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1.
Air gun seismic and 3.5 kHz profiling data from the Gulf of Patras, western Greece, show that it is occupied by a small asymmetric graben with several geometric similarities to the larger-scale graben in the Gulf of Corinth to the east. Major listric faulting characterizes the southern flank of the graben whilst the northern flank represents an associated rollover structure affected by antithetic and synthetic faulting. The present phase of subsidence is of Holocene age, but buried growth faults suggest earlier subsidence in the Gulf. The average rate of subsidence through the Holocene is estimated to be 10 mm/year.The Gulf of Patras graben, together with the Gulf of Corinth graben and the Megara basin, represent a continuous system of WNW-ESE trending grabens in a broad zone of intense seismicity within the Aegean domain. Individual grabens are offset and are interconnected by NE-SW trending fault systems.  相似文献   

2.
Geometrical analysis of planar domino-style normal faults rooted into a dipping basal detachment fault allows derivation of equations which relate: (1) horizontal extension within the upper plate; (2) dip of the detachment; (3) final fault dips; (4) rotation that faults and beds undergo; and (5) net slip on domino-style faults. Past geometrical models have focused on extremely idealized and non-unique geometries, in which domino-style faults are parallel and similar cut-off points are all at the same elevation after faulting. This corresponds to evenly spaced domino-style faults above a horizontal detachment. Considering non-parallel faults and dipping detachments introduces unique geometries, which allows calculation, for example, of permissible depth ranges to the detachment. Horizontal extension varies significantly: (1) with dip of the detachment; and (2) for synthetic and antithetic cases, in which the domino-style faults dip in the same or opposite direction, respectively, as the detachment. When other factors (e.g. rotation and fault dips) are held constant, horizontal extension greatly increases for moderate detachment dips and moderately decreases for antithetic detachment dips, as compared to the horizontal detachment case. This is important because the synthetic case has been widely reported.  相似文献   

3.
青藏高原中部第四纪左旋剪切变形的地表地质证据   总被引：7，自引：5，他引：2  
在青藏铁路的格尔木—拉萨段进行的活动断裂调查发现,在沱沱河—五道梁之间宽约150km的地段内发育了多条由北西西向次级断层左列分布构成的北西西向和北西向左旋张扭性断裂带,在断裂带之间则发育"S"型的北东向裂陷盆地和雁列分布的菱形裂陷盆地,盆地边界断裂也为左旋张扭性质。上述断裂带和裂陷带主要形成于第四纪,它们构成了宽约150km的不均匀的左旋简单剪切变形域,该变形域的整体活动性较弱,属于弱的不均匀剪切变形域。但其中的二道沟断陷盆地是个例外,该盆地边界断裂的垂直活动速率约为0 5mm/a,左旋活动速率介于0 8～1 0mm/a之间。而在整个左旋剪切变形带累计的左旋走滑速率不会超过6mm/a,它们所调节的昆仑山与唐古拉山之间的地壳南北缩短量也可能仅占总缩短量的15%～30%。上述弱剪切变形域与强烈左旋走滑的昆仑断裂系共同构成了高原中部的左旋剪切变形带,它们在印度板块与欧亚板块强烈碰撞的构造动力学背景下,起着调节青藏高原南北向缩短的重要作用。  相似文献   

4.
The Patras, Corinth, and northern Saronic gulfs occupy a 200-km-long, N120° trending Pleistocene rift zone, where Peloponnese drifts away from mainland Greece. The axes of Patras and Corinth basins are 25 km apart and linked by two transfer-fault zones trending N040°. The older one defines the western slope of Panachaïkon mountain, and the younger one limits the narrow Rion–Patras littoral plain. Between these two faults, the ca. 4-km-thick Rion–Patras series dips 20–30° SSW. It is part of the Patras gulf synrift deposits, which pile in an asymmetric basin governed by a fault dipping ca. 25–35° NNE, located in the southern Gulf of Patras. Mapping of this fault to the east in northern Peloponnese shows that it is an inactive north-dipping low-angle normal fault (0° to 30°N), called the northern Peloponnese major fault (NPMF). The structural evolution of the NPMF was different in the gulfs of Patras and Corinth. In the Gulf of Patras, it is still active. In northern Peloponnese, footwall uplift and coeval southward tilting flattened the fault and locked its southern part. Steeper normal faults formed north of the locked area, connecting the still active northern part of the NPMF to the surface. After several locks, the presently active normal faults (Psathopyrgos, Aigion, Helike) trend along the southern shore of the Gulf of Corinth. This migration of faults caused the relative 25 km northward shift of the Corinth basin, and the formation of NE–SW trending transfer-faults between the Corinth and Patras gulfs.  相似文献   

