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Sample records for tube-in-tube slip joint

  1. Avoiding leakage flow-induced vibration by a tube-in-tube slip joint

    SciTech Connect

    Mulcahy, T.M.

    1984-10-01

    Parameters and operating conditions (a stability map) were determined for which a specific slip-joint design did not cause self-excited lateral vibration of the two cantilevered, telescoping tubes forming the joint. The joint design featured a localized annular constriction. Flowrate, modal damping, tube engagement length, and eccentric positioning were among the parameters tested. Interestingly, all self-excited vibrations could be avoided by following a simple design rule: place constrictions only at the downstream end of the annular region between the tubes. Also, overall modal damping decreased with increased flowrate, at least initially, for upstream constrictions while the damping increased for downstream constrictions.

  2. Conceptual optimization using genetic algorithms for tube in tube structures

    SciTech Connect

    Pârv, Bianca Roxana; Hulea, Radu; Mojolic, Cristian

    2015-03-10

    The purpose of this article is to optimize the tube in tube structural systems for tall buildings under the horizontal wind loads. It is well-known that the horizontal wind loads is the main criteria when choosing the structural system, the types and the dimensions of structural elements in the majority of tall buildings. Thus, the structural response of tall buildings under the horizontal wind loads will be analyzed for 40 story buildings and a total height of 120 meters; the horizontal dimensions will be 30m × 30m for the first two optimization problems and 15m × 15m for the third. The optimization problems will have the following as objective function the cross section area, as restrictions the displacement of the building< the admissible displacement (H/500), and as variables the cross section dimensions of the structural elements.

  3. EPOXIDATION OF SMALL ORGANIC MOLECULES USING A SPINNING TUBE-IN-TUBE REACTOR

    EPA Science Inventory

    The commodity-scale epoxidation of several organic molecules has been carried out using a Spinning Tube-in-Tube (STTr) reactor (manufactured by Kreido Laboratories). This reactor, which embodies and facilitates the use of Green Chemistry principles and Process Intensification, a...

  4. PROGRESS IN PROCESS INTENSIFICATION: SYNTHESIS OF IMIDAZOLE DERIVATIVES USING A SPINNING TUBE-IN-TUBE REACTOR

    EPA Science Inventory

    The high purity, high throughput synthesis of a number of imidazole derivatives using a spinning tube-in-tube reactor (STT®, Kreido Laboratories, Camarillo California) has been carried out. The STT® reactor allows the high throughput production of high purity imidazole derivativ...

  5. PROGRESS IN PROCESS INTENSIFICATION: SYNTHESIS OF IMIDAZOLE DERIVATIVES USING A SPINNING TUBE-IN-TUBE REACTOR

    EPA Science Inventory

    The high purity, high throughput synthesis of a number of imidazole derivatives using a spinning tube-in-tube reactor (STT, Kreido Laboratories, Camarillo California) has been carried out. The STT reactor allows the high throughput production of high purity imidazole derivativ...

  6. Hysteresis modeling of clamp band joint with macro-slip

    NASA Astrophysics Data System (ADS)

    Qin, Zhaoye; Cui, Delin; Yan, Shaoze; Chu, Fulei

    2016-01-01

    Clamp band joints are commonly used to connect spacecrafts with launch vehicles. Due to the frictional slippage between the joint components, hysteresis behavior might occur at joint interfaces under cyclic loading. The joint hysteresis will bring friction damping into the launching systems. In this paper, a closed-form hysteresis model for the clamp band joint is developed based on theoretical and numerical analyses of the interactions of the joint components. Then, the hysteresis model is applied to investigating the dynamic response of a payload fastened by the clamp band joint, where the nonlinearity and friction damping effects of the joint is evaluated. The proposed analytical model, which is validated by both finite element analyses and quasi-static experiments, has a simple form with sound accuracy and can be incorporated into the dynamic models of launching systems conveniently.

  7. Performance of multi tubes in tube helically coiled as a compact heat exchanger

    NASA Astrophysics Data System (ADS)

    Nada, S. A.; El Shaer, W. G.; Huzayyin, A. S.

    2014-12-01

    Multi tubes in tube helically coiled heat exchanger is proposed as a compact heat exchanger. Effects of heat exchanger geometric parameters and fluid flow parameters; namely number of inner tubes, annulus hydraulic diameter, Reynolds numbers and input heat flux, on performance of the heat exchanger are experimentally investigated. Different coils with different numbers of inner tubes, namely 1, 3, 4 and 5 tubes, were tested. Results showed that coils with 3 inner tubes have higher values of heat transfer coefficient and compactness parameter (bar{h} Ah ). Pressure drop increases with increasing both of Reynolds number and number of inner tubes. Correlations of average Nusselt number were deduced from experimental data in terms of Reynolds number, Prandtl number, Number of inner coils tubes and coil hydraulic diameter. Correlations prediction was compared with experimental data and the comparison was fair enough.

  8. COMMODITY SCALE SYNTHESIS OF 1-METHYLIMIDAZOLE BASED IONIC LIQUIDS USING A SPINNING TUBE-IN-TUBE REACTOR

    EPA Science Inventory

    The continuous large-scale preparation of several 1-methylimidazole based ionic liquids was carried out using a Spinning Tube-in-Tube (STT) reactor (manufactured by Kreido Laboratories). This reactor, which embodies and facilitates the use of Green Chemistry principles and Proce...

  9. Role of individual lower limb joints in reactive stability control following a novel slip in gait

    PubMed Central

    Yang, Feng; Pai, Yi-Chung

    2010-01-01

    Instability after slip onset is a key precursor leading to subsequent falls during gait. The purpose of this study was to determine the impact of reactive muscular response from individual lower limb joints on regaining stability control and impeding a novel, unannounced slip during the ensuing single-stance phase. Ten young adults resultant moments at three lower limb joints of both limbs, initially derived by an inverse-dynamics approach from empirical data, were optimized to accurately reproduce the original motion before being applied as input to the control variables of their individualized forward-dynamics model. Systematic alteration of the moments of each joint caused corresponding changes in the displacement and velocity of the center of mass (COM) and base of support (BOS) (i.e., their state variables, xCOM, ?COM, xBOS, ?BOS), and in the COM stability. The model simulation revealed that these joints had little influence on ?COM, but had substantial impact on ?BOS reduction, leading to improving the COM stability, mostly from knee flexors, followed by hip extensors, of the slipping limb. Per unit reactive increase in normalized knee flexor or hip extensor moments and per unit reactive reduction in commonly observed plantar-flexor moments could lead to as much as 57.72 10.46 or 22.33 5.55 and 13.09 2.27 units of reduction in normalized ?BOS, respectively. In contrast, such influence was negligible from the swing limb during this period, irrespective of individual variability. PMID:19896133

  10. A comparative study on the lithium-ion storage performances of carbon nanotubes and tube-in-tube carbon nanotubes.

    PubMed

    Xu, Yi-Jun; Liu, Xi; Cui, Guanglei; Zhu, Bo; Weinberg, Gisela; Schlögl, Robert; Maier, Joachim; Su, Dang Sheng

    2010-03-22

    A comparative study of the electrochemical performances of carbon nanotubes and tube-in-tube carbon nanotubes reveals a dependence effect of lithium-ion storage behavior on the detailed nanostructure of carbon nanotubes. In particular, the impurity that graphitic particles or graphene fragments inherently present in carbon nanotubes plays a crucial role in the lithium-ion storage capacity of the carbon nanotubes. Compared to acid-washed carbon nanotubes, the assembly of graphitic impurity fragments in the tube-in-tube structures hinders lithium-ion diffusion, thus drastically decreasing the rate performance of lithium-ion storage. Significantly, our results indicate that the lithium-ion storage capacity of carbon nanotubes as anode electrodes can be improved or controlled by optimizing the microstructure composition of impurity graphitic nanoparticles or graphene fragments in the matrix of the carbon nanotubes. PMID:20029929

  11. Erythorbic acid promoted formation of CdS QDs in a tube-in-tube micro-channel reactor

    SciTech Connect

    Liang, Yan; Tan, Jiawei; Wang, Jiexin; Chen, Jianfeng; Sun, Baochang; Shao, Lei

    2014-12-15

    Erythorbic acid assistant synthesis of CdS quantum dots (QDs) was conducted by homogeneous mixing of two continuous liquids in a high-throughput microporous tube-in-tube micro-channel reactor (MTMCR) at room temperature. The effects of the micropore size of the MTMCR, liquid flow rate, mixing time and reactant concentration on the size and size distribution of CdS QDs were investigated. It was found that the size and size distribution of CdS QDs could be tuned in the MTMCR. A combination of erythorbic acid promoted formation technique with the MTMCR may be a promising pathway for controllable mass production of QDs.

  12. Deep coseismic slip of the 2008 Wenchuan earthquake inferred from joint inversion of fault stress changes and GPS surface displacements

    NASA Astrophysics Data System (ADS)

    Chen, Qiang; Yang, Yinghui; Luo, Rong; Liu, Guoxiang; Zhang, Kui

    2015-07-01

    Geodetic data are increasingly being used to infer coseismic slip distribution due to its advantages of wide coverage and high accuracy. However, it is difficult to obtain a comprehensive rupture pattern at depth when a source model is only constrained by geodetic surface deformation. In this study, a joint inversion approach incorporating stress changes and GPS surface displacements is explored and applied to characterize the fault slip of the 2008 Mw 7.9 Wenchuan earthquake, China. The earthquake data for the 20-year period before the main quake, which are collected from the background seismicity catalogues, and one month of aftershock data are statistically analysed to determine the fault stress changes based on the Dieterich model. The coseismic surface deformation measurements from 158 GPS surveying sites are jointly used to constrain the solution. Our preferred rupture model reveals four high-slip concentrations on the Yingxiu-Beichuan fault and one on the subparallel PengGuan fault. The spatial distribution suggests that the coseismic slip occurs not only above the hypocentre but also with a significant thrusting motion, with a mean slip of 8.5 m and a maximum of 9.7 m at a depth of 10-16 km. A significant high-slip concentration is found for the first time in this study. The coseismic faulting extends toward ∼16 km southwest of the Yingxiu-Beichuan fault and has a dextral strike-slip with a mean displacement of 4.8 m at a depth of 7-19 km. The joint inversion model misfits (GPS: 1.7 cm, stress change: 0.02 MPa) exhibit a good compatibility between the two types of datasets. The derived slip model, which has an improved resolution at depth, explains 98% of the coseismic surface displacements and 93% of the fault stress changes.

  13. In situ modifying of carbon tube-in-tube nanostructures with highly active Fe(2)O(3) nanoparticles.

    PubMed

    Bai, Shuli; Zhao, Jianghong; Du, Guixiang; Zheng, Jianfeng; Zhu, Zhenping

    2008-05-21

    A novel in situ method based on a liquid membrane templated self-assembly process is employed to modify carbon tube-in-tube nanostructures (TTCNTs) with Fe(2)O(3) nanoparticles. The as-obtained Fe(2)O(3) modified TTCNTs (Fe(2)O(3)/TTCNTs) nanocomposites are well constructed and the Fe(2)O(3) nanoparticles are well dispersed and decorated on the outer, inner and intramolecular surfaces of TTCNTs. In addition, the Fe(2)O(3)/TTCNTs nanocomposites are employed as catalysts for selective catalytic reduction (SCR) of NO with NH(3) and show high SCR catalytic activity, indicating that the novel multiple intramolecular channels and unique surface chemistry of the TTCNTs should play an important role in improving the properties of TTCNTs. PMID:21825743

  14. Synthesis and characterization of a novel tube-in-tube nanostructured PPy/MnO{sub 2}/CNTs composite for supercapacitor

    SciTech Connect

    Li, Juan; Beijing National Laboratory for Molecular Sciences , State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 ; Que, Tingli; Huang, Jianbin; Beijing National Laboratory for Molecular Sciences , State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871

    2013-02-15

    Graphical abstract: A novel tube-in-tube nanostructured PPy/MnO{sub 2}/CNTs composite have been successfully fabricated. Its inner tubules are CNTs and the outer tubules are template-synthesized PPy. Most MnO{sub 2} nanoparticles are sandwiched between the inner and outer wall, some relatively large particles are also latched onto the outside wall of the PPy tube. The composite yields a good electrochemical reversibility through 1000 cycles’ cyclic voltammogram (CV) test and galvanostatic charge–discharge experiments at different current densities. Display Omitted Highlights: ► We fabricate a ternary organic–inorganic complex of PPy/MnO{sub 2}/CNTs composite. ► We characterize its morphological structures and properties by several techniques. ► The composite possesses the typical tube-in-tube nanostructures. ► Most MnO{sub 2} nanoparticles are sandwiched between the inner CNTs and outer PPy wall. ► The composite has good electrochemical reversibility for supercapacitor. -- Abstract: Ternary organic–inorganic complex of polypyrrole/manganese dioxide/carbon nanotubes (PPy/MnO{sub 2}/CNTs) composite was prepared by in situ chemical oxidation polymerization of pyrrole in the host of inorganic matrix of MnO{sub 2} and CNTs, using complex of methyl orange (MO)/FeCl{sub 3} was used as a reactive self-degraded soft-template. The morphological structures of the composite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopic (HRTEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD), respectively. All the results indicate that the PPy/MnO{sub 2}/CNTs composite possesses the typical tube-in-tube nanostructures: the inner tubules are CNTs and the outer tubules are template-synthesized PPy. MnO{sub 2} nanoparticles may either sandwich the space between the inner and outer tubules or directly latch onto the wall of the PPy tubes. The composite yields a good electrochemical reversibility through 1000 cycles’ cyclic voltammogram (CV) test in the potential range of −0.6 to 0.4 V and its specific capacitance was up to 402.7 F g{sup −1} at a current density of 1 A g{sup −1} in galvanostatic charge–discharge experiment.

  15. Experimental investigation of the dynamic installation of a slip joint connection between the monopile and tower of an offshore wind turbine

    NASA Astrophysics Data System (ADS)

    Segeren, M. L. A.; Hermans, K. W.

    2014-06-01

    The failure of the traditional grouted connections of offshore wind turbines has led to the investigation of alternatives that provide a connection between the foundation pile and the turbine tower. An alternative to the traditional joint is a steel-to-steel connection also called a slip joint. To ensure a proper fit of the slip joint a dynamic installation of the joint is proposed. In this contribution, the effectiveness of harmonic excitation as an installation procedure is experimentally investigated using a 1:10 scaled model of the joint. During the dynamic installation test the applied static load, settlements and dynamic response of the joint are monitored using respectively load cells, taut wires and strain gauges placed both inside and outside the conical surfaces. The results show that settlement occurs only when applying a harmonic load at specific forcing frequencies. The settlement stabilizes to a certain level for each of the specific frequencies, indicating that a controlled way of installation is possible. The results show that it is essential to vibrate at specific frequencies and that a larger amplitude of the harmonic force does not automatically lead to additional settlement.

  16. Second free radial forearm flap for urethral reconstruction after partial flap necrosis of tube-in-tube phalloplasty with radial forearm flap: a report of two cases.

    PubMed

    Tchang, Laurent A H; Largo, René D; Babst, Doris; Wettstein, Reto; Haug, Martin D; Kalbermatten, Daniel F; Schaefer, Dirk J

    2014-01-01

    We present a salvage procedure to reconstruct the neo-urethra after partial flap necrosis occurring in free radial forearm flap (RFF) phalloplasty for sex reassignment surgery. Two cases of tube-in-tube phalloplasty using a free sensate RFF are described in which partial flap necrosis occurred involving the complete length of the neo-urethra and a strip of the outer lining of the neo-phallus. Neo-urethra-reconstruction was performed with a second RFF from the contralateral side providing well-vascularized tissue. No flap-related complications were observed. Twelve months postoperatively, both patients were able to void while standing. A satisfactory aesthetic appearance of the neo-phallus could be preserved with an excellent tactile and erogenous sensitivity. Using this technique, we successfully salvaged the neo-urethra and reconstructed the outer lining of the neo-phallus PMID:24038531

  17. Triggered slip on a back reverse fault in the Mw6.8 2013 Lushan, China earthquake revealed by joint inversion of local strong motion accelerograms and geodetic measurements

    NASA Astrophysics Data System (ADS)

    Zhang, Guohong; Hetland, Eric A.; Shan, Xinjian; Vallée, Martin; Liu, Yunhua; Zhang, Yingfeng; Qu, Chunyan

    2016-03-01

    The 2013 Mw6.8 Lushan, China earthquake occurred in the southwestern end of the Longmenshan fault zone. We jointly invert local strong motion data and geodetic measurements of coseismic surface deformation, including GPS and InSAR, to obtain a robust model of the rupture process of the 2013 Lushan earthquake. Our joint inversion best model involves the rupture of two opposing faults during the Lushan earthquake, a main fault and a secondary fault. It is only when the secondary fault is included that both the GPS and InSAR measurements are fit along with the near-field strong motion. Over 75% of the computed moment was released in slip on the main fault segment, a northwest dipping, listric thrust fault, with buried thrust and dextral strike-slip at hypocenter depths, and with only minor slip closer to the surface. The secondary fault mainly involved oblique thrust slip or pure dextral strike-slip at shallower depths, and accounts for just under 24% of the moment released in the Lushan earthquake. Coulomb stress changes of about 0.5 MPa on the secondary fault segment at the time coseismic slip initiated on that fault indicate that slip was likely triggered by the coseismic slip on the main blind thrust fault. Our coseismic slip model is consistent with a sub-horizontal and east-west to southeast-northwest trending most compressive stress. Our inferred coseismic slip model is also consistent with previous GPS derived models of strain accumulation on the Longmenshan fault system.

  18. Seismic and Aseismic Slip on the San-Jacinto Fault Near Anza, CA, from Joint Analysis of Strain and Aftershock Data

    NASA Astrophysics Data System (ADS)

    Inbal, A.; Avouac, J. P.; Ampuero, J. P.

    2014-12-01

    The San-Jacinto Fault (SJF) is the most active fault in southern California, which together with the southern San-Andreas Fault accommodates a large fraction of the motion across the plate boundary. Seismicity along the SJF is distributed over several fault segments with distinct spatio-temporal characteristics. One of these segments, known as the Anza seismic gap, is a 25 km long strand almost devoid of seismicity. In recent years, four M4-5 events occurred SE of the gap. Despite their moderate magnitudes, these earthquakes triggered rich aftershock sequences and pronounced afterslip that lasted for several weeks, and was well captured by nearby PBO borehole strain meters. A similar transient was remotely triggered by the 2010 El Mayor-Cucapah earthquake. Geodetic and seismic observations following a local M5.4 mainshock indicate that afterslip propagated unilaterally towards the NW at speed of about 5 km/day. We infer the distribution of slip via a joint inversion of the aftershock and strain data. Our approach is based on Dieterich's (1994) model relating the evolution of seismicity rate to applied stresses, within the framework of rate-and-state friction. This approach provides resolution power at depths inaccessible to the surface geodetic network. Moreover, it allows us to gain important insights onto the fault mechanical properties. We apply this inversion scheme to episodes that occurred during 2010. Remarkably, we find that the cumulative moment released post-seismically during the locally triggered transient is 5-10 times larger than the moment of the mainshock. We show that the data favour a model in which deep slip transients, which may develop due to local or remote earthquakes, occur on a weak, close-to-velocity-neutral fault. The transients increase the stress along the Anza gap, and trigger earthquakes outside it through static stress transfer.

  19. Fault Slip Rates in the Western U.S. From a Joint Fit to Geologic Offsets, GPS Velocities, and Stress Directions

    NASA Astrophysics Data System (ADS)

    Bird, P.

    2008-12-01

    I merge the SCEC, WGCEP, PBO, & WSM community datasets in neotectonic deformation models for the western US. In California I use: (1) fault traces, dips, and slip senses from WGCEP Fault Models 2.1 or 2.2; (2) fault offset rates and uncertainties obtained by Bird [2007, Geosphere, 3(6)] from offsets in the USGS Paleosites Database; (3) a 2006 California joint GPS solution for interseismic benchmark velocities by Shen, King, Wang, and Agnew; and (4) stress-direction indicators from World Stress Map. In other western United States I use: (5) my collection of fault traces and offset rates as documented in Bird [2007]; and (6) selected GPS velocities from PBO. All are fit by weighted least-squares in kinematic F-E program NeoKinema. As described previously, this program (a) interpolates stress directions to determine their uncertainties, (b) attempts to minimize off-fault strain-rates and align them with stress, and (c) iteratively corrects geodetic velocities from short-term to long-term using local dislocation-in-halfspace corrections. All datasets can be fit at a common level of 1.8 standard errors (RMS or N2 norm). If "acceptable" fit is defined as N2 < 2 for all datasets, there is a range of acceptable models, defining a range of long-term fault slip rates and (anelastic) continuum strain-rates. In preferred model GCN2008060, the mean long-term slip rates for trains of the San Andreas fault are (SE to NW): Coachella 15 mm/a, San Gorgonio Pass-Garnet Hill 6, San Bernardino South 12, San Bernardino North 19, Mojave South 16, Mojave North 17, Big Bend 15, Carrizo 25, Cholame 26, Parkfield 31, Creeping 29, Santa Cruz Mt. 23, Peninsula 18, North Coast 16, and Offshore 9 mm/a. Up to Cajon Pass, these all agree with 2007 WGCEP [2008], but my Mojave N and S and Big Bend rates are much slower, my Carrizo and Cholame rates are marginally slower, and my North Coast and Offshore rates are much slower. These differences are due to greater amounts of permanent (anelastic) straining off the mapped fault traces in NeoKinema, relative to the elastic-microplate models of 2007 WGCEP [2008]. I have not been able to lower the RMS continuum strain rate in these models below 5×10-16 /s (=1.6%/Ma). Such distributed straining results from gaps and geometric incompatibilities in the fault network and from geologic/geodetic discrepancies. This straining probably also occurs on faults (which are not part of WGCEP Fault Models), and it probably also produces earthquakes.

  20. Biomechanics of slips.

    PubMed

    Redfern, M S; Cham, R; Gielo-Perczak, K; Grönqvist, R; Hirvonen, M; Lanshammar, H; Marpet, M; Pai, C Y; Powers, C

    2001-10-20

    The biomechanics of slips are an important component in the prevention of fall-related injuries. The purpose of this paper is to review the available literature on the biomechanics of gait relevant to slips. This knowledge can be used to develop slip resistance testing methodologies and to determine critical differences in human behaviour between slips leading to recovery and those resulting in falls. Ground reaction forces at the shoe-floor interface have been extensively studied and are probably the most critical biomechanical factor in slips. The ratio of the shear to normal foot forces generated during gait, known as the required coefficient of friction (RCOF) during normal locomotion on dry surfaces or 'friction used/achievable' during slips, has been one biomechanical variable most closely associated with the measured frictional properties of the shoe/floor interface (usually the coefficient of friction or COF). Other biomechanical factors that also play an important role are the kinematics of the foot at heel contact and human responses to slipping perturbations, often evident in the moments generated at the lower extremity joints and postural adaptations. In addition, it must be realized that the biomechanics are dependent upon the capabilities of the postural control system, the mental set of the individual, and the perception of the environment, particularly, the danger of slipping. The focus of this paper is to review what is known regarding the kinematics and kinetics of walking on surfaces under a variety of environmental conditions. Finally, we discuss future biomechanical research needs to help to improve walkway-friction measurements and safety. PMID:11794762

  1. Joint Determination of Slip and Stress Drop in a Bayesian Inversion Approach: A Case Study for the 2010 M8.8 Maule Earthquake

    NASA Astrophysics Data System (ADS)

    Wang, Lifeng; Zöller, Gert; Hainzl, Sebastian

    2015-02-01

    Stress drop is a key factor in earthquake mechanics and engineering seismology. However, stress drop calculations based on fault slip can be significantly biased, particularly due to subjectively determined smoothing conditions in the traditional least-square slip inversion. In this study, we introduce a mechanically constrained Bayesian approach to simultaneously invert for fault slip and stress drop based on geodetic measurements. A Gaussian distribution for stress drop is implemented in the inversion as a prior. We have done several synthetic tests to evaluate the stability and reliability of the inversion approach, considering different fault discretization, fault geometries, utilized datasets, and variability of the slip direction, respectively. We finally apply the approach to the 2010 M8.8 Maule earthquake and invert for the coseismic slip and stress drop simultaneously. Two fault geometries from the literature are tested. Our results indicate that the derived slip models based on both fault geometries are similar, showing major slip north of the hypocenter and relatively weak slip in the south, as indicated in the slip models of other studies. The derived mean stress drop is 5-6 MPa, which is close to the stress drop of ~7 MPa that was independently determined according to force balance in this region Luttrell et al. (J Geophys Res, 2011). These findings indicate that stress drop values can be consistently extracted from geodetic data.

  2. Slip stacking

    SciTech Connect

    Kiyomi Koba and James Steimel

    2002-09-19

    We have started beam studies for ''slip stacking''[1] in the Main Injector in order to increase proton intensity on a target for anti-proton production. It has been verified that the system for slip stacking is working with low intensity beam. For a high intensity operation, we are developing a feedback[2][3] and feedforward system.

  3. Co-seismic and post-seismic slip from multiple earthquakes in the northern Chilean subduction zone: Joint study using InSAR, GPS, and seismology

    NASA Astrophysics Data System (ADS)

    Pritchard, M. E.; Ji, C.; Simons, M.

    2002-12-01

    Several large subduction zone earthquakes (Mw > 7) occurred in the region near Antofagasta, Chile between 1987-1998. Here, we investigate the spatial and temporal relationship between these events and any associated post-seismic slip. We use InSAR, GPS, and seismic data to constrain the distribution of slip on the subduction zone interface for the July 30, 1995, Mw 8.1 earthquake. Only InSAR and seismic observations are available for the Mw 7.1 earthquake on January 30, 1998. We find that the seismic data is particularly useful in providing spatial resolution of co-seismic slip for the 1998 earthquake. For earlier earthquakes in 1987 and 1988, only seismic data is available. Our current inversion, as well as previous results from others, suggest that there is little slip during the 1995 earthquake near a 1987 Mw 7.5 event. Our analysis further suggests that little moment from the 1995 slip distribution released near a 1988 Mw 7.2 event. According to our model for the 1995 event, the 1998 event occurred down-dip of the 1995 rupture. In other words, preliminary models indicate that these events do not overlap significantly and appear to be tilling up the slab interface. Compared with other recent large subduction zone earthquakes (e.g., Jalisco, Mexico, 1995), post-seismic slip from the Mw 8.1 Antofagasta earthquake is small. The satellite line of sight displacements are of order a few cm, comparable to the noise. This signal strongly correlates with topography in most of our interferograms, suggesting a possible atmospheric origin. However, when the InSAR data from several tracks is combined with horizontal GPS displacements (Klotz et al., 2001), we are able to bound the magnitude and distribution of after-slip on the fault.

  4. Kinematic Slip Model for 12 May 2008 Wenchuan-Beichuan Mw 7.9 Earthquake from Joint Inversion of ALOS, Envisat, and Teleseismic Data

    NASA Technical Reports Server (NTRS)

    Fielding, Eric; Sladen, Anthony; Avouac, Jean-Philippe; Li, Zhenhong; Ryder, Isabelle; Burgmann, Roland

    2008-01-01

    The presentations explores kinematics of the Wenchaun-Beichuan earthquake using data from ALOS, Envisat, and teleseismic recordings. Topics include geomorphic mapping, ALOS PALSAR range offsets, ALOS PALSAR interferometry, Envisat IM interferometry, Envisat ScanSAR, Joint GPS-InSAR inversion, and joint GPS-teleseismic inversion (static and kinematic).

  5. Tube-in-tube thermophotovoltaic generator

    DOEpatents

    Ashcroft, J.; Campbell, B.; DePoy, D.

    1998-06-30

    A thermophotovoltaic device includes at least one thermal radiator tube, a cooling tube concentrically disposed within each thermal radiator tube and an array of thermophotovoltaic cells disposed on the exterior surface of the cooling tube. A shell having a first end and a second end surrounds the thermal radiator tube. Inner and outer tubesheets, each having an aperture corresponding to each cooling tube, are located at each end of the shell. The thermal radiator tube extends within the shell between the inner tubesheets. The cooling tube extends within the shell through the corresponding apertures of the two inner tubesheets to the corresponding apertures of the two outer tubesheets. A plurality of the thermal radiator tubes can be arranged in a staggered or an in-line configuration within the shell. 8 figs.

  6. Tube-in-tube thermophotovoltaic generator

    DOEpatents

    Ashcroft, John; Campbell, Brian; DePoy, David

    1998-01-01

    A thermophotovoltaic device includes at least one thermal radiator tube, a cooling tube concentrically disposed within each thermal radiator tube and an array of thermophotovoltaic cells disposed on the exterior surface of the cooling tube. A shell having a first end and a second end surrounds the thermal radiator tube. Inner and outer tubesheets, each having an aperture corresponding to each cooling tube, are located at each end of the shell. The thermal radiator tube extends within the shell between the inner tubesheets. The cooling tube extends within the shell through the corresponding apertures of the two inner tubesheets to the corresponding apertures of the two outer tubesheets. A plurality of the thermal radiator tubes can be arranged in a staggered or an in-line configuration within the shell.

  7. 14 CFR 27.935 - Shafting joints.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 27.935 Shafting joints. Each universal joint, slip joint, and other shafting joints whose lubrication is necessary for operation must...

  8. Blast joint

    SciTech Connect

    Uherek, R.J.; Claycomb, J.R.

    1989-12-26

    This patent describes a blast joint. It comprises: at least two tubular members having threaded opposed ends; a plurality of erosion resistant rings encasing the tubular members; support means for supporting the erosion resistant rings about the tubular member; coupling shield means supported on at least one of the tubular members in telescoping relation about the erosion resistant rings; at least one tubular open ended slip sleeve mounted about the erosion resistant rings on the tubular members for providing a surface for engagement by pipe slips for suspending the tubular members in a well bore; and connector means for connecting the tubular members to form the blast joint.

  9. Electromechanical slip sensor

    NASA Technical Reports Server (NTRS)

    Bejczy, A. K.; Park, S.

    1980-01-01

    Sensor indicates direction of slip and slip rate of objects handled by remote manipulators. Freely movable spheroid with staggered pattern of surface indentations rotates in direction of slipping body, tilting shaft with conductive disk plate. Plate assembly is bent toward contact corresponding to direction of slip and is flicked by indentations at rate corresponding to slip rate. Slip direction and rate are determined using LED's arranged circularly or microcomputer with CRT display.

  10. Adaptive regularization of earthquake slip distribution inversion

    NASA Astrophysics Data System (ADS)

    Wang, Chisheng; Ding, Xiaoli; Li, Qingquan; Shan, Xinjian; Zhu, Jiasong; Guo, Bo; Liu, Peng

    2016-04-01

    Regularization is a routine approach used in earthquake slip distribution inversion to avoid numerically abnormal solutions. To date, most slip inversion studies have imposed uniform regularization on all the fault patches. However, adaptive regularization, where each retrieved parameter is regularized differently, has exhibited better performances in other research fields such as image restoration. In this paper, we implement an investigation into adaptive regularization for earthquake slip distribution inversion. It is found that adaptive regularization can achieve a significantly smaller mean square error (MSE) than uniform regularization, if it is set properly. We propose an adaptive regularization method based on weighted total least squares (WTLS). This approach assumes that errors exist in both the regularization matrix and observation, and an iterative algorithm is used to solve the solution. A weight coefficient is used to balance the regularization matrix residual and the observation residual. An experiment using four slip patterns was carried out to validate the proposed method. The results show that the proposed regularization method can derive a smaller MSE than uniform regularization and resolution-based adaptive regularization, and the improvement in MSE is more significant for slip patterns with low-resolution slip patches. In this paper, we apply the proposed regularization method to study the slip distribution of the 2011 Mw 9.0 Tohoku earthquake. The retrieved slip distribution is less smooth and more detailed than the one retrieved with the uniform regularization method, and is closer to the existing slip model from joint inversion of the geodetic and seismic data.

  11. Electro-optical hybrid slip ring

    NASA Astrophysics Data System (ADS)

    Hong, En

    2005-11-01

    The slip ring is a rotary electrical interface, collector, swivel or rotary joint. It is a physical system that can perform continuous data transfer and data exchange between a stationary and a rotating structure. A slip ring is generally used to transfer data or power from an unrestrained, continuously rotating electro-mechanical system in real-time, thereby simplifying operations and eliminating damage-prone wires dangling from moving joints. Slip rings are widely used for testing, evaluating, developing and improving various technical equipment and facilities with rotating parts. They are widely used in industry, especially in manufacturing industries employing turbo machinery, as in aviation, shipbuilding, aerospace, defense, and in precise facilities having rotating parts such as medical Computerized Tomography (CT) and MRI scanners and so forth. Therefore, any improvement in slip ring technology can impact large markets. Research and development in this field will have broad prospects long into the future. The goal in developing the current slip ring technology is to improve and increase the reliability, stability, anti-interference, and high data fidelity between rotating and stationary structures. Up to now, there have been numerous approaches used for signal and data transfer utilizing a slip ring such as metal contacts, wires, radio transmission, and even liquid media. However, all suffer from drawbacks such as data transfer speed limitations, reliability, stability, electro-magnetic interference and durability. The purpose of the current research is to break through these basic limitations using an optical solution, thereby improving performance in current slip ring applications. This dissertation introduces a novel Electro-Optical Hybrid Slip Ring technology, which makes "through the air" digital-optical communication between stationary and rotating systems a reality with high data transfer speed, better reliability and low interference susceptibility. A laboratory scale non-contact Electro-Optical Hybrid Slip Ring system was successfully constructed, and its performance was determined. Experimental results affirmed the advantages of this new technology over current slip ring design.

  12. Coseismic and post-seismic slip of the 2009 L'Aquila (central Italy) MW 6.3 earthquake and implications for seismic potential along the Campotosto fault from joint inversion of high-precision levelling, InSAR and GPS data

    NASA Astrophysics Data System (ADS)

    Cheloni, D.; Giuliani, R.; D'Anastasio, E.; Atzori, S.; Walters, R. J.; Bonci, L.; D'Agostino, N.; Mattone, M.; Calcaterra, S.; Gambino, P.; Deninno, F.; Maseroli, R.; Stefanelli, G.

    2014-05-01

    After the April 6th 2009 MW 6.3 (ML 5.9) L'Aquila earthquake (central Italy), we re-measured more than 100 km of high-precision levelling lines in the epicentral area. The joint inversion of the levelling measurements with InSAR and GPS measurements, allowed us to derive new coseismic and post-seismic slip distributions and to describe, with high resolution details on surface displacements, the activation and the slip distribution of a secondary fault during the aftershock sequence that struck the Campotosto area (major event MW 5.2). Coseismic slip on the Paganica fault occurred on one main asperity, while the afterslip distribution shows a more complex pattern, occurring on three main patches, including both slips on the shallow portions and on the deeper parts of the rupture plane. The comparison between coseismic and post-seismic slip distributions strongly suggests that afterslip was triggered at the edges of the coseismic asperity. The activation of a segment of the Campotosto fault during the aftershock sequence, with a good correlation between the estimated slipping area, moment release and distribution of aftershocks, raises the opportunity to discuss the local seismic hazard following the occurrence of the 2009 L'Aquila mainshock. The Campotosto fault appears capable of generating earthquakes as large as historical events in the region (M > 6.5) or as small as the ones associated with the 2009 sequence. In the case that the Campotosto fault is accumulating a significant portion of the current interseismic deformation, the 2009 MW > 5 events will have released only a small amount of the accumulated elastic strain, and then a significant hazard still remains in the area. Continuing geodetic monitoring and a densification of the GPS networks in the region are therefore needed to estimate the tectonic loading across the different recognized active fault systems in this part of the Apennines.

  13. 14 CFR 27.935 - Shafting joints.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Shafting joints. 27.935 Section 27.935... STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 27.935 Shafting joints. Each universal joint, slip joint, and other shafting joints whose lubrication is necessary for operation must...

  14. 14 CFR 27.935 - Shafting joints.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Shafting joints. 27.935 Section 27.935... STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 27.935 Shafting joints. Each universal joint, slip joint, and other shafting joints whose lubrication is necessary for operation must...

  15. 14 CFR 29.935 - Shafting joints.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Shafting joints. 29.935 Section 29.935... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 29.935 Shafting joints. Each universal joint, slip joint, and other shafting joints whose lubrication is necessary for operation...

  16. 14 CFR 29.935 - Shafting joints.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Shafting joints. 29.935 Section 29.935... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 29.935 Shafting joints. Each universal joint, slip joint, and other shafting joints whose lubrication is necessary for operation...

  17. 14 CFR 29.935 - Shafting joints.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Shafting joints. 29.935 Section 29.935... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 29.935 Shafting joints. Each universal joint, slip joint, and other shafting joints whose lubrication is necessary for operation...

  18. 14 CFR 27.935 - Shafting joints.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Shafting joints. 27.935 Section 27.935... STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 27.935 Shafting joints. Each universal joint, slip joint, and other shafting joints whose lubrication is necessary for operation must...

  19. 14 CFR 29.935 - Shafting joints.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Shafting joints. 29.935 Section 29.935... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 29.935 Shafting joints. Each universal joint, slip joint, and other shafting joints whose lubrication is necessary for operation...

  20. 14 CFR 27.935 - Shafting joints.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Shafting joints. 27.935 Section 27.935... STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 27.935 Shafting joints. Each universal joint, slip joint, and other shafting joints whose lubrication is necessary for operation must...

  1. 14 CFR 29.935 - Shafting joints.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Shafting joints. 29.935 Section 29.935... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 29.935 Shafting joints. Each universal joint, slip joint, and other shafting joints whose lubrication is necessary for operation...

  2. Slipped Capital Femoral Epiphysis

    MedlinePlus

    ... is held in place with a single central screw. This screw keeps the thigh bone from slipping and will ... including in-situ fixation with more than one screw) are used less often. Ask your doctor to ...

  3. SLIP CASTING METHOD

    DOEpatents

    Allison, A.G.

    1959-09-01

    S>A process is described for preparing a magnesium oxide slip casting slurry which when used in conjunction with standard casting techniques results in a very strong "green" slip casting and a fired piece of very close dimensional tolerance. The process involves aging an aqueous magnestum oxide slurry, having a basic pH value, until it attains a specified critical viscosity at which time a deflocculating agent is added without upsetting the basic pH value.

  4. Behavior of jointed pipelines

    SciTech Connect

    Singhal, A.C.

    1984-06-01

    Experimental data on the axial, bending and torsional behavior of ductile cast iron pipes with rubber gasket joints is presented. Analytical expressions are provided which predict the resistance mechanisms and behavior of the joints. The bending mechanism is found to be quite different from the axial and torsional mechanism. By repeating the tests in a specially designed soil box, the effects of burial depths are determined. A joint stiffness matrix including axial, bending and torsional effects is provided. The slip behavior of the joint changes the stiffness values, however this occurence may be dealt with by using an appropriate flag system placed within a computer program. To minimize axial compressional stresses and interlocking bending stresses at the joint, a minor geometrical change in the joint needs to be made. Joints with larger lip lengths provide more flexibility when subjected to axial compression or joint bending rotations.

  5. Inorganic glass ceramic slip rings

    NASA Technical Reports Server (NTRS)

    Glossbrenner, E. W.; Cole, S. R.

    1972-01-01

    Prototypes of slip rings have been fabricated from ceramic glass, a material which is highly resistant to deterioration due to high temperature. Slip ring assemblies were not structurally damaged by mechanical tests and performed statisfactorily for 200 hours.

  6. Nucleation and growth of strike slip faults in granite.

    USGS Publications Warehouse

    Segall, P.; Pollard, D.P.

    1983-01-01

    Fractures within granodiorite of the central Sierra Nevada, California, were studied to elucidate the mechanics of faulting in crystalline rocks, with emphasis on the nucleation of new fault surfaces and their subsequent propagation and growth. Within the study area the fractures form a single, subparallel array which strikes N50o-70oE and dips steeply to the S. Some of these fractures are identified as joints because displacements across the fracture surfaces exhibit dilation but no slip. The joints are filled with undeformed minerals, including epidote and chlorite. Other fractures are identified as small faults because they display left-lateral strike slip separations of up to 2m. Slickensides, developed on fault surfaces, plunge 0o-20o to the E. The faults occur parallel to, and in the same outcrop with, the joints. The faults are filled with epidote, chlorite, and quartz, which exhibit textural evidence of shear deformation. These observations indicate that the strike slip faults nucleated on earlier formed, mineral filled joints. Secondary, dilational fractures propagated from near the ends of some small faults contemporaneously with the left-lateral slip on the faults. These fractures trend 25o+ or -10o from the fault planes, parallel to the direction of inferred local maximum compressive stress. The faults did not propagate into intact rock in their own planes as shear fractures. -from Authors

  7. Refining the shallow slip deficit

    NASA Astrophysics Data System (ADS)

    Xu, Xiaohua; Tong, Xiaopeng; Sandwell, David T.; Milliner, Christopher W. D.; Dolan, James F.; Hollingsworth, James; Leprince, Sebastien; Ayoub, Francois

    2016-03-01

    Geodetic slip inversions for three major (Mw > 7) strike-slip earthquakes (1992 Landers, 1999 Hector Mine and 2010 El Mayor-Cucapah) show a 15-60 per cent reduction in slip near the surface (depth < 2 km) relative to the slip at deeper depths (4-6 km). This significant difference between surface coseismic slip and slip at depth has been termed the shallow slip deficit (SSD). The large magnitude of this deficit has been an enigma since it cannot be explained by shallow creep during the interseismic period or by triggered slip from nearby earthquakes. One potential explanation for the SSD is that the previous geodetic inversions lack data coverage close to surface rupture such that the shallow portions of the slip models are poorly resolved and generally underestimated. In this study, we improve the static coseismic slip inversion for these three earthquakes, especially at shallow depths, by: (1) including data capturing the near-fault deformation from optical imagery and SAR azimuth offsets; (2) refining the interferometric synthetic aperture radar processing with non-boxcar phase filtering, model-dependent range corrections, more complete phase unwrapping by SNAPHU (Statistical Non-linear Approach for Phase Unwrapping) assuming a maximum discontinuity and an on-fault correlation mask; (3) using more detailed, geologically constrained fault geometries and (4) incorporating additional campaign global positioning system (GPS) data. The refined slip models result in much smaller SSDs of 3-19 per cent. We suspect that the remaining minor SSD for these earthquakes likely reflects a combination of our elastic model's inability to fully account for near-surface deformation, which will render our estimates of shallow slip minima, and potentially small amounts of interseismic fault creep or triggered slip, which could `make up' a small percentages of the coseismic SSD during the interseismic period. Our results indicate that it is imperative that slip inversions include accurate measurements of near-fault surface deformation to reliably constrain spatial patterns of slip during major strike-slip earthquakes.

  8. Mechanism of slip and twinning

    NASA Technical Reports Server (NTRS)

    Rastani, Mansur

    1992-01-01

    The objectives are to: (1) demonstrate the mechanisms of deformation in body centered cubic (BCC), face centered cubic (FCC), and hexagonal close-packed (HCP)-structure metals and alloys and in some ceramics as well; (2) examine the deformed microstructures (slip lines and twin boundaries) in different grains of metallic and ceramic specimens; and (3) study visually the deformed macrostructure (slip and twin bands) of metals and alloys. Some of the topics covered include: deformation behavior of materials, mechanisms of plastic deformation, slip bands, twin bands, ductile failure, intergranular fracture, shear failure, slip planes, crystal deformation, and dislocations in ceramics.

  9. Are non-slip socks really 'non-slip'? An analysis of slip resistance

    PubMed Central

    Chari, Satyan; Haines, Terrence; Varghese, Paul; Economidis, Alyssia

    2009-01-01

    Background Non-slip socks have been suggested as a means of preventing accidental falls due to slips. This study compared the relative slip resistance of commercially available non-slip socks with other foot conditions, namely bare feet, compression stockings and conventional socks, in order to determine any traction benefit. Methods Phase one involved slip resistance testing of two commercially available non-slip socks and one compression-stocking sample through an independent blinded materials testing laboratory using a Wet Pendulum Test. Phase two of the study involved in-situ testing among healthy adult subjects (n = 3). Subjects stood unsupported on a variable angle, inclined platform topped with hospital grade vinyl, in a range of foot conditions (bare feet, non-slip socks, conventional socks and compression stockings). Inclination was increased incrementally for each condition until slippage of any magnitude was detected. The platform angle was monitored using a spatial orientation tracking sensor and slippage point was recorded on video. Results Phase one results generated through Wet Pendulum Test suggested that non-slip socks did not offer better traction than compression stockings. However, in phase two, slippage in compression stockings was detected at the lowest angles across all participants. Amongst the foot conditions tested, barefoot conditions produced the highest slip angles for all participants indicating that this foot condition provided the highest slip resistance. Conclusion It is evident that bare feet provide better slip resistance than non-slip socks and therefore might represent a safer foot condition. This study did not explore whether traction provided by bare feet was comparable to 'optimal' footwear such as shoes. However, previous studies have associated barefoot mobilisation with increased falls. Therefore, it is suggested that all patients continue to be encouraged to mobilise in appropriate, well-fitting shoes whilst in hospital. Limitations of this study in relation to the testing method, participant group and sample size are discussed. PMID:19706167

  10. Slipping with the waste (a wheelie bin hand injury).

    PubMed

    Parkes, Rebekah; Weerasuriya, Thisara; Gibson, Suzy

    2015-01-01

    A right hand dominant man in his 60s was moving his wheelie bin when he tripped and landed still holding on to the handle. His hand was trapped between the handle and the ground. He sustained lacerations at the level of the proximal interphalangeal joints of all the fingers of his right hand. The index and middle fingers had damage to the proximal phalangeal articular cartilage and central slip. The central slip loss in the middle finger required reconstruction. The wounds healed without complication by 4 weeks, at which point the patient's fingers were mobilised; he regained almost full range of movement by 3 months. PMID:26126509

  11. Frictional resistance to accelerating slip

    NASA Astrophysics Data System (ADS)

    Gu, J. C.

    1984-09-01

    General analytical expressions for the friction stress and state variable, based on a rate and state-dependent constitutive friction law proposed by Dieterich and Ruina, have been obtained as an explicit function of slip rate V or slip time t or slip displacement δ under the assumption that slip acceleration a is constant or piecewise constant. Properties of the solutions have been discussed, and reviewed, for uniformly accelerating (or decelerating) slip, the following. 1. Frictional stress increases (or decreases) with increasing time, or slip rate, or slippage at the beginning of motion, until a maximum (or a minimum) value (when it exists) has been reached, then decreases (or increases), and finally approaches a special frictional state, namely a steady state, for which stress depends on instantaneous slip rate. 2. The maximal value of frictional stress is dependent on acceleration a; the larger the a, the larger the magnitude of the maximum. The energy expense ɛ needed to overcome the frictional stress has been estimated. And therefore the optimal value of acceleration for saving energy for a slipping mechanical system has been obtained. The energy release rate G for an abrupt rupture process of a crack or fault has been estimated.

  12. A Reduced Order, One Dimensional Model of Joint Response

    SciTech Connect

    DOHNER,JEFFREY L.

    2000-11-06

    As a joint is loaded, the tangent stiffness of the joint reduces due to slip at interfaces. This stiffness reduction continues until the direction of the applied load is reversed or the total interface slips. Total interface slippage in joints is called macro-slip. For joints not undergoing macro-slip, when load reversal occurs the tangent stiffness immediately rebounds to its maximum value. This occurs due to stiction effects at the interface. Thus, for periodic loads, a softening and rebound hardening cycle is produced which defines a hysteretic, energy absorbing trajectory. For many jointed sub-structures, this hysteretic trajectory can be approximated using simple polynomial representations. This allows for complex joint substructures to be represented using simple non-linear models. In this paper a simple one dimensional model is discussed.

  13. Suppression of strike-slip fault systems

    NASA Astrophysics Data System (ADS)

    Curren, I. S.

    2012-12-01

    In orogens elongated parallel to a great circle about the Euler pole for the two bounding plates, theory requires simple-shear deformation in the form of distributed deformation or velocity discontinuities across strike-slip faults. This type of deformation, however, does not develop at all plate boundaries requiring toroidal motion. Using the global plate boundary model, PB2002 [Bird, 2003], as the basis for identifying areas where expected simple-shear deformation is absent or underdeveloped, it was also possible to identify two potential causes for this behavior: (1) the presence of extensive fracturing at right angles to the shear plane and (2) regional cover of flood basalts or andesites with columnar joints. To test this hypothesis, a new plane-stress finite-strain model was developed to study the effects of such pre-existing structures on the development of simple shear in a clay cake. A homogenous kaolinite-water mixture was poured into a deforming parallelogram box and partially dried to allow for brittle and plastic deformation at and below the surface of the clay, respectively. This was floated on a dense fluid foundation, effectively removing basal friction, and driven by a motor in a sinistral direction from the sides of the box. Control experiments produced classic Riedel model fault assemblages and discrete, through-going primary deformation zones (PDZs); experiments with pre-existing structures developed the same, though subdued and distributed, fault assemblages but did not develop through-going PDZs. Although formation of strike-slip faults was underdeveloped at the surface in clay with pre-existing structures, offset within the clay cake (measured, with respect to a fixed point, by markers on the clay surface) as a fraction of total offset of the box was consistently larger than that of the control experiments. This suggests that while the extent of surface faulting was lessened in clay with pre-existing structures, slip was still occurring at depth. Selected areas on Earth with anomalously undeveloped strike-slip faulting where plate models would predict otherwise were compared with results from the analog model experiments in this study. Physical similarities between this model and Brothers Fault Zone (BFZ), Walker Lane (WL) and the South Iceland Seismic Zone (SISZ) imply that strike-slip faulting may be suppressed at the surface in these regions due to the presence of pre-existing structures. Filled circles show offset required for breakthrough faulting, empty circles denote lower limit of breakthrough. Triangles show clay offset as a fraction of box offset. Note that clays with pre-existing structures showed larger offsets although breakthrough did not occur.

  14. Joint swelling

    MedlinePlus

    Swelling of a joint ... Joint swelling may occur along with joint pain . The swelling may cause the joint to appear larger or abnormally shaped. Joint swelling can cause pain or stiffness. After an ...

  15. Characterizing the Relationship of Tremor and Slip during Recent ETS Events in Northern Cascadia using Strainmeters, GPS, and Tremor Observations

    NASA Astrophysics Data System (ADS)

    Krogstad, R. D.; Schmidt, D. A.

    2014-12-01

    We investigate the relationship between slip and tremor during multiple recent slow slip events in northern Cascadia. While the relationship of geodetically detectable slow slip and nonvolcanic tremor appears to be broadly coincident, the exact spatial and temporal characteristics remain unclear at a finer scale. Typical GPS derived slip distributions tend to be spatially and temporally smoothed and offset slightly updip of tremor distributions. These discrepancies may be real, or they may be a consequence of the resolution of GPS data or an artifact of the inversion methodology. Borehole strainmeters provide additional independent geodetic constraints for characterizing slip, provide greater temporal resolution, and greater precision than GPS. However, various non-tectonic artifacts and other sources of error have limited the number of usable stations and made deriving reliable information from strainmeters during slip events difficult. We utilize strainmeters with low levels of noise and minimal observable artifacts to constrain forward models and to provide additional independent observations in joint geodetic inversions with GPS data. A series of slip distributions are derived by inverting strainmeter and GPS data using the Kalman-filter-based Extended Network Inversion Filter. To compare the tremor distributions to the geodetically derived slip we also construct slip distributions using tremor occurrences as a proxy for localized slip on the plate interface. The magnitude of slip per tremor occurrence is then scaled to best match the observed surface displacements. Separate slip distributions informed by GPS and tremor are then used to predict strain time series. The comparisons between strain predictions and observations produce mixed results. This may indicate that that tremor and slip are not always coincident. This is particularly evident during the Aug. 2010 event, where the peak GPS-derived slip is located in a region with decreased tremor activity. Preliminary results also show that shifting the peak tremor-derived slip updip a few kilometers decreases the overall misfit of the displacements, supporting the conclusion that the peak tremor activity occurs slightly downdip of the peak slip.

  16. Packer slips for CRA completion

    SciTech Connect

    Lane, A.R.; Wheeler, R.B.; Jackson, A.T.

    1992-07-21

    This patent describes a slip anchor stud for use in combination with a well packer comprising a main body portion having a length dimension and a radius dimension, a plurality of ribs formed on the main body portion.

  17. Slips of the Typewriter Key.

    ERIC Educational Resources Information Center

    Berg, Thomas

    2002-01-01

    Presents an analysis of 500 submorphemic slips of the typewriter key that escaped the notice of authors and other proofreaders and thereby made their way into the published records of scientific research. (Author/VWL)

  18. Slip of Spreading Viscoplastic Droplets.

    PubMed

    Jalaal, Maziyar; Balmforth, Neil J; Stoeber, Boris

    2015-11-10

    The spreading of axisymmetric viscoplastic droplets extruded slowly on glass surfaces is studied experimentally using shadowgraphy and swept-field confocal microscopy. The microscopy furnishes vertical profiles of the radial velocity using particle image velocimetry (PIV) with neutrally buoyant tracers seeded in the fluid. Experiments were conducted for two complex fluids: aqueous solutions of Carbopol and xanthan gum. On untreated glass surfaces, PIV demonstrates that both fluids experience a significant amount of effective slip. The experiments were repeated on glass that had been treated to feature positive surface charges, thereby promoting adhesion between the negatively charged polymeric constituents of the fluids and the glass surface. The Carbopol and xanthan gum droplets spread more slowly on the treated surface and to a smaller radial distance. PIV demonstrated that this reduced spreading was associated with a substantial reduction in slip. For Carbopol, the effective slip could be eliminated entirely to within the precision of the PIV measurements; the reduction in slip was less effective for xanthan gum, with a weak slip velocity remaining noticeable. PMID:26418827

  19. Effects of lower extremity muscle fatigue on the outcomes of slip-induced falls

    PubMed Central

    Parijat, Prakriti; Lockhart, Thurmon E.

    2010-01-01

    Slip-induced fall accidents continue to be a significant cause of fatal injuries and economic losses. Identifying the risk factors causing slip-induced falls is key to developing better preventive measures to reduce fall accidents. Although epidemiological studies suggest localised muscle fatigue may be one of the risk factors for slip-induced falls, there has been no documented biomechanical study examining the relationship between fatigue and fall accidents. As such, the overall objective of the current study was to investigate the effects of localised muscle fatigue of the quadriceps on the slip initiation and slip recovery phases of slip-induced falls. Sixteen healthy, young participants were recruited to walk across a vinyl floor surface in two different sessions (fatigue and no fatigue). Kinematic and kinetic data were collected using a 3-D motion analysis system and force plates during both sessions. Results suggest that localised muscle fatigue of the quadriceps affected various kinematic and kinetic gait variables that are linked with a higher risk of slip-induced falls. Additionally, the results indicated that localised muscle fatigue of the knee extensor muscle caused a delayed response in producing an effective joint moment and base of support using the trailing limb to recover from a fall. The findings from this study indicate that localised muscle fatigue is a potential risk factor causing slip-induced falls. PMID:19034783

  20. Slip-Cast Superconductive Parts

    NASA Technical Reports Server (NTRS)

    Wise, Stephanie A.; Buckley, John D.; Vasquez, Peter; Buck, Gregory M.; Hicks, Lana P.; Hooker, Matthew W.; Taylor, Theodore D.

    1993-01-01

    Complex shapes fabricated without machining. Nonaqueous slip-casting technique used to form complexly shaped parts from high-temperature superconductive materials like YBa(2)Cu(3)O(7-delta). Such parts useful in motors, vibration dampers, and bearings. In process, organic solvent used as liquid medium. Ceramic molds made by lost-wax process used instead of plaster-of-paris molds, used in aqueous slip-casting but impervious to organic solvents and cannot drain away liquid medium. Organic-solvent-based castings do not stick to ceramic molds as they do to plaster molds.

  1. Slip length measurement using BBM

    NASA Astrophysics Data System (ADS)

    Ahmadzadegan, Adib; Snoeyink, Craig

    2015-11-01

    We will be presenting experimental characterizations of slip lengths of fluids in nano/micro channels. These channels are becoming increasingly important in sensor and separations applications. However, crucial questions still remain on the mechanisms that govern slip-length behavior. We used Bessel Beam microscopy (BBM), a novel super-resolution imaging system, in conjunction with TIRF system. These two, together led us to be able to do Particle Tracking Velocimetry with significantly higher accuracy than previously possible. We will be presenting results demonstrating the feasibility of this approach and advantages that make this method unique.

  2. Interfacial Slip in Soap Films with Hydrosoluble Polymer

    NASA Astrophysics Data System (ADS)

    Adelizzi, E. A.; Berg, S.; Troian, S. M.

    2003-11-01

    The thickness of a Newtonian soap film entrained at small capillary number should scale as Ca^2/3 provided the bounding surfaces are rigid. Previous studies show that soap films containing associating, low concentration, high molecular weight (M_w) polymer exhibit strong deviations from this scaling. We report results by laser interferometry of the entrained film thickness for the associating pair SDS/PEO over a large range in polymer molecular weight. Direct comparison to predictions of hydrodynamic models based on viscoelastic behavior shows poor agreement.Modification of the Frankel analysis to account for mobile films through a Navier slip condition yields good agreement. In addition, the slip length Ls increases as M_w^3/5, consistent with a correlation based on a polymer chain size for freely jointed chains with excluded volume effects. Although developed to explain slip at liquid-solid interfaces, the Tolstoi-Larson prediction that Ls scales as the polymer size agrees favorably with our results. Whether the slip behavior is due to Marangoni effects cannot be ruled out.

  3. Hydrodynamic slip in silicon nanochannels

    NASA Astrophysics Data System (ADS)

    Ramos-Alvarado, Bladimir; Kumar, Satish; Peterson, G. P.

    2016-03-01

    Equilibrium and nonequilibrium molecular dynamics simulations were performed to better understand the hydrodynamic behavior of water flowing through silicon nanochannels. The water-silicon interaction potential was calibrated by means of size-independent molecular dynamics simulations of silicon wettability. The wettability of silicon was found to be dependent on the strength of the water-silicon interaction and the structure of the underlying surface. As a result, the anisotropy was found to be an important factor in the wettability of these types of crystalline solids. Using this premise as a fundamental starting point, the hydrodynamic slip in nanoconfined water was characterized using both equilibrium and nonequilibrium calculations of the slip length under low shear rate operating conditions. As was the case for the wettability analysis, the hydrodynamic slip was found to be dependent on the wetted solid surface atomic structure. Additionally, the interfacial water liquid structure was the most significant parameter to describe the hydrodynamic boundary condition. The calibration of the water-silicon interaction potential performed by matching the experimental contact angle of silicon led to the verification of the no-slip condition, experimentally reported for silicon nanochannels at low shear rates.

  4. Slip rate and tremor genesis in Cascadia

    NASA Astrophysics Data System (ADS)

    Wech, Aaron G.; Bartlow, Noel M.

    2014-01-01

    At many plate boundaries, conditions in the transition zone between seismogenic and stable slip produce slow earthquakes. In the Cascadia subduction zone, these events are consistently observed as slow, aseismic slip on the plate interface accompanied by persistent tectonic tremor. However, not all slow slip at other plate boundaries coincides spatially and temporally with tremor, leaving the physics of tremor genesis poorly understood. Here we analyze seismic, geodetic, and strainmeter data in Cascadia to observe for the first time a large, tremor-generating slow earthquake change from tremor-genic to silent and back again. The tremor falls silent at reduced slip speeds when the migrating slip front pauses as it loads the stronger adjacent fault segment to failure. The finding suggests that rheology and slip-speed-regulated stressing rate control tremor genesis, and the same section of fault can slip both with and without detectable tremor, limiting tremor's use as a proxy for slip.

  5. Slipping properties of ceramic tiles / Quantification of slip resistance

    NASA Astrophysics Data System (ADS)

    Terjek, Anita

    2013-12-01

    Regarding the research and application of ceramic tiles there is a great importance of defining precisely the interaction and friction between surfaces. Measuring slip resistance of floor coverings is a complex problem; slipperiness is always interpreted relatively. In the lack of a consistent and clear EU standard, it is practical to use more method in combination. It is necessary to examine the structure of materials in order to get adequate correlation. That is why measuring techniques of surface roughness, an important contributor to slip resistance and cleaning, is fundamental in the research. By comparing the obtained test results, relationship between individual methods of analysis and values may be determined and based on these information recommendations shall be prepared concerning the selection and application of tiles.

  6. A computational model for three-dimensional jointed media with a single joint set; Yucca Mountain Site Characterization Project

    SciTech Connect

    Koteras, J.R.

    1994-02-01

    This report describes a three-dimensional model for jointed rock or other media with a single set of joints. The joint set consists of evenly spaced joint planes. The normal joint response is nonlinear elastic and is based on a rational polynomial. Joint shear stress is treated as being linear elastic in the shear stress versus slip displacement before attaining a critical stress level governed by a Mohr-Coulomb faction criterion. The three-dimensional model represents an extension of a two-dimensional, multi-joint model that has been in use for several years. Although most of the concepts in the two-dimensional model translate in a straightforward manner to three dimensions, the concept of slip on the joint planes becomes more complex in three dimensions. While slip in two dimensions can be treated as a scalar quantity, it must be treated as a vector in the joint plane in three dimensions. For the three-dimensional model proposed here, the slip direction is assumed to be the direction of maximum principal strain in the joint plane. Five test problems are presented to verify the correctness of the computational implementation of the model.

  7. Static stress drop associated with brittle slip events on exhumed faults

    NASA Astrophysics Data System (ADS)

    Griffith, W. A.; di Toro, G.; Pennacchioni, G.; Pollard, D. D.; Nielsen, S.

    2009-02-01

    We estimate the static stress drop on small exhumed strike-slip faults in the Lake Edison granodiorite of the central Sierra Nevada (California). The subvertical strike-slip faults were exhumed from 4 to 15 km depth and were chosen because they are exposed in outcrop along their entire tip-to-tip lengths of 8-12 m. Slip nucleated on joints and accumulated by crystal-plastic shearing (forming quartz mylonites from early quartz vein filling in joints) and successive brittle faulting (forming epidote-bearing cataclasites). The occurrence of thin, ≤300 μm wide, pseudotachylytes along some small faults throughout the study area suggests that some, if not all, of the brittle slip on the study area faults may have been seismic. We suggest that the contribution of brittle, cataclastic slip to the total slip along the studied cataclasite-bearing small faults may be estimated by the length of epidote-filled, rhombohedral dilatational jogs (rhombochasms) distributed quasi-periodically along the length of the faults. The interpretation that slip recorded by rhombochasms occurred in single events is based on evidence that (1) epidote crystals are randomly oriented and undeformed within the rhombochasm; (2) cataclasite in principal slip zones does not include clasts of previous cataclasite, and (3) rhombochasm lengths vary systematically along the length of the faults with slip maximum occurring near the fault center, tapering to the fault tips. We thereby constrain both the rupture length and slip. On the basis of these measurements, we calculate stress drops ranging over 90-250 MPa, i.e., one to two orders of magnitude larger than typical seismological estimates for earthquakes, but similar in magnitude to seismological estimates of small (slip events described in the present study occurred along small, deep-seated faults, and, given the calculated stress drops and observations that brittle faults exploited joints sealed by quartz-bearing mylonite, we conclude that these were "strong" faults.

  8. Joint Problems

    MedlinePlus

    ... Information Causes & Symptoms Diagnosis & Tests Care & Treatment Lifestyle & ... Facts & Information What are Joint Problems? Your musculoskeletal system is constructed of bones, muscles, and joints. The ...

  9. Accessory slips of the extensor digiti minimi.

    PubMed

    Li, Jing; Mao, Qing Hua

    2014-01-01

    During the educational dissection of a 69-year-old Chinese male cadaver, an extensor digiti minimi (EDM) with five slips on the right hand was discovered. Except for the two slips of the little finger, the two radial slips were inserted into the dorsal aponeurosis of the middle finger and the ring finger, respectively. The middle slip was connected to the junctura tendinum in the fourth intermetacarpal spaces. Variations in this region are of paramount importance for the reconstructive surgeons, who may utilize the accessory slips to restore functional capacity of the fingers. PMID:24970007

  10. Coseismic and postseismic slip of the 2004 Parkfield earthquake from space-geodetic data

    USGS Publications Warehouse

    Johanson, I.A.; Fielding, E.J.; Rolandone, F.; Burgmann, R.

    2006-01-01

    We invert interferometric synthetic aperture radar (InSAR) data jointly with campaign and continuous global positioning system (GPS) data for slip in the coseismic and postseismic periods of the 2004 Parkfield earthquake. The InSAR dataset consists of eight interferograms from data collected by the Envisat and Radarsat satellites spanning the time of the earthquake and variable amounts of the postseismic period. The two datasets complement each other, with the InSAR providing dense sampling of motion in the range direction of the satellite and the GPS providing more sparse, but three-dimensional measurements of ground motion. The model assumes exponential decay of the postseismic slip with a decay time constant of 0.087 years, determined from time series modeling of continuous GPS and creepmeter data. We find a geodetic moment magnitude of M 6.2 for a 1-day coseismic model and Mw 6.1 for the entire postseismic period. The coseismic rupture occurred mainly in two slip asperities; one near the hypocenter and the other 15-20 km north. Postseismic slip occurred on the shallow portions of the fault and near the rupture areas of two M 5.0 aftershocks. A comparison of the geodetic slip models with seismic moment estimates suggests that the coseismic moment release of the Parkfield earthquake is as little as 25% of the total. This underlines the importance of aseismic slip in the slip budget for the Parkfield segment.

  11. Fiber-Reinforced Slip Castings

    NASA Technical Reports Server (NTRS)

    Blome, J. C.; Drennan, D. N.; Keeser, H. M.

    1982-01-01

    Addition of silica fibers greatly reduces shrinkage and cracking during casting of ceramics. Fiber-reinforced slip-cast silica ceramics are also tougher and have lower dielectric loss. Silica fibers are hyperpure material containing only 1 part per million total metal-ion impurities. Hyperpure fibers ensure high reflectance and allow casting to be fired at temperature greater than 2,200 degrees F without loss of strength from devitrification.

  12. Flow-induced vibrations-1987

    SciTech Connect

    Au-Yang, M.K.; Chen, S.S.

    1987-01-01

    This book contains 20 selections. Some of the titles are: Acoustic resonance in heat exchanger tube bundles--Part 1. Physical nature of the phenomenon; Theoretical and experimental studies on heat exchanger U-bend tube bundle vibration characteristics; Experimental model analysis of metallic pipeline conveying fluid; Leakage flow-induced vibration of an eccentric tube-in-tube slip joint; and A study on the vibrations of pipelines caused by internal pulsating flows.

  13. Spatial slip behavior of large strike-slip fault belts: Implications for the Holocene slip rates of the eastern termination of the North Anatolian Fault, Turkey

    NASA Astrophysics Data System (ADS)

    Zabcı, Cengiz; Sançar, Taylan; Akyüz, H. Serdar; Kıyak, Nafiye Güneç

    2015-12-01

    We present new data on Holocene slip rates for the eastern end of the North Anatolian Fault (NAF) by using the optically stimulated luminescence ages of the offset terrace deposits at two sites, where a total of four displaced landforms was studied. Each offset feature was analyzed independently, and three different assumptions were made for all the offsets, depending on whether the age of the upper tread (upper tread reconstruction), the lower tread (lower tread reconstruction), or all bounding surfaces (intermediate solution) were used in dating of the terrace risers. The deflected geometry of the risers strongly suggests the use of either the intermediate solution or the upper tread reconstruction. The joint slip rate distributions for the upper tread reconstructions and the intermediate solutions were modeled as 13.0 + 1.8 / -1.4 and 14.3 + 5.8 / -2.4 mm/yr (2σ), respectively. Although the intermediate solution covers the full range of ages for the measured displacements, the curved geometry of the terrace risers suggests that the initiations of the riser offsets are most probably close to the abandonment ages of the upper terrace treads. Therefore, we accepted the joint slip rate of the intermediate solution but suggested that the average rate for the main displacement zone of the eastern NAF should be close to its lower limits. This slower rate with respect to previous estimates suggests that the total deformation is not only accommodated on the main displacement zone but is also distributed along the secondary faults to the south of the easternmost segments of the NAF.

  14. Molecular scale simulation of homopolymer wall slip.

    PubMed

    Dorgan, John R; Rorrer, Nicholas A

    2013-04-26

    The first molecular scale simulation of highly entangled polydisperse homopolymers that is capable of capturing all three regions--no slip, weak slip, and strong slip--of the hydrodynamic boundary condition is presented. An on-lattice dynamic Monte Carlo technique capable of correctly capturing both unentangled and entangled polymer dynamics is used to study the molecular details of wall slip phenomena for homopolymers and energetically neutral walls. For unentangled chains (those exhibiting Rouse dynamics) weak slip is not present but evidence of strong slip is manifest at very high shear rates. For entangled chains (of sufficient length to exhibit reptation dynamics), both weak and strong slip are observed. Consistent with numerous experimental studies, disentanglement and cohesive failure occur at high shear rates. Disentanglement is clearly evidenced in a nonlinear velocity profile that exhibits shear banding, in an excess of chain ends at the slip plane, and perhaps most importantly in a nonmonotonic stress versus shear rate response. The chain end density exhibits a pretransitional periodicity prior to disentanglement. Unentangled Rouse chains do not show this pretransitional response or a bifurcation in their stress versus shear rate response. Finally, it is shown that when polydispersity is introduced, slip phenomena are severely reduced and the inherent constitutive bifurcation is limited to a small region. Predictions are in post facto agreement with many experiments, are distinct from existing results obtained using molecular dynamics simulation techniques, and shed light on fundamental mechanisms of polymer wall slip. PMID:23679746

  15. Long-term acceleration of aseismic slip preceding the Mw 9 Tohoku-oki earthquake: Constraints from repeating earthquakes

    NASA Astrophysics Data System (ADS)

    Mavrommatis, Andreas P.; Segall, Paul; Uchida, Naoki; Johnson, Kaj M.

    2015-11-01

    A decadal-scale deformation transient preceding the 2011 Mw 9 Tohoku-oki, Japan, earthquake was reported from continuous GPS data and interpreted as accelerating aseismic slip on the Japan Trench megathrust. Given the unprecedented nature of this transient, independent confirmation of accelerating slip is required. Here we show that changes in the recurrence intervals of repeating earthquakes on the Japan Trench megathrust in the period 1996 to 2011 are consistent with accelerating slip preceding the Tohoku-oki earthquake. All sequences of repeating earthquakes with statistically significant trends in recurrence interval (at 95% confidence) offshore south central Tohoku occurred at an accelerating rate. Furthermore, estimates of the magnitude of slip acceleration from repeating earthquakes are consistent with the completely independent geodetic estimates. From a joint inversion of the GPS and seismicity data, we infer that a substantial portion of the megathrust experienced accelerating slip, partly surrounding the eventual rupture zone of the Mw 9 earthquake.

  16. Fault roughness evolution with slip (Gole Larghe Fault Zone, Italian Alps)

    NASA Astrophysics Data System (ADS)

    Bistacchi, A.; Spagnuolo, E.; Di Toro, G.; Nielsen, S. B.; Griffith, W. A.

    2011-12-01

    Fault surface roughness is a principal factor influencing fault and earthquake mechanics. However, little is known on roughness of fault surfaces at seismogenic depths, and particularly on how it evolves with accumulating slip. We have studied seismogenic fault surfaces of the Gole Larghe Fault Zone, which exploit precursor cooling joints of the Adamello tonalitic pluton (Italian Alps). These faults developed at 9-11 km and 250-300°C. Seismic slip along these surfaces, which individually accommodated from 1 to 20 m of net slip, resulted in the production of cm-thick cataclasites and pseudotachylytes (solidified melts produced during seismic slip). The roughness of fault surfaces was determined with a multi-resolution aerial and terrestrial LIDAR and photogrammetric dataset (Bistacchi et al., 2011, Pageoph, doi: 10.1007/s00024-011-0301-7). Fault surface roughness is self-affine, with Hurst exponent H < 1, indicating that faults are comparatively smoother at larger wavelengths. Fault surface roughness is inferred to have been inherited from the precursor cooling joints, which show H ≈ 0.8. Slip on faults progressively modified the roughness distribution, lowering the Hurst exponent in the along-slip direction up to H ≈ 0.6. This behaviour has been observed for wavelengths up to the scale of the accumulated slip along each individual fault surface, whilst at larger wavelengths the original roughness seems not to be affected by slip. Processes that contribute to modify fault roughness with slip include brittle failure of the interacting asperities (production of cataclasites) and frictional melting (production of pseudotachylytes). To quantify the "wear" due to these processes, we measured, together with the roughness of fault traces and their net slip, the thickness and distribution of cataclasites and pseudotachylytes. As proposed also in the tribological literature, we observe that wearing is scale dependent, as smaller wavelength asperities have a shorter interaction distance and are consumed faster with slip than larger ones. However, in faults, production of cataclasites and pseudotachylytes changes the contact area of sliding surfaces by interposing a layer of wear products. This layer may preserve from wearing asperities that are smaller in amplitude than the layer thickness, thus providing a mechanism that is likely to preserve small amplitude/wavelength roughness. These processes have been considered in a new spectral model of wear, which allows to model wear for self-affine surfaces and includes the accumulation of wear products within the fault zone. This model can be used to generalize our results and contribute to reconstruct a realistic model of a seismogenic fault zone (http://roma1.rm.ingv.it/laboratori/laboratorio-hp-ht/usems-project).

  17. Analysis of minor fractures associated with joints and faulted joints

    NASA Astrophysics Data System (ADS)

    Cruikshank, Kenneth M.; Zhao, Guozhu; Johnson, Arvid M.

