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1.
Active blocks and strong seismic activity in North China region   总被引:1,自引:0,他引:1  
The active North China block consists of three second-order blocks: Ordos, North China Plain, and East Shandong-Huanghai Sea blocks. Two active tectonic zones, the Anyang-Heze- Linyi and Tangshan-Cixian zones, exist in the active North China Plain block and have separated the active block into 3 third-order active blocks, Taihangshan, Hebei-Shandong, and Henan-Huai blocks. The 3 third-order active blocks are characterized by their entire motion and are clearly different in their Cenozoic structures and deep structures. The active boundary tectonic zones between the third-order active blocks are less than those between the first- and second-order active blocks in their movement strength, extent, and seismic activity. The density of M ≥ 6 earthquakes in the boundary zones between active blocks is higher than that within the blocks by 9-22 times in the North China region, up to one order of magnitude on average. M ≥ 7 earthquakes occurred basically in the boundary zones between active blocks. The difference is not occasional, but reflects the nature of intraplate movement and the characteristics of strong seismic activity and is the powerful evidence for hypothesis of active blocks.  相似文献   

2.
华北块体中等地震活动平静特征   总被引:2,自引:2,他引:0  
采用累计频度方法,对华北活动地块Ms≥5.5地震前中等地震聚集活动区的地震做了时空扫描,并对平静现象进行了定量分析,结果表明:对各Ⅱ级活动地块采用不同的扫描方法.在强震前都表现出明显的增强、平静过程,平静的时间长短与所给定的构造区域有关。本文给出了华北3个Ⅱ级活动地块的发震模式。对各活动地块分别进行了R值检验,表明3个活动地块采用不同的发震模式均具有较高的预报效能。  相似文献   

3.
地块活动与成组地震关系的初步探讨   总被引:11,自引:1,他引:10       下载免费PDF全文
中国大陆构造的成块性与中国地震活动的成组性构成中国地震构造和地震活动的一个突出现象.本文在前人对中国大陆地震成组划分的结果和地块划分方案的基础上,研究了中国大陆地块与成组地震活动之间的关系,发现大部分强震分布于地块边界断层上,成组地震的孕育和发生与块体活动有关.由成组地震震中分布图表现出来的地块活动方式主要有4种:单缝式活动型、单地块活动型、多地块活动型和地块内部活动型.地块活动频度以单缝式活动型为最高,在成组地震中则以单地块活动型为多.大陆内部各地块的活动性有差别,东部比较活跃的地块有太行山和华北平原地块,西部比较活跃的地块有川滇和昆仑-松潘地块.   相似文献   

4.
Introduction ZHANG and ZHONG (1977), ZHANG, et al (1978) and ZHANG (1984) pointed out that Chinese mainland is divided into two parts by the NS-trending tectonic belt, i.e., the eastern area and the western area, and each area is divided into tectonic blocks by faults. In the eastern area, the faults are trending NNE and NNW, mainly NNE, and the long axis strike of blocks is nearly trending NS. In the western area, faults are trending NEE and NWW, mainly NWW, long axis strike …  相似文献   

5.
中国大陆活动地块边界带与强震活动   总被引:59,自引:9,他引:59       下载免费PDF全文
本文在前人对中国大陆及周边活动地块研究和划分的基础上,系统研究了6个Ⅰ级活动地块区和22个Ⅱ级活动地块之间共26个活动边界带的构造变形与强震活动,包括强震分布与活动边界带的关系,边界带构造活动速率与地震活动水平及强震复发期等的关系. 给出了边界带强震活动水平与构造活动速率之间的线性关系和强震复发期长短与构造活动速率的反向变化关系. 从而进一步揭示了中国大陆活动地块构造及其块体运动特征,以及块体边界带的构造变形对强震的控制作用.  相似文献   

