Spatial Variability of Rock Depth in Bangalore Using Geostatistical, Neural Network and Support Vector Machine Models

Geospatial technology is increasing in demand for many applications in geosciences. Spatial variability of the bed/hard rock is vital for many applications in geotechnical and earthquake engineering problems such as design of deep foundations, site amplification, ground response studies, liquefaction, microzonation etc. In this paper, reduced level of rock at Bangalore, India is arrived from the 652 boreholes data in the area covering 220 km². In the context of prediction of reduced level of rock in the subsurface of Bangalore and to study the spatial variability of the rock depth, Geostatistical model based on Ordinary Kriging technique, Artificial Neural Network (ANN) and Support Vector Machine (SVM) models have been developed. In Ordinary Kriging, the knowledge of the semi-variogram of the reduced level of rock from 652 points in Bangalore is used to predict the reduced level of rock at any point in the subsurface of the Bangalore, where field measurements are not available. A new type of cross-validation analysis developed proves the robustness of the Ordinary Kriging model. ANN model based on multi layer perceptrons (MLPs) that are trained with Levenberg–Marquardt backpropagation algorithm has been adopted to train the model with 90% of the data available. The SVM is a novel type of learning machine based on statistical learning theory, uses regression technique by introducing loss function has been used to predict the reduced level of rock from a large set of data. In this study, a comparative study of three numerical models to predict reduced level of rock has been presented and discussed.     

Geostatistical modeling of the geological uncertainty in an iron ore deposit

This paper addresses the problem of quantifying the joint uncertainty in the grades of elements of interest (iron, silica, manganese, phosphorus and alumina), loss on ignition, granulometry and rock types in an iron ore deposit. Sampling information is available from a set of exploration drill holes. The methodology considers the construction of multiple rock type outcomes by plurigaussian simulation, then outcomes of the quantitative variables (grades, loss on ignition and granulometry) are constructed by multigaussian joint simulation, accounting for geological domains specific to each quantitative variable as well as for a stoichiometric closure formula linking these variables. The outcomes are validated by checking the reproduction of the data distributions and of the data values at the drill hole locations, and their ability to measure the uncertainty at unsampled locations is assessed by leave-one-out cross validation.Both the plurigaussian and multigaussian models offer much flexibility to the practitioner to face up to the complexity of the variables being modeled, in particular: (1) the contact relationships between rock types, (2) the geological controls exerted by the rock types over the quantitative variables, and (3) the cross-correlations and stoichiometric closure linking the quantitative variables. In addition to this flexibility, the use of efficient simulation algorithms turns out to be essential for a successful application, due to the high number of variables, data and locations targeted for simulation.     

Computer simulation of defect structure in sillimanite and mullites

 Defect structure and the defect formation in mullites and sillimanites have been investigated using computer simulation techniques. From point defect chemistry and computer simulations, oxygen vacancies are identified as the majority defect responsible for oxygen transport in mullite. The defect formation energies are between 3 and 4 eV. Using supercell calculation methods, the random structure is identified to be stable in mullites, whereas the ordered structure can be confirmed to be more stable in sillimanite. An energy of 0.7–1.0 eV for the association of oxygen vacancies with cations is estimated. Received: 11 May 2001 / Accepted: 12 December 2001     

An investigation of the environmental loads of Shei-Pa National Park in Taiwan

 Recreation is one of the functions of national parks. Nevertheless, heavy tourism has started to impose serious problems on the maintenance of some national parks in Taiwan. This study has tried to survey as well as calculate the impact problems resulting from park tourism in terms of environmental loads. A simple method is proposed to calculate the quantity of environmental loads. Only visitor information from questionnaires and per capita data are needed in the calculation process. Shei-Pa National Park was taken as an example. The water demand, the electricity used and the various forms of the environmental loads, including wastewater and solid waste discharge, were all surveyed and calculated on a per capita basis. Received: 21 July 1999 · Accepted: 8 November 1999     

Plan for a groundwater monitoring network in Taiwan

 In Taiwan, rapid economic growth, rising standards of living, and an altered societal structure have in recent years put severe demands on water supplies. Because of its stable quantity and quality, groundwater has long been a reliable source of water for domestic, agricultural, and industrial users, but the establishment of a management program that integrates groundwater and surface-water use has been hampered by the lack of groundwater data. In 1992, the Department of Water Resources (DWR) initiated a program entitled "Groundwater Monitoring Network Plan in Taiwan." Under this program, basic groundwater data, including water-level and water-quality data, are being collected, and a reliable database is being established for the purpose of managing total water resources. This paper introduces the goals, implementation stages, and scope of that plan. The plan calls for constructing 517 hydrogeologic survey stations and 990 groundwater monitoring wells within 17 years. Under this program, water-level fluctuations are continuously monitored, whereas water-quality samples are taken for analysis only at the initial drilling stage and, subsequently, at the time when a monitoring well is being serviced. In 1996, the DWR and the Water Resources Planning Commission were merged to form today's Water Resources Bureau. Received, July 1997 · Revised, February 1998 · Accepted, January 1998     

