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1.
The SW part of the Baltic Sea between Scania, Rügen, Bornholm and Mön constitutes a complex crustal transition between the Baltic Shield and the accreted Phanerozoic provinces of the West European Platform. An integrated interpretation of marine reflection seismic data sets from the BABEL AC line and two commercial surveys offshore NE Germany and S Sweden have resulted in a complete view of the structural framework in the area. The general seismic picture can best be detected by two characteristic sets of reflection phases. The lower set is dominated by slightly dipping and vertically displaced prominent reflectors corresponding to downfaulted Lower Palaeozoic strata on top of the Precambrian basement. The upper set represents Mesozoic and Cenozoic coherent reflection phases including a thick Upper Cretaceous unit. The Caledonian deformation front is identified in the southern part of the investigated area as the border against which basement rocks have been affected by Caledonian metamorphism and deformation. Major structural elements also include the N–S trending Agricola–Svedala Fault and North Rügen-Skurup Fault. Several NW–SE trending faults are also identified including the Nordadler–Kamien Fault, Jutland–Mön Fault, Carlsberg Fault, Romeleåsen Fault Zone and the Fyledalen Fault Zone. The sedimentary record from NE German offshore wells and Scanian boreholes is compared with the seismic data. The Cambro-Silurian strata are composed mainly of quartzitic sandstones, shales and biomicritic limestones. The Silurian is dominated by grey, micaceous shale and micaceous siltstone deposited in a marginal basin. Upper Palaeozoic strata are merely encountered in the southernmost part of the investigated area. These include Zechstein strata. The Mesozoic deposits are dominated by a thick Cretaceous sequence of mainly limestones with interbedded sandstones.  相似文献   

2.
Fifteen earthquakes (Mw 4.1–6.4) occurring at ten major segments of the Sumatran Fault Zone (SFZ) were analyzed to identify their respective fault planes. The events were relocated in order to assess hypocenter uncertainty. Earthquake source parameters were determined from three-component local waveforms recorded by IRIS-DMC and GEOFON broadband lA networks. Epicentral distances of all stations were less than 10°. Moment tensor solutions of the events were calculated, along with simultaneous determination of centroid position. Joint analysis of hypocenter position, centroid position, and nodal planes produced clear outlines of the Sumatran fault planes. The preferable seismotectonic interpretation is that the events activated the SFZ at a depth of approximately 14–210 km, corresponding to the interplate Sumatran fault boundary. The identification of this seismic fault zone is significant to the investigation of seismic hazards in the region.  相似文献   

3.
塔里木盆地中部航磁异常带新解译   总被引：5，自引：0，他引：5       下载免费PDF全文
横亘于塔里木盆地中部的纬向航磁高ΔTa异常带,一直是探讨盆地及深部基底的物质组成及结构构造的焦点。根据钻井及地震资料综合分析,发现满加尔坳陷中南部上奥陶统内发育大型地震反射异常体,平面上主要由8个地震反射异常体近东西向呈带状展布,与盆地中部航磁高ΔTa异常带相关。从地层发育及地震相特征分析,这些地震反射异常体应为辉绿岩-玄武岩等基性火成岩体,且与航磁ΔTa异常带上的磁力高相对应。异常体具有垂直向下的通道,与断裂及岩浆活动通道有关。盆地中部高航磁异常带为多期构造易活动带,反映了满加尔坳陷震旦纪与中晚奥陶世处于拉张的构造背景。  相似文献   

