一种通过共轭地震确定地壳的内摩擦特性的方法

A method of determination of the internal friction characteristics within the Earth′s crust through conjugate earthquakes

应用国内外24个具有“X”形或“L”形(不完整的“X”形)共轭破裂特征的地震资料,以及云南鲁甸、盈江两次共轭破裂地震的详细重定位数据,运用库仑破坏准则揭示的脆性破裂的共轭破裂角与介质的内摩擦系数之间的关系,测定与计算了地震共轭角与地壳的内摩擦系数,探讨了库仑破坏准则与安德逊破裂理论应用于宏观尺度破裂即天然地震问题.结果表明,在国际、国内不同地区不同年代的多次共轭破裂地震中,共轭角与内摩擦系数的优势分布分别为65°~75°与0.27~0.47.在同一地区或相近地区发生的地震,其共轭角与内摩擦系数在数值上也相近.库仑破坏准则与破裂的安德逊理论,不但适用于实验室的小样本岩石破裂实验结果,而且适用于宏观尺度破裂即天然地震.通过共轭角的测定,可以确定地壳的内摩擦系数,是一种增进对地壳的内摩擦特性的认识的简易、直接的方法.

The authors collected 24 seismic data in Chinese mainland and abroad with“X”-shaped or“L”-shaped(incomplete“X”-shaped)conjugate rupture characteristics,as well as detailed relocation data of two conjugate rupture earthquakes both in Ludian and Yingjiang,Yunnan Province in China.Using the Coulomb failure criterion to reveal the relationship between the conjugate rupture angle of brittle fracture and the internal friction coefficient of the medium,the seismic conjugate angle and the internal friction coefficient of the Earth′s crust were measured and calculated.The Coulomb failure criterion and Anderson′s theory of fracture are applied to the macro-scale rupture,that is,the problem of spontaneous earthquakes.The research in this paper shows that the dominant distributions of conjugate angle and internal friction coefficient in multiple conjugate rupture earthquakes in various regions and time periods are 65°~75°and 0.27~0.47,respectively.For earthquakes occurring in the same or adjacent areas,the conjugate angle and internal friction coefficient are also similar in value.The Coulomb failure criterion and Anderson′s theory of fracture are not only applicable to the experimental results of small samples of rock fractures in the laboratory,but also applicable to macro-scale fractures,that is,spontaneous earthquakes.Through the measurement of the conjugate angle,the internal friction coefficient of the Earth′s crust can be determined,which is a simple and direct method,and is helpful to improve our understanding of the friction characteristics of the Earth′s crust.