Velocity Model Research Articles

Modelling of P-wave velocity changes in coal seams with increased depth: a case study

Seismic profiling in a coal seam enables the determination of anomalous changes in the P-wave velocity compared to reference velocity at a specific mining depth, indicating potential stress changes. This information can improve the coal exploitation processes in advance at greater depths, especially in seismic hazard areas. This study aims to update the empirical mathematical formula for calculating reference P-wave velocities in coal seams by including new data measured at greater depths. The research was performed at the Zofiówka Coal Mine in the geological and mining conditions of the Upper Silesian Coal Basin in Poland. The analysis involved the study of 276 velocity values including 24 new velocity values measured at depths ranging from 704 to 1073 metres in the period 2009–2024. Through regression analysis, the standard model was modified. The new model provides more reliable velocity anomaly calculations and accurately reflects the geomechanical conditions at greater depths in the Zofiówka Coal Mine. The calculation procedure can be utilised to develop velocity models for various geological and geomechanical conditions in underground mines that exploit coal seams at continuously increasing depths.

Conceptualizing a load and volume autoregulation integrated velocity model to minimize neuromuscular fatigue and maximize neuromuscular adaptations in resistance training.

Resistance training (RT) load and volume are considered crucial variables to appropriately prescribe and manage for eliciting the targeted acute responses (i.e., minimizing neuromuscular fatigue) and chronic adaptations (i.e., maximizing neuromuscular adaptations). In traditional RT contexts, load and volume are generally pre-prescribed; thereby, potentially yielding sub-optimal outcomes. A RT concept that individualizes programming is autoregulation: a systematic two-step feedback process involving, (1) monitoring performance and its constituents (fitness, fatigue, and readiness) across multiple time frames (short-, moderate-, and long-term); and (2) adjusting programming (i.e., load and volume) to elicit the targeted goals (i.e., responses and adaptations). A growing body of load and volume autoregulation research has accelerated recently, with several meta-analyses suggesting that autoregulation may provide a small advantage over traditional RT. Nonetheless, the existing literature has typically conceptualized these current autoregulation methods as standalone practices, which has limited their extensive utility in research and applied settings. The primary purpose of this review was three-fold. Initially, we synthesized the current methods of load and volume autoregulation, while disseminating each method's main advantages and limitations. Second, we conceptualized a theoretical Integrated Velocity Model (IVM) that integrates the current methods for a more holistic perspective of autoregulation that may potentially augment its benefits. Lastly, we illustrated how the IVM may be compared to the current methods for future directions and how it may be implemented for practical applications. We hope that this review assists to contextualize a novel autoregulation framework to help inform future investigations for researchers and practices for RT professionals.

A Novel Non-Line-of-Sight Error Mitigation Algorithm Using Double Extended Kalman Filter for Ultra-Wide Band Ranging Technology

In complex indoor environments, target tracking performance is impacted by non-line-of-sight (NLOS) noises and other measurement errors. In order to fix NLOS errors, a Double Extended Kalman filter (DEKF) algorithm is proposed, which refers to a kind of cascaded structure composed of two Kalman filters. In the proposed algorithm, the first filter is a classic Kalman filter (KF) and the second is an Extended Kalman filter (EKF). The time of arrival (TOA) measurements collected by multiple stationary ultra-wide band (UWB) sensors are used. Residual errors between the measured TOA and the prediction from the first KF are used to adjust the covariance of the first KF accordingly. Then, we use the estimated distance state of the first KF as a measurement vector of the second EKF in order to obtain a smoother observation. One of the advantages of the proposed algorithm is that it is able to perform target tracking with a good accuracy even without or with only one line-of-sight(LOS) TOA measurement for a period of time without prior information of the NLOS noise, which may be difficult to obtain in practical applications. Another advantage is that the accuracy does not significantly decrease when NLOS noises persist for a long period of time. Finally, the proposed DEKF can maintain high-precision positioning characteristics in both the constant velocity (CV) model and the constant acceleration (CA) model for LOS/NLOS environments. In the case of mixed LOS/NLOS environments, the RMSE of the proposed algorithm can be kept within 5 cm, while the RMSEs of other compared algorithms are easily beyond tens of centimeters. At the same time, when the confidence of RMSE is set to 95% for 1000 MC simulations, the confidence interval of the proposed algorithm is the smallest, and the mean value is 3–5 times closer to the true value compared to other algorithms. Simulation and experimental results show that the proposed algorithm performs much better than other state-of-the-art algorithms, particularly in severe mixed LOS/NLOS environments.

