Background Stress Research Articles

Stability of Pulse‐Like Earthquake Ruptures

AbstractPulse‐like ruptures arise spontaneously in many elastodynamic rupture simulations and seem to be the dominant rupture mode along crustal faults. Pulse‐like ruptures propagating under steady state conditions can be efficiently analyzed theoretically, but it remains unclear how they can arise and how they evolve if perturbed. Using thermal pressurization as a representative constitutive law, we conduct elastodynamic simulations of pulse‐like ruptures and determine the spatiotemporal evolution of slip, slip rate, and pulse width perturbations induced by infinitesimal perturbations in background stress. These simulations indicate that steady state pulses driven by thermal pressurization are unstable. If the initial stress perturbation is negative, ruptures stop; conversely, if the perturbation is positive, ruptures grow and transition to either self‐similar pulses (at low background stress) or expanding cracks (at elevated background stress). Based on a dynamic dislocation model, we develop an elastodynamic equation of motion for slip pulses and demonstrate that steady state slip pulses are unstable if their accrued slip b is a decreasing function of the uniform background stress τb. This condition is satisfied by slip pulses driven by thermal pressurization. The equation of motion also predicts quantitatively the growth rate of perturbations and provides a generic tool to analyze the propagation of slip pulses. The unstable character of steady state slip pulses implies that this rupture mode is a key one determining the minimum stress conditions for sustainable ruptures along faults, that is, their “strength.” Furthermore, slip pulse instabilities can produce a remarkable complexity of rupture dynamics, even under uniform background stress conditions and material properties.

The effect of dicarbonyl stress on the development of kidney dysfunction in metabolic syndrome \u2013 a transcriptomic and proteomic approach

Background and aimsDicarbonyl stress plays an important role in the pathogenesis of microvascular complications that precede the formation of advanced glycation end products, and contributes to the development of renal dysfunction. In renal cells, toxic metabolites like methylglyoxal lead to mitochondrial dysfunction and protein structure modifications.In our study, we investigated the effect of methylglyoxal on metabolic, transcriptomic, metabolomic and proteomic profiles in the context of the development of kidney impairment in the model of metabolic syndrome.Materials and methodsDicarbonyl stress was induced by intragastric administration of methylglyoxal (0.5 mg/kg bw for 4 weeks) in a strain of hereditary hypertriglyceridaemic rats with insulin resistance and fatty liver.ResultsMethylglyoxal administration aggravated glucose intolerance (AUC0–120p < 0.05), and increased plasma glucose (p < 0.01) and insulin (p < 0.05). Compared to controls, methylglyoxal-treated rats exhibited microalbuminuria (p < 0.01). Targeted proteomic analysis revealed increases in urinary secretion of pro-inflammatory parameters (MCP-1, IL-6, IL-8), specific collagen IV fragments and extracellular matrix proteins. Urine metabolomic biomarkers in methylglyoxal-treated rats were mainly associated with impairment of membrane phospholipids (8-isoprostane, 4-hydroxynonenal).Decreased levels of glutathione (p < 0.01) together with diminished activity of glutathione-dependent antioxidant enzymes contributed to oxidative and dicarbonyl stress. Methylglyoxal administration elevated glyoxalase 1 expression (p < 0.05), involved in methylglyoxal degradation. Based on comparative transcriptomic analysis of the kidney cortex, 96 genes were identified as differentially expressed (FDR < 0.05). Network analysis revealed an over-representation of genes related to oxidative stress and pro-inflammatory signalling pathways as well as an inhibition of angiogenesis suggesting its contribution to renal fibrosis.ConclusionOur results support the hypothesis that dicarbonyl stress plays a key role in renal microvascular complications. At the transcriptome level, methylglyoxal activated oxidative and pro-inflammatory pathways and inhibited angiogenesis. These effects were further supported by the results of urinary proteomic and metabolomic analyses.

