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1.
The morphotectonic framework of the Central Apennines is given by faulted blocks bounded by normal faults, mostly trending NW–SE, NNW–SSE and NE–SW, which cut previous compressive structures. Such a structural setting is consistent with the focal mechanisms of the earthquakes which often occur in this area. In this paper, three lithologically different normal fault-generated mountain fronts are analysed in order to assess the relations between their geomorphic features and active tectonics. They border the Norcia depression (Sibillini Mts, Umbria), the Amatrice–Campotosto plateau (Laga Mts, Lazio) and the Fucino basin (Marsica Mts, Abruzzi). The Norcia depression is bounded by a N20°W trending normal fault to the east and by a parallel antithetic fault to the west. The main fault has a 1000 m throw and gives rise to a wide fault escarpment, characterized by: (1) sharp slope breaks due to low angle gravity faults; (2) important paleolandslides; and (3) several fault scarplets on the piedmont belt affecting Quaternary deposits. The Amatrice–Campotosto plateau is delimited by the western slope of Mt Gorzano which runs along a N20°W trending normal fault having a 1500m throw. Minor parallel faults dislocate Quaternary landforms. Large-scale massmovements also occur here. The Fucino basin was struck by the 1915 Avezzano earthquake (I=XI MCS) which produced extensive surface faulting along two parallel NW trending normal fault escarpments on the eastern border of the basin. There is paleoseismic evidence including buried gravity graben in Late Glacial gravels and tectonic dip-slip striations on Holocene calcitic crusts covering bedrock normal fault planes. These data suggest that active extensional tectonics plays a major role in the slope morphogenesis of the Central Apennines and they indicate the importance of geomorphic analysis in seismic zonation of this area. 相似文献
2.
F. Calamita M. Coltorti D. Piccinini P. P. Pierantoni A. Pizzi M. Ripepe V. Scisciani E. Turco 《Journal of Geodynamics》2000,29(3-5)
Analyses of structural and geomorphological data combined with remote sensing interpretation confirm previous knowledge on the existence of an extensional Quaternary tectonic regime in the Colfiorito area (Umbro-Marchean Central Apennines). This is characterized by a maximum principal axis of finite strain oriented approx. NE–SW, which is the result of a progressive deformation process due to pure and radial extension. Surface geological data, the crustal tectonic setting (reconstructed using a CROP 03 seismic reflection profile), and seismological data relative to the autumn 1997 Colfiorito earthquake sequence constrain the following seismotectonic model. We interpret the seismogenic SW-dipping low-angle normal fault pictured by seismic data as an inverted thrust ramp located in the basement at depth between 5 and 10 km. The surface projection of this seismogenic structure defines a crustal box within which high-angle normal faults are responsible for the deformation of the uppermost crust. The regional patterns of pre-existing basement thrusts therefore control the seismotectonic zoning of the area that cannot be directly related to the high-angle normal fault systems which cut through different crustal boxes; the latter system records, in fact, re-shear along pre-existing normal faults. Moreover, Quaternary slip-rates relative to high-angle normal faults in the Central Apennines are closely related to seismic hazard within each crustal box. 相似文献
3.
