Smoothed Particle Hydrodynamics for modelling landslide–water interaction problems

Landslides - This work aims to develop a Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) in-house code for modelling landslide–water interaction problems. While we consider the...     

Studying the Evolution of Earthquake Network Measures for the Main Shock on June 24, 2015 in Egypt

Geotectonics - The monitoring of network measures, such as degree centrality, betweenness centrality, and clustering coefficient is performed, aiming to identify the periods that the earthquake...     

Automatic identification of fake patterns caused by short-width wavelets in seismic data

Despite the popularity of using the Haar wavelet filter in many applications, it sometimes introduces fake patterns into the multi resolution analysis (MRA) of seismic data. In this work, we compared different wavelet filters to demonstrate that these patterns are fake and not part of the original waveforms and to show that they are a result of using the Haar wavelet filter as a short-width wavelet. To achieve this, many seismic waveforms from two different sources: the Egyptian National Seismic Network (ENSN) and the High Sensitivity Seismograph Network Japan (Hi-net) are used with different wavelet filters. We propose an algorithm based on an autoregressive (AR) model to detect these patterns automatically and fully.     

Microchemical Characterization of Natural Gold and Copper Alloys from the Ancient Um Shashoba Gold Mine,South Egypt

The SEM-EDX technique was applied to investigate Au, and Cu＋Sn alloyed grains in the mineralization of the Um Shashoba mine for achieving further understanding of occurrences, internal structures and microchemistry of Au and Cu alloys and associated minerals, and mineralization type. This study is aiming at the genetic history of ore-bearing fluid events, geochemical evaluation and exploration significance. The results showed that the mineralization could be considered as a single major episode generated by metamorphic mesothermal solution rich in sulfides and unsaturated respect to Au. It was differentiated into many stages; started with formation of auriferous pyrite that was pseudomorphed by secondary hematite, limonite and goethite. Three phases of Au alloy were precipitated, and Cu＋Sn and Ag-rich alloys were produced respectively and followed by deposition of two generations of barren pyrite. Calcite and ankerite were crystalized, surrounded and partially replaced some of early formed minerals. Finally, barren muscovite recrystallized around and inside both later formed carbonate minerals that were free of any sign of Au in their structures. The processes of deformation, recrystallization, annealing, dissolution, remobilization and re-precipitation played the most important roles in the genetic history of the mineralization.     

A geostatistically based approach to the identification of aquifer transmissivities in Yolo Basin, California

A geostatistically based approach is developed for the identification of aquifer transmissivities in Yolo Basin, California. The approach combines weighted least-squares with universal kriging and cokriging techniques in an overall scheme that (1)considers a prioriknown information on aquifer transmissivity and specific capacities of wells, (2)considers uncertainties in water level and transmissivity data, and (3)estimates the reliability of the generated transmissivity values. Minimization of a global least-squares function that incorporates calibration and plausibility criteria leads to a transmissivity map that shows a good agreement with pumping-test results.     

Growth of the marsh elder<Emphasis Type="Italic">Iva frutescens</Emphasis> in relation to duration of tidal flooding

Iva frutescens is a common shrub at the upland fringe of salt marshes throughout the East and Gulf Coasts of North America. Within a marsh, its location and relative size are governed largely by the degree of flooding by seawater.Iva’s wide distribution and restricted location within salt marshes may make it a useful indicator of overall conditions of the marshes. This work was designed to provide basic information on the age and growth ofI. frutescens, especially as they relate to the degree of flooding that is needed in order to investigateIva’s potential as an indicator. Cross-sections of older stems (living and standing dead) from salt marshes in Rhode Island, United States, were examined in order to age stems and estimate their growth rate from cumulative increase in woody tissue. Most stems were six yr old or less, suggesting that aboveground structures live for only a few years. Stem diameter correlated with growth rate and aboveground biomass. Elevation at the root zone was used to estimate the duration that plants were flooded, which was negatively correlated with stem diameter. The most robust plants came from sites that were flooded only up to 6–7% of the total time during the growing season. No plants were found in areas flooded more than 30% of the time.     

Événements panafricains dans l'Adrar Souttouf (Sahara marocain)

The Adrar Souttouf belt (Western Sahara) lies in the northern part of the Mauritanide belt and was considered as a part of the Hercynian Mauritanian-Appalachian belt. Recently the presence of a Panafrican protolith (595 Ma) was evidenced by the age of inherited zircons from an eclogitic unit and led to consider complex Panafrican events included in the Hercynian belt, as in the central and southern Mauritanide belt. Our new field survey completed by ten KAr dating (whole rocks and separate minerals) confirmed that multiphased Panafrican formations outcrop within the center of the Adrar Souttouf massif. Diverse events ranged from ca. 1000 to 500 Ma, some of them being indicative of an oceanic type environment and metamorphism. The 1000 Ma metamorphic event is recorded for the first time in the West African craton. A large Hercynian remobilisation is also evidenced. To cite this article: M. Villeneuve et al., C. R. Geoscience 338 (2006).     

Evaporation estimates from Nasser Lake, Egypt, based on three floating station data and Bowen ratio energy budget

Nasser Lake is located in a hyper-arid region in the south of Egypt. Evaporation is by far the most important factor in explaining the water losses from the lake. To obtain better management scenarios for Nasser Lake, an accurate estimation of the lake evaporation losses thus is essential. This paper presents an update of previous evaporation estimates, making use of local meteorological and hydrological data collected from instrumented platforms (floating weather stations) at three locations on the lake: at Raft, Allaqi, and Abusembel (respectively at 2, 75, and 280 km upstream of the Aswan High Dam). Results from six conventional evaporation quantification methods were compared with the values obtained by the Bowen ratio energy budget method (BREB). The results of the BREB method showed that there is no significant difference between the evaporation rates at Allaqi and Abusembel. At Raft, higher evaporation rates were obtained, which were assumed to be overestimated due to the high uncertainty of the Bowen ratio (BR) parameter. The average BR value at Allaqi and Abusembel was used to eliminate this overestimates evaporation. Variance-based sensitivity and uncertainty analyses on the BREB results were conducted based on quasi-Monte Carlo sequences (Latin Hypercube sampling). The standard deviation of the total uncertainty on the BREB evaporation rate was found to be 0.62 mm day^?1. The parameter controlling the change in stored energy, followed by the BR parameter, was found to be the most sensitive parameters. Several of the six conventional methods showed substantial bias when compared with the BREB method. These were modified to eliminate the bias. When compared to the BREB-based values, the Penman method showed most favorably for the daily time scale, while for the monthly scale, the Priestley–Taylor and the deBruin–Keijman methods showed best agreement. Differences in mean evaporation estimates of these methods (against the BREB method) were found to be in the range 0.14 and 0.36 mm day^?1. All estimates were based calculations at the daily time scale covering a 10-year period (1995–2004).