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Palaeochannels are remnants of rivers or stream channels filled with younger sediments over the period of time. In ancient times, these rivers/channels were thriving in phenomenal conditions, but due to frequent tectonic activities, they lost the direction of their original path and were gradually either lost or buried under thick beds of younger alluvium. Palaeochannels act as reservoirs for fresh groundwater since they are made up of coarser sediments and were formerly flowing rivers. Depending on the groundwater regime and local topography, these could either be saturated or dry. The palaeochannels have high groundwater potential if saturated. These are ideal sites for artificial groundwater recharge, if dry. The identification of palaeochannels becomes quite challenging if they are buried under thick deposits of finer younger sediments. In the present study, an attempt has been made to characterize the Saraswati River Palaeochannel in parts of Yamuna Nagar and Kurukshetra districts of Haryana by using surface and subsurface geophysical methods. Till date, the palaeochannels in this area were mainly discerned on the basis of remote sensing only; therefore, geophysical characterization of these palaeochannels has been attempted in this study. In surface geophysical methods, electrical resistivity surveys, especially gradient resistivity profiling (GRP) and vertical electrical sounding (VES), were conducted in the study area, while electrical and natural gamma logging was used as subsurface geophysical approaches to identify the coarser sands of buried palaeochannels. The main objective of the study was to characterize the Saraswati River palaeochannel and analyze the quality of the groundwater stored in the palaeochannel in the study area. The findings were compared with the well-log data and were found in good agreement. [ABSTRACT FROM AUTHOR]

One of the geophysical techniques that may be used to define subsurface lithology is the geoelectric approach. The Schlumberger configuration's resistivity technique is used on the assumption that the distance between the potential electrodes is fixed. In contrast, the distance between the current electrodes progressively varies following the resistivity-to-depth curve and the resistivity table. This study aims to determine the lithology of the soil layer and the lithology of the soil layer that serves as an aquifer based on their respective resistivity values. The acquired data demonstrate the presence of multiple layers, including alluvium, sand, gravel, and andesite, in the subsurface lithology at two sites with a depth of 25 meters and a track length of 50 and 100 meters. Based on the resistivity curve to depth and the findings of data processing at the two data collecting sites, groundwater at location 1 (Gambesi Village) could not be identified in the resistivity table because of the location's hilly terrain and alluvial rock types. However, at location 2 (Sasa Village), groundwater was present at depths of 12.8 meters with thicknesses of 6.24 cm and 0.57 Ωm and at depths of 12.8 meters with thicknesses of 4.91 meters and 297 Ωm, respectively. This region slopes down from this position. [ABSTRACT FROM AUTHOR]

In water scarce and non-irrigated regions, groundwater is considered as one of the vital sources to fulfil the demand of fresh water for the survival of life and to meet with the crop water requirements. However, overexploitation and increased urbanization of groundwater in Rawalpindi City of Pakistan is causing a significant disturbance to cope with the water requirements. Therefore, a comprehensive study for assessment of subsurface lithology and groundwater depth is required to cope with increased water demands and to minimize the groundwater imbalance. In this study, electrical resistivity survey method was adopted for the assessment and identification of subsurface lithology and aquifer potential sites in the study area. ABEM SAS (signal averaging system) instrument was used for the collection of field data on which Schlumberger configuration was applied. The maximum current electrode spacing (AB) was 100–200 m based on the feasibility of the sites selected for the execution of the survey. Moreover, the field data was analyzed with the help of computer iteration software, i.e., IX1D, and data interpretation was made from the resistivity values and results were compared with the borehole log data obtained from Rawalpindi Development Authority (RDA) and previous studies. The results indicated that the deepest water table in Rawalpindi City is at municipal stadium with a depth of 51 m while the shallowest water table was found at Liaqat Bagh with a depth of 35 m. Furthermore, the analysis also demonstrated that the dominant strata of the study area were comprised of sandy clay, gravel and boulder sand, and gravel and average depth to the water table was 45.5 m. It is believed that the outcomes of this research work will help the relevant authorities in the selection of Managed Artificial Recharge (MAR) sites for Rawalpindi City, Pakistan. [ABSTRACT FROM AUTHOR]

