The self‐potential method in the geothermal exploration of Greece

Geophysics ◽  
1997 ◽  
Vol 62 (6) ◽  
pp. 1715-1723 ◽  
Author(s):  
George Apostolopoulos ◽  
Ioannis Louis ◽  
Evangelos Lagios
Keyword(s):  
Surrounding Medium ◽  
Geophysical Methods ◽  
Low Frequency ◽  
Potential Method ◽  
Geothermal System ◽  
Electrode Polarization ◽  
Geothermal Exploration ◽  
Contour Maps ◽  
Tectonic Features ◽  
Self Potential

Self‐potential (SP) anomalies are generated by flows of fluid, heat, and ions in the earth. SP investigations have been used to locate and delineate sources associated with such flows in three areas of geothermal interest in Greece—Lesvos Island, Loutra Hypatis (central Greece), and Nisyros Island. A combination of geophysical methods, with SP being the primary method, has been applied in these areas. The SP method is adversely influenced by various sources of noise. Field procedures have been suggested to minimize their effects by monitoring electrode polarization and telluric activity. The interpretation of SP contour maps is preferred to using profile data. A procedure was adopted for SP interpretation, and the results were satisfactory. However, this model is based on thermoelectric sources only and is not related directly to hot fluid movement. In all three survey areas, the geothermal zones delimited by the SP interpretation in combination with data acquired by other geophysical methods result in an integrated interpretation of the geothermal system. Since SP and very‐low‐frequency (VLF) anomalies can be generated by the same geological source (i.e., geothermal, highly conductive zone), the corresponding results are compared to provide a strong indication of the presence of geothermal zones. The activity of geothermal zones affects the conductivity of the surrounding medium, which also can be detected by dc resistivity and audio‐magnetotelluric (AMT) methods. In addition, geothermal zones can be related to various interfaces or tectonic features that can be detected by gravity or seismic methods.

Mapping groundwater contamination using dc resistivity and VLF geophysical methods–A case study

Geophysics ◽  
1997 ◽  
Vol 62 (1) ◽  
pp. 80-86 ◽  
Author(s):  
Alvin K. Benson ◽  
Kelly L. Payne ◽  
Melissa A. Stubben
Keyword(s):  
Electrical Resistivity ◽  
Cross Sections ◽  
Electromagnetic Induction ◽  
Geophysical Methods ◽  
Low Frequency ◽  
Hydrocarbon Contamination ◽  
Monitoring Wells ◽  
Contour Maps ◽  
A Site

Geophysical methods can be helpful in mapping areas of contaminated soil and groundwater. Electrical resistivity and very low‐frequency electromagnetic induction (VLF) surveys were carried out at a site of shallow hydrocarbon contamination in Utah County, Utah. Previously installed monitoring wells facilitated analysis of water chemistry to enhance interpretation of the geophysical data. The electrical resistivity and VLF data correlate well, and vertical cross‐sections and contour maps generated from these data helped map the contaminant plume, which was delineated as an area of high interpreted resistivities.

scholarly journals The self‐potential method in geothermal exploration

Geophysics ◽  
1979 ◽  
Vol 44 (2) ◽  
pp. 226-245 ◽  
Author(s):  
Robert F. Corwin ◽  
Donald B. Hoover
Keyword(s):  
Potential Method ◽  
Source Model ◽  
Irreversible Thermodynamics ◽  
Electrode Polarization ◽  
Coupling Coefficients ◽  
Spherical Source ◽  
Analytical Technique ◽  
Thermal Fluids ◽  
Geothermal Activity ◽  
Self Potential

Laboratory measurements and field data indicate that self‐potential anomalies comparable to those observed in many areas of geothermal activity may be generated by thermoelectric or electrokinetic coupling processes. A study using an analytical technique based on concepts of irreversible thermodynamics indicates that, for a simple spherical source model, potentials generated by electrokinetic coupling may be of greater amplitude than those developed by thermoelectric coupling. Before more quantitative interpretations of potentials generated by geothermal activity can be made, analytical solutions for more realistic geometries must be developed, and values of in‐situ coupling coefficients must be obtained. If the measuring electrodes are not watered, and if telluric currents and changes in electrode polarization are monitored and corrections made for their effects, most self‐potential measurements are reproducible within about ±5 mV. Reproducible short‐wavelength geologic noise of as much as ±10 mV, primarily caused by variation in soil properties, is common in arid areas, with lower values in areas of uniform, moist soil. Because self‐potential variations may be produced by conductive mineral deposits, stray currents from cultural activity, and changes in geologic or geochemical conditions, self‐potential data must be analyzed carefully before a geothermal origin is assigned to observed anomalies. Self‐potential surveys conducted in a variety of geothermal areas show anomalies ranging from about 50 mV to over 2 V in amplitude over distances of about 100 m to 10 km. The polarity and waveform of the observed anomalies vary, with positive, negative, bipolar, and multipolar anomalies having been reported from different areas. Steep potential gradients often are seen over faults which are thought to act as conduits for thermal fluids. In some areas, anomalies several kilometers wide correlate with regions of known elevated thermal gradient or heat flow.

