For the maximum probable earthquake in California, which is a reasonable maximum
earthquake for many other areas of the world, Fig. 22 may be used directly to obtain a
measure of the maximum displacement for unsymmetrical sliding. If the maximum resistance
coefficient is about O-16, or about one-third the maximum earthquake acceleration, the net
displacement will be about 1 ft. If the maximum resistance coefficient N is about 0.20 times
the maximum earthquake acceleration, or N equals 0.1, the maximum displacement is about
5 ft. The maximum displacement increases rapidly as N decreases. Values of N in the range
of 0.1 to 0.15 are not uncommon for earth dams designed for earthquake resistance. Of course,
a design with a somewhat smaller value of N would have a smaller displacement if the earthquake
were less intense. For an earthquake with a maximum acceleration of 0*25g, and a
maximum velocity of 15 in/set, the displacements computed would be one-fourth those quoted,
if the value of the ratio of N to A were the same. In other words, for the same relative value
of resistance coefficient, the displacement varies as the square of the ground velocity. This
displacement lowers the crest of the dam.