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 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 Deep Electrical Resistivity Tomography for a 3D picture of the most active sector of Campi Flegrei caldera

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
A. Troiano ◽  
R. Isaia ◽  
M. G. Di Giuseppe ◽  
F. D. A. Tramparulo ◽  
S. Vitale
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Three Dimensional ◽  
Campi Flegrei ◽  
Gaseous Emissions ◽  
Resistivity Tomography ◽  
Tectonic Reconstruction ◽  
Resistivity Model ◽  
Fumarole Field ◽  
First Time

Abstract The central sector of the Campi Flegrei volcano, including the Solfatara maar and Pisciarelli fumarole field, is currently the most active area of the caldera as regards seismicity and gaseous emissions and it plays a significant role in the ongoing unrest. However, a general volcano-tectonic reconstruction of the entire sector is still missing. This work aims to depict, for the first time, the architecture of the area through the application of deep Electrical Resistivity Tomography. We reconstructed a three-dimensional resistivity model for the entire sector. Results provide useful elements to understand the present state of the system and the possible evolution of the volcanic activity and shed solid bases for any attempt to develop physical-mathematical models investigating the ongoing phenomena.

scholarly journals Geophysical Investigation Using 3-Dimensional Grid-Formation for Subsurface Lithology Characterization (A Case Study of Ovia North East, Edo State, South South Nigeria)

2021 ◽  
pp. 182-194
Author(s):  
O. J. Airen ◽  
P. S. Iyere
Keyword(s):  
Electrical Resistivity ◽  
Three Dimensional ◽  
Geophysical Investigation ◽  
Clayey Sand ◽  
Resistivity Data ◽  
North East ◽  
Lateral Distance ◽  
Lateral Plane ◽  
Resistivity Model ◽  
Edo State

Geophysical investigations using three-dimensional (3D) grid formation was carried out in Ovia North East Local Government Area of Edo State, Nigeria for subsurface lithology characterisation so as to generate a comprehensive basemap of the study area. Twelve (12) traverses in form of a rectangular grid were occupied for the 2D Electrical Resistivity Imaging (ERI) using the Wenner array. The 2D were all collated to form the 3D grid. The 2D Electrical Resistivity data was processed by the inversion of the 2D apparent resistivity data using the DIPRO software to generate the 2D inverted resistivity section while the 3D inverted resistivity model was done by inverting all the twelve traverses using 3DEarthimager software to model the 3D cube. The results of the 2D ERI revealed three (03) to five (05) resistivity structures across the twelve traverses indicating clay/clayey sand, sand and sandstone on a 200 and 300 m lateral distance and corresponding depth of 39.6 and 57.3 m across each traverses. Resistivity values generally varies from 16.8 – 45302 Ωm across Traverse 1 – 12. The layer horizontal depth slices of the 3D inverted resistivity distribution are in six layers, which are; 0 - 5 m, 5 – 10.8 m, 10.8 – 17.4 m, 17.4 – 25 m, 25 – 33.7 m and 33.7 – 43.8 m. The 3D inverted resistivity model within the study area covered lateral plane (the roll axis), 300 m, in the x plane (the pitch axis), 200 m lateral distance was covered and in the depth plane (the yaw axis), a maximum depth of 66 m is imaged. The inverted 3D Resistivity values generally vary from 189 - 6149 Ωm across the study area. The resistivity structures delineated from the 3D model are clayey sand and sand.

Experimental investigation of through-thickness resistivity of unidirectional carbon fiber tows

2018 ◽  
Vol 53 (21) ◽  
pp. 2993-3003
Author(s):  
Hong Yu ◽  
Jessica Sun ◽  
Dirk Heider ◽  
Suresh Advani
Keyword(s):  
Electrical Resistivity ◽  
Carbon Fiber ◽  
Carbon Fibers ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Fiber Surface ◽  
Testing System ◽  
Fiber Volume ◽  
Resistivity Model ◽  
Good Agreement

In this study, the influence of type of carbon fiber, sizing amount on the fiber surface and the degree of compaction on the through-thickness electrical resistivity of dry unidirectional carbon fiber tows is investigated to validate the conduction pathways and mechanisms proposed by our previously reported micromechanics electrical resistivity model. An automated experimental setup has been developed and implemented, which measures the electrical resistivity and fiber volume fraction of carbon fiber tows under compression in real time. An extensive experimental study is conducted with five types of commercial PAN-based carbon fibers which vary in fiber diameter, number of fibers in a tow including two unsized fibers and three sized fibers with sizing amount of 0.25% and 1.0% by weight. The fiber volume fraction was increased by compacting the fiber tows using a mechanical testing system (Instron, Norwood, MA). The results show that the fiber sizing and fiber volume fraction impact the through-thickness electrical resistivity of carbon fiber tows. Sized fibers demonstrate 1–2 orders of magnitude higher electrical resistivity than the unsized fibers at lower fiber volume fractions (below 45%), while at higher fiber volume fraction (60%–70%), the electrical resistivity of the two fiber systems tends to be of similar magnitude. Fibers with more sizing (1 wt.%) demonstrated 10 times larger through-thickness resistivity than those with less sizing (0.25 wt.%), indicating the significant impact of fiber sizing on electrical resistivity. The results show good agreement with our micromechanics electrical resistivity model.

