The basal sliding surfaces in large rockslides are often composed
of several surfaces and possess a complex geometry. The exact morphology
and location in three dimensions of the sliding surface remains generally
unknown, in spite of extensive field and subsurface investigations,
such as those at the Åknes rockslide (western Norway). This knowledge
is crucial for volume estimations, failure mechanisms, and numerical
slope stability modeling. This paper focuses on the geomorphologic
characterization of the basal sliding surface of a postglacial rockslide
scar in the vicinity of Åknes. This scar displays a stepped basal
sliding surface formed by dip slopes of the gneiss foliation linked
together by steeply dipping fractures. A detailed characterization
of the rockslide scar by means of high-resolution digital elevation
models permits statistical parameters of dip angle, spacing, persistence,
and roughness of foliation surfaces and step fractures to be obtained.
The characteristics are used for stochastic simulations of stepped
basal sliding surfaces at the Åknes rockslide. These findings are
compared with previous models based on geophysical investigations.
This study discusses the investigation of rockslide scars and rock
outcrops for a better understanding of potential rockslides. This
work identifies possible basal sliding surface locations, which is
a valuable input for volume estimates, design and location of monitoring
instrumentation, and numerical slope stability modeling.