| Abstract: | We present a study of the motion of the ground in the near field of a preexisting vertical crack driven by excess tensile stress. Using the discrete wave number method, we make a complete representation of the three components of ground displacement resulting from a small incremental extension of the bottom tip of the crack and analyze the effects of the medium structure on the ground response. The results show the strong impulsive character of the dynamic motion near the source and demonstrate that the first motion is directed everywhere outward. Marked oscillations are observed in the ground response associated with the ringing of the crack faces triggered by the rupture. The displacement is dominantly vertical near the epicenter but becomes predominantly horizontal beyond the immediate source region. The presence of layers has a strong effect on the complexity and duration of the ground response. The static vertical and longitudinal displacements are respectively downward and inward in the epicentral area. |
