Rayleigh Wave Dispersion Research Articles

Relationship Between TEC Perturbations and Rayleigh Waves Associated With 2023 Turkey Earthquake Doublet

AbstractAn earthquake doublet occurred in Turkey on 6 February 2023, with propagating Rayleigh waves triggering perturbations in the ionospheric total electron content (TEC) for both the M 7.8 earthquake (EQ7.8) and the M 7.5 earthquake (EQ7.5). A discrepancy between the velocities of TEC perturbations and Rayleigh waves has been noted, but its causes remain unresolved in previous studies. In this study, we calculated the velocities of TEC perturbations and the frequency‐dependent velocities of Rayleigh waves, considering their intrinsic dispersive characteristics. To retrieve TEC, we utilized ground‐based Global Navigation Satellite System (GNSS) data from geostationary Earth orbit (GEO) satellites to mitigate the effects of moving ionospheric pierce points (IPPs) from orbiting satellites. The results reveal that the velocities of TEC perturbations (2.60 km/s for EQ7.8 and 2.77 km/s for EQ7.5) do not align with the velocities of Rayleigh waves across the entire frequency band (2.4–3.0 km/s for EQ7.8 and 2.6–3.5 km/s for EQ7.5). However, they are comparable within specific periods of 10–30 s due to dispersion effects for both EQ7.8 and EQ7.5. The dispersive Rayleigh waves, which exhibit significant amplification in the 10–30 s period range, are identified as the primary source of the pronounced coseismic TEC perturbations, particularly for EQ7.5.

Attenuation effects of seismic metamaterials based on local resonance and Rayleigh wave dispersion phenomena

Attenuation effects of seismic metamaterials based on local resonance and Rayleigh wave dispersion phenomena

Seismic Site Characterization and Region-Specific Seismic Site Parameter Relationships of Essex County, Ontario, Canada

Abstract We perform a multimethod in situ seismic field campaign to assess variability in local site conditions throughout Essex County, Ontario, Canada. Fundamental peak frequencies (f0HV) determined at 86 sites from microtremor horizontal-to-vertical spectral ratios (MHVSRs) increase southward from Windsor (∼1.7 Hz) to Amherstburg (>4 Hz) and eastward within Amherstburg (up to 17 Hz). We determine similar VS for individual subsurface layers at the 11 array sites from constrained shear wave velocity (VS) depth (z) profiles obtained by joint inversion of the site’s fundamental-mode Rayleigh-wave dispersion curve and f0HV. This indicates that the spatial variation in f0HV is driven primarily by the resonator depth, which shallows southward. We compile our 11 noninvasive VS depth profiles with an additional 86 VS profiles from previous invasive field testing, to develop a VS–depth relationship for Essex County’s postglacial sediments. Use of most other VS–z relationships available in eastern Canada underpredict the fundamental site frequency in Essex County because the average VS typical of those regions is lower. We find that the velocities for Montreal and Charlevoix (Canada) are closest to the velocities of our study area and consistent with Holocene alluvium deposits in the U.S. Geological Survey national crustal model. Compilation of in situ measurements at 172 sites throughout Essex County enables determination of three region-specific predictive relationships of important seismic site characterization metrics that are applied to generate regional seismic microzonation maps.

Full-parametric and joint inversion of multimode surface wave data for identifying glacial ice thickness and freezing extent in subglacial sediments via the hunger games search algorithm

Determining glacier ice thickness and the extent of freezing in subglacial sediments are crucial in glaciological studies. Noninvasive geophysical methods, such as multichannel analysis of surface waves, are typically used for these tasks. In this study, we introduce a novel metaheuristic called hunger games search (HGS), which simulates the hunger-driven instincts and behavioral decisions of animals for the full-parametric inversion of seismic surface waves. We apply HGS to determine layer thicknesses, densities, S-wave velocities, and primary wave velocities of different layers through the joint inversion of multimode Rayleigh wave dispersion curves (RWDCs). This marks the first study using HGS for the inversion of dispersion data. Sensitivity studies of model parameters prior to the inversion indicate the necessity of postinversion uncertainty evaluations to mitigate the effects of varying sensitivity levels. In addition, a parameter tuning study is carried out to maximize the performance of HGS. Compared with some swarm intelligence-based optimizers (particle swarm optimization, cuckoo search, gray wolf optimization, sparrow search optimization, and whale optimization algorithm), HGS outperforms in the inversion of synthetic multimode RWDCs with 10% uncertainties with respect to a simulated glacier structure. In real data applications, a data set acquired at Midtdalsbreen, an outlet of the Norwegian Hardangerjøkulen ice cap, is inverted using the tailored HGS metaheuristic. The results obtained are consistent with previous geophysical studies. Furthermore, our analysis reveals that the performance of HGS when dealing with real applications is not highly sensitive to the selection of layers within the range of five to eight. The accuracy of HGS is undoubtedly contaminated by a larger model space; however, additional depth information derived from colocated ground-penetrating radar data can be directly integrated into HGS to obtain satisfactory results again.

