D2.3 Strong motion parameters of selected events (update the national database ITACA

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1 D2.3 Strongmotionparametersofselected events (update the national database ITACA v1.1),revisedgmpe PacorF.(1),LuziL.(1),PugliaR.(1),D AmicoM.(1),BindiD.(2) (1) IstitutoNazionalediGeofisica e Vulcanologia, Milano, Italy (2) GFZ, Potsdam, Germany V1.0releasedonJuly15,2013 DPCINGVS2Project ConstrainingobservationsintoSeismicHazard

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3 FOREWORDS 4 ITACAV1.1 DATABASEARCHITECTUREANDWEB FILENAMES METADATAREVISION STRONGMOTIONDATA BYPRODUCTSFINALISEDTOTHEVALIDATIONOFSEISMICHAZARD GMPESOFINTEGRALPARAMETERSFROMITA10DATASET FUNCTIONALFORM COEFFICIENTSFORARIASINTENSITY,HOUSNERINTENSITYANDDURATION AREGIONALGMPEFORNORTHERNITALY NORTHERNITALYSTRONGMOTIONDATASET RANKINGOFEXISTINGGMPES GMPESFORNORTHERNITALY CONCLUSIONSANDPERSPECTIVES REFERENCES ANNEXES 29 DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page3

4 Forewords TheactivitiespertaintoTask2 Expandingtheobservations.ThemaingoalofthisTaskconcerns withthecollectionoforiginaldataofdifferentnature(instrumentalandnot)andtheoptimization oftheexistingonestowidenthecapabilitiestocompareseismichazardresultswithobservations. Inthisframework,threeactivitiesarecarriedout: 1)updatingtheItalianstrongmotiondatabaseITACA1.0(includingstrongmotiondatafrom2008 uptofebruary2011andthroughtherevisionofmetadataandpublicationofitacaversion )developingGroundMotionPredictionEquationsforintegralstrongmotionparameters,onthe baseofdatasetusedtocalibratetherecentitalianequations,forpeakaccelerationandspectral ordinates(ita10,bindietal.;2011) 3)compilationofaqualifiedstrongmotiondatasetfornorthernItalyafterthe2012Emiliaseismic sequenceandcalibrationofaregionalgroundmotionpredictionequations(gmpes). ITACAv1.1 The accelerometric data base ITACA v 1.1 contains the strong motion data and the relevant metadata acquired by the strong motion networks operated by the Italian Department of Civil Protectionfrom1972to2011(February).Strongmotiondatarelativetoeventsoccurredinthe period2009 February2011withmagnitudelargerthan3.0havebeenprocessedandaddedin thisproject.theitacav1.1.( Withrespecttothepreviousrelease,ITACA1.0(June2010,Pacoretal.,2011),themodifications regardsthedatabasearchitecture,aswellasthemetadatarevisions.furthermore,thenameand theheaderoftheasciiformatfilesusedtoarchivewaveformsandaccelerationresponsespectra hasbeenmodifiedinordertofollowtheinternationalstandardandincludefurtherinformation usefultoanalyzedata. Databasearchitectureandweb Thedatabasearchitecturehasbeenpartiallymodifiedinordertomakethedatabasemoreflexible tohostdatafromothercountriesthanitaly.inparticularallthefieldsstrictlyrelatedtotheitalian territoryhavebeenchangedintomoregenericfields. DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page4

5 Thestationtablehasbeensplitintotwoseparatetables,onecontainingtheattributesandthe othercontainingimages(photos,maps,etc.),inordertomakethedataretrievalfasterthroughthe web. Themapshowingallstation/eventsofthedatabasehasbeenaddedtothestation/eventquery pages.anexampleofmapisreportedinfigure1. Figure1.Stationinterface.(Searchquery:MinimumMaximumlatitude[44 47 ]andminimummaximum longitude[9 14 ]). The fault projection on the surface obtained from the DISS 3.0 catalogue ( stationsymbolshavebeencoloredaccordingtothepgavalues. Examples of the interface Event Detail is reported in Figure 2a and 2b for the 1997 Umbria earthquake(m6.0)andfor2009l Aquilaearthquake(M6.3),wherethefaultprojectionsarefrom DISSv3.0andfromtheinversionstudyofGallovicandZaradnik(2011),respectively.Theclosest recordingstationsprovingwaveformsincludedinitaca1.1arealsoplotted.thestarsindicatethe instrumentalepicentres. DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page5

6 Figure2a.WebPagerelativetoEventdetailforthe2 nd mainshockof1997umbriamarcheseismic sequence. Figure2b.WebPagerelativetoEventdetailforthemainshockof2009L Aquilaseismicsequence. DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page6