5.
The linkage between the development of south-facing Cretan graben and large-scale detachment faulting in the southern Aegean is unknown. Widespread Serravallian deposits in the Ierapetra graben of Crete supply constraints to Middle Miocene graben development in the southern Aegean. The Ierapetra graben, and by inference the Cretan graben in general, were hitherto believed to have formed as a result of sinistral transpression during N–S shortening. We argue that the formation of the Cretan graben is due to N–S extension. The south-dipping, N–S-extending Kritsa normal fault served as the master fault controlling graben development in the Ierapetra graben. The Kritsa normal fault is either an antithetic fault related to the top-N Cretan detachment or a synthetic fault associated with the top-S Ios detachment. The overall geometry and timing relationships lead us to favour a connection with the Ios detachment, which in turn implies a large-scale displacement on the Ios detachment.  相似文献   

6.
利用地震资料、油气勘探资料分析了南海北部大陆边缘珠江口-琼东南新生代盆地断裂系统的时空差异及动力学成因机制.珠江口-琼东南盆地古近系裂陷构造层以NE向、近EW向基底正断层构成的伸展断裂系统的几何学、运动学沿着盆地走向有明显变化,盆地内部隐伏的区域性和局部的NW向断裂及相关构造变形带构成伸展断裂系统之间的构造变换带.在空间上,区域性的云开、松涛-松南等NW向构造变换带以西为NE-NEE向正断层构成的"非拆离"伸展断层系,以东为NE向正断层、近EW向正断层(走滑正断层)复合而成的拆离伸展断层系.在时间上,古近纪裂陷作用可划分为早(文昌组沉积期)、中(恩平组/崖城组沉积期)、晚(珠海组/陵水组沉积期)3个有明显差异的裂陷期.裂陷早期,盆地西部以平面式正断层控制的简单地堑、半地堑为主,伸展量相对较小,东部则以铲式正断层控制的复式地堑、半地堑为主,伸展量相对大,断层向深部收敛在中地壳韧性层构成拆离的伸展断层系统.裂陷中期,琼东南盆地、珠江口盆地西部断裂具有继承性活动特点,珠江口盆地东部发育NWW-EW向伸展断层,并向深层切割早期浅层拆离断层,形成深层拆离伸展断层系统,而沿着云开构造变换带发育反转构造.裂陷晚期,琼东南盆地、珠江口盆地西部断裂具有活动性减弱特点,琼东南盆地东部发育NWW-EW向伸展断层,形成深层拆离伸展断层系统,而沿着琼中央构造变换带发育反转、走滑构造.珠江口-琼东南盆地不同区段断裂系统及其构造演化的差异性受盆地基底先存构造、地壳及岩石圈结构及伸展量等多方面因素的影响,拆离伸展断层系统与发育NWW向"贯穿"断裂的基底构造薄弱带、现今地壳局部减薄带相关,南海扩展由东而西的迁移诱导北部大陆边缘块体沿着先存NW向深大断裂发生走滑旋转是导致变换构造带两侧差异伸展的动力学原因,应力场及岩石圈热结构变化是引起拆离断层深度变化的重要因素.  相似文献   

