Occurrence Of Slip Research Articles

Atomistic Understanding of the Competition between Dislocation and Twinning in Silver under Nanoindentation

In this study, the competition mechanisms between dislocation slip and twinning in silver with a low stacking fault energy using molecular dynamics (MD) simulation from an atomistic point of view are reported. Herein, three crystallographic surface orientations of , , and are considered and compared. The indentation stress–strain curves are successfully obtained from the load–displacement curves of nanoindentation. The stress of , , and orientations drops at the strains of 0.140, 0.133, and 0.136, which corresponds to the yield stress of 3.83, 4.33, and 4.99 GPa, respectively. Dislocation slip and twinning simultaneously form in silver as indicated by the total potential energy of the system. Furthermore, the typical four‐, two‐, and sixfold symmetries of the out‐of‐plane displacement as in copper are not observed for , , and orientations in silver. Hence, this observation can be supported by the simultaneous occurrence of dislocation slip and twinning in silver.

Extreme rotational events in a forced-damped nonlinear pendulum.

Since Galileo's time, the pendulum has evolved into one of the most exciting physical objects in mathematical modeling due to its vast range of applications for studying various oscillatory dynamics, including bifurcations and chaos, under various interests. This well-deserved focus aids in comprehending various oscillatory physical phenomena that can be reduced to the equations of the pendulum. The present article focuses on the rotational dynamics of the two-dimensional forced-damped pendulum under the influence of the ac and dc torque. Interestingly, we are able to detect a range of the pendulum's length for which the angular velocity exhibits a few intermittent extreme rotational events that deviate significantly from a certain well-defined threshold. The statistics of the return intervals between these extreme rotational events are supported by our data to be spread exponentially at a specific pendulum's length beyond which the external dc and ac torque are no longer sufficient for a full rotation around the pivot. The numerical results show a sudden increase in the size of the chaotic attractor due to interior crisis, which is the source of instability that is responsible for triggering large amplitude events in our system. We also notice the occurrence of phase slips with the appearance of extreme rotational events when the phase difference between the instantaneous phase of the system and the externally applied ac torque is observed.

Characterization of Prismatic Slip in SiC Crystals by Chemical Etching Method

In 4H-silicon carbide crystals, basal plane slip is the predominant deformation mechanism. However, prismatic slip is often observed in single crystals grown by the physical vapor transport method as the diameter expands to 6 inches or larger. Thermal modeling has shown that occurrence of prismatic slip is attributed to increased radial thermal gradients. While X-ray topography can be used to characterize the presence and extent of prismatic slip, the feasibility of using the chemical etching method to assess the extent of prismatic slip in an industrial setting is investigated. The distribution of scallop shaped etch pits oriented along the directions that correspond to prismatic dislocations, correlate well with the results of the thermal model that predicts the occurrence of prismatic slip dislocations. This capability of the etch pit method to characterize prismatic slip can be used to manage radial thermal gradients during PVT growth.

Atomistic simulation for initiation of crystal slip deformation from surface of nanoscale copper single-crystal nanowires

In nano/micrometer-scale materials, dislocations accounting for crystal slip deformation are introduced from the surface because of lack of pre-existing dislocations inside the materials. The dislocation emission from the surface must play an important role in the formation of dislocation network structures in the nano/micrometer-scale materials under cyclic loading, which should differ from that in macroscale materials. The purpose of this study is to investigate the effect of the atomic-level structure of surfaces on the initiation of crystal slip deformation. We create copper single-crystal nanowire models with different surface structures by varying the cross-section shape and crystal orientation. To observe the initiation of the slip deformation from the surface, we conduct atomistic simulations of tensile deformation for these models. We also discuss the effect of the surface structure on the critical shear stress for slip occurrence from the surface. Our analyses reveal that the orientation of surface steps and the normal stress on the active slip plane are important factors affecting the slip occurrence. Thus, the slip occurs in a slip system so as to reduce the height of a surface step. The active slip system is affected by the cross-section shape and crystal orientation because the slip system is dependent on the relationship between slip planes and the orientation of the surface step. Our results also suggest that the cross-section shape and crystal orientation affect the critical shear stress because of the difference of the normal stress on the active slip plane according to these factors.

