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1.
本文利用中国数字地震台网位于东北地区的122个宽频地震台站的18个月记录的三分量连续地震噪声数据,采用互相关方法提取了Rayleigh和Love波经验格林函数,并利用时频自动分析技术获取了相应的相速度频散曲线.通过反演频散曲线,获得了Rayleigh和Love波周期为8~35s的二维相速度分布.结果表明,东北地区相速度的分布存在横向和垂向的不均匀性.短周期的相速度分布同地表地质构造密切相关,松辽盆地及山间沉积盆地呈现低速异常,而大兴安岭、小兴安岭及东部的一些山岭显示高速异常.随着周期的增加,位于中间的松辽盆地变为高低速相间,两侧的造山带呈现低速异常.这种异常的转变,可能是受构造活动或者莫霍面深度的影响.另外,在周期为20~35s频段内,Rayleigh和Love波同一周期的相速度在松辽盆地和位于吉林地区的郯庐断裂带表现不一致,表明可能存在径向各向异性. 相似文献
2.
采用与作者2014年发表的“大别-苏鲁及其邻近地区基于背景噪声的勒夫波群速度成像”文章相同的资料,用频时分析提取5 000余条瑞雷波和4 000余条勒夫波相速度频散曲线,反演得到了8—32 s的瑞雷波和勒夫波相速度分布图像．结果显示,瑞雷波与勒夫波相速度分布具有很好的一致性．8 s的相速度分布与地表构造特征相吻合,造山带与隆起区均表现为高速,盆地因其规模不同而显示不同程度的低速．随着周期的增大,大别 苏鲁的高速带由强变弱,但始终存在．16—24 s的高速可能主要受到中地壳高速的控制,而32 s的高速则可能与上地幔顶部的高速有关．比较大别造山带与苏鲁造山带的平均频散曲线,发现大别造山带和苏鲁造山带的勒夫波频散曲线均高于AK135模型计算的理论频散曲线,而瑞雷波则没有这一现象. 这可能意味着两个地区有比较强烈的径向各向异性． 相似文献
3.
大别-苏鲁造山带是中国大陆东部地区最重要的构造之一. 为了研究该地区的地壳上地幔速度结构,本文收集了国家数字地震台网和中国区域地震台网的山东、河南、安徽、江苏和湖北等省的144个宽频带地震台连续两年(2009年5月—2011年5月)的水平向地震记录(E分量和N分量)数据,首先对台站对之间E-E,E-N,N-N和N-E分量进行互相关,然后分别对这4个互相关分量采用相位权重叠加法进行叠加,最后旋转到横向分量(T-T)获得勒夫波经验格林函数(EGF);用频时分析(FTAN)方法获得4000余条勒夫波群速度频散曲线,并进一步反演得到了周期为6—40s的勒夫波群速度分布图.结果表明,周期为6—10s的勒夫波群速度分布与地表构造特征相吻合.大别造山带、苏鲁造山带、湖北西部隆起均表现为高速;华北盆地发育,表现为大面积的低速;江汉盆地、南襄盆地、合肥盆地等因其规模不同而显示不同程度的低速.在周期为6—30s的勒夫波群速度分布图上,大别和苏鲁地区均显示高速,已有的研究结果中地壳的低速并没有得到反映.其原因一方面可能与勒夫波群速度纵向分辨不高有关,另一方面高压变质岩深度分布可能比已有研究结果给出的要深. 6—30 s的分布图上郯庐断裂带及其邻近地区表现为不同程度的高速,可能与该地区白垩纪以来处于拉张构造体制,地幔物质受到扰动,造成物质上涌有关. 相似文献
4.
