Seismic Risk Maps Research Articles

Seismic Risk Mapping of Bridges Using HAZUS and ArcGIS: The Case of Surat City, India

Seismic Risk Mapping of Bridges Using HAZUS and ArcGIS: The Case of Surat City, India

Android-based framework for condition assessment of existing RC hospital buildings

Rapid visual screening (RVS) is a practically viable tool implemented all over the world to rank structures based on their seismic vulnerability. Seismic assessment of hospital buildings is essential in seismic-prone regions to ensure their structural integrity and readiness to provide emergency care and medical treatment after significant seismic events. Therefore, in the current study, an approach is developed that is similar to the proven methodologies reported in the literature, for the seismic evaluation of structural and non-structural elements of hospital buildings in a metropolitan city like Karachi. Karachi is located in the southwest of Pakistan and is vulnerable to earthquake and tsunami hazards. To this end, an android-based RVS system has been developed for large-scale seismic risk mapping of hospital buildings. The proposed system acquires the physical status of the building features in real time and identifies the building performance obtained from the calculated seismic risk index. Moreover, three case study hospital buildings were employed and analysed through the proposed RVS system. Results illustrate the performance of case study hospital buildings at organisational, structural and non-structural levels based on seismic risk indices.

National risk assessment of Italian school buildings: The MARS project experience

Strategic buildings, such as schools, play a crucial role in civil society. They are essential not only for the well-being of communities but also for their significance during the emergency and recovery phases following an earthquake. Reliable risk assessment is a powerful tool for implementing effective mitigation strategies. While considerable work has been already done in the literature to develop fragility curves and risk studies for residential buildings, there remains a noticeable gap in addressing risk assessment for school portfolios. As part of the 2019–2021 MARS (Seismic Risk MAps) project, funded by the Italian Civil Protection Department and involving the ReLUIS consortium along with the EUCENTRE foundation, a specific task was dedicated to evaluating seismic risk for the Italian school buildings. In this context, eight research units combined their expertise to develop a consensus-based vulnerability model, known as the “School-MARS model”. This model integrates fragility curves based on various approaches (i.e. empirical, mechanical-analytical, mechanical-numerical and hybrid) and is tailored to archetypes representative of the Italian school buildings. The main goal of the paper is outlining the methodology used to define the “School-MARS vulnerability model”. Moreover, the paper demonstrates the application of the latter for performing intensity-based and time-based risk analyses. Specifically, the results are presented in terms of damage distribution and usability ratings expected for the entire stock of Italian school building. Notably, these results indicate that approximately 26 % of Reinforced Concrete (RC) buildings and 31 % of Unreinforced Masonry (URM) structures may become unusable due to potential earthquakes expected in the next 50 years.

SICURO+: A web platform to raise awareness on seismic risk in Italy

Italy is a country with high seismic risk. In the past many catastrophic earthquakes have occurred causing severe damage to buildings and infrastructures, serious economic impacts, and the loss of thousands of human lives. To mitigate the impact of seismic risk, as well as of other risks, many efforts have been made, implementing preventive structural measures and acting to raise awareness in the community. In Italy, this need was strengthened with the emanation of the new Civil Protection Code (D.Lgs January 2, 2018 n.1), with the purpose of encouraging the participation of citizens and spreading risk knowledge and the culture of civil protection, thus contributing to “increase the resilience of communities” (art. 31). As part of the agreement between the Italian Civil Protection Department (ICPD) and EUCENTRE (European Centre for training and research in Earthquake Engineering), an interactive web-tool was developed to allow citizens to display the most updated seismic risk maps. These maps were produced in 2018 by the ICPD, with the relevant support of the scientific community operating in the field of seismic risk, in particular of ReLUIS (The Laboratories University Network of seismic engineering) and EUCENTRE. The web-tool, named SICURO+ (Information System for Risk Communication, www.sicuropiu.it), was created to raise awareness in citizens on seismic risk in the place where they live, work, or go on holiday. Communication strategies and behavioural techniques were designed and tested experimentally with the support of behavioural scientists, as part of an agreement between the National School of Administration and the Prime Minister's Office.

