At 06:58 local time on 19 September 2025 (18:58 UTC the previous evening), a magnitude 7.8 earthquake struck the seabed about 140 km off Petropavlovsk-Kamchatsky, the main city on Russia's remote Kamchatka Peninsula. On its own that is a major earthquake, larger than the M7.8 that levelled cities in Türkiye in 2023. Tsunami warnings went out for coasts within a thousand kilometres, and people filmed furniture swaying indoors, yet within a few hours the tsunami threat had passed with only minor sea-level fluctuations, and the regional governor reported no damage.
The real story is that this quake was not really its own event: it was an aftershock. Seven weeks earlier, on 29 July 2025, the same stretch of seabed had produced a colossal Mw 8.8, the largest earthquake anywhere since Japan's 2011 disaster. A quake that big tears open hundreds of kilometres of fault, and the crust around it spends months settling in a long, decaying rain of aftershocks. The 18 September M7.8, and the M7.4 five days before it, were simply the two biggest of those aftershocks, still releasing energy that an M8.8 leaves behind, which is why this event is read as a companion to the July mainshock rather than a stand-alone disaster.