scholarly journals Identifikasi Keanekaragaman Hayati dan Pemetaan Bawah Tanah Kampus Terpadu Universitas Muhammadiyah Palangkaraya Sebagai Media Objek Pembelajaran

2013 ◽  
Vol 13 (1) ◽  
pp. 94-105 ◽  
Author(s):  
Nurul Hikmah Kartini ◽  
Indah Sari Dewi
Keyword(s):  
Subsurface Layer ◽  
Potential Method ◽  
Learning Objects ◽  
Contour Maps ◽  
Lack Of Information ◽  
Porous Copper ◽  
Innovative Learning ◽  
Media Learning ◽  
Two Stages ◽  
Self Potential

Innovative learning in addition to varied models, strategies and methods, it is also necessary to approach. The lack of understanding of the basic concepts of science underpins researchers to create learning media for the identification of biodiversity and the subsurface layer in the form of underground layers. Lack of information on previous research regarding research at UM Palangkaraya Integrated Campus on Jl. Anggrek-Mahir Mahar made researchers try to link the environmental approach of UM Integrated Campus area Learning with the final achievement in the form of science media learning objects. This research method began with an initial theoretical study of science learning, followed by a field survey. Observations in the field will examine an area of ??1 ha identified as having higher biodiversity than others. After setting the plot point, the acquisition is carried out with 2 (two) stages, namely the identification of biodiversity with the sampling of flora and fauna that are at the plot point. The next stage is the acquisition of underground layer mapping using the Self Potential method with porous copper pot and CuSO4 solution. After the acquisition, continued data analysis of the two stages. Biodiversity in the form of flora and fauna types and layer contour maps are poured into learning object media. Hope in the future, researchers can continue mapping the surface and subsurface of the Palangkaraya UM Integrated Campus in an area of ??20 ha.

scholarly journals Complex geophysical investigation of the Kapušany landslide (Eastern Slovakia)

2016 ◽  
Vol 46 (2) ◽  
pp. 111-124 ◽  
Author(s):  
David Kušnirák ◽  
Ivan Dostál ◽  
René Putiška ◽  
Andrej Mojzeš
Keyword(s):  
Gamma Ray ◽  
Geophysical Methods ◽  
Potential Method ◽  
Structural Features ◽  
Geological Structure ◽  
Inverse Model ◽  
Gamma Ray Spectrometry ◽  
Geophysical Investigation ◽  
Self Potential

Abstract Geophysical survey is a very useful and popular tool used by engineering geologists to examine landslides. We present a case study from the Kapušany landslide, Eastern Slovakia, where a broad spectrum of geophysical methods were applied along two perpendicular profiles in order to compare the ability of the methods to detect as many structural features of the landslide as possible. The 2D Electrical Resistivity Tomography inverse model was capable of defining the geological structure of the landslide and defining the shear zone, however the resolution of the inverse model does not allow us to identify cracks or other minor features of the landslide. These, however, were well recorded in the results of Dipole Electromagnetic Imaging and the Self Potential method. In addition microgravimetry, Gamma-Ray Spectrometry and Soil Radon Emanometry were experimentally employed to validate the results obtained from electrical methods and afterwards final geological models, based on the integrated interpretation of all involved methods were constructed.

Integration of multi parameters geophysical models using PCA : application to geothermal exploration

2020 ◽  
Author(s):  
jean-michel ars ◽  
Pascal Tarits ◽  
Sophie Hautot ◽  
Mathieu Bellanger ◽  
Olivier Coutant
Keyword(s):  
Joint Inversion ◽  
Geophysical Methods ◽  
Principal Component ◽  
Total Variance ◽  
Geothermal System ◽  
Visual Interpretation ◽  
Orthogonal Axis ◽  
Geothermal Exploration ◽  
Massif Central ◽  
Wide Range

