scholarly journals Magma Reservoir Beneath Azumayama Volcano, NE Japan as Inferred from Three-dimensional Electrical Resistivity Image by Magnetotellurics

2021 ◽  
Author(s):  
Masahiro Ichiki ◽  
Toshiki Kaida ◽  
Takashi Nakayama ◽  
Satoshi Miura ◽  
Mare Yamamoto ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Percolation Threshold ◽  
Hydrothermal Fluid ◽  
Magma Reservoir ◽  
Silicic Rock ◽  
Effusive Eruption ◽  
Impermeable Wall ◽  
Water Saturated ◽  
Resistivity Image ◽  
Ne Japan

Abstract An electrical resistivity image beneath Azumayama Volcano, NE Japan is modeled using magnetotellurics to probe the magma/hydrothermal fluid distribution. The 3-D inversion modeling images the conductive magma reservoir beneath Oana crater at depths of 3–15 km. The resolution scale for the conductor is 5 km by checkerboard resolution tests and the 67 % and 90 % confidential intervals of resistivity are 0.2–5 Ωm and 0.02–70 Ωm, respectively, for the region of less than 3 Ωm resistivity. The shallower part of the conductor is not explained by a water-saturated (5.5 wt %) dacitic melt, and the more probable interpretation is that it consists of a water-saturated, dacitic melt-silicic rock-hydrothermal fluid complex. The deeper part of the conductor is interpreted as a water-saturated (8 wt %) andesitic melt-mafic rock complex. The Mogi inflation source determined from GNSS and tilt data is located near the top boundary of the conductor at a depth of 2.7–3.7 km, which suggests that the ascent of hydrothermal fluids exsolved from the dacitic melt is interrupted by the impermeable wall and conduit. Assuming two phases of hydrothermal fluid and silicic rock, the resistivity at the inflation source, regarded as the upper bound resistivity of the conductor, is realized by the hydrothermal fluid fraction below the percolation threshold porosity in an effusive eruption. This indicates that the percolation threshold porosity in an effusive eruption characterizes the impermeable wall and conduit associated with the Mogi inflation source.

scholarly journals Magma reservoir beneath Azumayama Volcano, NE Japan, as inferred from a three-dimensional electrical resistivity model explored by means of magnetotelluric method

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Masahiro Ichiki ◽  
Toshiki Kaida ◽  
Takashi Nakayama ◽  
Satoshi Miura ◽  
Mare Yamamoto ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Confidence Interval ◽  
Hydrothermal Fluid ◽  
Volume Fraction ◽  
Source Region ◽  
Three Dimensional ◽  
Magma Reservoir ◽  
Resistivity Model ◽  
Magnetotelluric Method ◽  
Ne Japan

AbstractAn electrical resistivity model beneath Azumayama Volcano, NE Japan, is explored using magnetotelluric method to probe the magma/hydrothermal fluid distribution. Azumayama is one of the most concerning active volcanoes capable of producing a potential eruption triggered by the 2011 Tohoku-Oki Earthquake. The three-dimensional resistivity model reveals a conductive magma reservoir (< 3 Ωm) at depths of 3–15 km below sea level (bsl). The 67% and 90% confidence intervals of resistivity are 0.2–5 Ωm and 0.02–70 Ωm, respectively, for the magma reservoir. We assumed dacitic melt + rock at a shallow depth of 4 km bsl and andesitic melt + rock at a greater depth of 9 km bsl. The confidence interval of resistivity cannot be explained by using dacitic melt + rock condition at a depth of 4 km bsl. This suggests that very conductive hydrothermal fluids coexist with dacitic melt and rock in the shallow part of the magma reservoir. For the depth of 9 km bsl, the 67% confidence interval of resistivity is interpreted as water-saturated (8.0 weight %) andesitic melt–mafic rock complex with melt volume fractions greater than 4 volume %, while the shear wave velocity requires the fluid and/or melt volume fraction of 6–7 volume % at that depth. Considering the fluid and/or melt volume fraction of 6–7 volume %, the conductive hydrous phase is likewise required to explain the wide range of the 67% confidence interval of resistivity. The Mogi inflation source determined from geodetic data lies on the resistive side near the top boundary of the conductive magma reservoir at a depth of 2.7 or 3.7 km bsl. Assuming that the resistivity of the inflation source region is above the upper bound of the confidence interval of resistivity for the conductive magma reservoir and that the source region is composed of hydrothermal fluid + rock, the resistivity of the source region is explained by a hydrothermal fluid volume fraction below 5 volume %, which is the percolation threshold porosity in an effusive eruption. This indicates that the percolation threshold characterizes the inflation source region.

scholarly journals Influence of Carbon Fiber Incorporation on Electrical Conductivity of Cement Composites

