Consideration on uncertainty (variance)

Establishment of design response spectra

Formulation of Design Basis

Earthquake Ground Motion Ss

f Comparison of impacts to facilities y

< Composite wave~|

reference I

( [Exceedance probability specific spectrum

Design basis earthquake ground motion Ss by the method with response spectra

Design basis earthquake ground motion Ss by the method with fault models

Figure 9.5.1 Formulation flow chart of design basis earthquake ground motion Ss ote£g)

3. Formulation of DBEGM Ss

All of the response spectra obtained for each of the earthquakes for investigation by the method “evaluation of earthquake ground motions with response spectra” are enveloped to establish the “Design Response Spectra” and considering the characteristics of earthquake ground motion, such as the durations, time-dependent changes of the amplitude-enveloping curves and others, an artificial earthquake wave is formulated as the DBEGM Ss.

By the method “evaluation of earthquake ground motions by the method with fault models”, an earthquake wave time history can be obtained directly, so it is formulated as the DBEGM Ss.

ii) DBEGM Ss based on earthquake ground motions with no specific earthquake source locations

The earthquake ground motions with no specific earthquake source locations should be considered commonly in all application cases irrespective of the detailed investigation results from around the site, because even the detailed investigations with due

consideration to the geological conditions of the site area cannot fully evaluate in advance all probable inland earth’s crust earthquakes which could occur near the site.

In the formulation, the observation records near the hypocenter which are obtained from the past earthquakes inside the inland earth’s crust (where the correlation between the hypocenter and the active faults is difficult to specify) should be collected, and the response spectra should be defined based on those records for hard ground (rock) by taking into account the ground material characteristics of the site. And considering the characteristics of earthquake ground motion, such as its duration, time-dependent change of the amplitude-enveloping curves and others, an artificial earthquake wave is formulated as DBEGM Ss..

The response spectra mentioned above should be established corresponding to the S wave velocity of the ground, based on the report of Kato et al. ^(RetS). Figure 9.5.3 shows horizontal response spectra for each S wave velocity.

It should be noted, however, that when the above

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NSRA, Japan