Modelling exposure and vulnerability from post-earthquake survey data with risk-oriented taxonomies: AeDES form, GEM taxonomy and EMS-98 typologies

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Abstract

Post-earthquake damage and usability surveys are fundamental in managing the emergency phase in the aftermath of a strong seismic event. In Italy, in addition to the damage and usability evaluation, this survey enables the collection of building geometrical and structural attributes related to seismic vulnerability. With the development of the Observed Damage Database (Da.D.O.) platform, most of the data collected during the post-earthquake inspections have been harmonized and made freely available to the scientific community. These data constitute an important heritage for scientific purposes but, until now, the potential for seismic risk assessment has not been fully exploited, partly because the format specifications are particular to the Italian environmental conditions, and the attributes are not directly related to existing risk-oriented classifications. In order to reliably extract the exposure and vulnerability information and harmonize it according to recognized international standards, an innovative methodology has been developed to convert the information collected through the AeDES form, used in Italy since 1997 for post-earthquake usability surveys, to formats more suitable for a large-scale risk evaluation. In the proposed approach, the information on the typological characteristics has been firstly described according to the taxonomy proposed by the Global Earthquake Model (GEM). Subsequently, using a score-based methodology, the most likely EMS-98 building classes have been assigned based on the observed GEM attributes. This methodology has been exemplified with the data of the 2009 L'Aquila earthquake, and the results highlight the great potential for post-event surveys to provide relevant information for Disaster Risk Reduction (DRR) activities.

Introduction

One of the first activities to be carried out after an earthquake is the damage and usability assessment. The post-earthquake surveys represent a crucial moment for effectively managing the emergency phase in order to decide whether the people could safely return to their houses or be hosted in temporary shelters. It is also a delicate evaluation because of possible strong aftershocks. The activities of post-earthquake surveys are carried out by expert technicians through the compilation of inspection forms. In Italy, until the late ‘90, post-earthquake surveys were carried out using specific formats prepared by the National Group for the Defence against Earthquakes (GNDT). Later on, a specific survey tool was developed by the GNDT and the National Seismic Survey (SSN) for “damage assessment, short term countermeasures for damage limitation and evaluation of the post-earthquake usability of ordinary buildings”, hereinafter referred to as AeDES form [1]. In addition to the damage and usability evaluation, this form allows for the collection of geometrical and structural attributes related to building vulnerability. In other countries such as Japan [2], Colombia [3], U.S. [4], New Zealand [5] and Greece [6], similar survey forms consider only the observed damage and very limited data are collected related to the vulnerability of the structures [7]. Specifically, in the U.S [4]. and New Zealand [5], limited data about the main structural material and the lateral load-bearing system are required. Even in Greece [6], partial information on the building characteristics is collected through the post-earthquake usability form, excluding any evaluation of the expected vulnerability.

Post-earthquake data are usually used to correlate seismic damage and building vulnerability [8]. Specifically, empirical methods are mainly based on the statistical processing of the observed damage data from seismic events. In order to overcome some limitations due to lack of quality and completeness of available data, the best compromise is the hybrid methodology [9] which combine empirical (e.g. Ref. [10]) and analytical (e.g. Ref. [11]) approaches.

Hence, the AeDES form is a unique tool that enables the management of post-earthquake phase and a wide availability of building information very useful for Disaster Risk Reduction (DRR) and prevention activities. These data were collected for individual buildings in the order of many tens of thousands for recent Italian events. In this framework, most of the data collected during the post-earthquake inspections carried out over the last 50 years were recently organized in the “Observed Damage Database” (Da.D.O.), platform of Civil Protection Department (DPC), developed by the Eucentre Foundation. The Da.D.O. [12] - [13] aims at collecting, cataloging and comparing data related to building features and seismic damage collected with different post-earthquake inspection forms during the ten most important Italian earthquakes (Table 9 in “Appendix”). As already mentioned above, these data represent a valuable source of exposure and vulnerability information and constitute an important heritage for different scientific purposes, including, e.g., the calibration of damage estimation models in terms of Damage Probability Matrices (e.g. Ref. [10]) or observational fragility curves (e.g. Refs. [14],- [15]) for damage scenarios and risk analysis. In this regard, some vulnerability models in the report of the DPC [16] were derived based on the actual damage data available in Da.D.O. It is worth mentioning that, in the DPC report [16], an overview of major risks in Italy (i.e., seismic, volcanic, tsunami, hydro-geological/hydraulic and extreme weather, droughts and forest fire risks) was reported. Specifically for seismic risk, an updated assessment was provided on the basis of state-of-the-art methodologies and tools developed in the last years.