Seismic analysis of buildings with basements

This research work analyzes how seismic waves affect buildings with basements that are usually studied independently: In surface structures the inertial forces originated by the movement of their base and in subway structures the deformations due to ground motion are considered. The building located in the city of Quito with twelve elevated floors and five subfloors is studied using nonlinear finite element modeling, considering that the subsoil depends on seismic excitations in a dynamic soil-basement-structure set, for which it is modeled together with its geotechnical components. The superstructure is integrated to the infrastructure and a time-history analysis is included with the most representative earthquakes can affect the building. The present investigation has three basic components: seismic, geotechnical, and structural, which are merged by means of specialized 3D structural engineering programs. In the seismic component, local and regional information about tectonic faults within Ecuador is collected; the building is then located on a seismic risk map and the magnitudes, types, and other parameters of the site where the building is located are determined. Using the results of the Earthquake Risk Assessment Project for the city of Quito (TREQ) and the Pacific Earthquake Engineering Research Center (PEER) database, three relevant seismic events are chosen for the time-history analysis that meet the seismic risk data for the building. For the geotechnical soil component, the geotechnical parameters of the original design of the building foundation, stratigraphy, and characteristics of soil solids, among others, are used. The structural component considers the type of material, geometry, dimensions, joints between elements and others of the original design for both basements and superstructure. The connection of these three components is carried out using Midas Gen and Midas GTS NX. The results of deformations as a function of time are compared with similar standards, studies, and investigations.

Loss Functions for the Risk Assessment of Residential Buildings

Within the ReLUIS 2019–2021 research project (Network of the University Laboratories of Seismic Engineering) supported by the Civil Protection Department (DPC), the Work Package WP4 “Seismic Risk and Damage Maps at National scale—MARS” aimed to update the 2018 version of the National Risk Assessment (NRA). One of the goals of the WP4—MARS was to collect, analyse and upgrade loss models to estimate direct economic losses, unusable buildings and casualties (Task 4.4—“Risk: evaluation of consequences and economic losses”). Task 4.4 aimed to carry out a critical review of the models available in the literature and subsequently specific comparisons to better understand the capability and reliability of the different models, in particular those adopted to calculate the seismic losses in the 2018 NRA. Furthermore, the derivation of new models in order to improve the results of the previous study was another goal of the project. The paper focuses on the assessment and calibration of models and tools to derive human casualties (deaths and injured) and usability rating as well as repair costs and population assistance costs associated with residential buildings damaged by seismic actions. In detail, the available literature on Casualty Estimation Models (CEMs) is analysed, and an updated model is calibrated to estimate human casualties for the Italian context. The model emphasises a relationship between the casualties and the severity of the damage. A strong correlation exists between the post-earthquake usability of buildings, damage state (DS), repair costs and time required to assist the population. According to data collected in the reconstruction processes of recent Italian earthquakes, fragility curves in terms of loss-of-usability for partially unusable and unusable buildings and the correlation between usability ratings (immediately available post-earthquake) and DS (easily computable by using existing empirical- or mechanical-based fragility functions) are defined. Finally, consequence functions able to associate direct costs (repair costs) and indirect costs (population assistance) have been calibrated as a function of buildings’ usability or damage state.

