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Showing papers on "Slip (materials science) published in 2003"


Journal ArticleDOI
20 Jun 2003-Science
TL;DR: It is proposed that ETS activity can be used as a real-time indicator of stress loading of the Cascadia megathrust earthquake zone and is called episodic tremor and slip (ETS).
Abstract: We found that repeated slow slip events observed on the deeper interface of the northern Cascadia subduction zone, which were at first thought to be silent, have unique nonearthquake seismic signatures. Tremorlike seismic signals were found to correlate temporally and spatially with slip events identified from crustal motion data spanning the past 6 years. During the period between slips, tremor activity is minor or nonexistent. We call this associated tremor and slip phenomenon episodic tremor and slip (ETS) and propose that ETS activity can be used as a real-time indicator of stress loading of the Cascadia megathrust earthquake zone.

1,129 citations


Journal ArticleDOI
23 May 2003-Science
TL;DR: Transmission electron microscope observations that provide evidence of deformation twinning in plastically deformed nanocrystalline aluminum underscore a transition from deformation mechanisms controlled by normal slip to those controlled by partial dislocation activity when grain size decreases to tens of nanometers, and they have implications for interpreting the unusual mechanical behavior of nanocrystaline materials.
Abstract: We report transmission electron microscope observations that provide evidence of deformation twinning in plastically deformed nanocrystalline aluminum The presence of these twins is directly related to the nanocrystalline structure, because they are not observed in coarse-grained pure aluminum We propose a dislocation-based model to explain the preference for deformation twins and stacking faults in nanocrystalline materials These results underscore a transition from deformation mechanisms controlled by normal slip to those controlled by partial dislocation activity when grain size decreases to tens of nanometers, and they have implications for interpreting the unusual mechanical behavior of nanocrystalline materials

1,039 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigate two simple configurations of steady pressure-driven Stokes flow in a circular pipe whose surface contains periodically distributed regions of zero surface shear stress and the effective slip length of the resulting flow is evaluated as a function of the degrees of freedom describing the surface heterogeneities, namely the relative width of the no-slip and no-shear stress regions and their distribution along the pipe.
Abstract: Nano-bubbles have recently been observed experimentally on smooth hydrophobic surfaces; cracks on a surface can likewise be the site of bubbles when partially wetting fluids are used. Because these bubbles may provide a zero shear stress boundary condition and modify considerably the friction generated by the solid boundary, it is of interest to quantify their influence on pressure-driven flow, with particular attention given to small geometries. We investigate two simple configurations of steady pressure-driven Stokes flow in a circular pipe whose surface contains periodically distributed regions of zero surface shear stress. In the spirit of experimental studies probing slip at solid surfaces, the effective slip length of the resulting flow is evaluated as a function of the degrees of freedom describing the surface heterogeneities, namely the relative width of the no-slip and no-shear stress regions and their distribution along the pipe. Comparison of the model with experimental studies of pressure-driven flow in capillaries and microchannels reporting slip is made and a possible interpretation of the experimental results is offered which is consistent with a large number of distributed slip domains such as nano-size and micron-size nearly flat bubbles coating the solid surface. Further, the possibility is suggested of a shear-dependent effective slip length, and an explanation is proposed for the seemingly paradoxical behaviour of the measured slip length increasing with system size, which is consistent with experimental results to date.

696 citations


Journal ArticleDOI
TL;DR: In this paper, the authors explore the evidence for slip, the possible mechanisms of slip, and the relation between slip and extrusion instabilities, and show that extrusion melts exhibit extrusion instability at sufficiently high levels of stress.
Abstract: ▪ Abstract Polymer melts exhibit extrusion instabilities at sufficiently high levels of stress, and they appear to exhibit wall slip. I explore the evidence for slip, the possible mechanisms of slip, and the relation between slip and extrusion instabilities.

548 citations


Journal ArticleDOI
TL;DR: In this article, a crystal-mechanics-based constitutive model was developed for polycrystalline hcp materials and evaluated for the room-temperature deformation of the magnesium alloy AZ31B.

537 citations


Journal ArticleDOI
TL;DR: In this paper, the internal strains within a polycrystalline magnesium alloy plate have been measured during tensile and compression testing in situ by neutron diffraction using an elasto-plastic self-consistent simulation code.

522 citations


Journal ArticleDOI
TL;DR: In this paper, the slip effects of water flow in hydrophilic and hydrophobic microchannels of 1 and 2 μm depth were examined experimentally, and the slip length was found to vary approximately linearly with the shear rate.
Abstract: The slip effects of water flow in hydrophilic and hydrophobic microchannels of 1 and 2 μm depth are examined experimentally. High-precision microchannels were treated chemically to enhance their hydrophilic and hydrophobic properties. The flow rates of pure water at various applied pressure differences for each surface condition were measured using a high-precision flow metering system and compared to a theoretical model that allows for a slip velocity at the solid surface. The slip length was found to vary approximately linearly with the shear rate with values of approximately 30 nm for the flow of water over hydrophobic surfaces at a shear rate of 105 s−1. The existence of slip over the hydrophilic surface remains uncertain, due to the sensitivity of the current analysis to nanometer uncertainties in the channel height.

