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Nowadays the salinization of freshwater resources due to seawater intrusion represent a worldwide issue. Accordingly, this study aims to identify and locate the freshwater-saltwater interface in the downstream part of the Nador wadi plain (Algeria), a coastal area characterized by a semi-arid mediterranean climate using a multi-methodologies approach including geophysical methods, hydrostatics approach, hydrochemical method, and piezometry situation. The investigation was carried out by the electrical survey and refraction seismic methods in the period of April-May 2018. Moreover, the hydrochemical and piezometry methods were used to confirm the results of the geophysical technique. The results of the present study case showed that the seawater intrusion interface is located at 420–1380 m from the shoreline. Additionally, the presence of the bedrock bulge (clay formation) at a distance ranging between 550 and 1050 m from the shoreline, plays the role of the natural hydraulic barrier for the seawater advance. The findings indicate that the identified seawater intrusion interface and the natural hydraulic barrier formed by the bedrock bulge are critical for managing groundwater resources in the Nador wadi plain. This methodology can be applied to other coastal plains worldwide to address the challenges of seawater intrusion and groundwater salinization. [ABSTRACT FROM AUTHOR]

Relevance. The necessity to improve the accuracy of analysis and prediction of potential fire hazard of rock-coal massifs by using electromagnetic methods of endogenous fire detection. Taking into consideration that the increase in coal temperature changes a number of its parameters, such as dielectric permittivity and electrical resistivity, it is reasonable to use the method of electromagnetic reconnaissance in locating the focus of fire. Aim. To analyze the theoretical and practical knowledge about the anomalies formed in the area of spontaneous combustion and to evaluate the effectiveness of electromagnetic methods for locating the spontaneous combustion zones of a coal massif. Objects. Physical parameters of the ignition zone of the coal massif, such as dielectric permittivity and electrical resistivity, as well as the range of the GPR central frequency, allowing clearly defining the boundaries of the ignited zone. Method. Reviewing the proposed methods of determining the parameters serving for correct location of the fire zone. For GPR it is necessary to determine the center frequency of the standard antenna unit and resolution, then to estimate the rational frequency range of GPR. Results. Allow us to draw conclusions about the methods used to determine the rational range of GPR center frequency – it can be calculated by solving the system of equations of the signal attenuation function and energy potential of GPR, by the experimental value of the target function, including the depth and detail of sounding as a function of frequency, or on the basis of a complex parameter of GPR, including the radiated power of the antenna, the number of accumulations and the reflection coefficient from the boundaries. Taking into account such physical features of the fire zone as drying the rock-angle massif and the shape of the anomalous zone, the rational range of the center frequency for the GPR "OKO-2" was determined.

The present work used the electrical resistivity approach to conduct a three-dimensional modeling and initial volume estimation of the limestone layer in the Mintom region located in southern Cameroon. In order to achieve the objectives of the study, a total of 21 electrical soundings spaced 250 m were first collected in the field using the Schlumberger array. These soundings were conducted along three profiles oriented in an east-west direction, spaced 500 m. Additionally, a geological survey was conducted to identify and emphasize the presence of limestone formations within the designated study region. The interpretation of the sounding data was conducted based on the analysis of the sounding curves. The interpretation outcomes, specifically resistivity and thickness, were compared with the geological field data, resulting in the development of lithostratigraphic logs for each sounding. The geological sections were constructed using the logs of the designated profile. The lithological logs were utilized to establish a lithological interface model and calculate the volume of the limestone layer at 260 ± 13 × 106 m3, utilizing the inverse distance method built into RockWorks software. A resistivity value is assigned to each geological layer in a sounding curve, allowing for the development of a resistivity variation model specific to the limestone layer. The proposed model facilitates the categorization of limestone layers based on their resistivity variations, thus serving as a fundamental reference for prospective exploratory activities within the designated study region. Our integrated approach provides a replicable model for a better understanding of the limestone reserve and effective management of this valuable resource. [ABSTRACT FROM AUTHOR]