Physiological role of thiamine and weed control treatments on faba bean and associated weeds grown under salt affected soil

Background and objectiveSalinity stress is an important abiotic stress that affect adversely on crop production, so using of natural compounds to improve plant tolerance to stress is very important.Materials and methodsTwo field experiments were conducted during two winter seasons of 2014/2015 and 2015/2016 at Tag El-Ezz Research Station of Agricultural Research Centre, Dakahliea Egypt. Field evaluation of the efficiency of weed-control treatments (unweeded, oxadiargyl, and two hand hoeing) and thiamine levels (0, 50, 75, and 100 mg/l) and their interactive effects on weeds, faba bean growth, yield, yield attributes, and some biochemical constitutes of seeds under salinity levels (1.37, 3.31, and 4.51 dS m−1).ResultsData revealed that number and dry weight of broad-leaved, narrow-leaved, and total weeds were significantly reduced by increasing salinity levels of soil from 1.37 to 4.51 dS m−1. In addition, the highest salinity level 4.51 dS m−1 caused the highest significant decreases in growth, yield, and yield attributes of faba bean. Meanwhile, increasing salinity level from 1.3 to 4.51 dS m−1caused significant increases in total soluble sugar, free amino acids, and proline contents of faba bean plant. Two hand hoeing treatment achieved the highest weed depression expressed in the lowest dry matter of total weeds. Also, two hand hoeing was the most effective weed control treatment in increasing growth, yield, yield attributes, and some biochemical constitutes of faba bean seeds followed by of oxadiargyl treatment. No significant differences between application of two hand-hoeing and oxadiargyl treatment on all studied parameters. Foliar treatment of faba bean plants with thiamine different concentrations could alleviate the harmful effects of different salinity levels.ConclusionWe could conclude that foliar application of thiamine at the rate of 100 mg/l caused the highest increases in all growth and yield parameters under investigation of faba bean plant. Interaction of 100 mg/l thiamine treatment and two hand hoeing was the most effective treatments on enhancing faba bean growth, yield, and its attributes under salinity levels. Results also indicated that free amino and proline works to increase faba bean plants ability to withstand salinity stress.

The relationship between perceived stress and problematic social networking site use among Chinese college students.

Background and aimsPerceived stress has been regarded as a risk factor for problematic social networking site (SNS) use, yet little is known about the underlying processes whereby confounding variables may mediate or moderate this relationship. To answer this question, this study examined whether depression and anxiety mediated the relationship between perceived stress and problematic SNS use, and whether these mediating processes were moderated by psychological resilience and social support.MethodsParticipants were 641 Chinese college students who completed anonymous questionnaires measuring perceived stress, depression/anxiety, psychological resilience, social support, and problematic SNS use.ResultsThe results showed that (a) depression/anxiety mediated the relationship between perceived stress and problematic SNS use; (b) the mediating effects of depression/anxiety on the association between perceived stress and problematic SNS use were moderated by psychological resilience. Specifically, the mediating effects of depression/anxiety were stronger for individuals with lower levels of psychological resilience, compared with those with higher levels of psychological resilience; and (c) the mediating effects of depression/anxiety were not moderated by social support, although social support was negatively related to depression/anxiety.Discussion and conclusionThis study can contribute to a better understanding of how and when perceived stress increases the risk of problematic SNS use, and implies the importance of enhancing psychological resilience in preventing problematic SNS use.

Relaxation Response of Critically Stressed Macroscale Surficial Rock Sheets

Rock environments both underground and on Earth’s surface show indications of energetic macroscale fracture. In tunnels and excavations, these manifest as rockbursts—energetic explosions of rock that can damage engineering projects, and may pose ongoing financial and safety risk as rock stresses adjust during post-failure relaxation. In natural settings at the surface, evidence for rockbursts exist in the form of tent-like structures of ruptured exfoliation sheets, but few direct observations of such events exist, precluding the analysis of how natural rock formations may evolve after rupture. Here we investigate the post-failure evolution of a granitic rock dome following rapid fracture events (i.e., surficial rockbursts) that occurred in California, USA during 2014–2016. Building upon previous work that showed a thermal stress origin for the observed fracturing, we investigate the return to background stress conditions (i.e., stress relaxation) observed in both short- (week, month) and long-term (multi-year) rock deformation trends. Acoustic emissions, deformation, and environmental monitoring data indicate that partially detached rock sheets forming the surface of the dome undergo fracture aperture closing during cooling periods, concurrent with reduction of rock stress by the source of forcing (i.e., thermal stress). However, with sufficient critical and/or subcritical fracture, our observations also show that rock sheets can become decoupled from the source of stress, resulting in a long-term return to background stress conditions. Our results provide insight into the cyclic and likely ephemeral nature of rock fracture in surficial rock domes, as well as in underground rockburst environments.

