Showing papers on "Slip (materials science) published in 2005"

The great Sumatra-Andaman earthquake of 26 December 2004

Abstract: The two largest earthquakes of the past 40 years ruptured a 1600-kilometer-long portion of the fault boundary between the Indo-Australian and southeastern Eurasian plates on 26 December 2004 [seismic moment magnitude (Mw) = 9.1 to 9.3] and 28 March 2005 (Mw = 8.6). The first event generated a tsunami that caused more than 283,000 deaths. Fault slip of up to 15 meters occurred near Banda Aceh, Sumatra, but to the north, along the Nicobar and Andaman Islands, rapid slip was much smaller. Tsunami and geodetic observations indicate that additional slow slip occurred in the north over a time scale of 50 minutes or longer.

Boundary slip in Newtonian liquids: a review of experimental studies

Abstract: For several centuries fluid dynamics studies have relied upon the assumption that when a liquid flows over a solid surface, the liquid molecules adjacent to the solid are stationary relative to the solid. This no-slip boundary condition (BC) has been applied successfully to model many macroscopic experiments, but has no microscopic justification. In recent years there has been an increased interest in determining the appropriate BCs for the flow of Newtonian liquids in confined geometries, partly due to exciting developments in the fields of microfluidic and microelectromechanical devices and partly because new and more sophisticated measurement techniques are now available. An increasing number of research groups now dedicate great attention to the study of the flow of liquids at solid interfaces, and as a result a large number of experimental, computational and theoretical studies have appeared in the literature. We provide here a review of experimental studies regarding the phenomenon of slip of Newtonian liquids at solid interfaces. We dedicate particular attention to the effects that factors such as surface roughness, wettability and the presence of gaseous layers might have on the measured interfacial slip. We also discuss how future studies might improve our understanding of hydrodynamic BCs and enable us to actively control liquid slip.

Rupture Process of the 2004 Sumatra-Andaman Earthquake

Abstract: The 26 December 2004 Sumatra-Andaman earthquake initiated slowly, with small slip and a slow rupture speed for the first 40 to 60 seconds. Then the rupture expanded at a speed of about 2.5 kilometers per second toward the north northwest, extending 1200 to 1300 kilometers along the Andaman trough. Peak displacements reached ∼15 meters along a 600-kilometer segment of the plate boundary offshore of northwestern Sumatra and the southern Nicobar islands. Slip was less in the northern 400 to 500 kilometers of the aftershock zone, and at least some slip in that region may have occurred on a time scale beyond the seismic band.

Enhanced deformation mechanisms by anisotropic plasticity in polycrystalline Mg alloys at room temperature

Abstract: This article presents room-temperature deformation mechanisms in polycrystalline Mg alloys. Dislocation slip of basal 〈a〉 and prismatic 〈a〉 types are shown to occur nearly at the same ease when the basal planes are tilted in such a way that the Schmid-factor ratio (equivalent to the critically resolved shear stress (CRSS) ratio) of prismatic 〈a〉 to basal 〈a〉 slip is larger than a value ranging from 1.5 to 2.0, depending on the initial texture distribution and grain size. Grain-boundary sliding (GBS) also occurs at room temperature up to 8 pct of total strain, enhanced by plastic anisotropy as well as by the increasing number of grain-boundary dislocations. Twinning plays an important role in both flow and fracture behaviors. Twins are induced mostly by stress concentrations caused by the anisotropic nature of dislocation slip. Twins can be classified into two types based on their shape: a wide lenticular type and a narrow banded type. The wide twins are $$\{ 10\bar 12\} $$ twins appearing in the early stage of deformation and accompany little change of surface height. The narrow twins are $$\{ 10\bar 11\} $$ or $$\{ 30\bar 32\} $$ appearing in the late stage of deformation and accompany a substantial change in surface height. The formation of the narrow twins seems to give rise to highly localized shear deformation within the twin, leading to strain incompatibility and to final failure.

