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1.
A two dimensional velocity model of the upper mantle has been compiled from a long-range seismic profile crossing the West Siberian young plate and the old Siberian platform. It revealed considerable horizontal and vertical heterogeneity of the mantle. A sharp seismic boundary at a depth of 400 km outlines the high-velocity gradient transition zone, its base lying at a depth of 650 km. Several layers with different velocities, velocity gradients and wave attenuation are distinguished in the upper mantle. They likewise differ in their inner structure. For instance, the uppermost 50–70 km of the mantle are divided into blocks with velocities from 7.9–8.1 to 8.4–8.6 km s?1.Comparison of the travel-time curves for the Siberian long-range profile with those compiled from seismological data for Europe distinguished large-scale upper mantle inhomogeneities of the Eurasian continent and allowed for the correlation of tectonic features and geophysical fields. The velocity heterogeneity of the uppermost 50–100 km of the mantle correlates with the platform age and heat flow, i.e., the young plates of Western Europe and Western Siberia have slightly lower velocities and higher heat flows than the ancient East European and Siberian platforms. At greater depths (150–250 km) the upper mantle velocities increase from the ocean to the inner parts of the continent. The structure of the transition zone differs significantly beneath Western Europe and the other parts of Eurasia. The sharp boundary at a depth of 400 km, traced throughout the whole continent as the boundary reflecting intensive waves, transforms beneath Western Europe into a gradient zone. This transition zone feature correlates with positions of the North Atlantic-west Europe geoid and heat-flow anomalies. 相似文献
2.
The long-range seismic profile Quartz, measured by the GEON Center (Ministry of Geology of the USSR), crosses a few large geostructures: the East European platform, Timan-Pechora plate, Northern Urals, West Siberian plate (WSP), and Altai. Observations of nuclear and chemical explosions were conducted on the profile. Joint processing of records from sources of both types provided detailed structures of the crust and upper mantle. They have confirmed the known patterns in the structure of these shells of the Earth and revealed new ones. Mountain roots are observed beneath the Urals and Altai, and areas of a higher heat flow are matched by lower velocity zones in the upper mantle. Moreover, it is shown that the Timan-Pechora plate is characterized by a two-layer crust untypical of other young plates of central Eurasia and the upper mantle has the same velocities beneath the ancient East European platform and the young Altai orogen. It is also shown that the vast region including the Timan-Pechora plate, Urals, and WSP is bounded on both sides by deep faults in the upper mantle dipping toward the center of Western Siberia. A few nearly continuous reflectors traceable in the upper mantle are represented by thin-layered heterogeneous beds. The largest horizontal heterogeneity is observed in the upper 100-km layer, often underlain by a lower velocity zone. The asthenosphere, as a layer of lower seismic velocities at the depth of a possible solidus (200–250 km), has not been revealed. The latter is evidently a feature specific to inner parts of the Eurasian continent; in marginal regions, e.g., in Western Europe, the asthenospheric layer is identified almost ubiquitously. 相似文献
3.
《Earth and Planetary Science Letters》2006,241(3-4):901-912
We have constrained the shear-wave structure of crust and upper mantle beneath Iceland by analyzing fundamental mode Rayleigh waves recorded at the ICEMELT and HOTSPOT seismic stations in Iceland. The crust varies in thickness from 20 to 28 km in western and northern Iceland and from 26 to 34 km in eastern Iceland. The thickest crust of 34–40 km lies in central Iceland, roughly 100 km west to the current location of the Iceland hotspot. The crust at the hotspot is ∼32 km thick and is underlain by low shear-wave velocities of 4.0–4.1 km/s in the uppermost mantle, indicating that the Moho at the hotspot is probably a weak discontinuity. This low velocity anomaly beneath the hotspot could be associated with partial melting and hot temperature. The lithosphere in Iceland is confined above 60 km and a low velocity zone (LVZ) is imaged at depths of 60 to 120 km. Shear wave velocity in the LVZ is up to 10% lower than a global reference model, indicating the influence of the Mid-Atlantic Ridge and the hotspot in Iceland. The lowest velocities in the LVZ are found beneath the rift zones, suggesting that plume material is channeled along the Mid-Atlantic Ridge. At depths of 100 to 200 km, low velocity anomalies appear at the Tjornes fracture zone to the north of Iceland and beneath the western volcanic zone in southwestern Iceland. Interestingly, a relatively fast anomaly is imaged beneath the hotspot with its center at ∼135 km depth, which could be due to radial anisotropy associated with the strong upwelling within the plume stem or an Mg-enriched mantle residual caused by the extensive extraction of melts. 相似文献
4.