Study of Spun Pile to Pile Cap Connection with Steel Jacket Strengthening

Spun piles in Indonesia are designed to behave as an elastic structure according to SNI8460:2017. The piles are designed with low confinement where the amount does not meet ASCE 7-16 requirements. Indonesia should apply a performance-based design for the bottom structure someday since the seismic demand tends to increase based on the current seismic risk map. Steel jackets are proposed to fulfill the need for transverse reinforcement, particularly at the connection region where the curvature demand is higher. The steel jacket was made from high-quality zincalume steel, a high-quality rolled steel that is customizable following the size of the spun pile and has a low cost. Experimental and numerical studies were conducted. A 500mm diameter spun pile was retrofitted with a steel jacket loaded vertically and horizontally. The experimental study applied the cyclic loading according to ACI374.2r, and 0.1fc'Ag vertical load was applied. The experimental study applied the cyclic loading according to ACI374.2r, and 0.1fc'Ag vertical load was applied. The experimental study found that the spun pile and grouted concrete interaction was not perfectly bonded. A further finite element study was conducted to understand the connection's performance thoroughly. Two parameters were investigated, the steel jacket's height and thickness. A numerical study performed pushover analysis on the 3D model using the ABAQUS software to see the effect of the height and moment-curvature analysis obtained from fiber section element from SAP software to study the impact of the thickness. The results were presented in terms of its strength and ductility.

Objective Evaluation of the Source Models for Seismic Hazard Investigations Using the Logic Tree Approach: Case Study Semnan, Iran

Probabilistic seismic hazard analysis (PSHA) has become a fundamental tool in assessing seismic hazards and for estimating seismic design and seismic safety evaluation of ground motions. This report describes a study to test and verify the numerical approaches and software used in PSHA on Semnan, one of the important cities of Iran country. The geological and seismological data are integrated into a probabilistic seismic hazard model for the region. Historical and instrumental earthquake data, geology, tectonics, fault activity, and seismic source models associated with seismic events are taken into account. A probabilistic approach within a logic-tree framework is used to calculate seismic hazard for Semnan. The results were also displayed in terms of uniform hazard spectra for rock sites for return periods of 100, 475 and 2475 years, which is deemed appropriate for structural design standards in the Iran building code. As the results of this study have been displayed on the map for different return periods and different natural periods, it can provide the basis for the preparation of new seismic risk maps.

Mapping the basement of the Cerdanya Basin (eastern Pyrenees) using seismic ambient noise

Abstract. Ambient seismic noise acquired in the Cerdanya Basin (eastern Pyrenees) is used to assess the capability of different methodologies to map the geometry of a small-scale sedimentary basin. We present results based on a 1-year-long broad-band deployment covering a large part of the eastern Pyrenees and a 2-month-long high-density deployment covering the basin with interstation distances around 1.5 km. The explored techniques include autocorrelations, ambient noise Rayleigh wave tomography, horizontal-to-vertical-spectra ratio (HVSR) and band-pass-filtered ambient noise amplitude mapping. The basement depth estimations retrieved from each of these approaches, based on independent datasets and different implicit assumptions, are consistent, showing that the deeper part of the basin is located in its central part, reaching depths of 600–700 m close to the Têt fault trace bounding the Cerdanya Basin to the NE. The overall consistency between the results from all the methodologies provides solid constraints to our basement depth estimation, although significant differences arise in some areas. The results also show that, when high-density seismic data are available, HVSR and ambient noise amplitude analysis in a selected frequency band are useful tools to quickly map the sedimentary 3D geometry. Beside this methodological aspect, our results help to improve the geological characterization of the Cerdanya Basin and will provide further constraints to refine the seismic risk maps of an area of relevant touristic and economic activity.

Influence of local site effects on seismic risk maps and ranking of Italian municipalities

