Recent Sea Level and Sea Surface Temperature Trends Along the Bangladesh Coast in Relation to the Frequency of Intense Cyclones     

Tariq Masood Ali Khan  O. P. Singh  Md. Sazedur Rahman 《Marine Geodesy》2013,36(2):103-116

The French Transportable Laser Ranging System (FTLRS) was deployed in the calibration site of satellite radar altimeters in Corsica over the 2002 and 2005 campaigns. The paper describes the different steps of SLR data processing. The average arcs RMS obtained are about 1–2 cm for Lageos-1&;-2, Starlette and Stella satellites; it is shown that the best results of satellite orbits determination and geocentric positioning are obtained with Eigen-Grace03s gravity model. The difference of FTLRS absolute 3D positioning, between 2002 and 2005, of about 7.7 mm (i.e., 2.6 mm/yr) is less than residual errors of ITRF2005 velocities (of about 4.3 mm/yr).  相似文献   

Traveltime computation with the linearized eikonal equation for anisotropic media   总被引：1，自引：0，他引：1  

Tariq Alkhalifah 《Geophysical Prospecting》2002,50(4):373-382

A linearized eikonal equation is developed for transversely isotropic (TI) media with a vertical symmetry axis (VTI). It is linear with respect to perturbations in the horizontal velocity or the anisotropy parameter η. An iterative linearization of the eikonal equation is used as the basis for an algorithm of finite-difference traveltime computations. A practical implementation of this iterative technique is to start with a background model that consists of an elliptically anisotropic, inhomogeneous medium, since traveltimes for this type of medium can be calculated efficiently using eikonal solvers, such as the fast marching method. This constrains the perturbation to changes in the anisotropy parameter η (the parameter most responsible for imaging improvements in anisotropic media). The iterative implementation includes repetitive calculation of η from traveltimes, which is then used to evaluate the perturbation needed for the next round of traveltime calculations using the linearized eikonal equation. Unlike isotropic media, interpolation is needed to estimate η in areas where the traveltime field is independent of η, such as areas where the wave propagates vertically.
Typically, two to three iterations can give sufficient accuracy in traveltimes for imaging applications. The cost of each iteration is slightly less than the cost of a typical eikonal solver. However, this method will ultimately provide traveltime solutions for VTI media. The main limitation of the method is that some smoothness of the medium is required for the iterative implementation to work, especially since we evaluate derivatives of the traveltime field as part of the iterative approach. If a single perturbation is sufficient for the traveltime calculation, which may be the case for weak anisotropy, no smoothness of the medium is necessary. Numerical tests demonstrate the robustness and efficiency of this approach.  相似文献   

Late Quaternary stratigraphy and paleo-oceanography of the Grand Banks continental margin, eastern Canada     

MAHMOOD ALAM  DAVID J. W. PIPER  H. BASIL S. COOKE 《Boreas: An International Journal of Quaternary Research》1983,12(4):253-261

Quaternary sediments cored on the continental slope off the Grand Banks and on nearby seamounts and abyssal hills have been correlated back to at least isotopic stage 6. using lithologic and hioslratigraphic markers and warm-cold cyclicity in microfossil assemblages. The sequence is dated using limited oxygen isotope and ^l4C data. The oldest continental slope cores penetrate to a glacial stade with an extrapolated age of 50. 0(H) B. P. The oldest scamount cores probably penetrate to isotopic stage 13. Watcrmass distribution over the area results from interaction of the Labrador Current with locally generated shelf water, and to a lesser extent, the Gulf Stream. Planktic foraminiferal assemblages and sedimentological evidence suggest that arctic Labrador Current core water extends onto the eastern Grand Banks only during full interglacials. During intcrstadials, this arctic core water is absent, probably because its source-was blocked by ice. Cold water during stadials probably results mostly from local cooling on the continental shelf.  相似文献   

Limnology of four saline lakes in western Victoria, Australia: I. Physico-chemical parameters     

Tariq A. Khan   《Limnologica》2003,33(4):316-326

Major physico-chemical parameters of four saline lakes (Lake Colac, Modewarre, Bolac and Tooliorook), in the volcanic plains of western Victoria (Australia), recorded bi-monthly between November 1999–September 2001 are described. Lakes are permanent, large (surface area range 3.5–29.6 km²) and shallow (mean depth range 1.5–3.9 m). Physico-chemical parameters revealed that lakes were homogenous with few differences between sites within lakes. Of the four lakes, Lake Modewarre had the highest salinity of 8 ppt with weak seasonal fluctuations in salinity in all the lakes. All the lakes were turbid (turbidity range 30–659 NTU), with low light penetration (suspended solids range 23–465 mg l⁻¹) and low Secchi depth (Secchi depth range 7.7–89 cm). pH of the lakes varied between 8.2–9.3 with low seasonal variations, indicating well buffered waters. Based on nutrient status, lakes were classified as eutrophic to highly eutrophic with higher nutrient concentrations. Nitrogen was limiting in one lake (Lake Colac) and phosphorus in the other three lakes. Meteorological events probably influence the physico-chemical parameters of these lakes strongly.  相似文献   

