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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
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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
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由走时和振幅解释地壳震相,取得美国西部新的地壳P波速度—深度函数,其地震折射剖面为犹他州Delta以西的剖面和科罗拉多州Lamar以西的剖面,前者位于盆地山脉省北部地区,后者位于落基山脉南部Great Plains地区。新地壳结构不只证实了较早推断的地壳结构的主要特点,而且得到更为详细的地壳速度变化范围。盆地山脉省的地壳特点是地壳 相似文献
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中国东西剖面的地壳 Q 结构研究 总被引：2，自引：0，他引：2
本文利用地震面波和体波的资料推断了一条横跨中国东西部剖面的地壳Q结构,并具体分析了中国大陆地台、山前皱褶带、高原和内陆盆地等几个典型构造单元内介质速度与吸收的特点。指出该剖面地壳的Q结构在深度上基本可以划分成上中下三层,其Q_β值分别为(100—300)、(200—550)和(30—190),它可能反映着地壳由弱固结层到低温低压的脆性层和高温高压的韧性层的变化,在横向构造上,以南北构造带为界分成东西两大部分。青藏高原的Q结构具有一定的特殊性。该东西剖面内中下层地壳Q值系统性偏低,这可能是中国地壳的一个普遍现象,在一定程度上反映着上地慢热活动的直接影响。该区震源深度的分布同地壳Q结构表现有良好的相关性,在东部地区绝大多数的构造地震发生在Q值较大的地壳中部层位内。作者由此推断,地壳中大多数的断层是自地表延续到中地壳附近,并认为温度较低、岩石较硬和岩体内有一定的断裂切割是地震易于发生的深部条件。 相似文献
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1982年,美国地质调查局在加州峡谷区域收集了六个地震折射剖面;三个轴向剖面,最大地检偏移为160km,三个与峡谷轴向垂直的短剖面。这篇文章介绍了中心主轴剖面的二维射线追踪和理论地震图模拟的研究成果。中部大峡谷轴部区域的地壳具有横向不均匀性,但是通常由沉积覆盖和可区分的上、中、下地壳所组成。沿着纵剖面沉积岩厚度为3—5km,速度随深度变化由1.64km/s增至4.0km/s,基底(上地壳)由四部分组成;(1)速度为5.4—5.8km/s的层厚度为1.0—1.5km。(2)速度为6.0—6.3km/s的层厚度为3—4km。(3)速度为6.5—6.6km/s的层厚度为1.5—3.0km。(4)以及一个厚1.5km的横向不均匀层,速度为6.8—7.0km/s。中地壳位于深11—14km处,厚度为5—8km,具有6.6—6.7km/s的速度。此剖面西北部,中地壳存在一个低速带,位于速度为6.8—7.0km/s层之下。下地壳位于深16—19km处,厚度为7—13km,速度是6.9—7.2km/s。在此模型中,由西北至东南,地壳厚度逐步由26km增至29km。 相似文献
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利用喀什-乌恰交汇区2004—2010年间的ENVISAT ASAR数据,采用层叠InSAR技术获得了喀什-乌恰交汇区地壳垂直形变速度场,并结合研究区GPS观测数据结果,分析了喀什-乌恰交汇区地壳形变特征。结果显示,喀什-乌恰交汇区地壳垂直形变速率约为?1—2mm/a,其中,乌恰南边的山区形变量最大,形变速率达到2mm/a,是整个研究区中隆升最明显的区域;而喀什、阿图什一带形变量比较小,基本在0—1mm/a。卡兹克阿尔特和阿图什南翼断裂为乌恰以南的隆升区域到喀什、阿图什垂直形变平稳区域的梯度带,这个区域吸收了1—2mm/a的垂直形变能量和7—9mm/a的水平形变能量,是喀什-乌恰交汇区中主要的地壳形变能量消耗地带。 相似文献
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收集了安徽、江西、浙江、江苏、湖北和河南6个省的区域地震台网138个宽频地震台站以及中国地质大学(北京)在长江中下游成矿带布设的19个流动宽频地震台站的三分量背景噪声数据,利用背景噪声面波层析成像方法,获得了长江中下游成矿带及其邻区地壳三维剪切波速度结构和径向各向异性特征.首先获得了5~38s周期的瑞利波和勒夫波相速度,结果显示短周期(16s)的瑞利波和勒夫波相速度与研究区内的主要地质构造单元具有良好的相关性,但在中长周期(20~30s)瑞利波相速度显示大别造山带东部为明显低速特征,而勒夫波相速度并未表现出异常特征.研究区域地壳三维有效剪切波速度和径向各向异性结果显示:苏北盆地和江汉盆地上地壳都表现为低速和正径向各向异性特征,华北克拉通东南部也表现为正径向各向异性,这可能与盆地浅部沉积层的水平层理结构相关.大别造山带中地壳显示为弱的正径向各向异性,同时其东部下地壳显示为低剪切波速度和强的正径向各向特征,可能是由于其在造山后发生了中下地壳的流变变形,引起各向异性矿物近水平排列所导致的.长江中下游成矿带内的鄂东南和安庆—贵池矿集区中地壳弱的负径向各向异性可能是由于深部岩浆向上渗透时所产生的有限应力导致结晶各向异性矿物的垂直排列所引起的.整个长江中下游成矿带下地壳都表现出正径向各向异性特征,可能是由于在伸展拉张的构造作用力下,下地壳矿物的晶格优势水平排列所引起的. 相似文献
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本文利用在我国台湾海峡采用大容量气枪震源开展海陆联测获得的广角地震测线HX9, 采用二维射线追踪法反演得到了HX9剖面的地壳二维速度结构和地壳界面形态, 初步探明了福建—台湾海峡海陆过渡带的深部构造． 结果表明: HX9剖面的地壳内存在两个速度间断面, 即C界面和莫霍面, 其中: C界面为上、 下地壳的分界面, 是一个小的速度不连续面, 速度变化值达0.08—0.16 km/s; 而地壳底部的莫霍面则有较大的速度反差, 变化值达1.02—1.29 km/s, 莫霍面上、 下的速度分别为6.75—6.97 km/s和8.00—8.07 km/s． 沿剖面的地壳界面形态总体起伏不大, 陆域上、 下地壳的厚度和界面变化趋势均相似, 从陆域到海域呈微倾斜变化趋势, 表现为减薄陆壳的特征． 莫霍面陆域埋深约为31.6 km, 向福建东南沿海逐渐减薄至27.4 km左右． 相似文献
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许健生 《地震地磁观测与研究》1992,(5)
根据安西、高台、兰州、天水地震台记录到的 S_p 震相资料测定了4个台附近局部地区的地壳厚度值。得出了在安西周围25—72km 环形区域内的平均地壳厚度值为58.8±2.1km;高台台周围25—68km 环形区域内的平均地壳厚度值为56.0±1.7km;兰州台周围25—50km 环形区域内的平均地壳厚度值为53.9±1.6km;天水台周围23—45km 环形区域内的平均厚度值为51±2.7km。甘肃地区地壳厚度的结果是西厚东薄,东西平均地壳厚度差达7.8km 左右。 相似文献
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本文用地震波前成像和射线数分布分析法对上世纪80年代在琼东北及雷州半岛地区完成的三条宽角反射/折射地震剖面的Pg波资料进行了处理,得到了三条测线下方的上地壳顶部P波速度结构及基底的空间展布形态特征.结果显示研究区域表现出较复杂的上部地壳结构特征,浅部P波速度结构的高、低速区域分别与地质构造上的一些凸起和凹陷相对应,用射线数分布分析法所显示的基底结构及形态特征与地震剖面穿过区域的地质构造有较好的对应关系,测线穿过的一些断裂下方P波速度结构表现为强烈的横向非均匀性. 相似文献
