Wave climate simulation for southern region of the South China Sea   总被引：2，自引：0，他引：2  

Ali Mirzaei  Fredolin Tangang  Liew Juneng  Muzneena Ahmad Mustapha  Mohd Lokman Husain  Mohd Fadzil Akhir 《Ocean Dynamics》2013,63(8):961-977

This study investigates long-term variability and wave characteristic trends in the southern region of the South China Sea (SCS). We implemented the state-of-the art WAVEWATCH III spectral wave model to simulate a 31-year wave hindcast. The simulation results were used to assess the inter-annual variability and long-term changes in the SCS wave climate for the period 1979 to 2009. The model was forced with Climate Forecast System Reanalysis winds and validated against altimeter data and limited available measurements from an Acoustic Wave and Current recorder located offshore of Terengganu, Malaysia. The mean annual significant wave height and peak wave period indicate the occurrence of higher wave heights and wave periods in the central SCS and lower in the Sunda shelf region. Consistent with wind patterns, the wave direction also shows southeasterly (northwesterly) waves during the summer (winter) monsoon. This detailed hindcast demonstrates strong inter-annual variability of wave heights, especially during the winter months in the SCS. Significant wave height correlated negatively with Niño3.4 index during winter, spring and autumn seasons but became positive in the summer monsoon. Such correlations correspond well with surface wind anomalies over the SCS during El Nino events. During El Niño Modoki, the summer time positive correlation extends northeastwards to cover the entire domain. Although significant positive trends were found at 95 % confidence levels during May, July and September, there is significant negative trend in December covering the Sunda shelf region. However, the trend appears to be largely influenced by large El Niño signals.  相似文献   

3-D crustal structure in the Agadir region (SW High Atlas,Morocco)     

Youssef Timoulali  Mustapha Meghraoui 《Journal of Seismology》2011,15(4):625-635

The 1960 Agadir earthquake (Mw 6.0) constitutes the most damaging earthquake event in Morocco. With the expansion of seismic networks during the last decade in Morocco, new seismic data have been collected in this region. The P and S arrivals at 19 stations located in Southern Morocco are used to investigate the lithosphere in the Agadir region. In this study, we use a linearized inversion procedure comprising two steps: (1) finding the minimal 1-D model and simultaneous relocation of hypocentres and (2) determination of local velocity structure using linearized inversion. The model parameterization in this method assumes a continuous velocity field. The resolution tests indicate that the calculated images give near true structure for the studied region from 0- to 45-km depth. The results show that the total crust thickness varies from 30 to 40 km in SW High Atlas and confirm the modest crustal tectonic shortening and thickening in the Atlas Mountains of Morocco. The inferred geological structure reconstructed from the calculated image illustrates the existence of fault-related folding. The evidence for coseismic ruptures in 1960 on the Kasbah anticline combined with the 1960 earthquake hypocentre located in the tomographic image determines the seismic potential of the active fault and related fold. The resulting tomographic image shows a high-velocity anomalies that could be associated with the location of deep active fault (10–30 km) associated with the fold structure. In the South Atlas, theses anomalies could be associated with the South atlas thrust front structure.  相似文献   

Comment on ‘Kisi O. 2007. Evapotranspiration modelling from climatic data using a neural computing technique. Hydrological Processes 21: 1925–1934’     

Hafzullah Aksoy  Aytac Guven  Ali Aytek  M. Ishak Yuce  N. Erdem Unal 《水文研究》2008,22(14):2715-2717

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Long-term seismicity in regions of present day low seismic activity: the example of western Europe     

Thierry Camelbeeck  Pierre Alexandre  Kris Vanneste  Mustapha Meghraoui 《Soil Dynamics and Earthquake Engineering》2000,20(5-8):405-414

