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1.
W. Dickson Cunningham Brian F. Windley D. Dorjnamjaa J. Badamgarov M. Saandar 《Earth and Planetary Science Letters》1996,140(1-4):67-81
The Gobi Altai region of southwestern Mongolia is a natural laboratory for studying processes of active, transpressional, intracontinental mountain building at different stages of development. The region is structurally dominated by several major E—W left-lateral strike-slip fault systems. The North Gobi Altai fault system is a seismically active, right-stepping, left-lateral, strike-slip fault system that can be traced along the surface for over 350 km. The eastern two-thirds of the fault system ruptured during a major earthquake (M = 8.3) in 1957, whereas degraded fault scarps cutting alluvial deposits along the western third of the system indicate that this segment did not rupture during the 1957 event but has been active during the Quaternary. The highest mountains in the Gobi Altai are restraining bend uplifts along the length of the fault system. Detailed transects across two of the restraining bends indicate that they have asymmetric flower structure cross-sectional geometries, with thrust faults rooting into oblique-slip and strike-slip master faults. Continued NE-directed convergence across the fault system, coupled with left-lateral strike-slip displacements, will lead to growth and coalescence of the restraining bends into a continuous sublinear range, possibly obscuring the original strike-slip fault system; this may be a common mountain building process.
The largely unknown Gobi-Tien Shan fault system is a major left-lateral strike-slip fault system (1200 km + long) that links the southern ranges of the Gobi Altai with the Barkol Tagh and Bogda Shan of the easternmost Tien Shan in China. Active scarps cutting alluvial deposits are visible on satellite imagery along much of its central section, indicating Quaternary activity. The total displacement is unknown, but small parallel splays have apparent offsets of 20 + km, suggesting that the main fault zone has experienced significantly more displacement. Field investigations conducted at two locations in southwestern Mongolia indicate that late Cenozoic transpressional uplift is still active along the fault system. The spatial relationship between topography and active faults in the Barkol Tagh and Bogda Shan strongly suggests that these ranges are large, coalescing, restraining bends that have accommodated the fault's left-lateral motion by thrusting, oblique-slip displacement and uplift. Thus, from a Mongolian perspective, the easternmost Tien Shan formed where it is because it lies at the western termination zone of the Gobi-Tien Shan fault system. The Gobi-Tien Shan fault system is one of the longest fault systems in central Asia and, together with the North Gobi Altai and other, smaller, subparallel fault systems, is accommodating the eastward translation of south Mongolia relative to the Hangay Dome and Siberia. These displacements are interpreted to be due to eastward viscous flow of uppermost mantle material in the topographically low, E–W trending corridor between the northern edge of the Tibetan Plateau and the Hangay Dome, presumably in response to the Indo-Eurasian collision 2500 km to the south. 相似文献
2.
GEOMORPHOLOGY OF THE GYARING CO FAULT ZONAL DRAINAGE SYSTEM AND ITS STRUCTURAL IMPLICATIONS 
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下载免费PDF全文 Strike-slip faults and normal faults are dominant active tectonics in the interior of Tibetan plateau and control a series of basins and lakes showing extension since the Late Cenozoic, by contrast with the thrust faulting along the orogenic belts bordering the plateau. The late Neotectonic movement of those faults is key information to understand the deformation mechanism for Tibetan plateau. The Gyaring Co Fault is a major active right-lateral strike-slip fault striking~300° for a distance of~240km in central Tibet, in south of Bangong-Nujiang suture zone. The Gyaring Co Fault merges with the north-trending Xainza-Dinggye rift near the southern shore of Gyaring Co. From NW to SE, Dongguo Co, Gemang Co-Zhangnai Co, Zigui Co-Gyaring Co form the Gyaring Co fault zonal drainage basin. Some scholars have noticed that the formation of lakes and basins may be related to strike-slip faults and rift, but there is no analysis on the Gyaring Co fault zonal drainage basin and its response to regional tectonics. In recent years, a variety of quantitative geomorphic parameters have been widely used in the neotectonic systems to analyze the characteristics of the basin and its response mechanism to the tectonic movement. In this paper, we applied ASTER GDEM data on the ArcGIS platform, extracted the Gyaring Co fault zonal drainage basin based on Google Earth images (Landsat and GeoEye) and field work. We acquired basic geomorphic parameters of 153 sub-basin (such as grade, relief, average slope, area) and Hypsometric Index (HI) value and curve. Statistical results have indicated significant differences in scale(area and river network grade)in north and south sides of the fault. Southern drainage basins' relief, slope, HI value are higher than the northern basins, and the overall shape of hypsometric curve of northern basins are convex compared with southern concavity. Along the strike of the Gyaring Co Fault, average slope, and HI value are showing generally increasing trending and hypsometric curve become convex from west to east. By comparing and analyzing the lithology and rainfall conditions, we found that they have little influence on the basic parameters and HI value of drainage basins. Therefore, the changes of basin topographic differences between northern and southern side of fault and profile reveal the Gyaring Co Fault has experienced differential uplift since the late Cenozoic, southern side has greater uplift compared to the north side, and the uplift increased from NW to SE, thus indicate that normal faulting of the Gyaring Co Fault may enhanced by the Xainza-Dinggye rift. The early uplift of the Gangdise-Nyainqentanglha Mountain in late Cenozoic might provide northward inclined pre-existing geomorphic surfaces and the later further rapid uplift on the Gangdise-Nyaingentanglha Mountain and Xainza-Dinggye rift might contribute to the asymmetrical development of the Gyaring Co fault zonal drainage basin. 相似文献
3.
