Seismic Reflection surveying measures the energy return from induced by an active seismic source that has been reflected from an acoustic contrast. At each subsurface boundary or acoustic contrast, across which the elastic and density parameters differ, a percentage of the energy in the wave is reflected back to the surface where it is recorded via geophones. If a boundary layer is horizontal, the reflection point will be half way between the shot and any given geophone. Reflecting boundaries are mapped out as the system can roll along the surface accounting for topographic corrections. Reflection data requires intense and complicated processing of the collected information.
By recording the time it takes for reflected energy to arrive at a receiver, it is possible to estimate the depth of the feature that generated the reflection. In this way, reflection seismology is similar to other geophysical investigation techniques such as ground penetrating radar (GPR) and sonar technologies.
The near surface geology is sounded and illuminated with seismic waves. Gehrig, Inc. currently measures the reflected waves with a 48-channel Geometrics Strataview seismograph shown above.