  In this work we obtain known and new supersymmetric extensions of diverse
asymptotic symmetries defined in three spacetime dimensions by considering the
semigroup expansion method. The super-$BMS_3$, the superconformal algebra and
new infinite-dimensional superalgebras are obtained by expanding the
super-Virasoro algebra. The new superalgebras obtained are supersymmetric
extensions of the asymptotic algebras of the Maxwell and the
$\mathfrak{so}(2,2)\oplus\mathfrak{so}(2,1)$ gravity theories. We extend our
results to the $\mathcal{N}=2$ and $\mathcal{N}=4$ cases and find that
R-symmetry generators are required. We also show that the new
infinite-dimensional structures are related through a flat limit $\ell
\rightarrow \infty$.
