Abstract
The North Sea and Western Norway is one of the seismically most active areas of Northern Europe. Until about 1980, only larger events (M l ≥ 3.5–4.0) were observed. Since then around 20 high gain stations have been installed, lowering the detection threshold down to about magnitude 2.2 for the northern North Sea (56–64°N, 0–10°E).
Distribution of the observed northern North Sea seismicity is analyzed using two catalogues: A 110 year macroseismic catalogue, and an 8 year instrumental catalogue. Short term seismicity is compared with the long term seismicity in terms of spatial distribution, time distribution, energy release and estimated recurrence periods. The last 8 years of activity seems to be representative of longer time periods, and shows an overall agreement with the macroseismic catalogue in spatial distribution. However, the macroseismic catalogue gives a 2.5 times higher annual seismic moment release than the instrumental catalogue.
Two large events in the instrumental catalogue (March 1983 and February 1986) clearly show the classical feature of seismic quiesence preceeding the main shocks. These shocks also caused a seismic reactivation of adjacent areas.
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© 1989 Kluwer Academic Publishers
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Havskov, J., Lindholm, C.D., Hansen, R.A. (1989). Temporal Variations in North Sea Seismicity. In: Earthquakes at North-Atlantic Passive Margins: Neotectonics and Postglacial Rebound. NATO ASI Series, vol 266. Springer, Dordrecht. https://doi.org/10.1007/978-94-009-2311-9_24
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DOI: https://doi.org/10.1007/978-94-009-2311-9_24
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