This paper examines major active faults and the present-day tectonic stress field in the East Tibetan Plateau by integrating available data from published literature and proposes a block kinematics model of the region...This paper examines major active faults and the present-day tectonic stress field in the East Tibetan Plateau by integrating available data from published literature and proposes a block kinematics model of the region. It shows that the East Tibetan Plateau is dominated by strike-slip and reverse faulting stress regimes and that the maximum horizontal stress is roughly consistent with the contemporary velocity field, except for the west Qinling range where it parallels the striking of the major strike-slip faults. Active tectonics in the East Tibetan Plateau is characterized by three faulting systems. The left-slip Kunlun-Qinling faulting system combines the east Kunlun fault zone, sinistral oblique reverse faults along the Minshan range and two major NEE-striking faults cutting the west Qinling range, which accommodates eastward motion, at 10--14 mm/a, of the Chuan-Qing block. The left-slip Xianshuihe faulting system accommodated clockwise rotation of the Chuan-Dian block. The Longmenshan thrust faulting system forms the eastern margin of the East Tibetan Plateau and has been propagated to the SW of the Sichuan basin. Crustal shortening across the Longmenshan range seems low （2-4 mm/a） and absorbed only a small part of the eastward motion of the Chuan-Qing block. Most of this eastward motion has been transmitted to South China, which is moving SEE-ward at 7-9 mm/a. It is suggested from geophysical data interpretation that the crust and lithosphere of the East Tibetan Plateau is considerably thickened and theologically layered. The upper crust seems to be decoupled from the lower crust through a decollement zone at a depth of 15-20 kin, which involved the Longmenshan fault belt and propagated eastward to the SW of the Sichuan basin. The Wenchuan earthquake was just formed at the bifurcated point of this decollement system. A rheological boundary should exist beneath the Longmenshan fault belt where the lower crust of the East Tibetan Plateau and the lithospheric mantle of the Yangze block are juxtaposed.展开更多
In this paper, we focus on the characteristics of the landslides developed in the epicentral area of AD 1556 M^8.5 Huaxian Earthquake, and discuss their relations to the active normal faults in the SE Weihe Graben, Ce...In this paper, we focus on the characteristics of the landslides developed in the epicentral area of AD 1556 M^8.5 Huaxian Earthquake, and discuss their relations to the active normal faults in the SE Weihe Graben, Central China. The results from analyzing high-resolution remote-sensing imagery and digital elevation models（DEMs）, in combination with field survey, demonstrate that：（i） the landslides observed in the study area range from small-scale debris/rock falls to large-scale rock avalanches;（ii） the landslides are mostly developed upon steep slopes of ≥30°; and（iii） the step-like normal-fault scarps along the range-fronts of the Huashan Mountains as well as the thick loess sediments in the Weinan area may facilitate the occurrence of large landslides. The results presented in this study would be helpful to assess the potential landslide hazards in densely-populated areas affected by active normal faulting.展开更多
Riedel shear system,which consists of some different oriented faults and derivative structures,is an important pattern of tectonic activity and stress regulation,which has been widely applied to the interpretation of ...Riedel shear system,which consists of some different oriented faults and derivative structures,is an important pattern of tectonic activity and stress regulation,which has been widely applied to the interpretation of intracontinental deformation.The Laolongwan Basin,located in the western Haiyuan fault zone at the northeastern Tibetan Plateau,is a key area to study the Cenozoic intracontinental deformation in the northeastern plateau,which formed a complex active fault system during the Cenozoic.However,the activity of these faults and their kinematic mechanism remain unclear.In this contribution,based on detailed structural interpretation of remote sensing image,field observations and OSL dating analysis,we propose a Riedel Shear model of active fault system in the Laolongwan Basin.Our observations show that this active fault system consist of four major faults,including the left strike-slip Hasi Shan fault and Zihong Shan fault with thrusting characteristics,the Southern Zihong Shan thrust fault and the Mijia Shan normal fault.The fault offset and OSL dating analyses suggest that the left-lateral slip rate of the Hasi Shan fault is~2.60-3.01 mm/a since ca.15 ka,whereas the Zihong Shan fault is~1.10-1.13 mm/a since ca.14 ka.Faultslip vectors analyses indicate that the active fault system related to the Riedel Shear in the Laolongwan Basin was controlled by the regional ENE-WSW compressive stress.This compression also caused the significant left-lateral strike-slip movement along the Haiyuan fault zone at the same time,which might result from the northeastward continuous expanding of the Tibetan Plateau during the Late Cenozoic.展开更多
As shallow salt lake resources are increasingly exploited,deep confined brine has become a strategic alternative due to its widespread distribution and significant reserve potential.However,unfavorable reservoir chara...As shallow salt lake resources are increasingly exploited,deep confined brine has become a strategic alternative due to its widespread distribution and significant reserve potential.However,unfavorable reservoir characteristics,particularly low permeability and poor recovery efficiency,have historically rendered these deposits uneconomic,restricting their utilization.Taking the Mahai Salt Lake in the Qaidam Basin as a representative case,this study investigates the structural controls on brine enrichment through an integrated approach.Previous long-term metallogenic studies and exploration data indicate occurrences of an extensional fault zone favorable for brine accumulation.Therefore,we applied InSAR deformation analysis to assess coseismic and postseismic surface responses.Combined with radon-222 emanation mapping,our findings reveal a strong spatial correlation between high-productivity brine boreholes and active fault systems.The existence of active faults enhance brine migration and storage,provided that the target reservoirs have substantial halite thickness and maintain relatively low clay-silt content.展开更多
The Taihang Mountain piedmont fault is a large-scale structure zone in north and east China which cross Beijing,with the NE-NNE extent spans approximately 620 km.It is very important to determine the fault zone activi...The Taihang Mountain piedmont fault is a large-scale structure zone in north and east China which cross Beijing,with the NE-NNE extent spans approximately 620 km.It is very important to determine the fault zone activity due to the close relation of active structures and earthquakes.Regarding the fault activity,there are three different opinions：1） it is a large deep fault zone;2） it is an active fault zone and an earthquake structure belt;and 3） it is not an earthquake structure belt.In order to ascertain the active character of the fault,the deep tectonic setting and the activity since the Quaternary were investigated using recent seismic and drilling data to make a joint interpretation.The investigation results show that the Taihang Mountain piedmont fault is not a large lithospheric fault because the early middle Pleistocene（Q（P2）） layers are offset by the fault and the late middle Pleistocene（Q（P2）） and late Pleistocene layers are not offset by the fault.We determine that the Taihang Mountain piedmont fault in the area is not an active fault and is also not a large lithospheric fault.This study result provides important geological and geophysical data for city planning and construction in Hebei province and, especially,has great significance for seismic hazard assessment of the capital area.展开更多