A Comparison of Death Anxiety, Intolerance of Uncertainty and Self-Esteem as Predictors of Social Anxiety Symptoms

AbstractThis study sought to examine the role of death anxiety as a transdiagnostic predictor of social anxiety symptomatology compared to self-esteem and intolerance of uncertainty, and to examine the relationship between measures of intrinsic and extrinsic religiosity and death anxiety. A total of 591 participants, 445 females, average age 38.0 years (SD = 14.5), completed an online survey including background questions, the Depression, Anxiety and Stress Scale, the Social Interaction Anxiety and Social Phobia Scale, the Rosenberg Self-Esteem Scale, the Intolerance of Uncertainty Scale, the Santa Clara Strength of Religious Faith Questionnaire, the Spirituality Scale, and the Death Anxiety Scale. No significant, independent relationship was found between death anxiety and social anxiety symptomatology, although self-esteem and intolerance of uncertainty were significant predictors of both measures of social anxiety, confirming the importance of these key transdiagnostic mediators as predictors of social anxiety symptomatology. A strong negative correlation was found between death anxiety and measures of both intrinsic and extrinsic religiosity in this general population sample not selected for high religious affiliation.

On the Propagation Path of Magma‐Filled Dikes and Hydrofractures: The Competition Between External Stress, Internal Pressure, and Crack Length

AbstractMixed‐mode fluid‐filled cracks represent a common means of fluid transport within the Earth's crust. They often show complex propagation paths which may be due to interaction with crustal heterogeneities or heterogeneous crustal stress. Previous experimental and numerical studies focus on the interplay between fluid overpressure and external stress but neglect the effect of other crack parameters. In this study, we address the role of crack length on the propagation paths in the presence of an external heterogeneous stress field. We make use of numerical simulations of magmatic dike and hydrofracture propagation, carried out using a two‐dimensional boundary element model, and analogue experiments of air‐filled crack propagation into a transparent gelatin block. We use a 3‐D finite element model to compute the stress field acting within the gelatin block and perform a quantitative comparison between 2‐D numerical simulations and experiments. We show that, given the same ratio between external stress and fluid pressure, longer fluid‐filled cracks are less sensitive to the background stress, and we quantify this effect on fluid‐filled crack paths. Combining the magnitude of the external stress, the fluid pressure, and the crack length, we define a new parameter, which characterizes two end member scenarios for the propagation path of a fluid‐filled fracture. Our results have important implications for volcanological studies which aim to address the problem of complex trajectories of magmatic dikes (i.e., to forecast scenarios of new vents opening at volcanoes) but also have implications for studies that address the growth and propagation of natural and induced hydrofractures.

Chronic Unexpected Mild Stress Destroys Synaptic Plasticity of Neurons through a Glutamate Transporter, GLT-1, of Astrocytes in the Ischemic Stroke Rat.

Background and Objective Chronic unexpected mild stress (CUMS) destroys synaptic plasticity of hippocampal regenerated neurons that may be involved in the occurrence of poststroke depression. Astrocytes uptake glutamate at the synapse and provide metabolic support for neighboring neurons. Currently, we aim to investigate whether CUMS inhibits synaptic formation of regenerated neurons through a glutamate transporter, GLT-1, of astrocytes in the ischemic stroke rats. Method We exposed the ischemic stroke rats to ceftriaxone, during the CUMS intervention period to determine the effects of GLT-1 on glutamate circulation by immunofluorescence and mass spectrometry and its influences to synaptic plasticity by western blot and transmission electron microscopy. Result CUMS evidently reduced the level of astroglial GLT-1 in the hippocampus of the ischemic rats (p < 0.05), resulting in smaller amount of glutamate being transported into astrocytes surrounding synapses (p < 0.05), and then expression of synaptophysin was suppressed (p < 0.05) in hippocampal dentate gyrus. The ultrastructures of synapses in dentate gyrus were adversely influenced including decreased proportion of smile synapses, shortened thickness of postsynaptic density, reduced number of vesicles, and widened average distance of the synaptic cleft (all p < 0.05). Moreover, ceftriaxone can promote glutamate circulation and synaptic plasticity (all p < 0.05) by raising astroglial GLT-1 (p < 0.05) and then improve depressive behaviors of the CUMS-induced model rats (p < 0.05). Conclusion Our study shows that CUMS destroys synaptic plasticity of regenerated neurons in the hippocampus through a glutamate transporter, GLT-1, of astrocytes in the ischemic stroke rats. This may indicate one potential pathogenesis of poststroke depression.

