In seismic investigations, a method of velocity analysis associated with the normal moveout correction (Δ‎T), which enables the root-mean-square velocity (v_rms) to be calculated down to a particular reflector for which the normal incidence two-way travel time (t₀) and Δ‎T are known for a given offset (x) such that v_rms = x/(2t₀Δ‎T)^1/2. Once v_rms is known, the depth (z) to the reflector can be calculated using z = v_rmst₀/2.