Balancing-Prioritized Anti-Slip Control of a Two-Wheeled Inverted Pendulum Robot Vehicle on Low-Frictional Surfaces with an Acceleration Slip Indicator

When a two-wheeled inverted pendulum (TWIP) robot vehicle travels on slippery roads, the occurrence of wheel slip extremely threatens its postural stability owing to the loss of wheel traction. If a severe wheel slip happens between the driving wheels and contact surfaces, no control techniques can guarantee the driving performance and stability of the TWIP robots in the absence of an extra wheel slip control strategy. In this paper, a TWIP-compatible countermeasure against the wheel slip phenomena is investigated for enhancing the reliability of the vehicle and the robustness of the motion control performance on low-frictional surfaces. To this end, we propose a balancing-prioritized anti-slip control method based on the maximum transmissible torque estimation, which is activated only when a wheel slip is detected by the acceleration slip indicator utilizing accessible data from the IMU and wheel encoders. It is proved that the TWIP vehicles applying the proposed method can successfully cope with low frictional surfaces while maintaining postural stability. Finally, comparative simulations and experiments demonstrate the effectiveness and feasibility of the proposed scheme.

Effect of Extrusion Ratio in Hot-Extrusion on Kink Deformation during Compressive Deformation in an αMg/LPSO Dual-Phase Magnesium Alloy Monitored by <i>In Situ</i> Neutron Diffraction

To elucidate the effect of extrusion ratio in hot-extrusion on the deformation behavior during compression of Mg97Zn1Y2 alloy containing about 25-vol% long-period stacking ordered phase (LPSO) in the HCP structured α matrix (αMg), in situ neutron diffraction measurements were performed under compressive loading using four types of samples: as-cast and after hot extrusion at 623 K with extrusion ratios of 5.0, 7.5 and 12.5. The macroscopic yielding was observed to appear by the occurrence of basal slip of αMg in the as-cast sample and at the onset of twinning in the hot extruded samples. The applied stress to initiate slip, twinning, and kinking increased by hot extrusion and then decreased with increasing extrusion ratio. LPSO shared higher stress than αMg and the ratio to the strength increased as the extrusion ratio increased. In the extruded samples, the phase stress levels in LPSO when kinking initiated were almost the same for the hot-extruded samples, around 580 MPa, regardless of the extrusion ratio.

Prospective cohort study of the relationship between milking machine liner slip, milking performance, and cow characteristics

We conducted a prospective cohort study to investigate the associations of machine milking liner slip with (1) milking performance and (2) cow characteristics. Parlor data including milk flow characteristics and data on the occurrence of milking machine liner slips from a 4,000-cow dairy with a thrice-daily milking schedule were obtained with electronic on-farm milk meters over a 2-mo period. We analyzed data from a total of 686,330 milking observations. A multivariable general linear mixed model revealed no association between liner slip and milking unit on time. Least squares means (95% confidence intervals, 95% CI) were 237 (235-238) s for milking observations with and without a liner slip. We observed statistically significant differences in average milk flow rate; however, these were biologically irrelevant. Least squares means were 3.40 (3.37-3.42) kg/min for a milking observation with and 3.42 (3.40-3.44) kg/min without a liner slip. A multivariable generalized linear mixed model showed an association between liner slip and cow characteristics. Compared with late-lactation cows, the odds ratios (OR, 95% CI) of occurrence of a liner slip were 2.03 (1.59-2.59) in early lactation cows and 1.26 (0.97-1.64) in cows from 101 to 200 days in milk. Presence of a nonlactating quarter increased the odds of liner slip occurrence [OR, 95% CI: 10.35 (8.02-13.35)]. Bimodal milking observations had higher odds of occurrence of a liner slip compared with milking observations with a unimodal milk flow curve [OR, 95% CI: 1.05 (1.005-1.09)]. A 1-kg increase in 2-min milk yield increased the odds of a liner slip [OR, 95% CI: 1.26 (1.25-1.28)]. We conclude that, in the study cohort presented herein, the negative effect of liner slips on milking performance can be diminished. The identified cow characteristics could offer unique opportunities to identify and manage cows at increased risk of liner slips.

