<p>The earthquake that occurred on the plate interface offshore of Kamchatka on 29 July 2025 gives an opportunity to re-estimate the source of the 1952 Kamchatka megathrust earthquake. Currently, there is no clear explanation on how the two interplate earthquakes ruptured the same plate interface within only 73&#xa0;years, which is a short time span to accumulate enough strain energy for the recent event. Both earthquakes generated Pacific-wide tsunamis; however, the 1952 event lacks the quality and quantity of data that are available for the 2025 event. In this study, tsunami waveforms from the 2025 earthquake, recorded by offshore DART buoy stations, are used to estimate fault slip distribution for this earthquake. The estimated seismic moment from the model is 1.13 × 10²² Nm (Mw 8.6), with a major slip region approximately 500&#xa0;km long located at a depth of 30&#xa0;km with maximum slip of 12&#xa0;m. Time-shift and amplitude-scaling coefficients are then derived by fitting observed coastal tsunami waveforms to simulations based on this reference model. These correction parameters and an additional time correction to account for the clock error of the records are then used in an inversion to produce a reliable slip distribution for the 1952 earthquake. That model gives a seismic moment for the 1952 earthquake of 2.04 × 10²² Nm (Mw 8.8) and suggests that this rupture was ~ 700&#xa0;km long with large slip of 18&#xa0;m also located at a depth of 30&#xa0;km. The earthquake source modeling results show that both earthquakes have relatively small slips at the shallowest segment of the plate interface near the trench.</p> Graphical abstract <p></p>