The research on the activity history of seismogenic faults is the basis for the research and prevention of natural disasters such as earthquakes and landslides. Dating has always been the focus and difficulty of the research on the activity history of fault. However, it is difficult to carry out geochronological surveys for faults and landslides evolution in the carbonated areas due to the lack of suitable dating materials, such as the region of south-eastern Tibet where the main lithology is carbonate bedrock. The exposure dating of cosmogenic nuclides is the main method to determine the activity history of fault. But the cosmic nuclides  36Cl and ¹⁴C dating methods still have some limitations, such as the complex generation mode of  36Cl being caused by fission under the action of cosmic rays, neutron capture and meson action, the yield of  36Cl being changed with chemical composition change of dating mineral(the range of 2-171atom/g·a), and so on. More importantly, the rapid rock weathering in the carbonate bedrock area is a big problem. Once exposed, the bedrock will start rapid weathering and erosion and dissolution. Therefore, it is necessary to find new dating materials or dating methods in carbonate bedrock areas, especially in areas with little or no quaternary sediments. When a large landslide moves on the sliding surface of carbonate bedrock, heat is often generated due to high-speed friction, and then the dynamic metamorphism can occur easily on the sliding surface to form recrystallized carbonate, which can be used to determine the active time of faults.

Carbonate is one of the main materials for ESR dating. As early as the 1970s, Ikeya made the first electron spin resonance(ESR)dating study of carbonates using stalactite calcite. After that, many researches on the ESR signal characteristics of carbonate(such as coral, shell, aragonite, stalagmite and etc)were carried out, and the carbonate ESR dating then became one of the main methods in Quaternary chronology and had been widely used. The recrystallized carbonate on the fault friction surface and the sliding surface of the landslide is a newly discovered dating material. Although its main component is calcium carbonate, its origin is different from the carbonate materials commonly used in ESR dating(such as stalagmite, stalactite, etc.), so it is necessary to study its characteristics of ESR dating.

The characteristics of recrystallized carbonate collected from the fault friction surface of Jianchuan section on Lijiang-Xiaojinhe Fault(Yin et al., 2021)and the sliding surface of Qiaojia landslide which is located at the intersection of Xiaojiang Fault and Zemuhe Fault(Liu et al., 2023)have been studied, including microstructure, thermal annealing characteristics, sunlight bleaching characteristics, and compared with the previous dating results of AMS ¹⁴C and OSL on sediments. Yin et al.(2021)and Liu et al.(2023)analyzed and demonstrated the feasibility and reliability of the recrystallized carbonate ESR dating method used in the analysis of bedrock fault and landslide activity in the carbonate bedrock area, and established the recrystallized carbonate ESR dating technology.

Therefore, the ESR dating of recrystallized carbonate is an effective dating technology and can be used widely for the studying of activity history of faults and landslides in carbonate bedrock areas. This paper introduced the latest research progress of recrystallized carbonate ESR dating in the Carbonate rock area of southwest China by Yin et al.(2021)and Liu et al.(2023). In this paper, the requirements for sample collection and the range of dating were proposed which provide technical support for dating of key geological samples for research on fault and landslide activity history, engineering exploration, active structure, and seismic risk assessment in Carbonate rock bedrock area.

