Reflection seismic imaging of the deeper structures at the Forsmark spent nuclear fuel repository site, central Sweden
2013 (English)In: Journal of Applied Geophysics, ISSN 0926-9851, Vol. 89, 21-34 p.Article in journal (Refereed) Published
The Forsmark area belongs to the Paleoproterozoic Svecokarelian orogen (c. 1.9-1.8. Ga), the principal geological entity inside the Fennoscandian Shield, and is the site where Sweden has proposed to store its spent nuclear fuel. Three major sub-vertical (at the surface), composite ductile and brittle deformation zones that strike in a WNW or NW direction are present in the area. In between these zones the bedrock is less deformed and considered suitable for a repository. We present reprocessed reflection seismic data from seven profiles in which we have focused on improving the images in the depth range 1-5. km by passing lower frequencies through the processing flow at the cost of poorer resolution in the near-surface realm. The new images indicate that sub-horizontal to moderately dipping structures are possibly more extensive at depth than previously thought. Three main deeper reflective zones have been identified, one that is sub-horizontal and two that dip moderately to the southwest. The sub-horizontal reflective zone may represent a 1.27-1.26. Ga dolerite sill at about 3. km depth. One of the moderately dipping reflective zones may originate either from another dolerite sill or from a brittle fault system. The other moderately dipping structure may be present throughout most of the area and could cut all three sub-vertical deformation zones at depth. The new images and corresponding interpretation do not require a re-evaluation of the Forsmark site for storage of spent fuel, but they do influence how to interpret the deeper structures and, as a consequence, the tectonic evolution of the area.
Place, publisher, year, edition, pages
2013. Vol. 89, 21-34 p.
Borehole, Crustal structures, Dolerite, Imaging, Shear Zones, Brittle deformation, Crustal structure, Deformation zone, Depth range, Fault system, Fennoscandian Shields, Geological-entities, Lower frequencies, Near-surface, Paleoproterozoic, Processing flow, Re-evaluation, Reflection seismic, Reflective zones, Shear zone, Spent nuclear fuel repository, Spent nuclear fuels, Tectonic evolution, Boreholes, Deformation, Gallium, Imaging techniques, Radioactive wastes, Seismology, Spent fuels, data interpretation, diabase, ductile deformation, orogeny, radioactive waste, repository, seismic data, seismic reflection, seismic tomography, structural geology, Forsmark, Sweden, Uppsala [Sweden]
IdentifiersURN: urn:nbn:se:uu:diva-194879DOI: 10.1016/j.jappgeo.2012.11.008ISI: 000315541100003OAI: oai:DiVA.org:uu-194879DiVA: diva2:606723