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

Abstract

Abstract. We propose the use of variable resolution boundaries based on central Voronoi tessellations (CVTs) to spatially aggregate building exposure models for risk assessment to various natural hazards. Such a framework is especially beneficial when the spatial distribution of the considered hazards presents intensity measures with contrasting footprints and spatial correlations, such as in coastal environments. This work avoids the incorrect assumption that a single intensity value from hazards with low spatial correlation (e.g. tsunami) can be considered to be representative within large-sized geo-cells for physical vulnerability assessment, without, at the same time, increasing the complexity of the overall model. We present decoupled earthquake and tsunami scenario-based risk estimates for the residential building stock of Lima (Peru). We observe that earthquake loss models for far-field subduction sources are practically insensitive to the exposure resolution. Conversely, tsunami loss models and associated uncertainties depend on the spatial correlations of the hazard intensities as well as on the resolution of the exposure models. We note that for the portfolio located in the coastal area exposed to both perils in Lima, the ground shaking dominates the losses for lower-magnitude earthquakes, whilst tsunamis cause the most damage for larger-magnitude events. For the latter, two sets of existing empirical flow depth fragility models are used, resulting in large differences in the calculated losses. This study, therefore, raises awareness about the uncertainties associated with the selection of fragility models and spatial aggregation entities for exposure modelling and loss mapping.

Epistemic uncertainty of probabilistic building exposure compositions in scenario-based earthquake loss models

“…That approach is useful for obtaining exposure descriptors (i.e., number of buildings belonging to a certain class, night-time residents, and replacement costs) under another reference (target) scheme in large-area exposure modelling applications. This can be done in terms of vulnerability descriptors for other hazard-reference schemes (e.g., Gomez-Zapata et al 2021a), thus extending its application beyond the field of seismic risk.…”

Calculating earthquake damage building by building: the case of the city of Cologne, Germany

“…However, the good agreement obtained herein cannot necessarily be generalised. The extent to which different resolutions of exposure lead to similar or dissimilar results depends on the scenario (proximity to the fault, spatial variability of site effects, resolution at which site characterisation is available) and the nature of the peril (e.g., Gomez-Zapata et al 2021 ).…”

Towards a Sensitivity Analysis in Seismic Risk with Probabilistic Building Exposure Models: An Application in Valparaíso, Chile Using Ancillary Open-Source Data and Parametric Ground Motions

“…Achieving higher resolutions was discarded because that would require further assumptions that would increase the uncertainties of such models. Moreover, since the resulting exposure models were input for seismic risk analyses, the use of higher resolution models would lead to important and unnecessary computational problems (e.g., [75,76]) that we preferred to reduce at this stage. This stemmed from the need to address the aleatory uncertainties implicit in a stochastic process, such as by generating thousands of realisations of spatially correlated ground motion fields [76].…”