Inversion from pressure and vertical velocity data

We used the pressure and vertical velocity component of the seafloor signal to invert for the near sea-floor parameters. The technique is the same as described before. The data were transformed into the frequency-radial wavenumber domain, the reflection coefficient was calculated and then inverted for the seafloor parameters. The inversion results can be seen in Table 8.

$$\phi \rho_2$$ v_p2 (m/s) v_s2 (m/s)

46 1661 - 0.6% 440 + 2% 2268 + 19.9%

Table 8: Inverted layer properties.

The inversion results show that the density is less well constrained and has significant errors. P-wave velocity and S-wave velocity are reasonably well determined. Figure 24 displays the theoretical reflection coefficient versus the inverted one. It is obvious that most discrepancy exists at pre-critical angles. This discrepancy is caused by the large error in the density, which mainly controls the near to pre-critical angles (see sensitivity analysis).

 

vzpp1avo Figure 24 Inverted AVO curve versus exact curve for P-Vz data.