The paper presents a study of focal mechanism of earthquakes and stress indicators for Iranian plateau and surrounding regions. All recorded earthquakes with magnitude of 4.5 and higher, occurred from 1964 to 2000, have been studied. The seismological data were taken from the International Seismological Centre (ISC) bulletin and Earthquake Data Report (EDR). More than 400 events of all earthquakes have been evaluated as good quality. Among them, 224 earthquakes are located in the Iranian plateau. Based on P-wave first arrival polarities, focal mechanism, orientation of the principle stress axes (P and T), nodal planes, and their corresponding errors in cases where more than one solution may fit the data, have been determined. Reliability of the fault plane solutions has been been evaluated by the values of the errors of P and T-axes orientations (less than 15°), the number of polarities (N≥ 30). and the score (S≥0.75). The average number of polarities for 774 earthquakes in the Iranian plateau is 88. The fault plane solutions indicate that the strike-slip and oblique faulting movements characterize the majority of the earthquake focal mechanism. 66 percent of the solutions correspond to the mechanism of dip-slip faulting. Dip-slip movements are mostly reverse. This is markedly in effect of the Arabia-Eurasia convergence by strike-slip and reverse faulting in seismotectonics of Iran. The Fohlich trinagle diagrams for Zagros, Alborz, east of Iran and Makran zones were presented. There are two alignment of the maximum compressional stress in each zone: NE-SW and NW-SE. The NE-SW direction in compatible with the main regional tectonic stress, whereas the NW-SE direction seems to be associated with local tectonic movements. The focal mechanisms obtained in this study are in general agreement with those of Centroid Moment Tensor (CMT) solutions reported by Harvard. However, the epicenters given by CMT method are generally misplaced by tens of kilometers from the locations reported by ISC or EDR. A reported by Dziewonski et al. (1981), such a discrepancy is well expected because the location of epicenters in the Harvard CMT corresponds to the centroid of seismic moment, rather than to the point if rupture nucleation.

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