ESDB100028 2025120214350000 Vladimir Kaftan crossref@gcras.ru Geophysical Center of the Russian Academy of Sciences Geophysical Center of the Russian Academy of Sciences Peter Dokukin People's Friendship University of Russia Vladimir Kaftan Geophysical Center RAS N. N. Titkov Kamchatka Branch of the Federal Research Center of the Geophysical Survey of the Russian Academy of Sciences, Petropavlovsk-Kamchatsky, Russia D. V. Chebrov Kamchatka Branch of the Geophysical Survey of the Russian Academy of Sciences, Petropavlovsk-Kamchatsky, Russia A synoptic animation of horizontal dilation deformation was constructed using continuous GNSS observations at stations in the Kuril-Kamchatka and Aleutian island arcs. Coordinate solutions for stations located on the Kamchatka Peninsula and the nearest islands, which are part of the regional KAMNET network, were provided by researchers from the Kamchatka Branch of the Unified Geophysical Service of the Russian Academy of Sciences. Coordinate data for the remaining stations in Russia, Japan, and the USA were obtained from the web archive of the Nevada Geodetic Laboratory (Reno, USA) [Blewitt et al., 2018]. The time series of GNSS station coordinates begins on January 1, 2020, and ends immediately after the Kamchatka megaquake of July 30, 2025, with an M8.8 magnitude. Approximately three years before the megathrust earthquake, anomalous zones of compression formed near the southwestern segment of the Kuril-Kamchatka Trench and extension near the northeastern segment. The compression zone is consistent with the pressure of the Pacific Plate on the Okhotsk microplate. The extension zone requires explanation. Its extreme place coincides with the position of an active mantle plume beneath the Meiji Guyot, close to the future epicentral zone of the strongest seismic event. The role of this extension in the mechanism of the megathrust earthquake's generation and discharge requires explanation. These two mutually opposing anomalies are consistent with the hypothesis of the existence of two microplates: the Okhotsk and Kamchatka. Extension northwest of Kamchatka coincides with the location of the Central Okhotsk Rise, which has continental crust. Throughout the entire observation period, the Kamchatka Peninsula has been in a state of weak compression. 2025 12 02 2025 Geophysical Center of the Russian Academy of Sciences Moscow, Russia Geophysical Center of the Russian Academy of Sciences Moscow, Russia 10.2205/esdb-kamchatka-hd-2025 2025120214350000 https://esdb.wdcb.ru/doi/2025/esdb-kamchatka-hd-2025.html