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1.
利用环渤海地区的天然地震P波到时资料,采用纬度和经度方向分别为05°×06°的网格划分,反演了该地区地壳上地幔的三维P波速度结构.初步结果表明,环渤海地区地壳上地幔的速度结构具有明显的横向不均匀性：京津唐地区地壳中上部的速度异常反映了浅表层的地质构造特征,造山带和隆起区对应于高速异常,坳陷区和沉积盆地对应于低速异常;地壳下部出现大规模的低速异常与华北地区广泛存在的高导层相对应,估计与壳内的滑脱层和局部熔融、岩浆活动有关;莫霍面附近的速度异常反映了地壳厚度的变化及壳幔边界附近热状态的差异;上地幔顶部大范围的低速异常可能是上地幔软流层热物质大规模上涌所致. 相似文献
2.
Crust and upper mantle structure of the Ailao Shan-Red River fault zone and adjacent regions 总被引：4，自引：1，他引：4
XU Yi LIU Jianhua LIU Futian SONG Haibin HAO Tianyao & JIANG Weiwei Institute of Geology Geophysics Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2005,48(2):156-164
Using arrival data of the body waves recorded by seismic stations, we reconstructed the velocity structure of the crust and upper mantle beneath the southeastern edge of the Tibetan Plateau and the northwestern continental margin of the South China Sea through a travel time tomography technique. The result revealed the apparent tectonic variation along the Ailao Shan-Red River fault zone and its adjacent regions. High velocities are observed in the upper and middle crust beneath the Ailao Shan-Red River fault zone and they reflect the character of the fast uplifting and cooling of the metamorphic belt after the ductile shearing of the fault zone, while low velocities in the lower crust and near the Moho imply a relatively active crust-mantle boundary beneath the fault zone. On the west of the fault zone, the large-scale low velocities in the uppermost mantle beneath western Yunnan prove the influence of the mantle heat flow on volcano, hot spring and magma activities, however, the upper mantle on the eas 相似文献
3.
Three dimensional shear wave velocity structure of the crust and upper mantle beneath China from ambient noise surface wave tomography 
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下载免费PDF全文 Xinlei Sun Xiaodong Song Sihua Zheng Yingjie Yang Michael H. Ritzwoller 《地震科学（英文版）》2010,23(5):449-463
We determine the three-dimensional shear wave velocity structure of the crust and upper mantle in China using Green's functions obtained from seismic ambient noise cross-correlation.The data we use are from the China National Seismic Network,global and regional networks and PASSCAL stations in the region.We first acquire cross-correlation seismograms between all possible station pairs.We then measure the Rayleigh wave group and phase dispersion curves using a frequency-time analysis method from 8 s to 60 s.After that,Rayleigh wave group and phase velocity dispersion maps on 1° by 1° spatial grids are obtained at different periods.Finally,we invert these maps for the 3-D shear wave velocity structure of the crust and upper mantle beneath China at each grid node.The inversion results show large-scale structures that correlate well with surface geology.Near the surface,velocities in major basins are anomalously slow,consistent with the thick sediments.East-west contrasts are striking in Moho depth.There is also a fast mid-to-lower crust and mantle lithosphere beneath the major basins surrounding the Tibetan plateau (TP) and Tianshan (Junggar,Tarim,Ordos,and Sichuan).These strong blocks,therefore,appear to play an important role in confining the deformation of the TP and constraining its geometry to form its current triangular shape.In northwest TP in Qiangtang,slow anomalies extend from the crust to the mantle lithosphere.Meanwhile,widespread,a prominent low-velocity zone is observed in the middle crust beneath most of the central,eastern and southeastern Tibetan plateau,consistent with a weak (and perhaps mobile) middle crust. 相似文献
4.
