Inhabitants of the tiny Baltic Sea island of Bornholm, near last year's Nord Stream pipeline explosions, were alarmed Saturday when "acoustic pressure waves from an unknown source" sparked tremors, as first reported by AP News.
Around 3 pm local time, GEUS, the Geological Survey of Denmark and Greenland, said they received dozens of calls from Bornholm residents about the ground shaking. Seismologists initially thought the source of the earthquake was a controlled explosion in nearby Poland but have since ruled that out.
"The seismologists can report that it is unlikely that the tremors originate from a controlled explosion in Poland, which was carried out shortly before the first reports of tremors on Bornholm," GEUS said.
GEUS said the tremors were "most likely acoustic pressure waves from one or more events somewhere in the atmosphere." It noted the seismic tremors were of a magnitude of 2.3. It wasn't clear what "caused these powerful pressure waves."
GEUS' seismographs located all over the country picked up tremors.
The small island is close to the site where both blasts destroyed parts of the Nord Stream pipeline last September.
Authorities have yet to reveal who was behind the Nord Stream pipeline attack, but journalist Seymour Hersh has reported the US blew up the Russia-to-Germany natural gas pipeline as part of a covert operation under the guise of the BALTOPS 22 NATO exercise.