Hypocentral distribution, focal mechanisms, and tectonic implications of Fennoscandian earthquakes, 1954–1978

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Abstract
Analysis of seismicity data for Fennoscandia for 1954–1978 has resulted in a comprehensive catalogue of 604 earthquakes, most of which with locations based on instrumental recordings. Detailed analysis of four well-recorded earthquakes near the NORSAR array has given very accurate focal depth estimates of 6,22,23 and 31 km, as well as one normal and two oblique-slip fault plane solutions. These and some other local events have been used for the construction of a crustal model for southeastern Norway. A short description is given of the outstanding 1978 Meløy earthquake sequence in northern Norway, where about 10 000 microearthquakes were recorded over only 10 weeks. The seismicity in the Oslo Graben area is taken to indicate that this is a general zone of weakness, with local geological conditions strongly influencing the focal mechanisms. There is increasing evidence suggesting that global tectonic movements are a key factor for the accumulation of regional stress in Fennoscandia.