Intermediate States between Statics and Dynamics and Seismic Emission in Granular Media

Seismic emission is the spontaneous emission of waves in a porous or fractured medium. There is still no explanation for the dependence of these phenomena on the medium parameters and pore structure, as well as for the transition from slow to fast movements. The paper proposes a description of the transition process from statics to dynamics using a model of a structured continuum. The most important parameters of the model are the specific surface area and porosity of the medium. The reason for the emission is that the forces caused by internal stresses are only on average equal to zero over a representative volume, being different at each point of the medium. It is shown that the model of a structured continuum predicts the emission of waves under static load and gives an estimate of the vibration periods. In this case, the characteristic vibration periods depend neither on the characteristic time of destruction of particles, nor on the loading time.