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本文分析了魏格纳等求得的重力位球谐系数,得出n≤11阶系数与大尺度地幔对流相关,而12≤n≤25阶系数反映小尺度地幔对流;计算了小尺度地幔对流引起的华北地区壳下应力场,该应力场具有挤压性质,挤压中心在山西临汾—洪洞一带(111.5°E;36°N),应力大小为0.2—0.75×10~8达因·厘米~(-2),整个应力场具有规则的中心对称特征;壳下应力场的几何特征与震源机制解的结果、大震裂缝走向与错动方式、地震的空间分布等均彼此具有良好的一致性,对唐山与海城地震,这种一致性尤为明显。看来,似乎小尺度地幔对流及其造成的壳下应力场对包括目前这次强震高潮在内的华北地区地震的孕震过程起着控制作用。
In this paper, the harmonic coefficients of gravitational potentials obtained by Wigner et al are analyzed. It is concluded that the n≤11 order coefficient is related to large-scale mantle convection while the 12≤n≤25 order coefficient reflects small-scale mantle convection. The small-scale mantle convection , The crustal stress field in North China caused by crustal stress is squeezed. The extrusion center is located in the Linfen-Hongdong area (111.5 ° E; 36 ° N) in Shanxi Province and the stress is 0.2-0.75 × 10-8 dyn Cm -2, the whole stress field has a regular center-symmetric characteristic. The geometric characteristics of the stress field under the shell and the solution of the source mechanism, the strike and dislocation modes of the major earthquakes and the spatial distribution of the earthquakes all have good Consistency is particularly evident for Tangshan and Haicheng earthquakes. It appears that small-scale convective currents in the mantle and the resulting sub-shell stress fields play a controlling role in the seismogenic process of the North China earthquake, including the current strong earthquake orgasm.