Upscaling of transmissivity,derived from specific capacity: a hydrogeomorphological approach applied to the Doon Valley aquifer system in India

Transmissivity (T) is one of the most important parameters in groundwater studies, and is generally estimated from pumping tests. T can also be deduced from abundantly available specific-capacity (Q/s) data by using analytical and/or empirical approaches, further upscaled by geostatistical methods. A different, remote sensing based, hydrogeomorphological approach is proposed, to upscale T from point- or well-scale to aquifer-scale, and it is applied to the piedmont alluvial aquifer system of Doon Valley in India. In the first step, Q/s and T data-pairs available from aquifer tests were used to establish an empirical, logarithmic relation. Subsequently, satellite imagery along with available data from published and unpublished maps, literature sources and ground surveys were used to divide the aquifer system into major hydrogeomorphological domains that control the groundwater occurrence and flow. Then, the T data derived from Q/s (using the empirical relation) and that available from pumping tests at well-scale were upscaled to aquifer-scale by averaging the T values within each hydrogeomorphological domain. Such a stratification approach is especially useful in areas where availability of only a few data-pairs of known Q/s and T limit the use of geostatistical techniques. A comparative study of the published empirical relations between Q/s and T in various hydrogeologic settings revealed that the relation obtained for Doon Valley aquifer system is close to that found for a similar alluvial aquifer system in Morocco.     

Laser-induced time-resolved luminescence as a tool for rare-earth element identification in minerals

 We have determined and distinguished a number of rare-earth elements in several minerals by use of laser-induced time-resolved luminescence spectroscopy. Unlike the conventional measurement of steady-state luminescence, the method allows discrimination between ions that emit in the same spectral range but have different decay times. The main new results are the following: decay time data for all REE luminescence centers; Tm³⁺, Pr³⁺, Er³⁺, Ho³⁺ luminescence in apatite, scheelite, zircon, calcite, and fluorite; Eu³⁺ luminescence in apatite, zircon, fluorite, calcite, danburite, and datolite. Received: 17 April 2000 / Accepted: 4 January 2001     

Water vulnerability assessment in karst environments: a new method of defining protection areas using a multi-attribute approach and GIS tools (EPIK method)

 Groundwater resources from karst aquifers play a major role in the water supply in karst areas in the world, such as in Switzerland. Defining groundwater protection zones in karst environment is frequently not founded on a solid hydrogeological basis. Protection zones are often inadequate and as a result they may be ineffective. In order to improve this situation, the Federal Office for Environment, Forests and Landscape with the Swiss National Hydrological and Geological Survey contracted the Centre of Hydrogeology of the Neuchatel University to develop a new groundwater protection-zones strategy in karst environment. This approach is based on the vulnerability mapping of the catchment areas of water supplies provided by springs or boreholes. Vulnerability is here defined as the intrinsic geological and hydrogeological characteristics which determine the sensitivity of groundwater to contamination by human activities. The EPIK method is a multi-attribute method for vulnerability mapping which takes into consideration the specific hydrogeological behaviour of karst aquifers. EPIK is based on a conceptual model of karst hydrological systems, which suggests considering four karst aquifer attributes: (1) Epikarst, (2) Protective cover, (3) Infiltration conditions and (4) Karst network development. Each of these four attributes is subdivided into classes which are mapped over the whole water catchment. The attributes and their classes are then weighted. Attribute maps are overlain in order to obtain a final vulnerability map. From the vulnerability map, the groundwater protection zones are defined precisely. This method was applied at several sites in Switzerland where agriculture contamination problems have frequently occurred. These applications resulted in recommend new boundaries for the karst water supplies protection-zones. Received: 27 October 1997 · Accepted: 4 July 1998     

