Mapping seismic vulnerability at urban scale: Discussion on relevant cartography representations and smoothing for urban planning purposes on the Oran case study

Abstract

Earthquake damage and loss scenarios are considered as a powerful tool to help in the design of efficient seismic mitigation policies. Moreover, at a city scale, adequate urban planning may significantly contribute to improve resilience through requalification of inherited urban fabrics and/or appropriate land use. In this perspective, the present paper investigates what could be the optimal graphic representation of probable losses at urban scale, which be most relevant for seismic risk management. The goal is to provide urban planners with guidelines on how to combine the use of vulnerability index-based damage estimates and GIS tools, to identify urban fabrics that need requalification. The proposed methodology consists in starting from damage estimates at the individual building scale, and using GIS (Geographic Information Systems) capacities to aggregate the expected damage on neighborhoods of increasing size, from blocks to large urban districts, in order to delimitate homogeneous urban zones. The criteria thus for choosing the optimal aggregation level are based on the need to obtain legible maps combining robust damage estimations -which implies statistics over a large enough number of buildings -, and a clear identification of the most vulnerable urban areas on which dedicated actions should be focused in priority.These methodologies are presented and tested on the example of the city of Oran (Algeria), and on the basis of a prior vulnerability study based on GNDT and RISK-UE vulnerability index approaches. The main outcome is the identification of different urban zones, which exhibit some homogeneity regarding both their average seismic response and their urban function. The most vulnerable urban fabrics require not only individual retrofitting measures at building scale; they also need urban requalification because it is more convenient to deal simultaneously with urban and safety considerations.

Variable-resolution building exposure modelling for earthquake and tsunami scenario-based risk assessment. An application case in Lima, Peru

“…In accordance with Vamvatsikos et al, (2010) and similar to other studies entailing spatial 415 comparison of risk estimates (e.g. Senouci et al, 2018), the loss values are normalized. Although the absolute value in the loss estimates is not affected by the aggregation entities (Figure 9), large differences arise when the normalised losses are actually mapped.…”

“…(1) To independently represent the building portfolio over a series of aggregation entities such as administrative units, or 100 equidimensional regular grids, and explore their individual contribution to the uncertainty in the losses imposed by certain hazard(s) to ultimately select a representative aggregation model. This option has been explored in Bal et al, (2010), Frolova et al, (2017, Senouci et al, (2018) and Kalakonas et al, (2020) for seismic vulnerability applications, and in Figueiredo and Martina, (2016) for flood vulnerability. These studies discuss the weakness of the physical vulnerability mapping at the individual building scale and over coarse aggregation areas, and highlight the importance of finding an optimal resolution for 105 building exposure modelling while minimizing the uncertainties in the losses estimates.…”

Evaluación de la vulnerabilidad sísmica de las edificaciones de la zona urbana del distrito de Chiquián, utilizando el model builder del ArcGIS

“…La creación del modelo de vulnerabilidad sísmica, a través de la integración gráfica de diferentes herramientas, permitió la automatización y la sistematización de la información, tal como muestra (Enviromental Systems Research Institute, 2016). La utilización de las nuevas herramientas y tecnologías del SIG en la creación del modelo de vulnerabilidad sísmica, permitirá una adecuada gestión del riesgo en la zona urbana del distrito de Chiquián, a través de su aplicación sencilla, teniendo en cuenta las recomendaciones de (Senouci et al, 2018).…”

“…Los resultados muestran que los edificios más vulnerables son las estructuras de mampostería reforzada con techos de teja de arcilla y los edificios más seguros son las de estructuras de mamposteria reforzada con techos de asbesto o techos de zinc. Senouci et al (2018), realizaron una investigación referida a la representación gráfica de los escenarios de daños y pérdidas por terremotos, a través de las estimaciones del índice de vulnerabilidad y las herramientas SIG que permitan una mejor planificación urbana. Los resultados muestran que las diferentes zonas de Orán (Argelia) tienen cierta homogeneidad en su respuesta sísmica y las zonas más vulnerables que requieren de una recalificación urbana.…”

Variable-resolution building exposure modelling for earthquake and tsunami scenario-based risk assessment: an application case in Lima, Peru

“…portfolio over a series of aggregation entities such as administrative units, or equidimensional regular grids, and explore their individual contribution to the uncertainty in the losses imposed by certain hazard(s) to ultimately select a representative aggregation model. This option has been explored in Bal et al (2010), Frolova et al (2017), Senouci et al (2018), and Kalakonas et al (2020) for seismic vulnerability applications and in Figueiredo and Martina (2016) for flood vulnerability. These studies discuss the weakness of physical vulnerability mapping at the individual building scale and over coarse aggregation areas and highlight the importance of finding an optimal resolution for building exposure modelling while minimising the uncertainties in the loss estimates.…”