以中国大陆西北地区地震层析成像的结果为基础，通过分析大陆块体内部岩石层和软流层的深部形态，提出西部造山带与相邻块体之间几种可能的碰撞类型：天山与塔里木之间存在地块的嵌入拼合、俯冲、岩石层拆离下沉以及层间插入等多种构造样式；青藏高原与北部地质单元之间存在十分清晰的深部边界，反映出上地幔物质向北扩展的痕迹；推测青藏高原的岩石层在向北运动的过程中由于受到塔里木刚性块体的阻滞发生弯曲甚至折断，但是祁连山以北较浅的软流层相当于一个开放边界，使高原的上地幔物质得以进一步向北迁移.大陆碰撞不仅造成中国西部造山带岩石层结构的变动，而且导致软流层中一部分熔融的岩浆体沿着碰撞边界上涌到岩石层底部，它们对青藏高原以及西部造山带的形成演化起到重要的作用. 相似文献
5.
利用地震层析成像结果分析了中国西部地区的上地幔速度结构,发现青藏高原北部至东南边缘上地幔顶部速度普遍偏低;随着深度的增加,低速区主要分布在羌塘、松潘—甘孜和云南西部地区,而印度大陆、塔里木、柴达木、鄂尔多斯和四川盆地均显示出较高的速度.上述速度分布与青藏高原及周边地区的岩石层结构和深部动力性质密切相关:其中羌塘地区的低速异常反映了青藏北部的地幔上涌和局部熔融,起因于印度大陆岩石层的向北俯冲;松潘—甘孜地区的低速异常与青藏东部的深层物质流动及四川盆地刚性岩石层的阻挡有关;而滇西地区的低速异常可能受到印缅块体向东俯冲作用的影响.以上三个区域构成青藏高原和周边地区的主要地幔异常区.相比之下,印度大陆、塔里木、柴达木、鄂尔多斯和四川盆地的高速异常反映了大陆构造稳定地区的岩石层地幔特点.根据速度变化推测,地幔上涌和韧性变形并非贯穿整个青藏高原,而是主要集中在羌塘、松潘—甘孜和滇西地区,上述构造效应不仅导致岩石层厚度减薄且引发了火山和岩浆活动. 相似文献
6.
利用秦岭─大别造山带及其毗邻地区３１０个地震台站记录到的区域地震２３６００条Ｐ波到时数据，重建了该区地壳和上地幔三维速度图像。结果表明：１．秦岭─大别造山带及其毗邻地区地壳和上地幔存在显著的横向不均匀性，直至１１０ｋｍ深度处依然明显。２．地壳上部的速度图像与地表地质构造密切相关：造山带隆起区显著高速；盆地及坳陷区明显低速。由速度鲜明对比勾勒出的秦岭─大别造山带南界基本上位于扬子北缘主边断裂带上。３．中地壳的速度图像表明，造山带内部的一些低速区对应于一些大型推覆构造。４．４０＋０ｋｍ深度处的速度图像反映了该区莫霍界面深度的起伏。大致以１０７°Ｅ为界，以东地区地壳厚度小于４０ｋｍ，以西地区大于４０ｋｍ，且呈现出往西地壳逐渐加厚的趋势。５．位于滦川、商县、丹凤的北秦岭构造带，上地幔顶部出现低速异常，异常速度值约为７．３９—７．５５ｋｍ／ｓ。结合地球物理测深的结果，可能是由下地壳、上地幔顶部的热过程所致。 相似文献
7.
利用秦岭─大别造山带及其毗邻地区３１０个地震台站记录到的区域地震２３６００条Ｐ波到时数据，重建了该区地壳和上地幔三维速度图像。结果表明：１．秦岭─大别造山带及其毗邻地区地壳和上地幔存在显著的横向不均匀性，直至１１０ｋｍ深度处依然明显。２．地壳上部的速度图像与地表地质构造密切相关：造山带隆起区显著高速；盆地及坳陷区明显低速。由速度鲜明对比勾勒出的秦岭─大别造山带南界基本上位于扬子北缘主边断裂带上。３．中地壳的速度图像表明，造山带内部的一些低速区对应于一些大型推覆构造。４．４０＋０ｋｍ深度处的速度图像反映了该区莫霍界面深度的起伏。大致以１０７°Ｅ为界，以东地区地壳厚度小于４０ｋｍ，以西地区大于４０ｋｍ，且呈现出往西地壳逐渐加厚的趋势。５．位于滦川、商县、丹凤的北秦岭构造带，上地幔顶部出现低速异常，异常速度值约为７．３９-７．５５ｋｍ／ｓ。结合地球物理测深的结果，可能是由下地壳、上地幔顶部的热过程所致。 相似文献
8.
