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Upon heating, ultrastable glassy films transform into liquids via a propagating equilibration front, resembling the heterogeneous melting of crystals. A microscopic understanding of this robust phenomenology is, however, lacking because experimental resolution is limited. We simulate the heterogeneous transformation kinetics of ultrastable configurations prepared using the swap Monte Carlo algorithm, thus allowing a direct comparison with experiments. We resolve the liquid–glass interface both in space and in time as well as the underlying particle motion responsible for its propagation. We perform a detailed statistical analysis of the interface geometry and kinetics over a broad range of temperatures. We show that the dynamic heterogeneity of the bulk liquid is passed on to the front that propagates heterogeneously in space and intermittently in time. This observation allows us to relate the averaged front velocity to the equilibrium diffusion coefficient of the liquid. We suggest that an experimental characterization of the interface geometry during the heterogeneous devitrification of ultrastable glassy films could provide direct experimental access to the long-sought characteristic length scale of dynamic heterogeneity in bulk supercooled liquids. [ABSTRACT FROM AUTHOR]

This study aims to reveal the control mechanism of viscoelastic (VE) energy dissipation braces with strong mechanical nonlinear characteristics on the seismic response of reinforced concrete (RC) frame structures. Firstly, a new STM32-Matlab-OpenSees joint hybrid test platform is developed by introducing OpenSees, which is convenient for structural modeling and fast for structural calculation. The overall architecture and operation of the hybrid test platform are comprehensively analyzed. Then, a series of simulated seismic hybrid tests on three-dimensional (3D) RC frame structures with VE energy dissipation braces under different seismic waves are successfully carried out. Lastly, the hybrid test results of this structure system at different working conditions are compared and analyzed comprehensively. The research results show that the developed platform breaks the boundary limitation that OpenSees relies on the framework software OpenFresco and can only be connected to specific control systems in the hybrid test. Thus, it greatly expands the application scope of flexible configuration controller and actuator categories for the hybrid test platform, and it also provides a good reference value for the establishment and implementation of similar hybrid test platforms. Under the action of various seismic waves, VE energy dissipation braces has good universality for the shock absorption of RC frame structures. The damping control effect and energy dissipation efficiency of VE energy dissipation braces are significantly different under various seismic waves. In the design of RC frame structures with VE energy dispersion braces, it is very necessary to conduct the seismic analysis of the structures under multiple ground motions with wide frequency domain. The additional position of VE energy dissipation braces should be an important analysis indicators in the optimization design of the structures. [ABSTRACT FROM AUTHOR]

Rayleigh wave isolation using metamaterials is a research hotspot in the engineering community, yet the development of relevant mitigation methods remains an open and challenging problem. Herein, we propose a new type of metasurface, known as an engineered metagrating, which is a special metasurface buried in soil and plays a role in shielding surface Rayleigh waves. Moreover, the total omnidirectional reflection characteristics and subwavelength properties exhibited by the proposed metasurface provide a more flexible reference for surface Rayleigh wave mitigation measures in practical engineering applications. This work can open new avenues for controlling the propagation of seismic surface waves. [ABSTRACT FROM AUTHOR]

This editorial, published in the journal Frontiers in Earth Science, focuses on multidisciplinary investigations into earthquake processes. The research aims to improve risk evaluation and prediction in seismically active areas. The editorial provides an overview of the published contributions, which cover topics such as earthquake precursors, observation techniques, modeling fault movement, and earthquake forecasting experiments. The document discusses various approaches and techniques used in earthquake research, including seismometers, ambient noise, numerical modeling, and seismic hazard assessment. It also explores the impact of seismic wave effects from meteorite impacts and the potential use of machine learning in detecting earthquake precursors. [Extracted from the article]

Fundamental mode surface wave data have often been used to construct global shear velocity models of the upper mantle under the so-called 'path average approximation', an efficient approach from the computational point of view. With the advent of full-waveform inversion and numerical wavefield computations, such as afforded by the spectral element method, accounting for the effects of the crust accurately becomes challenging. Here, we assess the merits of accounting for crustal and uppermost mantle effects on surface and body waveforms using fundamental mode dispersion data and a smooth representation of the shallow structure. For this we take as reference a model obtained by full-waveform inversion and wavefield computations using the spectral element method, model SEMUCB-WM1 and compare the waveform fits of synthetics to different parts of three component observed teleseismic records, in the period band 32–300 s for body waves and 40–300 s for surface waves and their overtones for three different models. The latter are: a dispersion-only based model (model Disp_20s_iter5), and two models modified from SEMUCB-WM1 by successively replacing the top 200 km (model Merged _200 km) and top 80 km (model Merged _80 km), respectively, by a model constrained solely by fundamental mode surface wave dispersion data between periods of 20 and 150 s. The crustal part of these three models (resp. SEMUCB-WM1) is constrained from dispersion data in the period range 20–60 s (resp. 25–60 s), using the concept of homogenization which is tailored to simplify complex geological features, enhancing the computational efficiency of our seismic modelling. We evaluate the fits to observed waveforms provided by these three models compared to those of SEMUCB-WM1 by computing three component synthetics using the spectral element method for five globally distributed events recorded at 200+stations, using several measures of misfit. While fits to waveforms for model 3 are similar to those for SEMUCB-WM1, the other two models provide increasingly poorer fits as the distance travelled by the corresponding seismic wave increases and/or as it samples deeper in the mantle. In particular, models 1 and 2 are biased towards fast shear velocities, on average. Our results suggest that, given a comparable frequency band, models constructed using fundamental mode surface wave data alone and the path average approximation, fail to provide acceptable fits to the corresponding waveforms. However, the shallow part of such a 3-D radially anisotropic model can be a good starting model for further full waveform inversion using numerical wavefield computations. Moreover, the shallow part of such a model, including its smooth crustal model, and down to a maximum depth that depends on the frequency band considered, can be fixed in full-waveform inversion iterations for deeper structure. This can save significant computational time when higher resolution is sought in the deeper mantle. In the future, additional constraints for the construction of the homogenized model of the crust can be implemented from independent short period studies, either globally or regionally. [ABSTRACT FROM AUTHOR]

We present our third and final generation joint P and S global adjoint tomography (GLAD) model, GLAD-M35, and quantify its uncertainty based on a low-rank approximation of the inverse Hessian. Starting from our second-generation model, GLAD-M25, we added 680 new earthquakes to the database for a total of 2160 events. New P -wave categories are included to compensate for the imbalance between P - and S -wave measurements, and we enhanced the window selection algorithm to include more major-arc phases, providing better constraints on the structure of the deep mantle and more than doubling the number of measurement windows to 40 million. Two stages of a Broyden–Fletcher–Goldfarb–Shanno (BFGS) quasi-Newton inversion were performed, each comprising five iterations. With this BFGS update history, we determine the model's standard deviation and resolution length through randomized singular value decomposition. [ABSTRACT FROM AUTHOR]

Backazimuthal variations in the shear wave splitting of core-refracted shear waves (SKS, SKKS and PKS phases, jointly referred to as X KS) at the Black Forest Observatory (BFO, Southwest Germany) indicate small-scale lateral and partly vertical variations of the seismic anisotropy. However, existing anisotropy studies and models for the nearby Upper Rhine Graben (URG) area in the northern Alpine foreland are mostly based on short-term recordings and by this suffer from a limited backazimuthal coverage and averaging over a wide or the whole backazimuth range. To identify and delimit laterally confined anisotropy regimes in this region, we carry out X KS splitting measurements at six neighbouring (semi-)permanent broad-band seismological recording stations (interstation distance 10–80 km). We manually analyse long-term (partly > 20 yr) recordings to achieve a sufficient backazimuthal coverage to resolve complex anisotropy. The splitting parameters (fast polarization direction |$\phi $|⁠ , delay time |$\delta t$|⁠) are determined in a single- and multi-event analysis. We test structural anisotropy models with one layer with horizontal or tilted symmetry axis and with two layers with horizontal symmetry axes (transverse isotropy). To account for lateral variations around a single recording site, modelling is compared for the whole and for limited backazimuth ranges. Based on this, we provide a 3-D block model with spatial variation of anisotropic properties. Based on delay times > 0.3 s and missing discrepancies between SKS and SKKS phases, which do not support lower mantle anisotropy, the found anisotropy is placed in the lithosphere and asthenosphere. The spatial distribution as well as the lateral and backazimuthal variations of the splitting parameters confirm lateral and partly vertical variations in anisotropy. On the east side of the URG, we suggest two anisotropic layers in the Moldanubian Zone (south) and one anisotropic layer in the Saxothuringian Zone (north). In the Moldanubian Zone, a change of the fast polarization directions is observed between the east and the west side of the URG, indicating different textures. At the boundary between the two terranes, an inclined anisotropy is modelled which may be related with deformation during Variscan subduction. Regarding the observation of numerous null measurements and inconsistent splitting parameters, especially (southwest of BFO) in the southern URG, different hypothesis are tested: scattering of the seismic wavefield due to small-scale lateral heterogeneities, a vertical a -axis due to a vertical mantle flow related to the Kaiserstuhl Volcanic Complex, as well as a different preferred orientation of the olivine crystals (not A-type, but C-type) due to specific ambient conditions (high temperature, water content). [ABSTRACT FROM AUTHOR]

This document explores the extraction of attenuation structure from ambient noise in seismic data. It provides an overview of the data preprocessing methods used to remove non-stationary signals and ensure energy distribution across frequency bands. The document also highlights theoretical challenges and areas for future investigation, including the impact of inhomogeneous noise source distribution and the validity of using only the fundamental mode in attenuation models. Overall, this research field shows promise for high-resolution imaging without the need for earthquake events. [Extracted from the article]

