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1.
《Geodinamica Acta》2013,26(1-3):127-143
The western part of the Polish Outer Carpathians is built up from the thrust, imbricated Upper Jurassic-Neogene flysch deposits. The following Outer Carpathian nappes have been distinguished: Magura Nappe, Fore-Magura group of nappes, Silesian, Subsilesian and Skole nappes. Interpretation of seismic and magnetotelluric survey from the region South of Wadowice, allows observation of relationship between basement and flysch nappes in the Outer Carpathians. It also allows identification of dislocation cutting both flysch nappes and their basement. All the Outer Carpathian nappes are thrust over the southern part of the North European Platform. The platform basement is composed of older Precambrian metamorphic rocks belonging to the Bruno-Vistulicum terrane. Sedimentary cover consists of Paleozoic, Mesozoic and Neogene sequences. The characteristic features of this boundary are horsts and troughs of general direction NW-SE, turning W-E. Faults cutting only the consolidated basement and the Paleozoic cover were formed during the Hercynian Orogeny in the Carboniferous and the Early Permian. Most of the older normal faults were covered by allochtonous flysch nappes forming thus the blind faults. During the last stage of the geodynamic development the Carpathians thrust sheets moved towards their present position. Displacement of the Carpathians northwards is related to development of dextral strike-slip faults of N—S direction. The orientation of this strike-slip fault zones zone more or less coincides with the surface position of the major faults perpendicular to the strike of the Outer Carpathian thrustsheets. The huge fault cuts formations from the Paleozoic basement through the flysch allochton between the boreholes in Sucha Beskidzka area. The displacement of nappes of the Carpathian overthrust and diapiric extrusion of plastic formations of the lower flysch units occurred along this fault. 相似文献
2.
柯坪塔格推覆构造几何学、运动学及其构造演化 总被引：29，自引：1，他引：29
大量野外构造地质调查和深部构造解释表明柯坪塔格推覆构造由多组倒转复式背斜、复式箱状背斜构成的推覆体及其前缘逆冲断裂组成 ,由寒武系—第四系组成的推覆体由北向南逆—斜冲 ,平面上构成向南凸出的弧形推覆构造 ;普昌断裂由各不相连的逆冲斜冲断裂段组成 ,而不是完整的一条走滑断层 ,各推覆体前缘逆冲断裂与各推覆体的普昌断裂段共同构成统一的前缘逆冲斜冲逆冲断裂和推覆构造系统 ;普昌断裂段以西的推覆体具有向东抬升、向西倾覆的鼻状构造特征 ,普昌断裂段以东的推覆体具有向西抬升、向东倾覆的鼻状构造特征 ,普昌基底隆起带是巴楚隆起隐伏在柯坪塔格推覆构造之下的部分。各推覆体前缘断裂在深部均归并于统一的寒武系底部的滑脱面 ,其南浅北深 ,东浅西深 (普昌隆起带以西 )或西浅东深 (普昌隆起带以东 ) (6 10km ) ,埋深较大区发育多组滑脱面。柯坪塔格推覆构造的形成时期为晚第四纪 ,为现今活动的推覆构造系统。文中认为各推覆体向南西的倾覆端基底滑脱面和中新生界内部的滑脱面没有贯通 ,是未来 6级以上地震的发震构造部位。 相似文献
3.
Maurice K. -Seguin 《Tectonophysics》1983,96(1-2)
An integrated interpretation of seismic reflection and gravity results yields an image of the structural units (nappes, overthrust sheets and underthrust slabs) of the Cambrian-Ordovician metasedimentary and metavolcanic sequences of the Appalachian province of southern Quebec at depth and the relative position of the underlying Precambrian crystalline basement. The tectonics related to crystalline Precambrian basement may be correlated with four interpretations and combinations of these. A décollement of Paleozoic sedimentary and volcanic piles over a rigid crystalline basement is most probable considering the interpretation of gravity and especially seismic data. The tectonic style at depth is rather unresolved from surface geological information. The elaboration of a two-dimensional model is constrained by physical properties of rocks, maximum depth extents of individual bodies and seismic reflectors in addition to surface geology. Finally, a minimum of 1500 km of shortening and Iapetan closing is suggested. 相似文献
4.
