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

2020 ◽  
Vol 110 (2) ◽  
pp. 427-440 ◽  
Author(s):  
Chuanbin Zhu ◽  
Fabrice Cotton ◽  
Marco Pilz
Keyword(s):  
Site Response ◽  
Response Spectrum ◽  
Amplitude Spectrum ◽  
Spectral Ratio ◽  
Peak Frequency ◽  
Fourier Amplitude ◽  
Resonant Frequencies ◽  
Overall Performance ◽  
Fourier Amplitude Spectrum ◽  
Hvsr Technique

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.

Site response analysis of liquefiable soil employing continuous wavelet transform

2022 ◽  
Vol 12 (1) ◽  
pp. 1-33
Author(s):  
D. Chavan ◽  
T.G. Sitharam ◽  
P. Anbazhagan
Keyword(s):  
Wavelet Transform ◽  
Site Response ◽  
Amplitude Spectrum ◽  
Ground Surface ◽  
Time History ◽  
Response Analysis ◽  
Fourier Amplitude ◽  
Acceleration Time ◽  
Liquefiable Soil ◽  
Fourier Amplitude Spectrum

Propagation of the earthquake motion towards the ground surface alters both the acceleration and frequency content of the motion. Acceleration time record and Fourier amplitude spectrum of the motion reveal changes in the acceleration and frequency content. However, Fourier amplitude spectrum fails to give frequency-time variation. Wavelet transform overcomes this difficulty. In the present study, site response analysis of a liquefiable soil domain has been investigated employing wavelet transform. Three earthquake motions with distinct predominant frequencies are considered. It is revealed that the moment soil undergoes initial liquefaction, it causes a spike in the acceleration time history. Frequency of the spikes is found to be greater than the predominant frequency of the acceleration-time history recorded at the ground surface from the analysis. Interestingly, the spikes belong to the sharp tips of the shear stress-shear strain curve. Immediately after the spike, acceleration deamplification is observed. Post-liquefaction deamplification (filtering) of the frequency components is also observed.

A statistical approach to account for azimuthal variability in single-station HVSR measurements

2020 ◽  
Vol 223 (2) ◽  
pp. 1040-1053
Author(s):  
Tianjian Cheng ◽  
Brady R Cox ◽  
Joseph P Vantassel ◽  
Lance Manuel
Keyword(s):  
Statistical Approach ◽  
Time Windows ◽  
Geometric Mean ◽  
Amplitude Spectrum ◽  
Spectral Ratio ◽  
Peak Frequency ◽  
Horizontal Component ◽  
Data Set ◽  
Single Station ◽  
Fourier Amplitude Spectrum

SUMMARY The horizontal-to-vertical spectral ratio (HVSR) of ambient noise is commonly used to infer a site's resonance frequency (${f_{0,site}}$). HVSR calculations are performed most commonly using the Fourier amplitude spectrum obtained from a single merged horizontal component (e.g. the geometric mean component) from a three-component sensor. However, the use of a single merged horizontal component implicitly relies on the assumptions of azimuthally isotropic seismic noise and 1-D surface and subsurface conditions. These assumptions may not be justified at many sites, leading to azimuthal variability in HVSR measurements that cannot be accounted for using a single merged component. This paper proposes a new statistical method to account for azimuthal variability in the peak frequency of HVSR curves (${f_{0,HVSR}}$). The method uses rotated horizontal components at evenly distributed azimuthal intervals to investigate and quantify azimuthal variability. To ensure unbiased statistics for ${f_{0,HVSR}}$ are obtained, a frequency-domain window-rejection algorithm is applied at each azimuth to automatically remove contaminated time windows in which the ${f_{0,HVSR}}$ values are statistical outliers relative to those obtained from the majority of windows at that azimuth. Then, a weighting scheme is used to account for different numbers of accepted time windows at each azimuth. The new method is applied to a data set of 114 HVSR measurements with significant azimuthal variability in ${f_{0,HVSR}}$, and is shown to reliably account for this variability. The methodology is also extended to the estimation of a complete lognormal-median HVSR curve that accounts for azimuthal variability. To encourage the adoption of this statistical approach to accounting for azimuthal variability in single-station HVSR measurements, the methods presented in this paper have been incorporated into hvsrpy, an open-source Python package for HVSR processing.

Near-Fault Baseline Correction Method and Appliction in Wenchuan Earthquake

2012 ◽  
Vol 166-169 ◽  
pp. 2517-2521
Author(s):  
Xiao Bo Peng ◽  
Xiao Jun Peng ◽  
Wei Lin Yang
Keyword(s):  
Wenchuan Earthquake ◽  
Response Spectrum ◽  
Amplitude Spectrum ◽  
Time History ◽  
Relative Displacement ◽  
Correction Method ◽  
Baseline Correction ◽  
Fourier Amplitude ◽  
Surface Rupture ◽  
Fourier Amplitude Spectrum

To eliminate the drifting in recordings from Ms8.0 Wenchuan earthquake, a modified two segments baseline correction method is brought up and systematic acceptance standard is presented. The method is applied to recordings from Qingping station and Bajiao station, which are closest stations to surface rupture traces. The effect of baseline correction on acceleration time history, Fourier amplitude spectrum and 5% damped relative displacement response spectrum is analyzed.