Large deformation of sand due to soil liquefaction is a major cause for seismic damage. In this study, the mechanisms and modeling of large post-liquefaction deformation of sand considering the significant influence of water absorption in shearing and seismic wave conditions. Assessment of case histories from past earthquakes and review of existing studies highlight the importance of the two factors. Based on the micro and macro scale mechanisms for post-liquefaction shear deformation, the mechanism for water absorption in shearing after initial liquefaction is revealed. This is aided by novel designed constant water-absorption-rate shear tests. Water absorption in shearing can be classified into three types, including partial water absorption, complete water absorption, and compulsory water absorption. Under the influence of water absorption in shearing, even a strongly dilative sand under naturally drained conditions could experience instability and large shear deformation. The mechanism for amplification of post-liquefaction deformation under surface wave load is also explained via element tests and theoretical analysis. This shows that surface wave-shear wave coupling can induce asymmetrical force and resistance in sand, resulting in asymmetrical accumulation of deformation, which is amplified by liquefaction. A constitutive model, referred to as CycLiq, is formulated to capture the large deformation of sand considering water absorption in shearing and seismic wave conditions, along with its numerical implementation algorithm. The model is comprehensively calibrated based on various types of element tests and validated against centrifuge shaking table tests in the liquefaction experiments and analysis projects (LEAP). The model, along with various numerical analysis methods, is adopted in the successful simulation of water absorption in shearing and Rayleigh wave-shear wave coupling induced large liquefaction deformation. Furthermore, the model is applied to high-performance simulation for large-scale soil-structure interaction in liquefiable ground, including underground structures, dams, quay walls, and offshore wind turbines. [ABSTRACT FROM AUTHOR]

The effects of phase shift (δ) between compression and shear waves, and consolidation stress ratio (Kc) on the liquefaction resistance of sand under simultaneous compression and shear wave loading is investigated using a hollow cylinder torsional shear apparatus. The differences caused by prior stress history (assessed using drained versus undrained preshear) highlight the importance of test protocols in undertaking research to explore the effects of complex dynamic loading paths. The liquefaction resistance of sand was highly dependent on the loading path. However, it was not affected much by variations in δ , if the horizontal shear stress ratio (τzθ/σmc′) and the ratio between shear stress increment and normal stress increment (ΔS/ΔN) were held constant. In tests with constant cyclic stress ratio (CSR), an increase in δ decreases the cyclic resistance because the increase in δ causes a reduction in the rate of deviatoric stress increment per degree of principal stress rotation. At a given CSR , for δ≠0 cases, a change in ΔS/ΔN does not affect the liquefaction resistance of sand because the magnitude and pattern of rotation is not affected much by ΔS/ΔN (for the ratios explored in this research). Increasing Kc or static shear stress ratio (αst) increased the cyclic resistance of the tested sand for ΔS/ΔN<1. The rate of increase in cyclic resistance with increasing αst decreases with the increase in ΔS/ΔN and was essentially unchanged for ΔS/ΔN=1. This observation, that the rate of increase in cyclic resistance with αst decreases with increasing ΔS/ΔN , is consistent with the observation in the literature that the cyclic triaxial loading yields higher static shear stress correction factor (Kα) than cyclic simple shear in loose sand. [ABSTRACT FROM AUTHOR]

• Derived newly the 3D exact solutions for free-field soil-liquid responses for oblique incident P or SV waves. • Derived 2.5D equivalent seismic forces for seabed for 3D incident waves. • Used 2.5D finite/infinite element method for seabed seismic analysis for 3D incident waves. • Investigated the effect of liquid depth on the solid responses under both sub- and super-critical conditions. • Observed the suppressive frequencies are closely related to vertical incident angle and liquid depth. The seismic behavior of underwater half-space under arbitrary 3D incidence of P- or SV-waves is analyzed by the 2.5D finite/infinite element method. Firstly, the 3D responses of solid and liquid in free field are newly derived exactly, which cover both the sub- and super-critical conditions. Then, the equivalent seismic forces acting on the solid boundary of the 2.5D finite/infinite element method are merely computed from the free-field displacement for given earthquakes. Subsequently, the equation of motions for the underwater half-space under arbitrary 3D incident seismic waves are established in the 2.5D finite/infinite element system, with the key parameters specified. The proposed method was verified against the previous 2D solutions and inversely computed free-field solutions in frequency domain. Major conclusions drawn from the present analysis include: (1) The effects of liquid, concerning enlargement, reduction or disturbance, on the seabed responses become stronger for increasing liquid depth under sub-critical condition; (2) The seabed interior responses are less sensitive to the variation in liquid depth under super-critical condition; and (3) Under the super- and sub-critical conditions, respectively, more attention should be given to the interior response for P-waves and to the seabed surface response for SV-waves. [ABSTRACT FROM AUTHOR]

The article discusses the Neodeterministic (NDSHA) approach to seismic hazard assessment, which aims to prevent seismic disasters rather than simply addressing their consequences. The NDSHA method takes into account the tensor nature of earthquake ground motions and has been proven reliable through experiments conducted over the past 25 years. The article also highlights the organization of the book "Earthquakes and Sustainable Infrastructure- Neodeterministic (NDSHA) Approach Guarantees Prevention Rather Than Cure," which compiles developments in the NDSHA approach and its application in various countries and regions. The book covers topics such as hazard analysis, earthquake forecasting, site response evaluation, and the seismic performance of infrastructure. This book provides a comprehensive exploration of seismic hazard assessment, focusing on the gap between engineering principles and the needs of seismologists, engineering seismologists, and policymakers. It emphasizes the importance of designing infrastructure to withstand future earthquakes and prevent damage. [Extracted from the article]

Estimating wave damping in carbonate rocks is complex due to their heterogeneous structure. For this reason, further research in this area is still necessary. Since the identification and evaluation of reservoir quality play an essential role in the optimal use of hydrocarbon resources, efforts are made to provide new solutions to achieve this goal by managing knowledge and accessing information from new tools such as the Vertical Seismic Profile (VSP). Seismic waves are deformed in frequency content and amplitude as they pass through the earth's layers. Part of the reduction in wavelength is related to the nature of the wave propagation and part to the geological properties, including porosity and fracture. Anisotropy and velocity model analysis, rather than the direct connection between reservoir parameters and seismic absorption coefficient, have received the majority of attention in earlier studies on the impact of reservoir parameters and fractures on changes in the quality factor. In this study, the correlation of the quality factor with parameters such as velocity deviation, fracture density, and permeability has been investigated, and an attempt has been made to define the quality factor as a tool to assess the quality of the reservoir. The statistical study using the multiple linear regression method found that fracture density is the most important parameter that follows the trend of the quality factor value. In the analysis, the quality factor showed a relatively good correlation with the permeability of the core data, so in the periods with maximum permeability, the quality factor had the lowest values. According to K-Means Clustering Analysis, 18% of the studied reservoir interval was evaluated as good quality, 33% as medium, 36% as poor, and 12% as hydrocarbon-free. This work provides insight into accessing reservoir quality using quality factor and velocity deviation logs and would be valuable for the development of reservoir quality prediction methods. Based on the study's results, it is recommended to apply this technique for modeling reservoir heterogeneity and assessing 2D and 3D seismic data to predict the reservoir quality of gas fields prior to drilling operations and reduce exploration risks. [ABSTRACT FROM AUTHOR]

Thirty-seven portable accelerometers were deployed in the eastern San Francisco Bay communities of Walnut Creek and Concord to study site response in a fault-bounded, urban, sedimentary basin. Local earthquakes were recorded for a period of two years from 2017 to 2019 resulting in 101 well-recorded events. Site response is estimated by two methods: the reference site spectral ratio method and a source-site spectral inversion method. The reference site spectral ratio method allows investigation of the variability of site amplification with source azimuth and frequency. The source-site spectral inversion method yields the best least-squares fit to site response for a database of ground-motion records. Both methods show substantial amplification in the Walnut Creek-Concord basin below 2 Hz indicating strong surface-wave development. Greater amplification is seen for sources aligned along the long axis of the basin. Inversion using close-in sources at short distances yields lower amplification at longer periods than the entire data set due to reduced surface-wave generation for steeper angles of incidence. Inversion of site response spectra for shallow shear-wave velocity using a global search algorithm yields VS30 values consistent with generalized mapping results based on geology and topography but with greater variability due to local site variations. 3D finite-element modeling shows greater amplification in the Walnut Creek-Concord basin with a basin-edge effect likely contributing to higher ground motions. Topography is also seen to lead to increased scattering and shadowing effects. [ABSTRACT FROM AUTHOR]

On-site earthquake early warning (EEW) requires the best estimates of earthquake magnitude and distance parameters within a few seconds after the P-wave arrival for estimating the subsequent S-wave parameters. The errors in the estimates of the earthquake P-wave parameters will propagate into the estimates of the S-wave parameters. To solve this problem, we used the methodology by Zhao and Zhao (2019), which uses the spectral ratio between the response spectral values of the first 3 s of the S wave and that of the first 3 s of the P wave, referred to as the R3P model. The modeling presented here was based on strong-motion records from the Next Generation Attenuation (NGA)-West2 dataset. We also used the spectral ratio between the response spectral values from the full records from the S-wave arrival time to the end of the record and that of the first 3 s P wave to develop a second EEW model (the RFP model). An advantage of these two models is that the magnitude and hypocentral distance are not required in considerable magnitude and distance ranges. This means that the errors in the estimated source and path parameters from the first 3 s of the P wave will not affect the model predictions. A theoretical justification for these results is that the magnitude and the distance scaling rates for the first 3 s of the P wave are similar to those of the first 3 s of the S wave. This may also apply to the full S-wave window within useful EEW magnitude and distance ranges. We also found that when the estimated magnitude and distance for a record are necessary, the effect of the corresponding errors would be smaller than using a ground-motion prediction equation (GMPE), because the magnitude and distance scaling rates from this study are smaller than those of many GMPEs. [ABSTRACT FROM AUTHOR]

