Earthquake source parameters in Norway determined with empirical Green’s functions

Norway experiences low to intermediate seismicity, mainly caused by ridge push of the Mid-Atlantic ridge. To gain a better understanding of local tectonics and fundamental physics, we used the empirical Green’s function (EGF) method to obtain earthquake source parameters in Norway. We validated our findings against earthquake source parameters obtained from spectral analysis. Between January 1990 and May 2018, we found 263 earthquake pairs eligible for the EGF method. The local magnitudes of the 107 master events range between 1.3 and 3.4. Based on the Brune (J Geophys Res 75(26):4997–5009, 1970 ) source model, we obtained stress drops between 0.4 and 355 bar. We observed an increase of stress drop with earthquake size in southern Norway and the Svalbard archipelago. Calculated fault radii between 80 and 320 m suggest that larger magnitudes are caused more by increase in slip than by increase in fault dimension. Hence, our results indicate that smaller earthquakes in southern Norway and the Svalbard archipelago deviate from the assumption of self-similarity. Stress drops obtained for northern Norway show only weak correlation with seismic moment and therefore fit into the theory of earthquake self-similarity.