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1.
Through study on trenches, analysis of recurrence characteristics and recurrence interval cluster/gap of strong earthquakes along the major active faults on the northern border of Ordos block, we found 62 paleoearthquakes that occurred in the late Quaternary, including 33 earthquakes occurring in the Holocene. The recurrence characteristics of the paleoearthquakes are different at three levels, segments, faults, and fault zones. The strong seismic sequence on the independent segments is mostly characterized by long- and short-interval recurrences, while that on the faults and in fault zone is characterized clearly by random and cluster recurrences. Results of the moving window test indicate that the probabilities of “temporal cluster or gap”, caused by random coincidence as opposed to intersegment contagion, are 64% and 70% for the Serteng piedmont fault and for the south-border fault of Wula Mountains, respectively, no clear interaction among the segments of each fault; while the probability is 26.8% for the whole fault zone, suggesting a clear interaction among the faults of this fault zone. These recurrence characteristics may imply an effect of the entire block motion on the recurrence of strong earthquakes. Moreover, the elapsed time for the Wujumeng Pass-Dongfeng Village segment of Serteng piedmont fault and the Tuzuo Banner-Wusutu and the Hohhot segments of Daqingshan piedmont fault has exceeded the average recurrence interval, hence these three segments may be the possible places for future strong earthquakes. 相似文献
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Geomorphic study on Wjiahe segment of Serteng piedmont fault,Inner Mongolia is made.Throuth analysis of the available data in combination with the results of predecessors‘studies it can be obtained that average vertical displacement rate is 0.48-0.75mm/a along the Wujiahe segment since the late Pleistocene(14.450-22.340ka BP)and 0.56-0.88mm/s since the early-middle Holocene(5.570-8.830ka BP).Analyzing paleoseismic phenomena revealed in the excavated 5trenches in combination with the results of predecessors‘studies of paleoearthquakes on the fault,we determine five paleoseismic events on the Wujiahe segment of Serteng piedmont fault since 27.0ka BP and the recurrence interval to be about 4.300-4.400ka,A cluster of paleoearthquakes occurred probably during 8.000-9.000ka BP and two paleoeismic events in 10.000-20.000ka BP may be missed.A comparison between height of fault scarps and sum of displacement caused by paleoseismic events revealed in trenches,and recurrence interval of paleoseismic events obtained from average displacement rate along the fault and the disloca-tion by one event suggest that three paleoseismic events are absent in Alagaitu trench.Two paleoseismic events may be absent on the whole active fault segment. 相似文献
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Ran Yongkang Fang Zhongjing Li Zhiyi Wang Jingbo and Li RuchengInstitute of Geology SSB Beijing China 《中国地震研究》1995,(1)
The northern boundary fault of Huailai-Zhuolu basin,Hebei Province,has a total length of 58 km and a general strike of NE.The geometry and feature of activity of the 5 segments of the fault greatly differ from each other.17 paleoseismic events have been recognized within 11 trenches excavated along the different segments of the fault.It is found that each segment is characterized by its distinct recurrence of paleoearthquakes.The recurrence intervals of strong earthquakes for each segment are 3500-7000 a for the shortest and 17,000-20,500 a for the longest.However,the recurrence interval of strong earthquakes for whole fault ranges between 750-8500 a.The boundary of the segments can be recognized as the junction,gap,bending,jog and salient of the fault.The length of the segment ranges between 7.5-14 km. 相似文献
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在考虑地震失稳的滑动－弱化特征后，研究了估计大地震重复间隔的问题，建议了一种计算大地震重复间隔的方法，给出了计算复发间隔的公式。同时，应用这个方法计算了海原断裂带、华山山前断裂带、贺兰山东麓断裂带和小江西支断裂带的８级大震复发间隔，它们分别为３４６６年、２０４３年、２６８８年和９７５年。这些数值与古地震研究给出的实际古地震复发间隔甚为一致，说明建议的计算方法可以应用于活动断裂地震复发时间和地震危险性的估计。 相似文献
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Paleoearthquakes in the Yanqing-Huailai basin and on the Haiyuan fault are studied in detail.The result indicates that the recurrence behavior of large earthquakes is of a wide variety.Characteristic earthquakes show the behavior characteristics of the activity of most faults,butthey are of different grades,the recurrence interval of large earthquakes is of staged nature,and the interaction between faults has effects on the recurrence sequence of large earthquakes.Thus,when the recurrence behavior of large earthquakes is staged in time or when thegradation of characteristic earthquakes has led to a sharp difference in recurrence intervalbetween paleoearthquakes of different intensities,for estimating the large earthquake risk bythe deterministic method and time-dependent probabilistic method,it is necessary to calculatethe recurrence interval value separately for each specific stage or grade in order that theaverage recurrence interval values of different stages can be determined. 相似文献