4.
Clues to the understanding of intra- and inter-plate variations in strength or stress state of the crust can be achieved through different lines of evidence and their mutual relationships. Among these parameters Bouguer gravity anomalies and seismic b-values have been widely accepted over several decades for evaluating the crustal character and stress regime. The present study attempts a multivariate analysis for the Shillong Plateau using the Bouguer gravity anomaly and the earthquake database, and establishes a causal relationship between these parameters. Four seismic zones (Zones I–IV), with widely varying b-values, are delineated and an excellent correlation between the seismic b-value and the Bouguer gravity anomaly has been established for the plateau. Low b-values characterize the southwestern part (Zone IV) and a zone (Zone III) of intermediate b-values separates the eastern and western parts of the plateau (Zones I and II) which have high b-values. Positive Bouguer anomaly values as high as +40 mgal, a steep gradient in the Bouguer anomaly map and low b-values in the southwestern part of the plateau are interpreted as indicating a thinner crustal root, uplifted Moho and higher concentration of stress. In comparison, the negative Bouguer anomaly values, flat regional gradient in the Bouguer anomaly map and intermediate to high b-values in the northern part of the plateau are consistent with a comparatively thicker crustal root and lower concentration of stress, with intermittent dissipation of energy through earthquake shocks. Further, depth wise variation in the b-value for different seismic zones, delineated under this study, allowed an appreciation of intra-plateau variation in crustal thickness from ∼30 km in its southern part to ∼38 km in the northern part. The high b-values associated with the depth, coinciding with lower crust, indicate that the Shillong Plateau is supported by a strong lithosphere.  相似文献   

5.
Recent interpretation of seismic sections and free-air gravity anomalies in offshore northern Taiwan reveals that the southern Taiwan–Sinzi Folded Zone began to form in late Middle Miocene, though it was mainly constructed in the Late Pliocene with strong reverse faulting and folding. Two westward progradational sequences were deposited in the shelf basin with sediments supplied from the southern Taiwan–Sinzi Folded Zone and the southern Ryukyu Arc. These two structures are displaced by several northwest-striking dextral strike–slip faults that were active in the early Quaternary when the clockwise-rotated southern Ryukyu Arc and the folded southern Taiwan–Sinzi Folded Zone were broken. It is believed that recent extension in the southern Okinawa Trough started in the early Quaternary because uplift on the southern Taiwan–Sinzi Folded Zone continued to latest Pliocene–early Quaternary. Paleogene–Miocene sediments of the East China Sea Shelf in the western part of the southern Okinawa Trough Basin are interpreted to indicate that the East China Sea Shelf Basin extended to the east of the southern Taiwan–Sinzi Folded Zone.  相似文献   

6.
The Alleppey Platform is an important morphological feature located in the Kerala-Konkan basin off the southwest coast of India. In the present study, seismic reflection data available in the basin were used to understand the sedimentation history and also to carry out integrated gravity interpretation. Detailed seismic reflection data in the basin reveals that:(1) the Alleppey Platform is associated with a basement high in the west of its present-day geometry(as observed in the time-structure map of the Trap Top(K/T boundary)),(2) the platform subsequently started developing during the Eocene period and attained the present geometry by the Miocene and,(3) both the Alleppey platform and the Vishnu fracture zone have had significant impact on the sedimentation patterns(as shown by the time-structure and the isochron maps of the major sedimentary horizons in the region). The 3-D sediment gravity effect computed from the sedimentary layer geometry was used to construct the crustal Bouguer anomaly map of the region.The 3-D gravity inversion of crustal Bouguer anomaly exhibits a Moho depression below the western border of the platform and a minor rise towards the east which then deepens again below the Indian shield. The 2-D gravity modelling across the Alleppey platform reveals the geometry of crustal extension,in which there are patches of thin and thick crust. The Vishnu Fracture Zone appears as a crustal-scale feature at the western boundary of the Alleppey platform. Based on the gravity model and the seismic reflection data, we suggest that the basement high to the west of the present day Alleppey platform remained as a piece of continental block very close to the mainland with the intervening depression filling up with sediments during the rifting. In order to place the Alleppey platform in the overall perspective of tectonic evolution of the Kerala-Konkan basin, we propose its candidature as a continental fragment.  相似文献   