Improved earthquake locations through a new 1-D P-wave velocity model for the Isthmus of Panama using particle swarm optimization method

Improved earthquake locations through a new 1-D P-wave velocity model for the Isthmus of Panama using particle swarm optimization method

Mapping site amplification with the dense recording of ambient vibration for the city of Lucerne (Switzerland): comparison between two approaches

Abstract Reliable site-specific amplification information can be retrieved using earthquake-based methods that involve the deployment of a permanent (or temporary) network of seismic recording stations. Such an endeavour may need to operate for years, especially within regions of high risk but low recurrence rates in seismic activity. Hence, time- and cost-effective approaches using ambient vibrations are gaining popularity. Among such techniques, the canonical correlation approach (CC) collates measured empirical amplification with its indicator computed from ambient vibrations (i.e. horizontal-to-vertical spectral ratios) for a training set of seismic stations, to predict site response at locations without earthquake recordings. Another method, the hybrid standard spectral ratio method (SSRh) takes advantage of simultaneous recordings of ambient vibrations that are adjusted using earthquake ground motion data using a limited number of instrumented sites to estimate local seismic soil response. We apply both methods in the Lucerne area (Switzerland), which is located on a soft sedimentary basin, and obtain consistent results that are comparable to amplification estimates derived solely from earthquake ground motion data. These results show significant linear amplification factors (8–10 or more) at the fundamental frequency of resonance of the sediments (0.8–2 Hz). However, both techniques show systematic differences in the spatial and frequency domains. The CC method tends to underestimate the amplification at the fundamental frequency, while the SSRh technique predicts higher amplification in the centre of the basin and lower amplification at the basin edges in comparison to the CC approach. The study discusses the impact of the limitations in the completeness of the calibration dataset, and variability introduced by the choice of the shear wave velocity model of the shallow subsurface and inelastic behaviour treatment for the CC method, as well as the influence of the measurement setup for the SSRh method.

Dimension synthesis of linkage mechanism with approximate poses and velocity constraints

This paper mainly addresses the problem of dimension synthesis for planar open chain two-rod (2R) mechanisms with velocity constraints and position-pose information in agricultural transplanting mechanism (TM). The method proposed in this study extends the dimension synthesis problem of planar 2R mechanisms, which takes position-pose into account, to the dimension synthesis considering both position-pose information and velocity information (PPIAVA) at certain pose points in the field of TM. The geometric constraints of the open chain 2R mechanism are extracted from the prerequisite conditions obtained by a series of given position-pose points and velocity constraints at some pose points to solve the dimension synthesis problem of the planar 2R mechanism. First, the Taylor formula is used to connect the characteristic of the derivative value at a certain point as coefficient with PPIAVA at a certain point. The mathematical model of position-pose and velocity is established by combining the relationship of rod length constraint and velocity direction characteristic. Secondly, the nonlinear equations established according to the position-pose information and velocity constraints are combined with the Lagrange equation and the extremum of the multivariate function to transform the appropriate objective function and then solved the equations. Finally, a transplanting mechanism is designed and tested by combining the solution results with the trajectory characteristics of the TM. The results show that this method is an effective synthesis method for smoothly solving the dimension synthesis problem of planar open chain 2R linkage mechanism with velocity constraints, which can extract geometric constraints from a given series of position-pose and velocity constraints at some poses.

Relocation of Recent Shallow Seismic Activity in the Alboran Sea (Western Mediterranean Sea): The 2021–2024, 2016, and 2004 Seismic Series