495 citations


Journal ArticleDOI
TL;DR: Fault permeability data from the Median Tectonic Line (MTL) in Mie Prefecture, Southwest Japan suggest that fault permeability models are currently too simplistic for such large structurally complex fault zones.

468 citations


Journal ArticleDOI
17 Jul 2003-Nature
TL;DR: It is suggested that talin1 initially forms a molecular slip bond between closely packed fibronectin–integrin complexes and the actin cytoskeleton, which can apply a low level of force to fibronECTin until many bonds form or a signal is received to activate a force response.
Abstract: Mechanical forces on matrix–integrin–cytoskeleton linkages are crucial for cell viability, morphology and organ function1. The production of force depends on the molecular connections from extracellular-matrix–integrin complexes to the cytoskeleton2,3. The minimal matrix complex causing integrin–cytoskeleton connections is a trimer of fibronectin's integrin-binding domain FNIII7-10 (ref. 4). Here we report a specific, molecular slip bond that was broken repeatedly by a force of 2 pN at the cellular loading rate of 60 nm s-1; this occurred with single trimer beads but not with monomer. Talin1, which binds to both integrins and actin filaments in vitro, is required for the 2-pN slip bond and rapid cytoskeleton binding. Further, inhibition of fibronectin binding to αvβ3 and deletion of β3 markedly decreases the 2-pN force peak. We suggest that talin1 initially forms a molecular slip bond between closely packed fibronectin–integrin complexes and the actin cytoskeleton, which can apply a low level of force to fibronectin until many bonds form or a signal is received to activate a force response.

460 citations


Journal ArticleDOI
TL;DR: In this article, the authors review geologic and other evidence constraining the thickness of the principal slip zone (PSZ) that accommodates the bulk of coseismic shear displacement during an individual rupture event.
Abstract: This article reviews geologic and other evidence constraining the thickness of the principal slip zone (PSZ) that accommodates the bulk of coseismic shear displacement during an individual rupture event. Surface deformation from rupturing may occupy swaths tens of meters or more in width, but trenches across active faults generally reveal that incremental slip is accommodated by a PSZ that is tens of centimeters or less in thickness. Geomorphic evidence, coupled with the observations from trenching, suggest a PSZ may stay well localized for distances of several kilometers through many rupture episodes. Mine exposures and exhumed fault zones demonstrate that PSZs separating different lithologies within the “fault core,” although contained within “damage zones” of variably fractured rock ranging up to hundreds of meters in thickness, often comprise just a few centimeters of gouge/ultracataclasite that have accommodated large finite displacements (>1 km). Microstructural studies demonstrate incremental slip localized still further down to 1–10 mm, as do other fault-rock assemblages (slickensides and slickenfibers, fault-veins of pseudotachylyte friction-melt, intravein septa in hydrothermal fault infills). The accumulated evidence indicates that localization of coseismic shearing to less than 10 cm on planar faults is widespread throughout the crustal seismogenic zone, with extreme localization to less than 1 cm not uncommon. However, some distributed coseismic shear may also develop, especially at rupture irregularities. Coseismic reduction of shear resistance from friction-melting (Δ T ∼ 1000°C) or from transient thermal pressurization of aqueous fluids (Δ T ∼ 100°C) requires slip during moderate-to-large earthquakes ( u > 1 m) to be restricted to narrow zones, respectively a few centimeters or tens of centimeters in thickness. Given the evidence for slip localization, the apparent scarcity of pseudotachylyte suggests either that seismic friction-melting is a rare phenomenon, or that pseudotachylyte is only rarely preserved in recognizable form within mature hydrated fault zones.

421 citations


Journal ArticleDOI
TL;DR: In this article, experimental observation of a deformation mechanism in nanocrystalline face-centered-cubic Al, partial dislocation emission from grain boundaries, which consequently resulted in deformation stacking faults (SFs) and twinning.
Abstract: We report experimental observation of a deformation mechanism in nanocrystalline face-centered-cubic Al, partial dislocation emission from grain boundaries, which consequently resulted in deformation stacking faults (SFs) and twinning. These results are surprising because (1) partial dislocation emission from grain boundaries has not been experimentally observed although it has been predicted by simulations and (2) deformation stacking faults and twinning have not been reported in Al due to its high SF energy.