Using Crustal-Scale Refraction Data for Joint Inversions of Rayleigh-Wave Dispersion Curves and H/V Spectral Ratios for Atlantic Coastal Plain Velocity Structure, Eastern United States

ABSTRACT Shallow shear-wave velocities (VS) sometimes are estimated from joint inversions of horizontal-to-vertical (H/V) spectral ratios and surface-wave dispersion curves derived from ambient noise or small active sources. Here, we evaluate carrying out these inversions using Rayleigh-wave dispersion curves computed from crustal-scale P-wave seismic refraction data. We use data from the 2014–2015 Eastern North American Margin (ENAM) experiment in Virginia and North Carolina, but similar seismic refraction data sets have been acquired over sedimentary basins of interest for seismic hazard studies, including in major urban areas. The ENAM project deployed a pair of ∼215 km long, northwest–southeast linear arrays with ∼300 m receiver spacing to record 11 dynamite shots, and 80 continuously recording seismometers with 5–6 km spacing along the same arrays to record offshore airguns. The arrays crossed the onland portion of the Atlantic Coastal Plain sediments, which are a seaward-thickening wedge of Cretaceous and younger sediments deposited mostly on crystalline bedrock. We compute Rayleigh-wave dispersion curves from 3 to 9 km long portions of the receiver arrays on each side of the dynamite shots, and we compute ambient-noise H/V ratios from the continuously recording seismometers. We use a genetic inversion algorithm in which forward velocity models in each “generation” are evaluated for misfits compared to the observed data, with subsequent generations constructed from the models with the smallest misfits. Velocities to depths of 500 m are defined well, as shown by a narrow range of velocities in the best-fit models, by the consistency between multiple inversion runs at a site, and by forward modeling of site responses. The resulting velocity cross-section of the Coastal Plain strata has seaward-dipping contours in the thinner portions of the Coastal Plain but smaller dips in the deeper portions. We interpret these results as showing that velocity contours in the ACP strata are influenced by a combination of lithology and overburden pressure. Results demonstrate that existing seismic refraction data have the potential for determining detailed shallow shear-wave velocity profiles.

Nonlinear joint inversion of Rayleigh and Love wave dispersion curves based on Pearson correlation coefficient and thickness mean sharing

AbstractThe joint inversion of Rayleigh and Love waves plays a crucial role in mitigating the non‐uniqueness of surface wave inversion results and enhancing the stability of these inversions. Existing approaches to the joint inversion of Rayleigh and Love wave dispersion curves, which rely on conventional objective functions, often struggle with complex stratigraphic configurations and yield results of limited accuracy. This study introduces two novel nonlinear joint inversion techniques for Rayleigh and Love waves: Pearson correlation coefficient and thickness mean sharing. The Pearson correlation coefficient approach employs the Pearson correlation coefficient and alternating iterative objective functions to synchronize the shear wave velocity structures derived from Rayleigh and Love waves, thereby enhancing the accuracy of the joint inversion. Conversely, the thickness mean sharing method computes an average of the thickness values obtained in each iteration of the inversion, utilizing the traditional joint inversion objective function. Tests on three distinct stratigraphic structures—characterized by increasing velocity, high‐speed hard interlayers and low‐speed soft interlayers—as well as on measured data, demonstrate that the proposed methods significantly improve the stability and accuracy of nonlinear joint inversion.

Research on the Influence of Surface Wave Dispersion Curve in Anisotropic Viscoelastic Media

Abstract Surface-wave dispersion curve inversion of S-wave velocity structure is one of the primary methods for revealing near-surface structures. However, near-surface structures have large anisotropy and strong attenuation characteristics. Previous studies have investigated that surface anisotropy and sediment attenuation parameters significantly impact the extraction of dispersive information. Quantitatively assessing the sensitivity of different parameters can provide a reference for accurate inversion of S-wave velocity. In this abstract, we utilize a 2-D VTI viscoelastic finite-difference method to simulate the propagation characteristics and dispersion features of Rayleigh wave in anisotropic and viscoelastic media. Then, we use the typical synthetic model to analyze the sensitivity of Rayleigh wave dispersion curves to viscoelastic and anisotropic parameters. The conclusion is that the anisotropic and attenuation parameters cause significant changes in the surface-wave phase velocity, and the viscoelasticity can cause the amplitude attenuation of the Rayleigh wave. The sensitivity of dispersion curves to anisotropic parameters is greater than that of viscoelastic parameters.

