scholarly journals A STUDY OF MICROTREMOR HVSR IN THE RIO-ANTIRIO AREA, (GREECE)

2017 ◽  
Vol 50 (3) ◽  
pp. 1194
Author(s):  
M.E. Norda ◽  
A. Prapiga ◽  
P. Paraskevopoulos ◽  
G.A Tselentis
Keyword(s):  
Fundamental Frequency ◽  
Main Part ◽  
Ambient Noise ◽  
Spectral Ratio ◽  
Recording Time ◽  
Seismic Stations ◽  
Central Greece ◽  
Hvsr Method

Horizontal to Vertical Spectral Ratio (HVSR) method has been applied on ambient noise records at the Rio- Antirio area (central Greece). The dataset used was recorded during 7 days by 12 temporary seismic stations deployed in the area. The stations were laid out along a profile and their interval was approximately 500m. The main part of the processing was done using Geopsy software. The aim of this study was to estimate the fundamental frequency at the station sites and its variation with time and azimuth. The processing results showed that for most stations along the profile, the peaks of the HVSR curve are not strong enough and often there are, more than one, peaks, which seem to be persistent during the whole recording time. When taking the azimuth into account, some of the stations show dominant and persistent directions were the HVSR ratio is stronger, while it has been observed that this direction could vary for different frequency peaks of the same stations. Finally, the top sediment layer’s geometry and thickness were estimated using Vs velocity results from nearby crosshole measurements.

Estimation of Site Dynamic Characteristics from Ambient Noise Measurements Using HVSR Method in Microzonation Study: Senggarang, Batu Pahat, Malaysia

2014 ◽  
Vol 931-932 ◽  
pp. 803-807 ◽  
Author(s):  
Ahmad Fahmy Kamarudin ◽  
Mohd Effendi Daud ◽  
Zainah Ibrahim ◽  
Ibrahim Azmi ◽  
Mohamad Khairani Yub ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Ambient Noise ◽  
Hazard Analysis ◽  
Resonance Effect ◽  
Spectral Ratio ◽  
Boundary Area ◽  
Contour Maps ◽  
The North ◽  
Hvsr Method ◽  
Noise Measurements

Site dynamic characteristics evaluation of fundamental ground frequency, Fo and amplification factor, Ao in Senggarang region were presented in 2D and 3D contour maps (microzonation maps) based on the ambient noise measurements carried out using Lennartz 1 Hz tri-axial seismometer sensors. Reliability of Fo and Ao determined from the ambient noise technique has become the main key components in seismic hazard analysis, resonance effect assessment, predictions of sedimentary layer and shear wave velocity, through cheaper, non-destructive and quick methodology. 73 points of ambient noise records were analyzed using Horizontal-to-Vertical Spectral Ratio (HVSR) method in the boundary area of 800 m x 800 m with the grid spacing of 100 m x 100 m. Significant peaks of mean HVSR curves were checked against the criterions proposed by the SESAME guideline. Slight difference of the Fo contours pattern between the North-South (NS) and the East-West (EW) directions was observed, but vice versa to the Ao contours between both directions. Significant peaks of Fo values were distributed from 1.61 to 6.35 Hz, whereas the Ao values were found from 3.18 to 9.39. Wide gap between the ranges of Fo and Ao in respective direction have shown to the variation of sediment thicknesses. Meanwhile, dominance shape of significant peak from the HVSR curves may indicate to a large velocity contrast presence underneath the ground surfaces.

scholarly journals Ambient Noise Analysis During Nyepi in Denpasar Using Horizontal-to-Vertical Spectral Ratio (HVSR) Method

2020 ◽  
Vol 18 (1) ◽  
pp. 23
Author(s):  
I Putu Dedy Pratama ◽  
Dwi Karyadi Priyanto ◽  
Pande Komang Gede Arta Negara
Keyword(s):  
Ambient Noise ◽  
Seismic Vulnerability ◽  
Amplification Factor ◽  
Noise Analysis ◽  
Spectral Ratio ◽  
Vulnerability Index ◽  
Dominant Frequency ◽  
Before And After ◽  
Hvsr Method ◽  
Index Value

Nyepi Day is a unique tradition where outdoor human activities stop 24 hours a day. Denpasar City is the region that has the most significant impact on this change because it is the capital province. This study aims to determine the effect of Nyepi on ambient noise in Denpasar on March 25, 2020. We installed a TDS sensor at the Denpasar Geophysics Station for 3x24 hours ie when Nyepi Day, before and after Nyepi as comparative data. The data is processed by the HVSR method to get the value of dominant frequency and amplification factor every hour. Compared to the day before and after Nyepi, the dominant frequency increased during Nyepi and the amplification factor decreased during Nyepi. Seismic vulnerability index value at Nyepi is 24 where there is a decrease of index 3,904 with a day before and after Nyepi. This is showed that Nyepi Day affected ambient noise in Denpasar.

