Periodic Characteristics of Strain Energy of Global M_S≥7.0 Seismic Activity Based on Welch Spectral Analysis

We extracted the global M_S ≥7.0 seismic activity period from 1700 to 2019 by using the Welch average method atlas. The results show that the earthquake period of M_S7.0-7.9 earthquake is about 8 a、10 a、51 a、11 a、17 a、12 a、19 a、39 a. The earthquake period of M_S ≥8.0 earthquake is about 10 a、46 a、22 a、8 a、20 a. For comparison with the solar cycle, we extracted the sunspot cycle from 1749 to 2019 by using the Fourier multi-cycle method. The significantly highest period is about 10-11 a (average 10.9 a), followed by about 90 a, 67 a, 8-9 a, 54 a. The linear regression analysis of sunspot activity cycle and M_S7.0-7.9, M_S≥8.0 earthquake cycle was carried out. The analysis results can be divided into two cases: one is 10 significant period correlation calculation, and the other is 7 significant period correlation calculation of 8-22 a. Both of them show very high correlation, and the correlation coefficient is above 0.95. However, the correlation value of the former is about 0.03 higher than that of the latter in M_S7 level earthquakes, and the correlation of M_S8 level earthquakes is basically the same. In addition, we compared the activity period extracted in this paper with the results of previous studies. The comprehensive analysis believes that the 8 a, 11 a, and 50 a periods obtained by different calculation methods and different research objects (period of strong earthquake, period of sunspot, period of geomagnetic main magnetic field) are consistent. The longer earthquake periods (approximately 80-100 a) are not significantly in strong earthquake activity.