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1.
Baroux  Avouac  Bellier  & Sébrier 《地学学报》1998,10(3):139-144
Oblique subduction at the Sunda Trench has produced transpressive deformation of the plate leading edge. A major feature is the right-lateral Great Sumatran Fault (GSF) which probably absorbs a significant fraction of the trench-parallel shear. The kinematics of Sunda relative to Australia are discussed on the basis of available GPS data, and geologically determined slip rates on the GSF. In spite of the uncertainty on the plate motion, several robust conclusions can be drawn. The predicted obliquity of the convergence increases northward along the Sumatra Trench, up to about 30°. Slip partitioning is nearly complete along the northern segment of the Sumatra Trench, where the GSF probably accommodates most of the trench parallel shear. Along the southern segment, where obliquity is less than about 20°, slip-partitioning is not complete as indicated by oblique thrusting at the subduction. There, only a fraction of the trench parallel motion of Australia relative to SE Asia is accommodated along the GSF. These observations suggest that the leading edge behaves like a plastic wedge, except that slip-partitioning, although incomplete, is observed even at low obliquities.  相似文献   

2.
The results of radiometric dating of granitic rocks around Kotanopan near the west coast of Central Sumatra indicate an average age of 45 million years.Granites from the Lassi Mass in the Padang Highlands, Central Sumatra, and the Lampong Mass, South Sumatra, possess radiometric ages of ca. 112 and ca. 88 m.y., respectively. Granites and other rocks from the offshore areas north of Java indicate an average age of 100 m.y.Late Cretaceous granitic rocks are present in the islands of the Sunda Shelf namely Anambas (ca. 86 m.y.), Tembelan (ca. 85 m.y.) and Natuna (ca. 75 m.y.).Late Paleozoic granites possessing ages of ca. 276–298 m.y. are encountered in the basement rocks near Djambi, South Sumatra.The outcome of this radiometric age dating proves to be significant for it permits a fresh analysis of the geological evolution of Indonesia based on the plate-tectonics concept.The Tertiary volcano-plutonic arc exposed along the west coast of Sumatra can be traced to the south coast of Java. The corresponding subduction zone can be found in the islands west of Sumatra and the submarine ridge south of Java.The Late Cretaceous plutonic belt of Sumatra does not continue to Java but passes north of it, running however parallel to the subduction zone of Java. These two zones merge in the Meratus Mountains of Southeast Kalimantan.Sumatra was already a volcano-plutonic arc during Permian time, suggesting that since this Period the margins of at least four lithospheric plates have remained near the side of the active Sumatran arc.The presence of Permian volcanic and granitic rocks in the Malay Peninsula and West Kalimantan, and the results of the radiometric age determination of granitic rocks from the islands situated in the Sunda Shelf area, point to the existence of other Permian and Cretaceous volcano-plutonic arcs east and north of the arcs previously described in Sumatra and Java. Thus a double volcano-plutonic arc with opposing Benioff zones must have existed during Permian and Cretaceous time in this area.The Schwaner Mountains of West Kalimantan are considered to be the place where volcano-plutonic arcs of different ages have merged together. The correlative subduction zones have to be sought in the so-called Danau Formation of West Kalimantan and the northern part of the Kuching zone, the Sibu zone of Serawak situated north of the Schwaner Mountains.The evolution and complex geology of the western part of Indonesia can only be understood by the supposition of the existence of megaplates and sub-plates generated from spreading centers situated in the Indian Ocean and presumably in the area of the South China Sea, respectively.  相似文献   

