Showing papers on "Slip (materials science) published in 1982"

Scaling laws for large earthquakes: Consequences for physical models

Abstract: It is observed that the mean slip in large earthquakes is linearly proportional to fault length and does not correlate with fault width. This observation is interpreted in the light of the two possible classes of models for large earthquakes: W models, in which stress drop and slip are determined by fault width, and L models, in which these parameters are fundamentally determined by fault length. In the W model interpretation, stress drop systematically increases with L/W , the aspect ratio, and, as a consequence, seismic moment. The correlation of slip with length means that the rupture length is determined by the dynamic stress drop. This conflicts with the observation that the length of large earthquakes is often controlled by adjacent rupture zones of previous earthquakes or by tectonic obstacles. It also conflicts with the observations for small earthquakes that stress drop is nearly constant and does not correlate with source radius over a broad range. In the L model interpretation, the correlation between slip and length means that stress drop is constant, namely about 7.5, 12, and 60 bars for interplate strike-slip, thrust, and Japanese intraplate earthquakes, respectively. L models require that the fault be mechanically unconstrained at the base. W models predict that mean particle velocity increases with fault length, but rise time is constant. L models predict the opposite.

Finite faults and inverse theory with applications to the 1979 Imperial Valley earthquake

Abstract: Using a representation theorem from elastodynamics, subsurface slip on a known fault is formulated as the solution to an inverse problem in which recorded surface ground motion is the data. Two methods of solution are presented: the least-squares method, which minimizes the squared differences between theory and data, and the constrained least-squares method which simultaneously maintains a set of linear inequalities. Instabilities in the solution are effectively eliminated in both methods, and the sensitivity of the solution to small changes in the data is quantitatively stated. The inversion methodology is applied to 77 components of near-field ground acceleration recorded during the 15 October 1979 Imperial Valley earthquake. The faulting is constrained to propagate bilaterally away from the epicenter at an average velocity of 90 per cent of the shear wave speed on a vertical fault plane extending from the surface to 10 km depth. Inequality constraints are used to keep the faulting sequence physically reasonable by maintaining right-lateral motion and positive slip velocity. The preferred solution is stable and provides a good fit to the data; it is also realistic and consistent with observed surface offsets and independent estimates of seismic moment

Source parameters of the 1980 Mammoth Lakes, California, earthquake sequence

Abstract: From the more than 1500 Mammoth Lakes earthquakes recorded on three-component digital seismographs (Spudich et al., 1981), 150 were used in an analysis of the locations, mechanism, and source parameters. A composite fault plane solution of nine earthquakes 3.9 ≤ M ≤ 5.1 defines a right-lateral strike slip mechanism on a steeply dipping nearly east-west plane striking S75°E or left-lateral strike slip on a nearly north-south plane striking N10°E. Vertical cross sections of well-located aftershocks indicate possibly three east-west planes that coincide with the locations of the four largest earthquakes with ML ≥ 6.0. Using the spectral analysis of S waves (Brune, 1970), source parameters for 67 earthquakes were determined. Forty-eight had magnitudes greater than or equal to 3.0. Seismic moments ranged from 9.20×1018 dyn cm to 2.33×1024 dyn cm. Earthquakes with seismic moment greater than about 1.0×1021 dyn cm had nearly constant stress drops (≃ 50 bars); earthquakes with seismic moment less than about 1.0×1021 dyn cm had stress drops that apparently decrease as seismic moment decreases.

