The gravity survey is intended basically detection and study of bodies and underground structures by means of the changes that the presence of these occurs in the Earth's gravitational field due to density differences between different types of rocks.

It is another method that uses a natural Newtonian field, the gravity, so you do not have to create pre and observations are to determine the value of gravity in a series of points (stations) covering, with varying density, study area.

The mass of the earth's crust in the first 5 km, is responsible for only 4.5 of the attractiveness diezmilésismas total land (mostly due to the mantle), so that variations in the density of the rocks that constitute the superficial part of the court order anomalies occur in a millionth of Earth's gravitational field and even less. Therefore, the gravity survey requires the use of instruments of great sensitivity and precision (about 10-8), as only bodies or structures can be detected when they differ in their density on the surrounding rocks (density contrast).

A gravity survey usually involves the identification of differences in gravity between a series of points called stations are distributed so that approximately uniform over the study area. The results are compared with those of an ideal model of land with subsoil of uniform density. The differences obtained in this comparative process, called reduction, called gravity anomalies and are the ones that are the basis for detection and identification of bodies or structures disturbing.

APLICATIONS:
The applications of this technique are varied:

• Search and exploration of mineral deposits (salt diapirs, sulfides, oil and gas, "screening" of the anomalies found by other methods such as electromagnetic, etc..)
• Undulations of the basement and detection of structures in the sedimentary layers, which are useful in Hydrogeology.
• Location of underground cavities, whether natural (karst terrain) or artificial (archeology).
• Tectonic studies and geological mapping,
• Etc.

In the example below we see that type of anomaly produce ... ... ... ....