Reflection seismology geometry

Identify the up and downgoing waves in the reflection seismology geometry in Figure 7 and load these waves into the multilayer matrix boundaries, equation (20).  

$$\left[ \begin{array} {c} 0 \\ E(Z) \end{array} \right] \e... ... \; \left[ \begin{array} {c} -R \\ 1 + R \end{array} \right]$$ (24)

From the first equation we may solve for R(Z)  

$$R(Z) \eq + {Z^k G(1/Z) \over F(Z) - Z^k G(1/Z)}$$ (25)

Given R(Z), the second equation in the set (24) gives us E(Z). Calculation of the wave fields on the earthquake geometry of Figure 8 is reserved for an exercise.