Using Open GNSS Stations to Determine Earth Surface Displacements and Ionospheric Response Following the Kamchatka Earthquake of July 29, 2025

This study analyzes crustal movements and ionospheric response triggered by the powerful MW 8.8 earthquake of July 29, 2025, using continuous GNSS observations from open geodetic network stations located on the Kamchatka Peninsula, Sakhalin Island, the coast of the Sea of Okhotsk, and the Kuril Islands. Significant coseismic horizontal and vertical coordinate changes were detected at GNSS stations on the Kamchatka Peninsula near Petropavlovsk-Kamchatsky (up to 65 cm horizontally and 8 cm vertically), in Severo-Kurilsk city (168 cm horizontally and 19 cm vertically), and on Sakhalin Island (up to 3 cm horizontally). The time delay of surface deformation propagation was estimated for stations in Petropavlovsk-Kamchatsky and Severo-Kurilsk. The ionospheric response to the earthquake was investigated, revealing concentric ionospheric disturbances propagating southwestward from the earthquake epicenter. Two modes of this disturbance were identified: a fast mode with a propagation velocity of 800–1300 m/s detectable during the first ~20 minutes, and a slow mode with velocity of 180–330 m/s observed approximately 40 minutes after the main shock.