The alluvial fan of the Shahdad in Derakt-Tangan River is one of the biggest alleviation in total dry area in the north eastern Kerman. This alluvial fan is formed effected by different materials erosion in drainage b...The alluvial fan of the Shahdad in Derakt-Tangan River is one of the biggest alleviation in total dry area in the north eastern Kerman. This alluvial fan is formed effected by different materials erosion in drainage basin of Derakt-Tangan River and laying these materials in the final part of this drainage basin called Lut. Tectonics activate with efficacy in the place of the settlement of the alluvial fan. The region, which is being studied, is one of the active tectonic regions. The severe tectonic activities in the studying region have been proved by several observations. One of the most important evidences in the region is the various faults in the area and implies to fan alluvium （from head to end）, study line profile in past and present. The most important fault of the region is the great fault of ＂Nay band＂, the southern fault of Shahdad and the series of faults having the direction of north-western to south-eastern and northern and southern. The drainage basin of alluvial fan of the Derakt-Tangan River leads from east to Kavir-lut, from west to the Baghe-Bala Mountains and Kalisaky from The aim of this article is the morphology of Derakt-Tangan north to the altitutes of Dahran and from south to the mountains of Jeffan river fan indicative on neotectonics in the region.展开更多
It has been proven by a number of earthquake case studies that an active fault-induced earthquake beneath a city can be devastating. It is an urgent issue for seismic hazard reduction to explore the distribution of ac...It has been proven by a number of earthquake case studies that an active fault-induced earthquake beneath a city can be devastating. It is an urgent issue for seismic hazard reduction to explore the distribution of active faults beneath the urban area and identify the seismic source and the risks underneath. As a pilot project of active fault exploration in China, the project, entitled “Active fault exploration and seismic hazard assessment in Fuzhou City”, started in early 2001 and passed the check before acceptance of China Earthquake Administration in August 2004. The project was aimed to solve a series of scientific issues such as fault location, dating, movement nature, deep settings, seismic risk and hazard, preparedness of earthquake prevention and disaster reduction, and etc. by means of exploration and assessment of active faults by stages, i.e., the preliminary survey and identification of active faults in target area, the exploration of deep seismotectonic settings, the risk evaluation of active seismogenic faults, the construction of geographic information system of active faults, and so on. A lot of exploration methods were employed in the project such as the detection of absorbed mercury, free mercury and radon in soil, the geological radar, multi-channel DC electrical method, tsansient electromagnetic method, shallow seismic refraction and reflection, effect contrast of explored sources, and various sounding experiments, to establish the buried Quaternary standard section of the Fuzhou basin. By summing up, the above explorations and experiments have achieved the following results and conclusions ：展开更多
Coal forming environments in the tectonically controlled intermontane Stephanian Cévennes coal basin (Massif central, France) show a complex interelationship between structural and sedimentological features. The ...Coal forming environments in the tectonically controlled intermontane Stephanian Cévennes coal basin (Massif central, France) show a complex interelationship between structural and sedimentological features. The study of the general structural features and the geometry of the coal beds developed during the different stages in the evolution of the basin, and the spatial relation of the lithofacial units to the early tectonic activities, lead the authors to suggest the following model. The synsedimentary faults that occurred as both intrabasinal and marginal faults controlled not only the spatial distribution, shape and thickness of the detrital rock units and coal seams, but also caused the inversion of the tectonic style. The marginal faults exercised important controls on the geometry of the basin and the distribution of lithofacial units. However due to the subsidence of the central part of the basin and the depocenter, and the to differences in the timing and intensity of the displacement the coal enrichment zones shifted both vertically and laterally. This eventually resulted in the inversion of the whole tectonic framework from semi graben through graben to a new semi graben. The style and rate of the tectonic movement and basin filling that occurred in the Stephanian Cévennes coal basin were in turn closely linked with the tectonic movement in the surrounding area. Therefore the authors propose that the environment and processes of coal formation in this basin are closely linked to its tectonic evolution.展开更多
