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1.
The 28 February, 2006 Tiab earthquake (Mw 6.0), is the first earthquake to have occurred in the transition zone between the Zagros continental collision and the Makran subduction zone for which the aftershock sequence is recorded by a temporary local seismic network. The epicentral distribution of the aftershocks is diffuse and we cannot define a simple alignment at the surface. The depth of the aftershocks increases gently northward and they are primarily concentrated between 15 and 21 km depth, implying a deeper seismogenic layer than the Zagros. Very low-angle thrust faulting deduced from this local study supports thrusting of the Arabian plate beneath central Iran at the southeastern end of the Zagros as suggested previously based on teleseismic data. The focal mechanism of the main shock indicates a thrust mechanism similar to that of other strong earthquakes in this region, while most of the focal mechanisms of the aftershocks are dominantly strike-slip. We propose that the strike-slip mechanisms belong to right-lateral fault systems that accommodate differential motion at the transition between the Zagros collision zone and the Makran subduction zone. If so, this suggests that the convergence between Arabia and central Iran is at present accommodated along the transition zone by a partitioning process.  相似文献   

2.
The microseismicity of the southeastern-most Zagros is examined by high-resolution data recorded by a temporary dense local seismic network. The seismicity defines a diffuse pattern, mostly located beneath folds in the southern part of the High Zagros Fault (HZF). Seismicity dips gently northward in the depth range 6–25 km, implying slip on a major intracrustal thrust fault extending to the north of the Main Zagros Reverse Fault (MZRF) which seems to connect to the Mountain Frontal Fault (MFF). Furthermore, observed focal mechanisms suggest transpressive motion on the HZF located west of the Zendan-Minab-Palami (ZMP) fault system and striking obliquely to the convergent motion. These observations suggest that the transition zone between the Zagros continental collision zone and the Makran oceanic subduction zone is not confined to the east of the ZMP and some part of the this diffuse transition is accommodated north of the Hormuz Strait in the west by partitioning between strike-slip and shortening components. The Zagros reverse domain is terminated by a transpressive tectonic regime. Moho depth beneath the MZRF, deduced from receiver functions, is almost 45 km thinner than is observed in the central and northern parts of the Zagros. These observations support a model of active underthrusting of the Arabian plate beneath central Iran in the southeastern-most Zagros.  相似文献   

3.
大地震(特别是8级以上的大地震)的发生必须满足2个基本条件:一个是震源附近要有超过岩石弹性极限的高应力背景;另一个是该处的岩石具有发生地震的能力,即在大地震孕育所需的时间尺度(几千年以上)内岩石能长期保持弹性。为考察第1个条件,分析了中国周边三大板块的作用力。认为太平洋板块在海沟附近的俯冲方式所产生的水平力分量较小,而且海沟离中国大陆较远,因此它对中国的地震影响不大;菲律宾海板块对台湾的碰撞使台湾及福建沿海地区为高应力区,但由于碰撞边界的长度只有200km左右,其影响范围不大;印度板块向北推挤是产生中国西部及华北高应力区的最主要原因,文中较详细分析了它的作用,并据此尝试性划分了3个对中国具有强烈影响的地震带。根据岩石的流变性质和地质形成时代把地质体分成了刚性、次刚性和较柔性3类。初步计算了刚性地块的弹性持续时间至少在1Ma以上,而柔性地块的弹性持续时间最多为1ka。因此,8级大地震的位置与刚性地块密切相关  相似文献   

4.
Makran is one of the largest accretionary prisms on Earth, formed by the closure of the Neotethys ocean which is now represented by its remnant, the Gulf of Oman. Tectonic evolution of the Makran island‐arc system is explored within the context of a north dipping subduction zone, with temporal variations in slab dip arrangement. In a Middle Jurassic–Early Paleocene steep slab dip arrangement, the Mesozoic magmatic arc and the Proto‐Jaz Murian depression, which was an intra‐arc extensional basin, were developed. This was associated with development of outer‐arc ophiolitic mélange and oceanward migration of the Bajgan–Durkan continental sliver, which is the continuation of the Sanandaj–Sirjan zone of the Zagros orogenic belt into the Makran region. In a Late Paleocene to Late Pliocene moderate to shallow slab dip arrangement, compression and tectonic inversion of the Proto‐Jaz Murian extensional basin into the Jaz Murian compressive basin was associated with the uplift of the southern part of the Jaz Murian Depression along the South Jaz Murian Fault, and emplacement of the Paleogene–Neogene magmatic arc, behind the Jaz Murian compressive basin. A shallow slab dip arrangement in the Quaternary led to the emplacement of a third magmatic arc inland, over the southern part of the Yazd–Tabas–Lut micro‐continental block. It is envisioned that the Makran island‐arc system will pass through similar tectonic events in the future, as the Zagros island‐arc system did in the past. However, a future remnant and/or residual basin similar to the present Gulf of Oman will continue to survive to the east.  相似文献   

