祁连山—六盘山地震带地壳各向异性特征初步研究

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

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。

In this study, the polarization of fast shear waves and time delay of low shear - wave beneath the 21 sta- tions in this area were computed using shear - wave Splitting Analysis Method （SAM） based on the seismic da- ta 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 characteris- tics 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 anisotro- py. However, the principle polarization direction, which is near NE direction, is obvious in Qilian Mountains - Liupan Mountains seismic belt.