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根据云南地区的基阶瑞利波相速度频散资料，用面波层析成像方法反演得到该区域中上地壳S波速度结构. 给出了研究区域内在4个深度上的S波速度水平分布图像和沿100.5°E、24°N、25°N、26°N及27°N的S波速度-深度剖面图. 结果表明：在小江断裂与红河断裂围成的川滇菱形块体内，26～30km深度处的速度明显低于周边地区，其南段从地表到15km深度均为明显的低速区域. 云南地区的强震（M＞6.0）震中位置与S波速度分布图像具有明显的相关性，主要分布于高速与低速的过渡区域. 相似文献
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Özcan Çakır 《Acta Geophysica》2018,66(6):1303-1340
The Turkish plate is covered by hundreds of accelerometer and broadband seismic stations with less than 50 km inter-station distance providing high-quality earthquake recordings within the last decade. We utilize part of these stations to extract the fundamental mode Rayleigh and Love surface wave phase and group velocity data in the period range 5–20 s to determine the crust structure beneath the Aegean region in southwest Turkey. The observed surface wave signals are interpreted using both single-station and two-station techniques. A tomographic inversion technique is employed to obtain the two-dimensional group velocity maps from the single-station group velocities. One-dimensional velocity–depth profiles under each two-dimensional mesh point, which are jointly interpreted to acquire the three-dimensional image of the shear-wave velocities underneath the study area, are attained by utilizing the least-squares inversion technique, which is repeated for both Rayleigh and Love surface waves. The isotropic crust structure cannot jointly invert the observed Rayleigh and Love surface waves where the radial anisotropic crust better describes the observed surface wave data. The intrusive magmatic activity related to the northward subducting African plate under the Turkish plate results the crust structure deformations, which we think, causing the observed radial anisotropy throughout complex pattern of dykes and sills. The magma flow resulting in the mineral alignment within dykes and sills contributes to the observed anisotropy. Due to the existence of dykes, the radial anisotropy in the upper crust is generally negative, i.e., vertically polarized S-waves (Vsv) are faster than horizontally polarized S-waves (Vsh). Due to the existence of sills, the radial anisotropy in the middle-to-lower crust is generally positive, i.e., horizontally polarized S-waves (Vsh) are faster than vertically polarized S-waves (Vsv). Similar radial anisotropic results to those of the single-station analyses are obtained by the two-station analyses utilizing the cross-correlograms. The widespread volcanic and plutonic rocks in the region are consistent with the current seismic interpretations of the crustal deformations. 相似文献
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We propose a new quantitative determination of shear wave velocities for distinct geological units in the Bohemian Massif,
Czech Republic (Central Europe). The phase velocities of fundamental Love wave modes are measured along two long profiles
(~200 km) crossing three major geological units and one rift-like structure of the studied region. We have developed a modified
version of the classical multiple filtering technique for the frequency-time analysis and we apply it to two-station phase
velocity estimation. Tests of both the analysis and inversion are provided. Seismograms of three Aegean Sea earthquakes are
