Site effect evaluation using spectral ratios with only one station

1993 ◽  
Vol 83 (5) ◽  
pp. 1574-1594
Author(s):  
Javier Lermo ◽  
Francisco J. Chávez-García
Keyword(s):  
Transfer Function ◽  
Rayleigh Waves ◽  
Site Effects ◽  
Spectral Ratio ◽  
Site Effect ◽  
Reference Station ◽  
Effect Evaluation ◽  
Spectral Ratios ◽  
S Wave ◽  
Dominant Period

Abstract The spectral ratio technique is a common useful way to estimate empirical transfer function to evaluates site effects in regions of moderate to high seismicity. The purpose of this paper is to show that it is possible to estimate empirical transfer function using spectral ratios between horizontal and vertical components of motion without a reference station. The technique, originally proposed by Nakamura to analyze Rayleigh waves in the microtremor records, is presented briefly and it is discussed why it may be applicable to study the intense S-wave part in earthquake records. Results are presented for three different cities in Mexico: Oaxaca, Oax., Acapulco, Gro., and Mexico City. These cities are very different by their geological and tectonic contexts and also by the very different epicentral distances to the main seismogenic zones affecting each city. Each time we compare the results of Nakamura's technique with standard spectral ratios. In all three cases the results are very encouraging. We conclude that, if site effects are caused by simple geology, a first estimate of dominant period and local amplification level can be obtained using records of only one station.

scholarly journals Reference stations for Christchurch

2012 ◽  
Vol 45 (4) ◽  
pp. 184-195 ◽  
Author(s):  
C. Van Houtte ◽  
O.-J. Ktenidou ◽  
T. Larkin ◽  
A. Kaiser
Keyword(s):  
Reference Site ◽  
Spectral Ratio ◽  
Site Effect ◽  
Reference Station ◽  
Topographic Effects ◽  
S Wave ◽  
Rock Outcrop ◽  
Soft Soils ◽  
Seismic Stations ◽  
Hvsr Method

During the Canterbury earthquake sequence, the observed level of ground motion on the soft soils of Christchurch was very strong and highly variable. Many studies are now emerging that analyse the amplification effect of these soft soils, usually by estimating a frequency-dependent amplification function relative to a rock outcrop station, or ‘reference site’. If the rock outcrop has its own amplification due to weathering or topographic effects, then the calculated amplification for the soil sites can be compromised. This study examines ten seismic stations in Canterbury to determine the best reference site for Christchurch, using the horizontal-to-vertical spectral ratio (HVSR) method for S-wave shaking. More broadly, this study uses HVSR to expand existing knowledge of the dynamic characteristics of seismic stations in the Canterbury area. Most rock stations show their own local amplification effects that reduce their individual ability to be used as reference stations. The recently installed Huntsbury station (HUNS) appears to be the best reference site for Christchurch, but this will need to be verified when more records become available. In the meantime, the D13C temporary station is currently the best reference station for site effect studies in both Christchurch and Lyttelton.

scholarly journals Seismological constraints on ice properties at Dome C, Antarctica, from horizontal to vertical spectral ratios

2010 ◽  
Vol 22 (5) ◽  
pp. 572-579 ◽  
Author(s):  
Jean-Jacques Lévêque ◽  
Alessia Maggi ◽  
Annie Souriau
Keyword(s):  
Wave Velocity ◽  
Spectral Ratio ◽  
Seismic Signal ◽  
Main Peak ◽  
Spectral Ratios ◽  
S Wave ◽  
Soil Response ◽  
Ice Cap ◽  
Antarctic Continent ◽  
The Antarctic