Contemporary crustal deformation around the southeast borderland of the Tibetan Plateau

Abstract: [1] We derive a detailed horizontal velocity field for the southeast borderland of the Tibetan Plateau using GPS data collected from the Crustal Motion Observation Network of China between 1998 and 2004. Our results reveal a complex deformation field that indicates that the crust is fragmented into tectonic blocks of various sizes, separated by strike-slip and transtensional faults. Most notably, the regional deformation includes 10–11 mm/yr left slip across the Xianshuihe fault, � 7 mm/yr left slip across the Anninghe-Zemuhe-Xiaojiang fault zone, � 2 mm/yr right slip across a shear zone trending northwest near the southern segment of the Lancang River fault, and � 3 mm/yr left slip across the Lijiang fault. Deformation along the southern segment of the Red River fault appears not significant at present time. The region south and west of the XianshuiheXiaojiang fault system, whose eastward motion is resisted by the stable south China block to the east, turns from eastward to southward motion with respect to south China, resulting in clockwise rotation of its internal subblocks. Active deformation is detected across two previously unknown deformation zones: one is located � 150 km northwest of and in parallel with the Longmenshan fault with 4–6 mm/yr right-slip and another is continued south-southwestward from the Xiaojiang fault abutting the Red River fault with � 7 mm/yr left slip. While both of these zones are seismically active, the exact locations of faults responsible for such deformation are yet to be mapped by field geology. Comparing our GPS results with predictions of various models proposed for Tibetan Plateau deformation, we find that the relatively small sizes of the inferred microblocks and their rotation pattern lend support to a model with a mechanically weak lower crust experiencing distributed deformation underlying a stronger, highly fragmented upper crust.

Development of the Nonlinear Bond Stress-Slip Model of Fiber Reinforced Plastics Sheet-Concrete Interfaces with a Simple Method

Abstract: In this paper, a new analytical method for defining the nonlinear bond stress-slip models of Fiber Reinforced Plastics (FRP) sheet-concrete interfaces through pullout bond test is proposed. With this method, it is not necessary to attach many strain gages on the FRP sheets for obtaining the strain distributions in FRP as well as the local bond stresses and slips. Instead, the local interfacial bond stress-slip models can be simply derived from the relationships between the pullout forces and loaded end slips. Based on a series of pullout tests, the bond stress-slip models of FRP sheet-concrete interfaces, in which different FRP stiffness, FRP materials (Carbon FRP, Aramid FRP, Glass FRP), and adhesives are used, have been derived. Only two parameters, the interfacial fracture energy and interfacial ductility index, which can take into account the effects of all interfacial components, are necessary in these models. Comparisons between analytical results and experimental ones show good accordance, indicating the reliability of the proposed method and the proposed bond stress-slip models.

The generalized Maxwell-slip model: a novel model for friction Simulation and compensation

Abstract: A novel, multistate friction model is presented, which is obtained from the Maxwell-slip model by replacing the usual Coulomb law at slip by a rate-state law. The form of the latter state equations is arrived at by comparison with a recently developed generic friction model as well as limiting behavior cases. The model is particularly suitable for quick simulation and control purposes, being both easy to implement and of high fidelity. This communication situates the model, by outlining its development background and structure, and highlights its basic characteristics.

