Exposed and hidden geohazards: contribution to the volcanic and seismic risk evaluation

The assessment of the volcanic and seismic hazards is still a huge problem for the entire humankind, since every year hundreds of human lives are lost and damages to the economy and to the cultural heritage for billions of euros are recorded. Any natural or industrial risk assessment takes into account two parameters: the probability that an event may occur “P“ and the damage “D” that the event may induce. The scientific community operates to better assess the P parameter either with a probabilistic (earthquakes) and a more deterministic (volcanoes) approach. For the volcanic risk assessment, the P parameter is currently tackled using multidisciplinary observation systems aimed of reconstructing evolution sceneries of ongoing phenomena. The damage parameter “D” is basically evaluated using economic factors that combine the vulnerability factors with their intrinsic value (e.g. buildings, infrastructures, economic activities, human casualties). The better is the evaluation of P and D parameters, the better will be the risk minimization capacity. The risk minimization has severe consequences on the population safety and on the activities planning (including economic, territorial, social etc.) for those area prone to the natural risks. Therefore, to minimize the risk it is necessary to affect the “damage” parameter besides the continuous enhancement of the monitoring methods. In coincidence of volcanic and seismic crises, however, a range of “hidden” effects occur and, unfortunately, they are not yet considered for the evaluation of the D parameter although they are closely related to the territorial planning of the volcanic and seismic-prone areas. Some examples, such as the contamination of drinkable waters, the anomalous degassing of CO₂ and radionuclides during seismic and volcanic crisis of the recent past, highlight the necessity of an accurate territorial planning where exposed and hidden natural processes are both considered to gain the result of a correct and effective territory management.