A vertical electrical sounding survey was carried out in northern Gaza Strip (Gaza City, Jibalya, Bayt Lahya and Bayt Hanun), Palestine to study the groundwater conditions and evaluate its quality and distribution. The survey included twenty-six (26) traverses with variable lengths in the range 200-500 m. The geoelectrical survey revealed that the resistivity of the study area varies in a wide range mostly 9 to 850 Ωm, subdivided into three subsurface zones. The first zone represents the dry sandstone and alluvial that attains the highest resistivities (100-850 Ωm) with variable thicknesses in the range 26-80 m beneath the whole study area. This zone is characterized by the presence of thin layers of clay and silt in some localities that reduced the resistivity to 15-25 Ωm. The second zone represents the fresh water saturated calcareous sandstone (locally named Kurkur) with resistivities in the range 22 -39 Ωm). The thicknesses of this zone is about 55-70 m in the western part of the study area and increased to 110 m in the east. The surface of this zone shows a gentle westward gradient, which indicates a general flow of water towards the Mediterranean Sea. The third zone represents saline water saturation with low resistivities, mostly 9 Ωm -10 Ωm close to the Mediterranean shore, located at 60 m below sea level and 100 m beneath the eastern side of the study area. Beneath the eastern part of the study area, an anomalous low resistivity of 2-3 Ωm is observed within the fresh water zone, which indicates groundwater pollution near the buffer zone caused by agriculture activities and untreated pumped wastewater. [ABSTRACT FROM AUTHOR]

In order to estimate the structural competency of the sub-surface geological features of the Construction site, the application was performed for data attainment using Schlumberger configuration of the resistivity profiling and Vertical Electrical Sounding (VES) around outer ring road of Mysore City. A 1D numerical reversal of discrete DC resistivity was applied to boost the results for better accomplishment of the study objective. For the edifice of geo-electric sections displaying the key geo-electric physiognomies of the geological entities existing in the subsurface region, the data obtained from the VES techniques were used. The interpretation outcomes reveals the geo-electric segments comprise of 3 to 4 layers explicitly: vegetative topsoil, highly weathered silty loam soil, moderately weathered rock and massive hard rock. The stratum thicknesses and resistivities vary from 1.2 - 1.55 m/31 - 132 Ohm-m, 0.2-3.875m/24 - 300 Ohmm and 2.5 - 12.76 m/27.2 - 1000 Ohm-m and 50 - 1840 Ohm-m respectively. Based on geophysical study of the region states, design of shallow substructure for average civil engineering projects in the extremely and moderately weathered layers are the most competent beds and for multistoried structures, the undeformed hard rock zone is formidable. [ABSTRACT FROM AUTHOR]

We investigate the applicability of offshore geoelectrical profiling in the littoral zone, e.g., for archaeological prospection, sediment classification and investigations on coastal ground water upwelling. We performed field measurements with a 20 m long multi-electrode streamer in inverse Schlumberger configuration, which we used to statistically evaluate measurement uncertainty and the reproducibility of offshore electric resistivity tomography. We compared floating and submerged electrodes, as well as stationary and towed measurements. We found out that apparent resistivity values can be determined with an accuracy of 1% to 5% (1σ) depending on the measurement setup under field conditions. Based on these values and focusing on typical meter-scale targets, we used synthetic resistivity models to theoretically investigate the tomographic resolution and depth penetration achievable near-beach underneath a column of brackish water of about 1 m depth. From the analysis, we conclude that offshore geoelectric sounding allows the mapping of archaeological stone settings. The material differentiation of low-porosity rock masses < 15% is critical. Submerged wooden objects show a significant resistivity contrast to sand and rocks. Distinguishing brine-saturated sandy sediments from cohesive silty-clayey sediments is difficult due to their equal or reversed resistivity contrasts. Submarine freshwater discharges in sandy aquifers can be localized well, though difficulties may occur if the seafloor encounters massive low-porosity rock masses. As to the measurement setups, submerged and floating electrodes differ in their spatial resolution. Whereas stone settings of 0.5 to 1 m can still be located with submerged electrodes within the uppermost 4 m underneath the seafloor, they have to be >2 m if floating electrodes are used. Therefore, we recommend using submerged electrodes, especially in archaeological prospection. Littoral geological and hydrogeological mapping is also feasible with floating electrodes in a more time-saving way.

