Shear-wave Profiles Research Articles

Seismic site classification based on constrained modeling of measured HVSR curve in regolith sites

Seismic site classification is the most widely accepted practical method in the design of seismic resistant infrastructure. The horizontal vertical spectral ratio (HVSR) technique for analyzing ambient noise data has been successfully applied to quantify site effects in the estimation of seismic site classes associated with seismic hazards. This successful application was mainly carried out in high impedance contrast sites. The present paper focuses on the application of the HVSR technique to regolith sites which were suggested by previous studies to be low in impedance contrast between the upper and underlying bedrock layers (< 4–5). A case study is examined which explores the central business district of Adelaide, South Australia and incorporates 10 in situ ambient noise measurements carried out across the city. Adelaide experienced more medium-sized earthquakes than any other capital city in Australia in the past half of the last century. Site amplification was also observed to occur in Adelaide. Ambient noise data were used to estimate the site predominant period and to infer the site shear wave profile, after establishing that the data were free from noises from an industrial source, checking the reliability of the HVSR ellipticity curve and validating the appropriateness of the adopted method and resulting shear wave models. The results show that the predominant fundamental period for Adelaide is 0.8s or higher, which suggests a subsoil class D according to the Australian Standard. Results of the inversion for the upper 30m shear wave velocities of Adelaide's subsoil layers varies from 194m/s to 418m/s, which are related to classes D to C (NEHRP classification system), classes D to B (Australian Standard classification system) or classes D/DE to C (regolith case classification system). These results are in a good agreement with several previous studies. This suggests a promising application of the HVSR analysis for seismic assessment at regolith sites.

Variability of Liver Shear Wave Measurements Using a New Ultrasound Elastographic Technique.

A new 2-dimensional (2D) shear wave elastographic (SWE) device has been developed for the noninvasive assessment of liver fibrosis. Guidelines on measurement acquisition parameters are not yet well established for this technique. Our study aimed to assess 2D SWE measurement variability and to determine the number of measurements required per patient to reliably assess liver stiffness. Two-dimensional SWE was assessed in 55 patients with mixed-etiology chronic liver disease on an Aplio 500 ultrasound system (Toshiba Medical Systems Corporation, Tochigi, Japan). Ten measurements were obtained per patient by an operator blinded to all preceding readings. Results were analyzed with clinical information obtained from medical records. The median interquartile range/median ratio for 2D SWE was 0.131 (quartiles 1-3, 0.089-0.174). Five readings provided an approximation within 0.11 m/s, or 4.2% of the median velocity of 10 measurements. Factors associated with increased measurement variability included body mass index (ρ = 0.388; P = .01), increased skin-to-liver capsule distance (ρ = 0.426; P = .002), and measurements taken within 1.5 cm of the liver capsule (P < .001). Measurements with heterogeneous shear wave profiles (indicated by a region of interest [ROI] SD/speed ratio > 0.15) showed greater deviation from the set's median velocity than those with an ROI SD/speed ratio of 0.15 or lower (0.42 versus 0.22 m/s; P = .001). Two-dimensional SWE showed low overall measurement variability, with a minimum of 5 readings providing equivalent precision to the existing method using 10 samples. Obesity, increasing abdominal wall thickness, subcapsular measurements and an ROI SD/speed ratio of greater than 0.15 were all associated with increased measurement variability. The ROI SD/speed ratio warrants further evaluation as a quality assessment metric, to allow objective operator assessment of individual 2D SWE measurement reliability in real time.

The river harbour of Ostia Antica - stratigraphy, extent and harbour infrastructure from combined geophysical measurements and drillings

We performed a combined geophysical and geoarchaeological survey of the harbour of ancient Ostia, Italy, to investigate the extent of the former harbour basin, the sedimentary infill and possible building remains around the harbour. Besides geoarchaeological results the paper highlights the advantage of combining vibracore drilling with different geophysical prospection methods, which are sensitive to different physical soil parameters. Geophysical methods applied were electrical resistivity tomography (ERT), ground penetrating radar (GPR) and seismics with shear and compressional waves. The extent and shape of the harbour basin were determined by ERT profiling. The ERT profiles were compiled into a 3D-model showing that the early lagoonal harbour basin was at least 100 m × 50 m wide. Its southern border was confirmed by GPR measurements clearly imaging the former land-water transition and the onset of ancient onshore building construction. At its eastern border a consolidated horizon could be mapped in 2–3 m depth by compressional wave tomography. This horizon most likely represents a cemented ramp, a small part of which had been excavated in a previous study. The sedimentary fill of the former harbour basin was investigated by a combination of vibracoring, ERT and seismics. The ERT profiles serve for inter- and extrapolating the vibracore stratigraphy from the coring locations over the whole harbour area. It turned out that one sedimentary unit, which is important for the harbour development, could not be resolved by ERT but clearly shows up in seismic velocity-depth profiles instead. It is a thin coarse-grained high-energy layer in 1–2 m depth, which was caused by a tsunami according to a previous study. This layer separates two harbour phases: an older lagoonal harbour phase underneath and a younger fluvial harbour phase above it. The high-energy layer represents a thin band of 100% increased shear wave velocity compared to the more fine-grained layers, in which it is embedded. This study is the first to show that tsunami-type sedimentary layers may be mapped by shear wave profiling.

