On Christmas Day, many Helsinki residents were startled by an earthquake. Yle reported that the police received multiple reports of a loud bang in the Käpylä area.
Toni Veikkolainen, a seismologist from the University of Helsinki said that the earthquake had a magnitude of 1.1 on the richter scale — it was the strongest earthquake recorded in Helsinki's measurement history.
Veikkolainen mentioned that citizen reports came from areas like Vallila, Käpylä, and Haaga.
"If this had occurred in the Baltic Sea or some remote wilderness, there might not have been any citizen reports," he said.
The earthquake shook the ground at around 6:30 pm and lasted less than a minute.
The epicentre of the earthquake was located in the Käpylä Olympic Village, near the intersection of Mäkelänkatu and Koskelantie.
The exact cause of the earthquake is not yet clear, but at this stage, it doesn't appear to be caused by human activity.
According to Veikkolainen, natural earthquakes in Finland are caused by factors such as the expansion of the Atlantic, land uplift, and local movements of water masses in the bedrock.
Residents report a loud bang
The earthquake was clearly heard and felt in Käpylä, near the northern end of Mäkelänkatu, according to Yle reporter Otso Karhu, who was on site.
"The sudden loud bang cut through the noise of traffic. I felt the tremor in my legs and body. I wouldn't have fallen because of it, but I was definitely startled."
Seismologist Veikkolainen explains that it is normal to hear a bang from an earthquake. He added that the seismic activity occurred near the surface, which is why the sound was more distinct.
"If it had originated deeper, the sound from the same-sized earthquake would likely have been more muffled."
Rare occurence
According to Veikkolainen, around a hundred earthquakes are detected annually in Finland. For instance, Helsinki experienced two earthquakes of less than one magnitude in September.
Veikkolainen states that an earthquake like the one on Christmas Day hasn't been felt in the Helsinki metropolitan area for over a decade.
The most recent natural earthquake in the region with a magnitude over one occurred in 2013. This 1.7 magnitude earthquake took place in Espoo.
The most significant earthquake in recent history in the nearby area occurred in Mäntsälä in 2011 with a magnitude of 2.6.