However, to date, the Da.D.O. potential for seismic risk assessment has not been fully exploited, partly because the format specifications are very particular to the Italian environmental conditions and the collected attributes are not directly related to existing risk-oriented classifications (e.g., PAGER-STR taxonomy [17], HAZUS taxonomy [18] or EMS-98 building types [19]). In fact, the AeDES data are not immediately suitable for wide-scale risk assessment applications dealing with hundreds of thousands of buildings. Usually, in risk analysis applications, small sets of MECE (Mutually Exclusive, Collectively Exhaustive) typological classes are used, with each class grouping structures with similar structural features and, therefore, expected comparable seismic performance. Therefore, in order to reliably extract the exposure and vulnerability information and match it according to recognized international standards, an innovative methodology has been developed to convert the information collected through the AeDES form to different formats more suitable for a large-scale risk evaluation and comparison.

In the proposed approach, the information on the typological characteristics has been firstly described according to the faceted taxonomy proposed by “Global Earthquake Model” (GEM, v2.0 [20]). The conversion process allows to harmonize the AeDES data, that are specific to the conditions to be found in Italy, in terms of a flexible taxonomy with a global scope. Moreover, this step enables to define an exposure model that is independent by the vulnerability/fragility component and could be also employed for the consideration of different, possibly concurrent hazards (multi-hazard analyses). However, the information in terms of GEM taxonomy (as well as the AeDES data) cannot be directly used for the large-scale seismic risk evaluations. Therefore, in a subsequent processing step, employing an attribute-based scoring methodology [21], the EMS-98 building classes [19] have been assigned based on the GEM attributes. In this way, an exposure model in terms of risk-oriented classes correlated to a specific fragility models (i.e., EMS-98 classes) can be defined and, then, the information based on field data (i.e., AeDES form) can be exploited for large-scale risk assessments. This methodology, based on the concept of fuzzy compatibility score ([22]), allows for an extensive characterization of the uncertainty underlying the class assignment process. Hence, the proposed approach allows to separately consider the data collection and the exposure modelling by ensuring the reproducibility of the results. Finally, this methodology has been exemplified with the data of the Mw 6.3 2009 L'Aquila earthquake by considering observed damage data and macroseismic intensity values as provided by the Da.D.O. platform. In this framework, Da.D.O. represents an invaluable tool, since it allows also to correlate the information related to exposure and vulnerability with observed damage.

Section snippets

Taxonomy description

The exposure component describes the collected data on the assets (buildings, infrastructure, lifelines) that are susceptible to be damaged by seismic events. As for buildings, two different taxonomy typologies can be used in order to describe the structural and non-structural characteristics, namely risk-oriented or faceted taxonomies [21]. For large-scale applications, specific risk-oriented taxonomies are usually employed, among which PAGER-STR taxonomy [17], HAZUS taxonomy [18] or European

Methodology

In this section, the methodology developed to convert the information collected through AeDES form to different formats is reported. In the first step of the proposed approach, the information on the typological characteristics has been described according to the GEM taxonomy (section 3.1). In a following processing step, using the score-based methodology proposed by Pittore et al. [21], an EMS-98 building class has been assigned to each surveyed building based on its GEM attributes (section 3.2

Application

The methodology above described has been applied to the data of the April 6, 2009 L'Aquila earthquake (Mw = 6.3 [35],- [36]) as provided by the Da.D.O. platform. The earthquake caused heavy and extensive damage in several villages with MCS (Mercalli-Cancani-Sieberg [28]) intensity values ranging from V to IX degree [37]. It is worth highlighting that MCS scale is usually adopted in the south of Europe, especially in Italy where it is currently used in the parametric earthquake catalogue [38]

