The tectonic belt stretches approximately 400km from Lushan County to Wenchuan County in an east-west direction. The Longmenshan fault zone can be geometrically divided into several sections, including the Houshan Fault, the Central Fault, the Qianshan Fault, and the Foreland Basin(Chengdu Plain)Deformation Zone. The Central Fault is the main segment of the active tectonic belt in the Longmenshan region, and the Yingxiu-Beichuan Fault is one of the most active segments within this central section. The Yingxiu-Beichuan Fault has experienced numerous moderate and strong earthquakes throughout its history, including the Wenchuan earthquake 2008. The 2008 Wenchuan earthquake was ahigh destructive natural disaster that profoundly impacted the Chinese mainland, leading to significant economic losses and casualties. This earthquake caused extensive building collapses, leading to the loss of tens of thousands of lives, and triggered severe secondary geological disasters such as landslides, rockfalls, and mudflows, severely affecting the normal operation of transportation and communication infrastructure. The Yingxiu-Beichuan Fault was one of the key surface rupture zones during this earthquake. However, there is still some uncertainty about the slip rate of this fault.

The Baisha River segment examined in this paper is located in the southern part of the Yingxiu-Beichuan Fault, measuring approximately 14km long. This area contains 14 fractures of varying lengths and complex geometric structures, forming a fracture zone that reaches a maximum width of nearly 300m. The overall orientation of the rupture zone is about 50 degrees; however, the orientation of each small secondary rupture varies, with differences ranging from 0 to 90 degrees. The coseismic displacement along the Baisha River section displays complexity and diversity. The thrust movement primarily occurs on the northern and western walls, with some local thrust faults. Additionally, the strike-slip motion is predominantly right-lateral, exhibiting a maximum horizontal displacement of approximately 4.8m, although some local areas show left-lateral displacement.

Previous studies have employed various techniques, such as geology and geodesy, resulting in a wide range of slip rate estimates from 0.07mm/a to 1.1mm/a. The slip rate of fault is a crucial factor for analyzing the characteristics of fault activity and for studying regional kinematics and dynamic mechanisms. According to river terrace longitudinal profiles estimates, the fault has a vertical slip rate of about 0.3mm/a to 0.6mm/a. Estimates based on displaced landforms indicate a vertical slip rate between 0.07mm/a and 1.1mm/a. According to GPS observations, the horizontal slip rate in the Longmenshan fault zone has a limit of 2mm/a, but the slip rate of individual faults is lower than 0.7mm/a.

In recent years, remote sensing techniques have been extensively utilized to study surface rupture zones, particularly during significant seismic events. This paper primarily employs aerial and QuickBird satellite images captured before and after the earthquake. The resolution of the aerial images is nearly 1m, while the QuickBird satellite images have a resolution of 0.6m, both of which allow for precise interpretation of tectonic landforms. River terraces consist of terraced units, including terraced surfaces, steep terraces, terrace fronts, and terrace backs. As geomorphic markers that are relatively easy to identify and measure, river terraces are among the most essential geomorphic units in the quantitative study of active tectonics. They also serve as crucial geological relics documenting Quaternary tectonic movements and climate changes. By examining river terraces and their deformations, researchers can discuss the timing and scale of tectonic activity, making this a long-term area of research.

This paper focuses on the Baisha River section, situated in the southern part of the Yingxiu-Beichuan Fault. We employed geological and geomorphological methods along with optically stimulated luminescence dating, remote sensing interpretation, field investigations, and data analysis to assess the slip rate of the Baisha River section of the Yingxiu-Beichuan Fault within the Longmenshan fault zone. Additionally, we analyze the spatio-temporal variation characteristics of this slip rate. This study constrains the slip rate of the Baishahe segment of the Yingxiu-Beichuan Fault in the Longmenshan fault zone using 10 terrace cross-sections and terrace ages. The results indicate that the Yingxiu-Beichuan Fault Baisha River segment has a vertical slip rate since the Late Pleistocene ranges from(0.10±0.02)mm/a to(0.30±0.05)mm/a. Considering that only one event, the 2008 Wenchuan earthquake, is associated with the T1 terrace, we believe the calculated rate based on the dislocation and age of the T1 terrace may significantly deviate from reality. If we exclude the sliding rate of the T1 terrace, the vertical slip rate since the late Quaternary ranges between(0.10±0.03)mm/a and(0.30±0.05)mm/a. The linear fitting results indicate that the average vertical sliding rate since the late Quaternary is approximately 0.19mm/a.

