Resistivity

Short explanation of the method

Geoelectric measurements are performed by sending direct current into the ground through two electrodes on the surface. The resistivity of the underlying geological material affects the current field between the electrodes and by measuring the electric voltage field between two other electrodes on the surface, the parameter apparent resistivity can be determined. This is a fictitious parameter and is a function of the location of the electrodes and of the real resistivity ranges in the underlying masses.

The measured potential can be related to bedrock and overburden resistivity, their geometry and distribution.

Resistivity values in the soil are determined by the type of loose material, water content and salinity. The measurements use different geometric arrangements of the electrodes, depending on the purpose of the measurements.

Electrical methods

Method

Resistance measurement

Equipotential

line

Induced

Polarization

Spontaneous

Potential

Measured Physical Parameter

Voltage drop at applied current. Apparent specific resistance.

The course of an applied voltage field

Time variation of applied voltage

Voltage drop in a natural voltage field

Calculated parameter

Location of boundaries between layers with different conductivity

Location and extent of electrically conductive structures.

Location and extent of formations with electrochemical polarizability.

Location of formations surrounding a natural voltage field

Application

Determination of loose material layers, boundaries between different types of sediments, depth to groundwater. Exploration for ores, petroleum, coal and minerals.

Ore and mineral exploration. Mapping of boundary lines between structures with a difference in electrical properties.

Exploration for ores, minerals and coal. Registration of clay content in sand.

Ore prospecting. Mapping of sedimentary formations, especially in connection with petroleum exploration; groundwater level.