Abstract <p>Krasheninnikov Volcano, which had shown no signs of activity for over 400 years, began erupting on August 2, 2025, with prolonged eruption of magma from the Northern Cone crater. The eruption was likely triggered by the Kamchatka megaearthquake of July 29, 2025 (<i>Mw</i> = 8.8). Using satellite radar interferometry methods based on images from the Sentinel-1 A and C satellites from two orbits, a complex deformation field was recorded in the territory of the volcano’s caldera during the period spanning the onset of the eruption. The horizontal extension component is particularly pronounced in the deformation field. The horizontal displacement of the surface to the west and east, calculated using data from two orbits, reaches 0.6 m in each direction. The vertical component of surface displacement of the volcanic edifice exceeds 0.26 m at the summit of the Southern Cone. Interpretation of the measured displacements using numerical mathematical modeling made it possible to determine the parameters of a giant vertical fracture that formed in the volcanic caldera during the intrusion of magmatic material from a deep chamber during the eruption. The fracture, 7–8 km in length, runs almost through the center of the caldera and deviates counterclockwise from the north–south direction by 12°. Based on the condition of the best agreement between theoretical and actual displacements, the fracture width is estimated at 1.5–2.2 m, the vertical extent is 2.0–2.9 km, and the depth of the upper edge is 1.25–1.5 km. The total volume of intruded material is estimated from 0.024 to 0.045 km³.</p>