Two-month continuous waveforms of 108 broadband seismic stations in Fujian Province and its adjacent areas are used to compute noise cross-correlation function (NCF). The signal quality of NCF is improved via the application of time-frequency phase weighted stacking. The Rayleigh and Love waves group velocities between 1s-20s are measured on the symmetrical component of the NCF with the multiple filter method. More than 5,000 Rayleigh wave dispersion curves and about 4,000 Love wave dispersion curves are obtained and used to invert for group velocity maps. This data set provides about 50km resolution that is demonstrated with checkerboard tests. Considering the off great circle effect in inhomogeneous medium, the ray path is traced based on the travel time field computed with a finite difference method. The inverted group velocity maps show good correlation with the geological features in the upper and middle crust. The Fuzhou basin and Zhangzhou basin showed low velocity on the short period group velocity maps. On the long period group velocity maps, the low velocity anomaly in the high heat flow region near Zhangzhou and clear velocity contrast across the Zhenghe-Dapu faults, which suggests that the Zhenghe-Dapu fault might be a deep fault. 相似文献
5.
南海处于欧亚板块、 菲律宾海板块、 太平洋板块和印度-澳大利亚板块的交汇处, 其地质和构造作用十分复杂．通过面波群速度成像, 给出了南海及邻区的三维横波速度分布并分析了其地球动力学意义．南海西部和南部新布设的地震台站使得利用单台法时路径覆盖比过去更好. 特别是在华南地区, 新的台站分布能够弥补该地区地震少且台站少造成的射线密度不够的缺点． 首先运用多重滤波法得到南海周边48个台站周期为14——130 s范围内的基阶瑞雷波频散曲线图; 接着通过子空间反演得到整个区域在不同周期时的群速度分布; 最后通过阻尼最小二乘反演得到不同深度切片上的横波速度分布及不同纵剖面上的横波速度分布． 结果显示: ① 海盆速度较高, 且速度分布很好地勾勒出海盆的轮廓. 浅层较高的横波速度说明海盆都具有洋壳性质, 而深部较高的横波速度则可能对应扩张中心生成洋壳后残留的高速物质． 不同海盆速度上的差异与它们的热流值和年龄大小一致．海盆下的高速异常在60 km以下消失, 且在一定深度范围内由低速区替代． 在低速区下200 km深度, 在南海海盆观测到一条NE-SW走向的高速异常, 可能与古俯冲带有关. ② 环南海出现明显的高速区, 对应俯冲带特征, 且这些高速区速度差异明显且有间断, 说明俯冲带的非均质性和俯冲角度的差异. ③ 在环南海高速区内侧（向南海侧）观测到不连续的低速区． 在浅层, 这些低速区反映了沉积层和地壳的厚度特征. 在地幔, 这些低速区可能对应于古太平洋俯冲带的地幔楔或者也可能反映了南海海盆停止扩张后残留的地幔熔融物质. ④ 南海海盆岩石圈的厚度为60——85 km． 相似文献
6.
Ambient noise surface wave tomography of the Makran subduction zone,south-east Iran:Implications for crustal and uppermost mantle structures 
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下载免费PDF全文 Seismic ambient noise of surface wave tomography was applied to estimate Rayleigh wave empirical Green's functions(EGFs) and then to study crust and uppermost mantle structure beneath the Makran region in south-east Iran.12 months of continuous data from January 2009 through January 2010,recorded at broadband seismic stations,were analyzed.Group velocities of the fundamental mode Rayleigh wave dispersion curves were obtained from the empirical Green's functions.Multiplefilter analysis was used to plot group velocity variations at periods from 10 to 50 s.Using group velocity dispersion curves,1-D vs velocity models were calculated between several station pairs.The final results demonstrate significant agreement to known geological and tectonic features.Our tomography maps display low-velocity anomaly with SW-NE trend,comparable with volcanic arc settings of the Makran region which may be attributable to the geometry of Arabian Plate subducting beneath the overriding the Lut block.The northward subducting Arabian Plate is determined by high-velocity anomaly along the Straits of Hormuz.At short periods(20 s),there is a sharp transition boundary between low- and high-velocity transition zone with the NW trending at the western edge of Makran which is attributable to the Minab fault system. 相似文献
7.
