MobileMT is a geophysical method used to investigate what lies beneath the Earth’s surface. It measures natural electromagnetic signals from lightning, without emitting any electrical signals itself. A sensor is suspended below a helicopter, which flies in straight lines, typically spaced 200 to 400 meters apart and at an altitude of about 120 meters above the ground. At the same time, a ground-based station records the electric fields.
By comparing the signals measured from the air and on the ground, the geophysicists can calculate how well the ground conducts electricity at different depths. The result is geological maps and cross-sections that reveal geological structures, such as the possible presence of conductive mineralization, rock layers, or groundwater, both shallow and deep underground.
Resources for further reading about the method:
- SGU, “Airborne Geophysical Measurements”, https://www.sgu.se/en/about-sgu/tasks-and-activities-new/geological-mapping-surveys/geophysical-mapping/airborne-geophysical-measurements/
- Expert Geophysics, “Mobile MT Airborne Survey”, https://www.expertgeophysics.com/wp-content/uploads/2020/01/EGL-MobileMT_19-08.pdf