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Probabilistic seismic risk assessment of Africa
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In the aftermath of an earthquake, the number of residents whose housing was destroyed is often used to approximate the number of people displaced (i.e., rendered homeless) after the event. While this metric can provide rapid situational awareness regarding potential long-term housing needs, more recent research highlights the importance of additional factors beyond housing damage within the scope of household displacement and return (e.g., utility disruption, tenure, place attachment). This study benchmarks population displacement estimates using this simplified conventional approach (i.e., only considering housing destruction) through three scenario models for recent earthquakes in Haiti, Japan, and Nepal. These model predictions are compared with officially reported values and alternate mobile location data-based estimates from the literature. The results highlight the promise of scenario models to realistically estimate population displacement and potential long-term housing needs after earthquakes, but also highlight a large range of uncertainty in the predicted values. Furthermore, purely basing displacement estimates on housing damage offers no view on how the displaced population counts vary with time as compared to more comprehensive models that include other factors influencing population return or alternative approaches, such as using mobile location data.
The increasing interest in seismic risk assessment in Morocco is due to the growing frequency of earthquakes, such as the one in Al Haouz in 2023, and the rapid population expansion in these areas. This study focuses on regions with moderate to high seismic activity to better understand the seismic risk in these areas. A critical aspect of this assessment is establishing damage (or fragility) curves, which are necessary for assessing damage levels and making decisions regarding the renovation or demolition of structures. However, a shortfall in seismic regulations is the constant behavior factor, regardless of seismicity level (zones 3, 4, and 5) or structure height. Moroccan seismic regulations (RPS2000) and international standards generally advocate for a fixed value of the behavior factor but often neglect crucial parameters such as structure height and local seismic intensity.
Blida (Algeria) is characterized by a high level of seismic exposure and vulnerability due to its dense population and the presence of aging buildings. The historical earthquake that occurred in 1825, with a moment magnitude (Mw7.1), underscored the urgent need for a thorough assessment of seismic risk in the area. Here, an extensive study conducted in downtown of the city of Blida to evaluate seismic risk and its consequences is presented. Geounits 141 and 148 emerged as the most severely affected in all the simulated earthquake scenarios indicating severe damage and casualties mainly for closest earthquakes (Blida and Bounaian, both with moment magnitude Mw7.1) but also for furthest earthquakes as Mouzaia El Affroun (Mw6.6), and Hammam Melouane (Mw6.5). The sensitivity analysis demonstrated the importance of the selection of the performance point computation method (improved displacement coefficient method -IDCM, modified capacity spectrum-MADRS, and nonlinear analysis method-N2) and the choice of the ground motion prediction equation. IDCM results are less influenced by the choice of the GMPE, but they provide higher damage results expressed as a mean damage ratio. Moreover, the study estimated potential human impacts in the Blida region, highlighting varying levels of impact on different geounits under different earthquake scenarios. The study's primary findings from seismic risk assessments in the studied region highlight its high susceptibility to earthquakes and can be summarized as follows: The mean damage ratio will be 52.6% ± 1.4%, 50.9% ± 1.6%; 31.8% ± 3.4% and 21.4% ± 3.1% for the Blida, Bounaian, Mouzaia El Affroun and Hammam Melouane earthquakes respectively.
Building performance is a broad subject whose meaning covers the ability of structures to serve the intended function based on a well-defined criterion such as the assessment of functional, physical, environmental, or even social attributes considered jointly or separately. Building failures and general collapses are some of the most severe consequences of failed performance of buildings which have a great impact on livelihoods yet have remained persistent in Kenya over decades despite various interventions. This paper analyses building performance based on observable attributes and sentiments of respondents collected from construction project sites across Kenya. The study aimed to characterize buildings that are likely to fail physically and functionally at different stages based on five factors drawn from the literature as institutional, ethical, financial, legal, and technical factors, with the intention of proposing the necessary stop-gap measures. The study employed a cross-sectional (survey) design in which quantitative research methods were applied to collect and analyze data from a random sample of 400 building construction projects selected through proportionate cluster sampling across the 47 counties of Kenya. A semi-structured questionnaire was used to gather data on the perception of industry professionals, building users, and generally the stakeholders on the identified area of the research. Data was analyzed using descriptive statistics, factor analysis, and regression analysis. The physical performance of buildings appeared to cause an alarming concern with elements such as wall and slab stability recording poor scores. Based on functional performance the aspects of disability mainstreaming and compliance to green building standards were noted to be under-performing. Multiple Regression analysis results revealed that institutional, ethical, financial, legal, and technical factors explained 17.1% of the variability in building performance. Notably, only ethical, legal, and technical factors were the statistically significant predictors of building performance. The study thus recommends a detailed review, restructuring, and optimization of the ethical, legal, and technical environment of building construction management to enhance buildings performance.
This study presents the most recent development of a nationwide earthquake risk model for non-engineered masonry buildings in Malawi. Due to its location within the East African Rift, Malawi experienced several moderate earthquakes that caused seismic damage and loss. Recently, a new probabilistic seismic hazard model has been developed by considering fault-based seismic sources, in addition to conventional areal sources. The most recent 2018 national census data provide accurate exposure information for Malawian people and their assets at detailed spatial resolutions. To develop seismic fragility functions that are applicable to Malawian housing stocks, building surveys and experimental tests of local construction materials have been conducted. By integrating these new developments of seismic hazard, exposure, and vulnerability modules, a quantitative seismic building collapse risk model for Malawi is developed on a national scale. For the rapid computation of seismic risk curves at individual locations, an efficient statistical approach for approximating the upper tail distribution of a seismic hazard curve is implemented. Using this technique, a seismic risk curve for a single location can be obtained in a few seconds, thereby, this can be easily expanded to the whole country with reasonable computational times. The results from this new quantitative assessment tool for seismic impact will provide a sound basis for risk-based disaster mitigation policies in Malawi.
Background
The initial phase of earthquake hazard assessment involves the consolidation of diverse magnitude scales, thereby requiring the homogenization of various magnitudes. Moment magnitude (Mw) emerges as the preferred descriptor for a range of magnitudes, encompassing local magnitude (ML), teleseismic magnitude (e.g., mb and MS), duration magnitudes (MD), and other magnitude proxies. Unlike alternative scales, Mw does not exhibit saturation at high magnitudes, enhancing its reliability. To achieve uniformity in magnitude representation, diverse regression techniques are employed, with the General Orthogonal Regression (GOR) method being widely regarded as the most dependable, accounting for uncertainty in both independent and dependent variables.