5.
We analyzed digital seismic records in order to extend back in time the catalog of regional centroid moment tensors (RCMTs) for the Cyprus region. We applied the analysis and inversion methodology also used for the present-day seismicity on seismograms recorded at regional distance. We computed 18 new regional CMTs of earthquakes of moderate magnitude (4.8 ≤ M ≤ 5.5) which occurred in the Cyprus region for the time span 1977–1996. These new focal mechanisms improved the knowledge given by the previously computed solutions carried out by other institutions, as well as the dataset of available earthquake source parameters. The complete focal mechanism database contributed to better define the deformation styles in the study area and to obtain a detailed characterization of the geodynamics of the Cyprus area. New RCMTs support the hypothesis that Cyprus is located in the middle of the transition area from subduction to continental collision along the Africa–Arabian–Eurasian boundary. In particular, data confirm (a) this transition zone is strictly located west of Cyprus, probably related to a tear in the subduction system, and (b) the still active compression in the Cyprus Arc can be seen as a starting point of the continental collision eastward.  相似文献   

6.
A probabilistic seismic hazard analysis (PSHA) was conducted to establish the hazard spectra for a site located at Dubai Creek on the west coast of the United Arab Emirates (UAE). The PSHA considered all the seismogenic sources that affect the site, including plate boundaries such as the Makran subduction zone, the Zagros fold-thrust region and the transition fault system between them; and local crustal faults in UAE. PSHA indicated that local faults dominate the hazard. The peak ground acceleration (PGA) for the 475-year return period spectrum is 0.17 g and 0.33 g for the 2,475-year return period spectrum. The hazard spectra are then employed to establish rock ground motions using the spectral matching technique.  相似文献   

7.
东亚地震活动的时空分布及其与区域应力场的关系   总被引：2，自引：0，他引：2       下载免费PDF全文
徐纪人  赵志新 《地震学报》1991,13(3):287-294
来自板块之间相对运动的构造力可以传递到大陆地壳,从而形成了大陆内部的地震应力场.在某一地区,包括小地震在内的地震活动性的分布可以反映该地区的应力场的变化.根据这一观点,本文根据大量的震源机制解的结果以及最近500年的地震活动资料,详细地研究了东亚地区内几个地区的区域应力场的特征.其结果表明,来自太平洋板块相对欧亚板块的俯冲所形成的构造力,控制了从华北地区到南北地震带北段的应力场.本文根据小震的地震活动变化的特征,讨论了日本一部分地区由地震活动性的变化所反映的区域应力场的变化.中国西部以及印度-澳大利亚和欧亚大陆板块边界地区,最近大约100年地震活动性的同步变化表明,来自印度-澳大利亚板块和欧亚板块碰撞所产生的构造力,传递到了中国西部.印度-澳大利亚板块和欧亚大陆板块边界,以及中国西部的地震活动,现在依然处在地震活动高潮期.   相似文献   

8.
Teleseismic activity in the Makran region of southeastern Iran and southwestern Pakistan prior to the great earthquake (Ms=8) of 1945 can be characterized in terms of two stages. First, during the period 30 (or more) to 10 years prior to the main event, the frequency of occurrence of moderate to large earthquakes was relatively high in the region between the impending rupture zone and the volcanic arc to the northwest. These events probably occurred near the down-dip limit of seismic activity within the subducted slab. Second, activity was concentrated along the coast during the ten years immediately preceding the great earthquake and most of this activity was confined to the vicinity of the epicenter of the 1945 earthquake. These patterns are similar in some respects to those observed prior to some large earthquakes in other parts of the world.Three observations concerning the pre-1945 seismicity suggest it was associated with the preparation for rupture of the zone that eventually broke during the great earthquake in 1945: (1) The activity before 1945 is located either within the 1945 rupture zone or between this zone and the volcanic arc to the northwest; (2) No activity of similar magnitude and occurrence rate is observed elsewhere along the Makran plate boundary; and (3) The region that was active prior to 1945 has been relatively quiet since the decline in aftershock activity associated with the 1945 shock. The current quiescence may be related to the release of stress during the 1945 earthquake.Recent seismicity in the region west of that affected prior to 1945 suggests that this western region may be the site of the next large earthquake. Events along the coast are grouped at both ends of a seismically quiet zone, producing a distribution similar to the donut pattern identified by Mogi. In addition, one moderate-magnitude earthquake occurred within the subducted slab to the northwest of the donut pattern along the coast. This moderate-magnitude earthquake, the first to occur in the region immediately west of the 1945 rupture zone since the advent of instrumental recording, may be analogous to the activity of stage one associated with the 1945 earthquake. While by no means providing conclusive evidence of an impending earthquake, the characteristic patterns identified in the recent seismicity indicate that this region should be closely monitored in the future.Lamont-Doherty Geological Observatory Contribution Number 2853.  相似文献   