燕山式板内造山带基本特征与动力学探讨 总被引：68，自引：10，他引：58
板内造山带的基本特征是前期已经固结的岩石圈重新活化。前期地壳基底的复活对后期构造的控制和造山期新生的构造对前期地壳的改造是板内造山作用的两大特征。燕山地区元古宙东西向基底断裂带在中生代的复活控制了区域盖层的构造,表现为沿古断裂的斜滑作用形成的正花状和负花状构造对中生代盖层沉积盆地及其构造的控制,形成盆缘逆冲断层;在基底和盖层中形成羽列式断层及大型Ｓ Ｃ 式排列的褶皱和断裂组合。其中的逆冲推覆构造也与发育于板缘的不同,主要为基底卷入型。幔源热活动导致强烈的岩浆活动和地壳被加热、软化,从而诱发变形是造山期新生的特点。燕山的纬向构造被ＮＮＥ向太行山构造带所叠加,以及许多以变质核杂岩和岩浆底辟为代表的垂向构造穿插其中,组成了燕山式板内造山带的主要构造格局。地球内部物质的垂向调整,幔源物质和热流的上升是板内造山带的主因。重力和地球自转引起的切向力是形成板内造山带表层构造的不可忽视的力源 相似文献
5.
It has been observed that the intensity of underwater gas flares unexpectedly increased after the deep-focus (625.9 km) earthquake that occurred in the Sea of Okhotsk on August 14, 2012. In this regard, we have analyzed the data resulting from interpretation of the focal mechanism for the strike-slip earthquakes which occurred in the Benioff seismic zone of the subducting Pacific Plate within the Sea of Okhotsk region over the period from 1977 to 2010. The NNW sinistral and NE dextral faults are found to form a conjugate system due to the WNW stress field. We have established that the dextral faults are mostly common at a depth of about 200 km along the Kuril Islands extension, while the sinistral ones are concentrated in the Nosappu Fracture Zone and traced to the NNW down to a depth of 680 km. The area of the gas flare discharge and gas hydrate accumulations have the same (NNW) direction. Thus, we have revealed that the Nosappu Fracture Zone appears to be a structure which controls fluid fluxes, providing permeability of the subducting slab of the Pacific Plate for ascending fluids from the lower mantle. 相似文献
6.
郯庐断裂带的形成与演化：综述 总被引：81，自引：0，他引：81
从历史的与整体的观点出发，综合了地质、地貌、地球化学与地球物理的资料，系统地研究了郯庐断裂带各阶段的形态学、运动学以及动力学机制。认为此断裂带开始形成于中、晚三叠世，其长度小于１５００ｋｍ，切割深度小于１５～２０ｋｍ，此时最大左行走滑断距为４３０ｋｍ左右。侏罗纪（２０８～１３５Ｍａ）与中始新世－渐新世（５２～２３．３Ｍａ），此断裂带表现为逆断层活动，断层面受挤压较紧闭。白垩纪－早始新世（１３５～５２Ｍａ），郯庐断裂呈现为略带右行走滑的正断层（走滑断距不超过１００ｋｍ），郯庐断裂带与其北部切割深度约为３０～４０ｋｍ。中新世－更新世（２３．３～０．７３Ｍａ）断裂带表现为带有左行走滑的正断层，走滑断距约５０ｋｍ，断裂带切割深度在５０～８０ｋｍ之间。中更新世（０．７３Ｍａ以来）断裂带又变成略带右行走滑的逆断层，走滑断距不足１００ｍ。由于断裂带形成以来的剥蚀深度不大，地表的断层岩都是碎裂岩与断层泥。沿此断裂带在早白垩世构成了中国东部重要的内生金属成矿带。 相似文献
7.
