2.5-D seismic tomographic modelling of the crustal structure of north-western Spitsbergen based on deep seismic sounding
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ORIGINAL RESEARCH PAPER
2.5-D seismic tomographic modelling of the crustal structure of north-western Spitsbergen based on deep seismic soundings Wojciech Czuba
Received: 22 November 2006 / Accepted: 6 July 2007 / Published online: 1 August 2007 Springer Science+Business Media B.V. 2007
Abstract Deep seismic sounding measurements were performed in the continent-ocean transition zone of the northern Svalbard continental margin in 1985 and 1999. Data from seismic profile AWI-99200 and from additional crossing profiles were used to model the seismic crustal structure of the study area. Seismic energy (airgun and TNT shots) was recorded by land (onshore) seismic stations, ocean bottom seismometers (OBS), and hydrophone systems (OBH). 3-D tomographic inversion methods were applied to test the previous 2-D modelling results. The results are similar to the earlier 2-D modelling, supplemented by new off-line information. The continental crust thins to the west and north. A minimum depth of about 6 km to the Moho discontinuity was found east of the Molloy Deep. The continent-ocean transition zone to the east is characterized by a complex seismic velocity structure according to the 2-D model and consists of several different crustal blocks. The zone is covered by deep sedimentary basins. Sediment thicknesses reach a maximum of 5 km. The Moho interface deepens to 28 km depth beneath the continental crust of Svalbard. Keywords 3-D seismic modelling Continental margins Crustal structure Svalbard Tomography
Introduction Spitsbergen is the main island of the Svalbard Archipelago located in the north-western corner of the Barents Sea W. Czuba (&) Institute of Geophysics, Polish Academy of Sciences, ks. Janusza 64, Warsaw 01-452, Poland e-mail: [email protected]
continental platform, and bordered by passive continental margins to the west and north (Fig. 1, insert map). The region is an interesting and important area for understanding the evolution of the North Atlantic and Arctic Oceans. This is the youngest region of the Atlantic and Arctic Oceans giving a good source to study processes leading to their opening. The development of these continental margins is strongly connected to the history of rifting and subsequent sea-floor spreading in the North Atlantic Ocean (Jackson et al. 1990; Lyberis and Manby 1993a; Lyberis and Manby 1993b; Ohta 1994). The Svalbard continental margin has been studied by geophysical surveys over the last 30 years, mainly based on multichannel seismic reflection, sonobuoy refraction, gravity and magnetic measurements. However previous investigations provided only limited information about the crystalline basement and deep crustal structure of this area (e.g., Guterch et al. 1978; Sellevoll 1982; Davydova et al. 1985; Faleide et al. 1991; Sellevoll et al. 1991; Czuba et al. 1999). This article presents results of seismic studies in the region (Fig. 1) across a transition zone between oceanic and continental crust, including sedimentary basins, fracture zones and, presumably, a spreading zone.
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