On the bifurcation of the Biot slow wave in a porous medium

Propagation of the slow Biot wave is investigated within the low-frequency range. For the first time it is proven theoretically that longitudinal wave of the second kind is not propagatory if its wave number is lower than some critical value. This critical wave number is a bifurcation point, above which longitudinal wave of the second kind becomes to be propagatory. Asymptotical formulae for phase velocity and attenuation of P2 wave are derived