Hazard Analysis Approach Research Articles

An extended HAZOP analysis approach with dynamic fault tree

An extended hazard and operability (HAZOP) analysis approach with dynamic fault tree is proposed to identify potential hazards in chemical plants. First, the conventional HAZOP analysis is used to identify the possible fault causes and consequences of abnormal conditions, which are called deviations. Based on HAZOP analysis results, hazard scenario models are built to explicitly represent the propagation pathway of faults. With the quantitative analysis requirements of HAZOP analysis and the time-dependent behavior of real failure events considered, the dynamic fault tree (DFT) analysis approach is then introduced to extend HAZOP analysis. To simplify the quantitative calculation, the DFT model is solved with modularization approach in which a binary decision diagram (BDD) and Markov chain approach are applied to solve static and dynamic subtrees, respectively. Subsequently, the occurrence probability of the top event and the probability importance of each basic event with respect to the top event are determined. Finally, a case study is performed to verify the effectiveness of the approach. Results indicate that compared with the conventional HAZOP approach, the proposed approach does not only identify effectively possible fault root causes but also quantitatively determines occurrence probability of the top event and the most likely fault causes. The approach can provide a reliable basis to improve process safety.

A Study on Implementing Food Safety Management System in Bottling Plant

This study provides the need for implementing Food Safety Management System (FSMS) to ensure the safety of the drinking water. Procedural challenges faced in adaptation of ISO 22000:2005 Food Safety Management Standards for a bottling company to achieve its safety goals. For implementing the FSMS, the general and documentation requirement with modular approach and the Management responsibility for their food safety policy, hygienic design, specifying the program for cleaning and sanitisation, equipment maintenance, control for strict raw materials and analysis of critical control point (CCP) are taken care of. For guarantee food safety, before the implementation the Pre-requisite Programs is followed for controlling the generic hazards. The systematic approach for Hazard analysis with the help of a practical approach model gets a control on non-conforming product/material and also for potentially unsafe products. The implementation of FSMS covers all the manufacturing operations, from receipt of raw materials, material storage, processing, packaging, warehousing and distribution.

A proposed probabilistic seismic tsunami hazard analysis methodology

We expand on existing probabilistic tsunami hazard analysis (PTHA) approaches by presenting a methodology wherein the epistemic uncertainties associated with tsunami timing, generation, and propagation are separated from aleatory uncertainties. The contributions of epistemic and aleatory uncertainties to the overall uncertainty in tsunami hazard are evaluated through a two-level Monte Carlo analysis. The total epistemic uncertainty contribution defines the variance of the tsunami inundation hazard distribution. Through Bayesian inference, the available catalog of tsunami runup data is used to refine the hazard estimate, where the prior distribution is weighted by epistemic uncertainties. The general PTHA framework is further modified to include a hazard function accounting for peak water elevation, velocity, duration of inundation, and warning time. We carry out a formal sensitivity analysis of the tsunami generation and propagation on the feasible model parameter space using the multi-objective generalized sensitivity analysis algorithm. Parameters showing a significant influence on tsunami hazard include the tidal elevation, moment magnitude (M w), the Gutenberg–Richter (G–R) distribution β parameter, epicenter location, and the rake angle. Parameters showing minimal influence on tsunami hazard include the G–R maximum seismic moment magnitude (M max) parameter, strike angle, dip angle, seismic depth and Manning’s roughness. As a proof of concept, the methodology is applied to a case study of tsunami hazard posed to National Oceanic and Atmospheric Administration Station 9411406 (Oil Platform Harvest, CA, USA) by seismic sources along the Aleutian Islands, AK.

Requirements for improved process hazard analysis (PHA) methods

In order to develop better process hazard analysis (PHA) approaches, weaknesses in current approaches first must be identified and understood. Criteria can then be developed that new and improved approaches must meet. Current PHA methods share common weaknesses such as their inability specifically to address multiple failures, their identification of worst-consequence rather than worst-risk scenarios, and their focus on individual parts of a process. There has been no comprehensive analysis of these systemic weaknesses in the literature. Weaknesses are identified and described in this paper to assist in the development of improved approaches. Knowledge of the weaknesses also allows PHA teams to compensate for them to the extent possible when performing studies.Key criteria to guide the development of improved methods are proposed and discussed. These criteria include a structure that facilitates meaningful brainstorming of scenarios, ease of understanding and application of the method by participants, ability to identify scenarios efficiently, completeness of scenario identification, exclusion of extraneous scenarios, ease of updating and revalidating studies, and ease of meeting regulatory requirements. Some proposals are made for moving forward with the development of improved methods including the semi-automation of studies and improvements in the training of team members.

