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1.
断裂晚第四纪滑动速率及现今GPS观测揭示了青藏高原向北扩展与高原边缘隆升的运动特征.主要断裂晚第四纪滑动速率及跨断裂GPS应变速率的结果表明,青藏高原北部边缘的断裂以低滑动速率（＜10 mm/a）为主,特别是两条边界断裂：阿尔金断裂和海原—祁连山断裂.两条主要边界断裂上的滑动速率分布显示了断裂间滑动速率转换及调整特征.阿尔金断裂自95°E以西的8～12 mm/a稳定滑动速率,向东逐渐降低到最东端的约1～2 mm/a,而海原断裂自哈拉湖一带开始发育后滑动速率为1～2 mm/a,到祁连一带（101°E以东）增大到相对稳定的4～5 mm/a,直到过海原后转向六盘山一带,滑动速率降低到1～3 mm/a,甚至更低.滑动速率的变化及分布特征显示,阿尔金断裂滑动主要是通过祁连山内部隆起及两侧新生代盆地变形引起的缩短来吸收的,海原—祁连山断裂的低滑动速率及沿断裂运动学特征表明断裂尾端的陇西盆地变形及六盘山的隆起是断裂左旋走滑速率的主要吸收方式.这一变形特征表明,青藏高原北部边缘的变形模式是一种分布式的连续变形,变形发生自高原内部,边界断裂的走滑被高原内部变形所吸收.  相似文献   

2.
Jinta Nanshan Fault is an important fault in northeast front of Qing-Zang Plateau, and it is crucial for determining the eastern end of Altyn Tagh Fault. However, there is still debate on its significant strike-slip movement. In this paper, we study the Late Quaternary activity of Jinta Nanshan Fault and its geological and geomorphic expressions by interpreting aerial photographs and high-resolution remote sensing images, surveying and mapping of geological and geomorphic appearances, digging and clarifying fault profiles and mapping deformation characteristics of micro-topographies, then we analyze whether strike-slip activity exists on Jinta Nanshan Fault. We get a more complete fault geometry than previous studies from most recent remote sensing images. Active fault traces of Jinta Nanshan mainly include 2 nearly parallel, striking 100°~90° fault scarps, and can be divided into 3 segments. West segment and middle segment form a left stepover with 2~2.5km width, and another stepover with 1.2km width separates the middle and east segment. We summarize geomorphic and geologic evidence relating to strike slip activity of Jinta Nanshan Fault. Geomorphic expressions are as follows:First, fault scarps with alternating facing directions; second, sinistral offset of stream channels and micro-topographies; third, pull-apart basins and compressive-ridges at discontinuous part of Jinta Nanshan Fault. Geologic expressions are as follows:First, fault plane characteristics, including extremely high fault plane angle, unstable dip directions and coexistence of normal fault and reverse fault; second, flower structures. Strike-slip rate was estimated by using geomorphic surface age of Zheng et al.(2013)and left-lateral offset with differential GPS measurements of the same geomorphic surface at field site in Fig. 4e. We calculated a strike-slip rate of (0.19±0.05)mm/a, which is slightly larger than or almost the same with vertical slip rate of (0.11±0.03)mm/a from Zheng et al.(2013). When we confirm the strike-slip activity of Jinta Nanshan, we discuss its potential dynamic sources:First, eastern extension of Altyn Tagh Fault and second, strain partitioning of northeastward extension of Qilian Shan thrust belt. The first one is explainable when it came to geometric pattern of several E-W striking fault and eastward decreasing strike slip rate, but the former cannot explain why the Heishan Fault, which locates between the the Altyn Tagh Fault and Jinta Nanshan Fault, is a pure high angle reverse fault. The latter seems more explainable, because oblique vectors may indeed partition onto a fault and manifest strike-slip activity.  相似文献   