An automatic differentiation-based gradient method for inversion of the shear wave equation in magnetic resonance elastography: specific application in fibrous soft tissues

Quantitative and accurate measurement of in vivo mechanical properties using dynamic elastography has been the scope of many research efforts over the past two decades. Most of the shear-wave-based inverse approaches for magnetic resonance elastography (MRE) make the assumption of isotropic viscoelasticity. In this paper, we propose a quantitative gradient method for inversion of the shear wave equation in anisotropic media derived from a full waveform description using analytical viscoelastic Green formalism and automatic differentiation. The abilities and performances of the proposed identification method are first evaluated on numerical phantoms calculated in a transversely isotropic medium, and subsequently on experimental MRE data measured on an isotropic hydrogel phantom, on an anisotropic cryogel phantom and on an ex vivo fibrous muscle. The experiments are carried out by coupling circular shear wave profiles generated by acoustic radiation force and MRE acquisition of the wave front. Shear modulus values obtained by our MRE method are compared to those obtained by rheometry in the isotropic hydrogel phantom, and are found to be in good agreement despite non-overlapping frequency ranges. Both the cryogel and the ex vivo muscle are found to be anisotropic. Stiffness values in the longitudinal direction are found to be 1.8 times and 1.9 times higher than those in the transverse direction for the cryogel and the muscle, respectively. The proposed method shows great perspectives and substantial benefits for the in vivo quantitative investigation of complex mechanical properties in fibrous soft tissues.

High-resolution shear-wave seismics across the Carlsberg Fault zone south of Copenhagen — Implications for linking Mesozoic and late Pleistocene structures

The Carlsberg Fault zone (CFZ) is a NNW-SSE striking structure close to the transition zone between the Danish Basin and the Baltic Shield. We examine the fault evolution by combining very-high-resolution onshore shear-wave seismic data, one conventional onshore seismic profile and marine reflection seismic profiles. The faulting geometry indicates a strong influence of Triassic subsidence and rifting in the Central European Basin System. Growth strata within the CFZ surrounding Höllviken Graben reveal syntectonic sedimentation in the Lower Triassic, indicating the opening to be a result of Triassic rifting. In the Upper Cretaceous growth faulting documents continued rifting. These findings contrast the Late Cretaceous to Paleogene inversion tectonics in neighboring structures, such as the Tornquist Zone. The high-resolution shear-wave seismic method was used to image faulting in Quaternary and Danian layers in the CFZ. The portable compact vibrator source ElViS III S8 was used to acquire a 1150m long seismic section on the island Amager, south of Copenhagen. The shallow subsurface in the investigation area is dominated by Quaternary glacial till deposits in the upper 5–11m and Danian limestone below. In the shear-wave profile, we imaged the uppermost 30m of the western part of CFZ. The complex fault zone comprises normal block faults and one reverse block fault. The observed faults cut through the Danian as well as the Quaternary overburden. Hence, there are strong indicators for ongoing faulting, like mapped faulting in Quaternary sediments and ongoing subsidence of the eastern block of the CFZ as interpreted by other authors. The lack of earthquakes localized in the fault zone implies that either the frequency of occurring earthquakes is too small to be recorded in the observation time-span, or that the movement of the shallow sub-surface layers may be due to other sources than purely tectonic processes.

4-D ultrafast shear-wave imaging.

