National Institute of Geophysics

Rabat, Morocco

National Institute of Geophysics

Rabat, Morocco
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Sammouda M.,URAC 13 | Gueraoui K.,URAC 13 | Gueraoui K.,University of Ottawa | Driouich M.,URAC 13 | And 2 more authors.
International Review on Modelling and Simulations | Year: 2011

The objective of this work is to establish a numerical code in order to study the natural convection in a cylinder heated from bellow and filled with a porous media which has a variable porosity. A generalized non-Darcian porous medium model for natural convective flow has been developed taking into account the viscous forces within the fluid, The porosity of the medium is assumed to vary exponentially with distance from the wall. The dimensionless equations reveal some important dimensionless numbers controlling this phenomenon such as the thermal Rayleigh number, Ra, the number of Darcy, Da, the number of Prandtl, Pr, the aspect ratio, RA, and the porosity, e{open}. It is found that the variable porosity has an effect on the flow and the heat transfer rate. The established numerical code can also be used in various other industrial applications. © 2011 Praise Worthy Prize S.r.l. - All rights reserved.


Petrov P.,National Institute of Geophysics | Yankova R.,Medical University-Pleven | Jordanova N.,National Institute of Geophysics | Jordanova D.,National Institute of Geophysics | Tsacheva T.,Institute of Physical Chemistry BAS
12th International Multidisciplinary Scientific GeoConference and EXPO - Modern Management of Mine Producing, Geology and Environmental Protection, SGEM 2012 | Year: 2012

Dust is the most important factor determining urban air quality. Pollens also cause respiratory allergic diseases in sensitized people, especially in industrialized cities where pollen's reactivity is enhanced by increased air pollution. In our study, a combination of magnetic methods, aerobiological studies and microscopic observations on settled dust from indoor and outdoor environment is presented. Magnetic susceptibility of outdoor dust is always higher than that of the indoor dust, suggesting that the major indoor magnetic component comes from outdoor dust, which penetrates inside. The amount of mineral particles of sizes less than 3 microns, normalized to the total number of inorganic particles, was found roughly proportional to registered monthly PM10 variations in each city. The main magnetic mineral in outdoor dust, identified by thermomagnetic analysis of magnetic susceptibility, is magnetite (Fe3O4). Bulk magnetic susceptibility does not show seasonal variations, in contrast to pollen abundance. In all cities peaks in pollen abundance are registered in months April-June. SEM observations coupled with EDX analyses show the presence of several fractions in outdoor dust: combustion-derived spherical metallic particles; lithogenic irregularlyshaped particles, as well as plentiful pollen grains with welded metallic small grains on their surfaces. This finding suggests that significant part of anthropogenic metallic particles is absorbed on pollens' surface and possibly increases pollens' allergic reactivity. © SGEM2012 All Rights Reserved by the International Multidisciplinary Scientific GeoConference SGEM.


Onana P.N.E.,Université Ibn Tofail | Toto E.A.,Université Ibn Tofail | Zouhri L.,Polytechnic Institute of LaSalle Beauvais | Chaabane A.,Université Ibn Tofail | And 2 more authors.
Bulletin of Engineering Geology and the Environment | Year: 2011

The paper describes the tectonic evolution of the Central High Atlas and the Ouarzazate basin in Morocco, noting that many of the tectonic phenomena follow the previous structural lines. Although the area is one of relatively low seismicity, its location in an intra plate part of the African Plate and its high morphology, the effects of an earthquake could be considerable. This study combines seismic records from 1900 to 2007 with the integration of existing tectonic and structural information to better define the seismogenic zones. A newly identified cluster of epicenters in a NNW-SSE linear zone may be related to the Imilchil fault, where the earthquakes with magnitudes of 4-5 at depths of 5-20 km have been identified. Recent work in the Ouarzazate basin indicated that the Amekchoud fault ramp could generate seismic events with magnitudes as large as 6.4 Mw. © 2011 Springer-Verlag.


Petrov P.,National Institute of Geophysics | Jordanova N.,National Institute of Geophysics | Jordanova D.,National Institute of Geophysics
12th International Multidisciplinary Scientific GeoConference and EXPO - Modern Management of Mine Producing, Geology and Environmental Protection, SGEM 2012 | Year: 2012

Magnetic properties of road dust collected from six Bulgarian cities were used as proxies for monitoring urban pollution during May 2009 - November 2010. Magnetic susceptibility shows maximum values during winter months, coherent with increased PM10 levels. In contrast, saturation remanent magnetization exhibits maxima in summer-autumn season and minima in winter. It is suggested that this magnetic parameter reflects traffic-related anthropogenic pollution. Heavy metal analyses show increased concentrations of Pb, Cu, Cr, Zn. Correlation analysis of the data set containing magnetic parameters and heavy metals content reveals existence of very strong negative correlation between the lead content and the ratio of anhysteretic remanence to magnetic susceptibility. It indicates that lead is reversely linked to fine grained magnetic fraction. The ratio of oxalate to dithionite extractible iron, which is related to the ferrimagnetic oxides capable of carrying anhysteretic remanence, is directly linked to Pb content as deduced by chemical extraction data. © SGEM2012 All Rights Reserved by the International Multidisciplinary Scientific GeoConference SGEM.


