Initial and boundary condition

Assuming the slowness along the surface is constant s₀, we can find following initial conditions:  

$$\left\{ \begin{array} {lll} p(x,z) & = & -s_0 x \\ p_x(x,z) & = & -s_0 \\ p_z(x,z) & = & 0.\end{array}\right.$$ (9)

The boundary conditions are similar to those described in the last section.