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

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

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

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

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

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

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

At 02:04 a.m. on May 22, 2021, a M_S7.4 earthquake occurred in the Maduo County, Qinghai Province, China. Its epicenter is located within the Bayan Har block in the north-central Tibetan plateau, approximately 70km south of the eastern Kunlun fault system that defines the northern boundary of the block. In order to constrain the seismogenic fault and characterize the co-seismic surface ruptures of this earthquake, field investigations were conducted immediately after the earthquake, combined with analyses of the focal parameters, aftershock distribution, and InSAR inversion of this earthquake.
This preliminary study finds that the seismogenic fault of the Maduo M_S7.4 earthquake is the Jiangcuo segment of the Kunlunshankou-Jiangcuo Fault, which is an active NW-striking and left-lateral strike-slip fault. The total length of the co-seismic surface ruptures is approximately 160km. Multiple rupture patterns exist, mainly including linear shear fractures, obliquely distributed tensional and tensional-shear fractures, pressure ridges, and pull-apart basins. The earthquake also induced a large number of liquefaction structures and landslides in valleys and marshlands.
Based on strike variation and along-strike discontinuity due to the development of step-overs, the coseismic surface rupture zone can be subdivided into four segments, namely the Elinghu South, Huanghexiang, Dongcaoarlong, and Changmahexiang segments. The surface ruptures are quite continuous and prominent along the Elinghu south segment, western portion of the Huanghexiang segment, central portion of the Dongcaoarlong segment, and the Huanghexiang segment. Comparatively, coseismic surface ruptures of other portions are discontinuous. The coseismic strike-slip displacement is roughly determined to be 1~2m based on the displaced gullies, trails, and the width of cracks at releasing step-overs.

To establish an experimental, practical and open scientific experimental platform for earthquake monitoring and prediction, with reference to that of the southern California earthquake center(SCEC), China Earthquake Administration initiated a project for an experimental field in Sichuan and Yunnan Province in 2014. The chosen area is a seismically active region in the southeastern margin of the Tibetan plateau. A series of work compiling basic maps have been launched to collect fundamental data of this area including geologic structure, earthquake geology, geophysics, geodesy, and geochemistry. The map of earthquake surface ruptures in this region is one of these basic maps. This paper presents the compilation of this map. It includes earthquake epicenters, earthquake surface ruptures, faults, strata, magmatic rocks, and geographical data. This work summarized 87 destructive earthquakes, and 22 earthquake surface rupture zones, and analyzed the distribution characterization of earthquake epicenters, strata and magmatic rocks. The content in the map is reliable and integrated. This work will provide reliable earthquake-geology data for establishing geodynamics models and other future research of the national experimental field of earthquake monitoring and prediction in Sichuan and Yunnan Province.

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.

Living with disaster is an objective reality that human must face especially in China. A large number of earthquake case studies, such as the 2008 Wenchuan earthquake, 2010 Yushu earthquake, 2014 Ludian earthquake, have demonstrated that earthquake heavy damage and casualties stem from ground-faulting or rupturing along seismogenic active fault, near-fault high ground accelerations and building catastrophic structural failure. Accordingly, avoidance of active faults may be an important measure to effectively reduce earthquake hazard, which may encounter in the future, but how to avoid an active fault and how much a setback distance from the active fault is required to ensure that the ground faulting and rupturing has no any direct impact on buildings. This has been the focus of debate both for domestic and foreign scholars. This paper, first of all, introduces the definition of active fault. Then, quantitative analyses are done of the high localization of earthquake surface ruptures and relationship between the localized feature of the coseismic surface ruptures and building damages associated with the measured widths of the historical earthquake surface rupture zones, and an average sstatistic width is obtained to be 30m both for the earthquake surface rupture zones and heavy damage zones along the seismogenic fault. Besides, the widths of the surface rupture zones and spatial distribution of the building damages of the 1999 Chi-Chi earthquake and 2008 Wenchuan earthquake have also been analyzed to reveal a hanging-wall effect:Width of surface rupture zone or building damage zone on the hanging-wall is 2 or 3 times wider than that on its foot-wall for a dip-slip fault. Based on these latest knowledge learnt above, issues on avoidance object, minimum setback distance, location requirement of active fault for avoidance, and anti-faulting design for buildings in the surface rupture zone are further discussed. Finally, we call for national and local legislatures to accelerate the legislation for active fault survey and avoidance to normalize fault hazard zoning for general land-use planning and building construction. This preventive measure is significantly important to improve our capability of earthquake disaster reduction.

