摘要
岩石圈各向异性主要由上地幔矿物晶格优势排列方向和上地壳内裂缝、裂隙的定向分布造成.在各向异性特征显著区域,利用SKS震相剪切波分裂获得的延迟时间高达1.5 s以上.本文根据方位各向异性,利用广义反射透射系数矩阵方法正演S波接收函数,研究各向异性对不同反方位角接收函数转换震相走时的影响.我们发展了基于HTI模型各向异性走时校正的方法,成功的在单层和多层(快轴方向相同或不同)的各向异性介质中对齐不同反方位角接收函数的Moho面和LAB的转换震相走时.我们将该方法应用于在青藏高原东北缘的流动台站,试图在各向异性强度较大区域对实测数据转换震相走时的校正效果进行测试.结果表明:各向异性走时校正能够加强单台接收函数转换震相的可追踪性,能量增强的叠后转换震相在时深转换后更利于对界面深度的识别与判断;在考虑三维成像的情况下,我们的各向异性校正方法对提高成像结果的准确性有重要意义.
It is commonly accepted that the seismic anisotropy of the lithosphere is mainly attributed to stress-induced alignment of cracks in the crust and strain-induced olivine lattice-preferred in the upper mantle.Parameters of such seismic anisotropy provide crucial evidence for deducing the subsurface deformation beneath regions of active tectonics.When traveling through anisotropic media,shear waves(such as Ps,S,ScS and SKS phases)split into fast and slow waves,resulting in a large time delay,which can be used to image lithosphere by S wave receiver functions.This work proposes a new method of such imaging.We firstly investigate the backazimuthal variation of theoretical S Receiver Functions(SRFs)arrival time in anisotropic media based on the generalized reflection and transmission coefficients method.We develop a novel technique for correcting travel time variation of SRFs from different backazimuths.Synthetic tests prove the feasibility and robustness of the phase arrival time correction.We further verify the feasibility of the correction of arrival time for real data by applying the method to 2 examples from the northeastern Tibetan Plateau.The results show that energy of summed conversion phases is enhanced,making the depth of converted interface after travel time correction easier to identify.Our method would be helpful in improving the quality of 3-D receiver function imaging.
作者
陈一方
齐少华
陈九辉
郭飚
李顺成
赵盼盼
CHEN YiFang;QI ShaoHua;CHEN JiuHui;GUO Biao;LI ShunCheng;ZHAO PanPan(State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2020年第5期1844-1855,共12页
Chinese Journal of Geophysics
基金
国家自然科学基金项目(41590862,41704095)
国家重点研发项目(2017YFC1500103)资助.
关键词
各向异性
接收函数
走时校正
时深转换
Seismic anisotropy
Receiver function
Arrival time correction
Time-depth conversion
