Heterogeneous Stress Research Articles

Chemo‐Mechanics Interplay Dictates Interface Instability and Asymmetry in Plating and Stripping of Sodium Metal Electrodes

AbstractThe development of practical sodium (Na) metal batteries is hindered by key challenges including dendrite growth, dead metal formation, and unstable solid electrolyte interphase (SEI) growth. A fundamental understanding of the chemo‐mechanical interactions at the Na/SEI interface is critical for designing stable Na metal electrodes. In this work, the coupled electrochemical‐mechanical processes governing the morphological evolution and stability of Na metal during plating and stripping are investigated. The heterogeneous nature of transport and morphological interactions at the Na/SEI interface is revealed to result in nonuniform mechanical overpotentials and reaction fronts, eventually leading to Na filaments or pits. The spatio‐temporal evolution of stress heterogeneities during Na plating and stripping is shown to be asymmetric, manifesting in varying morphological nonuniformities and instability modes. The crucial role of external pressure in modulating the electrochemical‐transport interactions, the mechanical response of Na, and the localized reaction currents and stresses at the Na/SEI interface is demonstrated. At different external pressure conditions, the correlation between transport heterogeneities in the SEI and the onset and propagation of interface instability has been delineated. This work highlights the need for synergistic tailoring of external pressure and SEI heterogeneity toward achieving stable electrodeposition and dissolution in Na metal electrodes.

Earthquake Nucleation and Slip Behavior Altered by Stochastic Normal Stress Heterogeneity

AbstractIn recent laboratory experiments, varying nucleation locations of accelerating slip with changing nucleation lengths were observed. Spatial variations in effective normal stress, due to the controlling influence on fault strength and fracture energy, play an important role. We quantitatively explain how spatially heterogeneous effective normal stresses affect earthquake nucleation and slip behavior. We simulate a meter‐scale laboratory experiment in a numerical earthquake sequence model with stochastically variable normal stresses. We identify five regimes of earthquake nucleation and slip behaviors, controlled by the ratio of the heterogeneity wavelength to the nucleation length . When , full ruptures are observed. Slip rates and recurrence intervals are similar to those on homogeneous faults with comparable averaged normal stress. When , slow slip events and partial ruptures occur frequently and the nucleation length of each earthquake depends on the local stress level. We find locations of nucleation and arrest in both low and high normal stress regions (LSR and HSR, respectively) when and are of the same magnitude. When , earthquakes nucleate in LSRs, and arrest in HSRs. However, HSRs and LSRs switch these roles when . Interestingly, we observe that nucleation migrates from an LSR to its neighboring HSR in one earthquake, when is between the minimum and maximum local nucleation lengths. We observe a large amount of aseismic slip and associated stress drop in the initial LSR, which might be linked to the migration of foreshocks as documented in natural and laboratory observations. This improved understanding of earthquake nucleation is important in estimating the seismic potential of different fault patches for natural and induced seismicity.

Crystallization and Heterogeneous Local Stress Distribution in Hydrogen-Bonded Polymers: Molecular Dynamics Simulations of Polyamide 6 (PA6)

Crystallization and Heterogeneous Local Stress Distribution in Hydrogen-Bonded Polymers: Molecular Dynamics Simulations of Polyamide 6 (PA6)

Clonal Integration Promotes the Photosynthesis of Clonal Plant Under Heterogeneous Pb and/or Pyrene Stress.

Clonal plants can support the growth of their ramets in heterogeneous environments through clonal integration between the ramets. However, the role of clonal integration in modulating ramet photosynthesis under toxic stress, especially combined stress, is unclear. This study examines the impact of clonal integration on Zoysia japonica under three heterogeneous stresses (Pb, pyrene, and Pb+Pyrene) with two stolon connection conditions (connected and disconnected). Our results show that clonal integration significantly enhances PN, gs, Ci, E, and CE while reducing WUE. It also improves ΦPSII, Fv'/Fm', Fv/Fm, Fv/F0, and qP while reducing NPQ. Clonal integration lowers MDA levels, increases SOD activity, and mitigates the decline in CAT and POD activity, resulting in increased biomass under stress. Furthermore, we observed that the synergistic effects of the Pb+Pyrene mixture negatively impacted the adaptability of clonal integration. Our study underscores the role of clonal integration in maintaining photosynthesis and supporting the success of clonal plants in toxic environments.

