迭部5.9级地震爆破地震波动力学特性的变化

VARIATIONS OF THE DYNAMIC CHARACTERISTICSOF SEISMIC WAVES GENERATED BYINDUSTRIAL EXPLOSIONS BOTH BEFORE ANDAFTER THE Ms=5.9 DIEBU,GANSU EARTHQUAKE

本文利用遥测传输台网可见记录和磁带记录对厂坝炮爆破进行地震波动力学特性分析,发现各次爆破记录有一致性。对失真信号进行滤波处理,经凝聚函数分析证明了爆源的一致性。对1987年1月8日迭部Ms=5.9地震的分析,表明由于介质状态的改变,记录到的地震波优势频率向高频方向移动。在近震中有关台站上,地震波位移谱出现多峰与能量分散现象,拐角频率也向高频方向移动,振幅比呈现低—高—发震的形态。在地震前二十几天,主频处地震波衰减小,而震后明显变大。上述特征可能与该地震孕育过程中应力水平和介质状态变化有关。

Visual and magnetic tape recordings of seismic waves generated by Changba industrial blasts are obtained on Lanzhou teleseismic network. Analysis of the dynamic features of such blast-induced seismic wave records shows that various blasts present similarities. The distorted waves are filtered, and the similarity of the source functions is proved through analysing the coherence function. The dynamic characteristics of the seismic waves during the preparation process of the Ms = 5.9 Diebu, Gansu earthquake is found to be the following: a) The dominant and corner frequencies of the seismic waves move to higher values; b) The displacement spectra of the seismic waves present multi-peak and energy dispersion features; c) The amplitude ratio shows the pattern of low value-higher value-earthquake occurrence and d) About 20-plus days before the Diebu earthquake, the seismic wave amplitude near the dominant frequency show decreased attenuation, whereas they again present evident increases after the shock. The characteristies mentioned above might be associated with the stress level and the changes in the media conditions during the earthquake-preparation process.