Studies have shown that sand has a complex chemistry with unique geological and environmental significance. This paper analyses a survey conducted in the Yenagoa local government area in Bayelsa State, Nigeria, to estimate sand chemistry using vertical electrical sounding. The study aims to determine the volume of sand deposits and their chemistry in an area measuring 100 meters by 50 meters. Nine Vertical Electrical Sounding Points were acquired using Terrameter SAS 1000. The results showed that the survey area had four to six geoelectric layers with VES 1, VES 3 to VES 9 containing HA curves, while VES 2 had HK curves. The resistivity distribution ranged from 1.05 to 22.73 m, with resistivity varying from 113.8 to 1942 Om across the survey area. The estimated volume of sand within the survey area was approximately 688,059 tonnes, with the chemical content being suitable for domestic and building purposes. The sand deposits are also ideal for engineering and construction due to their inherent water permeability and storage ability. Further investigation is recommended to study construction sand deposits beyond the surveyed areas. [ABSTRACT FROM AUTHOR]

The results of experiments on electrical sounding of the near-surface layer of the Earth's crust in the fault zone, which have involved a recording of seismoacoustic and seismic noise in the close zone near the source (the primary dipole source), are represented. The experiments were carried out in 2021–2022 in the southern part of the Central Sakhalin fault with the use of the generator of electric pulses developed at IMGG FEB RAS, output electric power being up to 3 kW. The aim was to reveal seismoacoustic signatures of the medium reaction to the soundings with current pulses of 5–13 A. The generator provided significantly higher current in the dipole than its typical characteristics in the case of soundings for electrical exploration by resistance methods, as well as in the case of conventional seismic and electrical exploration. At the same time, the range of current amplitudes was much smaller in comparison with the case of a deep sounding based on application of geophysical MHD generators or other extra high-power electric pulses units. Up to now, the inverse seismoelectric effect has remained practically unexplored at currents in the “intermediate” range of ~10 A and scale lengths of the order of few hundreds of meters. The presence or absence of the medium reaction to electrical soundings was distinguished by the records of molecular-electronic sensors developed by R-sensors LLC: the CME-6111 broadband seismometer and the hydrophone, installed at a distance of about 50 m from one of the poles of the electric dipole source. An increase in the average level of seismoacoustic noise during electrical soundings was revealed, which is essentially a variety of the inverse seismoelectric effect of the second kind (excitation of elastic waves during an electric current run in a two-phase medium). Previously, no similar signature of medium reaction to the current pulses was noted in the close zone adjacent to one of the dipole electrodes. The noise level increase occurs almost without delay after the start of electrical soundings, and this is in accordance with the previously obtained results on the responses of seismic acoustic emission to powerful current pulses, which were used for a deep sounding in the Northern Tien Shan.

The present work used the electrical resistivity approach to conduct a three-dimensional modeling and initial volume estimation of the limestone layer in the Mintom region located in southern Cameroon. In order to achieve the objectives of the study, a total of 21 electrical soundings spaced 250 m were first collected in the field using the Schlumberger array. These soundings were conducted along three profiles oriented in an east–west direction, spaced 500 m. Additionally, a geological survey was conducted to identify and emphasize the presence of limestone formations within the designated study region. The interpretation of the sounding data was conducted based on the analysis of the sounding curves. The interpretation outcomes, specifically resistivity and thickness, were compared with the geological field data, resulting in the development of lithostratigraphic logs for each sounding. The geological sections were constructed using the logs of the designated profile. The lithological logs were utilized to establish a lithological interface model and calculate the volume of the limestone layer at 260 ± 13 × 106 m3, utilizing the inverse distance method built into RockWorks software. A resistivity value is assigned to each geological layer in a sounding curve, allowing for the development of a resistivity variation model specific to the limestone layer. The proposed model facilitates the categorization of limestone layers based on their resistivity variations, thus serving as a fundamental reference for prospective exploratory activities within the designated study region. Our integrated approach provides a replicable model for a better understanding of the limestone reserve and effective management of this valuable resource.

