Search

To enhance the seismicity analysis within a given seismic region, it is crucial to establish a unified earthquake catalog with minimized uncertainties. The preparation of such a unified catalog needs scaling relationships to convert different magnitude types to a homogeneous magnitude. Among the plethora of magnitude types, the moment magnitude (Mw) stands out as a widely utilized metric in modern earthquake risk and recurrence analysis. Hence, the key objective of this study is to expand the Mw earthquake dataset specifically for the Northern Algeria region and its surrounding areas, providing a valuable resource for researchers investigating seismicity in this region and for earthquake magnitudes homogenization. To achieve this objective, surface wave (Ms) and body wave (mb) magnitudes obtained from international agencies were standardized to Mw using newly developed regional empirical relationships based on the general orthogonal regression method (GOR). The use of GOR for magnitude conversions has gained popularity in recent years. However, a critical aspect when employing the GOR method is estimating the standard deviations associated with different magnitude types and subsequently determining the error variance ratio. To address this, the present study leverages recent research works to approximate the standard deviations associated with various magnitudes. By calculating the error variance ratio, derived from the estimation of magnitude uncertainties, the general orthogonal regression method was effectively applied to achieve the desired earthquake magnitude homogenization. Notably, this study fills a significant gap in research conducted in Algeria by developing regional empirical relationships using GOR with appropriate values of the error variance ratio. The expanded Mw dataset serves as a dependable resource used for other earthquake magnitudes homogenization, hence the preparation of a more extensive and unified Mw earthquake catalog for Northern Algeria and its neighboring areas. [ABSTRACT FROM AUTHOR]

The main goal of this work is summed up in a univariate chaotic analysis of the runoff series using a topological approach. As such, nineteen series of daily runoff from eight large watersheds in northern Algeria were analyzed. Firstly, preliminary analyses of two traditional dynamic and metric approaches have been tested. In the dynamic approach, three algorithms have shown that the largest Lyapunov exponent for the series is positive, which supports the hypothesis of the existence of chaos. In the metric approach, the Grassberger and Procaccia algorithm clearly shows the saturation of the correlation dimension, which indicates the existence of deterministic dynamics for all studied stations. Secondly, the application of the topological approach in this study constitutes in itself a new contribution to the demonstration of chaos in hydrology by using the recurrence plot (RP) and the recurrence quantification analysis (RQA). As such, the RP structures of the runoff series seem to be more comparable to chaotic systems. In addition, RQA parameters give high values of determinism and laminarity, which supports the hypothesis of the existence of deterministic chaos. The presence of chaos in the runoff series can be identified by the existence of a strong probability of recurrence, indicating a fairly low level of complexity and fairly high predictability. Ultimately, the comparison of these approaches together made it possible to confirm the hypothesis according to which the process generating the runoff series is deterministic and suggests low-dimensional chaotic dynamics. [ABSTRACT FROM AUTHOR]

The Algerian hedgehog, which is an endemic Mediterranean species, is a nocturnal and terrestrial insectivorous mammal. Atelerix algirus’ populations are widespread in various habitats comprising human agglomeration, such as rural, suburban or natural ecosystems. However, the impact of the habitat’s characteristics on its diet remains unknown in Algeria. To contribute to a better understanding of this question, we have analysed 158 faeces samples of the Algerian hedgehog in three different areas: urban, suburban and natural area.The findings show that the Algerian hedgehog is an opportunistic species. It feeds on several classes of Arthropoda, but the harvester ant Messor barbarus dominates largely its menu with AR = 74.81% in the diverse habitats. Furthermore, the HAC and FCA analyses confirm the positive impact of the level of urbanisation and the anthropogenic activity on the Algerian hedgehog prey richness in the north of Algeria (79 prey species and 5574 individuals ingested in the urban area, compared to 64 prey species and 3188 individuals ingested in the natural zone).

In Algeria, at the present time, there are no rainwater harvesting systems (RWHS) registered with the public authorities as an alternative to the public water supply. This is explained by numerous factors, the most important being inhabitants' acceptance. The aim of this article is to investigate the current level of acceptance of an RWHS as a viable method for backing up the public water supply system. Our hypothesis is that inhabitants' acceptance can be improved by the increasing awareness of the benefits of an RWHS. For the purposes of this study, an RWHS located in northern Algeria was designed, and its benefits were measured and discussed with the direct participation of residents living in the building. The first benefit was the potential potable water saving (PPWS) and the second was the benefit-cost ratio (BCR). The PPWS was estimated at 51 m3/year. The BCR was estimated at 7% (15% with local council funding). This paper shows that, in the case of an existing building, inhabitant acceptance of an RWHS depends on three factors: (1) the amount of rainwater delivered by the RWHS; (2) the cost of building and managing it; and (3) the extent of the modifications made to the building. [ABSTRACT FROM AUTHOR]

The Algerian hedgehog, which is an endemic Mediterranean species, is a nocturnal and terrestrial insectivorous mammal. Atelerix algirus' populations are widespread in various habitats comprising human agglomeration, such as rural, suburban or natural ecosystems. However, the impact of the habitat's characteristics on its diet remains unknown in Algeria. To contribute to a better understanding of this question, we have analysed 158 faeces samples of the Algerian hedgehog in three different areas: urban, suburban and natural area. The findings show that the Algerian hedgehog is an opportunistic species. It feeds on several classes of Arthropoda, but the harvester ant Messor barbarus dominates largely its menu with AR = 74.81% in the diverse habitats. Furthermore, the HAC and FCA analyses confirm the positive impact of the level of urbanisation and the anthropogenic activity on the Algerian hedgehog prey richness in the north of Algeria (79 prey species and 5574 individuals ingested in the urban area, compared to 64 prey species and 3188 individuals ingested in the natural zone). [ABSTRACT FROM AUTHOR]

