scholarly journals Viscous fault creep controls the stress-dependence of modelled earthquake statistics

2021 ◽  
Author(s):  
Adam Beall ◽  
Martijn van den Ende ◽  
Jean-Paul Ampuero ◽  
Ake Fagereng
Keyword(s):  
Fault Zone ◽  
Probabilistic Models ◽  
High Stress ◽  
Seismic Hazard Assessment ◽  
Fault Creep ◽  
Magnitude Distribution ◽  
Regional Seismicity ◽  
Earthquake Statistics ◽  
Earthquake Size ◽  
Stress Dependent

The ability to estimate the likelihood of particular earthquake magnitudes occurring in a given region is critical for seismic hazard assessment. Earthquake size and recurrence statistics have been empirically linked to stress state, however there is ongoing debate as to which fault-zone processes are responsible for this link. We numerically model combined viscous creep and frictional sliding of a fault-zone, where applied shear stress controls the interplay between these mechanisms. This model reproduces the stress-dependent earthquake magnitude distribution observed in nature. At low stress, many fault segments creep and impede ruptures, limiting earthquake sizes. At high stress, more segments are close to frictional failure and large earthquakes are more frequent. Contrasts in earthquake statistics between regions, with depth and through time, may be explained by stress variation, which could be used in the future to further constrain probabilistic models of regional seismicity.

scholarly journals Mapping the <i>b</i>-values along the Longmenshan fault zone before and after the 12 May 2008, Wenchuan, China, <i>M<sub>S</sub></i> 8.0 earthquake

2008 ◽  
Vol 8 (6) ◽  
pp. 1375-1385 ◽  
Author(s):  
Y. Z. Zhao ◽  
Z. L. Wu
Keyword(s):  
Fault Zone ◽  
High Stress ◽  
B Value ◽  
Slip Distribution ◽  
Longmenshan Fault Zone ◽  
Magnitude Distribution ◽  
The North ◽  
Significant Difference ◽  
Before And After ◽  
Longmenshan Fault

Abstract. The b-value in the Gutenberg-Richter frequency-magnitude distribution, which is assumed to be related to stress heterogeneity or asperities, was mapped along the Longmenshan fault zone which accommodated the 12 May 2008, Wenchuan, MS 8.0 earthquake. Spatial distributions of b-value before and after the Wenchuan earthquake, respectively, were compared with the slip distribution of the mainshock. It is shown that the mainshock rupture nucleated near to, but not within, the high-stress (low b-value) asperity in the south part of the Longmenshan fault, propagating north-eastward to the relatively low stress (high b-value) region. Due to the significant difference between the rupture process results from different sources, the comparison between slip distribution and pre-seismic b-value distribution leads to only conclusion of the rule-of-thumb. The temporal change of b-value before the mainshock shows a weak trend of decreasing, being hard to be used as an indicator of the approaching of the mainshock. Distribution of b-values for the aftershocks relates the termination of the mainshock rupture to the harder patch along the Longmenshan fault to the north.

scholarly journals Intermediate-Temperature Creep Deformation and Microstructural Evolution of an Equiatomic FCC-Structured CoCrFeNiMn High-Entropy Alloy

Entropy ◽  
2018 ◽  
Vol 20 (12) ◽  
pp. 960 ◽  
Author(s):  
Chengming Cao ◽  
Jianxin Fu ◽  
Tongwei Tong ◽  
Yuxiao Hao ◽  
Ping Gu ◽  
...  
Keyword(s):  
Activation Energy ◽  
Dynamic Recrystallization ◽  
Creep Deformation ◽  
High Stress ◽  
Intermediate Temperature ◽  
Tensile Creep ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Stress Region ◽  
Stress Dependent

The tensile creep behavior of an equiatomic CoCrFeNiMn high-entropy alloy was systematically investigated over an intermediate temperature range (500–600 °C) and applied stress (140–400 MPa). The alloy exhibited a stress-dependent transition from a low-stress region (LSR-region I) to a high-stress region (HSR-region II). The LSR was characterized by a stress exponent of 5 to 6 and an average activation energy of 268 kJ mol−1, whereas the HSR showed much higher corresponding values of 8.9–14 and 380 kJ mol−1. Microstructural examinations on the deformed samples revealed remarkable dynamic recrystallization at higher stress levels. Dislocation jogging and tangling configurations were frequently observed in LSR and HSR at 550 and 600 °C, respectively. Moreover, dynamic precipitates identified as M23C6 or a Cr-rich σ phase were formed along grain boundaries in HSR. The diffusion-compensated strain rate versus modulus-compensated stress data analysis implied that the creep deformation in both stress regions was dominated by stress-assisted dislocation climb controlled by lattice diffusion. Nevertheless, the abnormally high stress exponents in HSR were ascribed to the coordinative contributions of dynamic recrystallization and dynamic precipitation. Simultaneously, the barriers imposed by these precipitates and severe initial deformation were referred to so as to increase the activation energy for creep deformation.

