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1.
Using the P-and S-wave arrivals from the 150 earthquakes distributed in Tibetan Plateau and its neighboring areas, recorded by Tibetan seismic network, Sichuan seismic network, WWSSN and the mobile network situated in Tibetan Plateau, we have obtained the average P-and S-wave velocity models of the crust and upper mantle for this region:
(1)  The crust of 70 km average thickness can be divided into two main layers: 16 km thick upper crust with P-wave velocity 5.55 km/s and S-wave velocity 3.25 km/s; and 54 km thick lower crust with P-wave velocity 6.52 km/s and S-wave velocity 3.76 km/s.
(2)  The p-wave velocity at the upper most mantle is 7.97 km/s, and the S-wave 4.55 km/s. The low velocity layer in the upper mantle occurs approximately at 140 km deep with a thickness of about 55–62 km. The prominent velocity gradient beneath the LVZ is comparable to the gradient above it.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, Supp., 573–579, 1992.  相似文献   

2.
南北地震带岩石圈S波速度结构面波层析成像   总被引：13，自引：8，他引：5       下载免费PDF全文
本文利用天然地震面波记录和层析成像方法,研究了南北地震带及邻近区域的岩石圈S波速度结构和各向异性特征.结果表明南北地震带的东边界不但是地壳厚度剧变带,也是地壳速度的显著分界.其西侧中下地壳的S波速度显著低于东侧,强震大多发生在低速区内部和边界.青藏高原东缘中下地壳速度显著低于正常大陆地壳,在松潘甘孜地块和川滇地块西部大约25～45 km深度存在壳内低速层;这些低速特征与高原主体的低速区相连,有利于下地壳物质的侧向流动.地壳的各向异性图像与下地壳流动模式相符,即下地壳物质绕喜马拉雅东构造结运动,东向的运动遇到扬子坚硬地壳阻挡而变为向南和向北东的运动.面波层析成像结果支持青藏高原地壳运动的下地壳流动模型.南北地震带的岩石圈厚度与其东侧的扬子和鄂尔多斯地块相似但速度较低.川滇西部地块上地幔顶部(莫霍面至88 km左右)异常低速;松潘甘孜地块上地幔盖层中有低速夹层(约90～130 km深度).岩石圈上地幔的速度分布图像与地壳显著不同,在高原主体与川滇之间存在北北东向高速带,可能会阻挡地幔物质的东向运动.上地幔各向异性较弱且与地壳的分布图像显然不同.因此青藏高原岩石圈地幔的构造运动具有与地壳不同的模式,软弱的下地壳提供了壳幔运动解耦的条件.  相似文献   

3.
S-wave velocity structure beneath the Ailaoshan-Red River fault was obtained from receiver functions by using teleseismic body wave records of broadband digital seismic stations. The average crustal thickness, Vp/Vs ratio and Poisson’s ratio were also estimated. The results indicate that the interface of crust and mantle beneath the Ailaoshan-Red River fault is not a sharp velocity discontinuity but a characteristic transition zone. The velocity increases relatively fast at the depth of Moho and then increases slowly in the uppermost mantle. The average crustal thickness across the fault is 36―37 km on the southwest side and 40―42 km on the northeast side, indicating that the fault cuts the crust. The relatively high Poisson’s ratio (0.26―0.28) of the crust implies a high content of mafic materials in the lower crust. Moreover, the lower crust with low velocity could be an ideal position for decoupling between the crust and upper mantle.  相似文献   

