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1.
In this paper, the discrepancy between the movements of intraplate blocks and plates isdiscussed, and the method to divide the intraplate active blocks is presented by selecting Bursaformula as the kinematic model for the intraplate blocks. Based on the data of three GPScampaigns in North-China network in l995, 1996 and l999, respectively, the northern area inNorth China is divided into eight small blocks with the mathematical model and methodpresented in this paper. The divided blocks based on tbe horizontal and vertical crustalmovements in the paper are consistent or approximate with each other in the area as a whole.The divided blocks in the paper is also basically accordant with the neotectonic movement,which indicates that the current movement of active blocks in this area is the succession anddevelopment of neotectonic movement. Moreover, some new activity characteristics in the areahave been revealed by the tectonic units divided with the horizontal crustal movement.  相似文献   

2.
Through numerical simulation for GPS data, aseism/c negative dislocation model for crustal horizontal movement during 1999-2001 in the northeast margin of Qinghai-Xizang block is presented, combined with the spatial distri-bution of apparent strain field in this area, the characteristics of motion and deformation of active blocks and their boundary faults, together with the place and intensity of strain accumulation are analyzed. It is shown that: a) 9 active blocks appeared totally clockwise motion from eastward by north to eastward by south. Obvious sinistral strike-slip and NE-NEE relative compressive motion between the blocks separated by Qilianshan-Haiyuan fault zone was discovered; b) 20 fault segments (most of them showed compression) locked the relative motion between blocks to varying degrees, among the total, the mid-east segment of Qilianshan fault (containing the place where it meets Riyueshan-Lajishan fault) and the place where it meets Haiyuan fault and Zhuanglanghe fault, more favored accumulation of strain. Moreover, the region where Riyueshan-Lajishan fault meets north boundary of Qaidam block may have strain accumulation to some degree, c) Obtained magnitude of block velocities and locking of their boundaries were less than relevant results for observation in the period of 1993-1999.  相似文献   

3.
INTRODUCTIONThe constant accumulation of large-range ,high-accuracy GPS observation data makes it possibleto studythe crustal movement in a range as large as possible .The demarcation of crustal blocks withdifferent deformation trends in the studied area and the elimination of the abnormal deformationinformation withinthe blocks ,are prerequisites to gain a correct acquisition of all parameters of theblock movement .The methods of dividing active blocks mainlyinclude 2 classes :one is ba…  相似文献   

4.
In order to study the present crustal movement and geodynamics in China‘s continent, a countrywide GPS monitoring network consisting of 22 stations was set up evenly on major tectonic blocks in China‘s continent in the early 1990s. Three-phase observations using the network were carried out in 1992, 1994, and 1996, respectively. In this paper, the data processing and accuracy of the three-phase observations are examined and the basic characteristics of present block movement in China‘s continent are analyzed based on the data of three-phase repeated observations. The study result indicates that the accuracy of data obtained in three-phase observations on the GPS network reaches 10-8 ～ 10-9, which is adequate to the need of monitoring of crustal movement. A model for block movement in China‘s continent constructed based on the result of the three-phase observations has effectively tested the results of geological and geophysical studies. In global framework, China‘s continent as a whole shows its clear eastward motion and its regional movement relative to Siberian block is characterized by that the western China is mainly affected by northward subduction and pushing of Indian Plate. Qinghai-Xizang Plateau shows clear eastward lateral slip simultaneously with longitudinal compression. It is more favorable to the escape model for the continent. Block movement of eastern China is under the combined effect of Indian, Pacific,and Philippine plates, resulting in northeastern and eastern motions of eastern China up to southeastern coastal region where the effect of Philippine Plate strengthens.  相似文献   

