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Sample records for pacific plate interface

  1. Faulting within the Pacific plate at the Mariana Trench: Implications for plate interface coupling and subduction of hydrous minerals

    NASA Astrophysics Data System (ADS)

    Emry, Erica L.; Wiens, Douglas A.; Garcia-Castellanos, Daniel

    2014-04-01

    We investigate faulting within the incoming Pacific plate at the Mariana subduction trench to understand stresses within the bending plate, regional stresses acting upon the plate interface, and the extent of possible faulting-induced mantle serpentinization. We determine accurate depths by inverting teleseismic P and SH waveforms for earthquakes occurring during 1990-2011 with Global Centroid Moment Tensor (GCMT) solutions. For earthquakes with Mw 5.0+, we determine centroid depths and source time functions and refine the fault parameters. Results from Central Mariana indicate that all earthquakes are extensional and occur at centroid depths down to 11 km below the Moho. At the Southern Mariana Trench, extensional earthquakes continue to 5 km below the Moho. One compressional earthquake at 34 km below the seafloor suggests stronger plate interface coupling here. In addition, we model the stress distribution within the Pacific plate along two bathymetric profiles extending seaward from the Mariana subduction trench axis to better understand whether our earthquake depth solutions match modeled scenarios for plate bending under applied external forces. Results from our flexure models match the locations of extensional and compressional earthquakes and suggest that the Pacific plate at Southern Mariana is experiencing larger, compressional stresses, possibly due to greater interplate coupling. Additionally, we conclude that if extensional faulting promotes the infiltration of water into the subducting plate mantle, then the top 5-15 km of the Pacific plate mantle are partially serpentinized, and a higher percentage of serpentinization is located near the Central Mariana trench where extensional events extend deeper.

  2. Relative motions between oceanic plates of the Pacific Basin

    NASA Astrophysics Data System (ADS)

    Engebretson, David C.; Cox, Allan; Gordon, Richard G.

    1984-11-01

    Appendix tables are available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C., 20009. Document B84-012; $2.50. Payment must accompany order. Relative motion poles describing the displacement histories between the Pacific plate and once adjacent oceanic plates (Farallon, Kula, Izanagi I, Izanagi II, and Phoenix) were derived for the late Mesozoic and Cenozoic eras. Because fracture zone and magnetic anomaly data are generally available from the Pacific plate but not from adjacent plates, a new method of analysis for onesided data was required. This analysis produced stage poles and rates of relative plate motion and estimates of their confidence regions. The following are the main conclusions drawn from our analysis: (1) For time intervals of the order of 107 years, termed stages, relative motion poles for plate pairs remained nearly fixed. Between stages, shifts in poles were commonly both large and abrupt. Within stages, rates of plate motion were commonly observed to change markedly, indicating that plates changed speed more frequently than they changed direction. (2) The relative motions of all of the plates analyzed changed at about chron M11 (135 Ma), chron 34 (85 Ma), and chron 25 (56 Ma). (3) During the Early Cretaceous there were five oceanic plates in the Pacific basin rather than the four recognized by previous workers. (4) To determine the number of Farallon plates that existed to the east of the Pacific plate during the time interval from chron 34 (85 Ma) to chron 25 (56 Ma), fracture zones and magnetic anomalies that record Pacific-Farallon spreading from the northern, central, and southern Pacific plate were analyzed separately and collectively. The analysis shows that a single Pacific-Farallon relative motion pole and a single rate are consistent with all of the data. (5) Spreading rates along the Pacific-Kula ridge decreased markedly between chrons 32b and 25 (72-56 Ma), probably in response to the arrival of buoyant Kula lithosphere at a subduction zone northwest of the Bering Sea. (6) Soon after chron 25 (56 Ma), a major reorganization is recorded along the Pacific-Farallon boundary. The Kula-Farallon boundary is also thought to have changed during this reorganization. (7) Kula-Pacific anomalies north of anomaly 25 are modeled by assuming continued Kula-Pacific spreading after chron 25 (56 Ma). (8) Probably by chron 18 (43 Ma), Pacific-Kula spreading had ceased and the Kula-Farallon ridge system had evolved into alignment with the Pacific-Farallon spreading direction. However, the timing of these events is uncertain because Pacific-Kula data younger than chron 25 (56 Ma) are sparse.

  3. Physics-Based 3-D Simulation for Earthquake Generation Cycles at Plate Interfaces in Subduction Zones

    NASA Astrophysics Data System (ADS)

    Hashimoto, Chihiro; Fukuyama, Eiichi; Matsu'ura, Mitsuhiro

    2014-08-01

    The generation of interplate earthquakes can be regarded as a process of tectonic stress accumulation and release, driven by relative plate motion. We completed a physics-based simulation system for earthquake generation cycles at plate interfaces in the Japan region, where the Pacific plate is descending beneath the North American and Philippine Sea plates, and the Philippine Sea plate is descending beneath the North American and Eurasian plates. The system is composed of a quasi-static tectonic loading model and a dynamic rupture propagation model, developed on a realistic 3-D plate interface model. The driving force of the system is relative plate motion. In the quasi-static tectonic loading model, mechanical interaction at plate interfaces is rationally represented by the increase of tangential displacement discontinuity (fault slip) across them on the basis of dislocation theory for an elastic surface layer overlying Maxwell-type viscoelastic half-space. In the dynamic rupture propagation model, stress changes due to fault slip motion on non-planar plate interfaces are evaluated with the boundary integral equation method. The progress of seismic (dynamic) or aseismic (quasi-static) fault slip on plate interfaces is governed by a slip- and time-dependent fault constitutive law. As an example, we numerically simulated earthquake generation cycles at the source region of the 1968 Tokachi-oki earthquake on the North American-Pacific plate interface. From the numerical simulation, we can see that postseismic stress relaxation in the asthenosphere accelerates stress accumulation in the source region. When the stress state of the source region is close to a critical level, dynamic rupture is rapidly accelerated and develops over the whole source region. When the stress state is much lower than the critical level, the rupture is not accelerated. This means that the stress state realized by interseismic tectonic loading essentially controls the subsequent dynamic rupture process.

  4. Plate geometry and kinematics modeling to explain South Central Pacific volcanism and plate re-organization

    NASA Astrophysics Data System (ADS)

    Clouard, Valerie; Gerbault, Muriel

    2010-05-01

    We present here a model applied to the Pacific plate for a mechanism governing plate motion related to the plate geometry and kinematics. We start from the observation that from the Kermadec Tonga trench to the Easter microplate, a group of recent and presumed non-deep Pacific hotspots forms a wide east-west channel, and hypothesize that this is not a coincidence. We develop plane strain numerical models of an area corresponding to the Pacific plate from the mid-oceanic ridge to the subduction zone under the Australian plate, with differential velocities applied on the northern and southern part of the plate because of absolute trench motions. Our 2D models indicate a shear band, associated to a change from compressional stresses to the south to tensional stresses to the north, which develop after 10 Myr between the Australian plate corner and the Easter microplate. We propose that the South Central Pacific (SCP) intraplate volcanism is related to this process, and may represent the first step of a future plate re-organization, which will eventually break the Pacific plate in a southern and a northern plate due to intraplate stresses. Lithospheric extension associated with a fertile mantle source is necessary for the presence hotspots when these are not related to a deep mantle plume. To fully explain the SCP volcanism, we show that there is no relation between present-day SCP and the old Northwestern Pacific volcanism, except that it was created over the same mantle region before 70Ma, which represents the very fertile mantle needed.

  5. Geodetic Evidence of Post-2011 Acceleration of the Pacific Plate

    NASA Astrophysics Data System (ADS)

    Heki, K.; Mitsui, Y.

    2014-12-01

    Oceanic plates may accelerate after large inter-plate earthquakes (Anderson, Science 1975). This was indirectly substantiated by Heki and Mitsui (EPSL 2013), who analyzed crustal deformation of an island arc after megathrust earthquakes. Here we show direct evidence of postseismic acceleration of the Pacific Plate from the data of a Global Navigation Satellite System (GNSS) station on the Minami-torishima (Marcus) Island ~2000 km off the Pacific coast of Japan. Heki and Mitsui (2013) found the enhancement of the inter-plate coupling in NE Japan on segments adjacent to those ruptured in the 2003 Tokachi-Oki (Mw8.0) and the 2011 Tohoku-Oki (Mw9.0) earthquakes. They inferred that the subduction of the Pacific Plate slab significantly accelerated after these earthquakes. During interseismic periods, the balance between the down-dip (slab pull and ridge push) and up-dip (viscous traction and interplate coupling) forces realizes convergence rate constant over geological timescales. A megathrust event reduces interplate coupling, and the down-dip forces temporarily exceed the other. The accelerated subduction realizes under the new balance and continues until the interplate coupling recovers. In the Marcus Island, the closest island on the Pacific Plate to the Japan Trench, continuous GNSS observations started in 2002, and showed linear movement toward WNW of ~7.7 cm/year (in the nnr-NUVEL1 frame). This station showed coseismic jump of ~1 cm toward the epicenter in the 2011 Tohoku-oki earthquake. At the same time, the velocity showed distinct increase of ~10 percent without changing the azimuth, resulting in post-2011 speed of ~8.5 cm/year. This is difficult to explain with a simple postseismic viscous relaxation in a stratified earth, and would be the direct evidence of the postseismic acceleration of the Pacific Plate. Such an acceleration is, however, not seen in Hawaii, ~6000 km away from the fault.

  6. Baja transfer by partial coupling with the Pacific plate

    NASA Astrophysics Data System (ADS)

    Plattner, C.; Malservisi, R.; Govers, R.; Iaffaldano, G.

    2008-12-01

    The Baja California (BAJA) microplate was ruptured from the North American (NAM) plate ~ 12 Ma ago and since then translated with the Pacific (PAC) plate. The microplates' transport mechanism has been explained by partial coupling with the PAC plate. According to this theory, the young oceanic lithosphere from the Farallon-Pacific spreading center approaching North America was too buoyant to be subducted. Therefore a zone of increased lithospheric coupling developed between the partially subducted Farallon slabs and the overlying NAM margin. In consequence both, the subduction and the seafloor spreading slowed down and ceased. With the development of this coupling region west of BAJA the main PAC-NAM plate boundary jumped into the NAM continent, east of BAJA. After a phase of distributed extension in the the Protogulf region the new plate boundary localized along the Gulf of California. We use a numerical modeling technique to test the dynamic conditions of BAJA transport as seen from present-day and from geologic plate motion studies. Using the kinematic data we test the necessary coupling forces for BAJA transport, as well as, geometrical constraints along the PAC-BAJA coupling zone. Evaluating the transport conditions at different stages of the plate boundary evolution we want to learn about necessary pre-conditions for the BAJA transfer, in particular along the Gulf of California.

  7. Guadalupe Island, Mexico as a new constraint for Pacific plate motion

    NASA Astrophysics Data System (ADS)

    Gonzalez-Garcia, J. J.; Prawirodirdjo, L.; Bock, Y.; Agnew, D.

    2003-08-01

    We use GPS data collected on Isla de Guadalupe and in northern Baja California, Mexico, to estimate site velocities relative to Pacific plate motion. The velocities of all three geodetic monuments on Guadalupe fit a rigid Pacific plate model with residuals of 1 mm/yr. Using the Guadalupe data and data from five IGS stations on the Pacific plate (CHAT, KOKB, KWJ1, MKEA, and THTI) we estimate an angular velocity for this plate that is consistent with other recently-published estimates. Our results indicate that Isla de Guadalupe lies on the Pacific plate, and that GPS data collection on the island usefully constrains Pacific plate motion and rigidity.

  8. Paleogene tropical Pacific: Clues to circulation, productivity, and plate motion

    NASA Astrophysics Data System (ADS)

    Moore, T. C.; Backman, Jan; Raffi, Isabella; Nigrini, Catherine; Sanfilippo, Annika; PäLike, Heiko; Lyle, Mitchell

    2004-09-01

    Stratigraphic data from 63 Deep Sea Drilling Project and Ocean Drilling Program (ODP) sites that sample the lower Neogene and Paleogene sediments of the tropical Pacific have been compiled and put on the biostratigraphic and paleomagnetic timescale refined by ODP Leg 199 scientists. Sediment accumulation rates have been calculated for ten intervals ranging in age from 10 to 56 Ma and have been plotted for the midpoint of each interval at the associated paleoposition for each site used. A fixed hot spot model was used for reconstruction of the Pacific lithospheric plate. All such reconstructed intervals show the development of a tongue of high accumulation rates associated with the oceanographic divergence at the geographic equator. The development of this equatorial band is weakest between 46 and 56 Ma, the time of the peak warmth in Paleogene climate. Possible motion of the Hawaiian hot spot or true polar wander between 46 and 56 Ma appears to have had little effect on the plate rotation estimate of the position of the equator. In addition to temporal changes in the calcite compensation depth and in productivity, the biggest change in the patterns of sediment accumulation rates in the eastern tropical Pacific was the development of a relatively strong divergence between 6° and 10°N, near the region of divergence between the modern North Equatorial Current and the North Equatorial Counter Current. Changes in the equatorial circulation appear to be associated in time with the opening and closing of oceanic gateways, particularly the complex closing of the Caribbean-Pacific gateway.

  9. Tectonic Fabric of the Cocos Plate and Conjugate Pacific Plate Crust Near Mexico

    NASA Astrophysics Data System (ADS)

    Stock, J. M.

    2014-12-01

    Existing satellite gravity data, along with publicly available single beam bathymetry, multibeam bathymetry, and shipboard and satellite magnetic anomalies were compiled to make an updated map of tectonic features of the Cocos Plate offshore Mexico and the conjugate crust on the Pacific Plate. The area includes the northern Cocos plate as far south as the Tehuantepec Ridge, and Pacific plate crust on both sides of the Mathematician Rise. This thus includes the modern East Pacific Rise (EPR), the submarine rift margins that bound it - Moctezuma and Manzanillo Troughs - and features previously identified such as the Orozco and O'Gorman Fracture Zones near the Middle America Trench (MAT). The goal was to use existing data to evaluate the likely features that may have existed on the now subducted Cocos Plate crust north of the Clarion Fracture Zone-Tehuantepec Ridge. This can then be compared to seismic imaging of the downgoing slab and geochemical variations along the Mexican Volcanic Arc. Bathymetric slopes were computed automatically from multibeam data gridded at 200 m, 300 m, and 400 m pixel size, and processed to remove signals of circular features such as seamounts, and regions of low slope, while emphasizing higher slopes controlled by linear abyssal hill fabric and fracture zones. Tectonic fabrics at all 3 scales are generally similar. In the resulting tectonic fabric map, the domain of modern East Pacific Rise spreading is clearly visible, truncating older fabrics at the Manzanillo Trough on the east and the Moctezuma Trough on the west. The Orozco Fracture Zone lies entirely within the young part of this crustal province and does not reach the Manzanillo Trough or the MAT. Hence, it is not a feature of the downgoing Cocos Plate and should not be used to explain variations in geochemistry of the arc or geometric variations in the subducted plate. A zone of E-W to ENE-WSW oriented abyssal hills and lineated magnetic anomalies in a bathymetric low between the Moctezuma Trough and the Mathematician Rise forms a separate crustal province, truncated by the Moctezuma Trough. There is a possible conjugate fragment of this older province preserved east of the Manzanillo Trough, next to the MAT. Thus, features of the downgoing Cocos Plate appear to be more complicated than has been envisioned in most previous interpretations.

  10. Missing western half of the Pacific Plate: Geochemical nature of the Izanagi-Pacific Ridge interaction with a stationary boundary between the Indian and Pacific mantles

    NASA Astrophysics Data System (ADS)

    Miyazaki, Takashi; Kimura, Jun-Ichi; Senda, Ryoko; Vaglarov, Bogdan S.; Chang, Qing; Takahashi, Toshiro; Hirahara, Yuka; Hauff, Folkmar; Hayasaka, Yasutaka; Sano, Sakae; Shimoda, Gen; Ishizuka, Osamu; Kawabata, Hiroshi; Hirano, Naoto; Machida, Shiki; Ishii, Teruaki; Tani, Kenichiro; Yoshida, Takeyoshi

    2015-09-01

    The source mantle of the basaltic ocean crust on the western half of the Pacific Plate was examined using Pb-Nd-Hf isotopes. The results showed that the subducted Izanagi-Pacific Ridge (IPR) formed from both Pacific (180-˜80 Ma) and Indian (˜80-70 Ma) mantles. The western Pacific Plate becomes younger westward and is thought to have formed from the IPR. The ridge was subducted along the Kurile-Japan-Nankai-Ryukyu (KJNR) Trench at 60-55 Ma and leading edge of the Pacific Plate is currently stagnated in the mantle transition zone. Conversely, the entire eastern half of the Pacific Plate, formed from isotopically distinct Pacific mantle along the East Pacific Rise and the Juan de Fuca Ridge, largely remains on the seafloor. The subducted IPR is inaccessible; therefore, questions regarding which mantle might be responsible for the formation of the western half of the Pacific Plate remain controversial. Knowing the source of the IPR basalts provides insight into the Indian-Pacific mantle boundary before the Cenozoic. Isotopic compositions of the basalts from borehole cores (165-130 Ma) in the western Pacific show that the surface oceanic crust is of Pacific mantle origin. However, the accreted ocean floor basalts (˜80-70 Ma) in the accretionary prism along the KJNR Trench have Indian mantle signatures. This indicates the younger western Pacific Plate of IPR origin formed partly from Indian mantle and that the Indian-Pacific mantle boundary has been stationary in the western Pacific at least since the Cretaceous.

  11. Fast Paleogene Motion of the Pacific Hotspots from Revised Global Plate Circuit Constraints

    NASA Technical Reports Server (NTRS)

    Raymond, C.; Stock, J.; Cande, S.

    2000-01-01

    Major improvements in late Cretaceous-early Tertiary Pacific-Antarctica plate reconstructions, and new East-West Antarctica rotations, allow a more definitive test of the relative motion between hotspots using global plate circuit reconstructions with quantitative uncertainties.

  12. Trans-Pacific Bathymetry Survey crossing over the Pacific, Antarctic, and Nazca plates

    NASA Astrophysics Data System (ADS)

    Abe, N.; Fujiwara, T.

    2013-12-01

    Multibeam bathymetric data reveals seafloor fabrics, i.e. abyssal hills and fracture zones, distribution of seamounts and/or knolls and are usually smaller than the detectable size by global prediction derived from satellite altimetry. The seafloor depths combined with shipboard gravity data indicate the structure of oceanic lithosphere, thermal state, and mantle dynamics and become more accurate data set to estimate fine-scale crustal structures and subsurface mass distribution. We present the ~22000 km long survey line from the northeast Japan through to the equator at the mid-Pacific on to the southwest Chilean coast collected during the JAMSTEC R/V Mirai MR08-06 Leg-1 cruise in January-March 2009. The cruise was as a part of SORA2009 (Abe, 2009 Cruise report) for geological and geophysical studies in the southern Pacific, and was an unprecedented opportunity to collect data in the regions of the Pacific Ocean where it has been sparsely surveyed using state-of-the-art echo-sounding technology. Our multibeam bathymetric and shipboard gravity survey track crossed over the Pacific, the Antarctic, and the Nazca plates, and covered lithospheric ages varying from zero to 150 Ma. Strikes of lineated abyssal hills give critical evidences for future studies of the plate reconstruction and tectonic evolution of the old Pacific Plate because magnetic lineations are unconstrained on the seafloor in the Cretaceous magnetic quiet (125-80 Ma) zone. Consecutive trends of lineated abyssal hills and fracture zones indicate stable tectonic stress field originated from the Pacific Antarctic Ridge (PAR) and the Chile Ridge spreading systems. The seafloor fabric morphology revealed a clear boundary between the PAR and the Chile Ridge domains. The observed bathymetric boundary is probably a part of a trace of the Pacific-Antarctic-Farallon (Nazca) plate's triple junction. The result will be constraint for future studies of the plate reconstruction and tectonic evolution of the PAR, the Chile Ridge, and the Antarctic Plate. Fluctuation of the seafloor fabric strikes on Chile Ridge off-ridge flank suggests instability of tectonic stress field. The seafloor fabric may be largely influenced by the tectonic structure of offsets at fracture zones system separated by short ridge segments. The offset length by fracture zones is short at the flank. The offset of fracture zone increases with age decrease due to ridge jumps (Bourgois et al., 2000 JGR) or change in spreading rates (Matsumoto et al., 2013 Geochem. J.). The dominant stress may vary spatially or temporally, during the fracture zone evolution. Abyssal hills elongated in the direction originated from the Chile Ridge system and fracture zones having long offset lengths distinctly bisect at right angles. We also detected many small seamounts and knolls superimposed on the seafloor fabrics. These are considered to be constructed by excess magmatism at a mid-ocean ridge or intra-plate volcanism.

  13. Pacific-North America plate motions - New results from very long baseline interferometry

    NASA Technical Reports Server (NTRS)

    Ward, Steven N.

    1990-01-01

    The state of Pacific-North America plate interaction is updated using newest VLBI measurements and newly developed rigid plate tectonic models. Particular attention is given to examining the extent of relative motion between the Pacific plate and the North America plate as measured from their stable interiors, the evidence of Pacific plate deformation off the central California coast, and the distribution of path integrated deformaton east of the San Andreas fault. The information obtained on these questions is discussed in the framework of implications for lithospheric rheology and earthquake hazard.

  14. A new GPS velocity field for the Pacific Plate - Part 1: constraints on plate motion, intraplate deformation, and the viscosity of Pacific basin asthenosphere

    NASA Astrophysics Data System (ADS)

    DeMets, C.; Mrquez-Aza, Bertha; Cabral-Cano, Enrique

    2014-12-01

    We combine new, well-determined GPS velocities from Clarion, Guadalupe and Socorro islands on young seafloor in the eastern Pacific basin with newly estimated velocities for 26 GPS sites from older seafloor in the central, western and southern parts of the Pacific Plate to test for deformation within the interior of the Pacific Plate and estimate the viscosity of the asthenosphere below the plate. Relative to a Pacific Plate reference frame defined from the velocities of the 26 GPS sites in other areas of the Pacific Plate, GPS sites on Clarion and Guadalupe islands in the eastern Pacific move 1.2 0.6 mm yr-1 (1?) towards S09W 38 and 1.9 0.3 mm yr-1 towards S19E 10, respectively. The two velocities, which are consistent within their 95 per cent uncertainties, both differ significantly from Pacific Plate motion. Transient volcanic deformation related to a 1993-1996 eruption of the Socorro Island shield volcano renders our GPS velocity from that island unreliable for the tectonic analysis although its motion is also southward like those of Clarion and Guadalupe islands. We test but reject the possibilities that drift of Earth's origin in ITRF2008 or unmodelled elastic offsets due to large-magnitude earthquakes around the Pacific rim since 1993 can be invoked to explain the apparent slow southward motions of Clarion and Guadalupe islands. Similarly, corrections to the Pacific Plate GPS velocity field for possible viscoelastic deformation triggered by large-magnitude earthquakes since 1950 also fail to explain the southward motions of the two islands. Viscoelastic models with prescribed asthenospheric viscosities lower than 1 1019 Pa s instead introduce statistically significant inconsistencies into the Pacific Plate velocity field, suggesting that the viscosity of the asthenosphere below the plate is higher than 1 1019 Pa s. Elastic deformation from locked Pacific-North America Plate boundary faults is also too small to explain the southward motions of the two islands. Horizontal thermal contraction of the plate interior may explain the motion observed at Clarion and Guadalupe islands, as might long-term tectonic deformation of the plate interior.

  15. Circum-arctic plate accretion - Isolating part of a pacific plate to form the nucleus of the Arctic Basin

    USGS Publications Warehouse

    Churkin, M., Jr.; Trexler, J.H., Jr.

    1980-01-01

    A mosaic of large lithospheric plates rims the Arctic Ocean Basin, and foldbelts between these plates contain numerous allochthonous microplates. A new model for continental drift and microplate accretion proposes that prior to the late Mesozoic the Kula plate extended from the Pacific into the Arctic. By a process of circumpolar drift and microplate accretion, fragments of the Pacific basin, including parts of the Kula plate, were cut off and isolated in the Arctic Ocean, the Yukon-Koyukuk basin in Alaska, and the Bering Sea. ?? 1980.

  16. Plate motion controls on back-arc spreading. [Cenozoic movement in Western Pacific

    NASA Technical Reports Server (NTRS)

    Fein, J. B.; Jurdy, D. M.

    1986-01-01

    The motions of the subducting and the overriding plates influence the spatial and temporal distribution of back-arc spreading. Cenozoic plate motions in hot spot-fixed and no-net-rotation reference frames were studied with attention to correlations between changes in motion and episodes of back-arc spreading in the western Pacific. The results suggest that major back-arc opening occurs when both the overriding plate retreats from the trench in an absolute sense and the subducting plate undergoes a significant speed-up. Neither phenomenon alone is sufficient to initiate spreading. Three major plate velocity increases can be identified in the Cenozoic: (1) the Pacific plate 5-9 Ma; (2) the Indian plate at 27 Ma; and (3) the Pacific plate at 43 Ma, due to its shift from northerly to more westerly motion. At the present time, the Indian and Philippine are the only overriding plates that are retreating from their Pacific trenches and back-arc spreading occurs only on these two retreating plates. Although the Indian plate has been retreating for at least 25 Ma, back-arc spreading began only following the Pacific plate speed-up 5-9 Ma. Earlier, during the Indian plate speed-up, no overriding plates were retreating strongly and no back-arc spreading epsiodes are preserved from this time. For the earliest Pacific plate shift at 43 Ma, the Eurasian plate was not advancing, thus creating the only favorable plate kinematic conditions in the Cenozoic for back-arc basin formation in this region. It is unclear whether extension in the Japan Sea is a result of these conditions.

  17. Laser Shockwave Technique For Characterization Of Nuclear Fuel Plate Interfaces

    SciTech Connect

    James A. Smith; Barry H. Rabin; Mathieu Perton; Daniel Lévesque; Jean-Pierre Monchalin; Martin Lord

    2012-07-01

    The US National Nuclear Security Agency is tasked with minimizing the worldwide use of high-enriched uranium. One aspect of that effort is the conversion of research reactors to monolithic fuel plates of low-enriched uranium. The manufacturing process includes hot isostatic press bonding of an aluminum cladding to the fuel foil. The Laser Shockwave Technique (LST) is here evaluated for characterizing the interface strength of fuel plates using depleted Uranium/Mo foils. LST is a non-contact method that uses lasers for the generation and detection of large amplitude acoustic waves and is therefore well adapted to the quality assurance of this process. Preliminary results show a clear signature of well-bonded and debonded interfaces and the method is able to classify/rank the bond strength of fuel plates prepared under different HIP conditions.

  18. Laser shockwave technique for characterization of nuclear fuel plate interfaces

    NASA Astrophysics Data System (ADS)

    Perton, M.; Lévesque, D.; Monchalin, J.-P.; Lord, M.; Smith, J. A.; Rabin, B. H.

    2013-01-01

    The US National Nuclear Security Agency is tasked with minimizing the worldwide use of high-enriched uranium. One aspect of that effort is the conversion of research reactors to monolithic fuel plates of low-enriched uranium. The manufacturing process includes hot isostatic press bonding of an aluminum cladding to the fuel foil. The Laser Shockwave Technique (LST) is here evaluated for characterizing the interface strength of fuel plates using depleted Uranium/Mo foils. LST is a non-contact method that uses lasers for the generation and detection of large amplitude acoustic waves and is therefore well adapted to the quality assurance of this process. Preliminary results show a clear signature of well-bonded and debonded interfaces and the method is able to classify/rank the bond strength of fuel plates prepared under different HIP conditions.

  19. Laser shockwave technique for characterization of nuclear fuel plate interfaces

    SciTech Connect

    Perton, M.; Levesque, D.; Monchalin, J.-P.; Lord, M.; Smith, J. A.; Rabin, B. H.

    2013-01-25

    The US National Nuclear Security Agency is tasked with minimizing the worldwide use of high-enriched uranium. One aspect of that effort is the conversion of research reactors to monolithic fuel plates of low-enriched uranium. The manufacturing process includes hot isostatic press bonding of an aluminum cladding to the fuel foil. The Laser Shockwave Technique (LST) is here evaluated for characterizing the interface strength of fuel plates using depleted Uranium/Mo foils. LST is a non-contact method that uses lasers for the generation and detection of large amplitude acoustic waves and is therefore well adapted to the quality assurance of this process. Preliminary results show a clear signature of well-bonded and debonded interfaces and the method is able to classify/rank the bond strength of fuel plates prepared under different HIP conditions.

  20. 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.

  1. Break-up spots: Could the Pacific open as a consequence of plate kinematics?

    NASA Astrophysics Data System (ADS)

    Clouard, Valérie; Gerbault, Muriel

    2008-01-01

    The South Central Pacific is the location of an abnormal concentration of intraplate volcanism. Noting that this volcanism is present from the Kermadec Tonga trench to the Easter microplate and forms a wide east-west channel, we propose to explain its occurrence in relation to the Pacific plate geometry and kinematics. We construct 2D numerical models of stress and strain within the Pacific plate using its velocity field and boundary conditions. The models indicate a shear band, associated to a change from compressional stresses to the south to tensional stresses to the north, which develop after 10 Myr between the Australian plate corner and the Easter microplate. We propose that the Central Pacific intraplate volcanism is related to this process, and may represent the first step of a future plate re-organization which will eventually break the Pacific plate in a southern and a northern plate due to intraplate stresses. Present-day intraplate volcanism would define break up spots of the future border.

  2. Neotectonics of the Macquarie Ridge Complex, Australia-Pacific plate boundary

    NASA Astrophysics Data System (ADS)

    Massell, C.; Coffin, M. F.; Mann, P.; Mosher, S.; Frohlich, C.; Duncan, C. S.; Karner, G.; Ramsay, D.; Lebrun, J.-F.

    2000-06-01

    New marine geophysical data along the Macquarie Ridge Complex, the Australia-Pacific plate boundary south of New Zealand, illuminate regional neotectonics. We identify tectonic spreading fabric and fracture zones and precisely locate the Australia-Pacific plate boundary along the Macquarie Ridge Complex. We interpret a ˜5-10 km wide Macquarie Fault Zone between the two plates along a bathymétrie high that extends nearly the entire length of the Australia-Pacific plate boundary south of New Zealand. We conclude that this is the active Australia-Pacific strike-slip plate boundary. Arcuate fracture zones become asymptotic as they approach the plate boundary. A broad zone of less intense deformation associated with the plate boundary extends ˜50 km on either side of the Macquarie Fault Zone. Marine geophysical data suggest that distinct segments of the plate boundary have experienced convergence and strike-slip deformation, although teleseismic evidence overwhelmingly indicates strike-slip motion along the entire surveyed boundary today. The McDougall and southernmost Puysegur segments show no evidence for past underthrusting, whereas data from the Macquarie and Hjort segments strongly suggest past convergence. The present-day strike-slip plate boundary along the Macquarie Ridge Complex coincides with the relict spreading center responsible for Australia-Pacific crust in the region. Our conceptual model for the transition from seafloor spreading to strike-slip motion along the Macquarie Ridge Complex addresses the decreasing length of spreading center segments and spacing between fracture zones, as well as the arcuate bend of the fracture zones that become asymptotic to the current transform plate boundary.

  3. Elastostatic bending of a bimaterial plate with a circular interface

    NASA Astrophysics Data System (ADS)

    Ogbonna, Nkem

    2015-08-01

    The elastostatic bending of an arbitrarily loaded bimaterial plate with a circular interface is analysed. It is shown that the deflections in the composite solid are directly related to the deflection in the corresponding homogeneous material by integral and differential operators. It is further shown that, by a simple transformation of elastic constants, the Airy stress function induced in the composite by a stretching singularity can be deduced from the deflection induced by a bending singularity. This result is significant for reduction of mathematical labour and for systematic construction of solutions for more complex structures with circular geometry.

  4. Constraining Late Cretaceous to mid Eocene plate boundaries in the southwest Pacific

    NASA Astrophysics Data System (ADS)

    Matthews, K. J.; Williams, S.; Whittaker, J. M.; Müller, D.; Clarke, G. L.; Seton, M.; Flament, N. E.

    2013-12-01

    The southwest Pacific has undergone a complex tectonic history since the Late Cretaceous, involving multiple episodes of subduction, back-arc spreading and continental deformation. Starkly contrasting reconstructions have been proposed for this period, ranging from tectonic quiescence with no plate boundary between the Lord Howe Rise (LHR) and Pacific, to widespread subduction and back-arc spreading, and this disparity reflects sparse and ambiguous data. Placing further constraints on these reconstructions is crucial for a variety of applications, from global-scale geodynamic studies using plate circuits to basin-scale studies of paleogeographic evolution and vertical motions. Geologic and kinematic data from the southwest Pacific are reviewed to better constrain the tectonic history of the region from the Late Cretaceous to mid Eocene, including the timing and location of plate boundary activity. This facilitates better constraints on the time-dependent evolution of the southwest Pacific plate circuit so that motion between plate pairs is consistent with geologic data and known tectonic regimes. The southwest Pacific comprised three spreading ridges during this time: in the Southeast Indian Ocean, Tasman Sea and Amundsen Sea. However, at least one, and possibly two other plate boundaries also accommodated relative motions: in the West Antarctic Rift System (WARS) and between the LHR and Pacific. Uncertainties in the timing and nature of plate boundaries prevent the construction of a robust reconstruction model and the implementation of a southwest Pacific plate circuit. Some previous plate models include continuous subduction east of the LHR throughout the Late Cretaceous-Cenozoic, while an alternative scenario involves the absence of plate boundaries between the LHR and Pacific until 45 Ma. Geologic observations suggests that subduction initiated to the east of New Caledonia at c. 55 Ma, including dyke emplacement and metamorphism in New Caledonia, and arc-type rocks dredged from the Tonga forearc. These geologic and kinematic data do not require a plate boundary between the LHR and Pacific from c. 84-55 Ma, in agreement with previous studies. A plate boundary may have existed before 55 Ma, however net convergence/divergence at this boundary would have been minor, with a possible strike-slip component. By combining geologic observations with a kinematic analysis, we propose that from 0-55 Ma an Antarctic plate circuit must be used in reconstructions, in which LHR-Pacific motion is unconstrained. From 55-74 Ma Antarctic or Australian circuits can be reconciled with regional geology when revised relative motion histories at the Australian-Antarctic ridge and in the WARS are adopted. A well-constrained Antarctic circuit predicts <50 km of strike-slip motion at a LHR-Pacific boundary. Alternatively, an Australian circuit assuming the LHR was part of the Pacific plate, predicts 100-150 km of extension in the WARS, that is orthogonal in the Ross Sea and oblique further east. Prior to 74 Ma neither plate circuit is preferable, as more data are needed to better constrain regional spreading histories.

  5. Late Cretaceous to mid Eocene plate boundaries in the southwest Pacific

    NASA Astrophysics Data System (ADS)

    Matthews, Kara J.; Dietmar Müller, R.; Whittaker, Joanne; Flament, Nicolas; Seton, Maria

    2013-04-01

    The late Cretaceous to mid Eocene history of the southwest and southernmost Pacific has been subject to starkly contrasting interpretations, ranging from relative tectonic quiescence with the Lord Howe Rise (LHR) being part of the Pacific plate to a dynamic subduction setting. In the first scenario the Tasman Sea would have formed as a consequence of divergence between the Pacific and Australian plates, whereas in the second scenario it would have formed as a marginal basin associated with subduction. The first scenario is supported by a number of arguments, including a lack of evidence for deformation and tectonic activity in New Zealand during this period and a geodynamic modelling inference, namely that the bend in the Hawaiian-Emperor chain can be better reproduced if the LHR is part of the Pacific plate. The second scenario is supported by regional plate kinematic models reconciling a variety of observations including back-arc basin formation and destruction through time and the history of arc-continent collisions. The primary problem with the first scenario is the use of a plate circuit that leaves relative motion between East and West Antarctica unconstrained, leading to an improbable history of periodic compression and extension. The main problem with the alternative scenario is a lack of sampled late Cretaceous volcanic arc rocks east of the LHR. We analysed available geological and geophysical data to constrain the locations of and movements along the plate boundaries in the southwest and southern Pacific from the late Cretaceous to mid Eocene, and assessed how Pacific plate motion is best quantified during this period. Geological and geophysical evidence suggests that a plate boundary separated the Pacific plate from the LHR. The distribution of lower mantle slab material that is imaged by seismic tomography beneath New Zealand is best explained if subduction occurred to the east of the LHR during the entire late Cretaceous to mid Eocene period. Rocks from ophiolitic nappes in the North Island of New Zealand, New Caledonia and Papua New Guinea show evidence of having formed in a back-arc basin during this period, consistent with a subduction zone near the LHR. Although New Zealand is commonly viewed as tectonically quiescent at this time, deformation at several locations to the east and west of the present-day Alpine Fault suggests that a plate boundary cut through Zealandia during Tasman Sea opening. As the LHR was not attached to the Pacific plate and subduction occurred to the east and north of the LHR we suggest that Pacific plate motion is best quantified using a plate circuit through East and West Antarctica, avoiding this zone of southwest Pacific subduction. Future work should focus on better constraining the location of and motion along the late Cretaceous-mid Eocene plate boundary through New Zealand to enable the use of a plate circuit via Australia.

  6. Tectonic implications of post-30 Ma Pacific and North American relative plate motions

    USGS Publications Warehouse

    Bohannon, R.G.; Parsons, T.

    1995-01-01

    The Pacific plate moved northwest relative to North America since 42 Ma. The rapid half rate of Pacific-Farallon spreading allowed the ridge to approach the continent at about 29 Ma. Extinct spreading ridges that occur offshore along 65% of the margin document that fragments of the subducted Farallon slab became captured by the Pacific plate and assumed its motion proper to the actual subduction of the spreading ridge. This plate-capture process can be used to explain much of the post-29 Ma Cordilleran North America extension, strike slip, and the inland jump of oceanic spreading in the Gulf of California. Much of the post-29 Ma continental tectonism is the result of the strong traction imposed on the deep part of the continental crust by the gently inclined slab of subducted oceanic lithosphere as it moved to the northwest relative to the overlying continent. -from Authors

  7. Extension Along the Australian-Pacific Transpressional Transform Plate Boundary Near Macquarie Island

    NASA Astrophysics Data System (ADS)

    Daczko, N. R.; Wertz, K. L.; Mosher, S.; Coffin, M. F.

    2002-12-01

    The Australian-Pacific transform plate boundary fault zone along the Macquarie and McDougall segments of the Macquarie Ridge Complex, south of New Zealand, is characterized by dominantly normal faults and pull-apart basins, in apparent conflict with the regional transpressional tectonic setting. We propose that present day curvature of the transform is inherited from a preexisting divergent plate boundary and that the overall extensional kinematics shown by faults along the main plate boundary trace and exposed on Macquarie Island result from local stresses related to right steps in the plate boundary faults and not to the current transpressional setting. Transpression along the Australian-Pacific transform plate boundary has resulted in uplift of the 1500 km long Macquarie Ridge Complex. Macquarie Island, the only exposure of the complex, sits atop a 5 km high, 50 km wide submarine ridge of oceanic crust and lies 4.5 km east of the major active plate boundary fault zone. Thus, Macquarie Island and the surrounding sea floor provide a unique opportunity to study an active oceanic transform fault using complimentary datasets that include marine geophysics and land based geology. Mapping of recent faults affecting the topography of Macquarie Island shows the island is extensively cut by high angle normal faults forming pull-apart basins. Furthermore, evidence for reverse motion is rare. Using marine geophysical data, including bathymetry, reflectivity and seismic reflection data, collected along the Australian-Pacific plate boundary to the north and south of the island, we have defined a 5-15 km wide plate boundary zone. Within this zone a series of en echelon faults step to the right along the main plate boundary trace. At the right stepping fault terminations, elongate depressions (up to 10 km wide and 1.2 km deep) parallel the plate boundary. We interpret the depressions as responding to local stresses located at extensional relay zones or pull-apart basins.

  8. Thermal Performance Evaluation of Friction Stir Welded and Bolted Cold Plates with Al/Cu Interface

    NASA Astrophysics Data System (ADS)

    Lakshminarayanan, A. K.; Suresh, M.; Sibi Varshan, M.

    2015-05-01

    An attempt is made to design and fabricate a cold plate with aluminum-copper dissimilar interface joined by friction stir welding. Optimum welding conditions for obtaining sound-quality corner and T joints with an aluminum-copper interface were established. Welded cross sections of the friction stir welded cold plate were analyzed to understand the bonding characteristics. Computational fluid dynamics (CFD) was used to evaluate the fluid-flow characteristics and thermal resistance of friction stir welded cold plate and the resulted are compared with the conventional bolted cold plate configuration. For CFD modeling of a cold plate with a dissimilar interface, a new methodology is proposed. From the CFD analysis and experimental results, it is observed that friction stir welded cold plate offered better thermal performance compared to the bolted cold plate and it is due to the metallurgical bonding at the aluminum-copper interface with the dispersion of copper particles.

  9. Pacific plate slab pull and intraplate deformation in the early Cenozoic

    NASA Astrophysics Data System (ADS)

    Butterworth, N. P.; Müller, R. D.; Quevedo, L.; O'Connor, J. M.; Hoernle, K.; Morra, G.

    2014-08-01

    Large tectonic plates are known to be susceptible to internal deformation, leading to a~range of phenomena including intraplate volcanism. However, the space and time dependence of intraplate deformation and its relationship with changing plate boundary configurations, subducting slab geometries, and absolute plate motion is poorly understood. We utilise a buoyancy-driven Stokes flow solver, BEM-Earth, to investigate the contribution of subducting slabs through time on Pacific plate motion and plate-scale deformation, and how this is linked to intraplate volcanism. We produce a series of geodynamic models from 62 to 42 Ma in which the plates are driven by the attached subducting slabs and mantle drag/suction forces. We compare our modelled intraplate deformation history with those types of intraplate volcanism that lack a clear age progression. Our models suggest that changes in Cenozoic subduction zone topology caused intraplate deformation to trigger volcanism along several linear seafloor structures, mostly by reactivation of existing seamount chains, but occasionally creating new volcanic chains on crust weakened by fracture zones and extinct ridges. Around 55 Ma, subduction of the Pacific-Izanagi ridge reconfigured the major tectonic forces acting on the plate by replacing ridge push with slab pull along its northwestern perimeter, causing lithospheric extension along pre-existing weaknesses. Large-scale deformation observed in the models coincides with the seamount chains of Hawaii, Louisville, Tokelau and Gilbert during our modelled time period of 62 to 42 Ma. We suggest that extensional stresses between 72 and 52 Ma are the likely cause of large parts of the formation of the Gilbert chain and that localised extension between 62 and 42 Ma could cause late-stage volcanism along the Musicians volcanic ridges. Our models demonstrate that early Cenozoic changes in Pacific plate driving forces only cause relatively minor changes in Pacific absolute plate motion directions, and cannot be responsible for the Hawaiian-Emperor bend (HEB), confirming previous interpretations that the 47 Ma HEB does not primarily reflect an absolute plate motion event.

  10. Pacific Plate slab pull and intraplate deformation in the early Cenozoic

    NASA Astrophysics Data System (ADS)

    Butterworth, N. P.; Müller, R. D.; Quevedo, L.; O'Connor, J. M.; Hoernle, K.; Morra, G.

    2014-01-01

    Large tectonic plates are known to be susceptible to internal deformation, leading to a range of phenomena including intraplate volcanism. However, the space and time dependence of intraplate deformation and its relationship with changing plate boundary configurations, subducting slab geometries, and absolute plate motion is poorly understood. We utilise a buoyancy driven Stokes flow solver, BEM-Earth, to investigate the contribution of subducting slabs through time on Pacific Plate motion and plate-scale deformation, and how this is linked to intraplate volcanism. We produce a series of geodynamic models from 62 to 42 Ma in which the plates are driven by the attached subducting slabs and mantle drag/suction forces. We compare our modelled intraplate deformation history with those types of intraplate volcanism that lack a clear age progression. Our models suggest that changes in Cenozoic subduction zone topology caused intraplate deformation to trigger volcanism along several linear seafloor structures, mostly by reactivation of existing seamount chains, but occasionally creating new volcanic chains on crust weakened by fracture zones and extinct ridges. Around 55 Ma subduction of the Pacific-Izanagi ridge reconfigured the major tectonic forces acting on the plate by replacing ridge push with slab pull along its north-western perimeter, causing lithospheric extension along pre-existing weaknesses. Large scale deformation observed in the models coincides with the seamount chains of Hawaii, Louisville, Tokelau, and Gilbert during our modelled time period of 62 to 42 Ma. We suggest that extensional stresses between 72 and 52 Ma are the likely cause of large parts of the formation of the Gilbert chain and that localised extension between 62 and 42 Ma could cause late-stage volcanism along the Musicians Volcanic Ridges. Our models demonstrate that early Cenozoic changes in Pacific plate driving forces only cause relatively minor changes in Pacific absolute plate motions, and cannot be responsible for the Hawaii-Emperor Bend (HEB), confirming previous interpretations that the 47 Ma HEB does not reflect an absolute plate motion event.

  11. Paleomagnetism of the Joban Seamount Chain: Its origin and tectonic implications for the Pacific plate

    NASA Astrophysics Data System (ADS)

    Masalu, Desiderius C. P.; Tamaki, Kensaku; Sager, William W.

    1997-03-01

    The paleomagnetism of 10 seamounts from the Joban Seamount Chain (northwestern Pacific) were studied using a method that calculates mean magnetization parameters by an inversion of magnetic anomaly and edifice bathymetry. Of the 10 seamounts, eight gave results consistent with other paleomagnetic studies of Pacific seamounts. Joban seamounts appear to have formed at two different mean paleolatitudes, contrary to what would be expected for a single hotspot origin. Furthermore, six of the consistent poles plot along the 129 to 82 Ma portion of the Pacific plate apparent polar wander path (APWP), implying the seamounts formed mainly during the mid- to Late Cretaceous. Two other poles, from Iwaki and Hitachi seamounts, are located northwest of the older end of the established Pacific APWP, possibly indicating Early Cretaceous ages. Because Iwaki and Hitachi seamounts are located in the middle of the chain, age does not progress along the chain, arguing against a single-hotspot origin. Perhaps the chain formed by recurrent volcanism along a line of weakness or by another mechanism. Iwaki and Hitachi seamounts display smaller northward drift compared to the others, consistent with the Pacific plate drifting southward from Late Jurassic or Early Cretaceous to mid-Cretaceous time.

  12. Bathymetry of the Pacific plate and its implications for thermal evolution of lithosphere and mantle dynamics

    NASA Astrophysics Data System (ADS)

    Zhong, Shijie; Ritzwoller, Michael; Shapiro, Nikolai; Landuyt, William; Huang, Jinshui; Wessel, Paul

    2007-06-01

    A long-standing question in geodynamics is the cause of deviations of ocean depth or seafloor topography from the prediction of a cooling half-space model (HSC). Are the deviations caused entirely by mantle plumes or lithospheric reheating associated with sublithospheric small-scale convection or some other mechanisms? In this study we analyzed the age and geographical dependences of ocean depth for the Pacific plate, and we removed the effects of sediments, seamounts, and large igneous provinces (LIPs), using recently available data sets of high-resolution bathymetry, sediments, seamounts, and LIPs. We found that the removal of seamounts and LIPs results in nearly uniform standard deviations in ocean depth of ˜300 m for all ages. The ocean depth for the Pacific plate with seamounts, LIPs, the Hawaiian swell, and South Pacific super-swell excluded can be fit well with a HSC model till ˜80-85 Ma and a plate model for older seafloor, particularly, with the HSC-Plate depth-age relation recently developed by Hillier and Watts (2005) with an entirely different approach for the North Pacific Ocean. A similar ocean depth-age relation is also observed for the northern region of our study area with no major known mantle plumes. Residual topography with respect to Hillier and Watts' HSC-Plate model shows two distinct topographic highs: the Hawaiian swell and South Pacific super-swell. However, in this residual topography map, the Darwin Rise does not display anomalously high topography except the area with seamounts and LIPs. We also found that the topography estimated from the seismic model of the Pacific lithosphere of Ritzwoller et al. (2004) generally agrees with the observed topography, including the reduced topography at relatively old seafloor. Our analyses show that while mantle plumes may be important in producing the Hawaiian swell and South Pacific super-swell, they cannot be the only cause for the topographic deviations. Other mechanisms, particularly lithospheric reheating associated with "trapped" heat below old lithosphere (Huang and Zhong, 2005), play an essential role in causing the deviations in topography from the HSC model prediction.

  13. Extension along the Australian-Pacific transpressional transform plate boundary near Macquarie Island

    NASA Astrophysics Data System (ADS)

    Daczko, Nathan R.; Wertz, Karah L.; Mosher, Sharon; Coffin, Millard F.; Meckel, Tip A.

    2003-09-01

    The Australian-Pacific transform plate boundary fault zone along the Macquarie and McDougall segments of the Macquarie Ridge Complex (MRC), south of New Zealand, is characterized by dominantly normal faults and pull-apart basins, in apparent conflict with the regional transpressional tectonic setting. We propose that present-day curvature of the transform is inherited from a preexisting divergent plate boundary and that the overall extensional kinematics shown by faults along the main plate boundary trace and exposed on Macquarie Island result from local stresses related to right-lateral, right stepping, en echelon plate boundary faults and not to the current transpressional setting. Transpression along the Australian-Pacific transform plate boundary has resulted in uplift along the ˜1500 km long Macquarie Ridge Complex. Macquarie Island, the only subaerial exposure of the complex, sits atop a ˜5 km high, ˜50 km wide submarine ridge of oceanic crust and lies ˜4.5 km east of the major active plate boundary fault zone. Thus Macquarie Island and the surrounding seafloor provide a unique opportunity to study an active oceanic transform fault using complementary marine geophysical and land-based geological data. Mapping of recent faults affecting the topography of Macquarie Island shows that the island is extensively cut by high-angle normal faults forming pull-apart basins. Furthermore, evidence for reverse motion is rare. Using marine geophysical data, including swath bathymetry, reflectivity, and seismic reflection data, collected along the Australian-Pacific plate boundary north and south of the island, we have defined a 5-15 km wide plate boundary zone. A series of right stepping en echelon faults, within this zone, lies along the main plate boundary trace. At the right stepping fault terminations, elongate depressions (≤10 km wide and 1.2 km deep) parallel the plate boundary, which we interpret as extensional relay zones or pull-apart basins. We propose that transpression is partitioned into en echelon strike-slip faults at the plate boundary and a convergent component that flexes the crust, causing the anomalous bathymetric ridge and trough morphology of the McDougall and Macquarie segments of the MRC.

  14. Constraints on Pacific plate kinematics and dynamics with global positioning system measurements

    NASA Technical Reports Server (NTRS)

    Dixon, T. H.; Golombek, M. P.; Thornton, C. L.

    1985-01-01

    A measurement program designed to investigate kinematic and dynamic aspects of plate tectonics in the Pacific region by means of satellite observations is proposed. Accuracy studies are summarized showing that for short baselines (less than 100 km), the measuring accuracy of global positioning system (GPS) receivers can be in the centimeter range. For longer baselines, uncertainty in the orbital ephemerides of the GPS satellites could be a major source of error. Simultaneous observations at widely (about 300 km) separated fiducial stations over the Pacific region, should permit an accuracy in the centimeter range for baselines of up to several thousand kilometers. The optimum performance level is based on the assumption of that fiducial baselines are known a priori to the centimeter range. An example fiducial network for a GPS study of the South Pacific region is described.

  15. New type volcanism along fractures on the flexural Cretaceous Pacific Plate

    NASA Astrophysics Data System (ADS)

    Hirano, N.; Takahashi, E.; Hirata, T.; Yamamoto, J.; Machida, S.; Ishii, T.; Abe, N.

    2005-12-01

    No present-day volcanic activity had been documented on a Cretaceous lithosphere so far. However, Hirano et al. (2001) reported a young basalt (6 Ma) on the 130 Ma Pacific Plate in the Japan Trench. Through our expedition for the young volcanoes in the NW Pacific conducted during the KR04-08 cruise of JAMSTEC R/V KAIREI in June 2004, apparently quite young lavas were dredged from a knoll. The site is located on the eastern edge of the outer-rise, and at the inferred eruption site for the 6 Ma lavas found in the Japan Trench. Young (<1 Ma) volcanoes of strongly alkaline magma was discovered on the Early Cretaceous (135 Ma) Pacific Plate. Major and trace element compositions of lavas suggest the magma from asthenosphere. Noble gas isotopes of bubbles in the quenched glasses clearly show that the source of magma is similar to MORB rather than that of OIB. The WNW-ESE alignments of knolls are perpendicular to hinge lines on the flexural outer-rise. The eruption occurred along the maximum horizontal compression due to the down-warping of the Pacific Plate for sub-crustal magma injection. An old lithosphere may be deformed or flexed due to seamount-loading, and due to bending related to the plate subduction. Large curvatures of the lithosphere might cause brittle fractures. The location of this study coincides with the concave part of the outer-rise. Some workers have supposed that the highly alkaline magma leaks on the flexural part of lithosphere such as the flexural arch and rejuvenated stages, which are far from the active shield volcanoes at the Hawaiian and the Samoan islands. Hence, the asthenospheric melt may be able to escape to the surface wherever the lithosphere is flexed and fractured, and this young volcano might be such an example.

  16. Propagation of the Hawaiian-Emperor volcano chain by Pacific plate cooling stress

    USGS Publications Warehouse

    Stuart, W.D.; Foulger, G.R.; Barall, M.

    2007-01-01

    The lithosphere crack model, the main alternative to the mantle plume model for age-progressive magma emplacement along the Hawaiian-Emperor volcano chain, requires the maximum horizontal tensile stress to be normal to the volcano chain. However, published stress fields calculated from Pacific lithosphere tractions and body forces (e.g., subduction pull, basal drag, lithosphere density) are not optimal for southeast propagation of a stress-free, vertical tensile crack coincident with the Hawaiian segment of the Hawaiian-Emperor chain. Here we calculate the thermoelastic stress rate for present-day cooling of the Pacific plate using a spherical shell finite element representation of the plate geometry. We use observed seafloor isochrons and a standard model for lithosphere cooling to specify the time dependence of vertical temperature profiles. The calculated stress rate multiplied by a time increment (e.g., 1 m.y.) then gives a thermoelastic stress increment for the evolving Pacific plate. Near the Hawaiian chain position, the calculated stress increment in the lower part of the shell is tensional, with maximum tension normal to the chain direction. Near the projection of the chain trend to the southeast beyond Hawaii, the stress increment is compressive. This incremental stress field has the form necessary to maintain and propagate a tensile crack or similar lithosphere flaw and is thus consistent with the crack model for the Hawaiian volcano chain.?? 2007 The Geological Society of America.

  17. Viscous fingering in the Earth's mantle beneath western North American and the Pacific plate

    NASA Astrophysics Data System (ADS)

    Weeraratne, D. S.; Parmentier, E.; Lekic, V.

    2012-12-01

    The recent advent of high resolution seismic tomography provided by the USArray project in western North American and ocean bottom seismometer deployments on the seafloor have shown a critical link between surface geology, volcanic observations and deep mantle structure. A unique pattern of volcanic lineaments have been observed on the south Pacific seafloor which form a group of parallel linear volcanic chains. Recently, similar features have been proposed on continental plates in western North America as a group of Cenozoic volcanic lineaments consisting of the Yellowstone, St George, Colorado Mineral Belt, and Jimenez volcanic trends. In both the North American continent and Pacific ocean case, an array of seismometers were deployed and seismic tomography images reveal a set of regularly spaced, linear, parallel low velocity anomalies that align in the direction of plate motion and correlate with surface volcanism. Here we consider a fluid dynamic model of viscous fingering in the asthenospheric mantle which links deep mantle flow to surface volcanic observations. We present results from physical fluid experiments scaled to mantle dynamics which indicate that Saffman-Taylor instabilities or viscous fingering may form in the asthenosphere beneath moving tectonic plates. Scaling indicates that the wavelength of fingering (l_f) is strongly dependent on asthenospheric channel thickness (B) as l_f = 4B. The presence of a mobile overriding plate acts to align fingers in the direction of plate motion propagating both upstream and downstream. Tomography images indicate that fingering wavelengths may be significantly larger beneath continental plates compared to oceanic plates. Further scaling between laboratory fluid experiments and mantle seismic tomography including comparison of surface volcanic lineaments, tomographic imaging, and lithosphere-asthenosphere thickness will be presented.