In this paper, the earthquake hazard parameters (λ m,b and M max) from the maximum likelihood method for the raw catalogue and declustered catalogues have been used to discuss the effect of the aftershocks on the ear...In this paper, the earthquake hazard parameters (λ m,b and M max) from the maximum likelihood method for the raw catalogue and declustered catalogues have been used to discuss the effect of the aftershocks on the earthquake hazard estimation. The declustered catalogues have been compiled from the raw catalogues by deleting the aftershocks in different time interval after main shock according to the criteria for the aftershock activity period. As an example, Hebei seismic zone is taken to show the effect of the aftershock on the earthquake hazard assessment because three strong earthquakes with the aftershocks occurred from 1966 to 1976. The results have been shown that the effect of the aftershocks on the parameters λ m,b is significant. The difference between the clustered and declustered catalogues has reached in seismic activity rate and recurrence period, at most, 45% and 90%, respectively. But the difference in M max is smaller. Based on this, the suggestion that the aftershocks should be omitted in the estimation of the earthquake hazard could be made, but how long the aftershocks activity duration is still left to the future research.展开更多
Based on the research and the division of the active tectonic blocks and their boundaries on the Chinese mainland, the feature of the large earthquake activities on the 24 boundaries between the 6 active tectonic bloc...Based on the research and the division of the active tectonic blocks and their boundaries on the Chinese mainland, the feature of the large earthquake activities on the 24 boundaries between the 6 active tectonic block regions (grade Ⅰ) and the 22 active tectonic blocks (grade Ⅱ) are studied. The seismicity levels on the active tectonic block boundaries are discussed considering the large earthquake frequency and the released strain energy in unit distance and time. The theoretic maximal magnitude and the recurrence period of each boundary are then calculated from the G-R relation. By comparing this with the actual earthquake records, it is found that the intensities of the earthquake deduced from the seismic activity parameter (a/b) on the main active boundaries on the Chinese mainland are consistent with that of the natural earthquakes. Meanwhile, an inverse relation is found between the recurrence periods of large earthquakes and the tectonic motion rate on the boundaries. These results show that the a, b values of each boundary obtained in this paper are valuable. In addition, the present seismic activities and hazards of these boundaries are also probed into with the historical data and their elapsed time on each boundary based on the hypothesis that the large earthquakes satisfy Poisson distribution.展开更多
On the basis of locating by the geochemical prospecting, shallow seismic sounding, drilling, geological profiling, and neogeochronological dating, we first found out the dislocation amount along the Liaocheng-Lankao b...On the basis of locating by the geochemical prospecting, shallow seismic sounding, drilling, geological profiling, and neogeochronological dating, we first found out the dislocation amount along the Liaocheng-Lankao buried fault since the Quaternary and the age of its latest activity phase and determined that the upper break point by the fault dislocation reaches 20 m below the surface. The latest activity phase was in the early Holocene and the fault is a shallow-buried active fault. An average dislocation rate along the fault is 0.12 nun/a since the Quaternary. Thus, it is a buried active fault with intermediate to strong movement strength in the eastern China.展开更多
The Funan-Huoqiu area is located in the border tectonic belt between the North China and South China active block regions. By means of seismological and geological surveys and synthetic analysis, evidences of tectonic...The Funan-Huoqiu area is located in the border tectonic belt between the North China and South China active block regions. By means of seismological and geological surveys and synthetic analysis, evidences of tectonic deformation in lower intensity have been found in the area since Late Pleistocene, where small earthquakes are distributed linearly along the main faults, conjugate shear joints are developed in the Upper Pleistocene nearby the faults. In the south of the studied region, fissures with different lengths, widths and directions occurred successively in Gushi, Huoqiu, Funan and other places of the area, in the 1970’s, and the direction of the fissures is approximately consistent with that of the Feizhong fault and Wanglaorenji fault. The authors hold that the clustering of small earthquakes, the conjugate shear joints developed in the Upper Pleistocene, the crumpled deformation of materials on fault plane, and the development of modern surface fissures in the area all reflect that the energy in the crust was slowly released, and that the weak deformation took place in corresponding faults. There was only one destructive earthquake taking place in the area (the Jiangkouji {M_S43/4} earthquake). Altogather, there has been weak activity in the area since the Late Quaternary, and it is mainly shown as a creep-slip.展开更多
