NEAR SURFACE VELOCITY STRUCTURE OF ANDALUCIA (SOUTHERN SPAIN) AND ALBORAN SEA REGION FROM 0.15-2.0 HZ RAYLEIGH WAVES

  A methodology that has been applied for a relatively short time on Seismology is the modelling of very shallow structures from the inversion of dispersion values (group velocity of short period Rg waves). This is possible, because the very short period Rg wave group velocity is sensitive to the variations in the structure of shear velocity for the shallowest layers of the crust. In this line, we have undertaken in the present work, the determination of the shear velocity models for Andalucia and Alboran Sea region (southern Iberia), by means of the generalized inversion of dispersion curves corresponding to Rg waves (short period Rayleigh waves). We use digital filtering techniques, which provide a significant improvement in the signal-to-noise ratio helping to determine a reasonable model for velocity of shear waves. The dispersion curves obtained shows the complexity of the average structure crossing for the waves in each path analysed. We have inverted the average dispersion curves obtained for every path analysed in order to obtain theoretical shear-velocity models, according to the generalized inversion theory. The results obtained show the existence, in the study area, of strong lateral variations in the physical properties of the materials for a rank of depths between 0 to 5 km. The higher velocity values correspond to paths which crossing older structures, whereas the lower values correspond to the paths crossing younger structures.Una metodología que ha sido aplicada desde hace poco tiempo en Sismología, es el modelado de estructuras muy superficiales a partir de la inversión de valores de dispersión (velocidad de grupo de ondas Rg de corto periodo). Esto es posible, debido a que la velocidad de grupo de las ondas Rg de corto periodo, es sensible a las variaciones en la estructura de la velocidad de cizalla de las capas más superficiales de la corteza. En esta línea, nosotros hemos emprendido el presente trabajo: la determinación de los modelos de velocidad de cizalla para la región de Andalucía y mar de Alborán (sur de Iberia), por medio de la inversión generalizada de curvas de dispersión correspondientes a ondas Rg (ondas Rayleigh de periodo corto). Nosotros usamos técnicas de filtrado digital, las cuales proporcionan una significativa mejora en la razón señal-ruido, ayudando a determinar un modelo razonable para la velocidad de las ondas de cizalla. Las curvas de dispersión obtenidas muestran la complejidad de la estructura media cruzada por las ondas en cada trayectoria analizada. Nosotros hemos invertido las curvas de dispersión medias obtenidas para cada trayecto analizado, con el objeto de obtener modelos teóricos de velocidad de cizalla, de acuerdo con la teoría de la inversión generalizada. Los resultados obtenidos muestran la existencia, en el área de estudio, de fuertes variaciones laterales en las propiedades físicas de los materiales dentro de un rango de profundidad que va desde 0 a 5 km. Los valores más altos de velocidad corresponden a trayectos que cruzan las estructuras más antiguas, mientras que los valores más bajos corresponden a trayectorias que cruzan las estructuras más recientes

Influence of gravel and adjuvant on the compressive strength and water absorption of concrete.

Concrete is the most commonly used material in civil engineering, given its economic cost and ease of manufacture. Its strength depends on the characteristics of its constituents. A good mix makes it possible to build solid, durable and economical structures. The present work aims to characterize the gravel of the Eastern region (quarry of eastern Morocco) by granulometric analysis and water absorption. Then, the studied gravel is used to produce three types of concrete (B20, B25 and B30), which were assessed in terms of water absorption and compressive strength. The last step is to study the effect of an adjuvant, more specifically a water reducer, on mechanical characteristics of local concrete. B25 concrete was chosen for the last step since it is the most used type in the region. Results show that adding a water reducer adjuvant, in this case 'Chrysoplast', can improve the compressive strength of concrete if the percentage added is accurately determined

Near surface velocity structure of Andalucia (Southern Spain) and alboran sea region from 0.15-2.0 HZ rayleigh waves

