Neogene units folding evidence of active tectonic in the North West Birjand

The north-west Birjand area tectonics is mainly affected by performance of western part of the Shekarab fault Zone. The results of the morphotectonic indexes include Smf,Vf, Er, SL, suggesting high amounts for SL (707) and Er (0.58) and lower values for Vf (0.94) and Smf (1.14), with neotectonic evidences such as cutting and tilting in Quaternary sediements, three abandoned river terrace levels and fault scarps, indicate the tectonics activity in this area. The stream fractal dimensions for western part of fault is 1.393 that also confirms tectonic activity. Cross section traced perpendicular to the fault zone represents three parallel east-west direction fault. Due to the occurrence of lateral migration in this area and adaptation epicenter of the recent earthquake above of north-west birjand thrus-fold, we suggest the rising in deposits along the F2 fault as fault related-folding. This anticline is asymmetric fold with more slope southern flanks than the northern flanke and also represent rising more on the northern flanks and with the performance of the back thrust with the slope to the south, rising anticline has been made. Due to the difference between the northern and southern flanks slopes of the anticline in the north-west Birjand and also difference between junction points of the anticline to the plains in northen and southern plain, and also due to the occurance of scarps parallel to the main faul because of growth and laterial migration in faults that they are show themself by topographical changes in the folding section, we consider the folding in the north west Birjand as fault propagation related-folding.