7.
The Diamantina ～120 km-diameter ring feature, a unique feature in western Queensland, is manifested by a near-360° circular drainage pattern, radial creeks and a coincident radiometric K–Th–U pattern. The structure has been studied in the context of an investigation of the nature and origin of Australian circular structures. Geophysical signatures, including total magnetic intensity (TMI), gravity and seismic reflection transect data from the region of the ring feature are examined to help test the origin of the structure. A western subdued TMI arc with a ～110 km diameter is offset by ～30 km eastward from the western rim of the drainage ring. Bouguer anomaly data show a gravity low near the centre of the ring structure, but no outer circular pattern. Two recent seismic transects indicate a moderately reflective to weakly reflective crust below flat lying strata of the Jurassic–Cretaceous Eromanga and Permian–Triassic Galilee basins, and above a usually well-defined ～39–45 km-deep Moho. An approximately ～100 km-wide seismically non-reflective to weakly reflective zone overlapping the Diamantina ring feature separates crust of different seismic reflection character to either side. The nature of the seismic non-reflective crust is unknown. A potential interpretation of the ring structure in terms of asteroid impact cannot be confirmed or rejected given the present state of knowledge, owing to (1) the near-30 km depth of the seismically non-reflective zone along the transects; and (2) the shift of the TMI part ring zone relative to the geomorphic expression of the Diamantina ring feature. A test of the nature and origin of the Diamantina ring feature requires a cored drill hole near the centre of the TMI ring structure.  相似文献   

8.
A ～400 km long deep crustal reflection seismic survey was acquired in central Victoria, Australia, in 2006. It has provided information on crustal architecture across the western Lachlan Orogen and has greatly added to the understanding of the tectonic evolution. The east-dipping Moyston Fault is confirmed as the suture between the Delamerian and western Lachlan Orogens, and is shown to extend down to the Moho. The Avoca Fault, the boundary between the Stawell and Bendigo Zones, is a west-dipping listric reverse fault that intersects the Moyston Fault at a depth of about 22 km, forming a V-shaped geometry. Both the Stawell and Bendigo Zones can be divided broadly into a lower crustal region of interlayered and imbricated metavolcanic and metasedimentary rocks and an upper crustal region of tightly folded metasedimentary rocks. The Stawell Zone was probably part of a Cambrian accretionary system along the eastern Gondwanaland margin, and mafic rocks may have been partly consumed by Cambrian subduction. Much of the Early Cambrian oceanic crust beneath the Bendigo Zone was not subducted, and is preserved as a crustal-scale imbricate thrust stack. The seismic data have shown that a thin-skinned structural model appears to be valid for much of the Melbourne Zone, whereas the Stawell and Bendigo Zones have a thick-skinned structural style. Internal faults in the Stawell and Bendigo Zones are mostly west-dipping listric faults, which extend from the surface to near the base of the crust. The Heathcote Fault Zone, the boundary between the Bendigo and Melbourne Zones, extends to at least 20 km, and possibly to the Moho. A striking feature in the seismic data is the markedly different seismic character of the mid to lower crust of the Melbourne Zone. The deep seismic reflection data for the Melbourne Zone have revealed a multilayered crustal structure that supports the Selwyn Block model.  相似文献   

9.
Understanding the formation and the development of salt structures is very important especially because they are of significant economical interest. Detailed understanding of this process will help reservoir prediction and hydrocarbon recovery. In this work, we use a combination of geological observations along with the interpretation of geophysical data (seismic and Bouguer anomaly data) to better constrain the geology of the Jbel Cheid structure. The shape of Triassic body of Jbel Cheid (Northern Tunisian Atlas) structure and its geodynamic evolution have been determined by gravity analyses and 2.5D modeling, correlated with others geophysical data (seismic) and geological observations. Semi-automatic structural analysis was performed before modeling, to identify lateral gravity discontinuities. The complete Bouguer and residual gravity anomaly maps indicate a positive amplitude gravity anomaly over the Triassic evaporitic outcrop (Jbel Cheid) and prominent NE–SW-trending features associated with the boundary of the Triassic rocks and surrounded layers. The seismic profile shows a thickness variation of post-salt layers. Taking into account the 2.5D gravity model, seismic profile and surface data, geodynamic evolution of Jbel Cheid can be subdivided on three stages (reactive, active, and passive) which well correlated to the model proposed by Vendeville (2002).  相似文献   

