The frequent confusion between the concepts of risk, vulnerability and seismic hazard, recommended precisely distinguish these concepts. Seismic risk, according to the definition proposed in 1980 by the U.N.E.S.C.O. in the publication "Earthquakes", is expressed according to the following expression:
SEISMIC RISK = DANGER * VULNERABILITY * COST.
Seismic risk(Seismic Risk): is the probability that the social or economic consequences caused by an earthquake match or exceed defaults to a location or given geographic area.
To get it convolucionan three elements: [R] = [H] * [V] * [SL]
The seismic hazard:It is the probability that the value of a certain parameter that measures the movement of soil (intensity; acceleration..), is exceeded in a given period of time, also called period of exposure. For example, a period of return of 500 years for a degree of intensity MSK VII is equivalent to saying that: there is a 10% probability of occurrence of an earthquake of intensity equal to or exceeding grade VIII over a period of 50 years exhibition either the annual probability of occurring an earthquake measuring VIII or higher is 0.2 per cent per annum during the period of years definedthat is to say that the soil does not suffer a greater than a specified intensity shock.
Seismic vulnerability: is the quantification of the damage or extent of damage is expected to suffer a certain structure or group of structures, subjected or subjected to the dynamic action of shaking of the ground of a certain intensity. For example, would be tantamount to saying that 30% of the buildings built with reinforced concrete would suffer serious harm if an earthquake measuring VIII in a particular city.
Seismic losses: is the (now euros) evaluation of material costs and loss of life caused by the occurrence of an earthquake, bearing in mind the vulnerability of buildings and infrastructure.
The seismic danger only depends on the geographic location of the site while the seismic vulnerability and losses depend on the constructive characteristics of the area and its socio-economic characteristics.
Probabilistic models of of calculation of seismic hazard: