Science.gov

Sample records for tube-in-tube slip joint

  1. Slip joint connector

    NASA Technical Reports Server (NTRS)

    Thomas, Frank P. (inventor)

    1994-01-01

    A slip joint connector for joining first and second structural elements together is presented. The connector has a first body member attachable to the first structural element and a second body member attachable to the second structural element. The first body member has a male protuberance including a conical portion and the second body member has a conical receptacle for cooperatively receiving the conical portion of the protuberance. The protuberance includes a bridging portion for spacing the conical portion from the remainder of the first body member and the second body member has a well communicating with the conical receptacle for receiving the bridging portion. The conical male portion internally carries a nut while the second body member may receive a bolt through the receptacle to be threadedly received by the nut to secure the first and second body members tightly together.

  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. 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...

  4. 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...

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

    EPA Science Inventory

    The high purity, high throughput synthesis of a number of imines (Schiff bases) using a spinning tube-in-tube reactor (STT, Kreido Laboratories, Camarillo, CA) has been carried out. The STT reactor allows the high throughput production of high purity imines from a wide variety of...

  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. Longitudinal joint systems in slip-formed rigid pavements. Volume 4: Recommendations for alternate joint systems and for strengthening existing joints

    NASA Astrophysics Data System (ADS)

    Korbus, L.; Barenberg, E. J.

    1981-11-01

    Load transfer across joints is a key factor in the performance of PCC pavements. The common load transfer devices in longitudinal joints for airport pavements have for many years been concrete keyways. Many of these keyways fail under heavy aircraft loads and are very difficult to construct using slip-formed pavers. Alternate joint systems which are potentially more reliable than keyways and which can be constructed using slip-formed pavers are presented in the report. Also, procedures are described for retrofitting existing slabs with devices to provide load transfer across joints or cracks. Laboratory and field tests with these load transfer devices are described, and data on their performance are presented. Recommendations for joint designs for PCC airport pavements are given based on the level of traffic anticipated.

  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. Flow chemistry: intelligent processing of gas-liquid transformations using a tube-in-tube reactor.

    PubMed

    Brzozowski, Martin; O'Brien, Matthew; Ley, Steven V; Polyzos, Anastasios

    2015-02-17

    CONSPECTUS: The previous decade has witnessed the expeditious uptake of flow chemistry techniques in modern synthesis laboratories, and flow-based chemistry is poised to significantly impact our approach to chemical preparation. The advantages of moving from classical batch synthesis to flow mode, in order to address the limitations of traditional approaches, particularly within the context of organic synthesis are now well established. Flow chemistry methodology has led to measurable improvements in safety and reduced energy consumption and has enabled the expansion of available reaction conditions. Contributions from our own laboratories have focused on the establishment of flow chemistry methods to address challenges associated with the assembly of complex targets through the development of multistep methods employing supported reagents and in-line monitoring of reaction intermediates to ensure the delivery of high quality target compounds. Recently, flow chemistry approaches have addressed the challenges associated with reactions utilizing reactive gases in classical batch synthesis. The small volumes of microreactors ameliorate the hazards of high-pressure gas reactions and enable improved mixing with the liquid phase. Established strategies for gas-liquid reactions in flow have relied on plug-flow (or segmented flow) regimes in which the gas plugs are introduced to a liquid stream and dissolution of gas relies on interfacial contact of the gas bubble with the liquid phase. This approach confers limited control over gas concentration within the liquid phase and is unsuitable for multistep methods requiring heterogeneous catalysis or solid supported reagents. We have identified the use of a gas-permeable fluoropolymer, Teflon AF-2400, as a simple method of achieving efficient gas-liquid contact to afford homogeneous solutions of reactive gases in flow. The membrane permits the transport of a wide range of gases with significant control of the stoichiometry of reactive gas in a given reaction mixture. We have developed a tube-in-tube reactor device consisting of a pair of concentric capillaries in which pressurized gas permeates through an inner Teflon AF-2400 tube and reacts with dissolved substrate within a liquid phase that flows within a second gas impermeable tube. This Account examines our efforts toward the development of a simple, unified methodology for the processing of gaseous reagents in flow by way of development of a tube-in-tube reactor device and applications to key C-C, C-N, and C-O bond forming and hydrogenation reactions. We further describe the application to multistep reactions using solid-supported reagents and extend the technology to processes utilizing multiple gas reagents. A key feature of our work is the development of computer-aided imaging techniques to allow automated in-line monitoring of gas concentration and stoichiometry in real time. We anticipate that this Account will illustrate the convenience and benefits of membrane tube-in-tube reactor technology to improve and concomitantly broaden the scope of gas/liquid/solid reactions in organic synthesis. PMID:25611216

  10. The relation between primary osteoarthritis of the trapeziometacarpal joint and supernumerary slips of the abductor pollicis longus tendon.

    PubMed

    Schulz, C U; Anetzberger, H; Pfahler, M; Maier, M; Refior, H J

    2002-06-01

    We have studied whether accessory abductor pollicis longus slips inserting into the thenar eminence or trapezium influence the incidence and severity of trapeziometacarpal joint osteoarthritis. The right first extensor compartment of 73 cadavers was dissected and trapeziometacarpal degeneration was graded macroscopically. The main abductor pollicis longus tendon which inserted at the metacarpal base was accompanied by supernumerary APL slips in 96% of cases. Thenar or trapezial slips occurred frequently but coexisted in only one case. The incidence of trapeziometacarpal arthritis was not influenced by the number of accessory slips or whether they inserted onto the thenar eminence or the trapezium. PMID:12074609

  11. 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

  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. Tube-in-tube reactor as a useful tool for homo- and heterogeneous olefin metathesis under continuous flow mode.

    PubMed

    Skowerski, Krzysztof; Czarnocki, Stefan J; Knapkiewicz, Pawe?

    2014-02-01

    A tube-in-tube reactor was successfully applied in homo- and heterogeneous olefin metathesis reactions under continuous flow mode. It was shown that the efficient removal of ethylene facilitated by connection of the reactor with a vacuum pump significantly improves the outcome of metathesis reactions. The beneficial aspects of this approach are most apparent in reactions performed at low concentration, such as macrocyclization reactions. The established system allows achievement of both improved yield and selectivity, and is ideal for industrial applications. PMID:24167003

  14. 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.

  15. Analysis of the Region of Validity of Equations for Calculating Heat Exchangers of the Tube-in-Tube Type

    NASA Astrophysics Data System (ADS)

    Moshinskii, A. I.

    2015-09-01

    Based on the traditional model with direct flow and counterflow of heat transfer agents in a stationary regime, the operation of a heat exchanger of the tube-in-tube type is analyzed. Account is taken of the natural limitations for the model that are connected with the possibility of practical realization of the similarity numbers involved in the equations of the model, as well as with the conditions (assumptions) invoked in the derivation of the model. A comparison of the efficiency of heat transfer in the noted regimes of heat transfer agent motions is made. For the purposes of this comparison, it is proposed to use an averaged value of the function that represents the ratio of efficiencies with heat transfer agent direct flow and counterflow over the region of possible values of similarity numbers. The necessary calculations and illustrations are presented.

  16. IN-SITU MONITORING OF PRODUCT STREAMS FROM A SPINNING TUBE-IN-TUBE REACTOR USING A METTLER-TOLEDO REACT-IR

    EPA Science Inventory

    A Mettler-Toledo ReactIR system has been used for in-line, real-time monitoring of the product stream from a spinning tube-in-tube reactor (STT, Kreido Laboratories, Camarillo California). This combination of a process intensified continuous-flow reactor and an in-situ analytic...

  17. Average boiling and condensation heat transfer coefficients of the zeotropic refrigerant mixture R22/R142b in a coaxial tube-in-tube heat exchanger

    SciTech Connect

    Meyer, J.P.; Bukasa, J.M.; Kebonte, S.A.

    2000-02-01

    Average boiling and condensation heat transfer coefficients were determined experimentally for a coaxial tube-in-tube heat exchanger used in hot water heat pumps. During manufacturing, the heat exchanger geometry used for the experiments changed from round tubes to elliptical tubes as no spacers were used to keep the inner tube from touching the outer tube. The refrigerant used was two different mixtures of R22 with R142b in mass ratios of 80%/20% and 60%/40%. The results were compared to theoretical results for straight tubes. It was concluded that the theoretical modes do not predict the heat transfer coefficients very well in coaxial tube-in-tube heat exchangers where the annulus touches the inside of the outer tube.

  18. Encapsulating MWNTs into hollow porous carbon nanotubes: a tube-in-tube carbon nanostructure for high-performance lithium-sulfur batteries.

    PubMed

    Zhao, Yi; Wu, Wangliang; Li, Jiaxin; Xu, Zhichuan; Guan, Lunhui

    2014-08-13

    A tube-in-tube carbon nanostructure (TTCN) with multi-walled carbon nanotubes (MWNTs) confined within hollow porous carbon nanotubes is synthesized for Li-S batteries. The structure is designed to enhance the electrical conductivity, hamper the dissolution of lithium polysulfide, and provide large pore volume for sulfur impregnation. As a cathode material for Li-S batteries, the S-TTCN composite with 71 wt% sulfur content delivers high reversible capacity, good cycling performance as well as excellent rate capabilities. PMID:24897930

  19. 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.

  20. 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 chargedischarge experiments at different current densities. Display Omitted Highlights: ? We fabricate a ternary organicinorganic 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 organicinorganic 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 chargedischarge experiment.

  1. Inference of Co-Seismic Slip Distribution Via a Joint Inversion of GPS and Aftershock Data Sets: The 2004 Parkfield Example

    NASA Astrophysics Data System (ADS)

    Ziv, A.

    2010-12-01

    Since the advent of space geodesy in the late eighties, ground motion data are being commonly used to infer co-seismic slip distributions. The prime objective of these studies is to identify barriers and/or asperities along the rupture plane. This, in turn, may shed light on the rupture physics and help to discriminate between different models. A serious problem when utilizing geodetic data to infer co-seismic slip distribution is the rapid drop of the resolving power with depth. I will show that use of high quality relocated aftershock data together with aftershock constitutive laws can alleviate this problem. I choose the 2004 Parkfield earthquake as a case study, because its rupture geometry is well constrained and since high quality earthquake catalog is available. Furthermore, the available InSAR data for that earthquake is problematic, as it includes significant contributions from the San Simeon 2003 post-seismic relaxation, as well as (at least) two days of Parkfields post-seismic relaxation. I will describe how the 2004 Parkfield co-seismic slip distribution can be inferred via joint inversion of GPS and aftershock data sets. I will show that good fit to both data sets can only be obtained for a constitutive friction parameter that is two to three orders of magnitude smaller than the laboratory values. Finally, I will discuss the implications for fault friction and aftershock physics.

  2. Localized fault slip to the trench in the 2010 Maule, Chile Mw = 8.8 earthquake from joint inversion of high-rate GPS, teleseismic body waves, InSAR, campaign GPS, and tsunami observations

    NASA Astrophysics Data System (ADS)

    Yue, Han; Lay, Thorne; Rivera, Luis; An, Chao; Vigny, Christophe; Tong, Xiaopeng; Bez Soto, Juan Carlos

    2014-10-01

    The 27 February 2010, Mw 8.8 Maule earthquake ruptured ~500 km along the plate boundary offshore central Chile between 34S and 38.5S. Establishing whether coseismic fault offset extended to the trench is important for interpreting both shallow frictional behavior and potential for tsunami earthquakes in the region. Joint inversion of high-rate GPS, teleseismic body waves, interferometric synthetic aperture radar (InSAR), campaign GPS, and tsunami observations yields a kinematic rupture model with improved resolution of slip near the trench. Bilateral rupture expansion is resolved in our model with relatively uniform slip of 5-10 m downdip beneath the coast and two near-trench high-slip patches with >12 m displacements. The peak slip is ~17 m at a depth of ~15 km on the central megathrust, located ~200 km north from the hypocenter and overlapping the rupture zone of the 1928 M ~8 event. The updip slip is ~16 m near the trench. Another shallow near-trench patch is located ~150 km southwest of the hypocenter, with a peak slip of 12 m. Checkerboard resolution tests demonstrate that correctly modeled tsunami data are critical to resolution of slip near the trench, with other data sets allowing, but not requiring slip far offshore. Large interplate aftershocks have a complementary distribution to the coseismic slip pattern, filling in gaps or outlining edges of large-slip zones. Two clusters of normal faulting events locate seaward along the plate motion direction from the localized regions of large near-trench slip, suggesting that proximity of slip to the trench enhanced extensional faulting in the underthrusting plate.

  3. Localized Fault Slip to the Trench in the 2010 Maule, Chile Mw = 8.8 Earthquake from Joint Inversion of High-Rate GPS, Teleseismic Body Waves, InSAR, and Tsunami Observations

    NASA Astrophysics Data System (ADS)

    Yue, H.; Lay, T.; Rivera, L. A.; An, C.; Vigny, C.; Tong, X.

    2014-12-01

    The 27 February 2010, Mw 8.8 Maule earthquake ruptured ~500 km along the plate boundary offshore of central Chile between 34S and 38.5S. Intense ground shaking and large tsunami inundation combined to take more than 500 lives. The co-seismic slip distribution has previously been investigated using geodetic, seismic and tsunami observations, yielding consistent locations of the largest slip in a region extending from 34S to 35.5S. However, it remains uncertain whether co-seismic fault offset extended to the trench, which is important for interpreting both shallow frictional behavior and potential for tsunami earthquakes in the region. Joint inversion of high-rate GPS, teleseismic body waves, InSAR, and tsunami observations yields a kinematic rupture model with improved resolution of slip near the trench. Two up-dip large-slip (>15 m) patches are resolved along a bi-lateral rupture with relatively uniform 5-10 m slip down-dip beneath the coast. Both up-dip patches have significant slip in localized regions extending to the trench. The peak slip is ~22 m at a depth of ~15 km on the central megathrust, located ~200 km north from the hypocenter and overlapping the rupture zone of the 1928 M ~8 event. The slip decreases at shallower depth, but is still about ~20 m near the trench. The peak slip is ~15 m in a shallow near-trench patch located ~150 km southwest of the hypocenter. Checker-board resolution tests demonstrate that the tsunami data are critical to resolution of slip near the trench, with other data sets allowing, but not requiring slip far offshore. The stability of the joint inversion reduces the need for regularization. Larger events in the aftershock sequence have a complementary distribution to the co-seismic slip pattern, filling in gaps or outlining edges of large-slip zones. Two clusters of normal faulting events locate seaward along the plate motion direction from the localized regions of large near-trench slip, suggesting that proximity of slip to the trench enhanced extensional faulting in the underthrusting plate.

  4. 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.

  5. Unusual combination of lesions of the traumatic hand: closed central slip laceration of the extensor and interphalangeal thumb joint's dislocation (a case report)

    PubMed Central

    Boussakri, Hassan; Azarkane, Mohamad; Dahmani, Omar; Elidrissi, Mohamad; Shimi, Mohamed; Elibrahimi, Abdelhalim; Elmrini, Abdelmajid

    2014-01-01

    From the functional standpoint, the hand is one of the most important organs of the body. However, its significance depends largely upon the pincer action of the thumb-index. The management of traumatic lesions of the hand is nowadays subject of numerous scientific discussions. We present here the case of a patient with a recent laceration of the central slip of the extensor tendon with boutonniere deformity linked to a dislocated interphalangeal thumb of the same hand with a loss of force of the clip thumb and index finger. This combination is a rare lesional of the traumatic hand that has not been previously reported in any orthopedic literature. It was observed after adopting the orthopedic treatment that the range of motion of its joint was at the same level as its healthy side without observing any redislocations during the 6-month follow-up period. PMID:25426188

  6. Unusual combination of lesions of the traumatic hand: closed central slip laceration of the extensor and interphalangeal thumb joint's dislocation (a case report).

    PubMed

    Boussakri, Hassan; Azarkane, Mohamad; Dahmani, Omar; Elidrissi, Mohamad; Shimi, Mohamed; Elibrahimi, Abdelhalim; Elmrini, Abdelmajid

    2014-01-01

    From the functional standpoint, the hand is one of the most important organs of the body. However, its significance depends largely upon the pincer action of the thumb-index. The management of traumatic lesions of the hand is nowadays' subject of numerous scientific discussions. We present here the case of a patient with a recent laceration of the central slip of the extensor tendon with boutonniere deformity linked to a dislocated interphalangeal thumb of the same hand with a loss of force of the clip thumb and index finger. This combination is a rare lesional of the traumatic hand that has not been previously reported in any orthopedic literature. It was observed after adopting the orthopedic treatment that the range of motion of its joint was at the same level as its healthy side without observing any redislocations during the 6-month follow-up period. PMID:25426188

  7. 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

  8. 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).

  9. 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.

  10. 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.

  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. Slips of the Tongue.

    ERIC Educational Resources Information Center

    Motley, Michael T.

    1985-01-01

    The study of slips of the tongue (which offers glimpses of processes underlying speech) is facilitated by several research techniques which induce slips in the laboratory setting. Several of these techniques and results obtained are discussed. Results often support the hypothesis that verbal slips reveal hidden anxieties. (DH)

  13. 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.

  14. Acoustic emissions during deformation of jointed rock

    SciTech Connect

    Holcomb, D.J.; Teufel, L.W.

    1984-12-31

    As an aid to understanding and monitoring the behavior of jointed rock masses, we have done a series of experiments on samples of Grouse Canyon tuff containing sawcut joints. The tuff was selected because it is under consideration as a disposal medium for nuclear wastes. The samples were instrumented to measure axial and transverse displacements and AE rates. Testing was done in a servocontrolled machine at displacement rates of 2 x 10{sup -5} in/sec, and confining pressures ranging from 1500 to 6000 psi. Four modes of slip on joints were identified. First, stable sliding accompanied by a steady rate of AE. Second, stick-slip with a sharp drop in load, large displacements but no premonitory AE or slip. Third, stick-slip, as in mode 2, but with premonitory AE and slip. Fourth, stable stick-slip where the load dropped and the displacements increased but the process was slow and culminated in stable sliding. Mode 4 exhibited premonitory AE and slip and after the event, a steady rate of AE during sliding. In all cases where premonitory slip or stable sliding occurred there was a corresponding occurrence of AE, indicating slip is related to damage to the joint surfaces and adjacent material. Monitoring AE would be a useful method of detecting slip and the extent of slip in modes 1, 3, and 4. Increasing slip rate leads to increasing AE rate. However, mode 2 stick-slip appears to be undetectable by this method.

  15. 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...

  16. 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...

  17. 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...

  18. 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...

  19. 14 CFR 27.935 - 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. 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...

  20. 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...

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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.

  6. 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.

  7. SlipChip

    PubMed Central

    Du, Wenbin; Li, Liang; Nichols, Kevin P.; Ismagilov, Rustem F.

    2009-01-01

    The SlipChip is a microfluidic device designed to perform multiplexed microfluidic reactions without pumps or valves. The device has two plates in close contact. The bottom plate contains wells preloaded with many reagents; in this paper plates with 48 reagents were used. These wells are covered by the top plate that acts as a lid for the wells with reagents. The device also has a fluidic path, composed of ducts in the bottom plate and wells in the top plate, which is connected only when the top and bottom plate are aligned in a specific configuration. Sample can be added into the fluidic path, filling both wells and ducts. Then, the top plate is slipped, or moved, relative to the bottom plate so the complementary patterns of wells in both plates overlap, exposing the sample-containing wells of the top plate to the reagent-containing wells of the bottom plate, and enabling diffusion and reactions. Between the two plates, a lubricating layer of fluorocarbon was used to facilitate relative motion of the plates. This paper implements this approach on a nanoliter scale using devices fabricated in glass. Stability of preloaded solutions, control of loading, and lack of cross-contamination were tested using fluorescent dyes. Functionality of the device was illustrated via crystallization of a model membrane protein. Fabrication of this device is simple and does not require a bonding step. This device requires no pumps or valves and is applicable to resource-poor settings. Overall, this device should be valuable for multiplexed applications that require exposing one sample to many reagents in small volumes. One may think of the SlipChip as an easy-to-use analogue of a preloaded multi-well plate, or a preloaded liquid-phase microarray. PMID:19636458

  8. Slip on Superhydrophobic Surfaces

    NASA Astrophysics Data System (ADS)

    Rothstein, Jonathan P.

    2010-01-01

    This review discusses the use of the combination of surface roughness and hydrophobicity for engineering large slip at the fluid-solid interface. These superhydrophobic surfaces were initially inspired by the unique water-repellent properties of the lotus leaf and can be employed to produce drag reduction in both laminar and turbulent flows, enhance mixing in laminar flows, and amplify diffusion-osmotic flows. We review the current state of experiments, simulations, and theory of flow past superhydrophobic surfaces. In addition, the designs and limitations of these surfaces are discussed, with an eye toward implementing these surfaces in a wide range of applications.

  9. Slip flow in graphene nanochannels.

    PubMed

    Kannam, Sridhar Kumar; Todd, B D; Hansen, J S; Daivis, Peter J

    2011-10-14

    We investigate the hydrodynamic boundary condition for simple nanofluidic systems such as argon and methane flowing in graphene nanochannels using equilibrium molecular dynamics simulations (EMD) in conjunction with our recently proposed method [J. S. Hansen, B. D. Todd, and P. J. Daivis, Phys. Rev. E 84, 016313 (2011)]. We first calculate the fluid-graphene interfacial friction coefficient, from which we can predict the slip length and the average velocity of the first fluid layer close to the wall (referred to as the slip velocity). Using direct nonequilibrium molecular dynamics simulations (NEMD) we then calculate the slip length and slip velocity from the streaming velocity profiles in Poiseuille and Couette flows. The slip lengths and slip velocities from the NEMD simulations are found to be in excellent agreement with our EMD predictions. Our EMD method therefore enables one to directly calculate this intrinsic friction coefficient between fluid and solid and the slip length for a given fluid and solid, which is otherwise tedious to calculate using direct NEMD simulations at low pressure gradients or shear rates. The advantages of the EMD method over the NEMD method to calculate the slip lengths/flow rates for nanofluidic systems are discussed, and we finally examine the dynamic behaviour of slip due to an externally applied field and shear rate. PMID:22010725

  10. 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.

  11. 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.

  12. Mechanism of slip and twinning

    NASA Astrophysics Data System (ADS)

    Rastani, Mansur

    1992-06-01

    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.

  13. Low-Friction Joint for Robot Fingers

    NASA Technical Reports Server (NTRS)

    Ruoff, C. F.

    1985-01-01

    Mechanical linkage allows adjacent parts to move relative to each other with low friction and with no chatter, slipping, or backlash. Low-friction joint of two surfaces in rolling contact, held in alinement by taut flexible bands. No sliding friction or "stick-slip" motion: Only rolling-contact and bending friction within bands. Proposed linkage intended for finger joints in mechanical hands for robots and manipulators.

  14. {110} Slip with {112} slip traces in bcc Tungsten

    PubMed Central

    Marichal, Cecile; Van Swygenhoven, Helena; Van Petegem, Steven; Borca, Camelia

    2013-01-01

    While propagation of dislocations in body centered cubic metals at low temperature is understood in terms of elementary steps on {110} planes, slip traces correspond often with other crystallographic or non-crystallographic planes. In the past, characterization of slip was limited to post-mortem electron microscopy and slip trace analysis on the sample surface. Here with in-situ Laue diffraction experiments during micro-compression we demonstrate that when two {110} planes containing the same slip direction experience the same resolved shear stress, sharp slip traces are observed on a {112} plane. When however the {110} planes are slightly differently stressed, macroscopic strain is measured on the individual planes and collective cross-slip is used to fulfill mechanical boundary conditions, resulting in a zig-zag or broad slip trace on the sample surface. We anticipate that such dynamics can occur in polycrystalline metals due to local inhomogeneous stress distributions and can cause unusual slip transfer among grains. PMID:23989456

  15. Formation and Suppression of Strike-Slip Fault Systems

    NASA Astrophysics Data System (ADS)

    Curren, Ivy S.; Bird, Peter

    2014-11-01

    Strike-slip faults are a defining feature of plate tectonics, yet many aspects of their development and evolution remain unresolved. For intact materials and/or regions, a standard sequence of shear development is predicted from physical models and field studies, commencing with the formation of Riedel shears and culminating with the development of a throughgoing fault. However, for materials and/or regions that contain crustal heterogeneities (normal and/or thrust faults, joints, etc.) that predate shear deformation, kinematic evolution of strike-slip faulting is poorly constrained. We present a new plane-stress finite-strain physical analog model developed to investigate primary deformation zone evolution in simple shear, pure strike-slip fault systems in which faults or joints are present before shear initiation. Experimental results suggest that preexisting mechanical discontinuities (faults and/or joints) have a marked effect on the geometry of such systems, causing deflection, lateral distribution, and suppression of shears. A lower limit is placed on shear offset necessary to produce a throughgoing fault in systems containing preexisting structures. Fault zone development observed in these experiments provides new insight for kinematic interpretation of structural data from strike-slip fault zones on Earth, Venus, and other terrestrial bodies.

  16. 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

  17. Acoustic emissions during deformation of intact and jointed welded tuff

    SciTech Connect

    Holcomb, D.J.; Teufel, L.W.

    1982-07-01

    Monitoring of acoustic emissions (AE) has been widely used as a means of detecting failure in intact rock. For intact rock the technique is simple, because an increasing rate of AE is usually a sign of impending failure. However, most large rock masses contain numerous joints and the behavior of the joints controls the properties of the rock mass. In particular, the failure mode often becomes stable or unstable slip (stick-slip) on a joint at stresses well below those required for failure of the intact rock. As an aid to understanding and monitoring the behavior of jointed rock masses, we have done a series of experiments on intact and artificially jointed samples of Grouse Canyon tuff. The tuff was selected because it is under consideration as a disposal medium for nuclear wastes. The samples were instrumented to measure axial and transverse displacements and AE rates. Testing was done in a servo-controlled machine at axial displacement rates of 5 x 10{sup -5} cm/sec, and confining pressures ranging from 10 to 40 MPa. For the jointed samples four modes of slip were identified. First, stable sliding accompanied by a steady rate of AE. Second, stick-slip with a sharp drop in load, large displacements but no premonitory AE or slip. Third, stick-slip, as in mode 2, but with premonitory AE and slip. Fourth, slow stick-slip where the load dropped and the displacements increased but the process was slow and culminated in stable sliding. Mode 4 exhibited premonitory AE and slip and after the event, a steady rate of AE during sliding. There seemed to be no way to predict which mode would occur at a given point in the test. In all cases where stable or unstable slip occurred there was a corresponding occurrence of AE. This indicates that slip is related to damage to the joint surfaces and adjacent material. Monitoring AE would be a useful method of detecting slip.

  18. 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.

  19. 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.

  20. 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)

  1. Slip characteristics of San Andreas Fault transition zone segments

    NASA Astrophysics Data System (ADS)

    Johanson, Ingrid Anne

    Transition zones are areas of mixed behavior that divide areas of velocity strengthening and velocity weakening frictional parameters. Their slip characteristics have implications for the underlying mechanism for interseismic creep, the relationship between aseismic slip and earthquakes, and the seismic potential of the transition zones. Two transition zones on the San Andreas fault in California, USA are included in this work; the San Juan Bautista and the Parkfield segments. They are analyzed in three phases of the earthquake cycle; the interseismic, coseismic and postseismic. The San Juan Bautista segment currently undergoes only moderate seismicity. However, six M?6 earthquakes occurred near the SJB segment between 1840 and 1899. A joint inversion of Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) measurements was performed to determine its current rate and distribution of interseismic creep. The model resolves two low-slip asperities surrounded by creep, indicating that its behavior arises from the heterogeneous distribution of fault frictional properties. InSAR and GPS data were also used to constrain models of coseismic and post-seismic slip in the 2004 Parkfield earthquake. The models indicate that coseismic and postseismic slip occurred in separate regions of the fault, suggesting that the distribution of frictional parameters on the fault exerted some control over the size of the earthquake. The postseismic model included nearly equal amounts of slip as the coseismic, suggesting that this is an important method of relieving stress along areas of the fault that slip aseismically and that these areas may not participate in earthquakes. The sensitivity of the Parkfield segment to outside stresses was also explored. Static stress changes from the 2003 San Simeon earthquake encouraged right-lateral strike slip on the Parkfield segment. While there is no clear correlation between the distribution of slip in the 2004 Parkfield earthquake and stress changes from the San Simeon earthquake; the 2004 event's hypocenter occurred in an area that experienced increased shear stress. Small stress changes from San Simeon postseismic slip also correlate with the 2004 event's hypocenter, suggesting that the Parkfield segment may have responded very sensitively to the small stress changes imparted by the previous events.