The -866G/A polymorphism in the promoter of the UCP2 gene is associated with risk for type 2 diabetes and with decreased insulin levels

Background and aimOxidative stress and impaired insulin secretion is an underlying major risk factor for the development of type 2 diabetes (T2D). Uncoupling protein-2 (UCP2) is involved in the regulation of reactive oxygen species production, insulin secretion, and lipid metabolism. Based on this we aimed to find an association of UCP2 (G-866A) polymorphism with the risk of T2D in South Indian population. MethodsA total of 318 T2D patients and 312 controls were enrolled in this study. All the study subjects were genotyped for UCP2 (G-866A) polymorphism using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Fasting blood glucose, HbA1c, serum lipid profile, systolic and diastolic blood pressure were measured by standard biochemical methods. Fasting serum insulin level was measured by ELISA. ResultsIn UCP2 (G-866A) polymorphism, the distribution of GA (46%) and AA (14%) genotypes were significantly higher in T2D patients than the healthy controls. The frequency of GA and AA genotypes have high risk towards the development of T2D with an Odds Ratio (OR) of 1.55 (P = 0.01) and 2.04 (P = 0.01) respectively. Moreover, SNP-866 G>A allele was found to be significantly associated with T2D (OR = 1.48, P = 0.001, 95% CI = 1.16–1.88). Further, the UCP2 AA genotype showed significantly decreased level of insulin by the reduction in pancreatic β-cell function in T2D patients. ConclusionUCP2 (G-866A) polymorphism may play a crucial role in the pathogenesis of insulin secretion thus leads to the development of T2D.

(249) Modulators of Burn Injury-Related Pain in Mice: The Search for Modulators in the Transition from Acute to Chronic Pain

Acute pain is prevalent following burn injury and can transition to chronic pain in over 50% of patients. Prolonged acute pain is an important component that leads to chronic pain. Our research investigates burn injury-related pain and searches for risk factors that influence acute-to-chronic pain transitions. The present work tests whether dietary intervention, genetic background or pre-injury stress affects thermal and mechanical hypersensitivity associated with 2° burn of the mouse hindpaw. Under Avertin anesthesia, (200 µL/10g body weight), the paw of the mouse was placed on a metal block with a surface temperature of 65°C for 15 seconds. A 5-g weighted pouch was placed on the dorsum of the paw to maintain pressure between the heel and the heat source. A visible scar is evident 5-7 days after the injury. Mechanical and thermal thresholds were assessed at baseline, and at 1, 3, 7, 14, 21, 28, and 33 days post-burn injury. Our results reveal that mice which undergo a burn develop significant ipsilateral thermal hypersensitivity and mechanical allodynia that resolves to baseline thresholds by 12 days (thermal) or 30 days (mechanical). Consumption of the high-fat diet did not alter the severity or duration of burn-induced thermal or mechanical hypersensitivity. At sacrifice, mice with a burn injury had a significant increase in degranulated epidermal mast cells (p=0.036). Ongoing experiments are comparing the response of A/J inbred mice that exhibit an anxious phenotype to hindpaw burn injury. Also, repeated foot shock stress in mice induces chronic stress and exacerbates cutaneous and visceral pain. Additional experiments are testing whether A/J mice exposed to foot shock stress for 10 continuous days and undergo burn injury have altered severity or duration of altered thermal and mechanical thresholds. Results from these new studies will be presented and compared to previous findings associated with dietary interventions.

A study on seismicity in the Yunnan region by using the multidimensional stress release model

The long-term seismic activity in the Yunnan region has attracted much attention due to frequent occurrences of disastrous earthquakes. We investigated the seismicity of the Yunnan region using the multidimensional stress release model (MSRM) to evaluate the long-term seismic hazard. MSRM combines three factors that affect earthquake occurrence, i.e., initial stress background, tectonic loading, and coseismic stress transfer, and can simulate and forecast the spatiotemporal seismicity. In this study, a complete catalog comprising 28 strong earthquakes (M ≥ 6.5) after 1900 in the Yunnan region was investigated using MSRM. We calculated the spatiotemporal variations of seismicity rates, and found that strong earthquakes occur at locations with higher seismic activity. Comparisons between the seismicity rates at the epicenter locations immediately before and after strong earthquakes show that the seismicity rates in the vicinity of the epicenters significantly decrease after strong earthquakes. The estimated seismicity rates at the ending time (January 1, 2025) suggest that strong earthquake potential in the section between Kunming and Huaning of the Xiaojiang fault and the northeastern section of the Lijiang-Xiaojinhe fault should receive more attention, while the seismicity in the southwestern part decreases and the seismicity in the middle segment of the Red River fault remains low.

