Seismic risk is defined in the prototype developed within the SERGISAI project as the convolution of three factors:
Seismic Risk = Seismic Hazard * Induced Physical Hazard * Systemic Vulnerability
Seismic Hazard includes all direct physical effects produced by an earthquake.
Induced Physical Hazard refers to those events, like landslides, that might be triggered by ground motion.
Systemic Vulnerability refers to the vulnerability of urban and regional systems, which cannot be considered only as the sum of the vulnerability of exposed structures.
The complexity of urban and human settlements suggests to substitute the concept of chain of losses to the simple couple hazard/hit system. The earthquake represents the triggering factor of this chain, whereas the consequential damage does not depend only upon the severity of the seismic input, but also upon many other "tightly coupled" factors.
In very general terms seismic risk is defined here as the probability of losses directly or indirectly caused by earthquakes, losses that might be suffered by the population and by the built environment. No single dimension approach is exhaustive, especially if the risk assessment is carried out not for a specific purpose, but for a comprehensive task, like civil protection or land use planning. A multicriteria approach has been implicitly chosen in this project. Damage assessment is normally done individually either for residential buildings, special buildings, critical facilities, or infrastructure and lifelines. Difficulties arise in putting together those objects to produce a comprehensive picture of what might happen in a region or in an urban area.
A step towards a more systemic approach has been looked for in this work, so as to identify what has been called the potential chain of losses. This idea can be developed both in the time dimension, by analysing the consequences of the earthquake during the emergency, the recovery and reconstruction; as well as in the spatial dimension, by extending the scope of the analysis beyond the core of the disaster and by considering different geographical scales.
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SERGISAI - Contract Number: ENV4-CT96-0279 (DG 12 DTEE)
Project Coordinator: Gaetano Zonnozonno@irrs.mi.cnr.it