7 Filenames FollowingthestandardoftheSeedmanualv2.4thefilenameshavethefollowingstructure: net_code.station_code.location_code.channel_code.d.date.time.processing_type.waveform_type.format whereformatandcodesaregivenasintable1. Table1:standardformatfilenamefordataprovidedbyITACA1.1. net_code station_code location_code channel_code Date Time processing_type waveformtype Format istheinternationalnetworkcode(2characters) isthestationcode(3to5characters) isthecodewhichindicateswhetherthestationisinstalledatgroundlevel(empty),orat differentgroundlevels(codesfrom01to10) indicatesthewaveformtypeandthecomponentandhas3digits: 1)1digitforthebandcode(inourcaseH=HighBroadBand) 2)1digittoindicatethewaveformtype N,L,G=unprocessedacceleration(thecodesaretheonesusedbydifferentnetworks) 3)1digittoindicatetheorientationcode ZNE(TraditionalVertical,NorthSouth,EastWest) 123Orthogonalcomponentsbutnontraditionalorientations istheeventdateasyyyymmdd istheeventorigintimeashhmmss iseitherx(unprocessed)orc(processed) iseitheracc(acceleration)vel(velocity)dis(displacement)sa(accelerationspectrum) PSV(pseudovelocityspectrum)SD(displacementspectrum) isthefileformat(.seed,.mseed,.sacand.ascforasciiformat) Example:theaccelerationrecordedbytheDepartmentofCivilProtectionnetwork(net_code:IT) at S. Giuliano di Puglia scuola (station_code: SGIB), NS component, on 2002/11/12 at 09:27:00 GMT,unprocessed,ASCIIformatwithheader,willhavethefollowingname: IT.SGIB.HNN.D X.ACC.ASC DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page7

8 Metadatarevision SomerevisionsofmetadatahavebeenintroducedinITACA1.1,suchas: Friulisequence:focalmechanisms,locationsandfaultstrikeanddiparederivedfrom Barbanoetal.(1985)orSlejkoetal.(1999); UmbriaMarchesequence:locations,focalmechanismsandfaultstrikeanddipare derivedfromchiaraluceetal.(2004)orspecificstudiesinliterature; L Aquilasequence:locations,focalmechanismsandfaultstrikeanddiparederived fromchiaraluceetal(2011)orspecificstudiesinliterature; 4. The rest of focal mechanisms and Mw ( ) are derived from RCMT ( 5. Fortheeventsthatarenotinthepreviouscases,focalmechanismsandfaultstrikeanddip arederivedfromfrepolietal.(1997)andfrepoliandamato(2000); 6. ThecoordinatesofTolmezzodigastations(TLM1,TLM2andTLB)andthesiteclassification hasbeenrevised; 7. ThecoordinatesoftheMajanotemporaryandpermanentstations(MAA,MAT,MAP,MJS, MAIandMAJ)havebeenrevised; 8. TheEc8soilclassificationofthesitesequippedwithaccelerometerssince2007havebeen revised,onthebaseofthegeologicalmapat1:100,000scale strongmotiondata ThestrongmotiondatasetofITACA1.0hasbeenupdated,addingabout1,200strongmotiondata withm>3.0recordedintheperiodtime (March),reachingatotalofabout40,000 threecomponentprocessedwaveformsrecorded(figure3)intheperiod ThenewdatahavebeenuniformlyprocessedfollowingtheprocedureofITACA(Paoluccietal., 2011;Pacoretal.,2011). DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page8

9 Themaincontributioncomesfromthe2009L Aquilaseismicsequencethatprovidesmorethan 800 records. The most of the events occurred along the central Apennines belt and are characterized by depth between 5 and 20km with normal fault mechanism. Deeper events (between20and30km)wererecorded:insouthernitalyandinnorthernapennines(2008parma seismicsequence). Figure3.TimedistributionofmaximumPGAandPGVforITACA1.1intheperiod Figure4showsthemagnitudedistancedistributionofITACAv1.1upto200kmintheperiod ,incomparisonwithdistributionofdataupto2007. Thenewdatabettersampletheshortdistancerange(<10kmfromtheepicentres)inthe magnituderange (Figure4,right). Figure4.MagnitudedistancedistributionforITACA1.0upto200km(left)andforthenewdataset composedbystrongmotiondataintheperiod (centre).ontheright:magnitudedistributionfor ITACA1.1upto2007(redbars)andfordatasetintheperiod (greybars). DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page9

10 Byproductsfinalisedtothevalidationofseismichazard Several data selections and maps have been derived from the ITACA 1.1 database, in order to promotetheseismichazardvalidation,pursuedbytask6.thesedatasetareprovidedasannexes intableformat,andtheyaregoingtobeimplementedonawebgisbyuringvgrottaminarda. Namelytheyare: 1. Activeaccelerometricstationsinthelast30years; 2. Maxima recorded by the single seismic station: horizontal components of following parameters:pga,pgv,andspectralacceleration(5%damping)at0.1,0.3and1s; 3. Maximarecordedbythesingleseismicstationfordifferenttimeintervals: ; (mainlyanaloginstruments)andsince1995(mainlydigitalinstruments); 4. StationsthathaverecordedPGAlargerthan100gal,since1972; 5. RecordingstationsclassifiedasinEC8provisions. GMPEsofIntegralparametersfromITA10dataset During the first phase of the project, GMPEs of integral parameters (Arias Intensity, Housner Intensity,duration)havebeenrequired,inordertofacilitatetheconversionamonginstrumental andmacroseismicobservations.wederivedthemfromthedatasetusedbybindietal.,2011,for thesocalledita10gmpe. Functionalform TheparametricmodeloftheGMPEisbasedonthefunctionalformusedbyBindietal.(2011): log Y e1 F ( R, M ) F ( M ) F F 10 D M S sof [1] wherethedistancef D andmagnitudef M functionalformsaregivenby: F D c 1 c2 M M ref log10 RJB h / Rref c3 RJB h Rref ( R, M ) [2] DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page10