AbstractThe French-Italian Concordia (CCD) seismological station at Dome C is one of two observatories setup on the ice cap in the interior of the Antarctic continent. We analysed the seismic signal due to ambient noise at this station and at three temporary stations 5 km away from Concordia, in order to specify the ice properties beneath them. A method based on the horizontal to vertical (H/V) spectral ratio, commonly used to analyse soil response in seismic regions, was applied to the Antarctic stations. The main peak in the spectral ratios is observed at frequencies 6.7–8 Hz at the Dome C stations, but it is not observed at another station on the ice cap, QSPA, where the sensor is buried at 275 m depth. This peak can be explained by a 23 m thick unconsolidated snow or firn layer with a low S-wave velocity of 0.7 km s-1, overlying a consolidated layer with S-wave velocity 1.8 km s-1. Despite the non-uniqueness of the solutions obtained by fitting the H/V spectra, this model is preferred because the depth of the velocity contrast coincides with the density at which ice particles arrange themselves in a continuous, dense lattice. A small variability of this structure is observed around Dome C.

scholarly journals The horizontal-to-vertical spectral ratio and its applications

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Rong Xu ◽  
Lanmin Wang
Keyword(s):  
Shear Wave ◽  
Velocity Structure ◽  
Site Response ◽  
Mineral Exploration ◽  
Spectral Ratio ◽  
Site Effect ◽  
Research Area ◽  
Site Classification ◽  
S Wave ◽  
Borehole Data

AbstractThe horizontal-to-vertical spectral ratio (HVSR) has been extensively used in site characterization utilizing recordings from microtremor and earthquake in recent years. This method is proposed based on ground pulsation, and then it has been applied to both S-wave and ambient noise, accordingly, in practical application also different. The main applications of HVSR are site classification, site effect study, mineral exploration, and acquisition of underground average shear-wave velocity structure. In site response estimates, the use of microtremors has been introduced long ago in Japan, while it has long been very controversial in this research area, as there are several studies reporting difficulties in recognizing the source effects from the pure site effects in noise recordings, as well as discrepancies between noise and earthquake recordings. In practice, the most reliable way is the borehole data, and the theoretical site response results were compared with the HVSR using shear wave to describe site response. This paper summarizes the applications of the HVSR method and draws conclusions that HVSR has been well applied in many fields at present, and it is expected to have a wider application in more fields according to its advantages.

EVALUATION OF S-WAVE AMPLIFICATION SPECTRUM USING MICROTREMORS

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
Hayato Nishikawa ◽  
Tomiya Takatani
Keyword(s):  
Site Effects ◽  
Estimation Method ◽  
Ground Surface ◽  
Spectral Ratio ◽  
S Wave ◽  
Wave Amplification ◽  
Measurement Results ◽  
Microtremor Measurement ◽  
Microtremor Measurements ◽  
Amplification Spectrum

To evaluate the site effects above the engineering base rock with an S-wave velocity of 300m/s, microtremor measurements on the ground surface were conducted in Maizuru, Japan. An estimation method of S-wave amplification spectrum using the microtremor H/V spectral ratio was applied at the ground surface, estimating S-wave amplification spectrum without any ground information based on the microtremor measurement results. It was found that the evaluation of S-wave amplification spectrum needs a revision on the microtremor H/V spectral ratio, using some coefficients on the microtopography classification and the shape of the microtremor H/V spectral ratio.

A Robust Method for Assessing 3-D Topographic Site Effects: A Case Study at the LSBB Underground Laboratory, France

2012 ◽  
Vol 28 (3) ◽  
pp. 1097-1115 ◽  
Author(s):  
Emeline Maufroy ◽  
Víctor M. Cruz-Atienza ◽  
Stéphane Gaffet
Keyword(s):  
Site Effects ◽  
Amplification Factor ◽  
Three Dimensional ◽  
Reference Method ◽  
Spectral Ratio ◽  
Site Effect ◽  
Point Sources ◽  
Ratio Method ◽  
Double Couple

By means of three-dimensional (3-D) numerical simulations, including the Laboratoire Souterrain à Bas-Bruit (LSBB) topography, we carefully analyze site effects assessments yielded by two approaches: the classical site to reference spectral-ratio method (SRM) and the statistical median reference method (MRM). We show for both isotropic and double-couple point sources that a 94% reduction in the number of stations of a regularly spaced array yields MRM site-effect estimates within 5% of those obtained from the absolute regional median, and within 20% using a 98% station reduction with irregularly located sites. In contrast, the SRM yielded site-effect overestimates greater than 50% in some areas and up to 100% in specific sites, which makes the MRM much more robust than the SRM. We determined a 33% probability to exceed an amplification factor of 2, and an 8% probability to exceed a factor of 3 due to topography in the surroundings of the sharpest summit of the LSBB area.