The existence of several magnitude scales in the compiled earthquake catalogs of a specific region has made the development of regional relations connecting magnitude scales a necessity, especially for creating a homogeneous seismic catalog in which all magnitudes should be converted to a preferred magnitude scale. To consistently estimate all magnitude ranges and avoid the saturation problem for large earthquakes, the preference is always given to the moment magnitude Mw scale, wherein the most complete and reliable catalog used worldwide is the Global Centroid Moment Tensor (GCMT). However, to our knowledge, no study has yielded regional (in Algeria) relationships for converting different magnitudes to the moment magnitude (Mw,GCMT). The main reason is typically due to the lack of data pairs of different magnitude scales with Mw (GCMT). To overcome this issue, in this research paper, the moment magnitudes data used for northern Algeria (the area bounded by 32° to 39° N and 3° W to 10° E) have been taken principally from the GCMT catalog and enhanced with the European–Mediterranean Regional Centroid Moment Tensor catalogs RCMT and ZUR-CMT. Regarding this latter, it has been demonstrated in the literature that for the Mediterranean regions, a minor correction should be addressed before merging its data with the GCMT and RCMT catalogs, which are perfectly correlated. To accomplish this task, the magnitude scales tested against Mw are the surface wave magnitude, MS, and the body wave magnitude mb issued from the international seismological sources of ISC and NEIC for the same boundaries. As long as the earthquake magnitudes, in general, are affected by errors of comparable size, the best and most reliable regression method that considers the errors in both dependent and independent variables for linear conversion problems is the General Orthogonal Regression, which is adopted and applied herein to develop the regional relations. [ABSTRACT FROM AUTHOR]

In Algeria, at the present time, there are no rainwater harvesting systems (RWHS) registered with the public authorities as an alternative to the public water supply. This is explained by numerous factors, the most important being inhabitants’ acceptance. The aim of this article is to investigate the current level of acceptance of an RWHS as a viable method for backing up the public water supply system. Our hypothesis is that inhabitants’ acceptance can be improved by the increasing awareness of the benefits of an RWHS. For the purposes of this study, an RWHS located in northern Algeria was designed, and its benefits were measured and discussed with the direct participation of residents living in the building. The first benefit was the potential potable water saving (PPWS) and the second was the benefit-cost ratio (BCR). The PPWS was estimated at 51 m3/year. The BCR was estimated at 7% (15% with local council funding). This paper shows that, in the case of an existing building, inhabitant acceptance of an RWHS depends on three factors: (1) the amount of rainwater delivered by the RWHS; (2) the cost of building and managing it; and (3) the extent of the modifications made to the building.

Rainfall erosivity is a critical factor affecting soil erosion and agricultural productivity. This study aims to analyze rainfall erosivity in the northern region of Algeria using a hybrid approach that combines empirical and modeling techniques. The primary objectives are to identify homogeneous regions, assess their susceptibility to climate change, and determine the wet and dry periods impacting the study area. Additionally, the modified Fournier Index (MFI) is calculated over 76-years (1941–2016) using data from 33 pluviometric stations. The results reveal distinct wet and dry periods in the study area, with abundant rainfall occurring in winter/autumn and spring, followed by a summer drought. The northern region exhibits high erosivity levels, ranging from severe to very severe, while the southeast and other regions experience low to moderate erosivity. Region 4 demonstrates the highest rain aggressiveness and moderate to severe erosion throughout the study period. Spatial analysis shows an increasing MFI gradient from west to east and south to north. Furthermore, the study establishes a positive correlation between MFI and the Southern Oscillation Index, indicating that El Niño and La Niña have a significant influence on sedimentary production. Overall, this research provides valuable insights into rainfall erosivity patterns in Northern Algeria, aiding in the identification of high-risk areas and supporting sustainable land management strategies. [ABSTRACT FROM AUTHOR]

A reliable site characterization of a seismic monitoring station helps in the objective determination of the local magnitude. Therefore, 17 broadband stations of the Algerian seismic monitoring network, installed in various geological and topographic contexts, were selected to estimate site responses using earthquake and ambient vibration data. Results showed that most stations exhibited site-effects. At the Neogene topographic surface stations, the site response showed two frequency peaks. The first in low-frequency domain was observed at higher altitudes and varied inversely with elevation along a profile across the structure, which might be related to lithological site-effects. The second high-frequency peak, which is nearly constant along the profile, was also observed in the Mesozoic/Paleogene structures. This amplification was explained by the topographic site-effects. Based on these findings, deconvolution of the non-flat site responses of the studied stations from the seismic recording is recommended before any seismological application. It is shown that the seismic bedrock of northern Algeria is primarily Mesozoic, with shear wave velocity ≥ 1500 m/s. [ABSTRACT FROM AUTHOR]

This study presents a local magnitude scale (M L) based on the original Richter definition and designed for use within the Algerian Digital Seismic Network (ADSN). The magnitude scale is derived from the analysis of 17,377 zero-peak maximum amplitude traces extracted from the vertical component, simulated as Wood-Anderson seismograms. These traces are taken from a dataset of 1901 earthquakes recorded between January 1, 2010, and June 1, 2022, at a minimum of five stations in the ADSN network. To better account for the attenuation of direct and refracted waves in northern Algeria, amplitude decay analysis reveals the presence of two transition distances at 90 and 190 km, resulting in three segments. A distance correction term, −log 10 (A0), is introduced and described by the following trilinear function: − log A 0 = 0.6747 ∗ lo g 10 R + 0.0002 ∗ R + 1.6306 R ≤ 90 1.7736 ∗ lo g 10 R + 0.0002 ∗ R − 0.5169 90 < R ≤ 190 2.4580 ∗ lo g 10 R + 0.0002 ∗ R − 2.0765 R > 190 R represents the hypocentral distance in kilometers. The derived distance correction formula provides a well-constrained M L relationship for northern Algeria that is valid over a distance range of 5 to 600 km. Compared to other local magnitude relationships, the methodology proposed in this study consistently gives M L values slightly higher than those calculated by the Southern California relationship over all distances, with an average difference of 0.2 units. We computed corrections for 72 stations by minimizing the M L residuals. These corrections range from −0.50 to 0.54, highlighting the influence of local site effects on the amplitude of the seismic signal. The magnitude residuals using our magnitude relationship and incorporating the station corrections, show that the standard deviation has improved significantly, from 0.34 to 0.24. An M L relationship specific to the northern Algerian region provides a valuable tool for seismic monitoring, hazard assessment, and earthquake research in the region. • The first local magnitude scale has been developed in Northern Algeria. • This new scale will aid in creating a more accurate and homogenized earthquake catalog for Algeria. • Station corrections have been determined for 72 different geological sites. • The new scale will significantly improve seismic hazard studies in Northern Algeria [ABSTRACT FROM AUTHOR]

