Recent Developments in the Risk Component of the Openquake-Engine

Abstract eng:
The OpenQuake-engine is the open-source software for seismic hazard and risk analysis developed by the Global Earthquake Model (GEM) Foundation. This paper describes some of the recent advancements in the risk component of the OpenQuake-engine. This tool now incorporates a probabilistic damage calculator using seismic hazard derived using the classical CornellMcGuire approach. This calculator is particularly useful in studies where the probability of exceedance or occurrence of different damage states for a single site over a certain time period needs to be estimated. Key metrics such as the annual probability of collapse of structures can be computed using this calculator. Furthermore, this calculator also enables performing comparative assessments of the seismic collapse risk for different structures at different locations in a region. In a demonstrative study, this module is used to perform a probabilistic seismic collapse risk assessment for buildings of different classes located in the city of Oakland, CA. Such studies for appraising the collapse risk are useful for the development of policies for region-wide risk mitigation strategies for existing structures, or to assess the most adequate seismic design for the region of interest. The capabilities of the scenario damage and loss calculators of the OpenQuake-engine are illustrated by simulating a possible repeat of the destructive 1906 M7.9 San Francisco earthquake on the San Andreas fault. The potential structural damage and loss due to this event are estimated using the OpenQuake-engine and the effect of various modelling choices such as the ground motion prediction equation or the site conditions model are studied. The OpenQuake-engine makes it possible to model both the spatial correlation in ground motions and the loss correlation amongst assets of the same class, and also to propagate uncertainties in the hazard and risk models right up to the final loss results. Epistemic uncertainty in the choice of a source model, or the ground motion model for a particular tectonic region type, or in the parameters of the source model are handled within the OpenQuake-engine through the use of logic-trees. The stochastic event-based loss calculator based on the Monte Carlo approach is employed in a set of case studies involving a residential exposure model located in the San Francisco Bay Area, CA.

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