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利用距离2013年岷县漳县地震最近的固定台站岷县台2008-2009年的远震接收函数,确定了该地震震源区及临近区域的地壳厚度和波速比。结果表明:岷县台下方地壳速度结构的横向非均匀性较强,各方位接收函数差异较大,特别是震源区与临近区域存在明显的差别。临近区域的中下地壳存在明显的低速层,而震源区中下地壳中存在明显的高速区;且震源区地壳平均波速比为1.76,上地壳的波速比仅为1.62。据此推断:震源区是坚硬的上地壳覆盖在较软的中下地壳之上,岷县漳县地震破裂有可能是下地壳流的活动导致上地壳的破裂。 相似文献
3.
S-wave crustal and upper mantle’s velocity structure in the eastern Tibetan Plateau — Deep environment of lower crustal flow 总被引：11，自引：0，他引：11
Wang ChunYong Lou Hai Lü ZhiYong Wu JianPing Chang LiJun Dai ShiGui You HuiChuan Tang FangTou Zhu LuPei Paul Silver 《中国科学D辑(英文版)》2008,51(2):263-274
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
4.
Chun-Yong Wang Hai Lou Paul G. Silver Lupei Zhu Lijun Chang 《Earth and Planetary Science Letters》2010,289(3-4):367-376
We determined crustal structure along the latitude 30°N through the eastern Tibetan Plateau using a teleseismic receiver function analysis. The data came mostly from seismic stations deployed in eastern Tibet and western Sichuan region from 2004 to 2006. Crustal thickness and Vp/Vs ratio at each station were estimated by the H–k stacking method. On the profile, the mean crustal thickness and Vp/Vs ratio were found to be 62.3 km and 1.74 in the Lhasa block, 71.2 km and 1.79 near the Bangong–Nujiang suture, 66.3 km and 1.80 in the Qiangtang block, 59.8 km and 1.81 in the Songpan–Garze block, and 42.9 km and 1.76 in the Yangtze block, respectively. The estimated crustal thicknesses are consistent with predictions based on the topography and the Airy isostasy, except near the Bangong–Nujiang suture and in the Qiangtang block where the crust is 5–10 km thicker than predicted, indicating that the crust may be denser, possibly due to mafic underplating. We also inverted receiver functions for crustal velocity structure along the profile, which reveals a low S-wave velocity zone in the lower crust beneath the eastern Tibetan Plateau, although the extent of the low-velocity zone varies considerably. The low-velocity zone, together with previous results, suggests limited partial melting and localized crustal flow in the lower crust of the eastern Tibetan Plateau. 相似文献
5.
Preliminary study of crust-upper mantle structure of the Tibetan Plateau by using broadband teleseismic body waveforms 总被引：2，自引：0，他引：2
Lu-Pei Zhu Rong-Sheng Zeng Francis T. Wu Thomas J. Owens George E. Randall 《地震学报(英文版)》1993,6(2):305-316
As part of a joint Sino-U.S. research project to study the deep structure of the Tibetan Plateau, 11 broadband digital seismic
recorders were deployed on the Plateau for one year of passive seismic recording. In this report we use teleseimic P waveforms
to study the seismic velocity structure of crust and upper mantle under three stations by receiver function inversion. The
receiver function is obtained by first rotating two horizontal components of seismic records into radial and tangential components
and then deconvolving the vertical component from them. The receiver function depends only on the structure near the station
because the source and path effects have been removed by the deconvolution. To suppress noise, receiver functions calculated
from events clustered in a small range of back-azimuths and epicentral distances are stacked. Using a matrix formalism describing
the propagation of elastic waves in laterally homogeneous stratified medium, a synthetic receiver function and differential
receiver functions for the parameters in each layer can be calculated to establish a linearized inversion for one-dimensional
velocity structure.
Preliminary results of three stations, Wen-quan, Golmud and Xigatze (Coded as WNDO, TUNL and XIGA), located in central, northern
and southern Plateau are given in this paper. The receiver functions of all three stations show clear P-S converted phases.