The July, 22, 2013 M_S6.6 Minxian-Zhangxian earthquake occurred in the Lintan-Dangchang Fault belt which is located in the northeast Tibet Plateau. Recent tectonic activities show that the Lintan-Dangchang Fault is a thrust fault with strike-slip component. However, the spatial pattern and mechanism of the recent tectonic activity along this fault have not been analysed in detail before the occurrence of the Minxian-Zhangxian earthquake. For better understanding the differential recent tectonic uplift of this fault, drainage basins and river networks were extracted based on ASTER GDEM data in this study. Hypsometric integral and the stream length gradient were calculated. The geomorphic indices analysis results suggest the differential tectonic uplift along the Lintan-Dangchang Fault. The areas experiencing strong tectonic uplift were identified which locate at the west of the Lintan County and around Minxian County. Besides, high geomorphic indices values are associated with epicenters of the historical earthquakes, which demonstrates the importance of the quantitative geomorphic analysis. Our results suggest that the overall tectonic uplift along the Lintan-Dangchang Fault is not very strong. However, certain segments which are experiencing relative high tectonic uplift have the potential of generating moderate or even large earthquakes. Under the regional NE-SW compressional stress caused by the northeastward expansion of the Bayankala block, the tectonic uplift of the fault may relate to the local stress concentration.

By use of existing active faults, GPS monitoring data and other information and supposing a block-like motion, the Tibetan Plateau can be divided into multiple first-order and second-order blocks in accordance with basic definition of active block, and the block kinematic model with slip vector is given. Then by analysis of the relationship between the earthquake series, including the 2014 Ludian and Jinggu earthquakes, occurring in the Tibetan Plateau in the past more than a decade and the block motion, the themed areas for future surface rupturing earthquakes are determined to be related to the eastward or southeastward motion of the Bayan Har and Qiangtang blocks. The risk fault segments for the future earthquakes may include the southeastern segment of the Xianshuihe Fault, the Anninghe Fault, the Daliangshan Fault, the southern segment of the Xiaojiang Fault and the southeastern segment of the Red River Fault as well as the Maqin-Maqu segment of the eastern Kunlun Fault. In the earthquake monitoring and prediction tests, attention should be paid to the different structural strain patterns around the specific block boundary faults.

The April 20,2013,M_S 7.0 Lushan earthquake occurred along the southwestern part of the Longmen Shan Fault zone. Tectonics around the epicenter area is complicated and several NE-trending faults are developed. Focal mechanisms of the main shock and inversions from finite fault model suggest that the earthquake occurred on a northeast-trending,moderately dipping reverse fault,which is consistent with the strike and slip of the Longmen Shan Fault zone. NE-trending ground fissures and soil liquefaction along the fissures,heavy landslides along the Dachuan-Shuangshi and Xinkaidian Faults were observed during the field investigations. No surface ruptures were found in the field work. GPS data indicate that the fault on which this earthquake occurred is a fault east of or near the Lushan county and the earthquake also triggered slip on the fault west of the Lushan county. Field observations,GPS data,focal fault plane,focal depth,and distribution of the aftershocks suggest, that the seismogenic structure associated with the M_S 7.0 Lushan earthquake is the décollement beneath the folds of the eastern Longmen Shan. Slip along this decollement generated the earthquake,and also triggered the slip along the Dachuan-Shuangshi and Xinkaidian Faults.

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.