Investigation of Relationship between the Response and Fourier Spectral Ratios Based on Statistical Analyses of Strong-Motion Records

2020 ◽  
pp. 2150008
Author(s):  
Haizhong Zhang ◽  
Yan-Gang Zhao
Keyword(s):  
Seismic Design ◽  
Site Effects ◽  
Epicentral Distance ◽  
Ground Motions ◽  
Scaling Law ◽  
Ground Surface ◽  
Strong Motion ◽  
Spectral Ratio ◽  
Spectral Ratios ◽  
Earthquake Scenario

In both seismic design and probabilistic seismic-hazard analyses, site effects are typically characterized as the ratio of the response spectral ordinate on the ground surface to that on the bedrock based on the scaling law borrowed from the Fourier spectral ordinate. Recent studies have shown that different from the Fourier spectral ratio (FSR), the response spectral ratio (RSR) does not purely reflect the site effects but also depends on the earthquake scenario even for linear analysis. However, previous studies are limited to theoretical analysis. This study statistically compares the two spectral ratios by analyzing many actual seismic ground motions recorded at nearby soil and rock sites. It is observed that the average RSR and FSR have similar overall shapes, and their maximum values occur at approximately the same period; however, the values around the peak are clearly different with FSRs consistently exceeding the RSRs. The RSR–FSR relationship depends on the earthquake scenario and the oscillator damping; their difference at periods longer than the site’s fundamental period decreases as the magnitude and epicentral distance increase, and the RSRs generally approach the FSRs as the oscillator damping decreases.

scholarly journals Site Effect Potential in Fond Parisien, in the East of Port-au-Prince, Haiti

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 175
Author(s):  
Sophia Ulysse ◽  
Dominique Boisson ◽  
Valmy Dorival ◽  
Kelly Guerrier ◽  
Claude Préptit ◽  
...  
Keyword(s):  
Site Effects ◽  
Geophysical Methods ◽  
Spectral Ratio ◽  
Site Effect ◽  
Seismic Properties ◽  
Fine Sediments ◽  
The North ◽  
Seismic Motion ◽  
Sediment Deposits ◽  
Hvsr Technique

In the frame of a Belgo-Haitian cooperation project (PIC 2012–2016), a study of the local seismic hazard was performed in Fond Parisien, an area located on the foothills of the “Massif de la Selle”, along the easternmost portion of the Enriquillo Plantain Garden Fault (EPGF). The H/V Spectral Ratio (HVSR) technique was applied to study the resonance frequency of the target areas and the azimuth of the wave field. The amplification factors were estimated using Standard Spectral Ratios obtained from earthquakes recorded by a temporary seismic network. Using the Multichannel Analysis of Surface Waves method, the seismic properties of the shallow layers were investigated. Then, the results were compared to local Electrical Resistivity Tomography data. These results highlight, in the central part of Fond Parisien, an E-W zone of low velocities ranging from 200 m/s to 450 m/s and low resistivities between 1 Ωm and 150 Ωm, due both to tectonic folding of the rocks and to the presence of sediment filling in the eastern part. The latter is marked, in most of its sites, by resonances at one or more frequencies ranging from 0.7 Hz to 20 Hz. Infiltration and storage of brackish water in the underground layers also contribute to the low resistivity values. With the noise HVSR data, we also evidenced a significant influence of the EPGF on the main orientation of the seismic wavefield as in the vicinity of this fault, the azimuths are parallel to the orientation of the fault. Overall, the results also show greater potential for site effects in the block formed by the sedimentary basin and strong amplification of the seismic ground motion for the sites bordering the basin to the north and west. We interpret the amplification in the north and south-west as probably originating from topographic irregularities locally coupled with sediment deposits, while in the center of the western part, the site effects could be explained by the presence of folds and related weakened and softened rocks. By the integration of several geophysical methods, we could distinguish areas where it is possible to build more safely. These zones are located in the northern part and encompass Quisqueya Park and neighboring areas as well as the village “La Source” in the southern part. In the rest of Fond Parisien, i.e., in the more central and eastern parts, buildings should be erected with caution, taking into account the nearby presence of the EPGF and the influence of fine sediments on the amplification of the seismic motion.

