Dipole-dipole Resistivity Research Articles

Magnetic and resistivity imaging of a probable fault within the Precambrian crystalline rocks in Ogbomoso, Southwestern Nigeria

A linear structure which is interpreted to be a fault was identified within the Precambrian basement complex rocks of the Ogbomoso Southwest Sheet 222 geological map, southwest Nigeria. The ground magnetic and electrical resistivity methods were used to investigate the structure and determine its physical characteristics. Five (5) traverses with lengths varying from 700–800 m and trending approximately NW–SE were established perpendicularly to the suspected fault. Total magnetic field data were acquired at 10 m interval, corrected for diurnal variation and inverted into 2D magnetic models using the Geosoft Oasis montaj software package. Dipole-Dipole resistivity data were acquired along the traverses using a dipole length of 20 m with expansion factor n varying from 1 to 5 and modelled to generate 2D resistivity structures with the DIPPROTM software package. Thirty-seven (37) depth sounding datasets were acquired, quantitatively interpreted and the results used to generate geoelectric sections across the suspected geologic feature. Three major magnetic dyke lineaments D1, D2 and D3 (60 – 164 m wide and 70 – ∞ depth extent) characterised by peak negative (−44 to −81 nT) magnetic anomalies and equivalent resistivity lineaments R1, R2 and R3 (50 – 140 m wide and 40 to >60 m depth extent) typified by low resistivity (10 – 750 Ωm) vertical discontinuities were delineated. The northern edges of lineaments D2 and R2 coincide significantly with the spatial location of the suspected fault F1 – F1 while D1 and R1 and D3 and R3 correlated and are newly identified parallel faults F2 – F2 and F3 – F3 to F1 – F1 and probably syngenetic with it.

Application of 2D resistivity from geoelectrical methods with dipole dipole configuration for identification of land slides in Citeko Village, Cisarua, Bogor District, West Java

At present, many methods are used to discussed about landslide problems, especially regarding the slip field from the perspective of a one-disciplinary or multidisciplinary approach. One of the approach is using the 2D resistivity geoelectrical method. This research has been carried out to identify landslide and slip fields in Citeko Village, Cisarua District, Bogor Regency using the dipole-dipole resistivity configuration on geoelectrical method. Measurements were made in three passes with 235 metress in length and 5 metress in electrode distance. Data were processed using Res2dinv software, and the results showed that in the study, area lithology of its subsurface rocks was detected, including alluvium and sand layers, weathered material, up to volcanic rocks. Then, there are also clay layers, silt clay layers, and sandstones. The slip fields could be analyzed like a clay layer with resistivity values ranging from 42.3 Ωm−1 to 155 Ωm−1, and its position was in line 1 and line 2, with a depth of 8.5 metres - 16.4 metres. It also identified in line 3 at the depth of 16.4 metres. Then, based on the interpretation of resistivity 3D modeling with Rockworks software from geoelectric data, it shows that the direction of the landslide tends to be centered towards the Northwest to the West, this is also supported by visual observations in the field.

Groundwater Aquifer Vulnerability Assessment using a Dar-Zarrouk Parameter in a Proposed Aboru Residential Estate, Lagos State, Nigeria

The need to build an automobile mechanic settlement, abattoir and a proposed meat processing factory at Aboru residential estate necessitated a geophysical assessment (using a Dar-Zarrouk parameter – longitudinal unit conductance, S) of the vulnerability of the subsurface aquifers in the study area against the expected long-term anthropogenic impacts of these facilities on the groundwater system. Thirteen (13) Vertical Electrical Sounding (VES) points and four (4) Dipole-Dipole resistivity profile lines were occupied on four traverse lines across the study area. Isoresistivity and Isopach maps were generated and Total Longitudinal Unit Conductance, S of the earth materials overlying the aquifer was computed and the aquifer protective capacity (APC) map was generated. The VES delineated four (4) geo-electric layers namely; topsoil, pebbly/lateritic sand, clay/clayey/silty sand and sandstone. The depth to the sandstone aquifer ranges from 30.6 – 39.4 m with resistivity values ranging from 851 – 1437 Ωm. The iso-resistivity and isopach maps reveal that the near surface lateritic materials with resistivity values ranging from 350 – 1150 Ωm and thicknesses ranging from 2 – 29 m are pervious. The Total Longitudinal Unit Conductance, S varies from 0.0164 - 0.1168 mhos indicating a poor to weak protective capacity rating across the study area and the APC map reveals that the north-eastern and western parts of the study area show areas with weak protective capacity ratings while other areas are characterized by poor protective capacity rating. As such, the establishment of the proposed service facilities in the study area is strongly discouraged as the nature of their operations has a high potential to contaminate and eventually pollute the sub-surface aquifers on the long-run. If however the inevitability of their establishment cannot be set-aside, then secondary measures must be taken to forestall a direct impact of their operations on the subsurface. Keywords : Aquifer, Dar-Zarrouk, Vulnerability, Longitudinal Unit Conductance

