Gravimetrybased

Gravimetry-based methods rely on measurements of the local gravitational acceleration, g, to infer the distribution and movement of mass in the Earth and in engineered systems. By detecting small variations in g, these methods reveal density contrasts, mass changes, and structural features beneath the surface or within a material.

The principle is that gravity is produced by all nearby matter; spatial variations in g reflect differences in density and mass distribution. Gravimetry can be used to detect subterranean structures, monitor water storage, study tectonics, or track surface loading from infrastructure or natural processes.

There are two main classes of gravimetry: absolute gravimetry, which yields an absolute value of g at a location with high precision, and relative gravimetry, which records changes in g between points or over time. Absolute instruments include free-fall and corner-cube interferometers, and newer approaches employ atom interferometry. Relative devices typically use spring-based sensors or superconducting mechanisms to detect small changes in gravity, allowing continuous monitoring.

Applications span geodesy, volcanology, hydrology, mineral and oil exploration, and environmental monitoring. Gravity data are often corrected for tides, atmospheric pressure, ocean loading, and topography to produce Bouguer or Free-Air gravity anomalies, which highlight subsurface mass variations.

Limitations include sensitivity to environmental noise, instrument drift, and calibration needs, as well as the requirement for stable conditions during measurements. The field has evolved from classic Cavendish-type experiments to modern high-precision and quantum-based gravimeters, expanding the utility of gravity measurements in science and industry.