At 4:00am on October 11, 2018, under the influence of heavy and continuous rainfall, a large-scale rocky landslide occurred in the Baige village of Bolo Town, Jiangda County, Tibet Autonomous Region, which is located at the upper reach of the Jinsha River. During its sliding, the landslide body is cut out from the upper part of the high and steep slope and falls rapidly, and the lower rock mass is continuously scraped, which increases the volume remarkably. With the disintegration of the landslide mass, the landslide mass is transformed into a fast and remote debris flow sliding. The massive debris flow materials rapidly flowed down to block the Jinsha River, forming a barrier dam. Then the lake rose and flooded many roads. At 5:00pm on the October 12^th, the barrier dam was overtopped and gradually washed by the river to form a drainage channel. At 9:00am on the 13^th, the dam was completely flushed open, accomplishing the flood discharge and relieving the danger caused by the landslide. At 5:00pm on November 3, 2018, the trailing edge of the Baige landslide experienced a sliding rupture, which led to the debris flow, at a high speed, piled up the dam from the first landslide, and blocked the Jinsha River again. The height of the second barrier dam was 50m higher than the first one, forming a larger barrier lake. After the landslide occurred, the water level of the upper reaches of the barrier lake continued to rise, and Jiangda County, Boro Town, Baiyu County Jinsha Town and other towns on the upper reaches of the Jinsha River were flooded. After the second floodwater released, a large scale flood occurred in Jinsha River, which caused the flooding of cities and towns in the middle and lower reaches in Sichuan, Yunnan and other riverside areas, and destructed roads and bridges, posing a great threat to the lives and property of people and the safety of infrastructure such as hydropower stations. The water level of the dammed lake was lowered by artificially constructing a diversion channel to eliminate the danger of dam break and avoid the occurrence of greater flood hazards. On the basis of field investigation on the landslide site, it is found that after the first landslide, three potential unstable rock masses were found at the trailing edge and both sides of the landslide. According to radar monitoring, three potential unstable rock masses at the trailing edge of the landslide are still continuously deformed, with obvious activity, and there is a risk of blocking the Jinsha River again. The author was monitoring constantly the unstable rock of the trailing edge of the Baige landslide for 7.5 days adopting D-InSAR. The surveillance results indicate that there is a slight sliding on the upper side of the landslide and there are four major deformation regions on the upper edge of the landslide. Besides, four measuring data points, selected within the four major deformation areas, show that the deformation value is 200mm and the deformation rate on the landslide top reaches 300mm/day, which suggests that the current landslide is still not stable and there is the risk of blocking the Jinsha River by the landslide. This paper, using PFC2D, simulates the stability of unstable rock on the trailing edge of landslide under the influence of gravity, torrential rain, and earthquake and analyzes the landslide’s stability scientifically in terms of simulation results. The simulation results show that the slope only deforms slowly under static action, without obvious destabilizing sliding. The initial deformation of the slope is basically consistent with the results of radar monitoring displacement, indicating that the sliding body of the slope still has a sliding trend under static action, and is not stable. Under the action of heavy rainfall, with the increase of time step, the deformation and displacement of slope is also increasing. In the process of operation, tensile cracks gradually appear in the slope, and continue to develop until it is cut through, and instability failure occurs. The ground motion is input from the bottom of the slope model in the form of velocity. When the model is running, tensile cracks first occur at the back edge of the slope on the right side. As the shear failure occurs in the middle of the slope and the tensile crack at the back edge goes through, the whole slope becomes unstable and fails. But on the whole, it’s basically stable. The simulation results show that the unstable rock in the trailing edge of the landslide will still lose stability under the inducing factors such as heavy rainfall and earthquake. It’s necessary to take appropriate engineering measures such as slope cutting to control the unstable rock, and the real-time monitoring and early warning system should be set up to eliminate the hidden danger caused by the slide of unstable rock blocking the Jinsha River again in time. At the same time, this paper also provides reference significance for further understanding the development and evolution process, as well as the deformation failure mechanism of landslide and debris flow in alpine regions. It also provides theoretical guidance for emergency measures and disaster prevention and mitigation after a disaster happens.

Historical records with time information are useful for determining the time of earthquake events, while the investigation of historical damage phenomena such as earthquake-triggered landslides can help determine the magnitude of historical earthquakes by analyzing the correlation among historical earthquake-caused landslides, historical earthquakes and related active faults. A series of small basins were developed along the southern segment of the Xiaojiang Fault(XJF), with relatively flat and open topography and concentrated human activities. In most of the southern segment of the XJF, the terrain is relative flat, but some landslide accumulations are still clear, which are obviously different from the surrounding settings and are easy to be identified. Based on remote sensing interpretation and field investigations, landslides with different scales have developed in more than 10 locations along the southern segment of the XJF. Some of them are large with a volume of more than 1 million m³, and some are small with a volume of less than 100 000m³. They are the ancient landslides with a stable state. These landslides are mainly distributed in basins and their border areas with gentle terrain slopes. They are likely to be earthquake landslides rather than rainfall induced. The main scarp angles of these landslides are relatively concentrated, most of which are between 29~31 degrees, indicating that these landslides are caused by one geological event. We use light detection and ranging(LiDAR) measurement technology to obtain the digital elevation model(DEM)data of the landslide development section. The generated three-dimensional topographic shadow map presented in this paper suggests that there is a close relationship between these landslides and the latest surface ruptures of the southern segment of the XJF, indicating that these landslides should be triggered by the latest seismic event along the southern segment of XJF. The fault section was faulted in the latest earthquake events on the surface, triggering clusters of landslides. Based on the age test results of samples from the trench on the landslide body and historical literature data, the co-seismic landslides were triggered in 1606AD. According to the latest research results of the earthquake surface rupture zone in the southern segment of the XJF and empirical formula, combined with the comparative analysis on the intensity of geological disasters and the number of casualties of different earthquake cases, the authors re-assess the magnitude of the 1606 Jianshui earthquake and find that the magnitude of this historical earthquake could not be less than 7½(≥7.5). It means that the southern segment of the XJF, as a part of Xianshuihe-Xiaojiang fault(XSH-XJF) system, shows strong activity and has the ability to generate large earthquakes. GPS observations have verified that the crustal material on the southeastern margin of the Tibetan plateau rotates clockwise around the Eastern Himalaya Syntaxis(EHS), which requires a continuous left-lateral strike-slip fault system as the eastern boundary. The results presented in this paper are useful for deeper study of such an eastern boundary.

