Seismic methods use an artificial energy source to create seismic waves that are reflected or refracted at rock strata limits. This helps to assess the trend of strata and ground structure in 3D or for a profile. The amplitude of reflected waves provides conclusions about the rock type. The artificial energy source could be simply a hammer and a plate , a special vehicle equipped with a punching plate, or an air gun or air shock blower mounted on a ship at sea.
