简介：TheelectrondensityrecordedonboardtheDEMETERsatellitewasanalyzedtosearchforpossibleanomaliesbeforeearthquakesbothinspaceandtime.Todistinguishpre-earthquakeanomaliesfromtheotheranomaliesrelatedtogeomagneticactivity,datawerefilteredusingtheK_pindex.Theanalysisisbasedonthecomparisonofdatarecordedcloselytoearthquakesinspaceandtimeandpastdataforthesamearea.InanalyzingdataaroundthetimeandlocationofthePu'erandWenchuanearthquakes,obviousanomaliesinelectrondensitywerefoundclosetotheepicenters,andsomeremarkabledisturbancesweredetectedbeforetheearthquakesoccurred.Theresultswerefinallycomparedwiththoseofpreviousworksthatusedthesamedatabutemployeddifferentanalysismethods.Goodagreementwasfoundwhichsuggeststhattheseanomalieshaveacloserelationtotheearthquakepreparation.