2020 ◽  
Vol 10 (24) ◽  
pp. 8993
Author(s):  
Ilhwan You ◽  
Seung-Jung Lee ◽  
Goangseup Zi ◽  
Daehyun Lim
Keyword(s):  
Electrical Conductivity ◽  
Electrical Resistivity ◽  
Carbon Fiber ◽  
Percolation Threshold ◽  
Cement Composite ◽  
Electrode Spacing ◽  
Cement Composites ◽  
Different Types ◽  
The Difference

This study investigated the effects of carbon fiber (CF) length, electrode spacing, and probe configuration on the electrical conductivity of cement composites. Accordingly, 57 different types of samples were prepared, considering three different CF lengths, five different CF contents, three different electrode spacings, and two different probe configurations. This research found that the influence of CF length on the electrical resistivity of cement composite depends electrode spacing. For the cement composite with wide electrode spacing of 40 mm, its resistivity decreased as increasing CF length as in the previous study. However, when the electrode spacing is 10 mm, which is narrow (10 mm), the resistivity of the cement composite rather increased with increasing CF length. The results implied that when an electrode is designed for the cement composite incorporating CF, the CF length should be short compared to the electrode spacing. The percolation threshold of CF measured by the two-probe configuration was 2% or more. This is higher than that measured by the four-probe configuration (1%). At a lower CF content than 2%, the two-probe configuration gave higher resistivity of the cement composite than the four-probe configuration. However, the difference coming from the different probe configurations was marginal as increasing the CF content.

Temperature dependence of electrical resistivity of water‐saturated rocks

1987 ◽  
Author(s):  
Francisco J. Llera ◽  
Motoyuki Sato ◽  
Katsuto Nakatsuka ◽  
Hidekichi Yokoyama
Keyword(s):  
Electrical Resistivity ◽  
Temperature Dependence ◽  
Water Saturated

scholarly journals EFFECTS OF MIX PROPORTION ON ELECTRICAL RESISTIVITY OF CONCRETE WITH FLY ASH

2017 ◽  
Vol 7 (2) ◽  
pp. 53-65
Author(s):  
Su Wai Hnin ◽  
Pakawat Sancharoen ◽  
Somnuk Tangtermsirikul
Keyword(s):  
Compressive Strength ◽  
Electrical Resistivity ◽  
Fly Ash ◽  
Chloride Penetration ◽  
Mix Proportion ◽  
Binder Ratio ◽  
Saturated Concrete ◽  
Paste Content ◽  
Water Saturated ◽  
Water Binder Ratio

The aim of this paper is to investigate the effects of mix proportion on electrical resistivity of concrete with fly ash. The electrical resistivity of concrete is measured by using four Wenner probes. The varied parameters in this study were water/binder ratio, fly ash content, and paste content. Electrical resistivity of water-saturated concrete at several different ages was studied and compared with compressive strength and rapid chloride penetration. Based on experimental results, a good relationship was obtained between results of compressive strength and rapid chloride penetration with electrical resistivity of concrete. The results of this study can be applied further to predict electrical resistivity of concrete when mix proportions are provided. According to the results, lower water/binder ratio concrete had higher resistivity than those with higher water/binder ratios. When cement was replaced at 40% by fly ash, electrical resistivity increased four times when compared to that of OPC concrete.

scholarly journals Morphology and Properties of Aminosilane Grafted MWCNT/Polyimide Nanocomposites

2008 ◽  
Vol 2008 ◽  
pp. 1-15 ◽  
Author(s):  
Siu-Ming Yuen ◽  
Chen-Chi M. Ma ◽  
Chin-Lung Chiang ◽  
Chih-Chun Teng
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Resistivity ◽  
Glass Transition ◽  
Transition Temperature ◽  
Percolation Threshold ◽  
Multiwalled Carbon ◽  
Mwcnt Content ◽  
Glass Transition Temperatures ◽  
Novel Method ◽  
Polyimide Composites

This investigation presents a novel method for modifying multiwalled carbon nanotubes (MWCNTs). The morphology, electrical resistivity, and percolation threshold of MWCNT/Polyimide nanocomposites were studied. Acid-modified MWCNTs reacted with (3-aminopropyl)triethoxysilane by ionic bonding, and were then mixed with polyamic acid via imidization. TEM microphotographs reveal that silane-grafted MWCNTs were connected to each other. The electrical resistivity of silane-grafted MWCNT/polyimide decreased substantially below than that of acid-treated MWCNTs when the silane-modified MWCNT content was lower than 2.4 wt%. The percolation threshold of the MWCNT/polyimide composites is 1.0 wt% for silane-modified MWCNT and exceeds 7.0 wt% for acid-modified MWCNT. The acid-modified MWCNT/polyimide composites possess slightly higher glass transition temperatures than that of pure polyimide. The glass transition temperature of the polyimide increased significantly with silane-modified MWCNT content. Tensile properties of the polyimide have been improved with the MWCNTs content.

