In　this　study,　the　seismic　response　of　the　fluid-structure　interaction　(FSI)　of　an　undersea　tunnel　in　a　broken　fault　zone　during　a　bidirectional　earthquake　is　examined.　An　undersea　tunnel　FSI　model　that　accounts　for　the　effects　of　the　viscoelastic　artificial　boundary,　seepage,　and　dynamic　liquid　pressure,　and　considers　the　rock　mass　as　a　saturated　porous　medium,　is　created　through　finite　element　analysis　software　ADINA.　The　seismic　response　of　the　undersea　tunnel　is　determined　by　considering　both　horizontal　and　vertical　ground　motion　and　analyzing　the　time　history　curve　of　the　displacement,　acceleration,　and　principal　stress　of　the　lining　key　point.　Numerical　results　show　that　(1)　the　maximum　displacement,　acceleration,　and　tensile　stress　of　the　lining　structure　are　all　present　in　the　vault　area;　(2)　the　time　history　curves　of　the　displacement,　acceleration,　and　principal　stress　of　the　key　points　follow　a　similar　variation　law;　(3)　the　vertical　displacement　of　the　lining　structure　is　greater　than　its　horizontal　displacement;　and　(4)　tensile　areas　generally　appear　in　the　vault　and　inverted　arch,　but　the　hance　is　in　the　compression　state.　(C)　2013　Elsevier　Ltd.　All　rights　reserved.