In water resources management, modeling water balance factors is necessary to control dams, agriculture, irrigation, and also to provide water supply for drinking and industries. Generally, conceptual and physical models present challenges to find more hydro-climatic parameters, which show good performance in the assessment of runoff in different climatic regions. Accordingly, a dynamic and reliable model is proposed to estimate inter-annual rainfall-runoff in five climatic regions of northern Algeria. This is a new improvement of Ol'Dekop's equation, which models the residual values obtained between real and predicted data using artificial neuron networks (ANNs), namely by ANN1 and ANN2 sub-models. In this work, a set of climatic and geographical variables, obtained from 16 basins, which are inter-annual rainfall (IAR), watershed area (S), and watercourse (WC), were used as input data in the first model. Further, the ANN1 output results and De Martonne index (I) were classified, and were then processed by ANN2 to further increase reliability, and make the model more dynamic and unaffected by the climatic characteristic of the area. The final model proved the best performance in the entire region compared to a set of parametric and non-parametric water balance models used in this study, where the R2Adj obtained from each test gave values between 0.9103 and 0.9923. [ABSTRACT FROM AUTHOR]

Prediction of groundwater flow fluctuations is considered an important step in understanding groundwater systems at this scale and facilitating sustainable groundwater management. The objective of this study is to determine the factors that influence and control groundwater flow fluctuations in a specific geomorphologic situation, by developing a forecasting model and examining its potential for predicting groundwater flow using limited data. Models for prediction of groundwater flow are developed based on artificial neural networks (ANNs). Neural networks with different numbers of hidden layer neurons were developed using climatic and geomorphological characteristics as input variables, giving predicted groundwater flow as the output. To evaluate enhanced performance models, several regression statistical parameters are compared. As an example, relative mean square error in groundwater flow prediction by ANN and correlation coefficient are 0.015 and 97%, respectively. The results of the study clearly show that ANNs can be used to predict groundwater flow in shallow aquifers of northern Algeria with reasonable accuracy even in the case of limited data. HIGHLIGHTS Combine hydrological and climatic data to estimate groundwater flows.; Test the performance of ANN's models to understand the behavior of groundwater.; Large-scale groundwater flow modeling for better management of water resources.; Proposal of a predictive model for a global vision of the distribution of groundwater.; Determining the order of importance of indicators that can influence groundwater flows.;

A single backscattering method is used to estimate coda quality factor functions (Qc) from coda-wave attenuation for the Algiers vicinity and eastern part of the Mitidja Basin. The frequency-dependent Qc relation is determined using a high-quality data set with good signal-to-noise ratios (SNR > 5) of 228 accelerogram waveforms of local earthquakes in the magnitude range 2.3–5.3, with focal depth varying from 1.3 to 31 km and epicentral distances less than 65 km. We studied the frequency and lapse time dependence of coda-wave attenuation through the variation of coda window length of 20, 30 and 35 s for seven frequency bands in the range of 1.5–24 Hz. The obtained average Qc increases with increasing coda window length, implying an increase in sampled depth. The Qc of horizontal components (N and E) are slightly lower than the Qc of the vertical component (Z). The obtained low values of Qc and high values of frequency-dependent parameter n indicate that the penetration depth that consists of the crust and part of the upper mantle beneath the Algiers region is seismically active with a high level of heterogeneity. The average frequency-dependent Qc values in the three directions are QcZ = (69.76 ± 2.98)f(0.82 ± 0.01), QcN = (60.2 ± 4.86)f(0.88 ± 0.03) and QcE = (59.63 ± 5.07)f(0.88 ± 0.03) with a coda window length of 20 s in which the penetration depth is 56.2 km and the covered area is 8141 km2. [ABSTRACT FROM AUTHOR]

Abstract Extreme hydrologic events are commonly described by several dependent characteristics, such as duration, volume and peak flow for floods. Traditionally in Algeria and North Africa, flood frequency analysis (FFA) is conducted as a univariate approach focusing separately on each single of flood characteristics. On the other hand, elsewhere, multivariate FFA studies have been conducted focusing on some FFA steps (especially modelling). The current study aims to consider complete multivariate FFA at‐site case studies in northern Algeria using 11 hydrometric stations. It is also among the first studies dealing with multivariate FFA in a complete way by considering all the required steps of the analysis (multivariate outliers detection, multivariate assumptions testing and copula fitting) and on datasets from Algeria. Multivariate stationarity, homogeneity and independence assumptions have been well verified before modelling. The Weibull distribution is mostly selected as margin distribution for the duration, volume and peak flow series. Frank, Clayton and Gumbel copulas are commonly selected to describe the dependence structure on the three flood pairs of variables. These findings should be interesting in water management and flood risk assessment in these regions. Combining these flood characteristics enables the design of more efficient hydraulic structures.

The objective of the study presented herein is to provide an accurate climate classification on the basis of aridity in northern Algeria. The aridity indices used in this study were the De Martonne index (IDM), the Emberger index (IEmberger), and the United Nations Environment Program index (IUNEP), generally admitted in the Mediterranean region. The data required for their calculation were taken from 37 meteorological stations, and processed in a Geographical Information System (GIS) environment to generate climate classification maps according to each index. Generally, the three indices revealed the prevalence of semi-arid conditions in the study area. Similar climate classifications were identified with the IUNEP and the IDM, while the IEmberger has identified larger arid extent. The obtained maps were then validated against the long-term soil moisture data extracted from a gridded global data set. The validation results indicated that the three indices gave very satisfactory results since they showed strong correlation coefficients with the soil moisture data. However, the IEmberger slightly outperformed the IUNEP and the IDM with coefficients of determination (R2) of 0.80, 0.78, and 0.77, respectively. The seasonal investigation of aridity allowed to identify regions and seasons in which irrigation is needed for the main crops cultivated in the study area. [ABSTRACT FROM AUTHOR]