Electrically Inferred Subsurface Fractures in the Crystalline Hard Rocks of an Experimental Hydrogeological Park, Southern India

Geophysics ◽  
2021 ◽  
pp. 1-43
Author(s):  
Ved Prakash Maurya ◽  
Subash Chandra ◽  
Sahebrao Sonkamble ◽  
K. Lohith Kumar ◽  
ERUGU NAGAIAH ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Time Lapse ◽  
Granitic Rocks ◽  
Aquifer Recharge ◽  
Flow Paths ◽  
Resistivity Model ◽  
Subsurface Fractures ◽  
Water Saturated ◽  
And Inversion

We investigated a network of fractures forming the flow paths within the crystalline granitic rocks of an experimental hydrogeological park (EHP) with the help of electrical resistivity surveys. The experimental study located at managed aquifer recharge (MAR) site of EHP has measured a distinct variation in the apparent resistivity for deeper electrical signals that localize the presence of interconnected water-saturated fractures. Usually, profiles close to the MAR tank depict low apparent resistivity values from deep signals across in-situ fractures and resistivity amplitude increases away from the tank. We modeled and simulated the presence of water-saturated fractures by a simple three-layered model having embedded shallow heterogeneities in the saprolite layer, vertically interconnected multiple thin conductive horizontal layers in the fissured zone, and an underlain un-weathered crystalline granitic basement. These fractures produce a distinct variation in the resistivity both for modeling and inversion exercises. The decadal time-lapse electrical resistivity surveys, after the establishment of the MAR tank, mark similar repetitive main features with a distinct drop in resistivity depicting the presence of water-saturated fractures. An overview of 3D resistivity model characterizes the subsurface heterogeneities, presence of possible flow paths for shallow depths <30 m, and indicative of possible flows in the interconnected deep fractures for depths >30m.

Percolation Effects on Electrical Resistivity and Electron Mobility

2012 ◽  
Vol 5 (1) ◽  
Author(s):  
J. Weddell ◽  
A. Feinerman
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Aspect Ratio ◽  
Porous Material ◽  
Percolation Threshold ◽  
Electron Mobility ◽  
Past Research ◽  
Practical Applications ◽  
Percolation Thresholds ◽  
Theoretical Results

Percolation, defined as the study of transport across a porous material, can be used to determine transport quantities of a material such as electrical and thermal conductivity. Observing the way electrons flow across a porous conductive sheet is a common way that percolation studies are performed, and has many practical applications in electronics. This study determines how elliptical pores cut into a conductive sheet affect the percolation threshold; the remaining area of the conductive sheet when the current across it first becomes zero. Past research has been performed on this topic which yielded theoretical results of the percolation thresholds, and this study aims to verify those results experimentally. This study shows that as the aspect ratio of an ellipse approaches zero, the percolation threshold approaches one. This report also establishes a novel experimental method of studying percolating networks.

The borehole-fluid effect in electrical resistivity imaging

Geophysics ◽  
2010 ◽  
Vol 75 (4) ◽  
pp. F107-F114 ◽  
Author(s):  
Joseph A. Doetsch ◽  
Ilaria Coscia ◽  
Stewart Greenhalgh ◽  
Niklas Linde ◽  
Alan Green ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Electrical Contact ◽  
Test Site ◽  
High Resistivity ◽  
Rock Formation ◽  
Radar Images ◽  
Grid Approach ◽  
1D Model ◽  
Resistivity Image

Fluid that fills boreholes in crosswell electrical resistivity investigations provides the necessary electrical contact between the electrodes and the rock formation but it is also the source of image artifacts in standard inversions that do not account for the effects of the boreholes. The image distortions can be severe for large resistivity contrasts between the rock formation and borehole fluid and for large borehole diameters. We have carried out 3D finite-element modeling using an unstructured-grid approach to quantify the magnitude of borehole effects for different resistivity contrasts, borehole diameters, and electrode configurations. Relatively common resistivity contrasts of 100:1 and borehole diameters of 10 and [Formula: see text] yielded, for a bipole length of [Formula: see text], apparent resistivity underestimates of approximately 12% and 32% when using AB-MN configurations and apparent resistivity overestimates of approximately 24% and 95% when usingAM-BN configurations. Effects are generally more severe at shorter bipole spacings. We report the results obtained by either including or ignoring the boreholes in inversions of 3D field data from a test site in Switzerland, where approximately 10,000 crosswell resistivity-tomography measurements were made across six acquisition planes among four boreholes. Inversions of raw data that ignored the boreholes filled with low-resistivity fluid paradoxically produced high-resistivity artifacts around the boreholes. Including correction factors based on the modeling results for a 1D model with and without the boreholes did not markedly improve the images. The only satisfactory approach was to use a 3D inversion code that explicitly incorporated the boreholes in the actual inversion. This new approach yielded an electrical resistivity image that was devoid of artifacts around the boreholes and that correlated well with coincident crosswell radar images.

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