Journal ArticleDOI
TL;DR: In this article, the authors performed gas flow experiments in a shallow microchannel, 1.14±0.02 μm deep, 200 μm wide, etched in glass and covered by an atomically flat silicon wafer.
Abstract: We perform gas flow experiments in a shallow microchannel, 1.14±0.02 μm deep, 200 μm wide, etched in glass and covered by an atomically flat silicon wafer. The dimensions of the channel are accurately measured by using profilometry, optical microscopy and interferometric optical microscopy. Flow-rate and pressure drop measurements are performed for helium and nitrogen, in a range of averaged Knudsen numbers extending up to 0.8 for helium and 0.6 for nitrogen. This represents an extension, by a factor of 3 or so, of previous studies. We emphasize the importance of the averaged Knudsen number which is identified as the basic control parameter of the problem. From the measurements, we estimate the accommodation factor for helium to be equal to 0.91±0.03 and that for nitrogen equal to 0.87±0.06. We provide estimates for second-order effects, and compare them with theoretical expectations. We estimate the upper limit of the slip flow regime, in terms of the averaged Knudsen number, to be 0.3±0.1, for the two gases.

Journal ArticleDOI
TL;DR: In this article, the authors used an efficient and rigorous numerical procedure for elastodynamic analysis of earthquake sequences on slowly loaded faults developed by Lapusta et al. and found that small events appear at the transition from the locked to creeping behavior toward the bottom of the seismogenic zone.
Abstract: [1] Earthquake nucleation and early seismic propagation are studied in a two-dimensional strike-slip fault model with depth-variable properties. The fault is governed by the Dieterich-Ruina rate and state friction law. We use an efficient and rigorous numerical procedure for elastodynamic analysis of earthquake sequences on slowly loaded faults developed by Lapusta et al. [2000]. We find that for decreasing values of the characteristic slip distance of the friction law, small events appear at the transition from the locked to creeping behavior toward the bottom of the seismogenic zone. Small and large events have very similar nucleation phases in our simulations. Here, by ‘‘nucleation phase’’ we mean gradually accelerating aseismic slip in a small slowly expanding zone before the breakout of the dynamic, seismically detectable event. Moment acceleration (to which velocity seismograms are proportional) in early stages of seismic propagation exhibits irregular fluctuations, in the form of speedups and slowdowns in the moment release rate, consistently with observations as reported by Ellsworth and Beroza [1995]. Our simulations show that such irregular moment acceleration can, at least in part, be due to the heterogeneous stress distribution imprinted on the fault by the arrest of previous small events and by stress concentrations at the borders of creeping regions and to partial arrest of the rupture in velocity-strengthening fault regions which inhibit seismic slip. INDEX TERMS: 7209 Seismology: Earthquake dynamics and mechanics; 7260 Seismology: Theory and modeling; 3220 Mathematical Geophysics: Nonlinear dynamics; 7230 Seismology: Seismicity and seismotectonics; 3230 Mathematical Geophysics: Numerical solutions; 8164 Tectonophysics: Stresses—crust and lithosphere; KEYWORDS: earthquake nucleation phase, event clustering, irregular moment release, stress concentrations, rate and state friction, earthquake sequences

