共查询到20条相似文献，搜索用时 15 毫秒
1.
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
2.
The role of the gravitational potential of the lithosphere in the formation of a global stress field
The global stress field appearing in the Earth’s lithosphere under the action of forces caused by the difference of gravitational
potential is calculated. An original algorithm is proposed and the operational Earth Stresses program code is developed. The
data on the topography, thickness, and density of the Earth’s crust and the upper mantle, as well as the gravitational anomalies
and thermal conditions in the lithosphere were taken into account in the calculations. A comparison of the calculation results
and the observed data makes it possible to conclude that the action of the forces of the difference of the gravitational potential
alone is sufficient to explain the features of the first order of the stress field in the Earth’s lithosphere. 相似文献
3.
Jorge A. Mendiguren Frank M. Richter 《Physics of the Earth and Planetary Interiors》1978,16(4):318-326
Intraplate stresses in middle South America are not negligible. We report thrust-faulting mechanisms for five intraplate earthquakes, which indicate a dominant horizontal deviatoric compressional stress oriented in a NW-SE direction. We conclude that this state of stress is due to forces connected with spreading on the Mid Atlantic Ridge and resistive forces exerted by the Caribbean plate to the north and the Nazca plate to the west. The existence and nature of the resistive forces is inferred from earthquake mechanisms and geological evidence presented in other studies. All the available intraplate stress data for Nazca and South America indicate that both plates are under deviatoric compression generated at spreading centers. The absence of tensional earthquake focal mechanisms, particularly in the Nazca plate near the trench, suggests that the forces associated with the gravitational sinking of subducted lithosphere are locally compensated. We present a simple numerical calculation of a non-subducting plate to show how the compressional deviatoric stresses in middle South America can be used to estimate an upper bound of about 1021 P for the viscosity of the mantle. 相似文献
4.
冲绳板块位于菲律宾海板块向欧亚板块俯冲形成的西太平洋边缘活动带上,构造应力场图像及其动力学机制表现得相当复杂．采用伪三维有限元方法,以WSM2008 观测应力场数据的应力取向和应力型两方面指标作为主要约束,对冲绳板块构造应力场进行了数值模拟．通过对计算结果的分析,对模型涉及的各种作用力作出了估计．在此基础上,对冲绳板块岩石层的状态,以及该地区的板块动力学特征进行了探讨,并得到了以下一些初步认识:① 软流层静压推力控制着该地区构造应力场的基本形态;② 冲绳海槽的演化过程,例如该地区的岩石层减薄与其下地幔流的上升等,也在很大程度上影响了该地区的板内应力场空间分布特征;③ 琉球俯冲带边界力的作用是分段的,不同区段作用力对板内应力场的影响有所不同． 相似文献
5.
We used the focal mechanisms of crustal earthquakes (depth <40 km) in the period 1909–2012 and the available GPS velocities, derived from the data collected between 1999 to 2011, to estimate the magnitude and directions of maximum principal stress and strain rates in Iran. The Pearson product moment correlation was used to find the correlation between the stress field obtained from the focal mechanism stress inversion and that obtained using the seismic and geodetic strain rates. Our assumption is that stresses in a continuum are produced by tectonic forces and the consequent deformation on the crustal scale. Therefore, the direction of the stress and strain (or strain rate) are ideally to be the same. Our results show a strong correlation between the directions of the principal components of stress and strain (rate) obtained using the different data/methods. Using weighted average analysis, we present a new stress map for Iran. 相似文献
6.
It is commonly assumed that the stress state at passive margins is mainly dominated by ridge push and that other stress sources have only a limited temporal and/or spatial influence. We show, by means of numerical modelling, that observed variations in lithosphere structure and elevation from a margin towards continental interiors may also produce significant gravitational potential stresses competing with those induced by ridge push forces. We test this hypothesis on an actual case where abundant geological and geophysical datasets are available, the shelf of southern Norway and adjacent southern Norwegian mountains (or Southern Scandes). The modelling results are consistent with the main features of three key-observables: (1) undulations of the truncated geoid (reflecting variations in gravitational potential energy in the lithosphere), (2) significant stress rotations both offshore and onshore and (3) the seismicity pattern of southern Norway. The contribution of the Southern Scandes to the regional stress pattern appears to be far more significant than previously anticipated. In addition, the modelling provides a physical explanation for the enigmatic seismicity of southern Norway. Gravitational potential stresses arising from variations in the lithospheric structure between a passive margin and its continental borderlands, can exert a significant control on the dynamic evolution of the margin in concert with ridge push. 相似文献
7.