The region of Boudnib is located in southeast Morocco and depends on the territorial region of Drâa-Tafilalet and the province of Errachidia. It has a water deficit due to the lack of rainfall in the region and the overexploitation of groundwater. 76 electrical drillings were drilled and correlated with borehole and seismic reflection data to understand and identify the structure and geometry of the deep aquifer to facilitate the selection of future boreholes and wells. After the interpretation of all data of vertical electrical sounding, we exploited it to make an interpretation of the results. Indeed, we have established an isohypse of the resistant roof maps also geoelectric sections representing the different electrical discontinuities present in the study area, their nature as well as the zones favorable to the exploitation of the Turonian aquifer waters. [ABSTRACT FROM AUTHOR]

In order to find out the slip surface of the highway slope, the transient surface wave and the symmetric four-level electrical sounding method were used for comprehensive geophysical exploration. The position, shape and range of the potential slip surface were successfully identified. The geological section of the sliding body can be efficiently and accurately provided with basic data for landslide treatment design. The application of engineering examples shows that transient surface wave imaging is accurate and intuitive in the identification of sliding surface and, and can provide wave speed parameters; electrical sounding method can provide resistivity parameters of different geological bodies, and can perform transient surface waves. the combination of the two methods can greatly reduce the ambiguity of geophysical prospecting. Combined with a small number of drilling holes, it can provide a more accurate landslide body geological profile, which can play an important role in the detection of unstable highway slopes.

It is very important for the safe and stable operation of power grid to detect the location and scope of mined-out area under transmission line accurately and efficiently by comprehensive geophysical method. According to the geophysical properties of goaf, resistivity method, electromagnetic method and seismic method are often used to detect goaf, but due to the actual interference and geophysical multi-solution, a single geophysical exploration method is often difficult to achieve ideal results. In this paper, the symmetrical quadrupole section resistivity method and shallow seismic reflection method are used to detect the mined-out area under the high-voltage overhead line. The study shows that the resistivity method and seismic method are mutually validated and complementary, which effectively reduces the multi-resolution of single geophysical method interpretation, and improves the detection resolution and the reliability of interpretation results. It provides an effective basis for delineating goaf.

With growing urbanization and associated aquifer overexploitation added to ongoing climatic changes effects (with related sea level rise), coastal aquifers are increasingly threatened by marine transgression. This results in an increase of salt content in underground waters leading to expensive salt removal treatments. The aim of this study is to perform a spatio-temporal monitoring of the fresh to salt water interface using vertical electrical sounding in the Nador plain (Tipaza region, North Algeria), using a Schlumberger electrode array. The fresh to salt water interface is marked by a resistivity contrast reaching 50 Ω m in fresh water formations and less than 10 Ω m for formations with saline water. Three campaigns were conducted a year apart in May 2015, 2016 and 2017. The results illustrate a recurrent interface oscillation over time in response to seasonal changes and overexploitation. Furthermore, the fresh to salt water interface is particularly observed to rise over time away from the sea due to overexploitation and related upconing. Clay layers present natural barriers against an otherwise very large salt water intrusion at depth, portioning at depth the intrusion process. This study highlights the effectiveness of electrical sounding, repeated over time and automated. It demonstrates to be as a valuable tool for environmental assessment and water quality management, including the monitoring of salt water intrusion processes in clay bearing alluvial formations. [ABSTRACT FROM AUTHOR]

The Schlumberger vertical electrical sounding method was used to detect aquifer levels in Abraka, Obiaruku and Umutu communities in Delta State respectively. The study recorded the aquifer level in Obiaruku to be between 26m to 34m. In Abraka the aquifer level lied between 20m to about 30m while in Umutu, it was between 50m to 100m. Borehole data showed that portable drinking water lies between 20m to 100m and could easily be assessed in these areas. [ABSTRACT FROM AUTHOR]

The Schlumberger vertical electrical sounding method was used to detect aquifer levels in Abraka, Obiaruku and Umutu communities in Delta State respectively. The study recorded the aquifer level in Obiaruku to be between 26m to 34m. In Abraka the aquifer level lied between 20m to about 30m while in Umutu, it was between 50m to 100m. Borehole data showed that portable drinking water lies between 20m to 100m and could easily be assessed in these areas.

