用二进小波分析方法对华北地区强震活动期的研究

Study of the Seismicity of Strong Earthquakes in North China on the Basis of Wavelet-transform Analysis

利用二进小波变换对华北地区 130 0～ 1996年的强震时间序列进行了多尺度分解 ,并据此划分了不同的地震活动期。认为公元 130 0年之后 ,华北地区的强震存在两个平静期 (135 0～ 14 5 0年、 170 0～ 1780年 )和两个活跃期 (14 5 0～ 170 0年、 1780～ 1996年 )。与以往华北强震的活动期划分方案进行比较 ,本文的结果在总体规律上与以前的研究差别不大 ,但在第三、第四地震活动期中活跃期起始界限的划分上比其它方法略有提前 ,而在平静期的划分上相对较短。文中采用 32a尺度的小波分析信号进行分析 ,既考虑了较大尺度上地震的活动特征 。

The Binary wavelet transform is employed to decompose the strong-earthquake sequence which lasts from 1300 to 1996 into multi-scale signals. And the whole strong earthquake sequence is divided into different seismic periods. According to the analysis results, the strong earthquakes in north China can be classified into two quiet periods (one lasts from 1350 to 1450, another from 1700 to 1780) and two active periods (one lasts from 1450 to 1700 and another from 1780 to 1996). Compared with the previous results , the results got in this paper show a little difference in general, but the starting years of the active period in the third period and the forth period are shifted to an earlier time. So, the two quiet periods are shortened. The reason why the 32-year scale is applied in wavelet analysis in this paper is because of the fact that the characteristic of seismicity in the large scale is taken into account and a small amount of missing earthquakes can only have a little influence on the results.