Fracture zones or mafic sills?: Seismic waveform tomography at the Forsmark spent nuclear fuel repository, eastern central Sweden
2012 (English)In: Society of Exploration Geophysicists. Expanded Abstracts with Biographies, ISSN 1052-3812, 1-5 p.Article in journal (Refereed) Published
The Swedish Nuclear Fuel and Waste Management Company (SKB) has been carrying out extensive studies at the Forsmark nuclear waste repository site in the eastern part of central Sweden since 2002. An important component of the studies has been reflection seismic surveys which are useful for locating and characterizing sites for storage of spent nuclear fuel in the crystalline bedrock. Identification of sub-horizontal to gently dipping seismic reflections is especially important since these may represent transport routes for radionuclides. Studies have shown that such reflections can be generated by water filled fracture zones that have a lower velocity than the surrounding bedrock. However, lithological changes, I.e. mafic sills, may also be responsible for reflections in some cases. At the Forsmark site, it is difficult to distinguish fracture zones from mafic sills in the standard reflection seismic processed sections. However, since mafic sills usually have a positive velocity contrast with the background velocity field while fractures zones have a negative one, the two possibilities could be differentiated if we could reconstruct the underground velocity field. Waveform tomography has the potential to perform this reconstruction, and allowing us to discriminate between fractures zones and mafic sills. In this study we test this potential of seismic waveform tomography and conclude that the reflections investigated most likely are generated at low velocity fracture zones.
Place, publisher, year, edition, pages
2012. 1-5 p.
Inverse theory, Tomography, Seismic tomography, Controlled source seismology, Fractures and faults
Earth and Related Environmental Sciences Geophysics
IdentifiersURN: urn:nbn:se:uu:diva-187132DOI: 10.1190/segam2012-0697.1OAI: oai:DiVA.org:uu-187132DiVA: diva2:573792