Variable rupture mode of the subduction zone along the ecuador-colombia coast

Abstract: Three large earthquakes occurred within the rupture zone of the 1906 Colombia-Ecuador earthquake (M_W = 8.8): in 1942 (M_S = 7.9); 1958 (MS = 7.8); and 1979 (M_S = 7.7). We compared the size and mechanism of these earthquakes by using long-period surface waves, tsunami data, and macroseismic data. The 1979 event is a thrust event with a seismic moment of 2.9 × 10^(28) dyne-cm, and represents subduction of the Nazca plate beneath South America. The rupture length and direction are 230 km and N40°E, respectively. Examination of old seismograms indicates that the 1906 event is also a thrust event which ruptured in the northeast direction. The seismic moment estimated from the tsunami data and the size of the rupture zone is 2 × 10^(29) dyne-cm. The 1942 and 1958 events are much smaller (about 1/5 to 1/10 of the 1979 event in the seismic moment) than the 1979 event. We conclude that the sum of the seismic moments of the 1942, 1958, and 1979 events is only Formula of that of the 1906 event despite the fact that the sequence of the 1942, 1958, and 1979 events ruptured approximately the same segment as the 1906 event. This difference could be explained by an asperity model in which the fault zone is held by a discrete distribution of asperities with weak zones in between. The weak zone normally behaves aseismically, but slips abruptly only when it is driven by failure of the asperities. A small earthquake represents failure of one asperity, and the rupture zone is pinned at both ends by adjacent asperities so that the effective width and the amount of slip are relatively small. A great earthquake represents failure of more than one asperity, and consequently involves much larger width and slip.

Three-dimensional finite difference simulation of fault dynamics: Rectangular faults with fixed rupture velocity

Abstract: We analyze three-dimensional finite difference solutions for a simple shear-crack model of faulting to determine the effects of fault length and width on the earthquake slip function. The fault model is dynamic, with only rupture velocity, fault dimensions, and dynamic stress-drop prescribed. The numerical solutions are accurate for frequencies up to 5 Hz, and are combined with asymptotic results for shear cracks in order to characterize the slip function at higher frequencies. Near the hypocenter, the slip velocity exhibits a square-root singularity whose intensity increases with hypocentral distance. At distances greater than the fault width, w , growth of the velocity intensity ceases, and the slip function becomes nearly invariant with distance along the fault length. Closed-form expressions are developed for the dependence of static slip ( s ∞), slip rise time ( TR ), and slip velocity intensity ( V ) on fault geometry. Along the center line of a long, narrow fault, at hypocentral distances exceeding w , these expressions reduce to s ∞ ≈ w Δτ/μ, TR ≈ 0.5 w/vR , and V ≈ √ w /2 vR Δτ/μ, where Δτ is the dynamic stress drop, μ the shear modulus, and vR the rupture velocity. The numerical results imply that uniform-dislocation kinematic earthquake models in which slip is represented by a ramp time function will underpredict high-frequency ground motion relative to low-frequency ground motion. A further implication of the numerical solutions is that the nature of inelastic processes at the advancing edge of a long fault will depend on fault width, but will be independent of rupture length.

The influence of orientation on the stress rupture properties of nickel-base superalloy single crystals

Abstract: The influence of orientation on the stress rapture properties of MAR-M247 single crystals was studied. Stress rupture tests were performed at 724 MPa and 774 °C where the effect of anisotropy is prominent. The mechanical behavior of the single crystals was rationalized on the basis of the Schmid factors for the operative slip systems and the lattice rotations which the crystals underwent during deformation. The stress rupture lives at 774 °C were found to be greatly influenced by the lattice rotations required to produce intersecting slip, because second-stage creep does not begin until after the onset of intersecting slip. Crystals which required large rotations to become oriented for intersecting slip exhibited a large primary creep strain, a large effective stress level at the onset of steady-state creep, and consequently, a short stress rupture life. Those crystals having orientations within about 25° of the [001] exhibited significantly longer lives when their orientations were closer to the [001]-[011] boundary of the stereographic triangle than to the [001]-[1l 1] boundary, because they required smaller rotations to produce intersecting slip and the onset of second-stage creep. Thus, the direction off the [001], as well as the number of degrees off the [001], has a major influence on the stress rapture lives of single crystals in this temperature regime.

