Inference for cumulative risk model under step-stress experiments and its application in nanocrystalline data

With the popularity of step-stress accelerated life testing, researchers are exploring more possibilities for models that relate the life distributions under different stress levels. Cumulative risk model assumes that the effects of stress changes have a lag period before they are fully observed, which guarantees the continuity of the hazard rate function. This paper studies the cumulative risk model for Lomax distribution with step-stress experiments. For maximum likelihood estimation, Newton-Rapson method is adopted to get point estimates. Meanwhile, the asymptotic normality of the maximum likelihood estimator is used to obtain asymptotic confidence intervals. For Bayesian estimation, point estimates and highest posterior density credible intervals under squared error loss function with informative prior and non-informative prior are derived using Metropolis-Hastings method and Metropolis-Hastings within Gibbs algorithm. To evaluate the effects of stress change time and the length of lag period, as well as the performance of different methods, numerical simulations are conducted. Then a real nanocrystalline data set is analyzed.

The Effect of Wind Stress on Seasonal Sea-Level Change on the Northwestern European Shelf

Projections of relative sea-level change (RSLC) are commonly reported at an annual mean basis. The seasonality of RSLC is often not considered, even though it may modulate the impacts of annual mean RSLC. Here, we study seasonal differences in 21st-century ocean dynamic sea-level change (DSLC, 2081-2100 minus 1995-2014) on the Northwestern European Shelf (NWES) and their drivers, using an ensemble of 33 CMIP6 models complemented with experiments performed with a regional ocean model. For the high-end emissions scenario SSP5-8.5, we find substantial seasonal differences in ensemble mean DSLC, especially in the southeastern North Sea. For example, at Esbjerg (Denmark), winter mean DSLC is on average 8.4 cm higher than summer mean DSLC. Along all coasts on the NWES, DSLC is higher in winter and spring than in summer and autumn. For the low-end emissions scenario SSP1-2.6, these seasonal differences are smaller. Our experiments indicate that the changes in winter and summer sea-level anomalies are mainly driven by regional changes in wind-stress anomalies, which are generally southwesterly and east-northeasterly over the NWES, respectively. In spring and autumn, regional wind-stress changes play a smaller role. We also show that CMIP6 models not resolving currents through the English Channel cannot accurately simulate the effect of seasonal wind-stress changes on he NWES. Our results imply that using projections of annual mean RSLC may underestimate the projected changes in extreme coastal sea levels in spring and winter. Additionally, changes in the seasonal sea-level cycle may affect groundwater dynamics and the inundation characteristics of intertidal ecosystems.

Effect of Music on Stress Parameters in Dogs during a Mock Veterinary Visit

Veterinary visits can be stressful for dogs, but how their wellbeing changes during a visit is not well understood. Music therapy has been successfully used in clinical practice to alleviate stress and anxiety in people. The present study aimed to understand how canine stress changes during a veterinary visit, establish the effect of music, and highlight measures which may be of practical use. In a randomized crossover design, dogs were exposed to no music and a bespoke piece of classical music at a tempo designed to match their resting heart rate during a mock veterinary visit. Dogs were scored as more “afraid” during the physical examination compared to when they were in the hospital kennel (p < 0.001). Salivary cortisol, IgA, and infrared temperature all increased significantly (p < 0.05) from baseline to post-kennel and post-examination, with no effect of music treatment. Core body temperature (p = 0.010) and the odds of ‘relaxed’ lips (p = 0.020) were lower when dogs were exposed to music compared to control visits. Overall, dogs experienced changes in physiology and behavior, indicative of increased stress, over the course of the visit. Additional research is required to further understand the effect that bespoke music may have in alleviating canine stress during veterinary visits.

Tectonic Context and Possible Triggering of the 2019–2020 Puerto Rico Earthquake Sequence

An historically unprecedented seismic moment was released by crustal events of the 2019–2020 earthquake sequence near southwest Puerto Rico. The sequence involved at least two, and perhaps three interacting fault systems. The largest Mw 6.4 event was likely triggered by left lateral strike-slip events along the eastern extension of the North Boquerón Bay-Punta Montalva fault zone. The mainshock occurred in a normal fault zone that extends into a region where previous studies documented extensional deformation, beyond the Ponce fault and the Bajo Tasmanian fault. Coulomb stress changes by the mainshock may have triggered further normal-faulting aftershocks, left lateral strike-slip events in the region where these two fault zones interacted, and possibly right lateral strike-slip aftershocks along a third structure extending southward, the Guayanilla fault zone. Extension directions of the seismic sequence are consistently north-northwest–south-southeast-oriented, in agreement with the Global Navigation Satellite Systems-inferred motion direction of eastern Hispaniola relative to western Puerto Rico, and with crustal stress estimates for the overriding plate boundary zone.