The paper addresses the Late Cenozoic fault tectonics and the stress state of the Earth’s crust within the Mongolian microplate,
embracing Central and Western Mongolia. We analyze the results of reconstructing the stress fields and the tectonic deformations
in the zones of active faulting, located at the uplands and in the intermountain trenches, which bound the microplate (Mongolian
Altai; Gobi Altai; Dolinoozersk trough; Khan-Taishir-Nuruu, Khan-Houkhei, and Bolnai uplands) and the Khangai dome. Deformations
related with the northeastern general-scale collisional compression are concentrated along the periphery of the Mongolian
microplate, and the maximum compression is focused on its western and southern boundaries, thus forming the right- and the
left-lateral transpressive structures of the Mongolian and Gobi Altai. The deformations associated with the shortening of
the Earth’s crust involve not only the mountain ridges framing the block, but also the intermountain troughs that separate
the Gobi and Mongolian Altai from the Khangai dome, and the southern portion of the Khangai Uplift. The diversity in the deformations
within the central Khengai region ensues from the coupling of tension caused by the dynamical impact of the mantle anomaly,
which is located east of 100°E, with a regional NE compression. Owing to the relatively rigid Khangai block, the deformations
are transferred to the northern bound of this structure, namely the seismically active North Khangai fault. The role of compression
increases to the west of the zone, where it conjugates with the transpressive structures of the Mongolian Altai. The tension
becomes more important in the western part of this zone where the releasing bends are formed. A region characterized by extra
tension is localized also to the east of 100° E. In terms of the gradient in the lithosphere thickness and the structure types
of the upper crust, the submeridional line running along 100°E is interpreted as the key interblock boundary. 相似文献
4.
The North Pine Fault System (NPFS) in SE Queensland belongs to a series of NNW-striking sinistral faults that displaced Paleozoic to Cenozoic rock units in eastern Australia. We have studied the geometry and kinematics of the NPFS by utilizing gridded aeromagnetic data, digital elevation models, and field observations. The results indicate that all segments of the NPFS were subjected to sinistral reverse strike-slip faulting. Restorations of displaced magnetic anomalies indicate sinistral offsets ranging from ∼3.4 to ∼8.2 km. The existence of a (possibly) Late Triassic granophyre dyke parallel to one of the fault segments, and the occurrence of NNW-striking steeply dipping strike-slip and normal faults in the Late Triassic-Early Cretaceous Maryborough Basin, indicate that the NPFS has likely been active during the Mesozoic. We propose that from Late Cretaceous to early Eocene, NNW-striking faults in eastern Australia, including the NPFS, were reactivated with oblique sinistral-normal kinematics in response to regional oblique extension associated with the opening of the Tasman and Coral Seas. This interpretation is consistent with the modeled dominant NNE- to NNW-directed horizontal tensional stress in the Eocene. The latest movements along the NPFS involved sinistral transpressional kinematics, which was possibly related to far-field contractional stresses from collisional tectonics at the eastern and northern boundaries of the Australian plate in the Cenozoic. This sinistral-reverse oblique kinematics of the NPFS in the Cenozoic is in line with ∼ESE to ENE orientations of the modeled maximum horizontal stress in SE Queensland. 相似文献
5.