Field variability of landslide model parameters

 A data set of parameters (slope, soil depth and soil shear strength) relevant to spatially distributed modelling of shallow landslides triggered by rain and snowmelt events was determined from field measurements in 250 grid elements of dimensions 25 m (downslope)×10 m (across slope) in an area of 250 m×250 m on a hillslope in Scotland. These data provide an unusually detailed basis for the evaluation of spatial variability and uncertainty in model parameterisation. The variations in slope and soil strength are represented adequately by normal distributions; a Weibull distribution is suggested for the soil depth data. The factor of safety calculated at each point in the grid was shown partially to identify observed landslides, with a number of false predictions of occurrence. Trend analysis and semivariogram analysis of the data set suggest that the use of kriging could improve upon this approach to landslide prediction by providing areal estimates of parameters at the grid element scale with associated error bounds. Received: 30 October 1996 · Accepted: 25 June 1997     

Electronic and magnetic structure of vivianite: cluster molecular orbital calculations

The electronic and magnetic structure of the octahydrophosphate vivianite, Fe₃(PO₄)₂·8H₂O, has been investigated by cluster molecular orbital calculations in local spin density approximation. Optical and Mössbauer spectra are well reproduced by the calculations, and the differences between the two iron sites can be correlated with differences in the geometrical structure of the first coordination sphere. The spin structure within the crystallographic ac plane is derived and explained on the basis of different superexchange pathways via edges of the phosphate tetrahedra. The calculations demonstrate that quite large clusters (up to 118 atoms) are necessary to arrive at reliable results.     

Physically based modelling of shallow landslide sediment yield at a catchment scale

 A shallow landslide erosion and sediment yield component, applicable at the basin scale, has been incorporated into the physically based, spatially distributed, hydrological and sediment transport modelling system, SHETRAN. The component determines when and where landslides occur in a basin in response to time-varying rainfall and snowmelt, the volume of material eroded and released for onward transport, and the impact on basin sediment yield. Derived relationships are used to link the SHETRAN grid resolution (up to 1 km), at which the basin hydrology and final sediment yield is modelled, to a subgrid resolution (typically around 10–100 m) at which landslide occurrence and erosion is modelled. The subgrid discretization, landslide susceptibility and potential landslide impact are determined in advance using a geographic information system (GIS), with SHETRAN then providing information on temporal variation in the factors controlling landsliding. The ability to simulate landslide sediment yield is demonstrated by a hypothetical application based on a catchment in Scotland. Received: 30 October 1996 · Accepted: 25 June 1997     

Paleocollapse structure as a passageway for groundwater flow and contaminant transport

 Paleocollapse structure is a rock collapse, resulting from the failure in the geological history of the bedrock overlying karstified limestone. Depending on the present hydrogeological conditions within the area of paleocollapse and the internal properties of these structures, they can provide a means to facilitate groundwater flow and contaminant transport. Inactive paleocollapse structures can be reactivated by human activities such as dam construction, mining underground minerals, pumping groundwater, and development of landfills. They can also be reactivated by natural events such as earthquakes and neotectonic movements. In the mines of northern China, sudden inflow of karst water from Ordovician limestone into drifts and mining stopes through paleocollapse structures has caused significant economic loss. Water pumping tests and accompanied dye traces are effective approaches of locating water-conducting paleocollapse structures. Grouting is probably the best means of preventing them from becoming geohazards. Received: 26 November 1996 · Accepted: 17 June 1997     

Hydrogeological investigation of a groundwater contamination site in southern Taiwan

 Groundwater samples taken from wells adjacent to a food machinery manufacturing plant in southern Taiwan indicate that there is a serious phenolic contamination. To understand the hydrogeological properties, and to prepare for remedial action, a series of hydrogeological investigations were conducted. Investigative work included collecting background information, analyzing existing data, measuring the groundwater, and conducting a slug test, pumping and recovery test, aerial photography analysis and electrical resistivity survey. Results from these investigations show that the local groundwater aquifer may be classified as an unconfined or confined formation, depending on the thickness of the interbedded clay layer. The direction of local groundwater flow is from southwest to northeast, with high transmissivity. The contaminant moves much more slowly than the average groundwater velocity, and it is limited to an area centered around the plant. The local geology of the contaminated area exhibits significant heterogeneity; it is not likely to have been formed by natural sedimentation. Data from the field aerial photography analysis and electrical resistivity survey also suggest that this shallow formation may result from artificial back-filling. Received: 1 September 1994 · Accepted: 28 December 1995     