Based on the convection and diffusion mechanisms of radon migration, in this paper we deduce the two-dimensional differential equation for radon transportation in the overburden above active fault zones with an unlimi...Based on the convection and diffusion mechanisms of radon migration, in this paper we deduce the two-dimensional differential equation for radon transportation in the overburden above active fault zones with an unlimited extension along the strike. Making use of the finite difference method, the radon concentration distribution in the overburden above active faults is calculated and modeled. The active fault zone parameters, such as the depth and the width of the fault zone, and the value of radon concentration, can be inverted from the measured radon concentration curve. These realize quantitative interpretation for radon concentration anomalies. The inversion results are in good agreement with the actual fault zone parameters.展开更多
Strong earthquakes (moment magnitude M<sub>W</sub> ≥ 5.5) are uncommon in Tuscany and surroundings (central Italy). The last strong seismic event occurred a century ago (September 7, 1920 Garfagnana, M<...Strong earthquakes (moment magnitude M<sub>W</sub> ≥ 5.5) are uncommon in Tuscany and surroundings (central Italy). The last strong seismic event occurred a century ago (September 7, 1920 Garfagnana, M<sub>W</sub> = 6.53). The paucity of seismic instrumental recordings hinders the identification of the tectonic regime active in Tuscany. On the other hand, the geological and geomorphological pieces of evidence collected so far, concerning potential active and capable faults, are scarce, fragmentary and ambiguous. In this work I shed light on the active deformation of Tuscany by using two independent approaches: earthquake source mechanisms and GNSS (GPS) geodetic measurements. I have considered 41 small seismic events (M<sub>W</sub> ≤ 5.1) that occurred in the study area during the last decade. The related source mechanisms (retrieved by the Time Domain Moment Tensor method) define a relatively clear picture of the active deformation: extension along the northern Apennine watershed and strike-slip regime within inner Tuscany, up to the Tyrrhenian coast. This pattern broadly agrees with the horizontal strain field reconstructed by the geodetic velocity field. The latter has been constrained by a network of 840 GPS stations located in Italy and neighboring countries, operating in the last 20 years.展开更多
Active fault creep slip induces deformation of rock mass buried deeply in fault zones that significantly affect the operational safety of long linear projects passing through it.Displacement distribution patterns of r...Active fault creep slip induces deformation of rock mass buried deeply in fault zones that significantly affect the operational safety of long linear projects passing through it.Displacement distribution patterns of rock masses in active fault zones which have been investigated previously are the key design basis for such projects.Therefore,a discrete element numerical model with different fault types,slip time,dip angles,and complex geological features was established,and then the creep slip for normal,reverse,and strike-slip faults were simulated to analyze the displacement distribution in the fault rock mass.A disk rotation test system and the corresponding laboratory test method were developed for simulating rock mass displacement induced by creep slippage of faults.A series of rotation tests for softand hard-layered specimens under combined compression and torsional stress were conducted to verify the numerical results and analyze the factors influencing the displacement distribution.An S-shaped displacement distribution independent of fault dip angle was identified corresponding to reverse,normal,and strike-slip faults.The results indicated that the higher the degree of horizontal extrusion,the softer the rock mass at the fault core,and the higher the degree of displacement concentration in the fault core;about 70%of the creep slip displacement occurs within this zone under 100 years of creep slippage.展开更多
The detailed geological mapping, conducted in the Damxung-Yangbajain basin, shows that there are many types of deposits formed since the Pliocene. The oldest sediments are formed during the Pliocene. The most prominen...The detailed geological mapping, conducted in the Damxung-Yangbajain basin, shows that there are many types of deposits formed since the Pliocene. The oldest sediments are formed during the Pliocene. The most prominent sediments are three sets of moraines and fluvioglacial deposits. The ESR, U-series and OSL dates indicate they are formed about 700-500 ka B.P., 250-125 ka B.P. and 75-12 ka B.P. respectively and indicate that there are three glacial periods since the mid-Pleistocene in the Nyainqentanglha Range. Along the southeast side of the Nyainqentanglha Range, the main southeast dipping fault zone which bounds the Damxung-Yangbajain Graben on its western edge was mapped. The fault zone consists of three secondary fault zones and their initiation ages that the fault zones became active gradually decrease southeastward. Prominent faulting occurred in about 700-500 ka B.P., 350-220 ka B.P., -140 ka B.P. and 70-50 ka B.P. since the mid-Pleistocene. The height of fault scarps which offset the sediments formed since the mid-Pleistocene suggest that the vertical slip rates change between 0.4 -2 mm/a and the cumulative average vertical movement at rates of 1.1±0.3 mm/a during the Quaternary period and the Holocene vertical throw rate is 1.4±0.6 mm/a along the fault zones on the western side of the Damxung-Yangbajain Graben.展开更多
It is important to explore active faults in urban areas and their surroundings for earth- quake disaster mitigation. Satellite remote sensing techniques can play an important role in such active fault exploration. It ...It is important to explore active faults in urban areas and their surroundings for earth- quake disaster mitigation. Satellite remote sensing techniques can play an important role in such active fault exploration. It can not only reveal the pattern of active faults and active tectonics on a macroscop- ic scale, but also monitor the occurrence, development and rules of temporal-spatial evolution of active faults. In this paper, we use the Hangzhou area as an example to introduce methods of extracting de- tailed active fault information when covered by thick unconsolidated Quaternary sediment, using im- age enhancement and image fusion etc. to improve the definition and precision of satellite images and presenting a three-dimensional （3D） image to illustrate tectono-geomorphic features along the relevant faults. We have also collected aeromagnetic anomaly data, shallow seismic exploration data and dating data, and carried out field surveys to validate the characteristics of active faults based on remote sens- ing images. The results revealed about the faults showed a high consistency with traditional geological knowledge, and demonstrate that it is feasible to explore active faults in a weakly active tectonic area by using satellite remote sensing techniques and contribute to large engineering projects and research on neotectonics.展开更多
