The Minimum Urban Structure

The prevention of damages caused by earthquakes has always been faced considering the resistance of the artifacts to the strains produced by the earthquakes. After the earthquake in Southern Italy (1980) there has been awareness that seismic vulnerability of settlements cannot only be associated with the safety of buildings. In scientific literature the methodology used for urban seismic risks the same as building seismic risk, and considers these three factors: hazard, vulnerability and loss. Hazard depends on the seismic activity of an area and on its geological feature; vulnerability is the susceptibility of a building to be damaged by a seismic event; loss is defined as the economic and social losses caused by damage and failures resulting from an earthquake. The resistance to earthquake in a settlement also depends on the performances that these artifacts supply under a systemic point of view. The vulnerability of a settlement depends not only on building performance but also on the function of structures and infrastructure. The vulnerability of an urban system measures the relationship between the intensity of the seismic event and the extent of the damage to the urban system. Is it possible to reduce urban vulnerability guaranteeing the safety of strategic structures and infrastructure vital to the urban system, providing guarantee that a set of vital performances of the urban system remains active after an earthquake? Minimum Urban Structure is suggested: it is a system of routes,