Initiation and arrest of earthquake ruptures due to elongated overstressed regions

The initiation of natural and induced earthquakes is promoted in fault areas where shear stress is close to fault strength. In many real-world situations, these overstressed fault areas (or ‘asperities’) are very elongated; for example, in the case of a fault intersecting a reservoir subject to fluid-injection, or the stress concentration along the bottom of a seismogenic zone induced by deep fault creep. Theoretical estimates of the minimum overstressed asperity size leading to runaway rupture and of the final size of self-arrested ruptures are only available for 2-D problems and for 3-D problems with an asperity aspect ratio close to one. In this study, we determine how the nucleation of ruptures on elongated asperities, and their ensuing arrest, depends on the size and aspect ratio of the asperity and on the background stress. Based on a systematic set of 3-D dynamic rupture simulations assuming linear slip-weakening friction, we find that if the shortest asperity side is smaller than the 2-D critical length, the problem effectively reduces to a 2-D problem in which rupture nucleation and arrest are controlled by the shortest length of the asperity. Otherwise, nucleation and rupture arrest are controlled by the asperity area, with a minor exception: for asperities with shortest side slightly larger than the 2-D critical length, arrested ruptures are smaller than predicted by the asperity area. The fact that rupture arrest is dominantly controlled by area, even for elongated asperities, corroborates the finding that observed maximum magnitudes of earthquakes induced by fluid injection are consistent with the theoretical relation between the magnitude of the largest self-arrested rupture and the injected volume. In the context of induced seismicity, our simulations provide plausible scenarios that could be either favourable or challenging for traffic light systems and provide mechanical insights into the conditions leading to these situations.

Long-Term Evolution of the Deviatoric Background Stress in the Focal Region of the 2011 Tohoku-Oki Earthquake

On 11 March 2011, a giant interplate earthquake of magnitude Mw 9.1 struck Tohoku-Oki area in eastern Japan. The earthquake is acknowledged to have permanently altered the stress field in and around the focal region. To capture the temporal change of the overall stress field, I examined 1251 focal mechanisms, from the NIED MT catalog, that occurred before and after the Tohoku-Oki earthquake from January, 2006 to January, 2017 in the focal region near the subducting slab. The examined observations were grouped into six periods, and based on the selected NIED MT catalog, the stress regime in each period was obtained by using the damped stress tensor inversion method. Based on the temporal evolution of stress rotation, the corresponding deviatoric stress level was estimated using a simplified 2D model. Results of the 10-year seismic stress cycle show that several years before the Tohoku-Oki earthquake, the stress accumulation level seems to have experienced an acceleration process. Studies suggest that this increasingly critically stress state combined with the sufficiently reduced coupling rate off the Tohoku area finally resulted in the unprecedented megathrust event. The coseismic process was violent and released almost all of the deviatoric stress that presented before the main shock. The resultant stress state even reached frictional overshoot. Thus, the postseismic stress pattern in the source region was reshaped significantly, especially for the upper plate and updip portion of the lower plate. After the main shock near the rupture surface, a surprisingly rapid and high-level stress reloading occurred within several postseismic years. To reconcile the classical subduction zone earthquake generation cycle model, the event may be described as an instantaneously decoupled stress state between the upper and inner plates.

Prevalence of smoking in nursing professionals of a cardiovascular hospital.

to identify the prevalence of smoking in nursing professionals and to determine the relationship of the habit with clinical and socio-demographic characteristics. nursing professionals of a cardiovascular hospital answered a questionnaire on smoking and dependence degree, socio-demographic characteristics, personal and family background, smoking characteristics, motivational stages, depression, perceived and occupational stress. The relationship between the explanatory variables and smoking was investigated. among 656 participants, 77.6% were non smokers, 12.2% former smokers, and 10.2% smokers. Most were female, with complete high school, Catholic, married, household income between three and five minimum wages, position as nursing assistant, had double shifts, and were responsible for family income. The nicotine dependence of smokers ranged from low to moderate. the study has shown low prevalence of smoking in nursing professionals. Education level, religion, marital status, job position, responsibility for family income, history of depression and alcoholism, chest "wheezing" and other symptoms were significantly associated with being a smoker or former smoker.