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Copyright of Larhyss Journal is the property of Biskra University, Research Laboratory in Subterranean & Surface Hydraulics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A geophysical prospecting by electrical method has been carried out in the region of Mrirt located in the heart of the causse of the Middle Atlas. The purpose of this geophysical study is to identify the geometry and the deep structure of the aquifer of the Lias and draw the schema of its hydrogeological function to determine the potential areas for the implantation of the Surveys of recognition. To achieve this objective, 39 Schlumberger Electrical Soundings have been carried out in the study area. The treatment of the geophysical measures has been achieved by using the software WinSEV 6 of GEOSOFT. The interpretation of the results has allowed revealing two aquifers assigned to the limestones and dolomitic lands of the middle and lower Lias, separated by a clay layer whose thickness varies between 5 and 10m. The roof of these two aquifers presents a wave structure, which goes back and thickens toward the south east of the study area in the direction of the outcrops of limestone and dolomitic lands of the Lias generally fractured where their thickness reaches a maximum value of 52 m. The compilation of the geophysical prospecting results with the geological and hydrogeological data and their integration into a GIS database has allowed creating a map of high productivity areas of the aquifers found in the study area. This card is a basic document to determine the sites with the greatest potential for the implantation of the drilling with high probability of success.

This paper presents the geophysical investigation for groundwater at Gbongudu area, Akobo Ojurin, Ibadan, Southwestern Nigeria. The area is underlain by the crystalline basement complex rocks and accessibility to potable water especially in the dry period of the year has been a major challenge. The Vertical Electrical Sounding using the Schlumberger configuration was employed. Twelve (12) vertical electrical sounding points were established in order to delineate the geo-electric layers in the area as well as evaluate the groundwater potential. The results are presented as profiles, geologic sections, curves, and maps. The VES results revealed a maximum of five geo-electric layers, viz: topsoil/lateritic sand, shale/clay, weathered layer, fractured basement and fresh basement respectively. Geo-electric sounding results were critically analyzed and interpreted. The yields of wells dug in most of these locations may be insufficient, even for domestic use because of its relatively small thicknesses. However, at a depth of 9.1 m a fracture zone occurs in VES 6 with resistivity value of 17.8 Ωm suggesting the presence of groundwater. Groundwater potential in this area is low on the average with VES 6 and VES 7 considered to be the main aquifer units suitable for groundwater exploration. Keywords: basement complex, electrical sounding, groundwater, exploration, aquifers

Ambiguities in geophysical inversion results are always present. How these ambiguities appear in most cases open to interpretation. It is interesting to investigate ambiguities with regard to the parameters of the models under study. Residual Function Dispersion Map (RFDM) can be used to differentiate between global ambiguities and local minima in the objective function. We apply RFDM to Vertical Electrical Sounding (VES) and TEM Sounding inversion results. Through topographic analysis of the objective function we evaluate the advantages and limitations of electrical sounding data compared with TEM sounding data, and the benefits of joint inversion in comparison with the individual methods. The RFDM analysis proved to be a very interesting tool for understanding the joint inversion method of VES/TEM. Also the advantage of the applicability of the RFDM analyses in real data is explored in this paper to demonstrate not only how the objective function of real data behaves but the applicability of the RFDM approach in real cases. With the analysis of the results, it is possible to understand how the joint inversion can reduce the ambiguity of the methods. [ABSTRACT FROM AUTHOR]

Peatlands are valuable but fragile ecosystems with diverse biogeochemical and hydrological functions, so their characterization requires non-destructive investigation. We studied adjacent alpine peatlands of similar size, at the same altitude, and exposed to identical climatic conditions, but with differing topographic and geologic settings producing contrasting ecohydrological functioning; one is a rainwater-fed bog, the other is a groundwater-fed fen. Two intentionally simple geoelectrical techniques were applied to obtain rapid geophysical fingerprints of these peatlands: vertical electrical sounding (VES) and self-potential (SP). Strongly contrasting results agree with conceptual understandings of bogs and fens. The bog VES displays a high-resistivity near-surface layer, corresponding to lowly-mineralized rainwater, while resistivity in the fen is two orders of magnitude lower due to more highly-mineralized groundwater. The SP profile of the bog indicates radially-divergent drainage, while the profile of the fen points to lateral groundwater inflow from adjacent slopes. The paired-peatland approach made possible identification and isolation of the effects of hydrological functioning on geophysical properties, while eliminating possible differences due to climate or altitude. Most importantly, this study shows that very few and simple geophysical measurements can produce critical near-real-time data on hydrologic properties of peatlands - which is especially important for inaccessible high alpine locations. [ABSTRACT FROM AUTHOR]

