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1.
《Physics of the Earth and Planetary Interiors》1981,25(1):64-70
This paper presents a study of the tectonic stresses in central Asia based on an interpretation of satellite gravity data for mantle convection and supplemented with published fault plane solutions of earthquakes. Northwest-southeast to north-south compressional stresses exist in the Tien Shan region where reverse faulting dominates. The maximum compressive stress is oriented approximately northeast-southwest in the regions of Altai and southern Mongolia. Farther north, compressive stress gives way to tensional stress which causes normal faulting in the Baikal rift system. It is also shown that all of the tectonic stresses in the Tibetan plateau and Himalayan frontal thrust are related to the convection-generated stress patterns inferred from satellite gravity data. These results suggest that the complex crustal deformation in central Asia can be convincingly described by the deformation of the lithosphere on top of the up- and down-welling asthenospheric material beneath it. This observational fact may not only upset the simple view of the fluid crustal model of the Tibetan plateau, but also provide some useful constraints for the future development of deformation theory of continental crust. 相似文献
2.
R. A. Umurzakov 《Izvestiya Physics of the Solid Earth》2010,46(5):379-386
This study presents the results of stress field reconstruction for the epicentral zones of large-magnitude earthquakes in
some folded-mountain regions of western Tien Shan. Field studies, including geostructural and tectonophysical interpretations,
performed for the Talas-Suusamyr, Chatkal-Kurama, Turkestan-Zarafshan, Gissar and Nurata-Kyzylkum regions allow the reconstruction
of some regional components of the tectonic stress field. The nearly E-W orientations of the lower-order compressional axes
are identified in the Chatkal-Kurama and Turkestan-Zarafshan mountain areas. Detailed structural-dynamical diagrams of several
epicentral zones and reconstructions of focal mechanisms of some strong earthquakes are derived from the geostructural data.
The coincidence of the present-day stress field manifested in the earthquake sources and the recent stress field derived from
the geostructural determinations is revealed. The focal mechanisms of the strong earthquakes in the folded-mountain regions
of western Tien Shan relate to the thrust/strike-slip faulting and breakup of large tectonic blocks. 相似文献
3.
研究帕米尔高原的构造变形特征对于理解印度板块向北推挤过程中的应变分配方式以及应力转换模式具有重要的意义.本文利用区域GPS应变场、地震应变场与震源应力场分析帕米尔高原的构造形变特征.主要结论为:(1)该区域变形主要以NNW-SSE或近N-S向的挤压为主,在高原内部伴有明显的近ENE-WSW或E-W向拉张,应力方向在帕米尔高原与塔吉克盆地区域呈现逆时针旋转的趋势,而在塔里木盆地则显示几乎与帕米尔高原的一致的应力状态,这可能与两侧盆地块体的强度差异有关.(2)安德森断层参数A∅显示帕米尔高原北缘与西侧区域为逆断层应力状态,在高原内部为正断层应力状态,这与GPS应变的结果显示的应变主要集中在主帕米尔断裂与阿莱谷地附近而在高原内部应变较低是一致的,另外应力在喀喇昆仑断裂北段的方向基本平行于断层走向,以及断层北端较低的滑动速率,这说明了地壳挤压缩短可能是帕米尔高原主要的的构造变形特征,并不支持由于边界走滑断裂导致的应变分异或者块体挤出的模式.(3)综合考虑地震应变方向与SHmax从帕米尔北部NNW-SSE方向到天山北部的近N-S方向的转换,GPS应变方向在帕米尔高原两侧盆地都存在不同程度的旋转,应力场安德森参数A∅显示的应力状态以及SKS的结果显示的近ENE-WSW方向,我们认为印度板块向北推挤与天山造山带碰撞导致帕米尔高原不对称的径向逆冲是帕米尔高原现今构造变形的主要成因与构造模式. 相似文献
4.
Contemporary tectonics in the Tien Shan region 总被引：1，自引：0，他引：1
James Ni 《Earth and Planetary Science Letters》1978,41(3):347-354
New fault plane solutions of recent earthquakes, along with previously published fault plane solutions, field geologic data, and faults interpreted from LANDSAT imagery indicate thrust faulting in the Tien Shan region. For most of the fault plane solutions compressive stress axes are nearly horizontal and trending approximately north-south, perpendicular to the trend of the Tien Shan fold belts. Contemporary tectonics of the Tien Shan region can be interpreted as resulting from convergence of the Indian and Eurasian plates. 相似文献
5.
6.