3.
The Haiyuan-Liupanshan fault,an active tectonic feature at the Tibetan Plateau's northeastern boundary,was ruptured by two MS earthquakes(1920 and 1927)bracketing an unbroken section(the Tianzhu seismic gap).A high seismic hazard is expected along the gap.To monitor deformation characteristics and do a seismic risk assessment,we made measurements at two newly built campaign-mode Global Positioning System(GPS) stations and 13 pre-existing stations in 2013 and 2014.Adding existing data from 1999 to 2014,we derived a new velocity field.Based on the horizontal velocity,we used three block models to invert the deformation of four crustal blocks.The results suggest non-uniform deformation in the interior of the Lanzhou block,the Ordos block and the Alaxan block,but uniform deformation in the Qilian block.Fault slip rates derived from block models show a decreasing trend from west to east,(2.0-3.2 mm/a on the Haiyuan fault to 0.9-1.5 mm/a on the Liupanshan fault).The Haiyuan fault evidences sinistral striking-slip movement,while the Liupanshan fault is primarily thrusting due to transformation of the displacement between the strike-slip and crustal shortening.The locking depth of each segment along the Haiyuan fault obtained by fitting the fault parallel velocities varies drastically from west to east(21.8-7.1 km).The moment accumulation rate,calculated using the slip rate and locking depth,is positively correlated with the locking depth.Given the paucity of large seismic events during the previous millennium,the Tuolaishan segment and the Maomaoshan segment have higher likelihood of nucleation for a future event.  相似文献   

4.
The sinistral strike-slip characteristic of the Altyn Tagh Fault gradually disappears near the Jiuxi Basin at the west end of Hexi Corridor, and the Kuantanshan Fault and the northern marginal fault of Heishan on its east are thrust structures. There are two faults distributed in the north of Kuantanshan, namely, the Taerwan-Chijiaciwo Fault and the Ganxiashan Fault, both are featured with obvious activity. Predecessors thought that the Taerwan-Chijiaciwo Fault is a thrust fault with low movement rate, but there is few detailed study on its horizontal motion. Is there horizontal strike-slip movement in the northern marginal fault of Kuantanshan? This issue has an important significance to further explore the structural transformation mode between the Altyn Tagh strike-slip faults and the northern thrust faults in the north margin of Qilianshan. Using high resolution remote sensing images and field work, such as combining with UAV SfM photogrammetry, the paper studies the strike-slip characteristics of the Taerwan-Chijiaciwo Fault and Ganxiashan Fault on the northern margin of Kuantanshan, and get two preliminary understandings:(1) The northern marginal fault of Kuantanshan is an active right-lateral strike-slip fault with thrust component, the horizontal to vertical dislocation ratio is about 3-4 times. Based on the statistics of dislocation amount of the gullies and terraces along the north marginal Kuantanshan fault, it is preliminarily estimated that the late Pleistocene right-lateral strike-slip rate is about 0.2-0.25 mm/a and the Holocene right-lateral strike-slip rate is about 0.5-1.5 mm/a. (2) The main driving force to the tectonics at the western end of Hexi Corridor, where the northern marginal fault of Kuantanshan locates, comes from the northward extrusion of the Qilian Mountains, which results in the right-lateral strike-slip of the northern marginal fault of Kuananshan and the thrust movement of several faults inside the Jiuxi Basin. The effect of the Altyn Tagh Fault on other tectonic structures is not obvious in this region.  相似文献   