4.
The preliminary interpretation of deep seismic sounding in western Yunnan   总被引：2，自引：0，他引：2  
The preliminary interpretation of Project western Yunnan 86–87 is presented here. It shows that there obviously exists lateral velocity heterogeneity from south to north in western Yunnan. The depth of Moho increases from 38 km in the southern end of the profile to 58 km in its northern end. The mean crustal velocity is low in the south, and high in the north, about 6.17–6.45 km/s. The consolidated crust is a 3-layer structure respectively, the upper, middle and lower layer. P 1 0 is a weak interface the upper crust, P 2 0 and P 3 0 are the interfaces of middle-upper crust and middle-lower crust respectively. Another weak interface P 3 0′ can be locally traced in the interior of the lower crust. Interface Pg is 0–6 km deep, interface P 1 0 9.2–16.5 km deep, and interfaces P 2 0 and P 3 0 respectively 17.0–26.5 km, 25.0–38.0 km deep. The velocity of the upper crust gradually increases from the south to the north, and reaches its maxmium between Nangaozhai and Zhiti, where the velocity of basement plane reaches 6.25–6.35 km/s, then it becomes small northward. The velocity of the middle crust varies little, the middle crust is a low velocity layer with the velocity of 6.30 km/s from Jinhe-Erhai fault to the north. The lower crust is a strong gradient layer. There exists respectively a low velocity layer in the upper mantle between Jinggu and Jingyunqiao, and between Wuliangshan and Lancangjiang fault, the velocity of Pn is only 7.70–7.80 km/s, it is also low to the north of Honghe fault, about 7.80 km/s. Interface P6/0 can be traced on the top of the upper mantle, its depth is 65 km in the southern end of the profile, and 85 km in the northern end. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 427–440, 1993.  相似文献   

5.
    
Based on the long period surface wave data recorded by the China Digital Seismograph Network (CDSN), theQ R of fundamental mode Rayleigh wave with periods from 10 s to 146 s is determined for the eastern Sino-Korean paraplatform in this paper. TheQ β models of the crust and upper mantle are respectively obtained for the 4 paths, with the aid of stochastic inverse method. It shows that in the eastern Sino-Korean paraplatform, the average crustalQ β is about 200, and that there exists a weak attenuation layer in the middle crust (about 10–20 km deep) which is possibly related to earthquake-prone layer. A strong attenuation layer (lowQ) of 70 km thick extensively exists in the uppermost mantle, with the buried depth about 80 km. The averageQ R of fundamental mode Rayleigh wave is between the value of stable tectonic region and that of active tectonic region, and much close to the latter. Contribution No. 96A0001, Institute of Geophysics, SSB, China. Funded by the Chinese Joint Seismological Science Foundation.  相似文献   

6.
利用2002~2003年中国地震局地质研究所台阵实验室以唐山大震区为中心布设的40个流动宽频带地震台站和首都圈数字台网的33个宽频带台站的远震数据,采用接收函数非线性反演方法得到其中72个宽频带台站下方60 km深度范围内的S波速度结构.根据得到的各台站下方地壳上地幔的S波速度结构,并综合刘启元等（1997）用接收函数非线性反演方法得到的延怀盆地15个宽频带流动台站下方的地壳上地幔S波速度结构模型,给出了39°N～41°N,114°E~119.5°E区域内沿不同走向、不同深度S波速度分布.由于综合了利用首都圈数字地震台网的宽频带台站以及流动地震台阵的观测数据,本文给出了较前人同类研究空间分辨率更好的结果.结果表明: (1)研究区的速度结构,特别是怀来以东的速度结构十分复杂.在10~20 km深度范围内,研究区地壳具有高速和低速异常块体的交错结构.研究区中上地壳速度结构主要被与张渤地震带大体重合的NW向高速条带和穿越唐山大震区的NE向高速条带所控制,而其中下地壳的速度结构主要为延怀—三河—唐山地区上地幔隆起所控制.(2)研究区内存在若干壳内S波低速体,它们主要分布在唐山,三河及延怀盆地等地区.在这些地区,壳内低速体伴随着壳幔界面的隆起和上地幔顶部速度结构的横向变化.(3)地表断层分布与地壳速度结构分区有较好的相关性,表明断层对不同块体有明显的控制作用.其中,宝坻断裂,香河断裂和唐山断裂均为超壳断裂.(4)首都圈内大地震的分布与壳内低速体及上地幔顶部的速度结构有密切关系.对于唐山大地震的成因,仅考虑板块作用引起的水平应力场是不够的,有必要充分重视由于上地幔变形引起的地壳垂直变形和上地幔物质侵入造成的热效应.  相似文献   

