Comparative Analysis of Two Methods for Instrumental Intensity Estimations using the Database Accumulated during Recent Large Earthquakes in Japan

2008 ◽  
Vol 24 (2) ◽  
pp. 513-532 ◽  
Author(s):  
Vladimir Sokolov ◽  
Takashi Furumura
Keyword(s):  
Amplitude Spectrum ◽  
Strong Motion ◽  
Seismic Intensity ◽  
Spectral Amplitude ◽  
Fourier Amplitude ◽  
Spectral Content ◽  
Narrow Frequency Band ◽  
Fourier Amplitude Spectrum ◽  
Instrumental Intensity ◽  
Large Earthquakes

A database containing records from nine large earthquakes in Japan, obtained by K-NET and KIK-net strong motion stations, was used for the analysis of two techniques for the estimation of instrumental seismic intensity from accelerograms. The first technique is the standard method for JMA intensity evaluation from filtered three-component accelerograms. The second technique is the so-called FAS-intensity, which was developed for MM and MSK scales and which is based on the correlation between levels of the Fourier Amplitude spectrum (FAS) and observed intensity. The relation between these two types of instrumental intensities ( JMAI and spectral MMI) may be described by linear function for intensities larger than JMAI 3.5–4 and MMI 5.0–5.5, but large discrepancy arises at small intensities. The variation is most probably caused by differences in the spectral content of the ground motions, since the JMAI calculation is sensitive to the spectral amplitude within a narrow frequency band around 0.5 Hz.

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.

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.

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).

On the Correlation of Seismic Intensity with Fourier Amplitude Spectra

1998 ◽  
Vol 14 (4) ◽  
pp. 679-694 ◽  
Author(s):  
V. Yu Sokolov ◽  
Yu K. Chernov
Keyword(s):  
Seismic Waves ◽  
Distribution Patterns ◽  
Seismic Intensity ◽  
Earthquake Ground Motion ◽  
Intensity Level ◽  
Fourier Amplitude ◽  
Ground Acceleration ◽  
Amplitude Spectra ◽  
Narrow Frequency Band ◽  
Recent Earthquakes

This paper presents a method for estimating the seismic intensity (MMI or MSK scale) using Fourier amplitude spectra of ground acceleration. The method implies that the severity of earthquake ground motion is determined by spectral amplitudes in a relatively narrow frequency band: so-called “representative frequencies”, at decreasing frequencies (from 7-8 Hz for small intensities to 0.7-1.0 Hz for MMI=VIII-IX) with increasing intensity level. It is examined through estimation of probable intensity at a site using recordings of recent earthquakes in several seismic regions, and prediction of intensity distribution patterns for the Coalinga, California earthquake of May 2, 1983, and the Spitak, Armenia earthquake of December 7, 1988. Seismic hazard maps, in terms of intensity levels based upon the proposed approach, should describe regional features of seismic waves excitation and propagation, as well as local ground conditions.

scholarly journals Bizarre Waveforms in Strong Motion Records

2015 ◽  
Vol 2015 ◽  
pp. 1-17
Author(s):  
Baofeng Zhou ◽  
Haiyun Wang ◽  
Lili Xie ◽  
Yanru Wang
Keyword(s):  
Response Spectrum ◽  
Amplitude Spectrum ◽  
Time History ◽  
Strong Motion ◽  
Ratio Method ◽  
Asymmetric Waveform ◽  
Baseline Drift ◽  
Strong Motion Records ◽  
Before And After ◽  
Fourier Amplitude Spectrum

This paper collects a rich set of strong motion records in some typical earthquakes domestic and abroad, checks its seismic events, converts the data format, corrects the zeroline and draws the waveform. Four kinds of abnormal phenomena on the acceleration waveform are revealed, such as spike, asymmetric waveform, obvious baseline drift, and strong motion records packets separation. Then reasonable processing approaches are derived from the preliminary analysis of the generation mechanism for abnormal phenomena. In addition to the effects on time history, Fourier amplitude spectrum and response spectrum are studied before and after strong motion records correction. It is shown that (1) mechanism of spikes is rather complicated; however spikes can be eliminated by “jerk” method, ratio method, and the consistency of the three-component PGA time; (2) mechanism of the asymmetric waveform is of diversity; however, to some extent, the Butterworth low-pass filtering can be applied to correct it; (3) two pieces of strong motion record packets can be connected by searching continuous and repeated data; (4) the method of cumulative adding can be used to find the clear baseline drift; (5) the abnormal waveform directly affects the characteristics of time history and frequency spectrum.

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