5.
The giant sinistral Altyn Tagh Fault(ATF)is the northern boundary of the Tibetan Plateau. It has been playing important role in adjusting the India-Eurasia collision and the tectonic evolution of the northeastern Tibetan Plateau. Knowledge of the evolution of the ATF can provide comprehensive understanding of the processes and mechanisms of the deformation of the Tibetan Plateau. However, its timing of commencement, amount of displacement and strike-slip rate, as well as the tectonic evolution of the region are still under debate. South of the ATF, there exist a series of oroclinal-like arcuate structures. Knowledge of whether these curved geometries represent original curvatures or the bending of originally straight/aligned geological units has significant tectonic implications for the evolution of the ATF. The Yingxiongling arcuate belt in the western Qaidam Basin and the northern Qaidam marginal thrust belt(NQMTB)north of the Qaidam Basin are the two typical arcuate thrust belts, where the former has a "7-types" structure, and the latter has a reverse "S-type" structure. Successive Cenozoic sediments are well exposed and magnetostratigraphically dated in both belts. Paleomagnetic declination has great advantage to reveal vertical-axis rotations of geological bodies since they become magnetized. Recently conducted paleomagnetic rotation studies in different parts of these two thrust belts revealed detailed Cenozoic rotation patterns and magnitudes of the region. By integrating these paleomagnetic rotation results with regional geometric features and lines of geological evidence, we propose that these two arcuate thrust belts were most likely caused by different rotations in different parts of these curvatures, due to the sinistral strike-slip faulting along the ATF, rather than originally curved ones. The Yingxiongling arcuate belt was shaped by the significant counterclockwise(CCW)rotations of its northwestern half(the Akatengnengshan anticline)near the ATF during~16~11Ma BP, while its southeastern half(the Youshashan anticline)had no significant rotations since at least~20Ma BP. The geometry of the NQMTB was developed firstly by remarkable clockwise rotations of its middle part during~33~14Ma BP, and later possibly CCW rotations of its northwestern part during the Middle to Late Miocene, similar to that of the northwestern part of the Yingxiongling arcuate belt. The characteristics of two-stage strike-slip evolution of the ATF since the Early Oligocene were enriched:1)During the Early Oligocene to mid-Miocene, fast strike-slip faulting along the ATF was proposed to accommodate the eastward extrusion of the northern Tibetan Plateau with its sinistral shear confined to the fault itself. While in the NQMTB and farther east area in the Qilian Shan, its sinistral shear was transferred to the interior of the plateau and was accommodated by deformation of differential crustal shortenings and block rotations in these regions. Thus, the displacement along the ATF west of the NQMTB is larger than that east of the NQMTB. 2)Since the mid-late Miocene, sinistral shear of the ATF was widespread distributed within the northern Tibetan Plateau, instead of concentrated to the fault itself. Its sinistral offsets were partially absorbed by the shortening deformation within the Qaidam Basin and the Qilian Shan, leading the offsets along the ATF decreasing to the east. With the sinistral frictional drag of blocks(the Tarim Basin and the Altyn Tagh Range)on the other side during the second stage evolution of the ATF, a transitional zone south of the ATF was likely developed by remarkable CCW rotations during the Middle to Late Miocene, which is probably confined to east of the Tula syncline. Combining the sinistral offsets along the ATF derived from the paleomagnetic rotations during the Early Oligocene to mid-late Miocene and that by piercing points since the Late Miocene, the post Oligocene strike-slip offsets were constrained as at least~350~430km for the reference in the western Qaidam Basin and~380~460km for the reference in the NQMTB, with an average slip rate of at least~10.6~13.9mm/a. The post Early Oligocene offsets are consistent with the widely accepted offsets of~300~500km obtained by piercing point analyses.  相似文献   

6.
The Altyn Tagh Fault (ATF) is a major boundaryfault on the northern margin of the Qinghai-TibetanPlateau and is also the longest sinistral strike-slip faultat a lithospheric scale in the Eurasian Plate. Its exis-tence has directly affected regional features of neotec-tonics, topography, geomorphology, Quaternary geol-ogy, recent crustal deformation, seismicity, climatechange and ecological environment for fauna and florain China[1—6]. The sinistral slip on the ATF and activethrusting-fo…  相似文献   

7.
The Daliangshan tectonic zone is a rhombic area to the east of the Anninghe and Zemuhe fault zones in the middle segment of the Xianshuihe-Xiaojiang fault system along the southeast margin of the Qinghai-Xizang (Tibet) Plateau. Since the Cenozoic era, the neotectonic deformation in the Daliangshan tectonic zone has presented not only sinistral slip and reverse faulting along the Daliangshan fault zone, but also proximate SN-trending crust shortening. It is estimated that the average crust shortening in the Daliangshan tectonic zone is 10.9±1.6 km, with a shortening rate of 17.8±2.2% using the method of balanced cross-sections. The crust shortening from folding occurred mainly in the Miocene and the Pliocene periods, lasting no more than 8.6 Ma. Based on this, a crust shortening velocity of 1.3±0.2 mm/a can be estimated. Compared with the left offset along the Daliangshan fault zone, it is recognized that crust shortening by folding plays an important part in transferring crustal deformation southeastward along the Xianshuihe-Xiaojiang fault system.  相似文献   

