基于Welch谱分析的全球M_(S)≥7.0地震活动应变能周期特征

Periodic Characteristics of Strain Energy of Global M_(S)≥7.0 Seismic Activity Based on Welch Spectral Analysis

利用Welch平均法周期图谱对1700—2019年全球M_(S)≥7.0地震的活动周期进行提取,结果显示:M_(S)7.0~7.9地震的周期约为8 a、10 a、51 a、11 a、17 a、12 a、19 a、39 a;M_(S)≥8.0地震的周期约为10 a、46 a、22 a、8 a、20 a。为了与太阳活动周期对比,利用傅里叶去多周期方法提取1749—2019年太阳黑子周期,显著性最高的周期约为10~11 a(平均10.9 a),其次约为90 a、67 a、8~9 a、54 a。对太阳黑子活动周期与M_(S)7.0~7.9、M_(S)≥8.0地震周期进行线性回归分析,分2种情况:其一为10个显著周期相关计算,其二为8~22 a 7个显著周期相关计算,均显示具有较高的相关性,相关系数均在0.95以上,但在7级水平地震中,前者相关系数高于后者约0.03,8级水平地震相关性基本一致。将本文提取的活动周期与前人研究结果进行综合分析,认为不同计算方法、研究对象(强震周期、太阳黑子周期、地磁主磁场周期)得到的约8 a、11 a、50 a周期是一致的,更长的周期(约80~100 a)在强震活动方面显著性不强。

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_(S)7.0-7.9 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_(S)7.0-7.9,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_(S)7 level earthquakes,and the correlation of M_(S)8 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.