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
9.
中国境内天山地壳上地幔结构的地震层析成像 总被引：23，自引：5，他引：18
根据横跨中国境内天山的库车—奎屯宽频带流动地震台阵和区域地震台网记录的近震和远震P波走时数据,利用地震层析成像方法重建了沿该地震台阵剖面下方400 km深度范围内地壳上地幔的P波速度结构.结果表明：沿新疆库车—奎屯剖面,天山地壳具有明显的横向分块结构,且南、北天山地壳显示了较为强烈的横向变形特征,表明塔里木地块对天山地壳具有强烈的侧向挤压作用;在塔里木和准噶尔地块上地幔顶部有厚度约60～90 km的高速异常体,塔里木—南天山下方的高速异常体产生了较为明显的弯曲变形,而准噶尔—北天山下方的高速异常体向南一直俯冲到中天山南侧边界下方300 km的深度,两者形成了不对称对冲构造;在塔里木和准噶尔地块下方150～400 km深度存在上地幔低速体,其中塔里木地块一侧的上地幔低速物质上涌到南天山地块的下方;在塔里木—南天山200～300 km深度范围的上地幔存在高速异常体,它可能是地幔热物质向上迁移过程融断的塔里木岩石圈的拆离体. 上述结果表明,塔里木地块的俯冲可能涉及整个岩石圈深度,但其前缘仅限于南天山的北缘;青藏高原隆升的远程效应可能不但驱动塔里木岩石圈向北俯冲,同时还造成天山造山带南侧上地幔物质的涌入;天山造山带上地幔广泛存在的低速异常有助于其上地幔的变形,而上地幔物质的强烈非均匀性应有助于推动天山造山带上地幔小尺度地幔对流的形成;根据研究区地壳上地幔速度结构特征推断,新近纪以来天山快速隆升的主要力源来自青藏高原快速隆升的远程效应,相对软弱的上地幔为加速天山造山带的变形和隆升创造了必要条件. 相似文献
10.
Using records of continuous seismic waveforms from 609 broadband seismic stations in the South China Block and its adjacent areas in 2010–2012, empirical Green's functions of surface waves were obtained from cross-correlation functions of ambient noise data between these stations. High quality phase velocity dispersion curves of Rayleigh waves were obtained using time-frequency analysis. These interstation dispersion curves were then inverted to build Rayleigh wave phase velocity maps at periods of 6–50 s. The results of phase velocity maps indicate that phase velocities at 6–10 s periods are correlated with the geological features in the upper crust. Major basins and small-scale grabens and basins display slow velocity anomalies; while most of the orogenic belts and the fold belts display high velocity anomalies. With the gravity gradient zone along Taihang Mountain to Wuling Mountain as the boundary for the phase velocity maps at period of 20–30 s, the western area mainly displays low velocity anomalies, while the eastern side shows high velocity anomalies. Phase velocities in the eastern South China Block south to the Qinling-Dabie orogenic belt is higher than that in the eastern North China Block to the north, which is possibly due to the differences of tectonic mechanisms between the North China Craton and the South China Block. The phase velocities at periods of40–50 s are possibly related to the lateral variations of the velocity structure in the lower crust and upper mantle: The low-velocity anomalies in the eastern part of the Tibetan Plateau are caused by the thick crust; while the Sichuan Basin and the southern part of the Ordos Basin display distinct high-velocity anomalies, reflecting the stable features of the lithosphere in these blocks. The lateral variation pattern of phase velocities in the southern part of the South China Block is not consistent with the surface trace of the block boundary in the eastern Yunnan Province and its vicinities. The phase velocities in the Sichuan Basin are overall slow at short periods and gradually increase with period from the central part to the edge of the basin, indicating the features of shallower basement in the center and overall stable lithospheric mantle of the basin. The middle and upper crust of the southern Ordos Basin in the North China Block is heterogeneous, while in lower crust and the uppermost mantle the phase velocities mainly exhibit high anomalies. High-velocity anomalies are widespread at the middle of the Qinling-Dabie orogenic belt, as well as the areas in southeastern Guangxi with Caledonian granite explosion, but its detailed mechanism is still unclear. 相似文献
11.
