scholarly journals Resistivity Data Modeling for Subsurface Volcanostratigraphy Construction of Cibadak Sub-Watershed, Bogor, West Java, Indonesia.

2021 ◽  
Vol 6 (2) ◽  
pp. 74-80
Author(s):  
Muhammad Kurniawan Alfadli ◽  
Undang Mardiana ◽  
Nanda Natasia ◽  
Febriwan Mohammad ◽  
Deden Zaenudin Mutaqin
Keyword(s):  
Subsurface Layer ◽  
Grid Method ◽  
High Elevation ◽  
High Resistivity ◽  
Pyroclastic Material ◽  
Resistivity Method ◽  
Model Interpretation ◽  
Correlation Parameters ◽  
Volcanic Facies ◽  
Area Product

In Mt. Salak, there are six volcanic facies divided by eruption time seen from geomorphology data analysis and to identified the subsurface layer DC Resistivity method is applied. Beside resistivity, geostatistical parameters also influence the result model interpretation, so for obtain best model correlation parameters such as tilting, surfacing, variogram, grid method, and logarithmic distribution is applied. Using 18 points of acquisition data subsurface model is produce and then section model made to describe vertical resistivity distribution then correlated with facies lithology model. Based on that, produce three facies resistivity type namely: 0 – 100 Ohm.m (Low Resistivity Value) Interpreted as pyroclastic material composed as tuff and breccia that lies under lava. 100 – 300 Ohm.m (Medium Resistivity Value) Interpreted as breccia lithology type. Harder that pyroclastic material due to by this product is avalanches of lava. And >300 Ohm.m (High Resistivity Value) Interpreted as lava lithology that lies at high elevation and the hardest lithology in this area. From the model, pyroclastic layer that is modeled found at low elevation and based on the direction it described as oldest facies layer, but at the bottom of this layer lies high resistivity value that unknown product. It can be Mt. Pangrango product due to at low elevation predicted as combine area product from product of Mt. Salak and Pangrango. High resistivity value show lava lithology and lava facies located in high elevation and medium resistivity describe breccia lithology as avalanche product of lava (youngest pyroclastic facies) and found at 500 – 100 meters msl.

scholarly journals Exploring the regolith with electrical resistivity tomography in largescale surveys: electrode spacing related issues and possibility

2020 ◽  
Author(s):  
Laurent Gourdol ◽  
Rémi Clément ◽  
Jérôme Juilleret ◽  
Laurent Pfister ◽  
Christophe Hissler
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Large Scale ◽  
Electrical Resistivity Tomography ◽  
Subsurface Layer ◽  
Electrode Spacing ◽  
High Resistivity ◽  
Constant Thickness ◽  
Resistivity Tomography

Abstract. Within the Critical Zone, regolith plays a key role in the fundamental hydrological functions of water collection, storage, mixing and release. Electrical Resistivity Tomography (ERT) is recognized as a remarkable tool for characterizing the geometry and properties of the regolith, overcoming limitations inherent to conventional borehole-based investigations. For exploring shallow layers, a small electrode spacing (ES) will provide a denser set of apparent resistivity measurements of the subsurface. As this option is cumbersome and time-consuming, smaller ES – albeit offering poorer shallow apparent resistivity data – are often preferred for large horizontal ERT surveys. To investigate the negative trade-off between larger ES and reduced accuracy of the inverted ERT images for shallow layers, we use a set of synthetic conductive/resistive/conductive three-layered soil–saprock/saprolite–bedrock models in combination with a reference field dataset. Our results suggest that an increase in ES causes a deterioration of the accuracy of the inverted ERT images in terms of both resistivity distribution and interface delineation and, most importantly, that this degradation increases sharply when the ES exceeds the thickness of the top subsurface layer. This finding, which is obvious for the characterization of shallow layers, is also relevant even when solely aiming for the characterization of deeper layers. We show that an oversized ES leads to overestimations of depth to bedrock and that this overestimation is even more important for subsurface structures with high resistivity contrast. To overcome this limitation, we propose adding interpolated levels of surficial apparent resistivity relying on a limited number of ERT profiles with a smaller ES. We demonstrate that our protocol significantly improves the accuracy of ERT profiles when using large ES, provided that the top layer has a rather constant thickness and resistivity. For the specific case of large-scale ERT surveys the proposed upgrading procedure is cost-effective in comparison to protocols based on small ES.

