Citation
Hydrogeological properties of fault zones in a karstified carbonate aquifer (Northern Calcareous Alps, Austria)

Material Information

Title:
Hydrogeological properties of fault zones in a karstified carbonate aquifer (Northern Calcareous Alps, Austria)
Series Title:
Hydrogeology Journal
Creator:
Bauer, H.
Schröckenfuchs, T. C.
DEcker, K.
Publisher:
Springer
Publication Date:
Language:
English
Physical Description:
1 online resource

Subjects

Subjects / Keywords:
Carbonate rocks ( lcsh )
Fault zones ( lcsh )
Genre:
serial ( sobekcm )
Location:
Austria

Notes

Abstract:
This study presents a comparative, field-based hydrogeological characterization of exhumed, inactive fault zones in low-porosity Triassic dolostones and limestones of the Hochschwab massif, a carbonate unit of high economic importance supplying 60 % of the drinking water of Austria’s capital, Vienna. Cataclastic rocks and sheared, strongly cemented breccias form low-permeability (<1 mD) domains along faults. Fractured rocks with fracture densities varying by a factor of 10 and fracture porosities varying by a factor of 3, and dilation breccias with average porosities >3 % and permeabilities >1,000 mD form high-permeability domains. With respect to fault-zone architecture and rock content, which is demonstrated to be different for dolostone and limestone, four types of faults are presented. Faults with single-stranded minor fault cores, faults with single-stranded permeable fault cores, and faults with multiple-stranded fault cores are seen as conduits. Faults with single-stranded impermeable fault cores are seen as conduit-barrier systems. Karstic carbonate dissolution occurs along fault cores in limestones and, to a lesser degree, dolostones and creates superposed high-permeability conduits. On a regional scale, faults of a particular deformation event have to be viewed as forming a network of flow conduits directing recharge more or less rapidly towards the water table and the springs. Sections of impermeable fault cores only very locally have the potential to create barriers.

Record Information

Source Institution:
University of South Florida Library
Holding Location:
University of South Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
K26-05068 ( USFLDC DOI )
K26.5068 ( USFLDC handle )

USFLDC Membership

Aggregations:
Karst Information Portal

Postcard Information

Format:
Serial

Downloads

This item is only available as the following downloads:


Full Text

PAGE 1

PAPERHydrogeologicalpropertiesoffaultzonesinakarstifiedcarbonate aquifer(NorthernCalcareousAlps,Austria)H.Bauer1 &T.C.Schrckenfuchs1&K.Decker1Received:17July2015/Accepted:14February2016 # TheAuthor(s)2016.ThisarticleispublishedwithopenaccessatSpringerlink.comAbstract Thisstudypresentsacomparative,field-based hydrogeologicalcharacterizationofexhumed,inactivefault zonesinlow-porosityTriassicdolostonesandlimestonesof theHochschwabmassif,acarbonateunitofhigheconomic importancesupplying60%ofthedrinkingwaterofAustria ’ s capital,Vienna.Cataclasticrocksandsheared,strongly cementedbrecciasformlow-permeability(<1mD)domains alongfaults.Fracturedrockswithfracturedensitiesvaryingby afactorof10andfractureporositiesvaryingbyafactorof3, anddilationbrecciaswithaverageporosities>3%andpermeabilities>1,000mDformhigh-permeabilitydomains.With respecttofault-zonearchitectureandrockcontent,whichis demonstratedtobedifferentfordolostoneandlimestone,four typesoffaultsarepresented.Faultswithsingle-strandedminorfaultcores,faultswithsingle-strandedpermeablefault cores,andfaultswithmultiple-strandedfaultcoresareseen asconduits.Faultswithsingle-strandedimpermeablefault coresareseenasconduit-barriersystems.Karsticcarbonate dissolutionoccursalongfaultcoresinlimestonesand,toa lesserdegree,dolostonesandcreatessuperposedhighpermeabilityconduits.Onaregionalscale,faultsofaparticulardeformationeventhavetobeviewedasforminganetworkofflowconduitsdirectingrechargemoreorlessrapidly towardsthewatertablean dthesprings.Sectionsof impermeablefaultcoresonlyverylocallyhavethepotential tocreatebarriers. Keywords Fracturedrocks Carbonaterocks Faultzones Hydrogeologicalproperties AustriaIntroductionFaultzonesintheuppercrustproducepermeabilityheterogeneitiesthathavealargeimpactonsubsurfacefluidmigration andstoragepatterns(e.g.Agostaetal. 2010 2012 ;Caineetal. 1996 ;Faulkneretal. 2010 ;Jourdeetal. 2002 ;Mitchelland Faulkner 2012 ;ShiptonandCowie 2003 ;Shiptonetal. 2006 ; WibberleyandShimamoto 2003 ;Wibberleyetal. 2008 ).In shallowcrustaldepths,primarydeformationmechanismssuch ascataclasis,deformationbanding,brecciationandfracturing aresimilarforcrystalline,siliciclasticandcarbonaterocks,but water – rockinteractionincarbonateshasthepotentialtogeneratecompletelydifferentpermeabilitycharacteristics impactingfluidflowinaquifers(e.g.KimandSanderson 2009 ;Micarellietal. 2006 ).Thepresentstudyinvestigates thestructuralandhydrauliccharacteristicsoffaultzonesina low-porositycarbonateandtheirpotentialimpactonregional aquifersystemschargingspringsofmajorimportance. Faultsrevealawiderangeofhydraulicbehaviours,acting asconduits,barriersormixedconduit-barriersystems(Aydin 2000 ;Benseetal. 2013 forfullreviews;Caineetal. 1996 ; Faulkneretal. 2010 ).Thehydraulicbehaviouroffaultzones isgovernedbyinitialhost-rockcomposition,deformation mechanismsworkingduringfault-zoneevolution,fault-zone architectureandalterationoffaultzones(e.g.dissolution weathering).Thestandardfaultcore – damagezonemodel (Billietal. 2003 ;Caineetal. 1996;Chesteretal. 1993 ; Rawlingetal. 2001 )isstillwidelyused,althoughitwas Electronicsupplementarymaterial Theonlineversionofthisarticle (doi:10.1007/s10040-016-1388-9)containssupplementarymaterial, whichisavailabletoauthorizedusers. H.Bauer helene.bauer@univie.ac.at1DepartmentofGeodynamicsandSedimentology,Universityof Vienna,Althanstrae14,1090Vienna,Austria HydrogeolJ DOI10.1007/s10040-016-1388-9

PAGE 2

demonstratedbymanyauthorsthatitoversimplifiestheactual complexityoffaultzones(e.g.Bonsonetal. 2007 ;Childs etal. 2009 ;Faulkneretal. 2010 ).Distribution,quantity,and connectivityofdifferentfaultcomponentsstronglyinfluence permeabilityandmayvaryacrossandalongfaultstrike,and overtime(Lunnetal. 2008 ;Petracchinietal. 2012 ;Schulz andEvans 2000 ;ShiptonandCowie 2001 ).Processeslike fault-segmentlinkageandinteractionexplainsomeofthese observedcomplexfaultgeometries(e.g.Bonsonetal. 2007 ; Childsetal. 2009 ;Faulkneretal. 2010 ;KimandSanderson 2009 ;Lunnetal. 2008 ).Along-livedhistoryofprogressive deformationcanbeexpectedtoleadtoamorecomplexbuildupoffaultswithpotentiallyasymmetricpermeabilitystructures(WibberleyandShimamoto 2003 ).Fault-zonethickness showsaclearpositivecorrelationwithdisplacement(Bense etal. 2013 ;Childsetal. 2009 )butisstronglydependingonthe overalldeformationhistory(SavageandBrodsky 2011 ; Shiptonetal. 2006 andreferencescitedthere). Fault-zonehydrogeologicalpropertiesincrystallineand siliciclasticrockshavebeenstudiedextensively(e.g.Benseand Person 2006;Benseetal. 2013 forfullreviews;Faulkneretal. 2008;Lerayetal. 2013;MitchellandFaulkner 2008, 2009),since theserockshostsomeoftheworld ’ smostactivelargefaultsor importanthydrocarbonreservoirs.Incrystallinerocks,faultcores containbrecciasandgougeso fstronglyreducedpermeability alongtheprincipalslipplane,whereasfracturedrocksofthe damagezonesformpermeableconduitsorientedparalleltothe faultplane(Caineetal. 1996).Faultzonesinhigh-porosity siliciclasticrocksexhibitcataclas ticfaultcoreswithpermeabilities reducedbyupto2 – 3ordersofmagnitude(BalsamoandStorti 2010).Damage-zonepermeabilityisinfluencedandgovernedby deformation-bandnetworks,thatdisplayzonesofreducedpermeability(Rathetal. 2011 ;Stortietal. 2003),andfracturesthat enhancedamage-zonepermeability(Eichhubletal. 2009). Thereisvastliteratureoncarbonatefaultzonesthataregenerallycharacterizedbywidezonesoffracturedrock(distributed strain)andnarrowzonesoffaultrocks(zonesoflocalizedstrain; Aydin 2000;Benseetal. 2013 forfullreviews;Faulkneretal. 2010).However,thesubsurface hydrogeologicalbehaviourof faultsincarbonateaquifersisverydifficulttodetermine(e.g. Celicoetal. 20 06 )aswater/rockinteractions(dissolutional weathering)producetransient,heterogeneousandanisotropic permeabilitystructures(Agostaetal. 2007;Agosta 2008 ). Withinhigh-porositycarbonates(Antonellinietal. 2014 ; Billietal. 2003 2007 ;BilliandStorti 2004 ;Billi 2005a ; Micarellietal. 2006 ),porecollapse,graincrushing,rotationenhancedabrasionandcalciteprecipitationwithincataclastic rocksinthefaultcoreleadtoasignificantporosityreduction. Inaddition,deformationbandingandstyloliteformationreducepermeabilitywithinthedamagezone(Tondietal. 2006 ). Faultcoreswithinlow-porositycarbonatescontain cataclasticfaultrockswithlowporosityandpermeability (e.g.AgostaandKirschner 2003 ;Agostaetal. 2007 ;Agosta 2008 ;BilliandDiToro 2008 ;Billietal. 2008 ;Stortietal. 2003 ).Inthedamagezone,porosityandpermeabilityare expectedtoincreaseandarecontrolledbyconnectivityand anisotropyoffracturenetworks(Agostaetal. 2010;Billi 2005b)and/orbrecciazones(e.g.Billi 2005a;Hausegger etal. 2010 ;Tarasewiczetal. 2005 ). Thequantificationofthisfracture-relatedporosityandpermeabilityposesamajorchallenge,sinceindividualfracture characteristicssuchaslength,spacing,aperture,orientation, connectivityanddistributionmayvaryovershortdistances, depthandtime.Faultzonescontaininglargevolumesof damage-zonerockandcomparablysmallvolumesof cataclasticfault-coreactasfirst-orderpermeabilityfeatures withincarbonatereservoirs(Guerrieroetal. 2010). Statisticalanalysisoffracturesusingscanlinetechniques (e.g.Agostaetal. 2010 ;Billi2005b ;Guerrieroetal. 2010 ; Guerrieroetal. 2013 ;Kornevaetal. 2014 )showthatfracture arraysinunfaultedhost-rocksareusuallymoreisotropic, whereasfracturearrayswithinfaultdamagezonesarecharacterizedbyanisotropies.Fractureapertureandfractureconnectivityiscontrollingthepermeabilityinfracturedmedia, resultingineitherextremelychannelizedormoredistributed flowpaths(e.g.deDreuzyetal. 2002 ).Breccias,resulting fromvariousdeformationprocesseslikerockpulverization (Doretal. 2006 ;Mitchelletal. 2011 ),orhydrofracturing (Tarasewiczetal. 2005 )maycausepermeabilityenhancementsofupto4or5ordersofmagnitude(Walkeretal. 2013 ),while,ontheotherhand,cementationduetotheinteractionwithfluids(e.g.Agostaetal. 2012 ;Baqusetal. 2010 ; Micarellietal. 2006 )and/orshearingwillresultinareduction of permeability. Thisstudyfocusesonthehydrogeologicalcharacterizationofinactivefaultzoneslocatedinacarbonatekarst plateau(Hochschwabmassif)ofmajorhydrogeological importance,sincetheareasuppliesaround60%ofthe drinkingwaterforAustria ’ scapital,Vienna.Karstfeaturesandspringsintheareahavebeeninvestigatedand monitoredintenselyoverthelastyears(seeunpublished reportbyDeckerinTable 1 ;DeckerandReiter 2001; Kuschnig 2009 ;Plan 2002, 2005;PlanandDecker 2006 ;Planetal. 2009 2010 ).Surfacekarstificationfeaturesandcavesarepreferentiallyfollowingfaultzonesof acertaindeformationstage(seeunpublishedreportby DeckerinTable 1 ;PlanandDecker 2006).Thedetailed hydrogeologicalpropertiesoffaultzonesarepoorly known.Theobjectiveofthiss tudyistocharacterizeand classifyanumberoftypicalfaultzonesinthisareawith respecttoarchitecturalbuild-up,fault-coreanddamagezonethickness,typeandextentoffaultrocksandtheirhydraulicproperties,damage-zonefracturedensitiesand karstificationoffaultzones.Inamoreregionalcontext,the potentialimpactofthesefaultzonesonthebehaviourofthe karst-watersystemwillbediscussed. HydrogeolJ

