Geophysical Surveys
Geophysical surveys are non-invasive techniques used to investigate subsurface geological properties and structures by measuring variations in physical properties of rocks and soil. Common properties measured include density, magnetism, electrical conductivity, seismic velocity, and natural radioactivity. By detecting how these properties change across a study area, geophysicists create images and maps of subsurface features without requiring excavation or drilling.
Primary Methods
Seismic surveys use sound waves or explosions to probe the Earth’s interior, measuring how waves reflect and refract through different rock layers. Gravity surveys measure variations in gravitational attraction caused by density differences in subsurface materials. Magnetic surveys detect variations in Earth’s magnetic field caused by magnetized rocks. Electrical and electromagnetic methods measure how materials conduct or resist electrical current, revealing subsurface composition and moisture content. Radiometric surveys detect natural radioactivity from elements like potassium and uranium, useful for identifying specific rock types.
Applications
Geophysical surveys support diverse applications including oil and gas exploration, groundwater assessment, mineral prospecting, geothermal resource evaluation, and environmental site characterization. They are also employed in engineering geology to evaluate foundation conditions, detect buried infrastructure, and assess subsurface hazards. Archaeological surveys use geophysical methods to locate buried structures and artifacts without excavation. The choice of method depends on the target depth, desired resolution, subsurface conditions, and project objectives.