SH Waves Research Articles

Seismic Response of a Shallow Asymmetrical V-Shaped Canyon with Cliffs under SH Waves Propagation

Seismic Response of a Shallow Asymmetrical V-Shaped Canyon with Cliffs under SH Waves Propagation

Mathematical modelling for seismic affected zoning of tunnel cavity section under SH wave incidence and shaking table verification

Mathematical modelling for seismic affected zoning of tunnel cavity section under SH wave incidence and shaking table verification

Frequency-Division Multiplexing of Chevron EMAT for Orthogonally Polarized SH Waves

Frequency-Division Multiplexing of Chevron EMAT for Orthogonally Polarized SH Waves

Stochastic Green’s Function Method Considering Non-Uniform Rise Time Distribution to Simulate 3D Broadband Ground Motion

The stochastic Green’s function method has been widely used in the field of ground motion simulation in recent years. It is generally assumed that the rise time of each subfault is the same in this method. Since the rise time significantly influences the amplitude of simulation results in the intermediate frequency band, to improve the accuracy of stochastic Green’s function method for near-fault broadband ground motion simulation, referring to the numerical simulation results of Day, the rise time is assumed to be non-uniformly distributed on the fault, and an improved approximate expression of rise time on a rectangular fault considering that the rupture starting point may be at any position and the aspect ratio may be arbitrary is proposed. Additionally, the contributions of P, SV and SH wave are considered, respectively, and an improved stochastic Green’s function method is proposed for 3D broadband ground motion simulation. Taking the 1994 Northridge earthquake in America and 2013 Lushan earthquake in China as examples, under different subfault division numbers, the synthesized source spectra are compared with the omega-squared theoretical source spectra of the large earthquake, and the simulated ground motions at observation points are compared with observed records to verify the effectiveness of the improved method. The results show that when the Northridge earthquake fault and Lushan earthquake fault are divided into 9 × 10 subfaults and 11 × 7 subfaults, respectively, the simulation results obtained using the improved method are close to the observed records in the broadband frequency range. Therefore, the improved method can effectively simulate the 3D ground motion in near-fault regions.

Propagation characteristics of SH waves in piezoelectric–piezomagnetic sandwich structures

Propagation characteristics of SH waves in piezoelectric–piezomagnetic sandwich structures

Comparison of Torsional and SH Waves in Isotropic and Anisotropic Media Based on Laboratory Measurements

Abstract Utilization of the torsional wave signal has been reported in medical testing and engineering detection. A torsional wave is a shear-wave train whose vibrating direction (polarization) forms a torsional motion. However, there are a lack of understanding of its characteristics and potential for subsurface investigations. Here, compressional (P), shear (S) and torsional (T) transducers are constructed using different piezoelectric-transformer (PZT) chips in the laboratory and the characteristics of the torsional (T) wave propagating in isotropic and fracture-induced anisotropic media are analyzed in line with conventional P- and S-waves, covering waveform, amplitude, arrival time and velocity at different propagating angles. The results indicate that the velocity and anisotropy values measured using the T transducer are almost the same as the SH wave. For propagation in isotropic and anisotropic media, the wavefield generated by the T transducer is very simple with no mode conversions and source-generated interferences, which is similar to the SH wavefield, whilst the SV wavefield comprises of a series of complex events from mode conversions and interferences. For propagating in fluid- saturated fractured rocks, the torsional wavefield also comprises of a fast and slow wave train, which is referred to as torsional-wave splitting, and is similar to the shear wave splitting from S transducers. Furthermore, the anisotropy parameters measured using P, S and T transducer show a good correlation with the fracture density, and the P wave anisotropy is higher in air saturated rocks than water saturated rocks, while the shear wave anisotropy measured by S transducer and T transducer are sensitive to fracture density. Similar to the P transducer, the T transducer is polarization-independent, or directional invariant. Therefore, utilizing the T transducer may simplify the field logistics during 3D shear-wave surveys. However, field torsional wave generation is a major issue that needs further study.