The co-seismic rupture is one of the important contents in active tectonic mapping.As the late Quaternary landform is a basic recording medium for the recent deformation of active fault,such as the co-seismic rupture,it is quite useful to acquire the activity information of the active fault from various landforms.We implemented a field work along the southeastern segment of the Xianshuihe Fault,mapped the rupture and excavated some trenches.The preservation characteristics of the surface rupture of the 1786 Moxi earthquake were discussed for the glacial area of the Tibetan plateau,the fluvial and flooding area and seriously eroded area at the margin of the Tibetan plateau,respectively.The cracks and offsets were preserved continuously in the glacial landforms such as the moraines and glacial outwashes along Kangding to Yajiageng segment.As the landforms in the fluvial and flooding area were unstable under strong erosion and rapid deposition,the surface rupture can be discovered in the trenches excavated in Yuejinping village and Ertaizi village with gaps for some previous earthquakes.There was no deposition from the erosion landform to record the surface rupture.We can only infer the earthquake effected area and the ruptured fault from the indirect relationship between landslides and the earthquake strong motion or the fault rupturing.Based on the integrated analysis with the geometry and tectonic setting of the southeastern segment of the Xianshuihe Fault,the Kangding-Tianwan segment of the Xianshuihe Fault was taken as the seismogenic fault of the 1786 Moxi earthquake,and the total length of the rupture is about 80 kilometers.

Cosmogenic dating(in situ cosmogenic nuclides)has been widely used in geologic and geographic domain along with the application of accelerator mass spectrometry(AMS)and highly sensitive conventional noble-gas mass spectrometry in the early 1980s,since Raymond Davis and Oliver Schaffer proposed that cosmogenic nuclides produced within minerals at the surface of the earth could be applied to geological problems.At present,this dating method is used to study glacier,desert and relief evolution,volcano development and active structure movement etc.There are a lot of materials which can be used in cosmogenic dating method.Because of its tight crystal structure,quartz can minimize possible contamination by meteoric ¹⁰Be,and also for its low ²⁷Al content,it becomes an ideal material for cosmogenic dating method.During the process of the isolation of ¹⁰Be and ²⁶Al from quartz sample,quartz isolation and purification are one of the key steps.HCl/H₂O₂ and HF/HNO₃ leaching is a safe method used to isolate and purify the quartz samples widely.However,there is defect about the method.It takes more time for sample preparation and curtails the life of instrument.Based on the above method,three experiments were designed to compare with the primary one.The results of experiment reveal that the purification efficiency can be enhanced by increasing the leaching solution concentration and the amount of sample,and ultrasonic cleaner can be replaced by hotplate /magnetic stirrer.

Data from remote sensing played important roles in the rescue during the 2008 Wenchuan earthquake and reconstruction after the great disaster.It also has much realistic significance to implement a rapid interpretation and geological study from those data.Analysis was made on the characteristics of optical remote sensing image,such as shadows and texture,and geological and geomorphological features of the surface rupture from field investigation.The interpretation marks of the post-earthquake optical remote sensing image were concluded for the fault scarp of the great Wenchuan earthquake.Based on the optical imaging,the shadow forming and interpretation characteristics of different kinds of fault scarp were analyzed for the Wenchuan earthquake.The imaging time and the occurrence of fault scarps make a constraint on the forming of shadows and its interpretation for fault scarps.Analysis based on characteristics of imaging and rupture styles gives a new insight on the limitation in the application of remote sensing data of co-seismic surface deformation,and also a certain proposal for the emergency aerial remote sensing in the future.

The paper carries out geometric segmentation of the eastern segment of East Kunlun Active Fault(Maqin-Maqu segment)based on the interpretation of ETM and QuickBird satellite images and using segmental signs of strike-slip fault,such as geometric and tectonic discontinuities in combination of geomorphic features and fault zone materials. In this study,we divide the Kunlun Active Fault(Maqin-Maqu segment)into eight segments,geometrically,namely,Dongqinggou,Dawutan,Kendingna,Xikehe,Tangdi,Maqu,Moxi and Luocha. Faults in the former seven segments are developed en echelon,of which,that in the Tangdi and Maqu segments are of right-stepping en echelon,and the rest are of left-stepping. The space between steps is small and well-connected. Beside the stepover,the segmentation indicators also include the bend of fault strike and the intersection of fault with others. Luocha segment is divided mainly by the strike bend. The east Kunlun Fault intersects with the Awancang Fault and Xikehe-Maqu Fault at the south side of Mohatang,which is taken as an indicator of segmentation of the Xikehe segment. The extensive landform and evidence of paleo-seismic rupture indicate that the Maqin-Maqu segment has experienced numerous movements. The fault splays out from northwest to southeast,which has good correlation with the slip rate gradients along the Eastern Kunlun Fault.