5.
In the paper, the establishment, measurement, data-processing program and monitoring accuracy of the GPS seismic monitoring network in North China, especially in the Capital-Circle area, have been presented briefly. The relation of horizontal crustal deformation to tectonic movement, stress-field variation and seismicity has been analyzed in detail. The results indicate that the accuracy of GPS measurement has reached the order of 10-9 and the annual rate of horizontal crustal deformation in North China is about 4 ~5 mm. Horizontal crustal movement is a direct indication of the regional stress field. Therefore, by monitoring the time-sequence variation of horizontal crustal motion, it would be possible to investigate the change in the stress field, to analyze the tendency of seismicity and to determine the seismogenic zones.  相似文献   

6.
In this paper,the corresponding relation of the evolutionary characteristics of geodetic deformation fields with seismic activity for more than 20 years in the North-South seismic zone and East of Qinghai-Xizang Mess has been investigated.Not only is geodetic deformation in non-homogeneity for the space-time distribution but also deformation fields are in macroscopic similarity for the identical time interval.The inherited tectonic movement is a total tendency of recent crustal movement,and the motion mode is in undulations.There are stages of accumulation and release-adjusting of strain energy in crustal movement processes,which may be the dynamic mechanism of relatively quiet and active seismicity.The analysis of the crustal movement tendency since 1991 is of some significance for judging the stress state and the large seismic situation in the area.  相似文献   

7.
Quasi-trijunction is a type of popular structure for certain scale tectonic blocks in a continent. There are two kinds of quasi-trijunction in the conjoining area formed due to rotation of continental blocks. They are the clockwise type and the anticlockwise type of quasi-trij unction. The shape of a quasi-trij unction may be gradually changed associated with block rotation and tectonic evolution, but, sediments and structure in the conjoining area can record the history of tectonic evolution. Thus, studying a quasi-trij unction can reveal regional tectonic evolution.Regional tectonic movement, plane strain partitioning and characteristics of seismic activity can be studied based on kinematics and geometric analysis of a quasi-trijunction.The quasi-trijunction is a surface structure controlled by deep crustal movement. Tectonic activity may be different in three branches. In the quasi-trijunction in the northeastern corner of Qinghai-Xizang Plateau, the NWW-trending Qilianshan-Hexi corridor fault zone w  相似文献   

8.
Based on the geodetic data taken from the National GPS Network established by China Climbing Program "Investigation of Crust Motion and Geodynamics in Modern Time",we derived the movement velocities of the GPS sites. In terms of the power series expansion of a rotation function for horizontal velocities on a spherical surface proposed by Haines and Holt (1993), we computed the horizontal velocity and strain-rate field. We preliminarily studied the appearances and characteristics of the present-day crustal movement and deformation in the Chinese mainland with the computed results. The researches demonstrated: ① The present-day crustal movement and deformation in the Chinese mainland are being jointly controlled by Indian, Pacific and Philippines Ocean Plates and Siberia-Mongolia block, and these three large plates and block form a situation of tripartite confrontation, but Indian Plate seems to play a leading role; ② The North-South Earthquake Zone plays an important adjustment role in the present-day crustal movement and deformation process, displaying clear characteristics of demarcation line of tectonics in large areas; ③ There seems to be another adjustment zone along the latitude line approximate N35°, but its characteristics are less obvious than that of the former; ④ Dynamic actions of these three large plates and block on the Chinese mainland are dynamic stable; appearing in stable push-press velocities. These results are generally accorded with the results determined from geology, geophysics, and seismology. By the contrast with seismicities, it appears preliminarily that there is some corresponding relation between intense shear strain zone and future strong seismicity area, but this problem needs further examination of earthquake examples.  相似文献   

9.
Introduction According to the negative dislocation model (Matsu′ura et al, 1986), the relative motion be-tween active blocks under contemporary crustal movement is likely to be partially blocked on the boundaries. Suppose the lower ductile zone of boundary could slip freely, while due to the fric-tional resistance, etc., the upper brittle zone would restrict such kind of relative motion, so as to give rise to stress and strain accumulation. Namely, the surface displacement in the block bound-…  相似文献   

