渤海湾及其邻区壳幔速度结构研究与综述

利用渤海湾及其邻区的10多条地震测深剖面段观测资料，对部分剖面进行二维射线追踪、走时拟合及合成地震图计算，获得了本区地壳上地幔速度结构．结果表明，地壳上地幔结构在纵向和横向上具有明显的不均匀性．在冀中坳陷东北部的永清附近、黄骅坳陷的渤海湾和济阳坳陷的垦利附近存在上地幔隆起，隆起处的地壳厚度分别约为31, 28和29 km．根据地震波动力学及运动学特征和二维速度结构中的地震界面与速度等值线起伏变化，推测该区有3条地壳深断裂带，在地壳深断裂带一侧或两侧上地壳存在5.90～6.10 km/s的低速层(体)．      

Study and review on crust-mantle velocity structure in Bohai Bay and its vicinity

Introduction Bohai Bay, along with its adjacent areas, is one of the seismically active areas in North China. Understanding its crust/upper-mantle structural characteristics and lateral heterogeneity of the medium in this area is of great significance to the study of seismogenic environment, thus improvimg the level of earthquake prediction. For years, scientists have studied the area by gravity and magnetic methods (FENG, et al, 1989), geothermal field (WU, et al, 1988; TIAN, ZHANG, 19…     

Crustal wide-angle reflection imaging along Lianxian-Gangkou profile in Guangdong province,China

A 400 km-long wide-angle seismic experiment along Lianxian-Gangkou profile in South China was carried out to study contact relationship between southeast continental margin of Yangtze block and northwest continental margin of Cathaysia block. We reconstructed crustal wide-angle reflection structure by the depth-domain pre-stack migration and the crustal velocity model constructed from the traveltime fitting. The wide-angle reflection section shows different reflection (from crystalline basement and Moho) pa...     

Crustal wide-angle reflection imaging along Lianxian-Gangkou profile in Guangdong province,China

A 400 km-long wide-angle seismic experiment along Lianxian-Gangkou profile in South China was carried out to study contact relationship between southeast continental margin of Yangtze block and northwest continental margin of Cathaysia block. We reconstructed crustal wide-angle reflection structure by the depth-domain pre-stack migration and the crustal velocity model constructed from the traveltime fitting. The wide-angle reflection section shows different reflection (from crystalline basement and Moho) pattern beneath the Yangtze and Cathaysia blocks, and suggests the Wuchuan-Sihui fault is the boundary between them. A cluster of well-developed reflections on Moho and in its underlying topmost mantle probably comes from alternative thin layers, which may be seismic signature of strong interaction between crust and mantle in the tectonic environment of lithosphere extension.     

Study on crust-mantle tectonics and its velocity structure along the Beijing-Huailai-Fengzhen profile

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Crustal structure of Dabieshan orogenic belt

The crustal structures ofP velocity and density on the deep seismic sounding profile across the Ilabieshan orogenic belt are presented. There is a 5-km-thick crustal “root” between the Yuexi and Xiaotian where the elevation is highest on the profile. An apparent Moho offset of 4. 5 km beneath the Xiaotian-Mozitan fault marks the paleo-suture of the Triassic collision. A high-velocity anomaly zone at the depth below 3 km beneath the ultra-high pressure (UHP) zone may be correlated to the higher content of UHP metamorphic rocks. Project supported by the National Natural Science Foundation of China and the Joint Earthquake Science Foundation.     

Group velocity distribution of Rayleigh waves and crustal and upper mantle velocity structure of the Chinese mainland and its vicinity

Introduction A lot of results have been achieved on the study of crust and upper mantle structure in Chinese mainland by the surface wave dispersion. The seismometer can be classified into three types based on the development from the analog to digital instrument. FENG, et al (1981) measured the dispersion curves of group and phase velocity along 28 paths, with 19 earthquakes recorded by 15 base analog seismic stations, subdivided the Chinese mainland into 5 blocks and obtained the average c…     

Sounding of electrical structure of the crust and upper mantle along the eastern border of Qinghai-Tibet Plateau and its tectonic significance

Sounding and study on electrical structure of the crust and upper mantle within the eastern border region of Qinghai-Tibet Plateau by using the magnetotelluric sounding (simply MT) method permitted us to understand the characteristics of specific electrical structure in the region. The sounding result clearly revealed that: (1) The Xianshuihe fault zone represents a large-scale lithospheric fault and is an important boundary fault of the rhombic Sichuan-Yunnan block. (2) The sounded region is a strong earthquake-prone zone. The different crustal media of blocks on both sides of the fault became an important deep background for the strong seismo-active zone. (3) A large-scale low-resistivity layer is found to exist at a depth more than ten kilometers beneath the northern part of the rhombic Sichuan-Yunnan block. Its electrical resistivity is only several to tens Ω?m. The layer northeastward extends down at an angle of 45°. It is related to an obstacle to the lateral squeeze of Qinghai-Tibet Plateau and eastward flow of mass by the rigid block. It is inferred from the characteristics of electrical property of deep media that the northern part of the recent rhombic Sichuan-Yunnan block is in a thermal state and is one of the recently fairly active blocks. (4) The lithosphere in the sounded region is gradually thickened from the western segment (northern Sichuan-Yunnan block) to east (Yangtze block).     

