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Sample records for zone plates fzps

  1. Fresnel zone plate with apodized aperture for hard X-ray Gaussian beam optics.

    PubMed

    Takeuchi, Akihisa; Uesugi, Kentaro; Suzuki, Yoshio; Itabashi, Seiichi; Oda, Masatoshi

    2017-05-01

    Fresnel zone plates with apodized apertures [apodization FZPs (A-FZPs)] have been developed to realise Gaussian beam optics in the hard X-ray region. The designed zone depth of A-FZPs gradually decreases from the center to peripheral regions. Such a zone structure forms a Gaussian-like smooth-shouldered aperture function which optically behaves as an apodization filter and produces a Gaussian-like focusing spot profile. Optical properties of two types of A-FZP, i.e. a circular type and a one-dimensional type, have been evaluated by using a microbeam knife-edge scan test, and have been carefully compared with those of normal FZP optics. Advantages of using A-FZPs are introduced.

  2. Fresnel zone plate stacking in the intermediate field for high efficiency focusing in the hard X-ray regime

    DOE PAGES

    Gleber, Sophie -Charlotte; Wojcik, Michael; Liu, Jie; ...

    2014-11-05

    Focusing efficiency of Fresnel zone plates (FZPs) for X-rays depends on zone height, while the achievable spatial resolution depends on the width of the finest zones. FZPs with optimal efficiency and sub-100-nm spatial resolution require high aspect ratio structures which are difficult to fabricate with current technology especially for the hard X-ray regime. A possible solution is to stack several zone plates. To increase the number of FZPs within one stack, we first demonstrate intermediate-field stacking and apply this method by stacks of up to five FZPs with adjusted diameters. Approaching the respective optimum zone height, we maximized efficiencies formore » high resolution focusing at three different energies, 10, 11.8, and 25 keV.« less

  3. Analysis of Fresnel Zone Plates Focusing Dependence on Operating Frequency

    PubMed Central

    Fuster, José Miguel; Candelas, Pilar; Castiñeira-Ibáñez, Sergio; Pérez-López, Sergio

    2017-01-01

    The focusing properties of Fresnel Zone Plates (FZPs) against frequency are analyzed in this work. It is shown that the FZP focal length depends almost linearly on the operating frequency. Focal depth and focal distortion are also considered, establishing a limit on the frequency span at which the operating frequency can be shifted. An underwater FZP ultrasound focusing system is demonstrated, and experimental results agree with the theoretical analysis and simulations. PMID:29206137

  4. Depth of focus enhancement of a modified imaging quasi-fractal zone plate

    PubMed Central

    Zhang, Qinqin; Wang, Jingang; Wang, Mingwei; Bu, Jing; Zhu, Siwei; Gao, Bruce Z.; Yuan, Xiaocong

    2013-01-01

    We propose a new parameter w for optimization of foci distribution of conventional fractal zone plates (FZPs) with a greater depth of focus (DOF) in imaging. Numerical simulations of DOF distribution on axis directions indicate that the values of DOF can be extended by a factor of 1.5 or more by a modified quasi-FZP. In experiments, we employ a simple object–lens–image-plane arrangement to pick up images at various positions within the DOF of a conventional FZP and a quasi-FZP, respectively. Experimental results show that the parameter w improves foci distribution of FZPs in good agreement with theoretical predictions. PMID:24285908

  5. Depth of focus enhancement of a modified imaging quasi-fractal zone plate.

    PubMed

    Zhang, Qinqin; Wang, Jingang; Wang, Mingwei; Bu, Jing; Zhu, Siwei; Gao, Bruce Z; Yuan, Xiaocong

    2012-10-01

    We propose a new parameter w for optimization of foci distribution of conventional fractal zone plates (FZPs) with a greater depth of focus (DOF) in imaging. Numerical simulations of DOF distribution on axis directions indicate that the values of DOF can be extended by a factor of 1.5 or more by a modified quasi-FZP. In experiments, we employ a simple object-lens-image-plane arrangement to pick up images at various positions within the DOF of a conventional FZP and a quasi-FZP, respectively. Experimental results show that the parameter w improves foci distribution of FZPs in good agreement with theoretical predictions.

  6. Stacked Fresnel Zone Plates for High Energy X-rays

    NASA Astrophysics Data System (ADS)

    Snigireva, Irina; Snigirev, Anatoly; Vaughan, Gavin; Di Michiel, Marco; Kohn, Viktor; Yunkin, Vyacheslav; Grigoriev, Maxim

    2007-01-01

    A stacking technique was developed in order to increase focusing efficiency of Fresnel zone plates (FZP) at high energies. Two identical Si chips each of which containing 9 FZPs were used for stacking. Alignment of the chips was achieved by on-line observation of the moiré pattern. The formation of moiré patterns was studied theoretically and experimentally at different experimental conditions. To provide the desired stability Si-chips were bonded together with slow solidification speed epoxy glue. A technique of angular alignment in order to compensate a linear displacement in the process of gluing was proposed. Two sets of stacked FZPs were experimentally tested to focus 15 and 50 keV x rays. The gain in the efficiency by factor 2.5 was demonstrated at 15 keV. The focal spot of 1.8 μm vertically and 14 μm horizontally with 35% efficiency was measured at 50 keV. Forecast for the stacking of nanofocusing FZPs was discussed.

  7. High-resolution high-efficiency multilayer Fresnel zone plates for soft and hard x-rays

    NASA Astrophysics Data System (ADS)

    Sanli, Umut T.; Keskinbora, Kahraman; Gregorczyk, Keith; Leister, Jonas; Teeny, Nicolas; Grévent, Corinne; Knez, Mato; Schütz, Gisela

    2015-09-01

    X-ray microscopy enables high spatial resolutions, high penetration depths and characterization of a broad range of materials. Calculations show that nanometer range resolution is achievable in the hard X-ray regime by using Fresnel zone plates (FZPs) if certain conditions are satisfied. However, this requires, among other things, aspect ratios of several thousands. The multilayer (ML) type FZPs, having virtually unlimited aspect ratios, are strong candidates to achieve single nanometer resolutions. Our research is focused on the fabrication of ML-FZPs which encompasses deposition of multilayers over a glass fiber via the atomic layer deposition (ALD), which is subsequently sliced in the optimum thickness for the X-ray energy by a focused ion beam (FIB). We recently achieved aberration free imaging by resolving 21 nm features with an efficiency of up to 12.5 %, the highest imaging resolution achieved by an ML-FZP. We also showed efficient focusing of 7.9 keV X-rays down to 30 nm focal spot size (FWHM). For resolutions below ~10 nm, efficiencies would decrease significantly due to wave coupling effects. To compensate this effect high efficiency, low stress materials have to be researched, as lower intrinsic stresses will allow fabrication of larger FZPs with higher number of zones, leading to high light intensity at the focus. As a first step we fabricated an ML-FZP with a diameter of 62 μm, an outermost zone width of 12 nm and 452 active zones. Further strategies for fabrication of high resolution high efficiency multilayer FZPs will also be discussed.

  8. Hard X-ray focusing by stacked Fresnel zone plates

    NASA Astrophysics Data System (ADS)

    Snigireva, Irina; Snigirev, Anatoly; Kohn, Viktor; Yunkin, Vyacheslav; Grigoriev, Maxim; Kuznetsov, Serguei; Vaughan, Gavin; Di Michiel, Marco

    2007-09-01

    Stacking technique was developed in order to increase focusing efficiency of Fresnel zone plates at high energies. Two identical Si chips each of which containing Fresnel zone plates were used for stacking. Alignment of the chips was achieved by on-line observation of the moiré pattern from the two zone plates. The formation of moiré patterns was studied theoretically and experimentally at different experimental conditions. To provide the desired stability Si-chips with zone plates were bonded together with slow solidification speed epoxy glue. Technique of angular alignment in order to compensate a linear displacement in the process of gluing was proposed. Two sets of stacked FZPs were produced and experimentally tested to focus 15 and 50 keV X-rays. Gain in the efficiency by factor 2.5 was demonstrated at 15 keV. Focal spot of 1.8 μm vertically and 14 μm horizontally with 35% efficiency was measured at 50 keV. Forecast for the stacking of nanofocusing Fresnel zone plates was discussed.

  9. Fibonacci-like zone plate

    NASA Astrophysics Data System (ADS)

    Cheng, Shubo; Liu, Mengsi; Xia, Tian; Tao, Shaohua

    2018-06-01

    We present a new family of diffractive lenses, Fibonacci-like zone plates, generated with a modified Fibonacci sequence. The focusing properties and the evolution of transverse diffraction pattern for the Fibonacci-like zone plates have been analytically investigated both theoretically and experimentally and compared with the corresponding Fresnel zone plates of the same resolution. The results demonstrate that the Fibonacci-like zone plates possess the self-similar property and the multifocal behavior. Furthermore, the Fibonacci-like zone plate beams are found to possess the self-reconstruction property, and would be promising for 3D optical tweezers, laser machining, and optical imaging.

  10. The generalized mean zone plate

    NASA Astrophysics Data System (ADS)

    Xia, Tian; Cheng, Shubo; Tao, Shaohua

    2018-06-01

    In this paper a generalized mean zone plate is proposed, which generates twin foci located at the positions satisfying the expression of the generalized mean, which includes the m-golden mean, precious mean, and so on. The generalized mean zone plate can be designed to generate twin foci with various position ratios. The diffraction properties of the generalized mean zone plates have been investigated with simulations and experiments. The results show that the ratio of the positions of the twin foci for the generalized mean zone plate can be designed with the selected zone plate parameters.

  11. High-performance etching of multilevel phase-type Fresnel zone plates with large apertures

    NASA Astrophysics Data System (ADS)

    Guo, Chengli; Zhang, Zhiyu; Xue, Donglin; Li, Longxiang; Wang, Ruoqiu; Zhou, Xiaoguang; Zhang, Feng; Zhang, Xuejun

    2018-01-01

    To ensure the etching depth uniformity of large-aperture Fresnel zone plates (FZPs) with controllable depths, a combination of a point source ion beam with a dwell-time algorithm has been proposed. According to the obtained distribution of the removal function, the latter can be used to optimize the etching time matrix by minimizing the root-mean-square error between the simulation results and the design value. Owing to the convolution operation in the utilized algorithm, the etching depth error is insensitive to the etching rate fluctuations of the ion beam, thereby reducing the requirement for the etching stability of the ion system. As a result, a 4-level FZP with a circular aperture of 300 mm was fabricated. The obtained results showed that the etching depth uniformity of the full aperture could be reduced to below 1%, which was sufficiently accurate for meeting the use requirements of FZPs. The proposed etching method may serve as an alternative way of etching high-precision diffractive optical elements with large apertures.

  12. Broadband polarization gratings for efficient liquid crystal display, beam steering, spectropolarimetry, and Fresnel zone plate

    NASA Astrophysics Data System (ADS)

    Oh, Chulwoo

    displays is the polymer-PG display, which allows an immediate brightness improvement (up to a factor of two) of conventional LC displays by replacing absorbing polarizers with achromatic PGs as thin, transmissive polymer films. We demonstrate the first proof-of-concept prototype projector based on the polymer-PG display and we also discuss optical design considerations and challenges toward a viable solution for our ultrabright pico-projector applications of the polymer-PG display. Second, two novel beam steering concepts based on the PG diffraction have been proposed. The polarization-sensitive diffraction of the PGs provides very attractive beam steering operations with ultra-high efficiency over wide steering angles by all-thin-plate electro-optical systems. We developed a non-mechanical, wide-angle beam steering system using stacked PGs and LC waveplates, and we also demonstrated a continuous beam steering using two rotating PGs, named the Risley grating as a thin-plate version of the Risley prism. The third PG application is in imaging and non-imaging spectropolarimetry. We have shown a snapshot, hyperspectral, full-Stokes polarimeter using inline PGs and quarter-waveplates. The use of PGs as a new polarimetric element for astronomical instruments in the mid-wave IR wavelengths also has been proposed to overcome current limitations of existing IR polarimeters. In the last part of this Dissertation, we introduce a polarization-type Fresnel zone plates (P-FZPs), comprising of spatially distributed linear birefringence or concentric PG (CPG) patterns. Effective fabrication methods of P-FZPs have been developed using polarization holography based on the Michelson interferometer and photoalignment of LC materials. We demonstrated high-quality P-FZPs, which exhibit ideal Fresnel-type lens effects, formed as both LC polymer films and electro-optical LC devices. We also discuss the polarization-selective lens properties of the P-FZPs as well as their electro-optical switching

  13. Rapid prototyping of Fresnel zone plates via direct Ga(+) ion beam lithography for high-resolution X-ray imaging.

    PubMed

    Keskinbora, Kahraman; Grévent, Corinne; Eigenthaler, Ulrike; Weigand, Markus; Schütz, Gisela

    2013-11-26

    A significant challenge to the wide utilization of X-ray microscopy lies in the difficulty in fabricating adequate high-resolution optics. To date, electron beam lithography has been the dominant technique for the fabrication of diffractive focusing optics called Fresnel zone plates (FZP), even though this preparation method is usually very complicated and is composed of many fabrication steps. In this work, we demonstrate an alternative method that allows the direct, simple, and fast fabrication of FZPs using focused Ga(+) beam lithography practically, in a single step. This method enabled us to prepare a high-resolution FZP in less than 13 min. The performance of the FZP was evaluated in a scanning transmission soft X-ray microscope where nanostructures as small as sub-29 nm in width were clearly resolved, with an ultimate cutoff resolution of 24.25 nm, demonstrating the highest first-order resolution for any FZP fabricated by the ion beam lithography technique. This rapid and simple fabrication scheme illustrates the capabilities and the potential of direct ion beam lithography (IBL) and is expected to increase the accessibility of high-resolution optics to a wider community of researchers working on soft X-ray and extreme ultraviolet microscopy using synchrotron radiation and advanced laboratory sources.

  14. Linear optical pulse compression based on temporal zone plates.

    PubMed

    Li, Bo; Li, Ming; Lou, Shuqin; Azaña, José

    2013-07-15

    We propose and demonstrate time-domain equivalents of spatial zone plates, namely temporal zone plates, as alternatives to conventional time lenses. Both temporal intensity zone plates, based on intensity-only temporal modulation, and temporal phase zone plates, based on phase-only temporal modulation, are introduced and studied. Temporal zone plates do not exhibit the limiting tradeoff between temporal aperture and frequency bandwidth (temporal resolution) of conventional linear time lenses. As a result, these zone plates can be ideally designed to offer a time-bandwidth product (TBP) as large as desired, practically limited by the achievable temporal modulation bandwidth (limiting the temporal resolution) and the amount of dispersion needed in the target processing systems (limiting the temporal aperture). We numerically and experimentally demonstrate linear optical pulse compression by using temporal zone plates based on linear electro-optic temporal modulation followed by fiber-optics dispersion. In the pulse-compression experiment based on temporal phase zone plates, we achieve a resolution of ~25.5 ps over a temporal aperture of ~5.77 ns, representing an experimental TBP larger than 226 using a phase-modulation amplitude of only ~0.8π rad. We also numerically study the potential of these devices to achieve temporal imaging of optical waveforms and present a comparative analysis on the performance of different temporal intensity and phase zone plates.

  15. Strength of plate coupling in the southern Ryukyu subduction zone

    NASA Astrophysics Data System (ADS)

    Doo, Wen-Bin; Lo, Chung-Liang; Wu, Wen-Nan; Lin, Jing-Yi; Hsu, Shu-Kun; Huang, Yin-Sheng; Wang, Hsueh-Fen

    2018-01-01

    Understanding the strength of a plate coupling is critical for assessing potential seismic and tsunamic hazards in subduction zones. The interaction between an overriding plate and the associated subducting plate can be used to evaluate the strength of plate coupling by examining the mantle lithospheric buoyancy. Here, we calculate the mantle lithosphere buoyancy across the northern portion of the southern Ryukyu subduction zone based on gravity modeling with the constraints from a newly derived P-wave seismic velocity model. The result indicates that the strength of the plate coupling in the study area is relatively strong, which is consistent with previous observations in the southernmost Ryukyu subduction zone. Because few large earthquakes (Mw > 7) have occurred in the southern Ryukyu subduction zone, a large amount of energy is locked and accumulated by plate coupling, that could be released in the near future.

  16. Optimized square Fresnel zone plates for microoptics applications

    NASA Astrophysics Data System (ADS)

    Rico-García, José María; Salgado-Remacha, Francisco Javier; Sanchez-Brea, Luis Miguel; Alda, Javier

    2009-06-01

    Polygonal Fresnel zone plates with a low number of sides have deserved attention in micro and nanoptics, because they can be straightforwardly integrated in photonic devices, and, at the same time, they represent a balance between the high-focusing performance of a circular zone plate and the easiness of fabrication at micro and nano-scales of polygons. Among them, the most representative family are Square Fresnel Zone Plates (SFZP). In this work, we propose two different customized designs of SFZP for optical wavelengths. Both designs are based on the optimization of a SFZP to perform as close as possible as a usual Fresnel Zone Plate. In the first case, the criterion followed to compute it is the minimization of the difference between the area covered by the angular sector of the zone of the corresponding circular plate and the one covered by the polygon traced on the former. Such a requirement leads to a customized polygon-like Fresnel zone. The simplest one is a square zone with a pattern of phases repeating each five zones. On the other hand, an alternative SFZP can be designed guided by the same criterion but with a new restriction. In this case, the distance between the borders of different zones remains unaltered. A comparison between the two lenses is carried out. The irradiance at focus is computed for both and suitable merit figures are defined to account for the difference between them.

  17. Theoretical model of the helium zone plate microscope

    NASA Astrophysics Data System (ADS)

    Salvador Palau, Adrià; Bracco, Gianangelo; Holst, Bodil

    2017-01-01

    Neutral helium microscopy is a new technique currently under development. Its advantages are the low energy, charge neutrality, and inertness of the helium atoms, a potential large depth of field, and the fact that at thermal energies the helium atoms do not penetrate into any solid material. This opens the possibility, among others, for the creation of an instrument that can measure surface topology on the nanoscale, even on surfaces with high aspect ratios. One of the most promising designs for helium microscopy is the zone plate microscope. It consists of a supersonic expansion helium beam collimated by an aperture (skimmer) focused by a Fresnel zone plate onto a sample. The resolution is determined by the focal spot size, which depends on the size of the skimmer, the optics of the system, and the velocity spread of the beam through the chromatic aberrations of the zone plate. An important factor for the optics of the zone plate is the width of the outermost zone, corresponding to the smallest opening in the zone plate. The width of the outermost zone is fabrication limited to around 10 nm with present-day state-of-the-art technology. Due to the high ionization potential of neutral helium atoms, it is difficult to build efficient helium detectors. Therefore, it is crucial to optimize the microscope design to maximize the intensity for a given resolution and width of the outermost zone. Here we present an optimization model for the helium zone plate microscope. Assuming constant resolution and width of the outermost zone, we are able to reduce the problem to a two-variable problem (zone plate radius and object distance) and we show that for a given beam temperature and pressure, there is always a single intensity maximum. We compare our model with the highest-resolution zone plate focusing images published and show that the intensity can be increased seven times. Reducing the width of the outermost zone to 10 nm leads to an increase in intensity of more than 8000

  18. Zone plate lenses for X-ray microscopy

    NASA Astrophysics Data System (ADS)

    Vladimirsky, Y.; Kern, D. P.; Chang, T. H. P.; Attwood, D. T.; Iskander, N.; Rothman, S.; McQuaide, K.; Kirz, J.; Ade, H.; McNulty, I.; Rarback, H.; Shu, D.

    1988-04-01

    Fresnel zone plate lenses with feature sizes as small as 50 nm have been constructed and used in the Stony Brook/NSLS scanning X-ray microscope with 3.1 nm radiation from Brookhaven's X-17 mini-undulator. The zone plates were fabricated at IBM using electron beam writing techniques, moiré pattern techniques to monitor ellipticity, and a double development/double plating technique to provide additional thickness in the central region. A spatial resolution down to 75 nm was measured in the microscope. Using these zone plates, biological images were obtained of unaltered subcellular components. The images highlight protein concentration in unsectioned, unfixed, and unstained enzymatic granules in an aqueous environment.

  19. Soft x-ray microscope with zone plates at UVSOR

    NASA Astrophysics Data System (ADS)

    Watanabe, Norio; Shimanuki, Yoshio; Taniguchi, Mieko; Kihara, Hiroshi

    1993-01-01

    A soft x-ray microscope with zone plates was set up at UVSOR (Okazaki, Japan). A 0.41 micrometers line and space pattern was clearly distinguished using an objective zone plate with the outermost zone width of 0.41 micrometers . Modulation transfer functions were measured at wavelengths of 3.1 nm and 5.4 nm, and compared with theoretical calculations. Considering the resolution of a microchannel plate used as a detector, the agreement is fairly good. With this microscope, some biological specimens such as diatoms, spicule of trepang, crab and rabbit muscles, human blood cells, human chromosomes, and magnetotactic bacterium were observed at 3.1 nm and 5.4 nm. With an environmental chamber (wet cell) using polypropylene foils as windows, wet specimens were observed at a wavelength of 4.6 nm. Images of spicule of trepang, human blood cell, and cultured protoplast of plant cell stained by methyl mercury were observed with good contrast.

  20. Sharp acoustic vortex focusing by Fresnel-spiral zone plates

    NASA Astrophysics Data System (ADS)

    Jiménez, Noé; Romero-García, Vicent; García-Raffi, Luis M.; Camarena, Francisco; Staliunas, Kestutis

    2018-05-01

    We report the optimal focusing of acoustic vortex beams by using flat lenses based on a Fresnel-spiral diffraction grating. The flat lenses are designed by spiral-shaped Fresnel zone plates composed of one or several arms. The constructive and destructive interferences of the diffracted waves by the spiral grating result in sharp acoustic vortex beams, following the focal laws obtained in analogy with the Fresnel zone plate lenses. In addition, we show that the number of arms determines the topological charge of the vortex, allowing the precise manipulation of the acoustic wave field by flat lenses. The experimental results in the ultrasonic regime show excellent agreement with the theory and full-wave numerical simulations. A comparison with beam focusing by Archimedean spirals also showing vortex focusing is given. The results of this work may have potential applications for particle trapping, ultrasound therapy, imaging, or underwater acoustic transmitters.

  1. A Fresnel zone plate collimator: potential and aberrations

    NASA Astrophysics Data System (ADS)

    Menz, Benedikt; Bräuninger, Heinrich; Burwitz, Vadim; Hartner, Gisela; Predehl, Peter

    2015-09-01

    A collimator, that parallelizes an X-ray beam, provides a significant improvement of the metrology to characterize X-ray optics for space instruments at MPE's PANTER X-ray test facility. A Fresnel zone plate was selected as a collimating optic, as it meets a good angular resolution < 0.1n combined with a large active area > 10 cm2. Such an optic is ideally suited to illuminate Silicon Pore Optic (SPO) modules as proposed for ATHENA. This paper provides the theoretic description of such a Fresnel zone plate especially considering resolution and efficiency. Based on the theoretic results the collimator setup performance is analyzed and requirements for fabrication and alignment are calculated.

  2. Ti/Al multilayer zone plate and Bragg-Fresnel lens.

    PubMed

    Koike, M; Suzuki, I H; Komiya, S; Amemiya, Y

    1998-05-01

    By using a helicon plasma sputtering technique, a one-dimensional Ti/Al multilayer zone plate with an outermost layer width of 76 nm has been successfully fabricated. A Bragg-Fresnel lens has been made by combining this zone plate with a Ge(422) crystal. Comparison of the Ti/Al multilayer zone plate with the Ag/Al zone plate is discussed in terms of focusing efficiency.

  3. Geophysical Limitations on the Habitable Zone: Volcanism and Plate Tectonics

    NASA Astrophysics Data System (ADS)

    Noack, Lena; Rivoldini, Attilio; Van Hoolst, Tim

    2016-04-01

    Planets are typically classified as potentially life-bearing planets (i.e. habitable planets) if they are rocky planets and if a liquid (e.g. water) could exist at the surface. The latter depends on several factors, like for example the amount of available solar energy, greenhouse effects in the atmosphere and an efficient CO2-cycle. However, the definition of the habitable zone should be updated to include possible geophysical constraints, that could potentially influence the CO2-cycle. Planets like Mars without plate tectonics and no or only limited volcanic events can only be considered to be habitable at the inner boundary of the habitable zone, since the greenhouse effect needed to ensure liquid surface water farther away from the sun is strongly reduced. We investigate if the planet mass as well as the interior structure can set constraints on the occurrence of plate tectonics and outgassing, and therefore affect the habitable zone, using both parameterized evolution models [1] and mantle convection simulations [1,2]. We find that plate tectonics, if it occurs, always leads to sufficient volcanic outgassing and therefore greenhouse effect needed for the outer boundary of the habitable zone (several tens of bar CO2), see also [3]. One-plate planets, however, may suffer strong volcanic limitations. The existence of a dense-enough CO2 atmosphere allowing for the carbon-silicate cycle and release of carbon at the outer boundary of the habitable zone may be strongly limited for planets: 1) without plate tectonics, 2) with a large planet mass, and/or 3) a high iron content. Acknowledgements This work has been funded by the Interuniversity Attraction Poles Programme initiated by the Belgian Science Policy Office through the Planet Topers alliance, and results within the collaboration of the COST Action TD 1308. References Noack, L., Rivoldini, A., and Van Hoolst, T.: CHIC - Coupling Habitability, Interior and Crust, INFOCOMP 2015, ISSN 2308-3484, ISBN 978

  4. Owen Fracture Zone: The Arabia-India plate boundary unveiled

    NASA Astrophysics Data System (ADS)

    Fournier, M.; Chamot-Rooke, N.; Rodriguez, M.; Huchon, P.; Petit, C.; Beslier, M. O.; Zaragosi, S.

    2011-02-01

    We surveyed the Owen Fracture Zone at the boundary between the Arabia and India plates in the NW Indian Ocean using a high-resolution multibeam echo-sounder (Owen cruise, 2009) for search of active faults. Bathymetric data reveal a previously unrecognized submarine fault scarp system running for over 800 km between the Sheba Ridge in the Gulf of Aden and the Makran subduction zone. The primary plate boundary structure is not the bathymetrically high Owen Ridge, but is instead a series of clearly delineated strike-slip fault segments separated by several releasing and restraining bends. Despite an abundant sedimentary supply by the Indus River flowing from the Himalaya, fault scarps are not obscured by recent deposits and can be followed over hundreds of kilometres, pointing to very active tectonics. The total strike-slip displacement of the fault system is 10-12 km, indicating that it has been active for the past ~ 3 to 6 Ma if its current rate of motion of 3 ± 1 mm yr- 1 has remained stable. We describe the geometry of this recent fault system, including a major pull-apart basin at the latitude 20°N, and we show that it closely follows an arc of small circle centred on the Arabia-India pole of rotation, as expected for a transform plate boundary.

  5. Mechanical design of multiple zone plates precision alignment apparatus for hard X-ray focusing in twenty-nanometer scale

    SciTech Connect

    Shu, Deming; Liu, Jie; Gleber, Sophie C.

    An enhanced mechanical design of multiple zone plates precision alignment apparatus for hard x-ray focusing in a twenty-nanometer scale is provided. The precision alignment apparatus includes a zone plate alignment base frame; a plurality of zone plates; and a plurality of zone plate holders, each said zone plate holder for mounting and aligning a respective zone plate for hard x-ray focusing. At least one respective positioning stage drives and positions each respective zone plate holder. Each respective positioning stage is mounted on the zone plate alignment base frame. A respective linkage component connects each respective positioning stage and the respectivemore » zone plate holder. The zone plate alignment base frame, each zone plate holder and each linkage component is formed of a selected material for providing thermal expansion stability and positioning stability for the precision alignment apparatus.« less

  6. Thin Fresnel zone plate lenses for focusing underwater sound

    SciTech Connect

    Calvo, David C., E-mail: david.calvo@nrl.navy.mil; Thangawng, Abel L.; Nicholas, Michael

    A Fresnel zone plate (FZP) lens of the Soret type creates a focus by constructive interference of waves diffracted through open annular zones in an opaque screen. For underwater sound below MHz frequencies, a large FZP that blocks sound using high-impedance, dense materials would have practical disadvantages. We experimentally and numerically investigate an alternative approach of creating a FZP with thin (0.4λ) acoustically opaque zones made of soft silicone rubber foam attached to a thin (0.1λ) transparent rubber substrate. An ultra-thin (0.0068λ) FZP that achieves higher gain is also proposed and simulated which uses low-volume fraction, bubble-like resonant air ringmore » cavities to construct opaque zones. Laboratory measurements at 200 kHz indicate that the rubber foam can be accurately modeled as a lossy fluid with an acoustic impedance approximately 1/10 that of water. Measured focal gains up to 20 dB agree with theoretical predictions for normal and oblique incidence. The measured focal radius of 0.68λ (peak-to-null) agrees with the Rayleigh diffraction limit prediction of 0.61 λ/NA (NA = 0.88) for a low-aberration lens.« less

  7. Thin Fresnel zone plate lenses for focusing underwater sound

    NASA Astrophysics Data System (ADS)

    Calvo, David C.; Thangawng, Abel L.; Nicholas, Michael; Layman, Christopher N.

    2015-07-01

    A Fresnel zone plate (FZP) lens of the Soret type creates a focus by constructive interference of waves diffracted through open annular zones in an opaque screen. For underwater sound below MHz frequencies, a large FZP that blocks sound using high-impedance, dense materials would have practical disadvantages. We experimentally and numerically investigate an alternative approach of creating a FZP with thin (0.4λ) acoustically opaque zones made of soft silicone rubber foam attached to a thin (0.1λ) transparent rubber substrate. An ultra-thin (0.0068λ) FZP that achieves higher gain is also proposed and simulated which uses low-volume fraction, bubble-like resonant air ring cavities to construct opaque zones. Laboratory measurements at 200 kHz indicate that the rubber foam can be accurately modeled as a lossy fluid with an acoustic impedance approximately 1/10 that of water. Measured focal gains up to 20 dB agree with theoretical predictions for normal and oblique incidence. The measured focal radius of 0.68λ (peak-to-null) agrees with the Rayleigh diffraction limit prediction of 0.61 λ/NA (NA = 0.88) for a low-aberration lens.

  8. X-ray ptychography using randomized zone plates

    DOE PAGES

    Morrison, G. R.; Zhang, F.; Robinson, Ian K.; ...

    2018-05-31

    We have developed a randomized grating condenser zone plate (GCZP) that provides a μm-scale probe for use in x-ray ptychography. This delivers a significantly better x-ray throughput than probes defined by pinhole apertures, while providing a clearly-defined level of phase diversity to the illumination on the sample, and helping to reduce the dynamic range of the detected signal by spreading the zero-order light over an extended area of the detector. The first use of this novel x-ray optical element has been demonstrated successfully for both amplitude and phase contrast imaging using soft x-rays on the TwinMic beamline at the Elettramore » synchrotron.« less

  9. X-ray ptychography using randomized zone plates

    SciTech Connect

    Morrison, G. R.; Zhang, F.; Robinson, Ian K.

    We have developed a randomized grating condenser zone plate (GCZP) that provides a μm-scale probe for use in x-ray ptychography. This delivers a significantly better x-ray throughput than probes defined by pinhole apertures, while providing a clearly-defined level of phase diversity to the illumination on the sample, and helping to reduce the dynamic range of the detected signal by spreading the zero-order light over an extended area of the detector. The first use of this novel x-ray optical element has been demonstrated successfully for both amplitude and phase contrast imaging using soft x-rays on the TwinMic beamline at the Elettramore » synchrotron.« less

  10. Hidden Earthquake Potential in Plate Boundary Transition Zones

    NASA Astrophysics Data System (ADS)

    Furlong, Kevin P.; Herman, Matthew; Govers, Rob

    2017-04-01

    Plate boundaries can exhibit spatially abrupt changes in their long-term tectonic deformation (and associated kinematics) at triple junctions and other sites of changes in plate boundary structure. How earthquake behavior responds to these abrupt tectonic changes is unclear. The situation may be additionally obscured by the effects of superimposed deformational signals - juxtaposed short-term (earthquake cycle) kinematics may combine to produce a net deformational signal that does not reflect intuition about the actual strain accumulation in the region. Two examples of this effect are in the vicinity of the Mendocino triple junction (MTJ) along the west coast of North America, and at the southern end of the Hikurangi subduction zone, New Zealand. In the region immediately north of the MTJ, GPS-based observed crustal displacements (relative to North America (NAm)) are intermediate between Pacific and Juan de Fuca (JdF) motions. With distance north, these displacements rotate to become more aligned with JdF - NAm displacements, i.e. to motions expected along a coupled subduction interface. The deviation of GPS motions from the coupled subduction interface signal near the MTJ has been previously interpreted to reflect clock-wise rotation of a coastal, crustal block and/or reduced coupling at the southern Cascadia margin. The geologic record of crustal deformation near the MTJ reflects the combined effects of northward crustal shortening (on geologic time scales) associated with the MTJ Crustal Conveyor (Furlong and Govers, 1999) overprinted onto the subduction earthquake cycle signal. With this interpretation, the Cascadia subduction margin appears to be well-coupled along its entire length, consistent with paleo-seismic records of large earthquake ruptures extending to its southern limit. At the Hikurangi to Alpine Fault transition in New Zealand, plate interactions switch from subduction to oblique translation as a consequence of changes in lithospheric structure of

  11. High efficiency x-ray nanofocusing by the blazed stacking of binary zone plates

    NASA Astrophysics Data System (ADS)

    Mohacsi, I.; Karvinen, P.; Vartiainen, I.; Diaz, A.; Somogyi, A.; Kewish, C. M.; Mercere, P.; David, C.

    2013-09-01

    The focusing efficiency of binary Fresnel zone plate lenses is fundamentally limited and higher efficiency requires a multi step lens profile. To overcome the manufacturing problems of high resolution and high efficiency multistep zone plates, we investigate the concept of stacking two different binary zone plates in each other's optical near-field. We use a coarse zone plate with π phase shift and a double density fine zone plate with π/2 phase shift to produce an effective 4- step profile. Using a compact experimental setup with piezo actuators for alignment, we demonstrated 47.1% focusing efficiency at 6.5 keV using a pair of 500 μm diameter and 200 nm smallest zone width. Furthermore, we present a spatially resolved characterization method using multiple diffraction orders to identify manufacturing errors, alignment errors and pattern distortions and their effect on diffraction efficiency.

  12. Imaging megathrust zone and Yakutat/Pacific plate interface in Alaska subduction zone

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Abers, G. A.; Li, J.; Christensen, D. H.; Calkins, J. A.

    2012-12-01

    We image the subducted slab underneath a 450 km long transect of the Alaska subduction zone. Dense stations in southern Alaska are set up to investigate (1) the geometry and velocity structure of the downgoing plate and their relation to slab seismicity, and (2) the interplate coupled zone where the great 1964 (magnitude 9.3) had greatest rupture. The joint teleseismic migration of two array datasets (MOOS, Multidisciplinary Observations of Onshore Subduction, and BEAAR, Broadband Experiment Across the Alaska Range) based on teleseismic receiver functions (RFs) using the MOOS data reveal a shallow-dipping prominent low-velocity layer at ~25-30 km depth in southern Alaska. Modeling of these RF amplitudes shows a thin (3-6.5 km) low-velocity layer (shear wave velocity less than 3 km/s), which is ~20-30% slower than normal oceanic crustal velocities, between the subducted slab and the overriding North America plate. The observed low-velocity megathrust layer (with Vp/Vs ratio exceeding 2.0) may be due to a thick sediment input from the trench in combination of elevated pore fluid pressure in the channel. The subducted crust below the low-velocity channel has gabbroic velocities with a thickness of 11-15 km. Both velocities and thickness of the low-velocity channel abruptly increase as the slab bends in central Alaska, which agrees with previously published RF results. Our image also includes an unusually thick low-velocity crust subducting with a ~20 degree dip down to 130 km depth at approximately 200 km inland beneath central Alaska. The unusual nature of this subducted segment has been suggested to be due to the subduction of the Yakutat terrane. Subduction of this buoyant crust could explain the shallow dip of the thrust zone beneath southern Alaska. We also show a clear image of the Yakutat and Pacific plate subduction beneath the Kenai Peninsula, and the along-strike boundary between them at megathrust depths. Our imaged western edge of the Yakutat terrane, at

  13. Hard X-ray multilayer zone plate with 25-nm outermost zone width

    NASA Astrophysics Data System (ADS)

    Takano, H.; Sumida, K.; Hirotomo, H.; Koyama, T.; Ichimaru, S.; Ohchi, T.; Takenaka, H.; Kagoshima, Y.

    2017-06-01

    We have improved the performance of a previously reported multilayer zone plate by reducing its outermost zone width, using the same multilayer materials (MoSi2 and Si) and fabrication technique. The focusing performance was evaluated at the BL24XU of SPring-8 using 20-keV X-rays. The line spread function (LSF) in the focal plane was measured using a dark-field knife-edge scan method, and the point spread function was obtained from the LSF through a tomographic reconstruction principle. The spatial resolution was estimated to be 30 nm, which is in relatively good agreement with the calculated diffraction-limited value of 25 nm, while the measured diffraction efficiency of the +1st order was 24%.

  14. Zone plate method for electronic holographic display using resolution redistribution technique.

    PubMed

    Takaki, Yasuhiro; Nakamura, Junya

    2011-07-18

    The resolution redistribution (RR) technique can increase the horizontal viewing-zone angle and screen size of electronic holographic display. The present study developed a zone plate method that would reduce hologram calculation time for the RR technique. This method enables calculation of an image displayed on a spatial light modulator by performing additions of the zone plates, while the previous calculation method required performing the Fourier transform twice. The derivation and modeling of the zone plate are shown. In addition, the look-up table approach was introduced for further reduction in computation time. Experimental verification using a holographic display module based on the RR technique is presented.

  15. Fresnel zone plate light field spectral imaging simulation

    NASA Astrophysics Data System (ADS)

    Hallada, Francis D.; Franz, Anthony L.; Hawks, Michael R.

    2017-05-01

    Through numerical simulation, we have demonstrated a novel snapshot spectral imaging concept using binary diffractive optics. Binary diffractive optics, such as Fresnel zone plates (FZP) or photon sieves, can be used as the single optical element in a spectral imager that conducts both imaging and dispersion. In previous demonstrations of spectral imaging with diffractive optics, the detector array was physically translated along the optic axis to measure different image formation planes. In this new concept the wavelength-dependent images are constructed synthetically, by using integral photography concepts commonly applied to light field (plenoptic) cameras. Light field cameras use computational digital refocusing methods after exposure to make images at different object distances. Our concept refocuses to make images at different wavelengths instead of different object distances. The simulations in this study demonstrate this concept for an imager designed with a FZP. Monochromatic light from planar sources is propagated through the system to a measurement plane using wave optics in the Fresnel approximation. Simple images, placed at optical infinity, are illuminated by monochromatic sources and then digitally refocused to show different spectral bins. We show the formation of distinct images from different objects, illuminated by monochromatic sources in the VIS/NIR spectrum. Additionally, this concept could easily be applied to imaging in the MWIR and LWIR ranges. In conclusion, this new type of imager offers a rugged and simple optical design for snapshot spectral imaging and warrants further development.

  16. Imaging megathrust zone and Yakutat/Pacific plate interface in Alaska subduction zone

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Abers, G. A.; Li, J.; Christensen, D. H.; Calkins, J. A.

    2013-05-01

    We image the subducted slab underneath a 450 km long transect of the Alaska subduction zone. Dense stations in southern Alaska are set up to investigate (1) the geometry and velocity structure of the downgoing plate and their relation to slab seismicity, and (2) the interplate coupled zone where the great 1964 (magnitude 9.3) had greatest rupture. The joint teleseismic migration of two array datasets (MOOS, Multidisciplinary Observations of Onshore Subduction, and BEAAR, Broadband Experiment Across the Alaska Range) based on teleseismic receiver functions (RFs) using the MOOS data reveal a shallow-dipping prominent low-velocity layer at ~25-30 km depth in southern Alaska. Modeling of these RF amplitudes shows a thin (<6.5 km) low-velocity layer (shear wave velocity of ~3 km/s), which is ~20-30% slower than normal oceanic crustal velocities, between the subducted slab and the overriding North American plate. The observed low-velocity megathrust layer (with P-to-S velocity ratio (Vp/Vs) exceeding 2.0) may be due to a thick sediment input from the trench in combination of elevated pore fluid pressure in the channel. The subducted crust below the low-velocity channel has gabbroic velocities with a thickness of 11-12 km. Both velocities and thickness of the low-velocity channel abruptly increase as the slab bends in central Alaska, which agrees with previously published RF results. Our image also includes an unusually thick low-velocity crust subducting with a ~20 degree dip down to 130 km depth at approximately 200 km inland beneath central Alaska. The unusual nature of this subducted segment has been suggested to be due to the subduction of the Yakutat terrane. We also show a clear image of the Yakutat and Pacific plate subduction beneath the Kenai Peninsula, and the along-strike boundary between them at megathrust depths. Our imaged western edge of the Yakutat terrane, at 25-30 km depth in the central Kenai along the megathrust, aligns with the western end of the

  17. Sub-25-nm laboratory x-ray microscopy using a compound Fresnel zone plate.

    PubMed

    von Hofsten, Olov; Bertilson, Michael; Reinspach, Julia; Holmberg, Anders; Hertz, Hans M; Vogt, Ulrich

    2009-09-01

    Improving the resolution in x-ray microscopes is of high priority to enable future applications in nanoscience. However, high-resolution zone-plate optics often have low efficiency, which makes implementation in laboratory microscopes difficult. We present a laboratory x-ray microscope based on a compound zone plate. The compound zone plate utilizes multiple diffraction orders to achieve high resolution while maintaining reasonable efficiency. We analyze the illumination conditions necessary for this type of optics in order to suppress stray light and demonstrate microscopic imaging resolving 25 nm features.

  18. Plate coupling across the northern Manila subduction zone deduced from mantle lithosphere buoyancy

    NASA Astrophysics Data System (ADS)

    Lo, Chung-Liang; Doo, Wen-Bin; Kuo-Chen, Hao; Hsu, Shu-Kun

    2017-12-01

    The Manila subduction zone is located at the plate boundary where the Philippine Sea plate (PSP) moves northwestward toward the Eurasian plate (EU) with a high convergence rate. However, historically, no large earthquakes greater than Mw7 have been observed across the northern Manila subduction zone. The poorly understood plate interaction between these two plates in this region creates significant issues for evaluating the seismic hazard. Therefore, the variation of mantle lithospheric buoyancy is calculated to evaluate the plate coupling status across the northern Manila subduction zone, based on recently published forward gravity modeling constrained by the results of the P-wave seismic crustal structure of the TAIGER (Taiwan Integrated Geodynamic Research) project. The results indicate weak plate coupling between the PSP and EU, which could be related to the release of the overriding PSP from the descending EU's dragging force, which was deduced from the higher elevation of the Luzon arc and the fore-arc basin northward toward the Taiwan orogen. Moreover, serpentinized peridotite is present above the plate boundary and is distributed more widely and thickly closer to offshore southern Taiwan orogen. We suggest that low plate coupling may facilitate the uplifting of serpentinized mantle material up to the plate boundary.

  19. Deformation and stress change associated with plate interaction at subduction zones: a kinematic modelling

    NASA Astrophysics Data System (ADS)

    Zhao, Shaorong; Takemoto, Shuzo

    2000-08-01

    The interseismic deformation associated with plate coupling at a subduction zone is commonly simulated by the steady-slip model in which a reverse dip-slip is imposed on the down-dip extension of the locked plate interface, or by the backslip model in which a normal slip is imposed on the locked plate interface. It is found that these two models, although totally different in principle, produce similar patterns for the vertical deformation at a subduction zone. This suggests that it is almost impossible to distinguish between these two models by analysing only the interseismic vertical deformation observed at a subduction zone. The steady-slip model cannot correctly predict the horizontal deformation associated with plate coupling at a subduction zone, a fact that is proved by both the numerical modelling in this study and the GPS (Global Positioning System) observations near the Nankai trough, southwest Japan. It is therefore inadequate to simulate the effect of the plate coupling at a subduction zone by the steady-slip model. It is also revealed that the unphysical assumption inherent in the backslip model of imposing a normal slip on the locked plate interface makes it impossible to predict correctly the horizontal motion of the subducted plate and the stress change within the overthrust zone associated with the plate coupling during interseismic stages. If the analysis made in this work is proved to be correct, some of the previous studies on interpreting the interseismic deformation observed at several subduction zones based on these two models might need substantial revision. On the basis of the investigations on plate interaction at subduction zones made using the finite element method and the kinematic/mechanical conditions of the plate coupling implied by the present plate tectonics, a synthesized model is proposed to simulate the kinematic effect of the plate interaction during interseismic stages. A numerical analysis shows that the proposed model

  20. Characteristics of phase-correcting fresnel zone plates and elliptical waveguides

    NASA Astrophysics Data System (ADS)

    Wiltse, James C.

    1994-02-01

    The primary area of activity has been concentrated on the investigations relating to Fresnel zone plate antennas. A secondary effort has dealt with the characteristics of propagation in waveguides of elliptical cross section. In both cases, applications at microwave and millimeter-wavelengths have been emphasized. Thorough literature searches were conducted, and the results are given in Appendices A and B. The zone plate work has dealt with both transmission and reflection types, and has included considering the off-axis-fed cases. In the latter case, the plate may consist of elliptical zones, rather than the usual circular configuration. In general, the characteristics studied include far-field patterns, focal region fields, off-axis performance, bandwidth, and aberrations. In the case of propagation in elliptical waveguides, the attenuation and modal properties were studied for enclosed metal waveguides, coaxial transmission lines, and various surface waveguides.

  1. Astigmatism correction in x-ray scanning photoemission microscope with use of elliptical zone plate

    SciTech Connect

    Ade, H.; Ko, C.; Anderson, E.

    1992-03-02

    We report the impact of an elliptical, high resolution zone plate on the performance of an initially astigmatic soft x-ray scanning photoemission microscope. A zone plate with carefully calibrated eccentricity has been used to eliminate astigmatism arising from transport optics, and an improvement of about a factor of 3 in spatial resolution was achieved. The resolution is still dominated by the source size and chromatic aberrations rather than by diffraction and coma, and a further gain of about a factor of 2 in resolution is possible. Sub 100 nm photoemission microscopy with primary photoelectrons is now within reach.

  2. Geodetic investigation of plate spreading along a propagating ridge: the Eastern Volcanic Zone, Iceland

    NASA Astrophysics Data System (ADS)

    Scheiber-Enslin, Stephanie E.; Lafemina, Peter C.; Sturkell, Erik; Hooper, Andrew J.; Webb, Susan J.

    2011-12-01

    Hotspot-ridge interactions lead to the dynamic evolution of divergent plate boundaries, including propagating and overlapping ridge segments. In southern Iceland, the Eastern Volcanic Zone (EVZ) formed approximately 2-3 Ma ago during the last eastward ridge jump from the Western Volcanic Zone (WVZ), and is propagating to the southwest into the Tertiary lithosphere of the Eastern Volcanic Flank Zone. North America-Eurasia relative plate motion is partitioned between the Eastern and WVZs. We utilize new terrestrial (dry-tilt) and space (GPS and InSAR) geodetic data to investigate the nature of plate spreading and magma-tectonic interaction at the southern terminus of this propagating ridge system. We present a new GPS derived horizontal velocity field covering the period 1994-2006, new InSAR analyses for the periods 1993-2000 and 2003-2007, and models of plate spreading across this region. The velocity field indicates horizontal surface deformation consistent with plate spreading across and the propagation of the EVZ. The dry-tilt and InSAR data show transient deformation signals associated with magmatic processes. The velocity field is corrected for these transient deformation sources in order to investigate the nature of secular plate motion. Our model results indicate a decrease in spreading rate from northeast (15 mm yr-1) to southwest (9 mm yr-1) across the Torfajökull caldera and the intersection of the South Iceland Seismic Zone and EVZ, consistent with the propagating ridge model. Plate spreading south of the intersection demonstrates that spreading must be partitioned with the Reykjanes Peninsula to the west at this latitude. Our results also constrain the minimum flux (0.05 km3 km-1 kyr-1) of magma to this segment of the Mid-Atlantic Ridge and indicate that the Hekla magmatic system strains the Torfajökull caldera during pre- and co-eruptive periods.

  3. Abrupt Upper-Plate Tilting Upon Slab-Transition-Zone Collision

    NASA Astrophysics Data System (ADS)

    Crameri, F.; Lithgow-Bertelloni, C. R.

    2017-12-01

    During its sinking, the remnant of a surface plate crosses and interacts with multiple boundaries in Earth's interior. The most-prominent dynamic interaction arises at the upper-mantle transition zone where the sinking plate is strongly affected by the higher-viscosity lower mantle. Within our numerical model, we unravel, for the first time, that this very collision of the sinking slab with the transition zone induces a sudden, dramatic downward tilt of the upper plate towards the subduction trench. The slab-transition zone collision sets parts of the higher-viscosity lower mantle in motion. Naturally, this then induces an overall larger return flow cell that, at its onset, tilts the upper plate abruptly by around 0.05 degrees and over around 10 Millions of years. Such a significant and abrupt variation in surface topography should be clearly visible in temporal geologic records of large-scale surface elevation and might explain continental-wide tilting as observed in Australia since the Eocene or North America during the Phanerozoic. Unravelling this crucial mantle-lithosphere interaction was possible thanks to state-of-the-art numerical modelling (powered by StagYY; Tackley 2008, PEPI) and post-processing (powered by StagLab; www.fabiocrameri.ch/software). The new model that is introduced here to study the dynamically self-consistent temporal evolution of subduction features accurate subduction-zone topography, robust single-sided plate sinking, stronger plates close to laboratory values, an upper-mantle phase transition and, crucially, simple continents at a free surface. A novel, fully-automated post-processing includes physical model diagnostics like slab geometry, mantle flow pattern, upper-plate tilt angle and trench location.

  4. Actively dewatering fluid-rich zones along the Costa Rica plate boundary fault

    NASA Astrophysics Data System (ADS)

    Bangs, N. L.; McIntosh, K. D.; Silver, E. A.; Kluesner, J. W.; Ranero, C. R.; von Huene, R.

    2012-12-01

    New 3D seismic reflection data reveal distinct evidence for active dewatering above a 12 km wide segment of the plate boundary fault within the Costa Rica subduction zone NW of the Osa Peninsula. In the spring of 2011 we acquired a 11 x 55 km 3D seismic reflection data set on the R/V Langseth using four 6,000 m streamers and two 3,300 in3 airgun arrays to examine the structure of the Costa Rica margin from the trench into the seismogenic zone. We can trace the plate-boundary interface from the trench across our entire survey to where the plate-boundary thrust lies > 10 km beneath the margin shelf. Approximately 20 km landward of the trench beneath the mid slope and at the updip edge of the seismogenic zone, a 12 km wide zone of the plate-boundary interface has a distinctly higher-amplitude seismic reflection than deeper or shallower segments of the fault. Directly above and potentially directly connected with this zone are high-amplitude, reversed-polarity fault-plane reflections that extend through the margin wedge and into overlying slope sediment cover. Within the slope cover, high-amplitude reversed-polarity reflections are common within the network of closely-spaced nearly vertical normal faults and several broadly spaced, more gently dipping thrust faults. These faults appear to be directing fluids vertically toward the seafloor, where numerous seafloor fluid flow indicators, such as pockmarks, mounds and ridges, and slope failure features, are distinct in multibeam and backscatter images. There are distinctly fewer seafloor and subsurface fluid flow indicators both updip and downdip of this zone. We believe these fluids come from a 12 km wide fluid-rich segment of the plate-boundary interface that is likely overpressured and has relatively low shear stress.

  5. X-ray microscopy with high-resolution zone plates: recent developments

    NASA Astrophysics Data System (ADS)

    Schneider, Gerd; Wilhein, Thomas; Niemann, Bastian; Guttman, P.; Schliebe, T.; Lehr, J.; Aschoff, H.; Thieme, Juergen; Rudolph, Dietbert M.; Schmahl, Guenther A.

    1995-09-01

    In order to expand the applications of x-ray microscopy, developments in the fields of zone plate technology, specimen preparation and imaging techniques have been made. A new cross- linked polymer chain electron beam resist allows us to record zone plate pattern down to 19 nm outermost zone width. High resolution zone plates in germanium with outermost zone widths down to 19 nm have been developed. In addition, phase zone plates in nickel down to 30 nm zone width have been made by electroplating. In order to enhance the image contrast for weak absorbing objects, the phase contrast method for x-ray microscopy was developed and implemented on the Gottingen x-ray microscope at BESSY. The effects of x ray absorption on the structure of biological specimen limits the maximum applicable radiation dose and therefore the achievable signal to noise ratio for an artifact-free x-ray image. To improve the stability especially of biological specimen, a cryogenic object chamber has been developed and tested. It turns out that at the operating temperature T less than or equal to 130 K unfixed biological specimen can be exposed to a radiation dose of 109 - 1010 Gy without any observable structural changes. A multiple-angle viewing stage allows us to take stereoscopic images with the x-ray microscope, giving a 3D-impression of the object. As an example for the applications of x-ray microscopy in biology, erythrocytes infected by malaria parasite have been examined. Studies of the aggregation of hematite by sodium sulfate gives an example for the application of x-ray microscopy in the field of colloid research.

  6. Diffuse Extension of the Southern Mariana Margin: Implications for Subduction Zone Infancy and Plate Tectonics

    NASA Astrophysics Data System (ADS)

    Martinez, F.; Stern, R. J.; Kelley, K. A.; Ohara, Y.; Sleeper, J. D.; Ribeiro, J. M.; Brounce, M. N.

    2017-12-01

    Opening of the southern Mariana margin takes place in contrasting modes: Extension normal to the trench forms crust that is passively accreted to a rigid Philippine Sea plate and forms along focused and broad accretion axes. Extension also occurs parallel to the trench and has split apart an Eocene-Miocene forearc terrain accreting new crust diffusely over a 150-200 km wide zone forming a pervasive volcano-tectonic fabric oriented at high angles to the trench and the backarc spreading center. Earthquake seismicity indicates that the forearc extension is active over this broad area and basement samples date young although waning volcanic activity. Diffuse formation of new oceanic crust and lithosphere is unusual; in most oceanic settings extension rapidly focuses to narrow plate boundary zones—a defining feature of plate tectonics. Diffuse crustal accretion has been inferred to occur during subduction zone infancy, however. We hypothesize that, in a near-trench extensional setting, the continual addition of water from the subducting slab creates a weak overriding hydrous lithosphere that deforms broadly. This process counteracts mantle dehydration and strengthening proposed to occur at mid-ocean ridges that may help to focus deformation and melt delivery to narrow plate boundary zones. The observations from the southern Mariana margin suggest that where lithosphere is weakened by high water content narrow seafloor spreading centers cannot form. These conditions likely prevail during subduction zone infancy, explaining the diffuse contemporaneous volcanism inferred in this setting.

  7. The Panama North Andes Plate Bounday Zone from Interpreted Radar Images, Geologic Mapping and Geophysical Anomalies

    NASA Astrophysics Data System (ADS)

    Hernandez, O.; Alexander, G. C.; Garzon, F.

    2013-05-01

    Satellite geodetics shows the existence of the rigid Panama microplate converging on west to east with The North Andean block. Seismic studies indicate that this plate boundary zone has compressive east-west stresses. Interpretation from magnetic and gravity data suggest that the thickness of the sedimentary sequence of The Atrato basin, reaches 10.5 km and that the Mande magmatic arc is a tectonic pillar, bounded by faults. The interpretation of seismic lines shows the basement of the Urabá Basin is affected by normal faults that limit blocks sunk and raised, a sedimentary sequence that is wedged against the Mande magmatic arc and becomes thicker towards the east. It also shows a thrust fault that connects Neogene sediments of Sinu fold belt with the Urabá Basin. The collision of the Panama arc with the Western Cordillera leads to the existence of a low-angle subduction zone inclined to the east involving the partition of the oceanic plate, drawing up of a trench and subducting plate bending. Before the Panama arc collision with the Western Cordillera, granitic intrusion had occurred that gave rise to the Mande magmatic arc, causing bending and rise of the oceanic crust. This effort generated tensional bending at the top of the crust that led to the formation of raised and sunken blocks bounded by normal faults, within which lies the tectonic pillar which forms the Mande magmatic arc. Upon the occurrence of the collision, it was launched the end of the connection between the Pacific Ocean and Caribbean Sea and the formation of the Uraba forearc basins and the Atrato basin. Panama - North Andes Plate boundary Zone 2d Modeling of the Panama - North Andes Plate Bounday Zone

  8. Interlaced zone plate optics for hard X-ray imaging in the 10 nm range

    DOE PAGES

    Mohacsi, Istvan; Vartiainen, Ismo; Rosner, Benedikt; ...

    2017-03-08

    Multi-keV X-ray microscopy has been particularly successful in bridging the resolution gap between optical and electron microscopy. However, resolutions below 20 nm are still considered challenging, as high throughput direct imaging methods are limited by the availability of suitable optical elements. In order to bridge this gap, we present a new type of Fresnel zone plate lenses aimed at the sub-20 and the sub-10 nm resolution range. By extending the concept of double-sided zone plate stacking, we demonstrate the doubling of the effective line density and thus the resolution and provide large aperture, single- chip optical devices with 15 andmore » 7 nm smallest zone widths. The detailed characterization of these lenses shows excellent optical properties with focal spots down to 7.8 nm. Furthermore, beyond wave front characterization, the zone plates also excel in typical imaging scenarios, verifying their resolution close to their diffraction limited optical performance.« less

  9. Interlaced zone plate optics for hard X-ray imaging in the 10 nm range

    SciTech Connect

    Mohacsi, Istvan; Vartiainen, Ismo; Rosner, Benedikt

    Multi-keV X-ray microscopy has been particularly successful in bridging the resolution gap between optical and electron microscopy. However, resolutions below 20 nm are still considered challenging, as high throughput direct imaging methods are limited by the availability of suitable optical elements. In order to bridge this gap, we present a new type of Fresnel zone plate lenses aimed at the sub-20 and the sub-10 nm resolution range. By extending the concept of double-sided zone plate stacking, we demonstrate the doubling of the effective line density and thus the resolution and provide large aperture, single- chip optical devices with 15 andmore » 7 nm smallest zone widths. The detailed characterization of these lenses shows excellent optical properties with focal spots down to 7.8 nm. Furthermore, beyond wave front characterization, the zone plates also excel in typical imaging scenarios, verifying their resolution close to their diffraction limited optical performance.« less

  10. Trps1 deficiency enlarges the proliferative zone of growth plate cartilage by upregulation of Pthrp.

    PubMed

    Nishioka, Katsuhiro; Itoh, Shunji; Suemoto, Hiroki; Kanno, Seiji; Gai, Zhibo; Kawakatsu, Motohisa; Tanishima, Hiroyuki; Morimoto, Yoshifumi; Hatamura, Ikuji; Yoshida, Munehito; Muragaki, Yasuteru

    2008-07-01

    We have reported that elongation of the columnar proliferative zone of long bone growth plates in Trps1-/- mice during the late fetal stage in the previous study [1]. Since expression of Trps1 protein was found to overlap with that of mRNAs for Indian hedgehog (Ihh), PTH/PTHrP receptor (PPR), and PTHrP, we hypothesized that Trps1 may inhibit the hypertrophic differentiation of chondrocytes by interacting with the Ihh/PTHrP feedback loop. To investigate whether Trps1 has a role in this Ihh/PTHrP feedback loop, we compared the growth plates of Trps1-/- mice and wild-type (Trps1+/+) mice. Immunohistochemistry showed that Trps1 protein was strongly expressed in the periarticular and prehypertrophic zones of the fetal growth plate in wild-type mice on embryonic day 18.5 (E18.5). On the other hand, Ihh, PPR, and PTHrP mRNAs were predominantly expressed in the prehypertrophic zone at this stage of development. While expression of Ihh and PPR by prehypertrophic chondrocytes was unaffected in the growth plates of Trps1-/- mice, the range of PTHrP expression was expanded toward the proliferating zone in these mice. Quantitative real-time PCR analysis demonstrated upregulation of PTHrP in the epiphyseal growth plates of Trps1-/- mice. Furthermore, promoter analysis combined with the chromatin immunoprecipitation (ChIP) assay demonstrated that direct binding of Trps1 to the PTHrP promoter suppressed the transcription of PTHrP. Finally, organ culture of E14.5 tibiae in the absence or the presence of Pthrp revealed that the proliferative zone of the tibial growth plate was elongated by culture with Pthrp compared to that of control tibiae. Taken together, these data provide the first genetic evidence that lack of Trps1 leads to overexpression of PTHrP, and that Trps1 is required to maintain the normal organization of chondrocytes in the growth plate.

  11. High-aspect ratio zone plate fabrication for hard x-ray nanoimaging

    NASA Astrophysics Data System (ADS)

    Parfeniukas, Karolis; Giakoumidis, Stylianos; Akan, Rabia; Vogt, Ulrich

    2017-08-01

    We present our results in fabricating Fresnel zone plate optics for the NanoMAX beamline at the fourth-generation synchrotron radiation facility MAX IV, to be used in the energy range of 6-10 keV. The results and challenges of tungsten nanofabrication are discussed, and an alternative approach using metal-assisted chemical etching (MACE) of silicon is showcased. We successfully manufactured diffraction-limited zone plates in tungsten with 30 nm outermost zone width and an aspect ratio of 21:1. These optics were used for nanoimaging experiments at NanoMAX. However, we found it challenging to further improve resolution and diffraction efficiency using tungsten. High efficiency is desirable to fully utilize the advantage of increased coherence on the optics at MAX IV. Therefore, we started to investigate MACE of silicon for the nanofabrication of high-resolution and high-efficiency zone plates. The first type of structures we propose use the silicon directly as the phase-shifting material. We have achieved 6 μm deep dense vertical structures with 100 nm linewidth. The second type of optics use iridium as the phase material. The structures in the silicon substrate act as a mold for iridium coating via atomic layer deposition (ALD). A semi-dense pattern is used with line-to-space ratio of 1:3 for a so-called frequency-doubled zone plate. This way, it is possible to produce smaller structures with the tradeoff of the additional ALD step. We have fabricated 45 nm-wide and 3.6 μm-tall silicon/iridium structures.

  12. Seismic evidence for deep fluid circulation in the overriding plate of subduction zones

    NASA Astrophysics Data System (ADS)

    Tauzin, B.; Reynard, B.; Bodin, T.; Perrillat, J. P.; Debayle, E.

    2015-12-01

    In subduction zones, non-volcanic tremors are associated with fluid circulations (Obara, 2002). Their sources are often located on the interplate boundary (Rogers and Dragert, 2003; Shelly et al, 2006; La Rocca, 2009), consistent with fluids released by the dehydration of subducted plates (Hacker et al., 2003). Reports of tremors in the overriding continental crust of several subduction zones in the world (Kao et al., 2005; Payero et al., 2008; Ide, 2012) suggest fluid circulation at shallower depths but potential fluid paths are poorly documented. Here we obtained seismic observations from receiver functions that evidence the close association between the shallow tremor zone, electrical conductivity, and tectonic features of the Cascadia overriding plate. A seismic discontinuity near 15 km depth in the crust of the overriding North American plate is attributed to the Conrad discontinuity. This interface is segmented, and its interruption is spatially correlated with conductive regions and shallow swarms of seismicity and non-volcanic tremors. These observations suggest that shallow fluid circulation, tremors and seismicity are controlled by fault zones limiting blocks of accreted terranes in the overriding plate (Brudzinski and Allen, 2007). These zones constitute fluid "escape" routes that may contribute unloading fluid pressure on the megathrust. Obara, K. (2002). Science, 296, 1679-1681. Rogers, G., & Dragert, H. (2003). Science, 300, 1942-1943. Shelly, D. R., et al. (2006). Nature, 442, 188-191. La Rocca, M., et al. (2009). Science, 323, 620-623. Kao, H., et al. (2005). Nature, 436, 841-844. Payero, J. S., et al. (2008). Geophysical Research Letters, 35. Ide, S. (2012). Journal of Geophysical Research: Solid Earth, 117. Brudzinski, M. R., & Allen, R. M. (2007). Geology, 35, 907-910.

  13. Nonvolcanic Deep Tremors in the Transform Plate Bounding San Andreas Fault Zone

    NASA Astrophysics Data System (ADS)

    Nadeau, R. M.; Dolenc, D.

    2004-12-01

    Recently, deep ( ˜ 20 to 40 km) nonvolcanic tremor activity has been observed on convergent plate boundaries in Japan and in the Cascadia region of North America (Obara, 2002; Rodgers and Dragert, 2003; Szeliga et al., 2004). Because of the abundance of available fluids from subduction processes in these convergent zones, fluids are believed to play an important role in the generation of the tremor activity. The transient rates of tremor activity in these regions are also observed to correlate either with the occurrence of larger earthquakes (Obara, 2002) or with geodetically determined transient creep events that release large amounts of strain energy deep beneath the locked Cascadia megathrust (M.M. Miller et al., 2002; Rodgers and Dragert, 2003; Szeliga et al., 2004). These associations suggest that nonvolcanic tremor activity may participate in a fundamental mode of deep moment release and in the triggering of large subduction zone events (Rodgers and Dragert, 2003). We report the discovery of deep ( ˜ 20 to 45 km) nonvolcanic tremor activity on the transform plate bounding San Andreas Fault (SAF) in central California where, in contrast to subduction zones, long-term deformation directions are horizontal and fluid availability from subduction zone processes is absent. The source region of the SAF tremors lies beneath the epicentral region of the great 1857 magnitude (M) ˜ 8, Fort Tejon earthquake whose rupture zone is currently locked (Sieh, 1978). Activity rate transients of the tremors occurring since early 2001 also correlate with seismicity rate variations above the tremor source region.

  14. Realization of arbitrarily long focus-depth optical vortices with spiral area-varying zone plates

    NASA Astrophysics Data System (ADS)

    Zheng, Chenglong; Zang, Huaping; Du, Yanli; Tian, Yongzhi; Ji, Ziwen; Zhang, Jing; Fan, Quanping; Wang, Chuanke; Cao, Leifeng; Liang, Erjun

    2018-05-01

    We provide a methodology to realize an optical vortex with arbitrarily long focus-depth. With a technique of varying each zone area of a phase spiral zone plate one can obtain optics capable of generating ultra-long focus-depth optical vortex from a plane wave. The focal property of such optics was analysed using the Fresnel diffraction theory, and an experimental demonstration was performed to verify its effectiveness. Such optics may bring new opportunity and benefits for optical vortex application such as optical manipulation and lithography.

  15. Binary zone-plate array for a parallel joint transform correlator applied to face recognition.

    PubMed

    Kodate, K; Hashimoto, A; Thapliya, R

    1999-05-10

    Taking advantage of small aberrations, high efficiency, and compactness, we developed a new, to our knowledge, design procedure for a binary zone-plate array (BZPA) and applied it to a parallel joint transform correlator for the recognition of the human face. Pairs of reference and unknown images of faces are displayed on a liquid-crystal spatial light modulator (SLM), Fourier transformed by the BZPA, intensity recorded on an optically addressable SLM, and inversely Fourier transformed to obtain correlation signals. Consideration of the bandwidth allows the relations among the channel number, the numerical aperture of the zone plates, and the pattern size to be determined. Experimentally a five-channel parallel correlator was implemented and tested successfully with a 100-person database. The design and the fabrication of a 20-channel BZPA for phonetic character recognition are also included.

  16. Subwavelength and directional control of flexural waves in zone-folding induced topological plates

    NASA Astrophysics Data System (ADS)

    Chaunsali, Rajesh; Chen, Chun-Wei; Yang, Jinkyu

    2018-02-01

    Inspired by the quantum spin Hall effect shown by topological insulators, we propose a plate structure that can be used to demonstrate the pseudospin Hall effect for flexural waves. The system consists of a thin plate with periodically arranged resonators mounted on its top surface. We extend a technique based on the plane-wave expansion method to identify a double Dirac cone emerging due to the zone-folding in frequency band structures. This particular design allows us to move the double Dirac cone to a lower frequency than the resonating frequency of local resonators. We then manipulate the pattern of local resonators to open subwavelength Bragg band gaps that are topologically distinct. Building on this method, we verify numerically that a waveguide at an interface between two topologically distinct resonating plate structures can be used for guiding low-frequency, spin-dependent one-way flexural waves along a desired path with bends.

  17. Deep low-frequency earthquakes in tremor localize to the plate interface in multiple subduction zones

    USGS Publications Warehouse

    Brown, Justin R.; Beroza, Gregory C.; Ide, Satoshi; Ohta, Kazuaki; Shelly, David R.; Schwartz, Susan Y.; Rabbel, Wolfgang; Thorwart, M.; Kao, Honn

    2009-01-01

    Deep tremor under Shikoku, Japan, consists primarily, and perhaps entirely, of swarms of low-frequency earthquakes (LFEs) that occur as shear slip on the plate interface. Although tremor is observed at other plate boundaries, the lack of cataloged low-frequency earthquakes has precluded a similar conclusion about tremor in those locales. We use a network autocorrelation approach to detect and locate LFEs within tremor recorded at three subduction zones characterized by different thermal structures and levels of interplate seismicity: southwest Japan, northern Cascadia, and Costa Rica. In each case we find that LFEs are the primary constituent of tremor and that they locate on the deep continuation of the plate boundary. This suggests that tremor in these regions shares a common mechanism and that temperature is not the primary control on such activity.

  18. Sub-100nm, Maskless Deep-UV Zone-Plate Array Lithography

    DTIC Science & Technology

    2004-05-07

    The basic idea is to use fiducial grids, fabricated using interference lithography (or a derivative thereof) to determine the placement of features...sensed, and corrections are fed back to the beam-control electronics to cancel errors in the beam’s position. The virtue of interference lithography ...Sub-100nm, Maskless Deep-UV Zone-Plate Array Lithography Project Period: March 1, 2001 – February 28, 2004 F i n a l R e p o r t Army Research

  19. Planar techniques for fabricating X-ray diffraction gratings and zone plates

    NASA Technical Reports Server (NTRS)

    Smith, H. I.; Anderson, E. H.; Hawryluk, A. M.; Schattenburg, M. L.

    1984-01-01

    The state of current planar techniques in the fabrication of Fresnel zone plates and diffraction gratings is reviewed. Among the fabrication techniques described are multilayer resist techniques; scanning electron beam lithography; and holographic lithography. Consideration is also given to: X-ray lithography; ion beam lithography; and electroplating. SEM photographs of the undercut profiles obtained in a type AZ 135OB photoresistor by holographic lithography are provided.

  20. Characteristics of Phase-Correcting Fresnel Zone Plates and Elliptical Waveguides

    DTIC Science & Technology

    1994-02-01

    elektronika, No. 9, pp. 1681-1688, 1985) B. K. Goto and H. Banjo, "Angle Eikonals of Plane and Spherical Zone Plates," Journal of the Optical Society o...CARLuncover, NTIS (technical reports), and MATHSCI on DIALOG information services. The INSPec and ENGIneering databases were readily available to the...authors via the Georgia Institute of3 Technology electronic library system, while the remaining databases were consulted by library personnel. Ultimately, a

  1. Heterogeneity in Subducting Slab Influences Fluid Properties, Plate Coupling and Volcanism: Hikurangi Subduction Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Eberhart-Phillips, D. M.; Reyners, M.; Bannister, S. C.

    2017-12-01

    Seismicity distribution and 3-D models of P- and S-attenuation (1/Q) in the Hikurangi subduction zone, in the North Island of New Zealand, show large variation along-arc in the fluid properties of the subducting slab. Volcanism is also non-uniform, with extremely productive rhyolitic volcanism localized to the central Taupo Volcanic zone, and subduction without volcanism in the southern North Island. Plate coupling varies with heterogeneous slip deficit in the northern section, low slip deficit in the central section, and high slip deficit (strong coupling) in the south. Heterogeneous initial hydration and varied dehydration history both are inferred to play roles. The Hikurangi Plateau (large igneous province) has been subducted beneath New Zealand twice - firstly at ca. 105-100 Ma during north-south convergence with Gondwana, and currently during east-west convergence between the Pacific and Australian plates along the Hikurangi subduction zone. It has an uneven downdip edge which has produced spatially and temporally localized stalls in subduction rate. The mantle wedge under the rhyolitic section has a very low Q feature centred at 50-125 km depth, which directly overlies a 150-km long zone of dense seismicity. This seismicity occurs below a sharp transition in the downdip extent of the Hikurangi Plateau, where difficulty subducting the buoyant plateau would have created a zone of increased faulting and hydration that spent a longer time in the outer-rise yielding zone, compared with areas to the north and south. At shallow depths this section has unusually high fracture permeability from the two episodes of bending, but it did not experience dehydration during Gondwana subduction. This central section at plate interface depths less than 50-km has low Q in the slab crust, showing that it is extremely fluid rich, and it exhibits weak plate coupling with both deep and shallow slow-slip events. In contrast in the southern section, where there is a large deficit in

  2. Stress on the seismogenic and deep creep plate interface during the earthquake cycle in subduction zones

    NASA Astrophysics Data System (ADS)

    Ruff, Larry J.

    2001-04-01

    The deep creep plate interface extends from the down-dip edge of the seismogenic zone down to the base of the overlying lithosphere in subduction zones. Seismogenic/deep creep zone interaction during the earthquake cycle produces spatial and temporal variations in strains within the surrounding elastic material. Strain observations in the Nankai subduction zone show distinct deformation styles in the co-seismic, post-seismic, and inter-seismic phases associated with the 1946 great earthquake. The most widely used kinematic model to match geodetic observations has been a 2-D Savage-type model where a plate interface is placed in an elastic half-space and co-seismic slip occurs in the upper seismogenic portion of the interface, while inter-seismic deformation is modeled by a locked seismogenic zone and a constant slip velocity across the deep creep interface. Here, I use the simplest possible 2-D mechanical model with just two blocks to study the stress interaction between the seismogenic and deep creep zones. The seismogenic zone behaves as a stick-slip interface where co-seismic slip or stress drop constrain the model. A linear constitutive law for the deep creep zone connects the shear stress (σ) to the slip velocity across the plate interface (s') with the material property of interface viscosity (ζ ) as: σ = ζ s'. The analytic solution for the steady-state two-block model produces simple formulas that connect some spatially-averaged geodetic observations to model quantities. Aside from the basic subduction zone geometry, the key observed parameter is τ, the characteristic time of the rapid post-seismic slip in the deep creep interface. Observations of τ range from about 5 years (Nankai and Alaska) to 15 years (Chile). The simple model uses these values for τ to produce estimates for ζ that range from 8.4 × 1013 Pa/m/s (in Nankai) to 6.5 × 1014 Pa/m/s (in Chile). Then, the model predicts that the shear stress acting on deep creep interface averaged over

  3. Theoretical Investigation of Calculating Temperatures in the Combining Zone of Cu/Fe Composite Plate Jointed by Explosive Welding

    NASA Astrophysics Data System (ADS)

    Qu, Y. D.; Zhang, W. J.; Kong, X. Q.; Zhao, X.

    2016-03-01

    The heat-transfer behavior of the interface of Flyer plate (or Base Plate) has great influence on the microcosmic structures, stress distributions, and interface distortion of the welded interface of composite plates by explosive welding. In this paper, the temperature distributions in the combing zone are studied for the case of Cu/Fe composite plate jointed by explosive welding near the lower limit of explosive welding. The results show that Flyer plate (Cu plate) and Base Plate (Fe plate) firstly almost have the same melting rate in the explosive welding process. Then, the melting rate of Cu plate becomes higher than that of Fe plate. Finally, the melt thicknesses of Cu plate and Fe plate trend to be different constants, respectively. Meanwhile, the melting layer of Cu plate is thicker than that of Fe plate. The research could supply some theoretical foundations for calculating the temperature distribution and optimizing the explosive welding parameters of Cu/Fe composite plate to some extent.

  4. Constraining the hydration of the subducting Nazca plate beneath Northern Chile using subduction zone guided waves

    NASA Astrophysics Data System (ADS)

    Garth, Tom; Rietbrock, Andreas

    2017-09-01

    Guided wave dispersion is observed from earthquakes at 180-280 km depth recorded at stations in the fore-arc of Northern Chile, where the 44 Ma Nazca plate subducts beneath South America. Characteristic P-wave dispersion is observed at several stations in the Chilean fore-arc with high frequency energy (>5 Hz) arriving up to 3 s after low frequency (<2 Hz) arrivals. This dispersion has been attributed to low velocity structure within the subducting Nazca plate which acts as a waveguide, retaining and delaying high frequency energy. Full waveform modelling shows that the single LVL proposed by previous studies does not produce the first motion dispersion observed at multiple stations, or the extended P-wave coda observed in arrivals from intermediate depth events within the Nazca plate. These signals can however be accurately accounted for if dipping low velocity fault zones are included within the subducting lithospheric mantle. A grid search over possible LVL and faults zone parameters (width, velocity contrast and separation distance) was carried out to constrain the best fitting model parameters. Our results imply that fault zone structures of 0.5-1.0 km thickness, and 5-10 km spacing, consistent with observations at the outer rise are present within the subducted slab at intermediate depths. We propose that these low velocity fault zone structures represent the hydrated structure within the lithospheric mantle. They may be formed initially by normal faults at the outer rise, which act as a pathway for fluids to penetrate the deeper slab due to the bending and unbending stresses within the subducting plate. Our observations suggest that the lithospheric mantle is 5-15% serpentinised, and therefore may transport approximately 13-42 Tg/Myr of water per meter of arc. The guided wave observations also suggest that a thin LVL (∼1 km thick) interpreted as un-eclogitised subducted oceanic crust persists to depths of at least 220 km. Comparison of the inferred seismic

  5. Seismicity and structure of Nazca Plate subduction zone in southern Peru

    NASA Astrophysics Data System (ADS)

    Lim, H.; Kim, Y.; Clayton, R. W.; Thurber, C. H.

    2016-12-01

    We define subducting plate geometries in the Nazca subduction zone by (re)locating intra-slab earthquakes in southern Peru (2-18°S) and taking previously published converted phase analysis results, to clarify the slab geometry and inferred relationships to the seismicity. We also provide both P- and S-wave velocities of the subducting Nazca Plate and mantle wedge portions close to the slab using double-difference tomography (Zhang and Thurber, 2003) to understand upper plate volcanism and subduction process. A total of 492 regional earthquakes from August 2008 to February 2013 recorded from the dense seismic array (PeruSE, 2013) are selected for the relocation and tomography. The relocated seismicity shows a smooth contortion in the slab-dip transition zone for 400 km between the shallow (25°)-to-flat dipping interface in the north and 40°-dipping interface in the south. We find a significant slab-dip difference (up to 10°) between our results and previously published slab models along the profile region sampling the normal-dip slab at depth (>100 km). Robust features in both P- and S-wave tomography inversions are dipping low-velocity slabs down to 100 km transitioning to higher-velocities at 100-140 km in both flat slab and dipping slab regions. Differences in the velocities of the mantle wedge between the two regions may indicate different hydration states in the wedge.

  6. Seismicity and structure of Nazca Plate subduction zone in southern Peru

    NASA Astrophysics Data System (ADS)

    Lim, H.; Kim, Y.; Clayton, R. W.

    2015-12-01

    We image the Nazca plate subduction zone system by detecting and (re)locating intra-slab earthquakes in southern Peru. Dense seismic arrays (PeruSE, 2013) were deployed along four lines to target geophysical characterization of the subduction system in the transition zone between flat and normal dipping segments of the Nazca plate (2-15°S). The arc volcanism is absent near the flat slab segment, and currently, the correlation between the location of the active volcanic front and corresponding slab depth is neither clear nor consistent between previously published models from seismicity. We detect 620 local earthquakes from August 2008 to February 2013 by manually picking 6559 and 4145 arrival times for P- and S-phases, respectively. We observe that the S-phase data is helpful to reduce the trade-off between origin time and depth of deeper earthquakes (>100 km). Earthquake locations are relocated to constrain the Nazca slab-mantle interface in the slab-dip transition zone using 7322 measurements of differential times of nearby earthquake pairs by waveform cross-correlation. We also employ the double-difference tomography (Zhang and Thurber, 2003) to further improve earthquake source locations and the spatial resolution of the velocity structure simultaneously. The relocated hypocenters clearly delineate the dipping Wadati-Benioff zone in the slab-dip transition zone between the shallow- (25°) to-flat dipping slab segment in the north and the normal (40°) dipping segment in the south. The intermediate-depth seismicity in the flat slab region stops at a depth of ~100 km and a horizontal distance of ~400 km from the trench. We find a significant slab-dip difference (up to 10°) between our relocated seismicity and previously published slab models along the profile region sampling the normal-dip slab at depth (>100 km).

  7. Plate-boundary kinematics in the Alps: Motion in the Arosa suture zone

    NASA Astrophysics Data System (ADS)

    Ring, Uwe; Ratschbacher, Lothar; Frisch, Wolfgang

    1988-08-01

    The Arosa zone forms a melange complex along the Penninic/Austroalpine boundary and belongs to the main Alpine suture zone. Accretion and plate collision occurred during Cretaceous and lower Tertiary time. A mixture of ophiolitic rocks and pelagic sediments is imbricated with flysch and blocks of Austroalpine (continental) derivation. We present a description of deformation structures, an analysis of strain, and a kinematic interpretation based on structural work. Deformation histories of imbricates show a translation path that was west-directed between ca. 110 and 50 Ma and north-directed thereafter. The kinematics of the Arosa zone agrees with the recently deduced displacement history of the Austroalpine units in the Eastern Alps during the Cretaceous orogeny. This calls for a predominantly top-to-the-west imbrication of Austroalpine and Penninic units and is in contradiction to what is inferred in most models of the Eastern Alps. A direct relation between the deformation along the Austroalpine margin and relative plate motion existed.

  8. Strength of the Subduction Plate Interface beneath the Seismogenic Zone: A Microstructural Investigation of Deformation Mechanisms within a Phyllosilicate- and Amphibole-rich Shear Zone

    NASA Astrophysics Data System (ADS)

    Seyler, C.; Kirkpatrick, J. D.; Šilerová, D.

    2017-12-01

    Localization of strain at plate boundaries requires rheological weakening of the lithosphere. The rheology of the subduction plate interface is dictated by the dominant grain-scale deformation mechanisms. However, little is known about the deformation mechanisms within phases commonly found in subduction zones, such as phyllosilicates and amphiboles. We investigate the Leech River Shear Zone on Vancouver Island, British Columbia to explore deformation processes downdip of the seismogenic zone and evaluate the bulk rheology of the plate interface. This shear zone juxtaposes a metamorphosed accretionary prism against a metabasaltic oceanic plateau, representing a paleo-plate interface from the ancient Cascadia subduction zone. Preliminary geothermometry results record a prograde deformation temperature of 573.6±11.2 ˚C in the overriding accretionary wedge, and the hornblende-chlorite-epidote-plagioclase mineral assemblage suggests upper greenschist to lower amphibolite facies metamorphism of the downgoing oceanic crust. Detailed mapping of the plate interface documents a 200 m wide mylonitic shear zone developed across the lithologic contact. Asymmetric shear fabrics, isoclinal folding, boudinage, and a steeply plunging, penetrative stretching lineation are consistent with sinistral-oblique subduction. Numerous discordant quartz veins are variably sheared into sigmoidal shapes as well as isoclinally folded and boudinaged, indicating cyclical synkinematic fracture and vein formation. At the grain-scale, interconnected, anastomosing layers of muscovite, chlorite, and graphite in the accretionary prism rocks likely deformed through kinking and dislocation glide. Framework minerals such as quartz and feldspar deformed by dislocation creep. In the metabasalt, hornblende and chlorite form a continuous S—C fabric in which asymmetric hornblende porphyroclasts deformed by rigid grain rotation and dissolution-precipitation creep. The strength of the subduction plate

  9. Links Between Earthquake Characteristics and Subducting Plate Heterogeneity in the 2016 Pedernales Ecuador Earthquake Rupture Zone

    NASA Astrophysics Data System (ADS)

    Bai, L.; Mori, J. J.

    2016-12-01

    The collision between the Indian and Eurasian plates formed the Himalayas, the largest orogenic belt on the Earth. The entire region accommodates shallow earthquakes, while intermediate-depth earthquakes are concentrated at the eastern and western Himalayan syntaxis. Here we investigate the focal depths, fault plane solutions, and source rupture process for three earthquake sequences, which are located at the western, central and eastern regions of the Himalayan orogenic belt. The Pamir-Hindu Kush region is located at the western Himalayan syntaxis and is characterized by extreme shortening of the upper crust and strong interaction of various layers of the lithosphere. Many shallow earthquakes occur on the Main Pamir Thrust at focal depths shallower than 20 km, while intermediate-deep earthquakes are mostly located below 75 km. Large intermediate-depth earthquakes occur frequently at the western Himalayan syntaxis about every 10 years on average. The 2015 Nepal earthquake is located in the central Himalayas. It is a typical megathrust earthquake that occurred on the shallow portion of the Main Himalayan Thrust (MHT). Many of the aftershocks are located above the MHT and illuminate faulting structures in the hanging wall with dip angles that are steeper than the MHT. These observations provide new constraints on the collision and uplift processes for the Himalaya orogenic belt. The Indo-Burma region is located south of the eastern Himalayan syntaxis, where the strike of the plate boundary suddenly changes from nearly east-west at the Himalayas to nearly north-south at the Burma Arc. The Burma arc subduction zone is a typical oblique plate convergence zone. The eastern boundary is the north-south striking dextral Sagaing fault, which hosts many shallow earthquakes with focal depth less than 25 km. In contrast, intermediate-depth earthquakes along the subduction zone reflect east-west trending reverse faulting.

  10. Femtosecond laser-ablated Fresnel zone plate fiber probe and sensing applications

    NASA Astrophysics Data System (ADS)

    Tan, Xiaoling; Geng, Youfu; Chen, Yan; Li, Shiguo; Wang, Xinzhong

    2018-02-01

    We investigate the Fresnel zone plate (FZP) inscribed on multimode fiber endface using femtosecond laser ablation and its application in sensing. The mode transmission through fiber tips with FZP is investigated both by the beam propagation method theoretically and by measuring the beam images with a charge-coupled device camera experimentally, which show a good agreement. Such devices are tested for surface-enhanced Raman scattering (SERS) using the aqueous solution of rhodamine 6G under a Raman spectroscopy. The experimental results demonstrate that the SERS signal is enhanced benefiting from focal ability of FZP, which is a promising method for the particular biochemical spectra sensing applications.

  11. Beam propagation modeling of modified volume Fresnel zone plates fabricated by femtosecond laser direct writing.

    PubMed

    Srisungsitthisunti, Pornsak; Ersoy, Okan K; Xu, Xianfan

    2009-01-01

    Light diffraction by volume Fresnel zone plates (VFZPs) is simulated by the Hankel transform beam propagation method (Hankel BPM). The method utilizes circularly symmetric geometry and small step propagation to calculate the diffracted wave fields by VFZP layers. It is shown that fast and accurate diffraction results can be obtained with the Hankel BPM. The results show an excellent agreement with the scalar diffraction theory and the experimental results. The numerical method allows more comprehensive studies of the VFZP parameters to achieve higher diffraction efficiency.

  12. Water, oceanic fracture zones and the lubrication of subducting plate boundaries—insights from seismicity

    NASA Astrophysics Data System (ADS)

    Schlaphorst, David; Kendall, J.-Michael; Collier, Jenny S.; Verdon, James P.; Blundy, Jon; Baptie, Brian; Latchman, Joan L.; Massin, Frederic; Bouin, Marie-Paule

    2016-03-01

    We investigate the relationship between subduction processes and related seismicity for the Lesser Antilles Arc using the Gutenberg-Richter law. This power law describes the earthquake-magnitude distribution, with the gradient of the cumulative magnitude distribution being commonly known as the b-value. The Lesser Antilles Arc was chosen because of its along-strike variability in sediment subduction and the transition from subduction to strike-slip movement towards its northern and southern ends. The data are derived from the seismicity catalogues from the Seismic Research Centre of The University of the West Indies and the Observatoires Volcanologiques et Sismologiques of the Institut de Physique du Globe de Paris and consist of subcrustal events primarily from the slab interface. The b-value is found using a Kolmogorov-Smirnov test for a maximum-likelihood straight line-fitting routine. We investigate spatial variations in b-values using a grid-search with circular cells as well as an along-arc projection. Tests with different algorithms and the two independent earthquake cataloges provide confidence in the robustness of our results. We observe a strong spatial variability of the b-value that cannot be explained by the uncertainties. Rather than obtaining a simple north-south b-value distribution suggestive of the dominant control on earthquake triggering being water released from the sedimentary cover on the incoming American Plates, or a b-value distribution that correlates with on the obliquity of subduction, we obtain a series of discrete, high b-value `bull's-eyes' along strike. These bull's-eyes, which indicate stress release through a higher fraction of small earthquakes, coincide with the locations of known incoming oceanic fracture zones on the American Plates. We interpret the results in terms of water being delivered to the Lesser Antilles subduction zone in the vicinity of fracture zones providing lubrication and thus changing the character of the

  13. Rheological structure of the lithosphere in plate boundary strike-slip fault zones

    NASA Astrophysics Data System (ADS)

    Chatzaras, Vasileios; Tikoff, Basil; Kruckenberg, Seth C.; Newman, Julie; Titus, Sarah J.; Withers, Anthony C.; Drury, Martyn R.

    2016-04-01

    How well constrained is the rheological structure of the lithosphere in plate boundary strike-slip fault systems? Further, how do lithospheric layers, with rheologically distinct behaviors, interact within the strike-slip fault zones? To address these questions, we present rheological observations from the mantle sections of two lithospheric-scale, strike-slip fault zones. Xenoliths from ˜40 km depth (970-1100 ° C) beneath the San Andreas fault system (SAF) provide critical constraints on the mechanical stratification of the lithosphere in this continental transform fault. Samples from the Bogota Peninsula shear zone (BPSZ, New Caledonia), which is an exhumed oceanic transform fault, provide insights on lateral variations in mantle strength and viscosity across the fault zone at a depth corresponding to deformation temperatures of ˜900 ° C. Olivine recrystallized grain size piezometry suggests that the shear stress in the SAF upper mantle is 5-9 MPa and in the BPSZ is 4-10 MPa. Thus, the mantle strength in both fault zones is comparable to the crustal strength (˜10 MPa) of seismogenic strike-slip faults in the SAF system. Across the BPSZ, shear stress increases from 4 MPa in the surrounding rocks to 10 MPa in the mylonites, which comprise the core of the shear zone. Further, the BPSZ is characterized by at least one order of magnitude difference in the viscosity between the mylonites (1018 Paṡs) and the surrounding rocks (1019 Paṡs). Mantle viscosity in both the BPSZ mylonites and the SAF (7.0ṡ1018-3.1ṡ1020 Paṡs) is relatively low. To explain our observations from these two strike-slip fault zones, we propose the "lithospheric feedback" model in which the upper crust and lithospheric mantle act together as an integrated system. Mantle flow controls displacement and the upper crust controls the stress magnitude in the system. Our stress data combined with data that are now available for the middle and lower crustal sections of other transcurrent fault

  14. Interlaced zone plate optics for hard X-ray imaging in the 10 nm range

    NASA Astrophysics Data System (ADS)

    Mohacsi, Istvan; Vartiainen, Ismo; Rösner, Benedikt; Guizar-Sicairos, Manuel; Guzenko, Vitaliy A.; McNulty, Ian; Winarski, Robert; Holt, Martin V.; David, Christian

    2017-03-01

    Multi-keV X-ray microscopy has been particularly successful in bridging the resolution gap between optical and electron microscopy. However, resolutions below 20 nm are still considered challenging, as high throughput direct imaging methods are limited by the availability of suitable optical elements. In order to bridge this gap, we present a new type of Fresnel zone plate lenses aimed at the sub-20 and the sub-10 nm resolution range. By extending the concept of double-sided zone plate stacking, we demonstrate the doubling of the effective line density and thus the resolution and provide large aperture, singlechip optical devices with 15 and 7 nm smallest zone widths. The detailed characterization of these lenses shows excellent optical properties with focal spots down to 7.8 nm. Beyond wave front characterization, the zone plates also excel in typical imaging scenarios, verifying their resolution close to their diffraction limited optical performance.

  15. Interlaced zone plate optics for hard X-ray imaging in the 10 nm range

    PubMed Central

    Mohacsi, Istvan; Vartiainen, Ismo; Rösner, Benedikt; Guizar-Sicairos, Manuel; Guzenko, Vitaliy A.; McNulty, Ian; Winarski, Robert; Holt, Martin V.; David, Christian

    2017-01-01

    Multi-keV X-ray microscopy has been particularly successful in bridging the resolution gap between optical and electron microscopy. However, resolutions below 20 nm are still considered challenging, as high throughput direct imaging methods are limited by the availability of suitable optical elements. In order to bridge this gap, we present a new type of Fresnel zone plate lenses aimed at the sub-20 and the sub-10 nm resolution range. By extending the concept of double-sided zone plate stacking, we demonstrate the doubling of the effective line density and thus the resolution and provide large aperture, singlechip optical devices with 15 and 7 nm smallest zone widths. The detailed characterization of these lenses shows excellent optical properties with focal spots down to 7.8 nm. Beyond wave front characterization, the zone plates also excel in typical imaging scenarios, verifying their resolution close to their diffraction limited optical performance.

  16. Atomic layer deposition frequency-multiplied Fresnel zone plates for hard x-rays focusing

    DOE PAGES

    Moldovan, Nicolaie; Divan, Ralu; Zeng, Hongjun; ...

    2017-12-01

    The design and fabrication of Fresnel zone plates for hard x-ray focusing up to 25 keV photon energies with better than 50 nm imaging half-pitch resolution is reported as performed by forming an ultrananocrystalline diamond (UNCD) scaffold, subsequently coating it with atomic layer deposition (ALD) with an absorber/phase shifting material, followed by back side etching of Si to form a diamond membrane device. The scaffold is formed by chemical vapor-deposited UNCD, electron beam lithography, and deep-reactive ion etching of diamond to desired specifications. The benefits of using diamond are as follows: improved mechanical robustness to prevent collapse of high-aspect-ratio ringmore » structures, a known high-aspect-ratio etch method, excellent radiation hardness, extremely low x-ray absorption, and significantly improved thermal/dimensional stability as compared to alternative materials. Central to the technology is the high-resolution patterning of diamond membranes at wafer scale, which was pushed to 60 nm lines and spaces etched 2.2-mu m-deep, to an aspect ratio of 36:1. The absorber growth was achieved by ALD of Ir, Pt, or W, while wafer-level processing allowed to obtain up to 121 device chips per 4 in. wafer with yields better than 60%. X-ray tests with such zone plates allowed resolving 50 nm lines and spaces, at the limit of the available resolution test structures.« less

  17. Detailed Image of the Subducting Plate and Upper mantle Seismic Discontinuities in the Mariana Subduction Zone

    NASA Astrophysics Data System (ADS)

    Tibi, R.; Wiens, D. A.; Shiobara, H.; Sugioka, H.; Yuan, X.

    2006-12-01

    We use P-to-S converted teleseismic phases recorded at island and ocean bottom stations in Mariana to image the subducting plate and the upper mantle seismic discontinuities in the Mariana subduction zone. The land and seafloor stations which operated from June 2003 to May 2004, were deployed within the framework of the MARGINS Subduction Factory experiment of the Mariana system. The crust in the sudducting plate is observed at about 80--90 km depth beneath the islands of Saipan, Tinian and Rota. For most of the island stations, a low velocity layer is imaged in the forearc at depth between about 20 and 60 km, with decreasing depths toward the arc. The nature of this feature is not yet clear. We found evidence for double seismic discontinuities at the base of the transition zone near the Mariana slab. A shallower discontinuity is imaged at depths of ~650--715 km, and a deeper interface lies at ~740-- 770 km depth. The amplitudes of the seismic signals suggest that the shear velocity contrasts across the two features are comparable. These characteristics support the interpretation that the discontinuities are the results of the phase transformations in olivine (ringwoodite to post-spinel) and garnet (ilminite to perovskite), respectively, for the pyrolite model of mantle composition.

  18. MT2D Inversion to Image the Gorda Plate Subduction Zone

    NASA Astrophysics Data System (ADS)

    Lubis, Y. K.; Niasari, S. W.; Hartantyo, E.

    2018-04-01

    The magnetotelluric method is applicable for studying complicated geological structures because the subsurface electrical properties are strongly influenced by the electric and magnetic fields. This research located in the Gorda subduction zone beneath the North American continental plate. Magnetotelluric 2D inversion was used to image the variation of subsurface resistivity although the phase tensor analysis shows that the majority of dimensionality data is 3D. 19 MT sites were acquired from EarthScope/USArray Project. Wepresent the image of MT 2D inversion to exhibit conductivity distribution from the middle crust to uppermost asthenosphere at a depth of 120 kilometers. Based on the inversion, the overall data misfit value is 3.89. The Gorda plate subduction appears as a high resistive zone beneath the California. Local conductive features are found in the middle crust downward Klamath Mountain, Bonneville Lake, and below the eastern of Utah. Furthermore, mid-crustal is characterized by moderately resistive. Below the extensional Basin and Range province was related to highly resistive. The middle crust to the uppermost asthenosphere becomes moderately resistive. We conclude that the electrical parameters and the dimensionality of datain the shallow depth(about 22.319 km) beneath the North American platein accordance with surface geological features.

  19. Low-Stress Upper Plate Near Subduction Zones and Implications for Temporal Changes in Loading Forces

    NASA Astrophysics Data System (ADS)

    Wang, K.; Hu, Y.; Yoshida, K.

    2016-12-01

    Subduction megathrusts are weak, often with effective friction coefficients as low as 0.03. Consequently, differential stress (S1 - S3) in the nearby upper plate is low. Compression due to plate coupling and tension due to gravity are in a subtle balance that can be tipped by small perturbations. For example, the 2011 M=9 Tohoku-oki earthquake, which has a rupture-zone-average stress drop of only a few MPa, switched offshore margin-normal stress from compression to tension and affected seismicity pattern and stress directions of various parts of the land area. The low differential stress is also reflected in spatial variations of stresses, such as with changes in topography. In the Andes, crustal earthquake focal mechanisms change from thrust-faulting in low-elevation areas to normal-faulting in high-elevation areas. Given the lack of evidence for a pervasively weak crust, the low differential stress may indicate that in general the crust near subduction zones is not critically stressed. If so, crustal earthquakes do not represent pervasive failure but only local failure due to stress, material, and fluid pressure heterogeneity. If distributed permanent deformation that creates topography is not the norm, it either happens in brief episodes or took place in the past. The outer wedge may enter a compressively or extensionally critical state due to coseismic strengthening or weakening, respectively, of the shallow megathrust in largest interplate earthquakes. Temporal changes in loading forces must occur also at much larger temporal and spatial scales in response to changes in the nature of the subducting plate and other tectonic conditions. We propose that submarine wedges and high topography in the upper plate attain their geometry in geologically brief episodes of high differential stress. They normally stay in a low-stress stable state, but their geometry often reflects high-stress episodes of critical states in the past. In other words, rocks have a sustained

  20. Movies of Finite Deformation within Western North American Plate Boundary Zone

    NASA Astrophysics Data System (ADS)

    Holt, W. E.; Birkes, B.; Richard, G. A.

    2004-12-01

    Animations of finite strain within deforming continental zones can be an important tool for both education and research. We present finite strain models for western North America. We have found that these moving images, which portray plate motions, landform uplift, and subsidence, are highly useful for enabling students to conceptualize the dramatic changes that can occur within plate boundary zones over geologic time. These models use instantaneous rates of strain inferred from both space geodetic observations and Quaternary fault slip rates. Geodetic velocities and Quaternary strain rates are interpolated to define a continuous, instantaneous velocity field for western North America. This velocity field is then used to track topography points and fault locations through time (both backward and forward in time), using small time steps, to produce a 6 million year image. The strain rate solution is updated at each time step, accounting for changes in boundary conditions of plate motion, and changes in fault orientation. Assuming zero volume change, Airy isostasy, and a ratio of erosion rate to tectonic uplift rate, the topography is also calculated as a function of time. The animations provide interesting moving images of the transform boundary, highlighting ongoing extension and subsidence, convergence and uplift, and large translations taking place within the strike-slip regime. Moving images of the strain components, uplift volume through time, and inferred erosion volume through time, have also been produced. These animations are an excellent demonstration for education purposes and also hold potential as an important tool for research enabling the quantification of finite rotations of fault blocks, potential erosion volume, uplift volume, and the influence of climate on these parameters. The models, however, point to numerous shortcomings of taking constraints from instantaneous calculations to provide insight into time evolution and reconstruction models

  1. Revised Pacific-Antarctic plate motions and geophysics of the Menard Fracture Zone

    NASA Astrophysics Data System (ADS)

    Croon, Marcel B.; Cande, Steven C.; Stock, Joann M.

    2008-07-01

    A reconnaissance survey of multibeam bathymetry and magnetic anomaly data of the Menard Fracture Zone allows for significant refinement of plate motion history of the South Pacific over the last 44 million years. The right-stepping Menard Fracture Zone developed at the northern end of the Pacific-Antarctic Ridge within a propagating rift system that generated the Hudson microplate and formed the conjugate Henry and Hudson Troughs as a response to a major plate reorganization ˜45 million years ago. Two splays, originally about 30 to 35 km apart, narrowed gradually to a corridor of 5 to 10 km width, while lineation azimuths experienced an 8° counterclockwise reorientation owing to changes in spreading direction between chrons C13o and C6C (33 to 24 million years ago). We use the improved Pacific-Antarctic plate motions to analyze the development of the southwest end of the Pacific-Antarctic Ridge. Owing to a 45° counterclockwise reorientation between chrons C27 and C20 (61 to 44 million years ago) this section of the ridge became a long transform fault connected to the Macquarie Triple Junction. Following a clockwise change starting around chron C13o (33 million years ago), the transform fault opened. A counterclockwise change starting around chron C10y (28 millions years ago) again led to a long transform fault between chrons C6C and C5y (24 to 10 million years ago). A second period of clockwise reorientation starting around chron C5y (10 million years ago) put the transform fault into extension, forming an array of 15 en echelon transform faults and short linking spreading centers.

  2. Seismofocal zones and mid-ocean ridges - look outside of the plate paradigm

    NASA Astrophysics Data System (ADS)

    Anokhin, Vladimir; Kholmianskii, Mikhail

    2014-05-01

    Seismofocal zones and mid-ocean ridges - look outside of the plate paradigm Vladimir M. Anokhin, Mikhail A. Kholmianskii Configuration of the seismofocal zones (SFZ), visible in a real position of the focuses of earthquakes, has a significant step component (jagged) expressed by the presence of several sub-horizontal "seismoplanes", which concentrates focuses of earthquakes (depths 10, 35 km and other). Orientation of seismolines inside of SFZ tends to 4 main directions: 0-5 dgr, 120-145 dgr, 40-55 dgr, 85-90 dgr. These facts suggest significantly block, a terraced structure of the body of Benioff zone. The borders of blocks have orientation according directions regmatic net of the Earth. In accordance with this, SFZ can be presented as the most active segments of the border of the crossing: «continent-ocean», having the following properties: - block (terraced) structure; - in some sites - dive under the continental crust (in present time); - prevailing compression (in present time), perhaps, as the period of the oscillatory cycle; Infinite "subduction" in SFZ is unlikely. One of the areas where there is proof of concept of far "spreading" is the southernmost tip of the mid-oceanic Gakkel ridge in the Laptev sea (Arctic ocean). Here active "spreading" ridge normal approaches to the boundary of the continental crust - the shelf of the Laptev sea. On the shelf there are a number of subparallel NW grabens. NE fault zone Charlie, controlling the continental slope is established stepped fault without shift component. This means that the amount of extending of the offshore grabens does not significantly differ from the scale of spreading in the Gakkel ridge. However, the total spreads grabens (50-100 km) 6-10 times less than the width of the oceanic crust (600 km) in the surrounding area. Conclusion: the oceanic crust in the Laptev sea was formed mainly not due to "spreading". It is very likely that here was sinking and the processing of continental crust in the ocean

  3. Experimental constraints and theoretical bases for microstructural damage in plate boundary shear zones

    NASA Astrophysics Data System (ADS)

    Skemer, P. A.; Cross, A. J.; Bercovici, D.

    2016-12-01

    (Ultra)mylonites from plate boundary shear zones are characterized by severe grain-size reduction and well-mixed mineral phases. The evolution from relatively undeformed tectonite protoliths to highly deformed (ultra)mylonites via the formation of new grain and phase boundaries is described as microstructural `damage.' Microstructural damage is important for two reasons: grain-size reduction is thought to result in significant rheological weakening, while phase mixing inhibits mechanical recovery and preserves the zone of weakness to be reactivated repeatedly throughout the tectonic cycle. Grain-size reduction by dynamic recrystallization has been studied extensively in both geologic and engineered materials, yet the progressive mixing of mineral phases during high pressure/temperature shear - the other essential element of damage or mylonitization - is not well understood. In this contribution we present new experimental results and theory related to two distinct phase mixing processes. First, we describe high strain torsion experiments on calcite and anhydrite mixtures and a simple geometric mixing model related to the stretching and thinning of monophase domains. Second, we describe a grain-switching mechanism that is driven by the surface-tension driven migration of newly formed interphase triple junctions. Unlike dynamic recrystallization, which occurs at relatively small strains, both phase mixing mechanisms described here appear to require extremely large strains, a prediction that is consistent with geologic observations. These data suggest that ductile shear zones experience long, transient intervals of microstructural evolution during which rheology is not at steady state. Microstructural damage may be interpreted as the product of several interconnected physical processes, which are collectively essential to the preservation of long-lived, Earth-like plate tectonics.

  4. Thermochronology and tectonics of the Leeward Antilles: Evolution of the southern Caribbean Plate boundary zone

    USGS Publications Warehouse

    van der Lelij, Roelant; Spikings, Richard A.; Kerr, Andrew C.; Kounov, Alexandre; Cosca, Michael; Chew, David; Villagomez, Diego

    2010-01-01

    Tectonic reconstructions of the Caribbean Plate are severely hampered by a paucity of geochronologic and exhumation constraints from anastomosed basement blocks along its southern margin. New U/Pb, 40Ar/39Ar, apatite fission track, and apatite (U-Th)/He data constrain quantitative thermal and exhumation histories, which have been used to propose a model for the tectonic evolution of the emergent parts of the Bonaire Block and the southern Caribbean Plate boundary zone. An east facing arc system intruded through an oceanic plateau during ~90 to ~87 Ma and crops out on Aruba. Subsequent structural displacements resulted in >80°C of cooling on Aruba during 70–60 Ma. In contrast, exhumation of the island arc sequence exposed on Bonaire occurred at 85–80 Ma and 55–45 Ma. Santonian exhumation on Bonaire occurred immediately subsequent to burial metamorphism and may have been driven by the collision of a west facing island arc with the Caribbean Plate. Island arc rocks intruded oceanic plateau rocks on Gran Roque at ~65 Ma and exhumed rapidly at 55–45 Ma. We attribute Maastrichtian-Danian exhumation on Aruba and early Eocene exhumation on Bonaire and Gran Roque to sequential diachronous accretion of their basement units to the South American Plate. Widespread unconformities indicate late Eocene subaerial exposure. Late Oligocene–early Miocene dextral transtension within the Bonaire Block drove subsidence and burial of crystalline basement rocks of the Leeward Antilles to ≤1 km. Late Miocene–recent transpression caused inversion and ≤1 km of exhumation, possibly as a result of the northward escape of the Maracaibo Block.

  5. Repeating Deep Very Low Frequency Earthquakes: An Evidence of Transition Zone between Brittle and Ductile Zone along Plate Boundary

    NASA Astrophysics Data System (ADS)

    Ishihara, Y.; Yamamoto, Y.; Arai, R.

    2017-12-01

    Recently slow or low frequency seismic and geodetic events are focused under recognition of important role in tectonic process. The most western region of Ryukyu trench, Yaeyama Islands, is very active area of these type events. It has semiannual-like slow slip (Heki et.al., 2008; Nishimura et.al.,2014) and very frequent shallow very low frequency earthquakes near trench zone (Ando et.al.,2012; Nakamura et.al.,2014). Arai et.al.(2016) identified clear reverse phase discontinuity along plate boundary by air-gun survey, suggesting existence of low velocity layer including fluid. The subducting fluid layer is considered to control slip characteristics. On the other hand, deep low frequency earthquake and tremor observed at south-western Honshu and Shikoku of Japan are not identified well due to lack of high-quality seismic network. A broadband seismic station(ISG/PS) of Pacific21 network is operating in last 20 years that locates on occurrence potential area of low frequency earthquake. We tried to review continuous broadband record, searching low frequency earthquakes. In pilot survey, we found three very low frequency seismic events which are dominant in less than 0.1Hz component and are not listed in earthquake catalogue. Source locates about 50km depth and at transition area between slow slip event and active area of general earthquake along plate boundary. To detect small and/or hidden very low frequency earthquake, we applied matched filter analysis to continuous three components waveform data using pre-reviewed seismogram as template signal. 12 events with high correlation are picked up in last 10 years. Most events have very similar waveform, which means characteristics of repeating deep very low frequency earthquake. The event history of very low frequency earthquake is not related with one of slow slip event in this region. In Yaeyama region, low frequency earthquake, general earthquake and slow slip event occur dividing in space and have apparent

  6. Electrical conductivity of the Cascadia subduction zone and implications for the plate interface

    NASA Astrophysics Data System (ADS)

    Livelybrooks, D.; Bedrosian, P.; Egbert, G. D.; Key, K.; Schultz, A.; Parris, B. A.; Yang, B.; Bowles-martinez, E.

    2016-12-01

    The Magnetotelluric Observations of Cascadia using a Huge Array (MOCHA) experiment resulted in the collection of 146 amphibious, long-period magnetotelluric stations acquired between 2012 and 2014. These data, supplemented with the previously-acquired CAFÉ, EMSLAB, SWORMT and EarthScope (MT) Transportable Array stations, have been interpreted to provide electrical conductivity models of Cascadia spanning from the trench eastward through the Cascades, and extending to about 150km depth. We have a particular interest in understanding the roles electrically-conductive, aqueous fluids play in Cascadia subduction processes at or near the plate interface, thus inversions of data are predisposed to accommodate an initially-resistive (McCrory et al. 2014) slab. Beginning at the mantle wedge corner, 3-D inversions reveal significant, latitudinal variation in the conductivity, with enhanced conductivity at 47oN and south at 42oN. Two-dimensional inversions at 44.5oN allowing for a step discontinuity at the Moho give two distinct zones of conductance, one at the MWC tip (c.f. Furukowa, 2009) and another further down-dip, with a conductivity `plume' directed eastwards. At depths of between 20-25km we image a latitudinally-discontinuous resistive lower crust immediately overlying resistive subducted slab. This implies a lack of free fluids near the plate interface. Krogstad et al. (2016) have analyzed historic uplift data and can model the presence of an inboard `secondary locked zone' near 44.5oN. One explanation for both observations—a down-dip, `pinned interface' that is shielding the traditionally-modeled off-shore locked zone from stress accumulation, would explain the paucity of seismicity observed off the north-central Oregon coast during the four-year Cascadia Initiative. At coastal longitudes a narrow, supra-slab conductive zone is imaged at 22km depth with a southern termination at 45oN. It is notable that some researchers place the inboard boundary of the (mostly

  7. Investigating Transition Zone Thickness Variation under the Arabian Plate: Evidence Lacking for Deep Mantle Upwellings

    NASA Astrophysics Data System (ADS)

    Juliá, J.; Tang, Z.; Mai, P. M.; Zahran, H.

    2014-12-01

    Cenozoic volcanic outcrops in Arabia - locally known as harrats - span more than 2000 km along the western half of the Arabian plate, from eastern Yemen to southern Syria. The magmatism is bimodal in character, with older volcanics (30 to 20 My) being tholeiitic-to-transitional and paralleling the Red Sea margin, and younger volcanics (12 Ma to Recent) being transitional-to-strongly-alkalic and aligning in a more north-south direction. The bimodal character has been attributed to a two-stage rifting process along the Red Sea, where the old volcanics would have produced from shallow sources related to an initial passive rifting stage, and young volcanics would have originated from one or more deep-seated mantle plumes driving present active rifting. Early models suggested the harrats would have resulted from either lateral flow from the Afar plume in Ethiopia, or more locally from a separate mantle plume directly located under the shield. Most recently, tomographic images of the Arabian mantle have suggested the northern harrats could be resulting from flow originating at a deep plume under Jordan. In this work, we investigate the location of deep mantle plumes under the Arabian plate by mapping transition zone thickness with teleseismic receiver functions. The transition zone is bounded by seismic discontinuities, nominally at 410 and 660 km depth, originating from phase transitions in the olivine-normative component of the mantle. The precise depth of the discontinuities is strongly dependent on temperature and, due to the opposing signs of the corresponding Clapeyron slopes, positive temperature anomalies are expected to result in thinning of the transition zone. Our dataset consists of ~5000 low-frequency (fc < 0.25 Hz) receiver function waveforms obtained at ~110 broadband stations belonging to a number of permanent and temporary seismic networks in the region. The receiver functions were migrated to depth and stacked along a ~2000 km long record section

  8. Seismic attenuation structure beneath Nazca Plate subduction zone in southern Peru

    NASA Astrophysics Data System (ADS)

    Jang, H.; Kim, Y.; Clayton, R. W.

    2017-12-01

    We estimate seismic attenuation in terms of quality factors, QP and QS using P and S phases, respectively, beneath Nazca Plate subduction zone between 10°S and 18.5°S latitude in southern Peru. We first relocate 298 earthquakes with magnitude ranges of 4.0-6.5 and depth ranges of 20-280 km. We measure t*, which is an integrated attenuation through the seismic raypath between the regional earthquakes and stations. The measured t* are inverted to construct three-dimensional attenuation structures of southern Peru. Checkerboard test results for both QP and QS structures ensure good resolution in the slab-dip transition zone between flat and normal slab subduction down to a depth of 200 km. Both QP and QS results show higher attenuation continued down to a depth of 50 km beneath volcanic arc and also beneath the Quimsachata volcano, the northernmost young volcano, located far east of the main volcanic front. We also observe high attenuation in mantle wedge especially beneath the normal subduction region in both QP and QS (100-130 in QP and 100-125 in QS) and slightly higher QP and QS beneath the flat-subduction and slab-dip transition regions. We plan to relate measured attenuation in the mantle wedge to material properties such as viscosity to understand the subduction zone dynamics.

  9. The memory of the accreting plate boundary and the continuity of fracture zones

    USGS Publications Warehouse

    Schouten, Hans; Klitgord, Kim D.

    1982-01-01

    A detailed aeromagnetic anomaly map of the Mesozoic seafloor-spreading lineations southwest of Bermuda reveals the dominant magnetic grain of the oceanic crust and the character of the accreting boundary at the time of crustal formation. The magnetic anomaly pattern is that of a series of elongate lobes perpendicular to the fracture zone (flowline) trends. The linear sets of magnetic anomaly peaks and troughs have narrow regions of reduced amplitude anomalies associated with the fracture zones. During the period of Mesozoic geomagnetic polarity reversals (when 1200 km of central North Atlantic seafloor formed), the Atlantic accreting boundary consisted of stationary, elongate, spreading center cells that maintained their independence even though sometimes only minor spatial offsets existed between cells. Normal oceanic crustal structure was formed in the spreading center cells, but structural anomalies and discontinuities characteristic of fracture zones were formed at their boundaries, which parallel flowlines of Mesozoic relative plate motion in the central North Atlantic. We suggest that the memory for a stationary pattern of independent spreading center cells resides in the young brittle lithosphere at the accreting boundary where the lithosphere is weakest; here, each spreading center cell independently goes through its cylce of stress buildup, stress release, and crustal accretion, after which its memory is refreshed. The temporal offset between the peaks of the accretionary activity that takes place within each cell may provide the mechanism for maintaining the independence of adjacent spreading center cells through times when no spatial offset between the cells exists.

  10. Extended residence time centrifugal contactor design modification and centrifugal contactor vane plate valving apparatus for extending mixing zone residence time

    DOEpatents

    Wardle, Kent E.

    2017-06-06

    The present invention provides an annular centrifugal contactor, having a housing adapted to receive a plurality of flowing liquids; a rotor on the interior of the housing; an annular mixing zone, wherein the annular mixing zone has a plurality of fluid retention reservoirs with ingress apertures near the bottom of the annular mixing zone and egress apertures located above the ingress apertures of the annular mixing zone; and an adjustable vane plate stem, wherein the stem can be raised to restrict the flow of a liquid into the rotor or lowered to increase the flow of the liquid into the rotor.

  11. Tectonic lineaments in the cenozoic volcanics of southern Guatemala: Evidence for a broad continental plate boundary zone

    NASA Technical Reports Server (NTRS)

    Baltuck, M.; Dixon, T. H.

    1984-01-01

    The northern Caribbean plate boundary has been undergoing left lateral strike slip motion since middle Tertiary time. The western part of the boundary occurs in a complex tectonic zone in the continental crust of Guatemala and southernmost Mexico, along the Chixoy-Polochic, Motogua and possibly Jocotan-Chamelecon faults. Prominent lineaments visible in radar imagery in the Neogene volcanic belt of southern Guatemala and western El Salvador were mapped and interpreted to suggest southwest extensions of this already broad plate boundary zone. Because these extensions can be traced beneath Quaternary volcanic cover, it is thought that this newly mapped fault zone is active and is accommodating some of the strain related to motion between the North American and Caribbean plates. Onshore exposures of the Motoqua-Polochic fault systems are characterized by abundant, tectonically emplaced ultramafic rocks. A similar mode of emplacement for these off shore ultramafics, is suggested.

  12. Simulation and experimental study of aspect ratio limitation in Fresnel zone plates for hard-x-ray optics.

    PubMed

    Liu, Jianpeng; Shao, Jinhai; Zhang, Sichao; Ma, Yaqi; Taksatorn, Nit; Mao, Chengwen; Chen, Yifang; Deng, Biao; Xiao, Tiqiao

    2015-11-10

    For acquiring high-contrast and high-brightness images in hard-x-ray optics, Fresnel zone plates with high aspect ratios (zone height/zone width) have been constantly pursued. However, knowledge of aspect ratio limits remains limited. This work explores the achievable aspect ratio limit in polymethyl methacrylate (PMMA) by electron-beam lithography (EBL) under 100 keV, and investigates the lithographic factors for this limitation. Both Monte Carlo simulation and EBL on thick PMMA are applied to investigate the profile evolution with exposure doses over 100 nm wide dense zones. A high-resolution scanning electron microscope at low acceleration mode for charging free is applied to characterize the resultant zone profiles. It was discovered for what we believe is the first time that the primary electron-beam spreading in PMMA and the proximity effect due to extra exposure from neighboring areas could be the major causes of limiting the aspect ratio. Using the optimized lithography condition, a 100 nm zone plate with aspect ratio of 15/1 was fabricated and its focusing property was characterized at the Shanghai Synchrotron Radiation Facility. The aspect ratio limit found in this work should be extremely useful for guiding further technical development in nanofabrication of high-quality Fresnel zone plates.

  13. Shading of a computer-generated hologram by zone plate modulation.

    PubMed

    Kurihara, Takayuki; Takaki, Yasuhiro

    2012-02-13

    We propose a hologram calculation technique that enables reconstructing a shaded three-dimensional (3D) image. The amplitude distributions of zone plates, which generate the object points that constitute a 3D object, were two-dimensionally modulated. Two-dimensional (2D) amplitude modulation was determined on the basis of the Phong reflection model developed for computer graphics, which considers the specular, diffuse, and ambient reflection light components. The 2D amplitude modulation added variable and constant modulations: the former controlled the specular light component and the latter controlled the diffuse and ambient components. The proposed calculation technique was experimentally verified. The reconstructed image showed specular reflection that varied depending on the viewing position.

  14. Optical image encryption using fresnel zone plate mask based on fast walsh hadamard transform

    NASA Astrophysics Data System (ADS)

    Khurana, Mehak; Singh, Hukum

    2018-05-01

    A new symmetric encryption technique using Fresnel Zone Plate (FZP) based on Fast Walsh Hadamard Transform (FWHT) is proposed for security enhancement. In this technique, bits of plain image is randomized by shuffling the bits randomly. The obtained scrambled image is then masked with FZP using symmetric encryption in FWHT domain to obtain final encrypted image. FWHT has been used in the cryptosystem so as to protect image data from the quantization error and for reconstructing the image perfectly. The FZP used in proposed scheme increases the key space and makes it robust to many traditional attacks. The effectiveness and robustness of the proposed cryptosystem has been analyzed on the basis of various parameters by simulating on MATLAB 8.1.0 (R2012b). The experimental results are provided to highlight suitability of the proposed cryptosystem and prove that the system is secure.

  15. Depth compensating calculation method of computer-generated holograms using symmetry and similarity of zone plates

    NASA Astrophysics Data System (ADS)

    Wei, Hui; Gong, Guanghong; Li, Ni

    2017-10-01

    Computer-generated hologram (CGH) is a promising 3D display technology while it is challenged by heavy computation load and vast memory requirement. To solve these problems, a depth compensating CGH calculation method based on symmetry and similarity of zone plates is proposed and implemented on graphics processing unit (GPU). An improved LUT method is put forward to compute the distances between object points and hologram pixels in the XY direction. The concept of depth compensating factor is defined and used for calculating the holograms of points with different depth positions instead of layer-based methods. The proposed method is suitable for arbitrary sampling objects with lower memory usage and higher computational efficiency compared to other CGH methods. The effectiveness of the proposed method is validated by numerical and optical experiments.

  16. Generation of the Submicron Soft X-Ray Beam Using a Fresnel Zone Plate

    NASA Astrophysics Data System (ADS)

    Nishikino, M.; Kawazome, H.; Tanaka, M.; Kishimoto, M.; Hasegawa, N.; Ochi, Y.; Kawachi, T.; Sukegawa, K.; Yamatani, H.; Nagashima, K.; Kato, Y.

    We have developed a fully coherent x-ray laser at 13.9 nm and the application research has been started. The generation of submicron x-ray beam is important for the application of high intensity x-ray beam, such as the non-linear optics, the material science, and the biology. The submicron x-ray bee am is generated by the soft x-ray laser with using a Fresnel zone plate. The spot diameter is estimated about 680 nm (290 nm at FWHM) by the theoretical calculation. In this experiment, the diameter of the x-ray beam is measured by the knife-edge scan. The diameter and the intensity are estimated 730 nm (310 nm at FWHM) and 3x1011 W/cm2, respectively.

  17. Note: Measurement of synchrotron radiation phase-space beam properties to verify astigmatism compensation in Fresnel zone plate focusing optics

    NASA Astrophysics Data System (ADS)

    Kagoshima, Yasushi; Miyagawa, Takamasa; Kagawa, Saki; Takeda, Shingo; Takano, Hidekazu

    2017-08-01

    The intensity distribution in phase space of an X-ray synchrotron radiation beamline was measured using a pinhole camera method, in order to verify astigmatism compensation by a Fresnel zone plate focusing optical system. The beamline is equipped with a silicon double crystal monochromator. The beam size and divergence at an arbitrary distance were estimated. It was found that the virtual source point was largely different between the vertical and horizontal directions, which is probably caused by thermal distortion of the monochromator crystal. The result is consistent with our astigmatism compensation by inclining a Fresnel zone plate.

  18. A study on the prenatal zone of ultrasonic guided waves in plates

    NASA Astrophysics Data System (ADS)

    Thomas, Tibin; Balasubramaniam, Krishnan

    2017-02-01

    Low frequency guided wave based inspection is an extensively used method for asset management with the advantage of wide area coverage from a single location at the cost of spatial resolution. With the advent of high frequency guided waves, short range inspections with high spatial resolution for monitoring corrosion under pipe supports and tank annular plates has gained widespread interest and acceptance. One of the major challenges in the application of high frequency guided waves in a short range inspection is to attain the desired modal displacements with respect to the application. In this paper, an investigation on the generation and formation of fundamental S0 mode is carried out through numerical simulation and experiments to establish a prenatal zone for guided waves. The effect of frequency, thickness of the plate and frequency-thickness (f*d) is studied. The investigation reveals the existence of a rudimentary form with similar modal features to the fully developed mode. This study helps in the design and development of a high frequency guided wave generator for particular applications which demands waves with very less sensitivity to the surface and loading during the initial phase which immediately evolves to a more sensitive wave towards the surface on propagation for the detection of shallow defects.

  19. Tremor Hypocenters Form a Narrow Zone at the Plate Interface in Two Areas of SW Japan

    NASA Astrophysics Data System (ADS)

    Armbruster, J. G.

    2015-12-01

    The tremor detectors developed for accurately locating tectonic tremor in Cascadia [Armbruster et al., JGR 2014] have been applied to data from the HINET seismic network in Japan. In the overview by Obara [Science 2002] there are three strong sources of tectonic tremor in southwest Japan: Shikoku, Kii Pen. and Tokai. The daily epicentral distributions of tremor on the HINET web site allow the identification of days when tremor in each source is active. The worst results were obtained in Shikoku, in spite of the high level of tremor activity observed there by others. This method requires a clear direct arrival of the S and P waves at the stations for coherence to be seen, so scattering and shear wave splitting are possible reasons for poor results there. Relatively wide station spacing, 19-30 km, is another possible reason. The best results were obtained in Tokai with stations STR, HRY and TYE spacing 18-19 km, and Kii Pen. with stations KRT, HYS and KAW spacing 15-22 km. In both of those areas the three station detectors see strong episodes of tremor. If detections with three stations are located by constraining them to the plate interface, a pattern of persistent sources is seen, with some intense sources. This is similar to what was seen in Cascadia. Detections with four stations give S and P arrival times of high accuracy. In Tokai the hypocenters form a narrow, 2-3 km thick, zone dipping to the north, consistent with the plate interface there. In Kii Pen. the hypocenters dip to the northwest in a thin, 2-3 km thick, zone but approximately 5 km shallower than a plate interface model for this area [Yoshioka and Murakami, GJI 2007]. The overlap of tremor sources in the 12 years analyzed here suggests relative hypocentral location errors as small as 2-3 km. We conclude that the methods developed in Cascadia will work in Japan but the typical spacing of HINET stations, ~20 km, is greater than the optimum distance found in analysis of data from Cascadia, 8 to 15 km.

  20. Multilayer on-chip stacked Fresnel zone plates: Hard x-ray fabrication and soft x-ray simulations

    SciTech Connect

    Li, Kenan; Wojcik, Michael J.; Ocola, Leonidas E.

    2015-11-01

    Fresnel zone plates are widely used as x-ray nanofocusing optics. To achieve high spatial resolution combined with good focusing efficiency, high aspect ratio nanolithography is required, and one way to achieve that is through multiple e-beam lithography writing steps to achieve on-chip stacking. A two-step writing process producing 50 nm finest zone width at a zone thickness of 1.14 µm for possible hard x-ray applications is shown here. The authors also consider in simulations the case of soft x-ray focusing where the zone thickness might exceed the depth of focus. In this case, the authors compare on-chip stacking with, andmore » without, adjustment of zone positions and show that the offset zones lead to improved focusing efficiency. The simulations were carried out using a multislice propagation method employing Hankel transforms.« less

  1. Imaging the deep structures of the convergent plates along the Ecuadorian subduction zone through receiver function analysis

    NASA Astrophysics Data System (ADS)

    Galve, A.; Charvis, P.; Regnier, M. M.; Font, Y.; Nocquet, J. M.; Segovia, M.

    2017-12-01

    The Ecuadorian subduction zone was affected by several large M>7.5 earthquakes. While we have low resolution on the 1942, 1958 earthquakes rupture zones extension, the 2016 Pedernales earthquake, that occurs at the same location than the 1942 earthquake, give strong constraints on the deep limit of the seismogenic zone. This downdip limit is caused by the onset of plasticity at a critical temperature (> 350-450 °C for crustal materials, or serpentinized mantle wedge, and eventually > 700 °C for dry mantle). However we still don't know exactly where is the upper plate Moho and therefore what controls the downdip limit of Ecuadorian large earthquakes seismogenic zone. For several years Géoazur and IG-EPN have maintained permanent and temporary networks (ADN and JUAN projects) along the margin to register the subduction zone seismological activity. Although Ecuador is not a good place to perform receiver function due to its position with respect to the worldwide teleseismic sources, the very long time deployment compensate this issue. We performed a frequency dependent receiver function analysis to derive (1) the thickness of the downgoing plate, (2) the interplate depth and (3) the upper plate Moho. These constraints give the frame to interpretation on the seismogenic zone of the 2016 Pedernales earthquake.

  2. Lithospheric Structure of the Incoming Nazca Plate Adjacent to the 2014 Iquique Earthquake Rupture Zone

    NASA Astrophysics Data System (ADS)

    Myers, E. K.; Trehu, A. M.; Davenport, K. K.; Roland, E. C.

    2017-12-01

    The 2014 Iquique Mw 8.1 earthquake occurred within a 500-km long segment of the Peru-Chile subduction zone that had not experienced a significant earthquake since 1877. This event did not fill the entire seismic gap and details of the deformation, along with local gravity anomalies, point to a geologic control on slip behavior. To better constrain along-strike changes in geologic or morphologic features and the correlation with earthquake rupture, the 2016 PICTURES (Pisagua-Iquique Crustal Tomography to Understand the Region of the Earthquake Source) experiment collected multichannel seismic (MCS) and ocean bottom seismometer (OBS) data from across the deformation front and incoming Nazca plate within the area of the 2014 earthquake. Here, we provide a first look at MCS reflection data from this experiment that images the Nazca plate along an uninterrupted 170 km line perpendicular to the region of greatest slip, acquired using the R/V Langseth's 12.5 km streamer and 6600 cc gun array. We summarize structural features of the incoming oceanic lithosphere and present a preliminary 2D velocity model that spans the Nazca outer rise to the trench along the Iquique Ridge (IR). The IR represents a broad, high oceanic feature (HOF) that roughly spans the entire seismic gap. The source of buoyancy and reduced seismic velocities of the IR swell are thought to be produced by isostatically compensated, overthickened crust or anomalously low density mantle due to heating or serpentinization, and we explore these two hypotheses using our preliminary velocity model. Past outer rise deformation modeling suggests a significant bending moment and vertical force at the trench axis, a source for broad, homogenous coupling as the HOF converges the margin. However, decreased incoming sediment and rough topography associated with numerous large seamounts may also lead to a thin subduction channel, influencing heterogeneous rupture behavior. Seaward of the Iquique 2014 event, our initial

  3. Dynamic Linkages Between the Transition Zone & Surface Plate Motions in 2D Models of Subduction

    NASA Astrophysics Data System (ADS)

    Arredondo, K.; Billen, M. I.

    2013-12-01

    While slab pull is considered the dominant force controlling plate motion and speed, its magnitude is controlled by slab behavior in the mantle, where tomographic studies show a wide range of possibilities from direct penetration to folding, or stagnation directly above the lower mantle (e.g. Fukao et al., 2009). Geodynamic studies have investigated various parameters, such as plate age and two phase transitions, to recreate observed behavior (e.g. Běhounková and Cízková, 2008). However, past geodynamic models have left out known slab characteristics that may have a large impact on slab behavior and our understanding of subduction processes. Mineral experiments and seismic observations have indicated the existence of additional phase transitions in the mantle transition zone that may produce buoyancy forces large enough to affect the descent of a subducting slab (e.g. Ricard et al., 2005). The current study systematically tests different common assumptions used in geodynamic models: kinematic versus free-slip boundary conditions, the effects of adiabatic heating, viscous dissipation and latent heat, compositional layering and a more complete suite of phase transitions. Final models have a complete energy equation, with eclogite, harzburgite and pyrolite lithosphere compositional layers, and seven composition-dependent phase transitions within the olivine, pyroxene and garnet polymorph minerals. Results show important feedback loops between different assumptions and new behavior from the most complete models. Kinematic models show slab weakening or breaking above the 660 km boundary and between compositional layers. The behavior in dynamic models with a free-moving trench and overriding plate is compared to the more commonly found kinematic models. The new behavior may have important implications for the depth distribution of deep earthquakes within the slab. Though the thermodynamic parameters of certain phase transitions may be uncertain, their presence and

  4. Consolidation patterns during initiation and evolution of a plate-boundary decollement zone: Northern Barbados accretionary prism

    USGS Publications Warehouse

    Moore, J.C.; Klaus, A.; Bangs, N.L.; Bekins, B.; Bucker, C.J.; Bruckmann, W.; Erickson, S.N.; Hansen, O.; Horton, T.; Ireland, P.; Major, C.O.; Moore, Gregory F.; Peacock, S.; Saito, S.; Screaton, E.J.; Shimeld, J.W.; Stauffer, P.H.; Taymaz, T.; Teas, P.A.; Tokunaga, T.

    1998-01-01

    Borehole logs from the northern Barbados accretionary prism show that the plate-boundary decollement initiates in a low-density radiolarian claystone. With continued thrusting, the decollement zone consolidates, but in a patchy manner. The logs calibrate a three-dimensional seismic reflection image of the decollement zone and indicate which portions are of low density and enriched in fluid, and which portions have consolidated. The seismic image demonstrates that an underconsolidated patch of the decollement zone connects to a fluid-rich conduit extending down the decollement surface. Fluid migration up this conduit probably supports the open pore structure in the underconsolidated patch.

  5. Viewing zones in three-dimensional imaging systems based on lenticular, parallax-barrier, and microlens-array plates.

    PubMed

    Son, Jung-Young; Saveljev, Vladmir V; Kim, Jae-Soon; Kim, Sung-Sik; Javidi, Bahram

    2004-09-10

    The viewing zone of autostereoscopic imaging systems that use lenticular, parallax-barrier, and microlens-array plates as the viewing-zone-forming optics is analyzed in order to verify the image-quality differences between different locations of the zone. The viewing zone consists of many subzones. The images seen at most of these subzones are composed of at least one image strip selected from the total number of different view images displayed. These different view images are not mixed but patched to form a complete image. This image patching deteriorates the quality of the image seen at different subzones. We attempt to quantify the quality of the image seen at these viewing subzones by taking the inverse of the number of different view images patched together at different subzones. Although the combined viewing zone can be extended to almost all of the front space of the imaging system, in reality it is limited mainly by the image quality.

  6. More are better, but the details matter: combinations of multiple Fresnel zone plates for improved resolution and efficiency in X-ray microscopy

    SciTech Connect

    Li, Kenan; Jacobsen, Chris

    Fresnel zone plates used for X-ray nanofocusing face high-aspect-ratio nanofabrication challenges in combining narrow transverse features (for high spatial resolution) along with extended optical modulation along the X-ray beam direction (to improve efficiency). The stacking of multiple Fresnel zone plates along the beam direction has already been shown to offer improved characteristics of resolution and efficiency when compared with thin single zone plates. Using multislice wave propagation simulation methods, here a number of new schemes for the stacking of multiple Fresnel zone plates are considered. These include consideration of optimal thickness and spacing in the axial direction, and methods tomore » capture a fraction of the light otherwise diffracted into unwanted orders, and instead bring it into the desired first-order focus. In conclusion, the alignment tolerances for stacking multiple Fresnel zone plates are also considered.« less

  7. Time-alternating method based on single-sideband holography with half-zone-plate processing for the enlargement of viewing zones.

    PubMed

    Mishina, T; Okano, F; Yuyama, I

    1999-06-10

    The single-sideband method of holography, as is well known, cuts off beams that come from conjugate images for holograms produced in the Fraunhofer region and from objects with no phase components. The single-sideband method with half-zone-plate processing is also effective in the Fresnel region for beams from an object that has phase components. However, this method restricts the viewing zone to a narrow range. We propose a method to improve this restriction by time-alternating switching of hologram patterns and a spatial filter set on the focal plane of a reconstruction lens.

  8. Structure zone diagram and particle incorporation of nickel brush plated composite coatings

    PubMed Central

    Isern, L.; Impey, S.; Almond, H.; Clouser, S. J.; Endrino, J. L.

    2017-01-01

    This work studies the deposition of aluminium-incorporated nickel coatings by brush electroplating, focusing on the electroplating setup and processing parameters. The setup was optimised in order to increase the volume of particle incorporation. The optimised design focused on increasing the plating solution flow to avoid sedimentation, and as a result the particle transport experienced a three-fold increase when compared with the traditional setup. The influence of bath load, current density and the brush material used was investigated. Both current density and brush material have a significant impact on the morphology and composition of the coatings. Higher current densities and non-abrasive brushes produce rough, particle-rich samples. Different combinations of these two parameters influence the surface characteristics differently, as illustrated in a Structure Zone Diagram. Finally, surfaces featuring crevices and peaks incorporate between 3.5 and 20 times more particles than smoother coatings. The presence of such features has been quantified using average surface roughness Ra and Abbott-Firestone curves. The combination of optimised setup and rough surface increased the particle content of the composite to 28 at.%. PMID:28300159

  9. Structure zone diagram and particle incorporation of nickel brush plated composite coatings

    NASA Astrophysics Data System (ADS)

    Isern, L.; Impey, S.; Almond, H.; Clouser, S. J.; Endrino, J. L.

    2017-03-01

    This work studies the deposition of aluminium-incorporated nickel coatings by brush electroplating, focusing on the electroplating setup and processing parameters. The setup was optimised in order to increase the volume of particle incorporation. The optimised design focused on increasing the plating solution flow to avoid sedimentation, and as a result the particle transport experienced a three-fold increase when compared with the traditional setup. The influence of bath load, current density and the brush material used was investigated. Both current density and brush material have a significant impact on the morphology and composition of the coatings. Higher current densities and non-abrasive brushes produce rough, particle-rich samples. Different combinations of these two parameters influence the surface characteristics differently, as illustrated in a Structure Zone Diagram. Finally, surfaces featuring crevices and peaks incorporate between 3.5 and 20 times more particles than smoother coatings. The presence of such features has been quantified using average surface roughness Ra and Abbott-Firestone curves. The combination of optimised setup and rough surface increased the particle content of the composite to 28 at.%.

  10. On gravity from SST, geoid from SEASAT, and plate age and fracture zones in the Pacific

    NASA Technical Reports Server (NTRS)

    Marsh, B. D.; Marsh, J. G.; Williamson, R. G.

    1983-01-01

    Data from an additional 50 satellite-to-satellite tracking (SST) passes were combined with earlier measurements of the high degree and order (n, m, 12) gravity in the central Pacific. A composite map was produced which shows good agreement with conventional GEM models. Data from the SEASAT altimeter was reduced and found to agree well with both the SST and the GEM fields. The maps are dominated especially in the east, by a pattern of roughly east-west anomalies with a transverse wavelength of about 2000 km. Further comparison with regional bathymetric data shows a remarkably close correlation with plate age. Each anomaly band is framed by those major fracture zones having large offsets. The regular spacing of these fractures seems to account for the fabric in the gravity fields. Other anomalies are accounted for by hot spots. The source of part of these anomalies is in the lithosphere itself. The possible plume size and ascent velocity necessary to supply deep mantle material to the upper mantel without complete thermal equilibration is considered.

  11. Extension and transtension in the plate boundary zone of the northeastern Caribbean

    SciTech Connect

    Speed, R.C.; Larue, D.K.

    1991-03-01

    The authors propose that the Caribbean (Ca)-North American (NA) plate boundary zone (pbz) from the Puerto Rico Trench to the Venezuelan Basin from Mona Canyon east has been in left-transtension over the last 15-20 ma. A boundary-normal component of extension occurs throughout the pbz and is a principal cause of the Puerto Rico Trench. Such extension is due to WNW velocity of NA-Ca and the northward pullaway of NA from its S-dipping slab, which is below Puerto Rico. Strike slip motion may be taken up among terranes in the pbz by rigid CCW rotation and by oblique slip at theirmore » boundaries. Rotation of the largest terrane, Puerto Rico-Virgin Islands (PRVI), has caused such major structures as the Muertos thrust and Anegada Passage. The model implies NA-Ca velocity estimated from Cayman transforms is more accurate than that from slip vectors from seisms in the NA slab.« less

  12. The application of Fresnel zone plate based projection in optofluidic microscopy.

    PubMed

    Wu, Jigang; Cui, Xiquan; Lee, Lap Man; Yang, Changhuei

    2008-09-29

    Optofluidic microscopy (OFM) is a novel technique for low-cost, high-resolution on-chip microscopy imaging. In this paper we report the use of the Fresnel zone plate (FZP) based projection in OFM as a cost-effective and compact means for projecting the transmission through an OFM's aperture array onto a sensor grid. We demonstrate this approach by employing a FZP (diameter = 255 microm, focal length = 800 microm) that has been patterned onto a glass slide to project the transmission from an array of apertures (diameter = 1 microm, separation = 10 microm) onto a CMOS sensor. We are able to resolve the contributions from 44 apertures on the sensor under the illumination from a HeNe laser (wavelength = 633 nm). The imaging quality of the FZP determines the effective field-of-view (related to the number of resolvable transmissions from apertures) but not the image resolution of such an OFM system--a key distinction from conventional microscope systems. We demonstrate the capability of the integrated system by flowing the protist Euglena gracilis across the aperture array microfluidically and performing OFM imaging of the samples.

  13. Structure zone diagram and particle incorporation of nickel brush plated composite coatings.

    PubMed

    Isern, L; Impey, S; Almond, H; Clouser, S J; Endrino, J L

    2017-03-16

    This work studies the deposition of aluminium-incorporated nickel coatings by brush electroplating, focusing on the electroplating setup and processing parameters. The setup was optimised in order to increase the volume of particle incorporation. The optimised design focused on increasing the plating solution flow to avoid sedimentation, and as a result the particle transport experienced a three-fold increase when compared with the traditional setup. The influence of bath load, current density and the brush material used was investigated. Both current density and brush material have a significant impact on the morphology and composition of the coatings. Higher current densities and non-abrasive brushes produce rough, particle-rich samples. Different combinations of these two parameters influence the surface characteristics differently, as illustrated in a Structure Zone Diagram. Finally, surfaces featuring crevices and peaks incorporate between 3.5 and 20 times more particles than smoother coatings. The presence of such features has been quantified using average surface roughness Ra and Abbott-Firestone curves. The combination of optimised setup and rough surface increased the particle content of the composite to 28 at.%.

  14. The Iceland Plate Boundary Zone: Propagating Rifts, Migrating Transforms, and Rift-Parallel Strike-Slip Faults

    NASA Astrophysics Data System (ADS)

    Karson, J. A.

    2017-11-01

    Unlike most of the Mid-Atlantic Ridge, the North America/Eurasia plate boundary in Iceland lies above sea level where magmatic and tectonic processes can be directly investigated in subaerial exposures. Accordingly, geologic processes in Iceland have long been recognized as possible analogs for seafloor spreading in the submerged parts of the mid-ocean ridge system. Combining existing and new data from across Iceland provides an integrated view of this active, mostly subaerial plate boundary. The broad Iceland plate boundary zone includes segmented rift zones linked by transform fault zones. Rift propagation and transform fault migration away from the Iceland hotspot rearrange the plate boundary configuration resulting in widespread deformation of older crust and reactivation of spreading-related structures. Rift propagation results in block rotations that are accommodated by widespread, rift-parallel, strike-slip faulting. The geometry and kinematics of faulting in Iceland may have implications for spreading processes elsewhere on the mid-ocean ridge system where rift propagation and transform migration occur.

  15. The Queen Charlotte-Fairweather Fault Zone - The Knife-Edged Pacific-North American Plate Boundary

    NASA Astrophysics Data System (ADS)

    Greene, H. G.; Barrie, J. V. J.; Brothers, D. S.; Nishenko, S. P.; Conway, K.; Enkin, R.; Conrad, J. E.; Maier, K. L.; Stacy, C.

    2016-12-01

    Recent investigations of the Queen Charlotte-Fairweather (QC-FW) Fault zone using multibeam echosounder bathymetric and 3.5-kHz sub-bottom profile data show that the fault zone is primarily represented by a single linear structure with small, localized pull-apart basins suggestive of transtension. Water column acoustical data imaged gas plumes concentrated along the fault zone with plume columns extending as much as 700 m above the crest of mud volcanoes. Piston cores indicate that the fault zone cuts hard-packed dense sands that have been dated as Pleistocene in age. The newly discovered fluids associated with the southern half of the fault zone and volcanic edifices with oceanic and continental plate petrologic affinities suggest that the QC-FW is a leaky transform system. Two independent investigations, one in the north part and one in the central part of the fault zone, using two different types of piercing points, found that the slip rate along at least a 200 km length was consistent at between 40-55 mm/yr. since about 14 ka, equivalent to the relative plate motion between the Pacific and North American plates in the NE Pacific region. We surmise that the QC-FW is accommodating most, if not all, of relative motion along a single primary strand without any detectable partitioning of motion onto other faults. This right-lateral strike-slip fault zone is expressed on the seafloor as a very straight feature that probably represents nearly pure strike-slip motion.

  16. High-Resolution P'P' Precursor Imaging of Nazca-South America Plate Boundary Zones and Inferences for Transition Zone Temperature and Composition

    NASA Astrophysics Data System (ADS)

    Gu, Y. J.; Schultz, R.

