Geology

How to Calculate and Solve for Geoid Height Anomaly for an Ocean Basin | Gravity

August 24, 2020 by Loveth Idoko

The image above represents genoid height anomaly for an ocean basin.

To compute for genoid height anomaly for an ocean basin, one essential parameter is needed and this parameter is depth (d).

The formula for calculating genoid height anomaly for an ocean basin:

Δh ≃ 3.85d (0.7 – 0.046d)

Where:

Δh = Geoid Height Anomaly for an Ocean Basin
d = Depth

Let’s solve an example;
Find the genoid height anomaly for an ocean basin when the depth is 20.

This implies that;

d = depth = 20

Δh ≃ 3.85d (0.7 – 0.046d)
Δh ≃ 3.85(20) (0.7 – 0.046(20))
Δh ≃ 77 (0.7 – 0.919)
Δh ≃ 77 (-0.219)
Δh ≃ -16.93

Therefore, the genoid height anomaly for an ocean basin is -16.93 m.

How to Calculate and Solve for Geoid Height Anomaly for Crustal and Mantle Densities | Gravity

August 24, 2020 by Loveth Idoko

The image above represents genoid height anomaly for crustal and mantle densities.

To compute for genoid height anomaly for crustal and mantle densities, one essential parameter is needed and this parameter is height (h₁).

The formula for calculating genoid height anomaly for crustal and mantle densities:

Δh ≃ 6h₁ (0.7 + 0.066h₁)

Where:

Δh = Geoid Height Anomaly for Crustal and Mantle Densities
h₁ = Height

Let’s solve an example;
Find the genoid height anomaly for crustal and mantle densities when the height is 12.

This implies that;

h₁ = Height = 12

Δh ≃ 6h₁ (0.7 + 0.066h₁)
Δh ≃ 6(12) (0.7 + 0.066(12))
Δh ≃ (72) (0.7 + (0.792))
Δh ≃ (72) (1.492)
Δh ≃ 107.424

Therefore, the genoid height anomaly for crustal and mantle densities is 107.424 m.

How to Calculate and Solve for Bouguer Anomaly | Gravity

August 24, 2020 by Loveth Idoko

The image above represents bourger anomaly.

To compute for bourger anomaly, three essential parameters are needed and these parameters are Free Air Correction (g_F), Bouguer Correction (δg_B) and Terrain Correction (δg_T).

The formula for calculating bourger anomaly:

g_B = g_F – δg_B + δg_T

Where:

g_B = Bouguer Anomaly
g_F = Free Air Correction
δg_B = Bouguer Correction
δg_T = Terrain Correction

Let’s solve an example;
Find the bourger anomaly when the free air correction is 14, the bourger anomaly is 18 and the terrian correction is 20.

This implies that;

g_F = Free Air Correction = 14
δg_B = Bouguer Correction = 18
δg_T = Terrain Correction = 20

g_B = g_F – δg_B + δg_T
g_B = 14 – 18 + 20
g_B = 14 – 38
g_B = -24

Therefore, the bourger anomaly is -24 mGal.

How to Calculate and Solve for Elevation Correction | Gravity

August 24, 2020 by Loveth Idoko

The image above represents elevation correction.

To compute for elevation correction, two essential parameters are needed and these parameters are Free Air Correction (δg_F) and Bouguer Correction (δg_B).

The formula for calculating elevation correction:

δg_E = δg_F – δg_B

Where:

δg_E = Elevation Correction
δg_F = Free Air Correction
δg_B = Bouguer Correction

Let’s solve an example;
Find the elevation correction when the free air correction is 12 and the bourger correction is 17.

This implies that;

δg_F = Free Air Correction = 12
δg_B = Bouguer Correction = 17

δg_E = δg_F – δg_B
δg_E = 12 – 17
δg_E = -5

Therefore, the elevation correction is -5 mGal.

Calculating the Free Air Correction when the Elevation Correction and the Bourger Correction is Given.

δg_F = δg_E + δg_B

Where;

δg_F = Free Air Correction
δg_E = Elevation Correction
δg_B = Bouguer Correction

Let’s solve an example;
Find the free air correction when the elevation correction is 34 and the bourger correction is 21.

This implies that;

δg_E = Elevation Correction = 34
δg_B = Bouguer Correction = 21

δg_F = δg_E + δg_B
δg_F = 34 + 21
δg_F = 55

Therefore, the free air correction is 55.