When 1D response analysis fails: application of Earthquake HVSR in Site-Specific Amplification Estimation

2020 ◽  
Author(s):  
Chuanbin Zhu ◽  
Marco Pilz ◽  
Fabrice Cotton
Keyword(s):  
Transfer Function ◽  
Resonant Frequency ◽  
Goodness Of Fit ◽  
Spectral Ratio ◽  
Spectral Shape ◽  
Response Analysis ◽  
Specific Information ◽  
S Wave ◽  
Site Specific ◽  
Empirical Correction

<p>Ground response analyses (GRA) model the vertical propagation of SH waves through flat-layered media (1DSH) and are widely carried out to evaluate local site effects in practice. Horizontal-to-vertical spectral ratio (HVSR) technique is a cost-effective approach to extract certain site-specific information, e.g., site resonant frequency, but HVSR values cannot be directly used to approximate the level of S-wave amplification. Motivated by the work of Kawase et al. (2019), we propose a procedure to correct earthquake HVSR amplitude for direct amplification estimation. The empirical correction, in essence, compensates HVSR by generic vertical amplifications grouped by vertical fundamental resonant frequency (f<sub>0v</sub>) and 30 m average shear-wave velocity (V<sub>S30</sub>) via k-mean clustering. In this investigation, we evaluate the effectiveness of the corrected HVSR in approximating observed amplification in comparison with 1DSH modelling. To the end, we select a total of 90 KiK-net surface-downhole recording sites which are found to have no velocity contrasts below downhole sensor and thus of which surface-to-borehole spectral ratio (SBSR) can be taken as its empirical transfer function (ETF). 1DSH-based theoretical transfer function (TFF) is computed in the linear domain considering the uncertainty in V<sub>S</sub> profile through randomization. Five goodness-of-fit metrics are adopted to gauge the closeness between observed (ETF) and predicted (i.e., TTF and corrected HVSR) amplifications in both amplitude and spectral shape. The major finding of this study is that the empirical correction procedure to HVSR is highly effective, and the corrected HVSR has a “good match” in both spectral shape (Pearson’s r > 0.6) and amplitude (Index of agreement d > 0.6) at 74% of the investigated sites, as opposed to 17% for 1DSH modelling. In addition, the HVSR-based empirical correction does not need a site model and thus has great potentials in site-specific seismic hazard assessments.</p>

Lateral propagation effects observed at Parkway, New Zealand. A case history to compare 1D versus 2D site effects

1999 ◽  
Vol 89 (3) ◽  
pp. 718-732 ◽  
Author(s):  
Francisco J. Chávez-García ◽  
William R. Stephenson ◽  
Miguel Rodríguez
Keyword(s):  
New Zealand ◽  
Site Effects ◽  
Reference Station ◽  
Spectral Ratios ◽  
Generalized Inversion ◽  
Propagating Waves ◽  
Vertical Ground ◽  
Frequency Domain Techniques ◽  
Lateral Heterogeneities ◽  
Lateral Propagation

Abstract The importance of 2D or 3D site effects has been shown by theoretical studies. However, there is a lack of observational evidence of site effects due to lateral heterogeneities. We have evaluated 1D and 2D site effects in the data obtained by a dense seismograph array that operated for more than 2 months in the alluvial basin of Parkway, New Zealand. 1D site effects were evaluated using three independent techniques: spectral ratios relative to a reference station, spectral ratios of horizontal relative to vertical ground motion, and a generalized inversion scheme. Site effects due to lateral heterogeneity were investigated in detail for two events using frequency-wavenumber analysis. Our results show that it is not possible to separate 1D from 2D site effects using frequency-domain techniques. This explains the scatter obtained from standard 1D data analysis: the 1D resonance peaks will be more or less contaminated with laterally propagating waves for different events.

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