The sabotage attack on the Nord Stream-1 and Nord Stream-2 gas pipelines was probably planned in advance. For this, they could use an explosive device that was thrown into the sea a few weeks before its detonation. This is reported by The Times.
Concrete and steel pipelines are said to have been ruptured by apparent underwater explosions of the magnitude of a minor earthquake.
According to a British defense source, the most likely scenario was that Russia secretly delivered an autonomous underwater vehicle with cargo to separate locations on pipelines built to transport Russian gas to Europe.
The submersible could have been launched from a small vessel, such as a fishing boat, months ago, and then the explosive devices were dropped alongside the pipeline. Yes, the devices could be triggered by a noise source of a certain frequency, which was dropped into the water at the right moment.
Björn Lund, a member of the Swedish Seismological Network, noted that more than 100 kg of dynamite or TNT could be needed to cause such strong explosions.