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1.
The Late Cenozoic basins in the Weihe–Shanxi Graben, North China Craton are delineated by northeast-striking faults. The faults have, since a long time, been related to the progressive uplift and northeastward expansion of the Tibetan Plateau. To show the relation between the basins and faults, two Pliocene–Pleistocene stratigraphic sections(Chengqiang and Hongyanangou) in the southern part of the Nihewan Basin at the northernmost parts of the graben are studied herein. Based on the sedimentary sequences and facies, the sections are divided into three evolutionary stages, such as alluvial fan-eolian red clay, fan delta, and fluvial, with boundaries at ~2.8 and ~1.8 Ma. Paleocurrent indicators, the composition of coarse clastics, heavy minerals, and the geochemistry of moderate–fine clastics are used to establish the temporal and spatial variations in the source areas. Based on features from the middlenorthern basin, we infer that the Nihewan Basin comprises an old NE–SW elongate geotectogene and a young NW–SE elongate subgeotectogene. The main geotectogene in the mid-north is a half-graben bounded by northeast-striking and northwest-dipping normal faults(e.g., Liulengshan Fault). This group of faults was mainly affected by the Pliocene(before ~2.8–2.6 Ma) NW–SE extension and controlled the deposition of sediments. In contrast, the subgeotectogene in the south was affected by northwest-striking normal faults(e.g., Huliuhe Fault) that were controlled by the subsequent weak NE–SW extension in the Pleistocene. The remarkable change in the sedimentary facies and provenance since ~1.8 Ma is possibly a signal of either weak or strong NE–SW extension. This result implies that the main tectonic transition ages of ~2.8–2.6 Ma and ~1.8 Ma in the Weihe–Shanxi Graben are affected by the Tibetan Plateau in Pliocene–Pleistocene.  相似文献   

2.
Tertiary sequence boundaries are mapped on reflection seismic sections in the northern part of the Danish Central Trough, North Sea. The geometry of the sequence boundaries and the isopach maps of the sequences are used as indicators of differential subsidence. The Tertiary tectonic evolution is subdivided into: (i) Late Palaeocene and Early Oligocene episodes of inversion along the NNW–SSE striking Arne–Elin Trend (ii) Early Oligocene to Pliocene episodes of differential subsidence across pre-Tertiary fault trends. The observed differential subsidence and inversion is related to pre-Tertiary faults and fault trends, and dating of the sequences shows that the tectonic phases were contemporaneous with tectonic events in NW Europe. It is suggested that the differential subsidence-inversion is controlled by reactivation of pre-Tertiary faults/fault-trends by block movements due to an interaction of the Alpine collision and the opening of the Atlantic.  相似文献   

3.
Segmentation, propagation, and linkage of normal faults often occur in regions of active extension, and observations of the distribution and structural properties of segment boundaries can provide important insights for seismic hazard assessment. In this study, we carry out quantitative geomorphological analysis to evaluate the relative tectonic activity along the Langshan Piedmont Fault (LPF), which bounds the NW margin of the Hetao Graben, North China. On the basis of obtained morphometric indices (HI, BS, Smf, VF, SLK, and χ), tectonic knickpoint heights, footwall topography, and small unmanned aerial vehicles (sUAV)-based field observations, we demonstrate that: (i) The Langshan landscape is in a state of disequilibrium in response to active rock uplift and channel incision; (ii) The LPF consists of two major fault segments with lengths of 65 and 95 km, respectively, which likely have been linked with each other; (iii) Rupturing of the whole of one segment can generate an earthquake of Mw ~7.3–7.5, and earthquake magnitude may reach Mw ~7.8 if the entire fault trace of ~160 km is ruptured, posing a significant seismic risk in the western Hetao Graben. These findings would further our understanding of normal fault evolution through space and time in actively extending regions.  相似文献   

