Local Site Effects in the Town of Benevento (Italy) from Noise Measurements

Maresca, Rosalba; Castellano, M.; Matteis, Raffaella De; Saccorotti, Gilberto; Vaccariello, P.

doi:10.1007/s00024-003-2376-2

Cited by 22 publications

(10 citation statements)

References 17 publications

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“…There exist, however, a few cases of disagreement: either H/V curves are flat and fail to exhibit the amplification witnessed by other techniques (Moya et al 2000;Haghshenas et al 2003), or the frequency of the H/V peak is different from values indicated by other techniques (Volant et al 1998;Zaré et al 1999;Haghshenas et al 2003;Maresca et al 2003). Satoh et al (2001) also report a case where the correlation of H/V peak frequency and fundamental frequency of site exhibits some restrictions: microtremor H/V peak frequencies roughly coincide with those of receiver function and SSR for S-waves only for frequencies lower than 1 Hz and peak amplitude larger than 3.…”

Section: Previous Experimental Results: a Short Reviewmentioning

confidence: 97%

Empirical evaluation of microtremor H/V spectral ratio

Haghshenas

Bard

Theodulidis

et al. 2008

Bull Earthquake Eng

229

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International audienceThe objective of this work is to perform a purely empirical assessment of the actual capabilities of the horizontal-to-vertical (H/V) spectral ratio technique to provide reliable and relevant information concerning site conditions and/or site amplification. This objective has been tackled through the homogeneous (re)processing of a large volume of earthquakes and ambient noise data recorded by different research teams in more than 200 sites located mainly in Europe, but also in the Caribbean and in Tehran. The original recordings were first gathered in a specific database with information on both the sites and recorded events. Then, for all sites close to an instrumented reference, average site-to-reference spectral ratios (“spectral ratio method” (SSR)) were derived in a homogeneous way (window selection, smoothing, signal-to-noise ratio threshold, averaging), as well as H/V ratios (“HVSRE–RF”) on earthquake recordings. H/V ratios were also obtained from noise recordings at each site (either specific measurements, or extracted from pre- or post-event noise windows). The spectral curves resulting from these three techniques were estimated reliable for a subset of 104 sites, and were thus compared in terms of fundamental frequency, amplitude and amplification bandwidth, exhibiting agreements and disagreements, for which interpretations are looked for in relation with characteristics of site conditions. The first important result consists in the very good agreement between fundamental frequencies obtained with either technique, observed for 81% of the analyzed sites. A significant part of the disagreements correspond to thick, low frequency, continental sites where natural noise level is often very low and H/V noise ratios do not exhibit any clear peak. The second important result is the absence of correlation between H/V peak amplitude and the actual site amplification measured on site-to-reference spectral ratios. There are, however, two statistically significant results about the amplitude of the H/V curve: the peak amplitude may be considered as a lower bound estimate of the actual amplification indicated by SSR (it is smaller for 79% of the 104 investigated sites), and, from another point of view, the difference in amplitude exhibits a questioning correlation with the geometrical characteristics of the sediment/basement interface: large SSR/HV differences might thus help to detect the existence of significant 2D or 3D effects

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Section: Previous Experimental Results: a Short Reviewmentioning

confidence: 97%

Empirical evaluation of microtremor H/V spectral ratio

Haghshenas

Bard

Theodulidis

et al. 2008

Bull Earthquake Eng

229

View full text Add to dashboard Cite

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“…Many authors (e.g. Mucciarelli 1998;Rodriguez and Midorikawa 2002;Maresca et al 2003) have questioned the existence of simple direct correlation between HVNR spectral amplitude values and the site amplification. The HVNR from ambient vibrations are sometimes ''non-informative'', particularly in the case of significant lateral heterogeneity giving rise to 2D/3D effects and velocity inversion that influence the vertical component of motion (Di Giacomo et al 2005;Castellaro and Mulargia 2009;Panzera et al 2013).…”