7.
Extension in the Afar depression occurs on steeply dipping normal faults of many scales. An estimate for cumulative extension can be derived by summing the heave of these faults using digital topographic data, supplemented by field observations of fault dip. If it can be established that the distribution of faults exhibits self-similarity, an estimate of the contribution from faults too small to appear on the digital imagery can be incorporated into the integrated estimate for cumulative extension. A field study of faulting was undertaken within the Dobe and Guma grabens of Central Afar. A fractal dimension of 0.48 was obtained for the measured population of fault throws (n = 92) in 3 traverses totaling 42 km, a value interpreted to represent the dominant contribution to extension from faults with large throw. The local extension rate across Guma graben is estimated to be between 0.06 and 0.24 mm/year. The higher topographic position of the floor of Guma graben, relative to the sediment filled, adjacent floors of Dobe and Immino grabens is perhaps an indication of a slower rate of extension across Guma graben as compared to Dobe and Immino grabens, assuming they all initiated at the same time.  相似文献   

8.
The Gulf of Corinth, Greece, is a 110-km-long by 30-km-wide active graben displaying strong seismicity hosted both on north and south dipping normal faults. This complex fault pattern consists of two fault populations, offshore and onshore. The offshore fault population is investigated by densely arranged seismic reflection profiles during the last 20 years, whereas the onshore fault population displays spectacular and well exposed faults, delineated by high accuracy mapping. We analyzed fault length and throw, in order to study the scaling properties of 136 well-determined offshore and onshore faults and the comparison between the two datasets. We examined the statistical properties on both fault populations, in order to describe the role of segmentation in the growth of faults and the different stages of the evolution of the fault networks.Our results on power law relationships associated with the scaling properties of the fault zones in the Gulf of Corinth, suggest that both fault populations are bi-fractal, providing the initiation of a sature state in deformation. In addition, the vertical throw of faults shows that both fault populations have similar properties but different distributions below and above 5 km, respectively. Displacement–length ratios, show that faults larger than 9 km appear to accumulate throw without any dramatic change to their length. These observations combined with other geophysical studies within the Gulf, suggest that the characteristic fault lengths of 5 km and 9 km can be correlated to the crustal mechanical structure and the seismicity of the Gulf.  相似文献   

9.
The Isparta Angle (IA) is a reverse Λ-shaped morphotectonic structure located to the north of Antalya Gulf in the Eastern Mediterranean Sea. It resulted from the northward curvature of the originally E–W-trending Tauride orogenic belt owing to the nappe emplacements and related clockwise and anti-clockwise rotations in a time period of Early Paleocene to Early Pliocene. The IA is included in the southwest Anatolian tensional neotectonic domain and characterized by a series of grabens and horsts bounded by active normal faults of dissimilar length and trend. The evolutionary history of the graben-horst system is episodic. It is evidenced by two graben fills. These are older and modern (younger) graben fills separated by an intervening angular unconformity. The modern graben fill is nearly flat-lying (non-deformed) whereas older graben fill was deformed into a series of anticlines and synclines with ENE-trending curvi-linear axes by a short-term compressive tectonic regime operated in NNW–SSE direction during Late Pliocene. The diagnostic structures taking a part in the development of grabens and shaping the northern section of the IA are the margin-boundary normal faults. They occur in numerous single and several fault zones displaying a basin ward facing step-like land shape. Most of fault segments, particularly the master faults, are active and have a capacity of creating destructive earthquakes with a magnitude (up to Mw?=?7.0). This is evidenced by both the historical and instrumental period earthquakes. Both the focal mechanism solution of earthquakes and the stereographic plots of slip-plane data, measured on the active margin-boundary faults of various grabens comprising the IA, on the Schmidt lower hemisphere net obviously reveal that the IA is under the influence of the tensional neotectonic regime, not a compressive tectonic regime, i.e. the sinistral strike-slip shearing along the Pliny arc has not propagated yet onshore, and its commencement age is Early Quaternary.  相似文献   

10.
A number of basins are observed to extend inland from the coasts on both sides of the Gulf of Aden. The basins are orientated at approximately right angles to the spreading direction and intersect the coasts at the meeting of sheared and rifted continental margins. They appear to be grabens, one wall of which is continuous with the half graben of the neighbouring rifted margin. It is suggested that these were once parts of a number of discrete rifts arranged en-echelon along a zone of lithospheric weakness during the early opening of the Gulf of Aden, which became redundant when transform faults formed. The proposed development of rifts and transform faults is similar to that of a spreading centre, transform fault, spreading centre pattern developed in the freezing wax model of Oldenburg and Brune (1975). The Gulf of Suez at the northern end of the Red Sea is interpreted in a similar way since it has a number of features in common with the basins in the continents adjacent to the Gulf of Aden.  相似文献   

