Seismicity and seismic hazard

Our research is focused on determining source mechanisms for recent earthquakes in Finland, on identifying active faults associated with earthquakes, and on gaining informa­tion on the in situ stresses causing earthquakes. We also develop automatic methods for analysing seismic events recorded by a sparse regional network.

Seismic hazard studies associated with nuclear power plants and enhanced geothermal systems are one of the recent topics.

The Working Group on Historical Seismology in Northern Europe was established in 2003. Northern Europe covers Fennoscandia, the Baltic countries and NW Russia, and ‘historical' refers to pre-instrumental times. Most of the work focuses on the years between 1750 and 1960. At this stage of analysis only macroseismic datasets are under investigation. The working group has two main objectives: to create a digital database of historical earthquakes in Northern Europe and to investigate the earthquakes using modern methodologies.

The first objective is quite practical. Information on historical earthquakes in the region can currently be found in numerous reports, often written in local languages, and may be somewhat arduous to find. A digital database is a very convenient means to store and investigate these observations.

Besides constructing the database, the Working Group aims at studying pre-instrumental earthquakes in the region with the help of recent geoscientific knowledge and modern methodologies. Many of the available studies are contemporary with the earthquakes and do not meet the research standards of today.

The participating institutions are currently

  • Department of Information Science, University of Uppsala, Sweden; 
  • Kort & Matrikelstyrelsen, Copenhagen, Denmark; 
  • Department of Earth Science, University of Bergen, Bergen, Norway; 
  • National Research Institute of Astronomy and Geophysics, Cairo , Egypt; 
  • Institute of Seismology, University of Helsinki, Helsinki, Finland; 
  • Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia; 
  • State Geological Survey of Latvia, Riga Latvia;
  • Geological Survey of Lithuania, Vilnius, Lithuania

From the Institute of Seismology: 
Päivi Mäntyniemi

The instrumental seismicity record must be viewed in conjunction with the pre-instrumental (historical) data to obtain an improved perspective on seismicity. This is especially important in less active regions such as the Fennoscandian Shield.

Written documents testifying to the effects of earthquakes in different times and places are investigated. Original documentation is typically preferred to copies, and eyewitnesses and experts have the highest priority as authors. The textual information needs to be parameterized for seismic-hazard analyses. The research is pursued along two avenues: by studying individual key earthquakes and by developing methodologies suited for the region.

One project targets the border region between Finland and the Russian North. The region is divided by different state borders in the past, language, and traditions, all of which pose obstacles in the study of pre-instrumental seismicity. The ongoing initiative aims at overcoming these obstacles by investigating the earthquakes in co-operation between seismologists from the contiguous countries.

 

Project Evogy addresses the issue of Ground Motion Prediction Equations (GMPEs) needed for seismic-hazard analyses. In the computation of the probability of ground motion exceedance, the specification and parameterization of a seismic source model must be accompanied by appropriate relations for ground motion attenuation. A database of seismic recordings of the Finnish National Seismic Network is constructed and used to develop a GMPE for Finland and adjacent areas covering the frequency range of engineering interest.

The project is carried out in cooperation between the Institute of Seismology of the University of Helsinki and the VTT Technical Research Centre of Finland Ltd.