Several European countries are affected by seismic risk, both for the frequency of earthquakes that have historically affected them and for magnitude achieved by earthquakes themselves. Europe is located in convergence zone between African and Eurasian plate; this is the main cause of its seismicity. Earthquake create serious damage to people and buildings and have a negative social and economic impact. Some of economic operators are included in legislation for major accident risks. These operators are chemical plants, pharmaceutical companies, refineries, fuel depots, power plants, steel mills, etc., that holding dangerous substances above certain thresholds fall within the scope of the European Directive 2012/18/EU (Seveso III Directive). In the Seveso III Directive, for the first time explicitly, the legislator refers to natural causes (for example earthquakes and floods) to obtain a detailed description of possible major-accident scenarios and their probabilities or the conditions in which they can occur. Purpose of this paper is to work out a preliminary analysis using an index method for the "Natech risk assessment induced by earthquake" which provides the basis for identifying critical units of plant. After this analysis, plant manager will be able to elaborate main corrective actions for prevention and mitigation.