  2. Frictional melt and seismic slip

    NASA Astrophysics Data System (ADS)

    Nielsen, S.; di Toro, G.; Hirose, T.; Shimamoto, T.

    2008-01-01

    Frictional melt is implied in a variety of processes such as seismic slip, ice skating, and meteorite combustion. A steady state can be reached when melt is continuously produced and extruded from the sliding interface, as shown recently in a number of laboratory rock friction experiments. A thin, low-viscosity, high-temperature melt layer is formed resulting in low shear resistance. A theoretical solution describing the coupling of shear heating, thermal diffusion, and extrusion is obtained, without imposing a priori the melt thickness. The steady state shear traction can be approximated at high slip rates by the theoretical form ?ss = ?n1/4 (A/?) ? under a normal stress ?n, slip rate V, radius of contact area R (A is a dimensional normalizing factor and W is a characteristic rate). Although the model offers a rather simplified view of a complex process, the predictions are compatible with experimental observations. In particular, we consider laboratory simulations of seismic slip on earthquake faults. A series of high-velocity rotary shear experiments on rocks, performed for ?n in the range 1-20 MPa and slip rates in the range 0.5-2 m s-1, is confronted to the theoretical model. The behavior is reasonably well reproduced, though the effect of radiation loss taking place in the experiment somewhat alters the data. The scaling of friction with ?n, R, and V in the presence of melt suggests that extrapolation of laboratory measures to real Earth is a highly nonlinear, nontrivial exercise.

  3. 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

  4. Stress inversion using slip tendency

    NASA Astrophysics Data System (ADS)

    McFarland, John M.; Morris, Alan P.; Ferrill, David A.

    2012-04-01

    The in situ stress state is an important controlling factor for the slip behavior of faults and fractures in the earth's crust and hence for the productivity of faulted and fractured hydrocarbon reservoirs. Current methods for stress tensor estimation rely on slip vector field data; however, this information is not generally available from data sets that are commonly used in the oil and gas industry. This work presents a new stress inversion approach where slip tendency is used as a proxy for fault displacement, which can easily be extracted from data sets routinely used by the oil and gas industry. The inversion approach is demonstrated using a data set obtained from the Canyon Lake Gorge in Comal County, Texas.

  5. Joint swelling

    MedlinePLUS

    ... care provider if you have: Unexplained joint swelling Joint swelling after an injury ... Your health care provider will examine you. The joint will be closely examined. You will be asked about your joint swelling, such as when it began, ...

  6. 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.

  7. An analysis of a joint shear model for jointed media with orthogonal joint sets; Yucca Mountain Site Characterization Project

    SciTech Connect

    Koteras, J.R.

    1991-10-01

    This report describes a joint shear model used in conjunction with a computational model for jointed media with orthogonal joint sets. The joint shear model allows nonlinear behavior for both joint sets. Because nonlinear behavior is allowed for both joint sets, a great many cases must be considered to fully describe the joint shear behavior of the jointed medium. An extensive set of equations is required to describe the joint shear stress and slip displacements that can occur for all the various cases. This report examines possible methods for simplifying this set of equations so that the model can be implemented efficiently form a computational standpoint. The shear model must be examined carefully to obtain a computationally efficient implementation that does not lead to numerical problems. The application to fractures in rock is discussed. 5 refs., 4 figs.

  8. 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

  9. Coseismic and Postseismic Slip of the 2004 Parkfield Earthquake from GPS and InSAR data

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

    We present the results of an inversion of space geodetic data for slip in the coseismic and postseismic periods of the 2004 Parkfield earthquake. The data is a combination of InSAR data from the ENVISAT and RADARSAT satellites, and campaign and continuous GPS measurements. The InSAR data consists of eight interferometric pairs spanning the earthquake and variable-length portions of the pre- and post-seismic periods. We fit a model including an interseismic slip rate, coseismic offsets from the San Simeon and Parkfield earthquakes and a post-Parkfield earthquake exponential decay to daily time series of the GPS-derived displacements. We use the results of the GPS time-series fit for the Parkfield coseismic offsets and amplitudes of the postseismic exponential decay in the joint inversion. The model used in the inversion assumes that slip in the postseismic period evolves as an exponential decay and we simultaneously solve for coseismic slip and the amplitude of the postseismic exponential. With this model formulation, the distribution of postseismic slip is not allowed to change with time, only its magnitude. The model resolves nearly equal amounts of slip for the coseismic and postseismic time periods. This result underlines the importance of aseismic slip in the slip budget for the Parkfield segment of the San Andreas fault. The two periods also show an inverse correspondence in their slip distributions. The coseismic rupture occurred mainly in two high-slip asperities; the smaller occurring near the hypocenter and the larger occurring 10-20 km north. Shallow postseismic slip took place mainly on the fault areas surrounding the coseismic rupture, including the rupture areas of two Mw5.0 aftershocks.

  10. Effects of material property variations on slip estimates for subduction interface slow-slip events

    NASA Astrophysics Data System (ADS)

    Williams, Charles A.; Wallace, Laura M.

    2015-02-01

    We investigate the influence of elastic heterogeneity on geodetic inversions of slow-slip events by inverting for slip distributions of four events along the Hikurangi Margin, New Zealand. We generate Green's functions using a finite element code in conjunction with a New Zealand-wide seismic velocity model to assign elastic properties. We find that these heterogeneous models typically require ~20% less slip than homogeneous models in cases where the slip is deep or there is reasonable geodetic coverage above the slipping region. In cases where the slip is shallow (and mostly offshore) and there is little geodetic coverage directly above the slipping region, the heterogeneous models can predict significantly larger amounts of slip (42% in our study). These changes in the predicted amounts of slip have important implications for quantifying slip budgets accommodated by slow slip at subduction zones worldwide.

  11. 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.

  12. Strength or power, which is more important to prevent slip-related falls?

    PubMed

    Han, Longzhu; Yang, Feng

    2015-12-01

    Falls are a serious health and medical concern facing older adults worldwide. Both muscle strength and power have been related to falls among older adults. The primary purpose of this study was to identify which one of these two muscular performances is more important in preventing a slip-related fall. Twenty-six healthy young adults participated in this study. Their muscle strength (torque) and power capacities were assessed at the right knee under maximum voluntary isometric (flexion and extension) and isokinetic (concentric extension and flexion at three different contraction speeds: 60deg/s, 120deg/s, and 180deg/s) contractions, respectively. They were then subjected to an identical and unannounced slip during gait on a treadmill under the protection of a safety harness after walking regularly for five times on the treadmill. Accuracy of predicting slip outcome (fall vs. recovery) was examined for each muscle performance measurement using logistic regression. Results showed that overall the joint power capacity measurements predicted the slip outcome among these subjects with higher accuracy than did the joint torque capacity measurements. Such results suggested that muscle power could be more closely related to a fall initiated by a slip during gait. The findings from the present study could provide guidance to identify individuals at increased risk of falling using the joint power capacity measurement and to design effective fall prevention training paradigms aiming at maximizing muscle power among older adults and others with physical disabilities. PMID:26378820

  13. A slow slip event along the northern Ecuadorian subduction zone

    NASA Astrophysics Data System (ADS)

    Nocquet, J.; Mothes, P. A.; Vallee, M.; Regnier, M.

    2009-12-01

    Rapid subduction of the Nazca plate beneath the Ecuador-Colombia margin (~58 mm/yr) has produced one of the largest megathrust earthquake sequence during the last century. The 500-km-long rupture zone of the 1906 (Mw = 8.8) event was partially reactivated by three thrust events; in 1942 (Mw = 7.8), 1958 (Mw = 7.7), and 1979 (Mw = 8.2), whose rupture zones abut one another. New continuously-recording GPS stations installed along the Ecuadorian coast, together with campaign sites observed since 1994 indicate that the current velocities results from the superimposition of a NNE motion the crustal North Andean Block occurring at ~8 mm/yr in Ecuador and the elastic deformation involved by partial locking of the subduction interface. We first estimate the long-term kinematics of the North Andean block in a joint inversion including GPS data, earthquake slip vectors and quaternary slip rates on major faults. The inversion provides a Euler pole located at long. -107.8E, lat. 36.2N, 0.091/Ma and indicates little internal deformation of the North Andean Block (wrms=1.3 mm/yr). Residual velocities with respect to the North Andean Block are then modeled in terms of elastic locking along the subduction interface. Models indicate that the subduction interface is partially locked (50%) up to a depth of 40 km. Finally, we report a transient event that occurred in early 2008 near the Ecuador-Colombia border. The magnitude of the trenchward displacement is 13 mm, with uplift of similar magnitude. While the total duration of the slip event is 5 months, the horizontal time series clearly shows two sub-phases of slip with approximatively similar magnitud of displacement and duration, separated by 6 weeks. Modelling indicates that the slip occurs at 40 km depth, immediately below downdip extension of the locked zone.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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 250-300C. 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).

  1. Development of strike-slip faults in the dolomites of the Sella Group, Northern Italy

    NASA Astrophysics Data System (ADS)

    Mollema, Pauline N.; Antonellini, Marco

    1999-03-01

    The dolomites in the Sella Group, Northern Italy, were intensely jointed and faulted during the Alpine orogeny. Field observation of joints, joint-zones, and faults are the basis for a model for fault development in dolomite. We propose that joints developed parallel to the maximum compressive stress direction and were homogeneously distributed throughout the Sella Group before faults became localized (fault pre-nucleation stage). With ongoing deformation, the joints were localized into en-chelon arrays also called joint-zones. These joint-zones are incipient faults and are characterized by small dilation (?1 mm) of the individual joints, narrow joint spacing (1-15 mm), a high number of joints in the array (up to thousands), high joint-overlap, and joint-array angles between 10 and 40. The next stage in fault development involves the break up of the rock bridges in the joint-zones and the localization of shear. Joint-zones with pockets of breccia are the smallest faults encountered and accommodate strike-slip offsets of 5-7 mm, whereas joint-zones with a continuous breccia zone accommodate offsets of 1-3 cm. Faults with offsets of more than 1 m are characterized by a breccia zone 0.5-15 m wide, and high joint densities in the wall-rock. The absence of a distinct granular structure of the dolomites of the Sella Group and the shallow depth of burial during Alpine deformation (less than 1000 m) may have promoted the growth and localization of joints, their linking via cross-joints, and the formation of continuous faults.

  2. Process for slip casting textured tubular structures

    DOEpatents

    Steinlage, Greg A. (West Lafayette, IN); Trumble, Kevin P. (West Lafayette, IN); Bowman, Keith J. (West Lafayette, IN)

    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.

  3. 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.

  4. Stick and slip actuators (SSA)

    NASA Astrophysics Data System (ADS)

    Schmitt, Carl; Breguet, Jean-Marc; Bergander, Arvid; Clavel, Reymond

    2000-10-01

    Stick and Skip Actuators (SSA) are particularly well adapted to micro- robotics. A simple design, a very high intrinsic resolution (a few nanometers) and a high rigidity make them especially interesting in high precision micro-manipulations. Moreover, a smart design allows to combine the guiding and actuating function. The mechanical interface between the piezo-elements and the guiding mechanisms in an important point of the stick and slip actuators. The design of this interface and the choice of the material are very important. Both aspects have an impact on the rigidity, which has an influence on the behavior of the actuator. They have also an incidence onf the reliability (lifetime) because the design gives the contact condition and the material the wear resistance. In addition, a loading system allowing to keep the mechanical contact at this interface has a direct effect on the contact pressure. In order to confirm the performance of SSA, prototypes have been developed at the ISR. Their designs have bene made for application in optical microscopy, for manipulators in industrial assembly of micro- engineering products, for micro-factory, chemical and bio-engineering equipment for research or routine tasks, such as testing, screening etc. This paper presents a short description of several SSA made by the IRS and describes the parameters characterizing the stick and slip motion and the mechanical interface.

  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. 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.

  7. The Elusive Slipped Capital Femoral Epiphysis

    PubMed Central

    Johnson, Bruce C.; Klabunde, Lori A.

    1995-01-01

    Slipped capital femoral epiphysis is the most common disorder of the hip in young adolescents. Although it is not completely understood, predictive indicators give clues as to who is at risk. Slipped capital femoral epiphysis need not be painfully disabling. Many children are quite active during an active slip. Any child between the ages of 10 and 15 years presenting with thigh, knee, and/or hip pain and no special history of trauma should have a good hip examination to rule out slipped capital femoral epiphysis. ImagesFig 2.Fig 3.Fig 4.Fig 5. PMID:16558322

  8. 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

  9. 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.

  10. 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

  11. Outcomes following subcapital osteotomy for severe slipped upper femoral epiphysis.

    PubMed

    Vanhegan, I S; Cashman, J P; Buddhdev, P; Hashemi-Nejad, A

    2015-12-01

    Slipped upper femoral epiphysis (SUFE) is the most common hip disorder to affect adolescents. Controversy exists over the optimal treatment of severe slips, with a continuing debate between in situ fixation versus corrective surgery. We present our experience in a series of 57 patients presenting with severe unilateral SUFE (defined > 50) managed with a subcapital cuneiform osteotomy. Between 2001 and 2011, 57 patients (35 male, 22 female) with a mean age of 13.1 years (9.6 to 20.3, SD 2.3) were referred to our tertiary referral institution with a severe slip. The affected limb was rested in slings and springs before corrective surgery which was performed via an anterior Smith-Petersen approach. Radiographic analysis confirmed an improvement in mean head-shaft slip angle from 53.8(o) (standard deviation (sd) 3.2) pre-operatively to 9.1(o) (sd 3.1) post-operatively, with minimal associated femoral neck shortening. In total 50 (88%) patients were complication free at a mean follow-up of seven years (2.8 to 13.9 years, sd 3). Their mean Oxford hip score was 44 (37 to 48) and median visual analogue pain score was 0 out of 10 (interquartile range 0 to 4). A total of six patients (10.5%) developed avascular necrosis requiring further surgery and one (1.8%) patient developed chondrolysis but declined further intervention. This is a technically demanding operation with variable outcomes reported in the literature. We have demonstrated good results in our tertiary centre. Cite this article: Bone Joint J 2015;97-B:1718-25. PMID:26637690

  12. 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

  13. 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.

  14. "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

  15. Environmental study of miniature slip rings

    NASA Technical Reports Server (NTRS)

    Radnik, J. L.

    1967-01-01

    Investigation studied the long term operation of miniature slip ring assembles in high vacuum of space and included the influence of ring, brush, and insulator materials on electrical noise and mechanical wear. Results show that soft metal vapor plating and niobium diselenide miniature slip rings are beneficial.

  16. Salton Sea Satellite Image Showing Fault Slip

    USGS Multimedia Gallery

    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...

  17. 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

  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 Astrophysics Data System (ADS)

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

    1984-05-01

    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. 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.

  1. 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, ...

  2. 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

  3. The effect of slip variability on earthquake slip-length scaling

    NASA Astrophysics Data System (ADS)

    Liu-Zeng, Jing; Heaton, Thomas; DiCaprio, Christopher

    2005-09-01

    There has been debate on whether average slip in long ruptures should scale with rupture length L, or with rupture width W. This scaling discussion is equivalent to asking whether average stress drop ??, which is sometimes considered an intrinsic frictional property of a fault, is approximately constant over a wide range of earthquake sizes. In this paper, we examine slip-length scaling relations using a simplified 1-D model of spatially heterogeneous slip. The spatially heterogeneous slip is characterized by a stochastic function with a Fourier spectrum that decays as k-?, where k is the wavenumber and ? is a parameter that describes the spatial smoothness of slip. We adopt the simple rule that an individual earthquake rupture consists of only one spatially continuous segment of slip (i.e. earthquakes are not generally separable into multiple disconnected segments of slip). In this model, the slip-length scaling relation is intimately related to the spatial heterogeneity of the slip; linear scaling of average slip with rupture length only occurs when ? is about 1.5, which is a relatively smooth spatial distribution of slip. We investigate suites of simulated ruptures with different smoothness, and we show that faults with large slip heterogeneity tend to have higher ratios than those with spatially smooth slip. The model also predicts that rougher faults tend to generate larger numbers of small earthquakes, whereas smooth faults may have a uniform size distribution of earthquakes. This simple 1-D fault model suggests that some aspects of stress drop scaling are a consequence of whatever is responsible for the spatial heterogeneity of slip in earthquakes.

  4. Fault Gouge Velocity Characteristics During Slow-Slip and Stick-Slip Under Laboratory Conditions

    NASA Astrophysics Data System (ADS)

    Johnson, P. A.; Scuderi, M.; Leeman, J.; Riviere, J. V.; Ferdowsi, B.; Carmeliet, J.; Marone, C.

    2014-12-01

    Tectonic faults slip with velocities that range from very slow (slow-slip) to very fast, including dynamic stick-slip and earthquakes. We have reproduced slow and fast slip in the laboratory to gain insight into physical differences that may aid in our interpretation of these phenomena in the Earth. Here we present results for slow and fast slip on simulated faults in the laboratory under static normal stresses of 1-8 MPa and shearing rates of 0.1-100 ?m/second. We apply shear to a central block bounded by two gouge layers, held in place by the static load. Simultaneous to shearing we measure acoustical time-of-flight across the gouge layers to quantify the evolution of gouge wavespeed preceding, during and following slip events. At the fixed static stresses studied, we find that stick-slip may occur over a spectrum of grain sizes ranging from order 5-150 micron at least (Mimusil or glass beads of varying dimension); in contrast slow-slip only occurs for fine grain materials such as Minusil (fine-grained white crystalline silica of order 5 micron in diameter). In both cases the gouge compacts at the time of slip associated with a gouge material increase in velocity. Following slip, the gouge material progressively dilates and the material velocity progressively decreases up to slip time, when the process repeats. Numerical simulation will help us understand the fast (stick-slip) and slow (slow-slip) processes. It is plausible that grain sizes influence slow and fast slip in faults in the earth, and the velocity changes observed in the laboratory fault gouge may also exist in fault zones.

  5. Geodetic Measurements of the Guerrero Slow Slip Events: Implications for Large Earthquakes in the Guerrero Gap

    NASA Astrophysics Data System (ADS)

    Bekaert, D. P.; Hooper, A. J.; Samsonov, S. V.; Wright, T. J.; Gonzlez, P. J.; Pathier, E.; Kostoglodov, V.

    2014-12-01

    Estimates of elastic strain accumulated in the Guerrero seismic gap, Mexico, have conceived a potential for Mw 8.0-8.4 subduction thrust earthquake. While several large slow slip events (SSEs) have occurred in the area it remains unclear how the SSEs change the stress field in the Guerrero seismic region, and what their implications are for future devastating earthquakes. On 18 April 2014, the Mw 7.2 Petatlan earthquake, followed by two Mw 6.4 and 6.1 events on 8 and 10 May 2014, occurred on the western edge of the Gap, while a new large slow slip event was ongoing, suggesting that it may have triggered the earthquakes. Slow slip studies have mainly relied on GNSS. In Guerrero the low station distribution restricts their ability to resolve the spatial extent of the SSE. We apply a time-series Interferometric Synthetic Aperture Radar (InSAR) analysis to estimate the spatial extent and magnitude of deformation caused by a slow slip event in 2006, and jointly invert GNSS and InSAR for slow slip on the subduction interface. We assume rectangular dislocation patches, and use Markov chain Monte Carlo sampling to obtain a full error distribution of the model unknowns. Correlation between our estimated slow slip region and the location of non-volcanic tremor, as well as an ultra-slow velocity layer, supports the hypothesis of a common source potentially related to high pore pressures. We find slow slip extends up to 7 km depth, well within the Guerrero Gap. We observe a spatial correlation between slow slip and a high slip deficit region. Even accounting for the stress released by SSEs, we find the Guerrero Gap still has a potential for Mw ~7.8-8 earthquake. We also present results for the 2014 SSE, using RADARSAT-2 data. We analyse whether slow slip could triggered the recent earthquakes, by investigating the spatial extent of the SSE and its relationship to the coseismic slip. Our results have implications for the timings of megathrust earthquakes in other subduction zones.

  6. 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.

  7. 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.

  8. 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 (CNTs), 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.

  9. 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

  10. Dynamical stability of slip-stacking particles

    NASA Astrophysics Data System (ADS)

    Eldred, Jeffrey; Zwaska, Robert

    2014-09-01

    We study the stability of particles in slip-stacking configuration, used to nearly double proton beam intensity at Fermilab. We introduce universal area factors to calculate the available phase space area for any set of beam parameters without individual simulation. We find perturbative solutions for stable particle trajectories. We establish Booster beam quality requirements to achieve 97% slip-stacking efficiency. We show that slip-stacking dynamics directly correspond to the driven pendulum and to the system of two standing-wave traps moving with respect to each other.

  11. Electrostatic precursors to granular slip events

    PubMed Central

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

    2012-01-01

    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

  12. 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

  13. 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.

  14. PREDICTED THRESHOLD AGAINST BACKWARD BALANCE LOSS FOLLOWING A SLIP IN GAIT

    PubMed Central

    Yang, Feng; Anderson, Frank C.; Pai, Yi-Chung

    2008-01-01

    The purpose of this study was to use a 7-link, moment-actuated human model to predict, at liftoff of the trailing foot in gait, the threshold of the center of mass (COM) velocity relative to the base of support (BOS) required to prevent backward balance loss during single stance recovery from a slip. Five dynamic optimization problems were solved to find the minimum COM velocities that would allow the simulation to terminate with the COM above the BOS when the COM started 0.25, 0.5, 0.75, 1.0, and 1.25 foot lengths behind the heel of the stance foot (i.e., behind the BOS). The initial joint angles of the model were based on averaged data from experimental trials. Foot-ground contact was modeled using 16 visco-elastic springs distributed under the stance foot. Slipping was modeled by setting the sliding coefficient of friction of these springs to 0.02. The forward velocity of the COM necessary to avoid a backward balance loss is nearly two times larger under slip conditions than under non-slip conditions. The predicted threshold for backward balance loss following a slip agreed well with experimental data collected from 99 young adults in response to 927 slips during walking. In all trials in which a subjects COM had a velocity below the predicted threshold, the subjects recovery foot landed posterior to the slipping foot as predicted. Finally, combining experimental data with optimization, we verified that the 7-link model could more accurately predict gait stability than a 2-link model. PMID:18538329

  15. Beam loading compensation for slip stacking

    SciTech Connect

    James Steimel; Tim Berenc; Claudio Rivetta

    2003-06-04

    This paper discusses the beam loading compensation requirements to make slip stacking practical in the Fermilab main injector. It also discusses some of the current plans for meeting these requirements with a digital, direct RF feedback system.

  16. 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

  17. 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.

  18. 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

  19. 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

  20. Slip boundary conditions over curved surfaces.

    PubMed

    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. PMID:26871153

  1. Subgrain boundaries and slip systems in quartz

    NASA Astrophysics Data System (ADS)

    Kilian, Rdiger

    2015-04-01

    At elevated temperatures, quartz usually deforms by dislocation glide and dislocation creep. Textures (crystallographic preferred orientations) and microstructures are commonly used to infer the kinematics and physical conditions of deformation. However, it is debatable whether a given texture, represented by a pole figure, is universally indicative of a specific deformation temperature or recrystallization mechanism or e.g. is rather related to strain. Quartz veins in synkinematic, felsic dikes from the footwall of the Mohave Wash detachment fault in the Chemehuevi Mountains are studied by EBSD, CIP and universal stage. Mm-sized quartz grains are homogeneously stretched with aspect ratios of up to 30. Minor recrystallization takes place by subgrain rotation. Three different groups of highly stretched quartz grains can be defined: Grains with peripheral c-axes at a high angle to the foliation (Z-grains), grains with central c-axes perpendicular to the lineation (Y-grains) and grains with c-axes intermediately between the former two (O-grains). The three types of grains do not show a significant difference in their aspect ratios. Bulk pole figures show a kinked single c-axes girdle with a central maximum and an a-axes maximum parallel to the lineation. Misorientation analysis and the orientation of subgrain boundaries are used to make inferences on slip systems. Z-grains are interpreted to be suitable for basal (c)-slip, Y-grains for prism {m}-slip, which is compatible with the bulk misorientation distribution function of entire grains. O-grains could be interpreted as suitably oriented for rhomb {r/z/pi/pi'} slip, however, this is not supported by the bulk misorientation distribution function. Individual subgrain boundaries in Y-grains and Z-grains expected for the 'easy' slip systems {m} and (c) with tilt character ({a} parallel boundaries with [c] or misorientation axes, respectively), are limited to small (< 2) misorientation angles. Subgrain boundaries with higher misorientation angles relate to variable slip systems, showing tilt, twist or mixed mode character. Many of those slip systems have a low Schmid factor. O-grains rarely show subgrain boundaries that can directly be related to rhomb or rhomb-slip. Most common subgrain boundaries are tilt {a}[c]-boundaries, tilt {a}-boundaries or mixed mode boundaries, hence deformation is interpreted to occur mostly by combined {m} and (c)-slip rather than rhomb slip. Based on the homogeneous microstructure without a low temperature overprint, it is inferred that deformation took place in a rather narrow temperature range. Grains deform homogeneously, independent on their orientation with different slip systems involved. A temperature effect on the activity of individual slip system is not recognizable. Suitably oriented (c) and {m} slip systems seem to result in lattice bending rather than abundant subgrain boundaries. Subgrain boundaries related to other slip systems contribute to subgrain rotation and subsequent recrystallization but not essentially to stretching of grains and rather ensure strain compatibility. The observations indicate that many prominent subgrain boundaries might not relate to the main strain producing slip system and grain orientation does not necessarily prescribe the involved slip systems.

  2. Acoustic emissions during deformation of intact and jointed welded tuff

    NASA Astrophysics Data System (ADS)

    Holcomb, D. J.; Teufel, L. W.

    1982-07-01

    Monitoring of acoustic emissions (AE) has been widely used as a means of detecting failure in intact rock. For intact rock the technique is simple, because an increasing rate of AE is usually a sign of impending failure. However, most large rock masses contain numerous joints and the behavior of the joints controls the properties of the rock mass In particular, the failure mode often becomes stable or unstable slip (stick-slip) on a joint at stresses well below those required for failure of the intact rock. As an aid to understanding and monitoring the behavior of jointed rock masses, we have done a series of experiments on intact and artificially jointed samples of Grouse Canyon tuff. The tuff was selected because it is under consideration as a disposal medium for nuclear wastes. The samples were instrumented to measure axial and transverse displacements and AE rates.

  3. 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.

  4. Ceramic joints

    DOEpatents

    Miller, Bradley J. (Worcester, MA); Patten, Jr., Donald O. (Sterling, MA)

    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.

  5. Nonlinear Dynamical Triggering of Slow-Slip

    NASA Astrophysics Data System (ADS)

    Johnson, P. A.; Knuth, M. W.; Kaproth, B. M.; Carpenter, B. M.; Guyer, R. A.; Le Bas, P.; Daub, E. G.; Marone, C.

    2010-12-01

    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 (~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 [We gratefully acknowledge the support of the U. S. Department of Energy through the LANL/LDRD Program for this work].

  6. 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.