Journal ArticleDOI
TL;DR: Delvaux et al. as mentioned in this paper presented a discussion on the methodology of stress inversion with, in particular, the use of different types of brittle fractures in addition to the commonly used fault-slip data, the problem of data selection and the optimization functions.
Abstract: Analysis of tectonic stress from the inversion of fault kinematic and earthquake focal mechanism data is routinely done using a wide variety of direct inversion, iterative and grid search methods. This paper discusses important aspects and new developments of the stress inversion methodology as the critical evaluation and interpretation of the results. The problems of data selection and separation into subsets, choice of optimization function, and the use of non-fault structural elements in stress inversion (tension, shear and compression fractures) are examined. The classical Right Dihedron method is developed in order to estimate the stress ratio R, widen its applicability to compression and tension fractures, and provide a compatibility test for data selection and separation. A new Rotational Optimization procedure for interactive kinematic data separation of fault-slip and focal mechanism data and progressive stress tensor optimization is presented. The quality assessment procedure defined for the World Stress Map project is extended in order to take into account the diversity of orientations of structural data used in the inversion. The range of stress regimes is expressed by a stress regime index R', useful for regional comparisons and mapping, All these aspects have been implemented in a computer program TENSOR, which is introduced briefly. The procedures for determination of stress tensor using these new aspects are described using natural sets of fault-slip and focal mechanism data from the Baikal Rift Zone. Analysis of fault kinematic and earthquake focal mechanism data for the reconstruction of past and present tectonic stresses are now routinely done in neotectonic and seismotectonic investigations. Geological stress data for the Quaternary period are increasingly incorporated in the World Stress Map (WSM) (Muller & Sperner 2000; Muller et at. 2000; Sperner et at. 2003). Standard procedures for brittle fault-slip data analysis and stress tensor determination are now well established (Angelier 1994; Dunne & Hancock 1994). They commonly use fault-slip data to infer the orientations and relative magnitude of the principal stresses. A wide variety of methods and computer programs exist for stress tensor reconstruction. They are either direct inversion methods using least square minimization (Carey-Gailhardis & Mercier 1987; Angelier 1991; Sperner et at. 1993) or iterative algorithms that test a wide range of possible tensors (Etchecopar et at. 1981) or grid search methods (Gephart 1990b; Hardcastle & Hills 1991; Unruh et at. 1996). The direct inversion methods are faster but necessitate more complex mathematical developments and do not allow the use of complex minimization functions. The iterative methods are more robust, use simple algorithms and are also more computer time intensive, but the increasing computer power reduces this inconvenience. This paper presents a discussion on the methodology of stress inversion with, in particular, the use of different types of brittle fractures in addition to the commonly used fault-slip data, the problem of data selection and the optimization functions. Two methodologies for stress inversion are presented: new developments of the classical Right Dihedron method and the new iterative Rotational Optimization method. Both methods use of the full range of brittle data available and have been adapted for the inversion of earthquake focal mechanisms. The interpretation of the results is also discussed for two important aspects: the quality assessment in view of the World Stress Map standards and the expression of the stress regime numerically as a Stress Regime Index for regional comparisons and mapping. All aspects discussed have been implemented in the TENSOR program (Delvaux 1993a), which can From: NIEUWLAND, D. A. (ed.) New Insights into Structural Interpretation and Modelling, Geological Society, London, Special Publications, 212, 75-100. 0305-8719/03/$15 © The Geological Society of London 2003. 76 D. DELVAUX & B. SPERNER be obtained by contacting the first author. A program guideline is also provided with the program package. Stress inversion methodologies Stress analysis considers a certain volume of rocks, large enough to sample a sufficiently large data set of slips along a variety of different shear surfaces. The size of the volume sampled should be much larger than the dimensions of the individual brittle structures. For geological indicators, relatively small volumes or rock (100-1000 m") are necessary to sample enough fault-slip data, while for earthquake focal mechanisms, volumes in the order of 1000-10 000 krrr' are needed. Stress inversion procedures rely on Bott's (1959) assumption that slip on a plane occurs in the direction of the maximum resolved shear stress. Inversely, the stress state that produced the brittle microstructures can be partly reconstructed knowing the direction and sense of slip on variably oriented fault planes. The slip direction on the fault plane is inferred from frictional grooves or slickenlines. The data used for the inversion are the strike and dip of the fault plane, the orientation of the slip line and the shear sense on the fault plane. They are collectively referred to as fault-slip data. Focal mechanisms of earthquakes are also used in stress inversion. The inversion of fault-slip data gives the four parameters of the reduced stress tensor: the principal stress axes al (maximum compression), a2 (intermediate compression) and a3 (minimum compression) and the Stress Ratio R = (a2 a3)/(al a3). The two additional parameters of the full stress tensor are the ratio of extreme principal stress magnitudes (a3/al) and the lithostatic load, but these two cannot be determined from fault data only. We refer to Angelier (1989, 1991, 1994) for a detailed description of the principles and procedures of fault-slip analysis and palaeostress reconstruction. Weare aware of the inherent limitations of any stress inversion procedures that apply also to the discussion proposed in this paper (Dupin et al. 1993; Pollard et al. 1993; Nieto-Samaniego & Alaniz-Alvarez 1996; Maerten 2000; Roberts & Ganas 2000). The question was raised as to whether fault-slip inversion solutions constrain the principal stresses or the principal strain rates (Gephart 1990a). We will not discuss this question here, and leave readers to form their own opinions on how to interpret the inversion results. The brittle microstructures (faults and fractures) are used in palaeostress reconstructions as kinematic indicators. The stress inversion scepticals (e.g. Twiss & Unruh 1998) argue that kinematic indicators are strain markers and consequently they cannot give access to stress. Without entering in such debate, we consider here that the stress tensor obtained by the inversion of kinematic indicators is a function that models the distribution of slip on every fault plane. For this, there is one ideal stress tensor, but this one is only certainly active during fault initiation. After faults have been initiated, a large variety of stress tensors can induce fault-slip by reactivation. Stress and strain relations In fault-slip analysis and palaeostress inversion, we consider generally the activation of pre-existing weakness planes as faults. Weakness planes can be inherited from a sedimentary fabric such as bedding planes, or from a previous tectonic event. A weakness plane can be produced also during the same tectonic event, just before accumulating slip on it, as when a fault is neoformed in a previously intact rock mass. The activated weakness plane F can be described by a unit vector n normal to F (bold is used to indicate vectors). The stress vector a acting on the weakness plane F has two components: the normal stress v in the direction of nand the shear stress T, parallel to F. These two stress components are perpendicular to each other and related by the vectorial relation a= v + T. The stress vector a represents the state of stress in the rock and has rrl , a2 and a3 as principal stress axes, defining a stress ellipsoid. The normal stress v induces a component of shortening or opening on the weakness plane in function of this sign. The slip direction d on a plane is generally assumed to be parallel to the shear stress component T of the stress vector a acting on the plane. It is possible to demonstrate that the direction of slip d on F depends on the orientations of the three principal stress axes, the stress ratio R = (a2 a3)/(al a3) and the orientation of the weakness plane n (Angelier 1989, 1994). The ability of a plane to be (re)activated depends on the relation between the normal stress and shear stress components on the plane, expressed by the friction coefficient: If the characteristic friction angle cP of the weakness plane F with the stress vector a acting on it overcomes the line of initial friction, the weakness plane will be activated as a fault. Otherwise, no movement will occur on it. This line is defined by the cohesion factor and the initial friction angle cPo. TECTONIC STRESS INVERSION AND THE TENSOR PROGRAM 77 Data types and their meaning in stress

