\documentclass{article}

\usepackage{arydshln}

\begin{document}
\[
\left( \begin{array}{ccc;{2pt/2pt}ccc}
a_{11} & a_{12} & a_{13} & 1 & 0 & 0\\ \cline{4-5}
a_{21} & a_{22} & a_{23} & 0 & 1 & 0\\ \hdashline[5pt/2pt]
a_{31} & a_{32} & a_{33} & 0 & 0 & 1
\end{array}\right)
\]

\end{document}
