Seismic methods employ seismic waves to image the subsurface.  A source, such as a sledge hammer or shot gun shell, is used to generate seismic waves which travel through the subsurface.  These waves reflect and refract when the come in contact with a interface of differing seismic velocity.  Geophones are used to record the amplitude and arrival time of the seismic energy as it returns to the surface.  This data may be used to interpret the subsurface.

This technique can be used to map stratigraphic boundaries, identify subsurface structures such as faults and folds, and locate the water table.   

The Near Surface Geophysics Lab at Kutztown University owns a Geometrics 24-channel Geode Seismograph.