  Thermodynamic equations for a solid and a solid continuum under stress are
derived on the basis of a multicomponent mean field Markov process for
thermofluctuation kinetics of microcracks. The resulting continuum is viscous
elastoplastic continuum with damage. It can radiate elastic waves . The
existence of phase transitions with microcrack density as an order parameter is
proved for a stationary state of a special model of solid. For a finite large
system the distribution of the logarithmic power of acoustic emission at a
critical point is similar to the distribution of the logarithmic energy of
earthquakes.
