Date of Award

Winter 2016

Project Type

Thesis

Program or Major

Earth Sciences

Degree Name

Master of Science

First Advisor

Andrew A. Armstrong

Second Advisor

Thomas C. Weber

Third Advisor

John E. Hughes Clarke

Abstract

A reliable understanding of seafloor characteristics can have innumerous application in a variety of fields of knowledge, such as ocean mapping and defense. In the last decades, studies associating backscatter intensity to seafloor characterization has increased based on the principle that different types of seabed may provide, a priori, different reflectivity responses patterns. Those differences in intensity can be used to attempt seafloor classification.

This thesis proposes to evaluate the potential usage of multi-frequency backscatter as an additional tool for seafloor characterization. Modern multibeam systems are able to provide high resolution bathymetry and backscatter data. The echosounder used to collect data for this research was a Kongsberg EM 2040, which can transmit using three different center frequencies (200, 300 and 400 kHz). The dataset was collected using the three available frequencies and it was investigated under two different perspectives: The first consists of interpreting how backscattering strength curves may vary when the same frequency is used to ensonify different types of substrates. This approach can be used to establish a connection between acoustic wavelength and intensity levels, and the results can have a huge application in seafloor characterization. The second consists of verifying the existence of any frequency dependency when the same type of seabed is ensonified with different frequencies.

In addition to the two types of investigation listed in the previous paragraph, some of the corrections that had been applied to the raw data during the data acquisition process were compared to more accurate post-processing models. Those comparisons were made in order to evaluate if the approximations made by the acquisition software could impact the usage of BS as a seafloor characterization tool.

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