7.
A teleseismic profile consisting of 26 stations was deployed along 30°N latitude in the eastern Tibetan Plateau. By use of the inversion of P-wave receiver function, the S-wave velocity structures at depth from surface to 80 km beneath the profile have been determined. The inversion results reveal that there is significant lateral variation of the crustal structure between the tectonic blocks on the profile. From Linzhi north of the eastern Himalayan Syntaxis, the crust is gradually thickened in NE direction; the crustal thickness reaches to the maximum value (∼72 km) at the Bangong-Nujiang suture, and then decreased to 65 km in the Qiangtang block, to 57–64 km in the Bayan Har block, and to 40–45 km in the Sichuan Basin. The eastern segment of the teleseismic profile (to the east of Batang) coincides geographically with the Zhubalong-Zizhong deep seismic sounding profile carried out in 2000, and the S-wave velocity structure determined from receiver functions is consistent with the P-wave velocity structure obtained by deep seismic sounding in respect of the depths of Moho and major crustal interfaces. In the Qiangtang and the Bayan Har blocks, the lower velocity layer is widespread in the lower crust (at depth of 30–60 km) along the profile, while there is a normal velocity distribution in lower crust in the Sichuan Basin. On an average, the crustal velocity ratio (Poisson ratio) in tectonic blocks on the profile is 1.73 (σ = 0.247) in the Lhasa block, 1.78 (σ = 0.269) in the Banggong-Nujiang suture, 1.80 (σ = 0.275) in the Qiangtang block, 1.86 (σ = 0.294) in the Bayan Har blocks, and 1.77 (σ = 0.265) in the Yangtze block, respectively. The Qiangtang and the Bayan Har blocks are characterized by lower S-wave velocity anomaly in lower crust, complicated Moho transition, and higher crustal Poisson ratio, indicating that there is a hot and weak medium in lower crust. These are considered as the deep environment of lower crustal flow in the eastern Tibetan Plateau. Flowage of the ductile material in lower crust may be attributable to the variation of the gravitational potential energy in upper crust from higher on the plateau to lower off plateau. Supported by the National Natural Science Foundation of China (Grants No. 40334041 and 40774037) and the International Cooperation Program of the Ministry of Science and Technology of China (Grant No. 2003DF000011)  相似文献   

8.
On the basis of data of long period Rayleigh surface wave, we select 43 two-station paths which cover the eastern China thoroughly. By using the improved method of multi-filtration, we obtain the group velocity and amplitude spectrum, and then get attenuation factor for each paths. We employ Talentola inversion method to get local attenuation factor, and further invert the three-dimension Q β image under the crust and upper mantle in the eastern Chinese continent. The Q β image shows the following basic characters. There is correlation between the seismic activity and Q β structure under the crust and upper mantle in North China region. The Yangtze block begins to collide with and subduct to the North China block from the southern border of the Qinling in the southern Shaanxi. In the large part of Yangtze quasi-platform appear an obvious high Q β area at 88 km deep. In the east of Sichuan depression platform, the juncture of Sichun and Guizhou, and the Jiangnan block near the juncture of Guizhou and Hunan, the lateral variation of Q β in the crust is little, and there is a high-Q β layer no thinner than 40 km in the top mantle. In the Dian-Qian fold and fracture region between Yunnan and Guizhou, the vertical variation of Q β at the region of the crust and upper mantle is little, there is a low-Q β layer in the top mantle, about 40 km thick, low-Q β layer of the upper mantle begins to appear at about 95 km deep. In the east of Yangtze quasi-platform and the central and eastern part of the South China fold system, the Moho is smooth, the lateral variation of Q β in the crust is also little, low-Q β layer of the upper mantle begins to appear at about 85 km deep.  相似文献   

