2000年7～9月强地震的前兆次声波测量研究

Measurements and Study of the Precursory Infrasonic Waves of Strong Earthquakes from July to September,2000

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 0年 7～ 9月强地震的前兆次声波P -t曲线及波速波向图 ,经过快速傅立叶变换得到其三维动态频谱。频谱分析结果表明 :(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)到逐渐加强 (4 0～ 80Pa)或更大 ;周期先分散在 2～ 19分钟或 2 0～ 6 5分钟 ,最后连成一片 (2～ 6 5分钟 ) ;波形明显不同于流星雨次声、大风次声和雷雨次声 ;(2 )强震前兆次声三维动态频谱的最大振幅不仅受震级大小影响 ,而且与震源距离及深度都有关 ;(3)初步解释了强震前兆次声的产生机理和传播机制 ;(4 )若两地的三点阵波向相交 ,可预测震中位置。故地震前兆次声波的测量研究 。

A new method about measurement of the precursory infrasonic waves of strong earthquake is introduced.A tripartite array in Changping,Beijing was arranged.The infrasonic signals(P-t curve,velocity and direction of wave) stimulated by strong earthquakes from July to Sept,2000 were observed.With fast Fourier transformation,the three-dimensional dynamic frequency spectra were obtained.The results of the spectrum analysis are as follows:(1)10 days or so before occurrence of strong earthquakes,the precursory infrasound of earthquakes with strong amplitude and measurable direction can often be observed.The spectrum characteristics are the amplitudes of precursory infrasound vary from weak(10-20 Pa)to strong(40-80 Pa)or even stronger;their periods are in 2～19 min and 20～65 min respectively at first,and then became 2～65min.Their waveforms are distinctly different from that of meteror shower and strong wind.(2)The maximal amplitude of the precursory infrasound measured is related to not only the magnitude of earthquake,but also the distance and depth of epicenter and other factors.(3)The generating and propagating mechanism of the precursory infrasound of earthquakes are preliminarily explained.(4)If the directions of two remote tripartite arrays intersect,the location of epicenter will be obtained.So the measurements of the precursory infrasound could become a new and more effective method of impending prediction of strong earthquake.