Site characterisation in Kangra Valley (NW Himalaya, India) by inversion of H/V spectral ratio from ambient noise measurements and its validation by multichannel analysis of surface waves technique

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.

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Horizontally orthogonal distributed acoustic sensing array for earthquake- and ambient-noise-based multichannel analysis of surface waves

Geophysical Journal International ◽

10.1093/gji/ggaa293 ◽

2020 ◽

Vol 222 (3) ◽

pp. 2147-2161

Author(s):

Bin Luo ◽

Whitney Trainor-Guitton ◽

Ebru Bozdağ ◽

Lisa LaFlame ◽

Steve Cole ◽

...

Keyword(s):

Rayleigh Wave ◽

Surface Waves ◽

Love Wave ◽

Ambient Noise ◽

Wave Dispersion ◽

Wave Component ◽

Multichannel Analysis ◽

Distributed Acoustic Sensing ◽

Love Wave Dispersion

SUMMARY A 2-D orthogonal distributed acoustic sensing (DAS) array designed for seismic experiments was buried horizontally beneath the Kafadar Commons Geophysical Laboratory on the Colorado School of Mines campus at Golden, Colorado. The DAS system using straight fibre-optic cables is a cost-efficient technology that enables dense seismic array deployment for long-term seismic monitoring, favouring both earthquake-based and ambient-noise-based surface wave analysis for subsurface characterization. In our study, the horizontally orthogonal DAS array records ambient noise data for a period of about two months from November 2018 to January 2019. During this time, the array also detected seismic signals from an ML3.6 earthquake at Glenwood Springs, Colorado, which exhibit opposite signal polarities in the orthogonal DAS section recordings. We derive the transformation matrix for DAS strain measurements in horizontally orthogonal cables to retrieve both Rayleigh and Love wave dispersion information from the single-component DAS signals using the 2-D multichannel analysis of surface waves method. In addition, ambient noise interferometry is applied to long-term DAS noise recordings. Our theoretical derivation demonstrates that Rayleigh and Love wave Green's functions are coupled in the noise cross-correlation functions (NCFs) of DAS receiver pairs. Stacking NCFs over the horizontally orthogonal DAS array can constructively recover the radial Rayleigh wave component but destructively suppress the Love wave component. The multimodal Monte Carlo inversion of the earthquake-based Rayleigh wave and Love wave dispersion measurements and the noise-based Rayleigh wave measurement reveals a 1-D layered structure that agrees qualitatively with geological surveys of the site. Our study demonstrates that although straight fibre-optic cables lack broadside sensitivity, using appropriate DAS array configuration and seismic array methods can extend the seismic acquisition ability of DAS and enable its application to a broad range of scenarios.

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New empirical relationship between resonance frequency and thickness of sediment using ambient noise measurements and joint-fit-inversion of the Rayleigh wave dispersion curve for Kangra Valley (NW Himalaya), India

Environmental Earth Sciences ◽

10.1007/s12665-020-09000-8 ◽

2020 ◽

Vol 79 (11) ◽

Cited By ~ 2

Author(s):

Praveen Kumar ◽

Ambrish Kumar Mahajan

Keyword(s):

Rayleigh Wave ◽

Resonance Frequency ◽

Dispersion Curve ◽

Ambient Noise ◽

Empirical Relationship ◽

Wave Dispersion ◽

Nw Himalaya ◽

Noise Measurements ◽

Rayleigh Wave Dispersion

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

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.16536 ◽

2004 ◽

Vol 36 (3) ◽

pp. 1467 ◽

Cited By ~ 6

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.

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

Natural Hazards and Earth System Sciences Discussions ◽

10.5194/nhessd-1-1319-2013 ◽

2013 ◽

Vol 1 (2) ◽

pp. 1319-1353 ◽

Cited By ~ 1

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.

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