A magnitude 7.8 earthquake struck off the coast of the Kamchatka Peninsula Monday, between Alaska and Russia, at 23:34 GMT today (4:34 p.m. Pacific time).
The quake, originally declared to be 7.7 and then 7.4 by the Pacific Tsunami Warning Center (PTWC), was later upgraded to 7.8 by the U.S. Geological Survey.
The PTWC has since declared there to be no tsunami threat from the quake, having posted on its website: "Based on all available data, the tsunami threat from this earthquake has now passed."
The quake's shallow epicentre was 10 kilometres below the seabed, near the westernmost islands of Alaska's Aleutian chain.
The volcanically active Kamchatka Peninsula has been the site of major earthquakes and tsunamis in the past century, including an 8.5 event in 1923 that caused a six-metre tsunami to hit Hawaii, and a 1952 quake measured at 9.0 that generated tsunami waves locally as high as 15 metres that killed as many as 15,000 people.