This course provides a comprehensive overview of the topic of geophysical surveys using electrical and electromagnetic methods. All materials, including soil and rock, have an intrinsic property, resistivity, that governs the relation between the current density and the gradient of the electrical potential.

Variations in the resistivity of earth materials, either vertically or laterally, produce variations in the relations between the applied current and the potential distribution as measured on the surface, and thereby reveal something about the composition, extent, and physical properties of the subsurface materials. The various electrical geophysical techniques distinguish materials through whatever contrast exists in their electrical properties. Materials that differ geologically, such as described in a lithologic log from a drill hole, may or may not differ electrically, and therefore may or may not be distinguished by an electrical resistivity survey.

Properties that affect the resistivity of a soil or rock include porosity, water content, composition (clay mineral and metal content), salinity of the pore water, and grain size distribution.

Topics:

• Intro to Electrical / Electromagnetic Geophysical Survey Methods
• Self-Potential Method
• Equipotential and Mise-a-la-masse Methods
• Resistivity Methods
• Induced Polarization
• Time-Domain Electromagnetic Techniques for Resistivity Sounding
• Frequency-Domain Electromagnetic Methods
• Terrain Conductivity
• Metal Detector Surveys
• Ground-Penetrating Radar

Intended Audience: This course is intended for professional land surveyors as well as petroleum, civil, geotechnical, environmental, and other engineering professionals whose job description may require an intermediate knowledge of electrical and electromagnetic geophysical surveying methods.

Publication Source: USACE