Measurements of Sediment Interface and Subbottom Properties

This paper describes a series of measurements of sediment properties during SAX04 and discusses the implications of these properties to sediment acoustics. Between September 20 and October 30, 2004, 15 measurements were taken using IMP2, a sediment conductivity system developed to study sediment interface and subbottom properties. During this period, there were several weather events strongly influencing the sediment properties, ranging from Hurricane Ivan to a subsequent tropical storm. The IMP2 measurements clearly show the sediment ripple changes corresponding to the change of sea conditions. The large, non-symmetric ripples resulting from the hurricane decayed to a more symmetric form over time, while mud suspended in the water column was found trapped just beneath the interface. In between the weather events, biological activity on the bottom modified the bottom ripple features. Complementary cores were taken at the same sites where IMP2 was deployed, and cores confirmed the depth and location of the imbedded mud found by IMP2. Bottom roughness data were also taken at and near the IMP2 measurements using analog and digital stereo photography. These roughness measurements extend the IMP2 estimation of roughness power spectra to much higher spatial frequencies.

Presented at the International Conference on Underwater Acoustic Measurements: Technologies and Results, held in Crete, Greece, on 28 Jun-1 Jul 2005. Published in the Proceedings of the International Conference on Underwater Acoustic Measurements: Technologies and Results, 2005. Prepared in collaboration with Applied Physics Laboratory, University of Washington, Seattle, WA. The original document contains color images.