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对含一组裂纹的平板模型的有限元计算表明,在断层滑动后,其附近应力场发生了较大变化,有的应力场方向几乎偏转了90°。这可能是震前P轴偏转的一种力学机制。当把裂纹间的关系类比为一组断层时,计算结果表明,断层的滑动将影响附近断层,使有的断层滑动的可能性增大,而有的断层滑动的可能性减小,即对有的断层起了“加震”作用,而对有的起了“减震”作用。由此看出,成组发生的地震间表现出“自序性”。依此自序特点对华北第三、四活动期中地震幕作了划分,结果与其它研究所划分的一致。因此,本项研究也是对地震幕物理涵义的一种探讨。
The finite element analysis of a flat plate model with a set of cracks shows that the stress field in the fault zone changes greatly after the fault slips, and some of the stress field directions are almost deflected by 90 °. This may be a mechanistic mechanism of pre-earthquake P-axis deflection. When the relationship between the cracks is analogized to a group of faults, the calculation results show that the slip of the fault will affect the nearby fault, making it more likely that some faults will slip, while others have less possibility of sliding, that is, The fault played a “plus shock” role, while some played a “shock absorption” effect. It can be seen from the above that the earthquakes occurred in groups showed “orderliness”. According to the characteristics of this sequence, the seismic curtains in the third and fourth active periods of North China are divided and the results are consistent with those of other research institutes. Therefore, this study is also a discussion on the physical meaning of seismic screen.