8.
In this study, vertical deformation of different regions of Yunnan area in 1993-2013, 2001-2006, 2011-2017 is obtained using observational data of precise leveling. The results show that:1) In the whole, Yunnan area exhibits uplifting in the east of Yunnan and subsiding in the south of Yunnan, which is well consistent with the current horizontal velocity field obtained by GPS. In the east of Yunnan, southeastward horizontal velocity at the east boundary of Sichuan-Yunnan block is significantly decreased, which indicates extrusion deformation. This result is in accordance with the result that there is uplift in the east of Yunnan with precise leveling data. GPS velocity field rotates clockwise at Eastern Himalayan Syntaxis, therefore east-west extension is formed in central and southern Yunnan, which coincides with crustal subsidence observed by precise leveling. 2)The vertical movement in the northwest of Yunnan mainly exhibits the succession movement of basin subsidence and mountain uplift, in which, in the rift zone, Chenghai Basin, Qina Basin, Binchuan Basin and Midu Basin distributed along Chenghai Fault are all in the sinking state and the sinking velocity of Binchuan Basin located in the end of the sinistral strike-slip Chenghai Fault is the maximum. The sinking velocity of Dali Basin distributed along Honghe Fault is approximately 0.5mm/a and the sinking velocity of Midu Basin is approximately 1mm/a under the comprehensive action of right-lateral Honghe Fault and left-lateral Chenghai Fault. On the northwest boundary of the fault zone, the vertical movement of the basins (Lijiang Basin, Jiangchuan Basin)under the control of the nearby Lijiang-Jianchuan Fault is not obvious and the nearby mountain area exhibits uplift. 3)In the Honghe Fault, the southern region still possesses strong activity. Seeing from the leveling profile and vertical deformation field, the Honghe Fault still possesses the significance of block boundary fault and strong activity. GPS velocity field reveals that the southeast movement velocity of the Sichuan-Yunnan rhombic block is rapidly decreased near Xiaojiang Fault and the earth's crust is shortened and deformed. In the vertical deformation field, the uplift is formed near Xiaojiang Fault and there is obvious vertical deformation gradient. 4)Notably, deformation contour in the junction of Qujiang Fault and Xiaojiang Fault is characterized by four quadrant distribution, which indicates the possibility of earthquake.  相似文献   

9.
The Ximalin fault is the northwest section of the Ximalin-Shuiquan fault, which is part of the north-edge fault zone of the Yanghe Basin, located in the conjunction of the Zhangjiakou-Bohai fault zone and Shanxi fault-depression basin, and its structural geometry and deformation characteristics can facilitate the research on the interaction of the two tectonic belts. In this paper, data of geological surveys and geophysical exploration are used to study this fault exhaustively, concerning its geometry, structural features and activity as well as its relationship with adjacent faults and rule in the deformation transform of the north-edge fault zone of the Yanghe Basin. The results show that the Ximalin Fault is a strike-slip feature with thrust component. Its vertical slip rates are 0.17mm/a and 0.25~0.38mm/a, and the horizontal slip rate is 0.58~0.67mm/a and 0.50mm/a during the late Middle Pleistocene and Holocene, respectively. It is formed alternately by the NW-trending main faults and secondary NE-trending faults, of which the former is characterized by high-angle reverse with sinistral strike-slip, and the latter shows normal faulting. The two sets of structures have specific structural geometry relations, and the motion manners and deformation characteristics match each other. During the active process of the north-edge fault of the Yanghe Basin, the NW trending Ximalin fault played a role similar to a transform fault in deformation change and stress transfer, and its sinistral strike slip activity accommodated the NE trending normal faulting at the both ends.  相似文献   