3.
Spatial and temporal analysis of global seismological data 1964–2005 reveals a distinct teleseismic earthquake activity producing a columnar-like formation in the continental wedge between the Krakatau volcano at the surface and the subducting slab of the Indo-Australian plate. These earthquakes occur continuously in time, are in the body-wave (m b) magnitude range 4.5–5.3 and in the depth range 1–100 km. The Krakatau earthquake cluster is vertical and elongated in the azimuth N30°E, suggesting existence of a deep-rooted fault zone cutting the Sunda Strait in the SSW-NNE direction. Possible continuation of the fault zone in the SW direction was activated by an intensive 2002/2003 aftershock sequence, elongated in the azimuth of N55°E. Beneath the Krakatau earthquake cluster, an aseismic gap exists in the Wadati-Benioff zone of the subducting plate at the depths 100–120 km. We interpret this aseismic gap as a consequence of partial melting inhibiting stress concentration necessary to generate stronger earthquakes, whereas the numerous earthquakes observed in the overlying lithospheric wedge beneath the volcano probably reflect magma ascent in the recent plumbing system of the Krakatau volcano. Focal depth of the deepest events (~100 km) of the Krakatau cluster constrains the location of the primary magma generation to greater depths. The ascending magmatic fluids stress fault segments within the Sunda Strait fault zone and change their friction parameters inducing the observed tectonic earthquakes beneath Krakatau.  相似文献   

4.
A suite of tsunami spaced evenly along the subduction zone to the south of Indonesia (the Sunda Arc) were numerically modelled in order to make a preliminary estimate of the level of threat faced by Western Australia from tsunami generated along the Arc. Offshore wave heights from these tsunami were predicted to be significantly higher along the northern part of the west Australian coast than for the rest of the coast south of the town of Exmouth. In particular, the area around Exmouth may face a higher tsunami hazard than other areas of the West Australian coast nearby. Large earthquakes offshore of Java and Sumbawa are likely to be a greater hazard to WA than those offshore of Sumatra. Our numerical models indicate that a magnitude 9 or above earthquake along the eastern part of the Sunda Arc has the potential to significantly impact a large part of the West Australian coastline. The Australian government reserves the right to retain a non-exclusive, royalty free license in and to any copyright.  相似文献   

5.
Earthquake foci suggest that the India plate has been underthrust in the Sunda Arc to depths increasing from little more than 200 km beneath central Sumatra to well over 600 km beneath the Java Sea. Geological differences between Sumatra and Java do not fully account for the anomaly. The explanation would appear to lie with an oblique India-Eurasia convergence caused by the rotation, relative to Eurasia, of the Sunda backarc area. Sinistral movements on several southeast-trending wrench faults in the region between Yunnan and Java appear to have been responsible. Backarc rotation also explains the pattern of Cenozoic volcanicity in Sumatra, and resolves controversy over the nature of the Andaman Basin, which may be interpreted as a rhombochasm forming behind a locally divergent plate margin.  相似文献   

6.
B. Sundvoll  B.T. Larsen   《Tectonophysics》1994,240(1-4):173-189
A revised assessment of architecture and pre-rift fabric connections of the Oslo Rift has been undertaken and linked to a new appraisal of observations and data related to the initial phase of the rift evolution. In addition to half-graben segmentation, accommodation zones and transfer faults are readily identified in the linking sectors between the two main grabens and between graben segments. Axial flexures are proposed between facing half-grabens. The accommodation zones were generally sites of volcanism during rifting. Pre-rift tectonic structures played an influential role in the rift location and development. The deviant N-S axis of the Vestfold graben segment is viewed as related to pre-rift structural control through faults and shear zones. This area was probably a site of Proterozoic/Palaeozoic crustal and lithospheric attenuation.

Field evidence suggests that the rift started as a crustal sag with no apparent surface faulting in a flat and low-lying land at a time about 305–310 Ma. Volcanism, sub-surface sill intrusion and faulting started about simultaneously some time after the initial sag (300–305 Ma). Faulting and basaltic volcanism were initially localized to transfer faults along accommodation zones and a NNW-SSE transtensional zone along the eastern margin of the incipient Vestfold graben segment. This transtensional zone was probably created by right-lateral simple shear tracing pre-rift structures in response to a regional stress field with the tensional axis normal and the maximum compressional axis parallel to the NNE-SSW-trending rift axis.  相似文献   