10.
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   

11.
Following the 11 March 2011 Japan MW9.0 earthquake, frequent moderate and small events occurred on the Yishu fault zone and its either side. Using continuous GPS data and a sliding block model, this work studies the relationship between the energy release of these shocks and the block relative motion of either side of the Yishu fault zone. The results show that(1)the equivalent magnitude M from released energy and the two blocks' relative motion are well correlated when earthquakes are selected in a retrieval circle(whose center is the midpoint of the Yishu fault zone)with a radius of 250~500km and using a sliding time window of 3~10 months. The best correlation coefficient between M and the two blocks' relative motion is 0.74 and the T test shows a significant linear correlation between them.(2)Spatial distribution of the correlation coefficients shows that the relative motion of the blocks on both sides affects the energy release in the area from the north part of Yishu fault zone to the Jiaodong Peninsula area and southwest Shandong-Henan border area obviously.(3)Since June 2014, the relative motion of the two blocks on both sides of the Yishu fault zone presents a wave of change, which may be an expression of the accumulation of seismic strain energy in the Yishu fault zone and its two sides. The linear relationship between the equivalent magnitude M from released energy and two blocks' relative motion V can be fitted by linear equation M=0.51*V+3.9, showing that strain energy accumulation could be released by the moderate and small earthquakes in a timely manner, which may favorable to delay the seismic risk in the study area. It also shows, on the other hand, that earthquake energy was not released so completely in the study area since the end of 2015 to 2016, which is likely associated with the Changdao earthquake swarm in 2017.  相似文献   

12.
基于活动块体的基本概念,综合对研究区内活动断裂带空间展布、地震活动性等资料的分析将巴颜喀拉块体东部及邻区划分为巴颜喀拉块体（I）、华南块体（Ⅱ）、川滇块体（Ⅲ）和西秦岭块体（IV）等4个一级块体.利用GPS形变场、地球物理场等资料结合F检验法,将巴颜喀拉块体划分为阿坝（I1）、马尔康（I2）和龙门山（I3）3个次级块体,将西秦岭块体划分为岷县（IV1）和礼县（IV2） 2个次级块体.利用分布在各个块体内部的GPS测站,计算各活动块体及块体边界断裂带的运动变形特征.结果表明：各活动块体的整体运动包括平移和旋转运动;东昆仑断裂带、甘孜—玉树断裂带和鲜水河断裂带的滑动速率明显高于龙门山断裂带的滑动速率;巴颜喀拉块体东部走向北西或北西西的边界断裂表现出左旋拉张的特性;走向北东的边界断裂带,除成县—太白断裂带外,均表现出右旋走滑兼挤压的活动特征.巴颜喀拉块体的东向运动存在自西向东的速度衰减,衰减主要被龙日坝断裂带和岷江断裂带分解吸收,其中龙日坝断裂带的水平右旋分解非常明显,约为~4.8±1.6 mm/a,岷江断裂带的水平分解较弱.龙门山断裂带被马尔康、龙门山和岷县等次级块体分成南、中、北三段,龙门山断裂带中段上的主压应变率要明显小于龙门山断裂带南段上的应变率,其北西侧变形幅度从远离断裂带较大到靠近断裂带逐渐减小,表明其在震前已经积累了较高的应变能,有利于发生破裂滑动.汶川地震后,地表破裂带和余震分布揭示的断裂带运动性质自南西向北东由以逆冲运动为主,逐渐转为逆冲兼走滑的特征可能与龙门山断裂带中段所受主压应力方向自南西向北东的变化有关.马尔康、龙门山和岷县3个次级块体与华南块体之间较低的相对运动速度以及龙门山断裂带低应变率、强闭锁的特征都决定了汶川地震前龙门山断裂带低滑动速率的运动特征.  相似文献   

