ERSC 3V93 Lecture Notes - Lecture 8: Bouguer Anomaly, Gravity Anomaly, Theoretical Gravity
27 Apr 2016
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Document Summary
The gravity anomaly g we are attempting to measure is small in comparison to large time varying and spatial changes in gravity. Remove these effects by applying several correction factors" to raw field measurements. Instrument drift: earth tides, latitudinal corrections, free air corrections, bouguer corrections, terrain corrections. Temperature changes and elastic creep in springs cause g reading to change gradually with time. Usually less than about 1 2 mgal (10 g. u. ) Drift is monitored by repeating reading at same station at different times of day (every 1 2 hours) to produce a drift curve. Gravitational attraction of the sun and the moon distorts the shape of the earth as well as ocean surface. Amount the earth distorts is small (cm"s) but large enough to to affect gravity reading. In order to measure drift and tidal effects, several base station locations are set up and reoccupied repeatedly during the course of the survey.
