The Sichuan-Yunnan region is located in the southeastern part of the Qinghai-Tibet Plateau. Because of the compression and collision dynamics of the Indian Plate and the Eurasian Plate, the tectonic deformation is strong and seismic activities occur frequently. There have been many earthquakes above magnitude 7.0 in history. A series of active fault zones have developed in the region, among which the Sichuan-Yunnan rhombus block bounded by multiple active faults has attracted great research interests in recent years. The Longpan-Qiaohou fault zone is a boundary fault of the Sichuan-Yunnan rhombus block. The fault zone starts from Longpan in the north, passes through Jiuhe, Jianchuan, and Shaxi in the south, and ends at Qiaohou. It is about 120km long and the fault trend is 15°~20°. This fault zone is large in scale and highly active, with frequent seismic activity, complex mechanical properties, and variable movement patterns. The Mesozoic movement was intense. In the early Cenozoic, compression-thrust movement was dominant, and in the late Cenozoic, tension-strike movement was dominant. Since the Holocene, the fault zone has been characterized by left-lateral strike-slip movement with normal faulting properties, and earthquakes of magnitude 5 or above have occurred many times. Therefore, studying the activity of this fault zone is of great significance for the prediction and evaluation of regional strong earthquake risk. Thick calcite veins are well developed on the Henancun Fault of the Jianchuan section of the Longpan-Qiaohou fault zone, providing very valuable materials for fault dating. Calcite veins are coseismic rapid precipitation formed during seismic activity or syntectonic precipitation that filled along fractures after seismic activity. Therefore, their ages represent the latest time at which seismic activity occurred. Previous studies have shown that tensional fissures formed during coseismic events can close in a short period of time(days to months), suggesting that the filling of calcite veins within fault fissures is a relatively rapid process. This paper uses the ESR method to conduct dating study on the calcite veins in the study area. The results show that the ages of the four calcite veins(HNC-ESR01, HNC-ESR02, HNC-ESR03 and HNC-ESR04) are: (7.1±0.8)ka, (7.1±0.9)ka, (7.3±1.7)ka and (6.9±1.5)ka, respectively. The age results are concentrated, and the average age is(7.1±1.3)ka, indicating that the fault was active no later than(7.1±1.3)ka. The age results are consistent within the error range with the second paleoseismic event time revealed by trenching work in the area(between(6 130±30)a BP and(6 320±40)a BP), indicating that the dating of ESR in the fault zone is an effective dating method for the study of active tectonics and paleo-earthquakes. It is an effective chronological method for research, but it can be seen that compared with ¹⁴C and luminescence dating, the error of ESR results is relatively large. For faults with short earthquake recurrence intervals, it is still very challenging to accurately judge their activity. In the follow-up work, it is necessary to further improve the experimental process and reduce experimental errors, including refinement of sample pretreatment, accurate monitoring of irradiation dose, and accurate calculation of dose rate. In addition, by using five fitting functions(LIN, SSE, DSE, EXP+LIN and D_gamma)to calculate the equivalent dose values of calcite vein samples in this study, we found that the SSE function is capable of providing the best fitting effect.

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.

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.

