龙门山断裂带中上地壳速度结构的短周期环境噪声成像

本文利用在龙门山断裂带周边布设的57个台站自2008年11月至2009年11月为期一年的垂直分量连续地震环境噪声数据,通过短周期地震环境噪声成像方法,获得了龙门山断裂带中北段地壳25km深度范围的S波精细速度结构.结果表明:(1)龙门山断裂带周边区域10km以上的速度结构与地表断裂的分布形态具有良好的一致性,速度结构控制了龙门山主要断层的深部延展特征;在15km及以下深度,S波速度结构呈现沿龙门山和沿岷山隆起走向的交叉构造格局,由此造成的速度结构差异可能影响了汶川地震的破裂过程;(2)速度结构随深度的分布特征为龙门山断裂带主要断层的深部延伸形态给出了良好的约束,结果进一步确认了龙门山断裂中段的高角度铲型断裂构造特征;(3)研究区的南端发现了龙门山断裂下方20km以下深度具有与松潘地块中地壳低速层相关的低速结构的迹象,这可能是汶川地震破裂带南段22km左右深度存在脆韧转换带的一个证据.研究结果显示出密集台阵和短周期环境噪声成像方法在地壳浅部精细结构和断层探测研究中具有巨大潜力.     

新乡及邻区三维地壳速度结构

应用区域地震台网1981-2011年的地震到时资料,对新乡及邻区地壳三维速度结构和震源参数进行了联合反演,获得了该区地壳的三维速度结构图像.结果显示:0~4 km深度层位的速度分布基本反映出了研究区浅部地形的分布特征,凹陷盆地速度低,山脉位于速度的过渡区,隆起区多位于高速区,横向速度分布差异较大;其余各深度层速度横向分布存在非均匀性,与地形分布特征也存在着一定的联系;速度剖面整体显示区域地壳可以分为上、中、下三个分层,上地壳速度横向变化较小;中、下地壳的界面速度横向起伏变化较大,局部地区呈现上隆或凹陷状;根据速度的分布差异,以及所勾画的深部断裂的轮廓展布,对该区的深部构造有了较深认识:汤西断裂、汤东断裂显示错断较深,倾角较陡,有延伸到中地壳底部的趋势;郑州-开封断裂带、新乡-商丘断裂,与人工地震剖面相同位置处及地质剖面有着较好的对应.     

北京及附近地区地壳速度结构与构造

利用研究区多条地震测深剖面段观测资料解释及多条剖面段的模型数据计算出了研究区结晶基底及莫霍面深度等深线结果,对该地区地壳深部速度结构与构造进行了较详细研究.结果表明,地壳深部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;研究区莫霍面等深线总体特征显示出从东向西逐渐加深趋势,局部区域显示异常变化,变化...     

南北地震带滇西南地区地壳速度结构与构造研究:勐海-耿马-泸水深地震探测剖面结果

位于南北地震带南段的滇西南地区是中国地质构造运动和地震活动较为强烈的地区之一.该区的地质构造背景和深部物理场特征研究是重要的基础科学问题.2013年,在滇西南地区完成了一条长600 km的勐海-耿马-泸水深地震宽角反射/折射和高分辨地震折射联合探测剖面,利用获得11次爆破地震记录截面上6组清楚的壳内P波震相,采用有限差分反演和射线走时正演拟合技术构建了该区的基底速度结构和地壳二维P波速度结构模型.结果显示:沿剖面地壳厚度由南向北逐渐加厚,基底形态呈现出明显的横向起伏变化,在南汀河断裂带附近,基底结构呈现出凹、隆相间的变化形态,基底埋深最浅处约为1.0 km,在腾冲与澜沧附近,基底埋深约为5.0 km.该区中、下地壳速度总体呈现出随深度的增加而增大的变化特征,在块体边界和断裂构造带的下方,速度等值线出现明显紊乱和P波速度的突变.本区莫霍面深度由南向北逐渐加深,且横向起伏变化较大,莫霍面最浅处位于勐海附近,其深度约为32.0 km,最深处位于腾冲附近,深约40.5 km.在耿马与永德之间,莫霍面出现快速上隆和下凹的明显变化,其变化幅度约为4.0 km.在南汀河断裂带、龙陵-瑞丽断裂、大盈江断裂和腾冲火山区的下方,基底速度结构、地壳二维P速度结构、剖面平均速度分布和壳内界面展布还出现从基底至莫霍面顶部的明显变化,显示出断裂构造带下方的地壳速度和介质物性与其两侧的地壳物质具有明显的差异,暗示这些断裂不但具有一定的规模,而且可能延伸至下地壳或上地幔顶部.该区地震主要发生在10~20 km的深度范围内,且地震活动呈现出与壳内介质速度差异、断裂带分布的相关性.研究结果可为分析研究滇西南地区地震活动的深部构造背景、地震精确定位、构建发震构造模型等提供重要的壳幔结构数据,为评价该区的地震危险性和防震减灾规划的制定提供重要参考.     