10.
Influenced by the far-field effect of India-Eurasia collision, Tianshan Mountains is one of the most intensely deformed and seismically active intracontinental orogenic belts in Cenozoic. The deformation of Tianshan is not only concentrated on its south and north margins, but also on the interior of the orogen. The deformation of the interior of Tianshan is dominated by NW-trending right-lateral strike-slip faults and ENE-trending left-lateral strike-slip faults. Compared with numerous studies on the south and north margins of Tianshan, little work has been done to quantify the slip rates of faults within the Tianshan Mountains. Therefore, it is a significant approach for geologists to understand the current tectonic deformation style of Tianshan Mountains by studying the late Quaternary deformation characteristics of large fault and fold zones extending through the interior of Tianshan. In this paper, we focus on a large near EW trending fault, the Baoertu Fault (BETF) in the interior of Tianshan, which is a large fault in the eastern Tianshan area with apparent features of deformation, and a boundary fault between the central and southern Tianshan. An MS5.0 earthquake event occurred on BETF, which indicates that this fault is still active. In order to understand the kinematics and obtain the late Quaternary slip rate of BETF, we made a detailed research on its late Quaternary kinematic features based on remote sensing interpretation, drone photography, and field geological and geomorphologic survey, the results show that the BETF is of left-lateral strike-slip with thrust component in late Quaternary. In the northwestern Kumishi basin, BETF sinistrally offsets the late Pleistocene piedmont alluvial fans, forming fault scarps and generating sinistral displacement of gullies and geomorphic surfaces. In the bedrock region west of Benbutu village, BETF cuts through the bedrock and forms the trough valley. Besides, a series of drainages or rivers which cross the fault zone and date from late Pleistocene have been left-laterally offset systematically, resulting in a sinistral displacement ranging 0.93~4.53km. By constructing the digital elevation model (DEM) for the three sites of typical deformed morphologic units, we measured the heights of fault scarps and left-lateral displacements of different gullies forming in different times, and the result shows that BEFT is dominated by left-lateral strike-slip with thrust component. We realign the bended channels across the fault at BET01 site and obtain the largest displacement of 67m. And we propose that the abandon age of the deformed fan is about 120ka according to the features of the fan. Based on the offsets of channels at BET01 and the abandon age of deformed fan, we estimate the slip rate of 0.56mm/a since late Quaternary. The Tianshan Mountains is divided into several sub-blocks by large faults within the orogen. The deformation in the interior of Tianshan can be accommodated or absorbed by relative movement or rotation. The relative movement of the two sub-blocks surrounded by Boa Fault, Kaiduhe Fault and BETF is the dominant cause for the left-lateral movement of BETF. The left-lateral strike-slip with reverse component of BETF in late Quaternary not only accommodates the horizontal stain within eastern Tianshan but also absorbs some SN shortening of the crust.  相似文献   

11.
The two mainstream deformation models of the Tibet plateau are continental escape model and crustal thickening model, the former suggests that the NW-trending Karakoram Fault, Gyaring Co Fault, Beng Co Fault and the Jiali Fault as the Karakoram-Jiali fault zone is the southern border belt and that the dextral strike-slip rate is estimated as up to 10~20mm/yr. However, research results in recent years show that the slip rates along those faults are significantly less than earlier estimates. Taylor et al. (2003)suggest that the conjugate strike-slip faults control the active deformation in the central Tibet. The lack of research on the slip behavior of the NE-trending faults in the central Tibet Plateau constrains our understanding of the central Tibet deformation model. Thus, we choose the NE-direction Qixiang Co Fault located at the north of the Gyaring Co Fault as research object. Based on the interpretation of satellite images, we found several faulted geomorphic sites. Using RTK-GPS ground control point and unmanned aerial vehicle (UAV)topographic surveying, we obtained less than 10cm/pix-resolution digital elevation model (DEM)in the Yaqu town site. We used the LaDiCaoz_v2.1 software to automatically extract the left-lateral offset of the largest gully on the terrace T2 surface, which is (21.3±7.1)m, and the vertical dislocation of the scarp on the terrace T2 surface, which is (0.9±0.1)m. The age of both U-series dating samples on the terrace T2 is (4.98±0.17)ka and (5.98±0.07)ka, respectively. The Holocene left-lateral slip rate along Qixiang Co Fault is (3.56±1.19)mm/a and the vertical slip rate is (0.15±0.02)mm/a. The kinematic characteristics of the sinistral strike-slip with normal slip coincide with the eastward motion of the central Tibet plateau, and its magnitude is in agreement with its conjugate Gyaring Co Fault, suggesting that the deformation pattern of the central Tibetan plateau complies with the conjugate strike-slip faults mode.  相似文献   