This study was carried out using vertical electrical sounding (VES) to evaluate the groundwater potential and the aquifer protective capacity of Northern Paiko. Sixty vertical electrical soundings were obtained across the study area using Schlumberger electrode configuration. Three to four geoelectric layers were delineated from the interpreted results. The stratigraphy of the subsurface shows: topsoil (62.8-3082 Ωm), weathered layer (15.2-80 368 Ωm), fractured layer (191-236 672 Ωm), and the fresh basement (79.9-308 865 Ωm). The weathered layer was delineated as the major aquiferous horizon. From the results, the resistivity, thickness, and longitudinal conductance maps were drawn. It was observed that groundwater potential is low in about 76.7% of the study area. This study has also shown that the aquifer protective capacity of most parts of the study area is poor (83.3%), thus rendering the aquifer vulnerable to contamination. [ABSTRACT FROM AUTHOR]

Esta investigación, retoma el método de la Regresión Anidada para el procesamiento digital de datos geoeléctricos, aplicado en 1970 por Marquardt, Hoerl y Kennard, y en 1973 por Joseph Robert Inman, incorporando parámetros estadísticos robustos, que permitan obtener mejores resultados de valores de resistividad aparente y espesores en sistemas linealmente dependientes, utilizando para tal fin, el Método del Sondeo Eléctrico Vertical bajo la configuración electródica tipo Schlumberger en la Parroquia Olegario Villalobos del Municipio Maracaibo. Esta información geoeléctrica es procesada con el Método de Ghosh, aplicando modelos lineales que generan curvas de resistividad aparente para posteriormente optimizar con el método de la Regresión Anidada las variables obtenidas. El error medio y la varianza residual, entre otros, indican la desviación de los residuales, el rango de estimación y el nivel de ruido en la data; este último definido en 3%, es el producto de la relación entre el error medio porcentual y la desviación estándar, la cual, define parámetros confiables en la fase de interpretación de los perfiles geoeléctricos. Estos perfiles indican la presencia de acuíferos de agua dulce, con un tope de 30 m, una base de 80 m y un caudal de 2 L/seg, en el sector del colegio la Merced.This investigation, is based on the Ridge Regression method for the processing digital of geoelectrics data, applied in 1970 by Marquardt, Hoerl and Kennard, and in 1973 by Joseph Robert Inman, which involve robust statistical parameters to obtain better results of apparent resistivity values and thickness for lineally dependent systems, using, the Vertical Electric Sound Method under the Schlumberger electrodic configuration in the Parish Olegario Villalobos of the Municipality Maracaibo. This geoelectric information is processed with the Ghosh Method, applying lineal models that generate curves of apparent resistivity for optimizing the obtained variables with the Ridge Regression method, the half error and the residual variance, among other indicate the residual deviation, the estimate range and the noise level on the data, the last one is defined in 3% as a, product of the relationship between the half percentage error and the standard deviation which define reliable parameters in the interpretation phase of the is geoelectrics these profile indicate the presence of fresh water aquifer, with a top of 30 m, a base of 80 m profile and a flow of 2 L/seg, in the sector Las Mercedes school.

The present study aims to investigate the ground water accumulations present in the area located west of the Gulf of Suez, to face the new urbanization settlements of industrial national projects in the study area using geoelectrical and magnetic measurements. Magnetic data interpretation was carried out using the RTP magnetic data (or, through analyzing the RTP aeromagnetic map) to determine the depth to the surface of basement rocks and delineate the trends of structural elements. The results of magnetic interpretation indicated that the depth to the basement surface is ranging from 1200 to 3500 m and the trends of encountered structural elements are mainly NE–SW, NW–SE, NNW–SSE and E–W directions. Seventeen vertical electrical soundings of Schlumberger configuration were measured with AB/2 ranging from 1.5 m to 1500 m at the southern part of the study area. The results of quantitative interpretation of geoelectrical data indicated that the subsurface section consists of six different geoelectrical units; the first unit represents the Quaternary gravel and sand of high resistivity values and thickness of about a few meters. The second geoelectrical unit exhibits moderate resistivity values ranging from 23 to 100 ohm m and thickness ranging from 4.5 to 67 m which represents the fresh water aquifer in the study area, while the lithology of this layer consists of sandstone and limestone which belongs to the Upper Miocene. The third geoelectrical unit is composed of sandy clay and limestone which belongs to the Middle Miocene deposits and shows low resistivity values ranging from 6 to 7 ohm m and thickness ranging from 44.5 m to 66 m. This third layer represents the second aquifer (brackish water). The fourth geoelectrical unit consists of limestone and clayey limestone which belongs to the Lower Miocene deposits and exhibits moderate resistivity values ranging from 16 to 33 ohm m, while the thickness of this unit ranges from 47–102 m. This layer represents the third aquifer (brackish water). The fifth geoelectrical unit reveals very low resistivity values of about 2–5 ohm m and consists of clay and sandstone of the Oligocene and Upper Eocene deposits. The sixth geoelectrical unit is the bottommost unit in the studied subsurface section and exhibits moderate resistivity values in a range of about 22–35 ohm m and consists of limestone of the Middle Eocene deposits. [ABSTRACT FROM AUTHOR]

