A Swiss reconnaissance mission to Morocco highlights how the geological characteristics of the High Atlas and vulnerable building typologies contributed to severe earthquake damage. The team's observations aim to improve earthquake resilience strategies for both Switzerland and other vulnerable mountain regions. A Swiss reconnaissance mission, led by scientists and engineers from the Swiss Earthquake Society for Earthquake Engineering and Structural Dynamics (SGEB), was sent to Morocco following the September 2023 earthquake. The team inspected building damage, documented prevalent construction typologies, and analyzed building mechanisms in affected areas. Their findings aim to inform Switzerland's risk mitigation strategies and contribute to international research on earthquake resilience in similar vulnerable mountain regions. The mission took place between November 23 and 27, 2023, when the team visited several of the hardest-hit towns, including Talat N'Yaaqoub, Imgdal, Tafeghaghte, and Amizmiz. According to the observations published Tuesday on Nature, the most severe damage caused by the earthquake was concentrated within 60 km of the epicenter, particularly in rural villages in the High Atlas foothills. This was not just due to the intensity of the earthquake but also due to site effects such as geology, rugged terrain, sedimentary basins, and resonance effects that amplified the seismic waves. For example, in Tafeghaghte, located 15 km from the epicenter, nearly every building was destroyed, and similar damage was observed in Talat N'Yaaqoub. Vulnerable building typologies The damage was also significant due to the building typologies and construction mechanisms of the affected region, especially traditional buildings in the High Atlas. The team remarked that earthen structures like adobe and rammed earth suffered extensive damage. Vulnerabilities included weak material interfaces, poor interlocking at corners, and insufficient reinforcement, leading to vertical cracks and wall overturning. Similarly, in the Medina of Marrakech, damage was also observed due to several factors. The team explained that the seismic vulnerability of these buildings depends not only on their own structural and material characteristics but also on their position within the aggregate, the geometric and structural features of adjacent buildings, and the connections between them. Lack of maintenance and unregulated modifications, including extensions that negatively impact structural behavior, are also cited as reasons for vulnerability. Several historic buildings, including the Koutoubia and Kasbah Mosques, sustained damage, particularly their minarets, which were vulnerable due to their height and resonance, according to the researchers. On the other hand, modern concrete buildings in Marrakech performed better due to earthquake-resistant design. The SGEB team's observations from the 2023 Al Haouz reconnaissance mission emphasize how geological, topographical, and site-specific factors can amplify seismic hazards, signaling that similar studies can help enhance resilience to future earthquakes.