ANALYSIS OF SH-WAVES IN ANISOTROPIC FIBER-REINFORCED MEDIUM OVER LINEARLY VARYING INHOMOGENEOUS SUBSTRATE UNDER NON-LOCAL ELASTICITY

An analytical technique employing the variable separable method has been used in an attempt to precisely grasp and assess the impact of the property non-local elasticity upon the wave transmission response of an anisotropic fiber-reinforced material embedded over a semi-infinite, inhomogeneous medium that changes linearly. As depth increases, the stiffness and density of a semi-infinite substrate are believed to alter linearly. Availing the Whittaker function, a relation about dispersion has been acquired to analyze the response of SH waves. The visual representation depicts a significant influence of non-local elasticity on the propagation of SH-wave modes. Special cases have been found assessing the concurrency of the model with the original form equation of Love wave. The effects of non-locality, fiber-reinforcement parameters, and inhomogeneity parameters carry implications in designing and gradation of material characteristics some important parameters on the wave characteristics of the studied model.

Fast concrete crack depth detection using low frequency ultrasound array SH waves data

Fast detection of the depths of surface-open cracks plays an important role in evaluating the damage conditions of concrete elements. The presence of surface-open cracks and other anomalies inside concrete complicates the ultrasonic wave field and thus severely undermines the precision of traditional nondestructive testing methods. This study introduces independently developed low-frequency ultrasonic array detection equipment. The detector adopts a doubled-ray coverage strategy to enhance the imaging stability under noisy conditions. Moreover, we propose an imaging method called the crack focusing-synthetic aperture focusing technique (CF-SAFT), through which both reflected and transmitted surface waves are removed so that only diffracted SH waves converge to their origins. An extra instantaneous phase analysis is supplemented to highlight the diffraction points. We test the effectiveness of our method through a multitude of numerical examples and a model experiment. Successful depth identification was obtained regardless of different geometries of the cracks or interference from the steel reinforcements. The superiority of our method is further verified through noisy ultrasonic data and complex scenarios.

On the viscoelastic-electromagnetic-gravitational analogy

The analogy between electromagnetism and gravitation was achieved by linearizing the tensorial gravitational equations of general relativity and converting them into a vector form corresponding to Maxwell’s electromagnetic equations. On this basis, we use the equivalence with viscoelasticity and propose a theory of gravitational waves. We add a damping term to the differential equations, which is equivalent to Ohm’s law in electromagnetism and Maxwell’s viscosity in viscoelasticity, to describe the attenuation of the waves. The differential equations in viscoelasticity are those of cross-plane shear waves, commonly referred to as SH waves. A plane-wave analysis gives the phase velocity, the energy velocity, the quality factor and the attenuation factor of the field as well as the energy balance. To obtain these properties, we use the analogy with viscoelasticity; the properties of electromagnetic and gravitational waves are similar to those of shear waves. The presence of attenuation means that the transient field is generally a composition of inhomogeneous (non-uniform) plane waves, where the propagation and attenuation vectors do not point in the same direction and the phase velocity vector and the energy flux (energy velocity) are not collinear. The polarization of cross-plane field is linear and perpendicular to the propagation-attenuation plane, while the polarization of the field within the plane is elliptical. Transient wave fields in the space–time domain are analyzed with the Green function (in homogeneous media) and with a grid method (in heterogeneous media) based on the Fourier pseudospectral method for calculating the spatial derivatives and a Runge–Kutta scheme of order 4 for the time stepping. In the examples, wave propagation at the Sun–Earth and Earth–Moon distances using quadrupole sources is considered in comparison to viscoelastic waves. The Green and grid solutions are compared to test the latter algorithm. Finally, an example of propagation in heterogeneous media is presented.

Upper mantle structure beneath the Mongolian region from multimode surface waves: Implications for the western margin of Amurian plate

Multimode phase speeds of surface waves are used to build a new radially anisotropic S wave model in the eastern Eurasian and Mongolian regions. Our dataset includes seismic waveforms of over 1655 teleseismic events (Mw≥5.8) from 2009 to 2021, recorded at permanent and temporary stations in and around Mongolia. The multimode dispersion curves of Love and Rayleigh waves were extracted using the nonlinear waveform fitting method for individual seismograms. Then, we retrieved phase speed maps for each mode and frequency, incorporating finite-frequency effects. Finally, localized multimode dispersion curves extracted from the phase speed maps were inverted for local 1-D SV and SH wave profiles, which are combined into a radially anisotropic 3-D shear wave model. Our new model exhibits significant lateral variations of S wave speeds at 70–100 km depth beneath Mongolia, i.e., slow anomalies in the tectonically active western Mongolia in contrast to fast anomalies in stable eastern Mongolia. In the radial anisotropy model, SH waves are faster than SV waves in most areas of the Mongolian lithosphere above 100 km depth, except for the northeast of the Altay Mountains. The Hangay Dome region is characterized by significantly slower velocities that may relate to its uplifting. A large-scale low velocity beneath the northeast of the Hangay Dome with a slower SV wave speed than SH may indicate the existence of partially molten layers. This study also reveals distinct lateral variations of S wave speeds across the boundary between the Amurian and Eurasian plates, characterized by the fast anomaly in eastern Mongolia, corresponding to the lithosphere in the western Amurian plate.

