Research in Regional Seismic Monitoring
NORWEGIAN SEISMIC ARRAY (NORSAR) KJELLER
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During the last decades, a network of sensitive regional arrays has been installed in northern Europe in preparation for the global seismic monitoring network under the Comprehensive Nuclear-Test-Ban treaty CTBT. This regional network, which comprises stations in Fennoscandia, Spitsbergen and NW Russia provides a detection capability for the European Arctic that is close to mb 2.5, using the Generalized Beamforming GBF method for automatic phase association and initial location estimates. We have continued our studies to use data from the regional networks operated by the Kola Regional Seismological Centre KRSC and NORSAR to assess the seismicity and characteristics of regional phases of the BarentsKara Sea region, as well as the application to seismic event screening. We have studied the seismicity i.e. seismic events apart from confirmed nuclear explosions of the Western RussiaNovaya Zemlya region for the past 25 years, and found an average of less than one seismic event per year exceeding mb 3.5. Thus, the event occurrence in this region is so low that no event of mb 3.5 and greater located in this region should be screened out in the IDC screening process. The same consideration could apply in some other regions of the world, and the study of detailed seismicity patterns is an important part of the further screening developments. In discrimination studies, our results for the European Arctic show that the PS discriminant should be applied with great caution in this region, and further research is required. The regional MSmb discriminant has considerable promise, and the shorter-period energy available in surface waves recorded at regional distances can be exploited in improving the monitoring capabilities during periods with strong interfering surface waves from large distant earthquakes. We recommend that the current efforts to improve mb determinations and to reconcile the current mb values with the historic magnitude scale be continued.