    In this paper, we use fracture mechanics to interpret conditions responsible for secondary cracks that adorn joints and faulted joints in the Entrada Sandstone in Arches National Park, U.S.A. Because the joints in most places accommodated shearing offsets of a few mm to perhaps 1 dm, and thus became faulted joints, some of the minor cracks are due to faulting. However, in a few places where the shearing was zero, one can examine minor cracks due solely to interaction of joint segments at the time they formed. We recognize several types of minor cracks associated with subsequent faulting of the joints. One is the kink, a crack that occurs at the termination of a straight joint and whose trend is abruptly different from that of the joint. Kinks are common and should be studied because they contain a great deal of information about conditions during fracturing. The sense of kinking indicates the sense of shear during faulting: a kink that turns clockwise with respect to the direction of the main joint is a result of right-lateral shear, and a kink that turns counterclockwise is a result of left-lateral shear. Furthermore, the kink angle is related to the ratio of the shear stress responsible for the kinking to the normal stress responsible for the opening of the joint. The amount of opening of a joint at the time it faulted or even at the time the joint itself formed can be estimated by measuring the kink angle and the amount of strike-slip at some point along the faulted joint. Other fractures that form near terminations of pre-existing joints in response to shearing along the joint are horsetail fractures. Similar short fractures can occur anywhere along the length of the joints. The primary value in recognizing these fractures is that they indicate the sense of faulting accommodated by the host fracture and the direction of maximum tension. Even where there has been insignificant regional shearing in the Garden Area, the joints can have ornate terminations. Perhaps the simplest is a veer, where the end of one joint segment turns gradually toward a nearby joint segment. The veer is a result of a nearby, shear-stress-free face such as a joint surface. Our greatest difficulty has been explaining long overlap of parallel joint segments, that is, the lack of veer. The only plausible explanation we know is suggested by the research of Cottrell and Rice, that high compression parallel to the joint segments will tend to prevent the joints from turning toward one another. The most interesting and puzzling fractures are stepped joints and associated echelon cracks, in which the slight misalignment of the stepped joints suggests mild left-lateral shear, while the strong misalignment of echelon cracks that continue the traces of the stepped joints suggests strong right-lateral shear. The stepped joints are thought to reflect local left-lateral shearing that acted over an area of several thousand square metres, whereas the stepped echelon cracks reflect local interaction between the tips of nearby joints propagating in different directions.

  18. Multicycle slip distribution along a laboratory fault

    USGS Publications Warehouse

    Chi-Yu, King

    1991-01-01

    Slip distribution along a laboratory fault, which consists of eight spring-connected blocks that are elastically driven to slide on a frictional surface, has been examined for a "long' sequence of slip events to test the applicability of some conceptual models. The distributions of large slip events are found to be quite variable and do not fit the uniform slip or characteristic earthquake models. The rupture initiation points are usually not near the corresponding maximum slip points, in contrast to observations by Thatcher (1990) and by Fukao and Kikuchi (1987) that earthquake hypocenters are commonly near corresponding regions of maximum slip in the fault planes. The results suggest that earthquake prediction monitoring efforts should not be limited to a small region near an asperity but should be spread out to cover the entire fault segment in a seismic gap in order to detect the condition of simultaneous strain buildup. -from Author

  19. Process for slip casting textured tubular structures

    DOEpatents

    Steinlage, Greg A.; Trumble, Kevin P.; Bowman, Keith J.

    2002-01-01

    A process for centrifugal slip casting a textured hollow tube. A slip made up of a carrier fluid and a suspended powder is introduced into a porous mold which is rotated at a speed sufficient to create a centrifugal force that forces the slip radially outward toward the inner surface of the mold. The suspended powder, which is formed of particles having large dimensional aspect ratios such as particles of superconductive BSCCO, settles in a textured fashion radially outward toward the mold surface. The carrier fluid of the slip passes by capillary action radially outward around the settled particles and into the absorbent mold. A layer of mold release material is preferably centrifugally slip cast to cover the mold inner surface prior to the introduction of the BSCCO slip, and the mold release layer facilitates removal of the BSCCO greenbody from the mold without fracturing.

  20. Fault slip distribution and fault roughness

    NASA Astrophysics Data System (ADS)

    Candela, Thibault; Renard, François; Schmittbuhl, Jean; Bouchon, Michel; Brodsky, Emily E.

    2011-11-01

    We present analysis of the spatial correlations of seismological slip maps and fault topography roughness, illuminating their identical self-affine exponent. Though the complexity of the coseismic spatial slip distribution can be intuitively associated with geometrical or stress heterogeneities along the fault surface, this has never been demonstrated. Based on new measurements of fault surface topography and on statistical analyses of kinematic inversions of slip maps, we propose a model, which quantitatively characterizes the link between slip distribution and fault surface roughness. Our approach can be divided into two complementary steps: (i) Using a numerical computation, we estimate the influence of fault roughness on the frictional strength (pre-stress). We model a fault as a rough interface where elastic asperities are squeezed. The Hurst exponent ?, characterizing the self-affinity of the frictional strength field, approaches ?, where ? is the roughness exponent of the fault surface in the direction of slip. (ii) Using a quasi-static model of fault propagation, which includes the effect of long-range elastic interactions and spatial correlations in the frictional strength, the spatial slip correlation is observed to scale as ?, where ? represents the Hurst exponent of the slip distribution. Under the assumption that the origin of the spatial fluctuations in frictional strength along faults is the elastic squeeze of fault asperities, we show that self-affine geometrical properties of fault surface roughness control slip correlations and that ?. Given that ? for a wide range of faults (various accumulated displacement, host rock and slip movement), we predict that ?. Even if our quasi-static fault model is more relevant for creeping faults, the spatial slip correlations observed are consistent with those of seismological slip maps. A consequence is that the self-affinity property of slip roughness may be explained by fault geometry without considering dynamical effects produced during an earthquake.

  1. Learning to predict slip for ground robots

    NASA Technical Reports Server (NTRS)

    Angelova, Anelia; Matthies, Larry; Helmick, Daniel; Sibley, Gabe; Perona, Pietro

    2006-01-01

    In this paper we predict the amount of slip an exploration rover would experience using stereo imagery by learning from previous examples of traversing similar terrain. To do that, the information of terrain appearance and geometry regarding some location is correlated to the slip measured by the rover while this location is being traversed. This relationship is learned from previous experience, so slip can be predicted later at a distance from visual information only.

  2. Bayesian estimation of slip distribution based on von Karman autocorrelation

    NASA Astrophysics Data System (ADS)

    Hooper, A. J.; Bekaert, D. P.

    2014-12-01

    Geodetic observations from techniques such as InSAR and GNSS are routinely used to invert for earthquake fault slip distributions. However, in order to regularize the inversions, extra arbitrary assumptions about the smoothness of the slip distribution are usually included. In previous work we explored a new approach for constraining the slip distribution based on a random vector model following a von Karman autocorrelation function, which has empirical support from a stochastic analysis of seismic finite-source slip inversions. We implemented the random vector constraint in a Bayesian fashion and used a Markov chain Monte Carlo (MCMC) algorithm to derive the posterior joint probability distribution for each of the slipping patches. The von Karman function depends on two parameters: correlation length and Hurst number (related to fractal dimension). In our inversions we used the empirically derived maximum likelihood values for these two parameters, which differ in along-strike and down-dip directions, and with fault mechanism. However, the inversion results depend strongly on the chosen values for correlation length and Hurst number, and the empirically derived histograms show that there is in fact quite some variation between earthquakes with the same mechanism. In our extended approach we treat these two parameters as hyperparameters, with the prior probability distribution constrained by the empirical histograms. The values are thus also allowed to vary in our Bayesian inversion scheme. In this way, the uncertainty in the parameters that define the autocorrelation function is also included in the posterior probability distribution for the slipping patches. To ensure that our MCMC algorithm converges rapidly, we have implemented a variation to the usual MCMC approach, in which the maximum step size for each of the model parameters is initially updated regularly, until optimal values are achieved. In comparisons between our new approach and a more standard approach based on smoothing, we find the solutions with maximum posterior probability sometimes differ markedly. Even more significant, however, is the difference in the uncertainty of our results, with our new method leading to a solution with a much tighter constraint.

  3. Bulk metallic glasses deform via slip avalanches.

    PubMed

    Antonaglia, James; Wright, Wendelin J; Gu, Xiaojun; Byer, Rachel R; Hufnagel, Todd C; LeBlanc, Michael; Uhl, Jonathan T; Dahmen, Karin A

    2014-04-18

    For the first time in metallic glasses, we extract both the exponents and scaling functions that describe the nature, statistics, and dynamics of slip events during slow deformation, according to a simple mean field model. We model the slips as avalanches of rearrangements of atoms in coupled shear transformation zones (STZs). Using high temporal resolution measurements, we find the predicted, different statistics and dynamics for small and large slips thereby excluding self-organized criticality. The agreement between model and data across numerous independent measures provides evidence for slip avalanches of STZs as the elementary mechanism of inhomogeneous deformation in metallic glasses. PMID:24785049

  4. Development of a liquid metal slip ring

    NASA Technical Reports Server (NTRS)

    Weinberger, S. M.

    1972-01-01

    A liquid metal slip ring/solar orientation mechanism was designed and a model tested. This was a follow-up of previous efforts for the development of a gallium liquid metal slip ring in which the major problem was the formation and ejection of debris. A number of slip ring design approaches were studied. The probe design concept was fully implemented with detail drawings and a model was successfully tested for dielectric strength, shock vibration, acceleration and operation. The conclusions are that a gallium liquid metal slip ring/solar orientation mechanism is feasible and that the problem of debris formation and ejection has been successfully solved.

  5. Molecular Scale Simulation of Homopolymer Wall Slip

    NASA Astrophysics Data System (ADS)

    Dorgan, John R.; Rorrer, Nicholas A.

    2013-04-01

    The first molecular scale simulation of highly entangled polydisperse homopolymers that is capable of capturing all three regions—no slip, weak slip, and strong slip—of the hydrodynamic boundary condition is presented. An on-lattice dynamic Monte Carlo technique capable of correctly capturing both unentangled and entangled polymer dynamics is used to study the molecular details of wall slip phenomena for homopolymers and energetically neutral walls. For unentangled chains (those exhibiting Rouse dynamics) weak slip is not present but evidence of strong slip is manifest at very high shear rates. For entangled chains (of sufficient length to exhibit reptation dynamics), both weak and strong slip are observed. Consistent with numerous experimental studies, disentanglement and cohesive failure occur at high shear rates. Disentanglement is clearly evidenced in a nonlinear velocity profile that exhibits shear banding, in an excess of chain ends at the slip plane, and perhaps most importantly in a nonmonotonic stress versus shear rate response. The chain end density exhibits a pretransitional periodicity prior to disentanglement. Unentangled Rouse chains do not show this pretransitional response or a bifurcation in their stress versus shear rate response. Finally, it is shown that when polydispersity is introduced, slip phenomena are severely reduced and the inherent constitutive bifurcation is limited to a small region. Predictions are in post facto agreement with many experiments, are distinct from existing results obtained using molecular dynamics simulation techniques, and shed light on fundamental mechanisms of polymer wall slip.

  6. The slipping rib syndrome: A case report

    PubMed Central

    van Delft, E.A.K.; van Pul, K.M.; Bloemers, F.W.

    2016-01-01

    We present a case report and review of literature about slipping rib syndrome, a syndrome rarely recognized and often un or misdiagnosed. In literature there is no clear consensus about the diagnosis and treatment. We present a case of a 47 year old man who was diagnosed with slipping rib syndrome after a cycling incident 8 years ago. Also, we developed a flow chart according the diagnostic and therapeutic steps in the treatment of slipping rib syndrome. Central massage Knowledge and treatment of the slipping rib syndrome can prevent chronic complaints and unnecessary comprehensive treatment. PMID:27082995

  7. Slip resistance of non-slip socks--an accelerometer-based approach.

    PubMed

    Hübscher, Markus; Thiel, Christian; Schmidt, Jens; Bach, Matthias; Banzer, Winfried; Vogt, Lutz

    2011-04-01

    The present study investigated the relative slip resistance of commercially available non-slip socks during gait. Twenty-four healthy subjects (29.3±10.4 years) participated in the study. Each subject completed 4 different test conditions (barefoot, non-slip socks, conventional socks, backless slippers) in a randomized, balanced order. The slip resistance was estimated by measuring the heel deceleration time using a heel-mounted accelerometer. Repeated measures ANOVA and post hoc paired-sample t-test with Bonferroni correction were used for statistical analysis. Compared to barefoot walking absolute deceleration times [ms] were significantly increased when wearing conventional socks or slippers. No significant differences were observed between the barefoot and non-slip socks conditions. The present study shows that non-slip socks improved slip-resistance during gait when compared to conventional socks and slippers. Future investigations should verify the present findings in hospital populations prone to slip-related falls. PMID:21440441

  8. Slow slip events in Guerrero, Mexico, and consequences on strain accumulation over the past 15 years.

    NASA Astrophysics Data System (ADS)

    Radiguet, M.; Cotton, F.; Cavalié, O.; Pathier, E.; Kostoglodov, V.; Vergnolle, M.; Campillo, M.; Walpersdorf, A.; Cotte, N.; Santiago, J.; Franco, S.

    2012-12-01

    Continuous Global Positioning System (cGPS) time series in Guerrero, Mexico, reveal the widespread existence of large Slow Slip Events (SSEs) at the boundary between the Cocos and North American plates. The existence of these SSEs asks the question of how seismic and aseismic slips complement each other in subduction zones. We examined the last three SSEs that occurred in 2001/2002, 2006 and 2009/2010, and their impact on the strain accumulation along the Guerrero subduction margin. We use continuous cGPS time series and InSAR images to evaluate the surface displacement during SSEs and inter-SSE periods. The slip distributions on the plate interface associated with each SSE, as well as the inter-SSE (short-term) coupling rates are evaluated by inverting these surface displacements. Our results reveal that the three analyzed SSEs have equivalent moment magnitudes of around 7.5 and their lateral extension is variable.The slip distributions for the three SSEs show that in the Guerrero gap area, the slow slip occurs at shallower depth (updip limit around 15-20 km) than in surrounding regions. The InSAR data provide additional information for the 2006 SSE. The joint inversion of InSAR and cGPS data confirms the lateral variation of the slip distribution along the trench, with shallower slip in the Guerrero seismic gap, west of Acapulco, and deeper slip further east. Inversion of inter-SSE displacement rates reveal that during the inter-SSE time intervals, the interplate coupling is high in the area where the slow slip subsequently occurs. Over a 12 year period, corresponding to three cycles of SSEs, our results reveal that the accumulated slip deficit in the Guerrero gap area is only ¼ of the slip deficit accumulated on both sides of the gap. Moreover, the regions of large slip deficit coincide with the rupture areas of recent large earthquakes. We conclude that the SSEs account for a major portion of the overall moment release budget in the Guerrero gap. If large subduction thrust earthquakes occur in the Guerrero gap, their recurrence time is probably increased compared to adjacent regions.

  9. Slipping on pedestrian surfaces: methods for measuring and evaluating the slip resistance.

    PubMed

    Wetzel, Christoph; Windhövel, Ulrich; Mewes, Detlef; Ceylan, Orhan

    2015-01-01

    Tripping, slipping and falling accidents are among the types of accident with a high incidence. This article describes the requirements concerning slip resistance, as well as the state of the art of slip resistance measurement standards in the European Community and the USA. The article also describes how risk assessment can be performed in the field. PMID:26414511

  10. Slip segmentation and slow rupture to the trench during the 2015, Mw8.3 Illapel, Chile earthquake

    NASA Astrophysics Data System (ADS)

    Melgar, Diego; Fan, Wenyuan; Riquelme, Sebastian; Geng, Jianghui; Liang, Cunren; Fuentes, Mauricio; Vargas, Gabriel; Allen, Richard M.; Shearer, Peter M.; Fielding, Eric J.

    2016-02-01

    The 2015 Mw8.3 Illapel, Chile earthquake is the latest megathrust event on the central segment of that subduction zone. It generated strong ground motions and a large (up to 11 m runup) tsunami which prompted the evacuation of more than 1 million people in the first hours following the event. Observations during recent earthquakes suggest that these phenomena can be associated with rupture on different parts of the megathrust. The deep portion generates strong shaking while slow, large slip on the shallow fault is responsible for the tsunami. It is unclear whether all megathrusts can have shallow slip during coseismic rupture and what physical properties regulate this. Here we show that the Illapel event ruptured both deep and shallow segments with substantial slip. We resolve a kinematic slip model using regional geophysical observations and analyze it jointly with teleseismic backprojection. We find that the shallow and deep portions of the megathrust are segmented and have fundamentally different behavior. We forward calculate local tsunami propagation from the resolved slip and find good agreement with field measurements, independently validating the slip model. These results show that the central portion of the Chilean subduction zone has accumulated a significant shallow slip deficit and indicates that, given enough time, shallow slip might be possible everywhere along the subduction zone.

  11. Joint Disorders

    MedlinePlus

    A joint is where two or more bones come together, like the knee, hip, elbow, or shoulder. Joints can be damaged by many types of injuries or diseases, including Arthritis - inflammation of a joint. It causes pain, stiffness, and swelling. Over time, ...

  12. Spatial and Temporal Evolution of Fault Slip on the Longitudinal Valley Fault Taiwan

    NASA Astrophysics Data System (ADS)

    Thomas, M.; Avouac, J.; Champenois, J.; Lee, J.

    2012-12-01

    The Longitudinal Valley Fault (LVF) in Eastern Taiwan is an exceptional example of a fault with high slip rate that produces both seismic and aseismic slip. This particular fault accounts for more than a third of the 9 cm/yr oblique convergence rate across Taiwan. Deformation of anthropogenic features shows that aseismic creep accounts for a significant fraction of fault slip near the surface whereas a fraction of the slip is also seismic since this fault has produced large M>6.5 earthquakes in 1951 and 2003. In this study, we analyze a dense set of geodetic and seismological data around the LVF including campaign-mode GPS measurements, times-series of daily solutions for Continuous GPS stations (CGPS), accelerometeric records of the 2003 Chenkung earthquake, and leveling measurements. To enhance the spatial resolution provided by these data we complement them with inSAR measurements produced from a series of ALOS images processed with the permanent scatter technique. The data, which cover the entire LVF and span the period from 1992 to 2010 are inverted for the temporal evolution of fault slip a depth using the Principal Component Analysis base Inversion Method (PCAIM). The technique allows the joint inversion of these diverse data, thus taking the advantage of the spatial resolution afforded by the inSAR data and the temporal resolution afforded by the CGPS data. We find that 1- seismic slip during the 2003 Chengkung earthquake occurred on a fault patch which had remained partially locked in the interseismic period; 2- the seismic rupture propagated partially into a zone of shallow aseismic interseismic creep but failed to reach the surface; 3- that aseismic afterslip occurred around but mostly updip of the ruptured area. The study allows estimating the fault slip budget (the fraction of aseismic and seismic slip) over the seismogenic depth range, and placing constraints on the fault frictional properties and their variations with space.

  13. "Walking-mode maps" based on slip/non-slip criteria.

    PubMed

    Yamaguchi, Takeshi; Hokkirigawa, Kazuo

    2008-01-01

    "Walking-Mode Maps", based on Slip/Non-Slip criteria, are proposed. Slip/Non-Slip criteria are expressed as follows: for a slip to occur: |F(h)/F(n)|(h) > or = mu(s) or |F(h)/F(n)|(t) > or = mu(s); for no slip to occur: |F(h)/F(n)|(h) < mu(s) or |F(h)/F(n)|(t) < mu(s). |F(h)/F(n)|(h) and |F(h)/F(n)|(t) are the maximum peak value of the traction coefficient at heel-strike and toe-off respectively, and mu(s) is the static friction coefficient between shoe sole and walkway. The "Walking-Mode Map" for the level-surface shows the possible regime of each walking mode as Slip, Slip possible or No slip. Our results, which are based upon a small population and strictly-specified test conditions, indicate that a static friction coefficient higher than 0.47 will prevent both forward and backward slips under our test conditions and under a range of step lengths of 0.55 to 0.95 m and walking speeds of 1.0 to 1.9 m/s. We also found that shorter steps reduce the chance of a slip. A "Walking-Mode Map" for inclined-surface ambulation has also been developed. The inclined-surface results show the friction and inclination-angle-related regime of each walking mode: Slip, Forward slip at heel-strike phase in descending, Backward slip at toe-off phase in ascending, or No slip. Again, extreme caution must be taken in generalizing these small-sample results (n=1, for the inclined tests) to the general population. PMID:18270447

  14. Salton Sea Satellite Image Showing Fault Slip

    Landsat satellite image (LE70390372003084EDC00) showing location of surface slip triggered along faults in the greater Salton Trough area. Red bars show the generalized location of 2010 surface slip along faults in the central Salton Trough and many additional faults in the southwestern section of t...

  15. Episodic tremor and slip on the Cascadia subduction zone: the chatter of silent slip.

    PubMed

    Rogers, Garry; Dragert, Herb

    2003-06-20

    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. PMID:12738870

  16. Structured surfaces for a giant liquid slip.

    PubMed

    Lee, Choongyeop; Choi, Chang-Hwan; Kim, Chang-Jin Cj

    2008-08-01

    We study experimentally how two key geometric parameters (pitch and gas fraction) of textured hydrophobic surfaces affect liquid slip. The two are independently controlled on precisely fabricated microstructures of posts and grates, and the slip length of water on each sample is measured using a rheometer system. The slip length increases linearly with the pitch but dramatically with the gas fraction above 90%, the latter trend being more pronounced on posts than on grates. Once the surfaces are designed for very large slips (>20 microm), however, further increase is not obtained in regular practice because the meniscus loses its stability. By developing near-perfect samples that delay the transition from a dewetted (Cassie) to a wetted (Wenzel) state until near the theoretical limit, we achieve giant slip lengths, as large as 185 microm. PMID:18764458

  17. Structured Surfaces for a Giant Liquid Slip

    NASA Astrophysics Data System (ADS)

    Lee, Choongyeop; Choi, Chang-Hwan; Kim, Chang-Jin “Cj”

    2008-08-01

    We study experimentally how two key geometric parameters (pitch and gas fraction) of textured hydrophobic surfaces affect liquid slip. The two are independently controlled on precisely fabricated microstructures of posts and grates, and the slip length of water on each sample is measured using a rheometer system. The slip length increases linearly with the pitch but dramatically with the gas fraction above 90%, the latter trend being more pronounced on posts than on grates. Once the surfaces are designed for very large slips (>20μm), however, further increase is not obtained in regular practice because the meniscus loses its stability. By developing near-perfect samples that delay the transition from a dewetted (Cassie) to a wetted (Wenzel) state until near the theoretical limit, we achieve giant slip lengths, as large as 185μm.

  18. [Evaporating Droplet and Imaging Slip Flows

    NASA Technical Reports Server (NTRS)

    Larson, R. G.

    2002-01-01

    In this report, we summarize work on Evaporating Droplet and Imaging Slip Flows. The work was primarily performed by post-doc Hue Hu, and partially by grad students Lei Li and Danish Chopra. The work includes studies on droplet evaporation and its effects on temperature and velocity fields in an evaporating droplet, new 3-D microscopic particle image velocimetry and direct visualization on wall slip in a surfactant solution. With the exception of the slip measurements, these projects were those proposed in the grant application. Instead of slip flow, the original grant proposed imaging electro-osmotic flows. However, shortly after the grant was issued, the PI became aware of work on electro-osmotic flows by the group of Saville in Princeton that was similar to that proposed, and we therefore elected to carry out work on imaging slip flows rather than electro-osmotic flows.

  19. The role of water in slip casting

    NASA Technical Reports Server (NTRS)

    Mccauley, R. A.; Phelps, G. W.

    1984-01-01

    Slips and casting are considered in terms of physical and colloidal chemistry. Casting slips are polydisperse suspensions of lyophobic particles in water, whose degree of coagulation is controlled by interaction of flocculating and deflocculating agents. Slip casting rate and viscosity are functions of temperature. Slip rheology and response to deflocculating agents varies significantly as the kinds and amounts of colloid modifiers change. Water is considered as a raw material. Various concepts of water/clay interactions and structures are discussed. Casting is a de-watering operation in which water moves from slip to cast to mold in response to a potential energy termed moisture stress. Drying is an evaporative process from a free water surface.

  20. Prediction of slips: an evaluation of utilized coefficient of friction and available slip resistance.

    PubMed

    Burnfield, J M; Powers, C M

    2006-08-15

    The purpose of this study was to investigate the relationship between measures of floor surface slip resistance and an individual's peak utilized coefficient of friction (COFU) on the probability of a slip occurring during level walking. Video, kinematic and ground reaction force data were recorded simultaneously as subjects walked at a self-selected speed during conditions of normal and reduced floor surface slip resistance. Peak COFU during weight acceptance was calculated and the available floor surface slip resistance was measured using the variable incidence tribometer (VIT). Separate logistic regression analyses identified that knowledge of the available slip resistance (as measured by the VIT) in combination with an individual's peak COFU allowed for greater accuracy in classifying slip outcomes (89.5%; p = 0.004), while knowledge of only the available slip resistance reduced the accuracy of categorization to 78.9% (p = 0.021). PMID:16803728

  1. STUDY ON EARTHQUAKE DAMAGE IN DUCTILE IRON PIPE JOINT

    NASA Astrophysics Data System (ADS)

    Kumaki, Yoshihiro; Miyajima, Masakatsu

    In recent year, most of water pipe damages caused by earthquakes have been reported by pull out at joint. Ductile iron pipe are classified as mechanical type for earthquake-proof or non-earthquake-proof joint and slip-on type for non-e-proof joint. The earthquake proof joint never been damaged in the past earthquakes but the damage for another types of joint occurred frequently. Since the type of joint depends on the manufaction age and pipe diameter. Therefore, it could be estimated the relation between the damage rate and joint type. This paper focused on this issue. The resistance force against pull out at joint was clarified by the experiments and the results are discussed. Finally the earthquake adaptability for the different joint types is proposed.

  2. Comparison of slip distribution of large slow slip events in Guerrero subduction zone

    NASA Astrophysics Data System (ADS)

    Cotton, F.; Vergnolle, M.; Thollon, O.; Campillo, M.; Manighetti, I.; Cotte, N.; Walpersdorf, A.; Kostoglodov, V.

    2008-12-01

    Aseismic slow slip events (SSEs) have been reported in most of the well geodetically instrumented subduction zones worldwide (Japan, Cascadia, Mexico, New Zealand, Costa Rica, Alaska). For most of the observed SSEs, the slip distribution on the subduction interface was inferred from the surface GPS displacements to be located at the downdip extension of the seismogenic zone, in the conditionally stable frictional regime. Hence, the stress transfer due to the SSEs on the seismogenic zone should advance the occurrence time of the next strong subduction earthquake. Since the installation of the GPS network, the Guerrero gap area, Mexico, has been affected by large SSEs in 1998, 2002, 2006. We have analyzed the Mexican permanent GPS data describing the 2002 and 2006 SSEs, so that to determine and compare their slip distribution. The resolution analysis made on those data shows that the slip distribution is dependent on the number and location of the GPS stations. The slip distribution inferred for the 2006 SSE, for which the GPS network was denser, is thus much better resolved than that for the 2002 event. The inversion result is not unique. However, for each event, all possible solutions draw a similar, overall slip distribution pattern. Both events are similar in terms of equivalent moment magnitude (7.4 to 7.6) and of maximum slip amplitude on the interface (up to 20 cm). By contrast, the size and location of the slip zone differ from one event to the next: In 2002, the zone sustaining slow slip spreads through the entire Guerrero subduction segment plus the western part of the Oaxaca subduction segment (~400 x 150 km); the slip is quite evenly distributed over the entire zone, though maximum slip concentrates both at the down dip limit of the seismogenic zone and in the stably slipping region. In 2006, slip occurs only in the Guerrero gap thus over an area twice smaller (~230 x 150 km) than before; in the west, the maximum slip is located both in the seismogenic zone and at its downdip extension, whereas in the east, the maximum slip localizes in the transition and stably slipping zone. Our results thus show that slip distribution and location of maximum slip markedly differ from one large SSE to the next. This suggests that the 2002 and 2006 events are parts of a complex multi-events sequence. Furthermore, in both events, slow slip occurred both in the seismogenic zone and below it. This demonstrates that SSEs play a role in the seismic cycle that is more complex than previously thought. This makes them a crucial element to be taken into account in seismic hazard assessment.

  3. Maximum slip in earthquake fault zones, apparent stress, and stick-slip friction

    USGS Publications Warehouse

    McGarr, A.; Fletcher, Joe B.

    2003-01-01

    The maximum slip, observed or inferred, for a small patch within the larger fault zone of an earthquake is a remarkably well-constrained function of the seismic moment. A large set of maximum slips, mostly derived from slip models of major earthquakes, indicate that this parameter increases according to the cube root of the seismic moment. Consistent with this finding, neither the average slip rate for the patches of maximum slip nor the apparent stresses of earthquakes show any systematic dependence on seismic moment. Maximum average slip rates are several meters per second independent of moment and, for earthquakes in continental crustal settings, the apparent stress is limited to about 10 MPa. Results from stick-slip friction experiments in the laboratory, combined with information about the state of stress in the crust, can be used to predict, quite closely, the maximum slips and maximum average slip rates within the fault zones of major earthquakes as well as their apparent stresses. These findings suggest that stick-slip friction events observed in the laboratory and earthquakes in continental settings, even with large magnitudes, have similar rupture mechanisms.

  4. Electrostatic precursors to granular slip events.

    PubMed

    Shinbrot, Troy; Kim, Nam H; Thyagu, N Nirmal

    2012-07-01

    It has been known for over a century that electrical signals are produced by material failure, for example during crack formation of crystals and glasses, or stick-slip motion of liquid mercury on glass. We describe here new experiments revealing that slip events in cohesive powders also produce electrical signals, and remarkably these signals can appear significantly in advance of slip events. We have confirmed this effect in two different experimental systems and using two common powdered materials, and in a third experiment we have demonstrated that similar voltage signals are produced by crack-like defects in several powdered materials. PMID:22689956

  5. Improved Slip Casting Of Ceramic Models

    NASA Technical Reports Server (NTRS)

    Buck, Gregory M.; Vasquez, Peter; Hicks, Lana P.

    1994-01-01

    Improved technique of investment slip casting developed for making precise ceramic wind-tunnel models. Needed in wind-tunnel experiments to verify predictions of aerothermodynamical computer codes. Ceramic materials used because of their low heat conductivities and ability to survive high temperatures. Present improved slip-casting technique enables casting of highly detailed models from aqueous or nonaqueous solutions. Wet shell molds peeled off models to ensure precise and undamaged details. Used at NASA Langley Research Center to form superconducting ceramic components from nonaqueous slip solutions. Technique has many more applications when ceramic materials developed further for such high-strength/ temperature components as engine parts.

  6. Friction of water slipping in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Ma, Ming D.; Shen, Luming; Sheridan, John; Liu, Jefferson Zhe; Chen, Chao; Zheng, Quanshui

    2011-03-01

    Liquid slip is essential in nanofluidic systems, as shrinking channel size leads to a dramatic increase in flow resistance and thus high-energy consumption for driving nonslip flow. Using large-scale nonequilibrium molecular dynamics simulation of water flowing in carbon nanotubes (CNT’s), we show that the relationship between the CNT wall-water interfacial friction stress and slip velocity follows a transition-state-theory-based inverse hyperbolic sine function, which remains universally valid regardless of wetting properties, CNT chiralities, and CNT sizes, and holds for all slip velocities from 0 to 1400 m/s. The finding could benefit the research in desalination and other chemical purification techniques.

  7. Slip mechanisms in complex fluid flows.

    PubMed

    Hatzikiriakos, Savvas G

    2015-10-28

    The classical no-slip boundary condition of fluid mechanics is not always a valid assumption for the flow of several classes of complex fluids including polymer melts, their blends, polymer solutions, microgels, glasses, suspensions and pastes. In fact, it appears that slip effect in these systems is the rule and not the exemption. The occurrence of slip complicates the analysis of rheological data, although it provides new opportunities to understand their behavior in restricted environments delineating additional molecular mechanisms i.e. entropic restrictions due to limitations in the number of molecular conformations. This article discusses these complexities and provides future research opportunities. PMID:26345121

  8. Flow and slip transition in nanochannels.

    PubMed

    Li, Long; Mo, Jingwen; Li, Zhigang

    2014-09-01

    We experimentally investigate the Poiseuille flows in nanochannels. It is found that the flow rate undergoes a transition between two linear regimes as the shear rate is varied. The transition indicates that the nonslip boundary condition is valid at low shear rate. When the shear rate is larger than a critical value, slip takes place and the slip length increases linearly with increasing shear rate before approaching a constant value. The results reported in this work can help advance the understanding of flow slip in nanochannels. PMID:25314525

  9. Multiparameter investigation of gravitational slip

    SciTech Connect

    Daniel, Scott F.; Caldwell, Robert R.; Cooray, Asantha; Serra, Paolo; Melchiorri, Alessandro

    2009-07-15

    A detailed analysis of gravitational slip, a new post-general relativity cosmological parameter characterizing the degree of departure of the laws of gravitation from general relativity on cosmological scales, is presented. This phenomenological approach assumes that cosmic acceleration is due to new gravitational effects; the amount of spacetime curvature produced per unit mass is changed in such a way that a universe containing only matter and radiation begins to accelerate as if under the influence of a cosmological constant. Changes in the law of gravitation are further manifest in the behavior of the inhomogeneous gravitational field, as reflected in the cosmic microwave background, weak lensing, and evolution of large-scale structure. The new parameter {pi}{sub 0} is naively expected to be of order unity. However, a multiparameter analysis, allowing for variation of all of the standard cosmological parameters, finds that {pi}{sub 0}=0.09{sub -0.59}{sup +0.74}(2{sigma}), where {pi}{sub 0}=0 corresponds to a cosmological constant plus cold dark matter universe under general relativity. Future probes of the cosmic microwave background (Planck) and large-scale structure (Euclid) may improve the limits by a factor of 4.

  10. Slip compensation at fault damage zones along earthquake surface ruptures

    NASA Astrophysics Data System (ADS)

    Choi, J.; Kim, Y.

    2013-12-01

    Surface ruptures associated with earthquake faulting commonly comprise a number of segments, and the discontinuities form tip and linking damage zones, which are deformed regions consisting of secondary features. Stress transferring or releasing, when seismic waves pass through the discontinuities, could produce different slip features depending on rupture propagation or termination. Thus, slip patterns at fault damage zones can be one of the key factors to understand fault kinematics, fault evolution and, hence, earthquake hazard. In some previous studies (e.g. Peacock and Sanderson, 1991; Kim and Sanderson, 2005), slip distribution along faults to understand the connectivity or maturity of segmented faults system have commonly been analyzed based on only the main slip components (dip-slip or strike-slip). Secondary slip components, however, are sometimes dominant at fault damage zones, such as linkage and tip zones. In this study, therefore, we examine slip changes between both main and secondary slip components along unilaterally propagated coseismic strike-slip ruptures. Horizontal and vertical components of slip and the slip compensation patterns at tip and linking damage zones are various from slip deficit (decrease in both slip components) through slip compensation (increase of vertical slip with horizontal slip decrease) to slip neutral. Front and back tip zones, which are classified depending on main propagation direction of earthquake ruptures, show different slip patterns; slip compensation is observed at the frontal tip whilst slip deficit occurs at the back tip zone. Average values of the two slip components and their compensative patterns at linking damage zones are closely related with the ratio of length to width (L/W) of linkage geometry; the horizontal slip is proportional to the ratio of L/W, whilst the vertical slip shows little dependence on the value L/W. When the L/W is greater than ~2, average values of two slip components are almost similar to those of the main traces. In contrast, when the L/W < 2, the vertical slip is either increased or decreased as the horizontal slip is decreased, depending on the maturity of the linking zone. Thus, we argue that slip patterns at linking damage zones may be controlled by the LW-ratio of linking damage zones and hence structural maturities of the segmented fault systems. In conclusion, slip patterns at fault damage zones along earthquake surface ruptures are various depending on the maturity of linkage zones and/or the rupture propagation direction. Therefore, the consideration of slip compensation as well as damage structures along surface ruptures must be very useful to understand fault evolution and, hence, to assess seismic hazards around active fault systems.

  11. Ceramic joints

    DOEpatents

    Miller, Bradley J.; Patten, Jr., Donald O.

    1991-01-01

    Butt joints between materials having different coefficients of thermal expansion are prepared having a reduced probability of failure of stress facture. This is accomplished by narrowing/tapering the material having the lower coefficient of thermal expansion in a direction away from the joint interface and not joining the narrow-tapered surface to the material having the higher coefficient of thermal expansion.

  12. Slip boundary conditions over curved surfaces

    NASA Astrophysics Data System (ADS)

    Guo, Lin; Chen, Shiyi; Robbins, Mark O.

    2016-01-01

    Molecular dynamics simulations are used to investigate the influence of surface curvature on the slip boundary condition for a simple fluid. The slip length is measured for flows in planar and cylindrical geometries with a range of wall-fluid interactions. As wall curvature increases, the slip length decreases dramatically for closely packed surfaces and increases for sparse ones. The magnitude of the changes depends on the crystallographic orientation and differs for flow along and perpendicular to the direction of curvature. These different patterns of behavior are related to the curvature-induced variation in the ratio of the spacing between fluid atoms to the spacing between minima in the potential from the solid surface. The results are consistent with a microscopic theory for the viscous friction between fluid and wall that expresses the slip length in terms of the lateral response of the fluid to the wall potential and the characteristic decay time of this response.

  13. Slip-stream corrections performance computation

    NASA Technical Reports Server (NTRS)

    Warner, Edward P

    1920-01-01

    This report is an analysis of experiments performed by Eiffel on the air velocity in slip stream of a propeller, and also includes a theoretical discussion of the magnitude of the velocity in different propellers.

  14. Slip-mediated dewetting of polymer microdroplets.

    PubMed

    McGraw, Joshua D; Chan, Tak Shing; Maurer, Simon; Salez, Thomas; Benzaquen, Michael; Raphaël, Elie; Brinkmann, Martin; Jacobs, Karin

    2016-02-01

    Classical hydrodynamic models predict that infinite work is required to move a three-phase contact line, defined here as the line where a liquid/vapor interface intersects a solid surface. Assuming a slip boundary condition, in which the liquid slides against the solid, such an unphysical prediction is avoided. In this article, we present the results of experiments in which a contact line moves and where slip is a dominating and controllable factor. Spherical cap-shaped polystyrene microdroplets, with nonequilibrium contact angle, are placed on solid self-assembled monolayer coatings from which they dewet. The relaxation is monitored using in situ atomic force microscopy. We find that slip has a strong influence on the droplet evolutions, both on the transient nonspherical shapes and contact line dynamics. The observations are in agreement with scaling analysis and boundary element numerical integration of the governing Stokes equations, including a Navier slip boundary condition. PMID:26787903

  15. Action slips during whole-body vibration.

    PubMed

    Ishimatsu, Kazuma; Meland, Anders; Hansen, Tor Are S; Kåsin, Jan Ivar; Wagstaff, Anthony S

    2016-07-01

    Helicopter aircrew members engage in highly demanding cognitive tasks in an environment subject to whole-body vibration (WBV). Sometimes their actions may not be according to plan (e.g. action slips and lapses). This study used a Sustained Attention to Response Task (SART) to examine whether action slips were more frequent during exposure to WBV. Nineteen participants performed the SART in two blocks. In the WBV block participants were exposed to 17 Hz vertical WBV, which is typical of larger helicopter working environments. In the No-WBV block there was no WBV. There were more responses to the rare no-go digit 3 (i.e. action slips) in the WBV block, and participants responded faster in the WBV block. These results suggest that WBV influences response inhibition, and can induce impulsive responding. WBV may increase the likelihood of action slips, mainly due to failure of response inhibition. PMID:26611989

  16. Slip casting alumina with Na-CMC

    SciTech Connect

    Ruys, A.J.; Sorrell, C.C.

    1996-11-01

    Many forming methods are in common use for engineering ceramics. Of these, slip casting is an ideal forming method because of its low cost, simplicity and flexibility, potential for uniform particle packing and suitability to the production of articles of intricate shape. Slip casting nonclay materials, such as alumina, requires the use of both a deflocculant and a binder. There are many commercially available deflocculants and binders that can be tested in alumina casting slips. However, determination of a suitable deflocculant/binder combination and quantification of the optimal additions of the deflocculant/binder pair can be time consuming. Certain deflocculants are capable of acting as binders. One such additive is sodium carboxymethylcellulose (Na-cmc), a cellulose ether. Na-cmc is a powerful binder. It is a member of the carbohydrate binder group--the binder group with the strongest binding power. It is capable of acting as a deflocculant in glazes and nonclay casting slips.

  17. Macroscopic Quantum Cotunneling of Phase Slips

    NASA Astrophysics Data System (ADS)

    Belkin, Andrey; Belkin, Maxim; Vakaryuk, Victor; Khlebnikov, Sergei; Bezryadin, Alexey

    2014-03-01

    Quantum phenomena that do not have analogues in the classical world include quantum superposition and tunneling. Despite significant efforts invested into demonstration of quantum effects at the macroscopic level, the main principles that govern the transition from classical to quantum are not well understood. Here we report a study of macroscopic quantum tunneling of phase slips that involve both superconducting and normal degrees of freedom in a superconducting nanowire loop. We discover that in addition to single phase slips that unwind the phase difference along the loop by 2 ?, there are transitions that change the phase by 4 ?. Experimentally we identify the regime in which, surprisingly, 4 ? phase slips are more likely than 2 ? ones. We interpret our observations in terms of macroscopic cotunneling effect defined as an exact synchronization of two macroscopic phase slip events. The work was supported by grant the DOE Award No. DE-FG0207ER46453, and the NSF No. DMR10-05645

  18. Methodology for the interpretation of fault-slip seismicity in a weak shear zone

    NASA Astrophysics Data System (ADS)

    Sainoki, Atsushi; Mitri, Hani S.

    2014-11-01

    Fault-slip related seismic events that occur in underground mines could inflict severe damage to underground openings; thus a proper estimation of fault-slip potential in active mining areas is of paramount importance in assessing its risk. It is not uncommon in underground mines that large seismic events take place away from stopes being extracted, where fault-slip potential is presumed not to be high enough to result in those seismic events. In the present paper, fault-slip related seismic events taking place within a weak shear zone in Garson Mine, Sudbury, Canada are investigated. First, in order to understand the stress states of rockmass in the mine, numerical analysis is carried out with a 3D mine-wide model whilst assuming isotropic elasticity. The result obtained from the analysis reveals that the shear stress of rockmass in a weak shear zone does not reach the maximum shear strength determined by Mohr-Coulomb failure criterion with basic friction angles of the rockmass. The result contradicts a fact that quite a few seismic events have been actually recorded in the regions with micro seismic monitoring systems installed in the mine. As an interpretation of that, it is postulated that variations in shear stiffness within the shear zone contribute to the generation of high slip potential resulting in the occurrence of those seismic events. In order to justify the postulation, numerical analysis is additionally carried out, in which the shear zone is modelled with transversely isotropic models, of which shear stiffness is decreased in the same direction as a measured joint orientation in the shear zone. For source regions of those seismic events, isotropic models are used without decreasing its shear stiffness, thus resulting in the discrepancy in shear stiffness between the source regions and other areas in the shear zone. The result obtained from the analysis verifies that fault-slip potential drastically increases within the source regions due to the difference in shear stiffness. It is further found out from dynamic analysis in which fault-slip is simulated with Barton's shear strength model that the increasing slip potential is high enough to cause large seismic events in the regions. In the present study, the interpretation of seismic events occurring within a weak shear zone is provided, and a methodology to simulate high fault-slip potential that could be generated within the shear zone is developed. The methodology can be used with back analysis to determine the mechanical properties of the weak shear zone, which lead to the better estimation of fault-slip potential.

  19. Temporomandibular Joint, Closed

    MedlinePlus

    ... Gallery > Oral Health > The Temporomandibular Joint, Closed The Temporomandibular Joint, Closed Main Content Title: The Temporomandibular Joint, Closed Description: The temporomandibular joint connects the ...

  20. Nonlinear dynamical triggering of slow slip

    SciTech Connect

    Johnson, Paul A; Knuth, Matthew W; Kaproth, Bryan M; Carpenter, Brett; Guyer, Robert A; Le Bas, Pierre - Yves; Daub, Eric G; Marone, Chris

    2010-12-10

    Among the most fascinating, recent discoveries in seismology have been the phenomena of triggered slip, including triggered earthquakes and triggered-tremor, as well as triggered slow, silent-slip during which no seismic energy is radiated. Because fault nucleation depths cannot be probed directly, the physical regimes in which these phenomena occur are poorly understood. Thus determining physical properties that control diverse types of triggered fault sliding and what frictional constitutive laws govern triggered faulting variability is challenging. We are characterizing the physical controls of triggered faulting with the goal of developing constitutive relations by conducting laboratory and numerical modeling experiments in sheared granular media at varying load conditions. In order to simulate granular fault zone gouge in the laboratory, glass beads are sheared in a double-direct configuration under constant normal stress, while subject to transient perturbation by acoustic waves. We find that triggered, slow, silent-slip occurs at very small confining loads ({approx}1-3 MPa) that are smaller than those where dynamic earthquake triggering takes place (4-7 MPa), and that triggered slow-slip is associated with bursts of LFE-like acoustic emission. Experimental evidence suggests that the nonlinear dynamical response of the gouge material induced by dynamic waves may be responsible for the triggered slip behavior: the slip-duration, stress-drop and along-strike slip displacement are proportional to the triggering wave amplitude. Further, we observe a shear-modulus decrease corresponding to dynamic-wave triggering relative to the shear modulus of stick-slips. Modulus decrease in response to dynamical wave amplitudes of roughly a microstrain and above is a hallmark of elastic nonlinear behavior. We believe that the dynamical waves increase the material non-affine elastic deformation during shearing, simultaneously leading to instability and slow-slip. The inferred triggered slow-slip on the San Andreas Fault at Parkfield, CA., due to December, 2003 Mw6.5 San Simeon Earthquake (Breguier et al., Science 321, p.1478, 2008) shows very similar characteristics to what we observe in the laboratory, suggesting an extremely low in situ effective stress or a weak fault and a nonlinear-dynamical triggering mechanism.

  1. Slip-Related Changes in Plantar Pressure Distribution, and Parameters for Early Detection of Slip Events

    PubMed Central

    Choi, Seungyoung; Cho, Hyungpil; Kang, Boram; Lee, Dong Hun; Kim, Mi Jung

    2015-01-01

    Objective To investigate differences in plantar pressure distribution between a normal gait and unpredictable slip events to predict the initiation of the slipping process. Methods Eleven male participants were enrolled. Subjects walked onto a wooden tile, and two layers of oily vinyl sheet were placed on the expected spot of the 4th step to induce a slip. An insole pressure-measuring system was used to monitor plantar pressure distribution. This system measured plantar pressure in four regions (the toes, metatarsal head, arch, and heel) for three events: the step during normal gait; the recovered step, when the subject recovered from a slip; and the uncorrected, harmful slipped step. Four variables were analyzed: peak pressure (PP), contact time (CT), the pressure-time integral (PTI), and the instant of peak pressure (IPP). Results The plantar pressure pattern in the heel was unique, as compared with other parts of the sole. In the heel, PP, CT, and PTI values were high in slipped and recovered steps compared with normal steps. The IPP differed markedly among the three steps. The IPPs in the heel for the three events were, in descending order (from latest to earliest), slipped, recovered, and normal steps, whereas in the other regions the order was normal, recovered, and slipped steps. Finally, the metatarsal head-to-heel IPP ratios for the normal, recovered, and slipped steps were 6.1±2.9, 3.1±3.0, and 2.2±2.5, respectively. Conclusion A distinctive plantar pressure pattern in the heel might be useful for early detection of a slip event to prevent slip-related injuries. PMID:26798603

  2. Compliant joint

    NASA Technical Reports Server (NTRS)

    Eklund, Wayne D. (Inventor); Kerley, James J. (Inventor)

    1990-01-01

    A compliant joint is provided for prosthetic and robotic devices which permits rotation in three different planes. The joint provides for the controlled use of cable under motion. Perpendicular outer mounting frames are joined by swaged cables that interlock at a center block. Ball bearings allow for the free rotation of the second mounting frame relative to the first mounting frame within a predetermined angular rotation that is controlled by two stop devices. The cables allow for compliance at the stops and the cables allow for compliance in six degrees of freedom enabling the duplication or simulation of the rotational movement and flexibility of a natural hip or knee joint, as well as the simulation of a joint designed for a specific robotic component for predetermined design parameters.

  3. Joint pain

    MedlinePlus

    ... or conditions. It may be linked to arthritis , bursitis , and muscle pain . No matter what causes it, ... Autoimmune diseases such as rheumatoid arthritis and lupus Bursitis Chondromalacia patellae Crystals in the joint: gout (especially ...

  4. Constraining Paleoearthquake Slip Distributions with Coral Microatolls

    NASA Astrophysics Data System (ADS)

    Lindsay, A.; McCloskey, J.; nic Bhloscaidh, M.; Murphy, S.

    2014-12-01

    Key to understanding the threat posed by large megathrust earthquakes is identifying where the potential for these destructive events exists. Studying extended sequences of earthquakes, Slip Deficit and Stress Evolution modelling techniques may hold the key to locating areas of concern. However, as well as using recent instrumentally constrained slip distributions they require the production of high resolution source models for pre-instrumental events. One place we can attempt this longer term modelling is along the Sunda Trench with its record of large megathrust earthquakes dating back centuries. Coral microatolls populating the intertidal areas of the Sumatran Forearc act as long-term geodetic recorders of tectonic activity. Repeated cycles of stress accumulation and release alter relative sea levels around these islands. Growth of corals, controlled by the level of the lowest tide, exploit interseismic rises in sea level. In turn, they experience die-offs when coseismic drops in sea level lead to subaerially exposure. Examination of coral stratigraphy reveals a history of displacements from which information of past earthquakes can be inferred. We have developed a Genetic Algorithm Slip Estimator (GASE) to rapidly produce high resolution slip distributions from coral displacement data. GASE recombines information held in populations of randomly generated slip distributions, to create superior models, satisfying observed displacements. Non-unique solutions require multiple iterations of the algorithm, producing a suite of models from which an ensemble slip distribution is drawn. Systematic testing of the algorithm demonstrates its ability to reliably estimate both known synthetic and instrumentally constrained slip distributions based on surface displacements. We will present high-resolution source models satisfying published displacement data for a number recent and paleoearthquakes along the Sunda trench, including the great 1797 and 1833 events.

  5. Progressive slip after removal of screw fixation in slipped capital femoral epiphysis: two case reports

    PubMed Central

    2012-01-01

    Introduction In slipped capital femoral epiphysis the femoral neck displaces relative to the head due to weakening of the epiphysis. Early recognition and adequate surgical fixation is essential for a good functional outcome. The fixation should be secured until the closure of the epiphysis to prevent further slippage. A slipped capital femoral epiphysis should not be confused with a femoral neck fracture. Case presentation Case 1 concerns a 15-year-old boy with an adequate initial screw fixation of his slipped capital femoral epiphysis. Unfortunately, it was thought that the epiphysis had healed and the screw was removed after 11 weeks. This caused new instability with a progressive slip of the femoral epiphysis and subsequently re-fixation and a subtrochanteric correction osteotomy was obligatory. Case 2 concerns a 13-year-old girl with persistent hip pain after screw fixation for slipped capital femoral epiphysis. The screw was removed as lysis was seen around the screw on the hip X-ray. This operation created a new unstable situation and the slip progressed resulting in poor hip function. A correction osteotomy with re-screw fixation was performed with a good functional result. Conclusion A slipped epiphysis of the hip is not considered ‘healed’ after a few months. Given the risk of progression of the slip the fixation material cannot be removed before closure of the growth plate. PMID:23181447

  6. Spectrum of slip behaviour in Tohoku fault zone samples at plate tectonic slip rates

    NASA Astrophysics Data System (ADS)

    Ikari, Matt J.; Ito, Yoshihiro; Ujiie, Kohtaro; Kopf, Achim J.

    2015-11-01

    During the 2011 Tohoku-oki earthquake, extremely extensive coseismic slip ruptured shallow parts of the Japan Trench subduction zone and breached the sea floor. This part of the subduction zone also hosts slow slip events (SSE). The fault thus seems to have a propensity for slip instability or quasi-instability that is unexpected on the shallow portions of important fault zones. Here we use laboratory experiments to slowly shear samples of rock recovered from the Tohoku-oki earthquake fault zone as part of the Japan Trench Fast Drilling Project. We find that infrequent perturbations in rock strength appear spontaneously as long-term SSE when the samples are sheared at a constant rate of about 8.5 cm yr-1, equivalent to the plate-convergence rate. The shear strength of the rock drops by 3 to 6%, or 50 kPa to 120 kPa, over about 2 to 4 h. Slip during these events reaches peak velocities of up to 25 cm yr-1, similar to SSE observed in several circum-Pacific subduction zones. Furthermore, the sheared samples exhibit the full spectrum of fault-slip behaviours, from fast unstable slip to slow steady creep, which can explain the wide range of slip styles observed in the Japan Trench. We suggest that the occurrence of SSE at shallow depths may help identify fault segments that are frictionally unstable and susceptible to large coseismic slip propagation.

  7. Kids' Slips: What Young Children's Slips of the Tongue Reveal about Language Development

    ERIC Educational Resources Information Center

    Jaeger, Jeri J.

    2005-01-01

    The study of speech errors, or "slips of the tongue," is a time-honored methodology which serves as a window to the representation and processing of language and has proven to be the most reliable source of data for building theories of speech production planning. However, until "Kids' Slips," there has never been a corpus of such errors from…

  8. Digital slip frequency generator and method for determining the desired slip frequency

    DOEpatents

    Klein, Frederick F.

    1989-01-01

    The output frequency of an electric power generator is kept constant with variable rotor speed by automatic adjustment of the excitation slip frequency. The invention features a digital slip frequency generator which provides sine and cosine waveforms from a look-up table, which are combined with real and reactive power output of the power generator.

  9. The Scaling of the Slip Weakening Distance (Dc) With Final Slip During Dynamic Earthquake Rupture

    NASA Astrophysics Data System (ADS)

    Tinti, E.; Fukuyama, E.; Cocco, M.; Piatanesi, A.

    2005-12-01

    Several numerical approaches have been recently proposed to retrieve the evolution of dynamic traction during the earthquake propagation on extended faults. Although many studies have shown that the shear traction evolution as a function of time and/or slip may be complex, they all reveal an evident dynamic weakening behavior during faulting. The main dynamic parameters describing traction evolution are: the yield stress, the residual kinetic stress level and the characteristic slip weakening distance Dc. Recent investigations on real data yield the estimate of large Dc values on the fault plane and a correlation between Dc and the final slip. In this study, we focus our attention on the characteristic slip weakening distance Dc and on its variability on the fault plane. Different physical mechanisms have been proposed to explain the origin of Dc, some of them consider this parameter as a scale dependent quantity. We have computed the rupture history from several spontaneous dynamic models imposing a slip weakening law with prescribed Dc distributions on the fault plane. These synthetic models provide the slip velocity evolution during the earthquake rupture. We have therefore generated a set of slip velocity models by fitting the "true" slip velocity time histories with an analytical source time function. To this goal we use the Yoffe function [Tinti et al. 2005], which is dynamically consistent and allows a flexible parameterization. We use these slip velocity histories as a boundary condition on the fault plane to compute the traction evolution. We estimate the Dc values from the traction versus slip curves. We therefore compare the inferred Dc values with those of the original dynamic models and we found that the Dc estimates are very sensitive to the adopted slip velocity function. Despite the problem of resolution that limits the estimate of Dc from kinematic earthquake models and the tradeoff that exists between Dc and strength excess, we show that to correctly retrieve the original Dc it is necessary to reproduce the details of the slip velocity function. In particular, the fast slip positive acceleration, the peak slip velocity and its duration.

  10. Discrete Element Modeling of Stick-Slip Instability and Induced Microseismicity

    NASA Astrophysics Data System (ADS)

    Khazaei, Cyrus; Hazzard, Jim; Chalaturnyk, Rick

    2016-03-01

    Using Particle Flow Code, a discrete element model is presented in this paper that allows direct modeling of stick-slip behavior in pre-existing weak planes such as joints, beddings, and faults. The model is used to simulate a biaxial sliding experiment from literature on a saw-cut specimen of Sierra granite with a single fault. The fault is represented by the smooth-joint contact model. Also, an algorithm is developed to record the stick-slip induced microseismic events along the fault. Once the results compared well with laboratory data, a parametric study was conducted to investigate the evolution of the model's behavior due to varying factors such as resolution of the model, particle elasticity, fault coefficient of friction, fault stiffness, and normal stress. The results show a decrease in shear strength of the fault in the models with smaller particles, smaller coefficient of friction of the fault, harder fault surroundings, softer faults, and smaller normal stress on the fault. Also, a higher rate of displacement was observed for conditions resulting in smaller shear strength. An increase in b-values was observed by increasing the resolution or decreasing the normal stress on the fault, while b-values were not sensitive to changes in elasticity of the fault or its surrounding region. A larger number of recorded events were observed for the models with finer particles, smaller coefficient of friction of the fault, harder fault surroundings, harder fault, and smaller normal stress on the fault. The results suggest that it is possible for the two ends of a fault to be still while there are patches along the fault undergoing stick-slips. Such local stick-slips seem to provide a softer surrounding for their neighbor patches facilitating their subsequent stick-slips.

  11. Discrete Element Modeling of Stick-Slip Instability and Induced Microseismicity

    NASA Astrophysics Data System (ADS)

    Khazaei, Cyrus; Hazzard, Jim; Chalaturnyk, Rick

    2015-02-01

    Using Particle Flow Code, a discrete element model is presented in this paper that allows direct modeling of stick-slip behavior in pre-existing weak planes such as joints, beddings, and faults. The model is used to simulate a biaxial sliding experiment from literature on a saw-cut specimen of Sierra granite with a single fault. The fault is represented by the smooth-joint contact model. Also, an algorithm is developed to record the stick-slip induced microseismic events along the fault. Once the results compared well with laboratory data, a parametric study was conducted to investigate the evolution of the model's behavior due to varying factors such as resolution of the model, particle elasticity, fault coefficient of friction, fault stiffness, and normal stress. The results show a decrease in shear strength of the fault in the models with smaller particles, smaller coefficient of friction of the fault, harder fault surroundings, softer faults, and smaller normal stress on the fault. Also, a higher rate of displacement was observed for conditions resulting in smaller shear strength. An increase in b-values was observed by increasing the resolution or decreasing the normal stress on the fault, while b-values were not sensitive to changes in elasticity of the fault or its surrounding region. A larger number of recorded events were observed for the models with finer particles, smaller coefficient of friction of the fault, harder fault surroundings, harder fault, and smaller normal stress on the fault. The results suggest that it is possible for the two ends of a fault to be still while there are patches along the fault undergoing stick-slips. Such local stick-slips seem to provide a softer surrounding for their neighbor patches facilitating their subsequent stick-slips.

  12. Hairpin river loops and slip-sense inversion on southeast Asian strike-slip faults

    NASA Astrophysics Data System (ADS)

    Lacassin, Robin; Replumaz, Anne; Hervé Leloup, P.

    1998-08-01

    In the Golden Triangle region of southeast Asia (northern Thailand, Laos and Burma, southern Yunnan), the Mekong, Salween, and neighboring rivers show hairpin geometries where they cross active strike-slip faults. Restoration of young, left-lateral offsets of these rivers leaves residual right-lateral bends of many kilometers. We interpret these hairpins as evidence of late Cenozoic slip-sense inversion on these faults, about 5 to 20 Ma. Near the Red River fault, stress field and slip-sense inversion occurred ca. 5 Ma. This implies that the present course of these large rivers has existed for at least several million years. Pliocene Quaternary slip rates, possibly on the order of 1 mm/yr, are inferred on each of the strike-slip faults of the Golden Triangle.

  13. Active and recent strike-slip tectonics

    NASA Astrophysics Data System (ADS)

    Nur, Amos; Boccaletti, Mario

    An international workshop cosponsored by the Department of Geology, University of Florence, Italy and the Department of Geophysics, Stanford University, Stanford, Calif., was held in Florence, Italy, April 18-20, 1989,on the topic of active and recent strike-slip tectonics in the continental crust. Workshop participants from Turkey, Ethiopia, Israel, Greece, and various universities in Italy, Spain, West Germany, France, the United Kingdom, Brazil, and the United States reported on a broad range of studies involving strike-slip faulting in continental crustal setting. As it turned out, much of the work reported on involved aspects of strike-slip faulting that are only poorly understood, especially crustal deformation, which is distributed over a multiplicity of faults, or even fault domains.One of the rewarding aspects of this workshop was the diversity of geographic areas and geological settings covered by the reporters. The north and east Anatolian faults, the Dead Sea transform zone, western Turkey, north and central Greece, Malta, Sicily, southern Italy, the bethic Cordillera in southern Spain, Tunisia, Tibet and southwest China, offshore Brazil, Alaska, Nevada, and California. A recurring observation reported for all those areas was mixed mode faulting, i.e., the coterminous or sequential occurrence of strike-slip and normal faulting, or strike-slip and thrust, and in many instances also strikeslip, normal and thrust faulting in a single tectonic setting.

  14. Slip in viscous contact-line movement

    NASA Astrophysics Data System (ADS)

    van Lengerich, Henrik; Steen, Paul; Breuer, Kenneth

    2011-11-01

    The typical continuum fluid dynamics formulation cannot be used to model the spreading of a liquid on a solid because a stress singularity prevents contact-line motion. It is well known that this situation can be remedied by introducing a slip. We perform Stokes-flow simulations with slip and compare these with experiments. In the experiment, liquid (squalane) is forced through two parallel sapphire plates (roughness 0.6nm), and the meniscus shape and its speed are measured. The slip-length for this liquid/solid pair has been measured previously in an independent experiment absent of contact lines (T. Schmatko et. al. PRL 94, 244501). The same geometry is used in a boundary integral method simulation, accurate to within a few molecular diameters in the vicinity of the contact-line. The slip-length in the simulations can be varied such that the meniscus shape matches the experiment. Preliminary results suggest this slip-length is an order of magnitude lower than that reported by Schmatko. Now at the University of Minnesota TC

  15. Breddin's Graph For Fault and Slip Data

    NASA Astrophysics Data System (ADS)

    Célérier, B.

    A simple plot of rake versus strike of fault and slip or earthquake focal mechanism data provides insight into the stress regime that caused slippage on these faults provided one of the principal stress direction is near vertical. By overlaying an abacus on this plot, one can evaluate both the orientation of the horizontal principal stress directions and the stress tensor aspect ratio, (s1-s2)/(s1-s3), where s1, s2, s3 are the principal stress magnitudes ranked in decreasing order. The underlying geometrical properties are that the slip data that are near strike-slip, and that are mainly found on steeply dipping planes, constrain the horizontal principal stress directions whereas the slip data that are near dip-slip and that occur on shallow dipping planes striking away from the principal stress directions constrain the stress tensor aspect ratio. This abacus is an extension of the Breddin's abacus used to analyze two dimensional deformation in structural geology and it is used in a similar fashion. Its application to synthetic and natural monophase data show both its usefulness and limitation. It is not intended to replace stress inversion techniques because of limiting assumptions, but it is expected to provide insight into the complexity of natural data set from a simple viewpoint.

  16. Asymmetrical slip propensity: required coefficient of friction

    PubMed Central

    2013-01-01

    Background Most studies in performing slips and falls research reported their results after the ipsilateral leg of subjects (either right foot or left foot) was guided to contact the contaminated floor surface although many studies indicated concerns for asymmetries of legs in kinematic or kinetic variables. Thus, the present study evaluated if dominant leg’s slip tendency would be different from non-dominant leg’s slip tendency by comparing the Required Coefficient of Friction (RCOF) of the two lower limbs. Findings Forty seven health adults participated in the present study. RCOF was measured when left or right foot of subjects contacted the force platforms respectively. Paired t-test was performed to test if RCOF and heel velocity (HCV) of dominant legs was different from that of non-dominant legs. It was suggested that the asymmetry in RCOFs and HCV between the two lower limbs existed. The RCOFs of non-dominant legs were higher than that of dominant legs. Conclusions The results indicated that asymmetry in slip propensity, RCOF, was existed in lower extremity. The results from the study suggested that it would be benefit to include a variable, such as asymmetry, in slips and falls research. PMID:23902896

  17. Slip resistant properties of footwear on ice.

    PubMed

    Gao, Chuansi; Abeysekera, John; Hirvonen, Mikko; Grönqvist, Raoul

    2004-05-15

    Current research on slipperiness of footwear has mainly focused on floors and lubricated floors. Slips and falls on icy and snowy surfaces involve not only outdoor workers, but also pedestrians and the general public; and occur in cold regions and in winter season in many parts of the world. However, in comparison with the size of the problem, research on slips and falls on icy and snowy surfaces has been scarce. The objective of this paper is to explore the slip resistant properties of footwear (soling materials, roughness and hardness) on ice. The coefficients of kinetic friction of four different soling materials (synthetic rubber, nitrile rubber, natural rubber and polyurethane) were measured on ice (-12 degrees C). The outsole roughness and hardness were also measured. Results showed that the polyurethane soling did not perform better than synthetic rubber, nitrile rubber and natural rubber on pure hard ice (-12 degrees C). Soling roughness was positively correlated with the coefficient of kinetic friction. The most slip resistant soling material (polyurethane) on floors and lubricated floors may not provide sufficient slip resistance on ice. PMID:15204296

  18. Evidence for slip partitioning and bimodal slip behavior on a single fault: Surface slip characteristics of the 2013 Mw7.7 Balochistan, Pakistan earthquake

    NASA Astrophysics Data System (ADS)

    Barnhart, W. D.; Briggs, R. W.; Reitman, N. G.; Gold, R. D.; Hayes, G. P.

    2015-06-01

    Deformation is commonly accommodated by strain partitioning on multiple, independent strike-slip and dip-slip faults in continental settings of oblique plate convergence. As a corollary, individual faults tend to exhibit one sense of slip - normal, reverse, or strike-slip - until whole-scale changes in boundary conditions reactivate preexisting faults in a new deformation regime. In this study, we show that a single continental fault may instead partition oblique strain by alternatively slipping in a strike-slip or a dip-slip sense during independent fault slip events. We use 0.5 m resolution optical imagery and sub-pixel correlation analysis of the 200 + km 2013 Mw7.7 Balochistan, Pakistan earthquake to document co-seismic surface slip characteristics and Quaternary tectonic geomorphology along the causative Hoshab fault. We find that the 2013 earthquake, which involved a ∼6:1 strike-slip to dip-slip ratio, ruptured a structurally segmented fault. Quaternary geomorphic indicators of gross fault-zone morphology reveal both reverse-slip and strike-slip deformation in the rupture area of the 2013 earthquake that varies systematically along fault strike despite nearly pure strike-slip motion in 2013. Observations of along-strike variations in range front relief and geomorphic offsets suggest that the Hoshab fault accommodates a substantial reverse component of fault slip in the Quaternary, especially along the southern section of the 2013 rupture. We surmise that Quaternary bimodal slip along the Hoshab fault is promoted by a combination of the arcuate geometry of the Hoshab fault, the frictional weakness of the Makran accretionary prism, and time variable loading conditions from adjacent earthquakes and plate interactions.

  19. Quantifying slip balance in the earthquake cycle: Coseismic slip model constrained by interseismic coupling

    NASA Astrophysics Data System (ADS)

    Wang, Lifeng; Hainzl, Sebastian; Mai, P. Martin

    2015-12-01

    The long-term slip on faults has to follow, on average, the plate motion, while slip deficit is accumulated over shorter timescales (e.g., between the large earthquakes). Accumulated slip deficits eventually have to be released by earthquakes and aseismic processes. In this study, we propose a new inversion approach for coseismic slip, taking interseismic slip deficit as prior information. We assume a linear correlation between coseismic slip and interseismic slip deficit and invert for the coefficients that link the coseismic displacements to the required strain accumulation time and seismic release level of the earthquake. We apply our approach to the 2011 M9 Tohoku-Oki earthquake and the 2004 M6 Parkfield earthquake. Under the assumption that the largest slip almost fully releases the local strain (as indicated by borehole measurements), our results suggest that the strain accumulated along the Tohoku-Oki earthquake segment has been almost fully released during the 2011 M9 rupture. The remaining slip deficit can be attributed to the postseismic processes. Similar conclusions can be drawn for the 2004 M6 Parkfield earthquake. We also estimate the required time of strain accumulation for the 2004 M6 Parkfield earthquake to be ~25 years (confidence interval of [17, 43] years), consistent with the observed average recurrence time of ~22 years for M6 earthquakes in Parkfield. For the Tohoku-Oki earthquake, we estimate the recurrence time of ~500-700 years. This new inversion approach for evaluating slip balance can be generally applied to any earthquake for which dense geodetic measurements are available.

  20. Slip rate and slip magnitudes of past earthquakes along the Bogd left-lateral strike-slip fault (Mongolia)

    USGS Publications Warehouse

    Prentice, Carol S.; Rizza, M.; Ritz, J.F.; Baucher, R.; Vassallo, R.; Mahan, S.

    2011-01-01

    We carried out morphotectonic studies along the left-lateral strike-slip Bogd Fault, the principal structure involved in the Gobi-Altay earthquake of 1957 December 4 (published magnitudes range from 7.8 to 8.3). The Bogd Fault is 260 km long and can be subdivided into five main geometric segments, based on variation in strike direction. West to East these segments are, respectively: the West Ih Bogd (WIB), The North Ih Bogd (NIB), the West Ih Bogd (WIB), the West Baga Bogd (WBB) and the East Baga Bogd (EBB) segments. Morphological analysis of offset streams, ridges and alluvial fans—particularly well preserved in the arid environment of the Gobi region—allows evaluation of late Quaternary slip rates along the different faults segments. In this paper, we measure slip rates over the past 200 ka at four sites distributed across the three western segments of the Bogd Fault. Our results show that the left-lateral slip rate is∼1 mm yr–1 along the WIB and EIB segments and∼0.5 mm yr–1 along the NIB segment. These variations are consistent with the restraining bend geometry of the Bogd Fault. Our study also provides additional estimates of the horizontal offset associated with the 1957 earthquake along the western part of the Bogd rupture, complementing previously published studies. We show that the mean horizontal offset associated with the 1957 earthquake decreases progressively from 5.2 m in the west to 2.0 m in the east, reflecting the progressive change of kinematic style from pure left-lateral strike-slip faulting to left-lateral-reverse faulting. Along the three western segments, we measure cumulative displacements that are multiples of the 1957 coseismic offset, which may be consistent with a characteristic slip. Moreover, using these data, we re-estimate the moment magnitude of the Gobi-Altay earthquake at Mw 7.78–7.95. Combining our slip rate estimates and the slip distribution per event we also determined a mean recurrence interval of∼2500–5200 yr for past earthquakes along the different segments of the western Bogd Fault. This suggests that the three western segments of the Bogd Fault and the Gurvan Bulag thrust fault (a reverse fault bounding the southern side of the Ih Bogd range that ruptured during the 1957 earthquake) have similar average recurrence times, and therefore may have ruptured together in previous earthquakes as they did in 1957. These results suggest that the western part of the Bogd Fault system, including the Gurvan Bulag thrust fault, usually behaves in a ‘characteristic earthquake’ mode.

  1. Slip rate and slip magnitudes of past earthquakes along the Bogd left-lateral strike-slip fault (Mongolia)

    USGS Publications Warehouse

    Rizza, M.; Ritz, J.-F.; Braucher, R.; Vassallo, R.; Prentice, C.; Mahan, S.; McGill, S.; Chauvet, A.; Marco, S.; Todbileg, M.; Demberel, S.; Bourles, D.

    2011-01-01

    We carried out morphotectonic studies along the left-lateral strike-slip Bogd Fault, the principal structure involved in the Gobi-Altay earthquake of 1957 December 4 (published magnitudes range from 7.8 to 8.3). The Bogd Fault is 260 km long and can be subdivided into five main geometric segments, based on variation in strike direction. West to East these segments are, respectively: the West Ih Bogd (WIB), The North Ih Bogd (NIB), the West Ih Bogd (WIB), the West Baga Bogd (WBB) and the East Baga Bogd (EBB) segments. Morphological analysis of offset streams, ridges and alluvial fans-particularly well preserved in the arid environment of the Gobi region-allows evaluation of late Quaternary slip rates along the different faults segments. In this paper, we measure slip rates over the past 200 ka at four sites distributed across the three western segments of the Bogd Fault. Our results show that the left-lateral slip rate is ~1 mm yr-1 along the WIB and EIB segments and ~0.5 mm yr-1 along the NIB segment. These variations are consistent with the restraining bend geometry of the Bogd Fault. Our study also provides additional estimates of the horizontal offset associated with the 1957 earthquake along the western part of the Bogd rupture, complementing previously published studies. We show that the mean horizontal offset associated with the 1957 earthquake decreases progressively from 5.2 m in the west to 2.0 m in the east, reflecting the progressive change of kinematic style from pure left-lateral strike-slip faulting to left-lateral-reverse faulting. Along the three western segments, we measure cumulative displacements that are multiples of the 1957 coseismic offset, which may be consistent with a characteristic slip. Moreover, using these data, we re-estimate the moment magnitude of the Gobi-Altay earthquake at Mw 7.78-7.95. Combining our slip rate estimates and the slip distribution per event we also determined a mean recurrence interval of ~2500-5200 yr for past earthquakes along the different segments of the western Bogd Fault. This suggests that the three western segments of the Bogd Fault and the Gurvan Bulag thrust fault (a reverse fault bounding the southern side of the Ih Bogd range that ruptured during the 1957 earthquake) have similar average recurrence times, and therefore may have ruptured together in previous earthquakes as they did in 1957. These results suggest that the western part of the Bogd Fault system, including the Gurvan Bulag thrust fault, usually behaves in a 'characteristic earthquake' mode. ?? 2011 The Authors Geophysical Journal International ?? 2011 RAS.

