A probabilistic seismic hazard model for North Africa

African seismicity is predominantly localized along the East African Rift System (EARS), which is the major active tectonic feature of Sub-Saharan Africa. Besides the EARS, however, significant seismicity also occurs along a wide belt bounding the Mediterranean coastline. This tectonically active region extends discontinuously from Morocco to Egypt and its activity is controlled by the complex interaction between the Nubian and Eurasian plates, varying from transpression in the Atlas orogen in the west to transtension in the east. A record of large earthquake events is documented for the whole region, some of them causing moderate to severe levels of damage, mostly because of the high vulnerability of local buildings and structures, a condition which is still largely persistent in many areas. Currently, a number of seismic hazard models exist at local and national scales for North Africa, developed within independent projects and created using inhomogeneous data sources and different processing techniques. Unfortunately, such diversity makes their direct comparison problematic, obscuring the differences in seismic hazard across neighbouring areas and preventing the development of comprehensive long-term risk mitigation strategies. In fact, the last effort to produce a homogenized model for the whole Africa continent dates back to the GSHAP project, which is almost 20 years old. The creation of a unique seismic hazard model for North Africa, uniform across countries, is therefore a main concern. Since its inception, the Global Earthquake Model Foundation (GEM) is committed to the creation of a worldwide mosaic of high-quality, reproducible and openly accessible seismic hazard models, uniformly represented using the format adopted by the OpenQuake engine (OQ), a state-of-the-art, free and open-source software package for seismic hazard and risk assessment. We describe the development of a new comprehensive PSHA model for North Africa using GEM tools. The source model combines active faults and distributed seismicity, the former constrained from published geological descriptions and geodetic data, while the latter from the harmonisation of published earthquake catalogues.