  7. 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

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

    DOEpatents

    Klein, Frederick F. (Monroeville, PA)

    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. 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.

  10. 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.

  11. 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

  12. 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

  13. Injuries from slips and trips in construction.

    PubMed

    Lipscomb, Hester J; Glazner, Judith E; Bondy, Jessica; Guarini, Kenneth; Lezotte, Dennis

    2006-05-01

    Construction injuries preceded by a slip or trip were documented using data from the building of the Denver International Airport (Denver, Colorado, USA), the largest construction project in the world at the time. Slips and trips occurred at a rate of 5/200,000 h worked accounting for 18% of all injuries and 25% of workers' compensation payments, or more than $10 million. Slips contributed to the vast majority (85%) of same-level falls and over 30% of falls from height, as well as a significant number of musculoskeletal injures sustained after slipping or tripping but without falling. The injury burden would have been under-recognized in analyses of most coded compensation records. In contrast to other types of injuries, the most common contributing factors were environmental in nature including conditions of walking and working surfaces, terrain and weather. Due to the very dynamic nature of construction work, reducing slips and trips will require a focus on environmental and organizational solutions that evolve as the site changes and the construction project evolves. PMID:16212931

  14. 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.

  15. Smoothing and roughening of slip surfaces in direct shear experiments

    NASA Astrophysics Data System (ADS)

    Sagy, Amir; Badt, Nir; Hatzor, Yossef H.

    2015-04-01

    Faults in the upper crust contain discrete slip surfaces which have absorbed a significant part of the shear displacement along them. Field measurements demonstrate that these surfaces are rough at all measurable scales and indicate that surfaces of relatively large-slip faults are statistically smoother than those of small-slip faults. However, post faulting and surface erosion process that might affect the geometry of outcrops cannot be discounted in such measurements. Here we present experimental results for the evolution of shear surface topography as function of slip distance and normal stress in direct shear experiments. A single prismatic fine grain limestone block is first fractured in tension mode using the four-point bending test methodology and then the fracture surface topography is scanned using a laser profilometer. We then shear the obtained tensile fracture surfaces in direct shear, ensuring the original fracture surfaces are in a perfectly matching configuration at the beginning of the shear test. First, shearing is conducted to distances varying from 5 to 15 mm under constant normal stress of 2MPa and a constant displacement rate of 0.05 mm/s using two closed-loop servo controlled hydraulic pistons, supplying normal and shear forces (Davidesko et al., 2014). In the tested configuration peak shear stress is typically attained after a shear displacement of about 2-3 mm, beyond which lower shear stress is required to continue shearing at the preset displacement rate of 0.05 mm/s as is typical for initially rough joints. Following some initial compression the interface begins to dilate and continues to do so until the end of the test. The sheared tensile fracture surface is then scanned again and the geometrical evolution, in term of RMS roughness and power spectral density (PSD) is analyzed. We show that shearing smooth the surface along all our measurements scales. The roughness ratio, measured by initial PSD / final PSD for each wavelength, increases as a function of slip amount. The roughness measured after slip can be fitted by a power-law similar to that of the initial tensile surface. In the next series of experiments a similar procedure is applied when the roughness evolution is measured as a function of increasing normal stress for a fixed displacement amount of 10 mm. While samples sheared under a constant normal stress of 5 MPa generated surface smoothing, shearing under normal stress of 7.5 MPa to 15 MPa exhibited surface roughening at the measured range of scales. We find that roughening is correlated with the attained peak shear stress values, stress drop (peak shear stress minus residual shear stress) and with wear accumulation, a novel measurement procedure of which is developed here. Analysis of the sheared samples shows that roughening is generated by sets of dense fractures that significantly damaged the sample in the immediate proximity to large asperities. This roughening is related to penetrative damage during transient wear in rough surfaces.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Joint pain

    MedlinePLUS

    ... both rest and exercise are important. Warm baths, massage, and stretching exercises should be used as often ... Does keeping the joint elevated help? Do medicines, massage, or applying heat reduce the pain? What other ...

  1. Joint Problems

    MedlinePLUS

    ... ankles and toes. Other types of arthritis include gout or pseudogout. Sometimes, there is a mechanical problem ... for more information on osteoarthritis, rheumatoid arthritis and gout. How Common are Joint Problems? Osteoarthritis, which affects ...

  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. Slip in the 2003 San Simeon earthquake and its effect on the Parkfield segment

    NASA Astrophysics Data System (ADS)

    Johanson, I.; Brgmann, R.

    2006-12-01

    The M6.5 San Simeon earthquake, which occurred on 12/22/2003, was a thrust event on the Oceanic fault in the Coast Ranges of central California, ~50 km from the Parkfield segment of the San Andreas fault. It is the largest recorded earthquake in this region. That it occurred just ten months before the highly anticipated, and ~15 year "late", Parkfield earthquake on 9/28/2004, lends itself to speculation that there is a causal relationship. To constrain the fault plane geometry and slip distribution of the San Simeon earthquake, we construct three interferograms from ERS and Envisat data, obtained through WInSAR. Two span both the coseismic and portions of the postseismic period (12/9/2003 - 9/14/2004, 7/9/2003 - 4/14/2004) and one contains purely postseismic deformation (12/31/2003 - 2/4/2004). We also include coseismic and postseismic GPS displacements. All three interferograms and the GPS data are jointly inverted to simultaneously determine both the coseismic and postseismic slip distributions. The distributed slip models are then used to calculate the static stresses imposed on the Parkfield segment. Preliminary results show that the coseismic rupture increased the Coulomb failure stress (CFS) for right-lateral strike-slip on the entire Parkfield segment by more than 0.1 bar, when an effective coefficient of friction (?^') of 0.4 is used. 0.1 bars is a threshold found by other authors to correlate with aftershock triggering; changes in CFS above this level may be considered significant. The stresses produced by the postseismic slip are much smaller; less than 0.1 bar throughout the Parkfield segment. However the sense of the change in CFS was to encourage right-lateral slip at Parkfield.

  4. 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.

  5. 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.

  6. Pressure slip casting of silicon nitride

    SciTech Connect

    Richter, H.J.

    1995-09-01

    This paper discusses the potential of pressure slip casting for components made of technical ceramic materials. The tests carried out on pressure slip casting and pressure filtration of silicon nitride show that the highest green density will be obtained if a slurry is used which is completely deflocculated and does not contain any binding agent. Penetration of fine particles into the porous plastic mould cannot be completely prevented but can be reduced to a large extent by the proper selection of the pressure-time regime.

  7. 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.

  8. 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.

  9. 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.

  10. The Slip History of the 2004 Slow Slip Event on the Northern Cascadia Subduction Zone

    NASA Astrophysics Data System (ADS)

    Gao, H.; Schmidt, D. A.

    2006-12-01

    We estimate the down-dip slip distribution and propagation path of the 2004 slow slip event on the Cascadia subduction zone. In recent years, slow slip events have been detected in Cascadia with a regular recurrence interval. Such slow earthquakes can release strain energy which may eventually trigger a large thrust earthquake in the subduction zone. We process the continuous GPS data from the PBO, PANGA, and WCDA networks from April 10th to August 15th using the GAMIT/GLOBK processing package. Daily solutions are determined for 30 stations. The secular displacement in the Pacific Northwest is northeastward, consistent with the plate convergence direction. During the slow slip event, GPS stations move toward the southwest, as observed for previous slow slip events, opposite to their longer-term northeastern movement. The average cumulative horizontal displacement observed at benchmarks ranges from 2 to 4 mm over a time span of 5 to 18 days. Our analysis indicates that the occurrence of transient displacement is first detected south of Puget Sound in early May. Following a distinct break in activity, the event is observed at stations north of the Olympic Pennisula in mid-July. Transient displacement concludes at stations on southern Vancouver Island in late July. We discretize the Juan de Fuca-North American plate interface into subfaults and solve for the down- dip slip history using the Extended Network Inversion Filter. Station DRAO, located in western Canada, is selected as our reference GPS site because it is unaffected by transient displacements from the slow slip event. Slip is found to propagate along-strike to the north at an equivalent speed of approximately 6-17 km per day. The maximum slip is observed beneath Victoria. Several characteristics of the 2004 event are different from the 2003 event. Specifically, the 2004 event propagated northward from southern Puget Sound with an obvious period of inactivity in June, while the 2003 event propagated bi-directionally and continuously.

  11. 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.

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Slip complexity in earthquake fault models.

    PubMed

    Rice, J R; Ben-Zion, Y

    1996-04-30

    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. PMID:11607669

  1. Geodetically derived fault slip distribution model for the May, 11th 2011 Lorca earthquake (SE, Spain)

    NASA Astrophysics Data System (ADS)

    Gonzalez, P. J.; Tiampo, K. F.; Palano, M.; Cannav, F.; Fernandez, J.

    2011-12-01

    The Alhama de Murcia Fault (AMF) is a compound multisegmented right-lateral to reverse fault system. The AMF is one the longest faults in the Eastern Betics Shear zone (Southeastern Spain). In the last decades its seismogenic potential has been evaluated and earthquake maximum magnitudes were forecast based on paleoseismic and dating data. On May 11th, 2011 a moderate (Mw 5.1) earthquake shook the region, causing 9 casualties and severe damages in Lorca city (Murcia region). The reported location of the aftershocks sequence did not follow any particular trend; furthermore in-situ geology surveys did not identify any fault slip related ground deformation. To contribute to a better seismic hazard assessment, we need to locate and, if possible, characterize the fault-slip distribution that generated the earthquake. In this work, we detected small but significant ground deformation in the epicentral area by using geodetic (GPS and satellite radar interferometry) data. Geodetic data was processed by using a stack of differential radar interferometry (corrected for a known subsidence contribution and estimating their error budget), daily GPS estimated coordinates and high-rate 1-Hz GPS data. We jointly inverted the detected static coseismic displacements (a GPS station and two ENVISAT interferograms from different tracks) for the fault plane geometry parameters by using a rectangular dislocation model embedded in a homogeneous elastic half-space. The best-fitting fault plane follows closely the geologically derived AMF geometry (NE-SW strike trend and dipping ~60-70o to NW). Later, the obtained model geometry was extended and divided into patches to allow for a detailed analysis of the fault slip distribution pattern. Slip distribution indicates that slip occurred in a single patch with reverse and right-lateral motion (with peak fault slip magnitude of ~9 cm). However, the modelling results also indicate that the fault slip was shallower along the centre and southwest of the city of Lorca. The shallower character of the slip probably caused the relative intense ground acceleration recorded at the Lorca city (0.4g) and increased the building damages. We show that the Lorca earthquake was generated by a simple segment (6-8 km long) slightly dipping to the NW of the AMF system. This study also represents the first modern geodetically observed ground deformation signature due to seismic activity in the Iberian Peninsula.

  2. 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.

  3. 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).

  4. 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.

  5. SYNTHESIS OF ORGANIC EPOXIDES USING A SPINNING TUBE-IN-TUBE REACTOR

    EPA Science Inventory

    The U.S. Environmental Protectiion 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 chemcial synthesis. The STT...

  6. 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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 Lvy 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 Lavalle (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). Lavalle (2008) described that Lvy white noise that generates fLm is more appropriate than the Gaussian white noise which generates fBm. In addition, if the 'alpha' parameter of the Lvy law, which governs the degree of attenuation of tails of the probability distribution, is 2.0, then the Lvy 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 ' - ?') of k versus E(k) holds for all earthquakes. 2) For example, ? = 3.70 and ? = 1.96 for the Tohoku earthquake (2011) and ? = 4.16 and ? = 2.00 for the Haiti earthquake (2010). For these cases, the Gauss' law is appropriate because alpha is almost 2.00. 3) However, ? = 5.25 and ? = 1.25 for the Peru earthquake (2007) and ? = 2.24 and ? = 1.57 for the Simeulue earthquake (2008). For these earthquakes, the Lvy law is more appropriate because ? is far from 2.0. 4) Although Lavalle (2003, 2008) concluded that the Lvy 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. Lavalle and Archuleta, 2003, Stochastic modeling of slip spatial complexities for the 1979 Imperial Valley, California, earthquake, GEOPHYSICAL RESEARCH LETTERS, 30(5). Lavalle, 2008, On the random nature of earthquake source and ground motion: A unified theory, ADVANCES IN GEOPHYSICS, 50, Chap 16.

  11. 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.

  12. 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.

  13. 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.

  14. Wall slip and fluidity in emulsion flow

    NASA Astrophysics Data System (ADS)

    Paredes, Jos; Shahidzadeh, Noushine; Bonn, Daniel

    2015-10-01

    The microscopic origin of apparent wall slip is studied systematically using a confocal laser scanning microscope coupled to a rheometer. We obtain flow curves on a model emulsion from classical macroscopic measurements that are compared with flow curves obtained from microscopic measurements. By controlling the wetting properties of the shearing walls, we show that the characteristic length used in the so-called fluidity model, proposed by Goyon et al. [Nature (London) 454, 84 (2008), 10.1038/nature07026], can be understood in terms of roughness induced by adsorbed droplets on the surface. Additionally, we disentangle two different effects that contribute to the difference between micro- and macrorheology. Both effects manifest themselves as gap-dependent viscosities due to either the formation of a lubricating layer close to the shearing walls or cooperative effects when the flow is strongly confined. Finally, we show that the cooperative effects can also be translated into an effective slip velocity.

  15. 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.

  16. Frictional slip of granite at hydrothermal conditions

    NASA Astrophysics Data System (ADS)

    Blanpied, Michael L.; Lockner, David A.; Byerlee, James D.

    1995-07-01

    Sliding on faults in much of the continental crust likely occurs at hydrothermal conditions, i.e., at elevated temperature and elevated pressure of aqueous pore fluids, yet there have been few relevant laboratory studies. To measure the strength, sliding behavior, and friction constitutive properties of faults at hydrothermal conditions, we slid laboratory granite faults containing a layer of granite powder (simulated gouge). Velocity stepping experiments were performed at temperatures of 23 to 600C, pore fluid pressures PH2O of 0 ("dry") and 100 MPa ("wet"), effective normal stress of 400 MPa, and sliding velocities V of 0.01 to 1 ?m/s (0.32 to 32 m/yr). Conditions were similar to those in earlier tests on dry granite to 845C by Lockner et al. (1986). The mechanical results define two regimes. The first regime includes dry granite up to at least 845 and wet granite below 250C. 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 350C. 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. We infer that one or more fluid-assisted deformation mechanisms are activated in the second, hydrothermal, regime and operate concurrently with cataclastic flow. Slip in the first (cool and/or dry) regime is characterized by pervasive shearing and particle size reduction. Slip in the second (hot and wet) regime is localized primarily onto narrow shear bands adjacent to the gouge-rock interfaces. Weakness of these boundary shears may result either from an abundance of phyllosilicates preferentially aligned for easy dislocation glide, or from a dependence of strength on gouge particle size. Major features of the granite data set can be fit reasonably well by a rate- and temperature-dependent, three-regime friction constitutive model (Chester, this issue). We extrapolate the experimental data and model fit in order to estimate steady state shear strength versus depth along natural, slipping faults for sliding rates as low as 31 mm/yr. We do this for two end-member cases. In the first case, pore pressure is assumed hydrostatic at all depths. Shallow crustal strength in this case is similar to that calculated in previous work from room temperature friction data, while at depths below about 9-13 km (depending on slip rate), strength becomes less sensitive to depth but sensitive to slip rate. In the second case, pore pressure is assumed to be near-lithostatic at depths below 5 km. Strength is low at all depths in this case (<20 MPa, in agreement with observations of "weak" faults such as the San Andreas). The predicted depth of transition from velocity weakening to velocity strengthening lies at about 13 km depth for a slip rate of 31 mm/yr, in rough agreement with the seismic-aseismic transition depth observed on mature continental faults. These 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.

  17. Slip casting of advanced ceramics and composites

    NASA Astrophysics Data System (ADS)

    Schilling, C. H.; Aksay, I. A.

    1987-03-01

    Particle packing arrangements in slip cast (colloidal filtration) articles uniquely affect the evolution of grain size and porosity defect distributions during sintering. These particle packing arrangements are influenced by the physical properties of colloidal structures in suspension and the resulting processes of agglomerate restructuring and pore closure during consolidation. Key parameters affecting cast layer packing structures are the particle size distribution, interparticle potential, hydrodynamic stresses in suspensions, and the combined effect of hydrodynamic and compaction stresses in cast layers. Experiments with electrostatically stabilized aqueous alumina systems illustrate specific effects of interparticle potential on slip casting rates and microstructure evolution during sintering. In addition, experiments were conducted that illustrate microstructure variations caused by differential sedimentation velocities and agglomerate growth kinetic effects.

  18. 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.

  19. 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.

  20. 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)

  1. Slip-trace-induced vicinal step destabilization

    NASA Astrophysics Data System (ADS)

    Coupeau, C.; Camara, O.; Drouet, M.; Durinck, J.; Bonneville, J.; Colin, J.; Grilh, J.

    2016-01-01

    Gold single crystals were deformed by uniaxial compression tests with the help of an experimental apparatus that allows one to characterize in situ, by UHV scanning tunneling microscopy, the evolution of surface structures under stress. It is demonstrated that the slip traces resulting from the emergence of moving dislocations at the free surface highly modify the organization of the vicinal steps. A model based on energetic considerations is proposed and discussed to explain the observed phenomenon.

  2. Earthquake slip between dissimilar poroelastic materials

    NASA Astrophysics Data System (ADS)

    Dunham, Eric M.; Rice, James R.

    2008-09-01

    A mismatch of elastic properties across a fault induces normal stress changes during spatially nonuniform in-plane slip. Recently, Rudnicki and Rice showed that similar effects follow from a mismatch of poroelastic properties (e.g., permeability) within fluid-saturated fringes of damaged material along the fault walls; in this case, it is pore pressure on the slip plane and hence effective normal stress that is altered during slip. The sign of both changes can be either positive or negative, and they need not agree. Both signs reverse when rupture propagates in the opposite direction. When both elastic and poroelastic properties are discontinuous across the fault, steady sliding at a constant friction coefficient, f, is unstable for arbitrarily small f if the elastic mismatch permits the existence of a generalized Rayleigh wave. Spontaneous earthquake rupture simulations on regularized slip-weakening faults confirm that the two effects have comparable magnitudes and that the sign of the effective normal stress change cannot always be predicted solely from the contrast in elastic properties across the fault. For opposing effects, the sign of effective normal stress change reverses from that predicted by the poroelastic mismatch to that predicted by the elastic mismatch as the rupture accelerates, provided that the wave speed contrast exceeds about 5-10% (the precise value depends on the poroelastic contrast and Skempton's coefficient). For faults separating more elastically similar materials, there exists a minimum poroelastic contrast above which the poroelastic effect always determines the sign of the effective normal stress change, no matter the rupture speed.

  3. 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

  4. 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.

  5. 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.

  6. Slip length crossover on a graphene surface.

    PubMed

    Liang, Zhi; Keblinski, Pawel

    2015-04-01

    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. PMID:25854252

  7. 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.

  8. 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.

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

    PubMed

    Uchida, Naoki; Iinuma, Takeshi; Nadeau, Robert M; Brgmann, 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Great Earthquakes With and Without Large Slip to the Trench

    NASA Astrophysics Data System (ADS)

    Mori, J. J.

    2013-12-01

    The 2011 Tohoku-oki earthquake produced a huge amount of slip (40 to 60 meters) on the shallow portion of the subduction zone close to the trench. This large displacement was largely unexpected for this region and caused the very large and damaging tsunami along the northeast coast of Honshu. For other subduction zones around the world, we examine the possibility of large slip to the trench in past large and great earthquakes. Since the trench region is generally far offshore, it is often difficult to resolve the amount of slip from onland geodetic and strong-motion data. We use a variety of observations, including slip distribution models, aftershock locations, local coastal deformation, and tsunami heights to determine which events likely had large amounts of slip close to the trench. Tsunami earthquakes, such as 1992 Nicaragua and 2006 Java likely had large shallow slip. Some typical subduction earthquakes, such as 1968 Tokachi-oki and 2003 Tokachi-oki (located in regions north of the source area of the 2011 Tohoku-oki earthquake) likely did not. We will discuss possible factors that influence the slip distribution on the shallow area of subduction megathrusts. Using results from the Japan Trench Fast Drilling Project (JFAST) which sampled the fault in the region of large slip, we can begin to understand the conditions of very large fault slip. Are there characteristic features in the material properties for faults that have large slip ? Can we determine if these regions have high plate coupling and accumulate stress ?

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Role of osteotomy in the treatment of slipped capital femoral epiphysis.

    PubMed

    Crawford, A H

    1996-01-01

    The treatment of severe slipped capital femoral epiphysis (SCFE) remains problematic. Treatment of most mild and moderate cases has been simplified, not by our increasing knowledge of physiology or molecular genetics, but by the advances in radiographic imaging, metallurgy, and the development of cannulated screw technology. Most centers agree that the placement of a single pin or screw across the center of the epiphysis, stabilizing the unreduced epiphysis and keeping the implant out of the joint space until physeal closure is achieved, is the most efficient and effective method for the majority of slips. Despite this knowledge and improvement in early results, the problems of avascular necrosis and chondrolysis have not been eliminated. Of more concern for patients whose severe unreduced SCFE has been pinned in situ is the secondary problem of the altered biomechanics of the lower extremity, leaving the hip in extension, the limb externally rotated and shortened. Most series show poor long-term results of realignment osteotomies; however, most series also show poor long-term results of severe slips treated by any means. These population groups are historically the same. Current radiographic imaging and implant design may eliminate most of the technical problems encountered with the accuracy and stability of realignment osteotomies, thereby allowing earlier motion, which may improve our results. The current status of realignment osteotomies is reviewed. PMID:8811539

  3. 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 ? is given by N ?-0.7. If we assume that seismic moment is proportional to ? 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 ?1/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.

  4. Wireless slips and falls prediction system.

    PubMed

    Krenzel, Devon; Warren, Steve; Li, Kejia; Natarajan, Bala; Singh, Gurdip

    2012-01-01

    Accidental slips and falls due to decreased strength and stability are a concern for the elderly. A method to detect and ideally predict these falls can reduce their occurrence and allow these individuals to regain a degree of independence. This paper presents the design and assessment of a wireless, wearable device that continuously samples accelerometer and gyroscope data with a goal to detect and predict falls. Lyapunov-based analyses of these time series data indicate that wearer instability can be detected and predicted in real time, implying the ability to predict impending incidents. PMID:23366815

  5. 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.

  6. 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

  7. Boundary Slip and Surface Interaction: A Lattice Boltzmann Simulation

    NASA Astrophysics Data System (ADS)

    Chen, Yan-Yan; Yi, Hou-Hui; Li, Hua-Bing

    2008-01-01

    The factors affecting slip length in Couette geometry flows are analysed by means of a two-phase mesoscopic lattice Boltzmann model including non-ideal fluid-fluid and fluid-wall interactions. The main factors influencing the boundary slip are the strength of interactions between fluid-fluid and fluid-wall particles. Other factors, such as fluid viscosity, bulk pressure may also change the slip length. We find that boundary slip only occurs under a certain density (bulk pressure). If the density is large enough, the slip length will tend to zero. In our simulations, a low density layer near the wall does not need to be postulated a priori but emerges naturally from the underlying non-ideal mesoscopic dynamics. It is the low density layer that induces the boundary slip. The results may be helpful to understand recent experimental observations on the slippage of micro flows.

  8. 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

  9. EMG and kinematic responses to unexpected slips after slip training in virtual reality.

    PubMed

    Parijat, Prakriti; Lockhart, Thurmon E; Liu, Jian

    2015-02-01

    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 (VR training and control). Both groups went through three sessions including baseline slip, training, and transfer of training on slippery surface. The training group experienced 12 simulated slips using a visual perturbation induced by tilting a VR scene while walking on the treadmill and the control group completed normal walking during the training session. Kinematic, kinetic, and electromyography 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

  10. 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.

  11. 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.

  12. Geodetic slip rates in the southern San Andreas Fault system: Investigation of the effects of heterogeneous elastic structure

    NASA Astrophysics Data System (ADS)

    Lindsey, E. O.; Fialko, Y.

    2011-12-01

    We investigate the importance of fault geometry and crustal heterogeneity on estimates of slip rates and locking depths of the Southern San Andreas fault (SAF) and San Jacinto fault (SJF). Previous estimates of geodetic slip rates in the Salton Sea region based on dislocation models have generally inferred a higher slip rate on the SAF (21-26 mm/yr) compared to the SJF (12-19 mm/yr). The inferred geodetic slip rate on the SAF is higher than recent geologic estimates representing average slip rates on time scales of 10^4-10^6 years. We investigate to what extent the geodetically inferred slip rate might be biased by incorrect assumptions about the fault geometry and neglect of spatial variations in crustal rigidity. To address this issue, we use a forward model that incorporates heterogeneous elastic moduli computed from the SCEC CVM-H seismic tomography model of Southern California. In our inversions we allow for a non-vertical SAF and a "blind" segment of the SJF, the previously suggested southern continuation of the Clark fault. The models are compared to surface velocities derived from a combination of all available continuous and campaign GPS sites in the region, processed in a consistent North American fixed frame (NAFD), and InSAR data spanning 18 years (1992-2010). These data sources are strongly complementary: while InSAR provides higher spatial resolution in the near-fault region, we find that GPS sites located more than 10 locking depths from the fault are required to resolve the trade-off between locking depth and fault slip rate. The parameter space is examined using an efficient Monte Carlo algorithm which approximates the joint probability distribution for the model parameters and allows for a formal evaluation of uncertainties and trade-offs. We estimate slip rates of 15(+/-2) mm/yr for the Southern San Andreas fault and a total of 23(+/-3) mm/yr for the two closely spaced branches of the southern San Jacinto fault, in reasonable agreement with geologic estimates. The locking depths are estimated at 9(+/-3) km and 16(+/-3) km for the SAF and SJF, respectively. The incorporation of realistic elastic properties serves to increase the estimated locking depths on both faults by 2-3 km, and decreases the estimated slip rate on the San Andreas fault by several mm/yr in comparison to a homogeneous elastic model.

  13. 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

  14. 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.

  15. 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 ?m. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. 2014 Boso Slow Slip Event: the Source Slip Process based on Tilt and GNSS Measurements

    NASA Astrophysics Data System (ADS)

    Hirose, H.; Matsuzawa, T.; Kimura, T.; Kimura, H.

    2014-12-01

    Around the Boso Peninsula, Japan, slow slip events (SSEs) accompanying earthquake swarms recur with repeating intervals between two to seven years, associated with the subduction of the Philippine Sea Plate (PHS) from the Sagami trough beneath the Kanto metropolitan area. These SSEs share an almost identical source area for each episode, which is adjacent to the source area of the Kanto megathrust earthquakes. Because both of the SSEs and the earthquakes are slip events on the same PHS plate interface, understandings on factors that control the recurrence behavior of the SSEs provides important information not only for the nature of the SSEs itself, but also about the slip property on the plate interface. The latest event occurred in January 2014, i.e., it is the shortest interval of 27 months after the previous event in October 2011 (Ozawa, 2014) while the average recurrence interval is 61 months for over 30 years since 1983 (Hirose et al., 2012). Although the recurrence intervals could be modulated by stress changes caused by nearby large earthquakes, such as the 2011 Tohoku earthquake and its afterslip (Hirose et al., 2012), there is no such large earthquake or other phenomenon that can hasten the latest SSE, and thus other factors are required for the shortening of the interval. In order to clarify factors that control the recurrence intervals, we estimated the source slip processes for the recent SSEs whose crustal deformations have been observed with tiltmeters and GNSS. The 2007 and 2011 SSEs have similar size in seismic moment (Hirose et al., 2014), while the 2014 SSE has a smaller seismic moment than the two previous SSEs. The maximum stress drop for the 2014 SSE is estimated as about 1/2 of those for the 2007 and 2011 SSEs. Although we can not specify mechanisms that hastened the occurrence of the latest SSE, this might suggest that the strength of the source area might have reduced and the slip event occurred at a lower stress level.

