East-west crustal structure and "down-bowing" Moho under the northern Tibet revealed by wide-angle seismic profile   总被引：5，自引：2，他引：5  

张中杰  李英康  王光杰  滕吉文  S.Klemperer  李敬卫  范进义  陈赟 《中国科学D辑(英文版)》2002,45(6)

We recognized 6 sets of reflecting P- and S-wave events from Moho and other interfaces within the crust, respectively, with the wide-angle seismic data acquired from 510 km-long Selincuo-Ya'anduo profile in the northern Tibet, fitted the observed events with forward modeling, and interpreted crustal structure of P- and S-wave velocities and Poisson's ratio under the profile. The results demonstrate that the crustal structure between Yarlungzangbo and Bangong-Nujiang sutures changes abruptly, and the crust is the thickest at the middle part of the profile with thickness of 80 km or more. The "down-bowing" Moho is the striking feature for the crustal variation along the west-east direction. The Moho uplifts with steps, and the uplifting rate westward is greater than that eastward. The heterogeneity of P- and S-wave velocities exists both vertically and horizontally, and one lower velocity layer (LVL) exists with the depth range of 27-34 km and the thickness range of 5-7 km. For the upper crust, Poisson's ratio is the lowest at the middle part of the profile; for the lower crust, the Poisson's ratio at the east segment is lower than that at west segment, which means that the crustal rigidity for the upper crust is different from the lower crust, and the lower crust under the east segment of the profile is more ductile. We infer that the substance in the lower crust endured eastward flow along with the collision between Eurasian and Indian plates, and the "down-bowing" Moho is attributable to the multi-phase E-W tectonic processes.  相似文献   

2000年云南姚安Ms6.5地震余震序列S波分裂研究   总被引：10，自引：1，他引：10  

钱晓东  李白基  秦嘉政 《中国地震》2002,18(2):157-165

本文利用云南姚安MS6 5地震后在震中附近架设的 3个三分向数字记录台站的地震资料 ,对该区S波分裂进行研究。结果表明 :① 2 36条处于横波窗内的记录S波分裂现象明显 ;②延迟时间大部份在 3 5～ 10 5ms km范围 ,平均值为 7 0ms km ;③快波偏振方向大部份在N140°E～N16 4°E范围 ,平均值为N15 2 4°E ;④快波的优势偏振方向与主震的发震断裂 (马尾菁断裂 )和余震的发震破裂方向不一致 ,而与该区的主压应力方向比较符合 ;⑤姚安地震余震序列的S波分裂是应力场控制的EDA裂隙各向异性的结果。  相似文献   

JOINT INVERSION OF SURFACE WAVE DISPERSION AND RECEIVER FUNCTIONS FOR CRUSTAL AND UPPERMOST MANTLE STRUCTURE BENEATH CHINESE TIENSHAN AND ITS ADJACENT AREAS          下载免费PDF全文

KONG Xiang-yan  WU Jian-ping  FANG Li-hua  CAI Yan  FAN Li-ping  WANG Wei-lai 《地震地质》1979,42(4):844-865

The Tienshan orogenic belt is one of the most active intracontinental orogenic belts in the world. Studying the deep crust-mantle structure in this area is of great significance for understanding the deep dynamics of the Tienshan orogen. The distribution of fixed seismic stations in the Tianshan orogenic belt is sparse. The low resolution of the existing tomographic results in the Tienshan orogenic belt has affected the in-depth understanding of the deep dynamics of the Tienshan orogenic belt. In this paper, the observation data of 52 mobile seismic stations in the Xinjiang Seismic Network and the 11 new seismic stations in the Tienshan area for one-year observations are used. The seismic ambient noise tomography method is used to obtain the Rayleigh surface wave velocity distribution image in the range of 10~50s beneath the Chinese Tienshan and its adjacent areas (41°~48° N, 79°~91° E). The joint inversion of surface wave and receiver function reveals the S-wave velocity structure of the crust and uppermost mantle and the crustal thickness below the station beneath the Chinese Tienshan area(41°~46° N, 79°~91° E). The use of observation data from mobile stations and new fixed seismic stations has improved the resolution of surface wave phase velocity imaging and S-wave velocity structure models in the study area.
The results show that there are many obvious low-velocity layers in the crust near the basin-bearing zone in the northern Tienshan Mountains and the southern Tienshan Mountains. There are significant differences in the structural characteristics and distribution range of the low-velocity zone in the northern margin and the southern margin. Combining previous research results on artificial seismic profiles, receiver function profiles, teleseismic tomography, and continental subduction simulation experiments, it is speculated that the subduction of the Tarim Basin and the Junggar Basin to the Tienshan orogenic belt mainly occurs in the middle of the Chinese Tienshan orogenic belt, and the subduction of the southern margin of the Tienshan Mountains is larger than that of the northern margin, and the subduction of the eastern crust is not obvious or in the early subduction stage. There are many low-velocity layers in the inner crust of the Tienshan orogenic belt, and most of them correspond to the strong uplifting areas that are currently occurring. The thickness of the crust below the Tienshan orogenic belt is between 55km and 63km. The thickness of the crust(about 63km)is the largest near the BLT seismic station in the Bazhou region of Xinjiang. The average crustal thickness of the Tarim Basin is about 45km, and that of the Junggar Basin is 47km. The S-wave velocity structure obtained in this study can provide a new deep basis for the study of the segmentation of the Tienshan orogenic belt and the difference of the basin-mountain coupling type.  相似文献   

