Horizontal-to-vertical　spectral　ratio　(HVSR)　of　both　earthquake　and　ambient　noise　are　applied　to　perform　inversions　of　the　subsurface　velocity　structure　of　a　certain　site,　however,　their　mechanisms　differ　significantly.　A　comparative　study　on　earthquake　HVSR　(EHV)　and　noise　HVSR　(NHV)　for　the　same　site　is　rare,　hence,　herein,　a　case　study　is　conducted　on　the　Xiangtang　vertical-array　observation　station,　located　in　the　city　of　Tangshan,　northern　China.　The　earthquake　and　noise　records　observed　at　this　array　station　are　used　to　investigate　the　spectral　characteristics　of　EHV　and　NHV.　Differences　between　the　EHV　and　NHV　are　compared,　and　the　possible　causes　for　the　differences　are　explored.　Further,　the　mechanismsof　the　EHV　and　NHVare　discussed,　and　the　suggestions　about　HVSR　inversion　are　offered.　The　results　of　this　study　show　that　the　EHV　and　NHV　significantly　differ　in　the　spectral　shape　and　amplitude　in　the　medium-to-high　frequency　band.　Typically,　the　amplitude　of　the　observed　EHV　in　the　frequency　band　larger　than　two　times　of　the　predominant　frequency　(f(0))　is　higher　than　that　of　the　observed　NHV;　the　mechanisms　of　the　EHV　and　NHV　show　clear　differences.　For　frequencies　larger　than　2f(0),　the　observed　EHV　is　better　explained　by　the　theoretical　body-wave　HVSR,　and　the　observed　NHV　is　better　explained　by　the　theoretical　full-wave　HVSR.　Therefore,　when　performing　an　inversion　to　obtain　subsurface　velocity　structure　using　HVSR,　one　must　carefully　distinguish　the　data　sources　and　choose　the　correct　forward　method　to　obtain　more　reliable　results.　(C)　2020　Elsevier　B.V.　All　rights　reserved.