In the present study, we have estimated the coda Q (QC) and the geometrical spreading factor (gamma) for the Saurashtra region that is located in the western part of the Deccan Volcanic Province, Gujarat, India. The waveform data from the seismic network operated by the Institute of Seismological Research, Gandhinagar, are used for the analysis. We have used records of a total of 221 local earthquakes with epicentral distances less than 70 km from the seismic stations. The moment magnitude range of the earthquakes is 2.5-5.3, and the depth range is 1-22 km. The QC has been estimated at five central frequencies (1.5, 3, 6, 12, and 20 Hz) using 20, 30, and 40 s window lengths for vertical, north-south, and east-west components, respectively. The obtained QC values show that the attenuation in the region has a strong dependence on frequency and points toward a heterogeneous medium. The geometrical spreading factors are also estimated for two cases, that is, with and without Q at the same central frequencies and window lengths. The average geometrical spreading factors with Q are 1.37, 1.48, 1.40, 1.08, and 1.04, at central frequencies 1.5, 3, 6, 12, and 20 Hz, respectively, whereas it is 1.59, 1.53, 1.47, 1.19, and 1.14, respectively, in the absence of Q. The estimated values also indicate that the medium is heterogeneous in the Saurashtra region. The estimated region-specific coda Q and the geometrical spreading factor may help in the modeling of strong ground motions and assessment of the seismic hazard for the Saurashtra region. [ABSTRACT FROM AUTHOR]

The time-averaged shear-wave velocity in the top 30 m, VS30, is used to represent the site condition in many ground-motion models (GMMs). Regionalized GMMs account for regional differences in the in(VS30) scaling by including region-specific coefficients for the site term. For example, recent GMMs developed for subduction zone earthquakes as part of the Next Generation Attenuation-Subduction (NGA-Sub) project include region-specific VS30 scaling for seven regions: South America, Central America, Japan, New Zealand, Taiwan, Cascadia (Pacific Northwest America), and Alaska. Of these seven regions, South America has the largest within-event standard deviation. One cause for the larger within-event standard deviation is a weaker relation between VS30 and the site term in South America compared to other regions. A cause for this weak correlation is that most of the VS30 values for the South American region in the NGA-Sub data set are based on proxies. The relation between VS30 and the site term improves significantly for periods less than 1 s if only stations with measured VS30 are considered, but the correlation is weak for periods greater than 1 s even for stations with measured VS30, indicating that, for the South America region, VS30 is not well correlated with the deeper shear-wave velocity profile that controls the long-period amplification. To improve the site terms for South America, we develop a model based on the horizontal-to-vertical spectral ratio (HVSR) from microtremors, similar to the approach used by Pinilla-Ramos et al. (2022) for California. The data set includes 660 recordings from 51 earthquakes recorded at 274 sites. The site-term model includes the period-dependent HVSR amplitude and the geometric mean of the average HVSR amplitude over the frequency band of 0.25 to 15 Hz. Including these two parameters reduces the standard deviation of site-specific site terms over the period range 0.3-3 s, with the largest reduction in the period range 1-2 s. This site-term model can be incorporated into subduction GMMs and implemented in probabilistic seismic hazard analyses for South America. [ABSTRACT FROM AUTHOR]

To estimate predicted ground motion from a teleseismic slip model, we use a low- and high-frequency hybrid method to simulate the regional, strong ground motions observed following the 18 April 2014 moment magnitude (MW) 7.3 Papanoa, Mexico, earthquake. To generate the regional ground motion at low frequencies (<1 Hz), a teleseismically derived, finite-fault, kinematic model is used to define the earthquake source, taking into account slip-model variations identified with a parameter sampling approach that considers possible errors in the fault geometry, the hypocenter depth, and the rupture velocity. A 3D crustal model is used to calculate the low-frequency ground motions using a finite-element calculation that includes topography and considers variations in the source model to estimate the uncertainty in the calculations. High frequencies (>1 Hz) are added using a 1D full-wave propagation code that estimates uncertainties by considering multiple random distributions of slip with different spatial correlation lengths. The synthetic, broadband (0.05-10.0 Hz) ground motions are obtained by combining the low- and high-frequency portions match filtered at 1 Hz. These synthetic ground motions are compared with the regional observations using velocity records, peak ground acceleration, and medians of the orientation-independent response spectra of the horizontal components (RotD50) calculated at periods of 0.2, 0.3, 0.5, 1.0, 2.0, 3.0, 5.0, 7.5, and 10.0 s. The results indicate that ground motions estimated at these periods using our hybrid approach based primarily on a teleseismically derived source model are comparable to the values observed for the 2014 Papanoa earthquake at regional distances. The approach could be used to estimate strong-motion spectral levels expected for regions with limited local and regional recordings and could also fill in magnitude or distance gaps in ground-motion prediction relations utilized in the assessment of seismic hazard. [ABSTRACT FROM AUTHOR]

In geophysical inference problems, quantification of data uncertainties is required to balance the data-fitting ability of the model and its complexity. The transdimensional hierarchical Bayesian approach is a powerful tool to evaluate the level of uncertainty and determine the complexity of the model by treating data errors and model dimensions as unknown. In this article, we take account of the uncertainty through the whole procedure, thus developing a two-step fully Bayesian approach with coupled uncertainty propagation to estimate the crustal isotropic and radial anisotropy (RA) model based on Rayleigh and Love dispersion as well as receiver functions (RFs). First, 2D surface-wave tomography is applied to determine period-wise ambient noise phase velocity maps and their uncertainty for Rayleigh and Love waves. Probabilistic profiles of the isotropic average VS and RA as a function of depth are then derived at station sites by inverting the local surface-wave dispersion and model errors and RFs jointly. The workflow is applied to a temporary seismic broadband array covering all of Sri Lanka. The probabilistic results enable us to effectively quantify the uncertainty of the final RA model and provide robust inferences. The shear-wave velocity results show that the range of Moho depths is between 30 and 40 km, with the thickest crust (38-40 km) beneath the central Highland Complex. Positive RA (VSH > VSV) observed in the upper crust is attributed to subhorizontal alignment of metamorphic foliation and stretched layers resulting from deformation. Negative RA (VSH > VSV) in the midcrust of central Sri Lanka may indicate the existence of melt inclusions and could result from the uplift and folding process. The positive RA in the lower crust could be caused by crustal channel flow in a collision orogeny. [ABSTRACT FROM AUTHOR]

The P-wave peak distribution in azimuth and takeoff angles, corrected for the distance through empirical attenuation laws, can reveal the radiation pattern amplitude of the source (Tarantino et al., 2019). This piece of information, jointly combined with the available polarities and S-wave peak amplitudes, can provide the full focal mechanism, constraining the solution also when only a few seismic station records are available, that is, in the case of microseismicity. We proposed a new technique, named P-, S-wave amplitude, and polarities (P-SAP), designed to compute the focal mechanism by jointly inverting the P-, S-wave amplitude ratios and P-wave polarities in a Bayesian framework and employing the octree strategy (Fang et al., 1996) to explore the space of possible solutions. The outputs are strike, dip, and rake angles of the most likely triplet (principal and auxiliary planes) with the related uncertainties, as well as other multiple solutions, if present. We tested the methodology to synthetic data, and we applied it to a microseismic sequence that occurred in Irpinia region, southern Italy. A background microseismicity occurs in a volume delimited by the faults activated during the 1980 M 6.9 Irpinia earthquake. This faults system is complex and composed of northwest-southeast-striking normal faults along the Apennines chain and an approximately east-west-oriented strike-slip fault, deep-seated in the Potenza area. A network of three-component accelerometers and velocimeters are currently deployed to monitor the area. The major topic of this work is validating the proposed P-SAP methodology for microseismicity studies. We also inferred the optimum stress tensor of the sequence, confirming that the microseismicity is controlled by the regional stress field and can reveal characteristics useful to highlight behaviors of larger-scale seismicity. [ABSTRACT FROM AUTHOR]

The objective functions adopted by earthquake early warning (EEW) location algorithms are inadequate for out-of-network earthquakes. As a result, the real-time locations of these earthquakes are often erroneous. The consequences of mislocating out-of-network earthquakes are that their magnitudes are miscalculated, and the loci of their shaking predictions map are shifted. Given that the largest earthquakes occur in subduction settings, improving real-time out-of-network earthquake location is of great importance. In this study, the Virtual Dynamically Assembled Array Algorithm (ViDA³) is introduced, which addresses the location issue of offshore and off-network earthquakes. The guiding principle underlying the new EEW location algorithm is that standard seismic networks may be viewed as a collection of medium-sized seismic arrays, with each array consisting of three or more network stations. The potential of array seismology for EEW against out-of-network earthquakes stems primarily from the slowness vector, which points at the direction of the epicentral region. Thus, this region may be constrained merely by intersecting two or more such vectors. In addition, the length of the slowness vector depends on the hypocentral distance and depth and is thus vital for addressing an acute problem in a subduction setting--discriminating between upper crust and deep slab earthquakes. Furthermore, when the slowness of the P phase is known, the slowness of the S phase is deduced, and the S-phase arrival is searched for using the shift-and-sum practice. What makes ViDA³ so attractive is that, in locations where a real-time network is already in place, these added values may be achieved without extra hardware or substantial budget requirements. We present the result of ViDA³ real-time operation on a shallow earthquake offshore Vancouver Island and the result of its replay on a deep slab earthquake in northern Chile. performance is further assessed using a dataset of seismograms from the Mendocino Triple Junction area. It is concluded that ViDA³ location scheme outperforms currently available EEW location algorithms for out-of-network earthquakes. [ABSTRACT FROM AUTHOR]