6.
On the basis of summarizing the circulation characteristics and mechanism of earthquakes with magnitude 7 or above in continental China, the spatial-temporal migration characteristics, mechanism and future development trend of earthquakes with magnitude above 7 in Tibetan block area are analyzed comprehensively. The results show that there are temporal clustering and spatial zoning of regional strong earthquakes and large earthquakes in continental China, and they show the characteristics of migration and circulation in time and space. In the past 100a, there are four major earthquake cluster areas that have migrated from west to east and from south to north, i.e. 1)Himalayan seismic belt and Tianshan-Baikal seismic belt; 2)Mid-north to north-south seismic belt in Tibetan block area; 3)North-south seismic belt-periphery of Assam cape; and 4)North China and Sichuan-Yunnan area. The cluster time of each area is about 20a, and a complete cycle time is about 80a. The temporal and spatial images of the migration and circulation of strong earthquakes are consistent with the motion velocity field images obtained through GPS observations in continental China. The mechanism is related to the latest tectonic activity in continental China, which is mainly affected by the continuous compression of the Indian plate to the north on the Eurasian plate, the rotation of the Tibetan plateau around the eastern Himalayan syntaxis, and the additional stress field caused by the change of the earth's rotation speed.
Since 1900AD, the Tibetan block area has experienced three periods of high tides of earthquake activity clusters(also known as earthquake series), among which the Haiyuan-Gulang earthquake series from 1920 to 1937 mainly occurred around the active block boundary structural belt on the periphery of the Tibetan block region, with the largest earthquake occurring on the large active fault zone in the northeastern boundary belt. The Chayu-Dangxiong earthquake series from 1947 to 1976 mainly occurred around the large-scale boundary active faults of Qiangtang block, Bayankala block and eastern Himalayan syntaxis within the Tibetan block area. In the 1995-present Kunlun-Wenchuan earthquake series, 8 earthquakes with MS7.0 or above have occurred on the boundary fault zones of the Bayankala block. Therefore, the Bayankala block has become the main area of large earthquake activity on the Tibetan plateau in the past 20a. The clustering characteristic of this kind of seismic activity shows that in a certain period of time, strong earthquake activity can occur on the boundary fault zone of the same block or closely related blocks driven by a unified dynamic mechanism, reflecting the overall movement characteristics of the block. The migration images of the main active areas of the three earthquake series reflect the current tectonic deformation process of the Tibetan block region, where the tectonic activity is gradually converging inward from the boundary tectonic belt around the block, and the compression uplift and extrusion to the south and east occurs in the plateau. This mechanism of gradual migration and repeated activities from the periphery to the middle can be explained by coupled block movement and continuous deformation model, which conforms to the dynamic model of the active tectonic block hypothesis.
A comprehensive analysis shows that the Kunlun-Wenchuan earthquake series, which has lasted for more than 20a, is likely to come to an end. In the next 20a, the main active area of the major earthquakes with magnitude 7 on the continental China may migrate to the peripheral boundary zone of the Tibetan block. The focus is on the eastern boundary structural zone, i.e. the generalized north-south seismic belt. At the same time, attention should be paid to the earthquake-prone favorable regions such as the seismic empty sections of the major active faults in the northern Qaidam block boundary zone and other regions. For the northern region of the Tibetan block, the areas where the earthquakes of magnitude 7 or above are most likely to occur in the future will be the boundary structural zones of Qaidam active tectonic block, including Qilian-Haiyuan fault zone, the northern margin fault zone of western Qinling, the eastern Kunlun fault zone and the Altyn Tagh fault zone, etc., as well as the empty zones or empty fault segments with long elapse time of paleo-earthquake or no large historical earthquake rupture in their structural transformation zones. In future work, in-depth research on the seismogenic tectonic environment in the above areas should be strengthened, including fracture geometry, physical properties of media, fracture activity behavior, earthquake recurrence rule, strain accumulation degree, etc., and then targeted strengthening tracking monitoring and earthquake disaster prevention should be carried out.  相似文献   