scholarly journals Hippocampal 2-Arachidonoyl Glycerol Signaling Regulates Time-of-Day- and Stress-Dependent Effects on Rat Short-Term Memory

2020 ◽  
Vol 21 (19) ◽  
pp. 7316
Author(s):  
Alessia Santori ◽  
Maria Morena ◽  
Matthew N. Hill ◽  
Patrizia Campolongo
Keyword(s):  
Recognition Memory ◽  
Short Term Memory ◽  
Memory Performance ◽  
High Stress ◽  
Time Of Day ◽  
Stress Conditions ◽  
Short Term ◽  
Term Memory ◽  
Stress Dependent ◽  
Arachidonoyl Glycerol

Background: Cannabinoids induce biphasic effects on memory depending on stress levels. We previously demonstrated that different stress intensities, experienced soon after encoding, impaired rat short-term recognition memory in a time-of-day-dependent manner, and that boosting endocannabinoid anandamide (AEA) levels restored memory performance. Here, we examined if two different stress intensities and time-of-day alter hippocampal endocannabinoid tone, and whether these changes modulate short-term memory. Methods: Male Sprague-Dawley rats were subjected to an object recognition task and exposed, at two different times of the day (i.e., morning or afternoon), to low or high stress conditions, immediately after encoding. Memory retention was assessed 1 hr later. Hippocampal AEA and 2-arachidonoyl glycerol (2-AG) content and the activity of their primary degrading enzymes, fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), were measured soon after testing. Results: Consistent with our previous findings, low stress impaired 1-hr memory performance only in the morning, whereas exposure to high stress impaired memory independently of testing time. Stress exposure decreased AEA levels independently of memory alterations. Interestingly, exposure to high stress decreased 2-AG content and, accordingly, increased MAGL activity, selectively in the afternoon. Thus, to further evaluate 2-AG’s role in the modulation of short-term recognition memory, rats were given bilateral intra-hippocampal injections of the 2-AG hydrolysis inhibitor KML29 immediately after training, then subjected to low or high stress conditions and tested 1 hr later. Conclusions: KML29 abolished the time-of-day-dependent impairing effects of stress on short-term memory, ameliorating short-term recognition memory performance.

Ageing and yield behaviour in model soft colloidal glasses

2009 ◽  
Vol 367 (1909) ◽  
pp. 5051-5071 ◽  
Author(s):  
C. Christopoulou ◽  
G. Petekidis ◽  
B. Erwin ◽  
M. Cloitre ◽  
D. Vlassopoulos
Keyword(s):  
Glassy State ◽  
High Stress ◽  
Elastic Solid ◽  
Elastic Response ◽  
Slow Step ◽  
Recoverable Strain ◽  
Highly Nonlinear ◽  
Yield Behaviour ◽  
Colloidal Glasses ◽  
Stress Dependent

We use multi-arm star polymers as model soft colloids with tuneable interactions and explore their behaviour in the glassy state. In particular, we perform a systematic rheological study with a well-defined protocol and address aspects of ageing and shear melting of star glasses. Ageing proceeds in two distinct steps: a fast step of O (10 3  s) and a slow step of O (10 4  s). We focus on creep and recovery tests, which reveal a rich, albeit complex response. Although the waiting time, the time between pre-shear (rejuvenation) of the glassy sample and measurement, affects the material’s response, it does not play the same role as in other soft glasses. For stresses below the yield value, the creep curve is divided into three regimes with increasing time: viscoplastic, intermediate steady flow (associated with the first ageing step) and long-time evolving elastic solid. This behaviour reflects the interplay between ageing and shear rejuvenation. The yield behaviour, as investigated with the stress-dependent recoverable strain, indicates a highly nonlinear elastic response intermediate between a low-stress Hookean solid and a high-stress viscoelastic liquid, and exemplifies the distinct characteristics of this class of hairy colloids. It appears that a phenomenological classification of different colloidal glasses based on yielding performance may be possible.

