depth reflected by the third order-wavelet and fourth order-wavelet transform detail of the Bouguer gravity anomalies is up to 9～11km and 15～18km,respectively.The results show that the Fei Huanghe Fault extends to Jiuding in southeast direction.The cutting depth is up to 8～9km.The NW-trending Fei Huanghe Fault cut the NE-trending Shaolou Fault,resulting in the change of the tectonic line of the latter from striking N 60°E to N 45°E.Moreover,the Fei Huanghe Fault didn't cut the Tanlu Fault.It is a pre-Quaternary Fault with weak activity.

Based on structural data of the Minghuazhen Formation(N₁²—N₂)and base of Quaternary system from Research Center of China Offshore Petroleum Company,there are about 600 faults developed in the region from Yellow River Estuary to the Changxing Island.Among them,nearly 500 faults trend NE-NEE,amounting to 83 percent of the whole fault group.The faults are about 5～20km long,and the longest one is 40～50km.Some of this set of faults result from reactivation of NE—NEE trending Tertiary faults,and the rest are the newly-generated.They form a NE-striking fault zone about 50km wide with right-lateral strike slip component.This fault zone is not controlled by Tertiary faults;it is a newly generated fault zone during Neogene.It proves the former speculation of the existence of the newly-formed Yellow River Estuary-Northwest Miao fault zone.

The occurrence of earthquake is related to active structure,so the active structure is key to seismogeological study.For the broad field of vision of RS technology,it can play an important role in macro-active structure study.Furthermore,the ability of multi-temporal,multi-spectral,high-resolution,dynamic monitoring and so on also makes RS a very important tool for geological application.The studies of active fault using RS image were based on optical image before,therefore the study depends considerably on the fieldwork because of the limited information available from image.In the paper,we combine optical image with SAR image and implement image fusion,as a result,we can obtain more information and interpret more features of active fault.The paper puts emphasis on the study of distribution of active fault in Hainan Island utilizing satellite image.First,MSS,TM and SAR images are selected as the basis datum;preprocessing and image enhancements are manipulated for data fusion to highlight more features of geological body and extract more texture,tonal and other structure features to improve the efficiency of RS image greatly.Then the expression of geological physiognomy is analyzed,the symbol for interpretation is established,and each geological body on image is analyzed.At last,the geologic and geomorphic feature of the study area is analyzed generally,and detailed description of development of active fault in the northern area of Hainan Island is presented.After image processing and interpretation,we can conclude that there are mainly three groups of active faults striking EW,NW and NE,respectively in Qiongbei area.The EW-and NW-trending faults have great effect on the geologic and geomorphic development of the region.The image feature of active fault is clear,the phenomena of crustal movement such as linear distributed lake,volcano crater and flexed coastline,exist on the earth surface or near surface.The three groups of faults intersect with each other and have different movement intensities,which make the crust of the study area bitty and the physiognomic feature various.The movement of EW-and NW-trending faults is strong in this area.Along the NW-trending faults between Wangwu-Wenjiao and Puqian-Qinglan faults,the crustal deformation is intense in the Neoid period.Analysis indicates that the EW-and NW-trending active faults are highly active since the Quaternary,which affect significantly the stability of crust of the northern Hainan Island.

