Fault displacement modelling using 3D vector fields

In history matching and sensitivity analysis, flexibility in the structural modelling is of great importance. The ability to easily generate multiple realizations of the model will have impact both on the updating workflow in history matching and uncertainty studies based on Monte Carlo simulations. The main contribution to fault modelling by the work presented in this paper is a new algorithm for calculating a 3D displacement field applicable to a wide range of faults due to a flexible representation. This gives the possibility to apply this field to change the displacement and thereby moving horizons and fault lines. The fault is modelled by a parametric format where the fault has a reference plane defined by a centre point, dip and strike angles. The fault itself is represented as a surface defined by a function z = f(x,y), where x, y and z are coordinates local to the reference plane, with the z-axis being normal to the plane. The displacement associated with the fault outside the fault surface is described by a 3D vector field. The displacement on the fault surface can be found by identifying the intersection lines between horizons and the fault surface (fault lines), and using kriging techniques to fill in values at all points on the surface. Away from the fault surface the displacement field is defined by a monotonic decreasing function which ensures zero displacement at a specified distance from the fault. An algorithm is developed where the displacement can be increased or decreased according to user-defined parameters. This means that the whole displacement field is changed and points on horizons around the fault can be moved accordingly by applying the modified displacement field on them. The interaction between several faults influencing the same points is taken care of by truncation rules and the ordering of the faults. The method is demonstrated on a realistic synthetic case based on a real reservoir.     

Late Quaternary marine-based Kara Sea ice sheets: a review of terrestrial stratigraphic data highlighting their formation

Reconstructions of the Late Quaternary glacial history of the Kara Sea area show repeated build-up of ice-sheet domes over the shallow epicontinental Kara Sea. Inferred ice divides were situated over the central Kara Sea, and the ice sheet repeatedly inundated the surrounding coastal areas of western Siberia. Geological fingerprinting of the Kara Sea ice sheet include end moraine zones, raised beaches, tills, glaciotectonic deformations and coarsening-upward sediment sequences, reflecting isostatic rebound cycles. This paper reviews evidence from several areas along the perimeter of the Kara Sea, suggesting that peripheral sites were critical for the initiation of the large Kara Sea ice sheet. Ice-sheet inception progressed with the formation of local ice caps that later coalesced on the adjacent shelf with globally falling sea levels, eventually merging and growing into a large ice dome.     

Spatio-temporal prediction of daily temperatures using time-series of MODIS LST images

A computational framework to generate daily temperature maps using time-series of publicly available MODIS MOD11A2 product Land Surface Temperature (LST) images (1 km resolution; 8-day composites) is illustrated using temperature measurements from the national network of meteorological stations (159) in Croatia. The input data set contains 57,282 ground measurements of daily temperature for the year 2008. Temperature was modeled as a function of latitude, longitude, distance from the sea, elevation, time, insolation, and the MODIS LST images. The original rasters were first converted to principal components to reduce noise and filter missing pixels in the LST images. The residual were next analyzed for spatio-temporal auto-correlation; sum-metric separable variograms were fitted to account for zonal and geometric space-time anisotropy. The final predictions were generated for time-slices of a 3D space-time cube, constructed in the R environment for statistical computing. The results show that the space-time regression model can explain a significant part of the variation in station-data (84%). MODIS LST 8-day (cloud-free) images are unbiased estimator of the daily temperature, but with relatively low precision (±4.1°C); however their added value is that they systematically improve detection of local changes in land surface temperature due to local meteorological conditions and/or active heat sources (urban areas, land cover classes). The results of 10–fold cross-validation show that use of spatio-temporal regression-kriging and incorporation of time-series of remote sensing images leads to significantly more accurate maps of temperature than if plain spatial techniques were used. The average (global) accuracy of mapping temperature was ±2.4°C. The regression-kriging explained 91% of variability in daily temperatures, compared to 44% for ordinary kriging. Further software advancement—interactive space-time variogram exploration and automated retrieval, resampling and filtering of MODIS images—are anticipated.     

Calibrating adaptive antenna arrays for high-integrity GPS

A major challenge in using GPS guidance for aircraft final approach and landing is to reject interference that can jam reception of the GPS signals. Antenna arrays, which use space–time adaptive processing (STAP), significantly improve the signal to interference plus noise ratio, but at the possible expense of distorting the received signals, leading to timing biases that may degrade navigation performance. Rather than a sophisticated calibration approach to remove biases introduced by STAP, this paper demonstrates that a relatively compact calibration strategy can substantially reduce navigation biases, even under elevated interference conditions. Consequently, this paper develops an antenna bias calibration strategy for two classes of adaptive array algorithm and validates this method using both simulated and experimental data with operational hardware in the loop. A proof-of-concept system and an operational prototype are described, which implement the adaptive antenna algorithms and deterministic corrections. This investigation demonstrates that systems with adaptive antenna arrays can approach the accuracy and integrity requirements for automatic aircraft landing, and in particular for sea-based landing on board aircraft carriers, while simultaneously providing significant attenuation of interference. Evidence suggests that achieving these goals is possible with minimal restrictions on system hardware configuration—specifically, limitations on the permissible level of antenna anisotropy and the use of sufficient analog-to-digital converter resolution.     