Methods
This study utilized the International Seismological Centre (ISC) Catalogue (http://www.isc.ac.uk/) to compile an array of events related to the East Africa Rift System (EARS). Subsequently, the General Orthogonal Regression method was applied to merge and harmonize the collected data. Furthermore, the research computed Gutenberg-Richter b-values using the newly unified magnitude.
Results
Notably, the conversion relationships between magnitude proxies, including MS-mb, mb-Mw, MS-Mw, and ML-Mw, exhibited robust correlations, with coefficients of 0.86, 0.80, 0.88, and 0.94, respectively. In contrast, the relationship between ML and mb proxies revealed a notably weaker correlation, registering a coefficient of 0.54. Ultimately, the study identified a magnitude of completeness and a b-value of 3.8 and 0.71, respectively, for the EARS region, providing valuable insights for earthquake hazard assessment in this area.
Conclusion
Generally, the homogeneous catalogue is a step forward in seismicity assessment and geodynamic activities in the EARS. Hence, developing the empirical equations for the area is essential for future studies on seismic hazards and engineering applications due to the peculiarity of EARS’s geological and tectonic characteristics.
The southern East African rift system (EARS) is geologically rare considering its early-stage continental rift setting combined with a deep seismogenic zone. Several seismically vulnerable communities are located within this tectonically active region, resulting in a significant seismic risk. However, the ground motion and seismic hazard analyzes necessary to increase the earthquake preparedness in the region have been limited due to the relatively short instrumentation history and scarce ground motion data available. Here, we present a newly compiled ground motion database for the southern EARS which is critically lacking and preventing local ground motion studies. This database includes a regional catalog of 882 earthquakes spanning 1994–2022 (magnitudes 3–6.5) with available waveform records within epicentral distances of 300 km. Three different velocity models were used to relocate 256, 255, and 252 events, respectively, to quantify depth sensitivity, relocating events down to depths of 35–40 km. The final database contains 10,725 time-series records from 353 stations along with P- and S-wave phase arrivals for each record. The ground motion database contains peak ground acceleration and velocity and 5% damped pseudo-spectral acceleration for 291 frequencies from 1.0 to 30 Hz for the horizontal components. In addition, a Fourier amplitude spectrum table for 212 frequencies from 0.1 to 30 Hz is included. The database is accessible through the ISC repository ( https://doi.org/10.31905/4GGVBFBE ).
Rapid and uncontrolled urbanisation in many parts of Africa is a significant driver of earthquake risk. New constructions are usually built with no compliance with seismic codes, which results in a critical increase in the vulnerability of the building stock. To quantitatively assess the potential consequences of unregulated urbanisation, this study investigates the effect of building code enforcement and urban expansion on the future earthquake loss in the city of Blantyre, Malawi. The analysis, performed within a probabilistic loss assessment framework, estimates the net present value of 30-year aggregated seismic loss for different urban expansion rates and code enforcement scenarios. The results show that high urbanisation rates and lack of building regulations could lead to a threefold increase in average seismic losses in the next thirty years. On the contrary, effective code enforcement could cap the seismic loss increase at 13%, highlighting the financial gain from effective disaster risk reduction programmes.
An open Global Risk Model was published by the GEM Foundation in 2018, a multi-year effort (2014-2018) made possible through bilateral collaborations and regional projects. This model encompassed a global mosaic of probabilistic seismic hazard models, a global exposure dataset, and a set of vulnerability models. These components were combined within the OpenQuake- engine to produce several seismic hazard and risk results, including seismic hazard maps for a set of return period and intensity measures, average annualized losses at the smallest administrative level for each country, and identification of the regions with the highest risk globally. Since its initial publication, several improvements have been made to each of the components (i.e., hazard, exposure, vulnerability, and risk). The key features of each revision are described in this paper, as well as a comparison of the differences in risk results between the 2018 model and today’s model.
A uniform and comprehensive classification system, often referred to as taxonomy, is fundamental for the characterization of building portfolios for natural hazard risk assessment. A building taxonomy characterizes assets according to attributes that can influence the likelihood of damage due to the effects of natural hazards. Within the scope of the Global Earthquake Model (GEM) initiative, a building taxonomy (GEM Building Taxonomy V2.0) was developed with the goal of classifying buildings according to their seismic vulnerability. This taxonomy contained 13 building attributes, including the main material of construction, lateral load-resisting system, date of construction and number of stories. Since its release in 2012, the taxonomy has been used by hundreds of experts working on exposure and risk modeling efforts. These applications allowed the identification of several limitations , which led to the improvement and expansion of this taxonomy into a new classification system compatible with multi-hazard risk assessment. This expanded taxonomy (named GED4ALL) includes more attributes and several details relevant for buildings exposed to natural hazards beyond earthquakes. GED4ALL has been applied in several international initiatives, enabling the identification of the most common building classes in the world, and facilitating compatibility between exposure models and databases of vulnerability and damage databases.
This article aims to provide an overview of successive seismic zonations inmainland France and probabilistic seismic hazard studies performed over the previous ¼30 years. A short presentation is given on the engineering and regulatory framework that shapes the background of seismic zonation and hazard studies, followed by a scientific overview of published probabilistic seismic hazard estimations.
The components of these past PSHA studies are summarized (seismic source models, groundmotion models, management of uncertainties). The evolution of hazard estimates with time is displayed for a set of representative cities. Finally, three generations of official seismic zonation maps in France are presented (1967, 1986, 2004), and the evolution of methods and results is highlighted.
This review shows that the academic community has previously had little involvement in this topic. As current zonation relies on outdated models, there is an opportunity for scientific and engineering communities to efficiently work together to build the next generation of probabilistic seismic hazard models for France.
Earthquake vulnerability Malawi Residential buildings Unreinforced masonry Masonry panel test data Orthotropic model In-plane damage Out-of-plane damage A B S T R A C T Malawi is an earthquake-prone country that lies within the East African Rift. A large proportion of its population lives in non-engineered single-storey constructions made of clay bricks and low-strength mortar. Walls are typically single-skin and often lack adequate wall-to-wall connections, leaving them vulnerable to seismic actions. This work reports a comprehensive study on the seismic fragility of unreinforced masonry buildings of the Malawi housing stock. The probability of exceeding different levels of in-plane/out-of-plane damage is estimated by considering the aleatory and epistemic uncertainties of the problem. Inter-building and intra-building variability are accounted for by adopting material test results and building survey data collected in Malawi. The in-plane capacity of building walls is calculated through a finite element model that considers the orthotropic properties of masonry. The out-of-plane capacity is computed using an analytical solution, developed for walls in one way bending. In addition, record-to-record variability is considered. The new country-specific fragility models result more conservative that global estimates, which reflects the high vulnerability of Malawian masonry buildings. These fragilities can be integrated into catastrophe modelling platforms for earthquake risk assessment in Malawi and in the wider East African region.
