Harmonic by harmonic removal technique for improving vibroseis data quality

In this paper, an improved method is presented to reduce vibrator harmonic distortion, one harmonic at a time and the method is illustrated with both simulated and field data. This method improves on the previous method that treated all the harmonics at once. The significant contribution in this procedure is a considerable reduction for the harmonics without any alteration for the weakest signals possibly present in positive and negative times. The core of the proposed technique depends on an accurate simulation for all the harmonics one by one existing in the positive and negative times of the data after cross‐correlation with the fundamental sweep and then subtracting the simulated harmonics from the original data using an optimization procedure. The steps and mathematical equations of the procedure are explained in detail in the body of the article in the section titled ‘harmonic by harmonic attenuation procedure’. Accordingly, a well‐developed procedure for enhancing the vibroseis data quality in both down‐ and up‐sweep data is illustrated. The procedure was tested on both synthetic and field data sets.     

Semial ophiolite veins of United Arab Emirates―A fluid inclusions study

Calcite and quartz veins in the gabbroic and dunite rocks of the Semial ophiolite (UAE) were selected for fluid inclusion analysis. The inclusions contain both aqueous low-salinity and hydrocarbon-dominated fluids. Mi-crothermometry data indicate that the aqueous fluids contain 0.22 to 1.45 equivalent wt% NaCl and occasionally contain traces of hydrocarbons. Homogenization to liquid occurred between 91 and 152℃. Modeling based on these fluid inclusion observations indicates that the trapping conditions of t...     

Petrological and mineralogical characteristics of younger granites and pegmatites in the Wadi Haleifiya area,southeastern Sinai,Egypt

This study is concerned with the radioactivity and mineralogy of the younger granites and pegmatites in the Wadi Haleifiya area, southeastern Sinai Peninsula, Egypt. The area is occupied by metasediments, migmatites, older and younger granites. Most of these rocks, especially granites, are dissected by mafic and felsic dykes as well as pegmatites. The younger granites are represented by three main varieties: monzogranites, syenogranites and alkali feldspar granites. The monzogranite consists essentially of quartz, plagioclase, potash feldspar and biotite with minor musco-vite. Iron oxide, titanite, zircon and allanite are the main accessory minerals. Syenogranite is massive, medium- to coarse-grained and commonly exhibits equigranular and hypidiomorphic textures. It is made up essentially of potash feldspar, quartz, plagioclase and biotite. Iron oxides, allanite, epidote, titanite, and zircon are accessory minerals. The alkali feldspar granite consists mainly of perthite, quartz, alkali amphibole (arfvedsonite and riebekite), biotite, sub-ordinate plagioclase and aegirine. Iron oxide, zircon and apatite are accessory minerals, whereas chlorite and sas-surite are secondary minerals. The altered monzogranite and pegmatite recorded high radioelement contents. The eU reaches up to 120 (av.=82×10-6) in the altered monzogranite and up to 55 (av.=27×10-6) in the pegmatites. The high radioactivity in the altered monzogranite is due to the presence of thorite, uranothorite and metamict zircon. In the pegmatites, it is re-lated to the presence of uranophane, uranothorite, thorite, zircon, samarskite, monazite, xenotime, magnetite, ilmen-ite, hematite and rutile.     

Mineralogy,M-type tetrad effect and radioactivity of altered granites at the G. Abu Garadi shear zone,central Eastern Desert,Egypt

