华北地区地壳上地幔速度各向异性研究

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...

Velocity anisotropy in the crust and upper mantle of North China

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 S-wave 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 vertical 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 160km; 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 surface 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 be increased and more splitting measurements are needed in order to establish a quantitative or semi-quantitative 3D anisotropy model.