In the scientific investigation on the M_S 8.0 Wenchuan earthquake,different high-precision measuring instruments,such as electronic total station,GPS RTK,3D laser scanner,etc.were used widely to survey the landscape of co-seismic surface ruptures,and a wealth of information with the earthquake deformation were recorded timely,which ensured the quantitative analysis of related data.In this paper,we explored the characteristics of different means used in the micro-geomorphology survey and analyzed the advantages of different portfolios of the above-mentioned methods.Then,focusing on the examples,we discussed the advantages and limitations of three-dimensional laser scanner in recording and analyzing the information of seismic surface ruptures.Also we gave the prospects of the methods' application.

The geodatabase of scientific investigation of Wenchuan earthquake stores many field investigation data,such as the data of field geological survey sites,the surface rupture belts,the Quaternary faults in the earthquake region,paleoseismological trenches,folds,etc.Moreover,it includes some collection data,such as strata data,the catalog of the Wenchuan mainshock and aftershocks,the relocation catalog of aftershocks of the Wenchuan earthquake,the catalog of historical strong earthquake.The field data are recorded,edited,analysed,mapped and output with ArcGis,a powerful function in Gis software.The geodatabase of scientific investigation of M_S8.0 Wenchuan earthquake was initially established,which includes the basic seismological information and realizes the integrated management of spatial location and attribute information.Data can be queried,analyzed and processed for the need of the correlation analysis of the data.Seismic tectonic map and surface rupture map can be drawn with the geodatabase,which can provide the basis for the determination of safety distance from the risky seismic rupture zones in post-disaster reconstruction and for the construction of the Wenchuan earthquake geographic information system.

In the paper,the seism ic damage to reservoirs in Sichuan Province has been analyzed by field in-vestigation and data collection of the damages of the M_S8.0 W enchuan earthquake.The results show that the damage of the M_S8.0 W enchuan earthquake is 1 or 3 degrees higher than the seism ic intensi-ties provided by the reservoir seism ic safety assessments in Sichuan Province.This reveals certain questions behind the reservoir seism ic safety assessment in this region.Because of the short earth-quake record history,there has been no pred icting of earthquake larger than the largestmagnitude of historical earthquake,and thus,the risk of the Lomenshan active faultwas greatly underestimated,re-sulting that fissures,seepage and partial collapse occurred widely on the dams ofmany reservoirs.The paleoearthquake method is an importantmeans of d istinguishing active fault in reservoir seism ic risk assessment and improving the accuracy and reliability of the assessment results.

A 240km-long co-seismic surface rupture was produced along the Beichuan-Yingxiu Fault during the 2008 Wenchuan earthquake.We made a detailed survey at representative sites along the surface rupture and analyzed the data based on the geometry between the benchmark and deformation.The co-seismic vertical slip,horizontal dip-slip shortening,strike slip and moving direction of the hanging-wall were calculated based on the survey data of these sites.Results show that the spatial distribution of the co-seismic deformation of the fault varies a lot along the fault.The maximal horizontal slip,as we got till now,is located in the Shenxigou site of Hongkou with a value of 4.98m,and the maximal strike slip is also located in the same site with a value of 4.5m.The maximal vertical displacement is located to the northeast of Shenxigou with a value of 5.7～6.7m.The average horizontal slip for the NE trending fault is 1～2m,and the average vertical slip is 3m.But horizontal and vertical slip for the NW-trending branch from Xiaoyudong to Caoba is only 0.5～1.5m.The data from Leigu town show that the gravity deformation resulting from the fault-related landslide was perhaps superimposed on the tectonic one.The dip angles of the fault at the surveyed sites calculated from the horizontal shortening and vertical displacement indicate that the Beichuan-Yingxiu Fault is a steep dipping reverse fault with some strike-slip.From the comparison between field results and geophysical inversion,we believe that the spatial distribution of co-seismic fault-slip is related to the barriers and rupture process along the fault plane.

