Seismic Hazard Assessment of District Mansehra,Khyber Pakhtoonkhawa,Pakistan

The site of Mansehra is located seismically in an active regime,known as the Crystalline Nappe Zone and Hazara-Kashmir Syntaxis in NW Himalayas,Pakistan.Seismic Hazard Assessment(SHA) for the site has been carried out by considering the earthquake source zones,selection of appropriate attenuation equations,near fault effects and maximum potential magnitude estimation.The Mansehra Thrust,Oghi Fault,Banna Thrust,Balakot Shear Zone,Main Boundary Thrust,Panjal Thrust,Jhelum Fault and Muzaffarabad Fault and,further to the south,the Sanghargali,Nathiagali,and Thandiani Thrusts are the most critical tectonic features within the 50 km radius of Mansehra.Using the available instrumental seismological data from 1904 to 2007,SHA has been carried out.Other reactivated critical tectonic features in the area have been investigated.Among them the Balakot-Bagh fault,with the fault length of 120 km from Balakot to Poonch,has been considered as the most critical tectonic feature on the basis of geological/structural/seismological data.The potential earthquake of maximum magnitude 7.8 has been assigned to the Balakot-Bagh fault using four regression relations.The peak ground acceleration value of 0.25 g(10% probability of exceedance for 50 years) and 0.5 g has been calculated with the help of the attenuation equation using probabilistic and deterministic approaches.