4.
In order to unravel the tectonic evolution of the north-central sector of the Sicily Channel (Central Mediterranean), a seismo-stratigraphic analysis of single- and multi-channel seismic reflection profiles has been carried out. This allowed to identify, between 20 and 50 km offshore the central-southern coast of Sicily, a ~80-km-long deformation belt, characterized by a set of WNW–ESE to NW–SE fault segments showing a poly-phasic activity. Within this belt, we observed: i) Miocene normal faults reactivated during Zanclean–Piacenzian time by dextral strike-slip motion, as a consequence of the Africa–Europe convergence; ii) releasing and restraining bend geometries forming well-developed pull-apart basins and compressive structures. In the central and western sectors of the belt, we identified local transpressional reactivations of Piacenzian time, attested by well-defined compressive features like push-up structures and fault-bend anticlines. The reconstruction of timing and style of tectonic deformation suggest a strike-slip reactivation of inherited normal faults and the local subsequent positive tectonic inversion, often documented along oblique thrust ramps. This pattern represents a key for an improved knowledge of the structural style of foreland fold-and-thrust belts propagating in a preexisting extensional domain. With regard to active tectonics and seismic hazards, recent GPS data and local seismicity events suggest that this deformation process could be still active and accomplished through deep-buried structures; moreover, several normal faults showing moderate displacements have been identified on top of the Madrepore Bank and Malta High, offsetting the Late Quaternary deposits. Finally, inside the northern part of the Gela Basin, multiple slope failures, originated during Pleistocene by the further advancing of the Gela Nappe, reveal tectonically induced potential instability processes.  相似文献   

5.
The region around Wadakkancheri, Trichur District, Kerala is known for microseismic activity, since 1989. Studies, subsequent to 2nd December 1994 (M =4.3) earthquake, identified a south dipping active fault (Desamangalam Fault) that may have influenced the course of Bharathapuzha River. The ongoing seismicity is concentrated on southeast of Wadakkancheri and the present study concentrated further south of Desamangalam Fault. The present study identifies the northwestern continuity of NW–SE trending Periyar lineament, which appears to have been segmented in the area. To identify the subtle landform modifications induced by ongoing tectonic adjustments, we focused on morphometric analysis. The NW–SE trending lineaments appear to be controlling the sinuosity of smaller rivers in the area, and most of the elongated drainage basins follow the same trend. The anomalies shown in conventional morphometric parameters, used for defining basins, are also closely associated with the NW–SE trending Periyar lineament/s. A number of brittle faults that appear to have been moved are consistent with the present stress regime and these are identified along the NW–SE trending lineaments. The current seismic activities also coincide with the zone of these lineaments as well as at the southeastern end of Periyar lineament. These observations suggest that the NW–SE trending Periyar lineaments/faults may be responding to the present N–S trending compressional stress regime and reflected as the subtle readjustments of the drainage configuration in the area.  相似文献   

6.
The aim of this paper was to provide a significant case‐history concerning the evolution of a segmented system of extensional faults and related basins, investigated by a set of seismic reflection profiles. We investigated two kinematically linked semi‐grabens, developed at the hangingwall of two opposite‐dipping normal faults: the Vallo di Diano and Auletta basins, located in the southern Apennines, one of the most seismically active regions of the Italian peninsula. Our interpretation suggests that the Pliocene–Quaternary tectonic history consists of a single extensional phase, where the major NW–SE trending normal faults, generating the basins, and the strike‐slip and transtensional faults connecting adjacent normal fault segments, simultaneously act, being part of the same extensional system. We also conclude that major normal faults, bordering the basins, should be considered as potential seismogenic sources in the seismic hazard evaluation.  相似文献   

7.

In order to unravel the tectonic evolution of the north-central sector of the Sicily Channel (Central Mediterranean), a seismo-stratigraphic analysis of single- and multi-channel seismic reflection profiles has been carried out. This allowed to identify, between 20 and 50 km offshore the central-southern coast of Sicily, a ~80-km-long deformation belt, characterized by a set of WNW–ESE to NW–SE fault segments showing a poly-phasic activity. Within this belt, we observed: i) Miocene normal faults reactivated during Zanclean–Piacenzian time by dextral strike-slip motion, as a consequence of the Africa–Europe convergence; ii) releasing and restraining bend geometries forming well-developed pull-apart basins and compressive structures. In the central and western sectors of the belt, we identified local transpressional reactivations of Piacenzian time, attested by well-defined compressive features like push-up structures and fault-bend anticlines. The reconstruction of timing and style of tectonic deformation suggest a strike-slip reactivation of inherited normal faults and the local subsequent positive tectonic inversion, often documented along oblique thrust ramps. This pattern represents a key for an improved knowledge of the structural style of foreland fold-and-thrust belts propagating in a preexisting extensional domain. With regard to active tectonics and seismic hazards, recent GPS data and local seismicity events suggest that this deformation process could be still active and accomplished through deep-buried structures; moreover, several normal faults showing moderate displacements have been identified on top of the Madrepore Bank and Malta High, offsetting the Late Quaternary deposits. Finally, inside the northern part of the Gela Basin, multiple slope failures, originated during Pleistocene by the further advancing of the Gela Nappe, reveal tectonically induced potential instability processes.

