GATE Geology and Geophysics Practice Quiz

Question 1

In a normal fault, if slickenside lineations indicate pure dip-slip movement on a plane dipping 60°, which principal stress axis is most likely vertical during faulting?

Accepted Answer

σ1 vertical

Question 2

A reverse fault shows clear dip-slip striations. Under Anderson's theory, which principal stress axis is expected to be vertical?

Accepted Answer

σ3 vertical

Question 3

For an optimally oriented Coulomb shear fault in an isotropic rock with friction coefficient μ = tanφ, the angle between σ1 and the fault plane is approximately:

Accepted Answer

45° - φ/2

Question 4

A fault-slip inversion yields principal stress orientations reliably, but the absolute magnitudes of σ1, σ2, and σ3 remain unknown. The main reason is that most inversion methods use:

Accepted Answer

Only orientations and slip directions, giving a reduced stress tensor

Question 5

A conjugate set of shear fractures forms symmetrically about the maximum compressive stress direction. If the acute bisector between the two sets is known, it most nearly indicates the orientation of:

Accepted Answer

σ1