Temporal and Frequency-Based Variations in Seafloor Bathymetry and Acoustic Properties
Abstract
In previous years, we focused on acquiring (ONR surveys 2007-2009) and processing (HIPS and SIS from CARIS software) multibeam data from several shallow water sites in the Gulf of Mexico with multiple multibeam, side scan, and sub-bottom profiler systems, all acquired from the same vessel, at the same time, using the same motion reference unit and GPS. The preliminary results indicate a relatively large (>100m) amount of lateral seafloor movement in the West Delta area offshore Louisiana, proposed by the PIs to be related to mud flows triggered by hurricane events (Garcia-Garcia and Orange, 2010). The bathymetric data reveal several distinctively shaped (and thus traceable) blocks at the seafloor have been displaced downslope up to 140m over a 1.5 year period (Figures 1a and 1b). Our goal is to expand these preliminary observations and to quantify, on a per block basis, the vector motion (distance and direction) of each, where possible, and to understand the implications for the area and structures in it. Seafloor data acquired in the Panama City, Florida, area show seasonal, but less pronounced, differences in the seafloor between the surveys. Data acquired at the same time using two different frequency multibeam systems, a low frequency of 95 kHz and a high frequency of 300 kHz, demonstrated differences between the systems. In all our surveys, the lower frequency (95 kHz) yields a deeper seafloor depth than the higher frequency system; our preliminary interpretation is that the lower frequency system penetrates the uppermost (least consolidated) sediment in muddy areas an average of 0.4-0.8m in comparison to the high resolution (300 KHz) system (Figures 1c and 1d; other survey sub-areas document a difference of up to 2-3m at wreck sites). Our goal is to further investigate these differences. Recently, Scheider et al., 2010 have confirmed a difference in 8-10 m water bottom depth between a 12 kHz and 95 kHz system in 100m water depth, where the low frequency pen
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 2011
- Accession Number
- ADA557247
Entities
People
- Ana Garcia-garcia
- Daniel L. Orange
Organizations
- University of California, Santa Cruz