11.
The easternmost sector of the Gulf of Corinth, the Beotia area in Central Greece, is an area with active normal faults located between the two major rift structures of Central Greece, the Gulf of Corinth and the North Gulf of Evia. These active normal faults include WNW to E–W and NE to ENE-trending faults affect the landscape and generate basin and range topography within the Beotia. We study four normal fault zones and drainage basin geometry in the easternmost sector of the Gulf of Corinth to document the impact of active tectonics on the landscape evolution. Fault and drainage geometry are investigated based on detailed field mapping and high-resolution digital elevation models. Tectonic geomorphic analysis using several parameters of active tectonics provides information concerning the relative tectonic activity and fault growth. In order to detect areas of lateral stream migration that could indicate recent tectonic activity, the Transverse Topographic Symmetry Factor and the Asymmetry Factor are used to analyse drainage basin geometry in six large drainage basins and a drainage domain covering the study area. Our results show that vertical motions and tilting associated with normal faulting influence the drainage geometry and its development. Values of stream-gradient indices (SL) are relatively high close to the fault traces of the studied fault zones suggesting high activity. Mountain-front sinuosity (Smf) mean values along the fault zones ranges from 1.08 to 1.26. Valley floor width to valley height ratios (Vf) mean values along the studied fault zones range between 0.5 and 1.6. Drainage basin shape (BS) mean values along the fault zones range from 1.08 to 3.54. All these geomorphic parameters and geomorphological data suggest that the analyzed normal faults are highly active. Lateral fault growth was likely produced by primarily eastward propagation, with the WNW to E–W trending faults being the relatively more active structures.  相似文献   

12.
张建培 《地质科学》2013,(1):291-303
综合运用地震剖面解释结果和构造编图成果,对东海西湖凹陷平湖斜坡带断裂系统按发育规模和形成期次进行分类,分析了断裂系统的平、剖面展布特征,采用古落差法和活动速率法研究了断裂运动学特征,结合区域应力场特征探讨了其成因机制。结果表明,平湖斜坡带断裂系统可划分为4个断裂带,由北至南依次为孔雀亭同向断裂带、武云亭反向断裂带、平湖同向断裂带和平南堑式断裂带。平湖斜坡带以发育多米诺、地堑、梳妆、正牵引等伸展构造样式为主,局部(如平湖同向断裂带)见微弱反转构造。断裂运动学特征研究表明,断裂活动高峰期具有分带性,平湖同向断裂带断层活动性最强,孔雀亭同向断裂带和武云亭反向断裂带次之,平南堑式断裂带最弱。平湖斜坡带断裂系统的发生、发展是应力集中与断层间相互影响共同作用的结果,是对东海陆架盆地构造演化过程的局部响应。  相似文献   

13.
Interpretation of seismic data from the Lufeng Sag of the Pearl River Mouth Basin (PRMB) in the northern part of South China Sea shows that different intersection patterns developed in the cover units above basement normal faults. A series of analogue models are used to investigate the intersection patterns and deformation in the sedimentary cover sequences above a basement horst bounded by two non-parallel faults. Modelling results show that during their upward propagation, the basement faults may intersect within the cover sequences and form a graben above the basement horst. Length and width of the graben increase with cover thickness. The strike and dip intersection points are controlled directly by the thickness of the cover sequences, dip and strike of the basement faults, and width of the basement horst. The intersection point migrates along the axis of the graben toward the wide end of the basement horst, when the cover sequence thickens. In contrast, it migrates toward the narrow end of the basement horst, where both fault dip and angle of strike difference increase. The intersection point moves upward with increasing width of the basement horst crest. Model profiles also indicate that in the presence of a ductile layer between the cover and basement such intersection patterns do not form. Interpretation of seismic data and model results show that the intersection pattern developed in the Lufeng Sag is a result of propagation of basement faults into cover units during different extension stages of the basin. Results of this study can be applied to many other sedimentary basins where such fault intersection patterns are likely to form when non-parallel conjugate basement faults are active during sedimentation.  相似文献   