  2. Fault zone structure and seismic slip localization in dolostones, an example from the Southern Alps, Italy

    NASA Astrophysics Data System (ADS)

    Fondriest, Michele; Smith, Steven A. F.; Di Toro, Giulio; Zampieri, Dario; Mittempergher, Silvia

    2012-12-01

    Fault zones cutting limestones and dolostones represent significant seismogenic sources worldwide. The structure of an exhumed strike-slip fault zone hosted in dolostones, the Borcola Pass Fault Zone (BPFZ, Italian Southern Alps), was studied by means of field and microstructural analysis. Ambient conditions of faulting were ca. 1.6-1.7 km and 50 C. The BPFZ consists of a >80 m wide damage zone cut by three systems of sub-vertical secondary faults striking approximately N-S, E-W and NW-SE. N-S and E-W striking faults reactivated pre-existing Jurassic-Paleogene joints with spacing between 0.2 and 0.5 m, whereas NW-SE striking faults were newly formed during post-Paleogene activity associated with movements along the nearby Schio-Vicenza Line. The core of the BPFZ consists of dolostone fault rock lenses bound by slip zones up to 10 cm thick. Both the principal and secondary slip zones consist of cement-supported dolomitic cataclasites and dolomite-filled veins. Some slip zones contain a sub-centimeter thick vein-like cataclastic layer (Layer-A) located immediately beneath the slip surface that truncates another cataclasite below (Layer-B). Detailed microstructural and clast size distribution analysis suggests that Layer-A experienced fluidization (cuspate-lobate boundaries, injection structures, strong grain sorting: D < 1 for clast diameters smaller than 300 ?m) possibly related to fast fault slip following seismic ruptures. In light of these observations a conceptual model is proposed for the formation of Layer-A, and the structure of the BPFZ is compared to that of an active seismogenic fault cutting carbonates.

  3. Slip, Crystal Orientation, and Damage Evolution During Thermal Cycling in High-Strain Wafer-Level Chip-Scale Packages

    NASA Astrophysics Data System (ADS)

    Zhou, Bite; Zhou, Quan; Bieler, Thomas R.; Lee, Tae-kyu

    2015-03-01

    Wafer-level chip-scale package samples with pre-cross-sectioned edge rows were thermally cycled to study microstructure evolution and damage development. Electron backscattered diffraction (EBSD) and high-energy x-ray diffraction were used to obtain Sn grain orientations and the average coefficient of thermal expansion normal to the board in every joint of the package for samples in the as-fabricated and thermally cycled conditions. The results indicated a near-random distribution of joint orientation. Optical, scanning electron microscopy, and EBSD methods were used to characterize microstructure changes in pre-cross-sectioned samples due to thermal cycling. Slip trace analysis and Orientation Imaging Microscopy™ (OIM) show that slip systems with high Schmid factors (estimated global shear stress based on the package neutral point) are responsible for the observed microstructure evolution during thermal cycling, which provides information about slip systems that are more easily activated. Two joints were analyzed in detail to evaluate slip activity at different stages of their thermal history. The first case showed that a solidification twin grain boundary misorientation deviated from the twin relationship due to slip activity during thermal cycling, which can influence damage development and the path of crack propagation. The second case showed a new grain orientation developing due to gradual lattice rotation about the Sn [110] axis by a continuous recrystallization mechanism. This rotation was correlated with the operation of slip system . Small tin whiskers emerged from the initially polished chip interface and grew with increasing thermal cycles until a crack developed in the solder that relieved the stress. As the local stresses are not known experimentally, this analysis provides observations that can be compared with a crystal plasticity model simulation.

  4. Slipped Capital Femoral Epiphysis in Atypical Patients.

    PubMed

    Whyte, Noelle; Sullivan, Christopher

    2016-04-01

    When patients who are thin present with knee pain, it can be easy to overlook the possibility of slipped capital femoral epiphysis (SCFE). Although 80% of patients with a "slip" are obese, thin children are not immune to this problem. Endocrinopathies, especially hypothyroidism, can be associated with SCFE. This article describes guidelines for evaluating patients for a slip and highlights some important considerations for the atypical SCFE. Patients with open growth plates with thigh or knee pain should routinely have a hip examination as part of the evaluation. Plain radiographs, with an emphasis on obtaining a frog lateral image, are usually sufficient to make the diagnosis of SCFE. Patients diagnosed with SCFE should be immediately referred to an orthopedic surgeon because treatment for this condition is always surgical. [Pediatr Ann. 2016;45(4):e128-e134.]. PMID:27064469

  5. Quake clamps down on slow slip

    NASA Astrophysics Data System (ADS)

    Wallace, Laura M.; Bartlow, Noel; Hamling, Ian; Fry, Bill

    2014-12-01

    Using continuous GPS (cGPS) data from the Hikurangi subduction zone in New Zealand, we show for the first time that stress changes induced by a local earthquake can arrest an ongoing slow slip event (SSE). The cGPS data show that the slip rate in the northern portion of the 2013/2014 Kapiti SSE decreased abruptly following a nearby intraslab earthquake. We suggest that deceleration of the Kapiti SSE in early 2014 occurred due to a tenfold increase in the normal stress relative to shear stress in the SSE source, induced by the nearby Mw 6.3 earthquake, consistent with expectations of rate and state friction. Our observation of an abrupt halting/slowing of the SSE in response to stress changes imposed by a local earthquake has implications for the strength of fault zones hosting SSEs and supports the premise that static stress changes are an important ingredient in triggering (or delaying) fault slip.

  6. Wall slip of bubbles in foams

    NASA Astrophysics Data System (ADS)

    Saugey, A.; Drenckhan, W.; Weaire, D.

    2006-05-01

    We present a computational analysis of the flow of liquid foam along a smooth wall, as encountered in the transport of foams in vessels and pipes. We concentrate on the slip of the bubbles at the wall and present some novel finite element calculations of this motion for the case of fully mobile gas/liquid interfaces. Our two-dimensional simulations provide for the first time the bubble shapes and entire flow field, giving detailed insight into the distribution of stresses and dissipation in the system. In particular, we investigate the relationship between the drag force and the slip velocity of the bubble, which for small slip velocities obeys power laws, as predicted by previous semianalytical treatments.

  7. A Bayesian inversion for slip distribution of 1 Apr 2007 Mw8.1 Solomon Islands Earthquake

    NASA Astrophysics Data System (ADS)

    Chen, T.; Luo, H.

    2013-12-01

    On 1 Apr 2007 the megathrust Mw8.1 Solomon Islands earthquake occurred in the southeast pacific along the New Britain subduction zone. 102 vertical displacement measurements over the southeastern end of the rupture zone from two field surveys after this event provide a unique constraint for slip distribution inversion. In conventional inversion method (such as bounded variable least squares) the smoothing parameter that determines the relative weight placed on fitting the data versus smoothing the slip distribution is often subjectively selected at the bend of the trade-off curve. Here a fully probabilistic inversion method[Fukuda,2008] is applied to estimate distributed slip and smoothing parameter objectively. The joint posterior probability density function of distributed slip and the smoothing parameter is formulated under a Bayesian framework and sampled with Markov chain Monte Carlo method. We estimate the spatial distribution of dip slip associated with the 1 Apr 2007 Solomon Islands earthquake with this method. Early results show a shallower dip angle than previous study and highly variable dip slip both along-strike and down-dip.

  8. A new automated cycle slip detection and repair method for a single dual-frequency GPS receiver

    NASA Astrophysics Data System (ADS)

    Liu, Zhizhao

    2011-03-01

    This paper develops a new automated cycle slip detection and repair method that is based on only one single dual-frequency GPS receiver. This method jointly uses the ionospheric total electron contents (TEC) rate (TECR) and Melbourne-Wübbena wide lane (MWWL) linear combination to uniquely determine the cycle slip on both L1 and L2 frequencies. The cycle slips are inferred from the information of ionospheric physical TECR and MWWL ambiguity at the current epoch and that at the previous epoch. The principle of this method is that when there are cycle slips, the MWWL ambiguity will change and the ionospheric TECR will usually be significantly amplified, the part of artificial TECR (caused by cycle slips) being significantly larger than the normal physical TECR. The TECR is calculated based on the dual-frequency carrier phase measurements, and it is highly accurate. We calculate the ionospheric change information (including TECR and TEC acceleration) using the previous epochs (30 epochs in this study) and use the previous data to predict the TECR for the epoch needing cycle slip detection. If the discrepancy is larger than our defined threshold 0.15 TECU/s, cycle slips are regarded to exist at that epoch. The key rational of method is that during a short period (1.0 s in this study) the TECR of physical ionospheric phenomenon will not exceed the threshold. This new algorithm is tested with eight different datasets (including one spaceborne GPS dataset), and the results show that the method can detect and correctly repair almost any cycle slips even under very high level of ionospheric activities (with an average Kp index 7.6 on 31 March 2001). The only exception of a few detected but incorrectly repaired cycle slip is due to a sudden increased pseudorange error on a single satellite (PRN7) under very active ionosphere on 31 March 2001. This method requires dual-frequency carrier phase and pseudorange data from only one single GPS receiver. The other requirement is that the GPS data rate ideally is 1 Hz or higher in order to detect small cycle slips. It is suitable for many applications where one single receiver is used, e.g. real-time kinematic rover station and precise point positioning. An important feature of this method is that it performs cycle slip detection and repair on a satellite-by-satellite basis; thus, the cycle slip detection and repair for each satellite are completely independent and not affected by the data of other satellites.

  9. Frictional Melting of Peridotite and Seismic Slip

    NASA Astrophysics Data System (ADS)

    di Toro, G.; Del Gaudio, P.; Han, R.; Hirose, T.; Nielsen, S.; Shimamoto, T.; Cavallo, A.

    2008-12-01

    The evolution of the frictional strength along a fault at seismic slip rates (about 1 m/s) is one of the main factors controlling earthquake mechanics. In particular, friction-induced rock melting and melt lubrication during seismic slip may be typical at mantle depths, based on field studies, seismological evidence, torsion experiments and theoretical studies. To investigate the (1) dynamic strength of faults and (2) the frictional melting processes in mantle rocks, we performed 20 experiments with the Balmuccia peridotite in a high- velocity rotary shear apparatus. Experiments were conducted on cylindrical samples (21.8 mm in diameter) over a wide range of normal stresses (5.4 to 16.1 MPa), slip rates (0.23 to 1.14 m/s) and displacements (1.5 to 71 m). The dynamic strength of experimental faults evolved with displacement: after a peak (first strengthening) at the initiation of slip, fault strength abruptly decreased (first weakening), then increased (second strengthening) and eventually decreased (second weakening) towards a steady-state value. The microstructural and geochemical (FE-SEM, EPMA and EDS) investigation of the slipping zone from experiments interrupted at different displacements, revealed that second strengthening was associated with the production of a grain-supported melt-poor layer, while second weakening and steady-state with the formation of a continuous melt-rich layer. The temperature of the frictional melt was up to 1780 Celsius. Microstructures formed during the experiments were identical to those found in natural ultramafic pseudotachylytes. By performing experiments for increasing normal stresses and slip rates, steady-state shear stress slightly increased with increasing normal stress (friction coefficient of 0.15) and, for a given normal stress, decreased with increasing slip rate. The dependence of steady-state shear stress with normal stress and slip rate is described by a constitutive equation for melt lubrication. The presence of microstructures similar to those found in natural pseudotachylytes and the determination of a constitutive equation that describes the experimental data, might allow to extrapolate the experimental observations to natural conditions and to the study of rupture dynamics in mantle rocks.

  10. Slipping processes in residual badlands reliefs

    NASA Astrophysics Data System (ADS)

    Díaz-Hernández, Jose Luis; Yepes, Jorge

    2010-05-01

    We define slips as structures developed by more or less saturated colloidal suspension that slide down the walls of residual reliefs found in badlands. These suspensions seem to originate in the soils crowning gully reliefs and also from rainwater dripping onto the walls of poorly cemented sediments such as siltstone. We call this process slipping and the resulting morphologies represent a group of minor badlands forms, often linked to piping and fluting. Slipping occurs according to the following sequence of forms: 1. Mud droplets. These are irregular linear structures caused by mud droplets sliding down sub-vertical walls. The droplet is usually found at the end of a small channel. These morphologies represent the course of the sliding droplets that become fossilized and not the impact of the droplets on the sediment. 2. Slips sensu stricto. These are uninterrupted surface structures covering sub-vertical walls to a greater or lesser extent. The thickness of this type of covering varies from a few millimetres to 5cm. The inner structure of the slips consists of small laminas (» 100mm) and on the exterior they often present drip channels. A special case of these forms is butterfly structures, which appear in isolation, with repetitive patterns and the appearance of a winged insect stuck to the wall. 3. Pseudo-stalactites. These are free-standing conical regrowths with some similarity to stalactites in a karst cave. They occur when slips grow to over 5cm thick. The growth of these forms is similar to that of slips, with external superposition of fine, concentric layers with no central pore. A variety of these pseudo-stalactites are nodulous stalactites whose genesis is unknown. In this context, we should mention the existence of occasional stalagmites. In other cases, curtains of pseudo-stalactites can be found where these patterns are repeated finely. A more evolved stage of this form is the coalescence of pseudo-stalactites, representing a massive advance of this process. Pseudo-stalactites are normally found as vertical, but occasionally they lean, indicating movement of unstable blocks. The process can present recycling when some of the forms described become detached and fall. This is more likely on poorly sheltered surfaces, exposed to wind and the direct impact of rain and frost. All forms of slips suggests that these morphologies depend on the varying characteristics of the colloidal suspensions causing them, and constitute intermediate stages in the retention of sediments from erosion, which are very different to the alluvial sediments stored in the drainage network.

  11. Slipping magnetic reconnection in coronal loops.

    PubMed

    Aulanier, Guillaume; Golub, Leon; Deluca, Edward E; Cirtain, Jonathan W; Kano, Ryouhei; Lundquist, Loraine L; Narukage, Noriyuki; Sakao, Taro; Weber, Mark A

    2007-12-01

    Magnetic reconnection of solar coronal loops is the main process that causes solar flares and possibly coronal heating. In the standard model, magnetic field lines break and reconnect instantaneously at places where the field mapping is discontinuous. However, another mode may operate where the magnetic field mapping is continuous but shows steep gradients: The field lines may slip across each other. Soft x-ray observations of fast bidirectional motions of coronal loops, observed by the Hinode spacecraft, support the existence of this slipping magnetic reconnection regime in the Sun's corona. This basic process should be considered when interpreting reconnection, both on the Sun and in laboratory-based plasma experiments. PMID:18063789

  12. Momentum compaction and phase slip factor

    SciTech Connect

    Ng, K.Y.; /Fermilab

    2010-10-01

    Section 2.3.11 of the Handbook of Accelerator Physics and Engineering on Landau damping is updated. The slip factor and its higher orders are given in terms of the various orders of the momentum compaction. With the aid of a simplified FODO lattice, formulas are given for the alteration of the lower orders of the momentum compaction by various higher multipole magnets. The transition to isochronicity is next demonstrated. Formulas are given for the extraction of the first three orders of the slip factor from the measurement of the synchrotron tune while changing the rf frequency. Finally bunch-length compression experiments in semi-isochronous rings are reported.

  13. The mechanics of stick-slip

    USGS Publications Warehouse

    Byerlee, J.D.

    1970-01-01

    Physical mechanisms that have been proposed to explain the occurrence of stick-slip motion during frictional sliding have been examined in the light of results obtained from experiments with rocks and brittle minerals. An instability caused by sudden brittle fracture of locked regions on surfaces in contact is the most likely explanation for stick-slip during dry frictional sliding of brittle rocks at room temperature. Areas requiring further study and the uncertainties in applying the results of laboratory experiments to earthquake studies are emphasized. ?? 1970.

  14. Update on slip and wear in multi-layer azimuth track systems

    NASA Astrophysics Data System (ADS)

    Juneja, Gunjeet; Kan, Frank W.; Antebi, Joseph

    2006-06-01

    Many antennas, such as the 100-m Green Bank Telescope, use a wheel-on-track systems in which the track segments consist of wear plates mounted on base plates. The wear plates are typically 2 to 3 inches thick and are case hardened or through hardened. The base plates are usually 3 to 4 times thicker than the wear plates and are not hardened. The wear plates are typically connected to the base plates using bolts. The base plates are supported on grout and anchored to the underlying concrete foundation. For some antennas, slip has been observed between the wear plate and base plate, and between the base plate and the grout, with the migration in the wheel rolling direction. In addition, there has been wear at the wear plate/base plate interface. This paper is an update on the evaluation of GBT track retrofit. The paper describes the use of three-dimensional non-linear finite element analyses to understand and evaluate the behavior of (1) the existing GBT wheel-on-track system with mitered joints, and (2) the various proposed modifications. The modifications include welding of the base plate joints, staggering of the wear plate joints from the base plate joints, changing thickness of the wear plate, and increasing bolt diameter and length. Parameters included in the evaluation were contact pressure, relative slip, wear at the wear plate/base plate interface, and bolt shears and moments.

  15. 46 CFR 154.528 - Piping joints: Flange type.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... and Process Piping Systems § 154.528 Piping joints: Flange type. (a) A flange must be one of the following types: (1) Welding neck. (2) Slip-on. (3) Socket weld. (b) If the piping is designed for a... less; or (3) Welding neck. (c) If the piping is designed for a temperature lower than −55 °C (−67...

  16. 46 CFR 154.528 - Piping joints: Flange type.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... and Process Piping Systems § 154.528 Piping joints: Flange type. (a) A flange must be one of the following types: (1) Welding neck. (2) Slip-on. (3) Socket weld. (b) If the piping is designed for a... less; or (3) Welding neck. (c) If the piping is designed for a temperature lower than −55 °C (−67...

  17. Inertial Aided Cycle Slip Detection and Identification for Integrated PPP GPS and INS

    PubMed Central

    Du, Shuang; Gao, Yang

    2012-01-01

    The recently developed integrated Precise Point Positioning (PPP) GPS/INS system can be useful to many applications, such as UAV navigation systems, land vehicle/machine automation and mobile mapping systems. Since carrier phase measurements are the primary observables in PPP GPS, cycle slips, which often occur due to high dynamics, signal obstructions and low satellite elevation, must be detected and repaired in order to ensure the navigation performance. In this research, a new algorithm of cycle slip detection and identification has been developed. With the aiding from INS, the proposed method jointly uses WL and EWL phase combinations to uniquely determine cycle slips in the L1 and L2 frequencies. To verify the efficiency of the algorithm, both tactical-grade and consumer-grade IMUs are tested by using a real dataset collected from two field tests. The results indicate that the proposed algorithm can efficiently detect and identify the cycle slips and subsequently improve the navigation performance of the integrated system. PMID:23202164

  18. Inertial aided cycle slip detection and identification for integrated PPP GPS and INS.

    PubMed

    Du, Shuang; Gao, Yang

    2012-01-01

    The recently developed integrated Precise Point Positioning (PPP) GPS/INS system can be useful to many applications, such as UAV navigation systems, land vehicle/machine automation and mobile mapping systems. Since carrier phase measurements are the primary observables in PPP GPS, cycle slips, which often occur due to high dynamics, signal obstructions and low satellite elevation, must be detected and repaired in order to ensure the navigation performance. In this research, a new algorithm of cycle slip detection and identification has been developed. With the aiding from INS, the proposed method jointly uses WL and EWL phase combinations to uniquely determine cycle slips in the L1 and L2 frequencies. To verify the efficiency of the algorithm, both tactical-grade and consumer-grade IMUs are tested by using a real dataset collected from two field tests. The results indicate that the proposed algorithm can efficiently detect and identify the cycle slips and subsequently improve the navigation performance of the integrated system. PMID:23202164

  19. Effects of quadriceps fatigue on the biomechanics of gait and slip propensity

    PubMed Central

    Parijat, Prakriti; Lockhart, Thurmon E

    2008-01-01

    This study examines how lower extremity fatigue of the quadriceps alters gait variables related to slip propensity. Sixteen healthy young adults were recruited to walk across vinyl floor surfaces in states of fatigue and no fatigue. Kinematic and kinetic data were collected using a three-dimensional motion analysis system and force plates. The results indicated a significant increase in both the heel contact velocity and required coefficient of friction and a decrease in the transitional acceleration of the whole body center of mass and peak knee joint moment in the fatigue trials. Thus, suggesting that slip propensity could increase with fatigue. Additionally, there was increased knee flexion and reduced ankle dorsiflexion at the heel contact phase of the gait cycle during fatigue trials. These findings provide new insights into the biomechanical relationship between localized muscle fatigue and gait parameters associated with slip propensity. The present study concluded that localized muscle fatigue affects gait parameters and hence can be considered as a potential risk factor for slip-induced falls. PMID:18514522

  20. Statistical Analysis of the Surface Slip Profiles and Slip Models for the 2008 Wenchuan Earthquake

    NASA Astrophysics Data System (ADS)

    Lavallee, D.; Shao, G.; Ji, C.

    2009-12-01

    The 2008 Wenchuan earthquake provides a remarkable opportunity to study the statistical properties of slip profiles recorded at the surface. During the M 8 Wenchuan earthquake, the surface ruptured over 300 km along the Longmenshan fault system. The surface slip profiles have been measured along the fault for a distance of the order of 270 km without any significant change in the strike direction. Field investigations suggest that the earthquake generated a 240 km surface rupture along the Beichuan segment and 72 km surface rupture along the Guanxian segment. Maximum vertical and horizontal slip of 10 m and 4.9 m have been observed along the Beichuan fault. Measurements include the displacement parallel and perpendicular to the fault as well as the width of the rupture zone. However, the recorded earthquake slip profiles are irregularly sampled. Traditional algorithms used to compute the discrete Fourier transform are developed for data sampled at regularly spaced intervals. It should be noted that interpolating the slip profile over a regular grid is not appropriate when investigating the spectrum functional behavior or when computing the discrete Fourier transform. Interpolation introduces bias in the estimation of the Fourier transform that adds artificial correlation to the original data. To avoid this problem, we developed an algorithm to compute the Fourier transform of irregularly sampled data. It consists essentially in determining the coefficients that best fit the data to the Sine and Cosine functions at a given wave number. We compute the power spectrum of the slip profiles of the Wenchuan earthquakes. In addition, we also compute the power spectrum for the slip inversions computed for the Wenchuan earthquakes. To model the functional behavior of the spectrum curves, we consider two functions: the power law function and the von Karman function. For all the slip models, we compute the parameters of the power law function and the von Karman function that best fit the spectrum curves. We also compute the probability density function of the slip profiles. The spectrum obtained for the surface slip profiles are compared to the spectrum computed for the slip profile recorded at the surface on the Arifiye segment of the North Anatolian Fault zone and a kinematic source inversion for the 1999 Izmit (Turkey) earthquake and the spectrum computed for the slip profile recorded during the 2001 Kunlunshan earthquake.

  1. Organic Synthesis in a Spinning Tube-in-Tube (STT) Reactor

    EPA Science Inventory

    Continuous-flow reactors have been designed to minimize and potentially overcome the limitations of heat and mass transfer that are encountered in chemical reactors and further experienced upon scale up of a reaction. With process intensification, optimization of the reaction i...

  2. GREEN REACTION CHEMISTRIES PERFORMED IN THE SPINNING TUBE-IN-TUBE (STT) REACTOR

    EPA Science Inventory

    The U. S. Environmental Protection Agency (USEPA) and Kreido Laboratories have established a Cooperative Research and Development Agreement (CRADA) collaboration, to develop and commercialize green and sustainable chemistries in the area of industrial chemical synthesis. Utilizi...

  3. PROCESS INTENSIFIED GREEN REACTION CHEMISTRIES PERFORMED IN THE SPINNING TUBE-IN-TUBE (STT®) REACTOR

    EPA Science Inventory

    The U. S. Environmental Protection Agency (USEPA) and Kreido Laboratories have established a Cooperative Research and Development Agreement (CRADA) collaboration, to develop and commercialize green and sustainable chemistries in the area of industrial chemical synthesis. Utilizi...

  4. Organic Synthesis in a Spinning Tube-in-Tube (STT¢) Reactor

    EPA Science Inventory

    Continuous-flow reactors have been designed to minimize and potentially overcome the limitations of heat and mass transfer that are encountered in chemical reactors and further experienced upon scale up of a reaction. With process intensification, optimization of the reaction i...

  5. GENERALIZATION OF TREADMILL-SLIP TRAINING TO PREVENT A FALL FOLLLOWING A SUDDEN (NOVEL) SLIP IN OVER-GROUND WALKING

    PubMed Central

    Yang, Feng; Bhatt, Tanvi; Pai, Yi-Chung

    2012-01-01

    The purposes of the study were to determine 1) whether treadmill-slip training could reduce the likelihood of falls during a novel slip in over-ground walking, and 2) to what extent such (indirect) training would be comparable to (direct) over-ground-slip training. A treadmill-slip training group (Group A, n=17) initially experienced repeated perturbations on treadmill intended to simulate forward-slip in over-ground walking. Perturbation continued and its intensity reduced when necessary to ensure subjects successful adaptation (i.e., when they could land their trailing foot ahead of the slipping foot in at least 3 of 5 consecutive trials). They then experienced a novel slip during over-ground walking. Another 17 young adults in Group B experienced an identical novel slip that served as the controls. They then underwent more slip trials during over-ground walking. Their 16th slip trial was analyzed to represent the over-ground-slip training effect. Eight subjects (47%) in Group A fell upon their first treadmill slip, while all adapted successfully after a minimum of 15 slip trials. Upon the novel slip during over-ground walking, none of them fell in comparison to four subjects (23.5%) fell in Group B upon the same trial (p<0.05). Group As control of stability, both proactive and reactive, was significantly better than that of Group Bs on their first over-ground slip, while the level of improvement derived from indirect treadmill training was not as strong as that from direct over-ground-slip training, as demonstrated in Group Bs 16th slip trial (p<0.001). These results clearly demonstrated the feasibility of fall reduction through treadmill-slip training. PMID:23141636

  6. The Distribution of Fault Slip Rates and Oblique Slip Patterns in the Greater Los Angeles, CA Region

    NASA Astrophysics Data System (ADS)

    Harper, H.; Marshall, S. T.

    2014-12-01

    The Los Angeles basin is host to a complex network of active strike-slip, reverse, and oblique slip faults. Because of the large metropolitan region occupying the basin, even moderately large earthquakes (M6+) pose a significant natural hazard. Since geologic estimates have not fully characterized the distribution of active fault slip rates in the region, we use a mechanical model driven by geodetically-measured shortening rates to calculate the full three-dimensional fault slip rate distributions in the region. The modeled nonplanar fault geometries are relatively well-constrained, and use data from the SCEC community fault model. Area-weighted average fault slip rates predicted by the model match previously measured geologic slip rates in most cases; however, some geologic measurements were made in locations where the slip rate is non-characteristic of the fault (e.g. near a fault tip) and the geologic slip rate estimate disagrees with the model-predicted average slip rate. The largest discrepancy between the model predictions and geologic estimates occurs on the Sierra Madre fault, which has a model-predicted slip rate approximately 2 mm/yr greater than the geologic estimates. An advantage of the model is that it can predict the full three-dimensional mechanically compatible slip distribution along all modeled faults. The fault surface slip distribution maps show complex oblique slip patterns that arise due to the nonplanar geometries and mechanical interactions between intersecting and neighboring faults. For example, the Hollywood fault exhibits a net slip of 0.7 mm/yr at depth which increases to 1.6 mm/yr where it is intersected by the Santa Monica fault in the near-surface. Model results suggest that nearly all faults in the region have an oblique component of slip at depth, so slip rate estimates of only dip or strike-slip may underestimate the total net slip rates and seismic hazards in the region.

  7. Joint lubrication.

    PubMed

    McCutchen, C W

    1983-01-01

    The fine-pored, easily compressed articular cartilage provides animal joints with self-pressurized hydrostatic (weeping) lubrication. The solid skeletons of the cartilages press against each other, but so lightly that their rubbing is lubricated successfully by synovial fluid--a boundary lubricant too weak to lubricate ordinary bearings. PMID:6317095

  8. Oblique slip in Laramide foreland arches

    SciTech Connect

    Erslev, E.A.; Selvig, B.; Molzer, P. . Dept. of Earth Resources)

    1993-03-01

    Don Wise was one of the first structural geologists to recognize the complex, four-dimensional (space and time) nature of basement-involved faulting in the Rocky Mountain foreland. His focus on both small scale kinematic indicators and regional tectonic hypotheses has provided a launching point for many Rocky Mountain geologists. The implications of the anastomosing patterns of Laramide foreland arches on models of regional stress and strain have provoked considerable debate. Hypotheses range from those invoking multiple stages of lateral compression from different directions to single-stage models necessitating a component of strike-slip motion in east-west and north-south arches. These hypotheses were tested using slickenline analysis of minor faulting in structures with different orientations. In Wyoming, structures paralleling the dominant northwest structural trend have slickenlines in the NE-SW vertical plane, consistent with shortening and compression in this direction. The east-west Owl Creek and Casper Mountain structures also have NE-SW trending slickenlines, indicating slip oblique to these arches. In Colorado, minor faults in the north-south margin of the northeastern Front Range also indicate oblique slip, with shortening in the NE-SW quadrant. The actual trend of the slickenlines is more easterly, however, suggesting a change of slip trajectory with latitude, not time, possibly in response to identation by the Colorado Plateau.

  9. Searching for aseismic slip in subduction zones

    NASA Astrophysics Data System (ADS)

    Reverso, Thomas; Marsan, David; Helmstetter, Agnès

    2013-04-01

    Aseismic slip is known to occur in subduction zones. This phenomenon is of paramount importance for understanding earthquake hazard, and for estimating the potential for future mega-thrust events. Aseismic slip is however difficult to detect exept for the largest cases, for which geodesy is the most useful type of data. Here, we propose a systematic detection of aseismic slip events, based on seismicity data. We search for transient increases in background seismicity rate in subduction zones, that would indicate the presence of aseismic slip. To that purpose, we make use of an ETAS model in space and time, to distinguish earthquakes due to background seismicity from aftershocks. We optimize the model parameters, and test the sensitivity of the results with changes in parameters. Given the 'best' model, we measure the statistical significance of the departure of the local (in time and space) background rate with the 'normal' background rate. Significant departure then indicates the need to temporary increase the background rate in order to explain the observed earthquake occurrences. We thus can single out such episodes of aseismic transients, and characterize their duration and spatial extent.

  10. Hydrodynamic slip length as a surface property

    NASA Astrophysics Data System (ADS)

    Ramos-Alvarado, Bladimir; Kumar, Satish; Peterson, G. P.

    2016-02-01

    Equilibrium and nonequilibrium molecular dynamics simulations were conducted in order to evaluate the hypothesis that the hydrodynamic slip length is a surface property. The system under investigation was water confined between two graphite layers to form nanochannels of different sizes (3-8 nm). The water-carbon interaction potential was calibrated by matching wettability experiments of graphitic-carbon surfaces free of airborne hydrocarbon contamination. Three equilibrium theories were used to calculate the hydrodynamic slip length. It was found that one of the recently reported equilibrium theories for the calculation of the slip length featured confinement effects, while the others resulted in calculations significantly hindered by the large margin of error observed between independent simulations. The hydrodynamic slip length was found to be channel-size independent using equilibrium calculations, i.e., suggesting a consistency with the definition of a surface property, for 5-nm channels and larger. The analysis of the individual trajectories of liquid particles revealed that the reason for observing confinement effects in 3-nm nanochannels is the high mobility of the bulk particles. Nonequilibrium calculations were not consistently affected by size but by noisiness in the smallest systems.

  11. Multi-level slip-link modeling

    NASA Astrophysics Data System (ADS)

    Schieber, Jay

    2014-03-01

    That the dynamics of concentrated, high-molecular-weight polymers are largely governed by entanglements is now widely accepted, and typically understood by the tube model. Although the original idea for slip-links was proposed at the same time as tubes, only recently have detailed, quantitative mathematical models arisen based on this picture. We argue here for the use of a slip-link model that has strong connections to atomistic, multichain levels of description, agrees with non-equilibrium thermodynamics, applies to any chain architecture and can be used in linear or non-linear rheology. We present a hierarchy of slip-link models that are connected to each other through successive coarse graining. One might choose a particular member of the hierarchy depending on the problem at hand, in order to minimize computational effort. In particular, the most detailed level of description has four parameters, three of which can be determined directly from atomistic simulations. The least-detailed member is suitable for predicting non-linear, non-uniform flow fields. We will show how using this hierarchy of slip-link models we can make predictions about the nonlinear rheology of monodisperse homopolymer melts, polydisperse melts, or blends of different architectures.

  12. Slip Dynamics in Small Scale Crystals

    NASA Astrophysics Data System (ADS)

    Maass, Robert; Derlet, Peter; Greer, Julia; Volkert, Cynthia

    2015-03-01

    Classical work showed that dislocation velocities are strongly dependent on applied stress. Numerous experiments have validated this for individual or groups of dislocations in macroscopic crystals by using imaging techniques combined with either mechanical data or time resolved topological data. Developments in small scale mechanical testing allow to correlate the intermittency of collective dislocation motion with the mechanical response. Discrete forward surges in displacement can be related to dislocation avalanches, which are triggered by the evolving dislocation sub-structure. We study the spatiotemporal characteristics of intermittent plastic flow in quasi-statically sheared single crystalline Au crystals with diameters between 300 nm and 10000 nm, whose displacement bursts were recorded at several kHz (Scripta Mater. 2013, 69, 586; Small, available online). Both the crystallographic slip magnitude, as well as the velocity of the slip events are exhibiting power-law scaling as. The obtained slip velocity distribution has a cubic decay at high values, and a saturated flat shoulder at lower velocities. No correlation between the slip velocity and the applied stress or plastic strain is found. Further, we present DD-simulations that are supportive of our experimental findings. The simulations suggest that the dynamics of the internal stress fields dominate the evolving dislocation structure leading to velocities that are insensitive to the applied stress - a regime indicative of microplasticity.

  13. Slip casting and nitridation of silicon powder

    NASA Technical Reports Server (NTRS)

    Seiko, Y.

    1985-01-01

    Powdered Silicon was slip-cast with a CaSO4 x 0.5H2O mold and nitrided in a N atm. containing 0 or 5 vol. % H at 1000 to 1420 deg. To remove the castings, the modeling faces were coated successively with an aq. salt soap and powdered cellulose containing Na alginate, and thus prevented the sticking problem.

  14. PRODUCTION OF SLIP CAST CALCIA HOLLOWWARE

    DOEpatents

    Stoddard, S.D.; Nuckolls, D.E.; Cowan, R.E.

    1963-12-31

    A method for producing slip cast calcia hollow ware in which a dense calcia grain is suspended in isobutyl acetate or a mixture of tertiary amyl alcohol and o-xylene is presented. A minor amount of triethanolamine and oleic acid is added to the suspension vehicle as viscosity adjusting agents and the suspension is cast in a plaster mold, dried, and fired. (AEC)

  15. Volcanism and aseismic slip in subduction zones

    SciTech Connect

    Acharya, H.

    1981-01-10

    The spatial and temporal relationship of volcanism to the occurrence of large earthquakes and convergent plate motion is examined. The number of volcanic eruptions per year in a convergent zone is found to be linearly related to the aseismic slip component of plate motion. If the aseismic slip rate is low (coupling between converging plates is strong), then the primary manifestation of tectonic activity is the occurrence of large earthquakes with only infrequent volcanic activity. If, however, the aseismic slip rate is high (coupling is weak), then there are few large earthquakes, and volcanism is the principal manifestation of tectonic activity. This model is consistent with the spatial distribution of large earthquakes and active volcanoes in the circum-Pacific area. It is tested by examining the extent of volcanic activity in the rupture zones of the 1952--1973 sequence of earthquakes in the Japan--Kurile Islands area. The number of volcanic euptions along these zones during the interval between large earthquakes is used to compute the aseismic slip rates for these segments, based on the relationship developed in this study. The aseismic slip rates so computed agree with those determined from the earthquake history of the area and rates of plate motion. The agreement suggests that in the interval between large earthquakes, the aseismic plate motion is manifested in a specific number of volcanic eruptions. Therefore in areas with adequate historial data it should be possible to use the model developed in this study to monitor volcanic eruptions for long-term prediction of large earthquakes.

  16. Effective slip lengths for longitudinal shear flow over partial-slip circular bubble mattresses

    NASA Astrophysics Data System (ADS)

    Crowdy, Darren

    2015-12-01

    The problem of longitudinal shear flow over a circular bubble mattress with partial slip and protrusion angle 90o is solved in a quasi-analytical fashion by a novel transform scheme recently devised by the author. The general approach can be readily adapted to other mixed boundary value problems. From the analysis explicit approximations for the effective slip lengths are found as a function of the Navier-slip parameter and the area fraction of the surface covered by protrusions. These new approximation formulas for the slip lengths both unify and extend those based on empirical polynomial fits to numerical data given recently by Ng and Wang (2011 Fluid Dyn. Res. 43 065504).

  17. Development of compact slip detection sensor using dielectric elastomer

    NASA Astrophysics Data System (ADS)

    Choi, Jae-young; Hwang, Do-Yeon; Kim, Baek-chul; Moon, Hyungpil; Choi, Hyouk Ryeol; Koo, Ja Choon

    2015-04-01

    In this paper, we developed a resistance tactile sensor that can detect a slip on the surface of sensor structure. The presented sensor device has fingerprint-like structures that are similar with the role of the humans finger print. The resistance slip sensor that the novel developed uses acrylo-nitrile butadiene rubber (NBR) as a dielectric substrate and graphene as an electrode material. We can measure the slip as the structure of sensor makes a deformation and it changes the resistance through forming a new conductive route. To manufacture our sensor, we developed a new imprint process. By using this process, we can produce sensor with micro unit structure. To verify effectiveness of the proposed slip detection, experiment using prototype of resistance slip sensor is conducted with an algorithm to detect slip and slip is successfully detected. We will discuss the slip detection properties.

  18. Geologic evidence for multiple slip weakening mechanisms during seismic slip in crystalline rock

    NASA Astrophysics Data System (ADS)

    Kirkpatrick, J. D.; Shipton, Z. K.

    2009-12-01

    We examine exhumed seismogenic faults to investigate the mechanisms that may have achieved dynamic fault weakening during ancient ruptures. Field and microscope observations imply more than one weakening mechanism must have been active during slip events on the faults. Pseudotachylytes that are continuous over the scale of field exposures are indicative of melt lubrication. A fault breccia crosscutting earlier formed cataclasites was mobilized during faulting and possibly represents a pressurized fault rock that resulted from thermal pressurization or elastohydrodynamic lubrication. In some faults, pseudotachylytes are developed in patches several meters long. Cataclasites in which there is no evidence for melting are present immediately along strike from the pseudotachylyte patches. By considering the energy required for melting, we show that the pseudotachylytes must have formed during ruptures larger than the patches, implying that the cataclasites also accommodated seismic slip. The distribution of fault rock types shows that the frictional response to slip during a single event was spatially variable. Reworked pseudotachylytes also indicate that coseismic processes change over time at a point on a fault. These observations emphasize that macroscopic dynamic fault weakening is a function of multiple coeval processes at microscales to mesoscales. Detailed observations of the discontinuous pseudotachylytes show that slip zone thickness is the critical parameter that controls active coseismic processes. The frictional response of a fault to slip is therefore dependent on the internal structure of faults; given the along-strike heterogeneity of most mapped fault zones, the coexistence of multiple slip weakening mechanisms in a single earthquake will be common.

  19. Downscaling of slip distribution for strong earthquakes

    NASA Astrophysics Data System (ADS)

    Yoshida, T.; Oya, S.; Kuzuha, Y.

    2013-12-01

    We intend to develop a downscaling model to enhance the earthquake slip distribution resolution. Slip distributions have been obtained by other researchers using various inversion methods. As a downscaling model, we are discussing fractal models that include mono-fractal models (fractional Brownian motion, fBm; fractional Lévy motion, fLm) and multi-fractal models as candidates. Log - log-linearity of k (wave number) versus E (k) (power spectrum) is the necessary condition for fractality: the slip distribution is expected to satisfy log - log-linearity described above if we can apply fractal model to a slip distribution as a downscaling model. Therefore, we conducted spectrum analyses using slip distributions of 11 earthquakes as explained below. 1) Spectrum analyses using one-dimensional slip distributions (strike direction) were conducted. 2) Averaging of some results of power spectrum (dip direction) was conducted. Results show that, from the viewpoint of log - log-linearity, applying a fractal model to slip distributions can be inferred as valid. We adopt the filtering method after Lavallée (2008) to generate fBm/ fLm. In that method, generated white noises (random numbers) are filtered using a power law type filter (log - log-linearity of the spectrum). Lavallée (2008) described that Lévy white noise that generates fLm is more appropriate than the Gaussian white noise which generates fBm. In addition, if the 'alpha' parameter of the Lévy law, which governs the degree of attenuation of tails of the probability distribution, is 2.0, then the Lévy distribution is equivalent to the Gauss distribution. We analyzed slip distributions of 11 earthquakes: the Tohoku earthquake (Wei et al., 2011), Haiti earthquake (Sladen, 2010), Simeulue earthquake (Sladen, 2008), eastern Sichuan earthquake (Sladen, 2008), Peru earthquake (Konca, 2007), Tocopilla earthquake (Sladen, 2007), Kuril earthquake (Sladen, 2007), Benkulu earthquake (Konca, 2007), and southern Java earthquake (Konca, 2006)). We obtained the following results. 1) Log - log-linearity (slope of the linear relationship is ' - ν') of k versus E(k) holds for all earthquakes. 2) For example, ν = 3.70 and α = 1.96 for the Tohoku earthquake (2011) and ν = 4.16 and α = 2.00 for the Haiti earthquake (2010). For these cases, the Gauss' law is appropriate because alpha is almost 2.00. 3) However, ν = 5.25 and α = 1.25 for the Peru earthquake (2007) and ν = 2.24 and α = 1.57 for the Simeulue earthquake (2008). For these earthquakes, the Lévy law is more appropriate because α is far from 2.0. 4) Although Lavallée (2003, 2008) concluded that the Lévy law is more appropriate than the Gauss' law for white noise, which is later filtered, our results show that the Gauss law is appropriate for some earthquakes. Lavallée and Archuleta, 2003, Stochastic modeling of slip spatial complexities for the 1979 Imperial Valley, California, earthquake, GEOPHYSICAL RESEARCH LETTERS, 30(5). Lavallée, 2008, On the random nature of earthquake source and ground motion: A unified theory, ADVANCES IN GEOPHYSICS, 50, Chap 16.

  20. Joint assembly

    NASA Technical Reports Server (NTRS)

    Wilson, Andrew (Inventor); Punnoose, Andrew (Inventor); Strausser, Katherine (Inventor); Parikh, Neil (Inventor)

    2010-01-01

    A joint assembly is provided which includes a drive assembly and a swivel mechanism. The drive assembly features a motor operatively associated with a plurality of drive shafts for driving auxiliary elements, and a plurality of swivel shafts for pivoting the drive assembly. The swivel mechanism engages the swivel shafts and has a fixable element that may be attached to a foundation. The swivel mechanism is adapted to cooperate with the swivel shafts to pivot the drive assembly with at least two degrees of freedom relative to the foundation. The joint assembly allows for all components to remain encased in a tight, compact, and sealed package, making it ideal for space, exploratory, and commercial applications.

  1. The balance of frictional heat production, thermal pressurization, and slip resistance on exhumed mid-crustal faults (Adamello batholith, Southern Italian Alps)

    NASA Astrophysics Data System (ADS)

    Griffith, W. A.; di Toro, G.; Pollard, D. D.

    2005-12-01

    Exhumed faults cutting the Adamello batholith (Italian Alps) were active ca. 30 Ma at seismogenic depths of 9-11 km. The faults "exploited preexisting joints and can be classified into three groups containing: (A) only cataclasite (a fault rock with no evidence of melting), (B) cataclasite and pseudotachylyte (solidified friction-induced melts produced during earthquakes), and (C) only pseudotachylyte. The majority of pseudotachylyte-bearing faults in this outcrop overprint pre-existing cataclasites (Type B), suggesting a transition between slip styles; however, some faults exhibiting pseudotachylyte and no cataclasite (Type C) display evidence of only one episode of slip. Faults of Type A never transitioned to frictional melting. We attempt to compare faults of type A, B, and C in terms of a simple one-dimensional thermo-mechanical model introduced by Lachenbruch (1980) describing the interaction between frictional heating, pore fluid pressure, and shear resistance during slip. The interaction of these three parameters influences how much elastic strain is relieved during an earthquake. For a conceptualized fault zone of finite thickness, the interplay between the shear resistance, heat production, and pore fluid pressure can be expressed as a non-linear partial differential equation relating these processes to the strain rate acting within a fault zone during a slip event. The behavior of fault zones in terms of these coupled processes during an earthquake depends on a number of parameters, such as thickness of the principal slipping zone, net coseismic slip, fault rock permeability and thermal diffusivity. Ideally, the governing equations should be testable on real fault zones if the requisite parameters can be measured or reasonably estimated. The model can be further simplified if the peak temperature reached during slip and the coseismic slip rate can be constrained. The contrasting nature of slip on the three Adamello fault types highlights (1) important differences between slip processes on cataclastic and melt-producing faults at depth and (2) some limitations of applicability of such models to real faults.

  2. Effects of slip, slip rate, and shear heating on the friction of granite

    USGS Publications Warehouse

    Blanpied, M.L.; Tullis, T.E.; Weeks, J.D.

    1998-01-01

    The stability of fault slip is sensitive to the way in which frictional strength responds to changes in slip rate and in particular to the effective velocity dependence of steady state friction ????ss/?? ln V. This quantity can vary substantially with displacement, temperature and slip rate. To investigate the physical basis for this behavior and the possible influence of shear heating, we slid initially bare granite surfaces in unconfined rotary shear to displacements of hundreds of millimeters at normal stresses, ??n, of 10 and 25 MPa and at room temperature. We imposed step changes in slip rate within the range 10-2 to 103.5 ??m/s and also monitored frictional heating with thermistors embedded in the granite. The transient response of ?? to slip rate steps was fit to a rate- and state-dependent friction law using two state variables to estimate the values of several parameters in the constitutive law. The first 20 mm of slip shows rising friction and falling ????ss/?? ln V; further slip shows roughly constant friction, ????ss/?? ln V and parameter values, suggesting that a steady state condition is reached on the fault surface. At V ??? 10 ??m/s, ????ss/?? ln V = -0.004 ?? 0.001. At higher rates the response is sensitive to normal stress: At ??n = 25 MPa granite shows a transition to effective velocity strengthening (????ss/?? ln V = 0.008 ?? 0.004) at the highest slip rates tested. At 10 MPa granite shows a less dramatic change to ????ss/?? ln V ??? 0 at the highest rates. The maximum temperature measured in the granite is ???60??C at 25 MPa and 103.5 ??m/s. Temperatures are in general agreement with a numerical model of heat conduction which assumes spatially homogeneous frictional heating over the sliding surface. The simplest interpretation of our measurements of ????ss/?? ln V is that the granite is inherently veocity weakening (?????ss/??? In V 0 mimics velocity strengthening. These results have implications for the frictional behavior of faults during earthquakes. High slip rates may cause a switch to effective velocity strengthening which could limit peak coseismic slip rate and stress drop. For fluid-saturated faults, strengthening by this mechanism may be partly or fully offset by weakening due to thermal pressurization of a poorly drained pore fluid.

  3. A STUDY ON HIGH STRENGTH BOLTED JOINT WITH METAL-SPRAYED CONTACT SURFACES

    NASA Astrophysics Data System (ADS)

    Minami, Kuniaki; Saito, Masamichi; Yokoyama, Hideki; Sugimoto, Ichiro; Nojima, Takao; Masunaga, Toshihiko; Nagasaki, Eiji

    Slip coefficient of high-strength bolt friction joints is well known to depend on the condition of contact surfaces. The coefficient is determined as 0.4 in the Specifications for Highway Bridges and the Design Standards for Railway Structures and Commentary (Steel Structures) in Japan, in the condition of roughened contact surfaces with mill scale removed or painted contact surfaces with inorganic zinc rich paint. However, the slip coefficient with metal-sprayed surfaces is not clear. For the joints with metalsprayed surfaces, hot-dip galvanized bolts are applied and such bolts are tightened by turn-of-nut method. However, it is unclear how much axial force is induced into the bolts in the joints with metal-sprayed surfaces. In order to examine slip coefficient of the bolted joints with metal-sprayed contact surfaces slip tests of high strength bolted joints were carried out. On the basis of above examinations, the slip coefficient with metal-sprayed surfaces is proposed in this paper. To clarify the induced axial force of the bolts, bolt-tightening tests were carried out. Considering bolt diameter, bolt length, induced axial forces and their relaxation, nut rotation angles are proposed in relation to different bolt size.

  4. Relationships between Slow Slip and Earthquakes at the Brittle-Ductile Transition of Subduction Zones

    NASA Astrophysics Data System (ADS)

    Brudzinski, M. R.; Colella, H.; Skoumal, R.; Cabral-Cano, E.; Arciniega-Ceballos, A.; Graham, S. E.; DeMets, C.; Sit, S. M.; Holtkamp, S. G.

    2014-12-01

    Following the discovery of episodic tremor and slip, one of the key questions raised is whether the phenomena can be a harbinger of megathrust earthquakes. Several recent large subduction earthquakes have provided an opportunity to investigate this question. The March 20, 2012 Mw 7.4 Ometepec earthquake in southern Mexico represents one such opportunity as it occurred in an area with a joint seismic and geodetic network in the source region that can examine whether patterns in the episodic tremor and slip were related to the earthquake. GPS data indicate that a 5-month-long slow slip episode (SSE) migrated toward and reached the vicinity of the mainshock source zone a few weeks before the earthquake. With multi-station waveform matching of templates constructed from visible aftershock signals, we find an increase in seismic activity during the SSE. The fault patches represented by these templates fill in the gap between the earthquake epicenter and the primary SSE. Analysis of other seismic swarms in Oaxaca near the down-dip end of the seismogenic zone with multi-station template matching also shows an increase in seismicity during SSEs. This evidence adds to a growing number of published accounts that indicate slow slip, whether geodetically or seismically inferred, is becoming a more commonly observed pre-earthquake signature. We use RSQSim earthquake simulations to model these scenarios using a subduction interface with a shallow seismogenic zone, deep SSE zone, and a microseismicity zone in between. Simulations where the microseismicity zone is assigned varying effective normal stresses and slip speeds over small distances generate cases in which microseismicity primarily occurs when a SSE migrates up-dip to the point enough stress is transferred to nucleate an earthquake on elements with a higher effective normal stress. Together these observations support the notion that SSE can trigger traditional earthquakes, not just tremor and low-frequency earthquakes.

  5. The Long Term Slip Deficit Budget and the Seismic Cycle.

    NASA Astrophysics Data System (ADS)

    McCloskey, John; Simao, Nuno; Lindsay, Tony; NicBhloscaidh, Mairead; Murphy, Shane; Natawidjaja, Danny; Nalbant, Suleyman

    2013-04-01

    Estimates of spatially heterogeneous coupling between plates in subduction zones provide a basis for forecasting high slip in future events; strong coupling between earthquakes, producing rapid strain accumulation, should be correlated with high slip during the next earthquake. However, studies comparing coupling and slip do not show the expected correlation . We test the hypothesis that slip is governed, not only by coupling, but by the long term history of loading and slip on the fault; strongly coupled locations which have experienced large slip in recent earthquakes may have low slip-deficit, a measure of accumulated strain energy on the fault, despite their relatively high slip-deficit rate. Using reconstructions of slip in historical and recent earthquakes under the Mentawai Islands, W. Sumatra, we show that coupling is strongly correlated with slip accumulated over several events on the same segment rather than on any single earthquake. This observation is inconsistent with the idea of a characteristic earthquake and even of an earthquake cycle which together form the basis of of deterministic earthquake forecasting . Instead it suggests that slip-deficit is accumulated according to the plate convergence rate moderated by the strength of coupling and is relaxed heterogeneously during slip events which need show no repeatability either in time or in space; the slip deficit budget, at least for the Mentawai megathrust segment, needs balanced only over hundreds of years. This implies that slip-deficit estimated by reconstruction of slip and loading over long times, is necessary to understand the current state of stress on active faults.

  6. Joint Replacement Surgery

    MedlinePlus

    ... Trial Journal Articles Arthritis July 2014 Joint Replacement Surgery: Health Information Basics for You and Your Family What Is Joint Replacement Surgery? Joint replacement surgery is removing a damaged joint ...

  7. A Matlab toolbox to analyze slip transfer through grain boundaries

    NASA Astrophysics Data System (ADS)

    Mercier, D.; Zambaldi, C.; Bieler, T. R.

    2015-04-01

    Slip transmission across grain boundaries is an essential micromechanical processes during deformation of polycrystalline materials. Slip transmission processes can be characterized based on the geometrical arrangement of active slip systems in adjacent grains and the value of the critical resolved shear stress acting on the incoming and possible outgoing slip systems. We present a Matlab toolbox which enables quantification of grain boundary slip transfer properties and comparison with experiments. Using a graphical user interface, experimental grain boundary data can be directly exported as input files for crystal plasticity finite element simulation of bicrystal experiments.

  8. Dynamical role of slip heterogeneities in confined flows.

    PubMed

    Vayssade, Anne-Laure; Lee, Choongyeop; Terriac, Emmanuel; Monti, Fabrice; Cloitre, Michel; Tabeling, Patrick

    2014-05-01

    We demonstrate that flows in confined systems are controlled by slip heterogeneities below a certain size. To show this we image the motion of soft glassy suspensions in microchannels whose inner walls impose different slip velocities. As the channel height decreases, the flow ceases to have the symmetric shape expected for yield-stress fluids. A theoretical model accounts for the role of slip heterogeneities and captures the velocity profiles. We generalize these results by introducing a length scale, valid for all fluids, below which slip heterogeneities dominate the flow in confined systems. General implications of this notion, concerning the interplay between slip and confinement, are presented. PMID:25353802

  9. Frictional melting of peridotite and seismic slip

    NASA Astrophysics Data System (ADS)

    Del Gaudio, P.; di Toro, G.; Han, R.; Hirose, T.; Nielsen, S.; Shimamoto, T.; Cavallo, A.

    2009-06-01

    The evolution of the frictional strength along a fault at seismic slip rates (about 1 m/s) is a key factor controlling earthquake mechanics. At mantle depths, friction-induced melting and melt lubrication may influence earthquake slip and seismological data. We report on laboratory experiments designed to investigate dynamic fault strength and frictional melting processes in mantle rocks. We performed 20 experiments with Balmuccia peridotite in a high-velocity rotary shear apparatus and cylindrical samples (21.8 mm in diameter) over a wide range of normal stresses (5.4-16.1 MPa), slip rates (0.23-1.14 m/s), and displacements (1.5-71 m). During the experiments, shear stress evolved with cumulative displacement in five main stages (stages 1-5). In stage 1 (first strengthening), the coefficient of friction μ increased up to 0.4-0.7 (first peak in friction). In stage 2 (abrupt first weakening), μ decreased to about 0.25-0.40. In stage 3 (gradual second strengthening), shear stress increased toward a second peak in friction (μ = 0.30-0.40). In stage 4 (gradual second weakening), the shear stress decreased toward a steady state value (stage 5) with μ = 0.15. Stages 1 and 2 are of too short duration to be investigated in detail with the current experimental configuration. By interrupting the experiments during stages 3, 4, and 5, microstructural (Field Emission Scanning Electron Microscope) and geochemical (Electron Probe Micro-Analyzer and Energy Dispersive X-Ray Spectroscopy) analysis of the slipping zone suggest that second strengthening (stage 3) is associated with the production of a grain-supported melt-poor layer, while second weakening (stage 4) and steady state (stage 5) are associated with the formation of a continuous melt-rich layer with an estimated temperature up to 1780°C. Microstructures formed during the experiments were very similar to those found in natural ultramafic pseudotachylytes. By performing experiments at different normal stresses and slip rates, (1) the "thermal" (as it includes the thermally activated first and second weakening) slip distance to achieve steady state from the first peak in strength decreased with increasing normal stress and slip rate and (2) the steady state shear stress slightly increased with increasing normal stress and, for a given normal stress, decreased with increasing slip rate. The ratio of shear stress versus normal stress was about 0.15, well below the typical friction coefficient of rocks (0.6-0.8). The dependence of steady state shear stress with normal stress was described by means of a constitutive equation for melt lubrication. The presence of microstructures similar to those found in natural pseudotachylytes and the determination of a constitutive equation that describes the experimental data allows extrapolation of the experimental observations to natural conditions and to the study of rupture dynamics in mantle rocks.

  10. Phase Slips in Oscillatory Hair Bundles

    NASA Astrophysics Data System (ADS)

    Roongthumskul, Yuttana; Shlomovitz, Roie; Bruinsma, Robijn; Bozovic, Dolores

    2013-04-01

    Hair cells of the inner ear contain an active amplifier that allows them to detect extremely weak signals. As one of the manifestations of an active process, spontaneous oscillations arise in fluid immersed hair bundles of in vitro preparations of selected auditory and vestibular organs. We measure the phase-locking dynamics of oscillatory bundles exposed to low-amplitude sinusoidal signals, a transition that can be described by a saddle-node bifurcation on an invariant circle. The transition is characterized by the occurrence of phase slips, at a rate that is dependent on the amplitude and detuning of the applied drive. The resultant staircase structure in the phase of the oscillation can be described by the stochastic Adler equation, which reproduces the statistics of phase slip production.

  11. Smectite-illite transition during coseismic slip

    NASA Astrophysics Data System (ADS)

    Takahashi, M.; Kitajima, H.

    2013-12-01

    Few evidences for coseismic slip events are preserved in natural fault rocks except pseudotachylytes showing a clear evidence of melting caused by frictional shear at high slip rates [e.g., Spray, 1987; Tsutsumi and Shimamoto, 1997; Hirose and Shimamoto, 2005]. Higher maturity of vitrinite of coal fragments is observed in the fault cores recovered from the Nankai accretionary prism [Sakaguchi eta al., 2011], and also in the friction experiments sheared at seismic slip rates [Kitamura et al., 2012], implying that local heating is caused by frictional shear during earthquakes. Another possible evidence for coseismic slip is illitization of smectite clay along faults observed in the present and ancient accretionary prisms [Yamaguchi et al., 2011; Kameda et al., 2013]. Kameda et al. [2013] have estimated the fault activity using the kinetics of smectite-illite transition, which is determined in the studies on long-term diagenetic processes of smectite-illite transition and may not be appropriate for the short-tem reaction caused by frictional heating associated with coseismic slip. Here we report on high-speed friction experiments on synthetic smectite-quartz mixtures. The goals of our experiments are: (1) to reproduce the illitization of smectite clay (Na-montmorillonite) during coseismic shear and (2) to obtain better kinetic parameters to estimate the fault activity of coseismic slip. The friction experiments were conducted on the rotary-shear apparatus at AIST. One gram of the synthetic gouge of smectite-quartz (70:30 wt.%) mixture was sheared at slip velocity of 1.3 m/s, normal stress of 1 MPa, and up to displacement of 55 m. Because cation exchange between sodium ion in smectite and potassium ion in fluid is required for the illitization, we used gouge samples dampened with two different pore fluid media: (1) 1 mol/L aqueous solution of potassium chloride (KCl) and (2) pure water. Friction coefficient of the gouge sheared with potassium rich fluid is 0.45 at peak and 0.12 at steady state, and approximately two times greater than friction coefficient of the gouge sheared with pure water (0.27 at peak and 0.05 at steady state). Pore fluid chemistry largely affects the frictional strength of gouge and thus probably temperature evolution within the gouge. X-ray diffraction analysis of the post-experiment gouges with ethylene glycol treatment indicate illite generation in the gouge sheared with potassium-rich fluid; i.e., smectite is partly transformed to illite by the frictional heating. The gouge sheared with pure water, on the other hand, shows no evidence for illite generation. We will present more experimental results and derive interrelationships between the degree of the illitization, slip velocity, shear displacement, frictional strength, temperature, and concentrations of the potassium ion in pore fluid.

  12. Slip complexity in earthquake fault models.

    PubMed Central

    Rice, J R; Ben-Zion, Y

    1996-01-01

    We summarize studies of earthquake fault models that give rise to slip complexities like those in natural earthquakes. For models of smooth faults between elastically deformable continua, it is critical that the friction laws involve a characteristic distance for slip weakening or evolution of surface state. That results in a finite nucleation size, or coherent slip patch size, h*. Models of smooth faults, using numerical cell size properly small compared to h*, show periodic response or complex and apparently chaotic histories of large events but have not been found to show small event complexity like the self-similar (power law) Gutenberg-Richter frequency-size statistics. This conclusion is supported in the present paper by fully inertial elastodynamic modeling of earthquake sequences. In contrast, some models of locally heterogeneous faults with quasi-independent fault segments, represented approximately by simulations with cell size larger than h* so that the model becomes "inherently discrete," do show small event complexity of the Gutenberg-Richter type. Models based on classical friction laws without a weakening length scale or for which the numerical procedure imposes an abrupt strength drop at the onset of slip have h* = 0 and hence always fall into the inherently discrete class. We suggest that the small-event complexity that some such models show will not survive regularization of the constitutive description, by inclusion of an appropriate length scale leading to a finite h*, and a corresponding reduction of numerical grid size. Images Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:11607669

  13. IMPROVED MAGNESIUM OXIDE SLIP CASTING METHOD

    DOEpatents

    Stoddard, S.D.; Nuckolls, D.E.

    1963-12-31

    A process for making an aqueous magnesium oxide slip casting slurry comprising the steps of mixing finely ground fused magnesium oxide with water, milling the slurry for at least 30 hours at a temperature of 2-10 deg C (the low temperature during milling inhibiting the formation of hydrated magnesium oxide), discharging the slurry from the mill, adding hydrochloric acid as a deflocculent, and adding a scum inhibitor is presented. (AEC)

  14. Dynamics and wheel's slip ratio of a wheel-legged robot in wheeled motion considering the change of height

    NASA Astrophysics Data System (ADS)

    Ding, Xilun; Li, Kejia; Xu, Kun

    2012-09-01

    The existing research on dynamics and slip ratio of wheeled mobile robot (WMR) are derived without considering the effect of height, and the existing models can not be used to analyze the dynamics performance of the robot with variable height while moving such as NOROS-II. The existing method of dynamics modeling is improved by adding the constraint equation between perpendicular displacement of body and horizontal displacement of wheel into the constraint conditions. The dynamic model of NOROS-II in wheel motion is built by the Lagrange method under nonholonomic constraints. The inverse dynamics is calculated in three different paths based on this model, and the results demonstrate that torques of hip pitching joints are inversely proportional to the height of robot. The relative error of calculated torques is less than 2% compared with that of ADAMS simulation, by which the validity of dynamic model is verified. Moreover, the relative horizontal motion between fore/hind wheels and body is produced when the height is changed, and thus the accurate slip ratio can not be obtained by the traditional equation. The improved slip ratio equations with the parameter of the vertical velocity of body are introduced for fore wheels and hind wheels respectively. Numerical simulations of slip ratios are conducted to reveal the effect of varied height on slip ratios of different wheels. The result shows that the slip ratios of fore/hind wheels become larger/smaller respectively as the height increases, and as the height is reduced, the reverse applies. The proposed research of dynamic model and slip ratio based on the robot height provides the effective method to analyze the dynamics of WMRs with varying height.

  15. Slip length crossover on a graphene surface

    SciTech Connect

    Liang, Zhi; Keblinski, Pawel

    2015-04-07

    Using equilibrium and non-equilibrium molecular dynamics simulations, we study the flow of argon fluid above the critical temperature in a planar nanochannel delimited by graphene walls. We observe that, as a function of pressure, the slip length first decreases due to the decreasing mean free path of gas molecules, reaches the minimum value when the pressure is close to the critical pressure, and then increases with further increase in pressure. We demonstrate that the slip length increase at high pressures is due to the fact that the viscosity of fluid increases much faster with pressure than the friction coefficient between the fluid and the graphene. This behavior is clearly exhibited in the case of graphene due to a very smooth potential landscape originating from a very high atomic density of graphene planes. By contrast, on surfaces with lower atomic density, such as an (100) Au surface, the slip length for high fluid pressures is essentially zero, regardless of the nature of interaction between fluid and the solid wall.

  16. Periodic slow slip triggers megathrust zone earthquakes in northeastern Japan

    NASA Astrophysics Data System (ADS)

    Uchida, Naoki; Iinuma, Takeshi; Nadeau, Robert M.; Bürgmann, Roland; Hino, Ryota

    2016-01-01

    Both aseismic and seismic slip accommodate relative motion across partially coupled plate-boundary faults. In northeastern Japan, aseismic slip occurs in the form of decelerating afterslip after large interplate earthquakes and as relatively steady slip on uncoupled areas of the subduction thrust. Here we report on a previously unrecognized quasi-periodic slow-slip behavior that is widespread in the megathrust zone. The repeat intervals of the slow slip range from 1 to 6 years and often coincide with or precede clusters of large [magnitude (M) ≥ 5] earthquakes, including the 2011 M 9 Tohoku-oki earthquake. These results suggest that inherently periodic slow-slip events result in periodic stress perturbations and modulate the occurrence time of larger earthquakes. The periodicity in the slow-slip rate has the potential to help refine time-dependent earthquake forecasts.

  17. Free energy of dislocations in a multi-slip geometry

    NASA Astrophysics Data System (ADS)

    Kooiman, M.; Hütter, M.; Geers, M. G. D.

    2016-03-01

    The collective dynamics of dislocations is the underlying mechanism of plastic deformation in metallic crystals. Dislocation motion in metals generally occurs on multiple slip systems. The simultaneous activation of different slip systems plays a crucial role in crystal plasticity models. In this contribution, we study the energetic interactions between dislocations on different slip systems by deriving the free energy in a multi-slip geometry. In this, we restrict ourselves to straight and parallel edge dislocations. The obtained free energy has a long-range mean-field contribution, a statistical contribution and a many-body contribution. The many-body contribution is a local function of the total dislocation density on each slip system, and can therefore not be written in terms of the net dislocation density only. Moreover, this function is a strongly non-linear and non-convex function of the density on different slip systems, and hence the coupling between slip systems is of great importance.

  18. Periodic slow slip triggers megathrust zone earthquakes in northeastern Japan.

    PubMed

    Uchida, Naoki; Iinuma, Takeshi; Nadeau, Robert M; Bürgmann, Roland; Hino, Ryota

    2016-01-29

    Both aseismic and seismic slip accommodate relative motion across partially coupled plate-boundary faults. In northeastern Japan, aseismic slip occurs in the form of decelerating afterslip after large interplate earthquakes and as relatively steady slip on uncoupled areas of the subduction thrust. Here we report on a previously unrecognized quasi-periodic slow-slip behavior that is widespread in the megathrust zone. The repeat intervals of the slow slip range from 1 to 6 years and often coincide with or precede clusters of large [magnitude (M) ≥ 5] earthquakes, including the 2011 M 9 Tohoku-oki earthquake. These results suggest that inherently periodic slow-slip events result in periodic stress perturbations and modulate the occurrence time of larger earthquakes. The periodicity in the slow-slip rate has the potential to help refine time-dependent earthquake forecasts. PMID:26823425

  19. Tremor and the Depth Extent of Slip in Large Earthquakes

    NASA Astrophysics Data System (ADS)

    BEroza, G. C.; Brown, J. R.; Ide, S.

    2013-05-01

    We survey the evidence for the distribution of tremor and mainshock slip. In Southwest Japan, where tremor is well located, it outlines the down-dip edge of slip in the 1944 and 1946 Nankai earthquakes. In Alaska and the Aleutians, tremor location and slip distributions in slip are subject to greater uncertainty, but within that uncertainty they are consistent with the notion that tremor outlines the down-dip limit of mainshock slip. In Mexico, tremor locations and the extent of rupture in large (M > 7) earthquakes are also uncertain, but show a similar relationship. Taken together, these observations suggest that tremor may provide important information on the depth extent of rupture in large earthquakes where there have been no large earthquakes to test that hypothesis. If applied to the Cascadia subduction zone, it suggests slip will extend farther inland than previously assumed. If applied to the San Andreas Fault, it suggests slip will extend deeper than has previously been assumed.

  20. Uncovering the geodetic signature of silent slip through repeating earthquakes

    NASA Astrophysics Data System (ADS)

    Frank, William B.; Radiguet, Mathilde; Rousset, Baptiste; Shapiro, Nikolaï M.; Husker, Allen L.; Kostoglodov, Vladimir; Cotte, Nathalie; Campillo, Michel

    2015-04-01

    Slow transient slip that releases stress along the deep roots of plate interfaces is most often observed on regional GPS networks installed at the surface. The detection of slow slip is not trivial if the dislocation along the fault at depth does not generate a geodetic signal greater than the observational noise level. Instead of the typical workflow of comparing independently gathered seismic and geodetic observations to study slow slip, we use repeating low-frequency earthquakes to reveal a previously unobserved slow slip event. By aligning GPS time series with episodes of low-frequency earthquake activity and stacking, we identify a repeating transient slip event that generates a displacement at the surface that is hidden under noise prior to stacking. Our results suggest that the geodetic investigation of transient slip guided by seismological information is essential in exploring the spectrum of fault slip.

  1. Spatiotemporal evolution of seismic and aseismic slip on the Longitudinal Valley Fault, Taiwan

    NASA Astrophysics Data System (ADS)

    Thomas, Marion Y.; Avouac, Jean-Philippe; Champenois, Johann; Lee, Jian-Cheng; Kuo, Long-Chen

    2014-06-01

    The Longitudinal Valley Fault (LVF) in eastern Taiwan is a high slip rate fault (about 5 cm/yr), which exhibits both seismic and aseismic slip. Deformation of anthropogenic features shows that aseismic creep accounts for a significant fraction of fault slip near the surface, whereas a fraction of the slip is also seismic, since this fault has produced large earthquakes with five Mw>6.8 events in 1951 and 2003. In this study, we analyze a dense set of geodetic and seismological data around the LVF, including campaign mode Global Positioning System(GPS) measurements, time series of daily solutions for continuous GPS stations (cGPS), leveling data, and accelerometric records of the 2003 Chenkung earthquake. To enhance the spatial resolution provided by these data, we complement them with interferometric synthetic aperture radar (InSAR) measurements produced from a series of Advanced Land Observing Satellite images processed using a persistent scatterer technique. The combined data set covers the entire LVF and spans the period from 1992 to 2010. We invert this data to infer the temporal evolution of fault slip at depth using the Principal Component Analysis-based Inversion Method. This technique allows the joint inversion of diverse data, taking the advantage of the spatial resolution given by the InSAR measurements and the temporal resolution afforded by the cGPS data. We find that (1) seismic slip during the 2003 Chengkung earthquake occurred on a fault patch which had remained partially locked in the interseismic period, (2) the seismic rupture propagated partially into a zone of shallow aseismic interseismic creep but failed to reach the surface, and (3) that aseismic afterslip occurred around the area that ruptured seismically. We find consistency between geodetic and seismological constraints on the partitioning between seismic and aseismic creep. About 80-90% of slip on the southern section of LVF in the 0-26 km, seismogenic depth range, is actually aseismic. We infer that the clay-rich Lichi Mélange is the key factor promoting aseismic creep at shallow depth.

  2. Slip of polydisperse polymers: Molecular weight distribution above and below the plane of slip

    NASA Astrophysics Data System (ADS)

    Sabzevari, Seyed Mostafa; Strandman, Satu; Wood-Adams, Paula Marie

    2015-04-01

    When strong slip occurs during the drag flow of highly entangled polybutadienes (PBD) in a sliding plate rheometer equipped with stainless steel parallel plates, a thin film of polymer debris remains on the substrate after the slip. This debris is assumed to be formed by the disentanglement process that occurs in strong slip at a distance of about one molecular size from the plate. In order to evaluate the composition of the debris we collected it with tetrahydrofuran and subjected it to gel permeation chromatography. It was found that the molecular weight distribution (MWD) of the debris is significantly different from that of the bulk. Moreover, in mixtures prepared from long and short PBDs with distinctly different molecular weight distributions, the MWD of the debris was found to be richer in low molecular weight components and leaner in the high molecular weight components compared to the bulk. This information is important since it reveals the compositional difference between the bulk and interfacial layer above and below the plane of slip. The difference in MWD is likely a consequence of the strong slip in which some of long chains are pulled away from the surface-adsorbed chains by the flow leaving a debris lean in the high molecular weight component.

  3. Simulation of Tremor and Slow Slip Earthquakes Along a Strike-Slip Fault

    NASA Astrophysics Data System (ADS)

    Payton, K. A.; Cochran, E. S.; Richards-Dinger, K. B.; Dieterich, J. H.; Harrington, R. M.; Kroll, K.

