gravity anomaly的意思|示意

Gravity anomaly is a term used to describe areas of the world where the local gravitational field differs significantly from the mean free-air gravity. Usually, the anomaly is expressed in terms of the acceleration due to gravity, measured in milligals, which is defined as a thousandth of a gal (a gal is a unit of acceleration equal to one centimeter per second squared).

Gravity anomalies are usually measured by instruments such as gravimeters and can be used to infer information about the local structure of the earth. For example, because the gravity field inside a homogeneous sphere is twice that of a homogeneous ellipsoid, an area with an unusually high gravity anomaly could suggest the possibility of a large body of dense material such as ore.

Gravity anomalies can also be used to detect changes in the land surface, such as faults or depressions. In addition, gravity anomalies can be used to detect seafloor features such as ridges and trenches.

Gravity anomalies have been used extensively to map the subsurface structure of the Earth over the past few decades. Such maps have revealed large-scale structures such as mantle plumes, which are more easily detected than with seismic studies alone. They have also been used to map the structure of sedimentary basins, which are often difficult to study using seismic methods.

Gravity anomaly maps are also used for navigation and surveying, as well as for determining the size and shape of the Earth. In some cases, gravity anomaly maps can be used to determine the age of geological features such as mountains.

In conclusion, gravity anomaly is a term used to describe areas where the local gravitational field differs significantly from the mean free-air gravity. Gravity anomalies can be used to infer information about the subsurface structure of the Earth, detect seafloor features, and also for navigation and surveying.