المؤلفون: Aravantinos-Zafiris, Nikos, Chondrogiannis, Kyriakos Alexandros, id_orcid:0 000-0003-3771-7040, Thomsen, Henrik R., Dertimanis, V.K., Colombi, A., Sigalas, M.M., Chatzi, Eleni, id_orcid:0 000-0002-6870-240X

المصدر: Geophysical Journal International, 238 (1)

مصطلحات موضوعية: Acoustic properties, Guided waves, Seismic attenuation, Site effects, Surface waves and free oscillations, Wave propagation

الوصف: In this work, the propagation and attenuation of vertically polarized surface waves when interacting with terraced slopes is studied experimentally and numerically. To validate the devised simulation, a laboratory-scale physical model is tested in order to examine the attenuation properties of this well-known artificial landform. The experiment involves formation of a terraced slope, in a laboratory setup, via use of an unconsolidated granular medium made of silica microbeads. This granular medium exhibits a gravity-induced power-law stiffness profile, resulting in a depth-dependent velocity profile. A piezoelectric actuator was used to excite vertically polarized surface acoustic modes localized near the surface of the medium. The three components of the particle velocity field of these modes were measured by means of a 3-D laser Doppler vibrometer. In accordance with the terraced slope, a simple inclined plane was further tested to investigate and highlight the differences in terms of wave propagation along these two different ground formations. The results of this research provide significant experimental evidence that the terraced slopes form mechanisms which attenuate low-frequency surface waves, thus acting as metasurfaces. This work suggests the use of laboratory-scale physical models to investigate the wave propagation in different landforms, which extend beyond typical horizontal ground morphologies, and which could be linked to atypical wave propagation properties, possibly even influencing propagation of seismic waves. ; ISSN:0956-540X ; ISSN:1365-246X

وصف الملف: application/application/pdf

العلاقة: info:eu-repo/semantics/altIdentifier/wos/001215584800003; info:eu-repo/grantAgreement/SNF/R'Equip/205418; info:eu-repo/grantAgreement/EC/H2020/813424; info:eu-repo/grantAgreement/EC/H2020/863179; http://hdl.handle.net/20.500.11850/673625Test

الإتاحة: https://doi.org/20.500.11850/67362510.3929/ethz-b-00067362510.1093/gji/ggae150Test
https://hdl.handle.net/20.500.11850/673625Test

المؤلفون: Schade, Malte, Bösch, Cyrill, Hapla, Václav, id_orcid:0 000-0002-9190-2207, Fichtner, Andreas

المصدر: Geophysical Journal International, 238 (1)

مصطلحات موضوعية: Numerical modelling, Computational seismology, Theoretical seismology, Wave propagation, Quantum computing

الوصف: Quantum computing has attracted considerable attention in recent years because it promises speedups that conventional supercomputers cannot offer, at least for some applications. Though existing quantum computers (QCs) are, in most cases, still too small to solve significant problems, their future impact on domain sciences is already being explored now. Within this context, we present a quantum computing concept for 1-D elastic wave propagation in heterogeneous media with two components: a theoretical formulation and an implementation on a real QC. The method rests on a finite-difference approximation, followed by a sparsity-preserving transformation of the discrete elastic wave equation to a Schrödinger equation, which can be simulated directly on a gate-based QC. An implementation on an error-free quantum simulator verifies our approach and forms the basis of numerical experiments with small problems on the real QC IBM Brisbane. The latter produce simulation results that qualitatively agree with the error-free version but are contaminated by quantum decoherence and noise effects. Complementing the discrete transformation to the Schrödinger equation by a continuous version allows the replacement of finite differences by other spatial discretization schemes, such as the spectral-element method. Anticipating the emergence of error-corrected quantum chips, we analyse the computational complexity of the best quantum simulation algorithms for future QCs. This analysis suggests that our quantum computing approach may lead to wavefield simulations that run exponentially faster than simulations on classical computers. ; ISSN:0956-540X ; ISSN:1365-246X

وصف الملف: application/application/pdf

العلاقة: info:eu-repo/semantics/altIdentifier/wos/001229657900001; http://hdl.handle.net/20.500.11850/676079Test

الإتاحة: https://doi.org/20.500.11850/67607910.3929/ethz-b-00067607910.1093/gji/ggae160Test
https://hdl.handle.net/20.500.11850/676079Test

المؤلفون: Aimar, Mauro, Foti, Sebastiano, Cox, Brady R

المساهمون: Aimar, Mauro, Foti, Sebastiano, Cox, Brady R

مصطلحات موضوعية: Elasticity and anelasticity, Fourier analysi, Seismic attenuation, Wave propagation