The Wenchuan earthquake(M_S=8.0)of May 12,2008 in Sichuan Province,China produced surface ruptures along the seismogenic reverse faults.It is very important to analyze the co-seismic surface ruptures quantitatively for the comprehension of tectonic behavior of the great earthquake.We discuss several issues about the quantitative analysis of co-seismic surface ruptures produced by reverse faults with some examples from Wenchuan earthquake.With the geometric relations between the parameters of deformation and survey data from planar and linear geomorphologic benchmark,solution methods for those parameters are provided.The vertical slip,horizontal dip-slip and dip angles on survey profiles were measured to calculate the actual deformation of the fault.The relationship between the apparent deformation and the real value was provided quantitatively for oblique profiles and linear benchmarks.We also made some discussions on the application of the survey data to the analysis of regional structural geometry and kinematics.

In the historical rocords,there have been no comparable earthquakes with the May 12 Wenchuan earthquake in Chengdu and Longmenshan mountain region.Then,whether the ancient earthquake traces with comparable magnitude in the geological records can be found has become an important scientific issue.The authors and other members of Wenchuan earthquake geological investigation team did fieldwork in the earthquake region for more than one month.Four trenches and one geologic section were excavated along the middle segment of surface faulting of both the central fault and the mountain front fault.And geomorphologic surfaces of deformation were measured.In this paper,we discuss the fact that there is prehistory large earthquake along the seismogenic fault of Wenchuan earthquake from analyzing the accumulated deformation of old and young fault scarps or geomorphologic surfaces,trenching,and comparing the activities of related faults and so on.The result shows that whether at Xiaoyudong,Leigu located on the central fault or Bailu,Hanwang on the mountain front fault,or at other places along the surface faulting of the the Wenchuan earthquake,the height of the fault scarp on the second terrace has a multiple relation with that on the first terrace after the Wenchuan earthquake.The 4 trenches reveal that the dislocation of the marker strata of the second terrace on both sides of fault is twice of that of the Wenchuan earthquake,which shows that there was an earthquake event with the same scale of surface deformation of this M_S8.0 Wenchuan earthquake between the formation time of the second terrace in Lomhmenshan area and the May 12 Wenhucan earthquake.

Field investigations show that the M_S8.0 Wenchuan earthquake of 12^th May 2008 ruptured two NW-dipping imbricate reverse faults along the Longmenshan Fault zone at the eastern margin of the Tibetan Plateau.This earthquake generated a 240km long surface rupture along the Beichuan-Yingxiu Fault characterized by right-lateral oblique faulting and a 90km long surface rupture along the Guanxian-Jiangyou Fault characterized by dip-slip reverse faulting.Maximum vertical and horizontal dispacements of 6.2m and 4.9m,respectively,were observed along the Beichuan-Yingxiu Fault,whereas a maximum vertical displacement of 3.5m occurred along the Guanxian-jiangyou Fault.This co-seismic surface rupture pattern,involving multiple structures,is among the most complicated of recent great earthquakes.Its surface rupture length is the longest among the co-seismic surface rupture zones for reverse faulting events ever reported.Aftershocks recorded by local network clearly outline the hanging wall of the Beichuan-Yingxiu Fault and indicate that the fault dips about 47? to the west.Industry seismic lines,in addition to surface ruptures and aftershocks,allow us to build a 3D model for the rupture geometry that shows crustal shortening is the dominant process along the Longmen Shan to accommodate long-term deformation.Oblique thrusting accomplished by the earthquake indicates that the east-southeastward extrusion of Tibet Plateau accommodates,in part,the continuing penetration of the Indian plate into the Eurasian plate,and this extrusion is transformed at the eastern margin of the Tibetan Plateau into crustal thickening and shortening along the Longmenshan Fault zone that is responsible for the growth of high topography in the region.

After Wenchuan Earthquake(M8.0),surface fractures in Beichuan and Yingxiu were investigated.It was found that the earthquake deformation zone strikes in NE-SW.Earthquake fracture is characterized by thrust faulting with small amount of strike-slip movement.The compressional shortening is 3～4m in Beichuan and the left-lateral strike-slip displacement is 0.4～0.5m in Yingxiu.

Some destructions in meizoseismal region of Wenchuan earthquake with magnitude 8,Sichuan,China are shown,and their seismic intensity is determined according to "The Chinese Seismic Intensity Scale".The type of earthquake-generating fault and some features of seismic destruction are discussed briefly.