The Anninghe fault is a large left-lateral strike-slip fault in southwestern China. It has controlled deposition and magmatic activities since the Proterozoic, and seismic activity occurs frequently. The Mianning-Xich...The Anninghe fault is a large left-lateral strike-slip fault in southwestern China. It has controlled deposition and magmatic activities since the Proterozoic, and seismic activity occurs frequently. The Mianning-Xichang segment of the Anninghe fault is a seismic gap that has been locked by high stress. Many studies suggest that this segment has great potential for large earthquakes(magnitude >7). We obtained three vertical velocity profiles of the Anninghe fault(between Mianning and Xichang) based on the inversion of P-wave first arrival times. The travel time data were picked from seismograms generated by methane gaseous sources and recorded by three linearly distributed across-fault dense arrays. The inversion results show that the P-wave velocity structures at depths of 0-2 km corresponds well with the local lithology. The Quaternary sediments have low seismic velocities, whereas the igneous rocks,metamorphic rocks, and bedrock have high seismic velocities. We then further discuss the fault activities of the two fault branches of the Anninghe fault in the study region based on small earthquakes(magnitudes between ML 0.5 and ML 2.5) detected by the Xichang array.The eastern fault branch is more active than the western branch and that the fault activities in the eastern branch are different in the northern and southern segments at the border of 28°21′N. The high-resolution models obtained are essential for future earthquake rupture simulations and hazard assessments of the Anninghe fault zone. Future studies of velocity models at greater depths may further explain the complex fault activities in the study region.展开更多
The Yinwashan and Xinminpu faults are located in the Jiuxi Basin in the western end of the Hexi Corridor. The determination of their activity and slip rates is of great significance for understanding the eastward exte...The Yinwashan and Xinminpu faults are located in the Jiuxi Basin in the western end of the Hexi Corridor. The determination of their activity and slip rates is of great significance for understanding the eastward extension of the Altyn Tagh fault. Based on geological and geomorphologic field survey, trench excavation, optically stimulated luminescence dating, we define the fault geometry and kinematic properties of the two faults. Based on fault scarps measurement using differential GPS and 10 Be surface exposure dating, we determined vertical slip rate of 0.09±0.01 mm/yr for the Yinwashan fault and 0.1±0.02 mm/yr for the Xinminpu fault. Using the dips observed in trenches and natural sections, we estimated horizontal shortening rates of 0.05±0.03 and 0.23±0.06 mm/yr, respectively. No significant strike slip motion is observed on these two faults, and we infer that this region was dominated by horizontal shortening in the Late Quaternary. Although the shortening rate is quite low on each individual fault, together with other faults in this area, these two faults have an essential role in transferring slip from the eastern end of the Altyn Tagh fault and in accommodating the northeastward growth of Tibetan Plateau.展开更多
Based on the earthquake data of 11 active intraplate fault zones of the Chinese mainland, we have studied the earthquake recurrence behaviors on entire active fault zones and their relations to those on individual fau...Based on the earthquake data of 11 active intraplate fault zones of the Chinese mainland, we have studied the earthquake recurrence behaviors on entire active fault zones and their relations to those on individual fault-segments. The results show that the earthquake recurrence on entire active fault zones, each of them is made up of multiple segments, displays three types of behavior, i.e., the clustering behavior, the random behavior, and the poor quasi-periodic behavior. The major one is the sparse clustering behavior, its recurrence process often exhibits that clusters (active periods) and gaps (quiescent periods) occur alternatively in varying degrees. The recurrence intervals within and between clusters, the durations of individual clusters, the earthquake number and strength of every cluster are all variable. The recurrence process is non-linear, there is neither the strength-time dependence nor the time-strength dependence. However, the earthquake recurrence processes on individual fault-segments are much more simple, and mainly display either the quasi-periodic or the time-predictable behaviors. Also, this study further discovers that the temporal clustering in earthquake recurrence process on entire fault zones is mainly caused by the rupture 'contagion' on different fault-segments within relatively short periods of time. Along active fault zones, the degree and orientation of rupture 'contagion' may vary with different seismic cycles, and the 'contagion' seems to be able to jump over unbroken 'gaps' on the fault zones.展开更多
The Yangtze River Economic Belt(YREB)spans three terrain steps in China and features diverse topography that is characterized by significant differences in geological structure and presentday crustal deformation.Activ...The Yangtze River Economic Belt(YREB)spans three terrain steps in China and features diverse topography that is characterized by significant differences in geological structure and presentday crustal deformation.Active faults and seismic activity are important geological factors for the planning and development of the YREB.In this paper,the spatial distribution and activity of 165 active faults that exist along the YREB have been compiled from previous findings,using both remote-sensing data and geological survey results.The crustal stability of seven particularly noteworthy typical active fault zones and their potential effects on the crustal stability of the urban agglomerations are analyzed.The main active fault zones in the western YREB,together with the neighboring regional active faults,make up an arc fault block region comprising primarily of Sichuan-Yunnan and a“Sichuan-Yunnan arc rotational-shear active tectonic system”strong deformation region that features rotation,shear and extensional deformation.The active faults in the central-eastern YREB,with seven NE-NNE and seven NW-NWW active faults(the“7-longitudinal,7-horizontal”pattern),macroscopically make up a“chessboard tectonic system”medium-weak deformation region in the geomechanical tectonic system.They are also the main geological constraints for the crustal stability of the YREB.展开更多
The Anninghe fault is one of the significant earthquake-generating fault zones in the Southwest China. Local historical record shows that a M2≥7 strong earthquake occurred in the year of 1536. On the basis of the det...The Anninghe fault is one of the significant earthquake-generating fault zones in the Southwest China. Local historical record shows that a M2≥7 strong earthquake occurred in the year of 1536. On the basis of the detailed air-photographic interpretation and field investigation, we have acquired the following knowledge： ① The average sinistral strike-slip rate since the Late Pleistocene is about 3～7 mm/a; ② There is important reverse faulting along the fault zone besides the main left-lateral strike-slip motion, and the shortening rate across the Anninghe fault zone due to the reverse faulting is about 1.7-4.0 mm/a. If the Xianshuihe fault zone is simply partitioned into the Anninghe and Daliangshan faults, we can also get a slip rate of 3-7 mm/a along the Daliangshan fault zone, which is the same as that on the Anninghe fault zone. Moreover, on the basis of our field investigation and the latest knowledge concerning the active tectonics of Tibetan crust, we create a dynamic model for the Anninghe fault zone.展开更多
