Applying a Simple Gravity Reduction isolates deep geological structures by systematically eliminating predictable gravitational variations caused by your location on Earth. The raw gravity reading you take in the field is influenced by latitude, elevation, and nearby rock mass. To extract the Bouguer Anomaly—the signal representing subsurface density anomalies—you must strip these layers away. The Core Anomaly Workflow
The calculation of a Simple Bouguer Anomaly follows a sequential mathematical path:
ΔgB=gobs−gn+ΔgFA−ΔgBPdelta g sub cap B equals g sub o b s end-sub minus g sub n plus delta g sub cap F cap A end-sub minus delta g sub cap B cap P end-sub is the Simple Bouguer Anomaly. gobsg sub o b s end-sub is your measured, field-observed gravity.
is the theoretical normal gravity at your specific latitude. is the Free-Air Correction. is the Simple Bouguer Plate Correction. Step-by-Step Data Corrections
[Raw Field Gravity] ──► Subtract Latitude (Normal) Gravity ──► Add Free-Air Correction (Elevation) ──► Subtract Bouguer Plate (Rock Mass) └──► = SIMPLE BOUGUER ANOMALY 1. Latitude Correction (Normal Gravity)
The Concept: Earth is an oblate spheroid that bulges at the equator and is flattened at the poles. Gravity is naturally stronger at the poles because they are closer to Earth’s center. The Action: Calculate the theoretical gravity (
) for your station’s latitude using the World Geodetic System (WGS84) or GRS80 reference ellipsoids. Subtract this value from your observed reading to remove global shape effects. 2. Free-Air Correction (FAC)
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