Metois M.,Italian National Institute of Geophysics and Volcanology | D'Agostino N.,Italian National Institute of Geophysics and Volcanology | Avallone A.,Italian National Institute of Geophysics and Volcanology | Chamot-Rooke N.,Ecole Normale Superieure de Paris | And 5 more authors.
Journal of Geophysical Research B: Solid Earth | Year: 2015

We present a new GPS velocity field covering the peri-Adriatic tectonically active belts and the entire Balkan Peninsula. From the velocities, we calculate consistent strain rate and interpolated velocity fields. Significant features of the crustal deformation include (1) the eastward motion of the northern part of the Eastern Alps together with part the Alpine foreland and Bohemian Massif toward the Pannonian Basin, (2) shortening across the Dinarides, (3) a clockwise rotation of the Albanides-Hellenides, and (4) a southward motion south of 44N of the inner Balkan lithosphere between the rigid Apulia and Black Sea, toward the Aegean domain. Using this new velocity field, we derive the strain rate tensor to analyze the regional style of the deformation. Then, we devise a simple test based on the momentum balance equation, to investigate the role of horizontal gradients of gravitational potential energy in driving the deformation in the peri-Adriatic tectonically active mountain belts: the Eastern Alps, the Dinarides, the Albanides, and the Apennines. We show that the strain rate fields observed in the Apennines and Albanides are consistent with a fluid, with viscosity η ∼ 3×1021 Pa s, deforming in response to horizontal gradients of gravitational potential energy. Conversely, both the Dinarides and Eastern Alps are probably deforming in response to the North and North-East oriented motion of the Adria-Apulia indenter, respectively, and as a consequence of horizontal lithospheric heterogeneity. © 2015. American Geophysical Union. All Rights Reserved.


Vassileva K.,National Institute of Geophysics | Atanasova M.,National Institute of Geophysics
8th Congress of the Balkan Geophysical Society, BGS 2015 | Year: 2015

The work presents a study of the earth crust movements for the territory of Bulgaria and north Greece on the base of new processing of GPS data from 36 GNSS permanent stations on the territory of study. One week data from each year are used from all four years 2011-2014. The estimated station coordinates and station velocity components in system ITRF2008 are transformed in the system ETRF2000 to be obtained the local movements of the stations as more representative of their behaviour. Combinations of the obtained relative velocity vectors of different stations are used for estimation of different relative Euler poles and rotations. Estimated Euler parameters are analyzed to be defined potential microplates of the study territory. The results confirm the motion of Moesia platform in direction and magnitude, determined by other researchers as well. A clear transition boundary between the Moesia platform and the southern Bulgaria zone is not found but it is found a counterclockwise rotation of the central-south part of the Maritsa zone. The behaviour of the stations of north-west and north-central Greece confirm the suggestion that they belongs to the Aegean extensional zone.


Vassileva K.,National Institute of Geophysics | Valev G.,University of Shumen
8th Congress of the Balkan Geophysical Society, BGS 2015 | Year: 2015

The paper presents a study of the earth crust movements for the territory of Bulgaria by applying the Finite Elements Method on the base of results from GPS data processing. The theoretical base of the developed by the authors FEM for the space is presented shortly. As an appropriate method for deformation analysis of large territories the proposed finite elements model is applied for the territory of Bulgaria using estimated Cartesian coordinates of BULiPOS GNSS network stations. One week GPS data from each of the five years 2009-2013 of BULiPOS network stations have been processed with Bernese software, version 5.0. The estimated Cartesian coordinates of the stations have been transformed into the system ETRF2000. These relative to the Eurasia stable plate station coordinates have been used in the finite elements model. On the base of the obtained results several areas of compressions and extensions could be distinguished but not quite clear. Generally it can be suggested that deformations in part of central, centraleast and south-east Bulgaria are of compression, in north-west, south-west and in part of central Bulgaria - of extension. More stations over the territory of the country will contribute to better clarification of deformation processes.