The Source Characteristics of the Mw6.4, 2016 Meinong Taiwan Earthquake from Teleseismic Data Using the Hybrid Homomorphic Deconvolution Method

The kinematic source rupture process of the 2016 Meinong earthquake (Mw = 6.4) in Taiwan was derived from apparent source time functions retrieved from teleseismic S-waves by using a refined homomorphic deconvolution method. The total duration of the rupture process was approximately 15 s, and one slip-concentrated area can be represented as the source model based on images representing static slip distribution. The rupture process began in a down-dip direction from the fault toward Tainan City, strongly suggesting that the rupture had a unilateral northwestern direction. The asperity with an area of approximately 15 × 15 km2 and the maximum slip of approximately 2 m were centered 12.8 km northwest of the hypocenter. Coseismic vertical deformation was calculated based on the source model. Compared with the results derived from InSAR (Interferometric Synthetic Aperture Radar) data, our results demonstrated that the location with maximum uplift was accurately well detected, but our maximum value was just approximately 0.4 times of the InSAR-derived value. It reveals that there are the other mechanisms to affect the vertical deformation, rather than only depending on the source model. At different depths, areas west, east, and north of the hypocenter maintained high values of Coulomb stress changes. This explains the mechanism behind aftershocks being triggered and provides a reference for predicting aftershock locations after a large earthquake. The estimated seismic spectral intensities, including spectral acceleration and velocity intensity (SIa and SIv), were derived. Source directivity effects caused damage to buildings, and we concluded that all damaged buildings were located within a SIa value of 400 gal. Destroyed buildings taller than seven floors were located in an area with a SIv value of 30 cm/s. These observations agree with those on damages caused by the 2010 Jiasian earthquake (ML 6.4) in Tainan, Taiwan.

A Hydrofracturing-Triggered Earthquake Occurred Three Years after the Stimulation

Hydrofracturing, used for shale gas exploitation, may induce felt, even damaging earthquakes. On 15 June 2019, an Mw2.8 earthquake occurred, spatially correlated with the location of earlier exploratory hydrofracturing operations for shale gas in Wysin in Poland. However, this earthquake was atypical. Hydrofracturing-triggered seismicity mainly occurs during stimulation; occasionally, it continues a few months after completion of the stimulation. In Wysin, there were only two weaker events during two-month hydrofracturing and then 35 months of seismic silence until the mentioned earthquake occurred. The Wysin site is in Gdańsk Pomerania broader region, located on the very weakly seismically active Precambrian Platform. The historical documents, covering 1000 years, report no natural earthquakes in Gdańsk Pomerania. We conclude, therefore, that despite the never observed before that long lag time after stimulation, the Mw2.8 earthquake was triggered by hydrofracturing. It is possible that its unusually late occurrence in relation to the time of its triggering technological activity was caused by changes in stresses due to time-dependent deformation of reservoir shales. The Wysin earthquake determines a new time horizon for the effect of HF on the stress state, which can lead to triggering earthquakes. Time-dependent deformation and its induced stress changes should be considered in shall gas reservoir exploitation plans.

Stress Accumulation and Earthquake Activity on the Great Sumatran Fault, Indonesia

The seismically active Sumatra subduction zone has generated some of the largest earthquakes in the instrumental record, and both historical accounts and paleogeodetic coral studies indicate such activity has historical recorded megathrust earthquakes and transferred stress to the surrounding, including the Great Sumatran Fault (GSF). Therefore, evaluating the stress transfer from these large subduction earthquakes could delineate the highly stressed area as potential-earthquake region along the GSF. In this study, we investigated eight megathrust earthquakes from 1797 to 2010 and resolved the accumulated Coulomb stress changes onto the 18 segments along the GSF. Additionally, we also estimated the rate of tectonic stress on the GSF segments which experienced large earthquake using the case of: (1) no sliver movement and (2) with sliver movement. Based on the historical stress changes of large earthquakes and the increase in tectonic stress rate, we analysed the historical stress changes time evolution on the GSF. The Coulomb stress accumulation of megathrust earthquakes between 1797-1907 increase the stress changes mainly on the southern part of GSF which followed by four major events between 1890-1943. The estimation of tectonic stress rates using case (1) produces low rate and long recurrence intervals which implies that the megathrust earthquakes plays an important role in allowing the GSF earthquake to occur. When implementing the arc-parallel sliver movement of case (2) to the calculation, the tectonic stress rates is 9 to 58 times higher than case (1) of no sliver movement. The observed slip rate of 15-16 mm/yr at the GSF is consistent with the recurrence interval for full-segment rupture of 100-200 years obtained from case (2). This suggests that the GSF earthquake is more controlled by the rapid arc-parallel forearc sliver motion. Furthermore, the analysis of stress changes time evolution model shows that some segments such as Tripa (North and South), Angkola, Musi and Manna appear to be brought back in their seismic cycles since these segments have experienced full-segment rupture and likely locked, increasing their earthquake hazard potentials.