These findings provide fundamental data for understanding the seismogenic structure of the Wenchuan earthquake and the overall characteristics of the Longmenshan fault zone, as well as for assessing its long-term seismic hazard.

Bedrock normal fault scarps, as classical topographic features and geomorphological markers along mountain range fronts, form in consolidated bedrock due to faulting in extensional settings. They generally preserve more complete records of paleo-earthquakes than fault scarps in unconsolidated sediments. With the development of technologies such as fault surface morphology measurement and terrestrial cosmogenic nuclide dating, bedrock fault planes have become a nice object for paleo-earthquake study in bedrock areas. The reconstruction of paleo-seismic history from a bedrock fault scarp in terms of the times, co-seismic slips and ages by a combination of quantitative morphological analysis, TCNs dating and other physical/chemical index has been proven feasible by several previous studies.

However, this success heavily relies on a suitable site selection along the bedrock fault scarp because erosional processes can exhume the bedrock fault surface, and the sedimentary processes can bury the bedrock fault surface. Namely, non-tectonic factors such as gully erosion, sediment burial, and anthropogenic activity make bedrock fault planes difficult to record and preserve paleo-seismic information.

Therefore, to successfully extract paleo-seismic information from the bedrock area, it is necessary to select suitable study points along the bedrock fault scarp in advance. Traditional survey and mapping methods are time-consuming and labor-intensive, and it is difficult to understand bedrock fault scarps. The resolution of satellite images cannot obtain the fine structure of bedrock fault scarps. Small unmanned aerial vehicle(sUAV), combined with Structure-from-Motion(SfM)photogrammetry has emerged over the last decade. It is used as an established workflow in acquiring topographic data by filling the spatial gap between traditional ground-based surveys and satellite remote sensing images. As a low-altitude photogrammetry technology, it can quickly obtain high-precision three-dimensional surface structures of bedrock fault scarps.

In this paper, taking the Majiayao bedrock fault scarp at the northern foot of Liulengshan in Shanxi Rift as an example, the high-precision and three-dimensional topographic data of the bedrock fault was obtained by using sUAV combined with SfM photogrammetry technology. The high-resolution and high-precision images of tectonic landforms can be obtained conveniently and efficiently by sUAV survey. The sUAV-obtained photos can be further processed by the SfM photogrammetry for generating a digital 3D structure of the bedrock fault scarp with true or shaded color.

The non-tectonic factors such as rock collapse, sediment burial, and gully erosion along the bedrock fault scarp are identified by interpreting the 3D model of the bedrock fault scarp. The profile shape characteristics of the erosion, burial and tectonic fault scarps are summarized through fine geomorphological interpretation and fault profile analysis. For the erosion profile, the hanging wall slope is down-concave, showing that the fault surface below the ground surface has been partially exposed. For the bury profile, the hanging wall slope shows an obvious concave-up shape, indicating that the lower part of the bedrock fault surface has been partially buried by the colluvium. For the tectonic profile, the hanging wall slope shows a smooth and stable slope, showing the exhumation of bedrock fault scarp is controlled purely by tectonics. Finally, the study sites suitable for paleo-earthquake study on bedrock fault surfaces were selected, showing the important role of sUAV aerial survey technology in the selection of paleo-earthquake study sites in bedrock areas.

