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Landslides are the main gravitational phenomena in the Neogene basins of Algeria. This feature is mainly favored by the lithological nature of the fill materials, the climate, and the slope morphology. They are known for their high residential concentration and urban development. For better management and planning of future projects in landslide-prone areas, the use of Landslide Susceptibility Maps (LSMs) is indispensable. This study proposes a combined statistical and limit equilibrium method for the analysis of slope stability and for the production of LSMs using GIS in the Aomar Neogene basin (Bouira, Algeria). For this purpose, different work steps were carried out. Initially, a landslide inventory map was prepared based on existing studies, high-resolution aerial photography and satellite imagery analysis, as well as on detailed fieldwork. Besides, the geotechnical characterization of each geological formation was determined from the physical and mechanical parameters of recent and old geotechnical studies conducted in the region. A total, 169 landslides were compiled and randomly divided into training (70%) and validation (30%) datasets. Furthermore, eight factors influencing landslide occurrence (including slope angle, lithology, slope aspect, elevation, drainage density, distance to the rivers, distance to the roads, and rainfall) were selected and applied for the analysis. Moreover, the inventoried landslide and their associated factors were taken into account when mapping landslide susceptibility in the Aomar Neogene basin using Frequency Ratio (FR) models in GIS. On the other hand, a two-dimensional limit equilibrium (LE) model was used to determine the landslide-prone zones with a distinctive stability factor for each slope and the failure surface depth. Then, we have been able to verify and validate the obtained results for the statistical method using the Area Under the Curve (AUC) value of the Receiver Operating Characteristics Curves (ROC) method. For the frequency ratio models, the AUC is 83.23%, and for the limit equilibrium method, the safety factor is less than one for a slope greater than 16°. Based on these findings, we draw the conclusion that the maps may be exploited as practical instruments for land use planning and risk reduction in the Aomar Neogene basin. [ABSTRACT FROM AUTHOR]

On November 22, 2020, a moment magnitude of Mw 3.5 earthquake struck the highly populated Nile Delta. This event marked the first recorded earthquake in this area. We employed the polarity of P and S wave first motions, as well as SH and SV amplitudes and their respective ratios (SH/P and SV/SH), to constrain the focal mechanism solution. Furthermore, considering Brune's circular source model, kinematic source parameters were estimated through spectral analysis of available and reliable seismic data. The obtained solution reveals an oblique-slip fault mechanism, characterized by strike, dip, and rake angles of 341º, 69º, and -47º, respectively. Additionally, the two fault planes exhibit trends aligned with the E-W and NNW directions. This normal fault mechanism with a strike component aligns with previously identified events in various active areas of Egypt, indicating a dominant extensional stress regime. The trend/plunge of the P and T axes are determined to be 299º/46º and 42º/13º, respectively. Moreover, the NE trending of the T axis agrees well with the current extension stress field prevalent along the eastern border of Egypt. The average seismic moment and moment magnitude values for P and SH waves are estimated to be 1.86 × 1014 Nm, and 3.5, respectively. Furthermore, the average source values of radius and stress drop are calculated to be 304 m, and 29 bar, respectively. Through a comparative and comprehensive analysis of fault mechanism solutions in the Nile Delta region and its surroundings, we have concluded that the fault structures in the Hinge Zone and Cairo-Suez Shear Zone exhibit similarities. This finding provides evidence that the geodynamic processes and fault style are identical. In conclusion, the provided information contributes to our understanding of the seismotectonic characteristics and earthquake hazard in the epicentral region. Moreover, this study serves as a motivation for future site response and seismic hazard analyses based on a scenario-based approach. [ABSTRACT FROM AUTHOR]

