*Method of separation of anomaly:1- Graphical method a- From profile: characterized by: 1- Separation is easy, especially when there are large and small scale structures. 2- Calculated from profile of the total Bouguer anomaly. 3- Not very accurate.

*a- From Bouguer Gravity map Map: characterized by: 1- It is simple process, become difficult when there are two structures of the same size. 2- Calculated from total Bouguer map. 3- Moderately it is accurate.

StationBouguerRegionalResidual1212102352693403010436360

*2030405060708090100110120130140Bouguer Gravity Map100110120130140708090150160Bouguer GravityRegional GravityResidual Gravity

*Analytical methods :There are several mathematical methods used for separation.1- Griffin method (circle and centre point).2- Second derivative method.3- Polynomial fitting.4- Upward and downward continuation.

A- Griffin method:The following steps have to be followed:1- Select a suitable circle of radius 1 cm, 2- Draw the circle on the transparent paper.3- The centre of the circle placed on a certain station, so that: a- Four stations are located on the circumference. b- Eight stations are located on the circumference.4- Regional gravity is calculated by:

*5- Repeat this process for all station.6- Determine Residual by:34 36 33 33 24 44 44 34 34 44 45 4636 37 33 37 29 41 41 34 34 43 43 4638 31 33 33 34 38 44 39 37 45 49 4834 35 30 33 24 44 44 34 34 44 45 4634 35 30 33 24 44 44 34 34 44 45 46

* 34 35 32 34 38 44 44 34 34 44 45 3 -2 5 -5 3 3 5 -6 -4 3 4

*Selecting Suitable circle:The most suitable separation process depend on best selection of the circle radius. There are the following cases:1- If the diameter of the circle is too small than the maximum dimension of an anomaly.A part of residual is separated, other part mixed with the regional.

ABECFDAB is not suitable circleCD is not true residualEF is true residualSeparation process is not successful and we can know that from the regional map

*ABECFD2- If the diameter of the circle is too large than the maximum dimension of an anomaly.A part of regional is calculated regional.AB is not suitable circleCD is not true residualEF is true residualSeparation process is not successful and we can know that from the residual mapReal residualResidual + Part of Regional

*3- If the diameter of the circle is Suitable compare to dimension of an anomaly.Residual completely separated from the Regional.ABECFDAB is suitable circleCD is true residual=EF is true residualReal residualReal Regional