Land and Ocean EM induction studies

Abstract

Gravity and magnetic surveys are routinely used to map deep seated structures by exploiting the variation in density or magnetic properties of crustal rocks. Gradations in electrical conductivity provide another physical property that can similarly be exploited. The workshop session on induction studies provided a timely reminder that modern advances in electro-magnetic techniques, now provide a sound basis to attempt a systematic study of the Australian lithosphere. The two techniques most commonly used are magnetometer arrays in which the spatial variations of the geomagnetic variation field is mapped over a given area, and the magneto-telluric technique (M.T.) in which the telluric currents are also recorded. Magnetometer arrays are effective in providing rapid aerial coverage, but their depth resolution is poor. MT has good depth resolution but is logistically complicated and expensive for dense aerial coverage.