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1.
ＮｕｍｅｒｉｃａｌｓｉｍｕｌａｔｉｏｎｏｆｔｈｅｄｅｔａｃｈｍｅｎｔｄｙｎａｍｉｃｓｉｎＮｏｒｔｈＣｈｉｎａＢａｓｉｎＤｏｎｇ－Ｎｉｎｇ；ＺＨＡＮＧ（张东宁）ａｎｄＲｏｎｇ－ＳｈｅｎｇＺＥＮＧ（曾融生）（ＩｎｓｔｉｔｕｔｅｏｆＧｅｏｐｈｙｓｉｃｓ，Ｓ... 相似文献
2.
论新疆活动构造特征与地震的关系(4) 总被引：1，自引：2，他引：1
中国西部在印度洋板块和欧亚板块的作用下,地壳形变十分强烈。新疆地区地壳形变受力方向为近南北—北北东向,南部地区受印度洋板块作用,北部地区则主要是受西伯利亚块体的作用,整体运动速率由南向北逐渐减弱,GPS测量结果得到的区域应力场分布和地震震源机制解与区域构造的展布及其活动表现都相吻合。 相似文献
3.
The crustal structures of the central Longmenshan along and its margins as related to the seismotectonics of the 2008 Wenchuan Earthquake 总被引：10，自引：0，他引：10
JIA ShiXu LIU BaoJin XU ZhaoFan LIU Zhi FENG ShaoYing ZHANG JianShi LIN JieYan TIAN XiaoFeng LIU QiaoXia &GUO WenBin 《中国科学:地球科学(英文版)》2014,57(4):777-790
In 2010, a 500-km-long wide-angle reflection/refraction seismic profile was completed, running northwest from the central Sichuan Basin. This profile orthogonally crosses the meizoseismal area of great Wenchuan earthquake of 12 May 2008, which occurred in the central part of the Longmenshan. The profile also passes through the northwestern Sichuan Plateau, along which a new deep seismic sounding observation system was set up that was much improved over previous datasets and enabled abundant observations to be recorded. Seismic wave phase records that reflect the structural characteristics of different tectonic blocks, especially the complicated phase features associated with the Wenchuan earthquake, were calculated and analyzed in detail. A 2D crustal P-wave velocity model for the orogenic belt in the central Longmenshan and its margins was determined, and crustal structure differences between the stable Sichuan Basin and the thickened northwestern Sichuan Plateau were characterized. Lithological variations within the upper and lower crust in the interior of the plateau, especially a great velocity decrease and plastic rheological properties associated with strong lithologic weakening in lower crust, were detected. From west to east in the lower crust beneath the orogenic belt lying between the Sichuan Basin and the northwestern Sichuan Plateau, a giant shovel-like upwelling is observed that dips gently in the lower part and at higher angles in the upper part; this is inferred to be related to the fault systems in the central Longmenshan. An upwelling in the upper-middle crust along the eastern margin of the orogenic belt is associated with steeply dipping thrusts that strongly uplift the upper crust and crystalline basement beneath a central fault system in the Longmenshan. The data, combined with an understanding of the regional tectonic stress field and previous geological results, enable a discussion of basin-and-range coupling, orogenic tectonics, the crustal fault system, and the seismogenic tectonic environment of the central Longmenshan along the eastern margin of the Qinghai-Tibet Plateau. 相似文献
4.