The time delays of these converted phases relative to direct P arrivals are: WNDO 7.9s (for NE direction) and 8.3s (for SE
direction), TUNL 8.2s, XIGA 9.0s. Such long time delays indicate the great thickness of crust under the Plateau. The differences
between receiver function of these three station shows the tectonic difference between southern and north-central Plateau.
The waveforms of the receiver functions for WNDO and TUNL are very simple, while the receiver function of XIGA has an additional
midcrustal converted phase. The S wave velocity structures at these three stations are estimated from inversions of the receiver
function. The crustal shear wave velocities at WNDO and TUNL are vertically homogeneous, with value between 3.5–3.6 km/s down
to Moho. This value in the lower crust is lower than the normal value for the lower crust of continents, which is consistent
with the observed strong Sn attenuation in this region. The velocity structure at XIGA shows a velocity discontinuity at depth
of 20 km and high velocity value of 4.0 km/s in the midcrust between 20–30 km depth. Similar results are obtained from a DSS
profile in southern Tibet. The velocity under XIGA decreases below a depth of 30 km, reaching the lowest value of 3.2 km/s
between 50–55 km. depth. This may imply that the Indian crust underthrusts the low part of Tibetan crust in the southern Plateau,
forming a “double crust”. The crustal thickness at each of these sites is: WNDO, 68 km; TUNL, 70 km; XI-GA, 80 km.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, Supp., 581–592, 1992. 相似文献
6.
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
7.
LOU Hai WANG ChunYong L ZhiYong YAO ZhiXiang DAI ShiGui & YOU HuiChuan Institute of Geophysics China Earthquake Administration Beijing China Earthquake Administration of Sichuan Province Chengdu 《中国科学D辑(英文版)》2009,(2)
Teleseismic P-wave receiver functions at 20 broadband seismic stations in the Longmenshan fault zone (LMFZ) and its vicinity were extracted, and the crustal thickness and the P- and S-wave velocity ratio were calculated by use of the H-k stacking algorithm. With the results as constraints, the S-wave ve-locity structures beneath each station were determined by the inversion of receiver functions. The crustal structure of the Rear-range zone is similar to that of the Songpan-Garze Block, whereas the velocity... 相似文献
8.
本文利用内蒙阿巴嘎地区布设的38个宽频带地震台站记录到的远震数据,采用P波接收函数共转换点叠加方法（CCP）揭示台站下方Moho面起伏形态,并利用H-κ方法进一步得到地壳厚度和壳内平均波速比值.结果显示,研究区地壳厚度为35~44 km,均值约为40 km,西南部的鄂尔多斯盆地边缘地壳较厚,东北部的阿巴嘎火山群地区地壳显著变薄.研究区地壳平均波速比值在1.70~1.87之间,均值为1.76,其中阿巴嘎火山地区波速比值明显偏高.CCP叠加结果显示研究区Moho界面较平缓,但在缝合带附近存在明显的变化.我们推测,新生代阿巴嘎火山地区薄的地壳和高波速比值可能是由于火山活动底侵作用引起上地幔铁镁质物质侵入下地壳所致. 相似文献
9.
地壳厚度和波速比是研究地壳结构和组分的两个重要参数,可为区域构造研究提供重要约束。接收函数被广泛地用于确定地壳厚度和波速比,例如H-κ方法或H-κ-c方法,但是该方法只能确定台站下方的地壳厚度和速度比,当地震台站分布稀疏时,很难约束台站间的横向不均匀性。另一方面,重力数据也可用于莫霍面的起伏变化研究,它在横向上覆盖很好,有较高的分辨率,但在纵向上分辨率相对较低。为此,本研究提出了一种联合反演算法求解莫霍面深度和地壳波速比参数。联合反演算法综合考虑了接收函数在纵向上的较高分辨率和重力数据在横向上的较高分辨率,同时拟合区域内所有台站上的接收函数和区域重力数据。模型测试表明联合反演算法较单一的接收函数反演更精确,特别是对于地壳厚度的确定。 相似文献
10.
