## 2 The Experimental Data
### The Geacoustic Inversion Procedure
The reduction sound speed is 2000 m s\({}^{-1}\). When \(c_{0}\) and \(K\) are low (blue dashed line), the bending refraction is not observed within the offset range used. Normalized offset \(X_{n}\) and normalized reduced time \(T_{n}\) were used for calculations in Equation (5). Figure 7a represents an example of the normalized weight function \(F_{norm}(K,c_{0},\ H_{2 best})\), where \(H_{2 best}=1000\) m was chosen from the highest \(F(c_{0},K,H_{2})\), i.e., the best fit, for source #2290. The combination of \(c_{0}\) and \(K\), for which the arrival of the bending refraction exceeded 7,200 m, was omitted from the estimations of \(F\) (white in Figure 7a). Source #2290 \(F_{norm}(K,c_{0})\) had a maximum at \(c_{0}=1535\) m s\({}^{-1}\) and \(K=0.75\) s\({}^{-1}\), from which it was gradually decreasing in all directions. Figure 7b depicts a set of arrival times that were simulated for three combinations of \(c_{0}\), \(K\), and \(H_{2}\) and overlaid with the experimentally chosen arrival times (white circles) from source gather #2290. The model strongly deviates from the experiment when \(c_{0}\) and \(K\) are either too low (blue dash-dot curve) or too high (green dotted curve). Figure 8a-c demonstrate the sensitivity of the geacoucistic inversion by separately showing the sensitivity of the normalized probability functions to each of the parameters, \(F(c_{0},K_{best},H_{2 best})\), \(F(c_{best},K,H_{2 best})\), and \(F(c_{best},\ K_{best},\ H_{2})\). Here \(c_{best}\), \(K_{best}\), and \(H_{best}\) are the best fit estimated between the experiment and the models, i.e., the set of matching parameters for which \(F(c_{0},K,H_{2})\) is the highest. The margin of error for the estimation of \(c_{0}\), \(K\), and \(H_{2}\) is estimated to correspond to the width of the respective weight function at the level above 0.95 of the maximal value (dashed line in Figure 8a-c). Figure 8d-i represent a set of modeled reduced times, overlaid with experimentally chosen reduced travel times, and their zoomed portions, respectively. Each row emphasizes the influence of a specific parameter, \(c_{0}\), \(K\) or \(H_{2}\), on the modeled arrival times. In Figure 8d,g, the arrival times are modeled for the constant parameters \(K=0.75\) s\({}^{-1}\), \(H_{2}=1000\), and \(c_{0}=1430\), 1535, 1600 m s\({}^{-1}\). The best match between the model and the experiment is achieved for \(c_{0}=1535\) m s\({}^{-1}\). If the sound speed is relatively low (i.e., \(c_{0}=1430\) m s\({}^{-1}\)), both the sub-bottom reflection and bending refraction travel-time  
Figure 8: A demonstration of the sensitivity of the geoacoustic inversion to each of the three parameters, \(c_{0}\) (top row), \(K\) (middle row), or \(H_{2}\) (bottom row), with the two remaining parameters kept constant at the estimated best-match values between the modeled and the experimental data (i.e., \(F(c_{0},K,H_{2})=1\)) **(a–c)**. The normalized weight functions \(F\) **(d–f)**. The respective simulated reduced arrival times (color coded as labeled on the right), overlaid with the experimentally chosen travel times (white circles). The points used in the calculation of F are depicted as red rectangles **(g–i)**. Zoomed views of the parts are framed in dashed rectangles **(d–f)**. branches deviate significantly downward and exhibit greater offsets from the experimental points (blue dash-dot curves). In contrast, if the sound speed is high, i.e., \(c_{0}\) = 1600 m s\({}^{-1}\), both the sub-bottom reflection and bending refraction travel-time branches deviate upward and exhibit lesser offsets from the experimental points (green dotted curves). Figure 8e,h represent a situation where \(c_{0}\) = 1535 m s\({}^{-1}\) and \(H_{2}\) = 1000 m, and \(K\) is varying from 0.6 to 1 s\({}^{-1}\). The best match is achieved when \(K\) = 0.75 s\({}^{-1}\). In a manner similar to the previous situation, when \(K\) is too high or too low, both the sub-bottom reflection and bending refraction travel-time branches significantly deviate (by -0.1 s) from the experimental data.