Uplift of Tibet Plateau and formation of Asian Monsoon greatly affect East Asian geomorphological evolution, climate change and environment systems. Thus, those phenomena also control the origin, size and direction of river systems. The Yangtze River, as the most important linkage between Tibet Plateau and the East Asian marginal seas, delivers large volumes of water, sediment, and associated chemicals from its headwater regions and tributaries to the East China Sea, significantly influencing sedimentary system evolution in its drainage basin. Therefore, the formation of the modern Yangtze River and its geological-time evolution history have been paid more and more attention to since the beginning of the last century. After debated for more than a century, the First Bend in Shigu area and the Three Gorges have been known as the key capture point of the Yangtze River’s evolution history. In particularly, the Three Gorges incision period remains greatly controversial, which mainly focuses on Cretaceous period-Neogene period, early Pleistocene period, and late Quaternary period.
The Yichang Gravel, just located downstream and outlet of the Three Gorges with an inverted triangle shape, is mainly distributed in western Jianghan Basin with over 1 000km². Because of its wide distribution and key geographical location, many typical profiles of Yichang Gravel have been the critical materials for studies on stratigraphic division, geomorphic evolution, and paleoenvironment change in middle Yangtze River Basin, especially on the Three Gorges incision history. Based on the previous field investigation, the Yichang gravel unconformably overlies the Cretaceous bedrocks and underlies the mid-Pleistocene vermicular red earth. In addition, studies on heavy mineral assemblages, Pb isotopic compositions of detrital K-feldspar grains, magnetic characteristics as well as pollen assemblage characteristics have showed that sediments in Yichang Gravel are mainly derived from upper Yangtze River Basin, such as Jinshangjiang drainage, Minjiang drainage, Jialingjiang drainage and Wujiang drainage. Based on the above comprehensive analysis, researchers demonstrated that the depositing time of Yichang Gravel can best constrain the Three Gorges incising time.
The absolute altitude of Yichang Gravel exceeds 110m, and many thick sand lens are developed from top to bottom of the profiles. In this study, we applied the quartz Ti-Li center ESR dating method in Yichang Gravel to determine its absolute formation age, and then to constrain the minimum cutting-through time of Three Gorges. Eight samples(SXY-1, SXY-2, YC-1—4, LJY-1, LJY-2)were collected from the sand lens at depths of 4m, 19m, 40m, 51m, 63m, 75m, 83m and 99m respectively from the top of the profile. At the same time, in order to evaluate the residual dose of Ti-Li center after sunlight bleaching, we also sampled four modern surface Yangtze River sediments near Yichang Gravel for ESR measurement.
The result shows that the quartz Ti-Li center ESR signal intensity of the 4 modern fluvial sediments samples are zero, which implies that the Ti-Li center ESR signal intensity of quartz in Yichang Gravel sand lens could be bleached to zero before the last burial. Thus, the above results indicate that the ESR dating results of this paper are reliable. The ESR absolute age from top to bottom of the profile is 0.73Ma BP,0.87Ma BP,0.98Ma BP,1.04Ma BP,1.05Ma BP,1.10Ma BP, 1.11Ma BP, 1.12Ma BP, respectively. The ESR dating results show that the Yichang Gravel began to deposit at about 1.12Ma BP until 0.73Ma BP, and the Ti-Li center ESR age indicates that the Yangtze River cut through Three Gorges area no later than 1.12Ma BP.

Strike-slip faults and normal faults are dominant active tectonics in the interior of Tibetan plateau and control a series of basins and lakes showing extension since the Late Cenozoic, by contrast with the thrust faulting along the orogenic belts bordering the plateau. The late Neotectonic movement of those faults is key information to understand the deformation mechanism for Tibetan plateau. The Gyaring Co Fault is a major active right-lateral strike-slip fault striking~300° for a distance of~240km in central Tibet, in south of Bangong-Nujiang suture zone. The Gyaring Co Fault merges with the north-trending Xainza-Dinggye rift near the southern shore of Gyaring Co. From NW to SE, Dongguo Co, Gemang Co-Zhangnai Co, Zigui Co-Gyaring Co form the Gyaring Co fault zonal drainage basin. Some scholars have noticed that the formation of lakes and basins may be related to strike-slip faults and rift, but there is no analysis on the Gyaring Co fault zonal drainage basin and its response to regional tectonics. In recent years, a variety of quantitative geomorphic parameters have been widely used in the neotectonic systems to analyze the characteristics of the basin and its response mechanism to the tectonic movement. In this paper, we applied ASTER GDEM data on the ArcGIS platform, extracted the Gyaring Co fault zonal drainage basin based on Google Earth images (Landsat and GeoEye) and field work. We acquired basic geomorphic parameters of 153 sub-basin (such as grade, relief, average slope, area) and Hypsometric Index (HI) value and curve. Statistical results have indicated significant differences in scale(area and river network grade)in north and south sides of the fault. Southern drainage basins' relief, slope, HI value are higher than the northern basins, and the overall shape of hypsometric curve of northern basins are convex compared with southern concavity. Along the strike of the Gyaring Co Fault, average slope, and HI value are showing generally increasing trending and hypsometric curve become convex from west to east. By comparing and analyzing the lithology and rainfall conditions, we found that they have little influence on the basic parameters and HI value of drainage basins. Therefore, the changes of basin topographic differences between northern and southern side of fault and profile reveal the Gyaring Co Fault has experienced differential uplift since the late Cenozoic, southern side has greater uplift compared to the north side, and the uplift increased from NW to SE, thus indicate that normal faulting of the Gyaring Co Fault may enhanced by the Xainza-Dinggye rift. The early uplift of the Gangdise-Nyainqentanglha Mountain in late Cenozoic might provide northward inclined pre-existing geomorphic surfaces and the later further rapid uplift on the Gangdise-Nyaingentanglha Mountain and Xainza-Dinggye rift might contribute to the asymmetrical development of the Gyaring Co fault zonal drainage basin.