6.
ANALYSIS OF EVOLUTION OF THE RIYUESHAN FAULT SINCE LATE PLEISTOCENE USING STRUCTURAL GEOMORPHOLOGY 下载免费PDF全文
下载免费PDF全文 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
7.
《Earth and Planetary Science Letters》2006,241(3-4):913-931
Evidence of long-term, late Cenozoic uplift, as well as strike-slip faulting, is revealed by topographic and geological features along the northern 500 km of the Dead Sea fault system (DSFS)—the transform boundary between the Arabian and African plates in the eastern Mediterranean region. Macro-geomorphic features are studied using a new, high-resolution (20 m pixel) digital elevation model (DEM) produced by radar interferometry (InSAR). This DEM provides a spatially continuous view of topography at an unprecedented resolution along this continental transform from 32.5° to 38° N. This section of the left-lateral transform can be subdivided into a 200 km long Lebanese restraining bend (mostly in Lebanon), and the section to the north (northwest Syria). Spatial variations in Cenozoic bedrock uplift are inferred through mapping of topographic residuals from the DEM. Additionally, high altitude, low-relief surfaces are mapped and classified in the Mount Lebanon and Anti Lebanon ranges that also provide references for assessing net uplift. These results demonstrate an asymmetric distribution of post-Miocene uplift between the Mt. Lebanon and Anti Lebanon ranges. Antecedent drainages also imply that a major episode of uplift in the Palmyride fold belt post-dates the uplift of the Anti Lebanon region. North of the restraining bend, the Late Miocene surface is preserved beneath spatially extensive lava flows. Hilltop remnants of this paleosurface demonstrate Pliocene-Quaternary uplift and tilting of the Syrian Coastal Range, adjacent to the DSFS north of the restraining bend. This late Cenozoic uplift is contemporaneous with strike-slip along the DSFS. Geometrical relationships between folds and strike-slip features suggest that regional strain partitioning may accommodate a convergent component of motion between the Arabian and African plates. This interpretation is consistent with regional plate tectonic models that predict 10–25° of obliquity between the relative plate motion and the strike of the DSFS north of the restraining bend. We suggest that this convergent component of plate motion is responsible for uplift along and adjacent to the DSFS in the Syrian Coastal Range, as well as within the Lebanese restraining bend. 相似文献
8.
The three-dimensional arrangement of volcanic deposits in strike-slip basins is not only the product of volcanic processes,
but also of tectonic processes. We use a strike-slip basin within the Jurassic arc of southern Arizona (Santa Rita Glance
Conglomerate) to construct a facies model for a strike-slip basin dominated by volcanism. This model is applicable to releasing-bend
strike-slip basins, bounded on one side by a curved and dipping strike-slip fault, and on the other by curved normal faults.
Numerous, very deep unconformities are formed during localized uplift in the basin as it passes through smaller restraining
bends along the strike-slip fault. In our facies model, the basin fill thins and volcanism decreases markedly away from the
master strike-slip fault (“deep” end), where subsidence is greatest, toward the basin-bounding normal faults (“shallow” end).
Talus cone-alluvial fan deposits are largely restricted to the master fault-proximal (deep) end of the basin. Volcanic centers
are sited along the master fault and along splays of it within the master fault-proximal (deep) end of the basin. To a lesser
degree, volcanic centers also form along the curved faults that form structural highs between sub-basins and those that bound
the distal ends of the basin. Abundant volcanism along the master fault and its splays kept the deep (master fault-proximal)
end of the basin overfilled, so that it could not provide accommodation for reworked tuffs and extrabasinally-sourced ignimbrites
that dominate the shallow (underfilled) end of the basin. This pattern of basin fill contrasts markedly with that of nonvolcanic
strike-slip basins on transform margins, where clastic sedimentation commonly cannot keep pace with subsidence in the master
fault-proximal end. Volcanic and subvolcanic rocks in the strike-slip basin largely record polygenetic (explosive and effusive)
small-volume eruptions from many vents in the complexly faulted basin, referred to here as multi-vent complexes. Multi-vent
complexes like these reflect proximity to a continuously active fault zone, where numerous strands of the fault frequently
plumb small batches of magma to the surface. Releasing-bend extension promotes small, multivent styles of volcanism in preference
to caldera collapse, which is more likely to form at releasing step-overs along a strike-slip fault.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
9.