11 M M h b2 M M h M M 2 b1 for M M h FM ( M ) [3] b3 h otherwise TheexplanatoryvariableMismagnitude,R(inkm)istheJoynerBooredistancewhenavailable andtheepicentraldistanceotherwise. ThefunctionalformF S inequation(1)representsthesiteamplificationanditisgivenbyf S =s j C j, forj=1,...4,wheres j arethecoefficientstobedeterminedthroughtheregressionanalysis,whilec j aredummyvariablesusedtodenotetheconsideredsiteclasses:ec8a,b,c,dande. ThefunctionalformF sof inequation(1)representsthestyleoffaultingcorrectionanditisgivenby F sof =f j E j,forj=1,...4,wheref j arethecoefficientstobedeterminedduringtheanalysisande j are dummyvariablesusedtodenotethedifferentfaultclasses:normal(nf),reverse(tf),strikeslip (SS)andunspecified(UN). ThevariablesM ref,m h,r ref (equations2and3)havebeenfixedto5.0,6.75and1km,respectively, aftertrialregressionsandafterbindietal.(2011). CoefficientsforAriasIntensity,HousnerIntensityandduration AsacomplementtothesetofGMPEsderivedbyBindietal.(2011)forthepredictionofPGA,PGV andaccelerationspectralordinates(at5%damping),thecoefficientsfortheariasintensity,the HousnerIntensityandtheduration,basedonstrongmotionintensity,havebeenderived. TheAriasIntensityisdefinedas: [4] The Housner Intensity is defined as the integral of the pseudovelocity response spectrum ( = 0.05)between0and2.5s. [5] The duration Dt based on the motion intensity is evaluated from the Arias Intensity function, whichisnormalizedwithrespecttoitsmaximumvalueia;thedurationcorrespondstothetime intervalt2t1,where(t1)=0.05and(t2)=0.95. The regressions are performed applying a random effect approach (Abrahamson and Youngs, 1992),consideringthegeometricmeanoftherecordedhorizontalcomponents,hereinafterGEOH, andtheverticalone,hereinafterz. The random effect approach is applied to determine the betweenevents, the withinevent componentsofvariability(alatiketal.,2010). DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page11

12 The regressions are performed constraining to zero the site coefficient for class A (rock). Two constrainsareappliedonthestyleoffaultingcoefficients:theunspecifiedfocalmechanismisset to0aswelltheaverageofcoefficientforstrike,normalandunknownfaultmechanism,i.e.(f1+f2 +f3=0). Coefficientb 3 hasbeenconstrainedtozero(maximummagnitudeinthedatasetequalto6.4)as wellasthecoefficientoftheanelasticattenuation,c3. ThecoefficientsofthecalibratedmodelsarelistedinTable2. Table2.CoefficientsforHousnerintensity,Ariasintensityandduration. GMPE Housner Arias Duration Coefficient intensity Intensity e b b b c c H c f f f f A B C D E betw with tot Figure5showsthecomparisonsbetweenpredictionsandobservationsforeventsM5.5andM 5.9,consideringthethreesetsofstrongmotionintegralparameters.Thecomparisonsareshown for two soil classes (A and C). A general good agreement is observed with some exceptions, especiallyforcsites. DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page12

13 HI [cm/s] AI [cm] cm/s T [s] T [s] T [s] 10 2 HI [cm/s] AI [cm] cm/s T [s] T [s] T [s] Figure5.Comparisonbetweenobservations(circles)andpredictions(continuouslines),consideringnormal eventswithm=5.5(topframes)andm=5.9(bottom),forsiteclassa(blacklineandbluecircles)andc (redlineandpinkcircles).thedataareextractedfromtheita10datasetinthemagnituderange and5.86.0,respectively.theshadedarearepresentsvalueswithinplus/minus1standarddeviation.left: HousnerIntensity,centre:AriasIntensity,right:SignificantDuration,Dt AregionalGMPEfornorthernItaly The2012Poplainseismicsequencerevealednewfeaturesoftheobservedgroundshakinglevels in northern Italy, that were not taken into account in previous models for the paucity of instrumentalobservations.thereforetheyrepresentaninvaluableinformationsourceforground motionstudiesinapoorlyinvestigatedareacharacterizedbypeculiaritiesas: a) Presenceofadeepalluvialcover:thePoplainisoneofthelargestsedimentarybasins intheworldwithanareaofabout50,000km 2 andasedimentthicknessvaryingfrom fewtensofmeterstoabout8km; b) Presenceofsurfacewavesintherecordings:besidestheamplificationduetothesoft surface layers, the basin structure may also trap the incoming seismic waves and convertbodywavesintosurfacewaves,thusprolongingthegroundshakingwithinthe

