Measure and study of precursory infrasonic waves of strong earthquakes
in May 2000
Journal of low frequency noise, vibration and active control, (2001)Abstract
The infrasonic signals (the P-t curve, the direction and horizontal
velocity of the wave and the three-dimensional dynamic frequency
spectrum) stimulated by seven strong earthquakes in May 2000 were
introduced. The results over a year are as follows: (1) 10 days or
so before the occurrence of a strong earthquake, the precursory infrasound
of the earthquake with strong amplitude and measurable direction
can often be observed. 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 showers and strong winds, (2) The maximal amplitude of
the precursory infrasound measured is related not only to the magnitude
of earthquake, but also to the distance and the depth of the epicentre
and some other factors. (3) The generating and propagating mechanism
of the precursory infrasound of the earthquake was preliminarily
explained. (4) If the directions of two tripartite arrays intersect,
the location of the epicentre can be predicted. Therefore measurements
of precursory infrasound could become a new and more effective method
of the imminent prediction of strong earthquakes.