    2014-12-01

    We use an earthquake simulator to investigate the conditions that may result in tectonic tremor. Tremor comprises small seismic events often associated with slow slip earthquakes (SSEs) that were initially discovered in subduction zones, but have subsequently been observed along transform faults such as the San Andreas Fault. For this study, our primary region of interest is the Parkfield-Cholame segment of the San Andreas, which is located between the locked segment to the south and the creeping segment to the north. Due to Parkfield's unique history of successive earthquakes at quasi-regular intervals, deep borehole seismometers were installed in this region, enabling the discovery of low-amplitude tectonic tremor. To better understand the fault properties that result in SSEs and tremor, we utilize the earthquake simulator RSQSim to simulate multi-cycle SSEs and tremor along a planar strike-slip fault. RSQSim is a computationally efficient method that uses rate- and state- dependent friction to simulate a wide range of event sizes for long time histories of slip [Dieterich and Richards-Dinger, 2010; Richards-Dinger and Dieterich, 2012]. RSQSim has been previously used to investigate slow slip events in Cascadia [Colella et al., 2011; 2012]. Here, we examine a suite of parameters to understand the influence of normal stress, rate-and-state constants a and b, and slip speed as well as the distribution of tremor patches on tremor and SSE occurrence. We compare the simulation results to previous tremor observations.

  4. Modeling of rock friction 2. Simulation of preseismic slip

    USGS Publications Warehouse

    Dieterich, J.H.

    1979-01-01

    The constitutive relations developed in the companion paper are used to model detailed observations of preseismic slip and the onset of unstable slip in biaxial laboratory experiments. The simulations employ a deterministic plane strain finite element model to represent the interactions both within the sliding blocks and between the blocks and the loading apparatus. Both experiments and simulations show that preseismic slip is controlled by initial inhomogeneity of shear stress along the sliding surface relative to the frictional strength. As a consequence of the inhomogeneity, stable slip begins at a point on the surface and the area of slip slowly expands as the external loading increases. A previously proposed correlation between accelerating rates of stable slip and growth of the area of slip is supported by the simulations. In the simulations and in the experiments, unstable slip occurs shortly after a propagating slip event traverses the sliding surface and breaks out at the ends of the sample. In the model the breakout of stable slip causes a sudden acceleration of slip rates. Because of velocity dependency of the constitutive relationship for friction, the rapid acceleration of slip causes a decrease in frictional strength. Instability occurs when the frictional strength decreases with displacement at a rate that exceeds the intrinsic unloading characteristics of the sample and test machine. A simple slider-spring model that does not consider preseismic slip appears to approximate the transition adequately from stable sliding to unstable slip as a function of normal stress, machine stiffness, and surface roughness for small samples. However, for large samples and for natural faults the simulations suggest that the simple model may be inaccurate because it does not take into account potentially large preseismic displacements that will alter the friction parameters prior to instability. Copyright ?? 1979 by the American Geophysical Union.

  5. Spatial Variations in Slip on Corrugated Reverse Fault Surfaces

    NASA Astrophysics Data System (ADS)

    Morris, A. C.; Marshall, S. T.

    2010-12-01

    Faults are inherently non-planar at many scales; however, most seismic hazard analyses and geophysical methods of determining fault slip rates utilize highly simplified fault geometries. To better understand the slip behavior and seismic potential of non-planar fault surfaces, we present results from a suite of numerical models of faults with sinusoidal corrugations in the down-dip direction. Variations in wavelength, amplitude, and loading angle are introduced to determine the effects on slip behavior and seismic moment release. We find that corrugated faults, in general, slip less than planar faults and obliquely-loaded corrugated faults have less strike-slip than a planar fault with the same tip line dimensions. Short wavelength, large amplitude faults slip the least, with small changes in amplitude more strongly effecting short wavelength faults. Additionally, short wavelength, large amplitude faults accumulate mostly dip slip and, in some cases, may have an average net slip vector with the opposite sense of slip compared to their planar counterparts. This reversal in slip sense is the result of variations in resolved stress, as fault corrugations become sub-parallel to the oblique loading. Though seismic energy release can be larger for some non-planar surfaces relative to a planar surface, seismic energy release is always less for obliquely-loaded faults. While non-planar surfaces typically slip less than planar surfaces, some non-planar surfaces can release a greater amount of seismic energy relative to planar surfaces, due to a greater surface area. These results indicate a strong dependence of fault behavior on surface geometry and suggest that surface corrugation may dramatically alter slip distributions and slip rates. Therefore, models incorporating highly simplified fault surface geometry have the potential to significantly misrepresent fault slip rates. Example of modeled fault surface mesh with down-dip corrugations.

  6. Detailed history of slip along the Sunda mega-thrust

    NASA Astrophysics Data System (ADS)

    Simão, Nuno; Lindsay, Anthony; Murphy, Shane; McCloskey, John; Bhloscaidh, Mairead Nic; Nalbant, Suleyman

    2013-04-01

    We undertook a reconstruction of more than 200 years of deformation on the Sunda mega-thrust using the history of vertical displacement recorded in the stratigraphy of coral micro-atolls. This reconstruction gave an unprecedented opportunity to understand the distributions of slip on the recent series of great earthquakes and its relationship with coupling. We have seen with the recent earthquakes that, whilst the slip-coupling relationship may be complex and certainly depends on the pre-stress, the greatest slip generally occurs in areas of high coupling. We have also seen that the spatial distributions of the greatest slip reveals tessellation between earthquakes. Using Monte Carlo techniques, we compare ground deformation produced by different fractal slip distributions with micro-atoll coral data to estimate slip distributions for the 1797 and 1833 historical earthquakes. The resulting slip estimations have a more realistic spatial distribution and provide a better fit to the micro-atoll data than previously published solutions. Preliminary results seem to imply that the 1797 and 1833 ruptures reveal a level of complementarity, where the greatest values of slip tessellate with the greatest slip values observed in the two great earthquakes of 2007 and the earthquake of 2010. In addition, the spatial stacking of all slips from all available earthquake slip distributions reveals a strong correlation with the spatial distribution of the coupling. Discrepancies in the spatial slip-coupling correlation, although strongly influenced by the uncertainties of the slip distributions, and with the 1797 and 1833 earthquakes playing a stronger role, can still be used as a way to pin-point possible areas of slip deficit when compared with the spatial distribution of coupling. This seems to imply that correspondence between the slip probability in 1797 and 1833 and present-day earthquakes slip and coupling appears to show the same basic relationship indicating that the broad geometry of this coupling has survived for more than one seismic cycle. It does not however imply that the slip on these earthquakes is predictable; it means simply that there is a low probability that high slip will occur in areas of weak coupling or where high levels of slip already occurred during these shocks.

  7. Shearing along faults and stratigraphic joints controlled by land subsidence in the Valley of Queretaro, Mexico

    NASA Astrophysics Data System (ADS)

    Carreón-Freyre, D.; Cerca, M.; Ochoa-González, G.; Teatini, P.; Zuñiga, F. R.

    2016-03-01

    Slip of nearly vertical faults or horizontal stratigraphic joints has provoked the shearing of at least 16 well casings in a period of over 10 years in the Valley of Queretaro aquifer, Mexico. Evidence integrated from field observations, remote surface-deformation monitoring, in-situ monitoring, stratigraphic correlation, and numerical modeling indicate that groundwater depletion and land subsidence induce shearing. Two main factors conditioning the stress distribution and the location of sheared well casings have been identified: (1) slip on fault planes, and (2) slip on stratigraphic joints. Additionally, the distribution of piezometric gradients may be a factor that enhances shearing. Slip on faults can be generated either by the compaction of sedimentary units (passive faulting) or by slip of blocks delimited by pre-existing faults (reactivation). Major piezometric-level declines and the distribution of hydraulic gradients can also be associated with slip at stratigraphic joints. Faults and hydraulic contrasts in the heterogeneous rock sequence, along with groundwater extraction, influence the distribution of the gradients and delimit the compartments of groundwater in the aquifer. Analogue modeling allowed assessment of the distribution of stress-strain and displacements associated with the increase of the vertical stress. Fault-bounded aquifers in grabens are common in the central part of Mexico and the results obtained can be applied to other subsiding, structurally controlled aquifer systems elsewhere.

  8. Shearing along faults and stratigraphic joints controlled by land subsidence in the Valley of Queretaro, Mexico

    NASA Astrophysics Data System (ADS)

    Carreón-Freyre, D.; Cerca, M.; Ochoa-González, G.; Teatini, P.; Zuñiga, F. R.

    2016-05-01

    Slip of nearly vertical faults or horizontal stratigraphic joints has provoked the shearing of at least 16 well casings in a period of over 10 years in the Valley of Queretaro aquifer, Mexico. Evidence integrated from field observations, remote surface-deformation monitoring, in-situ monitoring, stratigraphic correlation, and numerical modeling indicate that groundwater depletion and land subsidence induce shearing. Two main factors conditioning the stress distribution and the location of sheared well casings have been identified: (1) slip on fault planes, and (2) slip on stratigraphic joints. Additionally, the distribution of piezometric gradients may be a factor that enhances shearing. Slip on faults can be generated either by the compaction of sedimentary units (passive faulting) or by slip of blocks delimited by pre-existing faults (reactivation). Major piezometric-level declines and the distribution of hydraulic gradients can also be associated with slip at stratigraphic joints. Faults and hydraulic contrasts in the heterogeneous rock sequence, along with groundwater extraction, influence the distribution of the gradients and delimit the compartments of groundwater in the aquifer. Analogue modeling allowed assessment of the distribution of stress-strain and displacements associated with the increase of the vertical stress. Fault-bounded aquifers in grabens are common in the central part of Mexico and the results obtained can be applied to other subsiding, structurally controlled aquifer systems elsewhere.

  9. Long-term slip deficit and the forecasting of slip in future earthquakes

    NASA Astrophysics Data System (ADS)

    McCloskey, John; NicBhloscaidh, Mairead; Simao, Nuno

    2014-05-01

    In the last decade a series of devastating earthquakes have between them killed more than three-quarters of a million people. None of the events were formally forecast and have been repeatedly referred to a seismological 'surprises'. Here we argue that while earthquakes within the wide swath of diffuse deformation comprising the Alpine-Himalayan belt pose a set of particularly difficult set of challenges, earthquakes which are driven by high strain-rates at plate boundaries and which have relatively short nominal recurrence times might be forecast if the data exists to perform long-term slip deficit modelling and stress reconstruction. We show that two instrumentally recorded event on the Sumatran margin in 2007 and 2010 occurred in regions of high slip deficit identified by reconstruction of slip in historical earthquakes in 1797 and 1833 under the Mentawai Islands using more than 200 years of geodetic data recorded in the stratigraphy of coral micro-atolls growing there. In the presentation we will describe the data and a new Bayesian-Monte Carlo slip reconstruction technique. The technique is based on the stochastic forward modelling of many slip distributions each using the same set of elastic Green's functions to estimate, by superposition of contributions from each fault cell, the vertical displacement at the coral locations resulting from each simulated event. Every solution, weighted by its goodness of fit to the data, is added to a stack whose final values contain an estimate of the most likely distribution of slip in the historical earthquakes. Further, we estimate the Kullback-Liebler divergence over the fault area providing a non-arbitrary assessment of the spatial distribution of information gain, identifying regions of low- and high- model confidence. We then model the long-term slip deficit on the megathrust assuming a zero of stress immediately after the 1652 Mentawai Islands earthquake. We use the resulting slip deficit field to compute the entire stress field including both secular loading and earthquake interaction stresses. We show that the spatial distribution of energy release in the 2007 and 2010 earthquakes correlates strongly with regions of high slip deficit accumulated over the previous 350 years and that in principle both could have been identified as areas of particularly high seismic hazard. The following more general seismological lessons emerge from our work: 1 At least for this region of this margin, the characteristic earthquake concept entirely fails to explain the data 2 Earthquake slip tessellates the fault plane under the Mentawai Islands rather than repeatedly breaking the same patch. 3 The tessellation by high slip is largely constrained by the interface coupling distribution (which, of course, played no part in the slip reconstruction). 4 Homogeneous loading of a heterogeneous fault in a linear-elastic medium explains all the observations, no rheological time dependence is necessary. 5 Even small amounts of nonlinearity in the rupture process would ensure that this sequence will not be repeated, calling into question many long-standing, fundamental concepts in earthquake science.

  10. Direct numerical simulation of particle deposition onto a free-slip and no-slip surface

    NASA Astrophysics Data System (ADS)

    van Haarlem, Bas; Boersma, Bendiks J.; Nieuwstadt, Frans T. M.

    1998-10-01

    We consider here the direct numerical simulation (DNS) of channel flow with two different surfaces: a no-slip, fixed wall and on the opposite side a free-slip, free surface. The simulated velocity field agrees well with the experimental data for a free-surface flow obtained by Komori et al. [Int. J. Heat Mass Transf. 25, 513 (1982)]. The DNS is used to simulate particle trajectories, which are computed with a dynamic particle equation in which only the drag force given by the Stokes law is taken into account. For the particle time scale, nondimensionalized in terms of the fixed-wall friction velocity and the kinematic viscosity, we use the values τ+=5 and τ+=15. A statistically stationary condition is studied that is obtained by the introduction of a uniform distribution of particles at the beginning of the channel and by continuous removal through deposition at the two walls. The steady-state concentration distribution is nonuniform across the channel width, primarily due to the process whereby particles are trapped close to the surface. Moreover, we find that the wall-normal concentration profiles are self-similar. The deposition on both the no-slip and the free-slip wall can be described by a constant deposition coefficient, with for τ+=5 the larger value on the free-slip wall and for τ+=15 the opposite, i.e., the larger value over the no-slip wall. To study the deposition process in more detail we consider the cross channel particle fluxes and velocity statistics that are conditioned on deposition events. By means of instantaneous near-wall particle distributions we also consider the patterns of particles and their accumulation in certain areas of the flow. For a no-slip surface the well-known result that particles tend to collect in the low-speed streaks is confirmed. The patterns of particles near the free-slip surface are completely different, which can be explained in terms of the different types of coherent structures that are present near this surface.

  11. Coseismic slip distribution of the 1923 Kanto earthquake, Japan

    USGS Publications Warehouse

    Pollitz, F.F.; Nyst, M.; Nishimura, T.; Thatcher, W.

    2005-01-01

    The slip distribution associated with the 1923 M = 7.9 Kanto, Japan, earthquake is reexamined in light of new data and modeling. We utilize a combination of first-order triangulation, second-order triangulation, and leveling data in order to constrain the coseismic deformation. The second-order triangulation data, which have not been utilized in previous studies of 1923 coseismic deformation, are associated with only slightly smaller errors than the first-order triangulation data and expand the available triangulation data set by about a factor of 10. Interpretation of these data in terms of uniform-slip models in a companion study by Nyst et al. shows that a model involving uniform coseismic slip on two distinct rupture planes explains the data very well and matches or exceeds the fit obtained by previous studies, even one which involved distributed slip. Using the geometry of the Nyst et al. two-plane slip model, we perform inversions of the same geodetic data set for distributed slip. Our preferred model of distributed slip on the Philippine Sea plate interface has a moment magnitude of 7.86. We find slip maxima of ???8-9 m beneath Odawara and ???7-8 m beneath the Miura peninsula, with a roughly 2:1 ratio of strike-slip to dip-slip motion, in agreement with a previous study. However, the Miura slip maximum is imaged as a more broadly extended feature in our study, with the high-slip region continuing from the Miura peninsula to the southern Boso peninsula region. The second-order triangulation data provide good evidence for ???3 m right-lateral strike slip on a 35-km-long splay structure occupying the volume between the upper surface of the descending Philippine Sea plate and the southern Boso peninsula. Copyright 2005 by the American Geophysical Union.

  12. Constitutive relations for fault slip and earthquake instabilities

    NASA Astrophysics Data System (ADS)

    Rice, James R.

    1983-05-01

    Constitutive relations for fault slip are described and adopted as a basis for analyzing slip motion and its instability in the form of earthquakes on crustal faults. The constitutive relations discussed include simple rate-independent slip-weakening models, in which shear strength degrades with ongoing slip to a residual frictional strength, and also more realistic but as yet less extensively applied slip-rate and surface-state-dependent relations. For the latter the state of the surface is characterized by one or more variables that evolve with ongoing slip, seeking values consistent with the current slip rate. Models of crustal faults range from simple, single-degree-of-freedom spring-slider systems to more complex continuous systems that incorporate nonuniform slip and locked patches on faults of depth-dependent constitutive properties within elastic lithospheric plates that may be coupled to a viscoelastic asthenosphere. Most progress for the rate and state-dependent constitutive relations is at present limited to single-degree-of-freedom systems. Results for stable and unstable slip with the various constitutive models are summarized. Instability conditions are compared for spatially uniform versus nonuniform slip, including the elastic — brittle crack limit of the nonuniform mode. Inferences of constitutive and fracture parameters are discussed, based on earthquake data for large ruptures that begin with slip at depth, concentrating stress on locked regions within a brittle upper crust. Results of nonlinear stability theory, including regimes of complex sustained stress and slip rate oscillations, are outlined for rate and state-dependent constitutive relations, and the manner in which these allow phenomena like time-dependent failure, restrengthening in nearly stationary contact, and weakening in rapidly accelerated slip, is discussed.

  13. Complicated Recurrence of Slip Events on a Uniform Circular Asperity

    NASA Astrophysics Data System (ADS)

    Kato, N.

    2012-12-01

    Numerical simulation of repeated occurrence of slip events on a fault patch (asperity) is conducted to understand the mechanism of irregularity of the events. Seismic and geodetic observations indicate that episodic seismic/aseismic slip events repeatedly occur at almost the same area. For instance, magnitude of about 4.8 earthquakes had repeatedly occurred at intervals of 4.7 to 6.7 years off Kamaishi, northern Honshu, Japan. Quasi-periodic recurrence of episodic aseismic slip events (slow earthquakes) was found at the Nankai subduction zone, southwestern Japan, the Cascadia subduction zone, North America, etc. The recurrence intervals and magnitudes of slip events in each sequence are not constant, but some variability exists. Some researchers suggested that the variation in aseismic slip rate around a patch of slip events causes variation of loading rate. This results in variation of recurrence intervals. In the present study, we focus on irregularity of recurrence of slip events that originates from dynamics of fault slip. A two-dimensional planar fault in an infinite elastic medium is considered. The fault is uniformly shear loaded at a constant rate, and frictional stress acting on the fault is assumed to obey a rate- and state-dependent friction (RSF) law. A circular patch of radius r with velocity-weakening frictional property is embedded on a fault with velocity-strengthening frictional property elsewhere. A numerical simulation is conducted by varying the characteristic slip distance L of the RSF law. The critical radius rc for occurrence of unstable slip can be defined, and rc is proportional to L. When r >> rc, seismic slip events (earthquakes) repeatedly occur at a constant time interval. When r is a little larger than rc, recurrence of slip events becomes complex. We observe a period-2 cycle of slip events, where large and small events alternately occur. The cycle becomes more complex as r approaches rc and finally aperiodic (chaotic) slip pattern occurs. During the increase of slip complexity, a period-doubling sequence is observed. An iteration map of recurrence intervals of slip events is examined by taking a plot of Ti versus Ti-1, where Ti denotes the time interval between the ith and (i+1)th slip events. The iteration map is expressed by a simple curve, suggestive of predictability of the occurrence time of the next event from the previous time interval. To understand the cause of the variation of slip events, the distributions of shear stress on the fault before the slip events are examined. We observe a large variation of the shear stress distribution within the velocity-weakening region, which is generated by the preceding slip event and aseismic sliding during an interseismic period. To compare the simulation result of sequence of slip events on a velocity-weakening patch embedded in velocity-strengthening region, a numerical simulation of slip on a velocity-weakening patch enclosed by unbreakable barrier. In this case, no complex recurrence of slip events is observed. When r > rc, seismic slip events repeatedly occur at a constant interval. On the other hand, stable sliding occurs when r < rc. This result indicates that the complicated slip behavior for a velocity-weakening patch embedded in velocity-strengthening region comes from the interaction between the velocity-weakening and velocity-strengthening regions.

  14. Inertial and stick-slip regimes of unstable adhesive tape peeling.

    PubMed

    Dalbe, Marie-Julie; Villey, Richard; Ciccotti, Matteo; Santucci, Stéphane; Cortet, Pierre-Philippe; Vanel, Loïc

    2016-05-18

    We present an experimental characterization of the detachment front unstable dynamics observed during the peeling of pressure sensitive adhesives. We use an experimental set-up specifically designed to control the peeling angle θ and the peeled tape length L, while peeling an adhesive tape from a flat substrate at a constant driving velocity V. High-speed imaging allows us to report the evolution of the period and amplitude of the front oscillations, as well as the relative durations of their fast and slow phases, as a function of the control parameters V, L and θ. Our study shows that, as the driving velocity or the peeling angle increases, the oscillations of the peeling front progressively evolve from genuine "stick-slip" oscillations, made of alternating long stick phases and very brief slip phases, to sinusoidal oscillations of amplitude twice the peeling velocity. We propose a model which, taking into account the peeling angle-dependent kinetic energy cost to accelerate and decelerate the peeled tape, explains the transition from the "stick-slip" to the "inertial" regime of the dynamical instability. Using independent direct measurements of the effective fracture energy of the adhesive-substrate joint, we show that our model quantitatively accounts for the two regimes of the unstable dynamics. PMID:27050487

  15. Limited overlap between the seismic gap and coseismic slip of the great 2010 Chile earthquake

    NASA Astrophysics Data System (ADS)

    Lorito, S.; Romano, F.; Atzori, S.; Tong, X.; Avallone, A.; McCloskey, J.; Cocco, M.; Boschi, E.; Piatanesi, A.

    2011-03-01

    The Mw 8.8 mega-thrust earthquake and tsunami that occurred on 27 February 2010 offshore the Maule region, Chile, was not unexpected. A clearly identified seismic gap existed in an area where tectonic loading has been accumulating since the great 1835 earthquake. Here we jointly invert tsunami and geodetic data to derive a robust model for the coseismic slip distribution and induced coseismic stress changes. We compare these with past earthquakes and the preseismic locking distribution, to assess if the Maule earthquake has filled the seismic gap. We find that the main slip patch is located to the north of the gap, overlapping the rupture zone of the Mw 8.0 earthquake that occurred in 1928, with a secondary concentration of slip to the south. The seismic gap was only partially filled and a zone of high preseismic locking remains unbroken, inconsistent with the assumption that distributions of seismic rupture might be correlated with preseismic locking. Moreover, we conclude that increased stress on the unbroken patch may in turn have increased the probability of another major to great earthquake there in the near future.

  16. The 2012 Brawley swarm triggered by injection-induced aseismic slip

    NASA Astrophysics Data System (ADS)

    Wei, Shengji; Avouac, Jean-Philippe; Hudnut, Kenneth W.; Donnellan, Andrea; Parker, Jay W.; Graves, Robert W.; Helmberger, Don; Fielding, Eric; Liu, Zhen; Cappa, Frederic; Eneva, Mariana

    2015-07-01

    It has long been known that fluid injection or withdrawal can induce earthquakes, but the underlying mechanisms remain elusive. For example, the 2012 Brawley swarm, which produced two strike-slip shocks with magnitudes larger than 5.3 and surface ruptures in the close vicinity of a geothermal field, started with earthquakes about 5 km deeper than the injection depth (∼1.5 km). This makes the causality between the injection and seismicity unclear. Here, we jointly analyze broadband and strong motion waveforms, UAVSAR, leveling measurements and field observations to reveal the detailed seismic and aseismic faulting behaviors associated with the 2012 Brawley swarm. In particular, path calibration established from smaller events in the swarm allows waveform inversion to be conducted up to 3 Hz to resolve finite rupture process of the Mw 4.7 normal event. Our results show that the 2012 earthquake sequence was preceded by aseismic slip on a shallow normal fault beneath the geothermal field. Aseismic slip initiated in 2010 when injection rate rapidly increased and triggered the following earthquakes subsequently, including unusually shallow and relatively high frequency seismic excitations on the normal fault. In this example, seismicity is induced indirectly by fluid injection, a result of mediation by aseismic creep, rather than directly by a pore pressure increase at the location of the earthquakes.

  17. DEM simulation of growth normal fault slip

    NASA Astrophysics Data System (ADS)

    Chu, Sheng-Shin; Lin, Ming-Lang; Nien, Wie-Tung; Chan, Pei-Chen

    2014-05-01

    Slip of the fault can cause deformation of shallower soil layers and lead to the destruction of infrastructures. Shanchiao fault on the west side of the Taipei basin is categorized. The activities of Shanchiao fault will cause the quaternary sediments underneath the Taipei basin to become deformed. This will cause damage to structures, traffic construction, and utility lines within the area. It is determined from data of geological drilling and dating, Shanchiao fault has growth fault. In experiment, a sand box model was built with non-cohesive sand soil to simulate the existence of growth fault in Shanchiao Fault and forecast the effect on scope of shear band development and ground differential deformation. The results of the experiment showed that when a normal fault containing growth fault, at the offset of base rock the shear band will develop upward along with the weak side of shear band of the original topped soil layer, and this shear band will develop to surface much faster than that of single top layer. The offset ratio (basement slip / lower top soil thickness) required is only about 1/3 of that of single cover soil layer. In this research, it is tried to conduct numerical simulation of sand box experiment with a Discrete Element Method program, PFC2D, to simulate the upper covering sand layer shear band development pace and scope of normal growth fault slip. Results of simulation indicated, it is very close to the outcome of sand box experiment. It can be extended to application in water pipeline project design around fault zone in the future. Keywords: Taipei Basin, Shanchiao fault, growth fault, PFC2D

  18. Slip stacking experiments at Fermilab main injector

    SciTech Connect

    Kiyomi Koba et al.

    2003-06-02

    In order to achieve an increase in proton intensity, Fermilab Main Injector will use a stacking process called ''slip stacking''. The intensity will be doubled by injecting one train of bunches at a slightly lower energy, another at a slightly higher energy, then bringing them together for the final capture. Beam studies have started for this process and we have already verified that, at least for a low beam intensity, the stacking procedure works as expected. For high intensity operation, development work of the feedback and feedforward systems is under way.

  19. Episodic Tremor and Slip: Cycles Within Cycles

    NASA Astrophysics Data System (ADS)

    Creager, K. C.; Wech, A.; Vidale, J. E.

    2009-12-01

    Episodic tremor and slip (ETS) events, each with geodetically determined moment magnitudes in the mid-6 range, repeat about every 15 months under the Olympic Peninsula/southern Vancouver Island region. We have automatically searched for non-volcanic tremor in all 5-minute time windows both during the past five ETS events and during the two inter-ETS periods from February, 2007 through April, 2008 and June 2008 through April 2009. Inter-ETS tremor was detected in 5000 windows, which overlap by 50%, so tremor was seen 2% of the time. The catalog of 5-minute tremor locations cluster in time and space into groups we call tremor swarms, revealing 50 inter-ETS tremor swarms. The number of hours of tremor per swarm ranged from about 1 to 68, totaling 374 hours. The inter-ETS tremor swarms generally locate along the downdip side of the major ETS events, and account for approximately 45% of the time that tremor has been detected during the last two entire ETS cycles. Many of the inter-ETS events are near-carbon copies in duration, spatial extent and propagation direction, as is seen for the larger 15-month-interval events. These 50 inter-ETS swarms plus two major ETS episodes follow a power law relationship such that the number of swarms, N, exceeding duration τ is given by N ˜ τ-0.7. If we assume that seismic moment is proportional to τ as proposed by Ide et al. [Nature, 2007], we find that the tremor swarms follow a standard Gutenberg-Richter logarithmic frequency-magnitude relation, N ˜ 10-bMw, with b = 1.0, which lies in the range for normal earthquake catalogs. Furthermore, the major ETS events fall on the curve defined by the inter-ETS swarms, suggesting that the inter-ETS swarms are just smaller versions of the major 15-month ETS events. Only the largest events coincide with geodetically observed slip, suggesting that current geodetic observations may be missing nearly half of the total slip. Finally, crude estimates of the spatial dimensions of tremor swarms L suggest that L ˜ τ1/n where n is between 2 and 3. A value of 2 is consistent with slip propagation rates being controlled by a diffusional process. In contrast, n is observed to be about 1 for normal earthquakes because rupture generally propagates at a velocity close to the shear-wave speed.

  20. Fixed recurrence and slip models better predict earthquake behavior than the time- and slip-predictable models 1: repeating earthquakes

    USGS Publications Warehouse

    Rubinstein, Justin L.; Ellsworth, William L.; Chen, Kate Huihsuan; Uchida, Naoki

    2012-01-01

    The behavior of individual events in repeating earthquake sequences in California, Taiwan and Japan is better predicted by a model with fixed inter-event time or fixed slip than it is by the time- and slip-predictable models for earthquake occurrence. Given that repeating earthquakes are highly regular in both inter-event time and seismic moment, the time- and slip-predictable models seem ideally suited to explain their behavior. Taken together with evidence from the companion manuscript that shows similar results for laboratory experiments we conclude that the short-term predictions of the time- and slip-predictable models should be rejected in favor of earthquake models that assume either fixed slip or fixed recurrence interval. This implies that the elastic rebound model underlying the time- and slip-predictable models offers no additional value in describing earthquake behavior in an event-to-event sense, but its value in a long-term sense cannot be determined. These models likely fail because they rely on assumptions that oversimplify the earthquake cycle. We note that the time and slip of these events is predicted quite well by fixed slip and fixed recurrence models, so in some sense they are time- and slip-predictable. While fixed recurrence and slip models better predict repeating earthquake behavior than the time- and slip-predictable models, we observe a correlation between slip and the preceding recurrence time for many repeating earthquake sequences in Parkfield, California. This correlation is not found in other regions, and the sequences with the correlative slip-predictable behavior are not distinguishable from nearby earthquake sequences that do not exhibit this behavior.

  1. Slip statistics of dislocation avalanches under different loading modes.

    PubMed

    Maass, R; Wraith, M; Uhl, J T; Greer, J R; Dahmen, K A

    2015-04-01

    Slowly compressed microcrystals deform via intermittent slip events, observed as displacement jumps or stress drops. Experiments often use one of two loading modes: an increasing applied stress (stress driven, soft), or a constant strain rate (strain driven, hard). In this work we experimentally test the influence of the deformation loading conditions on the scaling behavior of slip events. It is found that these common deformation modes strongly affect time series properties, but not the scaling behavior of the slip statistics when analyzed with a mean-field model. With increasing plastic strain, the slip events are found to be smaller and more frequent when strain driven, and the slip-size distributions obtained for both drives collapse onto the same scaling function with the same exponents. The experimental results agree with the predictions of the used mean-field model, linking the slip behavior under different loading modes. PMID:25974504

  2. Knee joint replacement

    MedlinePlus

    Knee joint replacement is a surgery to replace a knee joint with a man-made joint. The artificial joint is called a prosthesis . ... cartilage and bone are removed from the knee joint. Man-made pieces are then placed in the ...

  3. Tsunami Modeling to Validate Slip Models of the 2007 M w 8.0 Pisco Earthquake, Central Peru

    NASA Astrophysics Data System (ADS)

    Ioualalen, M.; Perfettini, H.; Condo, S. Yauri; Jimenez, C.; Tavera, H.

    2013-03-01

    Following the 2007, August 15th, M w 8.0, Pisco earthquake in central Peru, Sladen et al. (J Geophys Res 115: B02405, 2010) have derived several slip models of this event. They inverted teleseismic data together with geodetic (InSAR) measurements to look for the co-seismic slip distribution on the fault plane, considering those data sets separately or jointly. But how close to the real slip distribution are those inverted slip models? To answer this crucial question, the authors generated some tsunami records based on their slip models and compared them to DART buoys, tsunami records, and available runup data. Such an approach requires a robust and accurate tsunami model (non-linear, dispersive, accurate bathymetry and topography, etc.) otherwise the differences between the data and the model may be attributed to the slip models themselves, though they arise from an incomplete tsunami simulation. The accuracy of a numerical tsunami simulation strongly depends, among others, on two important constraints: (i) A fine computational grid (and thus the bathymetry and topography data sets used) which is not always available, unfortunately, and (ii) a realistic tsunami propagation model including dispersion. Here, we extend Sladen's work using newly available data, namely a tide gauge record at Callao (Lima harbor) and the Chilean DART buoy record, while considering a complete set of runup data along with a more realistic tsunami numerical that accounts for dispersion, and also considering a fine-resolution computational grid, which is essential. Through these accurate numerical simulations we infer that the InSAR-based model is in better agreement with the tsunami data, studying the case of the Pisco earthquake indicating that geodetic data seems essential to recover the final co-seismic slip distribution on the rupture plane. Slip models based on teleseismic data are unable to describe the observed tsunami, suggesting that a significant amount of co-seismic slip may have been aseismic. Finally, we compute the runup distribution along the central part of the Peruvian coast to better understand the wave amplification/attenuation processes of the tsunami generated by the Pisco earthquake.

  4. An Inexpensive Device for Modelling Strike-Slip and Oblique-Slip Fault Zones.

    ERIC Educational Resources Information Center

    Larter, Richard C. L.; Allison, Iain

    1983-01-01

    Describes construction/use of a device to simulate structures produced in fault zones of dominantly strike-dip motion. Apparatus modifications allow simulation of transtension and transpression as well as pure strike-slip fault motion. Illustrates formation of several structures using the apparatus, comparing them with natural examples. Includes…

  5. EMG and Kinematic Responses to Unexpected Slips After Slip Training in Virtual Reality

    PubMed Central

    Parijat, Prakriti; Lockhart, Thurmon E.

    2015-01-01

    The objective of the study was to design a virtual reality (VR) training to induce perturbation in older adults similar to a slip and examine the effect of the training on kinematic and muscular responses in older adults. Twenty-four older adults were involved in a laboratory study and randomly assigned to two groups (virtual reality training and control). Both groups went through three sessions including baseline slip, training, and transfer of training on slippery surface. The training group experienced twelve simulated slips using a visual perturbation induced by tilting a virtual reality scene while walking on the treadmill and the control group completed normal walking during the training session. Kinematic, kinetic, and EMG data were collected during all the sessions. Results demonstrated the proactive adjustments such as increased trunk flexion at heel contact after training. Reactive adjustments included reduced time to peak activations of knee flexors, reduced knee coactivation, reduced time to trunk flexion, and reduced trunk angular velocity after training. In conclusion, the study findings indicate that the VR training was able to generate a perturbation in older adults that evoked recovery reactions and such motor skill can be transferred to the actual slip trials. PMID:25296401

  6. Parametric Study of Smooth Joint Parameters on the Shear Behaviour of Rock Joints

    NASA Astrophysics Data System (ADS)

    Bahaaddini, M.; Hagan, P. C.; Mitra, R.; Hebblewhite, B. K.

    2015-05-01

    This paper aims to study the shear behaviour of rock joints in a direct shear test using the particle flow code PFC2D. In this numerical approach, the intact rock is simulated by densely packed circular particles that are bonded together at their contact points; joint surfaces can be explicitly simulated using the modified smooth joint (SJ) model. In the modified SJ model for simulation of direct shear test, micro-scale slip surfaces (smooth joint contacts) are applied at contacts between the particles of the upper and lower blocks of the shear box and the mechanical behaviour of the joints is controlled by the micro-scale properties of the smooth joint contacts. Two joint profiles of standard JRC 10-12 and a sawtooth triangular joint with a base angle of 15° were selected for testing. The results of direct shear tests under different normal stresses on these two profiles show that for the sawtooth triangular joints under a normal stress of 1 MPa, the shearing mechanism is purely sliding, and for the JRC 10-12 profile under a normal stress of 4 MPa, the shearing of first-order asperities controls the shearing mechanism. A parametric study of the micro-properties of the smooth joints under these two different shearing mechanisms was undertaken. The results of this study show that the SJ normal stiffness and the SJ shear stiffness have insubstantial effect on the peak shear strength in sliding mode, but that the SJ normal stiffness has a significant effect on the dilation rate in both sliding and shearing modes.

  7. How well do surface slip measurements track slip at depth in large strike-slip earthquakes? The importance of fault structural maturity in controlling on-fault slip versus off-fault surface deformation

    NASA Astrophysics Data System (ADS)

    Dolan, James F.; Haravitch, Ben D.

    2014-02-01

    Comparisons of observed surface displacements with geodetically inferred slip at depth in six large (Mw⩾7.1) strike-slip earthquakes reveal a correlation between the structural maturity of the fault and the ratio of deep slip to surface slip that occurs on localized zones of surface rupture. Specifically, structurally immature faults (⩽25 km of total displacement) manifest only ∼50-60% of total slip on narrow fault surface traces versus ∼85-95% for structurally mature faults (⩾85 km total slip). The same pattern holds when structurally simple parts of a surface rupture are analyzed separately from parts that exhibit obvious structural complexity (e.g., discontinuous or multiple traces or significant dip slip). These results imply that geologic measurements of surface slip along structurally immature faults are likely to significantly underestimate the true slip at depth in large earthquakes. This observation has implications for a number of important problems, including determination of fault slip rates, which are based on surface offsets; earthquake probability assessments, which are based on geologic fault slip rates; comparisons of geologic and geodetic rate data in the search for strain transients; the structural evolution of fault zones; estimation of paleo-earthquake magnitudes based on geomorphic offsets; analyses of the relative importance of faulting vs. distributed deformation in accommodating relative plate motions in continental crust; the design and construction of infrastructure built near active faults; and possibly for the prediction of strong ground motions, which may at least partially depend on the degree of slip localization to the surface.

  8. Subduction zone structures and slip behavior in megathrust

    NASA Astrophysics Data System (ADS)

    Kodaira, S.; Nakanishi, A.; Nakamura, Y.

    2014-12-01

    Earthquake, tsunami and geodetic data show that co-seismic slips of a large megathrust earthquakes do not uniformly propagate along a plate boundary. For example, a clear segmentation of slip zones of magnitude-8 class megathrust earthquakes are well recognized in the Nankai Trough. Moreover, a lateral variation of the slips are revealed even in one segment. In the Japan Trench, the most characteristic slip behavior of the 2011 Tohoku-oki earthquake is an extremely large slip reaching to the trench axis, but geodetic, tsunami or teleseismic show the slip was heterogeneous near the trench. In order to examine whether those complex slip distributions are attributed by any distinct structural factor, we have been carried out active-source seismic surveys in the subduction seismogenic. In the Nankai Trough, large-scale subducted seamounts, ridges and doming structure intruded in an overriding accretion wedge are imaged. Comparing co-seismic slip distribution of the 1944 Tonankai and the 1946 Nankai earthquakes with the seismic images, we concluded that those structures are key factors to control the slip distributions. In the central part of the Japan Trench area, we fund a rough basement geometry is overprinted on the horst-and-graben structure. Those complex geometry of basement cause a strong lateral variation of the thickness of subducting pelagic/hemi-pelagic sediment. Many geological studies suggest that properties of the plate-boundary sediment attribute the large slip near the trench. We therefore plan to acquire additional high-resolution seismic data in the entire Japan Trench in order to examine a role of incoming sediment on the large slip to the trench axis. In this presentation we present an overview of the structural factors controlling slips in megathrust earthquakes, including new data acquired in the Nankai Trough and Japan Trench.

  9. Slip-localization within confined gouge powder sheared at moderate to high slip-velocity

    NASA Astrophysics Data System (ADS)

    Reches, Zeev; Chen, Xiaofeng; Morgan, Chance; Madden, Andrew

    2015-04-01

    Slip along faults in the upper crust is always associated with comminution and formation of non-cohesive gouge powder that can be lithified to cataclasite. Typically, the fine-grained powders (grain-size < 1 micron) build a 1-10 cm thick inner-core of a fault-zone. The ubiquitous occurrence of gouge powder implies that gouge properties may control the dynamic weakening of faults. Testing these properties is the present objective. We built a Confined ROtary Cell, CROC, with a ring-shape, ~3 mm thick gouge chamber, with 62.5 and 81.2 mm of inner and outer diameters. The sheared powder is sealed by two sets of seals pressurized by nitrogen. In CROC, we can control the pore-pressure and to inject fluids, and to monitor CO2 and H2O concentration; in addition, we monitor the standard mechanical parameters (slip velocity, stresses, dilation, and temperature). We tested six types of granular materials (starting grain-size in microns): Talc (<250), Kasota dolomite (125-250), ooides grains (125-250), San Andreas fault zone powder (< 840), montmorillonite powder (1-2), kaolinite powder and gypsum. The experimental slip-velocity ranged 0.001-1 m/s, slip distances from a few tens of cm to tens of m, effective normal stress up to 6.1 MPa. The central ultra-microscopic (SEM) observation is that almost invariably the slip was localized along principal-slip-zone (PSZ) within the granular layer. Even though the starting material was loose, coarse granular material, the developed PSZ was cohesive, hard, smooth and shining. The PSZ is about 1 micron thick, and built of agglomerated, ultra-fine grains (20-50 nm) that were pulverized from the original granular material. We noted that PSZs of the different tested compositions display similar characteristics in terms of structure, grain size, and roughness. Further, we found striking similarities between PSZ in the granular samples and the PZS that developed along experimental faults made of solid rock that were sheared at similar conditions. The ultra-fine grains and extreme slip localization in these experiments are generally similar to ultra-cataclasites found in exhumed faults-zones, and the intensely pulverized gouge found in drilling across active faults.

  10. Inverting measurements of surface slip on the Superstition Hills fault

    USGS Publications Warehouse

    Boatwright, J.; Budding, K.E.; Sharp, R.V.

    1989-01-01

    We derive and test a set of inversions of surface-slip measurements based on the empirical relation u(t)=uf/(1 + T/t)c proposed by Sharp and Saxton (1989) to estimate the final slip uf, the power-law exponent c, and the power-law duration T. At short times, Sharp's relation behaves like the simple power law, u(t)~u1tc, where u1 is the initial slip, that is, the slip at 1 day after the earthquake. At long times, the slip approaches the final slip asymptotically. The inversions are designed in part to exploit the accuracy of measurements of differential slip; that is, measurements of surface slip which are made relative to a set of nails or stakes emplaced after the earthquake. We apply the inversions to slip measurements made at 53 sites along the Superstition Hills fault for the 11 months following the M=6.2 and 6.6 earthqakes of 24 November 1987. -from Authors

  11. Strong dynamical effects during stick-slip adhesive peeling

    NASA Astrophysics Data System (ADS)

    Dalbe, Marie-Julie; Santucci, Stephane; Vanel, Loic; Cortet, Pierre-Philippe

    2014-03-01

    We consider the classical problem of the stick-slip dynamics observed when peeling an adhesive tape at a constant velocity. From fast imaging recordings, we extract the dependencies of the stick and slip phases durations with the imposed peeling velocity and peeled ribbon length. Predictions of Maugis and Barquins [in Adhesion 12, edited by K.W. Allen, Elsevier ASP, London, 1988, pp. 205-222] based on a quasistatic assumption succeed to describe quantitatively our measurements of the stick phase duration. Such model however fails to predict the full stick-slip cycle duration, revealing strong dynamical effects during the slip phase.

  12. Is the co-seismic slip distribution fractal?

    NASA Astrophysics Data System (ADS)

    Milliner, Christopher; Sammis, Charles; Allam, Amir; Dolan, James

    2015-04-01

    Co-seismic along-strike slip heterogeneity is widely observed for many surface-rupturing earthquakes as revealed by field and high-resolution geodetic methods. However, this co-seismic slip variability is currently a poorly understood phenomenon. Key unanswered questions include: What are the characteristics and underlying causes of along-strike slip variability? Do the properties of slip variability change from fault-to-fault, along-strike or at different scales? We cross-correlate optical, pre- and post-event air photos using the program COSI-Corr to measure the near-field, surface deformation pattern of the 1992 Mw 7.3 Landers and 1999 Mw 7.1 Hector Mine earthquakes in high-resolution. We produce the co-seismic slip profiles of both events from over 1,000 displacement measurements and observe consistent along-strike slip variability. Although the observed slip heterogeneity seems apparently complex and disordered, a spectral analysis reveals that the slip distributions are indeed self-affine fractal i.e., slip exhibits a consistent degree of irregularity at all observable length scales, with a 'short-memory' and is not random. We find a fractal dimension of 1.58 and 1.75 for the Landers and Hector Mine earthquakes, respectively, indicating that slip is more heterogeneous for the Hector Mine event. Fractal slip is consistent with both dynamic and quasi-static numerical simulations that use non-planar faults, which in turn causes heterogeneous along-strike stress, and we attribute the observed fractal slip to fault surfaces of fractal roughness. As fault surfaces are known to smooth over geologic time due to abrasional wear and fracturing, we also test whether the fractal properties of slip distributions alters between earthquakes from immature to mature fault systems. We will present results that test this hypothesis by using the optical image correlation technique to measure historic, co-seismic slip distributions of earthquakes from structurally mature, large cumulative displacement faults and compare these slip distributions to those from immature fault systems. Our results have fundamental implications for an understanding of slip heterogeneity and the behavior of the rupture process.

  13. Quantum phase slips in superconducting wires with weak inhomogeneities.

    PubMed

    Vanević, Mihajlo; Nazarov, Yuli V

    2012-05-01

    Quantum phase slips are traditionally considered in diffusive superconducting wires which are assumed homogeneous. We present a definite estimate for the amplitude of phase slips that occur at a weak inhomogeneity in the wire where local resistivity is slightly increased. We model such a weak link as a general coherent conductor and show that the amplitude is dominated by the topological part of the action. We argue that such weak links occur naturally in apparently homogeneous wires and adjust the estimate to that case. The fabrication of an artificial weak link would localize phase slips and facilitate a better control of the phase-slip amplitude. PMID:22681107

  14. Tremor during ice stream stick-slip

    NASA Astrophysics Data System (ADS)

    Lipovsky, B. P.; Dunham, E. M.

    2015-09-01

    During the 200 km-scale stick slip of the Whillans Ice Plain (WIP), West Antarctica, seismic tremor episodes occur at the ice-bed interface. We interpret these tremor episodes as swarms of small repeating earthquakes. The earthquakes are evenly spaced in time and this even spacing gives rise to spectral peaks at integer multiples of the recurrence frequency ~ 10-20 Hz. We conduct numerical simulations of the tremor episodes that include the balance of forces acting on the fault, the evolution of rate- and state-dependent fault friction, and wave propagation from the fault patch to a seismometer located on the ice. The ice slides as an elastic block loaded by the push of the upstream ice, and so the simulated basal fault patch experiences a loading velocity equal to the velocity observed by GPS receivers on the surface of the WIP. By matching synthetic seismograms to observed seismograms, we infer fault area ~ 10 m2, bed shear modulus ~ 10 MPa, effective pressure ~ 10 kPa, and state evolution distance ~ 1 μm. Large-scale slip events often occur twice daily, although skipped events have been increasing in frequency over the last decade. We observe that tremor seismic particle velocity amplitudes are greater during the double wait time events that follow skipped events. The physical mechanism responsible for these anomalously high seismic amplitudes may provide a window into near-future subglacial conditions and the processes that occur during ice stream stagnation.

  15. Frictional slip of granite at hydrothermal conditions

    USGS Publications Warehouse

    Blanpied, M.L.; Lockner, D.A.; Byerlee, J.D.

    1995-01-01

    To measure the strength, sliding behavior, and friction constitutive properties of faults at hydrothermal conditions, laboratory granite faults containing a layer of granite powder (simulated gouge) were slid. The mechanical results define two regimes. The first regime includes dry granite up to at least 845?? and wet granite below 250??C. In this regime the coefficient of friction is high (?? = 0.7 to 0.8) and depends only modestly on temperature, slip rate, and PH2O. The second regime includes wet granite above ~350??C. In this regime friction decreases considerably with increasing temperature (temperature weakening) and with decreasing slip rate (velocity strengthening). These regimes correspond well to those identified in sliding tests on ultrafine quartz. The results highlight the importance of fluid-assisted deformation processes active in faults at depth and the need for laboratory studies on the roles of additional factors such as fluid chemistry, large displacements, higher concentrations of phyllosilicates, and time-dependent fault healing. -from Authors

  16. Slip effects in a dewetting polymer microdroplets

    NASA Astrophysics Data System (ADS)

    Chan, T. S.; McGraw, J. D.; Maurer, S.; Salez, T.; Benzaquen, M.; Raphaël, É.; Jacobs, K.; Brinkmann, M.

    2014-11-01

    A non-equilibrium liquid drop sitting on a smooth substrate will contract or spread depending on the equilibrium contact angle and the initial shape of the drop. Previous studies assume a huge separation of length scales between the drop contact size R and the slip length b (typically b / R = 10-6-10-5). One well known example is that of a drop spreading over a completely wetting surface, which follows Tanner's law. In this study, we experimentally and theoretically investigate contractions of microscopic droplets in regimes where these two length scales are not widely separated (b / R = 10-2-1). These regimes become relevant in micro- and nano-fluidic systems. Instead of a quasi-static spherical shape during the evolution, the profiles display more complex shapes in these regimes. We find that: 1) the interface profile near the contact line evolves in a self-similar way in the early stage; 2) depending on b / R , the profile can develop a characteristic bump shape in the intermediate stage of the evolution. 3) at late times, the radius saturates exponentially with a certain time scale, which depends on the slip length.

  17. Statistics from granular stick-slip experiment

    NASA Astrophysics Data System (ADS)

    Abed Zadeh, Aghil; Bares, Jonathan; Behringer, Robert

    2015-03-01

    We carry out experiments to characterize stick-slip for granular materials. In our experiment, a constant speed stage pulls a slider which rests on a vertical bed of circular photoelastic particles in a 2D system. The stage is connected to the slider by a spring. We measure the force on the spring as well as the slider's acceleration by a force sensor attached to the spring and accelerometers on the slider. The distributions of energy release and time duration of avalanches during slip obey power laws. We apply a novel event recognition approach using wavelets to extract the avalanche properties. We compare statistics from the wavelet approach with those obtained by typical methods, to show how noise can change the distribution of events. We analyze the power spectrum of various quantities to understand the effect of the loading speed and of the spring stiffness on the statistical behavior of the system. Finally, from a more local point of view and by using a high speed camera and the photoelastic properties of our particles, we characterize the internal granular structure during avalanches. This work is supported by NSF Grant DMR1206351 and NASA Grant NNX10AU01G.

  18. Single-layer burial joints vs single-layer uplift joints in Eocene chalk from the Beer Sheva syncline in Israel

    NASA Astrophysics Data System (ADS)

    Bahat, Dov

    1999-03-01

    The single-layer (s.l.) joints that occur in the Lower Eocene chalks near Beer Sheva, Israel, developed during the burial history of the rock, whereas the s.l. joints in adjacent Middle Eocene chalks developed during the uplift stage. Characteristically, s.l. burial joints occur in orthogonal cross-fold and strike sets, and as conjugate sets. They precede normal faults and multi-layer joints, and they do not exhibit strike rotation, en chelon segmentation or fracture interaction with each other. These joints are generally closed, and during subsidence older beds fracture first. On the other hand, s.l. uplift joints do not occur in orthogonal or conjugate sets. They are post strike-slip faulting, contemporaneous with multi-layer joints, and exhibit strike rotation, en chelon segmentation and often interact with each other. They are occasionally opened up to several millimetres, and during uplift younger beds fracture first.

  19. Identification of maximum road friction coefficient and optimal slip ratio based on road type recognition

    NASA Astrophysics Data System (ADS)

    Guan, Hsin; Wang, Bo; Lu, Pingping; Xu, Liang

    2014-09-01

    The identification of maximum road friction coefficient and optimal slip ratio is crucial to vehicle dynamics and control. However, it is always not easy to identify the maximum road friction coefficient with high robustness and good adaptability to various vehicle operating conditions. The existing investigations on robust identification of maximum road friction coefficient are unsatisfactory. In this paper, an identification approach based on road type recognition is proposed for the robust identification of maximum road friction coefficient and optimal slip ratio. The instantaneous road friction coefficient is estimated through the recursive least square with a forgetting factor method based on the single wheel model, and the estimated road friction coefficient and slip ratio are grouped in a set of samples in a small time interval before the current time, which are updated with time progressing. The current road type is recognized by comparing the samples of the estimated road friction coefficient with the standard road friction coefficient of each typical road, and the minimum statistical error is used as the recognition principle to improve identification robustness. Once the road type is recognized, the maximum road friction coefficient and optimal slip ratio are determined. The numerical simulation tests are conducted on two typical road friction conditions(single-friction and joint-friction) by using CarSim software. The test results show that there is little identification error between the identified maximum road friction coefficient and the pre-set value in CarSim. The proposed identification method has good robustness performance to external disturbances and good adaptability to various vehicle operating conditions and road variations, and the identification results can be used for the adjustment of vehicle active safety control strategies.

  20. Comparison of Joint Modeling Approaches Including Eulerian Sliding Interfaces

    SciTech Connect

    Lomov, I; Antoun, T; Vorobiev, O

    2009-12-16

    Accurate representation of discontinuities such as joints and faults is a key ingredient for high fidelity modeling of shock propagation in geologic media. The following study was done to improve treatment of discontinuities (joints) in the Eulerian hydrocode GEODYN (Lomov and Liu 2005). Lagrangian methods with conforming meshes and explicit inclusion of joints in the geologic model are well suited for such an analysis. Unfortunately, current meshing tools are unable to automatically generate adequate hexahedral meshes for large numbers of irregular polyhedra. Another concern is that joint stiffness in such explicit computations requires significantly reduced time steps, with negative implications for both the efficiency and quality of the numerical solution. An alternative approach is to use non-conforming meshes and embed joint information into regular computational elements. However, once slip displacement on the joints become comparable to the zone size, Lagrangian (even non-conforming) meshes could suffer from tangling and decreased time step problems. The use of non-conforming meshes in an Eulerian solver may alleviate these difficulties and provide a viable numerical approach for modeling the effects of faults on the dynamic response of geologic materials. We studied shock propagation in jointed/faulted media using a Lagrangian and two Eulerian approaches. To investigate the accuracy of this joint treatment the GEODYN calculations have been compared with results from the Lagrangian code GEODYN-L which uses an explicit treatment of joints via common plane contact. We explore two approaches to joint treatment in the code, one for joints with finite thickness and the other for tight joints. In all cases the sliding interfaces are tracked explicitly without homogenization or blending the joint and block response into an average response. In general, rock joints will introduce an increase in normal compliance in addition to a reduction in shear strength. In the present work we consider the limiting case of stiff discontinuities that only affect the shear strength of the material.

  1. Crystal plasticity finite element analysis of deformation behaviour in SAC305 solder joint

    NASA Astrophysics Data System (ADS)

    Darbandi, Payam

    Due to the awareness of the potential health hazards associated with the toxicity of lead (Pb), actions have been taken to eliminate or reduce the use of Pb in consumer products. Among those, tin (Sn) solders have been used for the assembly of electronic systems. Anisotropy is of significant importance in all structural metals, but this characteristic is unusually strong in Sn, making Sn based solder joints one of the best examples of the influence of anisotropy. The effect of anisotropy arising from the crystal structure of tin and large grain microstructure on the microstructure and the evolution of constitutive responses of microscale SAC305 solder joints is investigated. Insights into the effects of key microstructural features and dominant plastic deformation mechanisms influencing the measured relative activity of slip systems in SAC305 are obtained from a combination of optical microscopy, orientation imaging microscopy (OIM), slip plane trace analysis and crystal plasticity finite element (CPFE) modeling. Package level SAC305 specimens were subjected to shear deformation in sequential steps and characterized using optical microscopy and OIM to identify the activity of slip systems. X-ray micro Laue diffraction and high energy monochromatic X-ray beam were employed to characterize the joint scale tensile samples to provide necessary information to be able to compare and validate the CPFE model. A CPFE model was developed that can account for relative ease of activating slip systems in SAC305 solder based upon the statistical estimation based on correlation between the critical resolved shear stress and the probability of activating various slip systems. The results from simulations show that the CPFE model developed using the statistical analysis of activity of slip system not only can satisfy the requirements associated with kinematic of plastic deformation in crystal coordinate systems (activity of slip systems) and global coordinate system (shape changes) but also this model is able to predict the evolution of stress in joint level SAC305 sample.

  2. Joint Instability and Osteoarthritis

    PubMed Central

    Blalock, Darryl; Miller, Andrew; Tilley, Michael; Wang, Jinxi

    2015-01-01

    Joint instability creates a clinical and economic burden in the health care system. Injuries and disorders that directly damage the joint structure or lead to joint instability are highly associated with osteoarthritis (OA). Thus, understanding the physiology of joint stability and the mechanisms of joint instability-induced OA is of clinical significance. The first section of this review discusses the structure and function of major joint tissues, including periarticular muscles, which play a significant role in joint stability. Because the knee, ankle, and shoulder joints demonstrate a high incidence of ligament injury and joint instability, the second section summarizes the mechanisms of ligament injury-associated joint instability of these joints. The final section highlights the recent advances in the understanding of the mechanical and biological mechanisms of joint instability-induced OA. These advances may lead to new opportunities for clinical intervention in the prevention and early treatment of OA. PMID:25741184

  3. Joint x-ray

    MedlinePlus

    X-ray - joint; Arthrography; Arthrogram ... x-ray technologist will help you position the joint to be x-rayed on the table. Once in place, pictures are taken. The joint may be moved into other positions for more ...

  4. Nature of slip transfer between strike-slip faults: The Eastern Sinai (Egypt) shear zone, Dead Sea Transform

    NASA Astrophysics Data System (ADS)

    Eyal, Yehuda; Eyal, Moshe

    2015-07-01

    The western margin of the Gulf of Elat (Aqaba), a sector of the Dead Sea Transform, is characterized by an N-S striking shear zone with cumulative sinistral (left-lateral) offset of 24 km. The crystalline basement in the study area is unique in its excellent rock and fault exposures forming a >50 km long, shear zone with abundant offset of linear features as well as the contact of the basement with the Infracambrian sub-horizontal peneplain. These features enable accurate measurement of the horizontal and vertical displacements along the major and secondary faults to ±50 m. The small vertical offset of the peneplain surface and a measurement of about 8° net-slip plunge along one of the major faults suggest that along all strike-slip faults, movement was almost pure horizontal slip. Part of this horizontal slip was transferred to neighboring major strike-slip faults by secondary strike-slip faults with negligible loss of displacement. The amount of horizontal slip transferred by normal faults, even in releasing bends, is small due to the high dip angle of these faults. Wide breccia zones and distributed deformation of a small fraction of the horizontal slip is observed when the angle between the strike-slip faults exceeds 30°.

  5. Spacesuit mobility knee joints

    NASA Technical Reports Server (NTRS)

    Vykukal, H. C. (Inventor)

    1979-01-01

    Pressure suit mobility joints are for use in interconnecting adjacent segments of an hermetically sealed spacesuit in which low torques, low leakage and a high degree of reliability are required. Each of the joints is a special purpose joint characterized by substantially constant volume and low torque characteristics and includes linkages which restrain the joint from longitudinal distension and includes a flexible, substantially impermeable diaphragm of tubular configuration spanning the distance between pivotally supported annuli. The diaphragms of selected joints include rolling convolutions for balancing the joints, while various joints include wedge-shaped sections which enhance the range of motion for the joints.

  6. Spacesuit mobility joints

    NASA Technical Reports Server (NTRS)

    Vykukal, H. C. (Inventor)

    1978-01-01

    Joints for use in interconnecting adjacent segments of an hermetically sealed spacesuit which have low torques, low leakage and a high degree of reliability are described. Each of the joints is a special purpose joint characterized by substantially constant volume and low torque characteristics. Linkages which restrain the joint from longitudinal distension and a flexible, substantially impermeable diaphragm of tubular configuration spanning the distance between pivotally supported annuli are featured. The diaphragms of selected joints include rolling convolutions for balancing the joints, while various joints include wedge-shaped sections which enhance the range of motion for the joints.

  7. Surface fault slip associated with the 2004 Parkfield, California, earthquake

    USGS Publications Warehouse

    Rymer, M.J.; Tinsley, J. C., III; Treiman, J.A.; Arrowsmith, J.R.; Ciahan, K.B.; Rosinski, A.M.; Bryant, W.A.; Snyder, H.A.; Fuis, G.S.; Toke, N.A.; Bawden, G.W.

    2006-01-01

    Surface fracturing occurred along the San Andreas fault, the subparallel Southwest Fracture Zone, and six secondary faults in association with the 28 September 2004 (M 6.0) Parkfield earthquake. Fractures formed discontinuous breaks along a 32-km-long stretch of the San Andreas fault. Sense of slip was right lateral; only locally was there a minor (1-11 mm) vertical component of slip. Right-lateral slip in the first few weeks after the event, early in its afterslip period, ranged from 1 to 44 mm. Our observations in the weeks following the earthquake indicated that the highest slip values are in the Middle Mountain area, northwest of the mainshock epicenter (creepmeter measurements indicate a similar distribution of slip). Surface slip along the San Andreas fault developed soon after the mainshock; field checks in the area near Parkfield and about 5 km to the southeast indicated that surface slip developed more than 1 hr but generally less than 1 day after the event. Slip along the Southwest Fracture Zone developed coseismically and extended about 8 km. Sense of slip was right lateral; locally there was a minor to moderate (1-29 mm) vertical component of slip. Right-lateral slip ranged from 1 to 41 mm. Surface slip along secondary faults was right lateral; the right-lateral component of slip ranged from 3 to 5 mm. Surface slip in the 1966 and 2004 events occurred along both the San Andreas fault and the Southwest Fracture Zone. In 1966 the length of ground breakage along the San Andreas fault extended 5 km longer than that mapped in 2004. In contrast, the length of ground breakage along the Southwest Fracture Zone was the same in both events, yet the surface fractures were more continuous in 2004. Surface slip on secondary faults in 2004 indicated previously unmapped structural connections between the San Andreas fault and the Southwest Fracture Zone, further revealing aspects of the structural setting and fault interactions in the Parkfield area.

  8. Strike-slip earthquakes on moderately-dipping faults

    NASA Astrophysics Data System (ADS)

    Van Horne, Anne; Hubbard, Judith; Sato, Hiroshi; Takeda, Tetsuya

    2014-05-01

    Moderate-angle faults that form under compressive stress regimes in subduction zones can slip laterally if the stress field subsequently reorients to strike-slip. We present three examples from Japan and Pakistan in which regional-scale thrust faults created in compressional structural settings have been reactivated as strike-slip faults in new, largely subhorizontal, stress fields. (1) In SW Japan, the Median Tectonic Line has a dip of 30-40°, yet it slips laterally in the slip-partitioned Nankai subduction margin. (2) Likewise, the source fault for the M7.9 Great Kanto earthquake was the Sagami megathrust, yet it exhibited predominantly strike-slip movement in the 1923 earthquake. (3) In Pakistan, the 2013 M7.7 Awaran earthquake occurred on a fault plane that dips 45° and showed largely strike-slip movement. These are regional-scale, moderate-angle faults that originated as thrust faults at the subduction interface (or in its associated fold-and-thrust belt) and now exhibit near-horizontal slip. While their current slip behavior suggests they should be oriented vertically or near-vertically, they are not. They have inherited a non-typical inclined geometry. Under what conditions does a thrust fault reactivate in a strike-slip stress field? The inherited fault plane must represent a significant preexisting crustal weakness whose coefficient of cohesion exceeds its coefficient of friction, allowing it to fail preferentially despite its unfavorable orientation. Details of the slip behavior for these faults in time and space suggest complex dynamics which will require further scrutiny.

  9. Seismic and aseismic slip on the central Peru megathrust.

    PubMed

    Perfettini, Hugo; Avouac, Jean-Philippe; Tavera, Hernando; Kositsky, Andrew; Nocquet, Jean-Mathieu; Bondoux, Francis; Chlieh, Mohamed; Sladen, Anthony; Audin, Laurence; Farber, Daniel L; Soler, Pierre

    2010-05-01

    Slip on a subduction megathrust can be seismic or aseismic, with the two modes of slip complementing each other in time and space to accommodate the long-term plate motions. Although slip is almost purely aseismic at depths greater than about 40 km, heterogeneous surface strain suggests that both modes of slip occur at shallower depths, with aseismic slip resulting from steady or transient creep in the interseismic and postseismic periods. Thus, active faults seem to comprise areas that slip mostly during earthquakes, and areas that mostly slip aseismically. The size, location and frequency of earthquakes that a megathrust can generate thus depend on where and when aseismic creep is taking place, and what fraction of the long-term slip rate it accounts for. Here we address this issue by focusing on the central Peru megathrust. We show that the Pisco earthquake, with moment magnitude M(w) = 8.0, ruptured two asperities within a patch that had remained locked in the interseismic period, and triggered aseismic frictional afterslip on two adjacent patches. The most prominent patch of afterslip coincides with the subducting Nazca ridge, an area also characterized by low interseismic coupling, which seems to have repeatedly acted as a barrier to seismic rupture propagation in the past. The seismogenic portion of the megathrust thus appears to be composed of interfingering rate-weakening and rate-strengthening patches. The rate-strengthening patches contribute to a high proportion of aseismic slip, and determine the extent and frequency of large interplate earthquakes. Aseismic slip accounts for as much as 50-70% of the slip budget on the seismogenic portion of the megathrust in central Peru, and the return period of earthquakes with M(w) = 8.0 in the Pisco area is estimated to be 250 years. PMID:20445628

  10. Instantaneous Slip Length in Superhydrophobic Microchannels

    NASA Astrophysics Data System (ADS)

    Hemeda, Ahmed; Tafreshi, Hooman; VCU Team

    2015-11-01

    Superhydrophobic (SHP) surfaces can be used to reduce the skin-friction drag in a microchannel. This favorable effect, however, can deteriorate over time if the surface geometry is not designed properly. This study presents a mathematical means for studying the time-dependent drag-reduction in a microchannel enhanced with SHP grooves of varying geometries. The performance of an SHP groove is found to be dependent on the interplay between the effects of the apparent contact angle of the air-water interface and the initial volume of the groove. The instantaneous slip length is calculated by solving the Navier-Stokes equations for flow in a microchannel with such SHP grooves, and the results are compared with the studies in the literature. National Science Foundation CMMI 1029924 and CBET 1402655.

  11. Effective slip on textured superhydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Gogte, Salil; Vorobieff, Peter; Truesdell, Richard; Mammoli, Andrea; van Swol, Frank; Shah, Pratik; Brinker, C. Jeffrey

    2005-05-01

    We study fluid flow in the vicinity of textured and superhydrophobically coated surfaces with characteristic texture sizes on the order of 10?m. Both for droplets moving down an inclined surface and for an external flow near the surface (hydrofoil), there is evidence of appreciable drag reduction in the presence of surface texture combined with superhydrophobic coating. On textured inclined surfaces, the drops roll faster than on a coated untextured surface at the same angle. The highest drop velocities are achieved on surfaces with irregular textures with characteristic feature size 8?m. Application of the same texture and coating to the surface of a hydrofoil in a water tunnel results in drag reduction on the order of 10% or higher. This behavior is explained by the reduction of the contact area between the surface and the fluid, which can be interpreted in terms of changing the macroscopic boundary condition to allow nonzero slip velocity.

  12. Floor/shoe slip resistance measurement.

    PubMed

    Chaffin, D B; Woldstad, J C; Trujillo, A

    1992-05-01

    A variety of slip measurement devices exist that provide estimates of both static and dynamic coefficient-of-friction (COF) values between one's shoes and the floor. Unfortunately, different shoe sole/heel materials, floor conditions, and contaminants will affect the tests in ways that result in widely varying COF estimates. This paper reviews the basic physics of such tests and describes a set of experiments to determine the static and dynamic COF values under operating conditions known to exist in different jobs. The results define a set of conditions wherein low (hazardous) COF values would exist (e.g., hard Neolite shoe material in contact with a wet, smooth walking surface). The results also question the use of light-load testing devices and static and slow speed reference COF values in the literature. PMID:1609738

  13. Regulating the working properties of porcelain slip

    SciTech Connect

    Karpilovskii, L.P.; Kralinina, L.N.; Makarov, V.A.; Sidorenko, Z.I.

    1986-05-01

    It was decided to introduce changes in the recipe of the clay part of the raw material to provide a reduction in the density and a restoration of the Prosyyanovsk kaolin (PK) slip's fluidity, the volume of the PK batch would be maintained, and the working properties of the body could be insured within the same limits as prevailed before recipe of the stone materials and the chemical composition of the porcelain would be left unchanged. The results indicate the effectiveness of using the analytical method for clay suspensions for operational assessment of the technical properties of raw materials and regulating the working properties of the body. The method of filtration analysis and determination of the elastic properties of the suspension can also be recommended for use in benefication combines. The advantage of the methods consists in the rapidity of carrying out the analysis which means where necessary can operationally intervene in the technological process.

  14. Slip flow through colloidal crystals of varying particle diameter.

    PubMed

    Rogers, Benjamin J; Wirth, Mary J

    2013-01-22

    Slip flow of water through silica colloidal crystals was investigated experimentally for eight different particle diameters, which have hydraulic channel radii ranging from 15 to 800 nm. The particle surfaces were silylated to be low in energy, with a water contact angle of 83°, as determined for a silylated flat surface. Flow rates through centimeter lengths of colloidal crystal were measured using a commercial liquid chromatograph for accurate comparisons of water and toluene flow rates using pressure gradients as high as 10(10) Pa/m. Toluene exhibited no-slip Hagen-Poiseuille flow for all hydraulic channel radii. For water, the slip flow enhancement as a function of hydraulic channel radius was described well by the expected slip flow correction for Hagen-Poiseuille flow, and the data revealed a constant slip length of 63 ± 3 nm. A flow enhancement of 20 ± 2 was observed for the smallest hydraulic channel radius of 15 nm. The amount of slip flow was found to be independent of shear rate over a range of fluid velocities from 0.7 to 5.8 mm/s. The results support the applicability of the slip flow correction for channel radii as small as 15 nm. The work demonstrates that packed beds of submicrometer particles enable slip flow to be employed for high-volume flow rates. PMID:23237590

  15. Room Temperature Slip in Titanium Diboride Produced by High Pressure.

    PubMed

    Vahldiek, F W; Mersol, S A; Lynch, C T

    1965-08-13

    Prismatic slip occurs in polycrystalline titanium diboride after applying 5 to 15 kilobars of hydrostatic pressure. Specimens were subjected to these pressures inside silver chloride matrices by means of a simple cylindrical piston device. The slip was of the type {1010} <1120>. Microhardness indentations produced similar results. PMID:17779183

  16. A Transformational Approach to Slip-Slide Factoring

    ERIC Educational Resources Information Center

    Steckroth, Jeffrey

    2015-01-01

    In this "Delving Deeper" article, the author introduces the slip-slide method for solving Algebra 1 mathematics problems. This article compares the traditional method approach of trial and error to the slip-slide method of factoring. Tools that used to be taken for granted now make it possible to investigate relationships visually,

  17. Slip Flow through Colloidal Crystals of Varying Particle Diameter

    PubMed Central

    Rogers, Benjamin J.; Wirth, Mary J.

    2012-01-01

    Slip flow of water through silica colloidal crystals was investigated experimentally for 8 different particle diameters, which have hydraulic channel radii ranging from 15 nm to 800 nm. The particle surfaces were silylated to be low in energy, with a water contact angle of 83°, as determined for a silylated flat surface. Flow rates through centimeter lengths of colloidal crystal were measured using a commercial liquid chromatograph for accurate comparisons of water and toluene flow rates using pressure gradients as high as 1010 Pa/m. Toluene exhibited no-slip Hagen-Poiseuille flow for all hydraulic channel radii. For water, the slip flow enhancement as a function of hydraulic channel radius was described well by the expected slip flow correction for Hagen-Poiseuille flow, and the data revealed a constant slip length of 63±3 nm. A flow enhancement of 20±2 was observed for the smallest hydraulic channel radius of 15 nm. The amount of slip flow was found to be independent of shear rate over a range of fluid velocities from 0.7 to 5.8 mm/s. The results support the applicability of the slip flow correction for channel radii as small as 15 nm. The work demonstrates that packed beds of submicrometer particles enable slip flow to be employed for high volume flow rates. PMID:23237590

  18. Role of Slip Mode on Stress Corrosion Cracking Behavior

    NASA Astrophysics Data System (ADS)

    Vasudevan, A. K.; Sadananda, K.

    2011-02-01

    In this article, we examine the effect of aging treatment and the role of planarity of slip on stress corrosion cracking (SCC) behavior in precipitation-hardened alloys. With aging, the slip mode can change from a planar slip in the underage (UA) to a wavy slip in the overage (OA) region. This, in turn, results in sharpening the crack tip in the UA compared to blunting in the OA condition. We propose that the planar slip enhances the stress concentration effects by making the alloys more susceptible to SCC. In addition, the planarity of slip enhances plateau velocities, reduces thresholds for SCC, and reduces component life. We show that the effect of slip planarity is somewhat similar to the effects of mechanically induced stress concentrations such as due to the presence of sharp notches. Aging treatment also causes variations in the matrix and grain boundary (GB) microstructures, along with typical mechanical and SCC properties. These properties include yield stress, work hardening rate, fracture toughness K IC , thresholds K Iscc, and steady-state plateau velocity ( da/ dt). The SCC data for a wide range of ductile alloys including 7050, 7075, 5083, 5456 Al, MAR M steels, and solid solution copper-base alloys are collected from the literature. Our assertion is that slip mode and the resulting stress concentration are important factors in SCC behavior. This is further supported by similar observations in many other systems including some steels, Al alloys, and Cu alloys.