用接收函数方法研究汶川和芦山地震之间未破裂段的地壳结构

芦山与汶川地震之间存在约40 km的地震空区.震源区和地震空区的深部构造背景的研究对深入了解中强地震的深部孕育环境及地震空区的地震活动性具有重要科学意义.利用本小组布设的15个临时观测地震台以及21个芦山科考台站和21个四川省地震局固定台站记录的远震数据,用H-K叠加方法得到各个台站的地壳厚度和平均泊松比,并构建了接收函数共转换点(CCP)偏移叠加图像以及反演得到台站下方的S波速度模型.我们的结果揭示了震源区和地震空区地壳结构特征差异:(1)汶川震源区的地壳平均泊松比为~0.28;芦山震源区为~0.29;而地震空区处于泊松比变化剧烈的区域;(2)汶川地震与芦山地震的震源区以西下方的Moho面呈现深度上的突变(这与前人的研究成果基本一致),分别从~44 km突变到~59 km,~40 km突变到~50 km,而地震空区地壳平均厚度呈现渐变性变化;(3)地震空区Moho面下凹且具有低速的上地壳.综合一维S波速度结构和H-k以及CCP的初步结果,这可能显示汶川地震的发震断裂在深部方向上向西倾斜并形成切割整个地壳的大型断裂;芦山地震则可能是由于上、下地壳解耦引起的;而地震空区处于两种地震形成机制控制区域的过渡带中.     

松潘-甘孜造山带地壳速度结构

位于川西地区的奔子栏——唐克深地震测深剖面以NNE走向穿越松潘——甘孜造山带．根据人工地震记录分析得到的震相走时和相关的振幅信息，确定了该剖面二维P波地壳速度结构．剖面的地壳结构可分为5层，其中第1，2，3层为上地壳；第4，5层为下地壳．上地壳中部普遍存在低速异常带，但龙日坝以北，这一低速带与其上覆的低速基底合为一体．同时，沿剖面的地壳速度结构具有较强的横向变化．据此，可将剖面分为4段，即甘孜——理塘断裂以南、甘孜——理塘断裂至鲜水河断裂、鲜水河断裂至龙日坝断裂和龙日坝断裂以北. 这与区域构造划分基本一致． 地壳厚度沿测线从南西向北东逐渐减薄，即从金沙江畔的62 km减小到黄河附近的52 km． 根据PmP震相分析，莫霍界面深度在鲜水河断裂两侧没有明显变化．全剖面的地壳平均速度较低，为6.30 km/s．奔子栏——唐克剖面揭示了该地区的造山带型地壳上地幔结构特征．鲜水河断裂带位于剖面的中部，该地区的上地壳速度为正异常，而下地壳和上地幔顶部存在负异常．笔者认为，这是一类有利于强震孕育和发生的深部构造环境．      

腾冲地区地壳速度结构的有限差分成像

利用流动台网和固定台站的地震观测数据,采用有限差分层析成像方法反演了腾冲及邻近地区的地壳P波速度结构,分析了腾冲火山区的岩浆活动和龙陵七级地震的深部构造成因.研究结果表明,腾冲火山区的地壳结构具有明显的非均匀性,浅表层偏低的速度主要为盆地内部的松散沉积层、新生代火山堆积及断裂附近的流体裂隙和热泉活动所致;5～15 km之间的高速体可能代表了早期火山通道内冷却固结的岩浆侵入体或难挥发的超铁镁质残留体;地壳深部的低速体则反映了熔融或半熔融的岩浆体,推断火山区下方的岩浆活动与龙陵七级地震震源区地壳深部的岩浆侵入来自同一源区--现今壳内岩浆活动的主要区域.龙陵震源区的地壳速度结构横向变化较大,怒江断裂东侧和龙陵断裂西侧为高速特征,介质应变强度较大,为应力积累的主要载体;两断裂之间的低速区向下延伸至下地壳,可能与地壳深部的岩浆侵入有关;龙陵断裂和怒江断裂明显控制了这一区域的岩浆活动,七级地震正是发生在断裂下方的速度边界附近.地壳介质强度的横向变化导致了震源区应力积累的不均一性,深部岩浆的聚集和动力作用是龙陵地区发生强震的主要原因.     

