With　the　development　of　ocean　engineering,　the　seismic　response　of　saturated　coral　sand　foundations　has　gained　attention.　Given　the　wide　gradation　characteristics　of　the　coral　sand　site,　it　can　be　mainly　categorized　into　two　types:　coral　gravelly　sand　sites　and　coral　sand　sites.　Two　centrifuge　shaking　table　tests　were　conducted　based　on　a　typical　island　reef　structure　to　investigate　the　differences　in　the　seismic　responses　between　these　two　types　of　sites　under　offshore　ground　motion.　The　propagation　of　ground　motion,　pattern　of　pore　pressure　development,　and　surface　settlement　of　the　sites　were　thoroughly　analyzed.　The　findings　revealed　significant　discrepancies　in　the　evolution　of　excess　pore　pressure　between　the　coral　gravelly　sand　and　coral　sand　sites.　The　coral　gravelly　sand　site　did　not　experience　liquefaction　owing　to　well-drained　channels,　whereas　partial　liquefaction　occurred　at　the　coral　sand　site　under　the　same　ground　motions.　Additionally,　a　substantial　amount　of　negative　pore　pressure　was　observed　in　the　shallow　layers　of　the　coral　gravelly　sand　site　when　the　excess　pore　pressure　ratios　were　low.　The　site　amplification　effect　increased　as　the　soil　depth　decreased　at　the　coral　gravelly　and　coral　sand　sites.　However,　liquefaction　caused　a　significant　attenuation　of　the　acceleration　in　the　shallow　layer　(z　=　1　m)　of　the　coral　sand　site.　Furthermore,　the　settlement　of　the　coral　gravelly　sand　site　continuously　developed　throughout　the　ground　motion,　including　both　the　excess　pore　pressure　accumulation　and　dissipation　stages.　In　contrast,　most　of　the　surface　settlement　at　the　coral　sand　site　occurred　during　the　pore　pressure　accumulation　stage.　©　2024　Elsevier　Ltd