The Le Châtelet gold deposit is unique among the mined deposits of the French Variscan basement in that the gold is not free but caught up in the arsenopyrite crystal lattice. Microstructural analysis shows that the Au-arsenopyrite quartz veins are hosted by north-trending dextral strike-slip faults resulting from NNE-SSW compression during the early Stephanian (around 300 Ma). Textural study indicates that vein emplacement was due to sequential dynamics related to spasmodic strike-slip movements along these brittle structures (seismic regime). The classic sequence begins with the slow crystallization of sulphide-free comb quartz followed by a co-deposition of microcrystalline quartz and needles of Au-arsenopyrite; the rapid crystallization of the Au-arsenopyrite-bearing microcrystalline quartz was due to a sudden drop in fluid pressure. The veins correspond to dilational jogs formed by a suction pump mechanism during a late phase of the Variscan orogeny; they were trapped in migmatite about 1 km below surface. 相似文献
8.
古新世以来郯庐断裂的位移量及其对莱州湾凹陷的控制 总被引：4，自引：2，他引：2
高分辨三维地震可视化及方差切片分析显示,郯庐断裂渤海海域莱州湾段北北东向断裂系发育。断层在水平方差切片上的拖拽现象、断裂带内部断层的组合关系以及凹陷沉积中心的迁移等,表明古新世以来该区存在右旋走滑运动。假设在东、西两支断层的走滑拉分作用下,根据可容纳空间不变原理,设计了三角形模型、长方形模型、半地堑型模型以及地堑型模型共四种模型,计算莱州湾凹陷南北长度和凹陷深度的关系,其中半地堑模型计算得到的郯庐断裂的水平位移为7km。结合断层的平面分布和断层的切割关系,表明古新世以来郯庐断裂的走滑拉分作用难以控制莱州湾凹陷的形成,走滑拉分作用只是在走滑断裂带内部形成了局部小型洼地,其规模很小,影响非常有限。 相似文献
9.
We localized crustal earthquakes in the Andean arc, between 35°S and 36°S, from December 2009 to May 2010. This research shows a seismicity increase, in a narrow longitudinal area, of more than nine times after the great Mw 8.8 Maule earthquake.The localized seismicity defines an area of ∼80 km long and ∼18 km wide and NNW to NNE trend. The Md magnitudes varied from 0.7 to 3.1 except for two earthquakes with Mw of 3.9 and 4.5, located in the northern end of the area. The focal mechanisms for these two last events were normal/strike-slip and strike-slip respectively.During 2011, a network of 13 temporary stations was installed in the trasarc region in Malargüe, Argentina. Sixty earthquakes were localized in the study region during an 8 month period.We explored how changes in Coulomb conditions associated with the mega-thrust earthquake triggered subsequent upper-plate events in the arc region. We assumed the major proposed structures as receiver faults and used previously published earthquake source parameters and slip distribution for the Maule quake. The largest contribution to static stress change, up to 5 bars, derives from unclamping resulting consistent with co-seismic dilatational deformation inferred from GPS observations in the region and subsidence in nearby volcanoes caused by magma migration.Three different Quaternary tectonic settings–extensional, strike-slip and compressional-have been proposed for the arc region at these latitudes. We found that the unclamping produced by the Maule quake could temporarily change the local regime to normal/strike-slip, or at least it would favor the activation of Quaternary NNE to N-trending dextral strike-slip faults with dextral transtensional movement. 相似文献
10.
