A seismologist confirms that the booms heard in Eno and Varkaus this week were earthquakes.
According to Oinonen, the earthquake east of Eno was a magnitude 2.3 earthquake.
– The quake has been very shallow, at a depth of 1-2 km.
The Varkaus earthquake, on the other hand, had a magnitude of 1.7.
– There has been another earthquake in Varkaus some time ago in a different place than this one on Sunday evening. It doesn’t shake very often there either.
Earthquakes are rare in eastern Finland
The most active areas for earthquakes in Finland are Kuusamo, Kouvola and the border area between Finland and Sweden.
Earthquakes are rare in Eastern Finland. They occur from time to time, even less often than annually. For example, according to Oinonen, no earthquakes have been detected in Eno before.
– The tension has been building up there in the bedrock for such a long time that now it was able to be triggered. The tension is caused by the fact that now the Atlantic is spreading and it produces tension in the bedrock even here in Finland.
There are up to a hundred earthquakes in Finland every year. The number has increased slightly, because nowadays there are more precise local networks, which allows us to detect even much smaller earthquakes.
– When smaller and smaller earthquakes are seen, their number also increases.
Oinonen believes that the number of earthquakes will remain pretty much the same in the future.
But how do you recognize an earthquake? According to Oinonen, similar signals come from explosions and collapses in addition to earthquakes.
– In explosions and earthquakes, the energy is distributed to different frequencies in different ways. It can be used to determine whether it is an explosion or an earthquake.