13.
巴颜喀拉块体北东地区现今水平运动与变形   总被引：2，自引：0，他引：2  
本文利用GPS数据研究了巴颜喀拉块体北东地区现今水平运动与变形特征。 在球坐标系中解算了各应变分量, 分析了应变率场的空间分布特征, 并与地球物理学和地震地质学研究结果进行了综合对比分析。 最新的GPS速度场结果表明, 巴颜喀拉块体北东地区与高原整体运动性质一样具有顺时针向南东方向旋转的特征, 自西向东和北东方向测站水平运动速度呈现明显的衰减特征。 应变场结果显示, 研究区以北东向的主压应变为主, 伴随着近北西向的张性应变。 应变较强的区域主要分布在活动块体的边界断裂东昆仑断裂带的东段塔藏段和龙门山断裂带上。 东昆仑断裂带东段塔藏段的主压应变明显, 结合地震地质和活动构造资料, 认为东昆仑断裂带东段塔藏段的运动性质自西向东发生了改变, 水平滑动速率逐渐减小, 垂向运动逐渐增强。 研究区GPS速度场和应变场的这一变形特征表明, 青藏高原内部的块体运动特征较为明显, 变形主要集中在作为活动块体边界的活动断裂带上, 边界断裂带的运动特征在调节活动块体间的相互运动中起着重要作用。  相似文献   

14.
Movement and strain conditions of active blocks in the Chinese mainland   总被引：2，自引：0，他引：2  
The definition of active block is given from the angles of crustal deformation and strain. The movement and strain parameters of active blocks are estimated according to the unified velocity field composed of the velocities at 1598 GPS stations obtained from GPS measurements carried out in the past years in the Chinese mainland and the surrounding areas. The movement and strain conditions of the blocks are analyzed. The active blocks in the Chinese mainland have a consistent E-trending movement component, but its N and S components are not consistent. The blocks in the western part have a consistent N-trending movement and the blocks in the eastern part have a consistent S-trending movement. In the area to the east of 90°E, that is the area from Himalayas block towards NE, the movement direction of the blocks rotates clockwisely and the movement rates of the blocks are different. Generally, the movement rate is large in the west and south and small in the east and north with a difference of 3 to 4 times between the rates in the west and east. The distributions of principal compressive strain directions of the blocks are also different. The principal strain of the blocks located to the west of 90oE is basically in the SN direction, the principal compressive strain of the blocks in the northeastern part of Qingzang plateau is roughly in the NE direction and the direction of principal compressive strain of the blocks in the southeastern part of Qingzang plateau rounds clockwisely the east end of Himalayas structure. In addition, the principal strain and shear strain rates of the blocks are also different. The Himalayas and Tianshan blocks have the largest principal compressive strain and the maximum shear strain rate. Then, Lhasa, Qiangtang, Southwest Yunnan (SW Yunnan), Qilian and Sichuan-Yunan (Chuan-Dian) blocks followed. The strain rate of the blocks in the eastern part is smaller. The estimation based on the stain condition indicates that Himalayas block is still the area with the most intensive tectonic activity and it shortens in the NS direction at the rate of 15.2±1.5 mm/a. Tianshan block ranks the second and it shortens in the NS direction at the rate of 10.1±0.9 mm/a. At present, the two blocks are still uprising. It can be seen from superficial strain that the Chinese mainland is predominated by superficial expansion. Almost the total area in the eastern part of the Chinese mainland is expanded, while in the western part, the superficial compression and expansion are alternatively distributed from the south to the north. In the Chinese mainland, most EW-trending or proximate EW-trending faults have the left-lateral or left-lateral strike-slip relative movements along both sides, and most NS-trending faults have the right-lateral or right-lateral strike-slip relative movements along both sides. According to the data from GPS measurements the left-lateral strike-slip rate is 4.8±1.3 mm/a in the central part of Altun fault and 9.8±2.2 mm/a on Xianshuihe fault. The movement of the fault along the block boundary has provided the condition for block movement, so the movements of the block and its boundary are consistent, but the movement levels of the blocks are different. The statistic results indicate that the relative movement between most blocks is quite significant, which proves that active blocks exist. Himalayas, Tianshan, Qiangtang and SW Yunnan blocks have the most intensive movement; China-Mongolia, China-Korea (China-Korea), Alxa and South China blocks are rather stable. The mutual action of India, Pacific and Philippine Sea plates versus Eurasia plate is the principal driving force to the block movement in the Chinese mainland. Under the NNE-trending intensive press from India plate, the crustal matter of Qingzang plateau moves to the NNE and NE directions, then is hindered by the blocks located in the northern, northeastern and eastern parts. The crustal matter moves towards the Indian Ocean by the southeastern part of the plateau.  相似文献   

