This paper accents the influence of the differentiation of plate subdu-ction zone and the interia of crust on earthquake mechanism.It holds that because of structure motion and the heterogeneity of the earth rotation velocity,the different diapire structure is apt to be formed at the top of basalt or the upper mantle near abyssal faults.The vertical force caused by such an uplift can make ground surface form synchronous rise and la-teral fall,and epicenter is often considered to lie in the sides or at the top of diapire structure.A superimposed epicenter stress field is made of the superimposition of the horizontal structure stress field and the verti-cal force of diapire structure.