A 3-D geoelectric model over mineralized zone of Ugonoba, Edo State, Nigeria

2021 ◽  
Vol 20 (1) ◽  
pp. 141-150
Author(s):  
V.B. Olaseni ◽  
J.O. Airen
Keyword(s):  
Mineral Resources ◽  
Electrode Spacing ◽  
High Resistivity ◽  
Clayey Sand ◽  
Resistivity Method ◽  
True Resistivity ◽  
Geological Features ◽  
Mineralized Zone ◽  
Formed Part ◽  
Block Models

The occurrence of solid minerals in Ugonoba community was investigated using the 3D electrical resistivity method. Data was acquired  using PASI 16GL Terrameter using the wenner electrode configuration with a view to delineating mineral deposits in the study area.  During the reconnaissance survey, the outlook of some geological features in the form of outcrops on the surface formed part of the motivation for the geophysical survey within the Ugonoba area. Ten traverses of 200 m maximum spread and 10m electrode spacing with total depth of 40.07 m were obtained in the study area to form a square grid. The acquired data was first processed and inverted using RES2DINV software to generate ten 2-D model images and later collated into 3-D using the inversion code of RES3DINV software which automatically determines a horizontal 3D depth slice, cubes and block models of resistivity distribution. These models generated were interpreted and used to ascertain the true resistivity, lithologic formation, depth extent to any buried mineral and aggregate deposited in the study area. The extracted 3D model images revealed evidence of some geological materials/minerals in the study area which fall within the high resistivity range of 2500 Ωm to 14376 Ωm. It can therefore be inferred from the standard resistivity table that the lithology of study area is composed of non-metallic type of mineral resources which are: clayey sand, lateritic clayey sand,  sandstone and limestone. The estimated quantity in metric ton for the dominant lithology (sandstone, granite and limestone) is ± 10% of 1,257,142.9 which can be commercially explored. Keywords: Wenner-wenner array, outcrop, minerals, RES3DINV, block models.

Detection of Unfavorable Karst Cavities in the Carbonaceous Bedrock Area at the Kaihua Segment of Hangzhou-Xinanjiang-Jingdezhen Expressway

2014 ◽  
Vol 919-921 ◽  
pp. 382-387
Author(s):  
Man Xu ◽  
Zhi Hua Chen ◽  
Bin Zeng ◽  
Wang Li Ye ◽  
Kai Fu Chen
Keyword(s):  
High Density ◽  
High Resistivity ◽  
Research Results ◽  
Low Resistivity ◽  
Resistivity Method ◽  
Physical Background ◽  
New Interpretation ◽  
Interpretation Method ◽  
Great Harm

The karst cavities can cause great harm to the construction or running of expressway. During the construction of expressway, the detection of these unfavorable geological objects is usually by use of high density resistivity method, and the physical background of the method is the combination of high resistivity of bedrock and low resistivity of karst cavities. In the study area, the Kaihua segment of Hangzhou-Xinanjiang-Jingdezhen Expressway, the widely distributed rich carbonaceous bedrock shows low resistivity, and the conventional interpretation idea of high density resistivity method is not applicable. The research results of this paper suggest that the U shape of relative high resistivity can be an indicative for detection of unfavorable geological objects such as karst cavities. 6 out of 11 boreholes drilled for purpose of calibration revealed karst cavities, and the karst ratio is from 1.2% to 10.3%, indicating the new interpretation method is feasible and reliable.

scholarly journals Resistivity Models of Pantar Island Geothermal System East Nusa Tenggara, Indonesia

2020 ◽  
Vol 5 (3) ◽  
pp. 127-132
Author(s):  
Yoqi Ali Taufan ◽  
I. Syafri ◽  
D. Risdianto ◽  
A. Zarkasyi ◽  
T. Rahadinata ◽  
...  
Keyword(s):  
Heat Source ◽  
3D Models ◽  
High Resistivity ◽  
Geothermal System ◽  
Geothermal Systems ◽  
Low Resistivity ◽  
Resistivity Method ◽  
Geological Conditions ◽  
The Difference ◽  
Clay Cover

