What is the difference between Bouguer and free-air gravity anomalies?

If only the latitude and free-air corrections have been applied, the quantity calculated is known as the free-air gravity (free-air anomaly). If, in addition, the Bouguer correction has been applied, the quantity is known as the (simple) Bouger gravity (or anomaly).

What is Bouguer gravity anomaly?

[ bōō-zhâr′ ] The difference between the expected value of gravity at a given location (taking into account factors such as latitude, longitude, altitude, and the rotation of the Earth) and its actual value.

What is the value of Bouguer correction?

The Bouguer spherical cap correction is the new standard method that accounts for the average mass and curvature of Earth with respect to the ellipsoid. This calculation uses the Bullard B Table. The default density of the Bouguer spherical cap is 2.67 g/cm3 (LaFehr 1991).

How is Bouguer gravity anomaly calculated?

I suggest you could use this simple formula: ΔgB = Δgf + 0.06889h, where ΔgB is the Bouguer anomaly, Δgf – the FAA and h is the depth to the ocean bottom in meters (h > 0). More generally, at sea ΔgB =Δgf +2πG(ρ−ρw)h, with 2πG= 0.04193 if gravity anomaly is in mgal, h in meters, and densities are in g/cm3.

Why are Bouguer anomalies negative over continental crust?

The Bouguer anomaly is positive over ocean basins and negative over high continental areas. This shows that the low elevation of ocean basins and high elevation of continents is compensated by the thickness of the crust at depth. The higher terrain is held up by the buoyancy of thicker crust “floating” on the mantle.

What is the difference between incomplete Bouguer reduction and complete Bouguer reduction?

Reduction. A Bouguer reduction is called simple (or incomplete) if the terrain is approximated by an infinite flat plate called the Bouguer plate. A refined (or complete) Bouguer reduction removes the effects of terrain more precisely.

What does a negative Bouguer mean?

What is Mantle Bouguer anomaly?

In geodesy and geophysics, the Bouguer anomaly (named after Pierre Bouguer) is a gravity anomaly, corrected for the height at which it is measured and the attraction of terrain. The height correction alone gives a free-air gravity anomaly.

What is complete Bouguer reduction?

A refined (or complete) Bouguer reduction removes the effects of terrain more precisely. The difference between the two is called the (residual) terrain effect (or (residual) terrain correction) and is due to the differential gravitational effect of the unevenness of the terrain; it is always negative.

What is a gravimeter used for?

The gravimeter measures the shape of seawater-filled cavities at the edge of some major fast-moving glaciers. Data about the amount of water under ice fills in a crucial gap in knowledge related to calving and melting of glaciers.

Where is the lowest gravity on Earth?

Mount Nevado Huascarán
Mount Nevado Huascarán in Peru has the lowest gravitational acceleration, at 9.7639 m/s2, while the highest is at the surface of the Arctic Ocean, at 9.8337 m/s2. “Nevado was a bit surprising because it is about 1000 kilometres south of the equator,” says Hirt.

What is a Gravimeter used for?