Over the last ten years, shear wave elastography (SWE) has seen considerable development and is now routinely used in clinics to provide mechanical characterization of tissues to improve diagnosis. The most advanced technique relies on the use of an ultrafast scanner to generate and image shear waves in real time in a 2-D plane at several thousands of frames per second. We have recently introduced 3-D ultrafast ultrasound imaging to acquire with matrix probes the 3-D propagation of shear waves generated by a dedicated radiation pressure transducer in a single acquisition. In this study, we demonstrate 3-D SWE based on ultrafast volumetric imaging in a clinically applicable configuration. A 32 × 32 matrix phased array driven by a customized, programmable, 1024-channel ultrasound system was designed to perform 4-D shear-wave imaging. A matrix phased array was used to generate and control in 3-D the shear waves inside the medium using the acoustic radiation force. The same matrix array was used with 3-D coherent plane wave compounding to perform high-quality ultrafast imaging of the shear wave propagation. Volumetric ultrafast acquisitions were then beamformed in 3-D using a delay-and-sum algorithm. 3-D volumetric maps of the shear modulus were reconstructed using a time-of-flight algorithm based on local multiscale cross-correlation of shear wave profiles in the three main directions using directional filters. Results are first presented in an isotropic homogeneous and elastic breast phantom. Then, a full 3-D stiffness reconstruction of the breast was performed in vivo on healthy volunteers. This new full 3-D ultrafast ultrasound system paves the way toward real-time 3-D SWE.

Modelling the impulse diffraction field of shear waves in transverse isotropic viscoelastic medium

The generation of shear waves from an ultrasound focused beam has been developed as a major concept for remote palpation using shear wave elastography (SWE). For muscular diagnostic applications, characteristics of the shear wave profile will strongly depend on characteristics of the transducer as well as the orientation of muscular fibers and the tissue viscoelastic properties. The numerical simulation of shear waves generated from a specific probe in an anisotropic viscoelastic medium is a key issue for further developments of SWE in fibrous soft tissues. In this study we propose a complete numerical tool allowing 3D simulation of a shear wave front in anisotropic viscoelastic media. From the description of an ultrasonic transducer, the shear wave source is simulated by using Field’s II software and shear wave propagation described by using the Green’s formalism. Finally, the comparison between simulations and experiments are successively performed for both shear wave velocity and dispersion profile in a transverse isotropic hydrogel phantom, in vivo forearm muscle and in vivo biceps brachii.

Condition Assessment of Cementitious Materials Using Surface Waves in Ultrasonic Frequency Range

Surface waves propagating in a medium provide information about the mechanical properties and condition of the material. Variations in the material condition can be inferred from changes in the surface wave characteristics. Multichannel analysis of surface waves (MASW) is a well-established surface wave method used for determination of the shear-wave profile of the soil layers near the surface. The MASW test configuration is also applicable to assess the condition of construction materials using appropriate frequency range. Previous studies on the detection of surface-breaking cracks in concrete elements, using the dispersion and attenuation of ultrasonic waves, were successful; however, a complete damage assessment of the whole element was not in the scope of these studies. In this study, different wave characteristics, such as Rayleigh wave velocity, wave attenuation, and phase velocity dispersion, are investigated to evaluate their sensitivity to the damage in a medium. The condition of a test specimen, which is a half-space medium made of cement and sand, is evaluated using ultrasonic transducers for different damage cases. The recorded signals are processed using the Fourier and wavelet transforms to determine the surface wave characteristics. A new dispersion index (DI) is introduced, which represents the global correlation between the dispersion of phase velocity and damage level. All features are found to be capable of reflecting the damage in the test medium with different levels of sensitivity. Among the investigated parameters, the proposed dispersion index shows high sensitivity and linear correlation with the damage.

Efficiency of horizontal-to-vertical spectral ratio (HVSR) in defining the fundamental frequency in Muscat Region, Sultanate of Oman: a comparative study

Muscat region is the most important political, economic, and densely populated region in the Sultanate of Oman. The proximity of Muscat region to the Oman Mountains and Makran subduction zones controls the earthquake hazard for Muscat. Evidences indicate the occurrence of a nearby historical earthquake with moderate magnitude M S = 5.5 in 1883. This event led to the damage of some villages near Nizwa City. The main objective of the current study is to compare the site characteristics of the region of interest in terms of the fundamental frequency using microtremors measurements with the numerical analysis results using one-dimensional (1-D) shear wave profiles. The microtremor measurements were performed at 99 sites distributed over the study region in order to calculate the horizontal-to-vertical spectral ratio (HVSR). The numerical modeling of horizontal shear (SH) waves in soil at the selected 99 sites are assessed by carrying out 1-D ground response analysis using the program SHAKE91. The required shear wave velocity profiles for the numerical modeling of SH-waves were derived using multichannel analysis of surface waves profiles. The amplification spectra have been evaluated for the soil column at each site location and the fundamental frequency obtained using SHAKE91 and HVSR are compared. Results were found to be compatible with the general surface geology of the region of interest and in most cases the HVSR is proved to be suitable for calculating the fundamental frequency in Muscat region.