Experimental investigation of the shear bond strength between HGM cement and shallow formation in deepwater environments

Due to its low density and high strength, hollow glass micro-sphere (HGM) has become a popular additive to cement slurry in deepwater cementing. The shear bond strength (SBS) between the well cement and formation ensures the safety and integrity of oil and gas wells. We designed a simulation experiment to measure the SBS between HGM cement and shallow formations in deepwater environments. We studied the evolution of the tensile force when pulling a simulated pipe string and cement ring out of the soil layer with a constant force. The results suggest that the HGM content and size of the cement ring have no effect on the change in the tensile force over time. At the peak of the tension curve, the cement ring and soil begin to slip, causing the tensile force to decrease with time. We divided this curve into two sections, with the peak value as the dividing point. The first section is the accumulating section where the tension increases without displacement of the cement ring and the soil. The second section is the dynamic slip section. Additionally, we proposed the concepts of static SBS and dynamic shear bond coefficient. The static SBS is the strength at the pull-off position, and the dynamic shear bond coefficient is the cementation coefficient of the cement ring in the dynamic slip stage. We divided the cement ring into segments along its length, calculated the shear bond coefficient of the cement ring at different depths, and studied the variation in the dynamic shear bond coefficient with depth. The static SBS increases with decreasing HGM content and casing size, and the static SBS of the small casing is significantly greater than those of the middle casing and the large casing. The dynamic shear bond coefficient decreases after the occurrence of dynamic slip. This study provides important insights into the evolution of the cement-formation SBS, and the results can provide guidance for future cementing design.

Mechanical responses of Al20.4Mo10.5Nb22.4Ta10.1Ti17.8Zr18.8 nanopillar under uniaxial compression

The mechanical responses of crystallographic orientations [001], [110], and [111] of Al 20.4 Mo 10.5 Nb 22.4 Ta 10.1 Ti 17.8 Zr 18.8 refractory high entropy alloy (RHEA) nanopillars under the uniaxial compression are investigated by the MD simulation using 2NN MEAM potential. The [001]-orientated nanopillar shows the widest elastic deformation regime with the yielding strain about 0.075, compared to the other two nanopillars with the yielding strains about 0.03~0.04. The strength of [111]-oriented nanopillar is the highest, which is about 36.3% and 117% higher than those of [001]- and [110]-oriented nanopillars, respectively. After the strain exceeds the ultimate one, the stress gradually declines with the increasing strain, and then displays small flow stress oscillation during plastic deformation, indicating the stresses saturate at the quasi-steady flow stress. For the [001]-orientated nanopillar, the extent of BCC-HCP phase transition is the most significant at strains below the flow stress regime. From strain 0 to the beginning of the flow stress regime, the local structural transition is the main deformation mechanism, and the dislocation slip becomes the dominant deformation mechanism within the flow stress regime. For the [110]-orientated nanopillar, the dislocation nucleates at the strain between the yielding and ultimate strains, and then the dislocation density increases sharply with the increasing strain until the occurrence of the dislocation slip. The dislocation slip and deformation twinning are two main deformation mechanisms for the [110]-orientated nanopillar. For the [111]-orientated nano-pillar, the dislocation nucleates at the strain larger than the ultimate strain when the stress undergoes an abrupt drop. After the dislocation nucleation, the dislocation density shows a distinct increase during the stress drop, leading to the appearance of dislocation lines. In the flow stress regime, the dislocation density gradually decreases from the maximum value about 600.17 10 19 m -2 to zero with the increasing strain. Local shear strain of [110]-oriented Al20.4Mo10.5Nb22.4Ta10.1Ti17.8Zr18.8 nanopillar during the compression • The mechanical responses of crystallographic orientations [001], [110], and [111] of Al 20.4 Mo 10.5 Nb 22.4 Ta 10.1 Ti 17.8 Zr 18.8 refractory high entropy alloy nanopillars under the uniaxial compression • 2NN MEAM potential parametrization process for the Al-Mo-Nb-Ta-Ti-Zr system using DFT calculation data. • Polyhedral template matching (PTM) method for monitoring the local structural transformation. • Atomic local shear strain for observing dislocation slip band growth • dislocation extraction algorithm (DXA) results for dislocation nucleation and evolution