Cristiano Collettini Massimiliano Barchi Cristina Pauselli Costanzo Federico Giampaolo Pialli 《Journal of Geodynamics》2000,29(3-5)
This paper deals with the geometry and kinematics of the active normal faults in northern Umbria, and their relationship with the seismicity observed in the area. In particular, we illustrate the contribution of seismic reflection data (a network of seismic profiles, NNW–SSE and WSW–ENE trending) in constraining at depth the geometry of the different active fault systems and their reciprocal spatial relationships. The main normal fault in the area is the Alto Tiberina fault, NNW trending and ENE dipping, producing a displacement of about 5 km, and generating a continental basin (Val Tiberina basin), infilled by up to 1500 m with Upper Pliocene–Quaternary deposits. The fault has a staircase trajectory, and can be traced on the seismic profiles to a depth of about 13 km. A set of WSW-dipping, antithetic faults can be recognised on the profiles, the most important of which is the Gubbio fault, bordering an extensional Quaternary basin and interpreted as an active fault based on geological, geomorphologic and seismological evidence. The epicentral distribution of the main historical earthquakes is strictly parallel to the general trend of the normal faults. The focal mechanisms of the major earthquakes show a strong similarity with the attitude of the extensional faults, mapped at the surface and recognised on the seismic profiles. These observations demonstrate the connection between seismicity in the area and the activity of the normal faults. Moreover, the distribution of the instrumental seismicity suggests the activity of the Alto Tiberina fault as the basal detachment for the extensional tectonics of the area. Finally, the action of the Alto Tiberina fault was simulated using two dimensional finite element modelling: a close correspondence between the concentration of shear stresses in the model and the distribution of the present earthquakes was obtained. 相似文献
4.
Shao Cuiru You Huichuan Cao Zhongquan Wang Chunyong Tang Fangtou Zhang Decheng Lou Hai Xu Guangyin Yang Qiyan Mei Tuo Xie Ping Yu Gang 《中国地震研究》2009,23(2):144-160
The Yarlung Tsangpo Grand Canyon region is located in the frontal zone of the eastern Himalayan syntaxis, where neo-tectonics and seismicity are intensive and closely related to each other. In the region, two sets of fault structures have developed, striking NNE-NE and NWW-NW, respectively. Investigation shows that they differ markedly in terms of scope, property, active times and intensity. The NWW-NW trending faults are large in size, and most are thrust and thrust strike-slip faults, formed in earlier times. The NEE-NE-strike faults are relatively small in size individually, with concentrated distribution, constituting the NNE-trending shear extensional fault zone, which is relatively younger with evident late Quaternary activities. Strong earthquakes occur mainly in the areas or zones of intensive differential movement of the Himalayas, e.g. along the deep and large fault zones around the crustal blocks. Most earthquakes of M≥7.0 are closely related to tectonics, where large-scale Holocene active faults are distributed with complicated fault geometry, or the faults of multiple directions intersect. Among them, earthquakes of M≥7.5 have occurred on the NW and NE-trending faults with a greater strike-slip component in the fault tectonic zones. 相似文献
5.
Stefano Catalano Giorgio De Guidi Gianni Lanzafame Carmelo Monaco Luigi Tortorici 《Journal of Geodynamics》2009,48(2):75-82
Structural observations carried out on the volcanic Island of Pantelleria show that the tectonic setting is dominated by NNE trending normal faults and by NW-striking right-lateral strike-slip faults with normal component of motion controlled by a ≈N 100°E oriented extension. This mode of deformation also controls the development of the eruptive fissures, dykes and eruptive centres along NNE–SSW belts that may thus represent the surface response to crustal cracking with associated magma intrusions. Magmatic intrusions are also responsible for the impressive vertical deformations that affect during the Late Quaternary the south-eastern segment of the island and producing a large dome within the Pantelleria caldera complex. The results of the structural analysis carried out on the Island of Pantelleria also improves the general knowledge on the Late Quaternary tectonics of the entire Sicily Channel. ESE–WNW directed extension, responsible for both the tectonic and volcano-tectonic features of the Pantelleria Island, also characterizes, at a greater scale, the entire channel as shown by available geodetic and seismological data. This mode of extension reactivates the older NW–SE trending fault segments bounding the tectonic troughs of the Channel as right-lateral strike-slip faults and produces new NNE trending pure extensional features (normal faulting and cracking) that preferentially develop at the tip of the major strike-slip fault zones. We thus relate the Late Quaternary volcanism of the Pelagian Block magmatism to dilatational strain on the NNE-striking extensional features that develop on the pre-existing stretched area and propagate throughout the entire continental crust linking the already up-welled mantle with the surface. 相似文献
6.
