四川地震辐射能量和视应力的研究

Research on the radiated energy and apparent strain of the earthquakes in Sichuan province

利用成都数字地震台网的波形记录资料,研究了四川地区地震辐射能量Es、σapp视应力等震源参数及相互关系.对时域波形数字记录首先进行数据处理,包括带通滤波,快速富氏变换,扣除仪器幅频特性;经反变换,回到时间域,给出数字波形时间序列,选取所有方向的整个p波和s波段数据;二次变换到频率域内计算速度和地动位移的功率谱积分,进而求得各台站记录的地震波辐射能量和视应力等震源参数.研究了2000年5月到2004年8月成都数字地震台网记录的224个3级以上地震的震源参数.四川地区地震辐射能量Es与地震矩M0,应力降Δσ与视应力σapp,视应力σapp与震级ML大体成正比.其中地震视应力σapp与震级分布数据较宽,地震视应力与破裂尺度ra的关系也较分散.同时研究了四川地区近年视应力σapp的空间分布.方法是将计算的σapp值在一定空间邻域内作平均,从而绘出等值线.分析结果表明,σapp值的相对高值区分布在四川南部的川滇交界和北部的川甘交界一带.同时研究了四川地区地震视应力值的时间分布.最后对中小地震视应力σapp及其他震源谱参数的意义作了讨论.

Using the wave recorded by Chengdu digital seismic net, we studied the focus parameters of the earthquakes in Sichuan province, such as radiated energy Ea, apparent strain σapp, etc and their mutual relationships. Firstly we 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. Their magnitude is not less than 3. From the focus parameters of the the 224 earthquakes, we can know the relationships between the radiated energy Ea and the moment M0 .the dropping stress Δσ and the apparent strain σapp .the apparent strain σapp and the magnitude ML 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 indicates 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 apparent 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 discuss the significance of the apparent strain and other focus parameters of the medium-small earthquakes.