造山带逆冲推覆构造研究的主要新进展 总被引：9，自引：0，他引：9
造山带逆冲推覆构造研究是造山带研究中最为重要的课题之一。造山带外带即前陆褶皱冲断带(主要发育盖层冲断推覆体,一般遵循薄皮构造变形规则)与造山带内带(主要是基底褶皱推覆体,呈现厚皮构造变形规律)结晶逆冲推覆构造的几何学、运动学特征存在较大差异,二者形成机制也不相同,但其间仍有紧密的联系。近20年来造山带逆冲推覆构造研究的主要新进展为:①前陆褶皱冲断带逆冲断层及其相关褶皱的几何学特征分析已趋定量化,对其组合类型与演化时序有了更全面的认识,且对前陆褶皱冲断带的发展演化模式取得了新的共识,即遵循临界库仑楔模式;②平衡剖面技术在前陆褶皱冲断带的应用已从二维平衡与复原演进到三维平衡与复原,且日渐计算机化;③对造山带内带结晶基底逆冲推覆构造的主要类型(C型与F型逆冲岩席)及其特征已有较深的理解;④对前陆褶皱冲断带与结晶基底逆冲构造的相互关系及其形成演化模式有了新认识。目前造山带逆冲推覆构造研究过程中存在的主要问题为:①造山带内带结晶逆冲推覆构造的研究比较薄弱;②造山带晚期走滑构造及伸展构造的叠加与改造使得造山带内结晶逆冲推覆构造更为复杂化,致使其研究难度加大;③全面、精细的造山带深部地球物理资料较缺乏;④造山带内结晶逆冲岩席变形变质历史与超高压变质岩的形成机制及折返过程之间的关系尚未揭示清楚。在今后研究过程中应加强对上述问题的深入研究。 相似文献
11.
Prantik Mandal B. Singh P. Nagendra A. K. Gupta 《Journal of the Geological Society of India》2017,89(4):363-368
We herein present source parameters and focal mechanism of a rare cratonic upper crustal earthquake of Mw4.0, which occurred at 8 km depth (centroid depth) below a region near Deogarh, Jharkhand. For our study, we used broadband waveform data from a seismic network of 15 three-component seismographs in the eastern Indian craton. The average seismic moment, moment magnitude and source radius are estimated to be 1.1 × 1015 N-m, 4.0 and 180.6 m, respectively. The high average stress drop of 14.27 MPa could be attributed to its lower-crustal origin. The mean corner frequency is calculated to be 4.1 Hz. To study the source mechanism, we perform a deviatoric constrained full waveform moment tensor inversion of multiple point sources on the band-passed (0.06 – 0.14 Hz) broadband displacement data of the Deogarh event, using ISOLA software. The best fit is obtained for the source at 8 km centroid depth, with a moment magnitude 3.7, and a right-lateral strike-slip mechanism with strike 162°, dip 72° and rake 169°. The P-axis orients N24°E, which is parallel to the direction of the absolute plate motion direction of Indian plate, while T-axis orients E-W, which is parallel to the strike of the pre-existing Damodar Graben (DG) of Gondwana age. The occurrence of this earthquake is attributed to the neotectonic reactivation of a fault associated with the E-W trending DG shear zone. 相似文献
12.
Analyses of deflected river channels, offset of basement rocks, and fault rock structures reveal that slip sense inversion occurred on major active strike-slip faults in southwest Japan such as the Yamasaki and Mitoke fault zones and the Median Tectonic Line (MTL). Along the Yamasaki and Mitoke fault zones, small-size rivers cutting shallowly mountain slopes and Quaternary terraces have been deflected sinistrally, whereas large-size rivers which deeply incised into the Mio-Pliocene elevated peneplains show no systematically sinistral offset or complicated hairpin-shaped deflection. When the sinistral offsets accumulated on the small-size rivers are restored, the large-size rivers show residual dextral deflections. This dextral offset sense is consistent with that recorded in the pre-Cenozoic basement rocks. S–C fabrics of fault gouge and breccia zone developed in the active fault zones show sinistral shear sense compatible with earthquake focal mechanisms, whereas those of the foliated cataclasite indicate a dextral shear sense. These observations show that the sinistral strike-slip shear fabrics were overprinted on dextral ones which formed during a previous deformation phase. Similar topographic and geologic features are observed along the MTL in the central-eastern part of the Kii Peninsula. Based on these geomorphological and geological data, we infer that the slip sense inversion occurred in the period between the late Tertiary and mid-Quaternary period. This strike-slip inversion might result from the plate rearrangement consequent to the mid-Miocene Japan Sea opening event. This multidisciplinary study gives insight into how active strike-slip fault might evolves with time. 相似文献
13.
