GEM Global Homogenised Earthquake Catalogue

The 2026 GEM global homogenised catalogue is a homogenised earthquake catalogue containing ~495 000 events between 1900 and 2024. The catalogue combines events above M4 from three global datasets: ISC-GEM (https://www.isc.ac.uk/iscgem/, currently v11.0), the Global Centroid-Moment-Tensor (https://www.globalcmt.org/) and comcat (https://earthquake.usgs.gov/data/comcat/) catalogues. To provide a single consistent magnitude type for PSHA, all events are homogenised to moment magnitude (Mw). Magnitude uncertainties from the original catalogues are propagated including uncertainties associated with any magnitude conversions. Where available, focal mechanism data, depth, magnitude and location uncertainties are retained. Original magnitude types and values from contributing catalogues are also included to help track event origins consistently.