  1. Estimating Fault Slip from the 1999 Hector Mine Earthquake Using ALSM

    NASA Astrophysics Data System (ADS)

    Borsa, A. A.; Hudnut, K. W.; Minster, J. B.

    2002-05-01

    The 1999 Hector Mine Earthquake generated visible surface faulting along almost 50km of sparsely vegetated, undeveloped terrain in California's Eastern Mojave Desert. Six months after the earthquake, the entire length of the Hector Mine fault zone was mapped by a scanning laser altimeter as part of a joint experiment between the U.S. Geological Survey, the Southern California Earthquake Center and the commercial firm, Aerotec LLC. This Airborne Laser Swath Mapping (ALSM) generated a digital elevation model (DEM) of a 150 meter-wide swath along the entire main rupture, with nominal horizontal postings of 40 cm and sub-decimeter vertical accuracy. As a first application of this data set, we are using the ALSM-derived DEM to estimate vertical and horizontal displacement along the Bullion Mountain section of the Hector Mine fault. Our algorithm uses the correlation of large numbers of points from both sides of the fault as the basis for slip determination. We take points from several-hundred-meter segments of rupture for each estimate and show the effect of varying the length of these segments. To correct for height effects due to ground slope which is usually neither parallel nor orthogonal to the fault trace, points on each side of the fault are projected into the fault plane using the fault-normal component of the local gradient. A slip vector is determined by inverting for the fault-plane displacement that minimizes the elevation difference between points projected from the two sides of the fault. We also show the effect of including an explicit matching of the topopgraphic gradient in the slip inversion, to complement the use of elevations alone. This extension would not be practical with standard ground-based techniques. Traditional field techniques estimate slip at distinct locations on the fault using individual terrain features. Our ALSM processing and interpretation yields a measure of average slip along entire segments of fault, spanning and including the discrete locations that are measured in the field. Since we have access to field measurements of slip for the Hector Mine earthquake, we make a direct comparison between those estimates and our own and provide possible explanations for differences between the two.

  2. The effect of sliding velocity on the mechanical response of an artificial joint in Topopah Spring Member tuff; Yucca Mountain Site Characterization Project

    SciTech Connect

    Olsson, W.A.

    1994-04-01

    A smooth artificial joint in Topopah Spring Member tuff was sheared at constant normal stress at velocities from 0 to 100 {mu}m/s to determine the velocity-dependence of shear strength. Two different initial conditions were used: (1) unprimed -- the joint had been shear stress-free since last application of normal stress, and before renewed shear loading; and (2) primed -- the joint had undergone a slip history after application of normal stress, but before the current shear loading. Observed steady-state rate effects were found to be about 3 times lager than for some other silicate rocks. These different initial conditions affected the character of the stress-slip curve immediately after the onset of slip. Priming the joint causes a peak in the stress-slip response followed by a transient decay to the steady-state stress, i.e., slip weakening. Slide-hold-slide tests exhibit time-dependent strengthening. When the joint was subjected to constant shear stress, no slip was observed; that is, joint creep did not occur. One set of rate data was collected from a surface submerged in tap water, the friction was higher for this surface, but the rate sensitivity was the same as that for surfaces tested in the air-dry condition.

  3. 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.

  4. Combined UAVSAR and GPS Estimates of Fault Slip for the M 6.0 South Napa Earthquake

    NASA Astrophysics Data System (ADS)

    Donnellan, A.; Parker, J. W.; Hawkins, B.; Hensley, S.; Jones, C. E.; Owen, S. E.; Moore, A. W.; Wang, J.; Pierce, M. E.; Rundle, J. B.

    2014-12-01

    Combined UAVSAR and GPS Estimates of Fault Slip for the M 6.0 South Napa Earthquake Andrea Donnellan, Jay Parker, Brian Hawkins, Scott Hensley, Cathleen Jones, Susan Owen, Angelyn Moore Jet Propulsion Laboratory, California Institute of Technology Marlon Pierce, Jun Wang Indiana University John Rundle University of California, Davis The South Napa to Santa Rosa area has been observed with NASA's UAVSAR since late 2009 as part of an experiment to monitor areas identified as having a high probability of an earthquake. The M 6.0 South Napa earthquake occurred on 24 August 2014. The area was flown 29 May 2014 preceeding the earthquake, and again on 29 August 2014, five days after the earthquake. The UAVSAR results show slip on a single fault at the south end of the rupture near the epicenter of the event. The rupture branches out into multiple faults further north near the Napa area. A combined inversion of rapid GPS results and the unwrapped UAVSAR interferogram indicate nearly pure strike slip motion. Using this assumption, the UAVSAR data show horizontal right-lateral slip across the fault of 19 cm at the south end of the rupture and increasing to 70 cm northward over a distance of 6.5 km. The joint inversion indicates slip of ~30 cm on a network of sub-parallel faults is concentrated in a zone about 17 km long. The lower depths of the faults are 5-8.5 km. The eastern two sub-parallel faults break the surface, while three faults to the west are buried at depths ranging from 2-6 km with deeper depths to the north and west. The geodetic moment release is equivalent to a M 6.1 event. Additional ruptures are observed in the interferogram, but the inversions suggest that they represent superficial slip that does not contribute to the overall moment release.

  5. 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.

  6. 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 24km. The crystalline basement in the study area is unique in its excellent rock and fault exposures forming a >50km 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 50m. 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.

  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. 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.

  11. 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.

  12. Joint Aspiration (Arthrocentesis)

    MedlinePLUS

    ... the joint. It is usually due to a bacterial infection in the joint. Joint aspiration helps to diagnose ... at the time of the test. If a bacterial infection such as septic arthritis is suspected, a culture ...

  13. 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 ...

  14. 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

  15. Oscillatory Magnetogasdynamic Slip Flow in a Microchannel

    NASA Astrophysics Data System (ADS)

    Agarwal, Ramesh

    2009-11-01

    The problem of pressure driven Magnetogasdynamic (MGD) slip flow with small rarefaction through a long micro-channel is considered. The flow is driven by steady or oscillatory pressure gradient. The study of MGD flows in microchannels is of great interest since they occur in magnetic thin films and other electromagnetic micro-scale devices. In obtaining the micro-fluidic solutions in the presence of a magnetic field, some additional physical, mathematical and numerical issues need to be considered. These issues deal with the scaling laws for micro-scale MHD flows and the relevant parameters such as Mach number, Reynolds number, Hartmann number, magnetic Reynolds number, and Knudsen number. For planar constant area micro-channel, it is possible to obtain the analytical solutions for both steady and oscillatory pressure driven flows. As physically expected, the higher value of the magnetic field (higher Hartmann number) flattens the velocity profile in the channel.

  16. Rover Slip Validation and Prediction Algorithm

    NASA Technical Reports Server (NTRS)

    Yen, Jeng

    2009-01-01

    A physical-based simulation has been developed for the Mars Exploration Rover (MER) mission that applies a slope-induced wheel-slippage to the rover location estimator. Using the digital elevation map from the stereo images, the computational method resolves the quasi-dynamic equations of motion that incorporate the actual wheel-terrain speed to estimate the gross velocity of the vehicle. Based on the empirical slippage measured by the Visual Odometry software of the rover, this algorithm computes two factors for the slip model by minimizing the distance of the predicted and actual vehicle location, and then uses the model to predict the next drives. This technique, which has been deployed to operate the MER rovers in the extended mission periods, can accurately predict the rover position and attitude, mitigating the risk and uncertainties in the path planning on high-slope areas.

  17. 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

  18. Slip Line Field Applied To Deep Drawing

    NASA Astrophysics Data System (ADS)

    Miguel, V.; Benet, J.; Coello, J.; Calatayud, A.; Martnez, A.

    2007-05-01

    Slip Line Field is a numerical method applied for modelling plane-strain processes. This method has been successfully checked properly for sheet drawing. Flange deformation in deep drawing is considered without change in thickness. A drawing mechanical test has been developed in order to reproduce the flange stresses state in sheet strips with the rolling direction selected. The fundamentals of this test, and some experimental results obtained from it, have been presented previously in different Congresses. In this work, an algorithm based on SLF has been implemented and theoretical results evaluated for different conditions. The algorithm have been applied to a mild DDQ steel and to a DDQ AISI 304 stainless steel. Theoretical and experimental results are compared. A good concordance in them has been found out under some conditions. One of the most important aspects is that it must not be considered tensile material properties but a modified behavior under multiaxial conditions.

  19. 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.

  20. 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.

  1. Rolling and slipping motion of Euler's disk.

    PubMed

    Caps, H; Dorbolo, S; Ponte, S; Croisier, H; Vandewalle, N

    2004-05-01

    We present an experimental study of the motion of a circular disk spun onto a table. With the help of a high speed video system, the temporal evolution of (i) the inclination angle alpha, (ii) the angular velocity omega, and (iii) the precession rate Omega are studied. The influence of the mass of the disk as well as the friction between the disk and the supporting surface are considered. Both inclination angle and angular velocity are observed to decrease according to a power law. We also show that the precession rate diverges as the motion stops. Measurements are performed very near the collapse as well as on long range times. Times to collapse have been also measured. Results are compared with previous theoretical and experimental works. The major source of energy dissipation is found to be the slipping of the disk on the plane. PMID:15244966

  2. 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 633 nm. A flow enhancement of 202 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

  3. 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.

  4. 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

  5. Partial slip in mesoscale contacts: dependence on contact size.

    PubMed

    Hanke, Sylvia; Petri, Judith; Johannsmann, Diethelm

    2013-09-01

    Using acoustic resonators, we have studied the occurrence and the magnitude of partial slip between glass spheres and polymer surfaces. The measurement relies on the shifts of resonance frequency and bandwidth, ?f and ??, induced by the contact as well as the dependence of ?f and ?? on the amplitude of oscillation. One often finds a decrease of ?f at elevated amplitudes, which goes back to partial slip (also "microslip"). Building on two different models of partial slip, we derive the frequency-amplitude relation from the force-displacement relation. In accordance with both models, the bandwidth is found to increase with amplitude in the partial slip regime. For the highest amplitudes and largest spheres investigated, one observes a decrease of bandwidth with amplitude, which is interpreted as a transition to gross slip. Deviating from both models of partial slip, ?f is sometimes found to be independent of amplitude in the low-amplitude range. Constant ?f implies linear force-displacement relations. The critical amplitude for the onset of partial slip depends on the contact radius, where partial slip is more pronounced for larger contacts. This finding can be explained by a smooth stress profile at the edge of the contact with no singularity. The stress at the edge might be lowered by nanoscale roughness, by capillary forces, or by the inability of the two surfaces to reestablish a sticking contact at the turning point of the oscillation. PMID:24125277

  6. 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,

  7. 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.

  8. 49 CFR 229.115 - Slip/slide alarms.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... remote control, the wheel slip/slide alarm of each locomotive shall be shown in the cab of the... road service, or continue in road service following a daily inspection, unless the wheel slip/slide protective device of whatever type (1) Is functioning for each powered axle under power; and (2)...

  9. 49 CFR 229.115 - Slip/slide alarms.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... remote control, the wheel slip/slide alarm of each locomotive shall be shown in the cab of the... road service, or continue in road service following a daily inspection, unless the wheel slip/slide protective device of whatever type (1) Is functioning for each powered axle under power; and (2)...

  10. SLIP: A Symmetric List Processing Language in PL-I.

    ERIC Educational Resources Information Center

    Leaf, William A.

    SLIP (Symmetric List Processing) is a list processing system designed to be added to a higher order language (PL-1 in this version) so that the user has available to him list processing powers. The primary value of such a system is its data handling power. Through SLIP, one can set up lists of data, scan those lists, alter them, and read or write

  11. 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,…

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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.

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

    PubMed

    Verberne, Berend A; Plmper, 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

  19. Superplastic nanofibrous slip zones control seismogenic fault friction

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  20. 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.

  1. 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.

  2. Lattice Boltzmann simulations of apparent slip in hydrophobic microchannels

    NASA Astrophysics Data System (ADS)

    Harting, J.; Kunert, C.; Herrmann, H. J.

    2006-07-01

    Various experiments have found a boundary slip in hydrophobic microchannel flows, but a consistent understanding of the results is still lacking. While Molecular Dynamics (MD) simulations cannot reach the low shear rates and large system sizes of the experiments, it is often impossible to resolve the needed details with macroscopic approaches. We model the interaction between hydrophobic channel walls and a fluid by means of a multi-phase lattice Boltzmann model. Our mesoscopic approach overcomes the limitations of MD simulations and can reach the small flow velocities of known experiments. We reproduce results from experiments at small Knudsen numbers and other simulations, namely an increase of slip with increasing liquid-solid interactions, the slip being independent of the flow velocity, and a decreasing slip with increasing bulk pressure. Within our model we develop a semi-analytic approximation of the dependence of the slip on the pressure.

  3. 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.

  4. 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 s) 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.

  5. 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.

  6. 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.

  7. 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

  8. 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 (Re? 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.

  9. 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 max and the maximum slip velocity u?max are obtained experimentally as: max= {2}/{u cu?max2}andu?max= {?? b}/{G}v where u c is the critical displacement, ??b 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 maxof the power spectral density of the slip acceleration increases with increasing normal stress; in particular, maxis found to be directly proportional to the normal stress ?n within the normal stress range less than 17 MPa as: max(kHz) = 4.0? n(MPa) ?n<17(MPa) maxincrease with an increase in u?max or max. All these results lead to the conclusion that max, u?max and max increase with increasing normal stress. This is consistent with a previous observation that ?b increases with increasing normal stress. The above empirical linear relation between max and ?n can be explained by a linear dependence of ??b on ?n. The size-scale dependence of physical parameters is discussed, and such size-scale dependent parameters as max 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.

  10. Repeated-Slip Training: An Emerging Paradigm for Prevention of Slip-Related Falls Among Older Adults

    PubMed Central

    Pai, YC; Bhatt, TS

    2009-01-01

    Falls frequently cause injury-related hospitalization or death among older adults. This article reviews a new conceptual framework on dynamic stability and weight support in reducing the risk for falls resulting from a forward slip, based on the principles of motor control and learning, in the context of adaptation and longer-term retention induced by repeated-slip training. Although an unexpected slip is severely destabilizing, a recovery step often is adequate for regaining stability, regardless of age. Consequently, poor weight support (quantified by reduction in hip height), rather than instability, is the major determinant of slip-related fall risk. Promisingly, a single session of repeated-slip training can enhance neuromechanical control of dynamic stability and weight support to prevent falls, which can be retained for several months or longer. These principles provide the theoretical basis for establishing task-specific adaptive training that facilitates the development of protective strategies to reduce falls among older adults. PMID:17712033

  11. 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.

  12. 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.

  13. 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.

  14. A range of fault slip styles on progressively misoriented planes during flexural-slip folding, Cape Fold Belt, South Africa

    NASA Astrophysics Data System (ADS)

    Fagereng, ke; Byrnes, Gregory

    2015-01-01

    Flexural slip folds are distinctive of mixed continuous-discontinuous deformation in the upper crust, as folding is accommodated by continuous bending of layers and localized, discontinuous slip along layer interfaces. The mechanism of localized, layer-parallel slip and the stress and fluid pressure conditions at which flexural slip occurs are therefore distinctive of shear localization during distributed deformation. In the Prince Albert Formation mudstone sequence of the Karoo Basin, the foreland basin to the Cape Fold Belt, folds are well developed and associated with incrementally developed bedding-parallel quartz veins with slickenfibers oriented perpendicular to fold hinge lines, locally cross-cutting axial planar cleavage, and showing hanging wall motion toward the fold hinge. Bedding-parallel slickenfiber-coated veins dip at angles from 18 to 83, implying that late increments of bedding-parallel shear occurred along unfavorably oriented planes. The local presence of tensile veins, in mutually cross-cutting relationship with bedding-parallel, slickenfiber-coated veins, indicate local fluid pressures in excess of the least compressive stress. Slickenfiber vein microstructures include a range of quartz morphologies, dominantly blocky to elongate-blocky, but in places euhedral to subhedral; the veins are commonly laminated, with layers of quartz separated by bedding-parallel slip surfaces characterized by a quartz-phyllosilicate cataclasite. Crack-seal bands imply incremental slickenfiber growth, in increments from tens of micrometers to a few millimeters, in some places, whereas other vein layers lack evidence for incremental growth and likely formed in single slip events. Single slip events, however, also involved quartz growth into open space, and are inferred to have formed by stick-slip faulting. Overall, therefore, flexural slip in this location involved bedding-parallel faulting, along progressively misoriented weak planes, with a range of slip increments.

  15. 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 .

  16. 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

  17. 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

  18. Methods for quantitatively determining fault slip using fault separation

    NASA Astrophysics Data System (ADS)

    Xu, S.-S.; Velasquillo-Martnez, L. G.; Grajales-Nishimura, J. M.; Murillo-Muetn, G.; Nieto-Samaniego, A. F.

    2007-10-01

    Fault slip and fault separation are generally not equal to each other, however, they are geometrically related. The fault slip ( S) is a vector with a magnitude, a direction, and a sense of the movement. In this paper, a series of approaches are introduced to estimate quantitatively the magnitude and direction of the fault slip using fault separations. For calculation, the known factors are the pitch of slip lineations ( ?), the pitch of a cutoff ( ?), the dip separation ( Smd) or the strike separation ( Smh) for one marker. The two main purposes of this work include: (1) to analyze the relationship between fault slip and fault separation when slickenside lineations of a fault are known; (2) to estimate the slip direction when the parameters Smd or Smh, and ? for two non-parallel markers at a place (e.g., a point) are known. We tested the approaches using an example from a mainly strike-slip fault in East Quantoxhead, United Kingdom, and another example from the Jordan Field, Ector County, Texas. Also, we estimated the relative errors of apparent heave of the normal faults from the Sierra de San Miguelito, central Mexico.

  19. 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

  20. 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

  1. 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

  2. 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.

  3. Geometry and lateral slip distribution along large thrust fault systems

    SciTech Connect

    Shaw, J.H.; Genovese, P.W.; Suppe, J. . Dept. of Geological and Geophysical Sciences)

    1992-01-01

    Quantitative relationships between fold and fault shapes allow detailed analyses of thrust fault geometries and slip histories. Fold limbs (kink bands) that grow by axial surface migration above bends in thrust faults record dip-slip motion. Folds imaged in high-resolution seismic reflection profiles record this total fault dip-slip and reflect causative thrust fault geometry. Growth (syntectonic) strata deposited during the active history of underlying thrusts develop limb widths equal to the amount of fault dip-slip since their deposition. Therefore, narrowing upward kink bands (growth triangles) form as sediments deposited earlier in the slip history record wider limb widths than do sediments deposited later. Ages of selected syntectonic strata (determined independently) in growth triangles allow estimates of long term fault-slip rates. Maps of axial surfaces that bound kink bands highlight changes in thrust fault geometry along strike and record lateral fault-slip distribution. In addition, end and offsets of kink bands in map view highlight fault terminations and lateral changes in thrust fault geometry. Detailed analyses of fold and fault geometries constrain balanced, three-dimensional structural models that show how large thrust faults develop and slip through time. These models and cross sections integrate G.P.S. measurements and seismicity from active thrust fault systems. Lateral variations in fold shape caused by changes in thrust fault geometry may form lateral closure along fold trends that trap hydrocarbons. Combined, fault slip rates and fault geometry yield estimates of the size and recurrence of potentially damaging earthquakes on blind thrust fault systems.

  4. 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.

  5. Finite fault modeling of oceanic strike-slip earthquakes

    NASA Astrophysics Data System (ADS)

    Aderhold, K.; Abercrombie, R. E.

    2014-12-01

    The depth extent of seismic rupture in oceanic lithosphere is thought to be limited by the 600 to 800C isotherm with the thermal structure generally characterized by a half-space cooling model. However, previous studies constraining this limit represent a limited number of individual faults and earthquakes and use a wide range of different methods. Observations of significantly deep slip at the 800C isotherm, supershear rupture velocities, and along-strike differences in seismic slip have been made for oceanic strike slip earthquakes (McGuire and Beroza, 2012; Yue et al., 2013; McGuire et al., 2012). To examine how seismic rupture is controlled, we look at a variety of earthquakes in different settings using the same method of finite fault modeling. We choose the largest and best recorded oceanic strike-slip earthquakes from tectonic settings of interplate transform, intraplate fracture zones, and strike-slip plate boundaries. These earthquakes are located in the Indian Ocean, near the South Sandwich Islands, on the edge of the Scotia Plate, off the coast of Alaska, and west of Australia, rupturing lithosphere with ages from 0 to 70 My. We first determine first motion and point source mechanisms from the first arriving P waves and later arriving pP, sP, and SH waves. Using the nodal planes of these mechanisms, we perform finite fault modeling at a range of constant rupture velocities and hypocenter depths. We determine which slip asperities are well-constrained by limiting the extent of the preferred model until the fit to the data is affected significantly. The rupture directivity, rupture speed, depth extent of slip, and along-strike distribution of slip is then compared between events to identify relationships to the tectonic setting, thermal structure inferred from lithospheric age, or other possible mechanisms for controlling slip. These strike-slip earthquakes also provide examples of rupture along a bimaterial fault plane, which have been shown to have a relationship between stress loading direction, rupture directivity, and rupture speed by previous studies. The results of this study will determine seismic slip distribution in the relatively simple structure of oceanic lithosphere, and provide a comparison for the more complex structure of continental strike-slip faults.

  6. 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.

  7. Evidence for Rapid Slip on Extensional Detachment Faults

    NASA Astrophysics Data System (ADS)

    Brady, R. J.

    2001-12-01

    Continental normal faults present significant seismic hazard within densely populated and rapidly-developing regions, yet the slip rates on such structures are generally poorly understood. Most work to date has focused on small, active fault scarps, which offset young sedimentary units, and typically show slip rates of 0-1 mm/yr. The few published studies of very large, old scarps or fault footwalls have suggested slip rates in the range of 3-8 mm/yr (i.e. John and Howard, 1995; Scott et al., 1998; Foster and John, 1999), but these have suffered from large errors. By using a low-closure-temperature thermochronometric system (single crystal (U-Th)/He in apatite), it has been established that a slip rate of 5.3 (+3.7/-1.6) mm/yr, persisting for a period of several millions of years during the mid-Miocene, occurred on the Buckskin-Rawhide detachment; preliminary data suggest that a similarly rapid slip rate also occurred on the nearby Whipple Mts. detachment. This calculated slip rate is very similar to, but more precise than, the rate calculated using apatite fission track ages from the Buckskin Mts. (6.6+/-5.9 mm/yr; Scott et al., 1998). Both the Buckskin-Rawhide detachment and the Whipple Mts. detachment lie within the Colorado River extensional corridor, along the California-Arizona border in the southwestern United States. Slip rates on both faults were determined by plotting (U-Th)/He in apatite cooling ages against distance in the fault slip direction. This approach assumes that each mineral cooling age records the time at which a given piece of rock moved upward through the intersection of a particular near-horizontal isotherm with the dipping fault plane. If that isotherm is stationary, this method allows a slip rate to be determined by recording the time at which each successive piece of rock on the fault plane moved past that same point. Because the (U-Th)/He in apatite method records cooling through a cool, shallow isotherm ( ~75 C), which should move relatively little during extension (c.f. Ketcham, 1996), approximating the isotherm as stationary during extension should result in an underestimate of the slip rate of less than 10%. Proof of such an alarmingly high slip rate raises questions regarding the potential seismic hazard posed by large-offset extensional faults, and the relationship between these rapidly-slipping, large-offset structures and the slower, smaller-offset faults that are more commonly observed as active structures.

  8. Simulations of slip flow on nanobubble-laden surfaces

    NASA Astrophysics Data System (ADS)

    Hyvluoma, J.; Kunert, C.; Harting, J.

    2011-05-01

    On microstructured hydrophobic surfaces, geometrical patterns may lead to the appearance of a superhydrophobic state, where gas bubbles at the surface can have a strong impact on the fluid flow along such surfaces. In particular, they can strongly influence a detected slip at the surface. We present two-phase lattice Boltzmann simulations of a flow over structured surfaces with attached gas bubbles and demonstrate how the detected slip depends on the pattern geometry, the bulk pressure, or the shear rate. Since a large slip leads to reduced friction, our results give assistance in the optimization of microchannel flows for large throughput.

  9. 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.

  10. Tectonic analysis of fault slip data sets

    NASA Astrophysics Data System (ADS)

    Angelier, Jacques

    1984-07-01

    Using data that include the direction and the sense of motion on individual fault surfaces determined by slickenside lineations, it is possible to reconstruct reduced stress tensors that correspond to the orientation of stress axes and to the ratio ? = (?2-?3)/(?1-?3) between principal stress values (?1??2??3, compression being positive). No assumption is made concerning the orientation of fault planes relative to stress axes, so that reactived faults are taken into account as well as newly created ones. Qualitative and quantitative methods for analysis of fault slip data were developed during the last 10 years. The practical limitation of the methods and the necessity for critical field observations are emphasized. These methods can be applied to focal mechanisms of earthquakes. A more complex analysis of heterogeneous data sets, involving an iterative separation of different stress systems, is also discussed. This analysis enables one to distinguish successive faulting events. Careful qualitative study in the field is in all cases essential.

  11. 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.

  12. 46 CFR 154.524 - Piping joints: Welded and screwed couplings.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 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...

  13. 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.

  14. 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

  15. 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.

  16. Slip ring experience in long duration space applications

    NASA Technical Reports Server (NTRS)

    Phinney, Damon D.

    1986-01-01

    Ball Aerospace experience with slip rings in space extends back to 1962. Over 40 multi-ring assemblies have been flown and continuous operating lifetimes greater than 8 years at up to 60 rpm have been demonstrated. Slip rings provide multi-channel transfer of electrical power and signals in assemblies that are small in size and weight, and low in cost. By use of multiple brushes and sufficient copper within the assembly, power transfer efficiency better than 99.95 percent for high voltage circuits can be achieved. A low slip ring failure rate based on actual space operation totalling billions of ring revolutions has been established. Well qualified suppliers who have been making slip rings for space use for over 25 years are available. It is hoped that the suspected problem in SEASAT will not be allowed to prejudice space system designer against these very useful mechanisms.

  17. 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

  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. 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.

  20. 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

  1. 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

  2. Relaxation in crystal plasticity with three active slip systems

    NASA Astrophysics Data System (ADS)

    Conti, Sergio; Dolzmann, Georg

    2016-01-01

    We study a variational model for finite crystal plasticity in the limit of rigid elasticity. We focus on the case of three distinct slip systems whose slip directions lie in one plane and are rotated by 120 with respect to each other, with linear self-hardening and infinite latent hardening, in the sense that each material point has to deform in single slip. Under these conditions, plastic deformation is accompanied by the formation of fine-scale structures, in which activity along the different slip systems localizes in different areas. The quasiconvex envelope of the energy density, which describes the macroscopic material behavior, is determined in a regime from small up to intermediate strains, and upper and lower bounds are provided for large strains. Finally sufficient conditions are given under which the lamination convex envelope of an extended-valued energy density is an upper bound for its quasiconvex envelope.

  3. 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

  4. Comparison of two shallow episodic tremor and slip events within the coseismic slip area of the 2011 Tohoku-Oki earthquake

    NASA Astrophysics Data System (ADS)

    Ito, Y.; Hino, R.; Ikari, M.