Study on crack formation and propagation in the galleries of the Dagangshan high arch dam in Southwest China based on microseismic monitoring and numerical simulation

The Dagangshan high arch dam, located in the area with complicated geological conditions and extremely high seismic intensity in Southwest China, has received substantial attention worldwide. Before the impoundment of the reservoir, continuous deep transverse cracks were observed in the low-elevation galleries of the arch dam. To investigate crack formation and propagation in the galleries of the high arch dam, microseismic monitoring and 3D finite element analysis of the galleries were performed during the filling process. The microseismic monitoring system was installed in the foundation gallery and the drainage gallery to detect microcracks around the galleries of the arch dam. The background stress field for crack formation and propagation in the galleries was studied based on 3D finite element modelling. The results indicate that the self-weight of high arch dam produces excessive circumferential tensile stresses at the arch crown of the galleries near the dam heel before impoundment, which is the cause of crack formation in the galleries of the Dagangshan high arch dam. As the impounded water level rises, the tensile stresses and the microseismicity in the galleries near the arch dam heel transfer to the galleries close to the arch dam toe, and the cracks in the galleries near the dam heel would not propagate further but be closed. However, cracking may occur in the gallery close to the dam toe if its microseismicity continues increasing. The conclusions have significant implications for reinforcement and operation of the galleries in similar high concrete arch dams.

Spatiotemporal Variations of Stress and Strain Parameters in the San Jacinto Fault Zone

We analyze the background stress field around the San Jacinto fault zone (SJFZ) in Southern California with a refined inversion methodology using declustered focal mechanisms of background seismicity. Stress inversions applied to the entire fault zone, and three focus areas with high level of seismicity, provide three-dimensional distributions of the maximum horizontal compression direction (SHmax), principal stress plunges, and stress ratio \(R = (\sigma_{1} - \sigma_{2} )/(\sigma_{1} - \sigma_{3} )\). The results are compared with coseismic strain parameters derived from direct summation of earthquake potencies and b values of frequency–size event statistics. The main stress regime of the SJFZ is strike-slip, although the northwest portion near Crafton Hills displays significant transtension. The SHmax orientation rotates clockwise with increasing depth, with the largest rotation (23°) observed near Crafton Hills. The principal stress plunges have large rotations below ~ 9 km, near the depth section with highest seismicity rates and inferred brittle–ductile transition zone. The rotations produce significant deviations from Andersonian strike-slip faulting, likely generating the observed increased dip-slip faulting of relatively deep small events. The stress ratio parameters and b value results are consistent with increasing number of dip-slip faulting below ~ 9 km. The derived coseismic strain parameters are in good agreement with the stress inversion results. No large-scale stress rotations are observed across the time of the 2010 Mw 7.2 El Mayor–Cucapah earthquake. The stress ratio near the Trifurcation area of the SJFZ changes after the El Mayor–Cucapah earthquake toward transpression, but this may have been produced by local M > 5.4 event or aseismic slip.

Detection of Stress Anomaly Produced by Interaction of Compressive Fault Steps in the West Bohemia Swarm Region, Czech Republic

AbstractObservations of the 2008–2014 seismic activity in West Bohemia, Czech Republic, provide evidence of interaction of compressive fault steps that created local stress anomaly and triggered a seismic sequence with exceptional properties. The West Bohemia is a geothermal area, characterized by persistent fluid‐driven seismicity in the form of earthquake swarms. The focal zone is formed by two weak and fluid‐eroded parallel strike‐slip faults with a step of about 200 m. The fault segments were activated successively by the 2008 and 2011 swarms with magnitudes of the strongest events of 3.8 and 3.7, respectively. In 2014, a fracture linking both segments was formed or activated by a mainshock‐aftershock sequence. The aftershock decay was very fast, and the focal mechanism of the strongest event with magnitude of 4.2 was inconsistent with the regional background stress. The stress inversion of 957 focal mechanisms revealed a stress anomaly characterized by interchanging the σ2 and σ3 principal stress axes in the area of fault interaction. The modeling of the Coulomb stress change confirmed that the stress anomaly could completely disturb the regional background stress and produce the rotation of the principal stress axes retrieved from focal mechanisms. The faults activated or newly formed within the compressive stress anomaly were of high strength, which caused the anomalous mainshock‐aftershock character of the 2014 activity and the rapid aftershock decay. Linking the two previously active isolated faults during the 2014 activity increased the expected moment magnitude Mw of a possible strongest earthquake from 5.0 to 5.4.