9.
On the basis of S wave information from Tai’an-Xinzhou DSS profile and with reference to the results from P-wave interpretation, the 2-D structures, including S-wave velocity V s, ratio γ between V p and V s; and Poisson’ s ratio σ, are calculated; the structural configuration of the profile is presented and the relevant inferences are drawn from the above results. Upwarping mantle districts (V s≈4.30 km/s) and sloping mantle districts (V s≈4.50 km/s) of the profile with velocity difference about −4% at the top of upper mantle are divided according to the differences of V s, γ and σ in different media and structures, also with reference to the information of their neighbouring regions; the existence of Niujiaqiao-Dongwang high-angle ultra-crustal fault zone is reaffirmed; the properties of low and high velocity blocks (zones) including the crust-mantle transitionalzone and the boudary indicators of North China rift valley are discussed. A comprehensive study is conducted on the relation of the interpretation results with earthquakes. It is concluded that the mantle upwarps, thermal material upwells through the high-angle fault, the primary hypocenter was located at the crust-mantle juncture 30.0∼33.0 km deep, and additional stress excited the M S=6.8 and M S=7.2 earthquakes at specific locations around 9.0 km below Niujiaqiao-Dongwang, the earthquakes took place around the high-angle ultra-crustal fault and centered in the brittle media and rock strata with low γ and low σ values. This subject is part of the 85-907-02 key project during the “8th Five-Year Plan” from the State Science and Technology Commission.  相似文献   

10.
中国西部及邻区岩石圈S波速度结构面波层析成像   总被引：7，自引：5，他引：2       下载免费PDF全文
黄忠贤  李红谊  胥颐 《地球物理学报》2014,57(12):3994-4004
本文利用瑞利波群速度频散资料和层析成像方法,研究了中国西部及邻近区域(20°N—55°N,65°E—110°E)的岩石圈S波速度结构.结果表明这一地区存在三个以低速地壳/上地幔为特征的构造活动区域:西蒙古高原—贝加尔地区,青藏高原,印支地区.西蒙古高原岩石圈厚度约为80 km,上地幔低速层向下延伸至300 km深度,说明存在源自地幔深部的热流活动.缅甸弧后的上地幔低速层下至200 km深度,显然与印度板块向东俯冲引起俯冲板片上方的热/化学活动有关.青藏高原地壳厚达70 km,边缘地区厚度也在50 km以上并且具有很大的水平变化梯度,与高原平顶陡边的地形特征一致.中下地壳的平均S波速度明显低于正常大陆地壳,在中地壳20~40 km深度范围广泛存在速度逆转的低速层,这一低速层的展布范围与高原的范围相符.这些特征说明青藏高原中下地壳的变形是在印度板块的北向挤压下发生塑性增厚和侧向流动.地幔的速度结构呈现与地壳显著不同的特点.在高原主体和川滇西部地区上地幔顶部存在较大范围的低速,低速区范围随深度迅速减小;100 km以下滇西低速消失,150 km以下基本完全消失.青藏高原上地幔速度结构沿东西方向表现出显著的分段变化.在大约84°E以西的喀喇昆仑—帕米尔—兴都库什地区,印度板块的北向和亚洲板块的南向俯冲造成上地幔显著高速;84°E—94°E之间上地幔顶部速度较低,在大约150~220 km深度范围存在高速板片,有可能是俯冲的印度岩石圈,其前缘到达昆仑—巴颜喀拉之下;在喜马拉雅东构造结以北区域,存在显著的上地幔高速区,可能阻碍上地幔物质的东向运动.川滇西部岩石圈底界深度与扬子克拉通相似,约为180 km,但上地幔顶部速度较低.这些现象表明青藏高原岩石圈地幔的变形/运动方式可能与地壳有本质的区别.  相似文献   

