Insights into large landslide mechanisms in tectonically active Agadir, Morocco: The significance of lithological, geomorphological, and soil characteristics

Landslide susceptibility assessment is crucial for land use planning, infrastructure development, and hazard mitigation, particularly in tectonically active regions where lithology and soil characteristics significantly influence slope stability. This study aims to evaluate landslide susceptibility in the Agadir Ida-Ou-Tanane province, a tectonically active area, using a hierarchical multicriteria analysis approach. Eight factors influencing landslide occurrence were considered: lithology, slope, LULC, distance to main faults, hypsometry, drainage density, road density, and aspect. Pairwise comparison matrices and expert opinion were employed to determine the relative importance of these factors. The consistency ratio (CR) was calculated to ensure the reliability of the judgments. The resulting landslide susceptibility map reveals a spatial distribution ranging from very low to very high susceptibility zones. Lithology, mainly clay, and limestone formations, emerged as the most influential factor due to the active tectonic context of the study area. The model was validated using observed landslide locations and the Area Under the Curve (AUC) method, yielding a reasonable validation accuracy. The findings indicate that integrating these factors, with a particular emphasis on lithology and soil characteristics, effectively identifies areas prone to landslides, making the resulting map a valuable tool for land use planning and risk management in the Agadir Ida-Ou-Tanane region. This study contributes to understanding landslide susceptibility in tectonically active areas and provides a practical foundation for future research and decision-making. Regularly monitoring and updating the landslide susceptibility map is necessary to ensure its continued relevance and utility for stakeholders

Tsunami hazard and buildings vulnerability along the Northern Atlantic coast of Morocco –the 1755-like tsunami in Asilah test-site

Abstract Background The Atlantic Coast of Morocco is prone to tsunami inundation. Therefore, in this region, earthquake-induced tsunami hazard has been intensively investigated leading to the development of a number of coastal inundation models. However, tsunami vulnerability remains not well understood to the same extent as the hazard. In this study, we use high-resolution numerical modeling, detailed field survey and GIS-based multi-criteria analysis to assess the building tsunami vulnerability and its sensitivity to the tide variations. Asilah located in the northwestern Atlantic coast of Morocco, where the impact from the 1755 tsunami is well documented, constitutes the area of this study. Results To model the source-to-coast tsunami processes we used the COMCOT (Cornell Multi-grid Coupled Tsunami Model) numerical code on a set of bathymetric/topographic grid layers (640 m, 160 m, 40 m and 10 m resolutions) with an initial sea-surface perturbation generated using Okada’s formulae and assuming an instantaneous seabed displacement. The tsunami source models in this study correspond to four 1755-like earthquake scenarios. Results show that Asilah’s built environment is highly vulnerable to the tsunami impact that can range from 1.99 to 2.46 km2 of inundation area, depending on the source and the tidal level considered. The level of building vulnerability decreases considerably when moving away from Asilah’s coastline. Moreover, the variation in the tidal level introduces large change in the modeled tsunami impact and, therefore, affects the level of building vulnerability. Conclusion Thus, we suggest considering the effect of the tide when simulating tsunami hazard and vulnerability, particularly, in coasts where tidal variations are significant. This study provides hazard and vulnerability maps that can be useful to develop the tsunami awareness of the Moroccan coastal population

Geological and geomorphic investigations on palaeo-landslide dammed the Tamourghout River (Middle Atlas, Morocco)

The Middle Atlas Mountains in Morocco are best known for their slope-active movements, where lithology, topographic relief, and seismotectonic are likely to cause slope instability problems. This study focused on geomorphological and geological investigations on palaeo-landslide blocked and dammed the Tamourghout river main bed (Taza, Morroco). The paper is essential due to the enormous proportions of the landslide and also because of the vast watershed lock-up by the dam (Tamda lake) and the recognition that a Tamourghout river has been and can be obstructed by a permanent landslid

Geochemical and mineralogical characterization of coastal sediments in Al-Hoceima Bay (Central Rif, Morocco)