Seismic tomography beneath the orogenic belts and adjacent basins of northwestern China 总被引：2，自引：0，他引：2
Three-dimensional velocity images of the crust and upper mantle beneath orogenic belts and adjacent basins of the northwestern
continent of China are reconstructed by seismic tomography, based on arrival data of P wave recorded in seismic networks in
Xinjiang, Qinghai, Gansu of China and Kyrgyzstan. The velocity images of upper crust demonstrate the tectonic framework on
the ground surface. High velocities are observed beneath orogenic belts, and low velocities are observed in the basins and
depressions that are obviously related to unconsolidated sediments. The velocity image in mid-crust maintains the above features,
and in addition low velocities appear in some earthquake regions and a low velocity boundary separates the western Tianshan
Mts. from eastern Tianshan Mts. The orogenic belts and the northern Tibetan plateau have a Moho depth over 50 km, whereas
the depths of the Moho in basins and depressions are smaller than 50 km. The velocity images of upper mantle clearly reveal
the colliding relationship and location of deep boundaries of the continental blocks in northwestern China, indicating a weakness
of the upper mantle structure of orogenic belts. The top depth of upper mantle asthenosphere varies from place to place. It
seems shallower under the northern Tibetan plateau, Altay and Qilian Mts., and deeper under the Tarim and Tianshan regions.
Hot mantle probably rose to the bottom of some orogenic belts along tectonic boundaries when continental blocks collided to
each other. Therefore their dynamic features are closely correlated to the formation and evolution of orogenic belts in northwestern
China. 相似文献
5.
云南思茅—中甸宽角反射/折射地震剖面切割松潘—甘孜、扬子和华南三个构造单元的部分区域. 我们利用初至波和壳内反射波走时层析成像获得地壳纵波速度结构. 在获得新的地壳速度结构模型基础上，利用地震散射成像思想和低叠加次数的叠前深度偏移方法重建了研究区的地壳、上地幔反射结构. 综合分析研究区地壳P波速度模型和壳内地震反射剖面发现：沿测线从北至南地壳厚度从约50 km减薄至35 km左右，地壳厚度的减薄量主要体现在下地壳，剖面北段下地壳厚度约为30 km，剖面南段下地壳厚度仅为15 km左右；上地幔顶部局部位置P波速度值偏低，一般为76～78 km/s，反映出云南地区是典型的构造活动区的特点.剖面沿线地壳内地震反射发育，其中莫霍强反射出现在景云桥下方；在景云桥弧形断裂带8～10 km深处出现宽约50 km的强反射带. 相似文献
6.
7.
P wave velocity structure of upper and middle crust beneath the Three Gorges reservoir dam and adjacent regions 总被引：3，自引：0，他引：3
The three-dimensional P wave velocity structures of upper and middle crust beneath the Three Gorges reservoir dam and adjacent
regions were reconstructed by means of the seismic tomography, using the absolute P-arrivals from the events observed by the
Three Gorges seismic network. Our preliminary study of the deep structure shows: (1) the lithology of the Huangling anticline,
integral and highly solidified, exhibits a uniformity. Down to a depth of 20 km, the Huangling anticline still shows high-velocity
anomalies. Note that the characteristics of the velocity images with the different depths are not the same; (2) the depth
of the sedimentary rocks beneath the entire Zigui basin is not constant, which is less than 6 km; (3) the top boundary of
the crystalline basement varies from 0 to 7 km, whereas the bottom one between 14 and 16 km; (4) the partially molten substances
of the upper mantle are located in the Badong-Zigui and its adjacent regions as well as nearby Peishi area. The development
and evolution of the current tectonics are associated with the cooling and solidifying process of the molten substances within
the upper mantle; (5) the different velocity structures of the deep crust in both east and west side of the Jiuwanxi fault
are to be investigated in order to understand the origin of gravitational gradient zone in the Three Gorge areas; and (6)
the velocities within the upper crust would be affected by reservoir water permeability.
Supported by National Natural Science Foundation of China (Grant No. 40574039), National Key Technology R& D Program (Grant
No. 2008BAC38B02) 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.