The neotectonic movement in the middle reaches of the Jinsha River is active and the earthquakes occur frequently. Lacustrine sediments are commonly distributed on both sides of the river with stable sedimentary environment, good horizontal continuity and relatively developed stratification, which are good carriers for recording paleo-seismic events. In this study, a large number of soft sedimentary deformation structures are found in the riverside lacustrine sediments in the Taoyuan Town area in the middle reaches of Jinsha River, with strong deformation and large scale. We focus on the comprehensive analysis of four soft-sedimentary deformation profiles. In which the profiled strata are mainly medium-fine sand and clay. And the soft sedimentary deformation structures mainly include sand liquefaction, rootless faults, clay lumps and folds.
Causes analysis: In the profiles of soft sedimentary deformation structures, there are medium and fine sand layers whose thickness is from thick to super thick. Sedimentary bedding has not been observed in the sand layer; and a large number of clay debris or lumps are involved in the sand layer, which are often filled between the adjacent clay lumps; and there are quicksand channels in the sand layer. All the features indicate that the sand layer in the study profiles has been liquefied. In the study profile, we found that the soft sedimentary deformation structure has the following characteristics: The faults found in the study profile extend downward and terminate in the lower liquefied sand layer and a large number of clay lumps. There are clay lumps in the place where the clay fold structure develops, and a large number of liquefied sand bodies are filled between the fold structures. The deformation structures in the profiles are not contrastive in terms of extension, chaotic deformation characteristics and obvious stress direction. Based on the characteristics of sand liquefaction and clay deformation in the above profile, it is inferred that the deformation structure in the profile is mainly due to sand liquefaction. The liquefaction strength of sand layer determines the deformation degree of clay layer.
Trigger factors analysis: There are many factors that can trigger the liquefaction deformation of the unconsolidated sediment, such as flood, freeze-thaw, collapse and earthquake, which can cause the liquefaction deformation of the sediment under certain conditions. In this paper, the possible trigger factors are analyzed based on the combination of the structural characteristics of soft sedimentary deformation, sedimentary environment and geological background of the area. First the stratigraphic characteristics also reflect the hydrostatic sedimentary environment at that time. The soft sedimentary deformation on such a large scale could not be mainly caused by the disturbance of lake waves. The research profiles are located at a sheltered bay with weak hydrodynamics, and no alluvial strata have been found in the upper part of the soft sedimentary deformation stratum. Moreover, the soft sedimentary deformation structure caused by flooding is often a small-scale curly layered structure, which has a large difference with the deformation structure and scale in the study profiles. This suggests that alluvial and diluvial events are not the main triggering factors of the deformation. Although the landslide is likely to occur near the study area, no trace of bedrock landslide is found near the study profiles. Therefore, the invasion of bedrock landslide into the sedimentary layer cannot be the triggering factor. Moreover, the occurrence of lacustrine sedimentary layer is nearly horizontal, which is a relatively stable sedimentary state, and it is impossible to form such a large-scale slump structure due to its own gravity effect. And we don't find any sliding surface in the profiles. Therefore, the collapse is ruled out. According to the geological background and geological survey of the study area, this area does not have the conditions triggered by volcanism, glaciation and freeze-thaw. Because of the active neotectonic movement and frequent earthquakes in the study area, and seismic actions are the main trigger factors for liquefaction. So it is considered that seismic action may be the main trigger factor for the strong liquefaction deformation in the study area. According to the previous studies, the relationship between the soft sedimentary deformation structure, the liquefaction thickness and the seismic strength is discussed, the magnitude of this ancient seismic event probably reached 7 or higher.
There are sand layers in the section of “soft sedimentary deformation structure” caused by earthquake, the lower stratum is sand layer and the upper stratum is clay layer. The thickness and deformation strength of the lower sand layer determine the strength of the deformation structure of the overlying clay layer. The upper and lower surface of the sand layer are undulating, and there are clay lumps in the sand layer. The deformation structure of clay layer is complex and there is no obvious deformation rule.