<p>Geophysical exploration of natural resources is challenging because of complex and/or narrow geological structures to image. Geophysical models should provide an image at a scale large enough to understand the complex geology but with the adequate resolution to resolve features like faults. One solution to overcome this difficulty is to integrate large multiphysics datasets to provide complementary insight of the geology. New approaches involve joint inversion of all datasets in a common process where models are coupled together. Geometrical or quantitative interpretation of the joint models image several physical properties shaping the same pattern of the target resources. In reality, models resulting from joint inversion are still challenging to interprete. Most of the joint inversion techniques are based on parameters relationship or geometrical constraint which imply common interfaces between models. This assumption may be wrong since geophysical methods have different sensitivity to the same geological object.</p><p>Geophysical integration cover a wide range of approach from the visual interpretation of model presented side by side to sophistical statistical analyses such as automatic clustering. We present here a geophysical models integration based on principal component analysis (PCA). PCA allow to gain insight on a multi-variable system with high level of interaction. PCA aims to reorganize the system by finding a new set of variables distributed along new orthogonal axis and keeping most of the variance from the data. Thus geophysical interaction are highlighted along components that can be interpreted in terms of patterns. We applied this integration method to gravity, ambient noise tomography and resistivity models obtained from joint inversion in the framework of unconventional geothermal exploration in Massif Central, France. PCA of the log-resistivity, the density contrast and the Vs velocity model has 3 independent components. The first one (PC1) representing 69% of the total variance of the system is highly influenced by the parameter coupling enforced in the joint inversion process. PC1 allows to point to geophysical structures that may be related to the geothermal system. The second component (PC2) represents 22% of the total variance and is strongly correlated to the resistivity distribution The correlation with the surface geology suggests that it may be a fault marker. The third component (PC1: 9% of the total variance) is still above the nul hypothesis and seems to describe the 3D geometry of the geological units. This statistical approach may help the geophysical interpretation into a possible geothermal conceptual model</p><p> </p>

Integration of Multi-geophysical Approaches to Identify Potential Pathways of Heavy Metals Contamination - A Case Study in Zeida, Morocco

2020 ◽  
Vol 25 (3) ◽  
pp. 415-423
Author(s):  
Ahmed Lachhab ◽  
El Mehdi Benyassine ◽  
Mohamed Rouai ◽  
Abdelilah Dekayir ◽  
Jean C. Parisot ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Seismic Velocity ◽  
Seismic Refraction ◽  
Geophysical Methods ◽  
Low Frequency ◽  
Electrical Current ◽  
P Wave ◽  
Low Resistivity ◽  
Refraction Tomography ◽  
Geophysical Surveys

The tailings of Zeida's abandoned mine are found near the city of Midelt, in the middle of the high Moulouya watershed between the Middle and the High Atlas of Morocco. The tailings occupy an area of about 100 ha and are stored either in large mining pit lakes with clay-marl substratum or directly on a heavily fractured granite bedrock. The high contents of lead and arsenic in these tailings have transformed them into sources of pollution that disperse by wind, runoff, and seepage to the aquifer through faults and fractures. In this work, the main goal is to identify the pathways of contaminated water with heavy metals and arsenic to the local aquifers, water ponds, and Moulouya River. For this reason, geophysical surveys including electrical resistivity tomography (ERT), seismic refraction tomography (SRT) and very low-frequency electromagnetic (VLF-EM) methods were carried out over the tailings, and directly on the substratum outside the tailings. The result obtained from combining these methods has shown that pollutants were funneled through fractures, faults, and subsurface paleochannels and contaminated the hydrological system connecting groundwater, ponds, and the river. The ERT profiles have successfully shown the location of fractures, some of which extend throughout the upper formation to depths reaching the granite. The ERT was not successful in identifying fractures directly beneath the tailings due to their low resistivity which inhibits electrical current from propagating deeper. The seismic refraction surveys have provided valuable details on the local geology, and clearly identified the thickness of the tailings and explicitly marked the boundary between the Triassic formation and the granite. It also aided in the identification of paleochannels. The tailings materials were easily identified by both their low resistivity and low P-wave velocity values. Also, both resistivity and seismic velocity values rapidly increased beneath the tailings due to the compaction of the material and lack of moisture and have proven to be effective in identifying the upper limit of the granite. Faults were found to lie along the bottom of paleochannels, which suggest that the locations of these channels were caused by these same faults. The VLF-EM surveys have shown tilt angle anomalies over fractured areas which were also evinced by low resistivity area in ERT profiles. Finally, this study showed that the three geophysical methods were complementary and in good agreement in revealing the pathways of contamination from the tailings to the local aquifer, nearby ponds and Moulouya River.