2D electrical resistivity imaging based on backpropagation artificial neural network

Dipole-dipole is one configuration design survey in electrical resistivity method which is common to interpreted shallow subsurface base on resistivity parameter, and the model can be developed using inversion formula. Otherwise, we developed some model without empirical mathematic formula; it is called Artificial Neural Network (ANN). ANN is a system which has a pattern like the human brain process to solve the complex problems. The research aims to develop a neural network algorithm using Matlab and compare the result 2D model resistivity between ANN and inversion by Res2Dinv (existing procedure) software. The research was done in Taman Rumah Kita (TRK) where located in Faculty of Science and Mathematics, Diponegoro University. A cylinder was buried in the center of TRK and getting the best architecture of the network and the value of Mean Square Error (MSE) of the output network. The backpropagation artificial neural network was built from many layers such as an input layer, hidden layer, and output layer and developed by Matlab programs. The Network train was tested using synthetic data and field data. The synthetic data was made with forwarding modeling method by Res2Mod software, and the field data was obtained by doing the measurement at the measurement site using dipole-dipole resistivity method. The comparing result models are present the best architecture obtained one input layer with three input units, three hidden layers with each layer has 100 neurons and one output layer that obtained by trial and error process. MSE obtained respectively in observation lines are 0.0210 at Line 1, and 0.0345 at Line 2.

INVESTIGATION OF JABUNG TEMPLE SUBSURFACE AT PROBOLINGGO, INDONESIA USING RESISTIVITY AND GEOMAGNETIC METHODS

Subsurface structural estimation has been investigated with dipole-dipole resistivity configuration and magnetic methods for mapping of Jabung Temple Archaeological Site located in Jabung Village, Paiton Sub-District, Probolinggo Regency, East Java with Resistivity meter OYO MacOhm and Proton Precession Magnetometer. This estimate aims to determine the spread and depth of the rocks below the surface of the Archaeological Site of Jabung Temple as well as a source of information for the discovery of ancient objects still buried in the soil. The acquisition of resistivity data was performed on ten measuring tracks and covered the measurement area of ± 37,900 m2. Six trajectory tracks are located around Menara Sudut Temple and four line are located in the area of Jabung Temple. The acquisition of magnetic data is made around the area of Jabung Temple at 924 points with spacing of 2.5 meters, with the area of 5,200 m2. Based on the interpretation of magnetic anomaly and resistivity data, the magnetic anomaly value, 22.6 nT due to andesite rock used as a temple booster (based on information obtained during the restoration of 1983/1984). The results of this study indicate that geoelectric and magnetic methods are very effective for the prediction of subsurface structures, especially in the archaeology field.