Margin-wide variations in slab dehydration in Cascadia and their relationship to slow slip

Slow slip events are observed in subduction zones globally, with a wide range of variations in behaviour, including the periodicity and magnitude of events. These variations are observed both within and across different subduction zones. Due to their role in controlling strain accumulation and potential nucleation of regular earthquakes, understanding the physical environment of slow slip events and the source of their observed variability is critical to understanding seismogenic processes. Here we calculate thermal models for 10 trench-normal profiles along the entirety of the Cascadia subduction zone. The models incorporate lateral changes in incoming plate age and sediment input, as well as slab geometry and overriding plate structure. Temperatures at the location of peak slow slip and tremor occurrence (depths of 30–40 km) vary from 525 °C in southern Cascadia, to 475 °C in central Cascadia, to 550 °C in northern Cascadia. The variability in thermal structure and slab geometry leads to changes in the rate of calculated fluid flux in the vicinity of the mantle wedge corner where slow slip events are observed. Fluid flux rates calculated within 25 km and 50 km downdip of the mantle wedge corner show an inverse relationship with the recurrence time of slow slip with highest value observed in southern Cascadia, followed by northern Cascadia, and then central Cascadia. Other along-strike variability in tremor behaviour, such as tremor strength, correlates spatially with changes in calculated fluid flux pattern but the relationship between these parameters is not readily defined. This study provides support for models where variations in the rate of fluid production in the vicinity of the mantle wedge corner are a potential mechanism controlling the rate of pore fluid pressure buildup and fluid release during slow slip. • Changes in subduction parameters affect fluid release along Cascadia. • Major sites of slab dewatering are observed beneath the mantle wedge corner. • Fluid flux rates show an inverse relationship with the recurrence time of slow slip. • Variability in tremor strength and density correlate spatially with flux pattern.

Experimental and numerical investigation of a novel vertically unconstrained steel inter-modular connection

Modular constructions are off-site prefabricated structures with transportable units assembled on-site. These units are linked together using mechanical connectors called “inter-modular connections”. Modular building structures are attractive from a constructional efficiency point of view if they include specific characteristics such as ease of on-site assembly and speed of construction. Accordingly, a vertically unconstrained inter-modular connection can considerably decrease the construction effort and promote the feasibility of the modular system if tension forces do not develop in columns when the structure is submitted to lateral loads. This study presents an efficient vertically unconstrained inter-modular connection, including a bolted tie plate and male–female components to ensure the connectivity of the diaphragms and columns. Two series of experimental tests are performed to examine the proposed inter-modular connection’s shear and axial force responses. The calibrated finite element models developed in ABAQUS software are used to study the in-plane shear behavior of a perforated plate acting as horizontal component of the inter-modular connection. The results show that the proposed connection has adequate ductile ultimate strength controlled by the yielding of the net section of the tie plate. However, removing the up-lift constraining mechanisms may lead to serviceability issues due to a potential slip occurrence between modular components constructed with tolerances. The experimental and numerical results/frameworks presented herein provide detailed behavioral information, including slip, yielding, and failure modes of the connection’s components. The captured behavior can be used to develop a simplified model of the proposed connection that can be used in detailed structural analyses.

