Causality between interplate (North Atlantic) and intraplate (Fennoscandia) seismicities

Abstract

Annual seismic energy release patterns have been calculated, for the time period 1917–1987, for Fennoscandia and the North Atlantic Ridge (NAR) between 40° N and 80° N. A brief visual comparison shows the great similarity between the energy release patterns in Fennoscandia and individual segments along the NAR. To express the observed resemblance quantitatively and to provide an objective test of the phenomenon, systematic cross-correlations between seismicities along various NAR segments and in Fennoscandia were carried out. The cross-correlations obtained are statistically significant and show maximum values for time lags mostly between 0 and −3 years. Negative time lags mean that the energy release in the NAR precedes that in Fennoscandia. The closest similarity is found between Fennoscandia and the ridge segment between Iceland and Jan Mayen (66°–71° N). Periodicities of 8, 13 and 38 years are seen in the energy release from both regions. The significant cross-correlations and consistent periodicities in the temporal patterns of seismic energy release along the NAR and in Fennoscandia serve as an indication of a tectonic connection between the interplate (NAR) and intraplate (Fennoscandia) seismicities.