'Tremor' evidence shows blast sank Kursk
Earthquake experts believe that a double set of earth tremors was responsible for the sinking of the Kursk.
It had previously been thought that the Russian nuclear sub had been involved in some kind of collision.
Seismic monitors around the Baltic have recorded two sets of shock waves on the day the Kursk was lost.
The US team says the first was recorded at only a few stations but the second, just over two minutes later and 250 times larger, was recorded more than 3,000 miles away.
Writing in Eos, the weekly newspaper of the American Geophysical Union, the experts have ruled an earth tremor.
They say the second blast was equal to between four and eight ship-to-ship missiles or one conventional cruise missile warhead.