Una metodología que ha sido aplicada desde hace poco tiempo en Sismología, es el modelado de estructuras muy superficiales a partir de la inversión de valores de dispersión (velocidad de grupo de ondas Rg de corto periodo). Esto es posible, debido a que la velocidad de grupo de las ondas Rg de corto periodo, es sensible a las variaciones en la estructura de la velocidad de cizalla de las capas más superficiales de la corteza. En esta línea, nosotros hemos emprendido el presente trabajo: la determinación de los modelos de velocidad de cizalla para la región de Andalucía y mar de Alborán (sur de Iberia), por medio de la inversión generalizada de curvas de dispersión correspondientes a ondas Rg (ondas Rayleigh de periodo corto). Nosotros usamos técnicas de filtrado digital, las cuales proporcionan una significativa mejora en la razón señal-ruido, ayudando a determinar un modelo razonable para la velocidad de las ondas de cizalla. Las curvas de dispersión obtenidas muestran la complejidad de la estructura media cruzada por las ondas en cada trayectoria analizada. Nosotros hemos invertido las curvas de dispersión medias obtenidas para cada trayecto analizado, con el objeto de obtener modelos teóricos de velocidad de cizalla, de acuerdo con la teoría de la inversión generalizada. Los resultados obtenidos muestran la existencia, en el área de estudio, de fuertes variaciones laterales en las propiedades físicas de los materiales dentro de un rango de profundidad que va desde 0 a 5 km. Los valores más altos de velocidad corresponden a trayectos que cruzan las estructuras más antiguas, mientras que los valores más bajos corresponden a trayectorias que cruzan las estructuras más recientes

Seismotectonics zoning of Morocco and adjacent region

In the present work, a new seismotectonics zoning of the Morocco and adjacent region is proposed. It is supported on a new database including recent geological (active faults, slip rates, geometrical characteristics, chronology of some recent tectonic phases) and geophysical (both instrumental and historical seismicity, focal mechanisms, nature of the crust) studies. In addition, the geodynamic context of the convergence of the Africa-Europe plates in the area, going from the Atlantic Ocean to the Mediterranean Sea through the Strait of Gibraltar, has been taken into account. The newly suggested seismotectonics zoning is not limited to the borders of northern Morocco. It considers all the seismic sources (up to 400 km of distance) able to generate large and destructive earthquakes, such as the 1755 Lisbon earthquake, located in the Azores-Gibraltar transforming fault. New catalogues including the historical and instrumental seismicity since 1045 to 2005, and active faults were elaborated and used in this work. The most influential parameters having effects on the definition of the source area characteristics were determined with a suitable accuracy. The new performed zoning includes 12 shallow seismotectonics sources, each one corresponding to a certain volume of the Earth’s crust, whose known data were used to determine its static and dynamic conditions. Each seismotectonics zone has been analysed and interpreted, presenting certain homogeneity in the seismic potential and mode of deformation, obtained from the seismicity data, the strain and the stresses. For zones including faults, we have specified the geometrical characteristics, the chronology of the different movements corresponding to the successive tectonic episodes, and the associated seismicity. This new zoning will provide an improved contribution for both future probabilistic studies on seismic hazard, determining the ground acceleration, and seismic risk in the north of Morocco

S-wave velocity images of the Dead Sea Basin provided by ambient seismic noise

Based on passive seismic interferometry applied to ambient seismic noise recordings between station pairs belonging to a small-scale array, we have obtained shear wave velocity images of the uppermost materials that make up the Dead Sea Basin. We extracted empirical Green’s functions from cross-correlations of long-term recordings of continuous data, and measured inter-station Rayleigh wave group velocities from the daily correlation functions for positive and negative correlation time lags in the 0.1–0.5 Hz bandwidth. A tomographic inversion of the travel times estimated for each frequency is performed, allowing the laterally varying 3-D surface wave velocity structure below the array to be retrieved. Subsequently, the velocity-frequency curves are inverted to obtain S-wave velocity images of the study area as horizontal depth sections and longitude- and latitude-depth sections. The results, which are consistent with other previous ones, provide clear images of the local seismic velocity structure of the basin. Low shear velocities are dominant at shallow depths above 3.5 km, but even so a spit of land with a depth that does not exceed 4 km is identified as a salt diapir separating the low velocities associated with sedimentary infill on both sides of the Lisan Peninsula. The lack of low speeds at the sampling depth of 11.5 km implies that there are no sediments and therefore that the basement is near 10–11 km depth, but gradually decreasing from south to north. The results also highlight the bowl-shaped basin with poorly consolidated sedimentary materials accumulated in the central part of the basin. The structure of the western margin of the basin evidences a certain asymmetry both whether it is compared to the eastern margin and it is observed in north–south direction. Infill materials down to ∼8 km depth are observed in the hollow of the basin, unlike what happens in the north and south where they are spread beyond the western Dead Sea shore

Tuberculous Duodenal Stenosis: Report of Two Cases

Duodenal tuberculosis is a rare clinical entity. The authors report and emphasize the lack of special clinical, radiological and endoscopic signs of duodenal tuberculosis. The diagnosis is affirmed, at laparotomy, out of the findings of peritoneal granulations or histology of lymphatic nodes. We report our experience of two cases of duodenal tuberculosis presenting with proximal intestinal obstruction and review the available literature