Instrumentation For Quantitative Microscopy

1977 ◽  
Vol 35 ◽  
pp. 206-209
Author(s):  
B. Ralph ◽  
A.R. Jones
Keyword(s):  
Volume Fraction ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Automatic Data ◽  
Phase Volume Fraction ◽  
Statistical Confidence ◽  
Resultant Data ◽  
Automatic Data Collection ◽  
Third Dimension ◽  
Evolution Of Microstructure

In all fields of microscopy there is an increasing interest in the quantification of microstructure. This interest may stem from a desire to establish quality control parameters or may have a more fundamental requirement involving the derivation of parameters which partially or completely define the three dimensional nature of the microstructure. This latter categorey of study may arise from an interest in the evolution of microstructure or from a desire to generate detailed property/microstructure relationships. In the more fundamental studies some convolution of two-dimensional data into the third dimension (stereological analysis) will be necessary.In some cases the two-dimensional data may be acquired relatively easily without recourse to automatic data collection and further, it may prove possible to perform the data reduction and analysis relatively easily. In such cases the only recourse to machines may well be in establishing the statistical confidence of the resultant data. Such relatively straightforward studies tend to result from acquiring data on the whole assemblage of features making up the microstructure. In this field data mode, when parameters such as phase volume fraction, mean size etc. are sought, the main case for resorting to automation is in order to perform repetitive analyses since each analysis is relatively easily performed.

The stabilization of B.C.C. Cu in Cu/Nb nanolayered composites

1996 ◽  
Vol 54 ◽  
pp. 228-229
Author(s):  
H. Kung ◽  
A.J. Griffin ◽  
Y.C. Lu ◽  
K.E. Sickafus ◽  
T.E. Mitchell ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Layer Thickness ◽  
Volume Fraction ◽  
Ion Beam ◽  
High Strength ◽  
Cross Sectional ◽  
Metastable Structure ◽  
High Resolution Tem ◽  
Potential Improvement ◽  
Two Phases

Materials with compositionally modulated structures have gained much attention recently due to potential improvement in electrical, magnetic and mechanical properties. Specifically, Cu-Nb laminate systems have been extensively studied mainly due to the combination of high strength, and superior thermal and electrical conductivity that can be obtained and optimized for the different applications. The effect of layer thickness on the hardness, residual stress and electrical resistivity has been investigated. In general, increases in hardness and electrical resistivity have been observed with decreasing layer thickness. In addition, reduction in structural scale has caused the formation of a metastable structure which exhibits uniquely different properties. In this study, we report the formation of b.c.c. Cu in highly textured Cu/Nb nanolayers. A series of Cu/Nb nanolayered films, with alternating Cu and Nb layers, were prepared by dc magnetron sputtering onto Si {100} wafers. The nominal total thickness of each layered film was 1 μm. The layer thickness was varied between 1 nm and 500 nm with the volume fraction of the two phases kept constant at 50%. The deposition rates and film densities were determined through a combination of profilometry and ion beam analysis techniques. Cross-sectional transmission electron microscopy (XTEM) was used to examine the structure, phase and grain size distribution of the as-sputtered films. A JEOL 3000F high resolution TEM was used to characterize the microstructure.

scholarly journals Magnetotelluric study in the Los Lagos Region (Chile) to investigate volcano-tectonic processes in the Southern Andes

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Maria Jose Segovia ◽  
Daniel Diaz ◽  
Katarzyna Slezak ◽  
Felipe Zuñiga
Keyword(s):  
Electrical Resistivity ◽  
Three Dimensional ◽  
Phase Changes ◽  
Fault System ◽  
Electrical Anisotropy ◽  
Mountain Range ◽  
Southern Andes ◽  
Nazca Plate ◽  
First Results ◽  
Dimensional Parameters

AbstractTo analyze the process of subduction of the Nazca and South American plates in the area of the Southern Andes, and its relationship with the tectonic and volcanic regime of the place, magnetotelluric measurements were made through a transversal profile of the Chilean continental margin. The data-processing stage included the analysis of dimensional parameters, which as first results showed a three-dimensional environment for periods less than 1 s and two-dimensional for periods greater than 10 s. In addition, through the geomagnetic transfer function (tipper), the presence of structural electrical anisotropy was identified in the data. After the dimensional analysis, a deep electrical resistivity image was obtained by inverting a 2D and a 3D model. Surface conductive anomalies were obtained beneath the central depression related to the early dehydration of the slab and the serpentinization process of the mantle that coincides in location with a discontinuity in the electrical resistivity of a regional body that we identified as the Nazca plate. A shallow conductive body was located around the Calbuco volcano and was correlated with a magmatic chamber or reservoir which in turn appears to be connected to the Liquiñe Ofqui fault system and the Andean Transverse Fault system. In addition to the serpentinization process, when the oceanic crust reaches a depth of 80–100 km, the ascending fluids produced by the dehydration and phase changes of the minerals present in the oceanic plate produce basaltic melts in the wedge of the subcontinental mantle that give rise to an eclogitization process and this explains a large conductivity anomaly present beneath the main mountain range.

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