Problem 5.1
This type of problem has been done before. You are given a stirke, an apparnet dip, and are asked for the value of the true dip. This time, we use a stereonet.
Given:
- \( \theta = 131^\circ \)
- \(\alpha = 33^\circ, \theta_\alpha = N90^\circ E \)
Find: \(\delta\)
- Plot Strike \(\theta\) on outside of stereonet, Red Dot
- Plot Apparent dip: \(\theta_\alpha, \alpha\), Black Dot
- Rotate Strike to North
- Draw Great Circle that intersects the Strike \(\theta\)and the Apparent Dip \(\alpha\), Fuchsia line
- Read the True dip \(\delta\) along East-West line
- Rotate back to the original position
Show Me
Problem 5.2
This is similar to problems you have attempted, but slightly different. Here you are given two apparent dips and asked for the strike and dip of the fault. Stereonets can help you here.
Given:
- \(\alpha_1 = 35^\circ, \theta_{\alpha 1} = 335^\circ E \)
- \(\alpha_2 = 19^\circ, \theta_{\alpha 2} = 220^\circ E \)
Find: \(\delta\)
- Plot Apparent dip #1: \(\theta_{\alpha 1}, \alpha_1\), Black Dot
- Plot Apparent dip #2: \(\theta_{\alpha 2}, \alpha_2\), Red Dot
- Rotate until both apparent dips are on the same great cirle
- Draw that Great Circle that intersects both apparent dips Fuchsia line
- Read the True dip \(\delta\) along East-West line
- Rotate back to the original position
Show Me
Problem 5.4
Here you are given two planes (1)the fault and (2) the limestone bed; you are asked for the intersection between those two planes, the ore shoot (a linear element).
Given:
- \(\theta_1, \delta_1 = 030^\circ, 35^\circ SE\)
- \(\theta_2, \delta_2 = 080^\circ, 75^\circ N\)
Find: Intersection of the planes
- Plot out the first plane: \(\theta_1, \delta_1\) Black line
- Plot out the second plane: \(\theta_2, \delta_2\) Red line
- Place dot at intersection of the lines: Fuchsia dot
- Rotate dot to East-West line
- Place dot on East-West line: Orange dot
- Measure Plunge along East-West Line
- Rotate back to original position
- Read the Trend where the orange dot is
Show Me
To find the pitch within a plane:
- Rotate plane of interset to the North South line
- Measure the pitch using small circles from the North to the intersection point
- Rotate back to the original position
Show Me - Pitch in Plane 1
Show Me - Pitch in Plane 2
Problem 5.8
This is a two tilt problem where you need to remove the tilting of the younger bed to find the "attitude of the older bed when the younger bed was deposited".
We will assume that the younger bed was deposited horizontally. This would make the "pole" to the younger bed, or its normal, vertical (in the center of the stereonet.
Given:
- Younger bed (black line): \(\theta_y,\delta_y = 045^\circ, 20^\circ SE\)
- Older bed (red line): \(\theta_o, \delta_o = 235^\circ, 60^\circ SE\)
Find Older bed attitude when younger bed was deposited, i.e. horizontal.
- Plot the younger bed \(\theta_y, \delta_y\)
- Plot the older bed \(\theta_o, \delta_o\)
- Convert the younger bed to a pole, black dot
- Convert the older bed to a pole, red dot
- Rotate the younger pole to the East west line
- Move the younger pole (gray dot) to center of the stereonet
- Move the older pole (fuchsia dot) the same distance and direction along a small circle
- Convert the older, rotated pole (fuchsia dot) to a plane
- Measure the orientation of the older, untilted bed (fuchsia line)
Show Me