Method
Introduction
A gravity survey measures small changes in Earth’s gravitational field that result from density contrasts in the subsurface. Denser materials produce a stronger gravitational response, while lower-density materials reduce the observed field.
Gravity data are typically acquired at stations distributed along profiles, grids, or regional traverses. Zonge reduces the observations to complete Bouguer anomaly data and related derivative products that help map structure, basin geometry, and density-driven targets.
Applications
Gravity surveys are a common tool for identifying density contrasts in the subsurface.
- Structural mapping, including fault zones and hanging-wall versus footwall contrasts
- Lithologic changes where density contrast is sufficient for detection
- Void detection in karst or engineered settings
- Alteration mapping and basin characterization
- Depth-to-bedrock mapping
- Direct detection support in favorable massive sulfide settings
- Monitoring concepts for CCUS and other reservoir-scale applications
Survey Design
| Parameter | Description |
|---|---|
| Depth | Depth is inferred from anomaly wavelength, density contrast, and the geometry of the causative body. |
| Station Spacing | Station spacing should generally be no greater than the lateral extent of the target and is ideally 1-2 times smaller than the target dimension. |
| Scale | Gravity surveys are effective from local investigations to large regional programs. |
| Cost | Gravity is typically low cost relative to many other geophysical methods. |
| Production | Daily production depends on spacing, terrain, access, and required repeatability. |
Instrumentation
- Gravity Meters: LCG-6, LaCoste & Romberg gravimeters and Scintrex CG-5 instruments where higher precision is required
- Positioning: Geodetic-grade GPS systems for accurate station location and elevation control
Deliverables
- Color-contoured plan-view maps of complete Bouguer anomaly at the selected reduction density
- Plan-view maps of horizontal gradient and first derivative products
- Additional modeling and interpretation outputs where project scope includes inversion or residual analysis
- 3D Inversion results
Case Studies and Resources
- Contact Zonge for gravity project examples, derivative product samples, and application notes relevant to your target.