E. Banda A. Udias St. Mueller J. Mezcua M. Boloix J. Gallart A. Aparicio 《Physics of the Earth and Planetary Interiors》1983,31(4):277-280
Major tectonic units of Spain have been investigated by deep seismic sounding experiments since 1974 to determine crustal structures and to delineate their differences. These areas are the central part of the Hercynian Meseta, and the Alpine chains: the Betic Cordillera in the south, including the Balearic promontory and the Alboran Sea, and the Pyrenees in the north.The main features of the crust and the upper mantle along a NNE-SSW cross-section from the Pyrenees to the Alboran Sea are described.The crust under the Meseta is typical of Hercynian areas found elsewhere in Europe, with an average thickness of 31 km, whereas the two Alpine regions are characterized by very large lateral inhomogeneities, such as rapid thickening of the crust to 50 and 40 km under the Pyrenees and the Betics, respectively. The deep-reaching E-W-trending North Pyrenean fault has a throw of 10–15 km at the base of the crust. A Pn velocity of 8.1 km s?1 is found under the entire Iberian Peninsula.In the Alboran Sea, strongly varying thicknesses of sediments, shallow variable depths to the Moho (～ 13 km under the Alboran ridge), and strong variations of Pn velocity between 7.5 and 8.2 km s?1 have been found. 相似文献
5.
自Global CMT和前人文献中搜索了1973～2015年间的34条中小地震震源机制解并进行分析,根据震级对每个地震震源机制解进行加权处理,采用网格搜索法反演了川滇菱形块体中部区域现今构造应力场。结果表明,川滇菱形块体中部区域整体以走滑断层类型为主,而西部呈现正断层类型;整个区域应力场受到近NW向挤压,NE向拉张,应力形因子为0.1。该区域应力场主张应力轴方向近水平,表明有横向的拉张作用。较低的应力形因子表明几乎处于NW-SE向和垂直向的双轴挤压及NE-SW向拉张的应力状态。这种应力状态来源于2种动力作用:(1)在青藏高原物质东流和华南块体阻挡作用下呈现NW-SE向挤压和NE-SW向拉张的走滑应力状态;(2)印度板块缅甸弧对该地区深部的NEE向低角度俯冲作用导致浅部地壳物质具有NEE-SWW向的拉张分量。这2种动力的共同作用导致该地区既出现走滑型地震,又出现正断型地震。 相似文献
6.
The Chi-Chi 1999 (ML = 7.3) earthquake generated a large number of aftershocks in the vicinity of the rupture plane. The spatial-temporal distribution of these aftershocks was recorded with high precision and thus provided a unique possibility to study whether the correlation between aftershocks and stress changes are primary due to coseismically induced stress changes (static), or whether stress relaxation processes (viscoelastic) in the lower crust contribute significantly to this correlation. From our analysis of a 3D finite element model simulating the viscoelastic stress changes due to the coseismic displacement and tectonic loading we found that the aftershocks are highly correlated with the stress variations (static and viscoelastic) caused by the main shock. Although we found that the correlation between seismicity rate changes and viscoelastic stress fluctuation is slightly better than that of the static stress changes, these differences can only be identified well in the lower crust. As a result, it is reasonable to conclude that static stress changes are the key mechanism for triggering early and shallow aftershocks in the upper crust. It is reasonable to infer that the viscoelastic relaxation in the lower crust does affect the occurrence of early aftershocks in the deep crust, but it does not significantly affect the shallow aftershocks. However, the stress changes induced from the lower crust gradually transfer to the upper crust and may influence the occurrence of aftershocks after a longer time period (>four Maxwell times). 相似文献
7.
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
8.
Mariusz Majdański 《Acta Geophysica》2012,60(1):59-75
A precise 3D model of the crust is necessary to start any tectonic or geodynamic interpretation. It is also essential for
seismic interpretations of structures lying below as well as for correct analysis of shallow structures using reflection seismics.
During the last decades, a number of wide-angle refraction experiments were performed on the territory of central and eastern
Europe (POLONAISE’97, CELEBRATION 2000, SUDETES 2003), resulting in many high quality 2D models. It is an interesting and
complicated transition zone between Precambrian and Palaeozoic Platforms. This paper presents 3D model of the velocity distribution
in the crust and upper mantle interpolated from 2D models of the structure along 33 profiles. The obtained model extends to
a depth of 50 km and accurately describes the main features of the crustal structures of Poland and surrounding areas. Different
interpolation techniques (Kriging, linear) are compared to assure maximum precision. The final model with estimated uncertainty
is an interesting reference of the area for other studies. 相似文献
9.