  18. The Hawaiian-Emperor Bend: A Record of Pronounced Change in Pacific Absolute Plate Motion

    NASA Astrophysics Data System (ADS)

    Wessel, P.; Kroenke, L. W.; Harada, Y.; Sterling, A.

    2002-12-01

    Following the development of the hot spot hypothesis (Morgan, 1971) there was almost unanimous agreement that the Hawaiian-Emperor Bend (HEB) was the archetypal example of a large change in absolute plate motion (APM) recorded by hot spot volcanism. Lately, however this conviction has come under renewed scrutiny. Norton (1995) analyzed the geological evidence for contemporaneous tectonic activity and found none, arguing instead that the HEB was a "nonevent" caused by southward drift of the Hawaiian plume. Earlier studies had argued that it was impossible to fit all Pacific hotspot trails without invoking drift (Molnar and Stock, 1987). Recent fluid dynamic modeling, suggesting southeast-ward drift of the Hawaiian plume (Steinberger and O'Connell, 1997), supports that view and is in accord with sparse paleomagnetic data. African APM models, when projected via the Antarctica plate circuit into the Pacific, fail to reproduce the HEB, suggesting that the HEB does not reflect APM changes (Cande et al., 1995). Finally, the lack of a major reorganization of the Pacific-Farallon ridge system following the HEB event seems to imply that no large APM change took place (Atwater, 1989). Collectively, these arguments put the fixed hotspot hypothesis on the defensive. Despite these arguments, we wish to point out several facts that caution against the quick dismissal of a fixed hotspot frame of reference for the Pacific. First, and contrary to Norton's conclusions, there are significant tectonic precursors that appear to be directly related to the HEB event. Second, modeling of the Pacific APM using both hotspotting (Wessel and Kroenke, 1997) and polygon finite rotations (Harada and Hamano, 2000) does allow numerous chains to be fit simultaneously without invoking hotspot drift. In particular, we find geometrical suggestions of several seamount trail bends apparently coeval with the HEB; however, lack of radiometric dates precludes firm determinations. Third, the differential motion (DM) vectors associated with the HEB plate motion change are approximately normal to the Vancouver-Pacific spreading axis at that time. If the DM vectors can be considered proxies for stresses, then they imply there would be no reason for the ridge to reorient itself significantly. Further south, along the Pacific-Farallon ridge, the small angular difference between the DM vectors and the spreading direction may have initiated numerous propagating rifts around Chron 19. The area where the largest DM occurs coincides with the oldest part of the Western Pacific. Here, the plate was already old and mechanically strong and no deformation can be found orthogonal to the DM directions. Fourth, the large dispersion of paleo-latitudes, the possibility of magnetic terrain effects, and potentially unrecognized tectonic deformation may leave room for alternative explanations such as true polar wander. Finally, although we cannot rule out the possibility that the Pacific hotspots group has moved together, it is our belief that some of the mismatch between Pacific and Africa APM derives from incomplete parameterization of the global plate circuit.

  19. 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 transtensional zone of long offset strike-slip faults and intervening basins (the modern Gulf of California basin and transform fault system). Within and adjacent to this zone the fault patterns continued to evolve, with new plate boundary strike-slip faults breaking into previously intact blocks of continent. These new strike-slip faults were not accompanied by any widespread zones of tectonic rotation. This suggests that if widespread rotations are occurring, plate boundary transtension has not yet localized and the strike-slip faults are not yet accommodating most of the plate boundary slip. The cessation of widespread and significant vertical axis rotations could indicate strain localization and the increasing importance of throughgoing strike-slip faults (a precursor to fully oceanic rifting) along a transtensional plate boundary.

  20. Interface-guided mode of Lamb waves in a two-dimensional phononic crystal plate

    NASA Astrophysics Data System (ADS)

    Huang, Ping-Ping; Yao, Yuan-Wei; Wu, Fu-Gen; Zhang, Xin; Li, Jing; Hu, Ai-Zhen

    2015-05-01

    We investigate the interface-guided mode of Lamb waves in a phononic crystal heterostructures plate, which is composed of two different semi-infinite phononic crystal (PC) plates. The interface-guided modes of the Lamb wave can be obtained by the lateral lattice slipping or by the interface longitudinal gliding. Significantly, it is observed that the condition to generate the interface-guided modes of the Lamb wave is more demanding than that of the studied fluid-fluid system. The interface-guided modes are strongly affected not only by the relative movement of the two semi-infinite PCs but also by the thickness of the PC plate. Project supported by the National Natural Science Foundation of China (Grant Nos. 11374068 and 11374066), the Science & Technology Star of Zhujiang Foundation of Guangzhou, China (Grant No. 2011J2200013), and the Natural Science Foundation of Guangdong, China (Grant No. S2012020010885).

  1. Global Plate Reconstructions, Pacific Plate Apparent Polar Wander, and the Origin of the Bend in the Hawaiian-Emperor Chain

    NASA Astrophysics Data System (ADS)

    Gordon, R. G.

    2011-12-01

    A key tectonic event near 50 Ma B.P. is the formation of the bend in the Hawaiian-Emperor hotspot track. A central question about the formation of the bend is whether it represents a change in plate motion or a change in motion of the Hawaiian hotspot or some combination of the two. In this presentation I will review results of mainly recent work with Rice collaborators and consider the implications for the bend. Koivisto et al. (2011) present an updated test of the fixed-hotspot approximation comparing the observed positions of Indo-Atlantic hotspot tracks with those predicted from Pacific plate hotspot tracks and the global plate motion circuit through Antarctica. This updated study indicates 2 to 5 mm/a motion between hotspots for the past 48 Ma,that is, since the formation of the bend in the Hawaiian-Emperor chain. The confidence limits include zero and thus are consistent with no motion between Pacific hotspots and Indo-Atlantic hotspots for the past 48 Ma. This does not necessarily imply that the hotspots are fixed, as the uncertainties allow for motion up to 8 to 12 mm/a, but does exclude higher rates. When we examine predictions for times preceding 48 Ma B.P. we obtain very different results, however, the apparent rates of inter-hotspot motion increase to about 45-55 ± 20 mm/a. One explanation is that hotspots moved rapidly relative to one another before 48 Ma B.P. and then slowed dramatically at roughly the age of the elbow. An alternative explanation is that as we go further back in time the global plate motion circuit through Antarctica is less reliable. The possibility of motion between East and West Antarctica will be considered. Paleomagnetic data can be used to discriminate between these alternatives. The paleomagnetic results of Petronotis & Gordon [1989], Acton & Gordon [1994], Horner-Johnson & Gordon [2010], Zheng et al. [this meeting], and Boswell et al. [this meeting] will be reviewed and implications discussed.

  2. Marine magnetic anomaly and magnetization of subducting Pacific Plate around the Japan Trench

    NASA Astrophysics Data System (ADS)

    Fujiwara, T.

    2013-12-01

    We studied marine magnetic anomaly in the northwestern margin of the Pacific Plate off Japan to examine whether the magnetic anomaly varies due to tectonic phenomenon caused by the plate subduction. For the sake of this study, we newly collected magnetic data aboard JAMSTEC cruises in the seaward area where was sparsely surveyed, and made a magnetic anomaly map by compilation of our data, data published by Geological Survey of Japan, and data from NGDC. The seafloor of the seaward slope of the Japan Trench is characterized by a series of parallel magnetic anomalies (Japanese Lineation Set) during M11-M7 (135-127 Ma). The anomalies are well lineated and have high-amplitudes of ~500-1000 nT peak-to-trough. The amplitudes of the anomalies gradually decay to the landward from the trench axis associated with the plate subduction. Equivalent magnetization was calculated from the magnetic anomaly to correct for effects of seafloor topography and increasing depth of subducting plate. Densely distributed seismic survey profiles in the study area enabled us to constrain the depth of the plate. On the seaward trench slope from the trench axis to a distance of ca. 100 km, horst-graben structure is developed and large steps grow associated with plate bending and normal faulting, which would cause some kind of destruction and mechanical disorganization of the magnetic layer by faulting. However, the magnetization is not influenced apparently there. The magnetization gradually decreases as the plate subduction proceeded. The apparent decay could reflect destruction and mechanical disorganization and/or chemical demagnetization of the topmost part of the oceanic crust along the plate boundary. The magnetization in reverse polarity decays larger than that in normal polarity. The result is indicative of reduction of remanence in the oceanic crust and induced magnetization possibly due to serpentinized uppermost mantle.

  3. The geochemical fingerprint of serpentinite- and crust-dominated plate-interface settings: some tectonic implications

    NASA Astrophysics Data System (ADS)

    Cannaò, Enrico; Scambelluri, Marco; Agostini, Samuele; Tonarini, Sonia

    2014-05-01

    The interface between converging plates is made of kilometre-thick domains where slab and upper plate mantle materials are tectonically slicied within a matrix dominated either by (meta)sedimentary/crustal rocks or by serpentinite. The latter may correspond to supra-subduction mantle altered by uprising slab fluids. Once formed, these plate-interface domains act as hydrated low-viscosity layers where tectonic stress and fluid-mediated mass transfer are strongly focussed. Here we present the geochemical study of two plate-interface environments: (1) serpentinite-rich, represented by the high-pressure serpentinites of the Ligurian Alps (Erro-Tobbio and Voltri Units); (2) sediment-dominated top slab mélange, represented by de-serpentinized garnet peridotite and chlorite harzburgite bodies (hosting eclogite and metarodingite) embedded in paragneiss and micaschist from Cima di Gagnone (Adula Unit, Central Alps). The Ligurian serpentinites derive from oceanic and wedge mantle tectonically coupled and dragged to depth during Alpine subduction: they may represent the hydrated precursors of the Cima di Gagnone peridotites. The B, Pb and Sr isotopic composition of the above sets of rocks helps defining tectonic and mass transfer processes during accretion of slab and suprasubduction mantle rocks in plate-interface domains, and to retrieve the imprint of fluids from these settings, which that ultimately affect arc magmatism. The serpentinized peridotites from Erro-Tobbio (ET) show high B (10-30 ppm), delta11B (10-25 per mil), B/Nb ratio (>380) and limited enrichment in 206Pb/204Pb (18.17-18,51) and 87Sr/86Sr (0.7046- 0.7060). Scambelluri & Tonarini (2012) interpreted the B and Sr isotopic imprint of ET as representative of upper plate mantle altered by slab-fluids. The B contents (up to 30 ppm), delta11B (18-30 per mil), B/Nb ratio (>900) and 206Pb/204Pb (18.09-18.22) of the Voltri serpentinites are similar to ET. Their 87Sr/86Sr (0.7079 to 0.7105) is higher than ET. The garnet peridotite and harzburgite from Gagnone have low B (up to 9 ppm), low B/Nb (<100) and high Pb and Sr isotopic ratios (206Pb/204Pb up to 18.84; 87Sr/86Sr 0.7124). Eclogite and HP metarodingite in the Gagnone peridotite show comparable values. The host metasediments and gneiss show higher B (6-16 ppm), 206Pb/204Pb (up to 18.98) and 87Sr/86Sr (0.7275). than peridotites and mafic rocks. All the Gagnone rocks have negative delta11B (ultramafic and mafic rocks = 0 to -10 per mil; country rocks = -3 to -12 per mil). The Gagnone peridotites reveal geochemical mixing between ultramafic and host crustal reservoirs. Considering that these peridotites derive from serpentinized protoliths, we expect that the initial high 11B of serpentinites was modified by two combined processes: (1) serpentine dehydration, releasing heavy B to fluids, and (2) exchange between ultramafic rocks and sediment-derived subduction fluids during burial and exhumation. The geochemical signature of the Voltri serpentinites is indicative of interaction with slab fluids enriched in heavy B-rich and in crust-derived components, such as in mantle rocks which evolved atop of the subducting slab. This implies that the slices of the downgoing slab are emplaced early during their burial history atop of the subducting plate. The geochemical signature of peridotites and host metasediments from Gagnone, points to significant exchange between ultramafic bodies and host rocks during prograde subduction prior to peak metamorphism. This again indicates accretion to the plate interface of slab and wedge materials during an early stage of subduction. Moreover, Voltri and Gagnone represent distinct reservoirs, showing positive versus negative delta11B. Serpentinite-dominated settings, like Voltri, produce high B and 11B fluids which can explain 11B-enrichment of much Pacific arcs. Differently, the sediment- and gneiss-dominated Gagnone mélange shows high B, negative δ11B, high radiogenic Pb and Sr: fluids released from such a mélange fit the composition of lavas from convergent margins affected by continental subduction.

  4. The 2011 Tohoku-oki Earthquake related to a large velocity gradient within the Pacific plate

    NASA Astrophysics Data System (ADS)

    Matsubara, Makoto; Obara, Kazushige

    2015-04-01

    We conduct seismic tomography using arrival time data picked by the high sensitivity seismograph network (Hi-net) operated by National Research Institute for Earth Science and Disaster Prevention (NIED). We used earthquakes off the coast outside the seismic network around the source region of the 2011 Tohoku-oki Earthquake with the centroid depth estimated from moment tensor inversion by NIED F-net (broadband seismograph network) as well as earthquakes within the seismic network determined by Hi-net. The target region, 20-48N and 120-148E, covers the Japanese Islands from Hokkaido to Okinawa. A total of manually picked 4,622,346 P-wave and 3,062,846 S-wave arrival times for 100,733 earthquakes recorded at 1,212 stations from October 2000 to August 2009 is available for use in the tomographic method. In the final iteration, we estimate the P-wave slowness at 458,234 nodes and the S-wave slowness at 347,037 nodes. The inversion reduces the root mean square of the P-wave traveltime residual from 0.455 s to 0.187 s and that of the S-wave data from 0.692 s to 0.228 s after eight iterations (Matsubara and Obara, 2011). Centroid depths are determined using a Green's function approach (Okada et al., 2004) such as in NIED F-net. For the events distant from the seismic network, the centroid depth is more reliable than that determined by NIED Hi-net, since there are no stations above the hypocenter. We determine the upper boundary of the Pacific plate based on the velocity structure and earthquake hypocentral distribution. The upper boundary of the low-velocity (low-V) oceanic crust corresponds to the plate boundary where thrust earthquakes are expected to occur. Where we do not observe low-V oceanic crust, we determine the upper boundary of the upper layer of the double seismic zone within high-V Pacific plate. We assume the depth at the Japan Trench as 7 km. We can investigate the velocity structure within the Pacific plate such as 10 km beneath the plate boundary since the rays from the hypocenter around the coseismic region of the Tohoku-oki earthquake take off downward and pass through the Pacific plate. The landward low-V zone with a large anomaly corresponds to the western edge of the coseismic slip zone of the 2011 Tohoku-oki earthquake. The initial break point (hypocenter) is associated with the edge of a slightly low-V and low-Vp/Vs zone corresponding to the boundary of the low- and high-V zone. The trenchward low-V and low-Vp/Vs zone extending southwestward from the hypocenter may indicate the existence of a subducted seamount. The high-V zone and low-Vp/Vs zone might have accumulated the strain and resulted in the huge coseismic slip zone of the 2011 Tohoku earthquake. The low-V and low-Vp/Vs zone is a slight fluctuation within the high-V zone and might have acted as the initial break point of the 2011 Tohoku earthquake. Reference Matsubara, M. and K. Obara (2011) The 2011 Off the Pacific Coast of Tohoku earthquake related to a strong velocity gradient with the Pacific plate, Earth Planets Space, 63, 663-667. Okada, Y., K. Kasahara, S. Hori, K. Obara, S. Sekiguchi, H. Fujiwara, and A. Yamamoto (2004) Recent progress of seismic observation networks in Japan-Hi-net, F-net, K-NET and KiK-net, Research News Earth Planets Space, 56, xv-xxviii.

  5. Evaluating Cenozoic equatorial sediment deposition anomalies for potential paleoceanographic and Pacific plate motion applications

    NASA Astrophysics Data System (ADS)

    Mitchell, Neil C.; Dubois, Nathalie

    2014-03-01

    If equatorial sediments form characteristic deposits around the equator, they may help to resolve the amount of northwards drift of the Pacific tectonic plate. Relevant to this issue, it has been shown that 230Th has been accumulating on the equatorial seabed faster than its production from radioactive decay in the overlying water column during the Holocene (Marcantonio et al. in Paleoceanography 16:260-267, 2001). Some researchers have argued that this reflects the deposition of particles with adsorbed 230Th carried by bottom currents towards the equator ("focusing"). If correct, this effect may combine with high pelagic productivity, which is also centered on the equator, to yield a characteristic signature of high accumulation rates marking the paleoequator in older deposits. Here we evaluate potential evidence that such an equatorial feature existed in the geological past. Seismic reflection data from seven meridional transects suggest that a band of equatorially enhanced accumulation of restricted latitude was variably developed, both spatially and temporally. It is absent in the interval 14.25-20.1 Ma but is well developed for the interval 8.55-14.25 Ma. We also examined eolian dust accumulation rate histories generated from scientific drilling data. A dust accumulation rate anomaly near the modern equator, which is not obviously related to the inter-tropical convergence zone, is interpreted as caused by focusing. Accumulation rates of Ba and P2O5 (proxies of export production) reveal a static equatorial signature, which suggests that the movement of the Pacific plate over the period 10-25 Ma was modest. The general transition from missing to well-developed focusing signatures around 14.25 Ma in the seismic data coincides with the mid-Miocene development of the western boundary current off New Zealand. This current supplies the Pacific with deep water from Antarctica, and could therefore imply a potential paleoceanographic or paleoclimatic origin. At 10.05-14.25 Ma, the latitudes of the seismic anomalies are up to ~2 different from the paleoequator predicted by Pacific plate-hotspot models, suggesting potentially a small change in the hotspot latitudes relative to the present day (although this inference depends on the precise form of the deposition around the equator). The Ba and P2O5 anomalies, on the other hand, are broadly compatible with plate models predicting slow northward plate movement over 10-25 Ma.

  6. Holocene Pacific North American plate interaction in southern Alaska: Implications for the Yakataga seismic gap

    NASA Astrophysics Data System (ADS)

    Lahr, John C.; Plafker, George

    1980-10-01

    The St. Elias, Alaska, earthquake (magnitude 7.1 Ms) on February 28, 1979, occurred along the complex Pacific North American plate boundary between Yakutat Bay and Prince William Sound, rupturing only a fraction of the seismic gap identified in that region. To aid in evaluating the potential for, and likely site of, a future earthquake occurring in the remainder of the gap, we have formulated a kinematic model of neotectonic deformation in southern Alaska from available geologic and seismic data. In this model the part of the North American plate bordering on the Gulf of Alaska is divided into three subblocks, which are partially coupled to the Pacific plate. On the basis of the model, the gap-filling rupture or ruptures would most likely be along the north-dipping thrust faults of the Pamplona zone between Icy Bay and the eastern end of the Aleutian Trench. If the accumulated strain of 3.8 m postulated for this region were released suddenly in one event involving the remainder of the gap, the result would be an earthquake as large as magnitude 8.

  7. Holocene Pacific - North American plate interaction in southern Alaska: implications for the Yakataga seismic gap.

    USGS Publications Warehouse

    Lahr, J.C.; Plafker, G.

    1980-01-01

    The St. Elias, Alaska, earthquake (magnitude 7.1 MS) on February 28, 1979, occurred along the complex Pacific-North American plate boundary between Yakutat Bay and Prince William Sound, rupturing only a fraction of the seismic gap identified in that region. To aid in evaluating the potential for, and likely site of, a future earthquake occurring in the remainder of the gap, we have formulated a kinematic model of neotectonic deformation in southern Alaska from available geologic and seismic data. In this model the part of the North American plate bordering on the Gulf of Alaska is divided into three subblocks, which are partially coupled to the Pacific plate. On the basis of the model, the gap-filling rupture or ruptures would most likely be along the north-dipping thrust faults of the Pamplona zone between Icy Bay and the eastern end of the Aleutian Trench. If the accumulated strain of 3.8 m postulated for this region were released suddenly in one event involving the remainder of the gap, the result would be an earthquake as large as magnitude 8. -Authors

  8. Late cretaceous polar wander of the pacific plate: evidence of a rapid true polar wander event

    PubMed

    Sager; Koppers

    2000-01-21

    We reexamined the Late Cretaceous-early Tertiary apparent polar wander path for the Pacific plate using 27 paleomagnetic poles from seamounts dated by (40)Ar/(39)Ar geochronology. The path shows little motion from 120 to 90 million years ago (Ma), northward motion from 79 to 39 Ma, and two groups of poles separated by 16 to 21 degrees with indistinguishable mean ages of 84 +/- 2 Ma. The latter phenomenon may represent a rapid polar wander episode (3 to 10 degrees per million years) whose timing is not adequately resolved with existing data. Similar features in other polar wander paths imply that the event was a rapid shift of the spin axis relative to the mantle (true polar wander), which may have been related to global changes in plate motion, large igneous province eruptions, and a shift in magnetic field polarity state. PMID:10642540

  9. Seismic velocity structure of the subducting Pacific plate in the Izu-Bonin region

    SciTech Connect

    Iidaka, Takashi; Mizoue, Megumi; Suyehiro, Kiyoshi )

    1992-10-01

    Observed travel time residual data from a spatially dense seismic network above deep earthquakes in the Izu-Bonin region are compared with 3D ray tracing calculations. The data are inconsistent with a homogeneous slab model and consistent with a heterogenous slab model with regional velocity variations. The residual data can be explained by a model that has a velocity gradient within the slab. In the subducting Pacific plate, the velocity near the center of the slab is faster than that near the upper boundary, and gradually decreases toward the bottom of the plate. A model with a velocity decrease of 3 percent, as predicted by a thermal profile, explains the observed data. 52 refs.

  10. Structure and deformation of the Kermadec forearc in response to subduction of the Pacific oceanic plate

    NASA Astrophysics Data System (ADS)

    Funnell, M. J.; Peirce, C.; Stratford, W. R.; Paulatto, M.; Watts, A. B.; Grevemeyer, I.

    2014-11-01

    The Tonga-Kermadec forearc is deforming in response to on-going subduction of the Pacific Plate beneath the Indo-Australian Plate. Previous research has focussed on the structural development of the forearc where large bathymetric features such as the Hikurangi Plateau and Louisville Ridge seamount chain are being subducted. Consequently, knowledge of the `background' forearc in regions of normal plate convergence is limited. We report on an ˜250-km-long multichannel seismic reflection profile that was shot perpendicular to the Tonga-Kermadec trench at ˜28°S to determine the lateral and temporal variations in the structure, stratigraphy and deformation of the Kermadec forearc resulting solely from Pacific Plate subduction. Interpretation of the seismic profile, in conjunction with regional swath bathymetry data, shows that the Pacific Plate exhibits horst and graben structures that accommodate bending-induced extensional stresses, generated as the trenchward dip of the crust increases. Trench infill is also much thicker than expected at 1 km which, we propose, results from increased sediment flux into and along the trench. Pervasive normal faulting of the mid-trench slope most likely accommodates the majority of the observed forearc extension in response to basal subduction erosion, and a structural high is located between the mid- and upper-trench slopes. We interpret this high as representing a dense and most likely structurally robust region of crust lying beneath this region. Sediment of the upper-trench slope documents depositional hiatuses and on-going uplift of the arc. Strong along-arc currents appear to erode the Kermadec volcanic arc and distribute this sediment to the surrounding basins, while currents over the forearc redistribute deposits as sediment waves. Minor uplift of the transitional Kermadec forearc, observed just to the north of the profile, appears to relate to an underlying structural trend as well as subduction of the Louisville Ridge seamount chain 250 km to the north. Relative uplift of the Kermadec arc is observed from changes in the tilt of upper-trench slope deposits and extensional faulting of the basement immediately surrounding the Louisville Ridge.

  11. How do long-offset oceanic transforms adapt to plate motion changes? The example of the Western Pacific-Antarctic plate boundary

    NASA Astrophysics Data System (ADS)

    Lodolo, Emanuele; Coren, Franco; Ben-Avraham, Zvi

    2013-03-01

    Oceanic transform faults respond to changes in the direction of relative plate motion. Studies have shown that short-offset transforms generally adjust with slight bends near the ridge axis, while long-offset ones have a remarkably different behavior. The western Pacific-Antarctic plate boundary highlights these differences. A set of previously unpublished seismic profiles, in combination with magnetic anomaly identifications, shows how across a former, ~1250 km long transform (the Emerald Fracture Zone), plate motion changes have produced a complex geometric readjustment. Three distinct sections are recognized along this plate boundary: an eastern section, characterized by parallel, multiple fault strand lineaments; a central section, shallower than the rest of the ridge system, overprinted by a mantle plume track; and a western section, organized in a cascade of short spreading axes/transform lineaments. This configuration was produced by changes that occurred since 30 Ma in the Australia-Pacific relative plate motion, combined with a gradual clockwise change in Pacific-Antarctic plate motion. These events caused extension along the former Emerald Fracture Zone, originally linking the Pacific-Antarctic spreading ridge system with the Southeast Indian ridge. Then an intra-transform propagating ridge started to develop in response to a ~6 Ma change in the Pacific-Antarctic spreading direction. The close proximity of the Euler poles of rotation amplified the effects of the geometric readjustments that occurred along the transform system. This analysis shows that when a long-offset transform older than 20 Ma is pulled apart by changes in spreading velocity vectors, it responds with the development of multiple discrete, parallel fault strands, whereas in younger lithosphere, locally modified by thermal anisotropies, tensional stresses generate an array of spreading axes offset by closely spaced transforms.

  12. Nicoya earthquake rupture anticipated by geodetic measurement of the locked plate interface

    NASA Astrophysics Data System (ADS)

    Protti, Marino; González, Victor; Newman, Andrew V.; Dixon, Timothy H.; Schwartz, Susan Y.; Marshall, Jeffrey S.; Feng, Lujia; Walter, Jacob I.; Malservisi, Rocco; Owen, Susan E.

    2014-02-01

    The Nicoya Peninsula in Costa Rica is one of the few places on Earth where the seismically active plate interface of a subduction zone is directly overlaid by land rather than ocean. At this plate interface, large megathrust earthquakes with magnitudes greater than 7 occur approximately every 50 years. Such quakes occurred in 1853, 1900 and 1950, so another large earthquake had been anticipated. Land-based Global Positioning System (GPS) and seismic measurements revealed a region where the plate interface was locked and hence accumulated seismic strain that could be released in future earthquakes. On 5 September 2012, the long-anticipated Nicoya earthquake occurred in the heart of the previously identified locked patch. Here we report observations of coseismic deformation from GPS and geomorphic data along the Nicoya Peninsula and show that the magnitude 7.6 Nicoya earthquake ruptured the lateral and down-dip extent of the previously locked region of the plate interface. We also identify a previously locked part of the plate interface, located immediately offshore, that may not have slipped during the 2012 earthquake, where monitoring should continue. By pairing observations of the spatial extent of interseismic locking and subsequent coseismic rupture, we demonstrate the use of detailed near-field geodetic investigations during the late interseismic period for identifying future earthquake potential.

  13. Can clay minerals account for the behavior of non-asperity on the subducting plate interface?

    NASA Astrophysics Data System (ADS)

    Katayama, Ikuo; Kubo, Tatsuro; Sakuma, Hiroshi; Kawai, Kenji

    2015-12-01

    Seismicity along the subducting plate interface shows regional variation, which has been explained by the seismic asperity model where large earthquakes occur at strongly coupled patches that are surrounded by weakly coupled regions. This suggests that the subduction plate interface is heterogeneous in terms of frictional properties; however, the mechanism producing the difference between strong and weak couplings remains poorly understood. Here, we propose that the heterogeneity of the fluid pathway and of the spatial distribution of clay minerals plays a key role in the formation of non-asperity at the subducting plate interface. We use laboratory measurements of frictional properties to show that clay minerals on a simulated fault interface are characterized by weak and slow recovery, whereas other materials such as quartz show relatively quick recovery and thereby strong coupling on the fault surface. Aqueous fluids change the mineralogy at the plate interface by producing clay minerals due to hydrate reactions, suggesting that the hydrated weakly coupled regions act as a non-asperity and form a barrier to rupture propagation along the plate boundary at the depths of seismogenic zone.

  14. Effect of interface morphology on the mechanical properties of titanium clad steel plates

    NASA Astrophysics Data System (ADS)

    Liu, Ji-xiong; Zhao, Ai-min; Jiang, Hai-tao; Tang, Di; Duan, Xiao-ge; Shui, Heng-yong

    2012-05-01

    Interface morphology has important influence on the bond quality of titanium clad steel plates. The mechanical properties of titanium clad steel plates with wavy and straight interfaces were investigated by tensile-shear tests and bending tests. The interface morphology of the plates was examined by optical microscopy (OM) and scanning electron microscopy (SEM). The experimental results show that the shear strength of a wavy interface is higher than that of a straight interface. A wavy interface is the guarantee for obtaining high shear strength to provide a greater shear resistance. During the macrobending process, cracks appear in the swirl of the wave tip and ferrotitanium intermetallics. For in-situ observing the bending process by SEM, the wave tip of a wavy interface and the massive ferrotitanium intermetallics of a straight interface are places where cracks initiate and propagate. The results are the same as those observed in the macrobending process. Because of high hardness, the wave tip and the massive ferrotitanium intermetallics are hard in terms of compatible deformation.

  15. Subcontinental-scale crustal velocity changes along the Pacific-North America plate boundary.

    PubMed

    Davis, J L; Wernicke, B P; Bisnath, S; Niemi, N A; Elósegui, P

    2006-06-29

    Transient tectonic deformation has long been noted within approximately 100 km of plate boundary fault zones and within active volcanic regions, but it is unknown whether transient motions also occur at larger scales within plates. Relatively localized transients are known to occur as both seismic and episodic aseismic events, and are generally ascribed to motions of magma bodies, aseismic creep on faults, or elastic or viscoelastic effects associated with earthquakes. However, triggering phenomena and systematic patterns of seismic strain release at subcontinental (approximately 1,000 km) scale along diffuse plate boundaries have long suggested that energy transfer occurs at larger scale. Such transfer appears to occur by the interaction of stresses induced by surface wave propagation and magma or groundwater in the crust, or from large-scale stress diffusion within the oceanic mantle in the decades following clusters of great earthquakes. Here we report geodetic evidence for a coherent, subcontinental-scale change in tectonic velocity along a diffuse approximately 1,000-km-wide deformation zone. Our observations are derived from continuous GPS (Global Positioning System) data collected over the past decade across the Basin and Range province, which absorbs approximately 25 per cent of Pacific-North America relative plate motion. The observed changes in site velocity define a sharp boundary near the centre of the province oriented roughly parallel to the north-northwest relative plate motion vector. We show that sites to the west of this boundary slowed relative to sites east of it by approximately 1 mm yr(-1) starting in late 1999. PMID:16810252

  16. Slow earthquakes associated with fault healing on a serpentinized plate interface

    PubMed Central

    Katayama, Ikuo; Iwata, Mutsumi; Okazaki, Keishi; Hirauchi, Ken-ichi

    2013-01-01

    Slow earthquakes that occur at subduction zones are distinct from regular earthquakes in terms of their slip behavior. We consider this difference to relate to localized hydration reactions at the plate interface that influence the frictional properties. The results of laboratory friction experiments indicate that simulated serpentine faults are characterized by a low healing rate and large slip-weakening distance compared with unaltered dry fault patches. These results are consistent with the slip mechanism of slow earthquakes, indicating that a locally serpentinized plate interface could trigger slow earthquakes, assisted by pore pressure build-up, whereas unaltered dry patches that remain strongly coupled are potential sites of regular earthquakes.

  17. 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.

  18. Accelerated pacific plate subduction following interplate thrust earthquakes at the Japan trench

    NASA Astrophysics Data System (ADS)

    Heki, Kosuke; Mitsui, Yuta

    2013-02-01

    Interplate thrust earthquakes are usually followed by afterslips, and they let the fore-arc move slowly trenchward. However, we do not know if the subducting oceanic plate is accelerated landward after such earthquakes. The westward velocity of Global Positioning System (GPS) stations in NE Japan show gradient decreasing from east to west reflecting the E-W contractional strain built up by the inter-plate coupling. Here we show that such coupling significantly enhanced (∼1.5 times) after the 2003 Tokachi-Oki earthquake (Mw 8.0), Hokkaido, in the segments adjacent to the ruptured fault. The coupling seems to be further enhanced (∼3 times) after the 2011 Tohoku-Oki earthquake (Mw 9.0). It is unlikely that interplate friction suddenly increased over such a large region, and relatively strong pre-2003 coupling there would not allow such enhancements even if full coupling is attained. Hence they are attributable to the temporary acceleration of the Pacific Plate subduction. We propose a simple 2-dimensional model in which down-dip acceleration of the slab let the force balance rapidly recover promoted by a thin low-viscosity layer on the slab surface. The accelerated subduction would account for temporary activations of regional interplate seismicity after megathrust earthquakes.

  19. Thermal study of interface between the Orbiter cold plate and typical Shuttle spacecraft payload flight electronics

    NASA Technical Reports Server (NTRS)

    Hwangbo, H.; Coyle, M. J.

    1979-01-01

    Spacelab provides a set of Freon line plumbing and cold plates for experiment equipments which are located in the Shuttle pallet and which need active thermal control. The reported study deals with the thermal problem of attaching a Command and Data Handling module with various electronic boxes whose combined footprints on the baseplate are much larger than the cold plate. A description of two modules and the cold plate assembly in the pallet is presented and a thermal model description is provided. The method employed in modeling heat pipes-honey-comb matrix is based upon an effective conductance between the heat pipe vapor and the walls of the heat pipe. The considered thermal models and a computer program are used to perform steady-state thermal analyses. The temperature gradients in the large module baseplate attached to the small cold plate are predicted as a function of the interface plate thickness.

  20. Geodetic evidence for low coupling on the Hellenic subduction plate interface

    NASA Astrophysics Data System (ADS)

    Vernant, Philippe; Reilinger, Robert; McClusky, Simon

    2014-01-01

    We develop a block model for the Aegean and surrounding areas, constrained by Global Positioning System (GPS), in order to investigate the degree of coupling on the Hellenic subduction interface (i.e., the fraction of the motion across the plate boundary accommodated by elastic strain accumulation). We use previously published models, and seismicity to define the geometry of the interface separating the down-going Nubian slab from the overriding Aegean. This model provides a good fit to the GPS observations; for the ∼200,000 km2 Aegean block the wrms of the residual velocities is 1.4 mm/yr for 80 GPS velocity estimates, approximately the 95% level of the GPS velocity uncertainties. We investigate the degree of coupling on the seismically active plate interface, the Hellenic trench splay fault (believed to be the source of the 365 AD Great Crete Earthquake and Tsunami), and the Kephalonia transform fault by comparing the modeled GPS residual velocity field for a range of coupling values. The GPS observations are almost insensitive to coupling on the Kephalonia transform fault, because of the vertical dip of the fault that creates interseismic deformation only close to the fault where few GPS sites exist. The absence of resolvable shortening of the leading edge of the Aegean Plate precludes coupling of more than 0.2 (20% of the full Nubia-Aegean convergence rate) on the modeled plate interface. Because of the shallow dip of the plate interface and trench splay fault, and high rate of convergence, if these boundaries were fully coupled, high elastic strain rates would be expected to extend well into the overriding Aegean plate. Based on our preferred value for the degree of coupling (0.1), and assuming characteristic earthquake behavior, we estimate a recurrence time for great earthquakes with slip similar to that for the 365 Crete event of 5700-8300 yr, consistent with the absence of subsequent great earthquakes on this segment of the subduction zone.

  1. Supraslab earthquakes above the Pacific-plate slab offshore Sanriku, NE Japan

    NASA Astrophysics Data System (ADS)

    Uchida, N.; Kirby, S. H.; Okada, T.; Hino, R.; Hasegawa, A.

    2009-12-01

    Double-difference relocation methods using P and S wave arrivals for the forearc earthquakes offshore Sanriku indicate that clusters of earthquakes are located above small repeating earthquakes that delineate the upper boundary of the Pacific plate. To assure good depth control, we restrict our study to events that are close to seismic stations. These "supraslab" earthquake clusters are regional features at depths of 25 to 50 km. The depth distribution of forearc Moho estimated from SP converted waves from repeating earthquake sources shows that the Moho depths becomes shallower from near the coastline (-30km) to the approximate eastern limit of the mantle wedge (-20km) and most of these clusters are below the depth of the forearc Moho. Re-entrants in the inner trench slope indicate that repeated collisions of seamounts have occurred in the past along the Japan trench. Our preliminary interpretation of supraslab clusters is that they represent seismicity in seamounts detached from the Pacific plate during slab descent, driven by the resistance of seamounts to subduction caused by their relief. Detachment during descent probably occurs on the sedimented and hydrothermally altered seafloor on which seamounts were originally constructed since these are known as zones of weakness during active island growth. Seamounts probably also fragment during subduction along weak seamount structures, such as former volcanic rifts and slump-block boundaries. Seamount crust is thus accreted to forearcs, possibly leading to a long-term component of near-coastal uplift. Supraslab earthquake clusters may be our most direct evidence of the fates of seamounts and suggest that tectonic underplating is actively occurring in this subduction system.

  2. Extensive deposits on the Pacific plate from Late Pleistocene North American glacial lake outbursts

    USGS Publications Warehouse

    Normark, W.R.; Reid, J.A.

    2003-01-01

    One of the major unresolved issues of the Late Pleistocene catastrophic-flood events in the northwestern United States (e.g., from glacial Lake Missoula) has been what happened when the flood discharge reached the ocean. This study compiles available 3.5-kHz high-resolution and airgun seismic reflection data, long-range sidescan sonar images, and sediment core data to define the distribution of flood sediment in deepwater areas of the Pacific Ocean. Upon reaching the ocean at the mouth of the Columbia River near the present-day upper continental slope, sediment from the catastrophic floods continued flowing downslope as hyperpycnally generated turbidity currents. The turbidity currents resulting from the Lake Missoula and other latest Pleistocene floods followed the Cascadia Channel into and through the Blanco Fracture Zone and then flowed west to the Tufts Abyssal Plain. A small part of the flood sediment, which was stripped off the main flow at a bend in the Cascadia Channel at its exit point from the Blanco Fracture Zone, continued flowing more than 400 km to the south and reached the Escanaba Trough, a rift valley of the southern Gorda Ridge. Understanding the development of the pathway for the Late Pleistocene flood sediment reaching Escanaba Trough provides insight for understanding the extent of catastrophic flood deposits on the Pacific plate.

  3. Roles of plate locking and block rotation in the tectonics of the Pacific Northwest

    NASA Astrophysics Data System (ADS)

    Ning, Zuoli

    The Pacific Northwest has potential for huge megathrust earthquakes. The influence of plate locking in the Cascadia subduction zone dominates crustal deformation off the shores of Washington and Oregon, but does not much affect areas far from the trench. The maximum principal strain rate epsilon 1 is -0.013 +/- 0.007 mustrain/yr in the Olympic Peninsula, 0.007 +/- 0.005 mustrain/yr in the Puget Sound, -0.005 +/- 0.005 mustrain/yr at Mt. Rainier, -0.004 +/- 0.005 mustrain/yr along the northern Oregon coast, and 0.011 +/- 0.006 mustrain/yr in central Oregon. The minimum principal strain rate epsilon2 is -0.083 +/- 0.008 mustrain/yr N56°E in the Olympic Peninsula, -0.034 +/- 0.007 mustrain/yr N63°E in the Puget Sound, -0.020 +/- 0.006 mustrain/yr N53°E at Mt. Rainier, -0.051 +/- 0.014 mustrain/yr N85°E along the northern Oregon coast, and -0.010 +/- 0.006 mustrain/yr N71°E in central Oregon. A new model of plate locking on the Cascadia subduction zone is similar to a model (1997). The uncertainty of the widths of the locked and transition zone in the model is about 25km--40km. Guided by computed site velocities, seismicity patterns, heat flow, volcanic data, and geological structures, we find it is necessary to divide the crust in the Pacific Northwest into separate moving blocks. We have analyzed a model in which the Oregon block is separated from the Washington block at latitude 46°. The Washington block has been further divided into 5-subblocks, three in the forearc and two in eastern Washington. We remove contributions of JDF plate locking from the site velocity field and determine a rotation pole and a strain rate for each sub-block. We conclude that Juan de Fuca plate locking has little direct effect on crustal earthquake occurrence in the Pacific Northwest (except for periodic megathrust earthquakes). In the Oregon block, plate locking and rigid block rotation are sufficient to explain GPS observations and the lower rate of seismicity in Oregon. The Washington block is more. The southwestern Washington sub-blocks have higher rotation rates and smaller residual strain rates than the northern sub-blocks. The Olympic sub-block shows the greatest north-south compression (0.017 mustrain/yr). The Puget Lowland sub-block and Mt. Rainier sub-block are shortening along a NNE direction, roughly consistent with the direction of maximum principal stress from fault plane solutions. The overall north-south shortening across the Puget Sound is 3mm/yr, sufficient to generate M7+ earthquakes in the future. NS compression dominates eastern Washington near Yakima which is also consistent with principal stress directions derived from fault plane solutions. Northeast Washington sub-block is currently poorly constrained by GPS data. As western Washington is pushed northward against the British Columbia, block rotation in Oregon is slowed down in Washington and the motion produces NS compression in northern Washington. The sub-blocks in southwestern WA act as a transition zone between Oregon and British Columbia. Residual strain rate is proportional to crustal seismicity. The great variation of residual strain rate in WA compared to Oregon may explain their crustal seismicity difference. GPS derived velocities in NE Washington are still too uncertain to determine the details of block rotation and strain rate there.

  4. The interface between cultural understandings: negotiating new spaces for Pacific mental health.

    PubMed

    Mila-Schaaf, Karlo; Hudson, Maui

    2009-02-01

    This theoretical paper introduces the concept of the "negotiated space", a model developed by Linda Tuhiwai Smith, Maui Hudson and colleagues describing the interface between different worldviews and knowledge systems. This is primarily a conceptual space of intersection in-between different ways of knowing and meaning making, such as, the i Pacific indigenous reference and the dominant Western mental health paradigm of the bio-psycho-social. When developing Pacific models of care, the "negotiated space" provides room to explore the relationship between different (and often conflicting) cultural understandings of mental health and illness. The "negotiated space" is a place ofp urposive re-encounter reconstructing and re-balancing of ideas and values in complementary realignments that have resonance for Pacific peoples living in Western oriented societies. This requires making explicit the competing epistemologies of the Pacific indigenous worldviews and references alongside the bio-psycho-social and identifying the assumptions implicit in the operating logic ofe ach. This is a precursor to being empowered to negotiate, resolve and better comprehend the cultural conflict between the different understandings. This article theorises multiple patterns of possibility of resolutions and relationships within the negotiated space relevant to research, evaluation, model, service development and quality assurance within Pacific mental health. PMID:19585741

  5. Paleomagnetism of Midway Atoll lavas and northward movement of the Pacific plate

    USGS Publications Warehouse

    Gromme, S.; Vine, F.J.

    1972-01-01

    Two deep drill holes through the reef limestones of Midway Atoll penetrated 120 m and 19 m of basaltic lavas that were dated by the KAr method at 18 my. Inclinations of natural remanent magnetization have been measured in 173 specimens cut from 57 core samples from 13 of the lava flows. The mean paleomagnetic inclination is 27.6?? ?? 6.8??, corresponding to a paleolatitude of 14.7?? ?? 4.2??. The present latitude of Midway is 28??, suggesting a northward component of motion of the Pacific plate of approximately 13?? or 1400 km in the last 18 my. The paleolatitude of Midway is thus not significantly different from the present latitude (19??) of the active volcanic island of Hawaii. The paleomagnetic data from the Midway basalts thus support the hypothesis of Wilson and Morgan that volcanic heat sources are fixed with respect to the Earth's mantle below the asthenosphere and their apparent migration with time is due to plate motion. ?? 1972.

  6. A passive and active seismic experiment near the Boso triple junction in the far northwestern part of the Pacific plate

    NASA Astrophysics Data System (ADS)

    Yamada, T.; Mochizuki, K.; Shinohara, M.; Machida, Y.; Shinbo, T.; Nakahigashi, K.; Yagi, T.; Abe, H.; Hashimoto, S.; Shoji, W.; Sato, T.; Mizuno, M.; Uehira, K.; Hino, R.; Murai, Y.; Oguma, K.

    2011-12-01

    The Pacific Plate subducts beneath northeastern Japan along the Japan Trench and beneath the Izu-Bonin-Mariana arc along the Mariana Trench. The Boso triple junction is located at between the Japan Trench and the Mariana Trench, and the southeastern end of the Sagami Trough where the Philippine Sea Plate subducts beneath northeastern Japan. It is thus a trench-trench-trench type triple junction. For the purpose of understanding the interaction between three plates and its effect to the Pacific Plate, we have performed a passive and active seismic experiment near the Boso triple junction in the far northwestern part of the Pacific plate. We deployed 10 Ocean Bottom Seismometers (OBSs) equipped with a three-componet 1Hz geophone mounted on gimbabl systems on KH09-3 cruise of R/V Hakuho-maru on July 2009, and recovered the OBSs by using M/V Shinchou-maru on October 2010.During the KH09-3 cruise, we shot by using an airgun array (6000 cubic inch in total) during 18 hours on three profiles. We obtained 442days' seismic data from July 29, 2009 to October 13, 2010 in the experiment. More than 2000 earthquakes were detected, and the foci form some clusters.

  7. Structural Response of the Menard Fracture Zone to Changes in Pacific-Antarctic Plate Motion

    NASA Astrophysics Data System (ADS)

    Croon, M. B.; Cande, S. C.; Stock, J. M.

    2005-12-01

    We present the results of a reconnaissance survey of swath MultiBeam and magnetic data of the Menard Fracture Zone. These data were mainly collected by the NSF (Office of Polar Programs) operated R/VIB Nathaniel Palmer during transits between Lyttelton, New Zealand and Punta Arenas, Chile between 1997 and 2005. Based on these data we analyzed the tectonic development and structural features of the Menard Fracture Zone. The data enable us to look at the evolution of the structures along the fracture zone between about 45 Ma (anomaly 20y) and the present. The Pacific-Antarctic spreading ridge at this latitude nucleated within a propagating rift system that birthed the Hudson microplate and formed the conjugate Henry and Hudson Troughs, which flank the fracture zone on either side (Eakins, 2000). Development of the Menard Fracture Zone resulted from tectonic realignment of the conjugate rifted margins. We used the trends of the Menard Fracture Zone and magnetic anomalies to determine a record of plate-motion changes. The Menard Fracture Zone experienced adaptations to changes in plate motion. We interpret the swathmap bathymetry data to examine how the Menard Fracture Zone evolved in response to these changes. The medium to fast spreading Pacific-Antarctic ridge generated about 1450 km of ocean crust on the east and 1550 km on the west limb. At its initiation there are 2 splays forming a narrow corridor of about 25 km. In this oldest part of the fracture zone volcanic ridges formed by transpression are clearly visible. Between 28 and 23 Ma (anomaly 10 to 6b) an adjustment in spreading direction narrows the corridor to roughly 10 to 15 km width. Roughly at 4 Ma the two splays apparently coalesce into a single offset. The northern fracture zone on the west limb and the fracture zones on the east limb of the Menard Fracture Zone are often barely or not visible on the bathymetry, due to burial by younger volcanism from overshot ridges on the inner volcanic highs. Small adjustments in direction of plate motion are also marked by occasional cross-cutting faults that offset the fracture zone splays up to 5 km.

  8. Bending-related Topographic Structures of the Subducting Plate in the Northwestern Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Nakanishi, M.; Manabe, I.; Oikawa, M.

    2012-12-01

    We present the elongated topographic structures associated with bending of the subducting oceanic plate along the western Kuril, Japan and Izu-Ogasawara trenches using multibeam bathymetric data. The trench-outer rise earthquake near the Japan Trench occurred in the same day after the 2011 Tohoku Earthquake. Several studies pointed out high occurrence probability of trench-outer rise earthquake after the 2011 Tohoku Earthquake in near future. Trench-outer rise earthquakes occur by reactivation or creation of normal faults caused as the oceanic lithosphere approaches a subduction zone and bends into the deep-sea trench. Bending-related faults in the oceanward trench slope are ubiquitous structures of oceanic plates incoming to trenches. In general, the faults are thought to be formed parallel or subparallel to the bending axis of the incoming plate, namely the trench axis. Oceanward slopes of several trenches have bending-related structure with a strike different from the trench axes (Masson, 1991; Kobayashi et al., 1998; Ranero et al., 2003). In these areas, abyssal hill fabric was reactivated instead of the creation of new faulting parallel to the trench axis. The Mesozoic Pacific Plate is subducting along the Kuril, Japan, Izu-Ogasawara, and Mariana trenches (Nakanishi et al. 1992). Kobayashi et al. (1998) investigated the bending-related structures of the oceanward trench slope of the western Kuril and northern Japan trenches using the multibeam data. They concluded that the abyssal hill fabric is revalidated when abyssal hill fabric trend within 30 degree of trench axes. To examine controlling factors for strikes of bending-related structures, it is indispensable to describe oceanic spreading fabric and to identify magnetic anomaly lineations. The oceanic spreading fabric consists of inherited abyssal hill fabric and other preexisting weak zones related to seafloor spreading process, which are fracture zones, non-transform offsets, and so on. The new bathymetric map demonstrated that most of bending-related topographic structures exist in the oceanward trench slopes deeper than 5600 m. The map revealed that bending-related topographic structures are developed parallel to the trench axis or inherited oceanic spreading fabric. Detailed identification of magnetic anomalies near the Japan Trench revealed curved lineations and discontinuity of lineations associated with propagation ridges. Comparison between the detailed bathymetric and magnetic anomaly lineation maps elucidated that abyssal hill fabrics were reactivated where the angle between abyssal hill fabrics and trench axis is less than about 30 degree.

  9. Dredged basalts from the western Nazca plate and the evolution of the East Pacific Rise

    NASA Astrophysics Data System (ADS)

    Campsie, John; Leonard Johnson, G.; Rasmussen, Mogens H.; Laursen, Jens

    1984-05-01

    Ocean-floor basalts and glasses were recovered from three stations along the western Nazca plate, from a sublinear topographic feature believed to represent the proto-East Pacific Rise (EPR), and include abyssal tholeiites, FeTi-basalts and glasses, as well as transitional and little fractionated compositions. When compared with their coexisting fresh glasses, the FeTi-basalts have higher total alkalies, TiO 2 and MgO, and lower FeO *, suggesting that they have also been affected by non-oxidative post-magmatic alteration processes. The FeTi-glasses form a remarkably uniform compositional group through space and time. A little fractionated composition having an Mg-number= 73, similar to those reported from the Mathematician Ridge, has higher Na 2O and TiO 2, and slightly lower CaO than similar compositions from the slowly accreting Mid-Atlantic Ridge. The basalts and glasses reported here exhibit the compositional diversity expected for propagating rifts and probably represent more than one volcanic episode. Both geochemical and geophysical interpretations support the inference that the EPR grew from Miocene times by the progressive growth and propagation of mantle perturbations, leaving a remnant sublinear zone of rough topography characteristic of slower accretion as the trace of the proto-EPR. Continuing translations and rotations of axial segments are occurring along the EPR, probably in response to self-reorganizations of mantle flow patterns arising from rapid melting and depletion of the source regions. The data allow the inference that the youthful rift systems of the eastern Pacific are far from thermodynamic equilibrium as might be expected if such systems were to drive fundamental life processes.

  10. A new GPS velocity field for the Pacific Plate - Part 2: implications for fault slip rates in western California

    NASA Astrophysics Data System (ADS)

    DeMets, C.; Márquez-Azúa, Bertha; Cabral-Cano, Enrique

    2014-12-01

    Lower and upper bounds for present deformation rates across faults in central California between the San Andreas Fault and Pacific coast are estimated from a new Global Positioning System (GPS) velocity field for central, western California in light of geodetic evidence presented in a companion paper for slow, but significant deformation within the Pacific Plate between young seafloor in the eastern Pacific and older seafloor elsewhere on the plate. Transects of the GPS velocity field across the San Andreas Fault between Parkfield and San Juan Buatista, where fault slip is dominated by creep and the velocity field thus reveals the off-fault deformation, show that GPS sites in westernmost California move approximately parallel to the fault at an average rate of 3.4 ± 0.4 mm yr-1 relative to the older interior of the Pacific Plate, but only 1.8 ± 0.6 mm yr-1 if the Pacific Plate frame of reference is corrected for deformation within the plate. Modelled interseismic elastic deformation from the weakly coupled creeping segment of the San Andreas Fault is an order-of-magnitude too small to explain the southeastward motions of coastal sites in western California. Similarly, models that maximize residual viscoelastic deformation from the 1857 Fort Tejon and 1906 San Francisco earthquakes mismatch both the rates and directions of GPS site motions in central California relative to the Pacific Plate. Neither thus explains the site motions southwest of the San Andreas fault, indicating that the site motions measure deformation across faults and folds outboard of the San Andreas Fault. The non-zero site velocities thus constitute strong evidence for active folding and faulting outboard from the creeping segment of the San Andreas Fault and suggest limits of 0-2 mm yr-1 for the Rinconada Fault slip rate and 1.8 ± 0.6 to 3.4 ± 0.4 mm yr-1 for the slip rates integrated across near-coastal faults such as the Hosgri, San Gregorio and San Simeon faults.

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

    USGS Publications Warehouse

    Brown, J.R.; Beroza, G.C.; Ide, S.; Ohta, K.; Shelly, D.R.; Schwartz, S.Y.; Rabbel, W.; Thorwart, M.; Kao, H.

    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. Copyright 2009 by the American Geophysical Union.

  12. Influence of phosphorous content on microstructure development at the Ni-P Plating/SAC interface

    NASA Astrophysics Data System (ADS)

    Huber, Zbigniew; Wojewoda-Budka, Joanna; Wierzbicka-Miernik, Anna; Sypien, Anna; Szczerba, Maciej; Zieba, Pawel

    2016-01-01

    Studies of the commonly used Ni-P surface finish of 4.3 and 11.6 wt. % of P content electroless plated on nickel substrates followed by their reaction with SAC305 solder were performed. It was demonstrated that the Ni-4.3P plating was crystalline, while the Ni-11.6P was mostly amorphous. The transformation of the Ni-P into Ni3P phase took place at 672 K and 605 K for low and high P amount, respectively. The activation energy ( E a ) of the crystallization processes in the Ni-P plating was lower for the Ni-11.6P plating. Interaction of SAC305 solder with both types of the inspected plating showed the creation of (Cu,Ni)6Sn5 phase in the form of thin layer and large scallops, while for Ni-11.6P/SAC305 interface also (Ni,Cu)3Sn4 phase. The thickness of these phases was larger in the case of low phosphorous containing plating. The Ni-11.6P plating after the reaction with SAC305 totally transformed into Ni12P5, while the enrichment in P up to 10.5 wt. % occurred in the Ni-4.3P which did not lead to the appearance of any NixPy type phases. After the reaction of plating with solder the Ni2SnP phase was not identified. This was related to the absence of spalling phenomenon of the intermetallics into solder. [Figure not available: see fulltext.

  13. Repeating deep tremors on the plate interface beneath Kyushu, southwest Japan

    NASA Astrophysics Data System (ADS)

    Yabe, Suguru; Ide, Satoshi

    2013-01-01

    In the subduction zone south of Kyushu Island, at the western extension of the Nankai subduction zone, southwest Japan, the age of the oceanic crust increases toward the south across the subducting Kyushu-Palau ridge. While tremor activity is very high in Nankai, tectonic tremors have only recently been discovered in Kyushu. In this study, we examined tremors beneath Kyushu using an improved version of the envelope correlation method. In doing so, we distinguished tremors from normal earthquakes and background noise using the criteria of source duration and the spectrum ratio between low and high frequencies. Accurate measurement of S- P times, using cross-correlation between vertical and horizontal seismograms, constrains the tremor depth precisely. Tremor activity is low and within a small region in southern Kyushu, where thick crust of the Kyushu-Palau ridge is being subducted, at depths between 35 and 45 km (i.e., shallower than intra-slab earthquakes by about 20 km), which is consistent with the location of the plate interface within uncertainties proposed in previous studies. Establishing precise depth estimates for tectonic tremors beneath Kyushu, which results from shear slip along the plate interface, is useful in defining the plate interface within the Nankai subduction zone.

  14. 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.

  15. A Geodetic Strain Rate Model for the Pacific-North American Plate Boundary, western United States

    NASA Astrophysics Data System (ADS)

    Kreemer, C.; Hammond, W. C.; Blewitt, G.; Holland, A. A.; Bennett, R. A.

