Evaluation of Fault Setback in Urban Area (A case study: South Mashhad Fault)

Safety design of structures concerning surface faulting effects such as shear and differential subsidence are very costly and in some cases are impossible. Then the appropriate approach for encountering surface faulting is to determine a suitable fault-avoidance zone. In this study, firstly the theorem of avoidance fault zone is presented, and then the setback area from the fault zone of South Mashhad fault is proposed. Recent studies show that South Mashhad fault is a right-lateral strike-slip fault with a normal component that cut the Quaternary sediments. In this work, the average slip rate and estimated return period for South Mashhad fault are 0.59 mm/yr and 2930 years, respectively.  Accordingly, the proposed avoidance zones in the south (hanging-wall) and north (foot-wall) of the fault are 80 and 70 meters, respectively. Considering the avoidance zones, many residential and other important structures are located in the avoidance zone of the South Mashhad fault.