Image-based reconnaissance geological mapping at 1:100,000 scale using Landsat TM data has delineated a college of Precambrian lithostructural domains within a 50,000-km2 region which encompasses the northern portion of the Archaean to Proterozoic granulite-grade Eastern Ghats Tectonic Province and the adjacent Archaean-Mesoproterozoic Singhbhum Craton. The domains identified in the present study display distinctive internal structures on satellite imagery. Most are bounded by clearly recognisable major shear zones and faults on imagery; displacement directions may frequently be ascertained through local reorientation of planar structures adjacent to large strike-slip shear zones and through juxtaposition of domains with different structuring.
The macroscopic/megascopic structural overview provided by the Landsat interpretation, supported by preliminary field investigation, suggests that the N-S shortening (E-W fold/thrust packages with associated NE and NW strike-slip faulting), is the dominant structural style in the northernmost part of the Eastern Ghats Tectonic Province, followed by regional dextral transpression, expressed in the form of major strike-slip faults. The largest of these structures (Kerajang Fault), which may be traced for over 250 km, has demonstrable Paleozoic-Mesozoic dextral motion associated with coal basin formation. A precursor Kerajang shear zone with dextral movement in excess of 100 km of indeterminate age may also have been instrumental in juxtaposing the Singhbhum Nucleus into its present position to the north of the Eastern Ghats Tectonic Province. 相似文献
14.
渤海海底地震仪探测试验及初步成果 总被引：4，自引：0，他引：4
利用大容量气枪枪阵震源和海底地震仪在渤海首次开展人工地震深部地球物理探测试验。本次试验布设一条NWW-SEE向垂直构造走向的勘测线,共投放海底地震仪51台,回收成功50台。试验结果和数据分析表明,所使用的枪阵有足够的能量输出,海底地震仪记录震相丰富,可识别到Ps,Pg,PmP,Pn等多种震相。初至波层析成像结果表明,9 km以上地层速度结构存在明显的横向不均匀性,渤中地区新生代沉积基底埋深5～6 km,结晶基底埋深约9 km,郯庐断裂带内存在"U"型下凹的相对低速体并有向下切割的趋势。此次试验是我国在渤海深部探测中的成功示范,有效填补了渤海海域深地震测深数据的空白,为渤海深部地壳结构研究及含油气盆地形成演化研究提供了重要的基础资料。 相似文献
15.
G. Musumeci 《Geodinamica Acta》2013,26(1-2):119-133
AbstractThe Monte Grighini Complex (Central-Western Sardinia) is a NW-SE trending metamorphic complex of Hereynian age made up of a medium grade Lower tectonic unit with mylonitie granitoids and a low grade Upper tectonic unit exposed in the westernmost and southernmost portions of this complex. The Lower Unit shows a prograde metamor phism from garnet to sillimanite zone and the transition from MP/MT to LP/HT metamorphism. The metamorphic climax was reached at the end of the main deformative phase 1)2 (600° C. 6 kbar). After the main tectonic and metamorphic phase. the Lower Unit was affected by a wide NW-SE trending ductile dextral wrench shear zone. Intrusive rocks emplaced within the shear zone yielded radiometric ages of 305-300 Ma. Shear deformation leads to low temperature C-S mylonites and retrograde phyllonitic rocks with subhorizontal NW-SE trending stretching lineations. Kinematic analysis of the shear zone points to a dextral sense of shear with an amount of ductile displacement of about 7 km. Later low angle N-S and E-W trending normal faults are associated with cataclastic zones separating the Lower Unit from the Upper one. These faults originated during a later evolutionary stage of the shear zone. This shows a progressive change of deformation regime from duetile wrenching to brittle normal faulting. The Monte Grighini Complex is a good example of ductile wrench tectonics. followed by uplift and extension in the Paleozoic basement of Sardinia. 相似文献
16.