The cedar processionary moth, Thaumetopoea bonjeani (Lepidoptera: Notodontidae), is a serious pest of the Atlas cedar Cedrus atlantica in north-western Africa and it is involved in the decline of this endangered tree species. Natural enemies of the cedar processionary moth are poorly known, especially for parasitoids, predators and pathogens of the larval-pupal life stages. Mature larvae were collected and examined in 2014 and 2015 in natural stands of Atlas cedar in the Djurdjura (northern Algeria), in occurrence with pine processionary moth Thaumetopoea pityocampa. The overall mortality rate of larvae of Thaumetopoea bonjeani ranged from 26.4% to 31.1%, with generalist predators and parasitoids being more effective than pathogens. Four primary parasitoid species were recorded, of which four tachinid flies and one braconid wasp, as well as four predatory beetles and one fungus. The most important species were the carabid Calosoma sycophanta and the tachinid Compsilura concinnata. The cooccurrence of T. bonjeani and T. pityocampa may offer to generalist natural enemies an extended period of availability of similar preys, as the two processionary moths have different life cycles. The sharing of natural enemies between the two species of Thaumetopoea can mitigate the outbreaks of both species. [ABSTRACT FROM AUTHOR]

Extreme hydrologic events are commonly described by several dependent characteristics, such as duration, volume and peak flow for floods. Traditionally in Algeria and North Africa, flood frequency analysis (FFA) is conducted as a univariate approach focusing separately on each single of flood characteristics. On the other hand, elsewhere, multivariate FFA studies have been conducted focusing on some FFA steps (especially modelling). The current study aims to consider complete multivariate FFA at‐site case studies in northern Algeria using 11 hydrometric stations. It is also among the first studies dealing with multivariate FFA in a complete way by considering all the required steps of the analysis (multivariate outliers detection, multivariate assumptions testing and copula fitting) and on datasets from Algeria. Multivariate stationarity, homogeneity and independence assumptions have been well verified before modelling. The Weibull distribution is mostly selected as margin distribution for the duration, volume and peak flow series. Frank, Clayton and Gumbel copulas are commonly selected to describe the dependence structure on the three flood pairs of variables. These findings should be interesting in water management and flood risk assessment in these regions. Combining these flood characteristics enables the design of more efficient hydraulic structures. [ABSTRACT FROM AUTHOR]

The Algerian hedgehog, which is an endemic Mediterranean species, is a nocturnal and terrestrial insectivorous mammal. Atelerixalgirus ' populations are widespread in various habitats comprising human agglomeration, such as rural, suburban or natural ecosystems. However, the impact of the habitat's characteristics on its diet remains unknown in Algeria. To contribute to a better understanding of this question, we have analysed 158 faeces samples of the Algerian hedgehog in three different areas: urban, suburban and natural area. The findings show that the Algerian hedgehog is an opportunistic species. It feeds on several classes of Arthropoda, but the harvester ant Messorbarbarus dominates largely its menu with AR = 74.81% in the diverse habitats. Furthermore, the HAC and FCA analyses confirm the positive impact of the level of urbanisation and the anthropogenic activity on the Algerian hedgehog prey richness in the north of Algeria (79 prey species and 5574 individuals ingested in the urban area, compared to 64 prey species and 3188 individuals ingested in the natural zone)., Competing Interests: No conflict of interest to declare Disclaimer: This article is (co-)authored by any of the Editors-in-Chief, Managing Editors or their deputies in this journal., (Amina Zidane, Ilham Sahki-Benabbas, Mohamed Ayoub Rahal, Riadh Moulaî.)

Abstract While ocean subduction at continental margins is a prominent process of plate tectonics, understanding how and where it begins is still being debated, especially because examples of emerging ocean–continent subduction in the world are rare. Northern Algeria is currently undergoing a slow compression deformation due to the ongoing African–Eurasian convergence. Active compressional seismic activity recorded both on land and at sea indicates that the margin might be transitioning from a passive stage to an active one. In order to test this hypothesis, we perform thermo-mechanical models of margin inversion. Varying thermal and rheological parameters as well as the geometry of the margin boundary, we find that tectonic inversion of a young passive margin localizes at the margin toe only if the latter is strongly heated (i.e., with an abrupt thermal gradient between oceanic and continental lithospheres); otherwise, deformation propagates into the weak, hot oceanic lithosphere. The presence of a thinned continental crust at the ocean–continent transition favors either subduction of the oceanic lithosphere when the transition zone plunges towards the continent, or an indentation of the lower continental crust by the oceanic lithosphere when the transition zone is vertical. If the oceanic lithosphere is directly in contact with the continental margin, subduction-like deformation occurs during the early stages of the model but rapidly gives place to intra-oceanic buckling and faulting. Comparing the results of the simulation to the active tectonic structures of the Algerian margin, we conclude that both processes (emerging subduction or indentation) are possible and that the presence of a thermal anomaly beneath the thinned continental margin is probable, in relation with slab rupture at depth or with other thermal weakening processes. Highlights • We model passive margin inversion on the North Algerian margin. • Strain localization requires a high geothermal gradient beneath the margin toe. • OCT made of thin continental crust helps localizing deformation. • Both incipient subduction or lower continental crust indentation can occur. [ABSTRACT FROM AUTHOR]

The modelling of the rainfall-runoff relationship plays an important role in risk reduction and prevention against water-related disasters and in water resources management. In this research, we have modelled the rainfall-runoff relationship using intelligent hybrid models for forecasting daily flow rates of the Sebaou basin located in northern Algeria. As such, two hybrid approaches of artificial intelligence have been used in this study. These approaches are based on the adaptive neuro-fuzzy inference system combined with hydrological signal decomposition techniques. The first is derived from the Hilbert-Huang transform called the empirical mode decomposition and the other is derived from the discrete wavelet transform called multiresolution analysis. The results obtained seem to be very encouraging and the techniques appear promising. The performances of the hybrid models are relatively much higher than the other models used for comparison in this study. Although the technique of parallel computing has been used and despite the power of the computing station, the relatively long computation time is the main disadvantage of these models. [ABSTRACT FROM AUTHOR]