横亘新疆境内的天山及其周边的西昆仑、阿尔金和阿尔泰是中国大陆著名的强构造运动区和地震活动带。在对新疆构造区应力环境、动力过程、断层运动变形特征和地震序列分析讨论的基础上,对新疆及其周缘主要构造区地震破裂方式和序列类型进行研究,得出如下结论:(1)西昆仑构造区受来自青藏块体和塔里木块体NS和NW向水平压应力和垂向力的作用,构造运动呈现出走滑与逆冲特征,震源破裂以走滑型为主,数量较少的逆断型地震主要分布在西昆仑帕米尔一侧的深震挤压区,正断型地震主要出现在西昆仑与阿尔金交汇的拉张盆地及附近。该区主余型地震占63%,6级以上地震序列也存在多震类型。(2)阿尔金断裂带位于西昆仑北缘断裂和北祁连断裂过渡带,受青藏块体向北和向西的推挤,断裂本身的左旋位移量通过两端逆冲挤压而转化,使得青藏高原北边界不断向外扩展。在此力源下,阿尔金断裂带震源破裂以走滑为主,也有少量的逆冲型地震。地震序列中主余型和孤立型地震占比相同(占44%)。(3)在印度板块和亚欧大陆碰撞效应影响下,天山地区产生近NNE向水平压应力,构造运动显现出带旋性特征的逆冲和走滑,震源破裂方式与之相吻合。而天山构造大跨度的空间展布、扩展形式的多样性和地震破裂的两重性,又影响到地震序列类型的多样性,使得主余型、孤立型和多震型地震在不同构造部位呈现优势分布。(4)阿尔泰的构造运动可能受到了来自印度板块与亚欧板块碰撞的远程效应和西伯利亚块体南向运动的双向影响,形成NNE和SW向水平挤压力,主要大型发震断裂做右旋剪扭错动,而一些深断裂则以逆冲运动为主。震源破裂呈现出走滑(占64%)和部分的逆冲(占27%),6级以上地震序列主要为主余型,5级左右地震则多为孤立型。 相似文献
10.
阿尔泰构造带的活动断裂主要为NW—NNW向。按构造位置可分为阿尔泰西缘活动断裂带、阿尔泰中央活动断裂带和阿尔泰东缘活动断裂带。阿尔泰东缘活动构造带由科布多(Hovd)活动断裂带、哈尔乌苏湖(Har Us)活动断裂带2条大型右旋走滑活动断裂和中间的挤压盆地带构成。在2条走滑断裂带上,前人发现多处地震地表破裂带。通过对阿尔泰东缘构造带中南段地区的野外调查,在哈尔乌苏湖断裂带中段的Jargalant断裂、科布多断裂带南段的Tugen gol断裂上新发现地震地表破裂带。其中,沿Jargalant断裂地震地表破裂带长约50km,右旋位错量约4~5m,是一次规模大、活动较新的破裂事件。可见,在阿尔泰东缘活动断裂带的不同断裂段上均有保存较好的地震地表破裂,显示阿尔泰东缘是活动强烈的地震构造带 相似文献
11.
The Cobequid-Chedabucto fault system of northern mainland Nova Scotia represents the surface expression of the Avalon-Meguma terrane boundary, but because it is exposed at high crustal levels in the Cobequid Highlands, the fault system provides little information as to the kinematic relationships of the two terranes in this area. In the eastern Cobequid Highlands, the Rockland Brook Fault (RBF) is exposed within the more deeply eroded highlands massif and juxtaposes units of widely varying ages and lithologies. Therefore, this fault is better suited to define the nature and timing of fault movement associated with Avalon-Meguma terrane interaction.In several large Carboniferous plutons along the length of the RBF, and in previously deformed Precambrian rocks, mylonitic foliation orientations are predominantly east-west trending and mineral lineations plunge southeast. Kinematic indicators such as minor fold vergence, porphyroclast systems, asymmetric boudins, shear-band fabrics, and preferred recrystallization orientations indicate dextral shear. These data are taken to infer that the central section of the RBF is dominated by dextral strike-slip motion. Transpression occurs locally where the RBF curves into restraining bends. Kinematic data in these bends indicate top to the northwest thrusting. At the easternmost extent of the RBF, high-level brittle normal faults predominate in the locally extensional environment. The timing of RBF movement is constrained only by the ca 360 Ma granite bodies which it deforms and by the Westphalian sedimentary rocks which are affected by only the latest stages of movement.These kinematic data are consistent with previously published kinematic models for the interaction of the southern margin of the Avalon Composite Terrane with the Meguma Terrane in mainland Nova Scotia. These models suggest that regional dextral shear was accompanied by localized components of transpressional thrusting, wrench tectonism, and small-scale sedimentary basin development during Devonian to Carboniferous terrane interaction. 相似文献
12.