12.
The northeastern margin of Tibetan plateau is an active block controlled by the eastern Kunlun fault zone, the Qilian Shan-Haiyuan fault zone, and the Altyn Tagh fault zone. It is the frontier and the sensitive area of neotectonic activity since the Cenozoic. There are widespread folds, thrust faults and stike-slip faults in the northeastern Tibetan plateau produced by the intensive tectonic deformation, indicating that this area is suffering the crustal shortening, left-lateral shear and vertical uplift. The Riyueshan Fault is one of the major faults in the dextral strike-slip faults systems, which lies between the two major large-scale left-lateral strike-slip faults, the Qilian-Haiyuan Fault and the eastern Kunlun Fault. In the process of growing and expanding of the entire Tibetan plateau, the dextral strike-slip faults play an important role in regulating the deformation and transformation between the secondary blocks. In the early Quaternary, because of the northeastward expansion of the northeastern Tibetan plateau, tectonic deformations such as NE-direction extrusion shortening, clockwise rotation, and SEE-direction extrusion occurred in the northeastern margin of the Tibetan plateau, which lead to the left-lateral slip movement of the NWW-trending major regional boundary faults. As the result, the NNW-trending faults which lie between these NWW direction faults are developed. The main geomorphic units developed within the research area are controlled by the Riyueshan Fault, formed due to the northeastward motion of the Tibet block. These geomorphic units could be classified as:Qinghai Lake Basin, Haiyan Basin, Datonghe Basin, Dezhou Basin, and the mountains developed between the basins such as the Datongshan and the Riyueshan. Paleo basins, alluvial fans, multiple levels of terraces are developed at mountain fronts. The climate variation caused the formation of the geomorphic units during the expansion period of the lakes within the northeastern Tibetan plateau. There are two levels of alluvial fans and three levels of fluvial terrace developed in the study area, the sediments of the alluvial fans and fluvial terraces formed by different sources are developed in the same period. The Riyueshan Fault connects with the NNW-trending left-lateral strike-slip north marginal Tuoleshan fault in the north, and obliquely connects with the Lajishan thrust fault in the south. The fault extends for about 180km from north to south, passing through Datonghe, Reshui coal mine, Chaka River, Tuole, Ketu and Xicha, and connecting with the Lajishan thrusts near the Kesuer Basin. The Riyueshan Fault consists of five discontinuous right-step en-echelon sub-fault segments, with a spacing of 2~3km, and pull-apart basins are formed in the stepovers. The Riyueshan Fault is a secondary fault located in the Qaidam-Qilian active block which is controlled by the major boundary faults, such as the East Kunlun Fault and the Qilian-Haiyuan Fault. Its activity characteristics provide information of the outward expansion of the northeastern margin of Tibet. Tectonic landforms are developed along the Riyueshan Fault. Focusing on the distinct geomorphic deformation since late Pleistocene, the paper obtains the vertical displacement along the fault strike by RTK measurement method. Based on the fault growth-linkage theory, the evolution of the Riyueshan Fault and the related kinetic background are discussed. The following three conclusions are obtained:1)According to the characteristics of development of the three-stage 200km-long steep fault scarp developed in the landforms of the late Pleistocene alluvial fans and terraces, the Riyueshan Fault is divided into five segments, with the most important segment located in the third stepover(CD-3); 2)The three-stage displacement distribution pattern of the Riyueshan Fault reveals that the fault was formed by the growths and connections of multiple secondary faults and is in the second stage of fault growth and connection. With CD-3 as the boundary, the faults on the NW side continue to grow and connect; the fault activity time on the SE side is shorter, and the activity intensity is weaker; 3)The extreme value of the fault displacement distribution curve indicates the location of strain concentration and stress accumulation. With the stepover CD-3 as the boundary, the stress and strain on NW side are mainly concentrated in the middle and fault stepovers. The long-term accumulation range of stress on the SE side is relatively dispersed. The stress state may be related to the counterclockwise rotation inside the block under the compression of regional tectonic stress.  相似文献   

13.
The Fodongmiao-Hongyazi Fault belongs to the forward thrust fault of the middle segment of northern Qilian Shan overthrust fault zone, and it is also the boundary between the Qilian Shan and Jiudong Basin. Accurately-constrained fault slip rate is crucial for understanding the present-day tectonic deformation mechanism and regional seismic hazard in Tibet plateau. In this paper, we focus on the Shiyangjuan site in the western section of the fault and the Fenglehe site in the middle part of the fault. Combining geomorphic mapping, topographic surveys of the deformed terrace surfaces, optically stimulated luminescence (OSL) dating, terrestrial cosmogenic nuclide dating and radiocarbon (14C) dating methods, we obtained the average vertical slip rate and shortening rate of the fault, which are ~1.1mm/a and 0.9~1.3mm/a, respectively. In addition, decadal GPS velocity profile across the Qilian Shan and Jiudong Basin shows a basin shortening rate of~1.4mm/a, which is consistent with geological shortening rates. Blind fault or other structural deformation in the Jiudong Basin may accommodate part of crustal shortening. Overall crustal shortening rate of the Jiudong Basin accounts for about 1/5 of shortening rate of the Qilian Shan. The seismic activity of the forward thrust zone of Tibetan plateau propagating northeastward is still high.  相似文献   

