中国西部及邻区的地壳三维速度结构  

THREE-DIMENSIONAL VELOCITY STRUCTURES OF THE CRUST IN WEST CHINA

作　　者：单新建[1] 冯德益[2] 宋仲和[3] 陈国英[3] 

机构地区：[1]新疆维吾尔自治区地震局 [2]天津地震局 [3]国家地震局地球物理研究所

出　　处：《内陆地震》1993年第2期142-150,共9页Inland Earthquake

摘　　要：用网格频散反演技术计算了155条瑞利面波混合频散数据,将中国大陆分为目前最小分格2°×2°,得到了中国西部及邻区深至80km地壳和上地幔顶部的三维剪切波SV速度结构。结果表明:(1)天山褶皱系地壳平均厚度为54km,上地壳平均速度为3.3km/s,下壳平均速度3.93km/s,上地幔盖层平均速度为4.64km/s,都偏大。北天山壳厚比天山薄,壳和上地幔盖层下均有低速层。(2)塔里木盆地中部地壳厚46km,到其边缘的昆仑山、天山地带壳厚增加到52～55km。壳内无低速层,壳平均速度很低,为3.49km/s,地表有9km的沉积层。(3)青藏高原莫霍面呈凹形,平均壳厚为67km,平均壳速度为3.58km/s。东西端存在壳内低速层,埋深为15～35km。(4)南北带为构造复杂的区域,莫霍面深度具有东高西低,南北两端高、中间低的特点,带内普遍存在壳内低速层。南北带从群速度、速度、莫霍面等深线都可看到明显的横向差异。(5)准噶尔盆地地壳厚47km,无壳内低速层,中地壳不明显。该区呈稳定的大陆壳结构。(6)柴达木盆地在正常速度的中壳顶部有一高速夹层,速度为3.72km/s,厚10km,上顶部埋深14km。In this paper, we introduced a mesh dispersion inversion method to proceed the Rayleigh wave of 155 selected paths by 'Display - Equalized Filter Frequency - Time Analysis' technique. We have obtained dispersion of the group velocity of surface wave from mixed-paths travelling through West China. The mesh dispersion inversion is proposed to extract pure-paths dispersion curves over all 2×2 in West China from the mixed-paths dispersion measurement. Then, we use Rodi's surface wave inversion program to inverse the three-dimensional SV -wave velocity structure to a depth of 80km, the result showed the lateral heterogenities in West China. The average thickness of the earth's crust under the Tibetan plateau is about 67 km. The thickness of the crust has been thickened gradually from the east to west, north to south. There are low velocity layers existing at the depth of 15 km to 35 km in Tibetan plateau and north-south seismic zone. There are also an uprising of materials in the south of north-south seismic zone. In the Tarim basin,the average SV-wave velocity is the lowest one, about 3. 49 km/s ,the thickness of the crust is about 46 - 52 km.

关 键 词：中国 速度结构 地震活动性 地壳 

分 类 号：P351.5[天文地球—空间物理学]