Detecting Site Resonant Frequency Using HVSR: Fourier versus Response Spectrum and the First versus the Highest Peak Frequency

Abstract

In this investigation, we examine the uncertainties using the horizontal-to-vertical spectral ratio (HVSR) technique on earthquake recordings to detect site resonant frequencies at 207 KiK-net sites. Our results show that the scenario dependence of response (pseudospectral acceleration) spectral ratio could bias the estimates of resonant frequencies for sites having multiple significant peaks with comparable amplitudes. Thus, the Fourier amplitude spectrum (FAS) should be preferred in computing HVSR. For more than 80% of the investigated sites, the first peak (in the frequency domain) on the average HVSR curve over multiple sites coincides with the highest peak. However, for sites with multiple peaks, the highest peak frequency (fp) is less susceptible to the selection criteria of significant peaks and the extent of smoothing to spectrum than the first peak frequency (f0). Meanwhile, in comparison to the surface-to-borehole spectral ratio, f0 tends to underestimate the predominant frequency (at which the largest amplification occurs) more than fp. In addition, in terms of characterizing linear site response, fp shows a better overall performance than f0. Based on these findings, we thus recommend that seismic network operators provide fp on the average HVSRFAS curve as a priority, ideally together with the average HVSRFAS curve in site characterization.

Using horizontal-to-vertical spectral ratios to construct shear-wave velocity profiles

“…Conventional H/V curves are computed based on Fourier amplitude spectra (FAS; e.g. SESAME Project, 2004) or response spectra (Zhu et al, 2020). Here, we estimate H/V curves from PSDs.…”

“…No smoothing is applied since smoothing will affect the picking of the exact fundamental resonance peak. For sites with multiple significant peaks, smoothing could result in a shift to higher frequencies and a bias in identification of the fundamental resonance peak (Zhu et al, 2020). Albarello and Lunedei (2013) present several alternative procedures to average the horizontal components for computing ambient noise H/V ratios and conclude that vector summation is the most physically logic averaging method; therefore, this averaging procedure has been applied to the two horizontal-component PSDs.…”

“…Based on the knowledge of the fundamental resonance frequency and layer thickness, one can determine constraints on the shear-wave velocity structure (Arai and Tokimatsu, 2004;Fäh et al, 2003;Parolai et al, 2002;Scherbaum et al, 2003;Tsai and Housner, 1970). Zhu et al (2020) presented an overview of the uncertainties of using Fourier amplitude spectra or response spectra and the identification of the fundamental resonance frequency. H/V spectral ratios can be calculated from seismic events, teleseismic phases or from the ambient seismic noise field.…”

“…In this paper, we apply the H/V methodology to estimate average shear-wave velocities of the soft Cenozoic sedimentary cover in Groningen, called the NSG, down to depths around 800 to 1000 m. However, instead of calculating the H/V from amplitude spectra, as suggested by Zhu et al (2020), we demonstrate how we obtain stable H/V spectral ratios by first calculating power spectral density (PSD) curves (McNamara and Buland, 2004) from each component of the recorded data before we apply the H/V division. We start off with using teleseismic body-wave phases, for which the interpretation in terms of body-wave resonances is straightforward.…”

Using Horizontal to Vertical Spectral Ratios to construct shear-wave velocity profiles

“…Based on the knowledge of the fundamental resonance frequency and layer thickness, one can determine constraints on the shear-wave velocity structure (Arai and Tokimatsu, 2004;Fäh et al, 2003;Parolai et al, 2002;Scherbaum et al, 2003;Tsai and Housner, 1970). Zhu et al (2020) presented an overview of the uncertainties of using Fourier amplitude spectra or response spectra and the identification of the fundamental resonance frequency. However, instead of calculating the H/V from amplitude spectra, as suggested by Zhu et al (2020), we demonstrate how we obtain stable H/V spectral ratios by first calculating Power Spectral Density (PSD) curves (McNamara and Buland, 2004) from the recorded data before we make the H/V division.…”