Estimation of the True Crystallite Modulus of Silk Fibers from the Relation between the X-ray-Analyzed Apparent Crystallite Modulus and Heterogeneous Stress Distribution

Estimation of the True Crystallite Modulus of Silk Fibers from the Relation between the X-ray-Analyzed Apparent Crystallite Modulus and Heterogeneous Stress Distribution

Quantifying Heterogeneous Degradation Pathways and Deformation Fields in Solid‐State Batteries

AbstractSolid‐state batteries are compelling candidates for next‐generation energy storage devices, promising both high energy density and improved safety, by utilizing metallic Li as the negative electrode. However, they suffer from poor cyclability and rate capability, which limits their wide application. Degradation in these devices occurs through complex mechanical, chemical and electrochemical pathways, all of which produce heterogeneous deformation fields. Therefore, isolating solid‐state degradation mechanisms, and explicitly linking them to the associated deformation fields requires a multimodal characterization strategy. Here, a novel 3‐D, in situ methodology for linking degradation to deformation in solid‐state cells is presented. X‐ray imaging is used to measure the morphological degradation, and combined with X‐ray diffraction to quantify (electro)chemical aspects. Finally, the heterogeneous stress fields from these various pathways are mapped in situ. This heterogeneity is shown globally, from the interface to the bulk electrolyte, as well as locally, around features such as cracks and voids. Through these analyses, it is possible to delineate the effects of solid electrolyte processing, cell assembly, and cycling on the end‐of‐life state of the cell. Moreover, the importance of stress mitigation in these cells is highlighted, with mean stresses around the interface and some cracks comfortably exceeding the elastic limit of Li.

Microstructural and Micromechanical Evolution of Olivine Aggregates During Transient Creep

AbstractTo examine the microstructural evolution that occurs during transient creep, we deformed samples of polycrystalline olivine to different strains that spanned the initial transient deformation. Two sets of samples with different initial grain sizes of 5 μm and 20 μm were deformed in torsion at T = 1,523 K, P = 300 MPa, and a constant shear strain rate of 1.5 × 10−4 s−1, during which both sets of samples experienced strain hardening. We characterized the microstructures at the end of each experiment using high‐angular resolution electron backscatter diffraction (HR‐EBSD) and dislocation decoration. In the coarse‐grained samples, dislocation density increased from 1.5 × 1011 m−2 to 3.6 × 1012 m−2 with strain. Although the same final dislocation density was reached in the fine‐grained samples, it did not vary significantly at small strains, potentially due to concurrent grain growth during deformation. In both sets of samples, HR‐EBSD analysis revealed that intragranular stress heterogeneity increased in magnitude with strain and that elevated stresses are associated with regions of high geometrically necessary dislocation density. Further analysis of the stresses and their probability distributions indicate that the stresses are imparted by dislocations and cause long‐range elastic interactions among them. These characteristics indicate that dislocation interactions were the primary cause of strain hardening during transient creep in our samples. A comparison of the results to the predictions of three recent models reveals that the models do not correctly predict the evolution in stress and dislocation density with strain in our experiments due to a lack of previous such data in their calibrations.

Homoclinic bifurcation of a rate-weakening patch in a viscoelastic medium and effect of strength contrast