    2012-04-01

    We present a model of crustal strain rates derived from GPS measurements of horizontal station velocities in the Pacific-North American plate boundary in the western United States. The model reflects a best estimate of present-day deformation from the San Andreas fault system in the west to the Basin and Range province in the east. Of the total 2,846 GPS velocities used in the model, 1,197 are derived by ourselves, and 1,649 are taken from (mostly) published results. The velocities derived by ourselves (the "UNR solution") are estimated from GPS position time-series of continuous and semi-continuous stations for which data are publicly available. We estimated ITRF2005 positions from 2002-2011.5 using JPL's GIPSY-OASIS II software with ambiguity resolution applied using our custom Ambizap software. Only stations with time-series that span at least 2.25 years are considered. We removed from the time-series continental-scale common-mode errors using a spatially-varying filtering technique. Velocity uncertainties (typically 0.1-0.3 mm/yr) assume that the time-series contain flicker plus white noise. We used a subset of stations on the stable parts of the Pacific and North American plates to estimate the Pacific-North American pole of rotation. This pole is applied as a boundary condition to the model and the North American - ITRF2005 pole is used to rotate our velocities into a North America fixed reference frame. We do not include parts of the time-series that show curvature due to post-seismic deformation after major earthquakes and we also exclude stations whose time-series display a significant unexplained non-linearity or that are near volcanic centers. Transient effects longer than the observation period (i.e., slow viscoelastic relaxation) are left in the data. We added to the UNR solution velocities from 12 other studies. The velocities are transformed onto the UNR solution's reference frame by estimating and applying a translation and rotation that minimizes the velocities at collocated stations. We removed obvious outliers and velocities in areas that we identified to undergo subsidence likely due to excessive water pumping. For the strain rate calculations we excluded GPS stations with anomalous vertical motion or annual horizontal periodicity, which are indicators of local site instability. First, we used the stations from the UNR solution to create a Delaunay triangulation and estimated the horizontal strain rate components (and rigid body rotation) for each triangle in a linear least-squares inversion using the horizontal velocities as input. Some level of spatial damping was applied to minimize unnecessary spatial variation in the model parameters. The strain rates estimates were then used as a priori strain rate variances in a method that fits continuous bi-cubic Bessel spline functions through the velocity gradient field while minimizing the weighted misfit to all velocities. A minimal level of spatial smoothing of the variances was applied. The strain rate tensor model is shown by contours of the second invariant of the tensor, which is a measure of the amplitude that is coordinate frame independent. We also show a map of the tensor style and of the signal-to-noise ratio of the model.

  16. A new fluid-solid interface algorithm for simulating fluid structure problems in FGM plates

    NASA Astrophysics Data System (ADS)

    Eghtesad, A.; Shafiei, A. R.; Mahzoon, M.

    2012-04-01

    The capability to track material interfaces, especially in fluid structure problems, is among the advantages of meshless methods. In the present paper, the Smoothed Particle Hydrodynamics (SPH) method is used to investigate elastic-plastic deformation of AL and ceramic-metal FGM (Functionally Graded Materials) plates under the impact of water in a fluid-solid interface. Instead of using an accidental repulsive force which is not stable at higher pressures, a new scheme is proposed to improve the interface contact behavior between fluid and solid structure. This treatment not only prevents the interpenetration of fluid and solid particles significantly, but also maintains the gap distance between fluid and solid boundary particles in a reasonable range. A new scheme called corrected smooth particle method (CSPM) is applied to both fluid and solid particles to improve the free surface behavior. In order to have a more realistic free surface behavior in fluid, a technique is used to detect the free surface boundary particles during the solution process. The results indicate that using the proposed interface algorithm together with CSPM correction, one can predict the dynamic behavior of FGM plates under the impact of fluid very promisingly.

  17. 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 underthrust section, but the increase is suppressed relative to that expected from normally consolidating sediments. The computed pore pressure increases landward from an overpressure ratio (λ * = hydrostatic pressure divided by the lithostatic overburden) of ˜ 0.6 at the deformation front to ˜ 0.77 where sediments have been subducted 15 km. The results of this preliminary analysis suggest that a 3-dimensional mapping of predicted effective normal stress in the seismic data volume is possible.

  18. Investigation on the Interface Morphologies of Explosive Welding of Inconel 625 to Steel A516 Plates

    NASA Astrophysics Data System (ADS)

    Mousavi, S. A. A. Akbari; Zareie, H. R.

    2011-01-01

    The purpose of this study is to produce composite plates by explosive cladding process. This is a process in which the controlled energy of explosives is used to create a metallic bond between two similar or dissimilar materials. The welding conditions were tailored through parallel geometry route with different operational parameters. In this investigation, a two-pronged study was adopted to establish the conditions required for producing successful solid state welding: (a) Analytical calculations to determine the weldability domain or welding window; (b) Metallurgical investigations of explosive welding experiments carried out under different explosive ratios to produce both wavy and straight interfaces. The analytical calculations confirm the experimental results. Optical microscopy studies show that a transition from a smooth to wavy interface occurs with an increase in explosive ratio. SEM studies show that the interface was outlined by characteristic sharp transition between two materials.

  19. Investigation on the Interface Morphologies of Explosive Welding of Inconel 625 to Steel A516 Plates

    SciTech Connect

    Mousavi, S. A. A. Akbari; Zareie, H. R.

    2011-01-17

    The purpose of this study is to produce composite plates by explosive cladding process. This is a process in which the controlled energy of explosives is used to create a metallic bond between two similar or dissimilar materials. The welding conditions were tailored through parallel geometry route with different operational parameters. In this investigation, a two-pronged study was adopted to establish the conditions required for producing successful solid state welding: (a) Analytical calculations to determine the weldability domain or welding window; (b) Metallurgical investigations of explosive welding experiments carried out under different explosive ratios to produce both wavy and straight interfaces. The analytical calculations confirm the experimental results. Optical microscopy studies show that a transition from a smooth to wavy interface occurs with an increase in explosive ratio. SEM studies show that the interface was outlined by characteristic sharp transition between two materials.

  20. Pacific plate-motion change at the time of the Hawaiian-Emperor bend constrains the viscosity of Earth's asthenosphere

    NASA Astrophysics Data System (ADS)

    Iaffaldano, Giampiero; Lambeck, Kurt

    2014-05-01

    Important constraints on asthenospheric viscosity come primarily from modeling the glacial rebound of the past 20 kyr, but remain somewhat loose because of the intrinsic resolving power of these models. We obtain narrower bounds by building on the notion that the asthenosphere also controls the ability to change plate motions over Myr. We focus on the Pacific kinematic change at the time of the Hawaiian-Emperor bend event, which is linked to the coeval inception of subduction in the Western Pacific. We sample plausible asthenospheric viscosity and thickness values by requiring the rate at which torque varied to generate the observed kinematics consistent with the nature of subduction initiation. Uncertainties on the bend event duration and the occurrence of Pacific hot spots drift do not hamper our results that suggest that the asthenosphere viscous response to vertical shear over kyr is consistent with that to horizontal shear over Myr.

  1. Pacific plate-motion change at the time of the Hawaiian-Emperor bend constrains the viscosity of Earth's asthenosphere

    NASA Astrophysics Data System (ADS)

    Iaffaldano, Giampiero; Lambeck, Kurt

    2015-04-01

    Important constraints on asthenospheric viscosity come primarily from modeling the glacial rebound of the past 20 kyr, but remain somewhat loose because of the intrinsic resolving power of these models. We obtain narrower bounds by building on the notion that the asthenosphere also controls the ability to change plate motions over Myr. We focus on the Pacific kinematic change at the time of the Hawaiian-Emperor bend event, which is linked to the coeval inception of subduction in the Western Pacific. We sample plausible asthenospheric viscosity and thickness values by requiring the rate at which torque varied to generate the observed kinematics consistent with the nature of subduction initiation. Uncertainties on the bend event duration and the occurrence of Pacific hot spots drift do not hamper our results that suggest that the asthenosphere viscous response to vertical shear over kyr is consistent with that to horizontal shear over Myr.

  2. 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.

  3. North America-Pacific plate boundary, an elastic-plastic megashear - Evidence from very long baseline interferometry

    NASA Technical Reports Server (NTRS)

    Ward, Steven N.

    1988-01-01

    Data obtained by Mark III VLBI measurements of radio signals from permanent and mobile VLBI sites for 5.5 years of observations, starting in October 1982, were used to derive a picture of the earth crust deformation near the North America-Pacific plate boundary. The data, which included the vector positions of the VLBI sites and their rate of change, were used for comparison with a number of lithospheric deformation models based upon the concept that the motions of points near the North America-Pacific plate boundary are a linear combination of North America and Pacific velocities. The best of these models were found to fit 95 percent of the variance in 139 VLBI length and transverse velocity observations. Instantaneous shear deformation associated with plate tectonics is apparently developing in a zone 450 km wide paralleling the San Andreas Fault; some of this deformation will be recovered through elastic rebound, while the rest will be permanently set through plastic processes. Because the VLBI data have not been collected for a significant fraction of the earthquake cycle, they cannot discriminate between elastic and plastic behaviors.

  4. Using aftershocks to Image the Subducting Pacific Plate in a Region of Deep Slow Slip, Hikurangi Margin, New Zealand

    NASA Astrophysics Data System (ADS)

    Jacobs, K. M.; Hirschberg, H.; Louie, J. N.; Savage, M. K.; Bannister, S. C.

    2014-12-01

    We present seismic migrations using aftershocks of two M>6 earthquakes as sources. The Southern Cook Strait earthquake sequence, beginning on 19 July 2013, included the 21 July M=6.5 and 16 August M=6.6 2013 earthquakes, which were the largest shallow earthquakes to strike the Wellington region since 1942. Following the two largest earthquakes we began the Seddon Earthquake Aftershock Structural Investigation (SEASI) and deployed a line of 21 seismometers stretching approximately 400 km along the strike of the Hikurangi subduction zone in order to use aftershocks to illuminate the structure of the subducted Pacific slab. The SEASI line ties into the SAHKE line, which was an array of up to 900 seismometers that recorded air gun and explosion shots in deployments from 2009-2011. The SAHKE project characterized the structures perpendicular to the strike of the subduction zone. Our results use the SAHKE line as a starting point and look for strike-parallel variations in the depth of the Moho and other structures. Previous studies have suggested potential changes along strike in this region, and deep slow slip events (> 35 km) are also observed north of Wellington, further indicating that variation in properties exists along slab strike. We have used 246 M > 3 earthquakes that occurred from September 2013 through January 2014 to create common receiver gathers. Multicomponent prestack depth migration of these receiver gathers, with operator antialiasing control and prestack coherency filtering, produces reflectivity sections using a 1-D velocity model derived from the SAHKE project. Relocation of aftershocks of the Seddon earthquakes using the deployment of a temporary array by New Zealand GeoNet facilitates the migration. An initial P-P migration shows a north-dipping reflector at 15-25 km depth under the earthquake sequence, and suggests the Moho at 20-25 km depth. From Wellington, a reflector dips very gently south from 25-35 km depth, which is probably the slab interface. These results are helping to build 3-D information about the plate interface. We hope that this will help us to understand future hazards posed by subduction thrust earthquakes in this region, and the feeding system for deep slow-slip earthquakes.

  5. Microstructure and Phase Constitution Near the Interface of Explosively Welded Aluminum/Copper Plates

    NASA Astrophysics Data System (ADS)

    Paul, Henryk; Lityńska-Dobrzyńska, Lidia; Prażmowski, Mariusz

    2013-08-01

    The microstructure changes and the phase constitution within the layers close to the bonding interface strongly influence the properties of bimetallic strips. In this work, the layers near the interface of explosively welded aluminum and copper plates were investigated by means of microscopic observations, mostly with the use of transmission electron microscopy (TEM) equipped with energy dispersive spectrometry (EDX). The study was focused on the identification of the intermetallic phases, the possible interdiffusion between the copper and the aluminum, and the changes in the dislocation structure of the parent plates. In macro-/mesoscale, the interfaces were outlined by a characteristic sharp transition indicating that there was no mechanical mixing between the welded metals in the solid state. In micro-/nanoscale, the layers adhering to the interface show typical deformed microstructure features, i.e., structure refinement, elongated dislocation cells, slip bands, and microtwins (in copper plate). The internal microstructure of the intermetallic inclusion is composed mostly of dendrites. The electron diffractions and TEM/EDX chemical composition measurements revealed three crystalline equilibrium phases of the γ-Al4Cu9, η-AlCu, and Θ-Al2Cu type (the last one was dominant). However, most of the observed phases of the general Cu m Al n type (also crystalline) do not appear in the equilibrium Al-Cu phase diagram. Inside the intermetallic inclusions, no significant regularity in the phase distribution with respect to the parent sheets was observed. Therefore, it was concluded that the processes occurring in the melt determined their local chemical composition.

  6. Pacific Plate Apparent Polar Wander and Latitudinal Shift of the Hawaiian Hotspot: A Brief Review and Future Prospects

    NASA Astrophysics Data System (ADS)

    Gordon, R. G.

    2005-05-01

    Except for young volcanic islands, the Pacific plate is largely lacking outcrop amenable to traditional paleomagnetic analysis. As a result, a wide variety of alternative methods have been developed for estimating pole positions including analysis of the magnetic anomalies over seamounts ("seamount poles"), shape analysis of magnetic anomalies due to seafloor spreading ("skewness poles"), analysis of the amplitudes of magnetic anomalies due to seafloor spreading, analysis of azimuthally unoriented piston cores and deep-sea drilling cores in both sedimentary and igneous rocks, and analysis of equatorial sediment facies. In the 1970s, studies of seamount poles, of skewness, and of equatorial sediment facies all provided strong evidence for northward motion of the Pacific plate, in general agreement with the northward motion of the Pacific plate predicted if it is assumed that the hotspots are fixed relative to the spin axis. Beginning in about 1980, however, strong evidence was obtained that the northward motion of the Pacific plate relative to the spin axis was less than its northward motion relative to the Hawaiian and other hotspots, implying a southward drift of the Hawaiian hotspot. Results from DSDP Leg 55 first demonstrated southward motion of the Hawaiian hotspot [Kono 1980, Jackson, Koizumi et al. 1980]. Morgan [1981] showed that paleomagnetic poles and hotspot tracks from the Indian and Atlantic Oceans (and bordering continents) predicted this southward motion if the Pacific hotspots are fixed relative to those in the Indo-Atlantic, while both move together relative to the spin axis. This coherent motion of global hotspots can be interpreted as the result of true polar wander. Gordon & Cape [1981] and Gordon [1982] analyzed equatorial sediment facies, published piston core paleomagnetic data, and skewness data. They showed that the data were mutually consistent and indicated southward motion of the Hawaiian hotspot relative to the spin axis consistent with Morgan's predictions. Since then, the apparent polar wander of the Pacific plate has been elaborated in considerably greater detail. Here I concentrate on the results from skewness. Because the ages of the magnetic anomalies analyzed are unambiguous and automatically known to the nearest polarity chron, the ages of skewness poles are precisely known. The geometry of spreading on the Pacific plate during Cenozoic and Late Cretaceous time enables the estimation of poles with very compact confidence regions. Poles have been determined for many different anomalies and give a detailed, but far from complete, view of Pacific plate apparent polar wander since 83 Ma. In contrast, results from igneous rocks obtained by deep sea drilling are far sparser, less accurate, and give only paleolatitudes and not unique poles. The data are nevertheless useful, especially for time intervals lacking magnetic reversals (i.e., the Cretaceous Normal Polarity Superchron) and to provide an independent test of the results from skewness and other approaches. These independent tests reveal a high level of consistency with skewness results, strongly supporting the usefulness and reliability of skewness analysis.

  7. Playing jigsaw with Large Igneous Provinces—A plate tectonic reconstruction of Ontong Java Nui, West Pacific

    NASA Astrophysics Data System (ADS)

    Hochmuth, Katharina; Gohl, Karsten; Uenzelmann-Neben, Gabriele

    2015-11-01

    The three largest Large Igneous Provinces (LIP) of the western Pacific—Ontong Java, Manihiki, and Hikurangi Plateaus—were emplaced during the Cretaceous Normal Superchron and show strong similarities in their geochemistry and petrology. The plate tectonic relationship between those LIPs, herein referred to as Ontong Java Nui, is uncertain, but a joined emplacement was proposed by Taylor (2006). Since this hypothesis is still highly debated and struggles to explain features such as the strong differences in crustal thickness between the different plateaus, we revisited the joined emplacement of Ontong Java Nui in light of new data from the Manihiki Plateau. By evaluating seismic refraction/wide-angle reflection data along with seismic reflection records of the margins of the proposed "Super"-LIP, a detailed scenario for the emplacement and the initial phase of breakup has been developed. The LIP is a result of an interaction of the arriving plume head with the Phoenix-Pacific spreading ridge in the Early Cretaceous. The breakup of the LIP shows a complicated interplay between multiple microplates and tectonic forces such as rifting, shearing, and rotation. Our plate kinematic model of the western Pacific incorporates new evidence from the breakup margins of the LIPs, the tectonic fabric of the seafloor, as well as previously published tectonic concepts such as the rotation of the LIPs. The updated rotation poles of the western Pacific allow a detailed plate tectonic reconstruction of the region during the Cretaceous Normal Superchron and highlight the important role of LIPs in the plate tectonic framework.

  8. Tidal stress influence on slow slip on the deep plate interface

    NASA Astrophysics Data System (ADS)

    Yabe, S.; Tanaka, Y.; Houston, H.; Ide, S.

    2014-12-01

    Tectonic tremors and slow earthquakes, which are detected in many subduction zones and transform faults, are characterized by various quantities, such as duration, recurrence interval, and the sensitivity to tidal stress. These characteristic quantities are spatially variable among regions and even within an individual region. It is also known that the seismic energy release by tremor also spatially varies (e.g., Maeda and Obara, 2009; Ando et al., 2012; Yabe and Ide, in review). We interpret the spatial variation in seismic energy rate (amplitude) of tremors to represent the variation of plate-interface strength, in which case the spatial variation of tidal sensitivity might correlate with that of seismic energy rate. To investigate such relation, we have investigated the spatial variation of tidal sensitivity in Nankai and Cascadia subduction zones. Although the spatial variation of tidal sensitivity has been investigated using the frequency spectrum at specific tidal frequency, we calculate the time history of tidal stressing on the plate interface and compare it with tremor activity to investigate their relation. Both body tide and ocean tide are included in the calculation of tidal stress. We calculated Green functions for the spherical Earth based on the method by Okubo and Tsuji (2001). The time history of sea surface level is calculated with the SPOTL program (Agnew, 2012). The fault planes of VLF estimated by Ide and Yabe (2014) are used to calculate stress on the plate interface. Tremors are more likely to occur when tidal shear stress is larger, in the subduction direction. Tremor rate appears to increase exponentially with tidal shear stress, as previously seen by Houston (2013, AGU). Although tidal sensitivity can be seen in many regions, some regions show particularly strong sensitivity. In some regions, tidal sensitivity can be seen clearly during the later portions of large SSEs, consistent with behavior reported by Houston (2013, AGU), while other regions show tidal sensitivity without large SSEs as well. In the regions where tidal sensitivity can be seen, the rake direction of VLF is consistent with the direction of maximum tidal shear stress on that fault plane. This observation might imply that tidal stress significantly modulates the timing of slow slip on the deep plate interface.

  9. Simulation of tectonic evolution of the Kanto basin of Japan since 1 Ma due to subduction of the Pacific and Philippine sea plates and collision of the Izu-Bonin arc

    NASA Astrophysics Data System (ADS)

    Hashima, Akinori; Sato, Toshinori; Sato, Hiroshi; Asao, Kazumi; Furuya, Hiroshi; Yamamoto, Shuji; Kameo, Koji; Miyauchi, Takahiro; Ito, Tanio; Tsumura, Noriko; Kaneda, Heitaro

    2015-04-01

    The Kanto basin, the largest lowland in Japan, developed by flexure as a result of (1) the subduction of the Philippine Sea (PHS) and the Pacific (PAC) plates and (2) the collision of the Izu-Bonin arc with the Japanese island arc. Geomorphological, geological, and thermochronological data on long-term vertical movements over the last 1 My suggest that subsidence initially affected the entire Kanto basin after which the area of subsidence gradually narrowed until, finally, the basin began to experience uplift. In this study, we modelled the tectonic evolution of the Kanto basin following the method of Matsu'ura and Sato (1989) for a kinematic subduction model with dislocations, in order to quantitatively assess the effects of PHS and PAC subduction. We include the steady slip-rate deficit (permanent locking rate at the plate interface) in our model to account for collision process. We explore how the arc-arc collision process has been affected by a westerly shift in the PHS plate motion vector with respect to the Eurasian plate, thought to have occurred between 1.0-0.5 Ma, using long-term vertical deformation data to constrain extent of the locked zone on the plate interface. We evaluated the change in vertical deformation rate for two scenarios: (1) a synchronous shift in the orientation of the locked zone as PHS plate motion shifts and (2) a delayed shift in the orientation of the locked zone following a change in plate motion. Observed changes in the subsidence/uplift pattern are better explained by scenario (2), suggesting that recent (<1 My) deformation in the Kanto basin shows a lag in crustal response to the shift in plate motion. We also calculated recent stress accumulation rates and found a good match with observed earthquake mechanisms, which shows that intraplate earthquakes serve to release stress accumulated through long-term plate interactions.

  10. Simulation of tectonic evolution of the Kanto Basin of Japan since 1 Ma due to subduction of the Pacific and Philippine Sea plates and the collision of the Izu-Bonin arc

    NASA Astrophysics Data System (ADS)

    Hashima, Akinori; Sato, Toshinori; Sato, Hiroshi; Asao, Kazumi; Furuya, Hiroshi; Yamamoto, Shuji; Kameo, Koji; Miyauchi, Takahiro; Ito, Tanio; Tsumura, Noriko; Kaneda, Heitaro

    2016-06-01

    The Kanto Basin, the largest lowland in Japan, developed by flexure as a result of (1) the subduction of the Philippine Sea (PHS) and the Pacific (PAC) plates and (2) the repeated collision of the Izu-Bonin arc fragments with the Japanese island arc. Geomorphological, geological, and thermochronological data on vertical movements over the last 1 My suggest that subsidence initially affected the entire basin after which the area of subsidence gradually narrowed until, finally, the basin began to experience uplift. In this study, we modeled the tectonic evolution of the Kanto Basin following the method of Matsu'ura and Sato (1989) for a kinematic subduction model with dislocations, in order to quantitatively assess the effects of PHS and PAC subduction. We include the steady slip-rate deficit (permanent locking rate at the plate interface) in our model to account for collision process. We explore how the latest collision of the Izu Peninsula block has been affected by a westerly shift in the PHS plate motion vector with respect to the Eurasian plate, thought to have occurred between 1.0-0.5 Ma, using long-term vertical deformation data to constrain extent of the locked zone on the plate interface. We evaluated the change in vertical deformation rate for two scenarios: (1) a synchronous shift in the orientation of the locked zone as PHS plate motion shifts and (2) a delayed shift in the orientation of the locked zone following the shift in plate motion. Observed changes in the uplift/subsidence pattern are better explained by scenario (2), suggesting that recent (< 1 My) deformation in the Kanto Basin shows a lag in crustal response to the plate motion shift. We also calculated stress accumulation rates and found a good match with observed earthquake mechanisms, which shows that intraplate earthquakes serve to release stress accumulated through long-term plate interactions.

  11. Slab break-off related to the Pacific-Izanagi ridge and the 50 Ma plate reorganization

    NASA Astrophysics Data System (ADS)

    Whittaker, J. M.; Seton, M.; Flament, N.; Gurnis, M.; Talsma, A. S.; Müller, R. D.

    2011-12-01

    A hemisphere-wide plate reorganization occurred approximately 50 million years ago, causing a plethora of tectonic events in the Pacific, Indian and Atlantic oceans. The ultimate driver of this reorganization, either a plate tectonic/top-down or a mantle flow/bottom-up mechanism, remains unresolved. Top-down mechanisms often invoke a dramatic change in slab pull due to the arrival of a mid ocean ridge or aseismic ridge at a subduction zone. Bottom-up mechanisms require sudden lateral or vertical changes in mantle flow. We use a combination of surface geology, plate reconstructions, forward geodynamic models and seismic tomography to investigate the effect a slab break-off event related to the intersection of the Pacific-Izanagi ridge and the East Asian subduction zone on the 50 Ma plate reorganization. The intersection of an active mid ocean ridge with a subduction zone commonly results in the formation of a slab window. Surface manifestations of an underlying slab window are observed in the geology of southern and central Japan including: the cessation of a major accretion phase in the late Cretaceous; elevated geothermal gradients and heat flux around 55 Ma; and the emplacement of the Okitsu Melange due to underlying hot, buoyant material at 55 Ma. The cessation of granitic plutonism in Korea suggests that subduction along the margin terminated at around 60-50 Ma before restarting again ~42 Ma. We independently reconstructed the now subducted ocean floor in Panthalassa based on the magnetic lineations preserved in the ocean floor in the western Pacific and following a simple, symmetrical spreading regime with inferred intermediate spreading rates. Our plate reconstructions result in the progressively southward arrival of the Pacific-Izanagi ridge parallel to the East Asian margin between 60-50 Ma, consistent with the geological observations listed above. In addition, we carry out a series of forward geodynamic models with imposed surface plate velocities, lithospheric age and assimilated subducted slabs. Our models result in slab break-off along the East Asian margin coincident with the 50 Ma plate reorganization. We compare the present-day mantle temperature field predicted by our models to seismic tomography images over East Asia. These images reveal a break in the continuity of slab material in the mid-mantle, compatible with the slab break-off observed in both the geological record and geodynamic models. Our results suggest that the 50 Ma hemisphere-wide plate reorganization could have been triggered by a plate-driven mechanism rather than by a change in mantle flow alone. We suggest that the major change in direction of Pacific mantle flow may have been a consequence of a cessation of the long-lasting subduction along the East Asian subduction zone around 50 Ma.

  12. Continent-continent collision at the Pacific/Australian plate boundary: Lithospheric deformation, mountain building, and subsequent scientific endeavors

    NASA Astrophysics Data System (ADS)

    Okaya, D. A.; Stern, T. A.; Davey, F. J.

    2012-12-01

    Continental collision occurs at strike-slip plate boundaries where transform motion and oblique convergence create processes of surficial mountain building and deformation within the deeper crust and lithospheric mantle. The Pacific/Australian transform plate boundary in South Island, New Zealand, is characterized by active oblique continent-continent collision with an associated Southern Alps orogen that exhibits both high exhumation rates and rapid strike-slip movement. Beginning in the 1990s, this system was the focus of a decade-long collaborative USA-New Zealand multi-disciplinary study to understand lithospheric structure and processes involved in this transpression. Funded primarily by the NSF Continental Dynamics program and the New Zealand Science Foundation, this project known as SIGHT (South Island Geophysical Transect) with its companion SAPSE (Southern Alps Passive Seismic Experiment) included the following disciplines that involved substantial field observation experiments: seismic reflection, explosion refraction, onshore-offshore wide-angle reflection/refraction, regional and teleseismic passive seismology, magnetotellurics, laboratory petrophysics, gravity, regional geological investigations, and rheological analyses. More than fifty scientists and students from both nations participated in the combined set of studies that have led to over forty-five journal publications, an AGU Monograph, and a dozen graduate theses. Primary results of the project indicate the Pacific-Australian strike-slip plate boundary (Alpine fault) is not vertical but is eastward dipping and rheologically weak based on diverse geophysical data. Most deformation is within the Pacific plate that hosts the Southern Alps orogen. High mantle seismic velocities vertically disposed beneath the orogen suggest Pacific and perhaps Australian mantle lithosphere contribute to a zone of plate-boundary-parallel distributed mantle shortening. The crustal root of the overlying Southern Alps is larger than needed to support surface topography, and is offset from its topographic high, consistent with dynamic thickening of the Pacific crust by the mantle thickening. Teleseismic shear wave splitting is evidence of a wide zone of distributed strain for the mantle portion of the plate boundary. The collective set of results from the South Island projects have led to a number of subsequent studies by various teams, based on follow-up questions, expanded observational expertise, and international collaborative alliances with in particular the New Zealand science community. These studies include a search for the full width of Pacific/Australian distributed mantle strain using marine OBS studies, the transition from strike-slip to plate boundary subduction to the north, the search and discovery of seismic tremor on the Alpine fault, and high resolution geophysical characterization of Alpine fault seismogenesis. The success of geophysically imaging a narrow island using both marine sides led different SIGHT scientists to carry out expanded efforts to study North Island subduction and separately Taiwan mountain building. These efforts benefited and were largely motivated from multi-disciplinary, multi-national collaborations as typically supported by the NSF Continental Dynamics program.

  13. Long-term coupling along the subduction plate interface: insights from exhumed rocks and models

    NASA Astrophysics Data System (ADS)

    Agard, P.; Angiboust, S.; Guillot, S.; Garcia-Casco, A.

    2012-04-01

    Fragments of subducted oceanic lithosphere returned along the plate interface convey crucial information regarding the thermal and rheological conditions of convergent plate boundaries. Combining evidence from exhumed rocks worldwide and the results of recently published thermo-mechanical models, we herein investigate how long-term mechanical coupling takes place along deep portions of the plate interface (40-80 km depth), for which there is no counterflow (unlike in accretionary prisms) and no other known mechanisms to return eclogites than interplate friction or buoyancy. Geological evidence indicates that, unlike subduction, exhumation is highly discontinuous. Besides, eclogites worldwide are found in essentially two types of tectonic setting, either as large scale (>km) slices with coherent PT estimates (W. Alps) or as isolated fragments (frequently m-hm) in a serpentinite- or sedimentary-rich matrix showing contrasting equilibration depths (with hints of punctuated exhumation and even reburial in some localities; Franciscan, Cuba, Sistan). This latter type tends to show warmer equilibration paths (although minor lawsonite-eclogite blocks can be found), whereas the larger tectonic slices from the former type remain systematically cold. Serpentinites are crucial for both in permitting decoupling and acting as a buoy, and fluid budget is important too in enhancing floatability and allowing large slices to survive. Numerical models implementing free migration of fluids in the subduction zone also show that the plate interface is strongly localized in the absence of fluids: mechanical decoupling efficiently occurs along the sediment veneer and/or at the top of the highly hydrothermalized crust. Whenever fluids are released in greater amounts (depending on initial fluid content and/or thermal structure), deformation becomes much more distributed and affects both the mantle wedge and the top of the downgoing lithosphere (hydrated crust and mantle top), thereby increasing mechanical coupling between the two plates. Based on natural data and numerical modelling we thus propose that rheological contrast chiefly controls mechanical decoupling (and early exhumation). On a steady-state basis the subduction interface is apparently efficiently decoupled. In this context, we hypothesize that the liberation of fluid through pulses (or a somewhat increased amount of fluids) is required to locally modify mechanical coupling and induce the slicing of large pieces of oceanic material along the subduction interface (type 1). By contrast, an extreme hydration of the subduction interface and mantle wedge will result in the formation of serpentinite melanges and extensive material mixing (e.g., cold plumes, mafic pods and localized melting; type 2). This latter situation may be promoted by young/fast/wet subduction, such as subduction initiation and/or subduction of young lithosphere or subduction of a particularly hydrated lithosphere section (e.g., at the ridge and/or prior to entering the trench). By contrast cold, slow subduction (type 1) will result in irregular hydration and localized coupling able to detach large slices.

  14. Revised magnetic polarity time scale for the Paleocene and early Eocene and implications for Pacific plate motion

    SciTech Connect

    Butler, R.F.; Coney, P.J.

    1981-04-01

    Magnetostratiographic studies of a continental sedimentary sequence in the Clark's Fork Basin, Wyoming and a marine sedimentary sequence at Gubbio, Italy indicate that the Paleocene--Eocene boundary occurs just stratigraphically above normal polarity zones correlative with magnetic anomaly 25 chron. These data indicate that the older boundary of anomaly 24 chron is 52.5 Ma. This age is younger than the late Paleocene age assigned by LaBrecque et al. (1977) and also younger than the basal Eocene age assigned by Ness et al. (1980). A revised magnetic polarity time scale for the Paleocene and early Eocene is presented in this paper. Several changes in the relative motion system between the Pacific plate and neighboring plates occurred in the interval between anomaly 24 and anomaly 21. A major change in absolute motion of the Pacific plate is indicated by the bend in the Hawaiian--Emperor Seamount chain at approx.43 Ma. The revised magnetic polarity time scale indicates that the absolute motion change lags the relative motion changes by only approx.3--5 m.y. rather than by >10 m.y. as indicated by previous polarity time scales.

  15. Can Mantle Transition Zone beneath the Caroline Plate, Equatorial Western Pacific Be Resolved Seismologically Using Available Dataset?

    NASA Astrophysics Data System (ADS)

    Kang, H.; Konishi, K.; Lee, S. M.

    2014-12-01

    The Caroline Plate, located in the equatorial Western Pacific, appears to be underlain by a stagnant slab. Even though the plate is surrounded by seismic zones of deep- and intermediate-depth earthquakes (originating from the Philippines, Banda Sea, Mariana and New Britain Island), available seismic dataset of source-receiver pair is limited due to the scarcity of land-based seismic stations. In particular, seismic stations are limited in the western and eastern sides of the Caroline Plate. In this study, we perform investigations on the seismic resolution using waveform inversion approach. Earthquake data sets in the last decade obtained from publicly available seismic stations were used to examine the presumed mantle transition zone (MTZ), whose depth ranges from 410 to 660 km in three dimensions. Our analysis shows that, although the current coverage may be marginally sufficient to assess the presence or absence of stagnant slab, the number of ray paths, especially towards the equator, is too limited to obtain high-resolution three-dimensional structure. Hence, it is important to install additional seismic stations (most likely, in the form of the broadband ocean bottom seismometers) around the Caroline Plate. A number of optimal sites are suggested based on our resolution tests. It is hoped that by placing additional ocean bottom seismometers several important issues regarding the nature of MTZ beneath Caroline Plate can be explored that could not be addressed by global tomography models alone such as its origin.

  16. Anatomy of the western Java plate interface from depth-migrated seismic images

    USGS Publications Warehouse

    Kopp, H.; Hindle, D.; Klaeschen, D.; Oncken, O.; Reichert, C.; Scholl, D.

    2009-01-01

    Newly pre-stack depth-migrated seismic images resolve the structural details of the western Java forearc and plate interface. The structural segmentation of the forearc into discrete mechanical domains correlates with distinct deformation styles. Approximately 2/3 of the trench sediment fill is detached and incorporated into frontal prism imbricates, while the floor sequence is underthrust beneath the d??collement. Western Java, however, differs markedly from margins such as Nankai or Barbados, where a uniform, continuous d??collement reflector has been imaged. In our study area, the plate interface reveals a spatially irregular, nonlinear pattern characterized by the morphological relief of subducted seamounts and thicker than average patches of underthrust sediment. The underthrust sediment is associated with a low velocity zone as determined from wide-angle data. Active underplating is not resolved, but likely contributes to the uplift of the large bivergent wedge that constitutes the forearc high. Our profile is located 100 km west of the 2006 Java tsunami earthquake. The heterogeneous d??collement zone regulates the friction behavior of the shallow subduction environment where the earthquake occurred. The alternating pattern of enhanced frictional contact zones associated with oceanic basement relief and weak material patches of underthrust sediment influences seismic coupling and possibly contributed to the heterogeneous slip distribution. Our seismic images resolve a steeply dipping splay fault, which originates at the d??collement and terminates at the sea floor and which potentially contributes to tsunami generation during co-seismic activity. ?? 2009 Elsevier B.V.

  17. Earthquake-cycle models of the Pacific-North America plate boundary at Point Reyes, California

    NASA Astrophysics Data System (ADS)

    Vaghri, A.; Hearn, E. H.

    2011-12-01

    At Point Reyes, California, about 36 mm/yr of Pacific-North America relative plate motion is accommodated by (from west to east) the San Andreas, Rodgers Creek, Napa and Green Valley faults. We have developed a suite of viscoelastic earthquake cycle models which take into account the timing and recurrence intervals of large earthquakes on these faults, and are calibrated to the current GPS velocity field. We infer a locking depth of about 12 km for all four faults, consistent with previous analyses of local hypocenter depths (e.g., d'Alessio et al, 2005). Low-viscosity viscous shear zones appear to be required for our models to fit the GPS velocities. In order to fit the high surface velocity gradient across this set of faults, the effective viscosity for the lower crust and mantle must exceed 10^20 Pa s. A modest contrast in effective viscosity of the lower crust and upper mantle across the San Andreas Fault, with higher viscosity values (at least 5 x 10^20 Pa s) to the east, is also indicated. In the region between the Rodgers Creek Fault and the Green Valley Fault, GPS data indicate a higher strain rate than our models can explain. Even after shifting the entire Green Valley Fault slip rate (9 mm/yr) westward to the Napa Fault, the misfit is not eliminated. Double-difference hypocenter data (Waldhauser and Schaff, 2008) suggest the presence of another fault zone between the Napa Fault and the Green Valley Fault, and that all three of these faults dip toward the west. This offsets their deep, creeping extensions several km from their surface traces. A preliminary model with a suitably offset, deep Green Valley Fault extension cuts the WRSS misfit to GPS site velocities by over a factor of two. Since non-vertical fault dips are often missed in seismic studies (e.g. Fuis et al., 2008), creeping shear zones at depth may routinely be offset by several kilometers from their surface traces, unless alternate evidence of their position at depth is available (e.g. Shelly et al., 2009). This may lead to incorrect inferences of material asymmetry, or errors in the attribution of slip rates to closely spaced, active faults.

  18. Effects of the Yakutat terrane collision with North America on the neighboring Pacific plate

    NASA Astrophysics Data System (ADS)

    Reece, R.; Gulick, S. P.; Christeson, G. L.; Barth, G. A.; van Avendonk, H.

    2011-12-01

    High-resolution bathymetry data show a 30 km N-S trending ridge within the deep-sea Surveyor Fan between the mouths of the Yakutat Sea Valley and Bering Trough in the Gulf of Alaska. The ridge originates in the north, perpendicular to and at the base of the continental slope, coincident with the Transition Fault, the strike-slip boundary between the Yakutat terrane (YAK) and the Pacific plate (PAC). The ridge exhibits greatest relief adjacent to the Transition Fault, and becomes less distinct farther from the shelf edge. Seismic reflection data reveal a sharp basement high beneath the ridge (1.1 sec of relief above "normal" basement in two-way travel time) as well as multiple similarly oriented strike-slip fault segments. The ridge, basement high, and faults are aligned and co-located with an intraplate earthquake swarm on the PAC, which includes four events > 6.5 Mw that occurred from 1987-1992. The swarm is defined by right-lateral strike-slip events, and is collectively called the Gulf of Alaska Shear Zone (GASZ). Based on the extent of historic seismicity, the GASZ extends at least 230 km into the PAC, seemingly ending at the Kodiak-Bowie Seamount Chain. Farther southwest, between the Kodiak-Bowie and Patton-Murray Seamount Chains, there is a large regional bathymetric low with an axis centered along the Aja Fracture Zone, perpendicular to the GASZ and Aleutian Trench. Basement and overlying sediment in the low are irregularly, but pervasively faulted. The GASZ and faulted bathymetric low could represent PAC deformation due to PAC-YAK coupling whereby YAK resistance to subduction is expressed as deformation in the thinner (weaker) PAC crust. The YAK is an allochthonous, basaltic terrane coupled to the PAC that began subducting at a low angle beneath North America (NA) ~25-40 Ma. Due to its 15-25 km thickness, the YAK is resistant to subduction compared to the normal oceanic crust of the PAC. As a result the plates developed differential motion along the Transition Fault and have different, convergent, vectors for motion relative to NA. Although a tear on the scale of the GASZ in normal oceanic crust is unusual, preexisting zones of weakness, such as the Aja Fracture Zone and bending faults at the flexural bulge, may have proven to be a kinematically favorable localization for strain. These results expand on a previous tectonic model wherein the differing YAK and PAC vectors caused the northern PAC to behave as two tectonic blocks, separated by the GASZ. In this model, the eastern block of the PAC exhibits a counter-clockwise rotation that accounts for motion along the Transition Fault and GASZ. We will analyze seismic reflection, bathymetric, magnetic, and gravity data in order to further investigate this intraplate deformation and the cause of strain localization in both areas. New bathymetric and 2D seismic reflection data will allow us to confirm whether the GASZ previously extended beyond the Kodiak-Bowie Seamount Chain and the current zone of active seismicity, as well as to characterize the GASZ at opposite ends.

  19. Finite Element Modeling of Laminated Composite Plates with Locally Delaminated Interface Subjected to Impact Loading

    PubMed Central

    Abo Sabah, Saddam Hussein; Kueh, Ahmad Beng Hong

    2014-01-01

    This paper investigates the effects of localized interface progressive delamination on the behavior of two-layer laminated composite plates when subjected to low velocity impact loading for various fiber orientations. By means of finite element approach, the laminae stiffnesses are constructed independently from their interface, where a well-defined virtually zero-thickness interface element is discreetly adopted for delamination simulation. The present model has the advantage of simulating a localized interfacial condition at arbitrary locations, for various degeneration areas and intensities, under the influence of numerous boundary conditions since the interfacial description is expressed discretely. In comparison, the model shows good agreement with existing results from the literature when modeled in a perfectly bonded state. It is found that as the local delamination area increases, so does the magnitude of the maximum displacement history. Also, as top and bottom fiber orientations deviation increases, both central deflection and energy absorption increase although the relative maximum displacement correspondingly decreases when in contrast to the laminates perfectly bonded state. PMID:24696668

  20. Finite element modeling of laminated composite plates with locally delaminated interface subjected to impact loading.

    PubMed

    Abo Sabah, Saddam Hussein; Kueh, Ahmad Beng Hong

    2014-01-01

    This paper investigates the effects of localized interface progressive delamination on the behavior of two-layer laminated composite plates when subjected to low velocity impact loading for various fiber orientations. By means of finite element approach, the laminae stiffnesses are constructed independently from their interface, where a well-defined virtually zero-thickness interface element is discreetly adopted for delamination simulation. The present model has the advantage of simulating a localized interfacial condition at arbitrary locations, for various degeneration areas and intensities, under the influence of numerous boundary conditions since the interfacial description is expressed discretely. In comparison, the model shows good agreement with existing results from the literature when modeled in a perfectly bonded state. It is found that as the local delamination area increases, so does the magnitude of the maximum displacement history. Also, as top and bottom fiber orientations deviation increases, both central deflection and energy absorption increase although the relative maximum displacement correspondingly decreases when in contrast to the laminates perfectly bonded state. PMID:24696668

  1. Into the Future: Continuing Evolution of the Pacific-Juan de Fuca-North America Plate System

    NASA Astrophysics Data System (ADS)

    McCrory, P. A.; Wilson, D. S.; Stanley, R. G.

    2007-12-01

    The death of a series of spreading ridge segments adjacent to California and Mexico starting about 28.5 Ma led to the piecewise destruction of a subduction regime and the opening of slab windows beneath the continent. The formation, growth, and healing of these slab windows has been a transient process marked at the surface by overprinted pulses of volcanism in the former forearc triggered by asthenospheric upwelling behind subducting slab edges. In the subsurface, where windows opened beneath thin forearc lithosphere, the shallow asthenosphere promoted a plastic mode of mechanical behavior in the lithosphere characterized by fault-block deformation. This plastic mode of deformation resulted mainly from (1) asthenosphere in direct contact with the lower crust instead of stronger lithospheric mantle; and (2) lower crust shifting from brittle to ductile behavior as a result of conductive heating. Our finite-rotation model built from quantitative reconstruction of Farallon-North America slab windows and their magmatic signatures allows us to investigate past and future fault-block kinematics of the North America continental margin. While the shallow asthenosphere thermally weakened coastal California and promoted plastic deformation in the lower crust, the actual fragmentation of the upper crust into fault blocks occurred in concert with retrograde motion of a partially subducted Monterey plate fragment following its capture by the Pacific plate ca. 19 Ma. This abrupt change from convergent to transtensional deformation initiated the pulling apart and clockwise pivoting of the adjacent western Transverse Ranges and California Borderlands region. A similar reversal in plate motion occurred adjacent to coastal Mexico following capture of a Magdalena plate fragment by the Pacific plate ca. 12.5 Ma. In this case, the transtensional strain that initiated Baja California pulling away from the Mexican continental margin was localized along already thermally weakened Comondu volcanic arc crust. In California, running our kinematic model into the future suggests that the current locus of strike-slip motion may shift to the east side of the Sierra Nevada Mountains, starting about 2 My from now as a result of convergence between the Sierra Nevada and Peninsular Range batholiths. Alternatively, the locus of fault slip may remain on the San Andreas fault, requiring new fragments to be broken from the southern Sierra Nevada and Mojave blocks, to make room for the Peninsular Range to slip past on their west side. Or perhaps, eastern parts of the Peninsular Range may transfer back to the North America plate, with the Whittier-Elsinore fault accommodating most of the relative plate motion.

  2. Predicting earthquakes along the major plate tectonic boundaries in the Pacific

    USGS Publications Warehouse

    Spall, H.

    1978-01-01

    In an article in the last issue of the Earthquake Information Bulletin ("Earthquakes and Plate Tectonics," by Henry Spall), we saw how 90 percent of the world's earthquakes occur at the margins of the Earth's major crustal plates. however, when we look at the distribution of earthquakes in detail, we see that a number of nearly aseismic regions, or seismic gaps, can be found along the present-day plate boundaries. Why is this? And can we regard these areas as being more likely to be the sites for future larger earthquakes than those segments of the plate boundaries that have ruptured recently. 

  3. Along-Arc Variation in Slab Surface Temperature Caused By 3D Material Circulation at the Plate Interface

    NASA Astrophysics Data System (ADS)

    Morishige, M.; Van Keken, P. E.

    2014-12-01

    In the northeast Japan arc, we can observe the along-arc variation of Quaternary volcano distribution, topography, seismic wave velocity, and Bouguer gravity anomaly whose characteristic wavelength is ~80 km. These observations may be related to 3D thermal structure in the mantle wedge and/or subducting Pacific slab. As a possible explanation of this, small-scale convection in the mantle wedge of thermal and chemical origin has been proposed so far. In this presentation, we will show another possible explanation for it. It is known mainly based on surface heat flow observation that the mantle wedge in this region is decoupled from the subducting Pacific slab down to ~80 km depth for geological time scale. We also observe that the down-dip limit of low angle thrust type earthquakes in this region is ~50 km depth. These suggest that in the northeast Japan arc, the mantle wedge and the slab decouples by brittle failure down to 50 km depth and by plastic deformation from 50 to 80 km depth. In order to test the effects of the plate interface on the thermal structure in this region, we construct 3D finite element models. The mantle flow is computed only in the mantle wedge, whereas temperature is computed for the whole model domain. We assume a thin, low viscosity layer just above the slab surface from 50 to 80 km depth to decouple the mantle wedge and the slab. We find that the along-arc variation in the slab surface temperature gradually develops with time. Its characteristic wavelength is ~100 km, which is comparable to or slightly higher than that observed. It arises because of the small-scale 3D circulation in the assumed low viscosity layer. The wavelength and the time of onset may depend on the viscosity and dimension of the low viscosity layer. Surface heat flow, on the other hand, does not show significant along-arc variation because forearc mantle is kept cold and hence rigid. These findings suggest that the observed along-arc variation in the northeast Japan arc originally comes from the variation in the slab surface temperature.

  4. Localized double-array stacking analysis of PcP: D″ and ULVZ structure beneath the Cocos plate, Mexico, central Pacific, and north Pacific

    USGS Publications Warehouse

    Hutko, Alexander R.; Lay, Thorne; Revenaugh, Justin

    2009-01-01

    A large, high quality P-wave data set comprising short-period and broadband signals sampling four separate regions in the lowermost mantle beneath the Cocos plate, Mexico, the central Pacific, and the north Pacific is analyzed using regional one-dimensional double-array stacking and modelling with reflectivity synthetics. A data-screening criterion retains only events with stable PcP energy in the final data stacks used for modelling and interpretation. This significantly improves the signal stacks relative to including unscreened observations, allows confident alignment on the PcP arrival and allows tight bounds to be placed on P-wave velocity structure above the core–mantle boundary (CMB). The PcP reflections under the Cocos plate are well modelled without any ultra-low velocity zone from 5 to 20°N. At latitudes from 15 to 20°N, we find evidence for two P-wave velocity discontinuities in the D″ region. The first is ∼182 km above the CMB with a δln Vp of +1.5%, near the same depth as a weaker discontinuity (<+0.5%) observed from 5 to 15°N in prior work. The other reflector is ∼454 km above the CMB, with a δln Vp of +0.4%; this appears to be a shallower continuation of the joint P- and S-wave discontinuity previously detected south of 15° N, which is presumed to be the perovskite to post-perovskite phase transition. The data stacks for paths bottoming below Mexico have PcP images that are well matched with the simple IASP91 structure, contradicting previous inferences of ULVZ presence in this region. These particular data are not very sensitive to any D″ discontinuities, and simply bound them to be <∼2%, if present. Data sampling the lowermost mantle beneath the central Pacific confirm the presence of a ∼15-km thick ultra-low velocity zone (ULVZ) just above the CMB, with δln Vp and δln Vs of around −3 to −4% and −4 to −8%, respectively. The ULVZ models predict previous S-wave data stacks well. The data for this region indicate laterally varying Vp discontinuities in D″, with one subregion having a δln Vp of 0.5% 140 km above the CMB. Beneath the north Pacific, the PcP arrivals are compatible with only weak ULVZ (δln Vp ∼ 0 to −3%), and there is a weak D″ reflector with δln Vp = 0.5%, near 314 km above the CMB. These results indicate localized occurrence of detectable ULVZ structures rather than ubiquitous ULVZ structure and emphasize the distinctiveness between the large low shear velocity province under the central Pacific and circum-Pacific regions.

  5. Pelagic and benthic ecology of the lower interface of the Eastern Tropical Pacific oxygen minimum zone

    NASA Astrophysics Data System (ADS)

    Wishner, Karen F.; Ashjian, Carin J.; Gelfman, Celia; Gowing, Marcia M.; Kann, Lisa; Levin, Lisa A.; Mullineaux, Lauren S.; Saltzman, Jennifer

    1995-01-01

    The distributions of pelagic and benthic fauna were examined in relation to the lower boundary of the oxygen minimum zone (OMZ) on and near Volcano 7, a seamount that penetrates this feature in the Eastern Tropical Pacific. Although the broad, pronounced OMZ in this region is an effective barrier for most zooplankton, zooplankton abundances, zooplankton feeding rates, and ambient suspended particulate organic carbon (POC) peaked sharply in the lower OMZ (about 740-800 m), in association with the minimum oxygen concentration and the increasing oxygen levels just below it. Zooplankton in the lower OMZ were also larger in size, and the pelagic community included some very abundant, possibly opportunistic, species. Elevated POC and scatter in the light transmission data suggested the existence of a thin, particle-rich, and carbon-rich pelagic layer at the base of the OMZ. Gut contents of planktonic detrifvores implied opportunistic ingestion of bacterial aggregates, possibly from this layer. Benthic megafaunal abundances on the seamount, which extended up to 730 m, peaked at about 800 m. There was a consistent vertical progression in the depth of first occurrence of different megafaunal taxa in this depth range, similar to intertidal zonation. Although the vertical gradients of temperature, salinity, and oxygen were gradual at the lower OMZ interface (in contrast to the upper OMZ interface at the thermocline), temporal variability in oxygen levels due to internal wave-induced vertical excursions of the OMZ may produce the distinct zonation in the benthic fauna. The characteristics of the lower OMZ interface result from biological interactions with the chemical and organic matter gradients of the OMZ. Most zooplankton are probably excluded physiologically from pronounced OMZs. The zooplankton abundance peak at the lower interface of the OMZ occurs where oxygen becomes sufficiently high to permit the zooplankton to utilize the high concentrations of organic particles that have descended through the OMZ relatively unaltered because of low metazoan abundance. A similar scenario applies to megabenthic distributions. Plankton layers and a potential short food chain (bacteria to zooplankton) at OMZ interfaces suggest intense utilization and modification of organic material, localized within a thin midwater depth zone. This could be a potentially significant filter for organic material sinking to the deep-sea floor.

  6. 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.

  7. Real feature of seismicity around Palau trench region, western Pacific: Is Palau trench aseismic silent plate boundary?

    NASA Astrophysics Data System (ADS)

    Ishihara, Y.; Shito, A.; Tanaka, S.; Suetsugu, D.

    2012-12-01

    Palau islands locate around plate converging zone in the western Pacific region. In the east off the Palau islands, obvious trench topography is developed whose bathymetry reaches about 6000 meters. Palau trench locates at the west side of Yap trench. However tectonic activity is quite different in the both trenches. Yap trench has active seismic activity associate with subduction process. Plate motion model shows clear convergent relative motion between Pacific plate and Philippine Sea plate at Yap trench. On the other hand, Palau trench doesn't have active seismicity according to ISC catalogue. In ten years in 2000's, only three small earthquakes are reported in ISC catalogue. Historically any great earthquake also is not reported. Recent plate motion model shows very low convergent motion at Palau trench though developed trench structure. Our group operates broadband seismic station at Palau (station code: PALU) for about 15 years. In our instant monitoring, local earthquakes sometime are recognized. We operated additional stations in Palau islands for six months to detect local earthquake and to locate hypocenters. Our objective of the research is evaluation of real seismicity of Palau region and final major interest is to understand tectonic activity of Palau trench. We install minimum network for hypocenter locating in Koror and Babeldaob islands, Palau that its array dimension is about 20 km. We use broadband seismographs and high resolution data loggers with GPS clock and solar power generators. We succeeded continuous recording without any troubles and clips of mass position. By careful motoring, we pick up greater than 70 local earthquakes in only six months. And we also tried to read the P and S wave arrival times. We succeeded to locate 27 hypocenters. The number of seismic events is much higher than initial estimation. The hypocenters locate east coast side of Palau islands where is trench side. The overview of distribution is parallel to trench. Estimated depth is distributed from 20 to 30 km. The determination is inaccurate and sparse distributed, but simple seismograms mean that these are not shallow crustal event. P and S wave amplitude analysis says that dip-slip type fault mechanism is dominant. This seismic activity may be strongly related with subduction process. These earthquakes are magnitude of 2 to 3. Seismicity of Palau area is much higher than initial estimation based on earthquake catalogue. These results mean that Palau trench has latent active seismic process and suggest that the trench may have convergent plate process than general understanding.

  8. Unlocking the Secrets of Slow Slip on the Plate Interface Using Cascadia LFEs

    NASA Astrophysics Data System (ADS)

    Sweet, J. R.; Creager, K. C.; Thomas, T.; Vidale, J. E.; Houston, H.

    2012-12-01

    Low-frequency earthquakes (LFEs) have been associated with tectonic tremor and slow slip on the deep extension of subduction zones (Japan, Cascadia, Alaska, Costa Rica) and major strike-slip faults (SAF). These tiny earthquakes are thought to represent small amounts of slip on the fault interface in places with very high pore fluid pressures and low effective stresses. Tectonic tremor has been shown to often consist of a superposition of many LFEs occurring at nearly the same time. Using data from the 2-year Array of Arrays (AofA) and 6-year CAFE experiments in northern Cascadia, we employ a matched-filter autocorrelation method to find new LFE families. Similar to the method of Brown et al. (GRL, 2008), ours makes use of efficient coding to minimize the significant computational time required. To date, we have identified and located 8 LFE families, all of which are very near the plate interface. By analyzing a 6-year history of individual LFE families, we find several new patterns that vary with downdip distance on the plate interface. The two end-member LFE families (LFE1 - farthest updip, and LFE4 - farthest downdip) illustrate the greatest differences in behavior. The recurrence interval of LFE activity increases updip. LFE1 is only active during major ETS episodes every 12-15 months, while LFE4 repeats every 2 weeks. This observation mirrors that already reported for tremor swarms in Cascadia (Wech et al., 2011, Nature GeoSci.), further supporting the idea that tremor and LFEs are closely linked. In addition, we observe that the duration of the initial burst of activity is longer for updip LFE families than for downdip ones. LFE1 exhibits an initial burst of frenzied activity that lasts ~4 hours, which we interpret to be the passage of the slow-slip rupture front. In contrast, LFE4 has initial bursts that last at most 1 hour (see Creager et al., this session). The different duration of bursts, combined with the different recurrence intervals, suggests that locations farther updip are capable of accumulating and releasing larger amounts of slip than locations farther downdip. This observation may provide insight into how frictional properties vary over the subduction interface. During each of the past 5 ETS episodes, LFE1 was active over a 5-day period following the initial burst. During these 5 days, most of the activity was concentrated in roughly 5 residual bursts (of duration <1hr) that occurred at exponentially increasing recurrence intervals. After 5 days, the residual bursts ceased and no activity was detected until the next ETS episode. In addition, nearly all of the residual bursts occurred during times of favorable tidal shear stress, suggesting that these later bursts occurred in an environment with very low stress such that small tidal fluctuations activate or inhibit slip. In contrast, the initial bursts occurred independently of the tidal stress. For the last 2 ETS episodes, the residual bursts correspond to rapid tremor reversals (RTRs) imaged by the AofA (see Thomas et al., this session). This observation may indicate that RTRs could be modulated and perhaps even triggered by favorable tidal stressing in the extremely low stress region behind the initial slip front. This idea is consistent with the proposal by Houston et al. (2011, Nature GeoSci.) that RTRs are associated with a slip-weakened plate interface.