本文搜集了2001—2013年间在太行山与燕山构造带交汇部位先后布设的4个宽频带流动地震台阵和首都圈固定地震台网共192个台站记录到的全球5.5级以上远震事件波形资料,综合采用接收函数H-κ和CCP叠加分析获得了134个基岩台站下方的地壳厚度和泊松比结果.综合分析与前人研究相吻合但更加精细的地壳约束分布信息,发现研究区域的地壳厚度和泊松比在整体上呈现出从西北到东南方向渐变的特征,在南北重力梯度带两侧及其附近呈现出明显的小尺度地壳结构和物质组分的差异,且可明显区分出太行山地区和燕山构造带及盆山交界处的地壳厚度与泊松比的相对差异,这可能反映了这些地区在华北克拉通的构造演化过程中所经历的不同地壳改造过程. 相似文献
11.
对呼包盆地周边七个台站的远震接收函数研究表明：研究区地壳厚度为43～46 km,地壳速度比和S波速度结构均无异常;阴山造山带岩石圈埋深为65～85 km,且上地幔S波平均速度偏低,是典型的异常地幔区.根据S波速度结构和地壳厚度随地形高程反比的变化关系,以及地表广泛出露的幔源玄武岩分布,推测该区地幔深部热物质上涌是阴山造山带隆升的原因之一.上升的软流层物质与地幔发生交代、侵蚀作用导致岩石圈减薄,S波速度降低.呼包盆地的形成可能与深部物质上涌造成的拉张效应有关. 相似文献
12.
利用青海和甘肃地震台网2007—2009年记录的远震波形资料,提取多频段P波接收函数,反演得到了青藏高原东北缘及相邻地块下方0~100km深度的地壳和上地幔S波速度结构.结果表明:(1)青藏高原东北缘的上、下地壳之间普遍存在一个S波速度低速层,其深度由南端的约35km向北变浅约为20km,推测该低速层为一壳内滑脱层,表明东北缘地区的上地壳变形与下地壳解耦,从滑脱层的深度分布可以认为青藏高原东北缘的地壳缩短自南向北进行,现阶段以上地壳增厚为主;(2)昆仑—西秦岭造山带的下地壳厚度较北侧的祁连地块薄,一种推测是西秦岭造山带的下地壳抗变形能力更强,也可能这种差异在块体拼合前已经存在;(3)青藏高原东北缘及鄂尔多斯和阿拉善地块的下地壳S波速度随深度的增加而增加,这种正梯度增加的S波速度结构反映较高黏滞性的下地壳,推测青藏高原东北缘的地壳结构不利于下地壳流的发育. 相似文献
13.
本文理论分析了具有不同沉积层和壳幔过渡带结构的接收函数及其相关的H-κ叠加结果,然后采用接收函数H-κ叠加和波形反演方法获得了具有复杂构造演化历史的中北安纳托利亚板块的地壳厚度(H)、V_P/V_S(κ)和V_S结构.理论分析表明:厚的沉积层或沉积层和厚的壳幔过渡带共存都会使H-κ叠加失效;渐变型壳幔过渡带导致H-κ叠加的H位于过渡带中间,且随着频率增大逐渐靠近过渡带上方;倒转型壳幔过渡带导致H-κ叠加具有多极值,其结果可能反应过渡带内最大波阻抗界面上的地壳结构;1km·s~(-1)的V_P变化会导致H-κ叠加的H变化7km,而κ变化较小.实际资料分析表明:中北安纳托利亚H,κ和V_S具有强烈的横向不均匀性,大部分区域沉积层厚度0.5km,局部地区壳幔过渡带厚度3km;北安纳托利亚断层切穿地壳,在局部地区可能存在流体;研究区存在残留古老的小陆块体.本文研究表明,仔细分析接收函数波形和其随方位角的变化特征且用其他地震学方法进行约束,有助于采用H-κ叠加方法获取复杂地壳结构信息. 相似文献
14.