Introduction: Masonry minarets in Old Cairo are highly susceptible to earthquake damage, particularly those not designed or updated to withstand seismic loads. Therefore, regular monitoring is necessary to ensure their safety and detect any deterioration or reduction in seismic performance. The direct loss of a minaret can lead to the collapse or severe damage to the structure itself. The cascading impacts of partial or complete minaret failure can have significant consequences for the immediate vicinity and the broader community. By studying the effects of earthquakes on minarets and developing mitigation strategies, countries can take proactive measures to protect these structures and ensure the safety of people. Objective: This study focuses on a specific type of Islamic architecture: the historic minarets in Cairo. The research aims to evaluate the seismic vulnerability of eight cultural heritage minarets in Cairo, identifying the parameters influencing their seismic behaviour and susceptibility to earthquake damage. Methods: The research utilizes empirical seismic vulnerability methods and ambient vibration measurements on eight minarets. An empirical approach compatible with the nature and style of the minarets is employed to evaluate their vulnerability using index values and curves. The method's validity is assessed, and areas of conformity and limitations are identified. Ambient vibration tests (AVTs) are also conducted using a temporary seismic network installed at various heights inside each minaret to determine their dynamic characteristics. Results: The seismic vulnerability Index (I_V) is calculated for the selected minarets based on the state of each vulnerability parameter. The contribution of each parameter to the final I_V values of the minarets are presented. Vulnerability curves are developed for each minaret, interpreting the conventional vulnerability indexes in terms of mean damage grades for seismic events with varying intensity on the EMS-98 scale. These mean damage grades can also indicate the expected damage levels of structural and non-structural minaret elements for events with different seismic intensity levels. AVTs are conducted at various heights on the selected minarets, and the dynamic characteristics are extracted from the recorded data. Variations in these characteristics are considered significant for structural health monitoring analysis. The peak-picking method is employed to directly extract each minaret's natural frequencies and mode shapes, as changes in dynamic characteristics are relevant to health monitoring analyses. Conclusions: The recent study examined the seismic vulnerability assessment of eight masonry minarets in the historic Old Cairo district. The assessment revealed vulnerability index values ranging from 10.3 to 26.1, indicating a concerning susceptibility to seismic events among these structures. Vulnerability curves were constructed for each minaret, visually representing potential damage scenarios across different levels of the EMS-98 intensity scale. These outcomes are significant as they facilitate prioritizing interventions to safeguard the most vulnerable minarets. Additionally, a novel empirical period equation was introduced to estimate the fundamental period of minarets in Old Cairo based on their heights. The equation was validated against field measurements and data from the literature. The study is limited by its focus on a specific category of minarets, specifically the historical masonry minarets in Old Cairo. Furthermore, limitations arise from the need for detailed finite element models to capture these minarets' dynamic responses accurately. Therefore, ongoing research involves the development of detailed finite element models and calibrating fundamental periods for the selected minarets. The anticipated results hold the potential to enhance our understanding of the structural dynamics of historical minarets, ultimately guiding the formulation of tailored seismic retrofitting and preservation strategies. These strategies, aimed at preserving these cherished cultural heritage assets, represent our collective commitment to ensure the endurance of these timeless landmarks for future generations. [ABSTRACT FROM AUTHOR]

In this research, we have compiled a catalogue of the worst tsunami earthquakes that caused destruction and losses in the northern coastal region of Egypt. Variability in seismic source parameters reflects the level of cognitive uncertainty that exists because most of these destructive tsunamis, if not all, occurred in the pre-instrumental period. We also synthesized a set of hypothetical tsunamis constrained by seismotectonic knowledge of the area of influence to embrace the uncertainty. We also collected the topo-bathymetry information available to make a simulation on the scale of the Egyptian north coast. The multiple scenarios were computed considering references and hypothetical scenarios, and results were presented in maps and tables for wave heights, inundation depth, and estimated arrivals. Comparisons were made between the results calculated in this study and those from previous studies. These were done to identify and measure the reasons for the difference and similarities. The results may contribute to developing risk reduction strategies and a national early warning system. Variability in tsunami intensity measures is prepared for the hypothetical scenarios due to the difference in the fault's magnitude, location, and geometry. Also, for the first time, temporally based scenarios the sea-level rise and delta sinking were considered in order to highlight the importance of multi-risk analysis for the region of interest. The insight on incorporating other hazards of the temporal resolution indicates a significant increase in inundated areas and wave height. Therefore, proper and detailed estimation of multi-hazard maps for the coastal region of the Nile Delta is highly required to protect the ongoing sustainable development and protect the people and their assets. [ABSTRACT FROM AUTHOR]

