'Constant Velocity GRadient model.' 0 1 1 / (Cartesian coordinates, velocities, loss factors) 0 1 0 1 0 1 / (boundaries of the model) 0 surfaces 1 simple block: / (bounded by no interface) 1 complex block: 1 / (list of simple blocks) 'END of surfaces' / (no data for surfaces) 'COMPLEX BLOCK' 1 'VP ' 1 (P wave velocity) 3 0 0 0 / (i.e. VP=W(X3), tension=0) 2 (numbers of grid points) 0 1 (X3 grid coordinates) 3 1 (velocities at grid points) 'END of complex blocks, end of the input data for the model' / ========================================================================