7.
The formation of the Makassar Strait, situated between southeast (SE) Kalimantan and western Sulawesi, is still subject of much debate. Different authors have proposed several hypotheses to explain its evolution. The only agreement between those several hypotheses is that SE Kalimantan and western Sulawesi once lay close together and that their separation is due to the opening of the Makassar Strait. The age and driving mechanism for this opening are, however, still poorly understood. The strait separates the stable core of the Eurasian Plate to the west from the very active region of the triple junction of three large plates to the east. To the north the strait is bounded by the Sulawesi Sea and to the south by the East Java Sea. The strait is roughly 100–200 km wide and 300 km long and is usually divided into the North and South Makassar basins, separated by the Paternoster Fault. The present study interprets the history of the Makassar Strait using seismic reflection profiles and gravity models, in addition to the compilation of geological information. Implications for the origin of rifting is also discussed. The result of the present study indicates that Makassar Strait was formed by the vertical sinking of a subducting oceanic plate to the east of western Sulawesi, leading to trench roll-back. This vertical sinking was accommodated by extension and rifting of continental crust above the subduction zone at a previous site of collision, causing the opening of Makassar Strait. The time of this trench roll-back marks the cessation of subduction.  相似文献   

8.
Eastern Indonesia is the zone of interaction between three converging megaplates: Eurasia, the Pacific and Indo-Australia. The geological basis for interpretations of the Tertiary tectonic evolution of Eastern Indonesia is reviewed, and a series of plate tectonic reconstructions for this region at 5 million year intervals covering the last 35 million years is presented.The oldest reconstruction predates the onset of regional collisional deformation. At this time a simple plate configuration is interpreted, consisting of the northward-moving Australian continent approaching an approximately E–W oriented, southward-facing subduction zone extending from the southern margin of the Eurasian continent eastwards into the Pacific oceanic domain. Beginning at about 30 Ma the Australian continental margin commenced collision with the subduction zone along its entire palinspastically-restored northern margin, from Sulawesi in the west to Papua New Guinea in the east. From this time until ca 24 Ma, the Australian continent indented the former arc trend, with the northward convergence of Australia absorbed at the palaeo-northern boundary of the Philippine Sea Plate (the present-day Palau-Kyushu Ridge).At ca 24 Ma the present-day pattern of oblique convergence between the northern margin of Australia and the Philippine Sea Plate began to develop. At about this time a large portion of the Palaeogene colliding volcanic arc (the future eastern Philippines) began to detach from the northern continental margin by left-lateral strike slip. From ca 18 Ma oblique southward-directed subduction commenced at the Maramuni Arc in northern New Guinea. At ca 12 Ma the Sorong Fault Zone strike-slip system developed, effectively separating the Philippines from the Indonesian tectonic domain. The Sorong Fault Zone became inactive at ca 6 Ma, since which time the tectonics of eastern Indonesia has been dominated by the anticlockwise rotation of the Bird’s Head structural block by some 30–40°.Contemporaneously with post-18 Ma tectonism, the Banda Arc subduction–collision system developed off the northwestern margin of the Australian continent. Convergence between Indo-Australia and Eurasia was accommodated initially by northward subduction of the Indian Ocean, and subsequently, since ca 8 Ma, by the development of a second phase of arc-continent collision around the former passive continental margin of NW Australia.  相似文献   

9.
Pumice flow from the 1883 Krakatau eruption significantly differs in both mineral and chemical compositions from any other volcanic rocks or ejecta of the Krakatau group, which belong to the tholeiitic series. Lithic fragments of granitic Rock, discovered in the pumice flow, are similar to West Malayan granitic rocks. No other granitic rock occurs throughout the Krakatau group, therefore, we consider that the granitic fragments came from the underlying complex at depths, where they were captured as foreign materials by the magma.It is possible that sialic crustal materials plunged into depths along a peculiar tectonic structure located at the Sunda Strait, which appears to be a sheared portion caused by deformation of the Sunda arc due to differential movement between the Indo-Australian oceanic plate and the Eurasian continental crust. The crustal materials were partially melted and produced a magma of granitic composition. The magma was mixed with or assimilated by an ascending basaltic magma originating probably from the upper mantle. This resulted in a dacitic magma distinctly dominant in silica, alkalis and volatile components, and the 1883 Krakatau eruption, characterized by the pumice flow of dacitic composition, took place.  相似文献   