    2013-12-01

    Knowledge of upper mantle transition zone stratification and composition is highly dependent on our ability to efficiently extract and properly interpret small seismic arrivals. A promising high-frequency seismic phase group particularly suitable for a global analysis is P'P' precursors, which are capable of resolving mantle structures at vertical and lateral resolution of approximately 5 and 200 km, respectively, owing to their shallow incidence angle and small, quasi-symmetric Fresnel zones. This study presents a simultaneous analysis of SS and P'P' precursors based on deconvolution, Radon transform and depth migration. Our multi-resolution survey of the mantle near Nazca-South America subduction zone reveals both olivine and garnet related transitions at depth below 400 km. We attribute a depressed 660 to thermal variations, whereas compositional variations atop the upper-mantle transition zone are needed to explain the diminished or highly complex reflected/scattered signals from the 410 km discontinuity. We also observe prominent P'P' reflections within the transition zone, especially near the plate boundary zone where anomalously high reflection amplitudes result from a sharp (~10 km thick) mineral phase change resonant with the dominant frequency of the P'P' precursors. Near the base of the upper mantle, the migration of SS precursors shows no evidence of split reflections near the 660-km discontinuity, but potential majorite-ilmenite (590-640 km) and ilmenite-perovskite transitions (740-750 km) are identified based on similarly processed high-frequency P'P' precursors. At nominal mantle temperatures these two phase changes may be seismically indistinguishable, but colder mantle conditions from the descending Nazca plate, the presence of water and variable Fe contents may cause sufficient separation for a reliable analysis. In addition, our preliminary results provide compelling evidence for multiple shallow lower-mantle reflections (at ~800 km) along the

  17. Style of Plate Spreading Derived from the 2008-2014 Velocity Field Across the Northern Volcanic Zone of Iceland

    NASA Astrophysics Data System (ADS)

    Drouin, V.; Sigmundsson, F.; Hreinsdottir, S.; Ofeigsson, B.; Sturkell, E.; Einarsson, P.

    2015-12-01

    The Northern Volcanic Zone (NVZ) of Iceland is a subaerial part of the divergent boundary between the North-American and Eurasian Plates. At this latitude, the full spreading between the plates is accommodated by the NVZ. We derived the plate boundary velocity field from GPS campaign and continuous measurements between 2008 and 2014, a time period free of any magma intrusion. Average velocities were estimated in the ITRF08 reference frame. The overall extension is consistent with 18 mm/yr in the 104°N direction spreading, in accordance with the MORVEL2010 plate motion model. We find that a 40km-wide band along the plate boundary accommodates about 75% of the full plate velocities. Within this zone, the average strain rate is approximately 0.35 μstrain/yr. The deformation field and the strain rate are, however, much affected by other sources of deformations in the NVZ. These include magmatic sources at the most active volcanic centers, glacial rebound near the ice-caps and geothermal power-plant water extraction. Magmatic sources include a shallow magma chamber deflation under Askja caldera, as well as under Þeistareykir and eventual deep magma inflation north of Krafla volcano. Vatnajökull ice cap melting causes large uplift and outward displacements in the southern part of the NVZ. The two geothermal power-plants near Krafla are inducing local deflations. Our GPS velocities show a 35° change in the direction of the plate boundary axis north of Askja volcano that we infer to be linked to the geometric arrangement of volcanic systems within the NVZ.We use a simple arctangent model to describe the plate spreading to provide constraints on the location and the locking depth of the spreading axis. For that purpose we divided the area in short overlapping segments having the same amount of GPS points along the plate spreading direction and inverted for the location of the center of the spreading axis and locking depth. With this simple model we can account for most

  18. Constraints on upper plate deformation in the Nicaraguan subduction zone from earthquake relocation and directivity analysis

    NASA Astrophysics Data System (ADS)

    French, S. W.; Warren, L. M.; Fischer, K. M.; Abers, G. A.; Strauch, W.; Protti, J. M.; Gonzalez, V.

    2010-03-01

    In the Nicaraguan segment of the Central American subduction zone, bookshelf faulting has been proposed as the dominant style of Caribbean plate deformation in response to oblique subduction of the Cocos plate. A key element of this model is left-lateral motion on arc-normal strike-slip faults. On 3 August 2005, a Mw 6.3 earthquake and its extensive foreshock and aftershock sequence occurred near Ometepe Island in Lake Nicaragua. To determine the fault plane that ruptured in the main shock, we relocated main shock, foreshock, and aftershock hypocenters and analyzed main shock source directivity using waveforms from the TUCAN Broadband Seismic Experiment. The relocation analysis was carried out by applying the hypoDD double-difference method to P and S onset times and differential traveltimes for event pairs determined by waveform cross correlation. The relocated hypocenters define a roughly vertical plane of seismicity with an N60°E strike. This plane aligns with one of the two nodal planes of the main shock source mechanism. The directivity analysis was based on waveforms from 16 TUCAN stations and indicates that rupture on the N60°E striking main shock nodal plane provides the best fit to the data. The relocation and directivity analyses identify the N60°E vertical nodal plane as the main shock fault plane, consistent with the style of faulting required by the bookshelf model. Relocated hypocenters also define a second fault plane that lies to the south of the main shock fault plane with a strike of N350°E-N355°E. This fault plane became seismically active 5 h after the main shock, suggesting the influence of stresses transferred from the main shock fault plane. The August 2005 earthquake sequence was preceded by a small eruption of a nearby volcano, Concepción, on 28 July 2005. However, the local seismicity does not provide evidence for earthquake triggering of the eruption or eruption triggering of the main shock through crustal stress transfer.

  19. High-speed X-ray microscopy by use of high-resolution zone plates and synchrotron radiation.

    PubMed

    Hou, Qiyue; Wang, Zhili; Gao, Kun; Pan, Zhiyun; Wang, Dajiang; Ge, Xin; Zhang, Kai; Hong, Youli; Zhu, Peiping; Wu, Ziyu

    2012-09-01

    X-ray microscopy based on synchrotron radiation has become a fundamental tool in biology and life sciences to visualize the morphology of a specimen. These studies have particular requirements in terms of radiation damage and the image exposure time, which directly determines the total acquisition speed. To monitor and improve these key parameters, we present a novel X-ray microscopy method using a high-resolution zone plate as the objective and the matching condenser. Numerical simulations based on the scalar wave field theory validate the feasibility of the method and also indicate the performance of X-ray microscopy is optimized most with sub-10-nm-resolution zone plates. The proposed method is compatible with conventional X-ray microscopy techniques, such as computed tomography, and will find wide applications in time-resolved and/or dose-sensitive studies such as living cell imaging.

  20. Faster scanning and higher resolution: new setup for multilayer zone plate imaging

    NASA Astrophysics Data System (ADS)

    Osterhoff, Markus; Soltau, Jakob; Eberl, Christian; Krebs, Hans-Ulrich

    2017-09-01

    Hard x-ray imaging methods are routinely used in two and three spatial dimensions to tackle challenging scientific questions of the 21st century, e.g. catalytic processes in energy research and bio-physical experiments on the single-cell level [1-3]. Among the most important experimental techniques are scanning SAXS to probe the local orientation of filaments and fluorescence mapping to quantify the local composition. The routinely available spot size has been reduced to few tens of nanometres; but the real-space resolution of these techniques can degrade by (i) vibration or drift, and (ii) spreading of beam damage, especially for soft condensed matter on small length scales. We have recently developed new Multilayer Zone Plate (MZP) optics for focusing hard (14 keV) and very hard (60 keV to above 100 keV) x-rays down to spot sizes presumably on 5 or 10nm scale. Here we report on recent progress on a new MZP based sample scanner, and how to tackle beam damage spread. The Eiger detector synchronized to a piezo scanner enables to scan in a 2D continuous mode fields of view larger than 20μm squared, or for high resolution down to (virtual) pixel sizes of below 2nm, in about three minutes for 255×255 points (90 seconds after further improvements). Nano-SAXS measurements with more than one million real-space pixels, each containing a full diffraction image, can be carried out in less than one hour, as we have shown using a Siemens star test pattern.

  1. Plate boundary and major fault system in the overriding plate within the Shumagin gap at the Alaska-Aleutian subduction zone

    NASA Astrophysics Data System (ADS)

    Becel, A.; Shillington, D. J.; Nedimovic, M. R.; Keranen, K. M.; Li, J.; Webb, S. C.; Kuehn, H.

    2013-12-01

    Structure in the overriding plate is one of the parameters that may increase the tsunamigenic potential of a subduction zone but also influence the seismogenic behavior and segmentation of great earthquake rupture. The Alaska-Aleutian margin is characterized by along-strike changes in plate interface coupling over relatively small distances. Here, we present trench normal multichannel seismic (MCS) profiles acquired across the Shumagin gap that has not broken in many decades and appears to be weakly coupled. The high fold, deep penetration (636 channel, 8-km long streamer, 6600 cu.in airgun source) MCS data were acquired as part of the ALEUT project. This dataset gives us critical new constraints on the interplate boundary that can be traced over ~100 km distance beneath the forearc with high variation in its reflection response with depth. These profiles also reveal the detailed upper plate fault structure and forearc morphology. Clear reflections in the overriding plate appear to delineate one or more large faults that cross the shelf and the upper slope. These faults are observed 75 km back from the trench and seem to branch at depth and connect to the plate interface within this gap at ~11 s twtt. We compare the reflective structure of these faults to that of the plate boundary and examine where it intersects the megathrust with respect of the expected downdip limit of coupling. We also compare this major structure with the seismicity recorded in this sector. The imaged fault system is associated with a large deep basin (~6s twt) that is an inherited structure formed during the pre-Aleutian period. Basins faults appear to have accommodated primarily normal motion, although folding of sediments near the fault and complicated fault geometries in the shallow section may indicate that this fault has accommodated other types of motion during its history that may reflect the stress-state at the megathrust over time. The deformation within the youngest sediment also

  2. The Devils Mountain Fault zone: An active Cascadia upper plate zone of deformation, Pacific Northwest of North America

    NASA Astrophysics Data System (ADS)

    Barrie, J. Vaughn; Greene, H. Gary

    2018-02-01

    The Devils Mountain Fault Zone (DMFZ) extends east to west from Washington State to just south of Victoria, British Columbia, in the northern Strait of Juan de Fuca of Canada and the USA. Recently collected geophysical data were used to map this fault zone in detail, which show the main fault trace, and associated primary and secondary (conjugate) strands, and extensive northeast-southwest oriented folding that occurs within a 6 km wide deformation zone. The fault zone has been active in the Holocene as seen in the offset and disrupted upper Quaternary strata, seafloor displacement, and deformation within sediment cores taken close to the seafloor expression of the faults. Data suggest that the present DMFZ and the re-activated Leech River Fault may be part of the same fault system. Based on the length and previously estimated slip rates of the fault zone in Washington State, the DMFZ appears to have the potential of producing a strong earthquake, perhaps as large as magnitude 7.5 or greater, within 2 km of the city of Victoria.

  3. Upper-Mantel Earthquakes in the Australia-Pacific Plate Boundary Zone and the Roots of the Alpine Fault

    NASA Astrophysics Data System (ADS)

    Boese, C. M.; Warren-Smith, E.; Townend, J.; Stern, T. A.; Lamb, S. H.

    2016-12-01

    Seismicity in the upper mantle in continental collision zones is relatively rare, but observed around the world. Temporary seismometer deployments have repeatedly detected mantle earthquakes at depths of 40-100 km within the Australia-Pacific plate boundary zone beneath the South Island of New Zealand. Here, the transpressive Alpine Fault constitutes the primary plate boundary structure linking subduction zones of opposite polarity farther north and south. The Southern Alps Microearthquake Borehole Array (SAMBA) has been operating continuously since November 2008 along a 50 km-long section of the central Alpine Fault, where the rate of uplift of the Southern Alps is highest. To date it has detected more than 40 small to moderate-sized mantle events (1≤ML≤3.9). The Central Otago Seismic Array (COSA) has been in operation since late 2012 and detected 15 upper mantle events along the sub-vertical southern Alpine Fault. Various mechanisms have been proposed to explain the occurrence of upper mantle seismicity in the South Island, including intra-continental subduction (Reyners 1987, Geology); high shear-strain gradients due to depressed geotherms and viscous deformation of mantle lithosphere (Kohler and Eberhart-Phillips 2003, BSSA); high strain rates resulting from plate bending (Boese et al. 2013, EPSL), and underthrusting of the Australian plate (Lamb et al. 2015, G3). Focal mechanism analysis reveals a variety of mechanisms for the upper mantle events but predominantly strike-slip and reverse faulting. In this study, we apply spectral analysis to better constrain source parameters for these mantle events. These results are interpreted in conjunction with new information about crustal structure and low-frequency earthquakes near the Moho and in light of existing velocity, attenuation and resistivity models.

  4. Along-Strike Electrical Conductivity Variations in the Incoming Plate and Shallow Forearc of the Cascadia Subduction Zone

    NASA Astrophysics Data System (ADS)

    Key, K.; Bedrosian, P.; Egbert, G. D.; Livelybrooks, D.; Parris, B. A.; Schultz, A.

    2015-12-01

    The Magnetotelluric Observations of Cascadia using a Huge Array (MOCHA) experiment was carried out to study the nature of the seismogenic locked zone and the down-dip transition zone where episodic tremor and slip (ETS) originates. This amphibious magnetotelluric (MT) data set consists of 8 offshore and 15 onshore profiles crossing from just seaward of the trench to the western front of the Cascades, with a north-south extent spanning from central Oregon to central Washington. The 71 offshore stations and the 75 onshore stations (red triangles in the image below) fit into the broader context of the more sparsely sampled EarthScope MT transportable array (black triangles) and other previous and pending MT surveys (other symbols). These data allows us to image variations in electrical conductivity along distinct segments of the Cascadia subduction zone defined by ETS recurrence intervals. Since bulk conductivity in this setting depends primarily on porosity, fluid content and temperature, the conductivity images created from the MOCHA data offer unique insights on fluid processes in the crust and mantle, and how the distribution of fluid along the plate interface relates to observed variations in ETS behavior. This abstract explores the across- and along-strike variations in the incoming plate and the shallow offshore forearc. In particular we examine how conductivity variations, and the inferred fluid content and porosity variations, are related to tectonic segmentation, seismicity and deformation patterns, and arc magma variations along-strike. Porosity inferred in the forearc crust can be interpreted in conjunction with active and passive seismic imaging results and may provide new insights on the origin of recently observed extremely high heat flow values. A companion abstract (Parris et al.) examines the deeper conductivity structure of the locked and ETS zones along the plate interface in order to identify correlations between ETS occurrence rates and inferred

  5. Radiocarbon evidence for extensive plate-boundary rupture about 300 years ago at the Cascadia subduction zone

    USGS Publications Warehouse

    Nelson, A.R.; Atwater, B.F.; Bobrowsky, P.T.; Bradley, L.A.; Clague, J.J.; Carver, G.A.; Darienzo, M.E.; Grant, W.C.; Krueger, H.W.; Sparks, R.; Stafford, Thomas W.; Stuiver, M.

    1995-01-01

    THE Cascadia subduction zone, a region of converging tectonic plates along the Pacific coast of North America, has a geological history of very large plate-boundary earthquakes1,2, but no such earthquakes have struck this region since Euro-American settlement about 150 years ago. Geophysical estimates of the moment magnitudes (Mw) of the largest such earthquakes range from 8 (ref. 3).to 91/2 (ref. 4). Radiocarbon dating of earthquake-killed vegetation can set upper bounds on earthquake size by constraining the length of plate boundary that ruptured in individual earthquakes. Such dating has shown that the most recent rupture, or series of ruptures, extended at least 55 km along the Washington coast within a period of a few decades about 300 years ago5. Here we report 85 new 14C ages, which suggest that this most recent rupture (or series) extended at least 900 km between southern British Columbia and northern California. By comparing the 14C ages with written records of the past 150 years, we conclude that a single magnitude 9 earthquake, or a series of lesser earthquakes, ruptured most of the length of the Cascadia subduction zone between the late 1600s and early 1800s, and probably in the early 1700s.

  6. Earthquake-driven fluid flow rates inferred from borehole temperature measurements within the Japan Trench plate boundary fault zone

    NASA Astrophysics Data System (ADS)

    Fulton, P. M.; Brodsky, E. E.

    2016-12-01

    Using borehole sub-seafloor temperature measurements, we have recently identified signatures suggestive of earthquake-driven fluid pulses within the Japan Trench plate boundary fault zone during a major aftershock sequence. Here we use numerical models to show that these signatures are consistent with time-varying fluid flow rates out of permeable zones within the formation into the borehole annulus. In addition, we also identify an apparent time-varying sensitivity of whether suspected fluid pulses occur in response to earthquakes of a given magnitude and distance. The results suggest a damage and healing process and therefore provides a mechanism to allow for a disproportionate amount of heat and chemical transport in the short time frame after an earthquake. Our observations come from an observatory installed across the main plate boundary fault as part of IODP's Japan Trench Fast Drilling Project (JFAST) following the March 2011 Mw 9.0 Tohoku-oki earthquake. It operated from July 2012 - April 2013 during which a Mw 7.3 earthquake and numerous aftershocks occurred. High-resolution temperature time series data reveal spatially correlated transients in response to earthquakes with distinct patterns interpreted to reflect advection by transient pulses of fluid flow from permeable zones into the borehole annulus. Typical transients involve perturbations over 12 m with increases of 10 mK that build over 0.1 days at shallower depths and decreases at deeper depths. They are consistently centered around 792.5 m below seafloor (mbsf) where a secondary fault and permeable zone have been independently identified within the damage zone above the main plate boundary fault at 820 mbsf . Model simulations suggest transient flow rates of up to 10-3m/s from the formation that quickly decrease. Comparison of characteristics of earthquakes identified in nearby ocean bottom pressure measurements suggest there is not a clear relationship between fluid pulses and static strain. There

  7. What controls interplate coupling? Implications from abrupt change in coupling on the Pacific plate across a border between two overlying plates in the southernmost extent of the NE Japan subduction zone

    NASA Astrophysics Data System (ADS)

    Uchida, N.; Hasegawa, A.; Nakajima, J.; Matsuzawa, T.

    2008-12-01

    In the southernmost extent of the NE Japan subduction zone, the Pacific plate (PA) is subducting beneath two different tectonic plates - the North American plate (NA) to the north and the Philippine Sea plate (PH) to the south. The change of overlying plate for the PA provides a good opportunity to test the influence of the overlying plate on interplate coupling. In the present study, detailed location of the border between the PH and NA overlying the PA is estimated from slip vectors of the interplate events. Then we compared the interplate coupling coefficients between the two regions overlain by the two plates based on the small repeating earthquake data. Analysis of slip vectors of interplate events shows that the slip vectors abruptly change their slip angles off Kanto. This suggests that the location of the border between the two overlying plates is extending northwestward from the triple junction. The distribution of interplate coupling coefficient estimated from the cumulative slip of small repeating earthquakes reveals a distinct change from south (ca. 0.3) to north (ca. 0.7) across this border. This border corresponds to the southern limit of M > 7 earthquakes and intense seismicity along the Japan Trench, again indicating the stronger coupling to the north. We also investigated the structure of the overlying plates from seismic tomography using a large number of travel-time data obtained from the nationwide seismograph network. The results reveal a distinct low-velocity zone just above the PA in the region overlain by the PH, whereas there is no low-velocity zone in the region overlain by the NA. These observations imply that the overlying plate controls large-scale coupling at the plate interface. Acknowledgement: We used waveforms from the seismic networks of University of Tokyo in addition to the data from Tohoku University. Arrival time data for seismic tomography and earthquake relocation are provided by the Japan Metrological Agency.

  8. Diapir versus along-channel ascent of crustal material during plate convergence: constrained by the thermal structure of subduction zones

    NASA Astrophysics Data System (ADS)

    Liu, M. Q.; Li, Z. H.

    2017-12-01

    Crustal rocks can be subducted to mantle depths, interact with the mantle wedge, and then exhume to the crustal depth again, which is generally considered as the mechanism for the formation of ultrahigh-pressure metamorphic rocks in nature. The crustal rocks undergo dehydration and melting at subarc depths, giving rise to fluids that metasomatize and weaken the overlying mantle wedge. There are generally two ways for the material ascent from subarc depths: one is along subduction channel; the other is through the mantle wedge by diapir. In order to study the conditions and dynamics of these contrasting material ascent modes, systematic petrological-thermo-mechanical numerical models are constructed with variable thicknesses of the overriding and subducting continental plates, ages of the subducting oceanic plate, as well as the plate convergence rates. The model results suggest that the thermal structures of subduction zones control the thermal condition and fluid/melt activity at the slab-mantle interface in subcontinental subduction channels, which further strongly affect the material transportation and ascent mode. Thick overriding continental plate and low-angle subduction style induced by young subducting oceanic plate both contribute to the formation of relatively cold subduction channels with strong overriding mantle wedge, where the along-channel exhumation occurs exclusively to result in the exhumation of HP-UHP metamorphic rocks. In contrast, thin overriding lithosphere and steep subduction style induced by old subducting oceanic plate are the favorable conditions for hot subduction channels, which lead to significant hydration and metasomatism, melting and weakening of the overriding mantle wedge and thus cause the ascent of mantle wedge-derived melts by diapir through the mantle wedge. This may corresponds to the origination of continental arc volcanism from mafic to ultramafic metasomatites in the bottom of the mantle wedge. In addition, the plate

  9. Diapir versus along-channel ascent of crustal material during plate convergence: Constrained by the thermal structure of subduction zones

    NASA Astrophysics Data System (ADS)

    Liu, Ming-Qi; Li, Zhong-Hai; Yang, Shao-Hua

    2017-09-01

    Subduction channel processes are crucial for understanding the material and energy exchange between the Earth's crust and mantle. Crustal rocks can be subducted to mantle depths, interact with the mantle wedge, and then exhume to the crustal depth again, which is generally considered as the mechanism for the formation of ultrahigh-pressure metamorphic rocks in nature. In addition, the crustal rocks generally undergo dehydration and melting at subarc depths, giving rise to fluids that metasomatize and weaken the overlying mantle wedge. There are generally two ways for the material ascent from subarc depths: one is along subduction channels; the other is through the mantle wedge by diapir. In order to study the conditions and dynamics of these contrasting material ascent modes, systematic petrological-thermo-mechanical numerical models are constructed with variable thicknesses of the overriding and subducting continental plates, ages of the subducting oceanic plate, as well as the plate convergence rates. The model results suggest that the thermal structures of subduction zones control the thermal condition and fluid/melt activity at the slab-mantle interface in subcontinental subduction channels, which further strongly affect the material transportation and ascent mode. The thick overriding continental plate and the low-angle subduction style induced by young subducting oceanic plate both contribute to the formation of relatively cold subduction channels with strong overriding mantle wedge, where the along-channel exhumation occurs exclusively to result in the exhumation of HP-UHP metamorphic rocks. In contrast, the thin overriding lithosphere and the steep subduction style induced by old subducting oceanic plate are the favorable conditions for hot subduction channels, which lead to significant hydration and metasomatism, melting and weakening of the overriding mantle wedge and thus cause the ascent of mantle wedge-derived melts by diapir through the mantle wedge

  10. Plate interaction in the NE Caribbean subduction zone from continuous GPS observations

    NASA Astrophysics Data System (ADS)

    ten Brink, Uri S.; López-Venegas, Alberto M.

    2012-05-01

    Kinematic similarities between the Sumatra and Puerto Rico Trenches highlight the potential for a mega-earthquake along the Puerto Rico Trench and the generation of local and trans-Atlantic tsunamis. We used the horizontal components of continuous GPS (cGPS) measurements from 10 sites on NE Caribbean islands to evaluate strain accumulation along the North American (NA) - Caribbean (CA) plate boundary. These sites move westward and slightly northward relative to CA interior at rates ≤2.5 mm/y. Provided this motion originates in the subduction interface, the northward motion suggests little or no trench-perpendicular thrust accumulation and may in fact indicate divergence north of Puerto Rico, where abnormal subsidence, bathymetry, and gravity are observed. The Puerto Rico Trench, thus, appears unable to generate mega-earthquakes, but damaging smaller earthquakes cannot be discounted. The westward motion, characterized by decreasing rate with distance from the trench, is probably due to eastward motion of CA plate impeded at the plate boundary by the Bahamas platform. Two additional cGPS sites in Mona Passage and SW Puerto Rico move to the SW similar to Hispaniola and unlike the other 10 sites. That motion relative to the rest of Puerto Rico may have given rise to seismicity and normal faults in Mona Rift, Mona Passage, and SW Puerto Rico.

  11. On gravity from SST, geoid from Seasat, and plate age and fracture zones in the Pacific

    NASA Technical Reports Server (NTRS)

    Marsh, B. D.; Marsh, J. G.; Williamson, R. G. (Principal Investigator)

    1984-01-01

    A composite map produced by combining 90 passes of SST data show good agreement with conventional GEM models. The SEASAT altimeter data were deduced and found to agree with both the SST and GEM fields. The maps are dominated (especially in the east) by a pattern of roughly east-west anomalies with a transverse wavelength of about 2000 km. Comparison with regional bathymetric data shows a remarkedly close correlation with plate age. Most anomalies in the east half of the Pacific could be partly caused by regional differences in plate age. The amplitude of these geoid or gravity anomalies caused by age differences should decrease with absolute plate age, and large anomalies (approximately 3 m) over old, smooth sea floor may indicate a further deeper source within or perhaps below the lithosphere. The possible plume size and ascent velocity necessary to supply deep mantle material to the upper mantle without complete thermal equilibration was considered. A plume emanating from a buoyant layer 100 km thick and 10,000 times less viscous than the surrounding mantle should have a diameter of about 400 km and must ascend at about 10 cm/yr to arrive still anomalously hot in the uppermost mantle.

  12. Plate interaction in the NE Caribbean subduction zone from continuous GPS observations

    USGS Publications Warehouse

    ten Brink, Uri S.; Lopez-Vegas, Alberto M.

    2012-01-01

    Kinematic similarities between the Sumatra and Puerto Rico Trenches highlight the potential for a mega-earthquake along the Puerto Rico Trench and the generation of local and trans-Atlantic tsunamis. We used the horizontal components of continuous GPS (cGPS) measurements from 10 sites on NE Caribbean islands to evaluate strain accumulation along the North American (NA) - Caribbean (CA) plate boundary. These sites move westward and slightly northward relative to CA interior at rates ≤2.5 mm/y. Provided this motion originates in the subduction interface, the northward motion suggests little or no trench-perpendicular thrust accumulation and may in fact indicate divergence north of Puerto Rico, where abnormal subsidence, bathymetry, and gravity are observed. The Puerto Rico Trench, thus, appears unable to generate mega-earthquakes, but damaging smaller earthquakes cannot be discounted. The westward motion, characterized by decreasing rate with distance from the trench, is probably due to eastward motion of CA plate impeded at the plate boundary by the Bahamas platform. Two additional cGPS sites in Mona Passage and SW Puerto Rico move to the SW similar to Hispaniola and unlike the other 10 sites. That motion relative to the rest of Puerto Rico may have given rise to seismicity and normal faults in Mona Rift, Mona Passage, and SW Puerto Rico.

  13. Free-Standing Zone Plate Optimized for He II 30.4 nm Solar Irradiance Measurements Having High Accuracy and Stability in Space

    NASA Astrophysics Data System (ADS)

    Seely, J. F.; McMullin, D. R.; Vest, R.; Sakdinawat, A.; Chang, C.; Jones, A. R.; Bremer, J.

    2015-12-01

    A zone plate was designed to record the He II 30.4 nm solar irradiance, was fabricated using electron beam lithography, and was absolutely calibrated using the NIST SURF synchrotron. The zone plate has an open support grid identical to those used to successfully launch transmission gratings in previous solar radiometers and is otherwise free-standing with no support membrane that would absorb EUV radiation. The measured efficiency of 3.0 ± 0.1% at 30.4 nm is consistent with detailed modeling of the efficiency and accounting for the geometrical transmittance of the support grid. The binary nature of the zone plate, consisting of opaque gold bars and open spaces with no support membrane, results in excellent long-term stability in space against contamination, radiation damage, and other effects that could alter the efficiency and instrument throughput. The zone plate's focusing property enables the rejection of out-of-band radiation by small apertures and high signal to background values that are superior to previous radiometers. The 4 mm outer diameter of the zone plate and the 25 mm focal length for 30.4 nm radiation enable a compact instrument that is attractive for small CubeSats and other space flight missions where resources are extremely limited.

  14. Compact and Light-Weight Solar Spaceflight Instrument Designs Utilizing Newly Developed Miniature Free-Standing Zone Plates: EUV Radiometer and Limb-Scanning Monochromator

    NASA Astrophysics Data System (ADS)

    Seely, J. F.; McMullin, D. R.; Bremer, J.; Chang, C.; Sakdinawat, A.; Jones, A. R.; Vest, R.

    2014-12-01

    Two solar instrument designs are presented that utilize newly developed miniature free-standing zone plates having interconnected Au opaque bars and no support membrane resulting in excellent long-term stability in space. Both instruments are based on a zone plate having 4 mm outer diameter and 1 to 2 degree field of view. The zone plate collects EUV radiation and focuses a narrow bandpass through a pinhole aperture and onto a silicon photodiode detector. As a miniature radiometer, EUV irradiance is accurately determined from the zone plate efficiency and the photodiode responsivity that are calibrated at the NIST SURF synchrotron facility. The EUV radiometer is pointed to the Sun and measures the absolute solar EUV irradiance in high time cadence suitable for solar physics and space weather applications. As a limb-scanning instrument in low earth orbit, a miniature zone-plate monochromator measures the extinction of solar EUV radiation by scattering through the upper atmosphere which is a measure of the variability of the ionosphere. Both instruments are compact and light-weight and are attractive for CubeSats and other missions where resources are extremely limited.

  15. Fluid Pressure in the Shallow Plate Interface at the Nankai Trough Subduction Zone

    NASA Astrophysics Data System (ADS)

    Tobin, H. J.; Saffer, D.

    2003-12-01

    The factors controlling the occurrence, magnitude, and other characteristics of great earthquakes is a fundamental outstanding question in fault physics. Pore fluid pressure is perhaps the most critical yet poorly known parameter governing the strength and seismogenic character of plate boundary faults, but unfortunately cannot be directly inferred through available geophysical sensing methods. Moreover, true in situ fluid pressure has proven difficult to measure even in boreholes. At the Nankai Trough, several hundred meters of sediment are subducted beneath the frontal portion of the accretionary prism. The up-dip portion of the plate interface is therefore hosted in these fine-grained marine sedimentary rocks. ODP Leg 190 and 196 showed that these rapidly-loaded underthrust sediments are significantly overpressured near the deformation front. Here, we attempt to quantitatively infer porosity, pore pressure, and effective normal stress at the plate interface at depths currently inaccessible to drilling. Using seismic reflection interval velocity calibrated at the boreholes to porosity, we quantitatively infer pore pressure to ˜ 20 km down-dip of the deformation front, to a plate interface depth of ˜ 6 km. We have developed a Nankai-specific velocity-porosity transform using ODP cores and logs. We use this function to derive a porosity profile for each of two down-dip seismic sections extracted from a 3-D dataset from the Cape Muroto region. We then calculate pore fluid pressure and effective vertical (fault-normal) stress for the underthrust sediment section using a compaction disequilibrium approach and core-based consolidation test data. Because the pore fluid pressure at the fault interface is likely controlled by that of the top of the underthrust section, this calculation represents a quantitative profile of effective stress and pore pressure at the plate interface. Results show that seismic velocity and porosity increase systematically downdip in the

  16. Lithosphere Structure of the Rivera Plate - Jalisco Block Contact Zone: Septentrional Region of the Islas Marías (Mexico)

    NASA Astrophysics Data System (ADS)

    Madrigal-Ávalos, L. A.; Nunez, D.; Escalona-Alcazar, F. D. J.; Nuñez-Cornu, F. J.; Barba, D. C., Sr.; Danobeitia, J.

    2017-12-01

    The western margin of Mexico is a tectonic complex region where large earthquakes occurred with very destructive consequences, including the generation of big tsunamis. This fact is mainly the result of the Rivera plate subduction beneath the North American plate and the Jalisco Block implying a high potential seismic risk. In the north, between the Tamayo Fracture Zone and the Mesoamerican Trench, the Islas Marías region is a complex tectonic limit within the interaction of the Rivera plate oceanic crust and the Jalisco Block continental crust. In order to know the shallow and deep structure of the Rivera plate - Jalisco Block contact zone and to be able to determine these potential seismic sources, the TSUJAL geophysical experiment was carried out from 2012 to 2016. As part of this project, we present the results of the processed and analyzed MCS and WAS data along the TS09 and RTSIM01 seismic transects, respectively, across the septentrional region of Islas Marías. These marine seismic lines are coincident with 110 km length for MCS and 240 km for WAS, and perpendicular to the coastline with SW-NE orientation. The seismic sources used in this work aboard RRS James Cook consisted of 12 guns with a total capacity for WAS data of 5800 in3 every 120 s and 3540 in3 every 50 m for MCS data. The MCS data were acquired with a 5.85 km length streamer with a 468 active channels, while the WAS data were recorded by a network of 4 OBS and 27 land seismic stations. After data processing and joint interpretation, it was possible to determine that shallow structure is mainly constituted by normal faults associated to graben structures forming sedimentary basins with non-deformed sediments in the basement. While the deep structure is characterized by depths from 9 to 12 km in the oceanic crust and 18 to 21 km in the continental crust. The deepest layers of the upper mantle were determined up to 35 km depth. In this study, it was possible to calculate a dip angle between 6

  17. Reducing risk where tectonic plates collide—U.S. Geological Survey subduction zone science plan

    USGS Publications Warehouse

    Gomberg, Joan S.; Ludwig, Kristin A.; Bekins, Barbara; Brocher, Thomas M.; Brock, John C.; Brothers, Daniel; Chaytor, Jason D.; Frankel, Arthur; Geist, Eric L.; Haney, Matt; Hickman, Stephen H.; Leith, William S.; Roeloffs, Evelyn A.; Schulz, William H.; Sisson, Thomas W.; Wallace, Kristi; Watt, Janet; Wein, Anne M.

    2017-06-19

    The U.S. Geological Survey (USGS) serves the Nation by providing reliable scientific information and tools to build resilience in communities exposed to subduction zone earthquakes, tsunamis, landslides, and volcanic eruptions. Improving the application of USGS science to successfully reduce risk from these events relies on whole community efforts, with continuing partnerships among scientists and stakeholders, including researchers from universities, other government labs and private industry, land-use planners, engineers, policy-makers, emergency managers and responders, business owners, insurance providers, the media, and the general public.Motivated by recent technological advances and increased awareness of our growing vulnerability to subduction-zone hazards, the USGS is uniquely positioned to take a major step forward in the science it conducts and products it provides, building on its tradition of using long-term monitoring and research to develop effective products for hazard mitigation. This science plan provides a blueprint both for prioritizing USGS science activities and for delineating USGS interests and potential participation in subduction zone science supported by its partners.The activities in this plan address many USGS stakeholder needs:High-fidelity tools and user-tailored information that facilitate increasingly more targeted, neighborhood-scale decisions to mitigate risks more cost-effectively and ensure post-event operability. Such tools may include maps, tables, and simulated earthquake ground-motion records conveying shaking intensity and frequency. These facilitate the prioritization of retrofitting of vulnerable infrastructure;Information to guide local land-use and response planning to minimize development in likely hazardous zones (for example, databases, maps, and scenario documents to guide evacuation route planning in communities near volcanoes, along coastlines vulnerable to tsunamis, and built on landslide-prone terrain);New tools

  18. Resolving plate structure across the seismogenic zone in Cascadia from onshore-offshore receiver function imaging

    NASA Astrophysics Data System (ADS)

    Audet, P.; Schaeffer, A. J.

    2017-12-01

    Studies of the forearc structure in the Cascadia subduction zone using teleseismic P-wave receiver function have resolved structures associated with deep fluid cycling, such as the basalt-to-eclogite reaction and fluid overpressure within the subducting oceanic crust, as well as the serpentinization of the forearc mantle wedge. Unfortunately, the updip extent of the over-pressured zone, and therefore the possible control on the transition from episodic slow slip to seismic slip, occurs offshore and is not resolved in those studies. The Cascadia Initiative (CI) has provided an opportunity to extend this work to the locked zone using teleseismic receiver functions from the deployment of a dense line of ocean-bottom seismograph stations offshore of Washington State, from the trench to the coastline. Here we calculate P-wave receiver functions using data from offshore (CI) and onshore (CAFE) broadband seismic stations. These data clearly show the various scattered phases associated with a dipping low-velocity layer that was identified in previous studies as the downgoing oceanic crust. These signals are difficult to untangle offshore because they arrive at similar times. We process receiver functions using a modified common-conversion point (CCP) stacking technique that uses a coherency filter to optimally stack images obtained from the three main scattered phases. The resulting image shows along-dip variations in the character of the seismic discontinuities associated with the top and bottom of the low-velocity layer. Combined with focal depth information of regular and low-frequency earthquakes, these variations may reflect changes in the material properties of the megathrust across the seismogenic zone in Cascadia.

  19. A viscoplastic shear-zone model for deep (15-50 km) slow-slip events at plate convergent margins

    NASA Astrophysics Data System (ADS)

    Yin, An; Xie, Zhoumin; Meng, Lingsen

    2018-06-01

    A key issue in understanding the physics of deep (15-50 km) slow-slip events (D-SSE) at plate convergent margins is how their initially unstable motion becomes stabilized. Here we address this issue by quantifying a rate-strengthening mechanism using a viscoplastic shear-zone model inspired by recent advances in field observations and laboratory experiments. The well-established segmentation of slip modes in the downdip direction of a subduction shear zone allows discretization of an interseismic forearc system into the (1) frontal segment bounded by an interseismically locked megathrust, (2) middle segment bounded by episodically locked and unlocked viscoplastic shear zone, and (3) interior segment that slips freely. The three segments are assumed to be linked laterally by two springs that tighten with time, and the increasing elastic stress due to spring tightening eventually leads to plastic failure and initial viscous shear. This simplification leads to seven key model parameters that dictate a wide range of mechanical behaviors of an idealized convergent margin. Specifically, the viscoplastic rheology requires the initially unstable sliding to be terminated nearly instantaneously at a characteristic velocity, which is followed by stable sliding (i.e., slow-slip). The characteristic velocity, which is on the order of <10-7 m/s for the convergent margins examined in this study, depends on the (1) effective coefficient of friction, (2) thickness, (3) depth, and (4) viscosity of the viscoplastic shear zone. As viscosity decreases exponentially with temperature, our model predicts faster slow-slip rates, shorter slow-slip durations, more frequent slow-slip occurrences, and larger slow-slip magnitudes at warmer convergent margins.

  20. Acoustic monitoring of earthquakes along the Blanco Transform Fault zone and Gorda Plate and their tectonic implications

    NASA Astrophysics Data System (ADS)

    Dziak, Robert Paul

    Hydroacoustic tertiary (T-) waves are seismically generated acoustic waves that propagate over great distances in the ocean sound channel with little loss in signal strength. Hydrophone recorded T-waves can provide a lower earthquake detection threshold and an improved epicenter location accuracy for oceanic earthquakes than land-based seismic networks. Thus detection and location of NE Pacific ocean earthquakes along the Blanco Transform Fault (BTFZ) and Gorda plate using the U.S. Navy's SOSUS (SOund SUrveillance System) hydrophone arrays afford greater insight into the current state of stress and crustal deformation mechanics than previously available. Acoustic earthquake information combined with bathymetry, submersible observations, earthquake source- parameter estimates, petrologic samples, and water-column chemistry renders a new tectonic view of the southern Juan de Fuca plate boundaries. Chapter 2 discusses development of seismo-acoustic analysis techniques using the well-documented April 1992 Cape Mendocino earthquake sequence. Findings include a hydrophone detection threshold estimate (M ~ 2.4), and T-wave propagation path modeling to approximate earthquake acoustic source energy. Empirical analyses indicate that acoustic energy provides a reasonable magnitude and seismic moment estimate of oceanic earthquakes not detected by seismic networks. Chapters 3 documents a probable volcanogenic T-wave event swarm along a pull-apart basin within the western BTFZ during January 1994. Response efforts yielded evidence of anomalous water-column 3He concentrations, pillow- lava volcanism, and the first discovery of active hydrothermal vents along an oceanic fracture zone. Chapter 4 discusses the detection of a NE-SW trending microearthquake band along the mid-Gorda plate which was active from initiation of SOSUS recording in August 1991 through July 1992, then abruptly ceased. It is proposed that eventual termination of the Gorda plate seismicity band is due to

  1. Deep Seismic Reflection Images across a Major Reactivated Fracture Zone in the Wharton Basin: Implications for the Location of the Plate Boundary between India and Australia

    NASA Astrophysics Data System (ADS)

    Carton, H. D.; Singh, S. C.; Hananto, N. D.; Martin, J.; Djajadihardja, Y. S.; Udrekh, U.; Franke, D.; Gaedicke, C.

    2012-12-01

    The equatorial Indian Ocean has long been recognized to be hosting extensive "intra-plate" deformation. To west of the Ninety-East Ridge (NER), The Central Indian Ocean Basin is characterized by N-S compression in a broad region with E-W trending folds and high-angle reverse faulting. To the east of NER in the Wharton Basin, deformation mainly occurs along reactivated N5°E-trending oceanic fracture zones with left-lateral strike-slip motion. Near longitude 93°E in the Wharton Basin runs a major reactivated fracture zone, along which the epicenters of the two recent Mw=8.6 and Mw=8.2 strike-slip earthquakes of April 11, 2012, and an Mw=7.2 foreshock that occurred in January 2012 are aligned. The April 11 events are the largest known oceanic events occurring away from the main plate boundaries. They ruptured a 20-40 km thick section of the oceanic lithosphere, i.e. down to depths at which no direct images of fault zones have been obtained so far. Deep seismic reflection data acquired in the Mw=8.6 earthquake rupture zone ~100 km north of the epicenter shows the presence of sub-Moho reflectivity down to 37 km depth in the oceanic mantle. We interpret these events as reflections off the earthquake-generating fault plane in the oceanic mantle, in accordance with results suggesting that brittle deformation of the oceanic lithosphere extends well into the mantle down to the 600°C isotherm. The fracture zone near 93°E separates lithospheres of contrasting crustal thicknesses (3.5-4.5 km versus 6 km) with a 10 Ma age difference, and therefore seems to act as a rheological boundary. We find that the deep reflections could originate from either a plane trending approximately N105°E, at high angle to the fracture zone, or from the fracture zone itself if the dip of the fault surface decreases from nearly vertical in the sediments to about 45° in the oceanic mantle. We propose that this fracture zone is a major tectonic boundary in the Wharton Basin, and that the three

  2. Hard x-ray spectroscopy and imaging by a reflection zone plate in the presence of astigmatism

    DOE PAGES

    Braig, Christoph; Lochel, Heike; Firsov, Alexander; ...

    2015-12-17

    Here, the feasibility of an off-axis x-ray reflection zone plate to perform wavelength-dispersive spectroscopy, on-axis point focusing, and two-dimensional imaging is demonstrated by means of one and the same diffractive optical element (DOE) at a synchrotron radiation facility. The resolving power varies between 3 × 10 1 and 4 × 10 2 in the range of 7.6 keV to 9.0 keV, with its maximum at the design energy of 8.3 keV. This result is verified using an adjustable entrance slit, by which horizontal (H) and vertical (V) focusing to 0.85 μm(H) and 1.29 μm(V) is obtained near the sagittal focalmore » plane of the astigmatic configuration. An angular and axial scan proves an accessible field of view of at least 0.6 arcmin × 0.8 arcmin and a focal depth of ±0.86 mm. Supported by the grating efficiency of around 17.5% and a very short pulse elongation, future precision x-ray fluorescence and absorption studies of transition metals at their K-edge on an ultrashort timescale could benefit from our findings.« less

  3. Identifying active interplate and intraplate fault zones in the western Caribbean plate from seismic reflection data and the significance of the Pedro Bank fault zone in the tectonic history of the Nicaraguan Rise

    NASA Astrophysics Data System (ADS)

    Ott, B.; Mann, P.

    2015-12-01

    The offshore Nicaraguan Rise in the western Caribbean Sea is an approximately 500,000 km2 area of Precambrian to Late Cretaceous tectonic terranes that have been assembled during the Late Cretaceous formation of the Caribbean plate and include: 1) the Chortis block, a continental fragment; 2) the Great Arc of the Caribbean, a deformed Cretaceous arc, and 3) the Caribbean large igneous province formed in late Cretaceous time. Middle Eocene to Recent eastward motion of the Caribbean plate has been largely controlled by strike-slip faulting along the northern Caribbean plate boundary zone that bounds the northern margin of the Nicaraguan Rise. These faults reactivate older rift structures near the island of Jamaica and form the transtensional basins of the Honduran Borderlands near Honduras. Recent GPS studies suggest that small amount of intraplate motion within the current margin of error of GPS measurements (1-3 mm/yr) may occur within the center of the western Caribbean plate at the Pedro Bank fault zone and Hess Escarpment. This study uses a database of over 54,000 km of modern and vintage 2D seismic data, combined with earthquake data and results from previous GPS studies to define the active areas of inter- and intraplate fault zones in the western Caribbean. Intraplate deformation occurs along the 700-km-long Pedro Bank fault zone that traverses the center of the Nicaraguan Rise and reactivates the paleo suture zone between the Great Arc of the Caribbean and the Caribbean large igneous province. The Pedro Bank fault zone also drives active extension at the 200-km-long San Andres rift along the southwest margin of the Nicaraguan Rise. Influence of the Cocos Ridge indentor may be contributing to reactivation of faulting along the southwesternmost, active segment of the Hess Escarpment.

  4. Distribution and migration of aftershocks of the 2010 Mw 7.4 Ogasawara Islands intraplate normal-faulting earthquake related to a fracture zone in the Pacific plate

    NASA Astrophysics Data System (ADS)

    Obana, Koichiro; Takahashi, Tsutomu; No, Tetsuo; Kaiho, Yuka; Kodaira, Shuichi; Yamashita, Mikiya; Sato, Takeshi; Nakamura, Takeshi

    2014-04-01

    describe the aftershocks of a Mw 7.4 intraplate normal-faulting earthquake that occurred 150 km east Ogasawara (Bonin) Islands, Japan, on 21 December 2010. It occurred beneath the outer trench slope of the Izu-Ogasawara trench, where the Pacific plate subducts beneath the Philippine Sea plate. Aftershock observations using ocean bottom seismographs (OBSs) began soon after the earthquake and multichannel seismic reflection surveys were conducted across the aftershock area. Aftershocks were distributed in a NW-SE belt 140 km long, oblique to the N-S trench axis. They formed three subparallel lineations along a fracture zone in the Pacific plate. The OBS observations combined with data from stations on Chichi-jima and Haha-jima Islands revealed a migration of the aftershock activity. The first hour, which likely outlines the main shock rupture, was limited to an 80 km long area in the central part of the subsequent aftershock area. The first hour activity occurred mainly around, and appears to have been influenced by, nearby large seamounts and oceanic plateau, such as the Ogasawara Plateau and the Uyeda Ridge. Over the following days, the aftershocks expanded beyond or into these seamounts and plateau. The aftershock distribution and migration suggest that crustal heterogeneities related to a fracture zone and large seamounts and oceanic plateau in the incoming Pacific plate affected the rupture of the main shock. Such preexisting structures may influence intraplate normal-faulting earthquakes in other regions of plate flexure prior to subduction.

  5. Influence of the Density Structure of the Caribbean Plate Forearc on the Static Stress State and Asperity Distribution along the Costa Rican Seismogenic Zone

    NASA Astrophysics Data System (ADS)

    Lücke, O. H.; Gutknecht, B. D.

    2014-12-01

    Most of the forearc region along the Central American Subduction Zone shows a series of trench-parallel, positive gravity anomalies with corresponding gravity lows along the trench and toward the coast. These features extend from Guatemala to northern Nicaragua. However, the Costa Rican segment of the forearc does not follow this pattern. In this region, the along-trench gravity low is segmented, the coastal low is absent, and the forearc gravity high is located onshore at the Nicoya Peninsula which overlies the seismogenic zone. Geodetic and seismological studies along the Costa Rican Subduction Zone suggest the presence of coupled areas beneath the Nicoya Peninsula prior to the 2012, magnitude Mw 7.6 earthquake. These areas had previously been associated with asperities. Previous publications have proposed a mechanical model for the generation of asperities along the Chilean convergent margin based on the structure of the overriding plate above the seismogenic zone in which dense igneous bodies disturb the state of stress on the seismogenic zone and may influence seismogenic processes. In Costa Rica, surface geology and gravity data indicate the presence of dense basalt/gabbro crust overlying the seismogenic zone where the coupling is present. Bouguer anomaly values in this region reach up to 120×10-5 m/s2, which are the highest for Costa Rica. In this work, the state of stress on the Cocos-Caribbean plate interface is calculated based on the geometry and mass distribution of a 3D density model of the subduction zone as interpreted from gravity data from combined geopotential models. Results show a correlation between the coupled areas at the Nicoya Peninsula and the presence of stress anomalies on the plate interface. The stress anomalies are calculated for the normal component of the vertical stress on the seismogenic zone and are interpreted as being generated by the dense material which makes up the forearc in the area. The dense material of the Nicoya

  6. Oblique collision and accretion of the Netherlands Leeward Antilles island arc: A structural analysis of the Caribbean-South American plate boundary zone

    NASA Astrophysics Data System (ADS)

    Beardsley, Amanda Gail

    2007-12-01

    The Netherlands Leeward Antilles volcanic island arc is an ideal natural laboratory to study the evolution of the Caribbean-South American plate boundary. The Leeward Antilles islands (Aruba, Curacao, and Bonaire) are located offshore western Venezuela, within the obliquely convergent diffuse plate boundary zone. Outcrop analysis, microthermometry, and 2D marine seismic reflection data provide evidence of three generations of regional deformation since the Late Cretaceous. Outcrop analysis of structural features, including faults, joints, and veins, characterizes the kinematic history of the islands. Fluid inclusion analysis of quartz and calcite veins coupled with apatite fission-track dating provides the island exhumation history. Finally, marine reflection seismic data processing and interpretation of newly acquired data elucidates offshore structures to integrate with our onshore results. The oldest regional deformation, resulting in both ductile (D1) and brittle (F 1) structures, is attributed to displacement partitioning along the arcuate Caribbean plate boundary. Associated crustal thinning initiated island exhumation, at a rate of 0.18 km/my, from a maximum burial depth of 6 km in the Late Cretaceous (˜89 Ma). Coeval with D1/F1 deformation and exhumation, stretching of the island arc resulted in extensive basin rifting that separated the island blocks. At ˜55 Ma, a change in the relative motion of the Caribbean plate altered plate boundary dynamics. Displacement along the right-lateral Caribbean transform fault and Oca - San Sebastian - El Pilar strike-slip fault system created a wrench tectonic regime within the diffuse plate boundary zone. A second generation of brittle structures (F2) developed while the islands were at a maximum burial depth of 2 km during the Paleocene/Eocene. Since ˜45 Ma, continued motion along the strike-slip fault systems and oblique plate convergence resulted in the youngest generation of structural features (F3). Regional

  7. Comment on Sub-15 nm Hard X-Ray Focusing with a New Total-Reflection Zone Plate

    SciTech Connect

    Specht, Eliot D

    2011-01-01

    Takano et al. report the focusing of 10-keV X-rays to a size of 14.4 nm using a total-reflection zone plate (TRZP). This focal size is at the diffraction limit for the optic's aperture. This would be a noteworthy result, since the TRZP was fabricated using conventional lithography techniques. Alternative nanofocusing optics require more demanding fabrication methods. However, as I will discuss in this Comment, the intensity distribution presented by Takano et al. (Fig. 4 of ref. 1) is more consistent with the random speckle pattern produced by the scattering of a coherent incident beam by a distorted optic than withmore » a diffraction-limited focus. When interpreted in this manner, the true focal spot size is {approx}70 nm: 5 times the diffraction limit. When a coherent photon beam illuminates an optic containing randomly distributed regions which introduce different phase shifts, the scattered diffraction pattern consists of a speckle pattern. Each speckle will be diffraction-limited: the peak width of a single speckle depends entirely on the source coherence and gives no information about the optic. The envelope of the speckle distribution corresponds to the focal spot which would be observed using incoherent illumination. The width of this envelope is due to the finite size of the coherently-diffracting domains produced by slope and position errors in the optic. The focal intensity distribution in Fig. 4 of ref. 1 indeed contains a diffraction-limited peak, but this peak contains only a fraction of the power in the focused, and forms part of a distribution of sharp peaks with an envelope {approx}70 nm in width, just as expected for a speckle pattern. At the 4mm focal distance, the 70 nm width corresponds to a slope error of 18 {micro}rad. To reach the 14 nm diffraction limit, the slope error must be reduced to 3 {micro}rad. Takano et al. have identified a likely source of this error: warping due to stress as a result of zone deposition. It will be interesting

  8. Frictional properties of silicic to calcareous ooze on the Cocos Plate entering the Costa Rica Subduction Zone

    NASA Astrophysics Data System (ADS)

    Tsutsumi, A.; Kameda, J.; Ujiie, K.

    2012-12-01

    Here we report experimental results on the frictional properties of the cover sediments on the Cocos plate incoming into the erosive Costa Rica subduction zone. Mechanical properties of the incoming sediments to subduction plate boundaries are essential to constrain subduction-related faulting processes. However, knowledge of the frictional properties of sediments composed of abundant biogenic component, such as spicules, diatoms, and radiolarians are limited. Experimental samples were silicic to calcareous ooze collected at a reference site (Site U1381) off shore Osa Peninsula during IODP Expedition 334 (Vannucchi et al., 2012). To be used in the experiments, the discrete samples was disaggregated, oven dried at 60 degrees centigrade for 24 hours. The experimental fault is composed of a 24.9 mm diameter cylinder of gabbro cut perpendicularly to the cylinder axis in two halves that are ground to obtain rough wall surfaces, and re-assembled with an intervening thin layer (~1.0 mm) disaggregated sample. Frictional experiments have been performed using a rotary-shear friction testing machine, at normal stresses up to 5 MPa, over a range of slip velocities from 0.0026 mm/s to 1.3 m/s, with more than ~150 mm of displacements for water saturated condition. Experimental results reveal that friction values at slow slip velocities (v < ~30 mm/s) are about ~0.7, of which level is comparable to the typically reported friction values for rocks. The experimental faults exhibited velocity-weakening at v < 0.3 mm/s and neutral to velocity-strengthening at 0.3 < v < ~3 mm/s. At higher velocities (v > ~30 mm/s), steady state friction decreases dramatically. For example, at a velocity of 260 mm/s, the friction coefficient for samples U1381A-9R and -10R show a gradual decrease with a large weakening displacement toward the establishment of a nearly constant level of friction at ~0.1. The velocity weakening behavior at slow velocities could provide a condition to initiate unstable

  9. The Ionian and Alfeo-Etna fault zones: New segments of an evolving plate boundary in the central Mediterranean Sea?

    NASA Astrophysics Data System (ADS)

    Polonia, A.; Torelli, L.; Artoni, A.; Carlini, M.; Faccenna, C.; Ferranti, L.; Gasperini, L.; Govers, R.; Klaeschen, D.; Monaco, C.; Neri, G.; Nijholt, N.; Orecchio, B.; Wortel, R.

    2016-04-01

    The Calabrian Arc is a narrow subduction-rollback system resulting from Africa/Eurasia plate convergence. While crustal shortening is taken up in the accretionary wedge, transtensive deformation accounts for margin segmentation along transverse lithospheric faults. One of these structures is the NNW-SSE transtensive fault system connecting the Alfeo seamount and the Etna volcano (Alfeo-Etna Fault, AEF). A second, NW-SE crustal discontinuity, the Ionian Fault (IF), separates two lobes of the CA subduction complex (Western and Eastern Lobes) and impinges on the Sicilian coasts south of the Messina Straits. Analysis of multichannel seismic reflection profiles shows that: 1) the IF and the AEF are transfer crustal tectonic features bounding a complex deformation zone, which produces the downthrown of the Western lobe along a set of transtensive fault strands; 2) during Pleistocene times, transtensive faulting reactivated structural boundaries inherited from the Mesozoic Tethyan domain which acted as thrust faults during the Messinian and Pliocene; and 3) the IF and the AEF, and locally the Malta escarpment, accommodate a recent tectonic event coeval and possibly linked to the Mt. Etna formation. Regional geodynamic models show that, whereas AEF and IF are neighboring fault systems, their individual roles are different. Faulting primarily resulting from the ESE retreat of the Ionian slab is expressed in the northwestern part of the IF. The AEF, on the other hand, is part of the overall dextral shear deformation, resulting from differences in Africa-Eurasia motion between the western and eastern sectors of the Tyrrhenian margin of northern Sicily, and accommodating diverging motions in the adjacent compartments, which results in rifting processes within the Western Lobe of the Calabrian Arc accretionary wedge. As such, it is primarily associated with Africa-Eurasia relative motion.

  10. Impact of The N - S Fracture Zone Along The Indo-Australia Plate Analyzed from Local Seismic Data In The Western Offshore of Sumatra, Indonesia

    NASA Astrophysics Data System (ADS)

    Haridhi, H. A.; Klingelhoefer, F.; Huang, B. S.; Lee, C. S.

    2015-12-01

    Large subduction earthquake have repeatedly occurred along the Sumatra and Andaman subduction zones where the Indo-Australia plate is subducting beneath the Eurasian plate. We have analyzed earthquake data from local seismic network along the Sumatra region that provided by the Meteorology Climatology Geophysical Agencies of Indonesia (MCGAI), giving a reliable P-wave velocity model by using joint inversion of picked P-wave travel time using VELEST and a re-scanned single channel seismic reflection of Sumatra cruise I and II. As much as 1,503 events are being analyzed, that is from two years and three months of data recording (2009/04 - 2011/07). The VELEST and DD technique are used to relocate all events by forcing the obtained velocity model. It is found that the surface deformation and earthquake cluster are strongly influenced by the impact of an N - S subparalel fracture zone along the Indo-Australia plate. This also explains the seismic gaps along the Sumatra and Andaman subduction zones. So far, the intriguing seismogenic behaviour and forearc structure are not well explained by the existing models. Therefore, the planned IODP Expedition 362 is trying to ground truth the scientific questions. The aftershock earthquake data are huge, but they will provide a gateway to help the understanding of this shallow megathrust slip and reduce its devastated harzards.

  11. Transformation of graphite by tectonic and hydrothermal processes in an active plate boundary fault zone, Alpine Fault, New Zealand

    NASA Astrophysics Data System (ADS)

    Kirilova, Matina; Toy, Virginia; Timms, Nicholas; Halfpenny, Angela; Menzies, Catriona; Craw, Dave; Rooney, Jeremy; Giorgetti, Carolina

    2017-04-01

    Graphite is a material with one of the lowest frictional strengths, with coefficient of friction of 0.1 and thus in natural fault zones it may act as a natural solid lubricant. Graphitization, or the transformation of organic matter (carbonaceous material, or CM) into crystalline graphite, is induced by compositional and structural changes during diagenesis and metamorphism. The supposed irreversible nature of this process has allowed the degree of graphite crystallinity to be calibrated as an indicator of the peak temperatures reached during progressive metamorphism. We examine processes of graphite emplacement and deformation in the Alpine Fault Zone, New Zealand's active continental tectonic plate boundary. Raman spectrometry indicates that graphite in the distal, amphibolite-facies Alpine Schist, which experienced peak metamorphic temperatures up to 640 ◦C, is highly crystalline and occurs mainly along grain boundaries within quartzo-feldspathic domains. The subsequent mylonitisation in the Alpine Fault Zone resulted in progressive reworking of CM under lower temperature conditions (500◦C-600◦C) in a structurally controlled environment, resulting in spatial clustering in lower-strain protomylonites, and further foliation-alignment in higher-strain mylonites. Subsequent brittle deformation of the mylonitised schists resulted in cataclasites that contain over three-fold increase in the abundance of graphite than mylonites. Furthermore, cataclasites contain graphite with two different habits: highly-crystalline, foliated forms that are inherited mylonitic graphite; and lower-crystallinity, less mature patches of finer-grained graphite. The observed graphite enrichment and the occurrence of poorly-organised graphite in the Alpine Fault cataclasites could result from: i) hydrothermal precipitation from carbon-supersaturated fluids; and/or ii) mechanical degradation by structural disordering of mylonitic graphite combined with strain-induced graphite

  12. Imaging b-value depth variations within the Cocos and Rivera plates at the Mexican subduction zone

    NASA Astrophysics Data System (ADS)

    Rodríguez-Pérez, Quetzalcoatl; Zuñiga, F. Ramón

    2018-06-01

    By a systematic mapping of the b-value along profiles perpendicular to the Mexican Wadati-Benioff zone, we obtained important characteristics pertaining the stress state and faulting style related to the subduction process. To this purpose, we used data from the earthquake catalog reported by the Servicio Sismologico Nacional (1988-2016). We investigate depth variations of the b-value for the Cocos and Rivera under North American plates interface, by a detailed analysis of 15 cross-sections. The obtained b-value profiles vary from 0.50 to 2.50, which nevertheless appear related to the faulting style and stress state. By comparing the locations and focal mechanism of the largest events with the b-values of the surrounding regions, our analysis corroborates the dependence of the b-value on the faulting style. Thrust events occur in regions of low and high b-value at depths <50 km. Normal-faulting events occur mainly in high b-value regions at all shallow (Z < 30 km) and intermediate depths (Z > 30 km), in agreement with global studies. These results support the hypothesis that differential stress processes may be behind the occurrence of the different faulting style. On the contrary, by analyzing the mean b-values for both types of faulting mechanism at each of the cross-sections, we found a significantly lower mean b-value related to normal faulting for those regions where the 8 (Mw 8.2) and 19 (Mw 7.1) September 2017 earthquakes occur. These results lead us to conclude that those regions experienced an increased stress state prone to the occurrence of normal-intraplate events. We also compare the b-value distribution with Vp and Q tomography studies obtaining a good correlation between them. We found evidence to relate b-value variations with subduction processes such as stress state due to tectonic and flexural conditions, and to a lesser extent to material heterogeneity and fluid dehydration.

  13. Role of the offshore Pedro Banks left-lateral strike-slip fault zone in the plate tectonic evolution of the northern Caribbean

    NASA Astrophysics Data System (ADS)

    Ott, B.; Mann, P.; Saunders, M.

    2013-12-01

    Previous workers, mainly mapping onland active faults on Caribbean islands, defined the northern Caribbean plate boundary zone as a 200-km-wide bounded by two active and parallel strike-slip faults: the Oriente fault along the northern edge of the Cayman trough with a GPS rate of 14 mm/yr, and and the Enriquillo-Plaintain Garden fault zone (EPGFZ) with a rate of 5-7 mm/yr. In this study we use 5,000 km of industry and academic data from the Nicaraguan Rise south and southwest of the EPGFZ in the maritime areas of Jamaica, Honduras, and Colombia to define an offshore, 700-km-long, active, left-lateral strike-slip fault in what has previously been considered the stable interior of the Caribbean plate as determined from plate-wide GPS studies. The fault was named by previous workers as the Pedro Banks fault zone because a 100-km-long segment of the fault forms an escarpment along the Pedro carbonate bank of the Nicaraguan Rise. Two fault segments of the PBFZ are defined: the 400-km-long eastern segment that exhibits large negative flower structures 10-50 km in width, with faults segments rupturing the sea floor as defined by high resolution 2D seismic data, and a 300-km-long western segment that is defined by a narrow zone of anomalous seismicity first observed by previous workers. The western end of the PBFZ terminates on a Quaternary rift structure, the San Andres rift, associated with Plio-Pleistocene volcanism and thickening trends indicating initial rifting in the Late Miocene. The southern end of the San Andreas rift terminates on the western Hess fault which also exhibits active strands consistent with left-lateral, strike-slip faults. The total length of the PBFZ-San Andres rift-Southern Hess escarpment fault is 1,200 km and traverses the entire western end of the Caribbean plate. Our interpretation is similar to previous models that have proposed the "stable" western Caribbean plate is broken by this fault whose rate of displacement is less than the threshold

  14. The northern Lesser Antilles oblique subduction zone: new insight about the upper plate deformation, 3D slab geometry and interplate coupling.

    NASA Astrophysics Data System (ADS)

    Marcaillou, B.; Laurencin, M.; Graindorge, D.; Klingelhoefer, F.

    2017-12-01

    In subduction zones, the 3D geometry of the plate interface is thought to be a key parameter for the control of margin tectonic deformation, interplate coupling and seismogenic behavior. In the northern Caribbean subduction, precisely between the Virgin Islands and northern Lesser Antilles, these subjects remain controversial or unresolved. During the ANTITHESIS cruises (2013-2016), we recorded wide-angle seismic, multichannel reflection seismic and bathymetric data along this zone in order to constrain the nature and the geometry of the subducting and upper plate. This experiment results in the following conclusions: 1) The Anegada Passage is a 450-km long structure accross the forearc related to the extension due to the collision with the Bahamas platform. 2) More recently, the tectonic partitioning due to the plate convergence obliquity re-activated the Anegada Passage in the left-lateral strike-slip system. The partitioning also generated the left-lateral strike-slip Bunce Fault, separating the accretionary prism from the forearc. 3) Offshore of the Virgin Islands margin, the subducting plate shows normal faults parallel to the ancient spreading center that correspond to the primary fabric of the oceanic crust. In contrast, offshore of Barbuda Island, the oceanic crust fabric is unresolved (fracture zone?, exhumed mantle? ). 4) In the direction of the plate convergence vector, the slab deepening angle decreases northward. It results in a shallower slab beneath the Virgin Islands Platform compared to the St Martin-Barbuda forearc. In the past, the collision of the Bahamas platform likely changed the geodynamic settings of the northeastern corner of the Caribbean subduction zone and we present a revised geodynamic history of the region. Currently, various features are likely to control the 3D geometry of the slab: the margin convexity, the convergence obliquity, the heterogeneity of the primary fabric of the oceanic crust and the Bahamas docking. We suggest that

  15. The Relationships of Upper Plate Ridge-Trench-Trench and Ridge-Trench-Transform Triple Junction Evolution to Arc Lengthening, Subduction Zone initiation and Ophiolitic Forearc Obduction

    NASA Astrophysics Data System (ADS)

    Casey, J.; Dewey, J. F.

    2013-12-01

    The principal enigma of large obducted ophiolite slabs is that they clearly must have been generated by some form of organized sea-floor spreading/plate-accretion, such as may be envisioned for the oceanic ridges, yet the volcanics commonly have arc affinity (Miyashiro) with boninites (high-temperature/low-pressure, high Mg and Si andesites), which are suggestive of a forearc origin. PT conditions under which boninites and metamorphic soles form and observations of modern forearc systems lead us to the conclusion that ophiolite formation is associated with overriding plate spreading centers that intersect the trench to form ridge-trench-trench of ridge-trench-tranform triple junctions. The spreading centers extend and lengthen the forearc parallel to the trench and by definition are in supra-subduction zone (SSZ) settings. Many ophiolites likewise have complexly-deformed associated mafic-ultramafic assemblages that suggest fracture zone/transform along their frontal edges, which in turn has led to models involving the nucleation of subduction zones on fracture zones or transpressional transforms. Hitherto, arc-related sea-floor-spreading has been considered to be either pre-arc (fore-arc boninites) or post-arc (classic Karig-style back arc basins that trench-parallel split arcs). Syn-arc boninites and forearc oceanic spreading centers that involve a stable ridge/trench/trench triple or a ridge-trench-transform triple junction, the ridge being between the two upper plates, are consistent with large slab ophiolite formation in an obduction-ready settting. The direction of subduction must be oblique with a different sense in the two subduction zones and the oblique subduction cannot be partitioned into trench orthogonal and parallel strike-slip components. As the ridge spreads, new oceanic lithosphere is created within the forearc, the arc and fore-arc lengthen significantly, and a syn-arc ophiolite forearc complex is generated by this mechanism. The ophiolite ages

  16. The metallogenic role of east-west fracture zones in South America with regard to the motion of lithospheric plates (with an example from Brazil)

    USGS Publications Warehouse

    Kutina, J.; Carter, William D.; Lopez, F.X.

    1978-01-01

    The role of east-west fracture zones in South America is discussed with regard to global fracturing and the motion of lithospheric plates. A set of major NW-trending lineaments has been derived which show a tendency to be spaced equidistantly and may correspond to a set of east-west fractures in the "pre-drift" position of the South American plate. Statistical analysis of linears in the ERTS-mosaics shows that NW-fractures are also among the most important ones in the Andes region, suggesting that the above major lineaments extend into the basement of the Andes. Some of the old major fractures, trending east-west in the present orientation of South America, are discussed and their NE orientation in the pre-drift position of the plate is considered. An example of structural control of ore deposition in the Brazilian Shield is presented, using the maps of the RADAM Project. It is concluded that the small tin-bearing granitic bodies concentrated in the region of Sao Felix do Xingu in the state of Para represent upper parts of an unexposed granitoid massif which is controlled by the intersection of a major east-west fracture zone probably represents westward extension of the Patos Lineament of the easternmost part of Brazil, connected with the east-west fracture zone of the Para state through the basement of the Maranhao Basin (Sineclise do Maranhao-Piaui). It is expected that the proposed "Patos-Para Lineament" extends further westward and may similarly control, at intersections with fractures of other trends, some mineralization centers in the western part of the state of Para and in the state of Amazonas.

  17. Segmentation along the Queen Charlotte Fault: The long-lived influence of plate-motion rotation and Explorer Ridge fracture zones

    NASA Astrophysics Data System (ADS)

    Miller, N. C.; Walton, M. A. L.; Brothers, D. S.; Haeussler, P. J.; Ten Brink, U. S.; Conrad, J. E.; Kluesner, J.; Andrews, B. D.

    2017-12-01

    The Queen Charlotte Fault (QCF) generally tracks the flow line for Pacific/North America (Pa/NA) relative motion since 20 Ma, indicating that the plate boundary localized along an optimally oriented small circle geometry. Rotation in Pa/NA motion at 10—12 Ma caused the QCF south of 53 N to be oblique to plate motion by 10—20. This oblique convergence appears to be accommodated in part by underthrusting of the Pacific Plate beneath Haida Gwaii and in part by slip on faults west of the QCF. On the west side of the QCF, a series of ridges and small basins oriented subparallel to either the QCF or relative plate motion form a 40-km-wide terrace. New high-resolution seismic reflection data image the seaward edge of the ridges as a vertical contact between horizontal or sometimes downwarped deep-sea sediments and west-vergent anticlinal structures within the ridges, supporting earlier interpretations that these ridges have accommodated some component of oblique motion. We argue that the ridges originated as step overs from fracture zones on Explorer Ridge, analogous to the current fault geometry at the southernmost end of the QCF. There, the Revere-Dellwood Fracture Zone (RDFZ) overlaps the QCF for 120 km and connects to the QCF via a more-optimally oriented extensional right step. 3.9—6.4 Mw strike-slip earthquakes along the RDFZ and a lack of contractional seafloor morphologies along the QCF south of the RDFZ-QCF right step suggest that the step over and reactivation along the RDFZ accommodates a majority of plate motion in this region. Kinematic reconstruction of ridges from 54—56 N indicates that they also originated in a similar location, potentially as right steps from either the RDFZ or Sovanco Fracture Zone. Similarly, the RDFZ flow path is coincident with a truncation of seafloor magnetic anomalies and the outer edge of the ridge-bounded terrace, which both parallel the QCF since at least the onset of Explorer Ridge spreading at 8 Ma. The RDFZ-QCF right

  18. New reductions of the Astrographic Catalogue. Plate adjustments of the Algiers, Oxford I and II, and Vatican Zones.

    NASA Astrophysics Data System (ADS)

    Urban, S. E.; Martin, J. C.; Jackson, E. S.; Corbin, T. E.

    1996-07-01

    The U. S. Naval Observatory is in the process of making new reductions of the Astrographic Catalogue using a modern reference catalog, the ACRS, and new data analysis and reduction software. Currently ten AC zones have been reduced. This papers discusses the reduction models and results from the Algiers, Oxford I and II, and Vatican zones (those of the Cape zone are discussed elsewhere). The resulting star positions will be combined with those of the U.S. Naval Observatory's Twin Astrograph Catalog to produce a catalog of positions and proper motions in support of the Sloan Digital Sky Survey.

  19. Modeling the Geometry of Plate Boundary and Seismic Structure in the Southern Ryukyu Trench Subduction Zone, Japan, Using Amphibious Seismic Observations

    NASA Astrophysics Data System (ADS)

    Yamamoto, Y.; Takahashi, T.; Ishihara, Y.; Kaiho, Y.; Arai, R.; Obana, K.; Nakanishi, A.; Miura, S.; Kodaira, S.; Kaneda, Y.