郯庐断裂带是贯穿我国东部北北东走向的一条深大断裂，其中南段及其邻区（115°E-121°E，29.5°N-35°N）穿过了大别造山带、苏鲁造山带、长江中下游成矿带及合肥盆地.为了研究该区域地壳速度结构及变形特征，我们使用安徽省和江苏省及其周边地区105个台站（固定台站98个，流动台站7个）的垂向连续波形数据，时间范围从2014年5月到2015年7月，共计14个月.利用背景噪声互相关方法，从垂直分量互相关函数中最终提取了2590条瑞利面波相速度频散曲线，反演得到周期范围为5~30 s的瑞利波方位各向异性相速度分布图，再反演每个网格点瑞利面波相速度频散得到一维层状横波速度模型，然后拼合起来组成三维横波速度模型.根据本文反演结果并综合已有资料，我们得出如下结论：（1）在北大别、蚌埠隆起、长江中下游成矿带、合肥盆地北部大桥凹陷区域存在中地壳横波高速体，可能与岩石圈和下地壳拆沉以及中生代中国东部大范围岩浆活动有直接关系，更深层原因可能与古太平洋俯冲相关；（2）苏鲁造山带南缘，垂直于嘉山响水断裂，从南向北中上地壳低速体深度变浅，这个低速体可能是高压/超高压变质岩与扬子板块接触处的破碎带，是扬子板块与华北板块接触的边界；（3）郯庐断裂合肥-嘉山段两侧以及大别造山带东缘短周期瑞利面波相速度快轴方向与郯庐断裂带走向基本一致，可能是三叠纪碰撞期与白垩纪时期的大规模左旋走滑活动的结果；（4）合肥盆地南部15~20 s周期的瑞利波相速度快轴方向为北西-南东向，反应该区域中下地壳快波方向为北西-南东向，推测是大别造山带折返的痕迹；（5）郯庐断裂带的结构和地震活动性存在明显的分段性，嘉山-郯城段郯庐断裂带现今地震活动性弱，但发生过较强的古地震，推断现今郯庐断裂带宿迁段可能处于闭锁状态，从长远来看要注意该地区发生大震的可能. 相似文献
8.
Surface wave dispersion curves from microearthquakes are used to obtain group velocity dispersion maps. The calculation of the local dispersion curves for each grid point from these maps then produces the input data to retrieve the 3D shear wave velocity model of the Tehran region. The group velocity maps indicate that the tomographic results agree well with the three main tectonic features and the geological units in the study area. The tomographic maps generally possess high-velocity structures across most of the mountain belts (Central Alborz and east-southeast mountains), whereas the Tehran Basin correlates to a low-velocity structure. Increasing the period in the study area highlights four independent low-velocity zones that reflect faults and fault junction systems. The shear wave velocity profiles indicate that the depth to bedrock exhibits southward variation ranging from ~?300 m to ~?1500 m. We also focus our analysis on the existence of faults within the shear wave profiles and discuss the low shear wave velocity anomalies deeper than 2 km result from the main fault structures (e.g., North Tehran, North-South Rey and Parchin). Furthermore, we argue that the dip angle of the North Tehran fault varies along fault strike, whereas the North-South Rey fault possesses a constant dip angle. Moreover, initial model uncertainties and checkerboard resolution tests are used to identify reliable and robust anomaly features in the 3D shear wave velocity model and 2D tomographic maps, respectively. Microearthquake analysis provides an effective approach for studying the upper crustal structure heterogeneity, especially the fault structure, of the Tehran region. 相似文献
9.
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
10.
中国东部海域地壳-上地幔瑞利波速度结构研究 总被引：17，自引：8，他引：9
为了进一步了解中国东部沿海及相邻海域的地壳－上地幔结构特征,对该区域的构造演化历史、地震活动及深部构造等方面研究提供一些基础资料,利用３１个数字地震台记录的高质量瑞利波资料,采用一种新的混合路径频散的网格反演方法（Ｏｃｃａｍ方法）,对中国东部海域瑞利波群速度横向不均匀分布进行了初步研究．根据反演得到的１０-１５０ｓ共３６个中心周期的群速度分布特征,以及几个典型地点的剪切波速度结构的深度变化,对研究区域内各构造单元的划分以及它们在速度结构和上地幔低速层埋深等方面的特征进行了讨论。 相似文献
11.
