Types of electrical resistivity methods

 In this article, I discussed the Types of electrical resistivity methods (Electrical profiling method and electrical sounding method) and the differences between them in detail.

Electrical Profiling method

The electrical profiling method is a geophysical approach used to map differences in electrical conductivity and explore subsurface conditions. Multiple electrodes placed at regular intervals are used to test the electrical resistivity along a profile line. An electrical current is run through the electrodes once they have been put into the ground. The resistivity distribution in the subsurface is ascertained from the voltage measurements that follow.

Key characteristics

• Identifies changes in resistivity along a profile line.

• Gives details on groundwater conditions, the presence of geological structures, and variations in subsurface lithology.

• Useful for finding faults or cracks, differentiating between different soil or rock types, and pinpointing possible groundwater supplies.

• Suitable for shallow subsurface investigations.

Electrical sounding method.

The resistivity distribution with depth in the subsurface can be found using the geophysical method known as the electrical sounding method. 

It entails utilizing a fixed electrode setup to test electrical resistance at various places. By injecting an electrical current into the ground through one or more electrodes and measuring the ensuing potential differences, the resistivity measurements are produced.

Key characteristics of electrical sounding method.

• Investigates or measures resistivity at various depths.

• Gives details on the subsurface resistivity's vertical variation, which is relevant to groundwater properties and lithological changes.

• Used to find prospective groundwater resources, assess aquifer features, and gauge the depth and thickness of subsurface layers.

• Depending on the exact equipment and methodology, can be used for both shallow and deep underground investigations.

Following are the differences between electrical profiling and electrical sounding method. 

Properties	Profiling method	Sounding method
Measurement Configuration	Measurements are taken along a profile line with multiple electrodes.	Measurements are taken at fixed points with a specific electrode configuration.
Information Obtained	Provides resistivity variations along the profile line, offering insights into lateral changes in subsurface conditions.	Provides resistivity variations with depth, allowing for the characterization of subsurface layers and identification of different geological features.
Depth of Investigation	Generally suitable for shallow investigations due to the electrode spacing and profile length limitations.	Can be used for both shallow and deep investigations, depending on the electrode configuration and equipment used.
Application	Primarily used for mapping lateral variations in subsurface resistivity and identifying geological structures.	Primarily used for determining the resistivity distribution with depth and assessing groundwater resources.