ACCURATE BOUNDARY CONDITIONS FOR FINITE ELEMENT MODELING OF MOVEMENT FIELD WITHIN IRAN TECTONIC PLATE

A reliable and efficient numerical model with a large number of degrees of freedom plays a crucial role in understanding and anticipating the lithosphere conditions in terms of tectonic activities. In this paper, spatial distribution of tectonic forces due to collision and coupling between the Arabian plate and the continental Eurasian plate in south-western Iran is investigated in detail through the inverse analysis of GPS data. In this research, the major causes of crustal deformations are assigned to two main factors; namely, the rate of tectonic forces and the far-field treatment. Available GPS data representing free surface movements is implemented to determine the mentioned factors. In other words, using GPS data of central Iran, the proposed inversion tool computes driving tectonic forces rate. Moreover, far-field boundary conditions are determined by means of a simple optimization algorithm seeking for the minimization of residuals. These residuals are differences between the calculated and the observed crustal movements. For far-field boundary conditions, a kind of fictitious boundary condition exploiting the concept of springs is represented. That is, peripheral truncated boundaries of the continental plate are covered by a set of springs whose stiffness coefficients are initially unknown. These stiffness coefficients are investigated in a manner in which a plausible pattern of problem components could be reproduced by the model. Due to complicated geometry, boundary conditions and irregularities of influential parameters of the environment, Finite Element (FE) method is quite applicable in this field of study. From a large scale point of view (i.e., taking a whole tectonic plate into account), FE modeling can elucidate the effects of individual driving forces, and is a valuable tool in modeling the intraplate stress field of single lithosphereplates. In the present study, the mentioned plate in Iran is simulated by two-dimensional plane-stress FE model. Numerical results show good agreement between GPS data of and the displacement field of model nodes. The proposed accurate model may provide better understanding of tectonic stress field of this zone, and detects potential seismogenic zones in central Iran.

ACCURATE BOUNDARY CONDITIONS FOR FINITE ELEMENT MODELING OF MOVEMENT FIELD WITHIN IRAN TECTONIC PLATE Keywords:

Inverse Problems , Finite Element Method , Iran , Boundary Conditions , Gps