It is a fundamental study for the research of evolution of Qinghai-Tibetan Plateau to resolve the kinematics of active boundary belt around the plateau quantitatively. With the measuring technology of photogrammetry and chronological method of analysis among regional climate,geomorphology and tectonics,we get a set of quantitative kinematical data for the main faults along the northern-eastern active boundary belt of Sichuan-Yunnan block. There were centre-symmetrical dip-slips locally in many fault segments while they were mainly strike-slip. With vector computation within a regional system including the north-east active boundary belt of Sichuan-Yunnan block and related blocks,we analyzed the longitudinal kinematical transformation and transversal slip partitioning quantitatively based on the parameters of main faults kinematics. From these data,there were a vertical uplift rate of 6.2mm/a in the Gonggashan area in distributed deformation form,and a mainly dip-slip fault at least with a rate of 1.45mm/a along the inner side of eastern terrace of Anninghe valley. We set up quantitative slip partitioning models for the northeast corner and eastern belt of Sichuan-Yunnan block. A quantitative kinematical model is set up for the regional system which consists of the northern-eastern active boundary belt of Sichuan-Yunnan block and related blocks.

It's the first time to observe the exhalation flux of soil Rn and CO₂ in Xidatan segment of East Kunlun active fault in September,2006 and first-hand data of the Rn and CO₂ in this fault were obtained.A significant Rn flux,reaching up to 433 mBq·m^-2·s^-1 and the concentration of Rn ranging from 505 up to 2380 Bq·m^-3 was observed in the excavated trench with 2～3 meters deep across the fault.On the surface,the Rn flux ranges from 7 to 28.19mBq·m^-2·s^-1,with the mean value of 14.7 mBq·m^-2·s^-1,similar to the world average.The CO₂ flux on the surface with an average value of 18.9g·m^-2·s^-1also remains similar to regular background values.It shows no systematic spatial variation up to a distance of 1.2 km from the fault and no clear change in the trench.But a high CO₂ flux of 421g·m^-2·s^-1 is observed at phyllite outcrops on a hill 3km north of the fault.A large Rn flux,503 mBq·m^-2·s^-1,is observed at the point where the maximal CO₂ flux is observed.These results indicate the advective pore gas transport from the subsurface to the atmosphere in the vicinity of the East Kunlun active fault zone.

According to the results of 1/10,000 stripped geologic mapping of the northwest segment of the Maxianshan north marginal fault and historical accounts of past events,we discuss in this paper the range of the magistoseismic area,seismogenic fault,pattern and combination feature of the surface ruptures of the 1125 A.D.Lanzhou M7 earthquake.The results show that the magistoseismic area of this earthquake is located in Lanzhou City and its southwest,and the epicenter can be located at the Xianshuigou area.The seismogenic fault of this earthquake is the Xianshuigou-Maquangou sub-segment on the northwest segment of the Maxianshan north marginal fault.This earthquake has produced a surface rupture zone of about 7km long and 300～1000m wide,extending along the seismogenic fault.The surface ruptures consist of earthquake fractures,fault scarps,seismic fissures,seismic landslides,and seismic pits.The surface rupture zone can be sub-divided into 2 sub-segments:the Maidiwan-Xianshuigou sub-segment in the southwest and the Damajiatan-Maquangou sub-segment in the northwest.Among them,the Maidiwan-Xianshuigou sub-segment consists of two parallel surface ruptures,while the Damajiatan-Maquangou sub-segment comprises a single surface rupture.Basing on large scale mapping,it is determined that the left-lateral displacement produced by this event is 2.4～2.5m,and the vertical offset is 0.45～0.92m.Regionally,the Maxianshan north marginal fault is located at the junction of the northern margin of the Qinghai-Xizang plateau and the northern segment of the North-south tectonic belt,which have been strongly active since neotectonic period.A rhombic block confined by major faults of different strikes is developed in this region,and we call it the Gansu-Ningxia rhombic block.The 1125 A.D.Lanzhou M7 earthquake just occurred on the western edge of the rhombic block,i.e.the Wuwei-Zhuanlanghe-Maxianshan Fault zone.The strong uplift and northeastward pushing of the active Qinghai-Xizang block may cause the stress relief on the boundary faults of the Gansu-Ningxia rhombic block,and hence the occurrence of several strong earthquakes.

