Reflection coefficient calculation from marine high resolution seismic reflection (Chirp) data and application to an archaeological case study

Chirp sub-bottom profilers produce high-resolution images of the near-surfa ce An attribute of the sea-bed reflection in chirp data are fluctuations in polarity between adjacent traces. Two models are proposed and presented to explain this: the first incorporates changes in an acoustic impedance grad ient at the sea bed; the second uses changes in the thickness of the upperm ost sediment layer. Mixing of adjacent traces produces a consistent polarit y for the sea-bed reflector. Reflection coefficients are calculated, using amplitude information derived from single-traces, and polarity information from trace mixing, with application to a marine archaeological case study. The reflection coefficient calculated for the top of a buried 18th century wooden wreck is -0.26.