\begin{table}%t4
%\centering
\par
 \caption{Numerical value of the Earth model
properties, from PREM.\label{tab4}}
$$
\begin{tabular}{lcl|lcl}
\hline\hline
$ \rho_{\rm f} $  & = & $10890 \;\rm  kg~ m^{-3}$ & $ \rho_{\rm s} $  & = & $12890\;\rm  kg~ m^{-3}$  \\
$ \rho_m $  & = & $4450 \; \rm kg ~m^{-3}$ & $\rho_M $  & = & $5514\; \rm kg~ m^{-3}$ \\
$ \mu_m $  & = & $1.76\; 10^{11} \; \rm Pa$  & $\mu_g $  & = & $1.64\; 10^{11} \;\rm  Pa$ \\
$ A $  & = & $8.38\; 10^{37}~\rm  kg ~ m^2$ & $A_{\rm f} $  & = & $9.26\; 10^{36}~\rm  kg ~ m^2$ \\
$ A_{\rm s} $  & = & $8.86\; 10^{34}\rm  kg ~ m^2$& $A_m $  & = &$7.38\; 10^{37}~\rm  kg ~ m^2$ \\
$ a $  & = & $6371 000~\rm m$& $ b $  & = & $3480 000 ~\rm m$ \\
$ c $  & = & $1221 000 ~\rm m $ & $ q_0 $  & = & $0.00345$ \\
\hline
\end{tabular}
$$
\end{table}