14.
Apatite fission-track analyses indicate that the Kazda? Massif in northwestern Anatolia was exhumed above the apatite partial annealing zone between 20 and 10 Ma (i.e. early-middle Miocene), with a cluster of ages at 17–14 Ma. The structural analysis of low-angle shear zones, high-angle normal faults and strike-slip faults, as well as stratigraphic analysis of upper-plate sedimentary successions and previous radiometric ages, point to a two-stage structural evolution of the massif. The first stage -encompassing much of the rapid thermal evolution of the massif- comprised late Oligocene-early Miocene low-angle detachment faulting and the associated development of small supradetachment grabens filled with a mixture of epiclastic, volcaniclastic and volcanic rocks (Küçükkuyu Fm.). The second stage (Plio-Quaternary) has been dominated by (i) strike-slip faulting related to the westward propagation of the North Anatolian fault system and (ii) normal faulting associated with present-day extension. This later stage affected the distribution of fission-track ages but did not have a component of vertical (normal) movement large enough to exhume a new partial annealing zone. The thermochronological data presented here support the notion that Neogene extensional tectonism in the northern Aegean region has been episodic, with accelerated pulses in the early-middle Miocene and Plio-Quaternary.  相似文献   

15.
Eight two-dimensional, multichannel seismic reflection lines were acquired, processed, and interpreted to study the structure of the Altar Basin, which is part of the Salton Trough tectonic province. We identified two basin-bounding zones characterized by different degrees of strain: the Cerro Prieto–Altar deformation zone (CPADZ) and the Altar–Caborca deformation zone (ACDZ). The CPADZ is bounded on the west by the Cerro Prieto fault and on the east by the Altar fault. To the north, the strike of both faults changes slightly from a NW to more NNW direction. In the CPADZ, the thickness of the crust decreases southward towards the Gulf of California, and is associated with a deformation-developing fault. The CPADZ has a rotation component orientating these faults in an oblique direction to the Cerro Prieto fault, whereas within the ACDZ, a geometric coherence of synthetic and antithetic faults exists, creating horsts and graben striking N37° W. The Altar fault is recognized by basement interruption, with a vertical component of ～1 km, striking at N37° W and dipping 83° SW. On the northeastern side of the Altar Basin, the basement configuration shows that the minimum time of basement record (～0.4 s of two-way travel time) and the time curve gradient decrease in the NE–SW direction. The depocentre is ～6 km deep in the central-west portion of the basin. We identified a graben between the Rosario and Tinajas Altas mountains (Rosario Basin). The extension–connection of the Altar and Rosario basins to the south is not well defined; nevertheless, these basins could represent the link between the Colorado River and the Gulf of California during the late Miocene, whereas this link was abandoned in the Pliocene as subsidence migrated towards the northwest into the Cerro Prieto and Laguna Salada basins.  相似文献   

16.
Photogrammetric analysis of aerial photographs is used to investigate morphological changes in two large landslides located adjacent to the active Marathias normal fault along the Gulf of Corinth, Greece. This E–W trending fault intersects at almost right angles a series of west-verging and east-dipping thrust faults, and has a clear geomorphic expression. The fault's structural signature, such as the trace length, displacement, segmentation, and scarp freshness resembles other normal faults within the Gulf of Corinth. Along this fault we mapped a series of landslides that are mainly concentrated at the near tip areas. Two of them are hosted in the damage zone formed by the intersecting normal and reverse faults. The Marathias and Sergoula landslides show a significant geomorphic evolution on aerial photographs from 1945 to 1991.