The time-dependent viscoelastic deformation of host rocks is important when considering the dynamics of fault behavior, specifically in brittle–ductile transitional regions or shallow subduction zones, because it relaxes stress heterogeneity and affects loading to the fault. For a rate-and-state fault embedded in a Maxwell viscoelastic medium, a previous study discovered a transition from repeated earthquakes to the permanent stuck of a rate-weakening patch (EQ–ST transition) with decreased viscoelastic relaxation time tc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${t}_{\ ext{c}}$$\\end{document}. This transition differs from the well-known seismic–aseismic transition explained by the Hopf bifurcation at the critical stiffness of an elastic system. To better understand the EQ–ST transition, quantifying the effect of heterogeneous frictional strength is important, because this effect is characteristic to the viscoelastic medium and is absent in the elastic limit. Previous experimental studies suggest a potential contrast in frictional strength Δf∗\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta {f}_{*}$$\\end{document} in such a way that a rate-weakening patch is stronger than a rate-strengthening region containing clay minerals. Here, we conducted two-dimensional, fully dynamic earthquake sequence simulations for a fault in a Maxwell viscoelastic medium; we investigated the EQ–ST transition in the two-dimensional parameter space of tc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${t}_{\ ext{c}}$$\\end{document} and Δf∗\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta {f}_{*}$$\\end{document}. With Δf∗=0.3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta {f}_{*}=0.3$$\\end{document}, the EQ–ST transition occurred at about 1 order of magnitude larger tc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${t}_{\ ext{c}}$$\\end{document} than in the case with Δf∗=0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta {f}_{*}=0$$\\end{document}. We constructed a coarse-grained model with only two degrees of freedom based on the spatial average. Consequently, the coarse-grained model behaves remarkably similar to the continuum model, and the EQ–ST transition is associated with a homoclinic bifurcation. The EQ–ST boundary in the parameter space can be quantitatively explained by considering elastic loading due to creep in the rate-strengthening region and unloading by viscoelastic relaxation of the stress heterogeneity comparable to Δf∗\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta {f}_{*}$$\\end{document}. A larger rate-weakening patch is anticipated to become aseismic earlier as tc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${t}_{\ ext{c}}$$\\end{document} decreases, because the elastic loading rate is inversely correlated with the patch size. This may be qualitatively consistent with the change in the size distribution of events around the brittle–ductile transition in observations and laboratory experiments; however, further investigations on, for example, the interactions of events and changes in frictional parameters with depth are required for quantitative discussion.Graphical abstract

Scale and Zoning Effects on Landscape Metrics for Assessing Ecological Stress from Urban Expansion

ContextLandscape metrics can effectively quantify urban landscape dynamics and their ecological stress, but incorrect metric, scale and zoning choices may lead to inaccurate result and biased land use planning.ObjectivesThis study aims to explore how the scale and zoning affected the magnitude and spatial pattern of ecological stress delineated by two related landscape metrics- Eco-erosion index(EEI) and percent of built-up area (PB).MethodsWe quantified ecological stress from urban expansion using EEI and PB across different scales and zoning patterns, based on 30 m land use and land cover (LULC) data of Shanghai, China. Descriptive and non-parametric statistics were used to analyze the sensitivity and spatial heterogeneity of EEI and PB in response to variations in grain size, extent, and zoning.ResultsOur findings indicate that EEI and PB are more sensitive to changes in extent than in grain size. EEI is better at capturing spatial heterogeneity of ecological stress in detail compared to PB at the same zoning pattern. Statistically, zoning patterns don't affect the ranking of ecological stress levels among study units. However, EEI using fine-scale zoning is more appropriate for highlighting discrepancies within the city than using broad-scale zoning at the same grain size. It is also recommended that the minimum study unit for EEI estimated with 30 m LULC grain size should be no smaller than a 5 km by 5 km grid cell.ConclusionsThis study emphasizes scale and zoning effects on EEI and PB, providing guidance for using these metrics to represent ecological stress and contributing to sustainable urban planning.

Ridgecrest Aftershock Stress Drops from P- and S-Wave Spectral Decomposition

ABSTRACT Seismic moment and stress drop are crucial for understanding earthquake rupture processes, but their estimates often have large uncertainties for small earthquakes. Stress drop is typically inferred from an earthquake’s source spectrum based on theoretical models, but poorly constrained path corrections and other modeling assumptions limit the accuracy of stress-drop estimates. Here, we compute stress drops using both P and S waves for the 2019 Ridgecrest earthquake sequence, compare their estimates, and evaluate the associated uncertainties. We use spectral decomposition and apply the analysis to both types of waves for the same set of earthquakes, adjusting some S-wave parameter choices to obtain overall consistency with our P-wave results. Our approach fixes the corner frequency of small calibration earthquakes to reduce scatter in the estimated source parameters of the larger earthquakes. We find that assuming a lower high-frequency fall-off rate for S waves yields more consistent absolute stress-drop estimates between P and S waves. Our stress-drop estimates appear to increase slightly with magnitude for earthquakes with magnitudes >∼3.4. Furthermore, we find that the stress-drop estimates using both types of data exhibit coherent spatial variations. Earthquakes near the Coso geothermal field tend to have lower stress drops, and earthquakes near the M 7.1 hypocenter have higher stress-drop estimates. This spatial pattern is consistently observed in both the P- and S-wave results. We find no strong correlation between our stress-drop estimates and the M 7.1 Ridgecrest earthquake slip distribution, suggesting a heterogeneous stress environment for the Ridgecrest fault system.