Journal ArticleDOI
TL;DR: The influence of surface roughness on the boundary condition for the flow of a Newtonian fluid near a hard wall has been investigated by measurement of the hydrodynamic drainage force and it is concluded that in most practical situations boundary slip takes place, leading to a reduction of the drainage force.
Abstract: The influence of surface roughness on the boundary condition for the flow of a Newtonian fluid near a hard wall has been investigated by measurement of the hydrodynamic drainage force. The degree of slip is found to increase with surface roughness. This leads to the conclusion that in most practical situations boundary slip takes place, leading to a reduction of the drainage force.

Journal ArticleDOI
TL;DR: In this article, the authors detected 321 earthquakes with very similar (cross-correlation coefficient > 0.95) waveforms on the plate boundary in the northeastern Japan subduction zone.
Abstract: [1] On the basis of a waveform similarity analysis, we detected 321 earthquake clusters with very similar (cross-correlation coefficient >0.95) waveforms on the plate boundary in the northeastern Japan subduction zone. Most of them were not found within the subducting Pacific plate with a few exceptions. Moreover, even on the plate boundary, they were not located in the large moment release areas of large interplate earthquakes that occurred recently or in the areas where the plates are inferred to be strongly coupled from GPS data analyses. These observations suggest that these similar earthquakes are caused by repeating slips of small asperities with a dimension of around 0.1 to 1 km surrounded by stable sliding areas on the plate boundary. If the aseismic slip portion in these small asperities is negligible, we can estimate the cumulative amount of aseismic slip in the area surrounding each asperity. In other words, repeating earthquake data potentially can be used to estimate the spatiotemporal aseismic slip distribution on the plate boundary. We estimated the spatial distribution of slip rate on the plate boundary from repeating earthquake data. The scaling relation between seismic moment and seismic slip by Nadeau and Johnson [1998] is used for the estimation of the slip amount by each repeating earthquake cluster. Obtained spatial distribution is consistent with that estimated from GPS data on land.

Journal ArticleDOI
TL;DR: In this paper, the authors compared areas of high coseismic slip, or asperities, for 29 of the largest Circum-Pacific megathrust earthquakes are compared to forearc structure revealed by satellite free-air gravity, bathymetry, and seismic profiling.
Abstract: [1] Published areas of high coseismic slip, or asperities, for 29 of the largest Circum-Pacific megathrust earthquakes are compared to forearc structure revealed by satellite free-air gravity, bathymetry, and seismic profiling. On average, 71% of an earthquake's seismic moment and 79% of its asperity area occur beneath the prominent gravity low outlining the deep-sea terrace; 57% of an earthquake's asperity area, on average, occurs beneath the forearc basins that lie within the deep-sea terrace. In SW Japan, slip in the 1923, 1944, 1946, and 1968 earthquakes was largely centered beneath five forearc basins whose landward edge overlies the 350°C isotherm on the plate boundary, the inferred downdip limit of the locked zone. Basin-centered coseismic slip also occurred along the Aleutian, Mexico, Peru, and Chile subduction zones but was ambiguous for the great 1964 Alaska earthquake. Beneath intrabasin structural highs, seismic slip tends to be lower, possibly due to higher temperatures and fluid pressures. Kilometers of late Cenozoic subsidence and crustal thinning above some of the source zones are indicated by seismic profiling and drilling and are thought to be caused by basal subduction erosion. The deep-sea terraces and basins may evolve not just by growth of the outer arc high but also by interseismic subsidence not recovered during earthquakes. Basin-centered asperities could indicate a link between subsidence, subduction erosion, and seismogenesis. Whatever the cause, forearc basins may be useful indicators of long-term seismic moment release. The source zone for Cascadia's 1700 A.D. earthquake contains five large, basin-centered gravity lows that may indicate potential asperities at depth. The gravity gradient marking the inferred downdip limit to large coseismic slip lies offshore, except in northwestern Washington, where the low extends landward beneath the coast. Transverse gravity highs between the basins suggest that the margin is seismically segmented and could produce a variety of large earthquakes.