FAS-Compatible Synthetic Signals for Equivalent-Linear Site Response Analyses

2018 ◽  
Vol 34 (1) ◽  
pp. 377-396 ◽  
Author(s):  
Margarita Chi-Miranda ◽  
Luis A. Montejo
Keyword(s):  
Site Response ◽  
Response Spectrum ◽  
Amplitude Spectrum ◽  
Extreme Value Statistics ◽  
Current Time ◽  
Equivalent Linear ◽  
Inelastic Demand ◽  
Design Response Spectrum ◽  
The Time Domain ◽  
Fourier Amplitude Spectrum

An alternative approach to generate the seismic input for equivalent-linear (EQL) site response analyses is proposed. The proposed approach encompasses the strengths from current time histories (THs) and random vibration theory (RVT) methods. It consists of the generation of synthetic signals in the time domain (analogous to the TH method) that are constructed to have a Fourier amplitude spectrum (FAS) compatible with the design response spectrum (analogous to the RVT method). Through this approach, the use of extreme value statistics (used in RVT and known to overestimate amplification functions) is avoided. Moreover, the need to develop an appropriate suite of realistic acceleration series, which is the most challenging and time-consuming part of the TH-based approach, is also circumvented. The methodology is evaluated through a comprehensive analysis that includes different site conditions, input spectral shapes, duration scenarios, levels of inelastic demand, and number of synthetic signals used.

scholarly journals The Influence of Typography on Algorithms That Predict the Speed and Comfort of Reading

2020 ◽  
Author(s):  
Arnold Wilkins ◽  
Katie Smith ◽  
Olivier Penacchio
Keyword(s):  
Amplitude Spectrum ◽  
Visual Comfort ◽  
Fourier Amplitude ◽  
Font Design ◽  
Spatial Regularity ◽  
Line Separation ◽  
Fourier Amplitude Spectrum

The speed with which text can be read is determined in part by the spatial regularity and similarity of vertical letter strokes as assessed by the height of the first peak in the horizontal autocorrelation of the text. The height of this peak was determined for two passages in 20 fonts. The peak was unaffected by the size of the text or its content but was influenced by the font design. Sans serif fonts usually had a lower peak than serif fonts because the presence of serifs resulted in a more even spacing of letter strokes. There were small effects of justification and font- dependent effects of font expansion and compression. The visual comfort of images can be estimated from the extent to which the Fourier amplitude spectrum conforms to 1/f. Students were asked to adjust iBooks to obtain their preferred settings of font and layout. The preference was predicted by the extent to which the Fourier amplitude spectrum approximated 1/f, which in turn was jointly affected by the design of the font, its weight and the ratio of x-height to line separation. The above algorithms can be usefully applied to any orthography to estimate likely speed and comfort of reading.

scholarly journals Seismic Response of Anchor + Hinged Block Ecological Slope by Shaking Table Tests

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Hui Su ◽  
Yijun Hang ◽  
Yongsheng Song ◽  
Kunming Mao ◽  
Dongyue Wu ◽  
...  
Keyword(s):  
Natural Frequency ◽  
Amplitude Spectrum ◽  
Shaking Table ◽  
Engineering Practice ◽  
Shaking Table Tests ◽  
Fourier Amplitude ◽  
Earthquake Excitation ◽  
Ecological Requirements ◽  
Acceleration Amplification ◽  
Fourier Amplitude Spectrum

Landslides caused by earthquakes and other natural disasters may cause serious economic and personal losses. Slope protections are usually applied in engineering practice to prevent significant slope slides and damages. Based on the mechanical and ecological requirements on slope protections, this paper put forward a new type of anchor + hinged block ecological slope and carried out shaking table tests on it and other three traditional slope protections for comparing. By shaking table tests, the acceleration amplification factors and Fourier amplitude spectrums of four different slope types are analyzed and compared to verify the suitability of this new slope protection under earthquakes. The results indicated that the natural frequency and the acceleration Fourier amplitude spectrum of the four tested slope protections change according to internal materials. The anchor + hinged block ecological slope has higher natural frequency comparing to traditional slopes, so the resonance cycle from earthquake excitation can effectively be avoided and as a result the anchor + hinged block ecological slope can achieve better seismic performance.

On: “Statistical Models for Interpreting Aeromagnetic Data” by A. Spector and F. S. Grant (GEOPHYSICS, v. 35, p. 293–302)

Geophysics ◽  
1971 ◽  
Vol 36 (3) ◽  
pp. 617-617
Author(s):  
Gudmundur Gudmundsson
Keyword(s):  
Power Spectrum ◽  
Statistical Models ◽  
Amplitude Spectrum ◽  
Magnetic Anomalies ◽  
Aeromagnetic Data ◽  
Fourier Amplitude ◽  
Rectangular Block ◽  
Single Block ◽  
Fourier Amplitude Spectrum

In their paper “Statistical Models for Interpreting Aeromagnetic Data,” Spector and Grant define the “power spectrum” of the magnetic anomalies over a single rectangular block as the squared Fourier amplitude spectrum. For their expression of the “power spectrum” of a single block, Spector and Grant quote Bhattacharyya (GEOPHYSICS, v. 31, p. 97–121).

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