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

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 degrees similar to 75 degrees and 0.27 similar to 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.