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 ( M W 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 ( M design ) 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 ( M W 6.8) and the 2004 Al-Hoceima earthquakes ( M W 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 γ EM σ M = 0.5 ( γ EM = 2) and 0.7 ( γ EM = 2.8) respectively, and the predicted peak ground acceleration were compared to recorded data. The results show that the Morocco catalogue with M design increment values could accurately forecast the ground shaking recorded for the 2023 earthquake. The analysis demonstrates that NDSHA maps M design extended may significantly reduce underprediction biases, especially for strong intraplate earthquakes. We conclude that M design 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. • Integration of M design into the NDSHA framework allows to address uncertainties and improve seismic hazard forecasting in Morocco. • The use of M design values improves the effectiveness of the seismic hazard maps for Morocco in forecasting the ground motion of the 8 September 2023 Al-Haouz earthquake ( M W 6.8). • The experiments performed show that a suitable Morocco catalogue, updated and enhanced including M design values, is necessary to obtain effective ground motion estimates. • The adoption of M design in NDSHA hazard assessment significantly reduces underpredictions, particularly for strong intraplate earthquakes.