Development of a Vs30 (NEHRP) map for the city of Ottawa, Ontario, Canada

2011 ◽  
Vol 48 (3) ◽  
pp. 458-472 ◽  
Author(s):  
D. Motazedian ◽  
J. A. Hunter ◽  
A. Pugin ◽  
H. Crow
Keyword(s):  
Shear Wave ◽  
Fundamental Frequency ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Seismic Refraction ◽  
Weighted Average ◽  
Spectral Ratio ◽  
Wave Impedance ◽  
Seismic Methods ◽  
The City

Four different seismic methods were used extensively to evaluate the shear wave velocity of soils and rock in the city of Ottawa, Canada, from which the travel-time weighted average shear wave velocity (Vs) from surface to 30 m in depth (Vs30) and the fundamental frequency (F0) were computed. Three main geological or geotechnical units were identified with distinct shear wave velocities: these consist of very loose thick post-glacial fine-grained sands, silts, and clays (Vs <150 m/s, thickness up to 110 m), firm glacial sediments (Vs ∼580 m/s, thickness ∼3 m), and very firm bedrock (Vs ∼1750–3550 m/s). The seismic methods applied were downhole interval Vs measurements at 15 borehole sites, seismic refraction–reflection profile measurements for 686 sites, high-resolution shear wave reflection “landstreamer” profiling for 25 km in total, and horizontal-to-vertical spectral ratio (HVSR) of ambient seismic noise to evaluate the fundamental frequency for ∼400 sites. Most of these methods are able to distinguish the very high shear wave impedance of and depth to bedrock. Sparse earthquake recordings show that the soil amplification is large for weak motion when the soil behaves linearly.

scholarly journals Lithological modelling based on shear wave velocity using horizontal to vertical spectral ratio (HVSR) inversion of ellipticity curve method to mitigate landslide hazards at the main road Of Samigaluh District, Kulon Progo Regency, Yogyakarta

2021 ◽  
Vol 325 ◽  
pp. 01009
Author(s):  
Skolastika Novita Widyadarsana ◽  
Eddy Hartantyo
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Spectral Ratio ◽  
Main Road ◽  
Landslide Hazards ◽  
Landslide Mitigation ◽  
Curve Method ◽  
Hvsr Technique ◽  
The City

Many landslides occur in Samigaluh District, Kulon Progo Regency, Yogyakarta, Indonesia. However, no research discusses landslides that often occur on the main road connecting the city of Yogyakarta and various tourist resorts in Samigaluh. This study aims at determining the soil vulnerability and lithology model at that main road as a contribution to landslide mitigation planning. This lithology model is based on shear wave velocity (Vs) and layer thickness derived by microtremor datasets. The data were processed by the inversion of the Horizontal to Vertical Spectral Ratio (HVSR) technique of the ellipticity curve method. The result of the study shows that the first layer is associated with topsoil which has Vs of 263 m/s, the second layer is clay which has Vs of 607 m/s, the third layer consists of clay, breccia, and pumice which has Vs of 1119 m/s, and the fourth layer is andesite bedrock which has Vs of 1721 m/s. Andesite is impermeable to water and can become a slip field for landslides. Clay, breccias, and pumice can absorb water so that their weight increases when it rains. When they are on an impermeable rock on a certain slope, a landslide occurs.

A study of horizontal-to-vertical component spectral ratio as a proxy for site classification in central Asia

2020 ◽  
Vol 223 (2) ◽  
pp. 1355-1377
Author(s):  
Farhad Sedaghati ◽  
Sahar Rahpeyma ◽  
Anooshiravan Ansari ◽  
Shahram Pezeshk ◽  
Mehdi Zare ◽  
...  
Keyword(s):  
Central Asia ◽  
Shear Wave ◽  
Fundamental Frequency ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Spectral Ratio ◽  
P Wave ◽  
Site Classification ◽  
Gaussian Shape ◽  
Resonance Frequencies