    2018-02-01

    Here we present the new model, the geometry of the subducted Philippine Sea Plate interface beneath the southern Ryukyu Trench subduction zone, estimated from seismic tomography and focal mechanism estimation by using passive and active data from a temporary amphibious seismic network and permanent land stations. Using relocated low-angle thrust-type earthquakes, repeating earthquakes, and structural information, we constrained the geometry of plate boundary from the trench axis to a 60 km depth with uncertainties of less than 5 km. The estimated plate geometry model exhibited large variation, including a pronounced convex structure that may be evidence of a subducted seamount in the eastern portion of study area, whereas the western part appeared smooth. We also found that the active earthquake region near the plate boundary, defined by the distance from our plate geometry model, was clearly separated from the area dominated by short-term slow-slip events (SSEs). The oceanic crust just beneath the SSE-dominant region, the western part of the study area, showed high Vp/Vs ratios (>1.8), whereas the eastern side showed moderate or low Vp/Vs (<1.75). We interpreted this as an indication that high fluid pressures near the surface of the slab are contributing to the SSE activities. Within the toe of the mantle wedge, P and S wave velocities (<7.5 and <4.2 km/s, respectively) lower than those observed through normal mantle peridotite might suggest that some portions of the mantle may be at least 40% serpentinized.

  20. GPS and seismological constraints on active tectonics and arc-continent collision in Papua New Guinea: Implications for mechanics of microplate rotations in a plate boundary zone

    NASA Astrophysics Data System (ADS)

    Wallace, Laura M.; Stevens, Colleen; Silver, Eli; McCaffrey, Rob; Loratung, Wesley; Hasiata, Suvenia; Stanaway, Richard; Curley, Robert; Rosa, Robert; Taugaloidi, Jones

    2004-05-01

    The island of New Guinea is located within the deforming zone between the Pacific and Australian plates that converge obliquely at ˜110 mm/yr. New Guinea has been fragmented into a complex array of microplates, some of which rotate rapidly about nearby vertical axes. We present velocities from a network of 38 Global Positioning System (GPS) sites spanning much of the nation of Papua New Guinea (PNG). The GPS-derived velocities are used to explain the kinematics of major tectonic blocks in the region and the nature of strain accumulation on major faults in PNG. We simultaneously invert GPS velocities, earthquake slip vectors on faults, and transform orientations in the Woodlark Basin for the poles of rotation of the tectonic blocks and the degree of elastic strain accumulation on faults in the region. The data are best explained by six distinct tectonic blocks: the Australian, Pacific, South Bismarck, North Bismarck, and Woodlark plates and a previously unrecognized New Guinea Highlands Block. Significant portions of the Ramu-Markham Fault appear to be locked, which has implications for seismic hazard determination in the Markham Valley region. We also propose that rapid clockwise rotation of the South Bismarck plate is controlled by edge forces initiated by the collision between the Finisterre arc and the New Guinea Highlands.

  1. Evidence for shallow dehydration of the subducting plate beneath the Mariana forearc: New insights into the water cycle at subduction zones

    NASA Astrophysics Data System (ADS)

    Ribeiro, J.; Stern, R. J.; Kelley, K. A.; Shaw, A. M.; Martinez, F.; Ohara, Y.

    2014-12-01

    Water is efficiently recycled at subduction zones. It is fluxed from the surface into the mantle by the subducted plate and back to the surface or crust through explosive arc volcanism and degassing. Fluids released from dehydrating the subducting plate are transfer agents of water. Geophysical modeling [1] and the geochemistry of arc glasses [2] suggest that at cold-slab subduction zones, such as the Mariana convergent margin, the downgoing plate mostly dehydrates beneath the volcanic arc front (≥ ~ 80 -100 km depth to slab) to trigger volcanism. However, there is a gap in our understanding of the water fluxes released beneath forearcs, as examples of forearc magmatism are extremely rare. Here, we investigate the Southernmost Mariana Forearc Rift (SEMFR), where MORB-like spreading occurred unusually close to the trench, sampling slab-derived aqueous fluids released at ~ 30 to 100 km depth from the subducted plate. Examining the trace element and water contents of olivine-hosted melt inclusions and glassy rinds from the young (2 - 4 Ma) and fresh SEMFR pillowed basalts provide new insights into the global water cycle. SEMFR lavas contain ~2 wt % H2O, and the olivine-hosted melt inclusions have the highest subduction-related H2O/Ce ratios (H2O/Ce = 6000 - 19000) ever recorded in arc magmas (H2O/Ce < 10600 and global averaged H2O/Ce < 3000). Our findings show that (i) slab-derived fluids released beneath forearcs are water-rich compared to the deeper fluids released beneath the arc system; and (ii) cold downgoing plates lose most of their water at shallow depths (~ 70 - 80 km slab depth), suggesting that water is efficiently recycled beneath the forearc (≥ 90%). 1. Van Keken, P.E., et al., Subduction factory: 4. Depth-dependent flux of H2O from subducting slabs worldwide. Journal of Geophysical Research: Solid Earth, 2011. 116(B1): p. B01401, DOI: 10.1029/2010jb007922. 2. Ruscitto, D.M., et al., Global variations in H2O/Ce: 2. Relationships to arc magma

  2. The 2017 Mw8.2 Tres Picos, Mexico Earthquake, an intraslab rupture crossing the Tehuantepec Fracture Zone stopped by a tear in the Cocos Plate

    NASA Astrophysics Data System (ADS)

    Wei, S.; Zeng, H.; WANG, X.; Qiu, Q.; Wang, T.; Li, L.; Chen, M.; Hermawan, I.; Wang, Y.; Tapponnier, P.; Barbot, S.

    2017-12-01

    On September 7th 2017, an Mw 8.2 intraslab earthquake ruptured beneath the Tehuantepec seismic gap in the Mexico subduction zone. We conducted a comprehensive investigation to characterize the earthquake rupture, including high-resolution back-projection, mainshock and large aftershocks relocation, aftershock moment tensor inversion, finite rupture model inversion jointly inverted from seismic waveform, static/high-rate GPS and InSAR images, and tsunami modeling. The back-projection results delineate a unilateral northwestward rupture about 150 km in length and 60s in duration, with a stable average rupture speed of 2.8 km/s. To reconcile multiple datasets, we used a two-segment fault geometry with near vertical dip angle (78°), and the second segment strikes slightly northward oriented, to mimic the rupture across the Tehuantepec Fracture Zone (FTZ) that separates the rupture into two segments. The joint inversion shows that the slip southeastern of TFZ dominates the moment release in the depth range of 30-50km during the first 40s. The second rupture segment released about 15% of the total moment, but with relatively larger contribution to the high-rate GPS, static geodetic and tide gauges data. Most of the large aftershocks occurred in the shallower part of the slab, with dominant thrust focal mechanism in agreement with slab bending. In contrast, the mainshock initiated at greater depth inside the slab, on a fault that may have formed near the trench and was reactivated by slab unbending, and was perhaps facilitated by dehydration. The comparison between the rupture model and the free air gravity anomaly suggests that the rupture was blocked westward by a low gravity anomaly zone. We interpret the difference in subducting speed and slab age across the TFZ and the Cocos plate gravity anomaly to be responsible for the abrupt stopping of the rupture at a tear zone inside the diving Cocos plate. Whether this earthquake will enhance future rupture on the plate

  3. Structure and composition of the plate-boundary slip zone for the 2011 Tohoku-Oki earthquake.

    PubMed

    Chester, Frederick M; Rowe, Christie; Ujiie, Kohtaro; Kirkpatrick, James; Regalla, Christine; Remitti, Francesca; Moore, J Casey; Toy, Virginia; Wolfson-Schwehr, Monica; Bose, Santanu; Kameda, Jun; Mori, James J; Brodsky, Emily E; Eguchi, Nobuhisa; Toczko, Sean

    2013-12-06

    The mechanics of great subduction earthquakes are influenced by the frictional properties, structure, and composition of the plate-boundary fault. We present observations of the structure and composition of the shallow source fault of the 2011 Tohoku-Oki earthquake and tsunami from boreholes drilled by the Integrated Ocean Drilling Program Expedition 343 and 343T. Logging-while-drilling and core-sample observations show a single major plate-boundary fault accommodated the large slip of the Tohoku-Oki earthquake rupture, as well as nearly all the cumulative interplate motion at the drill site. The localization of deformation onto a limited thickness (less than 5 meters) of pelagic clay is the defining characteristic of the shallow earthquake fault, suggesting that the pelagic clay may be a regionally important control on tsunamigenic earthquakes.

  4. A revised estimate of Pacific-North America motion and implications for Western North America plate boundary zone tectonics

    NASA Technical Reports Server (NTRS)

    Demets, Charles; Gordon, Richard G.; Stein, Seth; Argus, Donald F.

    1987-01-01

    Marine magnetic profiles from the Gulf of Californa are studied in order to revise the estimate of Pacific-North America motion. It is found that since 3 Ma spreading has averaged 48 mm/yr, consistent with a new global plate motion model derived without any data. The present data suggest that strike-slip motion on faults west of the San Andreas is less than previously thought, reducing the San Andreas discrepancy with geodetic, seismological, and other geologic observations.

  5. Stress Orientations and Strain Rates in the Upper Plate of a `Locked' subduction zone, at southernmost North Island, New Zealand

    NASA Astrophysics Data System (ADS)

    Evanzia, D. A. D.; Lamb, S. H.; Savage, M. K.

    2017-12-01

    The southern North Island, New Zealand is located at the southern Hikurangi Margin, where the Pacific Plate is obliquely subducting westward underneath the Australian Plate. The orientations of the principle stresses in the overriding plate are determined from microseismic focal mechanisms detected and located using the temporary SAHKE and permanent GeoNet seismic array operating during 2009-2010. The microseismic earthquakes are located with the NonLinLoc method, using a New Zealand specific 3D velocity model; only those earthquakes located above the modelled subduction plate interface are used. Strain rate parameters calculations are calculated using cGPS velocities from 56 stations located from the central North Island to the northernmost South Island, New Zealand. In the region west of the Tararua-range-bounding Wairarapa fault (the Western region), the orientations of stresses indicate a normal regime (S1: vertical; S2 & S3: horizontal), with SHmax trending ENE. In the Central Basin region (east of the Wairarapa fault) the orientations of the stresses indicate a reverse regime (S3: vertical; S1 & S2: horizontal), with SHmax orientated NW. The low seismicity rates in the Eastern region make the results unreliable. There is a distinct difference between the strain rate and vorticity on either side the Wairarapa fault. Strain rate and vorticity rates increase west and decreased east of the Wairarapa; this correlates well with the pattern of observed seismicity. The southern North Island is predominately contracting, except for a region on the West coast, where some expansion is occurs. This pattern of expansion in the West and contraction in the center of the study area, calculated from cGPS, is similar the stress inversion results calculated from focal mechanisms. These similarities suggest that the present stress and strain rates are collinear, as occurs in isotropic media.

  6. Paper microzone plates.

    PubMed

    Carrilho, Emanuel; Phillips, Scott T; Vella, Sarah J; Martinez, Andres W; Whitesides, George M

    2009-08-01

    This paper describes 96- and 384-microzone plates fabricated in paper as alternatives to conventional multiwell plates fabricated in molded polymers. Paper-based plates are functionally related to plastic well plates, but they offer new capabilities. For example, paper-microzone plates are thin (approximately 180 microm), require small volumes of sample (5 microL per zone), and can be manufactured from inexpensive materials ($0.05 per plate). The paper-based plates are fabricated by patterning sheets of paper, using photolithography, into hydrophilic zones surrounded by hydrophobic polymeric barriers. This photolithography used an inexpensive formulation photoresist that allows rapid (approximately 15 min) prototyping of paper-based plates. These plates are compatible with conventional microplate readers for quantitative absorbance and fluorescence measurements. The limit of detection per zone loaded for fluorescence was 125 fmol for fluorescein isothiocyanate-labeled bovine serum albumin, and this level corresponds to 0.02 the quantity of analyte per well used to achieve comparable signal-to-noise in a 96-well plastic plate (using a solution of 25 nM labeled protein). The limits of detection for absorbance on paper was approximately 50 pmol per zone for both Coomassie Brilliant Blue and Amaranth dyes; these values were 0.4 that required for the plastic plate. Demonstration of quantitative colorimetric correlations using a scanner or camera to image the zones and to measure the intensity of color, makes it possible to conduct assays without a microplate reader.

  7. Pore pressure development beneath the décollement at the Nankai subduction zone: Implications for plate boundary fault strength and sediment dewatering

    NASA Astrophysics Data System (ADS)

    Skarbek, Robert M.; Saffer, Demian M.

    2009-07-01

    Despite its importance for plate boundary fault processes, quantitative constraints on pore pressure are rare, especially within fault zones. Here, we combine laboratory permeability measurements from core samples with a model of loading and pore pressure diffusion to investigate pore fluid pressure evolution within underthrust sediment at the Nankai subduction zone. Independent estimates of pore pressure to ˜20 km from the trench, combined with permeability measurements conducted over a wide range of effective stresses and porosities, allow us to reliably simulate pore pressure development to greater depths than in previous studies and to directly quantify pore pressure within the plate boundary fault zone itself, which acts as the upper boundary of the underthrusting section. Our results suggest that the time-averaged excess pore pressure (P*) along the décollement ranges from 1.7-2.1 MPa at the trench to 30.2-35.9 MPa by 40 km landward, corresponding to pore pressure ratios of λb = 0.68-0.77. For friction coefficients of 0.30-0.40, the resulting shear strength along the décollement remains <12 MPa over this region. When noncohesive critical taper theory is applied using these values, the required pore pressure ratios within the wedge are near hydrostatic (λw = 0.41-0.59), implying either that pore pressure throughout the wedge is low or that the fault slips only during transient pulses of elevated pore pressure. In addition, simulated downward migration of minima in effective stress during drainage provides a quantitative explanation for down stepping of the décollement that is consistent with observations at Nankai.

  8. A wide-angle seismic survey of the Hecataeus Ridge, south of Cyprus: a microcontinental block from the African plate docked in a subduction zone?

    NASA Astrophysics Data System (ADS)

    Rahimi, Ayda; Welford, Kim; Hall, Jeremy; Hübscher, Christian; Louden, Keith; Ehrhardt, Axel

    2013-04-01

    Cyprus lies at the southern edge of the Aegean-Anatolian microplate, caught in the convergence of Africa and Eurasia. Subduction of the African plate below Cyprus has probably ceased and this has been attributed to the docking in the subduction zone of the Eratosthenes Seamount microcontinental fragment on the northern edge of the African plate. In early 2010, on R.V. Maria S. Merian, we conducted a wide-angle seismic survey to test the hypothesis that the Hecataeus Ridge, another possible microcontinental block lying immediately offshore SE Cyprus, might be related to an earlier docking event. The upper crust of southern Cyprus is dominated by ophiolites, with seismic velocities of up to 7 km s-1. A wide angle seismic profile along Hecataeus Ridge was populated with 15 Canadian and German ocean-bottom seismographs at 5 km intervals and these recorded shots from a 6000 cu. in. air gun array, fired approximately every 100 m. Rough topography of the seabed has made picking of phases and their modelling a demanding task. Bandpass and coherency filtering have enabled us to pick phases out to around 80 km. Tomographic inversion of short-range first arrivals provided an initial model of the shallow sub-seabed structure. Forward modelling by ray-tracing, using the code of Zelt and Smith, was then used to model crustal structure down to depths of around 20 km, with occasional evidence of reflections from deeper boundaries (Moho?). Modelling results provide good control on P-wave velocities in the top 20 km and some indications of deeper events. There is no evidence of true velocities approaching 7 km/s in the top 20 km below the Ridge that might indicate the presence of ophiolitic rocks. Regional gravity and magnetic field data tend to support this proposition. We thus conclude that Hecataeus Ridge is not composed of characteristically ophiolitic, Cyprus (upper plate) crust, and it might well be derived from the African (lower) plate.

  9. Dextral strike-slip along the Kapıdağ shear zone (NW Turkey): evidence for Eocene westward translation of the Anatolian plate

    NASA Astrophysics Data System (ADS)

    Türkoğlu, Ercan; Zulauf, Gernold; Linckens, Jolien; Ustaömer, Timur

    2016-10-01

    The northern part of the Kapıdağ Peninsula (Marmara Sea, NW Turkey) is affected by the E-W trending Kapıdağ shear zone, which cuts through calc-alkaline granitoids of the Ocaklar pluton resulting in mylonitic orthogneiss. Macroscopic and microscopic shear-sense indicators, such as SC fabrics, shear bands, σ-clasts and mica fish, unequivocally suggest dextral strike-slip for the Kapıdağ shear zone. Based on petrographic data, deformation microfabrics of quartz and feldspar, and the slip systems in quartz, the dextral shearing should have been active at T = 500-300 °C and P < 5 kbar. Published K-Ar and 39Ar-40Ar cooling ages of hornblende and biotite suggest that cooling below 500-300 °C occurred during the Eocene (ca. 45-ca. 35 Ma), meaning that the Kapıdağ shear zone should have been active during Middle to Late Eocene times. The differential stress related to the shearing was <50 MPa as is indicated by the size of recrystallized quartz grains. Based on the new and published data, it is concluded that the westward movement of the Anatolian plate might have been active almost continuously from the Middle Eocene until recent times.

  10. Variation of b and p values from aftershocks sequences along the Mexican subduction zone and their relation to plate characteristics

    NASA Astrophysics Data System (ADS)

    Ávila-Barrientos, L.; Zúñiga, F. R.; Rodríguez-Pérez, Q.; Guzmán-Speziale, M.

    2015-11-01

    Aftershock sequences along the Mexican subduction margin (between coordinates 110ºW and 91ºW) were analyzed by means of the p value from the Omori-Utsu relation and the b value from the Gutenberg-Richter relation. We focused on recent medium to large (Mw > 5.6) events considered susceptible of generating aftershock sequences suitable for analysis. The main goal was to try to find a possible correlation between aftershock parameters and plate characteristics, such as displacement rate, age and segmentation. The subduction regime of Mexico is one of the most active regions of the world with a high frequency of occurrence of medium to large events and plate characteristics change along the subduction margin. Previous studies have observed differences in seismic source characteristics at the subduction regime, which may indicate a difference in rheology and possible segmentation. The results of the analysis of the aftershock sequences indicate a slight tendency for p values to decrease from west to east with increasing of plate age although a statistical significance is undermined by the small number of aftershocks in the sequences, a particular feature distinctive of the region as compared to other world subduction regimes. The b values show an opposite, increasing trend towards the east even though the statistical significance is not enough to warrant the validation of such a trend. A linear regression between both parameters provides additional support for the inverse relation. Moreover, we calculated the seismic coupling coefficient, showing a direct relation with the p and b values. While we cannot undoubtedly confirm the hypothesis that aftershock generation depends on certain tectonic characteristics (age, thickness, temperature), our results do not reject it thus encouraging further study into this question.

  11. A Physical Metallurgical Basis for Heat-Affected Zone and Base-Plate Properties of a Microalloyed HSLA Steel.

    DTIC Science & Technology

    1986-12-01

    system.(a) Schematic diagram.(b) Equipment ...... 64 x * T-3136 FIGURE PAGE 13 Details of subsize charpy specimen and Gleeble HAZ microstructural...simulation specimen ......................................... 71 14 Macrograph profile of subsize charpy specimen illustrating notch location. (a) Specimen...shelf impact energy for subsize charpy specimens as a function of distance from the fusion zone boundary for various nominal heat inputs of both

  12. Mesozoic strike-slip movement of the Dunhua-Mishan Fault Zone in NE China: A response to oceanic plate subduction

    NASA Astrophysics Data System (ADS)

    Liu, Cheng; Zhu, Guang; Zhang, Shuai; Gu, Chengchuan; Li, Yunjian; Su, Nan; Xiao, Shiye

    2018-01-01

    The NE-striking Dunhua-Mishan Fault Zone (DMFZ) is one of two branches of the continental-scale sinistral Tan-Lu Fault Zone in NE China. The field data presented here indicate that the ca. 1000 km long DMFZ records two phases of sinistral faulting. The structures produced by these two phases of faulting include NE-SW-striking ductile shear belts and brittle faults, respectively. Mylonite-hosted microstructures and quartz c-axis fabrics suggest deformation temperatures of 450 °C-500 °C for the ductile shear belts. Combining new zircon U-Pb dates for 14 igneous rock samples analyzed during this study with the geology of this region indicates these shear belts formed during the earliest Early Cretaceous. This phase of sinistral displacement represents the initial formation of the DMFZ in response to the northward propagation of the Tan-Lu Fault Zone into NE China. A phase of Early Cretaceous rifting was followed by a second phase of sinistral faulting at 102-96 Ma, as evidenced by our new U-Pb ages for associated igneous rocks. Combining our new data with the results of previous research indicates that the DFMZ records a four-stage Cretaceous evolutionary history, where initial sinistral faulting at the beginning of the Early Cretaceous gave way to rifting during the rest of the Early Cretaceous. This was followed by a second phase of sinistral faulting at the beginning of the Late Cretaceous and a second phase of local rifting during the rest of the Late Cretaceous. The Cretaceous evolution of the DMFZ records the synchronous tectonic evolution of the NE China continent bordering the Pacific Ocean. Two phases of regional N-S compression generated the two phases of sinistral faulting within the DMFZ, whereas two-stage regional extension generated the two phases of rifting. The two compressive events were the result of the rapid low-angle subduction of the Izanagi and Pacific plates, whereas the two-stage extension was caused by the roll-back of these respective

  13. Source time functions of large Mexican subduction earthquakes, morphology of the Benioff Zone, age of the plate, and their tectonic implications

    NASA Astrophysics Data System (ADS)

    Singh, S. K.; Mortera, F.

    1991-12-01

    We study source parameters of large, shallow Mexican subduction zone earthquakes (95°W to 106°W) which occurred between 1928 and 1986 by modeling the P waves recorded on Galitzin-Wilip seismograph in DeBilt (DBN), Holland. For post-1962 events the source parameters retrieved from DBN seismograms alone agree well with those obtained from long-period World-Wide Standardized Seismograph Network records, giving us confidence in our results for pre-1962 events. All earthquakes are shallow (H˜10 to 20 km). With few exceptions the sources in Oaxaca (95°W to 99°W) are very simple. To the northwest of 99°W they are simple as well as complex. The ratio of surface wave to body wave seismic moment (Mos/MoP), which is a measure of long- to short-period radiation, is smaller in Oaxaca (˜ 1.5±0.5) than in the regions northwest of 99°W (˜3.1±1.3). These results suggest a change in the plate interface characteristics near 99°W. The sharp change in the rupture mode and the intersection of the O'Gorman Fracture Zone (OFZ) with the trench occur near 99°W. Two strike-slip events offshore, close to OFZ, suggest a segmentation of the subducting plate near 99°W. The age of the plate near the trench in Oaxaca is not well known; it is possible that it does not increase continuously from northwest to southeast in the region but jumps across 99°W. If so, then the older age of the subducted plate southeast of 99°W may be the cause of the distinct rupture mode of the Oaxaca earthquakes. The length of the Benioff zone, which is greatest below Oaxaca ( ≈ 400 km) and decreases toward the northwest, can be explained by the correlation between the length of the subducted slab and the product of the lithosphere age and convergence rate. The relative complexity of sources, the weaker background seismicity, and the lesser number of aftershocks northwest of Oaxaca may be explained by a stronger interface coupling resulting from subduction of younger oceanic slabs (˜5 to 13 m.y. old

  14. Shoreline-crossing shear-velocity structure of the Juan de Fuca plate and Cascadia subduction zone from surface waves and receiver functions

    NASA Astrophysics Data System (ADS)

    Janiszewski, Helen; Gaherty, James; Abers, Geoffrey; Gao, Haiying

    2017-04-01

    The Cascadia subduction zone (CSZ) is the site of the onshore-offshore Cascadia Initiative, which deployed seismometers extending from the Juan de Fuca ridge to the subduction zone and onshore beyond the volcanic arc. This array allows the unique opportunity to seismically image the evolution and along-strike variation of the crust and mantle of the entire CSZ. We compare teleseismic receiver functions, ambient-noise Rayleigh-wave phase velocities in the 10-20 s period band, and earthquake-source Rayleigh-wave phase velocities from 20-100 s, to determine shear-velocity structure in the upper 200 km. Receiver functions from both onshore and shallow-water offshore sites provide constraints on crustal and plate interface structure. Spectral-domain fitting of ambient-noise empirical Green's functions constrains shear velocity of the crust and shallow mantle. An automated multi-channel cross-correlation analysis of teleseismic Rayleigh waves provides deeper lithosphere and asthenosphere constraints. The amphibious nature of the array means it is essential to examine the effect of noise variability on data quality. Ocean bottom seismometers (OBS) are affected by tilt and compliance noise. Removal of this noise from the vertical components of the OBS is essential for the teleseismic Rayleigh waves; this stabilizes the output phase velocity maps particularly along the coastline where observations are predominately from shallow water OBS. Our noise-corrected phase velocity maps reflect major structures and tectonic transitions including the transition from high-velocity oceanic lithosphere to low-velocity continental lithosphere, high velocities associated with the subducting slab, and low velocities beneath the ridge and arc. We interpret the resulting shear-velocity model in the context of temperature and compositional variation in the incoming plate and along the strike of the CSZ.

  15. Shoreline-Crossing Shear-Velocity Structure of the Juan de Fuca Plate and Cascadia Subduction Zone from Surface Waves and Receiver Functions

    NASA Astrophysics Data System (ADS)

    Janiszewski, H. A.; Gaherty, J. B.; Abers, G. A.; Gao, H.

    2016-12-01

    The Cascadia subduction zone (CSZ) is the site of the onshore-offshore Cascadia Initiative, which deployed seismometers extending from the Juan de Fuca ridge to the subduction zone and onshore beyond the volcanic arc. This array allows the unique opportunity to seismically image the evolution and along-strike variation of the crust and mantle of the entire CSZ. We compare teleseismic receiver functions, ambient-noise Rayleigh-wave phase velocities in the 10-20 s period band, and earthquake-source Rayleigh-wave phase velocities from 20-100 s, to determine shear-velocity structure in the upper 200 km. Receiver functions from both onshore and shallow-water offshore sites provide constraints on crustal and plate interface structure. Spectral-domain fitting of ambient-noise empirical Green's functions constrains shear velocity of the crust and shallow mantle. An automated multi-channel cross-correlation analysis of teleseismic Rayleigh waves provides deeper lithosphere and asthenosphere constraints. The amphibious nature of the array means it is essential to examine the effect of noise variability on data quality. Ocean bottom seismometers (OBS) are affected by tilt and compliance noise. Removal of this noise from the vertical components of the OBS is essential for the teleseismic Rayleigh waves; this stabilizes the output phase velocity maps particularly along the coastline where observations are predominately from shallow water OBS. Our noise-corrected phase velocity maps reflect major structures and tectonic transitions including the transition from high-velocity oceanic lithosphere to low-velocity continental lithosphere, high velocities associated with the subducting slab, and low velocities beneath the ridge and arc. We interpret the resulting shear-velocity model in the context of temperature and compositional variation in the incoming plate and along the strike of the CSZ.

  16. Variations in seismic velocity distribution along the Ryukyu (Nansei-Shoto) Trench subduction zone at the northwestern end of the Philippine Sea plate

    NASA Astrophysics Data System (ADS)

    Nishizawa, Azusa; Kaneda, Kentaro; Oikawa, Mitsuhiro; Horiuchi, Daishi; Fujioka, Yukari; Okada, Chiaki

    2017-06-01

    The Ryukyu (Nansei-Shoto) island arc-trench system, southwest of Japan, is formed by the subduction of the Philippine Sea (PHS) plate. Among the subduction zones surrounding the Japan Islands, the Ryukyu arc-trench system is unique in that its backarc basin, the Okinawa Trough, is the area with current extensively active rifting. The length of the trench is around 1400 km, and the geological and geophysical characteristics vary significantly along the trench axis. We conducted multichannel seismic (MCS) reflection and wide-angle seismic surveys to elucidate the along-arc variation in seismic structures from the island arc to the trench regions, shooting seven seismic lines across the arc-trench system and two along-arc lines in the island arc and the forearc areas. The obtained P-wave velocity models of the Ryukyu arc crust were found to be heterogeneous (depending on the seismic lines), but they basically consist of upper, middle, and lower crusts, indicating a typical island arc structure. Beneath the bathymetric depressions cutting the island arc—for example, the Kerama Gap and the Miyako Saddle—the MCS record shows many across-arc normal faults, which indicates the presence of an extensional regime along the island arc. In the areas from the forearc to the trench, the subduction of the characteristic seafloor features on the PHS plate affects seismic structures; the subducted bathymetric high of the Amami Plateau is detected in the northern trench: the Luzon-Okinawa fracture zone beneath the middle and southern trenches. There are low-velocity (< 4.5 km/s) wedges along the forearc areas, except for off Miyako-jima Island. The characteristic high gravity anomaly at the forearc off Miyako-jima Island is caused not by a bathymetric high of a large-scale accretionary wedge but by shallower materials with a high P-wave velocity of 4.5 km/s.[Figure not available: see fulltext.

  17. Were they all giants? Perspectives on late Holocene plate-boundary earthquakes at the northern end of the Cascadia subduction zone

    NASA Astrophysics Data System (ADS)

    Hutchinson, Ian; Clague, John

    2017-08-01

    The relative magnitude of plate-boundary earthquakes at the northern end of the Cascadia subduction zone was assessed from the temporal concordance between the ages of coseismically buried late Holocene soils in southwest Washington, their counterparts in central and southern Cascadia, offshore turbidites, and paleoseismic deposits on the west coast of Vancouver Island. Only three of the seven buried soils in southwest Washington that can be reliably traced as buried soils or paleotsunami deposits in the coastal lowlands of south-central and southern Cascadia have well-dated counterparts in northern Cascadia. The three wide-ranging events date from Cascadia earthquakes Y (∼250 cal BP), U (∼1260 cal BP), and N (∼2520 cal BP). All three likely ruptured the entire plate margin, and therefore potentially qualify as ;giants; (Mw ≥ 9). Deposits that may derive from tsunamis generated by earthquakes S (∼1570 cal BP), L (∼2870 cal BP) and J (∼3360 cal BP) can also be found in northern Cascadia, but the ages of these deposits are not yet well-enough constrained to determine whether they are coeval with their southern counterparts. Earthquake W (∼850 cal BP), appears to be present in the northern Cascadia paleoseismic record, but yields considerably older ages than in central Cascadia, and may be missing from southernmost Cascadia. The onshore record of an offshore turbidite (T2) displays a similar spatio-temporal pattern to that of earthquake W.

  18. Tomographic Imaging of the Cascadia Subduction Zone and Juan de Fuca Plate System: Improved Methods Eliminate Artifacts and Reveal New Structures

    NASA Astrophysics Data System (ADS)

    Bodmer, M.; Toomey, D. R.; Hooft, E. E. E.; Bezada, M.; Schmandt, B.; Byrnes, J. S.

    2017-12-01

    Amphibious studies of subduction zones promise advances in understanding links between incoming plate structure, the subducting slab, and the upper mantle beneath the slab. However, joint onshore/offshore imaging is challenging due to contrasts between continental and oceanic structure. We present P-wave teleseismic tomography results for the Cascadia subduction zone (CSZ) that utilize existing western US datasets, amphibious seismic data from the Cascadia Initiative, and tomographic algorithms that permit 3D starting models, nonlinear ray tracing, and finite frequency kernels. Relative delay times show systematic onshore/offshore trends, which we attribute to structure in the upper 50 km. Shore-crossing CSZ seismic refraction models predict relative delays >1s, with equal contributions from elevation and crustal thickness. We use synthetic data to test methods of accounting for such shallow structure. Synthetic tests using only station static terms produce margin-wide, sub-slab low-velocity artifacts. Using a more realistic a priori 3D model for the upper 50 km better reproduces known input structures. To invert the observed delays, we use data-constrained starting models of the CSZ. Our preferred models utilize regional surface wave studies to construct a starting model, directly account for elevation, and use 3D nonlinear ray tracing. We image well-documented CSZ features, including the subducted slab down to 350 km, along strike slab variations below 150 km, and deep slab fragmentation. Inclusion of offshore data improves resolution of the sub-slab mantle, where we resolve localized low-velocity anomalies near the edges of the CSZ (beneath the Klamath and Olympic mountains). Our new imaging and resolution tests indicate that previously reported margin-wide, sub-slab low-velocity asthenospheric anomalies are an imaging artifact. Offshore, we observe low-velocity anomalies beneath the Gorda plate consistent with regional deformation and broad upwelling resulting

  19. Holocene faulting in the Bellingham forearc basin: upper-plate deformation at the northern end of the Cascadia subduction zone

    USGS Publications Warehouse

    Kelsey, Harvey M.; Sherrod, Brian L.; Blakely, Richard J.; Haugerud, Ralph A.

    2013-01-01

    The northern Cascadia forearc takes up most of the strain transmitted northward via the Oregon Coast block from the northward-migrating Sierra Nevada block. The north-south contractional strain in the forearc manifests in upper-plate faults active during the Holocene, the northern-most components of which are faults within the Bellingham Basin. The Bellingham Basin is the northern of four basins of the actively deforming northern Cascadia forearc. A set of Holocene faults, Drayton Harbor, Birch Bay, and Sandy Point faults, occur within the Bellingham Basin and can be traced from onshore to offshore using a combination of aeromagnetic lineaments, paleoseismic investigations and scarps identified using LiDAR imagery. With the recognition of such Holocene faults, the northernmost margin of the actively deforming Cascadia forearc extends 60 km north of the previously recognized limit of Holocene forearc deformation. Although to date no Holocene faults are recognized at the northern boundary of the Bellingham Basin, which is 15 km north of the international border, there is no compelling tectonic reason to expect that Holocene faults are limited to south of the international border.

  20. Direct Observations of In Situ Stress State in a 3 Kilometer Deep Borehole in the Upper Plate, Nankai Trough Subduction Zone: IODP Site C0002

    NASA Astrophysics Data System (ADS)

    Tobin, H. J.; Saffer, D. M.; Castillo, D. A.; Hirose, T.

    2016-12-01

    During IODP Expedition 348, borehole C0002F/N/P was advanced to a depth of 3058 m below the seafloor (mbsf) into the inner forearc accretionary wedge of the Nankai subduction zone (SW Japan), now the deepest scientific drilling ever into the ocean floor. The goals were to investigate the physical properties, structure, and state of stress deep within the hanging wall of a seismogenic subduction plate boundary. Mud pressure and gas monitoring, injection tests, leak-off tests (LOT), logging-while-drilling (LWD) measurements, and observations of mud losses and hole conditions provide both direct and indirect information about in situ pore pressure and stress state. The LOTs show that the minimum principal stress is consistently less than the vertical stress defined by the overburden, ruling out a thrust faulting stress state throughout the drilled section, and define a nearly linear gradient in Shmin from the seafloor to the base of the hole. Observations of mud loss and the lack of observed gas shows indicate that formation pore fluid pressure is not significantly (< 10 MPa) greater than hydrostatic. The maximum horizontal stress, estimated from borehole breakout width and pressure spikes during pack-off events, is close in magnitude to the vertical stress. Therefore the accretionary prism lies in either a normal or strike-slip faulting regime, or is transitional between the two, from 1 to 3 km depth. At 3002 mbsf we estimate that the effective stresses are: Sv' = 33 MPa; SHmax' = 25-36 MPa; and Shmin' = 18.5-21 MPa. Differential stresses are therefore low, on the order of 10-12 MPa, in the hanging wall of the subduction thrust. We conclude that (1) the inner wedge is not critically stressed in horizontal compression; (2) basal traction along the megathrust must be low in order to permit concurrent locking of the fault and low differential stresses deep within the upper plate; and (3) although low differential stresses may persist down to the plate boundary at 5000

  1. Generating cycle flow between dark and light zones with double paddlewheels to improve microalgal growth in a flat plate photo-bioreactor.

    PubMed

    Cheng, Jun; Xu, Junchen; Lu, Hongxiang; Ye, Qing; Liu, Jianzhong; Zhou, Junhu

    2018-08-01

    Double paddlewheels were proposed to generate cycle flow for increasing horizontal fluid velocity between dark and light zones in a flat plate photo-bioreactor, which strengthened the mass transfer and the mixing effect to improve microalgal growth with 15% CO 2 . Numerical fluid dynamics were used to simulate the cycle flow field with double paddlewheels. The local flow field measured with particle image velocimetry fitted well with the numerical simulation results. The horizontal fluid velocity in the photo-bioreactor was markedly increased from 5.8 × 10 -5  m/s to 0.45 m/s with the rotation of double paddlewheels, resulting in a decreased dark/light cycle period. Therefore, bubble formation time and diameter reduced by 24.4% and 27.4%, respectively. Meanwhile, solution mixing time reduced by 31.3% and mass transfer coefficient increased by 41.2%. The biomass yield of microalgae Nannochloropsis Oceanic increased by 127.1% with double paddlewheels under 15% CO 2 condition. Copyright © 2018 Elsevier Ltd. All rights reserved.

  2. A compact "water-window" microscope with 60-nm spatial resolution based on a double stream gas-puff target and Fresnel zone plate optics

    NASA Astrophysics Data System (ADS)

    Wachulak, Przemyslaw; Torrisi, Alfio; Nawaz, Muhammad F.; Adjei, Daniel; Bartnik, Andrzej; Kostecki, Jerzy; Wegrzynski, Łukasz; Vondrová, Šárka; Turňová, Jana; Fok, Tomasz; Jančarek, Alexandr; Fiedorowicz, Henryk

    2015-05-01

    Radiation with shorter illumination wavelength allows for extension of the diffraction limit towards nanometer scale, which is a straightforward way to significantly improve a spatial resolution in photon based microscopes. Soft X-ray (SXR) radiation, from the so called "water window" spectral range, λ=2.3-4.4 nm, which is particularly suitable for biological imaging due to natural optical contrast, providing much better spatial resolution than one obtained with visible light microscopes. The high contrast is obtained because of selective absorption of radiation by carbon and water, being constituents of the biological samples. We present a desk-top system, capable of resolving 60 nm features in few seconds exposure time. We exploit the advantages of a compact, laser-plasma SXR source, based on a double stream nitrogen gas puff target, developed at the Institute of Optoelectronics, Military University of Technology. The source, emitting quasi-monochromatic, incoherent radiation, in the "water widow" spectral range at λ = 2.88 nm, is coupled with ellipsoidal, grazing incidence condenser and Fresnel zone plate objective. The construction of the microscope with some recent images of test and real samples will be presented and discussed.

  3. Insights into a fossil plate interface of an erosional subduction zone: a tectono-metamorphic study of the Tianshan metamorphic belt.

    NASA Astrophysics Data System (ADS)

    Bayet, Lea; Moritz, Lowen; Li, Jilei; Zhou, Tan; Agard, Philippe; John, Timm; Gao, Jun

    2016-04-01

    Subduction zone seismicity and volcanism are triggered by processes occurring at the slab-wedge interface as a consequence of metamorphic reactions, mass-transfer and deformation. Although the shallow parts of subduction zones (<30-40 km) can be partly accessed by geophysical methods, the resolution of these techniques is insufficient to characterize and image the plate interface at greater depths (>60km). In order to better understand the plate interface dynamics at these greater depths, one has to rely on the rock record from fossil subduction zones. The Chinese Tianshan metamorphic belt (TMB) represents an ideal candidate for such studies, because structures are well exposed with exceptionally fresh high-pressure rocks. Since previous studies from this area focused on fluid-related processes and its metamorphic evolution was assessed on single outcrops, the geodynamic setting of this metamorphic belt is unfortunately heavily debated. Here, we present a new geodynamic concept for the TMB based on detailed structural and petrological investigations on a more regional scale. A ~11km x 13km area was extensively covered, together with E-W and N-S transects, in order to produce a detailed map of the TMB. Overall, the belt is composed of two greenschist-facies units that constitute the northern and southern border of a large high-pressure (HP) to ultra high-pressure (UHP) unit in the center. This HP-UHP unit is mainly composed of metasediments and volcanoclastic rocks, with blueschist, eclogite and carbonate lenses. Only the southern part of the HP-UHP unit is composed of the uppermost part of an oceanic crust (e.g., pillow basalts and deep-sea carbonates). From south to north, the relative abundance and size of blueschist massive boudins and layers (as well as eclogite boudins) decreases and the sequence is increasingly interlayered with metasedimentary and carbonate-rich horizons. This indicates that the subducted material was dominated by trench filling made of

  4. Geochemistry, petrology and geodynamic setting of the Urumieh plutonic complex, Sanandaj-Sirjan zone, NW Iran: New implication for Arabian and Central Iranian plate collision

    NASA Astrophysics Data System (ADS)

    Jafari, Amin; Fazlnia, Abdolnaser; Jamei, Susan

    2018-03-01

    The Urumieh plutonic complex, in the northernmost part of Sanandaj-Sirjan zone (SSZ) of Iran, consists of ten basic-acidic units which formed in response to subduction and continental collision of the SSZ with the Arabian plate to the south during Mid-Late Cretaceous times. Geochemically, the plutonic unit is divided into three distinct groups: I-type, S-type and A-type that mainly belong to calc-alkalic series. The I-type intrusions, especially mafic members, are enriched in LREE and LILE and possibly formed from metasomatized mantle wedge during the subduction of the Neo-Tethys oceanic crust beneath the SSZ. The felsic I-type rocks are depleted in Ba, Sr, Nb, Ta, Ti and Eu, but enriched in Rb, Th, K, Ce, U and La. These data suggest that they formed in deep crustal levels via partial melting of crustal sources by injection of hot mantle magmas. The S-type rocks are characterized by low Na2O (<3.02 wt%), high LILE, relatively high values of molar Al2O3/(MgO+FeO) and K2O/Na2O ratios combined with low CaO/(MgO+FeO*) ratios. These features show that the S-type granites originated from partial melting of a metapelitic to metagreywacke source. The A-type alkali feldspar granites formed through the slab break off after the continental collision in northwestern Iran by decompression melting of crustal protolith. The author's new model implies that collision between Arabian margin and north SSZ initiated in the Late Cretaceous and completed until Late Paleocene. In contrast, in the southeast, subduction was active during this period of time, but collision presumably occurred during the Middle to Late Miocene.

  5. Present-day stress tensors along the southern Caribbean plate boundary zone from inversion of focal mechanism solutions: A successful trial

    NASA Astrophysics Data System (ADS)

    Audemard M., Franck A.; Castilla, Raymi

    2016-11-01

    This paper presents a compilation of 16 present-day stress tensors along the southern Caribbean plate boundary zone (PBZ), and particularly in western and along northern Venezuela. As a trial, these new stress tensors along PBZ have been calculated from inversion of 125 focal mechanism solutions (FMS) by applying the Angelier & Mechler's dihedral method, which were originally gathered by the first author and published in 2005. These new tensors are compared to those 59 tensors inverted from fault-slip data measured only in Plio-Quaternary sedimentary rocks, compiled in Audemard et al. (2005), which were originally calculated by several researchers through the inversion methods developed by Angelier and Mechler or Etchecopar et al. The two sets of stress tensors, one derived from geological data and the other one from seismological data, compare very well throughout the PBZ in terms of both stress orientation and shape of the stress tensor. This region is characterized by a compressive strike-slip (transpressional senso lato), occasionally compressional, regime from the southern Mérida Andes on the southwest to the gulf of Paria in the east. Significant changes in direction of the maximum horizontal stress (σH = σ1) can be established along it though. The σ1 direction varies progressively from nearly east-west in the southern Andes (SW Venezuela) to between NW-SE and NNW-SSE in northwestern Venezuela; this direction remaining constant across northern Venezuela, from Colombia to Trinidad. In addition, the σV defined by inversion of focal mechanisms or by the shape of the stress ellipsoid derived from the Etchecopar et al.'s method better characterize whether the stress regime is transpressional or compressional, or even very rarely trantensional at local scale. The orientation and space variation of this regional stress field in western Venezuela results from the addition of the two major neighbouring interplate maximum horizontal stress orientations (

  6. Evolutionarily Conserved, Growth Plate Zone-Specific Regulation of the Matrilin-1 Promoter: L-Sox5/Sox6 and Nfi Factors Bound near TATA Finely Tune Activation by Sox9 ▿

    PubMed Central

    Nagy, Andrea; Kénesi, Erzsébet; Rentsendorj, Otgonchimeg; Molnár, Annamária; Szénási, Tibor; Sinkó, Ildikó; Zvara, Ágnes; Thottathil Oommen, Sajit; Barta, Endre; Puskás, László G.; Lefebvre, Veronique; Kiss, Ibolya

    2011-01-01

    To help uncover the mechanisms underlying the staggered expression of cartilage-specific genes in the growth plate, we dissected the transcriptional mechanisms driving expression of the matrilin-1 gene (Matn1). We show that a unique assembly of evolutionarily conserved cis-acting elements in the Matn1 proximal promoter restricts expression to the proliferative and prehypertrophic zones of the growth plate. These elements functionally interact with distal elements and likewise are capable of restricting the domain of activity of a pancartilaginous Col2a1 enhancer. The proximal elements include a Pe1 element binding the chondrogenic L-Sox5, Sox6, and Sox9 proteins, a SI element binding Nfi proteins, and an initiator Ine element binding the Sox trio and other factors. Sox9 binding to Pe1 is indispensable for functional interaction with the distal promoter. Binding of L-Sox5/Sox6 to Ine and Nfib to SI modulates Sox9 transactivation in a protein dose-dependent manner, possibly to enhance Sox9 activity in early stages of chondrogenesis and repress it at later stages. Hence, our data suggest a novel model whereby Sox and Nfi proteins bind to conserved Matn1 proximal elements and functionally interact with each other to finely tune gene expression in specific zones of the cartilage growth plate. PMID:21173167

  7. 3D geometry of a plate boundary fault related to the 2016 Off-Mie earthquake in the Nankai subduction zone, Japan

    NASA Astrophysics Data System (ADS)

    Tsuji, Takeshi; Minato, Shohei; Kamei, Rie; Tsuru, Tetsuro; Kimura, Gaku

    2017-11-01

    We used recent seismic data and advanced techniques to investigate 3D fault geometry over the transition from the partially coupled to the fully coupled plate interface inboard of the Nankai Trough off the Kii Peninsula, Japan. We found that a gently dipping plate boundary décollement with a thick underthrust layer extends beneath the entire Kumano forearc basin. The 1 April 2016 Off-Mie earthquake (Mw6.0) and its aftershocks occurred, where the plate boundary décollement steps down close to the oceanic crust surface. This location also lies beneath the trenchward edge of an older accretionary prism (∼14 Ma) developed along the coast of the Kii peninsula. The strike of the 2016 rupture plane was similar to that of a formerly active splay fault system in the accretionary prism. Thus, the fault planes of the 2016 earthquake and its aftershocks were influenced by the geometry of the plate interface as well as splay faulting. The 2016 earthquake occurred within the rupture area of large interplate earthquakes such as the 1944 Tonankai earthquake (Mw8.1), although the 2016 rupture area was much smaller than that of the 1944 event. Whereas the hypocenter of the 2016 earthquake was around the underplating sequence beneath the younger accretionary prism (∼6 Ma), the 1944 great earthquake hypocenter was close to oceanic crust surface beneath the older accretionary prism. The variation of fault geometry and lithology may influence the degree of coupling along the plate interface, and such coupling variation could hinder slip propagation toward the deeper plate interface in the 2016 event.

  8. Plate tectonics, damage and inheritance.

    PubMed

    Bercovici, David; Ricard, Yanick

    2014-04-24

    The initiation of plate tectonics on Earth is a critical event in our planet's history. The time lag between the first proto-subduction (about 4 billion years ago) and global tectonics (approximately 3 billion years ago) suggests that plates and plate boundaries became widespread over a period of 1 billion years. The reason for this time lag is unknown but fundamental to understanding the origin of plate tectonics. Here we suggest that when sufficient lithospheric damage (which promotes shear localization and long-lived weak zones) combines with transient mantle flow and migrating proto-subduction, it leads to the accumulation of weak plate boundaries and eventually to fully formed tectonic plates driven by subduction alone. We simulate this process using a grain evolution and damage mechanism with a composite rheology (which is compatible with field and laboratory observations of polycrystalline rocks), coupled to an idealized model of pressure-driven lithospheric flow in which a low-pressure zone is equivalent to the suction of convective downwellings. In the simplest case, for Earth-like conditions, a few successive rotations of the driving pressure field yield relic damaged weak zones that are inherited by the lithospheric flow to form a nearly perfect plate, with passive spreading and strike-slip margins that persist and localize further, even though flow is driven only by subduction. But for hotter surface conditions, such as those on Venus, accumulation and inheritance of damage is negligible; hence only subduction zones survive and plate tectonics does not spread, which corresponds to observations. After plates have developed, continued changes in driving forces, combined with inherited damage and weak zones, promote increased tectonic complexity, such as oblique subduction, strike-slip boundaries that are subparallel to plate motion, and spalling of minor plates.

  9. Using paleomagnetism to expand the observation time window of plate locking along subduction zones: evidence from the Chilean fore-arc sliver (38°S - 42°S)

    NASA Astrophysics Data System (ADS)

    Hernandez-Moreno, Catalina; Speranza, Fabio; Di Chiara, Anita

    2017-04-01

    Fore-arc crustal motion has been usually addressed by the analysis of earthquake slip vectors and, since the last twenty years, by velocity fields derived from Global Positioning System (GPS) data. Yet this observation time window (few decades) can be significantly shorter than a complete seismic cycle or constrained to interseismic periods where the postseismic deformation release, the vicinity of other important faults, and the slip partitioning in oblique subduction may hinder the finite deformation pattern. Paleomagnetic data may yield finite rotations occurring since rock formation, thus provide a much longer observation time span in the order of millions or tens of millions of years. The cumulative permanent or nonreversing deformation in function of the considered geological formation age can represent the average over many seismic cycles, thus significantly complement "instantaneous" information derived from seismic and GPS data. With the aim of evaluate the strike-variation and evolution of the plate coupling along the Chilean subduction zone, here we report on the paleomagnetism of 43 Oligocene-Pleistocene volcanic sites from the fore-arc sliver between 38°S and 42°S. Sites were gathered west of the 1000 km long Liquiñe-Ofqui dextral fault zone (LOFZ) that represents the eastern fore-arc sliver boundary. Nineteen reliable sites reveal that the fore arc is characterized by counterclockwise (CCW) rotations of variable magnitude, except at 40°S - 41°S, where ultrafast (>50°/Myr) clockwise (CW) rotations occur within a 30 km wide zone adjacent to the LOFZ. CCW rotation variability (even at close sites) and rapidity (>10°/Myr) suggest that the observed block rotation pattern is related to NW-SE seismically active sinistral faults crosscutting the whole fore arc. According to previously published data, CW rotations up to 170° also occur east of the LOFZ and have been related to ongoing LOFZ shear. We suggest that the occurrence and width of the eastern

  10. Cold plate

    DOEpatents

    Marroquin, Christopher M.; O'Connell, Kevin M.; Schultz, Mark D.; Tian, Shurong

    2018-02-13

    A cold plate, an electronic assembly including a cold plate, and a method for forming a cold plate are provided. The cold plate includes an interface plate and an opposing plate that form a plenum. The cold plate includes a plurality of active areas arranged for alignment over respective heat generating portions of an electronic assembly, and non-active areas between the active areas. A cooling fluid flows through the plenum. The plenum, at the non-active areas, has a reduced width and/or reduced height relative to the plenum at the active areas. The reduced width and/or height of the plenum, and exterior dimensions of cold plate, at the non-active areas allow the non-active areas to flex to accommodate surface variations of the electronics assembly. The reduced width and/or height non-active areas can be specifically shaped to fit between physical features of the electronics assembly.

  11. Tectonics of the Easter plate

    NASA Technical Reports Server (NTRS)

    Engeln, J. F.; Stein, S.

    1984-01-01

    A new model for the Easter plate is presented in which rift propagation has resulted in the formation of a rigid plate between the propagating and dying ridges. The distribution of earthquakes, eleven new focal mechanisms, and existing bathymetric and magnetic data are used to describe the tectonics of this area. Both the Easter-Nazca and Easter-Pacific Euler poles are sufficiently close to the Easter plate to cause rapid changes in rates and directions of motion along the boundaries. The east and west boundaries are propagating and dying ridges; the southwest boundary is a slow-spreading ridge and the northern boundary is a complex zone of convergent and transform motion. The Easter plate may reflect the tectonics of rift propagation on a large scale, where rigid plate tectonics requires boundary reorientation. Simple schematic models to illustrate the general features and processes which occur at plates resulting from large-scale rift propagation are used.

  12. The Influence of the Heat-Affected Zone Mechanical Properties on the Behaviour of the Welding in Transverse Plate-to-Tube Joints.

    PubMed

    Lozano, Miguel; Serrano, Miguel A; López-Colina, Carlos; Gayarre, Fernando L; Suárez, Jesús

    2018-02-09

    Eurocode 3 establishes the component method to analytically characterize the structural joints between beam and columns. When one of the members involved in the joint is a hollow section (i.e., a tube) there is a lack of information for the specific components present in the joint. There are two different ways to bridge the gap: experimental testing on the actual beam column joints involving tubular sections; or numerical modelization, typically by means of finite element analysis. For this second option, it is necessary to know the actual mechanical properties of the material. As long as the joint implies a welding process, there is a concern related to how the mechanical properties in the heat-affected zone (HAZ) influence the behavior of the joint. In this work, some coupons were extracted from the HAZ of the beam-column joint. The coupons were tested and the results were implemented in the numerical model of the joint, in an attempt to bring it closer to the experimental results of the tested joints.

  13. Thermal Models of the Costa Rica - Nicaragua Subduction Zone: the Effect of a Three-Dimensional Oceanic Plate Structure and Hydrothermal Circulation in the Temperature Distribution and Mantle Wedge Dynamics

    NASA Astrophysics Data System (ADS)

    Rosas, J. C.; Currie, C. A.; He, J.

    2014-12-01

    Over the last years several 2D thermo-mechanical models of the Costa Rica - Nicaragua Subduction Zone (CNSZ) have studied the thermal distribution of sections of the fault. Such investigations allow us to understand temperature-related aspects of subduction zones, like volcanism and megathrust earthquake locations. However, certain features of the CNSZ limit the range of applicability of 2D models. In the CNSZ, geochemical trends and seismic anisotropy studies reveal a 3D mantle wedge flow that departs from the 2D corner flow. The origin of this flow are dip variations (20o to 25o between Nicaragua and Costa Rica) and the presence of a slab window in Panama that allows material to flow into the mantle wedge. Also, the Central America trench has abrupt variations in surface heat flux that contrasts with steady changes in plate age and convergence rate. These variations have been attributed to hydrothermal circulation (HC), which effectively removes heat from the oceanic crust.In this project we analyze the thermal structure of the CNSZ. The objective is to study dehydration and metamorphic reactions, as well as the length of the megathrust seismogenic zone. We created 3D finite-element models that employ a dislocation creep rheology for the mantle wedge. Two aspects make our models different from previous studies: an up-to-date 3D slab geometry, and an implementation of HC by introducing a conductive proxy in the subducting aquifer, allowing us to model convective heat transport without the complex, high-Rayleigh number calculations. A 3D oceanic boundary condition that resembles the along-strike changes in surface heat flux is also employed. Results show a maximum mantle wedge flow rate of 4.69 cm/yr in the along-strike direction, representing more than 50% of the slab convergence rate. With respect to 2D models, analysis shows this flow changes temperatures by ~100 C in the mantle wedge near areas of strong slab curvature. Along the subducting interface, there is

  14. Mantle convection with plates and mobile, faulted plate margins.

    PubMed

    Zhong, S; Gurnis, M

    1995-02-10

    A finite-element formulation of faults has been incorporated into time-dependent models of mantle convection with realistic rheology, continents, and phase changes. Realistic tectonic plates naturally form with self-consistent coupling between plate and mantle dynamics. After the initiation of subduction, trenches rapidly roll back with subducted slabs temporarily laid out along the base of the transition zone. After the slabs have penetrated into the lower mantle, the velocity of trench migration decreases markedly. The inhibition of slab penetration into the lower mantle by the 670-kilometer phase change is greatly reduced in these models as compared to models without tectonic plates.

  15. Peen plating

    NASA Technical Reports Server (NTRS)

    Babecki, A. J. (Inventor); Haehner, C. L.

    1973-01-01

    A process for metal plating which comprises spraying a mixture of metallic powder and small peening particles at high velocity against a surface is described. The velocity must be sufficient to impact and bond metallic powder onto the surface. In the case of metal surfaces, the process has as one of its advantages providing mechanical working (hardening) of the surface simultaneously with the metal plating.

  16. Reducing risk where tectonic plates collide

    USGS Publications Warehouse

    Gomberg, Joan S.; Ludwig, Kristin A.

    2017-06-19

    Most of the world’s earthquakes, tsunamis, landslides, and volcanic eruptions are caused by the continuous motions of the many tectonic plates that make up the Earth’s outer shell. The most powerful of these natural hazards occur in subduction zones, where two plates collide and one is thrust beneath another. The U.S. Geological Survey’s (USGS) “Reducing Risk Where Tectonic Plates Collide—A USGS Plan to Advance Subduction Zone Science” is a blueprint for building the crucial scientific foundation needed to inform the policies and practices that can make our Nation more resilient to subduction zone-related hazards.

  17. The petrogenesis of the Early Permian Variscan granites of the Cornubian Batholith: Lower plate post-collisional peraluminous magmatism in the Rhenohercynian Zone of SW England

    NASA Astrophysics Data System (ADS)

    Simons, B.; Shail, Robin K.; Andersen, Jens C. Ø.

    2016-09-01

    The Early Permian Cornubian Batholith was generated during an extensional regime following Variscan convergence within the Rhenohercynian Zone of SW England. Its component granites can be classified, using mineralogical, textural and geochemical criteria, into five main types, all of which are peraluminous (A/CNK > 1.1): G1 (two-mica), G2 (muscovite), G3 (biotite), G4 (tourmaline) and G5 (topaz). G1 granites formed through up to 20% muscovite and minor biotite dehydration melting of a metagreywacke source at moderate temperatures and pressures (731-806 °C, > 5 kbar). Younger G3 granites formed through higher temperature, lower pressure (768-847 °C, < 4 kbar) biotite-dominated melting of a similar source. Partial melting was strongly influenced by the progressive lower-mid crustal emplacement of mafic igneous rocks during post-Variscan extension and a minor (< 5%-10%) mantle-derived component in the granites is possible. Two distinct fractionation series, G1-G2 and G3-G4, are defined using whole-rock geochemical and mineral chemical data. Variations in the major elements, Ba, Sr and Rb indicate that G1 and G3 granites underwent 15%-30% fractionation of an assemblage dominated by plagioclase, alkali feldspar and biotite to form more evolved G2 and G4 granites, respectively. Decreasing whole-rock abundances of Zr, Th and REE support the fractionation of zircon, monazite, apatite and allanite. Subsolidus alteration in G2 and G4 granites is indicated by non-primary muscovite and tourmaline and modification of major and trace element trends for G3-G4 granites, particularly for P2O5 and Rb. Topaz (G5) granites show low Zr, REE and extreme enrichment in Rb (up to 1530 ppm) and Nb (79 ppm) that cannot be related in a straightforward manner to continued differentiation of the G1-G2 or G3-G4 series. Instead, they are considered to represent partial melting, mediated by granulite facies fluids, of a biotite-rich restite following extraction of G1 and/or G3 magmas; they do

  18. The Impact of Mass Movement and Fluid Flow during Ridge Subduction inferred from Physical Properties and Zeolite Assemblage in the Upper Plate Slope of the Costa Rica Subduction Zone

    NASA Astrophysics Data System (ADS)

    Hamahashi, M.; Screaton, E.; Tanikawa, W.; Hashimoto, Y.; Martin, K. M.; Saito, S.; Kimura, G.

    2015-12-01

    The Costa Rica subduction zone offshore Osa Peninsula is known as an erosive margin with active seismicity and the subduction of the Cocos Ridge. One of the major unknowns in this margin is the nature of the unconformity at the base of the slope sediments in the upper plate and the high velocity materials below. To investigate the geologic processes across the unconformity, we examined the consolidation state and mineral assemblages of the sediments at the mid-slope Site 1380 drilled during IODP Expedition 344 by conducting microstructural observation, particle size analysis, X-ray fluorescence/diffraction analysis and resistivity measurement. The general compaction trend is controlled primarily by grain-size sorting and the physical property transition is likely caused by massive sediment removal under normal fault regime, thickness of which range between ~600-850 m determined from the composite porosity-depth curve. Across the unconformity between the late Pliocene~late Pleistocene silty clay (Unit 1) and late Pliocene~early Pleistocene clayey siltstone (Unit 2), the mineral/element components of the sediments is marked by the transitions in zeolite compositions; Unit 1 consists of laumontite and heulandite, whereas below the unconformity, Unit 2 sediments contain analcime, laumontite, and heulandite, but laumontite become less abundant at lower depth. The experienced temperature of the sediments in Unit 2 is estimated to have reached between ~86 and 122℃ as inferred from analcime burial diagenesis. This may correspond with the greater depth range prior to mass movement and normal faulting. The initial analcime burial diagenetic zone was likely cut off by the sediment removal across the unconformity, and later overprinted by high temperature fluid along the boundary forming laumontite and heulandite in the vicinity. These results illustrate that ridge subduction has substantial potential to cause mass movement, an extensional stress regime, and fluid flow from

  19. Beyond plate tectonics - Looking at plate deformation with space geodesy

    NASA Technical Reports Server (NTRS)

    Jordan, Thomas H.; Minster, J. Bernard

    1988-01-01

    The requirements that must be met by space-geodetic systems in order to constrain the horizontal secular motions associated with the geological deformation of the earth's surface are explored. It is suggested that in order to improve existing plate-motion models, the tangential components of relative velocities on interplate baselines must be resolved to an accuracy of less than 3 mm/yr. Results indicate that measuring the velocities between crustal blocks to + or - 5 mm/yr on 100-km to 1000-km scales can produce geologically significant constraints on the integrated deformation rates across continental plate-boundary zones such as the western United States.

  20. Martian plate tectonics

    NASA Astrophysics Data System (ADS)

    Sleep, N. H.

    1994-03-01

    The northern lowlands of Mars have been produced by plate tectonics. Preexisting old thick highland crust was subducted, while seafloor spreading produced thin lowland crust during late Noachian and Early Hesperian time. In the preferred reconstruction, a breakup margin extended north of Cimmeria Terra between Daedalia Planum and Isidis Planitia where the highland-lowland transition is relatively simple. South dipping subduction occured beneath Arabia Terra and east dipping subduction beneath Tharsis Montes and Tempe Terra. Lineations associated with Gordii Dorsum are attributed to ridge-parallel structures, while Phelegra Montes and Scandia Colles are interpreted as transfer-parallel structures or ridge-fault-fault triple junction tracks. Other than for these few features, there is little topographic roughness in the lowlands. Seafloor spreading, if it occurred, must have been relatively rapid. Quantitative estimates of spreading rate are obtained by considering the physics of seafloor spreading in the lower (approx. 0.4 g) gravity of Mars, the absence of vertical scarps from age differences across fracture zones, and the smooth axial topography. Crustal thickness at a given potential temperature in the mantle source region scales inversely with gravity. Thus, the velocity of the rough-smooth transition for axial topography also scales inversely with gravity. Plate reorganizations where young crust becomes difficult to subduct are another constraint on spreading age. Plate tectonics, if it occurred, dominated the thermal and stress history of the planet. A geochemical implication is that the lower gravity of Mars allows deeper hydrothermal circulation through cracks and hence more hydration of oceanic crust so that more water is easily subducted than on the Earth. Age and structural relationships from photogeology as well as median wavelength gravity anomalies across the now dead breakup and subduction margins are the data most likely to test and modify hypotheses

  1. Intermittent plate tectonics?

    PubMed

    Silver, Paul G; Behn, Mark D

    2008-01-04

    Although it is commonly assumed that subduction has operated continuously on Earth without interruption, subduction zones are routinely terminated by ocean closure and supercontinent assembly. Under certain circumstances, this could lead to a dramatic loss of subduction, globally. Closure of a Pacific-type basin, for example, would eliminate most subduction, unless this loss were compensated for by comparable subduction initiation elsewhere. Given the evidence for Pacific-type closure in Earth's past, the absence of a direct mechanism for termination/initiation compensation, and recent data supporting a minimum in subduction flux in the Mesoproterozoic, we hypothesize that dramatic reductions or temporary cessations of subduction have occurred in Earth's history. Such deviations in the continuity of plate tectonics have important consequences for Earth's thermal and continental evolution.

  2. Active faults and minor plates in NE Asia

    NASA Astrophysics Data System (ADS)

    Kozhurin, Andrey I.; Zelenin, Egor A.

    2014-05-01

    Stated nearly 40 yr ago the uncertainty with plate boundaries location in NE Asia (Chapman, Solomon, 1976) still remains unresolved. Based on the prepositions that a plate boundary must, first, reveal itself in linear sets of active structures, and, second, be continuous and closed, we have undertaken interpretation of medium-resolution KH-9 Hexagon satellite imageries, mostly in stereoscopic regime, for nearly the entire region of NE Asia. Main findings are as follows. There are two major active fault zones in the region north of the Bering Sea. One of them, the Khatyrka-Vyvenka zone, stretches NE to ENE skirting the Bering Sea from the Kamchatka isthmus to the Navarin Cape. Judging by the kinematics of the Olyutorsky 2006 earthquake fault, the fault zones move both right-laterally and reversely. The second active fault zone, the Lankovaya-Omolon zone, starts close to the NE margin of the Okhotsk Sea and extends NE up to nearly the margin of the Chukcha Sea. The fault zone is mostly right-lateral, with topographically expressed cumulative horizontal offsets amounting to 2.5-2.6 km. There may be a third NE-SW zone between the major two coinciding with the Penzhina Range as several active faults found in the southern termination of the Range indicate. The two active fault zones divide the NE Asia area into two large domains, which both could be parts of the Bering Sea plate internally broken and with uncertain western limit. Another variant implies the Khatyrka-Vyvenka zone as the Bering Sea plate northern limit, and the Lankovaya-Omolon zone as separating an additional minor plate from the North-American plate. The choice is actually not crucial, and more important is that both variants leave the question of where the Bering Sea plate boundary is in Alaska. The Lankovaya-Omolon zone stretches just across the proposed northern boundary of the Okhorsk Sea plate. NW of the zone, there is a prominent left-lateral Ulakhan fault, which is commonly interpreted to be a

  3. Corrugated cover plate for flat plate collector

    DOEpatents

    Hollands, K. G. Terry; Sibbitt, Bruce

    1978-01-01

    A flat plate radiant energy collector is providing having a transparent cover. The cover has a V-corrugated shape which reduces the amount of energy reflected by the cover away from the flat plate absorber of the collector.

  4. Safety Zones

    EPA Pesticide Factsheets

    These are established primarily to reduce the accidental spread of hazardous substances by workers or equipment from contaminated areas to clean areas. They include the exclusion (hot) zone, contamination reduction (warm) zone, and support (cold) zone.

  5. Florida: A Jurassic transform plate boundary

    USGS Publications Warehouse

    Klitgord, Kim D.; Popenoe, Peter; Schouten, Hans

    1984-01-01

    Magnetic, gravity, seismic, and deep drill hole data integrated with plate tectonic reconstructions substantiate the existence of a transform plate boundary across southern Florida during the Jurassic. On the basis of this integrated suite of data the pre-Cretaceous Florida-Bahamas region can be divided into the pre-Jurassic North American plate, Jurassic marginal rift basins, and a broad Jurassic transform zone including stranded blocks of pre-Mesozoic continental crust. Major tectonic units include the Suwannee basin in northern Florida containing Paleozoic sedimentary rocks, a central Florida basement complex of Paleozoic age crystalline rock, the west Florida platform composed of stranded blocks of continental crust, the south Georgia rift containing Triassic sedimentary rocks which overlie block-faulted Suwannee basin sedimentary rocks, the Late Triassic-Jurassic age Apalachicola rift basin, and the Jurassic age south Florida, Bahamas, and Blake Plateau marginal rift basins. The major tectonic units are bounded by basement hinge zones and fracture zones (FZ). The basement hinge zone represents the block-faulted edge of the North American plate, separating Paleozoic and older crustal rocks from Jurassic rifted crust beneath the marginal basins. Fracture zones separate Mesozoic marginal sedimentary basins and include the Blake Spur FZ, Jacksonville FZ, Bahamas FZ, and Cuba FZ, bounding the Blake Plateau, Bahamas, south Florida, and southeastern Gulf of Mexico basins. The Bahamas FZ is the most important of all these features because its northwest extension coincides with the Gulf basin marginal fault zone, forming the southern edge of the North American plate during the Jurassic. The limited space between the North American and the South American/African plates requires that the Jurassic transform zone, connecting the Central Atlantic and the Gulf of Mexico spreading systems, was located between the Bahamas and Cuba FZ's in the region of southern Florida. Our

  6. Inverse methods-based estimation of plate coupling in a plate motion model governed by mantle flow

    NASA Astrophysics Data System (ADS)

    Ratnaswamy, V.; Stadler, G.; Gurnis, M.

    2013-12-01

    Plate motion is primarily controlled by buoyancy (slab pull) which occurs at convergent plate margins where oceanic plates undergo deformation near the seismogenic zone. Yielding within subducting plates, lateral variations in viscosity, and the strength of seismic coupling between plate margins likely have an important control on plate motion. Here, we wish to infer the inter-plate coupling for different subduction zones, and develop a method for inferring it as a PDE-constrained optimization problem, where the cost functional is the misfit in plate velocities and is constrained by the nonlinear Stokes equation. The inverse models have well resolved slabs, plates, and plate margins in addition to a power law rheology with yielding in the upper mantle. Additionally, a Newton method is used to solve the nonlinear Stokes equation with viscosity bounds. We infer plate boundary strength using an inexact Gauss-Newton method with line search for backtracking. Each inverse model is applied to two simple 2-D scenarios (each with three subduction zones), one with back-arc spreading and one without. For each case we examine the sensitivity of the inversion to the amount of surface velocity used: 1) full surface velocity data and 2) surface velocity data simplified using a single scalar average (2-D equivalent to an Euler pole) for each plate. We can recover plate boundary strength in each case, even in the presence of highly nonlinear flow with extreme variations in viscosity. Additionally, we ascribe an uncertainty in each plate's velocity and perform an uncertainty quantification (UQ) through the Hessian of the misfit in plate velocities. We find that as plate boundaries become strongly coupled, the uncertainty in the inferred plate boundary strength decreases. For very weak, uncoupled subduction zones, the uncertainty of inferred plate margin strength increases since there is little sensitivity between plate margin strength and plate velocity. This result is significant

  7. Geometry of the Cocos Plate Under North American Plate

    NASA Astrophysics Data System (ADS)

    Perez-Campos, X.