Journal ArticleDOI
TL;DR: In this article, a linear long-wave approximation with a finite difference method was used to compute tsunami waveforms, and they employed modern bathymetry with nearshore grid spacing as small as 0.4 km.
Abstract: [1] The 1700 Cascadia earthquake attained moment magnitude 9 according to new estimates based on effects of its tsunami in Japan, computed coseismic seafloor deformation for hypothetical ruptures in Cascadia, and tsunami modeling in the Pacific Ocean. Reports of damage and flooding show that the 1700 Cascadia tsunami reached 1–5 m heights at seven shoreline sites in Japan. Three sets of estimated heights express uncertainty about location and depth of reported flooding, landward decline in tsunami heights from shorelines, and post-1700 land-level changes. We compare each set with tsunami heights computed from six Cascadia sources. Each source is vertical seafloor displacement calculated with a three-dimensional elastic dislocation model. For three sources the rupture extends the 1100 km length of the subduction zone and differs in width and shallow dip; for the other sources, ruptures of ordinary width extend 360–670 km. To compute tsunami waveforms, we use a linear long-wave approximation with a finite difference method, and we employ modern bathymetry with nearshore grid spacing as small as 0.4 km. The various combinations of Japanese tsunami heights and Cascadia sources give seismic moment of 1–9 × 1022 N m, equivalent to moment magnitude 8.7–9.2. This range excludes several unquantified uncertainties. The most likely earthquake, of moment magnitude 9.0, has 19 m of coseismic slip on an offshore, full-slip zone 1100 km long with linearly decreasing slip on a downdip partial-slip zone. The shorter rupture models require up to 40 m offshore slip and predict land-level changes inconsistent with coastal paleoseismological evidence.

Journal ArticleDOI
TL;DR: In this article, the resolved shear stresses for the different deformation systems were calculated from measured crystal orientations, in order to understand more clearly which glide systems are activated during deformation of polycrystalline material and how they are related to the formation of the cold rolling textures.
Abstract: Active glide and twinning systems have been studied by transmission electron microscopy (TEM) in samples of three Ti-alloys, T40 (Ti+1000 ppm O), T60 (Ti+2000 ppm O) and TiAl6V4 deformed up to 5% by uniaxial or biaxial tension. The aim of the work was to understand more clearly which glide systems are activated during deformation of polycrystalline material and how they are related to the formation of the cold rolling textures. In order to estimate the stresses necessary for the activation of the observed glide systems, the resolved shear stresses for the different deformation systems were calculated from measured crystal orientations. The main results are: in TiAl6V4 〈a〉, basal slip has a lower critical resolved shear stress, τc, than prismatic slip. 〈c+a〉 pyramidal glide shows a very low τc, which is up to two times larger than that for prismatic slip. Nevertheless, 〈c+a〉 glide systems were only rarely activated and twinning systems were never activated. Therefore, deformation with c-components may be accommodated by β-phase deformation or grain boundary sliding. The observed c-type texture is due to the strong basal glide. In T40, τc for 〈c+a〉 glide is up to 13 times higher than that for prismatic glide. However, 〈c+a〉 glide and twinning were strongly activated, leading to the observed t-type texture. In T60, the high oxygen content completely suppressed twinning and strongly reduced 〈c+a〉 glide. The less developed t-type texture is due to the combination of 〈c+a〉 and basal glide.

Journal ArticleDOI
TL;DR: In this article, a thermomechanical processing (TMP) was used to refine a Mg-based AZ61 alloy of initially coarse, recrystallized microstructure.
Abstract: Grain refinement in a Mg-based AZ61 alloy of initially coarse, recrystallized microstructure was successfully achieved by thermomechanical processing (TMP) consisting of two to three hot-rolling steps with large reductions per pass. Reductions as large as 85% (equivalent to a true strain of ≈1) were achieved without surface cracking. The underlying microscopic mechanisms operative during the TMP that allowed this hcp material to accommodate such large strains per pass were investigated by macro- and microtexture analysis. A significant decrease in the intensity of the initial basal texture was observed after the first pass. This was attributed to rotational dynamic recrystallization, a mechanism by which new recrystallized grains develop, with orientations favourable for basal slip. Upon subsequent passes, basal slip becomes the main deformation mechanism. Simultaneously, grain refinement takes place by continuous dynamic recrystallization. The fine-grained microstructure thus developed showed improved superplastic behaviour in comparison with that of similar alloys processed by more elaborate methods.

