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A method of estimation of occurrence probability of earthquake intensity at a given site from the results of a ten-year scale of earthquake prediction described with a probability of occurrence in a given "prediction cell" is proposed in this paper. 2316 cities and towns in China were analyzed by using this method. The probability of intensity Ⅵ-Ⅸ were given for every city. These results can be used for the earthquake insurance, loss estimation, and planning of disaster protection. 相似文献
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《中国地震研究》1997,(3)
The experimental study of the change of wave velocity in fault regions before instability of frictional sliding of rocks was conducted.Experiments show that before the instability of frictional sliding of rocks,the change of wave velocity cannot be observed along lines on one side of the fault,but the precursor of the decrease of wave velocity can be observed along lines across the fault.Therefore,when we try to predict the earthquakes of the stick-slip type in fault regions by using the anomaly of wave velocity,the measuring lines across the faults should be selected. 相似文献
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ShahidA.Khan M.AliShah M.Qaisar 《地震学报(英文版)》2003,16(4):382-394
Estimation of seismic hazard for the fast developing coastal area of Pakistan is carried out using deterministic and probabilistic approaches. On the basis of seismotectonics and geology, eleven faults are recognized in five seismic provinces as potential hazard sources. Maximum magnitude potential for each of these sources is calculated. Peak ground acceleration (PGA) values at the seven coastal cities due to the maximum credible earthquake on the relevant source are also obtained. Cities of Gwadar and Ormara with acceleration values of 0.21g and 0.25g respec-tively fall in the high seismic risk area. Cities of Turbat and Karachi lie in low seismic risk area with acceleration values of less than 0.1g. The Probabilistic PGA maps with contour interval of 0.05g for 50 and 100 years return period with 90% probability of non-exceedance are also compiled. 相似文献
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Yuan Daoyang Lei Zhongsheng Liu Baichi Cai Shuhu Liu Xiaofeng Wang Yongcheng 《中国地震研究》2002,16(4):351-362
Detailed examination of historical data of earthquakes and field investigations of loess landslide caused by the earthquake and tracing of active faults in Lanzhou area indicate that the Yijitanpu town,one of six towns of Jincheng city,was devastated by the 1125 Lanzhou earthquake.The citly is now located in the Vinylon Factory south of Hekou(River Mouth)in the Xigu distict of Lanzhou city.We delermined that the six old towns mentioned in historical records lie in an area stretching from the south of Xigu district to Hekou in Lanzhou.This is consistent with the distibution of loess landslides caused by the earthquake,the extension of Holocene active faults,and the distribution of traces of the seismic rupture zone.A comprehensive analysis shows that the seismogenic structure for the 1125 Lanzhou M7.0 earthquake should be the Xianshuigou fault segment at the western termination of the north-border active fault zone of the Maxianshan Mountains which are located in south of Lanzhou city with the distance of only 4km. 相似文献
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The Influence of Earth Temperature on the Dynamic Characteristics of Frozen Soil and the Parameters of Ground Motion on Sites of Permafrost 总被引：1，自引：0，他引：1
Wang Lanmin 《中国地震研究》2004,18(1):1-12
Earth temperature is one of the most important factors influencing the mechanical properties of frozen soil. Based on the field investigation of the characteristics of ground deformation and ground failure caused by the Ms8.1 earthquake in the west of the Kuniun Mountain Pass,China, the influence of temperature on the dynamic constitutive relationship, dynamic elastic modulus, damping ratio and dynamic strength of frozen soil was quantitatively studied by means of the dynamic triaxial test. Moreover, the characteristics of ground motion on a permafrost site under different temperatures were analyzed for the four profiles of permafrost along the Qinghai-Xizang (Tibet) Railway using the time histories of ground motionacceleration with 3 exceedance probabilities of the Kunlun Mountains area. The influences of temperature on the seismic displacement, velocity, acceleration and response spectrum on permafrost ground were studied quantitatively. A scientific basis was presented for earthquake disaster mitigation for engineering foundations, highways and underground engineering in permafrost areas. 相似文献
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《中国地震研究》1997,(2)
