EVOLUTION OF THE STRESS FIELD IN TEHRAN REGION DURING THE QUATERNARY

This study presents the first paleostress results obtained from the faulted Quaternary deposit in Tehran area. Stress inversion of ۱۶۷ fault-slip data and ۵۷ tension gashes at ۲۸ sites revealed threee stress stages. These staues indicate a clockwise rotation of stress. The oldest stress direction trending NW-SE has been responsible for the forming of folds and faults of A-formation (the oldest unit of Quaternary). The following directed stress N-S and NE-SW have affected only the overlaying younger unit (B-Formation) The timing of stress change from NW-SE to NE-SW (average azimuth ۰۳۰ for Tehran region) needs more study.