Site　resonance　frequency　is　a　crucial　parameter　for　estimating　site　effects.　However,　there　is　currently　no　consensus　on　how　to　identify　the　bedrock　interface　to　obtain　the　site　resonance　frequency.　In　this　study,　we　identified　43　stations　that　can　be　regarded　as　one-dimensional　sites　from　the　KiK-net　network　in　Japan,　which　consists　of　699　stations.　By　analyzing　the　horizontal-to-vertical　spectral　ratio and　surface-to-borehole　spectral　ratio of　strong　motion　observation　recordings,　the　fundamental　resonance　frequency　(f0)　of　these　43　sites　was　determined.　Subsequently,　the　correlation　between　the　f0　values　obtained　from　theoretical　noise　horizontal-to-vertical　spectral　ratio　(NHV)　with　different　bedrock　interfaces　and　the　f0　values　determined　from　observation　was　analyzed.　The　conclusion　shows　that　the　f0　is　primarily　influenced　by　shallow　interfaces　with　high　S-wave　impedance　contrasts (ICs).　Specifically,　when　the　bedrock　interface　is　taken　as　the　interface　with　ICs　greater　than　2.5　that　appears　for　the　first　time,　or　the　interface　with　ICs　greater　than　1.5　that　appears　for　the　second　time,　there　is　a　strong　correlation　(greater　than　0.86)　between　the　f0　values　obtained　from　theoretical　NHV　and　from　observation.　These　findings　can　provide　a　quantitative　reference　for　accurately　determining　the　fundamental　resonance　frequency.　©　2024　Tianjin　University　and　John　Wiley　&　Sons　Australia,　Ltd.