摘要
青藏高原板块之间的碰撞和持续汇聚伴随着高原的南北向缩短和东西向伸展,精细的地壳结构将有助于认识和理解高原内部变形以及高原隆升的动力学机制。基于高原中部流动地震台阵SANDWICH提供的观测数据,整合地震台网固定台站数据,开展背景噪声面波层析成像研究,获得了高原中部地壳瑞雷波相速度和方位各向异性分布。中地壳低速异常广泛分布于共轭走滑断层区,且低速异常区域各向异性快波方向近EW向。下地壳相速度和各向异性分布特征与中上地壳存在很大差异。结合其他证据,认为高原中部中地壳可能存在部分熔融和局部东向流动,促使了共轭走滑断层的形成,且中上地壳与下地壳的动力学机制可能处于解耦的状态。
The collision and continuous convergence between the two plates of the Qinghai-Tibet Plateau are accompanied by the N-S shortening and E-W extension of the plateau.The fine crustal structure will help to understand the dynamic mechanics of the internal deformation and uplift of the plateau.Based on the observation data recorded by the temporary seismic array SANDWICH in the central plateau and 30 permanent stations in National seismic network,we obtained Rayleigh wave phase velocity and azimuth anisotropy of the central plateau by the surface wave tomographic imaging of background noise.The results show that low-velocity anomalies in the middle crust are widely distributed in conjugate strike-slip fault areas,and the predominant direction of fast waves in the low-velocity anomaly area is close to E-W.In addition,the characteristics of phase velocity and azimuthal anisotropy in the lower crust are quite different from those in the middle and upper crust.Combined with other geophysical evidence,it's suggested that partial melting and local eastward flow may exist in the middle crust of the central plateau,which brings about the formation of conjugate strike-slip faults and may decouple the lower and the upper-middle crusts.
作者
谭萍
TAN Ping(Hebei Key Laboratory of Earthquake Dynamics,Institute of Disaster Prevention,Sanhe 065201,China)
出处
《防灾科技学院学报》
2021年第3期8-16,共9页
Journal of Institute of Disaster Prevention
基金
中央高校基本科研业务费专项(ZY20180235)
国家自然科学基金(41904055)
河北省自然科学基金(D2020512005)。
关键词
青藏高原
背景噪声
相速度
方位各向异性
共轭走滑断层
the Qinghai-Tibet Plateau
background noise
phase velocity
azimuthal anisotropy
conjugate strike-slip faults