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Uncertainties are common in the dating of paleoearthquakes.To improve the credibility of the dating of paleoearthquakes,analysis was done on fault activity,sedimentary environment and seismo-geomorphology to investigate paleoearthquakes along the Zemuhe active fault zone.Grouped trenches were excavated near Daqingliangzi,which revealed three palaeoearthquake events aged 160a,3100a and 5500a～8900a,respectively,including recurrence intervals of about 3000a.Sedimentary processes related to strike-slip fault type earthquakes were discussed,and a sedimentary model was put forward for strike-slip faults at hillsides where drumlin and reverse scarp developed. 相似文献
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川滇地区若干活动断裂带整体的强地震复发特征研究 总被引：15，自引：0，他引：15
我们根据历史地震资料，采用统计学方法研究了川滇地区7条活动断裂带整体的强地震复发特征。结果表明，这7条断裂带的强地震复发表现出趋于随机的、随机的、以及丛集的行为，复发过程不具有良好的准周期性，也不存在强度－时间或者时间－强度的相依性。组成断裂带的强震破裂段落的数量越多，复发过程就越复杂。相对的地震活跃期与平静期交替出现。其中，活跃期内地震复发间隔分布的离散性较大，可用Weibull分布近似描述；而平静期的持续时间分布的离散性较小，可用正态等分布近似描述。不同相对活跃期的持续时间及强震的数量差别很大，导致相对活跃期并非准周期重视。因此，基于断裂带整体强震复发间隔分布的中长期危险性概率评估仍然面临一定的困难。 相似文献
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《地震研究进展（英文）》2023,3(1):100177
The long-term earthquake prediction from 2021 to 2030 is carried out by researching the active tectonic block boundary zones in the Chinese mainland. Based on the strong earthquake recurrence model, the cumulative probability of each target fault in the next 10 years is given by the recurrence period and elapsed time of each fault, which are adopted from relevant studies such as seismological geology, geodesy, and historical earthquake records. Based on the long-term predictions of large earthquakes throughout the world, this paper proposes a comprehensive judgment scheme based on the fault segments with the seismic gap, motion strongly locked, sparse small-moderate earthquakes, and apparent Coulomb stress increase. This paper presents a comprehensive analysis of the relative risk for strong earthquakes that may occur in the coming 10 years on the major faults in the active tectonic block boundary zones in the Chinese mainland. The present loading rate of each fault is first constrained by geodetic observations; the cumulative displacement of each fault is then estimated by the elapsed time since the most recent strong earthquake. 相似文献
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Based on historical earthquake data, we use statistical methods to study integrated recurrence behaviors of strong earthquakes along 7 selected active fault zones in the Sichuan-Yunnan region. The results show that recurrences of strong earthquakes in the 7 fault zones display near-random, random and clustering behaviors. The recurrence processes are never quasiperiodic, and are neither strength-time nor time-strength dependent. The more independent segments for strong earthquake rupturing a fault zone has, the more complicated the corresponding recurrence process is. And relatively active periods and quiescent periods for earthquake activity occur alternatively. Within the active periods, the distribution of recurrence time intervals between earthquakes has relatively large discretion, and can be modelled well by a Weibull distribution. The time distribution of the quiescent periods has relatively small discretion, and can be approximately described by some distributions as the normal. Both the durations of the active periods and the numbers of strong earthquakes within the active periods vary obviously cycle by cycle, leading to the relatively active periods having never repeated quasi-periodically. Therefore, the probabilistic assessment for middle- and longterm seismic hazard for entireties of active fault zones based on data of historical strong earthquakes on the fault zones still faces difficulty. 相似文献
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A STUDY REVIEW ON CHARACTERISTICS OF SEISMIC ACTIVITY OF ACTIVE-TECTONIC BLOCK BOUNDARIES IN MAINLAND CHINA 
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下载免费PDF全文 More than 80 percent of strong earthquakes(M≥7.0)occur in active-tectonic block boundaries in mainland China, and 95 percent of strong earthquake disasters also occur in these boundaries. In recent years, all strong earthquakes(M≥7.0)happened in active-tectonic block boundaries. For instance, 8 strong earthquakes(M≥7.0)occurred on the eastern, western, southern and northern boundaries of the Bayan Har block since 1997. In order to carry out the earthquake prediction research better, especially for the long-term earthquake prediction, the active-tectonic block boundaries have gradually become the key research objects of seismo-geology, geophysics, geodesy and other disciplines. This paper reviews the