Earthquake nucleation on (aging) rate and state faults

Abstract: We obtain quasi-static, two-dimensional solutions for earthquake nucleation on faults obeying Dieterich's “aging” version of the rate and state friction equations. Two distinct nucleation regimes are found, separated by roughly a/b ∼ 0.5, where a and b are the constitutive parameters relating changes in slip rate V and state θ to frictional strength. When fault healing is unimportant (Vθ/D_c ≫ 1, where D_c is the characteristic slip distance for the evolution of θ), the nucleation zone spontaneously evolves toward a state of accelerating slip on a patch of fixed half length L_ν ≈ 1.3774(μ′D_c /bσ), where μ′ is the intrinsic stiffness of the medium and σ is the normal stress. This is the fixed length solution for which the stress intensity factor K = 0. Although this solution does not depend upon a/b explicitly, only for a/b < 0.3781 does healing remain unimportant as instability is approached. For a/b ≳ 0.5 and a wide range of slow loading conditions, Vθ/D_c ultimately approaches a quasi-constant value near 1, and the nucleation zone takes on the appearance of an expanding slip-weakening crack. A fracture energy balance indicates that in this regime the nucleation length asymptotically approaches π−1[b/(b − a)]2(μ′D_c /bσ), a result that is consistent with the numerical simulations despite considerable complexity asa approaches b. This suggests that nucleation lengths can sometimes be much larger than those found by Dieterich (e.g., by a factor of 100 for a/b = 0.95). For surfaces this close to velocity neutral, nucleation might produce signals detectable by surface seismometers for values of D_c at the upper end of the lab range (100 μm). However, the attributes of the aging law that give rise to such large nucleation lengths may be nonphysical; additional laboratory experiments are needed to address this issue.

Three-dimensional deformation caused by the Bam, Iran, earthquake and the origin of shallow slip deficit

Abstract: Our understanding of the earthquake process requires detailed insights into how the tectonic stresses are accumulated and released on seismogenic faults. We derive the full vector displacement field due to the Bam, Iran, earthquake of moment magnitude 6.5 using radar data from the Envisat satellite of the European Space Agency. Analysis of surface deformation indicates that most of the seismic moment release along the 20-km-long strike-slip rupture occurred at a shallow depth of 4‐5km, yet the rupture did not break the surface. The Bam event may therefore represent an endmember case of the ‘shallow slip deficit’ model, which postulates that coseismic slip in the uppermost crust is systematically less than that at seismogenic depths (4‐10km). The InSAR-derived surface displacement data from the Bam and other large shallow earthquakes suggest that the uppermost section of the seismogenic crust around young and developing faults may undergo a distributed failure in the interseismic period, thereby accumulating little elastic strain.

Block models of crustal motion in southern California constrained by GPS measurements

Abstract: [1] We estimate slip rates on major active faults in southern California using a block model constrained by Global Positioning System measurements of interseismic deformation. The block model includes the effects of block rotation and elastic strain accumulation consistent with a simple model of the earthquake cycle. Our estimates of the right-lateral strike-slip rate on the San Andreas fault vary by at least a factor of 5, from a high of 35.9 ± 0.5 mm/yr in the Carrizo Plain to a low of 5.1 ± 1.5 mm/yr through the San Bernadino segment. Shortening across the Puente Hills Thrust and left-lateral slip on the Raymond Hill fault are consistent with both thickening and escape tectonics in the Los Angeles Basin. Discrepancies between geodetic and geologic slip rate estimates along the San Andreas and San Jacinto faults, as well as in the Eastern California Shear Zone, may be explained by a temporal change in fault system behavior. We find no substantial evidence for long-term postseismic relaxation and infer that the viscosity of the lower crust/upper mantle may be relatively high (η > 1019 Pa s).

Boundary slip on smooth hydrophobic surfaces: intrinsic effects and possible artifacts.

Abstract: We report an accurate determination of the hydrodynamic boundary condition of simple liquids flowing on smooth hydrophobic surfaces using a dynamic surface force apparatus equipped with two independent subnanometer resolution sensors. The boundary slip observed is well defined and does not depend on the scale of investigation from one to several hundreds of nanometers, nor on shear rate up to $5\ifmmode\times\else\texttimes\fi{}{10}^{3}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$. The slip length of 20 nm is in good agreement with theory and numerical simulations concerning smooth nonwetting surfaces. These results disagree with previous data in the literature reporting very high boundary slip on similar systems. We discuss possible origins of large slip length on smooth hydrophobic surfaces due to their contamination by hydrophobic particles.

