Results of 2- and 3-D high-resolution seismic reflection surveying of surficial sediments

To investigate the potential of seismic reflection methods for studying surficial sediments, 2- and 3-D high-resolution surveys have been conducted across a plot of land adjacent to a landfill in northern Switzerland. Results of the reflection profiling demonstrated that closely spaced common-reflection points (less than or equal to 2.5 m) and high-fold (greater than or equal to 12) data were prerequisites for producing clear images at this site. For the 3-D survey, an area of 115 x 160 m(2) was covered with common-reflection points every 2.5 x 2.5 m(2). Three-dimensional migration of the resultant 18- to 70-fold data proved to be a critical step in correctly locating out-of-plane reflections and collapsing diffractions that were prominent features in the 2-D profile data. Within the 3-D data volume a conspicuous reflective zone and a marked decrease in reflection amplitudes at similar to 200 m depth delineates the bedrock surface. Immediately above this level are continuous reflections from flat-lying lacustrine sediments. These are in turn overlain by regions of strong reflected energy interpreted as either large erratic blocks, anomalous compaction zones, or gravel channels/lenses.