  相似文献   

8.
The synsedimentary tectonic activity evidenced in central and northern Tunisia points out the fact that the Campanian–Maastrichtian deposits are associated with several NW–SE and east–west normal faults. These results suggest that the east–west transform fault of North African Margin is still active during this stage. These data allow us to discuss a new geodynamic model for the North African Margin. To cite this article: M. Dlala, C. R. Geoscience 334 (2002) 135–140.  相似文献   

9.
《Tectonophysics》1999,301(1-2):95-109
The spatial–height analyses of deposits belonging to isotopic substages 5e and 5c indicate the occurrence of differential uplift in the Gibraltar Strait area. Maximum mean uplift rates do not reach values of 0.2 mm/year displaying a gentle deceleration from 0.15 to 0.10 mm/year for the last 128 ka. Maximum estimated rates are recorded in the central sector of the Gibraltar Strait. The combined analysis of the accumulated vertical movements before and after ISS 5c indicates that differential uplift is accommodated along NE–SW sinistral and NW–SE dextral (mostly inherited) strike-slip fault systems separating coastal segments of contrasting uplifting/subsiding behaviour. The occurrence of inversions in the relative vertical offsets along some of these faults arises when this combined analysis is performed. A model of `asymmetric' pure shear, defined by these two fault systems, generated in response to the roughly N–S convergence between the African and Eurasian plates, can explain the recorded uplift patterns. In this transpressive setting generated by the Africa–Eurasia continental collision the recent convergence (4 mm/year) is mostly released by shear processes and subsidiary E–W horizontal extension, whilst the recorded coastal uplift only represents a low percentage of the recent convergence rates.  相似文献   

10.
Rheological heterogeneities in the upper-crust have a close relationship with the fold position where rigid bodies could constitute initial perturbations that allow the nucleation of folds. Consequently, establish the position and geometry of anomalous rocks located in the upper-crust by geophysical studies help to understand the folded structure observed on surface. New geological observations in the field, along with gravity, magnetic, magnetotelluric and seismicity data, reveal the subsurface structure in the Sierra de Los Filabres–Sierra de Las Estancias folded region part of the Alpine belt in southern Spain. The geometry of the upper crust is determined by geological field data, 2D gravity models, 2D magnetic models and 2D MT resistivity model, while seismicity evidences the location of the deep active structures. These results allow us to propose that a basic rock body at 4 to 9 km depth has determined the nucleation and development of the Sierra de Los Filabres kilometric antiform. N-vergent large late folds are subjected to a variable present-day stress field. Earthquake focal mechanisms suggest the presence in depth of a regional NW–SE compressive stress field. However, most of the seismogenetic structures do not extend up to the surface, where NW–SE and WNW–ESE outcropping active normal faults are observed, thus indicating a NE–SW extension in the upper crust simultaneous to orthogonal NW–SE compression related to reverse faults and minor folds developed in the Eastern Almanzora Corridor and in the nearby Huércal–Overa Basin. The recent and active tectonic studies of cordilleras hinterland subjected to late folding greatly benefits from the integration of surface observations together with geophysical data.  相似文献   