Estimation of site effects in Delhi using standard spectral ratio

Delhi, a city of more than 10 million inhabitants, lies approximately 200km from Main Boundary Thrust (MBT) and 300km from Main Central Thrust (MCT), the two most active thrusts of the Himalayas. The city has a varying soil cover and some parts have thick sediments that can potentially amplify the earthquake shaking. Estimates of site effect in Delhi using the standard spectral ratio technique are available only at few locations and significantly differ from those computed from shear-wave profiles inferred from bore-hole penetration tests. Site effects have also been estimated in Delhi theoretically as well as using microtremor studies, yet their knowledge is significantly inadequate to assess true nature of ground amplification.In the present work, site amplification is estimated at 55 different sites in Delhi using data from 13 different earthquakes using the standard spectral ratio method. The site IMD Ridge (NDI) is taken as the reference site on the basis of local geology. The results show significant variations in amplification factor from one place to another. Higher amplification is observed at both banks of Yamuna river. There are some sites, where less or no amplification is observed. The predominant frequency is in general found to be lower near Yamuna banks than the other sites. Based on the observations, we also present an amplification map of the city.

Seismic property characterization of lithotypes cropping out in the Siracusa urban area, Italy

The town of Siracusa is located in the south-eastern coast of Sicily (southern Italy) in a wide inlet engraved into a limestone formation. This lithotype, which is overlaid by soft sediments such as sandy clays and detritus, can be considered as the local bedrock. Present study aims to investigate on the dynamic properties of main lithotypes outcropping in the study area and their relationships with the local seismic response. Non-invasive seismic prospecting techniques using the vertical component of surface waves (MASW and ReMi) were adopted, as well as ambient noise measurements, processed through the Nakamura technique. The best solution for the experimental dispersion curves was selected using the neighbourhood algorithm and information about the deeper part of the estimated shear wave profiles was obtained by considering the ellipticity of the fundamental peak. Moreover, a cluster analysis was performed to subdivide into homogeneous groups the experimental noise spectral ratios. Results obtained pointed out that the use of combined different methods provides a robust way to characterize the investigated soils and to reduce the problems linked to the non-uniqueness of solutions during the interpretation of geophysical data.

Shallow shear-wave velocity profiles and site response characteristics from microtremor array measurements in Metro Manila, the Philippines

This paper presents the outcome of reconnaissance surveys in metropolitan Manila (Metro Manilla), the Philippines, with the aim of mapping shallow shear-wave velocity structures. Metro Manila is a seismically active and densely populated region that is in need of detailed investigation of the subsurface structures, to assess local site effects in seismic hazard estimation. We conducted microtremor array observations and used the spatial autocorrelation method to estimate the shear-wave profiles at 32 sites in major geological settings in Metro Manila. We applied a hybrid genetic simulated annealing algorithm to invert phase velocity data from the spatial autocorrelation method to generate shear-wave velocity models near the global best-fit solution. The comparison between the inferred shear-wave velocity profiles and PS logging showed good agreement in terms of the fundamental mode of Rayleigh waves and site responses. Then, we utilised the inferred shear-wave velocity profiles to compute the site amplifications with reference to the motion in engineering bedrock. Subsequently, the site amplifications have been grouped, based on NEHRP site classes. The amplification factor has also been compared with the average shear-wave velocity of the upper 30 m at each site, to produce a power-law regression equation that can be used as a starting basis for further site-effects evaluation in the metropolis.

Comparison of surface wave techniques to estimate shear wave velocity in a sand and gravel sequence: Holme Pierrepont, Nottingham, UK

