Abstract: The analysis of hypocenter parameters by the tectonophysical method from data of earthquake cases shows that the stress drop,Δτ_sei is proportional to the slide velocity along a fault,V_sei,and the ratio (Ω=V_sei/Δτ_sei) is affected by the acting direction of principal stress,expressed by the slide angle θ. The frequency distribution of ratio Ω for a large amount of earthquake cases approximates to the Gaussian distribution with a mean value of Ω equal to about 0.092,which corresponds to the dominant sliding angle of about 60?. The proportional relationship between V_sei and Δτ_sei proves further the reasonableness of selecting stress drop to be an index of the sudden-instability criterion for earthquakes. In addition,the dependence of Ω on θ provides a new possible approach to estimating the direction of the principal stress.

Key words: Stress drop, Slide velocity, Direction of principal stress, Sudden-instability criterion

摘要： 震源参数的构造物理方法分析结果和实际震例资料表明,断层错动速度V_sei与应力降Δτ_sei成正比关系,而二者的比值Ω(=V_sei/Δτ_sei)受主应力作用方向(以错动角θ表示)的影响。对于大量震例来说,比值Ω的频数分布近似于正态分布,其平均值约为0.092,相当于震源的优势错动角60—61°。V_sei与Δτ_sei之间的正比关系进一步证明选用应力降作为震源突发失稳判别指标的合理性。Ω对θ的依存关系,则有可能为估计主应力方向提供一条新的途径。

关键词: 应力降, 错动速度, 主应力方向, 突发失稳判据