  9. The March 11, 2011 Tohoku-oki earthquake and cascading failure of the plate interface

    NASA Astrophysics Data System (ADS)

    Kiser, Eric; Ishii, Miaki

    2012-03-01

    A continuous back-projection analysis using data recorded in North America between March 9, 2011 and April 7, 2011 is applied to the Mw 9.0 2011 Tohoku-oki earthquake and the foreshocks and aftershocks of this event. As with the Mw 8.8 2010 Maule, Chile earthquake, back-projection results of the mainshock show variations in rupture behavior when data filtered to different frequency ranges are used. In particular, there is a relationship between the frequency of data used and the position along the dip direction of the energy release, with the highest-frequency result imaging energy at the down-dip edge of the rupture and progressively lower frequencies showing a continuous shift updip. In addition, these results show that late in the rupture (˜200 seconds after the hypocentral time), energy at all frequencies is imaged very close to the trench at about 37°N, which, with the energy imaged near and updip of the epicenter, may have acted as a tsunami source. Comparing the mainshock rupture area to the area that ruptured during M ≥ 6 foreshocks and aftershocks between March 9th and April 7th shows that total failure of the plate interface nearly doubled compared to the mainshock alone. Building upon the idea that the mainshock occurred through interactions between multiple segments, the results imply that the total failure area of the interface may represent the area that can rupture during a single event as a series of in-phase interface segments.

  10. Kinematics of the Chugach metamorphic complex, southern Alaska: Plate geometry in the north Pacific margin during the Late Cretaceous to Eocene

    NASA Astrophysics Data System (ADS)

    Scharman, Mitchell R.; Pavlis, Terry L.

    2012-08-01

    The Paleogene plate geometry of the north Pacific margin is poorly constrained because all of the plates involved, except the trailing Pacific plate, have been subducted. However, the kinematic history of the Chugach metamorphic complex in southern Alaska constrains plate configurations because of its link to ridge-subduction. We synthesize recent regional mapping of the complex, finite strain data, and geochronology to show that progressive deformation records the Paleogene triple junction interaction occurred over a period of less than 2 m.y. across ˜350 km of the margin. We document that 140-190 km of distributed dextral shear occurred across the complex during the latest phase of deformation in the complex. This analysis suggests dextral motion of at least 70-95 mm/yr which can account for most, or all, of the margin parallel plate motion during a brief period of the Eocene. We use these results to compare and evaluate possible plate configurations based on older and newer plate motion models. Using modern plate motion models it is difficult to reconcile a Kula-Farallon ridge-subduction model with the available data, but our preferred plate geometry model involving a Kula-Resurrection ridge provides a reasonable explanation for our observations.

  11. Non-coaxial horizontal shortening strains preserved in twinned amygdule calcite, DSDP hole 433, Suiko seamount, northwest pacific plate

    NASA Astrophysics Data System (ADS)

    Craddock, John P.; Pearson, Alene M.

    1994-05-01

    Core sections from the lower, basaltic portions of DSDP Hole 433 (total depth: 550.5 m) in Suiko seamount contain amygdule and vein fillings of calcite which contain mechanical twins. Analysis of the calcite twins reveals the presence of two horizontal shortening strains that are nearly orthogonal to one another; the azimuthal orientation of these strains is only known with respect to stratigraphic top and bottom as the cores are not oriented in any other manner. Maximum shortening strain magnitudes for the best-developed, positive expected value (PEV) twin lamellae set is -1.7%. For the lesser-developed, negative expected value (NEV) split, the preserved horizontal strain magnitude is -4.3%. Inferred compressive paleostress magnitudes were on the order of 26 MPa. Horizontal differential stresses of this magnitude could be: (1) associated with hotspot plumes; and/or (2) are transmitted to the central portions of thin oceanic plates from distant plate boundaries. Suiko seamount is composed of Paleocene basalts overlain by lithified middle Paleocene limestones, and is part of the Emperor seamount chain on the Pacific plate. The absence of secondary vein calcite in the overlying sediments suggests that the underlying amygdule calcite is Paleocene in age which indicates that the twinned calcite preserves a stress field reorganization (the NEV split) after the middle Paleocene that is oriented 64° from the earlier Paleocene stress field (the PEV split).

  12. First measurement of the displacement rate of the Pacific Plate near the Japan Trench after the 2011 Tohoku-Oki earthquake using GPS/acoustic technique

    NASA Astrophysics Data System (ADS)

    Tomita, Fumiaki; Kido, Motoyuki; Osada, Yukihito; Hino, Ryota; Ohta, Yusaku; Iinuma, Takeshi

    2015-10-01

    The subduction rate of an oceanic plate may accelerate after large earthquakes rupture the interplate coupling between the oceanic and overriding continental plates. To better understand postseismic deformation processes in an incoming oceanic plate, we directly measured the displacement rate of the Pacific Plate near the Japan Trench after the 2011 Tohoku-Oki earthquake using a GPS/acoustic technique over a period of 2 years (September 2012 to September 2014). The displacement rate was measured to be 18.0 ± 4.5 cm yr-1 (N302.0°E) relative to the North American Plate, which is almost twice as fast as the predicted interseismic plate motion. Because the sum of steady plate motion and viscoelastic response to the Tohoku-Oki earthquake roughly accounts for the observed displacement rate, we conclude that viscoelastic relaxation is the primary mechanism responsible for postseismic deformation of the Pacific Plate and that significant subduction acceleration did not occur at least not during the observation period.

  13. Seismological investigations of the subduction zone plate interface: New advances and challenges

    NASA Astrophysics Data System (ADS)

    Rietbrock, Andreas; Garth, Tom; Hicks, Stephen

    2015-04-01

    In the last decade, huge advances have been made in analysing the slip distribution of large megathrust earthquakes and how slip relates to geodetic locking, shedding light on the character of the seismic cycle in subduction zones. Recently, a number of studies have suggested that at convergent plate boundaries, geodetic locking may be closely related to slip distribution of subsequent large earthquakes, as found recently for the Maule 2010 and Tohoku 2011 earthquakes. However, the physical (e.g. seismic) properties along the subduction zone interface are still poorly constrained, posing a major limitation to our physical understanding of both geodetic locking and earthquake rupture process. Here, we present high-resolution seismic tomography results (P- and S-wave velocity), as well as earthquake locations to make a detailed investigation of seismic properties along the portion of the plate interface that ruptured during the 2010 Maule earthquake. Additionally, to test the robustness of our models, we performed numerous numerical tests including changes to the parameterization, synthetic recovery tests and bootstrap analysis. We find P-wave velocities of about 5.7 km/s at 10 km depth and linearly increasing to 7.5 km/s at a depth of 30 km. Between 30 km and 43 km, P-wave velocities are relatively constant at around 7.5 km/s before a subsequent increase to 8.3 km/s at larger depths (>60 km) is observed. The Poisson's ratio is significantly elevated, at values of up to 0.35 at shallow depths of 10km to 15km, before reaching less elevated values of 0.28-0.29 in the depth range between 20km and 43km. Comparison of these velocities to petrological models shows good agreement below 30 - 50 km depth. At shallower depths though P-wave velocities are significantly lower, which together with the elevated poisons ratio indicates that this portion of the mega thrust is highly hydrated, suggesting that material properties may in part control the seismogenic character of subduction megathrusts Comparison of our findings to other regional tomographic models from other subduction zones worldwide (Japan, Sumatra) shows excellent agreements with our results.

  14. Faunal breaks and species composition of Indo-Pacific corals: the role of plate tectonics, environment and habitat distribution

    PubMed Central

    Keith, S. A.; Baird, A. H.; Hughes, T. P.; Madin, J. S.; Connolly, S. R.

    2013-01-01

    Species richness gradients are ubiquitous in nature, but the mechanisms that generate and maintain these patterns at macroecological scales remain unresolved. We use a new approach that focuses on overlapping geographical ranges of species to reveal that Indo-Pacific corals are assembled within 11 distinct faunal provinces. Province limits are characterized by co-occurrence of multiple species range boundaries. Unexpectedly, these faunal breaks are poorly predicted by contemporary environmental conditions and the present-day distribution of habitat. Instead, faunal breaks show striking concordance with geological features (tectonic plates and mantle plume tracks). The depth range over which a species occurs, its larval development rate and genus age are important determinants of the likelihood that species will straddle faunal breaks. Our findings indicate that historical processes, habitat heterogeneity and species colonization ability account for more of the present-day biogeographical patterns of corals than explanations based on the contemporary distribution of reefs or environmental conditions. PMID:23698011

  15. Faunal breaks and species composition of Indo-Pacific corals: the role of plate tectonics, environment and habitat distribution.

    PubMed

    Keith, S A; Baird, A H; Hughes, T P; Madin, J S; Connolly, S R

    2013-07-22

    Species richness gradients are ubiquitous in nature, but the mechanisms that generate and maintain these patterns at macroecological scales remain unresolved. We use a new approach that focuses on overlapping geographical ranges of species to reveal that Indo-Pacific corals are assembled within 11 distinct faunal provinces. Province limits are characterized by co-occurrence of multiple species range boundaries. Unexpectedly, these faunal breaks are poorly predicted by contemporary environmental conditions and the present-day distribution of habitat. Instead, faunal breaks show striking concordance with geological features (tectonic plates and mantle plume tracks). The depth range over which a species occurs, its larval development rate and genus age are important determinants of the likelihood that species will straddle faunal breaks. Our findings indicate that historical processes, habitat heterogeneity and species colonization ability account for more of the present-day biogeographical patterns of corals than explanations based on the contemporary distribution of reefs or environmental conditions. PMID:23698011

  16. Modeling Thermal and Stress Behavior of the Fuel-clad Interface in Monolithic Fuel Mini-plates

    SciTech Connect

    Gregory K. Miller; Pavel G. Medvedev; Douglas E. Burkes; Daniel M. Wachs

    2010-08-01

    As part of the Global Threat Reduction Initiative, a fuel development and qualification program is in process with the objective of qualifying very high density low enriched uranium fuel that will enable the conversion of high performance research reactors with operational requirements beyond those supported with currently available low enriched uranium fuels. The high density of the fuel is achieved by replacing the fuel meat with a single monolithic low enriched uranium-molybdenum fuel foil. Doing so creates differences in the mechanical and structural characteristics of the fuel plate because of the planar interface created by the fuel foil and cladding. Furthermore, the monolithic fuel meat will dominate the structural properties of the fuel plate rather than the aluminum matrix, which is characteristic of dispersion fuel types. Understanding the integrity and behavior of the fuel-clad interface during irradiation is of great importance for qualification of the new fuel, but can be somewhat challenging to determine with a single technique. Efforts aimed at addressing this problem are underway within the fuel development and qualification program, comprised of modeling, as-fabricated plate characterization, and post-irradiation examination. An initial finite element analysis model has been developed to investigate worst-case scenarios for the basic monolithic fuel plate structure, using typical mini-plate irradiation conditions in the Advanced Test Reactor. Initial analysis shows that the stress normal to the fuel-clad interface dominates during irradiation, and that the presence of small, rounded delaminations at the interface is not of great concern. However, larger and/or fuel-clad delaminations with sharp corners can create areas of concern, as maximum principal cladding stress, strain, displacement, and peak fuel temperature are all significantly increased. Furthermore, stresses resulting from temperature gradients that cause the plate to bow or buckle in an unconstrained fuel plate configuration is greatly enhanced in a constrained fuel plate configuration. The sensitivities of the model and input parameters are discussed, along with some overlap of initial experimental observations using as-fabricated plate characterization and post-irradiation examination.

  17. High Resolution 40Ar/39Ar Geochronology of the Tuvalu Seamount Chain: Implications for Hotspot Longevity and Pacific Plate Motion.

    NASA Astrophysics Data System (ADS)

    Konrad, K.; Finlayson, V. A.; Koppers, A. A. P.; Konter, J.; Jackson, M. G.

    2014-12-01

    The Tuvalu seamount chain is a Mid-Pacific (4-11oS, 175-179oE) linear volcanic chain that was previously poorly sampled. Absolute plate motion (APM) models predict a long-lived relationship with hotspot activity in French Polynesia. The lack of detailed age data therefore results in a key chronologic gap in the geologic history of this hotspot and current APM models. Depending on the set of assumptions employed, previous APM models have disagreed on which known hotspot chain, if any, the Tuvalu volcanoes are associated with. Based on APM modeling and geochemical affinities (HIMU, 206Pb/204Pb > 20), Konter et al. (2008) argue that Rurutu Island (French Polynesia) represents the modern location of the hotspot that contributed volcanism to the Tuvalu seamounts. This model traces the hotspot chain from Rurutu through the region of modern day Samoa, the Tuvalu seamounts, the Gilbert ridge, and into the North & South Wake islands. This hypothesis suggests that a single HIMU mantle reservoir can exist and remain relatively geochemically consistent over 100 Myrs. On the contrary, the Wessel and Kroenke (2008) APM model suggest the Tuvalu seamounts and N & S Wake are unrelated. This model requires the N & S Wake chains to rotate significantly at the young end of the Gilbert Ridge resulting in a current hotspot location around 13-15oS and 156-155oW, away from any known active volcanism. During the summer of 2013, 25 Tuvaluan seamounts and 9 seamounts near the current Samoan chain were dredged onboard the R.V. Roger Revelle (expedition RR1310). Here we present 43 new 40Ar-39Ar ages covering 19 Tuvaluan seamounts and four seamounts within the Samoan hotspot track. These ages provide insights into the contributing hotspot for Tuvaluan volcanism and provide a new reference frame for constraining Pacific APM models. The corresponding chemical analyses for a subset of these seamounts will be presented by Finlayson et al. (this volume). Konter, J. G. et al. One hundred million years of mantle geochemical history suggest the retiring of mantle plumes is premature. Earth and Planetary Science Letters 275, 285-295, doi:10.1016/j.epsl.2008.08.023 (2008) Wessel, P. & Kroenke, L. W. Pacific absolute plate motion since 145 Ma: An assessment of the fixed hot spot hypothesis. Journal of Geophysical Research: Solid Earth (1978-2012) 113 (2008)

  18. Propagation behaviors of thickness-twist modes in an inhomogeneous piezoelectric plate with two imperfectly bonded interfaces.

    PubMed

    Jin, Feng; Li, Peng

    2012-01-01

    The thickness-twist modes in an inhomogeneous piezoelectric plate with two imperfectly bonded interfaces are analyzed, and an exact solution is obtained according to the spring-type relation from the equations of the linear theory of piezoelectricity. The frequency shift, the displacement and the stress components are all obtained and plotted. Both theoretical analysis and numerical examples show that the effect of mechanical imperfection is more evident than that of the electrical imperfection on the thickness-twist modes. Results show that the displacement and the stress components all change obviously due to the imperfectly bonded interfaces. The relationship between the frequency shift Δω and the non-dimensional number γ that is related to the imperfect interfaces is linear, which can be used to provide the foundation for a new experimental procedure for measuring the level of the interface bonding. PMID:21752416

  19. Fluid content along the subduction plate interface: how it impacts the long- (and short-) term rheology and exhumation modes

    NASA Astrophysics Data System (ADS)

    Agard, Philippe; Angiboust, Samuel; Guillot, Stéphane; Burov, Evgueni

    2015-04-01

    Over the last decade, many studies based on field, petrological and geophysical evidence have emphasized the link between mineral reactions, fluid release and seismogenesis, either along the whole plate interface (eg., Hacker et al., 2003) or at specific depths (e.g., ~30 km: Audet et al., 2009; ~70-80 km: Angiboust et al., 2012). Although they argue for a crucial influence of fluids on subduction processes, large uncertainties remain when assessing their impact on the rheology of the plate interface across space and time. Kilometer-scale accreted terranes/units in both ancient and present-day subduction zones potentially allow to track changes in mechanical coupling along the plate interface. Despite some potential biases (exhumation is limited and episodic, lasting no more than a few My if any, from prefered depths -- mainly 30-40 and 70-80 km, and there are so far only few examples precisely located with respect to the plate interface) their record of changes in fluid regime and strain localisation is extremely valuable. One striking example of the role of fluids on plate interface rheology during nascent subduction is provided by metamorphic soles (i.e., ~500 m thick tectonic slices welded to the base of ophiolites). We show that their accretion to the ophiolite indeed only happens across a transient, optimal time-T-P window (after < 1-2 My, at 1±0.2 GPa, 750-850°C) associated with fluid release and infiltration, leading to similar effective rheology on both sides (i.e., downgoing crust and mantle wedge). This maximizes interplate mechanical coupling, as deformation gets distributed over a large band encompassing the plate interface (i.e., a few km), and promotes detachment of the sole from the sinking slab. We also show how tectonic slicing during mature subduction likely relates to short-term fluid release and repeated seismicity, based on the Monviso exposures (W. Alps, a relatively continuous, 15 km long fragment of oceanic lithosphere exhumed from ~80 km depths), which preserve evidence of intraslab fluid flow and eclogitic, intermediate-depth seismicity of Mw ~4. We finally address how, in the long-term and at subduction scale, the overall fluid content and fluid regime may control the slicing, size and metastability of exhumed units. We propose that mechanical coupling varies through time, from weak to strong, as a function of the contrast of effective viscosity on either side of the interface: a young and wet subduction interface will promote the formation of knockers and sole accretion, whereas a fluid-present yet drier and colder one will lead to mainly metasedimentary underplated material and large-scale slivers of (metastable) oceanic lithosphere. This interpretation is supported by bi-phase numerical models (allowing for fluid migration driven by concentrations in the rocks, non-lithostatic pressure gradients and deformation, mantle wedge hydration and mechanical weakening of the plate interface) showing that the detachment of large-scale oceanic tectonic slices is in particular promoted by fluid migration along the subduction interface. [Hacker et al., Journal of Geophysical Research 2003; Audet et al., Nature, 2009; Angiboust et al., Geology 2012

  20. Eocene Plate Reorganisation and Subduction Initiation in the Western Pacific: What the Rocks can Tell us

    NASA Astrophysics Data System (ADS)

    Pearce, J. A.; Arculus, R. J.

    2002-12-01

    Over the past 25 years, two phases of ocean drilling, dredging of forearc terranes and field programs have provided a wealth of information on the earliest lithosphere to form after subduction. Our own systematic program of dating, petrology and isotope and element geochemistry of `protoarc' terranes throughout the Western Pacific makes a significant contribution to the overall database and highlights the following features. 1. The main period of `protoarc' development probably begans at about 49Ma (Cosca et al., 1998), consistent with the first impact between India and Tibet as an indirect causal mechanism, and is regional in extent. Normal arc development had started by at least 40Ma. 2. The volcanic series typically range from low-Ca boninites to depleted island arc tholeiites. Experiments suggest that both have potential temperatures close to those of MORB. Where information exists (e.g. ODP Leg 125 drilling), the low-Ca boninites are stratigraphically the oldest products and the tholeiites the youngest. 3. Geological evidence indicates that the protoarc terrane comprises a basement of mainly `SSZ ophiolite' crust overlain by volcanic edifices. However, oxygen fugacity-Cr# systematics in chromites from drilled peridotites (Parkinson and Pearce, 1998) demonstrate that only some of the `protoarc' basement lithosphere may have formed by a monogenetic episode such as sea-floor spreading. Some must also have resulted from interaction between boninite magmas and attenuated, pre-subduction MORB mantle lithosphere. 4. In the Izu-Bonin-Mariana region, Hf-Pb isotope fingerprinting (Pearce et al. 1999) demonstrates that the protoarc terrane formed when (old, cold) Pacific lithosphere first subducted beneath (young, hot) West Philippine Basin lithosphere - supporting models such as those of Uyeda and co-workers and Stern and Bloomer (1992). It also shows that, just as at the present day, Pacific volcanogenic and pelagic sediments contributed variably to the first subduction component. 5. Also in the Izu-Bonin-Mariana region, subduction initiation triggered shallow, fluid-induced melting of residual mantle that had just been generated at the West Philippine Basin Ridge. Thermal modeling indicates that the initial depth of re-melting was probably a function of ridge proximity. The isotope and geochemical data (an `adakitic', non-Pacific signature) raise the possibility that some melting was sufficiently shallow for fusion of lower crust as well as of shallow mantle. 6. The much-discussed involvement of a mantle plume remains open to debate. Isotopically, lavas do extend from MORB along the MORB-OIB array. However, in detail, the lavas are chemically distinct from known products of re-melting of plume material, such as those in North Tonga. Outstanding tasks include the establishment of the precise variations in time and space over what were thousands of kilometers of `protoarc': few samples have been well-dated and many areas are still poorly sampled. Although the IBM region is well-understood (though still debated) as described above, the tectonic reconstruction of subduction initiation to the south of this region is still extremely poorly constrained.

  1. Exhumation and Coupling at the Plate Interface: Large Tectonic Slices V. Melange Formation? Key Contexts and Possible Controlling Parameters

    NASA Astrophysics Data System (ADS)

    Agard, P.; Angiboust, S.; Guillot, S.; Garcia-Casco, A.

    2011-12-01

    Fragments of subducted oceanic lithosphere returned along the plate interface convey crucial information regarding the thermal and rheological conditions of convergent plate boundaries. Geological evidence indicate that, unlike subduction, exhumation is non-steady (Agard et al., Earth Sci. Rev. 2009). We herein focus on deep processes along the plate interface (40-80 km depth), for which there is no counterflow (unlike in accretionary prisms) and no other known mechanisms to return eclogites than interplate friction or buoyancy. These eclogites are of two major types: large scale (>km) slices with coherent PT estimates (W. Alps) versus isolated fragments (frequently m-hm) in a serpentinite- or sedimentary-rich matrix showing contrasting equilibration depths (with hints of punctuated exhumation and even reburial; Franciscan, Cuba, Sistan; e.g., Garcia-Casco et al., Geol. Acta 2006). This latter type tends to show warmer equilibration paths, whereas the larger tectonic slices from the former type remain systematically cold. Serpentinites are crucial for both in permitting decoupling and acting as a buoy, and fluid budget is important too in enhancing floatability and allowing large slices to survive (Angiboust and Agard, Lithos 2010). Numerical models implementing free migration of fluids in the subduction zone also show that the plate interface is strongly localized in the absence of fluids: mechanical decoupling efficiently occurs along the sediment veneer and/or at the top of the highly hydrothermalized crust. Whenever fluids are released in greater amounts (depending on initial fluid content and/or thermal structure), deformation becomes much more distributed and affects both the mantle wedge and the top of the downgoing lithosphere (crust and hydrated mantle top), thereby increasing mechanical coupling between the two plates. Based on natural data and numerical modelling we herein propose that rheological contrast chiefly controls mechanical decoupling. On a steady-state basis the subduction interface is apparently efficiently decoupled. In this context, we hypothetize that the liberation of fluid through pulses (or a somewhat increased amount of fluids) is required to locally modify mechanical coupling and induce the slicing of large pieces of oceanic material along the subduction interface (type 1). By contrast, an extreme hydration of the subduction interface and mantle wedge will result in the formation of serpentinite melanges and extensive material mixing (e.g., cold plumes, mafic pods and localized melting; type 2). This latter situation may be promoted by young/fast/wet subduction, such as subduction initiation and/or subduction of young lithosphere or subduction of a particularly hydrated lithosphere section (e.g., at the ridge and/or prior to entering the trench), whereas cold, slow subduction (type 1) will result in irregular hydration and localized coupling able to detach large slices.

  2. Transients in Pacific/North American Plate Boundary Deformation: Synthesis and Modeling of GPS and Borehole Strain Observations

    NASA Technical Reports Server (NTRS)

    Solomon, Sean C.; Frey, H. V. (Technical Monitor)

    2002-01-01

    This is the Final Technical Report on research conducted between 1 June 1997 and 14 September 2001 entitled "Transients in Pacific/North American plate boundary deformation: Synthesis and modeling of GPS and borehole strain observations." As the project title implies, our effort involved a geodetic study of strain transients, i.e., temporal variations in deformation rates, that occur within plate boundary zones and their relationship to earthquakes and plate motions. Important transients occur during and following large earthquakes, and there are also strain transients not apparently associated with earthquakes. A particularly intriguing class of transients, for which there is a modest but growing list of examples, are preseismic anomalies. Such earthquake precursors, if further documented and understood, would have obvious importance for earthquake hazard mitigation. Because the timescales for these diverse transients range over at least 6 orders of magnitude (minutes to years), no single geodetic technique is optimum. We therefore undertook a systematic synthesis of Global Positioning Satellite (GPS) and borehole strainmeter data in three areas in California where there are adequate numbers of both types of instruments (or their equivalent): the San Francisco Bay region (within the Bay Area Regional Deformation network), southern California (within the Southern California Integrated GPS Network), and Parkfield (where a two-color laser system provides a proxy for continuous GPS measurements). An integral component of our study was the elucidation of the physical mechanisms by which such transients occur and propagate. We therefore initiated the development of multiple forward models, using two independent approaches. In the first, we explored the response to specified earthquake slip in viscoelastic models that incorporated failure criteria and the geometry of major faults in California. In the second approach, we examined the dynamical response of a complex rheological medium to the application of a far-field stress imposed by plate motions. The forward models were used both to gain insight into the range of strain transients to be expected under different assumed mechanical conditions and to develop representations for strain fields that allow GPS, borehole, and other strain data to be combined in a self-consistent, yet well-determined, manner. The models also provided a basis for hypothesis testing, by which data from a strain transient well characterized by GPS and borehole observations were utilized to distinguish among competing candidates for the causative physical mechanism and the governing physical characteristics. During the three years of this project, continued to a fourth year through a no-cost extension of the grant, we published 14 papers and presented or co-authored 37 papers at national scientific meetings.

  3. Plume versus plate origin for the Shatsky Rise oceanic plateau (NW Pacific): Insights from Nd, Pb and Hf isotopes

    NASA Astrophysics Data System (ADS)

    Heydolph, Ken; Murphy, David T.; Geldmacher, Jörg; Romanova, Irina V.; Greene, Andrew; Hoernle, Kaj; Weis, Dominique; Mahoney, John

    2014-07-01

    Shatsky Rise, an early Cretaceous igneous oceanic plateau in the NW Pacific, comprises characteristics that could be attributed to either formation by shallow, plate tectonic-controlled processes or to an origin by a mantle plume (head). The plateau was drilled during Integrated Ocean Drilling Program (IODP) Expedition 324. Complementary to a recent trace element study (Sano et al., 2012) this work presents Nd, Pb and Hf isotope data of recovered lava samples cored from the three major volcanic edifices of the Shatsky Rise. Whereas lavas from the oldest edifice yield fairly uniform compositions, a wider isotopic spread is found for lavas erupted on the younger parts of the plateau, suggesting that the Shatsky magma source became more heterogeneous with time. At least three isotopically distinct components can be identified in the magma source: 1) a volumetrically and spatially most common, moderately depleted component of similar composition to modern East Pacific Ridge basalt but with low 3He/4He, 2) an isotopically very depleted component which could represent local, early Cretaceous (entrained) depleted upper mantle, and 3) an isotopically enriched component, indicating the presence of (recycled) continental material in the magma source. The majority of analyzed Shatsky lavas, however, possess Nd-Hf-Pb isotope compositions consistent with a derivation from an early depleted, non-chondritic reservoir. By comparing these results with petrological and trace element data of mafic volcanic rock samples from all three massifs (Tamu, Ori, Shirshov), we discuss the origin of Shatsky Rise magmatism and evaluate the possible involvement of a mantle plume (head).

  4. Deformation across the Pacific-North America plate boundary near San Francisco, California

    USGS Publications Warehouse

    Prescott, W.H.; Savage, J.C.; Svarc, J.L.; Manaker, D.

    2001-01-01

    We have detected a narrow zone of compression between the Coast Ranges and the Great Valley, and we have estimated slip rates for the San Andreas, Rodgers Creek, and Green Valley faults just north of San Francisco. These results are based on an analysis of campaign and continuous Global Positioning System (GPS) data collected between 1992 and 2000 in central California. The zone of compression between the Coast Ranges and the Great Valley is 25 km wide. The observations clearly show 3.8??1.5 mm yr-1 of shortening over this narrow zone. The strike slip components are best fit by a model with 20.8??1.9 mm yr-1 slip on the San Andreas fault, 10.3??2.6 mm yr-1 on the Rodgers Creek fault, and 8.1??2.1 mm yr-1 on the Green Valley fault. The Pacific-Sierra Nevada-Great Valley motion totals 39.2??3.8 mm yr-1 across a zone that is 120 km wide (at the latitude of San Francisco). Standard deviations are one ??. The geodetic results suggest a higher than geologic rate for the Green Valley fault. The geodetic results also suggest an inconsistency between geologic estimates of the San Andreas rate and seismologic estimates of the depth of locking on the San Andreas fault. The only convergence observed is in the narrow zone along the border between the Great Valley and the Coast Ranges.

  5. Unraveling The Complex Interaction Between The Southern Caribbean, Northwest South America And The Pacific Plates During The Cenozoic

    NASA Astrophysics Data System (ADS)

    Villagomez, D.; Spikings, R.

    2013-05-01

    We have studied the prominent Sierra Nevada de Santa Marta Massif (the highest peak in the world whose local base is at sea level, ~5.75km) in Northern Colombia and we are interested in quantifying the thermal and tectonic history of the Northernmost Andes during the Cenozoic in order to understand the complex interaction between the Caribbean, the South American and the Pacific plates. In order to do so, apatite fission track data (by the LA-ICP-MS method) has been used, collected along several traverses and a single vertical profile within the massif. Our results show that the easternmost part of Sierra Nevada de Santa Marta exhumed at elevated rates (≥0.2 Km/My) during 65-58 Ma in response to the collision of the Caribbean Plateau with north-western South America. A second pulse of exhumation (≥0.32 Km/My) during 50-40 Ma was probably driven by the underthrusting of the Caribbean Plate beneath northern South America. More southern portions of the Sierra Nevada de Santa Marta (the Sierra Nevada Province) exhumed rapidly during 26-29 Ma (~0.7 Km/My), whereas farther north, the northwestermost corner of the Sierra Nevada de Santa Marta (the Santa Marta Province) exhumed at elevated rates during 30-25 Ma and 25-16 Ma. Our thermochronological data show that the highest exhumation rates within the Sierra Nevada de Santa Marta progressed towards the northwest via the propagation of NW-verging thrusts. The late Oligocene-Miocene exhumation was mainly a consequence of compression originating at the Pacific margin of South America that also gave rise to uplift and exhumation in other regions of Eastern Colombia (e.g. in the Santander Massif). Major continental faults such as the left-lateral Santa Marta-Bucaramanga Fault have played an important role transferring the deformation, Exhumation of the Sierra Nevada de Santa Marta Massif is not recorded after ~16 Ma, which is unexpected, given the high elevation and high erosive power of the climate, implying that rock and surface uplift that gave rise to the current topography was probably very recent and there has been insufficient time to expose the fossil apatite partial annealing zone.

  6. Plate motion

    SciTech Connect

    Gordon, R.G. )

    1991-01-01

    The motion of tectonic plates on the earth is characterized in a critical review of U.S. research from the period 1987-1990. Topics addressed include the NUVEL-1 global model of current plate motions, diffuse plate boundaries and the oceanic lithosphere, the relation between plate motions and distributed deformations, accelerations and the steadiness of plate motions, the distribution of current Pacific-North America motion across western North America and its margin, plate reconstructions and their uncertainties, hotspots, and plate dynamics. A comprehensive bibliography is provided. 126 refs.

  7. Measuring present-day strain rates along the Fish Lake Valley fault system, Pacific-North America plate boundary

    NASA Astrophysics Data System (ADS)

    Johnson, C. W.; Frankel, K. L.; Newman, A. V.; Lifton, Z. M.

    2011-12-01

    A fundamental issue in modern tectonics is the degree to which spatial and temporal variations exist in strain accumulation and release along evolving plate boundaries. The eastern California shear zone (ECSZ) is located east of the San Andreas fault and contains a complex network of structures that accommodate ~25% of the relative displacement between the Pacific and North American plates. Geodetic data indicate strain accumulation at a rate of 12±2 mm/yr along four main structures in the ECSZ. The Death Valley-Fish Lake Valley fault, the prominent and longest fault in the ECSZ at ~300km, is observed to be the fastest slipping fault in the region storing elastic strain at a rate of 3-8 mm/yr. Recently determined long-term slip rates (103 - 106 year timescale) indicate a pattern of decreasing velocity moving north through Fish Lake Valley (FLV) from ~6 mm/yr to zero, presumably because strain is transferred onto extensional faults located to the east. This study intends to determine the short-term (decadal timescale) GPS-derived displacement fields along the FLV fault to test whether spatial patterns of geodetic and geologic rates are consistent through time. In a series of two GPS campaigns in 2010 and 2011, eleven geodetic monuments, spaced 15-20 km apart, were surveyed in and around FLV. In addition, campaign data from previous surveys has been acquired from UNAVCO. The combined data sets are used to calculate the relative motion along the fault. Modern strain rates will be presented in comparison to published long-term rates.

  8. Three-dimensional free vibration of arbitrarily shaped laminated micro-plates with sliding interfaces within couple stress theory

    NASA Astrophysics Data System (ADS)

    Kamali, M. T.; Shodja, H. M.; Forouzan, B.

    2015-03-01

    Free vibration of laminated micro-plates with arbitrary geometry and boundary conditions consisting of several micro-layers with free sliding/frictional sliding/perfect interfaces is of interest. The inter-layer bond in the direction normal to the interfaces is perfect, and thus the corresponding displacement component is continuous across the interfaces. The mentioned in-plane interface conditions may be realized by varying the stiffness of the sliding inter-layer spring of vanishing thickness. For free sliding and perfect interface conditions the stiffness→0 and ∞, respectively. Couple stress theory as a useful higher order continuum theory is utilized to formulate the problem. Subsequently, the corresponding Hamiltonian is presented. The three components of the displacement field in each layer are given by three distinct expressions; each expression consists of the product of a base function and three dimensional polynomials with unknown coefficients. The base functions are chosen according to the geometries of the system and the corresponding layer and to satisfy the homogeneous essential boundary conditions. For the enforcement of the displacement continuity in the direction normal to the interfaces, an appropriate series with unknown coefficients pertinent to each layer is added. The influences of the level of inter-layer imperfection and couple stress on the dynamical characteristics including the angular frequencies of free vibration and the corresponding mode shapes are addressed.

  9. Diffuse Pacific-North American plate boundary: 1000 km of dextral shear inferred from modeling geodetic data

    USGS Publications Warehouse

    Parsons, T.; Thatcher, W.

    2011-01-01

    Geodetic measurements tell us that the eastern part of the Basin and Range Province expands in an east-west direction relative to stable North America, whereas the western part of the province moves to the northwest. We develop three-dimensional finite element representations of the western United States lithosphere in an effort to understand the global positioning system (GPS) signal. The models are constrained by known bounding-block velocities and topography, and Basin and Range Province deformation is represented by simple plastic (thermal creep) rheology. We show that active Basin and Range spreading by gravity collapse is expected to have a strong southward component that does not match the GPS signal. We can reconcile the gravitational component of displacement with observed velocity vectors if the Pacific plate applies northwest-directed shear stress to the Basin and Range via the Sierra Nevada block. This effect reaches at least 1000 km east of the San Andreas fault in our models. ?? 2011 Geological Society of America.

  10. Deformation and Metasomatic Evolution at the Subduction Plate Interface As Viewed from Study of HP/UHP Metamorphic Rocks

    NASA Astrophysics Data System (ADS)

    Bebout, G. E.; Penniston-Dorland, S.

    2014-12-01

    We provide a view of lithologic makeup, deformation, and fluid-rock interaction along the deep forearc to subarc plate interface, based on insights gained from study of HP/UHP metamorphic rocks. Exposures of plate-boundary shear zones on which we base our perspective represent 30-80 km depths and are on Catalina Island and at Monviso, Syros, and New Caledonia. Each contains highly deformed zones with schistose matrix, commonly with a large ultramafic component, containing bodies of less deformed mafic, sedimentary, and ultramafic rocks. These "blocks" have varying geometries, are up to km-scale, and can preserve disparate P-T histories reflecting dynamics of incorporation and entrainment. Sheared matrices contain high-variance, hydrous mineral assemblages in some cases resembling metasomatic zones ("rinds") at block-matrix contacts, and rinds and matrices have homogenized isotopic compositions reflecting extensive fluid-rock interaction. Shearing and related physical juxtaposition of disparate metasomatic rocks can result in mixed or 'hybrid' chemical compositions. The chlorite-, talc-, and amphibole-rich schists developed by these processes can stabilize H2O to great depth and influence its cycling. Fluids (hydrous fluids, silicate melts) released within slabs necessarily interact with highly deformed, lithologically hybridized zones at the plate interface as they ascend to potentially enter mantle wedges. Fluids bearing chemical/isotopic signatures of hybrid rocks appear capable of producing arc magma compositions interpreted as reflecting multiple, chemically distinct fluids sources. Geophysical signatures of these rheologically weak zones are equivocal but many recognize the presence of zones of low seismic velocity at/near the top of slabs and attribute them to hydrated rocks. Whether rocks from this interface buoyantly ascend into mantle wedges, indicated in some theoretical models, remains largely untested by field and geophysical observations.

  11. Pacific-North American plate motion from very long baseline interferometry compared with motion inferred from magnetic anomalies, transform faults, and earthquake slip vectors

    NASA Technical Reports Server (NTRS)

    Argus, Donald F.; Gordon, Richard G.

    1990-01-01

    Geodetic VLBI measurements were used to test whether the Pacific-North American plate velocity averaged over several years of direct observation (1984-1987) equals that averaged over millions of years. It was also tested whether this velocity parallels the San Andreas fault, transform faults and earthquake slip vectors in the Gulf of California, and earthquake slip vectors along the Queen Charlotte fault, along the Alaskan peninsula, and along the Kamchatkan peninsula. The VLBI data provide an estimate of the direction of plate motion that is independent of estimates from fault azimuths and earthquake slip vectors. The Euler vector determined from VLBI was found to be nearly identical to the Euler vector of plate motion model NUVEL-1, which is based on the trends of transform faults, earthquake slip vectors, and spreading rates from marine magnetic anomalies that average motion since 3 Ma. The velocity between the Pacific and North American plates averaged over the past several years equals or nearly equals its velocity averaged over the past several million years, the difference along their boundary nowhere exceeding 4 + or - 7 mm/yr.

  12. The 2014 Mw6.2 Eketahuna earthquake, Hikurangi subduction zone - normal faulting in the subducted Pacific Plate crust

    NASA Astrophysics Data System (ADS)

    Abercrombie, R. E.; Bannister, S. C.; Francois-Holden, C.; Hamling, I. J.; Ristau, J. P.

    2014-12-01

    The 2014 January 20th M6.2 Eketahuna earthquake occurred in the subducted crust of the Pacific plate at the Hikurangi subduction zone, beneath North Island, New Zealand. Moment tensor analysis together with aftershock relocations show that this event was an oblique-normal faulting intraplate event, with hypocentre depth ca.30 km, and with rupture on a northwest-dipping fault extending through the subducted crust up to the subduction megathrust at ca.18-20 km depth. More than 3500 aftershocks were subsequently recorded by the New Zealand GeoNet network, with only minor migration of the aftershocks away from the inferred mainshock rupture, and with very few aftershocks within +/- 1 km of the subduction megathrust. The megathrust in this particular region is inferred to be interseismically locked with no seismic or aseismic slip, although slow slip is occurring ca.15-30 km down-dip (Wallace et al, 2013). Similar oblique-normal faulting events have previously occurred along the Hikurangi subduction margin, including in 1985 (ML5.7) and 1990 (Mw6.2). Earlier earthquakes in 1942 (Mw6.8) and 1921 (Mw6.8) are also inferred to have occurred at a similar depth within the subducted crust. The 1990 earthquake sequence occurred ~40 km along-strike from the 2014 Eketahuna event, and involved a Mw6.2 oblique-normal faulting event in the subducted crust, which was quickly followed by a Mw6.4 event in the overlying crust, with both thrust and dextral strike-slip components, possibly responding to deeper aseismic slip. Deeper earthquakes of similar type at other subduction margins are thought to be high stress drop. We calculate the stress drops of the mainshock and larger aftershocks, using a direct wave, empirical Green's function (EGF) approach that includes measurement uncertainties and objective criteria for assessing the quality of each spectral ratio (Abercrombie, 2013). We compare the results to those for earthquakes in other tectonic regions of New Zealand, calculated using the same method. We investigate whether there are any well-resolved differences in stress drop between these relatively deep earthquakes in the subducted plate and those in other tectonic environments. Wallace, L.M., et al., AGU 2013 Fall meeting abstracts, 2013. Abercrombie, 2013, JGR v118, 2013.

  13. New insights into North America-Pacific Plate boundary deformation from Lake Tahoe, Salton Sea and southern Baja California

    NASA Astrophysics Data System (ADS)

    Brothers, Daniel Stephen

    Five studies along the Pacific-North America (PA-NA) plate boundary offer new insights into continental margin processes, the development of the PA-NA tectonic margin and regional earthquake hazards. This research is based on the collection and analysis of several new marine geophysical and geological datasets. Two studies used seismic CHIRP surveys and sediment coring in Fallen Leaf Lake (FLL) and Lake Tahoe to constrain tectonic and geomorphic processes in the lakes, but also the slip-rate and earthquake history along the West Tahoe-Dollar Point Fault. CHIRP profiles image vertically offset and folded strata that record deformation associated with the most recent event (MRE). Radiocarbon dating of organic material extracted from piston cores constrain the age of the MRE to be between 4.1--4.5 k.y. B.P. Offset of Tioga aged glacial deposits yield a slip rate of 0.4--0.8 mm/yr. An ancillary study in FLL determined that submerged, in situ pine trees that date to between 900-1250 AD are related to a medieval megadrought in the Lake Tahoe Basin. The timing and severity of this event match medieval megadroughts observed in the western United States and in Europe. CHIRP profiles acquired in the Salton Sea, California provide new insights into the processes that control pull-apart basin development and earthquake hazards along the southernmost San Andreas Fault. Differential subsidence (>10 mm/yr) in the southern sea suggests the existence of northwest-dipping basin-bounding faults near the southern shoreline. In contrast to previous models, the rapid subsidence and fault architecture observed in the southern part of the sea are consistent with experimental models for pull-apart basins. Geophysical surveys imaged more than 15 ˜N15°E oriented faults, some of which have produced up to 10 events in the last 2-3 kyr. Potentially 2 of the last 5 events on the southern San Andreas Fault (SAF) were synchronous with rupture on offshore faults, but it appears that ruptures on three offshore faults are synchronous with Colorado River diversions into the basin. The final study was used coincident wide-angle seismic refraction and multichannel seismic reflection surveys that spanned the width of the of the southern Baja California (BC) Peninsula. The data provide insight into the spatial and temporal evolution of the BC microplate capture by the Pacific Plate. Seismic reflection profiles constrain the upper crustal structure and deformation history along fault zone on the western Baja margin and in the Gulf of California. Stratal divergence in two transtensional basins along the Magdalena Shelf records the onset of extension across the Tosco-Abreojos and Santa Margarita faults. We define an upper bound of 12 Ma on the age of the pre-rift sediments and an age of ˜8 Ma for the onset of extension. Tomographic imaging reveals a very heterogeneous upper crust and a narrow, high velocity zone that extends ˜40 km east of the paleotrench and is interpreted to be remnant oceanic crust.

  14. Extraordinary high ductility/strength of the interface designed bulk W-ZrC alloy plate at relatively low temperature

    PubMed Central

    Xie, Z. M.; Liu, R.; Miao, S.; Yang, X. D.; Zhang, T.; Wang, X. P.; Fang, Q. F.; Liu, C. S.; Luo, G. N.; Lian, Y. Y.; Liu, X.

    2015-01-01

    The refractory tungsten alloys with high ductility/strength/plasticity are highly desirable for a wide range of critical applications. Here we report an interface design strategy that achieves 8.5 mm thick W-0.5 wt. %ZrC alloy plates with a flexural strength of 2.5 GPa and a strain of 3% at room temperature (RT) and ductile-to-brittle transition temperature of about 100 °C. The tensile strength is about 991 MPa at RT and 582 MPa at 500 °C, as well as total elongation is about 1.1% at RT and as large as 41% at 500 °C, respectively. In addition, the W-ZrC alloy plate can sustain 3.3 MJ/m2 thermal load without any cracks. This processing route offers the special coherent interfaces of grain/phase boundaries (GB/PBs) and the diminishing O impurity at GBs, which significantly strengthens GB/PBs and thereby enhances the ductility/strength/plasticity of W alloy. The design thought can be used in the future to prepare new alloys with higher ductility/strength. PMID:26531172

  15. Extraordinary high ductility/strength of the interface designed bulk W-ZrC alloy plate at relatively low temperature

    NASA Astrophysics Data System (ADS)

    Xie, Z. M.; Liu, R.; Miao, S.; Yang, X. D.; Zhang, T.; Wang, X. P.; Fang, Q. F.; Liu, C. S.; Luo, G. N.; Lian, Y. Y.; Liu, X.

    2015-11-01

    The refractory tungsten alloys with high ductility/strength/plasticity are highly desirable for a wide range of critical applications. Here we report an interface design strategy that achieves 8.5 mm thick W-0.5 wt. %ZrC alloy plates with a flexural strength of 2.5 GPa and a strain of 3% at room temperature (RT) and ductile-to-brittle transition temperature of about 100 °C. The tensile strength is about 991 MPa at RT and 582 MPa at 500 °C, as well as total elongation is about 1.1% at RT and as large as 41% at 500 °C, respectively. In addition, the W-ZrC alloy plate can sustain 3.3 MJ/m2 thermal load without any cracks. This processing route offers the special coherent interfaces of grain/phase boundaries (GB/PBs) and the diminishing O impurity at GBs, which significantly strengthens GB/PBs and thereby enhances the ductility/strength/plasticity of W alloy. The design thought can be used in the future to prepare new alloys with higher ductility/strength.

  16. Geological Observation of the Young Petit-Spot Volcanoes on the Early Cretaceous Pacific Plate using SHINKAI 6500

    NASA Astrophysics Data System (ADS)

    Machida, S.; Hirano, N.; Ingle, S.; Ishii, T.; Abe, N.

    2005-12-01

    Young volcanoes are newly discovered on the cool, thick, and old Pacific Plate approximately 600 km ESE off the northern Japan Trench, during KR04-08 cruise using R/V Kairei (JAMSTEC) in 2004. The site was predicted lava eruption based on previous study for young alkali-basalt lavas (5.95 Ma) on the Japan Trench oceanward slope (the Kaiko knolls lava field). We named the Petit-Spot for such small and young volcanoes. Four SHINKAI 6500 submersible dives (dive #877 to #880) were performed in the Petit-Spot knolls and the Kaiko Knolls lava field during May 2005. Dives were initially targeted in the hopes of finding outcrops of lava flow, sampling rocks, observation of eruptive styles, and discussion of the stratigraphy of the monogenic Petit-Spot volcanoes. Three dives were conducted at the Petit-Spot lava field. One young knoll, named the Yukawa Knoll, discovered by the dredges (D-07, 08) during KR04-08 cruise was selected for dive #877. Two other knolls for dives #878 and #879 show the similar features of bathymetry and acoustic reflectivity to the Yukawa Knoll. In contrast, one site of knoll and fault wall for dive #880 situate in the Kaiko Knolls lava field, the Japan Trench oceanward slope. Dives were planned to ascending the slope from the foot of knoll with continuously observation of lavas and volcaniclastic sequences, and sampling along the slope. The basin or flat floor at the beginning of the dive was fully covered in soft pelagic sediment. We found oblong shaped pillow lavas and the pillow robes outcrops along the slope. However, outcrops are exhibited in limited area around the summit of knoll. Lavas commonly include peperites. Rock fragments sampled appear to be volcanic breccias containing clasts of lava enclosed in sedimentary rock; manganese coating on these breccias is thin, suggesting they were deposited recently. Based on above observation, we assumed that knolls in the Petit-Spot lava field show feeder dike or cryptdome like stratigraphy with some lava flows, in-situ and redeposited hyaloclastites, and water-chilled bumps. That is, basaltic lavas mainly inject into pelagic sediment layer. Furthermore, lavas show very high vesicularity in spite of high water pressure about 6000m deep, suggesting high volatile composition. Brecciated lava clasts containing peridotitic xenolith. These features may indicate that the Petit-Spot volcanoes also have aspect as a kind of abyssal diatreme induced in the oceanic lithosphere.

  17. Project NEPTUNE: an innovative, powered, fibre-optic cabled deep ocean observatory spanning the Juan de Fuca plate, NE Pacific

    NASA Astrophysics Data System (ADS)

    Barnes, C.; Delaney, J.

    2003-04-01

    NEPTUNE is an innovative facility, a deep-water cabled observatory, that will transform marine science. MARS and VENUS are deep and shallow-water test bed facilities for NEPTUNE located in Monterey Canyon, California and in southern British Columbia, respectively; both were funded in 2002. NEPTUNE will be a network of over 30 subsea observatories covering the 200,000 sq. km Juan de Fuca tectonic plate, Northeast Pacific. It will draw power via two shore stations and receive and exchange data with scientists through 3000 km of submarine fiber-optic cables. Each observatory, and cabled extensions, will host and power many scientific instruments on the surrounding seafloor, in seafloor boreholes and buoyed through the water column. Remotely operated and autonomous vehicles will reside at depth, recharge at observatories, and respond to distant labs. Continuous near-real-time multidisciplinary measurement series will extend over 30 years. Free from the limitations of battery life, ship schedules/ accommodations, bad weather and delayed access to data, scientists will monitor remotely their deep-sea experiments in real time on the Internet, and routinely command instruments to respond to storms, plankton blooms, earthquakes, eruptions, slope slides and other events. Scientists will be able to pose entirely new sets of questions and experiments to understand complex, interacting Earth System processes such as the structure and seismic behavior of the ocean crust; dynamics of hot and cold fluids and gas hydrates in the upper ocean crust and overlying sediments; ocean climate change and its effect on the ocean biota at all depths; and the barely known deep-sea ecosystem dynamics and biodiversity. NEPTUNE is a US/Canada (70/30) partnership to design, test, build and operate the network on behalf of a wide scientific community. The total cost of the project is estimated at about U.S. 250 million from concept to operation. Over U.S. 50 million has already been funded for design, development, and the test beds. NEPTUNE will be among the first of many such cabled ocean observatories. Much is to be gained by being among the scientific and industrial pioneers. The multidisciplinary data archive will be an amazing, expanding resource for scientists and students. The public will share in the research discoveries of one of the last unexplored places on earth through an extensive education/outreach program.

  18. Kinematic framework of the Cocos-Pacific Plate Boundary from 13°N to the Orozco TRANSFORM FAULT: RESULTS FROM AN EXTENSIVE MAGNETIC AND SEAMARC II SURVEY

    NASA Astrophysics Data System (ADS)

    Madsen, John A.; Fornari, Daniel J.; Edwards, Margo H.; Gallo, David G.; Perfit, Michael R.

    1992-05-01

    During the summer of 1987, magnetic anomaly data were collected by surface ship as part of an extensive SeaMARC II investigation of the East Pacific Rise (EPR) from 13°N to the Orozco transform. The survey extended to either side of the rise axis onto seafloor at least 1.8 million years (m.y.) in age, enabling the recent evolution of the structural and kinematic framework of the plate boundary to be studied in detail. North of 13°50'N there has been a major perturbation in the evolution of the plate boundary. Swaths of lineaments that trend oblique to EPR-parallel topography form a north pointing, V-shaped discordant zone on the Pacific and Cocos plates that is broadly symmetric about the EPR axis. On the Pacific plate a zone of discordant morphology 130 km long and between 6 and 14 km wide with a structural grain that is highly oblique to the present-day spreading direction is observed on seafloor 0.9-1.8 m.y. in age. A similar but more subtle feature of the same age is also present on the Cocos plate. These zones of discordant lineaments can be correlated with changes in the magnetic lineation pattern. On the Pacific plate the disturbed zone lies between anomalies J and 2, creating greater than normal distance between the anomalies. On the Cocos plate the disturbed zone is characterized by a distinct, high-amplitude, northwestward trending magnetic anomaly. The observed structural grain and the changes in the magnetic anomaly patterns associated with the disturbed zones are very similar to those observed at propagating ridges. Based on the magnetic anomalies, a propagation rate of 10.8 cm/yr in a N10°W direction is estimated for the past 1.8 m.y. A detailed examination of the structures developed within the disturbed zone on the Pacifc plate indicates that the rift propagation in this area can best be explained by the model of Wilson (1990) which involves cyclic rift failure with inward curvature of both rift tips. Plate adjustment to the propagation event is ongoing. There is a pronounced change in the morphology of the rise axis with distance from the propagation event. Close to and for ˜100 km behind the propagator tip, the EPR crest is not well developed and is characterized by a series of low (relief of 100-200 m) ridges and troughs with a poorly defined neovolcanic zone. Further away (>100 km) from the propagator tip the rise crest is a single, linear, horst-shaped ridge with a well-developed narrow axial graben at the axis of the ridge. Regional morphologic and magnetic data suggest that this cycle of rift propagation may have begun approximately 2.5 million years before present (m.y.B.P.) near the eastern ridge-transform intersection of the paleo-O'Gorman transform and is continuing today at the Orozco transform.

  19. Investigating crustal deformation associated with the North America-Pacific plate boundary in southern California with GPS geodesy

    NASA Astrophysics Data System (ADS)

    Spinler, Joshua C.

    The three largest earthquakes in the last 25 years in southern California occurred on faults located adjacent to the southern San Andreas fault, with the M7.3 1992 Landers and M7.1 1999 Hector Mine earthquakes occurring in the eastern California shear zone (ECSZ) in the Mojave Desert, and the M7.2 2010 El Mayor-Cucapah earthquake occurring along the Laguna Salada fault in northern Baja California, Mexico. The locations of these events near to but not along the southern San Andreas fault (SSAF) is unusual in that the last major event on the SSAF occurred more than 300 years ago, with an estimated recurrence interval of 215 +/- 25 years. The focus of this dissertation is to address the present-day deformation field along the North America-Pacific plate boundary in southern California and northern Baja California, through the analysis of GPS data, and elastic block and viscoelastic earthquake models to determine fault slip rates and rheological properties of the lithosphere in the plate boundary zone. We accomplish this in three separate studies. The first study looks at how strain is partitioned northwards along-strike from the southern San Andreas fault near the Salton Sea. We find that estimates for slip-rates on the southern San Andreas decrease from ~23 mm/yr in the south to ~8 mm/yr as the fault passes through San Gorgonio Pass to the northwest, while ~13-18 mm/yr of slip is partitioned onto NW-SE trending faults of the ECSZ where the Landers and Hector Mine earthquakes occurred. This speaks directly to San Andreas earthquake hazards, as a reduction in the slip rate would require greater time between events to build up enough slip deficit in order to generate a large magnitude earthquake. The second study focuses on inferring the rheological structure beneath the Salton Trough region. This is accomplished through analysis of postseismic deformation observed using a set of the GPS data collected before and after the 2010 El Mayor-Cucapah earthquake. By determining the slip-rates on each of the major crustal faults prior to the earthquake, we are able to model the pre-earthquake velocity field for comparison with velocities measured using sites constructed post-earthquake. We then determine how individual site velocities have changed in the 3 years following the earthquake, with implications for the rate at which the lower crust and upper mantle viscously relax through time. We find that the viscosity of the lower crust is at least an order of magnitude higher than that of the uppermost mantle, and hypothesize that this is due to mafic material emplaced at the base of the crust as the spreading center developed beneath the Salton Trough since about 6 Ma. The final study investigates crustal deformation and fault slip rates for faults in the northern Mojave and southern Walker Lane regions of the ECSZ. Previous geodetic studies estimated slip-rates roughly double those inferred via geological dating methods in this region for NW striking strike-slip faults, but significantly smaller than geologic estimates for the Garlock fault. Through construction of a detailed elastic block model, which selects only active fault structures, and applying a new, dense GPS velocity field in this region, we are able to estimate slip-rates for the strike-slip faults in the ECSZ that are much closer to those reported from geology.

