How a wave interacts with heterogeneous media has been pursued by many geophysicists.The complexity of subsurface heterogeneities is seismologically a relative concept to wavelengths of seismic waves.A growing perception is that velocity variations,propagation angles,and computational accuracies are closely related at a variety of scales.A tentative strategy to quantitatively evaluate the complexity of subsurface heterogeneous media is presented in this article to see what scales of geological heterogeneities to be captured by waves.We express complex subsurface structures as the slowness-and angularheterogeneity spectra to quantify velocity contrasts and dipping-angle distributions of complex geological structures.On the other hand,the scaling characteristics of a propagator are measured through dispersion analysis by its angular spectra plotted against refractive indexes and propagation angles,respectively.A parameter termed as imaging efficiency is introduced by associating the geological heterogeneity spectra with the propagator’s angular spectra to understand the coherent interference between the medium’s heterogeneity and the propagator’s scaling characteristics.Furthermore,a complexity coefficient can be defined to evaluate geological complexities in terms of propagators.The application of this strategy is demonstrated to the SEG/EAEG salt model. How a wave interacts with heterogeneous media has been pursued by many geophysicists. The complexity of subsurface heterogeneities is seismologically a relative concept to that of seismic waves. A growing perception is that velocity variations, propagation angles, and computational accuracies are closely related at a variety of scales. A tentative strategy to quantitatively evaluate the complexity of subsurface heterogeneous media is presented in this article to see what scales in geological heterogeneities to be captured by wavess.We express complex subsurface structures as the slowness-and angularheterogeneity spectra to quantify velocity conjugates and dipping-angle distributions of complex geological structures. On the other hand, the scaling characteristics of a propagator are measured through dispersion analysis by its angular spectra plotted against refractive indexes and propagation angles, respectively. A parameter termed as imaging efficiency is introduced by associating the geol ogical heterogeneity spectra with the propagator’s angular spectra to understand the coherent interference between the medium’s heterogeneity and the propagator’s scaling characteristics. Morerther, a complexity coefficient can be defined to evaluate geological complexities in terms of propagators. The application of this strategy is demonstrated to the SEG / EAEG salt model.