The G. Abu Garadi area is covered mainly by metasediments, alkali feldspar granites and stream sediments. The alkali feldspar granite is traversed by a major strike-slip fault trending in an N-S direction as well as two subordinate sets of faults trending NW to WNW for the first one and NE for the second one. These faults represent the shear zones affected by magmatic (syngenetic) as well as hydrothermal (epigenetic) activities causing alteration of the granitic rocks. The most common alteration features are albitization, greisenization and koalinitization. The mass balance calculations of the studied altered samples show enrichments in Zr, Y, Ni, U, Th and Ga and depletions in Zn, Sr, Nb, Ba, Pb, Cu and V. Only the greisenized samples exhibit a significant enrichment in Nb, ∑REE budget and pronounced lanthanide tetrad effect (M-type), especially TE1,4, while weakly expressed tetrad effects are for the other albitized and koalinitized samples. Mineralogically, the common accessory minerals in the altered samples include samarskite-(Y), betafite, uranothorite, zircon, fluorite and cassiterite. The greisenized granites contain high eU and eTh than the other altered types, where they are characterized by an assemblage of the radioactive minerals; samarskite-(Y), betafite, uranothorite in addition to zircon. The inter-element relationships between U and Th and also their ratios illustrate that the radioelement distribution in these granites is mainly governed by magmatic processes, in addition to post-magmatic ones. The distribution of chemical elements and the fractionation of some isovalents within the shear zone are largely controlled by the newly formed mineral phases. With respect to uranium mobilization, uranium migrated from the host alkali feldspar granites of G. Abu Garadi, while the shear zones acted as traps for the migrated uranium. Moreover, U migrated in the shear zone during greisenization and albitization, and migrated out during koalinitization.     

Temporal evolution of weathered cataclastic material in gravitational faults of the La Clapiere deep-seated landslide by mechanical approach

After a few years of research, the observation and the analysis of the deep-seated landslides suggest that these are mainly controlled by tectonic structures, which play a dominant role in the deformation of massif slopes. The La Clapière deep-seated landslide (Argentera Mercantour massif) is embedded in a deep-seated gravitational slope deformation affecting the entire slope, and characterized by specific landforms (trenches, scarps??). Onsite, the tangential displacement direction of the trenches and the scarps are controlled by the tectonic structures. The reactivation of the inherited fault in gravitational faults create a gouge material exposed to an additional mechanical and chemical weathering as well as an increased of leaching. The displacement of these reactivated faults gets increasingly important around the area of the La Clapière landslide and this since 3.6?ka BP. In this study, mechanical analysis and grain size distributions were performed and these data were analysed according to their proximity the La Clapiere landslide and times of initiation of the landslide by ¹⁰Be dating. Triaxial test results show that the effective cohesion decreases and the effective angle of internal friction increases from the unweathered area to the weathered area. The whole distribution of the grain size indicates that the further the shear zone is open or developed, the further the residual material loses its finest particles. This paper suggests that the mechanical evolution along the reactivated fault is influenced by the leaching processes. For the first time, we can extract from these data temporal behaviour of the two main mechanical parameters (cohesion and angle of internal friction) from the beginning of the La Clapiere landslide initiation (3.6 ka BP) to now.     

Contribution of gravity and magnetic data in delineating the subsurface structure of Hammam Faroun area, Gulf of Suez, Egypt

The Hammam Faroun has a particular importance due to its geothermal activity which constitutes the main geothermal resource of Egypt. The area is located on the Sinai Peninsula, a subplate bounded by two seismically active structural zones along the Gulf of Suez and Gulf of Aqaba. High-resolution ground-based gravity and magnetic data are available for the entire Hammam Faroun area, acquired as part of a national project to explore for mineral, geothermal, and hydrocarbon resources. Gravity and magnetic data were analyzed using Source Edge Detection and Source Parameter Imaging (SPI) techniques to image subsurface structures. These analyses show that the area is characterized by a set of northwest-striking faults lying parallel to the Gulf of Suez. Orthogonal patterns are also present, possibly related to rifting of the Gulf of Suez. Depth analysis using the SPI method indicates that surface faults extend to 5-km depth. Analysis of potential-field data elucidates the structurally complex subsurface structure of the Hammam Faroun area.     