SUMMARY Tien Shan of central Asia is known as one of the world's largest, youngest and most active intracontinental orogens. In this study, we implemented the horizontal-to-vertical spectral ratio (HVSR) technique as a widely used first-order approximation of the site effect parameters (i.e. fundamental frequency and site amplification). A set of data including 2119 strong-motion recordings from 468 earthquakes with hypocentral distances up to 500 km and small to moderate moment magnitudes ($ {M_{\rm{w}}}\sim $3.0–5.5) recorded by 24 broad-band stations from five different networks, located in Afghanistan, Tajikistan and Kyrgyzstan was deployed to investigate site-specific characteristics. We fitted a Gaussian-shape pulse function to evaluate fundamental frequencies and site amplifications. The HVSRs analysis revealed that although the majority of the stations (16 out of 24) show flat amplification functions, there are few stations with single sharp amplification functions. Then, we classified the stations based on the predominant frequency. Furthermore, we approximated the time-averaged shear wave velocity in the uppermost 30 m (${V_{{\rm{S}}30}}$) using the fundamental frequency and its corresponding amplitude. Moreover, we compared the HVSRs obtained from P waves, S waves, coda and pre-event noise. All peak frequencies including the fundamental frequency estimated from different seismic phases are in good agreement; whereas generally, the amplitude of the P-wave window is the lowest, the amplitudes of the S wave and noise windows are similar to the whole record and the amplitudes of early and late coda windows are the highest. We also observed that the HVSRs of noise using a 5 s window may have anomalous high amplitudes and peaks. These anomalous high amplitudes and peaks in the noise HVSRs indicate the existence of some unnatural sources or artefacts such as traffic and wind with specific resonance frequencies, suggesting 5 s ambient noise window is insufficient to capture site characteristics. Finally, to assess the reliability of the determined geotechnical results, we implemented a blind theoretical HVSR inversion to obtain representative shear wave velocity profiles as well as ${V_{{\rm{S}}30}}$ along with associated uncertainties for stations characterized by a single-peak HVSR curve using a Bayesian statistical framework.

scholarly journals Liquefaction hazard zonation mapping of the Saitama City, Japan

2010 ◽  
Vol 40 ◽  
pp. 69-76 ◽  
Author(s):  
Rama Mohan Pokhrel ◽  
Jiro Kuwano ◽  
Shinya Tachibana
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Hazard Zonation ◽  
Liquefaction Potential ◽  
Amplification Ratio ◽  
Liquefaction Hazard ◽  
Clayey Silt ◽  
The City ◽  
Very High

Liquefaction hazard zonation mapping of the Saitama City targeted on the Kanto Plain NW Edge Fault is described in this paper. The study involves the geotechnical properties of the alluvial soil of the city including Standard Penetration Test (SPT), shear wave velocity and other geological data analysis. The city being highly urbanized is situated on the soft soil (alluvial deposits) at the proximity of an active seismic fault that has increased the possibility of liquefaction hazard in the area. Kanto Plain NW Edge Fault is an active fault that lies very near to the Saitama City having the estimated possible earthquake magnitude of 7.4. The possible peak horizontal ground acceleration (amax) from this earthquake is calculated as from 0.15 g to 0.30 g. By considering all possible acceleration values the liquefaction potential maps were prepared and presented in this paper. Additionally, the shear wave velocity is very low and amplification ratio is very high at the marshy deposit but it has comparatively high velocity and low amplification ratio at the marine loam deposit area of the Omiya Plateau. In this paper the liquefaction potential of the area is expressed in terms of liquefaction potential index (PL). The PL value for the clayey silt deposit in the marshy area with shallow water table is very high. In addition, the PL value in the marine loam deposit of the Omiya Plateau is less which indicates that loam deposit has less liquefaction potential than marshy deposit. The map obtained from this study was validated with the field condition of the study area. Hence, it is expected that this study will assist in characterizing the seismic hazards and its mitigation and will provide valuable information for urban planning in the study area in future.

scholarly journals Investigation of Soil Characterization in Hatay Province in Turkey by Using Seismic Refraction, Multichannel Analysis of Surface Waves and Microtremor

2021 ◽  
Vol 24 (4) ◽  
pp. 473-484
Author(s):  
Cengiz Kurtuluş ◽  
Ibrahim Sertcelik ◽  
Fadime Sertçelik ◽  
Hamdullah Livaoğlu ◽  
Cüneyt Şaş
Keyword(s):  
Surface Waves ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Seismic Refraction ◽  
Strong Motion ◽  
Site Classification ◽  
Eurocode 8 ◽  
Site Class ◽  
Multichannel Analysis