Squeeze flow theory and applications to rheometry: A review

Abstract: The deformations and stresses during squeeze flows are evaluated for a wider class of materials than previously covered in articles on this subject. These include generalised Newtonian fluids, yield stress fluids, as well as elastic and viscoelastic materials. Wherever possible, results are given in a compact mathematical form. The effect of different boundary conditions (no slip, perfect slip and partial slip) and how these interact with different types of material behaviour to give a variety of macroscopic responses is also discussed. The significance of this in using squeeze flow as a rheometry method is highlighted and a state-of-the-art view of squeeze flow rheometry is given.

Can observations of earthquake scaling constrain slip weakening

Abstract: SUMMARY We use observations of earthquake source parameters over a wide magnitude range (M W ∼ 0‐7) to place constraints on constitutive fault weakening. The data suggest a scale dependence of apparent stress and stress drop; both may increase slightly with earthquake size. We show that this scale dependence need not imply any difference in fault zone properties for different sized earthquakes. We select 30 earthquakes well-recorded at 2.5 km depth at Cajon Pass, California. We use individual and empirical Green’s function spectral analysis to improve the resolution of source parameters, including static stress drop (�σ ) and total slip (S). We also measure radiated energy E S .W ecompare the Cajon Pass results with those from larger California earthquakes including aftershocks of the 1994 Northridge earthquake and confirm the results of Abercrombie (1995): µE S/M 0 � �σ (where µ = rigidity) and both E S/M 0 and �σ increase as M 0 (and S) increases. Uncertainties remain large due to model assumptions and variations between possible models, and earthquake scale independence is possible within the resolution. Assuming that the average trends are real, we define a quantity G � = (�σ − 2µES/M 0)S/ 2w hich is the total energy dissipation in friction and fracture minus σ 1 S ,w here σ 1 is the final static stress. If σ 1 = σ d, the dynamic shear strength during the last increments of seismic slip, then G � = G, the fracture energy in a slip-weakening interpretation of dissipation.

Aseismic slip transients emerge spontaneously in three-dimensional rate and state modeling of subduction earthquake sequences

Abstract: [1] To investigate the possible physical mechanisms of recently observed aseismic slip events in the Cascadia, Japan and Mexico subduction zones, we apply a Dieterich-Ruina rate and state friction law to a three dimensional model of a shallow subduction fault. That is loaded by imposed steady plate slip rate far downdip along the thrust interface. Friction properties are temperature and hence depth-dependent, such that sliding is stable at depths below about 30 km. The system is perturbed into a significantly nonuniform slip mode along strike by introducing small along-strike variations in the constitutive parameters a and (a − b). In addition to large heterogeneous earthquake slip at seismogenic depths, and associated postseismic transients, we found that slip events which have clearly aseismic slip rates emerge spontaneously around the downdip end of the seismogenic zone. Both transients which start well after a seismic event, and those which are triggered by other transients, are observed from the simulations. The slip velocity, depth range, and, sometimes, along-strike migration speed of simulated transients are similar to the observations from natural subduction zones. Unstable-stable transitional friction properties near the downdip end of the seismogenic zone are suggested to be an ingredient allowing such transients. Simulated transients can weaken the locking intensity of the updip seismogenic zone, while enhancing that of the transition zone. Spatial-temporal correlation of aseismic transients and nearby seismicity in the Guerrero, Mexico, area suggests that transients may signal a period of increased probability for nucleating their high-frequency counterparts, as damaging subduction thrust events.

Growth of molten zone as a mechanism of slip weakening of simulated faults in gabbro during frictional melting