In this paper a new kinematic and dynamic model on the Recent and active contractional deformation of the Catania region, eastern Sicily, is discussed. The study area represents one of the most seismically active region of the Mediterranean, located at the intersection between the front of the Sicily collision belt and the seismogenic Siculo-Calabrian Rift-Zone. The analysed contractional tectonics form an active triangle zone that originated from the tectonic inversion of a Lower-Middle Pleistocene extensional basin, which was located at the northern edge of the African foreland. The triangle zone consists of two antithetic ENE–WSW oriented thrust-ramps that show evidence of motion during the Holocene and bound a folded belt that involves alluvial deposits as young as 40 ka. These contractional structures represent the final product of the positive tectonic inversion of extensional features located, in the Hyblean Plateau in SE Sicily, along the flank of the active rift zone. The Late Quaternary motions along the inverted structures was accommodated to the west by a major N–S oriented left-lateral fault zone, which separates the active contractional domains from the adjacent sectors of the African margin. As a whole, the Late Quaternary contractional tectonics of SE Sicily have been related to a NW-verging crustal stacking, related to a Mantle intrusion beneath the Hyblean Plateau that developed as effect of the rift-flank deformation. The crustal lineaments, which compose the new kinematic model, represents potentially active seismogenic sources that might be considered in the frame of the seismotectonic picture of the Catania region. 相似文献
7.
Neotectonic Deformation of Pleistocene Deposits Along the Sudetic Marginal Fault,Southwestern Poland
The 160 km long Sudetic Marginal Fault (SMF) of Middle Silesia, southwestern Poland, is a main Alpine fault oriented NW–SE. This paper provides evidence of possible neotectonic activity in front of the SMF. The data are based on three exposures in the Roztoka–Mokrzeszow Graben near the city of Swidnica. Morphotectonic evidence in front of the SMF is also examined. Two sets of extensional deformation features are exposed and analysed. The main one includes gently inclined normal faults and flexures, with displacements in the bedrock of at least several metres. Based on the Quaternary stratigraphy of the region, the age of deformation is most probably Lower Saalian (Upper Pleistocene). The trigger for the deformation was probably the re-reactivation of the SMF and other faults due to the advance of the Lower Saalian Scandinavian ice-sheet into the Sudetic Mountains. The secondary deformation system includes sub-vertical, often conjugate faults with displacements up to 0·5 m superimposed on former structures. Its dominant normal faulting mode suggests an extensional stress regime that apparently coincides with the post-glacial glacioisostatic rebound. © 1997 John Wiley & Sons, Ltd. 相似文献
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9.
This work presents a structural model for earthquake faulting in the Umbria-Marche Apennines (Central Italy). The model is derived by an integrated analysis of geological, geophysical and seismological data. At regional scale, the distribution and character of the seismicity appear to be mainly controlled by a low-angle east-dipping normal fault (Altotiberina fault, AF). The latter is the lower boundary of an active, continuously deforming hangingwall block moving toward NE. Moderate magnitude earthquakes (4 < M < 6), such as the Norcia 1979 (M = 5.9), the Gubbio 1984 (M = 5.2) and the Colfiorito 1997 (Mmax = 5.9), occur within the active hangingwall block and are related to the activity of major west-dipping normal faults detaching on the AF. The geometry of the deep seismogenic structures is listric (as in the case of Colfiorito) or more complex, because of local reactivation of pre-existing low-angle thrust (e.g. Gubbio) or high-angle strike-slip faults (e.g. Norcia). For all the analysed earthquakes the rupture nucleation is located at the base of the aftershock volumes, near the line of intersection between the SW-dipping normal faults and the east-dipping AF basal detachment. The progressive increase in depth of the earthquake foci from the north–west (e.g. Gubbio, 6–7 km) to the south–east (e.g. Norcia, 11–12 km) appears to be related to the eastward deepening of the basal detachment. These seismotectonic features are relevant for determining the seismogenic potential of the Apennine active faults, which depends not only on the length of the faults, but also on the depth of the detachment zone as well. 相似文献
10.
