Geophysical surveys use physical methods at the Earth's surface to measure subsurface physical properties and anomalies. Types of geophysical surveys include gravity, magnetic, electrical, seismic, radiometric, and geothermal methods. The gravity method measures minute variations in gravity caused by differences in subsurface density and distance from the Earth's center. Gravity surveys can be aerial or land-based, using a highly sensitive gravimeter. Processed gravity data is plotted on maps showing variations due to subsurface densities, and is used for hydrocarbon exploration, mineral deposits, cavity detection, and other applications.

1. Geophysical survey
Gravity method

2. What is geophysical survey ?
Exploration geophysics is an applied branch of geophysics, which
uses physical methods, at the surface of the Earth to measure the
physical properties of the subsurface, along with the anomalies in
those properties.

3. Types of geophysical survey
1. Gravity methods
2. Magnetic methods
3. Electrical methods
4. Seismic methods
5. Radiometric methods &
6. Geothermal method

4. Gravity is the force by
which a planet or other
body draws objects
toward its center
What is gravity?

5. If the earth was a perfect sphere and was
composed of the same material throughout,
gravity would be the same anywhere on the
surface. However because the planet is slightly
squashed, gravity at the poles is slightly higher
than at the equator due to the slightly shorter
distance to the centre of the earth to the poles.

6. The strength of
gravitational field is
directly proportional
to the density of
subsurface
substances

7. Gravity method (or) gravity survey
•Gravity surveys measure minute variations in gravity.
Gravity at every point on the surface of the earth varies
slightly depending on:
• distance from the equator
• density of the underlying rocks

8. Gravity surveys can be can be either
aerial or land-based.
•How Is A Gravity Survey Done?

9. gravitymeter
Gravitymeter measures the variation in
earths gravitational fieldThe gravity
meter or gravimeter is a very delicate
instrument as. It is highly sensitive and
great care is required
Once the gravity measurements have
been collected data are processed by the
geophysicist.The data is then plotted as
a computer-generated map

10. Results obtained from gravitymeter
It shows variations in gravity due to the presence of subsurface substances of varying densities

11. Applications
of gravity
surveying
Hydrocarbon exploration
Estimation of, mineral deposits
Detection of sub-surface cavities (micro-gravity)
Location of buried rock valleys
Determination of glacier thickness
Shape of earth (geodesy)