PAGE 3

StudyareaGeologicalsetting TheHochschwabmassifispartoftheNorthernCalcareous Alps(NCA;seeFig. 1a ),a3 – 5kmthick,non-metamorphic, Permo-Mesozoicsedimentarysuccession(Tollmann 1976 ). TogetherwithweaklymetamorphosedPaleozoicsequences, theNCAformtheAustroalpinecovernappes(Linzeretal. 2002 ).ThestratigraphicsequenceswithintheHochschwab massif(seeFig. 1b )comprisePermiantoLateTriassicsedimentsof2,000-mtotalthickness(Mandletal. 2000;see unpublishedreportbyMandletal.inTable 1 )withWerfen Fm.,GutensteinFm.andSteinalmFm.makingupthestratigraphicbasisofthesuccession.Sandstonesandshalesofthe LowerTriassicWerfenFormationbuildthebasisofthecarbonatestrata,theWerfenshalesand/orPaleozoicshistsacting asregionalaquitards.ThecalcareousstratareflectfaciesdifferentiationsinceAnisiantimesresultinginthedevelopment ofcarbonateplatforms(dolostonesandlimestonesofthe SteinalmandWettersteinFm.inthecentralandnorthern Hochschwabmassif)andofreef,slopeandbasinallimestones (WettertsteinFm.,GrafensteigFm.,SonnschienFm., TremmelgarbenFm.;Fig. 1b ;Bryda 2001 ;seeunpublished reportbyMandletal.inTable 1 ). Fivestagesofdeformation(D1 – D5)areidentifiedinthe Hochschwabmassif(seeunpublishedreportbyDeckerin Table 1 ),themostimportantbeing(1)NW-directeddextral transpressionalstackingofnappesduringtheLate – Early CretaceoustolateEocene,(2)N-directedthrusting(EoceneOligocene)and(3)eastwardlateralextrusionofcrustal wedgesalong(E)NE-strikingsinistralstrike-slipfaultssuch astheSEMP(Salzach-EnnstalMariazell-Puchbergfault zone)duringtheMiocene(Deckeretal. 1994 ;Linzeretal. 1995 ) TheinvestigatedfaultzonesareallpartoftheSEMP,which is400kmlongandcrossesallAustroalpinetectonostratigraphicunits(Deckeretal. 1994 ;Linzeretal. 1995 2002 ;PeressonandDecker 1997 ;Ratschbacheretal. 1991 ), formingthelateralrampoftheeastwardextrusionofthe EasternAlpsinthecourseofthepost-collisionalexhumation oftheTauernwindow(Linzeretal. 2002 )(Fig. 1a ).ThecentralandeasternportionsoftheSEMParecharacterizedby brittledeformation(Frostetal. 2009 2011 )withatotaldisplacementofabout40km(Linzeretal. 2002).Inthe HochschwabmassiftheSEMPformsarestrainingbendcharacterizedbysinistraltranspressionalstrike-slipduplexesand compressionalflowerstructures(seeunpublishedreportby DeckerinTable 1 )(Fig. 1b ). Hydrogeologicalcontext ThemainHochschwabplateau,withthesummitat2, 277masl,coversaround83km2andisboundedbysteep valleys(valleyfloorsat500 – 700masl).Annualprecipitation intheplateauareaamountsto2,200mm/year.Numerous highlyproductivesprings,locatedontheNandNEslopeof theHochschwabmassif,providearound60%oftheViennese drinkingwater(Kuschnig 2009 ).Thepresentstudyfocuseson thecatchmentareaoftwoofthesesprings,theKlfferspring andthePfannbauernspring,wherelimestonesanddolostones, respectively,areexposed. TheKlfferspringisthebiggestspringintheEasternAlps withamaximumdischargeof34m3/s,measuredafterathunderstormevent.Thedischargeratiocalculatedfromdaily meansovertheyear2011givesadischargeratioof13 Table1 Unpublishedreportsassociatedwiththisstudy Author/sandaffiliation/sTitle(withEnglishtranslation)anddetails BauerFBerichtberdenimAuftragdesBundesministeriumsfrLandund ForstwirtschaftdurchgefhrtenMarkierungsversuch,Hochschwab, 1971(Reporttothefederalministryofagricultureandforestry regardingatracertestattheHochschwab,1971).Vienna,SpeleologicInstitute(1972) DeckerK UniversityofVienna, DepartmentforGeodynamicsandSedimentology Tektonik/StrukturgeologischeGrundlagen(Tectonics/structuralgeology). In:Mandletal.(ed)KarstwasserdynamikundKarstwasserschutz Hochschwab:GeologischeKarte(Karstwaterdynamicsandprotectionin theHochschwab:Geologicalmap).FolgeprojektHochschwabWest&Sd WA4A/F1998&StA028n.GeolSurvAustria,Vienna.(2000) MandlG,BrydaG,KreussO,MoserM,PavlikW. GeologicalSurveyofAustria, DepartmentSedimentaryGeology ErstellungmodernergeologischerKartenalsGrundlagefrkarsthydrogeologische SpezialuntersuchungenimHochschwabgebiet(Creatingmoderngeological mapsoftheHochschwabtotheuseinkarsthydrogeologicalinvestigations). ReporttotheVienneseWaterworks,Geol.Survey,Vienna.(2002) StadlerH,StroblE JoanneumResearch,ForschungsgesellschaftmbH, InstituteforWaterResources HydrogeologieHochschwabZusammenfassung(Hydrogeologyofthe Hochschwab:summary). JoanneumResearch,Graz,Austria(2006) HydrogeolJ

PAGE 4

(Fig. 1d ),indicativeforalowstoragecapacityoftheaquifer. TheKlfferspringemergesalongaN – Strendingstrike-slip fault,whichcutsandconnectsseveralE – Wtrendingfaultsin well-beddedintraplatformbasinallimestones (TremmelgrabenFm.)almostatthelowestpointofthekarst aquifer(Planetal. 2010 ).Infact,theKlfferspringconsistsof severalspringsranginginelevationfrom650to750masl, withthehigherspringsbeingactiveonlyduringperiodsof highdischarge.Allthesespringsarefedbythesamekarstwaterbody(seeunpublishedreportbyStadlerandStroblin Table 1 ).Basedonmass-balancecalculations,theassumed catchmentoftheKlfferspringhasanareaofaround57 – 70km2(Nachtnebeletal 2012;Planetal. 2010,see unpublishedreportbyStadlerandStroblinTable 1 ),which correspondsroughlytothemainHochschwabplateau.The meanresidencetimecalculatedfromanexponentialmodel withtritiumdatais0.8 – 1.5years(seeunpublishedreportby StadlerandStroblinTable 1 ). Theplateaushowsintensekarsti ficationwithkarstfeaturesat variousscales,includingdolines,smallpoljesandcaves.Field mappingrevealedatotalofmorethan7,000dolines(Plan 2002; PlanandDecker 2006).Poljesdevelopedontopofuplifted shalesandsandstonesoftheWerfenFm.,andmorethan600 caves,whicharetypicallyvadosecanyons,aredocumented, provingakarstwatertablebelow1,000masl(Plan 2005). Asingletracertest(unpublishedreportbyBauer,see Table 1 )usingUranininjectedinalargedolineintheNEpart oftheplateau(Fig. 1c )indicatedanE – Wdirecteddrainage patternparalleltothetopographyofthemassifandtowards thenorthernslopeoftheplateau.Thisisinaccordancewith surfacekarstfeaturesattheplateaushowingapreferredENE – WSWstrike(PlanandDecker 2006 ),followingfaultsformed bytheD3deformationstage(DeckerandReiter 2001 ). Duringtheinitialstagesoffieldwork,apreliminaryscreeningoffaultswasperformedonaregionalscale.Basedon criteriasuchaslocation,accessibilityandoutcropconditions, aselectionofcandidatesforfurtherfieldworkwas established.Arepresentativespectrumoffaultwidthsand deformationintensitiesiscoveredbytheselectedfaults.The N – S-trendingRingValleyiscutbyseveralcloselyspaced strike-slipfaults(horizontaldistancesof300 – 500m),belongingtotheD3deformationphasethatcanbetrackedvertically overseveralhundredmeters.Theoutcropsarelocatedatan elevationofaround1,000masl.Thisofferedthepossibilityto focusonfaultcharacteristicsrelativelyclosetothekarstwater tableandtheKlfferspringandtoconfirmwhetherstructural featuresintheareacreatedbytheD3faultingactaspotential conduits.Inaddition,thefaultA5intheBrunntalValleyata similarelevationhasbeenchosentoclarifywhetheramuch thickerfaultcorecouldpotentiallymakethefaultzoneactasa hydrogeologicalbarrier. SincetheHochschwabcontainssignificantvolumesof dolostones,twoD3faultslocatedindolostonesofthe catchmentofthePfannbauernspring,hadbeenaddedtothe dataset.ThePfannbauernspring,withanelevationof 793masl,islocatedontheeasternedgeoftheZeller StaritzenareaandemergesalongakarstifiedNE-strikingfault whichisexposedduringthespringtapping(Fig. 1b,c). Minimumandmaximummeandailydischargeis245and 304l/s,respectively(datafromeHyd;Fig. 1d ).Adischarge ratioof1.3calculatedfromdailymeansovertheyear2011is indicativeofahigherstoragecapacitywithinthecatchment areaandthepredominanceoffracturedoverkarstifiedrocks, whichisalsoreflectedbyhydrologicaldatathatshowalow variabilityofphysicalandchemicalparametersaswellaslow Ca/Mgratiosinthespringwater(seeunpublishedreportby StadlerandStroblinTable 1 ).Inaddition,waterfromthe Pfannbauernspringhas,with21years,thehighestmeanhydrologicresidencetimeofallspringsinthearea(eHyd 2014 ). FaultsA1andA2,(Fig. 1b,c )werechoseninordertoassess thepotentialimpactofrocktypeonfault-zonepropertiesand consequentlyontheregionalhydrogeology.MethodsTheinvestigationoffaultzonesintegratesfield-basedstructuralanalysis,fault-rockclassification,andfracture-network assessments.Thin-sectionanalysisincludingstandardtransmittedlightmicroscopy,electronmicroscopy(FEIInspectS) andEDXandporosity/permeabilitylaboratorymeasurements wereperformed.Thestandarddamagezone/faultcoreconcept isused,theformerbeinginfluencedbyfault-relatedfracturing withouttheformationofnewrocktypes,thelattercontaining newlyformedfaultrocks. Fault-rockclassification Whiletheinitialclassificationoffaultrocksduringfieldwork wasbasedonaqualitative,non-genetic,texturalscheme(e.g. Sibson 1977 1986 ),laterin-depthanalysisallowedtheFig.1a SimplifiedtectonicmapoftheEasternAlpsshowingthe NorthernCalcareaousAlpsandsomeofthemajorfaultsincludingthe SEMPfaultsystem,whichisofgreatimportancefortheareaof investigation. b GeologicalmapofHochschwabmassif(redrawnafter Bryda 2001 ).Stratigraphyincludesupto2,000-m-thicksequencesof platformcarbonatesandreef,slop eandbasinallimestones.Main plateau( 83km2, yellow-dashedboundary )containsadensefault network,dominatedby(N)NE – (S)SWorientedstrike-slipfaults. c Majorsprings(locatedontheNandEslopeoftheplateau)includethe Klfferspring(karsticlimestonedominatedcatchment, yellow-dashed boundary )andthePfannbauernspring(fractureddolostonedominated catchment, red-dashedboundary ).Atracertest(seeunpublishedreport byBauerinTable 1 )demonstratedthemajorroleofverticalENEstriking strike-slipfaultsonthedrainagepatternofHochschwabmassif. d Dischargecurves HydrogeolJ

PAGE 5

HydrogeolJ

PAGE 6

introductionofareferencetogeneticprocesses(e.g.Billi 2010 ;WoodcockandMort 2008 ). Abasicfault – rockdifferentiationofbrecciatedrock(0 – 10%matrix)andcataclasticrocks(10 – 100%matrix)was used.Cataclasticfaultrockstype1(Fig. 2a )aregrainsupportedfaultrockswithangularhost-rockfragmentsin pointcontactandcontain<20%fine-grainedmatrix.Type2 cataclasticfaultrocks(Fig. 2b )arecharacterizedby(1)higher contentsoffine-grainedmatrix(approximately>20%matrix) and(2)reducedgrainsizes. Dilationbreccias(Fig. 2c )showapersistentfragmentation ofinitiallyintacthostrock,contain0 – 10%matrixand/or cement,andlackevidenceofrelativedisplacement,shearing orrotationoffragments.Dissolution-precipitation(DP)breccias(Fig. 2d )containcm-scalehost-rockfragmentswithina pervasivenetworkofclay-rich,reddishstylolitesaccompaniedbyanetworkofcalcite-cementedveins. Fractureassessment Multiplescanlineswereusedtodetectfracturesetsandto measuretheiraveragespacing,withscanlinesperpendicular toeachfractureset.Thefractureapertureisnotincludedinthe analysissinceweatheringoffracturedrocksurfacesinhibits theirmeaningfulquantificationinthefield. Measurementsofmeanfracturespacingallowforavolumetricfracturecount.Thethree-dimensional(3D)fracture intensity( P32)istherebyquantitativelyexpressedinm2of jointsurfacesperm3ofrock(DershowitzandHerda 1992 ). P32isregardedasthebestfracture-intensitymeasureforsystemsconsistingofalargenumberoffractures. Baseduponfracturemeasurements,anempiricalclassificationschemeoffracturedrockswasestablishedthatallowed classifyinganddifferentiatingindividualcompartmentsofthe damagezones. Fourclassesoffracturedrockwereused(Fig. 2e – h )with individualclassesbeingbasedon(1)jointsetnumber,(2) averagedistanceofsub-paralleljoints,and(3)theblocksize ofjoint-delimitedblocks.Fractureclass1(FC1)referstovery littlefracturedhostrockwith P32<20m2/m3,fractureclass2 (FC2)has P32valuesrangingfrom20 – 60m2/m3,fracture class3(FC3)has P32valuesrangingfrom60 – 200m2/m3andfractureclass4(FC4)has P32values>200m2/m3.For adetailedlistof P32measurements(seeFigureS1oftheelectronicsupplementarymaterial( ESM ). Porosity/permeabilitymeasurements Porosityandpermeabilitymeasurementsweredoneon140 samplesoffaultrocksandfracturedhostrock.Astandard industryprocedure(AustrianStandards 1999 )wasusedto determinetotaleffective(matrixandfracture)porosityofsampledrocks.Samplesizewasselectedtocoverrepresentative volumesoffracturedrocks,dependingontheaveragefracture spacing(upto2,000cm3).Samplesweredriedintwosteps (48hintotal)at105Cinalaboratorytypedryingcabinet untilmasswasconstant — massofdriedsamples( md). Sampleswerethenputintoawaterquench.Thewatercolumn Fig.2 Rockclassification. a – b Cataclasitestype1( C1 )andtype2( C2 ) aredifferentiatedaccordingtograinsizeandmatrixcontent(C1<20% matrix,C2>20%matrix). c Dilationbrecciascontainhighvolumesof calcementsseparatingjigsaw-puzzledfragmentsofthehostrock. d Dissolution-precipitation( DP)brecciascontaininterconnectedclay seamsandcalcementedveins. e – h Fractureclasses1 – 4,which differentiateweaklyfracturedrock(FC1),moderatelyfracturedrock (FC2),intenselyfracturedrock(FC3)andveryintenselyfractured rock(FC4) HydrogeolJ