Numerical investigation on bending characteristic and ductile fracture of AA7075 thin-walled beam using advanced orthotropic plasticity and fracture models

Thin-walled structures manufactured from the 7075 aluminum alloy are gaining tremendous attention in the automotive industry for their potential to reduce vehicle weight. However, the bending characteristics and rupture behavior of the AA7075 thin-walled beams under unexpected collision events have not been extensively studied. This study aims to fill that gap through a detailed numerical investigation of the bending deformation and failure mechanism of AA7075 thin-walled beams under quasi-static three-point bending at room temperature. Full-size, three-dimensional numerical simulations of laboratory-scale AA7075-T6 hat-shaped beam were conducted using the ABAQUS/Explicit solver. The material elastic–plastic response is described by a rate-independent constitutive description, incorporating advanced non-quadratic orthotropic plasticity and anisotropic ductile fracture criteria via VUMAT subroutines. Results indicate that the simulations accurately reproduced experimental observations, including the loading-displacement curves and deformation patterns. The bending behavior of the AA7075-T6 thin-walled beams aligns with typical bending collapse mechanisms, consistent with Kecman’s theory. The rupture process exhibits ductile fracture characteristics, with heterogeneous stress distribution across the material thickness affecting crack initiation rates between the upper and lower surfaces. Notably, the stress state at the fracture’s half-thickness section approximates an equi-biaxial tension condition. These findings provide essential insights into the bending deformation and failure mechanisms of AA7075 thin-walled structures under unexpected impact loading.

Modified Centroid of Root Projection Method for Determining the Center of Resistance of a Tooth

Abstract Center of resistance (CR) has been widely accepted in dentistry as a reference point for controlling tooth moment, which depends on the direction of loading and the morphology of the periodontal ligament (PDL). In clinical practice, dentists estimate the location of CR based on the morphology of the root of teeth, which may lead to a misestimation of orthodontic treatment. A quick method was proposed to efficiently determine the CR by identifying the centroid of the root projection (CRP), according to the orthodontic force. However, the original CRP method was limited to single-rooted teeth, and it did not provide a strategy for handling the overlapping roots projection of multirooted teeth. To address this issue, we expanded the CRP method to accommodate multirooted teeth by calculating a weighted average of each root’s projection. We further validated the modified CRP method using finite element analysis (FEA) simulation for both single-rooted and multirooted teeth considering mesial–distal and buccal–lingual force directions. The evaluation of displacement distribution along the projection direction allowed us to assess translation and rotation movements, which confirmed that the centroid of root projection can accurately serve as the CR for the multirooted teeth. Additionally, we observed heterogeneous stress distributions in the multirooted teeth. Considering the well-acknowledged bone remodeling effect in response to local stress states, this indicated that comprehensive indexes beyond the CR are desired for evaluating or controlling tooth movement.

Spatiotemporal forecast of extreme events in a chaotic model of slow slip events

SUMMARY Seismic and aseismic slip events result from episodic slips on faults and are often chaotic due to stress heterogeneity. Their predictability in nature is a widely open question. In this study, we forecast extreme events in a numerical model. The model, which consists of a single fault governed by rate-and-state friction, produces realistic sequences of slow events with a wide range of magnitudes and interevent times. The complex dynamics of this system arise from partial ruptures. As the system self-organizes, the state of the system is confined to a chaotic attractor of a relatively small dimension. We identify the instability regions within this attractor where large events initiate. These regions correspond to the particular stress distributions that are favourable for near complete ruptures of the fault. We show that large events can be forecasted in time and space based on the determination of these instability regions in a low-dimensional space and the knowledge of the current slip rate on the fault.