ABSTRACT The Alboran Sea is a complex tectonic region and one of the most seismically active areas in the westernmost Mediterranean Sea. Its southern sector has been the scene of three significant earthquakes in the past 30 yr, the 1994 M 5.9 and 2004 M 6.3 Al Hoceima and the 2016 Mw 6.4 Alboran events. In this study, we perform a high-precision relocation of a selected subset of moderate-magnitude earthquakes of the three main seismic series that have occurred in this region in this century, the 2021–2024, 2016, and 2004 series, using all the available seismic data. We apply a two-step shared relocation procedure, first, a nonlinear probabilistic algorithm with a 3D velocity model for the Alboran–Betic–Rif system, and second, a double-difference relative method. Our results for the 2021–2024 and 2016 series show clustered epicenters along the nearby active fault systems in the area. The 2016 series displays an excellent spatial correlation with the Al-Idrisi fault and may be linked to it, whereas the 2021–2024 series could be associated to an unmapped structure to the east of Al-Idrisi, more fractured and of smaller dimensions, as inferred from its spatial–temporal magnitude distribution. Our solutions for the 2004 series confirm two clear and perpendicular epicentral alignments, which may be related to the Trougout fault. The overall depth distribution reveals shallow hypocenters mainly constrained in a seismogenic layer up to 15–20 km. Our results display a remarkable hypocentral clustering compared with the Instituto Geográfico Nacional (IGN) earthquake catalog solutions and an improvement in the accuracy and precision of earthquake locations, with mean horizontal and vertical uncertainties lower than ∼5 km, giving better constrained hypocenters over the IGN catalog. Our findings highlight the effectiveness of this methodology, especially in the case of offshore seismicity with poor azimuthal coverage, and may improve seismic hazard studies in the region.

Prediction Model for Flake Line Defects in Metallic Injection Molding: Considering Skin-Core Velocity and Alignment.

Metallic injection molding combines aluminum flake metallic pigments with polymers to directly produce components with metallic luster, improving production efficiency and reducing environmental impact. However, flake line defects that occur in regions where ribs or flow paths intersect remain a significant challenge. This study proposes a velocity model that considers the flow characteristics between the surface and core layers and an alignment model that incorporates the orientation of aluminum flakes to predict appearance defects. Through this approach, the mechanisms of appearance defect formation were systematized, and the appearance defects caused by flow velocity differences between the surface and core layers, flake alignment uniformity, and reflection angles were visualized. Both prediction models demonstrated a 50% prediction accuracy, successfully identifying two out of four observed defects. This research addresses the limitations of previous prediction methods, which only considered the surface layer, by introducing a novel approach that accounts for the core layer. It is expected to contribute to reducing defects and improving quality in industries requiring high-quality metallic appearances.

High-resolution synthetic seismic modelling: elucidating facies heterogeneity in carbonate ramp systems

Carbonate ramp systems present significant seismic interpretation challenges due to their pronounced facies heterogeneity, which frequently results in chaotic seismic outputs that obscure the underlying geological structures. The Porto Badisco Calcarenite in Salento, southern Italy, an Oligocene carbonate ramp, serves as the case study for this research, offering an analogue for understanding similar geological systems. By integrating fieldwork, laboratory analysis and MATLAB modelling, this study pioneers the use of detailed petrophysical data to construct innovative velocity models based on the velocity ranges of the different lithofacies analysed. These models distinctly illustrate the impact of facies heterogeneity on seismic velocities, providing fresh insights into acoustic impedance and variable propagation velocities across different facies constituting the carbonate ramp. Through advanced high-resolution synthetic seismic modelling conducted on carefully fine-tuned unmigrated stack sections, the research demonstrates how variations in petrophysical characteristics within measured ranges reflecting carbonate textures can dramatically alter seismic imaging. The innovative models, based on propagation velocity ranges, not only deepen the understanding of the seismic representation of lithofacies but also act as a potent tool for probing the subsurface architecture of complex carbonate systems, providing an interpretative key for the analysis of seismic images. This approach signifies a substantial advancement in seismic modelling that is aimed at refining interpretations and enhancing exploration strategies in carbonate ramp environments globally.

Unsupervised learning inversion of seismic velocity models based on a multi‐scale strategy

Unsupervised learning inversion of seismic velocity models based on a multi‐scale strategy

Croatian catalogue and database of focal mechanism solutions, characteristic mechanisms, and stress field properties in the Dinarides and the surrounding regions