Dispersion of Rayleigh waves along a mainly Atlantic path

Summary It is shown that the dispersion curve of Rayleigh waves of an Earthquake of Haiti as observed in Budapest agrees well with those obtained byEwing &Press, as well as byBerckhemer for Atlantic route, though the latter related to purely oceanic routes, while with the curves observed at Budapest 80% of the route refer to an oceanic, 20% to continental path.     

Upper mantle structure of the Apulian plate from Rayleigh waves

Phase velocities of Rayleigh waves for the Adriatic Sea area are obtained in the period range 25–190 sec along the path (l'Aquila-Trieste) AQU-TRI and 20–167 sec along the path (Trieste-Bari) TRI-BAI.The phase velocities are systematically higher than the known values for the surrounding regions. The data inversion indicates the presence of a lithosphere typical of stable continental areas with clear high-velocity lid (V _s 4.6 km/sec) overlying a well developed low velocity zone (V _s 4.2 km/sec).P. F. Geodinamica C.N.R., Roma Pubbl. N. 189.     

Anisotropy in the Earth's crust and uppermost mantle in southeastern Europe obtained from Rayleigh and Love surface waves

Digital seismograms from 25 earthquakes located in the southeastern part of Europe, recorded by three-component very broadband seismometers at the stations Vitosha (Bulgaria) and Muntele Rosu (Romania), were processed to obtain the dispersion properties of Rayleigh and Love surface waves. Rayleigh and Love group-velocity dispersion curves were obtained by frequency–time analysis (FTAN). The path-averaged shear-wave velocity models were computed from the obtained dispersion curves. The inversion of the dispersion curves was performed using an approach based on the Backus–Gilbert inversion method. Finally, 70 path-averaged velocity models (35 R-models computed from Rayleigh dispersion curves and 35 L-models computed from Love dispersion curves) were obtained for southeastern Europe. For most of the paths, the comparison between each pair of models (R-model and L-models for the same path) shows that for almost all layers the shear-wave velocities in the L-models are higher than in the R-models. The upper sedimentary layers are the only exception. The analysis of both models shows that the depth of the Moho boundary in the L-models is shallower than its depth in the R-models. The existence of an anisotropic layer associated with the Moho boundary at depths of 30–45 km may explain this phenomenon. The anisotropy coefficient was calculated as the relative velocity difference between both R- and L-models at the same depths. The value of this coefficient varies between 0% and 20%. Generally, the anisotropy of the medium caused by the polarization anisotropy is up to 10–12%, so the maximum observed discrepancies between both types of models are also due to the lateral heterogeneity of the shear-wave velocity structure of the crust and the upper mantle in the region.     

各国地壳上地幔深地震反射研究计划与进展

当前世界上采用的深部探测地球物理技术主要是地震学方法，七十年代以来，美、英、法、德、加拿大、澳大利亚等发达国家相继开展了各自的深地震反射研究计划ＣＯＣＯＲＰ、ＢＩＲＰＳ、ＥＣＯＲＳ、ＤＥＫＯＲＰ、ＬＩＴＨＯＰＲＯＢＥ＆ＡＣＯＲＰ。共完成深地震反射测线４万公里左右，获得了岩石圈的形成与演化，地球动力学过程，及地球深部构造等方面重要信息，从八十年代开始，我国在不同构造带上实施了１５００公里左右的深地震     

P-wave crustal velocity structure in western Sichuan and eastern Tibetan region

A deep seismic sounding profile located in the western Sichuan and eastern Tibetan region extends from Batang (Zhubalong) to Zizhong, Sichuan. It passes through the Songpan-Garzê Fold System and the Longmenshan Tectonic Zone, and ends in the Yangtze Craton. Based on the travel times of phases on the profile, incorporating information on the relevant amplitudes, we determined 2-D P-wave crustal velocity structure along the profile, analyzed the principle differences between the crustal and upper mantle structure in the Western Sichuan Plateau and Sichuan Basin, discussed the deep feature of the major faults on the profile, the tectonic relation between the Yangtze Craton and the Tibetan Plateau and the deep structural environment where strong earthquakes occurred.     

