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In addition, lateral variations of structure seem to be rather gentle at the many places
where measurements have been carried out.
Toendthissection,wecomebacktotheproblemofColima.H/Vspectralratiosofambi-
ent noise were not helpful to characterise site response in this city. For this reason, we
reoriented our study to go through properties of the subsoil and modelling of seismic
response. Ambient noise was recorded using linear arrays of stations. The recorded data
were analysed using both ReMi and SPAC methods. We observed a very good agree-
ment between the results obtained from these two methods (Figure 3.7). The resulting
phase velocity dispersion curves were inverted, and 1D profiles derived for eight sites
1000
a
800
600
400
200
0
5
10
15
20
25
Frequency [Hz]
1000
b
800
600
400
200
0
5
10
15
20
Frequency [Hz]
Fig. 3.7. Comparison between phase velocity dispersioncurves fromReMi
and SPAC methods at two sites inColima. The grey circles show the phase velocity
determined fromthe ReMi method. Open squares with error bars show the mean values
and thestandard errorsdetermined fromthe SPAC measurements. The solidline shows
the phase velocity dispersion curve computed fromthe S-wave velocity profile inverted
fromthe SPAC measurements