How fault creep makes its way!

2020 ◽  
Author(s):  
Sohom Ray ◽  
Dmitry Garagash
Keyword(s):  
Free Surface ◽  
Steady State ◽  
High Stress ◽  
Slip Rate ◽  
Interfacial Strength ◽  
Elastic Half Space ◽  
Entire Length ◽  
Fault Creep ◽  
Dynamic Event ◽  
First Case

&lt;p&gt;We model mechanics of an aseismic fault creep propagation and conditions when it may lead to the initiation of seismic slip. We do so by considering fault bounding medium to be elastically deformable and fault's interfacial strength to be slip rate- and state-dependent characterized by the steady-state rate-weakening. The fault is considered to be initially locked: a state of slip when interfacial slip velocity is considerably low and arbitrarily less than the steady-state sliding rate for given uniformly distributed prestress.&lt;/p&gt;&lt;p&gt;We find solutions for creep penetration into the fault under geologically relevant loading scenarios (e.g., that of a plate-bounding strike-slip faulting driven by the slip at depth, or that of a rate-weakening patch of a fault loaded by a creep on an adjacent rate-strengthening part due to, e.g., anthropogenic fluid injection). In all the cases, the creep makes its way as a self-similar traveling front characterized by high stress owed to the direct effect; however, the remaining creep profile exhibits a near steady-state sliding. This may imply that a choice from a set of rules for the evolution of state variable&amp;#8212;with identical linearizations about steady-state sliding&amp;#8212;has no bearing on the creep penetration. Further, we find that the prestress, close to or far from steady-state sliding stress, controls the rate and manner of the creep penetration.&lt;/p&gt;&lt;p&gt;We study slip propagation from an imposed dislocation accrued at a constant rate at one end of a homogeneous fault with the other end either at (1) the free surface of an elastic half-space or (2) strictly locked (buried) in the elastic full space. In both scenarios, no slip instability takes place over aseismic creep propagation distances relatable to the usual elasto-frictional nucleation lengthscale (e.g. Rubin &amp; Ampuero 2005). Instead, in the first case creep propagation leads to the nucleation of the first and all subsequent dynamic events of the emerging cycle at/near the free surface after the creep traversed the entire length of the fault. In the second case, the creep front traverses nearly the entire length of the fault, but, instead of nucleating a dynamic event, the front arrests at some distance from the buried fault end, followed by the continual accumulation of aseismic slip without ever nucleating a dynamic event. These results may be owed to the physical and geometrical invariance of the considered homogeneous fault and may signal the essential role of fault strength heterogeneity, either that of the normal stress and/or frictional properties (Ray &amp; Viesca, 2017, 2019), in defining its seismogenic character, i.e. under which conditions and where on the fault the earthquake slip instability can take place.&amp;#160;&lt;/p&gt;

scholarly journals Measurements of tectonic micro-displacements within the Idrija fault zone in the Učja valley (W Slovenia)

2020 ◽  
Vol 60 (1) ◽  
Author(s):  
Andrej Gosar
Keyword(s):  
Fault Zone ◽  
Active Fault ◽  
Average Rate ◽  
Active Faults ◽  
Slip Rate ◽  
Seismic Hazard Assessment ◽  
Vertical Displacements ◽  
Recent Activity ◽  
Insight Into ◽  
Horizontal Displacements

A recent slip-rate of an active fault is a very important seismotectonic parameter, but not easy to determine. Idrija fault, 120 km long, is a prominent geomorphologic feature with large seismogenic potential, still needed to be researched. Measurements of tectonic micro-displacements can provide insight into its recent activity. The Učja valley extends transversally to the Idrija fault and was therefore selected for the installation of TM 71 extensometer. Measurements on the crack within its inner fault zone are conducted from the year 2004. In 14 years of observations a systematic horizontal displacements with average rate of 0.21 mm/year and subordinate vertical displacements of 0.06 mm/year were established, proving the activity of this fault. An overview of methods of displacement measurements related to active faults and of newer interdisciplinary investigations of the Idrija fault is given. Displacement rates are beside for geodynamic interpretations important for improvement of seismotectonic models and thus for better seismic hazard assessment.