天山造山带作为世界上陆内最大的造山带之一,现今地震活动频繁,造山运动强烈,是开展陆内造山和内陆地震活动研究的天然试验场.本文利用整个天山造山带地区国内及国际台网的108个地震台站连续三年的背景噪声资料,提取了8~50 s周期的瑞利面波相速度频散曲线,并构建了整个天山造山带地区的二维瑞利面波相速度与方位各向异性分布图像.结果表明：浅部结构与地表的地质构造单元具有较大的相关性.低波速异常主要分布于沉积层厚度较大的盆地地区,而高波速异常主要分布于构造活动比较活跃的山脉地区.东天山地区中下地壳存在比较弱的低波速异常,而塔里木盆地和准噶尔盆地汇聚边缘的上地幔区域则表现为明显的高波速异常,各向异性快波方向呈现近NS向的特征,暗示着塔里木盆地和准噶尔盆地的岩石圈已经俯冲至东天山的下方.中天山地区的中下地壳至上地幔区域均呈现为明显的低波速异常,且各向异性快波方向变化比较复杂,表明中天山地区的整个岩石圈结构已经弱化,热物质上涌可能对介质的方位各向异性有一定的影响.西天山及帕米尔高原的上地幔区域存在低波速异常,各向异性表现为NW-SE方向,可能与欧亚板块的大陆岩石圈南向俯冲有关.塔里木盆地内部存在相对弱的低波速异常,推测塔里木盆地可能已经受到上涌的地幔热物质的侵蚀和破坏. 相似文献
12.
由于受到SN和EW双向挤压作用的综合影响,处于年轻高原与古老地块交接区的青藏高原东北部岩石圈强烈变形,构造活动十分活跃.为了整体性地了解青藏高原东北部重力场和深部动力学机制,本文基于EGM2008全球重力场模型数据,利用小波多尺度分析获得不同尺度的重力异常信息;同时反演了研究区的地壳厚度;通过构建穿越龙门山造山带和西秦岭造山带两条剖面的岩石圈密度结构模型,分析了地壳上地幔内不同介质的分布特征.研究结果表明,青藏高原东北部岩石圈显示十分复杂的塑性体的特征,其重力异常走向多以EW或SSE为主,反映了高原岩石圈物质向东运移的趋势;地壳厚度由西向东逐渐减薄,边缘造山带深部并没有发现"山根"痕迹,结合该地区低重力的特征,推测西秦岭—松潘构造结岩石圈发生过大规模地幔流底侵作用;地幔流上涌的动力可能来源于印度板块向欧亚大陆板块俯冲,激发了地幔流体侧向移动,在扬子地台和华北地台附近受到坚硬岩石圈的阻挡而被迫上移,并因此造成龙门山与西秦岭的隆升. 相似文献
13.
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
14.
Crustal structure of northeastern Tibetan plateau and Ordos block: Waveform interpretation of the Maqen-Jingbian seismic refraction profile 下载免费PDF全文
下载免费PDF全文 The Maqen-Jingbian wide-angle seismic reflection and refraction experiment was carried out in 1998, which aims at determining detailed structure in the crust and top of the upper mantle and understanding structural relation between the northeastern Tibetan plateau and the Ordos block. The 1-D crustal models inferred by waveform inversion show strong variations in crustal structure, which can be classified into four different types: ① an Ordos platform with the Proterozoic crust and two high-velocity layers in the northeast section, ② a transitional crust between the northeastern Tibetan plateau and the Ordos block across the Haiyuan earthquake zone, ③ the Qilian orogenic zone in the central part, and 4 the Qinling orogenic zone in the southwestern section. The Moho depth increases from ~42 km to ~62 km from the NE part to the SW part of the profile. The crystalline crust consists of the upper crust and lower crust in northeastern Tibetan plateau. There is an obviously low P-wave velocity layer dipping northeastward, which is 12–13 km thick, at the bottom of the upper crust in Qinling orogenic zone and Haiyuan earthquake zone. The lower crust is characterized by alternating high and low P-wave velocity layers. Beneath Ordos block, i.e., the NE part of the profile, the crust shows quite a smooth increase in P-wave velocity down to the Moho at a depth of about 42 km. 相似文献
15.
