geophysical techniques

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Detection Of Surface Water Leakage Through Limestone Cracks, Using Near Surface Geophysical Techniques.

Detection Of Surface Water Leakage Through Limestone Cracks, Using Near Surface Geophysical Techniques.

Near Surface Geophysical Techniques such as electrical resistivity tomography (ERT) ground penetrating radar (GPR) and Time Domain Electromagnetic (TEM) are useful techniques for delineating subsurface configurations such as stratigraphy, structural elements, caves and water saturated zones. The ERT technique is used to delineate the contamination, and buried objects, as well as to quantify some aquifer properties. Six 2-D electrical resistivity sections were measured using Wenner configurations. The spread length is about 45 m and the electrodes spacing are 1m, respectively, to reach a depth ranging from 8 to 10 m. The results indicate that, the subsurface section is divided into main three geo-electrical units, the first is fractured limestone, which exhibits high resistivity values ranging from 450 to 1000 ohm m. The second unit is corresponding to marl of moderate resistivity values from 100 to 250 ohm m. The third unit, which is the lower bed, exhibits very low resistivity values from 5 to 45 ohm m and corresponding to clayey marl with water. The presence of clay causes the most geotechnical problems, Also, the interpretation results of the obtained data for Wenner array were represented in the 3-D view to delineate the zones of very low resistivity values these values are corresponding to clayey marl saturated with water and have direct effect on the constructions and may cause cracks and fractures. In the present study, procedure on the processed GPR data, were displayed on 2D profiles that contain the expected anomalies. Because the study area is saturated with water, part of radar waves are attenuated and the reflections from the subsurface materials are weak. GPR and geoelectrical methods are used in the prospection of good electrical conductors at shallow depths. The obtained 1-D models were used as initial models for 1-D inversion of the TEM data, a trial and error modeling was applied to the comparable data sets to give
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Post flooding damage assessment of earth dams and historical reservoirs using non-invasive geophysical techniques

Post flooding damage assessment of earth dams and historical reservoirs using non-invasive geophysical techniques

1 2 Highlights 3  4 5 potential and microgravimetry to assess reservoir dam integrity  6 7 10 Validation of Geophysical techniques for detecting damages and seepage in reservoir embank[r]

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Estimation of bedrock depth for a part of Garhwal Himalayas using two different geophysical techniques

Estimation of bedrock depth for a part of Garhwal Himalayas using two different geophysical techniques

It has now been well established that the depth of bedrock is a key parameter in assessing the impact of local site conditions on seismic hazard analysis. Where conventional geotechnical testing like standard penetration test (SPT) or cone penetration test (CPT) requires a far greater cost and manpower to be used for such purposes, geophysical testing like ground-penetrating radar (GPR) and multichannel analysis of surface waves (MASW) may provide the researchers with more viable options to achieve conclusive evidence on bedrock depth. Application of geophysi- cal techniques has become more and more extensive and advanced in many geo-morphological studies since the early 2000s. Geophysical techniques require less time and effort, and the easy processing of the obtained data is the primary reason for their popularity. However, due to variability in subsoil mechanical properties, wave attenuation and dispersion and diverse geological boundary conditions, the results obtained through geophysical techniques are often ambiguous and non-unique. The interpretation of the obtained data also requires skill and experience, as the range may vary widely and more often than not consensus is difficult to achieve. In this paper, an endeavor has been made to coalesce the results of two widely used geophysical techniques, namely GPR and MASW to derive more conclusive evidence for the detection of bedrock depth in a part of Garhwal Himalayas. The study area comprises of two different cities of Uttarakhand, India. Both the sites possess different geo-morphological attributes and thus prove to be a perfect platform to conduct the experimentations. Both GPR and MASW testing have been performed and results are shown in graphical format. A comparison of the GPR survey with a conventional geotechnical testing (SPT) is also presented here. This study shows that GPR and MASW can provide complementary results in estimating bedrock depth.
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Reservoir assessment using non-invasive geophysical techniques

