Modeling of self‐potential anomalies near vertical dikes

Geophysics ◽  
1983 ◽  
Vol 48 (2) ◽  
pp. 171-180 ◽  
Author(s):  
David V. Fitterman
Keyword(s):  
Field Data ◽  
Source Region ◽  
The Self ◽  
Model Parameters ◽  
Dc Resistivity ◽  
Constant Intensity ◽  
Source Regions ◽  
Source Mechanisms ◽  
Self Potential ◽  
Sp Anomaly

The self‐potential (SP) Green’s function for an outcropping vertical dike is derived from solutions for the dc resistivity problem for the same geometry. The Green’s functions are numerically integrated over rectangular source regions on the contacts between the dike and the surrounding material to obtain the SP anomaly. The analysis is valid for thermoelectrical source mechanisms. Two types of anomalies can be produced by this geometry. When the two source planes are polarized in opposite directions, a monopolar anomaly is produced. This corresponds to the thermoelectrical properties of the dike being in contrast with the surrounding material. When the thermoelectric coefficients change monotonically across the dike, a dipolar anomaly is produced. In either case positive and negative anomalies are possible, and the greatest variation in potential will occur in the most resistive regions. Examples of the effect of changing different model parameters are given for sources that have constant intensity throughout the rectangular source regions. For these patch models the depth to the top of the source region is approximately equal to the distance between the minimum (or maximum) of the anomaly outside of the dike and the edge of the dike. Field data collected over a hot intrusive fissure are presented which have been modeled by the technique described.

Thermoelectrical self‐potential anomalies and their relationship to the solid angle subtended by the source region

Geophysics ◽  
1984 ◽  
Vol 49 (2) ◽  
pp. 165-170 ◽  
Author(s):  
David V. Fitterman
Keyword(s):  
Weighting Function ◽  
Solid Angle ◽  
Source Region ◽  
Geothermal Field ◽  
Observation Point ◽  
Constant Intensity ◽  
Self Potential ◽  
Sp Anomaly

The calculation of self‐potential (SP) anomalies produced by thermoelectric sources is shown to be equivalent to calculating the weighted solid angle subtended at the observation point by the source region and its images where the weighting function is the source intensity. This interpretation provides an easy way of visualizing the effect of different source geometries, and describes the nonuniqueness associated with SP sources. For example, changes in a model which keep the product of source intensity and area constant do not appreciably change the produced anomaly. Similarly, deepening a source requires an increase of source intensity or size to produce the same anomaly. When conductivity contrasts become small or nonexistent, the number of image sources becomes finite or zero, respectively, further simplifying the calculation. As an example, the SP anomaly of a dipping rectangular source of constant intensity is computed using the method. This model is applied to SP data from the East Mesa geothermal field.

Relationship of the self‐potential Green’s function to solutions of controlled source direct‐current potential problems

Geophysics ◽  
1979 ◽  
Vol 44 (11) ◽  
pp. 1879-1881 ◽  
Author(s):  
David V. Fitterman
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Direct Current ◽  
Streaming Potential ◽  
The Self ◽  
Simple Relationship ◽  
Controlled Source ◽  
Source Mechanisms ◽  
Vertical Contact ◽  
Self Potential

This note presents a simple relationship between the self‐potential (SP) Green’s function and the solution of the controlled‐source direct‐current (dc) potential problem which allows a simplified means of determining the SP Green’s function. An example of its application to the vertical contact problem will be presented. The case of a streaming potential source mechanism will be considered, although any of the SP source mechanisms described by Nourbehecht (1963) could be substituted.