Abstract Earthquake is a sudden release of energy due to faults. Natural calamities like earthquakes can neither be predicted nor prevented. However, the severity of the damages can be minimized by development of proper infrastructure which includes microzonation studies, appropriate construction procedures and earthquake resistant designs. The earthquake damaging effect depends on the source, path and site conditions. The earthquake ground motion is affected by topography (slope, hill, valley, canyon, ridge and basin effects), groundwater and surface hydrology. The seismic hazard damages are ground shaking, structural damage, retaining structure failures and lifeline hazards. The medium to large earthquake magnitude (
Tomorrow’s Cities is the £20m United Kingdom Research and Innovation (UKRI) Global Challenge Research Fund (GCRF) Urban Disaster Risk Hub. The Hub aims to support the delivery of the United Nation’s Sustainable Development Goals and priorities 1 to 3 of the Sendai Framework for Disaster Risk Reduction (DRR) 2015-2030. We work in four cities: Istanbul, Kathmandu, Nairobi, and Quito. We collaborate with local, national, and global organisations to strengthen disaster risk governance by undertaking integrated, multi-scale, and multi-disciplinary research to better understand natural multi-hazard risks and their drivers. Ongoing rapid urbanisation and urban expansion provide a time-limited opportunity to reduce disaster risk for the marginalised and most vulnerable in tomorrow’s cities. We aim to catalyse and support a transition from crisis management to pro-poor, multihazard risk-informed urban planning and people-centred decision-making in expanding cities worldwide. Tomorrow’s Cities is a fully-functioning, fully-funded international collaboration of communities, governance organisations, researchers, and risk professionals. We are developing our Phase 2 programme planned for 2021-24, which will build on the Phase 1 research and partnerships forged since our inception in early 2019. We seek global partners to co-produce and implement a new approach to risk reduction, through risksensitive design of tomorrow’s cities.
Malawi is located within the southern branch of the active East African Rift System,
where earthquakes of moment magnitude (M w ) 7.0 or greater can occur along major
faults. The majority of dwellings in the country are non-engineered unreinforced
masonry constructions, built by local artisans with little input from engineers. These
constructions are highly vulnerable to seismic events due to poor-quality materials and
lack of construction detailing. This study presents a new methodology to assess the
seismic fragility curves of typical dwellings located in the Central and Southern Malawi.
On-site inspections of buildings are carried out to assess geometrical and structural
features of 646 façades, and an experimental campaign is performed to characterise
the mechanical properties of local construction materials. The collected data allow the
identification of different building typologies in terms of quality of materials and
construction techniques. The critical failure modes for each of the inspected façade at
their ultimate limit state are evaluated analytically. Damage limit states are defined and
adopted to derive simplified Static Push-Over (SPO) curves, transformed into
incremental dynamic analysis (IDA) curves by using SPO2IDA. The IDA curves are
then used to obtain fragility curves for the specific damage limit states. The fragility
curves presented herein are the first to be calculated for these building typologies,
based on real data, and unfortunately, they show that buildings in Malawi are far more
vulnerable to earthquakes than estimated from previously available international
reference data. The fragility curves developed in this study may prove useful for
assessing the seismic risk of these building typologies in Malawi and other East African
countries.
Seismic fragility and vulnerability assessment is an essential step in the evaluation of probabilistic seismic risk. Ideally, models developed and calibrated for the building portfolio of interest would be readily available. However, the lack of damage data and insufficient analytical studies lead to a paucity of fragility and vulnerability models, in particular in the developing world. This study describes the development of an analytical fragility and vulnerability model covering the most common building classes at the global scale. Nearly five hundred functions were developed to cover the majority of combinations of construction material, height, lateral load resisting system and seismic design level. The fragility and vulnerability were derived using nonlinear time-history analyses on equivalent single-degree-of-freedom oscillators and a large set of ground motion records representing several tectonic environments. The resulting fragility and vulnerability functions were validated through a series of tests which include the calculation of the average annual loss ratio for a number of locations, the comparison of probabilities of collapse across all building classes, and the repetition of past seismic events. The set of vulnerability functions was used for the assessment of economic losses due to earthquakes as part of the global seismic risk model supported by the Global Earthquake Model Foundation.
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This study presents the seismic performance evaluation of the reinforced concrete (RC) frame designed as per Ethiopian (based on EN1998-1) and Chinese seismic codes to realize best practices within them. In the study, three-model RC frames with 4-, 8-, and 12-story are designed with the respective codes. Then, their seismic performances are evaluated using the nonlinear static (pushover) procedures of FEMA 356 and ATC 40 provisions. To validate the analysis result, dynamic nonlinear time history analysis is also made. The comparison parameters include elastic stiffness, peak strength, target displacement, and plastic hinge formation patterns in the structures. The results display many similarities in the global and local performances of the structures. Despite these, some noteworthy discrepancies are also noted. Besides, the performance point analysis revealed a significant difference in target displacement that reflects the two codes’ demand spectrum essential disagreements, particularly for the period of vibration greater than 2.0’s. In conclusion, the study highlighted the beneficial aspects of both codes, which will be useful for the future studies.
African seismicity is predominantly localized along the East African Rift System (EARS), which is the major active tectonic feature of Sub-Saharan Africa. Besides the EARS, however, significant seismicity also occurs along a wide belt bounding the Mediterranean coastline. This tectonically active region extends discontinuously from Morocco to Egypt and its activity is controlled by the complex interaction between the Nubian and Eurasian plates, varying from transpression in the Atlas orogen in the west to transtension in the east. A record of large earthquake events is documented for the whole region, some of them causing moderate to severe levels of damage, mostly because of the high vulnerability of local buildings and structures, a condition which is still largely persistent in many areas. Currently, a number of seismic hazard models exist at local and national scales for North Africa, developed within independent projects and created using inhomogeneous data sources and different processing techniques. Unfortunately, such diversity makes their direct comparison problematic, obscuring the differences in seismic hazard across neighbouring areas and preventing the development of comprehensive long-term risk mitigation strategies. In fact, the last effort to produce a homogenized model for the whole Africa continent dates back to the GSHAP project, which is almost 20 years old. The creation of a unique seismic hazard model for North Africa, uniform across countries, is therefore a main concern. Since its inception, the Global Earthquake Model Foundation (GEM) is committed to the creation of a worldwide mosaic of high-quality, reproducible and openly accessible seismic hazard models, uniformly represented using the format adopted by the OpenQuake engine (OQ), a state-of-the-art, free and open-source software package for seismic hazard and risk assessment. We describe the development of a new comprehensive PSHA model for North Africa using GEM tools. The source model combines active faults and distributed seismicity, the former constrained from published geological descriptions and geodetic data, while the latter from the harmonisation of published earthquake catalogues.