The surface ruptures produced by the 2016 M_W7.8 Karkoura earthquake, New Zealand are distributed in a belt with~170km long and~35km wide, trending generally in the NE-SW direction. There are at least 12 faults on which meter-scale displacements are identified and they were formed across two distinct seismotectonic provinces with fundamental different characteristics(Hamling et al., 2017; Litchfield et al., 2017). Although the trending directions of the seismic surface ruptures vary greatly at different locations, the ruptured faults can be generally divided into two groups with the NE to NEE direction and the NNW to N direction, respectively. The faults in the NNW-near NS direction are nearly parallel with 40~50km apart and featured by reverse movement with the maximum displacement of 5~6m. The faults in the NE-NNE direction, with the maximum of 25~30km apart are not continuous and featured by the dextral strike slip with the largest displacement of 10~12m. Even if some faults along the NE-NEE direction are end to end connected, their strikes differ by about 30°. The combination styles of the strike-slip fault surface ruptures along the NE-NEE direction can be merged into 3 categories, including en-echelon, bifurcation and parallel patterns. The scales of the fault surface ruptures with the same structural style could be obviously different in different areas, which results in significant changes in the widths of deformation zone, from tens of meters to hundreds of meters. En-echelon distributed surface rupture(section)can appear as a combination belt of meter-scale to dozens of meter-scale shear fracture with bulge and compressional shear fractures, and also can be characterized by the combination of the left-step en-echelon tensile shear fractures with a length of more than one hundred meters. The step-overs between surface rupture sections are clearly different in sizes, which can be dozens of meters, hundreds of meters to several kilometers. The spacing between parallel surface ruptures can be several meters, dozens of meters to several kilometers. Besides, as one of the prominent characteristics, the seismic surface ruptures caused by the Karkoura earthquake broke through the known distribution pattern of active faults. The surface ruptures can occur either on the previously thought inactive or unmapped faults, or break through the distribution range of previously realized active faults in the striking or lateral direction. The basic features about the distribution and widths of the surface ruptures induced by the 2016 M_W7.8 Karkoura earthquake, New Zealand presented in this paper might be helpful for understanding some seismic problems such as complex corresponding relationship between the active faults and the deep seismogenic structure, and the necessary measurements for engineering crossing active faults.

The southern segment of the Xiaojiang Fault (SSXF) is located at the intersection of the Xianshuihe-Xiaojiang Fault and Red River-Ailao Shan fault systems in the southeast margin of the Tibetan plateau. Based on the interpretation of remote sensing image, the SSXF clearly shows the linear feature and continuous distribution as a single, penetrating fault. It has a total length of about 70km, trends generally about 20° to the northeast and protrudes slightly in the middle to the east. A typically geomorphologic phenomenon about the synchronous left-lateral dislocation of ridges and gullies can be found at Liangchahe, Longtan Village along the SSXF. The distribution of faults, the sedimentary features, attitude variance and the primary dating results of the offset strata in the trench section across fault sag ponds reveal three paleoseismic events rupturing obviously the surface, which demonstrates that the SSXF has the ability of recurrence of strong earthquakes. High-precision topographic map about two gullies and the platform between them with synchronous dislocation is acquired by using the Trimble 5800 GPS real-time difference measurement system. The dislocation is (18.3±0.5)m. As the top geomorphologic surface between the above two gullies and their adjacent area, the terrace surface T₂ stopped accepting deposits at ~2606a, based on the linear regression analysis of three dating data. According to the geological method, a sinistral strike-slip rate of (7.02±0.20)mm/a on the SSXF in the Holocene is obtained, which has a good consistency with the results provided by using GPS data. The preliminary results about the Holocene activity and slip rate of the SSXF demonstrate that the southward or south-southeast motion of the Sichuan-Yunnan block in the SE Yunnan region has not been absorbed by the possible shortening deformation and the sinistral strike-slip rate of the SSXF has not been drastically reduced. The SSXF is a Holocene fault with obvious activity. This preliminary understanding provides some basic geological data for the seismic risk evaluation of the SSXF in the future, and for the establishment and inspection of the seismotectonic model about the Sichuan-Yunnan block.

