The　coastal　structures,　such　as　breakwaters　and　reefs,　are　usually　vulnerable　to　the　strong　earthquake　waves　propagating　through　their　bedrock　foundation.　This　study　proposes　a　2D　non-water　substructure　model　in　time　domain　for　breakwater-water-bedrock　(layered)　(BWB)　system,　where　the　fluid-solid　dynamic　interaction　is　embodied　by　added　mass　and　the　equivalent　seismic　loading　calculated　from　ocean　free-field　(without　structure)　accomplishes　the　inclined　incidence　of　P　or　SV　wave　with　any　angle.　Besides,　the　cutoff　boundaries　of　the　fluid　are　applied　exact　absorbing　boundary　conditions　(ABCs)　to　simulate　the　far-field　of　water　while　the　viscous-spring　ABCs　are　employed　to　simulate　the　far-field　of　bedrock.　Then,　the　accuracy　of　substructure　method　is　verified　by　some　numerical　examples.　However,　the　exact　added　mass　matrix　is　fully　populated　and　not　easy　to　use　for　general　software.　Therefore,　the　simplified　added　mass　models　for　water-bedrock　system,　water-structure　system　and　BWB　system　are　furtherly　developed,　including　the　relevant　simplified　formulas　fitted　by　curve　fitting　method.　Additionally,　the　numerical　results　indicate　the　good　effectiveness　of　proposed　model.　©　2022　Elsevier　Ltd