Dynamics of nonlinear-shaped solid particles occurrence of hydro-magnetic slip with comparative analysis of radiated ternary, hybrid and nanofluid flow in a rotating internally heating cylinder

Nowadays, the heat thrust liquid electric heater is generally used in profitable applications since it protects upto 2–3 times the energy of ordinary liquid electric heater. The heat pump makes use of a refrigerant for its process. The small-temperature refrigerant engrosses permitted heat from full of atmosphere midair in the evaporator which is crushed by an extremely well-organized electrical compressor to an extraordinary-temperature and high-pressure vapor refrigerant. For entire heat transfer connoisseurs, heat transfer performance in cooling and heating applications has become a top priority. Hence, research towards new heat transfer fluids is extremely intense and challenging. This investigation examines flow and heat transfer analysis in axisymmetric magnetohydrodynamic flow polyethylene glycol (PEG)-based nanofluid, hybrid nanofluid and ternary hybrid nanofluid flow induced by a swirling cylinder. Flow and heat transfer are analyzed and compared for three cases PEG-based copper oxide, magnesium oxide and zirconium oxide ternary nanofluid (PEG[Formula: see text][Formula: see text][Formula: see text]ZrO2[Formula: see text][Formula: see text][Formula: see text]CuO[Formula: see text][Formula: see text][Formula: see text]MgO), PEG-based copper oxide (PEG[Formula: see text][Formula: see text][Formula: see text]CuO) nanoparticles and PEG-based zirconium and magnesium oxide hybrid nanofluid (PEG[Formula: see text][Formula: see text][Formula: see text]ZrO2[Formula: see text][Formula: see text][Formula: see text]MgO). Shooting technique (R–K fourth-order) is employed to work out the flow equations numerically. Simulated results are displayed through graphs. The computational results are validated with the published research work and a modest concurrence is found. The main outcome of this study is found to be as follows: It is interesting to note that [Formula: see text] is lesser in nanofluid case compared with ternary and hybrid nanofluid cases. It is found that [Formula: see text] is more in ternary hybrid nanofluid compared with hybrid and nanofluid cases. Overall, it is observed that heat transfer rate is higher in nanofluid compared with ternary and hybrid nanofluid cases whereas lesser rate of heat transfers in ternary nanofluid case.

Flow and slip process of Santotrac 50‐based lubricant under high shear by molecular dynamic simulation

AbstractWe investigate flow and slip behaviour of Santotrac 50 molecules under high shear in Couette cell by means of Molecular Dynamic simulation to understand reduced friction force. Molecular chain stretches and oriented to shear direction, and move. Slip starts on metal surface at 2 × 108 s−1, and increases with shear rate. Slip length keeps scale at nanometre. Molecular conformation and occurrence of slip both indicate a reduced shear stress. Furthermore, when changing wettability, slip length increases in power law and thus decreases shear stress greatly. Occurrence of low‐density region near surface can explain slip. And thus, we extended apparent slip model, which divided lubricant into liquid layers with different viscosities, to elucidate the relationship between molecule distribution inner layer and slip on surface influenced by shear velocity and wettability. Above all, our research sheds light on flow and slip behaviour of complex fluid and can be applied in improving lubrication property.

Along-strike distribution of seismicity and large slow slip correlated with gravity at the Nankai Trough

Various earthquakes and slow slip phenomena occur in different locations in the down-dip direction at subduction zones, for example, at the Nankai Trough, Japan. Many earthquakes, tectonic tremors, and slow slip events have occurred on the deeper side of the source areas of the past megathrust earthquakes. We show that three regions with high background seismicity correspond to the source areas of the large (> equivalent moment magnitude 6.5) slow slip events. These regions do not correspond to active areas of tectonic tremors. We note that considering broad-scale variations along the strike of the subduction zone, the three regions also correspond to areas with low free-air gravity anomalies. This fact implies that widespread stress perturbations in the along-strike direction, possibly coupled with pore fluid effects, may control the occurrence of seismic and aseismic slip on subduction faults regardless of whether at the plate interface or within the plate.