  20. Did the 2010 Chile earthquake change the locking degree at neighboring plate interface segments of the Andean subduction zone?

    NASA Astrophysics Data System (ADS)

    Moreno, Marcos; Báez, Juan Carlos; Bedford, Jonathan; Quinteros, Javier; Tassara, Andres; Melnick, Daniel; Oncken, Onno; Vigny, Christophe; Bartsch, Mitja; Bevis, Michael; Soto, Hugo; Barrientos, Sergio; Ortega, Ismael; Valderas, Maria

    2014-05-01

    A widely held view is that lateral extents and magnitudes of great earthquakes are fundamentally controlled by the stress build-up along the plate interface as inferred from the degree of locking. Therefore, inferring the distribution of locking and its along-strike variations has become an essential tool for seismic and tsunami hazard assessment. Recent studies have explored the main parameters affecting the spatial distribution of locking degree, but the time evolution of locking has not yet been clearly documented. Here we used time-series of continuous GPS at adjacent segments (> 500 km distance) to the rupture zone of the 2010 Chile (Mw=8.8) earthquake to explore the differences in locking degree before (2008-2010) and after (2010-2013) this event. Results suggest that the interseismic velocity (landward displacements) increased both in the northern (27°S-32°S) and southern (41°S-45°S) unruptured segments. The variations of displacements can be explained by an increase and homogenization of the locking degree at areas that were creeping before the 2010 earthquake. The estimated increase of locking degrees have peaks of about 20% and 100% for the northern and southern regions respectively. The b-value, which parameterizes the frequency-magnitude distribution of seismicity, decreased after the 2010 earthquake in the northern segment (in the southern segment there is not enough seismicity for estimating b-value) from 1.2 to 0.7 indicating a tendency for asperities to be brought closer to failure due to increase of shear stresses on the plate interface. By means of a 3D thermo-mechanical subduction model we are able to simulate the dynamic response of the system and study the stress variations before and after the earthquake, supporting the rearrangment of shear stresses at adjacent segments. Our results suggest that locking degree can evolve over a short timescale due to the change of the stress regime induced by great earthquakes. We propose that the seismic cycle along a margin is a self-organized system in the sense of a lateral connected evolution of build-up and release of stress at different seismotectonic segments. Importantly, the 2010 earthquake may have increased the seismic potential of the northern and southern neighboring plate interface segments, which broke last in 1922 and 1960, respectively.

  1. A Serial Sample Loading System: Interfacing Multi-well plates with Microfluidic Devices

    PubMed Central

    Rane, Tushar D.; Zec, Helena; Wang, Jeff Tza-Huei

    2013-01-01

    There is an increasing demand for novel high-throughput screening (HTS) technologies in the pharmaceutical and biotechnological industries. The robotic sample handling techniques currently used in these industries, although fast, are still limited to operating in multi-well plates with the sample volumes per reaction in the microliter regime. Digital microfluidics offers an alternative for reduction in sample volume consumption for HTS but lacks a reliable technique for transporting large number of samples to the microfluidic device. In this report, we develop a technique for serial delivery of sample arrays to a microfluidic device from multi-well plates, through a single sample inlet. Under this approach, a serial array of sample plugs, separated by an immiscible carrier fluid, is loaded into a capillary and delivered to a microfluidic device. Similar approaches have been attempted in the past, however, either with a slower sample loading device like syringe pump or vacuum based sample loading with limited driving pressure. We demonstrated the application of our positive pressure based ‘Serial Sample Loading’ (SSL) system to load a series of sample plugs into a capillary. The adaptability of the SSL system to generate sample plugs with a variety of volumes in a predictable manner was also demonstrated. PMID:22885789

  2. Tapping of an Enriched Asthenospheric Layer at the Samoan Islands along Fractures Produced by Deformation of the Pacific Plate near the Tonga Trench

    NASA Astrophysics Data System (ADS)

    Dieu, J. J.; Hawkins, J. W.; Natland, J. H.

    2002-12-01

    Samoan basalts derive from mantle sources having a strong EMII signature (high 87Sr/86Sr, K, Rb, and Ba). Stratigraphy tied with radiometric dates reveal an increase, maximum, and waning of the influence of the EMII mantle component in the combined history of the shield volcanoes of successively younger islands, Upolu, Tutuila, and Ta\\`{ }u. This fluctuation is superimposed on, and independent of, Hawaiian-like shield-building, waning alkalic, and post-caldera alkalic stages of volcanism. It is inconsistent with any regular arrangement of EMII within the structure of a postulated mantle plume. The islands are surface expressions of longer east-trending submarine volcanic ridges or lineaments. These and several older shield lineaments appear in satellite-derived bathymetry as en echelon, straight or slightly curving volcanic ridges, each 100-500 km long. They formed in eastward succession on the Pacific Plate as it rode to the west past the strongly curving transform corner of the nearby Tonga trench. They trend more to the east than nested sigmoidal ridges of the mid-plate Hawaiian Islands, and are not nested. Another lineament ~500 km long is superimposed obliquely over the older Upolu and Tutuila lineaments, which it capped with locally extensive Quaternary-Historic post-erosional eruptives over a distance of >200 km. It closely parallels the transform portion of the trench, and formed along a narrow fracture that propagated along the crest of the arch in the Pacific plate that was produced by lateral bending of the plate into that part of the trench (1). The EMII influence along this lineament is strongest to the west, and all lavas along it are distinct from those of the older underlying lineaments in the Pb isotopes (2). The simplest interpretation of Samoan volcanism is that enriched components are irregularly concentrated in a layer or layers at the top of the asthenosphere that has been tapped along fractures produced by shear coupling acting on the edge of the Pacific lithospheric plate where it moves close to or bends toward the transform portion of the Tonga Trench. (1) Hawkins, JW, and Natland, JH, 1975. Earth Planet. Sci. Lett., 24: 427-439 (2) Hart, S.R., Staudigel, H., Koppers, A.P., Blusztajn, J., Baker, E.., Workman, R., Jackson, M., Hauri, E., Kurz, M., Sims, K., Fornari, D., Saal, A., and Lyons, S., 2000. Geochem. Geophys. Geosyst., 1: Paper 2000GC00108.

  3. Fast Displacement Rate of the Subducting Pacific Plate After the 2011 Tohoku-oki Earthquake Measured by GPS/Acoustic Surveys

    NASA Astrophysics Data System (ADS)

    Tomita, F.; Kido, M.; Osada, Y.; Iinuma, T.; Hino, R.; Ohta, Y.

    2014-12-01

    The 2011 Tohoku-oki earthquake was a huge interplate earthquake, which posed various issues against our previous perceptions on the subduction process. One of the unprecedented ideas is the acceleration of the subducting plate after the earthquake suggested by Heki and Mitsui (2013). They expect that temporal loss of interplate coupling following a huge interplate earthquake will cause acceleration in subducting rate; Onshore GPS observations after the 2003 Tokachi-oki earthquake also support this hypothesis. However, this is an indirect evidence of the acceleration, and hence direct geodetic evidence is needed to examine this hypothesis. Here, we have challenged to directly detect the subducting rate of the Pacific plate using GPS/Acoustic technique. We show the displacement rate of the site on the Pacific plate, where four times of surveys have been conducted for 1.5 years during Sept., 2012 - Mar., 2014. In each survey, we determine the precise locations of the center of the transponder array. The displacement rate is estimated from the linear regression of time-series of the array positions at four campaigns. This shows clear northwestward movement amount to 17.2±4.3 cm/yr relative to the North American plate. This rate is roughly twice as fast as the global steady motion of 8.3 cm/yr given in MORVAL. However, the observed fast movement can be interpreted not only as the acceleration of the subduction but also as the effect of viscoelastic responses that relax the coseismic elastic deformation. At this moment, we cannot quantitatively distinguish the two interpretations above. According to Heki and Mitsui (2013), the acceleration propagates southern Kuril area. This region would show low effect of viscoelastic relaxation. So, if seafloor observation in this region is conducted, it may reveal the presence or absence of the acceleration. In this presentation, we will show forthcoming seafloor observation data planned to be obtained on this September and discuss on this issue in detail.

  4. Along-trench variations in the seismic structure of the incoming Pacific plate at the outer rise of the northern Japan Trench

    NASA Astrophysics Data System (ADS)

    Fujie, Gou; Kodaira, Shuichi; Sato, Takeshi; Takahashi, Tsutomu

    2016-01-01

    To investigate along-trench variations in the seismic structure of the incoming oceanic plate and their effect on water transportation by the oceanic plate, we conducted a wide-angle seismic survey of a trench-parallel transect 270 km long on the outer rise of the northern Japan Trench. The resulting seismic structure models show that the central part of the transect is characterized by rough topography, thick oceanic crust, low seismic velocities, and high Vp/Vs ratios, suggesting pervasive fracturing and high water content (hydration) there. These observations are consistent with the presence of an ancient fracture zone associated with ridge propagation. The trenchward extension of this fracture zone corresponds to an area of low interplate seismicity, low seismic velocities, and high Vp/Vs ratio around the depth of the subduction interface. Our results suggest that this ancient scar on the oceanic plate influences along-trench variations in interplate seismic coupling through its effect on water transportation.

  5. Life and death of the resurrection plate: Evidence for its existence and subduction in the northeastern Pacific in Paleocene-Eocene time

    USGS Publications Warehouse

    Haeussler, P.J.; Bradley, D.C.; Wells, R.E.; Miller, M.L.

    2003-01-01

    Onshore evidence suggests that a plate is missing from published reconstructions of the northeastern Pacific Ooean in Paleocene- Eocene time. The Resurrection plate, named for the Resurrection Peninsula ophiolite near Seward, Alaska, was located east of the Kula plate and north of the Farallon plate. We interpret coeval near-trench magmatism in southern Alaska and the Cascadia margin as evidence for two slab windows associated with trench-ridge-trench (TRT) triple junctions, which formed the western and southern boundaries of the Resurrection plate. In Alaska, the Sanak-Baranof belt of near-trench intrusions records a west-to-east migration, from 61 to 50 Ma, of the northern TRT triple junction along a 2100-km-long section of coastline. In Oregon, Washington, and southern Vancouver Island, voluminous basaltic volcanism of the Siletz River Volcanics, Crescent Formation, and Metchosin Volcanics occurred between ca. 66 and 48 Ma. Lack of a clear age progression of magmatism along the Cascadia margin suggests that this southern triple junction did not migrate significantly. Synchronous near-trench magmatism from southeastern Alaska to Puget Sound at ca. 50 Ma documents the middle Eocene subduction of a spreading center, the crest of which was subparallel to the margin. We interpret this ca. 50 Ma event as recording the subduction-zone consumption of the last of the Resurrection plate. The existence and subsequent subduction of the Resurrection plate explains (1) northward terrane transport along the southeastern Alaska-British Columbia margin between 70 and 50 Ma, synchronous with an eastward-migrating triple junction in southern Alaska; (2) rapid uplift and voluminous magmatism in the Coast Mountains of British Columbia prior to 50 Ma related to subduction of buoyant, young oceanic crust of the Resurrection plate; (3) cessation of Coast Mountains magmatism at ca. 50 Ma due to cessation of subduction, (4) primitive mafic magmatism in the Coast Mountains and Cascade Range just after 50 Ma, related to slab-window magmatism, (5) birth of the Queen Charlotte transform margin at ca. 50 Ma, (6) extensional exhumation of high-grade metamorphic terranes and development of core complexes in British Columbia, Idaho, and Washington, and extensional collapse of the Cordilleran foreland fold-and-thrust belt in Alberta, Montana, and Idaho after 50 Ma related to initiation of the transform margin, (7) enigmatic 53-45 Ma magmatism associated with extension from Montana to the Yukon Territory as related to slab breakup and the formation of a slab window, (8) right-lateral margin-parallel strike-slip faulting in southern and western Alaska during Late Cretaceous and Paleocene time, which cannot be explained by Farallon convergence vectors, and (9) simultaneous changes in Pacific-Farallon and Pacific-Kula plate motions concurrent with demise of the Kula-Resurrection Ridge.

  6. Final amalgamation of the Central Asian Orogenic Belt in NE China: Paleo-Asian Ocean closure versus Paleo-Pacific plate subduction - A review of the evidence

    NASA Astrophysics Data System (ADS)

    Wilde, Simon A.

    2015-11-01

    The Central Asian Orogenic Belt (CAOB) evolved through complex closure of the Paleo-Asian Ocean from the Neoproterozoic to the late Phanerozoic. This caused the Chinese cratons to collide with Eurasia and led to the formation of the world's largest Phanerozoic orogenic belt. Ocean closure commenced in the west and was completed in the east near Changchun. Closure of the Paleo-Asian Ocean in NE China was along the Solonker-Xar Moron-Changchun-Yanji suture and this was likely completed in the Late Permian, although associated activity continued into the Triassic. There was an overlap in the latest Permian-Early Triassic between terminal activity associated with Paleo-Asian Ocean closure and the onset of tectonism associated with subduction of the Paleo-Pacific plate. This switch in geodynamic setting occurred at ~ 260-250 Ma, and is reflected by a relaxing of north-south directed compression and the onset of east-west directed processes related to Paleo-Pacific subduction. By the Early Jurassic, events associated with the westward advance of the Paleo-Pacific plate dominated, leading to extensive development of I-type granites as far inland as the Great Xing'an Range. From ~ 140 Ma, the Paleo-Pacific plate retreated eastward, resulting in an extensional setting in the Early Cretaceous, the effects of which were enhanced by regional thinning of the lithosphere, commonly attributed to delamination. Throughout this period, the eastern Asian margin was tectonically complex. The north-south oriented Jiamusi-Khanka(-Bureya) block was rifted away from the eastern margin of the CAOB in the Late Triassic, but was then re-united in the Jurassic by westward-advancing subduction that affected both the western and eastern margins of the block. Accretionary complexes continued to evolve in the Cretaceous along the whole eastern margin of Asia, with final accretion of the Nadanhada Terrane (part of the Sikhote-Alin accretionary terrane) with the CAOB at ~ 130 Ma, followed by the emplacement of S-type granites.

  7. Permian geodynamic setting of Northeast China and adjacent regions: closure of the Paleo-Asian Ocean and subduction of the Paleo-Pacific Plate

    NASA Astrophysics Data System (ADS)

    Li, J.-Y.

    2006-03-01

    Northeast China and adjacent regions are located in the central East Asian continent and consist tectonically of both the Paleo-Asian and Paleo-Pacific orogens between the Siberian platform and Sino-Korean (North China) block. This paper discusses some hotly-debated issues concerning the Permian geodynamic setting of these regions, based on a comprehensive analysis of available geological, geochemical, paleobiogeographical and paleomagnetic data. Spatial and temporal distribution of ophiolites and associated continental marginal sequences, Permian sedimentary sequences, spatial distribution and geochemistry of Permian magmatic rocks, and the evolution of paleobiogeographical realms imply: (1) that the Permian marine basins in northeast China and adjacent regions include remnants of the Paleo-Asian Ocean in southeastern Inner Mongolia and central Jilin Province, and active continental margins of the Paleo-Pacific Ocean; (2) that the suture between the Siberian and Sino-Korean paleoplates was finally emplaced in the Permian and is located in areas from Suolunshan (Solonker) eastwards through regions north to the Xar Moron river in southeastern Inner Mongolia, and then central Jilin province to the Yanji area; and (3) that the Permian crustal evolution of northeast China and adjacent regions, as well as parts of the Siberian paleoplate, was influenced by subduction of the Paleo-Pacific oceanic plate. Finally, the Permian tectonic framework and paleogeography of northeast China and adjacent regions in central East Asia are discussed briefly, and Early and Late Permian palinspastic reconstruction maps are provided.

  8. Cascadia tremor located near plate interface constrained by S minus P wave times.

    PubMed

    La Rocca, Mario; Creager, Kenneth C; Galluzzo, Danilo; Malone, Steve; Vidale, John E; Sweet, Justin R; Wech, Aaron G

    2009-01-30

    Nonvolcanic tremor is difficult to locate because it does not produce impulsive phases identifiable across a seismic network. An alternative approach to identifying specific phases is to measure the lag between the S and P waves. We cross-correlate vertical and horizontal seismograms to reveal signals common to both, but with the horizontal delayed with respect to the vertical. This lagged correlation represents the time interval between vertical compressional waves and horizontal shear waves. Measurements of this interval, combined with location techniques, resolve the depth of tremor sources within +/-2 kilometers. For recent Cascadia tremor, the sources locate near or on the subducting slab interface. Strong correlations and steady S-P time differences imply that tremor consists of radiation from repeating sources. PMID:19179527

  9. Tectonic slicing of subducting oceanic crust along plate interfaces: Numerical modeling

    NASA Astrophysics Data System (ADS)

    Ruh, J. B.; Le Pourhiet, L.; Agard, Ph.; Burov, E.; Gerya, T.

    2015-10-01

    Multikilometer-sized slivers of high-pressure low-temperature metamorphic oceanic crust and mantle are observed in many mountain belts. These blueschist and eclogite units were detached from the descending plate during subduction. Large-scale thermo-mechanical numerical models based on finite difference marker-in-cell staggered grid technique are implemented to investigate slicing processes that lead to the detachment of oceanic slivers and their exhumation before the onset of the continental collision phase. In particular, we investigate the role of the serpentinized subcrustal slab mantle in the mechanisms of shallow and deep crustal slicing. Results show that spatially homogeneous serpentinization of the sub-Moho slab mantle leads to complete accretion of oceanic crust within the accretionary wedge. Spatially discontinuous serpentinization of the slab mantle in form of unconnected patches can lead to shallow slicing of the oceanic crust below the accretionary wedge and to its deep slicing at mantle depths depending on the patch length, slab angle, convergence velocity and continental geothermal gradient. P-T paths obtained in this study are compared to natural examples of shallow slicing of the Crescent Terrane below Vancouver Island and deeply sliced crust of the Lago Superiore and Saas-Zermatt units in the Western Alps.

  10. Pacific plate apparent polar wander between 67 Ma and 44 Ma determined from the analysis of the skewness of both vector and scalar magnetic anomalies due to seafloor spreading

    NASA Astrophysics Data System (ADS)

    Zheng, L.; Gordon, R. G.; Horner-Johnson, B. C.

    2011-12-01

    Pacific plate apparent polar wander between 67 Ma and 44 Ma determined from the analysis of the skewness of both vector and scalar magnetic anomalies due to seafloor spreading The apparent polar wander (APW) path for the Pacific plate is important to the study of Pacific plate motions and their relation to circum-Pacific tectonics. It can be used to discriminate between alternative plate motion circuits, determine the motion of Pacific hotspots relative to the paleomagnetic axis, and test the fixed hotspot hypothesis. The pioneering investigations of Jean Francheteau and his colleagues of Pacific plate APW through the analysis of magnetic anomalies over seamounts helped to demonstrate that the Pacific plate has had substantial northward motion relative to the spin axis since Cretaceous time. We also investigate the APW of the Pacific plate through analysis of magnetic anomalies. Instead of anomalies over seamounts, however, we investigate the skewness (asymmetry) of magnetic anomalies due to seafloor spreading. In prior work, skewness analysis of shipboard magnetic profiles has been used to determine Pacific paleomagnetic poles for chron 25r (57 Ma B.P.; Petronotis et al., 1994), chron 27r to 31n (62 to 69 Ma B.P.; Acton and Gordon, 1991) and chron 32n (72 Ma B.P.; Petronotis and Gordon, 1999). Recently, vector aeromagnetic data from low paleolatitudes, combined with shipboard profiles from low paleolatitudes, were used to determine a paleomagnetic pole with compact confidence limits for anomaly 12r (32 Ma B.P.; Horner-Johnson and Gordon, 2010). Here we use the low-paleolatitude shipboard- and vector aero-magnetic profiles to determine new paleomagnetic poles for the Pacific plate. A new feature of our analysis is a correction for the spreading-rate dependence of anomalous skewness (Koivisto et al. 2011). We estimate anomalous skewness as a function of spreading rate for each anomaly by creating many synthetic profiles using the model of Dyment and Arkani-Hamed (1995) and by experimentally determining the phase shift that causes the resulting synthetic magnetic anomaly to best match a profile produced from a "standard" model for anomalies due to seafloor spreading that assumes simple vertical reversal boundaries (Boswell et al., 2011). Thus, we solve for only two adjustable parameters, the latitude and the longitude of the paleomagnetic pole. We focus on preliminary results from the skewness of crossings of magnetic anomalies 20r (44 Ma B.P.), 24r (55 Ma B.P.) and 30n/31n (67 Ma B.P.) between the Galapagos and Murray fracture zones on the Pacific plate. We choose this region of the Pacific plate because numerical experiments, similar to those conducted by Acton and Gordon (1991), show that these data contribute much more information about the location of paleomagnetic poles than do those from any other region of similar size. Implications for Pacific plate tectonics, motion between hotspots, and true polar wander will be discussed.

  11. Large-scale right-slip displacement on the East San Francisco Bay Region fault system, California: Implications for location of late Miocene to Pliocene Pacific plate boundary

    USGS Publications Warehouse

    McLaughlin, R.J.; Sliter, W.V.; Sorg, D.H.; Russell, P.C.; Sarna-Wojcicki, A. M.

    1996-01-01

    A belt of northwardly younging Neogene and Quaternary volcanic rocks and hydrothermal vein systems, together with a distinctive Cretaceous terrane of the Franciscan Complex (the Permanente terrane), exhibits about 160 to 170 km of cumulative dextral offset across faults of the East San Francisco Bay Region (ESFBR) fault system. The offset hydrothermal veins and volcanic rocks range in age from .01 Ma at the northwest end to about 17.6 Ma at the southeast end. In the fault block between the San Andreas and ESFBR fault systems, where volcanic rocks are scarce, hydrothermal vein system ages clearly indicate that the northward younging thermal overprint affected these rocks beginning about 18 Ma. The age progression of these volcanic rocks and hydrothermal vein systems is consistent with previously proposed models that relate northward propagation of the San Andreas transform to the opening of an asthenospheric window beneath the North American plate margin in the wake of subducting lithosphere. The similarity in the amount of offset of the Permanente terrane across the ESFBR fault system to that derived by restoring continuity in the northward younging age progression of volcanic rocks and hydrothermal veins suggests a model in which 80-110 km of offset are taken up 8 to 6 Ma on a fault aligned with the Bloomfield-Tolay-Franklin-Concord-Sunol-Calaveras faults. An additional 50-70 km of cumulative slip are taken up ??? 6 Ma by the Rogers Creek-Hayward and Concord-Franklin-Sunol-Calaveras faults. An alternative model in which the Permanente terrane is offset about 80 km by pre-Miocene faults does not adequately restore the distribution of 8-12 Ma volcanic rocks and hydrothermal veins to a single northwardly younging age trend. If 80-110 km of slip was taken up by the ESFBR fault system between 8 and 6 Ma, dextral slip rates were 40-55 mm/yr. Such high rates might occur if the ESFBR fault system rather than the San Andreas fault acted as the transform margin at this time. Major transpression across the boundary between the Pacific and North American plates at about 3 to 5 Ma would have resulted in the transfer of significant slip back to the San Francisco Peninsula segment of the San Andreas fault. Since that time, the ESFBR fault system has continued to slip at rates of 11-14 mm/yr. If this interpretation is valid, the ESFBR fault system was the Pacific-North American plate boundary between 8 and 6 Ma, and this boundary has migrated both eastward and westward with time, in response to changing plate margin geometry and plate motions.

  12. Pore pressure evolution at the plate interface along the Cascadia subduction zone from the trench to the ETS transition zone

    NASA Astrophysics Data System (ADS)

    Skarbek, R. M.; Rempel, A. W.; Schmidt, D. A.

    2010-12-01

    Pore fluid pressures in subduction zones are a primary control on fault strength and slip dynamics. Numerous studies document elevated pore pressures in the outer wedge along several margins. Seismic observations and the occurrence of non-volcanic tremor provide additional evidence for the presence of near-lithostatic pore pressures at the plate interface far down-dip from the trench (~35 km depth). Here we use numerical models in one and two dimensions to evaluate the pore pressure and compaction state of sediments on the subducting Juan de Fuca plate in Cascadia from the trench to the ETS zone. 2-D models allow pressure to diffuse vertically and also laterally normal to strike of the megathrust; 1-D models simulate only vertical diffusion. Model parameters are chosen with reference to two strike-normal profiles: one through central Oregon and one through the Olympic Peninsula of Washington. We examine temporal variations in sediment input to the trench and consider implications for fault strength and permeability as well as the down-dip extent to which compactive dewatering can be considered a significant fluid source. In 1-D, we use a general and fully nonlinear model of sediment compaction derived without making any assumptions regarding stress-strain or porosity-permeability relations and allowing finite strains. In contrast, most previous models of fluid flow in subduction zones have used linear models of diffusion that rely on assumptions of constant sediment permeability and infinitesimal strains for their formulation. Our nonlinear finite-strain model remains valid at greater depths, where stresses and strains are large. Boundary conditions in 1-D are constrained by pore pressure estimates along the megathrust fault that are based on seismic velocities (e.g. Tobin and Saffer, 2010) and data from consolidation tests conducted on sediments gathered during ODP Leg 204 (Tan, 2001). Initial conditions rely on input sediment thickness; while sediment thickness at the trench in Cascadia is fairly well constrained (~1-3 km) by seismic studies, it is less clear how much of the section is frontally accreted and how much is subducted with the downgoing plate. Along the Washington profile, Batt et al. (2001) estimated that 80-100% of the incoming sediment is frontally accreted, based on comparisons between accretionary flux at the trench and erosional flux in the Olympic Mountains. We assume that similar values hold for the Oregon profile as well. Values of permeability along the plate interface are extracted from 1-D models and used to parameterize 2-D models. 2-D modeling is motivated by the need to examine time dependency of sediment influx, as well as the influence of splay faults within the accretionary wedge. Preliminary results indicate that fluid flux resulting from sediment compaction is complete well up-dip of the ETS zone, where the magnitude of fluid flux associated with mineral dehydration reactions becomes more significant. Ongoing work is centered on incorporating the effects of dehydration fluid sources within our models of pore pressure evolution and examining the implications of our results on the dynamics of slow slip events.

  13. Relationship between compressional-wave velocity and porosity of sediments along subduction plate interface

    NASA Astrophysics Data System (ADS)

    Yamaguchi, M.; Hashimoto, Y.

    2012-12-01

    Evolution of physical properties of sediments along subduction interface has effects on wedge strength, wedge geometry, dewatering and dehydration processes, and seismic behavior. Sediments have initially more than 70% of porosity prior to subduction. Through underthrusting and accretion, porosity of sediments decreases by compaction and cementation to be lithified sediments. The purpose of this study is to understand evolution of physical properties from a state before subduction to a state within a wedge using a relationship between compressional-wave velocity and porosity. In this study, we obtained new data for sediments from a reference site in IODP NanTroSEIZE, Expedition 333. In addition to that, we have complied velocity-porosity relationships for the samples and also for previous studies from NanTroSEIZE (off Kumano) (Hashimoto et al., 2010, 2011), ODP Leg 190 (off Shikoku) (Hoffman and Tobin, 2004) and ODP Leg 170 (off Costa Rica) (Gettemy and Tobin, 2003). Velocity measurement procedure in this study to obtain new data is as following: Two pumps were used to control pore fluid pressure and confining pressure. The pore pressure of 1000kPa was kept under drained conditions. Confining (effective) pressure was increased stepwise in the measurements. Velocity measurements were conducted under isotropic pressure conditions. Confining pressure was pressurized in tens seconds and kept for more than 8 hours for next step to obtain equilibrium conditions between effective pressure and sediments strain. Lead zirconate titanate (PZT) shear wave transducers (500kHz) were used in a source-receiver pair to measure wave speed. Porosity and P-wave velocity ranges about 27 - 75% and 1.4 - 2.2 km/s in this study, respectively. In the comparison in Vp-porosity relationships between sedimetns from reference sites and others, sediments were classified into two, simply compacted sediments (reference site and slope sediments) and wedge sediments. Different trends in Vp-porosity relationships were observed for the classified sediments. For compacted sediments, Vp-porosity relationships are along the global empirical relationships (Erickson and Jarrard 1988) and almost within the area between normal and highly compaction curves. On the other hand, some of Vp-porosity relationships for wedge sediments represent trends with higher velocity at a porosity. Such trend was observed for wedge sediments from Site C0001 and C0004. Those higher Vp trend in Vp-porosity relationship for wedge sediments can be explained by shear strain of sediments and/or cementation. Even though the velocity measurements was conducted under hydrostatic condition, we examined the void ratio-porosity curve as a kind of compaction curve. On the basis of the curves, break points were observed at the pressure which corresponds to the effective pressure assuming the hydrostatic pore fluid pressure. The result suggests that the sediments were under condition of normal compaction. Some of void ratio-porosity curve represent a evidence of weak cement which can correspond with anomaly in porosity-depth curve in the shallow portion of the reference sites.

  14. Distribution and mechanism of Neogene to present-day vertical axis rotations, Pacific-Australian Plate Boundary Zone, South Island, New Zealand

    NASA Astrophysics Data System (ADS)

    Little, Timothy A.; Roberts, Andrew P.

    1997-01-01

    Remarkably little knowledge exists about mechanisms of vertical axis rotation in continental crust. Steeply dipping basement rocks in South Island, New Zealand, provide an opportunity to map the distribution of rotations across the Pacific-Australian plate boundary zone, and to delineate boundaries of rotated blocks in unusual detail. We synthesize new structural data with new and existing paleomagnetic data, with geodetic data, and with patterns of Neogene-Quaternary faulting in the strike-slip Marlborough fault system. For the past 20 m.y., vertical axis rotations have been hinged about two crustal-scale boundaries near the east coast. The NE hinge accommodated ˜50° of early-middle Miocene clockwise rotation, which caused deformation of the eastern ends of the Alpine-Wairau and Clarence strike-slip faults. The SW hinge has accommodated a further 30°-50° of finite clockwise rotation since ˜4 Ma and deflects active fault traces. The locus of rotation has shifted southwestward astride a subduction margin that is lengthening in that direction. Rotating rocks are pinned to the south against a locked collision zone where the continental Chatham Rise impinges against the margin. Slip on inland strike-slip faults is transformed seaward across a zone of fault termination into rigid body rotation of a large continental block that has been thrust eastward over the downgoing subducted slab of the Pacific plate. The rotation mechanism is a "migrating hinge," which resembles a flexed telephone book. Strike-slip faults are translated through a brecciated hinge region that does not coincide with a fixed material line in the rock.

  15. Late cretaceous pelagic sediments, volcanic ASH and biotas from near the Louisville hotspot, Pacific Plate, paleolatitude ∼42°S

    USGS Publications Warehouse

    Ballance, Peter F.; Barron, John A.; Blome, Charles D.; Bukry, David; Cawood, Peter A.; Chaproniere, George C.H.; Frisch, Robyn; Herzer, Richard H.; Nelson, Campbell S.; Quinterno, Paula; Ryan, Holly F.; Scholl, David W.; Stevenson, Andrew J.; Tappin, David G.; Vallier, Tracy L.

    1989-01-01

    Dredging on the deep inner slope of the Tonga Trench, immediately north of the intersection between the Louisville Ridge hotspot chain and the trench, recovered some Late Cretaceous (Maestrichtian) slightly tuffaceous pelagic sediments. They are inferred to have been scraped off a recently subducted Late Cretaceous guyot of the Louisville chain. In the vicinity of the Louisville hotspot (present location 50°26′S, 139°09′W; Late Cretaceous location ∼42°S, longitude unknown) Late Cretaceous rich diatom, radiolarian, silicoflagellate, foraminiferal and coccolith biotas, accumulated on the flanks of the guyot and are described in this paper. Rich sponge faunas are not described. ?Inoceramus prisms are present. Volcanic ash is of within-plate alkalic character. Isotope ratios in bulk carbonate δ18O − 2.63 to + 0.85, δ13C + 2.98 to 3.83) are normal for Pacific Maestrichtian sediments. The local CCD may have been shallower than the regional CCD, because of high organic productivity. In some samples Late Cretaceous materials have been mixed with Neogene materials. Mixing may have taken place on the flanks of the guyot during transit across the western Pacific, or on the trench slope during or after subduction and offscraping about 0.5 Ma.

  16. Earth's Decelerating Tectonic Plates

    SciTech Connect

    Forte, A M; Moucha, R; Rowley, D B; Quere, S; Mitrovica, J X; Simmons, N A; Grand, S P

    2008-08-22

    Space geodetic and oceanic magnetic anomaly constraints on tectonic plate motions are employed to determine a new global map of present-day rates of change of plate velocities. This map shows that Earth's largest plate, the Pacific, is presently decelerating along with several other plates in the Pacific and Indo-Atlantic hemispheres. These plate decelerations contribute to an overall, globally averaged slowdown in tectonic plate speeds. The map of plate decelerations provides new and unique constraints on the dynamics of time-dependent convection in Earth's mantle. We employ a recently developed convection model constrained by seismic, geodynamic and mineral physics data to show that time-dependent changes in mantle buoyancy forces can explain the deceleration of the major plates in the Pacific and Indo-Atlantic hemispheres.

  17. Spatially varying upper mantle of eastern China caused by Pacific Plate subduction: constraints from body-wave tomography and SKS wave splitting measurements

    NASA Astrophysics Data System (ADS)

    Zhao, L.; Zheng, T.; Allen, R. M.

    2011-12-01

    How does the subduction system influence the evolution of cratons is an interesting question. Eastern China, located at the eastern margin of the Eurasia plate, records the geodynamic evolution of the continent associated with the ongoing convergence of the Eurasia and (Paleo-) Pacific and Philippine plates during the Late Mesozoic to Cenozoic. Previous multidisciplinary studies, including geophysics, geology and geochemistry, suggest that the evolution of EC in the Late Mesozoic to Cenozoic exhibit significant temporal and spatial changes from north to south and from west to east. Eastern China is therefore an idea natural laboratory to investigate the evolutions of cratons in a subduction system. In this study, we investigate the upper mantle structures and anisotropy beneath eastern China. The tomographic images are reconstructed based on inversion of body-wave travel-times recorded by ~1300 stations from the updated China National Seismic Network and 9 temporary arrays. In the inversion, crustal corrections from an independent dataset were introduced a prior. SKS wave splitting measurements are made using dataset from ~500 new broadband stations. An overview of the upper mantle velocity images and available splitting results reveal strong spatial variations of upper mantle structures and anisotropy in eastern China. (1) The Vp, Vs and VP/VS images all display that the North China Craton and the South China Block have a strong contrast in the wavelength of velocity anomalies. In the North China Craton, smaller-scale and complex low-velocity structures are widespread in the eastern part; while in the South China Block, the broad Yangtze Craton to the west is high velocity while the Cathaysia Block to the east is predominantly low velocity. (2) The splitting observations are characterized by apparent diversity of anisotropy pattern in adjacent tectonic domains. In eastern part, the fast direction pattern is relative simple with majority trending ENE-WSW, while in the western part of eastern China, the fast directions exhibit strong variations in different tectonic domains. Based on these observations, we propose that the evolution of eastern China was dominated by the subduction of the Pacific plate, while the North China Craton and the South China Block have undergone different dynamic processes. References Zhao L., R. M. Allen, T.Y. Zheng, High-resolution body-wave tomography models of the upper mantle beneath eastern China and the adjacent area, in preparation for Geochem. Geophys. Geosyst., 2011.

  18. Compilation of Surface Creep on California Faults and Comparison of WGCEP 2007 Deformation Model to Pacific-North American Plate Motion

    USGS Publications Warehouse

    Wisely, Beth A.; Schmidt, David A.; Weldon, Ray J., II

    2008-01-01

    This Appendix contains 3 sections that 1) documents published observations of surface creep on California faults, 2) constructs line integrals across the WG-07 deformation model to compare to the Pacific ? North America plate motion, and 3) constructs strain tensors of volumes across the WG-07 deformation model to compare to the Pacific ? North America plate motion. Observation of creep on faults is a critical part of our earthquake rupture model because if a fault is observed to creep the moment released as earthquakes is reduced from what would be inferred directly from the fault?s slip rate. There is considerable debate about how representative creep measured at the surface during a short time period is of the whole fault surface through the entire seismic cycle (e.g. Hudnut and Clark, 1989). Observationally, it is clear that the amount of creep varies spatially and temporally on a fault. However, from a practical point of view a single creep rate is associated with a fault section and the reduction in seismic moment generated by the fault is accommodated in seismic hazard models by reducing the surface area that generates earthquakes or by reducing the slip rate that is converted into seismic energy. WG-07 decided to follow the practice of past Working Groups and the National Seismic Hazard Map and used creep rate (where it was judged to be interseismic, see Table P1) to reduce the area of the fault surface that generates seismic events. In addition to following past practice, this decision allowed the Working Group to use a reduction of slip rate as a separate factor to accommodate aftershocks, post seismic slip, possible aseismic permanent deformation along fault zones and other processes that are inferred to affect the entire surface area of a fault, and thus are better modeled as a reduction in slip rate. C-zones are also handled by a reduction in slip rate, because they are inferred to include regions of widely distributed shear that is not completely expressed as earthquakes large enough to model. Because the ratio of the rate of creep relative to the total slip rate is often used to infer the average depth of creep, the ?depth? of creep can be calculated and used to reduce the surface area of a fault that generates earthquakes in our model. This reduction of surface area of rupture is described by an ?aseismicity factor,? assigned to each creeping fault in Appendix A. An aseismicity factor of less than 1 is only assigned to faults that are inferred to creep during the entire interseismic period. A single aseismicity factor was chosen for each section of the fault that creeps by expert opinion from the observations documented here. Uncertainties were not determined for the aseismicity factor, and thus it represents an unmodeled (and difficult to model) source of error. This Appendix simply provides the documentation of known creep, the type and precision of its measurement, and attempts to characterize the creep as interseismic, afterslip, transient or triggered. Parts 2 and 3 of this Appendix compare the WG-07 deformation model and the seismic source model it generates to the strain generated by the Pacific - North American plate motion. The concept is that plate motion generates essentially all of the elastic strain in the vicinity of the plate boundary that can be released as earthquakes. Adding up the slip rates on faults and all others sources of deformation (such as C-zones and distributed ?background? seismicity) should approximately yield the plate motion. This addition is usually accomplished by one of four approaches: 1) line integrals that sum deformation along discrete paths through the deforming zone between the two plates, 2) seismic moment tensors that add up seismic moment of a representative set of earthquakes generated by a crustal volume spanning the plate boundary, 3) strain tensors generated by adding up the strain associated with all of the faults in a crustal volume spanning the plate

  19. TH-C-19A-09: Quantification of Transmission and Backscatter Factors as a function of Distance to Inhomogeneity Interface for Three Types of Surgical Implant Plates

    SciTech Connect

    Wilson, D; Mills, M; Wang, B

    2014-06-15

    Purpose: Carbon fiber materials have been increasingly used clinically, mainly in orthopedics, as an alternative to metallic implants because of their minimal artifacts on CT and MRI images. This study characterizes the transmission and backscatter property of carbon fiber plates (CarboFix Orthopedics, Herzeliya, Israel) with measurements for radiation therapy applications, and compares them to traditional Stainless Steel (SS) and Titanium (Ti) metal materials. Methods: For the transmission measurements, 1-mm-thick test plate was placed upstream from a plane parallel Markus chamber, separated by various thicknesses of polystyrene plates in 0.5 cm increments between 0 and 5 cm. With this setup, we quantified the radiation transmission as a function of distance to the inhomogeneity interface. The LINAC source to detector distance was maintained at 100 cm and 200 MU was delivered for each measurement. Two 3-cm solid water phantoms were placed at the top and bottom to provide build up. All the measurements were performed for 6 MV and 18 MV photons. The backscatter measurements had the identical setup, except that the test plate was downstream of the chamber from radiation. Results: The carbon fiber plates did not introduce any measureable inhomogeneity effect on the transmission and backscatter factor because of its low atomic number. In contrast, traditional metal implant materials caused up to 15% dose difference at upstream and 25% backscatter at downstream from radiation. Such differences decrease as the distance to the inhomogeneity interface increases and become unmeasurable at distance of 3 cm and 1 cm for upstream and downstream, respectively. Conclusion: A new type of carbon fiber implant plate was evaluated and found to have minimal inhomogeneity effect in MV radiation beams. Patients would benefit from a carbon based implant over metal for radiation therapy due to their minimal backscatter and imaging artifacts.

  20. SEISMICITY AND VOLCANISM IN THE PACIFIC NORTHWEST: EVIDENCE FOR THE SEGMENTATION OF THE JUAN DE FUCA PLATE.

    USGS Publications Warehouse

    Weaver, Craig S.; Michaelson, Caryl A.

    1985-01-01

    The distributions of earthquakes and late Cenozoic and Quaternary volcanism in Washington and northern Oregon change markedly across two northeast-striking lines, one near Mount Rainier and one near Mount Hood. On the basis of these observations and a comparison with the Nazoa subduction zone, we propose that the Juan de Fuca subduction zone is divided into two segments. Landward of the coastal thrust zone, we suggest the Juan de Fuca plate dips more steeply beneath the southern segment than beneath the northern segment. Refs.

  1. An unrecognized major collision of the Okhotomorsk Block with East Asia during the Late Cretaceous, constraints on the plate reorganization of the Northwest Pacific

    NASA Astrophysics Data System (ADS)

    Yang, Yong-Tai

    2013-11-01

    Interactions at plate boundaries induce stresses that constitute critical controls on the structural evolution of intraplate regions. However, the traditional tectonic model for the East Asian margin during the Mesozoic, invoking successive episodes of paleo-Pacific oceanic subduction, does not provide an adequate context for important Late Cretaceous dynamics across East Asia, including: continental-scale orogenic processes, significant sinistral strike-slip faulting, and several others. The integration of numerous documented field relations requires a new tectonic model, as proposed here. The Okhotomorsk continental block, currently residing below the Okhotsk Sea in Northeast Asia, was located in the interior of the Izanagi Plate before the Late Cretaceous. It moved northwestward with the Izanagi Plate and collided with the South China Block at about 100 Ma. The indentation of the Okhotomorsk Block within East Asia resulted in the formation of a sinistral strike-slip fault system in South China, formation of a dextral strike-slip fault system in North China, and regional northwest-southeast shortening and orogenic uplift in East Asia. Northeast-striking mountain belts over 500 km wide extended from Southeast China to Southwest Japan and South Korea. The peak metamorphism at about 89 Ma of the Sanbagawa high-pressure metamorphic belt in Southwest Japan was probably related to the continental subduction of the Okhotomorsk Block beneath the East Asian margin. Subsequently, the north-northwestward change of motion direction of the Izanagi Plate led to the northward movement of the Okhotomorsk Block along the East Asian margin, forming a significant sinistral continental transform boundary similar to the San Andreas fault system in California. Sanbagawa metamorphic rocks in Southwest Japan were rapidly exhumed through the several-kilometer wide ductile shear zone at the lower crust and upper mantle level. Accretionary complexes successively accumulated along the East Asian margin during the Jurassic-Early Cretaceous were subdivided into narrow and subparallel belts by the upper crustal strike-slip fault system. The departure of the Okhotomorsk Block from the northeast-striking Asian margin resulted in the occurrence of an extensional setting and formation of a wide magmatic belt to the west of the margin. In the Campanian, the block collided with the Siberian margin, in Northeast Asia. At about 77 Ma, a new oceanic subduction occurred to the south of the Okhotomorsk Block, ending its long-distance northward motion. Based on the new tectonic model, the abundant Late Archean to Early Proterozoic detrital zircons in the Cretaceous sandstones in Kamchatka, Southwest Japan, and Taiwan are interpreted to have been sourced from the Okhotomorsk Block basement which possibly formed during the Late Archean and Early Proterozoic. The new model suggests a rapidly northward-moving Okhotomorsk Block at an average speed of 22.5 cm/yr during 89-77 Ma. It is hypothesized that the Okhotomorsk-East Asia collision during 100-89 Ma slowed down the northwestward motion of the Izanagi Plate, while slab pull forces produced from the subducting Izanagi Plate beneath the Siberian margin redirected the plate from northwestward to north-northwestward motion at about 90-89 Ma.

  2. A mega shear zone in the Central Range of Taiwan and it's implication for the Late Mesozoic subduction of the paleo-Pacific plate

    NASA Astrophysics Data System (ADS)

    Yi, D. C.; Lin, C. W.

    2012-04-01

    The metamorphic basement "Tananao Complex" exposed in the eastern flank of the Central Range of Taiwan. The ancient Asian continental margin deposited a thick sequence of sandstone, shale, limestone and volcanic rocks that was the protolith of Tananao Complex. In Late Mesozoic Era, the thick sequence of rocks was subjected to several phases of metamorphism and deformation to form the pair metamorphic belts which were the western Tailuko Belt and the eastern Yuli Belt. The Tailuko belt is composed of phyllite, quartzite, quartz-mica schist, meta-conglomerate, gneiss, meta-basite, amphibolite, serpentinite, marble and meta-chert, etc. The Yuli belt is composed of a monotonous assemblage of quartz-mica schist, subordinate meta-basite and serpentinite, etc. It is believed that the boundary of the Tailuko belt and the Yuli belt is a large fault, but the field evidence of the fault has never been found. In this study, meso-scale field investigation of the lithologies and rock fabrics indicate that a mega shear zone, called "The Daguan shear zone", separated the Tailuko belt from the Yuli belt. The Daguan shear zone is a NNE trending and west dipping mega shear zone which is mainly composed of mylonitic dark gray quartz-mica schist and mica schist, intercalated with 1 to 2 centimeters thick of elongated meta-conglomerate band. The shear zone is composed of numerous meso-scale ductile shear zones. Additionally, the shaer zone is characterized by abundant varied quartz veins that have been refolded to lenticular or pod shape and nearly parallel to S2 cleavage. Compaed to the existing geological information of the Central Range, we believe that the Daguan shear zone played a role as the boundary of the subduction zone which the paleo-Pacific Plate subducted into the Eurasian Plate in Late Mesozoic Era.

  3. An analysis of the relaxation of laminar boundary layer on a flat plate after passage of an interface with application to expansion-tube flows

    NASA Technical Reports Server (NTRS)

    Gupta, R. N.

    1972-01-01

    The relaxation of the accelerating-gas boundary layer to the test-gas boundary layer over a flat plate in an expansion tube is analyzed. Several combinations of test gas and acceleration gas are considered. The problem is treated in two conically similar limits: (1) when the time lag between the arrival of the shock and the interface at the leading edge of the plate is very large, and (2) when this lag is negligible. The time-dependent laminar-boundary-layer equations of a binary mixture of perfect gases are taken as the flow-governing equations. This coupled set of differential equations, written in terms of the Lam-Crocco variables, has been solved by a line-relaxation finite-difference techniques. The results presented include the Stanton number and the local skin-friction coefficient as functions of shock Mach number and the nondimensional distance-time variable. The results indicate that more than 95 percent of the test-gas boundary layer exists over a length, measured from the leading edge of the plate, equal to about three-tenths of the distance traversed by the interface in the free stream.

  4. On gravity from SST, geoid from Seasat, and plate age and fracture zones in the Pacific. [Satellite-to-Satellite Tracking

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    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 mantle without complete thermal equilibration is considered. Previously announced in STAR as N84-11559

  5. Shear horizontal acoustic waves propagating along two isotropic solid plates bonded with a non-dissipative adhesive layer: Effects of the rough interfaces

    NASA Astrophysics Data System (ADS)

    Potel, Catherine; Bruneau, Michel; Foze N'Djomo, Ludovic C.; Leduc, Damien; Echcherif Elkettani, Mounsif; Izbicki, Jean-Louis

    2015-12-01

    The aim of this paper is to provide an analytical contribution which presents the application of shear-horizontal (SH)-guided waves for the characterisation of a bi-layered structure which consists of two isotropic plates adhesively bonded using a non-dissipative thin layer of glue. The thickness of the layer of glue is assumed to be non-negligible, and the interfaces between this layer of glue and the plates are both assumed to be roughened (parallel ridges with complex shape and depth profiles). The basis of the theoretical approach is an extension of the integral formulation, in the frame of SH modal couplings due to the roughness, which has been developed previously for SH-wave propagation over a single plate with a rough surface. This approach assumes that the average roughness height is a small fraction of the thicknesses of the waveguides (the plates) everywhere. The changes, due to the roughness, in the characteristics of the fields created by a harmonic source set at the entrance edge of the structure are expressed through the mapping of the displacement and stress perturbations. Preliminary tests of the effectiveness of the model are given; they rely on the phase-matching effects of periodic profiles and pseudo-random experimental profile.

  6. Microstructural Characterization of the U-9.1Mo Fuel/AA6061 Cladding Interface in Friction-Bonded Monolithic Fuel Plates Irradiated in the RERTR-6 Experiment

    NASA Astrophysics Data System (ADS)

    Keiser, Dennis D.; Jue, Jan-Fong; Miller, Brandon; Gan, Jian; Robinson, Adam; Medvedev, Pavel; Madden, James; Wachs, Dan; Clark, Curtis; Meyer, Mitch

    2015-09-01

    Low-enrichment (235U < 20 pct) U-Mo monolithic fuel is being developed for use in research and test reactors. The earliest design for this fuel that was investigated via reactor testing consisted of a nominally U-10Mo fuel foil encased in AA6061 (Al-6061) cladding. For a fuel design to be deemed adequate for final use in a reactor, it must maintain dimensional stability and retain fission products throughout irradiation, which means that there must be good integrity at the fuel foil/cladding interface. To investigate the nature of the fuel/cladding interface for this fuel type after irradiation, fuel plates were fabricated using a friction bonding process, tested in INL's advanced test reactor (ATR), and then subsequently characterized using optical metallography, scanning electron microscopy, and transmission electron microscopy. Results of this characterization showed that the fuel/cladding interaction layers present at the U-Mo fuel/AA6061 cladding interface after fabrication became amorphous during irradiation. Up to two main interaction layers, based on composition, could be found at the fuel/cladding interface, depending on location. After irradiation, an Al-rich layer contained very few fission gas bubbles, but did exhibit Xe enrichment near the AA6061 cladding interface. Another layer, which contained more Si, had more observable fission gas bubbles. In the samples produced using a focused ion beam at the interaction zone/AA6061 cladding interface, possible indications of porosity/debonding were found, which suggested that the interface in this location is relatively weak.

  7. Influence of Cumulative Boundary-Normal Convergence on Topography and Thrust Fault Development in Oceanic Lithosphere: The Australian-Pacific Plate Boundary South of New Zealand Since 10.9 Ma

    NASA Astrophysics Data System (ADS)

    Meckel, T. A.; Mann, P.; Mosher, S.; Coffin, M. F.

    2004-12-01

    Individual segments of the submarine Australian-Pacific plate boundary south of New Zealand have evolved with unique tectonic histories since ~10.9 Ma (anomaly 5o). This is the direct result of the variable orientation of the boundary and relatively close proximity of the Australian-Pacific poles of rotation. Interaction along the oceanic extent of the plate boundary involves oceanic lithosphere of broadly similar age (i.e. thermal structure), resulting in morphologic and structural differences that can be attributed primarily to the variability in the angle and rate of convergence with respect to the plate boundary orientation over the last 10.9 Ma. We use swath bathymetry data from three cruises to quantify the amount of deformation that has occurred along ~1500 km of the plate boundary south of New Zealand. We calculate volumes of crust within 75 km of the plate boundary to the east and west that are displaced from the average local seafloor depth, and compare those results to plate boundary-normal convergence along the boundary predicted by stage rotations since 5.9 Ma. Plate boundary-normal convergence and topography are compared considering active faulting observed at the seafloor to characterize the geodynamic evolution of the different regions. Analysis reveals that a boundary-normal convergence of ~100 km marks the transition from strike-slip dominated faulting to partitioned underthrusting and strike-slip faulting. We consider the topography and structural development at the Macquarie and McDougall segments of the MRC to reflect failure to initiate subduction, suggesting that topographic relief (deepest trench to ridge crest) at a convergent oceanic boundary can reach ~5 km before initiation, which could take 5.9 m.y. These estimates provide observational constraints for the deformation processes involved in the poorly understood topic of subduction initiation, and should be incorporated in numerical modeling of such processes in similar settings.

  8. Geochemical and tectonic implications on plate-interface evolution achieved from high-pressure ultramafic rocks in mélange settings

    NASA Astrophysics Data System (ADS)

    Cannaò, E.; Agostini, S.; Scambelluri, M.; Tonarini, S.

    2014-12-01

    Geochemical studies of fluid-mobile elements (FME) joined with B, Sr and Pb isotopic analyses of high-pressure mélanges terranes help constraining tectonic processes and mass transfer during accretion of slab and suprasubduction mantle in plate-interface domains. Here we focus on ultramafic rocks from two plate interface settings: (I) metasediment-dominated mélange (Cima di Gagnone, CdG, Adula Unit), where eclogite-facies de-serpentinized garnet peridotite and chlorite harzburgite lenses are embedded in paraschist; (II) dominated by high-pressure serpentinite (Erro-Tobbio, ET, and Voltri Units, VU, Ligurian Alps). CdG metaperidotite shows low [B], negative δ 11B and high Sr and Pb isotopic ratios. As, Sb loss from metasediment and gain by garnet and chlorite metaperidotite points to exchange between the two systems. Presence of As and Sb in eclogite-facies peridotite minerals and preferential low-T mobility of such elements suggest that exchange was during early subduction burial and prior to eclogitization. Based on high [B], positive δ11B, oxygen and hydrogen isotope, the ET serpentinties were recently interpreted as supra-subduction mantle flushed by slab fluids (Scambelluri & Tonarini, 2012, Geology, 40, 907-910). Their 206Pb/204Pb and 87Sr/86Sr isotope ratios range between 18.300-18.514 and 0.7048-0.7060, respectively. Compared with ET rocks, VU serpentinites have higher As, Sb (up to 1.3 and 0.39 ppm, respectively) and are enriched in radiogenic Sr (up to 0.7105 87Sr/86Sr). This signature reflects interaction with fluids that exchanged with sedimentary rocks, either in outer rise environments or during accretion atop the slab. In the above cases, the serpentinized mantle rocks fingerprint interaction with fluids from different sources, indicating a timing of accretion to plate interface domains. We provide evidence that serpentinized mantle slices of different size and provenance (slab or wedge) accreted to plate interface domains since early subduction stages. They also represent FME and radiogenic isotope sources for arcs and for deep mantle refertilization.

  9. Constraints on the plate interface at the Alaska-Aleutian subduction zone from MCS and OBS data of the ALEUT Project

    NASA Astrophysics Data System (ADS)

    Bécel, Anne; Shillington, Donna J.; Nedimovic, Mladen R.; Kuehn, Harold; Webb, Spahr C.