Copyright of Larhyss Journal is the property of Biskra University, Research Laboratory in Subterranean & Surface Hydraulics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The systematic study of bivalves collected from the Cenomanian-Turonian succession of the Bellezma-Batna Mountains (northeastern Algeria) led identification of nine species belonging to eight genera, three of which, Nicaisolopha nicaisei (Coquand) , Pterotrigonia (Scabrotrigonia) scabra (Lamarck), and Agelasina plenodonta Riedel, were recorded for the first time from the study area. Particular attention was paid to the rudist fauna, including Vaccinites praegiganteus (Toucas), Vaccinites rousseli (Douvillé), and Sauvagesia nicaisei (Coquand), occurring in very large numbers within composite biostromes (5 to 10 m-thick) composed of both hippuritids and radiolitids. A distribution map of Cenomanian-Turonian bivalves is established based on data from Algeria and other localities. The map shows that the most bivalve genera are widely distributed and some of them are probably cosmopolitan. They are present in northern Africa, Middle East, south and northern Europe, western Africa, and South America, with some taxa are also known from the south-eastern coast of Africa (Madagascar and South Africa) and India. • Data from the present study allows to characterize and describe, for the Cenomanian-Turonian succession of the Bellezma-Batna Mountains, northeastern Algeria, nine species of bivalves, belonging to eigth genera of the families Ostreidae, Megatrigoniidae, Cardiidae, Pholadomyidae, Dicerocardiidae, Hippuritidae, Radiolitoidae; • Bivalve fauna of the Bellezma-Batna Mountains are widely distributed, comparable to those reported from northern Morocco to Egypt, and that the Cenomanian-Turonian Tethyan bivalves of Bellezma-Batna Mountains are relatively scarce and little diversified, that the rudist fauna shows strong affinities with rudists from the Northern coast of the Tethyan region. • During the Late Cretaceous, the biogeographic pattern suggests that several benthic macrofauna groups had migrated via the shallow trans-Saharan seaway, which connected the southern Tethys margin and the incipient the South Atlantic Ocean. [ABSTRACT FROM AUTHOR]

Rapid urban growth, particularly in developing countries, is often accompanied by unplanned and highly vulnerable settlements which could lead to high seismic risk. This problem becomes even more pronounced when such developing countries are located in seismic prone regions, which, without a well-enforced seismic code, face high probability of major human and economic losses following a seismic event. With this in mind, large-scale rapid visual screening (RVS) procedures to perform seismic vulnerability assessment are of paramount importance to, at least, obtain a preliminary estimate of the risk to which buildings of a certain region are exposed to. RVS methods generally provide a seismic risk index based on the site hazard, the structural vulnerability and the exposure. This paper presents one of many available RVS procedures, applied and assessed for large-scale seismic vulnerability mapping of a case-study province in Northern Algeria. Based on data collected during ad-hoc field surveys, the index-based selected RVS methodology was adapted to the reinforced concrete (RC) portion of the building portfolio, featuring over 2900 buildings, to estimate its seismic vulnerability. Taking advantage of a large amount of available data, a parametric study was then performed to understand the effect of the individual variables used in the RVS method on the vulnerability indices of the different buildings. The consistency of the method, as evidenced by the results found across different building stock typologies, was also investigated to confirm the soundness of RVS approaches in large-scale assessments. Furthermore, in specific for the case-study region, the outcome of this study is extremely useful for preliminary identification of buildings (or building classes) more prone to earthquake damage and to assist decision-makers in planning seismic risk reduction strategies. [ABSTRACT FROM AUTHOR]

The estimation of precipitation quantiles has always been an area of great importance to meteorologists, hydrologists, planners and managers of hydrotechnical infrastructures. In many cases, it is necessary to estimate the values relating to extreme events for the sites where there is little or no measurement, as well as their return periods. A statistical approach is the most used in such cases. It aims to find the probability distribution that best fits the maximum daily rainfall values. In our study, 231 rainfall stations were used to regionalize and find the best distribution for modeling the maximum daily rainfall in Northern Algeria. The L-moments method was used to perform a regionalization based on discordance criteria and homogeneity test. It gave rise to twelve homogeneous regions in terms of L-Coefficient of variation ( L- CV), L-Skewness ( L- CS) and L-Kurtosis ( L- CK). This same technique allowed us to select the regional probability distribution for each group using the Z statistic. The generalized extreme values distribution (GEV) was selected to model the maximum daily rainfall of 10 groups located in the north of the steppe region and the generalized logistic distribution (GLO) for groups representing the steppes of Central and Western Algeria. The study of uncertainty by the bias and RMSE showed that the regional approach is acceptable. We have also developed maximum daily rainfall maps for 2, 5, 10, 20, 50 and 100 years return periods. We relied on a network of 255 rainfall stations. The spatial variability of quantiles was evaluated by semi-variograms. All rainfall frequency models have a spatial dependence with an exponential model adjusted to the experimental semi-variograms. The parameters of the fitted semi-variogram for different return periods are similar, throughout, while the nugget is more important for high return periods. Maximum daily rainfall increases from South to North and from West to East, and is more significant in the coastal areas of eastern Algeria where it exceeds 170 mm for a return period of 100 years. However, it does not exceed 50 mm in the highlands of the west. [ABSTRACT FROM AUTHOR]

Atmospheric pollution is a major concern in many countries. The case of Algeria's megacities which have known recently rapid urbanization and remarkable development in various sectors, demonstrates the air quality degradation. Moreover, the intensive industrial activities, inadequate waste disposal, mining, energy production and transport have introduced excessive amounts of pollutants into the ambient air. These factors are contributing to the increase in the number of potential sources of air contamination. The aim of the present study is to estimate the air pollution with nitrogen dioxide in the northern part of Algeria using the satellite and ground-base data. Assessment of atmospheric pollution with NO2 is carried out using to the data of satellite spectrometer EOS / OMI, information products Level 3 from Goddard Earth Sciences Data, (GES DISC) NASA for 2006-2009. According to the results study, the concentration of NO2 in the air of the metropolis of Algiers exceeds twice the value of the maximum allowable concentration. However, slightly lower content of NO2 in the air near the cities recorded Mascara, Skikda, Oran and Annaba. Based on the results of the present study, it was found an increased risk of accumulation of NO2 on the above urban agglomerations. The findings in this study will help to create awareness of air pollution to Algeria's policymakers in the mitigation of atmospheric pollution, and serve as a stepping stone towards air pollution monitoring, risk assessment of acid rains local and regional negative impact. [ABSTRACT FROM AUTHOR]