Structure and State of Stress of the Chilean Subduction Zone from Terrestrial and Satellite-Derived Gravity and Gravity Gradient Data 总被引：1，自引：1，他引：0
B. D. Gutknecht H.-J. Götze T. Jahr G. Jentzsch R. Mahatsente St. Zeumann 《Surveys in Geophysics》2014,35(6):1417-1440
It is well known that the quality of gravity modelling of the Earth’s lithosphere is heavily dependent on the limited number of available terrestrial gravity data. More recently, however, interest has grown within the geoscientific community to utilise the homogeneously measured satellite gravity and gravity gradient data for lithospheric scale modelling. Here, we present an interdisciplinary approach to determine the state of stress and rate of deformation in the Central Andean subduction system. We employed gravity data from terrestrial, satellite-based and combined sources using multiple methods to constrain stress, strain and gravitational potential energy (GPE). Well-constrained 3D density models, which were partly optimised using the combined regional gravity model IMOSAGA01C (Hosse et al. in Surv Geophys, 2014, this issue), were used as bases for the computation of stress anomalies on the top of the subducting oceanic Nazca plate and GPE relative to the base of the lithosphere. The geometries and physical parameters of the 3D density models were used for the computation of stresses and uplift rates in the dynamic modelling. The stress distributions, as derived from the static and dynamic modelling, reveal distinct positive anomalies of up to 80 MPa along the coastal Jurassic batholith belt. The anomalies correlate well with major seismicity in the shallow parts of the subduction system. Moreover, the pattern of stress distributions in the Andean convergent zone varies both along the north–south and west–east directions, suggesting that the continental fore-arc is highly segmented. Estimates of GPE show that the high Central Andes might be in a state of horizontal deviatoric tension. Models of gravity gradients from the Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite mission were used to compute Bouguer-like gradient anomalies at 8 km above sea level. The analysis suggests that data from GOCE add significant value to the interpretation of lithospheric structures, given that the appropriate topographic correction is applied. 相似文献
8.
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
9.
《Physics of the Earth and Planetary Interiors》1982,28(3):261-268
The Runcorn stress equations and 2–30° harmonic coefficients of the geopotential have been applied to determine the mantle convection pattern beneath China. The pattern is compared with geophysical and geological observations and it is found that the directional change belts of mantle flows coincide with the major fault belts between tectonic units of China. The stress field generated by mantle flows, except in the Tian Shan region, also coincide with the stress field of recent tectonic movement in China. The Tarim and Junggar basins are formed by tensional stresses due to divergent mantle convection currents under northwest China. The formation of the Qinhai-Xizang (Tibet) plateau is due mainly to the compression of the Tarim block and Indian plate, caused by convergent mantle convection currents. The shear-fault belts in central China (100–105°E) are generated by the running change belt of mantle flows, a well-known N-S seismic zone. In eastern China, tensional faults, grabens, lake and sea depressions are related to the eastward displacement of continental lithosphere exerted by eastward dispersal mantle flows under this region.This paper provides new material for further study of the force source mechanism of recent tectonic movement from the viewpoint of mantle convection currents. 相似文献
10.
Syntheses of the regional stress fields of the Japanese islands 总被引：4，自引：0，他引：4
Tetsuzo Seno 《Island Arc》1999,8(1):66-79
The principal stresses in northern Honshu and in central-southwest Japan are synthesized on the basis of the ridge push, slab pull and across-arc variation of differential forces due to crust/plate structural variation. Assuming a more compressive north–south horizontal stress in central Japan-northern Honshu than that of southwest Japan, the calculated principal stress profiles explain the observed stress fields in these areas: namely, a strike–slip fault type for southwest-central Japan and a reverse fault type for northern Honshu, both having east–west σHmax . Kyushu is characterized by the gradient of horizontal stresses both in the east–west and north–south directions, which cannot be explained by simple plate interactions or by crust/plate structural variation. Combined with other lines of evidence for existence of mantle upwelling in the East China Sea west of Kyushu, it is proposed that the stress gradient is produced by the viscous drag exerted by the flow spread laterally from the upwelling plume. The eastward movement of Kyushu and southwest Japan relative to Eurasia revealed by the recent Global Positioning System measurements conducted by the Geographical Survey Institute of Japan would be partly explained by this basal drag. 相似文献
11.
The effective elastic thickness of the lithosphere has an important role in constraining compositional structure, geothermal gradient and tectonic forces within the lithosphere and the thickness of this layer can be used to evaluate the earthquakes’ focal depth. Hence, assessment of the elastic thickness of the lithosphere by gravitational admittance method in Iran is the main objective of this paper. Although the global geopotential models estimated from the satellite missions and surface data can portray the Earth’s gravity field in high precision and resolution, there are some debates about using them for lithosphere investigations. We used both the terrestrial data which have been provided by NCC (National Cartographic Center of Iran) and BGI (Bureau Gravimetrique International), and the satellite-derived gravity and topography which are generated by EIGEN-GL04C and ETOPO5, respectively. Finally, it is concluded that signal content of the satellite-derived data is as rich as the terrestrial one and it can be used for the determination of the lithosphere bending. 相似文献
12.