9.
The study of mantle lithosphere plays a key role to reveal predominant tectonic setting process of a region. The current geological and tectonic setting of Iran is due to the ongoing continental–continental collision of the Arabian and Eurasian plates. We applied a combined P and S receiver function analysis to the teleseismic data of nine permanent broadband seismic stations of the International Institute of Earthquake Engineering and Seismology located in different tectonic zones of Iranian plateau. More than 4 years of data were used to estimate the thickness of the crust and mantle lithosphere. According to our results, the crust is 50 km thick beneath the Zagros fold and thrust belt (ZFTB). We found the maximum Moho depth of approximately 70 km under the Sanandaj-Sirjan zone (SSZ) indicating the overthrusting of the crust of Central Iran onto the Zagros crust along the main Zagros thrust (MZT). Below the northeasternmost part of the Urumieh–Dokhtar Magmatic Arc (UDMA) and Central Iran, the Moho becomes shallower and lies at 40 km depth. Towards northeast, beneath the Alborz zone, the crust is 55 km thick. Based on S receiver functions, we provided new insights into the thickness of the Arabian and Eurasian lithospheres. The location of the boundary between these plates was estimated to be beneath the SSZ, which is slightly shifted northeastward relative to the surficial expression of the MZT. Furthermore, the Arabian plate is characterized by the relatively thick lithosphere of about 130 km beneath the ZFTB reaching 150 km beneath the SSZ, where the thickest crust was also observed. This may imply that the shortening across the Zagros is accommodated by lithospheric thickening. In contrast, UDMA and Central Iran are recognized by the thin lithosphere of about 80–85 km. This thin lithosphere may be associated with the asthenospheric upwelling caused by either lithospheric delamination or Neo-Tethys slab detachment beneath the Zagros collision zone.  相似文献   

10.
We have performed 3-D scaled lithospheric experiments to investigate the role of the gravitational force exerted by a subducting slab on the deformation of the subducting plate itself. Experiments have been constructed using a dense silicone putty plate, to simulate a thin viscous lithosphere, floating in the middle of a large box filled with glucose syrup, simulating the upper mantle. We examine three different plate configurations: (i) subduction of a uniform oceanic plate, (ii) subduction of an oceanic-continental plate system and, (iii) subduction of a more complex oceanic-continental system simulating the asymmetric Africa-Eurasia system. Each model has been performed with and without the presence of a circular weak zone inside the subducting plate to test the near-surface weakening effect of a plume activity. Our results show that a subducting plate can deform in its interior only if the force distribution varies laterally along the subduction zone, i.e. by the asymmetrical entrance of continental material along the trench. In particular, extensional deformation of the plate occurs when a portion of the subduction zone is locked by the collisional process. The results of this study can be used to analyze the formation of the Arabian plate. We found that intraplate stresses, similar to those that generated the Africa-Arabia break-up, can be related to the Neogene evolution of the northern convergent margin of the African plate, where a lateral change from collision (Mediterranean and Bitlis) to active subduction (Makran) has been described. Second, intraplate stress and strain localization are favored by the presence of a weakness zone, such as the one generated by the Afar plume, producing a pattern of extensional deformation belts resembling the Red Sea-Gulf of Aden rift system.  相似文献   