A probabilistic approach for landslide hazard analysis

We present a general framework for probabilistic landslide hazard analysis. With respect to other quantitative hazard assessment approaches, this probabilistic landslide hazard analysis has the advantage to provide hazard curves and maps, and to be applicable to all typologies of landslides, if necessary accounting for both their onset and transit probability.The method quantifies, for a given slope location, the exceedance probability of being affected by a landslide with a specific local intensity within a reference time interval, i.e. the hazard curve, under the common assumption that landslides behave as a Poisson process. Hazard maps are calculated, reducing the hazard curve to single values by choosing a fixed probability of exceedance following standards or regulation requirements. The method is based on the assessment of a landslide onset frequency, a runout frequency for long-runout landslides, and the local definition of landslide intensity, which can be expressed through different parameters, according to landslide typology. For long runout landslides, the runout and spatially-varying intensity and uncertainty are considered.Hazard curves and maps play a fundamental role in the design and dimensioning of mitigation structures, in land planning and in the definition of risk and hazard management policies. Starting from the general framework, we apply the methodology for rockfall hazard analysis, and we test it in an area affected by the Christchurch 2011 earthquake, New Zealand, which triggered a large number of rockfalls, killing five people.

Probabilistic seismic hazard assessment of Himachal Pradesh and adjoining regions

Seismically active Himachal Pradesh and adjoining regions comprising Himalayan orogenic belt with the experience of the great Kangra earthquake of 1905, has high potential for river valley projects. There are already operating hydropower projects, some under construction and a few more coming up. In view of this it is important to know the ground motion nature for various locales. The present study is about estimation of Peak Ground Acceleration (PGA) for the state of Himachal Pradesh and adjoining regions using probabilistic seismic hazard analysis (PSHA) approach. Standard procedure for PSHA has been adopted for this study and peak ground motion has been estimated for 10% and 2% probability of exceedance in 50 years at the bed rock level considering two cases: (i) varying b-value for each source zone, (ii) constant b-value for each source zone. For 10% probability of exceedance in 50 years, the PGA values vary from 0.096 to 0.15 g and 0.09 to 0.26 g considering varying b-value, and constant b-value, respectively. In case of 2% probability of exceedance in 50 years, the PGA varies between 0.07 to 0.24 g considering varying b-values and 0.14 to 0.37 g considering constant b-values. Higher PGA values are observed in the southeast part considering varying b-values whereas the region situated around Kaurik Fault System (KFS) has shown higher PGA values in case of constant b-value.

EWaSAP: An early warning sign identification approach based on a systemic hazard analysis

Early warning signs and signals are perceivable sets of data which indicate in a timely manner the presence of flaws and threats to a system. Unfortunately, the structured identification and analysis of early warning signs is not readily supported by conventional hazard and risk analysis approaches. To address this problem, the STAMP Based Process Analysis (STPA) has been extended to incorporate the identification of early warning signs. The result is the Early Warning Sign Analysis based on the STPA (EWaSAP) approach. EWaSAP is described in this paper as well as the results of a case study using it in a critical process at a real world drinking water treatment works. After using EWaSAP, a significant increase on the predefined list of early warning signs was noted.

Neotectonic study of the Western Crete and implications for seismic hazard assessment