11.
This paper uses high-resolution images and field investigations, in conjunction with seismic reflection data, to constrain active structural deformation in the Kashan region of Central Iran. Offset stream beds and Qanats indicate right-lateral strike slip motion at a rate of about 2 mm/yr along the NW–SE trending Qom-Zefreh fault zone which has long been recognized as one of the major faults in Central Iran. However, the pattern of drainage systems across the active growing folds including deep incision of stream beds and deflected streams indicate uplift at depth on thrust faults dipping SW beneath the anticlines. Therefore, our studies in the Kashan region indicate that deformation occurs within Central Iran which is often considered to behave as a non-deforming block within the Arabia–Eurasia collision zone. The fact that the active Qom-Zefreh strike-slip fault runs parallel to the active folds, which overlie blind thrust faults, suggests that oblique motion of Arabia with respect to Eurasia is partitioned in this part of Central Iran.  相似文献   

12.
The NW–SE shortening between the African and the Eurasian plates is accommodated in the eastern Betic Cordillera along a broad area that includes large N‐vergent folds and kilometric NE–SW sinistral faults with related seismicity. We have selected the best exposed small‐scale tectonic structures located in the western Huércal‐Overa Basin (Betic Cordillera) to discuss the seismotectonic implications of such structures usually developed in seismogenic zones. Subvertical ESE–WNW pure dextral faults and E–W to ENE–ESW dextral‐reverse faults and folds deform the Quaternary sediments. The La Molata structure is the most impressive example, including dextral ESE–WNW Neogene faults, active southward‐dipping reverse faults and associated ENE–WSW folds. A molar M1 assigned to Mimomys savini allows for precise dating of the folded sediments (0.95–0.83 Ma). Strain rates calculated across this structure give ～0.006 mm a?1 horizontal shortening from the Middle Pleistocene up until now. The widespread active deformations on small‐scale structures contribute to elastic energy dissipation around the large seismogenic zones of the eastern Betics, decreasing the seismic hazard of major fault zones. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

13.
The Asturian Arc was produced in the Early Permian by a large E–W dextral strike–slip fault (North Iberian Megashear) which affected the Cantabrian and Palentian zones of the northeastern Iberian Massif. These two zones had previously been juxtaposed by an earlier Kasimovian NW–SE sinistral strike–slip fault (Covadonga Fault). The occurrence of multiple successive vertical fault sets in this area favoured its rotation around a vertical axis (mille-feuille effect). Along with other parallel faults, the Covadonga Fault became the western margin of a proto-Tethys marine basin, which was filled with turbidities and shallow coal-basin successions of Kasimovian and Gzhelian ages. The Covadonga Fault also displaced the West Asturian Leonese Zone to the northwest, dragging along part of the Cantabrian Zone (the Picos de Europa Unit) and emplacing a largely pelitic succession (Palentian Zone) in what would become the Asturian Arc core. The Picos de Europa Unit was later thrust over the Palentian Zone during clockwise rotation. In late Gzhelian time, two large E–W dextral strike–slip faults developed along the North Iberian Margin (North Iberian Megashear) and south of the Pyrenean Axial Zone (South Pyrenean Fault). The block south of the North Iberian Megashear and the South Pyrenean Fault was bent into a concave, E-facing shape prior to the Late Permian until both arms of the formerly NW–SE-trending Palaeozoic orogen became oriented E–W (in present-day coordinates). Arc rotation caused detachment in the upper crust of the Cantabrian Zone, and the basement Covadonga Fault was later resurrected along the original fault line as a clonic fault (the Ventaniella Fault) after the Arc was completed. Various oblique extensional NW–SE lineaments opened along the North Iberian Megashear due to dextral fault activity, during which numerous granitic bodies intruded and were later bent during arc formation. Palaeomagnetic data indicate that remagnetization episodes might be associated with thermal fluid circulation during faulting. Finally, it is concluded that the two types of late Palaeozoic–Early Permian orogenic evolution existed in the northeastern tip of the Iberian Massif: the first was a shear-and-thrust-dominated tectonic episode from the Late Devonian to the late Moscovian (Variscan Orogeny); it was followed by a fault-dominated, rotational tectonic episode from the early Kasimovian to the Middle Permian (Alleghenian Orogeny). The Alleghenian deformation was active throughout a broad E–W-directed shear zone between the North Iberian Megashear and the South Pyrenean Fault, which created the basement of the Pyrenean and Alpine belts. The southern European area may then be considered as having been built by dispersal of blocks previously separated by NW–SE sinistral megashears and faults of early Stephanian (Kasimovian) age, later cut by E–W Early Permian megashears, faults, and associated pull-apart basins.  相似文献   