The subsurface geological conditions of a geothermal system are vital objects to be considered in geothermal exploration. The Magnetotellurics survey was conducted to explore for geothermal potential in Pantar Island. This is to achieve deeper penetration compared to our previous study that adopted resistivity method to determine reservoir zones based on rock resistivity models. The difference in rock resistivity in geothermal systems provides subsurface geological information in the form of low resistivity that associated the clay cap zones (high conductive), the medium resistivity zones associated with the reservoir zones, and high resistivity associated with a heat source. The results of 2D and 3D models from MT data show that the low resistivity value (<20Ωm) as a clay cover zones, this layer from the surface to -1000 meters. Medium resistivity values ​​(20-100 Ωm) starting from depths -1000 meters to -2000 meters associated with reservoirs zones, high resistivity values (> 200 Ωm) starting from depths of -2000 meters are considered as heat source from the Pantar geothermal system.

Using Electric Resistivity Tomography and Borehole Logs to Detect Sedimentation Changes in a Gravel-Bed Ephemeral Channel

2021 ◽  
Author(s):  
Marcos A. Martínez-Segura ◽  
Carmelo Conesa-García ◽  
Pedro Pérez-Cutillas ◽  
Marco D. Vásconez-Maza
Keyword(s):  
Grain Size ◽  
Electrical Resistivity ◽  
Hydraulic Conductivity ◽  
Environmental Changes ◽  
Subsurface Layer ◽  
High Resistivity ◽  
Resistivity Tomography ◽  
Gravel Bed ◽  
Basin Scale ◽  
Borehole Logs

&lt;p&gt;Differences in deposit geometry and texture with depth along ephemeral gravel-bed streams strongly reflect fluctuations in bedload, which occur due to environmental changes at the basin scale and morphological channel adjustments. In this study, non-destructive methods, 2D and 3D electrical resistivity tomography(ERT), have been combined with datasets from borehole logs to identify, quantify and analyze the internal geometry of cross-sections of the gravel-bed ephemeral channel, known as Azoh&amp;#237;a Rambla (southeastern Spain). The electrical survey was performed through longitudinal and transverse profiles in two channel reaches, upper and middle stretches. Both profiles utilized 28 stainless steel electrodes reaching 14-30 m in length and an investigation depth of 3-5 m, approximately. Electrical resistivity values were correlated with data obtained from the samples collected from borehole logs (e.g. sediment strength, grain size distribution, compaction, porosity (&amp;#981;), and hydraulic conductivity (k)). To determine &amp;#981; and K granulometric and morphometric variables, such as shape-sphericity indices, particle sorting, effective grain-sizes and void ratios, were used.&lt;/p&gt;&lt;p&gt;The alluvial channel-fills showed the superposition of four layers with uneven thickness and arrangement: 1) a lower sandy-gravel body, scarcely thick, characterized by moderate resistivity (150-500 &amp;#937; &amp;#183; m); 2) a thicker intermediate layer, with moderate to high resistivity values (500 to 1600 &amp;#937; &amp;#183; m); and 3) an upper set composed of coarse gravel and supported matrix, ranging from 1600 to 3000 &amp;#937; &amp;#183; m, and a narrow subsurface layer, the most resistive (&gt; 3000 &amp;#937; &amp;#183; m), corresponding to the most recent armored deposits (gravel and pebbles). Consequently, the ERT results coupled with borehole data suggest that since the channel entrenchment in the Miocene marl substrate, different pulses of vertical sedimentary accretion were produced, denoting a general trend to increase in grain-size (coarsening-upwards) and hydraulic conductivity towards the top of the sedimentary sequence. This research was funded by ERDF/Spanish Ministry of Science, Innovation and Universities&amp;#8212;State Research Agency/Project CGL2017-84625-C2-1-R; State Program for Research, Development and Innovation Focused on the Challenges of Society.&lt;/p&gt;

Assessment of Subsurface Profile at SILC, Nusajaya by 2D Resistivity Method

2014 ◽  
Vol 695 ◽  
pp. 823-827
Author(s):  
Siti Norsalkini Mohd Akip Tan ◽  
Edy Tonnizam Mohamad ◽  
Rosli Saad ◽  
Mustaza M. Nordiana
Keyword(s):  
Electrode Spacing ◽  
High Resistivity ◽  
Iron Mineral ◽  
Resistivity Method ◽  
Survey Line ◽  
2D Resistivity Imaging ◽  
Actual Profile ◽  
Grade Ii ◽  
Physical And Chemical ◽  
2D Resistivity