Evolution of landslides in the study area appears to be correlated with two earthquake clusters that drive mass wasting in the order of 106 m3, significant drainage adjustment, and triggering of post-landslide river incision. We infer the following process sequence for these presumably earthquake-triggered landslides in the region: eroded material in Marathias landslide and reactivation of movement within the main body of the Sergoula landslide were observed in 1969 aerial photographs. Both landslides are deep-seated rotational rockslides. Obstruction or abandonment of channels due to the landslides establishes river incision and a dramatic increase of the rate of fan-delta progradation in the order of 1 m/yr. These large landslides are related to strong (M > 6.5) earthquakes concentrated along faults, and their reactivation period is almost a century, based on seismological or paleoseismological analyses.  相似文献   


17.
We present a series of high-resolution seismic reflection lines across the Yizre'el valley, which is the largest active depression in Israel, off the main trend of the Dead Sea rift. The new seismic reflection data is of excellent quality and shows that the valley is dissected into numerous small blocks, separated by active faults. The Yizre'el valley is found to consist of a series of half grabens, rather than a single half graben, or a symmetrical graben. The faults are generally vertical and appear to have a dominant strike-slip component, but some dip-slip is also evident. A marked zone of compression near Megido is associated with the intersection of the two largest faults in the valley, the Carmel fault and the Gideon fault. Variable trend of the faults reflects the complexity of the local geology along the boundary between the wide NW–SE trending Farah–Carmel fault zone and the E–W trending basins and ranges in the Lower Galilee. This tectonic complexity is likely to result from a highly variable stress pattern, modified by the structures inside it. Normal faulting in the valley occurred at an early stage of its development as a tectonic depression. However, strike-slip motion on the Carmel fault, and possibly also on some of the other faults, appears to have started together with the onset of normal faulting. Earthquake hazard in the area appears to be uniform as faults are distributed throughout the Yizre'el valley.  相似文献   

18.
《Geodinamica Acta》2013,26(3-4):167-208
The Denizli graben-horst system (DGHS) is located at the eastern-southeastern converging tips of three well-identified major grabens, the Gediz, the Küçük Menderes and the Büyük Menderes grabens, in the west Anatolian extensional province. It forms a structural link between these grabens and the other three NE-NW-trending grabens—the Çivril, the Ac?göl and the Burdur grabens—comprising the western limb of the Isparta Angle. Therefore, the DGHS has a critical role in the evolutionary history of continental extension and its eastward continuation in southwestern Turkey, including western Anatolia, west-central Anatolia, and the Isparta Angle. The DGHS is a 7-28-km wide, 62-km long, actively growing and very young rift developed upon metamorphic rocks of both the Menderes Massif and the Lycian nappes, and their Oligocene-Lower Miocene cover sequence. It consists of one incipient major graben, one modern major graben, two sub-grabens and two intervening sub-horsts evolved on the four palaeotectonic blocks. Therefore, the DGHS displays different trends along its length, namely, NW, E-W, NE and again E-W.

The DGHS has evolved episodically rather than continuously. This is indicated by a series of evidence: (1) it contains two graben infills, the ancient graben infill and the modern graben infill, separated by an intervening angular unconformity; (2) the ancient graben infill consists of two Middle Miocene-Middle Pliocene sequences of 660 m thickness accumulated in a fluvio-lacustrine depositional setting under the control of first NNW-SSE- and later NNE-SSW-directed extension (first-stage extension), and deformed (folded and strike-slip faulted) by a NNE-SSW- to ENE-WSW-directed phase of compression in the latest Middle Pliocene, whereas the modern graben infill consists of 350-m thick, undeformed (except for local areas against the margin-bounding active faults), nearly flat-lying fanapron deposits and travertines of Plio-Quaternary age; (3) the ancient graben infill is confined not only to the interior of the graben but is also exposed well outside and farther away from the graben, whereas the modern graben infill is restricted to only the interior of the graben. These lines of evidence imply an episodic, two-stage extensional evolutionary history interrupted by an intervening compressional episode for the DGHS.

Both the southern and northern margin-bounding faults of the DGHS are oblique-slip normal faults with minor right- and/or left-lateral strike-slip components. They are mapped and classified into six categories, and named the Babada?, Honaz, A?a??da?dere, Küçükmal?da?, Pamukkale and Kaleköy fault zones, and composed of 0.5-36-km long fault segments linked by a number of relay ramps. Total throw amounts accumulated on both the northern and southern margin-bounding faults are 1,050 m and 2,080 m, respectively. In addition, the maximum width of the DGHS and the thickness of the crust beneath it are more or less same (~ 28 km). The total of these values indicate a vertical slip rate of 0.15-0.14 mm/year and averaging 7% extension for the asymmetrical DGHS.