14.
G. F. Ufimtsev 《GeoJournal》1991,23(3):197-206
The Baikal rift valley, the central segment of the Baikal rift zone located in southern East Siberia, consists of two large depressions separated by an interdepressional uplift. The thickness of the Neogene-Quaternary sediments filling in the depression amounts to 5 km (Logatchev and Florensov 1978). The interdepressional uplift consists of subsiding residual steps and active tilted horsts.The NW slope of the Baikal rift is controlled by a system of faults diverging to the N. This system comprises tectonic scarps (faceted ridge spurs), an inclined piedmont surface and a summit slope. The facets indicate the position of the main dip slip faults behind which longitudinal strike slip faults are distributed. Between the branching faults, the so-called intermediate steps are situated. Their subsidence and destruction result in expansion of the rift valley. Transformation of normal faults into listric faults is manifested in the tectonic topography in the areas of the residual and intermediate steps. The large dimensions of the Baikal rift valley are evidently due to its being confined to the faults striking NE-SW.  相似文献   

15.
The slip rate predicted from geodetic and geomorphological measurements is quite uniform on ~800–1,000 km length of the Altyn Tagh and the Kunlun faults. GPS velocity field documents that tectonic loading on the two active faults changes greatly along their strikes. To explore the mechanical relationship between far‐field tectonic loading and fault slip‐rate accumulation, we built a 3D viscoelastic finite‐element model with fault motion governed by frictional strength of contact interfaces. Based on numerical experiments, it is found that the observed uniform slip rate could reflect lateral variation of frictional strength along fault strike. Variation of predicted frictional coefficient ranges from ~0.13 to ~0.02, verifying that the two active faults must be weak for their mechanical strength. In addition, the good fitness between the relatively weak segment of faults and the location of strong earthquakes suggests that seismic activity along the two faults could be related to their frictional strength.  相似文献   

16.
The Gafsa and Chotts intracratonic basins in south-central Tunisia are transitional zones between the Atlasic domain to the north and the Saharan platform to the south. The principal aim of this paper is to unravel the geodynamic evolution of these basins following an integrated approach including seismic, well log and gravity data. These data are used to highlight the tectonic control on the deposition of Jurassic and Lower Cretaceous series and to discuss the role of the main faults that controlled the basin architecture and Cretaceous–Tertiary inversion. The horizontal gravity gradient map of the study area highlights the pattern of discontinuities within the two basins and reveals the presence of deep E–W basement faults. Primary attention is given to the role played by the E–W faults system and that of the NW–SE Gafsa fault which was previously considered active since the Jurassic. Facies and thickness analyses based on new seismic interpretation and well data suggest that the E–W-oriented faults controlled the subsidence distribution especially during the Jurassic. The NW–SE faults seem to be key structures that controlled the basins paleogeography during Late Cretaceous–Cenozoic time. The upper Triassic evaporite bodies, which locally outline the main NW–SE Gafsa fault, are regarded as intrusive salt bodies rather than early diapiric extrusions as previously interpreted since they are rare and occurred only along main strike-slip faults. In addition, seismic lines show that Triassic rocks are deep and do not exhibit true diapiric features.  相似文献   

17.
The Philippine Sea Plate (PHS) simultaneously subducts northwestward and collides eastward with the Eurasian Plate (EU) in northeast Taiwan. These two tectonic events induce high seismic activity, which makes northeastern Taiwan one of the most seismically active zones in the world. To understand the mechanical processes at work, we used existing geophysical data and the aftershocks recorded following a recent large strike-slip event occurring within the PHS oceanic crust. During this event, a NW–SE trending left-lateral sub-parallel to the PHS/EU convergence vector was active. As a consequence of the collision/subduction plate geometry, we show that the lithosphere of the northwestern corner of the PHS has been torn in a NW–SE orientation. This tectonic feature is associated with an abrupt tectonic stress boundary and could generate large intra-plate earthquakes.  相似文献   

