Seismic Ground Motion - Dynamic Behavior of Concrete and Seismic Engineering - page 115

effect by means of lateral interferences of the diffracted waves on all the surface
irregularities;
- qualitatively, the situation is rather confused. Besides a few well documented
cases for which the in situ instrument observations reveal moderate amplifications
(crest/base spectral amplification between 2 and 3), in good accordance with the
numerical modeling, in many cases the observed amplifications are far more
important than the theoretical previsions obtained from sometimes sophisticated
models, which are either two- or three-dimensional. Thus, an important proportion
of the instrumented sites showed spectral amplifications around 10, whereas this
value was reached by only two simulations, and these resorted to other effects rather
than geometry alone (e.g. mechanical contrast).
Figure 3.4. Example of topographic amplification in the village of Castillon (maritime Alps),
severely damaged during the 1887 Ligure earthquake. The instrument transfer functions
(on top) show the amplification on the “summit” site compared with the
“Mercier” site (from [NEC 95])