Question

Two limbs of a vertical chevron fold strike S70°E and N55°E. The value of the interlimb angle of the fold is ............ (degree).

Hint:

To find the interlimb angle, subtract the strike angles of the two limbs, and if the result is greater than 180°, subtract it from 360° to get the acute angle.

Answer 1

Correct Answer: 55

Step 1: Understanding the concept of interlimb angle.
The interlimb angle in a fold is the angle between the two limbs of the fold. In this case, the two limbs strike S70°E and N55°E. The strike is the angle between the horizontal plane and the line of intersection of the plane with the Earth's surface. The interlimb angle is calculated by subtracting the strike angles of the two limbs.
Step 2: Calculating the interlimb angle.
We subtract the angle of the second limb (N55°E) from the first limb (S70°E). To do so, we convert the strikes to an angular difference:
- S70°E = 70° (measured clockwise from the north, which is equivalent to 180° + 70° = 250° from the north)
- N55°E = 55° from the north.
The difference between these two angles is:
\[ 250° - 55° = 195° \] The interlimb angle is then the acute angle formed between the two limbs, which is: \[ 180° - 195° = 55° \]
Step 3: Conclusion.
Therefore, the value of the interlimb angle is 55°.