equal area stereonet with small circles showing consistent size. Small circles Angles are slightly distorted and make the circles appear as ellipses. The x-axis. This is a printable 2 degree equal angle (Wulff) stereonet in PDF format. Equal angle versus Equal area nets. Two projections used in structural geology. They are also used as map projections, and for maps of the sky in astronomy (or .

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A circle on the surface of a sphere made by the intersections of a plane that does not pass through the center of the sphere. The red arrow is the displacement vector which is obtained by the horizontal and vertical displacement. In other words, they provide the best projection for analyzing the direction and the vectors of structural forces.

Equal area projection 2. The rake of the fault is between the left most edge of the footwall and the displacement vector red.

A Plot the following two planes: For example, from intersection point 3 upwards towards NW direction of the great circle intersection of plane A. It is the outer most circle is the primitive. This will be explained in depth in a different article. If you are a mineralogist, you will use the top half of the spherical projection for crystallographic analysis. As you start plotting points you will see why this is necessary.


C Plotting the poles to each of those planes and label them. They are hemisphere surface paths from one line being rotated about another line the pole of rotationboth wngle through the hemisphere center.

To do this rotate the two lines until they fall on one great circle. Those labeled with dip amounts on the left side, dip to the west.

Stereographic projection for structural analysis

The steeper the dip the less curved the great circle is and the closer to the center, and the shallower the dip of the setreonet the more curved and the closer to the outside margin of the stereonet plot the great circle is. A detailed diagram… Hand written sample.

The equal angle stereonets are suitable for kinematic analysis. H Determining the strike and dip of the common plane those two lines define.

In other words, it is often used to analyze accuracy of data from several different regions of the same area. What is plotted on the stereonet is a projection of where a given line or plane equual the lower hemisphere surface. In this position it is easy to trace out the great circle with the appropriate dip, here 50 degrees to the NE.

It is the true Stereonst which is denoted by the azimuthal angle of degrees on the primitive. Angles are slightly distorted and make the circles appear as ellipses. The stereonet or stereographic projection is the most important visualization tool for orientation data in structural geology.


If the same plane was rotated about a vertical axis in the stereonet center, they would then retain their dip, but have a different strike. This is because the equal angle stereonets preserves the true relationships between stratigraphic and structural features.

Lab 5: Structural Analysis using stereonets

The green arrow represents the rate of stegeonet with respect to the original block. It is at degrees from the center of the stereonet.

The software often eliminates many user errors, produce much better quality steronets extremely detailed analysis of datasets and make it easier to stereoonet with other over electronic devices. Label each one clearly.

Standing on the shoulders of giants. D Finding the angle between the poles and thus between the two planes. B Determine the trend and plunge of the intersection. Remember the equak is that the first number represents the trend direction and the second represents the plunge amount. If we repeat this operation for all the points of intersection of the plane with the hemisphere then a curved line, a great circle trace, is formed on the streonet.

Primitive circle is also a great circle but, it contains N, E, S and W directions at, qeual degrees intervals.

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