The northern Algeria forms the southern edge of the Western Mediterranean Sea that formed within the zone of convergence between the African and Eurasian plates. It represents a key area in the Mediterranean formation where controversial kinematic and geodynamical models are proposed. The current structure of northern Algeria is the result of the geodynamic evolution that occurred in the western Mediterranean. Several tomographic studies revealed the presence of velocity anomalies beneath the south of the western Mediterranean region. Namely, these anomalies suggest the existence of abnormally cold material in the asthenosphere, interpreted as the trace of subducted plunging panels (slab). Unfortunately, the lack of suitable data remains the main limit confronted by most tomographic studies in the northern Algeria, which remains to date one of the poorly studied regions in the western Mediterranean. During the recent decades, the seismological network in northern Algeria has significantly developed, giving rise to a significant increase in the amount of information given by the network database. This development motivated us to investigate the crust and the upper mantle structure beneath the northern Algeria using a non-linear teleseismic tomography method. An overall of 29 stations distributed along the northern part of Algeria have been used to collect 11018 P-waves from 2847 earthquakes recorded over ten years. The proposed model suggests the presence of high-velocity anomalies along of the northern Algeria. We interpreted these abnormal anomalies as a slab teared into two panels. A central segment bending along the Atlasic massif of Hodna and plunging under the Lesser Kabylia. The second segment at the North-East, shifted to the north plunging towards the NE. A series of Tellian high-velocity anomalies axes mark the limit between the African and the Eurasian plate. The south eastern region covered by our model (Aurès massif) is characterized by a low-velocity anomaly potentially linked to the remnant of the Mesozoic rifting. • A non-linear teleseismic tomography method image the deep structure under the whole northern Algeria down to about 170 km. • A high-velocity anomaly interpreted as a slab teared into two panels. • A central segment panel of WNW-ESE direction plunging under the Lesser Kabylia. • A second segment offset to the north, direction E-W extends over the Lasser Kabylie and plunging towards the NE. • A low-velocity observed under the Aurès massif and interpreted as a remnant of the Mesozoic rifting. [ABSTRACT FROM AUTHOR]

We analyzed the diet of four rhinolophids (Rhinolophus ferrumequinum, R. hipposideros, R. euryale and R. blasii) in the region of Kabylia Babors, in northern Algeria. Between March 2007 and January 2008 we sampled droppings at ten sites and carried out a morphological identification of prey remains. Three main groups of Arthropoda (Insecta, Chilopoda and Araneida) were preyed upon but frequencies varied across species. The insect prey most frequently preyed upon by R. ferrumequinum are Diptera (34.56%), mainly including Culicidae (10.40%), Chironomidae/ Ceratopogonidae (10.94%) and Tipulidae (4.28%), and also Lepidoptera (24.13%). In R. hipposideros droppings we found Diptera (41.58%) , Chironomidae/Ceratopogonidae (9.68%) and Tipulidae (6.45%). Also common were Lepidoptera (moths; 21.14%) and Hemiptera (11.68%). R.euryale ate mainly Diptera (29.00%), Chironomidae/Ceratopogonidae (7.14%) and Tipulidae (5.71%). The order Lepidoptera (moths) was also well represented (19.08%). R. blasii preyed on two groups of Arthropoda: Insecta (96.87%) and Chilopoda (4.34%). The most consumed insect prey was Diptera (37.50%), mainly Chironomidae/Ceratopogonidae (9.38%), Culicidae, Anisopodidae and Sphaeroceridae (6.25%). The order Trichoptera was also well represented in its diet (15.63%) and Lepidoptera accounted for 12.50%. The most interesting aspect of this study was that Chilopoda appeared in the diet of all species and that, albeit rarely, R. ferrumequinum also ate spiders. This result suggests that all species could glean prey from substrate, most probably as a strategy to better exploit the open habitats typical of the study area. [ABSTRACT FROM AUTHOR]

The objective of this paper is to classify the most adequate frequency laws to estimate the extreme floods in northern Algeria in the large Isser, Chellif and Côtiers Algérois Ouest drainage basins. The first step is to determine which laws could best represent the data used. The second step is to classify selected laws using various chosen criteria such as: BIC, AICc, and Schwartz criterion based on a priori and a posteriori probability concepts. The classification in this step is carried out using the unique information collected from observing each site, then working in the information collected from adjoining sites. Results show the prominence of the Gamma distribution. [ABSTRACT FROM AUTHOR]

The few scientific studies of the crust and upper mantle in Northern Algeria are based mainly on regional Western Mediterranean studies. This area has a certain degree of deformation due to its location between the African and Eurasian tectonic plates. This study continues previous studies reporting possible traces of subduction zones or hot spots throughout the Mediterranean basin. After installing 17 permanent broadband seismic stations in this area, we used teleseismic events recorded between 2007 and 2016 to define the shear wave velocity (Vs) structure as a function of depth by inverting the Rayleigh wave group velocity dispersion curves using the single-station method. The group velocity measurements for periods of 5–200 s were selected through the inversion of the regionalized dispersion curve to compute average 1-D shear-velocity models at area around station, which helped generate the relative shear velocity variation (Δ V i d) maps at different depths for the study area. From the variation of Vs, we deduced Moho depth ranges of 20–50 km for the study area. From the Δ V i d maps, we noticed that for layers deeper than 60 km, the failed subduction slab traces could be observed in the eastern part. The central-western part appears to be congruent with the direction of convergence between the two tectonic plates. This finding is consistent with the results obtained from the GPS study. • Algerian Digital Seismic Network helps well in recording teleseismic data. • Teleseimic exploited to identify deep Vs-structure in northwest of Africa. • Moho depth is in good agreement with the topographical framework. • Dispersion curve retrieved from a single station is useful for deep structure. • MFT and VFT techniques are used to extract group velocity curves. [ABSTRACT FROM AUTHOR]