Clustering current climate regions of Turkey by using a multivariate statistical method

In this study, the hierarchical clustering technique, called Ward method, was applied for grouping common features of air temperature series, precipitation total and relative humidity series of 244 stations in Turkey. Results of clustering exhibited the impact of physical geographical features of Turkey, such as topography, orography, land–sea distribution and the high Anatolian peninsula on the geographical variability. Based on the monthly series of nine climatological observations recorded for the period of 1970–2010, 12 and 14 clusters of climate zones are determined. However, from the comparative analyses, it is decided that 14 clusters represent the climate of Turkey more realistically. These clusters are named as (1) Dry Summer Subtropical Semihumid Coastal Aegean Region; (2) Dry-Subhumid Mid-Western Anatolia Region; (3 and 4) Dry Summer Subtropical Humid Coastal Mediterranean region [(3) West coast Mediterranean and (4) Eastern Mediterranean sub-regions]; (5) Semihumid Eastern Marmara Transition Sub-region; (6) Dry Summer Subtropical Semihumid/Semiarid Continental Mediterranean region; (7) Semihumid Cold Continental Eastern Anatolia region; (8) Dry-subhumid/Semiarid Continental Central Anatolia Region; (9 and 10) Mid-latitude Humid Temperate Coastal Black Sea Region [(9) West Coast Black Sea and (10) East Coast Black Sea sub-regions]; (11) Semihumid Western Marmara Transition Sub-region; (12) Semihumid Continental Central to Eastern Anatolia Sub-region; (13) Rainy Summer Semihumid Cold Continental Northeastern Anatolia Sub-region; and (14) Semihumid Continental Mediterranean to Eastern Anatolia Transition Sub-region. We believe that this study can be considered as a reference for the other climate-related researches of Turkey, and can be useful for the detection of Turkish climate regions, which are obtained by a long-term time course dataset having many meteorological variables.     

Étude de la circulation verticale dans l'estuaire du Saint‐Laurent au moyen de la modélisation mathématique

Résumé

Un modèle bidimensionnel dans le sens vertical est utilisé afin d'étudier et de simuler la circulation marine engendrée par la marée dans l'estuaire du Saint‐Laurent. A partir d'une schématisation de l'Estuaire et de conditions en niveaux d'eau et salinités aux extrémités aval et amont du domaine d'étude, ce modèle génère la répartition des hauteurs d'eau et les distributions longitudinales et verticales de vitesses et salinités. Les résultats permettent alors de déduire les circulations instantanées obtenues aux différentes heures de la marée. Celles‐ci mettent en évidence des phénomènes physiques caractéristiques de l'estuaire du Saint‐Laurent et qui ont été plusieurs fois observés. Parmi ceux‐ci, les processus les plus importants concernent les marées internes, la remontée d'eau profonde et les effets des gradients horizontaux de salinités sur les profils verticaux de vitesse.     

Recent trends in precipitation in Eastern Canada: Research note

Abstract

The changes in normal precipitation amounts from 1931–60 to 1951–80 are examined for stations in Eastern Canada. The area covered comprises the Maritime Provinces and those parts of Ontario and Quebec south of a line approximately 200 km north of Lakes Erie and Ontario and the St Lawrence River. Changes are computed for each of the four seasons and for the entire year. On the whole, precipitation has increased, especially in winter and summer. However, there is considerable variation throughout the area, with precipitation decreasing in some regions. General circulation models that simulate the effect of doubling atmospheric CO₂ also show an increase in precipitation.     

Storm surges in Canadian waters

Abstract

Storm surges in various Canadian waters are reviewed. Following a brief discussion of the weather systems that cause storm surges in Canadian coastal and inland waters, the mathematical formulations to describe the development of storm surges are given. In reviewing storm surges in the different Canadian waters, particular attention is given to describe the influence of the presence of sea ice on surge development and the impact of shallow coastal areas, where the coastline configuration is itself changed by the surge, on inland penetration of the storm surge. The Canadian waters that may be affected by storm surges include the east and west coasts, the Beaufort Sea, the Gulf of St. Lawrence and the St. Lawrence estuary, Hudson Bay and the Great Lakes.