September 18, 2025 Earthquake: Kamchatka Peninsula, Russia

Reference #13456:

Tectonic Summary

This September 18, 2025, M7.8 earthquake that occurred east of Petropavlovsk-Kamchatsky, Russia is an aftershock of the M8.8 Kamchatka Peninsula earthquake that struck on July 29, 2025. The aftershock resulted from shallow reverse faulting. As of its occurrence, the September 18, 2025, event is the largest aftershock recorded following the M8.8 mainshock, exceeding a nearby M7.4 aftershock that occurred on September 13. At the earthquake’s location, the Pacific Plate is moving west-northwest relative to the North American Plate at a rate of approximately 80 mm/year. The earthquake’s location and faulting mechanism are consistent with faulting along the subduction zone plate interface of the Kuril-Kamchatka arc.

Although earthquakes are often represented as points on maps, events of this magnitude are better described as slip across a broad fault area. Reverse faulting earthquakes of this size typically involve rupture dimensions of approximately 100 km in length and 50 km in width.