摘要
The infrasound monitors installed in the Three Gorges Reservoir Area by the Three Gorges Research Center for Geo-hazard of China University of Geosciences(Wuhan)had received abnormal signals before the onset of the Lushan earthquake(MS7.0,April 20,2013)and Yushu earthquake(MS5.2,June 26,2011).We analyzed the abnormal signals received by different stations using both Matlab filtration and wavelet analysis.The frequency of the precursory infrasonic signals predating the Lushan earthquake is mainly(0-4)×10-3Hz,and that of the Yushu earthquake is mainly(0-5)×10-3 Hz.The amplitude of the precursory infrasonic signal increases with the earthquake magnitude.After we analyzed the time difference of the abnormal signals received by Yesanguan and Zigui stations and the distance between the epicenter and the stations,we calculated that the velocity of the precursory ultra-low frequency infrasonic wave of the Yushu earthquake is 6.4m/s.To investigate the possibility of short-term and impending earthquake predictions,we developed a monitoring array,a big triangle array enclosing a small triangle array,to detect the location of the epicenter for the further researches.