Chief Scientists

David Knobles
Research Scientist
Knobles Scientific and Analysis, LLC

Preston Wilson
Professor
ARL:UT, UT Mech Eng Dept

SBCEX

Seabed Characterization Experiment

Experiment Overview

The Seabed Characterization Experiment will take place in 2017 at the site of the New England "Mud Patch" which is located 110 km south of Cape Cod, Massachusetts. This region is characterized by smooth bathymetry and a high content of silt and clay sized particles.

The main objectives of the Seabed Characterization Experiment are (1) to understand the physical mechanisms that control propagation in fine-grained sediments, (2) to quantify uncertainties in estimated seabed parameters, and (3) to assess the resulting geoacoustic models and inversion methods. These goals will be accomplished by obtaining direct measurements and/or inferring the values of the following parameters: compressional wave speed and attenuation, shear wave speed and attenuation, seabed roughness and volume scattering, and seabed layering and gradients. An emphasis will be placed on obtaining parameter values over a wide frequency band and on understanding the deterministic versus stochastic part of environment. The effects of parameter uncertainty will be quantified and a mapping parameter uncertainty to transmission loss uncertainty will be pursued. An understanding of how the seabed characterization affects sonar performance predictions, including effects on transmission loss, reverberation, clutter, ambient noise, and array coherence, will be sought.

Pilot Experiment

The Seabed Characterization Pilot Experiment was conducted in the late summer of 2015 on the R/V Sharp. The experiment consisted of two legs, with the first leg of the experiment concentrated on chirp and multibeam surveys and the second leg of the experiment focused on sediment coring. The measurements made during the pilot experiment are described below.

Chirp Survey

Multibeam Bathymetry Survey

Coring

Combustive Sound Source
Image 1, samples of mud from the seafloor
Bringing up samples of mud from the seafloor with the box core.
Image 2, A brittle star collected from the seafloor
A brittle star collected from the seafloor. Photo credit: Kelly Dorgan.
Image 3, brittle star inside the acoustic resonantor tube
A brittle star inside the acoustic resonantor tube. Photo credit: Gabe Venegas.
Image 4, TIG scanfish
UTIG scanfish. Photo credit: David Knobles.
Image 5, ARL:UT Combustive Sound Source
ARL:UT Combustive Sound Source. Photo credit: David Knobles.
Image 6, dolphins riding the bow wave
Dolphins riding the bow wave. Photo credit: Jason Sagers.
Image 7, container ship
Container ship on northern boundary of survey area. Photo credit: David Knobles
Image 8, deployment of the gravity core
Deployment of the gravity core.
Image 9, recovery of the gravity core.
Recovery of the gravity core.
Image 10, processing cores from the multicore
Processing cores from the multicore.
Image 11, the multicore on the fantail at sunset
The multicore on the fantail at sunset.
Image 12, deploying the parametric sonar at night
Deploying the parametric sonar at night.
Image 13, cutting a gravity core for measurement and storage
Cutting a gravity core for measurement and storage.
Image 14, transporting a core sample
Transporting a core sample collected by the multicore. Photo credit: Megan Ballard.
Image 15, marking a gravity core for cutting
Marking a gravity core for cutting. Photo credit: Megan Ballard.
Image 16, image of the seafloor
An image of the seafloor captured by a camera on the multicorer. Photo credit: Ellen Rossen.
Image 17, cutting a gravity core into 1 meter lengths
Cutting a gravity core into 1 meter lengths for measurement and storage. Photo credit: Megan Ballard.
Image 18, seapen found on the foot of the multicore
A seapen found on the foot of the multicore upon recovery. Photo credit: Megan Ballard.
For comments and questions, contact the webmaster at sbcex@arlut.utexas.edu