research results related to seismic activities in mainland China, as well as the main existing recognitions and problems as follows: 1)Most studies on seismic activities in active-tectonic block boundaries still remain at the statistical analysis level at present. However, the analysis of their working foundations or actual working conditions can help investigate deeply the seismic activities in the active-tectonic block boundaries; 2)Seismic strain release rates are determined by tectonic movement rates in active-tectonic block boundaries. Analysis of relations between seismic strain release rates and tectonic movement rates in mainland China shows that the tectonic movement rates in active-tectonic block boundaries of the eastern region are relatively slow, and the seismic strain release rates are with the smaller values too; the tectonic movement rates in active-tectonic block boundaries of the western region reveal higher values, and their seismic strain rates are larger than that of the eastern region. Earthquake recurrence periods of all 26 active-tectonic block boundaries are presented, and the reciprocals of recurrence periods represent high and low frequency of seismic activities. The research results point out that the tectonic movement rates and the reciprocals of recurrence periods for most faults in active-tectonic block boundaries exhibit linear relations. But due to the complexities of fault systems in active tectonic block boundaries, several faults obviously deviate from the linear relationship, and the relations between average earthquake recurrence periods and tectonic movement rates show larger uncertainties. The major reason is attributed to the differences existing in the results of the current earthquake recurrence studies. Furthermore, faults in active-tectonic boundaries exhibit complexities in many aspects, including different movement rates among various segments of the same fault and a certain active-tectonic block boundary contains some parallel faults with the same earthquake magnitude level. Consequently, complexities of these fault systems need to be further explored; 3)seismic activity processes in active-tectonic block boundaries present obvious regional characteristics. Active-tectonic block boundaries of the eastern mainland China except the western edge of Ordos block possess clustering features which indicate that due to the relatively low rate of crustal deformation in these areas, a long-time span is needed for fault stress-strain accumulation to show earthquake cluster activities. In addition, active-tectonic block boundaries in specific areas with low fault stress-strain accumulation rates also show seismic clustering properties, such as the clustering characteristics of strong seismic activities in Longmenshan fault zone, where a series of strong earthquakes have occurred successively, including the 2008 M8.0 Wenchuan, the 2013 M7.0 Lushan and the 2017 M7.0 Jiuzhaigou earthquakes. The north central regions of Qinghai-Tibet Plateau, regarded as the second-grade active-tectonic block boundaries, are the concentration areas of large-scale strike-slip faults in mainland China, and most of seismicity sequences show quasi-period features. Besides, most regions around the first-grade active-tectonic block boundary of Qinghai-Tibet Plateau display Poisson seismic processes. On one hand, it is still necessary to investigate the physical mechanisms and dynamics of regional structures, on the other hand, most of the active-tectonic block boundaries can be considered as fault systems. However, seismic activities involved in fault systems have the characteristic of in situ recurrence of strong earthquakes in main fault segments, the possibilities of cascading rupturing for adjacent fault segments, and space-time evolution characteristics of strong earthquakes in fault systems. 4)The dynamic environment of strong earthquakes in mainland China is characterized by “layering vertically and blocking horizontally”. With the progresses in the studies of geophysics, geochemistry, geodesy, seismology and geology, the physical models of different time/space scales have guiding significance for the interpretations of preparation and occurrence of continental strong earthquakes under the active-tectonic block frame. However, since the movement and deformation of the active-tectonic blocks contain not only the rigid motion and the horizontal differences of physical properties of crust-mantle medium are universal, there is still need for improving the understanding of the dynamic processes of continental strong earthquakes. So it is necessary to conduct in-depth studies on the physical mechanism of strong earthquake preparation process under the framework of active-tectonic block theory and establish various foundation models which are similar to seismic source physical models in California of the United States, and then provide technological scientific support for earthquake prevention and disaster mitigation. Through all kinds of studies of the physical mechanisms for space-time evolution of continental strong earthquakes, it can not only promote the transition of the study of seismic activities from statistics to physics, but also persistently push the development of active-tectonic block theory. 相似文献