11.
The Iranian Plateau does not appear to be a single crustal block, but an assemblage of zones comprising the Alborz—Azerbaijan, Zagros, Kopeh—Dagh, Makran, and Central and East Iran. The Gumbel’s III asymptotic distribution method (GIII) and maximum magnitude expected by Kijko—Sellevoll method is applied in order to check the potentiality of the each seismogenic zone in the Iranian Plateau for the future occurrence of maximum magnitude (Mmax). For this purpose, a homogeneous and complete seismicity database of the instrumental period during 1900–2012 is used in 29 seismogenic zones of the examined region. The spatial mapping of hazard parameters (upper bound magnitude (ω), most probable earthquake magnitude in next 100 years (M100) and maximum magnitude expected by maximum magnitude estimated by Kijko—Sellevoll method (max MK ? Smax) reveals that Central and East Iran, Alborz and Azerbaijan, Kopeh—Dagh and SE Zagros are a dangerous place for the next occurrence of a large earthquake.  相似文献   

12.
Tectonic forces from the relative movements between plates are transmitted into the continental crust, and then they create the earthquake generating stress field there. The space-time distribution of the seismic activity including the small earthquakes in a region reflects the variation of the stress field in the region. According to this idea, the characteristics of the stress fields in the various regions of East Asia have been analyzed in detail in this paper based on a lot of solutions of focal mechanisms and data of seismic activity during the last 500 years. The results indicate that the tectonic forces from the subduction of the Pacific Ocean plate underneath the Eurasian plate control the stress field in the region from North China to the northern part of the North-South Seismic Belt. The variation of the regional stress field shown by the variation of seismic activity in some regions of Japan has also been discussed based on characteristics of variation of the seimicity of small earthquakes. Synchronous variations of seismicity in the past 100 years or so in West China and in the boundary region between the Indo-Australian and Eurasian plates implicate that there is the transmission of tectonic forces into West China through the collision between the Indo-Australian and Eurasian plates. The active seismic activity in the boundary region between the Indo-Australian and the Eurasian plates and in West China is continuing consistently. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 287–294, 1991.  相似文献   

13.
The continental plate collision across the South Island of New Zealand is highly oblique (dextral) and bounded by oppositely verging ocean plate subduction zones. As such, the region can be considered as a type of ‘subduction scissor’. Within this tectonic context, we use three-dimensional computational geodynamic models to consider how convergent mantle lithosphere can be modified by scissor and strike–slip effects. Bounding subduction at both ends of the continental collision causes flow of the descending mantle lithosphere in the direction along strike of the model plate boundary, with thinning in the centre and thickening towards the subduction zones that bifurcates the continental mantle lithosphere root. With dipping bounding subduction, the mantle lithosphere root takes on a more complex morphology that folds over from one subduction polarity to the other, but remains as a continuous feature as it folds under the collision zone. In the absence of bounding subduction, the plate convergence causes a linear (along strike) mantle lithosphere root to develop. A rapid strike–slip motion between the converging plates transfers material in the plate boundary-parallel direction and tends to blur out features that develop in this direction—such as descending viscous instabilities. The along-strike variations in the morphology of the mantle lithosphere root that develop in the models—viz., thickening of the root towards the subduction edges, thinning in the centre—are consistent with recent, albeit poorly constrained, geophysical interpretations of the large-scale lithospheric structure of the South Island. We speculate that this reflects the nature of the evolution of the South Island collision as a limited continental segment of the plate boundary that it is dominated and guided by adjacent well-developed/developing ocean plate subduction.  相似文献   

14.
The Mawat ophiolite is part of the Mesozoic Neo‐Tethyan ophiolite belt of the Middle East and is located in the Zagros Imbricate Zone of Iraq. It represents fossil fragments of the Neo‐Tethyan oceanic lithosphere within the Alpine collisional system between the Arabian and Eurasia Plates. The first U–Pb zircon dating of the Daraban leucogranite from the Mawat ophiolite provides a 207Pb–206Pb age of 96.8 ± 6.0 Ma. The age is 59.0 ± 6.0 m.y. older than the previously published age of the Daraban leucogranite obtained by 40Ar–39Ar muscovite dating method. The U–Pb dating of magmatic zircons collected from the Daraban leucogranite, which intrudes into the Mawat ophiolite, reveals that melting of the pelagic sediment beneath the hot Zagros proto‐ophiolite in an intra‐oceanic arc environment led to anatexis at the subduction front and the generation of granitic melts at 96.8 ± 6.0 Ma, which were emplaced in the overlaying mantle wedge. This process was a response to the initial formation of the Neo‐Tethys ophiolite above a northeast‐dipping intra‐oceanic subduction zone at 96.8 ± 6.0 Ma. Published 40Ar–39Ar muscovite dating from the same leucogranite dike yields plateau ages of 37.7 ± 0.3 Ma, reflecting that the age was reset during the Arabia–Eurasia continental collision. Therefore, the bimodal age populations from the granitic intrusion in the Mawat ophiolite preserve a record of the subduction to the collision cycle of the Zagros Orogenic Belt. The 59.0 ± 6.0 m.y. age difference from the Daraban leucogranite represents the duration of the subduction‐collision cycle of the Zagros Orogenic Belt in the Kurdistan region of Iraq and the time span for the closure of the Neo‐Tethys Ocean along the northern margin of the Arabian plate.  相似文献   

