青藏高原东北缘莫霍界面的三维空间构造特征  

Three dimensional Moho geometry beneath the northeast edge of the Qinghai-Tibet Plateau

作　　者：赵金仁[1] 李松林[1] 张先康[1] 杨卓欣[1] 张成科[1] 刘宝峰[1] 张建狮[1] 潘素珍[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》2005年第1期78-85,共8页Chinese Journal of Geophysics

基　　金：国家重点基础研究发展规划项目 (G19980 40 70 2 )资助

摘　　要：通过在青藏高原东北缘设计专门的三维地震观测系统而获得的莫霍界面反射波 ,利用三维反演方法反演重建了该区莫霍 (M)界面的构造形态 ,得到了研究区M界面的三维构造图像和地壳深断裂的展布 .研究区M界面总体上由东北向西南方向呈逐渐下倾趋势 ,而在不同的块体内部又具有不同的倾斜态势 ,反映了不同块体之间的差异和复杂程度的不同 .鄂尔多斯块体M界面变化平缓 ,内部结构完整且坚硬 ;弧形构造区M界面的倾斜趋势发生了逆转 ,此现象可视为该区域在挤压、变形构造作用下M界面发生了明显的扭曲变形 ;秦祁块体M界面呈现出较陡的倾斜趋势 ,在本块东南端与弧形区结合部 ,M界面所显示出的局部隆起可视为地壳发生了强烈扭曲变形的迹象 .综合二维、三维结果认为 ,特殊而复杂的构造变形环境 ,为海原 8 6级大地震的孕育和发生提供了地质条件和深部背景 .Reflection seismic waves are recorded through a special three dimensional observation system designed at the northeast edge of the Qinghai-Tibet Plateau and the Moho geometry in the investigation region is reconstructed by a 3-D inversion method. The 3-D structure image of Moho geometry and the extension of deep crustal faults are inferred. In general, the Moho geometry beneath the survey region gradually dips down from northeast to southeast direction and has different dipping situations in the distinct block interiors, which reflects the difference among the different blocks and indicates that their complicated degrees are not alike. The Moho geometry beneath the Ordos block varies gently and its interior structure, which presents rigid properties, shows rather good integrity. The dipping trend of the Moho geometry below the arc tectonic region takes a turn, which maybe suggests that the Moho geometry has experienced obvious torsion deformation under compression and deforming tectonic action. The Moho geometry below the Qinqi block presents a rather steep dipping trend and at its southeast end, where it meets with the arc zone, the Moho geometry locally uprises, which may be regarded as the sign of strong torsion deformation in the crust. To synthesize the 2-D and 3-D results suggests that the special and complex tectonic deformation environment provides the deep geological and tectonic background for the Haiyuan earthquake with magnitude 8 6 of 1920

关 键 词：青藏高原东北缘 三维反演 地壳界面形态 局部起伏变形 

分 类 号：P541[天文地球—构造地质学]