14 basin(hanks,1975;hisadaetal.,1993;satoetal.,1999;joyner,2000;somervilleetal., 2004;Kagawaetal.,2004); c) Thrust fault mechanisms: the Po Plain earthquakes are attributed to a thrust fault system.thischaracteristicisremarkablebecause,beforethe2012,theitalianstrong motioncataloguewasmainlycomposedofrecordsfromearthquakeswithnormalfocal mechanismrecordedinthecentralsouthernapennines. NorthernItalystrongmotiondataset A data set specific for northern Italy has been assembled merging the data contained in the databaseitacav1.1andtherecordingsoftherecent2012emiliasequence,comingbothfrom INGV and DPC networks. The strongmotion dataset is composed by 2174 waveforms in the geographic window [43 30 N46 30 N latitude; 8 00 E13 50 E longitude] and in the period Itincludes136earthquakes(109ofthemrecordedbymorethan1stations)mainlylocatedinthe ToscoEmiliano Apennines, NorthEastern Italy andthe Po Plain. The number of stationsis 299, 248ofthemhavingmorethan1record.Figure6showsthelocationsofepicentresandstations usedtomakethenorthernitalystrongmotiondataset. Earthquake and station metadata were reviewed according to the most reliable sources. Focal mechanismsandmomentmagnitudes(m w )comefromspecificstudiesortheregionalcentroid Moment Tensor project ( and Pondrelli et al., 2001; 2002; 2006; 2007;2011).Before1982,locationsandmagnitudesofthemajoreventsaretakenfromliterature (e.g.,slejkoetal.,1999forthe1976friuliseismicsequence),whilelocationsandlocalmagnitudes (M l ) of the events from 1982 to 2010 come from the Italian Seismic Catalog (CSI 1.1, ( arederivedfromisidecatalogue( The recording stations were classified according to the average shear wave velocity of the uppermost30m,v S,30 (EC8:ComitéEuropéendeNormalisaon,2004),wherethevelocityofclassA islargerthan800m/s,bisintherange m/s,Cintherange m/s,andDisless than 180 m/s. Class E is characterized by 520 m of C or Dtype alluvium underlain by stiffer materialwithv S,30 800m/s(DiCapuaetal.,2011;ITACAdatabase, StationswithoutV S,30 measurements,wereclassifiedrevisingthegeologicalfeaturesonthebase ofgeologicalmaps(1:500,000scaleor1:100,000scaleforuncertainlocations). DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page14

15 Figure 6 a) Map of the epicenters (white circles) included in the DBN2 dataset together with the accelerometric stations. Black triangles: DPC stations; black squares: INGV stations; red box: epicentral area of the 2012 Emilia seismic sequence; black lines: regional borders. b) Zoom on the epicentral area of the 2012 Emilia sequence overlapped to the geological map (1: scale, Carta Geolomorfologica della Pianura Padana, 1997). Site classes (EC8, CEN 2004) are also reported. INGV temporary stations are classified as EC8 - C (CAS, MIR and T0) and are denoted by red squares with a dot. The geology of the Po plain is characterized by Pleistocene marine deposits overlapped by Holocene alluvial deposits. In the northern Apennines sandstones, marls, calcareous marls and chaotic deposits crop out. In Figure 7, the distribution of magnitude versus distance for this dataset is displayed by highlighting the records relative to the 2012Emilia events and by grouping the records on the basisoftheec8siteclasses.figure8showsthedistributionsofdistance(epicentralorjoynerand DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page15

16 Booredistance)andmagnitude(M l orm w )forthenorthernitalydataset.notethatalleventswith M>5.5arecharacterizedbymomentmagnitude.Figure9showsthedistributionofhypocentral depths,stylesoffaultingandsiteclassesaccordingtotheec8siteclassification.thenorthernitaly recordsmainlycomefromsuperficialseismicsources,intheuppermost15kmofthecrustandthe prevalentfocalmechanismisthrustfault.themaximumhypocentraldepthreaches70km Magnitude Ml/Mw Magnitude Ml/Mw Distance [km] Distance [km] Figure7.MagnitudedistancedistributionforthenorthernItalydataset.ThemagnitudeisMwifavailable, Mlotherwise;forthemostofeventswithM>5.5,thedistanceisJoynerandBooredistanceandepicentral distanceintheothercases.left:recordsfromtheemiliasequenceareindicatedbygreysquares,theother recordsareillustratedinyellow.right:recordsaregroupedaccordingtoec8siteclasses;ec8a:blue,ec8 B:grey,EC8C:yellow,EC8D:red,EC8E:green.Theredframeindicatesthedatasetextractedfor calibratingregionalgmpes # records # records # records R/Rjb [km] M w /Ml Mw/Ml Figure8.Distance(Left)andMagnitude(centre)distributionsoftherecordsincludedinthedataset.Grey barsindicatethenumberofstrongmotionrecordsrelativetothe2012emiliaseismicsequence.yellowbar indicateotherrecordsoccurredinnorthernitalyintheperiod( )theredframeindicatesthe datasetextractedforcalibratinggmpes.ontheright:local(lightgrey)andmomentmagnitude(red) distributions. DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page16

17 # records # records # records NF TF SS UN MEC 0 A B C D E SITE Depth [km] Figure9.Focalmechanisms(left),EC8sitecategories(centre)andhypocentraldepthsdistributionsof recordsincludedinthenorthernitalydataset.greybarsindicatethenumberofstrongmotionrecords relativetothe2012emiliaseismicsequence,theotherrecordsareillustratedinyellow.nf:normalfault; TF:thrustfault;SS:Strikefault;UN:unknownfocalmechanisms.Theredframeindicatesthedataset extractedforcalibratinggmpes RankingofexistingGMPEs The fit of the accelerometric observations of northern Italy has been tested against existing GMPEs, using the technique proposed by Scherbaum et al. (2009) which uses an information theoreticapproachfortheselectionandrankingofgmpes(beauvaletal.,2012).thestartingpoint oftheirmethodisthedefinitionofameaningfuldistancemeasurebetweenprobabilisticmodels. This measure is given by the so called Kullback Leibler (KL) divergence, which denotes the information loss when a model g is used to approximate a reference model f (Burnham and Anderson,2002). TheKLdivergencebetweentwomodelsrepresentedbytheirprobabilitydensityfunctionsfand gisdefinedas: [6] whereefisthestatisticalexpectationtakenwithrespecttof. InthecaseofGMPEselection,frepresentsthedatageneratingprocessandisonlyknown throughobservations.consequently,theterm,cannotbecalculated.however,the secondterm,canstillbeapproximatedviatheobservations(beauvaletal.,2012). Thisapproximationisthenegativeaveragesampleloglikelihood(LLH)definedby: [7] DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page17