11.
Using the seismic records of 83 temporary and 17 permanent broadband seismic stations deployed in Tangshan earthquake region and its adjacent areas (39°N–41.5°N, 115.5°E–119.5°E), we conducted a nonlinear joint inversion of receiver functions and surface wave dispersion. We obtained some detailed information about the Tangshan earthquake region and its adjacent areas, including sedimentary thickness, Moho depth, and crustal and upper mantle S-wave velocity. Meanwhile, we also obtained the vP/vS structure along two sections across the Tangshan region. The results show that: (1) the Moho depth ranges from 30 km to 38 km, and it becomes shallower from Yanshan uplift area to North China basin; (2) the thickness of sedimentary layer ranges from 0 km to 3 km, and it thickens from Yanshan uplift region to North China basin; (3) the S-wave velocity structure shows that the velocity distribution of the upper crust has obvious correlation with the surface geological structure, while the velocity characteristics of the middle and lower crust are opposite to that of the upper crust. Compared with the upper crust, the heterogeneity of the middle and lower crust is more obvious; (4) the discontinuity of Moho on the two sides of Tangshan fault suggests that Tangshan fault cut the whole crust, and the low vS and high vP/vS beneath the Tangshan earthquake region may reflect the invasion of mantle thermal material through Tangshan fault.  相似文献   

12.
According to a Sino-U. S. joint project, eleven broadband digital PASSCAL seismometers had been deployed inside the Tibetan Plateau, of which 7 stations were on the profile from Lhasa to Golmud and other 4 stations situated at Maxin, Yushu, Xigatze and Linzhi. Dispersions and phase velocities of the Rayleigh surface waves (10s–120s) were obtained on five paths distributed in the different blocks of Tibetan Plateau. Inversions of the S-wave velocity structures in Songpan-Ganzi block, Qiang-Tang block, Lhasa block and the faulted rift zone were obtained from the dispersion data. The results show that significant lateral variation of the S-wave velocity structures among the different blocks exists. The path from Wenquan to Xigatze (abbreviated as Wndo-Xiga) passes through the rift-zone of Yadong-Anduo. The phase velocities of Rayleigh waves from 10s to 100s on this path are significantly higher than that on other paths. The calculated mean crustal velocity on this path is 3.8 km/s, much greater than that on other paths, where mean crustal velocities of 3.4–3.5 km/s are usually observed. Low velocity zones with different thicknesses and velocities are observed in the middle-lower crust for different paths. Songpan-Ganzi block, located in the northern part of Tibetan Plateau is characterized by a thinner crust of 65 km thick and a prominent low velocity zone in the upper mantle. The low velocity zone with a velocity of 4.2 km/s is located at a depth form 115 km to 175 km. While in other blocks, no low velocity zone in the upper mantle is observed. The value of Sn in Songpan-Ganzi is calculated to be 4.5 km/s, while those in Qiang-Tang and Lhasa blocks are about 4.6 km/s. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, Supp., 566–573, 1992.  相似文献   

13.
The reflecting events from Moho and other interfaces within the crust are recognized from the wavefield characteristics of P- and S-wave for the 480km long wide-angle seismic profile between Peigu Tso and Pumoyong Tso. Then, seismic crustal structures of P- and S-wave velocities and Poisson ratio under the nearly east-west profile in southern Tibet are interpreted by fitting the observed traveltimes with the calculated ones by forward modelling. Our interpreting results demonstrate that the crustal thickness varies remarkably in the east-west direction, showing a pattern that the crust could be divided into three parts bounded by the west of Dingri and the east of Dinggyê, respectively, where the depth of Moho is about 71km for the western part, about 76km for the middle and about 74km for the eastern. There is one lower velocity layer (LVL) at the bottom of the upper crust with depth of 20–30 km. One of the distinct features is that the thickness of LVL abruptly thins from 24km on the west to 6km on the east. The other is that the velocity variation in the crust along east-west direction for both P- and S-wave displays a feature as quasi-periodic variation. The lower velocity (compared to the average value for the continent of the globe) in the lower crust and three sets of north-southward active normal faults are probably attributed to the coupling process of material delamination in the lower crust, crustal thicking and east-westward escape of the crustal material accompanied with the continental collision between India and Eurasia Plate.  相似文献   

