Rapid seismic risk assessment

Seismic risk in the form of impending disaster has been seen from past records that moderate-to-large earthquakes have caused the loss of life and property in all parts of Nepal. Despite the availability of new data, and methodological improvements, the available seismic hazard map of Nepal is about two decades old. So an updated seismic hazard model at the country level is imperative and logical. The seismic hazard and risk model constitute important tools for framing public policies toward land-use planning, building regulations, insurance, and emergency preparedness. In fact, the reliable estimation of seismic hazard and risk eventually minimizes social and economic disruption caused by earthquakes. In this frame of reference, the seismic risk assessment at a country level is elementary in reducing potential losses stemming from future earthquakes. Thus, this study investigates structural vulnerability, seismic risk, and the resulting possible economic losses owing to future earthquakes in Nepal. To this end, seismic risk assessment in Nepal is done using an existing probabilistic seismic hazard, a newly developed structural vulnerability, and recently released exposure data. The OpenQuake-engine, the open-source platform for seismic hazard and risk assessment from the Global Earthquake Model initiative, was used to calculate the seismic hazard and risk in Nepal. The seismic hazard and mean economic loss map were formulated for the 1, 2, 5, and 10 % probability of exceedance in 50 years. Finally, the distribution of building damage and corresponding economic losses due to the recurrence of the historical 1934 earthquake was presented in this study.

Use of fragility curves to assess the seismic vulnerability in the risk analysis of mountain tunnels

지진취약도 분석을 통하여 교량의 지진 위험도를 평가하였다. 지진취약도 분석에서는 교각 하부의 소성힌지의 거동을 주요 손상인자로 분석하였으며, 또한 한반도 지진재해지도를 근거로 하여 지진발생확률을 산정한 후 이들을 이용하여 교량의 성능단계에 따른 손상발생확률을 분석하였다. 이 연구에서는 교각에 직접 전달되는 지진이 아닌 암반노두에서의 지진의 최대지반가속도에 대하여 지진취약도를 분석하였으며, 비선형 지진해석을 위해서는 층상지반의 영향으로 증폭된 지진하중을 고려하였다. 제안된 방법으로 예제교량의 지진위험도를 분석하였으며, 면진받침이 설치된 교량에 대한 지진 위험도의 저감 효과를 정량적으로 분석하였고, 지진재해지도에서의 조건이 다른 지역에 시공되는 경우의 지진위험도를 분석함으로써 현 시방서의 타당성을 간접적으로 검토하였다. Seismic risk assessment of bridge is presented using fragility curves which represent the probability of damage of a structure virsus the peak ground acceleration. In theseismic fragility analysis, the structural damage is defined using the rotational ductility at the base of the bridge pier, which is obtained through nonlinear dynamic analysis for various input earthquakes. For the assessment of seismic risk of bridge, peak ground accelerations are obatined for various return periods from the seismic hazard map of Korea, which enables to calculate the probability density function of peak ground acceleration. Combining the probability density function of peak ground acceleration and the seismic fragility analysis, seismic risk assessment is performed. In this study, seismic fragility analysis is developed as a function of not the surface motion which the bridge actually suffers, but the rock outcrop motion which the aseismic design code is defined on, so that further analysis for the seismic hazard assessment may become available. Besides, the effects of the friction pot bearings and the friction pendulum bearings on the seismic fragility and risk analysis are examined. Lastly, three regions in Korea are considered and compared in the seismic risk assessment.

An increasing number of rapidly growing urban areas in Asia are becoming more vulnerable to seismic hazards in their development process. However, local authorities rarely integrate seismic risk into the procedure of emergency and land-use planning. This article explores the question of whether seismic risks for urban areas are increasing or diminishing over time, while trends such as population growth and land development in hazard-prone areas increase the potential for loss in disasters. The net effects of such urbanization factors are examined through the use of simulation models that estimate building inventory and seismic loss changes. Seismic losses are modeled for a comparative analysis under the same hypothetical earthquake events hitting at different points in a city area’s long-term development. A case study of seismic risk assessments is illustrated by the Hsinchu City, Taiwan. Results of a prospective analysis indicate that, for the same seismic events, overall risk is expected to increase due to a forecast 2.9 % growth in building inventory. This increment in loss is largely attributed to a large amount of initial buildings predicted to be developed into commercial and industrial uses. However, the spatial pattern of risk would change slightly; particularly, the southeastern, eastern, and some older core areas would be the most vulnerable and risky both at current and future time periods. The approach here enables city planners to incorporate seismic risk analysis into predisaster emergency and land-use planning to encourage risk-reduction strategies.