Viscosity of albite melt at high pressure and high temperature

 The viscosity of albite (NaAlSi₃O₈) melt was measured at high pressure by the in situ falling-sphere method using a high-resolution X-ray CCD camera and a large-volume multianvil apparatus installed at SPring-8. This system enabled us to conduct in situ viscosity measurements more accurately than that using the conventional technique at pressures of up to several gigapascals and viscosity in the order of 10⁰ Pa s. The viscosity of albite melt is 5.8 Pa s at 2.6 GPa and 2.2 Pa s at 5.3 GPa and 1973 K. Experiments at 1873 and 1973 K show that the decrease in viscosity continues to 5.3 GPa. The activation energy for viscosity is estimated to be 316(8) kJ mol⁻¹ at 3.3 GPa. Molecular dynamics simulations suggest that a gradual decrease in viscosity of albite melt at high pressure may be explained by structural changes such as an increase in the coordination number of aluminum in the melt. Received: 6 January 2001 / Accepted: 27 August 2001     

A concept of forming a structure of ecological indicators and indexes for regions sustainable development

 A complex method for assessing the ecological state of groundwater by using indicators and indexes of underground hydrosphere sustainable development, and of characterizing its quality, is given for an oil field. The concept of forming indicators and indexes of sustainable development has been elaborated for this purpose. When forming a structure of environment indicators, the developments of the European Organization for Economic Co-operation and Development (OECD) in this sphere were considered. New indicators are given and a structure of indexes quantitatively characterizing them is worked out. Indexes can be simple, complex, muldidisciplinary and inter-multidisciplinary by their structure. By their essence indexes are subdivided into five classes: indexes of quality, damage, interaction, hydrogeochemical and dynamic ones. The ecological state of groundwater is assessed by the following categories of sustainability: sustainable, slightly unsustainable, medium unsustainable, unsustainable, highly unsustainable, catastrophically unsustainable. Received: 23 November 1998 · Accepted: 14 September 1999     

Detrital chromites in metasediments of the East-Arabian continental margin in the Saih Hatat area: constraints for the palaeogeographic setting of the Hawasina and Semail basins (Oman Mountains)

 In Oman, the convergence between Arabia and Eurasia resulted in the Late Cretaceous overthrusting of oceanic crust and mantle lithosphere onto the Arabian continental margin. During this compressional event, a part of the continental plate was subducted to a depth of more than 60 km (0.5 GPa, 250–350  °C to more than 2.0 GPa, 550  °C) resulting in progressive metamorphism of the continental margin sediments, well exposed in the Saih Hatat tectonic window, northeastern Oman Mountains. We attempt to constrain the possibility of one continuous history of extension (starting along the east Arabian continental margin in the Permian) that was followed by one continuous history of convergence starting at 90 Ma near a dead oceanic ridge. This compression resulted in the observed progressive metamorphism by ophiolite overthrusting onto the continental margin. Constraining arguments are the palaeogeographic setting before ophiolite obduction of the As Sifah units and the Hawasina Complex near Ghurba. Detrital chromites in the Triassic–Cretaceous metasediments of the Hawasina Complex are compared with magmatic Semail chromites, and the whole-rock chemistry of these metasediments and associated metabasites are investigated. In contrast to former hypotheses, differences in the chemical composition between detrital and magmatic chromites, and the probable origin of all detrital chromites in the Hawasina Basin from Permian age oceanic rocks, suggest that the high-pressure metamorphic sediments of As Sifah can be considered as part of the basal deposits of the Hawasina Basin. Received: 1 September 1998 / Accepted: 18 January 1999     

Development and testing of a contamination potential mapping system for a portion of the General Separations Area, Savannah River Site, South Carolina

 A methodology was developed to evaluate and map the contamination potential or aquifer sensitivity of the upper groundwater flow system of a portion of the General Separations Area (GSA) at the Department of Energy's Savannah River Site (SRS) in South Carolina. A Geographic Information System (GIS) was used to integrate diverse subsurface geologic data, soils data, and hydrology utilizing a stack-unit mapping approach to construct mapping layers. This is the first time that such an approach has been used to delineate the hydrogeology of a coastal plain environment. Unit surface elevation maps were constructed for the tops of six Tertiary units derived from over 200 boring logs. Thickness or isopach maps were created for five hydrogeologic units by differencing top and basal surface elevations. The geologic stack-unit map was created by stacking the five isopach maps and adding codes for each stack-unit polygon. Stacked-units were rated according to their hydrogeologic properties and ranked using a logarithmic approach (utility theory) to establish a contamination potential index. Colors were assigned to help display relative importance of stacked-units in preventing or promoting transport of contaminants. The sensitivity assessment included the effects of surface soils on contaminants which are particularly important for evaluating potential effects from surface spills. Hydrogeologic/hydrologic factors did not exhibit sufficient spatial variation to warrant incorporation into contamination potential assessment. Development of this contamination potential mapping system provides a useful tool for site planners, environmental scientists, and regulatory agencies. Received: 1 April 1997 · Accepted: 4 November 1997     

