Results of 2‐ and 3‐D High‐Resolution seismic reflection surveying of surficial sediments

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Abstract
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 (≤ 2.5 m) and high‐fold (≥ 12) data were prerequisites for producing clear images at this site. For the 3‐D survey, an area of 115×160 m² was covered with common‐reflection points every 2.5×2.5 m². 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 ∼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.