Question

The attitude of a fault plane was measured to be 350°, 75°E. The rake of the slickenline on the fault plane was found to be 90°. Which of the faults listed below satisfy(ies) these observations?

• A. Dip-slip fault
• B. Normal fault
• C. Reverse fault
• D. Strike-slip fault

Answer 1

The Correct Option is A, B, C

To determine which type of fault is described by the given parameters, we need to understand the measured geological terms and their implications:

• The attitude of a fault plane is given as 350°, 75°E, which describes the orientation of the fault plane. Here, 350° is the azimuth or the strike direction, which is measured clockwise from the north, and 75°E is the dip direction, indicating the angle at which the fault plane is inclined from the horizontal surface.
• The rake of the slickenline is found to be 90°. The rake is the angle measured on the fault plane between the horizontal line parallel to the strike and the line of movement (slickenline). A rake of 90° indicates that the movement is directly down the dip.

Based on these measurements, we need to determine the type of faulting:

1. Since the rake is 90°, it signifies vertical movement along the fault plane. This vertical movement indicates a dip-slip component, rather than strike-slip, where movement is horizontal.
2. A dip-slip fault can be classified further into:
   • Normal fault: Where the hanging wall moves down relative to the footwall. This occurs under extensional stress.
   • Reverse fault: Where the hanging wall moves up relative to the footwall. This occurs under compressional stress.
3. Since both normal and reverse faults involve movement along the dip with a rake of 90°, they satisfy the given observations. However, strike-slip faults, involving horizontal movement with a low rake angle, do not match the given parameters.

Thus, the correct types of faults that satisfy the observations are:

• Dip-slip fault
• Normal fault
• Reverse fault