Induced Polarization Method
Induced Polarization (IP) is an electromagnetic method that uses electrodes with time-varying currents and voltages to map the variation of electrical chargeability (dielectric constant) in the Earth at low frequencies.
The time domain IP technique energizes the ground surface with an alternating square wave pulse via a pair of current electrodes. On most surveys, the IP/Resistivity measurements are made on a regular grid of stations along survey lines.
After the transmitter (Tx) pulse has been transmitted into the ground via the current electrodes, the IP effect is measured as a time diminishing voltage at the receiver electrodes. The IP effect is a measure of the amount of IP polarizable materials in the subsurface rock. Under ideal circumstances, IP chargeability responses are a measure of the amount of disseminated metallic sulfides in the subsurface rocks.
Also, from the IP measurements the apparent (bulk) resistivity of the ground is calculated from the input current and the measured primary voltage.
IP and Resistivity Data Inversion
IP and resistivity pseudosections can be difficult to interpret directly for complex geometries. Inversion techniques can provide objective earth models and resolve complex anomalies.
Enerson offers inversion of IP and resistivity data using the 2 and 3D forward modelling and inversion software developed by Geotomo Software.
Data from a variety of arrays can be combined
True depth sections and plan maps at specific depths can be produced
The 3D IP Method
Three dimensional IP surveys are designed to take advantage of the interpretational functionality offered by 3-D inversion techniques. Unlike conventional IP, the electrode arrays are no longer restricted to in-line geometry. Typically, current electrodes and receiver electrodes are located on adjacent lines. Under these conditions, multiple current locations can be applied to a single receiver electrode array and data acquisition rates can be significantly improved over conventional surveys.
Applications of Resistivity/IP method:
- Mining exploration (precious and base metal exploration)
- Groundwater and geothermal exploration
- Marble exploration (buried marble detection and 3D marble tomograhpy and fracture mapping)
- Environmental Studies (polluted area detection, waste disposal area studies)
- Geotechnics (cavity detection, slope stability studies)