14.
The Sürgü Fault Zone (SFZ) is located in SE Anatolia extending from Göksun in the west to Çelikhan in the east, where it bifurcates from the East Anatolian Fault Zone. A detailed analysis along the fault using satellite images, digital elevation models (DEMs) and aerial photographs revealed that the SFZ displays characteristic deformation patterns common to dextral strike-slip faults, including pressure ridges, displaced linear valleys, and deflected stream courses. In addition to this, fault slip data collected from 17 sites indicated that the SFZ is a dextral strike-slip fault zone having reverse and normal components in its western and eastern parts, respectively. The type of dip-slip components, orientation of the palaeostress configurations, and related structures along the fault are compatible with along strike variations of a strike-slip fault system that supports the dextral nature of the fault zone. Observed maximum cumulative stream deflections along the fault zone indicate that the dextral offset of the SFZ has been more than 3 km since the establishment of the stream network in the region. According to the preferred tectonic model suggested in this study, the present dextral motion along the SFZ occurs within a regional sinistral system related to westwards escape of the Maraş Block, squeezed between Anatolian Block and Arabian Plate in N–S direction.  相似文献   

15.
西秦岭临潭-宕昌断裂第四纪最新活动特征   总被引：2，自引：0，他引：2  
临潭-宕昌断裂是西秦岭造山带内一条重要的分支断裂,其最新活动特征是分析西秦岭构造变形的重要依据。临潭-宕昌断裂的新构造活动强烈,中强地震频繁,但目前对于断裂的新活动特征研究程度较低,未见有其全新世活动地质地貌证据的报道。文中基于遥感解译、宏观地貌分析研究断裂的长期活动表现和分段性;同时通过地质地貌考察、无人机摄影测量、差分GPS和放射性碳测年等方法定量研究断裂的新活动特征;最后基于研究结果探讨了断裂及附近区域的地震危险性和区域构造变形。结果表明:根据断层迹线收敛程度和宏观地貌差异,可将临潭-宕昌断裂分为西、中、东3段;断裂的运动性质以左旋走滑为主,兼具逆冲分量,左旋走滑使洮河及其支流、冲沟和山脊等发生同步左旋拐弯,最大左旋位移可达3km,逆冲分量使新近纪盆地边缘和内部形成300~500m的垂向位移;断裂的最新活动时代为全新世,限定了1次2 090~7 745a BP(置信度为2σ)的全新世古地震事件;全新世早期以来,临潭-宕昌断裂东段主干断裂的左旋走滑速率为0.86~1.65mm/a,垂直滑动速率为0.05~0.10mm/a。临潭-宕昌断裂分配了约2mm/a的左旋走滑分量,是东昆仑-西秦岭阶区变形分配的关键断裂之一。  相似文献   

16.
东昆仑活动断裂是青藏高原东北部一条重要的NWW向边界断裂。 玛曲断裂位于东昆仑断裂带的最东段。 根据野外考察结果认为玛曲断裂全新世以来活动强烈, 主要表现为左旋走滑运动, 并伴有正倾滑运动性质。 断错地貌特征明显, 断裂过玛曲县城以后, 沿黑河南岸穿过若尔盖草地向东, 直至岷山北端求吉附近。 通过两处断错地貌的全站仪器实测和测年资料讨论了玛曲断裂新活动特征和全新世滑动速率, 玛曲断裂全新世早期以来的平均水平滑动速率为6.29～5.71 mm/a, 全新世晚期以来的平均水平滑动速率为4.19～4.03 mm/a。  相似文献   

