Solution Exercise 1
a) The labeled blue lines are shown below.
b) Closure/compaction would lead to pressure solution seams and shearing mode fractures; opening mode would lead to joints, and shearing mode would lead to shear fractures or faults.
c) The difference in the displacement of adjacent points on the two faces of a fracture defines the displacement discontinuity, which is related to the kinematics of the movement. Thus, by analyzing the fractures one can define not only their formation but also their behavior through time. Following S.L. Crouch (1976), displacements along each fracture face may be assumed to be positive in the positive coordinate directions. Then, displacement discontinuity normal to the fracture Dn = 𝑈y+ − 𝑈y− defines an opening if positive and a closing if negative. Displacement discontinuity parallel to the fracture Ds = 𝑈x+ − 𝑈x− denotes shear displacement discontinuity.