# Gravity anomaly of a dipping prism

• whatsoever
In summary: D, which I needIn summary, the conversation discusses the process of writing a MATLAB script to calculate the gravity anomaly of a dipping prism using the equations of Hjelt published in a 1974 issue of Geoexploration. The equations involve Δg, G, Δρ, T0, u, v, and w, and there are two notes at the end of the page explaining the sign of each \phi. The conversation also mentions difficulty understanding the equations and suggests referencing Telford et al.'s 1990 book on Applied Geophysics for clearer notation and a better understanding of gravity methods.
whatsoever
I am trying to write a MATLAB script which calculates the gravity anomaly of a dipping prism, using the equations of Hjelt, published in Geoexploration in 1974, issue 1 volume 12.
Δg=G.Δρ.T0
where
http://img580.imageshack.us/img580/6528/41828644.png
and
http://img31.imageshack.us/img31/4226/phiih.png
at the end of the page there are two notes, the second one says:
"Note 2: The sign of each $\phi$ is positive, whenever there is an even number of 2s in the indices
of u, v and w. (u1, - v1 - w1, u1 - v2 - w2, etc.)"

I just can't get my head around what exactly this means and how to apply it.I have expanded the equations for each $\phi$, using the limits for u, v and w, but they are very long, so will post them only if needed.

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I had a quick read of the paper. Granted, the notation that the author uses is not clear and rather cumbersome.

I am not sure whether this helps, but if I were you, I would derive the gravity effect formula for a simple case (i.e. rectangular prism, semi-infinite slab, etc) and see how the results work out.

I do not have it at hand right now, but Telford et al., 1990 (Applied Geophysics) has a decent section on gravity methods. I would also take a look at Telford as I recall the notation is clearer.

cheers.

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I think Telford gives the equations only for 2D anomalies

1.

## What is a gravity anomaly of a dipping prism?

A gravity anomaly of a dipping prism refers to the difference between the measured gravity value and the theoretical gravity value of a prism-shaped geological structure that has a dip in its orientation. It is typically measured using gravity surveys and can provide valuable information about the subsurface geology.

2.

## How is a gravity anomaly of a dipping prism calculated?

The gravity anomaly of a dipping prism is calculated using the Bouguer correction, which takes into account the effects of the Earth's curvature and the density of the underlying rock layers. It is then compared to the expected gravity value for a horizontal prism to determine the anomaly.

3.

## What causes a gravity anomaly of a dipping prism?

A gravity anomaly of a dipping prism is caused by variations in the density of the subsurface geology. If the density of the dipping prism is different from that of the surrounding rock layers, it will create a gravitational attraction that differs from the expected value for a horizontal prism.

4.

## What information can be obtained from a gravity anomaly of a dipping prism?

A gravity anomaly of a dipping prism can provide information about the subsurface geology, such as the presence of faults, folds, or other structures that may be associated with mineral deposits. It can also help to map out the shape and orientation of the dipping prism.

5.

## How is a gravity anomaly of a dipping prism used in geological exploration?

A gravity anomaly of a dipping prism is often used as a tool in geological exploration to identify potential areas of interest for further investigation. It can help to locate mineral deposits, oil and gas reservoirs, and other geological features that may be economically valuable.

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