In western Europe, the knowledge of long-term seismicity is based on reliable historical seismicity and covers a time period of less than 700 years. Despite the fact that the seismic activity is considered as low in the region extending from the Lower Rhine Embayment to England, historical information collected recently suggests the occurrence of three earthquakes with magnitude around 6.0 or greater. These events are a source of information for the engineer or the scientist involved in mitigation against large earthquakes. We provide information relevant to this aspect for the Belgian earthquake of September 18, 1692. The severity of the damage described in original sources indicates that its epicentral intensity could be IX (EMS-98 scale) and that the area with intensity VII and greater than VII has at least a mean radius of 45 km. Following relationships between average macroseismic radii and magnitude for earthquakes in stable continental regions, its magnitude M_s is estimated as between 6.0 and 6.5. To extend in time our knowledge of the seismic activity, we conducted paleoseismic investigations in the Roer Graben to address the question of the possible occurrence of large earthquakes with coseismic surface ruptures. Our study along the Feldbiss fault (the western border of the graben) demonstrates its recent activity and provides numerous lines of evidence of Holocene and Late Pleistocene large earthquakes. It suggests that along the 10 km long Bree fault scarp, the return period for earthquakes with magnitude from 6.2 to 6.7 ranges from 10,000 to 20,000 years during the last 50,000 years. Considering as possible the occurrence of similar earthquakes along all the Quaternary faults in the Lower Rhine Embayment, a large earthquake could occur there each 500–1000 years. These results are important in two ways. (i) The evidence that large earthquakes occur in western Europe in the very recent past which is not only attested by historical sources, but also suggested by paleoseismic investigations in the Roer Graben. (ii) The existence of a scientific basis to better evaluate the long-term seismicity in this part of Europe (maximal magnitude and return period) in the framework of seismic hazard assessment.  相似文献   

Nonextensive dust acoustic waves in a charge varying dusty plasma     

Mustapha Bacha  Mouloud Tribeche 《Astrophysics and Space Science》2012,337(1):253-259

Our recent analysis on nonlinear nonextensive dust-acoustic waves (DA) [Amour and Tribeche in Phys. Plasmas 17:063702, 2010] is extended to include self-consistent nonadiabatic grain charge fluctuation. The appropriate nonextensive electron charging current is rederived based on the orbit-limited motion theory. Our results reveal that the amplitude, strength and nature of the nonlinear DA waves (solitons and shocks) are extremely sensitive to the degree of ion nonextensivity. Stronger is the electron correlation, more important is the charge variation induced nonlinear wave damping. The anomalous dissipation effects may prevail over that dispersion as the electrons evolve far away from their Maxwellian equilibrium. Our investigation may be of wide relevance to astronomers and space scientists working on interstellar dusty plasmas where nonthermal distributions are turning out to be a very common and characteristic feature.  相似文献   

Micro-CT and FIB–SEM imaging and pore structure characterization of dolomite rock at multiple scales     

Rajakumar S. Devarapalli  Amina Islam  Titly Farhana Faisal  Mohamed Sassi  Mustapha Jouiad 《Arabian Journal of Geosciences》2017,10(16):361

With improvements of imaging techniques and computational power, Digital Rock Physics (DRP) has been increasingly used to determine transport and elastic properties of reservoir core plugs. Since numerical computations highly rely on accurate 3D representations of the porous microstructure of the rocks, the imaging technique and the scale at which the imaging is performed is a critical parameter. In this paper, we introduce a multiscale imaging workflow that uses both micro-X-ray tomography (micro-XCT) and focused ion beam combined with scanning electron microscope (FIB–SEM) to characterize a dolomite rock from the microscale to the nanoscale. This allows for the accurate capture of the different heterogeneities that exist in the carbonate (texture, mineralogy, pore size). The reconstructed microporous structures were then used to successfully predict elastic and permeability properties of selected carbonate.  相似文献   

High-order Stochastic Simulation of Complex Spatially Distributed Natural Phenomena   总被引：1，自引：1，他引：0  

Hussein Mustapha  Roussos Dimitrakopoulos 《Mathematical Geosciences》2010,42(5):457-485

Spatially distributed and varying natural phenomena encountered in geoscience and engineering problem solving are typically incompatible with Gaussian models, exhibiting nonlinear spatial patterns and complex, multiple-point connectivity of extreme values. Stochastic simulation of such phenomena is historically founded on second-order spatial statistical approaches, which are limited in their capacity to model complex spatial uncertainty. The newer multiple-point (MP) simulation framework addresses past limits by establishing the concept of a training image, and, arguably, has its own drawbacks. An alternative to current MP approaches is founded upon new high-order measures of spatial complexity, termed “high-order spatial cumulants.” These are combinations of moments of statistical parameters that characterize non-Gaussian random fields and can describe complex spatial information. Stochastic simulation of complex spatial processes is developed based on high-order spatial cumulants in the high-dimensional space of Legendre polynomials. Starting with discrete Legendre polynomials, a set of discrete orthogonal cumulants is introduced as a tool to characterize spatial shapes. Weighted orthonormal Legendre polynomials define the so-called Legendre cumulants that are high-order conditional spatial cumulants inferred from training images and are combined with available sparse data sets. Advantages of the high-order sequential simulation approach developed herein include the absence of any distribution-related assumptions and pre- or post-processing steps. The method is shown to generate realizations of complex spatial patterns, reproduce bimodal data distributions, data variograms, and high-order spatial cumulants of the data. In addition, it is shown that the available hard data dominate the simulation process and have a definitive effect on the simulated realizations, whereas the training images are only used to fill in high-order relations that cannot be inferred from data. Compared to the MP framework, the proposed approach is data-driven and consistently reconstructs the lower-order spatial complexity in the data used, in addition to high order.  相似文献   