PAGE 7

wasinitiallychosenathalfthesampleheightsothatsaturation ofsamplescouldbeestablished.Afterwards,sampleswere completelycoveredwithwater(atleast3cmcover)fortwo times24htoensurefullsaturation.Wetsamplemasseswere weightedunderhydrostaticuplift( mh)andinair( ms). Rawdensitykg = m3 : b md rh = ms– mh 1 Totalporosity % : po ms– md = ms– mh 100 2 Theuncertaintiesofthismeasuringtechniquewereevaluatedbyrepeatedmeasurementsofselectedrocksshowing errorsarewithin0.1%oftotalporosity,whichisconsidered useful,becauseitallowsmeasuringporositiesofsampleslarge enoughtocontainarepresentativenumberoffractures.This approachisfavoredoverplugmeasurementswhicharelimitedtosamplesoffewcentimetersindiameter,wherefractures withspacingofafewcentimetersormorearenotincludedor completelyunderrepresented. N2porosityandpermeabilityofplugsizedsamples — 1.5in (3.81cm)diameter,0.72 – 3in(1.8 – 7.62cm)length — were measuredusingtheCorevalPoro700.Measurementswere doneusingthelowestconfiningpressure(13.79bar).Fault-zonearchitectureandfaultrockcontentFaultzonesindolostone Small,lowdisplacement(<10m)faultsindolostonearerepresentedby faultA1 ( localityKastenriegel ).ItisaNE – SW strikingstrike-slipfaultwithatotalwidthof8macrossthe strike(Fig. 3a ).Thefaultcontainsnumerousparallelcontinuousstrandsoftype1cataclasticrock(thicknessof0.5 – 5cm, seeFig. 3b,c )surroundedbya1-m-widezoneofveryintenselyfracturedhostrock(FC4;Fig. 3b ).Faultrocksareaccompaniedbysteeplydippingstriatedslickensidesandcloudy distributedvolumesofcementeddilationbreccias.Openvoids withindilationbrecciasindicatelocalizedhydrofracturing, andidiomorphiccrystalsshowthatcementsgrewwithinopen voids(Fig. 3d ).Evidenceforfluid-inducedfracturingcomes alsofromtensiongasheswithfibrouscalcite.Besidesfaultparalleltensiongashesanddilationbreccias,thedamagezone ischaracterizedbynetworksof interconnected,partially cementedfractures.Fractur edensitiesincreasefrom P32valuesof25m2/m3(outerdamagezone)to200m2/m3next tofaultrocks(Fig. 3b,f ).Thisincreasecomesfromareduced fracturespacingofallfracturesetsandapredominanceof fracturesorientatedsub-paralleltothemasterfault(lengths ofabout1 – 2m).Fracturearraysfurtheroutincludesteeply dipping,conjugatedN-strikingfractures,aswellassteeply dippingNE – SWfracturesandconjugatedNW-striking fractures.Fortheporositydistributionoffracturedrockand faultrocksseeFig. 3e andsection ‘ Lithologicaland hydrogeologicalcharacterizationofcarbonateprotolith,fracturedrockandfaultrock ’ ThefaultA2 ( localitySaugraben )extendsforatleast70m acrossstrikecontainingsignificantlyhighervolumesoffault rocksandmoreintenselyfracturedrocksthanfaultA1.The faultstrikes(E)NEandseparateslimestone(SE)from dolostone(NW);nomasterfaultisexposedbutispossibly locatedatthelithologicalcontactbetweenlimestoneand dolostone.Characteristicfeaturesaretheabsenceofthickcontinuousfaultrockindolostoneandastrongasymmetryofthe damagezonedependingonhost-rocklithology. Withinthedolostone,alternatingvolumesofveryintensely fracturedrock(FC4),calcite-cementeddilationbrecciasand numeroussub-parallelshearzoneswithstrandsofcataclastic faultrocksshowbroadlydistributeddeformationNofthe masterfault(Fig. 4a ).Dilationbrecciasandcataclasitesare concentratedintwo2 – 3-m-widefault-parallelvolumes(zones a1anda2inFig. 4a ).Cataclasticfaultrocksoftype1and2 withinthesevolumesareafewmmto5cmthickandbounded bysmall-scaledstriatedfaultplanes(<10mlength).Atleast6 cataclasticstrandsoccur,whicharetypicallyembeddedinFC 4dolostoneorindilationbreccias.Nosingleprincipalslip zoneisobservedinthedolostonebutdeformationisdistributed overseveralsmalllocalizedshearzones,whichpartiallylink uptoananastomosingnetwork(Fig. 4a ).Dilationbreccias (zonea2inFig. 4a)developoutofintacthostrockwhichis cutbynumerouscementedtensiongashes,whichfinallyconnecttoformfullydisintegratedcement-supportedbreccias. Largepartsofthedolostonedamagezoneareintensely fractured(FC3andFC4).FC4( P32>>200m2/m3)rocks arecompletelycohesion-less(uncemented)withafracture spacingof<2cm.Rocklithonsshownoevidencefordisplacementorshearing,fracturesareextensional,pervasively interconnectedandnotcemented(zonesa3anda4inFig. 4a ). FC3rockshave P32valuesof132and159m2/m3(Fig. 4c ). FC2rocksshowamaximumoffracturesorientedparallelto thestrikeofthefault(Fig. 4b ).Forporositydistributionof fracturedrockandfaultrocksee(Fig. 4d )andsection ‘ Lithologicalandhydrogeologicalcharacterizationofcarbonateprotolith,fracturedrockandfaultrock ’ Limestoneinthesoutherndamagezonecontainsfault-parallel,NE-strikingfaultplaneswithsub-horizontallineations andsinistralshearsense.Fractureintensityissignificantly lowerthaninthedolostone( P32value29m2/m3).Ingeneral, abouttwothirdsofthe70-m-widefaultzoneconsistofFC3 andFC4hostrock(zonesa3anda4inFig. 4a ). Faultzonesinlimestone FaultA3 ( locationRingValley )hasadistinctmasterfault withstriatedslickensidesandaverythinzoneof HydrogeolJ

PAGE 8

cataclasticfaultrockvaryingfromafewmmto20cm (Fig. 5a).Thecataclasticzonecontainscohesive,cemented type1cataclasticfaultrock,neitherbrecciasnorhighly fracturedrocksarepartofthefaultcore(Fig. 5c ).The damagezoneischaracterizedbylowfracturedensities (Fig. 5d,e )withamaximum P32valueof39m2/m3(FC2) evenadjacenttothemasterfault.Therockvolumeisdominatedbyafracturesetstrikingparalleltothemasterfaultand syntheticRiedelshears.Fracturesareafewmeterslongand spacedataveragedistancesof5cm(Fig. 5c ).Shortsubhorizontalfracturesabutagainstthesefractures.FurtherNW ofthefaultcore,Riedelshearparallelfracturesaremuchless abundantandtotalfracturedensitydropsto19m2/m3atabout 20mfromthefaultcore.Thedamagezonesouthofthemaster faultdoesnothaveafracturenetworkofsyntheticandantitheticRiedelshearsandlow P32valuesof15m2/m3(FC1). Fracturedrockandcataclasticfaultrockshaveporosities<2%.Porositiesofthefracturedrockareunderestimated, ashighfracturespacing(>10cm)withinFC2cannotbe adequatelysampled(Fig. 5c).Thefaultzoneshows karstificationalongthefaultcoreasdocumentedbyrelicts oferodedcavesinters(Fig. 5b )orientedparalleltothemaster fault.Withinthedamagezone,nokarstificationfeatureshave beenobserved. Fig.3a Low-displacement(<10m)dolostonefault(A1)containsa multiple-strandedcataclasticfaultcorewithpotentialincipientkarst featuresfoundintheupperhalfoftheoutcrop.Inthe white-dashedbox b c and d refertothelocationsoftherespectivefigureparts. b Faultzone profileshowingthedistributionoffaultrocksandvariablefracture densities. c Twostrandsofcataclasites(typeC1)aresurroundedby zonesof FC4hostrock andcementeddilationbreccias. d Dilation brecciascontainmacroscopicopenvoidsandpores. e Totaleffective porosities,rangingfrom1.5to3%averageforfracturedrocks.Faultrocktypesshowingvariableporos itiesduetodifferentdegreesof cementation. f Fracturedensities,increasingclosetocataclasticstrands anddilationbreccias(averageporositiesoffracturedrockremain<3%). R Riedelparallelfractures; MF masterfault HydrogeolJ

PAGE 9

FaultA4(locationRingValley)comprisesan 2-m-thick continuousfaultcorewithlargeE-strikingsub-verticalprincipalslipplanesandsub-horizontalsinistrallineations(Fig. 6a ). Thefaultcoreiscomposedofacontinuousstrandof cataclasticrockandbrecciatedaswellasintenselyfractured hostrock(FC4)andbreccia.FC4rockformslens-shaped compartmentsdelimitedbyfaultplanes(Fig. 6c ).The cataclasticzonereachesamaximumthicknessof40cm, Fig.4a Thehigher-displacementdolostonefaultA2hasnodefinitefault corebutseveralsub-parallel,anastomosing,cataclasticshearzoneswith ( a1 )cataclasitestype(C1)and(C2),max.10cmthick,and( a2 )two several-meters-thickfault-parallelzonesofcement-supporteddilation breccias.Additionally,dolostoneclassifiedas( a3 )FC3and( a4 )FC4, whichispervasivelyfractured(highdensitiesofuncemented,interconnectedtensilemicro-fractures),makesupaboutmorethantwo thirdsofthefaultzonevolume. b Thelimestonecontainssignificantly lowerfracturedensitieswithamaximumoffracturesorientedparallelto thefaultstrike. c Fracturedensitiesmeasuredoverthefault.Note:No fracturedensitymeasurementsofFC4rockcouldbedoneduetothehigh fracturedensities. d Totaleffectiveporosities,rangingfrom2.5to4%for fracturedrocks.Dilationbrecciasandcataclasticrocksreveal porosities>4%average.Unce mentedFC4rockscouldnotbe adequatelysampled HydrogeolJ

PAGE 10

containingacohesive,cementedtype2cataclasitemarking theprincipalslipplane.FC4hostrockincorporatedintothe faultcoreiscompletelydisintegrated(minorcemented)with lowcontentsoffine-grainedmatrix(Fig. 6b ).Adolomitic dilationbrecciawithcloudydistributionisfoundatthenorthernboundaryofthefaultcore,indicatingeitheradolomitizationalongthefaultcoreorprimaryimpuritiesinthelimestone hostrock. LimestonehostrockinthedamagezonecontainslargescalesyntheticandantitheticRiedelshears.Thesouthern damagezonecontainsamorethan20-m-widearrayofmajor syntheticRiedelshearswithconvex-upshapethatbranch fromthefaultcore(Fig. 6a ).FracturearrayscutbylargescaleRiedelshearsincludeN-strikingsubverticalfractures, sub-horizontalW-dippingfractures,andconjugatedSW-and NE-dippingfractures.Thedistributionoffracturedensities acrossthedamagezoneinaprofileperpendiculartothefault showsaslightincreaseof P32valuesfromtheouterdamage zonebyafactorof2towardsthefaultcoreinanapproximately10-m-widezone(Fig. 6f ).Ingeneral,fracturedensitiesare asymmetricallydistributedoverthedamagezone.Porosities increasefromFC2toFC4rockandarereducedwithinthe cataclasticfaultcore(seeFig. 6e andsection ‘ Lithologicaland hydrogeologicalcharacterizationofcarbonateprotolith,fracturedrockandfaultrock ’ ). Thefaultzoneiskarstifiedalongthefaultcore. Numerousrelictsofkarsticpi pesarelocatedalonganastomosing,large-scalefaultplanes(Fig. 6c ).Cataclasitesamplestakennexttoeachothershowaporosityof3.5and 6.5%,respectively.Theelevatedporosityisdueto inhomogeneouslydistributedvoidsformedbysecondary dissolutionoffine-grainedcat aclasticmatrix(seesection ‘ Lithologicalandhydrogeologicalcharacterizationofcarbonateprotolith,fracturedrockandfaultrock ’ ). Fig.5a Low-displacementlimestonefaultA3showsadistinctsubverticalmasterfaultwith b karstificationdocumentedbyrelictsofcave sinterswithincavitieslocatedalongthemasterfault. c Thefaultcoreis markedbyathindiscontinuouszoneofcm-thickcementedcataclasite type1(C1).Numeroussubparallel Riedelshears cutthehostrockwithin thedamagezone. d Thedamagezoneshowssystematicfracturesin Riedelshearorientation(anisotropicfracturepattern),butcontains e exclusivelylowfracturedensities( FC2 ). R Riedelparallelfractures; PSP principalslipplane; MF masterfault HydrogeolJ