18 where x = i= 1,...,N represents the data. Due toits negative sign, the negative average samplellhisnotameasureofclosenessbutameasureofthedistancebetweenamodelandthe datageneratingdistribution. In our application, the GMPEs represent the models and the observations the data generating distribution: a small LLH will indicate that the candidate GMPE is close to the model that has generatedthedata,whilealargellhcorrespondstoamodelthatislesslikelyofhavinggenerated thedata. FromthesetofGMPEsderivedforItalyweincludetheBindietal.(2011),hereafterITA10,based ontheitalianstrongmotiondataset,recordedupto2009andthemassaetal.(2008),hereafter MS08,basedonadatasetspecificforNorthernItaly,recordedupto2007.Threeglobalmodels havebeenselectedaswell,namelythecauzziandfaccioli(2008),hereaftercf08;andtheakkar and Bommer (2010), hereafter AB10. In addition to these GMPEs, we consider the Boore and Atkinson(2008)equation,extendedtowardthelowermagnitudes,hereafterBEA08_M,basedon global dataset but and for this reason, suitable for the context of the Po plain region. The characteristicsoftheselectedgmpesarereportedintable3andtable4. TheLLHparametershavebeencalculatedfor23periodsintherange0.04 4sandthenaveraged eitherovertheentireperiodrange,hereafterreferredtoasllh1,orconsidering5periods(0.1, 0.2, 0.3, 1.0 and 2.0s) selected according to Segou and Akkar et al. (2011) and Delavaud et al. (2012),hereafterreferredtoasLLH2. Table3.Characteristicofthe5selectedGMPEs.GM:geometricmeanofhorizontalcomponents,Max: Maximumofthehorizontalcomponents,GMRotI50:medianamplitudeoverallpossibleorientationsofa horizontalcomponent,n:normalfault,r:reversefaultt:thrustfault,s:strikefault,u:unknown. GMPE Region Comp MagnitudeRange Distance Range (km) ITA10 Italian GM Ms and Ml BEA_M Global GMRotI50/ GM Mw AB10 Eurasia GM Mw CF08 Global GM Mw 200 Rjb or Repi 200 Rjb 100 Rjb 150 Rhypo Site classification Style offaulting Depthrange (km) EC8 N,R/T,S,U 29 Vs,30 N,R,S,U 31 Vs,30< 360m/s; N,R/T,S 360>Vs,30<760m/s Vs,30>760m/s EC8 N,R/T,S 22 MS08 Italian Max Mw 100 Repi Vs,30<800m/s Vs,30>800m/s 60 Severalsubsetshavebeenextractedforthetest: DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page18

19 DBN2_GfivesubsetsofDBN,satisfyingtherangeofvalidityofeachGMPEaccordingtoTable3 NotethatbydefinitionITA10usesMlwhenMwisnotavailable; DBN2_G_Efive subset of the DBN_E composed of the Emilia records satisfying the range of validityofeachgmpe. TheresultsarereportedinTable5 Table4.Characteristicofthefunctionalformsofthe5selectedGMPEs. Model Magnitude scaling Saturation at short distances Geometrical spreading M-dependent Anelastic attenuation Site classification Style of Faulting ITA10 Quadratic Through pseudodepth BEA_M Quadratic Through pseudodepth x x Use categories x x Constrained using a subset of data Use Vs,30 values AB10 Quadratic Through x Use categories x pseudodepth CF08 Linear Hypocentral Use categories x or Vs,30 values MS08 Linear Through Use categories pseudodepth Table5.LLHvaluesforthefiveGMPEsandtheaccelerometricsubsets. Ml/Mw ITA10 CF08 MS08 AB10 BEA08_M DBN2_G LLH LLH x DBN2_G_E LHH LHH From the results we can conclude that ITA10 and CF08 could be both applied to predict the groundmotionofnorthernitaly,providingthelowestllhvaluesforawideperiodrange,intheir rangeofapplicability.however,cf08aswellasglobalmodels,haveamorestrictrangeofvalidity (magnitudelargerthan5anduseofvs30tocharacterizerecordingsites). Nevertheless,severalreasonmotivatesthedevelopmentofaregionalpredictiveequations:first of all, the limited number of studies on ground motion attenuation for this area and the DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page19