Abstract: [1] To understand how frictional melting affects fault instability, we performed a series of high-velocity friction experiments on gabbro at slip rates of 0.85-1.49 m s -1 , at normal stresses of 1.2-2.4 MPa and with displacements up to 124 m. Experiments have revealed two stages of slip weakening; one following the initial slip and the other immediately after the second peak friction. The first weakening is associated with flash heating, and the second weakening is due to the formation and growth of a molten layer along a simulated fault. The two stages of weakening are separated by a marked strengthening regime in which melt patches grow into a thin, continuous molten layer at the second peak friction. The frictional coefficient decays exponentially from 0.8-1.1 to 0.6 during the second weakening. The host rocks are separated completely by a molten layer during this weakening so that the shear resistance is determined by the gross viscosity and shear strain rate of the molten layer. Melt viscosity increases notably soon after a molten layer forms. However, a fault weakens despite the increase in melt viscosity, and the second weakening is caused by the growth of molten layer resulting in the reduction in shear strain rate of the molten layer. Very thin melt cannot be squeezed out easily from a fault zone so that the rate of melting would be the most critical factor in controlling the slip-weakening distance. Effect of frictional melting on fault motion can be predicted by solving a Stefan problem dealing with moving host rock/molten zone boundaries.

Fracture surface energy of the Punchbowl fault, San Andreas system.

Abstract: Fracture energy is a form of latent heat required to create an earthquake rupture surface and is related to parameters governing rupture propagation and processes of slip weakening. Fracture energy has been estimated from seismological and experimental rock deformation data, yet its magnitude, mechanisms of rupture surface formation and processes leading to slip weakening are not well defined. Here we quantify structural observations of the Punchbowl fault, a large-displacement exhumed fault in the San Andreas fault system, and show that the energy required to create the fracture surface area in the fault is about 300 times greater than seismological estimates would predict for a single large earthquake. If fracture energy is attributed entirely to the production of fracture surfaces, then all of the fracture surface area in the Punchbowl fault could have been produced by earthquake displacements totalling <1 km. But this would only account for a small fraction of the total energy budget, and therefore additional processes probably contributed to slip weakening during earthquake rupture.

Comparison of finite difference and boundary integral solutions to three-dimensional spontaneous rupture

Abstract: The spontaneously propagating shear crack on a frictional interface has proven to be a useful idealization of a natural earthquake. The corresponding boundary value problems are nonlinear and usually require computationally intensive numerical methods for their solution. Assessing the convergence and accuracy of the numerical methods is challenging, as we lack appropriate analytical solutions for comparison. As a complement to other methods of assessment, we compare solutions obtained by two independent numerical methods, a finite difference method and a boundary integral (BI) method. The finite difference implementation, called DFM, uses a traction-at-split-node formulation of the fault discontinuity. The BI implementation employs spectral representation of the stress transfer functional. The three-dimensional (3-D) test problem involves spontaneous rupture spreading on a planar interface governed by linear slip-weakening friction that essentially defines a cohesive law. To get a priori understanding of the spatial resolution that would be required in this and similar problems, we review and combine some simple estimates of the cohesive zone sizes which correspond quite well to the sizes observed in simulations. We have assessed agreement between the methods in terms of the RMS differences in rupture time, final slip, and peak slip rate and related these to median and minimum measures of the cohesive zone resolution observed in the numerical solutions. The BI and DFM methods give virtually indistinguishable solutions to the 3-D spontaneous rupture test problem when their grid spacing Δx is small enough so that the solutions adequately resolve the cohesive zone, with at least three points for BI and at least five node points for DFM. Furthermore, grid-dependent differences in the results, for each of the two methods taken separately, decay as a power law in Δx, with the same convergence rate for each method, the calculations apparently converging to a common, grid interval invariant solution. This result provides strong evidence for the accuracy of both methods. In addition, the specific solution presented here, by virtue of being demonstrably grid-independent and consistent between two very different numerical methods, may prove useful for testing new numerical methods for spontaneous rupture problems.

Earthquake slip weakening and asperities explained by thermal pressurization

Abstract: An earthquake occurs when a fault weakens during the early portion of its slip at a faster rate than the release of tectonic stress driving the fault motion. This slip weakening occurs over a critical distance, D(c). Understanding the controls on D(c) in nature is severely limited, however, because the physical mechanism of weakening is unconstrained. Conventional friction experiments, typically conducted at slow slip rates and small displacements, have obtained D(c) values that are orders of magnitude lower than values estimated from modelling seismological data for natural earthquakes. Here we present data on fluid transport properties of slip zone rocks and on the slip zone width in the centre of the Median Tectonic Line fault zone, Japan. We show that the discrepancy between laboratory and seismological results can be resolved if thermal pressurization of the pore fluid is the slip-weakening mechanism. Our analysis indicates that a planar fault segment with an impermeable and narrow slip zone will become very unstable during slip and is likely to be the site of a seismic asperity.

