Ground motion forecasting for the 2023 Al-Haouz and 2004 Al-Hoceima earthquakes in Morocco: The use of Mdesign definition

The 2023 Al-Haouz earthquake (MW 6.8) revealed shortcomings in Morocco's seismic hazard forecasts, evidencing the need for improved data and approaches. This study extends the Neo-Deterministic Seismic Hazard Assessment (NDSHA) to the use of design magnitude (Mdesign) definition. We validated the approach, through testing the performance of ground shaking maps computed for bedrock site condition with respect to the 2023 Al-Haouz (MW 6.8) and the 2004 Al-Hoceima earthquakes (MW 6.4). Using three seismicity catalogues (all truncated to 2012), we generated NDSHA ground shaking maps. Magnitudes were incremented, according to the Panza-Rugarli law, by γEMσM = 0.5 (γEM = 2) and 0.7 (γEM = 2.8) respectively, and the predicted peak ground acceleration were compared to recorded data. The results show that the Morocco catalogue with Mdesign increment values could accurately forecast the ground shaking recorded for the 2023 earthquake. The analysis demonstrates that NDSHA maps integrated by Mdesign may significantly reduce underprediction biases, especially for strong intraplate earthquakes. We conclude that Mdesign is a crucial prerequisite for reliable seismic hazard assessments in regions with sparse seismicity data, thereby enhancing predictive reliability for risk mitigation in Morocco and similar intraplate seismotectonic settings.