In an extensional basin,the process of hanging wall block rotation above a detachment fault zone is controlled by block geometry,the shape of the main normal faults,and the detachment depth.A formula for calculating the detachment depth of a tilted block is established in geometrical aspect from the tilting angle of the rotational block,dip angle of the main boundary fault,and the sedimentary thickness in the basin.The calculated result shows that the detachment depth of the tilted block,controlled by a rotational planar normal fault in the Linxian basin,on the eastern slope of Taihangshan Mountain,North China,is about 12.5 km,which is consistent with the analytic result of seismic data in the area.The value is similar to the estimated depth of the usual brittle ductile transition in a rift zone.The geometrical model presented in this paper,however,can provide a range of structural patterns of hanging wall and the detachment depth for reference in hydrocarbon exploration and earthquake processes. 相似文献
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Turbulence is one of the most common nature phenomena in everyday experience, but that is not adequately understood yet. This article reviews the history and present state of development of the turbulence theory and indicates the necessity to probe into the turbulent features and mechanism with the different methods at different levels. Therefore this article proves a theorem of turbulent transpor- tation and a theorem of turbulent intensity by using the theory of the nonequilibrium thermodynamics, and that the Reynolds turbulence and the Rayleigh-Bénard turbulence are united in the theorems of the turbulent intensity and the turbulent transportation. The macroscopic cause of the development of fluid turbulence is a result from shearing effect of the velocity together with the temperature, which is also the macroscopic cause of the stretch and fold of trajectory in the phase space of turbulent field. And it is proved by the observed data of atmosphere that the phenomenological coefficient of turbulent in- tensity is not only a function of the velocity shear but also a function of temperature shear, viz the sta- bility of temperature stratification, in the atmosphere. Accordingly, authenticity of the theorem, which is proved by the theory of nonequilibrium thermodynamics, of turbulent intensity is testified by the facts of observational experiment. 相似文献
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Estimate of influence of U-Th-K radiogenic heat on cooling process of granitic melt and its geological implications 总被引：2，自引：0，他引：2
ZHANG BangTong WU JunQi LING HongFei & CHEN PeiRong The State Key Laboratory for Mineral Deposits Research Department of Earth Sciences Nanjing University Nanjing China 《中国科学D辑(英文版)》2007,50(5):672-677
The U-Th-~(40)K concentrations of granite are on 1―2 orders of magnitude greater than those of basal- tic-ultrabasic rocks. Radiogenic heat of a granitic melt has significant influence on the cool- ing-crystallization period of the melt. In this paper we derived a formula to calculate prolongation period (tA) of cooling-crystallization of a granitic melt caused by radiogenic heat. Calculation using this for- mula and radioactive element concentrations (U=5.31×10-6; Th=23.1×10-6; K=4.55%) for the biotite adamellite of the Jinjiling batholith shows that the tA of the adamellite is 1.4 times of the cooling period of the granitic melt without considering radiogenic heat from the initial temperature (Tm=960℃) to crystallization temperature (Tc=600℃) of the melt. It has been demonstrated that the radiogenic heat produced in a granitic melt is a key factor influencing the cooling-crystallization process of the granitic melt, and is likely one of the reasons for inconsistence between emplacement ages and crystallization ages of many Meso-Cenozoic granitoids. 相似文献
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Fluvial terraces and their implications for Weihe River valley evolution in the Sanyangchuan Basin 总被引：2，自引：0，他引：2
《中国科学:地球科学(英文版)》2017,(3)
Fluvial terraces are important geomorphic markers for modern valley development.When coupled with numeric ages,terraces can provide abundant information about tectonic,climatic,paleohydrological and the paleoenvironmental changes.On the basis of the paleomagnetic,electron spin resonance(ESR) and optically stimulated luminescence(OSL) dating,in addition to an investigation of local loess-paleosol sequences,we confirmed that 13 fluvial terraces were formed,and then preserved,along the course of the Upper Weihe River in the Sanyangchuan Basin over the past 1.2 Ma.Analyses of the characteristics and genesis of these terraces indicate that they resulted from the response of this particular river system to climate change over an orbital scale.These changes can further be placed within the context of local and regional tectonic uplift,and represent an alternation between lateral migration