Fracture System of Kopet-Dagh Fold Belt, NE Bojnurd

The Northern Khorasan is one of important active tectonics area. The main faults are strike slip (dextral and sinistral) and minor faults are thrust faults. Many of thrust faults are older than strike- slip faults and some of them are younger and are active now. It is because of bending of strike-slip faults that converts, them into thrust faults. We recognized active faults based on their characteristics. In this area we have two series of tensile joints and two series of shear joints. Principal stresses have the fallowing attitudes: () - (()-). Strikeslip faults can be sympathetic. For example the 1997 Bojnurd earthquake on the Yekke-shakh fault affects Baba- aman and Gharlegh faults.