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Reprocessing of Geophysical Data, Comparison with Tunneling Results from the Bergen Ring-road and Subsequent RefractionNormal access

Authors: G.A. Tassis, J.S. Rønning, S. Rohdewald, T. Kirkeby and M. Wåle
Event name: 23rd European Meeting of Environmental and Engineering Geophysics
Session: Geophysics for Engineering Geology and Geotechnical Investigations II
Publication date: 03 September 2017
DOI: 10.3997/2214-4609.201702061
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 1.34Mb )
Price: € 20

The Geological Survey of Norway (NGU) has reprocessed various geophysical data from the Knappe tunnel in Bergen in collaboration with the Norwegian Public Roads Administration (NPRA) and Geophysix AS, the Geophysical company that originally collected, processed and traditionally interpreted refraction seismic data along the route of the tunnel. In this work we have compared different inversion schemes of refraction seismic data to each other but also to classic interpretations, resistivity profiles, geological mapping and actual observations done after the completion of the tunnel. In connection to the results obtained in the work described above, modeling was planned and carried out to test the efficiency of refraction seismic data inversion when applied to the detection of fracture zones in Norwegian settings (abrupt velocity changes between fracture, bedrock and possible overburden layers). Our goal is not to assess the Rayfract® software but instead to try and identify patterns created by known models when moderately knowledgeable inversion schemes are used and in this way attempt to correlate geophysical anomalies (seismic velocities) with weak zones on real refraction seismic data and plan future studies.

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