  19. A Transformational Approach to Slip-Slide Factoring

    ERIC Educational Resources Information Center

    Steckroth, Jeffrey

    2015-01-01

    In this "Delving Deeper" article, the author introduces the slip-slide method for solving Algebra 1 mathematics problems. This article compares the traditional method approach of trial and error to the slip-slide method of factoring. Tools that used to be taken for granted now make it possible to investigate relationships visually,…

  20. Three cases of slipped capital femoral epiphysis in one family.

    PubMed

    Skelley, Nathan W; Papp, Derek F; Leu, Dirk; Sargent, M Catherine

    2011-08-01

    Slipped capital femoral epiphysis is a relatively common disorder of the hip that affects children in late childhood and early adolescence, with an incidence in the United States of approximately 10 per 100,000. Although the diagnosis and treatment of slipped capital femoral epiphysis have been well described, the search for its cause and a method of early identification continues. Recent publications have suggested that there is a familial association among individuals with slipped capital femoral epiphysis, but there is no current genetic marker established for the disorder. This article reports a series of 3 biologically related Caucasian sisters who were athletic; had body mass indices <26 kg/m(2); had no record of any hormonal imbalances or endocrine abnormalities; had good nutrition; and presented with atypical characteristics of slipped capital femoral epiphysis. This is the first report of a series of 3 sisters with slipped capital femoral epiphysis in the United States. Our goals were to document our experience in the identification and treatment of these patients to highlight the complexities of slipped capital femoral epiphysis presentation patterning, to increase the awareness and reporting of familial cases of slipped capital femoral epiphysis by other physicians, and to encourage additional research in this area. As clinicians progress in the ability to diagnose and treat patients with slipped capital femoral epiphysis, they also must be mindful of the varying presentation characteristics. PMID:21815585

  1. Frictional resistance of faults during accelerating and decelerating earthquake slip

    NASA Astrophysics Data System (ADS)

    Sone, Hiroki; Shimamoto, Toshihiko

    2009-10-01

    The dynamic friction of faults during earthquake slip is a critical control on earthquake ruptures in the crust. Extrapolation of brittle crack theories to natural earthquakes has led to the commonly held view that fault friction reduces during rapid earthquake slip, a process known as slip-weakening. High-velocity gouge experiments and recent analyses of thermal pressurization and frictional melting support such a notion; however, these studies dealt with constant rates of slip along faults. Here we present the results of experiments aimed at understanding the frictional behaviour of fault zone materials under variable slip rates-conditions that are more representative of natural earthquakes. Our results show that faults undergo a sequence of strengthening, weakening and healing during acceleration and deceleration of slip. Such a sequence may be explained by the extrapolation of rate-and-state frictional behaviour at low slip velocities to more realistic slip rates, but involving different physical mechanisms and a different scale. The initial strengthening should impose a barrier for rupture growth into large earthquakes. The healing on decelerating fault motion may lead to pulse-like earthquake ruptures and static stress drops that are low in comparison with the dynamic stress changes.

  2. Slip, Trip, and Fall Injuries Among Nursing Care Facility Workers

    PubMed Central

    Bell, Jennifer L.; Collins, James W.; Tiesman, Hope M.; Ridenour, Marilyn; Konda, Srinivas; Wolf, Laurie; Evanoff, Bradley

    2015-01-01

    The objective of this research was to describe the slip, trip, and fall injury experience and trends in a population of nursing home workers, identify risk factors for slip, trip, and fall injuries, and develop prevention strategies for slip, trip, and fall hazards. Workers’ compensation injury claims data and payroll data from 1996 through 2003 were obtained from six nursing homes and used to calculate injury incidence rates. Narrative information was used to describe details of slip, trip, and fall events. A total of 86 slip, trip, and fall-related workers’ compensation claims were filed during the 8-year period. Slip, trip, and fall claim rates showed a nonsignificant increase during the 8-year period. Most slips, trips, and falls were attributed to hazards that can be mitigated (e.g., water on the floor or loose cords in a walkway). Nursing home workers experience more slip, trip, and fall-related injury claims than workers in other industries. Preventive programs should be implemented and evaluated in this industry. PMID:23521142

  3. Tremor during ice-stream stick slip

    NASA Astrophysics Data System (ADS)

    Lipovsky, B. P.; Dunham, E. M.

    2016-02-01

    During the 200 km-scale stick slip of the Whillans Ice Plain (WIP), West Antarctica, seismic tremor episodes occur at the ice-bed interface. We interpret these tremor episodes as swarms of small repeating earthquakes. The earthquakes are evenly spaced in time, and this even spacing gives rise to spectral peaks at integer multiples of the recurrence frequency ˜ 10-20 Hz. We conduct numerical simulations of the tremor episodes that include the balance of forces acting on the fault, the evolution of rate- and state-dependent fault friction, and wave propagation from the fault patch to a seismometer located on the ice. The ice slides as an elastic block loaded by the push of the upstream ice, and so the simulated basal fault patch experiences a loading velocity equal to the velocity observed by GPS receivers on the surface of the WIP. By matching synthetic seismograms to observed seismograms, we infer fault patch area ˜ 10 m2, bed shear modulus ˜ 20 MPa, effective pressure ˜ 10 kPa, and frictional state evolution distance ˜ 1 μm. Large-scale slip events often occur twice daily, although skipped events have been increasing in frequency over the last decade. The amplitude of tremor (recorded by seismometers on the ice surface) is greater during the double wait time events that follow skipped events. The physical mechanism responsible for these elevated amplitudes may provide a window into near-future subglacial conditions and the processes that occur during ice-stream stagnation.

  4. Slip Distribution and Seismic Moment of the 2010 and 1960 Chilean Earthquakes Inferred from Tsunami Waveforms and Coastal Geodetic Data

    NASA Astrophysics Data System (ADS)

    Fujii, Yushiro; Satake, Kenji

    2013-09-01

    The slip distribution and seismic moment of the 2010 and 1960 Chilean earthquakes were estimated from tsunami and coastal geodetic data. These two earthquakes generated transoceanic tsunamis, and the waveforms were recorded around the Pacific Ocean. In addition, coseismic coastal uplift and subsidence were measured around the source areas. For the 27 February 2010 Maule earthquake, inversion of the tsunami waveforms recorded at nearby coastal tide gauge and Deep Ocean Assessment and Reporting of Tsunamis (DART) stations combined with coastal geodetic data suggest two asperities: a northern one beneath the coast of Constitucion and a southern one around the Arauco Peninsula. The total fault length is approximately 400 km with seismic moment of 1.7 × 1022 Nm (Mw 8.8). The offshore DART tsunami waveforms require fault slips beneath the coasts, but the exact locations are better estimated by coastal geodetic data. The 22 May 1960 earthquake produced very large, ~30 m, slip off Valdivia. Joint inversion of tsunami waveforms, at tide gauge stations in South America, with coastal geodetic and leveling data shows total fault length of ~800 km and seismic moment of 7.2 × 1022 Nm (Mw 9.2). The seismic moment estimated from tsunami or joint inversion is similar to previous estimates from geodetic data, but much smaller than the results from seismic data analysis.

  5. Rock mechanics. Superplastic nanofibrous slip zones control seismogenic fault friction.

    PubMed

    Verberne, Berend A; Plümper, Oliver; de Winter, D A Matthijs; Spiers, Christopher J

    2014-12-12

    Understanding the internal mechanisms controlling fault friction is crucial for understanding seismogenic slip on active faults. Displacement in such fault zones is frequently localized on highly reflective (mirrorlike) slip surfaces, coated with thin films of nanogranular fault rock. We show that mirror-slip surfaces developed in experimentally simulated calcite faults consist of aligned nanogranular chains or fibers that are ductile at room conditions. These microstructures and associated frictional data suggest a fault-slip mechanism resembling classical Ashby-Verrall superplasticity, capable of producing unstable fault slip. Diffusive mass transfer in nanocrystalline calcite gouge is shown to be fast enough for this mechanism to control seismogenesis in limestone terrains. With nanogranular fault surfaces becoming increasingly recognized in crustal faults, the proposed mechanism may be generally relevant to crustal seismogenesis. PMID:25504714

  6. Seismicity triggered by fluid injection-induced aseismic slip

    NASA Astrophysics Data System (ADS)

    Guglielmi, Yves; Cappa, Frédéric; Avouac, Jean-Philippe; Henry, Pierre; Elsworth, Derek

    2015-06-01

    Anthropogenic fluid injections are known to induce earthquakes. The mechanisms involved are poorly understood, and our ability to assess the seismic hazard associated with geothermal energy or unconventional hydrocarbon production remains limited. We directly measure fault slip and seismicity induced by fluid injection into a natural fault. We observe highly dilatant and slow [~4 micrometers per second (μm/s)] aseismic slip associated with a 20-fold increase of permeability, which transitions to faster slip (~10 μm/s) associated with reduced dilatancy and micro-earthquakes. Most aseismic slip occurs within the fluid-pressurized zone and obeys a rate-strengthening friction law μ=0.67+0.045ln(vv0) with v0 = 0.1 μm/s. Fluid injection primarily triggers aseismic slip in this experiment, with micro-earthquakes being an indirect effect mediated by aseismic creep.

  7. Studies on the spermatogenic sulfogalactolipid binding protein SLIP 1

    SciTech Connect

    Lingwood, C.; Nutikka, A. )

    1991-02-01

    We have purified the testicular sulfogalactolipid binding protein SLIP 1 and shown by photoaffinity labeling that it contains an ATP binding site. Purified SLIP 1 was fluorescently labeled and shown to retain specific sulfogalactolipid binding function. This probe was used to investigate the topology of SLIP 1 binding sites on testicular germ cells. The binding pattern precisely coincided with the previously demonstrated asymmetric surface domains of sulfogalactoglycerolipid (SGG). Occasionally these SGG-containing, SLIP 1-binding cell surface domains exactly coincided with structural features on the cell surface as detected by differential interference contrast microscopy. These results demonstrate that SLIP 1/SGG interactions could provide an effective intercellular communication network between testicular germ cells within the seminiferous tubule.

  8. Stochastic stick-slip nanoscale friction on oxide surfaces.

    PubMed

    Craciun, A D; Gallani, J L; Rastei, M V

    2016-02-01

    The force needed to move a nanometer-scale contact on various oxide surfaces has been studied using an atomic force microscope and theoretical modeling. Force-distance traces unveil a stick-slip movement with erratic slip events separated by several nanometers. A linear scaling of friction force with normal load along with low pull-off forces reveals dispersive adhesive interactions at the interface. We model our findings by considering a variable Lennard-Jones-like interaction potential, which accounts for slip-induced variation of the effective contact area. The model explains the formation and fluctuation of stick-slip phases and provides guidelines for predicting transitions from stick-slip to continuous sliding on oxide surfaces. PMID:26751769

  9. Proposed Cavity for Reduced Slip-Stacking Loss

    SciTech Connect

    Eldred, J.; Zwaska, R.

    2015-06-01

    This paper employs a novel dynamical mechanism to improve the performance of slip-stacking. Slip-stacking in an accumulation technique used at Fermilab since 2004 which nearly double the proton intensity. During slip-stacking, the Recycler or the Main Injector stores two particles beams that spatially overlap but have different momenta. The two particle beams are longitudinally focused by two 53 MHz 100 kV RF cavities with a small frequency difference between them. We propose an additional 106 MHz 20 kV RF cavity, with a frequency at the double the average of the upper and lower main RF frequencies. In simulation, we find the proposed RF cavity significantly enhances the stable bucket area and reduces slip-stacking losses under reasonable injection scenarios. We quantify and map the stability of the parameter space for any accelerator implementing slip-stacking with the addition of a harmonic RF cavity.

  10. Learning and Prediction of Slip from Visual Information

    NASA Technical Reports Server (NTRS)

    Angelova, Anelia; Matthies, Larry; Helmick, Daniel; Perona, Pietro

    2007-01-01

    This paper presents an approach for slip prediction from a distance for wheeled ground robots using visual information as input. Large amounts of slippage which can occur on certain surfaces, such as sandy slopes, will negatively affect rover mobility. Therefore, obtaining information about slip before entering such terrain can be very useful for better planning and avoiding these areas. To address this problem, terrain appearance and geometry information about map cells are correlated to the slip measured by the rover while traversing each cell. This relationship is learned from previous experience, so slip can be predicted remotely from visual information only. The proposed method consists of terrain type recognition and nonlinear regression modeling. The method has been implemented and tested offline on several off-road terrains including: soil, sand, gravel, and woodchips. The final slip prediction error is about 20%. The system is intended for improved navigation on steep slopes and rough terrain for Mars rovers.

  11. Stochastic stick-slip nanoscale friction on oxide surfaces

    NASA Astrophysics Data System (ADS)

    Craciun, A. D.; Gallani, J. L.; Rastei, M. V.

    2016-02-01

    The force needed to move a nanometer-scale contact on various oxide surfaces has been studied using an atomic force microscope and theoretical modeling. Force-distance traces unveil a stick-slip movement with erratic slip events separated by several nanometers. A linear scaling of friction force with normal load along with low pull-off forces reveals dispersive adhesive interactions at the interface. We model our findings by considering a variable Lennard-Jones-like interaction potential, which accounts for slip-induced variation of the effective contact area. The model explains the formation and fluctuation of stick-slip phases and provides guidelines for predicting transitions from stick-slip to continuous sliding on oxide surfaces.

  12. Imaging fault slip variation along the central San Andreas fault from satellite, airborne InSAR and GPS

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Lundgren, P.; Fielding, E. J.; Hensley, S.

    2011-12-01

    The improved spatiotemporal resolution of surface deformation from recent satellite and airborne InSAR measurements provides great potential to improve our understanding of faulting processes and earthquake hazard for a given fault system. A major plate boundary fault in central California, the central San Andreas fault (CSAF) displays a spectrum of complex fault slip behaviors with creeping in its central segment that decreases towards its northwest and southeast ends where the fault transitions to being locked. In the north the CSAF branches into two sub-parallel faults that are both actively accommodating plate motion. To the south, near the Parkfield transition, large earthquakes have occurred with at least six Mw ~6.0 events since 1857, most recently in 2004. To understand the complexity and variety of fault slip behaviors and fault mechanics, we integrate satellite and airborne synthetic aperture radar (SAR) repeat pass interferometry (RPI) observations, with GPS measurements from the Plate Boundary Observatory (PBO) and regional campaign networks to estimate fault slip and shallow slip deficits along the CSAF. Existing C-band ERS-1/2, Envisat and Radarsat SAR data provide long archives of SAR data over the region but are subject to severe decorrelation. The Japan Aerospace Exploration Agency's ALOS satellite has made less frequent acquisitions (5-6/yr per track) since 2006 but its PALSAR L-band sensor provides much improved coherence compared to shorter wavelength radar data. More recently, the NASA UAVSAR airborne SAR has repeated fault perpendicular adjacent swaths imaged from opposing look directions and fault parallel swath flights over the CSAF over the past three years and provides an improved imaging of fault slip related deformation at finer spatial resolution than previous platforms (~6m at 12 azimuth x 3 range looks). Compared to C-band instruments, the UAVSAR provides nearly complete spatial coverage. Compared to the ALOS mission, the UAVSAR's flight paths are optimized for fault parallel motion sensitivity, whereas the ALOS satellite data were almost exclusively acquired on ascending paths that looked nearly perpendicular to the fault strike. Joint analysis of UAVSAR and ALOS RPI measurements show clear variability in deformation along fault strike. Initial modeling at selected fault transects from the creeping section using UAVSAR data suggests fault creep increases from the surface to a shallower depth and decreases at lower upper crustal depths (~6-9 km). The fault slip rate at depths greater than 12 km is weakly constrained and subject to long wavelength noise components. We are examining the integrated resolution capability of UAVSAR, ALOS, and GPS for estimating fault slip with the goal of mapping fault slip along the entire length of the CSAF in a systematic imaging effort.

  13. Double-taper slip-on drill string stabilizer

    SciTech Connect

    Beasley, T.R.

    1986-07-15

    A stabilizer is described for use on a drill collar which comprises: (a) a cylindrical body with: (i) a longitudinal bore, (ii) internally threaded end portions, (iii) a double-tapered inner surface extending between the end portion and a relatively thicker central portion; (b) a hollow end cap at each end of the body threaded externally to mate with the corresponding internally threaded portion of the body and having a circumferential groove in the internal surface thereof near the outboard end thereof; (c) double-tapered slip segments within each end of the body adapted to mate and wedge against the double-tapered inner surface at the end of the body upon entry of one of the end caps into the end of the body; the slip segments being distributed around the body, the slip segment having: (i) a longitudinal slot, and (ii) a circumferential recess in the exterior surface thereof near the outboard end of the slip segment facing the end cap, the circumferential recess defining a retaining lip on the external surface of the slip segment which fits within the circumferential groove in the end cap; (d) an expansible member configured to engage the inner surfaces of the slip segments as to urge the lips of the slip segments radially into the circumferential recess of the end cap; (e) a compressible renitent member positioned within the slip segment recess between the threaded terminus of the end cap and the slip segment so as to be compressed upon entry of the end cap into the body; and (f) a locking device interengaging the slip segment longitudinal slot and the body to resist rotational movement therebetween.

  14. Local tsunamis and distributed slip at the source

    USGS Publications Warehouse

    Geist, E.L.; Dmowska, R.

    1999-01-01

    Variations in the local tsunami wave field are examined in relation to heterogeneous slip distributions that are characteristic of many shallow subduction zone earthquakes. Assumptions inherent in calculating the coseismic vertical displacement field that defines the initial condition for tsunami propagation are examined. By comparing the seafloor displacement from uniform slip to that from an ideal static crack, we demonstrate that dip-directed slip variations significantly affect the initial cross-sectional wave profile. Because of the hydrodynamic stability of tsunami wave forms, these effects directly impact estimates of maximum runup from the local tsunami. In most cases, an assumption of uniform slip in the dip direction significantly underestimates the maximum amplitude and leading wave steepness of the local tsunami. Whereas dip-directed slip variations affect the initial wave profile, strike-directed slip variations result in wavefront-parallel changes in amplitude that are largely preserved during propagation from the source region toward shore, owing to the effects of refraction. Tests of discretizing slip distributions indicate that small fault surface elements of dimensions similar to the source depth can acceptably approximate the vertical displacement field in comparison to continuous slip distributions. Crack models for tsunamis generated by shallow subduction zone earthquakes indicate that a rupture intersecting the free surface results in approximately twice the average slip. Therefore, the observation of higher slip associated with tsunami earthquakes relative to typical subduction zone earthquakes of the same magnitude suggests that tsunami earthquakes involve rupture of the seafloor, whereas rupture of deeper subduction zone earthquakes may be imbedded and not reach the seafloor.

  15. Constraining fault constitutive behavior with slip and stress heterogeneity

    USGS Publications Warehouse

    Aagaard, B.T.; Heaton, T.H.

    2008-01-01

    We study how enforcing self-consistency in the statistical properties of the preshear and postshear stress on a fault can be used to constrain fault constitutive behavior beyond that required to produce a desired spatial and temporal evolution of slip in a single event. We explore features of rupture dynamics that (1) lead to slip heterogeneity in earthquake ruptures and (2) maintain these conditions following rupture, so that the stress field is compatible with the generation of aftershocks and facilitates heterogeneous slip in subsequent events. Our three-dimensional fmite element simulations of magnitude 7 events on a vertical, planar strike-slip fault show that the conditions that lead to slip heterogeneity remain in place after large events when the dynamic stress drop (initial shear stress) and breakdown work (fracture energy) are spatially heterogeneous. In these models the breakdown work is on the order of MJ/m2, which is comparable to the radiated energy. These conditions producing slip heterogeneity also tend to produce narrower slip pulses independent of a slip rate dependence in the fault constitutive model. An alternative mechanism for generating these confined slip pulses appears to be fault constitutive models that have a stronger rate dependence, which also makes them difficult to implement in numerical models. We hypothesize that self-consistent ruptures could also be produced by very narrow slip pulses propagating in a self-sustaining heterogeneous stress field with breakdown work comparable to fracture energy estimates of kJ/M2. Copyright 2008 by the American Geophysical Union.

  16. Polydimethylsiloxane SlipChip for mammalian cell culture applications.

    PubMed

    Chang, Chia-Wen; Peng, Chien-Chung; Liao, Wei-Hao; Tung, Yi-Chung

    2015-11-01

    This paper reports a polydimethylsiloxane (PDMS) SlipChip for in vitro cell culture applications, multiple-treatment assays, cell co-cultures, and cytokine detection assays. The PDMS SlipChip is composed of two PDMS layers with microfluidic channels on each surface that are separated by a thin silicone fluid (Si-fluid) layer. The integration of Si-fluid enables the two PDMS layers to be slid to different positions; therefore, the channel patterns can be re-arranged for various applications. The SlipChip design significantly reduces the complexity of sample handling, transportation, and treatment processes. To apply the developed SlipChip for cell culture applications, human lung adenocarcinoma epithelial cells (A549) and lung fibroblasts (MRC-5) were cultured to examine the biocompatibility of the developed PDMS SlipChip. Moreover, embryonic pluripotent stem cells (ES-D3) were also cultured in the device to evaluate the retention of their stemness in the device. The experimental results show that cell morphology, viability and proliferation are not affected when the cells are cultured in the SlipChip, indicating that the device is highly compatible with mammalian cell culture. In addition, the stemness of the ES-D3 cells was highly retained after they were cultured in the device, suggesting the feasibility of using the SlipChip for stem cell research. Various cell experiments, such as simultaneous triple staining of cells and co-culture of MRC-5 with A549 cells, were also performed to demonstrate the functionalities of the PDMS SlipChip. Furthermore, we used a cytokine detection assay to evaluate the effect of endotoxin (lipopolysaccharides, LPS) treatment on the cytokine secretion of A549 cells using the SlipChip. The developed PDMS SlipChip provides a straightforward and effective platform for various on-chip in vitro cell cultures and consequent analysis, which is promising for a number of cell biology studies and biomedical applications. PMID:26381390

  17. How informative are slip models for aftershock forecasting?

    NASA Astrophysics Data System (ADS)

    Bach, Christoph; Hainzl, Sebastian

    2013-04-01

    Coulomb stress changes (ΔCFS) have been recognized as a major trigger mechanism for earthquakes, in particular aftershock distributions and the spatial patterns of ΔCFS are often found to be correlated. However, the Coulomb stress calculations are based on slip inversions and the receiver fault mechanisms which both contain large uncertainties. In particular, slip inversions are usually non-unique and often differ strongly for the same earthquakes. Here we want to address the information content of those inversions with respect to aftershock forecasting. Therefore we compare the slip models to randomized fractal slip models which are only constrained by fault information and moment magnitude. The uncertainty of the aftershock mechanisms is considered by using many receiver fault orientations, and by calculating ΔCFS at several depth layers. The stress change is then converted into an aftershock probability map utilizing a clock advance model. To estimate the information content of the slip models, we use an Epidemic Type Aftershock Sequence (ETAS) model approach introduced by Bach and Hainzl (2012), where the spatial probability density of direct aftershocks is related to the ΔCFS calculations. Besides the directly triggered aftershocks, this approach also takes secondary aftershock triggering into account. We quantify our results by calculating the information gain of the randomized slip models relative to the corresponding published slip model. As case studies, we investigate the aftershock sequences of several well-known main shocks such as 1992 Landers, 1999 Hector Mine, 2004 Parkfield, 2002 Denali. First results show a huge difference in the information content of slip models. For some of the cases up to 90% of the random slip models are found to perform better than the originally published model, for some other cases only few random models are found performing better than the published slip model.

  18. Preslip and cascade processes initiating laboratory stick slip

    NASA Astrophysics Data System (ADS)

    McLaskey, Gregory C.; Lockner, David A.

    2014-08-01

    Recent modeling studies have explored whether earthquakes begin with a large aseismic nucleation process or initiate dynamically from the rapid growth of a smaller instability in a "cascade-up" process. To explore such a case in the laboratory, we study the initiation of dynamic rupture (stick slip) of a smooth saw-cut fault in a 76 mm diameter cylindrical granite laboratory sample at 40-120 MPa confining pressure. We use a high dynamic range recording system to directly compare the seismic waves radiated during the stick-slip event to those radiated from tiny (M -6) discrete seismic events, commonly known as acoustic emissions (AEs), that occur in the seconds prior to each large stick slip. The seismic moments, focal mechanisms, locations, and timing of the AEs all contribute to our understanding of their mechanics and provide us with information about the stick-slip nucleation process. In a sequence of 10 stick slips, the first few microseconds of the signals recorded from stick-slip instabilities are nearly indistinguishable from those of premonitory AEs. In this sense, it appears that each stick slip begins as an AE event that rapidly (~20 µs) grows about 2 orders of magnitude in linear dimension and ruptures the entire 150 mm length of the simulated fault. We also measure accelerating fault slip in the final seconds before stick slip. We estimate that this slip is at least 98% aseismic and that it both weakens the fault and produces AEs that will eventually cascade-up to initiate the larger dynamic rupture.

  19. Joint fluid Gram stain

    MedlinePlus

    Gram stain of joint fluid ... A sample of joint fluid is needed. The fluid sample is sent to a lab where a small drop is placed in a ... on how to prepare for the removal of joint fluid, see joint fluid aspiration .

  20. Drag reduction in Turbulent Channel Flow with Longitudinal Arrays of Slip/no-slip Stripes on the Walls

    NASA Astrophysics Data System (ADS)

    Rastegari, Amirreza; Akhavan, Rayhaneh

    2012-11-01

    Drag reduction in channels covered with longitudinal arrays of slip/no-slip stripes on the walls has been investigated using DNS with the lattice Boltzmann method. Computations were performed in channels of size 5 h × 2 . 5 h × 2 h at a Reb = 3600 (Reτ 0 ~ 230) with stripes of size 0 . 02 <= g / h = w / h <= 0 . 56 corresponding to 4 <=g+0 =w+0 <= 128 where g = w denotes the widths of the slip/no-slip stripes and h is the channel half-width. Unlike in laminar flow, where the magnitude of DR is controlled by geometrical parameters g / h and w / h , in turbulent flow the magnitude of DR is found to scale with g+0 =w+0 , independent of Reynolds number. DRs of 5 % , 11 % , 18 % , 23 % , 38 % , 47 % , and slip velocities of Us /Ub = 0 . 06 , 0 . 10 , 0 . 15 , 0 . 23 , 0 . 32 , 0 . 37 were observed for g+0 =w+0 = 4 , 8 , 16 , 32 , 64 , 128 , respectively. Analysis of the mechanism of DR reveals that in the LDR regime (DR < 25 % , g+0 <= 32 , Us /Ub < 0 . 25), DR is due to a combination of wall-slip and change in the anisotropy structure of turbulence near the wall, while in the HDR regime (DR > 30 % , g+0 >= 64 , Us /Ub > 0 . 3), DR is primarily due to cessation of turbulence production over the slip stripes due to the large slip velocities over these regions.

  1. [Total joint arthroplasty].

    PubMed

    Mibe, Junya; Yamamoto, Kengo

    2013-07-01

    Control of the disease activity is enabled due to the progress of drug therapy for rheumatoid arthritis. However, surgical treatments are necessary for unresponsive cases to the drug or for achieving higher QOL, and we can attain more tight control or cure by combination of drug therapy and surgical treatments. Total joint arthroplasty provides indolence, mobility, stability and is an useful joint reconstruction method. Shoulder and elbow joint work as a reach function together, and total joint arthroplasty become adaptation when extensive joint destruction or severe pain occurrs. With the usage of biologic agents joint repair is possible in small joints, but if the joint destruction progress in weight-bearing joints, repair is impossible and total joint arthroplasty can be required. PMID:23961679

  2. Constitutive relations between dynamic physical parameters near a tip of the propagating slip zone during stick-slip shear failure

    NASA Astrophysics Data System (ADS)

    Ohnaka, Mitiyasu; Kuwahara, Yasuto; Yamamoto, Kiyohiko

    1987-12-01

    Constitutive relations between physical parameters in the cohesive zone during stick-slip shear failure are experimentally investigated. Stick-slip was generated along a 40 cm long precut fault in Tsukuba granite samples using a servocontrolled biaxial loading apparatus. Dynamic behavior during local breakdown processes near a tip of the slipping zone is revealed; the slip velocity and acceleration are given as a function of the slip displacement and the cohesive (or breakdown) shear stress as a function of the slip velocity. A cycle of the breakdown and restrengthening process of stick-slip is composed of five phases characterized in terms of the cohesive strength and the slip velocity. The cohesive strength can degrade regardless of the slip velocity during slip instabilities. The maximum slip acceleration ümax and the maximum slip velocity u˙max are obtained experimentally as: ümax= {2}/{u cu˙max2}andu˙max= {Δτ b}/{G}v where u c is the critical displacement, Δτb the breakdown stress drop, G the rigidity and v the rupture velocity. These relations are consistent with Ida's theoretical estimation based on the cohesive zone model. The above formula gives good estimates for the maximum slip acceleration of actual earthquakes. The cutoff frequency ƒ maxof the power spectral density of the slip acceleration increases with increasing normal stress; in particular, ƒ maxis found to be directly proportional to the normal stress σn within the normal stress range less than 17 MPa as: ƒ max(kHz) = 4.0σ n(MPa) σn<17(MPa) ƒ maxincrease with an increase in u˙max or ümax. All these results lead to the conclusion that ümax, u˙max and ƒ max increase with increasing normal stress. This is consistent with a previous observation that τb increases with increasing normal stress. The above empirical linear relation between ƒ max and σn can be explained by a linear dependence of Δτb on σn. The size-scale dependence of physical parameters is discussed, and such size-scale dependent parameters as ümax and apparent fracture energy are scaled to the breakdown zone size regarded as a characteristic length, to extend the results obtained in the laboratory to an earthquake failure in the earth.

  3. Slow slip, tremor, and local earthquakes prior to the Mw 7.4 megathrust event in Oaxaca

    NASA Astrophysics Data System (ADS)

    Sit, S. M.; Brudzinski, M. R.; Graham, S. E.; Colella, H. V.; Holtkamp, S. G.; Ghouse, N.; Cabral-Cano, E.; Arciniega-Ceballos, A.; DeMets, C.

    2013-05-01

    The search for observations to demonstrate slow slip phenomena can trigger large and damaging earthquakes is fueled by theoretical predictions that slip in the deeper transitional zone can promote failure in the shallow seismogenic zone. If such a link is verified, then operational earthquake forecasting could be improved by incorporating more slow slip behaviors. The subduction zone in Oaxaca, Mexico provides an ideal locality to investigate this potential relationship, where a joint seismic-geodetic network provides a multi-year record of traditional earthquakes, tectonic tremor, and slow slip events (SSE) prior to the recent March 12, 2012 Mw 7.4 megathrust Ometepec earthquake. Geodetically detected SSEs are observed for 2-3 months every 1-2 years, where stronger signals originate in the updip portion of the transition zone. In the months preceding the Ometepec mainshock, visual inspection of GPS time series for the 2011-2012 SSE suggests a migration of slip from east to west, along strike toward the source region of the earthquake. Preliminary models of the time series confirm slip ends just downdip of the epicenter in the weeks prior to the earthquake. While slow slip activity is prominent in the months leading up to the mainshock, tremor activity remains near background levels for much of that time, particularly in the days leading up to the earthquake. Observations from single station frequency scanning, beginning in mid-2006 show tremor activity is located further down-dip than SSE and occur over relatively short time periods, 2-10 days and recurs as often as every 2-3 months. Curiously, if we look at the preceding year, more tremor activity is detected during the nearly 6-month 2011 slow slip event. To further investigate the relationship between SSEs, tremor, and megathrust earthquakes, we use a multi-station template waveform matching technique to detect and locate events several of orders of magnitude smaller than would be possible using traditional techniques. Visible aftershocks are used as templates to identify and characterize multi-year pre-event seismicity of specific "template families" near or within the eventual rupture zone. Preliminary analysis suggests that families of earthquakes in between the SSE and the Mw 7.4 epicenter are active in the weeks prior to the mainshock. Examination of several years of seismicity prior to the megathrust event shows that some families are more active during SSEs. Despite an unclear correlation between tremor and the megathrust event, preliminary results indicate a slow slip event and template earthquake families are active prior to the Ometepec earthquake. While detailed geodetic modeling is underway to better define the source zones of slow slip over time, our hypothesis is that periods of slow slip at the shallower end of the transition zone increase the potential for a megathrust event, whereas periods of slow slip focused towards the deeper end of the transition zone increase tremor activity.

  4. Nanocrystalline mirror-slip surfaces in calcite gouge sheared at sub-seismic slip rates

    NASA Astrophysics Data System (ADS)

    Verberne, B. A.; Plümper, O.; de Winter, D.; Niemeijer, A. R.; Spiers, C. J.

    2013-12-01

    If seismic-aseismic transitions in fault rocks are to be recognized from microstructures preserved in natural fault rocks, an understanding of the microphysical mechanisms that produce such microstructures is needed. We report on microstructures recovered from dry direct shear experiments on (simulated) dry calcite gouge, performed at 50 MPa normal stress, 18-150°C and low sliding velocities (0.1-10 μm/s). The mechanical data show a transition from velocity strengthening below ~80°C to velocity weakening slip at higher temperatures. We investigated both loose gouge fragments and thin sections, characterizing the microstructures at the mm- to nm-scales. All deformed samples split along a shear band fabric defined by mainly R1- and boundary shears. Viewed normal to the shear plane, these bands commonly showed shiny, elongate patches aligned, and striated, parallel to the shear direction. These patches were especially common in samples tested below 80°C, though shear band splitting was less well-developed above 80°C so that even if the shiny patches formed at higher temperature they were less frequently exposed. Scanning Electron Microscopy (SEM) applied to shiny patches formed in samples sheared at room temperature showed the presence of elongate, streaked out sub-micron-sized particles oriented parallel to the shear direction. Transmitted light optical microscopy of thin sections cut normal to the shear plane and parallel to the shear direction, combined with Focused Ion Beam (FIB) - SEM on loose gouge fragments, showed that the shiny surfaces correspond with shear bands characterized by extreme grain size reduction and sintered sub-micron-particles. Transmission Electron Microscopy (TEM) further revealed that the cores of the shear bands consist of nanocrystallites some 20 nm in size, with a Crystallographic Preferred Orientation (CPO). Our results demonstrate that mirror-like nanocrystalline slip zones can form in calcite gouge sheared at shallow crustal conditions at sub-seismic sliding velocities, in velocity strengthening as well as velocity weakening samples. This means that their presence cannot be used as a single diagnostic indicator for seismic slip in natural fault rocks. Our SEM and TEM observations suggest that, at room temperature, the frictional behavior of the shear bands is dominated by crystal plastic plus nanogranular flow mechanisms, rather than by brittle deformation processes - as inferred for frictional slip in some metals. We further suggest that it is the thermally activated nature of crystal plasticity that is responsible for the transition from velocity strengthening to velocity weakening slip that we observed at ~80°C. The inferred mechanism has important implications for understanding both the depth range of seismicity and the seismic cycle in tectonically-active carbonate terrains.

  5. Historic creep rate and potential for seismic slip along the Hayward Fault, California

    USGS Publications Warehouse

    Lienkaemper, J.J.; Borchardt, G.; Lisowski, M.

    1991-01-01

    The Hayward fault is considered the most likely source of one or more major earthquakes in the San Francisco Bay area in the next few decades. Historically, at least one, and probably two, major earthquakes (about M 6.8) occurred along the Hayward fault, one in 1836 and another in 1868. Little is known about the 1836 event, but the 1868 earthquake was accompanied by a surface rupture that extended as much as 41 km along the southern part of the fault. Although the amount of surface slip in 1868 is uncertain, right slip (including afterslip) reached at least several centimeters, and possibly several decimeters in places. This paper documents the spatial variation of creep rate along the Hayward fault since the 1868 earthquake. Creep (aseismic fault slip) occurs over at least 66 km and may extend over the fault's entire 82-km length, of which about 13 km lies underwater. Creep rate seems nearly constant over decades, but short-term variations occur. We derive creep rate mainly from our own systematic surveying of offset cultural features (curbs, fences, and buildings). On each feature we solve directly for accumulated creep by using multiple linear regression. Creep rate mostly falls in the range of 3.5–6.5 mm/yr; but systematic variation occurs along strike. Fault segments with distinctly higher and lower rates generally correspond to parts of the fault most salient from the overall average alinement of the fault. Most distinctive is a 4-km-long section near the south end of the fault that creeps at about 9 mm/yr. Such a high rate has occurred there at least since the 1920s and probably since the 1868 earthquake, as indicated by an offset railroad track built in 1869. We suggest that this 9 mm/yr slip rate may approach the long-term or deep slip rate that controls average recurrence interval between major earthquakes. If so, assuming an elastic rebound model, the potential for slip in large earthquakes below the surficial creeping zone is now ∼1.1 m in the southern (1868) segment of the fault and ≥ 1.4 m in the northern (1836?) segment. Subtracting surface creep rates from a long-term slip rate of 9 mm/yr gives present potential for surface slip in large earthquakes of up to 0.8 m, with an average of 0.6 m in the northern segment and 0.4 m in the southern segment. We present a simple hypothesis for rupture potential that is compatible with historic creep rate, microseismicity distribution, and geodetic data. If seismic rupture occurs on segments 41 km long by 10 km deep (7 km fully locked, 3 km creeping), today's potential for seismic moment release is 1.4 × 1019 and 1.1 × 1019 N m for both 1836? and 1868 segments, respectively, and 2.5 × 1019 N m for both segments jointly. Converting moment to magnitude gives ML 6.8 in the northern segment, ML 6.7 in the southern segment, and ML 7.0 for simultaneous rupture of both.

  6. Observations of premonitory acoustic emission and slip nucleation during a stick slip experiment in smooth faulted Westerly granite

    USGS Publications Warehouse

    Thompson, B.D.; Young, R.P.; Lockner, D.A.

    2005-01-01

    To investigate laboratory earthquakes, stick-slip events were induced on a saw-cut Westerly granite sample by triaxial loading at 150 MPa confining pressure. Acoustic emissions (AE) were monitored using an innovative continuous waveform recorder. The first motion of each stick slip was recorded as a large-amplitude AE signal. These events source locate onto the saw-cut fault plane, implying that they represent the nucleation sites of the dynamic failure stick-slip events. The precise location of nucleation varied between events and was probably controlled by heterogeneity of stress or surface conditions on the fault. The initial nucleation diameter of each dynamic instability was inferred to be less than 3 mm. A small number of AE were recorded prior to each macro slip event. For the second and third slip events, premonitory AE source mechanisms mimic the large scale fault plane geometry. Copyright 2005 by the American Geophysical Union.

  7. Stick-Slip Dynamics in Sheared Granular Material

    NASA Astrophysics Data System (ADS)

    Mair, K.

    2002-12-01

    The dynamics of sheared granular materials have wide application to faulting and earthquake mechanics. Despite much interest, their complex behaviour is not well understood. Detailed laboratory experiments can reveal how specific granular processes may influence macroscopic strength. Here I demonstrate how loading rate and grain rearrangements affect stick slip in simulated faults. Granular layers (3 mm thick) composed of spherical particles (100μm) were sheared under constant normal stress (5MPa) at a range of loading rates (0.1μm/s to 1 mm/s) in a direct shear apparatus. Changes in layer thickness were monitored to reveal particle dynamics during shear. Tests were conducted in a non-fracture load regime to minimise gouge evolution with accumulated slip. This provides a vital link between geophysical experiments involving pervasive grain fracture and numerical simulations where fracture is absent. During tests, I observe highly repetitive stick-slip events, characterized by a quasi-linear increase in stress, a stage of inelastic rollover then rapid dynamic stress drop correlating to stick, premonitory slip (creep) and rapid (coseismic) slip in the layer. Stress drop amplitudes are 0.2-0.7MPa (15-30% of failure stress). Analysis of many stick-slip cycles reveals a power law relation between stress drop amplitude and recurrence time, indicating a healing rate of 0.1MPa per decade. The yield in frictional strength prior to failure is directly associated with the onset of premonitory slip (5-75μm) in the granular layer. Also, layer dilation rate is enhanced at the onset of premonitory slip (dilation <5μm). Conversely, granular layers compact rapidly at the point of coseismic slip. These observations imply direct links between gouge dynamics and frictional strength. Importantly, I see a direct correlation between the stress drop amplitude and premonitory slip. This indicates that micro-mechanical rearrangements prior to coseismic slip control the characteristics of dynamic failure. I suggest the stick-slip instabilities in these sheared granular layers reflect the formation and collapse of fragile networks of stress chains. Furthermore, observations of dilation during premonitory slip support ideas that the transition of a granular material to a fluidised state may trigger the breakdown of stress chains and hence dynamic failure.

  8. Strain Wave during the Transient Process of Fault Unstable Slip

    NASA Astrophysics Data System (ADS)

    Guo, L.; Liu, L.

    2011-12-01

    The "stick-slip" model was proposed as an important mechanism for shallow-focus earthquakes. The study on the transient process of fault unstable slip failure is helpful for understanding the earthquake preparatory process, the mechanism of energy released, the precursor and after shake effect. Double shear frictional experiments are conducted for simulating "stick-slip" phenomenon, and a specially designed multi-channel super dynamic strain field observation system is employed to acquire dada continuously with the sample rate of 3,400 samples/second. The rock deformation process can be recorded in detail, especially in the moment of unstable slip (The unstable slip duration is less than two second in experiments). The strain results from super dynamic strain field observation system show that multi-frequency components and tremendous amplitude fluctuation are included in strain signals along the fault. There are three clear phases during the unstable slip progress: pre-slip (phase I), high-frequency strain vibration (phase II) and strain regulating to stop (phase III). Each phase has its own characteristics on duration, strain rate, frequency, amplitude and energy release. There are strong fluctuations in duration of approximately 70ms in phase II. The frequency and maximum amplitude are 300-400Hz and 150~300μɛ respectively. Main strain energy release takes place at phase II, less than one-tenth of the total slip time, so that the whole course of dislocation or stress drop would not be taken as earthquake simply at least in laboratory. The phase characteristic of the strain wave is probably its inherent attribute of unstable slip process and independent of dynamical loading conditions. The elastic rebound phenomena, considered as one classic earthquake generation model, can be observed clearly by analyzing the rotation of the principal strain axis with strain variation. The rotated angle ranges from 5° to 15° typically. The value and location of precursor slip in phase I are controlled and influenced primarily by the tectonic position. The instantaneous strain wave acquired during the process of fault unstable slip is valuable for describing the stick-slip process. The phase model of strain wave is a key to understanding fault rupture mechanism. The temporal and spatial variation of fault precursor slip may have some predictive significance for earthquake.

  9. A simple stick-slip and creep-slip model for repeating earthquakes and its implication for microearthquakes at Parkfield

    USGS Publications Warehouse

    Beeler, N.M.; Lockner, D.L.; Hickman, S.H.

    2001-01-01

    If repeating earthquakes are represented by circular ruptures, have constant stress drops, and experience no aseismic slip, then their recurrence times should vary with seismic moment as tr ?? Mo1/3. In contrast, the observed variation for small, characteristic repeating earthquakes along a creeping segment of the San Andreas fault at Parkfield (Nadeau and Johnson, 1998) is much weaker. Also, the Parkfield repeating earthquakes have much longer recurrence intervals than expected if the static stress drop is 10 MPa and if the loading velocity VL is assumed equal to the geodetically inferred slip rate of the fault Vf. To resolve these discrepancies, previous studies have assumed no aseismic slip during the interseismic period, implying either high stress drop or VL ??? Vf. In this study, we show that a model that includes aseismic slip provides a plausible alternative explanation for the Parkfield repeating earthquakes. Our model of a repeating earthquake is a fixed-area fault patch that is allowed to continuously creep and strain harden until reaching a failure threshold stress. The strain hardening is represented by a linear coefficient C, which when much greater than the elastic loading stiffness k leads to relatively small interseismic slip (stick-slip). When C and k are of similar size creep-slip occurs, in which relatively large aseismic slip accrues prior to failure. Because fault-patch stiffness varies with patch radius, if C is independent of radius, then the model predicts that the relative amount of seismic to total slip increases with increasing radius or Mo, consistent with variations in slip required to explain the Parkfield data. The model predicts a weak variation in tr with Mo similar to the Parkfield data.

  10. Experimental Characterization of Hysteresis in a Revolute Joint for Precision Deployable Structures

    NASA Technical Reports Server (NTRS)

    Lake, Mark S.; Fung, Jimmy; Gloss, Kevin; Liechty, Derek S.

    1997-01-01

    Recent studies of the micro-dynamic behavior of a deployable telescope metering truss have identified instabilities in the equilibrium shape of the truss in response to low-energy dynamic loading. Analyses indicate that these micro-dynamic instabilities arise from stick-slip friction within the truss joints (e.g., hinges and latches). The present study characterizes the low-magnitude quasi-static load cycle response of the precision revolute joints incorporated in the deployable telescope metering truss, and specifically, the hysteretic response of these joints caused by stick-slip friction within the joint. Detailed descriptions are presented of the test setup and data reduction algorithms, including discussions of data-error sources and data-filtering techniques. Test results are presented from thirteen specimens, and the effects of joint preload and manufacturing tolerances are investigated. Using a simplified model of stick-slip friction, a relationship is made between joint load-cycle behavior and micro-dynamic dimensional instabilities in the deployable telescope metering truss.

  11. Stick-Slip Friction of PDMS Surfaces for Bioinspired Adhesives.

    PubMed

    Xue, Longjian; Pham, Jonathan T; Iturri, Jagoba; Del Campo, Aránzazu

    2016-03-15

    Friction plays an important role in the adhesion of many climbing organisms, such as the gecko. During the shearing between two surfaces, periodic stick-slip behavior is often observed and may be critical to the adhesion of gecko setae and gecko-inspired adhesives. Here, we investigate the influence of short oligomers and pendent chains on the stick-slip friction of polydimethylsiloxane (PDMS), a commonly used material for bioinspired adhesives. Three different stick-slip patterns were observed on these surfaces (flat or microstructured) depending on the presence or absence of oligomers and their ability to diffuse out of the material. After washing samples to remove any untethered oligomeric chains, or after oxygen plasma treatment to convert the surface to a thin layer of silica, we decouple the contributions of stiffness, oligomers, and pendant chains to the stick-slip behavior. The stick phase is mainly controlled by the stiffness while the amount of untethered oligomers and pendant chains available at the contact interface defines the slip phase. A large amount of oligomers and pendant chains resulted in a large slip time, dominating the period of stick-slip motion. PMID:26903477

  12. Tactile Feedback of Object Slip Facilitates Virtual Object Manipulation.

    PubMed

    Walker, Julie M; Blank, Amy A; Shewokis, Patricia A; OMalley, Marcia K

    2015-01-01

    Recent advances in myoelectric prosthetic technology have enabled more complex movements and interactions with objects, but the lack of natural haptic feedback makes object manipulation difficult to perform. Our research effort aims to develop haptic feedback systems for improving user performance in object manipulation. Specifically, in this work, we explore the effectiveness of vibratory tactile feedback of slip information for grasping objects without slipping. A user interacts with a virtual environment to complete a virtual grasp and hold task using a Sensable Phantom. Force feedback simulates contact with objects, and vibratory tactile feedback alerts the user when a virtual object is slipping from the grasp. Using this task, we found that tactile feedback significantly improved a user's ability to detect and respond to slip and to recover the slipping object when visual feedback was not available. This advantage of tactile feedback is especially important in conjunction with force feedback, which tends to reduce a subject's grasping forces and therefore encourage more slips. Our results demonstrate the potential of slip feedback to improve a prosthesis user's ability to interact with objects with less visual attention, aiding in performance of everyday manipulation tasks. PMID:25861087

  13. Slip-accelerated falling drop along a vertical fiber

    NASA Astrophysics Data System (ADS)

    Wei, Hsien-Hung; Halpern, David

    2014-11-01

    Effects of wall slip on the motion of a falling drop along a vertical fiber are investigated theoretically. Using lubrication theory, we derive an interfacial evolution equation to describe how the drop's travelling speed and height vary with the Bond number and the slip length. Our numerical results reveal that the drop can travel much faster than the one without slip due to the dramatic increase in the travelling speed with the slip length. The drop height is also found to rapidly increase with the slip length, which is due to enchanced capillary draining from the film into the drop. For Bond number above some critical value, however, capillary draining is suppressed and hence so is the drop height. We determine how the critical Bond number varies with the slip length. For a sufficiently large Bond number, the relevant Kuramoto-Sivashinsky equation is also derived to reveal how the suppression of the capillary instability is mediated by slip effects in the weakly nonlinear regime.

  14. Laboratory observations of fault-normal vibrations during stick slip

    SciTech Connect

    Bodin, P.; Brown, S.; Matheson, D.

    1998-12-01

    We report laboratory observations of interface separation waves during stick slip on a fault in a uniform polymer material. Our observations, made at stress levels expected at midcrustal depths, share many macroscopic properties with ruptures of faults in rocks. We observed a drop in fault-normal stress shortly before the onset of, and during, stick slip at points along the fault during a rupture. We suggest that {ital P} wave energy in front of the propagating rupture tip is responsible for the drop in normal stress. We also interpret that stick slip took place within a traveling slip pulse, and we suggest that the dynamic stress drop within the slipping patch exceeded the overall static stress drop by a factor of at least 5 within a few millimeters of the fault. Our experiments did not resolve whether the fault surfaces actually separate or if fault-normal stress is just greatly reduced. In either case the net result is that fault slip is permitted to take place with much less frictional resistance than that expected from the applied load. Our observations provide laboratory evidence that fault-normal vibrations may play an important role in sustaining a rupture by facilitating the propagation of a transient instability. Faults may appear weak in part because they are dynamically weakened as they slip during rupture while retaining their strength during the interseismic period. {copyright} 1998 American Geophysical Union

  15. Slip-stick and the evolution of frictional strength.

    PubMed

    Ben-David, Oded; Rubinstein, Shmuel M; Fineberg, Jay

    2010-01-01

    The evolution of frictional strength has great fundamental and practical importance. Applications range from earthquake dynamics to hard-drive read/write cycles. Frictional strength is governed by the resistance to shear of the large ensemble of discrete contacts that forms the interface that separates two sliding bodies. An interface's overall strength is determined by both the real contact area and the contacts' shear strength. Whereas the average motion of large, slowly sliding bodies is well-described by empirical friction laws, interface strength is a dynamic entity that is inherently related to both fast processes such as detachment/re-attachment and the slow process of contact area rejuvenation. Here we show how frictional strength evolves from extremely short to long timescales, by continuous measurements of the concurrent local evolution of the real contact area and the corresponding interface motion (slip) from the first microseconds when contact detachment occurs to large (100-second) timescales. We identify four distinct and inter-related phases of evolution. First, all of the local contact area reduction occurs within a few microseconds, on the passage of a crack-like front. This is followed by the onset of rapid slip over a characteristic time, the value of which suggests a fracture-induced reduction of contact strength before any slip occurs. This rapid slip phase culminates with a sharp transition to slip at velocities an order of magnitude slower. At slip arrest, 'ageing' immediately commences as contact area increases on a characteristic timescale determined by the system's local memory of its effective contact time before slip arrest. We show how the singular logarithmic behaviour generally associated with ageing is cut off at short times. These results provide a comprehensive picture of how frictional strength evolves from the short times and rapid slip velocities at the onset of motion to ageing at the long times following slip arrest. PMID:20054393

  16. Predicting slips and falls considering required and available friction.

    PubMed

    Hanson, J P; Redfern, M S; Mazumdar, M

    1999-12-01

    This study investigated the relationship among measurements of friction, the biomechanics of gait, and actual slip and fall events. The goal was to develop a method for estimating the probability of slips and falls based on measurements of available friction and required friction. Five subjects wearing safety harnesses walked down a ramp at various angles with either a tile or carpeted surface under dry, wet or soapy conditions. Ramp angles of 0 degree, 10 degrees and 20 degrees were used to vary the shear and normal foot force requirements. The dynamic coefficient of friction (DCOF) of shoe, floor surface and contaminant interfaces was measured. Required friction was assessed by examining the foot forces during walking trials when no slips occurred. Slips with recoveries and slips resulting in falls were recorded and categorized using a force plate and high-speed video camera. These data were then incorporated into a logistic regression to model the probability of a slip or fall event occurring based on the difference between the COF required by the foot forces generated and the measured DCOF. The results showed that the number of slip and fall events increased as the difference between the required COF and the measured DCOF increased. The logistic regression model fit the data well, resulting in an estimate of the probability of a slip or fall event based on the difference between the measured and required friction. This type of model could be used in the future to evaluate slip resistance measurement devices under various environments and assist in the design of safer work environments. PMID:10643404

  17. Perception of slipperiness and prospective risk of slipping at work

    PubMed Central

    Courtney, Theodore K; Verma, Santosh K; Chang, Wen-Ruey; Huang, Yueng-Hsiang; Lombardi, David A; Brennan, Melanye J; Perry, Melissa J

    2013-01-01

    Objectives Falls are a leading cause of injury at work, and slipping is the predominant cause of falling. Prior research has suggested a modest correlation between objective measures (such as coefficient of friction, COF) and subjective measures of slipperiness (such as worker perceptions) in the workplace. However, the degree of association between subjective measures and the actual risk of slipping at the workplace is unknown. This study examined the association between perception of slipperiness and the risk of slipping. Methods 475 workers from 36 limited-service restaurants participated in a 12-week prospective cohort study. At baseline, demographic information was collected, participants rated floor slipperiness in eight areas of the restaurant, and work environment factors, such as COF, were measured. Restaurant-level and area-level mean perceptions of slipperiness were calculated. Participants then reported their slip experience at work on a weekly basis for the next 12 weeks. The associations between perception of slipperiness and the rate of slipping were assessed. Results Adjusting for age, gender, body mass index, education, primary language, mean COF, use of slip-resistant shoes, and restaurant chain, each 1-point increase in mean restaurant-level perception of slipperiness (4-point scale) was associated with a 2.71 times increase in the rate of slipping (95% CI 1.25 to 5.87). Results were similar for area-level perception within the restaurant (rate ratios (RR) 2.92, 95% CI 2.41 to 3.54). Conclusions Perceptions of slipperiness and the subsequent rate of slipping were strongly associated. These findings suggest that safety professionals, risk managers and employers could use aggregated worker perceptions of slipperiness to identify slipping hazards and, potentially, to assess intervention effectiveness. PMID:22935953

  18. Dynamic Ridges and Valleys in a Strike-Slip Environment

    NASA Astrophysics Data System (ADS)

    Duvall, Alison R.; Tucker, Gregory E.

    2015-10-01

    Strike-slip faults have long been known for characteristic near-fault landforms such as offset rivers and strike-parallel valleys. In this study, we use a landscape evolution model to investigate the longer-term, catchment-wide landscape response to horizontal fault motion. Our results show that strike-slip faulting induces a persistent state of disequilibrium in the modeled landscapes brought about by river lengthening along the fault alternating with abrupt shortening due to stream capture. The models also predict that, in some cases, ridges oriented perpendicular to the fault migrate laterally in conjunction with fault motion. We find that ridge migration happens when slip rate is slow enough and/or soil creep and river incision are efficient enough that the landscape can respond to the disequilibrium brought about by strike-slip motion. Regional rock uplift relative to baselevel also plays a role, as topographic relief is required for ridge migration. In models with faster horizontal slip rates, stronger rocks, or less efficient hillslope transport, ridge mobility is limited or arrested despite the continuance of river lengthening and capture. In these cases, prominent steep, fault-facing facets form along well-developed fault valleys. Comparison of landscapes adjacent to fast-slipping (>30 mm/yr) and slower-slipping (≤1 mm/yr or less) strike-slip faults in California, USA, reveals features that are consistent with model predictions. Our results highlight a potential suite of geomorphic signatures that can be used as indicators of horizontal crustal motion and geomorphic processes in strike-slip settings even after river capture has diminished or erased apparent offset along the fault.

  19. Real-time inversions for finite fault slip models and rupture geometry based on high-rate GPS data

    USGS Publications Warehouse

    Minson, Sarah E.; Murray, Jessica R.; Langbein, John O.; Gomberg, Joan S.

    2015-01-01

    We present an inversion strategy capable of using real-time high-rate GPS data to simultaneously solve for a distributed slip model and fault geometry in real time as a rupture unfolds. We employ Bayesian inference to find the optimal fault geometry and the distribution of possible slip models for that geometry using a simple analytical solution. By adopting an analytical Bayesian approach, we can solve this complex inversion problem (including calculating the uncertainties on our results) in real time. Furthermore, since the joint inversion for distributed slip and fault geometry can be computed in real time, the time required to obtain a source model of the earthquake does not depend on the computational cost. Instead, the time required is controlled by the duration of the rupture and the time required for information to propagate from the source to the receivers. We apply our modeling approach, called Bayesian Evidence-based Fault Orientation and Real-time Earthquake Slip, to the 2011 Tohoku-oki earthquake, 2003 Tokachi-oki earthquake, and a simulated Hayward fault earthquake. In all three cases, the inversion recovers the magnitude, spatial distribution of slip, and fault geometry in real time. Since our inversion relies on static offsets estimated from real-time high-rate GPS data, we also present performance tests of various approaches to estimating quasi-static offsets in real time. We find that the raw high-rate time series are the best data to use for determining the moment magnitude of the event, but slightly smoothing the raw time series helps stabilize the inversion for fault geometry.

  20. Butt Joint Tool Commissioning

    SciTech Connect

    Martovetsky, N N

    2007-12-06

    ITER Central Solenoid uses butt joints for connecting the pancakes in the CS module. The principles of the butt joining of the CICC were developed by the JAPT during CSMC project. The difference between the CSMC butt joint and the CS butt joint is that the CS butt joint is an in-line joint, while the CSMC is a double joint through a hairpin jumper. The CS butt joint has to carry the hoop load. The straight length of the joint is only 320 mm, and the vacuum chamber around the joint has to have a split in the clamp shell. These requirements are challenging. Fig.1 presents a CSMC joint, and Fig.2 shows a CS butt joint. The butt joint procedure was verified and demonstrated. The tool is capable of achieving all specified parameters. The vacuum in the end was a little higher than the target, which is not critical and readily correctable. We consider, tentatively that the procedure is established. Unexpectedly, we discover significant temperature nonuniformity in the joint cross section, which is not formally a violation of the specs, but is a point of concern. All testing parameters are recorded for QA purposes. We plan to modify the butt joining tool to improve its convenience of operation and provide all features necessary for production of butt joints by qualified personnel.

  1. Slip complexity in dynamic models of earthquake faults.

    PubMed Central

    Langer, J S; Carlson, J M; Myers, C R; Shaw, B E

    1996-01-01

    We summarize recent evidence that models of earthquake faults with dynamically unstable friction laws but no externally imposed heterogeneities can exhibit slip complexity. Two models are described here. The first is a one-dimensional model with velocity-weakening stick-slip friction; the second is a two-dimensional elastodynamic model with slip-weakening friction. Both exhibit small-event complexity and chaotic sequences of large characteristic events. The large events in both models are composed of Heaton pulses. We argue that the key ingredients of these models are reasonably accurate representations of the properties of real faults. PMID:11607671

  2. Local void and slip model used in BODYFIT-2PE

    SciTech Connect

    Chen, B.C.J.; Chien, T.H.; Kim, J.H.; Lellouche, G.S.

    1983-01-01

    A local void and slip model has been proposed for a two-phase flow without the need of fitting any empirical parameters. This model is based on the assumption that all bubbles have reached their terminal rise velocities in the two-phase region. This simple model seems to provide reasonable calculational results when compared with the experimental data and other void and slip models. It provides a means to account for the void and slip of a two-phase flow on a local basis. This is particularly suitable for a fine mesh thermal-hydraulic computer program such as BODYFIT-2PE.

  3. Local Flow Field and Slip Length of Superhydrophobic Surfaces.

    PubMed

    Schäffel, David; Koynov, Kaloian; Vollmer, Doris; Butt, Hans-Jürgen; Schönecker, Clarissa

    2016-04-01

    While the global slippage of water past superhydrophobic surfaces has attracted wide interest, the local distribution of slip still remains unclear. Using fluorescence correlation spectroscopy, we performed detailed measurements of the local flow field and slip length for water in the Cassie state on a microstructured superhydrophobic surface. We revealed that the local slip length is finite, nonconstant, anisotropic, and sensitive to the presence of surfactants. In combination with numerical calculations of the flow, we can explain all these properties by the local hydrodynamics. PMID:27081981

  4. Local Flow Field and Slip Length of Superhydrophobic Surfaces

    NASA Astrophysics Data System (ADS)

    Schäffel, David; Koynov, Kaloian; Vollmer, Doris; Butt, Hans-Jürgen; Schönecker, Clarissa

    2016-04-01

    While the global slippage of water past superhydrophobic surfaces has attracted wide interest, the local distribution of slip still remains unclear. Using fluorescence correlation spectroscopy, we performed detailed measurements of the local flow field and slip length for water in the Cassie state on a microstructured superhydrophobic surface. We revealed that the local slip length is finite, nonconstant, anisotropic, and sensitive to the presence of surfactants. In combination with numerical calculations of the flow, we can explain all these properties by the local hydrodynamics.

  5. Frictional Slip Resistance at Glacier Beds due to Rock Debris

    NASA Astrophysics Data System (ADS)

    Iverson, N. R.; Cohen, D.; Hooyer, T. S.; Thomason, J. F.; Moore, P. L.; Jackson, M.

    2008-12-01

    Slip at the bases of wet-based ice masses may share more in common with slip along crustal faults than previously suspected. The ice plain of Whillans ice stream moves by persistent slick-slip motion with associated basal seismicity (Wiens, et al., 2007, Nature) Additional evidence for stick-slip over shorter time and length scales comes from seismic studies elsewhere in Antarctica (Danesi et al., 2006, EPSL) and from Trapridge Glacier, where brief but large water pressure pulses in closed boreholes are interpreted to reflect stress transients associated with minute, episodic slip events (Kavanaugh, in press, JGR-ES). These observations indicate that slip resistance over some portions of glacier beds can be dominantly frictional, rather than viscous or viscoplastic as is commonly assumed for both hard and soft beds. Rock debris, either within basal ice or in a soft bed, is a source of such friction. Measurements at Engabreen, Norway, indicate that friction between debris in ice and a hard bed can locally be comparable to the bed shear stress, indicating that over some parts of the bed rock friction can exceed viscous drag on bedrock bumps. Laboratory studies of till deformation relevant to soft beds indicate that Coulomb models best approximate steady-state deformation but with subtle rate dependencies at small strains. Glacier slip across a till bed, triggered by high water pressure with associated shear relaxation of till, has been measured beneath several glaciers. Moreover, laboratory experiments indicate that resistance to this slip can decrease with increasing slip velocity, the converse of viscous rate strengthening. This velocity weakening is measured commonly in friction experiments with fault gouge and is a fundamental requirement for stick-slip motion and consequent seismicity. These subglacial and laboratory data, therefore, are broadly consistent with larger-scale observations of stick-slip and basal seismicity on some glaciers. The implication, in agreement with some models of glacier flow, is that sections of glacier beds with slip resistance dominated by debris friction may have little or no capacity for viscous rate strengthening. In such zones stable flow can be achieved only through interaction with adjacent ice.

  6. Pressure suit joint analyzer

    NASA Technical Reports Server (NTRS)

    Vykukal, H. C.; Webbon, B. W. (Inventor)

    1982-01-01

    A measurement system for simultaneously measuring torque and angular flexure in a pressure suit joint is described. One end of a joint under test is held rigid. A torque transducer is pivotably supported on the other movable end of a joint. A potentiometer is attached to the transducer by an arm. The wiper shaft of the potentiometer is gripped by a reference arm that rotates the wiper shaft the same angle as the flexure of joint. A signal is generated by the potentiometer which is representative of the joint flexure. A compensation circuit converts the output of the transducer to a signal representative of joint torque.

  7. Fault Slip Induced By Injection of Water and Pore Fluid Flow

    SciTech Connect

    Nemoto, Katsumi; Moriya, Hirokazu; Niitsuma, Hiroaki

    2006-05-15

    The model experiments which simulated shear slip induced by injection of pore fluid have been conducted under triaxial compressive stress condition using a roughened bare fault. The objective is to understand characteristics of the induced slip behaviour, especially after the slip initiation obeying Coulomb failure criterion and pore fluid behaviour associated with the induced slip. Experimental results showed that intermittent slip occurred in all the injection-induced slip experiments. Moreover, it was also found that the pore fluid flow into the fault increased instantaneously accompanying with dynamic slip, which represents a part of higher slip velocity (V > 0.05 mm/s, Vmax of 0.4 mm/s) in the intermittent slip. Quantitative estimation on the volume of the inflow of pore fluid during the dynamic slip suggested that a shear dilatancy would cause the instantaneous increase in pore fluid flow that occurred with the slip.

  8. Slip casting and pressure slip casting of Si{sub 3}N{sub 4} aqueous suspensions

    SciTech Connect

    Castanho, S.M.; Moreno, R.; Salomoni, A.; Stamenkovic, I.

    1995-09-01

    The stability of silicon nitride aqueous slips has been studied in order to obtain Si{sub 3}N{sub 4} pressureless sintered compacts. High solid content slips (up to 65 wt%) have been prepared by using tetramethylammonium hydroxide as dispersing agent. The effect of sintering aids on the rheology and casting conditions has been studied by slip casting and uniaxial pressure filtration. The casting rate, the green density and the microstructure of samples obtained from both slurry consolidation techniques have been compared taking into account the role of the sintering additives. Sintering of cast green specimens has been performed at 1750{degrees}C in N{sub 2} atmosphere.

  9. Laboratory observations of transient frictional slip in rock-analog materials at co-seismic slip rates and rapid changes in normal stress

    NASA Astrophysics Data System (ADS)

    Yuan, Fuping; Prakash, Vikas

    2012-08-01

    Knowledge of frictional (shear) resistance and its dependency on slip distance, slip velocity, normal stress, and surface roughness is fundamental information for understanding earthquake physics and the energy released during such events. In view of this, in the present study, plate-impact pressure-shear friction experiments are conducted to investigate the frictional resistance in a rock analog material, i.e. soda-lime glass, under interfacial conditions of relevance to fault rupture. The results of the experiments indicate that a wide range of frictional slip conditions exist at the slip interface ranging from initial no-slip and followed by slip weakening, slip strengthening (healing), and seizure all during a single slip event. The slip-weakening phase is understood to be most likely due to thermal-induced flash heating and incipient melting at asperity junctions, while the slip strengthening (slip-healing) phase is understood to be a result of coalescence and solidification of local melt patches on the slip interface. In addition, plate impact pressure-shear normal-stress change (drop) experiments are employed to probe the response of the slip interface due to sudden alterations in normal stress. In particular, the location (timing) of the stress drop is varied so as to investigate the behavior of the slip interface in its slip-weakening, slip-strengthening (healing) phase, or the seized phase, in response to sudden drop in normal stress. These experimental results provide a rich set of data to better understand the range of possible friction slip states that can be achieved and/or critically examine existing dynamic friction models for fault slip behavior.

  10. Experimental characterization of a flexible thermal slip sensor.

    PubMed

    Francomano, Maria Teresa; Accoto, Dino; Guglielmelli, Eugenio

    2012-01-01

    Tactile sensors are needed for effectively controlling the interaction between a robotic hand and the environment, e.g., during manipulation of objects, or for the tactile exploration of unstructured environments, especially when other sensing modalities, such as vision or audition, become ineffective. In the case of hand prostheses, mainly intended for dexterous manipulation of daily living objects, the possibility of quickly detecting slip occurrence, thus avoiding inadvertent falling of the objects, is prodromal to any manipulation task. In this paper we report on a slip sensor with no-moving parts, based on thermo-electrical phenomena, fabricated on a flexible substrate and suitable for integration on curved surfaces, such as robotic finger pads. Experiments performed using a custom made test bench, which is capable of generating controlled slip velocities, show that the sensor detects slip events in less than 50 ms. This response time is short enough for enabling future applications in the field of hand prosthetics. PMID:23202209

  11. GENERAL ELECTRIC SYNCHRONOUS MOTOR, SLIP RING END. NOTE THAT OUTSIDE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    GENERAL ELECTRIC SYNCHRONOUS MOTOR, SLIP RING END. NOTE THAT OUTSIDE FRAME IS ROTATING ARMATURE, AND STATOR IS IN CENTER. ARCH SUPPORTS BRAKE BAND. - Shenandoah-Dives Mill, 135 County Road 2, Silverton, San Juan County, CO

  12. View from water showing south facade and adjacent boat slips ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View from water showing south facade and adjacent boat slips (Facility Nos. S375 & S376) - U.S. Naval Base, Pearl Harbor, Boat House, Hornet Avenue at Independence Street, Pearl City, Honolulu County, HI

  13. Reconditioning fault slip inversions via InSAR data discretization

    NASA Astrophysics Data System (ADS)

    Ziv, Alon

    2016-02-01

    A major difficulty in inverting geodetic data for fault slip distribution is that measurement errors are mapped from the data space onto the solution space. The amplitude of this mapping is sensitive to the condition number of the inverse problem, i.e., the ratio between the largest and smallest singular value of the forward matrix. Thus, unless the problem is well-conditioned, slip inversions cannot reveal the actual fault slip distribution. In this study, we describe a new iterative algorithm that optimizes the condition of the slip inversion through discretization of InSAR data. We present a numerical example that demonstrates the effectiveness of our approach. We show that the condition number of the reconditioned data sets are not only much smaller than those of uniformly spaced data sets with the same dimension but are also much smaller than non-uniformly spaced data sets, with data density that increases towards the model fault.

  14. 4. From west side of boat slip; ore piles, unloaders, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. From west side of boat slip; ore piles, unloaders, blast furnaces, tube conveyors, ore conveyors, stock house, powerhouse. Looking north/northeast - Rouge Steel Company, 3001 Miller Road, Dearborn, Wayne County, MI

  15. Independence of slip velocities on applied stress in small crystals.

    PubMed

    Maaß, R; Derlet, P M; Greer, J R

    2015-01-21

    Directly tracing the spatiotemporal dynamics of intermittent plasticity at the micro- and nanoscale reveals that the obtained slip dynamics are independent of applied stress over a range of up to ∼400 MPa, as well as being independent of plastic strain. Whilst this insensitivity to applied stress is unexpected for dislocation plasticity, the stress integrated statistical properties of both the slip size magnitude and the slip velocity follow known theoretical predictions for dislocation plasticity. Based on these findings, a link between the crystallographic slip velocities and an underlying dislocation avalanche velocity is proposed. Supporting dislocation dynamics simulations exhibit a similar regime during microplastic flow, where the mean dislocation velocity is insensitive to the applied stress. Combining both experimental and modeling observations, the results are discussed in a framework that firmly places the plasticity of nano- and micropillars in the microplastic regime of bulk crystals. PMID:25178931

  16. Experimental Characterization of a Flexible Thermal Slip Sensor

    PubMed Central

    Francomano, Maria Teresa; Accoto, Dino; Guglielmelli, Eugenio

    2012-01-01

    Tactile sensors are needed for effectively controlling the interaction between a robotic hand and the environment, e.g., during manipulation of objects, or for the tactile exploration of unstructured environments, especially when other sensing modalities, such as vision or audition, become ineffective. In the case of hand prostheses, mainly intended for dexterous manipulation of daily living objects, the possibility of quickly detecting slip occurrence, thus avoiding inadvertent falling of the objects, is prodromal to any manipulation task. In this paper we report on a slip sensor with no-moving parts, based on thermo-electrical phenomena, fabricated on a flexible substrate and suitable for integration on curved surfaces, such as robotic finger pads. Experiments performed using a custom made test bench, which is capable of generating controlled slip velocities, show that the sensor detects slip events in less than 50 ms. This response time is short enough for enabling future applications in the field of hand prosthetics. PMID:23202209

  17. Slip and Air-Entrainment at Water-Solid Interfaces

    NASA Astrophysics Data System (ADS)

    Zhu, Yingxi Elaine; Sarangapani, Prasad; Mukhopadhyay, Ashis

    2006-03-01

    A number of recent studies performed with water flow past hydrophobic microchannels have reported the existence of `slip' at wall and suggested the existence of the interfacial gas layer as the underlying mechanism for the slip motion, yet the details are much disputed. We combine microscopy and advanced laser spectroscopy to directly and non-invasively detect the interfacial gas layer in flowing water past micro/nano-channels whose surface chemistry and gap spacing are varied. We observe that the dimension of the gas layer strongly depends on surface hydrophobicity and flow rates. Surprisingly, we have also observed the slip motion of water over hydrophilic surfaces with a strong dependence on liquid-loading conditions. We propose a mechanistic theory about air-entrainment that can account for our observations to elucidate the origin of the gas formation at water-solid interface and its consequence on slip motion.

  18. Frictional melting and stick-slip behavior in volcanic conduits

    NASA Astrophysics Data System (ADS)

    Kendrick, Jackie Evan; Lavallee, Yan; Hirose, Takehiro; di Toro, Giulio; Hornby, Adrian Jakob; Hess, Kai-Uwe; Dingwell, Donald Bruce

    2013-04-01

    Dome-building eruptions have catastrophic potential, with dome collapse leading to devastating pyroclastic flows with almost no precursory warning. During dome growth, the driving forces of the buoyant magma may be superseded by controls along conduit margins; where brittle fracture and sliding can lead to formation of lubricating cataclasite and gouge. Under extreme friction, pseudotachylyte may form at the conduit margin. Understanding the conduit margin processes is vital to understanding the continuation of an eruption and we postulate that pseudotachylyte generation could be the underlying cause of stick-slip motion and associated seismic "drumbeats", which are so commonly observed at dome-building volcanoes. This view is supported by field evidence in the form of pseudotachylytes identified in lava dome products at Soufrière Hills (Montserrat) and Mount St. Helens (USA). Both eruptions were characterised by repetitive, periodic seismicity and lava spine extrusion of highly viscous magma. High velocity rotary shear (HVR) experiments demonstrate the propensity for melting of the andesitic and dacitic material (from Soufrière Hills and Mount St. Helens respectively) at upper conduit stress conditions (<10 MPa). Starting from room temperature, frictional melting of the magmas occurs in under 1 s (<< 1 m) at 1.5 m/s (a speed that is achievable during stick-slip motion). At lower velocities melting occurs comparatively later due to dissipation of heat from the slip zone (e.g. 8-15 m at 0.1 m/s). Hence, given the ease with which melting is achieved in volcanic rocks, and considering the high ambient temperatures in volcanic conduits, frictional melting may thus be an inevitable consequence of viscous magma ascent. The shear resistance of the slip zone during the experiment is also monitored. Frictional melting induces a higher resistance to sliding than rock on rock, and viscous processes control the slip zone properties. Variable-rate HVR experiments which mimic rapid velocity fluctuations in stick-slip behavior demonstrate velocity-weakening behavior of melt, with a tendency for unstable slip. During ascent, magma may slip and undergo melting along the conduit margin. In the process the shear resistance of the slip zone is increased, acting as a viscous brake halting slip (the "stick" of stick-slip motion). Sufficient buoyancy-driven pressures from ascending magma below eventually overcome resistance to produce a rapid slip event (the "slip") along the melt-bearing slip zone, which is temporarily lubricated due to velocity-weakening. New magma below experiences the same slip event more slowly (as the magma decompresses) to produce a viscous brake and the process is repeated. This allows a fixed spatial locus that explains the repetitive drumbeat seismicity and the occurrence of "families" of similar seismic events. We conclude that stick-slip motion in volcanic conduits is a self-driving, frictional-melt-regulated force common to many dome building volcanoes.

