Geomorphic offsets displaced by coseismic surface rupture can be analyzed to identify earthquake recurrence behavior. Therefore, obtaining a sufficient and precise along-fault offset dataset is vital to identify long-term earthquake recurrence behavior. Furthermore, knowledge of along-fault slip distribution during a single-earthquake or multi-earthquakes is important for other reasons, including a better understanding of the relationship between earthquake size and coseismic displacements, fault kinematics and fault mechanics. A recent flourish of offsets-measuring software and high-resolution topographic data together offer an unprecedented opportunity to measure high-density fault offsets. Here, we introduce and compare two kinds of most popular software, LaDiCaoz and 3D_Fault_Offsets. We describe the workflow and principle of the two codes by taking a fault-offset example on the eastern Altyn Tagh Fault. LaDiCaoz iterates over the channel morphology and position parameters and determines the summed absolute elevation difference Σ[Δ(elevation)] between both transverse profiles. The optimal horizontal offset is defined by the parameter combination that results in the least mismatch between two profiles. Compared with LaDiCaoz, the principle of 3D_Fault_Offsets is more complicated by measuring the offset in three dimensions. It mathematically identifies and represents nine of the most prominent geometric characteristics of common sublinear markers along faults in three dimensions, such as the streambed(minimum elevation), top, free face and base of channel banks or scarps(minimum Laplacian, maximum gradient, and maximum Laplacian), and ridges(maximum elevation). By calculating best fit lines through the nine point clouds on either side of the fault, the code computes the lateral and vertical offsets between the piercing points of these lines onto the fault plane, providing nine lateral and nine vertical offset measures per marker. Through a Monte Carlo approach, the code calculates the total uncertainty on each offset. Although both 3D_Fault_Offsets and LaDiCaoz are developed based on the Matlab platform, there are significant differences in principles, linear marker, software interface, repeatability, input-file types, degree of automation, adaptability, output file types, etc. In this part, we compare and summarize their features, advantages, and disadvantages. Finally, we calculate the correlation of two groups of fault-offset data derived from the two methods along the eastern ATF. By doing this, we try to explore if the two methods can be crosschecked and to study how sinuosity of the linear geomorphic markers affect the measuring results. By discussing and comparing the accuracy of the two measuring methods, we consider that LaDiCaoz is better than 3D_Fault_Offsets in accuracy aspect. In our opinion, there exist some disadvantages in the both software, and higher automation and introduction of artificial intelligence will be the future development direction.

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.

High-magnitude earthquake refers to an earthquake that can produce obvious surface ruptures along its seismogenic fault and its magnitude M is at least equal to 7.0. Prediction and identification of locations, where the high-magnitude earthquakes will occur in potential, is one of the scientific goals of the studies on long-term faulting behavior of active faults and paleo-earthquakes, and is also the key problem of earthquake prediction and forecast. The study of the geological and seismological signatures for identifying M≥7.0 earthquake risk areas and their application is an important part of seismic prediction researches. It can not only promote the development of earthquake science, especially the progress of earthquake monitoring and forecasting, but also be positive for earthquake disaster prevention and effective mitigation of possible earthquake disaster losses. It is also one of the earthquake science problems which the governments, societies and the scientific communities are very concerned about and need to be addressed.
Large or great earthquakes, such as the 2008 Wenchuan earthquake(M8.0), the 2010 Yushu earthquake(M7.1), the 2013 Lushan earthquake(M7.0)and the 2015 Gorkha earthquake(M_W7.8), have unceasingly struck the Qinghai-Tibet Plateau and its surrounding areas, which have been attracting attention of a large number of geoscientists both at home and abroad. Owing to good coverage of the seismic networks and GPS sations, a lot of high-quality publications in seismicity, crustal velocity structure, faulting beihavior have been pressed, which gives us a good chance to summarize some common features of these earthquakes. In this paper, seismogenic structural model of these earthquakes, faulting behavior of seismogenic faults, crustal mechanical property, recent straining environment and pre-earthquake seismicity are first analyzed, and then, five kinds of common features for the sismogenic faults where those earthquakes occurred. Those five kinds of commom features are, in fact, the geological and seismological signatures for identifying M≥7.0 earthquake risk areas. The reliability of the obtained sigatures is also discussed in brief. At last, based on the results of 1:50000 active fault mapping, and published seismic tomography and fault-locking studies, an experimental identification of the risk areas for the future large/great earthquakes in the North China and the Qinghai-Tibet Plateau is conducted to test the scientificity and applicability of these obtained sigantures.

