Probabilistic seismic hazard assessment at global level

• A probabilistic seismic hazard analysis was conducted at global level.
• The same methodology was employed in all regions.
• A smoothed seismicity methodology was followed to calculate the a and b-values.
• A division of the Globe in tectonic regions was performed.
• Seismic hazard results were obtained in terms of intensity exceedance curves.

In the framework of the UNISDR׳s Global Assessment Report on Disaster Risk Reduction 2013, for the first time, a fully probabilistic seismic hazard assessment was conducted at global level, using the same methodology for the whole Globe, from which a set of stochastic scenarios for different intensities (spectral accelerations, 5% damping) was obtained and then used in a fully probabilistic risk analysis. First, the Globe was divided into a set of seismogenetic areas to which a maximum magnitude and a predominant tectonic environment type were assigned. A Gutenberg–Richter magnitude–frequency distribution was assumed for each region, with a and b-values computed using a smoothed-seismicity procedure based on the NEIC 1-USGS2 seismic catalog. This catalog was first subjected to a declustering process and completeness verification for several threshold magnitudes. Based on the tectonic environment assigned to each source, a ground motion prediction model was assigned accordingly. Probabilistic hazard computations were performed with program CRISIS 2012, which generated conventional hazard curves for different intensities and maps for various return periods, as well as a set of stochastic scenarios compatible with the CAPRA3 platform. These scenarios, in turn, were used to perform coarse-grain probabilistic risk computations.