The latest studies concerning seismic risk assessment in Italy were developed without considering the site geo-lithological effects, thus limiting the assessment to rock soil type. In this study, for the evaluation of site amplification effects, we used the results of recent works based on the Italian seismic microzonation data. As this first study is performed for the entire Italian territory at the municipality scale, the site amplification factors (AFs) have been assigned to the chief town of each of the 7715 Italian municipalities, assuming that the building stock is concentrated in that small area. The AFs have been compared with those foreseen by the Italian building code (NTC2018). The PGA amplification with the new AFs ranges from 1 to 2.2 bringing to an average increase of 75% in the hazard, compared to 27% if using the NTC2018 amplification. The seismic risk has been evaluated using the probabilistic hazard assessment adopted in the NTC2018 and recent vulnerability/exposure models developed for Italy. The residential building stock was subdivided into 5 vulnerability classes (3 for masonry and 2 for concrete) derived from the national census data and further refined using the construction age and building height. The results show that, for a rock site condition, the loss estimates are comparable with those of previous works in terms of casualties, homeless, and economic damage. The introduction of the site effects brings to a significant increase in the expected losses resulting higher than the historical data retrieved from a careful analysis of the major Italian earthquakes. This suggests the importance of developing new fragility curves based on updated AFs. To support the implementation of risk reduction programs, a seismic risk index is introduced, allowing a municipality ranking by risk, a cost estimation of the seismic retrofitting in the highest risk municipalities, and an assessment of the consequent risk reduction.

Seismic risk maps for the seismic risk management and reduction

The paper illustrates the seismic risk maps computed by the Authors for the residential building stock of Italy by using a general framework specifically set up for mapping seismic risk for a generic asset of interest. Seismic risk maps are computed taking into account a seismogenic model of the analyzed area, and properly characterizing vulnerability and exposure of an asset of interest. Seismic risks maps are computed for two different conditions, the former represents the so-called as-built condition, the latter one is computed assuming for the residential building stock a possible strategic retrofit program. These two maps are then used for investigating the financial sustainability of national seismic risk reduction programs, focusing the attention on the specific case of the national residential building stock of Italy.

An Italian platform for the seismic risk assessment of school buildings

The safety of school buildings is a highly relevant and topical issue and the earthquake is one of the actions from which they must be “protected”. Many factors affect it, both from the structural and non-structural point of view. To identify the most cost-benefit seismic mitigation program is fundamental to have an overview of the school heritage in our peninsula, the vulnerability and the seismic risk which schools are subjected to. In this context, within the MARS (Seismic Risk Maps) research project funded by the Italian Department of Civil Protection, an online platform developed by EUCENTRE, with the close collaboration of the Network of University Laboratories for Earthquake Engineering (ReLUIS) has been adopted to calculate the seismic risk of school buildings. The platform IRMA (Italian Risk MAps), initially focused only to residential buildings, has been further developed with a specific tool dedicated to the evaluation of seismic risk maps for school buildings at national level. It allows to upload different exposure/vulnerability models and sets of fragility curves and to combine them to obtain seismic risk maps at municipal, provincial, regional and national scale. The hazard integrated in IRMA corresponds to the hazard model adopted by the regulations at national level.

Time‐dependent seismic fragility curves for existing RC core‐wall buildings exposed to corrosion

AbstractThis work aims at investigating the seismic response of existing reinforced concrete core‐wall buildings with corroded bars erected in the marine environments, with the main focus on the dependency of seismic fragility curves on aging and degradation effects caused by environmental actions. The structural capacity is predicted by nonlinear finite‐element analyses, where the effect of chloride corrosion is implemented within the framework of PARC_CL_2.1 crack model. The proposed methodology is applied to a pre‐code six‐story reinforced concrete (RC) building with moment‐resisting (MR) frames and an internal core assumed as a testbed. For a given exposure class, pushover analyses are performed for different ages of the building. Time‐dependent fragility curves are then obtained through a procedure based on incremental static analysis. Different corrosion scenarios are assessed by considering deterioration effects applied either on the sole RC walls or on both walls and columns. The obtained results highlight that time‐dependent fragility curves are strongly affected by corrosion, therefore the date of construction should be considered in seismic risk mapping, not only for evaluating the effect of obsolete standard codes used in the design but also in terms of damage induced by aging and deterioration.