Wave scattering in a cracked exponentially graded magnetoelectroelastic half‐plane

AbstractAn exponentially graded with respect to depth magnetoelectroelastic (MEE) half‐plane containing two line or curvilinear cracks under time‐harmonic SH wave is studied. The defined mechanical problem is described by boundary integral equations (BIEs) along the cracks boundaries. The computational tool based on the non‐hypersingular traction boundary integral equation method (BIEM) is developed, verified and inserted in numerical simulations. It is based on the analytically derived Green's function and free‐field wave motion solution for exponentially graded MEE half‐plane. The dependence of the generalized stress intensity factors (SIFs) on the material gradient parameters, on the dynamic load characteristics, on the cracks position and their shape, on the dynamic interaction between cracks and between them and half‐plane boundary is numerically analyzed.

Near Stochiometric LiNbO3 Crystal: the Piezoelectric Features and the Shear Horizontal Guided Wave Transducer for Structural Health Monitoring up to 650 °C.

The application of shear horizontal (SH) guided wave transducers in high-temperature structural health monitoring (SHM) is a topic of significant interest across various industrial engineering sectors. In this study, we utilized the novelty piezoelectric crystal of near stoichiometric lithium niobate (NSLN), which exhibited a robust piezoelectric response (d15 = 77.6 pC/N@room temperature). Next, the pure thickness shear vibration mode d15' through size optimization was designed. It was demonstrated that the NSLN-based ultrasonic guided wave transducers utilizing the optimum d15' mode were proficient in transmitting and receiving pure fundamental SH wave (SH0 wave) along two orthogonal main directions (0° and 90°) over a wide frequency range (100-350 kHz), exhibiting strong response to the SH0 wave. Under the driving voltage of 100 V, the signal voltages of the NSLN-based transducer were found to be on the order of 200.3 and 11.8 mV at room temperature and high temperature of 650 °C, respectively. Moreover, the NSLN-based SH0 transducer showcased its better defect localization ability, and the signal-to-noise ratio (SNR) sensitivity of NSLN-based transducer was evaluated to be 16.1 dB at high temperature of 650 °C. To sum up, the ultrasonic wave transducer based on NSLN crystal demonstrated higher potential applications for in situ SHM under elevated temperatures.

Principal Stress Measurement by Propagation Velocity Estimation at No Stress Using Surface Anisotropy in Surface SH Wave Acoustoelasticity

Principal Stress Measurement by Propagation Velocity Estimation at No Stress Using Surface Anisotropy in Surface SH Wave Acoustoelasticity

Double-layer metasurface for blocking the fundamental SH wave

Abstract This work introduces a double-layer metasurface to isolate the fundamental shear horizontal wave (SH0 wave). The metasurface is designed to split the SH0 wave source into two parts and then manipulate the two waves to be out of phase and have equal amplitude upon reaching the end of the metasurface. This results in interference cancellation, effectively blocking the propagation of SH0 waves into the protected zone. Firstly, the metasurface is designed theoretically, utilizing rectangular strips to constitute the substructure. Subsequently, finite element simulations are conducted to verify the correctness of the theoretical design. Finally, the metasurface is fabricated using 3D printing, and its performance is evaluated through experiments. The results indicate that the metasurface can function as a cage for SH0 waves, trapping different types of SH0 waves located at any position within the cage. Furthermore, when the source of SH0 waves is positioned outside the cage, the metasurface can effectively impede their propagation into the interior region of the cage. The proposed double-layer metasurface provides a simple approach to blocking SH0 waves, which may have potential applications in practical engineering.

