In-Situ Ultrasonic Characterization of Patterns of Sediment Surface Roughness and Subsurface Volume Inhomogeneities.

摘要

Our goal is to take a mature technology that successfully images surface and sub-surface biogenic structure non-invasively in the laboratory (ultrasound) and convert the technology for use in marine systems in the field. We intend to convert one of our existing ultrasound machines (ALOKA SSD- 500) to a field-deployable unit by constructing a pressure housing for it waterproof to 50 m water depth. We will deploy the unit in the field with the use of divers during the summer in the sediments of Narragansett Bay, RI. Our research goal during field deployments is to determine patterns of sediment surface roughness to 1mm horizontal and vertical resolution and to determine the abundance of volume inhomogeneities (tubes, voids) in the upper 3 4 cm. We intend to sample before and after a sediment resuspension event, our hypothesis being that effects on subsurface volume inhomogeneities will be greater than effects on surface roughness patterns, similar to results of our laboratory studies. Based on laboratory results, simulated disturbance in the laboratory leads to the disappearance of subsurface volume inhomogeneities and a lesser smoothing of surface roughness features. The use of commercial ultrasonic sensors allows us to examine temporal patterns in biogenic structure and roughness on fine spatial scales (mm) without invasive disturbance.