This study illustrates that based on the high-precision three-dimensional surface structure of the bedrock fault plane from sUAV aerial survey, the existence of non-tectonic factors such as gully erosion, sedimentary burial and bedrock collapse can be clearly identified. These non-tectonic sites can be excluded when selecting suitable sites for paleo-earthquake study indoors. The shape analysis of bedrock fault scarp is also helpful to determine whether the bedrock fault surface is modified by surface process and suitable for paleo-seismic study. The sUAV aerial survey can play an important role in paleoseismic research in the bedrock area, which can accurately select the study points suitable for further paleo-seismic work in the bedrock area.

With the development and breakthrough of a series of techniques such as the fault surface morphology measurement, the geochemical element determination and Quaternary dating methods, it becomes possible to study paleo-earthquake using information recorded by the bedrock fault surface. At present, more and more scholars domestic and overseas have carried out a large number of paleo-earthquake studies on bedrock fault surfaces in different professional perspectives and have achieved a series of innovative results. This paper systematically introduces the development history, the current situation and the basic principles and applications of paleo-earthquake study on bedrock fault surface. Moreover, after the thorough discussion of the existing problems in paleo-earthquake research of bedrock fault surface, some suggestions for optimizing the current work are proposed. Finally, on the basis of comparison of the characteristics, advantages and disadvantages of various research methods, the prospects and development trends of the bedrock fault paleo-earthquake study are predicted. Lots of weaknesses and limitations in the current study are pointed out in this paper:Firstly, for the method of faullt surface morphology measurement, different morphological expression parameters exist nowadays, however, their advantages and disadvantages are unknown. Secondly, the TCNs method still has a large uncertainty in the age determination of the paleo-earthquake, and the mature cosmogenic nuclides dating methods is too few to meet the dating requirements of different lithologic fault surfaces. Besides, a reliable relationship between relative dating parameters such as morphologicl and physicochemical characteristics and the absolute dating method such as TCNs are not closely established to build a reliable chronology framework. The last but not the least, the lack of mechanical research on the physical and chemical biological processes that the bedrock fault surface experienced before and after the faulting and exposure, and insufficient multi-method comprehensive comparison are also the obstacles for the paleo-earthquake study on bedrock fault surface. It is suggested that in the future study of paleo-earthquakes on bedrock fault surfaces, more attention should be paid to the following aspects:Firstly, strengthen the evaluation of the reliability, applicability and accuracy of the parameters of each morphological model in time and improve the mathematical model of current dating techniques, optimize the mechanism of cosmogenic nuclide production, and introduce new high-precision dating technology timely; Secondly, strive to establish a reliable age framework between relative dating index(X)and absolute dating age(T)regionally; In addition, the morphological structure and mineral compositions of bedrock fault surface are analyzed proactively on the microscopic scale, and the mechanical study is conducted on a series of physical, chemical and biological processes that the fault surface experienced before and after the exposure. At last, comprehensive and comparative research need to be conducted by the multi-disciplinary and multi-method approaches. In conclusion, the paleo-earthquake study on the bedrock fault surface is going through the processes from the qualitative description to the quantitative expression, from the single-disciplinary method to the multi-disciplinary integration, from the exploration of a certain technical index to the comprehensive application of multi-source data technology. The combination of relative dating indicators(X)and absolute dating(T), and putting more emphasis on the mechanical study on the microscopic scale are the development trends of paleo-earthquake study on the bedrock fault surface. The close combination of the paleo-earthquake study of the bedrock fault surface with the traditional method of trenching conducted in the Quaternary sediment region is considered to help more effectively reconstruct a more complete paleo-earthquake sequence and the faulting history on the active fault zone, thus a more reasonable evaluation of the regional seismic hazard can be obtained.

