If seismic coefficients are defined, a seismic force will be applied to each slice as follows:
Seismic Force = Seismic Coefficient * Slice Weight
= Seismic Coefficient * area of slice * Unit Weight of slice material
Note that the acceleration due to gravity (g = 9.81 m/s2 for metric units) is already incorporated into the material Unit Weight entered in the Define Material Properties dialog (remember that the dimensions of Unit Weight are kN / m3), and therefore does not explicitly appear in the above equation.
The seismic force is applied through the centroid of each slice.