Predicted vs. observed performances of the L'Aquila gas network during the 2009 earthquake

Landslide and liquefaction, together with ground shaking, cause major damage on pipelines network during an earthquake. In the present work the simplified loss estimation methodology suggested by HAZUS was adapted and improved to account for Italian seismicity and local soil conditions, and then used to evaluate the effects of the 6th April 2009 L'Aquila earthquake on the gas network. The methodology was implemented in a GIS environment and applied on an area of about 550 km2 in the Aterno valley. Key factors of the methodology are the earthquake scenario (seismic hazard), and the geological and the subsoil properties, that allow defining the seismic demand, as well as the inventory, the typology and the specific properties of the pipelines, that help to characterise the fragility functions of the elements composing the network. Seismic demand was evaluated taking into account both transient ground deformation caused by the propagation of seismic waves (ground shaking) and permanent ground deformation caused by slope instability. The degree of damage was computed in terms of number of repairs per unit length of pipe associated to the seismic demand, expressed in terms of peak ground velocity, and permanent ground displacement, relevant to the 6th April 2009 earthquake event. Finally the predicted damage scenario was compared with that observed on a limited part of the network.