2013年8月31日8时4分, 云南省迪庆藏族自治州香格里拉县(28.12°N, 99.4°E)发生5.9级地震, 震源深度10 km.区域范围内历史地震频繁, 为滇西北地震多发区.据震源机制解结果, 此次地震为正断兼左旋走滑型地震, NW向截面产状与德钦-香格里拉-中甸断裂基本吻合.利用EIGEN-6C2模型对震中附近进行布格重力异常探讨, 震源位置位于莫霍面起伏部位, 下部地壳厚度不稳定之处; 而从P波速度与地壳结构剖面可知研究区上地壳底部存在低速层, 认为韧性低速层与地震能量的积聚和存储关系密切.而韧性低速(高导)层与德钦-中甸断裂交接部位, 是流变界面能量释放的位置, 即本次地震的震源位置.这为板内地震3层次构造模式提供了一个新的案例. 相似文献
17.
《Tectonophysics》2002,344(1-2):81-101
Geological, geomorphological and geophysical data have been used to determine the total displacement, slip rates and age of formation of the Arima–Takatsuki Tectonic Line (ATTL) in southwest Japan. The ATTL is an ENE–WSW-trending dextral strike-slip fault zone that extends for about 60 km from northwest of the Rokko Mountains to southwest of the Kyoto Basin. The ATTL marks a distinct topographic boundary between mountainous regions and basin regions. Tectonic landforms typically associated with active strike-slip faults, such as systematically-deflected stream channels, offset ridges and fault scarps, are recognized along the ATTL. The Quaternary drainage system shows progressive displacement along the fault traces: the greater the magnitude of stream channel, the larger the amount of offset. The maximum dextral deflection of stream channels is 600–700 m. The field data and detailed topographic analyses, however, show that pre-Neogene basement rocks on both sides of the ATTL are displaced by about 16–18 km dextrally and pre-Mio–Pliocene elevated peneplains are also offset 16–17 km in dextral along the ATTL. This suggests that the ATTL formed in the period between the development of the pre-Mio–Pliocene peneplains and deflection of the Quaternary stream channels.The geological, geomorphological and geophysical evidence presented in this study indicates that (1) the ATTL formed after the mid-Miocene, (2) the ATTL has moved as a dextral strike-slip fault with minor vertical component since its formation to late Holocene and (3) the ATTL is presently active with dextral slip rates of 1–3 mm/year and a vertical component of >0.3 mm/year. The formation of the ATTL was probably related to the opening of the Japan Sea, which is the dominant tectonic event around Japan since mid-Miocene. The case study of the ATTL provides insight into understanding the tectonic history and relationship between tectonic landforms and structures in active strike-slip faults. 相似文献
18.