The correlation between seismic and acoustic signals can be used to quantify the influence of earthquake ground motion on the output signals of infrasound sensors and thus evaluate the performance of infrasound sensors under field conditions. However, there have been relatively few studies, and earthquakes considered in those studies are large magnitude events. There remains a need to quantify correlation mechanisms at high frequencies using small earthquakes. In this study, we utilize a collocated seismoacoustic station BJT and a six-element infrasound array DQS to study different coupling mechanisms for infrasound sensors. From 2019 to 2021, 11 and 37 small magnitude earthquakes were detected by BJT and DQS, respectively. Seismoacoustic signals from these small magnitude earthquakes are used to compute the seismoacoustic spectral ratio and the observed spectral ratios are then compared with theoretical estimates. For local seismic-to-acoustic coupling (local infrasound), the highly local pressure field induced by high-frequency ground motion and the separation between seismoacoustic sensors reduce seismic and acoustic signal correlation, which prevents the use of small earthquakes in current studies. The seismic sensitivity of the infrasound sensor, MB3a is shown to be for ground acceleration or for ground velocity and may be an important source of high-frequency noise for an infrasound station using this sensor. Furthermore, an empirical relation is developed to constrain the characteristics of earthquakes that can generate coupled signals on the infrasound sensor. Our study complements previous work and provides insight into the improved interpretation of infrasound signals and methods of seismoacoustic station calibration. [ABSTRACT FROM AUTHOR]

Determining the depths of small crustal earthquakes is challenging in many regions of the world, because most seismic networks are too sparse to resolve trade-offs between depth and origin time with conventional arrival-time methods. Precise and accurate depth estimation is important, because it can help seismologists discriminate between earthquakes and explosions, which is relevant to monitoring nuclear test ban treaties and producing earthquake catalogs that are uncontaminated by mining blasts. Here, we examine the depth sensitivity of several physics-based waveform features for ~8000 earthquakes in southern California that have well-resolved depths from arrival-time inversion. We focus on small earthquakes (2 < ML < 4) recorded at local distances (<150 km), for which depth estimation is especially challenging. We find that differential magnitudes (MW/ML-MC) are positively correlated with focal depth, implying that coda wave excitation decreases with focal depth. We analyze a simple proxy for relative frequency content, ɸ ≊ log10(M0) + 3log10(fc)ɸ, and find that source spectra are preferentially enriched in high frequencies, or "blue-shifted," as focal depth increases. We also find that two spectral amplitude ratios Rg 0.5-2 Hz/Sg 0.5-8 Hz and Pg/Sg at 3-8 Hz decrease as focal depth increases. Using multilinear regression with these features as predictor variables, we develop models that can explain 11%-59% of the variance in depths within 10 subregions and 25% of the depth variance across southern California as a whole. We suggest that incorporating these features into a machine learning workflow could help resolve focal depths in regions that are poorly instrumented and lack large databases of well-located events. Some of the waveform features we evaluate in this study have previously been used as source discriminants, and our results imply that their effectiveness in discrimination is partially because explosions generally occur at shallower depths than earthquakes. [ABSTRACT FROM AUTHOR]

The detection of microseismic events with low signal-to-noise ratios (SNRs) can expand the seismic catalog and provide opportunities for a deeper understanding of subsurface reservoir features. We propose a novel polarization analysis method for comprehensively detecting S-wave arrival and P-S travel time of low-SNR events from the particle motion of P and S waves in the time and frequency domain. In most circumstances, the direct S-wave particle motion shows a flat plane, and that is perpendicular to the direct P-wave motion direction. We combine these two properties to detect the S-wave arrival of low-SNR events. Our previous study applied spectral matrix (SPM) analysis to characterize the 3D particle motion of P waves. However, SPM analysis had limitations in detecting S-wave arrivals. We then introduce the time-delay components of the SPM (complex spectral matrix [cSPM]) to characterize the S-wave particle motion, separate the S-wave from the noise, and detect S-wave arrivals. Using the cSPM analysis method, we assess the planarity and perpendicularity of the S-wave polarization in the time and frequency domains. We then define a characteristic function that detects S-wave arrivals by combining two properties, planarity and perpendicularity, to detect more low-SNR events. The P-S travel time is obtained by setting the threshold values for the P- and S-wave characteristic functions. We apply our method to 4 hr and 2 months of field data recorded at the Groningen field in the Netherlands. Our method successfully detects the P-S travel time of all catalog events and several additional undetected events. We locate the hypocenter of all events using the detected P-S travel times with a grid-based search method. [ABSTRACT FROM AUTHOR]

Estimating the corner frequency (fc) of an earthquake is of fundamental importance to improving our knowledge of the physics of the rupture that gives rise to a seismic event, while also having important implications by providing information on the high-frequency radiation for seismic hazard studies. However, the estimation of fc through spectral-fitting methods suffers from trade-offs with the estimation of seismic wave attenuation, making the obtained values precise but not necessarily accurate. For this reason, after a review of the source model proposed by Brune (1970), a new method of estimating fc, based on the phase fitting of Fourier spectra of the Brune's seismic pulse related to S-waves, called Fourier phase spectra fitting (FPS), is proposed and evaluated in this study. The method can be applied in cases in which Brune's model may be appropriate, while also considering the effects of propagation on impulse deformation, for which the synthetic tests have been conducted. The results, obtained first using synthetic seismograms generated under controlled conditions and then on a data set of recordings of real seismic events collected at the Groningen gas field in the Netherlands, showed the method to be promising (being accurate and precise) and at the same time pointed out its limitations, with its applicability being restricted to short hypocentral distances of <20 km. [ABSTRACT FROM AUTHOR]

Analysis of equations of motion by Moczo et al. (2022) led to the conclusion that the discrete (grid) representation of the heterogeneous medium must be wavenumber bandlimited up to the Nyquist frequency. This is a consequence of the spatial discretization. Mittet (2021a) reported that if the discrete grid model of medium coincides with the true medium up to some wavenumber, the simulated wavefield is accurate only up to a half of this wavenumber. Here, we present results of the systematic and comprehensive analysis focused on the principal limits of accuracy of numerically simulated wavefields. First, we analyze wavenumber spectra of (1) exact wavefields in a heterogeneous elastic medium, (2) wavenumber bandlimited wavefields, and (3) spatially discretized wavefields. Then, we derive spatial dependence of the frequency spectrum of waves generated by a finite source, and perturbing wavefields due to a small perturbation of the medium and due to a small wavenumber bandlimited perturbation of the medium. We analyze an interaction of an incoming wave with the medium perturbation through a change of phase difference and through wavenumber spectra. We draw conclusions on the wavenumber limitation of wavefields in the wavenumber bandlimited heterogeneous medium. We numerically verify the fundamental finding using exact solutions. The main consequence for the finite-difference (FD) modeling based on spatial discretization of the computational domain is: Due to spatial sampling, the medium must be wavenumber limited up to the Nyquist frequency. Then, the wavefield should not be sampled by less than four spatial grid spacings per shortest wavelength to obtain sufficiently accurate results. This applies to any heterogeneous FD scheme. [ABSTRACT FROM AUTHOR]

In previous studies, structure vibration control mainly focused on integer-order systems or commensurate fractional-order (FO) dynamics systems. In this paper, we propose an adaptive radial basis function (RBF) neural network feedback (ARBF-FK) controller for FO building structure vibration systems with viscoelastic (VE) dampers, uncertain structure parameters and unknown seismic waves. Firstly, use a FO multi-order state space description for FO building structural vibration systems. Then, the design of the ideal feedback controller is based on the stability theory of FO multi-order systems. Moreover, to reduce the cost and facilitate the practical implementation of the control, unknown earthquake seismic waves is approximated by a RBF neural network, the ARBF-FK controller is proposed. In addition, to guarantee the stability of the closed-loop control system and avoid falling into local optimum, network weights are adapted by the FO Lyapunov stability theory instead of gradient descent algorithms. Finally, the convergence rate of the system is analyzed and perform various tests on the ARBF-FK controller. The simulation results demonstrate that the ARBF-FK controller has superior performance and is very robust to control FO building structure vibration systems with uncertain structure parameters and unknown external earthquake excitation. • A FO multi-order state space description method of FO building vibration systems is constructed. • An online adaptive ARBF-FK robust control strategy for FO building vibration systems is proposed. • Adaptive weights of neural networks are derived using the FO Lyapunov theory. [ABSTRACT FROM AUTHOR]

The preface for the article collection "10 years after the 2011 Tohoku earthquake: a milestone of solid earth science" highlights the scientific discoveries made since the earthquake, thanks to near-field observations and existing knowledge about the northeastern Japan arc. The earthquake revealed dynamic frictional behaviors of the subduction interface and provided insights into subduction zone dynamics. The collection of research on the Tohoku earthquake is expected to benefit the understanding of subduction earthquakes worldwide. The preface also mentions various research papers included in the collection, covering topics such as coseismic stress drop, afterslip, seafloor observations, slow earthquake activity, tsunami deposits, paleoseismology, and numerical modeling of the earthquake cycle. Ongoing research on postseismic deformation and historical research on earthquake occurrence are also discussed. The authors express their appreciation to the reviewers and the editorial board for their contributions to the special issue. [Extracted from the article]

