The role of the urban system dysfunction in the assessment of seismic risk in the Mt. Etna area (Italy) (original) (raw)
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Engineering Geology for Society and Territory - Volume 5, 2014
The Disruption Index is used here for the assessment of urban disruption in the Mt. Etna area after a natural disaster. The first element of the procedure is the definition of the seismic input, which is based on information about the historical seismicity and seismogenic faults. The second element is the computation of the seismic impact on the building stock and infrastructure in the region considered. Information on urban-scale vulnerability was collected and a geographic information system was used to organize the data relating to buildings and network systems (e. g., typologies, schools, strategic structures, lifelines). The central idea underlying the definition of the Disruption Index is the identification and evaluation of the impacts on a target community, considering the physical elements that contribute most to the severe disruption. The results of this study are therefore very useful for earthquake preparedness planning and for the development of strategies to minimize the risks from earthquakes. This study is a product of the European "Urban Disaster Prevention Strategies using Macroseismic Fields and Fault Sources" project (UPStrat-MAFA European project 2013).
2012
SUMMARY This paper presents the ongoing activities for the assessment of the urban seismic risk at Mt. Etna volcano using the “Disruption Index” approach. We use updated information on the historic main seismicity, seismogenic faults and intensity attenuation that in a recent research project produced probabilistic seismic hazard maps and scenarios expressed in terms of macroseismic intensity. To apply the Disruption Index at Etna, we consider a probabilistic approach for seismic hazard evaluation based jointly on macroseismic fields and fault parameters. For information on the urban scale vulnerability, we use a GIS to organise data relating to buildings and network systems (e.g. typologies, schools, strategic structures, lifelines) related to the municipalities more exposed to seismic risk. The convolution of ground motion and vulnerability/ impact is based on a Monte Carlo simulation. We present here some preliminary results on the identification of nodes that are responsible for...
Disruption index, DI: an approach for assessing seismic risk in urban systems (theoretical aspects)
Bulletin of Earthquake Engineering, 2014
Urban systems are characterized by very complex interactions. After an earthquake, a wide variety of services, networks and urban facilities may be unavailable to the public during the system failure and recovery processes, thereby causing disruptions in the basic social needs of the affected area. After a disaster, communities face several challenges. For example, the lack of education may impose population migrations, or malfunctions in the electricity distribution system can produce electrical power outages of varying duration with respect to time and space, which generates consequences in the water distribution system, transportation, communications, etc. A methodology called the Disruption index (DI), based on graph theory, includes these multiple interdependencies. It has been developed to estimate the dysfunction of some fundamental dimensions of urban systems on a broad level, starting with the physical damages directly suffered by the exposed assets, proceeding to the impacts that each node has on the functional performance of the nodes depending on them, until reaching the top node. This paper presents the fundamental theory to support the DI concept. The DI provides the likely impacts and consequences of an earthquake in an urban area to fulfill hazard mitigation and provide civil protection agencies and local and state governments with a new decision-making instrument to reduce or prevent severe and recurrent impacts. The DI concept can also be extended to other natural and man-made disasters and may be used as a tool for optimizing the resources of the system components. Keywords Seismic risk • Interdependencies • Propagation • Disruption • Urban systems 1 Introduction A few short minutes may be all it takes to destroy not only lives but also schools, homes and livelihoods.
Bulletin of Earthquake Engineering, 2022
This paper presents a novel hybrid-based methodology devoted to develop urban fragility curves and damage probability matrices to predict likelihood seismic damage scenarios for small and medium Italian urban centres, considering URM buildings only. The concept of urban fragility curve consists of a single curve mean-representative of the seismic fragility of an entire area accounting for the combinations of building classes and their percentage, then they differ from those typological. The methodology has been developed with reference to Rocca di Mezzo, a small Italian urban centre located in the central Apennine area, Italy. Based on CarTiS inventory, building classes have been firstly recognized and urban fragility curves, representative for damage scenarios at Ultimate Limit State, developed. To predict damage scenarios from low to high-intensity earthquakes, an approach to define multi-damage urban fragility curves and damage probability matrices has been also presented. To this aim, a damage scale suffered by building classes has been defined by converting the final outcomes of the AeDES form (used in Italy for post-earthquake surveys) in the damage levels provided by the European Macroseismic Scale (EMS98). Data coming from urban fragility curves have been compared with the actual damage scenario recorded in Rocca di Mezzo after the 2009 L'Aquila's earthquake, in terms of both peak-ground acceleration and Mecalli-Cancani-Sieberg scale. The achieved results showed a good accordance between theoretical predictions and actual damage scenarios, coherent also with the damage scenarios occurred in other Italian historical centres hit by severe earthquakes over the years. Thus, the methodology can provide a first important indicator to support the development of emergently plans devoted to identify priority of interventions in such areas particularly vulnerable with respect to others.
