地震工程学报Issue(4)：1047-1058,12.DOI:10.3969/j.issn.1000-0844.2014.04.1047
新疆地区地壳S波速度结构及径向各向异性研究
Crustal S-wave Velocity Structure and Radial Anisotropy in Xinjiang Region
摘要
Abstract
Northwest China is an ideal site for studying the effects of mountain-basin coupling due to its complex topography and tectonic structure.In this study,we construct crustal shear wave velocity struc-ture and radial anisotropy in the crust and uppermost mantle in the Xinjiang region by ambient noise seis-mic tomography.The data include 9 months (2009 January to 2009 September)of three-component con-tinuous data recorded at 74 seismic stations of the China Provincial Digital Seismic Networks and regional Kyrgyzstan and Kazakhstan Networks.Empirical Rayleigh and Love wave Green’s functions are obtained from interstation cross-correlations.Group velocity and phase velocity dispersion curves between 8 s and 50 s periods are measured for each interstation path by applying the time-frequency analysis method with phase-matched processing.The group velocity and phase velocity maps show clear lateral variations that correlate well with major geological structures and tectonic units in the study regions.At short periods (<20 s),the basins show low group velocity and phase velocity,and the eastern part of Tarim Basin dis-plays relatively lower velocities than the western part.A small patch of high velocity is observed in the northwest part of Tarim Basin,indicating that the structure beneath Tarim Basin is not horizontally hom-ogeneous.The orogenic belt shows high velocity.As the period increases,the imprint of the sedimentary layers diminish.At long periods (>30 s),surface wave velocities are strongly influenced by crust thick-ness and shear velocities in the lower crust and uppermost mantle.High velocity is observed beneath the basins.In contrast,the Tianshan orogenic belt stands out as a low-velocity region. <br> SV and SH wave velocity structures of the crust and upper mantle are inverted from Rayleigh and Love wave dispersion maps.Because of thick sedimentation in the basins,S-wave velocities of the Tarim and Junggar basins are relatively low at shallow depth,whereas S-wave velocities of the mountain area are high due to the widely appearance of magmatic rocks.In the middle and lower crust,the basins show clear features with high velocities,whereas the Tianshan orogenic belt shows those with low velocity.In addi-tion,we compute the radial anisotropy by measuring the differences between SH wave and SV wave ve-locity.The Tianshan orogenic belt shows negative radial anisotropy,which reflects dominant vertical movement of the deep crustal materials during the process of crustal shortening and thickening beneath this belt.Western Tianshan displays stronger anisotropy than eastern Tianshan,which may be related to different blocking effects due to the Tarim Block.Positive radial anisotropy is a major characteristic of the Tarim Basin in the upper crust,and the velocity of the SH wave of horizontal polarization is faster than the SV wave of vertical polarization mainly due to the effects of the sedimentary layer.In the stable block, the radial anisotropy represents fossil anisotropy left in the latest large-scale tectonic movement.Because movement in the entire Tarim block resulted in mineral crystal arrangement dominated in the horizontal direction,the middle crust of the Tarim Basin shows positive radial anisotropy.关键词
新疆地区/塔里木盆地/背景噪声层析成像/群速度/相速度/径向各向异性Key words
Xingjian region/ambient noise tomography/group velocity/phase velocity/radial anisotropy分类
天文与地球科学引用本文复制引用
周铭,李红谊,李信富,谭静,孙三健,欧阳龙斌,郑丹..新疆地区地壳S波速度结构及径向各向异性研究[J].地震工程学报,2014,(4):1047-1058,12.基金项目
国家自然科学基金项目(40804007,41174050) （40804007,41174050）
中央高校基本科研业务费专项资金 （）
