Presentation of the Risk Modeller’s Toolkit, the Open-Source Software for Vulnerability Assessment of the Global Earthquake Model

Abstract eng:
In the last decade several software packages for seismic hazard and risk assessment have been released, thus making it easier for hazard and risk modellers to run complex analyses without the need to code their own implementations of the scientific algorithms. However, the development of the input models for such analyses is often an equally challenging task, and the availability of tools to support experts in this stage is still very limited. Three main input models are required for earthquake risk analysis: a seismic hazard model, an exposure dataset, and a set of physical fragility or vulnerability functions. The latter component describes the probability of damage or loss conditional on different levels of ground shaking, and assumes a special role since an improvement in the seismic performance of the building stock can directly reduce the associated seismic risk. This study presents the Risk Modeller’s Toolkit (RMTK), a suite of tools to support risk experts in the derivation and verification of fragility or vulnerability models. The development of the RMTK followed an open-source and transparent approach. Thus, its code can found in a public repository (https://github.com/GEMScienceTools/rmtk), and all of the implemented methodologies have been fully documented in the RMTK manual. The current version of the RMTK comprises four modules: 1) generation of structural models, represented by pushover curves or single-degree-of-freedom (SDOF) oscillators, to represent the variability in the capacity of the building stock; 2) conversion of results from multidegree-of-freedom models into the equivalent SDOF systems; 3) derivation of fragility functions by combining capacity models with sets of ground motion records or response spectra; 4) conversion of fragility models into vulnerability functions through the employment of damage-to-loss models. These modules contain some of the most well-known methodologies in seismic vulnerability assessment, which allow the propagation of a wide spectrum of aleatory uncertainties, such as the variability in the structural capacity of the building stock; uncertainty in the definition of the damage criterion; or the record-to-record variability. The employment of distinct fragility methodologies will inevitably lead to different results (epistemic variability), which may have a significant impact on the associated seismic risk estimates. The RMTK is currently being employed in the development of fragility functions for the most common building classes in South America, eastern Sub-Saharan Africa, Canada, Costa Rica and Nepal. The outcomes of the RMTK are fully compatible with the OpenQuake-engine, the open-source software for seismic hazard and risk analysis of the Global Earthquake Model initiative.

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