Home

Quick Links

Search

 
Interpretation and depth of investigation of gradient measurements in direct current geoelectricsNormal access

Author: R. Schulz
Journal name: Geophysical Prospecting
Issue: Vol 33, No 8, December 1985 pp. 1240 - 1253
DOI: 10.1111/j.1365-2478.1985.tb01362.x
Organisations: Wiley
Language: English
Info: Article, PDF ( 588.93Kb )

Summary:
Gradient measurements in a homogeneous electrical primary field can easily be interpreted for simple models. The simplified solution (conducting or resistant body in a homogeneous space in a homogeneous electrical field) is often sufficiently accurate, as comparisons with the exact solution (body of finite resistivity in a homogeneous half-space in a quasihomogeneous electrical field) show. The exact geometry of the body cannot be determined by gradient measurements; the same anomaly of apparent resistivity can be caused by different bodies. In particular, the similarity between a sphere and a cube of the same volume is very high.

There is a distinct influence of the resistivity of the overburden: the higher this resistivity is, the stronger is the effect caused by a buried body.

If a deviation of 10% of the apparent resistivity is assumed as the lower boundary at which a buried body can be detected by gradient measurements, the depth of investigation for a three-dimensional body is approximately equal to its width; in the two-dimensional case the thickness of the overburden can be twice the width. If the overburden has a resistivity which is higher than the resistivity of the substratum, these depths are greater. The greatest possible depth is approximately three times the width of the body.


Download
Back to the article list