If we perform another iteration of tomography we see further improvement.
Figure~\ref{fig:vel-final} shows our velocity model.  
The velocity has been further increased in the 
the chalk layer on both sides of the fault (`A' and `B').
On the right side we also see a break in the high
velocity zone developing (`C').  
In the Liassic
where the chalk velocity was increased in the first
iteration it has been decreased by the second iteration, especially
on the right side of the salt dome (`D').  
This decrease continues all the way to the salt edge.

\sideplot{vel-final}{width=3.0in,height=3.3in}{Final velocity.
The velocity has been further increased in the 
the chalk layer on both sides of the fault (`A' and `B').
On the right side we also see a break in the high
velocity zone developing (`C').  
In the Liassic
where the chalk velocity was increased in the first
iteration it has been decreased by the second iteration, especially
on the right side of the salt dome (`D').  
This decrease continues all the way to the salt edge.
}

%\plot{elf-semb-mig-final-ref}{width=6.0in,height=3.5in}{
%Semblance along the reflectors using final velocity model.}
%\plot{overlays.vel-final}{width=6.0in,height=8.5in}{CRP gathers after final migration.}

%The true test is the final migrated image.  If we look at the final migrated
%image we can see better continuity of the reflectors and 
%generally higher frequency image.  
%The final migration image  (Figure~\ref{fig:mig-final})  is quite similar
%to our initial image (Figure~\ref{fig:elf.mig.vel0}).  If we take a closer
%look at the top of the salt body (Figure~\ref{fig:mig-top}) 
%we can begin to see some differences.
%At location `A' and `C' we have done a better job defining the salt boundary.
%At `B'  the reflector is sharper and has a more realistic shape.
%If we look at the side of the salt dome, Figure~\ref{fig:mig-side},
%we can see more improvements.  The reflectors are  more continuous `A' and
%extend closer to the salt boundary `B'. I also have done a better
%job recovering the bottom salt reflector, `C'.


The migration (Figure~\ref{fig:elf-mig2}) using the new
velocity (Figure~\ref{fig:vel-final} has also improved.  
In the top portion of the image (Figure~\ref{fig:top.compare}) the
reflectors are of higher frequency (`A').  We have more coherent reflectors (`B')
and the top of salt reflection is somewhat improved (`C').  In the lower
and left portion of the image (Figure~\ref{fig:left.compare}) we
see a more coherent and believable bottom salt reflection (`A').
The reflectors bounding the salt on the left are more continuous (`B')
and of higher frequency (`C').  In the right hand portion of the
image (Figure~\ref{fig:right.compare}) 
we see further extension of reflectors (`A') and more coherency
in the reflections (`B').

\plot{top.compare}{width=6.0in,height=5.0in}{Result of migrating with
the initial velocity, top panel, and the final velocity, bottom panel.
The
reflectors are of higher frequency (`A').  We have more coherent reflectors (`B')
and the top of salt reflection is somewhat improved (`C').
}

\plot{left.compare}{width=6.0in,height=6.0in}{Result of migrating with
the initial velocity, top panel, and the final velocity, bottom panel.
We
see a more coherent and believable bottom salt reflection (`A').
The reflectors bounding the salt on the left are more continuous (`B')
and of higher frequency (`C').}

\plot{right.compare}{width=6.0in,height=6.0in}{Result of migrating with
the initial velocity, top panel, and the final velocity, bottom panel.
We  see further extension of reflectors (`A') and more coherency
in the reflections (`B').}

\plot{elf-mig2}{width=6.0in,height=7.5 in}{Migration result using
the velocity from Figure~\ref{fig:vel-final}.}



The CRP gathers (Figure~\ref{fig:moveout-vel2.steer}) are generally flatter
and more coherent.  The semblance along the reflectors
(Figure~\ref{fig:elf-sem-ref.vel2.steer})  is more continuous and  closer to zero  curvature.

\plot{elf-sem-ref.vel2.steer}{width=6.0in,height=3.5in}{Semblance panels from
ten of the reflectors used in tomography.}

\plot{moveout-vel2.steer}{width=6.0in,height=8.0in}{CRP gathers after the second iteration of tomography.}




%\plot{mig-final}{width=6.0in,height=3.3in}{Final migrated image.}
%\plot{mig-top}{width=6.0in,height=7.0in}{Comparison at the top of the salt dome.
%At location `A' and `C' we have done a better job defining the salt boundary.
%At `B' we can see that the reflector is sharper and has a more realistic shape.
%}
%
%
%\plot{mig-side}{width=6.0in,height=7.0in}{Comparison of the top of the salt dome. The reflectors are  more continuous `A' and
%extend closer to the salt boundary `B'. I also have done a better
%job recovering the bottom salt reflector, `C'.}
%
%%
