| Summary: | The Global Earthquake Model (GEM) Global Seismic Hazard Map (version 2023.1) poster replaces the previous version (2018.1) released in December 2018. This map depicts the geographic distribution of the Peak Ground Acceleration (PGA) with a 10% probability of being exceeded in 50 years, computed for reference rock conditions (shear wave velocity, VS,30 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 and by 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. The hatched areas in the map (e.g. Greenland) are currently not covered by an openly accessible hazard model. The underlying database is a dynamic framework capable of incorporating newly released open models. Due to possible model limitations, regions portrayed with low hazard may still experience potentially damaging earthquakes. The GEM Foundation plans to release future updates of this map regularly as new information becomes available. 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/.
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