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Moment tensor inversion was carried out to invert the source mechanism of the Ms = 7.3
May 10, 1997, Qaen-BiIjand, Iran, earthquake. Waveforms of long-period P-wave recorded by a number of stations of the Global Digital Seismic Network (GDSN) on vertical components were
used in the inversion. The inverted result shows one nodal plane of right-lateral strike-slip faulting and another of left-lateral strike-slip faulting. From the geological data, tectonic settings, field
observations and epicentral distribution of early aftershocks, the nodal plane striking in the azimuth of 3120 is preferred as fault plane. 1\vo principal axes lie almost horizontally and one
vertical. These show that the region is subject to a strong compression and pushing from Eurasia plate through the Afghanistan and Turkmenistan stable blocks. An average dislocation of jj Rj 70
em and a stress drop of 2.1 MPa can be inferred.