Abstract An Mw 8.8 megathrust earthquake occurred off the coast of the Kamchatka Peninsula on July 29, 2025 (UTC). This event was located in the same southern segment of the Kamchatka Trench as the 1952 Mw 9.0 Kamchatka earthquake, marking the occurrence of two major earthquakes in this segment with a remarkably short interval of 73 years. Understanding whether the 1952 and 2025 events originated from the same asperities or whether their ruptures were spatially complementary is critical for understanding the generation processes of great earthquakes in subduction zones. The 1952 earthquake is thought to have involved slips exceeding 10 m and reaching depths of 60 km, whereas the main rupture of the 2025 event is thought to have occurred at a shallower depth of approximately 30 km. However, accurately determining the rupture depth of an older event such as the 1952 earthquake is challenging. To provide additional information regarding the rupture depth of the 1952 event, this study investigated whether the depth (< 60 km) at the plate interface along the Kamchatka Trench is capable of accumulating sufficient slip deficit to generate a great earthquake. Using horizontal interseismic displacement rates from global navigational satellite system (GNSS) stations, we estimated the slip deficit rate distribution in the Kamchatka subduction zone using a reversible-jump Markov-chain Monte Carlo (RJ-MCMC) method with a prior distribution that promotes modeling sparsity. The results demonstrated that strong coupling existed in the southern segment at depths of 15–60 km, suggesting that it is possible for great earthquakes to occur in the deep part of the plate interface. To clarify the relationship between the 1952 and 2025 events further, a more detailed analysis of the coseismic slip and afterslip distributions of the 2025 earthquake is necessary. Graphical Abstract
Fumiaki Tomita (Mon,) studied this question.