江苏及邻区地壳上地幔结构研究

根据江苏及邻区大地构造单元和人工地震研究程度的不同,划分为下扬子地区、郯庐断裂带、大别山东段、苏鲁地块等地区,介绍了利用人工地震、天然地震层析成像及其它地球物理探测等方法对这一地区的深部构造研究结果。其中下扬子地区莫霍面的深度为28~33 km,横向不均匀,由西向东逐渐减薄;大别—苏鲁地区地表超高压变质带地壳波速特征主要表现在上地壳顶部的高速层,其厚度一般小于10 km;苏鲁地块地壳厚度约在32~33 km之间,明显高于周边地区;大别山地区沿造山带方向莫霍面变化平缓,地壳厚度33 km左右;横穿造山带方向起伏变化较大,莫霍面最深达41 km左右。天然层析成像研究范围大,分辨率较低。大别苏鲁地区人工地震测深工作较深入,但调查范围较小,主要在浅层,认识相对局部,有待于面上的大范围深部结构图像研究。     

Three-dimensional thermal structure of the Chinese continental crust and upper mantle

We invert S-wave velocities for the 3D upper-mantle temperatures, in which the position with a temperature crossing the 1300℃ adiabat is corresponding to the top of the seismic low velocity zone. The temperatures down to the depth of 80 km are then calculated by solving steady-state thermal conduction equation with the constraints of the inverted upper-mantle temperatures and the surface temperatures, and then surface heat flows are calculated from the crustal temperatures. The misfit between the calculated and observed surface heat flow is smaller than 20% for most regions. The result shows that, at a depth of 25 km, the crustal temperature of eastern China (500―600℃) is higher than that of western China (<500℃). At a depth of 100 km, temperatures beneath eastern and southeastern China are higher than the adiabatic temperature of 1300℃, while that beneath west China is lower. The Tarim craton and the Sichuan basin show generally low temperature. At a depth of 150 km, temperatures beneath south China, eastern Yangtze craton, North China craton and around the Qiangtang terrane are higher than the adiabatic temperature of 1300℃, but is the lowest beneath the Sichuan basin and the regions near the Indian-Eurasian collision zone. At a depth of 200 km, very low temperature occurs beneath the Qinghai-Tibet Plateau and the south to the Tarim craton.     

大同—阳高震区深部构造背景

利用通过本区的宽角反射／折射剖面资料对大同－阳高震区及邻区地壳上地幔速度结构与构造进行了详细的研究,结果表明,地壳上地幔速度结构与构造在纵向和横向上具有明显的不均一性,浅部基底断裂发育,对应其深部,根据波组特征,壳内界面及速度等值线起伏变化和低速异常体的边界等推测了地壳深断裂带,区内最明显的上地壳低速体位于大同－阳原附近,其南界存在地壳断裂,大同－阳高地震群与该低速异常体和深断裂有关。     

The phase velocities of Rayleigh waves and the lateral variation of lithospheric structure in Tibetan Plateau

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.     

渤海湾西南缘及其邻近地区地壳结构特征

利用2011年8月在渤海湾的探测剖面资料及其周缘地震测深剖面的结果,对渤海湾探测剖面的数据资料进行一、二维处理,计算和综合解释研究,获得了渤海湾西南缘及其邻近地区二维地壳速度结构和构造的基本特征、断层的空间展布特征和深浅部地质构造环境等.研究结果表明,沿剖面具有明显的层状结构,不同区域的地壳速度结构在纵向和横向上均具有明显的非均匀性.基底厚度由渤海湾附近向SW方向逐渐减薄,在220km桩号下方G界面的埋深为7.4km.中间层厚度变化较大,变化幅度达4.0kr.莫霍面由沿海向SW方向逐渐加深,变化幅度为2.0kr左右.     

Crustal structure beneath the Songpan—Garze orogenic belt

The Benzilan-Tangke deepseismic sounding profile in the western Sichuan region passes through the Song-pan-Garze orogenic belt with trend of NNE.Based on the travel times and the related amplitudes of phases in the record sections,the 2-D P-wave crustal structure was ascertained in this paper.The velocity structure has quite strong lateral variation along the profile.The crust is divided into 5layers,where the first,second and third layer belong to the upper crust,the forth and fifth layer belong to the lower crust.The low velocity anomaly zone gener-ally exists in the central part of the upper crust on the profile,and it integrates into the overlying low velocity basement in the area to the north of Ma‘erkang.The crustal structure in the section can be divided into 4parts:in the south of Garze-litang fault,between Garze-Litang fault and Xianshuihe fault,between Xianshuihe fault and Longriba fault and in the north of Longriba fault,which are basically coincided with the regional tectonics division.The crustal thickness decreases from southwest to northeast along the profile,that is ,from62km in the region of the Jinshajiang River to 52km in the region of the Yellow River.The Moho discontinuity does not obviously change across the Xianshuihe fault basesd on the PmP phase analysis.The crustal average velocity along the profile is lower,about 6.30 km/s.The Benzilan-Tangke profile reveals that the crust in the study area is orogenic.The Xianshuihe fault belt is located in the central part of the profile,and the velocity is positive anomaly on the upper crust,and negative anomaly on the lower crust and upper mantle.It is considered as a deep tectonhic setting in favor of strong earthquake‘s accumulation and occurrence.     

Velocity structure of the crust and upper mantle in Xingtai earthquake region and its adjacent area

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