PAGE 11

FaultA6(locationRingValley)islocatedabout800mSof faultA4andcontainsastronglykarstifiedfaultcorewitha sub-verticalE-strikingslicke nsidedsinistralmasterfault (Fig. 7a,b ).Themasterfaultisassociatedwithalaterally continuousupto15-cm-thickzoneofcohesivecataclastic faultrocks.Texturaldifferentiationwithinthecataclasticrocks showsa5-cm-thickcataclasitetype2(porosity2%)bearing theslickensidedmasterfault,embeddedina20-cm-thicktype 1cataclasticfaultrock(porosity4%).Thecataclasticrocks cutthroughaheterogeneousassemblageoffracturedandbrecciatedhostrock,separatedbynumerousconnected slickensidedfaultplanes(Fig. 7c ).Thesebrecciatedand fracturedrockassemblagesunderwentpronounceddeformationwithrespecttotheFC3hostrockandarethereforedescribedaspartofthefaultcore,similartofaultA4(Fig. 7c ). Onbothsidesofthecataclasites,anatleast4-m-thickzoneof extremelyfracturedrockislaterallycontinuous,unlikefault A4wheresimilarfracturedrocksarerestrictedtodiscontinuouslensesandisolatedrockvolumes.SmallvolumesofdilationbrecciasappearwithinFC4rocksandarecharacterized byabundantopenvoids(porosity>5%,Fig. 7h )between slightlydisplacedangularhost-rockfragments. ThedamagezoneadjacenttothefaultcorewithitsFC4 rocksandcataclasitesischaracterizedbyfracturedensitiesof Fig.6a LimestonefaultA4(80-m-widestrike),whichcontainsa2-mthick faultcore withseveralslicken-sidedfaultplanesandacontinuous cataclasticstrand(max.20-cmthickness,masterfault, MF ).Thehostrock outsidethefaultcoreiscutbymajorRiedel-shears( R )(moreabundantin southernDZ). b Thefaultcorecontainscataclasticfaultrockstype1and 2(C1,2)andintenselyfracturedandbrecciatedrockdelimitedbydistinct faultplanes. c Karstificationfeaturesboundtothefaultcore,alonginterconnectedfaultplanesencompassinglens-shaped( white-dashedarea ) compartmentsofveryintenselyfracturedhostrockandbreccias(cmto meters). d Fault-zoneprofileshowingthedistributionandgeometric relationsoffaultrocksandfracturedrocksthroughoutthefaultcoreand damagezone.Letters b and c refertothelocationsoftherespectivefigure parts. e Fracturedrockshowsanincreaseofeffectiveporositiesbya factor3.Cataclasiteshaveaverageporositiesof3%(6.5%indicating karstification). f Damage-zonefracturedensities<40m2/m3areremote fromthefaultcoreandupto76m2/m3closetothefaultcore. R Riedel parallelfractures; PSP principalslipplane HydrogeolJ

PAGE 12

about80m2/m3(FC3;Fig. 7f ).FracturearraysappearisotropicalthoughRiedel-parallelfracturesaremorepervasivein someareas.Somemajorfaultplanes,strikingparalleltothe masterfault,cuttheFC3hostrockandareaccompaniedby 10-cm-thickstrandsofFC4hostrock(Fig. 7g ).Thedamage zoneremotefromthefaultcoreisclassifiedasFC2(Fig. 7e ). Large-scalesyntheticRiedelshearsonlyoccurinanarrow zoneNofthefaultwherefracturedensitiesaresignificantly lowerthaninthedamagezonetotheS.Lowfracturedensities with P32valuesaround20m2/m3characterizetheseouter partsofthedamagezonethatextendabout70mtotheN andS.Porositiesoffracturedrock(Fig. 7h )are4%forFC 4and<2%forFC3(fordiscussionseesection ‘ Lithological andhydrogeologicalcharacterizationofcarbonateprotolith, fracturedrockandfaultrock ’ ). Thefaultcontainsrelictsofanancientkarstcavewitha diameterof7 – 8m(Fig. 7a,b ).Thecaveprofile,duetoits keyhole-shape,mayindicateinitialcaveformationunderphreaticconditionsandalaterswitchtovadoseconditions.Inthe upperpart,thecaveformedsymmetricallyaroundthemaster fault.Intheaccessiblepartofthefault,belowthecavelevel (Fig. 7b ),cataclasites,brecciasandFC4rocksareexposedin theiroriginalcontext.Onthemacroscopicscale,onlybreccias showexplicitsignsofsecondarydissolution(Fig. 7d ). FaultA5(locationGriesgasslBrunntalValley) .Though notinthecatchmentoftheKlfferspring,thisfaulthasbeen selectedbecauseitbelongstothesamedeformationphaseD3 astheotherfaults,albeitwithalargerdisplacement.Faultzonearchitectureandincreasedthicknessofthecataclastic faultcorearetheconsequenceofalargerslipdisplacement. Fig.7a – b LimestonefaultA6withstronglykarstifiedfaultcoreof severalmetersthickness.Arelictkarstcaveislocatedalongthemaster fault( MF ),wherecataclasites,brecciasandfracturedrockshavebeen completelyremoved.Belowthekarstcave,thefaultcoreisexcellently exposedwithalaterallycontinuouszoneofcataclasites(C1,2;upto severaldecimetersthick)andthereisacomplexmlangeofsecondary faultplanes(shownin c ),FC4rocksandbrecciatedrocks.Cataclasites andbrecciasarecemented. d Brecciasshowingkarstification. e – g Fracturedensitiesshowingsignificantincreasetowardsthefaultcore. Remotefromthefaultcore,thehostrockischaracterizedbyFC2( e ). f FC3hostrockclosertothefaultcore,showinguptofiveinter-connected fracturesets( FC1 – 5 ,spacing<7cm). g FC4hostrock,whichshows pervasive,interconnectedfractures,withspacing<2cm. h Porositiesare highestforfractured( FC4 )andbrecciatedrocks(about5%);cataclasites showreducedporosities. i P32valuesincreasebyafactor10fromFC2 rocktoFC4. R Riedelparallelfractures HydrogeolJ

PAGE 13

ThedominantstructuralelementsareENE-striking,sinistral strike-slipfaultplaneswith(sub)-horizontallineations. AssociatedmajorRiedelshearsstrikeNEwithsinistralreverselineationsconfirmingthatA5formsamajorflower structureatalocaltranspressionalfaultsegment(Fig. 8a ).The faultcoreismadeupofa4-m-widecataclasticfaultrockthat islaterallycontinuousthroughouttheavailableoutcrop. Grain-sizevariationswithinthecataclasticrocksareobserved butthebulkofthecataclasiteisaverycohesive,cemented type2cataclasite(porosity<2%;Fig. 8f ).Attheborderofthe cataclasticfaultcore,hostrockwasobservedthatispervasivelydissectedbystylolithicfaultplanes,andinsomeareasclayrichbrecciasaccompanyingsecondaryfaultsarebranching awayfromthemasterfault(Fig. 8e ).TheseDPbrecciasare restrictedtosomedecimetersinthicknessandhave porosities<2%. Fig.8a Large-scalelimestonestrike-slipfaultA5,showing characteristicsofcompressiveflowerstructure.Thereispossible karstificationininaccessiblepartsoffault( blackellipse). b The accessiblepartofthefault( orangebox in a )containsacontinuous4-mthickcataclasticfaultcoreandlarge-scale(>100m)branchingsecondary faultplanesthatcutand/ordelimitcompartmentsofbrecciatedand fracturedrock( FC3 FC4 ). c Fault-rockporositiesshowdecreasefrom type1cataclasites( C1 ;average3.8%)topressuresolutionbreccias( DP ; 1.6%)andfoliatedtype2cataclasites( C2 ;1%). d UncementedFC4 rockclosetothefaultcore; redmarks refertofracturesets. e – f Thefault core,showingzonedbuild-up,withclayDPbrecciasalongmargins( e ), followedbycataclasitetype1andfinallycataclasitestype2inthecenter ( f ). R Riedelparallelfractures; PSP principalslipplane; MF masterfault HydrogeolJ

PAGE 14

Thedamagezonenexttothefaultcoreischaracterizedby large-scale(>>10m)synthe ticNE-strikingslickensided Riedelshearswithsub-horizontallineations.Thehostrock betweentheRiedelshearsshowshighfracturedensities(FC 3or4;Fig. 8d ). P32valuesvarybetween100and200m2/m3. Thesevolumesofhighlyfracturedhostrockaredistributed asymmetricallyaroundthefaultcore.Theoverallthicknessof thefaultzoneisestimatedaround120m(Fig. 8b ). Unfortunately,notenoughmeasurementscouldbetakento comeupwithadetailedprofileoffracturedensitiesacross thefault. P32valueswithintheouterpartofthedamagezone areestimatedtodropsignificantlytoFC2levels;forporosity distributionseeFig. 8c ThefaultA5showsnokarstificationofthefaultcore,only amechanicalbreak-outofcataclasticfaultrocks,andnosignificantkarstificationwithinthedamagezone.Onlysubordinatedissolutionfeatures<1mareobservedalonglarge-scale secondaryfaultplanesbranchingfromthefaultcore.Potential relictsofkarstificationareobservedfromtheinaccessibleupperpartofthefault(darkellipseinFig. 8a )Lithologicalandhydrogeologicalcharacterization ofcarbonateprotolith,fracturedrockandfaultrockProtolith Lithology. LagoonalWettersteindolostoneistypicallya lightgreysucrosedolostonewithinfrequentrelictsof laminatedbindstonesanddasyclads.Dolostonehosting faultA1predominantlyconsistsofpolymodaldolomites (grainsizeof20 – 50 m)withminormicroporosityof isolatedporesandminorfractures(porediametersabout 5 – 20 m).DolostoneprotolithhostingfaultA2showsa slightlydifferent,polymodaltextureofvariabledolomite grainsizes(3 – 50 m;Fig. 9a).LagoonalWetterstein limestone(Fig. 9g)istypicallyalightgrey,finegrainedwackestonetobiospariticgrainstoneorrudstone withalgallumps,oncoids,for aminifers,bivalves,gastropodsandfrequentdasyclads,hostinglaminated bindstoneswithfenestralfabrics. Porosityandpermeability. Wettersteindolostone(D) andlimestone(L)hostrock(FC1)outsidefaultzones hasverylowporositiesof1.1%(D)and0.9%(L) (Fig. 10a,b ). Fracturedhostrock Lithology. Fractureclass1(FC1)withverylowfracturedensities(<20m2/m3)occursalonglow-displacementfaultsA1 andA3.FC2with2 – 3clearlyrecognizablefracturesetswith anaveragespacing>10cm(20 – 60m2/m3)isfoundalongall faultzones.Fracturesaresystematicand/ornon-systematic butarestillhighlyinterconnected.FC3rocksarefoundclose tofaultcoresandcontain3 – 5differentfracturesetswithaveragefracturespacingsof3 – 10cm.AnisotropieswithinFC3 rocksareobservedwherefracturesetsintheorientationof syn-andantitheticRiedelsaresystematicandtransectother moresubordinatefracturesets.Extremelycloselyfractured FC4containshighlyisotropic,systematicandinterconnected fracturearraysandisobservedclosesttofaultcoresinall faultsexceptforA3andA4. Porosityandpermeability. Comparingmeanporositiesof fracturedrocksshowsthatthedifferenceinthemeanporositybetweenFC2,3and4is2%atmaximum (Fig. 10a,b)inbothlimestoneanddolostone.Despitethis increaseofporositywithhigherfractureclass,evenFC3 andFC4rocksareeffectivelylow – porosityrocks.In addition,thereisasignificantspreadofmeasuredporositieswithintheindividualfractureclasses,withstandard deviationsvaryingfrom0.4(FC2)to1.4(FC4)whichis almostequaltothevariationofmeansofthedifferent classes. InFig. 10c ,fractureporosities(asubsetofthedatapointsin Figs. 10a,b )comingfromhandspecimensareplottedagainst P32valuescomingfromfieldobservations.Boththemodeled fractureaperture/porositycurvesandthechosenboundariesof fractureclassesareoverlain.Fourfactorscouldcontributeto theincreasingstandarddeviationofporositieswithincreasing fracturedensityandtothefactofhavingsimilarporosity measurementsfordifferentfracture-densityclassesobserved inFig. 10a,b .Firstly,beingthenaturalvariationofmatrix porosityintheprotolith,andsecondly,eachsampleoffracturedrockwillcontainnotonlyfracturesofasinglebutof varyingapertures.Fracturesofseeminglylargeapertures couldbeintroducedbythesamplingprocessduringwhich fracturesarewidenedmechanically.Thirdly,anincreasein intensityoffracturationofaprotolithwillleadtoanincrease offracturesofallaperturespresentinasample.Thus,toa higherdegree,micro-fracturesmaycontributetoporosity. Thiseffectishoweverrestrictedto<1%duetotheirsmall apertures.Andfourthly,withincreasedfracturedensity,and thushigherinitialpermeability,theprobabilityofcementation andconsequentlydestructionofporespaceincreases.Plug permeabilitiesrangefrom0.1to1.8mD(Fig. 10d ).Noplugs ofFC4dolostoneswithextremelyhighdensitiesof uncementedfracturescouldbedrilled. Dilationbreccias Lithology. Brecciasaretypicallyveryvariableintermsof volumeandspatialdistributionaroundthefaults,delimited bynon-planarboundarieswithmoreorlesscloudyspatial distribution(brecciapockets).Micro-structuralinvestigations showthatdolostonefaultscontaindilationbrecciaswith jigsawpuzzlesofangularfragmentsofhostrock(mm HydrogeolJ

