| 小江断裂带北段地壳浅层P波速度各向 异性观测的原理与数值试验 |
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| 引用本文： | 马起杨,许力生,严川,李春来,许康生.小江断裂带北段地壳浅层P波速度各向 异性观测的原理与数值试验[J].地震学报,2016,38(1):15-42. |
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| 作者姓名： | 马起杨 许力生 严川 李春来 许康生 |
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| 作者单位： | 1.中国北京 100081 中国地震局地球物理研究所; |
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| 基金项目： | 国家自然基金41474046中国地震局地球物理研究所基本业务费专项DQJB14B01 |
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| 摘 要： | 以二维情形下观测速度场为各向同性场和各向异性场的叠加为前提， 提出了一种利用走时残差估算地震波速度各向异性的方法， 即剩余慢度矢量法. 利用小江断裂带北段巧家流动地震台阵24个台站记录的3181次地震事件的P波走时残差， 采用剩余慢度矢量法计算了各观测台站周围水平方向上尺度为0.5°×0.5°, 震源深度为0—5 km的剩余慢度矢量， 由此得到了P波快波和慢波方向. 计算结果表明， 大部分观测台站周围的P波速度方向性较为一致， 快波方向为ESE向， 慢波方向为NNE向. 快波方向与小江断裂带北段应力场P轴方向较为一致， 而慢波方向与应力场T轴方向一致， 表明应力的长期作用可能是导致P波速度各向异性的重要原因.
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| 关 键 词： | 各向异性 P波速度 走时残差 小江断裂带北段 |
| 收稿时间： | 2015-06-17 |
Observation of P-wave velocity anisotropy of the shallow crust in the northern Xiaojiang fault zone:Principle and numerical tests |
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| Affiliation: | 1.Institute of Geophysics, China Earthquake Administration, Beijing 100081, China2.Earthquake Administration of Gansu Province, Lanzhou 730000, China |
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| Abstract: | This paper proposes a new technique， residual slowness vector technique (RST)， for estimating anisotropy of the seismic velocity using the resi-duals of traveling times assuming that 2-D observed velocity field is taken as the superposition of anisotropic field and isotropic one. And then the technique is applied to P traveling time residuals of 3181 events recorded by 24 stations of the Qiaojia Array， a mobile array of seismic broadband stations installed across the northern Xiaojiang fault zone. The residual slowness vectors are calculated within a scale of 0.5°×0.5° in the horizontal direction and 0—5 km in the vertical direction around the observation stations. Finally the polarization directions of the fast P-velocity and slow P-velocity are obtained at all the stations by using the RST. The results show that the directions of the P-velocity at most of the stations are in good agreement. The fast-P directions point to ESE， which nearly agrees with the P axis direction of stress field in northern Xiaojiang fault zone， while the slow-P directions point to NNE， which nearly agrees with the T axis direction， implying that long period of stress action might be one of the important factors causing the P wave velocity anisotropy in this region. |
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