English

As part of effort to examine the factors responsible for highway failure in the sedimentary terrain, geophysical survey involving Very Low Frequency Electromagnetic (VLF-EM), Schlumberger Vertical Electrical Sounding (VES), and dipole-dipole electrical resistivity techniques were carried out along Iruekpen-Ifon highway. This was aimed at using surface geophysics to characterize and identify the factors responsible the for road failures along Iruekpen-Ifon highway. ABEM WADI instrument was used to obtain electromagnetic-Very Low Frequency (VLF) field data, while ABEM resistivity meter was used to obtain electrical resistivity field data. The VLF-EM data were interpreted using the VLF Graphic software, VELFAN 1.0 double plot of filtered real and filtered imaginary against distance. The VES data obtained were interpreted using IP 2 Win software. Geoelectric parameters were used to generate the Dar Zarrouk second order parameters. 2-D inversion modeling of the dipole-dipole data was carried out using ZONDRES window software. VLF-EM result suggested varying degree of conductivity in the area and the wide spread of clay/metallic ore and water in the study area. Results show that the topsoil generally varies in composition from clay to clayey and laterite with resistivity values varying from 89 to 400 Ωm and thickness between 0.2 and 4.0 m. The fractured layers composed of clay and compacted clayey sand which represents the recent alluvial deposits with resistivity values of 2 to 89 Ωm and the thickness between 1.5 and 11 m. The fresh water zone is characterized by low resistivity ranging from 0.5 to 23 Ωm, which is diagnostic of saline water saturated with clay formation, fresh water ingression, and marls. The values of co-efficient of anisotropy (l) range from 1.03 to 2.19. The relatively higher values of λ (1.30 to 2.19) suggest that the subsurface rocks in these areas are likely to be more intensely fractured and more permeable. The saline water saturated with clay formation, fresh water ingression, fracture and marls clearly limit the lithological contacts and enhance high swelling potential which might be responsible for the road pavement failures in the studied area. Key words: Highway, resistivity, troubled roads, Dar Zarrouk, anisotropy.

Ground Magnetic, GPR, and Dipole-Dipole Resistivity for Landfill Investigation

Ground magnetic, ground penetrating radar (GPR), and dipole-dipole resistivity were carried out to environmentally investigate a landfill. In this context, these geophysical techniques were conducted to identify the subsurface contents of the landfill, furthermore, specify any possible leakage and/or contamination in the study area. The ground-magnetic survey carried out in the study area comprised 31 profiles each 120 m in length. Different wavelength filters were applied to the measured data. Vertical derivative, downward continuation, apparent susceptibility, band-pass, and analytical signal filters separated successfully the shallow sources. Whereas, upward continuation and low-pass Gaussian filters isolated significantly the deep magnetic sources. 3D Euler deconvolution (SI = 3) remarkably estimated the depths of the shallow sources (0 - 10 m) of the landfill contents. The conducted GPR and dipole-dipole resistivity allocated tangibly the locations and depths of the near surface anomalies. Both techniques didn’t reveal any possible leakage and/or contamination. Noteworthy, integration among magnetic, GPR, and dipole-dipole resistivity confirmed positively the results of each method. Nevertheless, some anomalies were recognized successfully by one technique and not by the others.

Surface DC resistivity survey of contamination Beneath Ido-Osun dumpsite, southwestern Nigeria

Surface DC resistivity techniques have been used to investigate the subsoil characteristics around an abandoned dumpsite in Ido Osun, Southwestern Nigeria. The aim was to delineate groundwater contamination, identify lithologic layers, locate possible leachate plumes, and assess the risk of groundwater pollution. Schlumberger vertical electrical sounding (VES) and Dipole-dipole resistivity profiling data were acquired at 20 m and 10 m intervals respectively along three northwest-southeast geophysical traverses. The geoelectric sections revealed four probable subsurface geoelectric layers which were considered to be topsoil, laterite, weathered/fractured bedrock and competent/fresh bedrock based on previous works. The weathered/fractured bedrock forms the groundwater reservoir in the area as interpreted from the over 98% occurrence of H, KH geoelectric curve types. The dipole-dipole sections showed several distinct low resistivity zones which extends into the weathered/fractured bedrock. These were interpreted as probable contamination plumes beneath the dumpsite.