中国南北带地壳和上地幔的三维速度图象 总被引：46，自引：7，他引：46
本文采用作者提出的地震层析成象法得到了中国南北带地壳和上地幔的三维速度图象。通过误差和分辨分析,以及同爆炸地震测深剖面的比较,证明了成象结果的可靠性。 成象结果表明:1.南北带的地壳和上地幔存在显著的横向不均匀性,深达450km这种不均匀性还依然存在;2.地壳上部的速度图象与地表的已知地质特征明显相关:四川盆地显著低速,康滇地轴显著高速;3.中地壳在很大范围内存在低速层,其最低速度值达5.60km/s;4.在25°N-38°N和100.0°E-103.2°E的长条带内,上地幔顶部出现低速异常,异常速度值约为7.49km/s。 成象结果还清晰地勾划了各块体间的焊接边界。120km深度的速度图象表明,扬子准地台自秦岭以南以龙门-大巴和盐源-丽江台缘褶带为其西部边界;西南以哀劳山褶皱带为界;东南则以右江褶皱带内的南盘江为界。 统计表明,地震活动与南北带的速度结构相关:从20km以上的速度图象发现,大地震大都发生在高速和低速间的过渡条带上。 相似文献
10.
本文利用30个基准台所记录的238条长周期面波资料,经过适配滤波和分格频散反演,得到中国大陆及邻区147个分格10-105s的纯路径频散,进而反演出青藏高原及邻近地区深至170km的剪切波三维速度结构.研究表明,青藏高原中西部地区和东部地区的地壳平均厚度分别为70±7km和65±7km,地壳平均剪切波速度分别为3.55和3.62km/s,上地幔顶盖平均速度分别为4.63和4.61km/s; 岩石层厚度均为120±10km;东部地区下地壳内30-40km深度处普遍存在低速层;青藏高原及其东侧的上地幔低速层内有横贯东西且明显向上隆起的低速腔.滇西缅北地区的地壳厚45±5km,上地壳及下地壳内都有低速层;上地幔顶盖的速度为4.42km/s,比青藏高原本体及恒河平原都低.恒河平原地壳厚34±2km,速度平均为3.45km/s;上地幔顶盖厚86±10km,速度平均为4.63km/s,顶盖内55-83km深处有一个低速夹层. 相似文献
11.
Two-dimensional crustal velocity models are derived from passive seismic observations for the Archean Karelian bedrock of north-eastern Finland. In addition, an updated Moho depth map is constructed by integrating the results of this study with previous data sets. The structural models image a typical three-layer Archean crust, with thickness varying between 40 and 52 km. P wave velocities within the 12–20 km thick upper crust range from 6.1 to 6.4 km/s. The relatively high velocities are related to layered mafic intrusive and volcanic rocks. The middle crust is a fairly homogeneous layer associated with velocities of 6.5–6.8 km/s. The boundary between middle and lower crust is located at depths between 28 and 38 km. The thickness of the lower crust increases from 5–15 km in the Archean part to 15–22 km in the Archean–Proterozoic transition zone. In the lower crust and uppermost mantle, P wave velocities vary between 6.9–7.3 km/s and 7.9–8.2 km/s. The average Vp/Vs ratio increases from 1.71 in the upper crust to 1.76 in the lower crust.The crust attains its maximum thickness in the south-east, where the Archean crust is both over- and underthrust by the Proterozoic crust. A crustal depression bulging out from that zone to the N–NE towards Kuusamo is linked to a collision between major Archean blocks. Further north, crustal thickening under the Salla and Kittilä greenstone belts is tentatively associated with a NW–SE-oriented collision zone or major shear zone. Elevated Moho beneath the Pudasjärvi block is primarily explained with rift-related extension and crustal thinning at ∼2.4–2.1 Ga.The new crustal velocity models and synthetic waveform modelling are used to outline the thickness of the seismogenic layer beneath the temporary Kuusamo seismic network. Lack of seismic activity within the mafic high-velocity body in the uppermost 8 km of crust and relative abundance of mid-crustal, i.e., 14–30 km deep earthquakes are characteristic features of the Kuusamo seismicity. The upper limit of seismicity is attributed to the excess of strong mafic material in the uppermost crust. Comparison with the rheological profiles of the lithosphere, calculated at nearby locations, indicates that the base of the seismogenic layer correlates best with the onset of brittle to ductile transition at about 30 km depth.We found no evidence on microearthquake activity in the lower crust beneath the Archean Karelian craton. However, a data set of relatively well-constrained events extracted from the regional earthquake catalogue implies a deeper cut-off depth for earthquakes in the Norrbotten tectonic province of northern Sweden. 相似文献
12.