Using the seismic method to detect active faults directly below cities is an irreplaceable prospecting technique. The seismic method can precisely determine the fault position. Seismic method itself can hardly determi...Using the seismic method to detect active faults directly below cities is an irreplaceable prospecting technique. The seismic method can precisely determine the fault position. Seismic method itself can hardly determine the geological age of fault. However, by considering in connection with the borehole data and the standard geological cross-section of the surveyed area, the geological age of reflected wave group can be qualitatively (or semi-quantitatively) determined from the seismic depth profile. To determine the upper terminal point of active faults directly below city, it is necessary to use the high-resolution seismic reflection technique. To effectively determine the geometric feature of deep faults, especially to determine the relation between deep and shallow fracture structures, the seismic reflection method is better than the seismic refraction method.展开更多
Analysis and study of the geometrical structure of the fault, tectonic features of late Quaternary movement, paleoseismic activity, and structural characteristics of boundaries between segments of the Sertengshan pied...Analysis and study of the geometrical structure of the fault, tectonic features of late Quaternary movement, paleoseismic activity, and structural characteristics of boundaries between segments of the Sertengshan piedmont fault permitted us to preliminarily determine the following 4 active segments of the fault: the Wujiahe segment (from Dongwugai Gully to Dahoudian Village), Wujumengkou Dongfeng Village segment (from Dahoudian to Delingshan), Dashetai segment (from Delingshan to Xiaoshetai Gully mouth), and the Ulan Hudong segment (from Xiaoshetai Gully mouth to Tailiang). The boundaries between them are the Dagoudian mountain spur, the Delingshan Mountain spur and the step zone at Xiaoshetai Gully mouth, respectively. The segments are independent for seismic activity. However, it is possible that joint ruptures between Wujiahe and Wujumengkou Dongfeng Village segments and between Dashetai and Ulan Hudong segments may occur.展开更多
In this paper, a historical review of the seismic network of Vietnam and the ability of the network to monitor earthquakes is presented. The seismic activity of Vietnam as a country of high seismicity in the last cent...In this paper, a historical review of the seismic network of Vietnam and the ability of the network to monitor earthquakes is presented. The seismic activity of Vietnam as a country of high seismicity in the last century and since the beginning of the new century is described. The current state of seismological research in Vietnam and cooperation with institutions outside of Vietnam is outlined.展开更多
A detailed investigation permitted us to obtain quantitative data concerning fine geometric structures of 4 faults of the active Maxianshan-Xinglongshan fault system and the latest movement along them. Of them the nor...A detailed investigation permitted us to obtain quantitative data concerning fine geometric structures of 4 faults of the active Maxianshan-Xinglongshan fault system and the latest movement along them. Of them the northern Maxianshan border fault is a large-scale, strongly active Holocene reverse sinistral strike-slip fault, the other 3 faults, the southern Maxianshan border fault and the southern Xinglongshan border and the northern Xinglongshan border faults are the accompanying active late-Pleistocene thrust faults, which are incorporated into the main strike-slip fault, the northern Maxianshan border fault at depth. It is the most important earthquake-controlling fault in the Lanzhou area, the fault influences and constrains the seismic activity in the area.展开更多