10.
《地学前缘(英文版)》2020,11(4):1123-1131
Collision between the Indian and Eurasian plates formed the ～2500 km long Yarlung Zangbo Suture Zone and produced the Himalaya mountains and Tibetan plateau.Here we offer a new explanation for tectonic events leading to this collision:that the northward flight of India was caused by an Early Cretaceous episode of subduction initiation on the southern margin of Tibet.Compiled data for ophiolites along the Yarlung Zangbo Suture Zone show restricted ages between 120 Ma and 130 Ma,and their supra-subduction zone affinities are best explained by seafloor spreading in what became the forearc of a north-dipping subduction zone on the southern margin of Tibet.The subsequent evolution of this new subduction zone is revealed by integrating data for arcrelated igneous rocks of the Lhasa terrane and Xigaze forearc basin deposits.Strong slab pull from this new subduction zone triggered the rifting of India from East Gondwana in Early Cretaceous time and pulled it northward to collide with Tibet in Early Paleogene time.  相似文献   

11.
Indian Ocean subduction zone is one of the most active plate margins of the globe as evident from its vast record of great magnitude earthquake and tsunami events. We use Bouguer admittance (Morlet isostatic response function) in Sumatra-Java subduction zones comprising both the subduction and over-riding plates to determine the lithospheric mechanical strength variations. We determine effective elastic thickness (T e ) for five oceanic windows (size 990 × 990 km2) by analyzing the admittance using Bouguer gravity and bathymetry data. The results show bimodal T e values < 20 km for Sumatra and 20−40 km for Java. The lower bimodal values obtained for Sumatra appears to correlate well with the zones of historical seismicity. This is in sharp contrast with Java subduction zone, which shows higher T e values (20–40 km) and apparently associated with low magnitude earthquakes. We suggest a strong and wide interseismic coupling for Sumatra between the subducting and over-riding plates, and deeper mantle contributing to low strength, shallow focus — high magnitude seismicity and vice versa for Java, leading to their seismogenic zonation.  相似文献   

12.
南美西北部典型含油气盆地构造特征   总被引：4，自引：1，他引：3  
依据盆地处于造山弧的位置不同,将南美西北部盆地群分为弧前盆地、弧内盆地和弧后盆地三类。同一动力学背景下在不同构造部位形成了三类盆地不同的构造特征。弧前盆地具有地垒-地堑式裂陷盆地特点,发育断块油气藏,是安第斯俯冲增生带之上的近东西向张性盆地;弧内盆地位于强烈挤压隆升的造山带之内,是造山带内局部变形相对较弱的地区,发育叠瓦逆冲断层、双重构造和冲起构造;弧后盆地以逆断层反转构造和低幅度背斜构造为主,断裂系统具有走滑性质,是斜向弱挤压环境下的产物,构造平面上具东西向分带的特点,圈闭类型主要是低幅度背斜和岩性圈闭。  相似文献   