الوصف: A robust, in situ estimate of shear-wave velocity VS and the small-strain damping ratio DS (or equivalently, the quality factor QS) is crucial for the design of buildings and geotechnical systems subjected to vibrations or earthquake ground shaking. A promising technique for simultaneously obtaining both VS and DS relies on the Multichannel Analysis of Surface Waves (MASW) method. MASW can be used to extract the Rayleigh wave phase velocity and phase attenuation data from active-source seismic traces recorded along linear arrays. Then, these data can be inverted to obtain VS and DS profiles. This paper introduces two novel methodologies for extracting the phase velocity and attenuation data. These new approaches are based on an extension of the beamforming technique which can be combined with a modal filter to isolate different Rayleigh propagation modes. Thus, the techniques return reliable phase velocity and attenuation estimates even in the presence of a multimode wavefield, which is typical of complex stratigraphic conditions. The reliability and effectiveness of the proposed approaches are assessed on a suite of synthetic wavefields and on experimental data collected at the Garner Valley Downhole Array and Mirandola sites. The resultsreveal that, under proper modelling of wavefield conditions, accurate estimates of Rayleigh wave phase velocity and attenuation can be extracted from active-source MASW wavefields over a broad frequency range. Eventually, the estimation ofsoil mechanical parameters also requires a robust inversion procedure to map the experimental Rayleigh wave parameters into soil models describing VS and DS with depth. The simultaneous inversion of phase velocity and attenuation data is discussed in detail in the companion paper.

العلاقة: volume:237; issue:1; firstpage:506; lastpage:524; numberofpages:19; journal:GEOPHYSICAL JOURNAL INTERNATIONAL; https://hdl.handle.net/11583/2987083Test; info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-85185218617; https://academic.oup.com/gji/article/237/1/506/7603994?login=trueTest

الإتاحة: https://doi.org/10.1093/gji/ggae051Test
https://hdl.handle.net/11583/2987083Test
https://academic.oup.com/gji/article/237/1/506/7603994?login=trueTest

المؤلفون: Aimar, Mauro, Foti, Sebastiano, Cox, Brady R

المساهمون: Aimar, Mauro, Foti, Sebastiano, Cox, Brady R

مصطلحات موضوعية: Elasticity and anelasticity, Inverse theory, Wave propagation

الوصف: This paper deals with in situ characterization of the small-strain shear-wave velocity VS and damping ratio DS from an advanced interpretation of Multi-channel Analysis of Surface Waves (MASW) surveys. A new approach based on extracting Rayleigh wave data using the CFDBFa method has been discussed in the companion paper. This paper focuses on mapping the experimental Rayleigh wave phase velocity and attenuation into profiles of VS and DS versus depth, which is achieved through a joint inversion procedure. The joint inversion of phase velocity and attenuation data utilizes a newly developed Monte Carlo global search algorithm, which implements a smart sampling procedure. This scheme exploits the scaling properties of the solution of the Rayleigh eigenvalue problem to modify the trial earth models and improve the matching with the experimental data. Thus, a reliable result can be achieved with a limited number of trial ground models. The proposed algorithm is applied to the inversion of synthetic data and of experimental data collected at the Garner Valley Downhole Array site, as described in the companion paper. In general, inverted soil models exhibit well-defined VS profiles, whereas DS profiles are affected by larger uncertainties. Greater uncertainty in the inverted DS profiles is a direct result of higher variability in the experimental attenuation data, the limited wavelength range at which reliable values of attenuation parameters can be retrieved, and the sensitivity of attenuation data to both DS and VS. Nonetheless, the resulting inverted earth models agree well with alternative in situ estimates and geological data. The results stress the feasibility of retrieving both stiffness and attenuation parameters from activesource MASW testing and the effectiveness of extracting in situ damping ratio estimates from surface wave data.