Reservoir assessment using non-invasive geophysical techniques

seepage, combined with drill testing (Antoine et al. 2015). Since air-filled voids provided an excellent dielectric con- stant contrast, GPR revealed to be suitable for identifying animal burrows in earthen embankments and levees. The GPR technique is an extensive investigation method that enables one to rapidly cover a wide area, locating voids, and it is easy to use with the possibility to inspect the col- lected data in real time. Nevertheless, GPR analysis needs expertise and modelling skills and embankments are various in natures and often made of conductive materials, such as clay, rendering the GPR survey very limited. It is more and more frequent to see in the literature reviews some evalua- tions of a full set of geophysical techniques in order to assess their suitability. For example, Fauchard and Meriaux (2007) wrote guidance on geophysical and geotechnical methods for diagnosing flood protection dikes. (Niederleithinger et al. 2012) assessed resistivity, electromagnetic, seismic, and GPR techniques at a test site along the Mulde River in eastern Germany, giving advantages and inconveniences of the techniques reviewed.
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Shallow geophysical techniques to investigate the groundwater table at the Great Pyramids of Giza, Egypt

Shallow geophysical techniques to investigate the groundwater table at the Great Pyramids of Giza, Egypt

near-surface geophysical techniques integrated with avail- able borehole hydrogeological data to investigate and char- acterize groundwater occurrences in the GPG. The GPG is located in the southwestern part of the greater Cairo region (Fig. 1). Geologically, the Giza Plateau is composed mainly of white limestone, cream and yellow argillaceous limestone, and dark grey dolomitic limestone of middle–upper Eocene age. The plateau rocks are commonly interbedded with thin marl layers in their upper part, which dips about 5–10 ◦ to the southeast (SE) direction. Steep escarpments border the plateau to the north and east directions as shown in Fig. 2 (Yehia, 1985; Mahmoud and Hamdan, 2002). Two regional groundwater aquifers underlie the Sphinx (Fig. 3); the Qua- ternary aquifer of Nile alluvium consists of graded sand and gravel with intercalations of clay lenses at different depths, with a water table at depth ranges between 1.5 and 4 m be- low the ground surface (b.g.s.). The second aquifer is a frac- tured carbonate aquifer that covers the area below the pyra- mid plateau and the Sphinx, where the water table ranges in depth from 4–7 m b.g.s. The recharge of the aquifer below the Sphinx area occurred mainly through water system leakage, irrigation, and mass urbanization (AECOM, 2010; El-Arabi et al., 2013).
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Geophysical explorations of archaeological shell matrix sites: evaluating geophysical techniques in determining the boundaries, structure and volume of buried shell deposits

Geophysical explorations of archaeological shell matrix sites: evaluating geophysical techniques in determining the boundaries, structure and volume of buried shell deposits

The second paper is Thompson et al. (2004), who trialled four geophysical methods for their study. As mentioned above the Magnetometry and EM were quickly discarded, but the electrical resistivity was deemed useful for large-scale horizontal surveys. The authors found the shell highly resistant compared to the surrounding sandy matrix, and so used the resistance meter to locate the mounds. The exact locations of two of the three larger mounds on Sapelo Island had been lost due to deflation, caused by removal of shell material for use as road fill. To locate the rings, grids of 20m by 20m were laid down from a baseline. The placement of these grids were based on field observations, as well as historical records and prior archaeological work. The survey was conducted using an RM15 resistance meter in a twin probe array, this layout allows for a fast horizontal survey of the shallow subsurface. Readings were taken in 0.5m intervals along transects spaced at 1m. The survey results were successful in locating clearly defined rings of higher resistance indicating shell deposits (see Figure 2.16).
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Geophysical characterisation of the groundwater surface water interface