Enhanced Tribological Performance of UHMWPE Composites Reinforced With Wollastonite: Biocompatibility and Wear Behavior

Abstract Ultra-high molecular weight polyethylene (UHMWPE) is often limited by poor tribological properties in artificial joints, leading to high wear-rates compared to metals and ceramics. This study explores the use of wollastonite, a natural mineral, as a filler to enhance the tribological performance of UHMWPE composites. X-ray diffraction (XRD) analysis revealed that wollastonite content and particle size inversely affected the crystallinity of the composite due to heterogeneous nucleation and stress concentration. The incorporation of wollastonite significantly improved the tribological performance, with wear-rate reductions of 71%, 69.81%, and 50.73% under dry friction, normal saline (NS) lubricant, and new-born calf serum (NBCS) lubricant conditions, respectively. The wear mechanisms in the composite were predominantly slight fatigue and abrasive wear, contrasting with the extrusion deformation and severe fatigue wear observed in neat UHMWPE. Additionally, simulated body fluid (SBF) immersion tests demonstrated the composite's ability to form a surface apatite-like deposition. These findings suggest that wollastonite reinforcement effectively enhances both mechanical and tribological properties of UHMWPE.

Evaluating In-Situ Stress State and Stress Heterogeneity by Hydraulic Fracturing and Image Logging in Changcun Coalbed Methane Area, North China

Evaluating In-Situ Stress State and Stress Heterogeneity by Hydraulic Fracturing and Image Logging in Changcun Coalbed Methane Area, North China

Efficacy of Nigella sativa seed oil against psychophysical stress induced irritable bowel syndrome and anxiety-like symptoms in Wistar rats.

Stressors play a critical role in the progression of irritable bowel syndrome (IBS). Heterogenous stress causes alterations in our bowel movements which can further cause anxiety and depression-like symptoms, decreasing the ability of individuals worldwide to function in social, academic, and employment settings. This study was aimed to investigate the effect of orally administered Nigella sativa (0.2mL/kg b.wt.) seed oil (NSSO) on stress-induced IBS, anxiety, and depression-like symptoms in Wistar rats. In the present study, modelling IBS induced anxiety and depression-like symptoms in rodents have been employed to correlate the pathophysiological mechanisms behind this disorder. Moreover, evaluation of ameliorative potential of traditionally used NSSO in IBS was also carried out. Present investigation indicated that acute stress of 1.5h daily for 20days induced hyper cortisol, gastrointestinal (GI) hypermotility, diarrhoea, altered levels of short chain fatty acids (SCFAs), and inflammation which are common symptoms of IBS. Furthermore, depression and anxiety-like symptoms were validated in test groups by various behavioral tests and decreased levels of 5-HT-Transporter mRNA gene expression, which are clear indicators of cognitive impairment. It is possible that these IBS-like symptoms may have contributed to the pathogenesis of cognitive deficits and depression. However, the anti-oxidative, anti-inflammatory, anti-spasmodic, and possibly the anti-anxiolytic properties of NSSO helped in the mitigation of altered gut-brain axis. Because the concurrent treatment of NSSO alleviated the symptoms of modified GI function and consequently, the anxious & depressive behavior of the animals. Overall, this research explored the protective efficacy of NSSO against stress-induced IBS and depression-like symptoms, shedding light on the potential of this natural compound as a therapeutic option in the field of gastroenterology and psychiatry.

Machine learning powered predictive modelling of complex residual stress for nuclear fusion reactor design

Fusion In-vessel components, assembled and maintained using laser welding, one of the most promising techniques, exhibit complex distributions of residual stress, microstructures, and material properties. These residual stresses can compromise structural integrity and lifespan of critical components. Although using advanced experimental measurements can evaluate the residual stress for individual case, extending the measurements to massive number of components are costly and time-consuming. Traditional machine learning (ML) models struggle to account for the heterogeneity and anisotropy of these stress distributions. Here, we develop a novel ML framework based on the Eurofer97 steel, the structural material for in-vessel components. The ML framework is trained on high-resolution residual stress data derived from recently-developed evaluation techniques. Combining with microstructures, the model enables prediction of heterogenous and anisotropic residual stress distribution. It successfully predicts the compressive residual stress in fusion zone (∼−200 MPa) balanced by tensile residual stress in heat affected zone (∼300 MPa), aligning closely with experimental results with the R-squared value of 0.989 and the mean square error of 10−4. Unlike experiments that take hours, the ML model provides predictions within seconds. It offers valuable insights into residual stress prediction for various joints, enhancing the reliability and lifetime prediction of in-vessel components.

