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Title:: Seismic Anisotropy in the Crust in Qilian Mountains-Liupan Mountains Seismic Belt

作者:: 潘宇航¹; 程建武¹; 鲍子文²; 蒲举¹; 1.中国地震局兰州地震研究所,甘肃兰州 730000; 2.安徽省地震局,安徽合肥 230000

Author(s):: PAN Yuhang¹; CHENG Jianwu¹; BAO Ziwen²; PU Ju¹; 1.Lanzhou Institute of Seismology,CEA,Lanzhou 730000,Gansu,China2.Earthquake Administration of Anhui province,Hefei 230000,Anhui,China

Keywords:: crustal anisotropy; shear-wave splitting; polarization; principal compressive stress

摘要:: 利用2010年1月至2015年12月甘肃省测震台网的地震波形资料,使用SAM方法,获得了祁连山—六盘山地震带地区21个台站的快剪切波偏振方向和慢剪切波的时间延迟,分析讨论了该地震带地壳介质各向异性空间分布特征。结果表明:大部分台站的快波偏振优势方向明显与区域内的主压应力方向一致,呈近NE-NEE方向,表明来自印度板块和欧亚板块的NNE或NE向的水平挤压应力控制了祁连山—六盘山地震带的中上地壳应力场。但局部区域的快剪切波偏振方向与断裂走向一致,表明该区各向异性具有差异性,主要是由复杂的活动构造所造成。

Abstract:: In this study,the polarization of fast shear waves and time delay of low shear-wave beneath the 21 stations in this area were computed using shear-wave Splitting Analysis Method(SAM)based on the seismic data during January 2010 to December 2015,recorded by the Gansu Regional Digital Seismic Network.Meanwhile,we also analysed and discussed the spatial distribution of the crust anisotropy characteristics in Qilian Mountains-Liupan Mountains seismic belt.Due to the impact of the regional principal compressive stress and local geological structure,the spatial distribution of polarization of the fast shear-wave shows partly complicated and localized characteristics.The second predominant polarization direction of fast shear-wave is consistent with strike direction of fault in local area,which indicates discreteness and differences about anisotropy.However,the principle polarization direction,which is near NE direction,is obvious in Qilian Mountains-Liupan Mountains seismic belt.