Computed displacements can vary significantly with slope
azimuth. Performing sliding block analyses using only the
recorded ground motion components implies that the slope
dips in one of those directions; the computed displacements
in other directions may be considerably greater or smaller
than in the directions of the recorded components. The degree
of azimuthal variability of computed displacements increases
with increasing yield acceleration. For relatively
high yield accelerations, driving forces may be strong
enough to produce permanent displacement for only a small
range of azimuths. The average value of permanent displacement
computed in the directions of the two recorded horizontal
components will generally be smaller than the average
permanent displacement for all possible slope azimuths—by
an amount that increases with decreasing yield acceleration
and is greater for slopes governed by cohesive soils than
frictional soils.