    2013-04-01

    In summer 2011, the Alaska Langseth Experiment to Understand the megaThrust (ALEUT) program acquired deep penetration multichannel seismic (MCS) reflection and ocean bottom seismometer (OBS) data along a part of the Aleutian-Alaska subduction zone that exhibits the full spectrum of coupling, from locked to freely slipping. The aim of this program is to characterize variations in the geometry and properties of the plate interface and relate them to downdip and along-strike changes in slip behavior and seismogenesis. Our study encompassed 1) the freely slipping Shumagin Gap; 2) the locked Semidi segment, which last ruptured in 1938, and 3) the locked western Kodiak asperity, the western extent of the 1964 M9.2 rupture. We acquired 3700 km of MCS data with the R/V Langseth along a series of strike and dip profiles that span the entire locked zone on the megathrust, its updip and downdip transitions to stable sliding and bending of the downgoing plate. MCS Data were acquired with a 6600 cu.in. airgun array and two 8-km-long streamers. Refraction data were acquired using the same source and short period OBS spaced at ~15 km along two ~400-km profiles coincident with MCS data across the Shumagin Gap and Semidi segment. Here we present results from MCS and OBS data regarding the plate interface reflectivity, geometry and dimensions as well as the structure and hydration of the downgoing plate. MCS data from all the dip profiles reveal reflections from the interplate interface from the trench, at ~7-8 s twtt or 5.5-6.0 km depth, to 120 km landward of the trench, at 10-12s twtt or 30-40 km depth, with high variation in its reflection response with depth. The downdip transition from the potentially locked region to stable sliding seems to be marked by a change in the plate interface reflection signature itself from a single reflection at shallower depth to a wide zone of reflectivity of up to a few seconds twtt at greater depth. Accretionary prism structure varies along strike but is quite narrow (~ 15-25 km) on all the profiles suggesting an erosive character of the margin before it became an accretionary margin. Above, or seaward of the transition from coupling to stable sliding, the decollement is not characterized by a continuous single reflection but rather consists of several strong reflection sections, especially within the Shumagin gap. Other reflections in the overriding plate appear to delineate one or more large faults are observed 75 km back from the trench and appear to connect to the plate interface within this gap at ~11 s twtt. These faults are associated with a large basin and 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 accommodate other types of motion during its history.Seaward of the trench, MCS data exhibit significant along-strike variations in the structure of the downgoing plate. Pronounced bending faulting, thin sediments (~0.5 km), rougher basement topography and clear Moho reflections are observed in oceanic lithosphere subducting in the weakly coupled Shumagin Gap, while less bending-related deformation and Moho reflectivity and thicker sediment thickness (~1.25 km) is associated with the subducting plate in the Semidi segment. The change in sediment thickness appears to be related to changes in the thickness of sediment being carried into the subduction zone near the plate boundary and in the style of deformation of the accretionary prism. These structural variations between the Shumagin gap and Semidi segment are accompanied by differences in the velocity structure of the downgoing plate based on OBS data. Reduced mantle velocities and altered crustal velocities in the oceanic plate are observed in the Shumagin Gap as it bends and subducts possibly due to hydration. Preliminary analysis suggests more modest decreases in mantle velocities in the Semidi segment, where less bending related faulting is observed. These along-strike variations in the structure of the downgoing plate can impact the conditions at the megathrust and the delivery of water and other volatiles to the seismogenic zone and to deeper levels of the subduction zone, where they may influence arc magmatism and intermediate depth seismicity.

  10. Neotectonic studies of northern Baja California, Mexico, with LANDSAT thematic mapper and SPOT panchromatic imagery: Partitioning of dextral and extensional strain at the Pacific-North America plate boundary

    NASA Technical Reports Server (NTRS)

    Miller, M. Meghan; Crippen, Robert E.; Dixon, Timothy H.

    1991-01-01

    Numerous studies of active faulting in southern California indicate that the San Jacinto, Elsinore, and adjacent faults west of the San Andreas fault accommodate a significant proportion of Pacific-North America relative plate motion. Because of the complex distribution of slip, little is known about the activities of these and similar structures in northern Baja California and the southward transition to the oceanic ridge transform-fault system in the Gulf of California. SPOT and LANDSAT Thematic Mapper imagery for northern Baja California was processed to optimize discrimination of lithologic and structural features. This data was used to suggest a preliminary kinematic framework for distribution of relative plate motion between 31 and 33 degrees north, in which continental borderland tectonics play an important role in partitioning of plate motion.

  11. New Insights into Strain Accumulation and Release in the Central and Northern Walker Lane, Pacific-North American Plate Boundary, California and Nevada, USA

    NASA Astrophysics Data System (ADS)

    Bormann, Jayne M.

    The Walker Lane is a 100 km-wide distributed zone of complex transtensional faulting that flanks the eastern margin of the Sierra Nevada. Up to 25% of the total Pacific-North American relative right-lateral plate boundary deformation is accommodated east of the Sierra Nevada, primarily in the Walker Lane. The results of three studies in the Central and Northern Walker Lane offer new insights into how constantly accumulating plate boundary shear strain is released on faults in the Walker Lane and regional earthquake hazards. This research is based on the collection and analysis of new of geologic and geodetic datasets. Two studies are located in the Central Walker Lane, where plate boundary deformation is accommodated on northwest trending right-lateral faults, east-northeast trending left-lateral faults, and north trending normal faults. In this region, a prominent set of left-stepping, en-echelon, normal fault-bounded basins between Walker Lake and Lake Tahoe fill a gap in Walker Lane strike slip faults. Determining how these basins accommodate shear strain is a primary goal of this research. Paleoseismic and neotectonic observations from the Wassuk Range fault zone in the Walker Lake basin record evidence for at least 3 Holocene surface rupturing earthquakes and Holocene/late Pleistocene vertical slip rates between 0.4-0.7 mm/yr on the normal fault, but record no evidence of right-lateral slip along the rangefront fault. A complementary study presents new GPS velocity data that measures present-day deformation across the Central Walker Lane and infers fault slip and block rotation rates using an elastic block model. The model results show a clear partitioning between distinct zones of strain accommodation characterized by (1) right-lateral translation of blocks on northwest trending faults, (2) left-lateral slip and clockwise block rotations between east and northeast trending faults, and (3) right-lateral oblique normal slip with minor clockwise block rotations on north trending faults. Block model results show that a component of right-lateral slip in the normal-fault bounded basins is required to adequately fit the GPS data. New GPS data from the Northern Walker Lane constrains present-day slip rates on the Mohawk Valley, Grizzly Valley, and Honey Lake fault zones. Block model results predict right-lateral slip rates of 2.2 +/- 0.2 mm/yr for the Mohawk Valley fault and 1.1 +/- 0.4 mm/yr for the Honey Lake fault. The GPS data do not require slip on the Grizzly Valley fault, although right-lateral slip rates up to 1.2 mm/yr are allowed without increasing the block model misfit. The present-day distribution of slip between the Honey Lake and Mohawk Valley faults is opposite that predicted by latest Quaternary and Holocene geologic slip rate estimates. A temporally variable Wallace-type strain release model that includes 104-year timescale variations in fault slip rate could reconcile both datasets.

  12. Implications of subduction and subduction zone migration of the Paleo-Pacific Plate beneath eastern North China, based on distribution, geochronology, and geochemistry of Late Mesozoic volcanic rocks

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Ma, Chang-Qian; Liao, Qun-An; Zhang, Jin-Yang; She, Zhen-Bing

    2011-10-01

    Several major volcanic zones are distributed across the eastern North China Craton, from northwest to southeast: the Greater Xing'an Range, Jibei-Liaoxi, Xishan, and Songliao Basins, and the Yanji, Huanghua, and Ludong volcanic zones. The Huanghua depression within the Bohai Bay Basin was filled by middle Late Mesozoic volcanic rocks and abundant Cenozoic alkaline basalts. Zircon LA-ICP-MS and SHRIMP U-Pb dating show that basic -intermediate volcanic rocks were extruded in the Early Cretaceous of 118.8 ± 1.0 Ma (weighted mean 206Pb/238U age), before Late Cretaceous acid lavas at 71.5 ± 2.6 Ma. An inherited zircon from andesite has a Paleoprotoerozoic core crystallization age of 2,424 ± 22 Ma (206Pb/207Pb age) indicating that the basement of the Bohai Bay Basin is part of the North China Craton. Early Cretaceous basic and intermediate lavas are characterized by strong enrichments in LREE and LILE and depletions in HREE and HFSE, indicating a volcanic arc origin related to oceanic subduction. Depletion in Zr only occurs in basic and intermediate volcanic rocks, while depletions in Sr and Ti exist only in acid samples, indicating that the acid series is not genetically related to the basic-intermediate series. Formation ages and geochemical features indicate that the Late Cretaceous acid lavas are products of crustal remelting in an extensional regime. Combined information from all these volcanic zones shows that subduction-related volcanic rocks were generated in the Jibei-Liaoxi and Xishan volcanic zones during the Early Jurassic, about 60 Ma earlier than their analogues extruded in the Huanghua and Ludong volcanic zones during the Early Cretaceous. This younging trend also exists in the youngest extension-related volcanism in each of these zones: Early Cretaceous asthenosphere-derived alkaline basalts in the northwest and Late Cretaceous in the southeast. A tectonic model of northwestward subduction and continuous oceanward retreat of the Paleo-Pacific Plate is proposed to explain the migration pattern of both arc-related and post-subduction extension-related volcanic rocks. As the subduction zone continuously migrated, active continental margin and backarc regimes successively played their roles in different parts of North China during the Late Mesozoic (J1-K2).

  13. Plating Tank Control Software

    Energy Science and Technology Software Center (ESTSC)

    1998-03-01

    The Plating Tank Control Software is a graphical user interface that controls and records plating process conditions for plating in high aspect ratio channels that require use of low current and long times. The software is written for a Pentium II PC with an 8 channel data acquisition card, and the necessary shunt resistors for measuring currents in the millampere range.

  14. The rupture pattern of the 2011 Tohoku earthquake and its relationship to the properties of the plate interface of the Northeastern Japan Arc

    NASA Astrophysics Data System (ADS)

    Zhang, H.; Ding, L.; Ge, Z.

    2011-12-01

    High-quality vertical component seismograms of teleseismic P waves recorded at 151 stations from the European seismic network have been used to image the rupture process of the 2011 Tohoku earthquake rapidly by a two-step back projection method. The spatio-temporal distribution of rupture fronts suggests that the earthquake ruptured northeastwards and southwestwards over a total length of over 340 km during at least 143 sec (as shown in Fig. 1). Three sub-events comprised of the Tohoku earthquake. The first sub-event ruptured northeastwards in the first 25 sec, and then turned to the northwest direction. The second sub-event ruptured at a relatively high rate of 2.78-4.70 km/s. The third sub-event ruptured with a direction variation from southwest to southeast near the latitude of 37 deg. In addition, considering that the first front of the second sub-event appeared at 74.6 sec and was about 28 km away from the epicenter, we propose that the second sub-event might have been triggered by the localized increase in tectonic stress in the vicinity of the hypocenter that resulted from the rupture of the first sub-event. Moreover, most of the rupture pattern, such as the average rupture velocities and the high-frequency energy bursts of sub-events can be associated with the lateral heterogeneities of the P and S wave velocity and Poisson's ratio (PR) structures well investigated by tomographic imaging (Zhao et al., 2007) on the plate interface of the Northeast Japan Arc. Therefore, the velocity and Passion's ratio of the plate interface may play a very significant role in the rupture of the 2011 Tohoku earthquake.

  15. Loss of implant-bone interface following distal radial locking-plate endoprosthesis limb-sparing surgery in a dog.

    PubMed

    Venzin, C; Grundmann, S; Montavon, P M

    2012-01-01

    An eight-year-old, neutered female Rottweiler was presented with lameness of seven days duration. Radiographs were consistent with a distal radial bone tumour. Limb-sparing surgery was performed using a commercially available endoprosthesis with a locking bone plate. Histopathological examination of the resected bone revealed an intraosseous fibrosarcoma, and postoperative adjuvant chemotherapy was initiated three weeks after surgery. Despite initial satisfactory limb function, lameness worsened four months after surgery. Radiographs revealed large areas of bone lysis around the proximal and distal screws, leading to significant resorption of the radius and radial carpal bone with subsequent construct failure. Further treatment was declined by the owner and the dog was subsequently euthanased. This case illustrates that implant failure is not necessarily averted by the use of locking (compared with non-locking) implants combined with an endoprosthesis to treat distal radial tumours in dogs. PMID:22098022

  16. Fault kinematics in northern Central America and coupling along the subduction interface of the Cocos Plate, from GPS data in Chiapas (Mexico), Guatemala and El Salvador

    NASA Astrophysics Data System (ADS)

    Franco, A.; Lasserre, C.; Lyon-Caen, H.; Kostoglodov, V.; Molina, E.; Guzman-Speziale, M.; Monterosso, D.; Robles, V.; Figueroa, C.; Amaya, W.; Barrier, E.; Chiquin, L.; Moran, S.; Flores, O.; Romero, J.; Santiago, J. A.; Manea, M.; Manea, V. C.

    2012-06-01

    New GPS measurements in Chiapas (Mexico), Guatemala and El Salvador are used to constrain the fault kinematics in the North America (NA), Caribbean (CA) and Cocos (CO) plates triple junction area. The regional GPS velocity field is first analysed in terms of strain partitioning across the major volcano-tectonic structures, using elastic half-space modelling, then inverted through a block model. We show the dominant role of the Motagua Fault with respect to the Polochic Fault in the accommodation of the present-day deformation associated with the NA and CA relative motion. The NA/CA motion decreases from 18-22 mm yr-1 in eastern Guatemala to 14-20 mm yr-1 in central Guatemala (assuming a uniform locking depth of 14-28 km), down to a few millimetres per year in western Guatemala. As a consequence, the western tip of the CA Plate deforms internally, with ≃9 mm yr-1 of east-west extension (≃5 mm yr-1 across the Guatemala city graben alone). Up to 15 mm yr-1 of dextral motion can be accommodated across the volcanic arc in El Salvador and southeastern Guatemala. The arc seems to mark the northern boundary of an independent forearc sliver (AR), pinned to the NA plate. The inversion of the velocity field shows that a four-block (NA, CA, CO and AR) model, that combines relative block rotations with elastic deformation at the block boundaries, can account for most of the GPS observations and constrain the overall kinematics of the active structures. This regional modelling also evidences lateral variations of coupling at the CO subduction interface, with a fairly high-coupling (≃0.6) offshore Chiapas and low-coupling (≃0.25) offshore Guatemala and El Salvador.

  17. The Fairway-Aotea Basin and the New Caledonia Trough, witnesses of the Pacific-Australian plate boundary evolution : from mid-Cretaceous cessation of subduction to Eocene subduction renewal

    NASA Astrophysics Data System (ADS)

    Collot, J.; Geli, L. B.; Lafoy, Y.; Sutherland, R.; Herzer, R. H.; Roest, W. R.

    2009-12-01

    The geodynamical history of the SW Pacific is controlled since the Mesozoic by the evolution of peri-Pacific subduction zones, in a trench retreat by slab roll-back process, which successively occurred along the Eastern Gondwana margin. In this context, most basins which formed after 45 Ma reached a stage of seafloor spreading, have recorded the inversions of the earth's magnetic field and present typical oceanic crust morphologies. By contrast, the New Caledonia and Fairway basins, which are narrower and present thick sedimentary covers have a less known and more controversial origin. Based on a regional geological synthesis and on interpretation of multichannel seismic reflection and refraction data, combined with drill hole data off New Zealand and a compilation of regional potential data, we distinguish 2 phases of the evolution of the Fairway-Aotea Basin (FAB) and the New Caledonia Trough (NCT), which reflect the evolution of the Gondwana-Pacific plate boundary: Phase 1: Mid Cretaceous formation of the FAB in a continental intra- or back- arc position of the Pacific-Gondwana subduction system. The formation of this shallow basin reflects the onset of continental breakup of the Eastern Gondwana margin during Cenomanian which was most probably caused by a dynamic change of the subduction zone through a verticalization of the slab. This event may be the result of the 99 Ma kinematic plate reorganization which probably led to subduction cessation along the Gondwana-Pacific plate boundary. A tectonic escape mechanism, in relation with the locking of the subduction zone by the Hikurangi Plateau, could also be responsible of the trench retreat leading to backarc extension. Phase 2: Regional Eocene-Oligocene uplift followed by rapid subsidence (3-4 km) of the system Lord Howe Rise - FAB - Norfolk Ridge . The structural style of this deformation leads us to suggest that detachment of the lower crust is the cause of subsidence. We therefore propose a model in which the system, initially shallow during Cretaceous (phase 1), would have greatly subsided during Eocene-Oligocene, giving birth to the NCT, as the renewal of the Australia-Pacific convergent plate boundary took place. This renewal of convergence at 45 Ma would have driven the lithosphere of the system to thicken (uplift), leading to a root instability and to its detachment in the mantle (subsidence). Superposed on these two main phases, some local effects, controlled by the geometry of the plate boundary, also appear. Particularly, latest late Eocene local deformation of the Northern NCB is documented, synchronously with the New Caledonian obduction. This asymmetrical deformation which lasted less than a few million years led to the uplift of the Fairway Ridge and the subsidence of the Eastern margin of the basin along NCs western coast (10 km vertical amplitude). We suggest that as the oceanic crust of the South Loyalty Basin was being obducted onto the Norfolk Ridge at 37 Ma, the NCB subsided under the effect of the overloading and underthrusted to accommodate the compressional deformation as a foreland flexural basin.

  18. The Turbulent Boundary Layer Near the Air-Water Interface on a Surface-Piercing Flat Plate

    NASA Astrophysics Data System (ADS)

    Washuta, Nathan; Masnadi, Naeem; Duncan, James H.

    2015-11-01

    Turbulent fluctuations in the vicinity of the water free surface along a flat, vertically oriented surface-piercing plate are studied experimentally using a laboratory-scale experiment. In this experiment, a meter-wide stainless steel belt travels horizontally in a loop around two rollers with vertically oriented axes, which are separated by 7.5 meters. This belt device is mounted inside a large water tank with the water level set just below the top edge of the belt. The belt, rollers, and supporting frame are contained within a sheet metal box to keep the device dry except for one 6-meter-long straight test section between rollers. The belt is launched from rest with a 3- g acceleration in order to quickly reach steady state velocity. This creates a temporally evolving boundary layer analogous to the spatially evolving boundary layer created along a flat-sided ship moving at the same velocity, with a length equivalent to the length of belt that has passed the measurement region since the belt motion began. Cinematic Stereo PIV measurements are performed in planes parallel to the free surface by imaging the flow from underneath the tank in order to study the modification of the boundary layer flow field due to the effects of the water free surface. The support of the Office of Naval Research under grant N000141110029 is gratefully acknowledged.

  19. Monitoring of slip at the transition zone on the plate interface estimated from non-volcanic deep low-frequency tremors in southwestern Japan

    NASA Astrophysics Data System (ADS)

    Ishida, R.; Hiramatsu, Y.; Obara, K.; Matsuzawa, T.

    2011-12-01

    In southwestern Japan, non-volcanic deep low-frequency (DLF) tremors (e.g., Obara, 2002) and short-term slow slip events (S-SSEs; e.g., Obara et al., 2004) occur in temporal and spatial coincidence with the active stages of DLF tremors (Obara et al., 2004). Based on this feature, Hiramatsu et al. (2008) proposed a method to monitor slip at the transition zone between the locked and aseismic slip zones on the plate interface using DLF tremors. In this study, we applied the method as the same way of previous studies (Hiramatsu et al., 2008; Hirose et al., 2010) and estimated the long-term average slip rate at the transition zone from DLF tremors in southwestern Japan. We also estimated the slip distributions of S-SSEs from DLF tremors using the modified envelope correlation method (ECM) tremor catalog (Maeda and Obara, 2009) and the hourly centroid tremor catalog (Obara et al., 2010) along with the ECM tremor catalog (Obara, 2002) in southwestern Japan. The modified ECM applied both the differential travel time and the spatial distribution of mean square amplitudes to estimate a tremor's spatial location and radiation energy. The hourly centroid tremor catalog is constructed using a clustering process to estimate centroid locations, revealing clear depth-dependent behavior of the tremor activity. The cumulative seismic moment from 2001 to 2009 increases at a constant rate, indicating a constant moment release rate in the long-term average. We estimated slip rate at the transition zone using the formula ˙ {M0} = μ S_˙ {U}, where ˙ {M0} is the moment release rate, μ the rigidity, S the fault area that is related to the slip of S-SSEs in each region, and ˙ {U} the slip rate. We obtained the slip rates of 4.1 ± 0.5 cm/yr, 3.7 ± 0.6 cm/yr, and 2.6 ± 0.2 cm/yr in the western Shikoku, northern Kii peninsula, and Tokai regions, respectively, at the transition zone through the analyzed period. The slip deficit rate at the transition zone in each region is 2.6cm/yr, 2.6cm/yr, and 1.5cm/yr, respectively (Kobayashi and Hashimoto, 2007; Tabei et al., 2007; Suito and Ozawa, 2009). The convergence rate of the Philippine Sea plate in each region is estimated to be 6.3-6.8 cm/yr, 5.0-6.5 cm/yr, and 3.0-4.0 cm/yr (Miyazaki and Heki, 2001; Hori et al., 2004). The estimated slips at the transition zone therefore compensate the difference between the convergence rate at the trench and the slip deficit rate at the transition zone of the subducting Philippine Sea plate. For the slip distributions of the S-SSEs, we assumed sub-faults with uniform slip on the plate interface and estimated the slip from the cumulative seismic moment in each sub-fault. As the result, the slip distribution of most S-SSEs correlates roughly with the slip distribution estimated from the inversion of tilt meter records (Hirose and Obara, 2010), indicating that this procedure is useful to determine the slip distribution of S-SSEs quickly and easily.

  20. Suloy, Pacific Ocean

    NASA Technical Reports Server (NTRS)

    1992-01-01

    A demarcation line identifies a convergence in the Pacific Ocean (1.5N, 133.0W) where two open ocean currents have interfaced. This interface phenomena was first observed in the White Sea by Soviet cosmonauts who coined the term `Suloy' to describe the event. At the actual interface, there is usually a slight upwelling as the currents clash, causing a shadow effect that can be observed and an audible hissing sound as the currents meet head on.

  1. A new regime of slab-mantle coupling at the plate interface and its possible implications for the distribution of volcanoes

    NASA Astrophysics Data System (ADS)

    Morishige, Manabu

    2015-10-01

    We investigate the effects of a thin, low viscosity layer just above the subducting slab on 3D thermal and flow structure in the mantle wedge by taking Northeast Japan as an example. The low viscosity layer assumed here is needed to explain the observed low surface heat flow and low seismic attenuation in the forearc by decoupling the mantle from the subducting slab. We find that when the viscosity in the low viscosity layer is sufficiently low, along-arc component of the flow arises inside the layer and produces along-arc temperature variation. It can also be considered as the along-arc changes in the degree of slab-mantle coupling at the plate interface. The onset time and the characteristic wavelength of the 3D flow depend on the viscosity and the extent of the low viscosity layer. In order to explain the observed spatial and temporal changes in the distribution of Quaternary volcanoes in Northeast Japan, the viscosity and the thickness of the low viscosity layer need to be < 5 ×1018 Pas and ˜6 km, respectively. The model proposed here is based on an assumption which is simpler and better constrained by observations compared to previous models. Therefore, it could be an alternative explanation of the distribution of volcanoes in Northeast Japan.

  2. Investigations on the micro-scale surface interactions at the tool and workpiece interface in micro-manufacturing of bipolar plates for proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Peker, Mevlut Fatih

    Micro-forming studies have been more attractive in recent years because of miniaturization trend. One of the promising metal forming processes, micro-stamping, provides durability, strength, surface finish, and low cost for metal products. Hence, it is considered a prominent method for fabricating bipolar plates (BPP) with micro-channel arrays on large metallic surfaces to be used in Proton Exchange Membrane Fuel Cells (PEMFC). Major concerns in micro-stamping of high volume BPPs are surface interactions between micro-stamping dies and blank metal plates, and tribological changes. These concerns play a critical role in determining the surface quality, channel formation, and dimensional precision of bipolar plates. The surface quality of BPP is highly dependent on the micro-stamping die surface, and process conditions due to large ratios of surface area to volume (size effect) that cause an increased level of friction and wear issues at the contact interface. Due to the high volume and fast production rates, BPP surface characteristics such as surface roughness, hardness, and stiffness may change because of repeated interactions between tool (micro-forming die) and workpiece (sheet blank of interest). Since the surface characteristics of BPPs have a strong effect on corrosion and contact resistance of bipolar plates, and consequently overall fuel cell performance, evolution of surface characteristics at the tool and workpiece should be monitored, controlled, and kept in acceptable ranges throughout the long production cycles to maintain the surface quality. Compared to macro-forming operations, tribological changes in micro-forming process are bigger challenges due to their dominance and criticality. Therefore, tribological size effect should be considered for better understanding of tribological changes in micro-scale. The integrity of process simulation to the experiments, on the other hand, is essential. This study describes an approach that aims to investigate the surface topography changes during long-run micro-stamping of BPPs, and establish relationships between surface roughness--corrosion resistance and surface roughness-contact resistance characteristics of BPPs. Formability levels of formed BPPs and repeatability characteristics of the process were investigated. In addition, blank thickness changes, von-Mises stress, plastic strain levels and distributions of micro-stamping process were determined via finite element analysis (FEA). Test results revealed that the surface roughness change for the stamping dies and BPPs was unsteady (no trend) due to the continuous change of surface topography (i.e. asperity deformation). Sub-micron range local plastic deformations on stamping dies led to surface topography changes on BPP in long-run manufacturing case. As surface defects trigger corrosion, the correlation between surface roughness and corrosion resistance of BPPs was found to be direct. Increasing number of surface irregularities (asperities) lowered contact surface area that resulted in increased contact resistance. ZrN coated BPPs, on the other hand, did not change surface roughness, however; it improved the protection of BPPs against corrosion significantly. In addition, ZrN coating increased the conductivity of BPPs and reduced the contact resistance between BPP and gas diffusion layer (GDL), at certain extent. As dimensional stability and repeatability was confirmed in forming of both uncoated and coated BPPs during the long run manufacturing, different formability levels were achieved for coated and uncoated samples. Lower channel height values were obtained for coated plates because of the different surface hardness of uncoated and coated plates. In tribological size effect part of study, micro stamping experiments using three different dies with distinct channel height values at different stamping force levels were performed. It was concluded that decrease in forming die dimensions led to increase in coefficient of friction as previously reported by other researchers as one of the consequences of tribological size effect. On the other hand, coefficient of friction values were not affected by the force levels used in the experiments and simulations, whereas plastic strain, equivalent stress, and formability levels were increased with increasing stamping force, as expected. In essence, this study proposed a methodology to investigate the long-run manufacturing effects on dimensional stability and surface characteristics of micro-stamped sheets. It also correlates these parameters to fuel cell performance measures such as interfacial contact and corrosion resistance.

  3. Seismicity near the slip maximum of the 1960 Mw 9.5 Valdivia earthquake (Chile): Plate interface lock and reactivation of the subducted Valdivia Fracture Zone

    NASA Astrophysics Data System (ADS)

    Dzierma, Yvonne; Thorwart, Martin; Rabbel, Wolfgang; Siegmund, Claudia; Comte, Diana; Bataille, Klaus; Iglesia, Paula; Prezzi, Claudia

    2012-06-01

    Understanding the processes behind subduction-related hazards is an important responsibility and major challenge for the Earth sciences. Few areas demonstrate this as clearly as south-central Chile, where some of the largest earthquakes in human history have occurred. We present the first observation of local seismicity in the Villarrica region (39°-40°S), based on a temporary local network of 55 stations installed from the Chilean coast into the Argentinian back-arc for one year. While consistent with the Chilean national catalog (SSN), our results allow us to observe smaller magnitudes with a completeness of about 2.0 and image the geometry of the Wadati-Benioff Zone from the Chile Trench down to 200 km. Offshore, a gap in interplate seismicity is observed in the region of the 1960 Valdivia earthquake slip. Above the interface, two offshore seismicity clusters possibly indicate ongoing stress relaxation. In the subducting Nazca Plate, we find a prominent seismicity cluster along the extrapolated trace of the oceanic Valdivia Fracture Zone (VFZ). The seismicity cluster is observed between 70 and 130 km depth and comprises mainly strike-slip events. It indicates weakening and reactivation of the major VFZ by dehydration of oceanic crust and mantle. Interpreting the subducted VFZ section as a localized reservoir of potential fluid release offers an explanation for the Villarrica volcanic complex that is located above the reactivated VFZ and shows the highest volcanic activity in South America. Crustal seismicity is observed near Puyehue volcano, which recently started to erupt (June 2011).

  4. 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.

  5. Channel plate for DNA sequencing

    DOEpatents

    Douthart, Richard J.; Crowell, Shannon L.

    1998-01-01

    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.

  6. Influence of elastomeric seal plate surface chemistry on interface integrity in biofouling-prone systems: Evaluation of a hydrophobic "easy-release" silicone-epoxy coating for maintaining water seal integrity of a sliding neoprene/steel interface

    NASA Astrophysics Data System (ADS)

    Andolina, Vincent L.

    The scientific hypothesis of this work is that modulation of the properties of hard materials to exhibit abrasion-reducing and low-energy surfaces will extend the functional lifetimes of elastomeric seals pressed against them in abrasive underwater systems. The initial motivation of this work was to correct a problem noted in the leaking of seals at major hydropower generating facilities subject to fouling by abrasive zebra mussel shells and extensive corrosion. Similar biofouling-influenced problems can develop at seals in medical devices and appliances from regulators in anesthetic machines and SCUBA diving oxygen supply units to autoclave door seals, injection syringe gaskets, medical pumps, drug delivery components, and feeding devices, as well as in food handling equipment like pasteurizers and transfer lines. Maritime and many other heavy industrial seal interfaces could also benefit from this coating system. Little prior work has been done to elucidate the relationship of seal plate surface properties to the friction and wear of elastomeric seals during sliding contacts of these articulating materials, or to examine the secondary influence of mineralized debris within the contacting interfaces. This investigation utilized the seal materials relevant to the hydropower application---neoprene elastomer against carbon steel---with and without the application of a silicone-epoxy coating (WearlonRTM 2020.98) selected for its wear-resistance, hydrophobicity, and "easy-release" capabilities against biological fouling debris present in actual field use. Analytical techniques applied to these materials before and after wear-producing processes included comprehensive Contact Angle measurements for Critical Surface Tension (CA-CST) determination, Scanning Electron Microscopic inspections, together with Energy Dispersive X-ray Spectroscopy (SEM-EDS) and X-Ray Fluorescence (XRF) measurements for determination of surface texture and inorganic composition, Multiple Attenuated Internal Reflection (MAIR-IR) and Microscopic Infrared Spectroscopy for organic surface compositional details, light microscopy for wear area quantification, and profilometry for surface roughness estimation and wear depth quantification. Pin-on-disc dynamic Coefficient of Friction (CoF) measurements provided data relevant to forecasts of seal integrity in dry, wet and biofouling-influenced sliding contact. Actual wear of neoprene seal material against uncoated and coated steel surfaces, wet and dry, was monitored after both rotary and linear cyclic wear testing, demonstrating significant reductions in elastomer wear areas and depths (and resultant volumes) when the coating was present. Coating the steel eliminated a 270% increase in neoprene surface area wear and an 11-fold increase in seal abrasive volume loss associated with underwater rusting in rotary experiments. Linear testing results confirm coating efficacy by reducing wear area in both loading regimes by about half. No coating delamination was observed, apparently due to a differential distribution of silicone and epoxy ingredients at the air-exposed vs. steel-bonded interfaces demonstrated by IR and EDS methods. Frictional testing revealed higher Coefficients of Friction (CoF) associated with the low-speed sliding of Neoprene over coated rather than uncoated steel surfaces in a wet environment, indicating better potential seal adhesion between the hydrophobic elastomer and coating than between the elastomer and intrinsically hydrophilic uncoated steel. When zebra mussel biofouling debris was present in the articulating joints, CoF was reduced as a result of a water channel path produced between the articulating surfaces by the retained biological matter. Easier release of the biofouling from the low-CST coated surfaces restored the seal integrity more rapidly with further water rinsing. Rapid sliding diminished these biofouling-related differences, but revealed a significant advantage in reducing the CoF of the elastomer-on-coating couples to less than 50% of the elastomer-on-steel couples in all conditions. These consolidated results indicate that general improvements in maintenance of seal integrity and functional lifetimes for other sliding joints exposed to potentially abrasive biofouling media can be obtained by coating the more-rigid seal-plate surfaces with low-CST, hydrophobic, wear-resistant materials such as the silicone-epoxy system characterized here.

  7. Recent plate motions and crustal deformation

    SciTech Connect

    Lisowski, M. )

    1991-01-01

    Reports by U.S. workers on geodetic measurements of recent plate motions or crustal deformation published in 1987-1990 are reviewed. The review begins with global plate motions, proceeds through plate boundaries in California, Alaska, and the Pacific Northwest, and finishes with volcanic phenomena, monument stability and longevity, and GPS relative position measurements. 184 refs.

  8. Refined Views of Strike-slip Fault Zones, Seismicity, and State of Stress Associated With the Pacific-North America Plate Boundary in Southern California

    NASA Astrophysics Data System (ADS)

    Hauksson, E.; Nicholson, C.; Shaw, J. H.; Plesch, A.; Shearer, P. M.; Sandwell, D. T.; Yang, W.

    2013-12-01

    The mostly strike-slip plate boundary in southern California is expressed as a system of late Quaternary faults or principal slip zones (PSZs), with numerous adjacent smaller slip surfaces. It is complex, even after large cumulative displacements, and consists of major fault systems with multi-stranded, non-planar fault geometry, including some in close proximity to each other. There are also secondary cross faults and low-angle detachments that interact with the PSZs accommodating main plate boundary motion. The loading of plate-tectonic strain causes the largest earthquakes along PSZs, moderate-sized events in their immediate vicinity, and small earthquakes across the whole region. We apply relocated earthquake and refined focal mechanism (1981-2013) catalogs, as well as other geophysical datasets to provide refined views of the 3D fault geometry of these active fault systems. To determine properties of individual fault zones, we measure the Euclidian distance from every hypocenter to the nearest PSZ. In addition, we assign crustal geophysical parameters such as heat flow value and shear or dilatation strain rates to each epicenter. We investigate seismogenic thickness and fault zone width as well as earthquake source processes. We find that the seismicity rate is a function of location, with the rate dying off exponentially with distance from the PSZ. About 80% of small earthquakes are located within 5 km of a PSZ. For small earthquakes, stress drops increase in size with distance away from the PSZs. The magnitude distribution near the PSZs suggests that large earthquakes are more common close to PSZs, and they are more likely to occur at greater depth than small earthquakes. In contrast, small quakes can occur at any geographical location. An optimal combination of heat flow and strain rate is required to concentrate the strain along rheologically weak fault zones, which accommodate the crustal deformation processes, causing seismicity. The regional trend of the focal mechanism-derived SHmax is almost bimodal, trending almost north along the San Andreas system, and to the north-northeast on either side. The transition zones from one state of stress to the other is sharp, following a trend from Yucca Valley to Imperial Valley to the east, and the western edge of the Peninsular Ranges to the west. Other local scale heterogeneities in the SHmax trend include NNW trends along the San Andreas fault near Cajon Pass, Tejon Pass, and the Cucapah Range. The regional variations in the SHmax trends are very similar to the pattern of GPS-measured maximum shortening axes of the surface strain rate tensor field, although the GPS strain field tends to be smoother and appears also to reflect some of the deformation in the upper mantle.

  9. Imaging the Structure of the Pacific-North American Plate Boundary using Airborne Laser Swath Mapping (ALSM) Data and Wavelet Analysis

    NASA Astrophysics Data System (ADS)

    Sanquini, A.; Cheung, K.; Gudmundsdottir, M. H.; Moon, S.; Lin, N.; Shelef, E.; Hilley, G. E.; Prentice, C. S.

    2011-12-01

    Since the 1906 San Francisco earthquake, geologists have noted that the topography of active fault zones is significantly modified by repeated fault ruptures over geologic time. Here, we present an analysis of fault zone topography generated by high-resolution Airborne Laser Swath Mapping (ALSM) data collected by the National Center for Airborne Laser Mapping (NCALM). The digital elevation models (DEMs) generated from the ALSM data reveal the location, orientation, and curvature of scarps associated with active, plate-boundary faults. In particular, we have examined topographic data from the B4 and Northern California data sets, as well as data from faults within the Eastern California Shear Zone. We used a wavelet-based convolution scheme, based on topographic forms modified from the profile scarp-diffusion model of Hanks et al. (1984), extended to encompass along-strike features. We applied this filtering methodology to digital topography along fault zones to estimate the best-fitting height, orientation, morphologic age, and associated Signal-to-Noise Ratio (SNR) of scarps found within these datasets. These results will be available to the community via a GIS web portal so that other workers can mine these data to understand patterns of fault-zone structure observed along the plate-bounding fault zones. To evaluate the utility of this methodology for identifying and characterizing fault scarps within the topographic swaths, we present sample results from the Calaveras fault, part of the San Andreas fault system in northern California. We found that along this fault, the filtering algorithm correctly identifies scarps characterized by ground surveys, previous analysis of aerial photography, and/or field mapping. However, some mapped fault traces with low SNR values because of their subtle morphologic expression are not identified by the algorithm. Similarly, some fluvial scarps that trend in a similar orientation to the overall fault zone are erroneously identified as fault scarps by the algorithm. Future work includes further refinement and field verification of the method, and eventual application to all on-land faults for which ALSM data are available within the western U.S. plate margin.

  10. Chemical and isotopic diversity in basalts dredged from the East Pacific Rise at 10°S, the fossil Galapagos Rise and the Nazca plate

    USGS Publications Warehouse

    Batiza, Rodey; Oestrike, Richard; Futa, Kiyoto

    1982-01-01

    The dredges from the East Pacific Rise at about 10°S recovered unusual transitional, light rare-earth element (LREE) enriched basalts which show a range of fractionation. On the basis of their chemical and isotopic abundances, it is unlikely that the lavas are related by a single simple process of magmatic differentiation. We suggest that the mantle source region of these basalts was chemically and isotopically heterogeneous. The chemistry of LREE-depleted tholeiitic basalt dredged from near the axis of the extinct Galapagos Rise indicates complex petrogenesis and differentiation. The presence of tholeiitic basalts here indicates that unlike the Guadalupe and Mathematician fossil ridges, the Galapagos Rise has not been the site of voluminous post-abandonment alkalic volcanism. Alkalic basalts of picritic bulk composition dredged from an elongate seamount near the Galapagos Rise do not represent liquid compositions. Instead, we suggest that these alkalic liquids contain added olivine and plagioclase xenocrysts. Although most of the samples analyzed are very fresh, a few have been altered. The latter exhibit characteristic chemical and isotopic effects of seawater alteration.

  11. Early Cretaceous arc volcanic suite in Cebu Island, Central Philippines and its implications on paleo-Pacific plate subduction: Constraints from geochemistry, zircon U-Pb geochronology and Lu-Hf isotopes

    NASA Astrophysics Data System (ADS)

    Deng, Jianghong; Yang, Xiaoyong; Zhang, Zhao-Feng; Santosh, M.

    2015-08-01

    The Philippine island arc system is a collage of amalgamated terranes of oceanic, continental and island arc affinities. Here we investigate a volcanic suite in Cebu Island of central Philippines, including basalt, diabase dike, basaltic pyroclastic rock and porphyritic andesite. LA-ICP-MS U-Pb geochronology of zircon grains from the porphyritic andesite and pyroclastic rock yielded ages of 126 ± 3 Ma and 119 ± 2 Ma, respectively, indicating an Early Cretaceous age. The age distribution of the detrital zircons from river sand in the area displays a peak at ca. 118 Ma, close to the age of the pyroclastic rock. The early Cretaceous volcanic rocks in the central Philippines were previously regarded as parts of ophiolite complexes by most investigators, whereas the Cebu volcanics are distinct from these, and display calc-alkaline affinity and island arc setting, characterized by high LREE/HREE ratios and low HFSE contents. These features are similar to the Early Cretaceous arc basalts in the Amami Plateau and east Halmahera in the northernmost and southernmost West Philippine Basin respectively. Zircon Hf isotopes of the pyroclastic rocks show depleted nature similar to those of the Amami Plateau basalts, implying the subducted Pacific-type MORB as probable source. Zircon Hf isotopes of the porphyritic andesite show slight enrichment relative to that of the pyroclastic rocks and MORB, indicating subducted sediments as a minor end-member in the source. The Hf isotopic compositions of the volcanic rocks are also reflected in the detrital zircons from the river sands. We propose that the volcanic rocks of Cebu Island were derived from partial melting of sub-arc mantle wedge which was metasomatized by dehydration of subducted oceanic crust together with minor pelagic sediments. Within the tectonic environment of Southeast Asia during Early Cretaceous, the volcanic rocks in Cebu Island can be correlated to the subduction of paleo-Pacific plate. The Early Cretaceous volcanic suites in Cebu Island along with the Early Cretaceous arc volcanic rocks, ophiolites and boninites in the southern-western-northern margin of West Philippine Basin are inferred to have formed within single subduction zone before the opening of the Philippine Sea Plate.

  12. Pacific Array

    NASA Astrophysics Data System (ADS)

    Kawakatsu, H.; Takeo, A.; Isse, T.; Nishida, K.; Shiobara, H.; Suetsugu, D.

    2014-12-01

    Based on our recent results on broadband ocean bottom seismometry, we propose a next generation large-scale array experiment in the ocean. Recent advances in ocean bottom broadband seismometry (e.g., Suetsugu & Shiobara, 2014, Annual Review EPS), together with advances in the seismic analysis methodology, have now enabled us to resolve the regional 1-D structure of the entire lithosphere/asthenosphere system, including seismic anisotropy (both radial and azimuthal), with deployments of ~10-15 broadband ocean bottom seismometers (BBOBSs) (namely "ocean-bottom broadband dispersion survey"; Takeo et al., 2013, JGR; Kawakatsu et al., 2013, AGU; Takeo, 2014, Ph.D. Thesis; Takeo et al., 2014, JpGU). Having ~15 BBOBSs as an array unit for 2-year deployment, and repeating such deployments in a leap-frog way (an array of arrays) for a decade or so would enable us to cover a large portion of the Pacific basin. Such efforts, not only by giving regional constraints on the 1-D structure, but also by sharing waveform data for global scale waveform tomography, would drastically increase our knowledge of how plate tectonics works on this planet, as well as how it worked for the past 150 million years. International collaborations might be sought.

  13. Transition from adakitic to bimodal magmatism induced by the paleo-Pacific plate subduction and slab rollback beneath SE China: Evidence from petrogenesis and tectonic setting of the dike swarms

    NASA Astrophysics Data System (ADS)

    Xia, Yan; Xu, Xisheng; Liu, Lei

    2016-02-01

    The late Mesozoic magmatic record of SE China is dominated by felsic volcanics and intrusions. However, this magmatism mainly occurred in coastal areas at 110-80 Ma, in contrast to poorly researched dike swarms that were emplaced inland at 165-120 Ma. Here, we focus on Early Cretaceous mafic and felsic dike swarms that provide new insights into the tectono-magmatic evolution of SE China. The swarms were intruded into Neoproterozoic plutons and include granodioritic porphyry, granitic porphyry, and diabase dikes. The granodioritic porphyry (128 ± 2 Ma) dikes are geochemically similar to adakitic rocks, suggesting that inland adakitic magmatism occurred between ca. 175 and ca. 130 Ma. The majority of these adakitic rocks are calc-alkaline and have Sr-Nd-Hf-O isotopic compositions that are indicative of derivation from a Neoproterozoic magmatic arc source within the lower crust. The granitic porphyry and diabase dikes were emplaced coevally at ca. 130 Ma, and the former contain high alkali and high field strength element (HFSE; e.g., Zr, Nb, Ce, and Y) concentrations that together with their high Ga/Al and FeOT/(FeOT + MgO) ratios imply an A-type affinity. The widespread ca. 130 Ma magmatism that formed the A-type granites and coeval diabase dikes defines a NE-SW trending inland belt of bimodal magmatism in SE China. The presence of mafic enclaves in some of the A-type granites, and the Sr-Nd-Hf isotopic compositions of the latter are indicative of inadequate mixing between the basement sediment-derived and coeval mantle-derived basaltic melts that define the bimodal magmatism. The transition from adakitic rocks to bimodal magmatism in the inland region of SE China indicates a change in the prevailing tectonic regime. This change was associated with an increase in the dip angle of the northwestward-subducting paleo-Pacific Plate beneath SE China between the Middle Jurassic and the Early Cretaceous. This resulted in a transition from a local intra-plate extensional tectonic regime induced by far-distance stress at the plate margin to a back-arc extensional regime induced by rollback of the subducted slab.

  14. Cenozoic reconstruction of southwest Pacific

    SciTech Connect

    Chun, Y.Y.; Kroenke, L.W.

    1986-07-01

    Poles of opening and spreading rates for some of the well-studied marginal basins in the southwest Pacific have been redetermined. Times of opening range from Late Cretaceous-Paleocene in the Tasman basin to middle Pliocene in the Bismarck Sea. The observed magnetic lineations in most of these basins show a relatively short duration of opening and relatively small area of total opening. Most of the smaller basins are bounded by troughs and arcuate island chains, some of which are inferred to be trenches and volcanic arcs situated along paleoconvergent boundaries. At least four successive paleoconvergent boundaries are believed to have formed between the Pacific and the Indian-Australian plates during the Cenozoic. Combining the newly determined poles of opening, spreading rates, and paleoplate boundary locations, a series of palinspastic maps of the southwest Pacific have been constructed for these times, relative to a fixed hot-spot frame of reference for both the Pacific and Indian-Australian plates.

  15. Remote Identification and Characterization of Fault Scarps Along the Pacific-North American Plate Boundary Using Airborne Laser Swath Mapping (ALSM) Data and Wavelet Analysis

    NASA Astrophysics Data System (ADS)

    Sanquini, A.; Hilley, G. E.; Prentice, C. S.

    2012-12-01

    Remote, automatic identification of the location, relative geomorphic age and orientation of possible fault scarps is explored and evaluated by applying wavelet analysis to high-resolution Airborne Laser Swath Mapping (ALSM) topographic data. This methodology compares a scarp model to digital elevation models (DEMs) created from ALSM data collected by the National Center for Airborne Laser Mapping along major faults in California. Fault scarp degradation is modeled using a diffusive transport rule. This modeled topographic form is used to create a wavelet based on the profile curvature of a scarp that is elongated in the out-of-profile dimension and rotated into a wide variety of orientations. This is convolved with the surface curvature computed from the ALSM DEM to isolate areas where the actual topography best conforms to the template. We present results from swaths constructed along active plate-boundary faults, including the Maacama and Rodgers Creek faults, the Calaveras and Paicines faults, the Green Valley fault, the Eastern California Shear Zone, and major sections of the San Andreas fault. In general, we find that this methodology performs well in automatically identifying previously mapped faults and it hints at the existence of faults that are not mapped. The method also identifies scarp forms that are clearly not created by faults, such as those along linear man-made structures and thus is not a fully automated solution. Future work includes quantification of false positive and negative rates of features identified as fault scarps in areas where the fault geometry has been mapped in the field, as well as the creation and application of a methodology that can identify scarps that are produced by multiple offset events.

  16. Pacific Lamprey

    Pacific Lamprey mouth suckers adhered to the glass at Bonneville Dam fish viewing window. The native Pacific Lamprey uses the fish ladder at Bonneville Dam.  This species plays a significant role in the foodweb and in Tribal

  17. Geochronology, geochemistry, and Hf isotopes of Jurassic intermediate-acidic intrusions in the Xing'an Block, northeastern China: Petrogenesis and implications for subduction of the Paleo-Pacific oceanic plate

    NASA Astrophysics Data System (ADS)

    Dong, Yu; Ge, Wen-chun; Yang, Hao; Xu, Wen-liang; Zhang, Yan-long; Bi, Jun-hui; Liu, Xi-wen

    2016-03-01

    Zircon U-Pb dating, whole-rock geochemistry, Hf isotopic compositions, and regional geological observations of Jurassic intermediate-acidic intrusions in the Xing'an Block, northeastern China, are presented to constrain their petrogenesis and the tectonic evolution of the Paleo-Pacific Ocean. Zircon U-Pb age dating indicates that the intrusions were emplaced in three stages: during the Early Jurassic (180-177 Ma), Middle Jurassic (171-170 Ma), and Late Jurassic (∼151 Ma). Despite the wide range in ages of the intrusions, the magmas of Jurassic acidic intrusions were likely derived from a similar or common source and experienced different degrees of magmatic differentiation, as inferred from their geochemical and Hf isotopic characteristics. The Jurassic acidic intrusions are characterized by high SiO2 and total Na2O + K2O, low MgO, and I-type affinities, suggesting that the primary magmas were derived from partial melting of lower crustal material. These findings, combined with their εHf(t) values and two-stage model ages, indicate the primary magmas originated from partial melting of juvenile crustal material accreted during the Neoproterozoic to Phanerozoic. The Middle Jurassic intermediate-acidic rocks (diorites and granodiorites of the TJ pluton) have SiO2 contents of 57.96-69.10 wt.%, MgO contents of 4.48-1.81 wt.%, and high Mg numbers (45-54). They are enriched in large ion lithophile elements (e.g., Rb, Ba, Th, U, and K) and light rare earth elements, depleted in high field strength elements (e.g., Nb, Ta, Zr, Hf, and Ti) and heavy rare earth elements, and have εHf(t) values of +6.5 to +9.1. These data suggest that the magma was derived from partial melting of a depleted mantle wedge that had been metasomatized by subduction-related fluids. According to these findings and previous studies that focused on contemporaneous magmatic-tectonic activity in northeastern China, we conclude that the generation of Jurassic intermediate-acidic intrusions in the Xing'an Block was related to subduction of the Paleo-Pacific oceanic plate.

  18. 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.

  19. Extension rate determination through the analysis of high-resolution LiDAR dataset and cosmogenic dating of the Fish Lake Valley fault zone: Implications for Pacific-North America plate boundary deformation

    NASA Astrophysics Data System (ADS)

    Ganev, P. N.; Dolan, J. F.; Frankel, K. L.; Finkel, R. C.

    2009-04-01

    The oblique normal-dextral Fish Lake valley fault (FLVF) accommodates much of the Pacific-North America plate boundary deformation in the northern part of the eastern California shear zone (ECSZ). New geologic slip rates from FLVF, near the California/Nevada border, provide constraints on the kinematic relationships among the major faults in this complex part of the Pacific-North America plate boundary. Analysis of light detection and ranging (LiDAR) data (1 m horizontal resolution and a decimeter vertical accuracy), coupled with cosmogenic nuclide 10Be geochronology, provides new insights into the late Pleistocene extension rate of this fault system. Right-lateral shear accommodates most of the deformation on the NW-striking FLVF, but fault segments that strike approximately N exhibit predominantly normal slip. This extension is manifest by east- to southeast- and west- to northwest- dipping normal fault scarps cutting late Pleistocene alluvial fans. LiDAR data are crucial to the recognition and analysis of these fault strands, allowing for a comprehensive study of all normal fault scarps that would be otherwise nearly impossible. The high vertical resolution of the LiDAR-derived digital elevation models, plus the ease of analysis using geographic information systems (GIS) software allow for the precise measurement of cumulative scarp heights across numerous scarps. Using these measurements and cosmogenic 10Be dates of the faulted alluvial fans we present the extension rates on the FLVF at four different locations, from south to north: Furnace Creek, Wildhorse Creek, Perry Aiken Creek, and Indian Creek. The vertical component of oblique slip (measured in ArcGIS 9.2 using LiDAR-derived DEMs) along the FLVF at Furnace Creek = 25 ± 1.3 m, Wildhorse Creek = 42 ± 2.1 m, Perry Aiken Creek = 85 ± 4.3 m, and Indian Creek = 75 ± 3.8 m. Previous work by Frankel et al. (2007, GRL) reported cosmogenic nuclide 10Be ages from the offset Furance Creek and Indian Creek alluvial fans of ~94 ka and ~71 ka, respectively. New cosmogenic 10Be dates from the offset alluvial deposits at Wildhorse Creek and Perry Aiken Creek yield ages of ~121 ka and ~71 ka, respectively. Combining displacement from LiDAR data and 10Be geochronology yields a vertical component of slip ranging from 0.3 mm/yr at Furnace Creek and Wildhorse Creek, to the south, to 1.2 mm/yr at Perry Aiken Creek, and 1.1 mm/yr at Indian Creek, to the north. These slip rates are generally in agreement with previous estimates based on alluvial fan morphology, soil development, and theodolite surveys. Assuming a 60° dip for the fault planes, we calculate late Pleistocene extension rates for the FLVF of 0.2, 0.2, 0.7 and 0.6 mm/yr, at the four sites, from south to north. Comparison of these rates with geodetic measurements of ~1 mm/yr of extension across the ECSZ north of the Garlock fault indicate that as much as half of the current rate of east-west extension in this part of western North America is accommodated along the FLVF. Our data also imply an increase in late Pleistocene extension rates from south to north, which is opposite the trend of the dextral slip rate along the FLVF. This discrepancy can be explained by an extensional transition zone in northern Fish Lake Valley that transfers slip between FLVF and the Walker Lane Belt to the north and east, and by westward transfer of slip onto the Saline Valley-Hunter Mountain-Panamint Valley fault system to the south and west. Determining the extension rates of the faults parallel or sub-parallel to the FLVF at the same latitude, such as the White Mountain and Sierra Nevada frontal faults, will further improve our understanding of how slip is accommodated and transferred from the ECSZ into the Walker Lane Belt along this important segment of the Pacific-North America plate boundary.

  20. Interface between Education and State Policy: Australia. Asia and the Pacific Programme of Educational Innovation for Development, Education and Polity, No. 2.

    ERIC Educational Resources Information Center

    Hughes, Phillip; And Others

    One of seven studies in the "Education and Polity" series, this document looks at alternative futures and the interface of education with four areas: communication; employment and leisure; state policy; and technology. The studies were commissioned during 1984 and were conducted by interdisciplinary teams: two in Australia, two in India, one in…

  1. Intermittent Plate Tectonics

    NASA Astrophysics Data System (ADS)

    Silver, P. G.; Behn, M. D.

    2006-12-01

    Intermittent Plate Tectonics A basic premise of Earth Science is that plate tectonics has been continuously operating since it began early in Earth's history. Yet, plate-tectonic theory itself, specifically the collisional phase of the Wilson Cycle, constitutes a process that is capable of stopping all plate motion. The plausibility of a plate-tectonic hiatus is most easily illustrated by considering the expected future of the present-day plate-tectonic configuration. Since the opening of the Atlantic at ~200 ma, the area of the Atlantic basin has been growing at the expense of the Pacific. If this trend continues, relative plate motion models predict that in ~350 my, the Pacific Ocean basin will effectively close leading to widespread continent-continent collisions. Since a continent-continent collision represents the termination of subduction locally, the accumulated effect of all collisions is to stop subduction globally. In this scenario, ridges would then stop spreading and young oceanic lithosphere would cool, reaching a steady-state thickness of 100 km in about 80 my, based on the properties of oceanic lithosphere today. This would constitute the stoppage of plate tectonics. The presumption that plate tectonics never stops in the face of continental collisions is equivalent to requiring that subduction flux is approximately constant through time, such that subduction initiation roughly balances subduction termination. Such a balance then raises several questions about the subduction initiation process. When and how does subduction initiate? Is there a detectible relationship between subduction cessation and subduction initiation? We can gain some guidance into these questions by examining the plate motion history over the last 200 my. Subduction initiation has occurred over the last 80 my in three intra- oceanic subduction zones: Aleutians, Marianas-Izu-Bonin and Tonga-Kermadec in the Pacific basin. In these cases, however, subduction initiation would not prevent the ultimate closure of the Pacific basin and thus the cessation of subduction. More noteworthy is where subduction is not initiating. First, there is no evidence for subduction initiation anywhere within the Atlantic basin (excluding the Caribbean and Scotia), despite the mature 100-200 my age of passive-margin oceanic lithosphere. The formation of the Alpine-Himalayan chain represents the cessation of roughly 10,000 km of subduction at about 35-50 ma, Yet, no new subduction zones have initiated south of India or Africa, the two major continents that participated in the collision. These examples illustrate that subduction does not immediately initiate following a continent-continent collision, and may lag by 10s if not 100s of millions of years. The stoppage of plate tectonics, or even a dramatic reduction in subduction flux, would have significant thermal consequences for the mantle. It would effectively mark a temporary switch to "stagnant-lid" tectonics, analogous to that found on Venus, resulting in a significant increase in global mantle potential temperature (30- 100°C per 100 my) and a possibly widespread increase in magmatic activity. Such a hiatus may have occurred in the Mid-Proterozoic (1.1-1.6Ga), an era characterized by the virtual absence of orogenic activity, the longest-lived passive margin (600 My), and the production of enigmatic "anorogenic" granites found over thousands of kilometers in a belt presently stretching from southwestern to northeastern North America.

