Investigation of various stress and strain determination methods and crustal shortening in Iran using focal mechanism of the earthquakes

In this research, stress, strain and crustal shortening were calculated in Iran using Kastrov and Molnar methods and also role of gridding in the estimations has been investigated. In this view, numbers of 637 earthquakes with moment magnitude greater than 5.5 in time interval of 1909-2016 were applied. Pressure and tension directions, seismic strain resulted by two methods (gridding and every earthquake individually) and also horizontal and vertical crustal displacement velocity were estimated. Pressure and tension directions and seismic strain deduced by earthquake focal mechanisms, were calculated in three manners: every earthquake individually, 1°×1° and tectonical grindings. Data processing shows that pressure and tension directions and seismic strain are intensely related to the kind of the gridding. Also, there is clear difference between estimation of the strain with the two methods of Kastrov and Molnar. Nevertheless, it could be concluded that maximum deformation is going on in Dasht-e Bayaz and Qaen area in the eastern Iran. Vertical velocity estimations in High Zagros and Zagros Foredeep are crustal thickening and thinning, respectively, which is in accordance well to tectonic of the area. Although, this estimation in eastern and western Alborz are uplift and subsidence, respectively, which the later one is not in accordance with Alborz tectonic with an oblique collision.