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1.
A working model of tectono-sedimentary evolution is proposed for the Cheb Basin, a polyhistory sedimentary basin formed between the late Oligocene and Pliocene by reactivation of basement fracture systems in the northwestern part of the Bohemian Massif. The basin is located at the intersection of the Ohe (Eger) Graben structural domain, characterized by dominance of NE-striking graben systems in present-day geology, and the NW-striking Cheb-Domalice Graben, a major strike-slip – dominated structure in Western Bohemia. The first significant depositional episode in the Cheb Basin coincides with the deposition of late Oligocene-Miocene clastics in the whole extensional system of the Ohe Graben, controlled by E-W – trending depocenters. The main structural feature of the Cheb Basin region at that time was a palaeohigh caused by a NW- trending accommodation zone separating minor E-W – trending depocentres. The second, late Pliocene, episode of sedimentation occurred under a very different kinematic regime than the Oligo-Miocene rift basin evolution. During this time, the present-day structure of the Cheb Basin and the Cheb-Domalice Graben formed as a consequence of sinistral displacement on the Mariánské Lázn Fault Zone. Reactivation of this strike-slip fault zone led to the formation of a horsetail splay of oblique-extensional faults at the northern termination of the Mariánské Lázn Fault Zone, which contained the present-day Cheb Basin. 相似文献
2.
The Chi‐Chi earthquake (MW = 7.6) took place in central western Taiwan in 1999. The earthquake caused reactivation of the Chelungpu Fault and resulted in 100‐km‐long surface ruptures. The fault strikes mostly north–south to NNE–SSW; however, the northern tip of the southern segment of the surface ruptures rotates clockwise to define an east–west trend, then jumps to a shorter NNW‐trending rupture. The largest vertical displacement is recorded in the Shihkang area of the Shihkang–Shangchi Fault Zone, where vertical slips are up to 8–10 m. The Shihkang–Shangchi Fault Zone displays a complex fault pattern as a linkage damage zone between two fault segments with the greatest concentration of faults and fractures. Our new interpretation, based on recent published geometric, kinematic, and geophysical studies on the Chi‐Chi earthquake fault, suggests that the Shihkang–Shangchi Fault Zone is not a simple termination zone, but may be an ‘overstep zone’ or a ‘transfer zone’. Slip analysis along the surface ruptures indicates that they are composed of three fault segments and the amount of slip partly depends on the intersection angle between slip direction and fault strike. Our numerical modeling for the area indicates that Coulomb stress changes are mainly concentrated on tips and bends of the surface ruptures. Slip patterns indicate that the fault propagates toward the northeast. Therefore, this study suggests high potential for future earthquake activity along the unruptured Shangchi segment. Hence, future geohazard studies should focus on the Shangchi segment to evaluate potential earthquakes, determine recurrence intervals, and reduce future earthquake hazards. 相似文献
3.
Vratislav Blecha Tomáš Fischer Petr Tábořík Jan Vilhem Radek Klanica Jan Valenta Petra Štěpančíková 《Studia Geophysica et Geodaetica》2018,62(4):660-680
The western part of the Bohemian Massif hosts an intersection of two regional fault zones, the SW-NE trending Oh?e/Eger Graben and the NNW-SSE trending Mariánské Lázně Fault, which has been reactivated several times in the geological history and controlled the formation of the Tertiary Cheb Basin. The broader area of the Cheb Basin is also related to permanent seismic activity of ML 3+ earthquake swarms. The Eastern Marginal Fault of the Cheb Basin (northern segment of the Mariánské Lázně Fault) separates the basin sediments and underlying granites in the SW from the Kru?né Hory/Erzgebirge Mts. crystalline unit in the NE. We describe a detailed geophysical survey targeted to locating the Eastern Marginal Fault and determining its geometry in the depth. The survey was conducted at the Kopanina site near the Nový Kostel focal zone, which shows the strongest seismic activity of the whole Western Bohemia earthquake swarm region. Complex geophysical survey included gravimetry, electrical resistivity tomography, audiomagnetotellurics and seismic refraction. We found that the rocks within the Eastern Marginal Fault show low resistivity, low seismic velocity and density, which indicates their deep fracturing, weathering and higher water content. The dip of the fault in shallow depths is about 60° towards SW. At greater depths, the slope turns to subvertical with dip angle of about 80°. Results of geoelectrical methods show blocky fabric of the Cheb Basin and deep weathering of the granite bedrock, which is consistent with geologic models based on borehole surveys. 相似文献
4.