The depth of the Los Angeles (LA) basin is a critical factor for seismic hazard assessment and active tectonic studies. By analyzing S‐waves generated by earthquakes below the basin that convert to P‐waves at the sediment‐bedrock interface, we estimate the maximum depth of the LA basin to be 9 km. This estimate depends on the velocities within and below the basin, and the depth presented here is based on the latest community velocity model. To map the basin depth, we use two dense arrays: the Community Seismic Network, a dense network of low‐cost accelerometers in schools across LA region, and a basin‐wide node survey conducted in 2022, consisting of about 300 geophones deployed for a month. Utilizing differential travel times between direct S and Sp converted phases of local earthquakes, we produce a detailed depth map of the LA basin. Plain Language Summary: A basin's depth influences how seismic waves resonate and amplify, affecting ground shaking during earthquakes. This information is vital for designing earthquake‐resistant buildings and infrastructure in the densely populated Los Angeles area, which sits atop a sedimentary basin. We collected data from two dense seismic sensor arrays: the Community Seismic Network, which uses low‐cost sensors placed in schools across the LA region, and a survey in 2022 using about 300 geophones deployed across the basin. By examining the travel times of seismic waves that convert at the sediment‐bedrock interface, we provided an independent measure of the basin's depth with dense coverage. Our findings show that the deepest part of the central Los Angeles Basin reaches over 9 km. Key Points: New dense arrays covering Los Angeles basin enable better characterization of basin structureSp converted phase provides an independent constraint on basin depthThe deepest part of the central Los Angeles basin has an averaged depth of over 9 km [ABSTRACT FROM AUTHOR]

The violent eruption of the Hunga (Tonga) submarine volcano on 15 January 2022 caused a 58 km‐heigh ash plume, catastrophic tsunami, and significant global seismic and infrasound waves. However, the physical mechanism underpinning its multiple‐explosive events remains unclear, and its resolvability relies on the seismic waveform source inversion. The studies of two different point‐source models, the seismic moment tensor (MT) and the single force (SF), have been performed separately for this eruption, which, interestingly, can explain the seismic data adequately. Here, we use a joint inversion of MT and SF to unravel a composite source of an explosion‐like MT and a significant upward force for the first major explosive event. Regarding the direction and magnitude, we propose that the upward force is likely a rebound force in response to the pressure drop on the seafloor because the water body above the volcano was abruptly uplifted by the shallow underwater explosion. Plain Language Summary: The physical process of the violent eruption of the Hunga (Tonga) submarine volcano on 15 January 2022 remains unclear. To date, the common source model for volcano eruptions—a single force (SF) and the common source model for earthquakes and explosions—a moment tensor (MT), have been inferred individually for this eruption. Interestingly, both can explain the recorded seismic signals reasonably well. A question arises whether a combination of sources is a better physical model. Therefore, we combine the MT and SF to represent the eruption process in this study. The source analysis for the first major event of this eruption reveals a possible composite process of a shallow underwater explosion and a significant upward force. The upward force is opposite the common downward‐reaction force to the material jetting. It is likely caused by the abrupt displacement of the water above the volcano resulting from the shallow underwater explosion. When the downward water pressure on the seafloor vanishes, the seafloor responds by an upward‐rebound force. Key Points: We perform probabilistic inversion of seismic waveform data to study the force equivalent system of the 2022 Hunga (Tonga) eruptionThe first major explosive event of the shallow eruption sequences may consist of an explosion‐like moment tensor and a large upward forceA possible mechanism of the accompanying upward force is the rebound force responding to the sudden pressure drop of uplifted water body [ABSTRACT FROM AUTHOR]

Ambient noise interferometry has become a common technique for monitoring slight changes in seismic velocity in a variety of contexts. However, the physical origin of the resolved small velocity fluctuations is not well established for long‐term seasonal effects. Here we propose a physical forward model of scattered waves in a deformable medium that includes acousto‐elastic effect, which refers to non‐linear elasticity with third‐order elastic constants. The model shows that small pressure perturbations of a few kPa due to seasonal variations in the water table can induce seismic velocity changes compatible with those measured at the surface by ambient noise interferometry. The results are consistent with field observations near the deep geothermal site of Rittershoffen (France). They illustrate the capability in modeling the diffuse wavefield from scattering synthetic waves to reproduce ambient noise signals for monitoring environmental and/or deep reservoir signals. Plain Language Summary: Monitoring the fine evolution of the Earth's crust either prior to catastrophic events such as earthquakes or landslides, or georesource exploitation, is an important objective for risk management. Ambient noise interferometry is one of the emerging tools for assessing the minute evolution of seismic velocities in the subsurface. However, the physical origin of the observed small velocity changes is not well established. Here we propose a physical model of scattered waves in a deformable medium that includes non‐linear elastic effects, which are not conventionally considered. The model shows that small pressure perturbations of a few kPa due to seasonal variations in the water table can induce seismic velocity changes compatible with those measured at the surface by ambient noise interferometry. The results are consistent with field observations near the deep geothermal site of Rittershoffen (France). They illustrate the capability in modeling scattered synthetic waves to reproduce ambient noise signals. Key Points: We develop an acousto‐elastic model for seismic wave scattering in a deforming layered subsurfaceStress fluctuations induced by seasonal water table variations are shown to be responsible for significant changes in seismic velocitiesThe model is providing an interpretation tool for environmental monitoring signals obtained from ambient seismic noise [ABSTRACT FROM AUTHOR]

This article presents a comprehensive study on the stability and failure mechanism of landslides in northwest mountainous areas under rainfall and earthquake conditions. The study focuses on the Lijie Beishan landslide as a typical case and combines on-site geological surveys with numerical simulations to evaluate its stability. The results show that the stability of the landslide decreases under static, rainfall, and earthquake conditions, with different failure modes observed. The study also compares different stability evaluation methods and provides valuable references for landslide stability evaluation in the region. The given text discusses the stability and failure process of a landslide using numerical simulation methods. The lower layer of the landslide is highly fragmented and prone to sliding due to its poor engineering properties. Human activities such as slope cutting and inappropriate land use contribute to the instability and sliding of the landslide. The text describes the principles and parameters used in the numerical simulation, including the use of finite element software and a viscoelastic constitutive model. The results of the simulation show the potential sliding surface and displacement of the landslide under different conditions. This document presents the results of a stability analysis of landslides in Lijie Beishan. The analysis was conducted under different conditions, including normal static, rainfall, and seismic conditions. The results indicate that the landslides have different failure modes and maximum deformations depending on the condition. The stability factor values were calculated to determine the stability state of the landslides, with values below 1 indicating instability. The analysis provides valuable information for understanding the [Extracted from the article]

Wide azimuth seismic data play an important role in deep reservoir prediction. According to the Paleogene clastic rock reservoir prediction, the high‐density and wide azimuth 3D seismic data acquisition of ocean bottom nodes was first carried out in a Chinese offshore oilfield in 2019. After high precision amplitude‐preserving processing, we obtained the high‐quality wide azimuth gathers. However, the research on anisotropy and reservoir prediction using wide azimuth seismic data mainly focuses on carbonate and bedrock intervals, which is not suitable for clastic rock reservoir prediction. Therefore, this paper innovatively proposes a clastic rock reservoir prediction method, which studies prestack reservoir prediction in the ray parameter domain based on wide azimuth ocean bottom node seismic data. Based on the azimuth gathers, we can obtain elastic parameters through prestack amplitude versus offset inversion, which is used to characterize the reservoir, so it is significant to obtain high precision elastic parameters in order to get highly reliable reservoir prediction results. In this paper, we develop an amplitude versus offset inversion method based on the Bayesian theory in ray parameter domain, the output of which is density, P‐wave impedance and Vp/Vs. These elastic parameters have high precision, and density data are valuable input for reservoir characterization because they are sensitive to the lithology of clastic rock reservoir at different orientations. In ray parameter domain inversion, the ray path of seismic wave propagation is considered polyline, which is more consistent with the actual situation; thus, extracted amplitudes of P gathers used in inversion are more accurate. In addition, the reflection coefficient formula in ray parameter domain has higher precision when the incident angle is large. The inversion based on the Bayesian theory can improve the stability of the inversion. Test on the actual data shows that the result of ray parameter domain inversion with a Bayesian scheme is more accurate, stable and reliable. Based on the above high precision density inversion results, an innovative wide azimuth data reservoir prediction technology based on elliptical short‐axis fitting was proposed. The actual prediction of the deep reservoir in the Bohai oilfield shows that sand thickness fitting prediction results in the short axis can best match the actual drilling sandstone thickness. The coincidence rate is 86% and the short‐axis fitting results are more in agreement with geological laws. Theoretical research and practical applications have shown that this method is feasible and effective, with high prediction accuracy, computational efficiency and strong application value. [ABSTRACT FROM AUTHOR]

