Blackwell Publishing Journal Backfiles 1879-2005
Data collected by temporary seismic networks and individual stations over a 7-yr period in the Svalbard Archipelago are integrated and used to study the seismicity and present-day tectonics of the archipelago and surrounding regions. Most of the continental seismic activity occurs in three concentrated zones, one in Heer Land near the eastern coast of the island of Spitsbergen and two, in close proximity to one another, on the island of Nordaustlandet. All three zones are in regions which have been devoid of major orogenic activity since the late Devonian. the Heer Land zone and at least one of the zones in Nordaustlandet define active faulting which has not been identified by surface mapping. the other zone in Nordaustlandet occurs in the region of a mapped system of faults, all branches of which are relatively minor. A number of smaller concentrations and individual earthquakes occur throughout much of the archipelago and surrounding continental shelves. Seismicity is currently low in the region of Tertiary orogenic activity in western Spitsbergen. A roughly linear pattern of minor activity in southern Spitsbergen occurs west of the Heer Land zone and extends at least 50 km southward. the major N-S faults in Spitsbergen which are thought to have accomodated large displacements in Devonian time are currently inactive, except perhaps at the southern termini of the Billefjorden and Lomfjorden fault zones, where they approach the Heer land seismic zone. Earthquakes located near the western continental margin of Spitsbergen may occur on segments of rifting and shearing which reflect the opening of the Greenland Sea during the Tertiary. the limited extent of the currently active zones of activity, their spatial stability over several years, and the lack of activity on the major faults of Svalbard argue against the existence of plate boundaries, along which motion is currently occurring, in the Svalbard region.All fault-plane solutions on Svalbard are consistent with a stress field characterized by E-W compression, whereas previously published fault-plane solutions for the ridge system west of Svalbard indicate E-W extension. the magnitude of the compressive stress increases from small values near the ridge system to values sufficiently large to dominate the regional seismicity of Svalbard over distances of 200–300 km.
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