Vegetation dynamics during the Pleistocene–Holocene transition and the beginning of farming are major topics for palaeoenvironmental sciences, especially interesting in ecologically sensitive areas, such as in North Africa. However, there are still important geographic and chronological gaps of environmental information in this region. Archaeobotanical record from Gueldaman GLD 1 deals with these issues, as it presents the longest archaeobotanical sequence available nowadays for Algeria, which includes these moments of major changes in landscapes. This topic has been approached from an interdisciplinary point of view, focused on the analysis of various types of plant remains that result in the reconstruction of both environment and use of plant resources. Results reveal the existence of a postglacial phase of plant colonization with Cupressaceae formations, which are gradually integrating some elements of sclerophyllous vegetation, such as several species of Pistacia , well documented both in charcoal and seed records. Neolithic levels show a shift in vegetation composition, as Olea europaea dominates the spectra, accompanied by strawberry tree and evergreen Quercus , among others. The presence of Olea in earlier chronologies has resulted from intrusions from the Neolithic levels: a set of radiocarbon dates has made it possible to evidence this process and detect the extent of the intrusions, which are inherent to cave records. • North Africa is a key region to know the dynamics of postglacial vegetation in the Mediterranean. • Gueldaman has provided archeobotanical information for a long sequence in Algeria. • Postglacial plant colonization and a later spread of sclerophyllous vegetation have been documented. • A taphonomic analysis has shown that the pre-Neolithic presence of Olea has resulted from intrusions from upper levels. • During Neolithic, Olea is a species of great economic relevance. [ABSTRACT FROM AUTHOR]

The southern Bibans region in northern Algeria is located in the external zone of the Tell fold-and-thrust belt. Field observations in this area together with seismic data integrated with previous studies provide evidence for a number of Tertiary deformation phases. Late Eocene Atlassic deformation was followed by Oligocene (?)-Aquitanian-Burdigalian compression, which was associated with the development of a foreland basin in front of a southerly-propagating thrust system. Gravity-driven emplacement of the Tellian nappes over the basin margin probably occurred during the Langhian-Serravallian-Tortonian. The Hodna Mountains structural culmination developed during the Miocene-Pliocene. Analysis of brittle structures points to continued north-south shortening during the Neogene, consistent with convergence between the African and Eurasian Plates. The unconformably underlying Mesozoic-Cenozoic autochthonous sequence in this area contains two potential source rock intervals: Cenomanian-Turonian and Eocene. Reservoir rocks include Lower Cretaceous siliciclastics and Upper Cretaceous to Palaeogene carbonates. Structural style has controlled trap types. Thus traps in the Tell fold-and-thrust belt are associated with folds, whereas structural traps in the Hodna area are associated with reactivated normal faults. In the latter area, there is also some evidence for base-Miocene stratigraphic traps. [ABSTRACT FROM AUTHOR]

Abstract: Available surface and industrial subsurface data provide the basis for a general balanced cross-section from the Sahara platform to the Mediterranean Sea in central Algeria. This section gives an overview of the whole Maghrebian orogen comprising from south to north the following structural domains: the intra-continental Atlas system; the External Tell system, deriving from the African palaeo-margin; the Flyschs domain, representing the cover of the former oceanic domain and, finally, the Kabylides domain of European affinities. Restoration of the southern segment of the section, comprising the Atlas and External Tell systems, yields a minimum value of 40 km (20%) of horizontal shortening. For this part of the section, a four-step kinematic scenario, built using the THRUSTPACK software, illustrates the main stages of the deformation history: (1) Late Eocene ‘Atlas’ deformation pulse, (2) Early Miocene deposition of a thick flexural sequence, (3) Middle–Late Miocene emplacement of the Tell nappes and (4) Late Miocene to present out-of-sequence thrusting. On this basis, a conceptual geodynamic model is proposed for the whole Maghrebian orogen. After the Atlas event, which just preceded the roll-back of the Tethyan slab, the model emphasises the role of subduction responsible for: (1) flexuration of the subducting plate (slab pull effect), (2) development of both accretionary prism and back-arc basin, and (3) late uplift linked to slab break-off. To cite this article: N. Benaouali-Mebarek et al., C. R. Geoscience 338 (2006). [Copyright &y& Elsevier]

Abstract: Active tectonics in Algeria is located in the northern part of the country, mainly in the Tell system. In this region, located at the Africa–Eurasia boundary, the tectonic activity expresses the convergence between the two main plates. This leads to the closure of the Neogene sedimentary basins and the ongoing Tell building. Offshore, present deformation affects the abyssal plain located close to the continent, by folding of the Plio-Quaternary sediments cover. Along the slope and the continental platform, active structures with a continental extension crosscut this region. The coastal tectonics generates the coastal uplift as it was shown during the last Boumerdes earthquake of 21 May 2003, where an average uplift of 0.50 m was measured. Onshore, the earthquakes occur along the boundaries of the Neogene sedimentary basins that are located along the coast. These basins underwent compressional deformations giving anticlines, reverse faults or thrust faults oriented NE–SW to NW–SE. These later active structures generated the most important earthquakes. In the High Plateau and the Saharan Atlas, a weak seismic activity is recorded. To cite this article: A. Yelles-Chaouche et al., C. R. Geoscience 338 (2006). [Copyright &y& Elsevier]

