Typhoon‐Driven Near‐Surface Groundwater Dynamics Revealed by Ambient Noise in the Mountain Watershed

Abstract Near‐surface groundwater dynamics (NSGD) regulate water residence time and downstream water resources in mountain watersheds, yet whether a single extreme rainfall event can reorganize near‐surface storage remains unclear. Here, we examine typhoon‐driven NSGD using ambient seismic noise from four stations, together with hydrological and meteorological records. Single‐station cross‐component correlations and the stretching method were applied to estimate seismic velocity changes ( dυ / υ ) at 4–8 Hz. Following the typhoon, has spatial variability, ranging from ∼10 days upstream to at least 3 months downstream. We attribute this delayed recovery to thicker colluvium and fractured bedrock that enhance subsurface water retention. Concurrent decreases in dυ / υ and increases in groundwater levels indicate transient vertical coupling between shallow and deeper systems. Continued post‐typhoon dυ / υ decreases suggest delayed lateral inflow from upstream, whereas later low‐intensity rainfall responses indicate subsequent decoupling. Our results show that a single typhoon prolonged watershed scale NSGD with insight for water residence time in mountainous regions.