Abstract: Based on the study of the genetic features of mineral associations and metamorphic facies in Miyun metamorphic rocks,the characters of repeated-seismic layers have been proposed in this paper.It is suggested that the differential deformation has a close relation to the generation of strong seisms.Taking the principal elements of flow cleavage and fracture cleavage as well as their dynamic implications into account,a generation process of strong earthquakes has been proposed: the mechanism of differential deformation causes an initiation of strong earthquakes.Briefly speaking,distinct rock types in a dynamically forced system are deformed asynchronously,so there should be a mutually-restricted force in the system.When the increase of the force has attained the critical limit,the initial steady state of the system is not maintained,leading to a change of the distance in the relating moment of force.During this process,the potential energy is transformed into kinetic energy,forming a shear-compressive thrust that will cause an initiation of strong earthquakes.Therefore,the force of differential deformation is a driving force of strong-seismic event.This mechanism is proposed in a qualitative consideration without any scale restriction.It is also considered that the equilibrium of distinct energies has been involved in this process.Based on the proposed mechanism,the relationship between slow deformation and quick earthquake generation,seismostructures and petrology have been demonstrated in this paper as well.