Asymptotic analysis of growing plane strain tensile cracks in elastic-ideally plastic solids

Abstract: An exact asymptotic analysis is presented of the stress and deformation fields near the tip of a quasistatically advancing plane strain tensile crack in an elastic-ideally plastic solid. In contrast to previous approximate analyses, no assumptions which reduce the yield condition, a priori, to the form of constant in-plane principal shear stress near the crack tip are made, and the analysis is valid for general Poisson ratio ν. Specific results are given for ν = 0.3 and 0.5, the latter duplicating solutions in previous work by L.I. Slepyan, Y.-C. Gao and the present authors. The crack tip field is shown to divide into five angular sectors of four different types ; in the order in which these sweep across a point in the vicinity of the advancing crack, they are : two plastic sectors which can be described asymptotically (i.e., as r → 0, where r is distance from the crack tip) in slip-line terminology as ‘constant stress’ and ‘centered fan’ sectors, respectively ; a plastic sector of non-constant stress which cannot be described asymptotically in terms of slip lines; an elastic unloading sector; and a trailing plastic sector of the same type as that directly preceding the elastic sector. Further, these four different sector types constitute the full set of asymptotically possible solutions at the crack tip. As is known from prior work, the plastic strain accumulated by a material point passing through such a moving ‘centered fan’ sector is O(ln r) as r → 0 ; it is proved in the present work that the plastic strain accumulated by a material point passing through the ‘constant stress’ sector ahead of a growing crack must be less singular than In r as r → 0. As suggested also in earlier studies, the rate of increase of opening gap δ at a point currently at a distance r behind, but very near, the crack tip is given for crack advance under contained yielding by δ = αJσ0+β(σ0E)a ln(Rr) where a is crack length, σ0 is tensile yield strength, E is Young's modulus, J is the value of the J-integral taken in surrounding elastic material, and the parameters α and R are undetermined by the asymptotic analysis. The exact solution for ν = 0.3 gives β = 5.462, which agrees very closely with estimates obtained from finite element solutions. An approximate analysis based on use of slip line representations in all plastic sectors is outlined in the Appendix.

Frictional heat and strength loss in some rapid landslides

Abstract: Frictional heat generated within fluid-saturated landslide slip zones can create an increase in pore fluid pressure. This rise in fluid pressure is enhanced by large values of friction coefficient, initial porosity and slide displacement, and by small values of slip zone thickness and compressibility. If maintained under conditions of fast slip, and small wall rock permeability and shear dilatancy, fluid pressure rise can induce rapid frictional strength loss during sliding. Moderate sliding can thereby be converted under certain conditions into catastrophic descent. The rate of temperature rise within a slip zone diminishes as pore fluid pressures rise. Vaporization seems possible only under restricted conditions, and results suggest that large gas pockets are not generally produced. However, rock melting or dissociation may be relatively common under portions of large slides. Frictional heat-induced fluid pressure enhancement is proposed as a possible explanation for the problem of low kinetic friction ...

Deformation of an island arc: Rates of moment release and crustal shortening in intraplate Japan determined from seismicity and Quaternary fault data

Abstract: The historical record of large (M > 6.9) earthquakes and geologically determined rates of slip on Quaternary faults in intraplate Japan (Honshu and Shikoku) are used to estimate the average rate of seismic moment release ( M˜) for the last 400 years and during the late Quaternary, respectively. Values of M˜ estimated from the two data sets are similar in regions where seismic activity is concentrated on land. We interpret this observation to suggest that M˜ in intraplate Japan has been constant during the late Quaternary and is relatively free from secular variation when averaged over periods of several hundreds of years. M˜ in Shikoku may be attributed almost solely to right-lateral slip of the median tectonic line (MTL). The easterly strike of the MTL is consistent with a compressive stress field that trends northwest. Crustal shortening of the Izu Peninsula taken up on a set of strike slip faults that show north by northwest compression is ≈1 mm/yr. Northeast Honshu is characterized by a set of reverse-type faults that trend northerly. Conversion of M˜ in northeast Japan to strain rates suggests that about 5% of the relative plate motion between Japan and the Pacific plate (≈9.7 cm/yr) is accommodated as a permanent east-west shortening (≈5 mm/yr) of northeast Honshu. The predominant deformation in central and western Honshu takes place as slip on a conjugate system of strike slip faults that strike northeast and southeast and show right-lateral and left-lateral motion, respectively. Crustal shortening, resulting from slip on faults, in central and western Honshu is 5 and 0.5 mm/yr, respectively, in an easterly direction. Central and western Honshu are in closest proximity to the Nankai trough, and hence, the stress field in these regions cannot simply be attributed to the accommodation of the relative (northwesterly) convergence of the Philippine Sea plate. The northward impingement of the Izu Peninsula into Honshu may influence stresses in central and western Japan, but a conclusive explanation of the stress field in central and western Honshu remains an enigma.

