Joint Land and Shallow-marine Seismic Investigations of Landslide Processes in the Bay of Trondheim, Mid-Norway

A combination of high-resolution shear-wave land-seismic and compressional-wave marine-seismic data was acquired to obtain information from the unconsolidated fjord-valley fill of the Trondheim harbour area, Norway. The sediments and overlying man-made fills were implicated in several near-shore mass-wasting processes, and land reclamation activities are still going on. A dense grid of high-resolution shallow marine seismics acquired over the prodeltaic sediments in the fjord was complemented by SH-polarized shear-wave reflection seismics on the land fill in the harbour. The shear-wave reflection seismic investigations achieved a highly resolved image of the fjord-valley fill, clear bedrock detection, and probably deeper structures. The bedrock surface is easily correlated between the marine (sleeve air-gun and sub-bottom profiling) and terrestrial seismic data sets. A few other major reflection events can be correlated between the land-seismic and the high-resolution marine data sets. This information enables shear-wave velocity calculation down to the bedrock and provides an indication of the stiffness of the sediments.