Methods and apparatus are provided for controlled source electromagnetic surveying. In particular, a time-varying electromagnetic signal is transmitted at a first location, and an electromagnetic signal responsive to the transmitted signal is received at a second location, wherein the received signal...http://www.google.de/patents/US7504829?utm_source=gb-gplus-sharePatent US7504829 - Methods and apparatus for subsurface geophysical exploration using joint inversion of steady-state and transient data
