Quantifying the uncertainty of geoacoustic parameter estimates for the New Jersey shelf by inverting air gun data

Abstract

This paper describes geoacoustic inversion of low frequency air gun data acquired during an experiment on the New Jersey shelf. Hybrid optimization and Bayesian inversion techniques based on matched field processing were applied to multiple shots from three air gun data sets recorded by a vertical line array in a long-range shallow water geometry. For the Bayesian inversions, full data error covariance matrix was estimated from a set of consecutive shots that had high temporal coherence and small spatial variation in source position. The effect of different data error information on the geoacoustic parameter uncertainty estimates was investigated by using the full data error covariance matrix, a diagonalized version of the full error covariance, and a diagonal matrix with identical variances. The comparison demonstrated that inversion using the full data error information provided the most reliable parameter uncertainty estimates. The inversions were highly sensitive to the near sea floor geoacoustic parameters, including sediment attenuation, of a simple single-layer geoacoustic model. The estimated parameter values of the model were consistent with depth averaged values (over wavelength scales) of a high resolution geoacoustic model developed from extensive ground truth information. The interpretation of the frequency dependence of the estimated attenuation is also discussed.

Acoustic mode radiation from the termination of a truncated nonlinear internal gravity wave duct in a shallow ocean area

“…20 The in situ water sound speed measurements on the NRL300 source mooring and a bottom model provided by a previous study 21 are used in the program. The calculation results, shown in Fig.…”

Seabed characteristics from ambient noise at three shallow water sites in Northern Indian Ocean

“…Geoacoustic inversion using noise field spatial coherence from low frequency air gun sources had been carried out by Jiang and Chapman 8 and the uncertainty of geoacoustic parameter estimates had been quantified. A time domain matched beam processing was also attempted by Jiang et al, 9 using broadband data from a long range propagation experiment, and the estimates agree well with ground truth information. Yang et al, 10 used a source and a ship towed line array system for estimating bottom properties and sub-bottom profiling.…”

Geoacoustic inversion using combustive sound source signals

“…Figure 3 (left panel) shows the compressional wave speeds in the top 40 m of the sediments estimated by the inversion scheme. The dashed line is the geoacoustic model proposed by Jiang et al (2007). They suggested this model for the SW06 experimental area based on chirp sonar inversions, grab samples, in situ probes, and shallow core measurements.…”

“…A geoacoustic model based on historic data from the experimental location (Jiang et al, 2007) was used in the beginning to initialize the parameter d͑u , ͒. Group velocities corresponding to each normal mode were used to compute d͑u , ͒ which were then assigned to time-frequency locations in the neighborhood of the normal mode.…”