We estimate Love wave empirical Green's functions from cross-correlations of ambient seismic noise to study the crust and uppermost mantle structure in Italy.Transverse-component ambient noise data from October 2005 through March 2007 recorded at 114 seismic stations from the Istituto Nazionale di Geofisica e Vulcanologia (INGV) national broadband network,the Mediterranean Very Broadband Seismographic Network (MedNet) and the Austrian Central Institute for Meteorology and Geodynamics (ZAMG) yield more than 2 000 Love wave group velocity measurements using the multiple-filter analysis technique.In the short period band (5-20 s),the cross-correlations show clearly one-sided asymmetric feature due to non-uniform noise distribution and high local activities,and in the long period band (20 s) this feature becomes weak owing to more diffusive noise distribution.Based on these measurements,Love wave group velocity dispersion maps in the 8-34 s period band are constructed,then the SH wave velocity structures from the Love wave dispersions are inverted.The final results obtained from Love wave data are overall in good agreement with those from Rayleigh waves.Both Love and Rayleigh wave inversions all reveal that the Po plain basin is resolved with low velocity at shallow depth,and the Tyrrhenian sea is characterized with higher velocity below 8 km due to its thin oceanic crust. 相似文献
12.
O'Leary González Leonardo Alvarez Mariangela Guidarelli Giuliano F. Panza 《Pure and Applied Geophysics》2007,164(10):1985-2007
An overview of the crust and upper mantle structure of Central America and the Caribbean region is presented as a result of
the processing of more than 200 seismograms recorded by digital broadband stations from SSSN and GSN seismic networks. Group
velocity dispersion curves are obtained in the period range from 10s to 40s by FTAN analysis of the fundamental mode of the
Rayleigh waves; the error of these measurements varies from 0.06 and 0.09 km/s. From the dispersion curve, seven tomographic
maps at different periods and with average spatial resolution of 500 km are obtained. Using the logical combinatorial classification
techniques, eight main groups of dispersion curves are determined from the tomographic maps and eleven main regions, each
one characterized by one kind of dispersion curves, are identified. The average dispersion curves obtained for each region
are extended to 150s by adding data from a larger-scale tomographic study (Vdovin et al., 1999) and inverted using a nonlinear procedure. A set of models of the S-wave velocity vs. depth in the crust and upper
mantle is found as a result of the inversion process. In six regions we identify a typically oceanic crust and upper mantle
structure, while in the other two the models are consistent with the presence of a continental structure. Two regions, located
over the major geological zones of the accretionary crust of the Caribbean region, are characterized by a peculiar crust and
upper mantle structure, indicating the presence of lithospheric roots reaching, at least, about 200 km of depth. 相似文献
13.
青藏高原东南缘是研究印度—欧亚板块碰撞过程、块体间相互作用和壳幔变形机制的重要地区.本文利用川滇地区流动地震台阵和固定地震台网共557个台站的连续波形数据,基于改进的背景噪声处理流程和分析方法得到了6023条瑞利波群速度频散曲线,反演获得了6~48s的瑞利波群速度分布图像.结果显示在四川盆地内部短周期群速度分布较好地揭示了盆地内沉积层厚度的横向变化.在30~48s周期,四川盆地西部群速度存在南低、北高的特征,推测是南部中下地壳和上地幔温度较高引起的.温度的增高降低了地壳的力学强度,在青藏高原东向挤压作用下盆地西南部地壳更易发生变形,并导致脆性上地壳在新生代产生地壳缩短和褶皱、断裂等地质活动.攀枝花及其周边地区从地壳浅部至上地幔深度的高速异常体,可能与基性和超基性岩的侵入有关.该高速体具有较大的介质强度,在一定程度上阻碍了青藏高原物质东南向的运移,这可能是造成丽江—小金河断裂两侧巨大高程差异的重要因素.自24s开始,南盘江盆地表现为明显的高速异常,与华南块体西南部其他区域的深部结构存在明显差异.反演的S波速度结构揭示,自中上地壳至上地幔,南盘江盆地的速度一直高于北侧其他区域.结合此地区的地壳运动模式,推测介质S波速度较高、力学强度较大的南盘江盆地对青藏高原物质的东南向逃逸具有一定的阻挡作用. 相似文献
14.