  19. Resistance induced by quantum phase-slips in superconducting nanowires

    NASA Astrophysics Data System (ADS)

    Tinkham, M.; Lau, C. N.; Markovic, N.

    2003-05-01

    We have measured the resistive transitions of ∼20 nanowires of superconducting amorphous MoGe with diameters ∼10 nm and lengths from 100 to 1000 nm. The transition width increases with decreasing cross-sectional area (i.e. increasing normal resistance per unit length) as described by the phenomenology including quantum phase-slips used by Giordano to explain his earlier data and also by the rather similar results of a microscopic theory of Golubev and Zaikin. The resistance well below Tc is much greater than can be explained by thermally activated phase-slips alone. We consider this to strongly support the reality of quantum phase-slips, and the basic correctness of these theories. The exact role of dissipation, whether from metal in the wire, from the carbon nanotube substrate, or from the electromagnetic environment, in reducing quantum phase-slips needs further clarification.

  20. Slipping zones from exhumed faults in dolostones (Borcola Pass Fault, Italian Southern Alps)

    NASA Astrophysics Data System (ADS)

    Fondriest, M.; Smith, S.; Di Toro, G.; Zampieri, D.

    2011-12-01

    Fault zones in limestones and dolostones represent significant seismogenic sources in many areas worldwide, including central Italy and the Italian Fore-Alps (e.g. Val di Noto 1693, estimated Mw = 6.9; Avezzano 1915, Mw = 6.7; Friuli 1976, Mw = 6.4; Irpinia 1980, Mw = 6.9; L'Aquila 2009, Mw = 6.3). Field and microstructural investigations of exhumed seismogenic fault zones and related fault rocks in carbonates are therefore important to document fault structure and the range of deformation processes active during the seismic cycle. The Borcola Pass Fault is a ca. N-S strike-slip branch of the Schio-Vicenza Line (a main lineament of the Italian Southern Alps) and is well exposed within a series of large dolostone quarries (Borcola Pass, Trento). Estimated depth and temperature conditions during faulting are ca. 1.6-1.7 km and 50°C. The fault zone consists of a > 80 m thick damage zone surrounding a 2-3 m thick fault core containing dolomitic fault rock lenses bounded by principal slip zones up to 10 cm thick. The damage zone is cut by three systems of secondary faults striking N-S, E-W and NW-SE. N-S and E-W striking faults reactivated inherited (Jurassic to Paleogene) regional-scale joints and have an average spacing between 0.2 to 0.5 m, whereas NW-SE striking faults were newly formed during post-Paleogene slip activity along the Borcola Pass Fault and the Schio-Vicenza Line. Both principal and secondary slip zones consist of cement-supported dolomitic cataclasites and dolomite-filled veins. Some slip zones contain a sub-centimetre thick vein-like cataclastic layer (Layer A) located immediately beneath the principal slip surface and above a cement-supported cataclasite (Layer B). Layer A is white in colour and consists of sub-rounded dolostone grains ranging between 300 μm and 2.5 mm in size, suspended in a dolomitic cement. Layer B is grey in colour and consists of sub-angular dolostone grains ranging between 5 μm and 1 cm in size within a dolomitic cement. According to image analysis investigations, Layer A has a lower 2-dimensional fractal dimension (D < 1) and better grain sorting than Layer B (D≈ 1.6). The boundary of Layer A towards the principal slip surface is cuspate-lobate and includes a 2-5 mm thick zoned ultracataclasite whereas towards Layer B the boundary is sharp and truncates clasts. Several injection veins depart from Layer A into Layer B. These microstructural data suggest that while grain fragmentation models (e.g. constrained comminution) can account for the clast size distribution found in Layer B (D ≈ 1.6), other physico-chemical (maybe coseismic) processes such as localized layer fluidization and grain sorting may result in the unusual textural characteristics, including the presence of injection veins, found in Layer A.

  1. Slip Updip of Tremor during the 2012 Cascadia ETS Event

    NASA Astrophysics Data System (ADS)

    Hall, K.; Houston, H.

    2014-12-01

    The interplay between tremor and slow slip during ETS has implications for the slip budget of the Cascadia subduction zone. In particular, it can constrain the downdip edge of the locked zone, which informs the hazard assessments for major cities including Seattle, Tacoma, and Vancouver. As shown by Houston (AGU abstract, 2012), slip inferred from GPS extended updip of the seismically-detected tremor in the 2010 M6.8 ETS event. Following the methods used on the 2010 ETS event, we used the PANGA GPS to measure the displacement vectors for 71 stations to analyze a large ETS event in 2012 that extended from Vancouver Island to Southern Washington. We implemented Principal Component Analysis to automatically select the direction and magnitude of the maximum displacement vector. We then inverted these GPS displacements for slip, using the Okada formulation of buried rectangular faults in a halfspace with a grid of 8 by 8 km subfaults based on the McCrory slab model. We performed inversions with either 0th or 2nd order Tikhonov regularization and found that over the 6 weeks of propagation, the 2012 ETS event released moment corresponding to M6.7, in three high-slip regions. We compared two different inversions, one where slip was allowed on a broad regional grid and a tremor-restricted inversion (TRI) where slip was restricted to grid locations where tremor had been detected in the 2012 ETS. We found that the TRI forced the slip to the updip edge of the grid where it reached above 10 cm, which is physically implausible given that this exceeds the slip that can accumulate in an inter-ETS time period. Additionally, the regional grid inversion indicates that 1 to 2 cm of slip occurred 10's of km updip of the western edge of tremor. This further supports the inference from the 2010 event that in northern Washington, the slow slip during an ETS event extends many kilometers updip of the western edge of tremor.

  2. Hip joint injection

    MedlinePlus

    ... injection is a shot of medicine into the hip joint. The medicine helps relieve pain and inflammation. It ... often caused by: Bursitis Arthritis Injury to the hip joint or surrounding area Overuse or strain from running ...

  3. Metatarsal phalangeal joint arthroscopy.

    PubMed

    Shonka, T E

    1991-01-01

    An overview of metatarsophalangeal joint (MPJ) arthroscopy is presented. Indications, technique, and perioperative management are discussed. The author believes it is the operative treatment of choice for various pathology encountered in this joint. PMID:2002183

  4. Temporomandibular Joint, Open

    MedlinePlus

    ... Search Text size: Website Contents NIDCR Home Oral Health Diseases and Conditions Gum Disease TMJ Disorders Oral Cancer Dry Mouth Burning Mouth Tooth Decay See All Oral Complications of Systemic Diseases Cancer ... Joint, Open The Temporomandibular Joint, Open ...

  5. Joint aspiration (image)

    MedlinePlus

    Synovial fluid analysis is a series of tests performed on synovial (joint) fluid to help diagnose and treat joint-related abnormalities. To obtain a synovial fluid sample, a needle is inserted into the knee ...

  6. Culture - joint fluid

    MedlinePlus

    Joint fluid culture ... fungi, or viruses grow. This is called a culture. If these germs are detected, other tests may ... is no special preparation needed for the lab culture. How to prepare for the removal of joint ...

  7. Large displacement spherical joint

    DOEpatents

    Bieg, Lothar F.; Benavides, Gilbert L.

    2002-01-01

    A new class of spherical joints has a very large accessible full cone angle, a property which is beneficial for a wide range of applications. Despite the large cone angles, these joints move freely without singularities.

  8. Temporomandibular Joint Dysfunction

    MedlinePlus

    The temporomandibular joint (TMJ) connects your jaw to the side of your head. When it works well, it enables you to ... For people with TMJ dysfunction, problems with the joint and muscles around it may cause Pain that ...

  9. Wheel rolling constraints and slip in mobile robots

    SciTech Connect

    Shekhar, S.

    1997-03-01

    It is widely accepted that dead reckoning based on the rolling with no slip condition on wheels is not a reliable method to ascertain the position and orientation of a mobile robot for any reasonable distance. We establish that wheel slip is inevitable under the dynamic model of motion using classical results on the accessibility and controllability in nonlinear control theory and an analytical model of rolling of two linearly elastic bodies.

  10. Wheel rolling constraints and slip in mobile robots

    SciTech Connect

    Shekhar, S.

    1996-06-01

    It is widely accepted that dead-reckoning based on the rolling with no-slip condition on the wheels is not a reliable method to ascertain the position and orientation of a mobile robot for any reasonable distance. The authors establish that wheel slip is inevitable under the dynamic model of motion using classical results on the accessibility and controllability in nonlinear control theory and an analytical model of rolling of two linearly elastic bodies.

  11. Wheel rolling constraints and slip in mobile robots

    SciTech Connect

    Shekhar, S.

    1997-03-01

    It is widely accepted that dead reckoning based on the rolling with no slip condition on wheels is not a reliable method to ascertain the position and orientation of a mobile robot for any reasonable distance. The author establishes that wheel slip is inevitable under the dynamic model of motion using classical results on the accessibility and controllability in nonlinear control theory and an analytical model of rolling of two linearly elastic bodies.

  12. Refining the Magnitude of the Shallow Slip Deficit

    NASA Astrophysics Data System (ADS)

    Xu, X.; Tong, X.; Sandwell, D. T.; Milliner, C. W.

    2013-12-01

    Geodetic inversions for co-sesimic slip for several major strike-slip ruptures (magnitude > 7) reveal that a peak in slip occurs between depths of 2 km and 9 km with a 10-40% reduction in slip at shallower depth. This has been termed the shallow slip deficit (SSD). The magnitude of this deficit is based on slip inversions using interferometric synthetic aperture radar (InSAR) and GPS data (e.g., Simons et al. 2002, Fialko 2004, Fialko et al. 2005). One potential uncertainty in these inversions is that the interferometric phase is commonly decorrelated close to the rupture. A lack of near-fault data could result in an underestimate of the magnitude of the shallow slip. In this study we try to improve the coverage of the near-field InSAR data using improved InSAR processing methods: 1) improved phase filtering (non boxcar) to better resolve areas of high phase gradient; 2) model-dependent range corrections to better align the images where offsets are large; 3) more complete phase unwapping by using SNAPHU that applies Lp-norm minimization to match the local derivatives with the measured derivatives as close as possible, and 4) carefully masking areas where geologists noted ground rupture. Our weighed slip inversion is based on improved line-of-sight unwrapped phase and azimuth offset from along track interferogram as well as pixel tracking offsets. In the case of the 1992 Landers these refinements provide significantly better phase recovery close to the fault, approaching from mean distances of approximately 5.6km(Asc Data) and 3.6km(Des Data) to less than 2km. Using these refined InSAR data we hope to provide improved estimates on the magnitude of the SSD.

  13. Refining the Magnitude of the Shallow Slip Deficit

    NASA Astrophysics Data System (ADS)

    Xu, X.; Tong, X.; Sandwell, D. T.; Milliner, C. W. D.

    2014-12-01

    Geodetic inversions for slip versus depth for several major (Mw > 7) strike-slip earthquakes (e.g. 1992 Landers, 1999 Hector Mine, 2010 El_Mayor-Cucapah) show a 10% to 40% reduction in slip near surface (depth < 2 km) compared to the slip at deeper depths (5 to 8 km). This has been called the shallow slip deficit (SSD). The large magnitude of this deficit has been an enigma since it cannot be explained by shallow creep during the interseismic period or by triggered slip from nearby earthquakes. One potential explanation for the SSD is that the previous geodetic inversions used incomplete data that do not go close to fault so the shallow portions of the slip models were poorly resolved and generally underestimated. In this study we improve the geodetic inversion, especially at shallow depth by: 1) refining the InSAR processing with non-boxcar phase filtering, model-dependent range corrections, more complete phase unwrapping by SNAPHU using a correlation mask and allowing a phase discontinuity along the rupture; 2) including near-fault offset data from optical imagery and SAR azimuth offsets; 3) using more detailed fault geometry; 4) and using additional campaign GPS data. With these improved observations, the slip inversion has significantly increased resolution at shallow depth. For the Landers rupture the SSD is reduced from 45% to 16%. Similarly for the Hector Mine rupture the SSD is reduced from 15% to 5%. We are assembling all the relevant co-seismic data for the El Major-Cucapah earthquake and will report the inversion result with its SSD at the meeting.

  14. Modelling Paleoearthquake Slip Distributions using a Gentic Algorithm

    NASA Astrophysics Data System (ADS)

    Lindsay, Anthony; Simão, Nuno; McCloskey, John; Nalbant, Suleyman; Murphy, Shane; Bhloscaidh, Mairead Nic

    2013-04-01

    Along the Sunda trench, the annual growth rings of coral microatolls store long term records of tectonic deformation. Spread over large areas of an active megathrust fault, they offer the possibility of high resolution reconstructions of slip for a number of paleo-earthquakes. These data are complex with spatial and temporal variations in uncertainty. Rather than assuming that any one model will uniquely fit the data, Monte Carlo Slip Estimation (MCSE) modelling produces a catalogue of possible models for each event. From each earthquake's catalogue, a model is selected and a possible history of slip along the fault reconstructed. By generating multiple histories, then finding the average slip during each earthquake, a probabilistic history of slip along the fault can be generated and areas that may have a large slip deficit identified. However, the MCSE technique requires the production of many hundreds of billions of models to yield the few models that fit the observed coral data. In an attempt to accelerate this process, we have designed a Genetic Algorithm (GA). The GA uses evolutionary operators to recombine the information held by a population of possible slip models to produce a set of new models, based on how well they reproduce a set of coral deformation data. Repeated iterations of the algorithm produce populations of improved models, each generation better satisfying the coral data. Preliminary results have shown the GA to be capable of recovering synthetically generated slip distributions based their displacements of sets of corals faster than the MCSE technique. The results of the systematic testing of the GA technique and its performance using both synthetic and observed coral displacement data will be presented.

  15. Variable slip coefficient in binary lattice Boltzmann models

    NASA Astrophysics Data System (ADS)

    Szalmás, Lajos

    2008-12-01

    We present a new method in order to obtain variable slip coefficient in binary lattice Boltzmann models to simulate gaseous flows. We present the Boundary layer theory. We study both the single-and multi-fluid BGK-type models as well. The boundary slip and the Knudsen layer are analyzed in detail. Benchmark simulations are carried out in order to compare the analytical derivation with the numerical results. Excellent agreement is found between the two analytical formalism and the numerical simulations.

  16. Complementary slip distributions of 200 years of megathrust earthquakes

    NASA Astrophysics Data System (ADS)

    McCloskey, J.; NicBhloscaidh, M.; Naylor, M.

    2012-12-01

    Coral paleo-geodesy on the Mentawai Islands off western Sumatra has produced a multi-seismic-cycle geodetic record which provides physical constraints on the slip distributions of large and great earthquakes. Using a Monte Carlo forward modelling method we have estimated the slip on the great 1797 and 1833 earthquakes and show that their most likely slip distributions are not only complementary but leave unruptured areas on the megathrust which appear to have been filled by the M8.4 and 7.9 Bengkulu earthquakes and the M7.8 Pagai earthquake. These results are consistent with a model in which slip in future earthquakes is controlled not only by secular loading and stress interaction between recent earthquakes, but also by the stress footprints of previous earthquakes potentially over many earthquake cycles. We discuss these results in the context of recent great earthquakes and suggest a mathematical formalism which unites observations of the evolution of slip deficit through heterogeneous tectonic loading, seismic and aseismic slip over many earthquakes. We apply the method to the Mentawai region including 330 years of heterogeneous loading of the Sunda megathrust and slip due to more than 30 historical and instrumentally recorded earthquakes. This complex slip deficit field is heterogeneous not only in the strain energy but also in the resolution and we introduce a new technique to clearly visualise both. We show that these results are consistent with the well published threat of a large tsunamigenic earthquake off western Sumatra and make some comments on constraining the threat.

  17. Foreshocks during the nucleation of stick-slip instability

    USGS Publications Warehouse

    McLaskey, Gregory C.; Kilgore, Brian D.

    2013-01-01

    We report on laboratory experiments which investigate interactions between aseismic slip, stress changes, and seismicity on a critically stressed fault during the nucleation of stick-slip instability. We monitor quasi-static and dynamic changes in local shear stress and fault slip with arrays of gages deployed along a simulated strike-slip fault (2 m long and 0.4 m deep) in a saw cut sample of Sierra White granite. With 14 piezoelectric sensors, we simultaneously monitor seismic signals produced during the nucleation phase and subsequent dynamic rupture. We observe localized aseismic fault slip in an approximately meter-sized zone in the center of the fault, while the ends of the fault remain locked. Clusters of high-frequency foreshocks (Mw ~ −6.5 to −5.0) can occur in this slowly slipping zone 5–50 ms prior to the initiation of dynamic rupture; their occurrence appears to be dependent on the rate at which local shear stress is applied to the fault. The meter-sized nucleation zone is generally consistent with theoretical estimates, but source radii of the foreshocks (2 to 70 mm) are 1 to 2 orders of magnitude smaller than the theoretical minimum length scale over which earthquake nucleation can occur. We propose that frictional stability and the transition between seismic and aseismic slip are modulated by local stressing rate and that fault sections, which would typically slip aseismically, may radiate seismic waves if they are rapidly stressed. Fault behavior of this type may provide physical insight into the mechanics of foreshocks, tremor, repeating earthquake sequences, and a minimum earthquake source dimension.

  18. Fault slip during a glacial cycle

    NASA Astrophysics Data System (ADS)

    Steffen, Rebekka; Wu, Patrick; Steffen, Holger; Eaton, Dave

    2013-04-01

    Areas affected by glacial isostatic adjustment (GIA) generally show uplift after deglaciation. These regions are also characterized by a moderate past and present-day seismicity, at seismic moment release rates that exceed those expected under stable tectonic conditions. Several faults have been found in North America and Europe, which have been activated during or after the last deglaciation. Large-magnitude earthquakes have generated fault offsets of up to 120 m. Due to the recent melting of Greenland and Antarctic ice sheets, an understanding of the occurrence of these earthquakes is important. With a new finite-element model, we are able to estimate, for the first time, fault slip during a glacial cycle for continental ice sheets. A two-dimensional earth model based on former GIA studies is developed, which is loaded with a hyperbolic ice sheet. The fault is able to move in a stress field consisting of rebound stress, tectonic background stress, and lithostatic stress. The sensitivity of this fault is tested regarding lithospheric and crustal thickness, viscosity structure of upper and lower mantle, ice-sheet thickness and width, and fault parameters including coefficient of friction, depth, angle and location. Fault throws of up to 30 m are obtained using a fault of 45° dipping below the ice sheet centre. The thickness of the crust is one of the major parameters affecting the total fault throw, e.g. higher values for a thinner crust. Most faults start to move close to the end of deglaciation, and movement stops after one thrusting/reverse earthquake. However, certain conditions may also lead to several fault movements after the end of glaciations.

  19. Predicting apparent slip at liquid-liquid interfaces without an interface slip condition

    NASA Astrophysics Data System (ADS)

    Poesio, Pietro; Damone, Angelo; Matar, Omar

    2015-11-01

    We show that if we include a density-dependent viscosity into the Navier-Stokes equations then we can describe, naturally, the velocity profile in the interfacial region, as we transition from one fluid to another. This requires knowledge of the density distribution (for instance, via Molecular Dynamics [MD] simulations, a diffuse-interface approach, or Density Functional Theory) everywhere in the fluids, even at liquid-liquid interfaces where regions of rapid density variations are possible due to molecular interactions. We therefore do not need an artificial interface condition that describes the apparent velocity slip. If the results are compared with the computations obtained from MD simulations, we find an almost perfect agreement. The main contribution of this work is to provide a simple way to account for the apparent slip at liquid-liquid interfaces without relying upon an additional boundary condition, which needs to be calculated separately using MD simulations. Examples are provided involving two immiscible fluids of varying average density ratios, undergoing simple Couette and Poisseuille flows. MIUR through PRIN2012-NANOBridge; Royal Society International Exchange Scheme (IE141486).

  20. Origins of oblique-slip faulting during caldera subsidence

    NASA Astrophysics Data System (ADS)

    Holohan, Eoghan P.; Walter, Thomas R.; SchöPfer, Martin P. J.; Walsh, John J.; Wyk de Vries, Benjamin; Troll, Valentin R.

    2013-04-01

    Although conventionally described as purely dip-slip, faults at caldera volcanoes may have a strike-slip displacement component. Examples occur in the calderas of Olympus Mons (Mars), Miyakejima (Japan), and Dolomieu (La Reunion). To investigate this phenomenon, we use numerical and analog simulations of caldera subsidence caused by magma reservoir deflation. The numerical models constrain mechanical causes of oblique-slip faulting from the three-dimensional stress field in the initial elastic phase of subsidence. The analog experiments directly characterize the development of oblique-slip faulting, especially in the later, non-elastic phases of subsidence. The combined results of both approaches can account for the orientation, mode, and location of oblique-slip faulting at natural calderas. Kinematically, oblique-slip faulting originates to resolve the following: (1) horizontal components of displacement that are directed radially toward the caldera center and (2) horizontal translation arising from off-centered or "asymmetric" subsidence. We informally call these two origins the "camera iris" and "sliding trapdoor" effects, respectively. Our findings emphasize the fundamentally three-dimensional nature of deformation during caldera subsidence. They hence provide an improved basis for analyzing structural, geodetic, and geophysical data from calderas, as well as analogous systems, such as mines and producing hydrocarbon reservoirs.

  1. Texture and pyramidal slip in Ti, Zr and their alloys

    SciTech Connect

    Pochettino, A.A.; Gannio, N. ); Edwards, C.V. ); Penelle, R. )

    1992-12-15

    Zirconium, titanium and their alloys have a high anisotropic plastic behavior. One way to show this behavior is to analyze the evolution of the Lankford coefficient (R ([alpha]), values of which are obtained from tensile tests along different directions in the sheet plane). The variation of R([alpha]) can be explained from the crystallographic texture and the active deformation mechanisms. Microstructural observations show that prismatic slip is the most active deformation mode in these materials, but no dimensional change in the [lt][bar c][gt] direction of grains is possible by the activation of the (10[bar 1]0) [lt] 1[bar 2]10[gt] slip alone; so deformation along [0001] has to be accommodated either by (10[bar 1]o) [lt]1[bar 2]13[gt] (or [lt][bar c] + [bar a][gt]) pyramidal slip or by twinning. Many transmission electron microscopy (TEM) studies have shown evidence for [lt][bar c] + [bar a][gt] slip activity, and some authors have reported slip on (1[bar 1]01) planes in Ti alloys. The purpose of this paper is to contribute with another analysis of pyramidal slip activity in hcp textured materials, such as Ti and Zr alloys, and of the hardening mechanisms for this deformation mode. This analysis is performed both in a direct way, by means of TEM observations of deformed samples, and in an indirect way, by different mechanical tests.

  2. Steadily propagating slip pulses driven by thermal decomposition

    NASA Astrophysics Data System (ADS)

    Platt, John D.; Viesca, Robert C.; Garagash, Dmitry I.

    2015-09-01

    Geophysical observations suggest that mature faults weaken significantly at seismic slip rates. Thermal pressurization and thermal decomposition are two mechanisms commonly used to explain this dynamic weakening. Both rely on pore fluid pressurization with thermal pressurization achieving this through thermal expansion of native solids and pore fluid and thermal decomposition by releasing additional pore fluid during a reaction. Several recent papers have looked at the role thermal pressurization plays during a dynamically propagating earthquake, but no previous models have studied the role of thermal decomposition. In this paper we present the first solutions accounting for thermal decomposition during dynamic rupture, solving for steady state self-healing slip pulses propagating at a constant rupture velocity. First, we show that thermal decomposition leads to longer slip durations, larger total slips, and a distinctive along-fault slip rate profile. Next, we show that accounting for more than one weakening mechanism allows multiple steady slip pulses to exist at a given background stress, with some solutions corresponding to different balances between thermal pressurization and thermal decomposition, and others corresponding to activating a single reaction multiple times. Finally, we study how the rupture properties depend on the fault properties and show that the impact of thermal decomposition is largely controlled by the ratio of the hydraulic and thermal diffusivities χ = αhy/αth and the ratio of pore pressure generated to temperature rise buffered by the reaction Pr/Er.

  3. Effects of Aging on the Biomechanics of Slips and Falls

    PubMed Central

    Lockhart, Thurmon E.; Smith, James L.; Woldstad, Jeffrey C.

    2010-01-01

    Although much has been learned in recent decades about the deterioration of muscular strength, gait adaptations, and sensory degradation among older adults, little is known about how these intrinsic changes affect biomechanical parameters associated with slip-induced fall accidents. In general, the objective of this laboratory study was to investigate the process of initiation, detection, and recovery of inadvertent slips and falls. We examined the initiation of and recovery from foot slips among three age groups utilizing biomechanical parameters, muscle strength, and sensory measurements. Forty-two young, middle-age, and older participants walked around a walking track at a comfortable pace. Slippery floor surfaces were placed on the track over force platforms at random intervals without the participants’ awareness. Results indicated that younger participants slipped as often as the older participants, suggesting that the likelihood of slip initiation is similar across all age groups; however, older individuals’ recovery process was much slower and less effective. The ability to successfully recover from a slip (thus preventing a fall) is believed to be affected by lower extremity muscle strength and sensory degradation among older individuals. Results from this research can help pinpoint possible intervention strategies for improving dynamic equilibrium among older adults. PMID:16553061

  4. Stick-slip statistics of a physical slider block model

    NASA Astrophysics Data System (ADS)

    Brueckl, Ewald; Lederbauer, Stefan; Mertl, Stefan; Roch, Karl-Heinz

    2010-05-01

    An exhibition concerning the various scientific, technical, and social aspects of earthquakes has been organized as an Austrian contribution to IYPE - International Year of Planet Earth. In order to support the understanding of the elastic rebound theory a physical slider block model has been constructed. This model consists of a granite base plate and a granite slider block, connected to a lever by a leaf spring. The lever is driven parallel to the base plate with a constant speed in the range of 1 - 10 mm/s. The lever can move about 1 m in one direction. Thereafter the polarity of displacement is changed automatically. Opto-electronic distance measuring modules measure the displacement of the constantly moving lever and the stick-slip movement of the slider block. A geophone mounted on the slider block receives the vibrations of the slider block during the slip. From theory a periodic slip has to be expected. However, because of slight spatial changes of friction between the base plate and the slider block, individual slip distances vary in the range of 2 - 20 mm. Besides the speed of the lever further parameters of the physical slider block model can be varied: normal force between base plate and slider block, grain size and thickness of quartz sand simulating fault gouge, and stiffness of the leave spring. The stick slip statistics and derived quantities (e.g., stress release) will be shown and the influence of the variable parameters on the stick slip behaviour analyzed.

  5. Slipped capital femoral epiphysis as a complication of growth hormone therapy.

    PubMed

    Wang, Shuo-Yu; Tung, Yi-Ching; Tsai, Wen-Yu; Chien, Yin-Hsiu; Lee, Jing-Sheng; Hwu, Wuh-Liang

    2007-02-01

    Slipped capital femoral epiphysis (SCFE) is a rare complication of growth hormone (GH) therapy. Here, we report three patients who developed SCFE during GH therapy. The first two patients had hypopituitarism and had started GH therapy at the age of 15 years 6 months and 13 years 9 months, respectively. SCFE developed 4 years and 1 year after GH therapy, respectively. The third patient had Prader-Willi syndrome with obesity and hypogonadism and began GH therapy at the age of 12 years and 11 months. SCFE developed 2 months after starting GH therapy. Pain over the hip joints or over the knees is an early sign of SCFE. Despite recommendation, none of the three patients continued GH therapy. A high index of suspicion during GH therapy in patients at high risk of SCFE is important for early diagnosis and appropriate management. PMID:17493896

  6. Joint Enrollment Report, 2014

    ERIC Educational Resources Information Center

    Iowa Department of Education, 2014

    2014-01-01

    The Iowa Department of Education collects information on joint enrollment in Iowa's 15 community colleges. Jointly enrolled students are high school students enrolled in community college credit coursework. Most jointly enrolled students enroll through Senior Year Plus (SYP) programs such as Postsecondary Enrollment Options (PSEO) and concurrent…

  7. Sacroiliac joint imaging.

    PubMed

    Tuite, Michael J

    2008-03-01

    The sacroiliac (SI) joint has several unique anatomical features that make it one of the more challenging joints to image. The joint is difficult to profile well on radiographic views, and therefore the radiographic findings of sacroiliitis are often equivocal. Computed tomography images can usually show the findings of sacroiliitis and osteoarthritis earlier than radiographs. Magnetic resonance imaging performed with proper sequences is excellent for diagnosing even very early sacroiliitis and for following treatment response. The SI joint is often involved in patients with osteoarthritis or one of the inflammatory spondyloarthritides, most notably ankylosing spondylitis. Ankylosing spondylitis often presents with sacroiliitis, which appears as erosions, sclerosis, and joint space narrowing, eventually leading to ankylosis. Several disorders can cause sacroiliitis-like changes of the joint, including hyperparathyroidism and repetitive shear-stress injuries in athletes. The joint can become painful during pregnancy as it widens and develops increased motion, and some postpartum women develop iliac sclerosis adjacent to the joint termed osteitis condensans ilii. Another cause of SI joint pain is a disorder called sacroiliac joint dysfunction, which typically has few abnormal imaging findings. Patients with SI joint dysfunction, as well as sacroiliitis, often get relief from image-guided SI joint therapeutic injections. PMID:18382946

  8. Scaling of micro-slip in tangentially loaded rock contact

    NASA Astrophysics Data System (ADS)

    Grzemba, Birthe; Pohrt, Roman; Teidelt, Elena; Popov, Valentin L.

    2014-05-01

    A dry contact between randomly rough surfaces is examined which is loaded in normal and tangential direction. If the tangential load is below the friction force, no macroscopic tangential movement takes place. Nevertheless, some part of the contact area will be in sticking and some will be in sliding state depending on the local stress configuration. This effect will be called micro-slip. The maximum value of this micro-slip is reached when the last contacting spot goes into sliding state. The maximum micro-slip is a core characteristic of the contact problem. It appears in rock friction laws as a characteristic length parameter, which is often empirically determined. It can be interpreted as the characteristic size of micro-contacts appearing in rate-and-state friction theory (1). The scaling behavior of this characteristic length parameter is not yet clarified (2). It is of special interest for geophysical applications, where laboratory experiments and real systems differ in size by several orders of magnitude. In former works many suggestions have been made on the scaling context of this length parameter: surface roughness, total slip length, shear strain and system size ((1),(3),(4),(5)) are some of the proposed connected parameters. We recently presented a theoretical estimation of the maximum micro-slip for randomly rough surfaces, which is based on the iterrelation of the normal and tangential contact problem. Using recent finding concerning the normal contact problem of randomly rough surfaces (6) we were able to suggest a scaling law for the maximum micro-slip. It suggests a power-law scaling with the present normal force (7). A numerical contact model using the boundary element method was implemented for comparison, both results coincide perfectly. In addition we will present experiments with rock-rock contact in the preface of instable sliding. The set-up is a single-block slider model. From high resolution measurements, we were able to capture the micro-slip preceding a global slip event in a stick-slip regime, including the maximum micro-slip. 1. Dieterich, James H. Time Dependent Friction and the Mechanics of Stick-Slip. 1978, Pure and Applied Geophysics, Vol. 116, pp. 790-806. 2. Scholz, C. H. The Critical Slip Distance for Seismic Faulting. 22/29, 1988, Nature, Vol. 336, pp. 761-763. 3. Ohnaka, M. A constitutive scaling law and a unified comprehension for frictional slip failure, shear fracture of intact rock, and earthquake rupture.B2, 2003, Journal of Geophysical Research: Solid Earth, Vol. 108, p. 2080. 4. Marone, C. and Kilgore, B. Scaling of critical slip distance for seismic faulting with shear strain in fault zones. 1993, Nature, Vol. 362, pp. 618-621. 5. Marone, C. and Cox, S.J.D. Scaling of Rock Friction Constitutive Parameters: The Effects of Surface Roughness and Cumulative Offset on Friction of Gabbro. 1994, Pure and Applied Geophysics, Vol. 143, pp. 359-385. 6. Pohrt, R. and Popov, V.L. Normal Contact Stiffness of Elastic Solids with Fractal Rough Surfaces. 2012, Physical Review Letters, Vol. 108, p. 104301. 7. Grzemba, B., et al. Maximum micro-slip in tangential contact of randomly rough self-affine surfaces. 2014, Wear, Vol. 309, pp. 256-258.

  9. Arch & Chord Joint Detail; Crossbracing Center Joint Detail; Chord, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Arch & Chord Joint Detail; Crossbracing Center Joint Detail; Chord, Panel Post, Tie & Diagonal Brace Joint Detail; Chord, Panel Post, Tie & Crossbracing Joint Detail - Dunlapsville Covered Bridge, Spanning East Fork Whitewater River, Dunlapsville, Union County, IN

  10. Joint slippage in the Hoffmann external fixator. No effect of loading rate in bench experiments.

    PubMed

    Drijber, F L; Finlay, J B

    1991-12-01

    For tibial fractures, half-frames, such as the Hoffmann fixation device, sometimes fail when subjected to weight-bearing loads. Because the joints of the Hoffmann system are known to slip, which could lead to frame failure, three interfaces of the standard Hoffmann joint were tested at different clamp torques and different rates of load application. No difference in mean slippage values was noted for any interface at similar clamp torques. Joint slippage and any subsequent frame failure are thus not related to rate of load application, but to the magnitude of the load alone. PMID:1767642

  11. Nucleation of Dynamic Slip on a Hydraulically Fractured Fault

    NASA Astrophysics Data System (ADS)

    Azad, M. H.; Garagash, D.; Satish, M.

    2014-12-01

    This work is concerned with the relationship between hydraulic fracturing injection and induced seismicity on a fault. This is applicable to safety hazard assessment of the nucleation of dynamic slip along the fault as a result of hydraulic fracturing injection into or near the fault. The hydraulic fracture (HF) injection into the fault can be purposeful, for instance to trigger an earthquake in more controllable conditions than would happen otherwise; or in order to use the open portion of the fault as a reservoir heat exchanger for the extraction of geothermal heat. It can be unintentional due to lack of accurate subsurface characterization prior to the injection. Injection with constant flow rate into an impermeable fault will initiate slip along the fault. The slip occurs due to the lack of frictional strength along the open part of the fault (the hydraulic fracture) as well as from the reduction of the normal stress ahead of the hydraulic fracture front. Slip in front of the hydraulic fracture is assumed to degrade the tensile strength of the fault to zero, so that the hydraulic fracture propagation takes place in the viscous-dominated regime (i.e. dominated by viscous losses in the fluid flow inside the fracture). In our model, the nucleation of dynamic slip is related to the slip-weakening nature of the friction, and depends on in-situ stresses, pressure distribution inside the hydraulic fracture, and the evolving length of the hydraulic fracture. The results of this study show that the growth of the fault slipping patch remains stable, with no episode of dynamic rupture, when the background shear stress τb is smaller than the residual shear strength τr of the fault under ambient conditions. Otherwise (τb > τr), nucleation takes place when the extent of the hydraulic fracture reaches the critical length ~ (μ/τp) δc, where μ is the elastic shear modulus of the rock, τp is the peak shear strength of the fault, and δc is the characteristic slip weakening distance. The size of the slipping patch ahead of the HF tip obeys roughly similar scaling. This scaling changes when τb is just slightly larger than τr in which case both critical hydraulic fracture and slipping patch lengths increase strongly with diminishing τb, and become unbounded when stress stability boundary (τb= τr) is approached.

  12. Effects of Tidal Modulation in Heterogeneous Models of Slow Slip

    NASA Astrophysics Data System (ADS)

    Skarbek, R. M.; Rempel, A. W.; Thomas, A.

    2014-12-01

    Since their discovery, numerous models have been put forward to explain the occurance of slow slip and associated tremor. These models invoke a wide array of causal mechanisms and are all successful in reproducing the first-order behavior of slow-slip events. Discriminating amongst the various proposed models requires looking at second-order effects of slow slip and tremor. Here, we consider the effects of tidal modulation on slow slip in subduction zones. A great deal of observational evidence has established that slow-slip and associated tremor are modulated by the small stress perturbations associated with tides and teleseismic events. Recent modeling studies that have examined the influence of tidal stresses (<10 kPa) have focused either on the effects of tidally induced changes in shear stress, or on changes in shear and normal stress that coincide. However, along the Cascadia margin, the relative phase of the tidally induced fault-normal and shear stresses depends on position along the plate boundary fault, and can vary from being in phase, to completely out of phase. We report on the predictions of models designed to examine the sensitivity of slow-slip in subduction zones to the phase shift γ between tidally induced normal and shear stress perturbations. We consider both simple spring-slider and 1-D elastodynamic models that are designed to mimic the effects of geologic heterogeneity by allowing for variations in the rate-and-state frictional parameters. For a given slow-slip event, spring-slider results indicate that the phase lag γv between the peak slip rate and the tidally induced shear stress perturbation depends on both the phase shift γ, and the perturbation amplitude. Models parameterized for Cascadia are capable of producing phase lags γv within the range (15◦ to 30◦) of those reported by Royer et al. (JGR, 2014). Additionally, our models predict that the correlation between tidally induced shear stress perturbations and resultant slip also depends on the phase shift γ. Our results indicate that the influence of tides, especially the effects of phase differences between tidaly induced shear and normal stresses, must be taken into account when evaluating the physical mechanisms of slow-slip and tremor.

  13. Reactivated strike slip faults: examples from north Cornwall, UK

    NASA Astrophysics Data System (ADS)

    Kim, Young-Seog; Andrews, Jim R.; Sanderson, David J.

    2001-10-01

    Several strike-slip faults at Crackington Haven, UK show evidence of right-lateral movement with tip cracks and dilatational jogs, which have been reactivated by left-lateral strike-slip movement. Evidence for reactivation includes two slickenside striae on a single fault surface, two groups of tip cracks with different orientations and very low displacement gradients or negative (left-lateral) displacements at fault tips. Evidence for the relative age of the two strike-slip movements is (1) the first formed tip cracks associated with right-lateral slip are deformed, whereas the tip cracks formed during left-lateral slip show no deformation; (2) some of the tip cracks associated with right-lateral movement show left-lateral reactivation; and (3) left-lateral displacement is commonly recorded at the tips of dominantly right-lateral faults. The orientation of the tip cracks to the main fault is 30-70° clockwise for right-lateral slip, and 20-40° counter-clockwise for left-lateral slip. The structure formed by this process of strike-slip reactivation is termed a "tree structure" because it is similar to a tree with branches. The angular difference between these two groups of tip cracks could be interpreted as due to different stress distribution (e.g., transtensional/transpressional, near-field or far-field stress), different fracture modes or fractures utilizing pre-existing planes of weakness. Most of the d- x profiles have similar patterns, which show low or negative displacement at the segment fault tips. Although the d- x profiles are complicated by fault segments and reactivation, they provide clear evidence for reactivation. Profiles that experienced two opposite slip movements show various shapes depending on the amount of displacement and the slip sequence. For a larger slip followed by a smaller slip with opposite sense, the profile would be expected to record very low or reverse displacement at fault tips due to late-stage tip propagation. Whereas for a smaller slip followed by larger slip with opposite sense, the d- x profile would be flatter with no reverse displacement at the tips. Reactivation also decreases the ratio of dmax/ L since for an original right-lateral fault, left lateral reactivation will reduce the net displacement ( dmax) along a fault and increase the fault length ( L). Finally we compare Crackington Haven faults with these in the Atacama system of northern Chile. The Salar Grande Fault (SGF) formed as a left-lateral fault with large displacement in its central region. Later right-lateral reactivation is preserved at the fault tips and at the smaller sub-parallel Cerro Chuculay Fault. These faults resemble those seen at Crackington Haven.

  14. Slip Running Reconnection in Magnetic Flux Ropes

    NASA Astrophysics Data System (ADS)

    Gekelman, W. N.; Van Compernolle, B.; Vincena, S. T.; De Hass, T.

    2012-12-01

    Magnetic flux ropes are due to helical currents and form a dense carpet of arches on the surface of the sun. Occasionally one tears loose as a coronal mass ejection and its rope structure can be detected by satellites close to the earth. Current sheets can tear into filaments and these are nothing other than flux ropes. Ropes are not static, they exert mutual ěc{J}×ěc{B} forces causing them to twist about each other and eventually merge. Kink instabilities cause them to violently smash into each other and reconnect at the point of contact. We report on experiments on two adjacent ropes done in the large plasma device (LAPD) at UCLA ( ne ˜ 1012, Te ˜ 6 eV, B0z=330G, Brope}\\cong{10G,trep=1 Hz). The currents and magnetic fields form exotic shapes with no ignorable direction and no magnetic nulls. Volumetric space-time data (70,600 spatial locations) show multiple reconnection sites with time-dependent locations. The concept of a quasi-separatrix layer (QSL), a tool to understand and visualize 3D magnetic field lines reconnection without null points is introduced. Three-dimensional measurements of the QSL derived from magnetic field data are presented. Within the QSL field lines that start close to one another rapidly diverge as they pass through one or more reconnection regions. The motion of magnetic field lines are traced as reconnection proceeds and they are observed to slip through the regions of space where the QSL is largest. As the interaction proceeds we double the current in the ropes. This accompanied by intense heating as observed in uv light and plasma flows measured by Mach probes. The interaction of the ropes is clearly seen by vislaulizng magnetic field data , as well as in images from a fast framing camera. Work supported by the Dept. of Energy and The National Science Foundation, done at the Basic Plasma Science Facility at UCLA.Magnetic Field lines (measured) of three flux ropes and the plasma currents associated with them

  15. Slipped capital femoral epiphysis (SCFE): a 12-year review.

    PubMed

    Kamarulzaman, M A; Abdul Halim, A R; Ibrahim, S

    2006-02-01

    Slipped capital femoral epiphysis (SCFE) is a relatively uncommon hip disorder in adolescents and its prevalence in Malaysia has not been studied. This retrospective study is undertaken to provide an overview of a 12-year review of SCFE treated in our institution. Fourteen patients (19 hips) with slipped capital femoral epiphysis (SCFE) admitted to Hospital UKM from 1990 to 2002 were reviewed with respect to demographic profile, functional outcome according to the Iowa Hip Score, and complications. There were ten boys (average age, 12.5 years) and four girls (average age, 12 years). Eight were Malays and six were Indians. The average body mass index was 26.1 verweight). The left hips (11 hips) were affected more than the right hips (eight hips). Five patients had bilateral slips. Thirteen hips were considered stable while the other six hips were unstable. The majority of cases were moderate slips (12 hips), four hips had severe slips while three hips had mild slips. Several methods of treatment were instituted. These include in situ cannulated screw fixation (11 hips), Knowles pin fixation (three hips) and gentle closed manipulative reduction with cannulated screw fixation (three hips). One patient with bilateral slips refused surgical treatment. Based on the Iowa Hip Score, most patients (nine) had satisfactory results (excellent or good), three had fair results while one patient had a poor result. Avascular necrosis developed in five hips while chondrolysis occurred in one hip. In situ cannulated screw fixation is the treatment of choice. SCFE is an uncommon condition in Malaysia. PMID:17042235

  16. Seismic velocity change and slip rate during the 2006 Guerrero (Mexico) slow slip event

    NASA Astrophysics Data System (ADS)

    Rivet, Diane; Radiguet, Mathilde; Campillo, Michel; Cotton, Fabrice; Shapiro, Nikolai; Krishna Singh, Shri; Kostoglodov, Vladimir

    2010-05-01

    We measure temporal change of the seismic velocity in the crust below the Guerrero region during the 2006 slow sleep event (SSE). We use repeated cross-correlations of ambient seismic noise recorded at 26 broad-band stations of the MesoAmerica Seismic Experiment (MASE). The cross-correlations are computed over 90 days with a moving window of 10 days from January 2005 to July 2007. To insure measurements independent of noise source variations, we only take into account the travel time change within the coda. For period of 8 to 20s, we observe a decrease in velocity starting in April 2006 with a maximum change of -0.3% of the initial velocity in June 2006. At these periods, the Rayleigh waves are sensitive to velocity changes down to the lower crust. In the other hand, we compute the deformation rate below the MASE array from a slip propagation model of the SSE observed by means of the displacement time-series of 15 continuous GPS stations. Slip initiates in the western part of the Guerrero Gap and propagates southeastward. The propagation velocity is of the order of 1 km/day. We then compare the seismic velocity change measured from continuous seismological data with the deformation rate inferred from geodetic measurements below the MASE array. We obtain a good agreement between the time of maximal seismic velocity change (July 2006) and the time of maximum deformation associated with the SSE (July to August 2006). This result shows that the long-term velocity change associated with the SSE can be detected using continuous seismic recordings. Since the SSE does not emit seismic waves, which interact with the superficial layers, the result indicates that the velocity change is due to deformation at depth.

  17. Interaction between slip events, erosion and sedimentation along an active strike-slip fault: Insights from analog models

    NASA Astrophysics Data System (ADS)

    Chatton, M.; Malavieille, J.; Dominguez, S.; Manighetti, I.; Romano, C.; Beauprêtre, S.; Garembois, S.; Larroque, C.

    2012-04-01

    Recovering information on past (i.e., last 102-104 yrs) large earthquakes on faults is a challenge. The classical approach -especially used on strike-slip faults- consists in searching morphological markers such as river channels, streams, alluvial fans, ridges or terrace risers, etc, that would be offset by the fault, and measure these offsets by reconstructing the original position and shape of the markers. Combined with the dating of the offset markers, this morphotectonic paleoseismological approach may provide information on the slips and ages of the most recent earthquakes on the fault under study. Yet, the approach is complex as it depends on the recognition of unambiguous paired markers on either side of the fault. And our capability to recognize similar markers on either side of a fault in turn greatly depends on the 'evolution' that these markers may have sustained subsequently to their very first slip disruption. Did the repeating earthquake slip events modify their surface appearance? Did their morphology and position (ex: burying, destruction, modification, etc) evolve with the sedimentation and erosion that might have occurred during the fault history? Etc. These questions have rarely been approached for they are difficult to address in natural settings. And as we are unable to answer them in the natural cases that we study, the slip reconstructions that we provide are generally uncertain as they are likely based on an incomplete or biased record of the past fault slips. Therefore, the objective of our work is to contribute to better understand and document the nature and 'evolution' of the morphological markers that are commonly used in morphotectonic and paleoseismological analyses, especially along strike-slip faults. We approach these questions experimentally. We have developed an original experimental set-up made to simulate repeated slip events on a strike-slip fault placed in a wet environment sustaining sedimentation and erosion. The fault device is indeed coupled with a rainfall system, while an optical measurement apparatus that includes digital cameras and a laser interferometer, allows observing and measuring continuously at very high resolution the evolution of the model surface morphology. The analog material is a mix of granular materials -glass microbeads, silica powder and plastic powder saturated in water, whose mass composition and, consequently, mechanical properties lead to a geometric scaling of about 1:10 000 and to a temporal scaling on the order of one second equivalent to a few dozens of years. The protocol allows monitoring together the evolution of the fault and that of the morphological markers that the fault progressively offsets as slip events are imposed. We have conducted several experiences in different settings and we will present the preliminary results that we have obtained. We basically could survey the formation and evolution of a strike-slip fault from its immature stages up to one hundred repeated slip events. Under the combined effects of accumulating slip, erosion and sedimentation, the model surface exhibits tectonic and morphological structures similar to natural features (Riedel's shears, pressure and shutter ridges, pull-apart basins, alluvial fans, terrace risers, braided rivers, etc), whose space and time evolution can be precisely analyzed. Deformation partitioning, sequential formation of alluvial terraces, stream captures, development of 'traps' filling with sediments, etc, are especially observed. The control on the imposed amplitude and frequency of the rainfall cycles allows us to examine the impact of these rainfalls on the fault morphology and the evolution of the associated morphological markers. Finally, we can compare the imposed slip events (number, amplitudes, repeat times) with the cumulative offsets eventually visible and measurable at the model surface. Marked discrepancies are found between imposed and final apparent offsets that shed light on the uncertainties that may affect the morphological and paleoseismological analyses performed on natural cases. We apply our results to further analyze one natural fault site in New Zealand (Terako, Hope fault), described in another session (Beauprêtre et al.).

  18. Late Quaternary Slip Rates of the Sumatran Fault

    NASA Astrophysics Data System (ADS)

    Bradley, K.; Sieh, K.; Natawidjaja, D.; Daryono, M. R.

    2013-12-01

    The Sumatran Fault accommodates a large portion of the right-lateral, trench-parallel component of relative motion between the northward-subducting India-Australia plates and the overriding Sunda plate. Slip rate estimates for this strike-slip fault have primarily been calculated by dividing the observed horizontal deflection across the fault trace of river valleys incised into voluminous caldera-derived tuffs by the radiometrically-dated eruption age of those tuffs, or by estimating the age of displaced river valleys from the length of the displaced channels [1]. These slip rates exhibited a dramatic northward increase in trench-parallel relative displacement that would have to be accommodated by trench-parallel stretching of the forearc sliver [2]. We present new slip rate estimates for the Sumatran Fault where it traverses the Toba, Maninjau, and Ranau tuffs in northern, central, and southern Sumatra. We re-mapped the deflected drainage networks using high-resolution satellite imagery, digital topography, and field observations. At Toba, the best-fitting slip rate is 13.8 × 0.3 mm/yr, about half the previously published estimate. At Maninjau, the best-fitting slip rate is 14.8 × 0.4 mm/yr, faster than the previous estimates of ~10-11 mm/yr. While a new slip rate for the Ranau area is pending the results of radiometric dating of the incised tuffs, we mapped lateral displacements of river valleys of ~230 m, much smaller than previously estimated displacement of ~2,500 m. The revised Late Pleistocene slip rates at Toba and Maninjau are similar to each other and compare favourably with recent GPS-derived slip-rate estimates for several segments of the Sumatran Fault, suggesting that ~40% of the trench-parallel displacement between the forearc islands and the backarc is accommodated on structures other than the Sumatran Fault [3], and that this situation has persisted for at least the past 50,000 to 74,000 years. [1](Bellier and Sébrier, GRL v.22, 1995) [2] (McCaffrey, Geology v.19, 1992) [3] (Feng et al., in prep.)

  19. How well do surface offsets represent earthquake slip at depth?

    NASA Astrophysics Data System (ADS)

    Haddad, D. E.; Zielke, O.; Arrowsmith, R.

    2013-12-01

    Earthquake ruptures originate in the base of the unstable velocity-weakening part of the seismogenic layer and propagate into the velocity-strengthening upper stability region. Resulting deformation is transmitted to Earth's topography by driving slip along faults and block motions. Two factors affect this process: (1) the three-dimensional geometrical complexity and roughness of fault segments that control rupture continuity, and (2) spatiotemporal strength variations of the seismogenic layer that control the mechanical behavior of the fault zone. Earth's topography preserves evidence of past earthquakes as localized strain along fault scarps and fractures or distributed strain via off-fault folding and warping. These structures may be modified postseismically via afterslip and geomorphically degraded years to decades after rupturing. We investigate how well displaced geomorphic markers represent coseismic slip as it is transmitted from the seismogenic layer through to Earth's surface. We use lidar-derived measurements of single- and multi-event offset geomorphic markers to provide surface constraints on surface slip distributions of past earthquakes. Using FIMozFric, a numerical earthquake simulator that incorporates complex geomechanical properties of the seismogenic layer, we test various fault structural configurations and mechanical properties of the 2010 El Mayor-Cucupah earthquake. Initial simulations investigate the effect of simple fault complexities, such as stepovers and bends, on surface offsets using a simple two-layered seismogenic zone geometry. We then explore the effect of varying the mechanical complexity of the seismogenic zone by varying the relative geometries of the velocity-weakening and velocity-strengthening portions, thus simulating the variable mechanical properties of the upper lithosphere through which earthquakes propagate. Our results show that the geometrical complexity of faults controls the distribution of surface slip. More importantly, our simulations demonstrate that the mechanical configuration of the seismogenic layer within which faults are embedded affects how slip is distributed along single fault geometries and partitioned across zones with multiple fault strands. Variability in the depth of the velocity-weakening/velocity-strengthening interface appears to control the magnitude of single-event surface slip. These results shed light on the ability to confidently interpret paleoseismic and topographic records of the magnitude and recurrence of earthquakes, especially in relation to slip in a single earthquake. This is an especially important insight for efforts such as the Uniform California Earthquake Rupture Forecast (UCERF3) that aim to use lidar-derived slip in the most recent event as geologic constraints for expected slip magnitudes of future earthquakes but without accounting for the detailed lithology and structure of a fault zone.

  20. Stick-Slip Characteristics of Sheared Granular Layers

    NASA Astrophysics Data System (ADS)

    Mair, K.; Frye, K. M.; Marone, C.

    2001-12-01

    Repeating earthquakes are a stick-slip phenomenon and indicate that faults must re-strengthen between dynamic rupture events. Mechanisms of re-strengthening are not well understood however laboratory experiments can help examine candidate processes and determine their influence on fault stability. Here we demonstrate how loading rate and gouge characteristics affect the stick-slip dynamics of simulated faults. We shear granular layers composed of spherical particles under constant normal stress (5MPa) at a range of loading rates (0.1-1000μ m/s) in a direct shear apparatus. Layers were 3mm thick and had mean grain size of 60-250μ m. Low stress conditions help to minimize gouge evolution. During tests, we observe highly repetitive stick-slip events, characterized by a gradual increase in stress, a small inelastic rollover and a rapid dynamic stress drop with audible energy release. Stress drop amplitudes are 0.2-0.7MPa (15-30% of failure stress). The stick and slip phases directly correlate with dilation and compaction of the layer by a few μ m indicating dynamic reorganization of the particles. Analysis of many stick-slip cycles reveals a negative power law relation between loading rate and recurrence time. We also see a power law relation between stress drop amplitude and recurrence time indicating a 0.1MPa per decade healing rate. Mean grain size (or grain number) has a small but systematic influence on layer dilation. Details of the strength curves prior to failure and their relationship to dilation reveal the importance of micro-mechanical rearrangements during stick-slip. We suggest that the instabilities in our experiments reflect the formation and collapse of particle stress chains. Particle roughness and size distribution of granular gouge play a key role in determining slip stability and, for unstable conditions, stick-slip characteristics. Our data qualitatively agree with previous observations however the healing rate we see is somewhat reduced. We find that for low stress conditions and shear within granular materials, stick-slip dynamics are more strongly influenced by geometrical processes than by chemically-assisted mechanisms.

  1. Estimation method of slip surface by ground surface displacement

    NASA Astrophysics Data System (ADS)

    Ishida, K.; Fujisawa, K.; Kojima, S.; Tanaka, H.

    2007-12-01

    After a landslide has occurred, it is important to take emergency countermeasures as soon as possible to prevent the damage from worsening. To do this, it is necessary to quickly identify the characteristics and size of movement of the landslide. However, conventional methods such as investigating the slip surface by taking core samples and monitoring the movement of land mass using vertical boring holes is time-consuming and involves risk, as the work must be carried out directly on the unstable landslide. This paper introduces a method of estimating the depth of the landslide slip surface using by ground surface displacement. The method involves dividing the landslide block and deriving a formula that approximates the line of the slip surface. Inputs for this method include the lengthwise section of the ground surface, displacement of ground surface, points of the scarp and tip of the landslide. We applied this method to several landslides and proved that the slip surface estimated by this method closely matched the actual surface determined by conventional methods, provided that measuring points were properly arranged. The results suggest that this method can estimate the slip surface of landslides. In future, it is necessary to improve systems of monitoring active landslide masses and methods of estimating their size in a quick, easy, and reliable manner to be practically applicable to disaster areas.

  2. Dynamics of stick-slip motion, Whillans Ice Stream, Antarctica

    NASA Astrophysics Data System (ADS)

    Winberry, J. Paul; Anandakrishnan, Sridhar; Wiens, Douglas A.; Alley, Richard B.; Christianson, Knut

    2011-05-01

    The stick-slip motion and associated seismic emissions of Whillans Ice Stream (WIS), West Antarctica are two of the many recent observations of unexpected ice sheet behavior that are challenging traditional models of rapid glacier motion. Here we find that the WIS slip events repeatedly nucleate from a sticky-spot located in the middle of the ice stream, acting similar to an asperity in traditional models of earthquake physics. This region shows less motion than surrounding areas during the inter-slip periods, thus, concentrating stress and producing a pulse of seismic energy at the onset of slip. The propagating rupture breaks through an additional asperity in the northern part of the ice stream, producing another pulse of seismic energy 6-12 min after initiation. Both asperities are regions of higher hydraulic potential than surrounding regions, suggesting they may have greater bed friction due to reduced water lubrication. Tidal pacing of the stress accumulation combined with fault healing controls the applied stress at failure, with higher stress giving faster propagation of the rupture front and higher slip velocities; these differences are reflected in the timing of the teleseismic arrivals. Our results highlight both the great sensitivity of large ice streams to small changes in external forcing and the importance of limited regions of the subglacial bed in controlling their motion, as well as providing insights to the mechanics of repeating earthquakes.

  3. Research on slip resistance measurements--a new challenge.

    PubMed

    Kim, In-Ju; Nagata, Hisao

    2008-01-01

    Slips, trips and falls are one of the most common causes of injuries and fatalities in the general community and industry. The control of such incidents involves a complex array of factors including the characteristics of each individual's footwear and gait dynamics, walking and working surfaces, and environmental conditions. Notwithstanding this complexity, slip resistance properties have been widely measured as a form of coefficient of friction (COF) index at the sliding interface between the shoes and floors. Since the COF measurements were commonly adopted to evaluate slip potentials, it has been found that there were controversies in the interpretation of COF measurement results. This study, therefore, was principally focused on broadening the knowledge base and developing new ideas on which improvements in the validity and reliability of slip resistance measurements might be made. To achieve this goal, crucial problems on the current concept of slip resistance measurement were extensively analysed by a tribological point of view where principle understanding of the shoe-floor friction and wear phenomena could be made. Based on this approach, new theoretical models were suggested. PMID:18270452

  4. Using fault displacement and slip tendency to estimate stress states

    NASA Astrophysics Data System (ADS)

    Morris, Alan P.; Ferrill, David A.; McGinnis, Ronald N.

    2016-02-01

    We suggest that faults in high slip tendency orientations tend to develop larger displacements than other faults. Consequently, faults that accumulate larger displacements are more likely to be reliable indicators of the longer term stress field and should be weighted accordingly in paleostress estimation. Application of a stress inversion technique that uses slip tendency analyses and fault displacements to interpret populations of coherent normal faults within the Balcones Fault System of south-central Texas provides stress estimates that are consistent with established regional stress analyses. Although the method does not require measurement of slip directions, these data, where available, and sensitivity analyses of the angular mismatch between measured slip directions and those predicted by inverted stress states provide high confidence in the stress estimates generated using slip tendency analyses. Close inspection of the fault orientation and displacement data further indicates that subpopulations of faults with orientations different from the regional pattern have formed in response to stress perturbations generated by displacement gradients on an adjacent seismic scale fault.

  5. Individualized menu slips improve the accuracy of patient food trays.

    PubMed

    Myers, E F; Knoz, S A; Gregoire, M B

    1991-11-01

    We evaluated the effect of five menu slip formats on worker preference and accuracy of food trays in a simulated hospital tray line. Menu slip formats were either individualized or preprinted, and various combinations of color coding, large type, and bold print were used to code the type of diet and the menu choices to be placed on the tray. Student volunteers who had not worked in hospital foodservice were used as tray line workers to reduce the possibility of prior preference for a menu slip format. Results indicate that menu slip format significantly affects both worker preference and the accuracy of assembled food trays. Errors were significantly lower with individualized formats that identified menu selections in bold print and type of diet in either large type or colored ink. The highest error rate was found with preprinted formats. An individualized menu slip that identified menu selections and diet orders with large type and bold print received the highest worker preference rating and resulted in the most accurate tray assembly. PMID:1939982

  6. Scaling analysis for the investigation of slip mechanisms in nanofluids

    NASA Astrophysics Data System (ADS)

    Savithiri, S.; Pattamatta, Arvind; Das, Sarit K.

    2011-07-01

    The primary objective of this study is to investigate the effect of slip mechanisms in nanofluids through scaling analysis. The role of nanoparticle slip mechanisms in both water- and ethylene glycol-based nanofluids is analyzed by considering shape, size, concentration, and temperature of the nanoparticles. From the scaling analysis, it is found that all of the slip mechanisms are dominant in particles of cylindrical shape as compared to that of spherical and sheet particles. The magnitudes of slip mechanisms are found to be higher for particles of size between 10 and 80 nm. The Brownian force is found to dominate in smaller particles below 10 nm and also at smaller volume fraction. However, the drag force is found to dominate in smaller particles below 10 nm and at higher volume fraction. The effect of thermophoresis and Magnus forces is found to increase with the particle size and concentration. In terms of time scales, the Brownian and gravity forces act considerably over a longer duration than the other forces. For copper-water-based nanofluid, the effective contribution of slip mechanisms leads to a heat transfer augmentation which is approximately 36% over that of the base fluid. The drag and gravity forces tend to reduce the Nusselt number of the nanofluid while the other forces tend to enhance it.

  7. Measurement of Quantum Phase-Slips in Josephson Junction Chains

    NASA Astrophysics Data System (ADS)

    Guichard, Wiebke

    2011-03-01

    Quantum phase-slip dynamics in Josephson junction chains could provide the basis for the realization of a new type of topologically protected qubit or for the implementation of a new current standard. I will present measurements of the effect of quantum phase-slips on the ground state of a Josephson junction chain. We can tune in situ the strength of the phase-slips. These phase-slips are the result of fluctuations induced by the finite charging energy of each junction in the chain. Our measurements demonstrate that a Josephson junction chain under phase bias constraint behaves in a collective way. I will also show evidence of coherent phase-slip interference, the so called Aharonov-Casher effect. This phenomenon is the dual of the well known Aharonov-Bohm interference. In collaboration with I.M. Pop, Institut Neel, C.N.R.S. and Universite Joseph Fourier, BP 166, 38042 Grenoble, France; I. Protopopov, L. D. Landau Institute for Theoretical Physics, Kosygin str. 2, Moscow 119334, Russia and Institut fuer Nanotechnologie, Karlsruher Institut fuer Technologie, 76021 Karlsruhe, Germany; and F. Lecocq, Z. Peng, B. Pannetier, O. Buisson, Institut Neel, C.N.R.S. and Universite Joseph Fourier. European STREP MIDAS, ANR QUANTJO.

  8. Biodegradable polymers: Wall slip, melt fracture, and processing aids

    NASA Astrophysics Data System (ADS)

    Othman, Norhayani; Noroozi, Nazbanoo; Jazrawi, Bashar; Mehrkhodavandi, Parisa; Schafer, Laurel; Hatzikiriakos, Savvas George

    2015-04-01

    The wall slip and melt fracture behaviour of several commercial polylactides (PLAs) and poly(ɛ-caprolactone), (PCLs) have been investigated. PLAs with molecular weights greater than a certain value were found to slip, with the slip velocity to increase with decrease of molecular weight consistent with wall slip data reported in the literature for other systems. The onset of melt fracture for the high molecular weight PLAs was found to occur at about 0.2 to 0.3 MPa, depending on the geometrical characteristics of the dies and independent of temperature. Similarly, sharkskin and gross melt fracture was observed for the case of PCLs depending on the molecular characteristics of the resins and the geometrical details of the capillary dies. It was also found that the addition of a small amount of PCL (typically 0.5 wt.%) into the PLA and vice versa is effective in eliminating and delaying the onset of melt fracture to higher shear rates in the capillary extrusion of PLA and PCL respectively. This is due to significant interfacial slip that occurs in the presence of PCL or PLA as well as to the immiscibility of the PLA/PCL blend system at all compositions.

  9. Path Following with Slip Compensation for a Mars Rover

    NASA Technical Reports Server (NTRS)

    Helmick, Daniel; Cheng, Yang; Clouse, Daniel; Matthies, Larry; Roumeliotis, Stergios

    2005-01-01

    A software system for autonomous operation of a Mars rover is composed of several key algorithms that enable the rover to accurately follow a designated path, compensate for slippage of its wheels on terrain, and reach intended goals. The techniques implemented by the algorithms are visual odometry, full vehicle kinematics, a Kalman filter, and path following with slip compensation. The visual-odometry algorithm tracks distinctive scene features in stereo imagery to estimate rover motion between successively acquired stereo image pairs, by use of a maximum-likelihood motion-estimation algorithm. The full-vehicle kinematics algorithm estimates motion, with a no-slip assumption, from measured wheel rates, steering angles, and angles of rockers and bogies in the rover suspension system. The Kalman filter merges data from an inertial measurement unit (IMU) and the visual-odometry algorithm. The merged estimate is then compared to the kinematic estimate to determine whether and how much slippage has occurred. The kinematic estimate is used to complement the Kalman-filter estimate if no statistically significant slippage has occurred. If slippage has occurred, then a slip vector is calculated by subtracting the current Kalman filter estimate from the kinematic estimate. This slip vector is then used, in conjunction with the inverse kinematics, to determine the wheel velocities and steering angles needed to compensate for slip and follow the desired path.

  10. Global Morphological Mapping of Strike-Slip Structures on Ganymede

    NASA Astrophysics Data System (ADS)

    Smith-Konter, B. R.; Cameron, M. E.; Seifert, F.; Pappalardo, R. T.; Collins, G. C.

    2014-12-01

    Many inferences of strike-slip faulting and distributed shear zones on Ganymede suggest that strike-slip tectonism may be important to the structural development of its surface and in the transition from dark to light (grooved) materials. To better understand the role of strike-slip tectonism in shaping Ganymede's multifaceted surface, we identify and map key examples of strike-slip morphologies (en echelon structures, strike-slip duplexes, laterally offset pre-existing features, and possible strained craters) from Galileo and Voyager images. Here we present the current state of these global mapping efforts, with particular emphasis given to complex structures associated with grooved terrain (e.g. Nun Sulci) and terrains transitional from dark to light terrain (e.g. the boundary between Nippur Sulcus and Marius Regio). These results are being synthesized into a global database representing an inferred sense of shear for fractures on Ganymede. This, combined with existing observations of extensional features, is helping to narrow down the range of possible principal stress directions that could have acted at the regional or global scale to produce grooved terrain. Moreover, these data sets, combined with mechanical models of shear failure and global stress sources, are providing constraints for testing possible mechanisms for grooved terrain formation on Ganymede.

  11. Wall slip in suspensions of thermo-responsive particles

    NASA Astrophysics Data System (ADS)

    Divoux, Thibaut; Lapeyre, Véronique; Ravaine, Valérie; Manneville, Sébastien

    2015-11-01

    Flows of suspensions are affected by wall slip, i.e. the fluid velocity vf in the vicinity of a boundary differs from the velocity vw of the latter due to the presence of a lubrication layer. Wall slip is quantified by the slip velocity vs, which is defined as vs = |vf -vw | and displays a power-law scaling with the stress σ at the wall. If the slip velocity of dilute suspensions robustly follows vs ~σp with p ~= 1 , there is no consensus regarding denser suspensions that are sheared in bulk, for which vs is reported to scale as a power-law of the stress with exponents inconsistently ranging between p ~= 0 and 2. By means of extensive rheometry coupled to velocimetry on a suspension of thermo-responsive particles, we show that such discrepancy is only apparent, and demonstrate that vs scales as a power law of the viscous stress σ -σc , where σc denotes the yield stress. Tunning the temperature reveals that such scaling holds true over a large range of packing fractions ϕ on both sides of the jamming point, and that the exponent p increases continuously with ϕ, from p = 1 (dilute suspensions) to p = 2 (dense assemblies). Our results pave the way for a unified description of wall slip. Initial Support for Exploratory Projects (PEPS) scheme (ANR-10-IDEX-03-02).

  12. Generalization of treadmill perturbation to overground slip during gait: Effect of different perturbation distances on slip recovery.

    PubMed

    Lee, Anna; Bhatt, Tanvi; Pai, Yi-Chung

    2016-01-25

    Treadmill-perturbation training (TM-training) may improve a person׳s fall-resistance, whereby adjusting slip distance can be a simple way to manipulate training intensity. The purpose of this study was to determine the effects of different slip distances in TM-training (12-cm vs. 18-cm) on its generalization to the recovery from a novel "free" slip during overground walking. Generalization here means the ability to apply learned skill from TM-training to slip recovery during overground walking. Thirty-six young adults in the TM_12 or the TM_18 group underwent either a 12-cm or an 18-cm slip during the treadmill walking for seven times, or in the control group were not exposed to any perturbation. Their responses were also contrasted with previously reported results from overground-perturbation training (OG-training) in which participants received either a 12-cm or an 18-cm slip during level walking with the same number of repetitions. Everyone was then exposed to the same generalization test during a novel "free" slip in overground walking. Their proactive and reactive control of stability was measured and compared. TM-training displayed a significant training effect in comparison to the control group (p<0.05), while most of the improvements were found in the reactive control of stability and were much-limited in comparison to that of OG-training. Also unlike OG-training, no significant differences were found between the results obtained from the TM_12 and the TM_18 groups (p>0.05). These results underscore the further needs to investigate the potential of the treadmill as a convenient instrument that can effectively deliver perturbation training. PMID:26653674

  13. Sustainable Chemistry, the Spinning Tube-in-Tube (STT(R)) Reactor and GREENSCOPE: Innovation and Industrial Partnerships

    EPA Science Inventory

    The chemical industry faces environmental, social and health challenges that are common across all economic sectors. From worker exposure to toxic substances, to product design and use, to the cost and handling of waste disposal, the industry must overcome numerous complex hurdle...

  14. Slip stream apparatus and method for treating water in a circulating water system

    DOEpatents

    Cleveland, Joe R.

    1997-01-01

    An apparatus (10) for treating water in a circulating water system (12) t has a cooling water basin (14) includes a slip stream conduit (16) in flow communication with the circulating water system (12), a source (36) of acid solution in flow communication with the slip stream conduit (16), and a decarbonator (58) in flow communication with the slip stream conduit (16) and the cooling water basin (14). In use, a slip stream of circulating water is drawn from the circulating water system (12) into the slip stream conduit (16) of the apparatus (10). The slip stream pH is lowered by contact with an acid solution provided from the source (36) thereof. The slip stream is then passed through a decarbonator (58) to form a treated slip stream, and the treated slip stream is returned to the cooling water basin (14).

  15. Slip stream apparatus and method for treating water in a circulating water system

    DOEpatents

    Cleveland, J.R.

    1997-03-18

    An apparatus is described for treating water in a circulating water system that has a cooling water basin which includes a slip stream conduit in flow communication with the circulating water system, a source of acid solution in flow communication with the slip stream conduit, and a decarbonator in flow communication with the slip stream conduit and the cooling water basin. In use, a slip stream of circulating water is drawn from the circulating water system into the slip stream conduit of the apparatus. The slip stream pH is lowered by contact with an acid solution provided from the source thereof. The slip stream is then passed through a decarbonator to form a treated slip stream, and the treated slip stream is returned to the cooling water basin. 4 figs.

  16. Surface-slip equations for multicomponent, nonequilibrium air flow

    NASA Technical Reports Server (NTRS)

    Gupta, Roop N.; Scott, Carl D.; Moss, James N.; Goglia, Gene

    1985-01-01

    Equations are presented for the surface slip (or jump) values of species concentration, pressure, velocity, and temperature in the low-Reynolds-number, high-altitude flight regime of a space vehicle. These are obtained from closed-form solutions of the mass, momentum, and energy flux equations using the Chapman-Enskog velocity distribution function. This function represents a solution of the Boltzmann equation in the Navier-Stokes approximation. The analysis, obtained for nonequilibrium multicomponent air flow, includes the finite-rate surface catalytic recombination and changes in the internal energy during reflection from the surface. Expressions for the various slip quantities have been obtained in a form which can readily be employed in flow-field computations. A consistent set of equations is provided for multicomponent, binary, and single species mixtures. Expression is also provided for the finite-rate species-concentration boundary condition for a multicomponent mixture in absence of slip.

  17. Preliminary soil-slip susceptibility maps, southwestern California

    USGS Publications Warehouse

    Morton, Douglas M.; Alvarez, Rachel M.; Campbell, Russell H.; Digital preparation by Bovard, Kelly R.; Brown, D.T.; Corriea, K.M.; Lesser, J.N.