Seabed property estimation from ambient-noise recordings: Part 2 — Scholte-wave spectral-ratio inversion

Geophysics ◽  
2007 ◽  
Vol 72 (4) ◽  
pp. U47-U53 ◽  
Author(s):  
Everhard Muyzert
Keyword(s):  
Ambient Noise ◽  
Spectral Ratio ◽  
Shear Velocity ◽  
Velocity Model ◽  
Surface Shear ◽  
Data Set ◽  
Recording Time ◽  
Near Surface ◽  
Scholte Waves ◽  
Scholte Wave

Having knowledge of the near-surface shear-velocity model is useful for various seismic processing methods such as shear-wave static estimation, wavefield separation, and geohazard prediction. I present a new method to derive a 2D near-surface shear-velocity model from ambient-noise recordings made at the seafloor. The method relies on inverting horizontal- and vertical-amplitude spectra of Scholte waves propagating in the seafloor. I compare the commonly used horizontal-over-vertical spectral ratio with three alternative spectral-ratio definitions through modeling. The modeling shows that the vertical-over-total spectral ratio has some favorable properties for inversion. I describe a nonlinear inversion method for the vertical-to-total spectral ratio of the Scholte waves and apply it to an ambient-noise data set recorded by an ocean-bottom-cable (OBC) system. A 1D near-surface shear-velocity model is derived through a joint inversion of the spectral-ratio and phase-velocity data. A 2D shear-velocity model is obtained through a local inversion of the spectral ratios averaged over small groups of receivers and shows evidence for lateral heterogeneity. The newly developed method for deriving near-surface shear-velocity distribution by inverting the Scholte-wave spectral ratio measured from seabed noise provides great opportunities for estimating the shallow-seabed shear velocity in deep water. Another benefit of the method is that, with the OBC system, no additional hardware is needed; only additional recording time is required. In this case, half an hour is sufficient.

scholarly journals Antarctic ice sheet thickness estimation using the horizontal-to-vertical spectral ratio method with single-station seismic ambient noise

2018 ◽  
Vol 12 (2) ◽  
pp. 795-810 ◽  
Author(s):  
Peng Yan ◽  
Zhiwei Li ◽  
Fei Li ◽  
Yuande Yang ◽  
Weifeng Hao ◽  
...  
Keyword(s):  
Ambient Noise ◽  
Ice Sheet ◽  
Sheet Thickness ◽  
Spectral Ratio ◽  
Ice Thickness ◽  
Antarctic Ice Sheet ◽  
Seismic Stations ◽  
Thickness Estimation ◽  
Seismic Ambient Noise ◽  
The Antarctic

Abstract. We report on a successful application of the horizontal-to-vertical spectral ratio (H / V) method, generally used to investigate the subsurface velocity structures of the shallow crust, to estimate the Antarctic ice sheet thickness for the first time. Using three-component, five-day long, seismic ambient noise records gathered from more than 60 temporary seismic stations located on the Antarctic ice sheet, the ice thickness measured at each station has comparable accuracy to the Bedmap2 database. Preliminary analysis revealed that 60 out of 65 seismic stations on the ice sheet obtained clear peak frequencies (f0) related to the ice sheet thickness in the H / V spectrum. Thus, assuming that the isotropic ice layer lies atop a high velocity half-space bedrock, the ice sheet thickness can be calculated by a simple approximation formula. About half of the calculated ice sheet thicknesses were consistent with the Bedmap2 ice thickness values. To further improve the reliability of ice thickness measurements, two-type models were built to fit the observed H / V spectrum through non-linear inversion. The two-type models represent the isotropic structures of single- and two-layer ice sheets, and the latter depicts the non-uniform, layered characteristics of the ice sheet widely distributed in Antarctica. The inversion results suggest that the ice thicknesses derived from the two-layer ice models were in good concurrence with the Bedmap2 ice thickness database, and that ice thickness differences between the two were within 300 m at almost all stations. Our results support previous finding that the Antarctic ice sheet is stratified. Extensive data processing indicates that the time length of seismic ambient noise records can be shortened to two hours for reliable ice sheet thickness estimation using the H / V method. This study extends the application fields of the H / V method and provides an effective and independent way to measure ice sheet thickness in Antarctica.