The paper presents a framework for the vulnerability analysis to assess seismic risk for the Republic of Georgia. Firstly, detailed inventory map of elements at risk was created. Here elements at risk are comprised of buildings and population. The grid of 0.025° size was created to summarize building and population data into the grid cells for further analysis. The custom programming script was created that summarizes the following information for each grid cell: the total number of buildings, total area of buildings, total population, total number of buildings per each taxonomy class and total area of buildings for each taxonomy class. Secondly, seismic hazard maps were calculated based on modern approach of selecting and ranking global and regional ground motion prediction equation for region. Thirdly, on the bases of empirical data that was collected for some earthquake intensity based vulnerability study were completed for Georgian buildings. Finally, probabilistic seismic risk assessment in terms of structural damage and casualties were calculated for the territory of Georgia for 2.8 km grid cells using obtained results. This methodology gave prediction of damage and casualty for a given probability of recurrence, based on a probabilistic seismic hazard model, population distribution, inventory, and vulnerability of buildings.

To assess the seismic failure risk of post electrical equipment, an assessment method considering different sorts of uncertainty of the post electrical equipment was proposed. The aleatory and epistemic uncertainties were considered in the assessment, and the parameters in seismic hazard function of different sites were fitted. To investigate the effects of the supporting structure on the seismic fragility and risk of post electrical equipment, case studies on ultra-high-voltage gas insulated switchgear bushings mounted on two different supporting frames were conducted. The results indicated that both the maximum tensile stress of the bushing and the maximum displacement of the supporting frames should be considered as the limit statuses of the post electrical equipment. The different sorts of uncertainty increase the seismic failure risk of the post electrical equipment, and should be considered in the assessment. Besides, for the pillar-type porcelain element equipment, the supporting frames with lower lateral stiffness generated higher seismic failure risk. In constrast to the case of retrofitting the supporting frame to increase the lateral stiffness, the annual seismic failure risk of the GIS bushing mounted on the retrofitted supporting frame decreased 101%. Besides, the seismic failure risk of the post electrical equipment is not positive correlated with the peak ground acceleration. In the performance-based seismic design of the electrical substation, the seismic failure risk of the electrical equipment should be considered.

Traditional seismic risk assessments often require specialized expertise and extensive computational time, making probabilistic seismic risk evaluations less accessible to practitioners and decision-makers. To reduce the barriers related to applications of quantitative seismic risk analysis, this paper develops a Quick Loss Estimation Tool (QLET) designed for rapid seismic risk assessment of Canadian buildings. By approximating the upper tail of a seismic hazard curve using an extreme value distribution and by integrating it with building exposure-vulnerability models, the QLET enables efficient computation of seismic loss curves for individual sites. The tool generates seismic loss exceedance probability curves and financial risk metrics based on Monte Carlo simulations, offering customizable risk assessments for various building types. The QLET also incorporates regional site proxy models based on average shear-wave velocity in the uppermost 30 m to enhance site-specific hazard characterization, addressing key limitations of global site proxy models and enabling risk-based seismic microzonation. The QLET streamlines hazard, exposure, and vulnerability assessments into a user-friendly tool, facilitating regional-scale risk evaluations within practical timeframes, making it particularly applicable to emergency preparedness, urban planning, and insurance analysis.

