 CSEM controlled source electro-magnetic is a deep-water offshore variant of controlled source audio magnetotellurics; CSEM is the name used in the offshore oil and gas industry.and for onshore exploration mostly Lotem is used in Russia, China the USA and Europe

Onshore CSEM / CSAMT may be effective where electromagnetic cultural noise (e.g.power lines, electric fences) present interference problems for natural-source geophysical methods.