PAGE 15

tocminsize)thatareseparatedbyaconnectedandpervasive networkoffracturesandveins,whicharepartiallyfilledwith eithercementsand/orminorfi ne-grainedmatrixparticles (Fig. 9b ).Dilationbrecciasareveryheterogeneouswhenit comestocementation.Theygenerallylackcrack-seal structuresbutshowevidenceformulti-stagecementgrowth. Cementsprecipitatedfromcalcitefluidssealedonlypartofthe porosity.Asaresult,highlyporousportionsarenextto completelycementedportions,evenonathin-sectionscale (Fig. 9c ). Fig.9 Dolostonemicrostructures. a Dolostoneprotolith(grainsize20 – 50 m),withminorprimaryporosity. b Dilationbreccias(faultA1): jigsaw-puzzledhost-ro ckfragmentsseparatedbycalcitecement. c Dilationbreccias:cementedmicro -fracturescutbyhighlyporous, uncementedfracture,filledwithfine-grainedhost-rockmaterial (localizedin-situpulverization). d FC4dolostone:highdensityof uncementedmicro-fractures. e Cataclasitetype2:grains<0.1mm, containinghighamountofmatrixporosity.Porespartiallysealedby calcitecements. f Cataclasitetype1:angular-shapedfragmentsand heterogeneouslydistributedma trix(connectedpores<0.2mm). Limestonemicro-structures; blue referstoporosity g Limestone protolith(grainsize<10 m):lowmatrixporosity. h Cataclasitetype2: richinfine-grainedmatrix(>50%)andlarger(>0.5mm)protolith fragments,whichhaveverylowporosity(pores<<5 m)dueto completecementationorrecrystallizationofmatrix( redboxed area detailedin i ). j Cataclasitetype2:dissolutionoffine-grainedmatrix ( blue ). k Cataclasticmatrix(connectedpores,diametersof5 – 50 m) withrelativelyhighporosities(upto6%). l Pressure-solutionbreccias: highproportionofcalcite-cementedveins,pervasivenetworkofclaybearingstylolites( brownlayers ) HydrogeolJ

PAGE 16

LimestonedilationbrecciasareobservedfromfaultsA6 andA4.Theyshowadifferentmicrostructuralbuild-upas thosefromdolostones,withlargergrains,lessmatrix,andless pronouncedgrain-sizereduction.A6dilationbrecciascontain asignificantamountofopenvoidsuptoseveralmmwide. BrecciasinA6areclosetotherelictcaveandaretherefore affectedbysecondarydissolution. Porosityandpermeability. Dolostonedilationbreccias haveanaverageporosityof3.9%,withastandarddeviation of1.5(Fig. 10b ).Thishighspreadindilationbrecciaporositiesisduetovariabledegreesofcementation.Asnodolostone dilationbrecciacouldbedrilledbecauseofthefragilenature oftheserocks,thepermeabilityoftheserockscanonlybe estimated.Permeabilityinhighlyporousdilationbrecciasis expectedtobesignificantlyenhancedwhencomparedto cataclasitesandslightlyfracturedrock.Wherecementation ispervasive(low-porositydilationbreccias),permeabilities canbeexpectedtobelow;however,nocompletelycemented dilationbrecciaswereobservedfromthinsections. LimestonedilationbrecciasofthefaultA6have1,5and 6.3%effectiveporosity(Fig. 10a ).Thesesignificantdifferencesinporositiesofsamplestakennexttoeachotherindicate thatsecondarydissolutionisaffectingdilationbreccias.This isdemonstratedbytwoplugstakenfromthesamehandspecimenhavingpermeabilitiesof551and2,214mD(Fig. 10d ). Dissolution-precipitationbreccias Lithology. Dissolutionprecipitationbreccias(DPbreccias)containlargeportionsofslickolitesproducedby densenetworksofstylolitesshowingawidespectrum oforientations.Stylolitesareheterogeneouslyspacedat distancesoffewmmuptofewcm.Theserocksadditionallycontainvariousproportionsofcalcite-cemented Fig.10 Porosity/permeabilitydata. a – b Porosityoflimestoneand dolostonefracturedrock.Thereisanincreaseof2%intheaverage porosityandpermeabilityfordilationbrecciasandcataclasites,with highstandarddeviationsduetoselectivecementation,grainandpore sizevariability,andsecondarydissolution. c Fractureporosityasa functionoffracturedensity;apertureaddsatmaximumafew%tototal porosity. d Plugpermeabilitiesarelow(<1mD)forfracturedrocks,fine grainedcataclasitesandDPbrecciasbutsignificantlyelevatedforsome cataclasitestype1(C1)anddilationbreccias HydrogeolJ

PAGE 17

veins.ThinsectionsofDPbreccias(Fig. 9l )showpervasive,multi-phasecalcite-cementedveinsathighanglesto(sub-)parallelstyloli tesproducingaclay-bearing, foliatedfaultrock.Clays(redtobrownishlayers)consistofmainlykaolinite,illiteandchloriteminerals. Porosityandpermeability. DPfaultrockshavealowaverageporosityof1.7%withastandarddeviationof0.8 (Fig. 10a ).Thelowporosityisaconsequenceofthepervasive cementationoftheserocksandthepassiveaccumulationof claymineralswithininterconnectedstylolites,althoughclay layersareaccompaniedbyparallelmicrofracturesthatcarry someporosity.PlugpermeabilityofDPbrecciasislowat 0.04mD(Fig. 10d ). Cataclasticfaultrocks Lithology. Type1cataclasticrocks(examplegiveninFig. 9f ) arefragment-supportedrocks.Fine-grainedmatrix(<20%)is distributedinhomogeneouslyorlocatedinshearband-like zonesthroughouttherock.Angularhost-rockfragmentsshow significantvariabilityinsize(cmtomm)andbadsorting. Type2cataclasites(Fig. 9e,h,j )arematrix-supported cataclasites.Theaveragesizeofhost-rockfragmentsisin generalsmallerthanintype1,andadvancedgrain-sizereduction-producedmatrixparticleswithagrainsize<5 m (Fig. 9k).Thematrixiscompletelycementedorrecrystallized(Fig. 9i ),resultinginverycohesiverocks. Porosityandpermeability. Porosityincataclasticrocksis carriedbythecataclasticmatrixandhasameanof2.9%with astandarddeviationof1.1fortype1andameanof4.1%with astandarddeviationof1.9fortype2cataclasites(limestone anddolostone),respectively.Standarddeviationswithinboth cataclasiteclassesareveryhigh,showingthatcataclasiteporositiesarenotfollowingthemacroscopiccriteriaofclassification.Severalfactorscontroltheporosityofcataclasites:(1) thesizeofmatrixgrainsandassociatedpores,(2)thedegreeof cementationorrecrystallizationand,forlimestone cataclasites,(3)secondarydissolution. Fordolostonecataclasites,similartodilationbreccias,the crucialfactoriscementation,asitpotentiallydestroysthe matrix-boundporosity.Type1andtype2cataclasites (Fig. 10b ),whetherfromlow-displacementA1faultorfrom high-displacementA2fault,containsignificantmatrixporosity,althoughthereismicroscopicevidenceforpartialcementationwithcalcite.Porediameterswithineachcataclasitemay varyfromseveral mtotensof m(Fig. 9e,f ),stillproducing effectiveporosities>4%. Limestonecataclasitestype1haveanaverageporosityof 2.8%withastandarddeviationof0.8,type2cataclasiteshave anaverageporosityof3.2%withastandarddeviationof1.8. Thinsectionsoftype2cataclasites(Fig. 9hi )showthatthe verylowporositiesresultfromahighproportionofcompletelycementedorrecrystallizedmatrix,leavingpores<<5 m insizewiththecontributionoffewisolatedfractures.Asimilarmechanismcanbeinferredforcohesivecataclasitestype1 withlowporosities.Secondarydissolutionisevidentfrom thin-sectionandhand-specimenswithcataclasticmatrixand largergrainspartiallydissolved(Fig. 9j,k ).Theconceptof karstifiedcataclasitesissupportedbythefactthatrocksamplestakennexttoeachotherandshowingalmostidentical microstructuresrevealdifferencesof3%intheirporosities. Karstificationisrestricte dtodistinctareaswithinthe cataclasitesandisnotpervasive(evenonthesamplescale). Plugpermeabilitiesoflow-porositycataclasiticrockstype 1and2are0.7mD(porosity2%),0.3mD(porosity1%)and 0.03mD(2%porosity).Thisillustratesthatporeswithinmost ofthecataclasitesaretoosmalltoresultinanysignificant permeability.AsinglesamplefromfaultA6classifiedas cataclasitetype1showsasignificantlyelevatedpermeability of228mD(porosity8%).Thisfaultrockwassamplednextto high-permeabilitydilationbreccias(2,214mD).DiscussionGenerationandhydrogeologicalsignificanceoffault-cores Faultzonesshowsignificantdifferencesandcomplexitiesin thebuild-upoftheirfaultcores.Thesedifferences,evenona cm-scale,canbeexplainedinconsiderationofthefault-zone modelafterChildsetal.( 2009 ),wherefaultsaredescribedas evolvingfromirregular,segmentedfaultsurfacesthatgetconnectedandbypassedduringincreaseofdisplacement.Faultzonecomplexityandultimatelyfault-rockthicknessarethen directlycontrolledbyfaultgeometry,statusofsegmentation/ linkage,andtotaldisplacement.Faultzonepropertiescanvary significantlywithinthesamelithologicalunit.Thisexplains whythestudiedfaultsofthesamedeformationstageshow(1) differencesinthedistributionandvolumeoffaultrockalong theirfaultcores,(2)lensesoflow-strainrocksnexttohighstrainrocksalongthefaultcore,and(3)brecciazonesthatare distributedinhomogeneouslyandshowweaklateralcontinuity.Fourtypesofdeformationprocessesareevidentfromthe faults:(1)cataclasis,(2)rockpulverization,(3)pressuresolutionand(4)fracturing. Cataclasisinitsstrictsense,withgrain-sizereductiondue tolocalizedshear,graintranslationandrollingandrounding ofgrains,isrestrictedtozonesoflocalized,higherstrainat masterfaultsandsecondaryfaultplanesinsomecasesmarked bycataclasitestype2rocks.Theseshowgrain-sizereduction bycomminution(producinghighvolumesoffine-grainedmatrix),shearfracturingandchipping,resemblingthe “ mature ” cataclasitefabricdescribedbyBilli( 2010 ).Cataclasitestype2 arealwaysverycohesiverocks,withcompletecementationor eventuallyrecrystallization(Smithetal. 2011 )ofthefinegrainedmatrix.Cataclasitestype1showonlylocalized HydrogeolJ

PAGE 18

portionsoffine-grainedmatrix,indicatingthattheserocksare formedby(intra-granular)extensionalfracturingandin-situ grain-sizereductionbycrushingofentireintermediatecomponentswithincreasingdeformation(Schrckenfuchsetal. 2015 ).Thisresultsinaheterogeneousmicro-structural build-up,whichtheauthorsthinkisalsoresponsibleforthe variableporosities. Fromplugpermeabilities(Fig. 11b )itisevidentthatfinegrainedcataclasiteshavetoberegardedasimpermeablefault rocks,asplugpermeabilitiesrangefrom0.5mDdownto 0.01mD.Onesampleshowssignificantlyelevatedpermeability(Fig. 11b )duetosecondarydissolution.Thepresentdata setunfortunatelydoesnotallowtoclarifywhethercataclasites withhigherporositieshaveelevatedpermeabilitiesandifyes, whetheraprocessdifferentfromsecondarydissolutioncould beresponsibleforthat;however,examplesfromtheliterature treatfine-grainedcataclasticrocksasimpermeable(Agosta andKirschner 2003 ;Agostaetal. 2007 ;Agosta 2008 ;Storti etal. 2003 ). Thelargestvolumesofdilationbrecciasareobservedfrom faultA2indolostone.Theformationofdilationbrecciashere isnotbyhydraulicfracturingwithincreasedfluidpressure (Tarasewiczetal. 2005 ),butbyrockpulverizationwithouta majorcontributionoffluids(Schrckenfuchsetal. 2015 ). Dilationbrecciasformedbyrockpulverizationduringdynamicearthquakerupturingarecharacterizedbysedimentationof fine-grainedparticleswithinopenvoids.Theylackcrack-seal texturesandcontainlargevolumesofuncemented,intensely fracturedrock.Asimilarmechanismhasbeenproposedfor dolostonefaultsbyFondriestetal.( 2015 ).Intermsofpermeability,dilationbrecciasinfaultA2representzonesofsignificantlyelevatedporosityandpermeabilityduringactive faulting.Secondarycementation,observedfromalldilation breccias,didnotoccurinafullysaturatedenvironment.This iswhyconnectivityandvolumeofopenvoidsandporesremainingafterthepartialcementationofdilationbrecciasis difficulttodeterminefrombothoutcropandmicro-scalebut couldexplainthehighspreadofporositieswithindilation breccias.Duetothelowcohesionandbadmechanical propertiesofthistypeofrock,noplugscouldbedrilledfor measurements.Fromhandspecimensandthinsections(see alsoSchrckenfuchsetal. 2015),theauthorsinterpret dolostonedilationbrecciasaspermeableunits. Dilationbrecciasobservedalonglimestonefaults(norock pulverization)areinterpretedtohaveformedalongdilational jogsalongthefaults(Tarasewiczetal. 2005 )orduetoconcentrationofstrainatinitialasperities(Childsetal. 2009 ), causinglocalizedhigh-densityfracturingofthehostrock (brecciation).Asdemonstratedbyplugs(Fig. 11b ),thepermeabilityofthistypeofbrecciais>1,000mD,whichcomes fromahighinitialpermeabilityaswellasfrompreferentially captureddissolutionalweathering,provenbydissolutioncavities.Ifthesetypesofbrecciasshowcementationofthepore spacecreatedbybrecciationorgrindingwithfurtherdisplacementalongthefaultzone(Fig. 11b cemented,sheareddilation breccia),thepermeabilityisstronglyreduced(0.2mD). Pressuresolutionintermsofsubordinateslickolitesisobservedfromalllimestonefaults.FaultA5provesthatpressure solutionhasthepotentialtoproducefaultrockswhichmay haveasignificantimpactonbulkpermeability.Theserocks formbydissolutionofthecarbonateprotolithandreprecipitationwithinconnectedfractures.Theycorrelatein theirmicrostructureswithrocksformedbyaseismic pressure-solutioncreep deformation(Gratier 2011;Tesei etal. 2013 ).Thesealingcapacityoftheserocksdependson thevolumeofDPbrecciasgenerated.InfaultA5,DPbreccias arerestrictedtoseveraltensofcentimeter-thickzonesassociatedwithbranchingsecondaryfaultplanes.DPbrecciasdisplaylocalizedbarriersclosetothefaultcorebutmajorportionsofthedamagezoneremotefromthefaultcorearenot affectedandremainpermeable. Themechanicsoffractureinitiationandpropagationare beyondthescopeofthiswork.Forlow-porosity(<10%) andpermeability(10Š 15m2)rocks,bulkporosityandpermeabilityareprimarilycontrolledbythefracture-networkproperties,whereindividualfractureswithamoderateaperture ( 100 – 250 m)canstillcontrollocalpermeability(Bense etal. 2013 ).Theavailabledatashowthattheincreaseof Fig.11a Densityofmacro-fractureswithdistancefromfaultcore.The highestfracturedensityisalwaysclosetothefaultcore.Zoneswithhigh fracturedensitiescanbeuptoseveralmetersthickandseemtocorrelate withthedisplacementmagnitudeoffaults. b Plugpermeabilitiesof fracturedhostrockarelowsinceplugsdonotsamplefractures. CataclasiteC 1 and 2 ,andDPbrecciashavelowpermeabilities,whereas dilationbrecciasandkarstifiedcataclasitesshowhighpermeabilities HydrogeolJ

