The 28th February, 1997, earthquake is the largest instrumentally recorded and the most destructive earthquake in Ardabil Province. It produced extensive damages and
heavy human lost. No significant surface rupture was observed in the field investigation. However, seismolog!cal evidence suggests that the rupture with a length of about 20 kill,
had a NW-SE trending left-lateral strike-slip mechanism. It was initiated in South-East and extended to North-West in a unilateral manner. The average stress drop was
estimated to be about 15 bar. The static displacement was calculated to be about 27cm