8.4-Magnitude Quake Near Russia Too Deep for Tsunami

An earthquake with a magnitude of 8.4 struck deep under the Sea of Okhotsk Thursday night, followed early this morning by a strong 6.8-magnitude aftershock.

Because of their depth, 378 and 387 miles, respectively, neither generated a tsunami nor caused any damage.

The first occurred at 7:44 p.m. Thursday with the second recorded at 4:56 a.m. today.

The epicenters of the tremors were less than 50 miles apart in the Sea of Okhotsk (pronounced oh-KOTSK) located between the Russian mainland and its Kamchatka Peninsula.

According to the US Geological Survey, they occurred in the area of a deep fault formed by the subduction of the North America plate beneath Eurasia at the Kuril-Kamchatka trench.

The USGS said the depths of the tremors suggest that they occurred deep within the lithosphere of the subducting Pacific plate, rather than at the zone where the plates collide.

The Kuril Islands south of Kamchatka have been the location for several strong earthquakes this year, including a 7.2-magnitude temblor on April 18.

The Kurils are a volcanic archipelago stretching from Kamchatka to Japan which, like the Kamchatka Peninsula, separate the Sea of Okhotsk from the North Pacific Ocean.

According to the USGS, the Kuril-Kamchatka arc is one of the most seismically active regions of the world, having produced seven great earthquake of 8.3 magnitude or greater since 1900. Several produced damaging tsunami, including the Sept. 25, 1983 Hokkaido earthquake.

The largest was a 9.0-magnitude event in 1952 that produced a tsunami with a 40-foot run-up that caused significant damage to the city of Severo-Kurilsk on the island of Paramushir south of Kamchatka.