1. . 
The horizontal displacement between points on either side of a fault, which can range from millimeters to kilometers. Perhaps the most readily visible examples of offset are features such as fences or roads that have been displaced by strike-slip faults, such as the San Andreas fault of California, USA.
Synonyms: offset well
2. . 
In surface seismic acquisition, the horizontal distance from source to receiver. In a vertical seismic profile, offset is the horizontal distance between the source and the wellhead or the surface projection of the receiver in the case of a deviated well. Offset between seismic source and receiver creates a delay, or moveout, in the arrival time of a reflection that can be corrected before stacking and can be used to determine velocity.
See: acquisition, arrival time, common-offset, extended spread, fold, geophone offset, lithostratigraphic inversion, moveout, mute, normal moveout, perpendicular offset, shotpoint, spread, tail mute, two-way traveltime, velocity analysis, vertical seismic profile, walkaway vertical seismic profile, zero-offset data