An innovative concept of metabarrier is presented for seismic Rayleigh wave attenuation, which consists of a periodic array of cylindrical water tanks acting as resonant units above the soil surface. A pertinent theoretical framework is developed and implemented in COMSOL Multiphysics. The framework treats the dynamics of the water tank by a well-established three-dimensional linear, pressure-based model for fluid-structure interaction under earthquake excitation, accounting for the flexibility of the tank wall; furthermore, the soil is idealized as a homogeneous and isotropic medium. Floquet-Bloch dispersion analysis of the unit cell demonstrates the presence of relevant band gaps in the low-frequency range below 20 Hz and in the higher frequency range as well. The dispersion analysis is validated by comparison with the frequency-domain analysis of a soil domain with a finite array of water tanks. The band gaps are of interest to attenuate seismic Rayleigh waves and, more generally, Rayleigh waves caused by other ground vibration sources such as road or railway traffic. The water-tank resonant units are readily tunable by varying the water level, which allows changing opening frequencies/widths of the wave attenuation zones. This is a remarkable advantage over alternative seismic metamaterials that, in general, are not designed to be tunable. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 2)'. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper proposes a simplified analytical solution for longitudinal seismic responses of a circular tunnel crossing a fault zone under longitudinally propagating shear waves. The transmissions and reflections of shear waves at two geological interfaces between the fault zone and intact rock are considered when calculating the free‐field displacement. An improved elastic foundation beam model considering different tangential contact conditions at the tunnel‒rock interface is also adopted. According to the continuous conditions at the two geological interfaces, explicit expressions for the tunnel displacement, bending moment, and shearing force are given. The effectiveness of the proposed analytical solution is validated via numerical simulations, and the importance of accounting for tangential contact conditions at the tunnel‒rock interface is emphasized. Moreover, parametric studies are performed to investigate the effects of the fault zone width, rock conditions, tunnel lining stiffness, tangential contact conditions, and earthquake frequency on the deformation and internal forces of tunnels subjected to seismic waves. This novel analytical solution can be utilized to quickly estimate the longitudinal seismic responses of circular tunnels crossing fault zones subjected to longitudinally propagating shear waves, particularly in the preliminary engineering design, and can be extended to geological conditions with multiple interfaces. [ABSTRACT FROM AUTHOR]

Tailings dams play a critical role in ensuring the safety of mining operations. However, earthquakes can cause breaches in these dams, resulting in significant casualties and property damage. This study investigates the dynamic response characteristics of uranium tailings dams subjected to seismic loading, employing the discrete element method. It specifically analyzes how seismic wave amplitude, frequency, and the friction angle of tailings sand affect the dams' dynamic response. The results reveal that the peak ground acceleration ratio (PGAR) exhibits an increasing–decreasing–increasing pattern with elevation. When the friction angle of the tailings sand exceeds 35°, the overall stability of the dam improves. Conversely, a friction angle below 25° significantly increases the risk of dam failure. Additionally, the dam shows a reduced dynamic response to seismic waves with frequencies exceeding 15 Hz. At lower frequencies, deformation and damage are primarily concentrated on the slope face, while at higher frequencies, damage is predominantly located at the bottom of the model. These findings provide a theoretical foundation and reference for the safe operation of tailings dams, highlighting their practical significance. [ABSTRACT FROM AUTHOR]

Channel wave seismic activity often occurs with thin and medium-thick coal seams being the main target layer. To address the problem of channel wave applicability detection in extremely thick coal seams, the propagation and identification characteristics of channel waves remain the focus of research. Therefore, this paper takes the in-seam wave exploration of a 27 m extremely thick coal seam as an example and uses the staggered mesh finite difference method to construct a three-dimensional medium model for numerical simulation. An analysis of the physical parameters of coal and rock, along with the dispersion characteristics of channel waves in extra-thick coal seams, is utilized, through the Zoeppritz equation and the total reflection propagation method, to calculate the imaging. We found the following: (1) The dispersion areas and weak dispersion areas along the detection direction are extremely thick coal seams. (2) There are apparent channel waves in extra-thick coal seams, with a waveform similar to body waves; the length of the wave train is shorter than that of the conventional channel wave, and the arrival time can be estimated accurately. The amplitude of the apparent channel wave is affected by the degree of dispersion, with lower attenuation and higher resolution. The characteristic of total reflection in extremely thick coal seams is that the incident angle is equal to the critical angle, and the dispersion characteristics are weak. (3) The channel waves with weak dispersion characteristics in extra-thick coal seams are mainly Love-type waves. [ABSTRACT FROM AUTHOR]

This study presents a numerical simulation approach used to investigate seismic-wave propagation in specific geological structures. Using the LS-DYNA software, the simulation incorporated a TNT explosion model to simulate seismic energy released during earthquakes. It provides a new method to investigate the propagation characteristics of seismic-waves within geological structures. Firstly, the measurement conditions and geological settings of the seismic event on 18 February 2012 in Northeast China are presented. Subsequently, a numerical simulation model of seismic-wave propagation is developed. The simulation result validates it by comparing it with recorded data from seismic stations, demonstrating a promising correspondence between the simulated and observed data. Additionally, the simulation simulates the seismic-wave propagation within water and layered geological structures, validating the numerical simulation model. The numerical model is an effective tool for simulating the propagation of seismic waves in geological structures. This study is important for evaluating seismic-wave propagation using the simulation method. [ABSTRACT FROM AUTHOR]

This paper presents the results of precise measurements of temperature and pore pressure in the "reservoir–well" system during the development of iron ore deposits of the Kursk Magnetic Anomaly (KMA) via blasting. For the observation period from October 2021 to June 2024, variations in compressibility, permeability and temperature in the upper Albian-Cenomanian confined aquifer, which is used for district water supply, were determined. The general trend in a decrease in water temperature was traced (from 12 °C to 11.4 °C). It was accompanied by an increase in the hydrostatic head (from 3.7 m to 7.4 m). Water temperature in the upper aquifer was measured for 9 industrial explosions in the mine and for 30 explosions in the quarry. For one explosion in the mine and five explosions in the quarry the coseismic changes in water temperature with amplitudes of 0.06–0.09 °C were established, while changes in pore pressure in the "reservoir–well" system were 0.4–2.2 kPa. Local changes in the permeability of the reservoir in the vicinity of the well (the skin effect) are considered to be the main factor that controls the coseismic response of temperature during industrial explosions. As the reservoir permeability increases, the water temperature in the "reservoir–well" system can decrease and vice versa. The same pattern was observed according to regime measurements performed in 2022–2023. The recorded coseismic responses of water temperature in the upper aquifer in the high-frequency range are similar to the effects observed during propagation of seismic waves originated from earthquakes in the low-frequency range at different sites all over the world for the seismic energy density of 0.05–0.45 J/m3. The observed variations in aquifer temperature in the "reservoir–well" system under episodic dynamic impacts are of particular interest from the point of view of activating hydrogeochemical processes that accompany the development of iron ore deposits. [ABSTRACT FROM AUTHOR]

China's southwestern region boasts abundant hydropower resources. However, the area is prone to frequent strong earthquakes. The areas surrounding dam sites typically have deep overburden, and the liquefaction of saturated sand foundations by earthquakes poses significant safety risks to the construction of high dams in the southwest. The effects of liquefaction and reinforcing measures on the foundations of rockfill dams on liquefiable overburden under seismic action are currently the subject of somewhat unsystematic investigations. The paper utilizes the total stress and effective stress methods, based on the equivalent linear model, to perform numerical simulations on the overburden foundations of rockfill dams. The study explores how factors such as dam height, overburden thickness, liquefiable layer depth, liquefiable layer thickness, ground motion intensity, and seismic wave characteristics affect the liquefaction of the overburden foundations. Additionally, it examines how rockfill dams impact the dynamic response, considering the liquefaction effects in the overburden. The results show that although the total stress method, which ignores the cumulative evolution of pore pressure during liquefaction, can reveal the basic response trend of the dam, its results in predicting the acceleration response are significantly biased compared to those of the effective stress method, which comprehensively considers the cumulative changes in liquefaction pore pressure. Specifically, when the effect of soil liquefaction is considered, the predicted acceleration response is reduced compared to that when liquefaction is not considered, with the reduction ranging from 4% to 30%; with increases in the thickness and burial depth of the liquefiable layer, the effective stress method considering liquefaction significantly reduces the predicted peak acceleration; the effect of liquefiable soil on the attenuation of the speed response is more sensitive to the low-frequency portion of the seismic wave. The study's findings are a significant source of reference for the planning and building of rockfill dams on liquefiable overburden. [ABSTRACT FROM AUTHOR]

In this study, the seismic performance of an ancient pagoda with significant historical and cultural values in China is upgraded by using overall friction pendulum bearing (OFPB) seismic isolation technology, This technique can be used to isolate the pagoda without damaging it. By implementing the OFPB seismic isolation retrofit on the pagoda and comparing and analyzing it with the unretrofitted seismic model, the response of the pagoda under the action of nine seismic waves of three types, namely, near-field earthquakes, far-field earthquakes, and common earthquakes, is investigated. The results show that the OFPB seismic isolation technique significantly reduces the seismic response of the ghats, in which the acceleration amplification factor is reduced by a maximum of 82.46%, the inter-story displacement is reduced by a maximum of 85.15%, and the base shear force is reduced by a maximum of 96.76%. In addition, the tensile damage of the ghats with OFPB seismic isolation was significantly controlled. While the model without seismic isolation has serious damage under the same seismic action and even faces the risk of collapse. The results of the study confirm that the OFPB seismic isolation technology plays a key role in improving the seismic performance of the tower, which is of great theoretical and practical significance to the protection of the tower, and provides an effective technical way for the protection of the tower in the seismic-prone areas. [ABSTRACT FROM AUTHOR]