Evidence for Dislocation Transport of Hydrogen in Aluminum

Abstract: The use of concurrent plastic straining during cathodic charging of equiaxed-grain, high purity 7075 aluminum has provided evidence that dislocations can transport large amounts of hydrogen deep into the interior of the alloy; as a direct consequence of this, highly brittle intergranular fracture ensues This effect is most pronounced for heat treatments that produce a microstructure which allows for planar dislocation arrays and long slip lengths The implications of these findings to the occurrence of hydrogen embrittlement in other alloy systems have been assessed

Strain, tilt, and rotation associated with strong ground motion in the vicinity of earthquake faults

Abstract: In the absence of near-field records of differential ground motion induced by earthquakes, we simulate the time histories of strain, tilt, and rotation in the vicinity of earthquake faults embedded in layered media. We consider the case of both strike-slip and dip-slip fault models and study the effect of different crustal structures. The maximum rotational motion produced by a buried 30-km-long strike-slip fault with slip of 1 m is of the order of 3 × 10 −4 rad while the corresponding rotational velocity is about 1.5 × 10 −3 rad/sec. A simulation of the San Fernando earthquake yields maximum longitudinal strain and tilt a few kilometers from the fault of the order of 8 × 10 −4 and 7 × 10 −4 rad. These values being small compared to the amplitude of ground displacement, the results suggest that most of the damage occurring in earthquakes is caused by translation motions. We also show that strain and tilt are closely related to ground velocity and that the phase velocities associated with strong ground motions are controlled by the rupture velocity and the basement rock shearwave velocity.

Strong-motion modeling of the imperial valley earthquake of 1979

Abstract: Twelve three-component strong-motion displacement records are modeled for the 1979 Imperial Valley earthquake to recover the distribution of slip on the Imperial fault plane. The final model, for which point source responses are calculated by a discrete wavenumber/finite element technique, uses a structure with gradients in material properties rather than layers. The effects of a velocity gradient are investigated by comparing synthetics with a layer-over-a-half-space model using generalized rays. It is shown that a uniform fault rupture model on a rectangular fault plane does not explain the data. The preferred fault model has slip concentrated below 5 km (in the basement material) and between the epicenter (5 km south of the international border) and Highway 80. Within this region, there appears to be two localized areas of larger dislocations; one just north of the border near Bonds Corner and a second under Interstate 8 at Meloland Overpass. A major arrival associated with large amplitude vertical accelerations (up to 1.7 g) is identified in the El Centro array records. This arrival has an S-P time of approximately 2.3 sec at many of the array stations and is modeled as originating from a localized source 8 km to the south of the array. The moment is estimated to be 5.0 × 10^(25) dyne-cm from the strong-motion records, which is consistent with teleseismic body-wave estimates. The preferred fault model is strike-slip with a 90° dip. The average strike is 143°. However to explain vertical waveforms near the fault trace, a corrugated or wiggly fault plane is introduced. The average rupture velocity is in the range 2.5 to 2.7 km-sec (0.8 to 0.9 times the basement shear-wave velocity). The preferred model has unilateral rupture propagation to the north, although the data would allow a small amount of propagation to the south. The estimated stress drop for the entire fault plane is only 5 to 10 bars; however, the stress drop over the more localized sources is about 200 bars. The fault model is consistent with the pattern of seismicity and observations of aseismic creep in the Imperial Valley and suggests that the southern half of the Imperial fault acts as a locked section which breaks periodically.

Number and orientation of fault sets in the field and in experiments

Abstract: Arrays of faults that can be grouped into multiple sets occur in the Entrada and Navajo Sandstones in southeastern Utah. The faults form a network that usually has a rhombohedral pattern both in map and cross-sectional views. Similar fault patterns were formed experimentally in cubic samples of sandstone, limestone, and granite deformed to failure with a polyaxial apparatus. The faulting theory of Anderson fails to explain both the number and the orientation of the faults observed in this study. However, the number and orientation of faults can be understood in terms of a theory of deformation of rock solely by slip along planes.

