Single-receiver geoacoustic inversion using modal reversal
Spectrograms of simulated fields for an impulsive source in a layered waveguide (arbitrary linear scale): (a) Simulated received signal and (b) corresponding warped signal (arbitrary linear scale). The waveguide consists of three isovelocity layers: Water column (, ), sediment layer (, , ) and semi-infinite basement (, ). The source and receiver depths are, respectively, and , and the range is .
Principle of modal filtering using warping.
Principle of the criterion computation for a given . Note that the modal reversal operation depends on mode number and on the parameter vector .
Sensitivity analysis and comparison with dispersion curve inversion. The continuous lines gives the normalized criterion value (corresponding scale is the vertical-left axis), while the dotted line shows the corresponding normalized misfit obtained using dispersion curve inversion (corresponding scale is the vertical-right axis). Each figure corresponds to a single parameter sensitivity: (a) Range, (b) sediment sound speed, (c) sediment density, (d) sediment width, (e) basement sound speed, and (f) basement density.
Estimation error and standard deviation depending on the SNR: (a) Range, (b) sound speed, and (c) density. Corresponding theoretical values are , , and .
Spectrograms of experimental signals: (a) Received signal and (b) corresponding warped signal (arbitrary linear scale).
Geoacoustic model of the environment. The sound speed profile in the water column corresponds to the in situ measurement, while the bottom sound speeds are estimated values from the literature (Ref. 25).
Experimental inversion results: Normalized criterion value (black dots) depending on (a) range, (b) sediment sound speed, (c) sediment density, (d) later width, (e) basement sound speed, and (f) basement density. The vertical gray lines give the final estimated value of each parameter.
Summary of MRI results and comparison with DCI results.a
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