18.
The Kemalpa?a Basin is one of the Quaternary basins in Western Anatolia and represents the south-western branch of the Gediz Graben system in this extensional province. This basin has been formed under the NNE–SSW trending extensional tectonic regime. It is bounded by a major fault, the Kemalpa?a Fault, in the south and it is bounded by a number of downstepping faults, called as Spilda?? Fault Zone, in the north. Both margin-bounding faults of the Kemalpa?a Basin are oblique-slip normal faults. In order to better understand the activities of these faults, we investigated the tectonic geomorphology of the Kemalpa?a Basin and interpreted the effect of tectonic activity on the geomorphological evolution using geomorphic markers such as drainage basin patterns, facet geometries and morphometric indices such as hypsometric curves and integral (HI), basin shape index (Bs), valley floor width-to-height ratio (Vf) and mountain front sinuosity (Smf). The morphometric analysis of 30 drainage basins in total and mountain fronts bounding the basin from both sides suggests a relatively high degree of tectonic activity. The mountain front sinuosity (Smf) generally varies from 1.1 to 1.3 in both sides of the basin suggesting the active fronts and facet slopes (12°–32°) suggest a relatively high degree of activity along the both sides of the Kemalpa?a Basin. Similarly, the valley floor width-to-height ratios (Vf) obtained from the both sides indicate low values varying from 0.043 to 0.92, which are typical values (<1) for tectonically active mountain fronts. The all values obtained are lower for the southern side. Therefore, we suggest that the tectonic activity of the Kemalpa?a Fault higher than the Spilda?? Fault Zone. This difference that can be arised from the different uplift rates also reveals the typical asymmetric characteristics of the Kemalpa?a Basin. Additionally, the trapezoidal facets which have been observed on the southern side of the basin indicate that the Kemalpa?a Fault is evolutionally more active as compared to the Spilda?? Fault Zone. The geomorphic indices indicate that the Quaternary landscape evolution of the Kemalpa?a Basin was governed by tectonic and erosional processes, and also the all results of morphometric analysis suggest a relatively high degree of tectonic activity along the faults bounding the Kemalpa?a Basin. Moreover, considering that active large normal faults with an average 15 km long can cause major earthquake, the earthquake hazard in the Kemalpa?a Basin should be investigated in detailed paleoseismological studies.  相似文献   

19.
福建漳州盆地活动断裂研究   总被引：1，自引：0，他引：1       下载免费PDF全文
本文从形态学和运动学的角度,确定并系统地研究了二十条主要活动断裂。北西向断裂以正-左行走滑型为主,北东向断裂以右行走滑-逆断层为主,两组断裂构成活动断裂网络。用 C14年龄数据计算得到了最近5990—1870年以来,各取样点地壳平均升降速率的变化范围是+3.53mm/a 至-0.65mm/a。用布仑法求得的九龙江活动断裂现代平均滑动速率是1.7mm/a。更新世至现代构造应力场的最大主压应力是以缓倾角、走向为 NW290°左右为特征的。350m 深处最大主压应力是700—760bar。两组断裂交汇形成的高渗透率带,对形成对流型中、低温热水型热田是十分有利的。此外,对该区的地震活动性亦进行了讨论。  相似文献   

20.
顺南地区位于塔里木盆地塔中隆起北部.受多期构造应力影响,该地区以走滑断裂大量发育为典型特征.对三维地震资料的精细解释和深入分析结果表明,研究区走滑断裂具有垂向分层、平面分段、多期次构造叠加的特征.顺南地区主要发育北东、北东东和北西向3组走滑断裂.北东向断裂活动性强,平面上发育雁列式断层及马尾状构造,剖面上主要发育对称花状、正花状与负花状上下分层叠置的复合花状构造.北东东和北西向断裂活动性较弱,剖面上以单条直立走滑断裂为主,平面上呈线性延伸或由多段同向走滑断层连接而成.根据断层构造样式和受力性质,将顺南1断裂沿走向划分为4段：2个复合花状-拉张段和2个简单花状-挤压段,拉张段和挤压段沿走向交替出现.顺南走滑断裂的形成主要经历了5期构造运动：加里东早期、加里东中期Ⅰ幕、加里东中期Ⅲ幕、加里东晚期-海西早期和海西晚期.其中,加里东中期Ⅰ幕和加里东中期Ⅲ幕为该区主要断层活动期.  相似文献   

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