Naser Khaji - Assist. Professor, Earthquake Engng. Division, Civil Engng. Dept., Faculty of Engng., Tarbiat Modares University, P.O. Box: ۱۴۱۱۵-۱۴۳, Tehran, Iran

This paper represents a numerical tool for estimation of subduction zones’ behavior for interseismic period. This involves a quasi-static approach according to the least-square method to derive slippage vectors at the interface (subduction fault). The Finite Element Method (FEM) allows easy treatment of complex boundary shape (interface zone) and internal variations of material properties. The FEM can simulate source geometry flexibly, and is also able to regard topographic configurations, geological regimes and various layered structures.AL157 The spatial distribution of the strength of interplate coupling between the Philippine Sea plate (as a subducting plate) and continental plate (overriding one) in the Tokai district (Central Japan) is investigated in detail through the Inverse Analysis of geodetic data.The standard equations of Inverse Problems offer a straightforward way for finding slippage vectors at the interface of two converging plates. One of the new aspects of the current study is evaluation of Green’s functions matrix by means of FEM. This concept enables us to overcome all limitations of traditional Inverse methods.To implement fault sliding in a continuum-based FEM program, Split Node Technique as a simple and efficient method is applied. This method does not increase the number of degrees of freedom and no net forces or moments are induced on the finite element mesh when isoparametric elements are used.An evaluation of the coupled zone of the soon-to-occur Tokai earthquake is one of the main results of present research. Some evidences such as the Back-slip pattern of Geodetic data play remarkable role to prove the validity of the proposed method