Uncertainty Analysis and Expert Judgment in Seismic Hazard Analysis

Abstract

The large uncertainty associated with the prediction of future earthquakes is usually regarded as the main reason for increased hazard estimates which have resulted from some recent large scale probabilistic seismic hazard analysis studies (e.g. the PEGASOS study in Switzerland and the Yucca Mountain study in the USA). It is frequently overlooked that such increased hazard estimates are characteristic for a single specific method of probabilistic seismic hazard analysis (PSHA): the traditional (CornellMcGuire) PSHA method which has found its highest level of sophistication in the SSHAC probability method. Based on a review of the SSHAC probability model and its application in the PEGASOS project, it is shown that the surprising results of recent PSHA studies can be explained to a large extent by the uncertainty model used in traditional PSHA, which deviates from the state of the art in mathematics and risk analysis. This uncertainty model, the Ang-Tang uncertainty model, mixes concepts of decision theory with probabilistic hazard assessment methods leading to an overestimation of uncertainty in comparison to empirical evidence. Although expert knowledge can be a valuable source of scientific information, its incorporation into the SSHAC probability method does not resolve the issue of inflating uncertainties in PSHA results. Other, more data driven, PSHA approaches in use in some European countries are less vulnerable to this effect. The most valuable alternative to traditional PSHA is the direct probabilistic scenariobased approach, which is closely linked with emerging neo-deterministic methods based on waveform modelling.

Lessons not yet learned from the Fukushima disaster

“…The most important root cause-the underestimation of the seismic and tsunami hazard-is not addressed at all. Despite the very poor hazard prediction results of traditional PSHA (Probabilistic Seismic Hazard Analysis), -nearly all recent large earthquakes (Tohoku earthquake and tsunami, Haiti (2010), Sichuan (2008), L'Aquila (2009) were underestimated in PSHA maps) the method is still in use and widely endorsed internationally although their systematic errors are very well-known as for instance is outlined in Klügel (2007Klügel ( , 2008Klügel ( , 2011. If this important lesson is not learned catastrophes like in Fukushima may repeat.…”

“…In Klügel (2011) I provided a detailed review of the associated methods. It was clearly demonstrated that the results of these methods are ambiguous.…”

Earthquake engineering needs and seismic hazard assessment

“…The data presented in Table 2 was used and the associated site intensities were calculated based on the equations used for the development of the Swiss national earthquake catalogue [24]. The general renewal process model (GRP) as described in detail [25] and as implemented in the reliability software tool WEIBULL++7© [26] was applied for the analysis. The type I GRP model was found to provide the best prediction of past earthquake observations.…”

“…Applying a Poissonian assumption for earthquake recurrence [1], this probability of exceedance is usually converted into a return period. The latter is frequently incorrectly interpreted as a temporal characteristic of the recurrence of earthquake ground motion accelerations although there is no basis for this interpretation and the above assumption [3].…”

Ship-borne Nonindigenous Species Diminish Great Lakes Ecosystem Services

“…SEJ is an established technique for probabilistic risk assessment (Apostolakis 1990;Cooke 1991;Aspinall 2010) and consequence analysis (Cooke and Goossens 2000). It has previously been used for several environmental applications including assessments of the likelihood of natural disasters (for example, volcanic eruption, dam failure; Aspinall and others 2003;Klugel 2011), the consequences of nuclear accidents (Cooke and Goossens 2000), the drivers of climate change (Morgan and others 2006;Lenton and others 2008), expected changes in fisheries and marine ecosystems (Rothlisberger and others 2010;Teck and others 2010) and increases in mortality attributable to air pollution (Roman and others 2008). The method has not previously been used to assess the ecosystem-level impacts of invasive species.…”