10.
In the Belledonne massif, the steep Paleozoic Belledonne Middle Fault (BMF) separates micaschists, displaying numerous landslides, from amphibolites. The massif is incised by the lower Romanche river valley. When crossing the BMF, the valley widens into a lozenge-shaped basin recently interpreted as an active pull-apart type structure associated with a major N110 striking Quaternary fault. Multidisciplinary investigations were carried out in the basin to check if this model has implications on the seismic and landslide hazard assessment. This study demonstrated the existence of a N80 sinistral strike slip Séchilienne Fault Zone (SFZ). This fault zone is suspected to offset the BMF by 375 m across the basin. Geophysical experiments revealed that the bedrock depth increases strongly in the basin, up to 350 m. Our study invalidates the active pull-apart origin of the basin and suggests it results from Quaternary glacial and fluvial erosion processes, magnified by the intersection of two inherited structures, the BMF and the SFZ.  相似文献   

11.
This paper presents a structural evolution study of the Farasan Bank using an integration of field work, remote sensing data, and regional Bouguer gravity data interpretation. The architecture of the Farasan Islands is influenced by normal faults parallel to the Red Sea rift axis delineating a series of graben and asymmetric half-graben structures as well as salt domes. Geological data suggest that the negative gravity anomaly over the Farasan Bank reflects thick salt deposits. The gravity data shows a general NW-SE trend with the main negative anomaly coincident with the Farasan Islands. Gravity data together with seismic reflection data suggest that salt diapirs are elongated and parallel to the main rift orientation (NW-SE). This indicates that salt deposition and diapirism was controlled by rift-related basement structures. Forward modeling of gravity data constrained by marine seismic reflection interpretation reveals that the evaporites directly overlie the basement in most places. No pre-evaporite formation was detected. Integration of the modeling with field observations and interpretations suggests that the Farasan Islands are in an area of active extension. Extension and salt diapirism on the flank of the mid-ocean ridge is likely to be synchronous with renewed spreading at 5 Ma.  相似文献   

12.
The Trans-Tanami Fault in the poorly exposed Paleoproterozoic Granites-Tanami Orogen of Western Australia is an ～100 km long curvilinear structure with ～6 km right lateral displacement. Multi-scale integration and analysis of aeromagnetic, gravimetric, reflection seismic and remote sensing data have constrained the relative timing and architectural relationship of this structure. Interpretation of regional scale long-wavelength potential field (gravity and magnetic) anomalies, which are commonly used to define first-order structures, show that the fault is not a terrane boundary. Structural interpretation of short-wavelength potential field data illustrates that the structural domains on either side of the fault represent the products of a non-homogeneous stress regime developed between rigid granitic plutons. Additionally, 2D joint forward modelling of gravity and magnetic data and interpretation of reflection seismic data confirms the vertical displacement across this fault to be negligible indicating a predominant lateral displacement. The lateral displacement along a portion of this structure has exploited a pre-existing plane of a north-dipping thrust fault. Where this early thrust fault terminates, the Trans-Tanami Fault displaces previously unfaulted rock as a wrench fault step-over. These observations differ from previous findings in the area by constraining the absolute displacement of this structure and through the recognition of a wrench fault system that includes lateral step-overs between re-activated early thrust fault planes.  相似文献   

13.
The Elbe Fault System (EFS) is a WNW-striking zone extending from the southeastern North Sea to southwestern Poland along the present southern margin of the North German Basin and the northern margin of the Sudetes Mountains. Although details are still under debate, geological and geophysical data reveal that upper crustal deformation along the Elbe Fault System has taken place repeatedly since Late Carboniferous times with changing kinematic activity in response to variation in the stress regime. In Late Carboniferous to early Permian times, the Elbe Fault System was part of a post-Variscan wrench fault system and acted as the southern boundary fault during the formation of the Permian Basins along the Trans-European Suture Zone (sensu [Geol. Mag. 134 (5) (1997) 585]). The Teisseyre–Tornquist Zone (TTZ) most probably provided the northern counterpart in a pull-apart scenario at that time. Further strain localisation took place during late Mesozoic transtension, when local shear within the Elbe Fault System caused subsidence and basin formation along and parallel to the fault system. The most intense deformation took place along the system during late Cretaceous–early Cenozoic time, when the Elbe Fault System responded to regional compression with up to 4 km of uplift and formation of internal flexural highs. Compressional deformation continued during early Cenozoic time and actually may be ongoing. The upper crust of the Elbe Fault System, which itself reacted in a more or less ductile fashion, is underlain by a lower crust characterised by low P-wave velocities, low densities and a weak rheology. Structural, seismic and gravimetric data as well as rheology models support the assumption that a weak, stress-sensitive zone in the lower crust is the reason for the high mobility of the area and repeated strain localisation along the Elbe Fault System.  相似文献   