An assessment of subsurface profile of a study area at Nusajaya. Johor was conducted using 2D resistivity method. The aims of the study are to determine the subsurface profile hence contouring the appearance of outcrop by 2D resistivity imaging. Subsurface structure can be delineated based on the physical and chemical parameter which is apparent resistivity of the medium. A survey line of 80m and minimum 2m electrode spacing was adopted using Pole-dipole array. Data acquisition on the survey line was completed and processed by using Res2Dinv software. The inversion model resistivity shows sandstone contains iron mineral (30-250 ohm-m) and weathered sandstone (500-1000 ohm-m). The lower part of the layer represents sandstone and siltstone exhibit high resistivity values of 1500-5000 ohm-m. The range from 30-1000 ohm-m correspond to the grade IV and V of sandstone in the actual profile. Meanwhile, the high range of the resistivity value matched the material with weathering grade II and III in ground mass. The deterioration of most physical properties was associated with the increase number of weathering grade.

scholarly journals Three-Dimensional Audio-Magnetotelluric Imaging including Surface Topography of the Cimabanshuo Porphyry Copper Deposit, Tibet

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1424
Author(s):  
Ping Qi ◽  
Yaotian Yin ◽  
Sheng Jin ◽  
Wenbo Wei ◽  
Liuyang Xu ◽  
...  
Keyword(s):  
Porphyry Copper ◽  
Three Dimensional ◽  
Copper Deposit ◽  
High Elevation ◽  
High Resistivity ◽  
3D Inversion ◽  
Alteration Zones ◽  
Ore Bodies ◽  
Intrusive Rocks ◽  
Western Segment

Cimabanshuo deposit is a newly discovered porphyry copper (Cu) deposit with giant metallogenic potential, found in the western segment of the Gangdese metallogenic belt, Tibet. The average elevation of the deposit is greater than 5500 m and the terrain on which it is found is steep and complex. Therefore, it is untraversed, and the existing exploration works on it are weak. We used 59 AMT sites belonging to an array covering the main, proven mineralization zone and ore bodies of this deposit for an analysis of its underground electrical structure. Dimensionality and strike analysis revealed the apparent three-dimensional (3D) features near the Cu ore bodies. 3D inversion with topography was conducted for the AMT array data. A large range of high-resistivity anomaly (~500–2000 Ωm) appears beneath the proven Cu mineralization zone and ore bodies, which is interpreted as intrusive rocks with potassic alteration. Although containing chalcopyrite, it is characterized by middle–high resistivity due to a low sulfide content and poor connectivity. Moreover, a series of scattered conductors (~10–300 Ωm) around the Cu ore bodies are distributed in the shallow layer from near the surface to ~200 m, possibly indicating phyllic alteration containing pyritization and connected metal sulfides. The proven ore bodies of Cimabanshuo are mainly located at the junction regions between high-resistivity intrusive rocks and high-conductivity sericitization alteration zones. According to this research, the 3D inversion with topography of AMT data can visually display the 3D distribution of intrusive rocks and alteration zones beneath porphyry Cu deposits in high-elevation regions, and provides a reference for further exploration works.

scholarly journals Resistivity Method for Characterising Subsurface Layers of Coastal Areas In South Sulawesi, Indonesia

2021 ◽  
Vol 6 (4) ◽  
pp. 217-225
Author(s):  
Rahmaniah ◽  
Ayusari Wahyuni ◽  
Muhammad Fauzy Ismullah Massinai ◽  
Abdul Mun'im ◽  
Muhammad Altin Massinai
Keyword(s):  
Coastal Area ◽  
Subsurface Layer ◽  
Least Square ◽  
2D Inversion ◽  
Resistivity Method ◽  
South Sulawesi ◽  
Subsurface Layers ◽  
Resistivity Minimum ◽  
Linear Least Square