Geophysical characterisation of the groundwater surface water interface

Since the advent of hydrogeophysics during the 1990s (Binley, 2015), geophysical techniques have evolved from their traditional exploratory usage to being capable of characterisation of hydrological states and dynamic processes. Additionally, in more recent years the field of biogeophysics, which aims to relate the biological processes and modifications of the subsurface to geophysical properties, has emerged (Atekwana and Slater, 2009). Biogeophysical applications have typically involved characterising reactive conditions (e.g. Naudet et al., 2003; Sassen et al., 2012; Chen et al., 2013), detecting biogeochemical by-products (e.g. Slater and Binley, 2006; Comas et al., 2007; 2014; Parsekian et al., 2011), or detecting changes to physical structure as a result of microbial activity (e.g. Williams et al., 2005; Slater et al., 2008). In addition, the usage of unmanned vehicles in environmental research has vastly increased and it is expected that automated deployment of miniaturised geophysical devices could become common in future years. In this section developments in: (1) electrical resistivity monitoring, (2) induced polarisation, (3) self-potential, (4) multi-coil electromagnetic induction, and (5) automated vehicles and their potential application in GW-SW characterisation are discussed.
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Electrical structure of the crust in Southeast Tasmania

Electrical structure of the crust in Southeast Tasmania

A variety of geophysical techniques including magnetotelluric, magnetovariational, potential field gravity and magnetic and transient electromagnetic techniques were used to investigate [r]

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Can Integrated Geophysical Investigations Solve an Archaeological Problem? The Case of the So-Called Domus septem Parthorum in Rome (Italy)

Can Integrated Geophysical Investigations Solve an Archaeological Problem? The Case of the So-Called Domus septem Parthorum in Rome (Italy)

The multi-approach results from the archaeological site of the so-called Domus septem Parthorum demonstrate how two different geophysical techniques with different characteristics can be combined to obtain a clear reconstruction of the shape of buried ruins. The anomalies are confirmed to be related to a Late Antiquity religious building (i.e., a Paleochristian basilica) with a rectangular geometry, an apse and a paved floor. Taking into consideration the several reuses of the area over the centuries, including the recent construction of a modern athletic stadium, the acquisition of important integrated archaeological datasets is essential to obtaining both a coherent answer to a historical interpretive problem and a coherent idea of the urban evolution in the past.
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Investigation of Geological Structures of Hydrogeological Importance of 1:100,000 Sheet 185 (Paiko) North-Central Nigeria Using Integrated Geophysical and Remote Sensing Techniques

Investigation of Geological Structures of Hydrogeological Importance of 1:100,000 Sheet 185 (Paiko) North-Central Nigeria Using Integrated Geophysical and Remote Sensing Techniques

Fractures inferred from both aerogeophysical and remote sensing data are usually verified by surface structural mapping and ground geophysical methods in groundwater exploration because inferred fractures may not always be water bearing. One of such ground geophysical techniques is Radial Vertical Electrical Sounding (RVES). RVES is a modified resistivity technique wherein the magnitude, intensity, and direction of electrical anisotropy are determined. This method has proved very successful in the delineation of subsurface geology and structures, especially for effective identification, behaviour and delineation of fracture orientations in the shallow subsurface of crystalline basement terrains [10], [11], [12], [2]. Communities within the Basement Complex terrains commonly suffer acute potable water shortages arising from the complex hydrogeological setting of the terrain [13], [14]. The poor success rate of water borehole drilling in the Basement Complex regions can be attributed to non-incorporation of hydrogeological concepts into the VES anomaly interpretations in borehole siting [15].
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Reconstructing Landscapes and Waterscapes in Thebes, Egypt

Reconstructing Landscapes and Waterscapes in Thebes, Egypt

We have begun to investigate the ancient landscapes, waterways and location of the River Nile within the Theban region using geophysical techniques, principally Electrical Resis- tivity [r]

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Applications of near surface geophysics in the search for graves in Maori urupa

Applications of near surface geophysics in the search for graves in Maori urupa

CHAPTER 4 - DATA COLLECTION AND PROCESSING 4.1 INTRODUCTION Three geophysical techniques were used at the Koukourarata and Wairewa sites: electromagnetics EM, magnetometer/gradiometer an[r]

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The Effect of 2 D Resistivity on Magnetic Field