scholarly journals Strong Waves from Pulsars and Morphologies in SNRs

1983 ◽  
Vol 101 ◽  
pp. 499-501
Author(s):  
Gregory Benford ◽  
Attilio Ferrari ◽  
Silvano Massaglia
Keyword(s):  
Large Amplitude ◽  
Crab Nebula ◽  
Surrounding Medium ◽  
Low Frequency ◽  
Optical Emission ◽  
Amplitude Wave ◽  
Surface Magnetic Field ◽  
Plasma Absorption ◽  
The Crab Nebula ◽  
Large Amplitude Wave

Canonical models for pulsars predict the emission of low–frequency waves of large amplitudes, produced by the rotation of a neutron star possessing a strong surface magnetic field. Pacini (1968) proposed this as the basic drain which yields to the pulsar slowing–down rate. The main relevance of the large amplitude wave (LAW) is the energetic link it provides between the pulsar and the surrounding medium. This role has been differently emphasized (Rees and Gunn, 1974; Ferrari, 1974), referring to absorption effects by relativistic particle acceleration and thermal heating, either close to the pulsar magnetosphere or in the nebula. It has been analyzed in the special case of the Crab Nebula, where observations are especially rich (Rees, 1971). As the Crab Nebula displays a cavity around the pulsar of dimension ∼1017cm, the function of the wave in sweeping dense gas away from the circumpulsar region is widely accepted. Absorption probably occurs at the inner edges of the nebula; i.e., where the wave pressure and the nebular pressure come into balance. Ferrari (1974) interpreted the wisps of the Crab Nebula as the region where plasma absorption occurs, damping the large amplitude wave and driving “parametric” plasma turbulence, thus trasferring energy to optical radiation powering the nebula. The mechanism has been extended to interpret the specific features of the “wisps” emission (Benford et al., 1978). Possibly the wave fills the nebula completely, permeating the space outside filaments with electromagnetic energy, continuously accelerating electrons for the extended radio and optical emission (Rees, 1971).

Mineral interfacial processes in the method of induced polarization

Geophysics ◽  
1984 ◽  
Vol 49 (7) ◽  
pp. 1105-1114 ◽  
Author(s):  
James D. Klein ◽  
Tom Biegler ◽  
M.D. Horne
Keyword(s):  
Frequency Domain ◽  
Diffusion Layer ◽  
Electrode Potential ◽  
Rotation Speed ◽  
Low Frequency ◽  
Rotating Disk ◽  
Active Species ◽  
Hydrodynamic Theory ◽  
Electrode Polarization ◽  
Disk Electrodes

A phenomenological laboratory investigation has been conducted of the IP response of pyrite, chalcopyrite, and chalcocite. The technique that was used is standard in electrochemistry and employs rotating disk electrodes. The effect of rotation is to stir the electrolyte and thus to restrict the maximum distance available for diffusion of electroactive aqueous species. For high rotation speed and low excitation frequencies, the mean diffusion length exceeds the thickness of the diffusion layer. The net effect is to reduce the electrode impedance at low frequency. The thickness of the diffusion layer and thus the impedance at low frequency can be controlled by the rotation speed. Measurements using rotating disk electrodes have been conducted in both the time domain and the frequency domain. For both pyrite and chalcopyrite, the results were the same: no dependence on rotation was observed. For frequency domain measurements with chalcocite, a strong dependence on rotation was observed. The interpreted diffusion layer thickness was found to depend on rotation speed to the [Formula: see text] power, in agreement with results predicted by hydrodynamic theory. The results of this study imply that there are two physical processes responsible for electrode polarization in the IP method. For chalcocite and perhaps other related copper sulfide minerals, the probable mechanism is diffusion of copper ions in the groundwater. In case, the phenomenon is correctly described by the Warburg impedance. Chalcocite’s distinctive response is thought to be related to its forming a reversible oxidation‐reduction couple with cupric ions in solution. No other common sulfide mineral forms a reversible couple with its cations in solution. For the other minerals of this study, the lack of dependence on rotation implies that diffusion of active species in the electrolyte is not the controlling process. Possible alternate mechanisms include surface controlled processes such as surface diffusion or adsorption phenomena. Ancillary data obtained during this study indicate the interface impedance of chalcopyrite is proportional to the electrode potential which in turn can be controlled by rotation speed, electrolyte composition, or application of an external dc current or voltage. This implies that the surface concentration of active species is dependent on electrode potential.

Sign in / Sign up

Export Citation Format

Share Document