14.
The Jiza' basin is located in the eastern part of Yemen, trending generally in the E–W direction. It is filled with Middle Jurassic to recent sediments, which increase in thickness approximately from 3,000 m to more than 9,000 m. In this study, block-35 of this sedimentary basin is selected to detect the major subsurface geological and structural features characterizing this basin and controlling its hydrocarbon potentials. To achieve these goals, the available detailed gravity and magnetic data, scale 1:100,000, were intensively subjected to different kinds of processing and interpretation steps. Also, the available seismic reflection sections and deep wells data were used to confirm the interpretation. The results indicated three average depth levels; 12.5, 2.4, and 0.65 km for the deep, intermediate, and shallow gravity sources and 5.1 and 0.65 km for the deep and shallow magnetic sources. Accordingly, the residual and regional anomaly maps were constructed. These maps revealed a number of high and low structures (horsts and grabens and half grabens), ranging in depth from 0.5 km to less than 4.5 km and trending mainly in the ENE, NW, and NE directions. However, the analytical signal for both gravity and magnetic data also showed locations, dimensions, and approximate depths of the shallow and near surface anomaly sources. The interpretation of the gravity and magnetic anomalies in the area indicated that the NW, NNW, ENE, and NE trends characterize the shallow to deep gravity anomaly sources; however, the NE, NW, and NNE trends characterize the magnetic anomaly sources, mainly the basement. Two-dimensional geologic models were also constructed for three long gravity anomaly profiles that confirmed and tied with the available deep wells data and previously interpreted seismic sections. These models show the basement surface and the overlying sedimentary section as well as the associated faults.  相似文献   

15.
大别山地震波速度剖面的重力拟合及花岗岩带   总被引：2，自引：1，他引：1       下载免费PDF全文
笔者对穿越大别山造山带的六安—大冶宽角反射地震剖面进行了重力拟合。拟合结果表明严格按宽角反射地震速度换算成的密度剖面所产生的是一个重力高,它反映出大别山是一个穹隆,与实测大别山重力低大相径庭。只有将位于大别山山根上,南北大别之间设置一个从地表直达莫霍界面的巨大低密度体,重力曲线才能得到很好的拟合。这个低密度体应为近北西走向的花岗岩带。它与反射地震剖面上石镇透明反射地震带位置吻合,但宽度远较反射地震透明带为大。重力曲线的拟合进一步说明,在华北陆块与扬子陆块碰撞后的白垩纪时,大别山出现一个伸展期,在这个时期,大别山穹隆形成,并伴随有大规模花岗岩的侵入,超高压变质岩从地壳中下部折返到地表。研究说明,联合应用反射地震、宽角反射地震和重力,进行综合解释是必要的,可以得到更令人信服的地质结论。  相似文献   