基于近震P波走时的南加州地区速度结构层析成像

采用2015—2018年南加州地区密集分布的宽频带地震台站记录的505个近震事件,利用AIC准则拾取了35 600个初至P波到时,应用FMTOMO软件进行走时层析成像,获得了该地区0～40 km深度的三维P波地壳速度结构,其分辨率达0.5°×0.5°×5 km。不同深度的速度结构表明:南加州地区P波速度不仅随深度的变化而变化,且该地区地壳具有明显的横向不均匀性。反演结果显示:中地壳以上的速度结构与地壳岩层和断层系统密切相关,下地壳以下的速度结构存在大范围低速区,呈现横向不均匀性。     

文安─蔚县─察右中旗剖面地壳上地幔速度结构与构造研究

利用文安～蔚县～察右中旗深地震测深剖面的资料，进行了一维、二维射线追踪走时拟合与合成地震图计算，获得了本区地壳上地幔速度结构。结果表明，地壳上地幔速度结构在纵向和横向上具有明显的不均一性。M面起伏较大，其埋深由冀中拗陷的31．0km向西至山西隆起区北部天镇达42．0km左右。浅部断裂较发育，根据对应其地壳深部界面及速度等值线起伏变化程度和反映断裂带附近各波组特征，推测了地壳深部断裂。     

2022年1月8日青海门源MS6.9地震深部构造背景浅析

2022年1月8日青海境内的托莱山—冷龙岭断裂附近发生了门源M_S6.9地震。结合地壳厚度、速度结构及各向异性等资料探讨了门源地震的深部构造特征,揭示了门源地震的发震位置与地壳结构变化的密切关联。结果显示:门源M_S6.9地震发生在地壳厚度和v_P/v_S值都出现快速空间变化的区域;大约在10—20 km深度范围内,震源位于P波速度从浅到深由高速变低速的垂向过渡区,同时也是S波速度和泊松比分布呈现明显横向变化的过渡区域,震源下方存在明显的低速区;冷龙岭断裂两侧相速度的方位各向异性变化比较明显。1月12日的M_S5.2余震震中紧邻2016年M_S6.4地震震中,揭示出2022年门源M_S6.9地震及其余震活动导致了冷龙岭断裂比较充分的破裂,两次门源地震主震之间及邻区短时间内难以积累更大能量,因而短时间内发生更大地震的可能性不大。青藏高原东北缘的持续向北扩展所导致的地表隆升和地壳增厚是该地区强震频发的主要构造成因。      

DEEP STRUCTURE OF NORTHERN HENAN PROVINCE AND ADJACENT AREAS DERIVED FROM GRAVITY AND SEISMIC SOUNDING DATA IN RELATION TO DISTRIBUTION OF EARTHQUAKES

We conduct the wave field separation of the gravity field for northern Henan Province and adjacent areas by the wavelet multi-scale decomposition method, and obtain multi-order gravity wavelet details and regional gravity field information. Then the Parker density surface inversion is used to invert the Moho interface. Based on the analysis of wavelet details in different orders and results of three seismic sounding profiles available in this area, we attempt to reveal the deep crustal structure of the study area. Research results show that the crustal structure is dominated by uneven density distribution accompanied by uplifts and depressions in the region with obvious heterogeneities of the density in horizontal and vertical directions. The gravity field characteristics in the middle-upper crust correspond to the surface topography, the lower crust is dominated by the large-scale high-low gravity anomalies, and several major depression basins show the characteristics of low velocity and low density. At the same time, the depth of the Moho interface changes greatly, which forms the block structure pattern of the regional crustal thickness. Among these features, the area with relatively large variations of the Moho is located in the transition zone of the basin to the Taihang Mountains, or exactly the Moho mutation belt. The Moho interface of the basin area as a whole is dominated by the uplift intertwined with local variations, of which the least and largest depths are 31km and 37km, respectively. Due to the gravity isostasy, the crustal thickness is larger(about 41km)in the northwest of the Taihang Mountains, with less average crustal density. In the study area, earthquakes tend to occur around the transition zone with density changes where the Moho is locally convex. The seismogenic mechanism may be associated with upwelling of upper mantle materials, low-velocity and low-density structures in the middle-lower crust and connection of deep large faults. Moreover, the deep large faults play a controlling role in the distribution of regional earthquakes.     

