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1、AdvancesinGeosciences地球科学前沿,2015,5(4),314-322PublishedOnlineAugust2015inHans.http://www.hanspub.org/journal/aghttp://dx.doi.org/10.12677/ag.2015.54032TheBasicPrincipleandDetectorofApplyingAbnormalChangesoftheGroupDelayDifferenceofEMWavestoShort-TermandImminent
2、EarthquakeForecastYoushanWang,ShaoyangWangSchoolofEarthandSpaceSciences,UniversityofScienceandTechnologyofChina,HefeiAnhuiEmail:wyss@ustc.edu.cnthththReceived:Jul.24,2015;accepted:Aug.12,2015;published:Aug.18,2015Copyright©2015byauthorsandHansPublishersInc.Thi
3、sworkislicensedundertheCreativeCommonsAttributionInternationalLicense(CCBY).http://creativecommons.org/licenses/by/4.0/AbstractThegroupdelaydifference(timedifference)betweentwoelectromagneticsignalsatagivenfre-quency,whicharelocatedalongthesameverticallinebuta
4、tdifferentdepthsandreachtheground,dependsonlyontheelectricconductivityandthethicknessofthestrata.Itisbelievedthattheconductivityofthedeeplayerundergoesabnormalvariationsjustbeforeearthquakes.Suchconductivityvariationscanbedetectedintermsoftheabnormalchangesoft
5、hegroupdelaydif-ference,andthustheabnormalchangesofthegroupdelaydifferencemaybeusedforshort-termandimminentearthquakeprediction.Basedonthisidea,wehavedevelopedanelectricfieldde-tectorandamagneticfielddetector.Theregularalternatingsignalof50Hzistreatedasacarrie
6、rwavesoastoachieveaminiaturizationoftheelectricfieldsensor,themagneticfieldsensor,andthedetectorasawhole,andapoint-by-pointprobingaswell.Theoperationfrequenciesofthedetectoraresettobe1Hzand0.2Hz,andnaturalsignalsarereceivedonthegroundwithclear,easilyidentifiab
7、leoutputwaveforms.Thispaperintroducesthebasicprincipleofapplyinggroupdelaydifferencetomeasuretheconductivityvariationsofdeeplayer,thestructureofthegroupdelaydifferencedetector,thenaturalsignalwaveformreceivedontheground,andtherecogni-tionmethodofusefulmessage.
8、Alsothepaperdiscussedtheproblemofwhetherelectromagneticwavesinthedeeplayerwithfrequencylessthanorequalto1Hzareabletoarriveatthegroundandtobereceived.KeywordsElectromagneticWaves,Gr
