On the recent global mean sea level changes: Trend extraction and El Niño's impact     

Mahdi Haddad  Habib TaibiSi Mohammed Mohammed Arezki 《Comptes Rendus Geoscience》2013,345(4):167-175

The spatial sampling offered by TOPEX and Jason series of satellite radar altimeters and its continuity during the last twenty years are major assets to provide an improved vision of the global mean sea level (GMSL). The objective of this paper is to examine the recent GMSL variations (1993–2012) and to investigate the correlation between the GMSL and ENSO (El Niño-southern oscillation) episodes. For this purpose, a mean sea level anomalies time series, obtained from TOPEX, Jason-1 and Jason-2 measurements, is used to determine the trend of GMSL changes by using a simplified form of an unobserved components model (namely UCM). Then, to investigate the impact of the ENSO phenomenon on the GMSL changes, we considered the sea surface temperature anomalies (SSTA) index over the Niño3 region (5N–5S 150W–90W). Cross wavelet transform and wavelet coherence analysis are performed to expose common power between the GMSL changes and the SSTA index and their relative phase in the time–frequency space. The results indicate that there are in the estimated GMSL's trend a number of fluctuations over short periods that are least partly related to the El Niño/La Niña episodes. Cross wavelet transform and wavelet coherence analysis indicate that a significant correlation between GMSL and ENSO occurred during 1997–1998, 2006–2007, 2009–2010 El Niño events and 2007–2008 and 2010–2011 La Niña ones. All these areas show in-phase relationship, suggesting that GMSL and SSTA index vary synchronously.  相似文献   

Prediction of settlement trough induced by tunneling in cohesive ground   总被引：1，自引：0，他引：1  

Mohammed Y. Fattah  Kais T. Shlash  Nahla M. Salim 《Acta Geotechnica》2013,8(2):167-179

Surface settlements of soil due to tunneling are caused by stress relief and subsidence due to movement of support by excavation. There are significant discrepancies between empirical solutions to predict surface settlement trough because of different interpretations and database collection by different authors. In this paper, the shape of settlement trough caused by tunneling in cohesive ground is investigated by different approaches, namely analytical solutions, empirical solutions, and numerical solutions by the finite element method. The width of settlement trough was obtained by the finite element method through establishing the change in the slope of the computed settlement profile. The finite element elastic-plastic analysis gives better predictions than the linear elastic model with satisfactory estimate for the displacement magnitude and slightly overestimated width of the surface settlement trough. The finite element method overpredicted the settlement trough width i compared with the results of Peck for soft and stiff clay, but there is an excellent agreement with Rankin’s estimation. The results show that there is a good agreement between the complex variable analysis for Z/D = 1.5, while using Z/D = 2 and 3, the curve diverges in the region faraway from the center of the tunnel.  相似文献   

Impact of the geomorphology and soil management on the development of waterlogging in closed drainage basins of Egypt and Saudi Arabia   总被引：1，自引：0，他引：1  

Mohammed El Bastawesy  Rafat Ramadan Ali  Khalid Al Harbi  Abdallah Faid 《Environmental Earth Sciences》2013,68(5):1271-1283

This paper investigates the interplay of the catchment geomorphology, hydrology and soil properties on the development of waterlogging and land degradation within different dry land catchments in Egypt and Saudi Arabia. Multi-temporal remote sensing data of the Landsat Thematic Mapper and Enhanced Thematic Mapper were collected and processed to detect the land cover changes and development of cultivations within the two areas. The Shuttle Radar Topography Mission Digital Elevation Model were hydrologically processed to delineate the catchment morphometrical parameters and to examine the spatial distribution of cultivated fields and their relation to the extracted drainage networks. The fluvial channels of the Farafra Oasis have largely been obliterated by the prevailing aridity and often buried under aeolian deposits. The soil of these areas are mainly lithic with a high calcium carbonate content, thus limiting the downward percolation of excess irrigation water and therefore develop perched water table and seepage through the buried fluvial channels. On the other hand, the cultivations of Tabuk catchment (which has similar geomorphologic setting to the Farafra Oasis) have shown no signs for waterlogging. This situation is could be related to the different soil properties; the spatial distribution of cultivated areas and the adopted irrigation methods via pivots. The inactive alluvial channels, landforms and irrigation methods have to be considered when planning for a new cultivation in dry land catchments to better control waterlogging hazard. The ‘dry-drainage’ concept can be implemented as the drainage and seepage water, which can be conveyed into certain abandoned playas for evaporation.  相似文献   

An overview of the diagenesis of the Upper Jurassic carbonates of Jubaila and Hanifa formations, central Saudi Arabia     

Mohammed H. Basyoni  Mohammed Khalil 《Arabian Journal of Geosciences》2013,6(2):557-572