Grain boundary strengthening in strongly textured magnesium produced by hot rolling

Abstract: The grain size dependence of the yield stress in hot rolled 99.87 pct magnesium sheets and rods was measured in the temperature range 77 K to 420 K. Hot rolling produced strong basal textures and, for a given grain size, the hot rolled material has a higher strength than extruded material. The yield strength-grain size relation in the above temperature range follows the Hall-Petch equation, and the temperature dependencies of the Hall-Petch constants σ0 and k are in support of the theory of Armstrong for hcp metals that the intercept σ0 is related to the critical resolved shear stress (CRSS) for basal slip (easy slip) and the slope k is related to the CRSS for prismatic slip (difficult slip) occurring near the grain boundaries. In the hot rolled magnesium, σ0 is larger and k is smaller than in extruded material, observations which are shown to result from strong unfavorable basal and favorable {1010} textures, respectively. Texture affects the Hall-Petch constants through its effect on the orientation factors relating them to the CRSS for the individual slip systems controlling them.

Perspectives in the mechanics of elastoplastic crystals

Abstract: The mechanics of metal crystals at finite strain is reappraised, when crystallographic slip is solely responsible for inelastic deformation. Arbitrary work-conjugate variables are used throughout, together with a slip measure that is unaffected by lattice distortion. The pioneering analysis of R. Hill and J.R. Rice (J. Mech. Phys. Solids20, 401. 1972) is amplified and in part recast. The existence of a plastic potential is proved from a new standpoint, which is believed to be more readily understandable and direct. The effect of lattice strain on slip-system geometry is expressed via an influence tensor ; this has the effect of linking apparently disparate elements of the theory. Subsequently the principal formulae are made explicit in terms of Green's measure of strain, supplemented by equations of transformation to other variables. The unique yield criterion that confers a normality structure is formulated in terms of a generalized Schmid stress, and associated rules of hardening in multislip are detailed. The available experimental data are briefly reviewed, more especially in relation to the ‘simple theory’ of hardening proposed by K.S. Havner and A.H. Shalaby (Proc. R. Soc.A358, 47. 1977).

Aftershocks of the Coyote Lake, California, earthquake of August 6, 1979: A detailed study

Abstract: Aftershock hypocenters and focal mechanism solutions for the Coyote Lake, California, earthquake reveal a geometrically complex fault structure, consisting of multiple slip surfaces. The faulting surface principally consists of two right stepping en echelon, northwest trending, partially overlapping, nearly vertical sheets and is similar in geometry to a slip surface inferred for the 1966 Parkfield, California, earthquake. The overlap occurs near a prominent bend in the surface trace of the Calaveras fault at San Felipe Lake. Slip during the main rupture, as inferred from the distribution of early aftershocks, appears to have been confined to a 14-km portion of the northeastern sheet between 4- and 10-km depth. Focal mechanisms and the hypocentral distribution of aftershocks suggest that the main rupture surface itself is geometrically complex, with left stepping imbricate structure. Seismic shear displacement on the southwestern slip surface commenced some 5 hours after the mainshock. Aftershocks in this zone define a single vertical plane 8 km long between 3- and 7-km depth. Within the overlap zone between the two main slip surfaces, the average strike of aftershock nodal planes is significantly rotated clockwise relative to the strike of the fault zone, in close agreement with the stress perturbations predicted by crack interaction models. Aftershock activity in the overlap zone is not associated with a simple dislocation surface. Space and time clustering within the entire aftershock set suggest an alternation of seismic displacement between the component parts of the fault zone. This alternation is consistent with local stress perturbations predicted by crack interaction models. We conclude that the fault structure is geometrically complex and that the displacements that occur on its component surfaces during the aftershock process dynamically interact by generating perturbations in the local stress field which, in turn, control the displacements. Table 5 is available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document J82-006; $1.00. Payment must accompany order.

