REDUCTION OF GRAVITY DATAPART I: WHY?!!!

By : Dr Amin Khalil

WHY ?!!Gravity field depends on : Mass Inverse of squared distance

The is not a sphere

Elliptical or flatened

Earth’s Radii

Re

Rp

Rp < Re

Hence g is changing with latitude

Important

The use of acceleration due to gravity to study the subsurface it is required to remove any unwanted effects, so that the effects from anomalous bodies are the only factors.

Are there other factors?

yes

Sea Level

Earth’s surface

• Sea level can be regarded as equipotential surface.•Earth’s surface possesses undulations.•Areas above sea level have less g•Areas below sea level have greater g Thus elevations of the earth’s surface affects g and this effect should be removed.

Excess mass

Increase in mass result is increase in g

What are the main types of gravity data reduction ?

1- latitude correction

2- Elevation correction

3- Bouguer correction

4- terrain correction