15.
张家口—渤海断裂带分段运动变形特征分析   总被引：1，自引：0，他引：1  
陈长云 《地震》2016,36(1):1-11
利用张家口—渤海断裂带(张渤带)及其邻区1999—2007年的GPS观测数据, 研究了该区域现今地壳水平速度场特征。 运用最小二乘配置方法获得应变率场的空间分布特征, 根据区域地壳主应变率、 面膨胀率和最大剪切应变率等形变场的空间变化, 分析了张渤带各分段的形变特征。 结果表明: 相对于欧亚框架, 研究区内GPS速度场以SE方向运动为主; 应变场以NE方向的主压应变为主, 伴随着近NW方向的张性应变; 整个张渤带及其邻区的高剪切变形区主要位于河北香河、 文安以及唐山等三个地区。 利用跨断层GPS剖面分析得到张渤带以左旋走滑为主, 兼有挤压运动。 华北平原块体和燕山块体的相对运动是张渤带左旋走滑的直接动力来源, 而印度板块与欧亚板块碰撞后继续向北的推挤作用则是张渤带运动变形的根本动力来源, 太平洋板块的作用相对较弱。  相似文献   

16.
The definition of active block is given from the angles of crustal deformation and strain. The movement and strain parameters of active blocks are estimated according to the unified velocity field composed of the velocities at 1598 GPS stations obtained from GPS measurements carried out in the past years in the Chinese mainland and the surrounding areas. The movement and strain conditions of the blocks are analyzed. The active blocks in the Chinese mainland have a consistent E-trending movement component, but its N and S components are not consistent. The blocks in the western part have a consistent N-trending movement and the blocks in the eastern part have a consistent S-trending movement. In the area to the east of 90°E, that is the area from Himalayas block towards NE, the movement direction of the blocks rotates clockwisely and the movement rates of the blocks are different. Generally, the movement rate is large in the west and south and small in the east and north with a difference of 3 to 4 times between the rates in the west and east. The distributions of principal compressive strain directions of the blocks are also different. The principal strain of the blocks located to the west of 90°E is basically in the SN direction, the principal compressive strain of the blocks in the northeastern part of Qingzang plateau is roughly in the NE direction and the direction of principal compressive strain of the blocks in the southeastern part of Qingzang plateau rounds clockwisely the east end of Himalayas structure. In addition, the principal strain and shear strain rates of the blocks are also different. The Himalayas and Tianshan blocks have the largest principal compressive strain and the maximum shear strain rate. Then, Lhasa, Qiangtang, Southwest Yunnan (SW Yunnan), Qilian and Sichuan-Yunan (Chuan-Dian) blocks followed. The strain rate of the blocks in the eastern part is smaller. The estimation based on the stain condition indicates that Himalayas block is still the area with the most intensive tectonic activity and it shortens in the NS direction at the rate of 15.2 ± 1.5 mm/a. Tianshan block ranks the second and it shortens in the NS direction at the rate of 10.1 ± 0.9 mm/a. At present, the two blocks are still uprising. It can be seen from superficial strain that the Chinese mainland is predominated by superficial expansion. Almost the total area in the eastern part of the Chinese mainland is expanded, while in the western part, the superficial compression and expansion are alternatively distributed from the south to the north. In the Chinese mainland, most EW-trending or proximate EW-trending faults have the left-lateral or left-lateral strike-slip relative movements along both sides, and most NS-trending faults have the right-lateral or right-lateral strike-slip relative movements along both sides. According to the data from GPS measurements the left-lateral strike-slip rate is 4.8 ± 1.3 mm/a in the central part of Altun fault and 9.8 ± 2.2 mm/a on Xianshuihe fault. The movement of the fault along the block boundary has provided the condition for block movement, so the movements of the block and its boundary are consistent, but the movement levels of the blocks are different. The statistic results indicate that the relative movement between most blocks is quite significant, which proves that active blocks exist. Himalayas, Tianshan, Qiangtang and SW Yunnan blocks have the most intensive movement; China-Mongolia, China-Korea (China-Korea), Alxa and South China blocks are rather stable. The mutual action of India, Pacific and Philippine Sea plates versus Eurasia plate is the principal driving force to the block movement in the Chinese mainland. Under the NNE-trending intensive press from India plate, the crustal matter of Qingzang plateau moves to the NNE and NE directions, then is hindered by the blocks located in the northern, northeastern and eastern parts. The crustal matter moves towards the Indian Ocean by the southeastern part of the plateau.  相似文献   