13.
Kyushu Island, Japan, is located at the junction of the Southwest Japan arc and the Ryukyu arc. There are two major late Cenozoic epithermal gold-silver provinces in Kyushu, which are termed the Northern and Southern provinces. The provinces are characterized by: 1) Pliocene volcanism dominated by calc-alkaline andesite, followed by Quaternary volcanism including extrusion of both calc-alkaline and tholeiitic magmas; 2) formation of extensional grabens; 3) Pliocene to Pleistocene mineralization, which was dominated by abundant low sulfidation (LS) epithermal deposits with a few high sulfidation (HS) examples. The two epithermal gold-silver provinces have evolved differently since about 5 Ma; the Northern province has exhibited diminished hydrothermal activity from the Pliocene to Pleistocene, whereas the Southern province has witnessed increased hydrothermal activity mainly in easterly and northerly directions. Changes of tectonic setting from the Pliocene to Pleistocene account for the variable trends in epithermal gold deposit formation. Westward oblique subduction of the Philippine Sea plate beneath the Southwest Japan arc caused development of the Hohi graben and arc-related volcanism at about 6 Ma. This was associated with widespread LS mineralization in and surrounding the Hohi graben, as is represented by the Bajo and Taio deposits. The subduction of the relatively buoyant Kyushu-Palau ridge during the early Pliocene strengthened the coupling between the slab and overriding Ryukyu arc, leading to polygenetic andesite volcanism with associated HS (Kasuga, Iwato, and Akeshi) and LS (Kushikino) mineral deposits forming in the Southern province. A change of the subduction direction of the Philippine Sea plate, from west to north-northwest in the early Pliocene, increased the orthogonal convergence rate between the Southwest Japan arc and the Philippine Sea plate, resulting in a decrease of volcanic and hydrothermal activity in the Hohi graben of the Northern province. The more northerly subduction of the Philippine Sea plate shifted the locus of the Kyushu-Palau ridge subduction northward, resulting in underplating of the older (85–60 Ma), negatively buoyant Amami basin oceanic slab in the Southern province, rather than continued subduction of the young (27–15 Ma), buoyant Shikoku basin slab. This replacement caused steepening of the slab angle and slab-rollback in the Southern province, which was associated with regional extension, an eastward shift of the Ryukyu volcanic front, and development of the Kagoshima and Shimabara grabens, as well as the Okinawa trough. Rhyolite and basalt volcanism, in addition to andesite volcanism, have occurred since 2 Ma in the area of the Ryukyu back arc; coincident LS mineralization at Hishikari and Ohkuchi was affiliated with the rhyolite volcanism. Another change of the subduction direction of the Philippine Sea plate to the northwest occurred at 2–1 Ma. The forearc sliver of the Southwest Japan arc shifted westward, in association with right-lateral strike-slip faulting along the Median tectonic line, due to the increase of the westward convergence rate. This shift resulted in shortening and cessation of graben development in the Hohi area, restricting the subsequent volcanism and related hydrothermal activity to the central part of the graben.  相似文献   

14.
Southern Cyprus is situated within a mosaic terrane that has been fragmented between the northward drifting African and Arabian plates and the Eurasian plate. Enormous uplift of the earth mantle in the Tróodos Mountains is explained by two models. The subduction model explains subduction along the Cyprean arc to be the driving force for uplift whereas after the restraining bend model westward squeezing of Cyprus along strike-slip faulting is responsible for the enormous uplift at restraining bends. Since its emergence as an island in early Miocene times, landscape formation on Cyprus has been strongly controlled by this uplift. Until the Plio-Pleistocene, a strait belt separated the southern unroofed ophiolitic core region-the Tróodos Mountains-from the folded Kyrenia range to the north. This former sea basin, nowadays the Mesaoría Basin, is linked with the Tróodos Mountains by a dissected glacis with a thick cover of river deposits. The highest and oldest river deposits (Apalós Formation) were studied in the Vlokkariá hill southwest of Lefkosía. The 45.5 m thick Apalós Formation of Early Pleistocene age exhibits 24 sedimentary units (Fluviatile Series). Their magnetostratigraphical characters align with the Matuyama chron including the Olduvai and Jaramillo subchrons thus comprising about 1.15 Ma within the Early Pleistocene. This fluvial stack indicates a very flat and deeply lying river environment flowing from a slowly uplifting Tróodos hinterland. It happened during the end of Early Pleistocene when the enhanced Tróodos uplift started the dissection of the stacked river plain.  相似文献   