Sammouda M.,URAC 13 | Sammouda M.,Abdus Salam International Center For Theoretical Physics | Gueraoui K.,URAC 13 | Gueraoui K.,University of Ottawa | And 3 more authors.
International Review of Mechanical Engineering | Year: 2012

Theoretical and numerical study of the phenomenon of natural convection in a cylindrical enclosure filled by a non-Darcy porous media and saturated by a Newtonian fluid. The porosity of the media considered is variable and approximated by an exponential function based on an empirical law and equal to the unity near the walls due to the effects of the walls. The hydrodynamic flow in the porous medium is governed by Forchheimer-Brinkman extension of Darcy model (EBFD) with non-uniform porosity. The dimensionless equations reveal some important dimensionless numbers controlling this phenomenon such as the thermal Rayleigh number, Ra, the number of Darcy, Da, the number of Prandtl, Pr, the aspect ratio, RA, and the porosity, ε. The results are discussed graphically. The heat exchange traduced by Nusselt number is also considered in the study. The results obtained under the limiting conditions were found to be in good agreement with the existing ones. The established numerical code can also be used in various other industrial applications. © 2012 Praise Worthy Prize S.r.l.


Shpynev B.G.,Russian Academy of Sciences | Kurkin V.I.,Russian Academy of Sciences | Ratovsky K.G.,Russian Academy of Sciences | Chernigovskaya M.A.,Russian Academy of Sciences | And 6 more authors.
Earth, Planets and Space | Year: 2015

This study investigates the impact of dynamical processes in the neutral atmosphere on the high-midlatitude ionosphere during two sudden stratospheric warming (SSW) events. For this purpose, the reanalysis meteorological data of the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) and UK Met Office (UKMO) were used in addition to that from the high-midlatitude chain of Russian ionosonde stations. The results show that the ionospheric response to the SSW events at high-midlatitudes depends on the position of the ionosonde stations relative to the stratospheric circulation pattern. Two well-pronounced effects were detected in this study. The first effect, observed in January 2009, was a negative effect in critical frequency (foF2) and a positive effect in F2 layer maximum (hmF2) above the border of a stratospheric cyclone and an anticyclone with northward flow direction. During a 6-day period, the ionosphere exhibited a sharply inhomogeneous longitudinal structure when ionosondes, displaced at a longitude of approximately 20°, showed differences of approximately 1 MHz in foF2 and more than 50 km in hmF2. The second feature, which was clearly observed in January 2013, implied a positive effect in foF2 up to approximately 2.5 MHz and a negative effect in hmF2 at approximately 10 km above the center of the stratospheric cyclone. We conclude that these effects were caused by upward transport of molecular gas to the lower thermosphere for the first case and a pulldown forcing of molecular species above the low-pressure zone inside the cyclone for the second case. Changes in the O+/N2 ratio in the lower thermosphere altered the O+ recombination rate and the corresponding variations of ionosphere parameters. © 2015 Shpynev et al.; licensee Springer.


News Article | October 26, 2016
Site: www.bbc.co.uk

Two strong earthquakes have hit central Italy, damaging buildings and injuring dozens of people. A 5.5-magnitude quake struck at 19:10 (17:10 GMT) near Visso in Macerata province, followed two hours later by a 6.1 magnitude tremor in the same area. Emergency teams have worked through the night. In August an earthquake killed about 300 people south of Visso. There are few reports of serious injuries but bad weather has been hampering efforts to assess the damage. Visso is 70km (45 miles) from Amatrice, which was badly damaged in the 6.2 magnitude quake in August. Wednesday's earthquakes were felt across central Italy, including in the capital, Rome, where buildings shook and doors and windows rattled. "Tens" of people were hurt, but only four people suffered serious injuries, Italy's civil protection chief Fabrizio Curcio said. The second earthquake was considerably stronger than the first and numerous smaller aftershocks have occurred. One witness told Italian TV he saw part of a building collapse in front of him. The town of Camerino is thought to have been badly damaged, and one resident told the BBC: "Everyone is leaving Camerino by foot or car to seek safety. Two churches are destroyed and many houses [have] fallen." In Campo, near Norcia in the Umbria region, the late 15th century San Salvatore church collapsed. It had been weakened by the earthquake in August. There are also reports of downed power lines, damage to historic buildings and a landslide on a main road north of Rome. The first earthquake, 7km south-west of Visso, was relatively shallow, at a depth of 9km (nearly six miles). The second, at 21:18 local time, was 2km northwest of Visso, at a depth of 10km. These tremors were linked to the August earthquake, Italian officials said. "Aftershocks can last for a long time, sometimes for months," AFP news agency quoted Mario Tozzi of Italy's National Institute of Geophysics as saying. Are you in an area affected by the earthquake? Tell us about your experience by emailing haveyoursay@bbc.co.uk. You can also contact us in the following ways:

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