16.
Serpentinite/talc‐matrix mélanges, bearing blocks of blueschist metavolcanics, occur within the Heathcote and Governor Fault Zones of the southern Lachlan Orogen. In the Heathcote Fault Zone, serpentinite‐matrix mélange consists of blocks or small pods of boninite, andesite, ultramafic rocks, chert and volcanogenic sandstone variably metamorphosed to prehnite‐pumpellyite, greenschist, or greenschist to blueschist facies. In the Governor Fault Zone, blueschist metavolcanics occur as blocks within serpentinite/talc matrix that is interleaved with prehnite‐pumpellyite to greenschist facies, intermediate pressure slate and phyllite. Ar/Ar dating of white mica from slaty mud‐matrix (broken formation) indicates that the main fabric development occurred at 446 ± 2 Ma. U–Pb (SHRIMP) dating of titanite from blueschists in the Governor Fault Zone indicates that metamorphism occurred at approximately 450 Ma, close to the time of mélange formation. Previously published, Ar/Ar dating of white mica from phyllite and biotite from metadiorite in the Heathcote Fault Zone suggest that blueschist metamorphism occurred at a similar time. These ages are supported by field relationships. Illite crystallinity and b0 data from white mica, and the preservation of blueschist blocks indicate that these fault zones maintained low temperatures both during and after intermediate‐ to high‐pressure metamorphism. Occurrences of blueschists in the Arthur Lineament of the Tyennan (Delamerian) Orogen in Tasmania, and in the New England Orogen, have different ages, and in conjunction with the occurrences described here, suggest that subduction‐accretion processes contributed significantly to the development of the Tasmanides from Cambrian through to Carboniferous times.  相似文献   

17.
扇三角洲是苏北盆地高邮凹陷戴南组较为发育的一种沉积类型,集中分布在凹陷南部陡坡带一侧,是该区一个重要的勘探领域。根据岩芯、测井、地震、粒度等资料,对高邮凹陷古近系戴南组扇三角洲的沉积特征进行了研究,建立了高邮凹陷戴南组的沉积相模式。根据单井沉积相、连井沉积相分析以及地震剖面反射特征和砂地比图综合分析,确定了戴南组各亚段沉积相的平面展布,编制了戴南组各亚段沉积相分布图。结果表明：高邮凹陷南部陡坡带地形陡,存在扇三角洲发育的条件,也存在反映浅水环境的岩性特点,成分成熟度和结构成熟度低反映了近物源的条件,还发现反映牵引流和重力流共存的沉积构造特点;从地震反射特征上看,反射结构不稳定,并发现向盆地边缘加厚的楔形地震相。在此基础上,重点对戴南组扇三角洲相各微相进行了分析,共划分出扇三角洲平原、扇三角洲前缘和前扇三角洲亚相,并进一步划分出水上分流河道、漫滩沼泽、水下分流河道、分流河道间和席状砂等微相,最后详细阐述了各微相的沉积特征。  相似文献   

18.
Christoffer Nielsen  H. Thybo   《Tectonophysics》2009,470(3-4):298-318
The Cenozoic Baikal Rift Zone (BRZ) is situated in south-central Siberia in the suture between the Precambrian Siberian Platform and the Amurian plate. This more than 2000-km long rift zone is composed of several individual basement depressions and half-grabens with the deep Lake Baikal at its centre. The BEST (Baikal Explosion Seismic Transect) project acquired a 360-km long, deep seismic, refraction/wide-angle reflection profile in 2002 across southern Lake Baikal. The data from this project is used for identification of large-scale crustal structures and modelling of the seismic velocities of the crust and uppermost mantle. Previous interpretation and velocity modelling of P-wave arrivals in the BEST data has revealed a multi layered crust with smooth variation in Moho depth between the Siberian Platform (41 km) and the Sayan-Baikal fold belt (46 km). The lower crust exhibits normal seismic velocities around the rift structure, except for beneath the rift axis where a distinct 50–80-km wide high-velocity anomaly (7.4–7.6 ± 0.2 km/s) is observed. Reverberant or “ringing” reflections with strong amplitude and low frequency originate from this zone, whereas the lower crust is non-reflective outside the rift zone. Synthetic full-waveform reflectivity modelling of the high-velocity anomaly suggests the presence of a layered sequence with a typical layer thickness of 300–500 m coinciding with the velocity anomaly. The P-wave velocity of the individual layers is modelled to range between 7.4 km/s and 7.9 km/s. We interpret this feature as resulting from mafic to ultra-mafic intrusions in the form of sills. Petrological interpretation of the velocity values suggests that the intrusions are sorted by fractional crystallization into plagioclase-rich low-velocity layers and pyroxene- and olivine-rich high-velocity layers. The mafic intrusions were probably intruded into the ductile lower crust during the main rift phase in the Late Pliocene. As such, the intrusive material has thickened the lower crust during rifting, which may explain the lack of Moho uplift across southern BRZ.  相似文献   

