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| Titel |
On the Relationship between Fourier and Response Spectra: Implications for the Adjustment of Empirical Ground-Motion Prediction Equations (GMPEs) |
| VerfasserIn |
Sanjay Bora, Frank Scherbaum, Nicolas Kuehn, Peter Stafford |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250134006
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| Publikation (Nr.) |
 EGU/EGU2016-14679.pdf |
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| Zusammenfassung |
| Often, scaling of response spectral amplitudes, (e.g., spectral acceleration) obtained from
empirical ground motion prediction equations (GMPEs), with respect to commonly
used seismological parameters such as magnitude, distance and site condition is
assumed/referred to be representing a similar scaling of Fourier spectral amplitudes. For
instance, the distance scaling of response spectral amplitudes is related with the
geometrical spreading of seismic waves. Such comparison of scaling of response spectral
amplitudes with that of corresponding Fourier spectral amplitudes is motivated by
that, the functional forms of response spectral GMPEs are often derived using the
concepts borrowed from Fourier spectral modeling of ground motion. As these
GMPEs are subsequently calibrated with empirical observations, this may not appear
to pose any major problems in the prediction of ground motion for a particular
earthquake scenario. However, the assumption that the Fourier spectral concepts persist
for response spectra can lead to undesirable consequences when it comes to the
adjustment of response spectral GMPEs to represent conditions not covered in the
original empirical data set. In this context, a couple of important questions arise,
e.g., what are the distinctions and/or similarities between Fourier and response
spectra of ground-motions? And, if they are different, then what is the mechanism
responsible for such differences and how do adjustments that are made to FAS
manifest in response spectra? We explore the relationship between the Fourier and
response spectrum of ground motion by using random vibration theory (RVT). With a
simple Brune (1970, 1971) source model, RVT-generated acceleration spectra for a
fixed magnitude and distance scenario are used. The RVT analyses reveal that the
scaling of low oscillator-frequency response spectral ordinates can be treated as
being equivalent to the scaling of the corresponding Fourier spectral ordinates.
However, the high oscillator-frequency response spectral ordinates are controlled by a
rather wide-band of Fourier spectral ordinates. In fact, the peak ground acceleration
(PGA), counter to the popular perception that it is a reflection of the high-frequency
characteristics of ground motion, is controlled by the entire Fourier spectrum of
ground-motion. Finally, it is demonstrated, how an adjustment made in Fourier
spectral amplitudes is different or similar to the same adjustment made in the response
spectral amplitudes. For this purpose, two cases: adjustments to the stress parameter
(Δσ) (source term) and to attributes reflecting site response (V s-κ0) are considered. |
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