Estimation of dispersion and attenuation of Rayleigh waves in viscoelastic inhomogeneous layered half-space based on spectral method

Estimation of dispersion and attenuation of Rayleigh waves in viscoelastic inhomogeneous layered half-space based on spectral method

Dispersion and ellipticity of Rayleigh waves in a soil substrate supporting resonant beams and plates

Dispersion and ellipticity of Rayleigh waves in a soil substrate supporting resonant beams and plates

Seismic structure of Iceland revealed by ambient noise Rayleigh wave tomography

As it is an ideal location for studying plume–ridge interactions, a clear image of the Icelandic upper mantle structure is necessary. We collect continuous seismic records from 164 stations and extract Rayleigh wave dispersion curves via the frequency-Bessel (F-J) transform method. Based on ambient noise tomography, we provide a new shear-wave velocity model of the Icelandic crust and uppermost mantle, extending to a depth of 120 km. The model is validated by the waveform simulation method and reveals extensive crustal low-velocity zones (LVZs) across both the neovolcanic and nonvolcanic zones of Iceland. These crustal LVZs may be attributed to elevated temperatures, partial melting, and lithological variations. A distinct LVZ beneath a depth of 60 km, mainly on the North American Plate, may correspond to Icelandic plume material. Additionally, hot plume material may be delivered to the crust through low-velocity conduits beneath the spreading mid-ocean ridge. There is a clear contrast between the uppermost mantle low-velocity zones (UMLVZs) in the western region and the uppermost mantle high-velocity zones in the eastern region, which may indicate asymmetric tectonic plates on both sides of the mid-ocean ridge. This asymmetry may be attributed to the multiple eastward jumps of the ridge systems. The eastern high-velocity body, meaning a cooler uppermost mantle than that of the western region, may act as a barrier to obstruct the eastward plume flow. Under plume–ridge interactions, plume material can affect crustal accretion and feed volcanic activity on the surface along the spreading Mid-Atlantic Ridge.

Subsurface anomaly assessment in asphalt layers using Rayleigh waves dispersion characteristics: a test-pit study

ABSTRACT Any subsurface anomaly present in asphalt pavement layers may lead to their localised progressive structural failure. The detrimental effects of such anomalies are not visible on the top surface in the early stages. It may cause a major cost escalation if gone unnoticed during construction or maintenance works. Hence, there is a need for their quick and reliable detection and assessment. Present study explores the non-destructive assessment of subsurface anomalies (such as void/buried utility, etc.) in asphalt layers. This work developed a simple experimental approach using the two-receiver Spectral Analysis of Surface Waves (SASW) method to generate the experimental dispersion curves (EDC) whose shape characteristics are utilised for the detection, location, and identification of subsurface anomalies. An in-situ asphalt pavement test-pit facility was developed consisting of a number of different sub-sections with various anomaly conditions. A test system utilising high-frequency accelerometers was custom-integrated for such assessments. Based on the EDC shape characteristics, a direct information extraction technique was developed which does not require backcalculation procedures. The study found the proposed technique to be reasonably applicable for a quick, non-destructive detection and assessment of the subsurface anomalies. Further extensive testing with different profiles, anomalies, and test conditions will help in further acceptance of this simple approach.

Translithospheric magma plumbing system fossilized in the Emeishan large igneous province

Lighting up the magma plumbing system beneath a large igneous province (LIP) is challenging because the complex magma migration paths are often covered by flood basalts and sediments. Here, we present a three-dimensional seismic image of the Permian Emeishan LIP in Southwest China, constructed by joint inversion of Rayleigh wave dispersions and receiver functions. The results outline a cylindrical, high-velocity anomaly extending to ~135 km depth below the inner zone of this continental LIP. The geometry and magnitude of the high-velocity anomaly suggest that it represents culminated crystallized materials of primary magmas, thereby mirroring a magma plumbing system fossilized in the lithosphere. Furthermore, our geodynamic models illustrate that the nearly vertical plumbing system was controlled by slow plate motion during the magma emplacement. The plume head beneath a nearly static plate has higher thermal buoyancy and thus promotes more intensive magma emplacement. This phenomenon may apply to other LIPs throughout Earth’s history

