A possible electro-magnetic emission (EME) associated with earthquakes are presented in the paper throughanalysis of the anomaly EME in ultra-low frequency range (ULF) observed at some sites before two earthquakesnear...A possible electro-magnetic emission (EME) associated with earthquakes are presented in the paper throughanalysis of the anomaly EME in ultra-low frequency range (ULF) observed at some sites before two earthquakesnear Beijing and the comparison with similar signals observed prior to the 1988 Armenia and 1989 Loma Prietaearthquakes. The anomaly features are as follows: ①the anomalous disturbances occur discontinuously severaldays before earthquakes and signal frequencies are higher remarkably than geomagnetic pulsation and magneticdisturbances during magnetic storms in ULF band and at least not lower than 1 Hz; ②similar signals are ohserved by similar observation systems at same site for the same earthquake ; ③the anomaly occurrence times andfrequencies at sites near the epicenter are earlier and higher respectively than that at farther sites; ④the signalenergy distribution in different frequency ranges may not be the same and the signal magnitudes may be relatedto earthquake magnitudes and greater earthquake may emit stronger EME signals; ⑤there may be a seismicmagnitude threshold for observable ULF EME anomalies and if smaller earthquakes possess of EME signals also,they may not be observed by the present observation system.展开更多
文摘A possible electro-magnetic emission (EME) associated with earthquakes are presented in the paper throughanalysis of the anomaly EME in ultra-low frequency range (ULF) observed at some sites before two earthquakesnear Beijing and the comparison with similar signals observed prior to the 1988 Armenia and 1989 Loma Prietaearthquakes. The anomaly features are as follows: ①the anomalous disturbances occur discontinuously severaldays before earthquakes and signal frequencies are higher remarkably than geomagnetic pulsation and magneticdisturbances during magnetic storms in ULF band and at least not lower than 1 Hz; ②similar signals are ohserved by similar observation systems at same site for the same earthquake ; ③the anomaly occurrence times andfrequencies at sites near the epicenter are earlier and higher respectively than that at farther sites; ④the signalenergy distribution in different frequency ranges may not be the same and the signal magnitudes may be relatedto earthquake magnitudes and greater earthquake may emit stronger EME signals; ⑤there may be a seismicmagnitude threshold for observable ULF EME anomalies and if smaller earthquakes possess of EME signals also,they may not be observed by the present observation system.
