Geostatistical methods applied to characterization of the heterogeneity of the migmatite formation at Olkiluoto, western Finland

Geostatistical methods were applied to study the character of the heterogeneity of the bedrock in the Olkiluoto area - a possible nuclear waste site in Finland. The structural model was deduced from the geological interpretations made earlier in the area and from the variogram analysis. Rock type, as a categorical variable, was mapped with sequential simulation and with the indicator principal component simulation (IPCS). In the Olkiluoto area, the latter method proved to produce more reliable images of the bedrock than the sequential simulation. The simulations indicate that the bedrock of Olkiluoto is rather heterogeneous. The accuracy of the simulations could be improved by using geophysical data and an advanced geological model incorporating the variation in the tectonic directions in the study area.