    2015-12-01

    The Cocos plate subducts under the North American plate with a complex geometry, and previous seismicity studies revealed some of this complexity. However, details of the geometry and the depth that the plate penetrates werelargely unknown. Since 2004, temporary experiments and the expansion of the permanent network of the Servicio Sismológico Nacional (SSN, Mexican National Seismological Service) have improved resolution of the plate geometry and have helped to map its descent into the upper mantle. Going from northwest to southeast, the Cocos plate appears to be fragmenting into north and south segments. The north segment subducts with an angle of ~30º and the south with an angle of ~10-15º. The transition is smooth near the trench and progresses to a tear at depth; this coincides with the projection of the Orozco Fracture Zone to depth. Also, this transition marks the limit of the presence to the south of an ultra slow velocity layer (USL) on top of the slab.South of this transition, the Cocos plate subducts horizontally , underplating the North American plate for a distance of ~140 to ~300 km from the trench. Along this horizontal region, silent slow events (SSE) and tectonic tremor (TT) have been observed. At a distance of 300 km from the trench (beneath central Mexico), the plate dives into the mantle with an angle of 76º to a depth of 500 km. This geometry changes abruptly to the south, marking the eastern limit of the USL. This change seems to be also characterized by a tear on the slab. Finally to the south, the Cocos plate subducts with a constant angle of 26º. This presentation summarizes the work of many contributors including A. Arciniega-Ceballos, M. Brudzinski, E. Cabral-Cano, T. Chen, R. Clayton,F. Cordoba-Montiel,P. Davis,S. Dougherty,F. Green, M. Gurnis, D. V. Helmberger, A. Husker,A. Iglesias, Y. Kim, V. Manea, D. Melgar, M. Rodríguez-Domínguez,S. K. Singh, T.-R. A. Song, C. M. Valdés-González, D. Valencia-Cabrera

  8. An updated digital model of plate boundaries

    NASA Astrophysics Data System (ADS)

    Bird, Peter

    2003-03-01

    A global set of present plate boundaries on the Earth is presented in digital form. Most come from sources in the literature. A few boundaries are newly interpreted from topography, volcanism, and/or seismicity, taking into account relative plate velocities from magnetic anomalies, moment tensor solutions, and/or geodesy. In addition to the 14 large plates whose motion was described by the NUVEL-1A poles (Africa, Antarctica, Arabia, Australia, Caribbean, Cocos, Eurasia, India, Juan de Fuca, Nazca, North America, Pacific, Philippine Sea, South America), model PB2002 includes 38 small plates (Okhotsk, Amur, Yangtze, Okinawa, Sunda, Burma, Molucca Sea, Banda Sea, Timor, Birds Head, Maoke, Caroline, Mariana, North Bismarck, Manus, South Bismarck, Solomon Sea, Woodlark, New Hebrides, Conway Reef, Balmoral Reef, Futuna, Niuafo'ou, Tonga, Kermadec, Rivera, Galapagos, Easter, Juan Fernandez, Panama, North Andes, Altiplano, Shetland, Scotia, Sandwich, Aegean Sea, Anatolia, Somalia), for a total of 52 plates. No attempt is made to divide the Alps-Persia-Tibet mountain belt, the Philippine Islands, the Peruvian Andes, the Sierras Pampeanas, or the California-Nevada zone of dextral transtension into plates; instead, they are designated as "orogens" in which this plate model is not expected to be accurate. The cumulative-number/area distribution for this model follows a power law for plates with areas between 0.002 and 1 steradian. Departure from this scaling at the small-plate end suggests that future work is very likely to define more very small plates within the orogens. The model is presented in four digital files: a set of plate boundary segments; a set of plate outlines; a set of outlines of the orogens; and a table of characteristics of each digitization step along plate boundaries, including estimated relative velocity vector and classification into one of 7 types (continental convergence zone, continental transform fault, continental rift, oceanic spreading ridge

  9. Sputtering and ion plating

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The proceedings of a conference on sputtering and ion plating are presented. Subjects discussed are: (1) concepts and applications of ion plating, (2) sputtering for deposition of solid film lubricants, (3) commercial ion plating equipment, (4) industrial potential for ion plating and sputtering, and (5) fundamentals of RF and DC sputtering.

  10. Seismic reflection imaging of two megathrust shear zones in the northern Cascadia subduction zone.

    PubMed

    Calvert, Andrew J

    2004-03-11

    At convergent continental margins, the relative motion between the subducting oceanic plate and the overriding continent is usually accommodated by movement along a single, thin interface known as a megathrust. Great thrust earthquakes occur on the shallow part of this interface where the two plates are locked together. Earthquakes of lower magnitude occur within the underlying oceanic plate, and have been linked to geochemical dehydration reactions caused by the plate's descent. Here I present deep seismic reflection data from the northern Cascadia subduction zone that show that the inter-plate boundary is up to 16 km thick and comprises two megathrust shear zones that bound a >5-km-thick, approximately 110-km-wide region of imbricated crustal rocks. Earthquakes within the subducting plate occur predominantly in two geographic bands where the dip of the plate is inferred to increase as it is forced around the edges of the imbricated inter-plate boundary zone. This implies that seismicity in the subducting slab is controlled primarily by deformation in the upper part of the plate. Slip on the shallower megathrust shear zone, which may occur by aseismic slow slip, will transport crustal rocks into the upper mantle above the subducting oceanic plate and may, in part, provide an explanation for the unusually low seismic wave speeds that are observed there.

  11. Biomechanical comparison of anterior cervical plating and combined anterior/lateral mass plating.

    PubMed

    Adams, M S; Crawford, N R; Chamberlain, R H; Bse; Sonntag, V K; Dickman, C A

    2001-01-01

    Previous studies showed anterior plates of older design to be inadequate for stabilizing the cervical spine in all loading directions. No studies have investigated enhancement in stability obtained by combining anterior and posterior plates. To determine which modes of loading are stabilized by anterior plating after a cervical burst fracture and to determine whether adding posterior plating further significantly stabilizes the construct. A repeated-measures in vitro biomechanical flexibility experiment was performed to investigate how surgical destabilization and subsequent addition of hardware components alter spinal stability. Six human cadaveric specimens were studied. Angular range of motion (ROM) and neutral zone (NZ) were quantified during flexion, extension, lateral bending, and axial rotation. Nonconstraining, nondestructive torques were applied while recording three-dimensional motion optoelectronically. Specimens were tested intact, destabilized by simulated burst fracture with posterior distraction, plated anteriorly with a unicortical locking system, and plated with a combined anterior/posterior construct. The anterior plate significantly (p<.05) reduced the ROM relative to normal in all modes of loading and significantly reduced the NZ in flexion and extension. Addition of the posterior plates further significantly reduced the ROM in all modes of loading and reduced the NZ in lateral bending. Anterior plating systems are capable of substantially stabilizing the cervical spine in all modes of loading after a burst fracture. The combined approach adds significant stability over anterior plating alone in treating this injury but may be unnecessary clinically. Further study is needed to assess the added clinical benefits of the combined approach and associated risks.

  12. Extended Plate and Beam Wall System

    SciTech Connect

    Gunderson, Patti

    Home Innovation Research Labs studied the extended plate and beam wall (EP&B) system during a two-year period from mid-2015 to mid-2017 to determine the wall’s structural performance, moisture durability, constructability, and costeffectiveness for use as a high-R enclosure system for energy code minimum and above-code performance in climate zones 4–8.

  13. Zone lines

    Treesearch

    Kevin T. Smith

    2001-01-01

    Zone lines are narrow, usually dark markings formed in decaying wood. Zone lines are found most frequently in advanced white rot of hardwoods, although they occasionally are associated both with brown rot and with softwoods.

  14. Portable Plating System

    NASA Technical Reports Server (NTRS)

    Flores, R.

    1984-01-01

    Plating system mounted on portable cart includes 30-gallon (23.5 liter) electrolyte tank, filler pump, heaters, replenishing anodes, plating rectifiers and tank rectifier to continously remove contaminants.

  15. Williamson Polishing & Plating Site

    EPA Pesticide Factsheets

    Williamson Polishing & Plating Co. Inc. was a plating shop located in the Martindale-Brightwood neighborhood of Indianapolis. The facility conducted job shop polishing and electroplating services. The vacant site contains a 14,651-square-foot building.

  16. Subduction and Plate Edge Tectonics in the Southern Caribbean

    NASA Astrophysics Data System (ADS)

    Levander, A.; Schmitz, M.; Niu, F.; Bezada, M. J.; Miller, M. S.; Masy, J.; Ave Lallemant, H. G.; Pindell, J. L.

    2012-12-01

    The southern Caribbean plate boundary consists of a subduction zone at at either end connected by a strike-slip fault system: In the east at the Lesser Antilles subduction zone, the Atlantic part of the South American plate subducts beneath the Caribbean. In the north and west in the Colombia basin, the Caribbean subducts under South America. In a manner of speaking, the two plates subduct beneath each other. Finite-frequency teleseismic P-wave tomography confirms this, imaging the Atlantic and the Caribbean subducting steeply in opposite directions to transition zone depths under northern South America (Bezada et al, 2010). The two subduction zones are connected by the El Pilar-San Sebastian strike-slip fault system, a San Andreas scale system that has been cut off at the Bocono fault, the southeastern boundary of the Maracaibo block. A variety of seismic probes identify where the two plates tear as they begin to subduct (Niu et al, 2007; Clark et al., 2008; Miller et al. 2009; Growdon et al., 2009; Huang et al., 2010; Masy et al., 2011). The El Pilar system forms at the southeastern corner of the Antilles subduction zone with the Atlantic plate tearing from South America. The deforming plate edges control mountain building and basin formation at the eastern end of the strike-slip system. In northwestern South America the Caribbean plate very likely also tears, as its southernmost element subducts at shallow angles under northernmost Colombia and the northern, nonsubducting part underthrusts the continental edge. The subducting segment rapidly descends to transition zone depths under Lake Maracaibo (Bezada et al., 2010). We believe that the flat slab produces the Merida Andes, the Perija, and the Santa Marta ranges. The nonsubducting part of the Caribbean plate underthrusts northern Venezuela to about the width of the coastal mountains (Miller et al., 2009), where the plate edge supports the coastal mountains, and controls continuing deformation.

  17. Accelerated plate tectonics.

    PubMed

    Anderson, D L

    1975-03-21

    The concept of a stressed elastic lithospheric plate riding on a viscous asthenosphere is used to calculate the recurrence interval of great earthquakes at convergent plate boundaries, the separation of decoupling and lithospheric earthquakes, and the migration pattern of large earthquakes along an arc. It is proposed that plate motions accelerate after great decoupling earthquakes and that most of the observed plate motions occur during short periods of time, separated by periods of relative quiescence.

  18. Subduction Drive of Plate Tectonics

    NASA Astrophysics Data System (ADS)

    Hamilton, W. B.

    2003-12-01

    shrinking oceans, forcing rapid Pacific spreading. Slabs suck forward overriding arcs and continental lithosphere, plus most subjacent mantle above the transition zone. Changes in sizes of oceans result primarily from transfer of oceanic lithosphere, so backarcs and expanding oceans spread only slowly. Lithosphere parked in, or displaced from, the transition zone, or mixed into mid-upper mantle, is ultimately recycled, and regional variations in age of that submerged lithosphere may account for some regional contrasts in MORB. Plate motions make no kinematic sense in either the "hotspot" reference frame (HS; the notion of fixed plumes is easily disproved) or the no-net-rotation frame (NNR) In both, for example, many hinges roll forward, impossible with gravity drive. Subduction-drive predictions are fulfilled, and paleomagnetic data are satisfied (as they are not in HS and NNR), in the alternative framework of propulsionless Antarctica fixed relative to sluggish lower mantle. Passive ridges migrate away from Antarctica on all sides, and migration of these and other ridges permits tapping fresh asthenosphere. (HS and NNR tend to fix ridges). Ridge migration and spreading rates accord with subduction drive. All trenches roll back when allowance is made for back-arc spreading and intracontinental deformation. Africa rotates slowly toward subduction systems in the NE, instead of moving rapidly E as in HS and NNR. Stable NW Eurasia is nearly stationary, instead of also moving rapidly, and S and E Eurasian deformation relates to subduction and rollback. The Americas move Pacificward at almost the full spreading rates of passive ridges behind them. Lithosphere has a slow net westward drift. Reference: W.B. Hamilton, An alternative Earth, GSA Today, in press.

  19. Seismic link at plate boundary

    NASA Astrophysics Data System (ADS)

    Ramdani, Faical; Kettani, Omar; Tadili, Benaissa

    2015-06-01

    Seismic triggering at plate boundaries has a very complex nature that includes seismic events at varying distances. The spatial orientation of triggering cannot be reduced to sequences from the main shocks. Seismic waves propagate at all times in all directions, particularly in highly active zones. No direct evidence can be obtained regarding which earthquakes trigger the shocks. The first approach is to determine the potential linked zones where triggering may occur. The second step is to determine the causality between the events and their triggered shocks. The spatial orientation of the links between events is established from pre-ordered networks and the adapted dependence of the spatio-temporal occurrence of earthquakes. Based on a coefficient of synchronous seismic activity to grid couples, we derive a network link by each threshold. The links of high thresholds are tested using the coherence of time series to determine the causality and related orientation. The resulting link orientations at the plate boundary conditions indicate that causal triggering seems to be localized along a major fault, as a stress transfer between two major faults, and parallel to the geothermal area extension.

  20. Angular shear plate

    DOEpatents

    Ruda, Mitchell C [Tucson, AZ; Greynolds, Alan W [Tucson, AZ; Stuhlinger, Tilman W [Tucson, AZ

    2009-07-14

    One or more disc-shaped angular shear plates each include a region thereon having a thickness that varies with a nonlinear function. For the case of two such shear plates, they are positioned in a facing relationship and rotated relative to each other. Light passing through the variable thickness regions in the angular plates is refracted. By properly timing the relative rotation of the plates and by the use of an appropriate polynomial function for the thickness of the shear plate, light passing therethrough can be focused at variable positions.

  1. An improved plating process

    NASA Technical Reports Server (NTRS)

    Askew, John C.

    1994-01-01

    An alternative to the immersion process for the electrodeposition of chromium from aqueous solutions on the inside diameter (ID) of long tubes is described. The Vessel Plating Process eliminates the need for deep processing tanks, large volumes of solutions, and associated safety and environmental concerns. Vessel Plating allows the process to be monitored and controlled by computer thus increasing reliability, flexibility and quality. Elimination of the trivalent chromium accumulation normally associated with ID plating is intrinsic to the Vessel Plating Process. The construction and operation of a prototype Vessel Plating Facility with emphasis on materials of construction, engineered and operational safety and a unique system for rinse water recovery are described.

  2. Volcano spacing and plate rigidity

    USGS Publications Warehouse

    ten Brink, Uri S.

    1991-01-01

    In-plane stresses, which accompany the flexural deformation of the lithosphere under the load of adjacent volcanoes, may govern the spacing of volcanoes in hotspot provinces. Specifically, compressive stresses in the vicinity of a volcano prevent new upwelling in this area, forcing a new volcano to develop at a minimum distance that is equal to the distance in which the radial stresses change from compressional to tensile (the inflection point). If a volcano is modeled as a point load on a thin elastic plate, then the distance to the inflection point is proportional to the thickness of the plate to the power of 3/4. Compilation of volcano spacing in seven volcanic groups in East Africa and seven volcanic groups of oceanic hotspots shows significant correlation with the elastic thickness of the plate and matches the calculated distance to the inflection point. In contrast, volcano spacing in island arcs and over subduction zones is fairly uniform and is much larger than predicted by the distance to the inflection point, reflecting differences in the geometry of the source and the upwelling areas.

  3. Pre-Cretaceous Tectonic Evolution of the Pacific Plate and Extension of the Geomagnetic Polarity Reversal Time Scale with Implications for the Origin of the Jurassic ’Quiet Zone

    DTIC Science & Technology

    1987-03-01

    MONITORING ORGANIZATION REPORT NUMBER(S) E OF PERFORMING ORGANIZATION 6b. OFFICE SYMBOL 7. NAME OF MO NG OR0 GANIZATION I (If applicable) Naval Ocean ...Zone" * DAVID W. HANDSCHUMACHER’, WILLIAM W. SAGER 2, THOMAS W.C. HILDE 3 and DEWEY R. BRACEY 4 Naval Ocean Research and Development Activiy, NSTL, MS...Pacific Ocean . New aeromagnetic data allowed the magnetic bight to be more accurately mapped from M21 to M28 and enabled the identification of low-amplitude

  4. Inter-plate aseismic slip on the subducting plate boundaries estimated from repeating earthquakes

    NASA Astrophysics Data System (ADS)

    Igarashi, T.

    2015-12-01

    Sequences of repeating earthquakes are caused by repeating slips of small patches surrounded by aseismic slip areas at plate boundary zones. Recently, they have been detected in many regions. In this study, I detected repeating earthquakes which occurred in Japan and the world by using seismograms observed in the Japanese seismic network, and investigated the space-time characteristics of inter-plate aseismic slip on the subducting plate boundaries. To extract repeating earthquakes, I calculate cross-correlation coefficients of band-pass filtering seismograms at each station following Igarashi [2010]. I used two data-set based on USGS catalog for about 25 years from May 1990 and JMA catalog for about 13 years from January 2002. As a result, I found many sequences of repeating earthquakes in the subducting plate boundaries of the Andaman-Sumatra-Java and Japan-Kuril-Kamchatka-Aleutian subduction zones. By applying the scaling relations among a seismic moment, recurrence interval and slip proposed by Nadeau and Johnson [1998], they indicate the space-time changes of inter-plate aseismic slips. Pairs of repeating earthquakes with the longest time interval occurred in the Solomon Islands area and the recurrence interval was about 18.5 years. The estimated slip-rate is about 46 mm/year, which correspond to about half of the relative plate motion in this area. Several sequences with fast slip-rates correspond to the post-seismic slips after the 2004 Sumatra-Andaman earthquake (M9.0), the 2006 Kuril earthquake (M8.3), the 2007 southern Sumatra earthquake (M8.5), and the 2011 Tohoku-oki earthquake (M9.0). The database of global repeating earthquakes enables the comparison of the inter-plate aseismic slips of various plate boundary zones of the world. I believe that I am likely to detect more sequences by extending analysis periods in the area where they were not found in this analysis.

  5. Anatomic fit of six different radial head plates: comparison of precontoured low-profile radial head plates.

    PubMed

    Burkhart, Klaus Josef; Nowak, Tobias E; Kim, Yoon-Joo; Rommens, Pol M; Müller, Lars P

    2011-04-01

    Bulky implants may lead to symptomatic soft tissue irritation after open reduction and internal fixation of radial head and neck fractures. The purpose of our study was to compare the anatomic fit of precontoured radial head plates. We stripped 22 embalmed human cadaveric radiuses of soft tissues. We investigated 6 radial head plates: (1) the Medartis radial head buttress plate (MBP), (2) the Medartis radial head rim plate (MRP), (3) the Synthes radial neck plate (SNP), (4) the Synthes radial head plate (SHP), (5) the Acumed radial head plate (AHP), and (6) the Wright radial head plate (WHP). Each plate was applied to each radial head at the place of best fit within the safe zone. We tested 4 parameters of anatomic fit: (1) plate-to-bone distance, (2) plate contact judged by 3 different observers, (3) pin-subchondral zone distance, and (4) plate-to-bone contact after adjustment of the plates. The MBP and MRP showed the lowest profile by objective measurements, the SNP and AHP had a moderate profile, and the SHP and WHP demonstrated the bulkiest profile. The subjective assessments also demonstrated the best fit for the MBP, a good fit for the SNP, a moderate fit for the MRP and AHP, and a poor fit for the SHP and WHP. The MBP, MRP, and AHP could always provide pin-subchondral zone contact, unlike the SHP, SNP, and WHP. After bending, significant improvement of plate-to-bone distance could only be seen for the MBP, MRP, and WHP. The ranking among plates remained the same except for the WHP, which showed a significantly lower plate-to-bone distance than the SHP. Currently available radial head implants are heterogeneous. The MBP and MRP showed the lowest profile and best anatomic fit. Owing to the complex radial head anatomy, to date there is no one radial head plate that perfectly fits all radial heads. Conformance of existing plates to the radial head and neck is not perfect. Careful plate selection and modification, when necessary, may minimize interference of this

  6. Multicolor printing plate joining

    NASA Technical Reports Server (NTRS)

    Waters, W. J. (Inventor)

    1984-01-01

    An upper plate having ink flow channels and a lower plate having a multicolored pattern are joined. The joining is accomplished without clogging any ink flow paths. A pattern having different colored parts and apertures is formed in a lower plate. Ink flow channels each having respective ink input ports are formed in an upper plate. The ink flow channels are coated with solder mask and the bottom of the upper plate is then coated with solder. The upper and lower plates are pressed together at from 2 to 5 psi and heated to a temperature of from 295 F to 750 F or enough to melt the solder. After the plates have cooled and the pressure is released, the solder mask is removed from the interior passageways by means of a liquid solvent.

  7. Extending Alaska's plate boundary: tectonic tremor generated by Yakutat subduction

    USGS Publications Warehouse

    Wech, Aaron G.

    2016-01-01

    The tectonics of the eastern end of the Alaska-Aleutian subduction zone are complicated by the inclusion of the Yakutat microplate, which is colliding into and subducting beneath continental North America at near-Pacific-plate rates. The interaction among these plates at depth is not well understood, and further east, even less is known about the plate boundary or the source of Wrangell volcanism. The drop-off in Wadati-Benioff zone (WBZ) seismicity could signal the end of the plate boundary, the start of aseismic subduction, or a tear in the downgoing plate. Further compounding the issue is the possible presence of the Wrangell slab, which is faintly outlined by an anemic, eastward-dipping WBZ beneath the Wrangell volcanoes. In this study, I performed a search for tectonic tremor to map slow, plate-boundary slip in south-central Alaska. I identified ∼11,000 tremor epicenters, which continue 85 km east of the inferred Pacific plate edge marked by WBZ seismicity. The tremor zone coincides with the edges of the downgoing Yakutat terrane, and tremors transition from periodic to continuous behavior as they near the aseismic Wrangell slab. I interpret tremor to mark slow, semicontinuous slip occurring at the interface between the Yakutat and North America plates. The slow slip region lengthens the megathrust interface beyond the WBZ and may provide evidence for a connection between the Yakutat slab and the aseismic Wrangell slab.

  8. Liquid zone seal

    DOEpatents

    Klebanoff, Leonard E.

    2001-01-01

    A seal assembly that provides a means for establishing multiple pressure zones within a system. The seal assembly combines a plate extending from the inner wall of a housing or inner enclosure that intersects with and is immersed in the fluid contained in a well formed in a tray contained within the enclosure. The fluid is a low vapor pressure oil, chemically inert and oxidation resistant. The use of a fluid as the sealing component provides a seal that is self-healing and mechanically robust not subject to normal mechanical wear, breakage, and formation of cracks or pinholes and decouples external mechanical vibrations from internal structural members.

  9. Mechanical obstacles to the movement of continent-bearing plates

    NASA Technical Reports Server (NTRS)

    Lowman, P. D., Jr.

    1985-01-01

    Selected geophysical problems associated with the concept of continental drift as an incidental corollary of plate movement are discussed. The problems include the absence of a suitable plate-driving mechanism for plates with continental leading edges, the absence of the low-velocity zone under shields, and continental roots of 400 to 700 km depths. It is shown that if continental drift occurs, it must use mechanisms not now understood, or that it may not occur at all, plate movement being confined to ocean basins.

  10. Finite stretching of an annular plate.

    NASA Technical Reports Server (NTRS)

    Biricikoglu, V.; Kalnins, A.

    1971-01-01

    The problem of the finite stretching of an annular plate which is bonded to a rigid inclusion at its inner edge is considered. The material is assumed to be isotropic and incompressible with a Mooney-type constitutive law. It is shown that the inclusion of the effect of the transverse normal strain leads to a rapid variation in thickness which is confined to a narrow edge zone. The explicit solutions to the boundary layer equations, which govern the behavior of the plate near the edges, are presented.

  11. Vadose zone water fluxmeter

    DOEpatents

    Faybishenko, Boris A.

    2005-10-25

    A Vadose Zone Water Fluxmeter (WFM) or Direct Measurement WFM provides direct measurement of unsaturated water flow in the vadose zone. The fluxmeter is a cylindrical device that fits in a borehole or can be installed near the surface, or in pits, or in pile structures. The fluxmeter is primarily a combination of tensiometers and a porous element or plate in a water cell that is used for water injection or extraction under field conditions. The same water pressure measured outside and inside of the soil sheltered by the lower cylinder of the fluxmeter indicates that the water flux through the lower cylinder is similar to the water flux in the surrounding soil. The fluxmeter provides direct measurement of the water flow rate in the unsaturated soils and then determines the water flux, i.e. the water flow rate per unit area.

  12. Is There Really A North American Plate?

    NASA Astrophysics Data System (ADS)

    Krill, A.

    2011-12-01

    Lithospheric plates are typically identified from earthquake epicenters and evidence such as GPS movements. But no evidence indicates a plate boundary between the North American and South American Plates. Some plate maps show them separated by a transform boundary, but it is only a fracture zone. Other maps show an "undefined plate boundary" or put no boundary between these two plates (check Google images). Early plate maps showed a single large American Plate, quite narrow east of the Caribbean Plate (Le Pichon 1968, Morgan 1968). The North and South American Plates became established by the leading textbook Earth (Press & Siever 1974). On their map, from a Scientific American article by John Dewey (1972), these new plates were separated by an "uncertain plate boundary." The reasons for postulating a North American Plate were probably more psychological than geological. Each of the other continents of the world had its own plate, and North American geologists naturally wanted theirs. Similarly, European geographers used to view Europe as its own continent. A single large plate should again be hypothesized. But the term American Plate would now be ambiguous ("Which plate, North or South?") Perhaps future textbook authors could call it the "Two-American Plate." Textbook authors ultimately decide such global-tectonic matters. I became aware of textbook authors' opinions and influence from my research into the history of Alfred Wegener's continental drift (see Fixists vs. Mobilists by Krill 2011). Leading textbook author Charles Schuchert realized that continental drift would abolish his cherished paleogeographic models of large east-west continents (Eria, Gondwana) and small oceans (Poseiden, Nereis). He and his junior coauthors conspired to keep drift evidence out of their textbooks, from the 1934-editions until the 1969-editions (Physical Geology by Longwell et al. 1969, Historical Geology by Dunbar & Waage 1969). Their textbooks ruled in America. Textbooks

  13. GOLD PLATING PROCESS

    DOEpatents

    Seegmiller, R.

    1957-08-01

    An improved bath is reported for plating gold on other metals. The composition of the plating bath is as follows: Gold cyanide from about 15 to about 50 grams, potassium cyanide from about 70 to about 125 grams, and sulfonated castor oil from about 0.1 to about 10 cc. The gold plate produced from this bath is smooth, semi-hard, and nonporous.

  14. Plating methods, a survey

    NASA Technical Reports Server (NTRS)

    Berkowitz, J. B.; Emerson, N. H.

    1972-01-01

    Results are presented of a comprehensive search of the literature available, much of which has been generated by the research centers of NASA and its contractors, on plating and coating methods and techniques. Methods covered included: (1) electroplating from aqueous solutions; (2) electroplating from nonaqueous solutions; (3) electroplating from fused-salt baths; (4) electroforming; (5) electroless plating, immersion plating, and mirroring; (6) electroplating from gaseous plasmas; and (7) anodized films and conversion coatings.

  15. CALUTRON FACE PLATE

    DOEpatents

    Brobeck, W.M.

    1959-08-25

    The construction of a removable cover plate for a calutron tank is described. The plate is fabricated of a rectangular frame member to which is welded a bowed or dished plate of thin steel, reinforced with transverse stiffening ribs. When the tank is placed between the poles of a magnet, the plate may be pivoted away from the tank and magnet and is adapted to support the ion separation mechanism secured to its inner side as well as the vacuum load within the tank.

  16. PLATES WITH OXIDE INSERTS

    DOEpatents

    West, J.M.; Schumar, J.F.

    1958-06-10

    Planar-type fuel assemblies for nuclear reactors are described, particularly those comprising fuel in the oxide form such as thoria and urania. The fuel assembly consists of a plurality of parallel spaced fuel plate mennbers having their longitudinal side edges attached to two parallel supporting side plates, thereby providing coolant flow channels between the opposite faces of adjacent fuel plates. The fuel plates are comprised of a plurality of longitudinally extending tubular sections connected by web portions, the tubular sections being filled with a plurality of pellets of the fuel material and the pellets being thermally bonded to the inside of the tubular section by lead.

  17. Electronic Equipment Cold Plates

    DTIC Science & Technology

    1976-04-01

    using fans or blowers to force the air through the cooling device». ^J^lJ^^i 5!°^ it ia ’«"^"o^ve. nonto«ic. nonfla—able, *nd possesses good ...Techniques GENERAL THERMAL CONTROL SYSTEMS AND THEIR REgUIREMENTS FLON DISTRIBUTION IN MANIFOLDS THE COLD PLATE IA ,! 1 3 S 12 15 33 32 32... IA .1 132 132 132 155 169 179 183 r (1) Air-Cooled Cold Plate No. (2) Air-Cooled Cold Plate No. (3) Air-cooled Cold Plate No. (4) Air-Cooled

  18. Motion of the Rivera plate since 10 Ma relative to the Pacific and North American plates and the mantle

    NASA Astrophysics Data System (ADS)

    DeMets, Charles; Traylen, Stephen

    2000-03-01

    To better understand the influence of Rivera plate kinematics on the geodynamic evolution of western Mexico, we use more than 1400 crossings of seafloor spreading magnetic lineations along the Pacific-Rivera rise and northern Mathematician ridge to solve for rotations of the Rivera plate relative to the underlying mantle and the Pacific and North American plates at 14 times since 9.9 Ma. Our comparison of magnetic anomaly crossings from the undeformed Pacific plate to their counterparts on the Rivera plate indicates that significant areas of the Rivera plate have deformed since 9.9 Ma. Dextral shear along the southern edge of the plate from 3.3-2.2 Ma during a regional plate boundary reorganization deformed the Rivera plate farther into its interior than previously recognized. In addition, seafloor located north of two rupture zones within the Rivera plate sutured to North America after 1.5 Ma. Anomaly crossings from these two deformed regions thus cannot be used to reconstruct motion of the Rivera plate. Finite rotations that best reconstruct Pacific plate anomaly crossings onto their undeformed counterparts on the Rivera plate yield stage spreading rates that decrease gradually by 10% between 10 and 3.6 Ma, decrease rapidly by 20% after ˜3.6 Ma, and recover after 1 Ma. The slowdown in Pacific-Rivera seafloor spreading at 3.6 Ma coincided with the onset of dextral shear across the then-incipient southern boundary of the Rivera plate with the Pacific plate. The available evidence indicates that the Rivera plate has been an independent microplate since at least 10 Ma, contrary to published assertions that it fragmented from the Cocos plate at ˜5 Ma. Motion of the Rivera plate relative to North America has changed significantly since 10 Ma, in concert with significant changes in Pacific-Rivera motion. A significant and robust feature of Rivera-North America motion not previously recognized is the cessation of margin-normal convergence and thus subduction from 2

  19. Global tectonic reconstructions with continuously deforming and evolving rigid plates

    NASA Astrophysics Data System (ADS)

    Gurnis, Michael; Yang, Ting; Cannon, John; Turner, Mark; Williams, Simon; Flament, Nicolas; Müller, R. Dietmar

    2018-07-01

    Traditional plate reconstruction methodologies do not allow for plate deformation to be considered. Here we present software to construct and visualize global tectonic reconstructions with deforming plates within the context of rigid plates. Both deforming and rigid plates are defined by continuously evolving polygons. The deforming regions are tessellated with triangular meshes such that either strain rate or cumulative strain can be followed. The finite strain history, crustal thickness and stretching factor of points within the deformation zones are tracked as Lagrangian points. Integrating these tools within the interactive platform GPlates enables specialized users to build and refine deforming plate models and integrate them with other models in time and space. We demonstrate the integrated platform with regional reconstructions of Cenozoic western North America, the Mesozoic South American Atlantic margin, and Cenozoic southeast Asia, embedded within global reconstructions, using different data and reconstruction strategies.

  20. Plate convergence and deformation, North Luzon Ridge, Philippines

    NASA Astrophysics Data System (ADS)

    Lewis, Stephen D.; Hayes, Dennis E.

    1989-10-01

    Marine geophysical and earthquake seismology data indicate that the North Luzon Ridge, a volcano-capped bathymetrie ridge system that extends between Luzon and Taiwan, is presently undergoing deformation in response to the relative motion between the Asian and Philippine Sea plates. Plate motion models predict convergence along the western side of the Philippine Sea plate, from Japan in the north to Indonesia in the south, and most of this plate margin is defined by active subduction zones. However, the western boundary of the Philippine Sea plate adjacent to the North Luzon Ridge shows no evidence of an active WNW-dipping subduction zone; this is in marked contrast to the presence of both the Philippine Trench/East Luzon Trough subduction zones to the south and the Ryukyu Trench subduction zone to the north. Crustal shortening, in response to ongoing plate convergence in the North Luzon Ridge region, apparently takes place through a complex pattern of strike-slip and thrust faulting, rather than by the typical subduction of oceanic lithosphere along a discreet zone. The curvilinear bathymetrie trends within the North Luzon Ridge represent the traces of active faults. The distribution of these faults, mapped by both multichannel and single-channel seismic reflection methods and earthquake seismicity patterns and focal mechanism solutions, suggest that right-lateral, oblique-slip faulting occurs along NE-trending faults, and left-lateral, oblique-slip faulting takes place on N- and NNW-trending faults. The relative plate convergence accommodated by the deformation of the North Luzon Ridge will probably be taken up in the future by the northward-propagating East Luzon Trough subduction zone.

  1. Caribbean tectonics and relative plate motions

    NASA Technical Reports Server (NTRS)

    Burke, K.; Dewey, J. F.; Cooper, C.; Mann, P.; Pindell, J. L.

    1984-01-01

    During the last century, three different ways of interpreting the tectonic evolution of the Gulf of Mexico and the Caribbean have been proposed, taking into account the Bailey Willis School of a permanent pre-Jurassic deep sea basin, the Edward Suess School of a subsided continental terrain, and the Alfred Wegener School of continental separation. The present investigation is concerned with an outline of an interpretation which follows that of Pindell and Dewey (1982). An attempt is made to point out ways in which the advanced hypotheses can be tested. The fit of Africa, North America, and South America is considered along with aspects of relative motion between North and South America since the early Jurasic. Attention is given to a framework for reconstructing Caribbean plate evolution, the evolution of the Caribbean, the plate boundary zones of the northern and southern Caribbean, and the active deformation of the Caribbean plate.

  2. Numerical modelling of instantaneous plate tectonics

    NASA Technical Reports Server (NTRS)

    Minster, J. B.; Haines, E.; Jordan, T. H.; Molnar, P.

    1974-01-01

    Assuming lithospheric plates to be rigid, 68 spreading rates, 62 fracture zones trends, and 106 earthquake slip vectors are systematically inverted to obtain a self-consistent model of instantaneous relative motions for eleven major plates. The inverse problem is linearized and solved iteratively by a maximum-likelihood procedure. Because the uncertainties in the data are small, Gaussian statistics are shown to be adequate. The use of a linear theory permits (1) the calculation of the uncertainties in the various angular velocity vectors caused by uncertainties in the data, and (2) quantitative examination of the distribution of information within the data set. The existence of a self-consistent model satisfying all the data is strong justification of the rigid plate assumption. Slow movement between North and South America is shown to be resolvable.

  3. Reconstructing plate motion paths where plate tectonics doesn't strictly apply

    NASA Astrophysics Data System (ADS)

    Handy, M. R.; Ustaszewski, K.

    2012-04-01

    The classical approach to reconstructing plate motion invokes the assumption that plates are rigid and therefore that their motions can be described as Eulerian rotations on a spherical Earth. This essentially two-dimensional, map view of plate motion is generally valid for large-scale systems, but is not practicable for small-scale tectonic systems in which plates, or significant parts thereof, deform on time scales approaching the duration of their motion. Such "unplate-like" (non-rigid) behaviour is common in systems with a weak lithosphere, for example, in Mediterranean-type settings where (micro-)plates undergo distributed deformation several tens to hundreds of km away from their boundaries. The motion vector of such anomalous plates can be quantified by combining and comparing information from two independent sources: (1) Balanced cross sections that are arrayed across deformed zones (orogens, basins) and provide estimates of crustal shortening and/or extension. Plate motion is then derived by retrodeforming the balanced sections in a stepwise fashion from external to internal parts of mountain belts, then applying these estimates as successive retrotranslations of points on stable parts of the upper plate with respect to a chosen reference frame on the lower plate. This approach is contingent on using structural markers with tight age constraints, for example, depth-sensitive metamorphic mineral parageneses and syn-orogenic sediments with known paleogeographic provenance; (2) Geophysical images of 3D subcrustal structure, especially of the MOHO and the lithospheric mantle in the vicinity of the deformed zones. In the latter case, travel-time seismic tomography of velocity anomalies can be used to identify subducted lithospheric slabs that extend downwards from the zones of crustal shortening to the mantle transitional zone and beyond. Synthesizing information from these two sources yields plate motion paths whose validity can be tested by the degree of

  4. Linking Incoming Plate Faulting and Intermediate Depth Seismicity

    NASA Astrophysics Data System (ADS)

    Kwong, K. B.; van Zelst, I.; Tong, X.; Eimer, M. O.; Naif, S.; Hu, Y.; Zhan, Z.; Boneh, Y.; Schottenfels, E.; Miller, M. S.; Moresi, L. N.; Warren, J. M.; Wiens, D. A.

    2017-12-01

    Intermediate depth earthquakes, occurring between 70-350 km depth, are often attributed to dehydration reactions within the subducting plate. It is proposed that incoming plate normal faulting associated with plate bending at the trench may control the amount of hydration in the plate by producing large damage zones that create pathways for the infiltration of seawater deep into the subducting mantle. However, a relationship between incoming plate seismicity, faulting, and intermediate depth seismicity has not been established. We compiled a global dataset consisting of incoming plate earthquake moment tensor (CMT) solutions, focal depths, bend fault spacing and offset measurements, along with plate age and convergence rates. In addition, a global intermediate depth seismicity dataset was compiled with parameters such as the maximum seismic moment and seismicity rate, as well as thicknesses of double seismic zones. The maximum fault offset in the bending region has a strong correlation with the intermediate depth seismicity rate, but a more modest correlation with other parameters such as convergence velocity and plate age. We estimated the expected rate of seismic moment release for the incoming plate faults using mapped fault scarps from bathymetry. We compare this with the cumulative moment from normal faulting earthquakes in the incoming plate from the global CMT catalog to determine whether outer rise fault movement has an aseismic component. Preliminary results from Tonga and the Middle America Trench suggest there may be an aseismic component to incoming plate bending faulting. The cumulative seismic moment calculated for the outer rise faults will also be compared to the cumulative moment from intermediate depth earthquakes to assess whether these parameters are related. To support the observational part of this study, we developed a geodynamic numerical modeling study to systematically explore the influence of parameters such as plate age and convergence

  5. Earthquakes and plate tectonics

    USGS Publications Warehouse

    Spall, H.

    1977-01-01

    An explanation is to be found in plate tectonics, a concept which has revolutionized thinking in the Earth sciences in the last 10 years. The theory of plate tectonics combines many of the ideas about continental drift (originally proposed in 1912 by Alfred Wegener in Germany) and sea-floor spreading (suggested originally by Harry Hess of Princeton University). 

  6. Blue Willow Story Plates

    ERIC Educational Resources Information Center

    Fontes, Kris

    2009-01-01

    In the December 1997 issue of "SchoolArts" is a lesson titled "Blue Willow Story Plates" by Susan Striker. In this article, the author shares how she used this lesson with her middle-school students many times over the years. Here, she describes a Blue Willow plate painting project that her students made.

  7. Implications of new gravity data for Baikal Rift zone structure

    NASA Technical Reports Server (NTRS)

    Ruppel, C.; Kogan, M. G.; Mcnutt, M. K.

    1993-01-01

    Newly available, 2D Bouguer gravity anomaly data from the Baikal Rift zone, Siberia, indicate that this discrete, intracontinental rift system is regionally compensated by an elastic plate about 50 km thick. However, spectral and spatial domain analyses and isostatic anomaly calculations show that simple elastic plate theory does not offer an adequate explanation for compensation in the rift zone, probably because of significant lateral variations in plate strength and the presence of subsurface loads. Our results and other geophysical observations support the interpretation that the Baikal Rift zone is colder than either the East African or Rio Grande rift.

  8. Plating To Reinforce Welded Joints

    NASA Technical Reports Server (NTRS)

    Otousa, J. E.

    1982-01-01

    Electrodeposition used to strengthen welded joints gouged, nicked, or suffered other mechanical damage. Plating cell, typically of acrylic plastic such as poly (Methylmetacrylate), is assembled around part to be plated. Areas not to be plated are masked with plater's tape. Weld area is plated in standard nickel-plating process.

  9. Petrologic implications of plate tectonics.

    PubMed

    Yoder, H S

    1971-07-30

    Petrologists can make significant contributions to the plate tectonic concept. Fixing the stability fields of the principal rock types involved will provide the limits of pressure and temperature of the various environments. Experimental determination of the partition coefficients of the trace elements will be helpful. Studies of the partial melting behavior of possible parental materials in the absence and presence of water, especially the undersaturated region, will contribute to the understanding of magma production. Experimental observations on the rheological properties of the peridotites below and just above the solidus will lead to a better evaluation of the convective mechanism. Measurement of the fundamental properties of rocks, such as the density of solids and liquids at high pressures and temperatures, would contribute to understanding the concepts of diapiric rise, magma segregation, and the low-velocity zone. Broader rock sampling of the oceanic areas of all environments will do much to define the petrologic provinces. The field petrologist specializing in the Paleozoic regions and Precambrian shields can contribute by examining those regions for old plate boundaries and devising new criteria for their recognition.

  10. Compressive strength of damaged and repaired composite plates

    NASA Technical Reports Server (NTRS)

    Finn, Scott R.; He, Yi-Fei; Springer, George S.; Lee, Hung-Joo

    1992-01-01

    Tests were performed assessing the effectiveness of repair in restoring the mechanical properties of damaged, solid composite plates made either of Fiberite T300/976 graphite-epoxy, Fiberite IM7/977-2 graphite-toughened epoxy, or ICI APC-2 graphite-PEEK. The plate length, the layup and the amount of damage were also varied. Damage was introduced in the plates either by impacting them with a solid projectile or by applying a transverse static load. Some (75 percent) or all (100 percent) of the damaged zone was then cut out, and the plate was repaired by plugging and patching the hole. The effectiveness of the repair was evaluated by measuring the compressive strengths of undamaged plates, damaged plates with no cutout, damaged plates with a cutout, and repaired plates. The data at an intermediate stage of repair provide information on the effect of each repair step on the compressive strength. The results indicated that for the solid plates used in these tests, the repair methods used herein did not improve the compressive strength of already damaged plates.

  11. Continental tectonics in the aftermath of plate tectonics

    NASA Technical Reports Server (NTRS)

    Molnar, Peter

    1988-01-01

    It is shown that the basic tenet of plate tectonics, rigid-body movements of large plates of lithosphere, fails to apply to continental interiors. There, buoyant continental crust can detach from the underlying mantle to form mountain ranges and broad zones of diffuse tectonic activity. The role of crustal blocks and of the detachment of crustal fragments in this process is discussed. Future areas of investigation are addressed.

  12. Motion of the Scotia sea plates

    USGS Publications Warehouse

    Thomas, C.; Livermore, R.; Pollitz, F.

    2003-01-01

    Earthquake data from the Scotia Arc to early 2002 are reviewed in the light of satellite gravity and other data in order to derive a model for the motion of plates in the Scotia Sea region. Events with magnitude ???5, which occurred on or near the boundaries of the Scotia and Sandwich plates, and for which Centroid Moment Tensor (CMT) solutions are available, are examined. The newer data fill some of the previous sampling gaps along the boundaries of the Scotia and Sandwich plates, and provide tighter constraints on relative motions. Variations in the width of the Brunhes anomaly on evenly spaced marine magnetic profiles over the East Scotia Ridge provide new estimates of Scotia-Sandwich plate spreading rates. Since there are no stable fracture zones in the east Scotia Sea, the mean azimuth of sea floor fabric mapped by sidescan is used to constrain the direction of spreading. 18 new rate estimates and four azimuths from the East Scotia Ridge are combined with 68 selected earthquake slip vectors from the boundaries of the Scotia Sea in a least-squares inversion for the best-fitting set of Euler poles and angular rotation rates describing the 'present-day' motions of the Scotia and Sandwich plates relative to South America and Antarctica. Our preferred model (TLP2003) gives poles that are similar to previous estimates, except for Scotia Plate motion with respect to South America, which is significantly different from earlier estimates; predicted rates of motion also differ slightly. Our results are much more robust than earlier work. We examine the implications of the model for motion and deformation along the various plate boundaries, with particular reference to the North and South Scotia Ridges, where rates are obtained by closure.

  13. Evolution of a Subduction Zone

    NASA Astrophysics Data System (ADS)

    Noack, Lena; Van Hoolst, Tim; Dehant, Veronique

    2014-05-01

    The purpose of this study is to understand how Earth's surface might have evolved with time and to examine in a more general way the initiation and continuance of subduction zones and the possible formation of continents on an Earth-like planet. Plate tectonics and continents seem to influence the likelihood of a planet to harbour life, and both are strongly influenced by the planetary interior (e.g. mantle temperature and rheology) and surface conditions (e.g. stabilizing effect of continents, atmospheric temperature), but may also depend on the biosphere. Employing the Fortran convection code CHIC (developed at the Royal Observatory of Belgium), we simulate a subduction zone with a pre-defined weak zone (between oceanic and continental crust) and a fixed plate velocity for the subducting oceanic plate (Quinquis et al. in preparation). In our study we first investigate the main factors that influence the subduction process. We simulate the subduction of an oceanic plate beneath a continental plate (Noack et al., 2013). The crust is separated into an upper crust and a lower crust. We apply mixed Newtonian/non-Newtonian rheology and vary the parameters that are most likely to influence the subduction of the ocanic plate, as for example density of the crust/mantle, surface temperature, plate velocity and subduction angle. The second part of our study concentrates on the long-term evolution of a subduction zone. Even though we model only the upper mantle (until a depth of 670km), the subducted crust is allowed to flow into the lower mantle, where it is no longer subject to our investigation. This way we can model the subduction zone over long time spans, for which we assume a continuous inflow of the oceanic plate into the investigated domain. We include variations in mantle temperatures (via secular cooling and decay of radioactive heat sources) and dehydration of silicates (leading to stiffening of the material). We investigate how the mantle environment influences

  14. Block structure and geodynamics of the continental lithosphere on plate boundaries

    NASA Astrophysics Data System (ADS)

    Gatinsky, Yu. G.; Prokhorova, T. V.; Romanyuk, T. V.; Vladova, G. L.

    2009-04-01

    Division of the Earth lithosphere on large plates must be considered only as the first and most general approximation in its structure hierarchy. Some transit zones or difuuse boundaries after other authors take place in lithosphere plate boundaries. The tectonic tension of plate interaction is transferred and relaxed within these zones, which consist of blocks limited by seismoactive faults. Vectors of block horizontal displacements often don't coincide with vectors of main plates and change together with changing block rigidity. As a rule the intensity the seismic energy at plate and transit zone boundaries decreases linearly with distancing from these boundaries and correlates with decreasing of velocities of block horizontal displacements. But sometimes the maximum of the energy manifestation takes place in inner parts of transit zones. Some relatively tight interblock zones established in central and east Asia are the most seismically active. They limited such blocks as Pamir, Tien Shan, Bayanhar, Shan, Japanese-Korean, as well as the north boundary of the Indian Plate. A seismic energy intensity of these zones can be compared with the energy of Pacific subduction zones. It is worthy to note that the majority catastrophic earthquakes took place in Central Asia just within interblock zones. A level of block displacement is situated mainly in the bottom or inside the Earth crust, more rare in the lithosphere mantle. Blocks with the most thick lithosphere roots (SE China, Amurian) are the most rigid and weakly deformed.

  15. Rigid and non-rigid micro-plates: Philippines and Myanmar-Andaman case studies

    NASA Astrophysics Data System (ADS)

    Rangin, Claude

    2016-01-01

    Generally, tectonic plates are considered as rigid. Oblique plate convergence favors the development of micro-plates along the converging boundaries. The north-south-trending Philippines archipelago (here named Philippine Mobile Belt, PMB), a few hundreds kilometers wide, is one of such complex tectonic zones. We show here that it is composed of rigid rotating crustal blocks (here called platelets). In Myanmar, the northernmost tip of the Sumatra-Andaman subduction system is another complex zone made of various crustal blocks in-between convergent plates. Yet, contrary to PMB, it sustains internal deformation with platelet buckling, altogether indicative of a non-rigid behavior. Therefore, the two case studies, Philippine Mobile Belt and Myanmar-Andaman micro-plate (MAS), illustrate the complexity of micro-plate tectonics and kinematics at convergent plate boundaries.

  16. Subduction and Plate Edge Tectonics in the Southern Caribbean

    NASA Astrophysics Data System (ADS)

    Levander, A.; Schmitz, M.; Niu, F.; Bezada, M. J.; Miller, M. S.; Masy, J.; Ave Lallemant, H. G.; Pindell, J. L.; Bolivar Working Group

    2013-05-01

    The southern Caribbean plate boundary consists of a subduction zone at at either end of a complex strike-slip fault system: In the east at the Lesser Antilles subduction zone, the Atlantic part of the South American plate subducts beneath the Caribbean. In the north and west in the Colombia basin, the Caribbean subducts under South America. In a manner of speaking, the two plates subduct beneath each other. Finite-frequency teleseismic P-wave tomography confirms this, imaging the Atlantic and the Caribbean plates subducting steeply in opposite directions to transition zone depths under northern South America (Bezada et al, 2010). The two subduction zones are connected by the El Pilar-San Sebastian strike-slip fault system, a San Andreas scale system that has been cut off at the Bocono fault, the southeastern boundary fault of the Maracaibo block. A variety of seismic probes identify subduction features at either end of the system (Niu et al, 2007; Clark et al., 2008; Miller et al. 2009; Growdon et al., 2009; Huang et al., 2010; Masy et al, 2011). The El Pilar system forms at the southeastern corner of the Antilles subduction zone with the Atlantic plate tearing from South America. The deforming plate edges control mountain building and basin formation at the eastern end of the strike-slip system. Tearing the Atlantic plate from the rest of South America appears to cause further lithospheric instability continentward. In northwestern South America the Caribbean plate very likely also tears, as its southernmost element subducts at shallow angles under northernmost Colombia but then rapidly descends to the transition zone under Lake Maracaibo (Bezada et al., 2010). We believe that the flat slab controls the tectonics of the Neogene Merida Andes, Perija, and Santa Marta ranges. The nonsubducting part of the Caribbean plate also underthrusts northern Venezuela to about the width of the coastal mountains (Miller et al., 2009). We infer that the edge of the underthrust

  17. Spaceflight and age affect tibial epiphyseal growth plate histomorphometry

    NASA Technical Reports Server (NTRS)

    Montufar-Solis, Dina; Duke, Pauline J.; Durnova, G.

    1992-01-01

    Growth plate histomorphometry of rats flown aboard the Soviet biosatellite Cosmos 2044, a 14-day spaceflight, was compared with that of control groups. In growth plates of flight animals, there was a significant increase in cell number per column and height of the proliferative zone and a reduction in height and cell number in the hypertrophy/calcification zone. No significant differences were found in matrix organization at the ultrastructural level of flight animals, indicating that although spacefligfht continues to affect bone growth of 15-wk-old rats, extracellular matrix is not altered in the same manner as seen previously in younger animals. All groups showed growth plate characteristics attributed to aging: lack of calcification zone, reduced hypertrophy zone, and unraveling of collagen fibrils. Tail-suspended controls did not differ from other controls in any of the parameters measured. The results suggest that growth plates of older rats are less responsive to unloading by spaceflight or suspension than those of younger rats and provide new evidence about the modifying effect of spaceflight on the growth plate.

  18. Reduction of astrometric plates

    NASA Technical Reports Server (NTRS)

    Stock, J.

    1984-01-01

    A rapid and accurate method for the reduction of comet or asteroid plates is described. Projection equations, scale length correction, rotation of coordinates, linearization, the search for additional reference stars, and the final solution are examined.

  19. Tectonic Plate Movement.

    ERIC Educational Resources Information Center

    Landalf, Helen

    1998-01-01

    Presents an activity that employs movement to enable students to understand concepts related to plate tectonics. Argues that movement brings topics to life in a concrete way and helps children retain knowledge. (DDR)

  20. What's On Your Plate?

    MedlinePlus

    ... Table of Contents What's On Your Plate? Smart Food Choices for Healthy Aging www.nia.nih.gov/health/ ... calories in" and "calories out," and making good food choices as you age. Shopping Tips See how planning ...

  1. Growth Plate Injuries

    MedlinePlus

    ... Download Download EPUB Download PDF What are they? Points To Remember About Growth Plate Injuries Injuries to ... Neurological disorders that cause people to lose their balance and fall. Some inherited disorders. Bone infections. Metabolic ...

  2. License plate recognition.

    DOT National Transportation Integrated Search

    2008-01-01

    License Plate Recognition (LPR) technology has been used for off-line automobile enforcement purposes. The technology has seen mixed success with correct reading rate around 60 to 70% depending on the specific application and environment. This limita...

  3. BAO Plate Archive Project

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.; Gigoyan, K. S.; Gyulzadyan, M. V.; Paronyan, G. M.; Abrahamyan, H. V.; Andreasyan, H. R.; Azatyan, N. M.; Kostandyan, G. R.; Samsonyan, A. L.; Mikayelyan, G. A.; Farmanyan, S. V.; Harutyunyan, V. L.

    2017-12-01

    We present the Byurakan Astrophysical Observatory (BAO) Plate Archive Project that is aimed at digitization, extraction and analysis of archival data and building an electronic database and interactive sky map. BAO Plate Archive consists of 37,500 photographic plates and films, obtained with 2.6m telescope, 1m and 0.5m Schmidt telescopes and other smaller ones during 1947-1991. The famous Markarian Survey (or the First Byurakan Survey, FBS) 2000 plates were digitized in 2002-2005 and the Digitized FBS (DFBS, www.aras.am/Dfbs/dfbs.html) was created. New science projects have been conducted based on this low-dispersion spectroscopic material. Several other smaller digitization projects have been carried out as well, such as part of Second Byurakan Survey (SBS) plates, photographic chain plates in Coma, where the blazar ON 231 is located and 2.6m film spectra of FBS Blue Stellar Objects. However, most of the plates and films are not digitized. In 2015, we have started a project on the whole BAO Plate Archive digitization, creation of electronic database and its scientific usage. Armenian Virtual Observatory (ArVO, www.aras.am/Arvo/arvo.htm) database will accommodate all new data. The project runs in collaboration with the Armenian Institute of Informatics and Automation Problems (IIAP) and will continues during 4 years in 2015-2018. The final result will be an Electronic Database and online Interactive Sky map to be used for further research projects. ArVO will provide all standards and tools for efficient usage of the scientific output and its integration in international databases.

  4. A diffuse plate boundary model for Indian Ocean tectonics

    NASA Technical Reports Server (NTRS)

    Wiens, D. A.; Demets, C.; Gordon, R. G.; Stein, S.; Argus, D.

    1985-01-01

    It is suggested that motion along the virtually aseismic Owen fracture zone is negligible, so that Arabia and India are contained within a single Indo-Arabian plate divided from the Australian plate by a diffuse boundary. The boundary is a zone of concentrated seismicity and deformation commonly characterized as 'intraplate'. The rotation vector of Australia relative to Indo-Arabia is consistent with the seismologically observed 2 cm/yr of left-lateral strike-slip along the Ninetyeast Ridge, north-south compression in the Central Indian Ocean, and the north-south extension near Chagos.

  5. Multiscale modeling of growth plate cartilage mechanobiology.

    PubMed

    Gao, Jie; Williams, John L; Roan, Esra

    2017-04-01

    Growth plate chondrocytes are responsible for bone growth through proliferation and differentiation. However, the way they experience physiological loads and regulate bone formation, especially during the later developmental phase in the mature growth plate, is still under active investigation. In this study, a previously developed multiscale finite element model of the growth plate is utilized to study the stress and strain distributions within the cartilage at the cellular level when rapidly compressed to 20 %. Detailed structures of the chondron are included in the model to examine the hypothesis that the same combination of mechanoregulatory signals shown to maintain cartilage or stimulate osteogenesis or fibrogenesis in the cartilage anlage or fracture callus also performs the same function at the cell level within the chondrons of growth plate cartilage. Our cell-level results are qualitatively and quantitatively in agreement with tissue-level theories when both hydrostatic cellular stress and strain are considered simultaneously in a mechanoregulatory phase diagram similar to that proposed at the tissue level by Claes and Heigele for fracture healing. Chondrocytes near the reserve/proliferative zone border are subjected to combinations of high compressive hydrostatic stresses ([Formula: see text] MPa), and cell height and width strains of [Formula: see text] to [Formula: see text] respectively, that maintain cartilage and keep chondrocytes from differentiating and provide conditions favorable for cell division, whereas chondrocytes closer to the hypertrophic/calcified zone undergo combinations of lower compressive hydrostatic stress ([Formula: see text] MPa) and cell height and width strains as low as [Formula: see text] to +4 %, respectively, that promote cell differentiation toward osteogenesis; cells near the outer periphery of the growth plate structure experience a combination of low compressive hydrostatic stress (0 to [Formula: see text] MPa) and

  6. Reaction-induced rheological weakening enables oceanic plate subduction.

    PubMed

    Hirauchi, Ken-Ichi; Fukushima, Kumi; Kido, Masanori; Muto, Jun; Okamoto, Atsushi

    2016-08-26

    Earth is the only terrestrial planet in our solar system where an oceanic plate subducts beneath an overriding plate. Although the initiation of plate subduction requires extremely weak boundaries between strong plates, the way in which oceanic mantle rheologically weakens remains unknown. Here we show that shear-enhanced hydration reactions contribute to the generation and maintenance of weak mantle shear zones at mid-lithospheric depths. High-pressure friction experiments on peridotite gouge reveal that in the presence of hydrothermal water, increasing strain and reactions lead to an order-of-magnitude reduction in strength. The rate of deformation is controlled by pressure-solution-accommodated frictional sliding on weak hydrous phyllosilicate (talc), providing a mechanism for the 'cutoff' of the high peak strength at the brittle-plastic transition. Our findings suggest that infiltration of seawater into transform faults with long lengths and low slip rates is an important controlling factor on the initiation of plate tectonics on terrestrial planets.

  7. Iberian plate kinematics: A jumping plate boundary between Eurasia and Africa

    USGS Publications Warehouse

    Srivastava, S.P.; Schouten, Hans; Roest, W.R.; Klitgord, Kim D.; Kovacs, L.C.; Verhoef, J.; Macnab, R.

    1990-01-01

    THE rotation of Iberia and its relation to the formation of the Pyrenees has been difficult to decipher because of the lack of detailed sea-floor spreading data, although several models have been proposed1-7. Here we use detailed aeromagnetic measurements from the sea floor offshore of the Grand Banks of Newfoundland to show that Iberia moved as part of the African plate from late Cretaceous to mid-Eocene time, with a plate boundary extending westward from the Bay of Biscay. When motion along this boundary ceased, a boundary linking extension in the King's Trough to compression along the Pyrenees came into existence. Finally, since the late Oligocene, Iberia has been part of the Eurasian plate, with the boundary between Eurasia and Africa situated along the Azores-Gibraltar fracture zone.

  8. Limb lengthening over plate

    PubMed Central

    Kulkarni, Ruta; Singh, Nishant; Kulkarni, Govind S; Kulkarni, Milind; Kulkarni, Sunil; Kulkarni, Vidisha

    2012-01-01

    Background: The limb lengthening over plate eliminates the associated risk of infection with limb lengthening over intramedullary nail. We present our experience of limb lengthening in 15 patients with a plate fixed on the proximal segment, followed by corticotomy and application of external fixator. Materials and Methods: 15 patients (7 females, 8 males) were included in this consecutive series. The average age was 18.1 years (range 8–35 years). Fifteen tibiae and one femur were lengthened in 15 patients. Lengthening was achieved at 1 mm/day followed by distal segment fixation with three or four screws on reaching the target length. Results: The preoperative target length was successfully achieved in all patients at a mean of 4.1 cm (range 1.8–6.5 cm). The mean duration of external fixation was 75.3 days (range 33–116 days) with the mean external fixation index at 19.2 days/cm (range 10.0–38.3 days/cm). One patient suffered deep infection up to the plate, three patients had mild procurvatum deformities, and one patient developed mild tendo achilles contracture. Conclusion: Lengthening over a plate allows early removal of external fixator and eliminates the risk of creating deep intramedullary infection as with lengthening over nail. Lengthening over plate is also applicable to children with open physis. PMID:22719123

  9. Cadmium plating replacements

    NASA Technical Reports Server (NTRS)

    Nelson, Mary J.; Groshart, Earl C.

    1995-01-01

    The Boeing Company has been searching for replacements to cadmium plate. Two alloy plating systems seem close to meeting the needs of a cadmium replacement. The two alloys, zinc-nickel and tin-zinc are from alloy plating baths; both baths are neutral pH. The alloys meet the requirements for salt fog corrosion resistance, and both alloys excel as a paint base. Currently, tests are being performed on standard fasteners to compare zinc-nickel and tin-zinc on threaded hardware where cadmium is heavily used. The Hydrogen embrittlement propensity of the zinc-nickel bath has been tested, and just beginning for the tin-zinc bath. Another area of interest is the electrical properties on aluminum for tin-zinc and will be discussed. The zinc-nickel alloy plating bath is in production in Boeing Commercial Airplane Group for non-critical low strength steels. The outlook is promising that these two coatings will help The Boeing Company significantly reduce its dependence on cadmium plating.

  10. The Sorong Fault Zone, Indonesia: Mapping a Fault Zone Offshore

    NASA Astrophysics Data System (ADS)

    Melia, S.; Hall, R.

    2017-12-01

    The Sorong Fault Zone is a left-lateral strike-slip fault zone in eastern Indonesia, extending westwards from the Bird's Head peninsula of West Papua towards Sulawesi. It is the result of interactions between the Pacific, Caroline, Philippine Sea, and Australian Plates and much of it is offshore. Previous research on the fault zone has been limited by the low resolution of available data offshore, leading to debates over the extent, location, and timing of movements, and the tectonic evolution of eastern Indonesia. Different studies have shown it north of the Sula Islands, truncated south of Halmahera, continuing to Sulawesi, or splaying into a horsetail fan of smaller faults. Recently acquired high resolution multibeam bathymetry of the seafloor (with a resolution of 15-25 meters), and 2D seismic lines, provide the opportunity to trace the fault offshore. The position of different strands can be identified. On land, SRTM topography shows that in the northern Bird's Head the fault zone is characterised by closely spaced E-W trending faults. NW of the Bird's Head offshore there is a fold and thrust belt which terminates some strands. To the west of the Bird's Head offshore the fault zone diverges into multiple strands trending ENE-WSW. Regions of Riedel shearing are evident west of the Bird's Head, indicating sinistral strike-slip motion. Further west, the ENE-WSW trending faults turn to an E-W trend and there are at least three fault zones situated immediately south of Halmahera, north of the Sula Islands, and between the islands of Sanana and Mangole where the fault system terminates in horsetail strands. South of the Sula islands some former normal faults at the continent-ocean boundary with the North Banda Sea are being reactivated as strike-slip faults. The fault zone does not currently reach Sulawesi. The new fault map differs from previous interpretations concerning the location, age and significance of different parts of the Sorong Fault Zone. Kinematic

  11. Bipolar battery plate

    NASA Technical Reports Server (NTRS)

    Rowlette, John J. (Inventor)

    1987-01-01

    A liquid-impermeable plate (10) having through-plate conductivity with essentially zero resistance comprises an insulator sheet (12) having a series of spaced perforations (14) each of which contains a metal element (16) sealingly received into the perforation (14). A low-cost plate can readily be manufactured by punching a thermoplastic sheet (40) such as polypropylene with a punching tool (52), filling the apertures with led spheres (63) having a diameter smaller than the holes (50) but larger than the thickness of the sheet, sweeping excess spheres (62) off the sheet with a doctor blade (60) and then pressing a heated platen (74) onto the sheet to swage the spheres into a cylindrical shape and melt the surrounding resin to form a liquid-impermeable collar (4) sealing the metal into the sheet.

  12. Reduced Plating Ignitron

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A (Inventor); Pearson, J Boise (Inventor)

    2014-01-01

    An ignitron apparatus has an airtight tubular housing having a first sealed end and a second sealed end. An anode is connected at the first sealed end, projecting into the housing, and a recess at the second sealed and forms a well which contains a quantity of liquid gallium or gallium alloy making up the cathode. An ignitor projects through the liquid metal and into the housing. The inner surface of the housing includes at least one plating-reduction structure to prevent electrical shorting of the apparatus caused by plating of the liquid metal.

  13. NICKEL PLATING PROCESS

    DOEpatents

    Hoover, T.B.; Zava, T.E.

    1959-05-12

    A simplified process is presented for plating nickel by the vapor decomposition of nickel carbonyl. In a preferred form of the invention a solid surface is nickel plated by subjecting the surface to contact with a mixture containing by volume approximately 20% nickel carbonyl vapor, 2% hydrogen sulfide and .l% water vapor or 1% oxygen and the remainder carbon dioxide at room temperature until the desired thickness of nickel is obtained. The advantage of this composition over others is that the normally explosive nickel carbonyl is greatly stabilized.

  14. Seismicity of the Earth 1900–2010 Australia plate and vicinity

    USGS Publications Warehouse

    Benz, Harley M.; Herman, Matthew; Tarr, Arthur C.; Hayes, Gavin P.; Furlong, Kevin P.; Villaseñor, Antonio; Dart, Richard L.; Rhea, Susan

    2011-01-01

    This map shows details of the Australia plate and vicinity not presented in Tarr and others (2010). The boundary of the Australia plate includes all fundamental plate boundary components: mid-ocean ridges, subduction zones, arc-continent collisions, and large-offset transform faults. Along the southern edge of the plate the mid-ocean ridge separates the Australia and Antarctica plates and its behavior is straightforward. In contrast, the other boundary segments that ring the Australia plate represent some of the most seismically active elements of the global plate boundary system, and some of the most rapidly evolving plate interactions. As a result, there are some very complex structures which host many large and great earthquakes

  15. Hydrodynamics of a flexible plate between pitching rigid plates

    NASA Astrophysics Data System (ADS)

    Kim, Junyoung; Kim, Daegyoum

    2017-11-01

    The dynamics of a flexible plate have been studied as a model problem in swimming and flying of animals and fluid-structure interaction of plants and flags. Motivated by fish schooling and an array of sea grasses, we investigate the dynamics of a flexible plate closely placed between two pitching rigid plates. In most studies on passive deformation of the flexible plate, the plate is immersed in a uniform flow or a wavy flow. However, in this study, the flexible plate experiences periodic deformation by the oscillatory flow generated by the prescribed pitching motion of the rigid plates. In our model, the pitching axes of the rigid plates and the clamping position of the flexible plate are aligned on the same line. The flexible plate shows various responses depending on length and pitching frequency of rigid plates, thickness of a flexible plate, and free-stream velocity. To find the effect of each variable on the response of the flexible plate, amplitude of a trailing edge and modal contribution of a flapping motion are compared, and flow structure around the flexible plate is examined.

  16. Defining the Fresnel zone for broadband radiation.

    PubMed

    Pearce, Jeremy; Mittleman, Daniel

    2002-11-01

    The concept of the Fresnel zone is central to many areas of imaging. In tomographic imaging, the transverse spatial resolution can be limited by the size of the first Fresnel zone, usually defined only for monochromatic radiation. With the increasing prevalence of broadband tomographic imaging systems, a generalization of this concept is required. Here, a proposed generalization is described in the context of femtosecond optics, and experimentally verified using terahertz time-domain spectroscopy. Based on this definition, a simple zone plate design is demonstrated.

  17. Seismicity and plate tectonics in south central Alaska

    NASA Technical Reports Server (NTRS)

    Van Wormer, J. D.; Davies, J.; Gedney, L.

    1974-01-01

    Hypocenter distribution shows that the Benioff zone associated with the Aleutian arc terminates in interior Alaska some 75 km north of the Denali fault. There appears to be a break in the subducting Pacific plate in the Yentna River-Prince William Sound area which separates two seismically independent blocks, similar to the segmented structure reported for the central Aleutian arc.

  18. On the relative significance of lithospheric weakening mechanisms for sustained plate tectonics

    NASA Astrophysics Data System (ADS)

    Araceli Sanchez-Maes, Sophia

    2018-01-01

    Plate tectonics requires the bending of strong plates at subduction zones, which is difficult to achieve without a secondary weakening mechanism. Two classes of weakening mechanisms have been proposed for the generation of ongoing plate tectonics, distinguished by whether or not they require water. Here we show that the energy budget of global subduction zones offers a simple yet decisive test on their relative significance. Theoretical studies of mantle convection suggest bending dissipation to occupy only 10-20 % of total dissipation in the mantle, and our results indicate that the hydrous mechanism in the shallow part of plates is essential to satisfy the requirement. Thus, surface oceans are required for the long-term operation of plate tectonics on terrestrial worlds. Establishing this necessary and observable condition for sustained plate tectonics carries important implications for planetary habitability at large.

  19. The Plate Tectonics Project

    ERIC Educational Resources Information Center

    Hein, Annamae J.

    2011-01-01

    The Plate Tectonics Project is a multiday, inquiry-based unit that facilitates students as self-motivated learners. Reliable Web sites are offered to assist with lessons, and a summative rubric is used to facilitate the holistic nature of the project. After each topic (parts of the Earth, continental drift, etc.) is covered, the students will…

  20. Prosthetic plate mandibular reconstruction.

    PubMed

    Davidson, M J; Gullane, P J

    1991-12-01

    The head and neck surgeon may choose one of several available methods to reconstruct the mandible following tumor ablation. This article discusses the use of metallic mandibular prostheses, the indications for alloplastic mandibular reconstruction, techniques of plate application (AO and THRP), and associated complications.

  1. BAO plate archive digitization

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.; Nikoghosyan, E. H.; Gigoyan, K. S.; Paronyan, G. M.; Abrahamyan, H. V.; Andreasyan, H. R.; Azatyan, N. M.; Kostandyan, G. R.; Khachatryan, K. G.; Vardanyan, A. V.; Gyulzadyan, M. V.; Mikayelyan, G. A.; Farmanyan, S. V.; Knyazyan, A. V.

    Astronomical plate archives created on the basis of numerous observations at many observatories are important part of the astronomical heritage. Byurakan Astrophysical Observatory (BAO) plate archive consists of 37,000 photographic plates and films, obtained at 2.6m telescope, 1m and 0.5m Schmidt telescopes and other smaller ones during 1947-1991. In 2015, we have started a project on the whole BAO Plate Archive digitization, creation of electronic database and its scientific usage. A Science Program Board is created to evaluate the observing material, to investigate new possibilities and to propose new projects based on the combined usage of these observations together with other world databases. The Executing Team consists of 11 astronomers and 2 computer scientists and will use 2 EPSON Perfection V750 Pro scanners for the digitization. The project will run during 3 years in 2015-2017 and the final result will be an electronic database and online interactive sky map to be used for further research projects.

  2. Unitary plate electrode

    NASA Technical Reports Server (NTRS)

    Rowlette, John J. (Inventor); Clough, Thomas J. (Inventor); Josefowicz, Jack Y. (Inventor); Sibert, John W. (Inventor)

    1985-01-01

    The unitary electrode (10) comprises a porous sheet (12) of fiberglass the strands (14) of which contain a coating (16) of conductive tin oxide. The lower portion of the sheet contains a layer (18) of resin and the upper layer (20) contains lead dioxide forming a positive active electrode on an electrolyte-impervious layer. The strands (14) form a continuous conduction path through both layers (16, 18). Tin oxide is prevented from reduction by coating the surface of the plate facing the negative electrode with a conductive, impervious layer resistant to reduction such as a thin film (130) of lead or graphite filled resin adhered to the plate with a layer (31) of conductive adhesive. The plate (10) can be formed by casting a molten resin from kettle (60) onto a sheet of glass wool (56) overlying a sheet of lead foil and then applying positive active paste from hopper (64) into the upper layer (68). The plate can also be formed by passing an assembly of a sheet ( 80) of resin, a sheet (86) of sintered glass and a sheet (90) of lead between the nip (92) of heated rollers (93, 95) and then filling lead oxide into the pores (116) of the upper layer (118).

  3. Nuclear reactor alignment plate configuration

    DOEpatents

    Altman, David A; Forsyth, David R; Smith, Richard E; Singleton, Norman R

    2014-01-28

    An alignment plate that is attached to a core barrel of a pressurized water reactor and fits within slots within a top plate of a lower core shroud and upper core plate to maintain lateral alignment of the reactor internals. The alignment plate is connected to the core barrel through two vertically-spaced dowel pins that extend from the outside surface of the core barrel through a reinforcement pad and into corresponding holes in the alignment plate. Additionally, threaded fasteners are inserted around the perimeter of the reinforcement pad and into the alignment plate to further secure the alignment plate to the core barrel. A fillet weld also is deposited around the perimeter of the reinforcement pad. To accomodate thermal growth between the alignment plate and the core barrel, a gap is left above, below and at both sides of one of the dowel pins in the alignment plate holes through with the dowel pins pass.

  4. 24 CFR 3285.405 - Severe wind zones.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... DEVELOPMENT MODEL MANUFACTURED HOME INSTALLATION STANDARDS Anchorage Against Wind § 3285.405 Severe wind zones. When any part of a home is installed within 1,500 feet of a coastline in Wind Zones II or III, the manufactured home must be designed for the increased requirements, as specified on the home's data plate (refer...

  5. Plate Motion and Crustal Deformation Estimated with Geodetic Data from the Global Positioning System

    NASA Technical Reports Server (NTRS)

    Argus, Donald F.; Heflin, Michael B.