A detailed study has been realized in the framework of a large-scale seismotectonic survey in Western Crete (Southern Greece), for the creation of a revised neotectonic map in a scale of 1:50.000, including the recognition and mapping of the main neotectonic faults and the evaluation of their seismic potential. For this reason, the faults under investigation were distinguished as active, possible active and inactive. Kinematic data and striations were used to estimate the corresponding stress field geometry. Two distinctive stress phases were recognized, operating after the Middle Miocene extensional exhumation of deep crustal rocks. The first N-S extension phase (D1) took place during Mid-Upper Miocene to Lower Pliocene, forming large normal faults, trending mainly E-W, that bound the large Neogene basins. The second phase (D2) took place during late Pliocene-Quaternary times, forming medium-to-large normal faults that trend mainly N-S, related to an E-W extension. In the E-W trending D1 faults, a younger strike-slip striation usually occurs, compatible with the later D2 kinematics. Smaller, mainly NE-SW trending faults, with significant lateral displacement, indicate a kinematic compatibility to the more recent D2 phase. Some of these faults act as transfer zones between the larger N-S trending D2 faults. Considering the fault length and the using several geological criteria for their seismic risk evaluation, we recognized 13 large major fault zones in the study area, six of which were considered as active, while three as possible active faults. Results obtained from the analysis of fault plane solution information verify both the determined active (D2 phase) stress field results, as well as the local kinematic behavior of the neotectonic faulting. Moreover, a detailed seismic hazard analysis, involving both probabilistic and deterministic approaches, shows a significant spatial variation of the various hazard measures, with the seismic hazard of the westernmost part of study area being controlled by the neighboring higher seismicity neotectonic faults

Seismic hazard map of Coimbatore using subsurface fault rupture

This study presents the future seismic hazard map of Coimbatore city, India, by considering rupture phenomenon. Seismotectonic map for Coimbatore has been generated using past earthquakes and seismic sources within 300 km radius around the city. The region experienced a largest earthquake of moment magnitude 6.3 in 1900. Available earthquakes are divided into two categories: one includes events having moment magnitude of 5.0 and above, i.e., damaging earthquakes in the region and the other includes the remaining, i.e., minor earthquakes. Subsurface rupture character of the region has been established by considering the damaging earthquakes and total length of seismic source. Magnitudes of each source are estimated by assuming the subsurface rupture length in terms of percentage of total length of sources and matched with reported earthquake. Estimated magnitudes match well with the reported earthquakes for a RLD of 5.2% of the total length of source. Zone of influence circles is also marked in the seismotectonic map by considering subsurface rupture length of fault associated with these earthquakes. As earthquakes relive strain energy that builds up on faults, it is assumed that all the earthquakes close to damaging earthquake have released the entire strain energy and it would take some time for the rebuilding of strain energy to cause a similar earthquake in the same location/fault. Area free from influence circles has potential for future earthquake, if there is seismogenic source and minor earthquake in the last 20 years. Based on this rupture phenomenon, eight probable locations have been identified and these locations might have the potential for the future earthquakes. Characteristic earthquake moment magnitude (M-w) of 6.4 is estimated for the seismic study area considering seismic sources close to probable zones and 15% increased regional rupture character. The city is divided into several grid points at spacing of 0.01 degrees and the peak ground acceleration (PGA) due to each probable earthquake is calculated at every grid point in city by using the regional attenuation model. The maximum of all these eight PGAs is taken for each grid point and the final PGA map is arrived. This map is compared to the PGA map developed based on the conventional deterministic seismic hazard analysis (DSHA) approach. The probable future rupture earthquakes gave less PGA than that of DSHA approach. The occurrence of any earthquake may be expected in near future in these eight zones, as these eight places have been experiencing minor earthquakes and are located in well-defined seismogenic sources.

Probabilistic Liquefaction Hazard Analysis for Four Canadian Cities

Changes to building codes in the last decade, lowering the probability at which design ground motions for geotechnical applications are defined, have led to an urgent need for a probabilistic approach/tool for liquefaction potential assessment. We propose a consistent approach for probabilistic liquefaction hazard analysis (PLHA) that is based on probabilistic seismic hazard analysis and incorporates a reliability- based liquefaction potential evaluation method based on shear-wave velocity data. The method directly takes the joint probability distribution of peak ground accelera- tion and moment magnitude into account. We demonstrate the method for four Canadian cities, employing our interim updated seismic hazard models for eastern and western Canada. Using the developed method and representative site profiles, PLHA is implemented for four major cities across Canada with the aim of investigating the impact of regional seismic characteristics on liquefaction hazard assessment. Sensitivity analysis indicates that different magnitude ranges of dominant contributing seismic events have significant impact on the extent of liquefaction hazard. More specifically, for a given seismic excitation level, the relatively high hazard contribu- tions from small-to-moderate earthquakes in eastern Canada leads to less significant liquefaction potential, in comparison with similar sites in western Canada.