17.
李满  肖骑彬  喻国 《地球物理学报》1954,63(11):4125-4143
阿尔金断裂带东段走滑速率沿断裂走向方向存在明显的流失现象,有关阿尔金断裂带的影响范围及走滑速率变化的机制需要有更多的深部结构证据来提供支撑.本文以阿尔金断裂带昌马段为窗口,获取了4条横穿阿尔金断裂带及相邻地区的大地电磁测深剖面.二维电性剖面显示在阿尔金断裂带北侧中上地壳以连续的高阻体为主,而南侧祁连山内部的深部电性结构在横向上有较为复杂的变化.这一点与区域构造背景相对应,即北侧的塔里木盆地东缘依然具有较好的整体性,南侧的祁连山是青藏高原北缘生长的最前端,变形强烈.在断裂带的结构特征上,阿尔金断裂带沿走向方向的切割深度在昌马盆地西侧发生了显著的降低,与阿尔金断裂带相对应的电性边界在这里向南偏移了约15 km,对应F18断裂,并与昌马盆地相接.祁连山北部的断裂带,包括昌马断裂、旱峡—大黄沟断裂总体呈现出低角度南倾的样式,切过高阻异常体的顶部.虽然昌马盆地可以起到连接断裂带的阶区的作用,将部分阿尔金断裂的走滑分量转移到盆地南侧的昌马断裂上,但是昌马断裂的走滑速率从西向东是增加的,东侧的走滑速率甚至大于阿尔金断裂沿走向方向的流失分量.我们认为在青藏高原北部主要断裂带的活动还是受印度—欧亚板块碰撞引起的远程挤压效应的影响,包括阿尔金断裂以及祁连山内部系列断层都处于斜向挤压应力环境.在这种基本构造模式下,阿尔金断裂、断裂F18、昌马盆地、昌马断裂构成了一个局部的走滑速率分解-转换-吸收体系,对局部应力状态产生影响.  相似文献   

18.
青藏高原中北部的巴颜喀喇地块是近年来强震最为活跃的地区,自1997年以来在地块周围发生了一系列7级以上地震.2014年于田MS7.3级地震就发生在该地块西边界附近的硝尔库勒盆地南缘,该区是阿尔金断裂、康西瓦断裂和东昆仑断裂等多组不同走向大型走滑活动断裂带的交汇部位,不同断裂走向的突然转变及滑动速率差异使该地区形成局部的拉张应力状态,发育了多条NE和近SN向的左旋正断裂. 通过余震分布、震源机制解结果等资料分析,认为此次地震的发震构造为阿尔金断裂西南端的一条次级断裂——硝尔库勒断裂,地震破裂特征为左旋走滑兼正断性质. 在巴颜喀喇地块这一轮的强震活动中,其北边界和东边界都显示块体向东挤出约7 m的位移量,但块体西边界产生的伸展量明显与整个块体向东的位移量不协调,2014年于田MS7.3级地震是巴颜喀喇地块向东挤出的构造响应和应变调整.模拟结果显示阿尔金主断裂上的库仑应力有所增加,东昆仑—柴达木地块可能为下一个强震活跃区,特别是阿尔金断裂的中西段,是今后应该重点关注和监视的地区.  相似文献   

19.
滇西北通甸-巍山断裂中段的晚第四纪滑动速率   总被引：2，自引：0，他引：2       下载免费PDF全文
通甸-巍山断裂属于红河断裂带的分支断裂,目前对该断裂中段的晚第四纪活动特征研究较少。野外地质地貌调查和年代学研究结果表明,通甸-巍山断裂中段是以右旋走滑运动为主,兼有张性正断的全新世活动断裂,其最新活动时代距今约2.2ka。晚更新世中晚期以来断裂中段平均水平滑动速率为1.25mm/a,全新世晚期以来垂直运动趋于增强。该研究不仅为该断裂的地震危险性评价工作提供了基础资料,而且有助于理解川滇菱形块体西南边界构造变形的空间分配特点  相似文献   

20.
本研究通过对东构造结及其周边地区主要断裂进行野外考察,通过GPS观测数据和地质、地球物理资料的综合分析,建立三维有限元模型;运用数值模拟方法对东构造结周边地区主要断裂现今运动特征进行模拟研究,取得一些初步的认识:(1)东构造结北侧和东侧地块总体上围绕构造结发生顺时针旋转,右旋走滑的东南边界断裂不是嘉黎断裂,可能是阿帕龙...  相似文献   

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