Understanding building damage through the lens of the Swiss post-seismic reconnaissance mission of 2023 Al Haouz, Morocco, earthquake

A team of scientists and engineers from Swiss institutions participated in a post-seismic reconnaissance mission in Morocco following the magnitude 6.8 earthquake of September 8, 2023. We visited different heavily affected towns and villages, located from 10 to 70 km epicentral distance, in the High Atlas Mountain and Marrakech. In this work, we report our observations from inspecting building damage in affected areas. We discuss the prevalent building typologies observed, their construction mechanisms, and the resulting structural and non-structural damage patterns. We also examine the potential site-related effects based on a literature review of the seismological and geological settings of the area. The earthquake's severe impact was due to its shallow depth and underlying geological complexities, including active faulting and diverse rock formations. The lack of earthquake-resistant construction practices significantly exacerbated the damage. Modern structures in Marrakech were largely unaffected while ancient ones in the Medina of Marrakech suffered partial damage. In rural High Atlas areas, buildings exhibited significant damage due to lack of seismic design as well as poor-quality materials. Our observations prompt us to believe that conducting site-specific hazard studies along with implementing earthquake-proofing measures involving local communities can foster resilience to future seismic events in this area.