Safety Requirements Analysis for Control Law Development of UAV Flight Control Systems

This paper investigates safety requirements analysis of unmanned aero vehicle flight control law development. A unified approach integrating failure hazard identification and control law applicability assessment is proposed for systematic identification of flight control law safety requirements from failures of both flight control system and other airborne systems. A human hazard analysis approach based on human/machine interfaces is developed for identification of safety requirements on control law logic design for preventing pilot operating error in flight. Application of proposed approach on a demo vehicle indicates that the approach proposed in this paper is effective in identification of safety requirements for flight control law development

Convex set theory-based seismic hazard analysis of low seismicity area

Historical seismic data and seismogenic information are quite scarce for the low seismicity region, and modeling the parameters uncertainties based on probabilistic model is suspicious. The convex set theory-based seismic hazard analysis approach is proposed. The uncertainties of b value, the annual occurrence rate v and the upper bound magnitude M u are described by the envelop bound convex model and the ellipsoidal bound convex model. Convex analysis method and China probabilistic seismic hazard analysis methodology are combined to perform a bound seismic hazard analysis for Ningbo city, China. The seismic intensity interval obtained using the bound seismic hazard analysis is compared with that calculated using China probabilistic seismic hazard analysis methodology. The sensitivity analysis indicates that the interval of seismic intensity is most sensitive to the annual occurrence rate v. Furthermore, the different convex models have little effect on the interval of seismic intensity.

The earthing of intrinsically safe barriers on offshore transportable equipment

The author has been involved during the last two years in the compliance of an offshore coiled-tubing unit which required certification to hazardous-area product standards and installation-standard compliance. As part of this work there was a need to investigate in greater depth the usage of zener barrier on board offshore transportable equipment. The question of earthing zener barriers offshore is reviewed and analysed from various sources – zener barrier manufacturers, international publications, standards and technical papers. This paper explains the difficulty of proper zener barrier earthing on board offshore transportable equipment. It proposes an engineering methodology to solve this issue. When zener barriers are still required, a solution is proposed for their earthing and the installation is studied with a hazard analysis and risk control (HARC) approach.

Logic-tree Approach for Probabilistic Tsunami Hazard Analysis and its Applications to the Japanese Coasts

For Probabilistic Tsunami Hazard Analysis (PTHA), we propose a logic-tree approach to construct tsunami hazard curves (relationship between tsunami height and probability of exceedance) and present some examples for Japan for the purpose of quantitative assessments of tsunami risk for important coastal facilities. A hazard curve is obtained by integration over the aleatory uncertainties, and numerous hazard curves are obtained for different branches of logic-tree representing epistemic uncertainty. A PTHA consists of a tsunami source model and coastal tsunami height estimation. We developed the logic-tree models for local tsunami sources around Japan and for distant tsunami sources along the South American subduction zones. Logic-trees were made for tsunami source zones, size and frequency of tsunamigenic earthquakes, fault models, and standard error of estimated tsunami heights. Numerical simulation rather than empirical relation was used for estimating the median tsunami heights. Weights of discrete branches that represent alternative hypotheses and interpretations were determined by the questionnaire survey for tsunami and earthquake experts, whereas those representing the error of estimated value were determined on the basis of historical data. Examples of tsunami hazard curves were illustrated for the coastal sites, and uncertainty in the tsunami hazard was displayed by 5-, 16-, 50-, 84- and 95-percentile and mean hazard curves.

MOX燃料加工施設に対する確率論的安全評価手法の開発

A Probabilistic Safety Assessment (PSA) procedure for Mixed Oxide (MOX) fuel fabrication facilities was developed. The procedure is a "two-part five-step" approach which takes characteristics of MOX fuel fabrication facilities into consideration. In the first part, so-called preliminary PSA, the hazard analysis approach was applied, which consists of two analysis steps: Functional Failure Modes and Effects Analysis (FFMEA) and Risk Matrix Analysis. The FFMEA analyzes a variety of functions of equipment composing the facility to identify potential abnormal events exhaustively. In the Risk Matrix Analysis, these potential events are screened to select abnormal events as candidates to be analyzed in the second part, using two-dimensional matrix based on the likelihood evaluated by probabilistic index method and maximum unmitigated radioactive release calculated by the Five-Factor Formula. For the selected abnormal events, in the second part, so-called detailed PSA, accident sequences, their occurrence frequencies and consequences are analyzed. These three analysis steps correspond to PSA procedure for nuclear power plant. The applicability of the PSA procedure was demonstrated through the trial application to model plant of MOX fuel fabrication facility.

