强地震的前兆次声波研究

利用在北京昌平安装的次声三点阵,对强地震前兆次声波进行了5年的连续观测。统计分析结果表明:强震前约10天内常能测到振幅很强的前兆次声。其三维动态频谱的特点是,振幅由弱逐渐加强,达到极值后变弱;先为长周期波(10-20分),紧跟着短周期波(5-10分),然后又出现更长的周期波,最后长短周期波一起出现。提前时间与三点阵到震中距离之间没有明显的关系,与震级之间也没有明显的关系。

Precursory infrasonic waves from strong earthquakes

Our five-years measurement of the precursory infrasonic waves from strong earthquake using a tripartite array setup in Changping, Beijing shows that, 10 days or so before occurrence of a strong earthquake, a precursory infrasound with strong amplitude can often be observed. The spectrum characteristics are: (1) the amplitudes of precursory infrasound vary from weak (10~30Pa) to strong (50~80Pa) or even stronger (150-300 Pa); their periods are in at first (10~20min), then decreases to (5~10min), and finally become (5~40min). Their waveforms are distinctly different from that of meteor shower and strong wind. (2) The time of advancement has no obvious relation with the magnitude of earthquake or the distance or depth of epicenter.