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.

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.

Reliability of Ambient Noise Horizontal-to-Vertical Spectral Ratio in Urban Environments: The Case of Thessaloniki City (Northern Greece)

2005 ◽  
Vol 162 (5) ◽  
pp. 891-912 ◽  
Author(s):  
A. A. Panou ◽  
N.P. Theodulidis ◽  
P.M. Hatzidimitriou ◽  
A.S. Savvaidis ◽  
C.B. Papazachos
Keyword(s):  
Ambient Noise ◽  
Spectral Ratio ◽  
Urban Environments ◽  
Northern Greece

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 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.

scholarly journals Combining recordings of earthquake ground-motion and ambient vibration analysis to estimate site response variability in the city of Lucerne, Switzerland

2021 ◽  
Author(s):  
Paulina Janusz ◽  
Vincent Perron ◽  
Christoph Knellwolf ◽  
Walter Imperatori ◽  
Luis Fabian Bonilla ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Urban Areas ◽  
Ambient Noise ◽  
Site Response ◽  
Spectral Ratio ◽  
Response Variability ◽  
Standard Spectral Ratio ◽  
Hazard And Risk ◽  
The City

&lt;p&gt;Estimation of site effects is an essential part of local seismic hazard and risk assessment, especially in densely populated urban areas. The goal of this study is to assess the site response variability in the city of Lucerne (Central Switzerland), located in a basin filled with unconsolidated deposits. Even though it is a low-to-moderate seismicity area, the long-term seismic risk cannot be neglected, in particular, because the region was struck by strong earthquakes in the past (i.e. Mw 5.9 in 1601).&lt;/p&gt;&lt;p&gt;To determine the spatial distribution of the soil response in the test area, we combined earthquake and ambient noise recordings using the Hybrid Standard Spectral Ratio method (SSRh) introduced by Perron et al. (2018). In the first step, we installed a temporary seismic network to record ground-motion from low-magnitude or distant earthquakes. At selected urban sites inside the sedimentary basin, the dataset was used to estimate the amplification factors with respect to a rock site using the Standard Spectral Ratio approach (SSR - Borcherdt, 1970). Then, a survey including several dozens of densely distributed single-station ambient noise measurements was performed which enabled us to estimate the basin response variability relative to the seismic stations of the temporary seismic network. Finally, we corrected the noise-based evaluation using the SSR amplification functions. To verify the useability of the presented technique in the Lucerne area, we applied the SSRh method also to the temporary stations, the resulting amplification functions largely coincide with the SSR curves. However, the daily variability of the noise wavefield due to human activities can slightly affect the results. We will also discuss the influence of the station distribution and density of the temporary network deployment.&lt;/p&gt;&lt;p&gt;The amplification model for the Lucerne area estimated using the SSRh method shows consistency with geological data. The results indicate that seismic waves can be amplified up to 10 times in some parts of the basin compared to the rock site. The highest amplification factors are observed for frequencies between 0.8 and 2Hz. This means a local significant increase in seismic hazard.&lt;/p&gt;&lt;p&gt;The presented work is a part of a detailed site response analysis study for the Lucerne area, considering 2D and 3D site effects and potential non-linear soil behaviour. This PhD project is performed in the framework of the Horizon 2020 ITN funded project URBASIS-EU, which focuses on seismic hazard and risk in urban areas.&lt;/p&gt;&lt;p&gt;REFERENCES&lt;/p&gt;&lt;p&gt;Borcherdt, R.D., 1970. Effects of local geology on ground motion near San Francisco Bay. Bull. Seismol. Soc. Am. 60, 29&amp;#8211;61.&lt;/p&gt;&lt;p&gt;Perron, V., G&amp;#233;lis, C., Froment, B., Hollender, F., Bard, P.-Y., Cultrera, G., Cushing, E.M., 2018. Can broad-band earthquake site responses be predicted by the ambient noise spectral ratio? Insight from observations at two sedimentary basins. Geophys. J. Int. 215, 1442&amp;#8211;1454.&lt;/p&gt;

scholarly journals Ambient noise measurements for preliminary microzoning studies in the city of Messina, Sicily

2018 ◽  
Vol 61 (2) ◽  
Author(s):  
Silvia Scolaro ◽  
Paolo Pino ◽  
Sebastiano D'Amico ◽  
Barbara Orecchio ◽  
Debora Presti ◽  
...  
Keyword(s):  
Ambient Noise ◽  
Noise Measurements ◽  
The City

scholarly journals New developments in ambient noise analysis to characterise the seismic response of landslide prone slopes

2013 ◽  
Vol 1 (2) ◽  
pp. 1319-1353 ◽  
Author(s):  
V. Del Gaudio ◽  
J. Wasowski ◽  
S. Muscillo
Keyword(s):  
Ambient Noise ◽  
Noise Analysis ◽  
Central Italy ◽  
Spectral Ratio ◽  
Specific Response ◽  
Accelerometer Data ◽  
Noise Sources ◽  
New Developments ◽  
Resonance Frequencies ◽  
Noise Measurements

Abstract. We report on new developments in the application of ambient noise analysis applied to investigate the dynamic response of landslide prone slopes to seismic shaking with special attention to the directional resonance phenomena recognised in previous studies. Investigations relying on the calculation of horizontal-to-vertical noise spectral ratio (HVNR) were carried out in the area of Caramanico Terme (central Italy) where an ongoing accelerometer monitoring on slopes with different characteristics offers the possibility of validation of HVNR analysis. The noise measurements, carried out in different times to test the result repeatability, revealed that sites affected by response directivity persistently show major peaks with a common orientation consistent with the resonance direction inferred from accelerometer data. At sites where directivity is absent, the HVNR peaks do not generally show a preferential orientation, with rare exceptions that could be linked to the presence of temporarily active sources of polarised noise. The observed spectral ratio amplitude variations can be related to temporal changes in site conditions, which can hinder the recognition of main resonance frequencies. Therefore, it is recommended to conduct simultaneous measurements at nearby sites within the same study area and to repeat measurements at different times in order to distinguish significant systematic polarisation caused by site specific response directivity from polarisation controlled by properties of noise sources. Furthermore, an analysis of persistence in noise recordings of signals with systematic directivity showed that only a~portion of recordings contains wave trains having a clear polarisation representative of site directional resonance. Thus a careful selection of signals for HVNR analysis is needed for a correct characterisation of site directional properties.

Minimetrò in Perugia as leverage for urban regeneration

TERRITORIO ◽  
2020 ◽  
pp. 148-163
Author(s):  
Luca Fondacci
Keyword(s):  
Urban Regeneration ◽  
Urban Environments ◽  
Low Carbon ◽  
Sustainable Mobility ◽  
Field Surveys ◽  
Peripheral Area ◽  
Alternative Means ◽  
Considerable Impact ◽  
The City ◽  
Historical Centre

In the 1970s, the fragile historical centre of the city of Perugia was a key area where the binomial of sustainable mobility and urban regeneration was developed and applied. At the turn of the xxi century, the low carbon automatic people-mover Minimetrò broadened that application from the city's historical centre to the outskirts, promoting the enhancement of several urban environments. This paper is the outcome of an investigation of original sources, field surveys and direct interviews, which addresses the Minimetrò as the backbone of a wide regeneration process which has had a considerable impact on the economic development of a peripheral area of the city which was previously devoid of any clear urban sense. The conclusion proposes some solutions to improve the nature of the Minimetrò as an experimental alternative means of transport.

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