Shear velocity structure of crust and uppermost mantle in China from surface wave tomography using ambient noise and earthquake data 总被引：1，自引：0，他引：1
We present a 3D model of shear velocity of crust and upper mantle in China and surrounding regions from surface wave tomography.We combine dispersion measurements from ambient noise correlation and traditional earthquake data.The stations include the China National Seismic Network,global networks,and all the available PASSCAL stations in the region over the years.The combined data sets provide excellent data coverage of the region for surface wave measurements from 8 to 120 s,which are used to invert for 3D shear wave velocity structure of the crust and upper mantle down to about150 km.We also derive new models of the study region for crustal thickness and averaged S velocities for upper,mid,and lower crust and the uppermost mantle.The models provide a fundamental data set for understanding continental dynamics and evolution.The tomography results reveal significant features of crust and upper mantle structure,including major basins,Moho depth variation,mantle velocity contrast between eastern and western North China Craton,widespread low-velocity zone in midcrust in much of the Tibetan Plateau,and clear velocity contrasts of the mantle lithosphere between north and southern Tibet with significant E–W variations.The low velocity structure in the upper mantle under north and eastern TP correlates with surface geological boundaries.A patch of high velocity anomaly is found under the eastern part of the TP,which may indicate intact mantle lithosphere.Mantle lithosphere shows striking systematic change from the western to eastern North China Craton.The Tanlu Fault appears to be a major lithosphere boundary. 相似文献
16.
From April,2003 to September,2004,a passive broadband seismic array consisting of 60 stations was deployed over the Tianshan orogenic belt by State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration.Among them,51 stations make up an about 500-km-long profile across the Tianshan Mountains from Kuytun to Kuqa.The receiver function profile and S-wave velocity structure of the crust and upper mantle down to 100 km deep are obtained by using the receiver function method (Liu et al.1996,2000).The main results can be summarized as follows:(1) A clear mountain root does not exist beneath the Tianshan Mountains,and the crust-mantle boundaries underneath the stations mostly have transitional structures.This implies that the material differentiation between the crust and mantle is not yet accomplished and the orogenic process is still going on.(2)The crust beneath the Tianshan Mountains has laterally blocked structures in direction perpendicular to the mountain strike,and the crust-mantle boundary has a clear dislocation structure.Both of them correspond to each other.(3)The offsets of the Moho discontinuity are highly correlated to the tectonic borders on the surface and that corresponding to the frontal southern Tianshan fault reaches to 14 km.This manifests that large vertical divergent movement took place between different blocks.This supports the discontinuous model of the Tianshan orogeny,and the Tarim block subduction is restricted only to the southern side of the South Tianshan.(4)Inside the upper and middle crust of the Tianshan Mountains exist several low-velocity bodies correlated with high seismicity located on the mountain-basin jointures on both sides of the mountain and between different blocks,and the low-velocity bodies on the mountain-basin jointures are inclined obviously to the mountain.This implies that the low-velocity bodies may be correlated closely to the thrust and subduction of the basins on both sides of the mountain,the splicing of adjacent blocks and the fast uplift of the Tianshan Mountains. 相似文献
17.
