Validation of One Predominant Frequency Presence in Seismic Ground Displacement by Means of Deformation Response Spectra

Abstract

There are very few results in the literature on spectral content of seismic ground displacement; nonetheless, these results are singular as most of the spectral content is limited to a very narrow low frequency band, contrary to ground acceleration. These few spectral characterizations have been obtained, expectedly, by means of power spectral or Fourier analyses of ground displacement records, only. As these records are not as reliable as ground acceleration records, the existence of a clear predominant frequency in ground displacement warrants confirmation through a different procedure. We propose a corroboration method of this highly narrow-band characteristic that is based on the more dependable acceleration signal, rather than on the same ground displacement record that is the subject of study. Specifically, displacement response spectra are analyzed (which rely on acceleration records) to verify previously observed neat predominant frequencies in ground displacement, which is a novelty.

Predominant Frequency in Near-Field Strong Ground Motion by Analysis of Displacement Response Spectra

“…Indeed, in the middle of Table 1, which is in chr order, we have the Chi Chi and Hector M. events which were recorded digitall inantly [9]. In fact, the low-cut frequency reached 0.02 Hz for Hector M. seism [10]. Moreover, for the later (in Table 1) Latin American events, including Sierr the cutoff frequency was around 0.03 Hz [6].…”

“…The hypothesis of this research is that clear resonant frequencies will be observed because neat predominant frequencies exist in Fourier or power spectra of ground displacement [5,6]. A theoretical basis for this, based on a generalized transmissibility concept, has been given by Morales recently (2023) [10]. Therefore, deformation response spectrum plots will be constructed, and an evident and clean predominant frequency will be observed, as shown in Figure 1, where peak response displacement (PRD) is plotted against natural frequency (instead of natural period, which is the other option).…”

“…Consequently, the spectral results based on ground displacement PSD [5,6] required validation or confirmation by a more reliable method [10]. One such proposal or methodology is to consider displacement response spectra, which are based on the more physical and dependable ground acceleration record [10].…”

“…Consequently, the spectral results based on ground displacement PSD [5,6] required validation or confirmation by a more reliable method [10]. One such proposal or methodology is to consider displacement response spectra, which are based on the more physical and dependable ground acceleration record [10]. Nevertheless, in this last reference, there is no attempt to define a predominant period in seismic ground motion, which is the main objective of this work.…”

“…Nevertheless, in this last reference, there is no attempt to define a predominant period in seismic ground motion, which is the main objective of this work. For this endeavor, or to increase the possibility of positive statistical results, the set of strong-motion records will be limited to near-field signals, which was not the case in the previous work as the objective was to corroborate the predominant frequencies observed when computing PSD of diverse ground displacement records [10].…”