Lithospheric flexure at fracture zones

Abstract: Studies attempting to demonstrate that lithospheric flexure occurs across the Pioneer and Mendocino fracture zones, and that the flexural topography is a topographic expression at these fracture zones, are presented. The flexure is modelled and compared with predicted depths with five bathymetric profiles which cross the two fracture zones at different ages. The model uses a thin elastic plate overlying an incompressible fluid half-space, and incorporates a temperature-dependent effective elastic thickness. Several conclusions were derived from this study. First, it is found that no significant slip on the fossil fault planes of the Mendocino and Pioneer fracture zones exists. In addition, the flexural amplitude is determined to increase with age. Finally, it is concluded that there is elastic coupling between the Mendocino and Pioneer fracture zones since the separation is less than a flexural wavelength.

The Fabric of Polycrystalline Ice Deformed in Simple Shear: Experiments in Torsion, Natural Deformation and Geometrical Interpretation

Abstract: Three cylinders of artificial ice have been deformed in torsion at about –10℃ up to finite shear strains γ of 0.6, 0.95 and 2. The initial random lattice orientation rapidly evolves into a bimodal distribution of the basal slip planes as already observed by Kamb (1972) and Duval (1981) for low-strains experiments near the melting point. For the γ = 0.6 and 0.95 experiments, one family of grains (> 50%) corresponds to basal planes tending to parallel the imposed shear plane; the basal planes of the other family make a broader maximum at about 60° from the shear plane. The direction of minimum concentration between the two populations approximately corresponds to the flattening plane or to the elongation direction of the strain ellipsoid. With increasing strain (γ = 2) the second submaximum vanishes and only the principal maximum parallel to the shear plane remains. This evolution is conformable with the data of Hudleston (1977) in a natural shear zone in glacial ice; it also compares remarkably well with Etchecopar's (1977) geometrical computer model of simple shear in the same range of γ values. Single slip on the basal plane with no preferential slip direction in that plane can explain the analogy between fabrics in ice deformed in plane strain and fabrics obtained from the two-dimensional computer model.The bimodal distribution reflects predominant slip on the basal plane; the progressively increasing heterogeneous strain enhances internal distorsion, rigid body rotation and recrystallization of grains unfavorably oriented for further slip, leading to the unimodal distribution. The adequacy of fabric analyses to infer the strain regime and the sense of shear in plastically deformed rocks is strengthened.

Long-term fault creep observations in central California

Abstract: The U.S. Geological Survey (USGS) has been monitoring aseismic fault slip in central California for more than 10 years as part of an earthquake prediction experiment. Since 1968, the USGS creep network has grown from one creep meter at the Cienega Winery south of Hollister to a 44-station network that stretches from Hayward, east of San Francisco Bay, to Palmdale in southern California. In general, the long-term slip pattern is most variable on sections of the faults where several magnitude 4 and larger earthquakes occurred during the recording period (e.g., Calaveras fault near Hollister and San Andreas fault between San Juan Bautista and Bear Valley). These fault sections are the most difficult to characterize with a single long-term slip rate. In contrast, sections of the faults that are seismically relatively quiet (e.g., San Andreas fault between Bear Valley and Parkfield) produce the steadiest creep records and are easiest to fit with a single long-term slip rate. Appendix is available with entire article on microfiche. Order from the American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document J82-004; $1.00. Payment must accompany order.

Analysis of near-source static and dynamic measurements from the 1979 Imperial Valley earthquake