Since the recorded historical period,the Kachchh Rift Basin(KRB)has encountered numerous moderate to large magnitude earthquakes.According to the series of seismicity research so far,there are several important points...Since the recorded historical period,the Kachchh Rift Basin(KRB)has encountered numerous moderate to large magnitude earthquakes.According to the series of seismicity research so far,there are several important points of debate regarding the tectonic history and evolution of the KRB,especially during the Quaternary period.Therefore,the main objective of the present research is to inspect and perceive the association amongst the strain build-up,earthquake provenance,landform evolution and progression as archived by the Quaternary deposits of the KRB.The previous studies demonstrated the evolutions of various landforms,such as the uplifted fluvial terraces,formation of the gorges,uplifted alluvial fan sequences,which can be ideally used to reconstruct the neotectonic history along active faults of KRB.Considering this,the analysis of the accessible and supportive data,including geochronology provided by earlier studies along with some new dataset for a superior knowledge on the Quaternary tectonic forces prevailing in the KRB,have been carried out.Furthermore,we also emphasized the differences and directions for future potential research issues.The observations of variability in uplift rates across the various active faults in the KRB suggest a complex geological history during the Quaternary period.The results show that the vertical uplift rate along the significant active faults range from 0.8 to 2.8 mm/yr,demonstrating the variable tectonic stress regime prevailing in the KRB.The uplift rates constricted from geomorphic and chronological aspects suggest that the tectonic movements within the Kachchh intraplate region is regulated by the fault segments and the present tectonic stress field is in accordance with the encompassing tectonic stress field associated with the northward movement of the Indian plate corresponding to the Eurasian plate.展开更多
Offshore active faults, especially those in the deep sea, are very difficultto study because of the water and sedimentary cover. To characterize the nature and geometry ofoffshore active faults, a combination of metho...Offshore active faults, especially those in the deep sea, are very difficultto study because of the water and sedimentary cover. To characterize the nature and geometry ofoffshore active faults, a combination of methods must be employed. Generally, seismic profiling isused to map these faults, but often only fault-related folds rather than fracture planes are imaged.Multi-beam swath bathymetry provides information on the structure and growth history of a faultbecause movements of an active fault are reflected in the bottom morphology. Submersible anddeep-tow surveys allow direct observations of deformations on the seafloor (including fracture zonesand microstructures). In the deep sea, linearly aligned cold seep communities provide indirectevidence for active faults and the spatial migration of their activities. The Western Sagami Bayfault (WSBF) in the western Sagami Bay off central Japan is an active fault that has been studied indetail using the above methods. The bottom morphology, fractured breccias directly observed andphotographed, seismic profiles, as well as distribution and migration of cold seep communitiesprovide evidence for the nature and geometry of the fault. Focal mechanism solutions of selectedearthquakes in the western Sagami Bay during the period from 1900 to 1995 show that the maximumcompression trends NW-SE and the minimum stress axis strikes NE-SW, a stress pattern indicating aleft-lateral strike-slip fault.展开更多
-On the basis of the data of geophysics and seismic activities, the analyses of the active faults, seismic activities and the sea floor unstable factors of the Zhujiang River Mouth Basin have been made so as to study ...-On the basis of the data of geophysics and seismic activities, the analyses of the active faults, seismic activities and the sea floor unstable factors of the Zhujiang River Mouth Basin have been made so as to study the characteristics of the compressional subactive continental margin of Cathaysian system, arc littoral strongly active fracture zone, the division of seismic subzone and seismic zone of the continental margin of northern South China Sea, the potential focal area, and to analyze the regional stability. We consider that the Zhujiang River Mouth Basin belongs to a stable or a moderately stable region.展开更多
The Ying-Qiong Basin is located on the northwestern margin of the South China Sea and at the junction of the South China Block and the Indochina Block.It is characterized by complex geological structures.The existing ...The Ying-Qiong Basin is located on the northwestern margin of the South China Sea and at the junction of the South China Block and the Indochina Block.It is characterized by complex geological structures.The existing seismic data in the study area is sparse due to the lack of earthquake activities.Because of the limited source energy and poor coverage of seismic data,the knowledge of deep structures in the area,including the spatial distribution of deep faults,is incomplete.Contrarily,satellite gravity data cover the entire study area and can reveal the spatial distribution of faults.Based on the wavelet multi-scale decomposition method,the Bouguer gravity field in the Ying-Qiong Basin was decomposed and reconstructed to obtain the detailed images of the first-to sixth-order gravitational fields.By incorporating the known geological features,the gravitational field responses of the main faults in the Ying-Qiong Basin were identified in the detailed fields,and the power spectrum analysis yielded the depths of 1.4,8,15,26.5,and 39 km for the average burial depths of the bottom surfaces from the first-to fifth-order detailed fields,respectively.The four main faults in the Yinggehai Basin all have a large active depth range:fault A(No.1)is between 5 and 39 km,fault B is between 26.5 and 39 km,and faults C and D are between 15 and 39 km.However,the depth of active faults in the Qiongdongnan Basin is relatively shallow,mainly between 8 and 26.5 km.展开更多
The most common method used to describe earthquake activity is based on the changes in physical parameters of the earth's surface such as displacement of active fault and seismic wave.However,such approach is not ...The most common method used to describe earthquake activity is based on the changes in physical parameters of the earth's surface such as displacement of active fault and seismic wave.However,such approach is not successful in forecasting the movement behaviors of faults.In the present study,a new mechanical model of fault activity,considering the shear strength on the fault plane and the influence of the resistance force,is established based on the occurrence condition of earthquake.A remote real-time monitoring system is correspondingly developed to obtain the changes in mechanical components within fault.Taking into consideration the local geological conditions and the history of fault activity in Zhangjiakou of China,an active fault exposed in the region of Zhangjiakou is selected to be directly monitored by the real-time monitoring technique.A thorough investigation on local fault structures results in the selection of two suitable sites for monitoring potential active tectonic movements of Zhangjiakou fault.Two monitoring curves of shear strength,recorded during a monitoring period of 6 months,turn out to be steady,which indicates that the potential seismic activities hardly occur in the adjacent region in the near future.This monitoring technique can be used for early-warning prediction of the movement of active fault,and can help to further gain an insight into the interaction between fault activity and relevant mechanisms.展开更多