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.

Active fault survey, which is one kind of fundamental researches for reducing disaster risk from earthquake, has been implemented by multiple governmental agencies since the early 1990s in China. Chinese government sponsored some active fault survey projects these years. These researches and projects use a series of thematic maps to describe their processes, results and achievement. Since geography information science was introduced in late 1990s and applied since 2000s to these active fault survey projects, seismologists and experts began to draw thematic maps by this new technology. A convenient and fast way for seismologists and experts to produce atlas of active fault survey products is an important accelerator to achieve these projects.This paper studies on the rapid methodology of producing active fault survey atlas, which is basically built on the processes and contents of active fault projects in recent years, and introduces the methodology on two aspects of standardization and software development. This study has been applied to the ongoing active fault survey projects, and resulted in more effective process, normative data and beautiful atlas. Thus these researches will be easier to be used in future application such as publication, internet sharing, and city development. This methodology has reference value to similar map-producing system in standardization and software development.

Over the past nearly 20 years, there is a huge development in active fault database related technologies in China, mass of active fault data has provided us important basis for researching on earthquake and disaster reduction, etc. However, with the appearance of huge amount of active fault data, lots of problems have emerged, such as data redundancy, inefficient management and information islands, etc. One of the major reasons is lack of efficient method to share the active fault data we owned.By study and comparison, we find that WebGIS is a good solution to solve the problem of active fault data publishing and sharing. WebGIS has well combined the advantages of traditional GIS and internet technologies, it could also share geographic data quickly, provide abundant browsing, searching and analysis functions. Based on the project of "China Earthquake Active Fault Detection—The North China Tectonic Region", and taking the foundational database information sharing platform of the active fault detection and survey as an example, the paper introduces the key technologies of active fault data sharing platform with latest WebGIS technology. The sharing system, which employs ArcGIS Server 10.0 as the GIS server, and utilizes MS-Silverlight technology at the client side, makes use of three-layer architecture which is popular in current B/S mode. To guarantee the security of the database on the internet, data source in the backend of the system is a simplified version of the active fault database of the North China tectonic region. Finally, the system has realized the publishing and sharing of 1 ︰ 50000 active fault mapping and main geophysical survey lines in North China tectonic region, and moreover, it provides some conventional map operations as well as fault searching and locating functions.The wide use of active fault data decides the significance of sharing system. It is very convenient to use this lightweight data sharing system to provide important basis for relevant industries, such as urban planning, land use and engineering site option, etc.

In this paper, adopting nonlinear finite-element method for faults with frictional contact, single fault and conjugate faults are calculated and compared respectively. And conjugate faults system is analyzed about its structural significance, combined with preparation and occurrence of strong earthquakes in the capital circle region. Study shows that seismogenic process of typical conjugated fault system from lock to unlock is well explained by Coulomb friction criteria, and unstable events can take place alternately along conjugate faults. The slip behavior of seismogenic tectonic model of great earthquake composed of two conjugate faults is verified. The numerical simulation as well as the analysis and discussion on the results provide scientific basis for earthquake forecasting and monitoring in areas where conjugate faults have developed.

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 Longmen Shan,located at the eastern margin of the Tibetan plateau,is a steep and high exhumation area. In recent years,the 2008 Wenchuan M_W7.9 earthquake and the 2013 Lushan M_S7.0 earthquake occurred,and researchers presented a lot of low-temperature thermochronology data of the Longmen Shan and adjacent area. In this paper,we provide 4 ZFT ages and 4 AFT ages for the southern segment of the Longmenshan Thrust Belt(LTB),where the low-temperature thermochronology data are still few. Combining with previous researches,we get the Cenozoic exhumation history of the Baoxing Massif,located at the southern segment of the LTB,and new knowledge about the Cenozoic activity of the southern segment of the LTB.The Baoxing Massif began quickly cooling in the early Cenozoic,with the cooling range exceeding 225℃,while the cooling range of the Pengguan Massif in the central segment of the Longmen Shan is between 185～225℃.The four AFT ages in the Baoxing Massif are between 2.7～5.0Ma,which are younger than that in the Pengguan Massif,and it indicates that the late-Cenozoic cooling rate of the Baoxing Massif is bigger than that of the Pengguan Massif. Under this assumption that the surface temperature is 15℃ and the paleo-geothermal gradient is 30℃/km,the average exhumation rate from 3～5Ma to present is about 0.63～1.17mm/yr. The low-temperature thermochronology data indicate that the differential exhumation is concentrated in the Beichuan-Yingxiu Fault and the Jiangyou-Guanxian Fault in the central segment of the LTB,while it is dispersed in a wider region along the two branches of the Shuangshi-Dachuan Fault and the faults and folds to the east,in the southern segment.