The forward and inverse problems of studying crustal stress state from breakout data of inclined boreholes are concisely stated. Direction of the maximum horizontal principal stress (compressive) and relative magnitudes of the horizontal stresses to the vertical stress in the upper crust in two regions of the Jizhong depression, the North of China, are obtained by analyzing the breakout data of 6 inclined wells. To get stable results in the analysis we searched for the unknown parameters both forwardly and inversely. The results show that the maximum azimuths of the horizontal principal compressive stresses in the central and southern part of the Jizhong depression are N86°E and N77°E, respectively, while the relative magnitudes of the three principal stresses in the upper crust (about 1000–4000 m) of the depression are variable. In the central part of the Jizhong depression we have foundS H :S V :S h =1.38:1.00:0.57, whereS H ,S V andS h are the maximum horizontal, vertical and minimum horizontal stress, respectively. This indicates that the present stress regime in this area is of strike-slip faulting type. In the southern part of the depression we have obtainedS H :S V :S h =0.80:1.00:0.62, indicating a normal faulting stress regime in the shallow part of the crust. 相似文献
10.
A three-dimensional model for the central Fennoscandian Shield was constructed for analysing the thermal, the rheological and the structural conditions in the lithosphere. The mesh covers a rectangular area in the southern Finland with horizontal dimensions of 500 km × 400 km and a depth extent of 100 km. Structural boundaries are derived from the several deep seismic soundings carried out in the area. Constructed model is first used in the calculation of the thermal and the rheological models and secondly in analysing the stress and the deformational conditions with the obtained rheology. Thermal and structural models are solved with the finite element method. The calculated surface HFD is between 40 and 48 mW m−2 in the Proterozoic southern part and below 40 mW m−2 in the older and northern Archaean part of the model. The calculated rheological strength shows a layered structure with two individual rheologically weak layers in the crust and strong layer in the upper part of the lower crust. The minimum brittle–ductile transition (BDT) depth is around 10 km in the southern part of the model while in the north and north-eastern parts the BDT depth is around 45–50 km. Comparison with the focal depth data shows that as most of the earthquakes occur no deeper than the depth of 10 km are they located in the brittle regime. Resulting stress conditions and possible regions of deformation after the model is subjected to pressure of 50 MPa reveals that the stress field is quite uniformly distributed in different crustal layers and that the elastic parameters control more the state of the stress than the applied rheological structure. In the upper crust, the stress intensity has values between 42 and 45 MPa whereas in the middle crust the values are around 50 MPa. Comparison of the 3-D model with earlier 2-D models shows that some differences in the results are to be expected. 相似文献
11.
12.
ＩｎｖｅｒｓｉｏｎｏｆｂｒｅａｋｏｕｔｄａｔａｆｒｏｍｉｎｃｌｉｎｅｄｂｏｒｅｈｏｌｅｓｆｏｒｓｔｒｅｓｓｓｔａｔｅｏｆｔｈｅｕｐｐｅｒｃｒｕｓｔｉｎＪｉｚｈｏｎｇ ｄｅｐｒｅｓｓｉｏｎＹＡＮ－ＸＩＡＮＧＹＵ（俞言祥）ａｎｄＺＨＯＮＧ－ＨＵＡＩＸＵ（... 相似文献
13.
Ｐｏｓｓｉｂｌｅｄｙｎａｍｉｃｓｏｆｎｏｒｍａｌ－ｆａｕｌｔｅａｒｔｈｑｕａｋｅｓｉｎｔｈｅｕｐｐｅｒｃｒｕｓｔｏｆｔｈｅｓｏｕｔｈｐａｒｔｏｆｔｈｅＱｉｎｇｈａｉ－ＸｉｚａｎｇＰｌａｔｅａｕ张东宁，许忠淮Ｄｏｎｇ－ＮｉｎｇＺＨＡＮＧａｎｄＺｈｏｎｇ... 相似文献
14.