A solubility and surface complexation study of a non-stoichiometric hydroxyapatite

The dissolution and surface complexation of a non-stoichiometric hydroxyapatite (Ca_8.4(HPO₄)_1.6(PO₄)_4.4(OH)_0.4), (HAP) was studied in the pH range 3.5-10.5, at 25 °C in 0.1 M Na(Cl). The results from well-equilibrated batch experiments, potentiometric titrations, and zeta-potential measurements were combined with information provided by Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The information from the analyses was used to design an equilibration model that takes into account dissolution, surface potential, solution and surface complexation, as well as possible phase transformations. The results from the XPS measurements clearly show that the surface of the mineral has a different composition than the bulk and that the Ca/P ratio of the surface layer is 1.4 ± 0.1. This ratio was also found in solution in the batches equilibrated at low pH where the dominating reaction is dissolution. In the batches equilibrated at near neutral pH values, however, the Ca/P ratio in solution attains values as high as 25, which is due to re-adsorption of phosphate ions to the HAP surface. The total concentration of protons as well as the total concentration of dissolved calcium and phosphate in solution were used to calculate a model for the dissolution and surface complexation of HAP. The constant capacitance model was applied in designing the following surface complexation model:

     

Patterns and Levels of Organochlorines (DDTs, PCBs, non-ortho PCBs and PCDD/Fs) in Male Harbour Porpoises (Phocoena phocoena) from the Baltic Sea, the Kattegat-Skagerrak Seas and the West Coast of Norway

Patterns and levels of chlorinated aromatic contaminants (DDTs, PCBs, non-ortho PCBs and PCDD/Fs) in blubber tissue were compared among six sample groups of male harbour porpoises (Phocoena phocoena) from the Baltic Sea, the Kattegat-Skagerrak Seas and the west coast of Norway. A principal component and classification analysis showed that mature harbour porpoises from the Baltic had significantly different contaminant patterns than animals from the Kattegat-Skagerrak and Norway. ANOVAs showed that mature porpoises from the Baltic had higher levels of ΣPCB and several individual PCBs and PCDD/Fs than the Kattegat-Skagerrak and the Norwegian samples and higher ΣDDT than the Norwegian. A comparison between immature porpoises showed that Baltic animals had higher levels of ΣPCDD/F than the corresponding sample from the Kattegat-Skagerrak. The levels of ΣDDT, ΣPCB and Σnon-ortho PCB were significantly higher in animals collected during 1978–81 compared to animals collected in 1988–90 indicating a temporal decline of these organochlorines in the Kattegat-Skagerrak Seas. The contaminant levels recorded in the Baltic Sea are a serious cause for concern and could have management implications for the already threatened harbour porpoises in this area.     

The Tarfala Mass Balance Programme

The Tarfala mass balance programme currently comprises seven glaciers distributed in two, one southerly and one northerly, east-west trending profiles. Of the studied glaciers, Storglaciären has the longest record spanning 1945 to present. The purpose of the programme is to study gradients in mass balance parameters across the northern Scandinavian mountains. The measurements of both winter and summer balance are carried out with significant redundancy each year. In order to maintain such a large programme with limited personnel, different measurement techniques and strategies are applied to the different glaciers according to a priority scale. Storglaciären is the most important glacier in the network and is measured with high accuracy and measurement density. Storglaciren is also used as a reference for all other glaciers in the programme. The other glaciers have sparser measurement systems and are sometimes measured using alternative methods such as snow radar. In general, Swedish glaciers are still responding to the major climatic warming around 1910–1920 by retreat, and the effect of very long response times. However, measured volume change indicates that most glaciers are close to or varying around a quasi-steady state.     

Time dependence of organic matter decay and mixing processes in Framvaren, a permanently anoxic fjord in South Norway