The Effect of 2 D Resistivity on Magnetic Field

Geophysical techniques sometimes produced disappointing results to solve engineering and environmental problems, particularly when a method, which lacked the precision required in a particular site investigation has been used, or when a method has been specified that is inappropriate to the problem under consideration. In some cases these difficulties could have been avoided by taking expert advice before initiating the survey. In other cases the planning stage of the geophysical data acquisition may also contributed to the problem during interpretation. Sometimes due to insufficient time some geophysicists trying to carry out an investigation using the two methods at once to save time in the field. Due to the improper planning, interpretation of the geophysical data by the geophysicist has not yielded the information expected by the engineer or client. It is often advisable to undertake a feasibility study at the field site to assess the suitability of the proposed geophysical techniques for the investigation of the geological problem. In this paper, two geophysical techniques were chosen (2- D resistivity and magnetic method) to see the effect of 2-D resistivity towards magnetic field data if the data acquisition was conducted at the same time.
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Testing alternative uses of electromagnetic data to reduce the prediction  error of groundwater models

Testing alternative uses of electromagnetic data to reduce the prediction error of groundwater models

Full stochastic approaches have been developed. For ex- ample, Ruggeri et al. (2013) developed a Bayesian simu- lation approach to estimate the hydraulic conductivity field from measurements of geophysical parameters. So far the method has only been used for estimation along short profile lines (Ruggeri et al., 2013, 2014), and the Bayesian scheme has not yet been extended to also involve hydrological data and groundwater modeling. Furthermore, the methodology of Ruggeri et al. (2013) requires the existence of a petro- physical relationship between electrical resistivity and hy- draulic conductivity; the relationship does not need to be known, in which case a data set of collocated measure- ments of electrical resistivity and hydraulic conductivity is required. An alternative Bayesian approach was presented by Hermans et al. (2015), who integrate multiple and multi- scale data types to falsify alternative structural models using a stochastic search method. The methodology was demon- strated for a field case using hydraulic head data and electri- cal resistivity tomography to constrain a hydrological model. Stochastic inversion approaches have been developed that in- vert electrical resistivity (ER) and hydrological data. Irving and Singha (2010), for example, describe a Markov chain Monte Carlo (McMC) method to estimate a binary hydraulic conductivity field from ER and tracer test data. As explained by Irving and Singha (2010, p. 13), their McMC approach is computationally expensive. Their demonstration examples were therefore 2-D and small in scale, and application to field data has not yet been attempted (Irving and Singha, 2010, p. 13).
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Training in Diamond Exploration

Training in Diamond Exploration

Participants from the National Geophysical Research Institute (NGRI) expressed that the training programme conducted covered all aspects of geological, geophysical and geochemic[r]

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Earthquake Segment Boundaries and Tsunamigenic Faults of the Kodiak Segment, Alaska-Aleutian Subduction Zone

Earthquake Segment Boundaries and Tsunamigenic Faults of the Kodiak Segment, Alaska-Aleutian Subduction Zone

In this thesis, I explore the geophysical expression of the presumed Kodiak segment boundaries by analyzing several geophysical datasets (potential fields, seismic reflection, and seis[r]

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Wrongful Geophysical Exploration

Wrongful Geophysical Exploration

leum v. 5 Scully owned a large parcel of swamp land in Louisiana for which defendant Shell had unsuccessfully attempted to negotiate exploration rights. While conduc[r]

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198306 pdf

198306 pdf

Several openings exist in the following areas: • Seismic data processing software development • Geophysical ,mapping and data base software development • Geophysical applications softwar[r]

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A geophysical investigation
of the Derwent Estuary

A geophysical investigation of the Derwent Estuary

modelled magnetic profile for the long lines, and the interpreted and uninterpreted seismic profiles for the short lines.. The magnetic modeling has all been done using dolerite sources [r]

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Neural networks in geophysical applications

Neural networks in geophysical applications

Other interesting preprocessing techniques to reduce input can be found in Almeida (1994). All of these are cast in the form of neural networks structures. Notice, however, that nearly always the individual components of the input are scaled to lie within well-defined ranges (e.g., between −1 and 1) to put the dynamic range of the input values within the most sen- sitive part of the activation functions. This often results in a more optimal use of the input. Hence, it may reduce the num- ber of hidden neurons. For instance, Le Cun et al. (1991) show that correcting each individual input value for the mean and standard deviation of this component in the training set will increase the learning speed. Furthermore, for data displaying
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