The anisotropy of Pg-wave velocity in the area of the central External Dinarides is measured by using arrival time data as reported by local and regional seismological stations. The observed velocity varies between 5.73 km/s (in the ESE-WNWdirection) and 6.20 km/s (in the SSW-NNE direction), indicating azimuthal anisotropy with symmetry axis azimuths of 23°±n 90°. These closely match the orientation of the principal stress axes in the region, as revealed by analyses of available fault-plane solutions. The observed anisotropy may be modelled by assuming a system of vertical/subvertical cracks in the upper crust, aligned under the influence of the regional tectonic stress field. 相似文献
15.
地壳应力场的研究是地震学中的一个基本课题。本文根据对四个方面资料的分析得到了华北地区（φ30°-41°N,λ105°-124°E）地壳应力场的基本特征。这些资料是:1.地震机制,包括1937年至1979年地震的断层面解和最近十多年中的小地震综合断层面解;2.地震时的地面裂缝;3.公元143年至1976年41次M≥6地震的等震线的长轴方位;4.某些大地震地区的大地测量结果。这是一个一致性相当好的应力场,其最大压应力轴为北东东向,最小压应力轴为北北西向,并且都近于水平向。 从一些大地震的观测事实来看,具有这种一致性应力场的范围要比华北地区大,在远离华北的地方,仍表现出同华北以内相似的地壳应力场。这个事实表明,上述地壳应力场的来源,不限于华北地壳内部,而同更大规模的构造运动有关。欧亚板块、印度洋板块同太平洋板块三者之间的相互作用,以及华北所处远离板块边缘的特殊位置,可能是造成该应力场特征的主要原因。 相似文献
16.
Vladimir Yu Semenov 《Acta Geophysica》2015,63(1):103-124
The first decade of 21st century is characterized by the appearance of new approaches to deep induction soundings. The theory of magnetovariation and magnetotelluric soundings was generalised or corrected. Spatial derivatives of response functions (induction arrows) were obtained for the ultra-long periods. New phenomena have been detected by this method: secular variations of the Earth’s apparent resistivity and the rapid changes of induction arrows over the last 50 years. The first one can be correlated with the number of earthquakes, and the second one–with geomagnetic jerks in Central Europe. The extensive studies of geoelectrical structure of the crust and mantle were realized in the frame of a series of international projects. New information about geoelectrical structures of the crust in Northern Europe and Ukraine was obtained by deep electromagnetic soundings involving controlled powerful sources. An influence of the crust magnetic permeability on the deep sounding results was confirmed. 相似文献
17.
为了研究西藏中、北部壳、幔导电性结构,讨论高原中、北部岩石圈热状态,1998年和1999年（INDEPTH（Ⅲ） MT）在西藏中、北部完成了德庆—龙尾错（500线）和那曲—格尔木（600线）超宽频带大地电磁深探测剖面的研究.研究结果表明,西藏中、北部以昆仑山断裂为界,其南北壳、幔电性结构有很大差异.昆仑山断裂以北地壳和上地幔为高阻区.而昆仑山以南,地壳和上地幔的导电性有明显的分层结构：地壳上部以不连续的高阻体为主,夹有局部低阻异常体,沿南北方向上地壳的电性结构复杂,具有不连续、分块的特点;但中、下地壳为大范围的高导异常区,区内发育有大规模、不相连续、产状各异的高导体,其电阻率均小于4Ωm;在班公—怒江和金沙江缝合带之下,壳内高导体都具有向上地幔延伸的趋势,存在连通壳、幔的低阻通道.根据西藏高原中、北部壳、幔电性结构的研究推断：如同藏南一样,这里也普遍存在部分熔融体和热流体,它们的成因主要与班公—怒江和金沙江缝合带的壳-幔热交换、热活动有关,这是两期形成的壳-幔热交换通道.其中,班公—怒江缝合带的壳-幔热交换通道形成时间比金沙江缝合带早.因此,研究区壳、幔的热活动是从南边和西边开始,向北、向东扩展,导致现今西藏中、北部地壳和上地幔的热流分布由西向东、由南向北增大. 相似文献
18.
