Blast on Kursk was felt from Norway to Alaska

Just after 8.28am last Saturday, shock waves from a massive explosion at the bottom of the Barents Sea were recorded by seismic equipment at a research institute in northern Norway.

Just after 8.28am last Saturday, shock waves from a massive explosion at the bottom of the Barents Sea were recorded by seismic equipment at a research institute in northern Norway.

Almost a week passed before scientists made the connection between the minor undersea earthquake they thought they had recorded and the subsequent disappearance of Russia's most modern nuclear-powered submarine with 118 officers and conscripts aboard.

Other monitoring stations as far away as Alaska, Scotland, and Germany also picked up the first blast, followed two minutes 15 seconds later by a second, louder explosion, which registered 3.47 on the Richter scale - the explosive power of nearly two tons of TNT.

The shock waves are believed to have come from two devastating blasts on board the Kursk, although Russian officials continue to insist that the most likely cause of its loss was a collision with another vessel. Whatever happened on board the Kursk, it was powerful enough to split the armoured 18,300-tonne submarine fromits blue-painted bows to its conning tower.

"The first explosion we recorded was probably the equivalent of less than 100kg (220lbs) of TNT, the second one of two tonnes," said Frode Ringdal, the scientific director of the Norwegian Seismic Array.

At first, the Norwegian scientists did not connect the seismic blip with the loss of the Kursk because the Russian navy admitted the disaster only on Monday. Even then, they said it had happened the previous day. Only in the middle of the week did naval spokesmen, without explanation, give a new date for the disaster.

The information from the Norwegian seismic institute is the most convincing evidence yet that the Kursk was sunk by an internal explosion, probably of one torpedo followed by other torpedoes stored nearby. This would explain the massive damage to the front of the hull, which was designed to withstand a direct hit from an enemy torpedo.

Senior Russian officials continue to insist that a more likely scenario is that the submarine was involved in a collision. Ilya Klebanov, the Deputy Prime Minister, said the Kursk, which was on naval exercises, may have hit a "huge, heavy object" 66 feet below the surface, which sent it immediately to the bottom. But he did not explain what this object could have been.

Any vessel, on the surface or underwater, that was hit by the mighty Kursk would have suffered serious damage, but the Russian navy has not said that any of the 30 vessels involved in the exercises had been hit. The US denies that any of its submarines were involved. Alexander Ushakov, deputy head of the Russian transport ministry's northern division, said there were no civilian ships in the area at the time the Kursk sank.

The Russian government has a lot riding on the exact circumstances in which the Kursk went down. It is wary of the political consequences of an accident which is having a greater impact on Russians than any disaster since the Chernobyl nuclear power station blew up in 1986. Not surprisingly, the Russian navy first suggested a foreign vessel had collided with the submarine.

Other possible explanations are a collision with the seabed, an explosion in the submarine's airtanks, a mine, or a combination of these factors.

But the most likely cause is the explosion of a single torpedo inside the Kursk, followed by the detonation ofsome or all of the 28 torpedoes with 1,000lb warheads stored in the submarine.

The unequivocal evidence from the Norwegian seismic station of two explosions, one small and the second large, confirms earlier reports from two US submarines monitoring the Russian manoeuvres.

Whatever happened to the Kursk it must have been of devastating force, since it has 10 separate watertight compartments. Western experts say 40 per cent of its hull would have to fill with water for it to plunge straight to the bottom. The crew had no time to send any message or release a buoy showing its position.

The Norwegian environmental pressure group Bellona says it doubts if a single torpedo exploding could have led to the disaster. It has a more complicated theory, which is that the pressurised airtanks of the submarine exploded.

This could have happened if a pilot, through human error, had steered the submarine into the seabed, or if the wall of an airtank, situated between the outer and inner hulls of the vessel, had ruptured.

If the Kursk did collide with another vessel, leaving a hole in its hull, then the most likely culprit is one of the ships and submarines taking part in the manoeuvres. But it is unlikely that even the Russian navy would have concealed this fact. The most probable explanation for the sinking of the submarine is an internal explosion.

If the direct cause of the disaster is still unclear, Russians have little doubt that the underlying reason is the decay of the Russian armed forces as a whole and the navy in particular. It has reduced its fleet by 1,000 vessels over the past 10 years. The number of its nuclear submarines has fallen by two-thirds, from 62 to 18, over the same period.

Admiral Vladimir Kuroyedov, the navy commander, said last month that unless he gets more money the fleet will have only 60 ships by 2016.

The ships still sailing are ill-maintained. An admiralty report last year said the navy's maintenance budget is only between 8 and 10 per cent of what it needs. There are reports in the Russian press that essential batteries needed by the Kursk were left on shore because they were being saved for later operations.

If human error was responsible for sinking the Kursk then this may be explained by lack of training, because few Russian submarines or surface vessels spend much time at sea. Navy pilots fly for only 40 hours a year. As one Russian commentator succinctly put it: "Sailors rust faster than steel."

Of the 16 nuclear-fuelled submarines carrying ballistic missiles, only three are normally at sea at any one time. Commanders are so desperate for funds that four years ago they offered to name their vessels after banks or businesses that would contribute to their upkeep. In 1995, a nuclear submarine reportedly came close to meltdown because its onshore electricity supply had been cut off by an electricity company which had not been paid.

Despite this, the naval manoeuvres in the Barents Sea, during which the Kursk sunk, were in preparation for an ambitious plan to send part of Russia's Northern Fleet to the Mediterranean, led by the aircraft carrier Admiral Kuznetsov, later this year. President Vladimir Putin confirmed yesterday that the move would still be made.

The torrent of misinformation which has poured out of the Russian navy since the Kursk went down is being interpreted as a deliberate attempt to deceive. But the failure to give the correct date for the sinking, the claim by Marshal Igor Sergeyev, the Defence Minister, that the crew were about to be rescued, the reports that the crew were tapping in morse code from the Kursk, all suggest a level of complete disorganisation within the upper ranks of the navy about how to handle the disaster.