Preliminary Study Of Extract Earthquake-related Information In Ionospheric From Satellite Data

Recent years, accompanying with the swift development of the internatioanlseimo electromagnetic satellites, fingding ionospheric precursors ofearthquakes from satellite data is a hot method.This paper is a part of the project of China EarthquakeAdministration on the data process and applicated research of china seimoelectromagnetic experimental satellite. The main task is to do some casestudies by using the data and tools of the satellite DEMETER.We reviewd some case studies about this aspect and had a sum-up thatthe ionospheric precursors of earthquakes usually appearnearly over the epicenterseveraldays before the earthquakes. Then we propose our case study as thesesteps: selection of the earthquakes-selection of the orbits-visualising and finding the precursors.We have done as followings using the data of DEMETER: we analysed 6strong earthquakes happened since July of 2004 with magnitude more than7 and Pu'er earthquake occurred in June 3rd 2007. As for the former study,the interval of each study is 9 days before the earthquake and the dayof the earthquak, the least distance between the satellite and theepicenter is less than 1300km and the orbits whose geomagnetic activityis strong are eliminated. After visualized analysis, some unusualobservation records are founded: some might relate to the earthquakeswhereas others may not be related to the event. For the Pu'er earthquakecase, we did the same research,but the space range is extended (leastdistance between the satellite and the epicenter is less than 2000km).Among the 284 orbits of DEMETER during the period, 29 with the tracepassing through the region within 2000 km apart from the epicenter, hasbeen selected to be studied. 7 anomalous events showing synchronousperturbations on the variations of the spectrogram of the electric filedand the variations of the density and temperature of the ions and electron,in contrast with the variations in its surrounding area, were found onthe dataset of the 7 orbits among the 29 ones. All of the 7 events havelow magnetic intensity, and 5 events were appearing in the space abovethe range of the studied area, the 5 events are thought to might beassociated with Pu'er earthquake.