Xiangshan-Tianjingshan Fault is one of the major active faults of the arc fault zone on the northeastern margin of the Qinghai-Tibet Plateau. The Yellow River in the Shapotou area flows through the fault and forms a perfect "Ω-shape" bend. Shapotou not only is a tourist mecca,but also a hotspot for studying the geomorphology,neotectonics,the uplift of Qinghai-Tibet Plateau and other issues. Xiangshan-Tianjingshan Fault is mainly a left-lateral strike-slip fault with a minor thrust component. So to study the fault's offsets is of vital importance. This paper,based on the characteristic of the distribution of the Yellow River terraces in the Shapotou Big Bend area,analyzes the offsets of the Xiangshan-Tianjingshan Fault since the formation of the terraces. The results reveal that 3 river terraces are developed on the right of the Yellow River in the Shapotou area,while there is no terrace developed on the left of the river. The maximum left-lateral displacement of Xiangshan-Tianjingshan Fault is less than 880m,and the slip rate is less than 5.18mm/a since 170ka BP.

The Changbaishan Tianchi volcano is one of the most famous volcanoes in China. It erupted many times in the Holocene time. The top of this volcano is regionally covered by some yellow material (pyroclastics), the origin of which has been under debating since its discovery. Based on the information provided by the eruption of Mount St Helens of USA on May 18th, 1980, in conjunction with the chemical composition and distribution characteristics of the yellow materials, we estimated that it resulted from hot water metasomatism during the Millennium eruption, rather than a separate product of an individual volcanic event.

Because of lack of Quaternary volcano activity in China,Quaternary sediments become the main dating material in the study of geological structure, topographic feature and environment evolution,etc.ESR is a potential dating method for the sediments older than 200ka.After sunlight bleaching or heating,the quartz ESR signals,including E'-,Ge-,Al-,Ti-center,can attenuate or be reset.The sediments deposited during Quaternary period only have the effect of sunlight bleaching before the last burial time.Therefore,the sunlight bleaching characteristics of ESR signal centers is one of the most important factors in ESR dating.In this study,the paper firstly makes a simple introduction on the ESR theoretical basis and the measuring process of dose rate(D) and equivalent dose(ED),and then,reviews the sunlight bleaching characteristics and the applications in Quaternary geochronology of different ESR signal centers.The E'-center ESR signal increases with the sunlight bleaching during first 72 hours,it is not suitable for the sediment dating.Ge-center ESR signal is bleachable and can be reset after several hours sunlight bleaching,so,it is the most light sensitive signal center.However,it is very difficult to measure the Ge-center ESR signal in laboratory because it is very weak.Al-center can attenuate 20 percent after 2 hours sunlight bleaching and after tens to hundreds of hours bleaching it still maintains a stable residual signal,50-80 percent.The remnant signals are not equal under different sediment environment.We usually gain a bigger age using Al-center ESR signal for the uncertain remnant.Ti-center ESR signals can be totally bleached after tens to hundreds of hours sunlight bleaching,and this ESR signal also has enough intensity for measurements.According to the review of all the ESR signal centers' sunlight bleaching characteristics and several successful application examples,we suggest that Ti-center ESR signal is more suitable than others for the ESR dating of Quaternary sediment.

