Experimental research on magnetic field variation in rock failure process and its significance for earthquake prediction

There are observable magnetic precursory anomalies in the lithosphere before the earthquake, but there is little research on the magnetic field effect law in the process of rock failure. In this paper, an experimental system for monitoring the magnetic field effect of rock failure is designed and established. The relationship between the magnetic field and the load, acoustic emission and electromagnetic radiation during the rock failure process is tested and analyzed. The mechanism of rock failure magnetic field and the significance of rock failure magnetic field effect on earthquake prediction are discussed. The results show that the rock can generate a magnetic field in the process of load failure, and there is a good correspondence between the magnetic induction intensity and the load change. In the early stage of loading, the fluctuation of magnetic induction intensity increases, and in the middle and late stage of loading, the magnetic field intensity increases significantly. When the main failure occurs, the magnetic field intensity increases rapidly and reaches the maximum value. The average correlation coefficient between the magnetic induction intensity and the cumulative acoustic emission count reaches 0. 825, which shows that the change of magnetic field can reflect the deformation and failure stage and state of rock. The generation of rock failure magnetic field is mainly related to the change of electrical property, and the change of moving charge or current generates magnetic field. The rock failure magnetic field and electromagnetic radiation belong to electromagnetic signals. The magnetic field signal is an extremely low frequency, continuous and pulsed signal, and the signal frequency is generally 0 similar to 20 Hz. Electromagnetic radiation signal is a transient and paroxysmal electromagnetic wave, and the signal frequency is generally kHz similar to MHz. Compared with electromagnetic radiation, the magnetic field precursor anomaly appears first, and the magnetic field monitoring results of rock failure are of great significance for evaluating the imminent earthquake prediction of earthquakes.