Norwegian seismology foundation Norsar detected an "explosive signal" near the Balticconnector gas pipeline at the time of its rupture on 8 October, but it cannot identify what caused the signal, the group has told Argus.
Norsar recorded seismic signals near the Balticconnector at 01:20 local time on 8 October that indicate a "possible explosion", it said on Tuesday evening. This corresponds closely with when the Finnish and Estonian gas system operators noticed a sudden drop in pressure on the Balticconnector, after which it was taken off line.
The seismic signal was located roughly 40km north of Paldiski in Estonia, close to where the Balticconnector crosses Nord Stream 1, and the magnitude of the seismic reading is estimated at 1.0 on the Richter scale. This is "much lower" than the Nord Stream explosion detected in September last year, Norsar said. The Nord Stream explosions registered a magnitude of 2.3. The location and magnitude estimates are still associated with some uncertainties, although Norsar is more confident in them than it was last night, it told Argus, adding that "detecting this can be compared to finding a needle in a haystack".
Asked by Argus if the source of the seismic reading could have been the sudden depressurisation of the pipe as gas quickly leaked out, as opposed to an explosion caused by TNT or other such explosives, Norsar said this was possible and the "root cause of the explosion is yet to be determined". "A sudden rupture in the pipeline can set up the explosion we registered, as can detonation of explosives," its chief executive Anne Lycke told Argus. But the signal's characteristics mean that Norsar is sure that it was not the result of an earthquake, Lycke said.
This observation contradicts conclusions from Estonia's geological service that "seismic data does not confirm an explosion, or if there was one, it was below the detection threshold".
The Balticconnector leak was probably caused by "external activity", although the exact cause is "not yet known", the office of the Finnish presidency said on Tuesday.
Politicians, military comment on leak
Various politicians and military officials have commented on the investigation.
While coming to hasty conclusions should be avoided, if the damage to the pipe was intentionally inflicted, then the only party with any motivation to do so is Russia, the head of the Estonian parliament's foreign affairs committee, Marko Mihkelson said, according to state news agency ERR. "The event is severe, and alarming, and we can state that if it should be the case [that Russia is behind it], then this would have been to test our reactions, readiness, actions, procedures, and also to gauge how secure supply is," Mihkelson said.
"The picture we have from the pipeline tells us that the damage had to have been done by something greater than a diver or unmanned submersible," Estonian defence minister Hanno Pevkur said. Estonia will "discuss with partners and allies additional security measures for the Baltic Sea if needed," prime minister Kaja Kallas said.
The Finnish national bureau of investigation is investigating the incident as aggravated sabotage, the head of its investigation department Timo Kilpelainen said yesterday, according to state news agency YLE. Kilpelainen said he did not want to compare this incident with Nord Stream, but noted that the damage was so significant that a decision was made to open a preliminary probe of aggravated sabotage. "A sabotage of this calibre requires a certain amount of know-how and special equipment," Kilpelainen said.
"It is important that the case is thoroughly investigated and not to quickly jump to conclusions," Finnish prime minister Petteri Opro said, according to YLE.
"Something has torn asunder this pipeline, from one side to the other," the head of the Estonian navy, Commodore Juri Saska, told ERR. "The pipe itself is encased in concrete, while it looks just as if this was torn away on one side and the concrete has broken or peeled off, specifically at that rupture point."