The quantitative analysis of morphologic characteristics of bedrock fault surface is a useful approach to study faulting history and identify paleo-earthquake. It is an effective complement to trenching technique, specially to identifying paleo-earthquakes in a bedrock area where the trenching technique cannot be applied. This paper focuses on the Luoyunshan piedmont fault, which is an active normal fault extending along the eastern boundary of the Shanxi Graben, China. There are a lot of fault scarps along the fault zone, which supply plentiful samples to be selected to our research, that is, to study faulting history and identify paleo-earthquakes in bedrock area by the quantitative analysis of morphologic characteristics of fault surfaces. In this paper, we calculate the 2D fractal dimension of two bedrock fault surfaces on the Luoyunshan piedmont fault in the Shanxi Graben, China using the isotropic empirical variance function, which is a popular method in fractal geometry. Results indicate that the fractal dimension varies systematically with height above the base of the fault surface exposures, indicating segmentation of the fault surface morphology. The 2D fractal dimension on a fault surface shows a ‘stair-like’ vertical segmentation, which is consistent with the weathering band and suggests that those fault surfaces are outcropped due to periodic faulting earthquakes. However, compared to the results of gneiss obtained by the former researchers, the characteristic fractal value of limestone shows an opposite evolution trend. 1)The paleo-earthquake study of the bedrock fault surface can be used as a supplementary method to study the activity history of faults in specific geomorphological regions. It can be used to fill the gaps in the exploration of the paleo-earthquake method in the bedrock area, and then broaden the study of active faults in space and scope. The quantitative analysis of bedrock fault surface morphology is an effective method to study faulting history and identify paleo-earthquake. The quantitative feature analysis method of the bedrock fault surface is a cost-effective method for the study of paleo-earthquakes in the bedrock fault surface. The number of weathered bands and band height can be identified by the segment number and segment height of the characteristic fractal dimension, and then the paleoearthquake events and the co-seismic displacement can be determined; 2)The exposure of the fault surface of the Luoyunshan bedrock is affected and controlled by both fault activity and erosion. A strong fault activity(ruptured earthquake)forms a segment of fault surface which is equivalent to the vertical co-seismic displacement of the earthquake. After the segment is cropped out, it suffers from the same effect of weathering and erosion, and thus this segment has approximately the same fractal dimension. Multiple severe fault activities(ruptured earthquake)form multiple fault surface topography. The long-term erosion under weak hydrodynamic conditions at the base of the fault cliff between two adjacent fault activities(intermittent period)will form a gradual slow-connect region where the fractal dimension gradually changes with the height of the fault surface. Based on the segmentation of quantitative morphology of the two fault surfaces on the Luoyunshan piedmont fault, we identified four earthquake events. Two sets of co-seismic displacement of about 3m and 1m on the fault are obtained; 3)The relationship between the fault surface morphology parameters and the time is described as follows:The fractal dimension of the limestone area decreases with the increase of the exposure time, which reflects the gradual smoothing characteristics after exposed. The phenomenon is opposite to the evolution of the geological features of gneiss faults acquired by the predecessors on the Huoshan piedmont fault; 4)Lithology plays an important role in morphology evolution of fault surface and the two opposite evolution trends of the characteristic fractal value on limestone and gneiss show that the weathering mechanism of limestone is different from that of the gneiss.

Since the 1970s, active tectonics has advanced from qualitative research to quantitative research. Many researchers focus on which qualitative parameters to obtain and how to obtain them. It is usually accepted that the following parameters are necessary for quantitative descriptions of active faults:length of a fault or segment, displacements, slip rates, and paleo-earthquake events. Because of the complex nature of problems concerned and limited capability of human recognition, there are still some errors and uncertainties in these parameters. Tectonic geomorphology provides a useful tool to help solve the problems above. Tectonic geomorphology could record long-term accumulation of tectonics, and quantize them by relevant parameters. Tectonic movements have been exerting significant influence upon formation of topography and landforms, and such processes are usually extremely slow over very long time which cannot be documented by human history and any instruments. Observations, especially direct measurements of various features of geomorphology can reveal details of tectonic movement, including slip on active faults. In the early time, such studies were usually limited in one or two parameters of geomorphology to characterize active tectonics. With rapid development of computer and DEM technologies, it is possible to use multiple parameters of landforms to describe regional tectonic activity. Previous work in this aspect focused on large scales, while a little on small scale faults or individual faults. And existing studies are mostly concerned with normal or thrust faults dominated by vertical motion. In this paper, we focus on the Nantinghe Fault, which is strike-slip fault. Based on high resolution DEM extracted from ALOS data, we extract 180 drainages along the Nantinghe Fault. Based on the relationship between deflection angles and faulting, we analyze the segmentation and activity. Using the distribution patterns of the factors, this study examines the geometry and activity of the Nantinghe Fault, which were obtained from comprehensive remote sensing interpretation and field investigations. The results provide an example for research on the relationship between faulting and landforms.