We use 15 seismic stations,crossing the Qinling orogen(QO),Weihe graben(WG)and Ordos block(OB),to study the crustal structures by receiver functions(RFs)methods.The results show quite a difference in crustal structures and materials of three tectonic units(orogenic belt,extentional basin and stable craton).The average crustal thickness in the northern QO is 37.8 km,and Poisson ratio is 0.247,which indicates the increase of felsic materials in QO.In the southern OB,the average crustal thickness is 39.2 km and Poisson ratio is 0.265.Comparatively high value of Poisson ratio is related with old crystallized base in the lower crust and shallow sediments.The artificial RFs reveal that low-velocity and thick sediments have a significant effect on phases of the Mohorovi i discontinuity(Moho).As a result,the Moho phases in WG are tangled.S-wave velocity(VS)inversion shows that there are shallow sediment layers with 4–8 km’s thickness and high velocity zones in the middle-lower crust in WG.Complex Moho structure and high velocity zone may have been induced by the activities of the Weihe faults series. 相似文献
15.
Structure and Significance of S-wave Velocity and Poisson’s Ratio in the Crust beneath the Eastern Side of the Qinghai-Tibet Plateau 总被引：2，自引：0，他引：2
The receiver functions of body waves of distant earthquakes obtained for the regions beneath 41 digital stations (Lhasa and
GANZ in Tibet, Mandalay and Rangoon in Myanmar, SHIO in India, CHTO in Thailand, and station network in Sichuan and Yunnan)
were used to invert for S-wave structure in the crust and upper mantle in Sichuan, Yunnan, and their surrounding areas. Meanwhile
the distribution characteristics of the Poisson’s ration and the crustal thickness in Sichuan and Yunnan areas were also obtained.
Results indicate that the depth of Moho beneath the eastern side of Qinghai-Tibetan plateau varies strikingly. It is obvious
that the greatest changes in crustal thickness occur in a north-south direction. The crustal thickness decreases from north
to south, being as thick as 70 km in eastern Tibet, the northern portion of our area of interest, and less than 30 km in Chaing
Mai and Rangoon, the southern portion of our area. There are, however, exceptions regarding the trend. The thickness exhibits
an east-west variation trend in the area from Ma’erkong-Kongding in Sichuan to Lijiang in Yunnan. In general the Jinpingshan-Longmenshan
fault and Anninghe fault can be taken as the boundaries of this exception area. The thickness in Kongding in the west is 68 km,
while it is only 39 km in Yongchuan in the east. Moreover the Poisson’s ratio values in the blocks of central Sichuan and
Sichuan-Yunnan Diamond are high, and a low velocity layer in the crust of this area can be obviously detected. The distribution
characteristics of the high Poisson’s ratio and the low velocity of the crust in this block correspond to the tectonic structure,
being in contrast with the surrounding areas. Combining with the distribution features of the modern tectonic stress field,
it is deduced that the Sichuan-Yunnan area is probably the channel through which the materials of the lithosphere flow eastward. 相似文献
16.
根据西秦岭构造带及其周边地区117个宽频带地震台站的高质量波形数据, 利用远震P波接收函数的H-k叠加方法, 求得地壳厚度和平均波速比. 通过分析地壳厚度、 波速比及其关系和接收函数CCP叠加剖面, 研究了该区域的地壳结构特征. 结果表明, 研究区域内地壳结构差异大, 呈过渡带特征. 地壳厚度总体上呈北北西向分布, 自西南向东北逐渐减小. 羌塘块体地壳厚度为72 km, 渭河盆地附近为39 km. 西秦岭构造带的地壳厚度为42—56 km, 南北向莫霍界面平坦. 研究区域P波与S波波速比平均为1.74, 其中西秦岭构造带平均为1.72. 较低的波速比主要分布在西秦岭构造带、 祁连山块体、 松潘—甘孜地块北部以及香山—天景山断裂区域, 这可能是由于含长英质酸性岩组分的上地壳叠置增厚而导致的. 该区域缺少超高波速比, 表明这一区域发生岩浆底侵或上地壳熔融的可能性很小. 综合分析表明, 西秦岭构造带及邻区的地壳结构主要是由于青藏高原隆升并在向东北向扩张中受到周边块体的阻挡而引起的地壳构造变形所致. 西秦岭构造带的莫霍界面变化和波速比分布与该构造带经历碰撞地壳增厚后的伸展走滑运动有关. 相似文献
17.