14.
We recognized 6 sets of reflecting P- and S-wave events from Moho and other interfaces within the crust, respectively, with the wide-angle seismic data acquired from 510 km-long Selincuo-Ya’anduo profile in the northern Tibet, fitted the observed events with forward modeling, and interpreted crustal structure of P- and S-wave velocities and Poisson’s ratio under the profile. The results demonstrate that the crustal structure between Yarlungzangbo and Bangong-Nujiang sutures changes abruptly, and the crust is the thickest at the middle part of the profile with thickness of 80 km or more. The “down-bowing” Moho is the striking feature for the crustal variation along the west-east direction. The Moho uplifts with steps, and the uplifting rate westward is greater than that eastward. The heterogeneity of P- and S-wave velocities exists both vertically and horizontally, and one lower velocity layer (LVL) exists with the depth range of 27–34 km and the thickness range of 5–7 km. For the upper crust, Poisson’s ratio is the lowest at the middle part of the profile; for the lower crust, the Poisson’s ratio at the east segment is lower than that at west segment, which means that the crustal rigidity for the upper crust is different from the lower crust, and the lower crust under the east segment of the profile is more ductile. We infer that the substance in the lower crust endured eastward flow along with the collision between Eurasian and Indian plates, and the “down-bowing” Moho is attributable to the multi-phase E-W tectonic processes.  相似文献   

15.
华北地区地壳上地幔S波三维速度结构   总被引：3，自引：0，他引：3  
利用华北地区大型流动地震台阵的记录资料,采用近震和远震联合成像方法,得到了水平分辨率0.5°×0.5°、深至600km的S波速度结构.研究结果表明,上地壳S波速度结构与地表地质构造基本一致,燕山—太行山山脉均呈现高速异常,延庆—怀来盆地、大同盆地表现为低速异常,华北盆地内部的拗陷和隆起分别呈现低速和高速.唐山地区中地壳、山西裂陷盆地中下地壳存在明显的低速异常,可能分别与流体和热物质作用有关,有利于形成孕育强震的地质构造环境.90km的速度结构图像依然与地表的构造特征有较大的相关性,可能说明深部结构对地表构造有一定的控制作用.燕山隆起区岩石圈的厚度可达120～150km左右,华北盆地的岩石圈厚度可能在80km左右,太行山地区的岩石圈厚度介于两者之间.山西裂陷盆地上地幔低速层较厚,反映了该区不稳定的构造环境造成了地幔热物质的上涌.华北盆地下方220～320km出现的高速异常体,可能揭示了华北盆地上地幔仍然存在拆沉后残留的难熔、高密度的古老岩石圈地幔.研究区东部地幔转换带呈低速异常,推测可能与太平洋板块俯冲至该区下方地幔转换带前缘120°E左右的俯冲板块相变脱水有关.  相似文献   

16.
三峡水库坝址及邻区中上地壳S波速度结构   总被引：3，自引：0，他引：3       下载免费PDF全文
利用三峡数字地震台网记录的Sg波到时资料,采用地震层析成像技术,重建了三峡水库坝址及邻区中上地壳的三维速度图象,研究了地壳深部构造,主要结论是:①黄陵背斜的岩性具有固结程度高、岩体均匀完整、埋藏深度至少达14 km的特征;②秭归盆地与边缘构造由于岩层一致,而速度结构相同;构造变形的强度决定了秭归盆地及周缘区域沉积层的厚...  相似文献   

17.
By processing S-wave data from the Fanshi-Huai'an-Taipusiqi DSS profile,which is a three-component,wide-angle reflection/refraction profile,and in the light of the results from P-wave interpretation,two-dimensional(2-D)structures of the crust and upper mantle are presented,including S-wave velocity Vs and the physical parameter of medium-Poisson's ratio a.Taking other geological and geophysical information into account,and with reference to the results from petrophysical experiments at home and abroad,we carried out interpretation and inference with respect to deep crustal structure,tectonics,and lithologic characters.It has been concluded that in the upper and middle crust,a values are mostly not greater than 0.25,and rocks,which generally assume brittle,are mainly composed of granite; the rocks in the lower layer of the upper crust between Yangyuan-Huai'an containing inorganic CO2 itself releases carbon; for the rocks in the lower crust and crust-mantle transitional zone,which are comparatively plasti  相似文献   