This paper reviews the history and progress of research on active tectonics in China and overseas.By giving a brief introduction on the history of active tectonic research in China and other countries,the paper sums u...This paper reviews the history and progress of research on active tectonics in China and overseas.By giving a brief introduction on the history of active tectonic research in China and other countries,the paper sums up the process and development of quantitative investigation of active tectonics since the 1980s.The focus is on the main efforts and progress made in China on certain aspects of research,such as basic surveys and applied investigation of active tectonics,the study of theories related to regional active tectonics and their kinematics and geodynamics,surveys on coupling relations between deep and shallow structures,active fault surveys and prospecting and seismic hazard assessment in urban areas,as well as the efforts made using Quaternary geochronology.Furthermore,the paper looks back on Chinese quantitative investigation of active tectonics in China and sums up cognitions derived from studies on the determination of several basic and measurable parameters of active tectonics.These parameters include the length of fault and fault segmentation,coseismic slip and cumulative slip,fault slip rate,the sequence of paleoearthquake events and the time elapsed since the most recent event.At the same time,efforts and progress made in China on assessing the long-term seismic potential for active faults and evaluating the risk from potential active fault movement have been reviewed by summarizing research on developing theories,models,methods and the application of time-dependent seismic potential to probabilistic assessment,magnitude estimation for potential earthquakes on active faults,and the forecast of potential risk caused by active fault movement.Finally,in consideration of the realities and problems in the research of active tectonics in China,the authors put forward several suggestions for issues worthy of more attention for further investigation in the future.展开更多
Seismicity around the Ordos Block in the northern part of China has been studied by the multifractal dimensions with the help of complete data set of earthquakes with M≥2.5 since 1977. Seven regions around this block...Seismicity around the Ordos Block in the northern part of China has been studied by the multifractal dimensions with the help of complete data set of earthquakes with M≥2.5 since 1977. Seven regions around this block have been examined where the eight large earthquakes with M≥6.0 for the complete data occurred. In order to display the temporal distribution of the correlation dimension D 2, a moving window of fixed number of events is used in every of the seven regions. Except for two regions with less seismic activity, all other five regions have obviously been found to display sudden changes of the correlation dimension for the events with M≥4.5.展开更多
Based on the studies of earthquake activity, tectonic movement, crustal shortening rate, fault activity, local stress field and historical characteristics of strong earthquake activities in Xinjiang, we divide the sou...Based on the studies of earthquake activity, tectonic movement, crustal shortening rate, fault activity, local stress field and historical characteristics of strong earthquake activities in Xinjiang, we divide the south part of Xinjiang into 4 seismotectonic zones, namely, the eastern segment of south Tianshan seismic belt, the Kalpin block, the Kashi-Wuqia junction zone, and the west Kunlun Mountains seismic belt. Using earthquake catalogues from Xinjiang since 1900, and on the basis of integrity analysis of earthquake records in different magnitude ranges, the seismicity state of different seismotectonic zones is analyzed quantificationaUy by calculating the mean value of annual strain energy release, annual rate of earthquakes with different lower limits of magnitude, b-value, and the parameter m of accelerating strain release model. The characteristic indexes of seismicity state for each of the seismic tectonic zones are then determined, which provide a quantitative basis for earthquake tendency analysis and judgment.展开更多
文摘The alluvial fan of the Shahdad in Derakt-Tangan River is one of the biggest alleviation in total dry area in the north eastern Kerman. This alluvial fan is formed effected by different materials erosion in drainage basin of Derakt-Tangan River and laying these materials in the final part of this drainage basin called Lut. Tectonics activate with efficacy in the place of the settlement of the alluvial fan. The region, which is being studied, is one of the active tectonic regions. The severe tectonic activities in the studying region have been proved by several observations. One of the most important evidences in the region is the various faults in the area and implies to fan alluvium （from head to end）, study line profile in past and present. The most important fault of the region is the great fault of ＂Nay band＂, the southern fault of Shahdad and the series of faults having the direction of north-western to south-eastern and northern and southern. The drainage basin of alluvial fan of the Derakt-Tangan River leads from east to Kavir-lut, from west to the Baghe-Bala Mountains and Kalisaky from The aim of this article is the morphology of Derakt-Tangan north to the altitutes of Dahran and from south to the mountains of Jeffan river fan indicative on neotectonics in the region.
