Synthetic seismograms of the two-layer model at a pore pressure of 8 MPa. The left-hand panels from left to right are the P-wave velocity, S-wave velocity, density, and synthetic seismogram. The right-hand panels from left to right are the P-wave velocity, S-wave velocity, density, synthetic seismogram and difference profile. In the plots of the P-wave velocity, S-wave velocity, and density, the curves are measured well log data, and the straight lines are block parameters. In each row, the synthetic seismogram on the far right is the difference profile between the synthetic seismograms on the left- and right-hand sides. a) The porosity is 0.18, while the CO₂ saturation is 5% on the left and 20% on the right; b) The porosity is 0.24, while the CO₂ saturation is 5% on the left and 20% on the right; c) The porosity is 0.34, while the CO₂ saturation is 5% on the left and 20% on the right.