PLACE DE LA CHIRURGIE DANS LA PRISE EN CHARGE DE LA MALADIE DE CROHN ANO-PERINEALE

Introduction: The attack ano-perinéale during the disease of Crohn is relatively frequent, with difficult treatment. Materials and methods: A retrospective study, spread out over six years, 12 patient collages in the service of visceral and proctologic surgery II of the military hospital of instruction Mohamed V of Rabat, were taken charges some for localizations anoperinéales of  Crohn’s disease  . Results: Ano-perinéale was noted has 38 years an average age, dominated especially by the dents in 83% of the cases. The diagnosis was evoked in front of the presence of the épithélio-giganto-cellular granulome among all patients, and retained on the whole of the arguments clinical, endoscopic, histological and evolutionary. The surgical treatment was a fistulectomy or a fistulotomy associated with drainage in 10 cases and a double fissurectomy with anoplastie at two others. The average retreat was of 19.42mois. The cicatrization was considered to be good in 3 cases, slow in 3cas, an anal stenos moderate in a case and a relapse of fistula in a case. On the functional level, one noted a hypotonic in 5cas and an anal incontinence at a case. Discussion: The anoperinéal lesions of Crohn’s disease are frequent, often awkward, chronic, repeating, extensive, complex and of difficult treatment. The treatment of these lesions remains still discussed, partly because of the difficulties of evaluation related to their diversity and their complexity. Currently the contribution of the modern medical treatment made it possible to avoid any surgical aggression which is likely to involve or to worsen disorders of the continence except required. Conclusion: The medical treatment must be always prescribed in first intention. As for the surgical treatment, it should be considered only in the event of no active Crohn’s disease.Introduction : L’atteinte ano-perinéale au cours de la maladie de Crohn est relativement fréquente et de traitement difficile. Nous rapportons une étude rétrospective dont le but est de discuter la prise en charge thérapeutique medico-chirurgicale de ces lésions. Matériels et méthodes : Une étude rétrospective, entre le premier Janvier 2000 et le 31 Décembre 2005 avec un recul de 19 mois, faite d’une série de12 patients opérés pour maladie de Crohn ano-perinéale au sein de service de chirurgie viscérale et proctologique II de l’hôpital militaire d’instruction Mohamed V, Résultats : La maladie de Crohn ano-perinéale a été notée à un âge moyen de 38 ans avec une prédominance masculine, dominé surtout par les fistules dans 83% des cas. Le diagnostic a été évoqué en postopératoire, devant la présence du granulome épithélio-giganto-cellulaire chez tous les malades, et retenu, après un bilan complémentaire réalisé à distance, sur l’ensemble des arguments cliniques, endoscopiques, histologiques et évolutifs. Un bilan de la maladie crohnienne a été réalisés, les LAP, en rapport avec la maladie de Crohn, étaient isolées chez  8 patients et associée à des lésions intestinales méconnues chez 4 patients. Le traitement chirurgical a été une fistulectomie ou une fistulotomie associée à un drainage en séton(10cas) et une double fissurectomie avec anoplastie (2cas). Le recul moyen était de 19 mois. La cicatrisation a été jugée bonne dans 3 cas, lente dans 3cas, une sténose anale modérée a été notée dans un cas et une récidive de fistule dans un cas. Sur le plan fonctionnel, on a noté une hypotonie sphinctérienne dans 5cas et une incontinence anale chez un cas. Discussion : Les lésions anoperinéales de la maladie de Crohn sont fréquentes, souvent gênantes, chroniques, récidivantes, extensives, complexes et de traitement difficile. Le traitement de ces lésions reste encore controversé, en partie du fait des difficultés d’évaluation liées à leur diversité et à leur complexité. Actuellement l’apport du traitement médical moderne permet d’éviter toute agression chirurgicale qui risque d’entraîner ou d’aggraver des troubles de la continence sphinctérienne sauf nécessité. Conclusion : Le traitement médical doit être toujours prescrit en première intention. Quant au traitement chirurgical, il ne doit être envisagé qu’en cas l’absence de maladie de Crohn active

Seismic risk in the city of Al Hoceima (north of Morocco) using the vulnerability index method, applied in Risk-UE project