基金the auspice of National Key Basic Project(973)(granted number 2008CB425702)National Science and Technology Project(granted Number SinoProbe-08)China Geological Survey project(granted number1212010670104)
文摘This paper examines major active faults and the present-day tectonic stress field in the East Tibetan Plateau by integrating available data from published literature and proposes a block kinematics model of the region. It shows that the East Tibetan Plateau is dominated by strike-slip and reverse faulting stress regimes and that the maximum horizontal stress is roughly consistent with the contemporary velocity field, except for the west Qinling range where it parallels the striking of the major strike-slip faults. Active tectonics in the East Tibetan Plateau is characterized by three faulting systems. The left-slip Kunlun-Qinling faulting system combines the east Kunlun fault zone, sinistral oblique reverse faults along the Minshan range and two major NEE-striking faults cutting the west Qinling range, which accommodates eastward motion, at 10--14 mm/a, of the Chuan-Qing block. The left-slip Xianshuihe faulting system accommodated clockwise rotation of the Chuan-Dian block. The Longmenshan thrust faulting system forms the eastern margin of the East Tibetan Plateau and has been propagated to the SW of the Sichuan basin. Crustal shortening across the Longmenshan range seems low （2-4 mm/a） and absorbed only a small part of the eastward motion of the Chuan-Qing block. Most of this eastward motion has been transmitted to South China, which is moving SEE-ward at 7-9 mm/a. It is suggested from geophysical data interpretation that the crust and lithosphere of the East Tibetan Plateau is considerably thickened and theologically layered. The upper crust seems to be decoupled from the lower crust through a decollement zone at a depth of 15-20 kin, which involved the Longmenshan fault belt and propagated eastward to the SW of the Sichuan basin. The Wenchuan earthquake was just formed at the bifurcated point of this decollement system. A rheological boundary should exist beneath the Longmenshan fault belt where the lower crust of the East Tibetan Plateau and the lithospheric mantle of the Yangze block are juxtaposed.
基金supported by the National Natural Science Foundation of China (No. 41502203)the Scientific Research Foundation for Returned Overseas Scholars of China (awarded to G. Rao)+1 种基金the Natural Science Foundation of Zhejiang Province (No. LY15D02001)a Science Project (No. 23253002)from the Ministry of Education, Culture, Sports, Science and Technology of Japan
文摘In this paper, we focus on the characteristics of the landslides developed in the epicentral area of AD 1556 M^8.5 Huaxian Earthquake, and discuss their relations to the active normal faults in the SE Weihe Graben, Central China. The results from analyzing high-resolution remote-sensing imagery and digital elevation models（DEMs）, in combination with field survey, demonstrate that：（i） the landslides observed in the study area range from small-scale debris/rock falls to large-scale rock avalanches;（ii） the landslides are mostly developed upon steep slopes of ≥30°; and（iii） the step-like normal-fault scarps along the range-fronts of the Huashan Mountains as well as the thick loess sediments in the Weinan area may facilitate the occurrence of large landslides. The results presented in this study would be helpful to assess the potential landslide hazards in densely-populated areas affected by active normal faulting.
基金financially supported by the Natural Science Foundation of Chongqing,China(No.cstc2020jcyj-msxm X0487)the Open Fund of Key Laboratory of Sedimentary Basins and Oil and Gas Resources,the Ministry of Natural Resources(No.cdcgs2022006)+2 种基金the National Natural Science Foundation of China(No.42072001)the China Geological Survey(No.DD20190018)the Science and Technology Innovation Fund for Postgraduates of Chongqing University of Science and Technology(No.YKJCX2220101)。
文摘Riedel shear system,which consists of some different oriented faults and derivative structures,is an important pattern of tectonic activity and stress regulation,which has been widely applied to the interpretation of intracontinental deformation.The Laolongwan Basin,located in the western Haiyuan fault zone at the northeastern Tibetan Plateau,is a key area to study the Cenozoic intracontinental deformation in the northeastern plateau,which formed a complex active fault system during the Cenozoic.However,the activity of these faults and their kinematic mechanism remain unclear.In this contribution,based on detailed structural interpretation of remote sensing image,field observations and OSL dating analysis,we propose a Riedel Shear model of active fault system in the Laolongwan Basin.Our observations show that this active fault system consist of four major faults,including the left strike-slip Hasi Shan fault and Zihong Shan fault with thrusting characteristics,the Southern Zihong Shan thrust fault and the Mijia Shan normal fault.The fault offset and OSL dating analyses suggest that the left-lateral slip rate of the Hasi Shan fault is~2.60-3.01 mm/a since ca.15 ka,whereas the Zihong Shan fault is~1.10-1.13 mm/a since ca.14 ka.Faultslip vectors analyses indicate that the active fault system related to the Riedel Shear in the Laolongwan Basin was controlled by the regional ENE-WSW compressive stress.This compression also caused the significant left-lateral strike-slip movement along the Haiyuan fault zone at the same time,which might result from the northeastward continuous expanding of the Tibetan Plateau during the Late Cenozoic.
基金supported by the National Key Research and Development Program Projects(2023YFC2906502 and 2018YFC0604801)。
文摘As shallow salt lake resources are increasingly exploited,deep confined brine has become a strategic alternative due to its widespread distribution and significant reserve potential.However,unfavorable reservoir characteristics,particularly low permeability and poor recovery efficiency,have historically rendered these deposits uneconomic,restricting their utilization.Taking the Mahai Salt Lake in the Qaidam Basin as a representative case,this study investigates the structural controls on brine enrichment through an integrated approach.Previous long-term metallogenic studies and exploration data indicate occurrences of an extensional fault zone favorable for brine accumulation.Therefore,we applied InSAR deformation analysis to assess coseismic and postseismic surface responses.Combined with radon-222 emanation mapping,our findings reveal a strong spatial correlation between high-productivity brine boreholes and active fault systems.The existence of active faults enhance brine migration and storage,provided that the target reservoirs have substantial halite thickness and maintain relatively low clay-silt content.