沉积盆地热演化史研究新进展   总被引：9，自引：0，他引：9  

任战利 《地球科学进展》1992,7(3):43-49

   沉积盆地热历史及其对有机质成熟度的影响是非常活致的研究课题。本文论述了这方面的新进展，其中包括古地温研究办法、盆地热历史类型及热历史重建。作者认为恢复沉积盆地沉积热历史应重视后期地温场的改造。
     相似文献   

裂变径迹分析法研究河北南梁金矿床成矿时代及其热历史   总被引：4，自引：0，他引：4  

袁万明  王世成  王兰芬 《矿物学报》2001,21(2):225-230

河北南梁（下营坊）金矿不同蚀变带中锆石和磷灰石裂变径迹实测年龄为153.9-103.3Ma，其成矿时代应属于燕山早期，成矿时间持续50Ma以上，成矿热历史总体上是早期温度高、冷却快，晚期温度低、冷却慢，转变时间在120Ma左右，转变温度在100℃左右，呈现两期热液成矿过程，第一期热液金矿矿活动发生在150Ma前后，与花岗斑岩体的侵位有关；第二期金成矿作用发生在135Ma前后，与流纹斑岩和岩浆隐爆角砾岩的形成有关。锆石裂变径迹年龄相当于早期成矿时代，磷灰石裂变径迹年龄相当于晚期成矿时代。矿区石英-绢云母化蚀变作用发生时间不仅比钾比蚀变早，而且持续时间亦比钾化长。  相似文献   

江苏东海片麻岩裂变径迹年龄和冷却历史     

杨刚  陈江峰  周泰禧  张巽  王世成 《矿物岩石地球化学通报》2001,20(4):306-308

本文测定了江苏东海科学超深钻选址地区地表和钻孔片麻岩样品的锆石和磷灰石的裂变径迹年龄。地表样品 97CK0 1的锆石裂变径迹年龄为 134± 11Ma ,磷灰石的裂变径迹年龄为 6 6 .8± 2 .5Ma。ZK2 30 4 85号样品磷灰石的裂变径迹年龄为 79.2± 2 .5Ma。由估计的锆石和磷灰石的裂变径迹封闭温度得到该地区从约2 2 5℃冷却到 10 0℃时的冷却速率为 (1.9± 0 .2 )℃ Ma ,在从约 10 0℃冷却到现在的冷却速率为 (1.0± 0 .1)℃ Ma。我们得到的结果不支持前人关于新生代加速冷却的结论 ,可能与地区的差异冷却有关。  相似文献   

兰坪盆地小格拉铜矿床地质特征及成矿时代初探   总被引：2，自引：0，他引：2  

李小明  龚文君  谭凯旋  龚革联 《华东地质学院学报》2001,24(1):17-18,72

小格拉铜矿床是位于兰坪盆地西北部的小型铜矿床，含银较丰富。矿体位于断裂破碎带中，出露在Csh^1和J2h^3地层中，因盆地隆升、矿体出露,而遭受氧化形成氧化矿与硫化矿各半的铜矿床。磷灰石裂变径迹数据表明：矿床形成年龄大于93．9Ma，其后经历了复杂的构造演化过程。  相似文献   

On the lines of the direction of S-waves     

Simón Gershanik 《Geophysical Journal International》1992,110(1):1-5

  相似文献   

横波地震基本理论的研究   总被引：10，自引：0，他引：10  

张树林 《地球科学进展》1992,7(2):17-23

The people have highly attached importance to the technipues of S-wave seismics. It is basic
premise of S一wave exploration or combining S-wave and P-wave study the basic theory for S-wave seismics. In the basic theory，especially，seismic-wave velocities(V_p,V_s) and its ratio(V_p,V_s) must be studied.
  相似文献   

Determination of Q _S, spreading factor and S-wave acceleration by inversion of seismic intensity data     

Jiashu Xie  Huicheng Shao 《地震学报(英文版)》1992,5(2):295-304

In this paper, on the basis of intensity data from 85 earthquakes occurred in China, the method of resolving overdetermined equations by using the damped least squares method is applied to inversing for the mean value of 1 s. S wave quality factor, the spreading factor and the S-wave acceleration at the foci of earthquakes in 7 regions of China. The relation between S-wave acceleration at the foci of earthquakes and magnitude is discussed. As an example, 2-DQ _S distribution in Taiwan Province is obtained by inversion. It is found that there exists some corresponding relation between this distribution and Bouguer gravitational anomaly and seismicity. Preliminary analysis and discussion on results of the inversion, and estimation of error inQ _S are made. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 202–211, 1991. The English version of this paper is improved by Professor Yushou Xie.  相似文献