2036 landslides were triggered by the 2010 Yushu earthquake from aerial photographs and remote sensing images interpreting,verified by selected field checking. In this paper,twelve factors that influence landslide occurrence,including distance from main co-seismic surface ruptures,peak ground acceleration (PGA),elevation,slope angle,slope aspect,slope curvature,slope position,distance from drainages,lithology,distance from faults,distance from roads,normalized difference vegetation index (NDVI),are selected as landslide hazard evaluation factors. Two types of landslide hazard index map are derived using two "weight of evidence" methods based on Geographical Information Systems (GIS) technology.The success rate of Add-"weight of evidence" method is 80.32%,and the success rate of Subtract-"weight of evidence" method is 80.19%,both are satisfactory.The resulting hazard evaluation maps are divided into five categories, i.e.extremely high,high,moderate,low,and extremely low,respectively.The landslide hazard maps can be used to identify and delineate unstable hazard-prone areas. It can also help planners to choose favourable locations for development schemes,such as infrastructures,buildings,road construction,and environmental protection.

In this paper,a statistical analysis is made using the gray clustering method on the earthquake inducing factors,such as dam height,storage capacity,regional stress state,fault activity,lithology medium conditions and seismic activity background,based on a database of reservoir-induced earthquakes,which includes 150 reservoir-induced earthquake cases and 532 large reservoirs data. Corresponding earthquake occurrence ratios are obtained and used as predictors for reservoir-induced earthquakes. According to the six quake-inducing factors,assessment is made on the maximum magnitude of reservoir-induced earthquake for the Three Gorges Reservoir dam area,the bayou of Xiangxi stream and the cross-river section of the Xiannushan Fault zone,the west Xietan,Badong,and on both banks of Shenlong stream. The results show that the upper-limit of magnitude at dam area is less than magnitude 3,that at the bayou of Xiangxi stream and the cross-river section of Xiannushan Fault zone is between magnitude 4～5,that at west of Xietan is less than magnitude 3,and that at the northern bank of badong and on both banks of the Shenlong stream is between magnitude 3～4.The results have been validated by the actual reservoir-induced seismicity after the impoundment of the Three Gorges Reservoir, with the M_L 2 earthquake at Xiaoxikou 4 km far away from the dam of the Three Gorges Reservoir on February 6, 2009, the M_S 4.1 earthquake at the bayou of Xiangxi stream and the cross-river section of the Xiannushan Fault zone on November 22,2008, the M_S 2.6 earthquake at the west Xietan on August 22, 2009, and the M_L 3.5 earthquake at the bank of Shenlong stream on December 14,2009.

The goal of the exploration to active fault is to understand its activities,relative parameters,the spatial distribution characteristics and its deep structures. There're three major stages for active fault exploration,namely, preparation stage,exploration stage and analysis stage. The construction of the database for each of these stages has different focus.
Based on the review of other articles about the development of active Fault database from international sources,the paper introduces the construction of databases based on the Technological System of China Earthquake Active fault Exploration project. And along with the development and implementation of the projects such as ‘Seismic Risk Assessment of Active fault in Key Earthquake Monitoring Areas in China’,‘China Earthquake Active Fault Exploration’, so on,database templates corresponding to each of the stages of active fault exploration are worked out according to the design idea,architecture and implementation of ArcGIS-based active fault database and the work procedure for active fault exploration. The main functions of the bulk storage software and data quality monitoring software developed for the construction of the database are introduced.
Due to the numerous data and the extensive sources as well as the complexity of the data acquisition during the building of database,there are chances to have either manual or systemic errors,and moreover,the data quality might be impacted,resulting in a database failing to represent the real activities of the active faults. On the other hand,the data stored in the database lacks consistency and integrity,thus,the database is ineffective and opposite to the original intention of its construction. The paper analyzes the main data sources used to establish the active fault database and the causes for generating low quality data,and discusses the advantages for building the active fault database simultaneously along with the implementation of active fault exploration.