20 availability of highquality data recorded on deep sediments both at short and intermediate distancefromtheepicentres,thathaveneverbeeninvestigatedinitaly.moreover,theresultson theperformanceofexistinggmpestopredictthegroundmotioninnorthernitalyshowedthatall the considered equations are not able to represent highfrequency motion, predicting values whicharelargerthantheobservations(luzietal.,2013).furthermore,thedatasetpresentssome peculiar features, that cannot be reproduced by existing GMPEs that are: i) low amplitudes at shortperiods,ii)attenuationwithdistancestronglydependentonfrequency;iii)amplificationof spectralordinatesinthedistancerangefrom80to100km,particularlyevidentatshortperiods (0.1s)(Luzietal.,2013). GMPEsfornorthernItaly The accelerometric data set for northern Italy has been used to derive new GMPE with the followingconstraints: magnituderange46.4; fourstylesoffaulting(nf,tf,ss,un); foursiteclasses(a,b,c,c1),wherec1andcareec8cclasslocatedinsideortheatthe border(oroutside)thepoplain,respectively.classesdandehavebeenneglectedsince verypoorlyrepresented.theintroductionofthec1classisbasedontheobservationsthat thewaveformsrelativetositeslocatedinthemiddleofthebasinhaveuncommonfeatures comparedwiththeec8cclassstrongmotionrecordings,duetotherelevant,andinmany casesdominant,presenceofsurfacewaves; Joyner Booredistanceorepicentraldistanceintherange0200km; earthquakedepthlowerthan30km; functionalformsasinita10(bindietal.,2011);seeeqs.(1),(2)and(3). A further constraint is that each station should have recorded more than 2 waveforms. No selection was done on the number of records per earthquake, since this choice would have reduced the number of events with fault mechanisms other than thrust. The final selection includes1539recordsfrom79earthquakesand173stations(seefigure6). AsresponsevariablethePGA(incm/s 2 )isconsidered,alongwith5%dampedspectralabsolute acceleration(s a,incm/s 2 )computedover24periodsintherange0.04 4s. Asinpreviouscases,theregressionsareperformedconstrainingtozerothesitecoefficientfor classa(rock).twoconstrainsareappliedonthestyleoffaultingcoefficients:theunspecifiedfocal mechanism is set to 0 as well the average of coefficient for strike, normal and unknown fault mechanism,i.e.(f1+f2+f3=0).coefficientb 3 hasbeenconstrainttozero(maximummagnitudein the data set equal to 6.4) as well as the coefficient of the anelastic attenuation, c3. The coefficientsoftheequationareshownintable6. DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page20

21 ThetrendofthesiteparametersinfunctionoftheperiodisshowninFigure10.Forcomparison thecoefficientsforclasscoftheita10gmpesarealsoreported.thesitecoefficientsforgeoh show expected trends: site class B (i.e. stiff sites) amplifies the entire period range with an amplitudepeakof0.25around0.3s,classcmoderatelyamplifiesthelongperiodrangeafter0.3s and class C1 causes a relevant amplification of long period ground motion, starting at 0.2s. At periodlargerthan0.6,theamplificationshavethemaximumvaluesfrom0.35and0.4forcases DBN2_B and DBN2_BH. For Z components, the B and C siteclass coefficients are smaller than GEOH:theyshowanalmostconstanttrend,withvaluesaround0.15.Completelydifferentisthe trend of the C1 coefficients: these sites are characterized by significant deamplification in the period range 0.2 1s, that could be due to high frequency attenuation properties of the deep sedimentsinthepoplain. GEOH_site DBN2_B Z_site B C C C-ITA T [s] T [s] Figure10.Sitecoefficientsobtainedforgeometricalmeanofthehorizontalcomponents(left)andvertical component(right). As example, in Figure 11, the PGA and spectral ordinates Sa at periods 0.3, 1 and 4s, for the geometricalmeanofthehorizontalcomponents(geoh),predictedbythegmpedevelopedinthis studyarecomparedtotheobservationsrelativetoc1soilclassforthrusteventsandmagnitude6. ThepredictionsofthemodelarealsocomparedwithITA10.ForITA10,Csiteclassisconsidered. On average, the predictions match reasonably well the observations over the entire distance range,forallperiods,bothforclassaandc1.however,itisimportanttonotethatclassasites includedinnorthernitalydatasetarealmostalllocatedatlargedistancesfromtheepicenter(r> 80km).Asconsequence,forthesesites,themodelisnotconstrainedclosetotheseismicsources. For C1 sites located over the fault, plotted at RJB = 0.1 km in Figures 11, good agreement is observedbetweenthepredictedspectralaccelerationlevelandrecordeddata,especiallyatlong periods.onthecontrary,thepredictedpgasarelargerthantheobservationsforgeoh. When we compare the ITA10 and the regional GMPEs, we observe that the mean predictions and associatederrorsareverysimilaratintermediateperiods(0.3 1s)anddistancelargerthan10km. Atlongperiods(T>2s),forGEOHandsoftsites(Figure11)theregionalGMPEpredictslargermeanvalues thanita10upto100km,causedbythelowfrequencyamplificationofthec1soilclass. DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page21

22 M6 SaT=0.3s 10 3 GEOHPGA 10 3 ClassC1 Sa [gal] 10 2 Sa [gal] JoynerBoore distance [km] JoynerBoore distance [km] SaT=1.0s SaT=4.0s Sa [gal] Sa [gal] JoynerBoore distance [km] JoynerBoore distance [km] Figure11.Comparisonsbetweenpredictions(median+/1standarddeviations;blacklinesforPGAandSa at0.3,1.0and2.0s)andobservations(symbols)forthrustfocalmechanism.theredlinescorrespondto ITA10predictionsforCclass.TheobservationsareextractedfromnorthernItalydatasetinthemagnitude range6.0+/0.1.