This investigation, is based on the Ridge Regression method for the processing digital of geoelectrics data, applied in 1970 by Marquardt, Hoerl and Kennard, and in 1973 by Joseph Robert Inman, which involve robust statistical parameters to obtain better results of apparent resistivity values and thickness for lineally dependent systems, using, the Vertical Electric Sound Method under the Schlumberger electrodic configuration in the Parish Olegario Villalobos of the Municipality Maracaibo. This geoelectric information is processed with the Ghosh Method, applying lineal models that generate curves of apparent resistivity for optimizing the obtained variables with the Ridge Regression method, the half error and the residual variance, among other indicate the residual deviation, the estimate range and the noise level on the data, the last one is defined in 3% as a, product of the relationship between the half percentage error and the standard deviation which define reliable parameters in the interpretation phase of the is geoelectrics these profile indicate the presence of fresh water aquifer, with a top of 30 m, a base of 80mprofile and a flow of 2 L/seg, in the sector Las Mercedes school.

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We investigate the applicability of offshore geoelectrical profiling in the littoral zone, e.g., for archaeological prospection, sediment classification and investigations on coastal ground water upwelling. We performed field measurements with a 20 m long multi-electrode streamer in inverse Schlumberger configuration, which we used to statistically evaluate measurement uncertainty and the reproducibility of offshore electric resistivity tomography. We compared floating and submerged electrodes, as well as stationary and towed measurements. We found out that apparent resistivity values can be determined with an accuracy of 1% to 5% (1σ) depending on the measurement setup under field conditions. Based on these values and focusing on typical meter-scale targets, we used synthetic resistivity models to theoretically investigate the tomographic resolution and depth penetration achievable near-beach underneath a column of brackish water of about 1 m depth. From the analysis, we conclude that offshore geoelectric sounding allows the mapping of archaeological stone settings. The material differentiation of low-porosity rock masses < 15% is critical. Submerged wooden objects show a significant resistivity contrast to sand and rocks. Distinguishing brine-saturated sandy sediments from cohesive silty-clayey sediments is difficult due to their equal or reversed resistivity contrasts. Submarine freshwater discharges in sandy aquifers can be localized well, though difficulties may occur if the seafloor encounters massive low-porosity rock masses. As to the measurement setups, submerged and floating electrodes differ in their spatial resolution. Whereas stone settings of 0.5 to 1 m can still be located with submerged electrodes within the uppermost 4 m underneath the seafloor, they have to be >2 m if floating electrodes are used. Therefore, we recommend using submerged electrodes, especially in archaeological prospection. Littoral geological and hydrogeological mapping is also feasible with floating electrodes in a more time-saving way. [ABSTRACT FROM AUTHOR]

Esta investigación, retoma el método de la Regresión Anidada para el procesamiento digital de datos geoeléctricos, aplicado en 1970 por Marquardt, Hoerl y Kennard, y en 1973 por Joseph Robert Inman, incorporando parámetros estadísticos robustos, que permitan obtener mejores resultados de valores de resistividad aparente y espesores en sistemas linealmente dependientes, utilizando para tal fin, el Método del Sondeo Eléctrico Vertical bajo la configuración electródica tipo Schlumberger en la Parroquia Olegario Villalobos del Municipio Maracaibo. Esta información geoeléctrica es procesada con el Método de Ghosh, aplicando modelos lineales que generan curvas de resistividad aparente para posteriormente optimizar con el método de la Regresión Anidada las variables obtenidas. El error medio y la varianza residual, entre otros, indican la desviación de los residuales, el rango de estimación y el nivel de ruido en la data; este último definido en 3%, es el producto de la relación entre el error medio porcentual y la desviación estándar, la cual, define parámetros confiables en la fase de interpretación de los perfiles geoeléctricos. Estos perfiles indican la presencia de acuíferos de agua dulce, con un tope de 30 m, una base de 80 m y un caudal de 2 L/seg, en el sector del colegio la Merced.