Conclusive remarks

Post-earthquake surveys represent a fundamental step in the management of the emergency phase in the aftermath of a strong earthquake. In Italy, further to damage data and usability rating, the field survey allows also the collection of valuable dimensional and structural attributes. The data related to Italian earthquakes occurred over the last 50 years were collected and organized on the Da.D.O. web-based platform. This represents a unique source of exposure and vulnerability information and

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This study was partially developed under the financial support of the Italian Department of Civil Protection, within the ReLUIS-DPC 2019–2021 project. This support is gratefully acknowledged.

References (41)

  • S.A. Anagnostopoulos et al.

    Post-earthquake emergency assessment of building damage, safety and usability - Part 1: Organization

    Soil Dynam. Earthq. Eng.

    (2008)
  • C. Lee et al.

    Mutually-exclusive-and-collectively-exhaustive feature selection scheme

    Appl. Soft Comput.

    (2018)
  • K.J. Zhu et al.

    A discussion on extent analysis method and applications of fuzzy AHP

    Eur. J. Oper. Res.

    (1999)
  • G. Bortolan et al.

    A review of some methods for ranking fuzzy subsets

    Fuzzy Set Syst.

    (1985)
  • C. Baggio et al.

    Field manual for post-earthquake damage and safety assessment and short-term countermeasures (AeDES). JRC scientific and technical reports, European commission, EUR22868, joint research centre, Institute for the protection and security of the citizen

    Luxembourg

    (2007)
  • A. Goretti et al.

    Post-earthquake Usability and Damage Evaluation of Reinforced Concrete Buildings Designed Not According to Modern Seismic Codes. JSPS Short Term Fellowship

    (2002)
  • Guía Ais

    Técnica para inspección de edificaciones después de un sismo: manual de campo, 3d edition. Asociación Colombiana de Ingeniería Sísmica and FOPAE

    Bogotà, Colombia

    (2009)
  • Field Manual: Post-earthquake Safety Evaluation of Buildings

    (2005)
  • Nzsee

    Building safety evaluation during a state of emergency guidelines for Territorial Authorities

    New Zealand Society for Earthquake Engineering

    (2009)
  • A. Masi et al.

    Procedures and experiences in the post-earthquake usability evaluation of ordinary buildings

    Boll. Geofis. Teor. Appl.

    (2016)
  • G.M. Calvi et al.

    The development of seismic vulnerability assessment methodologies over the past 30 years

    ISET J. Earthq. Technol.

    (2006)
  • A.J. Kappos

    An overview of the development of the hybrid method for seismic vulnerability assessment of buildings

    Structure and Infrastructure Engineering

    (2016)
  • M. Dolce et al.

    Earthquake damage scenarios of the building stock of Potenza (Southern Italy) including site effects

    Bull. Earthq. Eng.

    (2003)
  • A. Masi et al.

    Fragility curves of gravity-load designed RC buildings with regularity in plan

    Earthquakes and Structures

    (2015)
  • M. Dolce et al.

    Da.D.O. - a web-based tool for analyzing and comparing post-earthquake damage database relevant to national seismic events since 1976. Proceedings of the 17th Italian Conference on Earthquake Engineering

    Pistoia, Italy

    (2017)
  • M. Dolce et al.

    Observed damage database of past Italian earthquakes

    the Da.D.O. WebGIS. Bollettino di Geofisica Teorica ed Applicata

    (2019)
  • S. Lagomarsino et al.

    Macroseismic and mechanical models for the vulnerability and damage assessment of current buildings

    Bulletin of Earthquake Engineering

    (2006)
  • S. Lagomarsino et al.

    Fragility functions of masonry buildings

  • Italian Dpc

    Civil protection department, national risk assessment

    Overview of the potential major disasters in Italy: seismic, volcanic, tsunami, hydro-geological/hydraulic and extreme weather, droughts and forest fire risks

    (2018)
  • K. Jaiswal et al.

    A global building inventory for earthquake loss estimation and risk management

    Earthq. Spectra

    (2010)
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