العلاقة: volume:237; issue:1; firstpage:525; lastpage:539; numberofpages:15; journal:GEOPHYSICAL JOURNAL INTERNATIONAL; https://hdl.handle.net/11583/2987084Test; info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-85185219063; https://academic.oup.com/gji/article/237/1/525/7603992?login=trueTest

الإتاحة: https://doi.org/10.1093/gji/ggae050Test
https://hdl.handle.net/11583/2987084Test
https://academic.oup.com/gji/article/237/1/525/7603992?login=trueTest

المؤلفون: Kennett, Brian L.N., Lai, V.H., Miller, M.S., Bowden, Daniel, id_orcid:0 000-0003-3332-5146, Fichtner, Andreas

المصدر: Geophysical Journal International, 237 (1)

مصطلحات موضوعية: Distributed acoustic sensing, Site effects, Wave propagation, Seismology

الوصف: In the immediate vicinity of a source, there are strong gradients in the seismic wavefield that are tamed and modified in distributed acoustic sensing (DAS) recording due to combined effects of gauge-length averaging and local stacking on the local strain field. Close to a source broadside propagation effects are significant, and produce a characteristic impact on the local DAS channels. In the presence of topography, of surface or cable, additional effects are introduced that modify the expected signal. All these influences mean that the results of tap tests used to calibrate the channel positions along a DAS cable may give a distorted view of the actual geometry. Such effects can be important for detailed mapping of faulting processes and comparable features. ; ISSN:0956-540X ; ISSN:1365-246X

وصف الملف: application/application/pdf

العلاقة: info:eu-repo/semantics/altIdentifier/wos/001172490700002; info:eu-repo/grantAgreement/EC/H2020/821115; http://hdl.handle.net/20.500.11850/662886Test

الإتاحة: https://doi.org/20.500.11850/662886Test
https://doi.org/10.3929/ethz-b-000662886Test
https://doi.org/10.1093/gji/ggae055Test
https://hdl.handle.net/20.500.11850/662886Test

المؤلفون: Franceschina, Gianlorenzo, Tento, Alberto

المساهمون: Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione Milano, Milano, Italia, Retired, CNR - Istituto per la Dinamica dei Processi Ambientali, Milano, Italia

مصطلحات موضوعية: Earthquake ground motions, Seismic attenuation, Site effects, Wave propagation, Wave scattering and diffraction, 04.06. Seismology

الوصف: This article has been accepted for publication in Geophysical Journal International ©:The Author(s) 2023. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.Uploaded in accordance with the publisher's self-archiving policy. All rights reserved. ; Estimation of local seismic response plays a key role in assessing local seismic hazard and particularly in the design of shaking scenarios. Modelling local seismic response involves knowing of the shear wave velocity (Vs) and quality factor (Qs) profiles for the site in question. The many techniques that have been developed to assess Vs in surface deposits produce reliable measurements of Vs , but these rarely correspond to direct measurements of Qs . The latter is often considered through damping measures from laboratory tests on small-scale soil samples, which can provide information primarily on intrinsic attenuation, neglecting the contribution of scattering effects. In this paper, using seismic recordings obtained at the surface and in boreholes at 100 m depth, we estimate an average value of Qs of some characteristic alluvial deposits of the Po Plain (northern Italy). Data come from a microseismic network which sampled an almost uniform lithology in the central Po Plain and consisted of three surface and four borehole stations with an interstation distance of about 2 km. The average value of Qs of the shallowest 100 m of the sedimentary strata, Qs100, is estimated by considering: (1) the high-frequency attenuation of seismic waves due to propagation through the corresponding stratigraphy and (2) the interference between incident and surface-reflected waves observed at borehole stations. We parametrize the first through k0_100, the difference between the values of the spectral decay parameter kappa (k) estimated at the surface and at the boreholes depth, respectively. We use the second in order to compute Vs100, the time-averaged Vs referred to the uppermost 100 m stratigraphy. We obtain: k0_100 = (11 ± 3) ms, ...

العلاقة: Geophysical Journal International; /234 (2023); http://hdl.handle.net/2122/16919Test

الإتاحة: https://doi.org/10.1093/gji/ggad185Test
http://hdl.handle.net/2122/16919Test

المؤلفون: Bergamo, Paolo, id_orcid:0 000-0002-7738-2882, Marano, Stefano, Fäh, Donat

المصدر: Geophysical Journal International, 233 (3)

مصطلحات موضوعية: Elasticity and anelasticity, Joint inversion, Geomechanics, Seismic attenuation, Site effects, Wave propagation