    2003-01-01

    This group of maps shows relative susceptibility of hill slopes to the initiation sites of rainfall-triggered soil slip-debris flows in southwestern California. As such, the maps offer a partial answer to one part of the three parts necessary to predict the soil-slip/debris-flow process. A complete prediction of the process would include assessments of “where”, “when”, and “how big”. These maps empirically show part of the “where” of prediction (i.e., relative susceptibility to sites of initiation of the soil slips) but do not attempt to show the extent of run out of the resultant debris flows. Some information pertinent to “when” the process might begin is developed. “When” is determined mostly by dynamic factors such as rainfall rate and duration, for which local variations are not amenable to long-term prediction. “When” information is not provided on the maps but is described later in this narrative. The prediction of “how big” is addressed indirectly by restricting the maps to a single type of landslide process—soil slip-debris flows. The susceptibility maps were created through an iterative process from two kinds of information. First, locations of sites of past soil slips were obtained from inventory maps of past events. Aerial photographs, taken during six rainy seasons that produced abundant soil slips, were used as the basis for soil slip-debris flow inventory. Second, digital elevation models (DEM) of the areas that were inventoried were used to analyze the spatial characteristics of soil slip locations. These data were supplemented by observations made on the ground. Certain physical attributes of the locations of the soil-slip debris flows were found to be important and others were not. The most important attribute was the mapped bedrock formation at the site of initiation of the soil slip. However, because the soil slips occur in surficial materials overlying the bedrocks units, the bedrock formation can only serve as a surrogate for the susceptibility of the overlying surficial materials. The maps of susceptibility were created from those physical attributes learned to be important from the inventories. The multiple inventories allow a model to be created from one set of inventory data and evaluated with others. The resultant maps of relative susceptibility represent the best estimate generated from available inventory and DEM data. Slope and aspect values used in the susceptibility analysis were 10-meter DEM cells at a scale of 1:24,000. For most of the area 10-meter DEMs were available; for those quadrangles that have only 30-meter DEMs, the 30-meter DEMS were resampled to 10-meters to maintain resolution of 10-meter cells. Geologic unit values used in the susceptibility analysis were five-meter cells. For convenience, the soil slip susceptibility values are assembled on 1:100,000-scale bases. Any area of the 1:100,000-scale maps can be transferred to 1:24,000-scale base without any loss of accuracy. Figure 32 is an example of part of a 1:100,000-scale susceptibility map transferred back to a 1:24,000-scale quadrangle.

  18. Shock slip-relations for thermal and chemical nonequilibrium flows

    NASA Astrophysics Data System (ADS)

    Jinrong, Tang

    1996-05-01

    This paper appears to be the first where the multi-temperature shock slip-relations for the thermal and chemical nonequilibrium flows are derived. The derivation is based on analysis of the influences of thermal nonequilibrium and viscous effects on the mass, momentum and emergy flux balance relations at the shock wave. When the relaxation times for all internal energy modes tend to zero, the multi-tmperature shock slip-relations are converted into single-temperature ones for thermal equilibrium flows. The present results can be applied to flow over vehicles of different geometries with or without angles of attack. In addition, the present single-temperature shock slip-relations are compared with those in the literature, and some defects and limitations in the latter are clarified.

  19. Superplastic flow lubricates carbonate faults during earthquake slip

    NASA Astrophysics Data System (ADS)

    De Paola, Nicola; Holdsworth, Robert; Viti, Cecilia; Collettini, Cristiano; Faoro, Igor; Bullock, Rachael

    2014-05-01

    Tectonic earthquakes are hosted in the shallower portion of crustal fault zones, where fracturing and cataclasis are thought to be the dominant processes during frictional sliding. Aseismic shear in lower crust and lithospheric mantle shear zones is accomplished by crystal plasticity, including superplastic flow acting at low strain rates on ultrafine-grained rocks. Superplasticity has also been observed at high strain rates for a range of nano-phase alloys and ceramics, and could potentially occur in fine-grained geological materials, if deformed at high strain rates and temperatures. We performed a set of displacement-controlled experiments to explore whether superplastic flow can effectively weaken faults, and facilitate earthquake propagation. The experiments were performed on fine-grained synthetic gouges (63 < f < 93 μm) of undeformed, protolith carbonate rocks using a rotary shear apparatus, at target speed v = 1 ms-1, normal stresses σn = 12-18 MPa, displacements d from 0.009 to 1.46 m, room temperature and humidity conditions. Samples were recovered after each experiment to study the slip zone microstructures. The integration of experimental data and microstructural observations shows that during sliding at seismic velocity, brittle fracturing and cataclasis control shear localization and grain size reduction in the slip zone at relatively low temperatures (T ≤ 100 °C). Stress levels predicted by such behaviours match those measured during the experiments. As temperatures rise due to frictional heating (T ≥ 500 °C), dislocation creep mechanisms start to accommodate intragranular strain, and play a key role in producing nanoscale subgrains (< 200 nm) in the slip zone. At this stage, despite of the presence of nanoparticles in the slip zone and the attainment of seismic slip rates, the measured frictional strength of experimental faults still lies within Byerlee's range of values μ = 0.8. This suggests that the slip zone bulk strength at this stage is controlled by cataclastic frictional sliding rather than by dislocation creep or nanopowder lubrication mechanisms. When T ≥ 800 °C are attained, micro-textures diagnostic of diffusion-dominated grain boundary sliding are widespread within the slip zone, and suggest bulk superplastic flow. Flow stresses predicted by superplasticity constitutive laws at the slip zone temperatures, grain sizes and strain rates attained during the experiments match those we measured in the laboratory (μ = 0.16). We propose therefore that the activation of diffusion creep at high temperatures (T ≥ 800 °C) leads to slip zone-localised superplastic flow and that this causes the dynamic weakening of carbonate faults at seismic slip rates. Note, however, that both cataclasis and dislocation creep operating at lower temperatures, during the earlier stages of slip, are critical, precursory processes needed to produce the nanoscale grain sizes required to activate grainsize sensitive mechanisms during superplastic flow. Finally, the re-strengthening observed during the decelerating phase of deformation can be explained by the falling temperature "switching off" slip zone-localized superplasticity, leading to a return to frictional sliding. These results indicate that superplastic flow can effectively weaken faults, and facilitate earthquake propagation in the upper crust.

  20. Slip-boundary equations for multicomponent nonequilibrium airflow

    NASA Technical Reports Server (NTRS)

    Gupta, R. N.; Scott, C. D.; Moss, J. N.

    1985-01-01

    Equations are presented for the surface-slip (or jump) values of species concentration, pressure, velocity, and temperature in the low Reynolds number, high-altitude flight regime of a space vehicle. These are obtained from closed-form solutions of the mass, momentum, and energy flux equations by using the Chapman-Enskog velocity distribution function. This function represents a solution of the Boltzmann equation in the Navier-Stokes approximation. The analysis, obtained for nonequilibrium multicomponent airflow, includes the finite-rare surface catalytic recombination and changes in the internal energy during reflection from the surface. Expressions for the various slip quantities have been obtained in a form which can readily be employed in flow-field computations. A consistent set of equations is provided for multicomponent and binary mixtures and single-species gas. An expression is also provided for the finite-rate species-concentration boundary condition for a multicomponent mixture in the absence of slip.

  1. Fault slip rates in the modern new madrid seismic zone

    PubMed

    Mueller; Champion; Guccione; Kelson

    1999-11-01

    Structural and geomorphic analysis of late Holocene sediments in the Lake County region of the New Madrid seismic zone indicates that they are deformed by fault-related folding above the blind Reelfoot thrust fault. The widths of narrow kink bands exposed in trenches were used to model the Reelfoot scarp as a forelimb on a fault-bend fold; this, coupled with the age of folded sediment, yields a slip rate on the blind thrust of 6.1 +/- 0.7 mm/year for the past 2300 +/- 100 years. An alternative method used structural relief across the scarp and the estimated dip of the underlying blind thrust to calculate a slip rate of 4.8 +/- 0.2 mm/year. Geometric relations suggest that the right lateral slip rate on the New Madrid seismic zone is 1.8 to 2.0 mm/year. PMID:10550047

  2. Surface-slip equations for multicomponent nonequilibrium air flow

    NASA Technical Reports Server (NTRS)

    Gupta, R. N.; Scott, C. D.; Moss, J. N.

    1985-01-01

    Equations are presented for the surface-slip (or jump) values of species concentration, pressure, velocity, and temperature in the low-Reynolds number, high-altitude flight regime of a space vehicle. The equations are obtained from closed form solutions of the mass, momentum, and energy flux equations using the Chapman-Enskog velocity distribution function. This function represents a solution of the Boltzmann equation in the Navier-Stokes approximation. The analysis, obtained for nonequilibrium multicomponent air flow, includes the finite-rate surface catalytic recombination and changes in the internal energy during reflection from the surface. Expressions for the various slip quantities were obtained in a form which can be employed in flowfield computations. A consistent set of equations is provided for multicomponent, binary, and single species mixtures. Expression is also provided for the finite-rate, species-concentration boundary condition for a multicomponent mixture in absence of slip.

  3. ETS and tidal stressing: Fault weakening after main slip pulse

    NASA Astrophysics Data System (ADS)

    Houston, H.

    2013-12-01

    Time-varying stresses from solid Earth tides and ocean loading influence slow slip (Hawthorne and Rubin, 2010) and, consequently, the frequency of occurrence and intensity of tremor during ETS episodes (Rubinstein et al., 2008). This relationship can illuminate changes in the mechanical response of the rupture surfaces(s) during slip in ETS. I compare the influence of tidal loading when and after the propagating ETS slip front (estimated by tremor density in time) ruptures the fault at a given spot. Using estimates of slip fronts that I derived from tremor locations, I divide ETS tremor into two groups: that occurring within a day of the start of the inferred slip front and that occurring over several days thereafter. The tremor catalog used contains 50K waveform cross-correlation locations of tremor in 7 large ETS in northern Cascadia between 2005 and 2012. I calculate normal, shear and volumetric stresses due to the Earth and ocean tides at numerous locations on the inferred rupture plane of the ETS following the method of Hawthorne and Rubin (2010). The Coulomb stress increment at each tremor time and location is compared with tremor occurrence for the two groups of tremor. Unreasonable results appear if the effective frictional coefficient mu > 0.2, and results are most 'reasonable' when mu is very near or equal to zero. Following passage of the main slip pulse, tremor generation is notably more sensitive to tidal stressing. One kPa of encouraging tidal Coulomb stress boosts the occurrence of tremor after the main slip pulse by about 50% above the average value, while the same amount of discouraging stress decreases the occurrence of such tremor by a similar factor. The greater the encouraging or discouraging stress, the greater the effect. In contrast, tremor in the main slip pulse is much less affected by positive or negative tidal stresses. I interpret the greater sensitivity to tidal stressing of the tremor after the main slip pulse as a measure of the weakening of the fault plane following its initial rupture. Considering up- and down-dip sensitivities to tidal stress, tremor generation on the up-dip region is affected roughly 50% more by both positive and negative tidal stresses than tremor down-dip. Furthermore, for the down-dip tremor, there is less contrast in sensitivity to stress between the tremor at the main slip front and the later tremor, i.e., the fault downdip is both less sensitive to tidal stress and weakens less due to the rupture. These results are consistent with the timing and geometry of Rapid Tremor Reversals, which also indicate weakening of the fault after the main slip front has passed through a region (Houston et al., 2011). RTRs occur on updip parts of the fault, after the main slip front, and at times of encouraging tidal stress (Thomas et al., 2013).

  4. Probabilistic estimates of surface slip including the effects of creep and afterslip

    NASA Astrophysics Data System (ADS)

    Aagaard, B.; Lienkaemper, J. J.; Schwartz, D. P.

    2009-12-01

    We develop a methodology for probabilistic estimates of coseismic and postseismic surface slip for scenario earthquakes that explicitly includes the effects of creep and afterslip. We apply Monte Carlo simulations to include uncertainty from the Hanks and Bakun (2008) magnitude-area relation, distribution of slip, and the effect of creep on coseismic slip. We extract coseismic surface slip from a suite of kinematic slip models that are constructed following the same approach we used in kinematic rupture models for ground motion modeling of scenario events on the Hayward Fault (Aagaard, et al., 2008), with additional calibration for coseismic surface slip using empirical regressions and observations provided by Wells and Coppersmith (1994). The kinematic slip models include variation in earthquake magnitude, rupture length, slip distribution, and reduce the coseismic slip in creeping patches delineated by Funning et al. (2007). Postseismic slip in our analysis is based upon empirical regressions developed from afterslip measurements from the 1987 magnitude 6.6 Superstition Hills earthquake in southern California. We apply this methodology to a location on the Hayward fault in the San Francisco Bay area to characterize the coseismic and postseismic slip expected for magnitude 6.5-7.1 earthquakes. We find that creep decreases the expected coseismic slip and substantial afterslip may occur in the first few days following an earthquake. This analysis provides a significantly different temporal estimate of surface slip compared with conventional probabilistic estimates that ignore the effects of creep and postseismic slip.

  5. Offset of latest pleistocene shoreface reveals slip rate on the Hosgri strike-slip fault, offshore central California

    USGS Publications Warehouse

    Johnson, Samuel Y.; Hartwell, Stephen R.; Dartnell, Peter

    2014-01-01

    The Hosgri fault is the southern part of the regional Hosgri–San Gregorio dextral strike‐slip fault system, which extends primarily in the offshore for about 400 km in central California. Between Morro Bay and San Simeon, high‐resolution multibeam bathymetry reveals that the eastern strand of the Hosgri fault is crossed by an ∼265  m wide slope interpreted as the shoreface of a latest Pleistocene sand spit. This sand spit crossed an embayment and connected a western fault‐bounded bedrock peninsula and an eastern bedrock highland, a paleogeography resembling modern coastal geomorphology along the San Andreas fault. Detailed analysis of the relict shoreface with slope profiles and slope maps indicates a lateral slip rate of 2.6±0.9  mm/yr, considered a minimum rate for the Hosgri given the presence of an active western strand. This slip rate indicates that the Hosgri system takes up the largest share of the strike‐slip fault budget and is the most active strike‐slip fault west of the San Andreas fault in central California. This result further demonstrates the value and potential of high‐resolution bathymetry in characterization of active offshore faults.

  6. The evolving energy of propagating strike-slip fault segments

    NASA Astrophysics Data System (ADS)

    Cooke, M. L.; Madden, E. H.; McBeck, J.

    2014-12-01

    Step-overs and bends along strike-slip faults can serve as impediments to earthquake rupture. Over many earthquake cycles, these irregularities can develop slip deficits so that the local long-term strike-slip rates do not match the slip rates away from the bends and step-overs. Physical analog models show that bends and stepovers propagate new faults and evolve in order to more efficiently accommodate applied strike-slip thereby reducing off-fault deformation. Numerical models permit evaluation of the energy associated with fault propagation and can predict fault evolution over multiple earthquake cycles using work minimization. The algorithm GROW (GRowth by Optimization of Work) honors tensile and frictional failure criteria along pre-existing surfaces and at fault tips, while allowing the orientation of fault growth within the system to be governed by the global energy budget. In GROW, faults evolve in order to minimize deformation energy, thereby maximizing the mechanical efficiency of the entire system. Using GROW, we subject systems of two right-lateral, strike-slip faults that are initially right-stepping, with varying separation distances and strengths, to remotely applied displacement. We track the propagation paths across the intervening releasing bend. We find that fault strength and initial separation control fault linkage propensity and linkage patterns. In order to build insight into the efficiency gains provided by hard- versus soft-linkage, we also track the work budget of these fault systems as they evolve. For example, linkage of faults may reduce internal work while increasing frictional work and seismic work. Assuming that increasing efficiency correlates with increasing potential for a single earthquake to rupture both faults, this approach has utility for assessing the evolution of seismic hazard as segmented faults systems change over geologic time.

  7. Reduced Aftershock Productivity in Regions with Known Slow Slip Events

    NASA Astrophysics Data System (ADS)

    Collins, G.; Mina, A.; Richardson, E.; McGuire, J. J.

    2013-12-01

    Reduced aftershock activity has been observed in areas with high rates of aseismic slip, such as transform fault zones and some subduction zones. Fault conditions that could explain both of these observations include a low effective normal stress regime and/or a high temperature, semi-brittle/plastic rheology. To further investigate the possible connection between areas of aseismic slip and reduced aftershock productivity, we compared the mainshock-aftershock sequences in subduction zones where aseismic slip transients have been observed to those of adjacent (along-strike) regions where no slow slip events have been detected. Using the Advanced National Seismic System (ANSS) catalog, we counted aftershocks that occurred within 100 km and 14 days of 112 M>=5.0 slab earthquake mainshocks from January 1980 - July 2013, including 90 since January 2000, inside observed regions of detected slow slip: south central Alaska, Cascadia, the Nicoya Peninsula (Costa Rica), Guerrero (Mexico), and the North Island of New Zealand. We also compiled aftershock counts from 97 mainshocks from areas adjacent to each of these regions using the same criteria and over the same time interval. Preliminary analysis of these two datasets shows an aftershock triggering exponent (alpha in the ETAS model) of approximately 0.8, consistent with previous studies of aftershocks in a variety of tectonic settings. Aftershock productivity for both datasets is less than that of continental earthquakes. Contrasting the two datasets, aftershock productivity inside slow slip regions is lower than in adjacent areas along the same subduction zone and is comparable to that of mid-ocean ridge transform faults.

  8. Slip, swim, mix, pack: Fluid mechanics at the micron scale

    NASA Astrophysics Data System (ADS)

    Lauga, Eric

    This thesis is devoted to fluid behavior at the micrometer length scale and considers four different problems. We first address the topic of the no-slip boundary condition in Newtonian liquids. After reviewing the field, we present models for apparent slip in three distinct experimental settings: Steady pressure-driven flow over heterogeneous surfaces, unsteady drainage flow over surface-attached bubbles, and flow of passive tracers affected by electrical forces. In all cases, we evaluate the apparent slip lengths and compare them to experimental results. We then propose a new method to probe slip, based on the influence of surface slip on the Brownian motion near a surface of a colloidal particle. We finish by showing that slip has virtually no influence on the non-modal stability of shear flows, despite its strong influence on unstable modes. The second problem we consider addresses mixing in micro-devices. We show that microchannels which are obtained with a single step of microfabrication (that is, have constant height) are able to generate fully three-dimensional flows, and could therefore be used as single-step passive micro-mixers. The third problem we present proposes a mechanical model for the motion of the bacterium E. coli near solid boundaries. It has been observed that, near a solid surface, E. coli does not swim in a straight line but in clockwise circles, which we show is a consequence of the hydrodynamic interactions between the free-swimming bacterium and the surface. The final problem we consider addresses self-assembly of micro-particles. We show that when spherical particles located on a liquid droplet are forced to come together by evaporation of the droplet, the geometrical and mechanical constraints arising during the process lead to unique final clusters. This allows us to propose a methodology to fabricate different clusters.

  9. Towards a spatially and temporally constant Karakorum fault slip rate

    NASA Astrophysics Data System (ADS)

    Chevalier, M.; van der Woerd, J.; Tapponnier, P.; Li, H.; Ryerson, F. J.; Finkel, R. C.

    2012-12-01

    Constraining the Karakorum fault (KF) slip-rate is essential to understand the present-day kinematic role of large strike-slip faults in the deformation of Tibet. The range of geodetic and geologic slip-rates is ~0 - 11 mm/yr. Cumulative offsets of alluvial fans and terrace risers ranging from 38 to 220 m add new quantitative information on its late Quaternary slip-rate. Their ages were determined using 10Be surface-exposure dating of 74 samples collected at 3 alluvial sites along the Bangong - Chaxikang and Gar basin segments, southeast of Bangong Lake. The slip-rate during the 0 - 60 ka period is 2.9(+1.0/-0.6) mm/yr at GUN, >5.3(+4.3/-1.7) mm/yr at CK and >5.3(+3.1/-2.3) mm/yr at GF. These rates are in agreement with those determined to the southeast (>5.5±0.5 mm/yr at Manikala on one strand for the same period, Chevalier et al., 2005a,b; 7.1(+3.2/-1.7) mm/yr at Menshi and 7.9(+3.2/-2.5) mm/yr near Kailas across two strands, Chevalier et al., 2012) and to the northwest (4±1 mm/yr at Tangste, Brown et al., 2002; >5 mm/yr at Muji, Chevalier et al., 2011b, both on one strand, during the Holocene). We suggest that the minimum late Quaternary slip-rate along the entire length of the KF may be relatively constant along-strike at >5 mm/yr on one fault branch or >7 mm/yr across two branches. In addition to being spatially constant, this late Quaternary rate appears to be, within error, in agreement with most studies at various timescales and suggests that at first approximation, no major discrepancy exists between geodetic and geologic rates.

  10. Precursory Processes during Stick-Slip Experiments on Crustal Rocks

    NASA Astrophysics Data System (ADS)

    Passelègue, F. X.; Latour, S.; Schubnel, A.; Nielsen, S. B.; Bhat Suresh, H.; Madariaga, R. I.

    2014-12-01

    Recent seismological observations have highlighted increasing foreshock activity preceding the failure of large earthquakes. Foreshock sequences are the signature of a precursory slip during the nucleation of earthquakes, as observed both prior the Tohoku-Oki Mw 9.0 and the recent Iquique 2014 Mw 8.1 earthquakes. However, foreshocks are not systematic and the reason why they occur remains poorly understood. Recent advances in laboratory experiments allow to mimic seismic ruptures and to study the earthquake nucleation phase. Here, we track the occurrence of foreshocks prior to stick-slip instabilities in crustal rocks. Here we present the results of 6 experiments on saw cut granite samples submitted to triaxial loading under in-situ upper crustal condition that provide additional clues to understand the physical processes of foreshock dynamics. We obtained a catalog of more than 200 stick-slip cycles, composed of loading period and mainshock. Thirty STick-slip Events (STE) are preceded by a foreshock sequence. The moment and location of the 900 measured foreshocks are obtained using acoustic emission (AE) monitoring. We systematically observed that (i) the static friction coefficient, (ii) the stress drop and, consequently, (3) the moment magnitude (and total seismic slip) of the mainshock increases with increasing σn. In our experiments, an exponential acceleration of the precursory slip is systematically observed, but foreshocks are only observed when the normal stress becomes greater than 55MPa. This threshold corresponds to the normal stress above which the nucleation length becomes comparable to the size of typical fault asperities. In these conditions, the total cumulative moment of the foreshock sequence also increases exponentially up to failure, and the fault surface evolves like a cascading asperity model. This exponential growth implies that the nucleation phase has a characteristic time, i.e. that the foreshock sequence duration and moment release scales with the size of the main asperity which is eventually going to rupture.

  11. Active strike-slip faulting in El Salvador, Central America

    NASA Astrophysics Data System (ADS)

    Corti, Giacomo; Carminati, Eugenio; Mazzarini, Francesco; Oziel Garcia, Marvyn

    2005-12-01

    Several major earthquakes have affected El Salvador, Central America, during the Past 100 yr as a consequence of oblique subduction of the Cocos plate under the Caribbean plate, which is partitioned between trench-orthogonal compression and strike-slip deformation parallel to the volcanic arc. Focal mechanisms and the distribution of the most destructive earthquakes, together with geomorphologic evidence, suggest that this transcurrent component of motion may be accommodated by a major strike-slip fault (El Salvador fault zone). We present field geological, structural, and geomorphological data collected in central El Salvador that allow the constraint of the kinematics and the Quaternary activity of this major seismogenic strike-slip fault system. Data suggest that the El Salvador fault zone consists of at least two main ˜E-W fault segments (San Vicente and Berlin segments), with associated secondary synthetic (WNW-ESE) and antithetic (NNW-SSE) Riedel shears and NW-SE tensional structures. The two main fault segments overlap in a dextral en echelon style with the formation of an intervening pull-apart basin. Our original geological and geomorphologic data suggest a late Pleistocene Holocene slip rate of ˜11 mm/yr along the Berlin segment, in contrast with low historical seismicity. The kinematics and rates of deformation suggested by our new data are consistent with models involving slip partitioning during oblique subduction, and support the notion that a trench-parallel component of motion between the Caribbean and Cocos plates is concentrated along E-W dextral strike-slip faults parallel to the volcanic arc.

  12. Spontaneous, large stick-slip events in rotary-shear experiments as analogous to earthquake rupture

    NASA Astrophysics Data System (ADS)

    Zu, Ximeng; Reches, Zeev

    2015-04-01

    Experimental stick-slips are commonly envisioned as laboratory analogues of the spontaneous faults slip during natural earthquakes (Brace & Byerlee, 1966). However, typical experimental stick-slips are tiny events of slip distances up to a few tens of microns. To close the gap between such events and natural earthquakes, we develop a new method that produces spontaneous stick-slips with large displacements on our rotary shear apparatus (Reches & Lockner, 2010). In this method, the controlling program continuously calculates the real-time power-density (PD = slip-velocity times shear stress) of the experimental fault. Then, a feedback loop modifies the slip-velocity to match the real-time PD with the requested PD. In this method, the stick-slips occur spontaneously while slip velocity and duration are not controlled by the operator. We present a series of tens stick-slip events along granite and diorite experimental faults with 0.0001-1.3 m of total slip and slip-velocity up to 0.45 m/s. Depending on the magnitude of the requested PD, we recognized three types of events: (1) Stick-slips with a nucleation slip that initiates ~0.1 sec before the main slip which is characterized by temporal increase of shear stress, normal stress, and fault dilation; (2) Events resembling slip-pulse behavior of abrupt acceleration and intense dynamic weakening and subsequent strength recovery; and (3) Small, creep events during quasi-continuous, low- velocity slip with tiny changes of stress and dilation. The energy-displacement catalog of types (1) and (2) events shows good agreement with previous slip-pulse experiments and natural earthquakes (Chang et al., 2012). The present experiments indicate that power-density control is a promising experimental approach for earthquake simulations.

  13. Coulombic wall slip of concentrated soft-particle suspensions

    NASA Astrophysics Data System (ADS)

    Adams, Michael; Liu, Wei; Zhang, Zhibing; Fryer, Peter

    2013-06-01

    The coefficients of friction of concentrated soft-particle suspensions (tomato paste and a microgel suspension) were measured as a function of the slip velocity for a number of substrates. The data are interpreted using a micro-elastohydrodynamic model that is consistent with significant bulk frictional dissipation and an increase in the number of particle-wall contacts with increasing normal stress. The origin of the Coulombic slip, which has not been observed previously for pastes, is ascribed to the sensitivity of the lubricating film thickness.

  14. Self-excited stick slip oscillations of drill bits

    NASA Astrophysics Data System (ADS)

    Richard, Thomas; Germay, Christophe; Detournay, Emmanuel

    2004-08-01

    This Note studies the self-excited stick-slip oscillations of a rotary drilling system with a drag bit, using a discrete model which takes into consideration the axial and torsional vibration modes of the bit. Coupling between these two vibration modes takes place through a bit-rock interaction law which accounts for both frictional contact and cutting processes at the bit-rock interface. The cutting process introduces a delay in the equations of motion which is ultimately responsible for the existence of self-excited vibrations, exhibiting stick-slip oscillations under certain conditions. To cite this article: T. Richard et al., C. R. Mecanique 332 (2004).

  15. Stick-slip instability for viscous fingering in a gel

    NASA Astrophysics Data System (ADS)

    Puff, N.; Debrégeas, G.; di Meglio, J.-M.; Higgins, D.; Bonn, D.; Wagner, C.

    2002-05-01

    The growth dynamics of an air finger injected in a visco-elastic gel (a PVA/borax aqueous solution) is studied in a linear Hele-Shaw cell. Besides the standard Saffman-Taylor instability, we observe—with increasing finger velocities—the existence of two new regimes: (a) a stick-slip regime for which the finger tip velocity oscillates between 2 different values, producing local pinching of the finger at regular intervals; (b) a "tadpole" regime where a fracture-type propagation is observed. A scaling argument is proposed to interpret the dependence of the stick-slip frequency with the measured rheological properties of the gel.

  16. Early active short arc motion following central slip repair.

    PubMed

    McAuliffe, John A

    2011-01-01

    Open repairs of the central slip have traditionally been treated with 4 to 6 weeks of immobilization, followed by therapy to restore motion. Although rehabilitative efforts were usually directed at avoiding extension lag, loss of flexion was also commonly encountered. Early active short arc motion produces improved range of motion with shorter treatment time compared with static immobilization of the repaired central slip. The technique is straightforward but its success depends on attention to the details of splinting and exercise, and the patient's active cooperation and compliance. PMID:21193134

  17. Complications Related to the Treatment of Slipped Capital Femoral Epiphysis.

    PubMed

    Roaten, John; Spence, David D

    2016-04-01

    Slipped capital femoral epiphysis (SCFE) is a condition of the immature hip in which mechanical overload of the proximal femoral physis results in anterior and superior displacement of the femoral metaphysis relative to the epiphysis. The treatment of SCFE is surgical, as the natural history of nonsurgical treatment is slip progression and early arthritis. Despite advances in treatment, much controversy exists regarding the best treatment, and complication rates remain high. Complications include osteonecrosis, chondrolysis, SCFE-induced impingement, and related articular degeneration, fixation failure and deformity progression, growth disturbance of the proximal femur, and development of bilateral disease. PMID:26772949

  18. Slip effects on shearing flows in a porous medium

    NASA Astrophysics Data System (ADS)

    Khan, M.; Hayat, T.; Wang, Y.

    2008-02-01

    This paper deals with the magnetohydrodynamic (MHD) flow of an Oldroyd 8-constant fluid in a porous medium when no-slip condition is no longer valid. Modified Darcys law is used in the flow modelling. The non-linear differential equation with non-linear boundary conditions is solved numerically using finite difference scheme in combination with an iterative technique. Numerical results are obtained for the Couette, Poiseuille and generalized Couette flows. The effects of slip parameters on the velocity profile are discussed.

  19. Rupture of multiple catch-slip bonds: Two-state two-pathway catch-slip bonds.

    PubMed

    Gupta, V K

    2013-11-01

    We performed Monte Carlo simulation of the detachment of a polymorphonuclear (PMN) leukocyte immersed in a Newtonian fluid and adhered to a substrate by multiple catch-slip bonds. We found that at certain loading rates the interplay of multiple catch-slip bonds leads to a bimodal distribution of the bond rupture force. We also found that the low force peak in these bond rupture force distributions switches to a high force peak with a gradual increase in the loading rate. These trends in the bond rupture force distributions are characteristics of two-state systems. Consequently, though individual catch-slip bonds follow one-state two-pathway energy landscape, their interplay mimics a two-state two-pathway energy landscape. PMID:24272665

  20. Fault Slip Embedded in Creep: Insight into Tectonic Tremors and Slow Slip Events from Acoustic and Optical Monitoring of Fractures

    NASA Astrophysics Data System (ADS)

    Elkhoury, J. E.; Lengline, O.; Ampuero, J. P.; Schmittbuhl, J.

    2010-12-01

    Observations of temporal and spatial correlations between slow slip earthquakes and tectonic tremor activity suggest a physical relation between them. Early descriptions of mechanisms relating these phenomena simply attributed the relation between seismic and aseismic events to fluid mediated processes. More recent hypotheses suggest that tectonic tremors are bursts of seismic energy due to the rupturing of small asperities within slow slipping regions. Here we present laboratory results of a unique experimental setting aimed at understanding the response to transient loads of a system of small asperities embedded in creep as a model of tectonic tremor activity triggered by slow slip and modulated by tides. We performed mode I crack propagation experiments on glass bead blasted and annealed 2D interfaces of transparent material (Polymethylmethacrylate) where fracture fronts were confined to the 2D weakness plane of the heterogeneous interface. We monitored acoustic emissions (AE) with piezo-electric sensors surrounding the crack front line. We also optically monitored the rupture front line with up to 1000 frames per second. The experimental loading conditions produce quasi-static front propagation at slow average speeds. Image processing reveals de-pinning along the front that we characterize as intermittent opening during slow front propagation. AE locations strongly correlate to the spatiotemporal clustering of the de-penning events along the front. Moreover, this correlation is preserved at the time of imposed transient fluctuations in loading during front propagation. Using the analogy between mode I and modes II and III fractures, our results translate into intermittent slip on faults linked to clustering of seismic activity produced by the breakage of asperities embedded in creeping regions with no need of invoking fluid mediated processes. Thus our experiments help reveal the interplay between aseismic and seismic slip on faults. We also observe qualitative similarities between the growth and migration of the embedded slip events in our experiments and migration patterns of tectonic tremors.

  1. Kinematically Coupled Strike-Slip and Normal Faults in the Lake Mead Strike-Slip Fault System, Southeast Nevada

    NASA Astrophysics Data System (ADS)

    Kattenhorn, S. A.; Marshall, S. T.; Cooke, M. L.

    2008-12-01

    The Lake Mead fault system consists of a ~95 km long, northeast-trending zone of strike-slip faults of Miocene age that accommodate a total left-lateral offset of 20-65 km. We use a combination of detailed field mapping and numerical modeling to show that a previously unnamed left-lateral strike-slip segment of the Lake Mead fault system and a dense cluster of dominantly west-dipping normal faults acted in concert to accommodate regional left-lateral offset. We suggest that the strike-slip fault that we refer to as the Pinto Ridge fault: (1) was kinematically related to other faults of the Lake Mead fault system; (2) was responsible for the creation of the normal fault cluster at Pinto Ridge; and (3) utilized these normal faults as linking structures between separate strike-slip fault segments to create a longer, through-going fault. Results from numerical models demonstrate that the observed location and curving strike patterns of the normal fault cluster is consistent with the faults having formed as secondary structures as the result of the perturbed stress field around the slipping Pinto Ridge fault. Comparison of mechanical efficiency of various normal fault geometries within extending terranes suggests that the observed west dip of normal faults reflects a west- dipping anisotropy at depth, such as a detachment. The apparent terminations of numerous strike-slip faults of the Lake Mead fault system into west-dipping normal faults suggest that a west-dipping detachment may be regionally coherent.

  2. Slip sense inversion on active strike-slip faults in southwest Japan and its implications for Cenozoic tectonic evolution

    NASA Astrophysics Data System (ADS)

    Maruyama, Tadashi; Lin, Aiming

    2004-05-01

    Analyses of deflected river channels, offset of basement rocks, and fault rock structures reveal that slip sense inversion occurred on major active strike-slip faults in southwest Japan such as the Yamasaki and Mitoke fault zones and the Median Tectonic Line (MTL). Along the Yamasaki and Mitoke fault zones, small-size rivers cutting shallowly mountain slopes and Quaternary terraces have been deflected sinistrally, whereas large-size rivers which deeply incised into the Mio-Pliocene elevated peneplains show no systematically sinistral offset or complicated hairpin-shaped deflection. When the sinistral offsets accumulated on the small-size rivers are restored, the large-size rivers show residual dextral deflections. This dextral offset sense is consistent with that recorded in the pre-Cenozoic basement rocks. S-C fabrics of fault gouge and breccia zone developed in the active fault zones show sinistral shear sense compatible with earthquake focal mechanisms, whereas those of the foliated cataclasite indicate a dextral shear sense. These observations show that the sinistral strike-slip shear fabrics were overprinted on dextral ones which formed during a previous deformation phase. Similar topographic and geologic features are observed along the MTL in the central-eastern part of the Kii Peninsula. Based on these geomorphological and geological data, we infer that the slip sense inversion occurred in the period between the late Tertiary and mid-Quaternary period. This strike-slip inversion might result from the plate rearrangement consequent to the mid-Miocene Japan Sea opening event. This multidisciplinary study gives insight into how active strike-slip fault might evolves with time.

  3. Offset of Latest Pleistocene Shoreface Reveals Slip Rate on the Hosgri Strike-Slip Fault, Offshore Central California

    NASA Astrophysics Data System (ADS)

    Johnson, S. Y.; Hartwell, S. R.; Dartnell, P.

    2014-12-01

    The Hosgri fault is the southern part of the regional Hosgri-San Gregorio dextral strike-slip fault system, which extends primarily in the offshore region for about 400 km in central California. Between Morro Bay and San Simeon, high-resolution multibeam bathymetry reveals that the eastern strand of the Hosgri fault is crossed by a ~265-m-wide slope interpreted as the shoreface of a relict sand spit that formed during a period of relatively slower sea-level rise (Younger Dryas stadial) in the latest Pleistocene. This sand spit crossed an embayment and connected a western fault-bounded bedrock peninsula and an eastern bedrock highland, a paleogeography similar to modern geomorphology along coastal segments of the San Andreas fault. Detailed analysis of the relict shoreface with slope profiles and slope maps indicates a lateral slip rate of 2.6 ± 0.9 mm/yr. Because the Hosgri fault locally includes an active western strand, and regionally converges with several other faults, this slip rate should be considered a minimum for the Hosgri fault in central California and should not be applied for the entire Hosgri-San Gregorio fault system. This slip rate indicates that the Hosgri system takes up the largest share of the strike-slip fault budget and is the most active strike-slip fault west of the San Andreas fault in central California. This result further demonstrates the value and potential of high-resolution bathymetry in earthquake-hazard characterization of active offshore faults.

  4. "Nonfloating" universal joint

    NASA Technical Reports Server (NTRS)

    Appleberry, W. T.

    1978-01-01

    Modified crowned-spline joint is lightweight, durable, and requires minimum of parts. It does not use rubber cushions to limit play and is useful over wide temperature range. It has inner ball and socket to provide rigid connection with no axial play. Joint can be adapted to form pinned connection between segmented torque tubes.

  5. Geared Electromechanical Rotary Joint

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1994-01-01

    Geared rotary joint provides low-noise ac or dc electrical contact between electrical subsystems rotating relative to each other. Designed to overcome some disadvantages of older electromechanical interfaces, especially intermittency of sliding-contact and rolling-contact electromechanical joints. Hollow, springy planetary gears provide continuous, redundant, low-noise electrical contact between inner and outer gears.

  6. Compound solder joints

    NASA Technical Reports Server (NTRS)

    Batista, R. I.; Simonson, R. B.

    1976-01-01

    Joining technique prevents contamination, may be used to join dissimilar metal tubes, minimizes fluid and gas entrapment, expedites repairs, and can yield joints having leakage rates less than 0.000001 standard cubic cm He/min. Components of joint are solder sleeve, two solder rings, Teflon sleeve, and tubing to be joined.

  7. Joint Aspiration (Arthrocentesis)

    MedlinePlus

    ... Cerebral Palsy: Caring for Your Child All About Food Allergies Joint Aspiration (Arthrocentesis) KidsHealth > For Parents > Joint Aspiration (Arthrocentesis) Print A A A Text Size What's in this article? What It Is Why It's Done Preparation Procedure What to Expect Getting the Results Risks ...

  8. Sacroiliac joint pain - aftercare

    MedlinePlus

    The sacroiliac joint (SIJ) is a term used to describe the place where the sacrum and the iliac bones join. The ... The main purpose of the joint is to connect the spine and the pelvis. As a result, there is very little movement at the SIJ. Major reasons ...

  9. Joint Newspaper Operating Agreements.

    ERIC Educational Resources Information Center

    Parsons, Marie

    The number of competing daily newspapers in American cities has dwindled until only about 50 cities boast two papers. Of the newspapers in those cities, 23 now maintain separate editorial operations but have joint printing, advertising, and circulation departments. The concept of joint operation is 50 years old, dating from the Depression years…

  10. The influence of slip velocity and temperature on permeability during and after high-velocity fault slip

    NASA Astrophysics Data System (ADS)

    Tanikawa, W.; Mukoyoshi, H.; Tadai, O.; Hirose, T.; Lin, W.

    2011-12-01

    Fluid transport properties in fault zones play an important role in dynamic processes during large earthquakes. If the permeability in a fault zone is low, high pore-fluid pressures caused by thermal pressurization (Sibson, 1973) or shear-induced compaction (Blanpied et al., 1992) can lead to an apparent reduction of fault strength. Changes in porosity and permeability of fault rocks within a fault zone during earthquakes and the subsequent progressive recovery of these properties may have a large influence on earthquake recurrence (Sleep and Blanpied, 1992). A rotary shear apparatus was used to investigate changes of fluid transport properties in a fault zone by real-time measurement of gas flow rates during and after shearing of hollow sandstone and granite cylinders at various slip rates. Our apparatus measures permeability parallel to the slip plane in both the slip zone and wall rocks. In all cases, permeability decreased rapidly with an increase of friction, but recovered soon after slip, reaching a steady state within several tens of minutes. The rate of reduction of permeability increased with increasing slip velocity. Permeability did not recover to pre-slip levels after low-velocity tests but recovered to exceed them after high-velocity tests. Frictional heating of gases at the slip surface increased gas viscosity, which increased gas flow rate to produce an apparent permeability increase. The irreversible permeability changes of the low-velocity tests were caused by gouge formation due to wearing and smoothing of the slip surface. The increase of permeability after high-velocity tests was caused by mesoscale fracturing in response to rapid temperature rise. Changes of pore fluid viscosity contributed more to changes of flow rate than did permeability changes caused by shear deformation, although test results from different rocks and pore fluids might be different. References Blanpied, M.L., Lockner, D.A., Byerlee, J.D., 1992. An earthquake mechanism based on rapid sealing of faults. Nature 358, 574-576 Sibson, R.H., 1973. Interactions between temperature and pore fluid pressure during earthquake faulting: A mechanism for partial or total stress relief. Nature 243, 66-68. Sleep, N.H., Blanpied, M.L., 1992. Creep, compaction and the weak rheology of major faults. Nature 359, 687-692.

  11. Strategies for joint appointments.

    PubMed

    Royle, J; Crooks, D L

    1985-01-01

    The structure and policies governing joint appointments discussed above, are developed primarily through cooperation and collaboration between nursing service and education institutions. The joint appointee participates in the process of negotiation of salary, benefits and role responsibilities and exploration of the implications of the appointment for personal career development. Implementation and maintenance of the appointment requires the collaborative efforts of the joint appointee with both contracting agencies. Factors influencing the functioning of joint appointees have been identified and strategies to facilitate functioning presented. The joint appointee must be independent in thought and action yet adaptable to work within the boundaries of two social systems with differing values and expectations. Nursing management, peers and students can provide the support needed to overcome the frustrations and to achieve the rewards inherent in successful implementation of an exciting and innovative role. PMID:3852805

  12. Resonant slow fault slip in subduction zones forced by climatic load stress.

    PubMed

    Lowry, Anthony R

    2006-08-17

    Global Positioning System (GPS) measurements at subduction plate boundaries often record fault movements similar to earthquakes but much slower, occurring over timescales of approximately 1 week to approximately 1 year. These 'slow slip events' have been observed in Japan, Cascadia, Mexico, Alaska and New Zealand. The phenomenon is poorly understood, but several observations hint at the processes underlying slow slip. Although slip itself is silent, seismic instruments often record coincident low-amplitude tremor in a narrow (1-5 cycles per second) frequency range. Also, modelling of GPS data and estimates of tremor location indicate that slip focuses near the transition from unstable ('stick-slip') to stable friction at the deep limit of the earthquake-producing seismogenic zone. Perhaps most intriguingly, slow slip is periodic at several locations, with recurrence varying from 6 to 18 months depending on which subduction zone (or even segment) is examined. Here I show that such periodic slow fault slip may be a resonant response to climate-driven stress perturbations. Fault slip resonance helps to explain why slip events are periodic, why periods differ from place to place, and why slip focuses near the base of the seismogenic zone. Resonant slip should initiate within the rupture zone of future great earthquakes, suggesting that slow slip may illuminate fault properties that control earthquake slip. PMID:16915286

  13. Unified formulation for analysis of slopes with general slip surface

    SciTech Connect

    Espinoza, R.D.; Bourdeau, P.L. . School of Civil Engineering); Muhunthan, B. . Dept. of Civil and Environmental Engineering)

    1994-07-01

    The general availability of computers has provided efficient means of assessing the stability of slopes using several analytical methods. However, the increased use of computers coupled with a lack of unified presentation of the various methods sometimes leads to conflicting results. It is shown that the current analytical methods can be grouped into three categories based on the hypotheses used to describe the internal forces, namely: (1) the direction of the internal forces; (2) the height of the line of thrust; and (3) the shape of the distribution function of the internal shear forces. An analytical framework incorporating this idea is presented to facilitate and unify slope stability analysis with general slip surfaces. The study is a generalization of earlier work performed by Espinoza et al. for circular slip surfaces. The framework incorporates most current methods of analysis. The analytical model is implemented in a computer program. The program was used to study several case examples. On this basis, key issues associated with the influence of the internal shear forces on the factor of safety, for both circular and general slip failure surfaces, are discussed. It appears that for circular failure surfaces, even with heterogeneous soil stratigraphy the factor of safety is not affected by the choice of a particular hypothesis. On the contrary, for general slip surfaces this choice may significantly affect the results.

  14. Multi-Modal Monitoring of Slip Along Frictional Discontinuities

    NASA Astrophysics Data System (ADS)

    Hedayat, Ahmadreza; Pyrak-Nolte, Laura J.; Bobet, Antonio

    2014-09-01

    Seismic wave transmission and digital image correlation (DIC) are employed to study slip processes along frictional discontinuities. A series of biaxial compression experiments are performed on gypsum specimens with non-homogeneous contact surfaces. The specimens are composed of two blocks with perfectly mated contact surfaces with a smooth surface with low frictional strength on the upper half and a rough surface with high frictional strength on the lower half. Compressional, P, and shear, S, wave pulses were transmitted through the discontinuity while digital images of the specimen surface were acquired during the test. A distinct peak in the amplitude of transmitted wave occurs prior to the peak shear strength and is considered a "precursor" to the failure. Precursors indicate that slip initiates from the smooth surface and extends to the rough surface as the shear load is increased. From the DIC data, slip is identified as a jump in the displacement field along the fracture that initiates from the smooth surface and propagates to the rough surface. Precursors are associated with an increase in the rate of slip across the discontinuity and are a measure of the reduction in the fracture shear stiffness.

  15. Two-plane balance and slip-ring design

    NASA Technical Reports Server (NTRS)

    Luna, P. M.

    1985-01-01

    A 3.25 cm (1.28 in.) two plane balance and eight channel slip ring assembly has been designed to measure and transmit the thrust (667-N;150-lb) and torque (135-N-m;100-lb-ft) components produced by wind tunnel model turboprops and drive motors operating at 300 Hz.

  16. Micro-Vibration-Based Slip Detection in Tactile Force Sensors

    PubMed Central

    Fernandez, Raul; Payo, Ismael; Vazquez, Andres S.; Becedas, Jonathan

    2014-01-01

    Tactile sensing provides critical information, such as force, texture, shape or temperature, in manipulation tasks. In particular, tactile sensors traditionally used in robotics are emphasized in contact force determination for grasping control and object recognition. Nevertheless, slip detection is also crucial to successfully manipulate an object. Several approaches have appeared to detect slipping, the majority being a combination of complex sensors with complex algorithms. In this paper, we deal with simplicity, analyzing how a novel, but simple, algorithm, based on micro-vibration detection, can be used in a simple, but low-cost and durable, force sensor. We also analyze the results of using the same principle to detect slipping in other force sensors based on flexible parts. In particular, we show and compare the slip detection with: (i) a flexible finger, designed by the authors, acting as a force sensor; (ii) the finger torque sensor of a commercial robotic hand; (iii) a commercial six-axis force sensor mounted on the wrist of a robot; and (iv) a fingertip piezoresistive matrix sensor. PMID:24394598

  17. Slip and flow dynamics of polydisperse thin polystyrene films.

    NASA Astrophysics Data System (ADS)

    Sabzevari, Seyed Mostafa; McGraw, Joshua D.; Jacobs, Karin; Wood-Adams, Paula M.

    2015-03-01

    We investigate the slip of binary and ternary mixtures of nearly monodisperse polystyrene samples on Teflon-coated (AF2400) silicon wafers using dewetting experiments. Binary mixtures of long and short chains along with ternary mixtures with a fixed weight-average molecular weight Mw but different number-average molecular weight Mn were prepared. Thin films of ca. 200 nm were spin coated on mica from polymer solutions and transferred to Teflon substrates. Above the glass transition temperature Tg the films break up via nucleation and growth of holes. The hole growth rate and rim morphology are monitored as a function of Mn and annealing protocol of the films before transfer to Teflon substrates. Slip properties, accessed using hydrodynamic models, and flow dynamics are then examined and compared. We found that the rim morphology and slip of polystyrene blends on Teflon depends on the molecular weight distribution. Similarly, flow dynamics is affected by the presence of short chains in mixture. Moreover, we can provoke differences in slip by choosing appropriate annealing and film transfer protocols for PS films that have first been spin cast on mica surfaces.

  18. Slip velocity and velocity inversion in a cylindrical Couette flow.

    PubMed

    Kim, Sangrak

    2009-03-01

    Velocity inversion in a nanoscale cylindrical Couette flow is investigated with the Navier-Stokes (NS) equation and molecular-dynamics (MD) simulation. With general slip boundary conditions in the NS equation, the flow can be classified into five distinct profiles. The condition of velocity inversion is explored in the whole space of four dimensionless variables of beta , slip velocity ratio u('), radius ratio a('), and angular velocity ratio omega('). MD computer simulations are performed to estimate the constitutive coefficient of the slip velocities at the walls. The flow is generated by a rotating inner wall and a stationary outer wall in conformity with the theoretical result. By varying an attraction parameter in the Lennard-Jones potential, the slip velocities can be easily controlled. The theoretical predictions are compared with the simulation results. We find that in the intermediate range of the attraction parameter the two results are quite comparable to some extent, but at both extreme values of the attraction parameter, they are quite different. PMID:19392054

  19. Flash weakening of serpentinite at near-seismic slip rates

    NASA Astrophysics Data System (ADS)

    Kohli, Arjun H.; Goldsby, David L.; Hirth, Greg; Tullis, Terry

    2011-03-01

    To investigate the processes responsible for dynamic frictional weakening in antigorite serpentinite, we conducted single-velocity and velocity-stepping friction experiments at slip rates (V) from 0.01 to 0.4 m s-1, sliding displacements up to 40 mm, and a normal stress of 5 MPa. Single-velocity experiments demonstrate an approximately 1/V dependence of friction on velocity above a characteristic weakening velocity Vw ≈ 0.1 m s-1, consistent with theoretical predictions for flash heating and subsequent weakening of asperities. Velocity-stepping experiments impose stepwise increases in slip rate show stepwise weakening at slip rates above Vw. Scanning electron microscopy of experimental fault surfaces reveals nanoparticle gouge textures at raised sites (˜10 μm in diameter) in tests that exhibit dramatic weakening. Furthermore, X-ray diffraction analyses of fault gouge from the sliding surface document the formation of significant talc in these tests, indicating that weakening temperatures reached 500°C-700°C. In contrast, no talc is observed in samples for which V remained significantly below Vw. The observed value for Vw is consistent with published microphysical models for flash weakening when independent constraints on the thermal stability and contact strength of antigorite are considered. Finally, while serpentinite displays velocity-strengthening behavior at plate tectonic slip rates, our results indicate that seismic ruptures propagating into serpentinized regions in the shallow lithosphere may trigger seismicity or slow earthquakes, after limited amounts of displacement.

  20. Chaotic mixing in a planar, curved channel using periodic slip

    SciTech Connect

    Garg, P.; Picardo, J. R.; Pushpavanam, S.

    2015-03-15

    We propose a novel strategy for designing chaotic micromixers using curved channels confined between two flat planes. The location of the separatrix between the Dean vortices, induced by centrifugal forces, is dependent on the location of the maxima of axial velocity. An asymmetry in the axial velocity profile can change the location of the separatrix. This is achieved physically by introducing slip alternatingly at the top and bottom walls. This leads to streamline crossing and Lagrangian chaos. An approximate analytical solution of the velocity field is obtained using perturbation theory. This is used to find the Lagrangian trajectories of fluid particles. Poincare sections taken at periodic locations in the axial direction are used to study the extent of chaos. We study two microchannel designs, called circlet and serpentine, in which the Dean vortices in adjacent half cells are co-rotating and counter-rotating, respectively. The extent of mixing, at low Re and low slip length, is shown to be greater in the serpentine case. Wide channels are observed to have much better mixing than tall channels; an important observation not made for separatrix flows till now. Eulerian indicators are used to gauge the extent of mixing, with varying slip length, and it is shown that an optimum slip length exists which maximizes the mixing in a particular geometry. Once the parameter space of relatively high mixing is identified, detailed variance computations are carried out to identify the detailed features.

  1. Nonuniform seismic slip rates along the Middle America Trench

    SciTech Connect

    McNally, K.C.; Minster, J.B.

    1981-06-10

    Revised estimates of seismic slip rates along the Middle America Trench are lower on the average than plate convergence rates but match them locally (for example, Oaxaca). Along the Cocos-North American plate boundary this can be explained by nonuniformities in slip at points of aseismic ridge or fracture zone subduction. For at least 81 yr (and possibly several hundred years), no major (M/sub s/> or =7.5) shallow earthquake is known to have occurred near the Orozco Fracture Zone and Tehuantepec Ridge areas. Compared with the average recurrence periods for large earthquakes (33 +- 8 yr since 1898 and 35 +- 24 yr between 1542 and 1979), this suggests that either a large (M> or =8.4) event may be anticipated at such locations, or that these are points of aseismic subduction. Large coastal terraces and evidence suggesting tectonic uplift are found onshore near the Orozco Fracture zone. The larger discrepancy between plate convergence and seismic slip rates along the Cocos-Carribbean plate boundary is more likely due to decoupling and downbending of the subducted plate. We used the limited statistical evidence available to characterize both spatial and temporal deficiencies in recent seismic slip. The observations appear consistent with a possible forthcoming episode of more intense seismic activity. Based on a series of comparisons with carefully delineated aftershock zones, we conclude that the zones of anomalous seismic activity can be indentified by a systematic, automated analysis of the worldwide earthquake catalog (m/sub b/> or =4).

  2. Fast rupture propagation for large strike-slip earthquakes

    NASA Astrophysics Data System (ADS)

    Wang, Dun; Mori, Jim; Koketsu, Kazuki

    2016-04-01

    Studying rupture speeds of shallow earthquakes is of broad interest because it has a large effect on the strong near-field shaking that causes damage during earthquakes, and it is an important parameter that reflects stress levels and energy on a slipping fault. However, resolving rupture speed is difficult in standard waveform inversion methods due to limited near-field observations and the tradeoff between rupture speed and fault size for teleseismic observations. Here we applied back-projection methods to estimate the rupture speeds of 15 Mw ≥ 7.8 dip-slip and 8 Mw ≥ 7.5 strike-slip earthquakes for which direct P waves are well recorded in Japan on Hi-net, or in North America on USArray. We found that all strike-slip events had very fast average rupture speeds of 3.0-5.0 km/s, which are near or greater than the local shear wave velocity (supershear). These values are faster than for thrust and normal faulting earthquakes that generally rupture with speeds of 1.0-3.0 km/s.

  3. Effects of slip on oscillating fractionalized Maxwell fluid

    NASA Astrophysics Data System (ADS)

    Jamil, Muhammad

    2016-03-01

    The flow of an incompressible fractionalized Maxwell fluid induced by an oscillating plate has been studied, where the no-slip assumption between the wall and the fluid is no longer valid. The solutions obtained for the velocity field and the associated shear stress, written in terms of H-functions, using discrete Laplace transform, satisfy all imposed initial and boundary conditions. The no-slip contributions, that appeared in the general solutions, as expected, tend to zero when slip parameter θ → 0. Furthermore, the solutions for ordinary Maxwell and Newtonian fluids, performing the same motion, are obtained as limiting cases of general solutions. The solutions for fractionalized and ordinary Maxwell fluids for noslip condition also obtained as a special cases and they are similar to the solutions of classical Stokes' first problem of fractionalized and ordinary Maxwell fluid, if oscillating parameter ω = 0. Finally, the influence of the material, slip and the fractional parameters on the fluid motion, as well as a comparison among fractionalized Maxwell, ordinary Maxwell and Newtonian fluids is also analyzed by graphical illustrations.

  4. Wall slip across the jamming transition of soft thermoresponsive particles

    NASA Astrophysics Data System (ADS)

    Divoux, Thibaut; Lapeyre, Véronique; Ravaine, Valérie; Manneville, Sébastien

    2015-12-01

    Flows of suspensions are often affected by wall slip, that is, the fluid velocity vf in the vicinity of a boundary differs from the wall velocity vw due to the presence of a lubrication layer. While the slip velocity vs=|vf-vw| robustly scales linearly with the stress σ at the wall in dilute suspensions, there is no consensus regarding denser suspensions that are sheared in the bulk, for which slip velocities have been reported to scale as a vs∝σp with exponents p inconsistently ranging between 0 and 2. Here we focus on a suspension of soft thermoresponsive particles and show that vs actually scales as a power law of the viscous stress σ -σc , where σc denotes the yield stress of the bulk material. By tuning the temperature across the jamming transition, we further demonstrate that this scaling holds true over a large range of packing fractions ϕ on both sides of the jamming point and that the exponent p increases continuously with ϕ , from p =1 in the case of dilute suspensions to p =2 for jammed assemblies. These results allow us to successfully revisit inconsistent data from the literature and pave the way for a continuous description of wall slip above and below jamming.

  5. Micro-vibration-based slip detection in tactile force sensors.

    PubMed

    Fernandez, Raul; Payo, Ismael; Vazquez, Andres S; Becedas, Jonathan

    2014-01-01

    Tactile sensing provides critical information, such as force, texture, shape or temperature, in manipulation tasks. In particular, tactile sensors traditionally used in robotics are emphasized in contact force determination for grasping control and object recognition. Nevertheless, slip detection is also crucial to successfully manipulate an object. Several approaches have appeared to detect slipping, the majority being a combination of complex sensors with complex algorithms. In this paper, we deal with simplicity, analyzing how a novel, but simple, algorithm, based on micro-vibration detection, can be used in a simple, but low-cost and durable, force sensor. We also analyze the results of using the same principle to detect slipping in other force sensors based on flexible parts. In particular, we show and compare the slip detection with: (i) a flexible finger, designed by the authors, acting as a force sensor; (ii) the finger torque sensor of a commercial robotic hand; (iii) a commercial six-axis force sensor mounted on the wrist of a robot; and (iv) a fingertip piezoresistive matrix sensor. PMID:24394598

  6. Resistive phase-slip states in superconducting channels

    NASA Astrophysics Data System (ADS)

    Kulik, I. O.

    1980-08-01

    The theory of resistive behavior in long superconducting channels is outlined, based on two-fluid description of superconductivity in the vicinity of T c. The quantized resistance (phase-slip) states starting at currents lower than critical are shown to appear, in agreement with the experimental observation.

  7. Yushu Earthquake: rupture of a resistive strip-slip fault

    NASA Astrophysics Data System (ADS)

    Chen, X.; Tang, J.; Xiao, Q.; Dong, Z.

    2011-12-01

    On April 14, 2010, Yushu Ms7.1 earthquake occurred in Ganzi-Yushu fault which is the northwest extension of the famous Xianshuihe fault. The strike direction of the surface rupture of Yushu Earthquake is 310°, extending from the epicenter to the southeast as a left-lateral strike-slip fault. After the earthquake, data from a total of 77 sites along 6 MT profiles were acquired. The analysis and inversion results of the MT Data show that the Yushu earthquake generating fault is a strip-slip fault caught in two resistive zones. In the lower crust beneath the generating fault, there is a resistive abnormal body separating the conductive layers, suggesting that Yushu earthquake is a rupture of a resistive left-lateral strike-slip fault interacted with the both sides of resistive blocks. In addition, it also suggests that the Ganzi-Yushu-Xianshuihe fault may not be a main channel for the material flow of Tibet. Instead, it may be an isolation belt with high resistivity between Bayan Har active block and Chuandian active block. The two active blocks move to the southeast driven by the corresponding lower crust flows and interact with each other through the resistive belt, which results in forming a left-lateral strike-slip deformation and inducting a series of massive earthquarkes along the Ganzi-Yushu-Xianshuihe fault system.

  8. Regional Slip Tendency Analysis of the Great Basin Region

    DOE Data Explorer

    Faulds, James E.

    2013-09-30

    - The resulting along‐fault and fault‐to‐fault variation in slip or dilation potential is a proxy for along fault and fault‐to‐fault variation in fluid flow conduit potential. Stress Magnitudes and directions were calculated across the entire Great Basin. Stress field variation within each focus area was approximated based on regional published data and the world stress database (Hickman et al., 2000; Hickman et al., 1998 Robertson‐Tait et al., 2004; Hickman and Davatzes, 2010; Davatzes and Hickman, 2006; Blake and Davatzes 2011; Blake and Davatzes, 2012; Moeck et al., 2010; Moos and Ronne, 2010 and Reinecker et al., 2005). The minimum horizontal stress direction (Shmin) was contoured, and spatial bins with common Shmin directions were calculated. Based on this technique, we subdivided the Great Basin into nine regions (Shmin <070, 070140). Slip and dilation tendency were calculated using 3DStress for the faults within each region using the mean Shmin for the region. Shmin variation throughout Great Basin are shown on Figure 3. For faults within the Great Basin proper, we applied a normal faulting stress regime, where the vertical stress (sv) is larger than the maximum horizontal stress (shmax), which is larger than the minimum horizontal stress (sv>shmax>shmin). Based on visual inspection of the limited stress magnitude data in the Great Basin, we used magnitudes such that shmin/shmax = .527 and shmin/sv= .46. These values are consistent with stress magnitude data at both Dixie Valley (Hickman et al., 2000) and Yucca Mountain (Stock et al., 1985). For faults within the Walker Lane/Eastern California Shear Zone, we applied a strike‐slip faulting stress, where shmax > sv > shmin. Upon visual inspection of limited stress magnitude data from the Walker Lane and Eastern California Shear zone, we chose values such that SHmin/SHmax = .46 and Shmin/Sv= .527 representative of the region. Results: The results of our slip and dilation tendency analysis are shown in Figures 4 (dilation tendency), 5 (slip tendency) and 6 (slip tendency + dilation tendency). Shmin varies from northwest to east‐west trending throughout much of the Great Basin. As such, north‐ to northeast‐striking faults have the highest tendency to slip and to dilate, depending on the local trend of shmin. These results provide a first order filter on faults and fault systems in the Great Basin, affording focusing of local‐scale exploration efforts for blind or hidden geothermal resources.

  9. Do All Large Strike-slip Earthquakes Have Supershear Ruptures?

    NASA Astrophysics Data System (ADS)

    Wang, D.; Mori, J. J.; Koketsu, K.

    2013-12-01

    Studying the rupture speeds of earthquakes is of broad interesting for earthquake research because it has a large effect on the strong near-field shaking that causes damage during earthquakes. Also rupture speed is a key observation for understanding the controlling stresses and friction during an earthquake, yet the speed and its variations are usually difficult to determine. Using only far-field seismic waveforms, which is the only data available for many large earthquakes, there are problems for estimating the rupture speed with standard waveform inversions, due to trade-off between the rupture speed and the slip location. Here we applied a back projection method to estimate the rupture speeds of Mw ≥ 7.5 strike-slip earthquakes since 2001 which could be analyzed using Hi-net in Japan. We found that all events had very fast average rupture speeds of 3.0-6.0 km/s, which are near or greater than the local shear wave velocity (supershear). These values are faster than for thrust and normal faulting earthquakes that generally rupture with speeds of 1.0-3.0 km/s. Considering the depth-dependent shear-wave velocity, the average propagation speeds for all of the strike-slip events are closer to or greater than the shear wave velocity (Figure 1). For large strike-slip events, transition from subshear to supershear usually occurs within distances of 15 to 30 km from the initiation, which is probably the reason for the scarcity of observed supershear earthquakes for smaller magnitudes. Earthquakes with supershear ruptures can cause more damage than events with subshear ruptures because of the concentration of energy in the forward direction of the rupture. Numerical modeling shows strong focusing and other effects of energy at the rupture front which can intensify the ground motions. A recent example is the April 13, 2010 Qinghai, China earthquake (Mw 6.9), where a moderate-size event caused extensive damage in the Yushu region at the southeastern end of the fault. Careful evaluation of long and straight strike-slip faults should be emphasized for predicting strong ground motions due to supershear rupture. a: Average rupture speeds for Mw ≥ 7.5 strike-slip earthquakes. For comparison, dip-slip earthquakes are also shown. The blue dashed line presents the S wave velocity model of PREM for comparison. b: Rupture velocities are shown as ratio to the local S wave velocity, as a function of depth.

  10. Slip complexity and frictional heterogeneities in dynamic fault models

    NASA Astrophysics Data System (ADS)

    Bizzarri, A.

    2005-12-01

    The numerical modeling of earthquake rupture requires the specification of the fault system geometry, the mechanical properties of the media surrounding the fault, the initial conditions and the constitutive law for fault friction. The latter accounts for the fault zone properties and allows for the description of processes of nucleation, propagation, healing and arrest of a spontaneous rupture. In this work I solve the fundamental elasto-dynamic equation for a planar fault, adopting different constitutive equations (slip-dependent and rate- and state-dependent friction laws). We show that the slip patterns may be complicated by different causes. The spatial heterogeneities of constitutive parameters are able to cause the healing of slip, like barrier-healing or slip pulses. Our numerical experiments show that the heterogeneities of the parameter L affect the dynamic rupture propagation and weakly modify the dynamic stress drop and the rupture velocity. The heterogeneity of a and b parameters affects the dynamic rupture propagation in a more complex way: a velocity strengthening area (a > b) can arrest a dynamic rupture, but can be driven to an instability if suddenly loaded by the dynamic rupture front. Our simulations provide a picture of the complex interactions between fault patches having different frictional properties. Moreover, the slip distribution on the fault plane is complicated considering the effects of the rake rotation during the propagation: depending on the position on the fault plane, the orientation of instantaneous total dynamic traction can change with time with respect to the imposed initial stress direction. These temporal rake rotations depend on the amplitude of the initial stress and on its distribution. They also depend on the curvature and direction of the rupture front with respect to the imposed initial stress direction: this explains why rake rotations are mostly located near the rupture front and within the cohesive zone, where the breakdown processes take places. Finally, the rupture behavior, the fault slip distribution and the traction evolution may be changed and complicated including additional physical phenomena, like thermal pressurization of pore fluid (due to frictional heating). Our results involve interesting implications for slip duration and fracture energy.

  11. Airborne Antenna System for Minimum-Cycle-Slip GPS Reception

    NASA Technical Reports Server (NTRS)

    Wright, C. Wayne

    2009-01-01

    A system that includes a Global Positioning System (GPS) antenna and associated apparatus for keeping the antenna aimed upward has been developed for use aboard a remote-sensing-survey airplane. The purpose served by the system is to enable minimum- cycle-slip reception of GPS signals used in precise computation of the trajectory of the airplane, without having to restrict the airplane to maneuvers that increase the flight time needed to perform a survey. Cycle slip signifies loss of continuous track of the phase of a signal. Minimum-cycle-slip reception is desirable because maintaining constant track of the phase of the carrier signal from each available GPS satellite is necessary for surveying to centimeter or subcentimeter precision. Even a loss of signal for as short a time as a nanosecond can cause cycle slip. Cycle slips degrade the quality and precision of survey data acquired during a flight. The two principal causes of cycle slip are weakness of signals and multipath propagation. Heretofore, it has been standard practice to mount a GPS antenna rigidly on top of an airplane, and the radiation pattern of the antenna is typically hemispherical, so that all GPS satellites above the horizon are viewed by the antenna during level flight. When the airplane must be banked for a turn or other maneuver, the reception hemisphere becomes correspondingly tilted; hence, the antenna no longer views satellites that may still be above the Earth horizon but are now below the equatorial plane of the tilted reception hemisphere. Moreover, part of the reception hemisphere (typically, on the inside of a turn) becomes pointed toward ground, with a consequent increase in received noise and, therefore, degradation of GPS measurements. To minimize the likelihood of loss of signal and cycle slip, bank angles of remote-sensing survey airplanes have generally been limited to 10 or less, resulting in skidding or slipping uncoordinated turns. An airplane must be banked in order to make a coordinated turn. For small-radius, short-time coordinated turns, it is necessary to employ banks as steep as 45 , and turns involving such banks are times and for confining airplanes as closely as possible to areas to be surveyed. The idea underlying the design is that if the antenna can be kept properly aimed, then the incidence of cycle slips caused by loss or weakness of signals can be minimized. The system includes an articulating GPS antenna and associated electronic circuitry mounted under a radome atop an airplane. The electronic circuitry includes a microprocessor-based interface-circuit-and-data-translation module. The system receives data on the current attitude of the airplane from the inertial navigation system of the airplane. The microprocessor decodes the attitude data and uses them to compute commands for the GPS-antenna-articulating mechanism to tilt the antenna, relative to the airplane, in opposition to the roll or bank of the airplane to keep the antenna pointed toward the zenith. The system was tested aboard the hurricane- hunting airplane of the National Oceanic and Atmospheric Administration (NOAA) [see figure] during an 11-hour flight to observe the landfall of Hurricane Bret in late summer of 1999. No bank-angle restrictions were imposed during the flight. Post-flight analysis of the GPS trajectory data revealed that no cycle slip had occurred.considered normal maneuvers. These steep banks are highly desirable for minimizing flight

  12. Duration of slip-resistant shoe usage and the rate of slipping in limited-service restaurants: results from a prospective and crossover study.

    PubMed

    Verma, Santosh K; Zhao, Zhe; Courtney, Theodore K; Chang, Wen-Ruey; Lombardi, David A; Huang, Yueng-Hsiang; Brennan, Melanye J; Perry, Melissa J

    2014-01-01

    Several studies have indicated that slip-resistant shoes may have a positive effect on reducing the risk of slips and falls, a leading cause of injury at work. Few studies, however, have examined how duration of shoe usage affects their slip-resistance properties. This study examined the association between the duration of slip-resistant shoes usage and the self-reported rate of slipping in limited-service restaurant workers. A total of 475 workers from 36 limited-service restaurants in the USA were recruited to participate in a 12-week prospective study of workplace slipping. Of the 475 participants, 83 reported changing to a new pair of shoes at least once during the 12-week follow-up. The results show that slip-resistant shoes worn for less than six months were moderately more effective than those worn for more than six months. Changing to a new pair of shoes among those wearing slip-resistant shoes at baseline was associated with a 55% reduction in the rate of slipping (RR = 0.45, 95% CI = 0.23-0.89). Further research is needed to develop criteria for the replacement of slip-resistant shoes. PMID:25205136

  13. Rapid kinematic slip inversion with regional geophysical data: towards site-specific tsunami intensity forecasts.

    NASA Astrophysics Data System (ADS)

    Melgar, D.; Bock, Y.

    2014-12-01

    Rapid kinematic slip inversions immediately following earthquake rupture is traditionally limited to teleseismic data and delayed many hours after large events. Regional data such as strong motion is difficult to incorporate quickly into images of the source process because baseline offsets render the long period portion of the recording unreliable. Recently it's been demonstrated that high rate GPS can potentially produce rapid slip inversions for large events but is limited to very long periods. With an example of the 2011 M9 Tohoku-oki event we will demonstrate that the optimal on-the-fly combination of GPS and strong motion through a seismogeodetic Kalman filter produces reliable, broadband strong motion displacement and velocity waveforms that can be used for kinematic inversion. Through joint inversion of displacement and velocity waveforms we will show that it is possible to obtain a broadband image of the source. Furthermore, we will also show that it is possible to include offshore geophysical observables such as sea surface measurements of tsunami propagation from GPS buoys and ocean bottom pressure sensors into the kinematic inversion. These data better constrain the shallowest part of rupture. We will use the time-dependent deformation of bathymetry predicted from the inversion results as an initial condition for tsunami propagation and inundation modeling. Through a comparison to post-event survey observations we will demonstrate that it is possible to reproduce the inundation pattern along the coastline in great detail and argue that detailed site-specific forecast of tsunami intensity is achievable with current methods and instrumentation.

  14. Dynamic Strength of Peridotite at Seismic Slip Rates: Experimental Results

    NASA Astrophysics Data System (ADS)

    Del Gaudio, P.; di Toro, G.; Han, R.; Hirose, T.; Shimamoto, T.; Cocco, M.

    2006-12-01

    Ultramafic pseudotachylytes (solidified melts produced during seismic slip) decorate exhumed faults within the Balmuccia peridotite from the Ivrea zone (Italy). Unpublished studies suggest that these pseudotachylytes were produced in the upper-mantle/lower-crust. Kanamori et al. (1998) proposed extensive production of seismic melts during the Mw = 8.3 Bolivian 1994 deep focus (~600 km in depth) earthquake. It follows that seismic melting might occur in the mantle. We conducted high-velocity rock friction experiments with the Balmuccia peridotite to determine the dynamic strength of faults in the presence of ultramafic melts. During each experiment, shear stress evolved with displacement: after an initial peak shear stress, fault strength gradually decreased towards a steady-state value. Dynamic fault weakening was associated with the formation of a molten layer along the slipping zone. By performing experiments for increasing normal stresses (5 to 13 MPa) and slip rates (0.37÷1.14 m/s or ~seismic slip rates), steady-state shear stress (1) slightly increased with increasing normal stress and (2), for a given normal stress, decreased with increasing slip rate. The ratio between steady-state shear stress and normal stress was 0.13, well below the solid rock friction coefficient (~0.8). Experiments conducted under argon or fresh air flux yielded similar shear stress magnitudes, suggesting that olivine oxidation did not affect significantly the fault strength in the high-velocity experiments. The slight dependence of shear stress with normal stress suggests melt lubrication. Since the physics of melt lubrication is somehow predictable (see poster by Nielsen et al.), these experimental results might be extrapolated to the study of rupture dynamics in mantle rocks.

  15. Dehydration-induced porosity waves and episodic tremor and slip

    NASA Astrophysics Data System (ADS)

    Skarbek, Rob M.; Rempel, Alan W.

