PARSAN Geophysics

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Gravity and Magnetic

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Gravity Method is a potential field technique which measures variations in the Earth's gravitational field. These variations are caused by density contrasts in the near surface rock and sediment. Gravimetric surveys are carried out using extremely sensitive instruments capable of measuring tiny variations in the gravitational field. These surveys are always carried out in conjunction with a precise topographic survey, to enable terrain corrections to be carried out.

Typical applications are:

  • Regional geological mapping
  • Oil and gas exploration
  • Mineral exploration
  • Sediment thickness studies
  • Archaeological surveys
  • Void detection

Magnetic method is a passive method since it only measures the existing magnetic field strength, it does not amplify or modify it in any way. It is most often used in areas with minimal urban infrastructure, which tends to make interpretation difficult. A magnetometer can measure the total magnetic field strength passing through its sensor through the application of the principles of nuclear physics and quantum mechanics. Different types of magnetometer exist, each with different levels of precision and resolution. Most common are proton precession magnetometers, with cesium vapor magnetometers used for more specialized applications such as airborne surveys

Typical applications are as follows:

  • Location of buried ferromagnetic objects
  • Archaeology
  • Mineral exploration
  • Geological mapping