19.
Recent seismicity in and around the Gargano Promontory, an uplifted portion of the Southern Adriatic Foreland domain, indicates active E–W strike-slip faulting in a region that has also been struck by large historical earthquakes, particularly along the Mattinata Fault. Seismic profiles published in the past two decades show that the pattern of tectonic deformation along the E–W-trending segment of the Gondola Fault Zone, the offshore counterpart of the Mattinata Fault, is strikingly similar to that observed onshore during the Eocene–Pliocene interval. Based on the lack of instrumental seismicity in the south Adriatic offshore, however, and on standard seismic reflection data showing an undisturbed Quaternary succession above the Gondola Fault Zone, this fault zone has been interpreted as essentially inactive since the Pliocene. Nevertheless, many investigators emphasised the genetic relationships and physical continuity between the Mattinata Fault, a positively active tectonic feature, and the Gondola Fault Zone. The seismotectonic potential of the system formed by these two faults has never been investigated in detail. Recent investigations of Quaternary sedimentary successions on the Adriatic shelf, by means of very high-resolution seismic–stratigraphic data, have led to the identification of fold growth and fault propagation in Middle–Upper Pleistocene and Holocene units. The inferred pattern of gentle folding and shallow faulting indicates that sediments deposited during the past ca. 450 ka were recurrently deformed along the E–W branch of the Gondola Fault Zone.We performed a detailed reconstruction and kinematic interpretation of the most recent deformation observed along the Gondola Fault Zone and interpret it in the broader context of the seismotectonic setting of the Southern Apennines-foreland region. We hypothesise that the entire 180 km-long Molise–Gondola Shear Zone is presently active and speculate that also its offshore portion, the Gondola Fault Zone, has a seismogenic behaviour.  相似文献   

20.
沂沭断裂带纵贯山东省中部,属郯庐断裂带中段。在沂沭断裂带及其近区新元古代—新生代的沉积地层中,到目前,已识别出25个地震事件层位。这些地震事件层位的名称取自不同年代或年龄的含地震记录的岩石地层。大多数地震记录是震积岩,少部分为震火山岩,它们的时空分布支持该断裂带生成—活动与发展历史分2个阶段: 古郯庐断裂带阶段(新元古代—古生代)和中—新生代阶段。新元古代初鲁中至苏皖北部NNE向韧性剪切带的形成,沟通了秦岭大别与苏鲁洋间的NEE走向的转换断层,可能是沂沭断裂带或古郯庐断裂带的成因机制。在纵向上,古郯庐断裂带阶段形成了8个地震事件层位,其中5个地震事件层位较密集地分布于南华系至中下寒武统;中—新生代阶段形成了17个地震事件层位,其中12个层位较密集的分布于白垩系—古近系。因此,南华纪—早中寒武世、白垩纪—古近纪分别为2个发展阶段的强地震事件频繁发生时段。在这2个发展阶段,该断裂带地震活动的动力来源不同: 古郯庐断裂带阶段主要源于华北与华南板块的相向运动与碰撞;中—新生代阶段主要源于太平洋板块向欧亚大陆板块下俯冲。在横向上,有15个(占60%)地震事件层位分布在此断裂带内或由该断裂带内向两侧延伸,这体现了沂沭断裂带一直是研究区内发震构造的主体。所有地震事件地层分布于该断裂带纵中轴线两侧150~180,km以内的同沉积盆地,这证明该深大断裂带的两侧近区是强构造地震活动区。作者关于地震事件层位的时空分布的论述和图解,展示了该断裂带自形成以来的地震作用的过程与历史,清晰地勾绘出了这条长期活动地震带的影响范围,这不仅对分析此类深大活动断裂带及其附近由地震引发的软沉积物变形与地震作用具有重要意义,而且对评价此类地震带对地表和建筑物的地震破坏效应也具有重要意义。  相似文献   

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