The electrical resistivity technique which involved the Schlumberger depth sounding method and geochemical analyses of water samples collected from boreholes was used to investigate the suitability of groundwater aquifers in Abi for drinking and irrigation purposes. Fifty randomly located electrical resistivity data were collected, modeled, and interpreted after calibration with lithologic logs. Ten borehole water samples were collected and analysed to determine anion, cation concentrations and some physical and chemical parameters, such as water colour, temperature, total dissolved solids, and electrical conductivity. The results show that the lithostratigraphy of the study area is composed of sands, sandstones (fractured, consolidated and loosed), siltstones, shales (compacted and fractured) of the Asu River Group, Eze-Aku Formation which comprises the aquifer units, and the Nkporo Shale Formation. The aquifer conduits are known to be rich in silicate minerals, and the groundwater samples in some locations show a significant amount of Ca2+, Mg2+, and Na+. These cations balanced the consumption of H+ during the hydrolytic alteration of silicate minerals. The geochemical analysis of groundwater samples revealed dominant calcium-magnesium-carbonate- bicarbonate water facies. Irrigation water quality parameters, such as sodium absorption ratio, percentage of sodium, and permeability index, were calculated based on the physico-chemical analyses. The groundwater quality was observed to be influenced by the interaction of some geologic processes but was classified to be good to excellent, indicating its suitability for domestic and irrigation purposes. [ABSTRACT FROM AUTHOR]

This paper presents the geophysical investigation for groundwater at Gbongudu area, Akobo Ojurin, Ibadan, Southwestern Nigeria. The area is underlain by the crystalline basement complex rocks and accessibility to potable water especially in the dry period of the year has been a major challenge. The Vertical Electrical Sounding using the Schlumberger configuration was employed. Twelve (12) vertical electrical sounding points were established in order to delineate the geo-electric layers in the area as well as evaluate the groundwater potential. The results are presented as profiles, geologic sections, curves, and maps. The VES results revealed a maximum of five geo-electric layers, viz: topsoil/lateritic sand, shale/clay, weathered layer, fractured basement and fresh basement respectively. Geo-electric sounding results were critically analyzed and interpreted. The yields of wells dug in most of these locations may be insufficient, even for domestic use because of its relatively small thicknesses. However, at a depth of 9.1 m a fracture zone occurs in VES 6 with resistivity value of 17.8 Om suggesting the presence of groundwater. Groundwater potential in this area is low on the average with VES 6 and VES 7 considered to be the main aquifer units suitable for groundwater exploration. [ABSTRACT FROM AUTHOR]

Onshore applications of direct current resistivity (DCR) along shorelines suffer a short-circuit-like phenomenon due to electrical current flowing through a more conductive body of water rather than ground. Our study of the numerical simulation of DCR data with a three-dimensional forward model demonstrated that the apparent resistivity was reduced as a function of the sea depth and the distance of measurement site to the shoreline. Furthermore, it was concluded that the "marine effects" on DCR data (i.e. reduction in apparent resistivity) become nonnegligible as the ratio of half-electrode expansion (AB/2) to the distance to the shoreline is larger than one. The reduction in apparent resistivity reaches its highest levels as the ratio approaches ten. Our survey conducted along the coastal line of Northwest Turkey clearly showed that if the "marine effects" are left untreated, one- or two-dimensional inversion yields incorrect resistivities for underlying units and therefore undermines the credibility of survey results. In the paper suggestions are made to handle such situations. [ABSTRACT FROM AUTHOR]

In order to obtain more concrete and more accurate results when the modelling of the under surface structure of the investigated area is made with the usage of geophysical examinations, if the field conditions allow it is necessary to be applied more than one geophysical method. In this paper is elaborated the procedure of complex interpretation of a seismic and geo - electrical model. The seismic model is modelling the geological structure by determining the speeds of propagation of the elastic waves which depends from the geo - mechanical characteristics of the geological environments. The geo - electrical model is modelling the investigated area by registering the changes on the electrical field which depends from the conductivity of the geological environments. The parameters of the investigated area (the layers of different geological environments, their electrical conductivity and geo - mechanical characteristics as well as the depth of examination) that is elaborated in this paper provide acceptable conditions for applying the refractive seismic method and the method of geo - electrical sounding. The refractive models as well as the models of geo - electrical sounding are made synthetically while using the data obtained from geological and geo - mechanical examinations. With the interpretation of the refractive models are determined the different geological environments (by the different speeds of propagation of the elastic waves) as well as the boundary surfaces that separates them, whereas with the interpretation of the models of apparent electrical resistivity the different geological structures and the boundary surfaces between them are defined by their actual specific electrical resistance. As a final phase of the modelling in the paper is made correlation between the two models (seismic refraction and geo - electrical sounding) as well as comparison and interpolation between the interpreted results in order to obtain more concrete and more precise vision for the under surface structure of the investigated area. [ABSTRACT FROM AUTHOR]

