Characteristics of Vertical Ground Motions Recorded During the Lorna Prieta Earthquake

A study of a limited number of vertical ground motion acceleration-time histories recorded during the Loma Prieta earthquake of October 17, 1989 has been made. It has been found that maximum vertical ground motions may be greater than the horizontal ground motions in the near vicinity of the fault rupture zone. The limited records suggest that there is more spectral energy at very short structural periods in the vertical ground motions as compared with the horizontal ground motions. At longer periods, the vertical energy is significantly less, however, there is an increasing trend for very long structural periods