天山构造带位于中国大陆西北部,是典型的岩石圈陆内缩短造山带.本文利用新疆区域数字地震台网2009年1月至2014年12月的近场小地震波形资料,采用剪切波分裂分析对天山构造带及邻区的地壳各向异性特征进行研究,获得了研究区域内39个台站的快剪切波偏振方向和慢剪切波时间延迟.剪切波分裂参数的空间特征显示,研究区上地壳各向异性具有分区性,各向异性特征与局部构造、地壳介质变形和应力分布有关.天山构造带的快剪切波偏振呈现出两个优势方向的特点,第一优势方向大致平行于台站附近断裂和天山构造带的走向,与断裂构造和应力的综合影响有关,另一个优势方向反映了主压应力的直接作用.北天山山前断裂带东段的断裂弯折部位和南天山局部地区的剪切波分裂参数与东、西两侧不同,与准噶尔盆地、塔里木盆地的南北向挤压作用密切相关.快剪切波偏振优势方向的剧烈变化揭示,在准噶尔盆地和塔里木盆地双向挤压隆起的过程中,天山构造带产生了强烈的局部不均匀变形.塔里木盆地西侧快剪切波偏振具有两个优势方向,一个为NNE方向,与帕米尔高原受到印度一欧亚板块碰撞产生的北向挤压作用有关,另一个为NW方向,指出了塔里木盆地区域主压应力方向.准噶尔盆地北部也存在NE和NW两个快波偏振优势方向,主要与断裂的影响有关.天山构造带区域内的慢剪切波时间延迟总体上低于塔里木盆地西侧和准噶尔盆地北部,同时慢剪切波时间延迟的结果也进一步证实了天山构造带的局部强烈变形. 相似文献
7.
利用宽频带流动地震台阵GHENGIS和吉尔吉斯地震台网KNET记录的地震波走时数据,反演了中天山地区的Pn波速度结构和各向异性.结果表明,中天山上地幔顶部平均速度偏低,具有构造活动地区的特点和明显的横向非均匀性;中天山南部地幔上涌区的Pn波速度非常低,表明存在较高的热流活动.Pn波速度的变化与地震分布有着密切的对应关系：地震大都发生在中天山北部Pn波高速区上方,而南部的Pn波低速区上方几乎没有地震.这一现象说明地幔上涌引起高温极大地降低了岩石层地幔的强度,并以热传导的方式进入地壳使其失去地震破裂强度而发生韧性变形.中天山北部和南部的各向异性也存在一定的差异,南部各向异性的快波方向为近南北方向,与SKS波的各向异性特征基本一致,反映了地幔物质的迁移方向;北部各向异性的快波方向呈向南凸出的旋转趋势,估计与哈萨克地台南缘楚河盆地地壳块体向天山挤入造成应力场的改变和岩石层变形有关. 相似文献
8.
本文利用天山及其邻区布设的37个宽频带地震台站记录到的远震波形数据,分别采用最小能量法和旋转相关法对SKS和SKKS波震相进行了偏振分析,计算出了台站下方介质的S波分裂参数：快波的偏振方向（φ）和慢波延迟时间（δt）.本文研究结果表明：中天山内部大多数台站的各向异性快波方向呈NEE-SWW向,与天山走向平行,慢波时间延迟为0.4～1.7 s,这是塔里木、哈萨克斯坦的南北双向俯冲及其导致的天山地区岩石圈地幔南北向缩短变形的直接反映.本文研究发现中天山北部部分台站下方地震各向异性快波方向与慢波延时随方位角呈现规律性的变化,可能暗示该区上地幔各向异性不能仅用单层水平各向异性这一简单模式来解释.75°E以西的天山地区台站下方S波快波方向和延时具有强烈的横向变化,可能与研究区下方存在的小规模对流有关.中天山不同地段地震台站下方各向异性明显不同,进一步证实了天山地区构造变形的复杂性. 相似文献
9.
