Designation:D6820−02(Reapproved2007)StandardGuideforUseoftheTimeDomainElectromagneticMethodforSubsurfaceInvestigation1ThisstandardisissuedunderthefixeddesignationD6820;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1PurposeandApplication—Thisguidesummarizestheequipment,fieldprocedures,andinterpretationmethodsfortheassessmentofsubsurfacematerialsandtheirporefluidsusingtheTimeDomainElectromagnetic(TDEM)method.ThismethodisalsoknownastheTransientElectromagneticMethod(TEM),andinthisguideisreferredtoastheTDEM/TEMmethod.TimeDomainandTransientrefertothemeasurementofatime-varyinginducedelectromagneticfield.1.1.1TheTDEM/TEMmethodisapplicabletoinvestiga-tionofawiderangeofsubsurfaceconditions.TDEM/TEMmethodsmeasurevariationsintheelectricalresistivity(orthereciprocal,theelectricalconductivity)ofthesubsurfacesoilorrockcausedbybothlateralandverticalvariationsinvariousphysicalpropertiesofthesoilorrock.Bymeasuringbothlateralandverticalchangesinresistivity,variationsinsubsur-faceconditionscanbedetermined.1.1.2Electromagneticmeasurementsofresistivityasde-scribedinthisguideareappliedingeologicstudies,geotech-nicalstudies,hydrologicinvestigations,andformappingsubsurfaceconditionsatwastedisposalsites(1).2Resistivitymeasurementscanbeusedtomapgeologicchangessuchaslithology,geologicalstructure,fractures,stratigraphy,anddepthtobedrock.Inaddition,measurementofresistivitycanbeappliedtohydrologicinvestigationssuchasthedepthtowatertable,depthtoaquitard,presenceofcoastalorinlandgroundwatersalinity,andforthedirectexplorationforground-water.1.1.3GeneralreferencesfortheuseofthemethodareMcNeill(2),KeareyandBrooks(3),andTelfordetal(4).1.2Limitations:1.2.1ThisguideprovidesanoverviewoftheTDEM/TEMmethod.Itdoesnotprovideoraddressthedetailsofthetheory,fieldprocedures,orinterpretationoft...
