Amplitudes of Ag = 0.2 g and Ag = 0.3 g were assigned to the base
motion in Fig. 5, corresponding to N/A = 0.56 and N/A = 0.373. For
the sake of simplicity, iterations upon strain was not included in these
computations. Several different values of damping were considered for
each backfill; values less than 10% are not considered, because earthquakes
that mobilize less than 10% equivalent damping are probably not
strong enough to cause significant damage.