Massive Russian earthquake struck on 'megathrust fault'

Wednesday's quake has already triggered at least 10 aftershocks above magnitude 5, and they could continue for months

- Reuters

The 8.8 magnitude quake off Russia that triggered tsunami warnings across the Pacific occurred on what is known as a “megathrust fault”, where the denser Pacific Plate is sliding underneath the lighter North American Plate, scientists said.

The Pacific Plate has been on the move, making the Kamchatka Peninsula area off Russia's Far East coast where it struck especially vulnerable to such tremors - and bigger aftershocks cannot be ruled out, they said.

With its epicentre near the city of Petropavlovsk-Kamchat-sky, it was the biggest earthquake since the devastating Tohuku event in 2011, which caused a tsunami that sent Japan's Fukushima Daiichi nuclear plant into meltdown.

"The Kamchatka seismic zone is one of the most active subduction zones around the Pacific Ring of Fire, and the Pacific Plate is moving westwards at around 80 mm per year," said Roger Musson, honorary research fellow at the British Geological Survey.