(in vur’ zh∂n or in vur’ sh∂n) Deriving from field data a model to describe the subsurface that is consistent with the data; determining the cause from observation of effects. 1. Solution of the inverse problem (q.v.). Inversion means solving for a spatial distribution of parameters which could have produced an observed set of measurements. 2. Often, specifically, calculating acoustic impedance (or velocity) from a seismic trace, taken as representing the earth’s reflectivity. 3. Sometimes, migration (q.v.). 4. Finding the reciprocal. 5. The ‘‘inverse of A’’ is ‘‘not A=A’’; see gate. 6. The vertical reversal of the sense of movement of structural features because of a change in the stress pattern. Involves features such as an anticline becoming a syncline, a normal fault becoming a reverse fault, etc.