01 Dec 2003
TL;DR: In this article, a nonelastic two-dimensional dynamic calculation is done in which the slip zone is modeled as a fault plane and material off the fault is subject to a Coulomb yield condition.
Abstract: [1] Energy loss in a fault damage zone, outside the slip zone, contributes to the fracture energy that determines rupture velocity of an earthquake. A nonelastic two-dimensional dynamic calculation is done in which the slip zone is modeled as a fault plane and material off the fault is subject to a Coulomb yield condition. In a mode 2 crack-like solution in which an abrupt uniform drop of shear traction on the fault spreads from a point, Coulomb yielding occurs on the extensional side of the fault. Plastic strain is distributed with uniform magnitude along the fault, and it has a thickness normal to the fault proportional to propagation distance. Energy loss off the fault is also proportional to propagation distance, and it can become much larger than energy loss on the fault specified by the fault constitutive relation. The slip velocity function could be produced in an equivalent elastic problem by a slip-weakening friction law with breakdown slip Dc increasing with distance. Fracture energy G and equivalent Dc will be different in ruptures with different initiation points and stress drops, so they are not constitutive properties; they are determined by the dynamic solution that arrives at a particular point. Peak slip velocity is, however, a property of a fault location. Nonelastic response can be mimicked by imposing a limit on slip velocity on a fault in an elastic medium.

Journal ArticleDOI
TL;DR: CAS3D-2 as mentioned in this paper is a new 3D dislocation model to model interseismic deformation rates at the Cascadia subduction zone, which is considered a snapshot description of the deformation field that changes with time.
Abstract: [1] CAS3D-2, a new three-dimensional (3-D) dislocation model, is developed to model interseismic deformation rates at the Cascadia subduction zone. The model is considered a snapshot description of the deformation field that changes with time. The effect of northward secular motion of the central and southern Cascadia forearc sliver is subtracted to obtain the effective convergence between the subducting plate and the forearc. Horizontal deformation data, including strain rates and surface velocities from Global Positioning System (GPS) measurements, provide primary geodetic constraints, but uplift rate data from tide gauges and leveling also provide important validations for the model. A locked zone, based on the results of previous thermal models constrained by heat flow observations, is located entirely offshore beneath the continental slope. Similar to previous dislocation models, an effective zone of downdip transition from locking to full slip is used, but the slip deficit rate is assumed to decrease exponentially with downdip distance. The exponential function resolves the problem of overpredicting coastal GPS velocities and underpredicting inland velocities by previous models that used a linear downdip transition. A wide effective transition zone (ETZ) partially accounts for stress relaxation in the mantle wedge that cannot be simulated by the elastic model. The pattern of coseismic deformation is expected to be different from that of interseismic deformation at present, 300 years after the last great subduction earthquake. The downdip transition from full rupture to no slip should take place over a much narrower zone.

Journal ArticleDOI
TL;DR: In this paper, the authors present a conceptual model to explain the development of damage zones around faults in high-porosity sandstones, and modify a previously published theoretical model for fault growth in which displacement accumulates by repeated slip events on patches of the fault plane.

Journal ArticleDOI
22 Aug 2003-Science
TL;DR: A model of an episodically slipping friction-locked fault reproduces the observed quasi-periodic event timing, demonstrating an ice stream's ability to change speed rapidly and its extreme sensitivity to subglacial conditions and variations in sea level.
Abstract: A major West Antarctic ice stream discharges by sudden and brief periods of very rapid motion paced by oceanic tidal oscillations of about 1 meter. Acceleration to speeds greater than 1 meter per hour and deceleration back to a stationary state occur in minutes or less. Slip propagates at approximately 88 meters per second, suggestive of a shear wave traveling within the subglacial till. A model of an episodically slipping friction-locked fault reproduces the observed quasi-periodic event timing, demonstrating an ice stream's ability to change speed rapidly and its extreme sensitivity to subglacial conditions and variations in sea level.

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TL;DR: In this article, the authors considered the nucleation of instability on a slip-weakening fault subjected to a heterogeneous, locally peaked "loading" stress, and they derived the critical length for dynamic slip nucleation under spatially uniform prestress.
Abstract: [1] We consider the nucleation of instability on a slip-weakening fault subjected to a heterogeneous, locally peaked “loading” stress. That stress is assumed not only to gradually increase due to tectonic loading but also to retain its peaked character. The case of a linear stress versus slip law is considered in the framework of two-dimensional quasi-static elasticity for a planar fault. Slip initiates when the peak of the loading stress first reaches the strength level of the fault to start slip weakening. Then the size of the slipping region grows under increased loading stress until finally a critical nucleation length is reached, at which no further quasi-static solution exists for additional increase of the loading. That marks the onset of a dynamically controlled instability. We prove that the nucleation length is independent of the shape of the loading stress distribution. Its universal value is proportional to an elastic modulus and inversely proportional to the slip-weakening rate, and it is given by the solution to an eigenvalue problem. That is the same eigenvalue problem introduced by Campillo, Ionescu, and collaborators for dynamic slip nucleation under spatially uniform prestress on a fault segment of fixed length; the critical length that we derive is the same as in their case. To illustrate the nucleation process, and its universal feature, in specific examples, we consider cases for which the loading stress is peaked symmetrically or nonsymmetrically, and we employ a numerical approach based on a Chebyshev polynomial representation. Laboratory-derived and earthquake-inferred data are used to evaluate the nucleation size.

