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Preliminary Geoacoustic Inversion Results from SW06 Data

Preliminary Geoacoustic Inversion Results from SW06 Data. Ross Chapman. University of Victoria, BC, Canada. ONR Shallow Water Experiment 06 Workshop January, 30-31, 2007 San Diego, CA. Low Frequency Geoacoustics (Knorr: Aug 23 – Sept 06) Bill Hodgkiss, Peter Gerstoft, Chenfen Huang (MPL)

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Preliminary Geoacoustic Inversion Results from SW06 Data

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  1. Preliminary Geoacoustic Inversion Results from SW06 Data Ross Chapman University of Victoria, BC, Canada ONR Shallow Water Experiment 06 Workshop January, 30-31, 2007 San Diego, CA

  2. Low Frequency Geoacoustics (Knorr: Aug 23 – Sept 06) • Bill Hodgkiss, Peter Gerstoft, Chenfen Huang (MPL) • David Knobles et al (ARL) • Ross Chapman, Yongmin Jiang, (UVic) ONR SW06 Workshop, January, 30-31, 2007 San Diego, CA

  3. Objectives: • Geoacoustic model for common site • Broad frequency band • Well surveyed range dependence • Data sets used (at VLA1): • Low frequency tonals for 3 ranges • along ‘DJ’ track • Chirps at fixed range • Approaches: • MFI for tonal signals • single layer geoacoustic model • Reflection coefficient inversion • of fixed range chirp data ONR SW06 Workshop, January, 30-31, 2007 San Diego, CA

  4. Example of matched field inversion result – parameter uncertainty estimates at WP21 (~ 1km) ONR SW06 Workshop, January, 30-31, 2007 San Diego, CA

  5. Example of data processing for reflectivity coefficient inversion – Fixed range high frequency chirps • Sea floor & subbottom reflection • at VLA1 site • Sound speed and attenuation • from 2000 ~ 4000 Hz • Sound speed ~ 1580 m/s ONR SW06 Workshop, January, 30-31, 2007 San Diego, CA

  6. Preliminary low frequency geoacoustic model for ‘DJ’ track • sea floor sediment parameters over range dependent track • sediment sound speed: ~1600 m/s (50 – 900 Hz) • Some problems with the data: • MFI: no information in some tonal frequencies • Significant variation in signal level • Significant variation in SSP • Array geometry: hydrophone depths uncertain? • What other information do we need? • Chirp sonar track over DJ line; geoprobe data • Swell and wave direction & height • Source levels for LF and MF sound sources • ARL acoustic data from SWAMIs • Collaborations for geoacoustics: • Geoacoustic models for broad frequency band for • DJ track and Moray/VLA site • SWAMI site data ONR SW06 Workshop, January, 30-31, 2007 San Diego, CA

  7. Collaborations for geoacoustics: • Geoacoustic models for broad frequency band for • DJ track and Moray/VLA site: • MPL (LF < 4500 Hz) and APL (2 – 20 kHz) • SWAMI site data: ARL • long and short range geoacoustic inversion at sandy site • expect less variation in SSP • LF and MF data (chirps) • Experimental benchmark data set for inversion methods? • Target a JASAEL collection of preliminary results (2007)? • Hurricane Ernesto Noise data: SWAMIs ONR SW06 Workshop, January, 30-31, 2007 San Diego, CA

  8. Discussion Slides ONR SW06 Workshop, January, 30-31, 2007 San Diego, CA

  9. Energy Function: • final energy of each frequency in optimization: 0.2338038 • 0.00363505 ( 53Hz) 0.21442491(103Hz) 0.56934798(203Hz) 0.40013963(253Hz) • 0.57140428 (303Hz) 0.37056041(403Hz) 0.35731304(503Hz) 0.66464043(703Hz) ONR SW06 Workshop, January, 30-31, 2007 San Diego, CA

  10. WD=79.5, Rdvb = 8.2m WD=79.5m, Rdvb=11.8m WD=78.8, rdvb =8.2m, 8fres WD=78.8, rdvb =11.8m, 8fres ONR SW06 Workshop, January, 30-31, 2007 San Diego, CA

  11. WD=78.8, rdvb =9.05m, 8fres WD=78.8, rdvb =8.55m, 8fres WD=78.8, rdvb =11.8m, wp21 ssp WD=78.8, rdvb =11.8m, wp22 ssp ONR SW06 Workshop, January, 30-31, 2007 San Diego, CA

  12. WD=78.8, rdvb =11.8m, WP22 WD=78.8, rdvb =8.2m, WP22 WD=81.0, rdvb =11.8m, WP23 WD=81.0, rdvb =8.2m, WP23 ONR SW06 Workshop, January, 30-31, 2007 San Diego, CA

  13. Discussion: Way Point 21(0.98km), LF(5mins) + MF(5mins) Tonal, 8 fres ONR SW06 Workshop, January, 30-31, 2007 San Diego, CA

  14. Way Point 22(2.98km), LF(5mins) Tonal(53, 103 203, 253)Hz ONR SW06 Workshop, January, 30-31, 2007 San Diego, CA

  15. Way Point 23(4.98km), LF(5mins) Tonal(53, 103 203, 253)Hz ONR SW06 Workshop, January, 30-31, 2007 San Diego, CA

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