Abstract:The statistical method of power spectral analysis has been used to analyze three indexes of (1897-1977)global seismicity:annual seismic energy release(ΣE), annual number of large earthquakes(ΣN)and annual mean of large earthquake magnitude(M). Then, the finite impulse response(FIR) method is applied to construct the desired filter (F1, F2, F3, F4, F5, F6).
The power spectrum of ΣE and ΣN represents five peaks:8, 6.7, 4.4, 3.6, and 2.0years(Fig. 1), their cross-spectra and coherence coefficients are shown in Fig.2.The variation of ΣE after filtering may approximately be the inverse propertion to the long-term changes of sun-spot activities. The power spectrum of 6.7, 3.6, and 2.9 years of ΣN and ΣE is very similar to those of earth rotation(6.9, 3.7, and 2.9 years). In brief, it is suggested that the general tendency of global seismicity during the 1897-1977 period may be closely related to sun-spot activities and the earth rotation.