Error budget calculations in laboratory medicine: linking the concepts of biological variation and allowable medical errors

Background: Random, systematic and sporadic errors, which unfortunately are not uncommon in laboratory medicine, can have a considerable impact on the well being of patients. Although somewhat difficult to attain, our main goal should be to prevent all possible errors. A good insight on error-prone steps in the laboratory process is essential to achieving a structured system for error reduction. Methods: Here, the process of laboratory medicine is divided into phases, and for each phase, an error frequency is presented. While error frequencies in the laboratory (pre-analytical to post-analytical) have been reported elsewhere, we also include them in the present paper. In order to investigate error frequencies in the pre-pre- and post-post-analytical phases, clinicians were asked to carefully answer questions concerning their ordering strategies for laboratory investigation and their interpretation of results. Results: In the present study, the overall error rate in laboratory medicine was found to be 20.0%. The error percentages in the pre-pre- and post-post-analytical phase were about 12.0% and 5.0%, respectively. This indicates that, also on the clinical side, error reduction is desirable, especially in the requesting of laboratory investigation. Error reduction can be achieved through process redesigning by, for example, applying the Hazard Analysis and Critical Control Points approach. The error budget that clinicians might spend, based upon critical differences, is 26.9%. For the same test set and production circumstances, the overall biological variation is 7.9%. Clinicians thus take the error rates into account in their practical, daily use, and the ultimate achievable in laboratory medicine is biological variation. Conclusions: Several currently available software applications can aid error reduction in clinical chemistry. Both laboratory consultants and the use of information and communication technology are essential tools in optimizing the efficiency of laboratory medicine.

Engineering predictions of explosive layer formation in flammable-liquid spills

A model is described to predict the evaporation of a flammable-liquid spill and the subsequent formation of an explosive layer by mixing of the vapors with surrounding air. The model is intended for use in engineering predictions and is, therefore, designed to be easy to use and to produce answers within a very short time. To achieve these goals, simplifying assumptions have been introduced, the most important being the treatment of the flow field as one-dimensional (i.e., only variations in the vertical direction are taken into account). Special adjustments are made through submodels for effects that would not be addressed with sufficient accuracy by neglecting horizontal gradients. This is done to deal with forced ventilation and to treat the case where the vaporizing pool occupies only a fraction of the floor area of the enclosure. The model has been validated by comparison with available data from vaporizing pools and for diffusing heavy vapors; some of these comparisons are presented. Overall, agreement with experiment is found to be satisfactory and generally on the conservative side. This evaluation has confirmed the suitability of the formulation for use as a component in a comprehensive hazard-analysis approach that includes methods to predict the pressure increase from combustion of the explosive layer. Development of an integrated tool is currently under way.

Uncertainties in Seismic Hazard Maps for the New Madrid Seismic Zone and Implications for Seismic Hazard Communication

Earthquake risk assessment has been described as “a game of chance of which we still don't know all the rules” (Lomnitz, 1989). This challenge is illustrated by attempts to estimate the seismic hazard for parts of the central U.S. due to earthquakes in the New Madrid Seismic Zone (NMSZ). The U.S. Geological Survey National Seismic Hazard Maps predict that the seismic hazard in the area is surprisingly high, in some ways exceeding that in California. These predictions reflect crucial parameter assumptions, many of which have considerable uncertainty due to the absence of instrumental data from any but small earthquakes. Hence we explore the coupled questions of how the predicted hazard depends on various assumptions and how the uncertainties in estimates of hazard might be communicated to scientists, engineers, policy-makers, and others facing the challenge of deciding on seismic safety strategies that balance costs and benefits. At present, most seismic hazard assessment is done using the probabilistic seismic hazard analysis (PSHA) approach developed by Cornell (1968) and widely applied in engineering design ( e.g., Reiter, 1990; McGuire, 1995). An informative and entertaining overview of PSHA is given by Hanks and Cornell (1994). Major studies of seismic hazard in the central and eastern United States, including the NMSZ, were conducted in the 1980's by Lawrence Livermore National Laboratory (Bernreuter et al., 1985) and the Electric Power Research Institute (EPRI, 1986) for application to nuclear power plant licensing. A detailed study of the NMSZ was also carried out for the U.S. Department of Energy for the Gaseous Diffusion Plant in Paducah, Kentucky (Risk Engineering, 1999). Based on these and related efforts, and motivated bythe design and licensing needs of critical facilities, detailed consensus recommendations have been developed for conducting PSHA (SSHAC, 1997). It has become common to apply the PSHA method to …

