Earthquake Apparent Stress

Using the wave recorded by Chengdu and Yunnan digital seismic net, we studied the focus parameters of the earthquakes in Sichuan province, such as radiated energy Es, apparent strain σ_?pp etc and their mutual relationships. First pretreat the wave time series, including the bandpass channel filter of the wave data, FFT, getting rid of the amplitude-frequency characteristic of the viameter. Then carry out the IFFT returnning to the time domain, segmented selecting the whole data of p wave and s wave, at last carry out FFT once again to this selected data, segmented caculate the integral of the power spectral of the velocity and displacement in frequency domain, and go a step further we can get the focus parameters such as the radiated energy and the apparent strain etc.We selected 224 earthquakes recorded by Chengdu digital seismic net from 2000.5 to 2004.8, whose magnitude is not less than 3. From the focus parameters of the the 224 earthquakes, we can know the relationships between the radiated energy Es and the moment M_? the dropping stress △_σ and the apparent strain σ_?pp the apparent strain σ_?pp and the magnitude M_L. almost are direct ratio. In which the distribution data of the apparent strain and the magnitude is relative broad, the data between the apparent strain and the rupturing scale is scattering.We also stuied the spatial distribution of the apparent strain of the earthquakes in Sichuan province rencent years. By averaging the apparent strain values in definite space, we drawed out the isoline of the apparent strain. The result indicate that the relative high apparen strain area is in the boundary between the Sichuan and Yunnan province, at the south of Sichuan province. Another high apparen strain area is in the boundary between the Sichuan and Gansu province, at the northern part of Sichuan province. Meanwhile we studied the temporal distribution of the apparent strain in Sichuan province. At last we discussed the significance of the apparent strain and other focus parameters of the medium-small earthquakes.Using the same method we caculated the source parameters including the apparent stress of two earthquake sequences: one is Ludian earthquake sequence (Dec. 2003^Aug. 2004), another is Dayao and Yao' an earthquake sequence (2000²00); Discussed distribution of the apparent stress in the earthquake sequence, the result indicate that the variation of the source parameters including apparent stress in some area may be an evidence that there would occur another medium or larger earthquake at that area in the future.