    2013-12-01

    We describe two shallow (<20 km depth) episodic tremor and slip (ETS) events that occurred prior to the 2011 Tohoku-Oki earthquake and investigate their roles in this megathrust earthquake. These transient slow slip events were accompanied by long-duration seismic signals and were observed by ocean-bottom seismic and pressure sensors near the Japan Trench. The first ETS event occurred over a week in November 2008 and included a slow slip event that exhibited an equivalent moment magnitude of 6.8. Shortly prior to termination of the slow slip, an M6 earthquake was induced by the slow slip event at the down-dip of the slow slip rupture area. The second ETS event was observed from the end of January 2011 until just before the 2011 Tohoku-Oki earthquake and exhibited an equivalent moment magnitude of 7.0. This slow slip event induced the largest foreshock (M7.3 on March 9) and the March 11 mainshock of the 2011 Tohoku-Oki earthquake. The 2008 and 2011 slow slip events were different with respect to whether they continued or ceased to slip before inducing large interplate earthquakes at the down-dip end. In particular, the 2008 slow slip event induced M6 interplate earthquakes only after cessation of slipping, whereas the 2011 slow slip event induced the M7 interplate earthquake before slipping ceased. In fact, the 2011 slow slip event continued until at least March 9. This indicates that a slow slip event with a slip rate greater than 0.1 ?m/s occurred along the plate interface from the start of February until March 9 and suggests that the 2011 slow slip event triggered the largest foreshock on March 9, 2011. The observed slow slip events may have played a key role in inducing the huge coseismic slip near the trench. Here, we suggest a possible scenario for the occurrence of this slip. First, a slow slip event commenced approximately 40-70 km from the trench at a depth of approximately 10-15 km and continued until the start of the rupture of the 2011 Tohoku-Oki earthquake, triggering the largest (M7.3) foreshock. This foreshock accompanied the post-seismic slip event that occurred within the coseismic slip region. Moreover, the slip rate of the 2011 slow slip event may have increased owing to the rapid post-seismic slip of the largest foreshock. Then, a large positive velocity step was emitted from the hypocenter of the 2011 Tohoku-Oki earthquake and propagated to the slow slip fault. In terms of its frictional behavior, this velocity step was conditionally stable at low slip rates and exhibited strong velocity weakening at high slip rates. Finally, clear velocity-weakening behavior coincided with the arrival of the positive velocity step during propagation of the nearby large coseismic rupture into the slow slip source area. Our recent experimental studies of rock mechanics also demonstrated strong slip weakening in response to a velocity step, which was in turn associated with the dislocation velocity resulting from the transition from a slow slip event to coseismic slip. This suggests that preexisting slow slip events can control coseismic behavior, particularly if the associated coseismic rupture propagates during the occurrence of the slow slip.

  5. 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.

  6. 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.

  7. 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 50C. 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 ?m 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 ?m 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.

  8. 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.

  9. Nucleation and arrest of dynamic slip on a pressurized fault

    NASA Astrophysics Data System (ADS)

    Garagash, Dmitry I.; Germanovich, Leonid N.

    2012-10-01

    Elevated pore pressure can lead to reactivation of slip on pre-existing fractures and faults when the static Coulomb failure is reached locally. As the pressurized region spreads diffusively, slip can accumulate quasi-statically (paced by the pore fluid diffusion) or dynamically. In this work, we consider a prestressed fault with a locally peaked, diffusively spreading pore pressure field to study (1) conditions leading to the escalation of slip and nucleation of dynamic rupture and (2) rupture run-out distance before it is arrested. Nucleation appears in this model when the fault friction decreases from its peak value with slip, while arrest of dynamic propagation is imminent on aseismic faults (i.e., such that prestress?b is less than the residual fault strength ?rat ambient conditions). When fluid overpressure is a small-to-moderate fraction of the ambient value of normal effective stress (and prestress is large enough for fault slip to be activated by overpressure), dynamic rupture always nucleates, and the nucleation length increases with decreasing prestress practically independently of the overpressure value. Transition from the ultimately unstable (?b > ?r) to the ultimately stable (?b < ?r) fault loading is marked by a strong increase of the nucleation length (?1/(?b - ?r)2) as ?b approaches ?r from above. For aseismic faults (?b < ?r), no dynamic rupture is nucleated at large fluid overpressures for all but the smallest values of prestress. The largest run-out distances of dynamic slip on aseismic faults correspond to overpressure/prestress just sufficient for slip activation. In such cases, the dynamically accumulated slip can lead to enhanced, dynamic fault weakening, resulting in a sustained dynamic rupture and generating a large earthquake. This is consistent with field observations when the largest injection-induced seismicity occurred after fluid injection ended.

  10. 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.

  11. 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.

  12. 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.

  13. Spatiotemporal slip distributions of three long-term slow slip events beneath the Bungo Channel, southwest Japan, inferred from inversion analyses of GPS data

    NASA Astrophysics Data System (ADS)

    Yoshioka, Shoichi; Matsuoka, Yoshiko; Ide, Satoshi

    2015-06-01

    We estimated spatiotemporal slip distributions from three long-term slow slip events (L-SSEs) that occurred beneath the Bungo Channel at the convergent plate boundary between the subducting oceanic Philippine Sea plate and the continental Amurian plate in southwest Japan between 1997 and 1998, 2002 and 2004 and 2009 and 2011. For this purpose, we employed an inversion method using a Bayesian Information Criterion (ABIC), which included the following three prior constraints: the spatial slip distribution was smooth to some extent, slip directions were mostly oriented in the direction of plate convergence and the temporal change in slip was smooth to some extent. Our results revealed that the three L-SSEs had a common feature: slipped regions expanded southwestward at accelerating slip velocities. We also found that major slipped regions migrated southwestward by approximately 50-100 km yr-1. In contrast, southwestward and northeastward migration of the slipped regions, whose direction differed from event to event, was also identified before or after the periods when the slip velocities were at their greatest. Comparing the obtained spatiotemporal slip distributions of the three L-SSEs with slip-deficit rate distributions obtained in our previous study, we investigated the accumulation process of the slip deficit caused by slip-deficit rate distributions and the release processes of the slip deficit caused by the obtained spatiotemporal slip distributions of the three L-SSEs. At the western plate interface of the Bungo Channel, as the slip-deficit rate was small and the amounts of slips associated with the three L-SSEs were large, most of the accumulated slip deficit was estimated to have been released. In contrast, at the eastern plate interface, as the slip-deficit rate was large and the amounts of slips associated with the three L-SSEs were small, the slip deficit was estimated to have accumulated effectively. These results suggest that the slipped regions of the three L-SSEs and the strongly coupled region are not spatially complementary; the accumulated slip deficit showed spatial variation even at approximately the same depth range along the arc.

  14. Strike-slip sedimentation: Dead Sea basin

    SciTech Connect

    Manspeizer, W.

    1986-05-01

    The Dead Sea rift extends for 1000 km along a transform plate boundary that has had left-lateral displacement of 150 km since the Miocene. The rift consists of a series of en-echelon, left-stepping (looking north), north-striking, strike-slip faults that are joined by a series of grabens (e.g., the Dead Sea basin). This basin developed as an asymmetric rhomb-shaped graben with nearly vertical, north-striking normal border faults (east and west margins), north-northeast-dipping listric normal faults (south margin), and a south-facing inclined basement (north margin). Displacement along the transform produced three basins, whose depocenters migrated north where they received Miocene fluvial clastics, Pliocene marine evaporites, and Pleistocene-Holocene lacustrine sediments. Graben filling today is governed largely by tectonism, which modifies rift climates and morphology. As warm moist air from the Mediterranean Sea rises over the rift shoulders, it cools adiabatically, yielding up to 900 mm of rain water for high discharge, ephemeral streams that prograde vast prisms of coalescing shallow water fan deltas along the western border fault. The eastern basin margin, by contrast, is dominated by an active transform boundary, a narrow shelf, and a spectacular deep (750 m below MSL) that receives deep water clastics. Whereas the northern margin of the basin receives fine-grained clastics from the prograding delta of the Jordan River (a perennial stream, whose drainage basin lies in a humid terrane far to the north), the southern margin is dominated by evaporites that are precipitated in shallow water basins (upon adiabatic warming of descending air).

  15. 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.

  16. 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.

  17. Peeling-angle dependence of the stick-slip instability during adhesive tape peeling.

    PubMed

    Dalbe, Marie-Julie; Santucci, Stphane; Vanel, Loc; Cortet, Pierre-Philippe

    2014-12-28

    The influence of peeling angle on the dynamics observed during the stick-slip peeling of an adhesive tape has been investigated. This study relies on a new experimental setup for peeling at a constant driving velocity while keeping constant the peeling angle and peeled tape length. The thresholds of the instability are shown to be associated with a subcritical bifurcation and bistability of the system. The velocity onset of the instability is moreover revealed to strongly depend on the peeling angle. This could be the consequence of peeling angle dependance of either the fracture energy of the adhesive-substrate joint or the effective stiffness at play between the peeling front and the point at which the peeling is enforced. The shape of the peeling front velocity fluctuations is finally shown to progressively change from typical stick-slip relaxation oscillations to nearly sinusoidal oscillations as the peeling angle is increased. We suggest that this transition might be controlled by inertial effects possibly associated with the propagation of the peeling force fluctuations through elongation waves in the peeled tape. PMID:25363615

  18. Intersegmental coordination elicited by unexpected multidirectional slipping-like perturbations resembles that adopted during steady locomotion.

    PubMed

    Aprigliano, Federica; Martelli, Dario; Micera, Silvestro; Monaco, Vito

    2016-02-01

    This study aimed at testing the hypothesis that reactive biomechanical responses elicited by unexpected slipping-like perturbations delivered during steady walking are characterized by an intersegmental coordination strategy resembling that adopted during unperturbed walking. Fifteen healthy subjects were asked to manage multidirectional slipping-like perturbations delivered while they walked steadily. The planar covariation law of elevation angles related to lower limb segments was the main observed variable related to unperturbed and perturbed strides. Principal component analysis was used to verify whether elevation angles covaried, both before and after the onset of the perturbation, and, if so, the orientation of the related planes of covariation was compared. Results revealed that the planar covariation law of the unperturbed limb after onset of the perturbation was systematically similar to that seen during steady walking. This occurred despite differences in range of motion and intersubject variability of both elevation and joint angles. The analysis strongly corroborates the hypothesis that the planar covariation law emerges from the interaction between spinal neural networks and limb mechanical oscillators. In particular, fast and stereotyped reactive strategies may result from the interaction among activities of downstream neural networks encrypting well-trained motor schemes, such as those related to walking, limb dynamics, and sensory motor information gathered during the perturbation. In addition, our results allowed us to speculate that rehabilitative treatment based on unexpected perturbations and relying on the plasticity of the central nervous system may also be effective in eliciting unimpaired intralimb coordination in neurological patients. PMID:26561598

  19. CYCLIC MOTION ENCODING FOR ENHANCED MR VISUALIZATION OF SLIP INTERFACES

    PubMed Central

    Mariappan, Yogesh K; Glaser, Kevin J; Manduca, Armando; Ehman, Richard L

    2010-01-01

    Purpose To develop and test an MRI-based method for assessing the mechanical shear connectivity across tissue interfaces with phantom experiments and in vivo feasibility studies. Materials and Methods External vibrations were applied to phantoms and tissue and the differential motion on either side of interfaces within the media was mapped onto the phase of the MR images using cyclic motion encoding gradients. The phase variations within the voxels of functional slip interfaces reduced the net magnitude signal in those regions, thus enhancing their visualization. A simple two-compartment model was developed to relate this signal loss to the intravoxel phase variations. In vivo studies of the abdomen and forearm were performed to visualize slip interfaces in healthy volunteers. Results The phantom experiments demonstrated that the proposed technique can assess the functionality of shear slip interfaces and they provided experimental validation for the theoretical model developed. Studies of the abdomen showed that the slip interface between the small bowel and the peritoneal wall can be visualized. In the forearm, this technique was able to depict the slip interfaces between the functional compartments of the extrinsic forearm muscles. Conclusion Functional shear slip interfaces can be visualized sensitively using cyclic motion encoding of externally applied tissue vibrations. PMID:19787735

  20. 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

  1. 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 ? = ?hy/?th and the ratio of pore pressure generated to temperature rise buffered by the reaction Pr/Er.

  2. Biomechanical response to ladder slipping events: Effects of hand placement.

    PubMed

    Schnorenberg, Alyssa J; Campbell-Kyureghyan, Naira H; Beschorner, Kurt E

    2015-11-01

    Ladder falling accidents are a significant, growing and severe occupational hazard. The factors that contribute to falls from ladders and specifically those that influence the motor response from ladder falls are not well understood. The aims of this research were to determine the effects of hand placement (rung versus rail) on muscle activation onset and peak activity timing in response to slipping on a ladder and to sequence the timing of events following slip initiation. Fifteen unexpected slips from 11 experienced ladder climbers were induced with a freely spinning rung under the foot, while subjects were randomly assigned to a rung versus rail hand grasping strategy. EMG onset time and peak activity time from five bilateral muscles (semitendinosis, vastus lateralis, triceps, biceps and anterior deltoid) were analyzed. Results indicated that significantly slower muscle activation onset and peak response times occurred during rail hand placement, suggesting that grasping ladder rungs may be preferable for improving the speed of the motor response. The triceps muscle activated and reached peak activity earlier in the slip indicating that subjects may initially extend their arms prior to generating hand forces. The study also revealed that slips tended to occur around the time that a foot and hand were in motion and there were just two points of contact (one hand and the slipping foot). PMID:26431752

  3. 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.

  4. 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.

  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. Slip zone structure and processes in seismogenic carbonate faults

    NASA Astrophysics Data System (ADS)

    Bullock, R. J.; De Paola, N.

    2011-12-01

    High velocity rotary shear experiments performed at seismic slip velocities (>1 m/s) have shown that experimental faults are weak; with increasing displacement, friction coefficient values decrease from Byerlee's values (? = 0.6-0.85) to values of ~0.1. In carbonate rocks, experimental studies have shown that fault lubrication is due to the operation of multiple dynamic weakening mechanisms (e.g., flash heating, thermal pressurization, nanoparticle lubrication), which are thermally activated due to the frictional heat generated along localized slip surfaces during rapid slip. This study has set out to investigate whether evidence for the operation of these weakening mechanisms can be found in naturally occurring carbonate fault zones. Field studies were carried out on the active Gubbio fault zone (1984, Mw = 5.6) in the northern Apennines of Italy. Jurassic-Oligocene carbonates in the footwall are heavily deformed within a fault core of ~15 m thickness, which contains a number of very well exposed, highly localized principal slip surfaces (PSSs). Fault rocks are predominantly breccias and foliated cataclasites. Microstructural analyses of the PSSs reveal that slip is localized within very narrow principal slip zones (PSZs), ranging from 10-85 ?m in thickness, with sub-millimetre scale asperities. PSZs are composed of very fine-grained, orange-brown ultracataclasite gouge containing a high proportion of nano-sized particles. The ultracataclasite commonly displays a foliated texture and sub-micron scale zones of extreme shear localization. A broader slip zone, up to 1.5 mm wide and containing multiple slip surfaces, is associated with the most evolved PSSs; it is located on the opposite side of the PSS to the PSZ. Here, the host rock material is heavily fractured, abraded and altered, sometimes with an ultracataclasite matrix. The surrounding wall rock often appears to have a porous texture, and calcite crystals within the slip zone have altered rims with lobate textures, both of which may be indicative of thermally activated chemical reactions. Occasionally, mantled clasts are observed; these consist of a central, sub-rounded monomineralic clast of calcite, or a polymineralic clast of both calcite and clay particles, enclosed by a cortex of ultracataclasite. These are features which are thought to be a product of thermal pressurization processes operating in the slip zone. These microstructures are compared to those in experimentally deformed dolomite gouges, and the slip zone features are found to be strikingly similar. It is clear that as slip accumulates along PSSs, well-developed PSZs are formed with well-defined foliations and R- and Y-shears, indicating progressive localization of deformation. The similarities between the two sets of samples implies that the dynamic weakening mechanisms known to occur in experimental carbonate slip zones are indeed likely to be in operation in their naturally occurring counterparts. Specifically, slip localization in the fault core may be associated with frictional heating; slip zone roughness may be associated with flash heating; mantled clasts may be attributed to thermal pressurization; and nanoparticles may be associated with nanoparticle lubrication.

  7. 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.

  8. Cam deformity and hip degeneration are common after fixation of a slipped capital femoral epiphysis

    PubMed Central

    Klit, Jakob; Gosvig, Kasper; Magnussen, Erland; Gelineck, John; Kallemose, Thomas; Sballe, Kjeld; Troelsen, Anders

    2014-01-01

    Background and purpose Slipped capital femoral epiphysis is thought to result in cam deformity and femoroacetabular impingement. We examined: (1) cam-type deformity, (2) labral degeneration, chondrolabral damage, and osteoarthritic development, and (3) the clinical and patient-reported outcome after fixation of slipped capital femoral epiphysis (SCFE). Methods We identified 28 patients who were treated with fixation of SCFE from 1991 to 1998. 17 patients with 24 affected hips were willing to participate and were evaluated 1017 years postoperatively. Median age at surgery was 12 (1014) years. Clinical examination, WOMAC, SF-36 measuring physical and mental function, a structured interview, radiography, and MRI examination were conducted at follow-up. Results Median preoperative Southwick angle was 22o (IQR: 1227). Follow-up radiographs showed cam deformity in 14 of the 24 affected hips and a Tnnis grade > 1 in 1 affected hip. MRI showed pathological alpha angles in 15 affected hips, labral degeneration in 13, and chondrolabral damage in 4. Median SF-36 physical score was 54 (IQR: 4956) and median mental score was 56 (IQR: 5458). These scores were comparable to those of a Danish population-based cohort of similar age and sex distribution. Median WOMAC score was 100 (IQR: 84100). Interpretation In 17 patients (24 affected hips), we found signs of cam deformity in 18 hips and early stages of joint degeneration in 10 hips. Our observations support the emerging consensus that SCFE is a precursor of cam deformity, FAI, and joint degeneration. Neither clinical examination nor SF-36 or WOMAC scores indicated physical compromise. PMID:25175666

  9. 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.

  10. The onset and blocking of slip in nickel aluminide[001

    NASA Astrophysics Data System (ADS)

    Yang, Nan

    The onset of slip in an initially dislocation-free crystal is a fundamental process that underlies several elemental mechanical properties of crystalline materials. However, the onset of slip and the associated dislocation formation have not been studied satisfactorily or understood completely. The research of this fundamental process should impact the understanding of a number of phenomena that involve dislocations, particularly the brittle-to-ductile transition (BDT), interfacial relaxation, martensitic transformations, and the onset of plasticity in metal whiskers, low dislocation density semiconductor single crystals, and in nano-indentation tests. Using anisothermal creep test method, the onset of slip is studied in [001] NiAl single crystals that are effectively free of mobile dislocations. Under a constant stress and with a steadily increasing temperature, the onset of slip in [001] NiAl takes place abruptly at a well-defined initiation temperature. The slip vector is identified to be <110> by slip line and TEM observations. The initiation temperature decreases approximately linearly with stress, and increases approximately exponentially with the heating rate at high and low heating rates. There is an intermediate heating rate range in which the onset temperature is independent of the heating rate. The existence of a rate-independent onset temperature cannot be explained by the traditional theories of dislocation formation, but consistent with a cooperative process in dislocation formation. TEM observations show that the <110> slip is blocked by dislocation locking along both of the two <111> directions in the {110} glide plane. The locking is explained by the non-planar splitting of the screw component along the three-fold line directions. HRTEM observations of the locked <110> dislocations end-on show a compact core and rule out climb decomposition as the cause for the locking. The blocking of <110> slip by dislocation locking along two line directions is in contrast to <111> dislocations that are locked only along the screw orientations, and to <100> dislocations that are not locked at all. This explains why <110> slip is more difficult than <111> and <100> slips and the general absence of <110> dislocations in NiAl crystals. An intuitive explanation for the planar core of <100> dislocations is also given.

  11. Effects of perturbation-based slip training using a virtual reality environment on slip-induced falls.

    PubMed

    Parijat, Prakriti; Lockhart, Thurmon E; Liu, Jian

    2015-04-01

    The purpose of the current study was to design and evaluate the effectiveness of virtual reality training in improving recovery reactions and reducing fall frequency in older adults. Twenty-four older adults were recruited and randomly assigned to two groups (virtual reality training and control). Both groups underwent three sessions including baseline slip, training and transfer of training on slippery surface. Both groups experienced two slips, one during baseline and the other during the transfer of training trial. The training group underwent 12 simulated slips using a visual perturbation induced by tilting a virtual reality scene while walking on the treadmill and the control group performed normal walking during the training session. Kinematic and kinetic data were collected during all the sessions. Results demonstrated a reduced incidence of falls in the training group during the transfer of training trial as compared to the control group. The training group was able to transfer reactive control strategies learned during training to the second slip trial. The reactive adjustments included reduced slip distance. Additionally, gait parameters reflective of gait instability (stride length, step width, variability in stride velocity) reduced after walking in the VR environment for 15-20 min. The results indicated a beneficial effect of the virtual reality training in reducing slip severity and recovery kinematics in healthy older adults. PMID:25245221

  12. Late Pleistocene, Holocene, and decadal constancy of slip-rate of the Doruneh strike-slip fault, Iran.

    NASA Astrophysics Data System (ADS)

    Walker, R. T.; Fattahi, M.; Mousavi, Z.; Pathier, E.; Sloan, R. A.; Talebian, M.; Thomas, A. L.; Walpersdorf, A.

    2014-12-01

    The Doruneh left-lateral strike-slip fault of NE Iran has a prominent expression in the landscape, showing that the fault is active in the late Quaternary. Existing estimates of its slip-rate vary, however, which has led to suggestions that it may exhibit temporal changes in activity. Using high-resolution optical satellite imagery we make reconstructions of displacement across four alluvial fans that cross the Doruneh fault, and determine the ages of these fans using luminescence dating, combined with U-series dating of pedogenic carbonates in one case. The four fans, which vary in age from 10-100 kyr, yield estimates of slip rate of ~2-3 mm/yr. We compare the average slip-rate measurements to the rate of accumulation of strain across the Doruneh fault using GPS and InSAR measurements, and find that the slip-rate is likely to have remained constant - within the uncertainty of our measurements - over the last ~100 ka. The slip-rate that we measure is consistent with the E-W left-lateral Doruneh fault accommodating N-S right-lateral faulting by 'bookshelf' faulting, with clockwise rotation about a vertical axis, in a similar manner to the Eastern California Shear Zone.

  13. Joint Aspiration (Arthrocentesis)

    MedlinePLUS

    ... arthritis, or JRA), systemic lupus erythematosus (SLE), and Lyme disease. Joint aspiration is diagnostic but it also can ... Parents MORE ON THIS TOPIC Evaluate Your Child's Lyme Disease Risk Living With Lupus Bones, Muscles, and Joints ...

  14. 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 ...

  15. 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.

  16. 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 ...

  17. 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.

  18. 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…

  19. Nucleation and triggering of earthquake slip: effect of periodic stresses

    USGS Publications Warehouse

    Dieterich, J.H.

    1987-01-01

    Results of stability analyses for spring and slider systems, with state variable constitutive properties, are applied to slip on embedded fault patches. Unstable slip may nucleate only if the slipping patch exceeds some minimum size. Subsequent to the onset of instability the earthquake slip may propagate well beyond the patch. It is proposed that the seismicity of a volume of the earth's crust is determined by the distribution of initial conditions on the population of fault patches that nucleate earthquake slip, and the loading history acting upon the volume. Patches with constitutive properties inferred from laboratory experiments are characterized by an interval of self-driven accelerating slip prior to instability, if initial stress exceeds a minimum threshold. This delayed instability of the patches provides an explanation for the occurrence of aftershocks and foreshocks including decay of earthquake rates by time-1. A population of patches subjected to loading with a periodic component results in periodic variation of the rate of occurrence of instabilities. The change of the rate of seismicity for a sinusoidal load is proportional to the amplitude of the periodic stress component and inversely proportional to both the normal stress acting on the fault patches and the constitutive parameter, A1, that controls the direct velocity dependence of fault slip. Values of A1 representative of laboratory experiments indicate that in a homogeneous crust, correlation of earthquake rates with earth tides should not be detectable at normal stresses in excess of about 8 MPa. Correlation of earthquakes with tides at higher normal stresses can be explained if there exist inhomogeneities that locally amplify the magnitude of the tidal stresses. Such amplification might occur near magma chambers or other soft inclusions in the crust and possibly near the ends of creeping fault segments if the creep or afterslip rates vary in response to tides. Observations of seismicity rate variations associated with seasonal fluctuations of reservoir levels appear to be consistent with the model. ?? 1987.

  20. 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

  1. 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.

  2. A comparison of slip rate, recurrence interval, and slip per event on several well-characterized faults (Invited)

    NASA Astrophysics Data System (ADS)

    Weldon, R. J.; Lippoldt, R. C.; Scharer, K.; Streig, A. R.; Langridge, R. M.; Madugo, C. M.; Biasi, G. P.; Dawson, T. E.

    2013-12-01

    Rapid growth in the application of LiDAR and other modern geodetic techniques has led to an explosion in the number of micro-geomorphic offsets along faults that can be interpreted as displacement in one or several earthquakes. As a result of this new data there are an increasing number of places along faults for which data are available for the slip rate (based on the dated offset of a feature that is old enough to average out the seismic cycle), recurrence interval (based on a representative number of dated paleo-earthquakes), and slip per event (based on an adequate sample of micro-geomorphic or 3D-excavated offsets). Because these three datasets are largely independent, but related by accumulation and release of strain across the fault, comparing them can provide insight into how faults balance size and frequency of earthquakes. We discuss several examples of faults with closely co-located slip rate, recurrence interval, and slip per event data, including the Ana River fault, a small normal fault in Central Oregon, and portions of the San Andreas fault, the principal plate boundary fault in California. The Ana River fault offsets more than 11 Pleistocene shorelines different amounts that we have measured using a combination of LiDAR, ground-based surveying, and a DEM generated from a USGS topographic map with 5 foot contours. The ages of ~10 paleo-earthquakes are determined from trenches and other exposures into deep-water lacustrine deposits that contain ~50 dated volcanic ashes. The long-term slip rate, 0.05 mm/yr, is known from the total offset of dated late Pliocene basalts. We also use new data from the Santa Cruz segment of the northern San Andreas fault (NSAF) and the southern San Andreas fault (SSAF: Parkfield to Bombay Beach). On the NSAF, earthquakes in 1838, 1890, and 1906 have a total slip of 4 - 6 m while the slip rate (17 mm/yr) suggests it would take 2 - 3 centuries to accumulate this much strain. Data for the SSAF, which have recently been compiled for UCERF-3, include 12 sites with recurrence intervals, hundreds of micro-geomorphic offsets, including at least 7 places with closely-spaced progressively larger offsets that allow one to estimate the average slip per event, and slip rate estimates that vary from about 34 to 12 mm/yr, decreasing from Parkfield to San Gorgonio Pass and then increasing to the southern end of the SSAF. In general the 3 types of data are reasonably consistent (i.e. slip rate (mm/yr) = slip per event (mm) X recurrence interval (1/yr)). Recurrence intervals seem to be more variable than displacements, although displacement variability may be biased by difficulty resolving small offsets with geomorphic markers. Assuming slip rate is constant through time, in places where (or periods of time when) there are inconsistencies between the three parameters it appears to be due to the intervals between earthquakes varying more than displacements, i.e. short intervals are not associated with small enough displacements and long intervals do not yield unusually large displacements. Similarly, as the SSAF changes slip rate along strike the recurrence interval varies more than the size of slip events.

  3. Energy Partitioning during Frictional Sliding at Coseismic Slip Rates

    NASA Astrophysics Data System (ADS)

    Hirose, T.; Mizoguchi, K.