Seismic design and analysis of underground structures

Underground facilities are an integral part of the infrastructure of modern society and are used for a wide range of applications, including subways and railways, highways, material storage, and sewage and water transport. Underground facilities built in areas subject to earthquake activity must withstand both seismic and static loading. Historically, underground facilities have experienced a lower rate of damage than surface structures. Nevertheless, some underground structures have experienced significant damage in recent large earthquakes, including the 1995 Kobe, Japan earthquake, the 1999 Chi-Chi, Taiwan earthquake and the 1999 Kocaeli, Turkey earthquake. This report presents a summary of the current state of seismic analysis and design for underground structures. This report describes approaches used by engineers in quantifying the seismic effect on an underground structure. Deterministic and probabilistic seismic hazard analysis approaches are reviewed. The development of appropriate ground motion parameters, including peak accelerations and velocities, target response spectra, and ground motion time histories, is briefly described. In general, seismic design loads for underground structures are characterized in terms of the deformations and strains imposed on the structure by the surrounding ground, often due to the interaction between the two. In contrast, surface structures are designed for the inertial forces caused by ground accelerations. The simplest approach is to ignore the interaction of the underground structure with the surrounding ground. The free-field ground deformations due to a seismic event are estimated, and the underground structure is designed to accommodate these deformations. This approach is satisfactory when low levels of shaking are anticipated or the underground facility is in a stiff medium such as rock. Other approaches that account for the interaction between the structural supports and the surrounding ground are then described. In the pseudo-static analysis approach, the ground deformations are imposed as a static load and the soil-structure interaction does not include dynamic or wave propagation effects. In the dynamic analysis approach, a dynamic soil structure interaction is conducted using numerical analysis tools such as finite element or finite difference methods. The report discusses special design issues, including the design of tunnel segment joints and joints between tunnels and portal structures. Examples of seismic design used for underground structures are included in an appendix at the end of the report.

A deterministic–probabilistic approach for seismic hazard assessment

A recurrent criticism of the deterministic approaches for Seismic Hazard Analysis (SHA) is that they make use of a controlling earthquake (usually the maximum to have occurred within a given time and space domain) instead of the frequency of earthquake occurrence. We propose a deterministic method for SHA, in which, instead of a fixed controlling earthquake, the earthquake frequency is used. The method is based on the deterministic procedure, developed by Costa et al. [Costa et al., 1993. J. Appl. Geophys. 30, 149–160]. This procedure computes synthetic seismograms over a regular grid of receivers. The input for these estimations consists of available earthquake sources and structural models. The earthquake sources are modelled as follows: the seismogenic zones are divided into cells of dimension 0.2°×0.2° and a point source is placed in the centre of each cell. The magnitude of the maximum observed earthquake in the cell and the available focal mechanisms are then used to assign the seismic moment and the double-couple orientation to the source. In this study, the rate of earthquake occurrence is taken into account, using the recently computed [Molchan et al., 1997. Bull. Seismol. Soc. Am. 87, 1220–1229] Gutenberg–Richter parameters in each seismogenic zone in Italy. An annual probability of exceedance and an average return period are calculated for each event of a given magnitude. The average annual number of events producing ground motion exceeding a given value, and, therefore, an annual probability of exceedance, are then calculated at each receiver. The methodology allows us to estimate both the ground motion due to large and rare events as well as that due to small and frequent earthquakes, and the obtained results can be easily compared with the probabilistic studies (if available) for standard return periods. The approach for seismic hazard analysis proposed here has two outputs: a `deterministic' (i.e. fixed ground motion due to a fixed event), and a `probabilistic' (i.e. annual average number of events, or probability of ground motion exceedance over a given time period). The method we propose overcomes one of the most recurrent criticism of the deterministic approaches for SHA, and at the same time maintains their advantages: clear and realistic estimation of engineering parameters needed in the calculation of Seismic Risk. As an example, the `deterministic–probabilistic' approach has been applied to estimate the seismic hazard for the region of eastern Sicily in Italy.