7.
Based on high-precision data obtained in the past decade from GPS re-measurement in the North China Network, the Crustal Movement Observation Network of China (CMONOC) and GPS measurement along the Shanxi graben zone, the status and evolution of horizontal crustal movement in the North China region are analyzed. The results show that (1) the Yanshan tectonic zone (Zhangjiakou-Bohai Sea zone)is an active one with the largest horizontal strain in the North China region; The largest tendency differential movement of adjacent blocks is seen between the Yanshan block and the North China plain block; about 2mm/a (left lateral) ; (2)The significant horizontal differential movement along the boundaries of the North China region is characterized by right-lateral strike-slip movement at the middle-north segment on its west boundary (composed of Yinchuan and other active tectonic zones) and compressive movement at the south segment; while the Yinshan rift zone located along the west segment on its north boundary is dominated by tensile movement. Other boundaries and zones have no obvious differential movement; (3) On the whole, measurements of each period differ from one another, which might result from the nonlinear movement component as well as from the error effect. In the paper, results of the relative movement and strain in different periods are given for different blocks and boundary zones.  相似文献   

8.
华北成组强震孕育过程及预测研究   总被引:1,自引:0,他引:1  
刘蒲雄 《地震》2005,25(3):9-19
利用华北丰富的历史地震资料, 通过研究地震与块体活动的联系, 揭示了地震高潮期的形成过程。 认为地震高潮期成组强震的孕育与区域块体的运动方式相联系。 一个地震活动期可分为二个阶段, 在前期块体边界的运动是很不平衡的, 各组地震主要是由于各局部范围若干闭锁段破裂和破裂间相互作用的结果, 当沿块体边界的破裂发展到一定程度时, 这些边界所围的地块就会进入以整体运动为主的阶段, 这时块体边界的运动具有一定程度的同步性, 加之闭锁段破裂后不再重新闭锁, 从而导致块体边界闭锁段由弱到强渐进式的破裂过程, 直至一组强闭锁段完成破裂, 形成地震活动高潮。 这是成组强震形成的根本原因, 另外强震间的诱发作用也是强震成组发生的重要原因。 最后概述了如何利用以上模式预测地震高潮期的时间、 强度和主体活动场所。  相似文献   

9.
本文研究了日本内陆及其外围海域发生大地震后的地震活动迁移现象。在所研究的6个震例中,一个共同的特点是,地震活动的迁移总是沿着地壳内的活动地质构造带发生。有时可以根据地震活动的迁移来进一步确定活动构造带的存在。把板块边缘地区的地震活动类比为沿着力学偶合平面迁移和扩散,我们可以认为,岛上的活动构造带对应着地壳块体的力学相互作用边界。地震迁移的形式可能不只一种。在我们所研究的震例中发现了以下特征:地震迁移速度约为几km/年;大地震震源区之间存在着地震空区;在每一条地震带上有一定的地震活动周期。地震迁移的一种可能机制是:由于地壳块体的相对运动,在其边界上的凹凸不平区造成了构造应力集中,这些凹凸不平区相继地发生破裂,形成了地震迁移。  相似文献   

10.
Basic characteristics of active tectonics of China   总被引:84,自引:8,他引:76  
Active tectonics is inferred to all the structures which have been active since the late Pleisto-cene, 100—120 ka B.P., are still active recently, and will be active in a certain time period in the future, such as active faults, active folds, active basi…  相似文献   

11.
由跨断层形变测量反映的华北地块近期断裂活动特征   总被引:3,自引:0,他引:3  
通过对华北地块不同构造部位、不同地震活动时段的跨断层测量资料研究表明,华北地块对于NE走向断裂作用为主的构造单元(包括地块和边界带)的强震活跃时段的断层运动速率明显小于强震不活跃时段;对于NW走向断裂作用为主的构造单元,其强震活跃时段的断层运动速率明显大于强震不活跃时段;对于NE、NW走向断裂共同作用的构造单元,断层运动速率变化特征类似于NW走向断裂作用为主的构造单元。结果还表明,华北地块现今强震活动主要受NW走向断裂的控制。  相似文献   