Calculations of self‐potential anomalies near vertical contacts

Geophysics ◽  
1979 ◽  
Vol 44 (2) ◽  
pp. 195-205 ◽  
Author(s):  
David V. Fitterman
Keyword(s):  
Physical Mechanism ◽  
Chemical Potential ◽  
Source Region ◽  
Streaming Potential ◽  
Source Mechanism ◽  
Constant Intensity ◽  
Potential Gradients ◽  
Vertical Contact ◽  
Chemical Potential Gradients ◽  
Self Potential

The self‐potential anomalies due to streaming potential effects in the vicinity of a vertical contact are analyzed. This approach is different from most previous studies in that the source is tied to a specific physical mechanism instead of arbitrarily selected charge distributions or current sources. The analysis is valid for any source mechanism that can be thought of in terms of crosscoupled flows, e.g., the thermoelectric effect or chemical potential gradients. The anomalies tend to be antisymmetric across the contact with the magnitude of the anomaly being larger on the more resistive side of the contact. An analytic expression for the case of a constant intensity, rectangular source is derived from the general solution. The anomalies for this simple case are computable with a handheld calculator and can be used to estimate the location, extent, and magnitude of the anomaly source region. With this information it is possible to determine the most probable crosscoupling source mechanism.

scholarly journals A study of the self-potential field produced by a polarised inclined sheet in an electrically homogeneous and transversely anisotropic ground

2001 ◽  
Vol 34 (4) ◽  
pp. 1343
Author(s):  
Γ. Α. ΣΚΙΑΝΗΣ ◽  
Τ. Δ. ΠΑΠΑΔΟΠΟΥΛΟΣ ◽  
Δ. Α. ΒΑΪΟΠΟΥΛΟΣ
Keyword(s):  
Potential Field ◽  
The Self ◽  
Quantitative Interpretation ◽  
Potential Field Data ◽  
Synthetic Model ◽  
Transversely Anisotropic ◽  
Self Potential ◽  
Sp Anomaly ◽  
Interpretation Method ◽  
Inclined Sheet

In the present paper, the self-potential (sp) field is studied, which is produced by an inclined sheet (thin dyke) in an electrically homogeneous and transversely anisotropic ground. At first, the mathematical expression for the sp anomaly is deduced, by integration of the formula for the self-potential field produced by a point pole in a transversely anisotropic medium (Skianis & Herntmdez 1999). Then, the behavior of the sp curve is studied, for various angles of schistosity. The whole anomaly may be displaced along the horizontal axis and deformed in terms of amplitude and shape. Particular emphasis is given on the enhancement and suppression of the positive center of the self-potential, which depends on the values and orientations of the schistosity angle of the ground and the dip angle of the inclined sheet. These deformations of the sp anomaly, may introduce significant errors in the calculation of the parameters of the polarized body, if ground anisotropy is not taken into account. Therefore, new methodologies have to be developed, for a reliable quantitative interpretation of self-potential field data. In this paper, a direct interpretation method is proposed, which consists of two steps: In step one, the parameters of the inclined sheet are determined, assuming a homogeneous and isotropic ground. In this stage, any quantitative interpretation method, referred in the international bibliography, may be used. Secondly, the true parameters of the dyke are estimated, by a set of transformations in which the anisotropy coefficient and the schistosity angle are introduced. In order to apply this method, a priori information about ground anisotropy should be available, by dc geoelectrical and geological investigations. The efficiency of the method was tested on a synthetic model. In the first stage, the quantitative interpretation method of Murty & Haricharan 1985 was employed. In the second stage, the calculated parameters of the first step, served as input values of the transformations, and the real parameters of the inclined sheet were estimated. There was a good agreement between the parameter values of the synthetic model and the ones found by the proposed method. The results and conclusions of this paper, may be useful in detecting sulfide mineralization deposits or graphite.