太行山东缘汤阴地堑地壳结构和活动断裂探测

采用深、浅地震反射和钻孔地质剖面相结合的探测方法,对太行山东缘汤阴地堑的地壳结构和隐伏活动断裂进行了研究.结果表明,该区地壳厚度约36~42 km,莫霍面从华北平原区向太行山下倾伏.汤阴地堑是一个受汤东断裂控制的半地堑构造,其基底面形态与莫霍面展布呈"镜像"关系.汤东断裂是1条继承性的隐伏活动断裂,该断裂向上错断了埋深约20 m的中更新世晚期地层,向下延伸至上地壳底部.综合分析深地震反射和已有深地震宽角反射/折射剖面结果,发现深地震反射剖面上的中-下地壳强反射层和壳幔过渡带反射,与深地震宽角反射/折射剖面上出现的中-下地壳正负速度梯度变化层有着较好的对应关系,这表明本区中-下地壳和壳幔过渡带可能为一系列速度递变层或高低速物质的互变层,埋深约15~16 km的强反射带为上地壳与中-下地壳的转换带,壳幔过渡带的底界为地壳与地幔的分界.研究结果为深入理解该区的深部动力学过程、分析研究深浅构造关系、评价断裂的活动性提供了依据.     

利用爆破地震揭示华北克拉通基底的高分辨速度结构——大丰—包头折射剖面的探测结果

大丰—包头剖面以"高密度观测点距与炮距"为特点,我们在1334 km测线上获得了21炮高信噪比的地震资料.在对Pg波震相特点分析基础上利用反演方法处理、构建了基底的精细结构图像,揭示了沿剖面不同构造地块基底结构的差异.苏北盆地基底埋深4.5~9.0 km、苏鲁隆起1.5~2.0 km,基底埋深与速度结构的强烈起伏变化可视其为华北与扬子板块碰撞、挤压构造环境下形成复杂的构造格局在地震学上的体现;鲁西隆起区基底埋深浅、速度高,结构稳定;华北盆地Pg波到时滞后、视速度低,基底埋深7.0~10.km,速度结构与基底面存在局部的起伏变化.诸多现象揭示出该区为新生代沉积巨厚、规模较大的基底坳陷区.同时在盆地内不同构造单元基底结构呈局部分块、凹陷与凸起并存的构造格局,显示出新生代沉积活动显著、变化强烈、结构不稳定的构造特点;太行山前断裂、聊兰断裂是具有显著地震学标志的断裂构造带,断裂两侧基底界面呈现出"断崖式塌陷"和速度结构的强烈横向非均匀性.综合研究认为,太行山前断裂是华北地区一条重要的构造带,它的复杂性不仅体现在两侧地形地貌、地层介质的截然不同,其基底埋深及速度结构、地壳及地幔岩石圈结构均存在显著的差异,其重要的标志是太行山以东不仅地壳厚度发生了相当规模的减薄,岩石圈的厚度也明显减薄,亦即形成了华北克拉.通破坏在东西部其基底一地壳一岩石圈的结构在空间上具有明显的差异性及强烈的横向非均匀性.     