13.
W.-Y. Chung 《Pure and Applied Geophysics》2002,159(11-12):2567-2584
—?An intriguing observation in Greenland is a clear spatial correlation between seismicity and deglaciated areas along passive continental margins, a piece of evidence for earthquake triggering due to postglacial rebound. Another piece of evidence for induced seismicity due to deglaciation derives from earthquake source mechanisms. Sparse, low magnitude seismicity has made it difficult to determine focal mechanisms from Greenland earthquakes. On the basis of two normal faulting events along deglaciated margins and from the spatial distribution of epicenters, earlier investigators suggested that the earthquakes of Greenland are due to postglacial rebound. This interpretation is tested here by using more recent data. Broadband waveforms of teleseismic P waves from the August 10, 1993 (m b = 5.4) and October 14, 1998 (m b = 5.1) earthquakes have been inverted for moment tensors and source parameters. Both mechanisms indicate normal faulting with small strike-slip components: the 1993 event, strike = 348.9°, dip = 41.0°, rake =?56.3°, focal depth = 11?km, seismic moment = 1.03?×?1024 dyne-cm, and M w = 5.3; the 1998 event, strike = 61.6°, dip = 58.0°, rake =?95.5°, focal depth = 5?km, seismic moment = 5.72?×?1023 dyne-cm, and M w = 5.1. These and the two prior events support the theory that the shallow part of the lithosphere beneath the deglaciated margins is under horizontal extension. The observed stress field can be explained as flexural stresses due to removal of ice loads and surface loads by glacial erosion. These local extensional stresses are further enhanced by the spreading stress of continental crust and reactivate preexisting faults. Earthquake characteristics observed from Greenland suggest that the dominant seismogenic stresses are from postglacial rebound and spreading of the continental lithosphere. 相似文献
14.
Numerical experiments on studying the spatial fields and evolution of viscous overlithostatic horizontal stresses and pressure in the mantle and in the moving continent are carried out. The continent moves consistently with time-dependent forces, which act from the viscous mantle. By introducing the varying viscosity, we gain the possibility for taking into account the oceanic lithosphere and the difference between the viscosity of the upper and the lower mantle in the context of a purely viscous model. The typical overlithostatic horizontal stresses in the main part of the mantle are ±(7–9) MPa (70–90 bar); in the highly viscous regions and, particularly, in the subduction zones they are at least three times larger. The descending mantle flows in the depth interval from approximately 50 km to about 300 km are more sharply pronounced in the pressure field than in the field of horizontal stresses. At the considered stages of motion and in different parts, the continent is characterized by the following typical values of stresses: the overlithostatic pressure ranges from ?5 to +15 MPa; the horizontal overlithostatic tensile stress amounts up to ?4MPa (?40 bar); and the compressive stress in case of the overriding of the subduction zone attains +35 MPa (350 bar). 相似文献
15.
In this paper we investigate the sources of two kinds of forces to form the stress field in the lithosphere. These are the
drag force caused by mantle flow and the force system along plate boundaries. The results show that both forces control the
basic stress pattern in China and compressive stresses can fit with the stress patterns constructed by focal mechanisms,in-situ stress measurements in boreholes and that deduced from other geophysical and geological observation.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 295–306, 1991.
This research is sponsored by the Chinese Joint Seismological Science Fundation. 相似文献
16.
中国东北新生代板内火山广泛发育,其中诺敏河火山由于上地幔结构研究的匮乏,火山成因尚不明确.利用布设在诺敏河火山周围的40个流动台站所记录到的远震剪切波数据,测量得到82对各向异性参数和219个无效分裂结果.结果表明,研究区快慢波延迟时间变化范围为0.4～1.4s,平均0.78±0.21s;各向异性快波方向范围为N77°W—N18°E,绝大多数快波方向集中在N6.9°W±9.87°,平行于中生代晚期岩石圈伸展变形方向,推测由残留在岩石圈中的化石各向异性所引起.同时,在火山中心及周边部分台站,只观测到无效分裂而没有观测到有效分裂结果,可能是由于残存在岩石圈内的古老形变被上涌的热地幔物质所侵蚀. 相似文献
17.