I. V. Nizkous I. A. Sanina E. Kissling L. I. Gontovaya 《Izvestiya Physics of the Solid Earth》2006,42(4):286-296
Arrival times of P and S waves from local earthquakes in the Kamchatka area of the Kurile-Kamchatka Island Arc are used for calculating a spatial model of the elastic wave velocity distribution to a depth of 200 km. The lithosphere is shown to be strongly stratified in its velocity properties and laterally heterogeneous within the mantle wedge and seismic focal zone. A lower velocity layer (an asthenospheric wedge) is identified at depths of 70–130 km beneath the Eastern Kamchatka volcanic belt. The morphology of the Moho interface and the velocity properties of the crust are studied. The main tectonic structures of the region are shown to be closely interrelated with deep velocity heterogeneities. Regular patterns in the statistics of the earthquakes are analyzed in relation to variations in the elastic wave velocities in the focal layer. A mechanism of lithospheric block displacements along weakened zones of the lower crust and upper mantle is proposed. 相似文献
13.
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
14.
Crust and uppermost mantle structure of the Ailaoshan-Red River fault from receiver function analysis 总被引：5，自引：1，他引：5
XU Mingjie WANG Liangshu LIU Jianhua ZHONG Kai LI Hua HU Dezhao XU Zhen 《中国科学D辑(英文版)》2006,49(10):1043-1052
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
15.
通过对采自河北汉诺坝玄武岩中的下地壳和上地幔包体的详细研究 ,建立了本区下地壳—上地幔地温线。该地温线高于大洋地温线和古老地盾地温线 ,接近克拉通边缘的地温线 ,符合该区的大地构造环境。由该地温线建立的下地壳—上地幔地质结构剖面表明 ,该区下地壳主要由不同类型的麻粒岩相岩石组成 ,其化学成分以镁铁质为主 ,深度范围为 2 5～ 4 2km。上地幔由超镁铁质的二辉橄榄岩组成 ,在尖晶石二辉橄榄岩和石榴石二辉橄榄岩之间有一过渡层。由地温线确定的壳幔边界位于 4 2km附近 ,与地震资料确定的莫霍面一致 ,但在壳幔边界之上的下地壳底部有下地壳麻粒岩和超镁铁质岩的互层。这一现象可以解释在下地壳底部常见的层状反射层。该区岩石圈底界大约在 95km ,其下的软流层仍由石榴石二辉橄榄岩组成 相似文献
16.
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
17.
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
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利用云南数字地震台网的区域地震波形资料，对川滇地区的地壳上地幔速度结构进行了初步研究. 结果表明，川滇地区上地幔顶部P波速度较小，约78 km/s，P波速度在上地幔表现为较小的正速度梯度，S波在100～160 km深度范围内表现为弱低速层. 对于较短的观测路径，不同路径的平均P波和S波速度存在明显的横向变化. 与川滇菱形块体内部的速度结构不同，在块体边界附近可以观测到比较明显的上地壳低速层，我们认为它可能与块体边界的断裂带有关；川滇菱形块体内部存在的下地壳低速层，有利于块体向南滑动，而中上地壳没有明显低速结构，可能表明川滇菱形块体向南滑动的解耦深度至少在下地壳. 根据不同路径的反演结果，给出了云南中部地区地壳内部的平均速度结构. 相似文献
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利用文登—阿拉善左旗长观测距地震宽角反射/折射剖面东段资料,辩识出4组地壳震相和3组地幔盖层震相.采用二维射线追踪走时反演和正演拟合交替计算方法,得到了包括鲁东隆起和华北裂陷盆地在内的地壳和地幔盖层二维速度结构.研究结果表明:华北裂陷盆地基底深达6km以上,研究区壳内界面C1埋深约15km,C2界面深约25km,Moho面平均埋深约35km.上地壳速度6.0~6.1km·s-1,且横向变化较大;中地壳速度相对均匀约为6.2~6.4km·s-1;下地壳速度为6.5~7.0km·s-1,速度梯度较大.地壳平均速度与隆起和坳陷构造相关.研究区岩石圈底界面一般为75~80km,西端接近太行隆起构造时深至90km左右,向西呈明显加深趋势,地壳厚度呈现相同的增厚特征.地幔盖层上部速度8.0~8.2km·s-1,具明显正梯度特征.岩石圈平均速度在郯庐断裂带附近显著偏低.PmP和PLP震相存在不同程度的复杂性,意味着在本地区Moho界面和岩石圈界面有较为复杂的结构,可能具有一定厚度或过渡带性质.结合其他研究结果认为,地幔盖层和下地壳速度梯度、界面性质差异与华北克拉通破坏相关,意味着破坏是一个渐变、缓慢和不均匀的过程.郯庐断裂带附近的低速应是其为软弱带的证据. 相似文献
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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