Seismic reflections from depths of less than two meters

Abstract

Three distinct seismic reflections were obtained from within the upper 2.1 m of flood‐plain alluvium in the Arkansas River valley near Great Bend, Kansas. Reflections were observed at depths of 0.63, 1.46, and 2.10 m and confirmed by finite‐difference wave‐equation modeling. The wavefield was densely sampled by placing geophones at 5‐cm intervals, and near‐source nonelastic deformation was minimized by using a very small seismic impulse source. For the reflections to be visible within this shallow range, low seismic P ‐wave velocities (<300 m/s) and high dominant‐frequency content of the data (∼450 Hz) were essential. The practical implementation of high‐resolution seismic imaging at these depths has the potential to complement ground‐penetrating radar (GPR), chiefly in areas where materials exhibiting high electrical conductivity, such as clays, prevent the effective use of GPR. Potential applications of these results exist in hydrogeology and environmental, Quaternary, and neotectonic geology.