受新生代太平洋板块弧后扩张剧烈活动的地缘特性影响,冲绳海槽构造特征复杂,南、中、北段在热液活动、断裂性质、火成岩特性、扩张时代等方面存在显著不同,因此认识该区各段构造活动性对查清其复杂地质特征具有重要意义.本文依据前人通过磁异常反演得到的居里面深度资料,利用热模拟的方法,对冲绳海槽各段深、浅构造活动性进行了探讨.模拟结果表明,南段软流层构造活动强度约为中、北段的6倍,而岩石圈浅层构造活动却相对较弱.该结论与前人所得到的地质地球物理资料相符,主要表现为:相对于中、北段,南段在海槽总体演化历程上裂陷较深;海底火成岩岩浆源区较深,结晶分异程度较弱,同化混染程度较强;切穿沉积基底的大型断裂较为发育,而沉积层内部的小型断裂分布相对稀疏;沉积层岩浆侵入活动较弱,海底所呈现出的热液活动区数量较少;现代地震活动较多,震源深度较大.根据模拟结果与实际资料的对比分析我们可以推测:(1)冲绳海槽北段可能还有一些热液区没有被探测到,也可能在历史演化进程中失去活力,或者被第四系沉积物覆盖;(2)南段存在孕育更多热液活动区的潜力. 相似文献
11.
已有地质和地球物理研究结果表明,北京平原区存在有多条第四纪隐伏活动断裂和隐伏盆地.为了研究该区的地壳浅部结构、断裂的空间展布、断裂活动性以及深浅构造关系,2006年,在北京平原的西北部地区完成了1条60次覆盖的中深层地震反射剖面和跨断裂的浅层地震反射剖面.结果表明,沿剖面结晶基底埋深约为3～6 km在结晶基底以上,地震反射剖面揭示了一套连续性较好的强反射震相,应是新生代、中生代和古生代的沉积岩系;在结晶基底之下,为一系列横向连续性较差、能量较弱的短小反射事件,可能代表了变质程度较高的结晶变质岩系或不成层的其他岩体.中深层和浅层地震剖面揭示的断裂具有上下一致的对应关系和明显的第四纪活动,对本区地堑-地垒状盆岭构造和新生代地层厚度具有重要的控制作用.本项研究不仅可进一步提高对北京地区新构造活动的认识,而且研究中所采用的方法技术对其他地区的深浅构造探测研究也有借鉴意义 相似文献
12.
We investigate the geometry and kinematics of the faults exposed in basement rocks along the Strouma River in SW Bulgaria as well as the sequence of faulting events in order to place constraints on the Cenozoic kinematic evolution of this structurally complex domain. In order to decipher the successive stress fields that prevailed during the tectonic history, we additionally carried out an analysis of mesoscale striated faults in terms of paleostress with a novel approach. This approach is based on the P–T axes distribution of the fault-slip data, and separates the fault-slip data into different groups which are characterized by kinematic compatibility, i.e., their P and T axes have similar orientations. From these fault groups, stress tensors are resolved and in case these stress tensors define similar stress regimes (i.e., the orientations of the stress axes and the stress shape ratios are similar) then the fault groups are further unified. The merged fault groups after being filled out with those fault-slip data that have not been incorporated into the above described grouping, but which present similar geometric and kinematic features are used for defining the final stress regimes. In addition, the sequence of faulting events was constrained by available tectonostratigraphic data.Five faulting events named D1, D2, D3, D4 and D5 are distinguished since the Late Oligocene. D1 is a pure compression stress regime with σ1 stress axis trending NNE-SSW that mainly activated the WNW-ESE to ENE-WSW faults as reverse to oblique reverse and the NNW-SSE striking as right-lateral oblique contractional faults during the Latest Oligocene-Earliest Miocene. D2 is a strike-slip − transpression stress regime with σ1 stress axis trending NNE-SSW that mainly activated the NNW-SSE to N-S striking as right-lateral strike-slip faults and the ENE-WSW striking faults as left-lateral strike-slip ones during the Early-Middle Miocene. D3 extensional event is associated with a NW-SE to WNW-ESE extension causing the activation of mainly low-angle normal faults of NE-SW strike and NNE-SSW to NNW-SSE striking high-angle normal faults. D4 is an extensional event dated from Late Miocene to Late Pliocene. It activated NNW-SSE to NW-SE faults as normal faults and E-W to WNW-ESE faults as right-lateral oblique extensional faults. The latest D5 event is an N-S extensional stress regime that dominates the wider area of SW Bulgaria in Quaternary times. It mainly activated faults that generally strike E-W (ENE-WSW and WNW-ESE) normal faults, along