15.
Non-linear teleseismic S-phase tomography across the Zagros collision zone in southwestern Iran is used to determine a high-resolution image of the upper-mantle structure. The inversion was done using 41 high-quality earthquakes recorded by 19 broad-band and medium-band stations along a 620 km long profile across the collision zone. Smearing from strong crustal velocity anomalies into the upper-mantle is suppressed by travel-time corrections calculated based on a 3-D crustal model for the study area. Our results show that the relatively old and cold Arabian shield has a higher velocity (up to 6% faster, at depths between 70 and 300 km) than the younger lithosphere farther north in Central Iran. These two upper-mantle domains are separated by a sharp near-vertical transition whose surface expression coinciding with the Main Zagros Thrust.  相似文献   

16.
Recent developments of the Middle East catalog   总被引：8，自引：2，他引：6  
This article summarizes a recent study in the framework of the Global Earth model (GEM) and the Earthquake Model of the Middle East (EMME) project to establish the new catalog of seismicity for the Middle East, using all historical (pre-1900), early and modern instrumental events up to 2006. According to different seismicity, which depends on geophysical, geological, tectonic, and seismicity data, this region is subdivided to nine subregions, consisting of Alborz–Azerbaijan, Afghanistan–Pakistan, Saudi Arabia, Caucasus, Central Iran, Kopeh–Dagh, Makran, Zagros, and Turkey (Eastern Anatolia; after 30° E). After omitting the duplicate events, aftershocks, and foreshocks by using the Gruenthal method, and uniform all magnitude to Mw scale, 28,244 main events remain for the new catalog of Middle East from 1250 B.C. through 2006. The magnitude of completeness (Mc) was determined as 4.9 for five out of nine subregions, where the least values of Mc were found to be 4.2. The threshold of Mc is around 5.5, 5.0, 4.5, and 4.0, for the time after 1950, 1963, 1975, and 2000, respectively. The average of teleseismic depths in all regions is less than 15 km. Totally, majority of depth for Kopeh–Dagh and Central Iran, Zagros, and Alborz–Azerbaijan, approximately, is 15, 13, and 11 km and for Afghanistan–Pakistan, Caucasus, Makran, Turkey (after 30° E), and Saudi Arabia is about 9 km.  相似文献   

17.
地幔对流对全球岩石圈应力产生与分布的作用   总被引：16，自引：4，他引：12       下载免费PDF全文
利用动力学模拟方法研究地幔对流对于大尺度岩石圈内部应力场形成的作用. 地幔物质内部的密度横向非均匀及表面板块运动引起地幔流动,并在岩石圈底部产生一个应力场. 该应力场作为面力将造成岩石圈本身变形,从而产生岩石圈内部的应力分布. 模拟计算结果表明,大部分俯冲带及大陆碰撞带区域应力均呈现挤压特征,如环太平洋俯冲带及印度－欧亚碰撞带等;而东太平洋洋脊、大西洋洋脊及东非裂谷处应力状态均表现为拉张;并且绝大多数热点位置处于应力拉张区域,这与目前对全球构造应力状态的理解是一致的. 计算的岩石圈内部最大水平主压应力的方向与观测表现出相当的一致,其结果总体上吻合得较好,然而在局部区域（例如西北太平洋的俯冲带、青藏高原等地区）存在着较大的差异. 研究表明,地幔对流是造成岩石圈内部大尺度应力状态及分布的一个重要因素.  相似文献   