On the basis of comprehensive analyses of fault textures and geometry, the active methods, stress field, mechanism and time of the Yishu Fault Zone during the neotectonic period are discussed in this paper. The results show that the Yishu Fault Zone is a major mobile belt since the Quaternary. It consists of four major active faults with reverse dextral slip. Their active intensity increases eastwards and southwards. Fault-slip data from many active faults in the fault zone demonstrate that ENE-WSW compression predominated in the neotectonic period. Detailed field investigation shows that formation mechanism of shallow, active faults in the Yishu Fault Zone includes direct boundary fault reactivity, buried fault propagation, and reactivity of antithetic and truncating faults. In most cases, shallow, active faults in the fault zone are developed through direct reactivity or upward propagation of the previous four graben boundary faults. 相似文献
5.
Ayd?n Büyüksaraç 《Physics of the Earth and Planetary Interiors》2007,160(1):86-95
The residual aeromagnetic and gravity anomalies of inner East Anatolia, surveyed by the Mineral Research and Exploration (MTA) of Turkey, display complexities. Some faults, which are known and new lineaments, are drawn from maxspot map derived from the location of the horizontal gradient of gravity anomalies. Tectonic lineaments of inner East Anatolia exhibit similarities to the direction of East Anatolian Fault Zone. Anticlockwise rotation, approximately −30°, defined from disorientations of aeromagnetic anomalies. The lineaments obtained from maxspots map produced from the gravity anomalies and disoriented aeromagnetic anomalies are in-line with the mobilistic system revealed by the palaeomagnetic data. These Alpine age continental rotations caused westward wrenching of the global lithosphere and led to significant tectonic reactivation and deformations. GPS measurements, current tectonic knowledge and the results of the evaluation of potential field data were combined in a base map to demonstrate similarities. 相似文献
6.
A multi-scale 3-D crust velocity model in the Hefei-Chao Lake area around the southern segment of Tanlu Fault Zone 
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下载免费PDF全文 Lingli Li Huajian Yao Song Luo Junhui Li Xiaoli Wang Hongyu Ni Ziwen Bao 《地震科学（英文版）》2021,34(4):344-357
Regional high-precision velocity models of the crust are an important foundation for examining seismic activity, seismogenic environments, and disaster distribution characteristics. The Hefei-Chao Lake area contains the main geological units of Hefei Basin, with thick sediments and the Chao Lake depression. Several major concealed faults of the southern NNE-trending Tanlu Fault Zone cross this area. To further explore the underground distribution characteristics of the faults and their tectonic evolutionary relationship with adjacent tectonic units, this study used ambient noise data recorded by a seismic array deployed in Hefei City and Chao Lake, constructing a 3-D velocity model at the depth of 1–8 km. Then a multi-scale high-resolution 3-D velocity model of this area was constructed by this new upper crustal velocity model with the previous middle and lower crustal model. The new model reveals that a high-velocity belt is highly consistent with the strike of the Tanlu Fault Zone, and a low-velocity sedimentary characteristic is consistent with the Hefei Basin and Chao Lake depression. The distribution morphology of high and low velocity bodies shows that the sedimentary pattern of Hefei-Chao Lake area is closely related to the tectonic evolution of the Tanlu Fault Zone since the Mesozoic. This study also identifies multiple low-velocity anomalies in the southeastern Hefei City. We speculate that strong ground motion during the 2009 Feidong earthquake (magnitude of 3.5) was related to amplification by the thick sediments in the Hefei Basin. We also discuss further applications of multi-scale high-resolution models of the shallow layer to strong ground motion simulations in cities and for earthquake disaster assessments. 相似文献
7.
张渤带陆地段现代构造应力场的非均匀特征 总被引：6，自引：1，他引：5
依据活动构造展布及震中分布等情况,将张渤带(张家口-渤海断裂带)陆地段及邻近地区划分为6个应力区,利用格点尝试法计算了1967～2006年间这6个分区内的529个震源机制解.结果显示,6个分区的应力结构较为一致,均为走滑型应力结构;但在应力方向上有明显不同,其应力主轴方向有由西北端的NEE向至东南端的近EW向呈顺时针旋转的趋势.此外,以1976年唐山地震与1998年张北地震为时间界限,计算了张渤带陆地段3个构造交汇段(即张北-怀来段、南口-三河段、天津-塘沽段,简称西段、中段、东段)上的地震震源机制解及各构造段在不同时段的平均主应力轴分布,得到了应力场随时间的变化特征.其中,西段与中段的构造应力场变化复杂,其应力主轴方向在唐山地震后经调整已基本回复至唐山地震前的状态;而东段的平均应力主轴呈顺时针旋转,目前仍为近EW向.张渤带陆地段现代构造应力场的时空非均匀变化特征可能与周边块体的相互作用及两次中强地震(唐山地震与张北地震)有关. 相似文献
8.
