Earthquakes and Ground Motions - Earthquake Engineering for Structural Design - page 252

7.5.2 Main Characteristics of Near-source Ground Motions

The near-source earthquakes have some very specific features, which preserve the
characteristics of the source, due to the short source-site distance.
Rupture directivity. Figure 7.29 shows the effects of the rupture directivity for
the 1999 Chi-Chi earthquake, which is the result of slipping of a thrust fault. One
can see that the fault normal velocities of ground motions are larger than the

Parallel velocities Normal velocities

Figure 7.29 Velocity time histories of maximum velocity direction for the Chi-Chi
(Taiwan) earthquake (after Huang and Chen, 2000)