Earthquakes are a result of tectonic movements in the Earth’s crust. There is a decent amount of tectonic cracks in the Earth’s crust below the Baltics. For example, the Liepaja-Riga-Pleskava tectonic zone extends through Latvia’s territory from the south-west to the north-east from Liepaja to Valmiera and continues further to the east towards Pleskava.
But earthquakes can only appear if cracks are active. At the same time, it should be said that the overall activity of modern tectonic plates is not well-researched. A tectonic earthquake is a sign of an active tectonic crack. To be able to accurately predict earthquakes, it would be best to organize an observation system or create a so-called geodynamic monitoring. This monitoring includes seismological monitoring, water level and temperature measurements in boreholes and measurements of underground movements below the surface of the Earth, explains seismologist of Latvian Environment, Geology and Meteorology Centre Valery Nikulin.
There is a network of GPS stations in Latvia – LatPos. It has a total of 25 GPS stations. This network is mainly used for geodetic and cartographic purposes. But there is a possibility this network can be used for research of geodynamic movements.
According to historic data, there were three earthquakes near Lake Võrtsjärv in 1987. This information was acquired as a result of macro-seismic research. Earthquake intensity ranged within III-IV based on MSK-64 scale. There was another earthquake in the area even earlier – in 1823. Its intensity was IV-V based on MSK-64 scale. This makes Lake Võrtsjärv a relatively active seismic region.
Latvia has only one seismological station – Slitere. It is located in Dundaga. The station was opened in October 2006, it actively cooperates with Latvian State Environment, Geology and Meteorology Centre and Germany’s Earth Sciences Research Centre, located in Potsdam. GFZ helps coordinate international, global seismological monitoring network GEOFON. Cooperation with GFZ helps exchange data from other seismological monitoring stations in the Baltic region – Finland, Estonia, Lithuania, Poland, Denmark and Russia. This forms Baltic Virtual Seismic Network.
A total of 372 seismic events have been registered in the Baltic region over the course of 2016. 35 of those seismic events took place in Latvia, on the border between Latvia and Estonia and in the coastal area of the Baltic Sea. It is possible that there may have been more seismic events. Unfortunately, the range of BVSN is small, with an average coverage of 180 km for each station. The background of small seismic noises does not allow specialists identify weak seismic events, the specialist explains.
The last registered tectonic earthquake took place in Estonia, Pernava in February 2013. Its magnitude was modest – 1.1.
The small magnitudes of earthquakes commonly registered in the Baltic region may suggest that the Baltic region is a peaceful region. Nevertheless, it is important to remind of the most powerful earthquakes that took place in the regions in the past 40 years.
For example, an earthquake with a magnitude of 4.7 took place on Osmussaar Island in Estonia. After this earthquake, there had also been three weaker earthquakes or aftershocks.
In September 2004, two powerful earthquakes were registered in Kaliningrad with magnitudes of 5.0 and 5.2. Intensity of the earthquake reached 6-6.5 based on EMS-98 scale (modern counterpart of MSK-64 scale) in the epicenter. Kaliningrad earthquake had damaged 2,100 buildings, including schools and kindergartens, 20 people were seriously injured and one person died. Total losses reached USD 5.1 million.
Residents of Riga felt an earthquake in November 2010. Based on survey data and eyewitness reports, specialists concluded that tectonic shocks were caused by movement in Olaine-Incukalns and Bergu tectonic zone. Because Slitere seismological observation station is located 140 km away from the epicenter, it was not possible to isolate and identify the underground shock from regular seismic noise.
With that, the Baltic region has a relatively small seismic activity. Nevertheless, powerful earthquakes remain a possibility for the region.