Tsunami is one of the most devastating natural coastal disasters. Most of large tsunamis are generated by submarine earthquakes occurring in subduction zones. Tsunamis can also be triggered by volcano eruptions and large landslides. There are many records about "sea-overflow" in Chinese ancient books, which are not proved to be tsunamis. Tectonics and historical records analysis are import to forecast and prevention of tsunami. Consider the tectonic environment of the China sea, the possibility of huge damage caused by the offshore tsunami is very small. And the impact of the ocean tsunami on the Bohai sea, the Yellow sea, and the East China sea is also small. But in the South China Sea, the Manila subduction zone has been identified as a high hazardous tsunamigenic earthquake source region. No earthquake larger than M_W7.6 has been recorded in the past 100a in this region, suggesting a high probability for larger earthquakes in the future. If a tsunamigenic earthquake were to occur in this region in the near future, a tragedy with the magnitude similar to the 2004 Indian Ocean tsunami could repeat itself. In this paper, based on tectonics and historical records analysis, we have demonstrated that potential for a strong future earthquake along the Manila subduction zone is real. Using a numerical model, we have also shown that most countries in the South China Sea will be affected by the tsunamis generated by the future earthquake. For China, it implies that the maximum wave height over 4.0 meter on China mainland, especially the Pearl River Estuary. But the island, local relief maybe influence the maximum wave. But it takes nearly 3 hours to attack China mainland, if there is the operational tsunami warning system in place in this region, should be greatly reduced losses. And the simulated results are conformable to historical records. It indicates that the tsunami hazards from Manila trench to China mainland worthy of our attention and prevention.

On 8 August 8 2017, an M_S7.0 earthquake occurred in Jiuzhaigou County, Sichuan Province. Field geological investigations did not find any co-seismic surface rupture in the epicenter area, implying that the seismogenic structure is likely a hidden active fault. Based on the results of the relocated aftershocks, the seismogenic fault was simulated and characterized using the SKUA-GOCAD software. The three-dimensional model of the seismogenic fault was preliminarily constructed, which shows that the main shock of the Jiuzhaigou M_S7.0 earthquake occurred at the sharp bending area of the fault surface, similar to the geometry of the active fault that generated several major earthquakes in the Songpan area during 1973-1976. Our study suggests that high seismicity of this area may be closely related to the inhomogeneous geometry of the fault surface. In this work, we collected the historical earthquakes of M ≥ 6.5, and analyzed the geometric and kinematic features of the active faults in the study area. A three-dimensional fault model for the 10 main active faults was constructed, and its limitation in fault modeling was discussed. It could provide evidence for analyzing the seismotectonics of historical earthquakes, exploring the relationships between earthquakes and active faults, and predicting major earthquakes in the future.

Fault traces contain abundant information associated with the fracture process and mechanism, so an accurate and quantitative description of their geometric characteristics is of great significance to perceiving the generation and development of faults. We collected 52 co-seismic surface ruptures and 300 active fault traces from across the world to analyse their geometric characteristics by the method of power spectrum density. Our results show that (1)the average power spectrum density has a distinct three-segment charateristic in the frequency domain. In the low frequency domain it represents the geometric characteristics of the boundary of tectonic block. In the medium frequency domain, the power spectrum density reflects the processes of lateral growth and connection of secondary faults, and the turn point on the 100 meters scale represents the effective resampling length, below which the power spectrum density characteristics are meaningless. (2)In the middle and high frequency domains, the power spectrum density curves of co-seismic surface ruptures show that there are obvious differences in roughness among three fault types, i.e. reverse > normal > strike-slip, which indicates that the geometric characteristics of co-seismic surface ruptures are controlled by the fault types. (3)Compared with co-seismic surface ruptures, active fault traces have much lower power spectrum density, indicating the roughness of active fault traces becomes lower with increasing numbers of rupturing events and the lengths of active history, i.e., the fault roughness is inversly proportional to its maturity.

