The northern Chile region of the Nazca subduction zone ruptured in an earthquake in 1877, which induced a tsunami. The various magnitude estimates of this event are based on the evaluation of historical records, seismic intensities, and/or tide gauge information; however, its actual along‐strike extent is debated. Based on geodetic data, the previous studies have suggested that this region has the potential for an 8.2–8.8 event. We re‐evaluate the seismic potential of the region, accounting for the buildup rate of moment deficit along the megathrust, the earthquake magnitude–frequency distribution, and the physics of earthquakes. We combine an improved probabilistic estimate of moment deficit rate with results from dynamic models of the earthquake cycle, testing, in particular, the influence of a potential aseismic barrier near the city of Iquique, which may influence the extent and magnitude of large events in this region. We find that 8.8 is the most probable maximum magnitude earthquake in the region, and that the potential barrier likely has a limited impact considering uncertainties. We discuss the effect of the moment deficit rate on the fault, the b‐value, and the importance of postseismic processes on our results.