Global Seismic Hazard Map

The Global Earthquake Model (GEM) Global Seismic Hazard Map (version 2023.1) depicts the geographic distribution of the Peak Ground Acceleration (PGA) in terms of fraction of the acceleration of gravity, with a 10% probability of being exceeded in 50 years, computed for reference rock conditions (shear wave velocity, Vs30, of 760-800 m/s). The map was created by collating maps computed using national and regional probabilistic seismic hazard models developed by various institutions and projects, in collaboration with GEM Foundation scientists. The OpenQuake engine, an open-source seismic hazard and risk calculation software developed principally by the GEM Foundation, was used to calculate the hazard values. A smoothing methodology was applied to homogenise hazard values along the model borders (Pagani et al., 2018). The map is based on a database of hazard models described using the OpenQuake engine data format (NRML); those models implemented initially in other software formats were converted into NRML. While translating these models, various checks were performed to test the compatibility between the original and new results computed using the OpenQuake engine. Overall the differences between the original and translated model results are small notwithstanding some diversity in modelling methodologies implemented in different hazard modelling software. Some areas in the map (e.g. Greenland) are currently not covered by an openly accessible hazard model. Due to possible model limitations, regions portrayed with low hazard may still experience potentially damaging earthquakes. The raster is prepared by interpolating values calculated at points with ~6 km spacing using inverse distance weighting of nearest neighbours. The raster values will differ most from these original values in areas where hazard changes rapidly. Technical details on the compilation of the hazard maps and the underlying models - including updates to model components made by GEM - are available at https://hazard.openquake.org/