The effects of CNT type, alignment and dopants on piezoresistance in CNT fibres

Carbon nanotube fibres (CNTF) are piezoresistive, hence heralded as deformation sensors in applications ranging from flexible touch sensors to artificial skins and robotics. This work studies the piezoresistive behaviour of a wide range of CNT fibres from different sources, processing routes and microstructures. It provides a unifying view of the factors controlling piezoresistance in CNT fibres and related nanocarbon networks. We clarify the role of alignment and concentration of dopants and the constituent CNT type, demonstrating that the origin of piezoresistance in aligned fibres is the direct deformation of the constituent nanotubes, therefore, it is governed by the bulk modulus and thus the degree of CNT alignment. Doping through intercalation, which does not affect modulus or CNT separation, is detrimental to piezoresistive sensing, reducing the gauge factor proportionally to its decrease in resistivity. Aligned fibres show a quasi-linear piezoresistive response, with a positive change in resistance for all deformation modes applied: axial tension, axial or transverse compression. The axial gauge factor is shown to be proportional to fibre Young's modulus, with values of 2–9 for fibres spun from aerogels and above 30 for undoped fibres spun from liquid crystal solutions, respectively. Piezoresistance is attributed to the formation of internal barriers for conduction between metallic regions, which arise from the heterogeneous stress distribution along individual CNTs inherent in shear lag-type stress transfer. Commercial multifilament CNT yarns with a high degree of alignment and a format amenable for integration in large structures have demonstrated the piezoresistive gauge factors of 4 and sufficient sensitivity at strains below 1 % suitable for structural health monitoring of engineering structural composites.

Implications of a Reverse Polarity Earthquake Pair on Fault Friction and Stress Heterogeneity Near Ridgecrest, California

AbstractWe apply the Matrix Profile algorithm to 100 days of continuous data starting 10 days before the 2019 M 6.4 and M 7.1 Ridgecrest earthquakes from borehole seismic station B921 near the Ridgecrest aftershock sequence. We identify many examples of reversely polarized waveforms, but focus on one particularly striking earthquake pair with strongly negatively correlated P and S waveforms at B921 and several other nearby stations. Waveform‐cross‐correlation‐based relocation of these events indicates they are at about 10 km depth and separated by only 115 m. Individual focal mechanisms are poorly resolved for these events because of the limited number of recording stations with unambiguous P polarities. However, relative P and S polarity and amplitude information can be used to constrain the likely difference in fault plane orientation between the two events to be 5–20°. We explore possible models to explain these observations, including low effective coefficients of fault friction and short‐wavelength stress heterogeneity caused by prior earthquakes. Although definitive conclusions are lacking, we favor local stress heterogeneity as being more consistent with other observations for the Ridgecrest region.

Multiscale monitoring and analysis of complex rupture and source mechanisms of mining-related seismicity on fault networks

Mining-related seismicity poses significant challenges in underground coal mining due to its complex rupture mechanisms and associated hazards. To bridge gaps in understanding these intricate processes, this study employed a multi-local seismic monitoring network, integrating both in-mine and local instruments at overlapping length scales. We specifically focused on a damaging local magnitude (ML) 2.6 event and its aftershocks that occurred on 10 September 2022 in the vicinity of the 3308 working face of the Yangcheng coal mine in Shandong Province, China. Moment tensor (MT) inversion revealed a complex cascading rupture mechanism: an initial moment magnitude (Mw) 2.2 normal fault slip along the DF60 fault in an ESE–WNW direction, transitioning to a Mw 3.0 event as the FD24 and DF60 faults unclamped. The scale-independent self-similarity and stress heterogeneity of mining-related seismicity were investigated through source parameter calculations, providing valuable insights into the driving mechanism of these seismic sequences. The in-mine network, constrained by its low dynamic changes, captured only the nucleation phase of the DF60 fault. Furthermore, standard decomposition of the MT solution from the seismic network proved inadequate for accurately identifying the complex nature of the rupture. To enhance safety and risk management in mining environments, we examined the implications of source reactivation within the cluster area post-stress-adjustment. This comprehensive multiscale analysis offers crucial insights into the complex rupture mechanisms and hazards associated with mining-related seismicity. The results underscore the importance of continuous multi-local network monitoring and advanced analytical techniques for improved disaster assessment and risk mitigation in mining operations.