Z. I. AL-BESHER
Open Access
The spectra obtained by this way are known as pseudo-spec-
tra and is the cause of nomenclature PSA and PSV. An advan-
tage offered by pseudo spectra is that the calculation of SD is
the simplest and least time-consuming of the three spectra;
hence “Equations (13) and (14)” are a convenient way to esti-
mate the spectral velocity and acceleration. The response spec-
tra are calculated for three selected damping values of 0.03,
0.05 and 0.1 of the critical damping, which are chosen to be
relevant to various structural characteristics. Figure 7 repre-
sents the response spectra of Pseudo-spectral Acceleration at
10-km distance from Tabuk source zone.
Figure 7.
Response spectra for pseudo-spectral acceler ation at 10-km di s-
tance from Tabuk source zone.
Conclusion
The current study trials simulate high frequency ground-mo-
tion produced by the damaging earthquakes at the northwestern
part of Saudi Arabia. This is an area where no recording system
is installed for measuring such motion. The stochastic simula-
tion method was applied to estimate the maximum ground-
motion number of the selected points through Tabuk City. The
calculated ground motions are represented by PGA. In addition,
the Pseudo-Spectral Acceleration (PSA) was calculated as well
at these sites for simulation. An effective source in the area is
the Tabuk source zone, which is located to the northeast of
Tabuk City. The maximum moment magnitude of Mw = 7.5 ha s
been obtained from this zone, explains higher values of PGA
and PSA through the Tabuk City.
It is concluded that, the maximum Peak Ground Acceleration
was found to be 218 cm/sec2 (gal) at the bedrock while, the
response spectrum, which reflects the characteristics of earth-
quake and the nature of the recording site, is calculated at vari-
ous damping ratios (0.03, 0.05 and 0.1) of the critical damping.
The estimated values from present study have been compared
with those of the Global Seismic Hazard Assessment Program
(GSHAP, Grϋnthal et al., 1999) and Al-Haddad et al. (1994).
The estimated values of PGA in in maps of GSHAP and Al-
Haddad et al. (1994) are in good agreement with the results of
the present study.
The estimated PGA could contribute significantly to the de-
termination of the national seismic codes. These results could
be a tool for engineers, decision-makers and planners to miti-
gate the earthquake effects and allow them to plan earthquake
resistant design through Tabuk City.
Acknowledgements
The author is extremely grateful to the Research Center, col-
lege of Science, King Saud University for supporting this pro-
ject.
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