Linking surface kinematics to deepstructure of the Adriatic indenter near apotential switch in subduction polarity –theGiudicarieBelt(SouthernAlps)PIs:MarkR.Handy1,ChristianHaberland2,ElineLeBreton1;Postdoc:EmanuelKästle1;PhDs:AzamJoziNajafabadi2,VincentVerwater11–FU-Berlin;2-GFZ-PotsdamThis is a seismotectonic study of theGiudicarie Belt (GB), a transverse zone thatsubdivides the Alps into an eastern partmarked by orogen-parallel extrusion oforogenic crust and awestern partwithwell-developedpro-andretro-wedges(Fig.1).

Figure1:TectonicmapoftheAlpswithtargetarea(yellowbox)containingGiudicarieBelt(GB)Our project tests the idea that MiocenekinematicsattheleadingedgeoftheAdriaticindenter is related to a proposed switch insubductionpolarityalong theAlpinechainasimagedinbody-wavetomography,fromaSE-dipping slab anomaly in the west to asubvertical to north-dipping anomaly in theeast.The object is to trace both active andinactivefaultsassociatedwiththeGBdownto lithological,structuralandseismologicaldiscontinuities in the crust and uppermantle. Prime targets include (1) apotentiallithospherictearinthevicinityofthe GB, (2) a purported crustal wedge inthe Tauern Window area, and (3) thrustsextending from the GB and the easternSouthern Alps into the Veneto-Friuli

forelandbasin.Tomapthe3Dgeometryoffaults,wewillusedatafromSWATHDandthe AlpArray station network to pinpointlow-magnitude events and to delineateoffsets of rock-physical domains (Vp,Vp/Vs, Qp, Qs) by using local earthquaketomography.Thiswillbecomplimentedbystate-of-the-art structural and kinematic(fault-slip) analyses of thrusts and foldsalong 5 lithospheric profiles crossing keyparts of the GB and adjacent units of theSouthern and Eastern Alps (Fig. 2). Theresults will be integrated with data alongthe TRANSALP section as well as withexisting thermo-chronological data at thesurfacetodevelopafully4DmodeloflateAlpinecollisionandAdriaticindentation.

Figure3:TectonicmapoftheGiudicarieBeltandits5structuraldomains;blue-grayoutlinespartofthedenseseismicstationnetwork(SwathD)usedinthisstudy.Preliminary work shows that the magnitudeand rate of seismicity in the Giudicarie-Veneto-Friulitargetarea(Fig.3)allowtheuseof local earthquake tomography, double-difference localization and receiver functionstoimagetheMoho,aswellaskm-scaleshearzones in the crust and upper mantle. Theaforementioned lithospheric profiles will be

tectonically balanced and the resultingshorteningpatternsandratescomparedwithAdria-Europeconvergencetoseewhetherthekinematics have remained the same throughtime,orhavechangedinresponsetorotation,and possibly N-directed subduction of theAdriaticplate.

Figure 3 - Seismicity in the Central, Eastern andSouthernAlps:(a)SHAREcatalog1000–2006,ML>3; (b) Local networks, 13 months, ML 0-4(1.11.2014-30.11.2015). Events in (b) are color-codedaccordingtolocalnetworkspecified.ThisproposaladdressesSPPresearchthemes1,3and4,andispartofactivityfields1,3,4,and 5. Besides its dependence on thedensified station swaths and the AlpArraynetwork, it is closely linked to studies in theEasternAlps andTauernWindow (Pleugeretal.), at the transition from Alps to Dinarides(Grützner et al.), as well as to structuralthermochronology along the TRANSALPsection (Glotzbach & Kley) andthermomechanical modelling of reversals insubductionpolarity(Rümpker&Schmeling).TwoPhDsareinvolvedinthisprojectandwillwork in the Giudicarie, Veneto and Friuliareas:(1)AzamJoziNajafabadi(GFZ-Potsdam)willprocess the incomingdata fromSwathDand the AlpArray network to create crustmodels extending down to the base of thecrustmantle;(2)VincentVerwater(FU-Berlin)will gather fault-slip data and tectonicallybalance cross sections across the GB, theSouthernAlpsandthePeriadriaticFault.Theirwork is closely linked with the aim ofgenerating a series of 3D reconstructions ofcrustalandmantlestructuresreachingbackintime.

Collaboration is international, with a co-applicantinZürich(VincenzoPicotti,ETH)andcooperation partners in Austria (HannahPomella, Innsbruck; Bianca Heberer,Salzburg), Italy (Alfio Viganò, Trento; StefanoParolai, OGS), Slovenia (Marko Vrabec,Llubjana) and Switzerland (Tobias Diehl,EduardKissling,ETH).