The Taipei Basin is located in the northern part of the Taiwan Orogen. Although this extensional basin was developed in an active orogen,it has peculiar formation mechanism different from that of basins resulted from the collapse of orogen in general sense. However,little attention has been paid to this peculiarity in previous studies,so that the problem concerning the formation of the Taipei Basin has evoked much controversy. Recently,bore holes and seismic prospecting data have revealed that the Shanjiao Fault,which has controlled the formation of the basin,consists of 3 segments,rather than a fault. Each segment controlled one center of subsidence,and has not connected with the other segments. The activity of different segments is not uniform,and it becomes stronger with time toward northeast. At present,the strongest activity is concentrated on the middle and northern segments,while the southern segment is no longer active. A series of NW-trending faults in the basin are the secondary structures produced during the subsidence of the different subsidence centers. There are a series of volcanoes that had erupted around the basin,so the formation of the basin should be affected by magmatic activities around the basin. Because the development of the basin treaded on the heels of these volcanic activities,there were essential relationship between the formation of the basin and the volcanic activities around the basin. Geophysical data,the structural characteristics and the migration of depocenter have shown that the development of the Taipei Basin was resulted from the cooling and contraction of the magma body at depth. The magma body beneath the Taipei Basin is connected with the magma body beneath the Tatun volcanic cluster,and the cooling of the magma has migrated from southwest to northeast. Moreover,the Tatun volcanic cluster is currently in its stage of subsidence,so the formation of the Taipei Basin was not an independent phenomenon. Both the Taipei Basin and Tatun volcanic cluster belong to one larger extensional basin.

Dating the age of faulting is critical to the studies of active tectonics, paleoearthquake and neotectonics, but is sometimes difficult of access. At present, two methods are commonly used to date the age of the last faulting. The one is to date the direct products of faulting, such as fault gouge and colluvial wedge, while the other is to date the youngest sediment that was offset by faulting or the oldest sediment that was not affected by faulting. In the region from Tuoli to Yongdinghe River, western Beijing, three types of faulting can be identified along the Gaoliying fault. The first type is that the fault displaces the older loess layer, but is covered by the younger loess layer, such as the cases at Lujing and Xiaoyouying. The second type is observed at Xinkaikou, where the fault offsets the pre-Quaternary bedrocks, but does not affect the Quaternary covering layer (loess). The third type is identified at Xinzhuang village, where the fault dissects the pre-Quaternary bedrocks, resulting in fault gouge, but no Quaternary sediment covering the faults. According to the types of faulting and the characteristics of sediments, two dating methods were used to date the ages of faulting events on the Gaoliying fault in the region from Tuoli to Yongdinghe River, Beijing. Thermoluminescence dating method is suitable to dating eolian deposits, such as loess, and thus is used to date the loess samples affected by faulting or deposited after faulting. Electron Spin Resonance (ESR) dating method is currently the most reliable method to date fault gouge, and thus is used to date the ages of fault gouges collected from Xinzhuang and Dayuanshang villages, respectively. Based on the ages of faulting, it is coucluded that at least 3 faulting events had occurred on the Gaoliying fault at 270～360ka B.P., 130～140ka B.P and 1.8～4.2ka B.P, respectively.

The basic theory and the test way of the interwell motitoring technique based on the electrometric method are presented. By using the application cases in the Daqing oil field, the Dagang oilfield, and a Shanxi coal mine, it is demonstrated that this technique can play an important role in oil field development, the evaluation for technologic measures and exploration of coal bed gas. Its usefulness and popularization in the future are also described.

In this paper,the techniques and applications of SAR interferometry are introduced. After a brief historical review,geometric implementations and important processing techniques of SAR interferometry are described. Besides,this paper illustrates technical flowchart for the spaceborne INSAR processing chain and recommends the measurement of coeismic displacements Landers earthquake by means of INSAR. This paper shows INSAR possess a good application perspective in extracting three dimensional information of the Earth’s surface.

Fault movements tend to result in the variation of landscape and water system regime, which can be displayed directly or indirectly on TM images through color and spatial texture features. Data image processing techniques were used to extract and analyze the water system features,texture features and the water-bearing information of Xianshuihe region. Detailed study was made on the geometric morphological features and tectonic geological background of Xianshuihe active fault zone.

The structural environment and geometric features are important basic data for study of earthquake preparation in the Xianshuihe active fault zone. This paper analyses the structural and geometric features of Xianshuihe active fault by collecting,processing and explaining aeromagnet-ic data and data from pioneer's works,studies the structural environment,especially the deep-seated structure of Xianshuihe active fault, reveals the relation between the structural geometric features and the deep-seated structure,and discovers an circular magnetic body related to earthquake.