新生代期间强烈而持久的再生造山作用,在天山地区形成了大量近EW向逆断裂-褶皱带,引起地壳强烈缩短,穿插有NW向“类转换断层”,显示出天山地区近NS向不均匀的构造挤压作用;区域上地震构造主要为近EW向逆断裂-褶皱带或盲逆断层,其次为NW向“类转换断层”。巴楚-伽师地震区位于南天山柯坪塔格推覆构造系以南,NE向跨越极震区、长约50km的深地震反射探测表明,1997年伽师强震群的发震构造推测为NW向隐伏“类转换断层”,2003年巴楚-伽师地震(MS6·8)的发震构造为柯坪塔格推覆构造系南缘尚未出露地表的近EW向盲逆断层系 相似文献
13.
THE PALEOSEISMIC SURFACE RUPTURE AT SOUTH OF CENTRAL ALTYN TAGH FAULT AND ITS TECTONIC IMPLICATION 下载免费PDF全文
下载免费PDF全文 SHAO Yan-xiu YUAN Dao-yang LIU-ZENG Jing Jerome Van der Woerd LI Zhi-gang WU Lei LIU Fang-bin 《地震地质》1979,42(2):435-454
In this study, we described a 14km-long paleoearthquakes surface rupture across the salt flats of western Qaidam Basin, 10km south of the Xorkol segment of the central Altyn Tagh Fault, with satellite images interpretation and field investigation methods. The surface rupture strikes on average about N80°E sub-parallel to the main Altyn Tagh Fault, but is composed of several stepping segments with markedly different strike ranging from 68°N~87°E. The surface rupture is marked by pressure ridges, sub-fault strands, tension-gashes, pull-apart and faulted basins, likely caused by left-lateral strike-slip faulting. More than 30 pressure ridges can be distinguished with various rectangular, elliptical or elongated shapes. Most long axis of the ridges are oblique(90°N~140°E)to, but a few are nearly parallel to the surface rupture strike. The ridge sizes vary also, with heights from 1 to 15m, widths from several to 60m, and lengths from 10 to 100m. The overall size of these pressure ridges is similar to those found along the Altyn Tagh Fault, for instance, south of Pingding Shan or across Xorkol. Right-stepping 0.5~1m-deep gashes or sub-faults, with lengths from a few meters to several hundred meters, are distributed obliquely between ridges at an angle reaching 30°. The sub-faults are characterized with SE or NW facing 0.5~1m-high scarps. Several pull-apart and faulted basins are bounded by faults along the eastern part of the surface rupture. One large pull-apart basins are 6~7m deep and 400m wide. A faulted basin, 80m wide, 500m long and 3m deep, is bounded by 2 left-stepping left-lateral faults and 4 right-stepping normal faults. Two to three m-wide gashes are often seen on pressure ridges, and some ridges are left-laterally faulted and cut into several parts, probably owing to the occurrence of repetitive earthquakes. The OSL dating indicates that the most recent rupture might occur during Holocene.