N. G. Gamburtseva T. M. Sabitova D. D. Sultanov I. A. Sanina O. P. Kuznetsov I. V. Volkova O. A. Usol’tseva 《Izvestiya Physics of the Solid Earth》2006,42(4):271-281
Recent geodynamic processes in the Tien Shan region are studied by the analysis of time series of effective velocities and traveltime delays relative to the IASPEI-91 traveltime curve of the weakly refracted wave P n from nuclear explosions at the Semipalatinsk test site over the period of 1968–1989. The time series were constructed for 10 seismic stations located at distances of 800–1200 km from the test site in the regions of the Northern, Central, and Southern Tien Shan. The twenty-year period of observations at stations in the North Tien Shan showed a significant decrease in traveltime delays by 0.20–0.76 s, which corresponds to a 0.2–0.7% increase in seismic velocities. An opposite pattern is observed at stations of the Central and Southern Tien Shan: traveltime delays increased by 0.2–0.5 s and, accordingly, seismic velocities dropped by 0.2–0.5%. These results suggest the predominance of compression processes in the crust and upper mantle during the period of observations in Northern Tien Shan and extension processes in the Central and Southern Tien Shan. The series of velocities and traveltime residuals are characterized by the presence of rhythmic oscillations of various amplitudes and periods against a linear trend. A correlation between variations in kinematic parameters and yearly numbers of earthquakes is observed at all stations. Diagrams of the spectral time analysis reveal rhythms with periods of 2–3 and 5–7 yr. The data obtained in this study are consistent with results of studying the stress-strain state of the Tien Shan crust from focal mechanisms of earthquakes and the velocities of recent crustal movements from GPS data. It is found that the amplitude of variations in kinematic parameters of the P wave at stations located in seismically active regions (the Tien Shan, Kopet Dagh, the Caucasus, Altai, and Sayany) is two to five times higher compared to aseismic regions (the Russian and Kazakh plains). 相似文献
10.
Han-Shou Liu 《Physics of the Earth and Planetary Interiors》1978,16(3):247-256
Gravitational field models derived from satellite tracking and surface gravity data have been used to derive the forces in the earth's mantle under Asia. Based on studies of tectonic forces from these models, a subcrustal stress field under China has been obtained. The stresses are due to mantle convection. According to the stress patterns, the east and west China blocks and five seismic zones are identified. The tensional stresses exerted by the upwelling mantle convection flows under the crust of Tibet seem to be related to the Tibetan uplift. The compressional orogenic region from the southern tip of Lake Baikal, through Tien Shan, Hindu Kush and the Himalayas to northern Burma appears to be connected with the downwelling mantle convection flows. It is found that the directions of the subcrustal stresses under China are disposed perpendicularly to the major fault systems and seismic belts. The results of stress calculations show that the crust of north China should be in compression and that stresses within it should be sufficient to form the Shansi Graben and Linfen Basin Systems and fracture the lithosphere. This gives a possible explanation of why strong earthquakes occurred in north China which is an isolated narrow region of highest seismicity far from plate boundaries. The tensional stress fields, caused by the upwelling mantle convection flows, are found to be regions of structural kinship characterized by major concentrations of mineral and metal deposits in China. 相似文献
11.
A. D. Kostyuk N. A. Sycheva S. L. Yunga L. M. Bogomolov Y. Yagi 《Izvestiya Physics of the Solid Earth》2010,46(3):230-243
For evaluating the deformations of the Earth’s crust in the Northern Tien Shan, we calculated the mode and intensity of the
seismotectonic deformations (STD) for this region. The input for these calculations were the catalog data on the focal mechanisms
of earthquakes, obtained by wave inversion of the signals recorded at the Kyrgyz seismic network (KNET) for the period 1994–2006.
In the construction of STD maps, a modern approach to the classification of seismotectonic deformations was applied. This
approach distinguishes eleven typical patterns of deformation. The areal distributions of the Lode-Nadai coefficient, as well
as of the vertical component and the aspect angle of the deformed state were obtained. At the same time, based on the GPS
measurements in the Northern Tien Shan during 1994–2006, the rates of dilatation and shear deformation of the Earth’s crust
were estimated. A comparison between the directions of strain axes derived from the GPS data and from the earthquake focal
data is carried out. 相似文献
12.
The geological-geophysical and petrological-geochemical studies of the Earth’s crust and upper mantle are combined to estimate the state of the lithosphere at the junction zone of Tarim and Tien Shan. The laboratory measurements of electric conductivity in the rocks sampled from the upper mantle and lower crust considered against the geoelectrical and thermal models revealed lherzolite, granulite, and eclogite massifs in the deep section of the Tarim and Tien Shan junction zone. The experimental results suggest that the crustal thickness in the southern Tien Shan attained 35–40 km 70 Ma ago. 相似文献
13.