Thin-layered clay-rich fault gouges were observed on the near-surface fault plane of the Yingxiu-Beichuan Fault during the 2008 M_S 8.0 Wenchuan earthquake. In this paper,the authors investigate the microstructural features and mineralogy of the clay-rich fault gouge samples based on the stereoscopic and optical microscopic observation and X-ray diffraction analysis. These fault gouge samples were collected from the trench excavated at the Beichuan segment of the Yingxiu-Beichuan Fault,where the largest vertical offsets were observed at the earthquake surface ruptures. The results show that the typical microstructures of localized brittle deformation are well developed in the co-seismic fault gouge,including Y-shears,R1-shears(the angle between Y-shears and R1-shears is larger than 14°),R2-shears,P-shears,tension cracks and stepped fragmented grains. All these microstructures are commonly accepted as the result of seismic slip event. In addition,there are also some microstructures similar to those representative of the distributed ductile deformations developed well within the gouges,including P-foliation,elongated clast grains and asymmetric trails of elongated clastic grains. However,all these microstructures are developed only in the area between two parallel Y-shears,indicating that they were induced by the same slip event along the two shears. The microstructures mentioned above indicate the thrust movement of the fault during the Wenchuan earthquake. Field investigation shows that the new fault gouge is very narrow with the thickness of about 3mm,which indicates that the slip movement of the fault was constrained in a very narrow slip zone. The results of analysis show that the contents of feldspar and quartz in the gouges are lower than those in the wall rocks,while the content of clay in the gouges is higher than that in the wall rock. This may indicate that feldspar and quartz were converted partly into clay or clay-particle sized materials because of the friction energy induced by fault slip. Moreover,the frictional heating produced by fault slip might cause the conversion of the I/S mixed layer in the clay-rich gouge into the illite(probably including some chemical reactions of solution),which made the differences of the contents of the illite or the I/S mixed layer in the gouge and in the wall rocks. These results present some criterions for identification of the features of the fault movement.

As a kind of secondary disasters caused by strong earthquakes,earthquake-triggered landslide has drawn much attention in the world because of severe hazards it causes. The 2013 Lushan,China,earthquake triggered lots of landslides and provided an opportunity to test various kinds of methods which have been used in earthquake triggered landslides assessment. Based on the high-resolution satellite images and aerial photos,we preliminarily interpret landslides in the damaged region. It is found that almost all of the landslides took place in the area with seismic intensity above Ⅶ.Spatially,the triggered landslides are controlled by the causative faults in their distribution and mainly concentrate around the epicenter. Based on the Newmark's method model,critical acceleration a_c is used to predict potential landslides. Comparing with the landslides occurrences in the study area,the result of our calculation proves that Newmark's model is effective in seismic hazards analysis. Also,the landslide affected area is estimated by several methods and the difference between them is discussed.

The M_W 7.9 Wenchuan,China,earthquake is a large oblique reverse slip shock,whose main fault is dominated by reverse slip with right-lateral strike-slip component. It generated one of the longest and most complicated surface ruptures,and to many of the phenomena,we haven't had an appropriate interpretation or a common understanding,e.g.on the 7km-long NW-trending Xiaoyudong Fault and the coinstantaneous fracture on the two parallel thrust faults which are 11km apart on the north of Xiaoyudong area. Field investigation in the Xiaoyudong area shows clear co-seismic rupture and displacement,and on these bases,we analyzed the mechanism of the surface rupture in the Xiaoyudong area. Our study indicates that the change of attitude of Beichuan-Yingxiu Fault(BYF),that is,the ca.3.5km step-over in the west of the Xiaoyudong area,is the primary cause of the above complex phenomena. Specific mechanisms are as follows: 1)The dextral strike-slip of the BYF results in compressional uplift in the left-restraining step-over,creating a frontal reverse fault,known as the Xiaoyudong Fault. ; 2)The Pengguan Fault,which is parallel to and 11km apart from the BYF,is activated in the north of the step-over by a combination of the increased dip angle in the north of the step-over due to the ca.3.5km left step of the BYF and the lateral push of the hanging wall to the footwall of the BYF caused by the dextral strike-slip of the BYF.These results are helpful in deepening our understanding of the dynamic processes that produced surface ruptures during the Wenchuan earthquake. We also suggest that more attention shall be paid to the impact of the dextral strike-slip component,the change of primary fault's attitude and the difference of the rocks of the fault's two walls on the process and distribution of surface rupture.