18.
Structure and composition of the continental crust in East China   总被引：14，自引：0，他引：14  
Crustal structures of nine broad tectonic units in China, except the Tarim craton, are derived from 18 seismic refraction profiles including 12 geoscience transects. Abundances of 63 major, trace and rare earth elements in the upper crust in East China are estimated. The estimates are based on sampling of 11 451 individual rock samples over an area of 950 000 km2, from which 905 large composite samples are prepared and analyzed by 13 methods. The middle, lower and total crust compositions of East China are also estimated from studies of exposed crustal cross sections and granulite xenoliths and by correlation of seismic data with lithologies. All the tectonic units except the Tarim craton and the Qinling orogen show a four-layered crustal structure, consisting of the upper, middle, upper lower, and lowermost crusts. P-wave velocities of the bulk lower crust and total crust are 6.8–7.0 and 6:4–6.5 km/s, respectively. They are slower by 0.2–0.4 km/s than the global averages. The bulk lower crust is suggested to be intermediate with 58% SiO2 in East China. The results contrast with generally accepted global models of mafic lower crusi. The proposed total crust composition in East China is also more evolved than previous estimates and characterized by SiO2=64%, a significant negative Eu anomaly (Eu/Eu* = 0.80), deficits in Sr and transition metals, a near-arc magma La/Nd ratio (3.0), and a calculatedμ(238U/204Pb) value of 5. In addition, it has the following ratios of element pairs exhibiting similar compatibility, which are identical or close to the primitive mantle values: Zr/Hf=37, Nb/Ta=17.5, Ba/Th=87, K/Pb=0.12x104, Rb/Cs=25, Ba/Rb=8.94, Sn/Sm=0.31, Se/Cd=1.64, La/ As=10.3, Ce/Sb=271, Pb/Bi=57, Rb/TI=177, Er/Ag=52, Cu/Au=3.2×104, Sm/Mo=7.5, Nd/W=40, CI/Li=10.8, F/Nd=21.9, and La/B=1.8. Project supported by the National Natural Science Foundation of China (Grant Nos. 49625305, 49573183, 49673184, 49794043), the State Comission of Education, the Ministry of Geology and Mineral Resources of China (Grant No. 850514), the Open Laboratory of Constitution, Interaction and Dynamics of the Crust-Mantle System, and the Alexander-von-Humboldt Foundation of Germany.  相似文献   

19.
基于Love波相速度反演南北地震带地壳上地幔结构   总被引：5，自引：3，他引：2       下载免费PDF全文
收集了南北地震带区域地震台网中292个地震台站2008年1月至2011年3月期间的地震波形数据,由频时分析方法提取了Love波相速度频散曲线,经过反演得到了研究区内的Love波相速度分布.根据Love波纯路径频散,采用线性反演方法对0.25°×0.25°的网格点进行了一维S波速度结构反演,利用线性插值获取了南北地震带地区的三维S波速度结构.结果显示了松潘—甘孜地体和川滇菱形块体地区的下地壳具有明显的S波低速层分布,该异常分布特征支持解释青藏高原隆升及其地壳物质运移的下地壳流模型.在100至120km深度上,川滇菱形块体西北部呈现较强的S波高速异常,这可能是印度岩石圈板块沿喜马拉雅东构造结下插至该区域所致,该区域下地壳的低速软弱物质与上地幔的高速强硬物质形成了鲜明对比,暗示了地壳和上地幔可能具有不同的构造运动和变形方式,这为该区域的壳幔动力学解耦提供了条件.  相似文献   

20.
    
This paper describes synthetically the seismic activity, deep and shallow structures and rock dynamic features in and near Chaoyang—Yixian region. It is supposed that there is a low velocity layer in middle crust and the three-layered crustal velocities are all lower than that in both sides of the region. There exists uplifts of upper mantle and asthenosphere-low resistance layer. It is also studied the composition of matter of three-layered crust, low velocity layer, upper mantle and asthenosphere. In the end the direct relations between the deep and shallow structure, composition and the seismic activity and new activities of faults in this region are discussed. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 180–186, 1992.  相似文献   

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