12.
渤海、黄海和东海等中国东部海域在地质构造上是大陆向海的自然延伸,海域内的构造方向与大陆一致,均为NNE-NE向,但属于不同的二级大地构造单元,渤海和北黄海属于华北地块,南黄海属于扬子地块,东海属于华南地块。由于各地块与现今活动板块边界位置不同,构造与地震活动性差异较大,渤海和北黄海地区地震活动主要受印度板块与欧亚板块碰撞形成的东喜马拉雅构造节远场效应影响,地震活动强烈;南黄海地区以中强地震活动为主;东海地区地震活动主要受菲律宾海板块与欧亚板块碰撞形成的琉球俯冲带影响。冲绳海槽是正在形成的(活动的)边缘海盆地,不仅有浅源地震,且有中源地震活动。东海陆架盆地由于受冲绳海槽扩张的影响,停止发育,构造与地震活动相对较弱。  相似文献   

13.
Active tectonic blocks and strong earthquakes in the continent of China   总被引:9,自引:0,他引:9  
The primary pattern of the late Cenozoic to the present tectonic deformation of China is characterized by relative movements and interactions of tectonic blocks. Active tectonic blocks are geological units that have been separated from each other by active tectonic zones. Boundaries between blocks are the highest gradient of differential movement. Most of tectonic activity occurs on boundaries of the blocks. Earthquakes are results of abrupt releases of accumulated strain energy that reaches the threshold of strength of the earth's crust. Boundaries of tectonic blocks are the locations of most discontinuous deformation and highest gradient of stress accumulation, thus are the most likely places for strain energy accumulation and releases, and in turn, devastating earthquakes. Almost all earthquakes of magnitude greater than 8 and 80%-90% of earthquakes of magnitude over 7 occur along boundaries of active tectonic blocks. This fact indicates that differential movements and interactions of active tectonic blocks are the primary mechanism for the occurrences of devastating earthquakes.  相似文献   

14.
Active tectonic blocks and strong earthquakes in the continent of China   总被引:4,自引:0,他引:4  
The primary pattern of the late Cenozoic to the present tectonic deformation of China is characterized by relative movements and interactions of tectonic blocks. Active tectonic blocks are geological units that have been separated from each other by active tectonic zones. Boundaries between blocks are the highest gradient of differential movement. Most of tectonic activity occurs on boundaries of the blocks. Earthquakes are results of abrupt releases of accumulated strain energy that reaches the threshold of strength of the earth’s crust. Boundaries of tectonic blocks are the locations of most discontinuous deformation and highest gradient of stress accumulation, thus are the most likely places for strain energy accumulation and releases, and in turn, devastating earthquakes. Almost all earthquakes of magnitude greater than 8 and 80%–90% of earthquakes of magnitude over 7 occur along boundaries of active tectonic blocks. This fact indicates that differential movements and interactions of active tectonic blocks are the primary mechanism for the occurrences of devastating earthquakes.  相似文献   

15.
划分大陆活动地块的重要标志之一是它们在地壳结构间的差异。大陆不同地块具有不同的地壳结构特征。这些结构和构造上的不同反映了它们在地壳内部的变形特征和动力过程的差异。文中利用深地震宽角反射 /折射剖面的结果 ,讨论了青藏高原东北缘东昆仑巴颜喀拉地块、鄂尔多斯地块和华北地块唐山震区地壳结构的差异。它们分别是变形强烈的活动地块、内部变形小相对稳定的地块和现代发生过强震的活动地块。在地壳结构上它们之间的差别是明显的。这些差异表现在地壳的分层性质、上地壳和下地壳的结构、地壳结构的不均匀尺度、壳 /幔分界的性质、壳内低速层的分布、地壳界面、特别是莫霍面的构造形态等方面  相似文献   