The Fuyun Fault is a typical right-lateral strike-slip fault in Altay region where the crustal strain rate is very low. Field observations and restoration of horizontal offsets from the 3D LiDAR data obtained from 3 sites along the Funyun Fault further confirm that the average coseismic right-lateral slip of the 1931 Fuyun earthquake is (6.3±1.2)m,and the slip distribution is unusually flat over its entire length of the Fuyun Fault. The maximum slip is only (6.7±0.5)m under the Karaxingar Range,near to the central part of the surface rupture zone other than 10m to 14m as reported before. Co-located larger offsets,interpreted as cumulative offsets,allow us to define at least 4 more events in addition to the most recent. The cumulative slip distribution of each event seems to follow a similar flat pattern,supporting a characteristic earthquake model interpretation for the 5 last events. Several successive offset landforms are dated at 2 sites by cosmogenic dating method (¹⁰Be)to constrain the long-term right-lateral slip rate of (0.76±0.24)mm/a. An average characteristic slip of 6.3m,a maximum slip of ～6.7m and a slip rate of (0.76±0.24)mm/a yield a recurrence interval of (9 700±3 300)a. Then,great earthquakes on the Fuyun Fault,a right-lateral strike-slip fault follow a characteristic slip behavior with a low long-term slip rate and long recurrence interval,which is a faulting response to the far-field strain resulting from the collision between the Indian and Eurasian plates.

On April 14,2010 at 07:49 (Beijing time), a catastrophic earthquake with M_S 7.1 struck Yushu County, Qinghai Province, China. About 2036 landslides, covering an area of about 1.194km², were interpreted from aerial photographs and remote sensing imageries and verified by field check. And based on the above, the spatial distribution of the Yushu earthquake triggered landslides is presented in this paper. The distribution of the landslides was strongly dominated by main surface ruptures, and their types are varied, with the collapse-type landslide as the dominant. There are five genetic mechanisms of Yushu earthquake triggered landslides, they are: the slope-toe excavation type, the surface water infiltration induced slope slip type, the fault dislocation type, the shaking type, and post-quake snow melting and rainfall penetration type. Besides the main seismic surface ruptures, there are many slope fissures developed mainly on the SE end of the surface rupture zone on the SW wall, an area undergoing intensive compression in the earthquake.

Mass of data in geochemical,geophysical,geological,seismological and other aspects were collected for the national active fault database system in the Tenth Five-Year Plan.How to make use of these mass of data to produce thematic map for government's decision making in urban development planning,land use, significant engineering site selection and providing the scientific basis for urban earthquake resistance and disaster mitigation has become an issue worth studying.Automatic cartography solves this problem well.By summarizing,we find that most of present researches in automatic cartography care much about cartography process itself,rarely involve property and spatial data inspection. Thus, it is hard to ensure the accuracy of data and may lead to a drop in quality of automatic cartography.Firstly,this paper discusses the process of automatic cartography.Secondly,considering the actual situation of urban active fault detecting project,we propose to add inspection of automatic cartography and topology check to guarantee the quality of cartography.Thirdly,further research is done in the principle of automatic matching and topology checking to develop a feasible process for automatic matching and topology checking.Finally,a system is designed to realize the function of automatic matching.The techniques and methods used in this system have important reference value in mapping automation in other areas,such as climate,geography,resources and land use,etc.

In the paper,according to the related factors and characteristics of identified reservoir induced earthquakes,the parameters of reservoir induced earthquake database and library structure have been determined.Based on the database functions of ARCGIG geographic information system software,the reservoir induced earthquake database contains 131 reservoir induced earthquake cases in the would, 110 Class-Ⅰlarge reservoirs(larger than one thousand million cubic meters),200 ClassⅡlarge reservoirs (larger than one hundred million cubic meters and less than one thousand million cubic meters) and 70 reservoirs with dams higher than 100 meters in China.It has the functions of quick query,statistics and icons.After the Wenchuan earthquake,aftershocks endangered many reservoir's dams and people who were taking part in earthquake rescue and relief operations.Two days after the M_s8.0 Wenchuan earthquake,the distribution and basic information of large reservoirs in Sichuan Province and nearby regions was submitted.The government made timely earthquake emergency response decisions to ensure a safe relief.The reservoir induced earthquake database is not only a method provided to the government for quick decision-making,but also can be used nation-wide.