Exploring the influence of coupled interfacial imperfections on SH wave propagation in layered structures with sliding interaction

Exploring the influence of coupled interfacial imperfections on SH wave propagation in layered structures with sliding interaction

Reflection and transmission of SH waves at the interface of a V-notch and a piezoelectric/piezomagnetic half-space

Reflection and transmission of SH waves at the interface of a V-notch and a piezoelectric/piezomagnetic half-space

Effect of corrugation and rotation on SH wave propagation in an initially stressed functionally graded piezo-electric substrate

A rotating system that includes an initially stressed piezo-electric substrate was the subject of an analytical study of the SH waves. The substrate and vacuum bonding are in good contact with the corrugation, and the top border is treated as stress-free corrugation. About the upper barrier that is both electrically open as well as electrically short scenarios are taken into consideration. Dispersion equations for circumstances with a corrugated interface that are both electrically short as well as electrically open have been found. The SH wave characteristics through the framework suggested and circumstances dependent on different geometrical and physical factors have been investigated based on the numerical findings. The study looks at the simultaneous simulated outcomes of a number of physical factors that were produced in Mathematica 7 and include rotation, inhomogeneity, phase velocity, initial stress, and corrugated interface of SH wave distribution in a structure under discussion. The model under examination has potential applications in the creation of surface acoustic wave devices.

A semi-analytical approach for site-city interaction under oblique incident SH waves

In this paper, a semi-analytical approach was proposed for investigating the site-city interactions (SCI). The site was modelled as a horizontal layered half-space, while the building was represented as a collection of shear wall structures fixed on the surface of half-space. The total wave field was considered as a combination of free field and scattering wave field generated by buildings, simulated by direct stiffness method and Green's function, respectively. The coupling between the site and the city is achieved through the displacement continuity conditions at the bottom of the building. Finally, the impact and some influencing factors of SCI effect on site and buildings were studied. It is found that the SCI effect has a significant impact on surface displacement and building response. The SCI effect typically reduces surface displacement near cities and the amplitude of relative displacement of buildings, while increases the seismic duration of buildings. However, this influence will be affected by the incident angle, building layout, building height, and building spacing, so these factors should be comprehensively considered when analyzing the SCI effect. Through the case studies, it is demonstrated that this method can quickly calculate SCI models with complex factors without being limited by the number and thickness of soil layers, incidence angles, and different sizes and spacing of buildings.

Analytical solution for the kinematic response of end-bearing piles subjected to SH waves in a homogeneous layer by an improved beam-foundation model

This paper presents an analytical solution for evaluating kinematic response in piles subjected to shear waves. The proposed model treats the pile as a Timoshenko beam supported by a two parameter Winkler foundation, capturing both transverse and rotational ground reactions. Validation against both analytical and numerical solutions from the literature, particularly 3D finite element models, shows very good agreement. The proposed model generalizes different solutions currently applied in practice, covering various pile slenderness ratios and ground conditions. This approach addresses limitations in existing Euler-Bernoulli beam resting on Winkler or Vlasov-Pasternak foundation models, by incorporating shear distortions in the structure and ground friction at the interface. Shear stresses induced by the rotational springs are found to significantly influence the kinematic factors, as well as bending and, particularly, shear forces. Finally, simplified expressions for kinematic interaction factors and forces are provided for expedited analyses of practical engineering problems.

Response of semicircular canyons and movable cylindrical cavities to SH waves in anisotropic half-space geology

The development of tunnels or the laying of underground pipelines are essential engineering projects in modern society, and in canyon tunnels and underground pipeline projects, the surface motion and cavity edge motion have been topics of concern in ground vibration problems. We investigate the wave scattering problem in an elastic half-space anisotropic medium containing a semicircular canyon and a subsurface movable cylindrical cavity by using the wave function expansion method, the complex function method, and the mirror method. By deriving the governing equation and transforming it into the standard form of the Helmholtz equation satisfying the zero-stress boundary condition, we solve the corresponding displacement functions. Introducing a position correction coefficient, the scattered wavefield in a half-space anisotropic medium is constructed by the mirror method, which improves the problem of scattered wave source singularity in anisotropic half-space media. Then, combining the free boundary conditions with a Fourier series expansion method, we solve the unknown coefficients in the equations. The correctness of the method is verified by degenerating it to a classical analytic solution. Finally, using frequency- and time-domain analysis, we investigate the effects of the relevant parameters on the surface motion [Formula: see text], the dynamic stress concentration factor, and the displacement amplitude [Formula: see text]. The results indicate that rock anisotropy and the presence of semicircular canyons have a significant effect on the dynamic response of subsurface structures. This not only provides a theoretical basis for practical unlined tunnels or pipeline projects but also can provide a basis for seismic design of underground structures.