喜马拉雅构造带及其临近区域是印度板块与欧亚大陆板块挤压碰撞的前缘地带.本文利用GPS实测速度场与震源机制解数据分别计算了研究区域现今地壳岩石圈表面的GPS应变场及岩石圈内部的主应力分布,研究了印度板块持续挤压作用下板块边界带地壳岩石圈现今地壳形变的空间分布特征.结果显示,南北向的剧烈挤压变形与东西向的拉伸变形是现今青藏高原南缘地壳岩石圈的主要变形特征.其中南北向的地壳挤压变形主要集中在主前缘冲断带与雅鲁藏布江缝合带之间.东西方向上,南北走向的亚东—谷露断裂是区域地壳东西向伸展变形的重要分界断裂.75°E是研究区域地壳形变的另一条显著不连续边界,其西侧地壳主压应变强度低、方向弥散且最大主压应力方向一致性较差,而东侧地壳主压应变方向与主压应力方向以及地壳水平运动速度场方向均具有较好的一致性.布格重力异常的小波多尺度辨析结果显示该分界带与循喜马拉雅西构造结楔入欧亚大陆的印度板块密切相关. 相似文献
18.
ZHU ShouBiao & SHI YaoLin Institute of Crustal Dynamics China Earthquake Administration Beijing China Department of Geophysics Peking University Beijing China Laboratory of Computational Geodynamics Graduate University of Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2007,50(1):67-74
Based on data of principal stress orientation from focal mechanism and of geological features in China, we made pseudo-3D genetic algorithm finite element (GA-FEM) inversion to investigate the main forces acting on the Chinese continent and adjacent areas which form the Chinese tectonic stress field. The results confirm that plate boundary forces play the dominant role in forming the stress field in China, as noticed by many previous researchers. However, we also find that topographic spreading forces, as well as basal drag forces of the lower crust to the upper crust, make significant contribution to stresses in regional scale. Forces acting on the Chinese continent can be outlined as follows: the collision of the India plate to the NNE is the most important action, whereby forces oriented to the NW by the Philippine plate and forces oriented to the SWW by the Pacific plate are also important. Topographic spreading forces are not negligible at high topographic gradient zones, these forces are perpendicular to edges of the Tibetan Plateau and a topographic gradient belt running in the NNE direction across Eastern China. Basal drag forces applied by the ductile flow of the lower crust to the base of upper crust affect the regional stress field in the Tibetan Plateau remarkably, producing the clockwise rotation around the eastern Himalaya syntax. 相似文献
19.
Underground Measurements of Electromagnetic Radiation Related to Stress-induced Fractures in the Odenwald Mountains (Germany) 总被引：1，自引：0，他引：1
Marco Lichtenberger 《Pure and Applied Geophysics》2006,163(8):1661-1677
The regional stress field at Wald-Michelbach (Odenwald Mountains, Germany) induces a secondary stress field around the space
of the local railway tunnel. Resulting maximum shear stresses produce microfractures, which emit electromagnetic radiation
(EMR). From EMR measured along the cross section and the long axis of the tunnel, the regional stress field is determined
by a correlation of detected impulses per time with stresses calculated from the orientation of the tunnel, its diameter,
and topographic load. The major horizontal principal stress has an azimuth of 103°. At times, strongly alternating EMR values
are observed, which indicate electromagnetic disturbances of unknown origin. Such disturbances are identified by repeated
measurements and are not evaluated. The repeated measurements, which are not disturbed, differ with median 112 impulses per
100 ms. This difference corresponds to 0.037 MPa and indicates a good reproducibility of the results. Regional stress magnitudes
and the WNW-ESE orientation of the major horizontal principal stress indicate a minor N – S directed tensional force at the
western shoulder of the Upper Rhine Graben. 相似文献
20.
西沙群岛独特的构造位置决定了其构造运动背景和地壳应力场动力源的复杂性.位于西沙群岛石岛、深达1268.07m的西科1A井在1257.52m钻遇花岗岩基底.在1125.8~1262.0m开展5次水压致裂地应力测量,获得最大水平主应力为17.09~20.85MPa,最小水平主应力为15.97~18.29MPa,估算垂直主应力为22.86~26.68 MPa,地壳应力结构为SVSHSh,以垂直主应力为主导,该应力结构特征有利于正断层活动,表明西沙群岛地壳基底处于拉张的应力环境.受西沙海槽断层影响,水平应力值较低.印模测试显示基底地壳应力方向以近东西-北西向为主,与已有的GPS测量、横波分裂和面波反演结果较为吻合,显示西沙群岛岩石圈尺度上变形一致性较好.西沙群岛地壳应力场的力源受板块运动和地幔物质上涌作用联合制约.综合南海西北部实测地应力数据分析,显示该区域主应力方向较为一致,应处于统一、稳定的构造运动背景之中.西科1A井水压致裂试验是我国首次涉海深孔地壳应力测量,具有重要的地球动力学意义,提供了研究南海地球物理场的宝贵基础资料. 相似文献