The Geoelectrical method plays a critical role in exploration and reviving Qanats. DC resistivity method is a subtype of Geoelectrical method that has been used to explore and revive Qanats. Gaftaj is located about 25 kilometres north-west of Ferdows city, South Khorasan province, Iran. In this area, there are four main Qanats. In the paper, resistivity data have been surveyed by Schlumberger array and 36 electrical soundings was performed on two profiles. The apparent resistivity contour map was prepareded for tow profiles and near sonding. The results showed that excavation is not appropriate for revival of Qanats. Moreover, the result showed that gallery is the best option for revival of Qanats. The apparent resistivity contour map cleared a fault between Shale of the Mesozoic priod and Conglomerate of the Cenozoic priod in this region. Finally, drilling of wells was recommended on the fault for providing water in this region. [ABSTRACT FROM AUTHOR]

The article presents a time-lapse geoelectrical-geochemical study at a reactive coal washing waste pile in Northeastern Iran that is consisted of one dimensional (1D) electrical sounding with a Schlumberger array. The time-lapse methodology demonstrated the significant role of water in the resistivity changes within pile.

Abstract: Deltaic aquifers are complex due to the important heterogeneity of their structure and their hydrogeological functioning. Auger drilling provides localized, but very robust geological and hydrogeological information, while geophysical surveys can provide integrated subsurface information. An effective, easy-to-use and low-cost methodology combining geological/hydrogeological information from Auger drillings and the results from three geophysical techniques (Electromagnetic mapping, Electrical Sounding and Electrical Resistivity Tomography) is being developed to characterize the structure of a typical Mediterranean deltaic aquifer. A first hypothesis about hydrodynamic properties of the aquifer is also obtained. The study area is located in the Rhone delta (Middle Camargue/southern France). Integration of geophysical and geological techniques allowed identifying the presence and lateral extension of the Saint-Ferréol paleochannel, the vertical contact between lagoonal–fluvial deposits and the marine clayed silt that separate the superficial aquifer from the deeper aquifer. Likewise, high north–south heterogeneity and east–west homogeneity were highlighted in the study area. Presence of clay in sandy deposits in the low areas implies changes in lateral hydraulic permeability. This fact, jointed to the low hydraulic gradient, suggests a slow groundwater flow in the local system. The Rhone delta presents a typical configuration of a Mediterranean deltaic aquifer, thus this methodological approach can be used for similar deltaic Mediterranean systems. [Copyright &y& Elsevier]

Abstract: A joint inversion of gravity and geoelectrical data has been performed along a 100km long profile across the oil-bearing Potiguar rift basin in NE Brazil. The integrated approach is based on the connection between density and resistivity of a sedimentary sequence through the porosity. Seventy-one gravity stations and twenty-nine vertical electrical soundings were carried out across the central part of the Early Cretaceous basin in the Precambrian Borborema Province to apply the proposed joint inversion. Both the physical properties and geometry of the multilayer deep model were well constrained by a wide set of prior information obtained by surface mapping, geophysical logs and seismic sections. The results reveal a rift architecture formed by a 5000m thick half-graben structure separated by an intervening basement high and an extensive adjacent platform with a sedimentary infill of about 300m thick. The calculated model shows geometries for the sedimentary density/resistivity interfaces in agreement with the seismostratigraphic sequences revealed by seismic section, representing a substantial improvement in comparison with previously published gravity models. [Copyright &y& Elsevier]

I propose a fast method for constructing pseudosections of apparent resistivity from geoelectrical data collected for deep studies with continuous polar dipole-dipole arrays. Once a vertical section is fixed, each value of apparent resistivity is assigned to a point on the section and finally pseudosections are obtained by interpolation. This allows the geophysicist to represent a large amount of data in a fast and simple way, to perform a qualitative interpretation and to facilitate the quantitative interpretation.