الوصف: The use of surface wave measurements to derive an S-wave velocity profile of the subsurface has become a widely applied procedure; however, their potential use to reconstruct the S-wave material damping properties of the subsoil is generally overlooked, due to the difficulties in obtaining consistent surface wave amplitude information from field data and translating them into robust estimates of the dissipative properties of the near-surface. In this work, we adapt a wavefield decomposition technique for the processing of elastic surface wave data to the extraction of the complete set of properties of Rayleigh waves generated by a controlled source and propagating in dissipative geomaterials. Retrieved information includes multimodal phase velocity and ellipticity as well as the frequency-dependent attenuation coefficient. We exploit the key advantages of wavefield decomposition processing (joint interpretation of multicomponent recordings, coupled estimation of wave propagation parameters, modelling of multiple superimposing modes) to maximize the robustness of the retrieval of Rayleigh wave properties, especially of the dissipative ones. For the subsequent interpretation of Rayleigh wave dispersion, ellipticity and attenuation data we implement a joint Monte Carlo inversion yielding a coupled estimate of S-wave velocity and damping ratio profile for the subsurface; we incorporate a series of geophysical constraints to narrow down the searched parameter space to realistic soil models. We apply this processing and inversion scheme to a bespoke synthetic data set and to a field survey for the characterization of a strong motion station; in both cases, we succeed in retrieving Rayleigh wave multimodal dispersion, ellipticity and attenuation curves. From the inversion of data from the simulated seismogram we are able to reconstruct the properties of the synthetic model. As for the real case, we determine an S-wave velocity and damping ratio model for the soil column below the station, through which we are able to ...

وصف الملف: application/application/pdf

العلاقة: info:eu-repo/semantics/altIdentifier/wos/000926945200003; http://hdl.handle.net/20.500.11850/602524Test

الإتاحة: https://doi.org/20.500.11850/602524Test
https://doi.org/10.3929/ethz-b-000602524Test
https://doi.org/10.1093/gji/ggad010Test
https://hdl.handle.net/20.500.11850/602524Test

المؤلفون: Fichtner, Andreas, Hofstede, Coen

المصدر: Geophysical Journal International, 233 (1)

مصطلحات موضوعية: Inverse theory, Tomography, Seismic instruments, Theoretical seismology, Wave propagation

الوصف: We present a basic algorithm for optimal experimental design in distributed fibre-optic sensing. It is based on the fast random generation of fibre-optic cable layouts that can be tested for their cost-benefit ratio. The algorithm accounts for the maximum available cable length, lets the cable pass through pre-defined points of interest, avoids obstacles that the cable must not traverse, permits the adaptation of geometric complexity of different cable segments and allows for the incorporation of topography. Furthermore, the algorithm can be combined with arbitrary measures of the cost-benefit ratio, and its simplicity enables easy adaptations to the needs of specific applications. In addition to a description of the basic concept, we provide examples that illustrate the circumnavigation of obstacles, the steering of geometric complexity and the cable layout optimization in the presence of topographic variations. ; ISSN:0956-540X ; ISSN:1365-246X

وصف الملف: application/application/pdf

العلاقة: info:eu-repo/semantics/altIdentifier/wos/000894238900009; http://hdl.handle.net/20.500.11850/588742Test

الإتاحة: https://doi.org/20.500.11850/588742Test
https://doi.org/10.3929/ethz-b-000588742Test
https://doi.org/10.1093/gji/ggac458Test
https://hdl.handle.net/20.500.11850/588742Test

المؤلفون: Giammarinaro, Bruno, Tsarsitalidou, Christina, Hillers, Gregor, de Rosny, Julien, Seydoux, Léonard, Catheline, Stefan, Campillo, Michel, Roux, Philippe

المساهمون: Institute of Seismology, Department of Geosciences and Geography, Helsinki Institute of Urban and Regional Studies (Urbaria)

مصطلحات موضوعية: 114 Physical sciences, WAVE PROPAGATION, Surface waves, 1171 Geosciences, SEISMIC INTERFEROMETRY, SEISMIC NOISE, Numerical modelling, Body waves, Surface waves and free oscillations, Refocusing, Focal spot, GREENS-FUNCTION, CROSS-CORRELATION, PASSIVE ELASTOGRAPHY, CRUSTAL STRUCTURE, NOISE CORRELATION, FAULT ZONE, RETRIEVAL, TOMOGRAPHY, WESTERN, ARRAY

