Acoustics Bottom Characterization/Inversion

Bottom Characterization/Inversion
SW06 Workshop
1 February 2007
• Develop geoacoustic models for the SW06 site
• Synthesize regional geoacoustic information to develop
comprehensive models across 50 Hz - 20 kHz incorporating
known geoacoustic variability over the SW06 area
• Estimate geoacoustic model parameters using different inversion
methods and characterize their uncertainty
• Assess performance of different geoacoustic inversion methods
and quantify impact of water column and sea surface variability
Geographic Areas of (Near-Term) Primary Interest
• Vicinity of APL/UW Mooray and MPL VLA1 deployment site and
quasi-range-independent radial track to NE
• Vicinity of WHOI Shark array and radial tracks in sector from NE
through NW
• Sand ridge between ARL/UT SWAMI-32 and SWAMI-52 arrays
• Region with sub-seafloor channels to NE of SW06 site
Information Needed to Proceed
• Regional sound speed structure and temporal variability
• Deterministic sound speed fields where possible but EOFs,
correlation scales, and statistics are of particular interest
• Regional seafloor information
• Subbottom structure (e.g. “R” reflector depth) from chirp
profiler and direct in-situ measurements in upper 2 m (cone
penetrometer, SAMS, geoprobe)
Individual Objectives and Collaborations
Dahl / Tang
MF (1-20 kHz) data analysis and inversions
Bottom loss as a function of angle/frequency/orientation and comparison with insitu seafloor measurements
Inversion for geoacoustic properties over NE radial track (1-10 kHz)
Chirp data over same track as SWARM-95 air gun data
Radial tracks to Shark array
Chirp sonar data analysis for seafloor structure and correlation scales
SWAMI-32 short-range circular track data
20 km sand ridge track between SWAMI arrays
Hodgkiss / Gerstoft
Inversions along MPL VLA1 NE track line (LF/MF tonals, lightbulb data)
MPL VLA1 circular track and vertical source deployment reflection coeff analysis
Estimating Greens functions between hydrophone pairs using active source data
Inversions using LF (50-300 Hz) data from Shark out to 6 km
Towed CTD chain with J-15
Inversions using OMAS mobile source (600 and 900 Hz) and sonobuoy receivers
1.2 and 3.5 kHz TL run along NE track line
Inversions NE area with subbottom channels using 50-175 Hz drifting J-15 source
and 4 drifting buoys
LF inversions using CSS data
Impact of IWs in modest range (~1 km) inversions
Amplitude dependent inversions
Data null space projection method (minimize impact of fluctuating modes)
MF Inversions of CW tones from experiments on ‘DJ’ track
MF Inversions of LF and MF chirp data from circle at Moray/MPL-VLA1 site
Reflection coefficient inversion at circle at Moray/MPL-VLA1 site
• Mailing list for updates of common interest
• Workshop ~Jan/Feb 2008 (San Diego)