Olocenic alluvial aquifer of the River Cornia coastal plain (southern Tuscany, Italy): database design for groundwater management

 Hydrogeological research is in progress, utilizing GIS methods, with the principal aim of modelling the Olocenic alluvial aquifer of the River Cornia coastal plain (southern Tuscany, Italy), which has been exploited for drinking water, irrigation, and industrial uses. A consequence of exploitation has been the appearance of wide seawater intrusion. The alluvial aquifer has recently been subjected to new well fields for the supply of drinking water, with an increase of total average discharge of about 4×10⁶ m³/year. This paper presents results obtained from updating and integrating basic knowledge and structuring the database. The hydrogeological study allowed the recognition of the extension of areas that are characterized by a hydraulic head under the sea level, the progressive salinization of the aquifer, and the increase of water deficit in the aquifer which is produced by a progressive extraction of water superior to the natural recharge. In addition, benefits and disadvantages resulting from the location of new well fields in a hydrogeologically favourable zone, and the boundary conditions for much of the area studied have been defined. The GIS was used as support for making and updating the tabular and spatial database with the aim of integrating the local and regional hydrogeological knowledge. This study will permit the realization of a numerical simulation of the groundwater flow of the aquifer aimed at correcting the management of water resources, by means of the GIS-modelling integration. Received: 23 June 1998 · Accepted: 16 November 1998     

Hydrochemistry of aquifers in the southern Dead Sea area,southern Jordan

 The demand for water resources in the area south of the Dead Sea due to continued development, especially at the Arab Potash Company (APC) works necessitates that water quality in the area be monitored and evaluated based on the local geology and hydrogeology. The objective of this paper is to provide information on the past and present status of the main aquifers under exploitation or planned for future development. Two main aquifers are discussed: the Safi water field, presently being operated, and the Dhiraa water field, which is being developed. The aquifer developed in the Safi water field is shallow and fed by the Hasa fault system, which drains a significant portion of the Karak mountains. This aquifer seems to be well replenished within the core, where no obvious long-term degradation in water quality can be identified. However, in the low recharge areas within the distal portions of the alluvial fan, there has been a degradation in water quality with time. The degradation is caused by the dissolution of the Lisan Marl, which is present at the outskirts of the fan system, based on hydrochemistry of water in the wells. The Dhiraa field is a deep (800–950 m) aquifer drilled specifically for the extraction of brackish water present in the Kurnub aquifer. Available data indicate that there are at least three distinct water types within this field. These water types are variable in quality, and there may be potential for mixing of these waters, thus affecting the quality of the freshest waters presently available. Tritium and oxygen isotope analysis indicate that the water is old and possibly nonrenewable. Received: 24 July 1995 · Accepted: 26 September 1995     

An infrared and Raman spectroscopic study of gypsum at high pressures

 We present Raman and infrared spectra of gypsum to 21 GPa at 300 K. Our measurements encompass the internal modes of the (SO₄)⁻⁴ group that lie between 400 and 1150 cm⁻¹, hydroxyl-stretching vibrations between 3200 and 3600 cm⁻¹, and a libration and bending vibrations of the molecular H₂O group. All vibrations of the sulfate group have positive pressure shifts, while the hydroxyl-stretching and -bending vibrations have a mixture of positive and negative pressure shifts: the effect of pressure on the hydrogen bonding of the water molecule thus appears to be complex. Near 5 GPa, the two infrared-active bending vibrations of the water molecule coalesce, and the morphology of the hydroxyl-stretching region of the spectrum shifts dramatically. This behavior is consistent with a pressure-induced phase transition in gypsum in the vicinity of 5–6 GPa, which is observed to be reversible on decompression to zero pressure. The spectral observations are consistent with the onset of increased disorder in the position of the water molecule in gypsum: the sulfate vibrations are largely unaffected by this transition. The Raman-active symmetric stretch of the sulfate group undergoes an apparent splitting near 4 GPa, which is interpreted to be produced by Fermi resonance with an overtone of the symmetric bending vibration. The average mode Grüneisen parameter of the 20 vibrational modes we sample is less than 0.05, in contrast to the bulk thermal Grüneisen parameter of 1.20. Accordingly, the vibrations of both water and sulfate units within gypsum are highly insensitive to volumetric compaction. Therefore, in spite of the changes in the bonding of the water unit near 5 GPa, metastably compressed gypsum maintains strongly bound molecular-like units to over 20 GPa at 300 K. Received: 31 July 2000 / Accepted: 5 April 2001