Seismic monitoring of rock excavations, baseline at Olkiluoto nuclear waste repository site

The purpose of this work is to describe and define the benefits and drawback of the geophysical monitoring methods which can be utilized in the monitoring of nuclear waste repositories. The work concentrates on seismological tools only, and does not deal with any other geophysical methods which can be taken into consideration. The study was done by using the comprehensive seismic database of seismic events occurred in Fennoscandia and adjacent areas compiled by the Institute of Seismology. Online data from the Finnish national seismograph network station VAF is used to show the weekly and diurnal noise level variations. The station locates 200 kilometres from Olkiluoto area, and cannot present exactly the background noise at the repository site, but only shows the behaviour of seismic background noise, in general. Benefits and drawbacks of the seismic methods are discussed as well as future approaches of the seismic methods. (orig.)