Southwestwards the rupture trace disappears a few hundred meters north of a south dipping thrust scarp bounding uplifted and folded Plio-Quaternary sediments to the south. Thrust scarps can be followed southwestward for another 12km and suggest a connection with the south Pingding Shan Fault, a left-lateral splay of the main Altyn Tagh Fault. To the northeast the rupture trace progressively veers to the east and is seen cross-cutting the bajada south of Datonggou Nanshan and merging with active thrusts clearly outlined by south facing cumulative scarps across the fans. The geometry of this strike-slip fault trace and the clear young seismic geomorphology typifies the present and tectonically active link between left-lateral strike-slip faulting and thrusting along the eastern termination of the Altyn Tagh Fault, a process responsible for the growth of the Tibetan plateau at its northeastern margin. The discrete relation between thrusting and strike-slip faulting suggests discontinuous transfer of strain from strike-slip faulting to thrusting and thus stepwise northeastward slip-rate decrease along the Altyn Tagh Fault after each strike-slip/thrust junction. 相似文献
Southwestwards the rupture trace disappears a few hundred meters north of a south dipping thrust scarp bounding uplifted and folded Plio-Quaternary sediments to the south. Thrust scarps can be followed southwestward for another 12km and suggest a connection with the south Pingding Shan Fault, a left-lateral splay of the main Altyn Tagh Fault. To the northeast the rupture trace progressively veers to the east and is seen cross-cutting the bajada south of Datonggou Nanshan and merging with active thrusts clearly outlined by south facing cumulative scarps across the fans. The geometry of this strike-slip fault trace and the clear young seismic geomorphology typifies the present and tectonically active link between left-lateral strike-slip faulting and thrusting along the eastern termination of the Altyn Tagh Fault, a process responsible for the growth of the Tibetan plateau at its northeastern margin. The discrete relation between thrusting and strike-slip faulting suggests discontinuous transfer of strain from strike-slip faulting to thrusting and thus stepwise northeastward slip-rate decrease along the Altyn Tagh Fault after each strike-slip/thrust junction. 相似文献
14.
Along the border of the Adriatic microplate, pre-Alpine granulite-facies rocks from the deepest crust are outcropping at only two places: in the Ivrea Zone of the Southern Alps and in Southern Calabria. In these two areas the main features of the present crustal structures, i.e. overlapping of large continental crustal and upper mantle segments, are interpreted as resulting from their Hercynian geodynamic evolutions.The tilted, nearly complete crustal sections in both areas display very similar lithological sequences and experienced a common geological evolution, as deduced from petrological and radiometric dates. At the end of Hercynian time (～295 m.y.), the Ivrea body and the lower crustal rocks of Southern Calabria were contemporaneously sheared off from the upper mantle and uplifted into intermediate crustal levels, where they slowly cooled during Mesozoic time. The tectonic uplift was accompanied by granitoid plutonism and andesitic to rhyolitic volcanism, which continued after the Hercynian uplift.Considering the presently similar crustal structures and the Upper Carboniferous and Permian geological evolutions along the whole Adriatic plate boundary, the Ivrea Zone and Southern Calabria are used to resolve the pre-Alpine history of the boundary zone between the Adriatic and the Central European block: the uplift of the lower crustal/upper mantle flakes of the Adriatic block was due to flat overthrusting of these flakes on the continental crust of “Central Europe”. The material of the Central European crust underthrust (subducted) thereby melted during the re-equilibration of the geotherms which had been disturbed by the subduction process; this led to an extensive calc-alkaline plutonism and volcanism of crustal origin along the Adria boundary. In this boundary region, the overlying uppermost crustal levels (“Schiefergebirgsstockwerk”) were synchronously folded (“Asturian phase”) in response to the overlapping of the deeper crustal levels. Subsequently to the orogeny, the mountain chain was eroded and molasse basins developed on the overthrust Adriatic crustal segment during the Lower Permian.In this model, the granulite-facies flakes of the Ivrea Zone and of Southern Calabria are interpreted as pre-Hercynian lower crustal segments which were thrust into the middle crust during the Hercynian orogeny, thus giving rise to wave velocity inversions in the crust. Further, it is proposed that similar geodynamic processes have played a role in the genesis of the Conrad discontinuity which is present in many parts of the Hercynian fold belt. But only in the Ivrea Zone and in Southern Calabria the crustal discontinuities formed in Hercynian time were uplifted to the surface as a result of Alpine reactivation of the Adriatic boundary zone and due to their special positions in the bends of the Alpine-Apennine-Maghrebide mountain system.According to the present knowledge of the Carboniferous paleogeography and of the orogenic evolution on both sides of the Adria sufure zone, this fault zone was located within the European continent. Its role during the Hercynian orogeny is discussed envisaging two possibilities: an A-subduction zone or a subfluence zone (in the sense of Behr and Weber). 相似文献
15.