Direct measurement of the apparent slip length

Abstract: We measure velocity profiles in water flowing through thin microchannels, using particle image velocimetry combined with a nanopositioning system. From the velocity profiles, we determine the slip lengths in two cases: Smooth hydrophilic glass surfaces, and smooth hydrophobic glass surfaces, grafted with a monolayer of silane. The slip length is determined within $(\ifmmode\pm\else\textpm\fi{}100\phantom{\rule{0.3em}{0ex}}\mathrm{nm})$, i.e., five times more accurately than previous work. In all cases, we find that the slip length is below $100\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$.

Effect of deformation twinning on microstructure and texture evolution during cold rolling of CP-titanium

Abstract: The evolution of microstructure and texture during cold rolling of commercial-purity titanium (CP-Ti) was studied with particular reference to deformation twinning and dislocation slip. For low to intermediate deformation up to 40% in thickness reduction, the external strain was accommodated by slip and deformation twinning. In this stage, both compressive ( { 1 1 2 ¯ 2 } 〈 1 1 2 ¯ 3 ¯ 〉 ) and tensile ( { 1 0 1 ¯ 2 } 〈 1 0 1 ¯ 1 ¯ 〉 ) twins, as well as, secondary twins and tertiary twins were activated in the grains of favorable orientation, and this resulted in a heterogeneous microstructure in which grains were refined in local areas. For heavy deformation, between 60 and 90%, slip overrode twinning and shear bands developed. The crystal texture of deformed specimens was weakened by twinning but was strengthened by slip, resulting in a split-basal texture in heavily deformed specimens.

Surface displacements and source parameters of the 2003 Bam (Iran) earthquake from Envisat advanced synthetic aperture radar imagery

Abstract: [1] The Mw 6.6, 26 December 2003 Bam (Iran) earthquake was one of the first earthquakes for which Envisat advanced synthetic aperture radar (ASAR) data were available. Using interferograms and azimuth offsets from ascending and descending tracks, we construct a three-dimensional displacement field of the deformation due to the earthquake. Elastic dislocation modeling shows that the observed deformation pattern cannot be explained by slip on a single planar fault, which significantly underestimates eastward and upward motions SE of Bam. We find that the deformation pattern observed can be best explained by slip on two subparallel faults. Eighty-five percent of moment release occurred on a previously unknown strike-slip fault running into the center of Bam, with peak slip of over 2 m occurring at a depth of ∼5 km. The remainder occurred as a combination of strike-slip and thrusting motion on a southward extension of the previously mapped Bam Fault ∼5 km to the east.

Pressure sensitivity of olivine slip systems and seismic anisotropy of Earth's upper mantle.

Abstract: The mineral olivine dominates the composition of the Earth's upper mantle and hence controls its mechanical behaviour and seismic anisotropy Experiments at high temperature and moderate pressure, and extensive data on naturally deformed mantle rocks, have led to the conclusion that olivine at upper-mantle conditions deforms essentially by dislocation creep with dominant [100] slip The resulting crystal preferred orientation has been used extensively to explain the strong seismic anisotropy observed down to 250 km depth The rapid decrease of anisotropy below this depth has been interpreted as marking the transition from dislocation to diffusion creep in the upper mantle But new high-pressure experiments suggest that dislocation creep also dominates in the lower part of the upper mantle, but with a different slip direction Here we show that this high-pressure dislocation creep produces crystal preferred orientations resulting in extremely low seismic anisotropy, consistent with seismological observations below 250 km depth These results raise new questions about the mechanical state of the lower part of the upper mantle and its coupling with layers both above and below