and vertical incision,dependent upon the predominance of climatic and tectonic controls during different periods.Most of the terraces are strikingly similar in that they have several meters of paleosols which have developed directly on top of fluvial deposits located on the terrace treads,suggesting that the abandonment of terraces due to river incision occurred during the transitions from glacial to interglacial climates.The temporal and spatial differences in the distribution patterns of terraces located on either side of the river valley indicate that a tectonic inversion occurred in Sanyangchuan Basin at-0.62 Ma,and that this was characterized by a transition from overall uplift to depression induced by fault activity.Synthesized studies of the Basin's terraces indicate that formation of the modern valley of the Upper Weihe River may have begun in the late Early Pleistocene between1.4-1.2 Ma. 相似文献
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Himalaya is an active fold and thrust belt formed due to continent-continent collision between the Eurasian and Indian plates. It comprises a 3000 km long chain of mountains that span ∼1000 km across, with major boundary thrusts viz., Main Central Thrust (MCT), Main Boundary Thrust (MBT) and the Main Frontal Thrust (MFT). MFT is marked as mountain front and is the most active thrust; however, evidence of tectonic activity along MCT and MBT also exists.Tectonic activity along MFT created uplifted terraces which now serve as geomorphic archives of past tectonic events. The present study focussed on a glacial-fed river Sankosh that originates in northern Bhutan, and crosses MCT, MBT and MFT before joining the Brahmaputra River in Assam. Due to tectonic uplift, the river shows a deflection at MFT, incising and thus forming four levels of strath terraces. Luminescence chronology, geomorphic studies and analysis of satellite images suggest four levels of terraces T4 (highest level, 195 m asl), T3, T2 and T1 (lowest level, 120 m asl).The quartz was found insensitive for luminescence dating, and thus fading corrected Infra-Red Stimulated Luminescence (IRSL) ages on feldspar minerals were measured that provided ages of 143-77 ka (T4), 65-36 ka (T2) and 35-14 ka (T1), respectively. The T3 terrace was present only on the right bank of the river and could not be accessed. These ages accord with other studies at the Chalsa and Malbazar, North Bengal (west of the study area) and this regional disposition of similar ages suggest that these formed during glacial-interglacial periods. The strath terraces indicate a time-averaged tectonic uplift with a 0.5 mm/year rate over the past 150 ka. 相似文献
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XING Chengqi Ding Guoyu LU Yanchou Shen Xuhui Tian Qinjian YIN Gongming CHAI Zhizhang WEI Kaibo 《中国地震研究》2003,17(2):183-198
Where the Yellow River flows through the Haiyuan-Tongxin arc-form tectonic region on the northeastern side of the Qinghai-Xizang (Tibet) Plateau, as many as 10～21 basis and erosion terraces have been produced, among which the biggest altitude above river level is 401m and the formation age of the highest terrace is 1.57 Ma B.P. Based on comparative analysis of the Yellow River terraces located separately in the Mijiashan mountain, the Chemuxia gorge, the Heishanxia gorge and the other river terraces in the vast extent of the northern part of China, it has been found that the tectonic processes resulting in the formation of the terrace series is one of multi-gradational features, i.e., a terrace series can include the various terraces produced by tectonic uplifts of different scopes or scales and different ranks. The Yellow River terrace series in the study region can be divided into three grades. Among them, in the first grade there are 6 terraces which were formed separately at the same time in the vast extent of the northern part of China and represent the number and magnitude of uplift of the Qinghai-Xizang Plateau since 1.6 Ma B. P. ; in the second grade there are 5 terraces which were separately and simultaneously developed within the Haiyuan-Tianjingshan tectonic region and represent the number and magnitude of uplift of this tectonic region itself since 1.6Ma B. P.; in the third grade there are 10 terraces which developed on the eastern slope of the Mijiashan mountain and represent the number and amplitude of uplift of the Haiyuan tectonic belt itself since 1.6Ma B.P. Comparison of the terrace ages with loess-paleosoil sequence has also showed that the first grade terraces reflecting the vast scope uplifts of the Qinghai-Xizang Plateau are very comparable with climatic changes and their formation ages all correspond to the interglacial epochs during which paleosoils were formed. This implies that the vast extent tectonic uplifts resulting in river down-cutting are closely related to the warm-humid