  2. Accretion and Subduction of Oceanic Lithosphere: 2D and 3D Seismic Studies of Off-Axis Magma Lenses at East Pacific Rise 9°37-40'N Area and Downgoing Juan de Fuca Plate at Cascadia Subduction Zone

    NASA Astrophysics Data System (ADS)

    Han, Shuoshuo

    Two thirds of the Earth's lithosphere is covered by the ocean. The oceanic lithosphere is formed at mid-ocean ridges, evolves and interacts with the overlying ocean for millions of years, and is eventually consumed at subduction zones. In this thesis, I use 2D and 3D multichannel seismic (MCS) data to investigate the accretionary and hydrothermal process on the ridge flank of the fast-spreading East Pacific Rise (EPR) at 9°37-40'N and the structure of the downgoing Juan de Fuca plate at the Cascadia subduction zone offshore Oregon and Washington. Using 3D multichannel seismic (MCS) data, I image a series of off-axis magma lenses (OAML) in the middle or lower crust, 2-10 km from the ridge axis at EPR 9°37-40'N. The large OAMLs are associated with Moho travel time anomalies and local volcanic edifices above them, indicating off-axis magmatism contributes to crustal accretion though both intrusion and eruption (Chapter 1). To assess the effect of OAMLs on the upper crustal structure, I conduct 2-D travel time tomography on downward continued MCS data along two across-axis lines above a prominent OAML in our study area. I find higher upper crustal velocity in a region ~ 2 km wide above this OAML compared with the surrounding crust. I attribute these local anomalies to enhanced precipitation of alteration minerals in the pore space of upper crust associated with high-temperature off-axis hydrothermal circulation driven by the OAML (Chapter 2). At Cascadia, a young and hot end-member of the global subduction system, the state of hydration of the downgoing Juan de Fuca (JdF) plate is important to a number of subduction processes, yet is poorly known. As local zones of higher porosity and permeability, faults constitute primary conduits for seawater to enter the crust and potentially uppermost mantle. From pre-stack time migrated MCS images, I observe pervasive faulting in the sediment section up to 200 km from the deformation front. Yet faults with large throw and bright fault plane reflections that are developed under subduction bending are confined to a region 50-60 km wide offshore Oregon and less than ~45 km wide offshore Washington. Near the deformation front of Oregon margin, bending-related faults cut through the crust and extend to ~6-7 km in the mantle, whereas at Washington margin, faults are confined to upper and middle crust, indicating that Oregon margin has experienced more extensive bend faulting and related alteration. These observations argue against pervasive serpentinization in the slab mantle beneath Washington and suggest mechanisms other than dehydration embrittlement need to be considered to explain the intermediate depth earthquakes found along the Washington margin (Chapter 3). Using MCS images of a ~400 km along-strike profile ~10-15 km from the deformation front, I investigate the along-trench variation of the structure of downgoing JdF plate and its relation to the regional segmentation of Cascadia subduction zone. I observe that the propagator wakes within the oceanic plate are associated with anomalous basement topography and crustal reflectivity. Further landward, segment boundaries of ETS recurrence interval and relative timing align with the propagator traces within the subducting plate. I propose while the upper plate structure or composition may determine the threshold of fluid pore pressure at which ETS occur, the propagators may define barriers for ETS events that occur at the same time. I also observe a change in crustal structure near 45.8°N that is consistent with an increase in bend-faulting and hydration south of 45.8°N;. In addition, four previously mapped oblique strike-slip faults are associated with changes in Moho reflection, indicating that they transect the entire crust and may cause localized mantle hydration (Chapter 4).

  3. Global Plate Velocities from the Global Positioning System

    NASA Technical Reports Server (NTRS)

    Larson, Kristine M.; Freymueller, Jeffrey T.; Philipsen, Steven

    1997-01-01

    We have analyzed 204 days of Global Positioning System (GPS) data from the global GPS network spanning January 1991 through March 1996. On the basis of these GPS coordinate solutions, we have estimated velocities for 38 sites, mostly located on the interiors of the Africa, Antarctica, Australia, Eurasia, Nazca, North America, Pacific, and South America plates. The uncertainties of the horizontal velocity components range from 1.2 to 5.0 mm/yr. With the exception of sites on the Pacific and Nazca plates, the GPS velocities agree with absolute plate model predictions within 95% confidence. For most of the sites in North America, Antarctica, and Eurasia, the agreement is better than 2 mm/yr. We find no persuasive evidence for significant vertical motions (less than 3 standard deviations), except at four sites. Three of these four were sites constrained to geodetic reference frame velocities. The GPS velocities were then used to estimate angular velocities for eight tectonic plates. Absolute angular velocities derived from the GPS data agree with the no net rotation (NNR) NUVEL-1A model within 95% confidence except for the Pacific plate. Our pole of rotation for the Pacific plate lies 11.5 deg west of the NNR NUVEL-1A pole, with an angular speed 10% faster. Our relative angular velocities agree with NUVEL-1A except for some involving the Pacific plate. While our Pacific-North America angular velocity differs significantly from NUVEL-1A, our model and NUVEL-1A predict very small differences in relative motion along the Pacific-North America plate boundary itself. Our Pacific-Australia and Pacific- Eurasia angular velocities are significantly faster than NUVEL-1A, predicting more rapid convergence at these two plate boundaries. Along the East Pacific Pise, our Pacific-Nazca angular velocity agrees in both rate and azimuth with NUVFL-1A.

  4. Plating on stainless steel alloys

    SciTech Connect

    Dini, J.W.; Johnson, H.R.

    1981-09-11

    Quantitative adhesion data are presented for a variety of electroplated stainless steel type alloys. Results show that excellent adhesion can be obtained by using a Wood's nickel strike or a sulfamate nickel strike prior to final plating. Specimens plated after Wood's nickel striking failed in the deposit rather than at the interface between the substrate and the coating. Flyer plate quantitative tests showed that use of anodic treatment in sulfuric acid prior to Wood's nickel striking even further improved adhesion. In contrast activation of stainless steels by immersion or cathodic treatment in hydrochloric acid resulted in very reduced bond strengths with failure always occurring at the interface between the coating and substrate.

  5. Pore Fluid Pressure and State of Stress Above the Plate Interface from Observations in a 3 Kilometer Deep Borehole: IODP Site C0002, Nankai Trough Subduction Zone

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    During IODP Expedition 348 from October 2013 to January 2014, Site C0002 was drilled to more than 3000 meters' depth into the inner accretionary wedge at the Nankai Trough, setting a new depth record for scientific ocean drilling. It is the first hole to access the deep interior of an active convergent margin. Site C0002 is part of the NanTroSEIZE project off the Kii-Kumano region of Japan, designed to shed light on plate boundary fault zone processes near the up-dip edge of seismogenic locking and slip. The zone from 865 - 3056 meters below the sea floor was sampled via logging-while-drilling measurements, continuous sampling of drill cuttings, and limited coring. This interval was composed of lithified middle to late Miocene hemipelagic sediments and turbidites that are markedly deformed and dip steeply. P-wave speeds from sonic logs increase with depth to ~ 1600 meters, but are constant to slightly decreasing with depth from 1600 to 3050 meters. We hypothesize that this change in trend indicates the onset of elevated pore fluid pressure, but structural and lithologic factors may also play a role. We explore several methods for quantitative estimation of sonic-derived fluid pressure conditions in the inner wedge. A borehole leak-off test (LOT) and a series of borehole pressurization and injection tests were also performed, which we synthesize to estimate the least principal stress, or Shmin. Furthermore, downhole pressure while drilling (PWD) measurements recorded during borehole packoff events provide information on the maximum principal stress, SHmax. Taken together, the LOT and PWD observations suggest that the inner wedge at ~ 2000 meters depth is currently in a strike-slip stress regime, despite its position as the hanging wall of a main plate boundary thrust. This may be a transitional stress regime between shallow normal and deep thrust, controlled by depth-dependent magnitude of the tectonic convergence-related principal stress. Our results document for the first time the stress conditions and material properties in the deep interior of the upper plate to the shallow seismogenic zone.

  6. Intermittent plate tectonics?

    PubMed

    Silver, Paul G; Behn, Mark D

    2008-01-01

    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. PMID:18174440

  7. Reactivation of an old plate interface as a strike-slip fault in a slip-partitioned system: Median Tectonic Line, SW Japan

    NASA Astrophysics Data System (ADS)

    Sato, Hiroshi; Kato, Naoko; Abe, Susumu; Van Horne, Anne; Takeda, Tetsuya

    2015-03-01

    In models for strain-partitioning at obliquely-convergent plate boundaries, trench-parallel slip occurs on a vertical fault. Trench-parallel slip at the Nankai subduction zone, SW Japan, is mapped along the Median Tectonic Line (MTL) which dips approximately 40°N. To understand its structural context and how the MTL functions in this slip-partitioned system, we collected a set of three seismic profiles in the Kii peninsula south of Osaka, using a multi-scale acquisition strategy that provides increasingly fine resolution. To understand its fault kinematics, we analyzed microseismic activity in two locations on the fault, using source data from Japan's Hi-net monitoring network. Structural details suggest that the MTL functioned as a megathrust during subduction of the Cretaceous Sanbagawa HP metamorphic belt. Its current pattern of microseismicity shows that it behaves as a strike-slip fault with no indication of a vertical fault at or around its surface trace. Thus, trench-parallel slip at the Nankai is now accommodated on an inclined fault plane in an unusual form of partitioning. This system appears to have developed out of a two-phase tectonic history in which a thrust structure that formed under initial-phase compressive stresses has been reactivated as a strike-slip fault under subsequent-phase shear stresses. Its unusual kinematics show that shear failure can occur on an existing non-vertical fault plane at a regional scale in preference to the rupture of a new ideal (vertical) fault plane.

  8. High Stress Consolidation, Ultrasonic, and Permeability Measurements: Constraints on Physical Properties and In Situ Stress along the Costa Rica Subduction Plate Interface

    NASA Astrophysics Data System (ADS)

    Winner, A.; Saffer, D. M.; Valdez, R. D.

    2014-12-01

    Sediment permeability and consolidation behavior are key parameters in governing the drainage state and thus potential for excess pore fluid pressure in subduction zones. Elevated pore pressure, in turn, is one important control on the strength and sliding behavior of faults. Along many subduction margins, evidence of elevated, near-lithostatic, in situ pore pressure comes from high seismic reflectivity, low P-wave velocity (Vp), and high Vp/Vs ratios. This inference is broadly supported by numerical modeling studies that indicate elevated pore pressures are likely given high rates of burial and tectonic loading, combined with the low permeability of marine mudstones. Here, we report on a series of high-stress consolidation experiments on sediment core samples from the incoming Cocos plate obtained as part of Integrated Ocean Drilling Program (IODP) Expedition 344. Our experiments were designed to measure the consolidation behavior, permeability, and P-wave velocity of the incoming sediments over a range of confining stresses from .5 to 90 MPa. We explore a range of paths,including isostatic loading (σ1=σ2=σ3), K0 consolidation, in which the ratio of σ3/σ1 is maintained at ~0.6, and the trixial loading paths designed to maintain a near critical-state failure condition. In our tests, load is increased in a series of steps. After equilibration at each step, we conduct constant head permeability tests, and measure P-wave velocities in a "time of flight" mode. Initial results from isostatic loading tests on hemipelagic mudstone samples from 34 mbsf document consolidation and permeability-porosity trends, in which porosity decreases from 69% to 54% as stress in increased from .5 MPa to 15 MPa, and permeability decreases from 8.1 X 10-18 m2 at 1 MPa to 1.1 X 10-19 m2 at 15 MPa. P-wave velocity increases by 486-568 km/s over this effective stress range. Ultimately, data from our experiments will provide a robust basis for quantifying fluid content and pressure from seismic velocity and fault plane reflectivity at this margin, and provide data to parameterize forward models of fluid flow and consolidation.

  9. 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, earthquakes; the 1935 and the 1999 Chi-Chi, Taiwan, earthquakes; and the 1976 M7.6 Moro Gulf and 1990 M7.6 Luzon, Philippines, earthquakes.

  10. Present-day kinematics of the Rivera plate and implications for tectonics in southwestern Mexico

    NASA Technical Reports Server (NTRS)

    Demets, Charles; Stein, Seth

    1990-01-01

    A model for the present-day motion of the Rivera plate relative to the North America, Cocos, and Pacific plates is derived using new data from the Pacific-Rivera rise and Rivera transform fault, together with new estimates of Pacific-Rivera motions. The results are combined with the closure-consistent NUVEL-1 global plate motion model of DeMets et al. (1990) to examine present-day deformation in southwestern Mexico. The analysis addresses several questions raised in previous studies of the Rivera plate. Namely, do plate motion data from the northern East Pacific rise require a distinct Rivera plate? Do plate kinematic data require the subduction of the Rivera plate along the seismically quiescent Acapulco trench? If so, what does the predicted subduction rate imply about the earthquake recurrence interval in the Jalisco region of southwestern Mexico?

  11. No-net-rotation model of current plate velocities incorporating plate motion model NUVEL-1

    NASA Technical Reports Server (NTRS)

    Argus, Donald F.; Gordon, Richard G.

    1991-01-01

    NNR-NUVEL1 is presented which is a model of plate velocities relative to the unique reference frame defined by requiring no-net-rotation of the lithosphere while constraining relative plate velocities to equal those in global plate motion model NUVEL-1 (DeMets et al., 1990). In NNR-NUVEL1, the Pacific plate rotates in a right-handed sense relative to the no-net-rotation reference frame at 0.67 deg/m.y. about 63 deg S, 107 deg E. At Hawaii the Pacific plate moves relative to the no-net-rotation reference frame at 70 mm/yr, which is 25 mm/yr slower than the Pacific plate moves relative to the hotspots. Differences between NNR-NUVEL1 and HS2-NUVEL1 are described. The no-net-rotation reference frame differs significantly from the hotspot reference frame. If the difference between reference frames is caused by motion of the hotspots relative to a mean-mantle reference frame, then hotspots beneath the Pacific plate move with coherent motion towards the east-southeast. Alternatively, the difference between reference frames can show that the uniform drag, no-net-torque reference frame, which is kinematically equivalent to the no-net-rotation reference frame, is based on a dynamically incorrect premise.

  12. 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.

  13. 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.

  14. Plate-induced Miocene extension in southern California

    SciTech Connect

    Stuart, W.D. Univ. of California, Santa Barbara, CA )

    1992-01-01

    Miocene crustal extension in southern California can be explained by the interaction of tectonic plates in relative motion. The Pacific, Juan de Fuca, and Farallon (Guadalupe) plates are represented by flat elastic plates surrounded by an infinite elastic plate, the eastern part of which represents the North America plate. Forcing is by assigned subduction pull, and tractions at all plate boundaries satisfy a viscous constitutive law. Plate bottoms are stress-free. In the first part of the solution plate velocities and boundary tractions are found from static equilibrium. Then principal horizontal stresses and strains in plate interiors caused by tractions and subduction pull are found by a boundary element procedure. Using plate boundary geometry from Stock and Hodges for early- and mid-Miocene times, it is found that the portion of the North America plate margin between the Mendocino and Rivera triple junctions has maximum extensional strain directed westward. This result is generally consistent with directions associated with metamorphic core complex formation in southern California. The model is also consistent with extensional strain and rotation sense of crustal blocks in the vicinity of Los Angeles, as inferred by Luyendyk and others from paleomagnetic data. In the model the greatest extensional strain of the North America plate occurs near the Pacific-North America transform, in the area above the absent Farallon slab. Extension direction varies from northwest to southwest according to plate geometry, subduction pull (Juan de Fuca and Guadalupe), and plate boundary tractions.

  15. Using GPS, tide gauge and altimetry data to constrain subduction parameters at the Vanuatu plate boundary.

    NASA Astrophysics Data System (ADS)

    Ballu, V.; Bouin, M.; Baillard, C.; Calmant, S.; Pelletier, B.; Crawford, W. C.; Kanas, T.; Garaebiti, E.

    2012-12-01

    The Vanuatu subduction zone, Southwest Pacific, combines several features that makes it a particularly useful place to study seismic cycles. The convergence rate is high - approximately 12 cm/yr - and the seismic cycle relatively short. Measurements of interseismic motions are helped by relatively high vertical rates, the close proximity of some islands to the plate interface and the existence of very shallow seamounts on either side of the plate interface. The Vanuatu archipelago is part of the Pacific Ring of Fire: the Australian plate subducts eastward beneath the North Fiji basin, on the western border of the Pacific Plate. High topographic features on the diving plate may contribute to locking of the plates, which can play a major role in the genesis of destructive earthquakes. GPS network points were installed in the early 1990s and the geodesy network has been densified through the years, enabling us to map interseismic horizontal and vertical deformation rates throughout the archipelago. More recently, 8 continuous GPS stations were installed, along with 3 continuous seafloor pressure gauges very near to the plate interface. We show results from GPS data collected from 1996 to 2011, that we re-processed and combined into the ITRF2008 reference frame, and altimetry and seafloor pressure data from 1999 to 2010. The GPS results show that vertical deformation rates vary both across and along the archipelago. We believe that these variations result from variable distance to the plate limit and variable locking parameters. In some areas, subsidence rates are close to one centimeter per year. In the Torres islands (at the northern end of the archipelago) where villagers face recurrent coastal flooding, we showed that this flooding is due more to ground motion than to rise in the absolute sea level, even though the sea-level rise rates are locally high and the islands uplift over the long term. In the Central area of Vanuatu, we augmented the on-land network with two offshore sites using absolute pressure gauges. The sites - Wusi and Sabine Banks - are installed beneath altimetry satellite tracks, Wusi Bank on the over-riding plate and Sabine Bank on the subducting plate. The difference in the pressure records between the sites shows that Wusi Bank subsides by 11 +/- 3 mm/yr with respect to Sabine Bank. We combined the water depths derived from the pressure measurements with altimetry-derived sea-surface heights to tie these heights to a global reference frame: Wusi Bank subsides and Sabine Bank's vertical motion is near zero. Using a 2D elastic model and a finite-element code, we used the gradient of vertical deformation between the coast and the Wusi Bank site to discriminate between possible locked zone geometries. The best simple approximation is a 25° dipping, 30 km long fully locked zone, indicating that stress is currently accumulating west of Santo, Central Vanuatu. The movement of Wusi Bank is a key factor in constraining the dip and length of the locked zone, demonstrating the importance of offshore geodesy measurements.

  16. Coseismic Slip Distribution of the 2011 off the Pacific Coast of Tohoku Earthquake Deduced from Land and Seafloor Geodesy

    NASA Astrophysics Data System (ADS)

    Iinuma, T.; Kido, M.; Osada, Y.; Inazu, D.; Ohzono, M.; Tsushima, H.; Hino, R.; Ohta, Y.; Suzuki, S.; Fujimoto, H.; Miura, S.; Shinohara, M.

    2011-12-01

    The 2011 off the Pacific coast of Tohoku Earthquake (M9.0) occurred on 11 March 2011 off the Pacific coast of Tohoku district, northeastern Japan, where the Pacific plate is subducting beneath the overriding continental plate. A number of models of the coseismic slip distribution of this earthquake have been already proposed based on seismological, geodetic, and tsunami data. Here, we present comprehensive coseismic slip distribution model based not only on land GPS data but also on seafloor geodetic observations, which are obtained through recent observation cruises. We combined displacements at seafloor sites that are deduced from two different types of seafloor observations with the displacements at land GPS stations. One is the seafloor crustal deformation observation with GPS/Acoustic ranging (GPS/A). Horizontal displacements associated with the 2011 Tohoku earthquake at 2 GPS/A stations are estimated by comparing the station positions deduced from the observations before and after the earthquake. Another type of the seafloor data is seafloor water pressure that is observed by means of ocean bottom pressure gauge (OBP). We analyzed OBP data observed at 2 cabled and 4 self pop-up stations, and estimated vertical displacements due to the main shock. Displacements at 5 GPS/A stations of Japan Coast Guard [Sato et al., 2011, science] are also included to estimate the coseismic slip distribution of the earthquake. Estimated slip distribution of the 2011 Tohoku Earthquake shows following features. 1) The area of large slip ( > 20 m) is about 100 km x 200 km on the plate interface shallower than 30 km in depth. 2) There is no large slip occurred off southern Iwate prefecture on the plate interface throughout shallow to deep. 3) The latitudinal range of the area of large slip almost corresponds to the one of the area of strong interplate coupling zone off Miyagi prefecture. 4) Significant slip is estimated around the rupture area of 1978 M7.4 Miyagi-oki earthquake (40 ~ 50 km in depth). 5) No large slip is estimated on the shallow plate interface off Fukushima prefecture. These features clarify that the coseismic rupture of the 2011 Tohoku Earthquake is concentrated relatively narrow area off Miyagi prefecture and maximum slip is very large as compared to the empirical scaling law between released moment, fault size, and maximum slip of earthquakes on the subducting plate boundary. The results suggest that most slip occurred on the plate interface where continental crust contacts with the subducting oceanic crust. Off Miyagi prefecture, however, is an exceptional region where coseismic slip also has occurred on the plate interface under the continental mantle. The heterogeneity of the mantle wedge might control this slip heterogeneity in the crust-mantle contact zone. With respect to the shallow plate interface, there is no large slip is estimated off Iwate and Fukushima prefecture. Less accumulated strain due to the weak interplate coupling off Iwate prefecture and strain release due to the slow slip events that are detected by the activity of the small repeating earthquakes (e.g. in 2008) might cause it.

  17. 3-D simulation for the tectonic evolution around the Kanto Region of Japan using the kinematic plate subduction model

    NASA Astrophysics Data System (ADS)

    Hashima, A.; Sato, T.; Ito, T.; Miyauchi, T.; Kameo, K.; Yamamoto, S.

    2011-12-01

    In the Kanto region of Japan, we can observe one of the most active crustal deformations on the earth. In the southern part of the Boso peninsula to the south, the uplift rate is estimated to be 5 mm/yr from the height of marine terraces. From geological evidence, the Kanto mountains to the west are considered to uplift at 1mm/yr. In contrast, the center part of the Kanto region is stable or subsiding, covered by the Holocene sediments. The depth of the basement reaches 3 km at the deepest. Vertical deformation in the timescale of 1 Myr is being revealed by the analysis of the recent seismic reflection experiments compared with the heights of the dated sediment layers exposed on land. These crustal deformation occurs in a highly complex tectonic setting with four plates interacting with each other: beneath Kanto, situated on the Eurasian and North American plates, the Philippine sea plate subducts and the Pacific plate further descends beneath the North American and Philippine sea plates, forming the unique trench-trench-trench triple junction on the earth. In addition, the Izu-Bonin (Ogasawara) arc on the Philippine sea plate is colliding with the Japan islands due to the buoyancy of the arc crust. At the plate boundaries near the Izu-Bonin arc, large interplate earthquakes occurred at the Sagami trough in 1703 and 1923 (Kanto earthquake) and at the Nankai trough in 1707, 1854 and 1944. To reveal the crustal deformation under these plate-to-plate interactions, we use the kinematic plate subduction model based on the elastic dislocation theory. This model is based on the idea that mechanical interaction between plates can rationally be represented by the increase of the displacement discontinuity (dislocation) across plate interfaces. Given the 3-D geometry of plate interfaces, the distribution of slip rate vectors for simple plate subduction can be obtained directly from relative plate velocities. In collision zones, the plate with arc crust cannot easily descend because of its buoyancy. This can be represented by giving slip-rate deficit. When crustal deformation occurs, it also causes change in geometry of the plate boundary itself. Iterating this effect sequentially backward in time, we can reconstruct the past plate boundary geometry and past crustal deformation fields. Using the above model, we estimate the long-term slip-rate distribution due to plate subduction/collision to explain the crustal deformation in Kanto obtained from geological and geomorphological studies. The basic deformation pattern of the basin-forming movement in the Kanto plain and uplifts in the southern Boso peninsula and in the Kanto and Akaishi mountains cannot be explained by the collision restricted to the Izu peninsula only. It is necessary to assume wider collision extended to the neighboring Sagami and Suruga trough, which is consistent to the width of the arc crust of the Izu-Bonin arc. However, the degree of the collision is relatively small in these areas where large interplate earthquake occurs. The effect of temporal change in geometry of the plate interfaces is not so large in the timescale of 1 Myr.

  18. The Plate Boundary Observatory: Community Focused Web Services

    NASA Astrophysics Data System (ADS)

    Matykiewicz, J.; Anderson, G.; Lee, E.; Hoyt, B.; Hodgkinson, K.; Persson, E.; Wright, J.; Torrez, D.; Jackson, M.

    2006-12-01

    The Plate Boundary Observatory (PBO), part of the NSF-funded EarthScope project, is designed to study the three-dimensional strain field resulting from deformation across the active boundary zone between the Pacific and North American plates in the western United States. To meet these goals, PBO will install 852 continuous GPS stations, 103 borehole strainmeter stations, 28 tiltmeters, and five laser strainmeters, as well as manage data for 209 previously existing continuous GPS stations. UNAVCO provides access to data products from these stations, as well as general information about the PBO project, via the PBO web site (http://pboweb.unavco.org). GPS and strainmeter data products can be found using a variety of channels, including map searches, text searches, and station specific data retrieval. In addition, the PBO construction status is available via multiple mapping interfaces, including custom web based map widgets and Google Earth. Additional construction details can be accessed from PBO operational pages and station specific home pages. The current state of health for the PBO network is available with the statistical snap-shot, full map interfaces, tabular web based reports, and automatic data mining and alerts. UNAVCO is currently working to enhance the community access to this information by developing a web service framework for the discovery of data products, interfacing with operational engineers, and exposing data services to third party participants. In addition, UNAVCO, through the PBO project, provides advanced data management and monitoring systems for use by the community in operating geodetic networks in the United States and beyond. We will demonstrate these systems during the AGU meeting, and we welcome inquiries from the community at any time.

  19. Plate Motions From Space Geodesy

    NASA Astrophysics Data System (ADS)

    Argus, D. F.; Gordon, R. G.; Heflin, M. B.; Ma, C.; Eanes, R. J.

    2004-05-01

    We integrate results from satellite laser ranging (SLR), very long baseline interferometry (VLBI), and global positioning system (GPS) geodesy to determine GEODVEL, a set of the relative angular velocities of most of the earth's major plates. Using two decades of SLR data and two decades of VLBI data, we determine angular velocities and linear velocities more accurately than others have from just one decade of GPS data. We assign sites to plates on the basis of geologic observations: the distribution of major faults, the locations of large and historical earthquakes, other seismicity, and the distribution of high topographic relief generated by active deformation. The GEODVEL angular velocities differ insignificantly from a second set of plate angular velocities that we determine from site velocities in the International Terrestrial Reference Frame 2000 [Altamimi et al. 2002]. That the two sets of angular velocities are nearly equal suggests that both sets are accurate. The GEODVEL angular velocities differ significantly in places from prior estimates. In particular, several GEODVEL relative angular velocities differ significantly from the corresponding relative angular velocities of NUVEL-1A, which is based on 3.2-Myr-average spreading rates from marine magnetic anomalies, azimuths from bathymetric data along transform faults, and from earthquake slip vectors. Differences between GEODVEL and NUVEL-1A are large for angular velocities involving the Nazca plate and for North America-Pacific, Eurasia-Pacific, India-Eurasia, and Arabia-Eurasia. Some of these differences are presumably due to changes in plate velocities since 3.2 Ma, but some may be due to biases in NUVEL-1A. For example, we explore whether differences for the latter four angular velocities might be accounted for by incorporating motion across the east African rift, which is neglected in plate motion model NUVEL-1A. As another example, the GEODVEL and NUVEL-1A India-Australia relative velocities differ significantly, but the former agrees with a new set of angular velocities from plate reconstructions that recognize the existence of a separate, previously unrecognized Capricorn plate between the Indian and Australian plates [Royer and Gordon 1997].

  20. Seismic tomographic constraints on plate tectonic reconstructions of the Philippine Sea plate near East Asia

    NASA Astrophysics Data System (ADS)

    Wu, J. E.; Suppe, J.

    2011-12-01

    The Philippine Sea and Pacific plates play a key tectonic role at the edge of East Asia, with similar present-day absolute motions. The Philippine Sea slab dips northward under the Eurasian continent at the Ryukyu Trench & Nankai Trough. At Taiwan and south along the Manila Trench, the subduction polarity is flipped and the Eurasia-South China Sea slab dips eastward beneath the Philippine Sea plate. Cenozoic plate tectonic reconstructions of the Philippine Sea plate have been primarily constrained by paleomagnetic data and the seafloor spreading record. These indicate large northward motions from equatorial regions through the Cenozoic and significant Oligo-Miocene plate rotations, respectively, very different from present-day plate motions. In this study seismic tomographic data are used to add the significant constraint of subducted slab geometries and seismic velocities. Detailed 3D geometries of subducted slabs were mapped with GoCad software using the MITP08 seismic tomography dataset (Li et al., 2008), Benioff zone seismicities, and published local tomography. The slabs were then unfolded using GoCad and imported into GPlates reconstruction software to test current plate tectonic reconstructions of the Philippine Sea plate near East Asia. New constraints are provided by the geometries of the mapped slab edges, which indicate inconsistent plate overlaps and voids when applied to existing plate models. These data therefore provide significant constraints for improved models. The unfolded Eurasian-South China Sea slab is ~500 km long and has a N-S oriented edge parallel to transforms of the South China Sea. Velocity images reveal the locations of continent-ocean boundaries at the north and south ends of the Eurasian slab. At Taiwan, the unfolded Philippine Sea plate slab is ~850 km long and also has a N-S edge. These slab geometries imply that present-day east-dipping subduction along the Manila Trench began at a N-S transform-parallel zone between the Eurasian and Philippine Sea plates. Assuming present-day rates, the slab lengths imply that the fast Pacific-like NW motion of the Philippine Sea plate would have changed from its earlier northward motion no earlier than ~7 Ma. However earlier activation of the Manila Trench is likely given geologic constraints and require a slower speed-up to the present Pacific-like motions of the Philippine Sea plate. Further major constraints on earlier motion are provided by several detached slabs under the South China Sea and the West Philippine basin, by slabs of the southern Philippines and Molucca Sea, and by the larger Pacific and Indian Ocean slabs.

  1. Volcanism in response to plate flexure.

    PubMed

    Hirano, Naoto; Takahashi, Eiichi; Yamamoto, Junji; Abe, Natsue; Ingle, Stephanie P; Kaneoka, Ichiro; Hirata, Takafumi; Kimura, Jun-Ichi; Ishii, Teruaki; Ogawa, Yujiro; Machida, Shiki; Suyehiro, Kiyoshi

    2006-09-01

    Volcanism on Earth is known to occur in three tectonic settings: divergent plate boundaries (such as mid-ocean ridges), convergent plate boundaries (such as island arcs), and hot spots. We report volcanism on the 135 million-year-old Pacific Plate not belonging to any of these categories. Small alkalic volcanoes form from small percent melts and originate in the asthenosphere, as implied by their trace element geochemistry and noble gas isotopic compositions. We propose that these small volcanoes erupt along lithospheric fractures in response to plate flexure during subduction. Minor extents of asthenospheric melting and the volcanoes' tectonic alignment and age progression in the direction opposite to that of plate motion provide evidence for the presence of a small percent melt in the asthenosphere. PMID:16873612

  2. Northern east Pacific rise: Evolution from 25 m. y. B. P. to the present

    SciTech Connect

    Mammerickx, J.; Klitgord, K.D.

    1982-08-10

    The northeast Pacific topography and magnetic lineations (25 m.y. B.P. to the Present) record the traces of three major spreading reorganizations. Only one spreading center is observed today, but there is evidence for several ephemeral episodes of twin spreading accompanying the evolution from an extensive Pacific-Guadalupe plate boundary to a much shortened Pacific-Cocos and Pacific-Rivera plate boundary. The 25 m.y. B.P. plate reorganization culminated with the formation of the Guadalupe plate, bound by the Murray fracture zone to the north and the Cocos-Nazca spreading ridge to the south. Between 25 and 12.5 m.y. B.P. spreading continued while the plate retained the same general outline. The 12.5--11 m.y. B.P. reorganization resulted in the creation of a much shortened Pacific-Cocos plate boundary located in its early stages over the Mathematician seamounts and a much reduced Cocos-plate. The last reorganization (6.5--3.5 m.y. B.P.) resulted in the abandonment of the Mathematician spreading ridge as a Pacific-Cocos plate boundary in favor of the East Pacific Rise.

  3. Northern East Pacific Rise: Evolution from 25 m.y. B.P. to the present

    NASA Astrophysics Data System (ADS)

    Mammerickx, Jacqueline; Klitgord, Kim D.

    1982-08-01

    The northeast Pacific topography and magnetic lineations (25 m.y. B.P. to the Present) record the traces of three major spreading reorganizations. Only one spreading center is observed today, but there is evidence for several ephemeral episodes of twin spreading accompanying the evolution from an extensive Pacific-Guadalupe plate boundary to a much shortened Pacific-Cocos and Pacific-Rivera plate boundary. The 25 m.y. B.P. plate reorganization culminated with the formation of the Guadalupe plate, bound by the Murray fracture zone to the north and the Cocos-Nazca spreading ridge to the south. Between 25 and 12.5 m.y. B.P. spreading continued while the plate retained the same general outline. The 12.5-11 m.y. B.P. reorganization resulted in the creation of a much shortened Pacific-Cocos plate boundary located in its early stages over the Mathematician seamounts and a much reduced Cocos-plate. The last reorganizaton (6.5-3.5 m.y. B.P.) resulted in the abandonment of the Mathematician spreading ridge as a Pacific-Cocos plate boundary in favor of the East Pacific Rise.

  4. Plating on some difficult-to-plate metals and alloys

    SciTech Connect

    Dini, J.W.; Johnson, H.R.

    1980-02-01

    Electrodeposition of coatings on metals such as beryllium, beryllium-copper, Kovar, lead, magnesium, thorium, titanium, tungsten, uranium, zirconium, and their alloys can be problematic. This is due in most cases to a natural oxide surface film that readily reforms after being removed. The procedures we recommend for plating on these metals rely on replacing the oxide film with a displacement coating, or etching to allow mechanical keying between the substrate and plated deposit. The effectiveness of the procedures is demonstrated by interface bond strengths found in ring-shear and conical-head tensile tests.

  5. Pacific geomagnetic secular variation.

    PubMed

    Doell, R R; Cox, A

    1971-01-22

    We have considered several different types of records of long-period geomagnetic secular variation: direct measurements made in geomagnetic observatories; paleomagnetic measurements on Hawaiian lava flows with accurately known ages in the interval 0 to 200 years; paleomagentic measurements on Hawaiian lava flows with loosely determined ages within the interval 200 to 10,000 years ago; and worldwide paleomagnetic measurements of the average geomagnetic angular dispersion recorded in lava flows that formed during the past 0.7 million years. All these magnetic records indicate that, during this time, the nondipole component of the earth's field was lower in the central Pacific than elsewhere, as it is today. This, in turn, indicates that there is some type of inhomogeneity in the lower mantle which is coupled to the earth's core in such a way as to suppress the generation of the nondipole field beneath the central Pacific. With the present incomplete state of knowledge about the processes that give rise to the earth's field, it is uncertain whether undulations in the core-mantle interface or lateral variations in the composition and physical state of the lower mantle are ultimately responsible for the pattern of secular variation seen at the earth's surface. PMID:17736217

  6. PLUME investigates South Pacific Superswell

    NASA Astrophysics Data System (ADS)

    Barruol, G.

    The French Ministere de la Recherche is funding a multidisciplinary project, the Polynesian Lithosphere and Upper Mantle Experiment (PLUME), to image the upper mantle structures beneath French Polynesia. This region of the southwestern Pacific, which is far from any plate boundary comprises oceanic lithosphere with ages varying between 30 and 100 Ma, as well as two major fracture zones. The area is characterized by a "swarm" of volcanic island chains—the Society Islands, the Austral Islands, and the Marquesas—that may represent "hot spot" tracks [Duncan and McDougall, 1976]. The individual hot spots are superimposed on the large South Pacific Superswell [McNutt, 1998]. The region is also characterized by a large-scale, low-velocity anomaly in the lower-most mantle [Su et al., 1994] and anomalous converted phases from the 660-km discontinuity [Vinnik et al., 1997].

  7. Late Tectonic history of Beaufort Sea - North Pacific area

    SciTech Connect

    McWhae, J.R.H.

    1985-02-01

    The Kaltag fault (and its northern associated splay, the Rapid fault array) is the sheared suture between the Eurasian-Alaskan plate and the North American plate in the area between the Mackenzie Delta and the Alaskan Border. This condition has been maintained throughout considerable additional phases of faulting and folding from mid-Cretaceous to the present. Previously, the Alaskan plate had been the northwestern nose of the North America plate. The interplate suture was deflected to the north as the Canadian Shield was approached. The Kaltag fault continued northeastward 2000 km seaward of the Sverdrup rim, northwest of the Canadian Arctic Island, and north of Greenland. The driving force was directed from the southwest by the Eurasian plate after its collision in Early Cretaceous (Hauterivian) with the North American plate and the docking of north-moving exotic terranes from the Pacific. During the early Tertiary, perhaps in concert with the accretion of the Okhotsk block to the Asian plate north of Japan, the northern Pacific subduction zone jumped southward to the Aleutian Arc where it has persisted until today. A distance of 800 km separates the stable shelf of the Canadian craton, at the Alberta Foothills thrust belt, from the subduction zone off Vancouver Island. The foreland thrust belt and the accretion of exotic terranes in Mesozoic and Tertiary times extended the continental crust of the North American plate westward to the present active transform margin with the Pacific plate along the Queen Charlotte fault zone.

  8. The present-day number of tectonic plates

    NASA Astrophysics Data System (ADS)

    Harrison, Christopher G. A.

    2016-03-01

    The number of tectonic plates on Earth described in the literature has expanded greatly since the start of the plate tectonic era, when only about a dozen plates were considered in global models of present-day plate motions. With new techniques of more accurate earthquake epicenter locations, modern ways of measuring ocean bathymetry using swath mapping, and the use of space based geodetic techniques, there has been a huge growth in the number of plates thought to exist. The study by Bird (2003) proposed 52 plates, many of which were delineated on the basis of earthquake locations. Because of the pattern of areas of these plates, he suggested that there should be more small plates than he could identify. In this paper, I gather together publications that have proposed a total of 107 new plates, giving 159 plates in all. The largest plate (Pacific) is about 20 % of the Earth's area or 104 Mm2, and the smallest of which (Plate number 5 from Hammond et al. 2011) is only 273 km2 in area. Sorting the plates by size allows us to investigate how size varies as a function of order. There are several changes of slope in the plots of plate number organized by size against plate size order which are discussed. The sizes of the largest seven plates is constrained by the area of the Earth. A middle set of 73 plates down to an area of 97,563 km2 (the Danakil plate at number 80, is the plate of median size) follows a fairly regular pattern of plate size as a function of plate number. For smaller plates, there is a break in the slope of the plate size/plate number plot and the next 32 plates follow a pattern of plate size proposed by the models of Koehn et al. (2008) down to an area of 11,638 km2 (West Mojave plate # 112). Smaller plates do not follow any regular pattern of area as a function of plate number, probably because we have not sampled enough of these very small plates to reveal any clear pattern.

  9. Relationship between temperatures and fault slips on the upper surface of the subducting Philippine Sea plate beneath the Kanto district, central Japan

    NASA Astrophysics Data System (ADS)

    Yoshioka, Shoichi; Takagi, Rumi; Matsumoto, Takumi

    2015-05-01

    To elucidate the relationship between interplate temperatures and generation mechanisms for megathrust earthquakes and slow slip events (SSEs) in the Kanto district, central Japan, we performed numerical simulations on the thermal state. For this purpose, we newly developed a 2-D box-type thermal convection model that is able to handle the subduction of two oceanic plates: the young oceanic Philippine Sea (PHS) plate subducts following subduction of the old oceanic Pacific (PAC) plate beneath it. To constrain temperatures on the upper surface of the PHS plate, we used high-density Hi-net heat flow data on land. We found that low heat flow in the Kanto district was caused mostly by subduction of the cold PHS plate. To explain the heat flow distribution in the Kanto district in more detail, we needed to incorporate frictional heating at the plate interface on the seaward side of the corner of the mantle wedge, and temperature changes due to surface erosion and sedimentation associated with crustal deformation during the Quaternary on land into the models. The most suitable pore pressure ratio to explain the heat flow data was 0.98. The thermally estimated seismogenic zone corresponded well to the fault planes of the 1923 Taisho Kanto earthquake and the western half of the 1707 Genroku Kanto earthquake. The eastern half of the fault plane of the 1707 Genroku Kanto earthquake could be divided into two areas; the northwestern fault plane corresponded to the thermally estimated seismogenic zone, whereas the relationship between the southeastern fault plane and interplate temperatures was ambiguous. The off-Boso SSEs occurred on the plate interface at temperatures lower than approximately 250 °C, and the slipped region passed through the 150 °C isotherm, corresponding to the clay mineral phase transformation from smectite to illite. This might suggest that the SSEs occurred in relation to a dehydration process.

  10. Circum-Pacific diatomite deposits

    SciTech Connect

    North, F.K.

    1986-07-01

    Deformed diatomites of assured identification are all Oligocene or younger. They are not to be interpreted with oceanic diatom oozes as analogs, nor with California's Monterey Formation as prototype. All examples, apart from the unique Monterey, are deposits of relatively shallow waters at convergent plate or microplate boundaries: in arc-trench gaps or (less importantly) in immediate back-arc belts. Tethyan examples, along a collision boundary, are now slivers in the late stages of external flysch along the fronts of Alpine thrust belts. Circum-Pacific examples, at ocean-continent subduction boundaries, are preserved only on mountainous islands or peninsulas, the uplift (not folding) of which has protected the diatomites and their overlying evaporites from subduction. The control is tectonic and volcanic, not by water temperature or eustatism. Preserved deposits appear to be restricted to particular segments of the Pacific boundary delineated by Benioff zones having some significant minimum dip. The unique Monterey Formation owes its spectacular development and preservation to the conversion of an arc-trench boundary to a transform boundary, at a triple junction, before the diatomite was deposited. The Monterey's importance as an oil source sediment does not stem from its true diatomite component. Other Circum-Pacific diatomites are of negligible significance to the petroleum geologist, but are potentially minable for other uses in Japan, the Philippines, and Peru, and possibly in Chile.

  11. Environmental materials and interfaces

    SciTech Connect

    Not Available

    1991-11-01

    A workshop that explored materials and interfaces research needs relevant to national environmental concerns was conducted at Pacific Northwest Laboratory. The purposes of the workshop were to refine the scientific research directions being planned for the Materials and Interface Program in the Molecular Science Research Center (MSRC) and further define the research and user equipment to the included as part of the proposed Environmental and Molecular Science Laboratory (EMSL). Three plenary information sessions served to outline the background, objectives, and status of the MSRC and EMSL initiatives; selected specific areas with environmentally related materials; and the status of capabilities and facilities planned for the EMSL. Attention was directed to four areas where materials and interface science can have a significant impact on prevention and remediation of environmental problems: in situ detection and characterization of hazardous wastes (sensors), minimization of hazardous waste (separation membranes, ion exchange materials, catalysts), waste containment (encapsulation and barrier materials), and fundamental understanding of contaminant transport mechanisms. During all other sessions, the participants were divided into three working groups for detailed discussion and the preparation of a written report. The working groups focused on the areas of interface structure and chemistry, materials and interface stability, and materials synthesis. These recommendations and suggestions for needed research will be useful for other researchers in proposing projects and for suggesting collaborative work with MSRC researchers. 1 fig.

  12. Orthogonal femoral plating

    PubMed Central

    Auston, D. A.; Werner, F. W.; Simpson, R. B.

    2015-01-01

    Objectives This study tests the biomechanical properties of adjacent locked plate constructs in a femur model using Sawbones. Previous studies have described biomechanical behaviour related to inter-device distances. We hypothesise that a smaller lateral inter-plate distance will result in a biomechanically stronger construct, and that addition of an anterior plate will increase the overall strength of the construct. Methods Sawbones were plated laterally with two large-fragment locking compression plates with inter-plate distances of 10 mm or 1 mm. Small-fragment locking compression plates of 7-hole, 9-hole, and 11-hole sizes were placed anteriorly to span the inter-plate distance. Four-point bend loading was applied, and the moment required to displace the constructs by 10 mm was recorded. Results We found that a 1 mm inter-plate distance supported greater moments than a 10 mm distance in constructs with only lateral plates. Moments supported after the addition of a 9- or 11-hole anterior plate were greater for both 10 mm and 1 mm inter-plate distance, with the 11-hole anterior plate supporting a greater moment than a 9-hole plate. Femurs with a 7-hole anterior plate fractured regardless of lateral inter-plate distance size. Conclusion This suggests that the optimal plate configuration is to minimise lateral inter-plate distance and protect it with an anterior plate longer than seven holes. Cite this article: Bone Joint Res 2015;4:238. PMID:25715873

  13. Simulations of seismic hazard for the Pacific Northwest of the United States from earthquakes associated with the Cascadia subduction zone

    USGS Publications Warehouse

    Petersen, M.D.; Cramer, C.H.; Frankel, A.D.

    2002-01-01

    We investigate the impact of different rupture and attenuation models for the Cascadia subduction zone by simulating seismic hazard models for the Pacific Northwest of the U.S. at 2% probability of exceedance in 50 years. We calculate the sensitivity of hazard (probabilistic ground motions) to the source parameters and the attenuation relations for both intraslab and interface earthquakes and present these in the framework of the standard USGS hazard model that includes crustal earthquakes. Our results indicate that allowing the deep intraslab earthquakes to occur anywhere along the subduction zone increases the peak ground acceleration hazard near Portland, Oregon by about 20%. Alternative attenuation relations for deep earthquakes can result in ground motions that differ by a factor of two. The hazard uncertainty for the plate interface and intraslab earthquakes is analyzed through a Monte-Carlo logic tree approach and indicates a seismic hazard exceeding 1 g (0.2 s spectral acceleration) consistent with the U.S. National Seismic Hazard Maps in western Washington, Oregon, and California and an overall coefficient of variation that ranges from 0.1 to 0.4. Sensitivity studies indicate that the paleoseismic chronology and the magnitude of great plate interface earthquakes contribute significantly to the hazard uncertainty estimates for this region. Paleoseismic data indicate that the mean earthquake recurrence interval for great earthquakes is about 500 years and that it has been 300 years since the last great earthquake. We calculate the probability of such a great earthquake along the Cascadia plate interface to be about 14% when considering a time-dependent model and about 10% when considering a time-independent Poisson model during the next 50-year interval.

  14. Stochastic modelling of a large subduction interface earthquake in Wellington, New Zealand

    NASA Astrophysics Data System (ADS)

    Francois-Holden, C.; Zhao, J.

    2012-12-01

    The Wellington region, home of New Zealand's capital city, is cut by a number of major right-lateral strike slip faults, and is underlain by the currently locked west-dipping subduction interface between the down going Pacific Plate, and the over-riding Australian Plate. A potential cause of significant earthquake loss in the Wellington region is a large magnitude (perhaps 8+) "subduction earthquake" on the Australia-Pacific plate interface, which lies ~23 km beneath Wellington City. "It's Our Fault" is a project involving a comprehensive study of Wellington's earthquake risk. Its objective is to position Wellington city to become more resilient, through an encompassing study of the likelihood of large earthquakes, and the effects and impacts of these earthquakes on humans and the built environment. As part of the "It's Our Fault" project, we are working on estimating ground motions from potential large plate boundary earthquakes. We present the latest results on ground motion simulations in terms of response spectra and acceleration time histories. First we characterise the potential interface rupture area based on previous geodetically-derived estimates interface of slip deficit. Then, we entertain a suitable range of source parameters, including various rupture areas, moment magnitudes, stress drops, slip distributions and rupture propagation directions. Our comprehensive study also includes simulations from historical large world subduction events translated into the New Zealand subduction context, such as the 2003 M8.3 Tokachi-Oki Japan earthquake and the M8.8 2010 Chili earthquake. To model synthetic seismograms and the corresponding response spectra we employed the EXSIM code developed by Atkinson et al. (2009), with a regional attenuation model based on the 3D attenuation model for the lower North-Island which has been developed by Eberhart-Phillips et al. (2005). The resulting rupture scenarios all produce long duration shaking, and peak ground accelerations that, typically range between 0.2-0.7 g in Wellington city. Many of these scenarios also produce long period motions that are currently not captured by the current NZ design spectra.

  15. High-frequency Pn,Sn phases recorded by ocean bottom seismometers on the Cocos plate

    SciTech Connect

    McCreery, C.S.

    1981-05-01

    Data from ocean bottom seismometers located on the Cocos plate indicate that high-frequency Pn,Sn phases are generated by earthquakes along the subducting margin of that plate and are propagated across the plate. The Sn phase appears to be severely attenuated as it approaches the ridge crest. Estimates of Pn velocity are lower than previous extimates for western Pacific paths, which may indicate a relationship between Pn,Sn velocity and lithospheric age. High frequencies found in these phases suggest that Q for Pn,Sn propagation across the Cocos plate is similar to that for the western Pacific.

  16. Pacific subduction and Mesozoic mineralization in eastern China

    NASA Astrophysics Data System (ADS)

    Sun, W.; Ling, M.; Liang, H.; Ding, X.; Fan, W.; Yang, X.

    2009-12-01

    Northeastern China is well known for the removal of subcontinental lithosphere mantle of the North China craton in the Late Mesozoic and the Cretaceous giant igneous event, while southeastern China is famous for its large scale magmatism and mineralization from the Late Jurassic to the Early Cretaceous. All these can be plausibly interpreted by the interaction between eastern China and the subducting Pacific plate. From Jurassic to Cretaceous, Eastern China was related to the subduction of the Pacific plate under Eurasia in the south, concurrent with oblique subduction of the Izanagi plate in the north (Maruyama et al., 1997; Li and Li, 2007; Sun et al., 2007; Zhou et al., 2000). Cretaceous tectonic evolution of eastern China matches remarkably well with the drifting history of the Pacific plate. The most pronounced phenomena are: (1) eastern China large-scale orogenic lode gold (Au) mineralisation occurred contemporaneously with an abrupt change of ~80 degree in the drifting direction of the subducting Pacific plate, concurrent with the formation of the Ontong Java Plateau (Sun et al., 2007); (2) the subduction of the ridge between the Pacific and Izanagi Plates can plausibly explain the mineralization and rock distribution of the Lower Yangtze River mineralization belt (Ling et al., 2009); (3) southwestward subduction of the Pacific plate and corresponding slab rollback can feasibly interprete the formation of the late Mesozoic (180-125 Ma) magmatism and metallogenic events in SE China. Reference Li, Z. X., and Li, X. H., 2007, Formation of the 1300-km-wide intracontinental orogen and postorogenic magmatic province in Mesozoic South China: A flat-slab subduction model: Geology, v. 35, p. 179-182. Ling, M. X., Wang, F. Y., Ding, X., Hu, Y. H., Zhou, J. B., Zartman, R. E., Yang, X. Y., and Sun, W. D., 2009, Cretaceous ridge subduction along the Lower Yangtze River Belt, eastern China: Economic Geology, v. 104, p. 303-321. Maruyama, S., 1997, Pacific-type orogeny revisited: Miyashiro-type orogeny proposed: Island Arc, v. 6, p. 91-120. Sun, W. D., Ding, X., Hu, Y. H., and Li, X. H., 2007a, The golden transformation of the Cretaceous plate subduction in the west Pacific: Earth and Planetary Science Letters, v. 262, p. 533-542. Zhou, X. M., and Li, W. X., 2000, Origin of Late Mesozoic igneous rocks in Southeastern China: implications for lithosphere subduction and underplating of mafic magmas: Tectonophysics, v. 326, p. 269-287.

  17. Subduction Drive of Plate Tectonics

    NASA Astrophysics Data System (ADS)

    Hamilton, W. B.

    2003-12-01

    Don Anderson emphasizes that plate tectonics is self-organizing and is driven by subduction, which rights the density inversion generated as oceanic lithosphere forms by cooling of asthenosphere from the top. The following synthesis owes much to many discussions with him. Hinge rollback is the key to kinematics, and, like the rest of actual plate behavior, is incompatible with bottom-up convection drive. Subduction hinges (which are under, not in front of, thin leading parts of arcs and overriding plates) roll back into subducting plates. The Pacific shrinks because bounding hinges roll back into it. Colliding arcs, increasing arc curvatures, back-arc spreading, and advance of small arcs into large plates also require rollback. Forearcs of overriding plates commonly bear basins which preclude shortening of thin plate fronts throughout periods recorded by basin strata (100 Ma for Cretaceous and Paleogene California). This requires subequal rates of advance and rollback, and control of both by subduction. Convergence rate is equal to rates of rollback and advance in many systems but is greater in others. Plate-related circulation probably is closed above 650 km. Despite the popularity of concepts of plumes from, and subduction into, lower mantle, there is no convincing evidence for, and much evidence against, penetration of the 650 in either direction. That barrier not only has a crossing-inhibiting negative Clapeyron slope but also is a compositional boundary between fractionated (not "primitive"), sluggish lower mantle and fertile, mobile upper mantle. Slabs sink more steeply than they dip. Slabs older than about 60 Ma when their subduction began sink to, and lie down on and depress, the 650-km discontinuity, and are overpassed, whereas younger slabs become neutrally buoyant in mid-upper mantle, into which they are mixed as they too are overpassed. Broadside-sinking old slabs push all upper mantle, from base of oceanic lithosphere down to the 650, back under 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.

  18. Geodynamics of the Eastern Pacific Region, Caribbean and Scotia Arcs. Volume 9

    SciTech Connect

    Cabre, R.

    1983-01-01

    This book analyze the geodynamic phenomena related to the interaction of the eastern Pacific with the Americas between Canada and the Antarctic peninsula. Studies include the Cordilleran arcs and Juan de Fuca plate.

  19. Pacific microplate and the Pangea supercontinent in the Early to Middle Jurassic

    NASA Astrophysics Data System (ADS)

    Bartolini, Annachiara; Larson, Roger L.

    2001-08-01

    New biostratigraphic data based on radiolarians recovered from deep within the oceanic crustal section of Ocean Drilling Program Hole 801C in the western Pacific, along with existing radiometric information, date this oceanic crust as late Bajocian early Bathonian (170 165 Ma). The overlying basal sediments at Hole 801C are essentially identical in age (middle Bathonian, 164 162 Ma) to the basal sediments at Deep Sea Drilling Program Hole 534A in the central Atlantic. We estimate the time of formation of the Pacific plate as 175 170 Ma and the time of initial separation of the Pangea supercontinent in the central Atlantic as 190 180 Ma. We also identify a time of extensive subduction-zone magmatism (175 159 Ma) at the eastern and western edges of Pangea. We suggest that the initial plate separation of Pangea increased subduction rates at its outer margins and altered the plate boundaries in the Pacific superocean, leading to formation of the Pacific plate.

  20. Origin of the oceanic basalt basement of the Solomon Islands arc and its relationship to the Ontong Java Plateau-insights from Cenozoic plate motion models

    USGS Publications Warehouse

    Wells, R.E.

    1989-01-01

    Cenozoic global plate motion models based on a hotspot reference frame may provide a useful framework for analyzing the tectonic evolution of the Solomon Islands convergent margin. A postulated late Miocene collision of the Ontong Java Plateau (OJP) with a NE-facing arc is consistent with the predicted path of the OJP across the Pacific Basin and its Miocene arrival at the trench. Late-stage igneous activity (65-30 Ma) predicted for the OJP as it rode over the Samoan hotspot occurred in correlative stratigraphic sections on Malaita, the supposed accreted flake of OJP in the Solomon Islands arc. Convergence similar to the present velocities between Australia and the Pacific plates was characteristic of the last 43 million years. Prior to 43 Ma Pacific-Australia plate motions were divergent, seemingly at odds with geologic evidence for early Tertiary convergence, particularly in Papua New Guinea. A postulated South Pacific plate may have existed between Australia and the Pacific plate and would have allowed implied northward subduction along the northeastern Australia plate boundary that lasted into the early Eocene. Subsequent reorganization of plate motions in the middle Eocene correlates with middle Eocene marginal basin formation along ridges oblique to the main plate boundary. Cessation of spreading on the Pacific-South Pacific Ridge and its subsequent subduction beneath Asia followed the change in Pacific plate motion at 43 Ma. A trapped remnant of the extinct, NW-trending ridge may still lie beneath the western Philippine Sea. The terminal deformation, metamorphism and ophiolite obduction in the Eocene orogen of the southwest Pacific also correlates with the major change in Pacific plate motion at 43 Ma and the subsequent compression of the dying Eocene arc against outlying continental and oceanic crustal blocks of the Australian plate. The Solomon Islands oceanic basement may represent juxtaposition of oceanic plateaus of the Australian plate beneath overthrust, dismembered ophiolite derived from adjacent marginal basin crust. ?? 1989.