Mapping seismic risk awareness among construction stakeholders: The case of Iringa (Tanzania)

To cope with earthquakes, resistant housing is crucial. Too often essential construction techniques are not applied in the most vulnerable contexts. Local construction stakeholders have a major responsibility in reducing vulnerability of the built environment. This exploratory study investigates current seismic risk awareness in the region of Iringa (Tanzania) and discusses its implications for disaster resilience policy and practice. This medium seismic hazard risk area presents an interesting case-study to map risk awareness of key construction stakeholders. Our analysis covers seismic risk maps, governmental policy documentation and stakeholder awareness data. Data collection across 17 villages includes a poll with 21 mason and 15 school principals, and 5 interviews with a district engineer, a contractor, an architect and two homeowners. This sample illustrates the severe lack of risk awareness in Iringa. Our evidence reveals limited risk awareness across all community-based stakeholders, including absent risk awareness of local masons. High risk awareness was found in national governmental policy documents. We conclude that local seismic risk awareness is influenced by: (i) absent structural building codes that consider seismic forces, (ii) lack of risk communication campaigns by the government or NGOs, (iii) and limited freedom of speech linked to natural hazards. Our findings advocate for enhancement of risk awareness by: (i) development of a Tanzanian structural building code with recommendations for seismic resistance, (ii) better risk communication strategies to bridge the knowledge gap between governmental departments and communities, and (iii) exclusion of natural hazards from the list of prohibited communication topics in legislation.

Towards the updated Italian seismic risk assessment: exposure and vulnerability modelling

Within the 2019–2021 research agreement between the Civil Protection Department (DPC) and the Network of University Laboratories for Earthquake Engineering (ReLUIS), the work package WP4 “Seismic Risk Maps—MARS” is specifically devoted to update the 2018 release of the Italian National Seismic Risk Assessment. To this end, the previously considered models of hazard, exposure and vulnerability will be critically reviewed and updated by taking advantage also from the results deriving from other WPs of the DPC-ReLUIS research project. In the present paper some of the most relevant aspects that are being introduced in the development of the new Italian risk maps have been described and shortly analysed. First, a significant upgrade of the vulnerability model implemented in the new version of the platform used for risk calculation (IRMA) is proposed, where reference to the six EMS-98 classes is made also considering regional vulnerability features. Further, empirical data from observed real damage are integrated with results from numerical simulations (mechanical approach), in particular for reinforced concrete buildings. Finally, some special construction types such as schools, churches and bridges are included in order to provide a more comprehensive view of the national risk.

Fault importance index (FII) as earthquake source criteria for seismic zonation: case study of India

The organizations in different countries involved in seismic zoning modify the maps in response to various seismic events. The predictive ground motion is used in the analyses which may not be estimated using a single attenuation relation, because it is established on theoretical basis not with the actual ones and hence always errors are included in the analysis. However, the impact of faults is not considered in many of such seismic zoning efforts in several countries. An earthquake is generally triggered along the fault line; magnitude of generated earthquake depends on many factors, mainly the fault characteristics. Hence, the fault is the basic source of seismic activity and its presence and importance directly influences the seismic status of a region. In the present study a new term “fault importance index (FII)” is proposed which is a numeric value estimated from fault characteristics. The FII value for each of linear feature is calculated and relation is derived between the FII with earthquake intensity. The generated polynomial equations relate the past intensity spread with FII. The seismic risk zone map is then generated on the basis of FII. The developed seismic risk map has been compared to few earlier seismic maps and it can be used for design of buildings especially near the earthquake source.

