An 8.8-magnitude undersea earthquake struck early Wednesday off the coast of Russia’s Petropavlovsk-Kamchatsky, triggering tsunami waves in parts of Russia and Japan, and prompting alerts across the Pacific region.
According to the United States Geological Survey (USGS), the earthquake occurred at a shallow depth of 20.7 km, making it susceptible to aftershocks.
Another earthquake of the same magnitude followed soon after.
"Notable quake, preliminary info: M 8.0 -- 136 km ESE of Petropavlovsk-Kamchatsky, Russia," the USGS stated.
Two aftershocks followed, measuring 6.9 and 6.3 on the Richter scale.
"Notable quake, preliminary info: M 6.9 -- 147 km SE of Petropavlovsk-Kamchatsky, Russia," the USGS noted.
"Notable quake, preliminary info: M 6.3 – 131 km SE of Vilyuchinsk, Russia," it added.
Tsunami waves of up to 3–4 meters were recorded in Kamchatka, according to regional emergency minister Sergei Lebedev.
Evacuations were ordered in Kamchatka, Japan, and other locations, including Hawaii, where a tsunami watch remains in effect.
Russia's Emergencies Ministry said a tsunami hit the Far East coast, flooding a port town with around 2,000 residents.
"The tsunami flooded parts of the port town of Severo-Kurilsk... The population has been evacuated," the ministry said in a statement, according to Al Jazeera.
The July 29, 2025, M8.8 earthquake east of Petropavlovsk-Kamchatsky occurred due to shallow reverse faulting.
At the quake's location, the Pacific Plate is moving west-northwest relative to the North American Plate at approximately 77 mm/year.
Notably, the North American Plate extends westward beyond the continental landmass. The quake's location and fault motion are consistent with subduction zone activity along the Kuril-Kamchatka Arc, the USGS noted.
While earthquakes are often represented as points on a map, those of this size involve slip across a larger fault area. Reverse faulting events of this magnitude typically span about 390 km by 140 km (length × width).
The Kuril-Kamchatka Arc experiences frequent moderate-to-large quakes and has hosted 31 events of magnitude 6.5+ within 250 km of this epicenter over the past century.
This includes a M7.4 earthquake on July 20, 2025, which is now considered a foreshock to the M8.8 event of July 29, 2025.
The epicenter lies 45 km southeast of the 1952 M9.0 Kamchatka earthquake, which triggered a destructive, Pacific-wide tsunami, according to the USGS.
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