    2016-02-01

    Episodic tremor and slip (ETS) along the subduction interface takes place where there is abundant evidence for elevated, near-lithostatic pore pressures, at sufficiently great depths (30-45 km) that chemical dehydration reactions must act as their dominant source. We simulate fluid and heat flow while tracking the location of a vertically oriented, one-dimensional column of material as it subducts through the slow slip and tremor zone. The material in the column is transformed through a pressure-dependent and temperature-dependent dehydration reaction that we describe with a generalized nonlinear kinetic rate law. Column deformation is largely dominated by viscous creep, with a closure rate that depends linearly on porosity. This behavior causes the dehydration reaction to generate traveling porosity waves that transport increased fluid pressures within the slow slip region. To explore the possibility that the observed periodicity of slow slip and tremor in subduction zones can be explained by the migration of such porosity waves, we derive a dispersion relation that accurately describes our numerical results. We also obtain an expression for how the thickness of the dehydrating layer is expected to vary as a function of the parameters in the reaction rate law. Although the amplitudes of pore pressure perturbations rival those that are produced by known external forcings (e.g., tides or passing surface waves), our analysis suggests that given reasonable estimates of rock viscosity, permeabilities in the range 6.5×10-15 to 5×10-10 m2 are required for porosity wave trains to form at periods comparable to those of slow slip and tremor.

  16. Distribution of Slip at the Northern Sumatran Fault System

    NASA Technical Reports Server (NTRS)

    Genrich, J. F.; Bock, Y.; McCaffrey, R.; Prawirodirdjo, L.; Stevens, C. W.; Puntodewo, S. S. O.; Subarya, C.; Wdowinski, S.

    2000-01-01

    We model spatial variations in horizontal displacements of 117 geodetic sites measured during annual surveys in 1989-1996 with the Global Positioning System (GPS) as elastic strain across a locked strike-slip fault to infer the contemporary slip rate, locking depth, and location of the Sumatran fault (SF) in northern Sumatra (1 S-3 N). GPS-derived slip rate estimates increase slightly northward from 23 plus or minus 3 mm/yr at 0.8 deg S to 26 plus or minus 2mm/yr at 2.7 N. They agree with geologic estimates north of the Equator, but at 0.5 S they are about 10 mm/yr higher. Strain appears to be distributed asymmetrically about the fault. South of 2 N, about 5 mm/yr of shear is required within the offshore forearc, west of the fault, to achieve a closer agreement of fault locations inferred from GPS velocities with geologically identified traces of the SF. Locking depth estimates are on the order of 10-20 km. The western branch of the major fault bifurcation near 1 N slips at a rate five times higher than the eastern branch. The two main strands of the fault at the northwestern tip of Sumatra (5.5 N) appear to be nearly free of horizontal strain; significant slip must occur away from the two strands, probably further east at two other geologically active branches. The Banda Aceh embayment is extruded to the northwest at a rate of 5 plus or minus 2 mm/yr. Within the estimated velocity uncertainties of several mm/yr, fault-normal deformation along the SF is insignificant. Almost strain free, the northern part of the back-arc basin is part of a rigid Sunda shelf, while the northern forearc is subjected to 8 plus or minus 5 x 10 (exp -8)/yr of extension nearly parallel to the arc.

  17. Late Quaternary slip on the Santa Cruz Island fault, California

    USGS Publications Warehouse

    Pinter, N.; Lueddecke, S.B.; Keller, E.A.; Simmons, K.R.

    1998-01-01

    The style, timing, and pattern of slip on the Santa Cruz Island fault were investigated by trenching the fault and by analysis of offset late Quaternary landforms. A trench excavated across the fault at Christi Beach, on the western coast of the island, exposed deformation of latest Pleistocene to Holocene sediments and pre-Quaternary rocks, recording repeated large-magnitude rupture events. The most recent earthquake at this site occurred ca. 5 ka. Coastal terraces preserved on western Santa Cruz Island have been dated using the uranium-series technique and by extrapolation using terrace elevations and the eustatic record. Offset of terraces and other landforms indicates that the Santa Cruz Island fault is predominantly left lateral, having a horizontal slip rate of not more than 1.1 mm/yr and probably about 0.8 mm/yr. The fault also has a smaller reverse component, slipping at a rate of between 0.1 and 0.2 mm/yr. Combined with measurements of slip per event, this information suggests a long-term average recurrence interval of at least 2.7 k.y. and probably 4-5 k.y., and average earthquake magnitudes of Mw 7.2-7.5. Sense of slip, recurrence interval, and earthquake magnitudes calculated here for the Santa Cruz Island fault are very similar to recent results for other faults along the southern margin of the western Transverse Range, including the Malibu Coast fault, the Santa Monica fault, the Hollywood fault, and the Raymond fault, supporting the contention that these faults constitute a continuous and linked fault system, which is characterized by large but relatively infrequent earthquakes.

  18. Dynamic Mechanochemistry of Seismic Slip -Nano Spherules Lubrication

    NASA Astrophysics Data System (ADS)

    Tanaka, H.; Chen, W.; Chen, Y.; Song, Y.; Ma, K.

    2007-12-01

    The Chelungpu fault, which was activated during 1999Chi-Chi Earthquake, had been drilled (Hole A, B and C) to recover the earthquake slip zone materials. We present here the results of nano-scale observations for identified slip zone materials (Ma, Tanaka et al., 2006) by using HR-TEM and TXM technique. Minimum size of grains observed under HR-TEM is 3 nm. The grain size distribution for grains larger than 100 nm in diameter follows the fractal law and grain shape is highly irregular. Grains smaller than100 nm show some specific characteristics, that is, smaller the grains, more the spherical shapes and more equi-granular. Thus, the grains smaller than 100 nm are no longer described by fractal distribution model. By SAD and EDX analysis under HR-TEM, the nano spherules are mainly composed of crystallized quartz associated with minor amounts of carbonates and amorphous materials. Results of observations lead following three conclusions, (1) nano spherules are not generated just by fracturing based on their shapes and grain size distributions. (2) nano spherules would compose viscous materials enveloping larger fractured grains from SEM observations. (3) Mica clay minerals and feldspars are disappeared in ultra-fine grained layer. This implies that chemical process of dissolution - elements dissipation - SiO2 precipitation occurred associated with mechanical fracturing. Therefore nano spherules would be generated through mechano-chemical process during co-seismic slip. Dynamic shear strength drop by rapid slip experimentsare and formation of gelled materials are recently reported. Large differences of ultra-fine products between previous reports and our observations are existence of nano spherules and their crystallinity. If the nano- spherules are generated during seismic slip, dynamic weakening would be expected because mode of friction turns into rolling friction by huge amounts of equigranular and spherical grains. This may be alternative explanations for dynamic weakening. Quantitative process of dynamic fracturing will be discussed in our presentation.

  19. Evaluation of Gait and Slip Parameters for Adults with Intellectual Disability

    PubMed Central

    Haynes, Courtney A.; Lockhart, Thurmon E.

    2012-01-01

    Adults with intellectual disability (ID) experience more falls than their non-disabled peers. A gait analysis was conducted to quantify normal walking, and an additional slip trial was performed to measure slip response characteristics for adults with ID as well as a group of age-and gender-matched controls. Variables relating to gait pattern, slip propensity, and slip severity were assessed to compare the differences between groups. The ID group was found to have significantly slower walking speed, shorter step lengths, and increased knee flexion angles at heel contact. These gait characteristics are known to reduce the likelihood of slip initiation in adults without ID. Despite a more cautious gait pattern, however, the ID group exhibited greater slip distances indicating greater slip severity. This study suggests that falls in this population may be due to deficient slip detection or insufficient recovery response. PMID:22867766

  20. Cover For Duct Expansion Joint

    NASA Technical Reports Server (NTRS)

    Brown, A. R.

    1988-01-01

    Size and shape of cover reduces stress and increases strength. Cover for expansion joints on duct-work seals tightly while accommodating movement of joint. Provides ample bonding area on both members of joint.

  1. MISR JOINT_AS Data

    Atmospheric Science Data Center

    2014-07-21

    Joint Aerosol Product (JOINT_AS) The MISR Level 3 Products are global or regional ... field campaigns at daily and monthly time scales. The Joint Aerosol product provides a monthly global statistical summary of MISR ...

  2. Pressure vessel flex joint

    NASA Technical Reports Server (NTRS)

    Kahn, Jon B. (Inventor)

    1992-01-01

    An airtight, flexible joint is disclosed for the interfacing of two pressure vessels such as between the Space Station docking tunnel and the Space Shuttle Orbiter bulkhead adapter. The joint provides for flexibility while still retaining a structural link between the two vessels required due to the loading created by the internal/external pressure differential. The joint design provides for limiting the axial load carried across the joint to a specific value, a function returned in the Orbiter/Station tunnel interface. The flex joint comprises a floating structural segment which is permanently attached to one of the pressure vessels through the use of an inflatable seal. The geometric configuration of the joint causes the tension between the vessels created by the internal gas pressure to compress the inflatable seal. The inflation pressure of the seal is kept at a value above the internal/external pressure differential of the vessels in order to maintain a controlled distance between the floating segment and pressure vessel. The inflatable seal consists of either a hollow torus-shaped flexible bladder or two rolling convoluted diaphragm seals which may be reinforced by a system of straps or fabric anchored to the hard structures. The joint acts as a flexible link to allow both angular motion and lateral displacement while it still contains the internal pressure and holds the axial tension between the vessels.

  3. Triggered surface slips in the Salton Trough associated with the 1999 Hector Mine, California, earthquake

    USGS Publications Warehouse

    Rymer, M.J.; Boatwright, J.; Seekins, L.C.; Yule, J.D.; Liu, J.

    2002-01-01

    Surface fracturing occurred along the southern San Andreas, Superstition Hills, and Imperial faults in association with the 16 October 1999 (Mw 7.1) Hector Mine earthquake, making this at least the eighth time in the past 31 years that a regional earthquake has triggered slip along faults in the Salton Trough. Fractures associated with the event formed discontinuous breaks over a 39-km-long stretch of the San Andreas fault, from the Mecca Hills southeastward to Salt Creek and Durmid Hill, a distance from the epicenter of 107 to 139 km. Sense of slip was right lateral; only locally was there a minor (~1 mm) vertical component of slip. Dextral slip ranged from 1 to 13 mm. Maximum slip values in 1999 and earlier triggered slips are most common in the central Mecca Hills. Field evidence indicates a transient opening as the Hector Mine seismic waves passed the southern San Andreas fault. Comparison of nearby strong-motion records indicates several periods of relative opening with passage of the Hector Mine seismic wave-a similar process may have contributed to the field evidence of a transient opening. Slip on the Superstition Hills fault extended at least 9 km, at a distance from the Hector Mine epicenter of about 188 to 196 km. This length of slip is a minimum value, because we saw fresh surface breakage extending farther northwest than our measurement sites. Sense of slip was right lateral; locally there was a minor (~1 mm) vertical component of slip. Dextral slip ranged from 1 to 18 mm, with the largest amounts found distributed (or skewed) away from the Hector Mine earthquake source. Slip triggered on the Superstition Hills fault commonly is skewed away from the earthquake source, most notably in 1968, 1979, and 1999. Surface slip on the Imperial fault and within the Imperial Valley extended about 22 km, representing a distance from the Hector Mine epicenter of about 204 to 226 km. Sense of slip dominantly was right lateral; the right-lateral component of slip ranged from 1 to 19 mm. Locally there was a minor (~1-2 mm) vertical component of slip; larger proportions of vertical slip (up to 10 mm) occurred in Mesquite basin, where scarps indicate long-term oblique-slip motion for this part of the Imperial fault. Slip triggered on the Imperial fault appears randomly distributed relative to location along the fault and source direction. Multiple surface slips, both primary and triggered slip, indicate that slip repeatedly is small at locations of structural complexity.

  4. A simplified method for determining the number of independent slip systems in crystals

    NASA Technical Reports Server (NTRS)

    Cotton, J. D.; Kaufman, M. J.; Noebe, R. D.

    1991-01-01

    A novel method for determining the number of independent slip systems for any family or a combination of families of slip systems is proposed, which is more direct than previous approaches. This technique makes it possible to easily determine, from the known operative slip systems, if the material is slip-system-deficient. The method also makes it possible to determine if twinning may contribute additional deformation modes.

  5. Paleomagnetic and structural evidence for oblique slip in a fault-related fold, Grayback monocline, Colorado

    USGS Publications Warehouse

    Tetreault, J.; Jones, C.H.; Erslev, E.; Larson, S.; Hudson, M.; Holdaway, S.

    2008-01-01

    Significant fold-axis-parallel slip is accommodated in the folded strata of the Grayback monocline, northeastern Front Range, Colorado, without visible large strike-slip displacement on the fold surface. In many cases, oblique-slip deformation is partitioned; fold-axis-normal slip is accommodated within folds, and fold-axis-parallel slip is resolved onto adjacent strike-slip faults. Unlike partitioning strike-parallel slip onto adjacent strike-slip faults, fold-axis-parallel slip has deformed the forelimb of the Grayback monocline. Mean compressive paleostress orientations in the forelimb are deflected 15??-37?? clockwise from the regional paleostress orientation of the northeastern Front Range. Paleomagnetic directions from the Permian Ingleside Formation in the forelimb are rotated 16??-42?? clockwise about a bedding-normal axis relative to the North American Permian reference direction. The paleostress and paleomagnetic rotations increase with the bedding dip angle and decrease along strike toward the fold tip. These measurements allow for 50-120 m of fold-axis-parallel slip within the forelimb, depending on the kinematics of strike-slip shear. This resolved horizontal slip is nearly equal in magnitude to the ???180 m vertical throw across the fold. For 200 m of oblique-slip displacement (120 m of strike slip and 180 m of reverse slip), the true shortening direction across the fold is N90??E, indistinguishable from the regionally inferred direction of N90??E and quite different from the S53??E fold-normal direction. Recognition of this deformational style means that significant amounts of strike slip can be accommodated within folds without axis-parallel surficial faulting. ?? 2008 Geological Society of America.

  6. Joint Aspiration: Arthrocentesis

    PubMed Central

    Mackie, John William

    1987-01-01

    Joint aspiration is an easily mastered procedure used to confirm or rule out joint sepsis and crystal-induced arthrosis. It is routinely performed with or without local anaesthetic, or with cooling spray. The time spent obtaining the fluid is short. The procedure is safe, requiring no hospitalization, except in the case of diagnosed sepsis. Arthrocentesis is a necessary procedure to prove beyond reasonable doubt that infection is not the cause of the arthritis. The family physician must be familiar with this procedure and obtain fluid for analysis, or refer when joint fluid cannot be readily aspirated. (Can Fam Physician 1987; 33:2057-2062.) PMID:21263975

  7. Compliant Joints For Robots

    NASA Technical Reports Server (NTRS)

    Kerley, James J., Jr.

    1990-01-01

    Compliant joints devised to accommodate misalignments of tools and/or workpieces with respect to robotic manipulators. Has characteristics and appearance of both universal-joint and cable-spring-type flexible shaft coupling. Compliance derived from elastic properties of short pieces of cable. Compliance of joint determined by lengths, distances between, relative orientations, thickness of strands, number of strands, material, amount of pretwist, and number of short pieces of cable. Worm-drive mechanism used to adjust lengths to vary compliance as needed during operation.

  8. Constraints on fault slip rates of the southern California plate boundary from GPS velocity and stress inversions

    USGS Publications Warehouse

    Becker, T.W.; Hardebeck, J.L.; Anderson, G.

    2005-01-01

    We use Global Positioning System (GPS) velocities and stress orientations inferred from seismicity to invert for the distribution of slip on faults in the southern California plate-boundary region. Of particular interest is how long-term slip rates are partitioned between the Indio segment of the San Andreas fault (SAF), the San Jacinto fault (SJF) and the San Bernardino segment of the SAE We use two new sets of constraints to address this problem. The first is geodetic velocities from the Southern California Earthquake Center's (SCEC) Crustal Motion Map (version 3 by Shen et al.), which includes significantly more data than previous models. The second is a regional model of stress-field orientations at seismogenic depths, as determined from earthquake focal mechanisms. While GPS data have been used in similar studies before, this is the first application of stress-field observations to this problem. We construct a simplified model of the southern California fault system, and estimate the interseismic surface velocities using a backslip approach with purely elastic strain accumulation, following Meade et al. In addition, we model the stress orientations at seismogenic depths, assuming that crustal stress results from the loading of active faults. The geodetically derived stressing rates are found to be aligned with the stress orientations from seismicity. We therefore proceed to invert simultaneously GPS and stress observations for slip rates of the faults in our network. We find that the regional patterns of crustal deformation as imaged by both data sets can be explained by our model, and that joint inversions lead to better constrained slip rates. In our preferred model, the SJF accommodates ???15 mm yr-1 and the Indio segment of the SAF ???23 mm yr-1 of right-lateral motion, accompanied by a low slip rate on the San Bernardino segment of the SAF 'Anomalous' fault segments such as around the 1992 Mw = 7.3 Landers surface rupture can be detected. There, observed stresses deviate strongly from the long-term loading as predicted by our simple model. Evaluation of model misfits together with information from palaeoseismology may provide further insights into the time dependence of strain accumulation along the San Andreas system. ?? 2004 RAS.

  9. Shallow slip deficit due to large strike-slip earthquakes in dynamic rupture simulations with elasto-plastic off-fault response

    NASA Astrophysics Data System (ADS)

    Kaneko, Y.; Fialko, Y.

    2011-09-01

    Slip inversions of geodetic data from several large (magnitude ˜7) strike-slip earthquakes point to coseismic slip deficit at shallow depths (<3-4 km), that is, coseismic slip appears to decrease towards the Earth surface. While the inferred slip distribution may be consistent with laboratory-derived rate and state friction laws suggesting that the uppermost brittle crust may be velocity strengthening, there remains a question of how the coseismic slip deficit is accommodated throughout the earthquake cycle. The consequence of velocity-strengthening fault friction at shallow depths is that the deficit of coseismic slip is relieved by post-seismic afterslip and interseismic creep. However, many seismic events with inferred shallow slip deficit were not associated with either resolvable shallow interseismic creep or robust shallow afterslip. Hence, the origin of shallow 'slip deficit' remains uncertain. In this study, we investigate whether inelastic failure in the shallow crust due to dynamic earthquake rupture can explain the inferred deficit of shallow slip. Evidence for such failure is emerging from geologic, seismic and geodetic observations. We find that the amount of shallow slip deficit is proportional to the amount of inelastic deformation near the Earth surface. Such deformation occurs under a wide range of parameters that characterize rock strength in the upper crust. However, the largest magnitude of slip deficit in models accounting for off-fault yielding is 2-4 times smaller than that inferred from kinematic inversions of geodetic data. To explain this discrepancy, we further explore to what extent assumptions in the kinematic inversions may bias the inferred slip distributions. Inelastic deformation in the shallow crust reduces coseismic strain near the fault, introducing an additional 'artificial' deficit of up to 10 per cent of the maximum slip in inversions of geodetic data that are based on purely elastic models. The largest magnitude of slip deficit in our models combined with the bias in inversions accounts for up to 25 per cent of shallow slip deficit, which is comparable, but still smaller than 30-60 per cent deficit inferred from kinematic inversions. We discuss potential mechanisms that may account for the remaining discrepancy between slip deficit predicted by elasto-plastic rupture models and that inferred from inversions of space geodetic data.

  10. A possible restart of an interplate slow slip adjacent to the Tokai seismic gap in Japan

    NASA Astrophysics Data System (ADS)

    Ozawa, Shinzaburo; Tobita, Mikio; Yarai, Hiroshi

    2016-04-01

    The Tokai region of Japan is known to be a seismic gap area and is expected to be the source region of the anticipated Tokai earthquake with a moment magnitude of over 8. Interplate slow slip occurred from approximately 2001 and subsided in 2005 in the area adjacent to the source region of the expected Tokai earthquake. Eight years later, the Tokai region again revealed signs of a slow slip from early 2013. This is the first evidence based on a dense Global Positioning System network that Tokai long-term slow slips repeatedly occur. Two datasets with different detrending produce similar transient crustal deformation and aseismic slip models, supporting the occurrence of the Tokai slow slip. The center of the current Tokai slow slip is near Lake Hamana, south of the center of the previous Tokai slow slip. The estimated moments, which increase at a roughly constant rate, amount to that of an earthquake with a moment magnitude of 6.6. If the ongoing Tokai slow slip subsides soon, it will suggest that there are at least two different types of slow slip events in the Tokai long-term slow slip area: that is, a large slow slip with a moment magnitude of over 7 with undulating time evolution and a small one with a moment magnitude of around 6.6 with a roughly linear time evolution. Because the Tokai slow slip changes the stress state to one more favorable for the expected Tokai earthquake, intense monitoring is going on.

  11. An integrated perspective of the continuum between earthquakes and slow-slip phenomena

    USGS Publications Warehouse

    Peng, Zhigang; Gomberg, Joan

    2010-01-01

    The discovery of slow-slip phenomena has revolutionized our understanding of how faults accommodate relative plate motions. Faults were previously thought to relieve stress either through continuous aseismic sliding, or as earthquakes resulting from instantaneous failure of locked faults. In contrast, slow-slip events proceed so slowly that slip is limited and only low-frequency (or no) seismic waves radiate. We find that slow-slip phenomena are not unique to the depths (tens of kilometres) of subduction zone plate interfaces. They occur on faults in many settings, at numerous scales and owing to various loading processes, including landslides and glaciers. Taken together, the observations indicate that slowly slipping fault surfaces relax most of the accrued stresses through aseismic slip. Aseismic motion can trigger more rapid slip elsewhere on the fault that is sufficiently fast to generate seismic waves. The resulting radiation has characteristics ranging from those indicative of slow but seismic slip, to those typical of earthquakes. The mode of seismic slip depends on the inherent characteristics of the fault, such as the frictional properties. Slow-slip events have previously been classified as a distinct mode of fault slip compared with that seen in earthquakes. We conclude that instead, slip modes span a continuum and are of common occurrence.

  12. Strike-slip kinematics in Central and Eastern Iran: Estimating fault slip-rates averaged over the Holocene

    NASA Astrophysics Data System (ADS)

    Meyer, Bertrand; Le Dortz, Kristell

    2007-10-01

    According to GPS measurements, the right-lateral shear between Central Iran and Afghan blocks amounts to 16 mm/yr. A model based on very long-term estimates of fault-rates suggests the current shear originated about 5 Ma ago and has been accommodated by strike-slip faulting limited to the western (˜2 mm/yr, Gowk-Nayband fault) and eastern (˜14 mm/yr, Sistan system fault) edges of the Lut block. We have used high-resolution SPOT5 (pixel size 2.5 m) images to measure recent cumulative offsets and estimate slip-rates over shorter time periods that average several seismic cycles only. Recent offsets, a few tens of meters, have been found along the Anar fault inside the Central Iran plateau and along the Sistan faults east of the Lut. The offset-morphologies postdate the last incision of the network and are most probably of Holocene age (12 ± 2 ka). The corresponding slip-rates range between ˜0.5-0.75 mm/yr, ˜1.75-2.5 mm/yr, ˜1-5 mm/yr, ˜1-2.5 mm/yr for the Anar, East Neh, West Neh, and Asagie fault, respectively. These estimates suggest the GPS shear-rate across the Lut may not extrapolate over the Holocene. They also indicate strike-slip faulting is not confined to the Lut edges, but also occurs in Central Iran, suggesting the ongoing strike-slip tectonics might have originated between 8 and 22 Ma ago, earlier than considered previously and consistent with observations in NE Iran.

  13. Development of Surface Structures for Large Effective Slip: How Much Slip Is Possible in Ideal, Lab and Real Conditions?

    NASA Astrophysics Data System (ADS)

    Kim, Chang-Jin

    2009-11-01

    An ideal condition to reduce the drag of a liquid flowing on a solid surface is maintaining a lubricating gas layer between the solid and the liquid. For water flowing on a 1 or 10 μm-thick air layer, for example, the slip length is calculated to be roughly 50 or 500 μm, respectively - large enough to benefit a wide range of engineering applications. Unfortunately, however, the above ideal water-levitating condition is only imaginary, because such a liquid-gas meniscus cannot be sustained in nature. Instead, water-repelling structured surfaces bring us closer to the imaginary condition by minimizing the liquid-solid interface and keeping the water mostly on a layer of air. The underlying goal in developing a large-slip surface is, therefore, to create a condition as close as possible to the uniform air lubrication, which is often overlooked. For example, while a large contact angle on a superhydrophobic surface helps keep the liquid fakir, note that once levitated, the contact angle has little effect on increasing the slip length. Instead, the geometrical parameters of the surface structures, e.g., air fraction, pitch and depth of the structures, are the determining factors. A series of development efforts to create surfaces that bring us closer to the ideal air-lubricating condition will be presented, with the slip length currently measured as large as 400 μm. However, it will be also noted that they are valid only in laboratory conditions, where the sample is fabricated to near perfection and the pressure in the flowing liquid is under strict control. In real-life engineering conditions, which include high and fluctuating pressure, defective surfaces, and liquids full of impurities and particles, it remains to be seen if we will ever be able to create a slip surface that can be field-deployed - a millennium-old dream.

  14. Geometric and mechanical-stiffness controls on jointing in cataclastic deformation bands

    NASA Astrophysics Data System (ADS)

    Tindall, Sarah; Eckert, Andreas

    2015-08-01

    Cataclastic deformation bands on the Waterpocket Fold in southern Utah contain cross-cutting joints that terminate at the contacts between the deformation bands and surrounding sandstone. The mechanical contrast between sandstone host rock and stronger deformation bands is analogous to inter-bedded weak and strong layers in a sedimentary sequence, a situation known to result in joints preferentially forming in the stronger layers with joints perpendicular to layer boundaries. Deformation bands in the field area represent conjugate strike-slip shear zones, many with internal Riedel shear geometry, creating a three-dimensional network of mechanically strong zones in variable orientations. Joint attitudes were found to vary systematically as a function of deformation band strike, and the angle between each deformation band and its associated joints is perpendicular to neither the deformation band nor the far-field extension direction. Field observations are confirmed by 2D finite element models showing that local stress reorientation at boundaries between layers affects the mechanics of jointing. The stiffness contrast results in conditions for initiating joints contained in the deformation band, and also results in variable joint orientations in deformation bands with strike orientations oblique to the far-field extension direction. A higher stiffness contrast results in a greater angle between deformation band strike and band-contained joint strike.

  15. Improved orthopedic arm joint

    NASA Technical Reports Server (NTRS)

    Dane, D. H.

    1971-01-01

    Joint permits smooth and easy movement of disabled arm and is smaller, lighter and less expensive than previous models. Device is interchangeable and may be used on either arm at the shoulder or at the elbow.

  16. Knee joint replacement - discharge

    MedlinePlus

    ... ok to start again. People who have a prosthesis, such as an artificial joint, need to carefully ... in your wallet that says you have a prosthesis. You will need to take antibiotics before any ...

  17. Wrist joint assembly

    NASA Technical Reports Server (NTRS)

    Kersten, L.; Johnson, J. D. (Inventor)

    1978-01-01

    A wrist joint assembly is provided for use with a mechanical manipulator arm for finely positioning an end-effector carried by the wrist joint on the terminal end of the manipulator arm. The wrist joint assembly is pivotable about a first axis to produce a yaw motion, a second axis is to produce a pitch motion, and a third axis to produce a roll motion. The wrist joint assembly includes a disk segment affixed to the terminal end of the manipulator arm and a first housing member, a second housing member, and a third housing member. The third housing member and the mechanical end-effector are moved in the yaw, pitch, and roll motion. Drive means are provided for rotating each of the housings about their respective axis which includes a cluster of miniature motors having spur gears carried on the output drive shaft which mesh with a center drive gear affixed on the housing to be rotated.

  18. 46 CFR 154.524 - Piping joints: Welded and screwed couplings.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... penetration at the weld root except that for design temperatures colder than −10 °C (14 °F) the butt weld must... 979 kPa gauge (142 psig) must be removed after the weld is completed; (2) A consumable insert; or (3) An inert gas back-up on the first weld pass. (b) A slip-on welded joint with sleeves and...

  19. 46 CFR 154.524 - Piping joints: Welded and screwed couplings.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... penetration at the weld root except that for design temperatures colder than −10 °C (14 °F) the butt weld must... 979 kPa gauge (142 psig) must be removed after the weld is completed; (2) A consumable insert; or (3) An inert gas back-up on the first weld pass. (b) A slip-on welded joint with sleeves and...

  20. 46 CFR 154.524 - Piping joints: Welded and screwed couplings.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... penetration at the weld root except that for design temperatures colder than −10 °C (14 °F) the butt weld must... 979 kPa gauge (142 psig) must be removed after the weld is completed; (2) A consumable insert; or (3) An inert gas back-up on the first weld pass. (b) A slip-on welded joint with sleeves and...

  1. Seismic and aseismic slip on the central Peru megathrust (Invited)

    NASA Astrophysics Data System (ADS)

    Perfettini, H.; Avouac, J.; Kositsky, A.; Rémy, D.; Tavera, H.; Nocquet, J.; Chlieh, M.; Sladen, A.

    2010-12-01

    In the last couple of decades, advances in the analysis techniques and instrumentation have improved significantly our capability to document the different stages of the seismic cycle, namely the co-, post- and inter-seismic phases. To this respect, the Mw8.0 Pisco, Peru, earthquake of August 2007 is exemplary, with numerous data sets allowing exploring the details of each phase and studying their relationship. The post-seismic deformation following the mainshock is studied using a local network of continuous GPS stations together with various InSAR interferograms. Inversion for slip on the fault is carried on using the PCAIM inversion method (http://www.tectonics.caltech.edu/resources/pcaim/). The inversion shows two patches of significant afterslip located near the co-seismic asperities, in agreement with the idea that coseismic slip triggers afterslip. Aftershocks are located on top of the patches of high postseismic slip, while they are anti-correlated with the position of the co-seismic asperities, consistent with the idea that afterslip drive aftershocks. Post-seismic relaxation is consistent with rate and state friction, assuming a rate strengthening rheology. The most prominent of those post-seismic patches coincides with the subducting Nazca ridge, an area also characterized by a locally low interseismic coupling and which seems to have acted as a barrier to seismic rupture propagation repeatedly in the past. The ’seismogenic’ portion of the megathrust thus appears to be paved with interfingering of rate-weakening and rate-strengthening patches. The rate-strengthening patches are shown to contribute to an unsuspected high proportion of aseismic slip and to determine the extent and frequency of large interplate earthquakes. Aseismic slip accounts for as much as 50-70% of the slip budget on the seismogenic portion of the megathrust of central Peru and the return period of Mw 8.0 earthquakes in the Pisco area is estimated to 250 years, a value in good agreement with the 261 years between the 2007 Pisco earthquake and the previous large megathrust earthquake in this area which occurred in 1746.

  2. Fault core and slip zone geometry, wear and evolution

    NASA Astrophysics Data System (ADS)

    Shervais, K.; Kirkpatrick, J. D.

    2014-12-01

    The static strength and dynamic shear resistance of seismic faults depend on composition, shape, spatial variability, and distribution of asperities on fault surfaces. To characterize these qualities in a paleoseismic fault, we studied the Boyd Fault, a Laramide thrust exposed in crystalline rocks south of Palm Desert, CA. High-resolution digital elevation models of outcrops were rectified with fault strike and dip and used to map 62 m of exposed fault core in the field at three exposures over 175 m along fault strike. The fault core exhibits stratified layers of fault gouge of varying thicknesses with crosscutting relationships and discontinuous layers. One layer is interpreted as the most recent slip event because it crosscuts all the others and has injection veins branching into both the footwall and hanging wall. Microstructures and the presence of gouge injections indicate fluidization of the gouge throughout the fault slip zone during seismic slip. We compared the geometry of the most recent slip event to the fault core as a whole to constrain how the characteristics of the fault evolve with displacement. We found four "thresholds": a. the length scales at which the variance of 1. total fault core thickness and 2. the most recent gouge layer thickness do not fluctuate and remain stable, via experimental semivariograms; b. the length scale at which wear is scale dependent, via power spectral density (PSD) calculations from cross sections through the most recent layer and the fault core; and c. the scale at which fault wear transitions from inelastic to elastic, via the maximum length of hanging wall asperity clasts in the fault gouge. By comparing the most recent event with the core as a whole, these results indicate that faults smooth with displacement, but clast compositions provide evidence of preferential wear due to wall rock composition differences. In addition, slip zone thickness decreases and becomes less variable. We suggest the correlation length scale in the slip zone thickness defines the length scale of an asperity on the fault surface. Overall, our results indicate an evolution of the size and distribution of asperities, implying dynamic shear strength and the static strength of the fault also vary with increasing displacement.

  3. Dual megathrust slip behaviors of the 2014 Iquique earthquake sequence

    NASA Astrophysics Data System (ADS)

    Meng, Lingsen; Huang, Hui; Bürgmann, Roland; Ampuero, Jean Paul; Strader, Anne

    2015-02-01

    The transition between seismic rupture and aseismic creep is of central interest to better understand the mechanics of subduction processes. A Mw 8.2 earthquake occurred on April 1st, 2014 in the Iquique seismic gap of northern Chile. This event was preceded by a long foreshock sequence including a 2-week-long migration of seismicity initiated by a Mw 6.7 earthquake. Repeating earthquakes were found among the foreshock sequence that migrated towards the mainshock hypocenter, suggesting a large-scale slow-slip event on the megathrust preceding the mainshock. The variations of the recurrence times of the repeating earthquakes highlight the diverse seismic and aseismic slip behaviors on different megathrust segments. The repeaters that were active only before the mainshock recurred more often and were distributed in areas of substantial coseismic slip, while repeaters that occurred both before and after the mainshock were in the area complementary to the mainshock rupture. The spatiotemporal distribution of the repeating earthquakes illustrates the essential role of propagating aseismic slip leading up to the mainshock and illuminates the distribution of postseismic afterslip. Various finite fault models indicate that the largest coseismic slip generally occurred down-dip from the foreshock activity and the mainshock hypocenter. Source imaging by teleseismic back-projection indicates an initial down-dip propagation stage followed by a rupture-expansion stage. In the first stage, the finite fault models show an emergent onset of moment rate at low frequency (< 0.1 Hz), while back-projection shows a steady increase of high frequency power (> 0.5 Hz). This indicates frequency-dependent manifestations of seismic radiation in the low-stress foreshock region. In the second stage, the rupture expands in rich bursts along the rim of a semi-elliptical region with episodes of re-ruptures, suggesting delayed failure of asperities. The high-frequency rupture remains within an area of local high trench-parallel gravity anomaly (TPGA), suggesting the presence of subducting seamounts that promote high-frequency generation. Our results highlight the complexity of the interactions between large-scale aseismic slow-slip and dynamic ruptures of megathrust earthquakes.

  4. Assembly Of The SLIP1-SLBP Complex On Histone mRNA Requires Heterodimerization And Sequential Binding Of SLBP Followed By SLIP1

    PubMed Central

    Bansal, Nitin; Zhang, Minyou; Bhaskar, Aishwarya; Itotia, Patrick; Lee, EunHee; Shlyakhtenko, Lyudmila S; Lam, TuKiet T.; Fritz, Andrew; Berezney, Ronald; Lyubchenko, Yuri L; Stafford, Walter F.; Thapar, Roopa

    2013-01-01

    The SLIP1-SLBP complex activates translation of replication-dependent histone mRNAs. In this report, we describe how the activity of the SLIP1-SLBP complex is modulated by phosphorylation and oligomerization. Biophysical characterization of the free proteins shows that whereas SLIP1 is a homodimer that does not bind RNA, human SLBP is an intrinsically disordered protein that is phosphorylated at 23 Ser/Thr sites when expressed in a eukaryotic expression system such as baculovirus. The bacterially expressed unphosphorylated SLIP1-SLBP complex forms a 2:2 high affinity (KD < 0.9 nM) heterotetramer that is also incapable of binding histone mRNA. In contrast, phosphorylated SLBP from baculovirus has weak affinity (KD ~3 µM) for SLIP1. Sequential binding of phosphorylated SLBP to the histone mRNA stem-loop, followed by association with SLIP1 is required to form an “active” ternary complex. Phosphorylation of SLBP at Thr171 promotes dissociation of the heterotetramer to the SLIP1-SLBP heterodimer. Using alanine scanning mutagenesis we demonstrate that the binding site on SLIP1 for SLBP lies close to the dimer interface. A single point mutant near the SLIP1 homodimer interface abolished interaction with SLBP in vitro and reduced histone mRNA abundance in vivo. On the basis of these biophysical studies, we propose that oligomerization and SLBP phosphorylation may regulate the SLBP-SLIP1 complex in vivo. SLIP1 may act to sequester SLBP in vivo protecting it from proteolytic degradation as an inactive hetero-tetramer, or alternatively, formation of the SLIP1-SLBP hetero-tetramer may facilitate removal of SLBP from the histone mRNA prior to histone mRNA degradation. PMID:23286197

  5. Optimization of bonded joints

    NASA Technical Reports Server (NTRS)

    Ojalvo, I. U.

    1983-01-01

    A procedure for minimizing the elastic shear stress concentration in adhesive lap joints is presented. The proposed method is based upon tapering the adherends to achieve smooth stiffness transitions and uniform shear stresses. Both single and double lap splices are considered, but numerical examples are restricted to the case of double lap joints. Nonisotropic materials and nonoptimum design limitations, such as minimum and maximum thickness adherends, load-line eccentricity, and peel stresses are treated, and typical results are presented.

  6. High pressure ceramic joint

    DOEpatents

    Ward, M.E.; Harkins, B.D.

    1993-11-30

    Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present joint when used with recuperators increases the use of ceramic components which do not react to highly corrosive gases. Thus, the present joint used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present joint is comprised of a first ceramic member, a second ceramic member, a mechanical locking device having a groove defined in one of the first ceramic member and the second ceramic member. The joint and the mechanical locking device is further comprised of a refractory material disposed in the groove and contacting the first ceramic member and the second ceramic member. The present joint mechanically provides a high strength load bearing joint having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures. 4 figures.

  7. High pressure ceramic joint

    DOEpatents

    Ward, Michael E.; Harkins, Bruce D.

    1993-01-01

    Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present joint when used with recuperators increases the use of ceramic components which do not react to highly corrosive gases. Thus, the present joint used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present joint is comprised of a first ceramic member, a second ceramic member, a mechanical locking device having a groove defined in one of the first ceramic member and the second ceramic member. The joint and the mechanical locking device is further comprised of a refractory material disposed in the groove and contacting the first ceramic member and the second ceramic member. The present joint mechanically provides a high strength load bearing joint having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures.

  8. Panel Post & Diagonal Brace Joint Detail; Crossbracing Center Joint ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Panel Post & Diagonal Brace Joint Detail; Crossbracing Center Joint Detail; Chord, Panel Post, Tie Bar, & Diagonal Brace Joint Detail; Chord, Tie Bar, & Crossbracing Joint Detail - Medora Bridge, Spanning East Fork of White River at State Route 235, Medora, Jackson County, IN

  9. Slow Earthquakes and The Mechanics of Slow Frictional Stick-Slip

    NASA Astrophysics Data System (ADS)

    Marone, Chris; Scuderi, Marco; Leeman, John; Saffer, Demian; Collettini, Cristiano; Johnson, Paul

    2015-04-01

    Slow earthquakes represent one mode of the spectrum of fault slip behaviors ranging from steady aseismic slip to normal earthquakes. Like normal earthquakes, slow earthquakes can occur repetitively, such that a fault fails in a form of stick-slip failure defined by interseismic strain accumulation and slow, quasidynamic slip. The mechanics of frictional stick-slip and seismogenic faulting appear to apply to slow earthquakes, however, the mechanisms that limit dynamic slip velocity, rupture propagation speed, and the scaling between moment and duration of slow earthquakes are poorly understood. Here, we describe laboratory experiments that explore the mechanics of repetitive, slow frictional stick-slip failure. We document the role of loading stiffness and friction constitutive behavior in dictating the properties of repetitive, frictional stick-slip. Our results show that a spectrum of dynamic and quasidynamic slip velocities can occur in stick-slip events depending on the relation between loading stiffness k and the rheologic critical stiffness kc given, in the context of rate and state friction, by the ratio of the friction rate parameter (b-a) divided by the critical friction distance Dc. Slow slip is favored by conditions for which k is ~ equal to kc, whereas normal, fast stick slip occurs when k/kc < 1. We explore the role of elastic coupling and spatially extended slip propagation by comparing slow slip results for shear in a layer driven by forcing blocks of varying stiffness. We evaluate our data in the framework of rate and state friction laws and focus on the frictional mechanics of slow stick-slip failure with special attention paid to the connections between quasidynamic failure and mechanisms of the brittle-ductile transition in fault rocks.

  10. Probabilistic estimates of surface coseismic slip and afterslip for Hayward fault earthquakes

    USGS Publications Warehouse

    Aagaard, Brad T.; Lienkaemper, James J.; Schwartz, David P.

    2012-01-01

    We examine the partition of long‐term geologic slip on the Hayward fault into interseismic creep, coseismic slip, and afterslip. Using Monte Carlo simulations, we compute expected coseismic slip and afterslip at three alinement array sites for Hayward fault earthquakes with nominal moment magnitudes ranging from about 6.5 to 7.1. We consider how interseismic creep might affect the coseismic slip distribution as well as the variability in locations of large and small slip patches and the magnitude of an earthquake for a given rupture area. We calibrate the estimates to be consistent with the ratio of interseismic creep rate at the alinement array sites to the geologic slip rate for the Hayward fault. We find that the coseismic slip at the surface is expected to comprise only a small fraction of the long‐term geologic slip. The median values of coseismic slip are less than 0.2 m in nearly all cases as a result of the influence of interseismic creep and afterslip. However, afterslip makes a substantial contribution to the long‐term geologic slip and may be responsible for up to 0.5–1.5 m (median plus one standard deviation [S.D.]) of additional slip following an earthquake rupture. Thus, utility and transportation infrastructure could be severely impacted by afterslip in the hours and days following a large earthquake on the Hayward fault that generated little coseismic slip. Inherent spatial variability in earthquake slip combined with the uncertainty in how interseismic creep affects coseismic slip results in large uncertainties in these slip estimates.

  11. Slip history of the 1995 Kobe, Japan, earthquake determined from strong motion, teleseismic, and geodetic data

    USGS Publications Warehouse

    Wald, D.J.

    1996-01-01

    Near-source ground motions, teleseismic body waveforms, and geodetic displacements produced by the 1995 Kobe, Japan, earthquake have been used to determine the spatial and temporal dislocation pattern on the faulting surfaces. Analysis of the slip model indicates that the ground motions recorded within the severely damaged region of Kobe originated from the region of relatively low slip (about 1 m) deep beneath Kobe and not from the shallow, higher slip regions (about 3 m) beneath Aqaji Island. Although the slip was relatively low beneath Kobe, the combined effects of source rupture directivity, a short slip duration, and site amplification conspired to generate very damaging ground motions within the city.

  12. Predicting active slip systems in β-Sn from ideal shear resistance

    NASA Astrophysics Data System (ADS)

    Kinoshita, Y.; Matsushima, H.; Ohno, N.

    2012-04-01

    We analyse the ideal shear resistances of 15 nonequivalent slip systems in β-Sn using first-principles density functional theory. From the ideal shear resistance and Schmid's law, the orientation dependence of active slip systems in a β-Sn single crystal subjected to uniaxial tension is investigated. We find that (1\\,0\\,1)[\\bar{1}\\,0\\,1] has the lowest ideal shear resistance among the 15 slip systems. Our calculations indicate that, depending on crystal orientation, uniaxial tension activates seven nonequivalent groups of slip systems. The active slip systems for [1 0 0] and [1 1 0] orientations determined in this study agree with the experimental results.

  13. Self-healing slip pulses in dynamic rupture models due to velocity-dependent strength

    USGS Publications Warehouse

    Beeler, N.M.; Tullis, T.E.

    1996-01-01

    Seismological observations of short slip duration on faults (short rise time on seismograms) during earthquakes are not consistent with conventional crack models of dynamic rupture and fault slip. In these models, the leading edge of rupture stops only when a strong region is encountered, and slip at an interior point ceases only when waves from the stopped edge of slip propagate back to that point. In contrast, some seismological evidence suggests that the duration of slip is too short for waves to propagate from the nearest edge of the ruptured surface, perhaps even if the distance used is an asperity size instead of the entire rupture dimension. What controls slip duration, if not dimensions of the fault or of asperities? In this study, dynamic earthquake rupture and slip are represented by a propagating shear crack. For all propagating shear cracks, slip velocity is highest near the rupture front, and at a small distance behind the rupture front, the slip velocity decreases. As pointed out by Heaton (1990), if the crack obeys a negative slip-rate-dependent strength relation, the lower slip velocity behind the rupture front will lead to strengthening that further reduces the velocity, and under certain circumstances, healing of slip can occur. The boundary element method of Hamano (1974) is used in a program adapted from Andrews (1985) for numerical simulations of mode II rupture with two different velocity-dependent strength functions. For the first function, after a slip-weakening displacement, the crack follows an exponential velocity-weakening relation. The characteristic velocity V0 of the exponential determines the magnitude of the velocity-dependence at dynamic velocities. The velocity-dependence at high velocity is essentially zero when V0 is small and the resulting slip velocity distribution is similar to slip weakening. If V0 is larger, rupture propagation initially resembles slip-weakening, but spontaneous healing occurs behind the rupture front. The rise time and rupture propagation velocity depend on the choice of constitutive parameters. The second strength function is a natural log velocity-dependent form similar to constitutive laws that fit experimental rock friction data at lower velocities. Slip pulses also arise with this function. For a reasonable choice of constitutive parameters, slip pulses with this function do not propagate at speeds greater than the Raleighwave velocity. The calculated slip pulses are similar in many aspects to seismic observations of short rise time. In all cases of self-healing slip pulses, the residual stress increases with distance behind the trailing edge of the pulse so that the final stress drop is much less than the dynamic stress drop, in agreement with the model of Brune (1976) and some recent seismological observations of rupture.

  14. Quantum Phase Slips in Topological Josephson Junction Rings

    NASA Astrophysics Data System (ADS)

    Rodriguez Mota, Rosa; Vishveshwara, Smitha; Pereg-Barnea, Tami

    We study quantum phase slip processes (QPS) in a ring of N topological superconducting islands joined by Josephson junctions and threaded by magnetic flux. In this array, neighboring islands interact through the usual charge 2e Josephson tunneling and the Majorana assisted charge e tunneling. When the charging energy associated with the island's capacitance is zero, the energy vs. flux relation of the system is characterized by parabolas centered around even or odd multiples of the superconducting flux quantum, depending on the parity of the system. For small but non-zero charging energy, quantum fluctuations can lead to tunneling between these classical states. In this work, we calculate the amplitude of these tunneling processes, commonly known as quantum phase slips. We also add gate voltages to our system and study how the amplitude of QPS in these topological Josephson array is modified by Aharanov-Casher interference effects.

  15. A Novel Algorithm for Cycle Slip Detection and Repair

    NASA Astrophysics Data System (ADS)

    Sezen, U.; Arikan, F.

    2012-04-01

    Accurate and reliable estimation of ionospheric parameters are very important for correct functioning of communication, navigation and positioning satellite systems. In recent years, dual-frequency GPS receivers are widely used for estimation of Total Electron Content (TEC), which is defined as the line integral of the electron density along a ray path. Since both electron density and TEC are functions of solar, geomagnetic, gravitational and seismic activity, any disturbance along the ray path can be detected using GPS receiver observables. It is observed that, with the development of recent sophisticated receivers, disruptions due to the receiver antenna, hardware or outside obstructions are minimized. Most of the observed sudden disturbances are signal phase lock losses due to ionosphere. These sudden phase shifts are named as cycle slips and if not corrected, they may lead to positioning errors or incorrect TEC estimates. There are many methods in the literature that deal with cycle slips and their repairs, yet these methods are not matured to detect all kinds of cycle slips. Most algorithms require double differencing, and/or complicated Kalman Filters, Wavelet transforms, Neural Network models, and integration of external INS systems. In this study, we propose a fast and efficient algorithm for identifying the cycle slips on individual observables, classifying them for future investigations and finally repairing them for more accurate and reliable TEC estimates. The algorithm traces the pseudorange and phase observables and computes the geometry free combinations of L4 and P4. The sudden disturbances on L1, L2, P1, C1 and P2 are classified and noted for further use. Most of the cases, the disruptions are on phase observables, yet for a few occasions, a sudden disturbance is also observed on pseudorange observables. The algorithm, then, checks the epoch section where P4 exists continually. When a disruption on L1 or L2 occurs, it becomes evident on L4. When P4 and L4 sections are compared with each other, with the use of a common base, the sudden disruptions up to three epochs can be corrected using second order interpolation. For disruptions that continue for more than three epochs are considered to be separate sections and treated within that epoch section. Any cycle slip occuring within an epoch section is corrected efficiently using thresholds based on cumulative mean of the derivatives. With the efficient repair of cycle slips, Slant TEC (STEC) values can be reliably estimated, and by categorizing the cycle slips with respect to the observables, satellite and epoch, the reason of disturbance can be identified. The cycle slip detection and repair algorithm is incorporated into the web version of IONOLAB-TEC and they can be reached presently from the site www.ionolab.org. This study is supported by TUBITAK EEEAG under Grant No: 109E055.

  16. Magmatically triggered slow slip at Kilauea Volcano, Hawaii.

    PubMed

    Brooks, Benjamin A; Foster, James; Sandwell, David; Wolfe, Cecily J; Okubo, Paul; Poland, Michael; Myer, David

    2008-08-29

    We demonstrate that a recent dike intrusion probably triggered a slow fault-slip event (SSE) on Kilauea volcano's mobile south flank. Our analysis combined models of Advanced Land Observing Satellite interferometric dike-intrusion displacement maps with continuous Global Positioning System (GPS) displacement vectors to show that deformation nearly identical to four previous SSEs at Kilauea occurred at far-field sites shortly after the intrusion. We model stress changes because of both secular deformation and the intrusion and find that both would increase the Coulomb failure stress on possible SSE slip surfaces by roughly the same amount. These results, in concert with the observation that none of the previous SSEs at Kilauea was directly preceded by intrusions but rather occurred during times of normal background deformation, suggest that both extrinsic (intrusion-triggering) and intrinsic (secular fault creep) fault processes can lead to SSEs. PMID:18755967

  17. Wheel slip control of ABS using ER valve pressure modulator

    NASA Astrophysics Data System (ADS)

    Choi, Seung-Bok; Cho, Myung-Soo; Kim, Yong-Il; Choi, Young-Tai; Wereley, Norman M.

    2004-07-01

    This paper presents a wheel slip control via sliding mode controller for a new anti-lock brake system (ABS) of a passenger vehicle using electrorheological (ER) valve pressure modulator. The principal design parameters of the ER valves and hydraulic booster are appropriately determined by considering braking pressure variation during ABS operation. An electrically controllable pressure modulator using the ER valves is then constructed and its governing equations are derived. Subsequently, the pressure control performance of the new pressure modulator is experimentally evaluated. The governing equations of motion for a quarter car wheel model are derived and the sliding mode controller is formulated for wheel slip control. Hardware in the loop simulation (HILS) for braking performance evaluation is undertaken in order to demonstrate the effectiveness of the proposed ABS associated with the ER valve pressure modulator.

  18. EVOLUTION OF SLIPPED CAPITAL FEMORAL EPIPHYSIS AFTER NONSURGICAL TREATMENT

    PubMed Central

    Santili, Cláudio; Akkari, Miguel; Waisberg, Gilberto; Braga, Susana Reis; Kasahara, Akemi; Perez, Mauro Coura

    2015-01-01

    To evaluate the efficacy of conservative treatment of patients with slipped capital femoral epiphysis (SCFE) and the complications due to the progression of the disease. Methods: 18 patients (26 hips) seen consecutively from December 1996 to August 2006 at the Orthopedics Service of Santa Casa de Misericórdia de São Paulo, who had been referred from other services with a diagnosis of SCFE and were treated without surgery, were retrospectively analyzed. Results: Slip progression occurred in 19 hips (73%). Among the mild cases, eight remained mild, four became moderate and one became severe, according to the Southwick classification. Four out of the six originally moderate cases became severe and the two already severe cases worsened. Conclusion: Although today there is a consensus regarding the indication of surgical treatment for SCFE to prevent progression, some cases with confirmed diagnoses are still being treated conservatively. This is a major error, since it implies increased morbidity of the disease. PMID:27022585

  19. Bifurcations from steady sliding to stick slip in boundary lubrication

    NASA Astrophysics Data System (ADS)

    Batista, A. A.; Carlson, J. M.

    1998-05-01

    We explore the nature of the transitions between stick slip and steady sliding in models for boundary lubrication introduced in J. M. Carlson and A. A. Batista, Phys. Rev. E 53, 4153 (1996). The models are based on the rate and state approach which has been very successful in characterizing the behavior of dry interfaces [A. Ruina, J. Geophys. Res. 88, 10 359 (1983)]. Our models capture the key distinguishing features associated with surfaces separated by a few molecular layers of lubricant. Here we find that the transition from steady sliding to stick slip is typically discontinuous and sometimes hysteretic. When hysteresis is observed it is associated with a subcritical Hopf bifurcation. In either case, we observe a sudden and discontinuous onset in the amplitude of oscillations at the bifurcation point.

  20. Controversies in management of slipped capital femoral epiphysis

    PubMed Central

    Johari, Ashok N; Pandey, Ritesh A

    2016-01-01

    The traditional treatment of the hip with a slip of the capital femoral epiphysis has been an in situ fixation using a single screw. This has the sanctity of a long term result. Recent literature stresses the outcomes of failure to restore the upper femoral alignment and on the basis of the poor results makes a plea for capital realignment. This being a recent development, it lacks the support of long term follow up and it remains to be seen if this is a better alternative of managing displaced and unstable slipped capital femoral epiphysis. The authors look at some of the available literature on the subject to highlight these controversies and their implications for orthopedic surgeons. Other controversies pertain to contralateral fixation, duration of immobilization and amount of weight bearing after an in situ fixation. PMID:26925378

  1. Soft matter dynamics: Accelerated fluid squeeze-out during slip

    NASA Astrophysics Data System (ADS)

    Hutt, W.; Persson, B. N. J.

    2016-03-01

    Using a Leonardo da Vinci experimental setup (constant driving force), we study the dependency of lubricated rubber friction on the time of stationary contact and on the sliding distance. We slide rectangular rubber blocks on smooth polymer surfaces lubricated by glycerol or by a grease. We observe a remarkable effect: during stationary contact the lubricant is only very slowly removed from the rubber-polymer interface, while during slip it is very rapidly removed resulting (for the grease lubricated surface) in complete stop of motion after a short time period, corresponding to a slip distance typically of order only a few times the length of the rubber block in the sliding direction. For an elastically stiff material, poly(methyl methacrylate), we observe the opposite effect: the sliding speed increases with time (acceleration), and the lubricant film thickness appears to increase. We propose an explanation for the observed effect based on transient elastohydrodynamics, which may be relevant also for other soft contacts.

  2. Solute effect on basal and prismatic slip systems of Mg.

    PubMed

    Moitra, Amitava; Kim, Seong-Gon; Horstemeyer, M F

    2014-11-01

    In an effort to design novel magnesium (Mg) alloys with high ductility, we present a first principles data based on the Density Functional Theory (DFT). The DFT was employed to calculate the generalized stacking fault energy curves, which can be used in the generalized Peierls-Nabarro (PN) model to study the energetics of basal slip and prismatic slip in Mg with and without solutes to calculate continuum scale dislocation core widths, stacking fault widths and Peierls stresses. The generalized stacking fault energy curves for pure Mg agreed well with other DFT calculations. Solute effects on these curves were calculated for nine alloying elements, namely Al, Ca, Ce, Gd, Li, Si, Sn, Zn and Zr, which allowed the strength and ductility to be qualitatively estimated based on the basal dislocation properties. Based on our multiscale methodology, a suggestion has been made to improve Mg formability. PMID:25273695

  3. Electroosmosis of Powell-Eyring fluids under interfacial slip.

    PubMed

    Goswami, Prakash; Mondal, Pranab Kumar; Dutta, Sanmitra; Chakraborty, Suman

    2015-03-01

    We investigate the EOF of a Powell-Eyring fluid through a slit microchannel, employing Navier slip boundary condition. Using an analytical scheme consistent with the homotopy perturbation method, we bring out the alteration in the underlying flow dynamics as attributable to the nonlinear interactions between fluid rheology and electrostatics over interfacial scales. We validate the approximate analytical solutions by comparing those with results from numerical analysis. We unveil a regime of phenomenal amplification in the net volumetric flow rate, realized as a consequence of an intricate interplay between interfacial electromechanics, slipping hydrodynamics, and the flow rheology. Our results may have far ranging consequences in the design of various biomicrofluidic devises/systems, which are often used for the manipulation of non-Newtonain fluids. PMID:25502924

  4. A silent slip event on the deeper Cascadia subduction interface.

    PubMed

    Dragert, G; Wang, K; James, T S

    2001-05-25

    Continuous Global Positioning System sites in southwestern British Columbia, Canada, and northwestern Washington state, USA, have been moving landward as a result of the locked state of the Cascadia subduction fault offshore. In the summer of 1999, a cluster of seven sites briefly reversed their direction of motion. No seismicity was associated with this event. The sudden displacements are best explained by approximately 2 centimeters of aseismic slip over a 50-kilometer-by-300-kilometer area on the subduction interface downdip from the seismogenic zone, a rupture equivalent to an earthquake of moment magnitude 6.7. This provides evidence that slip of the hotter, plastic part of the subduction interface, and hence stress loading of the megathrust earthquake zone, can occur in discrete pulses. PMID:11313500

  5. Development and validation of a novel portable slip simulator.

    PubMed

    Aschan, Carita; Hirvonen, Mikko; Mannelin, Tarmo; Rajamäki, Erkki

    2005-09-01

    The objective was to develop, construct and validate a portable device suitable for measurements of pedestrian slip resistance in situ. The developed device proved to be precise enough and easy to use. The dynamic coefficient of friction (DCOF) values measured by it showed strong correlation (r> or = 0.990, p < 0.001) with the values measured by the force platform used as a reference. In addition, the measured DCOF values were in good consistency with those obtained when using the older laboratory device of the Institute, the slip simulator. Based on the use of the new, developed device it can be concluded that accurate friction measurements with actual footwear can be performed even with a moderate-sized but portable device. The developed slipmeter will be used to measure slipperiness of various walking surface conditions, e.g. at different work places and in walkways, in the near future. PMID:15970203

  6. Universal joint slippage as a cause of Hoffmann half-frame external fixator failure [corrected].

    PubMed

    Drijber, F L; Finlay, J B

    1992-11-01

    Slippage of the universal joints of external fixation devices is known to occur but its significance or incidence is often overlooked. In this study, controlled experiments were used to determine the relationship between joint slippage and the maximum loads a single half-frame could bear for the Hofmann device. The experiments showed that: (a) the joints slipped at minimal loads and (b) frame failure, i.e. loss of initial alignment of the frame components, was determined by joint slippage. The importance of the control of slippage cannot be overstated; the orthopaedic community must educate itself and its patients and guard against the problem in order to avoid complications secondary to slippage. PMID:1434575

  7. Stokes’ Second Problem for a Micropolar Fluid with Slip

    PubMed Central

    Florea, Olivia Ana; Roşca, Ileana Constanţa

    2015-01-01

    In this paper is presented the model of an incompressible micropolar fluid flow with slip using the initial and boundary conditions when the wall velocity is considered depending on the frequency of the vibration. Regarding the boundary conditions of the velocity at the wall, we remark that there is a discontinuity of the velocity at the fluid-wall interface. The solutions for velocity and microrotation with the given conditions are obtained using the method of numerical inversion of Laplace transform. PMID:26161780

  8. Slip Potential for Commonly Used Inclined Grated Metal Walkways

    PubMed Central

    Pollard, Jonisha P.; Heberger, John R.; Dempsey, Patrick G.

    2016-01-01

    Background No specific guidelines or regulations are provided by the Mine Safety and Health Administration for the use of inclined grated metal walkways in mining plants. Mining and other companies may be using walkway materials that do not provide sufficient friction, contributing to slip and fall injuries. Purpose The purpose of this study was to determine if there are significant differences in the required friction for different grated metal walkways during walking in diverse conditions. Methods The normalized coefficients of friction were measured for 12 participants while walking up and down an instrumented walkway with different inclinations (0°, 5°, 10°, 15°, and 20°) and with and without the presence of a contaminant (glycerol). Self-reported slip events were recorded and the required coefficients of friction were calculated considering only the anterior/posterior components of the shear forces. Additionally, the available coefficients of friction for these walkway materials were measured at the 0° orientation using a tribometer, with and without the presence of the contaminant, using a boot heel as well as Neolite as the test feet. Results The number of slips increased when the inclination angle reached 10° and above. Of all materials tested, the diamond weave grating was found to have the best performance at all inclines and when contaminated or dry. A high number of slips occurred for the perforated grating and serrated bar grating at 20° when contaminated. Conclusions Results of this study suggest that the diamond weave grating provides significantly better friction compared to serrated bar and perforated gratings, especially at inclines greater than 10°. PMID:26779388

  9. Interfacial slip friction at a fluid-solid cylindrical boundary

    NASA Astrophysics Data System (ADS)

    Kannam, Sridhar Kumar; Todd, B. D.; Hansen, J. S.; Daivis, Peter J.

    2012-06-01

    Recently we proposed a method to calculate the interfacial friction coefficient between fluid and solid at a planar interface. In this work we extend the method to cylindrical systems where the friction coefficient is curvature dependent. We apply the method to methane flow in carbon nanotubes, and find good agreement with non-equilibrium molecular dynamics simulations. The proposed method is robust, general, and can be used to predict the slip for cylindrical nanofluidic systems.

  10. Composite slip table of dissimilar materials for damping longitudinal modes

    DOEpatents

    Gregory, Danny L.; Priddy, Tommy G.; Smallwood, David O.; Woodall, Tommy D.

    1991-01-01

    A vibration slip table for use in a vibration testing apparatus. The table s comprised of at least three composite layers of material; a first metal layer, a second damping layer, and a third layer having a high acoustic velocity relative to the first layer. The different acoustic velocities between the first and third layers cause relative shear displacements between the layers with the second layer damping the displacements between the first and third layers to reduce the table longitudinal vibration modes.

  11. Slip on Curved Boundaries in the Lattice Boltzmann Model

    NASA Astrophysics Data System (ADS)

    Szalmás, Lajos

    We present a new boundary condition in the lattice Boltzmann method to model slip flow along curved boundaries. A requirement is formulated for the distribution functions based on the tunable momentum balance at the walls, which is shown to be equivalent to the constraint on the second moment. Numerical simulation of plane Couette flow in inclined channels and cylindrical Couette flow shows excellent agreement with the analytical results in the nearly continuum regime. Orientation effects on the velocity field are completely avoided.

  12. Inversion for slip distribution for the 2012 Costa Rica earthquake

    NASA Astrophysics Data System (ADS)

    McCormack, K. A.; Hesse, M. A.; Stadler, G.

    2014-12-01

    On 5 September 2012, a major megathrust earthquake (Mw=7.6) ruptured the plate interface beneath the Nicoya Peninsula, Costa Rica. This event was centered 12 km offshore of the central Nicoya coast, at a depth of 18 km. The maximum slip exceeded 2 meters, and the rupture spread outward along the plate interface to encompass 3000 km2 of the Nicoya seismogenic zone. More than 1700 aftershocks were recorded within the first 5 days. These aftershocks outlined two distinct rupture patches; one centered on the central coast and the other beneath the southern tip of the peninsula. We formulate a Bayesian inverse problem to infer the coseismic slip on the fault plane based on instantaneous surface displacements and changes in well heads in order to image the remaining "locked" patch that has been inferred previously. We compute the maximum a posteriori (MAP) estimate of the posterior slip distribution on the fault, and use a local Gaussian approximation around the MAP point to characterize the uncertainty. The elastic deformation is computed using a finite element method that allows for the spatial variation of elastic properties that has been observed in the crust overlying the seismogenic zone. We solve the optimization problem using gradients obtained from adjoints. The linearity of the inverse problem allows for the efficient solution of the optimal experimental design problem for the placement of the GPS stations to monitor the remaining locked patch. In the future, the results obtained here will provide the initial condition for a time-dependent poroelastic model for fault slip and fluid migration due to overpressure caused by a megathrust earthquake. This will provide constraints on the crustal permeability structure in a tectonically active region.

  13. The effect of boundary slip and cavitation on hydrodynamic pressure generation in pocket bearings

    NASA Astrophysics Data System (ADS)

    Muchammad, Tauviqirrahman, Mohammad; Pratomo, Ariawan Wahyu; Jamari, J.; Schipper, Dirk J.

    2016-04-01

    Surface texturing as well as boundary slip is an effective approach to increase the tribological performance, friction and load support of lubricated mechanical components. However, in a textured bearing with boundary slip, cavitation, which is generally neglected, is important, and it alters the flow behavior. Therefore, in this paper a novel analytical equation was proposed based on a modified Reynolds equation considering boundary slip and cavitation. The modified Reynolds equation was derived by following the general approach to deduce the Reynolds equation from the Navier-Stokes equation by assuming classical assumptions, except that boundary slip was present. A theoretical investigation was carried out to study the effect of boundary slip including cavitation on the pressure distribution of a pocket bearing. Different slip configurations (full slip, single slip and semi slip) were studied and compared to various pocket depths. The results indicated that the presence of boundary slip both on the leading edge of the contact and the pocket area (i.e. the "semi slip" case) could result in a significant improvement in the hydrodynamic pressure generation; thus, it causes an increased load support. The above improvement depends on the pocket depth of the bearing.

  14. Temporal variations in slip rate of the White Mountain Fault Zone, Eastern California

    NASA Astrophysics Data System (ADS)

    Kirby, Eric; Burbank, Douglas W.; Reheis, Marith; Phillips, Fred

    2006-08-01

    The evolution of fault slip through time may yield insight into the geodynamics of deforming lithosphere. Precise determination of temporal variations in fault slip is often hindered, however, by a dearth of markers of varying age from which to reconstruct fault slip. Here we determine slip rates across the White Mountain Fault Zone over the past ca. 0.8 Ma from displaced alluvial deposits preserved along the flank of the White Mountains. Displacement histories inferred from deposits containing the ˜ 760 ka Bishop Tuff contrast strongly with those inferred from Late Pleistocene alluvial fans dated by cosmogenic 36Cl, indicating that the fault has experienced significant temporal variations in slip rate. Oblique-slip rates over the past ˜ 760 ky are determined to have been > 0.9 m/ky parallel to a net slip vector plunging shallowly (< 20°) toward 340°-350°. Displacement of markers in Late Pleistocene alluvial deposits, in contrast, yield slip rates between 0.3 and 0.4 m/ky parallel to a vector plunging somewhat more steeply (20°-40°) toward 320°-340°. These variations in slip rate appear to have operated over timescales > ca. 70 ky, yet occurred on a well-established fault system. Moreover, the timing and magnitude of slip rate variation mimics behavior documented for the northern Fish Lake Valley fault zone. Together, our data provide evidence for coordinated slip rate variations across the Eastern California Shear Zone during the Pleistocene.

  15. Seismic responses to fluid pressure perturbations in a slipping fault

    NASA Astrophysics Data System (ADS)

    Derode, Benoit; Guglielmi, Yves; De Barros, Louis; Cappa, Frédéric

    2015-05-01

    Seismicity induced by fluid injection in a natural fault is investigated in situ in the near field of the source. We present synchronous seismic and hydromechanical measurements directly recorded in the decametric injection zone. The three main types of seismic events were recorded during injection and shut-in: high-amplitude and short duration seismic events (SE) (i.e., microearthquakes), low to constant amplitude and 5 to 17 s long tremor-like signals (TLS), and long period events (LP) with a narrow-frequency band content. Seismicity first initiates with a sequence of SE and TLS, when pressure is high (~3.5 MPa), slip is activated on the fault, which experiences a twentyfold increase of permeability. Then LP events appear to be associated to fluid leakage in the fault caused by dilation during slip. During shut-in, residual pressures as low as 0.6 MPa still trigger SE events. We show that the initial TLS sequence triggers when a progressive transition occurs from rupture controlled by effective stress variations close to the injection source to a large friction weakening-dominated slip on the fault. We conclude that the combination of these different seismic signal types may be a proxy to monitor fault instability associated to fluid pressure perturbations.

  16. An aseismic slip transient on the North Anatolian Fault

    NASA Astrophysics Data System (ADS)

    Rousset, Baptiste; Jolivet, Romain; Simons, Mark; Lasserre, Cécile; Riel, Bryan; Milillo, Pietro; ćakir, Ziyadin; Renard, François

    2016-04-01

    Constellations of Synthetic Aperture Radar (SAR) satellites with short repeat time acquisitions allow exploration of active faults behavior with unprecedented temporal resolution. Along the North Anatolian Fault (NAF) in Turkey, an 80 km long section has been creeping at least since the 1944, Mw 7.3 earthquake near Ismetpasa, with a current Interferometric Synthetic Aperture Radar (InSAR)-derived average creep rate of 8 ± 3 mm/yr (i.e., a third of the NAF long-term slip rate). We use a dense set of SAR images acquired by the COSMO-SkyMed constellation to quantify the spatial distribution and temporal evolution of creep over 1 year. We identify a major burst of aseismic slip spanning 31 days with a maximum slip of 2 cm, between the surface and 4 km depth. This result shows that fault creep along this section of the NAF does not occur at a steady rate as previously thought, highlighting a need to revise our understanding of the underlying fault mechanics.

  17. Slip wall modeling approaches for separated flows and heat transfer

    NASA Astrophysics Data System (ADS)

    Bose, Sanjeeb; Pierce, Brian; Moin, Parviz

    2014-11-01

    Resolution of near-wall turbulent structures is computational prohibitive, necessitating the need for wall-modeled large-eddy simulation approaches. Standard wall models are often formulated to represent the wall stress assuming an equilibrium, attached boundary layer. This assumption is invalid in complex flows that include transition to turbulence or boundary layer separation. A dynamic slip wall boundary condition has been recently proposed (Bose & Moin, PoF, 2014) as an alternative for wall-modeled LES, where a slip wall boundary condition is derived from the differentially filtered LES governing equations with no assumption on the state of the local boundary layer. Results will be presented from the application of the dynamic slip wall model to flows with 3D separation (asymmetric stalled diffuser) and from the extension of the model to the prediction of wall heat transfer (turbine blade). The wall modeled LES predicts the primary quantity of interest in these flows: the pressure recovery in the diffuser and the heat transfer coefficient on the turbine blade.

  18. Stick and slip actuators and parallel architectures dedicated to microrobotics

    NASA Astrophysics Data System (ADS)

    Breguet, Jean-Marc; Pernette, Eric; Clavel, Reymond

    1996-12-01

    Stick and slip actuators are particularly well adapted to microrobotics. A simple design, a very high intrinsic resolution (a few nanometers) and a high rigidity makes them specially interesting for high precision micro manipulations. Moreover, a smart design allows the user to combine the guiding and actuating functions. Parallel architectures are attractive to microrobotics too. They present a high rigidity and the actuators are fixed on the base. This paper deals with the integration of stick and slip actuators in a 6-degrees-of-freedom parallel structure dedicated to the micro assembly of optical components. In section 3 we describe and characterize inertial actuators using the stick and slip effect. We demonstrate their performances (velocity higher than 1.5 mm/s, 10 nm precision) and limits. In section 4 we describe the 6- degrees-of-freedom parallel architecture that we developed for our application and how the actuators are integrated into it. Its kinematics, the joins' forces and the working volume have been calculated. A resolution better than 30 nm is possible within a working volume of 140 mm3. Orientations of several degrees (up to plus or minus five degrees) are possible for the three rotational angles.

  19. Measurement of liner slips, milking time, and milk yield.

    PubMed

    O'Callaghan, E J

    1996-03-01

    Liner slip or rapid air leakage past the mouthpiece of the milking machine liner is related to high rates of new cases of mastitis. A real time technique was developed to monitor the air flow into the milking machine cluster during liner slips as well as to monitor milking time and milk yield using a commercial type pipeline milking system. The air flow into the cluster was measured by recording the pressure differences across an orifice plate placed in the air bypass of an air-milk separator using a differential pressure transducer. Milk yield was recorded by counting the number of milk releases from an electronic milk meter. The release solenoids of the milk meter were linked to a computer. The start and end of milking were manually recorded by switching a two-pole switch connected to a digital input card on the computer, which was programmed to record air flow, milk yield, and milking time. Milk yield, milking time, and air flows during liner slips were recorded simultaneously at each milking unit in an 11-unit herringbone parlor. The system was tested with an experiment with a 4 x 4 Latin square design using four treatments (clusters) and four treatment groups (22 cows per group). PMID:8708099

  20. Slip-stacking Dynamics and the 20 Hz Booster

    SciTech Connect

    Eldred, Jeffery; Zwaska, Robert

    2015-03-01

    Slip-stacking is an accumulation technique used at Fermilab since 2004 which nearly doubles the proton intensity. The Proton Improvement Plan II intensity upgrades require a reduction in slip-stacking losses by approximately a factor of 2. We study the single-particle dynamics that determine the stability of slip-stacking particles. We introduce universal area factors to calculate the available phase space area for any set of beam parameters without individual simulation. We show the particle loss as a function of time. We calculate the injection efficiency as a function of longitudinal emittance and aspect-ratio. We demonstrate that the losses from RF single particle dynamics can be reduced by a factor of 4-10 (depending on beam parameters) by upgrading the Fermilab Booster from a 15-Hz cycle-rate to a 20-Hz cycle-rate. We recommend a change in injection scheme to eliminate the need for a greater momentum aperture in the Fermilab Recycler.