Abstract Distributed Acoustic Sensing (DAS) provides dense, wide‐aperture observations potentially ideal for imaging earthquake rupture processes. By combining data from a ∼450 km‐long seafloor DAS array offshore Chile and a conventional seismic network, we image an Mw 6.0 intermediate‐depth earthquake ∼400 km away in Argentina, achieving km‐scale spatial resolution of its rupture process. Back‐projection imaging reveals two sub‐events and northward propagation across 6–8 km in ∼3 s. The results favor rupture on a north–south striking (∼350°), west‐dipping (∼53°) normal fault within the subducting slab, consistent with reactivation of a pre‐existing weakness plane such as an ancient outer‐rise fault or the fractured flank of a subducted seamount. This study demonstrates the capability of DAS to resolve moderate‐size (Mw 6) earthquake ruptures at regional distances with high resolution and wide coverage, greatly expanding the range of events that can illuminate the physics of earthquakes.