To date, eight meteoroid impacts have been identified in the seismic record of NASA's InSight mission on Mars, occurring either closer than 300~km or further than 3500~km. We report the association of a high-frequency marsquake, S0794a, with a new 21.5-m-diameter impact crater discovered at an intermediate distance of 1640~km in the tectonically active Cerberus-Fossae graben system. This impact enables the direct comparison between surface and subsurface sources, as well as providing the first data point in the critical gap between previous impacts, both in distance and crater size. Additionally, the location of this event necessitates a reassessment of previously assumed raypaths of seismic events thought to propagate along a slow crustal waveguide. We find that the raypaths instead penetrate and travel through the faster mantle, implying numerous identified marsquake epicentres should be relocated up to two times further from InSight, with implications for seismically derived impact rates and regional seismicity.