Summary Velocity dispersion in stratified media depends upon the impedance contrast between contiguous layers and the ratio (R) of the wavelength to the layer thickness. The goal of the present work is to understand the scale dependence of propagation velocities in periodically layered media. We based our analysis in 1-D wave equation forward modeling. The numerical simulation was performed on 9 layered models with impedance contrast ranging from 1.05 to 1.99. The analysis showed that the maximum R which RT can be used to estimate travel time is about 2, and the minimum which effective media theory is valid varies from 21 to 25. Mie and Rayleigh scattering zones are located near 4 and 5