Section: Forewordsmentioning

confidence: 99%

Seismic site effects observed on sediments and basaltic lavas outcropping in a test site of Catania, Italy

et al. 2015

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Ambient noise measurements and a set of 44 moderate magnitude earthquakes were used to study the role of local geology and morphology on the site response of a small hill in the northern part of Catania, on top of which the University Astronomical Observatory is located. The study area has a gentle topography with a flat surface at the top, and it is characterized by a complex sedimentary sequence lying between a clayey basement and an upper volcanic formation. The recorded data were processed through standard spectral ratio and horizontal-to-vertical spectral ratio techniques. Directional effects were also investigated by computing the spectral ratios after rotating the horizontal components of motion and performing polarization analysis. Results of noise and earthquakes analysis, although showing significant differences in amplitude, are comparable in frequency, especially in the sedimentary terrains. On the lava flows, spectral ratios show significant amplification of the vertical component, which appear related to a higher P velocity contrast with underlying soft sediments. Directional effects were identified in two frequency bands (0.2-0.4 and 1.0-10.0 Hz). The effects observed at the lower frequency interval are rather stable, and it spreads out in all the studied area. At higher frequencies, directional effects are variable and mostly observed on the slopes rather than at the hill top. Our findings appear linked to the complex wave field generated by the lithologic heterogeneities existing in the area which seem to be related to the alternation of sediments and basaltic lavas.

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“…These observations were supported by several theoretical 1‐D investigations (Field & Jacob 1993; Lachet & Bard 1994; Lermo & Chavez‐Garcia 1994; Wakamatsu & Yasui 1996; Tokeshi & Sugimura 1998), that have shown that noise synthetics computed using randomly distributed, near surface sources lead to H/V ratios sharply peaked around the fundamental S ‐wave frequency, when the surface layer exhibits a sharp impedance contrast with the underlying stiffer formations. However, some discussions are still under way about the applicability of this technique to evaluating the site amplification (Bard 1998; Bour et al 1998; Mucciarelli 1998; Al Yuncha & Luzon 2000; Maresca et al 2003; Rodriguez & Midorikawa 2003). If the shape of the H/V curves is controlled by the S ‐wave resonance within the sediments Nakamura (1989, 2000), then both H/V peak frequency and amplitude may be straightforward related to the soil transfer function (in term of fundamental resonance frequency and site amplification factor).…”

Section: Introductionmentioning

confidence: 99%

H/V ratio: a tool for site effects evaluation. Results from 1-D noise simulations

Bonnefoy-Claudet

Cornou

Bard

et al. 2006

Geophysical Journal International

417

201

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National audienceAmbient vibration techniques such as the H/V method may have the potential to significantly contribute to site effect evaluation, particularly in urban areas. Previous studies interpret the so-called Nakamura's technique in relation to the ellipticity ratio of Rayleigh waves, which, for a high enough impedance contrast, exhibits a pronounced peak close to the fundamental S-wave resonance frequency. Within the European SESAME project (Site EffectS assessment using AMbient Excitations) this interpretation has been tested through noise numerical simulation under well-controlled conditions in terms of source type and distribution and propagation structure. We will present simulations for a simple realistic site (one sedimentary layer over bedrock) characterized by a rather high impedance contrast and low quality factor. Careful H/V and array analysis on these noise synthetics allow an in-depth investigation of the link between H/V ratio peaks and the noise wavefield composition for the soil model considered here: (1) when sources are near (4 to 50 times the layer thickness) and surficial, H/V curves exhibit one single peak, while the array analysis shows that the wavefield is dominated by Rayleigh waves; (2) when sources are distant (more than 50 times the layer thickness) and located inside the sedimentary layer, two peaks show up on the H/V curve, while the array analysis indicates both Rayleigh waves and strong S head waves; the first peak is due to both fundamental Rayleigh waves and resonance of head S waves, the second is only due to the resonance of head S waves; (3) when sources are deep (located inside the bedrock), whatever their distance, H/V ratio exhibit peaks at the fundamental and harmonic resonance frequencies, while array analyses indicate only non-dispersive body waves; the H/V is thus simply due to multiple reflections of S waves within the layer. Therefore, considering that experimental H/V ratio (i.e. derived from actual noise measured in the field) exhibit in most cases only one peak, we conclude that H/V ratio is (1) mainly controlled by local surface sources, (2) mainly due to the ellipticity of the fundamental Rayleigh waves. Then the amplitude of H/V peak is not able to give a good estimate of site amplification facto

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Local Site Effects in the Town of Benevento (Italy) from Noise Measurements

Cited by 22 publications

References 17 publications

Empirical evaluation of microtremor H/V spectral ratio

Empirical evaluation of microtremor H/V spectral ratio

Seismic site effects observed on sediments and basaltic lavas outcropping in a test site of Catania, Italy

H/V ratio: a tool for site effects evaluation. Results from 1-D noise simulations

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