Physics
Fig. 209 A schematic showing the basics of a ZTEM survey: natural sources from solar energy lightning excite the earth; An airborne-receiver measures the vertical magnetic field component while a reference station on the surface measures the horizontal magnetic field components.
ZTEM is an electromagnetic method that uses natural sources to excite the earth. The physics are identical to the MT method, with the difference being that for ZTEM surveys, the vertical magnetic field is measured by an airborne system and the horizontal magnetic field components are measured at a single reference station on the earth’s surface. The physics of natural source methods are described on the MT physics page.