Applied Geophysics

Magnetics

magnetic meaurements

Magnetic measurements measure the Earth’s magnetic field. Objects in the subsurface with different magnetic susceptibility than the surrounding material and/or with remanent magnetization cause small-scale anomalies in the measured field. Magnetics is widely used as the first method in archaeological prospecting, because most archaeological objects have a magnetization and magnetic sensors, such as fluxgate magnetometers, are relatively inexpensive. Thus, several magnetometers can be used simultaneously to cover large areas in short time.

To get rid of temporal fluctuations in the Earth’ magnetic field that would obscure the anomalies of subsurface objects two methods can be applied: a) using a base station magnetometer that measures the temporal variations at a fixed place or b) using gradiometer magnetometers that measure the field with two sensors above each other and that are subtracted from each other.

Processing is relatively easy and fast compared to other methods and consists mainly of heading error correction and gridding onto a regular grid for display.

 

typical magnetic anomalies