On the electromagnetic response of a resistive cylinder buried in a conductive host

The frequency-domain electromagnetic response of a confined conductor buried in a resistive host has received much attention, particularly in the context of mineral exploration. In contrast, the problem of the electromagnetic response of a confined resistor buried in a conductive host has been less thoroughly studied. However, resistive targets are important in geotechnical and hydrologic studies, archaeological prospecting, and, more recently, offshore hydrocarbon exploration. I analytically address the problem of the electromagnetic response of a completely resistive cylindrical cavity buried in a conductive host in the presence of a simplified 2D electric dipole source. In contrast to the confined conductor, which channels and induces current systems, the confined resistor deflects current and produces additional eddy current systems in the conductive host. I apply this theory to model the response of a grounded electric dipole-dipole system operating over a range of frequencies from 0 Hz to 10 kHz, in the presence of a horizontal 5-m radius insulating cylinder located 1-m beneath the surface of a uniform earth. This represents a common hazard encountered during mining and civil engineering operations. Results show that such an insulating cavity increases the recorded electric field amplitude and phase delay at all transmitted frequencies. These observations suggest that a broadband electromagnetic prospecting system may provide additional information about the location and extent of a void, over and above a standard dipole-dipole resistivity survey. When the host skin depth is much larger than all other length scales, the response can be approximated by an equivalent single dipole unless the cylinder’s radius is much larger than its distance from the transmitter. This result provids a useful rule of thumb to determine the acceptable range over which a resistive target can be modeled by a distribution of dipoles.

Karstic water exploration using the Schlumberger VES and dipole-dipole resistivity profiling surveys in the Tepal area, west of Shahrood, Iran

To have sustainable development in a country, the need for clean groundwater resources is undoubted. Due to the importance and high quality of karstic waters in supplying water in Iran, especially in Shahrood city, this study aim to recognize and explore Karstic waters in southwest of Tepal area, Shahrood. For this purpose, the study used the integration of the results obtained from the methods of vertical electrical sounding (VES) and resistivity profiling. The VES surveys were performed in 10 sounding points using the Schlumberger array with electrode separations of a maximum 500 meters. The resistivity profiling surveys were carried out along four lines with a length of more than four kilometers using dipole-dipole electrode array with 75m electrode spacing and dipole steps 1 to 8 in the study area. Then, one-dimensional (1-D) modeling and interpretation of the sounding results, using master curves and IX1D software, and twodimensional (2-D) modeling and interpretation of the profiling results using Res2DINV were made. As a result of the interpretation and integration of the results, karstic water zones in the study area were recognized, and based on that, suitable locations for drilling to access and extract karstic groundwater were introduced.

Dipole-Dipole Resistivity Measurements of Weathered Soils Over Major Rock Types in a Humid Climate - A Case Study of Ashanti Region-Ghana

Ninety six (96) dipole-dipole resistivity sounding curves acquired with Mac-Ohm II resistivity meter over the Birimian, Intrusives, Tarkwaian and Voltaian rocks underlying Ashanti Region have been analyzed qualitatively to identify their characteristic shapes over each rock type. Geoelectrical sections have also been modeled from the curves and drill logs obtained close to the sounding points. Four (4) major three (3)-geoelectrical sections were identified. These were characterized by the H, A, Q and K- type curves which corresponded to the resistivity sequence r1>r2

Integration of very low-frequency electromagnetic (VLF-EM) and electrical resistivity methods in mapping subsurface geologic structures favourable to road failures

An integrated geophysical survey involving very low-frequency electromagnetic (VLF–EM) and the dipole-dipole electrical resistivity methods was carried out along the Auchi-Ibillo road in Igarra, Nigeria with a view to examining factors responsible for road failures in the area. Analysis of very low frequency electromagnetic current density sections and dipole-dipole pseudo-sections were made along three traverses. The (VLF–EM) revealed the presence of conductive zones and the dipole-dipole pseudo-sections delineated low resistivity clay enriched, water absorbing sections and a linear fracture zone or joint. The delineated clay section and the fracture zone are the major geologic factors responsible for road failures in the area. Key words: Electromagnetic, resistivity, Igarra, Nigeria, geologic factor, road failure.

