The 2012 Emilia earthquake (Italy): Geotechnical characterization and ground response analyses of the paleo-Reno river levees

In 2012NorthernItalywashitbyaseismicsequencewithearthquakesofmoderatelocalmagnitudesand shallow hypocentraldepths.AfterthemainshocksofMay20,collapseofbuildingsandlifelineruptures werewidelyobservedintheepicentralareawithinadistanceofabout15km,wherelargeacceleration valueswithprevailingverticalcomponentwererecorded.Locally,atagreaterdistance,intenseand spectacular liquefactioneffectswereobserved.Theymainlyaffectedtheearthenembankmentsoftheold Renoriverchannel(paleochannel),and,toalesserextent,theirimmediatesurroundings.Inthesefar- field areas,groundsurfaceaccelerationsweresignificantly lowandnotconsistentwiththespreadingand extentoftheobservedliquefactioneffects.Adetailedgeotechnicalsurveywasperformedtoidentify depth, locationandbehaviourofliquefied soillayersandtoanalysetheirinfluence ongroundresponse and surfaceliquefactioneffects.Resultsfrominsituandlaboratorytests,performedunderstaticand dynamic loadingconditions,arepresentedhereinandacompletegeotechnicalmodeloftheancient levees andtheunderlyingsoildepositisproposedfornumericalsite-specific seismicanalyses.More attention waspaidtoanalysingtheinfluence ofnon-linearbehaviourofinterbeddedliquefied sandson the expectedsurfacegroundmotion.Implicationsandlimitsoftheresultsobtainedarediscussedwith, finally,proposalsforadjustmentsto1-Dlinearequivalentmodelsoperatinginthefrequencydomain,for taking intoaccountstiffnessdegradationofliquefiable layersathighstrainlevels.