23 Table6.NorthernItalydataset:regressioncoefficientsforabsoluteaccelerationresponsespectra(see equationsfrom1to3)obtainedforthegeometricalmeanofthehorizontalcomponents(geoh). T a b1 b2 c1 c2 h PGA f1_nf f2_tf f3_ss s2_b s3_c s4_c1 be we tot DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page23

24 Table7.NorthernItalydataset:regressioncoefficientsforabsoluteaccelerationresponsespectra(see equationsfrom1to3)obtainedforverticalcomponents(z). T a b1 b2 c1 c2 h PGA f1_nf f2_tf f3_ss s2_b s3_c s4_c1 be we tot DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page24

25 Conclusionsandperspectives ThisreportdescribedtheactivitiesrelatedtocollectionandanalysisofItalianstrongmotiondata carried out within the S2 project with the goal of providing a set of proxies to be used for comparingseismichazardresultswithobservations. 1) The first activity concerned the updating of the Italian strong motion database (Itaca 1.0). The Italian Strong Motion Database, ITACA 1.0, was developed within projects S6 and S4, funded in the framework of the agreements between the Italian Department of Civil Protection (Dipartimento della Protezione Civile, DPC) and the Istituto Nazionale di Geofisica e Vulcanologia (INGV), starting from The version 1.0 of the database was released in 2010 including Italian strong motion data up to 2007 and the data recorded during the strongest events of 2008 (Parma, M 5.4) and 2009 (Abruzzo seismic events, with M > 4). The new version of database, Itaca 1.1, published in 2013 (July), is enriched of about 1000 records and contains about 4700 three-component waveforms in the period (march), mainly acquired by DPC through the Accelerometric National Network (RAN). With respect to Itaca 1.0, the structure and web interface have been modified in order to follow international standards and to make the database more flexible tohost data from other countries than Italy. In particular all the fields strictly related to the Italian territory have been changed into more generic fields. The long delay in releasing a new version of database is strictly related to the difficulty of its maintenance, especially if permanent funded structures, including technical and scientific expertise, are not planned to support it. This issue was already discussed by Ambraseys et al. (2004) and Pacor et al. (2011). In the future, the development and long-term support of ITACA will be also related to the success European Initiatives as EPOS, that has as objective the Integration of the existing national and trans-national research infrastructurers to increase access and use of the multidisciplinary data recorded by the solid Earth monitoring networks. 2) The second activity was relative to the integration of Italian predictive equations recently developed for PGA, PGV and Spectral ordinates (ITA10, Bindi et al, 2011) with integral ground motion parameters (Housner and Arias intensity and significant duration) In these way, a complete and consistent set of GMPEs is now available DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page25

26 for national territory, allowing applications in a number of problems in earthquake engineering. For example, peak ground acceleration and response spectra are usually adopted to evaluate hazard for seismic codes, while the Arias intensity is useful for several geotechnical applications, as liquefaction and ground failure (Kramer, 1996; Travasarou et al., 2003) and the Housner Intensity is found an effective parameter to correlate the severity of seismic events with building structural damage (Masi et al., 2011). 3) The third activity was devoted to compile a qualifies strong motion dataset for northern Italy, after the occurrence of the 2012 Emilia sequence (Mw 6.1 on 20 May and Mw 5.9 on 29 May 2012) and to investigate in detail the characteristic of the ground motion. The dataset was used to evaluate the performance of existing GMPEs in describing the ground motion in northern Italy and especially in the Po plain region. We found that within their range of validity, ITA10 and CF08 are both applicable to predict the ground motion of the Northern Italy, providing the lower LLH values for a wide period range. However, the dataset presents some peculiarities, i.e, i) low amplitudes at short periods, ii) large amplitude at long periods, especially for sites located in the Po plain, iii) attenuation with distance strongly dependent on frequency; iv) amplification of spectral ordinates in the distance range from 80 to 100km, particularly evident at short periods (0.1 s), that can be better described by regional model. This set of new GMPEs, valid the magnitude range 4 6.4, distances up to 200 km and hypocentral depth within 30 km, improves the existing attenuation equation derived for northern Italy, however it should be used with some recommendations, since the compiled North Italy data set is characterized by an unbalanced number of recordings (majority of thrust or reverse style of faulting, class A and B sites at large distance and C1 sites at short distances). As a consequence, the GMPEs derived in this study are proposed to evaluate the PGA and spectral ordinates in the Po plain area especially for very deep soft sites (C1 class) and thrust faults. DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page26

