  For a fundamental understanding of terrain relaxation occurring on sloped
surfaces of terrestrial bodies, we analyze the crater shape produced by an
impact on an inclined granular (dry-sand) layer. Owing to asymmetric ejecta
deposition followed by landsliding, the slope of the impacted inclined surface
can be relaxed. Using the experimental results of a solid projectile impact on
an inclined dry-sand layer, we measure the distance of centroid migration
induced by asymmetric cratering. We find that the centroid migration distance
$x_\mathrm{mig}$ normalized to the crater minor-axis diameter $D_\mathrm{cy}$
can be expressed as a function of the initial inclination of the target
$\tan\theta$, the effective friction coefficient $\mu$, and two parameters $K$
and $c$ that characterize the asymmetric ejecta deposition and oblique impact
effect: $x_\mathrm{mig}/D_\mathrm{cy}=K \tan\theta/(1-(\tan\theta/\mu)^2)+c$,
where $K=0.6$, $\mu=0.8$, and $c=-0.1$ to $0.3$. This result is consistent with
a previous study that considered the effect of asymmetric ejecta deposition.
The obtained results provide fundamental information for analyzing the
degradation of sloped terrain on planetary surfaces, such as crater-shape
degradation due to the accumulation of micro-impacts.