scholarly journals AMBIENT NOISE HORIZONTAL-TO-VERTICAL SPECTRAL RATIO FOR ASSESSING SITE EFFECTS IN URBAN ENVIRONMENTS: THE CASE OF THESSALONIKI CITY ( NORTHERN GREECE )

2004 ◽  
Vol 36 (3) ◽  
pp. 1467 ◽  
Author(s):  
A. A. Panou ◽  
N. Theodulidis ◽  
P. M. Hatzidimitriou ◽  
C. B. Papazachos ◽  
K. Stylianidis
Keyword(s):  
Fundamental Frequency ◽  
Ambient Noise ◽  
Spectral Ratio ◽  
Urban Environments ◽  
Macroseismic Data ◽  
Northern Greece ◽  
Contour Maps ◽  
Noise Measurements ◽  
The City ◽  
Amplitude Level

250 ambient noise measurements were performed in a dense grid (about 150mX150m) covering the historical center of the city of Thessaloniki (Northern Greece), that was strongly affected by the 20/6/1978 (M=6.5) damaging earthquake. The data were processed using the method of horizontal- to-vertical (H/V) spectral ratio (Nogoshi and Igarashi, 1971; Nakamura, 1989). In order to evaluate diurnal and seasonal variation (summer - winter) of the ambient noise H/V spectral ratio, systematic measurements were performed in eight sites. The fundamental frequency (fo) and the corresponding H/V amplitude level (Ao) from the ambient noise H/V spectral ratio for each site were calculated. Spatial interpolation of the fundamental frequency (fo) and the corresponding H/V amplitude level (Ao) was attempted between all points and respective contour maps were produced. Diurnal variation of the ambient noise H/V spectral ratio showed that it is preferable to perform measurements during the calm hours of a day, when manmade noise is relatively low. However, no systematic seasonal fluctuation effect on the ambient noise H/V spectral ratio was identified for the city of Thessaloniki. Contour maps of both fundamental frequency (fo) and corresponding H/V amplitude level (Ao) were compared versus the macroseismic data of the 1978 earthquake (Leventakis, 2003), as well as with related geological (IGME, 1978) and geotechnical (Anastasiadis et al., 2001) studies for the same area. Damage distribution due to 20/6/1978 earthquake (Penelis et al., 1985) was also converted to EMS_98 (European Macroseismic Scale, 1998). For seventy buildings, made of reinforced concrete, we have also compared the obtained results with the dynamic amplification of the buildings (Ubuilding) at the fundamental soil frequency (fo). The results encourage the use of ambient noise measurements along with the (H/V) spectral ratio technique as a nonexpensive and fast tool in microzonation studies to be carried out in urban environments.

Horizontal-to-Vertical Spectral Ratio (HVSR) IRIS Station Toolbox

2020 ◽  
Vol 91 (6) ◽  
pp. 3539-3549
Author(s):  
Manochehr Bahavar ◽  
Zack J. Spica ◽  
Francisco J. Sánchez-Sesma ◽  
Chad Trabant ◽  
Arash Zandieh ◽  
...  
Keyword(s):  
Ambient Noise ◽  
Spectral Ratio ◽  
Site Effect ◽  
Predominant Frequency ◽  
Density Estimates ◽  
Effect Analysis ◽  
Seismic Stations ◽  
Arctic Regions ◽  
Power Spectral ◽  
The Many

Abstract The horizontal-to-vertical spectral ratio (HVSR) for seismic ambient noise is a popular method that can be used to estimate the predominant frequency at a given site. In this article, we introduce the Incorporated Research Institutions for Seismology (IRIS) Data Management Center’s (DMC’s) openly available HVSR station toolbox. These tools offer a variety of ways to compute the spectral ratio by providing different averaging routines. The options range from the simple average of spectral ratios to the ratio of spectral averages. Computations take advantage of the available power spectral density estimates of ambient noise for the seismic stations, and they can be used to estimate the predominant frequency of the many three-component seismic stations available from the IRIS DMC. Furthermore, to facilitate the identification of the peaks in HVSR profiles for the assessment of the predominant frequency of station sites, the toolbox can also process the results of HVSR analysis to detect and rank HVSR peaks. To highlight the toolbox capabilities, three different examples of possible use of this toolbox for routine site-effect analysis are discussed: (1) site effects related to thawing in Arctic regions, (2) ground-motion amplification in urban area, and (3) estimation of station VS30.