Since 2015, the Global Earthquake Model (GEM) Foundation and its partners have been supporting regional programs and bilateral collaborations to develop an open global earthquake risk model. These efforts led to the development of a repository of probabilistic seismic hazard models, a global exposure dataset comprising structural and occupancy information regarding the residential, commercial and industrial buildings, and a comprehensive set of fragility and vulnerability functions for the most common building classes. These components were used to estimate probabilistic earthquake risk globally using the OpenQuake-engine, an open-source software for seismic hazard and risk analysis. This model allows estimating a number of risk metrics such as annualized average losses or aggregated losses for particular return periods, which are fundamental to the development and implementation of earthquake risk mitigation measures.
Malawi is located within the southern branch of the active East African Rift System, where earthquakes of Mw 7.0 (or greater) can occur along major faults. In Malawi, the majority of dwellings in both formal and informal settlements are non-engineered unreinforced masonry constructions, built by local artisans with little input from engineers. These constructions are highly vulnerable to seismic events due to poor materials and lack of construction detailing. This study develops analytical vulnerability functions that enable the assessment of seismic capacity of typical buildings in Malawi. Since the seismic vulnerability greatly depends on building characteristics, geometrical and structural data are collected by conducting semi-rapid surveys of 300 houses located in urban and rural areas of Central and Southern regions of Malawi. Mechanical properties of the local materials are also obtained from an experimental campaign. In this work, a mechanical method FaMIVE (Failure Mechanism Identification and Vulnerability Evaluation) is adopted and the effects of both in-plane and out-of-plane behaviour of the masonry structures are taken into consideration to derive capacity curves for seismic vulnerability assessment. Special attention is given to 1) the Malawian building typologies as described in the Word Housing Encyclopedia and 2) failure mode classes for the Malawian constructions as calculated by FaMIVE. Hence, the derived vulnerability functions can serve as a benchmark for typical buildings in Malawi. The results and conclusions are also relevant for other East African countries, where similar construction techniques are adopted.
The purpose of this study is to seismically evaluate reinforced concrete buildings in the northern region of Morocco. In the past, the area have suffered from numerous earthquakes, lately the 2004 earthquake near the city of Al Hoceima (Mw of 6.4 causing more than 600 fatalities) and the region is constantly subject to seismic threats. A total number of 2746 residential buildings from the cities of Al Hoceima and Imzouren have been investigated for the purposes of this study. The proposed method adapts the Japanese Seismic Index Method making it more time-efficient and tuned to the context of the Moroccan construction. The method is based on a visual inspection of buildings and an in-depth insight of how constructions are designed and built in the region. The results show that Imzouren is more exposed to damage than the city of Al Hoceima is, mainly due to the soil nature. The method also shows that as the building’s height increases, it becomes more vulnerable. Furthermore, constructions that comply with the seismic regulations have a significant capacity to withstand damage without collapsing unlike other non-engineered buildings that have an almost non-existent ductility and can collapse soon during intense earthquakes.
Abstract The present paper discusses the seismicity of Africa and the need for the implementation of vibration control strategies in Africa, erroneously considered as aseismic. The review catalogues information on the seismicity of Africa, attesting that virtually every region in the African continent has come under the threat of some form of seismic event. The magnitudes and intensities of these seismic activities has resulted in devastations, including: loss of lives, building and civil structures collapse, displacements of people, economic losses, psychological traumatization, and grave fear. Evidences available show that most of the devastations are accentuated by tremor induced collapse of buildings and civil structures. It is thus imperative for substantive, simply implementable, and sustainable proactive measures for controlling the threats of seismic events be discussed within the African context. Current mitigation strategies in Africa include the establishment of seismic codes which govern the design of civil structures. The challenge to the implementation and the effectiveness of the existing African seismic codes was briefly discussed, and new measures which can reduce seismic risks were also highlighted The submissions of the paper is envisaged will create awareness on the budding seismic activities in Africa and awaken relevant authorities on the need for timely and practicable mitigation strategies to be in place to avert the attendant catastrophes associated with seismic occurrences.
The main purpose of this study is to assess seismic risk and present earthquake loss scenarios for the city of Imzouren, in northern Morocco. An empirical approach was chosen to assess the seismic vulnerability of the existing buildings, using the Vulnerability Index Method (RISK-UE), and considering two earthquake scenarios (deterministic and probabilistic). Special concern was given to the seismic vulnerability in Imzouren since the 2004 earthquake (24 February, mw = 6.4) that struck the region and caused substantial damage. A site investigation was conducted in the city targeting more than 3000 residential buildings, which had been closely examined and catalogued to assess their seismic vulnerability. The results of the seismic risk assessment in the city are represented through damage to the buildings, harm to the population and economic loss. Generally, the results obtained from the deterministic approach are in agreement with the damage caused by the 2004 earthquake.
A study of the dynamics of building collapse in Ghana is lacking, notwithstanding the fact that several buildings have collapsed in recent times. This study analyzes the supervisory role and challenges of building inspectors in Kumasi to assess Ghana’s progress toward minimal or zero incidence of building collapse. It adopts the stratified random sampling technique to select 27 out of 35 building inspectors of the Kumasi Metropolitan Assembly (KMA), and a semistructured interview guide to gather data from same. Data gathered were presented and analyzed through tables and direct quotations. Findings revealed that, despite the legal requirement of notification by the developer, building inspectors are compelled to visit building sites to check on developers who may have begun development without notifying them. Many developers violate the legal provisions because of ignorance, delays in acquiring building permits, and the burden of transporting building inspectors at all stages of construction. Notably, building inspectors in Kumasi have not been able to control the rate of building collapse because of constraints such as inadequate logistics and manpower, and excessive political interference. In the current climate, the built environment will continue to pose a threat to human life and property investment. Although unpleasant to contemplate, the study concludes that Ghana may witness more building collapses in the near future, if the aforesaid challenges are not addressed. To avert this, it is recommended that building inspectors in Kumasi and Ghana be equipped and empowered by the state.
