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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy Department of Geology, 06520, Ankara-TURKEY, Tel:+90 312 2873430, Fax: +90 312 2854271, e- mail:cengizyildirim@mta.gov.tr 5- O 6- PC 7- YES 8- Omer Emre: YES, Cengiz Yildirim: YES, Ahmet Doğan:NO, Fuat Şaroğlu:NO 9- NONE Keywords: activefaults, kinematic, nw anatolia

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy (S) - IASPEI - International Association of Seismology and Physics of the Earth's Interior JSS004 Oral Presentation 1896 Deglacial earthquakes in Fennoscandia can be reconciled with stablecraton-core earthquake rates Dr. John Adams Geological Survey of Canada Geological Survey of Canada IASPEI It is believed that the weight of the Greenland and Antarctic ice sheets inhibits current earthquake activity (Johnston's 1987 hypothesis), and that when the Scandinavian ice sheet melted the stored strain energy was released in a burst of large earthquakes in immediate deglacial times. I test the hypothesis that, allowing for this effect, the long-term seismicity rate in Sweden is substantially the same as that of other Stable Craton Cores (SCCs). I tried to reconcile the per-unit-area rate of magnitude > 6 earthquakes from a) the low contemporary seismicity rate in Sweden, b) the high seismicity rate that occurred immediately following deglaciation, and c) the much lower rate from the past 8000 years (both b and c were taken from available paleoseismic catalogs) with the global SCC rate. The reconciliation needs an assessment of the completeness of the information and some additional assumptions. I conclude that the Swedish deglacial earthquakes appears to represent the release of ~50,000 years strain accumulation at a typical stable craton seismic activity release rate. In the long term, about 8 to 15 earthquakes of moment magnitude 6.0 or greater might be expected within a 100-km radius of a site during a future 100,000 year period (the full uncertainty is much larger than this best-estimate range). Past history indicates that much of this activity might be concentrated into a relatively short time window in the more distant future, or alternatively the analysis places a limit on the probability of a M>6 event in the near future. Keywords: deglacial, earthquakes, sweden

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