Past exam of the year 2 of the earth sciences (geology) course of the University of Oxford / 2025 / Paper 3 / 1 / b / ii / Solution

For the fully gas-filled reservoir,soBoth impedances are now smaller than those of the cap rock. Both reflections reverse seismic reflection polarity, with a substantially larger amplitude for the P wave reflection. Reading the right-hand $V_p$ endpoint instead as $1.20\mathrm{km}{\mathrm{s}}^{-1}$ would give $R_p\simeq -0.20$, preserving the interpretation.