Inmarineseismicexploration,ocean-bottomcabletechniquesaccuratelyrecordthemulticomponentseismicwavefield;however,theseismicwavepropagationinfluid–solidmediacannotbesimulatedbyasinglewaveequation.Inaddition,whentheseabedinterfaceisirregular,traditionalfinite-differenceschemescannotsimulatetheseismicwavepropagationacrosstheirregularseabedinterface.Therefore,anacoustic–elasticforwardmodelingandvector-basedP-andS-waveseparationmethodisproposed.Inthismethod,wepidethefluid–solidelasticmediawithirregularinterfaceintoorthogonalgridsandmaptheirregularinterfaceintheCartesiancoordinatessystemintoahorizontalinterfaceinthecurvilinearcoordinatessystemofthecomputationaldomainusingcoordinatestransformation.Theacousticandelasticwaveequationsinthecurvilinearcoordinatessystemareappliedtothefluidandsolidmedium,respectively.Attheirregularinterface,thetwoequationsarecombinedintoanacoustic–elasticequationinthecurvilinearcoordinatessystem.Wenextintroduceafullstaggered-gridschemetoimprovethestabilityofthenumericalsimulation.Thus,separateP-andS-waveequationsinthecurvilinearcoordinatessystemarederivedtorealizetheP-andS-waveseparationmethod.