In this study, shallow seismic surveys, including seismic refraction, Multichannel Analysis of Surface Waves (MASW), Refraction Microtremor (ReMi), and Microtremor measurements were conducted to estimate site characterization at 26 strong-motion stations of AFAD (Disaster and Emergency Management Presidency) in the province of Hatay, situated in one of the most seismically active regions in southern Turkey. The Horizontal to vertical spectral ratio (HVSR) technique was applied, using smoothed Fourier spectra derived from a long duration series to determine dominant frequency values at different amplification levels. Shear wave velocity up to 30 m of the ground was detected with MASW analysis. In the ReMi analysis, up to 80 m was reached with a corresponding average of 650 m/s shear wave velocity. The shear wave velocities estimated by the MASW method up to 30 m were compared with those found by the ReMi method, and they were observed to be very compatible. The province of Hatay was classified according to Vs30 based NEHRP Provisions, Eurocode-8, the Turkish Building Earthquake Regulation (TBDY-2018), and Rodriguez-Marek et al. (2001). The shear-wave velocity (Vs30), Horizontal to Vertical ratio’s (H/V) peak amplitude, dominant period, and site class of each site were determined. The H/V peak amplitudes range between 1.9 and 7.6, while the predominant periods vary from 0.23 sec to 2.94sec in the study area. These results are investigated to explain the consistency of site classification schemes.

ESTIMATION OF SHEAR-WAVE VELOCITY STRUCTURE USING MICROTREMOR MEASUREMENTS

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Zorigt Tumurbaatar ◽  
Hiroyuki Miura
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Urban Areas ◽  
Velocity Structure ◽  
Earthquake Hazard ◽  
Site Amplification ◽  
Spectral Ratios ◽  
Inversion Analysis ◽  
The City

Due to the recent construction boom in Ulaanbaatar city (UB), Mongolia, newly urban areas are rapidly expanded to the surrounded area of the city. According to the previous researches and reports, the thickness of the sedimentary basin in UB reaches 120m at the maximum in the area along the Tuul river. Therefore, the evaluation of site amplification is one of the essential parts of the estimation of earthquake hazard in this area. In this paper, the shear-wave velocity (Vs) structures in UB are estimated from single microtremor observations with the existing microtremor array observations. We carried out the microtremor observations at 50 sites and computed horizontal-to-vertical (H/V) spectral ratios. Inversion analysis is performed to the observed H/V spectral ratios based on the diffuse field approach (DFA) to determine the Vs structures. The site characterizations are evaluated from the amplification factors of the Vs structures.

Comparing Shear Wave Velocity Measurements from MASW and Downhole Seismic Methods

2012 ◽  
Author(s):  
Ahmed Ismail ◽  
Andrew Stumpf ◽  
Neil Anderson ◽  
William Dey
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Velocity Measurements ◽  
Seismic Methods

Development of Deep Shear Wave Velocity Profiles in the Canterbury Plains, New Zealand

2018 ◽  
Vol 34 (3) ◽  
pp. 1065-1089 ◽  
Author(s):  
Michael R. Deschenes ◽  
Clinton M. Wood ◽  
Liam M. Wotherspoon ◽  
Brendon A. Bradley ◽  
Ethan Thomson
Keyword(s):  
New Zealand ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Joint Inversion ◽  
Three Dimensional ◽  
Strong Motion ◽  
Spectral Ratio ◽  
Deep Basin ◽  
Velocity Models

Deep (typically > 1,000 m) shear wave velocity ( V S) profiles were developed across the Canterbury region of New Zealand at nine strong-motion stations using a combination of active and passive surface wave methods. A multimode, multimethod joint inversion process, which included Rayleigh and Love wave dispersion and horizontal-to-vertical spectral ratio data, was used to develop the V S profiles at each site. A priori geologic information was used in defining preliminary constraints on the complex geologic layering of the deep basin underlying the region, including velocity reversals in locations where interbedded terrestrial gravels and marine sediments are present. Shear wave profiles developed as part of this study had characteristics comparable to the profiles from 14 Christchurch sites detailed in a separate study. The profiles developed in the two studies were combined to form region-specific V S profiles for typical deposits, which can be used to improve the accuracy of current three-dimensional (3-D) crustal velocity models of the region.

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