Characterization of Shallow Sedimentary Layers in the Oran Region Using Ambient Vibration Data

This study investigates the structure of shear-wave velocities (Vs) in the shallow layers of the Oran region, north-west of Algeria, using non-invasive techniques based on ambient vibration arrays. The region has experienced several moderate earthquakes, including the historical Oran earthquake of 1790. Ambient vibration measurements were carried out at 15 sites throughout the study area. Two methods were used: spatial autocorrelation (SPAC) and frequency–wavenumber analysis (f-k), which allowed us to better constrain Rayleigh wave dispersion curves. The inversion of the dispersion curves derived from the f-k analysis allowed for estimating the shear-wave velocity profiles and the Vs30 value at the sites under study. The other important result of the present study is an empirical equation that has been proposed to predict Vs30 in the Oran region. The determination of near-surface shear-wave velocity profiles is an important step in the assessment of seismic hazard. This study has demonstrated the effectiveness of using ambient vibration array techniques to estimate the soil Vs structure.

Seismic Azimuthal Anisotropy Beneath the Alaska Subduction Zone

AbstractWe estimate depth‐dependent azimuthal anisotropy and shear wave velocity structure beneath the Alaska subduction zone by the inversion of a new Rayleigh wave dispersion dataset from 8 to 85 s period. We present a layered azimuthal anisotropy model from the forearc region offshore to the subduction zone onshore. In the forearc crust, we find a trench‐parallel pattern in the Semidi and Kodiak segments, while a trench‐oblique pattern is observed in the Shumagins segment. These fast directions agree well with the orientations of local faults. Within the subducted slab, a dichotomous pattern of anisotropy fast axes is observed along the trench, which is consistent with the orientation of fossil anisotropy generated at the mid‐ocean ridges of the Pacific‐Vancouver and Kula‐Pacific plates that is preserved during subduction. Beneath the subducted slab, a trench‐parallel pattern is observed near the trench, which may indicate the direction of mantle flow.

On the Origin of the Hawaiian Swell: Lithosphere and Asthenosphere Seismic Structure From Rayleigh Wave Dispersion

AbstractIn this study, we revisit the shear‐wave velocity structure of the lithosphere and asthenosphere surrounding the Hawaiian hotspot and Hawaiian swell using Rayleigh wave data spanning periods of 20–125 s from the PLUME project. A primary goal of this investigation is to probe the origin of the Hawaiian swell and the mechanism that elevates the topography, providing insights into mantle dynamics beneath hotspot swells. In the shear velocity model, the 30–70 km depth range is largely featureless with weak and local anomalies, indicating that the elevation of the Hawaiian swell cannot be attributed to upper lithospheric reheating or replacement. In contrast, at 80–150 km depth, a pronounced region of anomalously low velocities is well‐resolved, with the lowest velocities found beneath the Hawaii‐Maui‐Molokai part of the island chain. Minimum shear velocities are approximately 4.0 km/s at 100–120 km depth, which is an ∼8%‐10% velocity decrease relative to the surrounding velocities away from the swell. This pattern suggests that hot, buoyant mantle from deeper plume sources laterally spread out near the top of the normal oceanic asthenosphere. We find that the low‐velocity pattern in the asthenosphere exhibits a strong correlation with the overall shape of the Hawaiian swell topography. Assuming that density anomalies are proportional to shear velocity anomalies, we demonstrate that the anomalous elevation of the swell can be explained by the uplift of a 30‐km‐thick elastic plate loaded from below by this buoyant, low‐seismic‐velocity layer in the asthenosphere.

Two Effective Degrees of Freedom Can Represent the Dominant Features of Global Rayleigh Wave Dispersion Maps

AbstractObjectively exploring global variations in crust and upper mantle structure helps constrain fundamental aspects of Earth's plate tectonic and convective processes. Here we adopted a Variational Auto‐Encoder to explore the degrees of freedom of global Rayleigh wave dispersion maps at 4–40 mHz. We found that two latent variables sufficiently represent the global variations, suggesting inherent coupling between crustal and mantle seismic properties. We propose that the two extracted latent variables mostly correspond with crustal thickness and upper mantle thermal structure. The first variable shows low values for continental mountain belts and ocean spreading ridges, contrasted by high values for abyssal plains. The second variable shows low values for most oceanic lithosphere and Phanerozoic continental areas, contrasted by high values for Archean cratons. Latent space correlations indicate that continental lithosphere has more strongly coupled depth features than beneath the oceans, which might be a consequence of its longevity.