    2008-12-01

    Determination of the energy partitioning during an earthquake is key to understanding the physics of earthquakes (e.g., Kanamori and Rivera, 2006). Observations made on natural faults that have experienced earthquakes suggest that part of the energy dissipates into a volume of rock surrounding the fault though grain crushing processes, forming fault gouge (e.g., Wilson et al., 2005). Thus we performed high-velocity wear experiments using a rotary-shear apparatus, in order to estimate the partitioning of the frictional work into heat and surface energy during frictional sliding at nearly coseismic slip rates. In particular, we attempted to test whether the ratio of the energy partitioning varies as a function of slip rate. The ratio of dissipated energy as heat to the total frictional work was estimated from the difference between measured temperature around the sliding surfaces and calculated temperature by 2D-FEM on the assumption that all frictional work converts into heat. The surface energy was estimated based on the particle size distribution of the wear materials, which was determined by FE-SEM image analysis. The particles size ranged between 0.03 and 10 ?m in average diameter. In the experiments, hollow cylindrical specimens of gabbro were slid at slip rates of 0.004 to 0.3 m/s and normal stresses of 0.2 to 5.6 MPa under unconfined and dry conditions. Rock powder (gouge) was continuously produced by abrasive wear of initially bare fault surfaces during sliding. Because the sliding surfaces were not confined in the experiments, the gouge was extruded from the fault surfaces, resulting in shortening of axial length of specimen. In this study, we defined the dimensionless wear rate, given by that an axial shortening rate of the specimen was divided by slip rate. Then, we examined how the wear rate and temperature changed as a function of the rate of frictional work per a unit fault area, Ef, determined by shear stress multiplied by slip rate. Hereafter, Q and Us denote the rate of heat and surface energy per a unit fault area, respectively. Our experimental results can be summarized as follows. (1) The wear rate increased almost linearly with increasing Ef. The slope of the wear rate versus Ef was higher at lower slip rates, but it became constant at slip rate of >0.11m/s. This means that more gouge forms at lower slip rate for a given Ef. (2) The grain size distribution of the gouge developed at different experimental conditions was nearly identical; the calculated specific surface area from the size distribution was nearly constant (1.3 to 1.6 m2/g). Therefore the Us is proportional only to the wear rate. This indicates that the trend of the wear rate versus Ef curves corresponds to that of the Us versus Ef curves. (3) The results of (1) and (2) suggest that the ratio of the surface energy to the fictional work (Us/Ef) increases with increasing Ef and decreasing slip rate. The Us/Ef at Ef of 43 kJ/m2s was 0.012% and 0.009% at slip rates of 0.025 m/s and 0.11 m/s, respectively. (4) In contrast, the ratio of the energy dissipated as heat to the frictional work (Q/Ef) is independent of slip rate, and however it decreases with increasing Ef. The Q/Ef decreased from ~95% at Ef of 20 kJ/m2s to ~70% at Ef of 210 kJ/m2s. Our experiments at nearly coseismic slip conditions suggest that slip rate and Ef are important parameters to determine the energy partitioning of the frictional work during an earthquake.

  4. 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 Sbrier, GRL v.22, 1995) [2] (McCaffrey, Geology v.19, 1992) [3] (Feng et al., in prep.)

  5. 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

  6. Cross-slip Paths and Energetics in Al and Ag

    NASA Astrophysics Data System (ADS)

    Lu, Gang; Kioussis, Nicholas; Bulatov, Vasily; Kaxiras, Efthimios

    2000-03-01

    A new semi-discrete variational approach is developed for the energetics of dislocation cross-slip in FCC metals. In the new model, we let screw dislocations spread into two intersecting planes, glide and cross-slip planes. Within the Peierls-Nabarro formalism, the energy of a given core configuration is then determined by the elastic interaction between two continuously distributed dislocation densities and the associated misfit energies intergrated over the two planes. The ? surfaces entering the model are calculated from the density functional theory. We find an optimal cross-slip path and the associated cross-slip energy barrier in a series of constrained minmization calculations, starting from different initial core configurations. It turns out that screw dislocations in Al an Ag follow different cross-slip paths characterized by very different activation barriers. Our results are compared with the experimental and simulation data available in the literature. Our approach can also be used to study more complicated dislocation reactions over different glide planes.

  7. 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.

  8. Stokes flow in a pipe with distributed regions of slip

    NASA Astrophysics Data System (ADS)

    Lauga, Eric; Stone, Howard A.

    2002-11-01

    Steady pressure-driven Stokes flow in a circular pipe is investigated analytically in the case where the pipe surface contains periodically distributed transverse regions of zero surface shear stress. One physical motivation for this problem is the recent experimental observation of nanobubbles on smooth hydrophobic surfaces (Ishida et al. (2000) Langmuir vol. 16, Tyrrell and Attard (2001) Phys. Rev. Lett. vol. 87) while a second motivation is the possible presence of bubbles trapped on rough surfaces. The bubbles may provide a zero shear stress boundary condition for the flow and modify considerably the friction generated by the solid boundary. In the spirit of experimental studies probing apparent slip at solid surfaces, the effective slip length of the resulting macroscopic flow is evaluated numerically and asymptotically as a function of the relative width of the no-slip and no-shear stress regions and their distribution along the pipe. Comparison of the model with experimental studies of pressure-driven flow in capillaries and microchannels is made and a possible interpretation of the results is offered which is consistent with a large number of nano-size and micron-size bubbles coating the solid surface. Finally, an explanation for the seemingly paradoxical behavior of the measured slip length increasing with system size reported by Watanabe et al. (1999) (J. Fluid Mech. vol. 381) is proposed and the possibility of a shear-dependent effective slip length is suggested.

  9. 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.

  10. Surface roughness and effective stick-slip motion

    NASA Astrophysics Data System (ADS)

    Ponomarev, I. V.; Meyerovich, A. E.

    2003-02-01

    The effect of random surface roughness on hydrodynamics of viscous incompressible liquid is discussed. When the hydrodynamic decay length (the viscous wave penetration depth) is larger than the correlation radius (size) of random surface inhomogeneities, it is possible to replace a random rough surface by effective stick-slip boundary conditions on a flat surface with two constants: the stick-slip length and the renormalization of viscosity near the boundary. The stick-slip length and the renormalization coefficient are expressed explicitly via the correlation function of random surface inhomogeneities. The stick-slip length is always negative and the effective change of viscosity near the surface is positive signifying the effective average hampering of the hydrodynamic flows by the rough surface (stick rather than slip motion). A simple hydrodynamic model illustrates general hydrodynamic results. The effective boundary parameters are analyzed numerically for Gaussian, power-law and exponentially decaying correlators with various indices. The maximum on the frequency dependence of the dissipation allows one to extract the correlation radius (characteristic size) of the surface inhomogeneities directly from, for example, experiments with torsional quartz oscillators.

  11. 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.

  12. 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.

  13. 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.

  14. Soil slips and debris flows on terraced slopes

    NASA Astrophysics Data System (ADS)

    Crosta, G. B.; Dal Negro, P.; Frattini, P.

    Terraces cover large areas along the flanks of many alpine and prealpine valleys. Soil slips and soil slips-debris flows are recurrent phenomena along terraced slopes. These landslides cause damages to people, settlements and cultivations. This study investigates the processes related to the triggering of soil slip-debris flows in these settings, analysing those occurred in Valtellina (Central Alps, Italy) on November 2000 after heavy prolonged rainfalls. 260 landslides have been recognised, mostly along the northern valley flank. About 200 soil slips and slumps occurred in terraced areas and a third of them evolved into debris flows. Field work allowed to recognise the settings at soil slip-debris flow source areas. Landslides affected up to 2.5 m of glacial, fluvioglacial and anthropically reworked deposits overlying metamorphic basement. Laboratory and in situ tests allowed to characterise the geotechnical and hydraulic properties of the terrains involved in the initial failure. Several stratigraphic and hydrogeologic factors have been individuated as significant in determining instabilities on terraced slopes. They are the vertical changes of physical soil properties, the presence of buried hollows where groundwater convergence occurs, the rising up of perched groundwater tables, the overflow and lateral infiltration from superficial drainage network, the runoff concentration by means of pathways and the insufficient drainage of retaining walls.

  15. 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(?-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.

  16. Simple calculation measures NH sub 3 slip for cogeneration units

    SciTech Connect

    Anderson, C.M.; Billings, J.A. )

    1991-04-01

    This paper reports that government regulations restricting NO{sub x} emissions for New Stationary Sources have brought about an increased demand for deNO{sub x} systems. One such system is selective catalytic reduction (SCR). It uses ammonia in the presence of a catalyst to selectively reduce NO{sub x} emissions. Because of inherent inefficiencies in the SCR design, a small amount of NH{sub 3} slip becomes an additional exhaust stream pollutant discharged into the atmosphere. This discharge requires monitoring. Normally, ammonia is listed as a pollutant in the environmental permit to construct when an SCR system is specified for NO{sub x} reduction. Therefore, a method to report NH{sub 3} slip also will be required. Although the Code of Federal Regulations 40 CRF 60 does not specifically addressed NH{sub 3} slip, state agencies usually require reporting of NH{sub 3} emissions. An ammonia analyzer usually is installed for the measurement. However, other methods to monitor NH{sub 3} slip should be considered. One alternative is to calculate it. A cogeneration plant equipped with SCR using a specific configuration of instrumentation hardware and software will allow the NH{sub 3} slip to be calculated accurately.

  17. Variations in rupture speed, slip amplitude and slip direction during the 2008 Mw 7.9 Wenchuan Earthquake

    NASA Astrophysics Data System (ADS)

    Wen, Yi-Ying; Ma, Kuo-Fong; Oglesby, David D.

    2012-07-01

    Theoretical and observational evidence implies that variable rupture velocity may be associated with high fault slip and high moment release rates during earthquakes. We investigate this relationship for the 2008 Mw 7.9 Wenchuan China, Earthquake, which appears to have experienced a highly variable moment release rate. We used an empirical Green's function (EGF) deconvolution analysis of teleseismic waveforms to retrieve the primary rupture characters for this event. Based on field observations and the deconvolved source-time function from thrust and strike-slip EGFs, we divided the ruptured fault into three segments, allowing us to determine the spatial slip distribution with different average rupture velocities on each segment. We deployed a grid search analysis, in which we integrated the teleseismic waveform inversion and forward modelling of the regional surface wave to determine the optimum rupture speed in each fault segment. Our result shows that the 2008 Wenchuan Earthquake had slip amplitude, direction and rupture velocity that were highly spatially variable. The earthquake initially ruptured with nearly pure thrust motion and a slow rupture velocity of 1.7 km s-1. Then, the rupture speed increased up to 3.1-3.3 km s-1 and produced the largest slip on the second segment, where two parallel faults ruptured simultaneously. Rupture velocity then slowed down to 2.5-2.9 km s-1 on the final segment, which underwent primarily strike-slip motion. In total, the fault extended 300 km with an average rupture speed in the range of 2.6-2.9 km s-1. The high rupture speed (close to the shear wave velocity) in the second segment may be related to the simultaneous rupture of the two parallel faults on well-established pre-existing structures. The spatial distribution of rupture velocity and slip are likely related to the strongly rotational and 3-D deformation in the eastern Tibetan Plateau margin, which leads to the heterogeneous stress field of the Longmen Shan region.

  18. 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).

  19. 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.

  20. 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 ?m) of undeformed, protolith carbonate rocks using a rotary shear apparatus, at target speed v = 1 ms-1, normal stresses ?n = 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 ? = 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 (? = 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.

  1. 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.

  2. 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.

  3. Multiscale Stick-Slip Dynamics of Adhesive Tape Peeling.

    PubMed

    Dalbe, Marie-Julie; Cortet, Pierre-Philippe; Ciccotti, Matteo; Vanel, Loc; Santucci, Stphane

    2015-09-18

    Using a high-speed camera, we follow the propagation of the detachment front during the peeling of an adhesive tape from a flat surface. In a given range of peeling velocity, this front displays a multiscale unstable dynamics, entangling two well-separated spatiotemporal scales, which correspond to microscopic and macroscopic dynamical stick-slip instabilities. While the periodic release of the stretch energy of the whole peeled ribbon drives the classical macro-stick-slip, we show that the micro-stick-slip, due to the regular propagation of transverse dynamic fractures discovered by Thoroddsen et al. [Phys. Rev. E 82, 046107 (2010)], is related to a high-frequency periodic release of the elastic bending energy of the adhesive ribbon concentrated in the vicinity of the peeling front. PMID:26431019

  4. 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).

  5. 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.

  6. Precursory Processes during Stick-Slip Experiments on Crustal Rocks

    NASA Astrophysics Data System (ADS)

    Passelgue, 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 ?n. 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.

  7. 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 (>5.50.5 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 (41 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.

  8. 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.

  9. 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.

  10. 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).

  11. 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

  12. Quantum Phase Slips and Transport in Ultrathin Superconducting Wires

    SciTech Connect

    Zaikin, A.D.; Zaikin, A.D.; Golubev, D.S.; van Otterlo, A.; van Otterlo, A.; Zimanyi, G.T.

    1997-02-01

    We present a microscopic study of the quantum fluctuations of the superconducting order parameter in thin homogeneous superconducting wires at all temperatures below T{sub c}. The rate of quantum phase-slip processes determines the resistance R(T) of the wire, which is observable in very thin wires, even at low temperatures. Furthermore, we predict a new low-temperature metallic phase below a critical wire thickness in the 10-nm range, in which quantum phase slips proliferate. {copyright} {ital 1997} {ital The American Physical Society}

  13. 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.

  14. 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

  15. Stick-slip instability for viscous fingering in a gel

    NASA Astrophysics Data System (ADS)

    Puff, N.; Debrgeas, 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 observewith increasing finger velocitiesthe 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. Mechanics of Suture Joints

    NASA Astrophysics Data System (ADS)

    Li, Yaning; Song, Juha; Ortiz, Christine; Boyce, Mary; Ortiz Group/DMSE/MIT Team; Boyce Group/ME/MIT Team

    2011-03-01

    Biological sutures are joints which connect two stiff skeletal or skeletal-like components. These joints possess a wavy geometry with a thin organic layer providing adhesion. Examples of biological sutures include mammalian skulls, the pelvic assembly of the armored fish Gasterosteus aculeatus (the three-spined stickleback), and the suture joints in the shell of the red-eared slider turtle. Biological sutures allow for movement and compliance, control stress concentrations, transmit loads, reduce fatigue stress and absorb energy. In this investigation, the mechanics of the role of suture geometry in providing a naturally optimized joint is explored. In particular, analytical and numerical micromechanical models of the suture joint are constructed. The anisotropic mechanical stiffness and strength are studied as a function of suture wavelength, amplitude and the material properties of the skeletal and organic components, revealing key insights into the optimized nature of these ubiquitous natural joints.

  17. 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.

  18. 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.

  19. 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.

  20. 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...

  1. Sternoclavicular joint injuries.

    PubMed

    Ferrera, P C; Wheeling, H M

    2000-01-01

    Injuries to the sternoclavicular (SC) joint are infrequently encountered. However, retrosternal SC joint dislocations are potentially life-threatening injuries which must be recognized by the examining physician and treated as soon as possible. Plain radiography often fails to fully distinguish SC joint injuries, and computed tomography has emerged as the diagnostic modality of choice for defining the injury complex and surrounding injuries. We have encountered 6 cases of SC joint injuries over the past 3 years and describe their presentation and management. PMID:10674534

  2. 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.

  3. 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

  4. 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.

  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. Break-Even Point for a Proof Slip Operation

    ERIC Educational Resources Information Center

    Anderson, James F.

    1972-01-01

    Break-even analysis is applied to determine what magnitude of titles added per year is sufficient to utilize economically Library of Congress proof slips and a Xerox 914 copying machine in the cataloging operation of a library. A formula is derived, and an example of its use is given. (1 reference) (Author/SJ)

  7. 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.

  8. 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.

  9. Workplace slip, trip and fall injuries and obesity.

    PubMed

    Koepp, Gabriel A; Snedden, Bradley J; Levine, James A

    2015-01-01

    The objective of this study was to examine the relationship between slip, trip and fall injuries and obesity in a population of workers at the Idaho National Laboratory (INL) in Idaho Falls, Idaho. INL is an applied engineering facility dedicated to supporting the US Department of Energy's mission. An analysis was performed on injuries reported to the INL Medical Clinic to determine whether obesity was related to an increase in slip, trip and fall injuries. Records were analysed that spanned a 6-year period (2005-2010), and included 8581 employees (mean age, 47 11 years and body mass index [BMI], 29 5 kg/m(2); 34% obesity rate). Of the 189 people who reported slip, trip and fall injuries (mean age, 48 11 years), 51% were obese (P < 0.001 compared with uninjured employees), and their mean BMI was 31 6 kg/m(2) (P < 0.001). Obesity in this population was associated with a greater rate of slip, trip and fall injuries. PMID:25532054

  10. Chaotic mixing in a planar, curved channel using periodic slip

    NASA Astrophysics Data System (ADS)

    Garg, P.; Picardo, J. R.; Pushpavanam, S.

    2015-03-01

    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.

  11. Wear studies made of slip rings and gas bearing components

    NASA Technical Reports Server (NTRS)

    Furr, A. K.

    1967-01-01

    Neutron activation analysis techniques were employed for the study of the wear and performance characteristics of slip ring and rotor assemblies and of the problems arising from environmental conditions with special reference to surface contamination. Results showed that the techniques could be successfully applied to measurement of wear parameters.

  12. [Dyamic screw fixation for slipped capital femoral epiphysis. Treatment results].

    PubMed

    Hackenbroch, M H; Kumm, D A; Rtt, J

    2002-09-01

    Slipped capital femoral epiphysis always requires surgical treatment. The operative technique depends on the degree of dislocation and the type of the slip. The goal of treatment is to achieve physeal stability until the epiphyseal plate closes without harming the further femoral growth. In situ fixation is generally recommended for slipped capital femoral epiphyses of a mild degree. For this purpose the technique of dynamic screw fixation (DSF) is applicable using a long cannulated screw with a short thread.DSF is easy to handle, provides sufficient long-term fixation of the epiphysis, does not promote premature closure of the epiphysis, and engenders few complications. Therefore, this technique is also applicable for the prophylactic treatment of the contralateral unaffected hip, which we always perform. Moreover, DSF can be used following gentle reduction of acute epiphysiolysis, if the amount of eventual residual dislocation does not exceed 30 degrees. We report our results with dynamic screw fixation of 29 slipped capital femoral epiphyses of a mild degree, and the prophylactic dynamic screw fixation of 34 unaffected hips. The fixation technique achieved a reliable stabilization with no visible growth disturbance of the femoral neck in all cases. PMID:12232705

  13. 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

  14. Stress distribution in granular heaps using multi-slip formulation

    NASA Astrophysics Data System (ADS)

    Al Hattamleh, O.; Muhunthan, B.; Zbib, H. M.

    2005-06-01

    Many experiments on conical piles of granular materials have indicated, contrary to simple intuition that the maximum vertical stress does not occur directly beneath the sand-pile vertex but rather at some distance from the apex resulting in a ring of maximum vertical stress. Some recent experiments have shown that the observed stress dip is very much dependent on construction history. A multi-slip model has been proposed to investigate the stress dip phenomenon in granular heaps. The double-slip version of the model was implemented into ABAQUS and used to study the vertical stress distribution along the base of a granular pile. The numerical simulations show that plastic deformation is confined within the localized region around the apex while the rest of the pile is in an elastic state of deformation. Within the plastic region the stress distribution differs significantly depending on the initial active slip orientation. The results show that for homogenous state of granular materials such as those produced by a raining procedure the vertical stress profile along the base reached its peak at the apex (i.e. no dip was observed). On the contrary, granular heaps constructed by the use of a localized source such as a funnel resulted in a significant reduction in the stress distribution within the ring with the minimum attained beneath the peak (i.e. a dip). Therefore, we believe that the initial microstructure and thus the initial slip orientation resulting from sand deposition is the source of the stress dip phenomenon.

  15. Dynamic Action Units Slip in Speech Production Errors

    ERIC Educational Resources Information Center

    Goldstein, Louis; Pouplier, Marianne; Chen, Larissa; Saltzman, Elliot; Byrd, Dani

    2007-01-01

    In the past, the nature of the compositional units proposed for spoken language has largely diverged from the types of control units pursued in the domains of other skilled motor tasks. A classic source of evidence as to the units structuring speech has been patterns observed in speech errors--"slips of the tongue". The present study reports, for

  16. Wall slip across the jamming transition of soft thermoresponsive particles

    NASA Astrophysics Data System (ADS)

    Divoux, Thibaut; Lapeyre, Vronique; Ravaine, Valrie; Manneville, Sbastien

    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 ? 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??p 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 ? -?c , where ?c 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 ? on both sides of the jamming point and that the exponent p increases continuously with ? , 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.

  17. 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.

  18. 6. VIEW OF BARGE SLIP (CALLED MASON'S CANAL, WHICH EXTENDS ...

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

    6. VIEW OF BARGE SLIP (CALLED MASON'S CANAL, WHICH EXTENDS OFF THE SOUTH BRANCH OF THE CHICAGO RIVER) AND COAL DOCK; TO THE RIGHT IS THE EAST FACADE OF THE 1959 GENERATING STATION. LOOKING SOUTHWEST. - Commonwealth Electric Company, Fisk Street Electrical Generating Station, 1111 West Cermak Avenue, Chicago, Cook County, IL

  19. Adhesive slip process between a carbon nanotube and a substrate

    NASA Astrophysics Data System (ADS)

    Wu, Yu-Chiao; McGruer, Nicol E.; Adams, George G.

    2013-05-01

    Since their discovery in 1991, carbon nanotubes (CNTs) have been attractive components for nanoelectromechanical (NEM) devices because of their excellent mechanical and electrical properties. Several CNT-based NEM devices have been reported. Experimental investigations have discovered that the force required for a CNT to slip on a SiO2 substrate is almost constant in the range of contact lengths from 140 to 246 nm and increases with the contact length for greater lengths. This study develops a theory based on the continuum mechanics to explain this observed phenomenon. The critical force needed to cause the CNT to slip over the whole substrate is determined by applying a beam theory which includes the bending, shear, and axial deformations of the CNT. At the stick-slip transition, the work of adhesion contributes a concentrated force and a concentrated moment to produce discontinuities in the internal forces and moments of the CNT. The modelling results obtained here provide the external force required for complete slip versus a dimensionless parameter related to the shear stress and the contact length. A comparison of the modelling result and the experimental data from the literature shows good agreement.

  20. 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.

  1. Strike-slip Faulting On Ganymede, Now And Then

    NASA Astrophysics Data System (ADS)

    Pappalardo, Robert T.; Smith-Konter, B. R.; Cameron, M. E.; DeRemer-Keeney, L. C.; Nimmo, F.

    2012-10-01

    Strike-slip tectonism is important to the structural development of Ganymedes surface, and in the transition from dark to grooved terrain. Three distinct signatures of strike-slip faulting are recognized [1]: (1) en echelon structures, (2) strike-slip duplexes, and (3) laterally offset pre-existing features. As strike-slip faulting progressed, en echelon fractures (in both dark and grooved terrains) merged to define en echelon swaths, which can become distinct tectonic domains. Three morphological categories of strike-slip duplexes (spindle-shaped lensoid regions bounded by strike-slip faults) occur, suggesting an evolutionary sequence from discontinuous fractures in dark terrain, to lensoid bounding structures, to lensoid regions with subparallel internal structure in grooved terrain. Ganymedes 24 measured duplexes have an average length/width ratio of 2.4, on the low end of the terrestrial range [2]. Lateral offsets of pre-existing features betray the existence of some major strike-slip faults: Dardanus Sulcus (13W, 18S) is displaced 45 km by a prominent NE-SW trending fault. We model Coulomb shear failure on Ganymede, considering nonsynchronous rotation (NSR), and diurnal stresses both for present (0.0013) and possible past high ( 0.05) eccentricity [3]. We adopt NSR period 0.14 Ma; Love numbers h2 = 1.52 and l2 = 0.38; Youngs modulus 9.3 GPa; Poissons ratio 0.33; and fault depth 2 km. NSR shear stress resolved along the Dardanus fault is 0.3 MPa, sufficient to induce failure to 1.4 km for friction coefficient 0.3. For past high eccentricity, diurnal stress would have modulated NSR stress by 100 kPa through Ganymedes tidal cycle. This could have induced shear heating [4] and tidal walking [5], as modeled for Europa. References: [1] DeRemer and Pappalardo (2003), LPSC, 34, #2033; [2] Aydin and Nur (1982), Tectonics, 1, 91; [3] Showman and Malhotra (1997), Icarus, 127, 93; [4] Nimmo and Gaidos (2002), JGR, 107, 10.1029/2000JE001476; [5] Rhoden et al. (2012), Icarus, 218, 297.

  2. 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.

  3. 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.

  4. 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.

  5. Fault-Wear Under Constant Slip-Velocity: Experimental Observations

    NASA Astrophysics Data System (ADS)

    Boneh, Y.; Chang, J. C.; Lockner, D. A.; Reches, Z.

    2010-12-01

    Fault wear, which is a natural result of frictional slip, is a complex process that depends on rock properties (e.g., roughness, brittleness, hardness, strength, composition), and loading conditions (e.g., normal stress, slip velocity, slip history, temperature). Fault wear is indicated in the field primarily by the occurrence of gouge zones and slickenside striations. Analyses of natural faults suggest that gouge-thickness is proportional to fault-displacement over 6-8 orders of magnitude (Scholz, 1987). Experimental studies of fault-wear, which were mostly conducted under low-velocity and for short slip distances, indicate strong dependency of the wear-rate on normal stress. Our experimental study of fault-wear was conducted with a rotary shear apparatus that includes continuous monitoring of wear, friction, and temperature at slip velocities of 0.001-1 m/s and large displacements. Samples of Sierra white granite, approximately 7 cm-diameter, were sheared against each other at normal stress ranging between 0.48 and 6.9 MPa and at slip-velocities up to 0.5 m/s. The wear-rate was calculated from the continuously measured closure across the fault blocks, and presented here by the unit W= [(micron of surface wear) / (meter of slip distance)]. We observed three types of experiments: (1) experiments with transient stage of positive wear-rate (closure across the fault); (2) experiments with transient stage of negative wear-rate (dilation across the fault); and (3) experiments with quasi-constant wear-rate with no transient stage. The initial transient stages were followed by a steady-state wear-rate with low intensity of W=0.5-20 ?/m. The positive transient stage of type (1) corresponds to the well-known "running-in" stage of smoothening the initial roughness and high asperities (Wang and Scholz, 1984). The running-in stage in our experiments is characterize with high wear-rate intesntisy (W = 80-250 ?/m) that decays to the low steady-state values. The dilating transient stage of type (2) has negative wear-rate of -1 to -20 ?/m. Both transient stages decays to the steady state stage after slip of 2 to 10m. Synthesis of steady-state wear-rates intensities indicates that they are related to three parameters: (1) the normal stress, (2) the velocity-dependent friction, and (3) the loading power (=slip-velocity * shear-stress=rate of dissipated energy). We found that the wear-rate is linearly proportional to the normal stress, whereas it has more complex relations to the friction. Relating the Wear-rate to the loading power indicates very high intensity of wear-rate in both low and high loading power, and a minimum, low wear-rate under intermediate loading power. We present the first wear intensity map for granite, following Lim and Ashby (1967) and Deuis et al. (1997), that presents wear-rate intensity areas (mild, medium and severe) as function of normal stress and slip-velocity. We will discuss these controlling relations and their implications to gouge zones in the field.

  6. Compositional, mechanical and hydrologic controls on fault slip behavior

    NASA Astrophysics Data System (ADS)

    Ikari, Matt J.