Residual dip moveout in VTI media     

Tariq Alkhalifah  Maarten V. de Hoop 《Geophysical Prospecting》2005,53(1):1-12

Dip‐moveout (DMO) correction is often applied to common‐offset sections of seismic data using a homogeneous isotropic medium assumption, which results in a fast execution. Velocity‐residual DMO is developed to correct for the medium‐treatment limitation of the fast DMO. For reasonable‐sized velocity perturbations, the residual DMO operator is small, and thus is an efficient means of applying a conventional Kirchhoff approach. However, the shape of the residual DMO operator is complicated and may form caustics. We use the Fourier domain for the operator development part of the residual DMO, while performing the convolution with common‐offset data in the space–time domain. Since the application is based on an integral (Kirchhoff) method, this residual DMO preserves all the flexibility features of an integral DMO. An application to synthetic and real data demonstrates effectiveness of the velocity‐residual DMO in data processing and velocity analysis.  相似文献   

Vegetation and soil characteristics of the wasteland of Valika Chemical Industries near Manghopir, Karachi     

Tariq Mehmood  Zafar M. Iqbal 《Journal of Arid Environments》1995,30(4)

The vegetation of the wasteland of Valika chemical industries near Manghopir road, Karachi was studied. Nine plant communities were recognized based on dominant species. In these plant communities the vegetation was disturbed, mostly halophytic and dominated bySuaeda fruticosa,Tamarix indica,Salsola baryosma,Cressa cretica,Atriplex griffithii,Haloxylon recurvum,Indigofera hochstetteri,Prosopis julifloraandChenopodium album.The physico-chemical properties of the soils were also analysed. Soil texture was mostly sandy loam, which exhibited slight variations in the water-holding capacity. The soils contained a sufficient amount of CaCO₃⁻and exhibited mostly alkaline soil pH. The soils of the different plant communities had scarcely any organic matter or inorganic phosphorus. The exchangeable sodium in the soils of many halophytic plant communities was high, with appreciable concentrations of potassium.  相似文献   

Hydro-economic analysis of groundwater pumping for irrigated agriculture in California’s Central Valley,USA     

Josué Medellín-Azuara  Duncan MacEwan  Richard E. Howitt  George Koruakos  Emin C. Dogrul  Charles F. Brush  Tariq N. Kadir  Thomas Harter  Forrest Melton  Jay R. Lund 《Hydrogeology Journal》2015,23(6):1205-1216

  相似文献   

The evolution of an electrical fittings industrial cluster in Pakistan     

Ullah  Sana  Majeed  Muhammad Tariq  Arif  Babur Wasim 《GeoJournal》2021,86(6):2657-2670

GeoJournal - This study provides an evolution process of electrical fittings industrial cluster in Pakistan by using two rounds of survey dataset (2008 and 2017) taken from the electrical fittings...  相似文献   

Biostratigraphy,Depositional and Diagenetic Processes in Carbonate Rocks from Southern Lebanon: Impact on Porosity and Permeability     

Hammad Tariq JANJUHAH  Josep SANJUAN  Mohammad ALQUDAH  Mohamed K. SALAH 《《地质学报》英文版》2021,95(5):1668-1683

Carbonate rocks contain prolific hydrocarbon reserves all over the world, particularly in the Middle East. For exploration and production strategies, it is essential to understand carbonate reservoirs in terms of their internal characteristics, depositional environment, relative age, diagenetic processes and impact on petrophysical properties. This study has been performed on exposed Cretaceous, Paleocene and Miocene marine carbonate sedimentary sequences in two localities (Maghdoucheh and Qennarit) near the city of Sidon (Southern Lebanon). It represents the first comprehensive study that takes into consideration the carbonate reservoir facies, diagenetic history and reservoir quality in the area. Rocks at Maghdoucheh are mainly dominated by limestone beds showing sedimentary structures and erosive bases alternating with microfossil-rich silty marls, related to a shallowing upward sequence in a restricted marine platform environment. Shells of benthic foraminifera and mollusks dominate the fossil assemblage extracted from the studied rocks. The microfossil and nannofossil assemblage detected in the Maghdoucheh sections indicates a middle Miocene age. Rocks at Qennarit are composed of mudstone/wackestone limestone beds rich in planktonic foraminifera and nannofossils related to open marine conditions. Based on the nannofossil content, rocks from Qennarit 1 and 2 are Paleocene and Cretaceous in age, respectively. Four main types of microfacies have been identified, i.e. (1) microbioclastic peloidal calcisiltite, (2) pelagic lime mudstone and wackestone with planktonic microfossils, (3) grainstone/packstone with abundant foraminifera and (4) fenestral bindstones, mudstones and packstones with porostromate microstructures. The porosity-permeability (poro-perm) analysis of representative samples reveals moderate to good porosity but very low permeability. This is mainly due to the presence of large moldic pores that are isolated in nature. The diagenetic features are dominated by micritization and dissolution (both fabric selective and non-fabric selective). Among all diagenetic features, dissolution in both localities contributes to porosity enhancement, while micritization, cementation, compaction and the filled fractures have negative impacts on permeability; hence the overall reservoir quality.  相似文献   

Use of GIS,Statistics and Machine Learning for Groundwater Quality Management: Application to Nitrate Contamination     

Judeh  Tariq  Almasri  Mohammad N.  Shadeed  Sameer M.  Bian  Hanbing  Shahrour  Isam 《Water Resources》2022,49(3):503-514

Water Resources - Groundwater NO3 contamination (GNC) threatens the drinkability of water in many countries worldwide. It could cause serious health problems and sometimes lead to death. This paper...  相似文献