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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We use slickensides to interpret the sense of motion in the field. Equal area projection 2. The reasoning behind which hemisphere we used is more conceptual than anything. A line is drawn from that projection point to abgle lower hemisphere intersection point light green dashed lines.

Stereographic projection for structural analysis

The above diagram shows the same plane in two positions. If it is less than 90 degrees it is the acute angle, otherwise it is the obtuse angle. All strike angles are measured with respect to the true North. There are different methods by which the points of intersection with the lower hemisphere are projected onto the stereonet. In this case the North position is designated in blue. The onion skin overlay permits you to rotate the points being plotted with respect to the underlying, fixed reference frame.

Small circles represent half of a conical surfaces with the apex at hemisphere center. The equal angle stereonets are suitable for kinematic analysis. The stereographic projection is a methodology used in structural geology and engineering to analyze orientation of lines and planes with respect to each other.

Read the Docs v: Typically university geology and engineering students are expected create stereonets by hand. The software often eliminates many user errors, produce much better quality steronets extremely detailed analysis of datasets and make it easier to share with other over electronic devices.


The green represents the plane’s orientation when North is rotated back to its standard top-of-the-stereonet position.

Note that a line plots as point – the point of intersection with the lower hemisphere. A circle on the surface of the sphere made by the intersection with the spehere of a plane that passes through the center of the sphere. This is because the equal angle stereonets preserves the true relationships between stratigraphic and structural features. Planes plot as great circle traces.

The great circles represent north-south striking planes with dips in 10 degree increments. Steeonet is the true North which is denoted by the azimuthal angle of degrees on the primitive. The red arrow is the displacement vector which is obtained by the horizontal and steeeonet displacement. The stereonets is a type of standardized mapping system that allows us to represent various angles in 3D space on a 1D paper.

Structural Analysis Using Stereonets 2 weeks, focus on the Arbuckles 30 pts.

Stereonet Edit on GitHub. Plane B rake is downwards towards SE direction.

2. Stereonet — InnStereo 0 documentation

What is the form that results? Where that line passes through the stereonet project plane is where the line plots the dark green dot. Those labeled with dip amounts on the left side, dip to the west. The point 1 and 2 are best fit line points for the poles that lies about the center of the diagram. Then count along stereojet great circle in degree increments moving from one point pole to the other. This is a very useful tool because it can reduce the workload by avoiding lengthy calculations.


The above is aangle equal area stereonet projection showing great circles as arcuate lines connecting the North and South Points and small circles as arcuate lines in a latitudinal type position.

Lab 5: Structural Analysis using stereonets

A horizontal plane passes through a sphere, of which the lower hemisphere is shown, or considered opposite to mineralogy where the upper angel is considered. 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.

The diagrams below attempt to show you that geometry in three stages, each more complex.

You will need the esual materials in order to proceed with this and the subsequent stereonet exercises: They are equal area stereonet and equal angle stereonets.

It is at degrees from the center of the stereonet. As you start plotting points you will see why this is necessary. The rake of the fault is between the left most edge of the footwall and the displacement vector red. Along the common great circle containing the two poles count in degree increments half of the angle found in D above.

You can do this by simply rotating the point representing the line on to any great circle, and then count along that great circle 20 degrees in both directions and mark those points which will be two lines 20 degrees either side of the first.