On the Relationship Between Fault Permeability Increases, Induced Stress Perturbation, and the Growth of Aseismic Slip During Fluid Injection

AbstractFluid injections into the deep subsurface can, at times, generate earthquakes, but often, they only produce aseismic deformations. Here we analyze the influence of fault hydromechanical properties on the growth of injection‐induced aseismic slip. Using hydromechanical modeling, we show how permeability enhancement in addition to the background stress and frictional weakening has an important effect on the pressure diffusion and slip growth during injection. We find that the more pronounced the fault permeability enhancement, the stronger is the growth of the aseismic slip zone. The effect of enhanced permeability is more pronounced when the fault is initially close to failure. Our results show that aseismic slip grows beyond the pressurized zone when the fault permeability increases, while slip remains behind the pressurized zone when permeability does not vary from its initial preslip value. Thus, fault permeability increases should be considered as complementary mechanism to current models of fluid‐induced aseismic slip.

Intraplate Strike‐Slip Faulting, Stress Accumulation, and Shear Localization of a Crust‐Upper Mantle System With Nonlinear Viscoelastic Material

AbstractWe investigate the evolution of tectonic background stress and elastic as well as inelastic strain in a crust‐upper mantle system around an infinitely long vertical strike‐slip fault in a self‐consistent mechanical earthquake cycle model. In the early stage of the stress evolution, deformation of the crust and the upper mantle is dominated by a uniform simple shear. Shear localization in the lower crust starts when coseismic rupture extends to the entire brittle upper crust. Together with this transition, the earthquake recurrence intervals decrease by an order of magnitude due to a basal drag originated from a localized plastic flow of the lower crust. After the shear zone is fully developed in the lower crust, the fault slip rate catches up with the far‐field velocity and earthquakes starts to occur periodically. Such a steady state can be reached in several hundred thousand years from the beginning, which includes few hundreds of earthquake cycles. A shear zone with large cumulative strain needs a few million years to develop under an intraplate strike‐slip fault, which is much longer than the time for shear strain rate to be localized. The model successfully reproduced evolution of tectonic stress around an intraplate strike‐slip fault, interacting with the development of localized shear zone in the lower crust. The model demonstrates the importance of considering the whole mechanical system in which rheological structure and fault activities interacting with each other for the better understanding of the intraplate earthquakes.

An experimental investigation of the impact of critical and warm comments on state paranoia in a non-clinical sample

Background and objectivesInterpersonal stress is key to the development and maintenance of paranoia. Much attention has been given to the impact of interpersonal stressors, such as criticism, on outcomes in psychosis. Less attention has been given to the potentially protective effects of positive interpersonal factors. This study tested experimentally whether criticism and warm comments elicited changes in state paranoia. Whether warm comments provided protective effects when participants faced subsequent social exclusion was also examined. MethodA nonclinical sample (N = 97) was randomised to criticism, warm comments, or neutral comments conditions. Participants then played a virtual ball game (Cyberball), during which they were systematically excluded from the game. State paranoia was measured before and after the affective stimuli and after social exclusion. Self-esteem and trait paranoia were also measured. ResultsParanoia levels increased following exposure to criticism (p = .011). Paranoia was not significantly lower following exposure to warm comments (p = .203). Warm comments did not provide protection against the effects of subsequent social exclusion. The warm comments condition was the only condition in which significant increases in paranoia were seen following social exclusion (p = .004). LimitationsUse of a non-clinical sample limits generalisation to clinical populations. ConclusionsCriticism is sufficient to elicit increases in paranoia in non-clinical participants. Warm comments are insufficient to significantly reduce paranoia or provide protective effects against subsequent negative interpersonal experiences, highlighting the need to balance therapeutic warmth with amelioration of social stressors in paranoia.