Sensitivity Analysis of a Short-Cut Methodology for Assessing Earthquake-Related Na-Tech Risk

Abstract

Natural disasters may be powerful and prominent mechanisms of direct or indirect release of hazardous material (hazmat) (Young et al., 2004). If industrial sites are located in naturally hazard-prone areas, technological accidents may be triggered by natural events, such as storms, earthquakes, flooding, and lightning, generating the so-called Na-Tech (Natural and Technological) events and may modify as well as increase the impact and overall damage in surrounding areas (Galderisi et al., 2008). There is a wide range of literature on natural disasters and hazardous material accidents, but it is only in recent years that they have been treated as related events. Thus, Na-Tech events have begun to receive a significant amount of attention. Additionally, natural disasters have increased both in frequency and economic losses around the world (Young et al., 2004); therefore, there is increasing public awareness and interest from the scientific community. A qualitative methodology for the initial assessment of earthquake-related Na-Tech risk, where the full details of the method used in this work are discussed, (Busini et al., 2011) was developed as a screening tool to identify which situations require a much more expensive Quantitative Risk Analysis (QRA). The methodology, through suitable Key Hazard Indicators (KHIs), identifies the Na-Tech risk level associated with a given situation (i.e., a process plant located in a given territory), using the Analytical Hierarchy Process (AHP) as a multi-criteria decision tool for the evaluation of such KHIs. The methodology was validated by comparing its results with QRA results that involved Na-Tech events (Campedel et al., 2008). In this work, the sensitivity of the KHIs will be assessed, through the construction of specific case studies, in order to show the influence of certain variables upon the resulting values for scenarios related to fires, explosions and dispersion of toxic materials. In particular they will be analyzed: the influence upon the KHIs of the seismic vulnerability of different kind of tanks (unanchored, anchored and pressurized) and for different values of Peak Ground Acceleration (PGA); the influence upon the KHIs of the domino effect evaluated for different combinations of types of tanks (unanchored, anchored and pressurized); the influence upon the KHIs of the volatility of different substances, classified as compressed/liquefied gases, high volatility liquid, low volatility liquid and dusts.