The Altyn Tagh,Kunlun and Haiyuan Faults are three major left-lateral strike-slip faults with high geologic and GPS-derived horizontal slip rates as well as frequent surface-rupturing earthquakes in the northern Tibetan Plateau.There exist local structures,such as pull-apart basins in stepovers and sag ponds,where fine-grained and/or organic interfaulting sediments have been continuously filled and co-seismic faulting traces have been well preserved in those sediments.Trenching across the strike-slip faults and those local structures,stratum-logging of the trench walls and structural-stratigraphic examination can uncover basic features of the permanent and cumulative geologic deformation zone of a strike-slip fault that has experienced several surface-rupturing earthquake cycles.The geologic section of the Banguoba trench 9km east of Old A'kesai Town across the recent traces of the Altyn Tagh Fault records 7 paleoearthquake events with a co-seismic left-lateral slip of 7±1m for the latest event and its cumulative geologic deformation zone is only 8m in width.The geologic section of the western Old A'kesai trench across a pull-apart basin of the Altyn Tagh Fault records at least 4 paleoearthquake events and its permanent and cumulative geologic deformation zone is only 13m in width.The geologic section of the Xidatan trench across the Kunlun Fault reveals 5 paleoearthquake events and their cumulative geologic deformation zones are 12～13m in width.The Maqin trench across a pull-apart of the Kunlun Fault also reveals 5 paleo-earthquake events and most of the structural deformation,about 15m wide,is concentrated in the pull-apart,while the widest structural deformation,including the associated distortion nearby the boundary fault of the pull-apart,is less than 35m.Two trenches excavated across the southern and northern boundary faults of the Songshan pull-apart basin along the Maomaoshan-Laohuashan segment of the Haiyuan Fault show up 6 paleoevents and their permanent geologic deformation zones are less than 10m wide for single boundary fault.Of course,as a extensional jog,the pull-apart basin over a hundred meters wide will experience severe tensional and transtensional surface ruptures during an earthquake,and the pull-apart basin itself may be taken as one part of the permanent geologic deformation zone.Thus,the repeatedly faulting of the Altyn Tagh,Kunlun,and Haiyuan Faults during the past several surface-rupturing earthquake cycles is localized along their strike and the width of their permanent geologic deformation zone for a single strike-slip fault is over 10 meters,but less than 30 meters in general.

The Maxianshan north marginal fault belongs tectonically to the Kunlun-Qilian-Qinling Caledo～nian-Variscan orogenic belt.The northwest segment of the fault locates within the Mesozoic Lanzhou basin,consisting of Xianshuigou-Maquangou,Xinchenggou and Qingshizui sub-segments.The Xianshuigou-Maquangou sub-segment is 7km in length,and comprises two sub-parallel faults,having a general strike of 290°～300°,dipping NE or SW at an angle of 60° or more.The faults dissect mainly the Cretaceous system,and locally act as the boundary of the Cretaceous system with the Ordovician and Jurassic systems.Upwards,the faults cut through the late Pleistocene loess or the gravel bed of gully terrace,appearing as fault scarp or fault escarpment.This sub-segment was the active segment of the whole fault during late Pleistocene to Holocene periods.The faulting of this sub-segment was dominated by left-lateral strike-slipping.The left-lateral displacement along this sub-segment since late Holocene is 5～8m,and the displacement rate is 0.5～1.72mm/yr.The Xinchenggou sub-segment is about 1.6km long,striking 325°and dipping southwest at the angle of greater than 60°.This sub-segment can be assigned to reverse fault,dissecting the Cretaceous system,and is covered with the gravel bed of the third level terrace of the Yellow River and the late Pleistocene loess.This sub-segment,therefore,has no longer been active since late Pleistocene.The Qingshizui sub-segment is about 2.5km long,striking 280°～310°and dipping northeast at angles of 58°～80°,and can be assigned to normal fault.The fault dissects mainly the Cretaceous system,and locally becomes the boundary between the Cretaceous and Ordovician systems.The fault is also covered with the gravel bed of the third level terrace of the Yellow River and the late Pleistocene loess.This may indicate that this sub-segment has ceased its activity since late Pleistocene.Macroscopically,the middle and eastern segments of the Maxianshan north marginal fault,together with the Zhuanglanghe Fault have made up a right-stepped en echelon zone.The faulting process of the former during late Pleistocene-Holocene was dominated by left-lateral strike-slipping,while that of the later by right-lateral strike-slipping,so a compressional step-over was formed between the two faults.Therefore,the Xianshuigou-Maquangou sub-segment can be assigned to shear fault within the compressional step-over,and hence the latest activity of this sub-segment is later than that of the middle and eastern segments of the Maxianshan north marginal fault.

