1. The correction applied to a measurement of gravitational attraction to allow for the distance to the station from the theoretical reference surface and for the attraction of the rocks in this zone. It is a combination of the free-air and Bouguer corrections.

2. (static correction) The correction which is made to seismic travel-time data to compensate for irregular topography and to reduce the data to a common datum. Land ‘statics’ are extremely important in seismic surveying on land. As part of a ‘statics’ survey, refraction shooting is undertaken to determine the depth and velocity of the weathered zone (the low velocity layer, or LVL). This is done in order to design more effective seismic source parameters (e.g. ideally, the shot depth should be below the weathered layer) thereby optimizing the seismic reflection surveys which are undertaken after an LVL survey. In marine surveys, marine ‘statics govern the source– hydrophone geometry and provide a correction for the finite offset between the source arrays and the hydrophone streamer.