Applied Geophysics

Electromagnetic Induction

Electric current can be induced in the subsurface by artifical or natural electromagentic sources. By analysing the observed electric and magnetic field the conductivity of the subsurface an be derived.

Natural sources are:

  • lightnings
  • sprites (elctrical discharge between clouds and the ionosphree)
  • current flow in the ionoshpere
  • solar storms

 

Artifical sources for electromagnetic induction are:

  • alternating magnetic fields (frequency domain) and
  • abruptly interrupted static magnetic fields (time domain)

emiited by coils or antennas.