Computation and analysis of surface wave dispersion and attenuation in layered viscoelastic-vertical transversely isotropic media by the generalized R/T coefficient method

SUMMARY In this study, we propose a systematic and effective method, that is, an extended version of the generalized reflection/transmission (R/T) coefficient method, for computing the phase-velocity (${c}_r$) dispersion curves, attenuation coefficient ($\alpha $) curves, and eigenfunctions of both Rayleigh and Love waves as well as the ellipticity of Rayleigh waves in layered viscoelastic-vertical transversely isotropic (VTI) media. The numerical scheme of combining the root-searching method with the local optimization method is designed for determining the complex-valued modal solutions (i.e. complex wavenumber $k = {\omega {/ {\vphantom {\omega {{c}_r - i\alpha }}}} {{c}_r - i\alpha }}$) of surface waves. The near-surface sedimentary geological environment is taken as the model example because it is typical viscoelastic-VTI media. Besides the anisotropic-viscoelastic (AV) media, our algorithm can also compute surface waves in isotropic-elastic (IE), isotropic-viscoelastic (IV) and anisotropic-elastic (AE) media by resetting the corresponding parameters. Using the six-layer half-space models and in these four media, we verify the correctness of our algorithm by benchmarking the modal solutions against those from other methods. In the four-layer half-space model, by comparing the results of IE, IV, AE and AV media, we analyse the effects of velocity anisotropy, viscoelasticity and attenuation anisotropy on the dispersion and attenuation characteristics of both Rayleigh and Love waves in detail. Our study can provide a theoretical basis and useful tool for surface wave imaging considering the anisotropy and/or viscoelasticity of the medium, which has the potential to better investigate the solid Earth's internal structure.

Research and application of Rayleigh wave imaging based on the Born–Jordan time‐frequency distribution

AbstractCurrently, the horizontal resolution of Rayleigh wave exploration is low. In this study, we propose the Born–Jordan time‐frequency distribution to analyse Rayleigh waves. The seismic signal was filtered with a wavelet transform for denoising, and the Rayleigh wave was separated in the time domain. Using the Born–Jordan time‐frequency distribution, the time waveform of each frequency comprising the Rayleigh wave from every seismic channel was obtained, and the time difference of the Rayleigh wave with the same frequency was calculated, based on which the dispersion curve between the two channels was obtained. Combined with the multichannel Rayleigh wave dispersion curve, phase velocity and frequency imaging under the seismic arrangement were obtained. Applying this method to detect abnormal geological bodies in engineering investigations showed that hard geologic bodies, such as comcrete rocks, have high velocity and frequency, whereas weak ones have low velocity and frequency. This strategy facilitated the detection of fractured zones, underground goafs and obstacles during pipe‐jacking construction near the surface.

Lithospheric Evolution of the South‐Central United States Constrained by Joint Inversion of Receiver Functions and Surface Wave Dispersion

AbstractIn the present study, we use broadband seismic data recorded by 190 stations of the EarthScope program's Transportable Array to construct a 3‐D shear wave velocity model for the upper 180 km using a non‐linear Bayesian Monte‐Carlo joint inversion of receiver functions (RFs) and Rayleigh wave dispersion curves. Ambient noise and teleseismic data are used for obtaining Rayleigh wave phase velocity dispersion curves. A resonance removal filtering technique is applied to the RFs contaminated by reverberations from the thick sedimentary layers that cover most of the region. Our observations of the higher crustal shear velocities (∼3.40 km/s) beneath the Sabine Block (SB), along with the estimated relatively thicker crust (∼34.0 km) and lower crustal Vp/Vs estimates (∼1.80) in comparison with the rest of the Gulf Coastal Plain (GCP) (∼3.10 km/s for crustal shear velocities, ∼29.0 km for crustal thickness, and ∼1.90 for crustal Vp/Vs estimates), indicating that this crustal block has different crustal properties from the surrounding coastal plain regions. The southern Ouachita Mountains have a thin crust (∼30.0 km) and low mean crustal Vp/Vs value (∼1.73), suggesting that lower crustal delamination has occurred in this region. Low velocities in the upper mantle beneath most of the GCP are interpreted as a combined result of thin lithosphere, higher‐than‐normal temperatures, and possibly compositional variations.

Near-Surface Rayleigh Wave Dispersion Curve Inversion Algorithms: A Comprehensive Comparison

Near-Surface Rayleigh Wave Dispersion Curve Inversion Algorithms: A Comprehensive Comparison