Lupei Zhu Ying Tan Donald V. Helmberger Chandan K. Saikia 《Pure and Applied Geophysics》2006,163(7):1193-1213
We use the recordings from 51 earthquakes produced by a PASSCAL deployment in Tibet to develop a two-layer crustal model for
the region. Starting with their ISC locations, we iteratively fit the P-arrival times to relocate the earthquakes and estimate mantle and crustal seismic parameters. An average crustal P velocity of 6.2–6.3 km/s is obtained for a crustal thickness of 65 km while the P velocity of the uppermost mantle is 8.1 km/s. The upper layer of the model is further fine-tuned by obtaining the best synthetic
SH waveform match to an observed waveform for a well-located event. Green's functions from this model are then used to estimate
the source parameters for those events using a grid search procedure. Average event relocation relative to the ISC locations,
excluding two poorly located earthquakes, is 16 km. All but one earthquake are determined by the waveform inversion to be
at depths between 5 and 15 km. This is 15 km shallower, on average, than depths reported by the ISC. The shallow seismicity
cut-off depth and low crustal velocities suggest high temperatures in the lower crust. Thrust faulting source mechanisms dominate
at the margins of the plateau. Within the plateau, at locations with surface elevations less than 5 km, source mechanisms
are a mixture of strike-slip and thrust. Most events occurring in the high plateau where elevations are above 5 km show normal
faulting. This indicates that a large portion of the plateau is under EW extension. 相似文献
18.
19.
造山带地区的复合力系作用往往使Moho界面发生变形,局部表现为倾斜状态.为了得到这些区域精确地壳速度比结构,本文基于H-κ方法发展了H-κ-θ方法.该方法不仅考虑了倾斜Moho层的响应,同时利用径向和切向接收函数信息,增加了对扫描的约束.利用该方法对青藏高原东南缘地壳厚度和速度比结构进行研究,结果表明：研究区内地壳明显存在不均匀性,松潘—甘孜地体平均地壳厚度约为60 km,四川盆地西缘约为47 km,扬子地台约为43 km,三江块体和扬子地台东南缘已接近正常地壳厚度;松潘—甘孜地体与扬子地台相邻部位地壳平均地震波速度比（Vp/Vs）普遍偏高,且四川盆地西侧发现一绕盆地边缘的弧形高Vp/Vs异常区（>1.88）,我们推测该异常可能由青藏高原向东逃逸的地壳流体受到高强度的四川盆地阻挡,在其西侧堆积所致. 相似文献
20.
Velocity and density contrasts across the Moho interface of Guangdong province in south China constrained by receiver functions* 
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下载免费PDF全文 The P receiver function includes P-to-SV converted phases and multiple reverberations of the discontinuities in the crust and mantle. The time of these phases is related to the crustal thickness and vP/vS ratio, and the amplitude of these phases is mainly controlled by the velocity and density contrast of interfaces. By using H-κ stacking method, this work estimated the crustal thickness and vP/vS ratio beneath the stations in the Guangdong province of South China. The velocity and density contrast (δβ-δρ) scanning stacking algorithm of the receiver function is applied to constrain the velocity and density contrast of the Moho in Guangdong province. This work analyzed the results of the crustal thickness, vP/vS ratio, and the velocity and density contrasts of Moho. The results indicate that the velocity contrast is higher beneath Yangjiang area in western Guangdong province and Nanao area in eastern Guangdong, which has a strong correlation with the distribution of geothermal springs in local areas and the characteristics of high heat flow. The velocity contrast of Moho has also a good correlation with the vP/vS ratio and the crustal thickness, which indicates that there is a strong material composition contrasts of the Moho in the study area. Velocity and density contrasts of Moho in some local area (such as western Guangdong) are somewhat consistent with the seismic activities. 相似文献