Seismic
Reflection is commonly used to provide geological images of the subsurface,
particularly in oil and gas exploration. In this technique, seismic
impulses are generated in the ground, and seismic reflections are recorded
as they bounce off changes in acoustic contrast. Because different materials
reflect the energy in different ways, the returning signals can be used
to produce images of subsurface strata.
For
engineering survey operations the seismic source is generally either
a blank shotgun cartridge or a 'Betsy' 8-gauge industrial cartridge.
Either is capable of producing a consistent and repeatable seismic signal.
Processing
the data is a complex task that can now be readily carried out using
a desktop computer. A variety of programmes is available to do this
task : we are familiar with Kansas Geological Survey's "Eavesdropper';
we also use Promax or Interpex SPW for larger projects.