The Reconstruction of the pre Storegga Slide Seafloor and Stratigraphy Using a Dense Grid of 2D Seismic Records.

Wednesday, 17 December 2014
Carl Fredrik M Forsberg, Norwegian Geotechnical Institute, Oslo, Norway
This work was performed as part of the Storegga Slide study that was part of the Ormen Lange Gas Field development on the Mid Norwegian continental margin. The purpose of the reconstruction was to use seismic reflection data as a basis to provide slide volume estimates, pre slide stratigraphy and seafloor morphology that could be used as input to separate conceptual and numerical slide models.   A comprehensive database of 2D high resolution and 2D exploration seismic reflection profiles was used. Additionally, the seismic stratigraphy on both sides of the Storegga Slide scar was well known, but had to be applied/interpreted on most of the seismic sections in the database to provide geographical grids of the horizon depths.    The reconstruction was performed by "filling" The Storegga Slide scar from bottom up through interpolation and gridding of the thicknesses of successively younger units removed by the slide.    The estimated volume of the slide was 3500 km3 with a maximum removal of 500 m of overburden. The loss of overburden due sliding estimated from the reconstructon was confirmed at several sites where geotechnical boreholes had been drilled.