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  

High resolution velocity structure of the North China Craton basement by explosion seismic sounding——results from Dafeng-Baotou refraction profile

作　　者：赵金仁[1] 刘保金[1] 段永红[1] 潘素珍[1] 范振宇[1] 马策军 邓晓果 海燕[1] 王帅军[1] 李怡青[1] 

机构地区：[1]中国地震局地球物理勘探中心,郑州450002

出　　处：《地球物理学报》2017年第7期2628-2640,共13页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41474077;91214205;41474076);公益性行业(地震)科研专项(200908001)资助

摘　　要：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.Due to the high density of observation points and shot spacings, we obtained the 21- shot seismic data with high signal-to-noise ratio along the 1334 km long Dafeng-Baotou profile. On the basis of the analysis of the Pg wave phase characteristics, we processed the data by the inversion method and constructed the fine structure of the basement, revealing the discrepancy of basement structure in different tectonic blocks. The basement depth of Subei Basin is 4.5~9.0 km and of Sulu uplift is 1.5~2.0 km. Strong fluctuations of the burial depth and velocity structure may be considered as the seismologie manifestation of the collision and compression between North China and the Yangtze plate. The basement of Luxi uplift area shows the feature of shallow depth, high speed and stable structure, while the Pg wave characteristics in the North China Basin are lagged travel time, low apparent velocity, basement depth from 7.0 to 10.0 km, and the local fluctuations in the velocity structure and basement interface. Lots of phenomena above reveal that this area is a large-scale basement depression zone with thick Cenozoic sediment. Moreover, in different tectonic units of the basin, the basement tectonic pattern of local patch and coexistence of the depression and the uplift shows obvious tectonic characteristics, such as remarkble Cenozoic sedimentary activities, significant velocity and thickness changes and the unstable structure. Taihang Mountain piedmont fault and Liaolan fault are significant seismologic features. On both sides of these two faults, the velocity structure shows intensive lateral heterogeneity, and the basement interfaces collapse as cliff. This study reveals that the Taihang Mountain piedmont fault is an important tectonic zone in North China. Its complexity is not only reflected in different landforms and strata media on its both sides, but also reflected in the significant differences in the basement depth, velocity structure, the crust and even the mantle lithospheric structures. To the east of Taihang

关 键 词：大丰-包头地震剖面 Pg波特点的分区性 基底高分辨结构 基底界面起伏 速度结构非均匀 构造复杂的地震学证据 

分 类 号：P315[天文地球—地震学]