How Seismic Waves are used to look beneath  Earth's Surface
Valuable minerals such as petroleum are becoming more scarce as easy to get sources are depleted. Other sources exist but must be located one of the ways oil is located is by seismic profiling.

In seismic surveys, a shock wave is created by the following:

  • > compressed-air gun - shoots pulses of air into the water (for exploration over water)

  • > t    humper truck - slams heavy plates into the ground (for exploration over land)

  • > e    xplosives - drilled into the ground (for exploration over land) or thrown overboard (for exploration over water), and detonated

>  shock waves travel beneath the surface of the Earth and are reflected back by the various rock layers

> the reflections travel at different speeds depending upon the type or density of rock layers through which they must pass.

> the reflections of the shock waves are detected by sensitive microphones or vibration detectors -- hydrophones over water, seismometers over land.

> the readings are interpreted by seismologists for signs of oil and gas traps.

> here is a seismographic image of a salt dome a geological structure often related to oil reserves

> although the domes are often seismologically opaque the captured images can be analysed by computers to "clear up the image and reveal the presence of oil in areas often thought to be depleted of oil      <<<<<< back