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1、PUBLICATIONSJournalofGeophysicalResearch:EarthSurfaceRESEARCHARTICLEMechanicalandhydrologicpropertiesofWhillans10.1002/2016JF003863IceStreamtill:ImplicationsforbasalstrengthKeyPoints:andstick-slipfailure•Laboratorymeasurementsoftillphysicalpropertiesdocu
2、mentJ.R.Leeman1,R.D.Valdez1,R.B.Alley1,S.Anandakrishnan1,andD.M.Saffer1permeabilityandelasticproperties•Cyclicloadingduetotidesshouldlead1DepartmentofGeoscience,PennState,UniversityPark,Pennsylvania,USAtooverconsolidation,embrittlement,andstick-slipmotio
3、n•SonicvelocitymeasurementsareAbstractIcestreamstransportlargevolumesofinlandicetotheoceanandplayakeyroleinthemassconsistentwithloweffectivestressatthebaseoficestreamsbalanceoftheAntarcticicesheet.Therateandstyleoficestreambasalsliparegoverned,inpart,byt
4、heunderlyingtillwhosephysicalpropertiesarepoorlyconstrained.Toaddressthisproblem,weconductedaSupportingInformation:suiteoflaboratorymeasurementstodocumentthepermeability,stiffness,consolidationbehavior,and•SupportingInformationS1compressionalwavespeedsof
5、WhillansIceStreamtillsamples.Weinvestigatedtheeffectsofstepped172andcyclicloadingontheevolutionofthetill.Initialpermeabilitieswere3.8–4.9×10m(porositiesCorrespondenceto:28.1–31.8%),whichdecreasedto2.0×1019m2(20.4%)at10MPaeffectivestress.Pwavevelocities
6、spanfromJ.R.Leeman,2.26to3km/soverthiseffectivestressrangeandarewelldescribedbyaneffectivemediummodel.Thejleeman@psu.edulaboratorymeasurementswereusedtoparameterizea1-Dnumericalmodeltopredictthetill’sresponsetostressperturbations.Perturbationscorrespondi
7、ngtotidalperiodsproduceadrainedandstrengthenedlayerCitation:tensofcentimeterthick.Forperturbationsovertimescalesofweekstomonths,asexpectedfortillmotionoverLeeman,J.R.,R.D.Valdez,R.B.Alley,S.Anandakrishnan,andD.M.Safferbasementfeatures,thedrainedzoneisafe
8、wmetersthick.Thisstronglayercanbecomebrittleuponunloading(2016),Mechanicalandhydrologicandmayfacilitateobservedstick-slipmotion.ExtrapolationofoureffectivemediummodelsuggeststhatlowpropertiesofWhillansIceStreamtill:basalef