基金supported by the Fund Project:Subsidized by the Project of City Active Fault Detection and Seismic Risk Assessment in Hebei Province(Handan City).
文摘The Taihang Mountain piedmont fault is a large-scale structure zone in north and east China which cross Beijing,with the NE-NNE extent spans approximately 620 km.It is very important to determine the fault zone activity due to the close relation of active structures and earthquakes.Regarding the fault activity,there are three different opinions：1） it is a large deep fault zone;2） it is an active fault zone and an earthquake structure belt;and 3） it is not an earthquake structure belt.In order to ascertain the active character of the fault,the deep tectonic setting and the activity since the Quaternary were investigated using recent seismic and drilling data to make a joint interpretation.The investigation results show that the Taihang Mountain piedmont fault is not a large lithospheric fault because the early middle Pleistocene（Q（P2）） layers are offset by the fault and the late middle Pleistocene（Q（P2）） and late Pleistocene layers are not offset by the fault.We determine that the Taihang Mountain piedmont fault in the area is not an active fault and is also not a large lithospheric fault.This study result provides important geological and geophysical data for city planning and construction in Hebei province and, especially,has great significance for seismic hazard assessment of the capital area.
文摘Based on the convection and diffusion mechanisms of radon migration, in this paper we deduce the two-dimensional differential equation for radon transportation in the overburden above active fault zones with an unlimited extension along the strike. Making use of the finite difference method, the radon concentration distribution in the overburden above active faults is calculated and modeled. The active fault zone parameters, such as the depth and the width of the fault zone, and the value of radon concentration, can be inverted from the measured radon concentration curve. These realize quantitative interpretation for radon concentration anomalies. The inversion results are in good agreement with the actual fault zone parameters.
文摘Strong earthquakes (moment magnitude M<sub>W</sub> ≥ 5.5) are uncommon in Tuscany and surroundings (central Italy). The last strong seismic event occurred a century ago (September 7, 1920 Garfagnana, M<sub>W</sub> = 6.53). The paucity of seismic instrumental recordings hinders the identification of the tectonic regime active in Tuscany. On the other hand, the geological and geomorphological pieces of evidence collected so far, concerning potential active and capable faults, are scarce, fragmentary and ambiguous. In this work I shed light on the active deformation of Tuscany by using two independent approaches: earthquake source mechanisms and GNSS (GPS) geodetic measurements. I have considered 41 small seismic events (M<sub>W</sub> ≤ 5.1) that occurred in the study area during the last decade. The related source mechanisms (retrieved by the Time Domain Moment Tensor method) define a relatively clear picture of the active deformation: extension along the northern Apennine watershed and strike-slip regime within inner Tuscany, up to the Tyrrhenian coast. This pattern broadly agrees with the horizontal strain field reconstructed by the geodetic velocity field. The latter has been constrained by a network of 840 GPS stations located in Italy and neighboring countries, operating in the last 20 years.
基金Project(U1865203)supported by the Key Projects of the Yalong River Joint Fund of the National Natural Science Foundation of ChinaProjects(41941018,51879135)supported by the National Natural Science Foundation of China。
文摘Active fault creep slip induces deformation of rock mass buried deeply in fault zones that significantly affect the operational safety of long linear projects passing through it.Displacement distribution patterns of rock masses in active fault zones which have been investigated previously are the key design basis for such projects.Therefore,a discrete element numerical model with different fault types,slip time,dip angles,and complex geological features was established,and then the creep slip for normal,reverse,and strike-slip faults were simulated to analyze the displacement distribution in the fault rock mass.A disk rotation test system and the corresponding laboratory test method were developed for simulating rock mass displacement induced by creep slippage of faults.A series of rotation tests for softand hard-layered specimens under combined compression and torsional stress were conducted to verify the numerical results and analyze the factors influencing the displacement distribution.An S-shaped displacement distribution independent of fault dip angle was identified corresponding to reverse,normal,and strike-slip faults.The results indicated that the higher the degree of horizontal extrusion,the softer the rock mass at the fault core,and the higher the degree of displacement concentration in the fault core;about 70%of the creep slip displacement occurs within this zone under 100 years of creep slippage.
文摘The detailed geological mapping, conducted in the Damxung-Yangbajain basin, shows that there are many types of deposits formed since the Pliocene. The oldest sediments are formed during the Pliocene. The most prominent sediments are three sets of moraines and fluvioglacial deposits. The ESR, U-series and OSL dates indicate they are formed about 700-500 ka B.P., 250-125 ka B.P. and 75-12 ka B.P. respectively and indicate that there are three glacial periods since the mid-Pleistocene in the Nyainqentanglha Range. Along the southeast side of the Nyainqentanglha Range, the main southeast dipping fault zone which bounds the Damxung-Yangbajain Graben on its western edge was mapped. The fault zone consists of three secondary fault zones and their initiation ages that the fault zones became active gradually decrease southeastward. Prominent faulting occurred in about 700-500 ka B.P., 350-220 ka B.P., -140 ka B.P. and 70-50 ka B.P. since the mid-Pleistocene. The height of fault scarps which offset the sediments formed since the mid-Pleistocene suggest that the vertical slip rates change between 0.4 -2 mm/a and the cumulative average vertical movement at rates of 1.1±0.3 mm/a during the Quaternary period and the Holocene vertical throw rate is 1.4±0.6 mm/a along the fault zones on the western side of the Damxung-Yangbajain Graben.
基金supported by the Major Research Project of the Ministry of Land and Resources,China(No.1212011120887)
文摘It is important to explore active faults in urban areas and their surroundings for earth- quake disaster mitigation. Satellite remote sensing techniques can play an important role in such active fault exploration. It can not only reveal the pattern of active faults and active tectonics on a macroscop- ic scale, but also monitor the occurrence, development and rules of temporal-spatial evolution of active faults. In this paper, we use the Hangzhou area as an example to introduce methods of extracting de- tailed active fault information when covered by thick unconsolidated Quaternary sediment, using im- age enhancement and image fusion etc. to improve the definition and precision of satellite images and presenting a three-dimensional （3D） image to illustrate tectono-geomorphic features along the relevant faults. We have also collected aeromagnetic anomaly data, shallow seismic exploration data and dating data, and carried out field surveys to validate the characteristics of active faults based on remote sens- ing images. The results revealed about the faults showed a high consistency with traditional geological knowledge, and demonstrate that it is feasible to explore active faults in a weakly active tectonic area by using satellite remote sensing techniques and contribute to large engineering projects and research on neotectonics.