The 12 May 2008 Wenchuan Earthquake created about 240km-long surface fault ruptures along the Central Fault and about 72km along the Mountain Front Fault,two of the three sub-parallel secondary faults of Longmenshan thrust faults striking NE-SW,according to field investigation of surface faulting.From north to south,most of the widths of intense surface rupture zones are less than 40m,and above 1/2 are between 10～30m.Many buildings along fault surface ruptures were destroyed,including those with frame structure or reinforced concrete structure,and we also find some houses or buildings have withstood the strong earthquake and its aftershocks for their excellent performance of earthquake-resistance.The distance between fault scarps and the buildings are from 10 to 30 meters.Based on the field investigation,on the widths of surface rupture zones of historical strong earthquakes,and considering "crustal shortening" for inverse faulting and other various uncertainties,it is suggested that safety distance away from active fault in rebuilding is 25m.Within this distance,only one or two-storeyed buildings with higher standard of earthquake-resistance can be constructed,and public buildings,like schools and hospitals should be prohibited to build.

The investigation and study of fault activities are a basic work for urban earthquake prevention and disasters reduction.In order to find out the location,characteristics and activities of the Laoyachen Fault in Zhengzhou,the high-resolution shallow seismic P and S wave survey profiling across the Laoyachen Fault was carried out at the end of 2006,and different seismic sources along with combinations of diverse observation geometries with different parameters were used.The fine structures in different depths beneath the profile were obtained and the patterns as well as characteristics of the Laoyachen Fault were determined.The results show that the Laoyachen Fault,running in NW and dipping in NE,is a normal fault and its dip angle is about 60°～70°,which incises strata of Eocene,Permian,Carboniferous or Ordovician epoch and goes up to the top boundary of Eocene stratum at the 800～850m depth.There is no any reflector of offset stratum found in Q+N strata.The borehole geological sections across steep slopes of earth surface present that the layers inferred from reflected seismic wave groups of shallow seismic profile are well correspondent with boring geological layers.The borehole results reveal that the three reference laminas,i.e.the boundary between Malan loess and silt with clay soil at about 21m in depth,the calcareous gravel clay layer of 53.9m deep,and the calcareous silt layer of 61.9m deep,all have not depth variations at the two sides of surface steep slopes and are situated almost at the same ground surface elevations,which suggests that the steep slopes at the earth's surface should not result from the activities of Laoyachen Fault.In this study,through shallow seismic P wave and S wave exploration as well as combination of joint borehole geological sections,not only the location and characteristics of Laoyachen Fault was determined,but the geological and seismological evidences for the fault activity estimations were provided.

In the eastern mainland of China there are few cross sections of faults where dislocation of Quaternary strata can be observed. However,recently we found such a profile about 2km away from the Nanling county,Anhui Province(30°55'456″N,118°177'74″E),west to the highway from Nanling to Fanchang. This fault has been identified on the satellite image,but its trace is confined to the southern side of the Nanling Basin. Our field investigation indicates that the northwestern end of this fault lies at the Xiaodanyang-Fangshan Fault. It is only 20km long,striking in NW,dipping to southwest. From observations on the profile,it consists of two small fractures and has two periods of activity at least. The first active period is before middle Pleistocene time,or probably in early Pleistocene. And the second active period is in or after middle Pleistocene. Its latest motion is of thrust with an amount of dislocation of 40cm. This fault cross section shows that the NW-trending faults in the eastern Mainland of China have new activities,though on small scales in general.

The neotectonic movement and characteristics of fault activity in the Anqing-Ma'anshan section of the Changjiang River valley are analyzed on the basis of data obtained from field investigation,shallow seismic prospecting and drilling. The results show that during neotectonic time this river valley section and its both sides as a whole was dominated by weak and intermittent uplift movement. As a consequence,owing to the effect of the activity of NE-and NNE-trending faults,relatively strong vertical differential movement occurred in Wuwei-Anqing area during Paleogene-Neogene,and had continued to early and middle Pleistocene. The NE-NNE-trending and NW-trending faults were developed in the bed rocks of the valley and its both sides. The former was formed during Indo-Chinese epoch,while the later was formed during Yanshan epoch. The most recent active period of the larger faults controlling the development of Cenozoic Basins is middle Pleistocene,while the newest activity of the relatively small faults developed within pre-Cenozoic group is pre-Quaternary. The Quaternary system in the valley is \{10～\}50m thick,consisting mainly of Pleistocene-Holocene deposits. The isopach of these deposits is smoothly distributed,indicating normal valley deposition. Seismic activity along the valley and its both sides is relatively weak,and historically only 4 destructive earthquakes have been recorded. Among these events,the largest one is the M5(3/4) earthquake occurring at Chaohu in 1585,and the other events including one with M5(1/4) and two with M4(3/4). Since the beginning of instrumental records in 1970,the largest magnitude that has been recorded so far is ML 3.7. All these results may provide better constraints on the assessment of the crustal stability for this river valley section.