Bayesian Inversion for Cavity Investigation

ABSTRACT Geophysical investigation and Bayesian inversion have been performed to investigate the cavity structure. The targeted cavity is a lava cave in Cheju Island, Korea and the geometry of the cavity is already known. For the cavity detection, we have used the both dipole-dipole array resistivity and gravity method. Although the two methods generally have different objectives, common characteristics may be appeared in the cavity structure. That is, the resistivity value is high but the gravity one is low in the presence of the cavity. We choose the dipole-dipole array resistivity data as prior information for the Bayesian inversion of gravity data. We applied the indicator variogram modeling to transform the result of resistivity inversion to density information, as higher resistivity block has lower density one. This assumption is valid in Cheju Island where most of the rocks are composed of basalt. Generally, cavity investigation by single geophysical exploration is difficult to get effective result. However, this coupled interpretation proposes a new way to provide remarkable improvement and stability when compared to the result of single method.

The geophysical response of the Tusker gold deposit, Lake Victoria gold fields, Tanzania

The Tusker gold deposit is located in the Lake Victoria Goldfields of Tanzania. The deposit contains total estimated resources of 123.27 Mt at 1.15g/t Au, as at 5th September, 2006. Geophysical techniques trialled over the deposit include down hole measurements, airborne time domain electromagnetics, dipole-dipole induced polarisation and resistivity and airborne magnetics. Petrophysical measurements suggest the deposit is associated with a conductive and chargeable signature. This is confirmed by airborne EM and dipole-dipole IP and resistivity data. Magnetic data map the unmineralised magnetic mudstone package overlying the deposit, and show that stratigraphy is deformed.

Resistivity Probability Tomography Imaging at the Castle of Zena, Italy

We present the results of an electrical resistivity investigation performed at Castle of Zena (Castello di Zena), a 13th-century fortress located between the towns of Fiorenzuola and Piacenza in the Emilia Romagna Region (Northern Italy), in the frame of a project of restoration. Dipole-dipole resistivity tomographies were planned in three areas suspected of containing buried archaeo-architectural remnants. Data analysis has been made using a 3D tomography imaging approach based on the concept of occurrence probability of anomaly sources in the electrical resistivity distribution. The 3D tomography has allowed three interesting anomaly source areas to be identified in the 1-2 m depth range below ground level. Subsequent excavations have brought to light a giacciara, that is, a brickwork room for food maintenance, a furnace, and the basement of a wing of the castle destroyed in the 18th century, exactly in correspondence with the anomaly sources detected by the resistivity tomography.

Integrated geophysical mapping of the Ifewara transcurrent fault system, Nigeria

Integrated geophysical methods involving magnetic and dipole–dipole resistivity (DDR) were conducted across a prominent zone of weakness clearly observable in Landsat MSS and SLAR images in the Precambrian basement complex of southwestern Nigeria. Up till now, the location and existence of this megascopic structure have not been confirmed using geophysical methods. With the objective of delineating this weak zone and its structural attributes, three traverses were established at 500 m intervals across it, and geophysical measurements were made at 10 m intervals along these traverses. Qualitative interpretation of the magnetic data obtained shows a diagnostic signature of a near-vertical fault, trending along a NNE–SSW direction. Also, the quantitative interpretation of the data using the non-linear least-squares regression technique indicates that the width of the magnetic anomaly ranges from 90 to 150 m, its dip angle varies between 75° and 85°; the anomaly is concealed by a regolith of approximately 15 m thickness. Furthermore, a 2D resistivity inversion of the field resistivity data reveals a three-layer model, representing thin resistive topsoil underlain by weathered bedrock, resistive bedrock with a distinct low resistivity zone located within the bedrock. The most plausible explanation for this low resistivity zone is that it was formed by shearing activities during Late Precambrian times. Conclusively, the integrated approach employed in this research confirms the existence of the supposed Ifewara shear zone (ISZ).

Shallow geophysical investigations at the Akhmim archaeological site, Suhag, Egypt

Ground penetrating radar, electromagnetic terrain conductivity, and electric tomography have proven to be effective tools if they are combined together to investigate archeological sites. We have conducted a geophysical survey at the Akhmim archaeological site, the main objective of our survey is to locate additional buried structures for further excavation. Geophysical data were acquired in the area using the GEM-300 multi-frequency terrain conductivity profiler, the SIR 2000 ground penetrating radar, and the Syscal R2 resistivity meter systems. The results of the integrated interpretation show a number of buried features and a strong linear zone about 1 m wide that coincides with the suspected trend of a buried wall. There appears to be two parallel ridges of strong reflections on either side, indicating two parallel walls extended East-West and a room is identified at the bottom left corner of the site. Moreover, the interpretation results of some selected GPR and dipoledipole resistivity profiles adjacent to the open-air museum suggest the existence of a second statue of Ramses II to the right of the previously discovered statue which could still be buried in the sand.