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The Xiaojiang fault zone is located in the southeastern margin of the Tibetan plateau, the boundary faults of Sichuan-Yunnan block and South China block. The largest historical earthquake in Yunnan Province, with magnitude 8 occurred on the western branch of the Xiaojiang Fault in Songming County, 1833. Research on the Late Quaternary surface deformation and strong earthquake rupture behavior on the Xiaojiang Fault is crucial to understand the future seismic risk of the fault zone and the Sichuan-Yunnan region, even crucial for the study of tectonic evolution of the southeastern margin of Tibetan plateau. We have some new understanding through several large trenches excavated on the western branch of the Xiaojiang fault zone. We excavated a large trench at Caohaizi and identified six paleoseismic events, named U through Z from the oldest to the youngest. Ages of these six events are constrained at 40000-36300BC, 35400-24800BC, 9500BC-500AD, 390-720AD, 1120-1620AD and 1750AD-present. The Ganhaizi trench revealed three paleoearthquakes, named GHZ-E1 to GHZ-E3 from the oldest to the youngest. Ages of the three events are constrained at 3300BC-400AD, 770-1120AD, 1460AD-present. The Dafendi trench revealed three paleoearthquakes, named E1 to E3 from the oldest to the youngest, and their ages are constrained at 22300-19600BC, 18820-18400BC, and 18250-present. Caohaizi and Ganhaizi trenches are excavated on the western branch of the Xiaojiang Fault, the distance between them is 400m. We constrained four late Holocene paleoearthquakes with progressive constraining method, which are respectively at 500-720AD, 770-1120AD, AD 1460-1620 and 1833AD, with an average recurrence interval of 370~440a. Large earthquake recurrence in the late Holocene is less than the recurrence interval of~900a as proposed in the previous studies. Thus, the seismic hazard on the Xiaojiang Fault should be reevaluated. We excavated a large trench at Dafendi, about 30km away south of Caohaizi trench. Combining with previous paleoseismological research, it is found that the western branch of Xiaojiang Fault was likely to be dominated by segmented rupturing in the period from late of Late Pleistocene to early and middle Holocene, while it was characterized by large earthquakes clustering and whole segment rupturing since late Holocene. 相似文献
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龙陵 -澜沧新生断裂带的地震活动具频度高、强度大、周期短等特征 ,并以双震或震群型为主。断裂带由多条次级新生断层组成 ,呈斜列或共轭式展布 ,根据结构、规模、地震活动差异等因素把断裂带划分为 4个一级段、13个二级段 ,其中有 4个二级段又可划分出 8个三级段。历史上发生过大震、强震并有地震断层伴生的断层段为地震破裂单元 ;断裂带上晚第四纪有活动并有古地震事件 ,但无历史地震记载的地段为断层闭锁单元 ;次级断层之间的阶区或连接点为障碍体单元。从地震破裂特征分析 ,断裂带由破裂、闭锁、障碍体单元组成 ,根据地震、古地震、活断层、断层阶区的活动规律 ,断裂带可划分出 9个破裂单元、8个闭锁单元、10个障碍体单元。三者之间呈迁移、触发和转换能量的关系。根据这些关系和地震构造标志 ,对断裂带上未来可能发生大震、强震、中强震的地区分别作了预测。预测的危险区有 9个 ,其中大震区 1个 (永康 -永德地区 ) ,强震区 3个 (马站、石灰窑、酒房-勐混 ) ,中强震区 5个 (下顺江、里仁、大岗山、南明 -澜沧、勐遮 相似文献
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Xue-Ze Wen 《地震学报(英文版)》1993,6(4):993-1004
Spatial distribution of sources of strong and large earthquakes on the Xiaojiang fault zone in eastern Yunnan is studied according
to historical earthquake data. 7 segments of relatively independent sources or basic units of rupture along the fault zone
have been identified preliminarily. On every segment, time intervals between main historical earthquakes are generally characterized
by “time-predictable” recurrence behavior with indetermination. A statistic model for the time intervals between earthquakes
of the fault zone has been preliminarily established. And a mathematical method has been introduced into this paper to reckon
average recurrence interval between earthquakes under the condition of having known the size of the last event at a specific
segment. Based on these, ranges of the average recurrence intervals given confidence have been estimated for events of various
sizes on the fault zone. Further, the author puts forward a real-time probabilistic model that is suitable to analyze seismic
potential for individual segments along a fault zone on which earthquake recurrence intervals have been characterized by quasi-time-predictable
behavior, and applies this model to calculate conditional probabilities and probability gains of earthquake recurring on the
individual segments of the Xiaojiang fault zone during the period from 1991 to 2005. As a consequence, it has shown that two
parts of this fault zone, from south of Dongchuan to Songming and from Chengjiang to Huaning, have relatively high likelihoods
for strong or large earthquake recurring in the future.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 322–330, 1993. 相似文献
17.