Three different layers have been identified in Framvaren, which has a maximum water depth of 184 m. One oxic layer above the redoxcline at 18–20 m. One anoxic layer from 20 to 100 m which is occasionally ventilated by a flow over the sill (which has a depth of 2.5 m), and finally a stagnant layer below 100 m. Using the release rate of silica from the bottom and measurements of the concentration of HTO it is possible to make some calculations on the annual volume of interleaving in the layers 25–50 m, 50–75 m, and 75–100 m together with the advective flows. Reliable values of the sulfide concentration were obtained by precipitating and weighing HgS together with careful protection of all anoxic water samples with argon. The light yellow color of the precipitate in the depth range 25 to 80 m indicates that the occasional ventilation will cause such reactions as 0.50₂ + H₂S S(colloidal) + H₂O. The elemental sulfur, being stabilized with HS^–, is set free upon the precipitation of HgS. The new data for the concentration of sulfide give an acceptable stoichiometry for the decay reaction of organic matter. This is not the case with the data of Yao and Millero. The mean values for the concentrations of ammonium and phosphate agree with the new data of Yao and Millero. The mol/mol C/N ratio of 10.1 found in trapped material by Naess and coworkers (1988) agrees with the stoichiometry of the dissolved constituents, i.e. C/N = 9.92 ± 0.45. A denitrification reaction is suggested to explain the high values of C/N. The vertical diffusion coefficient at 100 m calculated from the depth profile of silica was 0.92 × 10^–6 m² s^–1 which lies in the range of values given by Fröyland. Finally, the ¹⁴C age of the total dissolved inorganic carbon (Ct) in the water below 90 m was about 1600 years indicating a bioproduction in the period 8000 years B.P. to A.D. 1853 when a channel was opened between the fjord outside (Helvikfjord) and Framvaren.     

Micas of the muscovite-lepidolite series from the fregeneda pegmatites (Salamanca,Spain)

Summary In the Fregeneda area different types of pegmatites can be recognized by their mineralogy, morphology, internal structure and field relationships. The most common type corresponds to a simple pegmatite with homogeneous internal structure, but zoned Li-bearing pegmatites also are relatively widespread. Cassiterite-bearing pegmatites are subordinate. The pegmatites are spatially associated to the Lumbrales granite. This is a parautochthonous, fine- to medium-grained, two-mica granite, one of the syntectonic massifs which were deformed during the third phase of Hercynian deformation. Representative micas selected from the different groups of pegmatites were studied to determine wether the pegmatites can be related by a common fractionation path, and how different pegmatite types are related to the spatially associated Lumbrales granite. Compositional variations in the micas depend on the pegmatite type. Muscovite coexisting with Li-micas in the Li-bearing pegmatites is one of the richest in Al₂O₃ (35.4–37.7 wt%) and the poorest in FeO (0.2–1.5 wt%) and MgO (0–0.3 wt%), whereas muscovite of the simple discordant pegmatites shows the highest FeO (2.2–3.3 wt%) and that from the Lumbrales granite is the richest in MgO (0.5–0.7 wt%) and TiO₂ (0.6–1.1 wt%). On the other hand, Sn (70–1168 ppm), Li (< 5–22253 ppm), F (880–21470 ppm), Cs (< 5–1696 ppm), Rb (800–9181 ppm) and other trace elements seem to increase with distance from the Lumbrales granite, and K/Rb decreases. According to this ratio, the exterior Li-bearing pegmatites are the more evolved, whereas the interior pegmatites are less evolved, and are richer in Cs, Li and Zn than other pegmatite types.

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Glimmerminerale der Muscovit-Lepidolith-Serie aus den Pegmatiten von Fregeneda, Salamanca, Spanien

Zusammenfassung Im Gebiet von Fregeneda sind auf Grund ihrer Mineralogie, Morphologie, Internstruktur und Geländebeziehungen verschiedene Pegmatittypen zu unterscheiden. Am häufigsten sind einfache homogen aufgebaute Pegmatite. Zonar gebaute Li-Pegmatite sind ebenfalls weit verbreitet, Zinnstein-führende Pegmatite treten hingegen zurück, Die Pegmatite sind räumlich mit dem Lumbrales Granit, einem paraautochtonen, fein- bis mittelkörnigen Zwei-Glimmergranit, assoziiert, Dieser gehört einem der syntektonischen Massive, die während der dritten Phase der hercynischen Deformation deformiert wurden, an. Repräsentative, aus den verschiedenen Pegmatittypen separierte Glimmerminerale wurden untersucht, um zu klären, inwieweit die Pegmatite über einen direkten Fraktionierungspfad zu verbinden sind und in welcher Beziehung sie zu dem Lumbrales Granit stehen. Die Variation der Zusammensetzung der Glimmer hängt vom Pegmatittyp ab. Muscovite, die mit Li-Glimmern koexistieren, sind die relativ Al₂O₃-reichsten (32–37.7 Gew.%) und Fe- (0.2–1.5 Gew.%.) und Mg-ärmsten (0–0.3 Gew.%). Jene aus dem Lumbrales Granit sind die reich an MgO (0.5–0.7) und TiO₂ (0.6–1.1 Gew.%). Die Gehalte von Sn (70–1168 ppm), Li (< 5–22253 ppm). F (880-21470 ppm), Cs (< 5–1696 ppm), Rb (800–9181 ppm) und anderer Spurenelemente nehmen mit der Entfernung vom Lumbrales Granit zu, während K/Rb abnimmt. Auf Grund dieses Verhältnisses sind die externen Li-führenden Pegmatite höher, die internen Pegmatite hingegen geringfügiger entwickelt. Erstere sind daher auch reicher an Cs, Li und Zn.

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With 4 Figures