The Huoshan piedmont fault is a small watershed region in Shanxi Province. We utilized the high-resolution DEM data and the stream-power incision model which describes the relationship between the tectonic uplift and fluvial incision to analyze the S-A double-log graph, concavity index (θ)and steepness index (logk_s) of the 64 channels across this fault and discuss their responses to the tectonic movement of the fault. The results show that (1)the S-A double-log graphs all exhibit an obvious convex form, which is the direct expression of the response to the situation that the bedrock uplift rate is higher than the fluvial incision rate. (2)All of the concavity index (θ)values of 64 channels are lower than 0.35 with an average value of 0.223, much lower than the empirical value (0.49)of the rivers in steady state. These low values are the quantitative reflections of the channels' slightly concave profiles. Meanwhile they imply that these channels across the fault are very young. There is no enough time for them to adjust the profiles through the fluvial incision to the steady state because of the fault's frequent and strong tectonic movements. (3)The steepness index values of the channels located in the Laoyeding Mt. are highest, while they are lower in the northern and southern mountains. Moreover, the steepness index values of the channels in the northern mountains, on average, are higher than those of the channels in the southern mountains. To a certain extent, this distribution of the steepness index corresponds to the difference in the uplift rates of the Huoshan piedmont fault. It means that the uplift rate of the middle fault segment in the Laoyeding Mt. is highest, and the uplift rate of the northern segment is higher than that of the southern segment.

The geological structure exposed by paleoearthquake trenches is the key material to the right cognition of fault activity and paleoearthquake. However, paleoearthquake trenching inevitably destroys active tectonic geomorphic evidence and trench exposures are usually difficult to reserve. The conventional process of recording the delicate geological information, manually constructing photomosaics by image-editing software, is time-consuming and produces undesirable artificial distortions. Herein, we explored the process of constructing trench orthophotomosaics and the 3D image model using the Image-based Modeling technology and applied it to the Liutiaohe trench across the Tianqiaogou-Huangyangchuan Fault, Gansu Province. Based on the 3D image modeling and orthophotomosaic, we firstly constructed the control points and scale bars on cleaned trench walls and collected photos of all sections of the trench with a digital camera in the field, and then reconstructed the 3D model of the trench through the Agisoft PhotoScan, an efficient image-based modeling software, and finally yielded the 3D image model of the trench and othophotomasaics of the trench exposures. The results show that the automated workflow can produce seamless, sub-millimeter-level high-resolution photomosaics more quickly, with precision in the centimeter range, and the 3D image model is of great help to identify strata and geological structures in trenches with much lower capital and labor costs and low expertise levels compared with LiDAR, meanwhile, the 3D archive benefits the share and communication and even allows future reinterpreting the site using new insights.

Geomorphology could record long-term accumulation of tectonic movement and quantify it by relevant parameters.But because the influences of other factors such as climate and lithology,how to use the relevant parameters to reveal the relationship between geomorphology and tectonics is a research hot spot.In this paper,we utilize the variogram method and the cellular fractal model to estimate parameters such as the fractal dimension (D) and ordinate intercept (γ) from the SRTM3 DEM using a moving window operation.We compare the distribution characteristics of the parameters in different climate and lithology.The results indicate that the correlation between the parameters and lithology or climate is very poor.The fractal dimension (D) reveals a very good correlation with tectonics,which is low in tectonically inactive areas and high in active areas.It implies that fractal dimension (D) may be a new method for research of regional tectonic movement.