PAGE 19

fracturedensitiestowardsthefaultcoreisneithercontinuous norhomogenous.Insomefaults,fracturedensitiesincrease significantlyatadistanceofabout10mfromthefaultcore, whereasinothers,compartmentswithlowerfracturedensities canoccurveryclosetothemasterfaultorevenindirect contactwithit(Fig. 11a ).Althoughtheauthorshavenoquantifiedhydraulicdataofhighlyfracturedrock,assamplesor plugswillonlydelivertheverylowmatrixpermeabilityofthe hostrock(Fig. 11b ),networksofmacrofracturesthatareinterconnectedanduncementedareinterpretedtobeanimportantcontributiontoflowalongfaultzones.Additionally,the authorsinterpretsystematicRiedel-andfault-parallelfractures withhighestlengthsasfeatureswithhigherpermeabilities, whichissupportedbyAgostaetal.( 2010 )andJourdeetal. ( 2002 )whoshowsignificantchannellingofflowintofocused flowpathsalongmajor,fault-parallelfractures. Fault-zoneclassificationandhydrogeologicalproperties Theinvestigatedfaultzonesarerepresentativeforfaults resultingfromtheD3deformationphaseintheHochschwab carbonatemassif.Fourcharacteristictypesoffaultzones (Fig. 12 )canbedistinguished. 1. Faultswithminorfaultcores areconduits(representedby faultA3).Thefaultcorecontainsacontinuousprincipal slipplane,butonlyverylocalized,disconnectedrather thancontinuouscompartmentsofcataclasticfaultrock. Fracture-densityincreasefromtheouterdamagezonetowardsthefaultcoreisrestricted(Fig. 11a ).Fracturesare pervasivelyconnectedanduncementedwithsystematic Riedelshear-parallelfractures.Relictkarst-cavefill provesthatsuchafaultdespiteitslowfracturedensity andminorfaultrockcontentstillhasthepotentialtoform ahigh-permeabilitystreak.Incipientkarstificationmost likelyhasbeensupportedbysignificantpermeabilityin awell-connectedfracturenetworkwithinthedamage zone.Despitethelowdisplacementandsubordinateimportanceintheregionalstructuralcontext,the hydrogeologicalfootprintofthistypeoffaultaspathway withintheaquifersystemshouldnotbeunderestimated. 2. Faultswithpersistent,single-stranded,permeablefault cores areconduits,characteristicformediumsizefaults inlimestone(faultsA4andA6).Theinternalarchitecture ofthefaultcoreiscomplex,containingasingleprincipal cataclasticzonewhichisverticallyandlaterallycontinuousbutvariableinthickness,aswellasmultiplelenticular bodiesofbrecciatedandhighlyfracturedrocksalongsecondaryanastomosingandinterconnectedfaultplanes. Cataclasticfaultrockshosttheprincipalslipplane(master fault),withstrainlocalizedwithinthinlayersofmature cataclasticrocks.Fracturedhostrockshowsmoreheterogeneitywithrespecttofracturedensityanddistribution whencomparedtofaultsoftype1.Fracturedensitiesincreasebyafactorof2fromFC2toFC3andafactorof10 fromFC2toFC4,respectively.Fracturedhostrockclose Fig.12 Thefourtypesoffault zonesthathavebeen differentiatedinthisstudy.Type 1 and 2 faultzonescanberegarded asconduitsintheaquifer,where fluidflowislocatedclosetoor withinfaultcoreswithinhighly fracturedandbrecciatedrocks. Thickandstronglycementedfault coreshavethepotentialtoform (local)barrierstoacross-fault flow(faultzonetype 3 ). However,enoughuncemented fracturevolumeremotefromthe coreisavailableforfluidflow. Faultzoneswithmultiplestrandedfaultcoresoftype 4 from dolostonescanberegardedas conduits,containingthelargest volumeofintenselyfractured, uncementedrockanddilation breccias HydrogeolJ

PAGE 20

tofaultcoresshowsasymmetrywithrespecttothemaster faultandcanbeFC2,FC3orFC4,demonstratinganonsystematicvariationoffracturedensitywithdistancefrom faultcore(Fig. 11a ).Fracturepatternsareanisotropic whereRiedelshearsandRiedel-parallelfracturesarepresent.Independentoffractureclass,fracturesformconnectednetworks.Relictsofkarstpipes(A4)andcaves(A6) adjacenttoprimaryandsecondaryfaultplanesindicate thatthefaultcoreratherthanthefractureddamagezone issubjectedtosecondarydissolution,whichisduetothe presenceofbrecciatedhostrockandahigh-densitynetworkoffaultplanes.Faultsofthistypeareconsideredto actashydrogeologicalpathways,withhighestpermeabilitycompartmentsadjacenttocataclasticzones wheremostofthebrecciatedandintenselyfracturedrocks arelocated. 3. Faultswithpersistent,single-stranded,impermeablefault coresareconduit-barriersystemsformedbylargefault displacement.TheyarerepresentedbyfaultA5.The cataclasticfaultcoreshowsastronglycementedtype2 cataclasitecontainingthemasterfault.Atthetransition fromdamagezonetotheseveralmeter-thickcataclastic faultcore,cementedandclay-bearingbrecciasarepresent. Thesearerestrictedtonarrow,sometensofcentimeters thick,zonesalongsecondaryfaultplanesbranchingfrom themasterfault.Cementationistheresultofpressuresolutionoftheprotolith,withdissolvedcalciteprecipitated withinpervasiveveinsandcracks.Theclaycomponentof brecciasderivesfromprimaryimpuritieswithinthelimestoneatthislocationorfromshalessmearedintothefault. Fracturedensitiesthroughoutthedamagezoneshowa similarheterogeneousdistributionasfaultsoftype2;however,theoveralldamagezonethicknessisatleastdoubled. Fromfieldevidence,thistypeoffaultisseenashavingthe potentialtoactasaconduit-barriersystemasorthogonal fluidflowacrossthefaultcorecouldbeinhibited.Fluid migrationisfault-parallelwithinthefracturedhostrock. Thedeformationhistoryofsuchlarge-scalefaultsmaybe verycomplex;asaconsequence,thehydrogeological characterizationshouldbedoneonacase-by-casebasis. 4. Faultswithmultiple-strandedfaultcoresindolostonesact asconduitsandarerepresentedbyfaultsA1andA2.A differentiationintoasinglefaultcoreandadamagezoneis notadequateforthistypeoffaultastheyhavemultiple branchedshearzoneshostingacomplexassemblageof cataclasticstrandsanddilationbreccias.Dilationbreccias andveryintenselyfracturedhostrockaredistributedover widepartsalongthefaultzonesandmakeuplargevolumesofrock.Principalslipplanesandcataclasticstrands shownosuchlateralcontinuitiesasobservedinthelimestonefaults,wheretheycanbetrackedoverseveralhundredmeters.Thisstructuralbuild-upclearlycontradictsa hydrogeologicalcharacterizationinthesenseofasingle faultcore/damagezonemodelbutisbetterdescribedwith amultiple-strandedfault-coremodel(Faulkneretal. 2010 ).Thelargevolumesofhighlyfractured,uncemented hostrock(upto30%)areseenashighlypermeabledomainsalongthefault.Varyingdeformationmechanisms havetobeinvokedtoexplainthedifferencesinstructural build-upandfaultcoresoflimestoneanddolostonefaults (see ‘ Generationandhydrogeologicalsignificanceof fault-cores ’ ).Ourstudyindicatesthatinadditionlithologicalcontrastsgovernfault-zonearchitectureanddeformationprocesses.Thisisinlinewithotherauthors(e.g. PeacockandSanderson 1992;Schpferetal. 2006 )who showedthatinitialfaultgeometryisalsocontrolledby mechanicalheterogeneityandindividualrheologyofthe hostrock.ThisisbestillustratedbythefaultA2,whichis locatedatthecontactoflimestoneanddolostone.The majorityofthedeformationisfocusedwithinthe dolostone,whereasthelimestoneadjacenttothefaultcontainsneitherpulverizedrocksnormultiple-stranded cataclasites.Theauthorssuggestthatprimarymicrofractureswithinthedolostoneallowfor(1)overallsignificantlyelevatedfracturedensitiesindolostonefaultscomparedtolimestonefaults,independentofdeformationprocessesormagnitudeofdisplacement,and(2)theformation ofmultiplecataclasticstrands.Onthecontrary,onlylimestonesdeformbypressure-solutioncreep.Forlimestone fault-zonetypes,thethicknessofcataclasiteanddegreeof cementationdeterminewhetherafaultactsasaconduitor barrier.Thedegreeofkarstification,whichhasbeenobservedfrequentlyinoutcropsandisabletoproducesuperposedflowconduitsofextremecapacity,will,atleastpartly,becontrolledbythefault-zonearchitectureandthe resultingpermeabilitydistribution.Indolostonefaultzones,highlypermeablecompartmentsoffracturedhost rockanddilationbrecciasareinterconnected.Cataclasite strands,representinglocalizedimpermeablefeatures,createpermeabilityanisotropiesandpotentialchannelfluid flowwithinthefracturedrock.Fromfieldevidence,it becomesobviousthat(1)laterallyandverticallyevery faultexhibits(significant)differencesintheamountof cataclasites,brecciatedrockandfracturedensities,even overfairlyshortdistances,and(2)thefaultzonesinvestigatedcoverawidespectrumofpossiblefault-zoneanatomiesrelatedtotheD3deformationstagewithinthestudy area.Fortheregionalscale,itbecomesimportanttonote thattheindividualfaultdifferencesareofminorsignificanceforthebehaviouroftheentireaquifersystem. Faultzonesonaregionalscale:flowconduitsorbarriers? Thevariabilityinthefault-zonearchitecturecapturesawide rangeofpossibleoutcomesofaparticulardeformationevent HydrogeolJ