In this paper, we outline the overview of the problem of intraplate seismicity and summarize our studies aimed at identifying potential earthquake sources in three regions located in continental environments. We study the French Massif Central situated within the West-European platform, the Gujarat area located at the northwestern edge of the Indian shield, and northeast Egypt located in the northeastern part of the African continent. These regions exhibit different levels of seismic activity. The French Massif Central reveals the lowest rate of seismicity, northeast Egypt exposes a low-to-moderate seismicity, and Gujarat reveals moderate seismicity with rare occurrence of strong events. We use a phenomenological approach for identifying possible locations of earthquakes, which is based on the pattern recognition applied to morphostructural data. The approach hypothesizes the nucleation of strong earthquakes at morphostructural nodes forming at the intersections of morphostructural lineaments, which are delineated by morphostructural zoning. Nodes are characterized by the pertinent geophysical and geological parameters, on the basis of which pattern recognition algorithm pinpoints capable nodes, i.e., the nodes where events of a certain sizes may occur. Seismic hazard assessment of continental regions is impeded because their seismic history is normally very pure. In such a situation, information on capable nodes is a necessary input for seismic hazard assessment. The example of northeast Egypt shows the exploiting capable nodes to assess seismic hazard by the Neo-Deterministic Seismic Hazard Assessment Methodology. [ABSTRACT FROM AUTHOR]

On 7th of August 2020, a Mw = 4.9 earthquake occurred in Mila province (Northeast Algeria). Consequently, more than 2000 houses were indirectly affected (partially damaged or collapsed) within 10 km from the earthquake's epicenter, in the locality of El Kherba. According to field surveys conducted 3 days after the earthquake, damages and casualties were directly linked to an earthquake-induced landslide that occurred after the main shock. This was evidenced by numerous cracks in the site's soil mainly perpendicular to the landslide direction. Local characteristics (i.e., geology, geomorphology) and anthropogenic activities expose this area to landslide hazard. This study shows the reliability of the ambient noise horizontal to vertical spectral ratio (HVSR) method in the characterization of an active landslide. Ambient noise records were processed through spectral ratio techniques to identify the landslide's geometry based on spectral responses analysis. The obtained results allowed the landslide's slip surface mapping and boundary delineation, which correlates well with the field observations. After the rotation of the signal's horizontal components, large variations in the experimental spectral ratios, in both amplitude and direction, revealed site effects (soil remoulding, crack network) on the soil dynamic behavior. [ABSTRACT FROM AUTHOR]

Seismogenic nodes capable of generating shallow earthquakes with M ≥ 5.0 have been identified in the northeast part of Egypt using the pattern recognition approach. The study region includes the Sinai Peninsula and the northern part of the Eastern Desert between the Nile River and the Red Sea, which comprises the new capital of Egypt and Suez Canal projects and represents a place for much future development. We apply a phenomenological approach based on pattern recognition for identifying seismogenic nodes. The methodology is based on the idea that earthquakes nucleate at nodes: specific structures forming around fault intersections. Morphostructural zoning (MZ) is applied to map nodes over the entire study region without using a priori knowledge of regional seismicity. The pattern recognition is employed to pinpoint seismogenic nodes where earthquakes with M ≥ 5.0 may occur in the future. As a result, seismogenic nodes capable of generating earthquakes with M ≥ 5.0 have been defined in the Sinai Peninsula and the northern part of the Eastern Desert. We also found characteristic geological-geophysical features that discriminate seismogenic nodes (D) from non-seismogenic ones (N). Information on the potential seismic sources represents the main issue in seismic hazard evaluation. Seismogenic nodes prone to earthquakes with M ≥ 5.0, as described in this work, may contribute to the definition of earthquake source zones in the northeast of Egypt because some of the D nodes are potential sources of seismic risk for critical facilities (e.g., Ismailia Tunnels) and large metropolitan areas (e.g., Nile Valley). This information can contribute to the revision of seismic zoning or microzoning and improve the performance of seismic hazard studies of Egypt by adding a new source of information about seismogenic nodes to the seismogenic zones. [ABSTRACT FROM AUTHOR]