Rapid seismic risk assessment method for museum exhibition halls based on seismic safety of artifacts

Soil types and depth of bedrock are not available for the majority of bridge embankments to allow detailed seismic analysis and risk assessment. The accompanying paper provides a quick methodology for preliminary seismic risk assessment, ranking, and prioritization of bridge embankments along priority routes. The objective of this paper is to apply the methodology to identify the seismic risk of 127 bridge embankments along I-24 in western Kentucky. The variables of each embankment including the geometry, type and properties of underlying soil, elevation of the natural ground line, and level of bedrock are estimated. The seismic slope stability capacity/demand ratio, displacement, and liquefaction potential of each bridge embankment are calculated. Three categories are presented to identify the failure risk of the embankments. A priority list of the embankments with the highest seismic risk of failure is generated for I-24 bridge embankments in western Kentucky during designated seismic events. The priority list will enable decision makers to decide on either carrying out further detailed evaluation or considering other appropriate actions for the embankments with the highest failure risk.

Nowadays, disasters in seismic-prone areas such as Italy and Chile, continue to cause dramatic human and economic consequences and affecting, among others, very ancient and historical churches, due to their high seismic vulnerability and probably due to the lack of risk management plans for the conservation of cultural property. This paper focuses on rapid seismic risk assessment by applying two simplified methods, based on expert judgement and observed damage, in old masonry churches, which aim to identify the most vulnerable elements and correlated threats that would act as site effects under the seismic action, for establishing intervention priority lists and for planning preventive conservation projects. The case studies are: the church of Sant’Agostino, built in stone masonry and located in Matera, an area with moderate seismicity in southern Italy; the church of San Francisco de Chiu Chiu, built in adobe and located in Calama, an area with average seismicity in the Andean northern Chile; and the church of San Francisco Baron, built in adobe and brick masonry, and located in Valparaiso, an area with high seismicity on the central coast of Chile.

This study evaluates and compares seismic risks associated with inland crustal earthquakes in Japan on the basis of published data available on the Japan Seismic Hazard Information Station (J-SHIS). First, taking account of prediction uncertainty of the attenuation law of seismic intensity, the evaluation method for population exposure (PEX) to seismic intensity is presented. The method is applied to 333 seismic events potentially caused by main active faults (154 cases) and other active faults (179 cases). The relationship between population exposure and the probability of occurrence of seismic events (“P-PEX relation”) and the resultant seismic risk curves are obtained. Generalized risk index which incorporates the effects of focusing on urgency (probability) or significance (PEX) is defined, producing various risk rankings of active faults.

This work investigates the effect of the level of detailing of site conditions as well as the selection of the fragility and vulnerability models on large scale seismic risk assessment. For this we consider the application of selected components of the recent European Seismic Hazard (ESHM20) and Risk (ESRM20) Models and we focus on Thessaloniki, Greece, a city which is very well documented in terms of local site conditions and exposure. Seismic risk results are compared in terms of expected damages and economic losses for a seismic hazard with a 475-year return period. The results indicate that the level of site conditions modelling does not significantly affect the estimated aggregate damages and economic losses at city scale, however significant discrepancies may occur at local scale. On the other hand, the selection of the vulnerability model for the building stock may considerably affect the intensity and the spatial distribution of damages, resulting in a considerable differentiation in the economic losses estimate.KeywordsESHM20ESRM20Site modellingSite amplificationFragility and vulnerability modelsSeismic risk model

Following U.S. Department of Energy Order 420.1 C for the mitigation of natural phenomena hazards, such as earthquakes, to nuclear facilities through periodic reassessments, Idaho National Laboratory (INL) has developed the Seismic Hazard Periodic Re-Evaluation Methodology (SHPRM). The SHPRM involves seven criteria that evaluate changes to the seismic hazard at a site due to changes in the input models/data over time. Should these changes to the seismic hazard result in an increase in the design or licensing-basis ground motion of the facility from that which the facility was designed for, the SHPRM includes a criterion for reevaluating the facility risk objectives. While the criteria corresponding to the reevaluation of the seismic hazard and the design basis have been previously demonstrated and published, there is currently no guidance on reevaluating seismic risk for the purpose of SHPRM. This paper complements the published reports and papers on the application of SHPRM by demonstrating the risk objectives criterion for a generic nuclear facility (GNF), thereby closing the loop on the application of the SHPRM. The GNF is assumed to be located at the INL site and designated as a Seismic Design Category-3 facility as per American Society of Civil Engineers (ASCE)/Structural Engineering Institute (SEI) 43-05. The demonstration includes a risk assessment for a baseline seismic hazard calculated in 2006 and an updated seismic hazard calculated in 2015. After presenting the baseline and the updated seismic hazard curves at this site, the state-of-practice methodology for calculating fragility functions for the facility is presented, along with the fragilities calculated for the GNF. Employing a fault tree analysis using the INL in-house seismic analysis and risk assessment software MASTODON, the seismic risks of collapse of the GNF for the baseline and updated seismic hazards are computed to be 5.27E−05 and 5.2E−06, respectively. The results show that not only the reevaluated seismic risk is smaller, but more importantly, that it meets the risk objectives set by ASCE/SEI 43-05.