Experimental dispersion curves of Rayleigh and Love waves along the Uppsala-Prague profile have been determined using records of several Italian earthquakes. To interpret the dispersion data, results of previous geophysical investigations in this region were first analyzed. Seven blocks of the crust and upper mantle were distinguished along the profile on the basis of deep seismic sounding and other seismic data. Layered models were proposed for these blocks. Computation of Rayleigh and Love waves shows a large differentiation of theoretical dispersion curves for the northern (Precambrian) and southern (Palaeozoic) part of the profile. A laterally inhomogeneous model for theUppsala - Prague profile, composed of the seven blocks, satisfies the surface wave data for the profile. Moreover, a mean layered model for the whole profile has also been proposed. 相似文献
15.
本文利用布设于陕西及其邻区的喜马拉雅二期流动地震台阵和区内的固定地震台网共计257个台站于2014—2015年记录到的连续波形资料，采用基于图像分析的相速度提取方法，得到了7 185条瑞雷波相速度频散曲线，反演获得了周期为5—40 s的瑞雷波相速度分布图像，其最小分辨率约为20 km。结果表明:各周期瑞雷波相速度图像具有明显的横向不均匀性，能够较好地反映出地壳及上地幔顶部的地质构造特征。周期为5—10 s的瑞雷波相速度分布与地表地质构造密切相关，且高低速异常的分界线与地块边界高度吻合；周期为15 s的瑞雷波相速度分布图像显示出，大部分断陷沉积盆地（渭河、天水等盆地）表现为低速异常，表明此区域的沉积层厚度较大；周期为20—40 s的相速度分布则受地壳厚度影响较大，青藏高原东北缘始终呈现出明显的低速异常，鄂尔多斯地块中、下地壳以高速异常为主，但周期为20—30 s的相速度低速异常区分布于青藏高原沿六盘山逆冲褶皱带并一直延伸至鄂尔多斯内部，由此推测该区域地下介质中存在一定程度的物质交换和融合。 相似文献
16.
秦岭—大别造山带西起青藏高原东北缘,东至郯庐断裂带,是华北板块和扬子板块之间的碰撞造山带.本文收集陕、豫、皖、赣、湘、鄂、渝等区域地震台网的160个宽频带地震台站连续两年地震背景噪声数据,用双台站互相关算法获得瑞利面波经验格林函数,提取相速度频散曲线,并根据面波层析成像反演得到秦岭—大别及邻区周期8~35 s范围内相速度分布图像.结果显示,大别地块在14 s相速度分布图中呈现低速异常,与8 s相速度分布图中的高速异常形成鲜明对比,反映大别HP/UHP(high pressure/ultrahigh pressure metamorphic rocks,高压/超高压变质岩)的影响仅存在于上地壳.25 s相速度图中,大致以太行一武陵重力梯度带为界,东部以高速异常为主,西部以低速异常为主,反映了地壳东薄西厚的结构特征.14~35 s相速度分布图显示郯庐断裂带南段东西两侧的显著差异,佐证了郯庐断裂带发生大规模左行平移运动时,其南段可能切入壳幔边界.同时,郯庐断裂带南段可能存在一个热物质上涌的通道,熔融的热物质通过该通道上升,混入大别地区的中下地壳,造成了红安一大别造山带的差异隆升.南秦岭与四川盆地东北部表现为低速异常,是否与青藏高原物质东流或者南秦岭的拆沉有关,还有待于进一步深入研究. 相似文献
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收集辽宁及其周边地区（吉林、河北、山东、内蒙）70个宽频带地震仪2012年连续背景噪声波形数据,基于地震背景噪声层析成像方法,得到研究区面波群速度及相速度图像。利用台站对互相关方法,提取瑞利面波格林函数,采用时频分析法（FTAN）获取2 416条相速度频散曲线,从中筛选1 661条信噪比较高的频散曲线。将研究区以0.25°×0.25°进行网格化,采用Ditmar等提出的层析成像反演方法,得到周期10—40 s的瑞利面波群速度及相速度结构分布图。与群速度结果相比,分辨率更高,研究区大部可达0.5°×0.5°（局部可达0.25°×0.25°）。结果表明,辽宁地区地壳及上地幔面波相速度结构存在显著的横向不均匀性。在周期10—15 s的群速度图中,浅层及中上地壳速度分布与研究区地形地貌及主要地质构造单元具有较好的对应关系,盆地及沉积层低速,山区隆起高速,且在高低速转换带多为地震孕震区;在周期20—30 s相速度结构图中,下地壳至上地幔顶部深度范围内,相速度速度结构主要受地壳厚度及渤海湾内巨厚沉积层的影响,在海城至大连区域内出现的低速异常推测为地下热物质上涌;随着深度的增加,在周期30—40 s的相速度图中,速度分布逐渐受控于莫霍面起伏,明显变化出现在辽东半岛,由高速变为低速。 相似文献
18.