    1995-01-01

    We use geodetic data taken over four years with the Global Positioning System (GPS) to estimate: (1) motion between six major plates and (2) motion relative to these plates of ten sites in plate boundary zones. The degree of consistency between geodetic velocities and rigid plates requires the (one-dimensional) standard errors in horizontal velocities to be approx. 2 mm/yr. Each of the 15 angular velocities describing motion between plate pairs that we estimate with GPS differs insignificantly from the corresponding angular velocity in global plate motion model NUVEL-1A, which averages motion over the past 3 m.y. The motion of the Pacific plate relative to both the Eurasian and North American plates is observed to be faster than predicted by NUVEL-1A, supporting the inference from Very Long B ase- line Interferometry (VLBI) that motion of the Pacific plate has speed up over the past few m.y. The Eurasia-North America pole of rotation is estimated to be north of NUVEL-1A, consistent with the independent hypothesis that the pole has recently migrated northward across northeast Asia to near the Lena River delta. Victoria, which lies above the main thrust at the Cascadia subduction zone, moves relative to the interior of the overriding plate at 30% of the velocity of the subducting plate, reinforcing the conclusion that the thrust there is locked beneath the continental shelf and slope.

  6. Forearc collapse, plate flexure, and seismicity within the downgoing plate along the Sunda Arc west of Sumatra

    NASA Astrophysics Data System (ADS)

    Craig, Timothy J.; Copley, Alex

    2018-02-01

    Deformation within the downgoing oceanic lithosphere seawards of subduction zones is typically characterised by regimes of shallow extension and deeper compression, due to the bending of the oceanic plate as it dips into the subduction zone. However, offshore Sumatra there are shallow compressional earthquakes within the downgoing oceanic plate outboard of the region of high slip in the 2004 Aceh-Andaman earthquake, occurring at the same depth as extensional faulting further seaward from the trench. A clear separation is seen in the location of intraplate earthquakes, with extensional earthquakes occurring further seawards than compressional earthquakes at the same depth within the plate. The adjacent section of the forearc prism west of Aceh is also anomalous in its morphology, characterised by a wide prism with a steep bathymetric front and broad, gradually-sloping top. This shape is in contrast to the narrower and more smoothly-sloping prism to the south, and along other subduction zones. The anomalous near-trench intraplate earthquakes and prism morphology are likely to be the result of the geologically-rapid gravitational collapse of the forearc, which leads to induced bending within the subducting plate, and the distinctive plateau-like morphology of the forearc. Such collapse of the forearc could be caused by changes through time of the material properties of the forearc rocks, or of the thickness of the sediments entering the subduction zone.

  7. The interpretation of crustal dynamics data in terms of plate motions and regional deformation near plate boundaries

    NASA Technical Reports Server (NTRS)

    Solomon, Sean C.

    1987-01-01

    The nature and dynamics of time-dependent deformation along major seismic zones including the influence of irregularities in fault geometry on the earthquake cycle, and the processes contributing to the state of stress and rates of strain in plate interior regions were studied. The principle findings of the research are discussed.

  8. Fracture process zone in granite

    USGS Publications Warehouse

    Zang, A.; Wagner, F.C.; Stanchits, S.; Janssen, C.; Dresen, G.

    2000-01-01

    In uniaxial compression tests performed on Aue granite cores (diameter 50 mm, length 100 mm), a steel loading plate was used to induce the formation of a discrete shear fracture. A zone of distributed microcracks surrounds the tip of the propagating fracture. This process zone is imaged by locating acoustic emission events using 12 piezoceramic sensors attached to the samples. Propagation velocity of the process zone is varied by using the rate of acoustic emissions to control the applied axial force. The resulting velocities range from 2 mm/s in displacement-controlled tests to 2 ??m/s in tests controlled by acoustic emission rate. Wave velocities and amplitudes are monitored during fault formation. P waves transmitted through the approaching process zone show a drop in amplitude of 26 dB, and ultrasonic velocities are reduced by 10%. The width of the process zone is ???9 times the grain diameter inferred from acoustic data but is only 2 times the grain size from optical crack inspection. The process zone of fast propagating fractures is wider than for slow ones. The density of microcracks and acoustic emissions increases approaching the main fracture. Shear displacement scales linearly with fracture length. Fault plane solutions from acoustic events show similar orientation of nodal planes on both sides of the shear fracture. The ratio of the process zone width to the fault length in Aue granite ranges from 0.01 to 0.1 inferred from crack data and acoustic emissions, respectively. The fracture surface energy is estimated from microstructure analysis to be ???2 J. A lower bound estimate for the energy dissipated by acoustic events is 0.1 J. Copyright 2000 by the American Geophysical Union.

  9. Evaluation of finger plate and flat plate connection design.

    DOT National Transportation Integrated Search

    2016-01-01

    This project investigates the cause(s) of premature deterioration of MoDOT finger plate and flat plate expansion devices : under high traffic volumes and then uses that information to design new Load and Resistance Factor Design (LRFD) : finger plate...

  10. Spatial regulation of bone morphogenetic proteins (BMPs) in postnatal articular and growth plate cartilage

    PubMed Central

    Garrison, Presley; Yue, Shanna; Hanson, Jeffrey; Baron, Jeffrey; Lui, Julian C.

    2017-01-01

    Articular and growth plate cartilage both arise from condensations of mesenchymal cells, but ultimately develop important histological and functional differences. Each is composed of three layers—the superficial, mid and deep zones of articular cartilage and the resting, proliferative and hypertrophic zones of growth plate cartilage. The bone morphogenetic protein (BMP) system plays an important role in cartilage development. A gradient in expression of BMP-related genes has been observed across growth plate cartilage, likely playing a role in zonal differentiation. To investigate the presence of a similar expression gradient in articular cartilage, we used laser capture microdissection (LCM) to separate murine growth plate and articular cartilage from the proximal tibia into their six constituent zones, and used a solution hybridization assay with color-coded probes (nCounter) to quantify mRNAs for 30 different BMP-related genes in each zone. In situ hybridization and immunohistochemistry were then used to confirm spatial expression patterns. Expression gradients for Bmp2 and 6 were observed across growth plate cartilage with highest expression in hypertrophic zone. However, intracellular BMP signaling, assessed by phospho-Smad1/5/8 immunohistochemical staining, appeared to be higher in the proliferative zone and prehypertrophic area than in hypertrophic zone, possibly due to high expression of Smad7, an inhibitory Smad, in the hypertrophic zone. We also found BMP expression gradients across the articular cartilage with BMP agonists primarily expressed in the superficial zone and BMP functional antagonists primarily expressed in the deep zone. Phospho-Smad1/5/8 immunohistochemical staining showed a similar gradient. In combination with previous evidence that BMPs regulate chondrocyte proliferation and differentiation, the current findings suggest that BMP signaling gradients exist across both growth plate and articular cartilage and that these gradients may

  11. Microchannel plate streak camera

    DOEpatents

    Wang, Ching L.

    1989-01-01

    An improved streak camera in which a microchannel plate electron multiplier is used in place of or in combination with the photocathode used in prior streak cameras. The improved streak camera is far more sensitive to photons (UV to gamma-rays) than the conventional x-ray streak camera which uses a photocathode. The improved streak camera offers gamma-ray detection with high temporal resolution. It also offers low-energy x-ray detection without attenuation inside the cathode. Using the microchannel plate in the improved camera has resulted in a time resolution of about 150 ps, and has provided a sensitivity sufficient for 1000 KeV x-rays.

  12. Bipolar battery plate

    NASA Technical Reports Server (NTRS)

    Rowlette, John J. (Inventor)

    1985-01-01

    A liquid-impermeable plate (10) having throughplate conductivity with essentially zero resistance comprises an insulator sheet (12) having a series of spaced perforations (14) each of which contains a metal element (16) sealingly received into the perforation (14). A low-cost plate can readily be manufactured by punching a thermoplastic sheet (40) such as polypropylene with a punching tool (52), filling the apertures with lead spheres (63) having a diameter smaller than the holes (50) but larger than the thickness of the sheet, sweeping excess spheres (62) off the sheet with a doctor blade (60) and then pressing a heated platen (74) onto the sheet to swage the spheres into a cylindrical shape and melt the surrounding resin to form a liquid-impermeable collar (4) sealing the metal into the sheet.

  13. Elastic plate spallation

    NASA Technical Reports Server (NTRS)

    Oline, L.; Medaglia, J.

    1972-01-01

    The dynamic finite element method was used to investigate elastic stress waves in a plate. Strain displacement and stress strain relations are discussed along with the stiffness and mass matrix. The results of studying point load, and distributed load over small, intermediate, and large radii are reported. The derivation of finite element matrices, and the derivation of lumped and consistent matrices for one dimensional problems with Laplace transfer solutions are included. The computer program JMMSPALL is also included.

  14. Grooved Armor Plate

    DTIC Science & Technology

    1935-05-16

    that many of the olateo tested do sux^ ass the reouired limita by a considerable margin. Therefore, the efficiency of these grooved plate...Plpte Thicknesn B>lll<tle .Llji^f - ./.. s... a’ ^ea:: of All RtSUltS !’ Teen of Rlgbeot lOf of All Reoultr. s/i«- 1830 an« 7/16" ?180

  15. Armor Plate Ballistic Testing

    DTIC Science & Technology

    1944-08-02

    sistanoe to penotration characteristics. However, it is one of the most important factors involved, and when the type of steel , its soundness and its...this test and not to use it in comparing radically differdnt types of plates, such as steel and Dural. Such a comparison can be made only by examining...in many oases, For this reason it became necessary to develop an additional test for the oharaoteristio in rolled armor ( steel "soundness) and cast

  16. Plated wire memory subsystem

    NASA Technical Reports Server (NTRS)

    Reynolds, L.; Tweed, H.

    1972-01-01

    The work performed entailed the design, development, construction and testing of a 4000 word by 18 bit random access, NDRO plated wire memory for use in conjunction with a spacecraft imput/output unit and central processing unit. The primary design parameters, in order of importance, were high reliability, low power, volume and weight. A single memory unit, referred to as a qualification model, was delivered.

  17. Generation of plate tectonics via grain-damage and pinning

    NASA Astrophysics Data System (ADS)

    Bercovici, D.; Ricard, Y. R.

    2012-12-01

    Weakening and shear localization in the lithosphere are essential ingredients for understanding how and whether plate tectonics is generated from mantle convection on terrestrial planets. The grain-damage and pinning mechanism of Bercovici & Ricard (2012) for lithospheric shear--localization proposes that damage to the interface between phases in a polycrystalline material like peridotite (composed primarily of olivine and pyroxene) increases the number of small Zener pinning surfaces that constrain mineral grains to ever smaller sizes regardless of creep mechanism. This effect allows a self-softening feedback in which damage and grain-reduction can co-exist with a grain-size dependent diffusion creep rheology; moreoever, grain growth and weak-zone healing are greatly impeded by Zener pinning thereby leading to long-lived relic weak zones. This mechanism is employed in two-dimensional flow calculations to test its ability to generate toroidal (strike-slip) motion from convective type flow and to influence plate evolution. The fluid dynamical calculations employ source-sink driven flow as a proxy for convective poloidal flow (upwelling/downwelling and divergent/convergent motion), and the coupling of this flow with non-linear rheological mechanisms excites toroidal or strike-slip motion. The numerical experiments show that pure dislocation-creep rheology, and grain-damage without Zener pinning (as occurs in a single-phase assemblages) permit only weak localization and toroidal flow; however, the full grain-damage with pinning readily allows focussed localization and intense, plate-like toroidal motion and strike-slip deformation. Rapid plate motion changes are also tested with abrupt rotations of the source-sink field after a plate-like configuration is developed; the post-rotation flow and material property fields are found to never recover or lose memory of the original configuration, leading to suboptimally aligned plate boundaries (e.g., strike-slip margins non

  18. Relative motions of the Australian, Pacific and Antarctic plates estimated by the Global Positioning System

    NASA Technical Reports Server (NTRS)

    Larson, Kristine M.; Freymueller, Jeff

    1995-01-01

    Global Positioning System (GPS) measurements spanning approximately 3 years have been used to determine velocities for 7 sites on the Australian, Pacific and Antarctic plates. The site velocities agree with both plate model predictions and other space geodetic techniques. We find no evidence for internal deformation of the interior of the Australian plate. Wellington, New Zealand, located in the Australian-Pacific plate boundary zone, moves 20 +/- 5 mm/yr west-southwest relative to the Australian plate. Its velocity lies midway between the predicted velocities of the two plates. Relative Euler vectors for the Australia-Antarctica and Pacific-Antarctica plates agree within one standard deviation with the NUVEL-1A predictions.

  19. Cenozoic forearc tectonics in northeastern Japan: Relationships between outer forearc subsidence and plate boundary kinematics

    NASA Astrophysics Data System (ADS)

    Regalla, Christine

    Here we investigate the relationships between outer forearc subsidence, the timing and kinematics of upper plate deformation and plate convergence rate in Northeast Japan to evaluate the role of plate boundary dynamics in driving forearc subsidence. The Northeastern Japan margin is one of the first non-accretionary subduction zones where regional forearc subsidence was argued to reflect tectonic erosion of large volumes of upper crustal rocks. However, we propose that a significant component of forearc subsidence could be the result of dynamic changes in plate boundary geometry. We provide new constraints on the timing and kinematics of deformation along inner forearc faults, new analyses of the evolution of outer forearc tectonic subsidence, and updated calculations of plate convergence rate. These data collectively reveal a temporal correlation between the onset of regional forearc subsidence, the initiation of upper plate extension, and an acceleration in local plate convergence rate. A similar analysis of the kinematic evolution of the Tonga, Izu-Bonin, and Mariana subduction zones indicates that the temporal correlations observed in Japan are also characteristic of these three non-accretionary margins. Comparison of these data with published geodynamic models suggests that forearc subsidence is the result of temporal variability in slab geometry due to changes in slab buoyancy and plate convergence rate. These observations suggest that a significant component of forearc subsidence at these four margins is not the product of tectonic erosion, but instead reflects changes in plate boundary dynamics driven by variable plate kinematics.

  20. Epeirogeny and plate tectonics

    NASA Technical Reports Server (NTRS)

    Menard, H. W.

    1975-01-01

    Vertical motions of the earth crust and their causes are considered in relation to epeirogenic phenomena. Factors discussed include: external loading and unloading; bending at subduction zones; internal density changes; and dynamic effects of mantle motion. The relationship between epeirogeny and drift is briefly reviewed along with oceanic epeirogeny.

  1. Seismic Velocity and Elastic Properties of Plate Boundary Faults

    NASA Astrophysics Data System (ADS)

    Jeppson, Tamara N.

    The elastic properties of fault zone rock at depth play a key role in rupture nucleation, propagation, and the magnitude of fault slip. Materials that lie within major plate boundary fault zones often have very different material properties than standard crustal rock values. In order to understand the mechanics of faulting at plate boundaries, we need to both measure these properties and understand how they govern the behavior of different types of faults. Mature fault zones tend to be identified in large-scale geophysical field studies as zones with low seismic velocity and/or electrical resistivity. These anomalous properties are related to two important mechanisms: (1) mechanical or diagenetic alteration of the rock materials and/or (2) pore fluid pressure and stress effects. However, in remotely-sensed and large-length-scale data it is difficult to determine which of these mechanisms are affecting the measured properties. The objective of this dissertation research is to characterize the seismic velocity and elastic properties of fault zone rocks at a range of scales, with a focus on understanding why the fault zone properties are different from those of the surrounding rock and the potential effects on earthquake rupture and fault slip. To do this I performed ultrasonic velocity experiments under elevated pressure conditions on drill core and outcrops samples from three plate boundary fault zones: the San Andreas Fault, California, USA; the Alpine Fault, South Island, New Zealand; and the Japan Trench megathrust, Japan. Additionally, I compared laboratory measurements to sonic log and large-scale seismic data to examine the scale-dependence of the measured properties. The results of this study provide the most comprehensive characterization of the seismic velocities and elastic properties of fault zone rocks currently available. My work shows that fault zone rocks at mature plate boundary faults tend to be significantly more compliant than surrounding crustal

  2. Ability of modern distal tibia plates to stabilize comminuted pilon fracture fragments: Is dual plate fixation necessary?

    PubMed

    Penny, Phillip; Swords, Michael; Heisler, Jason; Cien, Adam; Sands, Andrew; Cole, Peter

    2016-08-01

    The purpose of this study was to examine the screw trajectory of ten commercially available distal tibia plates and compare them to common fracture patterns seen in OTA C type pilon fractures to determine their ability to stabilize the three most common fracture fragments while buttressing anterolateral zones of comminution. We hypothesized that a single plate for the distal tibia would fail to adequately stabilize all three main fracture fragments and zones of comminution in complex pilon fractures. Ten synthetic distal tibia sawbones models were used in conjunction with ten different locking distal tibia plate designs from three manufacturers (Depuy Synthes, J&J Co, Paoli, PA; Smith & Nephew, Memphis, TN; and Stryker, Mawa, NJ). Both medial and anterolateral plates from each company were utilized and separately applied to an individual sawbone model. Three implants allowing variable angle screw placement were used. The location of the locking screws and buttress effect 1cm above the articular surface was noted for each implant using axial computed tomography (CT). The images were then compared to a recently published "pilon fracture map" using an overlay technique to establish the relationship between screw location and known common fracture lines and areas of comminution. Each of the three main fragments was considered "captured" by a screw if it was purchased by at least two screws thereby controlling rotational forces on each fragment. Three of four anterolateral plates lacked stable fixation in the medial fragment. Of the 4 anterolateral plates used, only the variable angle anterolateral plate by Depuy Synthes captured the medial fragment with two screws. All four anterolateral plates buttressed the area of highest comminution and had an average of 1.25 screws in the medial fragment and an average of 3 screws in the posterolateral fragment. All five direct medial plates had variable fixation within anterolateral and posterolateral fragments with an average of

  3. Potential Seismic Signatures of Megathrust Preparatory Zones

    NASA Astrophysics Data System (ADS)

    Parameswaran, R. M.; Maheswari, K.; Rajendran, K.

    2017-12-01

    The Mw 9.2, 2004 Sumatra earthquake awakened the otherwise inactive Andaman-Sumatra subduction zone (ASSZ), pushing it into an era of amplified seismicity. The subduction zone has since witnessed an array of inter- and intra-plate events along and around its trench. Several intra-plate events like the 2012 Wharton Basin earthquakes (Mw 8.6 and 8.2), are believed to be the triggered response of the plateward transmission of stresses due to the 2004 earthquake (Ishii et al., 2013). On the other hand, the Mw 7.5, 2009 33-km-deep intra-plate normal-faulting event in the northern Andaman segment is an example of outer-rise seismicity resulting from the post-seismic relaxation of the subducting slab (Andrade and Rajendran, 2011). These are aftermaths of a drastic change in the stress regime from compressional to extensional, following the 2004 megathrust event. But, pre-megathrust, aside from the inter-plate thrust mechanisms that are widely observed along the trench, how does the plate-motion-driven compression manifest in the regional seismicity? What happens to the stresses accumulating within the bending subducting slab; does it source deeper compressional events prior to a megathrust? The 2009 normal outer-rise earthquake was preceded by the 13 September 2002, Mw 6.5 Diglipur outer-rise thrust earthquake (22 km depth), both occurring at the northern terminus of the 2004-rupture, in the compressing forearc that experienced surface uplift pre-megathrust (Rajendran et al., 2003; Rajendran et al., 2007). This work, therefore, examines the slip models of such pre-event outer-rise thrust earthquakes along the stretch of the 2004 rupture zone in the ASSZ. The work is also being extended to understand the preparatory zones of other global megathrust earthquakes.

  4. Symmetries in laminated composite plates

    NASA Technical Reports Server (NTRS)

    Noor, A. K.

    1976-01-01

    The different types of symmetry exhibited by laminated anisotropic fibrous composite plates are identified and contrasted with the symmetries of isotropic and homogeneous orthotropic plates. The effects of variations in the fiber orientation and the stacking sequence of the layers on the symmetries exhibited by composite plates are discussed. Both the linear and geometrically nonlinear responses of the plates are considered. A simple procedure is presented for exploiting the symmetries in the finite element analysis. Examples are given of square, skew and polygonal plates where use of symmetry concepts can significantly reduce the scope and cost of analysis.

  5. Hypervelocity impact on shielded plates

    NASA Technical Reports Server (NTRS)

    Smith, James P.

    1993-01-01

    A ballistic limit equation for hypervelocity impact on thin plates is derived analytically. This equation applies to cases of impulsive impact on a plate that is protected by a multi-shock shield, and it is valid in the range of velocity above 6 km/s. Experimental tests were conducted at the NASA Johnson Space Center on square aluminum plates. Comparing the center deflections of these plates with the theoretical deflections of a rigid-plastic plate subjected to a blast load, one determines the dynamic yield strength of the plate material. The analysis is based on a theory for the expansion of the fragmented projectile and on a simple failure criterion. Curves are presented for the critical projectile radius versus the projectile velocity, and for the critical plate thickness versus the velocity. These curves are in good agreement with curves that have been generated empirically.

  6. Fuel cell end plate structure

    DOEpatents

    Guthrie, Robin J.; Katz, Murray; Schroll, Craig R.

    1991-04-23

    The end plates (16) of a fuel cell stack (12) are formed of a thin membrane. Pressure plates (20) exert compressive load through insulation layers (22, 26) to the membrane. Electrical contact between the end plates (16) and electrodes (50, 58) is maintained without deleterious making and breaking of electrical contacts during thermal transients. The thin end plate (16) under compressive load will not distort with a temperature difference across its thickness. Pressure plate (20) experiences a low thermal transient because it is insulated from the cell. The impact on the end plate of any slight deflection created in the pressure plate by temperature difference is minimized by the resilient pressure pad, in the form of insulation, therebetween.

  7. [Conventional plate osteosynthesis].

    PubMed

    Klaue, K

    2010-02-01

    Consolidation of bone is an essential clinical problem when treating fractures, fixing osteotomies and fusing joints. In most cases, the means of fixation are plates and screws. The goal is functional postoperative therapy by moving the adjacent joints and thus avoiding the deleterious disadvantages of long-lasting articular immobilization. Pre-operative planning, surgical approach, a good understanding of the precise mechanics of the structure and the biological answer for the various tissues are prerequisites of successful osteosynthesis. The choice of implants and the application of their versatility, as well as their adaptation to individual cases are the key to good results.

  8. Shuttle plate braiding machine

    NASA Technical Reports Server (NTRS)

    Huey, Jr., Cecil O. (Inventor)

    1994-01-01

    A method and apparatus for moving yarn in a selected pattern to form a braided article. The apparatus includes a segmented grid of stationary support elements and a plurality of shuttles configured to carry yarn. The shuttles are supported for movement on the grid assembly and each shuttle includes a retractable plunger for engaging a reciprocating shuttle plate that moves below the grid assembly. Such engagement at selected times causes the shuttles to move about the grid assembly in a selected pattern to form a braided article of a particular geometry.

  9. Light Armor Plate Development

    DTIC Science & Technology

    1923-07-28

    to thie time ot shipment will be ini- eluded, 06otioIjAs -- HistoT. On Dec ember 2S# lt~. uVeity -four plates -*ere raaivad fro* Watertown Are nal, Th...only AT .Jwi-ace Vvrl/ac e 914yramof specl .mens elsed for h7eat- treatment 12aiomArmor- P/ate Anyepstyatio,, Vi -oorner o! ogoii uipe’Aven va...tempering temperatures applied. Only oarburized specimens were suboted to the double- quenching treatment (see table IV). The purpose of this Waq to

  10. Plated wire memory subsystem

    NASA Technical Reports Server (NTRS)

    Carpenter, K. H.

    1974-01-01

    The design, construction, and test history of a 4096 word by 18 bit random access NDRO Plated Wire Memory for use in conjunction with a spacecraft input/output and central processing unit is reported. A technical and functional description is given along with diagrams illustrating layout and systems operation. Test data is shown on the procedures and results of system level and memory stack testing, and hybrid circuit screening. A comparison of the most significant physical and performance characteristics of the memory unit versus the specified requirements is also included.

  11. Reconciling surface plate motions with rapid three-dimensional mantle flow around a slab edge.

    PubMed

    Jadamec, Margarete A; Billen, Magali I

    2010-05-20

    The direction of tectonic plate motion at the Earth's surface and the flow field of the mantle inferred from seismic anisotropy are well correlated globally, suggesting large-scale coupling between the mantle and the surface plates. The fit is typically poor at subduction zones, however, where regional observations of seismic anisotropy suggest that the direction of mantle flow is not parallel to and may be several times faster than plate motions. Here we present three-dimensional numerical models of buoyancy-driven deformation with realistic slab geometry for the Alaska subduction-transform system and use them to determine the origin of this regional decoupling of flow. We find that near a subduction zone edge, mantle flow velocities can have magnitudes of more than ten times the surface plate motions, whereas surface plate velocities are consistent with plate motions and the complex mantle flow field is consistent with observations from seismic anisotropy. The seismic anisotropy observations constrain the shape of the eastern slab edge and require non-Newtonian mantle rheology. The incorporation of the non-Newtonian viscosity results in mantle viscosities of 10(17) to 10(18) Pa s in regions of high strain rate (10(-12) s(-1)), and this low viscosity enables the mantle flow field to decouple partially from the motion of the surface plates. These results imply local rapid transport of geochemical signatures through subduction zones and that the internal deformation of slabs decreases the slab-pull force available to drive subducting plates.

  12. Seismotectonic zoning of Azerbaijan territory

    NASA Astrophysics Data System (ADS)

    Kangarli, Talat; Aliyev, Ali; Aliyev, Fuad; Rahimov, Fuad

    2017-04-01

    Studying of the space-time correlation and consequences effect between tectonic events and other geological processes that have created modern earth structure still remains as one of the most important problems in geology. This problem is especially important for the East Caucasus-South Caspian geodynamic zone. Being situated at the eastern part of the Caucasian strait, this zone refers to a center of Alpine-Himalayan active folded belt, and is known as a complex tectonic unit with jointing heterogeneous structural-substantial complexes arising from different branches of the belt (Doburja-Caucasus-Kopetdag from the north and Pyrenean-Alborz from the south with Kura and South Caspian zone). According to GPS and precise leveling data, activity of regional geodynamic processes shows intensive horizontal and vertical movements of the Earth's crust as conditioned by collision of the Arabian and Eurasian continental plates continuing since the end of Miocene. So far studies related to the regional of geology-geophysical data, periodically used for the geological and tectonic modeling of the environment mainly based on the fixing ideology. There still remains a number of uncertainties in solution of issues related to regional geology, tectonics and magmatism, structure and interrelation of different structural zones, space-time interrelations between onshore and offshore complexes, etc. At the same time large dataset produced by surface geological surveys, deep geological mapping of on- and offshore areas with the use of seismic and electrical reconnaissance and geophysical field zoning methods, deep well drilling and remote sensing activities. Conducted new studies produced results including differentiation of formerly unknown nappe complexes of the different ages and scales within the structure of mountain-fold zones, identification of new zones containing ophiolites in their section, outlining of currently active faulting areas, geophysical interpretation of the deep

  13. Transform push, oblique subduction resistance, and intraplate stress of the Juan de Fuca plate

    USGS Publications Warehouse

    Wang, K.; He, J.; Davis, E.E.

    1997-01-01

    The Juan de Fuca plate is a small oceanic plate between the Pacific and North America plates. In the southernmost region, referred to as the Gorda deformation zone, the maximum compressive stress a, constrained by earthquake focal mechanisms is N-S. Off Oregon, and possibly off Washington, NW trending left-lateral faults cutting the Juan de Fuca plate indicate a a, in a NE-SW to E-W direction. The magnitude of differential stress increases from north to south; this is inferred from the plastic yielding and distribution of earthquakes throughout the Gorda deformation zone. To understand how tectonic forces determine the stress field of the Juan de Fuca plate, we have modeled the intraplate stress using both elastic and elastic-perfectly plastic plane-stress finite element models. We conclude that the right-lateral shear motion of the Pacific and North America plates is primarily responsible for the stress pattern of the Juan de Fuca plate. The most important roles are played by a compressional force normal to the Mendocino transform fault, a result of the northward push by the Pacific plate and a horizontal resistance operating against the northward, or margin-parallel, component of oblique subduction. Margin-parallel subduction resistance results in large N-S compression in the Gorda deformation zone because the force is integrated over the full length of the Cascadia subduction zone. The Mendocino transform fault serves as a strong buttress that is very weak in shear but capable of transmitting large strike-normal compressive stresses. Internal failure of the Gorda deformation zone potentially places limits on the magnitude of the fault-normal stresses being transmitted and correspondingly on the magnitude of strike-parallel subduction resistance. Transform faults and oblique subduction zones in other parts of the world can be expected to transmit and create stresses in the same manner. Copyright 1997 by the American Geophysical Union.

  14. Estimates of effective elastic thickness at subduction zones

    NASA Astrophysics Data System (ADS)

    Yang, An; Fu, Yongtao

    2018-06-01

    The effective elastic thickness (Te) is an important parameter that characterizes the long-term strength of the lithosphere. Estimates of Te at subduction zones have important tectonic and geodynamic implications, providing constraints for the strength of the oceanic lithosphere at a short-term scale. We estimated Te values in several subduction zones worldwide by using models including both surface and subsurface loads from the analysis of free-air gravity anomaly and bathymetric data, together with a moving window admittance technique (MWAT). Tests with synthetic gravity and bathymetry data show that this method is a reliable way to recover Te of oceanic lithosphere. Our results show that there is a noticeable reduction in the effective elastic thickness of the subducting plate from the outer rise to the trench axis for most studied subduction zones, suggesting plate weakening at the trench-outer rise of the subduction zones. These subduction zones have Te range of 6-60 km, corresponding to a wide range of isotherms from 200 to 800 °C. Different trenches show distinct patterns. The Caribbean, Kuril-Japan, Mariana and Tonga subduction zones show predominantly high Te. By contrast, the Middle America and Java subduction zones have a much lower Te. The Peru-Chile, Aleutian and Philippine subduction zones show considerable scatter. The large variation of the isotherm for different trenches does not show clear relationship with plate weakening at the outer rise.

  15. Phenomena after meteoroid penetration of a bumper plate

    NASA Technical Reports Server (NTRS)

    Todd, F. C.

    1971-01-01

    The analysis of hypervelocity impact of particles on a detector in space, with flow and shock penetration through fluid, plastic, and elastic zones was studied. The original paper and computer program on this topic is presented. Improvements in the program for the study of the formation of a cone of debris are discussed. The truncated apex of the cone is at the hole formed by the penetration of an initially spherical rock through a thin plate. A solution for the penetration of the thin plate was sought.

  16. Geological process of the slow earthquakes -A hypothesis from an ancient plate boundary fault rock

    NASA Astrophysics Data System (ADS)

    Kitamura, Y.; Kimura, G.; Kawabata, K.

    2012-12-01

    We present an integrated model of the deformation along the subduction plate boundary from the trench to the seismogenic zone. Over years of field based research in the Shimanto Belt accretionary complex, southwest Japan, yielded breaking-through discoveries on plate boundary processes, for example, the first finding of pseudotachylyte in the accretionary prism (Ikesawa et al., 2003). Our aim here is to unveil the geological aspects of slow earthquakes and the related plate boundary processes. Studied tectonic mélanges in the Shimanto Belt are regarded as fossils of plate boundary fault zone in subduction zone. We traced material from different depths along subduction channel using samples from on-land outcrops and ocean drilling cores. As a result, a series of progressive deformation down to the down-dip limit of the seismogenic zone was revealed. Detailed geological survey and structural analyses enabled us to separate superimposed deformation events during subduction. Material involved in the plate boundary deformation is mainly an alternation of sand and mud. As they have different competency and are suffered by simple shear stress field, sandstones break apart in flowing mudstones. We distinguished several stages of these deformations in sandstones and recognized progress in the intensity of deformation with increment of underthrusting. It is also known that the studied Mugi mélange bears pseudotachylyte in its upper bounding fault. Our conclusion illustrates that the subduction channel around the depth of the seismogenic zone forms a thick plate boundary fault zone, where there is a clear segregation in deformation style: a fast and episodic slip at the upper boundary fault and a slow and continuous deformation within the zone. The former fast deformation corresponds to the plate boundary earthquakes and the latter to the slow earthquakes. We further examined numerically whether this plate boundary fault rock is capable of releasing seismic moment enough to

  17. Anatomic Considerations for Plating of the Distal Ulna

    PubMed Central

    Hazel, Antony; Nemeth, Nicole; Bindra, Randy

    2015-01-01

    Purpose The purpose of our study was to examine the anatomy of the distal ulna and identify an interval that would be amenable to plating and would not cause impingement during wrist rotation nor irritation to the extensor carpi ulnaris (ECU) tendon. Methods Six cadaveric forearms were dissected and the arc of the articular surface of the distal ulna was measured. The distal ulna was divided up as a clock face, with the ulnar styloid being assigned the 12 o'clock position, and the location of the ECU was identified accordingly. The distance from the ulnar styloid to where the dorsal sensory ulnar nerve crosses from volar to dorsal was also measured. Based on these measurements a safe zone was defined. Results A safe zone was identified between the 12 and 2 o'clock position on the right wrist, and between the 10 and 12 o'clock on the left wrist. The dorsal sensory branch of the ulnar nerve crossed from volar to dorsal position at a variable location near the ulnar styloid. Two commercially available plates were utilized and could be placed in our designated interval and did not cause impingement when the forearm was rotated fully. Conclusion Our study demonstrates a location for plating of the distal ulna that avoids impingement during forearm rotation and that is outside of the footprint of the ECU subsheath. Clinical Relevance Plating of the distal ulna may be necessary with distal ulna fracture, and although plate placement may be dictated by the fracture pattern, it is important to understand the implications of plate placement. Although the ideal plate may not be possible because of comminution, the patient can be educated in regards to potential for tendon irritation, loss of motion, or need for hardware removal. PMID:26261745

  18. Combined visualization for noise mapping of industrial facilities based on ray-tracing and thin plate splines

    NASA Astrophysics Data System (ADS)

    Ovsiannikov, Mikhail; Ovsiannikov, Sergei

    2017-01-01

    The paper presents the combined approach to noise mapping and visualizing of industrial facilities sound pollution using forward ray tracing method and thin-plate spline interpolation. It is suggested to cauterize industrial area in separate zones with similar sound levels. Equivalent local source is defined for range computation of sanitary zones based on ray tracing algorithm. Computation of sound pressure levels within clustered zones are based on two-dimension spline interpolation of measured data on perimeter and inside the zone.

  19. Oceanic broad multifault transform plate boundaries

    NASA Astrophysics Data System (ADS)

    Ligi, Marco; Bonatti, Enrico; Gasperini, Luca; Poliakov, Alexei N. B.

    2002-01-01

    Oceanic transform plate boundaries consist of a single, narrow (a few kilometers wide) strike-slip seismic zone offsetting two mid-ocean ridge segments. However, we define here a new class of oceanic transform boundaries, with broad complex multifault zones of deformation, similar to some continental strike-slip systems. Examples are the 750-km- long, 120-km-wide Andrew Bain transform on the Southwest Indian Ridge, and the Romanche transform, where the Mid-Atlantic Ridge is offset by a lens-shaped, ˜900-km- long, ˜100-km-wide sliver of deformed lithosphere bound by two major transform valleys. One of the valleys is seismically highly active and constitutes the present-day principal transform boundary. However, strike-slip seismic events also occur in the second valley and elsewhere in the deformed zone. Some of these events may be triggered by earthquakes from the principal boundary. Numerical modeling predicts the development of wide multiple transform boundaries when the age offset is above a threshold value of ˜30 m.y., i.e., in extra-long (>500 km) slow-slip transforms. Multiple boundaries develop so that strike-slip ruptures avoid very thick and strong lithosphere.

  20. Zone separator for multiple zone vessels

    DOEpatents

    Jones, John B.

    1983-02-01

    A solids-gas contact vessel, having two vertically disposed distinct reaction zones, includes a dynamic seal passing solids from an upper to a lower zone and maintaining a gas seal against the transfer of the separate treating gases from one zone to the other, and including a stream of sealing fluid at the seal.

  1. Plate tectonics on the Earth triggered by plume-induced subduction initiation.

    PubMed

    Gerya, T V; Stern, R J; Baes, M; Sobolev, S V; Whattam, S A

    2015-11-12

    Scientific theories of how subduction and plate tectonics began on Earth--and what the tectonic structure of Earth was before this--remain enigmatic and contentious. Understanding viable scenarios for the onset of subduction and plate tectonics is hampered by the fact that subduction initiation processes must have been markedly different before the onset of global plate tectonics because most present-day subduction initiation mechanisms require acting plate forces and existing zones of lithospheric weakness, which are both consequences of plate tectonics. However, plume-induced subduction initiation could have started the first subduction zone without the help of plate tectonics. Here, we test this mechanism using high-resolution three-dimensional numerical thermomechanical modelling. We demonstrate that three key physical factors combine to trigger self-sustained subduction: (1) a strong, negatively buoyant oceanic lithosphere; (2) focused magmatic weakening and thinning of lithosphere above the plume; and (3) lubrication of the slab interface by hydrated crust. We also show that plume-induced subduction could only have been feasible in the hotter early Earth for old oceanic plates. In contrast, younger plates favoured episodic lithospheric drips rather than self-sustained subduction and global plate tectonics.

  2. Multiple plate hydrostatic viscous damper

    NASA Technical Reports Server (NTRS)

    Ludwig, L. P. (Inventor)

    1981-01-01

    A device for damping radial motion of a rotating shaft is described. The damper comprises a series of spaced plates extending in a radial direction. A hydraulic piston is utilized to place a load in these plates. Each annular plate is provided with a suitable hydrostatic bearing geometry on at least one of its faces. This structure provides a high degree of dampening in a rotor case system of turbomachinery in general. The damper is particularly useful in gas turbine engines.

  3. Ion plating for the future

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1981-01-01

    The ion plating techniques are classified relative to the instrumental set up, evaporation media and mode of transport. Distinction is drawn between the low vacuum (plasma) and high vacuum (ion beam) techniques. Ion plating technology is discussed at the fundamental and industrial level. At the fundamental level, the capabilities and limitations of the plasma (evaporant flux) and film characteristics are evaluated. On the industrial level, the performance and potential uses of ion plated films are discussed.

  4. Ion plating for the future

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1981-01-01

    The ion plating techniques are classified relative to the instrumental set up, evaporation media, and mode of transport. A distinction is drawn between the low vacuum (plasma) and high vacuum (ion beam) techniques. Ion plating technology is discussed at the fundamental and industrial level. At the fundamental level, the capabilities and limitations of the plasma (evaporant flux) and film characteristics are evaluated. And on the industrial level, the performance and potential uses of ion plated films are discussed.

  5. Channel plate for DNA sequencing

    DOEpatents

    Douthart, R.J.; Crowell, S.L.

    1998-01-13

    This invention is a channel plate that facilitates data compaction in DNA sequencing. The channel plate has a length, a width and a thickness, and further has a plurality of channels that are parallel. Each channel has a depth partially through the thickness of the channel plate. Additionally an interface edge permits electrical communication across an interface through a buffer to a deposition membrane surface. 15 figs.

  6. Optical Near-Field Plates

    DTIC Science & Technology

    2015-04-08

    AFRL-OSR-VA-TR-2015-0085 OPTICAL NEAR-FILED PLATES Roberto Merlin UNIVERSITY OF MICHIGAN Final Report 04/08/2015 DISTRIBUTION A: Distribution...03-2015 Final 09/01/2009-12/31/2014 Optical Near-Field Plates FA9550-09-1-0636 erlin, Roberto, D. The University of Michigan Ann Arbor, MI 48109...distribution unlimited Optical near-field plates were designed using antisymmetric plasmon modes to generate abrupt phase changes within a fraction of a

  7. Plating Bacteriophage M13.

    PubMed

    Green, Michael R; Sambrook, Joseph

    2017-10-03

    A plaque of bacteriophage M13 derives from infection of a single bacterium by a single virus particle. The progeny particles infect neighboring bacteria, which, in turn, release another generation of daughter virus particles. If the bacteria are growing in semisolid medium (e.g., containing agar or agarose), then the diffusion of the progeny particles is limited. Cells infected with bacteriophage M13 are not killed, but have a longer generation time than uninfected Escherichia coli In consequence, plaques appear as areas of slower-growing cells on a faster-growing lawn of bacterial cells. This protocol describes plating of bacteriophage M13 stocks. Plaques are readily detectable on top agar after 4-8 h of incubation at 37°C. © 2017 Cold Spring Harbor Laboratory Press.

  8. True Shear Parallel Plate Viscometer

    NASA Technical Reports Server (NTRS)

    Ethridge, Edwin; Kaukler, William

    2010-01-01

    This viscometer (which can also be used as a rheometer) is designed for use with liquids over a large temperature range. The device consists of horizontally disposed, similarly sized, parallel plates with a precisely known gap. The lower plate is driven laterally with a motor to apply shear to the liquid in the gap. The upper plate is freely suspended from a double-arm pendulum with a sufficiently long radius to reduce height variations during the swing to negligible levels. A sensitive load cell measures the shear force applied by the liquid to the upper plate. Viscosity is measured by taking the ratio of shear stress to shear rate.

  9. Glass-bead peen plating

    NASA Technical Reports Server (NTRS)

    Graves, J. R.

    1974-01-01

    Peen plating of aluminum, copper, and nickel powders was investigated. Only aluminum was plated successfully within the range of peen plating conditions studied. Optimum plating conditions for aluminum were found to be: (1) bead/powder mixture containing 25 to 35% powder by weight, (2) peening intensity of 0.007A as measured by Almen strip, and (3) glass impact bead diameter of at least 297 microns (0.0117 inches) for depositing-100 mesh aluminum powder. No extensive cleaning or substrate preparation is required beyond removing loose dirt or heavy oil.

  10. Laser-driven flyer plate

    DOEpatents

    Paisley, Dennis L.

    1991-01-01

    Apparatus for producing high velocity flyer plates involving placing a layer of dielectric material between a first metal foil and a second metal foil. With laser irradiation through an optical substrate, the first metal foil forms a plasma in the area of the irradiation, between the substrate and the solid portion of the first metal foil. When the pressure between the substrate and the foil reaches the stress limit of the dielectric, the dielectric will break away and launch the flyer plate out of the second metal foil. The mass of the flyer plate is controlled, as no portion of the flyer plate is transformed into a plasma.

  11. High Performance Flat Plate Solar Thermal Collector Evaluation

    SciTech Connect

    Rockenbaugh, Caleb; Dean, Jesse; Lovullo, David

    2016-09-01

    This report was prepared for the General Services Administration by the National Renewable Energy Laboratory. The Honeycomb Solar Thermal Collector (HSTC) is a flat plate solar thermal collector that shows promising high efficiencies over a wide range of climate zones. The technical objectives of this study are to: 1) verify collector performance, 2) compare that performance to other market-available collectors, 3) verify overheat protection, and 4) analyze the economic performance of the HSTC both at the demonstration sites and across a matrix of climate zones and utility markets.

  12. The Composition and Mineralogy of Exoplanets, Using the Hypatia Catalogue: Implications for Extrasolar Plate Tectonics and Mantle Convection

    NASA Astrophysics Data System (ADS)

    Putirka, K. D.; Rarick, J.

    2018-05-01

    Many exoplanets have pyroxenite mantle mineralogies, which may impede plate tectonics, due higher mantle viscosities and lid yield strengths; majorite-rich transition zones on these may also prevent subducted slabs from reaching lower mantle depths.

  13. Carte du Ciel, San Fernando zone

    NASA Astrophysics Data System (ADS)

    Abad, C.

    2014-06-01

    An updated summary of a future large astrometric catalogue is presented, based on the two most important astrometric projects carried out by the Real Instituto y Observatorio de la Armada de San Fernando (ROA). The goal is to make a catalogue of positions and proper motions based on ROA's Cart du Ciel (CdC) and the Astrographic Catalogue (AC) San Fernando zone plates, and the HAMC2 meridian circle catalogue. The CdC and AC plates are being reduced together to provide first-epoch positions while HAMC2 will provide second-epoch ones. New techniques have been applied, that range from using a commercial flatbed scanner to the proper reduction schemes to avoid systematics from it. Only thirty plates (out of 540) remain to be processed, due to scanning problems that are being solved.

  14. Root Apex Transition Zone As Oscillatory Zone

    PubMed Central

    Baluška, František; Mancuso, Stefano

    2013-01-01

    Root apex of higher plants shows very high sensitivity to environmental stimuli. The root cap acts as the most prominent plant sensory organ; sensing diverse physical parameters such as gravity, light, humidity, oxygen, and critical inorganic nutrients. However, the motoric responses to these stimuli are accomplished in the elongation region. This spatial discrepancy was solved when we have discovered and characterized the transition zone which is interpolated between the apical meristem and the subapical elongation zone. Cells of this zone are very active in the cytoskeletal rearrangements, endocytosis and endocytic vesicle recycling, as well as in electric activities. Here we discuss the oscillatory nature of the transition zone which, together with several other features of this zone, suggest that it acts as some kind of command center. In accordance with the early proposal of Charles and Francis Darwin, cells of this root zone receive sensory information from the root cap and instruct the motoric responses of cells in the elongation zone. PMID:24106493

  15. A model of convergent plate margins based on the recent tectonics of Shikoku, Japan

    NASA Technical Reports Server (NTRS)

    Bischke, R. E.

    1974-01-01

    A viscoelastic finite element plate tectonic model is applied to displacement data for the island of Shikoku, Japan. The flow properties and geometry of the upper portions of the earth are assumed known from geophysical evidence, and the loading characteristics are determined from the model. The nature of the forces acting on the Philippine Sea plate, particularly in the vicinity of the Nankai trough, is determined. Seismic displacement data related to the 1946 Nankaido earthquake are modeled in terms of a thick elastic plate overlying a fluidlike substratum. The sequence of preseismic and seismic displacements can be explained in terms of two independent processes operating on elastic lithospheric plates: a strain accumulation process caused by vertical downward forces acting on or within the lithosphere in the vicinity of the trench, and a strain release process caused by plate failure along a preexisting zone on weakness. This is a restatement of Reid's elastic rebound theory in terms of elastic lithospheric plates.

  16. Seismicity of the Earth 1900-2007, Nazca Plate and South America

    USGS Publications Warehouse

    Rhea, Susan; Hayes, Gavin P.; Villaseñor, Antonio; Furlong, Kevin P.; Tarr, Arthur C.; Benz, Harley

    2010-01-01

    The South American arc extends over 7,000 km, from the Chilean triple junction offshore of southern Chile to its intersection with the Panama fracture zone, offshore the southern coast of Panama in Central America. It marks the plate boundary between the subducting Nazca plate and the South America plate, where the oceanic crust and lithosphere of the Nazca plate begin their decent into the mantle beneath South America. The convergence associated with this subduction process is responsible for the uplift of the Andes Mountains, and for the active volcanic chain present along much of this deformation front. Relative to a fixed South America plate the Nazca plate moves slightly north of eastwards at a rate varying from approximately 80 mm/yr in the south to approximately 70mm/yr in the north.

  17. Creep of phyllosilicates at the onset of plate tectonics

    SciTech Connect

    Amiguet, Elodie; Reynard, Bruno; Caracas, Razvan

    Plate tectonics is the unifying paradigm of geodynamics yet the mechanisms and causes of its initiation remain controversial. Some models suggest that plate tectonics initiates when the strength of lithosphere is lower than 20-200 MPa, below the frictional strength of lithospheric rocks (>700 MPa). At present-day, major plate boundaries such as the subduction interface, transform faults, and extensional faults at mid-oceanic ridge core complexes indicate a transition from brittle behaviour to stable sliding at depths between 10 and 40 km, in association with water-rock interactions forming phyllosilicates. We explored the rheological behaviour of lizardite, an archetypal phyllosilicate of the serpentinemore » group formed in oceanic and subduction contexts, and its potential influence on weakening of the lithospheric faults and shear zones. High-pressure deformation experiments were carried out on polycrystalline lizardite - the low temperature serpentine variety - using a D-DIA apparatus at a variety of pressure and temperature conditions from 1 to 8 GPa and 150 to 400 C and for strain rates between 10{sup -4} and 10{sup -6} s{sup -1}. Recovered samples show plastic deformation features and no evidence of brittle failure. Lizardite has a large rheological anisotropy, comparable to that observed in the micas. Mechanical results and first-principles calculations confirmed easy gliding on lizardite basal plane and show that the flow stress of phyllosilicate is in the range of the critical value of 20-200 MPa down to depths of about 200 km. Thus, foliated serpentine or chlorite-bearing rocks are sufficiently weak to account for plate tectonics initiation, aseismic sliding on the subduction interface below the seismogenic zone, and weakening of the oceanic lithosphere along hydrothermally altered fault zones. Serpentinisation easing the deformation of the early crust and shallow mantle reinforces the idea of a close link between the occurrence of plate tectonics and

  18. 8-Nitro-cGMP promotes bone growth through expansion of growth plate cartilage.

    PubMed

    Hoshino, Marie; Kaneko, Kotaro; Miyamoto, Yoichi; Yoshimura, Kentaro; Suzuki, Dai; Akaike, Takaaki; Sawa, Tomohiro; Ida, Tomoaki; Fujii, Shigemoto; Ihara, Hideshi; Tanaka, Junichi; Tsukuura, Risa; Chikazu, Daichi; Mishima, Kenji; Baba, Kazuyoshi; Kamijo, Ryutaro

    2017-09-01

    In endochondral ossification, growth of bones occurs at their growth plate cartilage. While it is known that nitric oxide (NO) synthases are required for proliferation of chondrocytes in growth plate cartilage and growth of bones, the precise mechanism by which NO facilitates these process has not been clarified yet. C-type natriuretic peptide (CNP) also positively regulate elongation of bones through expansion of the growth plate cartilage. Both NO and CNP are known to use cGMP as the second messenger. Recently, 8-nitro-cGMP was identified as a signaling molecule produced in the presence of NO in various types of cells. Here, we found that 8-nitro-cGMP is produced in proliferating chondrocytes in the growth plates, which was enhanced by CNP, in bones cultured ex vivo. In addition, 8-nitro-cGMP promoted bone growth with expansion of the proliferating zone as well as increase in the number of proliferating cells in the growth plates. 8-Nitro-cGMP also promoted the proliferation of chondrocytes in vitro. On the other hand, 8-bromo-cGMP enhanced the growth of bones with expansion of hypertrophic zone of the growth plates without affecting either the width of proliferating zone or proliferation of chondrocytes. These results indicate that 8-nitro-cGMP formed in growth plate cartilage accelerates chondrocyte proliferation and bone growth as a downstream molecule of NO. Copyright © 2017. Published by Elsevier Inc.

  19. Lower plate serpentinite diapirism in the Calabrian Arc subduction complex.

    PubMed

    Polonia, A; Torelli, L; Gasperini, L; Cocchi, L; Muccini, F; Bonatti, E; Hensen, C; Schmidt, M; Romano, S; Artoni, A; Carlini, M

    2017-12-19

    Mantle-derived serpentinites have been detected at magma-poor rifted margins and above subduction zones, where they are usually produced by fluids released from the slab to the mantle wedge. Here we show evidence of a new class of serpentinite diapirs within the external subduction system of the Calabrian Arc, derived directly from the lower plate. Mantle serpentinites rise through lithospheric faults caused by incipient rifting and the collapse of the accretionary wedge. Mantle-derived diapirism is not linked directly to subduction processes. The serpentinites, formed probably during Mesozoic Tethyan rifting, were carried below the subduction system by plate convergence; lithospheric faults driving margin segmentation act as windows through which inherited serpentinites rise to the sub-seafloor. The discovery of deep-seated seismogenic features coupled with inherited lower plate serpentinite diapirs, provides constraints on mechanisms exposing altered products of mantle peridotite at the seafloor long time after their formation.

  20. Tectonics of the Nazca-Antarctic plate boundary

    NASA Technical Reports Server (NTRS)

    Anderson-Fontana, Sandra; Larson, Roger L.; Engeln, Joseph F.; Lundgren, Paul; Stein, Seth

    1987-01-01

    A new bathymetric chart of part of the Chile transform system is constructed, based mainly on an R/V Endeavor survey from 100 deg W to its intersection with the East Ridge of the Juan Fernandez microplate. A generally continuous lineated trend can be followed through the entire region, with the transform valley being relatively narrow and well-defined from 109 deg W to approximately 104 deg 30 min W. The fracture zone then widens to the east, with at least two probable en echelon offsets to the south at 104 deg and 102 deg W. Six new strike-slip mechanisms along the Chile Transform and one normal fault mechanism near the northern end of the Chile Rise, inverted together with other plate-motion data from the eastern portion of the boundary, produce a new best-fit Euler pole for the Nazca-Antarctic plate pair, providing tighter constraints on the relative plate motions.

  1. [PRECHORDAL AND MYOEPICARDIAL PLATES: TERMINOLOGICAL ASPECTS, THE PROBLEMS OF DEFINITION].

    PubMed

    Korolyov, V A; Pototskaya, O Yu

    2015-01-01

    Most accurately, the prechordal plate (PCP) can be defined as the zone of close contact of cells of endodermal epithelium and mesenchyme in the region between the oropharyngeal membrane and the notochord. This structure is involved in the induction of the anterior parts of the brain and, in particular, the pituitary gland, as well as in the formation of some of eye muscles and bones of the skull base (chordal chondrocranium). Further studies are needed to clarify PCP involvement in the development of pharynx, esophagus, and their derivatives, as well as to determine the source and the mechanisms of development of PCP mesenchymal cells. The term "prechordal plate" should not be confused with the Spemann's organizer, head organizer, oropharyngeal membrane, mesendoderm, head process and the prechordal mesoderm, which is common in the scientific literature. The term "myoepicardial plate" falsely indicates the common origin of myocardium and epicardium, thus its usage should be avoided.

  2. Dynamic topography in subduction zones: insights from laboratory models

    NASA Astrophysics Data System (ADS)

    Bajolet, Flora; Faccenna, Claudio; Funiciello, Francesca

    2014-05-01

    The topography in subduction zones can exhibit very complex patterns due to the variety of forces operating this setting. If we can deduce the theoretical isostatic value from density structure of the lithosphere, the effect of flexural bending and the dynamic component of topography are difficult to quantify. In this work, we attempt to measure and analyze the topography of the overriding plate during subduction compared to a pure shortening setting. We use analog models where the lithospheres are modeled by thin-sheet layers of silicone putty lying on low-viscosity syrup (asthenosphere). The model is shorten by a piston pushing an oceanic plate while a continental plate including a weak zone to localize the deformation is fixed. In one type of experiments, the oceanic plate bends and subducts underneath the continental one; in a second type the two plates are in contact without any trench, and thus simply shorten. The topography evolution is monitored with a laser-scanner. In the shortening model, the elevation increases progressively, especially in the weak zone, and is consistent with expected isostatic values. In the subduction model, the topography is characterized, from the piston to the back-wall, by a low elevation of the dense oceanic plate, a flexural bulge, the trench forming a deep depression, the highly elevated weak zone, and the continental upper plate of intermediate elevation. The topography of the upper plate is consistent with isostatic values for very early stages, but exhibits lower elevations than expected for later stages. For a same amount of shortening of the continental plate, the thickening is the same and the plate should have the same elevation in both types of models. However, comparing the topography at 20, 29 and 39% of shortening, we found that the weak zone is 0.4 to 0.6 mm lower when there is an active subduction. Theses values correspond to 2.6 to 4 km in nature. Although theses values are high, there are of the same order as

  3. Metal vapor arc ion plating

    DOEpatents

    Bertram, L.A.; Fisher, R.W.; Mattox, D.M.; Zanner, F.J.

    1986-09-09

    A method and apparatus for ion plating are described. The apparatus uses more negative than a first electrode voltage in a vacuum arc remelt system to attract low energy ions from the anode electrode to the article to be plated. 2 figs.

  4. Microplate and shear zone models for oceanic spreading center reorganizations

    NASA Technical Reports Server (NTRS)

    Engeln, Joseph F.; Stein, Seth; Werner, John; Gordon, Richard

    1988-01-01

    The kinematics of rift propagation and the resulting goemetries of various tectonic elements for two plates is reviewed with no overlap zone. The formation and evolution of overlap regions using schematic models is discussed. The models are scaled in space and time to approximate the Easter plate, but are simplified to emphasize key elements. The tectonic evolution of overlap regions which act as rigid microplates and shear zones is discussed, and the use of relative motion and structural data to discriminate between the two types of models is investigated. The effect of propagation rate and rise time on the size, shape, and deformation of the overlap region is demonstrated.

  5. Classification Model for Damage Localization in a Plate Structure

    NASA Astrophysics Data System (ADS)

    Janeliukstis, R.; Ruchevskis, S.; Chate, A.

    2018-01-01

    The present study is devoted to the problem of damage localization by means of data classification. The commercial ANSYS finite-elements program was used to make a model of a cantilevered composite plate equipped with numerous strain sensors. The plate was divided into zones, and, for data classification purposes, each of them housed several points to which a point mass of magnitude 5 and 10% of plate mass was applied. At each of these points, a numerical modal analysis was performed, from which the first few natural frequencies and strain readings were extracted. The strain data for every point were the input for a classification procedure involving k nearest neighbors and decision trees. The classification model was trained and optimized by finetuning the key parameters of both algorithms. Finally, two new query points were simulated and subjected to a classification in terms of assigning a label to one of the zones of the plate, thus localizing these points. Damage localization results were compared for both algorithms and were found to be in good agreement with the actual application positions of point load.

  6. Imaging the Subduction Plate Interface Using Low-Frequency Earthquakes

    NASA Astrophysics Data System (ADS)

    Plourde, A. P.; Bostock, M. G.

    2015-12-01

    Low-frequency Earthquakes (LFEs) in subduction zones are commonly thought to represent slip on the plate interface. They have also been observed to lie near or within a zone of low shear-wave velocity, which is modelled as fluid-rich upper oceanic crust. Due to relatively large depth uncertainties in absolute hypocenters of most LFE families, their location relative to an independently imaged subucting plate and, consequently, the nature of the plate boundary at depths between 30-45 km have not been precisely determined. For a selection of LFE families in northern Washington, we measure variations in arrival time of individual LFE detections using multi-channel cross-correlation incorporating both arrivals at the same station and different events (cross-detection data), and the same event but different stations (cross-station data). Employing HypoDD, these times are used to generate relative locations for individual LFE detections. After creating templates from spatial subgroups of detections, network cross-correlation techniques will be used to search for new detections in neighbouring areas, thereby expanding the local catalogue and enabling further subdivision. By combining the source ``arrays'' and the receiver arrays from the Array of Arrays experiment we plan to interrogate plate boundary structure using migration of scattered waves from the subduction complex as previously documented beneath southern Vancouver Island.

  7. Aseptic laboratory techniques: plating methods.

    PubMed

    Sanders, Erin R

    2012-05-11

    Microorganisms are present on all inanimate surfaces creating ubiquitous sources of possible contamination in the laboratory. Experimental success relies on the ability of a scientist to sterilize work surfaces and equipment as well as prevent contact of sterile instruments and solutions with non-sterile surfaces. Here we present the steps for several plating methods routinely used in the laboratory to isolate, propagate, or enumerate microorganisms such as bacteria and phage. All five methods incorporate aseptic technique, or procedures that maintain the sterility of experimental materials. Procedures described include (1) streak-plating bacterial cultures to isolate single colonies, (2) pour-plating and (3) spread-plating to enumerate viable bacterial colonies, (4) soft agar overlays to isolate phage and enumerate plaques, and (5) replica-plating to transfer cells from one plate to another in an identical spatial pattern. These procedures can be performed at the laboratory bench, provided they involve non-pathogenic strains of microorganisms (Biosafety Level 1, BSL-1). If working with BSL-2 organisms, then these manipulations must take place in a biosafety cabinet. Consult the most current edition of the Biosafety in Microbiological and Biomedical Laboratories (BMBL) as well as Material Safety Data Sheets (MSDS) for Infectious Substances to determine the biohazard classification as well as the safety precautions and containment facilities required for the microorganism in question. Bacterial strains and phage stocks can be obtained from research investigators, companies, and collections maintained by particular organizations such as the American Type Culture Collection (ATCC). It is recommended that non-pathogenic strains be used when learning the various plating methods. By following the procedures described in this protocol, students should be able to: Perform plating procedures without contaminating media. Isolate single bacterial colonies by the streak-plating

  8. Aseptic Laboratory Techniques: Plating Methods

    PubMed Central

    Sanders, Erin R.

    2012-01-01

    Microorganisms are present on all inanimate surfaces creating ubiquitous sources of possible contamination in the laboratory. Experimental success relies on the ability of a scientist to sterilize work surfaces and equipment as well as prevent contact of sterile instruments and solutions with non-sterile surfaces. Here we present the steps for several plating methods routinely used in the laboratory to isolate, propagate, or enumerate microorganisms such as bacteria and phage. All five methods incorporate aseptic technique, or procedures that maintain the sterility of experimental materials. Procedures described include (1) streak-plating bacterial cultures to isolate single colonies, (2) pour-plating and (3) spread-plating to enumerate viable bacterial colonies, (4) soft agar overlays to isolate phage and enumerate plaques, and (5) replica-plating to transfer cells from one plate to another in an identical spatial pattern. These procedures can be performed at the laboratory bench, provided they involve non-pathogenic strains of microorganisms (Biosafety Level 1, BSL-1). If working with BSL-2 organisms, then these manipulations must take place in a biosafety cabinet. Consult the most current edition of the Biosafety in Microbiological and Biomedical Laboratories (BMBL) as well as Material Safety Data Sheets (MSDS) for Infectious Substances to determine the biohazard classification as well as the safety precautions and containment facilities required for the microorganism in question. Bacterial strains and phage stocks can be obtained from research investigators, companies, and collections maintained by particular organizations such as the American Type Culture Collection (ATCC). It is recommended that non-pathogenic strains be used when learning the various plating methods. By following the procedures described in this protocol, students should be able to: ● Perform plating procedures without contaminating media. ● Isolate single bacterial colonies by the

  9. Impact damage of composite plates

    NASA Technical Reports Server (NTRS)

    Lal, K. M.; Goglia, G. L.

    1983-01-01

    A simple model to study low velocity transverse impact of thin plates made of fiber-reinforced composite material, in particular T300/5208 graphite-epoxy was discussed. This model predicts the coefficient of restitution, which is a measure of the energy absorbed by the target during an impact event. The model is constructed on the assumption that the plate is inextensible in the fiber direction and that the material is incompressible in the z-direction. Such a plate essentially deforms by shear, hence this model neglects bending deformations of the plate. The coefficient of restitution is predicted to increase with large interlaminar shear strength and low transverse shear modulus of the laminate. Predictions are compared with the test results of impacted circular and rectangular clamped plates. Experimentally measured values of the coefficient of restitution are found to agree with the predicted values within a reasonable error.

  10. Present-day plate motions

    NASA Technical Reports Server (NTRS)

    Minster, J. B.; Jordan, T. H.

    1977-01-01

    A data set comprising 110 spreading rates, 78 transform fault azimuths and 142 earthquake slip vectors was inverted to yield a new instantaneous plate motion model, designated RM2. The mean averaging interval for the relative motion data was reduced to less than 3 My. A detailed comparison of RM2 with angular velocity vectors which best fit the data along individual plate boundaries indicates that RM2 performs close to optimally in most regions, with several notable exceptions. On the other hand, a previous estimate (RM1) failed to satisfy an extensive set of new data collected in the South Atlantic Ocean. It is shown that RM1 incorrectly predicts the plate kinematics in the South Atlantic because the presently available data are inconsistent with the plate geometry assumed in deriving RM1. It is demonstrated that this inconsistency can be remedied by postulating the existence of internal deformation with the Indian plate, although alternate explanations are possible.

  11. The moving plate capacitor paradox

    NASA Astrophysics Data System (ADS)

    Davis, B. R.; Abbott, D.; Parrondo, J. M. R.

    2000-03-01

    For the first time we describe an apparent paradox concerning a moving plate capacitor driven by thermal noise from a resistor. A demon restores the plates of the capacitor to their original position, only when the voltage across the capacitor is small—hence only small forces are present for the demon to work against. The demon has to work harder than this to avoid the situation of perpetual motion, but the question is how? We explore the concept of a moving plate capacitor, driven by noise, a step further by examining the case where the restoring force on the capacitor plates is provided by a simple spring, rather than some unknown demon. We display simulation results with interesting behavior, particularly where the capacitor plates collide with each other.

  12. SAMI Automated Plug Plate Configuration

    NASA Astrophysics Data System (ADS)

    Lorente, N. P. F.; Farrell, T.; Goodwin, M.

    2013-10-01

    The Sydney-AAO Multi-object Integral field spectrograph (SAMI) is a prototype wide-field system at the Anglo-Australian Telescope (AAT) which uses a plug-plate to mount its 13×61-core imaging fibre bundles (hexabundles) in the optical path at the telescope's prime focus. In this paper we describe the process of determining the positions of the plug-plate holes, where plates contain three or more stacked observation configurations. The process, which up until now has involved several separate processes and has required significant manual configuration and checking, is now being automated to increase efficiency and reduce error. This is carried out by means of a thin Java controller layer which drives the configuration cycle. This layer controls the user interface and the C++ algorithm layer where the plate configuration and optimisation is carried out. Additionally, through the Aladin display package, it provides visualisation and facilitates user verification of the resulting plates.

  13. The interpretation of crustal dynamics data in terms of plate motions and regional deformation near plate boundaries

    NASA Technical Reports Server (NTRS)

    Solomon, Sean C.

    1987-01-01

    The focus of the research was in two broad areas during the most recent 6 month period: the nature and dynamics of time-dependent deformation along major seismic zones, including the influence of irregularities in fault geometry on the earthquake cycles, and the processes contributing to the state of stress and rates of strain in plate interior regions. The principal findings of the research to date are described.

  14. Performance optimization of plate heat exchangers with chevron plates

    SciTech Connect

    Muley, A.; Manglik, R.M.

    1999-07-01

    The enhanced heat transfer performance of a chevron plate heat exchanger (PHE) is evaluated employing (1) energy-conservation based performance evaluation criteria (PECs), and (2) the second-law based minimization of entropy generation principle. Single-phase laminar and turbulent flow convection for three different chevron-plate arrangements are considered. The influence of plate surface corrugation characteristics and their stack arrangements on the heat exchanger's thermal-hydraulic performance is delineated. Based on the different figures of merit, the results show that the extent of heat transfer enhancement increases with flow Re and chevron angle {beta} in laminar flow, but it diminishes with increasing Re in turbulentmore » flows. With up to 2.9 times higher Q, 48% lower A, and entropy generation number N{sub s,a} {lt} 1, relative to an equivalent flat-plate pack, chevron plates are found to be especially suitable in the low to medium flow rates range (20 {le} Re {le} 2,000). Also, there appears to be no significant advantage of using a mixed-plate over a symmetric-plate arrangement.« less

  15. Seismicity of the Indo-Australian/Solomon Sea Plate boundary in the Southeast Papua region

    NASA Astrophysics Data System (ADS)

    Ripper, I. D.

    1982-08-01

    Seismicity and earthquake focal mechanism plots of the Southeast Papua and Woodlark Basin region for the period January 1960 to May 1979 show that: (a) the West Woodlark Basin spreading centre extends from the deep West Woodlark Basin, through Dawson Strait into Goodenough Bay, Southeast Papua; (b) a southeast seismic trend in the West Woodlark Basin is associated with a left-lateral transform fault, but a gap exists between this zone and the seismic East Woodlark Basin spreading centre; (c) Southeast Papua Seismicity divides into a shallow earthquake zone in which the earthquakes occur mainly in the northeast side of the Owen Stanley Range, and an intermediate depth southwest dipping Benioff zone which extends almost from Mt. Lamington to Goroka. The Benioff zone indicates the presence of a southwest dipping slab of Solomon Sea Plate beneath the Indo-Australian Plate in the Southeast Papua and Ramu-Markham Valley region. This subduction zone has collided with the New Britain subduction zone of the Solomon Sea Plate along the Ramu-Markham Valley. The Solomon Sea Plate is now hanging suspended in the form of an arch beneath Ramu-Markham Valley, inhibiting further subduction beneath Southeast Papua.

  16. Balanced Orifice Plate

    NASA Technical Reports Server (NTRS)

    Kelley, Anthony R. (Inventor); Buskirk, Paul D. (Inventor)

    2006-01-01

    An orifice plate for use in a conduit through which fluid flows is defined by a central circular region having a radius R, and a ring-shaped region surrounding the central circular region. The ring-shaped region has holes formed therethrough with those holes centered at each radius R thereof satisfying a relationship A(sub R)=al(X(sub R)V(sub R)(sup b)) where A(sub R) is a sum of areas of those holes having centers at radius R, X(sub R) is a flow coefficient at radius R, V(sub R) is a velocity of the fluid that is to flow through the conduit at radius R, b is a constant selected to make at least one process variable (associated with the fluid that is to flow through the conduit) approximately equal at each radius R, and a is a constant that is equal to (X(sub R)A(sub R)V(sub R)(sup b)) at each radius R.

  17. Sub-Plate Overlap Code Documentation

    NASA Technical Reports Server (NTRS)

    Taff, L. G.; Bucciarelli, B.; Zarate, N.

    1997-01-01

    An expansion of the plate overlap method of astrometric data reduction to a single plate has been proposed and successfully tested. Each plate is (artificially) divided into sub-plates which can then be overlapped. This reduces the area of a 'plate' over which a plate model needs to accurately represent the relationship between measured coordinates and standard coordinates. Application is made to non-astrographic plates such as Schmidt plates and to wide-field astrographic plates. Indeed, the method is completely general and can be applied to any type of recording media.

  18. Role of Transtension in Rifting at the Pacific-North America Plate Boundary

    NASA Astrophysics Data System (ADS)

    Stock, J. M.

    2011-12-01

    Transtensional plate motion can be accommodated either in a localized zone of transtensional rifting or over a broader region. Broader zones of deformation can be classified either as diffuse deformation or strain partitioning (one or more major strike-slip shear zones geographically offset from a region of a extensional faulting). The Pacific-North America plate boundary in southwestern North America was transtensional during much of its history and has exhibited the full range of these behaviors at different spatial scales and in different locations, as recorded by fault motions and paleomagnetic rotations. Here we focus on the northern Gulf of California part of the plate boundary (Upper and Lower Delfin basin segments), which has been in a zone of transtensional Pacific-North America plate boundary motion ever since the middle Miocene demise of adjacent Farallon-derived microplates. Prior to the middle Miocene, during the time of microplate activity, this sector of North America experienced basin-and-range normal faults (core complexes) in Sonora. However there is no evidence of continued extensional faulting nor of a Gulf-related topographic depression until after ca 12 Ma when a major ignimbrite (Tuff of San Felipe/ Ignimbrite of Hermosillo) was deposited across the entire region of the future Gulf of California rift in this sector. After 12 Ma, faults disrupted this marker bed in eastern Baja California and western Sonora, and some major NNW-striking right-lateral faults are inferred to have developed near the Sonoran coast causing offset of some of the volcanic facies. However, there are major tectonic rotations of the volcanic rocks in NE Baja California between 12 and 6 Ma, suggesting that the plate boundary motion was still occurring over a broad region. By contrast, after about 6 Ma, diminished rotations in latest Miocene and Pliocene volcanic rocks, as well as fault slip histories, show that plate boundary deformation became localized to a narrower

  19. Providing plastic zone extrusion

    SciTech Connect

    Manchiraju, Venkata Kiran; Feng, Zhili; David, Stan A.

    Plastic zone extrusion may be provided. First, a compressor may generate frictional heat in stock to place the stock in a plastic zone of the stock. Then, a conveyer may receive the stock in its plastic zone from the compressor and transport the stock in its plastic zone from the compressor. Next, a die may receive the stock in its plastic zone from the conveyer and extrude the stock to form a wire.

  20. Vadose zone microbiology

    SciTech Connect

    Kieft, Thomas L.; Brockman, Fred J.