Crossline resistivity tomography for the delineation of anomalous seepage pathways in an embankment dam

Crossline resistivity tomography was developed to find out anomalous seepage pathways in an embankment dam. By applying crossline tomography to the investigation of embankment dams, leakage pathways can be effectively located because the crossline tomogram presents resistivity distribution in the horizontal plane of an embankment dam. To test the effectiveness of crossline tomography, we applied it to data from an experiment designed to delineate anomalous seepage pathways in the embankment dam. The method yields relatively accurate geoelectric structure of the dam when applied to synthetic data. In the crossline resistivity tomogram, abrupt discontinuities of a low resistivity band corresponding to the core of the dam can be interpreted as leakage pathways. Application to real data obtained from an embankment dam in Korea yields the result which accurately depicts two anomalous seepage pathways. The identified pathways were consistent with low resistivity zones in the dipole-dipole resistivity section obtained on the crest of the dam. One pathway was confirmed by visual inspection of the dam, and afterward, by trenching.

Geophysical Resistivity Imaging for Upper Layer of Shield TBM Tunnel Ceiling

ABSTRACT Recently shield TBM tunnelings are being applied to subway construction in Korean cities. Generally these kinds of tunnelings have the problems in the stability of ground such as subsidence because urban subway is constructed in the shallow depth. A sinkhole occurred on the road just above the tunnel during tunneling in Kwangju, so a survey for upper layer of the tunnel was needed. But conventional Ground Probing Radar can't be applicable due to the presence of steel-mesh screen in the shield segment, so no existent geophysical method is applicable in this site. Because the outer surface of each shield segment is electrically insulated, dipole-dipole resistivity method which is popular in engineering site investigation, was tried to this survey for the first time. Specially manufactured flexible ring-type electrodes were installed into the grouting holes at an interval of 2.4 m on the ceiling. The K-Ohm II system which has been developed by KIGAM and tested successfully in many sites, was used in this site. The system consists of 1000Volt-1Ampere constant-current transmitter, optically isolated 24 bit sigma-delta A/D conversion receiver—maximum 12 channel simultaneous measurements, and graphical automatic acquisition software for easy data quality check in real time. Borehole camera logging with circular white LED lighting was also done to investigate the state of the layer. Measured resistivity data lack of some stations due to failing opening lids of holes, shows general high-low trend well. The dipole-dipole resistivity inversion results discriminate (1) one approximately 4 meter diameter cavity (grouted but incompletely hardened, so low resistivity—less than 30ωm), (2) weak zone (100–200ωm), and (3) hard zone (high resistivity—more than 1000ωm) very well for the distance of 320 meters. The 2-D inversion neglects slight absolute 3-D effect, but we can get satisfactory and useful information. Acquired resistivity section and video tapes by borehole camera logging will be reserved and reused if some problem occurs in this site in the future.

Resistivity surveys near a waste-disposal site in the Qasr Tuba area of central Jordan

Direct current (DC) Schlumberger resistivity sounding and dipole-dipole resistivity profiling experiments were conducted at the border of an 2.2 long×1 km wide open waste disposal site in central Jordan. The site is on an approximately 20 m thick limestone, chert and chalk rock sequence and is surrounded by a series of hills. Lying upstream of an urban area, agricultural land and numerous groundwater wells, any contamination spreading from the waste disposal site could have a serious effect on the people and the environment. In this study, the subsurface resistivity distribution was mapped and compared with the data obtained from boreholes and aerial photographs. DC resistivity methods were found to be a fast and inexpensive data collection tool. The results obtained will be of use for engineering preparations and the operation of the site, as well as for monitoring any future pollution.