Pacific tsunami records suggest similar rupture locations of two great Kamchatka earthquakes only 73 years apart.

Whether seismic slip can far exceed the slip budget of a subduction megathrust over a short time has important implications to earthquake physics and hazards. The first modern test comes from two great Kamchatka earthquakes of moment magnitude 8.8 to 9.0 in 1952 and 2025. Here, we use tide gauge tsunami records across the Pacific to determine whether the two events ruptured the same or complementary fault areas. We extract records of the 1952 tsunami from analog marigrams at 52 tide gauge stations and minimize their time uncertainties by matching hindcast tides. The 1952 tsunami waveforms and travel times are remarkably similar to those of the 2025 event. Tsunami modeling shows that a range of relative rupture locations can produce the waveform similarity, but only nearly colocated ruptures can explain the travel time similarity. On the basis of conventional rationale, the 2025 earthquake consumed more than twice the megathrust slip deficit accrued since 1952. We explain the conundrum by fast energy accumulation in a viscoelastic Earth.