基金supported by the Key Research and Development Project of the Ministry of Science and Technology(Grant No.2018YFC1503400)。
文摘The Anninghe fault is a large left-lateral strike-slip fault in southwestern China. It has controlled deposition and magmatic activities since the Proterozoic, and seismic activity occurs frequently. The Mianning-Xichang segment of the Anninghe fault is a seismic gap that has been locked by high stress. Many studies suggest that this segment has great potential for large earthquakes(magnitude >7). We obtained three vertical velocity profiles of the Anninghe fault(between Mianning and Xichang) based on the inversion of P-wave first arrival times. The travel time data were picked from seismograms generated by methane gaseous sources and recorded by three linearly distributed across-fault dense arrays. The inversion results show that the P-wave velocity structures at depths of 0-2 km corresponds well with the local lithology. The Quaternary sediments have low seismic velocities, whereas the igneous rocks,metamorphic rocks, and bedrock have high seismic velocities. We then further discuss the fault activities of the two fault branches of the Anninghe fault in the study region based on small earthquakes(magnitudes between ML 0.5 and ML 2.5) detected by the Xichang array.The eastern fault branch is more active than the western branch and that the fault activities in the eastern branch are different in the northern and southern segments at the border of 28°21′N. The high-resolution models obtained are essential for future earthquake rupture simulations and hazard assessments of the Anninghe fault zone. Future studies of velocity models at greater depths may further explain the complex fault activities in the study region.
基金the Basic Research Project of Institute of Earthquake Science,CEA(No.2019IESLZ01)the National Science Foundation of China(No.41402186)。
文摘The Yinwashan and Xinminpu faults are located in the Jiuxi Basin in the western end of the Hexi Corridor. The determination of their activity and slip rates is of great significance for understanding the eastward extension of the Altyn Tagh fault. Based on geological and geomorphologic field survey, trench excavation, optically stimulated luminescence dating, we define the fault geometry and kinematic properties of the two faults. Based on fault scarps measurement using differential GPS and 10 Be surface exposure dating, we determined vertical slip rate of 0.09±0.01 mm/yr for the Yinwashan fault and 0.1±0.02 mm/yr for the Xinminpu fault. Using the dips observed in trenches and natural sections, we estimated horizontal shortening rates of 0.05±0.03 and 0.23±0.06 mm/yr, respectively. No significant strike slip motion is observed on these two faults, and we infer that this region was dominated by horizontal shortening in the Late Quaternary. Although the shortening rate is quite low on each individual fault, together with other faults in this area, these two faults have an essential role in transferring slip from the eastern end of the Altyn Tagh fault and in accommodating the northeastward growth of Tibetan Plateau.
基金Chinese Joint Seismological Science Foundation !(95-07-423).
文摘Based on the earthquake data of 11 active intraplate fault zones of the Chinese mainland, we have studied the earthquake recurrence behaviors on entire active fault zones and their relations to those on individual fault-segments. The results show that the earthquake recurrence on entire active fault zones, each of them is made up of multiple segments, displays three types of behavior, i.e., the clustering behavior, the random behavior, and the poor quasi-periodic behavior. The major one is the sparse clustering behavior, its recurrence process often exhibits that clusters (active periods) and gaps (quiescent periods) occur alternatively in varying degrees. The recurrence intervals within and between clusters, the durations of individual clusters, the earthquake number and strength of every cluster are all variable. The recurrence process is non-linear, there is neither the strength-time dependence nor the time-strength dependence. However, the earthquake recurrence processes on individual fault-segments are much more simple, and mainly display either the quasi-periodic or the time-predictable behaviors. Also, this study further discovers that the temporal clustering in earthquake recurrence process on entire fault zones is mainly caused by the rupture 'contagion' on different fault-segments within relatively short periods of time. Along active fault zones, the degree and orientation of rupture 'contagion' may vary with different seismic cycles, and the 'contagion' seems to be able to jump over unbroken 'gaps' on the fault zones.
基金This research is funded by the China Geological Survey project(DD20160268).
文摘The Yangtze River Economic Belt(YREB)spans three terrain steps in China and features diverse topography that is characterized by significant differences in geological structure and presentday crustal deformation.Active faults and seismic activity are important geological factors for the planning and development of the YREB.In this paper,the spatial distribution and activity of 165 active faults that exist along the YREB have been compiled from previous findings,using both remote-sensing data and geological survey results.The crustal stability of seven particularly noteworthy typical active fault zones and their potential effects on the crustal stability of the urban agglomerations are analyzed.The main active fault zones in the western YREB,together with the neighboring regional active faults,make up an arc fault block region comprising primarily of Sichuan-Yunnan and a“Sichuan-Yunnan arc rotational-shear active tectonic system”strong deformation region that features rotation,shear and extensional deformation.The active faults in the central-eastern YREB,with seven NE-NNE and seven NW-NWW active faults(the“7-longitudinal,7-horizontal”pattern),macroscopically make up a“chessboard tectonic system”medium-weak deformation region in the geomechanical tectonic system.They are also the main geological constraints for the crustal stability of the YREB.
基金Joint Seismological Science Foundation of China (105066)National Natural Science Foundation of China (40472109)the SASAKAWA Scientific Grant from the Japan Science Society.
文摘The Anninghe fault is one of the significant earthquake-generating fault zones in the Southwest China. Local historical record shows that a M2≥7 strong earthquake occurred in the year of 1536. On the basis of the detailed air-photographic interpretation and field investigation, we have acquired the following knowledge： ① The average sinistral strike-slip rate since the Late Pleistocene is about 3～7 mm/a; ② There is important reverse faulting along the fault zone besides the main left-lateral strike-slip motion, and the shortening rate across the Anninghe fault zone due to the reverse faulting is about 1.7-4.0 mm/a. If the Xianshuihe fault zone is simply partitioned into the Anninghe and Daliangshan faults, we can also get a slip rate of 3-7 mm/a along the Daliangshan fault zone, which is the same as that on the Anninghe fault zone. Moreover, on the basis of our field investigation and the latest knowledge concerning the active tectonics of Tibetan crust, we create a dynamic model for the Anninghe fault zone.