Speed vs. comfort: Testing the efficacy of a single question for predicting transit users’ route choices

2019 ◽  
Author(s):  
Joseph John Pyne Simons ◽  
Ilya Farber
Keyword(s):  
Data Collection ◽  
Efficient Method ◽  
Choice Task ◽  
The Self ◽  
Self Report ◽  
Model Parameters ◽  
Single Item ◽  
Alternative Approach ◽  
Single Question ◽  
Insight Into

Not all transit users have the same preferences when making route decisions. Understanding the factors driving this heterogeneity enables better tailoring of policies, interventions, and messaging. However, existing methods for assessing these factors require extensive data collection. Here we present an alternative approach - an easily-administered single item measure of overall preference for speed versus comfort. Scores on the self-report item predict decisions in a choice task and account for a proportion of the differences in model parameters between people (n=298). This single item can easily be included on existing travel surveys, and provides an efficient method to both anticipate the choices of users and gain more general insight into their preferences.

scholarly journals Mapping the Pollution Plume Using the Self-Potential Geophysical Method: Case of Oum Azza Landfill, Rabat, Morocco

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 961
Author(s):  
Meryem Touzani ◽  
Ismail Mohsine ◽  
Jamila Ouardi ◽  
Ilias Kacimi ◽  
Moad Morarech ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Water Table ◽  
Soil Surface ◽  
The Self ◽  
Drainage Network ◽  
Geophysical Method ◽  
Direct Measurements ◽  
Sandy Material ◽  
The City ◽  
Self Potential

The main landfill in the city of Rabat (Morocco) is based on sandy material containing the shallow Mio-Pliocene aquifer. The presence of a pollution plume is likely, but its extent is not known. Measurements of spontaneous potential (SP) from the soil surface were cross-referenced with direct measurements of the water table and leachates (pH, redox potential, electrical conductivity) according to the available accesses, as well as with an analysis of the landscape and the water table flows. With a few precautions during data acquisition on this resistive terrain, the results made it possible to separate the electrokinetic (~30%) and electrochemical (~70%) components responsible for the range of potentials observed (70 mV). The plume is detected in the hydrogeological downstream of the discharge, but is captured by the natural drainage network and does not extend further under the hills.

scholarly journals Implications of Self-Potential Distribution for Groundwater Flow System in a Nonvolcanic Mountain Slope

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Tada-nori Goto ◽  
Kazuya Kondo ◽  
Rina Ito ◽  
Keisuke Esaki ◽  
Yasuo Oouchi ◽  
...  
Keyword(s):  
Groundwater Flow ◽  
General Trend ◽  
Flow System ◽  
Ground Surface ◽  
Mountain Slope ◽  
Infiltration Process ◽  
Groundwater Flow System ◽  
Self Potential ◽  
Sp Anomaly ◽  
Fft Analysis

Self-potential (SP) measurements were conducted at Mt. Tsukuba, Japan, which is a nonvolcanic mountain, to infer groundwater flow system in the mountain. Survey routes were set around the northern slope, and the reliability of observed SP anomaly was checked by using SP values along parallel survey routes; the error was almost within 10 mV. The FFT analysis of the spatial SP distribution allows us a separation of raw data into two components with shorter and longer wavelength. In the shorter (altitudinal) wavelength than ∼200 meters, several positive SP peaks of more than 100 mV in magnitude are present, which indicate shallow perched water discharges along the slope. In the regional SP pattern of longer wavelength, there are two major perturbations from the general trend reflecting the topographic effect. By comparing the SP and hydrological data, the perturbation around the foothill is interpreted to be caused by heterogeneous infiltration at the ground surface. The perturbation around the summit is also interpreted to be caused by heterogeneous infiltration process, based on a simplified numerical modeling of SP. As a result, the SP pattern is well explained by groundwater flow and infiltration processes. Thus, SP data is thought to be very useful for understanding of groundwater flow system on a mountain scale.

Experimental study of the self-potential anomaly caused by coal fires

2017 ◽  
Vol 145 ◽  
pp. 124-132 ◽  
Author(s):  
Zhenlu Shao ◽  
Deming Wang ◽  
Yanming Wang ◽  
Xiaoxing Zhong ◽  
Yunxiang Zhang ◽  
...  
Keyword(s):  
Experimental Study ◽  
The Self ◽  
Coal Fires ◽  
Self Potential
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