I.INTRODUCTION It iS generally accepted that the stress state in the upper crust and upper mantle in the southernQinghai—Xiz~g Plateau is essentially extensional(Molnar and Tapponnier,1978;Chen and Molnar,1983:Armijo et a1.,1986).Data offocal.mechanism 相似文献
19.
On the dynamics of extensional basin 总被引：2，自引：0，他引：2
Geological and geophysical data from the North China-Bohai Basin and “Basin and Range” Province were examined and compared. They are similar to each other in many respects. Surficial geological structures are characterized by a series of half-grabens with their one flank constituted by normal fault. Those extensional structures usually extend to a depth of 6–8 km. Therefore, the stress condition in the upper 8 km can be written as $$\sigma _2 > \sigma _x > \sigma _y$$ wherex, y denote the directions of maximum compression and maximum tension on the horizontal plane, whilez signifies the vertical direction. Some people think that this kind of stress condition exists through the entire crust in the extensional basin. However, the focal mechanisms of the earthquakes in the extensional basins with focal depths usually at 12–20 km are dominated by strike-slip faults. The stress condition in the focal regions can be expressed by $$\sigma _x > \sigma _z > \sigma _y .$$ Geodetic measurements conducted before and after the Tangshan earthquake in 1976 and the Xingtai earthquake in 1966 showed that both horizontal and vertical surficial deformations with magnitudes of a similar order occurred during the earthquakes. The surficial deformations during the earthquakes can be explained by a summation of the motions produced by both stress fields in the upper crust and the middle crust. Dynamical processes other than the homogeneous horizontal regional tectonic field are required to explain the vertical variation of the stress condition in the upper and middle crusts. Evidence from the seismic refractions, reflections and the three-dimensional seismic tomography from both local earthquakes and teleseismic events provide convincing evidence that magmatic intrusions from the uppermost mantle to the middle crust occur near the hypocenters of both the Tangshan and Xingtai earthquakes. The variation from the extensional stress regime at the upper crust to the compressional stress regime in the middle and lower crusts is considered to be the common feature in extensional basins. And the magmatic intrusions from the upper mantle to the middle crust observed in the extensional basin is suggested to be its genetic cause. Numerical simulations of magmatic intrusion from the uppermost mantle to the middle crust were studied. Both the intruded compression and the thermal stress due to magmatic intrusion were considered, also the viscoelasticity of the middle and lower crusts were assumed. The results successfully explain the vertical variation of the stress condition in the crust and the process producing an extensional basin. 相似文献
20.
Crustal structures around the Yamato Basin in the southeastern Sea of Japan, inferred from recent ocean bottom seismography (OBS) and active-source seismological studies, are reviewed to elucidate various stages of crustal modification involved from rifting in the crust of the surrounding continental arc to the production of oceanic crust in the Yamato Basin of the back-arc basin. The northern, central, and southern areas of the Yamato Basin have crustal thicknesses of approximately 12–16 km, and lowermost crusts with P-wave velocities greater than 7.2 km/s. Very few units have P-wave velocities in the range 5.4–6.0 km/s, which corresponds to the continental upper crust. These findings, combined with previous geochemical analysis of basalt samples, are interpreted to indicate that a thick oceanic crust has been formed in these areas of the basin, and that this oceanic crust has been underplated by mantle-derived magma. In the central Yamato Basin, the original continental crust has been fully breached and oceanic crust has been formed. Conversely, the presence of a unit corresponding to the continental upper crust and the absence of a high-velocity part in the lower crust implies that the southwestern edge of the Yamato Basin has a rifted crust without significant intrusion. The Oki Trough has a crust that is 17–19 km thick with a high-velocity lower crust and a unit corresponding to the continental upper crust. The formation of the Oki Trough resulted from rifting with magmatic intrusion and/or underplating. We interpret these variations in the crustal characteristics of the Yamato Basin area as reflecting various instances of crustal modification by thinning and magmatic intrusion due to back-arc extension, resulting in the production of a thick oceanic crust in the basin. 相似文献