In the area around Kalpintag thrust system, earthquakes occurred frequently and intensively. The fundamental data and detailed investigation about active tectonics and the law of earthquake recurrence in this region are desiderated. So, 12 scenes of Landsat-7 ETM digital images are chosen and processed exclusively for the active tectonics. Then, two color composite images of 30m-resolution over the region are portrayed with bands 3-2-1 and bands 7-4-3 as R-G-B respectively, while two color composite images of 15m-resolution over the field workaround are fused with bands 3-2-1-8 and bands 7-4-3-8, respectively. With these resulting images, we designed some geological interpretation criteria for active tectonics of Kalpintag thrust system. According to these criteria, active tectonics of the area around Kalpintag thrust system are interpreted with scales of 500,000, while those of three sites on the field workaround are interpreted in detail with scales of 50000, by means of contrastive interpretation with two kinds of different images at one time. At last, the field investigation confirmed that the used techniques of processing and interpretation in this research were resultful.

Fuzhou basin is tectonically located in the eastern part of South China fold system,within the Fuding-Yunxiao Fault depression area of East Fujian volcanic depression zone. Based on detailed logging,and combined with results of other researchers,the preliminary summarization on sedimentary characteristics of late Pleistocene of Fuzhou basin is done. The depositing of Fuzhou basin began from about 56.5ka BP,sediments comprise gravel,sand,clay and silt,showing a depositional sequence with the granularity becoming small from lower to upper,and a bigger variation of lithologic properties in horizontal direction. There are three silt layers in late Quaternary strata of Fuzhou basin. The first and second layers developed during the middle and late Holocene,the depositing time of them is about from 7.86ka BP to 3ka BP to 3.08ka BP and they are the results of “Changle Transgression”; the third developed during the late of late Pleistocene and the depositing time is about from 44ka BP to 20ka BP and it is the result of “Fuzhou Transgression”. The buried late Quaternary sediments in Fuzhou basin can be divided into upper Pleistocene series and Holocene series,which include four formations from old to new. They are Longhai formation(Q³_pl),Dongshan formation (Qhd),Changle formation (Qhc)and Jiantian formation (Qhj) respectively. The Longhai formation can be divided into three members,the sediments of the lower member are celadon,yellow gravel and moderate coarse sand; the middle member is of gray clay,silt,sand and gravel,or interbed of silty clay and fine sand; the upper member is of yellow moderate coarse sand. Dongshan formation comprises gray silty sand and clay. Changle formation can be divided into two parts,the lower part is of interbed of silt and flour sand; the upper is of gray and plumbeous silt or douke silt. The Jiantian formation comprises light gray,brown clay.

There exist several groups of seismogenic active faults at the conjoined areas of the Chuandian,Bayankala and Huanan active blocks along the eastern margin of the Qinghai-Tibetan Plateau. Owing to existence of transverse secondary active faults,the Chuandian Block can be further divided into the Middle Yunnan and Northwestern Sichuan sub-blocks,and the Longmenshan sub-block at the easternmost end of the Bayankala Block. Joint exploration of the crustal structure shows that low-velocity layers exist in the crust of the Chuandian and Bayankala Blocks. These low velocity layers correspond also to high conducting layers and they are the cause of frequent earthquake occurrence in the upper crust. Geologic study and GPS surveying indicate that the tectonic motion of the blocks in this region is accounted to be a complex or superimposition of three basic types of motions: southeastward sliding,rotating on vertical axis,and uplifting,but there is difference in the geologic slip rate and GPS rate. Besides,this paper collects the database of the geologic slip rates and GPS slip rates for the active faults in the region and major scientific problems are also discussed at last.