which fault-bounded basins developed. The D1 and D2 events are interpreted as two progressive stages of transpressional tectonics related to the late stages of collision between Apulia and Eurasia plates. These processes gave rise to the lateral extrusion of the Rhodope and Balkan regions toward the SE along the Strouma Lineament. The D3 event is attributed to the latest stage of this collision, and represents the relaxation of the overthickened crust along the direction of the lateral extrusion. The D4 and D5 events are interpreted as post-orogenic extensional events related to the retreat of the Hellenic subduction zone since the Late Miocene and to the widespread back-arc Aegean extension still prevailing today. 相似文献
13.
Richard H. Sibson 《Pure and Applied Geophysics》2014,171(11):2867-2885
Whether or not ruptures nucleate in fluid-overpressured crust (λ v = P f/σ v > 0.4) is important because pore-fluids overpressured above hydrostatic lower fault frictional strength and may also vary through the earthquake cycle, acting as an independent variable affecting fault failure. Containment of fluid overpressure is precarious because pressure-dependent activation of faults and fractures allows drainage from overpressured portions of the crust. Discharge of fluids through activated fault-fracture permeability (fault-valve action) decreases overpressure so that subsequent failure depends on the cycling of both overpressure and frictional strength as well as tectonic stress. Geometric and mechanical considerations suggest that fluid overpressures are more likely to develop and be sustained in compressional/transpressional regimes as opposed to extensional/transtensional tectonic settings. On the basis of geophysical observations and force-balance analyses, subduction interface shear zones appear to be strongly but variably overpressured to near-lithostatic levels (λ v > 0.9) over the full depth range of seismogenic megathrusts. Strong overpressuring at seismogenic depths is also documented in active fold-thrust belts and in areas of ongoing compressional inversion (e.g., northern Honshu) where inherited normal faults are reactivated as steep reverse faults, requiring near-lithostatic overpressures (λ v → 1.0) at depths of rupture initiation. Evidence for overpressuring around strike-slip faults is less clear but tends to be strongest in areas of transpression. In areas of extensional tectonics coincident with particularly high fluid discharge, there is some evidence of overpressuring concentrated towards the base of the seismogenic zone. In general, because of the limited resolution of geophysical techniques, it is easier to make the case for rupture propagation through overpressured crust than to make a definitive case for the direct involvement of overpressured fluids in rupture nucleation, though in some instances the circumstantial evidence is compelling. An unresolved related issue is the heterogeneity of overpressuring. Do the active fault zones themselves serve as fluid conduits that are locally overpressured with respect to the surrounding crust? 相似文献
14.
2017年4月12日浙江临安发生了4.2级地震,在震中附近范围(35～50 km)内,主要发育3条断裂,分别为马金—乌镇断裂、湖州—临安断裂和昌化—普陀断裂,通过对这3条断裂开展野外地质调查、断层泥年龄样品测试等手段得出:北东向的马金—乌镇断裂、湖州—临安断裂均被近东西向的昌化—普陀为界分南北为两段,其中,马金—乌镇断裂北段以正断为主,南段以逆断为主,两段活动时代均为中更新世早期;湖州—临安断裂南北两段均以逆断为主,北段活动时代为中更新世早期,南段活动时代为前第四纪。昌化—普陀断裂以走滑活动为主,自西向东分为西、中、东三段,活动时代自西向东逐渐减弱,东段为前第四纪断裂,中西段为中更新世断裂。 相似文献
15.