climatic periods which can also resnit in river downward erosion after strong dry and cold climatic periods, and they have jointly formed the tectonic-climatic cycles. There exists no unanimous and specific relationship between the formation ages of the second and third grade terraces and climatic changes and it is shown that the formation of those terraces was most mainly controlled by tectonic uplifts of the Tianjingshan block and the Haiyuan belt. The river terraces in the study region, therefore, may belong to 2 kinds of formation cause. One is a tectonic-climatic cyclical terrace produced jointly by vast extent tectonic uplifts and climatic changes, and the terraces of this kind are extensively distributed and can be well compared with each other among regions. Another is a pulse-tectonic cyclical terrace produced by local tectonic uplifts as dominant elements, and their distribution is restricted within an active belt and can not be compared with among regions. 相似文献
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Ya Liu Xianyan Wang Qi Su Shuangwen Yi Xiaodong Miao Yiquan Li Huayu Lu 《地球表面变化过程与地形》2021,46(14):2788-2806
Upstream knickpoint propagation is an essential mechanism for channel erosion, carrying changes in base level, tectonics and climate across the landscape. Generally, the terraces on cross-sections at steady-state conditions have been widely reported. However, many landscapes in the field appear to be in a transient state. Here, we explore the mechanism of knickpoint initiation and fluvial evolution in a transient setting in the northeastern Tibetan Plateau. Analysis of channel profiles and terrace correlation indicates that the Yellow River is adjusted to match the increase in differentiated fault activity and climate change in a regional setting of continuous uplift. Consequently, a series of terraces were formed, and the number of terrace steps increased downstream, in the headwaters of the Yellow River. All terraces were dated using the optically stimulated luminescence method. The top terrace, distributed continuously in the whole basin with a gradient, was deposited during a cold period and abandoned at the climatic transition from cold to warm state, at approximately 14.6–9.5 ka. After that, one terrace formed at around 4.2 ka in the upper reach. In correlation with the continuous topographic gradient surface of this terrace, three terrace steps were formed in the down reach during the period from 9.5 ka to 4.2 ka. This phenomenon might indicate multiple phases of continuous headward migration of fluvial knickpoint waves and terrace formation during the downcutting. It was caused by fault activity and tectonic uplift of the gorge at the outlet of the basin, under influence of the gradual integration of the Yellow River from downstream. This phenomenon shows that the fluvial incision in a transient state along the high relief margin of the orogenic plateau can be caused by fault activity, in addition to widespread surface uplift, climatically driven lake spillover and the establishment of external drainage. 相似文献
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河流阶地面是一种时间性、连续性非常高的层状地貌面,利用跨断层地区的河流阶地变形可以定量地判别一个地区的断层活动性。青衣江横跨龙门山断裂带南段是一条区域性大河,由于龙门山南段构造活动强烈且河流阶地被侵蚀程度严重,为了在室内更好、更快地解译青衣江河流阶地,使野外调查工作更具有针对性,本文在龙门山南段青衣江流域小关子至飞仙村一段,采用航测遥感技术制作的2m分辨率DEM和1/5万数字高程模型,基于Arc GIS和MATLAB平台进行了阶地面提取和聚类分析,以模拟野外测量阶地的流程,试图通过计算机提取,快速获取该地区更多的残余地貌面,建立起较为完整的河流阶地纵剖面。研究结果表明:野外测量数据与计算机自动提取结果相似度较高,具有较好的一致性;在完整的阶地剖面中发现了芦山盆地内部阶地具有疑似拱曲现象;在大川-双石断裂附近阶地有翘起现象,推测芦山盆地西缘阶地拱曲是由大川-双石断裂东侧的一条未知断层引起的,大川-双石断裂附近阶地的翘起现象可能是在断层逆冲推覆过程中形成的,同时结合区域年代历史数据,推测该地区(芦山盆地至大川-双石断裂)至少在晚更新世曾发生过构造活动。 相似文献
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Laura Rodríguez-Rodríguez Loreto Antón Raimon Pallàs Daniel García-Castellanos Ivone Jiménez-Munt Candela Pastor-Martín 《地球表面变化过程与地形》2020,45(4):1013-1027
Fluvial terraces are used as geomorphic indicators for deciphering long-term landscape evolution. Knowing the distribution of fluvial terraces is essential for establishing former river profiles and their tectonic significance, for studying climate-modulated processes of terrace development, or for defining fluvial network adjustments in response to sudden base-level changes like those produced by fluvial captures. Multiple methods for automatic map production have been proposed based on the comparison of morphometric indices with those of the modern river course. Here we propose an alternative method to identify flat surfaces and scarps separating them from digital elevation models without setting comparisons with a modern river course and thus fully applicable to study flat landforms whatever their origin. Its application to the low-relief landscape of the Cenozoic Duero basin has allowed the improvement of previous geomorphological maps and the analysis of fluvial network adjustments in response to a sudden base-level fall after the opening of the Neogene endorheic basin towards the Atlantic Ocean. Reconstructed terrace long-profiles suggest an initial episode of fast vertical incision followed by a period of repeated planation–aggradation–incision with the formation of 14 to 13 unpaired terrace levels. Changes observed in the pattern of terrace profiles are discussed with regard to changes in regional tectonics and base-level variations. © 2019 John Wiley & Sons, Ltd. 相似文献