阿坝—遂宁宽角地震剖面重建藏东缘龙门山地区地壳速度结构

龙门山断裂带位于青藏高原东缘,在中生代和晚新生代经历强烈的构造变形,急剧抬升,是研究青藏高原隆升和扩展动力学过程的重要窗口.本文利用起伏地形下的高精度成像方法,对"阿坝一龙门山一遂宁"宽角反射/折射地震数据重新处理,通过走时反演重建研究区地壳速度结构.剖面自西向东跨越松潘一甘孜块体、龙门山断裂带和四川盆地,不同块体速度结构表现了显著的差异.松潘甘孜块体地表复理石沉积层内有高速岩体侵入,低速层低界面起伏不平反映了该区的逆冲推覆构造.中下地壳速度横向上连续变化,平均速度较低(约6.26 km·s~(-1)).四川盆地沉积层西厚东薄,并在西侧出现与挤压和剥蚀作用相关的压扭形态.中下地壳西薄东厚,平均速度较高(约6.39 km.s~(-1)).龙门山断裂带是地壳速度和厚度的陡变带,Moho面自西向东抬升约13 km.在整个剖面上Moho面表现为韧性挠曲,中下地壳横向上连续变化,推测古扬子块体已到达松潘甘孜块体下方.松潘甘孜块体下方中下地壳韧性变形,并在底部拖曳着被断裂切割的脆性上地壳,应力在不同断裂上积累和释放,诱发大量地震.     

Fine upper crustal structure of Jiashi strong earthquake swarm region in Xinjiang inferred from high resolution seismic refraction profile data

Introduction Jiashi-Artux area in southwest Xinjiang is one of the most active earthquake provinces at pre-sent in Chinese mainland. In the last century, about 3/4 strong earthquakes in Chinese mainland hit this area, and especially from January 21 to April 16 in 1997, 7 earthquakes with the magnituderanging from 6.0 to 6.9 occurred in a very small area of 9 km×18 km near Jiashi (ZHU et al, 1998). It has never taken place before in Chinese mainland that a series of strong earthquakes shoo…     

云南数字地震台站下方的S波速度结构研究

通过对云南数字地震台站的宽频带远震接收函数反演，获得了云南地区数字地震台站下方0-0km深度范围的S波速度结构.结果表明，云南地区地壳厚度变化剧烈，中甸、丽江等西北部地区，地壳厚度达62km左右，景洪、思茅和沧源等南部地区，地壳厚度仅为32-34km.厚地壳从西北部向东南方向伸展，厚度和范围逐渐减小，至通海一带地壳厚度减为42km，其形态和范围与小江断裂和元江断裂围成的川滇菱形块体相一致.地壳厚度较小的东、南部地区Moho面速度界面明显；在地壳厚度较大或变化剧烈的地区，Moho面大多表现为S波速度的高梯度带.云南地区S波速度结构具有很强的横向不均匀性.km深度以上，北部地区S波速度明显低于南部地区，在-20km深度范围内，北部地区的S波速度比南部地区高.地壳内部S波速度界面的连续性较差，低速层的深度和范围不一，近一半的台站下方不存在明显的低速层.受南部地区上地幔的影响，40-50km深度范围内，S波速度南部高、北部低，高速区随深度增加逐渐向北推移，低速异常区形态与川滇菱形块体的形态趋向一致.70-80km深度的上地幔速度分布与云南地区大震分布具有一定的相关性.     

Lithospheric structure and faulting characteristics of the Helan Mountains and Yinchuan Basin:Results of deep seismic reflection profiling

The Helan Mountains and Yinchuan Basin(HM-YB) are located at the northern end of the North-South tectonic belt,and form an intraplate tectonic deformation zone in the western margin of the North China Craton(NCC).The HM-YB has a complicated history of formation and evolution,and is tectonically active at the present day.It has played a dominant role in the complex geological structure and modern earthquake activities of the region.A 135-km-long deep seismic reflection profile across the HM-YB was acquired in early 2014,which provides detailed information of the lithospheric structure and faulting characteristics from near-surface to various depths in the region.The results show that the Moho gradually deepens from east to west in the depth range of 40-48 km along the profile.Significant differences are present in the crustal structure of different tectonic units,including in the distribution of seismic velocities,depths of intra-crustal discontinuities and undulation pattern of the Moho.The deep seismic reflection profile further reveals distinct structural characteristics on the opposite sides of the Helan Mountains.To the east,The Yellow River fault,the eastern piedmont fault of the Helan Mountains,as well as multiple buried faults within the Yinchuan Basin are all normal faults and still active since the Quaternary.These faults have controlled the Cenozoic sedimentation of the basin,and display a "negative-flower" structure in the profile.To the west,the Bayanhaote fault and the western piedmont fault of the Helan Mountains are east-dipping thrust faults,which caused folding,thrusting,and structural deformation in the Mesozoic stratum of the Helan Mountains uplift zone.A deep-penetrating fault is identified in the western side of the Yinchuan Basin.It has a steep inclination cutting through the middle-lower crust and the Moho,and may be connected to the two groups of faults in the upper crust.This set of deep and shallow fault system consists of both strike-slip,thrust,and normal faults formed over different eras,and provides the key tectonic conditions for the basin-mountains coupling,crustal deformation and crust-mantle interactions in the region.The other important phenomenon revealed from the results of deep seismic reflection profiling is the presence of a strong upper mantle reflection(UMR) at a depth of 82-92 km beneath the HM-YB,indicating the existence of a rapid velocity variation or a velocity discontinuity in that depth range.This is possibly a sign of vertical structural inhomogeneity in the upper mantle of the region.The seismic results presented here provide new clues and observational bases for further study of the deep structure,structural differences among various blocks and the tectonic relationship between deep and shallow processes in the western NCC.     