The master faults of the Babada?, Honaz, Küçükmal?da?, Pamukkale and Kaleköy fault zones are still active and have a potential seismicity with magnitudes 6 or higher. This is indicated by both the historical (1703 and 1717 seismic events) to recent (1965, 1976, 2000 seismic events) earthquakes sourced from margin-bounding faults and some diagnostic morphotectonic features, such as deflected drainage system, degraded alluvial fans with apices adjacent to fault traces, back-tilting of fault-bounded blocks, and actively growing travertine occurrences. The kinematic analyses of main fault-slip-plane data, Upper Quaternary fissure ridges and focal-mechanism solutions of some destructive earthquakes clearly indicate that the current continental extension (second-stage extension) by normal faulting in the DGHS continues in a (mean) 026° to 034° (NNE-SSW) direction.

Detailed and recent field geological mapping, stratigraphy of the Miocene-Quaternary basins, palaeostress analysis of fault populations and main margin-bounding faults of these basins, extensional gashes to fissures, and focal-mechanism solutions of destructive earth-quakes that have occurred in last century strongly indicate that extension is not unidirectional and confined only to western Anatolia, but also continues farther east across the Isparta Angle and west-central Anatolia, up to the Salt Lake fault zone in the east and the inönü-Eski?ehir fault zone in the north-northeast. Therefore, the term “southwest Turkey extensional province” is proposed in lieu of the term “west Anatolian extensional province”.  相似文献   

19.
为了研究含油气盆地中断裂对油气成藏与分布的控制作用,在断层侧向封闭机理及影响因素研究的基础上,对反向断裂下盘较顺向断裂上盘更易富集油气的机理进行了定量解释。结果表明,无论是反向断裂还是顺向断裂,均源于断层岩封闭油气,断层岩油气运移方向排替压力是影响其侧向封闭油气能力的主要因素。在断裂埋深、断裂倾角和地层岩性、地层倾角相同的条件下,理论上反向断裂断层岩泥质体积分数大于顺向断裂断层岩泥质体积分数,即反向断裂断层岩油气运移方向排替压力大于顺向断裂断层岩油气运移方向排替压力,反向断裂侧向封闭能力强于顺向断裂侧向封闭能力,造成反向断裂下盘较顺向断裂上盘更易富集油气。歧口凹陷板桥断裂下盘沙一段下部断层岩在反向条件和顺向条件下油气运移方向排替压力的实例研究结果表明,反向条件下较顺向条件下在油气运移方向有更高的排替压力,侧向封闭能力更强,更有利于油气在板桥断裂下盘沙一段储层中富集。  相似文献   

20.
Gravity, magnetic, and seismic surveys were conducted across the Wasatch fault zone east of Springville, Utah, near the mouth of Hobble Creek Canyon. The geophysical data were acquired, processed, and interpreted to determine possible locations of larger [total offset greater than 6 ft (1.8 m)], shallow normal faults within the fault zone. Interpretations of the individual data sets were integrated to help eliminate spurious readings and to strengthen the interpretations. Visual methods of integration, along with computer modeling, were chosen for this study. Furthermore, the geophysical data were correlated and integrated with available trench data and surface data. In addition to verifying locations of known faults, the geophysical surveys detected numerous possible additional faults not previously mapped. Of particular interest is a newly discovered graben structure near the southern end of the site, where building of new homes has recently been proposed.

New structural information about fault densities and styles was also determined from the surveys. The fault concentration for this site is 1.3 faults/100 ft (30.5 m), or one fault per 77 ft (23.5 m). Interpreted antithetic faults at the Hobble Creek site account for 65% of the total, while synthetic faults account for 35% with respect to the main fault strand.

Information derived from this study should be useful during planning and development of areas within the Wasatch fault zone. The characteristics of subsurface deformation can be used to gain a better understanding of the potential for surface rupture at a given site. This is also useful in planning appropriate site development and remedial measures to help mitigate hazards associated with large-magnitude earthquakes.  相似文献   


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