Residents on the Danish Baltic island of Bornholm felt a series of tremors on Saturday that rumbled, rattled, and even changed pressure in the ears of some people, according to AP News. But the source of the mini-quakes is unknown.
At first scientists thought that a nearby earthquake must have been the source of the shaking. When that was ruled out, they considered Poland's controlled explosions, about 90 miles away, as a possible source, but later said this theory was "unlikely." Now seismologists are pointing to "acoustic pressure waves" — but the source of these waves? "Unknown."
From AP News:
On Monday, the Geological Survey of Denmark and Greenland, an official body that monitors the underground, said the tremors were "not caused by earthquakes, but by pressure waves from an event in the atmosphere." However, they came from "an unknown source."
"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," the body known as GEUS said in a statement.
On Saturday, GEUS said it had received "more than 60" tips from people on Bornholm that "earthquake-like tremors" – described as a deep rumbling, shaking and rattling, changing pressure in the ear — had been reported in the afternoon on Bornholm. …
Police said they too were contacted by members of the public about the tremor on the eastern part of the island. Danish media reported that the tremors caused a crack in the wall of a house.
Fortunately, with a magnitude that reached only 2.3, nobody was hurt on the island of about 40,000 people.