Earthquake Resistant Engineering Structures IX, 2013
The quantitative measure of seismic vulnerability is a necessary requirement for prevention and for an optimal emergency management. Before L'Aquila's earthquake in 2009, the National Civil Protection, in collaboration with the University of L'Aquila, developed a model (Beolchini, "Definition of an indicator of urban vulnerability" (2003)) to evaluate the criticality seismic of urban centers by using a multidisciplinary approach. The study has led to the definition of an urban vulnerability index, that allows to identify the most critical urban centers and the problematic elements, in order to establish a hierarchy for preventative measures and for an efficient emergency management (Calvi et al. "Development of seismic vulnerability assessment methodologies over the past 30 years" (2006). One of the features of this evaluation is that it allows a simultaneous analysis of the multiple factors involved in risk assessment (Ferlito and Pizza "Modello di vulnerabilità di un centro urbano. Metodologia per la valutazione speditiva della vulnerabilità della viabilità d'emergenza" (2011); Ferlito et al. "Danger treblement de terre et mesure du risque à L'Aquila" (2010)). After the seismic event occurred, same tests have been done to verify the validity of the model on the part of buildings, by comparing the criticality evaluated and damage suffered by the buildings, taking into account the local effects resulting from operations of microzonation. The seismic vulnerability
2014
T Mt Etna region (Sicily, Italy) is one of the test areas studied in the European Project “Urban disaster Prevention Strategies using MAcroseismic fields and FAult sources” ( UPStrat-MAFA) to which the methodology of Disruption Index (hereafter DI), recently developed to evaluate the dysfunction of urban systems caused by earthquakes (Ferreira et al., 2014), has been applied on a trial basis. The central idea underlying the definition of DI is the identification of fundamental areas of human needs (housing, education, employment, food processing and distribution, and so on) which may be affected by earthquakes occurrence, of the functions (electricity and water supply, transportation, and so on) whose dysfunction can affect them, and of their dependencies network. The network of the dependencies is complex; disruption of one of the functions may affect one or more of the general areas of human needs, and a function may depend on other functions. All functions in turn depend on the p...
Key Engineering Materials, 2014
The seismic vulnerability assessment of a building requires a comprehensive knowledge of both building structural features and soils geophysical parameters. To achieve a vulnerability assessment at the urban scale a large amount of data would be necessary, with a consequent involvement of time and economical resources. The aim of this paper is hence to propose a simplified procedure to evaluate the seismic vulnerability of urban centres and possible seismic damage scenarios in order to identify critical areas and/or building typologies to plan future actions of seismic risk mitigation and prevention. The procedure is applied to the outstanding case study of the city of Florence. The research is based on the definition of major building typologies related to construction periods and type of the structural system (masonry or reinforced concrete), the identification of a set of sample buildings, the analysis of the dynamic behaviour and the evaluation of a vulnerability index with an expeditious approach. The obtained results allow to define potential vulnerability and post-event damage scenarios related to the expected levels of peak ground acceleration.
A Methodological Approach for the Evaluation of Urban and Territorial Seismic Vulnerability
Pure and Applied Geophysics, 2005
A methodology of urban and territorial vulnerability analysis related both to engineering studies and social priority levels is presented. Modelling an urban system as a set of elements and relations, the evaluation of seismic vulnerability is carried out through suitable functions that characterize the seismic reliability of the site in terms of the geotechnical reliability of the ground and a structural reliability of buildings regarding the importance of activities referable to each element of the system. The results of the study, represented in map form, allow a full characterization of the distribution of urban and territorial vulnerability aimed at a seismic risk mitigation.
Seismic vulnerability assessment at urban scale: state of the art and perspectives
2017
Italian territory is particularly sensitive to seismic actions. The Amatrice earthquake on August 24th 2016 confirmed this aspect. Such an event, nothing but extraordinary, has been able to cause huge and tragic damages. The direct knowledge of building features is the only prior measure to face seismic events. In order to get a realistic scenario of the urban damage distribution, the determination of useful seismic vulnerability assessment tools at urban scale becomes a priority. The widespread application of seismic vulnerability assessment sheets and the related data transformation into urban damage distribution plans is exactly what municipalities need. Main advantages are both in the chance of prior knowing the most affected areas to focus on for retrofitting interventions and in the possibility of organizing optimal emergency plans. In European framework, in the last decade, the Risk-UE project has played an important role. The Risk-UE project has proposed two methods for vuln...
An integrated earthquake vulnerability assessment framework for urban areas
Natural Hazards
In this paper, an integrated urban earthquake vulnerability assessment framework, which considers vulnerability of urban environment in a holistic manner and performs the vulnerability assessment for the neighborhood scale, is proposed. The main motivation behind this approach is the inability to implement existing vulnerability assessment methodologies for countries like Turkey, where the required data are usually missing or inadequate for the decision-makers in prioritization their limited resources for risk reduction in the administrative units from which they are responsible for. The methodology integrates socio-economical, structural, coastal, ground condition, vulnerabilities (fragilities), as well as accessibility to critical services. The proposed methodology is implemented for Eskisehir, which is one of the metropolitans of Turkey. In the implementation of the proposed framework, geographic information system (GIS) is used. While the overall vulnerabilities obtained for neighborhoods are mapped in GIS, the overall vulnerabilities obtained for buildings are visualized in 3D city model. The main reason behind using different mapping and visualization tools for vulnerabilities is to provide better ways for communicating with decision-makers. The implementation of the proposed vulnerability assessment methodology indicates that an urban area may have different vulnerability patterns in terms of structural, socio-economical, and accessibility to critical services. When such patterns are investigated, effective vulnerability reduction policies can be designed by the decision-makers. The proposed methodology well serves for this purpose.