Basedontheelasticdislocationtheory,multilayeredcrustalmodel,andrupturemodelobtainedbyseismicwaveforminversion,wecalculatedthecoandpost-seismicsurfacedeformationandgravitychangescausedbytheYushuMW6.9earthquakeoccurredonApril14,2010.TheobservedGPSvelocityfieldandgravityfieldinYushuareasaredisturbedbythecoandpost-seismiceffectsinducedbyYushuearthquake,thusthetheoreticalcoandpost-seismicdeformationandgravitychangeswillprovideimportantmodificationforthebackgroundtectonicmovementofYushuandsurroundingregions.ThetimerelaxationresultsshowthattheinfluencesofYushuearthquakeonYushuandsurroundingareaswilllastaslongas30to50years.Themaximumhorizontaldisplacement,verticalupliftandsettlementareabout1.96,0.27and0.16m,respectively,themaximalpositiveandnegativevalueofgravitychangesare8.892×10-7m·s-2and-4.861×10-7m·s-2,respectively.Significantspatialvariationscanbefoundonthecoandpost-seismiceffects:Theco-seismiceffectmainlyconcentratesintheregionneartherupturefault,whileviscoelasticrelaxationmostlyactsonthefarfield.Therefore,whenusingthegeodeticdatatoresearchtectonicmotion,weshouldnotonlyconsidertheeffectofco-seismiccausedbyearthquake,butalsopayattentiontotheeffectofviscoelasticrelaxation.