Gold–palladium mineralization at Bleïda Far West, Bou Azzer–El Graara Inlier, Anti-Atlas, Morocco     

Mustapha El Ghorfi  Thomas Oberthür  Frank Melcher  Volker Lüders  Abdelmajid El Boukhari  Lhou Maacha  Rachid Ziadi  Hssain Baoutoul 《Mineralium Deposita》2006,41(6):549-564

The structurally controlled Au–Pd mineralization at Bleïda Far West occurs in a volcano-sedimentary rock sequence in altered amphibolites and chlorite schists of the Neoproterozoic Bou Azzer–El Graara inlier. The Au–Pd mineralization is virtually sulfide-free; instead, gold is associated with hematite, barite, quartz, and calcite. The gold grains are silver- and palladium-bearing (up to 19 wt% Ag and 6.3 wt% Pd) and are intergrown with a distinct suite of mainly Pd-dominated platinum group minerals, namely mertieite-I/isomertieite, merenskyite, keithconnite, kotulskite, palladseite, and sperrylite, defining a Au–Pd–As–Sb–Se–Te chemical signature. Stable isotope and fluid inclusion studies indicate a wide range of fluid compositions with a prominent saline component. In conjunction with the mineral association, oxidizing fluids are indicated, and Au and PGE transport and deposition likely took place by chloride complexes in the epithermal range, at elevated f O₂ and/or low pH. It is still speculative whether the mineralization is late Pan-African (～600–550 Ma) in age, or connected with the Variscan orogeny (～330–300 Ma), or related to some other hydrothermal event. Common to all Au–Pd mineralizations worldwide (Brazil, Australia, UK), including Bleïda Far West, is their formation in the epithermal (<300°C) range; deposition mainly in brittle structures; sulfide-poor mineral assemblages comprising hematite, sulfate minerals, and selenides; and metal transport by, and deposition from, oxidized, chloride-rich fluids. These deposits are further characterized by noble metal abundances in the order Au>Pd>Pt and the chemical signature Au–Pd–Se–Te (±As, Sb, Bi). As such, the Au–Pd association represents a discrete style of gold mineralization distinct from other classes of gold deposits.  相似文献   

Comparison of approaches to spatial estimation in a bivariate context   总被引：6，自引：0，他引：6  

Mustapha Asli  Denis Marcotte 《Mathematical Geology》1995,27(5):641-658

The problem of estimating a regionalized variable in the presence of other secondary variables is encountered in spatial investigations. Given a context in which the secondary variable is known everywhere (or can be estimated with great precision), different estimation methods are compared: regression, regression with residual simple kriging, kriging, simple kriging with a mean obtained by regression, kriging with an external drift, and cokriging. The study focuses on 19 pairs of regionalized variables from five different datasets representing different domains (geochemical, environmental, geotechnical). The methods are compared by cross-validation using the mean absolute error as criterion. For correlations between the principal and secondary variable under 0.4, similar results are obtained using kriging and cokriging, and these methods are superior slightly to the other approaches in terms of minimizing estimation error. For correlations greater than 0.4, cokriging generally performs better than other methods, with a reduction in mean absolute errors that can reach 46% when there is a high degree of correlation between the variables. Kriging with an external drift or kriging the residuals of a regression (SKR) are almost as precise as cokriging.  相似文献   

Numerical modeling of the flow and transport of radionuclides in heterogeneous porous media     

Brahim Amaziane  Mustapha El Ossmani  Christophe Serres 《Computational Geosciences》2008,12(4):437-449

This paper is concerned with numerical methods for the modeling of flow and transport of contaminant in porous media. The numerical methods feature the mixed finite element method over triangles as a solver to the Darcy flow equation and a conservative finite volume scheme for the concentration equation. The convective term is approximated with a Godunov scheme over the dual finite volume mesh, whereas the diffusion–dispersion term is discretized by piecewise linear conforming triangular finite elements. It is shown that the scheme satisfies a discrete maximum principle. Numerical examples demonstrate the effectiveness of the methodology for a coupled system that includes an elliptic equation and a diffusion–convection–reaction equation arising when modeling flow and transport in heterogeneous porous media. The proposed scheme is robust, conservative, efficient, and stable, as confirmed by numerical simulations.   相似文献