In this study we investigate present-day seismicity and crustal deformation of Egypt based on a comprehensive earthquake catalog
from 1900 to 2004 by focal mechanism stress inversion and by recent GPS observations. Spatial distribution of earthquake epicenters
indicates that Egypt has been suffered from both interplate and intraplate earthquakes. Most earthquake activity (more than
70%) has been concentrated in northern Egypt along the geologically documented borders of Sinai subplate (northern Red Sea
and its two branches Suez rift and Aqaba–Dead Sea transform). The majority of inland earthquake focal mechanisms in Egypt
are normal with strike-slip component or strike-slip faulting events. Only a small minority, namely four events, exhibits
reverse faulting. The inversion method of Gephart and Forsyth (1984) was applied to calculate the orientation of the principle
stress axes and the shape of the stress tensor. The best fitting tensor in Egypt shows homogeneity stress field. The tension
stress regime is dominant in northern Egypt. The stress directions are well resolved by the 95% confidence limits, the relative
stress magnitude has a value of about 0.3. However, along southern Egypt the strike-slip regime is dominant. The shape factor
(R-value) is 0.5, which means that the deviatoric components of σ1 and σ3 are of the same magnitude, but of opposite signs. The average horizontal velocity of GPS stations in Egypt is 5.15± 1.1 mm/year
in mostly NNW direction. The results of deformation analysis indicate that the northern Egypt is deformed more than the southern
part. Only the Egyptian-Mediterranean coastal–Nile Delta zone dominates as a compression deformation area. However, an extensional
deformation has been observed throughout the rest of country. This means that the relative motion of African plate with respect
to both Eurasian and Arabian has highly controlled the deformation processes in Egypt. 相似文献
14.
The southern part of the Outer Zone of Southwest Japan including the Kii peninsula belongs to the tectonic ‘shadow zone’, where fewer conspicuous active faults and less Quaternary sediments develop than in the Nankai subduction zone and Inner Zone of Southwest Japan. In order to study the paleostress sequence of the Kii peninsula, we analyzed fault‐slip data and tension gashes at pilot sites of Early–Middle Miocene forearc sediments and Late Cretaceous accretionary complex. According to the results, six faulting events are reconstructed in sequence: (i) east–west extension (normal faulting); (ii) east–west compression and north–south extension (strike‐slip faulting); (iii) NNW–SSE compression and ENE–WSW extension (strike‐slip faulting); (iv) northeast–southwest compression and northwest–southeast extension (strike‐slip faulting); (v) WNW–ESE compression (strike‐slip or reverse faulting); and (vi) NNE–SSW extension. The north–south to NNW–SSE trending dyke swarm of Middle Miocene age in the Kii peninsula is thought to be related to Event 3, implying that Event 3 was active at least during the Middle Miocene. Because Event 6 is recognized solely at a site, the overall latest faulting event seems to be Event 5. Assuming that the compression results from the motion of the crust or plate, the compression direction of Event 5 is in good accordance with the present‐day WNW crustal velocity vectors of the Kii peninsula. The stress trajectory map of Southeast Korea and Southwest Japan reveals that the current compression directions of the Kii peninsula correspond to the combinatory stress fields of the Himalayan and Philippine Sea tectonic domains. 相似文献
15.
On 24 November 1983, a major earthquake occurred at 180 km depth beneath the Banda Sea. In the focal mechanism solution the pressure axis is almost horizontal, (azimuth 191°, plunge 02°) and the tension axis nearly vertical (plunge 88°). A comparison with the foreshock-aftershock pattern suggests that shear failure took place within the north-north-westerly dipping Benioff zone by thrust faulting along a southerly dipping plane. The focal mechanism solution does not conform to the usual pattern of the tension or compression axis being roughly parallel to the dip of the Benioff zone. Consequently the faulting could not have been caused by down-dip tension or compression within a sinking slab. 相似文献
16.
１９９７年１月２１日至４月１６日（北京时间）新疆伽师地区连续发生了７次６级以上 强烈地震．为了深入研究该强震群形成的构造背景,我们在伽师强震群区及其邻域大约 １１ ０００ｋｍ２的范围内布设了由 ３０台宽频带数字地震仪组成的流动地震台阵,台站的间距约５－ １０ｋｍ．利用远震体波接收函数的叠加偏移分析及其非线性反演技术,研究了台阵下方０－ １００ｋｍ深度范围内地壳、上地幔的三维Ｓ波速度结构．结果表明：１)Ｍｏｈｏ界面的深度在塔里 木盆地一侧为４０-５２ｋｍ,而在靠近天山一侧的褶皱变形区为６０-７６ｋｍ,南天山山前折皱变形 区的地壳厚度明显增大,地壳内部产生了明显变形;２)塔里木盆地北缘存在明显的不均匀性, 塔里木盆地与天山之间的接触变形关系显示了塔里木盆地向北北西方向的挤压作用,台阵下 方壳幔界面的地形与地表的地貌特征有较好的相关性,山前弧形褶皱带的形成与地下深部结 构及挤压作用有关;３)伽师强震群分布在壳幔界面梯度带的上方,该震群的成因可能与震源 区附近的隐伏断裂活动有关;４)由于震源处于褶皱变形区的地壳上部,相应的剪切模量较小, 这可能是伽师强震群应力降明显偏低的... 相似文献
17.