山西高原北部地壳上地幔地震波速结构与深部构造

对自河北文安经山西大同至内蒙古岱海的宽角反射／折射地震剖面资料进行了详细的研究。结果表明，地壳厚度由太行山山前地带的３６．０ｋｍ向山西高原增厚至４４．０ｋｍ。在太行山山前基底断裂、紫荆关断裂的下方和大同盆地的东侧存在着延伸至莫霍面的断裂带；太行山隆起区上地幔顶部的速度偏高，太行山山前地带和大同震区上地壳的下部有强烈的速度反转，大同地震与这里的异常的壳幔构造有关，太行山山前地带存在着发生潜在地震的深部构造条件     

VELOCITY CHARACTRISTICS OF SHANXI AND ADJACENT AREA AND ITS TECTONIC SIGNIFICANCE

In order to acquire a better velocity structure of the crustal and uppermost mantle beneath Shanxi area, we obtain the group and phase velocities of Rayleigh wave of the periods 8s to 50s in Shanxi and adjacent area using ambient seismic noise recorded at 216 broad-band stations. All available vertical-component time series for 2014 have been cross-correlated to yield estimates of empirical Rayleigh wave Green's function. Group and phase velocity dispersion curves for Rayleigh wave are measured for each interstation path by applying frequency-time analysis. It describes finer velocity structure of the crust and upper mantle in Shanxi, which reflects the geological structure characteristics at different depths. The resolution is within 50km and the resolution of part periods can reach 40km.The Rayleigh wave group and phase speed maps at short periods(8~18s and 10~22s)show clear correlations with shallow geological structures. Mountain areas on both sides of Shanxi depression zone show apparent high-velocity anomaly, except for low-velocity anomaly in the Taiyuan Basin, Linfen-Yuncheng Basin and Weihe Basin. Especially, the areas of Youyu County-Pianguan County-Kelan County-Shuozhou City and Jingle County-Lishi District of Lüliang City in Lüliang Mountains, and Yu County-Fuping County-Yi County and Yangcheng County-Licheng County in Taihang Mountains, present higher velocity anomaly. In addition, the velocity is lowest in the Weihe Basin, and the amplitude of low velocity decreases gradually from the south to the north of the basins in Shanxi, which probably is related to the process of gradual stretching and development of the Shanxi rift zone from the southwest to the northeast. The obvious velocity difference across the latitude of 38°N exists at 18~30s period of phase and 24~35s period of group velocity maps, which is probably related to the deep and shallow Moho depth variation in the south and north of Shanxi and the suture zone of ancient blocks including "hard" southern block and "soft" northern block. At the same time, the research result of receiver function reveals that partial melting of the lower crust occurs in the northern Taihang Mountains, while the southern section remains stable(Poisson's ratio is above 0.3 in the northern Taihang Mountains and 0.25~0.26 in the southern section). The phase velocity map at 30~50s period clearly shows NW velocity gradient belt, and the low velocity anomaly in the northeast side may be related to Cenozoic volcanism. Meanwhile, the eastern border of Ordos block is the western faults of central basins in Shanxi depression zone. However, some research results indicate that the above border is Lishi Fault in the surface, inferring that the Ordos block shows a shape of wide in the upper and narrow in the lower part from the surface to deep. The Datong volcanic area at 18~45s period of phase and 24~35s period of group velocity maps shows low velocity of trumpet shape from shallow to deep, related to the upwelling of hot material from lower mantle in the Cenozoic causing a large area of intense magmatic activity. It indicates the more specific upwelling channel of Datong volcanoes simultaneously.