【作者】 滕吉文； 尹周勋； 熊绍柏；

【Author】 Teng Jiwen Yin ZhouXun Xiong Shaobai (Institute of Geophysics,Chinese Academy of Sciences)

【机构】 中国科学院地球物理研究所；

【摘要】 本文根据1982年西藏高原北部地区色林错-蓬错-那曲-索县纵测线的人工地震探测资料,进行了震相分析对比.依据各波组的运动学特征和动力学特征,主要可以辨认出t₁（直达波）、t₃、t₄、t₅、和t₆等五组来自地壳中各层和莫霍界面的反射波.通过理论走时曲线拟合与反演,并用射线追踪和理论地震图等方法进行了反复计算,得出该测线上各地段的地壳结构模型.初步结果表明,藏北高原地区平均地壳厚度为70 km左右.地壳介质中纵波的平均速度为6.2—6.3 km/s,上地壳中P波速度为6.0—6.1 km/s,下地壳中P波速度为6.8 km/s左右.这里地壳由高低速相间的成层结构组成,在地壳的上部和下部均存在低速层,沉积盖层由西向东减薄.此外,用射线追踪方法讨论了该区地壳介质的横向不均匀性.更多还原

【Abstract】 In order to study the crustal structure and characteristics of the velocity distribution in the northern part of Xizang（Tibet） Plateau,a large scale of explosion seismic sounding of 500 km long in the Serlin Co-Peng Co-Naqu-Suo County region was conducted in 1982.There are three shot points on this profils.The Serlin Co and Yangando are at the ends of this profile.The Peng Co is at the middle of this profile.Combined shooting under water were carried out in the Serlin Co and the Peng Co with an additional combined shooting in a well at the Yangando where the charges of explosions are of 2 to 18 tons.Sixty analog tape recording stations were used for this observation. Seismic data of this profile and complicated seismic phases were analyzed and processed. We have identified a direct wave t₁ as well as reflected waves t₃、t₄、t₅ and t₆ from interfaces and Moho discontinuity.Each wave group has its own characteristics.Different methods of theoretical travel time curve,the ray tracing and synthetic seismogram are utilized in the process.The crustal structure models of each part in this profile are obtained.The primary results are as follows: 1.The crust beneath the Serlin Co -Peng Co -Naqu -Suo County region is of a multilayered structure with a crustal thickness of 70 km.Its average velocity is of 6.2-6.3 km/ sec.The average velocities in the upper and lower crust are of 6.0- 6.1 km / sec and 6.7-6.8 km/ sec respectively. 2.There exists a low velocity layer in both the upper and lower crust.The thickness is about 5 km at either parts.The layer velocities in the upper and lower crust are of 5.5-5.8 km/ sec and 6.1 km / sec respectively.The depths of the low velocity layer in the upper crust at the eastern and the western parts of the profile are different.The depth of the low velocity layer in the lower crust is of about 45 km. 3.There is a covering layer from the west of Naqu to the Serlin Co.The thickness is 1-4 km and with a layer velocity of about 3.5 km / sec.The thickness of the covering layer gradually decreases from the east of Naqu to the Suo County. 4.The lateral inhomogeneity of the crust within this area was studied by the ray tracing method. The field observation data used in the present study are jointly obtained in 1982 by the Chinese Ministry of Geology and Mineral Resources,the Institute of Geophysics,Chinese Academy of Sciences and the Insititute of Geophysics of Paris Sixth University,France.更多还原