This report presents the CroFMS catalogue and database of focal mechanism solutions (FMS). It is based on the first-motion polarity data for earthquakes in Croatia and the neighbouring regions, collected over last four decades. The current catalogue version contains FMS for 410 earthquakes that were computed consistently, using the same programs, velocity models, and sets of parameters. Its content is described in terms of distributions of the time and origin of polarity picks, magnitudes, epicentral distances of stations, the quality marks, the phases used, azimuthal gap and distance to the closest station. It was also shown that solutions from the CroFMS catalogue and those independently obtained from the moment tensor inversions are generally consistent.Comparison of observed FMS with the latest European model of active fault sources (EFSM20) revealed several inconsistencies, most notably in the Zagreb and Petrinja epicentral areas, the greater Rijeka region, the Central Adriatic archipelago, and in the zone of surface traces of the thrust fronts of the East-Bosnian–Durmitor and Drina–Ivanjica nappes in Bosnia and Herzegovina.Spatial averaging of FMS over the whole study area produced maps of characteristic focal mechanisms, which may be found useful in the seismic hazard assessment in the areas where active faults are not identified or characterised.A formal stress inversion of the focal mechanism solutions produced a map of maximum horizontal stress orientations across the study area, revealing localized lateral variations that had not been identified in previous studies.

Gabor-wavelet-activation implicit neural learning for full waveform inversion

Seismic full waveform inversion (FWI) is an efficient imaging method for estimating subsurface physical parameters. However, when the initial models are inaccurate or seismic data lack low frequencies, most traditional discrete grid-based FWI algorithms often encounter local minimum problems. Additionally, the inversion performance and computational cost are closely related to spatial resolution. Reparameterizing velocity models using neural networks (NNs) effectively mitigates local minimum issues. However, most NN-FWI approaches perform well when overparameterized and are limited to fixed grid-like representations. In contrast, implicit neural learning (INL) enables the representation of models at any resolution using a multilayer perception (MLP) network that learns a continuous function from discrete coordinates. To enhance the capability of INL, we developed a general Gabor-wavelet-activation INL approach and applied it to FWI, referred to as wavelet implicit neural learning FWI (WinFWI), using only the vertical particle-velocity. The constructed MLP was lightweight, which reduced the computational overhead. Numerical experiments on a synthetic block model and Marmousi2 model demonstrate the robustness of the proposed method to challenges such as parameter crosstalk. This was further validated using the Chevron 2014 blind test data. All comparisons show that our method is more general and robust than traditional and INL-based FWI algorithms. Moreover, additional feature visualization and numerical analysis illustrate the potential advantages of WinFWI in balancing computational cost and inversion accuracy.

Computational fluid dynamic modeling of pressure and velocity in a water aspirator

Computational fluid dynamic modeling of pressure and velocity in a water aspirator

Fatigue life prediction for CFRP laminates using multi-mode Lamb wave velocity and Bayesian model selection

Fatigue life prediction for CFRP laminates using multi-mode Lamb wave velocity and Bayesian model selection

Evidence for Magma‐Rich and Magma‐Poor Characteristics Across the Continent‐Ocean Transition Offshore Central Nova Scotia as Deduced From Vp/Vs Ratios Using 4‐Component Seismic Data

AbstractTo improve identification of crustal rock types within the continent‐ocean transition (COT) offshore Nova Scotia based on the standard approach of analyzing P‐wave velocities (Vp), we incorporate S‐wave velocity (Vs) modeling and determine Vp/Vs ratios. In this work, we construct detailed layered Vp and Vs models using four component wide‐angle ocean bottom seismometer data from profiles SMART‐2 and ‐3 across the central and southwestern Scotian margin, respectively. Along profile SMART‐3, the lower continental crust displays low Vp/Vs ratios (1.7), akin to felsic granulite. Vp/Vs ratios (1.7–1.9) within the COT suggest that syn‐rift volcanism and magmatism resulted in a basalt‐dominated upper crust overlying a thick layer (4–10 km) of laterally heterogeneous gabbroic underplate that jointly cover an estimated profile area of 1,230 . On Profile SMART‐2, we observe upper continental crust (Vp/Vs 1.7) with highly felsic composition within the continental and the COT domains. Serpentinized mantle (Vp/Vs 1.9) is interpreted within the seaward‐most segment of the transitional lower crust, alongside gabbroic underplate, based on its Vp/Vs ratio of 1.7–1.8 and high Vp of 6.9–7.4 km/s, notably thickening beneath the East Coast Magnetic Anomaly near the landward COT limit. Syn‐rift volcanism and magmatism SMART‐2 profile area is estimated at 513 . Our results portray the southwestern Scotian margin as magma‐rich, the northeastern as magma‐poor, and the central margin as a hybrid zone amalgamating characteristics from both. Regardless of margin type, the thinnest transitional crust is consistently observed toward its seaward termination leading into the full‐scale seafloor spreading.