    2001-01-17

    The vadose zone is defined as the portion of the terrestrial subsurface that extends from the land surface downward to the water table. As such, it comprises the surface soil (the rooting zone), the underlying subsoil, and the capillary fringe that directly overlies the water table. The unsaturated zone between the rooting zone and the capillary fringe is termed the "intermediate zone" (Chapelle, 1993). The vadose zone has also been defined as the unsaturated zone, since the sediment pores and/or rock fractures are generally not completely water filled, but instead contain both water and air. The latter characteristic results inmore » the term "zone of aeration" to describe the vadose zone. The terms "vadose zone," "unsaturated zone", and "zone of aeration" are nearly synonymous, except that the vadose zone may contain regions of perched water that are actually saturated. The term "subsoil" has also been used for studies of shallow areas of the subsurface immediately below the rooting zone. This review focuses almost exclusively on the unsaturated region beneath the soil layer since there is already an extensive body of literature on surface soil microbial communities and process, e.g., Paul and Clark (1989), Metting (1993), Richter and Markowitz, (1995), and Sylvia et al. (1998); whereas the deeper strata of the unsaturated zone have only recently come under scrutiny for their microbiological properties.« less

  1. Details: Elevation of Plate Typical Bay, SectionThrough Plate Typical Bay, ...

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

    Details: Elevation of Plate Typical Bay, Section-Through Plate Typical Bay, Section-Through Plate Center Bay, Elevation of Plate Center Bay - Contoocook Covered Bridge, Spanning Contoocook River, Hopkinton, Merrimack County, NH

  2. Fault interaction and stresses along broad oceanic transform zone: Tjörnes Fracture Zone, north Iceland

    NASA Astrophysics Data System (ADS)

    Homberg, C.; Bergerat, F.; Angelier, J.; Garcia, S.

    2010-02-01

    Transform motion along oceanic transforms generally occurs along narrow faults zones. Another class of oceanic transforms exists where the plate boundary is quite large (˜100 km) and includes several subparallel faults. Using a 2-D numerical modeling, we simulate the slip distribution and the crustal stress field geometry within such broad oceanic transforms (BOTs). We examine the possible configurations and evolution of such BOTs, where the plate boundary includes one, two, or three faults. Our experiments show that at any time during the development of the plate boundary, the plate motion is not distributed along each of the plate boundary faults but mainly occurs along a single master fault. The finite width of a BOT results from slip transfer through time with locking of early faults, not from a permanent distribution of deformation over a wide area. Because of fault interaction, the stress field geometry within the BOTs is more complex than that along classical oceanic transforms and includes stress deflections close to but also away from the major faults. Application of this modeling to the 100 km wide Tjörnes Fracture Zone (TFZ) in North Iceland, a major BOT of the Mid-Atlantic Ridge that includes three main faults, suggests that the Dalvik Fault and the Husavik-Flatey Fault developed first, the Grismsey Fault being the latest active structure. Since initiation of the TFZ, the Husavik-Flatey Fault accommodated most of the plate motion and probably persists until now as the main plate structure.

  3. Weldability evaluation of high tensile plates using GMAW process

    NASA Astrophysics Data System (ADS)

    Datta, R.; Mukerjee, D.; Rohira, K. L.; Veeraraghavan, R.

    1999-08-01

    High tensile plates, SAILMA-450 high impact (HI) (yield strength, 45 kg/mm2 minimum; ultimate tensile strength, 57 kg/mm2 minimum; elongation, 19% minimum; Charpy impact energy 2.0 kg.m at -20 °C minimum) were successfully developed at the Steel Authority of India Ltd., up to 32 mm plate thickness. Since then the steel has been extensively used for the fabrication of impellers, bridges, excavators, and mining machineries, where welding is an important processing step. The present study deals with the weldability properties of SAILMA-450 HI plates employing the gas metal arc welding process and carbon dioxide gas. Implant and elastic restraint cracking tests were conducted to assess the cold cracking resistance of the weld joint under different welding conditions. The static fatigue limit values were found to be in excess of minimum specified yield strength at higher heat input levels (9.4 and 13.0 kJ/cm), indicating adequate cold cracking resistance. The critical restraint intensities, K cr, were found to vary between 720 and 1280 kg/mm2, indicating that the process can be utilized for fabrication of structures involving moderate to low restraint intensities (200 to 1000 kg/mm2). Lamellar tear tests conducted using full thickness plates at heat input levels ranging from 10 to 27 kJ/cm showed no incidence of lamellar tear upon visual, ultrasonic, and four-section macroexamination. These tests were repeated using machined plates, such that the midthickness of the plates (segregated zone) corresponded to the heat affected zone of the weld. No cracks were observed, indicating good lamellar tear resistance of the weld joint. Optimized welding conditions were formulated based on these tests. The weld joint was subjected to extensive tests to assess the physical properties and soundness of the weld joint. The weld joint exhibited good strength (64.7 kg/mm2) and impact toughness (5.7 and 3.5 kg.m at -20 °C for weld metal and heat affected zone properties. Crack tip

  4. Structure of the tsunamigenic plate boundary and low-frequency earthquakes in the southern Ryukyu Trench

    PubMed Central

    Arai, Ryuta; Takahashi, Tsutomu; Kodaira, Shuichi; Kaiho, Yuka; Nakanishi, Ayako; Fujie, Gou; Nakamura, Yasuyuki; Yamamoto, Yojiro; Ishihara, Yasushi; Miura, Seiichi; Kaneda, Yoshiyuki

    2016-01-01

    It has been recognized that even weakly coupled subduction zones may cause large interplate earthquakes leading to destructive tsunamis. The Ryukyu Trench is one of the best fields to study this phenomenon, since various slow earthquakes and tsunamis have occurred; yet the fault structure and seismic activity there are poorly constrained. Here we present seismological evidence from marine observation for megathrust faults and low-frequency earthquakes (LFEs). On the basis of passive observation we find LFEs occur at 15–18 km depths along the plate interface and their distribution seems to bridge the gap between the shallow tsunamigenic zone and the deep slow slip region. This suggests that the southern Ryukyu Trench is dominated by slow earthquakes at any depths and lacks a typical locked zone. The plate interface is overlaid by a low-velocity wedge and is accompanied by polarity reversals of seismic reflections, indicating fluids exist at various depths along the plate interface. PMID:27447546

  5. Reaction-induced rheological weakening enables oceanic plate subduction

    PubMed Central

    Hirauchi, Ken-ichi; Fukushima, Kumi; Kido, Masanori; Muto, Jun; Okamoto, Atsushi

    2016-01-01

    Earth is the only terrestrial planet in our solar system where an oceanic plate subducts beneath an overriding plate. Although the initiation of plate subduction requires extremely weak boundaries between strong plates, the way in which oceanic mantle rheologically weakens remains unknown. Here we show that shear-enhanced hydration reactions contribute to the generation and maintenance of weak mantle shear zones at mid-lithospheric depths. High-pressure friction experiments on peridotite gouge reveal that in the presence of hydrothermal water, increasing strain and reactions lead to an order-of-magnitude reduction in strength. The rate of deformation is controlled by pressure-solution-accommodated frictional sliding on weak hydrous phyllosilicate (talc), providing a mechanism for the ‘cutoff' of the high peak strength at the brittle-plastic transition. Our findings suggest that infiltration of seawater into transform faults with long lengths and low slip rates is an important controlling factor on the initiation of plate tectonics on terrestrial planets. PMID:27562366

  6. High loading uranium fuel plate

    DOEpatents

    Wiencek, Thomas C.; Domagala, Robert F.; Thresh, Henry R.

    1990-01-01

    Two embodiments of a high uranium fuel plate are disclosed which contain a meat comprising structured uranium compound confined between a pair of diffusion bonded ductile metal cladding plates uniformly covering the meat, the meat having a uniform high fuel loading comprising a content of uranium compound greater than about 45 Vol. % at a porosity not greater than about 10 Vol. %. In a first embodiment, the meat is a plurality of parallel wires of uranium compound. In a second embodiment, the meat is a dispersion compact containing uranium compound. The fuel plates are fabricated by a hot isostatic pressing process.

  7. SubductionGenerator: A program to build three-dimensional plate configurations

    NASA Astrophysics Data System (ADS)

    Jadamec, M. A.; Kreylos, O.; Billen, M. I.; Turcotte, D. L.; Knepley, M.

    2016-12-01

    Geologic, geochemical, and geophysical data from subduction zones indicate that a two-dimensional paradigm for plate tectonic boundaries is no longer adequate to explain the observations. Many open source software packages exist to simulate the viscous flow of the Earth, such as the dynamics of subduction. However, there are few open source programs that generate the three-dimensional model input. We present an open source software program, SubductionGenerator, that constructs the three-dimensional initial thermal structure and plate boundary structure. A 3D model mesh and tectonic configuration are constructed based on a user specified model domain, slab surface, seafloor age grid file, and shear zone surface. The initial 3D thermal structure for the plates and mantle within the model domain is then constructed using a series of libraries within the code that use a half-space cooling model, plate cooling model, and smoothing functions. The code maps the initial 3D thermal structure and the 3D plate interface onto the mesh nodes using a series of libraries including a k-d tree to increase efficiency. In this way, complicated geometries and multiple plates with variable thickness can be built onto a multi-resolution finite element mesh with a 3D thermal structure and 3D isotropic shear zones oriented at any angle with respect to the grid. SubductionGenerator is aimed at model set-ups more representative of the earth, which can be particularly challenging to construct. Examples include subduction zones where the physical attributes vary in space, such as slab dip and temperature, and overriding plate temperature and thickness. Thus, the program can been used to construct initial tectonic configurations for triple junctions and plate boundary corners.

  8. A Plate Tectonic Model for the Neoproterozoic with Evolving Plate Boundaries

    NASA Astrophysics Data System (ADS)

    Merdith, Andrew; Collins, Alan; Williams, Simon; Pisarevsky, Sergei; Müller, Dietmar

    2017-04-01

    The Neoproterozoic was dominated by the formation of the supercontinent Rodinia, its break-up and the subsequent amalgamation of Gondwana, during which, the planet experienced large climatic variations and the emergence of complex life. Here we present a topological plate model of the Neoproterozoic based on a synthesis of available geological and palaeomagnetic data. Subduction zones, which are well preserved in the geological record, are used as a proxy for convergent margins; evidence for mid-ocean ridges and transform motion is less clearly preserved, though passive margins are used as a proxy for spreading centres, and evidence for strike-slip motions are used to model transform boundaries. We find that the model presented here only predicts 70% of the total length of subduction active today, though it models similar lengths of both transform and divergent boundaries, suggesting that we have produced a conservative model and are probably underestimating the amount of subduction. Where evidence for convergent, divergent or transform motion is not preserved, we interpret the locations of plate boundaries based on the relative motions of cratonic crust as suggested through either palaeomagnetic data or the geological record. Using GPlates, we tie these boundaries together to generate a plate model that depicts the motion of tectonic plates through the Neoproterozoic. We omit India and South China from Rodinia completely, due to long-lived subduction preserved on margins of India and conflicting palaeomagnetic data for the Cryogenian, but tie them together due to similar Tonian aged accretionary patterns along their respective (present-day) north-western and northern margins, such that these two cratons act as a "lonely wanderer" for much of the Neoproterozoic, and form their own tectonic plate. We also introduce a Tonian-Cryogenian aged rotation of the Congo-São Francisco Craton relative to Rodinia to better fit palaeomagnetic data and account for thick passive

  9. Plate tectonics beyond plate boundaries: the role of ancient structures in intraplate orogenesis

    NASA Astrophysics Data System (ADS)

    Heron, Philip; Pysklywec, Russell; Stephenson, Randell

    2015-04-01

    The development of orogens that occur at a distance from plate boundaries (i.e., `intraplate' deformation) cannot be adequately explained through conventional plate tectonic theory. Intraplate deformation infers a more complex argument for lithospheric and mantle interaction than plate tectonic theory allows. As a result, the origins of intraplate orogenesis are enigmatic. One hypothesis is the amalgamation of continental material (i.e., micro-plates) leaves inherent scars on the crust and mantle lithosphere. Previous studies into continent-continent collisions identify a number of scenarios from accretionary tectonics that affect the crust and mantle (namely, the development of a Rayleigh-Taylor instability, lithospheric underplating, lithospheric delamination, and lithospheric subduction). Any of these processes may weaken the lithosphere allowing episodic reactivation of faults within continental interiors. Hence, continental convergence (i.e., shortening) at a time after continental collision may cause the already weakened crust and mantle lithosphere to produce intraplate deformation. In order to better understand the processes involved in deformation away from plate boundaries, we present suites of continental shortening models (using the high-resolution thermal-mechanical modelling code SOPALE) to identify the preferred style of deformation. We model ancient structures by applying weak subduction scarring, changing the rheological conditions, and modifying the thermal structure within the lithosphere. To highlight the role of surface processes on plate and lithosphere deformation, the effect of climate-driven erosion and deposition on the tectonic structure of intraplate deformation is also addressed. We explore the relevance of the models to previously studied regions of intraplate orogenesis, including the Pyrenees in Europe, the Laramide orogen in North America, Tien Shan orogen in Central Asia, and Central Australia. The findings of the simulations with

  10. An Analysis of Wilson Cycle Plate Margins

    NASA Astrophysics Data System (ADS)

    Buiter, S.; Torsvik, T. H.

    2012-12-01

    The Wilson Cycle theory that oceans close and open along the same suture is a powerful concept in analyses of ancient plate tectonics. It implies that collision zones are structures that are able to localize extensional deformation for long times after the collision has waned. However, some sutures are seemingly never reactivated and already Tuzo Wilson recognized that Atlantic break-up did not follow the precise line of previous junction. We have reviewed margin pairs around the Atlantic and Indian Oceans with the aim to evaluate the extent to which oceanic opening used former sutures, summarize delay times between collision and break-up, and analyze the role of mantle plumes in continental break-up. We aid our analyses with plate tectonic reconstructions using GPlates (www.gplates.org). Although at first sight opening of the North Atlantic Ocean largely seems to follow the Iapetus and Rheic sutures, a closer look reveals deviations. For example, Atlantic opening did not utilize the Iapetus suture in Great Britain and rather than opening along the younger Rheic suture north of Florida, break-up occurred along the older Pan-African structures south of Florida. We find that today's oceanic Charlie Gibbs Fracture Zone, between Ireland and Newfoundland, is aligned with the Iapetus suture. We speculate therefore that in this region the Iapetus suture was reactivated as a transform fault. As others before us, we find no correlation of suture and break-up age. Often continental break-up occurs some hundreds of Myrs after collision, but it may also take over 1000 Myr, as for example for Australia - Antarctica and Congo - São Francisco. This places serious constraints on potential collision zone weakening mechanisms. Several studies have pointed to a link between continental break-up and large-scale mantle upwellings. It is, however, much debated whether plumes use existing rifts as a pathway, or whether plumes play an active role in causing rifting. We find a positive

  11. Cenozoic lithospheric deformation in Northeast Asia and the rapidly-aging Pacific Plate

    NASA Astrophysics Data System (ADS)

    Yang, Ting; Moresi, Louis; Zhao, Dapeng; Sandiford, Dan; Whittaker, Joanne

    2018-06-01

    Northeast Asia underwent widespread rifting and magmatic events during the Cenozoic. The geodynamic origins of these tectonic events are often linked to Pacific plate subduction beneath Northeast Asia. However, the Japan Sea did not open until the late Oligocene, tens of millions of years after Pacific Plate subduction initiation in the Paleocene. Moreover, it is still not clear why the Baikal Rift Zone extension rate increased significantly after the late Miocene, while the Japan Sea opening ceased at the same time. Geodynamic models suggest these enigmatic events are related to the rapidly-aging Pacific Plate at the trench after Izanagi-Pacific spreading ridge subduction. Subduction of the young Pacific Plate delayed the Japan Sea opening during the Eocene while advection of the old Pacific Plate towards the trench increases seafloor age rapidly, allowing the Japan Sea to open after the early Miocene. The Japan Sea opening promotes fast trench retreat and slab stagnation, with subduction-induced wedge zone convection gradually increasing its extent during this process. The active rifting center associated with wedge zone convection upwelling also shifts inland-ward during slab stagnation, preventing further Japan Sea spreading while promoting the Baikal Rift Zone extension. Our geodynamic model provides a good explanation for the temporal-spatial patterns of the Cenozoic tectonic and magmatic events in Northeast Asia.

  12. Subducting plate geology in three great earthquake ruptures of the western Alaska margin, Kodiak to Unimak

    USGS Publications Warehouse

    von Huene, Roland E.; Miller, John J.; Weinrebe, Wilhelm

    2012-01-01

    Three destructive earthquakes along the Alaska subduction zone sourced transoceanic tsunamis during the past 70 years. Since it is reasoned that past rupture areas might again source tsunamis in the future, we studied potential asperities and barriers in the subduction zone by examining Quaternary Gulf of Alaska plate history, geophysical data, and morphology. We relate the aftershock areas to subducting lower plate relief and dissimilar materials in the seismogenic zone in the 1964 Kodiak and adjacent 1938 Semidi Islands earthquake segments. In the 1946 Unimak earthquake segment, the exposed lower plate seafloor lacks major relief that might organize great earthquake rupture. However, the upper plate contains a deep transverse-trending basin and basement ridges associated with the Eocene continental Alaska convergent margin transition to the Aleutian island arc. These upper plate features are sufficiently large to have affected rupture propagation. In addition, massive slope failure in the Unimak area may explain the local 42-m-high 1946 tsunami runup. Although Quaternary geologic and tectonic processes included accretion to form a frontal prism, the study of seismic images, samples, and continental slope physiography shows a previous history of tectonic erosion. Implied asperities and barriers in the seismogenic zone could organize future great earthquake rupture.

  13. License plate recognition (phase B).

    DOT National Transportation Integrated Search

    2010-06-01

    License Plate Recognition (LPR) technology has been used for off-line automobile enforcement purposes. The technology has seen mixed success with correct reading rate as high as 60 to 80% depending on the specific application and environment. This li...

  14. Carbon-assisted flyer plates

    DOEpatents

    Stahl, D.B.; Paisley, D.L.

    1994-04-12

    A laser driven flyer plate is described utilizing an optical fiber connected to a laser. The end of the optical fiber has a layer of carbon and a metal layer deposited onto it. The carbon layer provides the laser induced plasma which is superior to the plasma produced from most metals. The carbon layer plasma is capable of providing a flatter flyer plate, converting more of the laser energy to driving plasma, promoting a higher flyer plate acceleration, and providing a more uniform pulse behind the plate. In another embodiment, the laser is in optical communication with a substrate onto which a layer of carbon and a layer of metal have been deposited. 2 figures.

  15. High resolution reconstructions of Southwest Indian Ridge plate motions during the Neogene: Comparison to GPS estimates and implications for global plate motion estimates

    NASA Astrophysics Data System (ADS)

    DeMets, C.; Merkouriev, S.; Sauter, D.; Calais, E.

    2013-12-01

    Plate kinematic data from the slow-spreading Southwest Indian Ridge (SWIR) are the primary source of information about relative movements between Antarctica and Africa over geologic time and are critical for linking the movements of plates in the Atlantic and Indian Ocean basins. We describe the first high-resolution model of SWIR plate kinematics from the present to 20 Ma, consisting of rotations based on 21 magnetic reversals with ~1 million-year spacing. The new rotations, which are derived from 4822 identifications of magnetic reversals C1n to C6no and 6000 crossings of 21 fracture zones and transform faults, describe in detail the ultra-slow motions of the Nubia, Lwandle, and Somalia plates north of the SWIR relative to the Antarctic plate. A search for the Nubia-Lwandle-Antarctic triple junction with all data since C5n.2 (11.0 Ma) gives a best location at the Andrew Bain transform fault (~32E), in accord with previous work. Plate kinematic data from the SWIR east of the Andrew Bain fracture zone support the existence of the previously proposed Lwandle plate at high confidence level. The likely diffuse Lwandle-Somalia plate boundary north of the SWIR is however only loosely constrained to 45E-52E. After calibrating the new rotations for the biasing effects of finite-width magnetic polarity transition zones (i.e. outward displacement), the new rotations reveal that SWIR plate motion has remained steady from the present back to 7.5 Ma, but was modestly faster (~25%) from 19.6 Ma to 7.5 Ma. GPS estimates of present SWIR plate motions based on more than 100 continuous GPS sites on the Antarctic, Nubia, and Somalia plates are remarkably consistent with SWIR velocities determined with the new geological reconstructions. The superb agreement between the two independent plate motion estimates validates both sets of estimates and our calibration for outward displacement. Implications of the new estimates, including evidence for anomalously wide outward displacement

  16. New observations on mid-plate volcanism and the tectonic history of the Pacific plate, Tahiti to Easter microplate

    NASA Astrophysics Data System (ADS)

    Searle, R. C.; Francheteau, J.; Cornaglia, B.

    1995-04-01

    We describe the geology and tectonics of a continuous swathe of seafloor between Tahiti and the western edge of the Easter microplate imaged by GLORIA and Sea Beam on two separate cruise transits in 1987 and 1988. The data reveal that mid-plate volcanism is common in this region, even on deep seafloor hundreds of kilometres from major lines of seamounts and islands. This supports the idea of a thin weak lithosphere over the Pacific Superswell, and the idea that the tops of major mantle plumes may spread out over diameters of the order of 1000 km. The mid-plate volcanism occurs in two distinct forms. Over most of our traverse it appears as fields of relatively young and acoustically strongly backscattering lava flows, often accompanied by groups of numerous small, circular volcanoes. East of 122° W (about chron 5A), however, we observed a distinct form: major, sharp-crested, constructional volcanic ridges, many tens of kilometres long, individually trending ENE, but lying en-echelon along an E-W regional trend. These ridges appear morphologically identical to the 'cross-grain ridges' seen elsewhere in the Pacific. We attribute their formation to magma supplied from the regionally hot mantle leaking along tectonic lines of weakness. However, although these ridges are parallel to fracture zone trends seen farther west, they are morphologically very different from any known fracture zone. Moreover, individual ridges are somewhat oblique to the tectonic spreading fabric around them, and so do not seem to follow actual fracture zone traces. The whole line of en-echelon ridges lies along part of the predicted trace of Fracture Zone 2 of Okal and Cazenave [15], and is probably its morphological expression. However, nowhere did we see a convincing 'conventional' fracture zone trace in or following the predicted position or orientation. We suggest instead that magma from an independent source has used lines of weakness along minor fracture zones to produce these en

  17. Global Dynamic Numerical Simulations of Plate Tectonic Reorganizations

    NASA Astrophysics Data System (ADS)

    Morra, G.; Quevedo, L.; Butterworth, N.; Matthews, K. J.; Müller, D.

    2010-12-01

    We use a new numerical approach for global geodynamics to investigate the origin of present global plate motion and to identify the causes of the last two global tectonic reorganizations occurred about 50 and 100 million years ago (Ma) [1]. While the 50 Ma event is the most well-known global plate-mantle event, expressed by the bend in the Hawaiian-Emperor volcanic chain, a prominent plate reorganization at about 100 Ma, although presently little studied, is clearly indicated by a major bend in the fracture zones in the Indian Ocean and by a change in Pacific plate motion [2]. Our workflow involves turning plate reconstructions into surface meshes that are subsequently employed as initial conditions for global Boundary Element numerical models. The tectonic setting that anticipates the reorganizations is processed with the software GPlates, combining the 3D mesh of the paleo-plate morphology and the reconstruction of paleo-subducted slabs, elaborated from tectonic history [3]. All our models involve the entire planetary system, are fully dynamic, have free surface, are characterized by a spectacular computational speed due to the simultaneous use of the multi-pole algorithm and the Boundary Element formulation and are limited only by the use of sharp material property variations [4]. We employ this new tool to unravel the causes of plate tectonic reorganizations, producing and comparing global plate motion with the reconstructed ones. References: [1] Torsvik, T., Müller, R.D., Van der Voo, R., Steinberger, B., and Gaina, C., 2008, Global Plate Motion Frames: Toward a unified model: Reviews in Geophysics, VOL. 46, RG3004, 44 PP., 2008 [2] Wessel, P. and Kroenke, L.W. Pacific absolute plate motion since 145 Ma: An assessment of the fixed hot spot hypothesis. Journal of Geophysical Research, Vol 113, B06101, 2008 [3] L. Quevedo, G. Morra, R. D. Mueller. Parallel Fast Multipole Boundary Element Method for Crustal Dynamics, Proceeding 9th World Congress and 4th Asian

  18. Selective Mode Focusing in a Plate of Arbitrary Shape Applying Time Reversal Mirrors

    DOE PAGES

    Payan, Cedric; Remillieux, Marcel C.; Bas, Pierre-Yves Le; ...

    2017-11-01

    In this study, a time reversal mirror is used to remotely focus symmetric or antisymmetric modes in a plate of arbitrary shape without the need of precise knowledge about material properties and geometry. The addition or subtraction of the forward motions recorded by two laser beams located on both sides of the plate allows, respectively, to focus a symmetric or an antisymmetric mode. The concept is validated using experimental and numerical analysis on an aluminum plate of complex machined geometry which exhibits various thicknesses as well as a bi-materials zone. Finally, the limitations and possible ways to overcome them aremore » then presented.« less

  19. Fundamental structure model of island arcs and subducted plates in and around Japan

    NASA Astrophysics Data System (ADS)

    Iwasaki, T.; Sato, H.; Ishiyama, T.; Shinohara, M.; Hashima, A.

    2015-12-01

    The eastern margin of the Asian continent is a well-known subduction zone, where the Pacific (PAC) and Philippine Sea (PHS) plates are being subducted. In this region, several island arcs (Kuril, Northeast Japan, Southwest Japan, Izu-Bonin and Ryukyu arcs) meet one another to form a very complicated tectonic environment. At 2014, we started to construct fundamental structure models for island arcs and subducted plates in and around Japan. Our research is composed of 6 items of (1) topography, (2) plate geometry, (3) fault models, (4) the Moho and brittle-ductile transition zone, (5) the lithosphere-asthenosphere boundary, and (6) petrological/rheological models. Such information is basic but inevitably important in qualitative understanding not only for short-term crustal activities in the subduction zone (particularly caused by megathrust earthquakes) but also for long-term cumulative deformation of the arcs as a result of strong plate-arc/arc-arc interactions. This paper is the first presentation of our research, mainly presenting the results of items (1) and (2). The area of our modelling is 12o-54o N and 118o-164o E to cover almost the entire part of Japanese Islands together with Kuril, Ryukyu and Izu-Bonin trenches. The topography model was constructed from the 500-m mesh data provided from GSJ, JODC, GINA and Alaska University. Plate geometry models are being constructed through the two steps. In the first step, we modelled very smooth plate boundaries of the Pacific and Philippine Sea plates in our whole model area using 42,000 earthquake data from JMA, USGS and ISC. For 7,800 cross sections taken with several directions to the trench axes, 2D plate boundaries were defined by fitting to the earthquake distribution (the Wadati-Benioff zone), from which we obtained equi-depth points of the plate boundary. These equi-depth points were then approximated by spline interpolation technique to eliminate shorter wave length undulation (<50-100 km). The obtained

  20. Selective Mode Focusing in a Plate of Arbitrary Shape Applying Time Reversal Mirrors

    SciTech Connect

    Payan, Cedric; Remillieux, Marcel C.; Bas, Pierre-Yves Le

    In this study, a time reversal mirror is used to remotely focus symmetric or antisymmetric modes in a plate of arbitrary shape without the need of precise knowledge about material properties and geometry. The addition or subtraction of the forward motions recorded by two laser beams located on both sides of the plate allows, respectively, to focus a symmetric or an antisymmetric mode. The concept is validated using experimental and numerical analysis on an aluminum plate of complex machined geometry which exhibits various thicknesses as well as a bi-materials zone. Finally, the limitations and possible ways to overcome them aremore » then presented.« less

  1. The relationship between plate velocity and trench viscosity in Newtonian and power-law subduction calculations

    NASA Technical Reports Server (NTRS)

    King, Scott D.; Hager, Bradford H.

    1990-01-01

    The relationship between oceanic trench viscosity and oceanic plate velocity is studied using a Newtonian rheology by varying the viscosity at the trench. The plate velocity is a function of the trench viscosity for fixed Rayleigh number and plate/slab viscosity. Slab velocities for non-Newtonian rheology calculations are significantly different from slab velocities from Newtonian rheology calculations at the same effective Rayleigh number. Both models give reasonable strain rates for the slab when compared with estimates of seismic strain rate. Non-Newtonian rheology eliminates the need for imposed weak zones and provides a self-consistent fluid dynamical mechanism for subduction in numerical convection models.

  2. How mantle slabs drive plate tectonics.

    PubMed

    Conrad, Clinton P; Lithgow-Bertelloni, Carolina

    2002-10-04

    The gravitational pull of subducted slabs is thought to drive the motions of Earth's tectonic plates, but the coupling between slabs and plates is not well established. If a slab is mechanically attached to a subducting plate, it can exert a direct pull on the plate. Alternatively, a detached slab may drive a plate by exciting flow in the mantle that exerts a shear traction on the base of the plate. From the geologic history of subduction, we estimated the relative importance of "pull" versus "suction" for the present-day plates. Observed plate motions are best predicted if slabs in the upper mantle are attached to plates and generate slab pull forces that account for about half of the total driving force on plates. Slabs in the lower mantle are supported by viscous mantle forces and drive plates through slab suction.

  3. Plate convergence, transcurrent faults and internal deformation adjacent to Southeast Asia and the western Pacific

    NASA Technical Reports Server (NTRS)

    Fitch, T. J.

    1971-01-01

    A model for oblique convergence between plates of lithosphere is proposed in which at least a fraction of slip parallel to the plate margin results in transcurrent movements on a nearly vertical fault which is located on the continental side of a zone of plate consumption. In an extreme case of complete decoupling only the component of slip normal to the plate margin can be inferred from underthrusting. Recent movements in the western Sunda region provide the most convincing evidence for decoupling of slip, which in this region is thought to be oblique to the plate margin. A speculative model for convergence along the margins of the Philippine Sea is constructed from an inferred direction of oblique slip in the Philippine region. This model requires that the triple point formed by the junction of the Japanese and Izu-Bonin trenches and the Nankai trough migrate along the Sagami trough.

  4. Frequency Response of an Aircraft Wing with Discrete Source Damage Using Equivalent Plate Analysis

    NASA Technical Reports Server (NTRS)

    Krishnamurthy, T.; Eldred, Lloyd B.

    2007-01-01

    An equivalent plate procedure is developed to provide a computationally efficient means of matching the stiffness and frequencies of flight vehicle wing structures for prescribed loading conditions. Several new approaches are proposed and studied to match the stiffness and first five natural frequencies of the two reference models with and without damage. One approach divides the candidate reference plate into multiple zones in which stiffness and mass can be varied using a variety of materials including aluminum, graphite-epoxy, and foam-core graphite-epoxy sandwiches. Another approach places point masses along the edge of the stiffness-matched plate to tune the natural frequencies. Both approaches are successful at matching the stiffness and natural frequencies of the reference plates and provide useful insight into determination of crucial features in equivalent plate models of aircraft wing structures.

  5. Segmented Subduction Across the Juan De Fuca Plate: Challenges in Imaging with an Amphibious Array

    NASA Astrophysics Data System (ADS)

    Hawley, W. B.; Allen, R. M.

    2014-12-01

    The Cascadia Initiative (CI) is an amphibious array spanning the Juan de Fuca plate from formation at the ridge to the destruction of the slab in the mantle beneath western North America. This ambitions project has occupied over 300 onshore and offshore sites, providing an unprecedented opportunity to understand the dynamics of oceanic plates. The CI project is now in its fourth and final year of deployment. Here we present constraints on the structure of the Juan de Fuca plate and its interaction with western North America. We identify segmentation along the Cascadia subduction zone that can be traced back onto the Juan de Fuca plate prior to subduction. These results give insight into the life cycle of oceanic plates, from their creation at a mid-ocean ridge to their subduction and subsequent recycling into the mantle.

  6. Global Positioning System offers evidence of plate motions in eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Burc Oral, M.; Reilinger, Robert E.; Nafi Toksöz, M.; King, Robert W.; Aykut Barka, A.; Kinik, Ibrahim; Lenk, Onur

    Geophysicists are using the Global Positioning System (GPS), a highly precise satellite navigation system, to monitor the slow movements (cm/yr) of the crustal plates composing the Earth's surface and the deformations where such plates interact. We report the results of repeated GPS measurements in the complex zone of interaction between the Eurasian, Arabian, and African plates in Turkey. The GPS observations made between 1988 and 1992 indicate that western, central, and east central Turkey are decoupled from the Eurasian plate and are moving as a more or less coherent unit about an axis located north of the Sinai peninsula. Other space-based measurements of crustal motion in Greece and along the Hellenic arc [Smith et al., 1994] suggest that this coherent motion includes southern Greece and the south central Aegean Sea. We refer to this region (shaded in Figure 1) as the Anatolian plate.

  7. GPS Monitoring of Subduction Zone Deformation in Costa Rica

    NASA Technical Reports Server (NTRS)

    Lundgren, Paul

    1997-01-01

    The subduction of the Cocos plate beneath Costa Rica is among the highest convergence rates in the world. The high subduction rate and nearness of the Nicoya Peninsula, Costa Rica to the Middle America Trench (MAT) provide a unique opportunity to map variations in interseismic strain of the crust above the seismogenic zone in response to variations in seismic coupling.

  8. When Boundary Layers Collide: Plumes v. Subduction Zones

    NASA Astrophysics Data System (ADS)

    Moresi, L. N.; Betts, P. G.; Miller, M. S.; Willis, D.; O'Driscoll, L.

    2014-12-01

    Many subduction zones retreat while hotspots remain sufficiently stable in the mantle to provide an approximate reference frame. As a consequence, the mantle can be thought of as an unusual convecting system which self-organises to promote frequent collisions of downgoing material with upwellings. We present three 3D numerical models of subduction where buoyant material from a plume head and an associated ocean-island chain or plateau produce flat slab subduction and deformation of the over-riding plate. We observe transient instabilities of the convergent margin including: contorted trench geometry; trench migration parallel with the plate margin; folding of the subducting slab and orocline development at the convergent margin; and transfer of the plateau to the overriding plate. The presence of plume material beneath the oceanic plateau causes flat subduction above the plume, resulting in a "bowed" shaped subducting slab. In the absence of a plateau at the surface, the slab can remain uncoupled from the over-riding plate during very shallow subduction and hence there is very little shortening at the surface or advance of the plate boundary. In plateau-only models, plateau accretion at the edge of the overriding plate results in trench migration around the edge of the plateau before subduction re-establishes directly behind the trailing edge of the plateau. The plateau shortens during accretion and some plateau material subducts. In a plateau-plus-plume model, accretion is associated with rapid trench advance as the flat slab drives the plateau into the margin. This indentation stops once a new convergent boundary forms close to the original trench location. A slab window formed beneath the accreted plateau allows plume material to flow from beneath the subducting plate to the underside of the overriding plate. In all of these models the subduction zone maintains a relatively stable configuration away from the buoyancy anomalies within the downgoing plate. The

  9. Plate mode velocities in graphite/epoxy plates

    NASA Technical Reports Server (NTRS)

    Prosser, W. H.; Gorman, M. R.

    1994-01-01

    Measurements of the velocities of the extensional and flexural plate modes were made along three directions of propagation in four graphite/epoxy composite plates. The acoustic signals were generated by simulated acoustic emission events (pencil lead breaks or Hsu-Neilson sources) and detected by by broadband ultrasonic transducers. The first arrival of the extensional plate mode, which is nondispersive at low frequencies, was measured at a number of different distances from the source along the propagation direction of interest. The velocity was determined by plotting the distance versus arrival time and computing its slope. Because of the large dispersion of the flexural mode, a Fourier phase velocity technique was used to characterize this mode. The velocity was measured up to a frequency of 160 kHz. Theoretical predictions of the velocities of these modes were also made and compared with experimental observations. Classical plate theory yields good agreement with the measured extensional velocities. For predictions of the dispersion of the flexural mode, Mindlin plates theory, which includes the effects of shear deformation and rotatory inertia was shown to give better agreement with the experimental measurements.

  10. Stress rotation across the Cascadia megathrust requires a weak subduction plate boundary at seismogenic depths

    NASA Astrophysics Data System (ADS)

    Li, Duo; McGuire, Jeffrey J.; Liu, Yajing; Hardebeck, Jeanne L.

    2018-03-01

    The Mendocino Triple Junction region is the most seismically active part of the Cascadia Subduction Zone. The northward moving Pacific plate collides with the subducting Gorda plate causing intense internal deformation within it. Here we show that the stress field rotates rapidly with depth across the thrust interface from a strike-slip regime within the subducting plate, reflecting the Pacific plate collision, to a thrust regime in the overriding plate. We utilize a dense focal mechanism dataset, including observations from the Cascadia Initiative ocean bottom seismograph experiment, to constrain the stress orientations. To quantify the implications of this rotation for the strength of the plate boundary, we designed an inversion that solves for the absolute stress tensors in a three-layer model subject to assumptions about the strength of the subducting mantle. Our results indicate that the shear stress on the plate boundary fault is likely no more than about ∼50 MPa at ∼20 km depth. Regardless of the assumed mantle strength, we infer a relatively weak megathrust fault with an effective friction coefficient of ∼0 to 0.2 at seismogenic depths. Such a low value for the effective friction coefficient requires a combination of high fluid pressures and/or fault-zone minerals with low inherent friction in the region where a great earthquake is expected in Cascadia.

  11. Stress rotation across the Cascadia megathrust requires a weak subduction plate boundary at seismogenic depths

    USGS Publications Warehouse

    Li, Duo; McGuire, Jeffrey J.; Liu, Yajing; Hardebeck, Jeanne L.

    2018-01-01

    The Mendocino Triple Junction region is the most seismically active part of the Cascadia Subduction Zone. The northward moving Pacific plate collides with the subducting Gorda plate causing intense internal deformation within it. Here we show that the stress field rotates rapidly with depth across the thrust interface from a strike-slip regime within the subducting plate, reflecting the Pacific plate collision, to a thrust regime in the overriding plate. We utilize a dense focal mechanism dataset, including observations from the Cascadia Initiative ocean bottom seismograph experiment, to constrain the stress orientations. To quantify the implications of this rotation for the strength of the plate boundary, we designed an inversion that solves for the absolute stress tensors in a three-layer model subject to assumptions about the strength of the subducting mantle. Our results indicate that the shear stress on the plate boundary fault is likely no more than about ∼50 MPa at ∼20 km depth. Regardless of the assumed mantle strength, we infer a relatively weak megathrust fault with an effective friction coefficient of ∼0 to 0.2 at seismogenic depths. Such a low value for the effective friction coefficient requires a combination of high fluid pressures and/or fault-zone minerals with low inherent friction in the region where a great earthquake is expected in Cascadia.

  12. Evolution of passive continental margins and initiation of subduction zones

    NASA Astrophysics Data System (ADS)

    Cloetingh, S. A. P. L.; Wortel, M. J. R.; Vlaar, N. J.

    1982-05-01

    Although the initiation of subduction is a key element in plate tectonic schemes for evolution of lithospheric plates, the underlying mechanisms are not well understood. Plate rupture is an important aspect of the process of creating a new subduction zone, as stresses of the order of kilobars are required to fracture oceanic lithosphere1. Therefore initiation of subduction could take place preferentially at pre-existing weakness zones or in regions where the lithosphere is prestressed. As such, transform faults2,3 and passive margins4,5 where the lithosphere is downflexed under the influence of sediment loading have been suggested. From a model study of passive margin evolution we found that ageing of passive margins alone does not make them more suitable sites for initiation of subduction. However, extensive sediment loading on young lithosphere might be an effective mechanism for closure of small ocean basins.

  13. Current Plate Motion Across the Southwest Indian Ridge: Implications for the Diffuse Oceanic Plate Boundary Between Nubia and Somalia

    NASA Astrophysics Data System (ADS)

    Horner-Johnson, B. C.; Cowles, S. M.; Gordon, R. G.; Argus, D. F.

    2001-12-01

    Prior studies of plate motion data along the Southwest Indian Ridge (SWIR) have produced results that conflict in detail. Chu & Gordon [1999], from an analysis of 59 spreading rates averaged over 3 Myr and of the azimuths of active transform faults, found that the data are most consistent with a diffuse Nubia-Somalia plate boundary where it intersects the SWIR. When they solve for the best-fitting hypothetical narrow boundary, they find that it lies near 37° E, east of the Prince Edward fracture zone. They find a Nubia-Somalia pole of rotation near the east coast of South Africa. In contrast, Lemaux, Gordon, and Royer [2001], from an analysis of 237 crossings of marine magnetic anomaly 5 (11 Ma), find that most of the motion is accommodated in a narrow zone, most likely along the ``inactive'' trace of the Andrew Bain fracture zone complex (ABFZC), which intersects the SWIR near 32° E. They find a pole well to the west of, and probably to the southwest of, the pole of rotation found by Chu & Gordon. Their pole indicates mainly strike-slip motion along the ``inactive'' ABFZC. To resolve these conflicting results, we determined a new greatly expanded and spatially much denser set of 243 spreading rates and analyzed available bathymetric data of active transform faults along the SWIR. The data show that the African oceanic lithosphere spreading away from the SWIR cannot simply be two plates divided by a single narrow boundary. Our interpretation of the data is as follows. Near the SWIR, there is a diffuse boundary with a western limit near the ABFZC and an eastern limit near 63.5° E. Slip is partitioned in this wide boundary. Somewhere near the ABFZC (most likely the ABFZC itself) is a concentrated locus of right-lateral shearing parallel to the ABFZC whereas contraction perpendicular to the ABFZC is accommodated east of the ABFZC, perhaps over a very broad zone.

  14. Cyp26b1 within the growth plate regulates bone growth in juvenile mice

    SciTech Connect

    Minegishi, Yoshiki; Department of Plastic and Reconstructive Surgery, University of Fukui Hospital, 23-3 Matsuokashimoaizuki, Eiheiji-cho, Yoshida-gun, Fukui 910-1193; Department of Plastic Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871

    Highlights: • Retinoic acid and Cyp26b1 were oppositely localized in growth plate cartilage. • Cyp26b1 deletion in chondrocytes decreased bone growth in juvenile mice. • Cyp26b1 deletion reduced chondrocyte proliferation and growth plate height. • Vitamin A-depletion partially reversed growth plate abnormalities caused by Cyp26b1 deficiency. • Cyp26b1 regulates bone growth by controlling chondrocyte proliferation. - Abstract: Retinoic acid (RA) is an active metabolite of vitamin A and plays important roles in embryonic development. CYP26 enzymes degrade RA and have specific expression patterns that produce a RA gradient, which regulates the patterning of various structures in the embryo. However, itmore » has not been addressed whether a RA gradient also exists and functions in organs after birth. We found localized RA activities in the diaphyseal portion of the growth plate cartilage were associated with the specific expression of Cyp26b1 in the epiphyseal portion in juvenile mice. To disturb the distribution of RA, we generated mice lacking Cyp26b1 specifically in chondrocytes (Cyp26b1{sup Δchon} cKO). These mice showed reduced skeletal growth in the juvenile stage. Additionally, their growth plate cartilage showed decreased proliferation rates of proliferative chondrocytes, which was associated with a reduced height in the zone of proliferative chondrocytes, and closed focally by four weeks of age, while wild-type mouse growth plates never closed. Feeding the Cyp26b1 cKO mice a vitamin A-deficient diet partially reversed these abnormalities of the growth plate cartilage. These results collectively suggest that Cyp26b1 in the growth plate regulates the proliferation rates of chondrocytes and is responsible for the normal function of the growth plate and growing bones in juvenile mice, probably by limiting the RA distribution in the growth plate proliferating zone.« less

  15. Complex Plate Tectonic Features on Planetary Bodies: Analogs from Earth

    NASA Astrophysics Data System (ADS)

    Stock, J. M.; Smrekar, S. E.

    2016-12-01

    We review the types and scales of observations needed on other rocky planetary bodies (e.g., Mars, Venus, exoplanets) to evaluate evidence of present or past plate motions. Earth's plate boundaries were initially simplified into three basic types (ridges, trenches, and transform faults). Previous studies examined the Moon, Mars, Venus, Mercury and icy moons such as Europa, for evidence of features, including linear rifts, arcuate convergent zones, strike-slip faults, and distributed deformation (rifting or folding). Yet, several aspects merit further consideration. 1) Is the feature active or fossil? Earth's active mid ocean ridges are bathymetric highs, and seafloor depth increases on either side; whereas, fossil mid ocean ridges may be as deep as the surrounding abyssal plain with no major rift valley, although with a minor gravity low (e.g., Osbourn Trough, W. Pacific Ocean). Fossil trenches have less topographic relief than active trenches (e.g., the fossil trench along the Patton Escarpment, west of California). 2) On Earth, fault patterns of spreading centers depend on volcanism. Excess volcanism reduced faulting. Fault visibility increases as spreading rates slow, or as magmatism decreases, producing high-angle normal faults parallel to the spreading center. At magma-poor spreading centers, high resolution bathymetry shows low angle detachment faults with large scale mullions and striations parallel to plate motion (e.g., Mid Atlantic Ridge, Southwest Indian Ridge). 3) Sedimentation on Earth masks features that might be visible on a non-erosional planet. Subduction zones on Earth in areas of low sedimentation have clear trench -parallel faults causing flexural deformation of the downgoing plate; in highly sedimented subduction zones, no such faults can be seen, and there may be no bathymetric trench at all. 4) Areas of Earth with broad upwelling, such as the North Fiji Basin, have complex plate tectonic patterns with many individual but poorly linked ridge

  16. Variations in the kinematics of deformation along the Zagros inclined transpression zone, Iran: Implications for defining a curved inclined transpression zone

    NASA Astrophysics Data System (ADS)

    Sarkarinejad, Khalil; Partabian, Abdolreza; Faghih, Ali

    2013-03-01

    The combination of inclined collision and plate boundary shape can control the nature of deformation and the sense of shear along a transpression zone. The present study investigated the effects of a boundary zone with curvilinear shape along a transpression zone on the kinematics of deformation. The kinematics of the Zagros transpression zone varies with the orientation of the zone boundary. Detailed structural and microstructural studies showed sinistral sense of shear on the southeastern part of the Zagros inclined transpression zone (Fars Arc), but dextral sense of shear on the northwestern part of the zone. It is inferred that the both senses of shear were developed coevally under a bulk general shear, regional-scale deformation along a curved inclined transpression miming the shape of the Fras Arc of the Zagros and the reentrant of the Bandar Abbas Syntaxis. The Zagros transpression zone formed by inclined continental collision between the Afro-Arabian continent and Iranian microcontinent.

  17. Insight into collision zone dynamics from topography: numerical modelling results and observations

    NASA Astrophysics Data System (ADS)

    Bottrill, A. D.; van Hunen, J.; Allen, M. B.

    2012-11-01

    Dynamic models of subduction and continental collision are used to predict dynamic topography changes on the overriding plate. The modelling results show a distinct evolution of topography on the overriding plate, during subduction, continental collision and slab break-off. A prominent topographic feature is a temporary (few Myrs) basin on the overriding plate after initial collision. This "collisional mantle dynamic basin" (CMDB) is caused by slab steepening drawing, material away from the base of the overriding plate. Also, during this initial collision phase, surface uplift is predicted on the overriding plate between the suture zone and the CMDB, due to the subduction of buoyant continental material and its isostatic compensation. After slab detachment, redistribution of stresses and underplating of the overriding plate cause the uplift to spread further into the overriding plate. This topographic evolution fits the stratigraphy found on the overriding plate of the Arabia-Eurasia collision zone in Iran and south east Turkey. The sedimentary record from the overriding plate contains Upper Oligocene-Lower Miocene marine carbonates deposited between terrestrial clastic sedimentary rocks, in units such as the Qom Formation and its lateral equivalents. This stratigraphy shows that during the Late Oligocene-Early Miocene the surface of the overriding plate sank below sea level before rising back above sea level, without major compressional deformation recorded in the same area. Our modelled topography changes fit well with this observed uplift and subsidence.

  18. Revisiting the physical characterisitics of the subduction interplate seismogenic zones

    NASA Astrophysics Data System (ADS)

    Heuret, Arnauld; Lallemand, Serge; Funiciello, Francesca; Piromallo, Claudia

    2010-05-01

    Based on the Centennial earthquake catalog, the revised 1964-2007 EHB hypocenters catalog and the 1976-2007 CMT Harvard catalog, we have extracted the hypocenters, nodal planes and seismic moments of worldwide subduction earthquakes for the 1900-2007 period. For the 1976-2007 period, we combine the focal solutions provided by Harvard and the revised hypocenters from Engdahl et al. (1998). Older events are extracted from the Centennial catalogue (Engdahl and Villasenor, 2002) and they are used to estimate the cumulated seismic moment only. The selection criteria for the subduction earthquakes are similar to those used by Mc Caffrey (1994), i.e., we test if the focal mechanisms are consistent with 1/ shallow thrust events (depth > 70 km, positive slips, and at least one nodal plane gets dip < 45°), and, 2/ the plate interface local geometry and orientation (one nodal plane is oriented toward the volcanic arc, the azimuth of this nodal plane ranges between ± 45° with respect to the trench one, its dip ranges between ± 20° with respect to the slab one and the epicentre is located seaward of the volcanic arc). Our study concerns segments of subduction zones that fit with estimated paleoruptures associated with major events (M > 8). We assume that the seismogenic zone coincides with the distribution of 5.5 < M < 7 subduction earthquakes. We provide a map of the interplate seismogenic zones for 80% of the trench systems including dip, length, downdip and updip limits, we revisit the statistical study done by Pacheco et al. (1993) and test some empirical laws obtained for example by Ruff and Kanamori (1980) in light of a more complete, detailed, accurate and uniform description of the subduction interplate seismogenic zone. Since subduction earthquakes result from stress accumulation along the interplate and stress depends on plates kinematics, subduction zone geometry, thermal state and seismic coupling, we aim to isolate some correlations between parameters. The

  19. Plate tectonics of the Mediterranean region.

    PubMed

    McKenzie, D P

    1970-04-18

    The seismicity and fault plane solutions in the Mediterranean area show that two small rapidly moving plates exist in the Eastern Mediterranean, and such plates may be a common feature of contracting ocean basins. The results show that the concepts of plate tectonics apply to instantaneous motions across continental plate boundaries.

  20. Tectonics and Current Plate Motions of Northern Vancouver Island and the Adjacent Mainland

    NASA Astrophysics Data System (ADS)

    Jiang, Y.; Leonard, L. J.; Henton, J.; Hyndman, R. D.

    2016-12-01

    Northern Vancouver Island comprises a complex transition zone along the western margin of the North America plate, between the subducting Juan de Fuca plate to the south and the transcurrent Queen Charlotte Fault to the north off Haida Gwaii. The tectonic history and seismic potential for this region are unclear. Here we present current plate motions for northern Vancouver Island and the adjacent mainland, determined from continuous and campaign GPS measurements processed in a consistent manner. Immediately to the north of the mid-Vancouver Island Nootka Fault Zone, the northern limit of Juan de Fuca plate subduction, GPS velocity vectors show slower Explorer plate subduction than the Juan de Fuca Plate. Off northernmost Vancouver Island, the Winona Block is possibly converging at a slow rate that decreases northward to zero. We find a constant northward margin-parallel translation of up to 5 mm/year from northern Vancouver Island extending to Alaska. The southern limit of this translation coincides with areas of high heat flow that may reflect extension and the northern limit of episodic tremor and slip (ETS) on the Cascadia megathrust. The origin of the northward translation is poorly understood. We find a mainland coastal shear zone extends as far south as northern Vancouver Island where the offshore plate boundary is likely subduction. The pattern of the observed coastal shear cannot reflect interseismic locking on a major offshore transcurrent fault. The geodetically determined mainland coastal zone velocities decrease landward from 5 to 0 mm/yr across a region where no active faults have been identified and there is very little current seismicity. In Haida Gwaii, oblique convergence is apparent in the GPS data, consistent with partitioning between margin-parallel and margin-perpendicular strain. After removing the margin parallel translation from the data, we determine an average maximum locking depth of 15 km for the Queen Charlotte transcurrent fault

  1. Plates for vacuum thermal fusion

    DOEpatents

    Davidson, James C.; Balch, Joseph W.

    2002-01-01

    A process for effectively bonding arbitrary size or shape substrates. The process incorporates vacuum pull down techniques to ensure uniform surface contact during the bonding process. The essence of the process for bonding substrates, such as glass, plastic, or alloys, etc., which have a moderate melting point with a gradual softening point curve, involves the application of an active vacuum source to evacuate interstices between the substrates while at the same time providing a positive force to hold the parts to be bonded in contact. This enables increasing the temperature of the bonding process to ensure that the softening point has been reached and small void areas are filled and come in contact with the opposing substrate. The process is most effective where at least one of the two plates or substrates contain channels or grooves that can be used to apply vacuum between the plates or substrates during the thermal bonding cycle. Also, it is beneficial to provide a vacuum groove or channel near the perimeter of the plates or substrates to ensure bonding of the perimeter of the plates or substrates and reduce the unbonded regions inside the interior region of the plates or substrates.

  2. Crustal stress across the northern Arabian plate and the relationship with the plate boundary forces

    NASA Astrophysics Data System (ADS)

    Yassminh, Rayan

    The region encompassing the collision of northern Arabia with Eurasia is a tectonically heterogeneous region of distributed deformation. The northern Arabia plate is bounded to the west by the subducting Sinai plate and the left-lateral Dead Sea transform. This complexity suggests that there are multiple competing processes that may influence regional tectonics in northern Arabia and adjacent areas. Earthquake mechanisms provide insight into crustal kinematics and stress; however, reliable determination of earthquake source parameters can be challenging in a complex geological region, such as the continental collision zone between the Arabian and Eurasian plates. The goal of this study is to investigate spatial patterns of the crustal stress in the northern Arabian plate and surrounding area. The focal mechanisms used in this study are based on (1) first-motion polarities for earthquakes recorded by Syrian earthquake center during 2000-2011, and (2) regional moment tensors from broadband seismic data, from Turkey and Iraq. First motion focal mechanisms were assigned quality classifications based on the variation of both nodal planes. Regional moment tensor analysis can be significantly influenced by seismic velocity structure; thus, we have divided the study area into regions based on tectonic units. For each region, the velocity model is described using a waveform-modeling technique prior to the regional moment tensor inversion. The resulting focal mechanisms, combined with other previously published focal mechanisms for the study area, provide a basis for stress inversion analysis. The resulting deviatoric stress tensors show the spatial distribution of the maximum horizontal stress varies from NW-SE along the Dead Sea Fault to the N-S toward the east. We interpret this to reflect the eastward change from the transform to collision processes in northern Arabia. Along the Dead Sea Fault, transposition of the sigma-1 and sigma-2 to vertical and horizontal

  3. Generation and Initiation of Plate Tectonics on Terrestrail Planets

    NASA Astrophysics Data System (ADS)

    Foley, Bradford J.

    The question of why plate tectonics occurs on Earth, but not on the other planets of our solar system, is one of the most fundamental issues in geophysics and planetary science. I study this problem using numerical simulations of mantle convection with a damage-grainsize feedback (grain-damage) to constrain the conditions necessary for plate tectonics to occur on a terrestrial planet, and how plate tectonics initiates. In Chapter 2, I use numerical simulations to determine how large a viscosity ratio, between pristine lithosphere and mantle, damage can offset to allow mobile (plate-like) convection. I then use the numerical results to formulate a new scaling law to describe the boundary between stagnant lid and plate-like regimes of mantle convection. I hypothesize that damage must reduce the viscosity of shear zones in the lithosphere to a critical value, equivalent to the underlying mantle viscosity, in order for plate tectonics to occur, and demonstrate that a scaling law based on this hypothesis reproduces the numerical results. For the Earth, damage is efficient in the lithosphere and provides a viable mechanism for the operation of plate tectonics. I apply my theory to super-Earths and map out the transition between plate-like and stagnant lid convection with a "planetary plate-tectonic phase" diagram in planet size-surface temperature space. Both size and surface temperature are important, with plate tectonics being favored for larger, cooler planets. This gives a natural explanation for Earth, Venus, and Mars, and implies that plate tectonics on exoplanets should correlate with size, incident solar radiation, and atmospheric composition. In Chapters 3 and 4 I focus on the initiation of plate tectonics. In Chapter 3, I develop detailed scaling laws describing plate speed and heat flow for mantle convection with grain-damage across a wide parameter range, with the intention of applying these scaling laws to the early Earth in Chapter 4. Convection with grain

  4. Necessary Conditions for Intraplate Seismic Zones in North America

    NASA Astrophysics Data System (ADS)

    Thomas, William A.; Powell, Christine A.

    2017-12-01

    The cause of intraplate seismic zones persists as an important scientific and societal question. Most intraplate earthquakes are concentrated in specific seismic zones along or adjacent to large-scale basement structures (e.g., rifts or sutures at ancient plate boundaries) within continental crust. The major intraplate seismic zones are limited to specific segments and are not distributed along the lengths of the ancient structures. We present a new hypothesis that major intraplate seismic zones are restricted to places where concentrated crustal deformation (CCD) is overprinted on large-scale basement structures. Examples where CCD affects the stability of specific parts of large-scale structures in response to present-day stress conditions include the most active seismic zones in central and eastern North America: Charlevoix, Eastern Tennessee, and New Madrid. Our hypothesis has important implications for the assessment of seismic hazards.

  5. Convergent Plate Boundary Processes in the Archean: Evidence from Greenland

    NASA Astrophysics Data System (ADS)

    Polat, A.

    2014-12-01

    The structural, magmatic and metamorphic characteristics of Archean greenstone belts and associated TTG (tonalite, trondhjemite and granodiorite) gneisses in southern West Greenland are comparable to those of Phanerozoic convergent plate margins, suggesting that Archean continents grew mainly at subduction zones. These greenstone belts are composed mainly of tectonically juxtaposed fragments of oceanic crust including mafic to ultramafic rocks, with minor sedimentary rocks. Volcanic rocks in the greenstone belts are characterized mainly by island arc tholeiitic basalts, picrites, and boninites. The style of deformation and geometry of folds in 10 cm to 5 m wide shear zones are comparable to those occur on 1 to 50 km scale in the greenstone belts and TTG gneisses, suggesting that compressional tectonic processes operating at convergent plate boundaries were the driving force of Archean crustal accretion and growth. Field observations and trace element data suggest that Archean continental crust grew through accretion of mainly island arcs and melting of metamorphosed mafic rocks (amphibolites) in thickened arcs during multiple tectonothermal events. Fold patterns on cm to km scale are consistent with at least three phases of deformation and multiple melting events generating TTG melts that intruded mainly along shear zones in accretionary prism and magmatic arcs. It is suggested that Archean TTGs were produced by three main processes: (1) melting of thickened oceanic island arcs; (2) melting of subducted oceanic crust; and (3) differentiation of basaltic melts originating from metasomatized sub-arc mantle wedge peridotites.

  6. Chondron curvature mapping in growth plate cartilage under compressive loading.

    PubMed

    Vendra, Bhavya B; Roan, Esra; Williams, John L

    2018-05-18

    The physis, or growth plate, is a layer of cartilage responsible for long bone growth. It is organized into reserve, proliferative and hypertrophic zones. Unlike the reserve zone where chondrocytes are randomly arranged, either singly or in pairs, the proliferative and hypertrophic chondrocytes are arranged within tubular structures called chondrons. In previous studies, the strain patterns within the compressed growth plate have been reported to be nonuniform and inhomogeneous, with an apparent random pattern in compressive strains and a localized appearance of tensile strains. In this study we measured structural deformations along the entire lengths of chondrons when the physis was subjected to physiological (20%) and hyper-physiological (30% and 40%) levels of compression. This provided a means to interpret the apparent random strain patterns seen in texture correlation maps in terms of bending deformations of chondron structures and provided a physical explanation for the inhomogeneous and nonuniform strain patterns reported in previous studies. We observed relatively large bending deformations (kinking) of the chondron structures at the interface of the reserve and proliferative zones during compression. Bending in this region may induce dividing cells to align longitudinally to maintain column formation and drive longitudinal growth. Copyright © 2018 Elsevier Ltd. All rights reserved.

  7. Surface crack problems in plates

    NASA Technical Reports Server (NTRS)

    Joseph, P. F.; Erdogan, F.

    1989-01-01

    The mode I crack problem in plates under membrane loading and bending is reconsidered. The purpose is to examine certain analytical features of the problem further and to provide some new results. The formulation and the results given by the classical and the Reissner plate theories for through and part-through cracks are compared. For surface cracks the three-dimensional finite element solution is used as the basis of comparison. The solution is obtained and results are given for the crack/contact problem in a plate with a through crack under pure bending and for the crack interaction problem. Also, a procedure is developed to treat the problem of subcritical crack growth and to trace the evolution of the propagating crack.

  8. Insert metering plates for gas turbine nozzles

    DOEpatents

    Burdgick, Steven S.; Itzel, Gary; Chopra, Sanjay; Abuaf, Nesim; Correia, Victor H.

    2004-05-11

    The invention comprises a metering plate which is assembled to an impingement insert for use in the nozzle of a gas turbine. The metering plate can have one or more metering holes and is used to balance the cooling flow within the nozzle. A metering plate with multiple holes reduces static pressure variations which result from the cooling airflow through the metering plate. The metering plate can be assembled to the insert before or after the insert is inserted into the nozzle.

  9. Seafloor spreading on the Southeast Indian Ridge over the last one million years: a test of the Capricorn plate hypothesis

    NASA Astrophysics Data System (ADS)

    Conder, James A.; Forsyth, Donald W.

    2001-05-01

    Plate motions in the Indian Ocean are inconsistent with a rigid Indo-Australian plate. An equatorial, diffuse boundary dividing the plate into separate Indian and Australian plates significantly improves the fit of kinematic plate models to the spreading rates, transform azimuths, and earthquake slip vectors on the spreading center boundaries. An additional boundary, further dividing the Australian plate into Australian and Capricorn plates has been proposed to account for much of the remaining inconsistency and the pattern of intraplate earthquakes [J.-Y. Royer, R.G. Gordon, Science 277 (1997) 1268-1274]. The proposed boundary is ˜2000 km wide where it intersects the Southeast Indian Ridge. Several recent geophysical cruises to the Southeast Indian Ridge, including a cruise within the proposed boundary, provide many new data for investigating the validity of the Capricorn plate model. These new observations strongly support the hypothesis that the Capricorn plate exists. Statistical tests of the data from the Southeast Indian Ridge alone are not sufficient to confirm it, but motion about the Rodriguez Triple Junction (RTJ) suggests some non-rigidity in the Antarctica-Australia-Somalia circuit. Inferred deformation with enforced closure about the RTJ leads to an estimate of plate motion consistent with the Capricorn plate model. However, the diffuse Capricorn-Australia boundary does not extend south of the St. Paul Fracture Zone, 800 km narrower than the previously proposed boundary.

  10. Interface waves in multilayered plates.

    PubMed

    Li, Bing; Li, Ming-Hang; Lu, Tong

    2018-04-01

    In this paper, the characteristic equation of interface waves in multilayered plates is derived. With a reasonable assumption undertaken for the potential functions of longitudinal and shear waves in the nth layer medium, the characteristic equation of interface waves in the N-layered plate is derived and presented in a determinant form. The particle displacement and stress components are further presented in explicit forms. The dispersion curves and wave structures of interface waves in both a three-layered Al-Steel-Ti and a four-layered Steel-Al-Steel-Ti plate are displayed subsequently. It is observed in dispersion curves that obvious dispersion occurs on the low frequency band, whereas the phase velocities converge to the corresponding true Stoneley wave mode velocities at high frequency, and the number of interface wave modes equals the number of interfaces in multilayered plates (if all individual interfaces satisfy the existence condition of Stoneley waves). The wave structures reveal that the displacement components of interface waves are relatively high at interfaces, and the amplitude distribution varies from frequency to frequency. In the end, a similarly structured three-layered Al-Steel-Ti plate is tested. In this experiment, theoretical group velocity and experimental group velocity are compared. According to the discussion and comparison, the predicted group velocities are in good agreement with the experimental results. Thus, the theory of interface wave in multilayered plates is proved. As a result, the proposed theoretical approach represents a leap forward in the understanding of how to promote the characteristic study and practical applications of interface waves in multilayered structures.

  11. Compiling an earthquake catalogue for the Arabian Plate, Western Asia

    NASA Astrophysics Data System (ADS)

    Deif, Ahmed; Al-Shijbi, Yousuf; El-Hussain, Issa; Ezzelarab, Mohamed; Mohamed, Adel M. E.

    2017-10-01

    The Arabian Plate is surrounded by regions of relatively high seismicity. Accounting for this seismicity is of great importance for seismic hazard and risk assessments, seismic zoning, and land use. In this study, a homogenous earthquake catalogue of moment-magnitude (Mw) for the Arabian Plate is provided. The comprehensive and homogenous earthquake catalogue provided in the current study spatially involves the entire Arabian Peninsula and neighboring areas, covering all earthquake sources that can generate substantial hazard for the Arabian Plate mainland. The catalogue extends in time from 19 to 2015 with a total number of 13,156 events, of which 497 are historical events. Four polygons covering the entire Arabian Plate were delineated and different data sources including special studies, local, regional and international catalogues were used to prepare the earthquake catalogue. Moment magnitudes (Mw) that provided by original sources were given the highest magnitude type priority and introduced to the catalogues with their references. Earthquakes with magnitude differ from Mw were converted into this scale applying empirical relationships derived in the current or in previous studies. The four polygons catalogues were included in two comprehensive earthquake catalogues constituting the historical and instrumental periods. Duplicate events were identified and discarded from the current catalogue. The present earthquake catalogue was declustered in order to contain only independent events and investigated for the completeness with time of different magnitude spans.

  12. Progress in thermomechanical control of steel plates and their commercialization

    PubMed Central

    Nishioka, Kiyoshi; Ichikawa, Kazutoshi

    2012-01-01

    The water-cooled thermomechanical control process (TMCP) is a technology for improving the strength and toughness of water-cooled steel plates, while allowing control of the microstructure, phase transformation and rolling. This review describes metallurgical aspects of the microalloying of steel, such as niobium addition, and discusses advantages of TMCP, for example, in terms of weldability, which is reduced upon alloying. Other covered topics include the development of equipment, distortions in steel plates, peripheral technologies such as steel making and casting, and theoretical modeling, as well as the history of property control in steel plate production and some early TMCP technologies. We provide some of the latest examples of applications of TMCP steel in various industries such as shipbuilding, offshore structures, building construction, bridges, pipelines, penstocks and cryogenic tanks. This review also introduces high heat-affected-zone toughness technologies, wherein the microstructure of steel is improved by the addition of fine particles of magnesium-containing sulfides and magnesium- or calcium-containing oxides. We demonstrate that thanks to ongoing developments TMCP has the potential to meet the ever-increasing demands of steel plates. PMID:27877477

  13. Progress in thermomechanical control of steel plates and their commercialization

    NASA Astrophysics Data System (ADS)

    Nishioka, Kiyoshi; Ichikawa, Kazutoshi

    2012-04-01

    The water-cooled thermomechanical control process (TMCP) is a technology for improving the strength and toughness of water-cooled steel plates, while allowing control of the microstructure, phase transformation and rolling. This review describes metallurgical aspects of the microalloying of steel, such as niobium addition, and discusses advantages of TMCP, for example, in terms of weldability, which is reduced upon alloying. Other covered topics include the development of equipment, distortions in steel plates, peripheral technologies such as steel making and casting, and theoretical modeling, as well as the history of property control in steel plate production and some early TMCP technologies. We provide some of the latest examples of applications of TMCP steel in various industries such as shipbuilding, offshore structures, building construction, bridges, pipelines, penstocks and cryogenic tanks. This review also introduces high heat-affected-zone toughness technologies, wherein the microstructure of steel is improved by the addition of fine particles of magnesium-containing sulfides and magnesium- or calcium-containing oxides. We demonstrate that thanks to ongoing developments TMCP has the potential to meet the ever-increasing demands of steel plates.

  14. Detection of earthquake swarms at subduction zones globally: Insights into tectonic controls on swarm activity

    NASA Astrophysics Data System (ADS)

    Nishikawa, T.; Ide, S.

    2017-07-01

    Earthquake swarms are characterized by an increase in seismicity rate that lacks a distinguished main shock and does not obey Omori's law. At subduction zones, they are thought to be related to slow-slip events (SSEs) on the plate interface. Earthquake swarms in subduction zones can therefore be used as potential indicators of slow-slip events. However, the global distribution of earthquake swarms at subduction zones remains unclear. Here we present a method for detecting such earthquake sequences using the space-time epidemic-type aftershock-sequence model. We applied this method to seismicity (M ≥ 4.5) recorded in the Advanced National Seismic System catalog at subduction zones during the period of 1995-2009. We detected 453 swarms, which is about 6.7 times the number observed in a previous catalog. Foreshocks of some large earthquakes are also detected as earthquake swarms. In some subduction zones, such as at Ibaraki-Oki, Japan, swarm-like foreshocks and ordinary swarms repeatedly occur at the same location. Given that both foreshocks and swarms are related to SSEs on the plate interface, these regions may have experienced recurring SSEs. We then compare the swarm activity and tectonic properties of subduction zones, finding that swarm activity is positively correlated with curvature of the incoming plate before subduction. This result implies that swarm activity is controlled either by hydration of the incoming plate or by heterogeneity on the plate interface due to fracturing related to slab bending.

  15. Alps, Carpathians and Dinarides-Hellenides: about plates, micro-plates and delaminated crustal blocks

    NASA Astrophysics Data System (ADS)

    Schmid, Stefan

    2014-05-01

    thickened crust ripped of the African plate, invaded the northern part of this oceanic embayment, virtually floating on asthenospheric mantle. The presently still surviving semi-detached Vrancea slab in Romania manifests of the combined effect of roll back and delamination of mantle lithosphere. On the other hand Tisza-Dacia, another crustal block formerly ripped off the European plate and forming a single entity since mid-Cretaceous times, also at least partly floating on asthenospheric mantle, invaded the Carpathian embayment from the south. Thereby the Tisza-Dacia crustal block underwent clockwise rotation by as much as 90° due to the corner effect of the Moesian platform firmly attached to Europe since mid-Cretaceous times (Ustaszewski et al. 2008). In the Dinaric-Aegean realm collision occurred much earlier than in the Alps and the Carpathians, i.e. at around the Cretaceous-Cenozoic boundary, provided that one accepts that there is yet no convincing evidence for the existence of a second "Pindos oceanic domain" closing later, i.e. in Eocene times. However, in spite of early collision, the old subduction zone that consumed the northern branch of Neotethys (Meliata-Vardar) since at least mid-Cretaceous times persisted in the eastern Hellenides (but not in the Dinarides) until now, penetrating the transition zone all the way to a depth of some 1500km (Bijwaard et al. 1998). Continued subduction of mantle lithosphere in the Aegean since 60 Ma was concomitant with complete delamination of lithospheric mantle and lower crust from non-subducted or re-exhumed high pressure crustal flakes of largely continental derivation that were piled up to form the subsequently extended Hellenic orogen (Jolivet & Brun 2010). At around 25 Ma when the southern branch of Neotethys (the present-day Eastern Mediterranean ocean) entered this subduction zone, massive extension and core complex formation in the upper plate combined with an acceleration of south-directed hinge retreat of the lower

  16. Heterogeneous structure of the incoming plate in the Japan Trench

    NASA Astrophysics Data System (ADS)

    Nakamura, Y.; Fujie, G.; Yamaguchi, A.; Kodaira, S.; Miura, S.