An investigation of the deformation and cracking mechanism of Mg–1Al–12Y alloys based on in-situ SEM/EBSD slip trace analysis

In this work, the deformation mechanism and cracking behavior of Mg–1Al–12Y alloys with different contents of long-period stacking ordered (LPSO) phase during in-situ tensile testing at ambient temperature were investigated in detail using a scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). The slip trace analysis results showed that the deformation of the three alloys was all dominated by dislocation slip and supplemented by extension twinning. The predominant slip deformation mode was basal <a> slip. The Mg–1Al–12Y alloy after solution treatment at 540 °C for 4 h (T4-4h) exhibited higher elongation due to greater non-basal slip activation (31.8%) and cross slip occurrence (10.4%) and lower twinning activity. This was primarily attributed to the fact that profuse lamellar LPSO phases in the matrix of T4-4h alloy promoted the activation of non-basal slip and inhibited the initiation of extension twins. In addition, crack nucleation of the three alloys was mainly concentrated at the grain boundaries and triple junction of the grain boundaries. Nucleation and crack propagation were mostly attributed to the surrounding grains with a hard orientation and the second phase at the grain boundaries, which was not conducive to coordinated deformation.

Detection of Slow Slip Events Using Wavelet Analysis of GNSS Recordings

ABSTRACT At many places, tectonic tremor is observed in relation to slow slip and can be used as a proxy to study slow slip events of moderate magnitude in which surface deformation is hidden in Global Navigation Satellite System (GNSS) noise. However, in subduction zones in which no clear relationship between tremor and slow slip occurrence is observed, these methods cannot be applied, and we need other methods to be able to better detect and quantify slow slip. Wavelets methods such as the Discrete Wavelet Transform and the Maximal Overlap Discrete Wavelet Transform (MODWT) are mathematical tools for analyzing time series simultaneously in the time and the frequency domains by observing how weighted differences of a time series vary from one period to the next. In this article, we use wavelet methods to analyze GNSS time series and seismic recordings of slow slip events in Cascadia. We use detrended GNSS data, apply the MODWT transform, and stack the wavelet details over several nearby GNSS stations. As an independent check on the timing of slow slip events, we also compute the cumulative number of tremor in the vicinity of the GNSS stations, detrend this signal, and apply the MODWT transform. In both the time series, we can then see simultaneous waveforms where timing corresponds to the timing of slow slip events. We assume that there is a slow slip event whenever there is a positive peak followed by a negative peak in the wavelet signal. We verify that there is a good agreement between slow slip events detected with only GNSS data and slow slip events detected with only tremor data for northern Cascadia. The wavelet-based detection method effectively detects events of magnitude higher than 6, as determined by independent event catalogs (e.g., Michel et al., 2019). As a demonstration of using the wavelet analysis in a region without significant tremor, we also analyze GNSS data from New Zealand and detect slow slip events that are spatially and temporally close to those detected previously by other studies.

Full-scale experimental investigation on the seismic performance of PC columns before and after repair of grouting defects

This research focused on investigating the influence of insufficient grouting on the seismic performance of precast concrete (PC) columns, connected using grouted sleeves, and validating the feasibility and reliability of the repair method for insufficient grouting. To realize these, five full-scale PC columns were tested under cyclic loads, including one specimen without grouting defects, two specimens with defect ratios of 45% and 60%, respectively, which were determined by previous cyclic test results of grouted sleeve connections (GSCs), and two repaired specimens which had initial defect ratios of 45% and 60%, respectively. The effects of defect ratios and repair actions were analyzed, and the test results indicated the following: 1) The bar slip dominated the failure of two specimens with defect ratios as expected, rather than the flexural failure mode for the specimen without defects. A rocking phenomenon was observed since the occurrence of bar slip, and the pinching phenomenon appeared for the corresponding hysteretic curves. The load-bearing, deformation and energy dissipation capacities were significantly lower than those of the specimens without defects. The increase in the defect ratio decreased the drift ratio associated with the bar-slip phenomenon, but the influence of the defect ratio on the seismic performance after the bar slip was negligible. 2) The bar-slip behavior was effectively prevented after the repair of insufficient grouting. Hence, the repaired specimens exhibited the expected flexural failure mode, and the load-bearing, deformation, and energy dissipation capacities were generally comparable with those of the specimen without defects. Rocking behavior and pinching phenomenon were not observed after repair. The negative influences of insufficient grouting were almost eliminated, thus validating the reliability of the repair method. The research outcome can serve as a reference for quality control of PC structures using GSCs.

