Spatial and temporal variations of Fennoscandian seismicity

• Published in: Geophysical Journal International
• Main Authors: Skordas, Efthimios, Kulhánek, Ota
• Format: Text
• Language: English
• Published: Oxford University Press 1992
• Subjects: Articles; Norway; Solberg; Fennoscandia; Fennoscandian
• Online Access: http://gji.oxfordjournals.org/cgi/content/short/111/3/577; https://doi.org/10.1111/j.1365-246X.1992.tb02113.x

We present an evaluation of the seismicity in Fennoscandia. b -values have been assessed for the region between 54–72°N and 4–32°E and for the time period 1967–83. A presented contour map with different b -values indicates the relative seismicity between different regions, during the time period considered. Strain release rate has also been mapped and recalculated to give the possible maximum-magnitude earthquake at a given point for time intervals of 17 and 90 yr. The observed time variation of b , in epicentral regions of some of the major earthquakes that occurred in Fennoscandia, reveals that b has the tendency to increase several years prior to the occurrence of the event and decreases again about two years before the event takes place. This has been the case for at least two of the major Fennoscandian events, i.e. for the Solberg 1983 earthquake in Sweden and the southwestern Norway event in 1989. On the other hand, similar changes in the behaviour of b have not been observed for the Skövde 1986 earthquake in southern Sweden. Space-time variations of b were studied for the region with the highest observed b -value, i.e. for the region between 64–68°N and 17–32°E (not associated with any particular event) as well as in the vicinity of the epicentre of the Solberg earthquake. We will be discussing temporal and spatial variations of b in relation to the state of stress in the region and we believe that a better understanding of the behaviour of b may well help our efforts towards medium-term earthquake prediction.