The biggest deep earthquake ever, of the magnitude of 8.3, occurred off the coast of Russia on May 24 this year, scientists have confirmed.

It had a seismic moment 30 per cent larger than that of the next largest, a 1994 earthquake 637 kilometres beneath Bolivia, researchers said. The earthquake that struck deep beneath the Sea of Okhotsk, recorded by several thousand seismic stations around the world, has left seismologists struggling to explain how it happened. — PTI