文摘It has been proven by a number of earthquake case studies that an active fault-induced earthquake beneath a city can be devastating. It is an urgent issue for seismic hazard reduction to explore the distribution of active faults beneath the urban area and identify the seismic source and the risks underneath. As a pilot project of active fault exploration in China, the project, entitled “Active fault exploration and seismic hazard assessment in Fuzhou City”, started in early 2001 and passed the check before acceptance of China Earthquake Administration in August 2004. The project was aimed to solve a series of scientific issues such as fault location, dating, movement nature, deep settings, seismic risk and hazard, preparedness of earthquake prevention and disaster reduction, and etc. by means of exploration and assessment of active faults by stages, i.e., the preliminary survey and identification of active faults in target area, the exploration of deep seismotectonic settings, the risk evaluation of active seismogenic faults, the construction of geographic information system of active faults, and so on. A lot of exploration methods were employed in the project such as the detection of absorbed mercury, free mercury and radon in soil, the geological radar, multi-channel DC electrical method, tsansient electromagnetic method, shallow seismic refraction and reflection, effect contrast of explored sources, and various sounding experiments, to establish the buried Quaternary standard section of the Fuzhou basin. By summing up, the above explorations and experiments have achieved the following results and conclusions ：
文摘Coal forming environments in the tectonically controlled intermontane Stephanian Cévennes coal basin (Massif central, France) show a complex interelationship between structural and sedimentological features. The study of the general structural features and the geometry of the coal beds developed during the different stages in the evolution of the basin, and the spatial relation of the lithofacial units to the early tectonic activities, lead the authors to suggest the following model. The synsedimentary faults that occurred as both intrabasinal and marginal faults controlled not only the spatial distribution, shape and thickness of the detrital rock units and coal seams, but also caused the inversion of the tectonic style. The marginal faults exercised important controls on the geometry of the basin and the distribution of lithofacial units. However due to the subsidence of the central part of the basin and the depocenter, and the to differences in the timing and intensity of the displacement the coal enrichment zones shifted both vertically and laterally. This eventually resulted in the inversion of the whole tectonic framework from semi graben through graben to a new semi graben. The style and rate of the tectonic movement and basin filling that occurred in the Stephanian Cévennes coal basin were in turn closely linked with the tectonic movement in the surrounding area. Therefore the authors propose that the environment and processes of coal formation in this basin are closely linked to its tectonic evolution.
文摘In this paper, the earthquake hazard parameters (λ m,b and M max) from the maximum likelihood method for the raw catalogue and declustered catalogues have been used to discuss the effect of the aftershocks on the earthquake hazard estimation. The declustered catalogues have been compiled from the raw catalogues by deleting the aftershocks in different time interval after main shock according to the criteria for the aftershock activity period. As an example, Hebei seismic zone is taken to show the effect of the aftershock on the earthquake hazard assessment because three strong earthquakes with the aftershocks occurred from 1966 to 1976. The results have been shown that the effect of the aftershocks on the parameters λ m,b is significant. The difference between the clustered and declustered catalogues has reached in seismic activity rate and recurrence period, at most, 45% and 90%, respectively. But the difference in M max is smaller. Based on this, the suggestion that the aftershocks should be omitted in the estimation of the earthquake hazard could be made, but how long the aftershocks activity duration is still left to the future research.
基金The work was supported bythe public welfare programofthe Ministry of Science and Technology of China (2004DIA3J010)the special preparatoryresearch of national keyfun-damental research project (2002CCD01700)the Young Scientists Funds of Institute of Earthquake Science , CEA(QN200401) .