During the M_S 8.0 Wenchuan earthquake,most of surface deformation zones show as flexural scarps or fault scarps,and surface ruptures in bedrock are rare.However,earthquake surface ruptures are entirely exposed in bedrock and discovered by authors near Xiaojiaqiao town of Anxian county.Based on careful analysis of the deformation characteristics and the inner structure of this rupture zone,and in combination with features of the regional earthquake surface ruptures,the authors hold that the earthquake surface ruptures are developed and extend mainly along the preexisting Yingxiu-Beichuan Fault during this earthquake,the faulting is right-reverse-slip movement at a low angle,and the maximum vertical co-seismic dislocation is 5.4 meters,which coincide with the measurements of the flexural scarps or fault scarps.

In this paper,the theoretical foundation of classification of focal mechanism solutions is drawn by the theory of shear dislocation,where the mechanisms of earthquake can be divided into the strike-slip fault,reverse fault and normal fault.The 124 focal mechanisms from Harvard University have been classified by the triangle diagram method in the area of Sichuan and Yunnan Provinces in China.The focal mechanisms of strike-slip,reverse and normal faulting have been discussed.These are the three deformation types in this area.The results show a SE-directed block movement of the Sichuan-Yunnan region.Along the Xianshuihe Fault,the Anninhe Fault,the Zemuhe Fault and the Xiaojiang Fault,large strike-slip movement and deformation have occurred.On the Sagaing Fault and the Longmenshan Fault,the reverse faulting mechanism dominates.The quick movement of the Red River Fault towards southeast driven by the Xiaojiang Fault forms a large tensional stress area between the Jinshajiang and the Xiaojinhe Fault.This constitutes the latest pattern of recent crustal deformation of Sichuan-Yunnan region and its adjacency.

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.

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.

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.

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.

1:250,000 regional seismotectonic map is one of graphic documents achieved in the urban active fault survey project.At present,the 1:250,000 regional seismotectonic maps of various cities are drawn mostly basing on the existing 1:200,000 geological maps.The available paper-made 1:200,000 geological maps are the graphic documents under Beijing 54 Coordinates Systems.However,according to Stipulation on Technical System for China Earthquake Active Fault Surveying issued by China Earthquake Administration,the 1:250,000 regional seismotectonic maps are the graphic documents under Xi'an 80 Coordinate Systems.This article introduces the basic concepts of coordinates systems and the map projection and proposes explicitly that when scanning and digitizing paper geological map,the coordinate's projection parameters indicated in the paper geological map shall be taken for setting up projection information.The conversion of screen coordinates to map coordinates is realized through space coordinate registration,and by projection conversion,the Beijing 54 Coordinates System is converted to Xi'an 80 Coordinates System.Finally,with the aid of ArcGIS software,the 1:250,000 regional seismotectonic maps are compiled based on 1:200,000 geologic maps.

The project of "Yinchuan active fault exploration and earthquake risk assessment" is aimed at strengthening the fundamental work of engineering construction for earthquake resistance and prevention in Yinchuan City.In order to achieve this general goal,a joint multi-disciplinary exploration of the Yinchuan buried fault and the Luhuatai fault has been carried out on the basis of collection and analysis of predecessors'data.This paper discusses the methods of constructing three-dimensional subsurface structure model of the project area of Yinchuan active fault exploration by using the achievements of the Yinchuan active fault exploration,and puts forward main work steps and suggestions for the model construction.The steps for 3D modeling of subsurface structure using active fault survey data are as follows:To collect and pre-process the data of seismic exploration of active fault;Using seismic interpretation software to interpret the fault and the bed position,draw bed plane structure map,and output the fault and bed position data,meanwhile,to further complete the 3D visual modeling with this software;To load fundamental data,bed plane and fault data into the 3D modeling software GOCAD,carry on the fault plane and the bed plane revision and reconstruct 3D model,construct three-dimensional cutting section,and demonstrate the three-dimensional model achievements.Since the seismic survey data are not standard,it increases the difficulty in earthquake data explanation and affects the explanation precision.Therefore,we propose to standardize the archiving of primary seismic survey data,add a cross line in the survey area of each active fault,and if possible,use the regional time-depth conversion used by petroleum sector to enhance the explanation precision of seismic section.

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.

