京、津、唐、张地区地震应力场的方向特征

ON THE CHARACTERISTIC OF DIRECTION OF THE EARTHQUAKE STRESS FIELD AROUND THE BEIJING AERA

  • 摘要: 根据1960年至1977年京、津、唐、张地区地震 P 波初动方向资料求出平均节面解, 给出判别结果可信度的曲线.推断本区构造应力场最大主压应力轴方向为北东65°—75°, 最小主压应力轴方向为北西15°—25°, 中等主应力轴基本直立, 应力场方向显现出均匀性和稳定性.估计地壳岩石的断层角不小于27°.推断引起本区地震的原因是受水平附加张力的作用.未发现唐山大震前平均节面解的显著改变.

     

    Abstract: The composite nodal-plane solutions of the earthquakes occurred in the area around Beijing during 1960 to 1977 are obtained on the basis of P wave onset data and also the confidence curves of the results. The directions of the maximum and minimum principal stresses are given as NE 65°—75° and NW 15°—25° respectively, whereas that of intermediate stress is nearly vertical. They appear to be uniform and stable in the entire area. The fault angle of the crustal rock is estimated not less then 27°. It is inferred that the earthquakes in the area are caused probably by the action of additional horizontal tension. No significant variation of the composite nodal-plane solutions was found before the great Tangshan earthquake.

     

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