Evaluation of seismicity of Karachi city in the context of modern building codes

Spectral acceleration is representative of seismic hazard in modern building codes as well as an important parameter used in seismic design these days. Karachi, an economic artery of Pakistan, is located in the vicinity of an active tectonic setting, i.e., triple junction, with uncertain seismicity. Keeping in view the modern seismic design practices, efforts are required to evaluate the seismic hazard of Karachi city in terms of spectral acceleration. This study is focused on the estimation of seismic hazard for the metropolitan city of Karachi in the context of modern building codes. The seismic potential of around 800–900-km circle was considered a threat for the city, and 13 seismic zones (A-1 to A-13) were identified as seismic sources. A seismicity model based on Gutenberg-Richter law was developed, identifying A-1 and A-11 as zones of high seismicity. The ground attenuation model recommended for the Middle East region proposed by Akkar and Bommer was utilized for the computation of different ground motion scenarios. Short-period, SS, and 1-s, S1, spectral acceleration values for considered region were calculated as 1.37 m/s2 and 0.41 m/s2, respectively. In addition, peak ground acceleration (PGA) values for Karachi city were observed to be in a range of 0.7–0.77 m/s2. The results of this study provide bases for the preparation of seismic risk maps, the estimation of earthquake insurance premiums, seismic zonation for region lying on Arabian and Indian plates, and the preliminary site evaluation of critical facilities.

GIS spatial modelling for seismic risk assessment based on exposure, resilience, and capacity indicators to seismic hazard: a case study of Pahang, Malaysia

Various techniques and frameworks for an evaluation of seismic vulnerability have been developed and established in previous studies. However, some techniques demand a significant amount of empirical data currently not readily available in developing countries. Therefore, this study proposes a new seismic risk evaluation method at the local district level. A holistic model was constructed for the purpose of assessing potential seismic vulnerability based on appropriate indices and their relative contribution towards vulnerability and coping capacity. It allowed the estimation of vulnerability in terms of exposure, resilience, and capacity factors. Then, utilization of Geographical Information System (GIS) tools resulted in the generation of a total vulnerability map via integration of the study variables to highlight the socio-economic and physical characteristics of vulnerability for the districts in Pahang, Malaysia. Subsequently, a seismic risk map of the study area was derived by overlying the derived map with the seismic hazard map. Consequently, the study revealed the highest levels of seismic risk were concentrated in the central-west of the Pahang region, namely the Bentong district. In contrast, the least vulnerable areas encompassed the Pekan and Jerantut areas, which were located in the eastern region. In brief, the study findings would serve as the foundation towards reducing the country’s vulnerability to disasters.

Seismic risk assessment of residential buildings in Italy

The last National Risk Assessment NRA for Italy was developed at the end of 2018 by the Department of Civil Protection (DPC) in response to the specific requirement of the Sendai Framework for Disaster Risk Reduction 2015–2030 to periodically adjourn the assessment of disaster risk. The methodology adopted to perform seismic risk assessment and build national seismic risk maps was specifically developed to comply with the recent Code for Civil Protection, issuing that, in addition to a solid scientific base, risk assessment should be characterized by a wide consensus of the scientific community. As a result, six research units belonging to two Centers of Competence of the DPC, namely ReLUIS (Network of university laboratories for seismic engineering) and EUCENTRE (European Centre for Training and Research in Earthquake Engineering), collaborated under the guidance and coordination of DPC to produce the recent updating of national seismic risk maps for the residential building stock. This paper describes the methodology adopted to develop the consensus-based national seismic risk assessment and presents the main results in terms of expected damage and impact measures (unusable buildings, homeless, casualties, direct economic losses).

Risk-based catastrophe bond design for a spatially distributed portfolio

Catastrophe bonds (CAT bonds) are risk-linked securities used by the insurance industry to transfer risks associated with the occurrence of natural disasters to the capital markets. Despite their growing importance, connected with the higher exposures to potential natural disasters, relatively few studies on CAT bond pricing, design and their application are available in the literature. In particular, the existing pricing formulations for pricing analysis do not account for uncertainties in model parameters and are not contextualized in a more general CAT bond coverage design procedure for an area of interest. For these reasons, this paper presents a general procedure for designing a CAT bond-based coverage for a spatially distributed portfolio against losses due to natural hazards, accounting also for model parameters uncertainties in CAT bond pricing process. The procedure is then applied to a case study represented by the residential building portfolio in Italy, proposing an ad-hoc CAT bond-based coverage against losses induced by earthquake occurrences, defined on the basis of the most recent version of the seismic risk map of Italy currently proposed in scientific literature.