analyzed. One of the two profiles is further divided into four shorter sub-profiles. The long profiles yield smooth dispersion
curves; while the curves of the sub-profiles have complicated shapes. Dispersion curve undulations are interpreted as period-dependent
apparent velocity anomalies caused both by different backazimuths of surface wave propagation and by surface wave mode coupling.
An appropriate backazimuth of propagation is found for each period, and the dispersion curves are corrected for this true
propagation direction. Both the curves for the long and short profiles are inverted for a 1D shear wave velocity model of
the crust. Subsurface shear wave velocities are found to be around 2.9 km/s for all four studied sub-profiles. Two of the
profiles crossing the older Moldanubian and Teplá-Barrandian units are characterized by higher velocities of 3.8 km/s in the
upper crust while for the Saxothuringian unit we find the velocity slightly lower, around 3.6 km/s at the same depths. We
obtain an indication of a shear wave low velocity zone above Moho in the Moldanubian and Teplá-Barrandian units. The area
of the Eger Rift (Teplá-Barrandian–Saxothuringian unit contact) is significantly different from all other three units. Low
upper crust velocities suggest sedimentary and volcanic filling of the rift as well as fluid activity causing the earthquake
swarms. Higher velocities in the lower crust together with weak or even missing Moho implies the upper mantle updoming. 相似文献
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Surface wave tomography of the crust and upper mantle of Chinese mainland and its neighboring region
Introduction The three-dimensional S wave velocity of Chinese mainland and its neighboring region in-verted by surface wave dispersion data plays an important role in studying the lateral variation of lithosphere and geodynamic process, and understanding the forming and evolution of Chinese mainland and the relationship between shallow and deep structures. The three-dimensional veloc-ity structures of China and its major tectonic blocks were respectively studied by SONG, et al (1993), ZHOU… 相似文献
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Surface wave dispersion is studied to obtain the 1-D average velocity structure of the crust in the Korean Peninsula by inverting
group- and phase-velocities jointly. Group velocities of short-period Rayleigh and Love waves are obtained from cross-correlations
of seismic noise. Multiple-filter analysis is used to extract the group velocities at periods between 0.5 and 20 s. Phase
velocities of Rayleigh waves in 10- and 50-s periods are obtained by applying the two-station method to teleseismic data.
Dispersion curves of all group and phase velocities are jointly inverted for the 1-D average model of the Korean Peninsula.
The resultant model from surface wave analysis can be used as an initial model for numerical modeling of observations of North
Korean events for a velocity model appropriated to the Korean Peninsula. The iterative process is focused especially on the
surface sedimentary layer in the numerical modeling. The final model, modified by numerical modeling from the initial model,
indicates that the crust shear wave velocity increases with depth from 2.16 km/s for a 2-km-thick surface sedimentary layer
to 3.79 km/s at a Moho depth of 33 km, and the upper mantle has a velocity of 4.70 km/s. 相似文献
17.