青藏高原是全球造山带研究的热点地区,此前在青藏高原开展的三维层析成像研究大多基于线性反演方法.本文利用青藏高原东缘及邻区布设的127个宽频带固定地震台站记录的连续波形资料,首先通过噪声互相关提取了3～50sRayleigh波群速度频散曲线并反演得到群速度分布,再进一步采用模拟退火法反演了研究区的三维S波速度及泊松比结构.结果显示:(1)松潘—甘孜地块的中下地壳低速异常主要分布在龙日坝断裂带、鲜水河断裂带、龙门山断裂带和岷山隆起所围限的区域,而该区域的中下地壳仅具有中等泊松比值,推测松潘—甘孜地块中下地壳的低速物质可能是青藏高原与扬子块体长期相互作用产生的塑性低速滑脱层;上地壳脆性物质在板块作用下沿中地壳低速滑脱层顶界面发生逆冲增厚,造成龙门山的持续抬升和地形起伏,并在构造边界带形成了应变积累和应力集中;而龙门山断裂带的上地壳低速软弱物质为地壳发生破裂提供了有利条件,从而在某种程度上促进了汶川地震和芦山地震的发生.(2)岷山隆起一带中下地壳的高泊松比异常呈"凸起"形态,结合前人研究发现的较高热流和岩石快速抬升现象,推测岷山隆起一带可能存在岩石圈的拆沉,导致地幔热物质上涌而形成下地壳高泊松比物质.(3)川滇地块的北部和南部具有不同的S波速度和泊松比分布特征.30km深度下川滇地块北部具有明显的低速异常,而该深度下并不具有明显的高泊松比值特征;此外剖面成像结果也显示川滇地块内的低速异常与高泊松比的分布不一致,因此川滇地块的研究结果不支持下地壳流模型.综合其他地震学证据,本文认为川滇地块的变形模式为上地壳纯剪切增厚,块体变形主要受块体内部的走滑断裂及活动边界断裂控制. 相似文献
16.
17.
Back-arc rifting in the Izu-Bonin Island Arc: Structural evolution of Hachijo and Aoga Shima Rifts 总被引：1，自引：0，他引：1
Adam Klaus Brian Taylor Gregory F. Moore Fumitoshi Murakami Yukinobu Okamura 《Island Arc》1992,1(1):16-31
Abstract Multi- and single-channel seismic profiles are used to investigate the structural evolution of back-arc rifting in the intra-oceanic Izu-Bonin Arc. Hachijo and Aoga Shima Rifts, located west of the Izu-Bonin frontal arc, are bounded along-strike by structural and volcanic highs west of Kurose Hole, North Aoga Shima Caldera and Myojin Sho arc volcanoes. Zig-zag and curvilinear faults subdivide the rifts longitudinally into an arc margin (AM), inner rift, outer rift and proto-remnant arc margin (PRA). Hachijo Rift is 65 km long and 20–40 km wide. Aoga Shima Rift is 70 km long and up to 45 km wide. Large-offset border fault zones, with convex and concave dip slopes and uplifted rift flanks, occur along the east (AM) side of the Hachijo Rift and along the west (PRA) side of the Aoga Shima Rift. No cross-rift structures are observed at the transfer zone between these two regions; differential strain may be accommodated by interdigitating rift-parallel faults rather than by strike- or oblique-slip faults. In the Aoga Shima Rift, a 12 km long flank uplift, facing the flank uplift of the PRA, extends northeast from beneath the Myojin Knoll Caldera. Fore-arc sedimentary sequences onlap this uplift creating an unconformity that constrains rift onset to ～1-2Ma. Estimates of extension (～3km) and inferred age suggest that these rifts are in the early syn-rift stage of back-arc formation. A two-stage evolution of early back-arc structural evolution is proposed: initially, half-graben form with synthetically faulted, structural rollovers (ramping side of the half-graben) dipping towards zig-zagging large-offset border fault zones. The half-graben asymmetry alternates sides along-strike. The present ‘full-graben’ stage is dominated by rift-parallel hanging wall collapse and by antithetic faulting that concentrates subsidence in an inner rift. Structurally controlled back-arc magmatism occurs within the rift and PRA during both stages. Significant complications to this simple model occur in the Aoga Shima Rift where the east-dipping half-graben dips away from the flank uplift along the PRA. A linear zone of weakness caused by the greater temperatures and crustal thickness along the arc volcanic line controls the initial locus of rifting. Rifts are better developed between the arc edifices; intrusions may be accommodating extensional strain adjacent to the arc volcanoes. Pre-existing structures have little influence on rift evolution; the rifts cut across large structural and volcanic highs west of the North Aoga Shima Caldera and Aoga Shima. Large, rift-elongate volcanic ridges, usually extruded within the most extended inner rift between arc volcanoes, may be the precursors of sea floor spreading. As extension continues, the fissure ridges may become spreading cells and propagate toward the ends of the rifts (adjacent to the arc volcanoes), eventually coalescing with those in adjacent rift basins to form a continuous spreading centre. Analysis of the rift fault patterns suggests an extension direction of N80°E ± 10° that is orthogonal to the trend of the active volcanic arc (N10°W). The zig-zag pattern of border faults may indicate orthorhombic fault formation in response to this extension. Elongation of arc volcanic constructs may also be developed along one set of the possible orthorhombic orientations. Border fault formation may modify the regional stress field locally within the rift basin resulting in the formation of rift-parallel faults and emplacement of rift-parallel volcanic ridges. The border faults dip 45–55° near the surface and the majority of the basin subsidence is accommodated by only a few of these faults. Distinct border fault reflections decreases dips to only 30° at 2.5 km below the sea floor (possibly flattening to near horizontal at 2.8 km although the overlying rollover geometry shows a deeper detachment) suggesting that these rifting structures may be detached at extremely shallow crustal levels. 相似文献
18.