The East African Rift System is the major active tectonic feature of the Sub-Saharan Africa region. Although the seismicity level of this divergent plate boundary can be described as moderate, several damaging earthquakes have been reported in historical times, and the seismic risk is exacerbated by the high vulnerability of the local buildings and structures. Formulation and enforcement of national seismic codes is therefore an essential future risk mitigation strategy. Nonetheless, a reliable risk assessment cannot be done without the calibration of an updated seismic hazard model for the region. A major limitation affecting the assessment of seismic hazard in Sub-Saharan Africa is the lack of basic information needed to construct source and ground motion models. The historical earthquake record is sparse, with significant variation in completeness over time across different regions. The instrumental catalogue is complete down to sufficient magnitude only for a relatively short time span. In addition, mapping of seismogenically active faults is still an on-going task, and few faults in the region are sufficiently constrained as to allow them to be directly represented within the seismic hazard model. Recent studies have identified major seismogenic lineaments, but there is substantial lack of kinematic information for intermediate-to-small scale tectonic features, information that is essential for the proper calibration of earthquake recurrence models. In this study, we use new data and Global Earthquake Model (GEM) computational tools such as the Hazard Modeller’s Toolkit and the OpenQuake engine to perform a pilot study of the seismic hazard associated with the East African Rift. The hazard model obtained has been created using the most recent information available from scientific literature, global bulletins and local earthquake catalogues, including those from AfricaArray projects. In this report, in accordance with the GEM philosophy, we describe in detail all working assumptions, main processing steps, data analyses and interpretations used for the model setup.
The Cairo earthquake (12 October 1992; mb = 5.8) is still and after 25 years one of the most painful events and is dug into the Egyptians memory. This is not due to the strength of the earthquake but due to the accompanied losses and damages (561 dead; 10,000 injured and 3000 families lost their homes). Nowadays, the most frequent and important question that should rise is “what if this earthquake is repeated today.” In this study, we simulate the same size earthquake (12 October 1992) ground motion shaking and the consequent social-economic impacts in terms of losses and damages. Seismic hazard, earthquake catalogs, soil types, demographics, and building inventories were integrated into HAZUS-MH to produce a sound earthquake risk assessment for Cairo including economic and social losses. Generally, the earthquake risk assessment clearly indicates that “the losses and damages may be increased twice or three times” in Cairo compared to the 1992 earthquake. The earthquake risk profile reveals that five districts (Al-Sahel, El Basateen, Dar El-Salam, Gharb, and Madinat Nasr sharq) lie in high seismic risks, and three districts (Manshiyat Naser, El-Waily, and Wassat (center)) are in low seismic risk level. Moreover, the building damage estimations reflect that Gharb is the highest vulnerable district. The analysis shows that the Cairo urban area faces high risk. Deteriorating buildings and infrastructure make the city particularly vulnerable to earthquake risks. For instance, more than 90 % of the estimated buildings damages are concentrated within the most densely populated (El Basateen, Dar El-Salam, Gharb, and Madinat Nasr Gharb) districts. Moreover, about 75 % of casualties are in the same districts. Actually, an earthquake risk assessment for Cairo represents a crucial application of the HAZUS earthquake loss estimation model for risk management. Finally, for mitigation, risk reduction, and to improve the seismic performance of structures and assure life safety and collapse prevention in future earthquakes, a five-step road map has been purposed.
The seismic risk potential for Malawi is high because traditional adobe and earthen structures are seismically vulnerable and large earthquakes of Mw7.0 or greater may occur in the Malawi Rift. To assess seismic risk of the Malawian communities quantitatively, data and models for exposure, hazard, and vulnerability modules that are suitable for Malawi are integrated. The developed risk model is applied to a retrospective appraisal of the past damaging 2009 Karonga earthquake sequence and to the future earthquake scenarios for long-term risk management purposes. The earthquake impact assessment results highlight that the collapse risk predictions of the Malawian settlements are particularly dependent on the inclusion of large-magnitude earthquakes from the active faults around Lake Malawi and the selection and combination of seismic vulnerability models.
Earthquakes are natural phenomena that occur at several places of the world. Severe earthquakes, when near inhabited districts, have caused extensive loss of life and property. Although some progress in the area of seismic prediction has been made, earthquakes cannot be accurately predicted in time, magnitude or location. Therefore, the main way of decreasing losses is to construct seismic resisting structures. Recent earthquakes illustrate that the older buildings, which are not designed to resist earthquakes, have been damaged rather than the buildings which have been designed according to seismic codes. Many existing buildings in Egypt were designed to resist the gravity loads only (GLD) without seismic provisions. The need is raised to study the vulnerability of these buildings to avoid a serious risk. In this paper, the light is shed on the significant contributions in the field of seismic vulnerability evaluation of buildings in order to suggest a suitable procedure for seismic evaluation of existing R.C. buildings in Egypt. Seismic evaluation was applied on the selected two case studies, one represents the GLD buildings and the other represents the buildings designed according to Egyptian code. Moreover, pushover analysis was conducted to investigate the vulnerability of these buildings.
Al Hoceima is one of the most seismic active regions in north of Morocco. It is demonstrated by the large seismic episodes reported in seismic catalogs and research studies. However, seismic risk is relatively high due to vulnerable buildings that are either old or don’t respect seismic standards. Our aim is to present a study about seismic risk and seismic scenarios for the city of Al Hoceima. The seismic vulnerability of the existing residential buildings was evaluated using the Vulnerability Index Method (Risk-UE). It was chosen to be adapted and applied to the Moroccan constructions for its practicality and simple methodology. A visual inspection of 1.102 buildings was carried out to assess the vulnerability factors. As for seismic hazard, it was evaluated in terms of macroseismic intensity for two scenarios (a deterministic and probabilistic scenario). The maps of seismic risk are represented by direct damage on buildings, damage to population and economic cost. According to the results, the main vulnerability index of the city is equal to 0.49, and the seismic risk is estimated as slight (main damage grade equal to 0.9 for the deterministic scenario and 0.7 for the probabilistic scenario). However, moderate to heavy damage is expected in areas located in the newer extensions, both in the east and west of the city. Important economic losses and damage to the population are expected in these areas as well. The maps elaborated can be a potential guide to the decision making in the field of seismic risk prevention and mitigation strategies in Al Hoceima.
Adobe buildings are vulnerable to seismic forces. Large scale destructions and casualties have been caused due to the collapse of adobe buildings during the past earthquakes. A significant number of adobe structures exist in different parts of Pakistan, similar to other parts of the world. Since Pakistan lies in a seismic active region, it is necessary to assess the level of vulnerability of these buildings in order to estimate associated losses during a seismic event. This paper presents the results of a study which was conducted to quantify damages to adobe buildings based on their fragility curves. The adobe buildings were found to be highly vulnerable to low intensity earthquakes. The vulnerability of these buildings has been compared with the European adobe buildings. It was noted that Pakistani adobe buildings were slightly less resistant to earthquakes as compared to similar buildings in Europe. Retrofitting solutions were suggested in order to increase the seismic capacity of adobe buildings in Pakistan.
