1. n. [Formation Evaluation]

The additional loss in amplitude of an electromagnetic wave emitted by an electromagnetic propagation or dielectric propagation measurement compared to that of a plane wave. The spreading loss depends on the geometry of the transmitter-receiver array and also on the dielectric properties of the formation. The same effect also causes a small correction to the propagation time.

See: attenuation,  broadside array,  dielectric propagation log,  electromagnetic propagation,  electromagnetic propagation measurement,  endfire array,  plane wave