    In order to examine the roles of a variety of factors that are likely important in regulating the occurrence or lack of seismic slip, I evaluate the results of numerous laboratory studies of fault behavior, focusing on the effects of fault mineralogy, mechanical effects, and interactions between fluids and faulting processes. More specifically, these experiments are designed to investigate the underlying mechanisms controlling the transition from aseismic slip at shallow levels in the crust to seismic slip at depth, known as the updip limit of the seismogenic zone. Results of laboratory experiments indicate that mineralogy of fault gouge is a major control on fault behavior. The clay mineral montmorillonite (smectite) has been noted for its potential effect on seismogenesis in subduction zones (as well as all faults in general) due to its ability to take up water in its crystal structure. Dehydration of montmorillonite tends to increase its frictional strength as well as increase its propensity for seismic slip, as documented by a decrease in the frictional velocity dependence parameter a-b. However, the observed decrease in a-b is assisted by both increasing relative quartz percentage and increasing normal stress, implying that the onset of seismic behavior with increasing depth should not be attributed solely to smectite dehydration. Furthermore, clay-rich gouges in general, including those consisting of montmorillonite, illite, and chlorite, are both frictionally weak (mu < 0.35) and velocity-strengthening (frictionally stable, a-b > 0) at fluid-saturated conditions and effective normal stresses up to 60 MPa. Sheared gouges may also exhibit low fault-perpendicular permeability (k < 1x10-18), making them candidates to host high pore pressure. This indicates that faults containing granular, clay-rich gouges are unlikely to show seismic behavior, due their velocity-strengthening nature and stabilizing hydro-mechanical effects resulting from low permeability. In comparing the frictional behavior of granular gouge and lithified fault rock as an analogue for cataclastic fault rocks at seismogenic depths, the lithification of fault rock is found to have a significant strengthening effect, however in phyllosilicate-rich rocks pre-existing foliation provides a weakening mechanism that offsets the strengthening due to lithification. This weakening depends on the intensity of foliation such that strongly foliated rocks, such as books of mica sheets, are significantly weaker than granular mica gouges. Very thick fault zones can exhibit a reduction in measured apparent friction, the magnitude of which may be related to the orientation of through-going R1 shears and internal structural complexity. Consistent velocity-strengthening behavior is observed for both lithified and granular phyllosilicate-rich samples despite the observation of slip localization features in microstructural analysis, suggesting that as an isolated parameter advanced lithification state of fault rock is also inadequate for allowing seismic slip nucleation. Collectively, the results of the experiments in this study have several important implications for fault slip behavior. Granular, unconsolidated phyllosilicate-rich gouges, such as those that are common at shallow depths in both subduction zones and strike-slip faults, will tend to be aseismic, a condition that may be related to their overall weakness. The transition from aseismic to seismic slip at the updip limit of the seismogenic zone should be driven by changes in pressure and temperature, due to the overall ambient conditions as well as inducing changes in the character of the fault material itself. These may include compositional changes and mechanical effects of the lithification process, such as consolidation and cementation. However, when tested as isolated variables, the dehydration of smectite, conversion of smectite to illite, and lithification of fault gouge were found to be insufficient in allowing unstable slip behavior. It is possible that these processes may still play a rol

  7. 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

  8. 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

  9. Global seismicity characteristics of subduction-to-strike-slip transitions

    NASA Astrophysics Data System (ADS)

    Bilich, Andria; Frohlich, Cliff; Mann, Paul

    2001-09-01

    There are at least 30 major plate boundary segments worldwide where the plate boundary changes from subduction to strike-slip; these include six triple junctions and 24 two-plate boundaries. This study investigates earthquake seismicity in the 24 two-plate subduction-to-strike-slip transition (SSST) regions by utilizing recently published earthquake relocations, ternary diagrams of focal mechanisms, and moment rate calculations. To facilitate cross-regional comparisons, we categorize the geometry of SSST plate boundaries in terms of (1) their radius of curvature, (2) their sense of curvature, that is, whether they are convex or concave as viewed from the downgoing plate, and (3) their tectonic complexity, that is, the variability of crustal thickness and the segmentation of the plate boundary trace. We observe three main trends in SSST regions: (1) there is a conspicuous scarcity of strike-slip earthquakes along plate boundary segments that plate motion models indicate are strike-slip boundaries; (2) in these apparent strike-slip segments, both the rate of occurrence of earthquakes of any kind and the moment release rate are low compared to adjacent subduction segments; and (3) there were few observable differences in seismicity between convex and concave boundaries. The observation that transform zones exhibit moment rate deficiencies, that is, have few large-magnitude earthquakes in the historical record, may have important implications for seismic hazard assessment in SSST regions. In particular, is motion along these boundaries aseismic with little seismic hazard, or is motion expressed in very large magnitude, infrequent, but potentially devastating earthquakes? In at least three such regions, New Zealand, the Philippines, and the Dominican Republic, paleoseismic evidence and the historical record of seismicity suggest that very large, infrequent earthquakes do occur.

  10. Major power law slip-weakening in laboratory gouge friction

    NASA Astrophysics Data System (ADS)

    Chambon, G.; Schmittbuhl, J.; Corfdir, A.

    2003-04-01

    We performed gouge-shearing experiments in a large-displacement ring-shear apparatus. The granular gouge (quartz sand) undergoes significant slip-weakening over seismic-like distances (0.5 m) and minor velocity-weakening over microscopic length scales (100 ?m). The reproducible decrease of gouge effective friction ? with shear displacement ? follows a power law: ? = ?_0 + A ?-?, with ? = 0.4. Such a slip-weakening process can be accounted for in an extended rate- and state-dependent friction law through a supplementary state variable. However, unlike classical state variables, the evolution law governing this new variable does not involve any characteristic length scale. Accordingly, slip-weakening is found independent of gouge grain size. Careful checks were performed to insure that observed weakening constitutes a real rheological property of the gouge. Moreover, microscopic origin of the slip-weakening has been investigated by means of a Correlation Image Velocimetry (CIV) technique applied to digital pictures of the sample. Most of the deformation appears localized in a 7 grain-wide, comminuted shear band. Nevertheless, CIV also reveals an intermittent, ongoing deformation outside this zone, whose magnitude slowly diminishes as shear displacement increases. This microscopic relaxation denotes a progressive decoupling between the shear zone and the bulk of the sample. Slow decrease of spatially-averaged shear strain <~ngle?rangle is well modeled by a hyperbolic law in displacement ?, without any characteristic length scale: <~ngle?rangle = ?_0 + a ?-1. We interpret the macroscopic slip-weakening as a consequence of the observed decoupling at micro-scale. When extrapolated to faults, this result shows that decimetric weakening distances, frequently reported during earthquakes, can be produced by complex structuring processes inside the gouge layer.

  11. 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.

  12. 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

  13. On Replicating the SLIP Technique: A Reply to Sinsabaugh and Fox.

    ERIC Educational Resources Information Center

    Motley, Michael T.

    1986-01-01

    Examines concerns raised about the Spoonerisms of Laboratory Induced Predisposition (SLIP) technique by Sinsabaugh and Fox. Indicates that these concerns are generally unfounded and discusses implications for optimal use of the SLIP technique. (JD)

  14. 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…

  15. 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.

  16. Campylobacter Prosthetic Joint Infection

    PubMed Central

    Vasoo, Shawn; Schwab, Jeramy J.; Cunningham, Scott A.; Robinson, Trisha J.; Cass, Joseph R.; Berbari, Elie F.; Walker, Randall C.; Osmon, Douglas R.

    2014-01-01

    A 75-year-old man was diagnosed with probable Campylobacter jejuni prosthetic knee infection after a diarrheal illness. Joint aspirate and operative cultures were negative, but PCR of prosthesis sonicate fluid was positive, as was stool culture. Nineteen additional cases of Campylobacter prosthetic joint infection reported in the literature are reviewed. PMID:24523462

  17. Shoulder Joint Replacement

    MedlinePLUS

    ... your area through the AAOS “Find an Orthopaedist” program on OrthoInfo.org. Copyright ©1995-2013 by the American Academy of Orthopaedic Surgeons. .org Shoulder Joint Replacement cont. Page ( 4 ) They can show loss of the normal joint space between bones, flattening or irregularity in the shape ...

  18. 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.

  19. 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

  20. Nonvolcanic Tremors and Intraslab Fluid Migration in Guerrero, Mexico, During Slow Slip Transients

    NASA Astrophysics Data System (ADS)

    Cruz-Atienza, V. M.; Husker, A. L.; Villafuerte, C. D.; Caballero, E.; Legrand, D.; Kostoglodov, V.

    2014-12-01

    Observations in different subduction zones have suggested that overpressured fluids close to the plate interface may be related to the origin of nonvolcanic tremors (NVT) and low frequency earthquakes (LFE). One condition for a causal relationship to exist between fluids and such seismicity is their spatial collocation. Fluids at nearly lithostatic pressures within the top few kilometers of the oceanic crust have been inferred in several subduction zones, including the province of Guerrero, Mexico. However, NVT hypocentral depths in this region have been poorly resolved so that casualty could not even be tested as a hypothesis. In this work, we report NVT relocations from a 3-year-catalog in Guerrero that includes the period of the Slow Slip Earthquake (SSE) of 2006. We used a new location technique called the "Tremor Energy and Polarization" (TREP) method (Cruz-Atienza et al., JGR, 2014), which jointly determines the source location and focal mechanism of sustained tremor signals by simultaneously inverting (1) the energy spatial distribution, (2) the energy spatial derivatives, and (3) the azimuthal direction of the particle motion polarization ellipsoid. In agreement with previous works, NVT epicentral locations concentrate between 200 and 230 km from the trench and then migrate ~40 km trenchward during the occurrence of the SSE. However, unlike earlier investigations, most NVT hypocenters lie at 43 km depth near the plate interface and have subparallel rake angles to the Cocos plate convergence direction. These results are consistent with independent locations and mechanisms of LFE in the region and allow us to examine the casualty hypothesis mentioned above. Poroelastic modeling of fluid transport during two SSEs in Guerrero (Villafuerte and Cruz-Atienza, AGU, 2014) show that fluids migrate towards the spots where this seismicity occurs with maximum velocities between 10-3 and 10-9 km/day, which are more than 3 orders of magnitude smaller than the LFE migration speeds. We conclude that fluid diffusive transport is not responsible of the NVT and LFE migration during the SSEs but instead that slip transients act as a long-term pumping process decreasing the effective pressure where the seismicity takes place as a consequence of small stress perturbations associated to the propagation of the aseismic slip.

  1. 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.

  2. 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.

  3. 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.

  4. 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 ?m-thick air layer, for example, the slip length is calculated to be roughly 50 or 500 ?m, 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 ?m. 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.

  5. 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.

  6. Charge-density-wave phase slip and contact effects in NbSe3

    NASA Astrophysics Data System (ADS)

    Maher, M. P.; Adelman, T. L.; Dicarlo, D. A.; McCarten, J. P.; Thorne, R. E.

    1995-11-01

    We describe a detailed experimental study of phase slip in the charge-density-wave (CDW) conductor NbSe3. Phase slip is required for conversion between CDW current and single-particle current near current contacts. For both CDW's in NbSe3, the CDW current Ic, proportional to the phase-slip rate, exhibits a diodelike dependence upon an excess voltage Vps, the phase-slip voltage. For a given Ic (slip rate), Vps increases strongly with decreasing temperature, and at corresponding temperatures is roughly an order of magnitude larger for the TP1 CDW than for the TP2 CDW. Current contacts applied to the side of the crystal may lead to inhomogeneous current injection and allow CDW deformations and slip to extend beyond the contacts. Voltage contacts shunt current out of the crystal, and may cause CDW deformations and slip in their vicinity. We describe improved measurements of phase slip using nonperturbing voltage contacts and end current contacts formed by selected-area ion implantation. The results are consistent with those obtained using side contacts, confirm the interpretation of Vps as the driving force behind phase slip, and provide information about the distribution of slip near the current contacts. The predictions of Ramakrishna et al. for phase slip by thermally activated of edge dislocation loops nucleation account for some qualitative features of our experiments but are in serious quantitative disagreement, suggesting that other slip mechanisms may be important.

  7. Repeated large Slow Slip Events at the southcentral Alaska subduction zone

    NASA Astrophysics Data System (ADS)

    Fu, Yuning; Freymueller, Jeffrey T.

    2013-08-01

    We identify and study an ongoing Slow Slip Event (SSE) in the southcentral Alaska subduction zone using GPS measurements. This is the second large SSE in this region since modern geodetic measurements became available in 1993. We divide the ongoing SSE into two phases according to their transient displacement time evolution; their slip distributions are similar to each other but slip rates are slightly different. This ongoing SSE occurs downdip of the main asperity that ruptured in the 1964 Alaska earthquake, on the same part of the subduction interface as the earlier 1998-2001 SSE. The average slip rate of this SSE is ?4-5 cm/yr, with a cumulative moment magnitude of Mw 7.5 (Mw 7.3 and Mw 7.1 For Phases I and II, respectively) through the end of 2012. The time and space dependence of the GPS displacements suggest that the slip area remained nearly the same during Phase I, while the slip rate increased with time. The SSEs occur on a transitional section of the subduction plate interface between the fully locked updip part and the freely slipping deeper part. During the 1964 earthquake, slip on the region of the SSE was much lower than slip in the updip region. Based on this observation and the repeated SSEs, we conclude that this part of the interface slips repeatedly in SSEs throughout the interseismic period and does not build up a large slip deficit to be released through large slip in earthquakes.

  8. The liquid metal slip ring experiment for the communications technology satellite

    NASA Technical Reports Server (NTRS)

    Lovell, R. R.

    1972-01-01

    The experiment is designed to demonstrate liquid metal slip ring (LMSR) performance in a space environment. An evaluation was made of the features of the LMSR where improvement in performance over conventional slip rings was expected. The primary measurements to be made in the experiment will allow a determination of the slip ring electrical resistance, between ring insulation and ring cleanliness.

  9. Surface slip associated with the 2014 South Napa, California earthquake measured on alinement arrays

    NASA Astrophysics Data System (ADS)

    Lienkaemper, J. J.; Brooks, B. A.; DeLong, S. B.; Domrose, C. J.; Rosa, C. M.

    2014-12-01

    The main rupture associated with the South Napa earthquake of Sept. 24, 2014 was ~15 km long from its epicenter (defined here as km 0, see figure below) to the surface rupture's north end (~km 15). Near km 10 a maximum of ~0.45 m dextral slip was most likely entirely coseismic, because it showed the same amount of slip at 12 days post-earthquake (d-PE) as it did at 1.5 d-PE. However, farther south (km~6) by 1-2 d-PE conspicuous growth of offsets on cultural features indicated high rates of afterslip (~10-20 cm/day) had occurred. Although afterslip is gradually slowing, it is expected to continue for many months or possibly years. To closely monitor this rapid afterslip, we installed four 70-140-m-long alinement arrays across the main rupture (labeled NLAR-NLOD on figure below), measuring slip to millimeter accuracy. A fifth array that spans a northeastern branch rupture has shown no afterslip. We have run early observations (to 26-d-PE) of afterslip (coupled with accumulated total slip as measured on adjacent offset cultural features) in the program AFTER (Boatwright et al., 1989). This analysis allows us to make preliminary estimates of initial (1 d-PE), final or total accumulated event slip, and coseismic estimates (i.e., projecting slip toward a ~0.5-1 s rise time). Thus far modeled slip on all four arrays indicates that final values of total (coseismic plus post-seismic) slip might be approaching the maximum coseismic slip as a limit (~0.4 0.1 m). The final values of total surface slip may thus become more uniform along the fault over time as compared to modeled heterogeneous seismic slip at depth. The timing of the surface slip release differs strikingly from south to north along the 2014 rupture; AFTER models suggest that slip south of the location of maximum slip (km 0-10) appears to have been dominantly postseismic (~50-100%), whereas north of the maximum slip (km 10-15) slip was mainly coseismic (~50-100%). The current AFTER model predicts that as surface slip along the fault approaches final values of total slip associated with this earthquake (e.g., ?1000 d-PE), the respective contributions to the total event surface slip integrated along the entire fault will approach being 27% coseismic slip and 73% postseismic slip. . . .

  10. 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.

  11. Dual megathrust slip behaviors of the 2014 Iquique earthquake sequence

    NASA Astrophysics Data System (ADS)

    Meng, Lingsen; Huang, Hui; Brgmann, 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.

  12. 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.

  13. The Slumgullion Natural Laboratory for Observing Slip Phenomena

    NASA Astrophysics Data System (ADS)

    Gomberg, J. S.; Schulz, W. H.; Bodin, P.; Kean, J. W.; Wang, G.; Coe, J. A.; MacQueen, P.; Foster, K.; Creager, K.

    2009-12-01

    Many natural systems release stresses by failure and sliding across surfaces; examples include landslides, glaciers, crustal- and plate-scale faults. Observational advances continue to reveal diversity in the seismic signals associated with fault slip and how such stress relaxation can occur, even on a single fault system. A particularly rich example are the episodes of slow fault slip near major subduction and transform plate boundaries that manifest as geodetically observed aseismic deformation abetted by a family of seismic signals depleted in high-frequencies relative to those from earthquakes (named episodic tremor and slip or ETS). While the driving forces and scales differ, there are striking parallels between some observations and models of ETS and of landslide behaviors; e.g. in both, postulated key controls include rate-dependent friction and strength modulated by pore-pressure changes, dilatancy during rapid shear, and subsequent consolidation. To explore common features and the underlying processes we are studying the Slumgullion landslide, an ideal natural laboratory for observing fault slip and associated seismic and aseismic phenomena. Unlike crustal- or plate-scale studies significant deformation can be measured within a single field season, because the Slumgullion moves at average rates of cm/day. Moreover, pore pressures, displacements, material properties, and environmental variables may be measured directly and continuously at several locations on the landslide (albeit not at the basal sliding surface). We have just completed a field experiment on the Slumgullion to test several hypotheses, particularly that slip along the basal surface and side-bounding faults occurs with comparable richness of aseismic and seismic modes as crustal- and plate-scale boundaries. To do so from August 18-26, 2009 we continuously monitored the displacement-field using a robotic electronic displacement meter and the seismic radiation with 88 vertical-component seismographs [see Bodin et al., companion abstract]. Although we have only begun examining the data thus far, the seismic data contain an abundance of network-wide coherent signals with an amazing variety of characteristics. Significant unsteady movement in the displacement field is evident in the geodetic data, as well as fluctuations in the pore-pressures and relevant environmental parameters. Schulz et al. (companion abstract) presents initial landslide observations. We will form and present implications for understanding the likely mechanisms of failure and slip within natural systems.

  14. 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 ...

  15. Joint Infection (Beyond the Basics)

    MedlinePLUS

    ... organisms and can occur in both natural and artificial joints (eg, after a knee replacement). A common ... called nongonococcal bacterial (septic) arthritis. Infection of an artificial joint is known as prosthetic joint infection. GONOCOCCAL ...

  16. 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.

  17. 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.

  18. 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

  19. Evaluation of the slip length in the slipping friction between background electrolytes and peptides through the modeling of their capillary zone electrophoretic mobilities.

    PubMed

    Deiber, Julio A; Piaggio, Maria V; Peirotti, Marta B

    2013-09-01

    This work analyzes and discusses several physicochemical peptide chain properties that may generate partial or total BGE slip boundary conditions on the surface of peptides migrating as spherical and aspherical particles in CZE. A definition of the BGE slip length is presented that is able to account the effect of particle curvature through the associated metrical coefficients. This definition allows the distinction between partial and total BGE slip lengths. It is also shown that the BGE slip length must be variable on orthotropic aspherical particles surfaces. PMID:23712447

  20. 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.

  1. 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

  2. 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

  3. 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.

  4. Clay anomaly responsible for Mexican slow slip earthquakes

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2012-07-01

    Over the past decade, seismologists have uncovered a previously unknown class of earthquakes. Known as slow slip earthquakes (SSEs), these events are marked by their long duration; periodic or repetitive nature; and substantial, though harmless, increases in the velocity of intersecting tectonic plates. In southern Mexico the subduction of the Cocos plate under the North American tectonic plate has been found to harbor SSEs that last for up to a year. Compared to traditional earthquakes, which occur because of a sudden lurch between two frictionally locked plates, SSEs have been traced to the deeper rock underlying this locked layer. The rock properties that lend this deeper layer to the occurrence of SSEs, however, are poorly known. Measuring how seismic waves propagate through the varying rock layers of the south Mexican fault, Song and Kim identify the properties of rock that make this particular system susceptible to slow slip earthquakes.

  5. 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.

  6. 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

  7. Determination of stress from slip data: Faults and folds

    NASA Astrophysics Data System (ADS)

    Michael, Andrew J.

    1984-12-01

    A new technique is derived to invert slickenside data for the stress field that caused the faulting episode. This inversion is simplified by the assumption that the magnitude of the tangential traction on the various fault planes, at the time of rupture, is similar. Study of three normal faulting regimes shows that the inversion derived with this assumption yields results that closely match older inversions that did not include the assumption. Hence the assumption may be valid and is shown to be justified by analyzing a simple fracture criterion. Application of slip data inversions is extended from faulting regimes to the slip on bedding plane faults in folding regimes. Comparison of the inversion results with the geometry of the folds shows this application to be successful, greatly increasing the number of data sets that can be used to find the paleostress field.

  8. 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

  9. 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.

  10. Controversies in management of slipped capital femoral epiphysis.

    PubMed

    Johari, Ashok N; Pandey, Ritesh A

    2016-02-18

    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

  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. 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

  15. Stokes Second Problem for a Micropolar Fluid with Slip

    PubMed Central

    Florea, Olivia Ana; Ro?ca, Ileana Constan?a

    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

  16. 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.

  17. Healthy Joints Matter

    MedlinePLUS

    ... of the quiz. NIAMS Kids Pages Healthy Joints Matter Download PDF (714 KB) October 2015 What exactly ... and never to “play through the pain”—no matter what anyone says—and to take care of ...

  18. [Biomechanics of temporomandibular joint].

    PubMed

    Kang, H; Yi, X

    2000-09-01

    Temporomandibular joint (TMJ) is one of the most intricate and complicate loading joints in the human body. Articular cartilage is characteristic of low infiltrative, porous viscoelastic material. In physiological condition, there is a stress-absorbing architecture system in the TMJ cartilage, which consists of collagen-proteoglycan-water gel network. TMJ disc is a specific connective tissue as stress concentration absorber between condyle and articular fossa, but it does not belong to fibrocartilage. Retrodiscal tissue has high compliance of which the role is to play volume-compensating mechanism in joint movement. Lateral wall is a complexed structure out of ligament and capsule with weak tensile strength and tensile rigidity. Therefore, prolonged oral parafunction will result in joint fatigue and failure. PMID:11285848

  19. Hip joint injection

    MedlinePLUS

    Cortisone shot - hip; Hip injection; Intra-articular steroid injections - hip ... can see where to place the medicine. The steroid medicine is slowly injected into the joint. After the injection, you will remain on the table for another ...

  20. 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.

  1. 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.

  2. Slip and wear in multilayer azimuth track systems

    NASA Astrophysics Data System (ADS)

    Kan, Frank W.; Antebi, Joseph

    2004-09-01

    Many antennas use wheel-on-track systems in which track segments consist of wear plates mounted on base plates. The hardened wear plates are typically connected to the base plates using bolts, and 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 migration in the wheel rolling direction. In addition, there has been wear at the wear plate/base plate interface. This paper describes the use of finite element models (FEM"s) of the wheel, track, and foundation to understand the behavior of the wheel-on-track system, and to evaluate possible retrofit concepts. The FEM"s are capable of representing friction and slip, and the opening and closing of gaps at the interfaces between the wheel, wear plate, base plate, and grout. The FEM"s can capture the behavior of the components as the wheel rolls forward. The paper also describes a method to estimate the amount of wear at the wear plate/base plate interface based on the relative slip and contact pressure between the wear plate and base plate.

  3. Velocity dependence of serpentinite friction promotes aseismic slip on faults

    SciTech Connect

    Reinen, L.A.; Weeks, J.D.; Tullis, T.E. . Dept. of Geological Sciences)

    1992-01-01

    Serpentinite is common on many crustal faults and it has been suggested that the presence of serpentine on these faults may promote aseismic slip. Consequently, the authors have experimentally measured the frictional constitutive response of both antigorite and lizardite polymorphs of serpentine to step changes in velocity. This was done at room temperature in rotary direct shear; normal stress was 25 MPa, and velocities ranged from 32 mm/yr to 3.2 [times] 10[sup 5] mm/yr. The frictional behavior of both serpentine polymorphs indicates that the presence of either one on a fault would result in aseismic creep in the shallow crust at typical plate motion rates. In contrast to other rock types, such as granite, both serpentinites display velocity-strengthening behavior at slow sliding velocities: below some transitional velocity, the frictional resistance increases with velocity, thus promoting stable aseismic slip. At faster velocities, however, frictional strength has a negative dependence on velocity (velocity weakening), which provides the potential for unstable sliding, leading to earthquakes. The coefficient of friction of the antigorite serpentinite is similar to that of other silicates, while that of the lizardite is much lower. The low frictional strength of lizardite may help explain some geologic observations that serpentine appears quite mobile during deformation in the crust. However, it is the velocity-strengthening behavior observed in both serpentinites at low sliding velocities, and not the frictional strength, that will promote aseismic slip on serpentine-bearing faults at typical rates of plate motion.

  4. Spiralling tapered slip-on drill string stabilizer

    SciTech Connect

    Beasley, T.R.; Teng, C.C.

    1986-12-23

    A stabilizer is described for use in a drilling string comprising: a substantially cylindrical body member having a central passageway to accommodate the drill sting, the inside surface of the body member defining a right-hand spiralling thread with a tapered trailing edge which spirals from a starting point on the body member. The thread terminates internally of the body member in an arcuate recess extending around the interior of the body member; a key member is secured to the inner wall surface of the recess of the body member, the key member having a lug extending longitudinally of the body member within the recess; a slip member adapted to thread within the body member between the body member and the drill string. The slip defines a right-hand thread with a matching tapered trailing edge configured to make up with the right-hand thread on the body member and to wedge between the body member and the drill string. One end of the slip terminates in a longitudinally disposed shoulder capable of abutting the lug upon threading of the clip within the body member.

  5. 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.

  6. Insights to slip behavior on rough faults using discrete element modeling

    NASA Astrophysics Data System (ADS)

    Fournier, Thomas; Morgan, Julia

    2012-06-01

    We simulate a range of fault slip behaviors using the discrete element method (DEM) to examine the controls on different slip modes on rough faults. Shear strain is imposed upon a 2-D bonded particle assemblage that contains a predefined fault. Slip modes on the fault vary from creep, to slow-slip, to stick-slip behavior, both spatially and temporally. The mode of slip is controlled largely by the local stress field along the fault, which depends on the local fault roughness. Portions of the fault that fail in relatively low normal stress regimes tend to slide continuously, whereas areas with high clamping stress produce stick-slip events. During stick-slip events, regions within the rupture zone that experience high slip are associated with physical asperities on the fault; ruptures terminate at barriers and through dissipation of the stored elastic energy. The simulated events show stress drops between 0.2-50 MPa, a slightly larger range than is inferred for natural earthquakes. Simulated events also have higher slip magnitudes than are observed during earthquakes for a given rupture length. The simulation produces many characteristics of fault behavior and is shown to be a successful avenue for future studies on the mechanics of fault slip.

  7. Relationship between large slip area and static stress drop of aftershocks of inland earthquake :Example of the 2007 Noto Hanto earthquake

    NASA Astrophysics Data System (ADS)

    Urano, S.; Hiramatsu, Y.; Yamada, T.