基金Ministry of Earth Science(MoES),Govt.of India for financial support((MoES/P.O.(Seismo)/1(270)/AFM/2015))under the Active Fault Mapping program。
文摘Since the recorded historical period,the Kachchh Rift Basin(KRB)has encountered numerous moderate to large magnitude earthquakes.According to the series of seismicity research so far,there are several important points of debate regarding the tectonic history and evolution of the KRB,especially during the Quaternary period.Therefore,the main objective of the present research is to inspect and perceive the association amongst the strain build-up,earthquake provenance,landform evolution and progression as archived by the Quaternary deposits of the KRB.The previous studies demonstrated the evolutions of various landforms,such as the uplifted fluvial terraces,formation of the gorges,uplifted alluvial fan sequences,which can be ideally used to reconstruct the neotectonic history along active faults of KRB.Considering this,the analysis of the accessible and supportive data,including geochronology provided by earlier studies along with some new dataset for a superior knowledge on the Quaternary tectonic forces prevailing in the KRB,have been carried out.Furthermore,we also emphasized the differences and directions for future potential research issues.The observations of variability in uplift rates across the various active faults in the KRB suggest a complex geological history during the Quaternary period.The results show that the vertical uplift rate along the significant active faults range from 0.8 to 2.8 mm/yr,demonstrating the variable tectonic stress regime prevailing in the KRB.The uplift rates constricted from geomorphic and chronological aspects suggest that the tectonic movements within the Kachchh intraplate region is regulated by the fault segments and the present tectonic stress field is in accordance with the encompassing tectonic stress field associated with the northward movement of the Indian plate corresponding to the Eurasian plate.
基金the Ministry of Science and Technology of China(G2000046704).
文摘Offshore active faults, especially those in the deep sea, are very difficultto study because of the water and sedimentary cover. To characterize the nature and geometry ofoffshore active faults, a combination of methods must be employed. Generally, seismic profiling isused to map these faults, but often only fault-related folds rather than fracture planes are imaged.Multi-beam swath bathymetry provides information on the structure and growth history of a faultbecause movements of an active fault are reflected in the bottom morphology. Submersible anddeep-tow surveys allow direct observations of deformations on the seafloor (including fracture zonesand microstructures). In the deep sea, linearly aligned cold seep communities provide indirectevidence for active faults and the spatial migration of their activities. The Western Sagami Bayfault (WSBF) in the western Sagami Bay off central Japan is an active fault that has been studied indetail using the above methods. The bottom morphology, fractured breccias directly observed andphotographed, seismic profiles, as well as distribution and migration of cold seep communitiesprovide evidence for the nature and geometry of the fault. Focal mechanism solutions of selectedearthquakes in the western Sagami Bay during the period from 1900 to 1995 show that the maximumcompression trends NW-SE and the minimum stress axis strikes NE-SW, a stress pattern indicating aleft-lateral strike-slip fault.
基金This study granted by the Scientific Foundation of the China Academy of Science, is one of the stage results of the subject (R850835). A symposium of the International Petroleum Geological Conference of Northern South China Sea Continental Shelf, 1987
文摘-On the basis of the data of geophysics and seismic activities, the analyses of the active faults, seismic activities and the sea floor unstable factors of the Zhujiang River Mouth Basin have been made so as to study the characteristics of the compressional subactive continental margin of Cathaysian system, arc littoral strongly active fracture zone, the division of seismic subzone and seismic zone of the continental margin of northern South China Sea, the potential focal area, and to analyze the regional stability. We consider that the Zhujiang River Mouth Basin belongs to a stable or a moderately stable region.
基金sup-ported by the National Natural Science Foundation of China(Nos.41530963,91858215 and 41906048)the Fundamental Research Funds for the Central Universities(No.201964015)the Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology(No.MMRZZ201801).
文摘The Ying-Qiong Basin is located on the northwestern margin of the South China Sea and at the junction of the South China Block and the Indochina Block.It is characterized by complex geological structures.The existing seismic data in the study area is sparse due to the lack of earthquake activities.Because of the limited source energy and poor coverage of seismic data,the knowledge of deep structures in the area,including the spatial distribution of deep faults,is incomplete.Contrarily,satellite gravity data cover the entire study area and can reveal the spatial distribution of faults.Based on the wavelet multi-scale decomposition method,the Bouguer gravity field in the Ying-Qiong Basin was decomposed and reconstructed to obtain the detailed images of the first-to sixth-order gravitational fields.By incorporating the known geological features,the gravitational field responses of the main faults in the Ying-Qiong Basin were identified in the detailed fields,and the power spectrum analysis yielded the depths of 1.4,8,15,26.5,and 39 km for the average burial depths of the bottom surfaces from the first-to fifth-order detailed fields,respectively.The four main faults in the Yinggehai Basin all have a large active depth range:fault A(No.1)is between 5 and 39 km,fault B is between 26.5 and 39 km,and faults C and D are between 15 and 39 km.However,the depth of active faults in the Qiongdongnan Basin is relatively shallow,mainly between 8 and 26.5 km.
文摘The most common method used to describe earthquake activity is based on the changes in physical parameters of the earth's surface such as displacement of active fault and seismic wave.However,such approach is not successful in forecasting the movement behaviors of faults.In the present study,a new mechanical model of fault activity,considering the shear strength on the fault plane and the influence of the resistance force,is established based on the occurrence condition of earthquake.A remote real-time monitoring system is correspondingly developed to obtain the changes in mechanical components within fault.Taking into consideration the local geological conditions and the history of fault activity in Zhangjiakou of China,an active fault exposed in the region of Zhangjiakou is selected to be directly monitored by the real-time monitoring technique.A thorough investigation on local fault structures results in the selection of two suitable sites for monitoring potential active tectonic movements of Zhangjiakou fault.Two monitoring curves of shear strength,recorded during a monitoring period of 6 months,turn out to be steady,which indicates that the potential seismic activities hardly occur in the adjacent region in the near future.This monitoring technique can be used for early-warning prediction of the movement of active fault,and can help to further gain an insight into the interaction between fault activity and relevant mechanisms.
