Following the April 6 2009 L’Aquila earthquake, a great effort has been carried out by numerous research institutions for seismic microzonation purposes of urban areas in order to evaluate the seismic potential of the main active faults of the epicentral area. This is the case of the active Mt. Pettino master extensional fault (hereafter PEF) which controls the tectono-sedimentary evolution of western L’Aquila Basin. PEF is near to a strongly urbanized area which coincides with its pediment. This condition shows a high seismic exposition, so that specifically devoted multidisciplinary investigations, organised in subsequent in-depth steps and whose results are presented here, permitted to fine-tune its seismic hazard evaluation. The investigations were mainly based on a seismic reflection profile orthogonal to the fault strike in its hangingwall. The seismic profile was interpreted by comparison with the geological outcropping data and the stratigraphic analysis of numerous boreholes, several of which reached the pre-Quaternary substratum. The main goals were double: (i) to improve the integrated geological-geophysical subsurface model for the evaluation of the local seismic amplification and (ii) to estimate the PEF seismic hazard through the study of the sedimentary infill evolution and the tectonic subsidence of the PEF hangingwall which were strictly interrelated with the PEF seismic history.