This study evaluated the application of surface wave methods to aggregate variability and thickness determinations. We compared the results of field assessments of sand and gravel sequences using three surface wave survey approaches. The first was a seismic refraction approach, the second, a continuous surface wave (CSW) survey approach, and the third adopted a multi-channel analysis of surface waves (MASW) technique to the original refraction field set-up and records. The sand and gravel sequences were highly heterogeneous and the shear wave profiles were not normally dispersive (i.e. did not exhibit a monotonic increase in velocity with depth), which had a significant effect upon the performance of the three field approaches. Both CSW and MASW approaches provided information over a broad spectrum from which velocity–depth profiles were produced, but the upper frequency of operation was limited in both methods because of poorer signal quality at higher frequencies. Shear wave velocity profiles obtained using vertically vibrating sources during CSW surveys were different from profiles obtained using a horizontally polarized source in the refraction survey. This was attributed to different propagation paths and modes of propagation, which were illustrated via additional tomographic inversion of the refraction travel times but could also be attributed to data inversion methods. Probing using an ultra-lightweight cone penetrometer, continuous reflection profiling using ground-penetrating radar, and also an active extraction programme at the field site provided the opportunity to directly observe the subsurface geology and verify field results. Within the sand and gravel sequence, high-velocity layers were associated with matrix-supported coarse gravel lenses, some of which were weakly cemented. Localized high- and low-velocity zones within the underlying bedrock were interpreted as being related to lithostratigraphic heterogeneity and the development of an upper, weathered zone.

Comment on ‘Shear wave profiles from surface wave inversion: the impact of uncertainty on seismic site response analysis’

We discuss a study on the effect of surface wave solution non-uniqueness on seismic site response. The inversion approach used in the considered paper may lead to a significant overestimation of the uncertainties due to solution non-uniqueness. We also address the numerical simulation of seismic site response. We apply a consistent framework to a synthetic dataset to show that, contrary to what is claimed in the considered study, the solution non-uniqueness has negligible effect in this specific case.

Reply to comment on ‘Shear wave profile from surface wave inversion: the impact of uncertainty on seismic site response analysis’

Socco et al (2012 J. Geophys. Eng. 9 241) comment on our study about the effect of non-uniqueness of surface wave solutions on seismic site response analysis. In particular, they refer to the approach we adopted for the selection of equivalent shear wave velocity profiles and argue that it leads to overestimation of the uncertainty due to the inherent ill-posedness of the problem. Moreover, for one of the synthetic cases of our original paper, they calculate a different set of equivalent velocity profiles, retrieving the corresponding amplification spectra. From these results, Socco et al claim that their general conclusion that the impact of solution non-uniqueness on seismic response simulations is negligible. In this reply we demonstrate that (a) the uncertainty bounds used by Socco et al in their prediction analysis, as a consequence of their surface wave inversion procedure, are unreasonably narrow; (b) consequently, their shaking predictions appear to suffer no impact from their underestimated uncertainty; and (c) their presented case shows an amplification spectrum that is only the result of assuming the existence of a bedrock at 150 m that causes resonance of the overlying layer—practically independent of the details of the S-wave velocity distribution.

Shear wave velocity in surface sediments

Surface sediments of different nature are common in Iceland. Natural soil sites and man-made fillings commonly serve as foundations for different types of structures. In Civil engineering work it is fundamental to know the geotechnical properties of these materials in the upper 20–30 m. A seismic method called Spectral Analysis of Surface Waves (SASW) has been used in recent decades in Iceland to measure and evaluate shear wave velocity at different natural sites as well as in man-made fillings. The method is fast and involves low cost equipment. It gives reliable results down to 20 m depth by using sledge as a seismic source and copes with both soft and stiff soil sites. Furthermore, the technique can be applied at coarse grained gravelly sites where it can be difficult to use borehole and penetration methods. We describe the methodology used in these projects and review all SASW measurements carried out in Iceland. The soil strata at all test sites are classified based on sieve analysis when possible. Natural sites and man-made fillings are kept separated. A database and an open web site are introduced where all the SASW results can be viewed and shear wave profiles for different soil types and unlike sites can be compared. The main aim with the database and the webpage is to give scientists and engineers access to this data and enable them to compare stiffness at different sites.

Shear wave profiles from surface wave inversion: the impact of uncertainty on seismic site response analysis

Inversion is a critical step in all geophysical techniques, and is generally fraught with ill-posedness. In the case of seismic surface wave studies, the inverse problem can lead to different equivalent subsoil models and consequently to different local seismic response analyses. This can have a large impact on an earthquake engineering design. In this paper, we discuss the consequences of non-uniqueness of surface wave inversion on seismic responses, with both numerical and experimental data. Our goal is to evaluate the consequences on common seismic response analysis in the case of different impedance contrast conditions. We verify the implications of inversion uncertainty, and consequently of data information content, on realistic local site responses. A stochastic process is used to generate a set of 1D shear wave velocity profiles from several specific subsurface models. All these profiles are characterized as being equivalent, i.e. their responses, in terms of a dispersion curve, are compatible with the uncertainty in the same surface wave data. The generated 1D shear velocity models are then subjected to a conventional one-dimensional seismic ground response analysis using a realistic input motion. While recent analyses claim that the consequences of surface wave inversion uncertainties are very limited, our test points out that a relationship exists between inversion confidence and seismic responses in different subsoils. In the case of regular and relatively smooth increase of shear wave velocities with depth, as is usual in sedimentary plains, our results show that the choice of a specific model among equivalent solutions strongly influences the seismic response. On the other hand, when the shallow subsoil is characterized by a strong impedance contrast (thus revealing a characteristic soil resonance period), as is common in the presence of a shallow bedrock, equivalent solutions provide practically the same seismic amplification, especially in the frequency range of engineering interest.