Urban earthquake disaster is mainly caused by abrupt rupturing of active fault.The seismic active fault database on active fault location,slip rates,and earthquake recurrence intervals can help the community effectively reduce earthquake losses,protect against loss of life and damage to property.In United States,New Zealand and other countries,some active fault databases have been built and they provide users with full and open information.In China,the first active tectonics database was built in early 1996.Nowadays,the development of urban active fault exploration makes it possible and necessary to construct an urban active fault information management system(UAFIMS).The UAFIMS aims to construct the basic databases of seismic active faults and their associated hazards as well as the GIS of seismic active fault hazards by utilizing high-performance computer and with the combination of the integrated secondary development of various commercial software.The databases and GIS will be used for urban planning and land use,major project siting,fortification against earthquake,architecture protection,rapid assessment of disaster,government decision-making,and the emergency relief during earthquake by the command departments.We adopt the object-oriented design ideas and method to devise the system,using prototype model for development and object-oriented software technology in VB to invoke ArcGIS background Arc-Objects components library for the integrated secondary development.The system uses C/S model in the LAN and B/S model in the WAN.It has a three-tier structure including user interface,applications and database.The database of exploration results of urban active faults is managed by the ways of classification,tiered storage and thematic organization enquiry,which contains the basic geographic information,geochemical exploration results,electromagnetic sounding data,ground-probing radar sounding data,shallow seismic reflection,deep seismic sounding profiles,as well as drilling data.As a spatial multimedia entity database for data integration,it is a collection of spatial geographical information,image information,text information and data information,and etc.Catering to the needs of results of major fault exploration and seismic hazard assessment projects,the system is designed with the concept of sufficiently displaying the various exploration results and being convenient for users to use and inquire.The application layer can be divided into three types of functions,that is,result displaying and consulting module,professional data analysis and calculation module,and system maintenance module.The system provides users with professional usage habits and simple graphical interface operation,and takes into account,as much as possible,the coordination of system interface to both the local area network and the wide area network.Based on the database of the urban active faults,and supported from spatial analysis,the UAFIMS incorporates geological,geophysical and geochemical data,and comprehensive enquiries and thematic analysis together,and possesses the functions of classification,inquiry,display and analysis,and etc.of the results of active fault exploration and interpretation.The fulfillment of the system provides a solid foundation and technological platform for the quantitative study of active faults,and it also offers scientific basis for urban planning and earthquake disaster reduction.

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.

In this paper,the relation of time,space and intensity characteristics,as well as focal mechanisms of earthquakes to fault activity in Beijing area has been analyzed.A tectonic deformation model for the upper crust of this region is developed in this paper in the light of the quantitative analysis of fault activity.The results show that the earthquakes in this region are distributed mainly along the NWW direction,forming a concentration belt of earthquakes.In addition,several earthquakes of above magnitude M_S 4.5 occurred along the NE-or NEE-trending faults.These two sets of fault form a conjugate fault system,on which earthquakes occur alternately in different active periods,and the average release rate of creep energy corresponds to the occurrence of one M_S 4.2 earthquake per year.The crust of Beijing region can be divided in to the Yanshan,North Shanxi,Taihangshan and Central Hebei blocks,which have an irregular boundary along the NWW direction.Under the action of the NEE-directed principal compressive stress,these NWW-arranged blocks were easily activated,resulting in concentration belts of earthquake of a certain scale along block boundaries.Moreover,earthquakes of above magnitude M_S 4.5 occurred along the conjugated NE-or NEE-trending faults.

The inner part of the Sichuan-Yunnan rhombic block is dissected by the Lijiang-Xiaojinhe Fault, and hence can be subdivided into Northwest Sichuan sub-block in the north and Central Yunnan sub-block in the south. The eastern boundary faults of these two sub-blocks are regularly characterized by left-lateral strike-slip, while the western boundary faults are characterized by right-lateral strike-slip. The slip rate of both the eastern and western boundary faults are significantly different. All these phenomena may indicate the composite movement of these sub-blocks characterized by southeastward horizontal slipping associated with clockwise rotation around a vertical axis during the Cenozoic time. Among them, the horizontal slip rate of the Southwest Sichuan sub-block is 5mm/a, and the angular velocity of clockwise rotation is about 1 4°/Ma, while those of the Central Yunnan sub-block are 3.5mm/a and 1 5°/Ma, respectively. About 90 oriented samples have been collected from Paleogene strata in Yaoan, Dayao, Yongren and Beimajie of Kunming within the Central Yunnan sub-block. The vectors of remanent magnetism of each sample (measured magnetic declination and inclination) have been obtained through alternating field demagnetization and thermal demagnetization. The comparison between the measured magnetic declination and the expected value shows that the accumulated clockwise rotation of the Central Yunnan sub-block of the Sichuan-Yunnan rhombic block since early Miocene has reached up to 30°～48°. The feature represented by the entire rotation of the sub-blocks accompanied by left-lateral slipping along the boundary active faults is consistent with the kinetic model of clockwise rotation of the block in left-lateral strike-slip faulting region.