This article presents a study of the wind-resistance and seismic behavior of steel frame elevator structures with square hollow section (SHS) members. The study was conducted by numerical analysis, it begins by examining the semi-rigid performance of SHS T-joints (beam-column joints) under in-plane bending moment, proposes a semi-rigid connection model for the joints, and then investigates the influence of semi-rigid joint effect on the performance of the steel elevators. Finite element (FE) results showed that the semi-rigid model can predict the moment-rotation response of the beam-column joints. The results also showed that the natural vibration period of the elevator with semi-rigid joints is 20% higher than that of an elevator with rigid joints. The semi-rigid joint effect causes the lateral drift of the elevator to increase by more than 47% under wind load, causing the maximum story drift of the elevator to exceed the limit specified in the current code. The semi-rigid joint effect causes the lateral displacement of the elevator to increase by approximately 15%-30% under the seismic waves of a rare earthquake. [ABSTRACT FROM AUTHOR]

Recently, Egypt had seismic activity. These seismic events have affected the stability of minarets, especially historical ones. Weight is one of the minaret's main stability factors. The main objective of the current research is to perform a three-dimensional (3D) assessment of an existing minaret, determine its accurate spatial model, document its current condition, examine its stability in the event of earthquakes, and identify the requisite measures to safeguard the minaret from any potential damage. The masonry to construct the minaret was used by extracting and examining specimens of this substance to determine its physical characteristics. The current work created three-dimensional models of the Abou-Ghanam El-Bialy minaret using a terrestrial laser scanner (TLS) to document its current condition, as well as minaret was subjected to a free vibration analysis using 3D finite element modeling. Finally, the minaret's seismic behavior was assessed utilizing mode forms, base responses, and normal stresses. The surveying method effectively documented the Minarets' existing case. The 3D seismic analysis showed that the minaret responded dynamically to earthquake loading, with mode shapes, base reactions, and normal stresses being crucial characteristics. Based on these data, we may suggest procedures to protect the minaret during seismic events. [ABSTRACT FROM AUTHOR]

In the generalized continuum mechanics (GCM) theory framework, asymmetric wave equations encompass the characteristic scale parameters of the medium, accounting for microstructure interactions. This study integrates two theoretical branches of the GCM, the modified couple stress theory (M-CST) and the one-parameter second-strain-gradient theory, to form a novel asymmetric wave equation in a unified framework. Numerical modeling of the asymmetric wave equation in a unified framework accurately describes subsurface structures with vital implications for subsequent seismic wave inversion and imaging endeavors. However, employing finite-difference (FD) methods for numerical modeling may introduce numerical dispersion, adversely affecting the accuracy of numerical modeling. The design of an optimal FD operator is crucial for enhancing the accuracy of numerical modeling and emphasizing the scale effects. Therefore, this study devises a hybrid scheme called the dung beetle optimization (DBO) algorithm with a simulated annealing (SA) algorithm, denoted as the SA-based hybrid DBO (SDBO) algorithm. An FD operator optimization method under the SDBO algorithm was developed and applied to the numerical modeling of asymmetric wave equations in a unified framework. Integrating the DBO and SA algorithms mitigates the risk of convergence to a local extreme. The numerical dispersion outcomes underscore that the proposed SDBO algorithm yields FD operators with precision errors constrained to 0.5‱ while encompassing a broader spectrum coverage. This result confirms the efficacy of the SDBO algorithm. Ultimately, the numerical modeling results demonstrate that the new FD method based on the SDBO algorithm effectively suppresses numerical dispersion and enhances the accuracy of elastic wave numerical modeling, thereby accentuating scale effects. This result is significant for extracting wavefield perturbations induced by complex microstructures in the medium and the analysis of scale effects. [ABSTRACT FROM AUTHOR]

Melting experiments of Fe3C were conducted to 85 GPa in laser‐heated diamond anvil cells with in situ X‐ray diffraction and post‐experiment textural observation. From the determined pressure‐temperature conditions of the melting curve for Fe3C, together with literature data on the melting point of diamond and eutectic point of the system Fe‐Fe3C/Fe7C3 under high pressures, we established a self‐consistent thermodynamic model for high‐pressure melting of the system Fe‐C including the mixing parameters for liquids. The results show that mixing of Fe and C liquids is negatively nonideal from 1 bar to the pressure at the center of the Earth. The departure from ideal mixing becomes progressively larger with increasing pressure, which leads to greatly stabilized liquids under core pressures. The modeled carbon content in eutectic melts under core pressures is 3.3–4.4 wt%. From the Gibbs free energy, we derived an internally consistent parameters for Fe‐C outer cores which included the crystallizing points at their bottoms, isentropic thermal profiles, and densities and longitudinal seismic wave speeds (Vp). While the addition of carbon in excess of the eutectic melt composition effectively reduces the density of iron liquid, the Vp of iron liquid is not greatly changed. Therefore, the low density and high Vp of PREM relative to pure iron cannot be reconciled by an Fe‐C liquid. Therefore, the Earth's core cannot be approximated by the system Fe‐C and should include another light element. Plain Language Summary: The presence or absence of carbon in the Earth's central core has long been discussed in order to account for the observed core density lower than iron because the identification of such light elements in the core will provide critical information about the origin and evolution of the solid Earth. The relevance of carbon in the Earth's core is testable by comparing the density and seismic wave velocities of candidate Fe‐C materials with observations. Here we present a new experiment‐based thermodynamic model for the system Fe‐C. We first determined the melting points of Fe3C to 85 GPa. We then assessed thermodynamic parameters of Fe‐C liquids, from the constrained pressure‐temperature conditions of the melting curve for Fe3C, together with literature data. From the established model, we consistently computed the properties of hypothetical Fe‐C liquid outer cores including the density and longitudinal seismic wave velocity. While a carbon concentration greater than 4 wt% effectively reduces the density of iron liquid, the seismic velocity is not greatly changed, and therefore carbon cannot reconcile the low density and high velocity nature of the Earth's outer core. Therefore, the Earth's core cannot be approximated by the system Fe‐C and should include another light element. Key Points: Melting experiments of Fe3C were conducted to 85 GPa in diamond anvil cells with in situ X‐ray diffraction and textural observationA thermodynamic model for melting of the system Fe‐C which is applicable to the center of the Earth was establishedThe Earth's core cannot be approximated by the system Fe‐C and should include another light element [ABSTRACT FROM AUTHOR]

The high sensitivity of VP/VS to the presence of melt makes images of VP/VS structure particularly useful in magmatic systems, but detailed three‐dimensional models of VP/VS structure in magmatic systems are often restricted to the upper crust where there is a concentration of seismic sources used for imaging. Ps‐P tomography is a new technique that has been used to image three‐dimensional crustal‐scale variations in VP/VS in regions with limited seismic instrumentation. We apply the Ps‐P tomography technique to a well‐constrained, independently imaged magmatic setting, Mount St. Helens, to outline the efficacy and limitations of this imaging approach. Our Ps‐P tomography model reveals previously imaged high VP/VS upper crustal magma reservoirs beneath active volcanic systems at Mount St. Helens, Mount Adams and the Indian Heaven Volcanic Field and low VP/VS anomalies associated with crystallized plutons. Our model also provides new VP/VS constraints in the lower crust that reveal a high VP/VS anomaly connecting the Mount St. Helens and Mount Adams reservoirs and a low VP/VS anomaly associated with lower crustal cumulates or mafic accreted terranes. Decimation tests further show that first order VP/VS structure is recoverable using as few as four recording seismometers. These images resemble those of independent, higher resolution images from traditional techniques, highlighting the utility of Ps‐P tomography for imaging three‐dimensional variations of VP/VS throughout the crust, including in data‐poor settings or with arrays not designed for structural seismic investigations, such as many volcano monitoring networks. Plain Language Summary: There are a variety of ways that seismic waves can be used to infer the three‐dimensional distribution of physical properties of the Earth including parameters like composition, temperature and the presence of partially molten rock (magma), but there are some parts of the Earth that are more difficult to see than others. The lower crust is one region of the Earth that is both important and difficult to image, but many traditional imaging tools require extensive and expensive data collection to see it. However, a technique called receiver function analysis, which highlights the recording of waves that convert from compressional (P) waves to shear (S) waves at physical boundaries in the Earth, can be used to see the entire crust at relatively low cost. This paper tests a method for imaging three‐dimensional crustal structure, including the lower crust, using measurements of those converted waves. Importantly, the paper tests this method at a data‐rich setting, Mount St. Helens in Washington state, USA, to illustrate how well it can be used in other data‐poor settings. The results show that the method, called Ps‐P tomography, works well and can be applied to data‐poor settings with confidence despite known limitations in resolution. Key Points: We use Ps‐P tomography to image the relative VP/VS crustal structure in the region surrounding Mount St. Helens, Washington state, USAPs‐P tomography model is correlated with previously imaged structure around the volcano, highlighting the accuracy of the techniquePs‐P tomography reveals VP/VS structure throughout the crust and is shown to be effective with as few as four available seismic stations [ABSTRACT FROM AUTHOR]