This work aims to characterize the morphosedimentaty dynamics of the shores of Al-Hoceima Bay through geochemical and mineralogical analysis of surface sediments. The results reveal a direct relationship between marine hydrodynamic forcing on the one hand and detrital inputs from land on the other. Calcimetric analysis makes it possible to highlight the transport and deposition processes at the beaches of Al-Hoceima bay. The difference in the reasonably high carbonate contents in the western beaches (Isli, Cala Bonita and Quemado) (> 60%) and low in the beaches of the central and eastern zone (Sfiha, Souani, Salina and Lharch) (≈ 15%) are mainly due to the influence of coastal currents, littoral drift, and fluvial action. The higher levels of heavy minerals in Lharch beach (18%) are expressed by volcanic outcrops of Cap Quelates and Jbel Tamsamen. The low values at the Souani and Tayth beaches (7% on average) are due to erosion by the two types of coastal drift, NW-SE and NNE-SSW, which carry the sediments of schist origin brought by the Oueds Ghiss and Nekôr. In contrast, the reasonably high contents in the Sfiha beach (12%) are attributed to the accumulation of allochthonous sediments by NW-SE littoral drift which carries sediments of volcanometamorphic origin from Rass Quelates

New sedimentary and geomorphic evidence of tsunami flooding related to an older events along the Tangier-Asilah coastal plain, Morocco

International audienc

Sediment characterization and dynamics in Lake Ifrah (Middle Atlas, Morocco)

International audienc

Pedological characteristics of soils in the watersheds of Oueds Nekôr and Ghiss (Central Rif; Morocco)

The objective of this work is the pedological characterization of soils in the watersheds of Oueds Nekôr and Ghiss. Several profiles were identified and sampled for Physico-chemical and sedimentological analyses (color index, magnetic susceptibility, pH, granulometry, water content, organic matter, and carbonates). The watersheds in question are roughly characterized by a soft and diversified lithology, a sparse vegetation cover, and a semi-arid Mediterranean climate. The soils in the Oued Nekôr watershed are of the silty type (> 50%), not very developed and relatively well-drained, and become well-drained stony in the steep and eroded areas. Soil pH varies between 7 and 8, reflecting low alkaline to alkaline soils. In the Oued Ghiss watershed, the sandstone-limestone or marl-schist soils are poorly differentiated in the steep slopes. The well-drained soils are gravelly, relatively alkaline, and show the beginning of rubefaction. Very locally on wooded flats, the soil profiles can become deep and well-differentiated due to colluvial accumulation. The dark brown eluvial A horizon is relatively rich in organic matter (3.6%). The well individualized illuvial B horizon has strongly rubbed concretions and is richer in organic matter (4.6%). The light beige C horizon corresponds to the strongly altered marl and limestone parent rock with low organic matter content (1.3%) and very low magnetic susceptibility values

Sediment characterization and dynamics in Lake Ifrah (Middle Atlas, Morocco)

International audienc

Storm surge and tsunami deposits along the Moroccan coasts: state of the art and future perspectives

International audienceThe Moroccan coasts are occasionally inundated by storm surges and tsunamis. Local historical archives recorded some of these events, such as the storm surge of 1913 CE and the tsunami of 1755 CE. The latter remains the most destructive event the country has ever faced, with major human and economic losses recorded mainly between the two cities of Tangier and Safi. The privileged way to prevent any hazard related to these events is to study their past occurrences and impacts. However, historical evidences about these natural hazards are often very scarce to determine their return periods and evaluate their intensities. The scientific community increasingly uses sedimentary archives from coastal environments, since they offer a viable complement to historical archives. Several studies using this approach have been conducted on the Moroccan coast in recent years; however, until now, there has been no review dealing with these studies, which is the main objective of this paper. Twenty sites with traces of coastal inundation deposits have been inventoried during this work, and most of them are located along the Atlantic coast. The Mediterranean side remains poorly studied despite the presence of tsunami and storm surge risks. The review draws attention also to the absence of chronological data for most of the coastal inundation deposits recognized up to now along the Moroccan coasts, which is a majorissue that prevents the determination of the return period of these events