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28 HisadaY.,AkiK.,TengT.(1993).ApplicationofNonstationaryRayDecompositiontoIdentifyingDeepSeismicBedrock ofthekantosedimentarybasin,japan.bulletinoftheseismologicalsocietyofamerica,vol.83, Joyner W. B. (2000). Strong Motion from Surface Waves in Deep Sedimentary Basin. Bulletin of the Seismological SocietyofAmerica,vol.90,S95S112. Kagawa,T.,B.Zhao,K.Miyakoshi,andK.Irikura(2004).Modelingof3DBasinStructuresforSeismicWaveSimulations BasedonAvailableInformationontheTargetArea:CaseStudyoftheOsakaBasin,Japan.Bulletinofthe Seismological KramerSL.GeotechnicalEarthquakeEngineering.PrenticeHall:UpperSaddleRiver,NJ,1996. Luzi,L.,Pacor,F.,Ameri,G.,Puglia,R.,Burrato,P.,Massa,M.,Augliera,P.,Franceschina,G.,Lovati,S.&Castro,R., 2012.OverviewonthestrongmotiondatarecordedduringtheMayJune2012Emiliaseismicsequence,Seis. Res.Lett.,84,118,doi: / MasiA,VonaM,MucciarelliM(2011)Selectionofnaturalandsyntheticaccelerogramsforseismicvulnerability studiesonrcframes.jstructengascespecialissuedevotedto EarthquakeGroundMotionSelectionand ModificationforNonlinearDynamicAnalysisofStructures 137(3): Massa M., Morasca P., Moratto L., Marzorati S., Costa G. and D. Spallarossa (2008). Empirical GroundMotion PredictionEquationsforNorthernItalyUsingWeakandStrongMotionAmplitudes,FrequencyContent,and DurationParameters,BulletinoftheSeismologicalSocietyofAmerica,Vol.98, Pacor,F.,R.Paolucci,L.Luzi,F.Sabetta,A.Spinelli,A.Gorini,M.Nicoletti,S.Marcucci,L.Filippi,andM.Dolce(2011), Overview of the Italian strong motion database ITACA 1.0, Bull Earthquake Eng, 9(6), , doi: /s PaolucciR,PacorF,PugliaR,AmeriG,CauzziC,MassaM(2011)RecordprocessinginITACA,thenewItalianstrong motion database. In: Akkar S, Gulkan P, Van Eck T (eds) Earthquake data in engineering seismology, geotechnical,geologicalandearthquakeengineeringseries,vol14,chapter8,pp Springer,Berlin PondrelliS.,A.Morelli,andG.Ekström,EuropeanMediterraneanRegionalCentroidMomentTensorcatalog:solutions foryears2001and2002,phys.earthplanet.int.,145,14,127147,2004. PondrelliS.,SalimbeniS.,A.Morelli,G.EkströmandBoschiE.,EuropeanMediterraneanRegionalCentroidMoment Tensorcatalog:Solutionsforyears2003and2004,Phys.EarthPlanet.Int.,164,12,90112,2007. PondrelliS.,SalimbeniS.,MorelliA.,EkströmG.,PostpischlL.,VannucciG.andBoschiE.,EuropeanMediterranean RegionalCentroidMomentTensorCatalog:solutionsfor ,Phys.EarthPlanet.Int.,inpress,2011. Pondrelli,S.,A.Morelli,G.Ekström,S.Mazza,E.Boschi,andA.M.Dziewonski,2002,EuropeanMediterranean regionalcentroidmomenttensors: ,phys.earthplanet.int.,130,71101,2002. Pondrelli,S.,S.Salimbeni,G.Ekström,A.Morelli,P.GasperiniandG.Vannucci,TheItalianCMTdatasetfrom1977to thepresent,phys.earthplanet.int.,doi: /j.pepi ,159/34,pp ,2006. Sato, T., R. W. Graves, and P. G. Somerville (1999). Threedimensional finitedifference simulations of longperiod strongmotionsinthetokyometropolitanareaduringthe1990odawaraearthquake(mj5.1)andthegreat 1923Kantoearthquake(MS8.2)inJapan,BulletinoftheSeismologicalSocietyofAmerica,Vol.89, Scherbaum F.,Delavaud E. and C. Riggelsen (2009). Model selection in seismic hazard analysis: An information theoreticperspective,bulletinoftheseismologicalsocietyofamerica,vol.99, Slejko,D.,Neri,G.,Orozova,I.,Renner,G.,&Wyss,M.(1999).StressFieldinFriuli(NEItaly)fromFaultPlaneSolutions ofactivityfollowingthe1976mainshock.bulletinoftheseismologicalsocietyofamerica,89(4), Somerville,P.G.,N.F.Collins,R.W.Graves,andA.Pitarka(2004).Anengineeringgroundmotionmodelforbasin generated surface waves, Proc. 13th World Conference on Earthquake Engineering, Vancouver, Canada, Paper515. TravasarouT,BrayJD,AbrahamsonNA.EmpiricalattenuationrelationshipforAriasintensity.EarthquakeEngineering andstructuraldynamics2003;32: DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page28

29 Annexes Tableparam_S2.xlsx:MaximumvaluesofHorizontalcomponentsforPeakGroundAcceleration (PGA), Peak Ground Velocity (PGV), Acceleration Spectral Ordinatesat T 0.1s, 0.3s and 1s observed at the single recording station included in the Italian strong motion database, ITACAv1.1 Table param_s2_ xlsx: Maximum values of Horizontal components for Peak Ground Acceleration(PGA),PeakGroundVelocity(PGV),AccelerationSpectralOrdinatesatT0.1s, 0.3s and 1s observed at the single recording station included in the Italian strong motion database,itacav1.1,intheperiod Table param_s2_ xlsx: Maximum values of Horizontal components for Peak Ground Acceleration(PGA),PeakGroundVelocity(PGV),AccelerationSpectralOrdinatesatT0.1s, 0.3s and 1s observed at the single recording station included in the Italian strong motion database,itacav1.1,intheperiod Tableparam_PGA_100.xlsx:MaximumHorizontalPeakGroundAcceleration(PGA)largerthan100 cm/s 2, observed at the single recording station included in the Italian strong motion database,itacav1.1 Table stations_ec8.xlsx: Ec8 site classifications of the recording stations included in the Italian strong motion database, ITACA v1.1. The site classes indicated with * means that the attribution is based on geological information and not on direct measurement of the averageshearwavevelocitybetween0and30metersdepth Table_stations_30anni.xlsx: List of the recording stations included in the Italian strong motion database,itacav1.1,operatingforatleast30yearswithoutanyinterruption DPCINGVS2Project ConstrainingobservationsintoSeismicHazard Page29