    2013-12-01

    The 2007 Noto Hanto earthquake (MJMA 6.9; hereafter referred to the main shock) occurred at 0:41(UTC) on March 25, 2007 at a depth of 11km beneath the west coast of Noto Peninsula, central Japan. The dominant slip of the main shock was on a reverse fault with a right-lateral slip and the large slip area was distributed from hypocenter to the shallow part on the fault plane (Horikawa, 2008). The aftershocks are distributed not only in the small slip area but also in the large slip area (Hiramatsu et al., 2011). In this study, we estimate static stress drops of aftershocks on the fault plane of the main shock. We discuss the relationship between the static stress drops of the aftershocks and the large slip area of the main shock by investigating spatial pattern of the values of the static stress drops. We use the waveform data obtained by the group for the joint aftershock observations of the 2007 Noto Hanto Earthquake (Sakai et al., 2007). The sampling frequency of the waveform data is 100 Hz or 200 Hz. Focusing on similar aftershocks reported by Hiramatsu et al. (2011), we analyze static stress drops by using the method of empirical Green's function (EGF) (Hough, 1997) as follows. The smallest earthquake (MJMA?2.0) of each group of similar earthquakes is set to the EGF earthquake, and the largest earthquake (MJMA?2.5) is set to the target earthquake. We then deconvolve the waveform of an interested earthquake with that of the EGF earthquake at each station and obtain the spectral ratio of the sources that cancels the propagation effects (path and site effects). Following the procedure of Yamada et al. (2010), we finally estimate static stress drops for P- and S-waves from corner frequencies of the spectral ratio by using a model of Madariaga (1976). The estimated average value of static stress drop is 8.21.3 MPa (8.62.2 MPa for P-wave and 7.81.3 MPa for S-wave). These values are coincident approximately with the static stress drop of aftershocks of other inland earthquakes in Japan (Ito et al., 2005; Iio et al., 2006) and independent of the seismic moment. We then compare the values with the coseismic slip distribution of the main shock reported by Horikawa (2008). If we define large slip areas as areas with a slip exceeding 1 m, the average value of static stress drop is 122.3 (MPa) in the area. On the other hand, the average value is 5.70.9 (MPa) outside the large slip area. These results suggest that aftershocks in the large slip area likely have larger values of static stress drop, which would reflect the spatial heterogeneity of shear strength and dynamic stress level. Our results are coincident with the result of Yamada et al. (2010).

  8. Slip resistance of industrial floor surfaces: development of an elastomer suited to in-situ measurement.

    PubMed

    Leclercq, S; Saulnier, H

    2001-01-01

    Slips contribute to 12% of occupational accidents. A slip resistant floor is a mean to prevent slipping accidents occurring in workshops. Floor slip resistance is often evaluated by measuring a friction index, proportional to the force opposing slipping of a reference elastomer on the floor surface under test. When implementing a portable appliance, slip resistance measurements carried out on lubricated floors were not stabilized. The authors advanced the hypothesis of oil impregnating the elastomer. A new elastomer suited to in-situ measurement has been developed to achieve stable measuring conditions. This study highlights the fact that the nature and characteristics of a reference elastomer must be specified when slip resistance measurements are carried out. PMID:11276267

  9. Slip-induced conservation laws for dislocation structures in the finite kinematic framework

    NASA Astrophysics Data System (ADS)

    Reina, Celia; Marian, Jaime

    2014-09-01

    In the present paper we develop a general framework that captures topological, geometric, and energetic aspects of slip surfaces to provide conservation laws for dislocation structures. In this work, dislocations act as the boundary of active slip regions that support a finite displacement jump, while treating the material outside the slip regions with a continuum mechanic framework in the setting of large deformations. Within this semicontinuous description, it is shown that the condition of slip imposes an important restriction on the shape of the slip surfaces regardless of the material structure. This catalog of shapes for the slip surfaces can be further restricted for crystalline materials, providing a simple geometric description of common dislocation processes such as cross slip or dislocation loop glide. In this setting, the classical Kirchhoff-type rule for the conservation of the Burgers vector emanates directly from the formulation, while recent conservation laws designed for partial dislocations in face centered cubic crystals are also naturally captured.

  10. Historic surface slip along the San Andreas Fault near Parkfield, California

    NASA Astrophysics Data System (ADS)

    Lienkaemper, J. J.; Prescott, W. H.

    1989-12-01

    The Parkfield Earthquake Prediction Experiment is focusing close attention on the 44-km-long section of the San Andreas fault that last ruptured seismically in 1966 (Ms 6.0). The 20-km-long central segment of the 1966 Parkfield rupture, extending from the mainshock epicenter at Middle Mountain southeastward to Gold Hill, forms a 1- to 2-km salient northeastward away from the dominant N40°W strike. Following the 1966 earthquake afterslip, aseismic slip has been nearly constant. Moderate Parkfield earthquakes have recurred on average every 21 years since 1857, when a great earthquake (M≈8) ruptured at least as far north as the southern Parkfield segment. Many measurements of slip have been made near Parkfield since 1966. Nevertheless, much of the history of surface slip remained uncertain, especially the total amount associated with the 1966 event. In 1985 we measured accumulated slip on the four oldest cultural features offset by the fault along the 1966 Parkfield rupture segment. We interpret net slip on each feature as a sum of event slip (sum of coseismic and rapid preseismic and postseismic slip) from Parkfield earthquakes and steady interseismic slip as measured over the last 20 years on nearby alinement arrays, creep meters, and trilateration lines. We assumed for each site that event slip was identical for the 1922, 1934, and 1966 Parkfield events and that long-term average rate of interseismic slip was constant between all events. Two fences on the southern segment, southeast of Gold Hill, indicate event slip of 13 and 15 cm and interseismic slip rate of 0.36 and 0.30 cm/yr since 1959 and 1908, respectively. At these sites, redundant independent data support our assumption that both event and interseismic slip occur uniformly. On the central segment, near Parkfield, both the 1934 and the 1966 ruptures offset a bridge built in 1932. Interseismic slip rate near the bridge has been about 1.1 cm/yr since 1966; thus we deduce an average event slip of 31 cm for the 1934 and 1966 earthquakes. On a parallel fault trace, 1 km to the southwest, slip was about 8 cm in 1966; thus total event slip summed across the entire fault zone near Parkfield was nearly 40 cm. On Middle Mountain, 4 km north of the 1966 mainshock epicenter, an offset fence indicates 17 cm of slip in 1966 and a 2.26-cm/yr interseismic slip rate since circa 1946. Thus the central segment of the 1966 rupture is characterized by much larger event slip (˜40 cm) than both distal segments (˜15 cm). This amount of surface slip per event is about twice what had been previously assumed. Larger 1966 surface slip in the central part of the rupture is geodetically compatible with a coseismic slip of 65±10 cm slip on a narrow, buried asperity between Middle Mountain and Gold Hill that has been inferred from the depth distribution of early aftershocks. Assuming our characteristic surface slip model, one can further deduce a deficit in slip since the great 1857 earthquake. Taking the long-term slip rate as 3.3 cm/yr, the surface slip deficit is 3±0.2 m south of Gold Hill but only 0.3±0.3 m northward from Parkfield.

  11. 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.

  12. High pressure ceramic joint

    DOEpatents

    Ward, Michael E. (Poway, CA); Harkins, Bruce D. (San Diego, CA)

    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.

  13. 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

  14. Comparison of Geodetic and Late Pleistocene Slip Rates for the Southern Dead Sea Fault System

    NASA Astrophysics Data System (ADS)

    Cochran, W. J.; Gomez, F.; Abu Rajab, J. S.; Al-Tarazi, E.

    2012-12-01

    Comparisons of short-term (geodetic) and Late Quaternary slip rates have been used to assess time-variable fault kinematics along various active faults, globally. Differences between such types slip rates may have implications for crustal rheology and/or temporal variations in plate motion. This research aims to compare the geodetically-derived slip rates with slip rates based on Late Pleistocene landforms along the southern Dead Sea fault system (DSFS). The DSFS is an active, left-lateral transform that accommodates differential movement between the Arabian and Sinai plates. A number of slip rates have been previously reported ranging from 2 to 6mm/yr. However, comparison of various slip rates requires ensuring that associated uncertainties are assessed using a standard. New GPS velocities from Jordan are combined with other available GPS data, and are used to model slip rates using elastic block models. Resulting slip rates are 4.3 to 5.3 mm/yr with fault locking depths of 8 - 15 km. Late Pleistocene rates are assessed from published observations, as well as new data. New mapping of offset alluvial fans in the southern Wadi Araba was facilitated by multi-spectral imagery and high-resolution digital elevation model. These fans correlate with regional aggradation events, with the resulting Late Pleistocene slip rates ranging from 4.2 to 5.1 mm/yr. Statistically, the geodetic and neotectonic slip rates are identical. Additionally, a 3-dimensional slip vector for the last earthquake in the northern Wadi Araba is constructed using close-range photogrammetry of a faulted Byzantine aqueduct that indicates both horizontal and vertical displacements. Previous studies suggested characteristic earthquake slip, so slip rates and this slip vector provide a means of assessing mean EQ recurrence interval, as well as the role of earthquakes in constructing the long-term topography along this part of the transform.

  15. On strike-slip faulting in layered media

    NASA Astrophysics Data System (ADS)

    Bonafede, Maurizio; Parenti, Beatrice; Rivalta, Eleonora

    2002-06-01

    We study the effects of structural inhomogeneities on the stress and displacement fields induced by strike-slip faults in layered media. An elastic medium is considered, made up of an upper layer bounded by a free surface and welded to a lower half-space characterized by different elastic parameters. Shear cracks with assigned stress drop are employed as mathematical models of strike-slip faults, which are assumed to be vertical and planar. If the crack is entirely embedded within the lower medium (case A), a Cauchy-kernel integral equation is obtained, which is solved by employing an expansion of the dislocation density in Chebyshev polynomials. If the crack is within the lower medium but it terminates at the interface (case B), a generalized Cauchy singularity appears in the integral kernel. This singularity affects the singular behaviour of the dislocation density at the crack tip touching the interface. Finally, the case of a crack crossing the interface is considered (case C). The crack is split into two interacting sections, each placed in a homogeneous medium and both open at the interface. Two coupled generalized Cauchy equations are obtained and solved for the dislocation density distribution of each crack section. An asymptotic study near the intersection between the crack and the interface shows that the dislocation densities for each crack section are bounded at the interface, where a jump discontinuity is present. As a corollary, the stress drop must be discontinuous at the interface, with a jump proportional to the rigidity contrast between the adjoining media. This finding is shown to have important implications for the development of geometrical complexities within transform fault zones: planar strike-slip faults cutting across layer discontinuities with arbitrary stress drop values are shown to be admissible only if the interface between different layers becomes unwelded during the earthquake at the crack/interface junction. Planar strike-slip faulting may take place only in mature transform zones, where a repetitive earthquake cycle has already developed, if the rheology is perfectly elastic. Otherwise, the fault cannot be planar: we infer that strike-slip faulting at depth is plausibly accompanied by en-echelon surface breaks in a shallow sedimentary layer (where the stress drop is lower than prescribed by the discontinuity condition), while ductile deformation (or steady sliding) at depth may be accommodated by multiple fault branching or by antithetic faulting in the upper brittle layer (endowed with lower rigidity but higher stress).

  16. Improved ceramic slip casting technique. [application to aircraft model fabrication

    NASA Technical Reports Server (NTRS)

    Buck, Gregory M. (Inventor); Vasquez, Peter (Inventor)

    1993-01-01

    A primary concern in modern fluid dynamics research is the experimental verification of computational aerothermodynamic codes. This research requires high precision and detail in the test model employed. Ceramic materials are used for these models because of their low heat conductivity and their survivability at high temperatures. To fabricate such models, slip casting techniques were developed to provide net-form, precision casting capability for high-purity ceramic materials in aqueous solutions. In previous slip casting techniques, block, or flask molds made of plaster-of-paris were used to draw liquid from the slip material. Upon setting, parts were removed from the flask mold and cured in a kiln at high temperatures. Casting detail was usually limited with this technique -- detailed parts were frequently damaged upon separation from the flask mold, as the molded parts are extremely delicate in the uncured state, and the flask mold is inflexible. Ceramic surfaces were also marred by 'parting lines' caused by mold separation. This adversely affected the aerodynamic surface quality of the model as well. (Parting lines are invariably necessary on or near the leading edges of wings, nosetips, and fins for mold separation. These areas are also critical for flow boundary layer control.) Parting agents used in the casting process also affected surface quality. These agents eventually soaked into the mold, the model, or flaked off when releasing the case model. Different materials were tried, such as oils, paraffin, and even an algae. The algae released best, but some of it remained on the model and imparted an uneven texture and discoloration on the model surface when cured. According to the present invention, a wax pattern for a shell mold is provided, and an aqueous mixture of a calcium sulfate-bonded investment material is applied as a coating to the wax pattern. The coated wax pattern is then dried, followed by curing to vaporize the wax pattern and leave a shell mold of the calcium sulfate-bonded investment material. The shell mold is cooled to room temperature, and a ceramic slip is poured therein. After a ceramic shell of desired thickness has set up in the shell mold, excess ceramic slip is poured out. While still wet, the shell mold is peeled from the ceramic shell to expose any delicate or detailed parts, after which the ceramic shell is cured to provide a complete, detailed, precision ceramic article without parting lines.

  17. Excitation of energy harvesters using stick-slip motion

    NASA Astrophysics Data System (ADS)

    Helseth, L. E.

    2014-08-01

    During the past decades a large number of energy harvesting systems with the ability to transform mechanical energy into electrical energy have been proposed, ranging from systems exhibiting pure sinusoidal motion to stochastic systems. However, to date little emphasis has been put on stick-slip motion as a method for excitation of energy harvesting systems. Stick-slip motion can be associated with both microscopic and macroscopic processes and is omnipresent. The motion can be characterized by two stages. In the first stage there is buildup of elastic energy with little associated motion, whereas in the second stage the elastic energy is released into kinetic energy. We study here the spectral signal characteristics of two different electrical generators excited by stick-slip motion: a piezoelectric macro fiber composite and a triboelectric generator. The force and the voltage generated during the motion were monitored, and we found that the signal spectral density of both variables changes with the frequency in a characteristic manner, thus classifying the slip-stick motion as a colored noise excitation scheme. The force spectral density in both systems was found to exhibit a power-law spectrum following an {{f}^{-2}} trend, where f is the frequency. The voltage spectral density was governed by the product of a high-pass filter, the force spectral density, and the intrinsic generator spectral density. Here the piezoelectric generator exhibited a nearly flat voltage spectral density below the cutoff frequency of the high-pass filter and an {{f}^{-2}} spectrum at higher frequencies, thus demonstrating that the piezoelectric coupling coefficient had a nearly flat frequency response. On the other hand, the triboelectric generator had a coupling coefficient with a spectral response that varied in a non-systematic manner, possibly related to the large number of contact sites and relaxation times occurring during operation. The average power delivered by the generators to a resistive load was also measured for sinusoidal mechanical excitations and was compared with the average power generated by stick-slip motion.

  18. Outcomes of subcapital cuneiform osteotomy for the treatment of severe slipped capital femoral epiphysis after skeletal maturity.

    PubMed

    Biring, G S; Hashemi-Nejad, A; Catterall, A

    2006-10-01

    We reviewed prospectively, after skeletal maturity, a series of 24 patients (25 hips) with severe acute-on-chronic slipped capital femoral epiphysis which had been treated by subcapital cuneiform osteotomy. Patients were followed up for a mean of 8 years, 3 months (2 years, 5 months to 16 years, 4 months). Bedrest with 'slings and springs' had been used for a mean of 22 days (19 to 35) in 22 patients, and bedrest alone in two, before definitive surgery. The Iowa hip score, the Harris hip score and Boyer's radiological classification for degenerative disease were used. The mean Iowa hip score at follow-up was 93.7 (69 to 100) and the mean Harris hip score 95.6 (78 to 100). Degenerative joint changes were graded as 0 in 19 hips, grade 1 in four and grade 2 in two. The rate of avascular necrosis was 12% (3 of 25) and the rate of chondrolysis was 16% (4 of 25). We conclude that after a period of bed rest with slings and springs for three weeks to gain stability, subcapital cuneiform osteotomy for severe acute-on-chronic slipped capital femoral epiphysis is a satisfactory method of treatment with an acceptable rate of complication. PMID:17012431

  19. Falls resulting from a laboratory-induced slip occur at a higher rate among individuals who are obese.

    PubMed

    Allin, Leigh J; Wu, Xuefang; Nussbaum, Maury A; Madigan, Michael L

    2016-03-21

    Falls due to slipping are a serious concern, with slipping estimated to cause 40-50% of all fall-related injuries. Epidemiological data indicates that older and obese adults experience more falls than young, non-obese individuals. An increasingly heavier and older U.S. population and workforce may be exacerbating the problem of slip-induced falls. The purpose of this study was to investigate the effects of obesity and age on slip severity and rate of falling resulting from laboratory-induced slips. Four groups of participants (young obese, young non-obese, older obese, older non-obese) were slipped while walking at a self-selected, slightly hurried pace. Slip severity (slip distance, slip duration, mean slip speed and peak slip speed) and slip outcome (fall or recovery) were compared between groups. Obese individuals experienced 22% faster slips than non-obese individuals in terms of mean slip speed (p=0.022). Obesity did not affect slip distance, slip duration or peak slip speed. Obese individuals also exhibited a higher rate of falls; 32% of obese individuals fell compared to 10% of non-obese (p=0.005). Obese individuals were more than eight times more likely to experience a fall than non-obese individuals when adjusting for age, gender and gait speed. No age effects were found for slip severity or slip outcome. These results, along with epidemiological data reporting higher fall rates among the obese, indicate that obesity may be a significant risk factor for experiencing slip-induced falls. Slip severity thresholds were also reported that may have value in developing controls for fall prevention. PMID:26897650

  20. Latest Pleistocene and Holocene slip rates on the Lone Mountain fault: Evidence for accelerating slip in the Silver Peak-Lone Mountain extensional complex

    NASA Astrophysics Data System (ADS)

    Lifton, Zachery M.; Frankel, Kurt L.; Newman, Andrew V.

    2015-03-01

    Determining the constancy of fault slip rates over time is critical in characterizing strain distribution across plate boundaries such as the Pacific-North American plate boundary in the western U.S. We present results from the Lone Mountain fault, a normal fault within the southern Walker Lane, that suggest slip rates there may have increased approximately twofold since the late Pleistocene. We combine detailed field surficial mapping, topographic surveying, and 10Be cosmogenic nuclide exposure ages to calculate new late Pleistocene and Holocene slip rates on the Lone Mountain fault. Alluvial fans with ages of 14.6 1.4 ka and 8.0 0.9 ka are vertically offset 10.2 0.6 m and 4.7 0.6 m, respectively, yielding vertical slip rates of 0.7 0.1 mm/yr and 0.6 0.1 mm/yr. These slip rates are faster than the rates of 0.1 to 0.4 mm/yr from earlier in the Pleistocene, defining a pattern of accelerating slip on the Lone Mountain fault over a timescale of 104 years. The possibility of accelerating slip rates in parts of the Walker Lane partially reconciles the observed discrepancy between long- and short-term slip rates in this region and elucidates the distribution of strain across an evolving plate boundary.

  1. Geometrical and mechanical factors that influence slipped capital femoral epiphysis: a finite element study.

    PubMed

    Castro-Abril, Hector A; Galvn, Fernando; Garzn-Alvarado, Diego A

    2015-09-01

    Slipped capital femoral epiphysis (SCFE) is an orthopedic pathology in which damage of the growth plate leads to the anterosuperior displacement of the femoral body in respect to the femoral head. Despite being a widely studied disease, its etiology is still unknown. This study was carried out to determine the influence of the physeal-diaphysis angle, body mass, the presence of the perichondrial ring, the type of physical activity, and physeal thickness on SCFE. For this purpose, a finite element analysis of the hip joint and the femur-physis interface was carried out. With the computational model, the Von Mises stresses along the growth plate were calculated and subsequently analyzed statistically to find their correlation with the studied factors. It was found that body mass, the type of physical activity, and the presence of the perichondrial ring had more statistical relevance for the physeal stresses than the physeal-diaphysis angle and the physeal thickness. Thus, our work suggests that changes in growth plate inclination and thickness do not influence the etiology of SCFE. PMID:26062006

  2. Workers' experience of slipping in U.S. limited-service restaurants.

    PubMed

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

    2010-09-01

    The leading cause of injuries among restaurant workers is same-level falls, a significant proportion of which result from slipping. This study examines the experience of limited-service restaurant workers with slipping, their use of slip-resistant shoes, and their floor-cleaning practices. A total of 475 workers from 36 limited-service restaurants in six U.S. states participated in a 12-week prospective cohort study on slipping in the workplace. At baseline, participants completed a survey that gathered information about their demographics, perceptions of floor slipperiness, use of slip-resistant shoes, floor cleaning practices, and number of slips experienced in the previous 4 weeks. During the subsequent 12 weeks, participants reported their slip experience weekly. Restaurant managers reported kitchen floor cleaning protocols and shoe policies. The overall rate of slipping during the 12 weeks of the prospective study was 0.44 slips per 40 work hours. The mean of the individual rate of slipping varied among the restaurants from 0.02 to 2.49 slips per 40 work hours, a rate ratio of more than 100 among the restaurants with the highest and the lowest rate of slipping. Such a large variation, which is unlikely due to chance alone (p < 0.05), suggests that some restaurants are better able to control slipping than others. The highest numbers of slips were reported in the sink and fryer areas, which were also identified by restaurant workers as being the most slippery. Liquid and grease were reported as floor contaminants in over 70% of the slips. In restaurants where slip-resistant shoes were provided by the employer, 91% of participants wore them; whereas if they were neither provided nor encouraged, only 53.5% wore them (p < 0.01). Use of enzyme-based floor cleaners was widespread (25/36). In these restaurants, however, 62% of the participants who were responsible for cleaning floors reported using hot/warm water, thus violating the manufacturer's cold water floor cleaning protocol. These findings suggest that focused prevention efforts based on practices from restaurants with low rates of slipping could decrease slipping hazards. PMID:20552500

  3. Rupture process of 2011 Mw7.1 Van, Eastern Turkey earthquake from joint inversion of strong-motion, high-rate GPS, teleseismic, and GPS data

    NASA Astrophysics Data System (ADS)

    Konca, A. Ozgun

    2015-10-01

    We analyzed the rupture process of the 2011 Mw7.1 Van, Eastern Turkey earthquake using teleseismic, strong-motion, 1-Hz GPS waveforms and static GPS displacement measurements. We performed data sensitivity analyses using four different rupture scenarios. Overall, when geodetic and seismic datasets are modeled jointly, slip distribution is well-constrained and rupture velocity can be obtained. The 2011 Van earthquake is a case where none of the available datasets are sufficient to constrain the slip distribution and the rupture kinematics on their own. This study confirms that rather than fitting one dataset perfectly, using multiple datasets jointly leads to a better-constrained slip distribution. The kinematic model obtained from the joint inversion of all the available data shows a 45-km-long bilateral rupture with two sub-events; one larger slip patch propagating up-dip and toward west of the hypocenter and a smaller second slip patch toward the east. The highest slip is to the west of the hypocenter with a peak value of 4.5 m. The slip is confined to the depths of 7.5 to 20 km and the shallower part of the fault remains unbroken. The average rupture velocity is around 3 km/s, close the Rayleigh wave velocity. The rupture is faster with shorter rise times for the larger sub-event toward the west, while the rise times are longer for the smaller sub-event to the east. This difference in seismic behavior might be related to the segmentation of the fault.

  4. Dissimilar metals joint evaluation

    NASA Technical Reports Server (NTRS)

    Wakefield, M. E.; Apodaca, L. E.

    1974-01-01

    Dissimilar metals tubular joints between 2219-T851 aluminum alloy and 304L stainless steel were fabricated and tested to evaluate bonding processes. Joints were fabricated by four processes: (1) inertia (friction) weldings, where the metals are spun and forced together to create the weld; (2) explosive welding, where the metals are impacted together at high velocity; (3) co-extrusion, where the metals are extruded in contact at high temperature to promote diffusion; and (4) swaging, where residual stresses in the metals after a stretching operation maintain forced contact in mutual shear areas. Fifteen joints of each type were prepared and evaluated in a 6.35 cm (2.50 in.) O.D. size, with 0.32 cm (0.13 in.) wall thickness, and 7.6 cm (3.0 in) total length. The joints were tested to evaluate their ability to withstand pressure cycle, thermal cycle, galvanic corrosion and burst tests. Leakage tests and other non-destructive test techniques were used to evaluate the behavior of the joints, and the microstructure of the bond areas was analyzed.

  5. Formation of Exfoliation Joints

    NASA Astrophysics Data System (ADS)

    Martel, S. J.

    2004-12-01

    The Earth's internal stresses interact with the topographic surface to affect many phenomena. Exfoliation joints, or sheeting joints, are widespread manifestations of this interaction. These opening-mode fractures form subparallel to the Earth's surface, bounding roughly concentric slabs of rock that resemble the layers of an onion. They occur worldwide in all major bedrock types, attain in-plane dimensions of hundreds of meters, exert a strong influence on groundwater flow, and help produce spectacular scenery, as in Yosemite National Park. The mechanism that causes them has been enigmatic. They are widely regarded as forming in response to "removal of overburden", but large fractures do not open in rocks merely by relieving a compressive stress. High fluid pressures, thermal effects, rock heterogeneity, and weathering also are rejected as primary causes of these fractures. Tensile stresses normal to the surface are required for large exfoliation fractures to open. Intriguingly, high surface-parallel compressive stresses are widely documented where exfoliation joints occur. Both numerical and analytical solutions for two-dimensional elastic bodies show that localized tensile stresses perpendicular to the ground surface must develop beneath certain topographies subject to strong compressive stresses parallel to the surface. This highly non-intuitive effect reflects the profound influence that topography can have on stresses near the surface of the Earth, and it can explain how exfoliation joints open. The theoretical results also indicate that exfoliation joint distributions could be used to infer the horizontal stresses near the Earth's surface.

  6. A theoretical study of induced-charge dipolophoresis of ideally polarizable asymmetrically slipping Janus particles

    NASA Astrophysics Data System (ADS)

    Boymelgreen, Alicia M.; Miloh, Touvia

    2011-07-01

    We consider the non linear electrophoretic transport of uncharged, ideally polarizable hydrodynamic Janus spheres, the inhomogeneity of which is produced by a variable Navier slip condition at the particle surface. A general, three dimensional formulation enabling calculation of the electrophoretic mobility of any patchy particle, with an arbitrary tensorial slip boundary condition is provided. The solution avoids the common assumption of an infinitely thin electric double layer (λ) and Navier slip coefficient (b) and is thereby valid for finite values of these parameters, which is of particular importance at the nanoscale. The specific case of a Janus sphere, consisting of two equal hemispheres, each with a different but constant slip boundary condition is solved semi-analytically and numerically. In the instance where the slip coefficients at each hemisphere are equal, induced charge electro-osmotic flow is evident at an increased rate as compared to a homogeneous sphere with no slip. If the slip coefficients differ from each other, the particle is found to self-align with the electric field and travel with the slip surface facing forward. The increased pumping rates and mobility found in the cases of the homogeneous and Janus spheres respectively, occur as a function of the ratio b/bλ λ and are most significant for the combination of a thin electric double layer (EDL) and large slip length. However, it is also illustrated that the size of the EDL independently dominates the effects of slip.

  7. Development of microsized slip sensors using dielectric elastomer for incipient slippage

    NASA Astrophysics Data System (ADS)

    Hwang, Do-Yeon; Kim, Baek-chul; Cho, Han-Jeong; Li, Zhengyuan; Lee, Youngkwan; Nam, Jae-Do; Moon, Hyungpil; Choi, Hyouk Ryeol; Koo, J. C.

    2014-04-01

    A humanoid robot hand has received significant attention in various fields of study. In terms of dexterous robot hand, slip detecting tactile sensor is essential to grasping objects safely. Moreover, slip sensor is useful in robotics and prosthetics to improve precise control during manipulation tasks. In this paper, sensor based-human biomimetic structure is fabricated. We reported a resistance tactile sensor that enables to detect a slip on the surface of sensor structure. The resistance slip sensor that the novel developed uses acrylonitrile-butadiene rubber (NBR) as a dielectric substrate and carbon particle as an electrode material. The presented sensor device in this paper has fingerprint-like structures that are similar with the role of the human's finger print. It is possible to measure the slip as the structure of sensor makes a deformation and it change