Basic provisions for design ground motions in seismic design codes of sub-Saharan African countries are critically reviewed. The seismic codes of Ethiopia, Kenya and Uganda are selected to represent the eastern region, Ghana to represent the west and South Africa to represent the south. The specific provisions considered are those pertaining to site effect and the recurrence period of the design earthquake. The codes are also compared with one another and with selected current international codes from the US and Europe, with respect to selected provisions. The provisions are further viewed from the perspective of the state of the art and the state of the practice. It has been concluded that these basic provisions in most of the sub- Saharan African codes considered are inadequate in guaranteeing safety of human life and limiting damage to property, suggesting a need for immediate updating, an exception being the South African code.
It is our belief that as engineers, geologists, seismologists, architects and designers we have the responsibility to improve the world's infrastructure, so that the world becomes a more resilient place to live. Too often we take the easy option of " doing what the code says " and not thinking about how we can improve the status quo. This is important everywhere but essential in the developing regions so the investments made can make a real difference. This paper is an example of work carried out at Arup to investigate the suitability and appropriateness of local codes in the East African region. The paper begins with examining the seismic hazard, by developing a new probabilistic seismic hazard model, then reviews the codes and makes recommendations for future development. The East African region was chosen since several major earthquakes have occurred over the last century but luckily there have been few fatalities. Will this continue to be the case as major cities in the region grow at a fast pace? Though these are still preliminary studies, and should be treated as such, we hope this information will allow more informed discussions with local governments, NGO's and investors so that more informed decisions can be made and hopefully the resilience of East African communities improved.
Throughout historical and recent times, Alexandria has suffered great damage due to earthquakes from both near- and far-field sources. Sometimes, the sources of such damages are not well known. During the twentieth century, the city was shaken by several earthquakes generated from inland dislocations (e.g., 29 Apr. 1974, 12 Oct. 1992, and 28 Dec. 1999) and the African continental margin (e.g., 12 Sept. 1955 and 28 May 1998). Therefore, this study estimates the earthquake ground shaking and the consequent impacts in Alexandria on the basis of two earthquake scenarios. The simulation results show that Alexandria affected by both earthquakes scenarios relatively in the same manner despite the number of casualties during the first scenario (inland dislocation) is twice larger than the second one (African continental margin). An expected percentage of 2.27 from Alexandria’s total constructions (12.9 millions, 2006 Census) will be affected, 0.19 % injuries and 0.01 % deaths of the total population (4.1 millions, 2006 Census) estimated by running the first scenario. The earthquake risk profile reveals that three districts (Al-Montazah, Al-Amriya, and Shark) lie in high seismic risks, two districts (Gharb and Wasat) are in moderate, and two districts (Al-Gomrok and Burg El-Arab) are in low seismic risk level. Moreover, the building damage estimations reflect that Al-Montazah is the highest vulnerable district whereas 73 % of expected damages were reported there. The undertaken analysis shows that the Alexandria urban area faces high risk. Informal areas and deteriorating buildings and infrastructure make the city particularly vulnerable to earthquake risks. For instance, more than 90 % of the estimated earthquake risks (buildings damages) are concentrated at the most densely populated (Al-Montazah, Al-Amriya, and Shark) districts. Moreover, about 75 % of casualties are in the same districts.
Since its inception in the 1960s, probabilistic seismic‐hazard analysis (PSHA) (Cornell, 1968; McGuire, 2004, 2008) has emerged as the principal methodology for assessing the potential hazard posed by earthquake ground motion in a broad range of contexts. Seismic‐hazard analysis serves different needs coming from a wide spectrum of users and applications. These may encompass engineering design, assessment of earthquake risk to portfolios of assets within the insurance and reinsurance sectors, engineering seismological research, and effective mitigation via public policy in the form of urban zoning and building design code formulation.
End users of seismic‐hazard analyses from different sectors of industry may often have specific requirements in terms of the types of results and, as a consequence, in terms of the methodologies preferred for calculation. A large majority of studies for the analysis of structural and geotechnical systems require the calculation of a target response spectrum derived from PSHA results (e.g., Lin et al. , 2013). Often the calculation of uniform hazard spectra is performed in conjunction with a disaggregation analysis, which in the simplest cases highlights the combinations of magnitude and distances, providing the largest contributions to a specific level of hazard for a particular intensity measure type, such as the spectral acceleration for a period close to the fundamental elastic period of a structure (Bazzurro and Cornell, 1999; Pagani and Marcellini, 2007). In contrast, in the insurance sector it is more common to use stochastic methodologies (e.g., Weatherill and Burton, 2010; Musson, 2012) to produce multiple realizations of the likely earthquake activity that may be pertinent to a portfolio of assets. Monte Carlo–based methods can provide results in a form that offers a practical comparison with past events and can better account for the temporal and spatial variability of earthquake shaking occurring on a distributed set …
This paper provides a critical overview of the background to the revisions which led to the formulation of Part 4, Seismic Loads, of the South African Standard SANS 10160. The paper also presents a comparison to demonstrate the calibration of the standard against other international standards. Eurocode 8 was used as the principle reference for the formulation of the revised clauses. The clauses for seismic design of SANS 10160 are based on the concept of regular buildings with suitable detailing to allow the necessary ductile behaviour. The paper points out a need to review the use of a redundancy factor which makes provision for a possible lower design peak ground acceleration value and the behaviour factor for reinforced concrete shear walls. The damage limitation criteria also need to be based on Eurocode 8. It is shown that the revised formulation provides lower design forces for regular buildings than in the current standard. This is, however, dependent on the choice of a design nominal peak ground acceleration for the various regions in the country. The available information on nominal peak ground acceleration is presented, and it is pointed out that a decision is needed on the choice of this important parameter for the seismic zones of South Africa.
Since the occurrence of the Cairo earthquake on October 1992, the design of structures for earthquakes became a major demand enforced in the Egyptian design codes. The seismic response of building structures can be estimated through utilization of a variety of analysis methods that range from simple equivalent static analysis to complex nonlinear dynamic analysis. The traditional approach is to employ equivalent static analysis methods, while current design practice is moving toward an increased emphasis on the nonlinear analysis method. The Egyptian code provisions for building seismic design adopt the traditional approach of equivalent static load method as the main method for evaluating seismic actions and recommend the response spectrum method for nonsymmetrical buildings. This study aims to evaluate the Egyptian code provisions for the seismic design of moment-resistant frame multi-story building through using nonlinear time history analysis. The analysis procedures are evaluated for their ability to predict deformation demands in terms of inter-story drifts, potential failure mechanisms and story shear force demands. The results of the analysis of the different approaches are used to evaluate the advantages, limitations, and ease of application of each approach for seismic analysis.