The data presented in this paper are related to the characterization of a subsurface layer of coastal area in South Sulawesi. This research will fill the gap in the resistivity method study which is this method not yet use in the coastlines area, especially area influenced by seawater and coastal condition impact like South Sulawesi. The method used in this study is the method of resistivity Wenner configuration by taking the data 1-2 lines each region with lengths 45 m, 75 m, 105 m, and 120 m respectively. Data processing using non-linear least square optimization with that of the 2D inversion software Res2Dinv. The results show that the area is underlain by two layers of lithologic sections. In some sections interpreted by sandy layer, clay, sandstone, alluvium, sandy in seawater and metal minerals. From the analysis of the layers, all regions show the resistivity minimum is 0.00849 Ωm and 8.04 Ωm maximum resistivity. The result of this research can give n insight to study the large coastal area subsurface.

scholarly journals Exploring the regolith with electrical resistivity tomography in large-scale surveys: electrode spacing-related issues and possibility

2021 ◽  
Vol 25 (4) ◽  
pp. 1785-1812
Author(s):  
Laurent Gourdol ◽  
Rémi Clément ◽  
Jérôme Juilleret ◽  
Laurent Pfister ◽  
Christophe Hissler
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Large Scale ◽  
Electrical Resistivity Tomography ◽  
Subsurface Layer ◽  
Electrode Spacing ◽  
High Resistivity ◽  
Constant Thickness ◽  
Resistivity Tomography

Abstract. Within the critical zone, regolith plays a key role in the fundamental hydrological functions of water collection, storage, mixing and release. Electrical resistivity tomography (ERT) is recognized as a remarkable tool for characterizing the geometry and properties of the regolith, overcoming limitations inherent to conventional borehole-based investigations. For exploring shallow layers, a small electrode spacing (ES) will provide a denser set of apparent resistivity measurements of the subsurface. As this option is cumbersome and time-consuming, larger ES – albeit offering poorer shallow apparent resistivity data – is often preferred for large horizontal ERT surveys. To investigate the negative trade-off between larger ES and reduced accuracy of the inverted ERT images for shallow layers, we use a set of synthetic “conductive–resistive–conductive” three-layered soil–saprock/saprolite–bedrock models in combination with a reference field dataset. Our results suggest that an increase in ES causes a deterioration of the accuracy of the inverted ERT images in terms of both resistivity distribution and interface delineation and, most importantly, that this degradation increases sharply when the ES exceeds the thickness of the top subsurface layer. This finding, which is obvious for the characterization of shallow layers, is also relevant even when solely aiming for the characterization of deeper layers. We show that an oversized ES leads to overestimations of depth to bedrock and that this overestimation is even more important for subsurface structures with high resistivity contrast. To overcome this limitation, we propose adding interpolated levels of surficial apparent resistivity relying on a limited number of ERT profiles with a smaller ES. We demonstrate that our protocol significantly improves the accuracy of ERT profiles when using large ES, provided that the top layer has a rather constant thickness and resistivity. For the specific case of large-scale ERT surveys the proposed upgrading procedure is cost-effective in comparison to protocols based on small ES.

scholarly journals Identification of Slip Surfaces Using the Geoelectric Imaging Method in the Kalirejo Area, Kokap District, Yogyakarta, Indonesia

2021 ◽  
Vol 6 (3) ◽  
pp. 234
Author(s):  
Rizqi Prastowo ◽  
Hurien Helmi ◽  
Obrin Trianda ◽  
Rofiqul Umam
Keyword(s):  
Human Activity ◽  
Slip Surface ◽  
High Resistivity ◽  
Imaging Method ◽  
Subsurface Structures ◽  
Resistivity Method ◽  
Slip Surfaces ◽  
Weathered Soil ◽  
The Social ◽  
Water Saturated

Landslides are a significant threat to the environment, infrastructure, and human activity, especially in mountainous and hilly areas. It is, therefore, important to accurately identify the social movements that trigger these processes. The resistivity method can investigate subsurface geological variations, including the potential for landslides. This research was conducted to investigate the subsurface structures in the Kalirejo Village area, Kokap District, Kulon Progo Regency, Yogyakarta regarding identifying the sliding location. This investigation includes five lines of tomographic geoelectric measurements. The results show that the slips surface is at a depth of about 5-10 m with a high resistivity value and the landslide material is weathered soil, and the slip surface is andesite. The resistivity of andesite in range 668-1600 Ωm. The landslide material's thickness is around 5-8 m with resistivity in the range 4,01-22.1 Ωm. Landslide material is water-saturated soil.

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