Calcite is a common matter in the fault zone and it is often related with fault movement,so its dating is of vital significance for studying the time of fault movement.At present,ESR method is one of the ways for measuring the age of calcite,but there are no final conclusions regarding the ESR signals and measurement conditions of calcite.The samples used in this article were picked from the east of Erhai,Yunnan.According to the preliminary study of the samples,we found that calcite was liable to generate unstable short-lived signal when it was artificially exposed.So before measuring,the samples were kept under the room temperature condition for at least 5 days to eliminate the jamming signals.Generally,in natural calcite,there are many ESR signal centers,among them,the ones,g=2.0040 and g=2.0023,respond well to absorbed dose,and can be used in the dating.Growth curves of these two signals indicate a linear growth at least in the range of 1500Gy.But it is indicated with the artificially fixed known dose method that different microwave powers have to be taken for g=2.0040 and g=2.0023 signals.If we consider the deviation of ED value is smaller than 5%,then the microwave power should be 0.8 or 2mW for the g=2.0040 signal,and the microwave power be 2mW or 5mW for the g=2.0023 signal.

The Weizhou Island is a volcanic island in the Beibu Bay. Volcanic activity on the island can be roughly divided into two stages, mainly in the Early-Middle Pleistocene and the Late Pleistocene separately. Eruptions of the Nanwan Volcano (late stage activity of Weizhou Volcanic Province) were typical phreatomagmatic eruptions, forming a big maar and thick ring walls of pyroclastics and debris. In this paper, we reported the OSL dating result of the sandstone xenoliths, which were trapped in the two volcanic pyroclastic layers of the Nanwan Volcano. The ages revealed that the activity of the Nanwan Volcano mainly occurred in ca 30ka ago, at the end of the Late Pleistocene.

In ESR dating,the age is given by the ratio of paleo-dose to annual dose. Generally,the paleo-dose is obtained by linear extrapolation in regeneration or additional irradiation method. Therefore,dose determination in manual irradiation becomes one of the important factors that effect reliability of the dating results. Usually,there are two ways to determine the dose of manual irradiation: one is called dose rate method,which calibrates the dose rate of the position by standard dosimeter before dating sample irradiation at the same position. Dose will be determined by the dose rate and irradiation time of the sample. In this method,Fricke dosimeter is usually used as standard dosimeter; the other is called concomitant method,which puts reference dosimeter together with the dating sample to the position before irradiation. They will be irradiated simultaneously and the dose will be given by the reference dosimeter. In this method,alanine dosimeter is generally used as the reference dosimeter. In the paper,these two methods are discussed. Two types of alanine dosimeter are used as reference dosimeters: one is pellet alanine dosimeter,the other is alanine film dosimeter. We use dose rate results that were calibrated one year ago to evaluate the current dose rates. Irradiation time is determined according to the nominal dose and the dose rate. However,the actual dose was determined by the alanine dosimeter that was irradiated with the dating sample together. Since it is not practical to calibrate the dose rate every time for every position before dating sample irradiation,the concomitant method that uses alanine dosimeter as reference to be irradiated with the dating sample together will be more practical and reliable compared with the dose rate method.

