VÄINÖN VÄRINÄ - THE LARGEST EARTHQUAKE IN THE HISTORY OF FINLAND
Did you know that the largest earthquake in the history of Finland occurred near Lake Lappajärvi?
The earth shook one ordinary Saturday night, on February 17, 1979 at 7.31. The earthquake received a memorial stone in 1992, which is now located in Alajärvi, in the yard of Luoma-aho nuorisoseuratalo. Väinön Värinä name comes from a name day which is celebrated by Väinö on the day of the earthquake.
Tip! Take your friend to the memorial stone and read the story together (link to the map at the end of the post).
The earthquake was 3.8 degrees on the Richter scale and its effects were noticeable in radius of about 100 kilometres.
The earthquake caused minor damage to the buildings. Less than ten minutes later there was another, quite strong earthquake for Finnish conditions - 2.6 on the Richter scale. It was noticeable within radius of about 70 kilometres.
According to geologist Teemu Öhman: "Finland is a geologically and seismically stable area. Earthquakes are very weak compared to other places in the world. Nevertheless about 15-30 earthquakes occur here annually. Most of them can only be detected by measuring devices. The main cause of earthquakes in Finland is the movement of continental plates: Eurasian and North American“.
Preliminary analysis showed that the center of the earthquake was exactly where the memorial stone is located nowadays at a depth of about 15 km, and the next quake three kilometres to the southeast. However, in 1986 the measurements were even more precise and showed the earthquake points located on the Pokela and Katajalahti side. Based on the latest survey from 2002, the Väinön Värinä earthquake occurred at a depth of 10 and 9 kilometres between Lakaniemi and Pyhälahti in Vimpel. Although the exact position cannot be given, it is certain that the Väinön Värinä earthquake occurred between Vimpeli and Alajärvi.
Particularly interesting is the fact that Väinön Värinä occurred inside the crater's rim, in the so-called terrace zone. It was mentioned for the first time in 2003 in Andreas Abels’ work. Terrace zones on the inner rim of impact crater are areas where it takes long time for the parent rock to recover. On the other hand, the period of 76 million years (Lappajärvi age) is very short compared to Finland's geological history, which is 3,000 million years long. The meteorite impact during the birth of Lake Lappajärvi was 5 km deep and cracks caused by the impact are noticeable at a depth of at least 10 km. It therefore is likely that the primary reason for Väinön Värinä earthquake to occur was the movement of the rock blocks at the rim of the crater as they still try to achieve their previous state.
Seven other earthquakes took place in or near Lappajärvi crater. Two of them occurred in summer of 2017. Two other earthquakes have been recorded inside the crater’s rim since 1970. It is not a coincidence: the asteroid collision 78 million years ago still has impact on the subsoil of lake Lappajärvi and its surroundings. It is possible that a similar earthquake will take place here soon.
Kraatterijärven Georeitti, destination 14
Memorial stone: Google Maps