Abstract: Gross features of the rupture mechanism of the 1979 Imperial Valley earthquake ( ML = 6.6) are inferred from qualitative analysis of near-source ground motion data and observed surface rupture. A lower bound on the event's seismic moment of 2.5 × 1025 dyne-cm is obtained by assuming that the average slip over the whole fault plane equals the average surface rupture, 40.5 cm. Far-field estimates of moment suggest an average slip over the fault plane of 105 cm, from which a static stress drop of 11 bars is obtained. An alternative slip model, consistent with the far-field moment, has 40.5 cm of slip in the upper 5 km of the fault and 120 cm of slip in the lower 5 km. This model suggests a static stress drop of 39 bars. From the lower estimate of 11 bars, an average strain drop of 32 µstrain is derived. This strain drop is four times greater than the strain that could have accumulated since the 1940 El Centro earthquake based on measured strain rates for the region. Hence, a major portion of the strain released in the 1979 main shock had been accumulated prior to 1940. Unusually large amplitude (500 to 600 cm/sec2) vertical accelerations were recorded at stations E05, E06, E07, E08, EDA of the EI Centro array, and the five stations of the differential array near EDA. Although the peak acceleration of 1705 cm/sec2 at E06 is probably amplified by a factor of 3 due to local site conditions, these large amplitude vertical accelerations are unusual in that they are evident on only a few stations, all of which are near the fault trace and at about the same epicentral range. Two possible explanations are considered: first, that they are due to a direct P wave generated from a region about 17 km north of the hypocenter, or second, that they are due to a PP phase that is unusually strong in the Imperial Valley due to the large P -wave velocity gradient in the upper 5 km of the Imperial Valley. Based on the distribution of both the horizontal and vertical offsets, it is likely that the rupture went beyond stations E06 and E07 during the main shock. By exploiting the antisymmetry of the parallel components of particle velocity between E06 and E07 and by examining polarization diagrams of the particle velocity at E06 and E07, an average rupture velocity in the basement of 2.5 to 2.6 km/sec between the hypocenter and station E06 is obtained. In addition, several lines of evidence suggest that the Imperial fault dips about 75° to the NE.

Boundary layer flow of a dusty fluid over a semi-infinite flat plate

Abstract: Both the drag force due to slip and the transverse force due to slip-shear have been considered in boundary layer equations. The solution has been found in a power series of non-dimensionalx, x being the distance in the down-stream direction. Solutions for high slip region and small slip region characterised byx≪1 andx≫1 respectively, have been found separately. In the high slip region the effect of increase in concentration parameter α of the dust particles is to increase the magnitude of the longitudinal fluid phase velocityu. Also the magnitude of the longitudinal particle slip velocityup-u is becoming maximum on the plate and decreasing along the plate withx. The transverse particle velocityvp is independent of α but it is directly proportional to β, the transverse force coefficient. An interesting result is thatvp is assuming small positive value on the plate. The transverse force has taken an important role in migration of particles away from the plate. In the small slip region the flow of dust particles is mainly governed by the fluid-phase. The effect of α on the flow field in this region is to decrease the boundary layer thickness. In this region the particles are having some tendency to accumulate near the plate. Lastly, it has been found that the shearing stress, skinfriction and the dimensionless drag-coefficient on the plate increase with increase of α.

Deformation modes of the α-phase of ti-6al-4v as a function of oxygen concentration and aging temperature

Abstract: The tensile properties of lamellar Ti-6A1-4V and the deformation modes of the α-phase of this alloy were investigated as a function of oxygen concentration and as a function of aging heat treatment. Oxygen affects the mechanical properties through microstructural modifications which depend on the choice of aging parameters. The variations in Young's modulus, yield strength, ultimate tensile strength, and ductility, are correlated with α/β volume ratio and with α-deformation characteristics. Homogeneityvs inhomogeneity of slip, change of the predominant slip modes from prismatic slip to fine planar slip on pyramidal planes, and the occurrence of Ti3Al precipitates influence the deformation behavior of the α-phase and thus influence the mechanical properties of the alloy. The deformation behaviors of the lesser β-phase regions were not investigated, and only speculations can be made on the extent of their influence on the alloy's mechanical properties.

Pressure solution lithification as a mechanism for the stick‐slip behavior of faults

Abstract: Many major faults, including a large fraction of the San Andreas, appear to be virtually quiescent between great earthquakes. The locked sections of the San Andreas near San Francisco and Los Angeles have little or no seismic activity on the primary fault trace, although secondary faults may be active. Stick-slip behavior on a fault can be explained in terms of a static coefficient of friction, which is larger than the dynamic or sliding coefficient. In this paper we propose a modification of the friction hypothesis in which chemical lithification (cementation) occurs on the fault between earthquakes. As the stress on the fault increases it becomes large enough to break the cemented bonds between particles causing slip on the fault. We treat this problem quantitatively, assuming that pressure solution is responsible for the cementation. An advantage of this model is that the hydrostatic pressure approaches the lithostatic pressure during cementation so that low fault strengths are predicted.