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

ONR SW06 Workshop, January, 30-31, 2007 San Diego, CA 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 Data sets used (at VLA1) : Low frequency tonals for 3 ranges along ‘DJ’ track Chirps at fixed range Objectives: Geoacoustic model for common site Broad frequency band Well surveyed range dependence 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 Example of matched field inversion result – parameter uncertainty estimates at WP21 (~ 1km)

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

ONR SW06 Workshop, January, 30-31, 2007 San Diego, CA final energy of each frequency in optimization: ( 53Hz) (103Hz) (203Hz) (253Hz) (303Hz) (403Hz) (503Hz) (703Hz) Energy Function:

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

ONR SW06 Workshop, January, 30-31, 2007 San Diego, CA WD=78.8, rdvb =9.05m, 8fresWD=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 WD=78.8, rdvb =11.8m, WP22WD=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 Discussion: Way Point 21(0.98km), LF(5mins) + MF(5mins) Tonal, 8 fres

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

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