Several dark-green or yellow-brown layers with different thickness have been found in the late Quaternary strata in the area of the Changjiang River and Jiantangjiang River. They are very hard,called “hard clay”. The top hard clay layer is called the first hard clay. There are the marine sediments on the first hard clay. The boundary of Holocene has been discussed based on the first hard clay. The first hard clay is found in Ningbo region too. 19 samples from the first hard clay,the marine sediments on the first hard clay and the layer under the first hard clay,were dated using optical luminescence and 14 C dating method to provide age control of its development. According to our dating results,the age of the original material of the first hard clay is 45～55ka BP. The first hard clay is uncontinuously distributed,being eroded by the later stages transgression in some places,and unconformable with the upper marine sediments. The lower limit of the marine bed may not be simply delineated as the Holocene boundary. It is possible that the marine sediments occurred at the end of late Pleistocene.

This paper introduces the results of shallow seismic exploration on five traverse lines across the Huangzhuang Gaoliying buried fault in the vicinity of Lishuiqiao,Beijing area. The section of the Huangzhuang Gaoliying fault in the vicinity of Lishuiqiao can be distinguished distinctly on the spot map,but the other sections of the fault along river valley are undistinguishable. The shallow seismic exploration and geological information reveal that the velocity model of the shallow part around the Lishuiqiao area is characterized by 4-layer structure. The layers 1 and 2 are located at a depth range of 0～150m beneath the surface,and they can be assigned to Tertiary or Quaternary deposits,having a velocity of 800m/s to 2000m/s. The layers 3 and 4 are identified at a depth range of 130m to 300m,which are bedrock consisting of mudstone and sandstone,having a velocity of larger than 2000m/s or 2500m/s. At shallow depth,the Huangzhuang-Gaoliying Fault in Lishuiqiao area is composed of two sub-parallel faults about 1300m apart from each other. The two faults are N23°E-striking,dipping southeast at an angle of 22° for the western fault and 87° for the eastern one. At a depth of 634m the two faults converge into one fault,appearing as a branching fault. The buried depth of the highest point of the hanging wall of the fault is 101m,while that of the footwall is 109 m. The throw of the fault is about 8m. It is concluded,therefore,that the fault is a normal fault with strike-slip component,dissecting the T₂ and T₃ stratigraphic interfaces.

The 14 November,2001 M_S8.1 West Kunlun Pass Earthquake is the largest event associated with the longest surface rupture that has occurred in the Tibetan Plateau since 1951. We made 291 surficial left lateral slip measurements and 111 net vertical slip measurements along the main fault zone. The displacement on the main fault strand is dominated by left lateral strike slip of 2.7m in average,with vertical slip component of mostly less than 1m. The maximum left lateral slip is 6.4m,with as much as 5.1m of vertical slip component. Sinistral surficial slip is quite variable along the main strand of the rupture at distance scales ranging from a few tens of meters to a few hundreds of kilometers,with slip gradient ranging between 10^-1～10^-4. The slip variations over short length scales (tens of meters to a few kilometers) might be caused by variations in thickness of unconsolidated sediments,fault strike and slip of the previous earthquake,distributed non brittle deformation and secondary fractures,complexities in fault geometry,and perhaps by measurement error. Despite this short wavelength variability,there is fairly regular long wavelength (tens to hundreds of kilometers) behavior to the east of the Buka Daban Peak. One notable characteristic of slip distribution along the faults is that very large surficial slips (as large as 5～6 meters) were observed at 5～6 sites located at different surface rupture segments in asymmetry to their left lateral slip functions. Slip on each of these rupture segments diminishes away from the highest slip site to its terminations with different slip gradients. This asymmetric distribution of slips may indicate the propagation direction of the rupture along the faults. This long wavelength variation in slip might be influenced by fault geometry,while the segmentation of the surface rupture zone might play a key role. It should be pointed out that the surficial slip (at both short and long length scales) is only a near field slip measured in the field by using tape measure. Therefore,it should be considered as a minimum value,and may represent the real variations in the amount of brittle slip on visible fractures at the surface,but it potentially underestimates the actual slip produced by the earthquake and slip distribution over the whole surface rupture due to the difficulty in identifying distributed non brittle deformation. This calls for caution in discriminating between one or multiple discrete events and in estimating the size of past and future earthquakes by using displaced deposits in trenches or offset geomorphologic features along strike slip prehistoric fault ruptures.

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.