15.
The eastern Himalayan syntaxis in southeastern Tibet consists of the Lhasa terrane, High Himalayan rocks and Indus‐Tsangpo suture zone. The Lhasa terrane constitutes the hangingwall of a subduction zone, whereas the High Himalayan rocks represent the subducted Indian continent. Our petrological and geochronological data reveal that the Lhasa terrane has undergone two stages of medium‐P metamorphism: an early granulite facies event at c. 90 Ma and a late amphibolite facies event at 36–33 Ma. However, the High Himalayan rocks experienced only a single high‐P granulite facies metamorphic event at 37–32 Ma. It is inferred that the Late Cretaceous (c. 90 Ma) medium‐P metamorphism of the southern Lhasa terrane resulted from a northward subduction of the Neo‐Tethyan ocean, and that the Oligocene (37–32 Ma) high‐P (1.8–1.4 GPa) rocks of the High Himalayan and coeval medium‐P (0.8–1.1 GPa) rocks of the Lhasa terrane represent paired metamorphic belts that resulted from the northward subduction of the Indian continent beneath Asia. Our results provide robust constraints on the Mesozoic and Cenozoic tectonic evolution of south Tibet.  相似文献   

16.
The Indonesian island of Sumatra, located in one of the most active zones of the Pacific Ring of Fire, is characterized by a chain of subduction‐zone volcanoes which extend the entire length of the island. As a group of volcanic geochemists, we embarked upon a five‐week sampling expedition to these exotic, remote, and in part explosive volcanoes (SAGE 2010; Sumatran Arc Geochemical Expedition). We set out to collect rock and gas samples from 17 volcanic centres from the Sumatran segment of the Sunda arc system, with the aim of obtaining a regionally significant sample set that will allow quantification of the respective roles of mantle versus crustal sources to magma genesis along the strike of the arc. Here we document our geological journey through Sumatra's unpredictable terrain, including the many challenges faced when working on active volcanoes in pristine tropical climes.  相似文献   

17.
跳出南海看南海——新特提斯洋闭合与南海的形成演化   总被引：6，自引：5，他引：1  
本文总结了笔者参与基金委重大研究计划"南海深海过程演变"的研究成果。我们发现南海和青藏高原都是新特提斯洋闭合的产物,而非前人所说的南海是由青藏高原碰撞导致的中南半岛逃逸所形成。与青藏高原碰撞隆升机制不同,南海是新特提斯闭合后期弧后拉张的结果。新特提斯洋位于北边的欧亚大陆与南面的非洲、印度和澳大利亚板块之间,呈东宽西窄的喇叭型。在西部,新特提斯洋向北的俯冲可能在侏罗纪就开始了,局部形成了弧后盆。约130Ma前,由于凯尔盖朗等大火成岩省的喷发,新特提斯洋脊也开始向北漂移。由于新特提斯洋东部宽度较大,弧后拉张明显,形成了古南海。新特提斯洋闭合过程中一个重大事件是洋脊俯冲:从菲律宾经福建及两广到青藏高原,均有100Ma左右的埃达克岩产出,是洋脊俯冲的产物。其中,菲律宾、福建、广东埃达克岩形成了斑岩铜金矿床;而在青藏高原,埃达克岩虽有矿化,但没有形成大规模的斑岩铜金矿床。同时期,华南出现了一次短暂的大规模挤压事件,与洋脊俯冲契合。这次挤压事件可能导致了古南海闭合的开始。与此同时,青藏高原冈底斯出现高温岩石——埃达克质紫苏花岗岩;其北面有～110Ma短时间内发生的大规模花岗岩事件。考虑到板块重建的结果,这些埃达克岩和华南短时间挤压事件的时空分布显示新特提斯洋脊在约100～110Ma,近似平行于俯冲带俯冲到了欧亚大陆之下;其前片下沉,扰动软流圈,形成大规模岩浆活动;后片则缓慢后撤,于～80Ma形成了A-型花岗岩。这些A-型花岗岩多属于A2型,受到了还原性板块俯冲的影响而普遍含锡,形成了全球60%的锡矿。俯冲板片的后撤,导致了拉张,可以合理解释南海北缘的"神狐运动"。随着俯冲板片后撤,俯冲角度加大,形成新的弧后拉张,于～33Ma出现洋壳,形成了南海。青藏高原碰撞引起的物质向东、南、北等各方向逃逸,对东亚大陆的构造格局也产生了重要的影响,但是并非南海拉张的主要控制因素。到～23Ma时,东经九十度海岭的俯冲阻挡了青藏高原下方地幔物质向东南方向逃逸,改变了东亚构造格局。同时,由于该海岭俯冲产生的向北东方向的挤压,造成印支半岛向西南挠曲,导致南海洋脊产生向南的跃迁。  相似文献   

