Geophysical Surveys
Geophysical surveys are non-invasive techniques used to investigate subsurface geological properties and structures by measuring physical properties of rocks and soil. These methods detect variations in density, magnetism, electrical conductivity, seismic velocity, and radioactivity to create images or maps of subsurface features without requiring excavation or drilling. By analyzing how these physical properties change across a study area, geophysicists can identify geological formations, locate mineral deposits, map groundwater resources, and assess structural features like faults and layering.
Common Methods
The primary geophysical survey techniques include seismic reflection and refraction, which use sound waves to image subsurface layers; gravity and magnetic surveys, which measure variations in gravitational and magnetic fields caused by density and mineral composition differences; electrical resistivity surveys, which inject electrical current to measure how rock formations conduct electricity; and ground-penetrating radar, which uses electromagnetic waves to detect shallow subsurface features. Each method has distinct advantages and limitations depending on the target depth, geological setting, and desired resolution.
Applications
Geophysical surveys support diverse applications across geology, engineering, and resource exploration. They are essential for hydrocarbon and mineral exploration, mapping aquifers for water resource management, assessing ground stability for construction projects, detecting contamination plumes in environmental investigations, and understanding geological hazards such as earthquakes and landslides. The choice of survey method depends on the specific investigation goals, subsurface geology, and practical constraints such as accessibility and budget.