The　Yaoshan　landslide,　situated　in　the　hilly　and　mountainous　terrain　of　southeastern　China,　exhibits　typical　episodic　sliding　behavior　driven　by　a　complex　subsurface　hydrogeological　system.　This　study　integrates　long-term　in-situ　monitoring　data　with　microtremor　survey　techniques　to　investigate　the　internal　mechanisms　underlying　its　intermittent　movement.　A　two-dimensional　apparent　S-wave　velocity　(Vx)　structure　was　constructed　for　the　key　sliding　area,　revealing　both　lateral　and　vertical　discontinuities　associated　with　lithological　boundaries　and　potential　slip　surfaces.　By　correlating　low-velocity　anomalies　with　borehole　lithology　and　observed　deep-seated　deformation　features,　the　depth　and　geometry　of　the　principal　slip　surface　were　identified.　Several　geophysical　cross-sections　revealed　bowl-shaped　depressions　within　the　landslide　mass,　where　interconnected　low-velocity　zones　likely　function　as　preferential　hydrological　pathways.　Monitoring　data　indicate　that　these　depressions　are　prone　to　rapid　pore　water　pressure　buildup　during　intense　rainfall,　which　can　trigger　reactivation　of　sliding.　Field　surveys　further　verified　the　hydraulic　connectivity　between　low-velocity　zones　and　surface　gullies,　suggesting　strong　coupling　between　surface　runoff　and　internal　groundwater　flow.　The　perennial　flow　in　gullies,　combined　with　long-term　seepage　through　colluvial　deposits,　may　accelerate　internal　erosion　within　the　slip　zone.　These　findings　offer　new　insights　into　the　hydro-mechanical　coupling　mechanisms　of　landslides　and　provide　a　scientific　foundation　for　risk　assessment　and　the　design　of　mitigation　measures　in　geologically　similar　settings.　©　2025　Elsevier　B.V.