\def\figdir{./Figs}
After  two iterations our conclusions from  the first
iteration are  mostly
reconfirmed.  The poorest quality result comes from {\it depth-laplacian}.
We have done a poor job recovering the anticline, Figure~\ref{fig:velb}.
The anticline structure comes out  much wider than  it is in the true model.
The low velocity does not extend through the anticline structure.
There is still significant error in the velocity function at
shallow depths outside the anticline. The migration result 
(Figure~\ref{fig:res.vel2.lapz})
is also poor. The
bottom reflector is still significantly bowed and
we still have a little residual moveout in the gathers.

\activesideplot{velb}{width=4.0in,height=4.0in}{CR}{The velocity after two iterations using
the four different methods.  Top-left is  {\it depth-laplacian}; top-right is
{\it depth-steering}; bottom-left  {\it tau-laplacian}; and 
bottom-right {\it tau-steering}.}

\activeplot{res.vel2.lapz}{width=6.0in,height=2.8in}{CR}{The migration result after
two iterations of  {\it depth-laplacian}}

Our result from {\it tau-laplacian} is somewhat better. We have done
a better job isolating and defining the top of the
anticline.  Our reflector position is  improved over the
{\it depth-laplacian} case, Figure~\ref{fig:res.vel2.tau}.
We have correctly positioned all but the bottom reflector and
have less  moveout in the CRP gathers. On the downside,
we still have significant error in the bottom reflector and
do not have the low velocity layer extended through the entire
anticline.

\activeplot{res.vel2.tau}{width=6.0in,height=2.8in}{CR}{The migration result after
two iterations of  {\it tau-laplacian}}

The {\it depth-steering} and {tau-steering} cases are of about equal quality.
Both results have done good job recovering the anticline shape in
the velocity model.  The depth case still shows some of the artificial low
velocity layer seen in the first iteration.
The migration  result in Figures~\ref{fig:res.vel2.steerz} and 
\ref{fig:res.vel2.steer} are nearly perfect.  Both have almost
perfectly positioned all of the reflectors and have very little
residual moveout in the CRP gathers.

\activeplot{res.vel2.steerz}{width=6.0in,height=2.8in}{CR}{The migration result after
two iterations of  {\it depth-steering}}

\activeplot{res.vel2.steer}{width=6.0in,height=2.8in}{CR}{The migration result after
two iterations of  {\it tau-steering}}
