【摘要】 介绍强地震前兆观测的一种新方法—次声波法 .在北京昌平安装次声三点阵 ,并测量到2 0 0 1年 2～ 4月强地震的前兆次声波P t曲线、波向和水平波速图及其三维动态频谱 .连续一年多的测量结果表明 :(1)强震前约 10天内常能测到振幅很强、方向可测的地震前兆次声 .其三维动态频谱的特点是 :振幅由弱 (10～ 2 0Pa)逐渐加强到 (40～ 80Pa)或更大 ;最后的周期范围很宽 (2～ 6 5分 ) ;波形明显不同于流星雨次声、大风次声和雷次声 .(2 )该三维动态频谱的最大振幅不仅受震级大小影响 ,而且与震源距离、深度及其它因素都有关 .(3)初步解释了强震前兆次声的产生机理和传播机制 .(4)若两个相距足够远的三点阵所测波向相交 ,可预测震中位置 .故进一步测量研究地震前兆次声波 ,有可能发展成为临震预报中一种较有效的新方法更多还原

【Abstract】 A new method about measurement of the precursory infrasonic waves of strong earthquake was introduced. A tripartite array was arranged in Changping, Beijing. The infrasonic signals (the P t curve, the direction and horizontal projection of downward velocity of the wave) stimulated by strong earthquakes during February April 2001 were observed. With fast Fourier transformation, the three dimensional dynamic frequency spectra were obtained. The results over a year are as follows∶ (1) 10 days or so before the occurrence of strong earthquake, the precursory infrasound of the earthquake with strong amplitude and measurable direction can often be measured. The characteristics of the spectrum are∶ the amplitudes of precursory infrasound increase from weak (10～20Pa) to strong (40～80Pa) or even stronger; the final periods become very wide (2～65min); their waveforms are distinctly different from those of meteor shower, strong wind and thunder. (2) The maximal amplitude of the spectrum of the precursory infrasound measured is related not only to the magnitude of earthquake, but also to the distance and the depth of the epicenter as well as some other factors. (3) The generating mechanism of the precursory infrasound of earthquake is that the long period deformational waves produced by pre slips before stick slips or crack propagation before rupture transmit to the atmosphere. The propagation of the precursory infrasound is because its attenuation is extremely small. Besides, sound waveguide of lower channel in the atmospheric layer plays an active role. (4) If the directions of two remote tripartite arrays intersect, the location of the epicenter can be predicted. Therefore the measure of the precursory infrasound could become a new and more effective method of the imminent prediction of strong earthquake.更多还原