文摘Based on the research and the division of the active tectonic blocks and their boundaries on the Chinese mainland, the feature of the large earthquake activities on the 24 boundaries between the 6 active tectonic block regions (grade Ⅰ) and the 22 active tectonic blocks (grade Ⅱ) are studied. The seismicity levels on the active tectonic block boundaries are discussed considering the large earthquake frequency and the released strain energy in unit distance and time. The theoretic maximal magnitude and the recurrence period of each boundary are then calculated from the G-R relation. By comparing this with the actual earthquake records, it is found that the intensities of the earthquake deduced from the seismic activity parameter (a/b) on the main active boundaries on the Chinese mainland are consistent with that of the natural earthquakes. Meanwhile, an inverse relation is found between the recurrence periods of large earthquakes and the tectonic motion rate on the boundaries. These results show that the a, b values of each boundary obtained in this paper are valuable. In addition, the present seismic activities and hazards of these boundaries are also probed into with the historical data and their elapsed time on each boundary based on the hypothesis that the large earthquakes satisfy Poisson distribution.
文摘On the basis of locating by the geochemical prospecting, shallow seismic sounding, drilling, geological profiling, and neogeochronological dating, we first found out the dislocation amount along the Liaocheng-Lankao buried fault since the Quaternary and the age of its latest activity phase and determined that the upper break point by the fault dislocation reaches 20 m below the surface. The latest activity phase was in the early Holocene and the fault is a shallow-buried active fault. An average dislocation rate along the fault is 0.12 nun/a since the Quaternary. Thus, it is a buried active fault with intermediate to strong movement strength in the eastern China.
文摘The Funan-Huoqiu area is located in the border tectonic belt between the North China and South China active block regions. By means of seismological and geological surveys and synthetic analysis, evidences of tectonic deformation in lower intensity have been found in the area since Late Pleistocene, where small earthquakes are distributed linearly along the main faults, conjugate shear joints are developed in the Upper Pleistocene nearby the faults. In the south of the studied region, fissures with different lengths, widths and directions occurred successively in Gushi, Huoqiu, Funan and other places of the area, in the 1970’s, and the direction of the fissures is approximately consistent with that of the Feizhong fault and Wanglaorenji fault. The authors hold that the clustering of small earthquakes, the conjugate shear joints developed in the Upper Pleistocene, the crumpled deformation of materials on fault plane, and the development of modern surface fissures in the area all reflect that the energy in the crust was slowly released, and that the weak deformation took place in corresponding faults. There was only one destructive earthquake taking place in the area (the Jiangkouji {M_S43/4} earthquake). Altogather, there has been weak activity in the area since the Late Quaternary, and it is mainly shown as a creep-slip.
文摘Using the seismic method to detect active faults directly below cities is an irreplaceable prospecting technique. The seismic method can precisely determine the fault position. Seismic method itself can hardly determine the geological age of fault. However, by considering in connection with the borehole data and the standard geological cross-section of the surveyed area, the geological age of reflected wave group can be qualitatively (or semi-quantitatively) determined from the seismic depth profile. To determine the upper terminal point of active faults directly below city, it is necessary to use the high-resolution seismic reflection technique. To effectively determine the geometric feature of deep faults, especially to determine the relation between deep and shallow fracture structures, the seismic reflection method is better than the seismic refraction method.
基金TheresearchwassupportedunderaprojectofStateKeyBasicResearchandDevelopmentPlan (G1 9980 4 0 7) China .
文摘Analysis and study of the geometrical structure of the fault, tectonic features of late Quaternary movement, paleoseismic activity, and structural characteristics of boundaries between segments of the Sertengshan piedmont fault permitted us to preliminarily determine the following 4 active segments of the fault: the Wujiahe segment (from Dongwugai Gully to Dahoudian Village), Wujumengkou Dongfeng Village segment (from Dahoudian to Delingshan), Dashetai segment (from Delingshan to Xiaoshetai Gully mouth), and the Ulan Hudong segment (from Xiaoshetai Gully mouth to Tailiang). The boundaries between them are the Dagoudian mountain spur, the Delingshan Mountain spur and the step zone at Xiaoshetai Gully mouth, respectively. The segments are independent for seismic activity. However, it is possible that joint ruptures between Wujiahe and Wujumengkou Dongfeng Village segments and between Dashetai and Ulan Hudong segments may occur.