根据详细的野外调查和剖面测绘成果,结合区域第四系测年结果等资料,对龙蟠—乔后断裂带桃源段新发现的桃源断裂、刀郭断裂、合江村断裂及已知的龙蟠—乔后断裂等4条主要断裂的晚第四纪活动特征进行研究。成果表明,龙蟠—乔后断裂带桃源段在晚第四纪的活动特征明显,活动强度中等,龙蟠—乔后断裂和合江村断裂属全新世活动断裂,桃源断裂和刀郭断裂属晚更新世断裂;晚更新世以来,龙蟠—乔后断裂和刀郭断裂以左旋走滑运动为主,而桃源断裂和合江村断裂则表现为正断走滑为主。这些断裂的活动性都不同程度地影响着研究区及附近区域的地震风险和构造稳定性。新的调查研究成果为深入认识龙蟠—乔后断裂带桃源段的晚第四纪活动性提供了新的资料,并可为深入理解该区的地震地质特征以及工程建设地震安全性评价等提供基础地质资料。 相似文献
16.
This study aims to contribute a possible explanation for magma migration within volcanoes located in contractional tectonic settings, based on field data and physically-scaled experiments. The data demonstrate the occurrence of large stratovolcanoes in areas of coeval reverse faulting, in spite of the widely accepted idea that volcanism can develop only in extensional/transcurrent tectonic settings. The experiments simulate the propagation of deformation from substrate reverse faults with different attitudes and locations into volcanoes. The substrate fault splits into two main shear zones within the volcano: A shallow-dipping one, with reverse motion, propagates towards the lower volcano flank, and a steeper-dipping one, with normal motion, propagates upwards. In plan view, the reverse fault zone is arcuate and convex outwards, whereas the normal fault zone is rectilinear. Structural field surveys at volcanoes located in contractional settings show similar features: The Plio–Quaternary Trohunco and Los Cardos–Centinela volcanic complexes (Argentina) lie above Plio–Quaternary reverse faults. The Late Pleistocene–Holocene El Reventador volcano (Ecuador) is also located in a coeval contractional tectonic belt. These volcanoes show curvilinear reverse faults along one flank and rectilinear extensional fracture zones across the crater area, consistent with the experiments. These data consistently suggest that magma migrates along the substrate reverse fault and is channelled along the normal fault zone across the volcano. 相似文献
17.
银川盆地是华北克拉通西部构造活动较为强烈的一个新生代断陷盆地.为了研究银川盆地的地壳浅部结构和活动断裂特征,我们利用2014年在银川盆地完成的深地震反射剖面数据,采用初至波层析成像方法得到了银川盆地高精度的基底P波速度结构和构造形态;考虑到仅根据速度结构剖面还难以确定断裂的准确位置、断层上断点埋深、断层的近地表构造组合样式等特征,研究中还采用浅层地震反射波勘探方法对银川盆地内的隐伏断裂和1739年平罗8.0级地震的地表破裂带浅部结构进行了高分辨率成像.研究结果表明:银川盆地与两侧地块的浅层P波速度结构和沉积盖层厚度差异较大,银川盆地总体呈现出明显的低速结构特征,盆地基底面起伏变化较大,基底最深处位于芦花台断裂和银川断裂之间的银川市下方,其深度约为7000~7200 m;贺兰山隆起区显示为明显的高速特征,地表出露中-古生代基岩地层,缺失新生代地层;鄂尔多斯地块西缘的浅层P波速度明显高于银川盆地,基底埋深相对较浅,推测其新生界地层厚度小于2500 m.浅层地震反射剖面揭示的地层反射界面形态和断裂的浅部构造特征非常清楚,黄河断裂、贺兰山东麓断裂、银川断裂和芦花台断裂不仅是错断盆地基底的断裂,而且还是第四纪以来的隐伏活动断裂,这些断裂的交替活动形成了"堑中堑"的盆地结构,并对银川盆地的形成、盆地内的新生代地层厚度和第四纪沉降中心具有重要的控制作用;在近地表这些断裂表现为由2~3条断层组成的"Y字形"断裂构造,且主断裂的最新活动可追踪至晚更新世末期或全新世,是构造继承性活动的结果.本文的研究结果不仅可为进一步分析银川盆地的基底结构、隐伏断裂特征和活动构造研究等提供新的地震学证据,而且还可为该区城市规划中避让活动断层提供科学依据. 相似文献
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Low-field anisotropy of magnetic susceptibility (AMS) analyses were performed on 532 samples collected in 36 (mostly lower Pliocene to lower Pleistocene) marine clay sites from the Crotone basin, a fore-arc basin located on top of the external Calabrian accretionary wedge. The Crotone basin formed since mid-late Miocene under a predominant extensional tectonic regime, but it was influenced thereafter by complex interactions with NW–SE left-lateral strike-faults bounding the basin, which also yielded post-1.2 Ma ∼30° counterclockwise block rotations. The basin is filled by continental to marine