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
19.
High-resolution Rayleigh wave phase velocity maps from ambient noise tomography in North China 下载免费PDF全文
下载免费PDF全文 Jiatie Pan 《地震科学（英文版）》2012,25(3):241-251
We presented high-resolution Rayleigh wave phase velocity maps at periods ranging from 5 s to 30 s in the northeast part of the North China Craton (NNCC). Continuous time-series of vertical component between October 2006 and December 2008, recorded by 187 broadband stations temporarily deployed in the NNCC region, have been cross-correlated to obtain estimated fundamental mode Rayleigh wave Greenos functions. Using the frequency and time analysis technique based on continuous wavelet transformation, we measured 3 667 Rayleigh wave phase velocity dispersion curves. High-resolution phase velocity maps at periods of 5, 10, 20 and 30 s were reconstructed with grid size 0.25° × 0.25°, which reveal lateral heterogeneity of shear wave structure in the crust and upper mantle of NNCC. For periods shorter than 10 s, the phase velocity variations are well correlated with the principal geological units in the NNCC, with low-speed anomalies corresponding to the major sedimentary basins and high-speed anomalies coinciding with the main mountain ranges. Within the period range from 20 s to 30 s, high phase velocity observed in eastern NCC is coincident with the thin crust, whereas low phase velocities imaged in central NCC is correlated to the thick crust. However, the low-velocity anomaly in the Beijing-Tianjin-Tangshan region displayed in the 20 s and 30 s phase maps may be associated with fluids. 相似文献
20.
3D <Emphasis Type="Italic">v</Emphasis><Subscript>P</Subscript> and <Emphasis Type="Italic">v</Emphasis><Subscript>S</Subscript> models of southeastern margin of the Tibetan plateau from joint inversion of body-wave arrival times and surface-wave dispersion data 下载免费PDF全文
下载免费PDF全文 A new 3D velocity model of the crust and upper mantle in the southeastern (SE) margin of the Tibetan plateau was obtained by joint inversion of body- and surface-wave data. For the body-wave data, we used 7190 events recorded by 102 stations in the SE margin of the Tibetan plateau. The surface-wave data consist of Rayleigh wave phase velocity dispersion curves obtained from ambient noise cross-correlation analysis recorded by a dense array in the SE margin of the Tibetan plateau. The joint inversion clearly improves the v S model because it is constrained by both data types. The results show that at around 10 km depth there are two low-velocity anomalies embedded within three high-velocity bodies along the Longmenshan fault system. These high-velocity bodies correspond well with the Precambrian massifs, and the two located to the northeast of 2013 M S 7.0 Lushan earthquake are associated with high fault slip areas during the 2008 Wenchuan earthquake. The aftershock gap between 2013 Lushan earthquake and 2008 Wenchuan earthquake is associated with low-velocity anomalies, which also acts as a barrier zone for ruptures of two earthquakes. Generally large earthquakes (M ≥ 5) in the region occurring from 2008 to 2015 are located around the high-velocity zones, indicating that they may act as asperities for these large earthquakes. Joint inversion results also clearly show that there exist low-velocity or weak zones in the mid-lower crust, which are not evenly distributed beneath the SE margin of Tibetan plateau. 相似文献