A New Method of Interpretation of Self‐potential Field Data

Abstract

In this paper a new, efficient method is worked out for the interpretation of self-potential field data. Interpretation of location, depth and dip of the ore body is made, using a pattern of equipotential lines. The negative center and the positive maximum of the potential are found and also the socalled " mid-value" point. The dip a, can be determined accurately for values between 5° and 85°. The method cannot be used for vertical polarization. The depth and location can be found with rela tive accuracy for <*> io°. The main advantage of this new method is the ease of interpretation and a greater accuracy for the high-dip angles.It should be stressed that, for correct and accurate interpretation, the positive maximum is as important as the negative center. Therefore, it should be carefully sought during the field work, and mapped to its full extent. INTRODUCTIONT he existing m ethods of interpretation of self-potential data, obtained from prospecting for ore bodies, are cumbersome and com m only involve a large am ount of guesswork.An elaborate theory for the surface distribution of potentials was worked out b y A. P etro vsk i.1 T he method of interpretation given b y P etro vsk i uses the cur rent densities, which are proportional to the derivatives of the potential curves for a fixed direction of traverse. T h is ob viates taking into account a base-line potential.A later method given b y W. Stern2 is based on form ulas derived from assuming the ore body to be a polarized bar. The potentials m easured in the field are used as such, which gives inaccuracies due to the absence of a fixed base line, relative to which the potentials are defined. In the theory the potential at a large distance is assumed to be zero. In the field, how ever, the zero-potential is difficult to obtain due to the presence of spurious potentials caused b y vegetation and percolation. It is also difficult to predetermine how fa r one has to go to find the " infinitypotential" for practical purposes, as the positive m axim um caused b y the ore can be far from the center of the ore body for low-dip angles.The interpretation here presented is based on P etro vsk i's theory, assum ing the ore body to be a polarized sphere. A " m id -valu e" point is introduced which elim inates the zero-line difficulties and does not require the use of current densities, saving much work and minimizing errors in the interpretation. 600T he " m id-value" point is an im provem ent on the " h alf-valu e" point idea which was outlined b y C. A. H eiland,3 for a vertica lly polarized sphere.A s only three points are used for the interpretation, all of which are well de fined b y the equipotential pattern, inaccuracies due to distortion b y topography are kept to a minimum. Figure 1 represents a hidden polarized sphere in a semi-infinite isotropic medium, and its image at equal distance above the fiat boundary surface. THE THEORY OF IN TERPR ETATIO NThe vertical plane through the plus and minus pole is called the plane of A N E W M ETH O D OF IN T E R P R E T A...

On the Origin and Interpretation of Self‐potential Anomalies*

“…Presumably, these quantities will bear some relation to the geometry of the ore body. Numerous previous authors, including Roy and Chowdhury (1959), Rao, Murphy and Reddy (1970), Paul (1965), Meiser (1961), Battacharya and Roy (1981), Fitterman (1979), andDe Witte (1948), have suggested such an approach for other models. Zachos (1963) has discussed a self-potential anomaly that occurs over an ore body in the Chalkidiki area of Northern Greece, and has compared the self-potential Fig.…”

A new inversion algorithm for estimating the best fitting parameters of some geometrically simple body to measured self-potential anomalies

“…Several graphical and numerical methods have been developed for Category II to determine the depth and the polarization properties of the causative body from the observed SP data. For example, Heiland (1940), De Witte (1948, Yungul (1950), Meiser (1962), Banerjee (1971), andFitterman (1979) introduced methods based on nomograms and standardised curves. Bhattacharya and Roy (1981), Rao and Babu (1983), Murty and Haricharan (1985), and Babu and Rao (1988) developed procedures for SP inversion based on a few characteristic points and distances.…”

Direct interpretation of self-potential anomalies produced by a vertical dipole

“…1016/j.jappgeo.2005.05.003 anomaly measured at ground surface. In most cases, the SP anomaly is simulated by a polarized sphere or horizontally elongated structures, such as sheets or cylinders (De Witte, 1948;Yü ngü l, 1950;Paul, 1965;Ram Babu and Atchuta Rao, 1988;Skianis et al, , 1995Abdelrahman et al, 2003 and many others). An alternative approach of solving the inverse problem with not any a priori assumption about the geometry of the SP source is proposed by Patella (1997), who has developed the ground surface self-potential tomography.…”