The Jubaila Formation (Upper Jurassic) in central Saudi Arabia has been divided into lower, middle, and upper parts purely on lithologic grounds. Each part consists of a major lower unit of lime mudstone and a minor upper unit of grainstone. This persistent change in the limestone facies is interpreted as a reflection of repeated shoaling up in the depositional shelf environment. It is a normal marine carbonate sequence that varies in thickness from 85 to 126 m. In the Hanifa Formation, the lowermost brown ledges in the section comprise a series of coarsening upward sequences which generally terminate in a fossiliferous/peloidal packstone and grainstone and subordinately lime mudstone facies. The middle slope member is yellow, blocky weathered shale and marl. Above this slope member are several thick beds of brown-coated fossiliferous wackestone, packstone, and grainstone with the association of lime mudstone in certain levels. These are fairly resistant ledges due to the occurrence of stromatoporoids. Dedolomitization occurs in the Jubaila Formation in various textural forms which include composite calcite rhombohedra, zonal dedolomitization, regeneration of predolomitization fabric of the limestone, and coarsely crystalline calcite mosaics with or without ferric oxide rhombic zones. Rhombohedral pores commonly occur in intimate association with dolomite, possibly resulting from the leaching of calcitized dolomite rhombohedra. The regional dedolomitization was most likely brought about by calcium sulfate solutions reacting with dolomites. The source of sulfate solutions is the dissolved anhydrite deposits of the Arab–Hith Formations, sometime before their erosion, and it takes place at or near an exposed surface. The Hanifa Formation shows various diagenetic features. These include dolomitization, dedolomitization, micritization, cementation, and recrystallization. Most of the examined samples of the Hanifa carbonates are dolomitized and subsequently dedolomitized as evidenced by the presence of iron-coated dolomite rhombs partially or completely calcitized. Dolomite also occurs in the lime mudstone, wackestone, packstone, and grainstone facies, while leaching of wackestone and packstone and dedolomitization of dolomite and dolomitic limestone followed by recrystallization are common processes.  相似文献   

Comment on Gazi et al. (2020): Detecting Coral Reef Degradation on St. Martin’s Island,Bangladesh?     

Tomascik  Tomas  Chowdhury  Mohammed Shah Nawaz  Bell  Tom 《Ocean Science Journal》2021,56(3):326-329

Ocean Science Journal - St. Martin’s Island is a small sedimentary island situated at the southernmost part of Bangladesh (20°37.6′ N and 92°19.3′ E). The island is...  相似文献   

Introduction to Special Section on Borehole Geophysics     

Mohammed N. Alfaraj 《Geophysical Prospecting》2012,60(6):1017-1017

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Ionospheric and geomagnetic disturbances during the 2005 Sumatran earthquakes     

Alina Marie Hasbi  Mohammed Awad Momani  Mohd Alauddin Mohd Ali  Norbahiah Misran  Kazuo Shiokawa  Yuichi Otsuka  Kiyohumi Yumoto 《Journal of Atmospheric and Solar》2009,71(17-18):1992-2005

This paper investigates the ionospheric and geomagnetic responses during the 28 March 2005 and 14 May 2005 Sumatran earthquakes using GPS and magnetometer stations located in the near zone of the epicenters. These events occurred during low solar and geomagnetic activity. TEC oscillations with periods of 5–10 min were observed about 10–24 min after the earthquakes and have horizontal propagation velocities of 922–1259 m/s. Ionospheric disturbances were observed at GPS stations located to the northeast of the epicenters, while no significant disturbances were seen relatively east and south of the epicenters. The magnetic field measurements show rapid fluctuations of 4–5 s shortly after the earthquake, followed by a Pc5 pulsation of 4.8 min about 11 min after the event. The correlation between the ionospheric and geomagnetic responses shows a good agreement in the period and time lag of the peak disturbance arrival, i.e. about 11–13 min after the earthquake.  相似文献   

Dynamic simulation of beam-like structure with a crack subjected to a random moving mass oscillator     

M.M.Ettefagh  M.H.Sadeghi  M.Rezaee 《地震工程与工程振动(英文版)》2009,8(3):447-458

In this paper,dynamic simulation of a beam-like structure with a transverse open crack subjected to a random moving mass oscillator is investigated.The simultaneous effect of a crack and a random oscillator has not been addressed up to now.The crack in the beam at different locations and with different depths is considered as one group of damage,each as an individual imperfection.In addition,bearing immobility is considered as another type of problem in the beam.Mass, stiffness,damping and velocity of th...  相似文献   

Simulated watershed responses to land cover changes using the Regional Hydro‐ecological Simulation System          下载免费PDF全文

Ibrahim Nourein Mohammed  David G. Tarboton 《水文研究》2016,30(6):986-986

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Air Surface Temperature Correlation with Greenhouse Gases by Using Airs Data Over Peninsular Malaysia     

Jasim Mohammed Rajab  M. Z. MatJafri  H. S. Lim 《Pure and Applied Geophysics》2014,171(8):1993-2011

The main objective of this study is to develop algorithms for calculating the air surface temperature (AST). This study also aims to analyze and investigate the effects of greenhouse gases (GHGs) on the AST value in Peninsular Malaysia. Multiple linear regression is used to achieve the objectives of the study. Peninsular Malaysia has been selected as the research area because it is among the regions of tropical Southeast Asia with the greatest humidity, pockets of heavy pollution, rapid economic growth, and industrialization. The predicted AST was highly correlated (R = 0.783) with GHGs for the 6-year data (2003–2008). Comparisons of five stations in 2009 showed close agreement between the predicted AST and the observed AST from AIRS, especially in the wet season (within 1.3 K). The in situ data ranged from 1 to 2 K. Validation results showed that AST (R = 0.776–0.878) has values nearly the same as the observed AST from AIRS. We found that O₃ during the wet season was indicated by a strongly positive beta coefficient (0.264–0.992) with AST. The CO₂ yields a reasonable relationship with temperature with low to moderate beta coefficient (?0.065 to 0.238). The O₃, CO₂, and environmental variables experienced different seasonal fluctuations that depend on weather conditions and topography. The concentration of gases and pollution were the highest over industrial zones and overcrowded cities, and the dry season was more polluted compared with the wet season. These results indicate the advantage of using the satellite AIRS data and a correlation analysis to investigate the effect of atmospheric GHGs on AST over Peninsular Malaysia. An algorithm that is capable of retrieving Peninsular Malaysian AST in all weather conditions with total uncertainties ranging from 1 to 2 K was developed.  相似文献