文摘In this paper, a historical review of the seismic network of Vietnam and the ability of the network to monitor earthquakes is presented. The seismic activity of Vietnam as a country of high seismicity in the last century and since the beginning of the new century is described. The current state of seismological research in Vietnam and cooperation with institutions outside of Vietnam is outlined.
文摘A detailed investigation permitted us to obtain quantitative data concerning fine geometric structures of 4 faults of the active Maxianshan-Xinglongshan fault system and the latest movement along them. Of them the northern Maxianshan border fault is a large-scale, strongly active Holocene reverse sinistral strike-slip fault, the other 3 faults, the southern Maxianshan border fault and the southern Xinglongshan border and the northern Xinglongshan border faults are the accompanying active late-Pleistocene thrust faults, which are incorporated into the main strike-slip fault, the northern Maxianshan border fault at depth. It is the most important earthquake-controlling fault in the Lanzhou area, the fault influences and constrains the seismic activity in the area.
基金funded by the"Experimental Exploration of Active Faults in Urban Areas(20041138)"project of the National Development and Reform Commission of China
文摘This paper reviews the history and progress of research on active tectonics in China and overseas.By giving a brief introduction on the history of active tectonic research in China and other countries,the paper sums up the process and development of quantitative investigation of active tectonics since the 1980s.The focus is on the main efforts and progress made in China on certain aspects of research,such as basic surveys and applied investigation of active tectonics,the study of theories related to regional active tectonics and their kinematics and geodynamics,surveys on coupling relations between deep and shallow structures,active fault surveys and prospecting and seismic hazard assessment in urban areas,as well as the efforts made using Quaternary geochronology.Furthermore,the paper looks back on Chinese quantitative investigation of active tectonics in China and sums up cognitions derived from studies on the determination of several basic and measurable parameters of active tectonics.These parameters include the length of fault and fault segmentation,coseismic slip and cumulative slip,fault slip rate,the sequence of paleoearthquake events and the time elapsed since the most recent event.At the same time,efforts and progress made in China on assessing the long-term seismic potential for active faults and evaluating the risk from potential active fault movement have been reviewed by summarizing research on developing theories,models,methods and the application of time-dependent seismic potential to probabilistic assessment,magnitude estimation for potential earthquakes on active faults,and the forecast of potential risk caused by active fault movement.Finally,in consideration of the realities and problems in the research of active tectonics in China,the authors put forward several suggestions for issues worthy of more attention for further investigation in the future.
文摘Seismicity around the Ordos Block in the northern part of China has been studied by the multifractal dimensions with the help of complete data set of earthquakes with M≥2.5 since 1977. Seven regions around this block have been examined where the eight large earthquakes with M≥6.0 for the complete data occurred. In order to display the temporal distribution of the correlation dimension D 2, a moving window of fixed number of events is used in every of the seven regions. Except for two regions with less seismic activity, all other five regions have obviously been found to display sudden changes of the correlation dimension for the events with M≥4.5.
基金supported by the Special Scientific Research Funds for Earthquake Studies, entitled "Development of Dynamic Evaluation System of Seismicity State in the Chinese Continent (Grant No. 200708020)"
文摘Based on the studies of earthquake activity, tectonic movement, crustal shortening rate, fault activity, local stress field and historical characteristics of strong earthquake activities in Xinjiang, we divide the south part of Xinjiang into 4 seismotectonic zones, namely, the eastern segment of south Tianshan seismic belt, the Kalpin block, the Kashi-Wuqia junction zone, and the west Kunlun Mountains seismic belt. Using earthquake catalogues from Xinjiang since 1900, and on the basis of integrity analysis of earthquake records in different magnitude ranges, the seismicity state of different seismotectonic zones is analyzed quantificationaUy by calculating the mean value of annual strain energy release, annual rate of earthquakes with different lower limits of magnitude, b-value, and the parameter m of accelerating strain release model. The characteristic indexes of seismicity state for each of the seismic tectonic zones are then determined, which provide a quantitative basis for earthquake tendency analysis and judgment.