sediments yielding one of the thickest and best-exposed Neogene succession available worldwide. The deep-marine facies – represented by blue-grey marly clays gave the best results, as they both preserved a clear magnetic fabric, and provided accurate chronology based on previously published magnetostratigraphy and calcareous plankton (i.e. foraminifers and nannofossils) biostratigraphy. Magnetic susceptibility range and rock magnetic analyses both indicate that AMS reflects paramagnetic clay matrix crystal arrangement. The fabric is predominantly oblate to triaxial, the anisotropy degree low (<1.06), and the magnetic foliation mostly subparallel to bedding. Magnetic lineation is defined in 30 out of 36 sites (where the e12 angle is <35°). By also considering local structural analysis data, we find that magnetic fabric was generally acquired during the first tectonic phases occurring after sediment deposition, thus validating its use as temporally dependent strain proxy. Although most of the magnetic lineations trend NW–SE and are orthogonal to normal faults (as observed elsewhere in Calabria), few NE–SW compressive lineations show that the Neogene extensional regime of the Crotone basin was punctuated by compressive episodes. Finally, compressive lineations (prolate magnetic fabric) documented along the strike-slip fault bounding the basin to the south support the significance of Pleistocene strike-slip tectonics. Thus the Crotone basin shows a markedly different tectonics with respect to other internal and western basins of Calabria, as it yields a magnetic fabric still dominated by extensional tectonics but also revealing arc-normal shortening episodes and recent strike-slip fault activity. The tectonics documented in the Crotone basin is compatible with a continuous upper crustal structural reorganization occurring during the SE-migration of the Calabria terrane above the Ionian subduction system. 相似文献
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Imene Meriem Benbakhti Said Maouche Djelloul Belhai Assia Harbi Jean-François Ritz Ghilles Rabai Ahmed Rezouk Fawzi Doumaz 《Journal of Seismology》2018,22(6):1549-1561
In this work, we reappraise the seismogenic potential of the geologic structures in the western Tell Atlas of Algeria, considered active host to moderate to low magnitude earthquakes. The direct identification of active faults is generally a difficult task in northern Algeria. The active tectonics in the Oran Plio-Quaternary age basin (Northwestern Algeria) is analyzed and characterized through a morpho-structural study combining topographic, geomorphologic, geological, and neotectonic data. Folds and fault scarps affecting Quaternary deposits show that the region is affected by compressional deformation still active nowadays, as shown by the recorded seismic activity. Our new observations enable a better understanding of the present seismotectonic context of the Oran region, particularly with regard to the magnitude and source of the 1790 Oran damaging event. The obtained result helps to shed some light on the elusive active tectonics characterizing this coastal area, and to assess regional seismic hazard, particularly in coastal zones where large seismogenic areas straddle the onshore–offshore zones. 相似文献