Taking tectonic geomorphology of southeastern Ganzi-Yushu Fault zone as the research object,and based on remote sensing interpretation,the paper investigates the late Quaternary activity of the southeastern segment of Ganzi-Yushu Fault zone through trenching and detailed field investigation on several typical sites. We analyze the landscapes and calculate the late Quaternary slip rates along the fault zone at the sites in Shengkang township,Renguo township,Cuoa township,and Ria township,respectively.The horizontal and vertical slip rates are (7.6?0.5)mm/a and (1.1?0.1)mm/a at Shengkang township,(8.0?0.3)mm/a and (1.1?0.1)mm/a at Renguo township. And horizontal slip rate of Cuoa township is (10.3?0.4)mm/a.The horizontal and vertical slip rates of Ria township are (10.8?0.8)mm/a and (1.1?0.1)mm/a,respectively. Both trenches at Renguo township and Cuoa township have revealed several paleoearthquake events. Though there are some differences in fault tectonic styles revealed between the two trenches,the fault motion on this segment is of strike-slip with a certain amount of thrust component on the whole. Associated with the analysis of paleoearthquake events and slip rate,it is found that the southeastern Ganzi-Yushu Fault zone is subject to intensive activity since late Quaternary,especially since Holocene.

Daliangshan Fault zone constitutes an important part of the eastern boundary of Sichuan-yunnan active block. The studies of slip rate along the fault is not only significant to the crust movement and deformation pattern on the southeast edge of Tibetan Plateau,but also has great value in seismic hazard assessment and mid-and long-term forecasting of earthquake of the Daliangshan region. Through detailed field work along the south segment of Daliangshan Fault zone,namely the Butuo Fault and the Jiaojihe Fault,and based on accurate RTK(GPS)survey for the alluvial fans and activity dating,we suggest that left-lateral slip rate of the south segment of the fault zone is between 2.5～4.5mm/a,and the slip rate of Jiaojihe Fault is slightly higher than that of the Butuo Fault. Due to partitioning of part of the strike-slip component on the Daliangshan Fault zone,there is an obvious deficit in the displacement and slip rate on the Anninghe-Zemuhe Fault,compared to the Xianshuihe and Xiaojiang Faults. Comparing to the slip rates between Daliangshan Fault and Anninghe-Zemuhe Fault,it is found that they have similar horizontal slip rate,indicating the seismicity level of the Daliangshan Fault will not be lower than that of Anninghe-Zemuhe Fault. As the Daliangshan Fault gradually replaces the role of Anninghe-Zemuhe Fault in the Xianshuihe-Xiaojiang Fault system,the seismicity on the Daliangshan Fault zone will increase,and the Dalianghan region will have a higher risk of earthquake damage.

When a reach of a stream is steepened with respect to the adjoining reach,it defines a topographic knickpoint.A knickpoint is supposed to be a response to the base-level changes,and the base-level of a drainage basin is influenced by the fault movement.The formation of a knickpoint on a gully long-profile,whose base-level is the footslope of the fault scarp,is associated very closely with the vertical movement of a fault,therefore,the ages of paleo-earthquake events can be estimated by the knickpoint series along the longitudinal profile of a gully.We have made a case study of the Huoshan Mts.Piedmont Fault,and extracted tens of gullies across the fault based on the high-resolution DEM data and identified out knickpoints in 23 gullies.There are 5 gullies with only one knickpoint which are laid on the fault.And there are two gullies having two knickpoints with the latest one laid on the fault.The positions of these knickpoints and their higher height ranging from 4～9m imply that there are several knickpoints superposed together and the knickpoints have not migrated upstream.The other 16 gullies respectively have 2～3 knickpoints.The latest knickpoints have been migrated upstream to a distance of 40～70m from the fault.The knickpoints of intermediate ages are at a distance of 150～150m upstream from the fault and the oldest ones at a distance of 300～500m.Under the conditions that the latest knickpoints are associated with the 1303 M_W8.0 Hongdong earthquake(Event Ⅲ)and that the gullies keep the same rate of headward erosion during the Holocene,Event Ⅱ is estimated to take place during 3336～2269a B.P. and Event Ⅰ is estimated to take place during 3336～2269a B.P. , respectively.The recurrence of events is about 1500～2600a.These results are consistent with those obtained through the trench investigations.