16.
方颖  江在森  顾国华 《地震研究》2007,30(2):152-156
介绍了用GPS连续观测资料反演断层运动的方法——网络滤波方法。用此方法探讨了华北地块边界带运动特征,并与发生在边界带附近和地块内部的地震活动及周边强震进行了比较,得出以下初步结论:郯庐大断裂和山西断陷盆地带的滑动量为1mm左右,整体活动水平有减弱的趋势;张家口—渤海断裂带滑动量为0.5mm左右,活动性逐渐增强;秦岭—大别山断裂内滑动量为0.5mm左右,活动性逐渐减弱。在2002年底至2003年底一年左右的时间内,华北地块边界带的滑动速率发生较大幅度的变化,同时,各边界带(秦岭—大别山断裂除外)的地震活动水平在2003年底达到高峰,说明边界带滑动速率急剧变化的结果导致边界带附近地震活动水平的加剧。另外,边界带滑动的特点表明了华北地块构造运动的整体性,推断华北地块的地壳运动可能与来自地球深部的地幔对流有关。  相似文献   

17.
强震造成的活动地块地壳形变差异探讨   总被引:1,自引:0,他引:1       下载免费PDF全文
20 0 1年 11月 14日发生在昆仑山口西的 8 1级地震 ,在地表产生了长度大于 35 0km的破裂带 ,最大水平位移 6m左右 ,为左旋走滑断层。在昆仑山口西 8 1级地震周围不同活动地块内不同构造部位布设的GPS基准站对地震的响应存在明显的差异。其中位于柴达木活动地块内部的德令哈基准站在地震的当天观测到 7 5mm的同震位移 ,位于川滇活动地块西南边界带的下关基准站在震后 3d发生了 6 8mm以上的明显位移 ,而位于同一地块内部的昆明基准站和位于祁连山活动地块内的西宁基准站、位于拉萨活动地块内的拉萨基准站震时和震后都没有产生明显的位移。GPS基准站的观测资料表明 ,强震所处的活动地块和其相邻活动地块对强震有明显的响应 ,如果相隔一活动地块 ,则受强震的影响较小 ;在活动地块内 ,活动强烈的边界带或其它活动较强的部位对强震引起的地壳形变的响应明显大于活动强度较弱的部位 ;强震对相邻活动地块影响的差异 ,主要与强震所处活动地块运动时对其产生的作用方式的差异有关  相似文献   

18.
中国大陆西部及周边地区地震活动特征的研究   总被引:2,自引:1,他引:2       下载免费PDF全文
探讨了中国周缘板块的联合作用对中国大陆地震的控制和影响,进一步研究了中国大陆西部及周边地区的地震活动特征。结果发现,该区域的地震活动除了有高潮和低潮的轮回特征外,还有相互消长的关系,并且地震相互消长有一个特定的比例。这一特点,对于中国大陆强震活动主体区的预测,尤其是对地震高潮期的结束时间提供了一个判据。  相似文献   

19.
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   

20.
文中收集了1999—2015年天山地震带及其周边地区的GNSS数据,计算得到了速度场结果,并利用弹性块体模型计算了研究区域内各块体的闭锁深度和主要断层的滑动速率。研究结果表明:南天山断裂带西段的迈丹断裂的缩短速率处于高值状态,达(-6.3±1.9) mm/a,高于南天山东段;北天山断裂带西段的缩短速率同样高于东段。利用主要断裂带的滑动速率计算出各地震带的地震矩积累变化及1900年以来的地震矩释放变化量,以分析地震矩亏损分布,结果显示北天山山前断裂、迈丹断裂、额尔齐斯断裂带北段和喀什河断裂西段存在较大的地震矩亏损,具有孕育7级以上地震的潜能,而北轮台断裂、柯坪断裂带中段则呈现地震矩盈余状态,在未来的一段时间内不具备发生强震的可能。  相似文献   

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