东昆仑活动断裂带及其强震活动 总被引：17，自引：0，他引：17
本文在简述东昆仑活动断裂带的构造背景与演化历史的基础上，重点叙述了该活动断裂带的展布，几何结构，第四纪运动和强震活动等特征，指出，这是一条具有长期演化历史，深部构造背景和第四纪乃至全新强烈活动的断裂带。因而在我国大地构造演化，尤其在青藏高原隆起形成，占有重要地位，同时，它还是我国西部地区一条主要的强震活动构造带，根据现代强震活动记录和在全带新发现的多期全新世古地震及其地表破裂带，分析了大震在断裂带 相似文献
18.
中国大陆地壳应变能密度年变化率图像与强震活动关系的初步探讨 总被引：5，自引：0，他引：5
以现代构造应力场和地壳运动的观测结果为约束条件,利用有限元方法计算了中国大陆地壳应变能密度年变化率,三维有限元模型采用粘弹性本构关系,包含了中国大陆主要活动断裂带,在青藏高原考虑了因高海拔地势蓄集的附加重力势能和地壳山根浮力作用。 相似文献
19.
Using borehole core analysis to reveal Late Quaternary paleoearthquakes along the Nankou-Sunhe Fault,Beijing 总被引：3，自引：0，他引：3
ShiMin Zhang DanDan Wang XuDong Liu GuoHong Zhang JunXiang Zhao MingHui Luo JunJie Ren Rui Wang YingLi Zhang 《中国科学D辑(英文版)》2008,51(8):1154-1168
The Nankou-Sunhe Fault is a buried active normal fault that traverses the urban area of Beijing.Its seismic risks have caused considerable concerns.This paper studies paleoearthquakes along this fault by analyzing and correlating bore-hole cores obtained from triple-tube coring,incorporating experience acquired from trenching.As a result,a model for identifying earthquake-derived colluvium by sediment-core analysis is proposed.Triple-tube coring technique is useful to collect continuous undis-turbed soil core near the Nankou-Sunhe Fault.By identifying fault-scarp colluviums,determining cumulative displacement,and analysing stratum thickening on the hanging wall,we are able to establish a preliminary paleoearthquake sequence consisting of 13 surface-rupturing events since 60 ka.The seismic history can be divided into three periods based on different recurrence intervals.Between 60 and 40 ka,three earthquakes occurred with recurrence interval of ～10 ka.From 40 to 25 ka,there were six earthquakes with the recurrence interval of about 2.5 ka.In the last 25 ka,four earthquakes have taken place with the recurrence interval varying considerably.The recurrence interval between the last three events is ～5 ka.Smaller recurrence intervals correspond to stages of faster fault slip.The coseismic displacement of a single event is 0.8 to 2.2 m,average 1.4 m,largely equivalent to moment magnitudes 6.7-7.1.This study demonstrates the feasibility of bore-hole drilling in investigating paleoearthquakes along normal faults.It also suggests that closely spaced boreholes with continuous undisturbed cores are essential for reconstructing the complete paleoearthquake sequence. 相似文献
20.
大凉山断裂带是大型走滑断裂鲜水河-小江断裂系的重要组成部分,其活动性是认识和探讨青藏高原东南缘现今地震活动和构造变形机制的重要基础资料。相较于中段和南段,关于大凉山断裂带北段活动性的相关研究成果,尤其是古地震资料非常缺乏。文中基于野外地质地貌调查,在石棉断裂联合村处开挖了一组(2个)探槽,揭露出断裂全新世活动的直接证据。通过古地震分析和炭样加速器质谱仪(AMS)测年,共获得了4次古地震事件:事件E1:20925—16850BC;事件E2:15265—1785BC;事件E3:360—1475AD;事件E4:1655—1815AD。其中包括全新世以来的3次事件,最新2次事件的复发间隔骤然缩短,反映断裂活动可能正在加剧。 相似文献