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

Post-earthquake damage and usability surveys are fundamental in managing the emergency phase in the aftermath of a strong seismic event, for instance deciding whether the people could safely come back to their houses or be hosted in temporary shelters. In Italy, in addition to the damage and usability evaluation, this survey enables the collection of geometrical and structural attributes highly related to seismic vulnerability. These data are collected for individual buildings in the order of many tens of thousands for recent events and represent a unique source of exposure and vulnerability information and a very useful tool for Disaster Risk Reduction (DRR) and prevention activities. With the development of the “Observed Damage Database” (Da.D.O.; Dolce et al., 2017) web-based platform, most of the data collected during the post-earthquake inspections carried out over the last 50 years has been harmonized and made freely available to the scientific community. These data constitute an important heritage for scientific purposes but, until now, their potential for seismic risk assessment has not been fully exploited, partly because the format specifications are very particular to the environmental conditions to be found in Italy, and the collected attributes are not directly related to existing risk-oriented classifications. In order to reliably extract the exposure, vulnerability and damage information collected for Italian earthquakes and harmonize it according to recognized international standards, an innovative methodology has been developed to convert the information collected through the “1° level form for post-earthquake damage and safety assessment and short term countermeasures in residential buildings” (AeDES form; Baggio et al., 2007; Masi et al., 2016) to different formats more suitable for a large-scale risk evaluation and comparison. In the proposed approach, the information on the typological characteristics is firstly described according to the taxonomy proposed by “Global Earthquake Model” (GEM) (v2.0, Brzev et al., 2013). In a following processing step, using a score-based methodology (Pittore et al., 2018), we can assign EMS-98 building classes (Grünthal, 1998) on the basis of the GEM attributes. The proposed method allows for an extensive characterization of the uncertainty underlying the conversion process, encoded by the use of a probabilistic framework. A similar approach can be used to map the damage data into the categories defined by the EMS-98 scale. This methodology has been exemplified with the data of the Mw 6.3 2009 L´Aquila earthquake as provided by the Da.D.O. platform, and the results highlight the great potential for post-event surveys to provide relevant information also for DRR and risk prevention activities.

Keywords: seismic risk, post-earthquake survey, exposure, taxonomy