| 震群活动的一种可能的触发机制 |
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| 引用本文： | 李兴才,冯树文. 震群活动的一种可能的触发机制[J]. 地震学报, 1983, 5(3): 297-303 |
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| 作者姓名： | 李兴才 冯树文 |
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| 作者单位： | 1. 国家地震局地球物理研究所2. 北京大学地球物理系 |
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| 摘 要： | 分析了1975年2月4目辽宁海城地震后的熊岳、1976年4月6日内蒙和林格尔地震后的凉城、以及1976年7月28日唐山大震后的宝坻等震群活动的时空分布特点.由位错模式计算了大地震在相应地区产生的附加应力(张应力)的大小(3——6巴),它和由这些震群中的小地震计算的应力降的大小相当.附加的张性应力相当于减小围压.根据不同应力途径的三轴压缩实验以及原地庄水诱发地震的试验结果指出,上述量级的应力变化可以在地壳浅处应力水平已经很高的地区触发地震活动.考虑到地下流体的扩散特性及其作用,初步解释了震群活动的高潮滞后大地震的观测事实,从而引出了大地震对其附近的震群活动的一种可能的触发机制.
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A POSSIBLE TRIGGERING MECHANISM FOR EARTHQUAKE SWARMS |
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| Affiliation: | 1. Institute of Geophysics, State Seismologioal Bureau;2. Department of Geophysics, Peking University |
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| Abstract: | The spatial and temporal distribution and characteristics for the following earthquake swarms occurred after large events have been analyzed. They are: Xiong Yue swarm after the Haicheng Earthquake of 1975, Liang Cheng swarm after the Helinger Earthquake of 1976 and Baodi swarm after the Tangshan Earthquake of 1976. The additional stress (tensile) of magnitudes 3-6 bars, corresponding to the magnitudes of stress drops, calculated for the small earthquakes of the swarms have been obtained by using the dislocation model. Such additional stress may be explained as caused by the decrease in confining pressure. On the basis of results of triaxial experiments on rock samples under high pressure with different courses of loading and the studies of earthquakes induced by injecting water into the rockmass in-situ, it is pointed out that additional stress of such magnitude could trigger shallow earthquakes in an area with high stress level. Considering the character and function fo fluid diffusion at depth, the observed facts that high swarm activity lags behind the major earthquake could be understood. Hence the major earthquake might be able to trigger the swarms in the surroundings. |
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