Explain how earthquakes can disrupt the frictional and gravitational forces within a slope.

a) Seismic waves reduce the amount of weight on the sediment grains and reduce the frictional forces between them.
b) Seismic waves increase the amount of weight on the sediment grains and reduce the frictional forces between them.
c) Seismic waves do not affect slopes.
d) Seismic waves increase the amount of weight on the sediment grains and increase the frictional forces between them.