Protolith ages and deformation mechanism of metamorphic rocks in the Zhangbaling uplift segment of the Tan-Lu Fault Zone 总被引：9，自引：0，他引：9
Protolith ages and Indosinian deformation mechanism of metamorphic rocks in the Zhangbaling uplift segment of the Tan-Lu Fault Zone are important, unsolved problems. Our LA-ICP-MS zircon dating work indicates that protolith ages of the greenschist-facies Zhangbaling Group are 754–753 Ma, and those of the amphibolite-facies Feidong Complex are 800–745 Ma. These rocks belong to the earliest cover of the Yangtze Plate. Their ages and metamorphic features suggest that the rocks did not come from the Dabie Orogen. The Indosinian structures in the Zhangbaling Group and lower Sinian strata formed in a flatlying ductile detachment zone with a shear sense of top-to-the-SSW whereas those in the underlying Feidong Complex are characterized by ENE-WSW inclined folds developed under a ductile regime. It is suggested therefore that the sinistral Tan-Lu Fault Zone of the Indosinian period is buried under the Hefei Basin west of the Zhangbaling uplift segment and the uplift segment is a displaced block neighboring the fault zone. Detachment deformation between the upper rigid and lower ductile crust during displacement of the Zhangbaling uplift segment resulted in the formation of the flat-lying ductile detachment zone and its underlying drag fold zone of a ductile regime. The protolith ages and deformation mechanism in the Zhangbaling uplift segment further prove sinistral origination of the Tan-Lu Fault Zone during the continent-continent collision of the North China and Yangtze plates and support the indentation model for the two-plate collision that considers the Tan-Lu Fault Zone as an oblique convergence boundary. 相似文献
9.
1933年叠溪发生7?级强震,关于此次地震的发震构造存在较大争议,有些学者认为NW向松坪沟断裂是此次地震的发震构造,另有学者认为近NS向岷江断裂南段才是这次地震的发震构造。本文根据成丛小震发生在大震断层面附近的原则,利用1990-2014年精定位小震目录,根据万永革等（2008）提出的震源断层面拟合方法,反演了叠溪地震震源断层走向、倾角和位置。断层走向和倾角分别是172.8°和82.9°,倾向偏向西。本文结果更支持岷江断裂南段为叠溪地震发震构造这一结论。 相似文献
10.
Vratislav Blecha Miroslav Štemprok Tomáš Fischer 《Studia Geophysica et Geodaetica》2009,53(3):295-314
We examined the shape of the Late Variscan Karlovy Vary granite massif located south of the Ohre/Eger graben in Northern Bohemia
by reinterpretation of existing gravity data on two perpendicular profiles. The granite body of about 360 km2 total outcrop size has the elongation ratio 0.35 with the major axis trending NE-SW. The SW part of the body was crossed
in the nineties by the seismic profile 9HR which localized the bottom of granites in a depth of about 10 km. We used this
value as a reference datum in our gravity profiles. We positioned one of our profiles along the seismic profile 9HR and the
other one perpendicularly, i.e. parallel with the elongation of the outcrop surface. We interpret the shape of the main granite
body in the vicinity of Karlovy Vary as a continuous desk whose floor is horizontal (or subhorizontal) and varies along its
whole extension about a depth of 10 km. This thickness is approximately identical with that of the Saxothuringian nappes imaged
by seismic reflection. The near surface upper contact of the granite body is mildly inclined, and outward dipping. It changes
to steep sides or inward inclined contacts in deeper levels. The Lesny-Lysina (Kynžvart) massif is a separate granite body
about 324 km thick, not continuously connected with the main Karlovy Vary massif. The gravity curve suggests that granites
often enclose in their endocontact large blocks of country metasediments or metabasites the existence of which is partly evidenced
by their outcrops outside the line of the profile. The granite body is found density-homogenous. Minor density differences
between granite varieties are caused mainly by more intense hydrothermal alterations in younger suite granites. We interpret
vertical conduits for the ascent of granitic magmas to be parallel to the Jáchymov-Gera and Ohře (Eger) lineaments or the
Mariánské Lázně fault zone as indicated by the elongation of some outcrops. However, they are not clearly imaged from the
gravity data. The effect of the depression of the Sokolov basin along the faults parallel with the Ohře (Eger) lineament is
shallow and it is not indicated by any change in the floor depth of the granite body. Comparison of the seismicity distribution
suggests that the hypocenters occur mostly outside of the granite bodies or near their contact with the country rock. 相似文献
11.
