Research On Earthquakes And Ionospheric Anomalies Detected By Ground GPS Observation Data

Now the opinions vary on mechanism of seism-ionospheric disturbances and its physical explanation. It is not clear to identify the possible relationship between earthquake and ionospheric anomalies. Based on the achievement of predecessor, this paper researches that based on the single layer ionosphere model, we have processed the observation data at some GPS observation stations and obtained total electron content(TEC)time series of the ionosphere, TEC for location of the sub-ionospheric point along observation and GPS satellite to study the epcentre region. We have studied the TEC anomalies of 27 Ms≥6.0 earthquakes which occurred in Chinese mainland during 2001-2008.Through Calculating TEC with GPS data, results show correctness and validity of this method. The main achievements of research include five aspects as follow.1)Results show that the TEC values above observation stations have negative anomalies of 13 times in 20earthquakes. TEC anomalies mainly appeared 1 day to 5 days before earthquakes; The TEC values above observation stations have positive anomalies of 3 times in 20 earthquakes. TEC anomalies mainly appeared 1 day after earthquakes,the day of earthquake occurrence; The TEC values above observation stations have no obvious anomaliese before and after earthquakes of 4 times in 20 earthquakes .2)The TEC have negative anomalies of 8 times in 13 earthquakes show the closer the station is to the epicenter, the larger the TEC anomalies becomes. The TEC values above GPS continuous observation stations 700km away from the epicenter have no obvious anomaliese before and after earthquakes, and TEC variation is within 0.5 TECU.3)Most of earthquake cases show that, TEC have no obvious anomaliese during earthquake, for location of the sub-ionospheric point along observation and GPS satellite. The result shows that the temporal-spatial characteristics of short-imminent anomalies of ionosphere and geomagnetic field are consistent.4)TEC negative anomalies mainly appeared 5 day,4 day,2 day,the day of earthquake occurrence, 5 day,2 day before earthquakes, and its probability is about 89%; TEC positive anomalies mainly appeared the day of earthquake occurrence,1 day after earthquakes.This paper results show that Characteristics of seism-ionospheric disturbances can be obtained with GPS observation data. It is possible to identify ionospheric anomalies before earthquakes from continuous GPS observation data.