Challenges for the Next Generation of Seismic Codes - Earthquake Engineering for Structural Design - page 492

in the future research works. There are some specialists who attributed part of
damage produced during the Northridge and Kobe earthquakes to the effect of the
vertical asynchrony of ground motions.
From the recorded ground motions in near-source areas, it is recognized that
the vertical ground motions are much larger than the horizontal ones. Therefore,
the vertical seismic component is a dominant parameter (in combination with the
horizontal motions) in the various near-source field regions, mainly due to
earthquakes caused by thrust (subduction) faults. As the vertical components of
ground motions are often neglected in the seismic design of structures, most
damage occurred in the near-source areas due to these vertical seismic components,
especially in new buildings, which were designed respecting the modern code
provisions for horizontal components.
Figure 10.16 Asynchrony of vertical movements (Gioncu et al, 2000).