Magnetic anomalies can help reveal the structure of the upper crust in regions with intermediate or basic igneous rocks, and their continuity is essential to determine the position of crustal faults. The southwestern Iberian Peninsula constitutes the foreland of the Betic Cordillera and is characterized by an elongated E-W dipole extending 200 km toward its external zones. The anomaly is related to the outcropping Monchique Alkaline Complex, characterized by rocks of moderate magnetic susceptibility (0.029 SI) intruding into the metapelitic host rock of the South Portuguese Zone. Analysis of aeromagnetic and field magnetic anomalies serves to constrain the geometry of this laccolith. Toward the east, the magnetic dipole has a 60 km long N-S sharp boundary that coincides with the southern part of the Guadiana River. Field magnetic and gravity anomalies confirm the presence of this structure. It is produced by a sharp step in the elongated anomalous body, with an E downthrown block, interpreted as the offset produced by a deep N-S crustal fault—the Guadiana Fault. Therefore, the Guadiana River has three long linear segments near its mouth, locally coinciding with a N-S trending joint set, that support the presence of this major fault. To date, no evidence of this tectonic discontinuity, coinciding with the Spanish-Portuguese border, has been reported. Magnetic research is essential for understanding the structure of wide regions intruded by intermediate and/or basic igneous rocks. 相似文献
12.
A NEW FINDING OF SURFACE RUPTURE ZONES ASSOCIATED WITH THE 1936 LINGSHAN M6(3/4) EARTHQUAKE,GUANGXI, CHINA 下载免费PDF全文
下载免费PDF全文 LI Xi-guang LI Bing-su PAN Li-li NIE Guan-jun WU Jiao-bing LU Jun-hong YAN Xiao-min LI Zhi-yong 《地震地质》2017,39(4):689-698
On April 1, 1936, an M6(3/4) earthquake occurred on the Fangcheng-lingshan Fault. This event is the biggest historical earthquake on the coastal seismic zone, South China ever. But so far, no any findings about the surface rupture of this event have been reported. This paper is the first to find several intact surface rupture zones associated with the 1936 Lingshan seismic event, in the areas of Gaotang, Jiaogengping etc. on the northeast segment of the Fangcheng-Lingshan Fault. According to the field work, the surface rupture stretches to 10km and distributes along NE direction in front of Luoyang Mountain, represented by earthquake scarp, extensional fracture, dextrally faulted gully and river system etc. The characteristics of surface ruptures and faulted landforms indicate that the surface rupture is of normal-dextral strike slip faulting. The trenching on this fault exposed that at least three seismic events have been recorded, including two historical earthquake events and the latest one is the 1936 Lingshan M6(3/4) earthquake. These surface rupture zones are the key to the detection of seismogenic structure and the re-estimate of magnitude of this event. The new finding of these surface rupture zones would be particularly significant for the detection of the seismogenic structure of Lingshan M6(3/4) earthquake. 相似文献
13.
The basic parameters for the earthquake with a moment magnitude (M W) of 5.2 on the 23rd of June 2010 have been investigated. The earthquake occurred on a hidden fault in the northwest direction about 60?km north-northeast of Ottawa in the Western Quebec Seismic Zone (WQSZ) and had a focal depth of about 21?km. The focal mechanism was a thrust type with strike in the northwest direction and dipping in the northeast direction. The relative relocations of seven larger aftershocks show that the source rupture area was about 6?km2. The b value of the aftershock sequence was 0.8?C1.0, and the decay rate of the aftershocks was faster than normal cases. The dominant seismogenic depths are about 12 to 22?km in most parts of the WQSZ, while the seismogenic depth along the Ottawa?CBonnechere Graben can be as deep as 28?km. Based on the seismic activity in the WQSZ and vicinity since 1961, it seems that the periods of moderate earthquakes are about 6?C10?years. 相似文献
14.
15.
