Near surface engineering geophysics

• geophysics: science that estimates earth properties from measurements at earth surface
• gephysics works at many scales from 1000's of km's to tens of cm.
• near-surface geophysics: non-invasive imaging of a variety of near surface (upper 100m or less) properties and structures
• basic principle of geophysical techniques (Fig)
• many different methods:
• electromagnetic (EM), radar (Fig)
• seismic (acoustic waves)
• electrical (direct electrical current)
• potential Field methods (Gravity and Magnetics)
• the most common techniques:


• typical applications:
• hydrogeological mapping
• pipeline, tank, and contamination mapping
• remediation monitoring
• arcaeology
• soil type mapping
• geotechnical applications (foundations, roads, tunnels)
• what can you expect from doing a geophysical survey
• additional information (data) to help you solve your problem
• data that you can not economically get any other way
• data that may help you set the location of wells & sampling points (more expensive than geophysics)
• large, continuous picture of the problem (bedrock  depth, stratigraphy)
• geologic framework of site
• infill of data between existing wells
• anomalies in subsurface physical properties that may represent the target
• what can’t you expect from doing a geophysical survey
• the answer
• unique interpretation of data
• 100% positive identification of target
• examples
• ground penetrating radar image, Maine (Fig)
• conductivity survey of abandoned industrial site in New York (Fig)
• Bangladesh resistivity cross section (Fig)
• BRF examples
• use geophysical techniques in the surrounding of the building
• GPS reading at the site
• magnetics
• EM (Fig 1,2) 2D isoplot
• ground-prenetrating radar (Fig 1,2,4,5,6)