本文基于Vening Meinesz区域均衡模型,通过试验不同参数计算Vening Meinesz均衡补偿深度,将其与CRUST1.0模型给出的莫霍面深度进行拟合,得到适应于天山及邻区的平均补偿深度、"地区性指标"以及区域补偿半径.结合地球重力场模型EIGEN-6C4与地形数据,利用球冠体积分方法进行地形效应、沉积层效应计算和均衡校正,得到了研究区的Vening Meinesz均衡重力异常.结果显示天山及邻区的均衡重力异常幅值在-110~120 mGal之间,表明了天山及周边盆地岩石圈所处于的均衡状态,同时揭示了研究区的壳幔密度分布特征.天山、塔里木盆地、准噶尔盆地等块体的地壳垂向形变可能部分地由均衡调整引起,且均衡调整趋势与地面形变测量结果相契合.通过对均衡重力异常成因的解释,从地壳均衡角度分析了该地区复杂的构造背景及其新生代以来的演化历程. 相似文献
18.
《中国科学:地球科学(英文版)》2017,(10)
As one of the world's most active intracontinental mountain belts, Tien Shan has posed questions for researchers regarding the formation of different tectonic units and active shallow seismicity. Here, we used a huge data set comprising of 7094 earthquakes from local, regional and teleseismic seismic stations. We used waveform modeling and multi-scale double-difference earthquake relocation technique to better constrain the source parameters of the earthquakes. The new set of events provided us with better initial earthquake locations for further tomographic investigation. We found that reverse-faulting earthquakes dominate the whole study area while the fault plane solutions for earthquakes beneath the northwestern Tarim Basin and the Main Pamir Thrust are diverse. There is a low-velocity anomaly beneath Bashkaingdy at depth of 80 km, and high-velocity anomalies beneath central Tien Shan at shallower depths. These observations are the keys to understand the mechanism of Tien Shan's formation because of Tarim Basin northward and Kazakh Shield's southward subduction in the south and north respectively. Velocities beneath western Tien Shan are relatively high. We thus infer that the Western Tien Shan is relatively less deformed than the eastern Tien Shan primarily due to a relatively brittle mantle. 相似文献
19.
While dendroclimatic studies have extended the knowledge of drought variations in Tien Shan, these have been almost exclusively based on tree-ring data from Tien Shan in China. We present a drought reconstruction for Almaty based on a tree-ring width chronology developed from sites of the Schrenk spruce in Tien Shan, Kazakhstan. The drought reconstruction, spanning AD 1785–2014, was developed by calibrating tree-ring series with the mean August to January standardized precipitation evapotranspiration index (SPEI). The drought reconstruction was verified with independent data and accounts for 41.9 % of the actual SPEI variance during the common period. The drought reconstruction compares well with some tree-ring-based drought/precipitation reconstructions from Western Tien Shan and reveals the large-scale drought signals of Western Tien Shan. The wavelet analysis indicates the existence of some decadal (60 and 11 years) and interannual (2.0–4.0 years) periodicities, which may potentially be the fingerprints of large-scale land–atmosphere–ocean circulations. This study provides the first long-term drought reconstruction and drought assessment for Almaty and will aid in future plans to address climate change of Kazakhstan. 相似文献
20.
Natural seismicity and induced seismic events are discussed in the context of the seismotectonic deformation method through the example of earthquakes in the Toktogul Reservoir region in the Central Tien Shan, Kirghizia. The parameters of seismotectonic deformation of various sites in the Toktogul Reservoir region are described, based on a statistical study of focal mechanisms. The relationship of induced seismicity to changes of water level in the reservoir is reviewed. The temporal stress-strain characteristics are investigated. Average focal mechanisms for the entire region, as well as areas in the immediate vicinity of Toktogul Dam are analyzed. The vertical component of seismotectonic deformation varies in time from compression to extension-opposite to what is expected from the influence of the reservoir load; strike-slip motions become oblique thrusts. Changes in the orientation of focal mechanisms coincide with the time of maximum rate of the filling of the reservoir. 相似文献