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at different stations, the differences of p curves in long period part above 4s is small and the
attenuate rate is almost same. It shows that the long period component of seismic ground motion
are almost same at same category of site with same epicentral distance in an earthquake and it is
almost not influenced by the small differences between the local site conditions of various
stations and other random factors.
TABLE 2
EARTHQUAKE DATA
No.
1
2
3
4
5
6
7
8
Date of earthquake
81.01.29
82.12.27
83.05.10
83.06.24
86.01.16
86.05.20
86.07.30
86.11.14
Magnitude
6.9
6.9
6.3
7.2
6.5
6.9
6.2
7.0
Epicentral
distance ( km )
31
118
35
116
22
36
6
79
Period (Second)
Figure 11: Dynamic magnification coefficient ft of the
accelerograms recorded at different stations in No.4
earthquake (damping ratio is 0,05)
Figure 12: Dynamic magnification coefficient /3 of the
accelerograms recorded at different stations in No.8
earthquake (damping ratio is 0.05)
2.3.3 Response spectral characteristics of accelerograms recorded at a station
Figures 13 and 14 show the /3 curves of accelerograms recorded in 8 events at Station COO and
1-03, respectively (damping ratio is 0.05 ), the magnitudes of these 8 earthquakes are all above 6,
and the epicentral distances are very different from 6km to 118km. It can be seen that the periods
corresponding to the peaks of response spectra are quite different, and the/3 values in long
period part of No.8 earthquake (dashed line in Figures 13 and 14) is much larger than that of any
other earthquakes.