华北地区地壳上地幔速度各向异性研究  

Velocity anisotropy in the crust and upper mantle of North China

作　　者：黄忠贤[1] 

机构地区：[1]中国地震局地壳应力研究所,北京100085

出　　处：《地球物理学报》2011年第3期681-691,共11页Chinese Journal of Geophysics

基　　金：中央公益性科研院所基本科研业务专项(ZDJ2007-1)资助

摘　　要：本文介绍面波反演得到的华北地区地壳上地幔速度各向异性分布图像,并与S波分裂的结果作初步的定性比较.不同周期瑞利波群速度的方位各向异性图像呈现显著的横向变化,与华北地区地壳上地幔的构造分块和垂直分层结构有比较密切的联系.在鄂尔多斯和阿拉善等稳定地块中,岩石圈地幔到160 km深度都保持比较一致的显著各向异性;而在发生过岩石圈减薄的华北克拉通东部,大约80～150 km深度范围内基本没有探测到方位各向异性,可能说明岩石圈减薄过程抹去了原有的各向异性印迹而且没有显著的水平构造运动造成新的方位各向异性.地球介质的各向异性具有明显的分层特征,面波的反演结果是如此,而S波分裂测量所表现的离散性,也可能是由各向异性的分层差异和倾斜的各向异性对称轴等因素引起.采用多层的各向异性模型,在多数情况下可以定性地解释面波反演和S波分裂结果之间的差异.进一步的工作要求增大面波的探测深度和改善分辨能力,获取更多的S波分裂测量资料,从而建立定量或半定量的三维各向异性模型.This paper presents the result of a surface wave study on azimuthal anisotropy in the crust and upper mantle of North China, and makes a preliminary comparison with the result of Swave splitting in the region. The anisotropy pattern of Rayleigh waves of different periods exhibits obvious lateral variation, which is closely related with the tectonic divisions and vertieal layering of the crust and upper mantle of North China. In the stable blocks of Ordos and Alashan significant anisotropy is rather uniform in the lithospheric mantle down to 160kin; while in the eastern part of the North China Craton, where lithosphere thinning occurred in Meso-Cenozoic time, no azimuthal anisotropy is detected in the depth range of 80-150km, which may indicate that lithospheric thinning erased previous anisotropy and no significant horizontal movement occurred to cause new azimuthal anisotropy. The anisotropy in the study region is characterized by obvious layering, as evidenced by the inversion result from surface waves. On the other hand the remarkable scatter of apparent splitting parameters may also be attributed to multi-layering and/or slanting symmetry axis of the anisotropy. Assuming a multi-layer anisotropy model, the differences between surfaee wave and S-wave splitting in most cases can be qualitatively explained. In the future study the detecting depth and resolving power of surface wave should beincreased and more splitting measurements are needed in order to establish a quantitative or semiquantitative 3D anisotropy model.

关 键 词：华北 地壳上地幔 面波 方位各向异性 S波分裂 

分 类 号：P315[天文地球—地震学]