Novel innervation of accessory slip of lateral head of gastrocnemius muscle

The two heads of the gastrocnemius muscle, as well as the plantaris and soleus muscles, forms the superficial muscular group in the posterior compartment of the leg. The incidental occurrence of accessory slip of the lateral head of the gastrocnemius muscle in the right lower limb, innervated by a twig from the common peroneal nerve, is described in this report. We identified an anomalous 8 cm long muscle in the right popliteal fossa during standard academic dissection of a male corpse at the Department of Anatomy. It was attached to the lateral side of the femur's popliteal surface proximally and joined the lateral head of the gastrocnemius distally. In the left lower limb, no similar variation was observed.

Bridging Spatiotemporal Scales of Normal Fault Growth During Continental Extension Using High‐Resolution 3D Numerical Models

AbstractContinental extension is accommodated by the development of kilometer‐scale normal faults, which grow during meter‐scale slip events that occur over millions of years. However, reconstructing the entire lifespan of a fault remains challenging due to a lack of observational data with spatiotemporal scales that span the early stage (&lt;106 yrs) of fault growth. Using three‐dimensional numerical simulations of continental extension and novel methods for extracting the locations of faults, we quantitatively examine the key factors controlling the growth of rift‐scale fault networks over 104–106 yrs. Early formed faults (&lt;100 kyrs from initiation) exhibit scaling ratios consistent with those characterizing individual earthquake ruptures, before evolving to be geometrically and kinematically similar to more mature structures developed in natural fault networks. Whereas finite fault lengths are rapidly established (&lt;100 kyrs), active deformation is transient, migrating both along‐ and across‐strike. Competing stress interactions determine the distribution of active strain, which oscillates between being distributed and localized. Higher rates of extension (10 mm yr−1) lead to more prominent stress redistributions through time, promoting episodic localized slip events. Our findings demonstrate that normal fault growth and the related occurrence of cumulative slip is more complex than that currently inferred from displacement patterns on now‐inactive structures, which only provide a space‐ and time‐averaged picture of fault kinematics and related seismic hazard.

Aftershock Regions of Aleutian‐Alaska Megathrust Earthquakes, 1938–2021

AbstractWith five earthquakes (1938, 1946, 1957, 1964, and 1965), the Aleutian‐Alaska subduction plate boundary ruptured a length of 3,548 km. We revisit these five earthquakes—first studied in detail by Sykes (1971, https://doi.org/10.1029/JB076i032p08021)—through probabilistic relocation of carefully selected mainshocks and aftershocks. Our final catalog of 324 events is established from a set of 12 mainshocks that includes all Mw ≥ 7.7 megathrust earthquakes. Using the relocated catalog, we create revised aftershock regions delimited both parallel and normal to the trench. These aftershock regions exhibit significant differences from previous studies, with the following basic findings: the 10 November 1938 Mw 8.3 earthquake extended further west, to the Shumagin Islands, and further east, into the Kodiak region, relative to the prevailing aftershock region established by McCann et al. (1979, https://doi.org/10.1007/978-3-0348-6430-5_2). The 01 April 1946 Mw 8.6 sequence was anomalously concentrated near the trench, which implies near‐trench coseismic slip that contributed to the exceptionally large tsunami. The 09 March 1957 Mw 8.6 aftershocks spanned a 1,230 km length with numerous aftershocks within the outer‐rise region of the incoming Pacific plate. The 28 March 1964 Mw 9.2 aftershocks extended east into the Pamplona thrust system (south of Icy Bay, Alaska), suggesting coseismic rupture into this region; this is consistent with coseismic static displacements, as well as current estimates of interseismic locking. The post‐1965 events we examine are all smaller than the earlier events, but since they occurred in an era of improved data collection (seismic, geodetic, and tsunami), they provide a better opportunity for assessing the link between the distribution of aftershocks and the occurrence of coseismic, postseismic, and interseismic slip.