Hierarchical decomposition of variance with applications in environmental mapping based on satellite images

A quadtree-based image segmentation procedure (HQ) is presented to map complex environmental conditions. It applies a hierarchical nested analysis of variance within the framework of multiresolution wavelet approximation. The procedure leads to an optimal solution for determining mapping units based on spatial variability with constraints on the arrangement and shape of the units. Linkages to geostatisiics are pointed out, but the HQ decomposition algorithm does not require any homogeneity criteria. The computer implementation can be parameterized by either the number of required mapping units or the maximum within-unit variance, or it can provide a spectrum of significances of nested ANOVA. The detailed mathematical background and methodology is illustrated by a salt-affected grassland mapping study (Hortobágy, Hungary), where heterogeneous environmental characteristics have been sampled and predicted based on remotely sensed images using these principles.     

Runoff Simulation of Three Gorges Area in the Upper Yangtze River during 1998 Flood Season

The contribution of areal precipitation of the catchment from Cuntan to Yichang (Three Gorges area) to eight flood peaks of the Upper Yangtze River (the upper reaches of the Yangtze River) is diagnosed for 1998 flood season. A rainfall-runoff model is employed to simulate runoffs of-this catchment. Comparison of observed and simulated runoffs shows that the rainfall-runoff model has a good capability to simulate the runoff over a large-scale river and the results describe the eight flood peaks very well. Forecast results are closely associated with the sensitivity of the model to rainfall and the calibration processes. Other reasons leading to simulation errors are further discussed.     

Geochemical exploration of a Precambrian Batholith, source of a Cu-W mineralization of the tourmaline breccia in Southern Finland

The Hämeenkyrö batholith is a round-shaped plutonic body of an areal size of 147 km². It is composed of calc-alkaline to alkaline rocks that intruded previously metamorphosed Svecofennian volcanogenic and sedimentary schists 1860 Ma ago. The Cu-W bearing tourmaline breccia of the Ylörvi deposit occurs in metavolcanic rocks close to the eastern contact of the batholith.The average sampling density in the batholith was 1 sample per km², and 175 samples were analyzed for Cu, Au, Ag, Ni, Pb, Co, Zn, S by AAS for SiO₂, TiO₂, Al₂O₃, FeO, MnO, MgO, CaO, Na₂O, K₂O, As, Sn and P by X-ray fluorescence. Mo and W were determined colorimetrically. Barth mesonorms were calculated for each sample and the rock type was determined according to Streckeisen's classification. Element distributions are displayed on contour maps.The rock types of the batholith exhibit an asymmetric concentric arrangement, the order from the center towards the margin being alkali-feldspar granite, syenogranite, monzogranite, quartz monzonite, quartz syenite, alkali-feldspar, quartz syenite, syenite and alkali-feldspar syenite. Anomalously high Cu, As, Sn, S, K₂O and Na₂O contents have been found at the eastern margin of the batholith in a N—S-trending zone, which is characterized by hydrothermal alteration phenomena, propylitization, tourmalinization and scapolitization. Three anomalous areas have been defined within this zone, one of them is associated with the Ylöjärvi deposit and the other two are regarded as exploration targets.     

A simple geometric model of sedimentary rock to connect transfer and acoustic properties

A simple rock model is presented which reproduces the measured hydraulic and electric transport properties of sedimentary rocks and connects these properties with each other, as well as with the acoustic propagation velocities and elastic moduli. The model has four geometric parameters (average coordination number Z of the pores, average pore radius r, average distance between nearest pores d, and average throat radius δ) which can be directly determined from the measured porosity Φ, hydraulic permeability k, and cementation exponent m of the rock via simple analytic expressions. Inversion examples are presented for published sandstone data, and for cores taken from Saudi Arabian, Upper Jurassic and Permian carbonate reservoirs. For sandstone, the inversion works perfectly; for carbonates, the derived rock model shows order-of-magnitude agreement with the structure seen in thin sections. Inverting the equations, we express the transfer properties Φ, k, and m as functions of r, d, δ, and Z. Formulae are derived for the bulk density D _b, formation factor F, and P-wave velocity in terms of the proposed geometrical parameters.     

Types and nature of fracture associated with Late Ordovician paleochannels of glaciofluvial Sarah Formation,Qasim region,Central Saudi Arabia

This study evaluates the Late Ordovician glaciofluvial deposits of the Sarah Formation and equivalent outcroppings in north, central, and southwestern Saudi Arabia. The Sarah Formation also covers a wide area in the subsurface and is considered as an important target for unconventional tight gas reservoir. Defining the fracture types, nature, and distribution in outcrop scale might help to establish a successful fracture simulation model and behavior for the Sarah tight gas reservoir in the subsurface. This study investigates fracture characteristics for the Sarah Formation at Sarah paleochannel outcrops. The study revealed three sets of fractures, which have EW, NS, and SE-NW directions, and these fractures vary from open, resistive, and filled to resistive fractures. The closed fractures are filled with ferruginated iron oxides and gypsum. The filled fractures (the thrust boundary) are found in the study area at the SE-NW strike fracture set, while open and resistive fractures are found mainly at S-N and E-W fracture sets, respectively. The syn-depositional filled fractures (iron oxides) are considered as the younger fracture sets while the open and resistive fractures are post-depositional fractures which may have resulted from uplift or tectonic movement. A general model representing the fracture pattern and the thrusting boundaries due to glacial movement was constructed. It has been noticed that the systematic occurrence of filled fractures (thrust boundaries) described the boundaries between different glacial events, which act as a fluid barrier (filled fractures) and decrease the reservoir quality. The finding of this study might be utilized as a guide and lead for exploration in the subsurface Sarah glacial deposits. It will also help to understand and speculate the nature pattern and distribution of fractures with the Sarah Formation.