天山山脉在新生代经历了强烈的构造隆升和地壳缩短作用,其周缘发生的地震活动是了解这一构造模式的窗口.对2016年呼图壁地震的发震构造有两种解读：向南倾斜的低角度逆断层和向北倾斜的高角度逆断层.中近场四台钻孔应变仪记录到了本次地震的同震响应,本文采用均质模型对IGP-CEA和USGS震源机制解进行模拟,结果显示发震断层为向北陡倾的反冲断层,15个原始方位和8个N-S、E-W方位观测值全部与预测值一致.对比天山北缘常见的低角度逆冲断层,反冲断层对构造隆升的贡献更有效,以断层倾角70°和19°计算,二者对隆升和缩短贡献比例分别为2.89：1和1：2.76.这一结果表明天山构造带内部的反冲构造同样具有单独发震的可能性,它们对天山现今的隆升高度同样起着不可忽视的作用. 相似文献
19.
Chen Zhengle Zhang Yueqiao Chen Xuanhua Wang Xiaofeng Ramon A. S. Zack W. B. 《中国科学:地球科学(英文版)》2001,44(1):103-111
The ENE-striking Altyn Tagh fault (ATF), extending along the northern edge of the Ti-betan Plateau, is one of the major important strike-slip faults, and has been known as one of the key areas to debate the eastward extrusion and crustral shortening models of the Tibetan Plateau during and after India-Asia collision. This paper mainly presents new evidence of Late Cenozoic sedimentary process to reconstruct the slip history of the ATF during the Late Cenozoic. Field measurements and laboratory analyses of the sedimentary characteristics in the Late Cenozoic basins in the central Altyn Tagh fault suggest that Late Cenozoic sedimentary sequence should be divided into three units according to facies changes. The paleo-topography reconstruction shows that the sedimentarion in these basins was tightly related with the fault, indicating that the ATF has experienced at least three stages of strike slipping in the Late Cenozoic. New geological data from the Late Cenozoic sedimentary basins and the formation of the present Suo’erkuli basin provide evidence for the displacement of the fault. The result shows that the 80–100 km left-lateral strike-slip displacement of the fault has been accumulated in the Late Cenozoic.
相似文献20.
Most models for fault growth and scaling are based on analysis of faults which display dip-slip (i.e. reverse, normal) and strike-slip kinematics; by contrast, little information is derived from faults displaying oblique-slip kinematics. Observations on mesoscopic transpressional faults from the Salinian Block of California and transtensional faults from the Southern Apennines of Italy reveal a complex kinematic history of fault propagation. Faults initially nucleate as isolate segments, which are later kinematically and mechanically linked via development of diffuse deformation zones and/or localised oblique connecting splays. The geometry of observed mesoscopic faults is similar to that of the host, larger structures, thus suggesting that the produced fault patterns are scale independent. Moreover, the overprinting relationships among minor fault-related fabrics permit to define a relative chronology within fault arrays, thus enabling a general sequence of structural stages to be correctly established. Based on minor fabrics and their overprinting relationships, a kinematic deformation model of fault growth by segment linkage is presented, which may have a wide applicability in the field of seismic hazard evaluation. 相似文献