scholarly journals Weaning Induces Stress-Dependent DNA Methylation and Transcriptional Changes in Piglet PBMCs

2021 ◽  
Vol 12 ◽  
Author(s):  
Ryan J. Corbett ◽  
Andrea M. Luttman ◽  
Kaitlin E. Wurtz ◽  
Janice M. Siegford ◽  
Nancy E. Raney ◽  
...  
Keyword(s):  
Dna Methylation ◽  
T Cell ◽  
Hpa Axis ◽  
T Cell Activation ◽  
Expression Patterns ◽  
High Stress ◽  
Differential Methylation ◽  
Model Organisms ◽  
Cell Immunity ◽  
Stress Dependent

Changes to the epigenome, including those to DNA methylation, have been proposed as mechanisms by which stress can induce long-term physiological changes in livestock species. Pig weaning is associated with dietary and social stress, both of which elicit an immune response and changes to the hypothalamic–pituitary–adrenal (HPA) axis. While differential methylation following stress has been assessed in model organisms, it remains poorly understood how the pig methylome is altered by stressors in production settings. We quantified changes in CpG methylation and transcript abundance in piglet peripheral blood mononuclear cells (PBMCs) following weaning and also assessed differential patterns in pigs exhibiting high and low stress response as measured by cortisol concentration and lesion scores. Blood was collected from nine gilt piglets 24 h before and after weaning, and whole-genome bisulfite sequencing (WGBS) and RNA-sequencing were performed on six and nine animals, respectively, at both time points. We identified 2,674 differentially methylated regions (DMRs) that were enriched within promoters of genes associated with lymphocyte stimulation and transcriptional regulation. Stress groups displayed unique differential methylation and expression patterns associated with activation and suppression of T cell immunity in low and high stress animals, respectively. Differential methylation was strongly associated with differential expression; specifically, upregulated genes were enriched among hypomethylated genes. We observed post-weaning hypermethylation of the glucocorticoid receptor (NR3C1) promoter and a significant decrease in NR3C1 expression (n = 9, p = 6.1 × 10–3). Our results indicate that weaning-associated stress elicits genome-wide methylation changes associated with differential gene expression, reduced T cell activation, and an altered HPA axis response.

scholarly journals EFEKTIVITAS PELATIHAN MANAJEMEN STRES DALAM PENURUNAN STRES KERJA PADA ANGGOTA BADAN SEARCH AND RESCUE NASIONAL (BASARNAS) KOTA PADANG

2020 ◽  
Vol 2 (1) ◽  
pp. 28-39
Author(s):  
Mutiara Ramadhani ◽  
Widia Sri Ardias
Keyword(s):  
Stress Management ◽  
Work Stress ◽  
Stress Level ◽  
Employee Performance ◽  
High Stress ◽  
Management Training ◽  
T Test ◽  
Measuring Instruments ◽  
Stress Management Training ◽  
Stress Dependent

The purpose of this study was to see what level of stress the work of members of the Padang City BASARNAS before being given training, and after being given stress management training. Furthermore, the research also highlighted the influence of stress management training in reducing work stress on members of the Padang City BASARNAS. The method used in this study is a quantitative method of experimental design with the technique of T-test test analysis with paired sample T-test that is processed with SPSS version 20.0 for Windows. The independent variables in this study were stress management training and work stress dependent variables. The population of this study are members of the Padang City BASARNAS. Using purposive sampling while the data collection techniques in this study use psychological measuring instruments in the form of scales, the scale of work stress totaling 24 items. The results showed that before being given stress management training 4 members of the Padang City BASARNAS had a high stress level category, and 4 people in the moderate category. After being given stress management training the stress level of BASARNAS members in Padang decreased by 5 people in the medium category, and 3 people in the low category. Effective stress management training reduces work stress on members of the Padang City BASARNAS as evidenced by the significant index results of 0,000 (<0.050). Similar training in areas of work with the potential for high levels of work stress is recommended to be carried out so that employee performance can be optimized due to efforts to manage employee stress. Keywords: Training, Stress Management, Job Stress, BASARNAS

Earthquake size & descriptive earthquake statistics

2021 ◽  
pp. 197-222
Author(s):  
Charles J. Ammon ◽  
Aaron A. Velasco ◽  
Thorne Lay ◽  
Terry C. Wallace
Keyword(s):  
Earthquake Statistics ◽  
Earthquake Size
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