PAGE 21

affectingdistinctlithologies.Permeabledamagezonesaswell asbothpermeableandimpermeablefaultcores,onascaleofa metertotensofmeters,canbedefined.Onthisscale,impermeableportionsofthefaultcoreforfaultzonestype1,2and4 disappearandre-appear,thefaultcoreinadditioniscross-cut bydissolutionfeaturesallowingcrossfaultflow.Thesefaults areconsideredconduitsonboththeoutcropandtheregional scale.Onthecontrary,thefaultcoreoffault-zonetype3may onanoutcropscaleactasalocalbarrierleadingtofocusingof flowwithinpermeablevolume sadjoiningthefaultcore. Regionalfieldworkindicatesthatincreasingthescale,the definitionofanimpermeablefaultcoremaybreakdownas thefaultmaybecutandoffsetbyotherfaults;thus,flow acrossthefaultmaynotbeexcluded. ThelimestonewatershedoftheHochschwabmassifischaracterizedbyintenseanddeep-reachingkarstification(Plan 2002 ).Theconceptofapermeableandinterconnectedfaultzonenetworkattheregionalscalewithonlysubordinate,locallyrestrictedfault-corebarriersissupportedbythedistributionofspringsinthewatershedwhichisthefocusofthisstudy. Springsemergeatthebaseofthecarbonatemassifwhereimpermeableunitsformthestratigraphicortectonicbaseandthe watertableintersectsthetopography.Infiltrationofwaterfrom rainorsnowmeltthroughthethickvadosezoneinlimestone happensalongpermeableportionsofthesub-verticalfault-network.Barriersinextensivefaultcoresonlylocallyfocusflow alongthefaultzone.Intenseprecipitationevents(thunderstorms,rapidsnowmeltduetowarmwinds)mayexceedthe transmissivecapacityofthefault-zonenetworkanddischarge mayoccurwherepermeablestreaksorkarstconduitsintersect thevalleyflanks;however,themajorityofpercolationstill takesplacedownwardstoaregionalwatertableandthenlaterallyfollowingthepressuredifferentialwithintheinterconnectedfaultnetworktowardsthesprings. Deptheffectonporosityandpermeabilityoffaultzones Allinvestigatedportionsofthefaultzonesarelocatedwithin thepresent-dayvadosezonebutatamaximumofafewhundredmetersfromthepresent-daywatertable.Outcropsin limestonesshowanoverburdenofseveralhundredmeters, whereasdolostoneoutcrops,ontheotherhand,arelocated atahigherelevationwithoutsignificantoverburden.Apossiblereductionoffractureapertureandthusporosityorpermeabilitydowntothewatertable,cannotbeassessed.Fracture aperturesmayshowadecreasedownwardstothephreatic zone,butfaultzonesareexpectedtoretainvolumesofelevatedpermeabilitiescomparedtothehostrock.Theremovalof rockduetoglacialerosionandtheexhumationoffaultoutcropsalongthevalleyflanksmayhaveslightlyincreasedfractureapertureandconsequentlyporosityandpermeability. Ingeneral,theoutcropsareconsideredrepresentativewith respecttotheparametersofthefault-zonenetworkinthe vadosezonerelativelyclosetothewatertable.Availabledata donotallowforaclearpictureofparametersofthefault-zone networkinthephreaticzone,whereasevidencefromoutcrops distributedovertheRingValley,ontheotherhand,indicates thatsomeoftheobservedkarstfeaturesdevelopedunderformerphreaticconditions.Thereforeitisassumedthatprocesses ofkarstificationinthepresent-dayphreaticzoneproducesimilarfeatures. Fault-rockvolumeandstoragecapacity ThehighdischargeratiooftheKlfferspringtestifiestothe overalllowstoragecapacityofthelimestonefault/karstsystem,whichisinlinewiththeresultsofthisstudy.Matrix porosityofthehostrockisnegligible,withsmallporethroats beinganadditionallimitation.Locally,beneficiallithologies and(micro-)jointsawayfromspecifiedfaultzonesmayaddto thestoragecapacityofthehostrock. Itisassumedthat,thoughconsideredtobequitelimitedon absoluteterms,asignificantpartofthestoragecapacityofthe Hochschwablimestonekarstaquiferresideswithinpores, fracturesandkarstfeaturesofaninterconnectedfault-zone network.Inordertoverifythisassumptionandtorelatethe storagecapacitytospringdischarge,aMonte-Carlosimulationofaconceptualfault-zonenetwork(seeFigureS2and TableS1ofthe ESM )wasperformed. Theunderlyingassumptionisafault-zonenetworkbetweenthebaseandtopspringoftheKlfferspringsystemat maximumfill( 100m;Planetal. 2010 )justbeforetheonset ofthewintermonthswithnoadditionalrechargeduringthe followingcoldmonthssinceprecipitationmostlyfallsas snow.Inordertoverifywhetherafault-zonenetworkwith theparametersresultingfromthisstudyononehandcould beassumedrepresentativefortheentirewatershedandonthe otherhandmaybeabletosupplythewinterbaseflowtothe abovesprings,orwhethersignificantadditionalstoragevolumehastobetakenintoaccount,arangeofpercentageof faultrockandcorrespondingaverageporositieswaschosenas input.Therangeofgross-rockvolumereflectstheuncertainty intheexactsizeofthewatershed. Resultsindicatethatinthemajorityofrealizationsthesimulatedfault-zonenetworkiseitherthesolecontributororcontributessignificantlytothestoragecapacity.Assumingonly veryminorcontributionofadditionalstoragefromthehost rock,aminimumofaround5%offault-zonevolumeover thewholecatchmentareaisrequiredtodeliverthebasedischargeofthemainspringsystem,avaluewhichisinlinewith theobservedspatialdistributionanddensityoffaultzones acrossthecatchment.Thesizeofthecatchmentandthereducedsurfacerunoffduetoitskarsticcharacteristicswould explainthat,insuchascenario,arelativelysmallpercentage offault-rockvolumeissufficienttoprovidethestoragecapacitytosustainbaseflow. HydrogeolJ

PAGE 22

Duetothehigherstoragecapacityofthejointsysteminthe dolostonehostrock,theeffectofprecipitationeventsonspring dischargeisingeneralmoredampenedthaninfaultedand karstifiedlimestone.Forlackofsufficientdata,itwasatthis stagenotpossibletodefineandverifyparametersofaconceptualfault-zonenetworkonaregionalscale.ItishoweverinterestingtonotethatthePfannbauernspring,whichdischarges fromadolostonewatershed,showsadeviatingbehaviorwhen simulatedbaseflowandmeasureddischargearecompared (Nachtnebeletal. 2012),whichpossiblyindicatesthesuperposedeffectofhigh-permeabilitystreaks(faultzones).ConclusionsThepresentstudyofshallowcrustalfaultsgivesanintegrated insightintothestructurallycontrolledcharacteristicsofsmalltomedium-sizefaultswhichformfirst-orderpermeability structureswithintheeconomicallyimportantHochschwab karstmassif(Austria). & Thisstudyconfirmsthatinmassive,low-porositycarbonatesthatlackpervasiveplanarfeaturessuchasbedding, faultsformthemostimportantcorridorsforpotentialfluid infiltration,migrationandkarstification. & Ourdataillustratesignificantdifferencesinthearchitecturalbuild-upoffaultzonesindolostone(multiplestrandedcataclasticfaultcoresofweaklateralcontinuity, highvolumesofintenselyfracturedrock)andlimestone (laterallydistinct,single-strandedfaultcores,Riedel-shear fracturesdominatingfracturepatterns). & Low-permeability(<1mD)cataclasticfaultrocksareonly abundantenoughinhigh-displacementfaultstoformbarriersonanoutcropscale. & Faultcoresoflowtomediumdisplacementfaultscontain domainsofbrecciatedandhighlyfracturedrocksalong theirlateralandverticalextensionandarethereforeseen asconduits.Thisinterpretationisunderlinedby karstificationfeatureswithinthefaultsthatarepredominantlylocatedalongthefaultcores. & Faultzonesareaccompaniedbysignificantfault-parallel volumesoffracturedhostrock.Fracturedensitiesvaryby afactorofupto10.Althoughmacro-fracturesareseenas prominentflow-controllingfeatures,methodsuseddonot allowforaproperquantificationoftheirhydrogeological properties. & Faultsareseenasflowconduitsonaregionalscale. Portionsofimpermeablefaultcorearenotexpectedto becontinuousandpersistentenoughtohavearegional impact.MonteCarlosimulationofaconceptualfaultnetworksupportstheviewthatmostofthestoragecapacityin thelimestonesresideswithintheporevolumeofthefaultzonenetwork.Acknowledgments OpenaccessfundingprovidedbyUniversityof Vienna.WethankWolfgangZerobinandGerhardKuschnigofthe ViennaWaterworksfortheirlong-timecooperationwiththeUniversity ofViennaandtheirgreatsupportforresearchinhydrogeology.Wethank thestaffoftheViennaWaterworksfortheirsupportduringthefieldwork andLukasPlanforsharinghisexpertiseonkarstandcavesatthe HochschwabaswellasAlbertKostnerforfruitfuldiscussionsandhis greathelponimprovingtheEnglish.Thepaperbenefitedfromtheconstructiveandveryhelpfulcommentsofthejournaleditorandassociate editorandfromthedetailedreviewsofAndreaBilliandtwoanonymous reviewers.ThisworkwasfundedbytheViennaWaterworks(Contract FA536018HydroFaults). OpenAccess ThisarticleisdistributedunderthetermsoftheCreative CommonsAttribution4.0InternationalLicense(http:// creativecommons.org/licenses/by/4.0/),whichpermitsunrestricteduse, distribution,andreproduction inanymedium,providedyougive appropriatecredittotheoriginalauthor(s)andthesource,providealink totheCreativeCommonslicense,andindicateifchangesweremade.ReferencesAgostaF(2008)Fluidflowpropertiesofbasin-boundingnormalfaultsin platformcarbonates,FucinoBasin,centralItaly.GeolSocLond SpecPubl299:277 – 291 AgostaF,KirschnerDL(2003)Fluidconduitsincarbonate-hosted seismogenicnormalfaultsofcentralItaly.JGeophysRes108: 2221.doi: 10.1029/2002JB002013 AgostaF,PrasadM,AydinA(2007)Physicalpropertiesofcarbonate faultrocks,FucinoBasin(centralItaly):implicationsforfaultseal inplatformcarbonates.Geofluids7:19 – 32 AgostaF,AlessandroniM,AntonelliniMetal(2010)Fromfracturesto flow:aquantitativeanalysisofanoutcroppingcarbonatereservoir. Tectonophysics490:197 – 213 AgostaF,RuanoP,RustichelliAetal(2012)Innerstructureanddeformationmechanismsofnormalfaultsinconglomeratesandcarbonategrainstones(GranadaBasin,BeticCordilleraSpain):inferences onfaultpermeability.JStructGeol45:4 – 20 AntonelliniM,CilonaA,TondiEetal(2014)Fluidflownumerical experimentsoffaultedporouscarbonates,northwestSicily(Italy). MarPetGeol55:186 – 201 AustrianStandards(1999)NORMEN1936:1999:determinationof realdensityandapparentdensity,andoftotalandopenporosity. https://www.austrian-standards.at .Accessed01February2012 AydinA(2000)Fractures,faults,andhydrocarbonentrapment,migration andflow.MarPetGeol17:797 – 814 BalsamoF,StortiF(2010)Grainsizeandpermeabilityevolutionofsoftsedimentextensionalsub-seismicandseismicfaultzonesinhighporositysedimentsfromtheCrotonebasin,southernApennines, Italy.MarPetGeol27:822 – 837 BaqusV,TravA,BenedictoAetal(2010)Relationshipsbetween carbonatefaultrocksandfluidflowregimeduringpropagationof theNeogeneextensionalfaultsofthePenedsbasin(Catalan CoastalRanges,NESpain).JGeochemExplor106:24 – 33 BenseVF,PersonM(2006)Faultsasconduit – barriersystemstofluid flowinsiliciclasticsedimentaryaquifers.WaterResourRes42: W0542.doi: 10.1029/2005WR004480 BenseVF,GleesonT,LovelessSEetal(2013)Faultzonehydrogeology. EarthSciRev127:171 – 192 BilliA(2005a)Grainsizedistributionandthicknessofbrecciaandgouge zonesfromthin(<1m)strike-slipfaultcoresinlimestones.JStruct Geol27:1823 – 1837 HydrogeolJ

