地震视应力的研究

【作者】 乔慧珍；

【导师】 刘斌； 程万正；

【作者基本信息】 中国科学技术大学 ， 固体地球物理， 2005， 硕士

【摘要】 利用四川和云南数字遥测地震台网的数字地震记录资料，根据布伦位错模式的波谱分析理论，在时间域内将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。在频率域内计算了2000年5月到2004年8月成都数字地震台网记录的224个3级以上地震的视应力等震源参数，分析了四川地区地震视应力在空间上的分布情况并比较各震源参数之间的关系。分析结果表明，σ_app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。四川地区地震辐射能量E_S与地震矩M₀，应力降△σ与视应力σ_app，视应力σ_app与震级M_L大体成正比。其中地震视应力与震级数据分布较宽，地震视应力σ_app与破裂尺度r_a的关系也较分散。鉴于2001年以来川滇菱形块体东边界地震活动增强，连续发生4级以上地震，形成中等地震条带，打破了多年以来的地震空区，对此带的地震视应力做了专门的研究：一是分震级区间研究了视应力值沿安宁可-则木河构造带的分布，二是研究了该构造带上中等地震的震源谱及参数差异。分析结果认为，安宁河构造带视应力相对则木河带更高，石棉-西昌段存在潜在的地震危险性。 用同样的方法，计算了鲁甸（2003年11月到2004年8月）、大姚姚安（2000年到2003年）地震序列的地震视应力，讨论了视应力等震源参数在地震序列中的时间分布情况，结果表明，某一地区的震源参数随时间的变化对于预测震源附近地区未来发生较强地震的可能性有一定的指导意义。更多还原

【Abstract】 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.更多还原