where h is focal depth, y is in cm∕s2, a = 0.578, b = 0.00355, e = 0.00661, S = -0.069, S_{R} = -0.210, S_{H} = -0.114, S_{M} = 0.023, S_{S} = 0.237 and σ_{T } = where σ = 0.213 and τ = 0.162.
S is the mean site coefficient, i.e. when do not consider site category.