PAGE 23

BilliA(2005b)Attributesandinfluenceonfluidflowoffracturesin forelandcarbonatesofsouthernItaly.JStructGeol27:1630 – 1643 BilliA(2010)Microtectonicsoflow-Plow-Tcarbonatefaultrocks.J StructGeol32:1392 – 1402.doi: 10.1016/j.jsg.2009.05.007 BilliA,DiToroG(2008)Fault-related carbonaterocksandearthquakeindicators:recentadvancesandfuturetrends.In:LandoweSJ,Hammler GM(eds)Structuralgeology:newresearch.Nova,Hauppauge,NY BilliA,StortiF(2004)Fractaldistributionofparticlesizeincarbonate cataclasticrocksfromthecoreofaregionalstrike-slipfaultzone. Tectonophysics384:115 – 128.doi: 10.1016/j.tecto.2004.03.015 BilliA,SalviniF,StortiF(2003)Thedamagezone-faultcoretransitionin carbonaterocks:implicationsforfaultgrowth,structureandpermeability.JStructGeol25:1779 – 1794.doi: 10.1016/S0191-8141(03) 00037-3 BilliA,ValleA,BrilliMetal(2007)Fracture-controlledfluidcirculation anddissolutionalweatheringinsinkhole-pronecarbonaterocks fromcentralItaly.JStructGeol29:385 – 395 BilliA,PrimaveraP,MicheleSetal(2008)Minimalmasstransferacross dolomiticgranularfaultcor es.GeochemGeophysGeosys9, Q01001.doi: 10.1029/2007GC001752 BonsonCG,ChildsC,WalshJetal(2007)Geometricandkinematic controlsontheinternalstructureofalargenormalfaultinmassive limestones:theMaghlaqFault,Malta.JStructGeol29:336 – 354 BrydaG(2001)Geologisc heKartierungimHo chschwabgebiet: EntscheidungshilfezurAbgrenzungvonQuelleinzugsgebieten [GeologicalmapoftheHochschwab:decisionguidanceforthediscriminationofspringcatchments].In:MandlGW,Geologische BundesanstaltArbeitstagung2001[Geologicalworkshopofthe GeologicalSurveyofAustria,report].GeologicalSurveyof Austria,Vienna CaineJS,EvansJP,ForsterCB(1996)Faultzonearchitectureandpermeabilitystructure.Geol24:1025 – 1028 CelicoF,PetrellaE,CelicoP(2006)Hydrogeologicalbehaviourofsome faultzonesinacarbonateaquiferofsouthernItaly:anexperimentallybasedmodel.TerraNov.18:308 – 313 ChesterFM,EvansJP,BiegelLR(1993) Internalstructureandweakening mechanismoftheSanAndreasFault.JGeophysRes98:771 – 786 ChildsC,ManzocciT,WalshJJetal(2009)Ageometricmodeloffault zoneandfaultrockthicknessvariations.JStructGeol31:117 – 127. doi: 10.1016/j.jsg.2008.08.009 deDreuzyJR,DavyP,BourO(2002)Hydraulicpropertiesoftwodimensionalrandomfracturenetworksfollowingpowerlawdistributionsoflengthandaperture.WaterResRes38:12.doi: 10.1029/ 2001WR001009 DeckerK,ReiterF,(2001)StrukturgeologischeMethodenzur CharakterisierungvonKarstwasserwegenimHochschwabmassiv [Structuralmethodsforthecharacterizationofkarstwaterflowpaths intheHochschwabmassif].In:MandlGW(ed)Geologische BundesanstaltArbeitstagung2001[WorkshopoftheGeological SurveyofAustria2001].Conf.Proc.,GeologicalSurveyAustria, Vienna DeckerK,PeressonH,FauplP(1994)DiemiozneTektonikder stlichenKalkalpen:Kinem atik,Palospannungund Deformationsauft eilungwhrendder “ lateralenExtrusion ” der Zentralalpen[MiocenetectonicsoftheEasternAlps:kinematics, paleostressesanddeformationpartitioningduringthelateralextrusionofthecentralAlps].AnnuRepGeolSurvAustria137(1):5 – 18 DershowitzWS,HerdaHH(1992)Interpretationoffracturespacingand intensity.Proceedingsofth e32ndUSSymposiumonRock Mechanics(USRMS),SantaFe,NM,AmericanRockMechanics Assoc.,Alexandria,VA,pp757 – 766 DorO,Ben-ZionY,RockwellTetal(2006)Pulverizedrocksinthe MojavesectionoftheSanAndreasFaultZone.EarthPlantSci Lett245:642 – 654 eHyd(2014)AbteilungWasserhaushalt:HydrographischesZentralbro imBundesministeriumfrLand-undForstwirtschaft,Umweltund Wasserwirtschaft[DepartmentofWaterSupply,Hydrographic CentralOffice,FederalMinistryofAgricultureandForestry, V ienna]. http://ehyd.gv.at/ .Accessed30September2014 EichhublP,DavatzesN,BeckerS(2009)StructuralanddiageneticcontroloffluidmigrationandcementationalongtheMoabFault,Utah. AmAssocPetGeolBull93:653 – 681.doi: 10.1306/02180908080 FaulknerDR,MitchelTM,RutterEHetal(2008)Onthestructureand mechanicalpropertiesoflargestrike-slipfaults.In:WibberleyCAJ, KurzW,ImberJetal(eds)Structureoffaultzones:implicationsfor mechanicalandfluid-flowproperties.GeolSocLondSpecPubl 299:139 – 150 FaulknerDR,JacksonCAL,LunnRJetal(2010)Areviewofrecent developmentsconcerningthestructure,mechanicsandfluidflow propertiesoffaultzones.JStructGeol32:1557 – 1575.doi: 10. 1016/j.jsg.2010.06.009 FondriestM,AretusiniS,DiToroGetal(2015)Fracturingandrock pulverizationalonganexhumedseismogenicfaultzonein dolostone:TheFoianaFaultZ one(SouthernAlps,Italy). Tectonophysics654:56 – 74 FrostE,DolanJ,SammisCetal(2009)Progressivestrainlocalizationin amajorstrike-slipfaultexhumedfrommidseismogenicdepths: Structuralobservationsfromth eSalzach-Ennstal-Mariazel Puchbergfaultsystem,Austria.JGeophysRes114.doi: 10.1029/ 2008JB005763 FrostE,DolanJ,Ratschbacheretal(2011)Directobservationoffault zonestructureatthebrittle-ductiletransitionalongtheSalzachEnnstal-Mariazell-Puchbergfa ultsystem,AustrianAlps.J GeophysRes116.doi: 10.1029/2010JB007719 GratierJ-P(2011)Faultpermeabilityandstrengthevolutionrelatedto fracturingandhealingepisodicprocesses(yearstomillennia):the roleofpressuresolution.OilGasSciTechnol66(3):491 – 506.doi: 10.2516/ogst/2010014 GuerrieroV,IannaceA,MazzoliSetal(2010)Quantifyinguncertainties inmulti-scalestudiesoffracturedreservoiranalogues:implemented statisticalanalysisofscanlinedatafromcarbonaterocks.JStruct Geol32:1271 – 1278 GuerrieroV,MazzoliS,IannaceAetal(2013)Apermeabilitymodelfor naturallyfracturedcarbonatereservoirs.MarPetGeol40:115 – 134 HauseggerS,KurzW,RabitschEetal(2010)Analysisoftheinternal structureofacarbonatedamagezone:implicationsforthemechanismsoffaultbrecciaformationandfluidflow.JStructGeol32: 1349 – 1362 JourdeH,FlodinEA,AydinAetal(2002)Computingpermeabilityof faultzonesineoliansandstonefromoutcropmeasurements.Am AssocPetGeolBull86:1187 – 1200 KimYS,SandersonD(2009)Inferredfluidflowthroughfaultdamage zonesbasedontheobservationofstalactitesincarbonatecaves.J StructGeol32:1305 – 1316.doi: 10.1016/j.jsg.2009.04.017 KornevaI,TondiE,AgostaFetal(2014)StructuralpropertiesoffracturedandfaultedCretaceousplatformcarbonates,MurgePlateau (southernItaly).MarPetGeol57:312 – 326.doi: 10.1016/j. marpetgeo.2014.05.004 KuschnigG(2009)ForschungsanstzezurBewltigungkommender HerausforderungenbeiderWasserversorgungvonGrostdten [Researchapproachesandcopingstrategiesforthewatersupplyof majorcities].WorkshopoftheGeologicalSurveyofAustria,Conf. Proc.,Leoben,Austria,August2009 LerayS,deDreuzyJR,BourOetal(2013)Numericalmodelingofthe productivityofverticaltoshallowlydippingfracturedzonesincrystallinerocks.JHydrol481:64 – 75.doi: 10.1016/j.jhydrol.2012.12. 014 LinzerHG,RatschbacherL,FrischW(1995)Transpressionalcollision structuresintheuppercrust:thefold-thrustbeltoftheNorthern CalcareousAlps.Tectonophysics242:41 – 61.doi:10.1016/00401951(94)00152-Y HydrogeolJ

PAGE 24

LinzerHG,DeckerK,PeressonHetal(2002)Balancinglateralorogenic floatoftheEasternAlps.Tectnonophysics354:211 – 237.doi: 10. 1016/S0040-1951(02)00337-2 LunnRJ,ShiptonZK,BrightAM(2008)Howcanweimproveestimates ofbulkfaultzonehydraulicproperties?In:WibberleyCAJ,KurzW, ImberJetal(eds)Theinternalstructureoffaultzones:implications formechanicalandfluid-flowproperties.GeolSocLondSpecPubl 299:139 – 150doi: 10.1144/SP299.14 MandlGW,BrydaG,KreussOetal(2000)Karstwasserdynamikund KarstwasserschutzHochschwab:GeologischeKarte[Karstwater dynamicsandprotectionHochschwab:geologicalmap].Endber. Geol.B.A.,Vienna,82pp MicarelliL,MorettiI,JaubertMetal(2006)Fractureanalysisinthe south-westernCorinthrift(Greece)andimplicationsonfaulthydraulicbehavior.Tectonophysics426:31 – 59 MitchellTM,FaulknerDR(2008)Experimentalmeasurementsofpermeabilityevolutionduringtriaxialcompressionofinitiallyintact crystallinerocksandimplicationsforfluidflowinfaultzones.J GeophysResSolidEarth113(B11) MitchellTM,FaulknerDR(2009)Thenatureandoriginofoff-fault damagesurroundingstrike-slipfaultzoneswithawiderangeof displacements:afieldstudyfromtheAtacamafaultsystem,northern Chile.JStructGeol31:802 – 816 MitchellTM,FaulknerDR(2012)Towardsquantifyingthematrixpermeabilityoffaultdamagezonesinlowporosityrocks.EarthPlanet SciLett339 – 340:24 – 31 MitchellTM,Ben-ZionY,ShimamotoT(2011)Pulverizedfaultrocks anddamageasymmetryalongtheArima-TakatsukiTectonicLine, Japan.EarthPlanetSciLett308:284 – 297 NachtnebelHP,SenonerT,StanzelPetal(2012)Climatechangeand impactsonwatersupply.WP4WaterResourRep,InstituteofWater Management,HydrologyandHydraulicEngineering(IWHW), UnivNatResourLifeSci,Vienna PeacockDCP,SandersonDJ(1992)Effectsoflayeringandanisotropyon faultgeometry.JGeolSoc149:793 – 802 PeressonH,DeckerK(1997)TheTertiarydynamicsofthenorthern EasternAlps(Austria):changingpaleostressesinacollisionalplate boundary.Tectonophysics272:125 – 157 PetracchiniL,AntonelliniA,BilliAetal(2012)Faultdevelopment throughfracturedpelagiccarbonatesoftheCingolianticline,Italy: possibleanalogforsubsurfacefluid-conductivefractures.JStruct Geol45:21 – 37 PlanL(2002)Spelologisch-tekt onischeCharakterisierungder KarstwasserwegeimEinzugsgebietderbedeutendstenQuelleder Ostalpen(Klfferquelle,Hochschwab)[Speleologicalandtectonic characterizationofkarsticflowpathsinthecatchmentofoneofthe mostimportantspringsintheEasternAlsp(Klfferspring)].MSc Thesis,Univ.Vienna,Austria PlanL(2005)Factorscontrollingcarbonatedissolutionratesquantifiedin afieldtestintheAustrianAlps.Geomorphology68:201 – 212 PlanL,DeckerK(2006)Quantitativekar stmorphologyoftheHochschwab plateau,EasternAlps,Austria.ZeitungGeomorphol147:29 – 56 PlanL,DeckerK,FaberRetal(2009)Karstmorphologyandgroundwatervulnerabilityofhighalpinekarstplateaus.EnvironGeol58: 285 – 297 PlanL,KuschnigG,StadlerH(2010)Klfferspring:themajorspringof theViennawatersupply(Austria).In:KresicN,StevanovicZ(eds) Groundwaterhydrologyofsprings.Elsevier,Amsterdam RathA,ExnerU,TscheggCetal(2011)Diageneticcontrolofdeformationmechanismsindeformationbandsinacarbonategrainstone. AmAssocPetGeolBull95:1369 – 1381 RatschbacherL,FrischW,LinzerHGetal(1991)Lateralextrusioninthe easternAlps,partII:structuralanalysis.Tectonics10:257 – 271.doi: 10.1029/90TC02623 RawlingGC,GoodwinLB,WilsonJL(2001)Internalarchitecture,permeabilitystructure,andhydrologicsignificanceofcontrastingfaultzonetypes.Geol27:43 – 46 SavageHM,BrodskyEE(2011)Collateraldamage:evolutionwithdisplacementoffracturedistributionandsecondaryfaultstrandsinfault damagezones.JGeophysRes116:2156 – 2202.doi: 10.1029/ 2010JB007665 SchpferMPJ,ChildsC,WalshJJ(2006)Localisationofnormalfaultsin multilayersequences.JStructGeol28:816 – 83 3 SchrckenfuchsT,BauerH,GrasemannBetal(2015)Rockpulverizationandlocalizationofastrike-slipfaultzoneindolomiterocks [Salzach-Ennstal-Mariazell-Puchbergfault,Austria].JStructGeol 78:67 – 85 SchulzSE,EvansJP(2000)Mesoscopicstructureofthepunchbowlfault, southernCalifornia,andthegeologicalandgeophysicalstructureof activefaults.JStructGeol22:913 – 930 ShiptonZK,CowiePA(2001)Damagezoneandslipsurfaceevolution overmicrontokmscalesinhighporosityNavajosandstone,Utah.J StructGeol23:1825 – 1844.doi: 10.1016/S0191-8141 ShiptonZK,CowiePA(2003)Aconceptualmodelfortheoriginoffault damagezonestructuresinhigh-porositysandstone.JStructGeol25: 333 – 344 ShiptonZ,SodenA,KirkpatrickJetal(2006)Howthickisafault?Fault displacement-thicknessscalin grevisited.In:AbercrombieR, McGarrA,ToroGDetal(eds)Earthquakes:radiatedenergyand thephysicsoffaulting.AGUMonographSeries170.AGU, Washington,DC,pp193 – 198 SibsonRH(1977)Faultrocksandfaultmechanism.JGeolSocLond 133:191 – 213 SibsonRH(1986)Brecciationprocessesinfaultzones:inferencesfrom earthquakerupturing.PureApplGeophys124:159 – 175 SmithSAF,BilliA,DiToroGetal(2011)Principalslipzonesinlimestone:microstructuralcharacterizationandimplicationsfortheseismiccycle(TreMontifault,centralApennines,Italy).PureAppl Geophys168:2365– 2393 StortiF,BilliA,SalviniF(2003)Particlesizedistributionsinnatural carbonatefaultrocks:insightsfornon-self-similarcataclasis.Earth PlantSciLett206(1 – 2):173 – 186 TarasewiczJPT,WoodcockNH,DicksonJAD(2005)Carbonatedilatationbreccias:examplesfromthedamagezonetotheDentFault, northwestEngland.GeolSocAmBull117:736 – 745 TeseiT,CollettiniC,VitiCetal(2013)Faultarchitectureanddeformationmechanismsinexhumedanaloguesofseismogenic-bearing thrusts.JStructGeol55:167 – 181 TollmannA(1976)DerBauderNrdlichenKalkalpen.Monographieder NrdlichenKalkalpen[Geologicalbuild-upoftheNorthern CalcareousAlps.Monographoft heNorthernAlps],3rdedn. Deiticke,Vienna TondiE,AntonelliniM,AydinAetal(2006)Therolesofdeformation bandsandpressuresolutionseamsinfaultdevelopmentincarbonategrainstonesofMajellaMountain,Italy.JStructGeol28: 376– 391 WalkerRJ,HoldsworthRE,ArmitagePJetal(2013)Faultzonepermeabilitystructureevolutioninbasalts.Geology41(1):59 – 62.doi: 10. 1130/G33508.1 WibberleyCAJ,ShimamotoT(2003)Internalstructureandpermeability ofmajorstrike-slipfaultzones:theMedianTectonicLineinMie Prefecture,southwestJapan.JStructGeol25:59 – 78 WibberleyCAJ,YieldingG,DiToroG(2008):Recentadvancesinthe understandingoffaultzoneinternalstructure:areview.In: WibberleyCAJ,KurzW,ImberJetal(eds)Theinternalstructure offaultzones:implicationsformechanicalandfluid-flowproperties. GeologicalSocietyLondon,London WoodcockNH,MortK(2008)Classificationoffaultbrecciasandrelated faultrocks.GeolMag145(3):435 – 440 HydrogeolJ