This paper presents the overall methodology and results of a seismic risk assessment performed on two facilities in California. The purpose of this study was to assess the financial risks associated with earthquakes at non-nuclear facilities. Analytical tools, assumptions and models applicable to the assessment of seismic risk to nuclear power plants were utilized in this study. Structural failures that could potentially result in loss of the buildings were evaluated and the ground acceleration levels that could induce failures of critical structures were calculated. A frequency distribution of earthquakes was next constructed based upon exceeding ground acceleration levels as a function of distance from identified seismic events and the estimated intensity of each seismic event. The ground accelerations associated with the structural failure data were then combined with the constructed frequency distribution to determine the frequency of seismic events that equaled or exceeded the ground acceleration levels that would induce structural failures on the two sites. The resulting distribution estimates the potential risk of earthquakes inducing structural failures as data input for the consequential financial risk associated with these failures. The methodology application discussed in this paper can be a valuable tool used by insurance companies and by commercial and industrial firms to identify areas of high seismic risk that can then be used to evaluate financial risk, adequacy and value of insurance coverage, and the need to perform a seismic upgrade program.

A better seismic design for building and other structures is the most effective way to reduce seismic risk and avoid earthquake disaster. Adoption and implementation of new seismic safety regulations and design standards have caused serious problems in many communities in the New Madrid region, including western Kentucky, however. The main reasons for these problems are (1) misunderstanding of the national seismic hazard maps and (2) confusion between seismic hazard and seismic risk. Both are caused by probabilistic seismic hazard analysis (PSHA). PSHA is a mathematical formulation derived from a probability analysis on the distribution of earthquake magnitudes, locations, and ground-motion attenuation. Some assumptions and distributions associated with PSHA have been found to be invalid in earth science, however. In addition, PSHA contains a mathematical error: equating a dimensionless quantity (the annual probability of exceedance – exceedance probability in one year) to a dimensional quantity (the annual frequency of exceedance with the unit of per year [1/yr]). Thus, PSHA is scientifically flawed and the resulting seismic hazard and seismic risk estimates are artifacts. The national seismic hazard curves and maps are artifacts because they were produced from PSHA, even though the inputs are scientifically sound. Although seismic hazard and seismic risk have often been used interchangeably, they are two fundamentally different concepts. Seismic hazard describes the natural phenomenon or property of an earthquake, whereas seismic risk describes the probability of loss or damage that could be caused by a seismic hazard. Seismic hazard and seismic risk play different roles in engineering design and other policy considerations. Furthermore, measures for seismic hazard mitigation are different from those for seismic risk reduction. The difficulties in the development of design ground motion for NEHRP provisions are caused by the use of the national seismic hazard maps which are neither seismic hazard nor seismic risk. The resulting design ground motions for building codes and other policy considerations are therefore problematic. California’s experience proves that deterministic/scenario seismic hazard analysis is an appropriate approach for seismic hazard assessment, seismic risk assessment, as well as *Kentucky Geological Survey, University of Kentucky, 504 Rose Street, Lexington, KY 40506; phone (859) 323-0564; fax (859)257-1147; e-mail: zmwang@uky.edu. 112 Seismic Hazard Design Issues in the Central United States engineering design and other policy considerations. Deterministic/scenario seismic hazard analysis is also appropriate for engineering design and other policy considerations in the New Madrid region, as well as other regions.