Generally Speaking, there are three types in the seismic activities. One of them is usually the type of major-after shock. They are related to
(1) The mode and the rate of the force;
(2) The physical characteristics of the rocklayer and the geological conditions in the focus region.
In this papcr we have discussed the characteristics from the viewpoint of energy ang based on geological conditions. It shows that the major-after shock activities usually occur in the second order tectonics connected with the major-fault.
The volume of the aftershock may be regarded as a region which has been deformed. The product of the critical value of the strain energy per unit volume in the rock and the after-shock volume is in the same order as the energy released by the major-shock.
We may calculate the strain value of the fracture from the strain energy pcr unit volume.
It is smaller than the value based on geodesy.