Abstract Modern earthquake loss models make use of earthquake catalogs relevant to the
seismic hazard assessment upon seismicity and seismotectonic analysis. The main objective
of this paper is to investigate a recently compiled catalog (National Institute of Meteorology or
INM catalog: 412-2011) and to generate seismic hazard maps through classical probabilistic
seismic hazard assessment (PSHA) and smoothed-gridded seismicity models for Tunisia. It
is now established with the local earthquake bulletin that the recent seismicity of Tunisia
is sparse and moderate. Therefore, efforts must be undertaken to elaborate a robust hazard
analysis for risk assessment and seismic design purposes. These recommendations follow
the recently published reports by the World Bank that describe the seismic risk in Tunis City
as being beyond a tolerable level with an MSK intensity level of VII. Some attempts were
made during the past two decades to assess the seismic hazard for Tunisia and they have
mostly failed to properly investigate the historical and instrumental seismicity catalog. This
limitation also exists for the key aspect of epistemic and random uncertainties impact on the
final seismic hazard assessment. This study also investigates new ground motion prediction
equations suitable for use in Tunisia. The methodology applied herein uses, for the first time
in PSHA of Tunisia, seismicity parameters integrated in logic tree framework to capture
epistemic uncertainties through three different seismic source models. It also makes use of
the recently released version of OpenQuake engine; an open-source tool for seismic hazard
and risk assessment developed in the framework of the Global Earthquake Model.
In recent decades, hundreds of studies have covered seismic vulnerability assessment and the derivation of fragility models. However, these studies primarily focus on structural damage and the associated repair costs. Assessing fatalities requires an evaluation of the proportion of damaged buildings that suffer partial or total collapse, as well as the expected fatality rates for occupants inside those collapsed buildings. To support these modeling needs, we reviewed past studies on casualties, existing proposals for collapse and fatality rates, and detailed damage databases that characterize different collapse mechanisms. Based on this review, collapse and fatality rates are proposed relative to a baseline building class. These rates are further calibrated considering reported fatalities since 1950 and the average annual fatalities estimated by the Global Seismic Risk Model of the Global Earthquake Model (GEM) Foundation. Results show that the probability of collapse tends to decrease with the number of stories, while fatality rates have the opposite trend. Furthermore, an open-access database of calibrated collapse and fatality rates is provided and can be used to assess fatalities due to earthquake scenarios or in probabilistic seismic risk analysis.
The quality and speed of the current earthquake fatality estimates in Italy, Greece, Spain, Morocco, and Algeria by Quake Loss Assessment for Response and Mitigation (QLARM) is analyzed. The positive conclusion is that all investigated major earthquake disasters have been recognized as red alerts. In all but one of the tests, the range of estimated fatalities bracketed the number of finally reported fatalities. In five out of nine test earthquakes, the range of likely fatalities was calculated in real time, that is, within minutes after the respective earthquakes. These earthquakes occurred during the last 20 yr and only the minimal information of point sources was available. Additional four tests were performed for fatal earthquakes that occurred in the twentieth century and for which magnitudes and extents of the ruptures are known. The negative conclusions are: (1) locations and properties of critical facilities, such as hospitals and schools are still not made available by some governments, although in the case of earthquake disasters, first responders should be informed about their conditions. (2) News media and governments still do not pay attention to the quantitative estimates of fatalities 26 min (median) after earthquakes by QLARM and instead disseminate underestimates by up to two orders of magnitude for days and weeks. (3) The directions and extents of ruptures remain unknown for days and weeks, leading to poor information on the spatial distribution of victims at first. (4) Source locations by different worldwide and local agencies differ by several to 20 km, which can lead to misestimates of fatalities up to 20,000. If rapid earthquake locations of quality were available in earthquake prone areas, such errors could be avoided, and the time to estimate numbers of fatalities could be reduced by an order of magnitude.
The global building exposure model is a mosaic of local and regional models with information regarding the residential, commercial, and industrial building stock at the smallest available administrative division of each country and includes details about the number of buildings, number of occupants, vulnerability characteristics, average built-up area, and average replacement cost. We aimed for a bottom-up approach at the global scale, using national statistics, socio-economic data, and local datasets. This model allows the identification of the most common types of construction worldwide, regions with large fractions of informal construction, and areas prone to earthquakes with a high concentration of population and building stock. The mosaic of exposure models presented herein can be used for the assessment of probabilistic seismic risk and earthquake scenarios. Information at the global, regional, and national levels is available through a public repository ( https://github.com/gem/global_exposure_model ), which will be used to maintain, update and improve the models.
Several destructive natural hazards have occurred throughout Africa over the past century, yet few comprehensive exposure models exist for the continent. The high population growth and rapid pace of urbanization within many African countries entail a significant potential for increased economic and human losses, particularly where substantial urban growth encroaches upon hazard-prone regions with inadequate land management and building design regulations. This study introduces a new exposure model for all African countries using national and global datasets with a uniform approach across the continent, developed for a baseline year (2020) and six future years (2025, 2030, 2035, 2040, 2045, and 2050). The exposure model was originally derived with subnational statistics, and then further spatially disaggregated using Earth Observation (EO) data. This refined spatial resolution allows the model to reflect a realistic population distribution within each country and thereby better characterizes the potential risk to natural hazards and allows identification of disaster risk hotspots. The results indicate the current concentrations of building stock in Africa, in addition to regions where the urban building stock is expected to nearly triple (such as in Central and East Africa) or at least double (such as in West and South Africa).
A regional seismic risk analysis for central-southern Malawi is conducted by focusing on the Bilila-Mtakataka Fault within the East African Rift System and by incorporating local information on population exposure and building vulnerability. The scenario-based earthquake risk assessments account for uncertainty in geometry , position, and rupture pattern of the Bilila-Mtakataka Fault as well as ground-motion variability and are based on the latest 2018 national census data. In addition, Malawi-specific seismic fragility functions, which were developed based on building surveys and laboratory tests of local construction materials, are implemented to reflect realistic seismic vulnerability of unreinforced masonry constructions in Malawi. The results from the earthquake risk assessments and sensitivity analyses based on alternative data and models highlight the importance of incorporating local information on seismic hazard characterisation, population data, and seismic vulnerability of buildings, in comparison with global data and models. For the considered case study region, individual effects of the above-mentioned model components tend to result in 20-30 % or greater differences in regional seismic risk metrics, such as the affected population experiencing a certain ground shaking intensity level or the number of collapsed housing units. The improved seismic hazard-risk assessments are more effective in informing future seismic risk mitigation policies and actions.