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An integrated field and numerical modelling study of controls on Late Quaternary fluvial landscape development (Tabernas,southeast Spain) 
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下载免费PDF全文 Martin R. Geach Willem Viveen Anne E. Mather Matt W. Telfer William J. Fletcher Martin Stokes Odile Peyron 《地球表面变化过程与地形》2015,40(14):1907-1926
The variability of Quaternary landforms preserved in the Tabernas basin of southeast (SE) Spain raises numerous questions concerning the roles of external forcing mechanisms (e.g. tectonics and/or climate) and internal landscape properties (e.g. lithological controls) in the evolution of the basin‐wide fluvial system over Late Quaternary timescales. In this study, we apply the FLUVER2 numerical model to investigate the significance of these landscape controls upon patterns of landscape evolution. We highlight the complications of generating realistic input datasets for use in the modelling of long‐term landscape evolution (e.g. discharge and runoff datasets). Model outputs are compared to extensive field mapping of fluvial terraces, their sedimentary architecture and optically stimulated luminescence dating results of the terraces. The results demonstrate the significance of non‐linear rates of flexural tectonic uplift towards the west of the Tabernas Basin which have controlled base levels throughout the Quaternary and promoted the formation of a series of diverging fluvial terraces. Our numerical model results further highlight the importance of climate cycles upon river terrace formation. Basin‐wide aggradation events were modelled during the transition from Marine Isotope Stage (MIS) 6 to 5 and the Last Glacial Maximum (LGM) as supported by field evidence. This aggradational pattern supports the regional hypothesis of terrace formation during global glacial cycles and cold‐to‐warm stage transitions and supports the use of sea surface temperature climate proxy data in the modelling exercise. The availability of sediments derived from the surrounding hillslopes and adjacent alluvial fans explains the generation of substantial terrace aggradations. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Geostatistical topographic analysis is widely recognized as a useful tool for the statistical reconstruction of planar geomorphic markers from relict surfaces. This work is aimed at improving the geostatistical approach used in previous works and developing a method for evaluating the incision rates of rivers in their lower catchments during the Late Quaternary. We chose the major valleys of the Adriatic foothills (central Italy), affected since Late Miocene by a differential tectonic uplift which is still active. In particular, (i) we applied the geostatistical analysis to reconstruct the original top‐surfaces of fluvial‐to‐coastal terrace bodies at the Metauro River and Cesano River mouths; (ii) we performed correlations between the height distribution of the alluvial terrace sequences and the Quaternary climatic curve to estimate the average long‐term fluvial incision rates in the lowermost reaches of the Metauro, Cesano, Misa and Esino Rivers. The obtained averaged incision rates have been interpreted also in the light of the Stream‐Length Gradient Index (SL Index), Steepness Index (Ks), and Concavity Index (θ) as proxies of the stream‐power per unit length. Results confirm that geostatistical and terrain analysis of topographic and geometric arrangements of fluvial and coastal terraces is an effective tool in detecting geomorphic and tectonic factors inducing perturbations on planar geomorphic markers. In particular, we better delineated the surface geometry and boundaries of well‐developed coastal fans at the mouths of the Metauro and Cesano Rivers, already recognized in previous works through sedimentological, morphostratigraphic, and chronological data. Moreover, we found evidence for cut‐and‐fill phases that took place during and immediately after the river aggradation of the late Quaternary glacial periods. Despite the Slope–Area analysis evidenced a widespread influence of the regional differential uplift on single river basin configuration, we observed some space and time variability of averaged incision rates for adjacent valleys, mainly explained by physiographic configuration and dynamics of drainage network. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献