الوصف: Numerical experiments of seismic wave propagation in a laterally homogeneous layered medium explore subsurface imaging at subwavelength distances for dense seismic arrays. We choose a time-reversal approach to simulate fundamental mode Rayleigh surface wavefields that are equivalent to the cross-correlation results of three-component ambient seismic field records. We demonstrate that the synthesized 2-D spatial autocorrelation fields in the time domain support local or so-called focal spot imaging. Systematic tests involving clean isotropic surface wavefields but also interfering body wave components and anisotropic incidence assess the accuracy of the phase velocity and dispersion estimates obtained from focal spot properties. The results suggest that data collected within half a wavelength around the origin is usually sufficient to constrain the used Bessel functions models. Generally, the cleaner the surface wavefield the smaller the fitting distances that can be used to accurately estimate the local Rayleigh wave speed. Using models based on isotropic surface wave propagation we find that phase velocity estimates from vertical-radial component data are less biased by P-wave energy compared to estimates obtained from vertical-vertical component data, that even strong anisotropic surface wave incidence yields phase velocity estimates with an accuracy of 1 per cent or better, and that dispersion can be studied in the presence of noise. Estimates using a model to resolve potential medium anisotropy are significantly biased by anisotropic surface wave incidence. The overall accurate results obtained from near-field measurements using isotropic medium assumptions imply that dense array seismic Rayleigh wave focal spot imaging can increase the depth sensitivity compared to ambient noise surface wave tomography. The analogy to elastography focal spot medical imaging implies that a high station density and clean surface wavefields support subwavelength resolution of lateral medium variations. ; Peer reviewed

وصف الملف: application/pdf

العلاقة: Giammarinaro , B , Tsarsitalidou , C , Hillers , G , de Rosny , J , Seydoux , L , Catheline , S , Campillo , M & Roux , P 2023 , ' Seismic surface wave focal spot imaging : numerical resolution experiments ' , Geophysical Journal International , vol. 232 , no. 1 , pp. 201–222 . https://doi.org/10.1093/gji/ggac247Test; ORCID: /0000-0003-2341-1892/work/120379680; ORCID: /0000-0001-9968-1915/work/120381032; bb08a9ef-7712-45df-a825-f600bafe1f31; http://hdl.handle.net/10138/349637Test; 000863420800001

الإتاحة: http://hdl.handle.net/10138/349637Test

المؤلفون: Kästle, Emanuel, Molinari, Irene, Boschi, Lapo, Kissling, Edi, AlpArray Working Group

المساهمون: Institute for Geological Sciences, Freie Universität Berlin, Germany, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione Bologna, Bologna, Italia, Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Bologna, Italy, Dipartimento di Geoscienze, Universitá degli Studi di Padova, Italy, Institut des Sciences de la Terre Paris, Sorbonne Université, CNRS-INSU, ISTeP UMR 7193, F-75005 Paris, France, Department of Earth Sciences, ETH Zürich, Switzerland, www.alparray.ethz.ch

مصطلحات موضوعية: Seismic anisotropy, Seismic interferometry, Seismic tomography, Wave propagation, Continental tectonics: compressional, 04.01. Earth Interior, 04.06. Seismology

الوصف: This article has been accepted for publication in Geophysical Journal International ©: The Authors 2021. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy. ; Ambient-noise records from the AlpArray network are used to measure Rayleigh wave phase velocities between more than 150,000 station pairs. From these, azimuthally anisotropic phase-velocity maps are obtained by applying the Eikonal tomography method. Several synthetic tests are shown to study the bias in the Ψ2 anisotropy. There are two main groups of bias, the first one caused by interference between refracted/reflected waves and the appearance of secondary wavefronts that affect the phase travel-time measurements. This bias can be reduced if the amplitude field can be estimated correctly. Another source of error is related to the incomplete reconstruction of the travel-time field that is only sparsely sampled due to the receiver locations. Both types of bias scale with the magnitude of the velocity heterogeneities. Most affected by the spurious Ψ2 anisotropy are areas inside and at the border of low-velocity zones. In the isotropic velocity distribution, most of the bias cancels out if the azimuthal coverage is good. Despite the lack of resolution in many parts of the surveyed area, we identify a number of anisotropic structures that are robust: in the central Alps, we find a layered anisotropic structure, arc-parallel at midcrustal depths and arc-perpendicular in the lower crust. In contrast, in the eastern Alps, the pattern is more consistently E-W oriented which we relate to the eastward extrusion. The northern Alpine forleand exhibits a preferential anisotropic orientation that is similar to SKS observations in the lowermost crust and uppermost mantle. ; German Science Foundation (SPP-2017, Project Ha 2403/21-1); Swiss National Science Foundation SINERGIA Project CRSII2-154434/1 (Swiss-AlpArray); Progetto Pianeta Dinamico, ...

العلاقة: Geophysical Journal International; 1/229 (2022); http://hdl.handle.net/2122/15034Test

الإتاحة: https://doi.org/10.1093/gji/ggab453Test
http://hdl.handle.net/2122/15034Test