Validity of the Refraction Microtremors (ReMi) Method for Determining Shear Wave Velocities for Different Soil Types in Egypt

The Refraction Microtremor (ReMi) method is being used around the world by the geotechnical and geophysical community to determine shear-wave velocities. This is due to its faster, less expensive and accurate determination of shear wave velocities, when compared to other methods used. Unlike standard crosshole and downhole techniques, ReMi does not require any drilling. It eliminates the problem of shear-wave source and quiet site that are pre-requisites for good seismic refraction surveys. In this paper we present refraction microtremors (ReMi) measurements done at sites underlain by different soil types in Egypt. The ReMi data were collected using standard refraction equipment employing 12, 24 or 48 channels. We used deep oceanographic noise and ambient noise including energy from power generators, pile drivers and traffic. The data were processed using the SeisOpt® ReMi? (© Optim, Inc.) software to reveal one-dimensional shear-wave velocity structures beneath the arrays. To access the validity of the method for the Egyptian soils, the shear-wave profiles obtained from the ReMi measurements were compared to downhole and crosshole data for different soils. Comparisons demonstrate the robustness of the ReMi technique for obtaining shear-wave velocities for different soil types in Egypt.

Mapping formation radial shear-wave velocity variation by a constrained inversion of borehole flexural-wave dispersion data

We have developed a novel constrained inversion method for estimating a radial shear-wave velocity profile away from the wellbore using dipole acoustic logging data and have analyzed the effect of the radial velocity changes on dipole-flexural-wave dispersion characteristics. The inversion of the dispersion data to estimate the radial changes is inherently a nonunique problem because changing the degree of variation or the radial size of the variation zone can produce similar wave-dispersion characteristics. Nonuniqueness can be solved by developing a constrained inversion method. This is done by constraining the high-frequency portion of the model dispersion curve with another curve calculated using the near-borehole velocity. The constraint condition is based on the physical principle that a high-frequency dipole wave has a shallow penetration depth and is therefore sensitive to the near-borehole shear-wave velocity. We have validated the result of the constrained inversion with synthetic data testing. Combining the new inversion method with four-component crossed-dipole anisotropy processing obtains shear radial profiles in fast and slow shear polarization directions. In a sandstone formation, the fast and slow shear-wave profiles show substantial differences caused by the near-borehole stress field, demonstrating the ability of the technique to obtain radial and azimuthal geomechanical property changes near the wellbore.

Rayleigh-wave mode separation by high-resolution linear Radon transform

Multichannel analysis of surface waves (MASW) method is an effective tool for obtaining vertical shear wave profiles from a single non-invasive measurement. One key step of the MASW method is generation of a dispersion image and extraction of a reliable dispersion curve from raw multichannel shot records. Because different Rayleigh-wave modes normally interfere with each other in the time and space domain, it is necessary to perform mode separation and reconstruction to increase the accuracy of phase velocities determined from a dispersion image. In this paper, we demonstrate the effectiveness of high-resolution linear Radon transform (LRT) as a means of separating and reconstructing multimode, dispersive Rayleigh-wave energy. We first introduce high-resolution LRT methods and Rayleigh-wave mode separation using high-resolution LRT. Next, we use synthetic data and a real-world example to demonstrate the effectiveness of Rayleigh-wave mode separation using high-resolution LRT. Our synthetic and real-world results demonstrate that (1) high-resolution LRT successfully separates and reconstructs multimode dispersive Rayleigh-wave energy with high resolution allowing the multimode energy to be more accurately determined. The horizontal resolution of the Rayleigh-wave method can be increased by extraction of dispersion curves from a pair of traces in the mode-separated shot gather and (2) multimode separation and reconstruction expand the usable frequency range of higher mode dispersive energy, which increases the depth of investigation and provides a means for accurately determining cut-off frequencies.