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STN-01 General contributions to neotectonics
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The 21st february 2008 svalbard earthquake: Relative location of the aftershock sequence and seismotectonic interpretation
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Myrto Pirli, NORSAR (Norway)
Steven Gibbons, NORSAR (Norway)
Hilmar Bungum, NORSAR (Norway)
Johannes Schweitzer, NORSAR (Norway)
Tormod Kværna, NORSAR (Norway)
Kuvvet Atakan, University of Bergen (Norway)
Jens Havskov, University of Bergen (Norway)
Lars Ottemøller, British Geological Survey (United Kingdom)
Mohammed Raeesi, University of Bergen (Norway)
Aleksander Guterch, Polish Academy of Sciences (Poland)
Wojciech Debski, Polish Academy of Sciences (Poland)
Pawel Wiejacz, Polish Academy of Sciences (Poland)
Michal Sawicki, Polish Academy of Sciences (Norway)
Berit Paulsen, NORSAR (Norway)
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A strong earthquake with a preliminary moment magnitude of about 6.0 occurred in Storfjorden off Svalbard, on 02:46 UTC 21st February 2008. The source of the event was located in the lower crust, approximately 85 km from Hornsund and 155 km from Longyearbyen. The USGS double-couple fast moment tensor solution describes normal-oblique strike-slip faulting. The sea region around Bear Island, situated south of Svalbard, constitutes the target area of an International Polar Year project that studies the continental margin, including deployment of new high-quality broadband instruments. The above mentioned earthquake, as well as the vast number of aftershocks that followed, were recorded by a number of seismic stations in the region. The geographic distribution of these stations, (Hornsund - HSP, the Spitsbergen array - SPITS, Hopen Island - HOP, Bear Island - BJO, and Ny Aalesund - KBS) enables the recording and analysis of the aftershock sequence. Array-based waveform correlation techniques applied to Spitsbergen array data provide an image of the clustering within the aftershock sequence. The addition of the 3-component single stations forms the basis for high accuracy relative location of the recorded events and the detailed mapping of their spatial distribution. When combined with the fault slip inversion results, the aftershock distribution provides a unique opportunity to study the details of the source rupture process. There are several potential factors that could explain the event, namely plate related forces, stresses related to lateral variations in crustal structure, and erosion and sedimentation processes. The EW maximum compression expressed by the moment tensor solution is a characteristic that has been observed before in the region.
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