Abstract: Based on seismicity patterns, tectonic background and gradual seismic changes, thstudy region, which covers China's mainland and its vicinity is divided into subregions and 20units. By using the earthquake(Ms26. 0) catalogue of the latest 100 years for the continentalregion, the strain energy released by earthquakes in each unit and each subregion is calculated.And the curves of the strain energy released by earthquakes changing with time are drawn af-ter slip averaged by time. They indicate that:(a) the released energy of earthquakes in eachsubregion is characterized by undulation with alternating high and low points and by multi-phases;(b) the active or quiet period is not absolute but relative;(c) it demonstrates that thedivision of the micro-dynamic periods for seismicity is appropriate. By further analyzing, con-sidering that there are three main factors that affect the change and migration of the majorsubregions of great earthquakes, they are as follows:(1) movement and its change of the In-dia plate, the Pacific plate and the Philippine plate controls the basic pattern of strong earth-quakes in the China's continent and its vicinity. Earthquakes and tectonic movement along theplate boundaries change with time in an uneven manner. Even along the same plate boundary,activity of each section is different from each other;(2) the heterogeneity of the continentalcrust has effect upon the structure of the ma jor seismic subregions;(3) the inheritance of crustdeformation affects the process of formation and migration of the ma jor seismic subregions.

Key words: China's mainland and its vicinity, Activity by subregions, Strain energy, Majorsubregions of great earthquakes