In December 2018, at the conclusion of its second implementation phase, the Global Earthquake Model (GEM) Foundation released its first version of a map outlining the spatial distribution of seismic hazard at a global scale. The map is the result of an extensive, joint effort combining the results obtained from a collection of probabilistic seismic hazard models, called the GEM Mosaic. Together, the map and the underlying database of models provide an up-to-date view of the earthquake threat globally. In addition, using the Mosaic, a synopsis of the current state-of-practice in modeling probabilistic seismic hazard at national and regional scales is possible. The process adopted for the compilation of the Mosaic adhered to the maximum extent possible to GEM’s principles of collaboration, inclusiveness, transparency, and reproducibility. For each region, priority was given to seismic hazard models either developed by well-recognized national agencies or by large collaborative projects involving local scientists. The version of the GEM Mosaic presented herein contains 30 probabilistic seismic hazard models, 14 of which represent national or sub-national models; the remainder are regional-scale models. We discuss the general qualities of these models, the underlying framework of the database, and the outlook for the Mosaic’s utility and its future versions.
Many years have passed since previous national seismic hazard maps were prepared for South Africa. In those maps, zone-less techniques were applied. The availability of more reliable seismicity and geological data has made it possible to update those maps using probabilistic seismic hazard analysis methodologies that take into consideration all available data. This paper presents a summary of the work conducted to produce the latest seismic hazard maps for South Africa. This involved the systematic compilation and homogenisation of an earthquake catalogue, which comprised both historical and instrumental events. The catalogue played a prominent role in the preparation and characterisation of the seismic source model. Two ground motion prediction equations were identified from available international models for regions that are tectonically similar to South Africa. These two models were then implemented in the hazard calculations, which were done using the OPENQUAKE software. Uncertainties associated with input parameters in both the seismic source and ground motion models were taken into account and implemented using the logic tree technique. Maps showing distribution of acceleration at three periods (0.0s, 0.15s and 2.0s) computed for 10% probability of exceedance in 50 years were produced.
The typology classification of any building is essential to understand its structural and architectural configuration, to empirically evaluate its vulnerability, or to provide the basis for creating a structural model and to analytically study its dynamic performance. A typology classification may help structural engineers, architects and urban planners to understand a building's behavior and response to any type of natural or man-made hazard as well as further assists in defining improvement techniques and long-term sustainable regional planning. The division of a building stock into distinct classes of building typologies and hence the definition of a thorough building classification scheme is a major prerequisite for any vulnerability or loss assessment study. A building's typology largely depends upon the local geology and geography, climatic conditions, socio-economic status of the occupants or owners, and to a large extent the locally available construction skills as well as natural resources (with respect to construction materials). The type of natural hazards a region has experienced in the past may also influence its prevalent construction typologies, at least if these hazards frequently occur in a certain period of time. The introduction of new construction technologies, design codes and/or building byelaws have further implications on the question of which building typologies are prevalent in a certain region, given that these legal provisions are implemented in daily construction practice. Focusing on Central and South Asian conditions, large variations exist in above stated factors. The region the Disaster Risk Management Initiative programme (DRMI), led by the Aga Khan Development Network (AKDN), is focused on here comprises of the Central Asian countries Tajikistan and Kyrgyzstan as well as the South Asian countries Afghanistan, India and Pakistan. As strong variations in the characteristics of a certain building typology may exist between different regions or even countries, the definition of building typology classes at a regional scale is a daunting task. The present article attempts to categorize the Central and South Asian building stock into a manageable number of regional building typologies based on extensive field studies in the different regions. It further includes a thorough review of the relevant building classification schemes, discusses empirical data collection, and defines the criteria for building classification. By reviewing the buildings’ dynamic performances, a final building classification for the region and a customized visual screening-based vulnerability scale is presented.
Probabilistic loss modeling can be used to develop risk reduction measures, such as the identification of regions more prone to human and economic losses, or to the development of financial mechanisms to transfer the earthquake risk from local governments to the private sector. This study addresses several critical issues in probabilistic loss modeling, and provides recommendations depending on the intended final use of the risk results. Modeling issues related with convergence in probabilistic event-based analysis; consideration of epistemic uncertainties within a logic tree; generation of different types of loss exceedance curves; and derivation of risk maps are thoroughly investigated. The Metropolitan Area of Lisbon is used to explore these issues, and it is demonstrated that different assumptions in the loss modeling process can lead to considerably different risk results. Furthermore, the findings and recommendations of this study are also relevant for institutions that promote the assessment of earthquake hazard and risk, such as the Global Earthquake Model Foundation.
South America, and in particular the Andean countries are exposed to high levels of seismic hazard, which, when combined with the elevated concentration of population and properties, has led to an alarming potential for human and economic losses. Although several fragility models have been developed in recent decades for South America, and occasionally used in probabilistic risk analysis, these models have been developed using distinct methodologies and assumptions, which renders any direct comparison of the results across countries questionable, and thus application at a regional level unreliable. This publication aims at obtaining a uniform fragility model for the most representative building classes in the Andean region, for large-scale risk analysis. To this end, sets of single-degree-of-freedom oscillators were created and subjected to a series of ground motion records using non-linear time history analyses, and the resulting damage distributions were used to derive sets of fragility functions.
The magnitude (M
S
)-6.2 earthquake that struck northwestern Guinea in late 1983 (Figure 1) killed nearly 300 people,sinjured about 1,500, destroyed more than 5,000 houses, and left some 18,000 people homeless. It serves as a recent example of the infrequent but oftentimes destructive nature of moderate to large earthquakes that occur in apparently aseismic to low-seismicity intraplate regions such as West Africa. These examples remind us of our vulnerability to natural hazards and particularly to uncommon events of this type.
Located at the North-Eastern part of Algeria (Tellian Atlas), Constantine has crucial administrative, economic, scientific and cultural importance. It has continuously experienced significant urban evolutions during the different periods of its history. The city is located in an active seismic region within Algeria and has been struck in the past by several moderate and strong earthquakes. The strongest earthquake recorded since the beginning of instrumental seismology took place on October 27, 1985 with a magnitude M 5.9. Constantine presents a high seismic risk, because of its dense housing and high population density (2,374 inhabitants/km . This requires a risk assessment in order to take preventive measures and reduce the losses in case of potential major earthquake. For this purpose, a scenario based approach is considered. The building damage assessment methodology adopted for the Algerian context is adapted from HAZUS approach. In the present case, the effective Algerian seismic code response spectrum (RPA 99/2003) is considered as a seismic hazard model. The prediction of the expected damages is performed for a set of almost 29,000 buildings.