Anelastic attenuation provides key insight in our understanding of thermal and rheological structures and the associated deformation and dynamic mechanisms of the Earth's deep interior. Unfortunately, attenuation tomography is advanced far behind wave‐speed tomography due to the challenge in properly excluding the complex effects of elastic heterogeneities on seismic wave amplitude. By taking advantage of phase tracking in seismic array analysis, here we derive a new theory of Helmholtz tomography that well accounts for attenuation, source radiation, and scattering, etc., and present a technique called Helmholtz Multi‐Event Tomography (HelMET) to retrieve the attenuation properly. The effectiveness of this method is then validated by synthetic inversions. Our synthetic seismograms are calculated using a newly developed three‐dimensional finite‐difference algorithm that accounts for physical dispersion and dissipation in anelastic media and remains accurate and stable even if strong attenuation exists. Compared to the traditional method poorly performed in the synthetic inversion, the HelMET well recovers the input attenuation anomalies, suggesting that this method can be used to successfully isolate attenuation from the complicated effects of elastic heterogeneities. Our results underline the implication of the new theory and method in accurately imaging high‐resolution attenuation structures and unambiguously interpreting the anelastic heterogeneities of the Earth by array‐based earthquake and ambient noise data with inexpensive computation. Plain Language Summary: Modeling attenuation from seismic‐wave amplitude records is important for understanding the temperature structures and dynamic features of the Earth's interior. But it is still challenging to robustly image attenuation because wave amplitudes are also influenced by other factors besides attenuation, particularly the so‐called scattering due to the complex effects of three‐dimensional wave‐speed and density distributions. Based on tracking surface‐wave travel times and amplitudes from seismic array data, here we upgrade the theory of Helmholtz tomography by accounting for the scattering effects. We then present a new method, named as Helmholtz Multi‐Event Tomography, for correctly solving for attenuation structures. We carry out synthetic inversions to verify the new theory and new method. We perform three‐dimensional forward simulations for seismic wave propagation in anelastic media. Our new method well recovers all input anomalies of attenuation, while the performance of traditional imaging is typically poor for various input models. Our results demonstrate the effectiveness of the new theory and new method in solving for attenuation structures. We prospect the new theory and new method are promising to generate accurate and precise models of attenuation from real data with low computational cost. Key Points: We upgrade the theory of surface‐wave Helmholtz tomography that accounts for attenuation, source radiation, and scattering effectsWe present a new method to isolate attenuation from array‐based surface‐wave phase and amplitude measurementsSynthetic inversions show that our method well recovers the input attenuation structure, yet the traditional method poorly performs [ABSTRACT FROM AUTHOR]

Body waves traversing the Earth's interior from a seismic source to receivers on the surface carry rich information about its internal structures. Their travel time measurements have been widely used in seismology to constrain Earth's interior at the global scale by mapping the time anomaly along their ray paths. However, picking the travel time of global seismic waves, suitable for studying Earth's fine‐scale structures, requires highly skilled personnel and is often fairly subjective. Here, we report the development of an automatic picker for PKIKP waves traveling through the inner core (IC), especially nearly along Earth's diameters, based on the latest advances in supervised deep learning. A convolutional neural network (CNN) we develop automatically determines the PKIKP onset on vertical seismograms near its theoretical prediction of cataloged earthquakes. As high‐quality manual onset picks of global seismic phases are limited, we employ a scheme to generate a synthetic supervised training data set containing 300,000 waveforms. The PKIKP onsets picked by our trained CNN automatic picker exhibit a mean absolute error of ∼0.5 s compared to 1,503 manual picks, comparable to the estimated human‐picking error. In an integration test, the automatic picks obtained from an extended waveform data set yield a cylindrically anisotropic IC model that agrees well with the models inferred from manual picks, which illustrates the success of this pilot model. This is a significant step closer to harvesting an unprecedented volume of travel time measurements for studying the IC or other regions of the Earth's deep interior. Plain Language Summary: Seismic body waves traversing the Earth's interior provide critical constraints on structures and dynamics of the Earth's deep interior, including the solid inner core (IC). The onset time of compressional waves from a seismic source passing through the IC, known as PKIKP waves, has been widely used to study the Earth's deepest shell. However, the collection of onset time picks meticulously analyzed by experienced analysts is scarce due to the labor‐intensive nature of the process. At the same time, large collections compiled by multiple data centers, such as the International Seismological Center's PKIKP onset data set, are inhomogeneous and deemed less reliable for inner‐core research than the data collected by individual researchers. Here, we develop an automatic PKIKP onset picker based on recent advancements in machine learning in computer vision, the convolutional neural network. We train the network with synthetic waveforms, mimicking the influence of the Earth's structure on the initial waveform shape. Our comprehensive tests benchmark the consistency between the automatically picked and the researcher‐examined data sets. The automatic picker allows for the further exploration of extensive seismic archives, enabling the study of the Earth's deep interior in greater detail with unprecedentedly large data sets. Key Points: We employed a convolutional neural network to automatically pick the onsets of inner‐core sensitive PKIKP wavesOur automatic picker approaches near human‐level precision and initially reproduces established inner‐core anisotropic modelsAutomatic phase onset measurements would open unprecedented avenues for studying the Earth's deep interior, including the inner core [ABSTRACT FROM AUTHOR]

Estimating the radiated energy of small‐to‐moderate (Mw < 5) earthquakes remains challenging because their energy decay significantly during wave propagation. Even when near‐source records are available, seismic waves pass through the shallow crust with strong attenuation, which can bias energy estimates. This study evaluated the degree of energy dissipation in the crust through modeling near‐source (<12 km) waveform data in northern Ibaraki Prefecture, Japan. High‐quality waveforms recorded at a downhole sensor confined by granite with high seismic velocity helped to investigate this issue. We first estimated the moment tensors for M1–4 events and computed their synthetic waveforms, assuming a tentative one‐dimensional attenuation (Q−1) model. We then modified the Q−1‐model in the 5–20 Hz range such that the frequency components of the synthetic and observed waveforms of microearthquakes (Mw < 1.7) matched. The results show that the Qs‐value is as low as 55 at depths of <4 km with no obvious frequency dependence. Using the derived Q−1‐model, we estimated the moment‐scaled radiated energy (eR) of 3,884 events with Mw 2.0–4.5. The median eR is 3.5 × 10−5, similar to the values reported for Mw > 6 events, with no obvious Mw dependence. If we use an empirically derived Qs‐model, the median eR becomes a one‐order underestimation (2.0 × 10−6). More than 70% of the energy is dissipated in the shallow crust for events with Mw < 4. These results demonstrate the need for an accurate understanding of shallow crustal attenuation for energy estimation of small events, even with near‐source high‐quality data. Plain Language Summary: A good understanding of the energy‐radiation characteristics of small earthquakes is the basis for understanding the differences in the generation processes between small and large earthquakes. However, estimating the radiated energy for small (Mw < 5) events is still challenging because their energy is significantly attenuated during wave propagation. To evaluate the degree of energy dissipation in the shallow crust, we used high‐quality near‐source (<12 km) waveform records from northern Ibaraki Prefecture, Japan. We estimated a depth‐dependent attenuation model by matching the synthetic and observed spectral amplitudes in multiple frequency bands. The results show that energy dissipation is fairly large in the shallow (<4 km) part. We used the derived attenuation structure to estimate the moment‐scaled energy (eR) of 3,884 small events (Mw 2.0–4.5). The median value was 3.5 × 10−5, which is similar to the values reported for larger (Mw > 6) events, with no obvious difference in magnitude. If we assume a standard attenuation value, the eR erroneously becomes too small (median of 2.0 × 10−6), requiring a significant increasing trend with magnitude. These results indicate the importance of accurately determining the attenuation of the shallow crust to estimate the energy radiation of small events, even when near‐source records are available. Key Points: We estimated a depth‐dependent Q‐model using high‐quality near‐source (<12 km) seismic data by matching observed and synthetic waveformsThe shallow (<4 km) crust has a low Qs‐value (∼55), influencing the estimation of the moment‐scaled radiated energy (eR) of small eventsThe eR of 3,884 Mw 2.0–4.5 events based on the refined Q‐model has a median value of 3.5 × 10−5 and does not show an obvious scale dependence [ABSTRACT FROM AUTHOR]

The study of the dynamic response characteristics of "W"-type deep canyon terrain to double-span concrete arch bridges under earthquake action holds great practical significance. In this research, a bridge in Sichuan Province is taken as the object of study. The boundary-integral equation method and peak frequency shift method are combined to apply an embedded linear time–history analysis algorithm to the finite element spatial dynamic calculation model of the entire bridge, resulting in an improved model. By comparing these two methods with model test results, the seismic response characteristics of the middle part of a "W" concrete arch bridge under different foundation depths and seismic intensities are examined. The boundary integral equation method was utilized to calculate ground motion response at any point on site, revealing a significant amplifying effect of increased seismic wave intensity on acceleration response at the top of the arch bridge. When input seismic wave intensity increased from 0.1 g to 0.3 g, maximum acceleration at buried depths of 3 m and 8 m in the middle of the arch bridge foundation increased by 102.63% and 79.16%, respectively, indicating that shallow buried depth structures are more sensitive to seismic wave intensity. Furthermore, using peak frequency shift rules for analyzing seismic wave propagation characteristics in "W"-type deep canyon topography confirms the sensitivity of shallow buried depth structures to seismic wave intensity and reveals the mechanism through which topography influences seismic wave propagation. This study provides a helpful method for understanding the propagation law and energy distribution characteristics of seismic waves in complex terrain. It was observed that the displacement at the top of the arch bridge increased significantly with an increase in seismic intensity. When subjected to 0.1 g, 0.2 g, and 0.3 g EI-Centro seismic waves, the maximum displacement at the top of the arch bridge model with a foundation buried depth of 3 m was 8 mm, 32 mm, and 142 mm, respectively. For arch bridge models with an 8-m foundation buried depth, these displacements were measured at 6.2 mm, 21 mm, and 68 mm, respectively. The results from model tests verified that increasing the depth of foundation burial effectively reduces the displacement at the top of the structure. Furthermore, by combining a boundary-integral equation method and peak-frequency shift method, this study accurately predicted significant influences on W-shaped double deep canyon topography from seismic response, and successfully captured stress concentration and seismic wave amplification/focusing effects on arch foot structures. The calculated results from both methods align well with model test data which confirm their effectiveness and complementarity when analyzing seismic responses under complex terrain conditions for bridge structures. [ABSTRACT FROM AUTHOR]