scholarly journals Antarctic ice sheet thickness estimation using the H/V spectral ratio method with single-station seismic ambient noise

2017 ◽  
Author(s):  
Peng Yan ◽  
Zhiwei Li ◽  
Fei Li ◽  
Yuande Yang ◽  
Weifeng Hao ◽  
...  
Keyword(s):  
Ambient Noise ◽  
Ice Sheet ◽  
Sheet Thickness ◽  
Spectral Ratio ◽  
Ice Thickness ◽  
Antarctic Ice Sheet ◽  
Seismic Stations ◽  
Thickness Estimation ◽  
Seismic Ambient Noise ◽  
The Antarctic

Abstract. The horizontal-to-vertical spectral ratio (H/V) method implemented at single stations using seismic ambient noise waveforms is a fast, noninvasive, efficient method to investigate the subsurface velocity structures of the shallow crust. In this study, we report on a successful application of the H/V method to estimate the Antarctic ice sheet thickness for the first time. Using three-component, five-day long, seismic ambient noise records gathered from more than 60 temporary seismic stations located on the Antarctic ice sheet, the ice thickness at each station was reliably measured. Preliminary analysis revealed that 60 out of 65 seismic stations on the ice sheet obtained clear peak frequencies (f0) related to the ice sheet thickness in the H/V spectrum. Thus, assuming that the isotropic ice layer lies atop a high velocity half-space bedrock, the ice sheet thickness can be calculated by a simple approximation formula. About half of the calculated ice sheet thickness were consistent with the Bedmap2 ice thickness values. To further improve the reliability of ice thickness measurements, two-type models were built to fit the observed H/V spectrum through non-linear inversion. The two-type models represent the isotropic structures of single and two-layer ice sheet, and the latter depicts the non-uniform, layered characteristics of the ice sheet widely distributed in Antarctica. The inversion results suggest that the ice thicknesses derived from the two-layer ice models were highly consistent with the Bedmap2 ice thickness database, and their ice thickness differences were within 300 m at almost all stations. Our results support previous finding that the Antarctic ice sheet is stratified. Extensive data processing indicates that the time length of seismic ambient noise records can be shortened to 1–2 hours for reliable ice sheet thickness estimation using the H/V method. This study extends the application fields of the H/V method and provides a complementary and independent way to measure ice sheet thickness in Antarctica.

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 The Soft Layer Thickness Estimation using Microtremor Measurement to Identify Landside Potential in Watukumpul, Central Java, Indonesia.

2021 ◽  
Vol 6 (1) ◽  
pp. 16-23
Author(s):  
Urip Nurwijayanto Prabowo ◽  
Akmal Ferdiyan ◽  
Ayu Fitri Amalia
Keyword(s):  
Layer Thickness ◽  
Spectral Ratio ◽  
Dominant Frequency ◽  
Soil Slope ◽  
Soft Layer ◽  
Thickness Estimation ◽  
Central Java ◽  
Hvsr Method ◽  
Microtremor Measurement ◽  
Potential Area

Watukumpul is an area that is prone to landslides, so determining the soft layer thickness is very important to identify the landslide potential. The soft layer thickness can be estimated using microtremor signal measurements which analyzed using the Horizontal to Vertical Spectral Ratio (HVSR). In this study,we measured microtremor signal of 33location around Watukumpul, Pemalang, Central Java area to determine soft layer thickness. Micretremor signal was analyzed based on theHVSR method using Geopsy software and follow the standard of the Sesame Europan Project. The results of the HVSR method are the HVSR curve that fulfills the reliable curve standard. HVSR curve shows that the dominant frequency of soft layer ranges from 1.36 – 7.62 Hz and the amplification values ranges from 9.00 – 41.45. The soft layer thickness value in the study area ranges from 17.58 - 103.60 meters. The high landslide potential area are located at W7, W8, W18, W30 and W32 where has thin soft layer and high soil slope.

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