Nappe displacement in the Scandinavian Caledonides 总被引：1，自引：0，他引：1
David G. Gee 《Tectonophysics》1978,47(3-4)
Large areas of the Scandinavian Caledonides are eroded to the level of the basement/cover contact. Relationships between the Precambrian crystalline basement (largely Svecofennian-Dalslandian, 1800-1000 m.y.) and cover sequences are exposed both in transverse profiles through the mountain belt and along the belt in the various windows. These relationships provide an unique opportunity for studying the basement configuration, character of basement involvement and general nappe geometry. Major allochthonous units of the central part of the Scandinavian Caledonides — the Offerdal, Särv and Seve-Köli Nappe Complex — have been shown to wedge out westwards, having been displaced eastwards from environments along and west of the present Norwegian coast. Recent investigations have shown that these units (the Offerdal, Särv and Seve) reappear in western Norway as major pinch-and-swell structures, the lenses reaching thicknesses in the order of 2 km and with long axes of several tens of kilometres. Within the western parts of the Swedish Caledonides the thicker parts of the lenses approximately coincide with the axes of the late synforms which fold basement and cover together. Further west, in Norway, the tensing appears to be unrelated to the geometry of these major folds.This evidence increases estimates of nappe displacement distance (now thought to be in the order of at least 1000 km). At the same time it emphasizes that translation may account for only about half of this amount, the rest being achieved by stretching of the nappes. Apparently, a nappe sequence built up in the west which subsequently collapsed, leading to continued displacement eastwards on to the Baltoscandian Platform. Whereas basement shortening is of the order of several tens to perhaps hundreds of kilometres in the western part of the central Scandes, it is of lesser importance from central Trøndelag eastwards, a distance of about two hundred kilometres, to the Caledonian Front.Biostratigraphic evidence from the late-orogenic intramontane basins, taken in relation to the youngest units involved in the nappes, requires nappe translation into western Norway to have occurred after the Llandoverian (Köli Supergroup) and prior to the (Ludlovian?) Downtonian (Hitra Formation) deposition in the intramontane basins. The nappes contain sequences derived from a variety of probable oceanic and continental margin environments, and this translation may greatly exceed the minimum estimate of five hundred kilometres. Further displacement eastwards occurred during uplift of seaboard Norway and accompanied sedimentation both in the intra- and extramontane basins. The latter were not finally influenced by the décollement tectonics until after the Early Devonian.This evidence suggests that a compressive regime dominated the early phases of orogenesis during basement shortening, build up of the nappe pile and translation of these denser units on to the western margin of the Baltoscandian Platform. This compression subsequently gave way to a gravity regime, collapse and stretching of the nappes dominating the late phases of displacement on to the Baltoscandian Platform. 相似文献
19.
Loreto Antón Alfonso Muñoz-Martin Gerardo De Vicente 《Central European Journal of Geosciences》2010,2(2):152-164
The study of intraplate tectonics is crucial for understanding the deformation within plates, far from active plate boundaries and associated stress transmission to the plate interiors. This paper examines the tectonic evolution of the Variscan basement at the western margin of the Cenozoic Duero basin. Located east of the Vilariça Fault System in NW Iberia, this intraplate zone is a relatively flat but elevated area with an intense NNE-SSW trending fault system and associated moderate seismicity. Although the area has played an important role in the Duero basin configuration, its Alpine to present-day tectonic evolution has not been well constrained. In order to characterize the successive paleostress fields, 1428 pairs of fault-striae were measured at 56 sites and two focal mechanisms were used. Stress inversion methods have been applied to analyze paleostress regimes. Results show the existence of three dominant maximum horizontal stress (Shmax) trends: N-S, NE-SW and E-W. Relative and absolute dating of the activated faults for each Shmax shows that the clearly predominant N-S paleostress field in the zone has been active since the Oligocene up to the present day; while a NE-SW stress field is found to have been active during the Cretaceous and an older E-W paleostress field was active in the earlier Alpine cycle (Late Triassic). 相似文献
20.
西昆仑山前冲断带断裂特征及构造单元划分 总被引：3，自引：1，他引：2
受新生代帕米尔构造结大幅度向北推移、旋转的影响,形成了弧形的西昆仑山前冲断带.本文主要通过野外地质调查、地震反射剖面的精细解释,对西昆仑山前冲断带最基本的组成部分-断裂进行系统研究.西昆仑山前冲断带内以发育与其弧形形态一致的逆冲断裂为主,但弧形冲断带中段的断裂具有挤压逆冲的同时兼有右行走滑性质.冲断带内还发育了NE 向和近EW向的走滑断裂,它们的发育时间和成因不尽相同,它们控制了冲断带内的变形,调节和改造了早期形成的构造.在对断裂系统研究的基础上,结合冲断带各个部位的结构特征和变形时间,将冲断带划分为9个次级构造单元.西昆仑山前冲断带开始发育于中新世中晚期,此后经历了上新世早期、上新世中晚期、早更新世早中期以及早更新世晚期四个演化阶段. 相似文献