Cyclic Learning Rate U-Shaped ResNet Embedded With Dual Attentions for Velocity Model Building

Cyclic Learning Rate U-Shaped ResNet Embedded With Dual Attentions for Velocity Model Building

Mechanisms for Layered Anisotropy and Anomalous Magmatism of Alaska Subduction System Revealed by Ambient Noise Tomography and the Wave Gradiometry Method

AbstractSeismic anisotropy can provide valuable constraints for the study of subduction zone dynamics. This study presents a high‐resolution 3‐D azimuthally anisotropic shear wave velocity model down to 230 km beneath Alaska via ambient noise tomography and wave gradiometry method. The model reveals layered anisotropy patterns related to subduction tectonics. The shear wave's fast directions in the Aleutian fore‐arc region exhibit trench‐parallel, trench‐normal, trench‐parallel, and trench‐normal variation relative to the trench trend with increasing depth. This anisotropic pattern may be attributed to the strike of fractures or faults in the overlying North American plate, subduction‐driven mantle wedge corner flow, preexisting fabrics in the subducting Pacific Plate, and entrained flow in the sub‐slab mantle, respectively. The depth‐dependent anisotropy pattern in the back‐arc mantle wedge reflects subduction‐induced corner flow, altered by the subducting slab's changing geometry. Moreover, the model provides new insights into the anomalous magmatism in the Alaskan subduction system. The 3‐D isosurface clearly shows the relatively high mantle wedge velocities beneath the Denali Volcanic Gap (DVG), suggesting a relatively dry and cold mantle wedge for the flat‐slab subduction of Yakutat slab. The absence of a magma source likely caused the DVG. The Wrangell Volcanic Field (WVF) is characterized by a similar depth‐dependent anisotropy pattern to the Aleutian‐Pacific subduction system, providing additional evidence for the presence of Wrangell Slab. The formation of WVF may be the result of combined effects of toroidal mantle upwelling around the edge of the Wrangell Slab and melting due to dehydration of the Wrangell Slab.

On the parameters of common settling velocity models for porous sediment aggregates

On the parameters of common settling velocity models for porous sediment aggregates

Joint Supervised and Semi-Supervised Seismic Velocity Model Building Based on VGU Network

Joint Supervised and Semi-Supervised Seismic Velocity Model Building Based on VGU Network

Crustal Structure of the Hikurangi Subduction Zone Revealed by Four Decades of Onshore‐Offshore Seismic Data: Implications for the Dimensions and Slip Behavior of the Seismogenic Zone

AbstractFour decades of seismic reflection, onshore‐offshore and ocean‐bottom seismic data are integrated to constrain a high‐resolution 3‐D P‐wave velocity model of the Hikurangi subduction zone. Our model shows wavespeeds in the offshore forearc to be 0.5–1 km/s higher in south Hikurangi than in the central and northern segments (VP ≤ 4.5 km/s). Correlation with onshore geology and seismic reflection data sets suggest wavespeed variability in the overthrusting plate reflects the spatial distribution of Late Jurassic basement terranes. The crustal backstop is 25–35 km from the deformation front in south Hikurangi, but this distance abruptly increases to ∼105 km near Cape Turnagain. This change in backstop position coincides with the southern extent of shallow slow‐slip, most of which occurs updip of the backstop along the central and northern margin. These relationships suggest the crustal backstop may impact the down‐dip extent of shallow conditional stability on the megathrust and imply a high likelihood of near/trench‐breaching rupture in south Hikurangi. North of Cape Turnagain, the more landward position of the backstop, in conjunction with a possible reduction in the depth of the brittle ductile transition, reduces the down‐dip width of frictional locking between the southern (∼100 km) and central Hikurangi margin by up‐to 50%. Abrupt transitions in overthrusting plate structure are resolved near Cook Strait, Gisborne and across the northern Raukumara Peninsula, and appear related to tectonic inheritance and the evolution of the Hikurangi margin. Extremely low forearc wavespeeds resolved north of Gisborne played a key role in producing long durations of long‐period earthquake ground motions.