18.
本文从构造-岩浆演化、典型矿床特征、构造-岩浆产物空间分布特征等方面,对冈底斯成矿带形成于195~80Ma的与俯冲-碰撞作用相关的斑岩(-矽卡岩)型铜矿的找矿方向进行了探讨。认为研究区与俯冲-碰撞作用相关的斑岩型铜矿大致可分为早-中侏罗世、晚侏罗-早白垩世、晚白垩世3个成矿时期,分别对应于雅鲁藏布江洋向北、班公湖怒江洋向南相向俯冲、班公湖怒江洋碰撞关闭、雅鲁藏布江洋向北持续俯冲、雅鲁藏布江洋向北晚期俯冲等构造-岩浆事件。与早期相向俯冲相关的雄村式矿床,在拉萨东部达孜-工布江达一带具有良好找矿前景;与中期俯冲-碰撞相关的多龙式矿床,在昂龙岗日、东恰错、桑日等火山岩浆弧区成矿条件较佳;与晚期俯冲相关的尕尔穷式矿床,在冈底斯东段和西段具有较大的找矿潜力。  相似文献   

19.
The annual b-value fluctuation patterns in Burmese subduction zone and Andaman–Sumatra subduction zone are evaluated from earthquake data (January 1990 to June 2016; Mw ³ 4.3) to identify seismic cycles with sequential dynamic phases as described in the ‘elastic failure model’ of Main et al. (1989). Two seismic cycles have been identified in Andaman–Sumatra subduction zone, one started in 1990 and ended on 2004 with occurrence of great Sumatra earthquake (Mw 9.0) and the other started in 2005 and continuing till date with the phase of crack coalescence and fluid diffusion (3A&B). Similarly, the subduction zone of Burma shows evidence of one incomplete seismic cycle within 1990–2016 and presently undergoing the crack coalescence and fluid diffusion (3A&B) phase. The analysis has prompted to subdivide the area into thirteen smaller seismic blocks (A to M) to analyse area specific seismic trend and vulnerability analysis employing Hurst Statistics. Hurst plots with the dynamic phases of ‘elastic failure model’ of earthquake generation is compared to assess the blocks with high seismic vulnerability. The analysis suggest that north Andaman zone (block G) and north Burma fold belt (block M) are seismically most vulnerable. Moreover, the seismic vulnerability of Tripura fold belt and Bangladesh plain (block K) is equally high.  相似文献   

20.
http://www.sciencedirect.com/science/article/pii/S1674987114001121   总被引：1，自引：0，他引：1  
The Chinese Tianshan belt of the southern Altaids has undergone a complicated geological evolution.Different theories have been proposed to explain its evolution and these are still hotly debated.The major subduction polarity and the way of accretion are the main problems.Southward,northward subduction and multiple subduction models have been proposed.This study focuses on the structural geology of two of the main faults in the region,the South Tianshan Fault and the Nikolaev Line.The dip direction in the Muzhaerte valley is southward and lineations all point towards the NW.Two shear sense motions have been observed within both of these fault zones,a sinistral one,and a dextral one,the latter with an age of 236-251 Ma.Structural analyses on the fault zones show that subduction has been northward rather than southward.The two shear sense directions indicate that the Yili block was first dragged along towards the east due to the clockwise rotation of the Tarim block.After the Tarim block stopped rotating,the Yili block still kept going eastward,inducing the dextral shear senses within the fault zones.  相似文献   

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