In　recent　years,　earthquake　rockfalls　have　occurred　frequently　all　over　the　world,　resulting　in　heavy　casualties　and　property　losses.　Unfortunately,　research　on　rockfall　dynamics　upon　earthquake　events　is　still　rare　due　to　limited　field　and　experimental　data,　and　restricted　to　numerical　simulations　of　only　two　dimensions.　In　order　to　primarily　reveal　the　role　of　earthquakes　on　rockfall,　this　study　focused　on　the　stability　of　rock　blocks　on　an　inclined　slope,　and　following　rockfall　dynamics　by　three-dimensional　discontinuous　deformation　analysis　(3-D　DDA).　First,　earthquake　input　methods　were　discussed　and　implemented　for　the　triangulated　regular　network　(TRN)　in　3-D　DDA.　The　effectiveness　was　verified　by　comparison　with　analytical　solution　results　of　a　single　block　on　the　inclined　slope　under　seismic　loads.　Further,　by　discussing　the　variations　of　the　boundary　chart　of　failure　modes,　it　indicated　that　the　block　was　more　prone　to　slide　even　with　a　large　friction　angle,　became　instability　under　seismic　conditions.　Moreover,　a　regular　dodecahedron　rock　block　was　released　on　a　stochastic　roughness　slope　with　two　platforms　through　parallel　realizations.　The　indices　of　the　movement　characteristics　of　the　block,　such　as　runout　distance,　lateral　displacement　range,　and　resting　position,　were　investigated.　The　results　showed　that　the　maximum　runout　distance　was　not　sensitive　to　seismic　load,　but　the　lateral　displacement　range　was　significantly　sensitive　to　seismic　load　and　increased　appreciably.　Through　the　3D-DDA　numerical　simulations,　both　rock　stability　and　rockfall　behaviors　under　earthquake　conditions　could　be　better　understood.　Furthermore,　it　will　be　helpful　to　by　analyzing　trajectories　and　kinetic　energies　predict　earthquake　rockfall　disasters　and　design　reasonable　protective　countermeasures　under　earthquake　scenarios.