Spatial correlation of ground motions in estimating seismic hazards to civil infrastructure - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 64

within-earthquake component, and Morikawa et al. (2008) obtained almost
similar values for between-earthquake and within-earthquake standard
deviations after the correction. Thus, the between-earthquake correlation
ρ η may vary, at a minimum, between 0.06 (Bommer et al. , 2003) and 0.5
(Morikawa et al. , 2008). The correlation coeffi cient is a relative quantity, so
the variation of ρ η is important, and equally the variation of the total stan-

dard deviation is important also.
The within-earthquake correlation should be evaluated for a given area
empirically. A dense observation of records from numerous earthquakes is
necessary for modelling the within-earthquake correlation structure; there-
fore the correlation structure has not been extensively investigated for
conventional ground-motion attenuation equations mentioned above.
Boore et al. (2003), Hok and Wald (2003) and Lin et al. (2006) considered
one or few particular earthquakes in California; Wang and Takada (2005)
analyzed separately a few earthquakes in Japan and the Chi-Chi earthquake
in Taiwan. Kawakami and Mogi (2003) used records from several earth-
quakes in Japan (the Chiba array 30 km east of Tokyo; SIGNAL array in
Tokyo), and Taiwan (SMART-1 array). Evans and Baker (2006) used the
NGA database (Power et al. , 2008), which is primarily based on the Cali-
fornian data and a few earthquakes in Taiwan (the Chi-Chi earthquake and
large aftershocks). Goda and Hong (2008a) and Jayaram and Baker (2009)
considered the Chi-Chi earthquake and some Californian earthquakes, and
Hong et al. (2009) analyzed Californian data only. More recently, Goda and
Atkinson (2009, 2010) used a large database collected in Japan (records
from the K-NET and KiK-net strong-motion networks) to study spatial
correlation for peak ground acceleration and pseudo-spectral acceleration
at different periods from 0.1 to 5.0 s. Sokolov et al. (2010, 2012) analyzed
characteristics of ground motion correlation using the database accumu-
lated in Taiwan. The European Strong-Motion database (ESD) and the
Italian Accelerometric Archive (ITACA) were used by Esposito and Iervo-
lino (2011) for evaluation of the spatial correlation of PGA and peak
ground velocity (PGV) residuals. Goda (2011) estimated event-specifi c
(inter-event) variability of spatial correlation (peak ground motions and
response spectra) using the consolidated ground-motion database consist-
ing of 41 well-recorded earthquakes (occurred mostly in Japan).
The results reported by these research works reveal a different rate of
decay of the within-earthquake correlation with separation distance. Table
3.1 summarizes the data used and the obtained results of some of the
studies. Among the possible reasons of the difference, it is possible to
mention different ground-motion prediction models, as well as different
ground motion parameters, that were used for the analysis. Figure 3.2a
compares within-earthquake correlation functions estimated for the 1999
Chi-Chi (Taiwan) earthquake in three research works. The ground-motion