18.
The thermal evolution of continental crust during active collision is modeled through numerical solutions of the two-dimensional heat conduction equation for a rapidly moving medium. The boundary conditions used in the modeling are derived from geological and geophysical observations from the active collision zone in the South Island of New Zealand. The problem domain over which the solutions are obtained consists of a 40 km horizontal by 25 km vertical spatial plane with a vertical discontinuity at 10 km from the western boundary. To the east of this discontinuity, vertical uplift rates of up to 10 mm/a occur over a timespan of up to 4 Ma. Temperature distributions are calculated at 10 ka intervals over the 4 Ma duration. A two-dimensional high-temperature region is established upon initiation of uplift of the eastern block due to the advective component carrying heat upwards more rapidly than it can be dissipated laterally from the problem domain. Temperatures within the upper 5 km are greater than 400°C after 2.25 Ma with geothermal gradients of up to 200°C/km attained within the upper 3 km. At times greater than 2.5 Ma, the vertical temperature distribution changes little while the anomalously high temperatures spread laterally into the stationary crust.Using rheological equations to describe the brittle behaviour of a water-saturated upper crust and the ductile behaviour of a quartz-dominated lower crust, together with the thermal distribution of the conduction models, the mechanical evolution of a collision zone is investigated. In addition to high crustal temperatures and associated high heat flow, rapid uplift produces a weakening of the crust by raising of the depth of transition from brittle to ductile behaviour. Within the zone of most rapid uplift, the brittle-ductile transition rises from 13 km to less than 5 km after 1.5 Ma of uplift. Further uplift reduces the brittle layer to 3 km thickness and causes lateral spreading of the low-strength zone. The reductions in crustal strength caused by the thermal weakening produce a high-strain zone within the region of maximum uplift which is incapable of sustaining large differential stresses. This causes horizontal and vertical stress transfer and results in shallow seismicity increases in the adjacent crust as well as in intermediate depth seismicity within the high-strength upper mantle.Because the thermal and mechanical anomalies discussed are a function of rapid uplift, all regions of active continental collision may be expected to exhibit similar behaviour. Some mechanical and thermal characteristics of the Himalayan collision zone are briefly examined in light of the numerical modeling.  相似文献   

19.
Through a detailed analysis of seismicity at the base of the transition zone, we obtain an updated value of the maximum reliable depth of confirmed seismicity, we investigate regional variation in the maximum depth of seismicity among those Wadati-Benioff zones which reach the bottom of the transition zone, and we attempt to quantify the maximum possible rate of seismic release in the lower mantle compatible with the failure to detect even a single event since the advent of modern seismological networks. We classify deep subduction zones into three groups: those whose seismicity does not reach beyond 620 km, those whose seismicity appears to terminate around 650–660 km, and Tonga-Kermadec (and the Vityaz cluster) whose seismicity extends to 685–690 km. We suggest that the depth extent of seismicity is controlled by the depth of the pv + mw transition responsible for the 660-km seismic discontinuity, which is deflected to greater depths in cold slabs than in warmer ones. We note that this transition marks the depth below which thermal perturbation of phase transitions no longer generates buoyancy anomalies and their large attendant down-dip compressive stresses and below which strain energy generated by other mechanisms may not accumulate to seismogenic levels due to superplastic weakness in fine-grained materials. We find that the maximum level of seismic activity in the lower mantle must be at least three orders of magnitude less than that observed in the transition zone.  相似文献   

20.
本文使用新疆区域数字地震台站记录的宽频带长周期数字波形资料,在时间域反演了2008年10月5日新疆乌恰6.8级地震的强余震及其周围先后发生的52次中等强度地震的矩张量解,结合Harvard大学在该区域的地震矩张量结果,研究了帕米尔东北缘的应力场分区特征.研究结果显示,位于印度板块向欧亚板块推挤的前缘及向北凸出的弧型构造的最北缘的卡兹克阿尔特弧形活动褶皱-逆断裂带,以逆冲推覆活动为主,并有部分走滑类型的地震,基本不存在正断层类型的地震;该弧型构造近东西走向的顶部(文中的西区)与其北西走向的东侧(文中的东区)的局部应力场最大主压应力方向不同,分别为NW、NNE方向,显示出在承受印度板块向欧亚板块俯冲作用的同时,东区也更多的受到了塔里木块体顺时针旋转作用的影响.位于帕米尔陆内俯冲和变形作用强烈、碰撞造成深源地震带东段的南区,地震以走滑错动为主, 逆断、正断层都有,显示出相对复杂的应力状态.位于帕米尔高原内部的西区和南区的应力场最大主压应力方向一致,由北向南,由最大主压应力轴接近水平,过渡为最大主张应力轴接近水平,一定程度揭示了板块俯冲的状态.结合南区和西区的地震深度差异及机制解中断层面的倾角,推测在中帕米尔的东部,由北向南的板块俯冲至150~170km深度,俯冲角度为60°左右.  相似文献   

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