The final publication is available at Springer via http://dx.doi.org/10.1007/s11069-016-2566-8Al Hoceima is one of the most seismic active regions in north of Morocco. It is demonstrated by the large seismic episodes reported in seismic catalogs and research studies. However, seismic risk is relatively high due to vulnerable buildings that are either old or don’t respect seismic standards. Our aim is to present a study about seismic risk and seismic scenarios for the city of Al Hoceima. The seismic vulnerability of the existing residential buildings was evaluated using the vulnerability index method (Risk-UE). It was chosen to be adapted and applied to the Moroccan constructions for its practicality and simple methodology. A visual inspection of 1102 buildings was carried out to assess the vulnerability factors. As for seismic hazard, it was evaluated in terms of macroseismic intensity for two scenarios (a deterministic and probabilistic scenario). The maps of seismic risk are represented by direct damage on buildings, damage to population and economic cost. According to the results, the main vulnerability index of the city is equal to 0.49 and the seismic risk is estimated as Slight (main damage grade equal to 0.9 for the deterministic scenario and 0.7 for the probabilistic scenario). However, Moderate to heavy damage is expected in areas located in the newer extensions, in both the east and west of the city. Important economic losses and damage to the population are expected in these areas as well. The maps elaborated can be a potential guide to the decision making in the field of seismic risk prevention and mitigation strategies in Al Hoceima.Peer ReviewedPostprint (author's final draft

Seafloor Morphology and Processes in the Alboran Sea

The seafloor of the Alboran Sea reflects its complex tectonic, sedimentary, and oceanography dynamics as a consequence of the geological context, involving interaction between the Eurasian and African plates, and oceanographic context, as it is where the Atlantic and Mediterranean waters meet. Their physiography has a semi-enclosed configuration characterized by two margins (the Spanish Iberian and North Africa—mostly Moroccan margins) enclosing deep basins. Tectonic activity is mainly attested by folds and faults that predominantly affect the central and eastern seafloor sectors, as well as numerous seamounts and fluid-flow features (pockmarks, mud volcanoes, and diapirs) that dot the seafloor. The sedimentary and oceanographic processes allow us to distinctly define two principal environments in the Alboran Sea: the shallow proximal margin (continental shelf); and the deep distal margin (continental slope and base of the slope) with the adjacent sub-basins. The shelf mostly comprises prodeltaic and infralittoral prograding wedges, with local bedform fields, submarine valleys, and wave-cut terraces. Coastal and fluvio-marine sedimentary processes, acting since the last glacial period, are responsible for these features. The deep marine environment is characterised by the ubiquity of contourites, whose continuity is interrupted by turbidite systems, canyons, and landslides. The alongslope action of the Mediterranean waters and their interfaces with the Atlantic water has been the main process governing transport, seafloor reworking, and sedimentation of contourites. Mass-movement processes are responsible for the formation of: (1) turbidite systems—turbidity flows and mass flows were dominant during the last glacial sea-level lowstand, evolving to dilute gravity flows during present interglacial high stand; and (2) landslides—the main triggering factors comprising over-steepening, seismicity, under consolidation due to overpressure by interstitial fluids, stratigraphy, and high sedimentation rates. Locally, still-undetermined biological activity in the Spanish and coral activity in the Moroccan margin generated fields of mounded bioconstructions. The seafloor morphology of the Alboran Sea offers interesting clues for assessing the main potential geological hazards, with tectonic seismicity and landslides (as well as their related tsunamis) being some of the most important potential hazards affecting coastal populations. In addition, the seafloor morphology in combination with assemblages of habitat-forming species enables habitat identification and mapping.En prens

Triggering Mechanisms of Tsunamis in the Gulf of Cadiz and the Alboran Sea: An Overview

The Gulf of Cadiz and the Alboran Sea are characterized by tectonic activity due to oblique convergence at the boundary between the Eurasian and Nubian plates. This activity has favoured a variety of tsunamigenic sources: basically, seismogenic faults and submarine landslides. The main tsunamigenic faults in the Gulf of Cadiz would comprise the thrust systems of Gorringe Ridge, Marquês de Pombal, São Vicente Canyon, and Horseshoe faults with a high susceptibility; meanwhile in the Alboran Sea would be the thrust system of the northern Alboran Ridge with high susceptibility, and the thrust systems of north Xauen and Adra margin, the transpressive segment of Al Idrissi fault, and the Yusuf-Habibas and Averroes faults, with moderate to high susceptibility. The areas with the greatest potential to generate tsunamigenic submarine landslides are in the Gulf of Cadiz, the São Vicente Canyon, Hirondelle Seamount, and Gorringe Ridge; and in the Alboran Sea are the southern and northern flanks of Alboran Ridge. Both sources are likely to generate destructive tsunamis in the Gulf of Cadiz, given its history of bigger earthquakes (>7 Mw) and larger landslides. To fully assess tsunamigenic sources, further work needs to be performed. In the case of seismogenic faults, research focuses on geometry, offsets, timing, paleoearthquakes, and recurrence, and in landslides on early post-failure evolution, age, events, and recurrence. In situ measurements, paleotsunami records, and long-term monitoring, in addition to major modelling developments, will be also necessary.Versión del edito