Earthquake and post-earthquake vulnerability assessment of urban gas pipelines network

Urban gas pipelines network as one of the most vital lifelines plays an important role in the level of vulnerability and earthquake damage. Iran is located on the Alpide earthquake belt, which is one of the highly earthquake-prone zones of the world. The first earthquake effect, which can damage pipelines, is the transient ground deformation caused by wave propagation. The second one is the permanent ground deformation, which refers to liquefaction, landslide, and ground failure. With the failure of the gas pipelines, a fire may also occur, and consequently, the indirect damage caused by the earthquake may even further increase. This paper investigates the seismic risk of the Asaluyeh city urban gas distribution network by regarding the all geo-seismic hazard using HAZUS methodology. The post-earthquake ignition is evaluated using fault tree method, and the consequences of the design earthquake are assessed using PHAST package. Finally, the network physical damage risk, human risk, and direct economic risk are all evaluated. The results show that three possible failures may happen in the Asaluyeh gas distribution network. While the probability of an ignition occurrence is 35% for leakage and 32% for breaking, the post-earthquake ignition can affect around 30 people.