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TL;DR: In this paper, the scale-dependent shear rupture of a broad range from laboratory-scale frictional slip failure and shear fracture of intact rock to field-scale rupture as an earthquake source can be unified by a single constitutive law.
Abstract: [1] It is widely recognized that some of the physical quantities inherent in a rupture are scale-dependent, and the scale dependence is one of the most no facts and features of rupture phenomena. The paper addresses how such scale-dependent shear rupture of a broad range from laboratory-scale frictional slip failure and shear fracture of intact rock to field-scale rupture as an earthquake source can be unified by a single constitutive law. Noting that the earthquake rupture is a mixed process between frictional slip failure and the shear fracture of intact rock, it is concluded that the constitutive law for the earthquake rupture be formulated as a unifying law that governs both frictional slip failure and shear fracture of intact rock. It is demonstrated that the slip-dependent constitutive law is such a unifying law, and a constitutive scaling law is derived from laboratory data on both frictional slip failure and shear fracture of intact rock. This constitutive scaling law enables one to provide a consistent and unified comprehension for scale-dependent physical quantities inherent in the rupture, over a broad range from small-scale frictional slip failure and shear fracture in the laboratory to large-scale earthquake rupture in the field.

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TL;DR: In this article, the three-dimensional transient response of the surface to both bedrock undulations and spatial variations in basal slipperiness for perturbations of arbitrary wavelengths is determined using perturbation methods.
Abstract: [1] Transmission of basal variability to a glacier surface is investigated using analytical models for a linearly viscous medium. The three-dimensional transient response of the surface to both bedrock undulations and spatial variations in basal slipperiness for perturbations of arbitrary wavelengths is determined using perturbation methods. Both information transfer toward the surface and lateral transmission of horizontal stresses are strongly affected by the slip ratio, that is, the ratio of basal sliding to deformational velocity. For any mean bedrock slope, and above a minimum value of slip ratio, the amplitude transfer of bedrock undulations toward the surface has a local maximum at undulation span corresponding to about 3–8 times the mean ice thickness. The transmission of basal variability to a glacier surface increases quite significantly with increasing slip ratio. This explains why the surfaces of fast flowing ice streams are more undulating than the slower moving bordering areas. At slip ratios higher than about 100, the flow of glaciers and ice sheets becomes nonlocal in the sense that surface velocities and buildup and propagation of surface undulations cannot be calculated accurately on the basis of local thickness and slope. Using linearized long-wave theories at these slip ratios, instead of the more accurate arbitrary wavelength theory, gives estimates of decay times that are an order-of-magnitude too small and phase velocities several times too large. The problem of the propagation and decay of small-amplitude surface undulations on glaciers in three dimensions is solved. Small-amplitude surface waves on glaciers are strongly diffusive and dispersive. Redistribution of mass on ice sheets and glaciers is a diffusion process, and it is misleading, albeit not mathematically incorrect, to describe the reaction of glaciers to surface perturbations in terms of a wave propagation.

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TL;DR: In this paper, a method for estimating dislocation densities is proposed, based on nucleation of loops at the shock front and their extension due to residual shear stresses behind the front.

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TL;DR: In this paper, the development of microstructure during equal-channel angular pressing (ECAP) of commercial-purity titanium was investigated to establish the mechanisms of grain refinement and strain accommodation.

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TL;DR: In this paper, the effects of shear slip on the deformation of steel-concrete composite beams were investigated, and it was found that including slip effects has significantly improved the accuracy of prediction.
Abstract: The present study investigated the effects of shear slip on the deformation of steel-concrete composite beams. The equivalent rigidity of composite beams considering three different loading types was first derived based on equilibrium and curvature compatibility, from which a general formula to account for slip effects was then developed. The predicted results were compared with measurements of six specimens tested in the present study and other available test results for both simply supported and continuous beams. It was found that including slip effects has significantly improved the accuracy of prediction. For typical beams used in practice, shear slip in partial composite beams has a significant contribution to beam deformation. Even for full composite beams, slip effects may result in stiffness reduction up to 17% for short span beams. However, slip effects are ignored in many design specifications that use transformed section method except that American Institute of Steel Construction ~AISC! specifications recommend a calculation procedure in the commentary. In the AISC procedure, stress and deflection calculations of partially composite girders are based on effective section modulus and moment of inertia to account for slip, while ignoring slip effects in full composite sections. For full composite sections, the effective section modulus and moment of inertia calculated with the AISC specifications are larger than that of present study, meaning that the specifications are not on the conservative side. For partial composite sections, the AISC predictions are more conservative than the present study.