17.
基于连续GPS数据,利用滑动块体模型研究了日本MW9.0地震前后沂沭断裂带两侧块体连续的相对运动状态,并研究其对区域地震活动的影响,结果表明日本地震以来：1）两侧块体呈右旋走滑兼挤压状态,平均走滑、挤压速率分别为0.9±0.1 mm·a-1和-0.7±0.1 mm·a-1,相比日本地震之前,运动过程更具起伏特征,可能与日本地震前后俯冲带两侧板块间相互运动状态的改变有关;2）沂沭断裂带两侧地区地震活动频次N、总释放能量折算震级M、地震活动度S值、地震b值与两侧块体相对运动的相关系数分别为0.66、0.69、0.74、-0.6,T检验显示相关性显著.在研究区地震能量集中释放阶段两侧块体相对运动方向和研究区主压应力方向一致,相对运动速率和地震活动强度变化具有同步特征,两侧块体相对运动对区域地震活动具有控制作用;3）莱州序列和乳山震群的发生可能与两侧块体相对运动促进的局部区域应力调整有关.  相似文献   

18.
鄂尔多斯块体周缘地区现今地壳水平运动与应变   总被引：7，自引：1，他引：6       下载免费PDF全文
位于青藏块体和华北块体之间的鄂尔多斯块体及其周缘地区是中国大陆构造活动最活跃的地区之一,从1300年至今,在块体周边断陷盆地和西南缘断裂带上发生了五次8级以上的地震.为了了解该地区现今地壳运动、应变状态以及断裂滑动分布,我们收集了中国大陆构造环境监测网络2009—2013年、国家GPS控制网、跨断陷盆地的8个GPS剖面等共527个流动站和32个连续站GPS观测数据,获得了高空间分辨率的地壳水平运动速度场,进一步用均匀弹性模型计算了应变率分布.结果表明,块体内部GPS站点向NEE方向运动,速度变化较小,应变率大多在(-1.0~1.0)×10~(-8)/a之间;山西断陷带构造运动与变形最为强烈,盆地相对于鄂尔多斯块体为拉张变形,应变率为(1.0~3.0)×10~(-8)/a,相对于东部山地则为挤压变形,应变率为(-2.0~-3.0)×10~(-8)/a,盆地西侧断裂(如罗云山断裂、交城断裂)以拉张运动为主,拉张速率为2~3mm·a-1,盆地东侧断裂主要以右旋缩短运动为主,速率为1~3mm·a-1;河套断陷带西部的临河凹陷处于较强的张性应变状态,应变率为(2.0~3.0)×10~(-8)/a;块体西南边缘处于压缩应变状态,应变率为(-1.0~-2.0)×10~(-8)/a,六盘山断裂存在明显的地壳缩短运动,速率约为2.1mm·a-1,速率在断裂附近逐渐减小,反映了断裂处于闭锁状态;相对于鄂尔多斯块体内部渭河断裂带为左旋运动,速率为1.0mm·a-1,盆地处在弱拉张变形状态.  相似文献   

19.
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   

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