Seismic hazard in terms of spectral acceleration ( SA) has been estimated for the first time in northern Algeria. For this purpose, we have used the spatially-smoothed seismicity approach. The present paper is intended to be a continuation of previous work in which we have evaluated the seismic hazard in terms of peak ground acceleration ( PGA) using the same methodology. To perform these evaluations, four complete and Poissonian seismic models have been used. One of them considers earthquakes with magnitudes above M S 6.5 in the last 300 years, that is, the most energetic seismicity in the region. Firstly, seismic hazard maps in terms of SA, at periods of 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, 1.5 and 2.0 sec, with 39.3% and 10% probability of exceedance in 50 years, have been obtained. Therefore, uniform hazard spectra ( UHS) are computed and examined in detail for twelve of the most industrial and populated cities in northern Algeria. All the reported results in this study are for rock soil and 5% of damping. It is noteworthy that, in the seismic hazard maps as well as in the UHS plots, we observe maximum SA values in the central area of the Tell. The higher values are reached in the Chleff region (previously El Asnam), specifically around the location of the destructive earthquakes of September 9, 1954 ( M S 6.8), and October 10, 1980 ( M S 7.3). These maximum values, 0.4 g and 1.0 g, are associated with periods of about 0.2 and 0.3 sec for return periods of 100 and 475 years, respectively. [ABSTRACT FROM AUTHOR]

The occurrence of the Algiers earthquake ( M 6.8) of May 21, 2003, has motivated the necessity to reassess the probabilistic seismic hazard of northern Algeria. The fact that this destructive earthquake took place in an area where there was no evidence of previous significant earthquakes, neither instrumental nor historical, strongly encourages us to review the seismic hazard map of this region. Recently, the probabilistic seismic hazard of northern Algeria was computed using the spatially smoothed seismicity methodology. The catalog used in the previous computation was updated for this review, and not only includes information until June 2003, but also considers a recent re-evaluation of several historical earthquakes. In this paper, the same methodology and seismicity models are utilized in an effort to compare this methodology against an improved and updated seismic catalog. The largest mean peak ground acceleration (PGA) values are obtained in northernmost Algeria, specifically in the central area of the Tell Atlas. These values are of the order of 0.48 g for a return period of 475 years. In the City of Algiers, the capital of Algeria, and approximately 50 km from the reported epicenter of this latest destructive earthquake, a new mean PGA value of 0.23 g is obtained for the same return period. This value is 0.07 g greater than that obtained in the previous computation. In general, we receive greater seismic hazard results in the surrounding area of Algiers, especially to the southwest. The main reason is not this recent earthquake by itself, but the significant increase in the mmax magnitude in the seismic source where the city and the epicenter are included. [ABSTRACT FROM AUTHOR]

Seismic hazard in terms of peak ground acceleration (PGA) has been evaluated in northern Algeria using spatially smoothed seismicity data. We present here a preliminary seismic zoning in northern Algeria as derived from the obtained results.Initially, we have compiled an earthquake catalog of the region taking data from several agencies. Afterwards, we have delimited seismic areas where the b and mmax parameters are different. Finally, by applying the methodology proposed by Frankel [Seismol. Res. Lett. 66 (1995) 8], and using four complete and Poissonian seismicity models, we are able to compute the seismic hazard maps in terms of PGA with 39.3% and 10% probability of exceedance in 50 years.A significant result of this work is the observation of mean PGA values of the order of 0.20 and 0.45 g, for return periods of 100 and 475 years, respectively, in the central area of the Tell Atlas. [Copyright &y& Elsevier]

The Tellian foreland in Algeria represents a part of the southern Tethyan margin during the Mesozoic. Its tectonic evolution includes a rifting stage during the Triassic and Liassic times characterised by tilted blocks and early diapiric events during the Liassic, a post-rift regime from Middle Jurassic up to the Late Cretaceous and basin inversion during the Tertiary related to the African and European plates convergence.The subsidence modelling supported by surface and subsurface data integration emphasises different subsidence phases.(1)Liassic subsidence phase under Tethyan and Atlantic control related to crustal thinning.(2)Late Jurassic, Cretaceous and Tertiary subsidence phases, where the first one is linked to diapiric events and the second in eastern Algeria to the effects of the rifting event developed more easterly in the Gulf of Gabe&grave;s and Sirte. The last one is flexural and occurs in foreland basins during the Tertiary.Taking into account the subsidence record of each structural domain, a correlation between tectonic events and the subsidence phases can be established. [Copyright &y& Elsevier]

Analysis of petroleum exploration data supplemented by paleostress data enabled discussion of the origin of the deformation in the western and central Saharan Atlas (Algeria). This intraplate area has recorded the breakup of Pangea (Late Triassic), the opening of the Maghrebian Tethys (since the Dogger) and subsequently its closure (Oligocene to Present). However, the two periods of strong coupling between Europe and Africa (late Lutetian and Pleistocene), which correspond to rapid uplifts of the Atlas system and important deformations, are not collision-related. They can be correlated to the beginning and the end of the development of the western Mediterranean Sea. [Copyright &y& Elsevier]

A common definition of seismic risk entails the quantification of three main elements: hazard, exposure of properties and societies, and corresponding vulnerability. When properly characterised, the vulnerability of a community or an asset is the easiest component to act upon, through governmental agencies and decentralised frameworks, when facing natural hazards. Algeria is a country with a relatively short history of seismic risk mitigation even though, in the past, the population suffered from many devastating earthquakes leading to large human and economic losses. Furthermore, until now, the actions taken to reduce such devastating effects have been of reduced impact. With this in mind, this paper investigates the social vulnerability and resilience level to natural hazards, with a specific focus on seismic risk, in the province of Blida, an important cultural and economic region in Northern Algeria. The evaluation is carried out through a hybrid methodology that puts together results from the well-known social vulnerability index or SoVI®, obtained from population data and national statistics, integrated with the Resilience Performance Scorecard (RPS) method, which qualitatively assesses the resilience of a population with reference to qualitative information gathered through public interest and participation. With such a methodology, this study aims to evaluate the societal factor and the impact on the population at risk through vulnerability mapping. The results allow identifying the areas and the social vulnerability dimensions requiring immediate addressing by regulatory and institutional frameworks that can increase preparedness levels, resource allocation, contingency planning, and efforts in raising public awareness. Following the use of census data and the participatory scheme, as well as a hybrid approach combining the two, it is seen that the province of Blida is characterised by medium levels of vulnerability. Following a simplified comparison, the SoVI approach results tend to underestimate the RPS ones. Such information will be useful to aid decision-makers and the exposed society itself to endure the effects of disastrous events. [ABSTRACT FROM AUTHOR]