Shear wave velocity structure of the crust and upper mantle underneath the Tianshan orogenic belt 总被引：9，自引：1，他引：9
LI Yu LIU QiYuan CHEN JiuHui LI ShunCheng GUO Biao & LAI YuanGen State Key Laboratory of Earthquake Dynamics Institute of Geology China Earthquake Administration Beijing China 《中国科学D辑(英文版)》2007,50(3):321-330
From April, 2003 to September, 2004, a passive broadband seismic array consisting of 60 stations was deployed over the Tianshan orogenic belt by State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration. Among them, 51 stations make up an about 500-km-long profile across the Tianshan Mountains from Kuytun to Kuqa. The receiver function profile and S-wave velocity structure of the crust and upper mantle down to 100 km deep are obtained by using the re-ceiver function method (Liu et al. 1996, 2000). The main results can be summarized as follows: (1) A clear mountain root does not exist beneath the Tianshan Mountains, and the crust-mantle boundaries underneath the stations mostly have transitional structures. This implies that the material differentia-tion between the crust and mantle is not yet accomplished and the orogenic process is still going on. (2) The crust beneath the Tianshan Mountains has laterally blocked structures in direction perpendicular to the mountain strike, and the crust-mantle boundary has a clear dislocation structure. Both of them correspond to each other. (3) The offsets of the Moho discontinuity are highly correlated to the tectonic borders on the surface and that corresponding to the frontal southern Tianshan fault reaches to 14 km. This manifests that large vertical divergent movement took place between different blocks. This sup-ports the discontinuous model of the Tianshan orogeny, and the Tarim block subduction is restricted only to the southern side of the South Tianshan. (4) Inside the upper and middle crust of the Tianshan Mountains exist several low-velocity bodies correlated with high seismicity located on the moun-tain-basin jointures on both sides of the mountain and between different blocks, and the low-velocity bodies on the mountain-basin jointures are inclined obviously to the mountain. This implies that the low-velocity bodies may be correlated closely to the thrust and subduction of the basins on both sides of the mountain, the splicing of adjacent blocks and the fast uplift of the Tianshan Mountains. 相似文献
18.
依据地震波速得到的上地幔温度和气象台站记录的地表温度为约束,结合地表热流和热导率观测数据,利用有限元方法计算了中国大陆及邻区岩石圈三维热结构.基于此温度结果和GPS观测得到的应变率数据,以滑动摩擦、脆性破裂和蠕变三种强度机制为约束,计算得到了中国大陆及邻区岩石圈三维流变结构.结果显示:弱强度和低等效黏滞性系数的下地壳在中国大陆及邻区普遍存在,并且下地壳的流变强度和等效黏滞性系数比上地壳和岩石圈地幔一般要低1~2个数量级;中国大陆范围内青藏高原存在着厚度最大、强度最低的下地壳;青藏高原的岩石圈强度和等效黏滞性系数比华北、华南和印度板块的都要低;岩石圈流变结构的横向分布特征与重力梯度带和地形过渡带比较一致. 相似文献
19.
根据流动数字地震台网提供的三分量地震波形记录资料,应用转换函数及快速模拟退火算法对腾冲－临沧地区30个地震台站下的地壳横波速度结构进行了反演.反演结果说明,研究区壳幔边界清晰、莫霍界面附近速度跳跃明显,由此得出该区地壳厚度在40 km左右、并具有从南向北增厚趋势.一个普遍的现象是,在腾冲-宝山地块下地壳存在明显的低速带,低速带的厚度在10～20 km间.研究结果进一步表明各台站下方上地幔速度结构复杂.这些结果为探讨青藏高原东南缘下地壳的侧向黏性流动、碰撞板块边界处壳幔物质交换等均提供了重要的地球物理证据,为探讨印-藏汇聚过程中青藏高原东构造结岩石圈变形、高原隆升及其深部动力学有一定理论意义. 相似文献
20.
对包含大别－苏鲁碰撞造山带在内的东经 １１２°－１２４°,北纬２８°－３９°区域进行地 震层析成像研究,重建其地壳及上部地幔的三维速度图像．结果表明：造山带岩石圈速度横 向不均匀性显著;大别造山带以商城－麻城断裂为界,东侧的大别地块与西侧红安地块在地 壳速度上是两个不同的速度块体;中地壳 １５-２５ｋｍ深度范围内存在低速带,与伸展滑脱构造 有关;南、北大别构造单元之下,莫霍面下凹,地壳内发育了速度为６．５－６．６ｋｍ／ｓ、向北倾斜的 相对高速体,与超高压变质岩体相对应;在大别－苏鲁造山带下方的上部地幔中存在向北倾 斜的板片状高速体,结合已有地质、地球化学证据推测,它是三叠纪俯冲的扬子地块的残留 体;俯冲板片在深部发生了断离．本文利用地震层析成像方法揭示的造山带岩石圈速度结构 细节,对研究与地表地质有关的地球动力学无疑是十分重要的． 相似文献