安宁河断裂带晚第四纪活动的基本特征及强震危险性分析 总被引：7，自引：0，他引：7
通过影像解译,结合野外地质调查,利用第四纪地貌填图、样品采集和差分GPS地貌面的测量等研究手段,对安宁河断裂带及其附近地区第四纪地貌特征与断层活动关系进行了研究,分析了安宁河断裂带晚第四纪以来的活动特征,探讨了该断裂上强震的危险性。结果表明,晚第四纪以来,安宁河断裂带有强烈左旋走滑和逆冲的双重运动特征,由此可将其划分为南、北两段,北段最后一次活动时间大约在公元15世纪,南段最后一次活动时间为1536年。安宁河断裂带北段的强震危险性大于南段,且未来地震的强度在7.5级左右。 相似文献
16.
利用云南东川地区10个宽频带流动台站的连续波形数据,采用基于深度学习的自动震相拾取方法和震相关联技术,对2020年东川ML4.2地震序列分别进行绝对定位和相对定位,获得了该地震序列的高精度地震定位结果,得到东川ML4.2地震序列的212个余震事件,约为中国地震台网目录给出的余震数目的5倍,丰富了ML≤3.0余震;精定位结果表明东川ML4.2主震震源深度为5.19 km,余震震源深度集中在3~6 km,余震序列分布长轴呈NNE向展布;此次地震发生在小江断裂带西支,发震构造与乌龙拉分盆地的构造演化有关。 相似文献
17.
使用芦山地震序列2013年4月20日至5月20日一个月的地震震相数据和MS4.0以上地震的波形数据, 通过双差定位方法得到了3398个地震的精定位结果, 利用时间域全波形反演方法得到17个地震的矩张量解。 综合分析地震双差定位结果和芦山地震序列中强地震震源机制解, 发现芦山地震发震构造由主震断层和次级反冲断层组成, 主震断层为一走向北东、 倾向北西、 倾角约为45°的高角度逆冲断层, 次级反冲断层与主震断层走向相同, 倾向相反, 两条断层均未出露地表。 主震和余震震源机制解均为逆冲型, 几乎没有走滑分量。 震源区主压应力方位为北西向, 与发震断层走向近乎垂直。 相似文献
18.
郯庐断裂带东地堑边界断层在断裂带演化过程和现今构造格局中都是重要断层,对该边界断层的第四纪活动性研究有助于了解郯庐断裂带的演化历史和地震活动性,而有关该边界断层第四纪活动性研究较少且至今尚无定论。本文通过浅层地震勘探和钻孔联合剖面相结合的方法,针对郯庐断裂带江苏段东地堑两边界断层开展系统的断层第四纪活动性研究,结果显示,昌邑-大店断裂(F_1)第四纪以来未见构造运动证据,白芬子-浮来山断裂(F_2)在第四纪早期曾发生有关活动,晚更新世以来未见活动迹象。 相似文献
19.
利用双差定位方法对玉树地震序列2010年4月14日至10月31日间发生的ML≥1.0地震进行双差定位,得到1545个地震的重定位结果.综合分析地震双差定位结果和玉树地震序列中强地震震源机制解,发现玉树MS7.3地震发震构造由北西向和北东东向两条相交断层组成,主震发生在北西走向的甘孜—玉树断裂带上,5月29日的MS5.9余震序列发生在北东东走向的一条隐伏断裂上,两条断裂均接近直立.甘孜—玉树断裂是羌塘地块和巴彦喀拉地块的构造边界,由于羌塘地块和巴颜喀拉地块的差异运动使甘孜—玉树断裂强耦合段应力高度积累,在应变能超过岩石强度时破裂失稳发生了MS7.3地震.主震断层的左旋滑动导致北东东向断层的正应力减小,库伦应力增加,45天后触发了MS5.9余震序列的活动. 相似文献
20.
南海北部海陆过渡带地壳结构的研究现状及展望 总被引：2，自引：0，他引：2
首先总结了前人在南海北部海陆过渡带获得的研究成果：由重磁异常、水深及卫星影像等资料推测滨海断裂带存在于南海北部海陆过渡地区：介绍了最近在南海北部海陆过渡地区开展的海陆地震联测试验,其结果显示有一个穿透整个地壳的低速破碎带发育于海陆过渡地区,推测它为滨海断裂带在速度上的表现,另外广泛分布于华南大陆的中地壳低速层在海陆过渡处也有较好发育;总结了天然地震层析成像在南海北部海陆过渡带的研究成果。最后结合目前的研究现状,指出了今后我们的研究方向：在逐步完善目前海陆地震联测试验的基础上,同时开展海陆过渡带的多道地震数据采集及地球化学研究：加强海陆过渡带的地震监测。进行震源机制解和人工地震与天然地震联合成像的研究。 相似文献