    2017-12-01

    We have conducted seismic surveys in around the Japan Trench subduction zone, northeastern Japan, to investigate the structural features of the incoming Pacific plate and the frontal prism. Thickness of the hemiplegic sediments on the deposited on the incoming Pacific plate shows the variation along trench axis between 200 and 600 ms two-way travel time (TWT). This is remarkably thinner than other subduction zones with megathrust earthquakes like Sumatra subduction zone. Off Miyagi, central part of the Japan Trench which is the main ruptured region of 2011 Tohoku earthquake, has 200 - 300 ms TWT of the incoming sediments thickness. Off Iwate, northern part of the Japan Trench, has thicker incoming sediments 500 ms TWT, and Off Fukushima, southern part of the Japan Trench, has 300 - 400 ms TWT. We found at least three areas with anomalously thin sediments; Area I: 38N 145N, Area II: 39.5N 144.5E, Area III: 39N 144.5N. At the Area I, located on the outer rise off Miyagi, the receiver function analysis using Ocean Bottom Seismograph data revealed the existence of PS conversion surfaces below the interpreted basement on the seismic sections. This implies that the interface between sediments and the igneous basement is located below the interpreted basement reflections. Previous studies suggested the existence of the petit spots in this Area I. Area II shows apparently very thin sediments near the trench axis on seismic profiles, where the petit spot volcanism was observed. Shallow sediment sampling conducted in this area indicates no major surface erosion. These observations suggest that the petit spot volcanism, like sill intrusion, masked the original deeper basement reflections and caused the apparent thin sediments on seismic profiles. Area III also has thin sediments and rough basement topography, which has possibly been caused by another petit spot activity. Petit spot area with apparent very thin sediments in the trench axis (Area II) is located next to the

  17. Plate convergence at the westernmost Philippine Sea Plate

    NASA Astrophysics Data System (ADS)

    Wu, Wen-Nan; Hsu, Shu-Kun; Lo, Chung-Liang; Chen, How-Wei; Ma, Kuo-Fong

    2009-03-01

    To understand the convergent characteristics of the westernmost plate boundary between the Philippine Sea Plate (PSP) and Eurasian Plate (EP), we have calculated the stress states of plate motion by focal mechanisms. Cataloged by the Harvard centroid moment tensor solutions (Harvard CMT) and the Broadband Array in Taiwan (BATS) moment tensor, 251 focal mechanisms are used to determine the azimuths of the principal stress axes. We first used all the data to derive the mean stress tensor of the study area. The inversion result shows that the stress regime has a maximum compression along the direction of azimuth N299°. This result is consistent with the general direction of the rigid plate motion between the PSP and EP in the study area. In order to understand the spatial variation of the regional stress pattern, we divided the study area into six sub-areas (blocks A to F) based on the feature of the free-air gravity anomaly. We compare the compressive directions obtained from the stress inversion with the plate motions calculated by the Euler pole and the Global Positioning System (GPS) analysis. As a result, the azimuth of the maximum stress axis, σ1, generally agrees with the directions of the theoretical plate motion and GPS velocity vectors except block C (Lanhsu region) and block F (Ilan plain region). The discrepancy of convergent direction near the Ilan plain region is probably caused by the rifting of the Okinawa Trough. The deviation of the σ1 azimuth in the Lanhsu region could be attributed to a southwestward extrusion of the Luzon Arc (LA) block between 21°N and 22°N whose northern boundary may be associated with the right-lateral NE-SW trending fault (i.e. Huatung Fault, HF) along the Taitung Canyon. Comparing the σ1 stress patterns between block C and block D, great strain energy along HF may not be completely released yet. Alternatively, the upper crust of block C may significantly have decoupled from its lower crust or uppermost mantle.

  18. Indentation and Lateral Escape in Western Ishtar Terra, Venus — An Analog for Deformation of the Archean Abitibi Subprovince, Superior Craton, Canada Without Plate Tectonics

    NASA Astrophysics Data System (ADS)

    Harris, L. B.; Bédard, J. H.

    2015-05-01

    Radar about Lakshmi Planum, Venus, shows regional transcurrent shear zones, folds and thrusts formed by indentation and lateral escape. The Archean Abitibi subprovince Canada shows identical structures suggesting a similar, non-plate tectonic origin.

  19. Temperature Models for the Mexican Subduction Zone

    NASA Astrophysics Data System (ADS)

    Manea, V. C.; Kostoglodov, V.; Currie, C.; Manea, M.; Wang, K.

    2002-12-01

    It is well known that the temperature is one of the major factors which controls the seismogenic zone. The Mexican subduction zone is characterized by a very shallow flat subducting interplate in its central part (Acapulco, Oaxaca), and deeper subduction slabs northern (Jalisco) and southern (Chiapas). It has been proposed that the seismogenic zone is controlled, among other factors, by a temperature. Therefore, we have developed four two-dimensional steady state thermal models for Jalisco, Guerrero, Oaxaca and Chiapas. The updip limit of the seismogenic zone is taken between 100 §C and 150 §C, while the downdip limit is thought to be at 350 §C because of the transition from stick-slip to stable-sliding. The shape of the subducting plate is inferred from gravity and seismicity. The convergence velocity between oceanic and continental lithospheric plates is taken as the following: 5 cm/yr for Jalisco profile, 5.5 for Guerrero profile, 5.8 for Oaxaca profile, and 7.8 for Chiapas profile. The age of the subducting plates, since they are young, and provides the primary control on the forearc thermal structure, are as the following: 11 My for Jalisco profile, 14.5 My for Guerrero profile, 15 My for Oaxaca profile, and 28 My for Chiapas profile. We also introduced in the models a small quantity of frictional heating (pore pressure ratio 0.98). The value of 0.98 for pore pressure ratio was obtained for the Guerrero profile, in order to fit the intersection between the 350 §C isotherm and the subducting plate at 200 Km from trench. The value of 200 km coupling zone from trench is inferred from GPS data for the steady interseismic period and also for the last slow aseismic slip that occurred in Guerrero in 2002. We have used this value of pore pressure ratio (0.98) for all the other profiles. For the others three profiles we obtained the following coupling extents: Jalisco - 100 km, Oaxaca - 170 km and Chiapas - 125 km (from the trench). Independent constrains of the

  20. Acoustic Reverse Time Migration of the Cascadia Subduction Zone Dataset

    NASA Astrophysics Data System (ADS)

    Jia, L.; Mallick, S.

    2017-12-01

    Reverse time migration (RTM) is a wave-equation based migration method, which provides more accurate images than ray-based migration methods, especially for the structures in deep areas, making it an effective tool for imaging the subduction plate boundary. In this work, we extend the work of Fortin (2015) and applied acoustic finite-element RTM on the Cascadia Subduction Zone (CSZ) dataset. The dataset was acquired by Cascadia Open-Access Seismic Transects (COAST) program, targeting the megathrust in the central Cascadia subduction zone (Figure 1). The data on a 2D seismic reflection line that crosses the Juan de Fuca/North American subduction boundary off Washington (Line 5) were pre-processed and worked through Kirchhoff prestack depth migration (PSDM). Figure 2 compares the depth image of Line 5 of the CSZ data using Kirchhoff PSDM (top) and RTM (bottom). In both images, the subducting plate is indicated with yellow arrows. Notice that the RTM image is much superior to the PSDM image by several aspects. First, the plate boundary appears to be much more continuous in the RTM image than the PSDM image. Second, the RTM image indicates the subducting plate is relatively smooth on the seaward (west) side between 0-50 km. Within the deformation front of the accretionary prism (50-80 km), the RTM image shows substantial roughness in the subducting plate. These features are not clear in the PSDM image. Third, the RTM image shows a lot of fine structures below the subducting plate which are almost absent in the PSDM image. Finally, the RTM image indicates that the plate is gently dipping within the undeformed sediment (0-50 km) and becomes steeply dipping beyond 50 km as it enters the deformation front of the accretionary prism. Although the same conclusion could be drawn from the discontinuous plate boundary imaged by PSDM, RTM results are far more convincing than the PSDM.

  1. A Simplified Model for the Effect of Weld-Induced Residual Stresses on the Axial Ultimate Strength of Stiffened Plates

    NASA Astrophysics Data System (ADS)

    Chen, Bai-Qiao; Guedes Soares, C.

    2018-03-01

    The present work investigates the compressive axial ultimate strength of fillet-welded steel-plated ship structures subjected to uniaxial compression, in which the residual stresses in the welded plates are calculated by a thermo-elasto-plastic finite element analysis that is used to fit an idealized model of residual stress distribution. The numerical results of ultimate strength based on the simplified model of residual stress show good agreement with those of various methods including the International Association of Classification Societies (IACS) Common Structural Rules (CSR), leading to the conclusion that the simplified model can be effectively used to represent the distribution of residual stresses in steel-plated structures in a wide range of engineering applications. It is concluded that the widths of the tension zones in the welded plates have a quasi-linear behavior with respect to the plate slenderness. The effect of residual stress on the axial strength of the stiffened plate is analyzed and discussed.

  2. A seismic reflection image for the base of a tectonic plate.

    PubMed

    Stern, T A; Henrys, S A; Okaya, D; Louie, J N; Savage, M K; Lamb, S; Sato, H; Sutherland, R; Iwasaki, T

    2015-02-05

    Plate tectonics successfully describes the surface of Earth as a mosaic of moving lithospheric plates. But it is not clear what happens at the base of the plates, the lithosphere-asthenosphere boundary (LAB). The LAB has been well imaged with converted teleseismic waves, whose 10-40-kilometre wavelength controls the structural resolution. Here we use explosion-generated seismic waves (of about 0.5-kilometre wavelength) to form a high-resolution image for the base of an oceanic plate that is subducting beneath North Island, New Zealand. Our 80-kilometre-wide image is based on P-wave reflections and shows an approximately 15° dipping, abrupt, seismic wave-speed transition (less than 1 kilometre thick) at a depth of about 100 kilometres. The boundary is parallel to the top of the plate and seismic attributes indicate a P-wave speed decrease of at least 8 ± 3 per cent across it. A parallel reflection event approximately 10 kilometres deeper shows that the decrease in P-wave speed is confined to a channel at the base of the plate, which we interpret as a sheared zone of ponded partial melts or volatiles. This is independent, high-resolution evidence for a low-viscosity channel at the LAB that decouples plates from mantle flow beneath, and allows plate tectonics to work.

  3. Intercellular signaling pathways active during and after growth and differentiation of the lumbar vertebral growth plate.

    PubMed

    Dahia, Chitra Lekha; Mahoney, Eric J; Durrani, Atiq A; Wylie, Christopher

    2011-06-15

    Vertebral growth plates at different postnatal ages were assessed for active intercellular signaling pathways. To generate a spatial and temporal map of the major signaling pathways active in the postnatal mouse lumbar vertebral growth plate. The growth of all long bones is known to occur by cartilaginous growth plates. The growth plate is composed of layers of chondrocyets that actively proliferate, differentiate, die and, are replaced by bone. The role of major cell signaling pathways has been suggested for regulation of the fetal long bones. But not much is known about the molecular or cellular signals that control the postnatal vertebral growth plate and hence postnatal vertebral bone growth. Understanding such molecular mechanisms will help design therapeutic treatments for vertebral growth disorders such as scoliosis. Antibodies against activated downstream intermediates were used to identify cells in the growth plate responding to BMP, TGFβ, and FGF in cryosections of lumbar vertebrae from different postnatal age mice to identify the zones that were responding to these signals. Reporter mice were used to identify the chondrocytes responding to hedgehog (Ihh), and Wnt signaling. We present a spatial/temporal map of these signaling pathways during growth, and differentiation of the mouse lumbar vertebral growth plate. During growth and differentiation of the vertebral growth plate, its different components respond at different times to different intercellular signaling ligands. Response to most of these signals is dramatically downregulated at the end of vertebral growth.

  4. Lithospheric Structure and Isostasy of Central Andes: Implication for plate Coupling

    NASA Astrophysics Data System (ADS)

    Mahatsente, R.; Rutledge, S.

    2017-12-01

    A significant section of the Peru-Chile convergent zone is building up stresses. The interseismic coupling in northern and southern Peru is significantly high indicating, elastic energy accumulation since the 1746 and 1868 earthquakes of magnitude 8.6 and 8.8 , respectively. Similar seismic patterns have also been observed in Central Chile. The plate interface beneath Central Chile is highly coupled, and the narrow zones of low coupling separate seismic gaps. The reasons for the seismic gaps and plate coupling are yet unknown, but the configuration of the slab is thought to be the main factor. Here, we assessed the locking mechanism and isostatic state of the Central Andes based on gravity models of the crust and upper mantle structure. The density models are based on satellite gravity data and are constrained by velocity models and earthquake hypocenters. The gravity models indicate a high-density batholithic structure in the fore-arc, overlying the subducting Nazca plate. This high-density body pushes downward on the slab, causing the slab to lock with the overlying continental plate. The increased compressive stress closer to the trench, due to the increased contact area between the subducting and overriding plates, may have increased the plate coupling in the Central Andes. Thus, trench parallel crustal thickness and density variations along the Central Andes and buoyancy force on the subducting Nazca plate may control plate coupling and asperity generation. The western part of the Central Andes may be undercompensated. There is a residual topography of 800 m in the western part of the Central Andes that cannot be explained by the observed crustal thicknesses. Thus, part of the observed topography in the western part of the Central Andes may be dynamically supported by mantle wedge flow below the overriding plate.

  5. Silurian to Early Carboniferous plate tectonic model of Central Europe

    NASA Astrophysics Data System (ADS)

    Golonka, Jan; Barmuta, Jan; Barmuta, Maria

    2014-05-01

    The presented plate tectonic model focuses on Silurian to Early Carboniferous evolution of Central Europe with special attention given to the Sudetes region (north and north-east part of the Bohemian Massif). During our studies, we tested alternative models focused on the position of the Armorican terranes, known as the Armorican Terrane Assembly (ATA) (e.g.: Matte, 2001) and tried to refine the existing reconstructions, which describe Armorica as an individual continent during the Late Silurian and Devonian (e.g. Lewandowski, 2003, Winchester, 2002). Our plate tectonic model depict that these small blocks were scattered along the northern margin of Gondwana, where they formed the "Armorican Spour" as suggested by Kroner and Romer (2013). The seaways were present between blocks. Because of the north dipping subduction zone along the southern margin of the Laurussia continent the back-arc basin and island arc were formed. The narrowing of the Rheic ocean led to the complicated collision of Gondwana and Laurussia. Three main stages of this event can be distinguished: (1) collision of the Armorican Spour with the Laurussian island arc, (2) back-arc basin closure, (3) final Gondwana and Laurussian collision. Those stages correlate well with Variscan Subduction Zone System proposed by Kroner and Romer (2013). Interactive modeling performed in GPlates, shows that the presented model is valid from kinematic and geometrical point of view. Kroner U., Romer R., L., 2013, Two plates - many subduction zones: the Variscan orogeny reconsidered. Gondwana Research, 24: 298-329. Lewandowski M., 2003, Assembly of Pangea: Combined paleomagnetic and paleoclimatic approach, Advances in Geophysics, 46: 199-236 Matte P., 2001, The Variscan collage and orogeny (480 290 Ma) and the tectonic definition of the Armorica microplate: a review. Terra Nova, 13: 122¨C128. Winchester J., A., The Pace TMR Network Team, 2002, Palaeozoic amalgamation of Central Europe: new results from recent

  6. Shallow depth of seismogenic coupling in southern Mexico: implications for the maximum size of earthquakes in the subduction zone

    NASA Astrophysics Data System (ADS)

    Suárez, Gerardo; Sánchez, Osvaldo

    1996-01-01

    Studies of locally recorded microearthquakes and the centroidal depths of the largest earthquakes analyzed using teleseismic data show that the maximum depth of thrust faulting along the Mexican subduction zone is anomalously shallow. This observed maximum depth of about 25 ± 5 km is about half of that observed in most subduction zones of the world. A leveling line that crosses the rupture zone of the 19 September 1985 Michoacan event was revisited after the earthquake and it shows anomalously low deformation during the earthquake. The comparison between the observed coseismic uplift and dislocation models of the seismogenic interplate contact that extend to depths ranging from 20 to 40 km shows that the maximum depth at which seismic slip took place is about 20 km. This unusually shallow and narrow zone of seismogenic coupling apparently results in the occurrence of thrust events along the Mexican subduction zone that are smaller than would be expected for a trench where a relatively young slab subducts at a rapid rate of relative motion. A comparison with the Chilean subduction zone shows that the plate interface in Mexico is half that in Chile, not only in the down-dip extent of the seismogenic zone of plate contact, but also in the distance of the trench from the coast and in the thickness of the upper continental plate. It appears that the narrow plate contact produced by this particular plate geometry in Mexico is the controlling variable defining the size of the largest characteristic earthquakes in the Mexican subduction zone.

  7. Comment on "Intermittent plate tectonics?".

    PubMed

    Korenaga, Jun

    2008-06-06

    Silver and Behn (Reports, 4 January 2008, p. 85) proposed that intermittent plate tectonics may resolve a long-standing paradox in Earth's thermal evolution. However, their analysis misses one important term, which subsequently brings their main conclusion into question. In addition, the Phanerozoic eustasy record indicates that the claimed effect of intermittency is probably weak.

  8. Survey of ion plating sources

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1979-01-01

    Ion plating is a plasma deposition technique where ions of the gas and the evaporant have a decisive role in the formation of a coating in terms of adherence, coherence, and morphological growth. The range of materials that can be ion plated is predominantly determined by the selection of the evaporation source. Based on the type of evaporation source, gaseous media and mode of transport, the following will be discussed: resistance, electron beam sputtering, reactive and ion beam evaporation. Ionization efficiencies and ion energies in the glow discharge determine the percentage of atoms which are ionized under typical ion plating conditions. The plating flux consists of a small number of energetic ions and a large number of energetic neutrals. The energy distribution ranges from thermal energies up to a maximum energy of the discharge. The various reaction mechanisms which contribute to the exceptionally strong adherence - formation of a graded substrate/coating interface are not fully understood, however the controlling factors are evaluated. The influence of process variables on the nucleation and growth characteristics are illustrated in terms of morphological changes which affect the mechanical and tribological properties of the coating.

  9. Plated wire random access memories

    NASA Technical Reports Server (NTRS)

    Gouldin, L. D.

    1975-01-01

    A program was conducted to construct 4096-work by 18-bit random access, NDRO-plated wire memory units. The memory units were subjected to comprehensive functional and environmental tests at the end-item level to verify comformance with the specified requirements. A technical description of the unit is given, along with acceptance test data sheets.

  10. Double-Plate Penetration Equations

    NASA Technical Reports Server (NTRS)

    Hayashida, K. B.; Robinson, J. H.

    2000-01-01

    This report compares seven double-plate penetration predictor equations for accuracy and effectiveness of a shield design. Three of the seven are the Johnson Space Center original, modified, and new Cour-Palais equations. The other four are the Nysmith, Lundeberg-Stern-Bristow, Burch, and Wilkinson equations. These equations, except the Wilkinson equation, were derived from test results, with the velocities ranging up to 8 km/sec. Spreadsheet software calculated the projectile diameters for various velocities for the different equations. The results were plotted on projectile diameter versus velocity graphs for the expected orbital debris impact velocities ranging from 2 to 15 km/sec. The new Cour-Palais double-plate penetration equation was compared to the modified Cour-Palais single-plate penetration equation. Then the predictions from each of the seven double-plate penetration equations were compared to each other for a chosen shield design. Finally, these results from the equations were compared with test results performed at the NASA Marshall Space Flight Center. Because the different equations predict a wide range of projectile diameters at any given velocity, it is very difficult to choose the "right" prediction equation for shield configurations other than those exactly used in the equations' development. Although developed for various materials, the penetration equations alone cannot be relied upon to accurately predict the effectiveness of a shield without using hypervelocity impact tests to verify the design.

  11. Repair Plate Research Results Released

    Treesearch

    Tom McLain

    1993-01-01

    The Pallet and Container Research Laboratory, Virginia Polytechnic Institute and State University, in cooperation with NWPCA and the Southern Research Station (USDA Forest Service), embarked on a research project two years ago to evaluate the use of metal connector plates (MCP) for the repair and reinforcement of stringer-class pallets. This article discusses the...

  12. Corrosion resistant metallic bipolar plate

    DOEpatents

    Brady, Michael P [Oak Ridge, TN; Schneibel, Joachim H [Knoxville, TN; Pint, Bruce A [Knoxville, TN; Maziasz, Philip J [Oak Ridge, TN

    2007-05-01

    A corrosion resistant, electrically conductive component such as a bipolar plate for a PEM fuel cell includes 20 55% Cr, balance base metal such as Ni, Fe, or Co, the component having thereon a substantially external, continuous layer of chromium nitride.

  13. The seismotectonics of plate boundaries

    NASA Technical Reports Server (NTRS)

    Berger, J.; Brune, J. N.; Goodkind, J.; Wyatt, F.; Agnew, D. C.; Beaumont, C.

    1981-01-01

    Research on the seismotectonics of plate boundaries is summarized. Instrumental development and an observational program designed to study various aspects of the seismotectonics of southern California and the northern Gulf of California are described. A unique superconducting gravimeter was further developed and supported under this program for deployment and operation at several sites. Work on Earth tides is also discussed.

  14. License Plate Recognition System for Indian Vehicles

    NASA Astrophysics Data System (ADS)

    Sanap, P. R.; Narote, S. P.

    2010-11-01

    We consider the task of recognition of Indian vehicle number plates (also called license plates or registration plates in other countries). A system for Indian number plate recognition must cope with wide variations in the appearance of the plates. Each state uses its own range of designs with font variations between the designs. Also, vehicle owners may place the plates inside glass covered frames or use plates made of nonstandard materials. These issues compound the complexity of automatic number plate recognition, making existing approaches inadequate. We have developed a system that incorporates a novel combination of image processing and artificial neural network technologies to successfully locate and read Indian vehicle number plates in digital images. Commercial application of the system is envisaged.

  15. A new global plate velocity model using space geodetic data, REVEL

    NASA Astrophysics Data System (ADS)

    Sella, G. F.; Dixon, T. H.; Mao, A.; Stein, S.

    2001-12-01

    Our model describes the relative velocities of 19 plates and continental blocks, and is derived from publicly available space geodetic (primarily GPS) data for the period 1993-2000. We include an independent and rigorous estimate for GPS velocity uncertainties in order to assess plate rigidity, and propagate these uncertainties to the velocity predictions. By excluding sites that may be influenced by seismic cycle effects within the plate boundary zone as well sites affected by glacial isostatic adjustment, we believe the plate velocity model is representative of geologically Recent motions (last ~10,000 years) and have termed it REVEL, for Recent velocity. Departures from short term rigid plate behaviour due to glacial isostatic adjustment are clearly observed for North America and Eurasia. Australia shows possible differences from rigid plate behavior in a manner consistent with its mapped intraplate stress field. We see statistically significant differences between the velocity predictions of REVEL-2000 and those of the NUVEL-1A geologic model for about one third of tested plate pairs. Pacific-North America motion and motion of the Caribbean plate with respect to North and South America are significantly faster than NUVEL-1A, presumably reflecting systematic errors in the geological model because the relevant rate data do not reflect the full plate rate. Many other differences between the geodetic and geological models appear to reflect real velocity changes over the last few million years. Nubia-Arabia and Arabia-Eurasia appear to be slowing, perhaps related to the collision of Arabia with Eurasia and consequent increased resistance to Arabia's northward motion Several other plate pairs, including Nazca-Pacific, Nazca-South America and Nubia-South America, are experiencing gradual slowing that dates back to about 25 Ma. This is the time of the initiation of the modern Andes mountains, and we speculate that associated crustal thickening on the leading edge of

  16. Subduction hinge migration: The backwards component of plate tectonics

    NASA Astrophysics Data System (ADS)

    Stegman, D.; Freeman, J.; Schellart, W.; Moresi, L.; May, D.

    2005-12-01

    There are approximately 50 distinct segments of subduction zones in the world, of which 40% have oceanic lithosphere subducting under oceanic lithosphere. All of these ocean-ocean systems are currently experiencing hinge-rollback, with the exception of 2 (Mariana and Kermadec). In hinge-rollback, the surface trace of the suduction zone (trench) is moving in the opposite direction as the plate is moving (i.e. backwards). Coincidentally, the fastest moving plate boundary in the world is actually the Tonga trench at an estimated 17 cm/yr (backwards). Although this quite important process was recognized soon after the birth of plate tectonic theory (Elsasser, 1971), it has received only a limited amount of attention (Garfunkel, 1986; Kincaid and Olson, 1987) until recently. Laboratory models have shown that having a three dimensional experiment is essential in order to build a correct understanding of subduction. We have developed a numerical model with the neccessary 3-D geometry capable of investigating some fundamental questions of plate tectonics: How does hinge-rollback feedback into surface tectonics and mantle flow? What can we learn about the forces that drive plate tectonics by studying hinge-rollback? We will present a quantatitive analysis of the effect of the lateral width of subduction zones, the key aspect to understanding the nature of hinge-rollback. Additionally, particular emphasis has been put on gaining intuition through the use of movies (a 3-D rendering of the numerical models), illustrating the time evolution of slab interactions with the lower mantle as seen in such fields as velocity magnitude, strain rate, viscosity, as well as the toroidal and poloidal components of induced flow. This investigation is well-suited to developing direct comparisons with geological and geophysical observations such as geodetically determined hinge retreat rates, geochemical and petrological observations of arc volcanics and back-arc ridge basalts, timing and

  17. Formation of Island Arc-Trench System due to Plate Subduction on the Basis of Elastic Dislocation Theory

    NASA Astrophysics Data System (ADS)

    Fukahata, Y.; Matsu'ura, M.

    2015-12-01

    The most conspicuous cumulative deformation in subduction zones is the formation of island arc-trench system. A pair of anomalies in topography and free-air gravity, high in the arc and low around the trench, is observed without exceptions all over the world. Since the 1960s, elastic dislocation theory has been widely used to interpret coseismic crustal deformation. For the modeling of longer-term crustal deformation, it is necessary to consider viscoelastic properties of the asthenosphere. By simply applying elastic-viscoelastic dislocation theory to plate subduction, Matsu'ura and Sato (1989, GJI) have shown that some crustal deformation remains after the completion of one earthquake cycle, which means that crustal deformation accumulates with time in a long term due to plate subduction. In fact, by constructing a plate interface model in and around Japan, Hashimoto, Fukui and Matsu'ura (2004, PAGEOPH) have demonstrated that the computed vertical displacements due to steady plate subduction well explain the observed free-air gravity anomaly pattern. Recently, we got a lucid explanation of crustal deformation due to plate subduction. In subduction zones, oceanic plates bend and descend into the mantle. Because the bending of oceanic plates is usually not spontaneous, there exists kinematic interaction between the oceanic and overriding plates, which causes cumulative deformation of the overriding plate. This may be understood based on the law of action and reaction: one is bending of an oceanic plate and the other is deformation of the overriding plate. As a special case, it is useful to consider plate subduction along a part of true circle. In this case, crustal deformation due to steady subduction is solely caused by the effect of gravity, because dislocation along a circle does not cause any intrinsic internal deformation. When an oceanic plate is descending along an arcuate plate interface from the right-hand side, according to dislocation theory, the oceanic

  18. Swath sonar mapping of Earth's submarine plate boundaries

    NASA Astrophysics Data System (ADS)

    Carbotte, S. M.; Ferrini, V. L.; Celnick, M.; Nitsche, F. O.; Ryan, W. B. F.

    2014-12-01

    The recent loss of Malaysia Airlines flight MH370 in an area of the Indian Ocean where less than 5% of the seafloor is mapped with depth sounding data (Smith and Marks, EOS 2014) highlights the striking lack of detailed knowledge of the topography of the seabed for much of the worlds' oceans. Advances in swath sonar mapping technology over the past 30 years have led to dramatic improvements in our capability to map the seabed. However, the oceans are vast and only an estimated 10% of the seafloor has been mapped with these systems. Furthermore, the available coverage is highly heterogeneous and focused within areas of national strategic priority and community scientific interest. The major plate boundaries that encircle the globe, most of which are located in the submarine environment, have been a significant focus of marine geoscience research since the advent of swath sonar mapping. While the location of these plate boundaries are well defined from satellite-derived bathymetry, significant regions remain unmapped at the high-resolutions provided by swath sonars and that are needed to study active volcanic and tectonic plate boundary processes. Within the plate interiors, some fossil plate boundary zones, major hotspot volcanoes, and other volcanic provinces have been the focus of dedicated research programs. Away from these major tectonic structures, swath mapping coverage is limited to sparse ocean transit lines which often reveal previously unknown deep-sea channels and other little studied sedimentary structures not resolvable in existing low-resolution global compilations, highlighting the value of these data even in the tectonically quiet plate interiors. Here, we give an overview of multibeam swath sonar mapping of the major plate boundaries of the globe as extracted from public archives. Significant quantities of swath sonar data acquired from deep-sea regions are in restricted-access international archives. Open access to more of these data sets would

  19. Seismicity of the Earth 1900-2013, seismotectonics of South America (Nazca Plate Region)

    USGS Publications Warehouse

    Hayes, Gavin P.; Smoczyk, Gregory M.; Benz, Harley M.; Furlong, Kevin P.; Villaseñor, Antonio

    2015-01-01

    The South American arc extends over 7,000 kilometers (km), from the Chilean margin triple junction offshore of southern Chile, to its intersection with the Panama fracture zone, offshore of the southern coast of Panama in Central America. It marks the plate boundary between the subducting Nazca plate and the South America plate, where the oceanic crust and lithosphere of the Nazca plate begin their descent into the mantle beneath South America. The convergence associated with this subduction process is responsible for the uplift of the Andes Mountains, and for the active volcanic chain present along much of this deformation front. Relative to a fixed South America plate, the Nazca plate moves slightly north of eastwards at a rate varying from approximately 80 millimeters/year (mm/yr) in the south, to approximately 65 mm/yr in the north. Although the rate of subduction varies little along the entire arc, there are complex changes in the geologic processes along the subduction zone that dramatically influence volcanic activity, crustal deformation, earthquake generation and occurrence all along the western edge of South America.

  20. PlateRunner: A Search Engine to Identify EMR Boilerplates.

    PubMed

    Divita, Guy; Workman, T Elizabeth; Carter, Marjorie E; Redd, Andrew; Samore, Matthew H; Gundlapalli, Adi V

    2016-01-01

    Medical text contains boilerplated content, an artifact of pull-down forms from EMRs. Boilerplated content is the source of challenges for concept extraction on clinical text. This paper introduces PlateRunner, a search engine on boilerplates from the US Department of Veterans Affairs (VA) EMR. Boilerplates containing concepts should be identified and reviewed to recognize challenging formats, identify high yield document titles, and fine tune section zoning. This search engine has the capability to filter negated and asserted concepts, save and search query results. This tool can save queries, search results, and documents found for later analysis.

  1. Insight into collision zone dynamics from topography: numerical modelling results and observations

    NASA Astrophysics Data System (ADS)

    Bottrill, A. D.; van Hunen, J.; Allen, M. B.

    2012-07-01

    Dynamic models of subduction and continental collision are used to predict dynamic topography changes on the overriding plate. The modelling results show a distinct evolution of topography on the overriding plate, during subduction, continental collision and slab break-off. A prominent topographic feature is a temporary (few Myrs) deepening in the area of the back arc-basin after initial collision. This collisional mantle dynamic basin (CMDB) is caused by slab steepening drawing material away from the base of the overriding plate. Also during this initial collision phase, surface uplift is predicted on the overriding plate between the suture zone and the CMDB, due to the subduction of buoyant continental material and its isostatic compensation. After slab detachment, redistribution of stresses and underplating of the overriding plate causes the uplift to spread further into the overriding plate. This topographic evolution fits the stratigraphy found on the overriding plate of the Arabia-Eurasia collision zone in Iran and south east Turkey. The sedimentary record from the overriding plate contains Upper Oligocene-Lower Miocene marine carbonates deposited between terrestrial clastic sedimentary rocks, in units such as the Qom Formation and its lateral equivalents. This stratigraphy shows that during the Late Oligocene-Early Miocene the surface of the overriding plate sank below sea level before rising back above sea level, without major compressional deformation recorded in the same area. This uplift and subsidence pattern correlates well with our modelled topography changes.

  2. Lower plate deformation structures along the Costa Rica erosive plate boundary - results from IODP Expedition 344 (CRISP 2)

    NASA Astrophysics Data System (ADS)

    Brandstätter, Jennifer; Kurz, Walter; Micheuz, Peter; Krenn, Kurt

    2015-04-01

    The primary objective of Integrated Ocean Drilling Program (IODP) Expedition 344 offshore the Osa Peninsula in Costa Rica was to sample and quantify the material entering the seismogenic zone of the Costa Rican erosive subduction margin. Fundamental to this objective is an understanding of the nature of both the subducting Cocos plate crust and of the overriding Caribbean plate. The subducting Cocos plate is investigated trying to define its hydrologic system and thermal state. The forearc structures recorded by the sediment deposited on the forearc, instead, document periods of uplift and subsidence and provide important information about the process of tectonic erosion that characterizes the Costa Rica margin. Offshore the western margin of Costa Rica, the oceanic Cocos plate subducts under the Caribbean plate, forming the southern end of the Middle America Trench. Subduction parameters including the age, convergence rate, azimuth, obliquity, morphology, and slab dip all vary along strike. The age of the Cocos plate at the Middle America Trench decreases from 24 Ma offshore the Nicoya Peninsula to 15 Ma offshore the Osa Peninsula. Subduction rates vary from 70 mm/y offshore Guatemala to 90 mm/y offshore southern Costa Rica. Convergence obliquity across the trench varies from offshore Nicaragua, where it is as much as 25° oblique, to nearly orthogonal southeast of the Nicoya Peninsula. Passage of the Cocos plate over the Galapagos hotspot created the aseismic Cocos Ridge, an overthickened welt of oceanic crust. This ridge is ~25 km thick, greater than three times normal oceanic crustal thickness. During IODP Expedition 344, the incoming Cocos plate was drilled at sites U1381 and U1414. Site U1381 is located ~4.5 km seaward of the deformation front offshore the Osa Peninsula and Caño Island. It is located on a local basement high. Basement relief often focuses fluid flow, so data from this site are likely to document the vigor of fluid flow in this area. Site U

  3. Plating Processes Utilizing High Intensity Acoustic Beams

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C. (Inventor); Denofrio, Charles (Inventor)

    2002-01-01

    A system and a method for selective plating processes are disclosed which use directed beams of high intensity acoustic waves to create non-linear effects that alter and improve the plating process. The directed beams are focused on the surface of an object, which in one embodiment is immersed in a plating solution, and in another embodiment is suspended above a plating solution. The plating processes provide precise control of the thickness of the layers of the plating, while at the same time, in at least some incidents, eliminates the need for masking.

  4. Avionics Box Cold Plate Damage Prevention

    NASA Technical Reports Server (NTRS)

    Stambolian, Damon B.; Larchar, Steven W.; Henderson, Gena; Tran, Donald; Barth, Tim

    2012-01-01

    Problem Introduction: 1. Prevent Cold Plate Damage in Space Shuttle. 1a. The number of cold plate problems had increased from an average of 16.5 per/year between 1990 through 2000, to an average of 39.6 per year between 2001through 2005. 1b. Each complete set of 80 cold plates cost approximately $29 million, an average of $362,500 per cold plate. 1c It takes four months to produce a single cold plate. 2. Prevent Cold Plate Damage in Future Space Vehicles.

  5. Consecutive Plate Acoustic Suppressor Apparatus and Methods

    NASA Technical Reports Server (NTRS)

    Doychak, Joseph (Inventor); Parrott, Tony L. (Inventor)

    1993-01-01

    An apparatus and method for suppressing acoustic noise utilizes consecutive plates, closely spaced to each other so as to exploit dissipation associated with sound propagation in narrow channels to optimize the acoustic resistance at a liner surface. The closely spaced plates can be utilized as high temperature structural materials for jet engines by constructing the plates from composite materials. Geometries of the plates, such as plate depth, shape, thickness, inter-plate spacing, arrangement, etc., can be selected to achieve bulk material-like behavior.

  6. Grain-damage hysteresis and plate tectonic states

    NASA Astrophysics Data System (ADS)

    Bercovici, David; Ricard, Yanick

    2016-04-01

    Shear localization in the lithosphere is an essential ingredient for understanding how and why plate tectonics is generated from mantle convection on terrestrial planets. The theoretical model for grain-damage and pinning in two-phase polycrystalline rocks provides a frame-work for understanding lithospheric shear weakening and plate-generation, and is consistent with laboratory and field observations of mylonites. Grain size evolves through the competition between coarsening, which drives grain-growth, and damage, which drives grain reduction. The interface between crystalline phases controls Zener pinning, which impedes grain growth. Damage to the interface enhances the Zener pinning effect, which then reduces grain-size, forcing the rheology into the grain-size-dependent diffusion creep regime. This process thus allows damage and rheological weakening to co-exist, providing a necessary positive self-weakening feedback. Moreover, because pinning inhibits grain-growth it promotes shear-zone longevity and plate-boundary inheritance. However, the suppression of interface damage at low interface curvature (wherein inter-grain mixing is inefficient and other energy sinks of deformational work are potentially more facile) causes a hysteresis effect, in which three possible equilibrium grain-sizes for a given stress coexist: (1) a stable, large-grain, weakly-deforming state, (2) a stable, small-grain, rapidly-deforming state analogous to ultramylonites, and (3) an unstable, intermediate grain-size state perhaps comparable to protomylonites. A comparison of the model to field data suggests that shear-localized zones of small-grain mylonites and ultra-mylonites exist at a lower stress than the co-existing large-grain porphyroclasts, rather than, as predicted by paleopiezometers or paleowattmeters, at a much higher stress; this interpretation of field data thus allows localization to relieve instead of accumulate stress. The model also predicts that a lithosphere that

  7. Spatio-temporal mapping of plate boundary faults in California using geodetic imaging

    USGS Publications Warehouse

    Donnellan, Andrea; Arrowsmith, Ramon; DeLong, Stephen B.

    2017-01-01

    The Pacific–North American plate boundary in California is composed of a 400-km-wide network of faults and zones of distributed deformation. Earthquakes, even large ones, can occur along individual or combinations of faults within the larger plate boundary system. While research often focuses on the primary and secondary faults, holistic study of the plate boundary is required to answer several fundamental questions. How do plate boundary motions partition across California faults? How do faults within the plate boundary interact during earthquakes? What fraction of strain accumulation is relieved aseismically and does this provide limits on fault rupture propagation? Geodetic imaging, broadly defined as measurement of crustal deformation and topography of the Earth’s surface, enables assessment of topographic characteristics and the spatio-temporal behavior of the Earth’s crust. We focus here on crustal deformation observed with continuous Global Positioning System (GPS) data and Interferometric Synthetic Aperture Radar (InSAR) from NASA’s airborne UAVSAR platform, and on high-resolution topography acquired from lidar and Structure from Motion (SfM) methods. Combined, these measurements are used to identify active structures, past ruptures, transient motions, and distribution of deformation. The observations inform estimates of the mechanical and geometric properties of faults. We discuss five areas in California as examples of different fault behavior, fault maturity and times within the earthquake cycle: the M6.0 2014 South Napa earthquake rupture, the San Jacinto fault, the creeping and locked Carrizo sections of the San Andreas fault, the Landers rupture in the Eastern California Shear Zone, and the convergence of the Eastern California Shear Zone and San Andreas fault in southern California. These examples indicate that distribution of crustal deformation can be measured using interferometric synthetic aperture radar (InSAR), Global Navigation

  8. Zoned mantle convection.

    PubMed

    Albarède, Francis; Van Der Hilst, Rob D

    2002-11-15

    We review the present state of our understanding of mantle convection with respect to geochemical and geophysical evidence and we suggest a model for mantle convection and its evolution over the Earth's history that can reconcile this evidence. Whole-mantle convection, even with material segregated within the D" region just above the core-mantle boundary, is incompatible with the budget of argon and helium and with the inventory of heat sources required by the thermal evolution of the Earth. We show that the deep-mantle composition in lithophilic incompatible elements is inconsistent with the storage of old plates of ordinary oceanic lithosphere, i.e. with the concept of a plate graveyard. Isotopic inventories indicate that the deep-mantle composition is not correctly accounted for by continental debris, primitive material or subducted slabs containing normal oceanic crust. Seismological observations have begun to hint at compositional heterogeneity in the bottom 1000 km or so of the mantle, but there is no compelling evidence in support of an interface between deep and shallow mantle at mid-depth. We suggest that in a system of thermochemical convection, lithospheric plates subduct to a depth that depends - in a complicated fashion - on their composition and thermal structure. The thermal structure of the sinking plates is primarily determined by the direction and rate of convergence, the age of the lithosphere at the trench, the sinking rate and the variation of these parameters over time (i.e. plate-tectonic history) and is not the same for all subduction systems. The sinking rate in the mantle is determined by a combination of thermal (negative) and compositional buoyancy and as regards the latter we consider in particular the effect of the loading of plates with basaltic plateaux produced by plume heads. Barren oceanic plates are relatively buoyant and may be recycled preferentially in the shallow mantle. Oceanic plateau-laden plates have a more pronounced

  9. Oil prospection using the tectonic plate model

    NASA Astrophysics Data System (ADS)

    Pointu, Agnès

    2015-04-01

    Tectonic plate models are an intellectual setting to understand why oil deposits are so uncommon and unequally distributed and how models can be used in actual oil and gas prospection. In this case, we use the example of the Ghawar deposit (Saudi Arabia), one of the largest producing well in the world. In the first step, physical properties of rocks composing the oil accumulation are studied by laboratory experiments. Students estimate the porosity of limestone and clay by comparing their mass before and after water impregnation. Results are compared to microscopic observations. Thus, students come to the conclusion that oil accumulations are characterized by superposition of rocks with very different properties: a rich organic source rock (clays of the Hanifa formation), a porous reservoir rock to store the petroleum in (limestones of the Arab formation) and above an impermeable rock with very low porosity (evaporites of the Tithonien). In previous lessons, students have seen that organic matter is usually mineralized by bacteria and that this preservation requires particular conditions. The aim is to explain why biomass production has been so important during the deposit of the clays of the Hanifa formation. Tectonic plate models make it possible to estimate the location of the Arabian Peninsula during Jurassic times (age of Hanifa formation). In order to understand why the paleo-location of the Arabian Peninsula is important to preserve organic matter, students have different documents showing: - That primary production of biomass by phytoplankton is favored by climatic conditions, - That the position of continents determinate the ocean currents and the positions of upwelling zones and zones where organic matter will be able to be preserved, - That north of the peninsula there was a passive margin during Jurassic times. An actual seismic line is studied in order to highlight that this extensive area allowed thick sedimentary deposits to accumulate and that fast

  10. Seismicity of the Earth 1900-2012 Philippine Sea plate and vicinity

    USGS Publications Warehouse

    Smoczyk, Gregory M.; Hayes, Gavin P.; Hamburger, Michael W.; Benz, Harley M.; Villaseñor, Antonio; Furlong, Kevin P.

    2013-01-01

    The complex tectonics surrounding the Philippine Islands are dominated by the interactions of the Pacific, Sunda, and Eurasia plates with the Philippine Sea plate (PSP). The latter is unique because it is almost exclusively surrounded by zones of plate convergence. At its eastern and southeastern edges, the Pacific plate is subducted beneath the PSP at the Izu-Bonin, Mariana, and Yap trenches. Here, the subduction zone exhibits high rates of seismic activity to depths of over 600 km, though no great earthquakes (M>8.0) have been observed, likely because of weak coupling along the plate interface. In the northeast, the PSP subducts beneath Japan and the eastern margin of the Eurasia plate at the Nankai and Ryukyu trenches, extending westward to Taiwan. The Nankai portion of this subduction zone has hosted some of the largest earthquakes along the margins of the PSP, including a pair of Mw8.1 megathrust events in 1944 and 1946. Along its western margin, the convergence of the PSP and the Sunda plate is responsible for a broad and active plate boundary system extending along both sides of the Philippine Islands chain. The region is characterized by opposite-facing subduction systems on the east and west sides of the islands, and the archipelago is cut by a major transform structure: the Philippine Fault. Subduction of the Philippine Sea plate occurs at the eastern margin of the islands along the Philippine Trench and its northern extension, the East Luzon Trough. On the west side of Luzon, the Sunda Plate subducts eastward along a series of trenches, including the Manila Trench in the north, the smaller Negros Trench in the central Philippines, and the Sulu and Cotabato trenches in the south. Twentieth and early twentyfirst century seismic activity along the boundaries of the Philippine Sea plate has produced seven great (M>8.0) earthquakes and 250 large (M>7) events. Among the most destructive events were the 1923 Kanto, the 1948 Fukui, and the 1995 Kobe, Japan

  11. Coastal zone management

    NASA Technical Reports Server (NTRS)

    Tilton, E. L., III

    1975-01-01

    A panel of federal and state representatives concerned with coastal zone affairs discussed their problems in this area. In addition, several demonstrations of the application of remote sensing technology to coastal zone management were described. These demonstrations were performed by several agencies in a variety of geographical areas.

  12. Investigating Aquatic Dead Zones

    ERIC Educational Resources Information Center

    Testa, Jeremy; Gurbisz, Cassie; Murray, Laura; Gray, William; Bosch, Jennifer; Burrell, Chris; Kemp, Michael

    2010-01-01

    This article features two engaging high school activities that include current scientific information, data, and authentic case studies. The activities address the physical, biological, and chemical processes that are associated with oxygen-depleted areas, or "dead zones," in aquatic systems. Students can explore these dead zones through both…

  13. Work zone safety analysis.

    DOT National Transportation Integrated Search

    2013-11-01

    This report presents research performed analyzing crashes in work zones in the state of New Jersey so as to : identify critical areas in work zones susceptible to crashes and key factors that contribute to these crashes. A field : data collection on ...

  14. California tree seed zones

    Treesearch

    John M. Buck; Ronald S. Adams; Jerrold Cone; M. Thompson Conkle; William J. Libby; Cecil J. Eden; Michel J. Knight

    1970-01-01

    California forest tree seed zones were established originally by Fowells (1946), with revisions proposed by Roy (1963) and Schubert (1966). The Forest Tree Seed Committee of the Northern California Section, Society of American Foresters, has revised the original zones and updated the recording system described in the earlier reports. Fowells' (1946) Research Note...

  15. Float Zone Workshop

    NASA Technical Reports Server (NTRS)

    Naumann, R. J.

    1980-01-01

    A summary of the Analytical Float Zone Experiment System (AFZES) concept is presented. The types of experiments considered for such a facility are discussed. Reports from various industrial producers and users of float zone material are presented. Special emphasis is placed on state-of-the-art developments in low gravity manufacturing and their applications to space processing.

  16. Longleaf pine site zones

    Treesearch

    Phillip J. Craul; John S. Kush; William D. Boyer

    2005-01-01

    The authors delineate six major climatic areas of the longleaf pine (Pinus palustris Mill.) region. They subdivide these areas into 21 site zones, each of which is deemed homogenous with respect to climate, physiography, and soils. The site zones are mapped and their climate, physiography, and soils described. The authors recommend that plantings of...

  17. Iowa Work Zone Fatalities

    DOT National Transportation Integrated Search

    2011-01-01

    From March through November, the Iowa DOT may have up to 500 road construction work zones, and each of the department's maintenance garages may establish one or more short-term work zones per day. Couple that with the work of cities and counties, and...

  18. Tomography reveals buoyant asthenosphere accumulating beneath the Juan de Fuca plate.

    PubMed

    Hawley, William B; Allen, Richard M; Richards, Mark A

    2016-09-23

    The boundary between Earth's strong lithospheric plates and the underlying mantle asthenosphere corresponds to an abrupt seismic velocity decrease and electrical conductivity increase with depth, perhaps indicating a thin, weak layer that may strongly influence plate motion dynamics. The behavior of such a layer at subduction zones remains unexplored. We present a tomographic model, derived from on- and offshore seismic experiments, that reveals a strong low-velocity feature beneath the subducting Juan de Fuca slab along the entire Cascadia subduction zone. Through simple geodynamic arguments, we propose that this low-velocity feature is the accumulation of material from a thin, weak, buoyant layer present beneath the entire oceanic lithosphere. The presence of this feature could have major implications for our understanding of the asthenosphere and subduction zone dynamics. Copyright © 2016, American Association for the Advancement of Science.

  19. Seismicity and deep structure of the Indo-Burman plate margin

    NASA Astrophysics Data System (ADS)

    Vaněk, J.; Hanuš, V.; Sitaram, M. V. D.

    Two differently inclined segments of the Wadati-Benioff zone beneath the Chin Hills and Naga Hills segments of the Indo-Burman Ranges were verified on the basis of the geometrical analysis of distribution of 566 earthquakes. The Wadati-Benioff zone and young calc-alkaline volcanism point to the existence of a Mio-Pliocene subduction with the trench at the western boundary of the Oligocene Indo-Burman orogenic belt. A system of ten seismically active fracture zones was delineated in the adjacent Indian and Burman plates, the tectonic pattern of which represents the eastern manifestation of the continental collision of the Indian and Eurasian plates. The position of historical disastrous earthquakes confirms the reality of this pattern.

  20. Tomography reveals buoyant asthenosphere accumulating beneath the Juan de Fuca plate

    NASA Astrophysics Data System (ADS)

    Hawley, William B.; Allen, Richard M.; Richards, Mark A.

    2016-09-01

    The boundary between Earth’s strong lithospheric plates and the underlying mantle asthenosphere corresponds to an abrupt seismic velocity decrease and electrical conductivity increase with depth, perhaps indicating a thin, weak layer that may strongly influence plate motion dynamics. The behavior of such a layer at subduction zones remains unexplored. We present a tomographic model, derived from on- and offshore seismic experiments, that reveals a strong low-velocity feature beneath the subducting Juan de Fuca slab along the entire Cascadia subduction zone. Through simple geodynamic arguments, we propose that this low-velocity feature is the accumulation of material from a thin, weak, buoyant layer present beneath the entire oceanic lithosphere. The presence of this feature could have major implications for our understanding of the asthenosphere and subduction zone dynamics.

  1. Introduction to the structures and processes of subduction zones

    NASA Astrophysics Data System (ADS)

    Zheng, Yong-Fei; Zhao, Zi-Fu

    2017-09-01

    Subduction zones have been the focus of many studies since the advent of plate tectonics in 1960s. Workings within subduction zones beneath volcanic arcs have been of particular interest because they prime the source of arc magmas. The results from magmatic products have been used to decipher the structures and processes of subduction zones. In doing so, many progresses have been made on modern oceanic subduction zones, but less progresses on ancient oceanic subduction zones. On the other hand, continental subduction zones have been studied since findings of coesite in metamorphic rocks of supracrustal origin in 1980s. It turns out that high-pressure to ultrahigh-pressure metamorphic rocks in collisional orogens provide a direct target to investigate the tectonism of subduction zones, whereas oceanic and continental arc volcanic rocks in accretionary orogens provide an indirect target to investigate the geochemistry of subduction zones. Nevertheless, metamorphic dehydration and partial melting at high-pressure to ultrahigh-pressure conditions are tectonically applicable to subduction zone processes at forearc to subarc depths, and crustal metasomatism is the physicochemical mechanism for geochemical transfer from the slab to the mantle in subduction channels. Taken together, these provide us with an excellent opportunity to find how the metamorphic, metasomatic and magmatic products are a function of the structures and processes in both oceanic and continental subduction zones. Because of the change in the thermal structures of subduction zones, different styles of metamorphism, metasomatism and magmatism are produced at convergent plate margins. In addition, juvenile and ancient crustal rocks have often suffered reworking in episodes independent of either accretionary or collisional orogeny, leading to continental rifting metamorphism and thus rifting orogeny for mountain building in intracontinental settings. This brings complexity to distinguish the syn

  2. Introduction to the structures and processes of subduction zones

    NASA Astrophysics Data System (ADS)

    Zheng, Yong-Fei; Zhao, Zi-Fu

    2017-09-01

    Subduction zones have been the focus of many studies since the advent of plate tectonics in 1960s. Workings within subduction zones beneath volcanic arcs have been of particular interest because they prime the source of arc magmas. The results from magmatic products have been used to decipher the structures and processes of subduction zones. In doing so, many progresses have been made on modern oceanic subduction zones, but less progresses on ancient oceanic subduction zones. On the other hand, continental subduction zones have been studied since findings of coesite in metamorphic rocks of supracrustal origin in 1980s. It turns out that high-pressure to ultrahigh-pressure metamorphic rocks in collisional orogens provide a direct target to investigate the tectonism of subduction zones, whereas oceanic and continental arc volcanic rocks in accretionary orogens provide an indirect target to investigate the geochemistry of subduction zones. Nevertheless, metamorphic dehydration and partial melting at high-pressure to ultrahigh-pressure conditions are tectonically applicable to subduction zone processes at forearc to subarc depths, and crustal metasomatism is the physicochemical mechanism for geochemical transfer from the slab to the mantle in subduction channels. Taken together, these provide us with an excellent opportunity to find how the metamorphic, metasomatic and magmatic products are a function of the structures and processes in both oceanic and continental subduction zones. Because of the change in the thermal structures of subduction zones, different styles of metamorphism, metasomatism and magmatism are produced at convergent plate margins. In addition, juvenile and ancient crustal rocks have often suffered reworking in episodes independent of either accretionary or collisional orogeny, leading to continental rifting metamorphism and thus rifting orogeny for mountain building in intracontinental settings. This brings complexity to distinguish the syn

  3. Cyclic stressing and seismicity at strongly coupled subduction zones

    USGS Publications Warehouse

    Taylor, M.A.J.; Zheng, G.; Rice, J.R.; Stuart, W.D.; Dmowska, R.

    1996-01-01

    We use the finite element method to analyze stress variations in and near a strongly coupled subduction zone during an earthquake cycle. Deformation is assumed to be uniform along strike (plane strain on a cross section normal to the trench axis), and periodic earthquake slip is imposed consistent with the long-term rate of plate convergence and degree of coupling. Simulations of stress and displacement rate fields represent periodic fluctuations in time superimposed on an average field. The oceanic plate, descending slab, and continental lithosphere are assumed here to respond elastically to these fluctuations, and the remaining mantle under and between plates is assumed to respond as Maxwell viscoelastic. In the first part of the analysis we find that computed stress fluctuations in space and time are generally consistent with observed earthquake mechanism variations with time since a great thrust event. In particular, trench-normal extensional earthquakes tend to occur early in the earthquake cycle toward the outer rise but occur more abundantly late in the cycle in the subducting slab downdip of the main thrust zone. Compressional earthquakes, when they occur at all, have the opposite pattern. Our results suggest also that the actual timing of extensional outer rise events is controlled by the rheology of the shallow aseismic portion of the thrust interface. The second part of the analysis shows the effects of mantle relaxation on the rate of ground surface deformation during the earthquake cycle. Models without relaxation predict a strong overall compressional strain rate in the continental plate above the main thrust zone, with the strain rate constant between mainshocks. However with significant relaxation present, a localized region of unusually low compressional, or even slightly extensional, strain rate develops along the surface of the continental plate above and somewhat inland from the downdip edge of the locked main thrust zone. The low strain rate

  4. 3-D Simulation of Tectonic Evolution in Mariana with a Coupled Model of Plate Subduction and Back-Arc Spreading

    NASA Astrophysics Data System (ADS)

    Hashima, A.; Matsu'Ura, M.

    2006-12-01

    We obtained the expressions for internal deformation fields due to a moment tensor in an elastic-viscoelastic layered holf-space. This unified formulation of internal deformation fields for shear faulting and crack opening enabled us to deal with the problem of tectonic deformation at a composite type of plate boundary zones. The tectonic deformation can be ascribed to mechanical interaction at plate boundaries, which make a closed circuit with the mode of relative plate motion changing from divergence to convergence through transcurrent motion. One of the rational ways to represent mechanical interaction at plate boundaries is specifying the increase rates of normal or tangential displacement discontinuity across plate interfaces. On the basis of such a basic idea we developed a 3-D simulation model for the nonlinear, coupled system of plate subduction and back-arc spreading in Mariana. Through numerical simulations we revealed the evolution process of back-arc spreading. At the first stage, steady plate subduction (shear faulting at a plate interface) gradually forms tensile stress fields in the back-arc region of the overriding plate. When the accumulated tensile stress reaches a critical level, back-arc spreading (crack opening) starts at a structurally weak portion of the overriding plate. The horizontal motion of the frontal part of the overriding plate due to back-arc spreading pushes out the plate boundary toward the oceanic plate. In steady-state plate subduction the shear stress acting on a plate interface must balance with the maximum frictional resistance (shear strength) of the plate interface. Therefore, the increase of shear stress at the plate interface leads to the increase of slip rate at the plate interface. The local increase of slip rate at the plate interface produces the additional tensile stress in the back-arc region. The increased tensile stress must be canceled out by the additional crack opening. Such a feedback mechanism between plate

  5. TESTING AND ACCEPTANCE OF FUEL PLATES FOR RERTR FUEL DEVELOPMENT EXPERIMENTS

    SciTech Connect

    J.M. Wight; G.A. Moore; S.C. Taylor

    2008-10-01

    This paper discusses how candidate fuel plates for RERTR Fuel Development experiments are examined and tested for acceptance prior to reactor insertion. These tests include destructive and nondestructive examinations (DE and NDE). The DE includes blister annealing for dispersion fuel plates, bend testing of adjacent cladding, and microscopic examination of archive fuel plates. The NDE includes Ultrasonic (UT) scanning and radiography. UT tests include an ultrasonic scan for areas of “debonds” and a high frequency ultrasonic scan to determine the "minimum cladding" over the fuel. Radiography inspections include identifying fuel outside of the maximum fuel zone and measurements and calculationsmore » for fuel density. Details of each test are provided and acceptance criteria are defined. These tests help to provide a high level of confidence the fuel plate will perform in the reactor without a breach in the cladding.« less

  6. Aluminum transfer method for plating plastics

    NASA Technical Reports Server (NTRS)

    Goodrich, W. D.; Stalmach, C. J., Jr.

    1977-01-01

    Electroless plating technique produces plate of uniform thickness. Hardness and abrasion resistance can be increased further by heat treatment. Method results in seamless coating over many materials, has low thermal conductivity, and is relatively inexpensive compared to conventional methods.

  7. 49 CFR 236.779 - Plate, top.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Definitions § 236.779 Plate, top. A metal plate secured to a locking bracket to prevent the cross locking from being forced out of the...

  8. Maps, Plates, and Mount Saint Helens.

    ERIC Educational Resources Information Center

    Lary, Barbara E.; Krockover, Gerald H.

    1987-01-01

    Describes a laboratory activity on plate tectonics which focuses on the connection between plate tectonics and the different types of volcanoes. Provides questions for discussion and includes suggestions for extending the activity. (ML)

  9. Purity test for copper-plating solutions

    NASA Technical Reports Server (NTRS)

    Mansfeld, F. B.

    1977-01-01

    Electrode configuration can be used to measure extent of impurities in acid-copper plating solution. It can be inserted into any plating tank and will show whether bath is clean or contaminated, within fifteen minutes.

  10. Plating by glass-bead peening

    NASA Technical Reports Server (NTRS)

    Babecki, A. J.; Haehner, C. L.

    1971-01-01

    Technique permits plating of primarily metallic substrates with either metals or nonmetals at normal temperature. Peening uses compressed air to apply concurrent streams of small glass beads and powdered plating material to the substrate.

  11. Antarctica: As seismic as other plates

    NASA Astrophysics Data System (ADS)

    Richman, Barbara T.

    Antarctica shakes, rattles, and rolls just as much as other slow-moving plates. Emile Okal, a Yale University seismologist, told colleagues at the AGU Fall Meeting that although the Antarctic plate is not moving across the earth as fast as other continents, it has a seismicity similar to other plates. His findings refute the claim that a ring of spreading ridges that surrounds the plate leaves Antarctica stress free.The small number of reports of plate seismicity, Okal explained, has been used to argue that the ridges that surround the plate are unable to transmit tectonic stresses and would make the Antarctic plate motionless and free of seismic stress. However, when Okal added up the total seismic energy released during the last 55 years, he found it similar to that of the African plate, which is comparable in size.

  12. 49 CFR 230.46 - Badge plates.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... TRANSPORTATION STEAM LOCOMOTIVE INSPECTION AND MAINTENANCE STANDARDS Boilers and Appurtenances Steam Gauges § 230.46 Badge plates. A metal badge plate showing the allowed steam pressure shall be attached to the...

  13. Locking of the Chile subduction zone controlled by fluid pressure before the 2010 earthquake

    NASA Astrophysics Data System (ADS)

    Moreno, Marcos; Haberland, Christian; Oncken, Onno; Rietbrock, Andreas; Angiboust, Samuel; Heidbach, Oliver

    2014-04-01

    Constraints on the potential size and recurrence time of strong subduction-zone earthquakes come from the degree of locking between the down-going and overriding plates, in the period between large earthquakes. In many cases, this interseismic locking degree correlates with slip during large earthquakes or is attributed to variations in fluid content at the plate interface. Here we use geodetic and seismological data to explore the links between pore-fluid pressure and locking patterns at the subduction interface ruptured during the magnitude 8.8 Chile earthquake in 2010. High-resolution three-dimensional seismic tomography reveals variations in the ratio of seismic P- to S-wave velocities (Vp/Vs) along the length of the subduction-zone interface. High Vp/Vs domains, interpreted as zones of elevated pore-fluid pressure, correlate spatially with parts of the plate interface that are poorly locked and slip aseismically. In contrast, low Vp/Vs domains, interpreted as zones of lower pore-fluid pressure, correlate with locked parts of the plate interface, where unstable slip and earthquakes occur. Variations in pore-fluid pressure are caused by the subduction and dehydration of a hydrothermally altered oceanic fracture zone. We conclude that variations in pore-fluid pressure at the plate interface control the degree of interseismic locking and therefore the slip distribution of large earthquake ruptures.

  14. Hierarchic models for laminated plates

    NASA Technical Reports Server (NTRS)

    Szabo, Barna A.; Actis, Ricardo L.

    1991-01-01

    The research conducted in the formulation of hierarchic models for laminated plates is described. The work is an extension of the work done for laminated strips. The use of a single parameter, beta, is investigated that represents the degree to which the equilibrium equations of three dimensional elasticity are satisfied. The powers of beta identify members in the hierarchic sequence. Numerical examples that were analyzed with the proposed sequence of models are included. The results obtained for square plates with uniform loading and homogeneous boundary conditions are very encouraging. Several cross-ply and angle-ply laminates were evaluated and the results compared with those of the fully three dimensional model, computed using MSC/PROBE, and with previously reported work on laminated strips.

  15. Collisional zones in Puerto Rico and the northern Caribbean

    NASA Astrophysics Data System (ADS)

    Laó-Dávila, Daniel A.

    2014-10-01

    Puerto Rico is an amalgamation of island arc terranes that has recorded the deformational and tectonic history of the North American-Caribbean Plate boundary. Four collisional zones indicate the contractional events that have occurred at the plate boundary. Metamorphism and deformation of Middle Jurassic to Early Cretaceous oceanic lithosphere during the Early Cretaceous indicate the earliest collisional event. Then, an ophiolitic mélange, mostly comprised of blocks of the metamorphosed oceanic lithosphere, was formed and emplaced in the backarc region during the Turonian-Coniacian deformational event. A possible collision with a buoyant block in the North American Plate caused late Maastrichtian-early Paleocene contraction that created fold-and-thrust belts and the remobilization and uplift of serpentinite bodies in the Southwest Block. Late Eocene-early Oligocene transpression was localized along the Southern and Northern Puerto Rico fault zones, which occur north and south of large granodiorite intrusions in the strong Central Block. The deformation was accommodated in pure shear domains of fold-and-thrust belts and conjugate strike-slip faults, and simple shear domains of large mostly left-lateral faults. In addition, it reactivated faults in the weak Southwest Block. This island-wide transpression is the result of a Greater Antilles arc and continental North American collision. The kinematic model of the structures described in Puerto Rico correlate with some structures in Hispaniola and Cuba, and shows how the northern boundary of the Caribbean Plate was shortened by collisions with continental lithosphere of the North American Plate throughout its history. The tectonic evolution of the Greater Antilles shows a history of collisions, in which the latest collision accretes Cuba to the North American Plate, reorganizes the plate boundary, and deforms with transpression Hispaniola and Puerto Rico. The latest collision in Puerto Rico shows the case in which an

  16. Ion plated electronic tube device

    DOEpatents

    Meek, T.T.

    1983-10-18

    An electronic tube and associated circuitry which is produced by ion plating techniques. The process is carried out in an automated process whereby both active and passive devices are produced at very low cost. The circuitry is extremely reliable and is capable of functioning in both high radiation and high temperature environments. The size of the electronic tubes produced are more than an order of magnitude smaller than conventional electronic tubes.

  17. Electroless metal plating of plastics

    DOEpatents

    Krause, Lawrence J.

    1986-01-01

    Process for plating main group metals on aromatic polymers is carried out by the use of a nonaqueous solution of a salt of an alkali metal in a positive valence state and a main group metal in a negative valence state with contact between the solution and polymer providing a redox reaction causing the deposition of the main group metal and the reduction of the polymer. Products from the process exhibit useful decorative and electrical properties.

  18. Electroless metal plating of plastics

    DOEpatents

    Krause, L.J.

    1982-09-20

    Process for plating main group metals on aromatic polymers is carried out by the use of a nonaqueous solution of a salt of an alkali metal in a positive valence state and a main group metal in a negative valence state with contact between the solution and polymer providing a redox reaction causing the deposition of the main group metal and the reduction of the polymer. Products from the process exhibit useful decorative and electrical properties.

  19. Electroless metal plating of plastics

    DOEpatents

    Krause, Lawrence J.

    1984-01-01

    Process for plating main group metals on aromatic polymers is carried out by the use of a nonaqueous solution of a salt of an alkali metal in a positive valence state and a main group metal in a negative valence state with contact between the solution and polymer providing a redox reaction causing the deposition of the main group metal and the reduction of the polymer. Products from the process exhibit useful decorative and electrical properties.

  20. PRETREATING URANIUM FOR METAL PLATING

    DOEpatents

    Wehrmann, R.F.

    1961-05-01

    A process is given for anodically treating the surface of uranium articles, prior to metal plating. The metal is electrolyzed in an aqueous solution of about 10% polycarboxylic acid, preferably oxalic acid, from 1 to 5% by weight of glycerine and from 1 to 5% by weight of hydrochloric acid at from 20 to 75 deg C for from 30 seconds to 15 minutes. A current density of from 60 to 100 amperes per square foot is used.

  1. Practical automatic Arabic license plate recognition system

    NASA Astrophysics Data System (ADS)

    Mohammad, Khader; Agaian, Sos; Saleh, Hani

    2011-02-01

    Since 1970's, the need of an automatic license plate recognition system, sometimes referred as Automatic License Plate Recognition system, has been increasing. A license plate recognition system is an automatic system that is able to recognize a license plate number, extracted from image sensors. In specific, Automatic License Plate Recognition systems are being used in conjunction with various transportation systems in application areas such as law enforcement (e.g. speed limit enforcement) and commercial usages such as parking enforcement and automatic toll payment private and public entrances, border control, theft and vandalism control. Vehicle license plate recognition has been intensively studied in many countries. Due to the different types of license plates being used, the requirement of an automatic license plate recognition system is different for each country. [License plate detection using cluster run length smoothing algorithm ].Generally, an automatic license plate localization and recognition system is made up of three modules; license plate localization, character segmentation and optical character recognition modules. This paper presents an Arabic license plate recognition system that is insensitive to character size, font, shape and orientation with extremely high accuracy rate. The proposed system is based on a combination of enhancement, license plate localization, morphological processing, and feature vector extraction using the Haar transform. The performance of the system is fast due to classification of alphabet and numerals based on the license plate organization. Experimental results for license plates of two different Arab countries show an average of 99 % successful license plate localization and recognition in a total of more than 20 different images captured from a complex outdoor environment. The results run times takes less time compared to conventional and many states of art methods.

  2. Electrically induced mechanical precompression of ferroelectric plates

    DOEpatents

    Chen, P.J.

    1987-03-02

    A method of electrically inducing mechanical precompression of ferroelectric plate covered with electrodes utilizes the change in strains of the plate as functions of applied electric field. A first field polarizes and laterally shrinks the entire plate. An outer portion of the electrodes are removed, and an opposite field partially depolarizes and expands the central portion of the plate against the shrunk outer portion. 2 figs.

  3. Electrochemical Assay of Gold-Plating Solutions

    NASA Technical Reports Server (NTRS)

    Chiodo, R.

    1982-01-01

    Gold content of plating solution is assayed by simple method that required only ordinary electrochemical laboratory equipment and materials. Technique involves electrodeposition of gold from solution onto electrode, the weight gain of which is measured. Suitable fast assay methods are economically and practically necessary in electronics and decorative-plating industries. If gold content in plating bath is too low, poor plating may result, with consequent economic loss to user.

  4. Electrically induced mechanical precompression of ferroelectric plates

    DOEpatents

    Chen, Peter J.

    1987-01-01

    A method of electrically inducing mechanical precompression of a ferroelectric plate covered with electrodes utilizes the change in strains of the plate as functions of applied electric field. A first field polarizes and laterally shrinks the entire plate. An outer portion of the electrodes are removed, and an opposite field partially depolarizes and expands the central portion of the plate against the shrunk outer portion.

  5. MTR plates modeling with MAIA

    SciTech Connect

    Marelle, V.; Dubois, S.; Ripert, M.

    2008-07-15

    MAIA is a thermo-mechanical code dedicated to the modeling of MTR fuel plates. The main physical phenomena modeled in the code are the cladding oxidation, the interaction between fuel and Al-matrix, the swelling due to fission products and the Al/fuel particles interaction. The creeping of the plate can be modeled in the mechanical calculation. MAIA has been validated on U-Mo dispersion fuel experiments such as IRIS 1 and 2 and FUTURE. The results are in rather good agreement with post-irradiation examinations. MAIA can also be used to calculate in-pile behavior of U{sub 3}Si{sub 2} plates as in the SHARE experimentmore » irradiated in the SCK/Mol BR2 reactor. The main outputs given by MAIA throughout the irradiation are temperatures, cladding oxidation thickness, interaction thickness, volume fraction of meat constituents, swelling, displacements, strains and stresses. MAIA is originally a two-dimensional code but a three-dimensional version is currently under development. (author)« less

  6. Episodic plate tectonics on Venus

    NASA Technical Reports Server (NTRS)

    Turcotte, Donald

    1992-01-01

    Studies of impact craters on Venus from the Magellan images have placed important constraints on surface volcanism. Some 840 impact craters have been identified with diameters ranging from 2 to 280 km. Correlations of this impact flux with craters on the Moon, Earth, and Mars indicate a mean surface age of 0.5 +/- 0.3 Ga. Another important observation is that 52 percent of the craters are slightly fractured and only 4.5 percent are embayed by lava flows. These observations led researchers to hypothesize that a pervasive resurfacing event occurred about 500 m.y. ago and that relatively little surface volcanism has occurred since. Other researchers have pointed out that a global resurfacing event that ceased about 500 MYBP is consistent with the results given by a recent study. These authors carried out a series of numerical calculations of mantle convection in Venus yielding thermal evolution results. Their model considered crustal recycling and gave rapid planetary cooling. They, in fact, suggested that prior to 500 MYBP plate tectonics was active in Venus and since 500 MYBP the lithosphere has stabilized and only hot-spot volcanism has reached the surface. We propose an alternative hypothesis for the inferred cessation of surface volcanism on Venus. We hypothesize that plate tectonics on Venus is episodic. Periods of rapid plate tectonics result in high rates of subduction that cool the interior resulting in more sluggish mantle convection.

  7. Heterogeneous coupling along Makran subduction zone

    NASA Astrophysics Data System (ADS)

    Zarifi, Z.; Raeesi, M.

    2010-12-01

    The Makran subduction zone, located in the southeast of Iran and southern Pakistan, extends for almost 900 km along the Eurasian-Arabian plate boundary. The seismic activities in the eastern and western Makran exhibit very different patterns. The eastern Makran characterized by infrequent large earthquakes and low level of seismicity. The only large instrumentally recorded earthquake in the eastern Makran, the 27 Nov. 1945 (Mw=8.1) earthquake, was followed by tsunami waves with the maximum run-up height of 13 m and disastrous effects in Pakistan, India, Iran and Oman. The western Makran, however, is apparently quiescent without strong evidence on occurrence of large earthquakes in historical times, which makes it difficult to ascertain whether the slab subducts aseismically or experiences large earthquakes separated by long periods exceeding the historical records. We used seismicity and Trench Parallel Free air and Bouguer Anomalies (TPGA and TPBA) to study the variation in coupling in the slab interface. Using a 3D mechanical Finite Element (FE) model, we show how heterogeneous coupling can influence the rate of deformation in the overriding lithosphere and the state of stress in the outer rise, overriding, and subducting plates within the shortest expected cycle of earthquake. We test the results of FE model against the observed focal mechanism of earthquakes and available GPS measurements in Makran subduction zone.

  8. 21 CFR 872.4760 - Bone plate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Bone plate. 872.4760 Section 872.4760 Food and... DENTAL DEVICES Surgical Devices § 872.4760 Bone plate. (a) Identification. A bone plate is a metal device intended to stabilize fractured bone structures in the oral cavity. The bone segments are attached to the...

  9. 21 CFR 872.4760 - Bone plate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Bone plate. 872.4760 Section 872.4760 Food and... DENTAL DEVICES Surgical Devices § 872.4760 Bone plate. (a) Identification. A bone plate is a metal device intended to stabilize fractured bone structures in the oral cavity. The bone segments are attached to the...

  10. 21 CFR 872.4760 - Bone plate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Bone plate. 872.4760 Section 872.4760 Food and... DENTAL DEVICES Surgical Devices § 872.4760 Bone plate. (a) Identification. A bone plate is a metal device intended to stabilize fractured bone structures in the oral cavity. The bone segments are attached to the...

  11. 21 CFR 872.4760 - Bone plate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Bone plate. 872.4760 Section 872.4760 Food and... DENTAL DEVICES Surgical Devices § 872.4760 Bone plate. (a) Identification. A bone plate is a metal device intended to stabilize fractured bone structures in the oral cavity. The bone segments are attached to the...

  12. 21 CFR 872.4760 - Bone plate.

    Code of Federal Regulations, 2012 CFR