The resonant behavior of a porous medium composed of periodic channel structures was studied. The natural frequencies of the dry pore system were obtained by theoretical analysis. The resonant frequencies of the saturated porous medium were calculated by numerical simulation, which considered the two-phase coupling effects of fluid and solid. The numerical results showed that most of the resonant frequencies of the saturated porous medium match with the natural frequencies of the corresponding dry porous medium but that some of the resonant frequencies are different from those of the solid matrix depending on the porosity of the pore system. Both the theoretical study and the numerical study suggest that the resonant frequencies of a porous medium are functions of the porosity or the fracture density. ¿ 2000 American Geophysical Union