The lithospheric structure of the Sinai Peninsula is shown by means of nine shear velocity profiles for depths ranging from
zero to 50 km, determined from the Rayleigh wave analysis. The traces of 30 earthquakes, which occurred from 1992 to 1999
in and around the study area, have been used to obtain Rayleigh wave dispersion. These earthquakes were registered by a broadband
station located in Egypt (KEG station). The dispersion curves were obtained for periods between 3 and 40 s, by digital filtering
with a combination of MFT and TVF filtering techniques. After that, all seismic events were grouped in source zones to obtain
a dispersion curve for each source-station path. These dispersion curves were inverted according to generalized inversion
theory, to obtain shear wave velocity models for each source-station path, which is the main goal of this study. The shear
velocity structure obtained for the Sinai Peninsula is shown through the shear velocity distributions with depth. These results
agree well with the geology and other geophysical results, previously obtained from seismic and gravity data. The obtained
velocity models suggest the existence of lateral and vertical heterogeneity. The shear velocity increases generally with depth
for all paths analyzed in the study area. Nevertheless, in some paths a small low velocity channel in the upper or lower crust
occurs. Along these profiles, it is found that the crustal structure of the Sinai Peninsula consists of three principal layers:
upper crust with a sedimentary layer and lower crust. The upper crust has a sedimentary cover of 2 km thick with an average
S-velocity of 2.53 km/s. This upper crust has a variable thickness ranging from 12 to 18 km, with S-wave velocity ranging
from 3.24 to 3.69 km/s. The Moho discontinuity is located at a depth of 30 km, which is reflected by a sharp increase in the
S-velocity values that jump from 3.70–4.12 to 4.33–4.61 km/s. 相似文献
18.
Crustal structure beneath Liaoning province and the Bohai Sea and its adjacent region in China based on ambient noise tomography 
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下载免费PDF全文 The velocity structure of the crust beneath Liaoning province and the Bohai sea in China was imaged using ambient seismic noise recorded by 73 regional broadband stations. All available three-component time series from the 12-month span between January and December 2013 were cross-correlated to yield empirical Green's functions for Rayleigh and Love waves. Phasevelocity dispersion curves for the Rayleigh waves and the Love waves were measured by applying the frequencytime analysis method. Dispersion measurements of the Rayleigh wave and the Love wave were then utilized to construct 2D phase-velocity maps for the Rayleigh wave at8–35 s periods and the Love wave at 9–32 s periods,respectively. Both Rayleigh and Love phase-velocity maps show significant lateral variations that are correlated well with known geological features and tectonics units in the study region. Next, phase dispersion curves of the Rayleigh wave and the Love wave extracted from each cell of the 2D Rayleigh wave and Love wave phase-velocity maps,respectively, were inverted simultaneously to determine the3 D shear wave velocity structures. The horizontal shear wave velocity images clearly and intuitively exhibit that the earthquake swarms in the Haicheng region and theTangshan region are mainly clustered in the transition zone between the low-and high-velocity zones in the upper crust, coinciding with fault zones, and their distribution is very closely associated with these faults. The vertical shear wave velocity image reveals that the lower crust downward to the uppermost mantle is featured by distinctly high velocities, with even a high-velocity thinner layer existing at the bottom of the lower crust near Moho in central and northern the Bohai sea along the Tanlu fault, and these phenomena could be caused by the intrusion of mantle material, indicating the Tanlu fault could be just as the uprising channel of deep materials. 相似文献
19.
Love-Rayleigh wave incompatibility and possible deep upper mantle anisotropy in the Iberian peninsula 总被引：1，自引：0，他引：1
Love and Rayleigh wave phase velocities are analyzed with the goal of retrieving information about the anisotropic structure of the Iberian lithosphere. The cross-correlation method is used to measure the interstation phase velocities between diverse stations of the ILIHA network at periods between 20 and 120 s. Despite the 2-D structure of the network, the Love wave data are too few to enable an analysis of phase velocity azimuthal variations. Azimuthal averages of Love and Rayleigh wave phase velocities are calculated and inverted both in terms of isotropic and anisotropic structures. Realistic isotropic models explain the Rayleigh wave and short-period Love wave phase velocities. Therefore no significant anisotropy needs to be introduced in the crust and down to 100 km depth in the upper mantle to explain our data. A discrepancy is observed only at long periods, where the data are less reliable. Love wave data at periods between 80 and 120 s remain 0.15 km/s faster than predicted by isotropic models explaining the long-period Rayleigh wave data. Possibilities of biases in the measurements due to interferences with higher modes are examined but seem unlikely. A transversely isotropic model with 8% of S-wave velocity anisotropy in the upper mantle at depths larger than 100 km can explain the whole set of data. In terms of a classical model of mantle anisotropy, this corresponds to 100% of the crystals perfectly oriented in the horizontal plane in a pyrolitic mantle. This is a rather extreme model, which predicts at time delay between 0 and 2 seconds for split SKS. 相似文献