  1. High-Repeatability, Robot Friendly, ORU Interface

    NASA Technical Reports Server (NTRS)

    Voellmer, George M. (Inventor)

    1992-01-01

    A robot-friendly coupling device for an Orbital Replacement Unit (ORU). The invention will provide a coupling that is detached and attached remotely by a robot. The design of the coupling must allow for slight misalignments, over torque protection, and precision placement. This is accomplished by using of a triangular interface having three components. A base plate assembly is located on an attachment surface, such as a satellite. The base plate assembly has a cup member, a slotted member, and a post member. The ORU that the robot attaches to the base plate assembly has an ORU plate assembly with two cone members and a post member which mate to the base plate assembly. As the two plates approach one another, one cone member of the ORU plate assembly only has to be placed accurately enough to fall into the cup member of the base plate assembly. The cup forces alignment until a second cone falls into a slotted member which provides final alignment. A single bolt is used to attach the two plates. Two deflecting plates are attached to the backs of the plates. When pressure is applied to the center of the deflecting plates, the force is distributed preventing the ORU & base plates from deflecting. This accounts for precision in the placement of the article.

  2. Plate tectonic reconstructions with continuously closing plates

    NASA Astrophysics Data System (ADS)

    Gurnis, Michael; Turner, Mark; Zahirovic, Sabin; DiCaprio, Lydia; Spasojevic, Sonja; Müller, R. Dietmar; Boyden, James; Seton, Maria; Manea, Vlad Constantin; Bower, Dan J.

    2012-01-01

    We present a new algorithm for modeling a self-consistent set of global plate polygons. Each plate polygon is composed of a finite list of plate margins, all with different Euler poles. We introduce a "continuously closed plate" (CCP), such that, as each margin moves independently, the plate polygon remains closed geometrically as a function of time. This method solves emerging needs in computational geodynamics to combine kinematic with dynamic models. Because they have polygons that are too widely spaced in time and have inconsistent motions between margins and plates, traditional global plate tectonic reconstructions have become inadequate for geodynamics. The CCP algorithm has been incorporated into the GPlates open-source paleogeographic system. The algorithm is a set of procedures and data structures that operate on collections of reconstructed geometric data to form closed plate polygons; the main data structures used for each plate polygon are based on a nested hierarchy of topological elements. Reconstructions with CCPs can be created, edited, visualized, and exported with GPlates. The native storage of the dynamic reconstructions is the GPlates Markup Language, GPML, which uses an XML-based file format called GML. We demonstrate the utility of the CCP method by creating a global reconstruction with continuously closing plates from 140 Ma to the present using data from existing, traditional reconstructions.

  3. Copper Map Plate Detail

    A portion of the engraving on the plate used to print points, lines, and text in black ink. Engravings on the plate are left-to-right reversed. This plate was cleaned and treated to improve the visibility of the engraving. The plate was used to print the Washington [D.C.] and vicinity, 1:31,680-sca...

  4. 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.

  5. Plate motions and deformations from geologic and geodetic data

    NASA Technical Reports Server (NTRS)

    Jordan, T. H.

    1986-01-01

    A satellite laser ranging experiment conducted by NASA since 1972 has measured the relative motion between the North America and Pacific plates in California. Based on these measurements, the 896-km distance between San Diego and Quincy, California, is shortening at 62 + or - 9 mm/yr. This geodetic estimate is consistent with the rate of motion between the two plates, calculated from geological data to be 53 + or - 3 mm/yr averaged over the past few million years.

  6. Modeling the mechanisms for the 100 Ma plate reorganisation

    NASA Astrophysics Data System (ADS)

    McKeon, R. L.; Morra, G.; Mller, D.; Seton, M.

    2009-12-01

    Several global plate tectonic reorganizations have been identified throughout Earth history at 300, 250, 220, 150, and 50 Ma and are often associated with major environmental change and phases of natural resource formation. The ultimate cause of such events is ascribed to either a plate driving mechanism with the mantle playing a passive role or to major mantle overturns driving plate tectonic episodicity. A significant yet often over-looked plate reorganization event occurred at the Albian/Cenomanian boundary. This ~100 Ma event is marked by a major bend in the fracture zones in the Indian Ocean from 310 to 360, a change in Pacific plate motion, as evidenced by the bend of the Mid-Pacific Mountains, Marcus Wake/Marshall Gilbert and Line Islands, and a period of peak ophiolite emplacement along the eastern margin of the Pacific rim. Coincident with the event is a regime change along the eastern Gondwana margin, from long-lived subduction to transtension, as well subsidence followed by rapid uplift in the sedimentary basins of central-eastern Australia (e.g. Eromanga and Surat basins). In order to analyze the possible mechanisms that may have triggered the ~100 Ma plate reorganization, we present preliminary results of combined regional and global geodynamic models performed with a recently developed, Multipole-accelerated Boundary Element Code (FMM-BEM) for solving the momentum equation in a spherical Earth. We generalize the problem to regional subduction initiation and expiration models around the Pacific and explicitly model the termination of subduction along the eastern Gondwana margin. We test the possibility that the termination of this subduction system triggered the larger plate reorganization at ~100 Ma. Our models will embed deep events; as slab avalanches and a general set of deep density and viscosity profiles. Finally, we assess the possible scenarios and mechanisms that may explain the ultimate causes of plate reorganization events.

  7. Marginal deformation of crustal plates as key to crustal motion, crustal spirals, and the driving force

    SciTech Connect

    Wood, B.G.M.

    1986-07-01

    Present plate tectonic models concentrate on compressive- and extensive-type plate margins, often incorporating shear margins as a subtype of compressive margins. However, if a single moving plate is considered, it becomes apparent that the leading edge is a compressive margin, the trailing edge is an extensive margin, and the lateral edges are shear margins. Conversely, if a plate's margin can be recognized by identifying areas of subduction (compression), rifting (extension), and strike slip and buckle folding (shearing), then not only can a plate be identified but its motion can also be inferred. The Pacific plate provides an excellent example. It is bounded by subduction trenches along its west-northwest margin, extension rifts along its east-southeast margin, and shear and buckle-fold complexes along its south-southwest and north-northeast margins. A west-northwest motion is inferred. As other major plates are examined, two striking features are revealed. A west-northwest to northwest motion is consistently identified, and the plates line up end to end forming a northwest-spiraling segmented band encircling the globe. The lateral margins of this band form the well-known Tethyan shear system. The plates comprising this band are of varying sizes and composition, and the extent of deformation along a plate margin is directly related to plate size. The Pacific and Eurasian plates dominate in size and marginal deformation. The tail of this north-spiraling ribbon of crustal plates is deformed in the Southern Hemisphere, most notably in the area of the African, Indian, and Australian plates. Each southern plate has a strong north component of motion as well as a counterclockwise spiraling action. The plates appear to have rotated in response to drag along the southern margin of the Pacific and Eurasian plates.

  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. Diffusion brazing nickel-plated stainless steel

    NASA Technical Reports Server (NTRS)

    Beuyukian, C. S.; Mitchell, M. J.

    1976-01-01

    To bond parts, sandwich assembly is made up of aluminum core, aluminum face sheet with brazing alloy interface, and nickel plated stainless steel part. Sandwich is placed between bottom and top glide sheet that is placed in stainless steel retort where assembly is bonded at 580 C.

  10. A Simple Model for the Vertical Crustal Movement Associated with the Earthquake Cycle Along the Pacific Coast of Northeast Japan

    NASA Astrophysics Data System (ADS)

    Sagiya, T.

    2013-12-01

    Before the 2011 M9.0 Tohoku-oki earthquake, rapid subsidence more than 5mm/yr has been observed along the Pacific coast of the Tohoku area by leveling, tide gauges, and GPS (Kato, 1979, Kato and Tsumura, 1979, El-Fiky and Kato, 1999). On the other hand, Stage 5e (~125 ka) marine terraces are widely recognized along the same area, implying the area is uplifting in a long-term. Ikeda (1999) hypothesized that these deformation signals reflect accumulation of elastic strain at the plate interface and there is a possibility of a giant earthquake causing a coastal uplift. However, the coastal area subsided as large as 1m during the 2011 main shock. Though we observe significant postseismic uplift, it is not certain if the preseismic as well as coseismic subsidence will be recovered. We construct a simple model of earthquake deformation cycle to interpret the vertical movement along the Pacific coast of northeast Japan. The model consists of a 40 km thick elastic lithosphere overlying a Maxwell viscoelastic asthenospher with a viscosity of 10^19 Pa s. Plate boundary is modeled as two rectangular faults located in the lithosphere and connected each other. As for the kinematic conditions of these faults, we represent the temporal evolution of fault slip as a sum of the steady term and the perturbation term following Savage and Prescott (1978). The first steady term corresponds to the long-term plate subduction, which contributes to long-term geomorphic evolution such as the marine terraces (Hashimoto et al., 2004). The second perturbation term represent earthquake cycle effects. We evaluate this effect under assumptions that earthquake occurrence is perfectly periodic, plate interface is fully coupled during interseismic periods, and the slip deficit is fully released by earthquakes. If the earthquake recurrence interval is shorter than the relaxation time of the structure, interseismic movement is in the opposite direction to the coseismic ones and changes almost linearly in time. On the other hand, if the earthquake recurrence is much longer than the relaxation time, we see significant temporal variation in the interseismic movement. If the shallow portion of the plate interface is locked over a long period, the coastal area has a postseismic uplift and then significant subsidence follows until the next earthquake. If the deeper portion of the plate interface is locked for a long time, we expect a significant coastal uplift in the interseismic period, which is inconsistent with the observation. The observed vertical movement can be reproduced only if the shallow portion has been locked for a long time and the deeper portion had earthquake much more frequently. Such a spatially heterogeneous behavior in earthquake recurrence is responsible for the enigmatic vertical movement along the northeast Japan. The result also indicates a high possibility of strain accumulation in the shallow portion of the plate interface when we observe a significant subsidence just above the deeper end of the locked zone.

  11. 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, oceanic transform fault, oceanic convergent boundary, subduction zone). Total length, mean velocity, and total rate of area production/destruction are computed for each class; the global rate of area production and destruction is 0.108 m2/s, which is higher than in previous models because of the incorporation of back-arc spreading.

  12. On the Origin of Plate Tectonics

    NASA Astrophysics Data System (ADS)

    Bercovici, D.

    2014-12-01

    The emergence of plate tectonics was Earth's defining moment. How and when platetectonics started is shrouded in mystery because of the paucity of observations in theArchean as well the challenge of understanding how plates are generated. The damage theoryof lithospheric weakening by grain-reduction provides a physical framework for plategeneration. This model builds on grain-scale processes to elucidate planetary-scaletectonics, and is consistent with lab and field observations of polycrystalline rocks andlithospheric shear zones. The grain-damage model accounts for the evolution of damage andhealing (by grain growth) at various planetary conditions, hence predicts plate boundaryformation and longevity, and how they depend on surface environment. For example, the onset of prototectonics is predicted to require clement conditions tokeep healing from erasing weak zones; conversely, cool conditions possibly requiredtectonics to draw down primordial CO2. Thus whether tectonics preceded a cool climate (andwater) or vice versa is immaterial as they likely needed each other or neither wouldexist. Sparse evidence that prototectonics co-initiated with liquid water hints at thelink between tectonics, water and surface conditions. The establishment of wide-spread plate tectonics started between >4Ga and 2.7Ga, and mayhave taken over a billion years to develop. Under Earth-like conditions, combininggrain-damage with intermittent Archean protosubduction produces persistent weak zones thataccumulate to yield well developed plates within 1Gyrs. In contrast, Venus' hottersurface conditions promotes healing and prohibits weak zone accumulation, which explainswhy plate tectonics failed to spread on our sister planet. Damage and weak-zone inheritance may also influence plate evolution and reorganization inthe modern era. Changes in plate direction, such as reflected in the Emperor-Hawaiianbend, leave weak zones misaligned with plate motion, causing oblique plate boundaries thatpersist for the age of the plate. Grain-damage within a cold subducting slab may alsocause its very rapid detachment, and the abrupt loss of the slab-pull force could accountfor precipitous changes in plate motion, such as for the Pacific plate at both 47Ma and6Ma.

  13. Data Access and Web Services at the EarthScope Plate Boundary Observatory

    NASA Astrophysics Data System (ADS)

    Matykiewicz, J.; Anderson, G.; Henderson, D.; Hodgkinson, K.; Hoyt, B.; Lee, E.; Persson, E.; Torrez, D.; Smith, J.; Wright, J.; Jackson, M.

    2007-12-01

    The EarthScope Plate Boundary Observatory (PBO) at UNAVCO, Inc., part of the NSF-funded EarthScope project, is designed to study the three-dimensional strain field resulting from deformation across the active boundary zone between the Pacific and North American plates in the western United States. To meet these goals, PBO will install 880 continuous GPS stations, 103 borehole strainmeter stations, and five laser strainmeters, as well as manage data for 209 previously existing continuous GPS stations and one previously existing laser strainmeter. UNAVCO provides access to data products from these stations, as well as general information about the PBO project, via the PBO web site (http://pboweb.unavco.org). GPS and strainmeter data products can be found using a variety of access methods, incuding map searches, text searches, and station specific data retrieval. In addition, the PBO construction status is available via multiple mapping interfaces, including custom web based map widgets and Google Earth. Additional construction details can be accessed from PBO operational pages and station specific home pages. The current state of health for the PBO network is available with the statistical snap-shot, full map interfaces, tabular web based reports, and automatic data mining and alerts. UNAVCO is currently working to enhance the community access to this information by developing a web service framework for the discovery of data products, interfacing with operational engineers, and exposing data services to third party participants. In addition, UNAVCO, through the PBO project, provides advanced data management and monitoring systems for use by the community in operating geodetic networks in the United States and beyond. We will demonstrate these systems during the AGU meeting, and we welcome inquiries from the community at any time.

  14. Seismicity Associated with a Stranded Plate Fragment Above the Juan de Fuca Slab in the Vicinity of the Mendocino Triple Junction

    NASA Astrophysics Data System (ADS)

    McCrory, P. A.; Waldhauser, F.; Oppenheimer, D. H.; Blair, J. L.

    2011-12-01

    Our new model of the subducted Juan de Fuca (JdF) plate beneath western North America, combined with the spatial resolution of double-differenced earthquake relocations, offers new insights regarding subsurface seismic sources in the complex tectonic setting near the Mendocino triple junction. Relocated seismicity resolves a double seismic zone within the slab beneath northwestern California that strongly constrains the location of the plate interface and delineates a cluster of seismicity ~10 km above the interface that includes the April 1992 M7.1 Cape Mendocino earthquake near its eastern edge. This cluster does not just represent aftershocks to the M7.1 event, but has persisted through time. About half of the earthquakes within the cluster occurred within the year following the April 1992 event. However, the remaining earthquakes either occurred within the 17 years preceding April 1992 or the 17 years following April 1993. The seismogenic structure forms a triangular shape approximately 80-km long in a north-south direction and up to 50-km long in a west-east direction. The structure is up to 8-km thick, and its surface dips gently landward from depths of ~6 to 14 km. Interpretation of the M7.1 event as occurring above the subduction interface requires a more complex slab geometry than previously envisioned. Specifically, the slab just east of the trench dips about 15° and then flattens to a dip of just a few degrees from ~15-25 km before it steepens again to about 25° from ~25-45 km, which is the maximum depth it can be imaged by hypocenters. The seismicity cluster is situated above the slab where it flexes concave upward in the transition from its initial moderate dip to a flat dip. Flat slab segments are observed elsewhere around the Pacific Rim where the subducting plate is relatively buoyant owing to young or thick oceanic crust, consistent with this JdF segment which is ~8-5 Ma where it enters the trench. These data provide compelling evidence that a significant fault with no surface expression exists in the forearc above the plate interface. We speculate that the seismicity cluster represents a detached fragment of oceanic plate that did not subduct and has been stranded within the accretionary prism, similar perhaps to the fragment of former Farallon plate found in the King Range not far to the south. Similar subsurface tectonic elements within the Cascadia forearc, such as remnants of the Resurrection plate, may also have the potential to generate damaging earthquakes-complicating our efforts to characterize earthquake hazards within the Cascadia subduction system.

  15. Pressurized bellows flat contact heat exchanger interface

    NASA Technical Reports Server (NTRS)

    Voss, Fred E. (Inventor); Howell, Harold R. (Inventor); Winkler, Roger V. (Inventor)

    1990-01-01

    Disclosed is an interdigitated plate-type heat exchanger interface. The interface includes a modular interconnect to thermally connect a pair or pairs of plate-type heat exchangers to a second single or multiple plate-type heat exchanger. The modular interconnect comprises a series of parallel, plate-type heat exchangers arranged in pairs to form a slot therebetween. The plate-type heat exchangers of the second heat exchanger insert into the slots of the modular interconnect. Bellows are provided between the pairs of fins of the modular interconnect so that when the bellows are pressurized, they drive the plate-type heat exchangers of the modular interconnect toward one another, thus closing upon the second heat exchanger plates. Each end of the bellows has a part thereof a thin, membrane diaphragm which readily conforms to the contours of the heat exchanger plates of the modular interconnect when the bellows is pressurized. This ensures an even distribution of pressure on the heat exchangers of the modular interconnect thus creating substantially planar contact between the two heat exchangers. The effect of the interface of the present invention is to provide a dry connection between two heat exchangers whereby the rate of heat transfer can be varied by varying the pressure within the bellows.

  16. 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.

  17. Plate tectonics and the Gulf of California region

    SciTech Connect

    Schmidt, N.

    1990-11-01

    The geology and tectonism of California have been influenced greatly by the collision and interaction between the Pacific plate and the North American plate. The forces generated by this interaction caused substantial horizontal movement along the San Andreas fault system and created the Gulf of California rift zone. This article summarizes the unique features of the gulf, describes the theory of plate tectonics, explains how tectonism may have affected the geologic evolution and physiography of the gulf, and illustrates the process by which the Colorado River became linked to the gulf.

  18. Mantle flow geometry from ridge to trench beneath the Gorda-Juan de Fuca plate system

    NASA Astrophysics Data System (ADS)

    Martin-Short, Robert; Allen, Richard M.; Bastow, Ian D.; Totten, Eoghan; Richards, Mark A.

    2015-12-01

    Tectonic plates are underlain by a low-viscosity mantle layer, the asthenosphere. Asthenospheric flow may be induced by the overriding plate or by deeper mantle convection. Shear strain due to this flow can be inferred using the directional dependence of seismic wave speeds--seismic anisotropy. However, isolation of asthenospheric signals is challenging; most seismometers are located on continents, whose complex structure influences the seismic waves en route to the surface. The Cascadia Initiative, an offshore seismometer deployment in the US Pacific Northwest, offers the opportunity to analyse seismic data recorded on simpler oceanic lithosphere. Here we use measurements of seismic anisotropy across the Juan de Fuca and Gorda plates to reconstruct patterns of asthenospheric mantle shear flow from the Juan de Fuca mid-ocean ridge to the Cascadia subduction zone trench. We find that the direction of fastest seismic wave motion rotates with increasing distance from the mid-ocean ridge to become aligned with the direction of motion of the Juan de Fuca Plate, implying that this plate influences mantle flow. In contrast, asthenospheric mantle flow beneath the Gorda Plate does not align with Gorda Plate motion and instead aligns with the neighbouring Pacific Plate motion. These results show that asthenospheric flow beneath the small, slow-moving Gorda Plate is controlled largely by advection due to the much larger, faster-moving Pacific Plate.

  19. 14. Date Plate, 'C.O. #836, Dwg. #12A, Full Size. For ...

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

    14. Date Plate, 'C.O. #836, Dwg. #12A, Full Size. For Portal Strut with Date Plate `DP' see dwg. #12' - Southern Pacific Railroad Shasta Route, Bridge No. 301.85, Milepost 301.85, Pollard Flat, Shasta County, CA

  20. 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.

  1. 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. PMID:17799689

  2. ASSEMBLY OF PARALLEL PLATES

    DOEpatents

    Groh, E.F.; Lennox, D.H.

    1963-04-23

    This invention is concerned with a rigid assembly of parallel plates in which keyways are stamped out along the edges of the plates and a self-retaining key is inserted into aligned keyways. Spacers having similar keyways are included between adjacent plates. The entire assembly is locked into a rigid structure by fastening only the outermost plates to the ends of the keys. (AEC)

  3. Paper terahertz wave plates.

    PubMed

    Scherger, Benedikt; Scheller, Maik; Vieweg, Nico; Cundiff, Steven T; Koch, Martin

    2011-12-01

    We present a low-cost terahertz wave plate based on form birefringence fabricated using ordinary paper. Measurements of the transfer function of the wave plate between polarizers closely agree with predictions based on the measured complex indices of refraction of the effective medium. For the design frequency, the dependence on wave plate angle also agrees with theory. PMID:22273881

  4. Convergent plate margin east of North Island, New Zealand

    SciTech Connect

    Davey, F.J; Hampton, M.; Lewis, K.

    1986-07-01

    The Indian-Pacific plate boundary passes along the eastern margin of North Island, New Zealand, with the Pacific plate being thrust under the Indian plate to the west. The continental slope forming the Indian plate margin is broad with a well-formed series of trench slope basins and intervening ridges along the continental slope and shelf, subparallel to the margin, and continuing onto land. Multichannel seismic reflection data recorded across this margin show a thick (2.5-km) sedimentary section overlying oceanic basement in the deep-water part of the profile, and part of this sedimentary section is apparently being subducted under the accretionary prism. At the toe of the continental slope, nascent thrusts, often showing little apparent offset but a change in reflection amplitude, occur over a broad region. Well-defined trench slope basins show several episodes of basin formation and thrusting and are similar to structural interpretations for adjacent onshore basins. A bottom simulating reflector, which may delineate a gas-hydrate layer, can be traced over the midslope part of the profile. A major reflector, interpreted as the base of the accretionary prism, can be traced discontinuously to the coast where it coincides with the top of a zone of high seismicity, considered to mark the top of the subducted Pacific plate.

  5. PACIFIC NORTHWEST CYBER SUMMIT

    SciTech Connect

    Lesperance, Ann M.; Matlock, Gordon W.; Becker-Dippmann, Angela S.; Smith, Karen S.

    2013-08-07

    On March 26, 2013, the Snohomish County Public Utility District (PUD) and the U.S. Department of Energy’s (DOE’s) Pacific Northwest National Laboratory (PNNL) jointly hosted the Pacific Northwest Cyber Summit with the DOE’s Office of Electricity Delivery and Energy Reliability, the White House, Washington State congressional delegation, Washington State National Guard, and regional energy companies.

  6. The Plate Boundary Observatory Cascadia Network: Development and Installation of a Large Scale Real-time GPS Network

    NASA Astrophysics Data System (ADS)

    Austin, K. E.; Blume, F.; Berglund, H. T.; Dittman, T.; Feaux, K.; Gallaher, W. W.; Mattioli, G. S.; Mencin, D.; Walls, C. P.

    2013-12-01

    The EarthScope Plate Boundary Observatory (PBO), through a NSF-ARRA supplement, has enhanced the geophysical infrastructure in in the Pacific Northwest by upgrading 232 Plate Boundary Observatory GPS stations to allow the collection and distribution of high-rate (1 Hz), low-latency (<1 s) data streams (RT-GPS). These upgraded stations supplemented the original 100 RT-GPS stations in the PBO GPS network. The addition of the new RT-GPS sites in the Pacific Northwest should spur new volcano and earthquake research opportunities in an area of great scientific interest and high geophysical hazard. Streaming RT-GPS data will enable researchers to detect and investigate strong ground motion during large geophysical events, including a possible plate-interface earthquake, which has implications for earthquake hazard mitigation. A total of 282 PBO stations were upgraded and added to the UNAVCO real-time GPS system, along with addition of 22 new meteorological instruments to existing PBO stations. Extensive testing of BGAN satellite communications systems has been conducted to support the Cascadia RT-GPS upgrades and the installation of three BGAN satellite fail over systems along the Cascadia margin will allow for the continuation of data flow in the event of a loss of primary communications during in a large geophysical event or other interruptions in commercial cellular networks. In summary, with these additional upgrades in the Cascadia region, the PBO RT-GPS network will increase to 420 stations. Upgrades to UNAVCO's data infrastructure included evaluation and purchase of the Trimble Pivot Platform, servers, and additional hardware for archiving the high rate data. UNAVCO staff is working closely with the UNAVCO community to develop data standards, protocols, and a science plan for the use of RT-GPS data.

  7. New estimates of subducted water from depths of extensional outer rise earthquakes at the Northwestern Pacific subduction zones

    NASA Astrophysics Data System (ADS)

    Emry, E. L.; Wiens, D. A.

    2012-12-01

    The presence of water within the subducting slab mantle may have important implications for subduction zone water budgets, intermediate depth earthquakes, and transport of water into Earth's deep mantle. However, the amount of water stored in hydrous slab mantle rocks prior to subduction is not well constrained. Large extensional faults formed as the plate bends at the subduction zone outer rise are thought to be the main pathway by which water can travel into and hydrate the slab mantle; yet for many subduction zones accurate depths of extensional outer rise faulting are also not well known. Therefore, we attempt to identify the maximum observed depth of extensional faulting, and thereby identify the possible depth extent of slab mantle hydration, by accurately locating and determining depths for outer rise and trench axis earthquakes at Northern and Western Pacific subduction zones. For each region, we relocate all earthquakes seaward of the trench axis as well as forearc earthquakes within 60 km landward of the trench axis using ISC arrival times and the hypocentroidal decomposition relative location algorithm. We then model P- and SH- waveforms and their associated depth phases for all earthquakes with Mw 5.0+ since 1990 that exhibit good signal-to-noise ratios and do not have shallow-dipping thrust focal mechanisms, which are indicative of subduction zone plate interface earthquakes. In total, we redetermined epicenters and depths for over 70 earthquakes at the Alaskan, Aleutian, Kamchatka, Kuril, Japan, and Izu-Bonin-Mariana trenches. We find that at most Pacific subduction zones there is evidence for extensional faulting down to 10-15 km within the top of the oceanic plate mantle, and in total, 95% of our analyzed extensional outer rise events occur within the crust or top 15 km of the mantle. However some regions, such as the Bonin and Aleutian Islands, show evidence for extensional faulting as deep as 20 km below the base of the crust. If the mantle of the subducting slab is hydrated down to ~15 km (with ~2-3.5 wt. % water), and assuming published values for the amount of water in the slab crust [1], then we expect that ~10^10 Tg/Myr of water are input into Northwestern Pacific subduction zones. This value for only the Northwestern Pacific subduction zones is then 10 times larger than previous global estimates [1] and indicates a need to reevaluate recent subduction water flux calculations. [1] Van Keken et al (2011), JGR, 116, B01401.

  8. Geographical distribution of shear wave anisotropy within marine sediments in the northwestern Pacific

    NASA Astrophysics Data System (ADS)

    Tonegawa, Takashi; Fukao, Yoshio; Fujie, Gou; Takemura, Shunsuke; Takahashi, Tsutomu; Kodaira, Shuichi

    2015-12-01

    In the northwestern Pacific, the elastic properties of marine sediments, including P-wave velocities ( Vp) and S wave velocities ( Vs), have recently been constrained by active seismic surveys. However, information on S anisotropy associated with the alignments of fractures and fabric remains elusive. To obtain such information, we used ambient noise records observed by ocean-bottom seismometers at 254 sites in the northwestern Pacific to calculate the auto-correlation functions for the S reflection retrieval from the top of the basement. For these S reflections, we measured differential travel times and polarized directions to reveal the potential geographical systematic distribution of S anisotropy. As a result, the observed differential times between fast and slow axes were at most 0.05 s. The fast polarization axes tend to align in the trench-parallel direction in the outer rise region. In particular, their directions changed systematically in accordance with the direction of the trench axis, which changes sharply across the junction of the Kuril and Japan trenches. We consider that a contributing factor for the obtained S anisotropy within marine sediments in the outer rise region is primarily aligned fractures due to the tensional stresses associated with the bending of the Pacific Plate. Moreover, numerical simulations conducted by using the three-dimensional (3D) finite difference method for isotropic and anisotropic media indicates that the successful extraction of S anisotropic information from the S reflection observed in this study is obtained from near-vertically propagating S waves due to extremely low Vs within marine sediments. In addition, we conducted an additional numerical simulation with a realistic velocity model to confirm whether S reflections below the basement can be extracted or not. The resultant auto-correlation function shows only S reflections from the top of the basement. It appears that such near-vertically propagating S waves obscure S reflections from interfaces below the basement.

  9. Deformation-related volcanism in the Pacific Ocean linked to the Hawaiian-Emperor bend

    NASA Astrophysics Data System (ADS)

    O'Connor, John M.; Hoernle, Kaj; Müller, R. Dietmar; Morgan, Jason P.; Butterworth, Nathaniel P.; Hauff, Folkmar; Sandwell, David T.; Jokat, Wilfried; Wijbrans, Jan R.; Stoffers, Peter

    2015-05-01

    Ocean islands, seamounts and volcanic ridges are thought to form above mantle plumes. Yet, this mechanism cannot explain many volcanic features on the Pacific Ocean floor and some might instead be caused by cracks in the oceanic crust linked to the reorganization of plate motions. A distinctive bend in the Hawaiian-Emperor volcanic chain has been linked to changes in the direction of motion of the Pacific Plate, movement of the Hawaiian plume, or a combination of both. However, these links are uncertain because there is no independent record that precisely dates tectonic events that affected the Pacific Plate. Here we analyse the geochemical characteristics of lava samples collected from the Musicians Ridges, lines of volcanic seamounts formed close to the Hawaiian-Emperor bend. We find that the geochemical signature of these lavas is unlike typical ocean island basalts and instead resembles mid-ocean ridge basalts. We infer that the seamounts are unrelated to mantle plume activity and instead formed in an extensional setting, due to deformation of the Pacific Plate. 40Ar/39Ar dating reveals that the Musicians Ridges formed during two time windows that bracket the time of formation of the Hawaiian-Emperor bend, 53-52 and 48-47 million years ago. We conclude that the Hawaiian-Emperor bend was formed by plate-mantle reorganization, potentially triggered by a series of subduction events at the Pacific Plate margins.

  10. 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.

  11. Malachite green photosensitive plates.

    PubMed

    Solano, C

    1989-08-15

    An experimental study of the behavior of malachite green sensitized plates was carried out. The transmittance variation of the irradiated plates was taken as a parameter. It has been observed that photoreduction in the malachite green plates is present only when ammonium dichromate is added to the plates. The introduction of external electron donors does not improve the photochemical reaction. It has been determined that malachite green molecules form a weak complex with the dichromate molecules and this complex can only be destroyed photochemically. This effect can explain the limited response of the malachite green dichromated plates. PMID:20555732

  12. 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.

  13. SKITTER/implement mechanical interface

    NASA Technical Reports Server (NTRS)

    Cash, John Wilson, III; Cone, Alan E.; Garolera, Frank J.; German, David; Lindabury, David Peter; Luckado, Marshall Cleveland; Murphey, Craig; Rowell, John Bryan; Wilkinson, Brad

    1988-01-01

    SKITTER (Spacial Kinematic Inertial Translatory Tripod Extremity Robot) is a three-legged transport vehicle designed to perform under the unique environment of the moon. The objective of this project was to design a mechanical interface for SKITTER. This mechanical latching interface will allow SKITTER to use a series of implements such as drills, cranes, etc., and perform different tasks on the moon. The design emphasized versatility and detachability; that is, the interface design is the same for all implements, and connection and detachment is simple. After consideration of many alternatives, a system of three identical latches at each of the three interface points was chosen. The latching mechanism satisfies the design constraints because it facilitates connection and detachment. Also, the moving parts are protected from the dusty environment by housing plates.

  14. 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.

  15. Metallic glass as a temperature sensor during ion plating

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Spalvins, T.; Buckley, D. H.

    1985-01-01

    The temperature of the interface and/or a superficial layer of a substrate during ion plating was investigated using a metallic glass of the composition Fe67Co18B14Si1 as the substrate and as the temperature sensor. Transmission electron microscopy and diffraction studies determined the microstructure of the ion-plated gold film and the substrate. Results indicate that crystallization occurs not only in the film, but also in the substrate. The grain size of crystals formed during ion plating was 6 to 60 nm in the gold film and 8 to 100 nm in the substrate at a depth of 10 to 15 micrometers from the ion-plated interface. The temperature rise of the substrate during ion plating was approximately 500 C. Discontinuous changes in metallurgical microstructure, and physical, chemical, and mechanical properties during the amorphous to crystalline transition in metallic glasses make metallic glasses extremely useful materials for temperature sensor applications in coating processes.

  16. Metallic glass as a temperature sensor during ion plating

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Spalvins, T.; Buckley, D. H.

    1984-01-01

    The temperature of the interface and/or a superficial layer of a substrate during ion plating was investigated using a metallic glass of the composition Fe67Co18B14Si1 as the substrate and as the temperature sensor. Transmission electron microscopy and diffraction studies determined the microstructure of the ion-plated gold film and the substrate. Results indicate that crystallization occurs not only in the film, but also in the substrate. The grain size of crystals formed during ion plating was 6 to 60 nm in the gold film and 8 to 100 nm in the substrate at a depth of 10 to 15 micrometers from the ion-plated interface. The temperature rise of the substrate during ion plating was approximately 500 C. Discontinuous changes in metallurgical microstructure, and physical, chemical, and mechanical properties during the amorphous to crystalline transition in metallic glasses make metallic glasses extremely useful materials for temperature sensor applications in coating processes.

  17. Tectonic map of the Circum-Pacific region, Pacific basin sheet

    USGS Publications Warehouse

    Scheibner, E.; Moore, G.W.; Drummond, K.J.; Dalziel, Corvalan Q.J.; Moritani, T.; Teraoka, Y.; Sato, T.; Craddock, C.

    2013-01-01

    Circum-Pacific Map Project: The Circum-Pacific Map Project was a cooperative international effort designed to show the relationship of known energy and mineral resources to the major geologic features of the Pacific basin and surrounding continental areas. Available geologic, mineral, and energy-resource data are being complemented by new, project-developed data sets such as magnetic lineations, seafloor mineral deposits, and seafloor sediment. Earth scientists representing some 180 organizations from more than 40 Pacific-region countries are involved in this work. Six overlapping equal-area regional maps at a scale of 1:10,000,000 form the cartographic base for the project: the four Circum-Pacific Quadrants (Northwest, Southwest, Southeast, and Northeast), and the Antarctic and Arctic Sheets. There is also a Pacific Basin Sheet at a scale of 1:17,000,000. The Base Map Series and the Geographic Series (published from 1977 to 1990), the Plate-Tectonic Series (published in 1981 and 1982), the Geodynamic Series (published in 1984 and 1985), and the Geologic Series (published from 1984 to 1989) all include six map sheets. Other thematic map series in preparation include Mineral-Resources, Energy-Resources and Tectonic Maps. Altogether, more than 50 map sheets are planned. The maps were prepared cooperatively by the Circum-Pacific Council for Energy and Mineral Resources and the U.S. Geological Survey and are available from the Branch of Distribution, U. S. Geological Survey, Box 25286, Federal Center, Denver, Colorado 80225, U.S.A. The Circum-Pacific Map Project is organized under six panels of geoscientists representing national earth-science organizations, universities, and natural-resource companies. The six panels correspond to the basic map areas. Current panel chairmen are Tomoyuki Moritani (Northwest Quadrant), R. Wally Johnson (Southwest Quadrant), Ian W.D. Dalziel (Antarctic Region), vacant. (Southeast Quadrant), Kenneth J. Drummond (Northeast Quadrant), and George W. Moore (Arctic Region). Project coordination and final cartography was being carried out through the cooperation of the Office of the Chief Geologist of the U.S. Geological Survey, under the direction of General Chairman, George Gryc of Menlo Park, California. Project headquarters were located at 345 Middlefield Road, MS 952, Menlo Park, California 94025, U.S.A. The framework for the Circum-Pacific Map Project was developed in 1973 by a specially convened group of 12 North American geoscientists meeting in California. The project was officially launched at the First Circum-Pacific Conference on Energy and Mineral Resources, which met in Honolulu, Hawaii, in August 1974. Sponsors of the conference were the AAPG, Pacific Science Association (PSA), and the Coordinating Committee for Offshore Prospecting for Mineral Resources in Offshore Asian Areas (CCOP). The Circum-Pacific Map Project operates as an activity of the Circum-Pacific Council for Energy and Mineral Resources, a nonprofit organization that promotes cooperation among Circum-Pacific countries in the study of energy and mineral resources of the Pacific basin. Founded by Michel T. Halbouty in 1972, the Council also sponsors conferences, topical symposia, workshops and the Earth Science Series books. Tectonic Map Series: The tectonic maps distinguish areas of oceanic and continental crust. Symbols in red mark active plate boundaries, and colored patterns show tectonic units (volcanic or magmatic arcs, arc-trench gaps, and interarc basins) associated with active plate margins. Well-documented inactive plate boundaries are shown by symbols in black. The tectonic development of oceanic crust is shown by episodes of seafloor spreading. These correlate with the rift and drift sequences at passive continental margins and episodes of tectonic activity at active plate margins. The recognized episodes of seafloor spreading seem to reflect major changes in plate kinematics. Oceanic plateaus and other prominences of greater than normal oceanic crustal thickness such as hotspot traces are also shown. Colored areas on the continents show the ages of deformation and metamorphism of basement rocks and the emplacement of igneous rocks. Transitional tectonic (molassic) and reactivation basins are shown by a colored boundary, and if they are deformed, a colored horizontal line pattern indicates the age of deformation. Colored bands along basin boundaries indicate age of inception, and isopachs indicate thickness of platform strata on continental crust and cover on oceanic crust. Colored patterns at separated continental margins show the age of inception of rift and drift (breakup) sequences. Symbols mark folds and faults, and special symbols show volcanoes and other structural features. Affiliations are as of compilation of the data. This map was created in quadrants and then compiled together. They are the Northwest land, Northwest Marine (different compilers), Northeast, Southwest and Southeast, and parts in plate-boundary sections.

  18. Asian American-Pacific American Relations: The Pacific American Perspective.

    ERIC Educational Resources Information Center

    Mamak, Alexander; Luce, Pat

    This report provides the Pacific American perspective on the current problems and future prospects of Asian and Pacific American relations in the context of Federal assistance. The report is divided into three parts. The first emphasizes the long history of contact between Asians and Pacific Islanders in the Pacific. This history, it is argued,…

  19. The age and origin of the Pacific islands: a geological overview.

    PubMed

    Neall, Vincent E; Trewick, Steven A

    2008-10-27

    The Pacific Ocean evolved from the Panthalassic Ocean that was first formed ca 750 Ma with the rifting apart of Rodinia. By 160 Ma, the first ocean floor ascribed to the current Pacific plate was produced to the west of a spreading centre in the central Pacific, ultimately growing to become the largest oceanic plate on the Earth. The current Nazca, Cocos and Juan de Fuca (Gorda) plates were initially one plate, produced to the east of the original spreading centre before becoming split into three. The islands of the Pacific have originated as: linear chains of volcanic islands on the above plates either by mantle plume or propagating fracture origin, atolls, uplifted coralline reefs, fragments of continental crust, obducted portions of adjoining lithospheric plates and islands resulting from subduction along convergent plate margins. Out of the 11 linear volcanic chains identified, each is briefly described and its history summarized. The geology of 10 exemplar archipelagos (Japan, Izu-Bonin, Palau, Solomons, Fiji, New Caledonia, New Zealand, Society, Galápagos and Hawaii) is then discussed in detail. PMID:18768382

  20. Microplate transfer by lithospheric coupling forces at the plate boundary

    NASA Astrophysics Data System (ADS)

    Plattner, C.; Malservisi, R.; Govers, R.; Iaffaldano, G.

    2009-04-01

    The Baja California (BAJA) microplate was ruptured from the North American (NAM) plate ~ 12 Ma ago and since then translated with the Pacific (PAC) plate. The microplates' transport mechanism has been explained by partial coupling with the PAC plate. According to this theory, the young oceanic lithosphere from the Farallon-Pacific spreading center approaching North America was too buoyant to be subducted. Therefore a zone of increased lithospheric coupling developed between the partially subducted Farallon slabs and the overlying NAM margin. In consequence both, the subduction and the seafloor spreading slowed down and ceased. With the development of this coupling region west of BAJA the main PAC-NAM plate boundary jumped inland east of BAJA, first delocalized in the Protogulf extensional province, and later localized along the Gulf of California. We use a numerical modeling technique to test the dynamic conditions of BAJA transport as seen from present-day and from geologic plate motion studies. Using the kinematic data we test the necessary coupling forces for BAJA transport, as well as, geometrical constraints along the PAC-BAJA coupling zone. Evaluating the transport conditions at different stages of the plate boundary evolution, we want to learn about necessary pre-conditions for the BAJA transfer.

  1. Geology and plate-tectonic development

    SciTech Connect

    Irwin, W.P.

    1990-01-01

    The San Andreas fault is a transform fault along the boundary between the Pacific and North American plates. Bedrock along the fault includes various lithologic units that range in age from Precambrian to Tertiary and younger. Some bedrock units that can be matched across the fault suggest strike-slip displacement of as much as 560 km. This chapter describes geologic formations of northern and central California, including Franciscan rocks, Coast Range ophiolite, Great Valley sequence, Coast Range thrust, Salinian block, displacement of pre-Quaternary rocks by the San Andreas fault, and the relation of geologic structure to seismic behavior. Formations of southern California which are described are the Transverse Ranges and the Salton Trough and displacement of basement rocks by the San Andreas fault. Plate-tectonic development of the San Andreas fault is also discussed.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Low loss dichroic plate

    NASA Technical Reports Server (NTRS)

    Woo, R. T.; Ludwig, A. C. (Inventor)

    1973-01-01

    A low loss dichroic plate is disclosed for passing radiation within a particular frequency band and reflecting radiation outside of that frequency band. The dichroic plate is comprised of a configuration of dipole elements defined by slots formed in a conductive plate. The slots are dimensioned so as to pass radiation of a selected frequency and are shaped so as to minimize the relationship between that frequency and the tilt angle of the plate relative to the direction of radiation. The slots are arranged so as to minimize signal power loss due to cross polarization effects.

  7. 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.

  8. 3D Simulation of the Entire Process of Earthquake Generation at Subduction-Zone Plate Boundaries

    NASA Astrophysics Data System (ADS)

    Matsu'Ura, M.; Hashimoto, C.; Fukuyama, E.

    2003-12-01

    In general, the entire process of earthquake generation consists of tectonic loading due to relative plate motion, quasi-static rupture nucleation, dynamic rupture propagation and stop, and restoration of fault strength. This process can be completely described by a coupled nonlinear system, which consists of an elastic/viscoelastic slip-response function that relates fault slip to shear stress change and a fault constitutive law that prescribes change in shear strength with fault slip and contact time. The shear stress and the shear strength are related with each other through boundary conditions on the fault. The driving force of this system is observed relative plate motion. The system to describe the earthquake generation cycle is conceptually quite simple. The complexity in practical modelling mainly comes from complexity in structure of the real earth. As a product of Crustal Activity Modelling Program (CAMP), which is one of the three main programs composing the Solid Earth Simulator project (1998-2003) promoted by MEXT, we have completed a physics-based predictive simulation model for the entire process of earthquake generation cycles in and around Japan, where the four plates of Pacific, North American, Philippine Sea and Eurasian are interacting with each other in a very complicated way. The total simulation system consists of a crust-mantle structure model, a tectonic loading model and a dynamic rupture model. First, we constructed a realistic 3D standard model of plate interfaces in and around Japan by applying an inversion technique to ISC hypocenter distribution data, and computed viscoelastic slip-response functions for this structure model. Second, we introduced the slip- and time-dependent fault constitutive law with an inherent strength-restoration mechanism as a basic equation governing the entire process of earthquake generation. Third, combining all these elements, we developed a simulation model for quasi-static stress accumulation due to relative plate motion. Fourth, we also developed a simulation model for dynamic rupture propagation on a 3D curved fault surface by applying BIEM. Finally, we connected the quasi-static stress accumulation model and the dynamic rupture propagation model through a simulation platform on the Earth Simulator, which is a high performance, massively parallel-processing computer system with 10 TB memories and 40 TFLOPS peak speed. Outputs of this simulation system are crustal deformation, internal stress changes and seismic wave radiation associated with seismic and/or aseismic slip at the plate interfaces. From comparison of these simulation outputs and observed data, we can extract useful information to estimate the past slip history and the present stress state at the plate interfaces by using an inversion technique. Given the past slip history and the present stress state, we can predict the next step fault slip and stress changes through computer simulation. In this presentation, as a demonstration, we show the result of 3D simulation of the entire process of earthquake generation cycle at the Tokachi-oki seismogenic region in northeast Japan.

  9. 11. GIRDER PARTIAL ELEVATION AND SECTIONS, 80 FOOT THROUGH PLATE ...

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

    11. GIRDER PARTIAL ELEVATION AND SECTIONS, 80 FOOT THROUGH PLATE GIRDER SPAN. (Also includes a Marking Diagram and a schedule of parts.) American Bridge Company, Ambridge Plant No. 5, sheet no. 1, dated April 7, 1928, order no. F5073. For U.S. Steel Products Company, Pacific Coast Depot, order no. SF578. For Southern Pacific Company, order no. 8873-P-28746. Scale 1/4 inch to one foot. - Napa River Railroad Bridge, Spanning Napa River, east of Soscol Avenue, Napa, Napa County, CA

  10. Changes in Plate Motion During Quaternary and Neogene Time (Invited)

    NASA Astrophysics Data System (ADS)

    Gordon, R. G.; Demets, C.; Argus, D.; Royer, J.

    2009-12-01

    We review some of the evidence for significant changes in plate motion during the past 25 Ma. We will review plate motions estimated over the past 0.78 to 3.2 Ma in the MORVEL set of relative plate angular velocities [DeMets, Gordon, and Argus, 2009], which are derived mainly from spreading rates from marine magnetic anomalies and from the azimuths of well-surveyed transform faults. We will also review plate relative angular velocities estimated from geodetic data while focusing on the GEODVEL set of relative plate angular velocities [Argus et al. 2009], which is determined from a combination of GPS, VLBI, SLR, and DORIS data. We will compare these two data sets to search for recent statistically significant changes in plate motion and, in some cases, discuss possible causes of these changes. We will also review Neogene changes in plate motion with a focus on the change in plate motion in the Indian and Pacific Oceans at about 6 to 8 Ma ago [e.g., Cande et al. 1995; DeMets, Gordon, and Royer 2005; Merkouriev and DeMets, 2006], which includes the onset of lithospheric folding in the equatorial Indian Ocean.

  11. The History of the Pacific Superplume

    NASA Astrophysics Data System (ADS)

    Suzuki, N.; Utsunomiya, A.; Maruyama, S.

    2001-12-01

    To understand the birth place and episodic activity of the Pacific superplume, we reconstructed the paleogeograhy of continents and oceanic plates from 1.0 Ga supercontinent Rodinia until now by adopting the most confident available data set to determine paleopositions of oceanic plateaus, seamounts, and oceanic arc, in addition to major continents, by using plate trajectory for the last 150Ma and for the farther back to 1.0Ga, by the paleomagnetic constraints tied with geologic connections. Our main focus is the frequency change of ancient activity of plume rocks that are now preserved in the accretionary complex around the circum-Pacific orogenic belts. Several conclusions are led through our reconstruction. (1) Cretaceous oceanic plateaus which present widespread in western Pacific (e.g., Manihiki Plateau, Shatsky Rise, Hess Rise, Mid-Pacific Mountain, Nauru Basin) are traced back and concentrated to the present active region of the Pacific superplume. This suggests that those were once formed a huge composite volcanoes as large as 4000 km x 2400 km across during the Cretaceous by superplume activity. These are equivalent to Australia or Tharsis bulge volcanic complex on Mars. The estimated thickness of oceanic crust ca. 30-40 km suggests that major parts may have been above sea-level during the Cretaceous time. The Cretaceous global warming may be related to this hyper-active superplume event which have carried mantle CO2 to the surface of 3.2 x 1021 g, assuming 0.3 wt% x 350 million km3 (magma volume) x 3.07 g/cm3 during 150-75 Ma. This CO2 output amount occupies as much as 37 wt% among the total output from mantle estimated by using erupted basaltic volume estimated by Larson (1991, Geology, 549-550) and present output rate of CO2. The similar episodic activity of Pacific superplume seems to have occurred at 750-700 Ma, 550-500Ma, 300-250Ma by considering the frequency of occurrences of greenstones in the accretionary complexes of the world. (2) Rodinia rifted and separated at 750Ma on the similar latitude to present active region of the Pacific superplume. This suggests that Pacific superplume may be born at 750Ma to break-up supercontinent Rodinia to support the original idea by Maruyama (1994, J. Geol. Soc. Japan, 100, 24-49) as African superplume may be born at 250-200 Ma to break-up Pangea. (3) At 1000Ma, the Grenvillian orogens cemented amalgamated collisional continents to form the supercontinent Rodinia. This suggests that the large amounts of oceanic slab must have subducted along the Grenvillian sutures and might have caused the birth of Pacific superplume.

  12. Growth Plate Injuries

    MedlinePlus

    ... place and immobilized. However, the growth plate fracture heals a great deal, especially in younger children. If it is not too displaced, the doctor may not need to put it back into position. In this case, it will strengthen with time. Type III: Fracture Through Growth Plate and Epiphysis ...

  13. 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). 

  14. MyPlate

    MedlinePlus

    ... Food Gallery Oils All About Oils How Are Oils Different from Solid Fats? Nutrients and Health Benefits Audience Children Preschoolers Kids ... Food Gallery Oils All About Oils How Are Oils Different from Solid Fats? Nutrients and Health Benefits MyPlate, MyWins MyPlate Moments ...

  15. 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.

  16. Present-day plate motions. [ocean bottom movements

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    An instantaneous plate-motion model, Relative Motion 2 (RM2), is obtained by inverting a data set comprising 110 spreading rates, 78 transform fault azimuths, and 142 earthquake slip vectors. RM2 is compared with angular velocity vectors which best fit the data along individual plate boundaries and, while the model performs close to optimally in most regions, attention is directed to those regions which are not suitably described by the model. Reasons for the discrepancies between RM2 and observations for the India-Antarctica plate boundary, the Pacific-India plate boundary, and the east-west trending transform fault azimuths observed in the French-American Mid-Ocean Undersea Study area are discussed.

  17. Turbine vane plate assembly

    SciTech Connect

    Schiavo Jr., Anthony L.

    2006-01-10

    A turbine vane assembly includes a turbine vane having first and second shrouds with an elongated airfoil extending between. Each end of the airfoil transitions into a shroud at a respective junction. Each of the shrouds has a plurality of cooling passages, and the airfoil has a plurality of cooling passages extending between the first and second shrouds. A substantially flat inner plate and an outer plate are coupled to each of the first and second shrouds so as to form inner and outer plenums. Each inner plenum is defined between at least the junction and the substantially flat inner plate; each outer plenum is defined between at least the substantially flat inner plate and the outer plate. Each inner plenum is in fluid communication with a respective outer plenum through at least one of the cooling passages in the respective shroud.

  18. Sizing plate heat exchangers

    SciTech Connect

    Kerner, J. )

    1993-11-01

    Since their commercial debut in the 1930s, plate heat exchangers have found widespread use in the chemical process industries (CPI). Today, more than two dozen firms market this space-saving and highly efficient type of heat exchanger. One reason for the popularity of plate heat exchangers is that their overall heat-transfer coefficient (U) is superior to that of shell-and-tube heat exchangers [1,2,3,4]. In clean water-to-water service, for example, a shell-and-tube heat exchanger has a U value of 350 Btu/ft[sup 2]-h-F, much lower than the 1,000 of a plate design at the same pressure drop. However, the plate heat exchanger's much higher U values also mean that fouling factors have a much greater effect on calculations of exchanger surface area. The right fouling factor is the key to specifying plate heat exchanger areas correctly.

  19. 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.

  20. Recent Intraplate Volcanism on Young Pacific Seafloor

    NASA Astrophysics Data System (ADS)

    Scheirer, D.; Forsyth, D.; Donnelly, K.; Webb, S.; Hosford, A.; Langmuir, C.

    2002-05-01

    On leg 16 of R/V Melville's Cook Expedition (Nov-Dec 2001), we discovered evidence for recent volcanism along ridges and seamounts of young Pacific plate between 12-16degS. The patterns of this intraplate activity will shed light on the circulation and melting of mantle and the nature of lithospheric deformation associated with volcanic ridges and seamount chains beyond the region influenced by seafloor spreading processes at the neighboring East Pacific Rise. As part of the GLIMPSE experiment, we collected multibeam, sidescan sonar, potential field, seismic refraction, single-channel reflection, and microearthquake data over crust ranging in age from 1-7 Ma, and we collected rocks at 46 successful dredge and waxcore stations. The greater sidescan sonar reflectivity of the Hotu, Matua, and Brown volcanic areas relative to adjacent seafloor indicates their substantially younger ages. This is confirmed by the recovery of abundant, fresh lavas in the dredge hauls. The Hotu complex is less reflective than the adjacent Matua complex; given the age-resolution of sonar reflectivity, we infer that Hotu was last active between 100-200 ka and that Matua may have been very recently active. This trend is confirmed by the freshness of the basaltic glass from these two sites and will be confirmed directly with Ar-Ar dating of the basalts. The Sojourn Ridge, a 400 km long ridge to the north of Hotu and Matua, does not have sonar or sample evidence for recent activity, but the Brown Ridge immediately to the east (on younger crust) is very reflective and returned very fresh glasses along its nearly 200 km length. The Thanksgiving Seamounts, a chain mid-way between Hotu/Matua and Sojourn/Brown, does not appear to be recently active, based on sonar and sample inspection; it formed as a near-axis seamount chain similar to many chains identified in this area of the Pacific. Substantial melts are produced locally in the mantle beneath plate aged 1-7 Ma, these melts erupt on the seafloor over distances 100-200 km in the direction of plate motion, and properties of the Pacific lithosphere and asthenosphere in this area lead to this unusual intraplate activity. Continued geochemical and geophysical analysis, including results from an ongoing year-long passive OBS experiment, will demonstrate how mantle motions such as small-scale, longitudinal convection lead to melting and how properties of the lithosphere impede or promote ascent of that melt to the seafloor.

  1. A review of the tectonic evolution of the Northern Pacific and adjacent Cordilleran Orogen

    NASA Astrophysics Data System (ADS)

    Jakob, Johannes; Gaina, Carmen; Johnston, Stephen T.

    2014-05-01

    Numerous plate kinematic models for the North Pacific realm have been developed since the advent of plate tectonics in the early seventies (e.g Atwater (1970), Mammerickx and Sharman (1988)). Although published kinematic models are consistent with the broad scale features of the North Pacific, the link between plate motions and the evolution of the North American Cordillera remains poorly understood. Part of the problem lies in conflicting interpretations of geological versus paleomagnetic data sets, with the result being a lack of consensus regarding: the paleolocation of key geological units; the paleogeography of terrane formation and amalgamation; the motion, boundaries and even existence of oceanic plates; and the character (e.g. trend of subduction) and position of plate boundaries within the northern Pacific basin. Remnants of the Farallon and Kula plates, and some short-lived microplates, demonstrate the complicated tectonic evolution of the oceanic realm west of the North American margin (e.g. Rea and Dixon (1983); McCrory and Wilson (2013); Shephard et al. (2013)). The creation and destruction of major tectonic plates and microplates has presumably left a record in the Cordilleran orogen of western North America. However, working backward from the geological relationships to plate reconstructions remains difficult. Here we investigate the relationship between the plate motions of the Pacific Ocean and the terrane movements in the North American Cordillera by revising the marine magnetic and gravity anomalies of the northern Pacific. In particular, we reevaluate plate boundaries at times of major changes in plate geometry of the Pacific, Kula, Chinook and Farallon plates from C34n onward. Our focus is also on the plate geometries of the Resurrection, Eshamy and Siletz-Crescent plates during the time between anomaly C26 and C12, and the links between plate interactions and on-shore tectonic events recorded in the geological record of Vancouver Island, including the accretion of the Pacific Rim and Crescent terranes to Wrangellia between C25 and C18. References: Atwater, T. (1970). Implications of plate tectonics for the Cenozoic tectonic evolution of western North America. Geological Society of America Bulletin, 81, 3513-3536. McCrory, P. a., & Wilson, D. S. (2013). A kinematic model for the formation of the Siletz-Crescent forearc terrane by capture of coherent fragments of the Farallon and Resurrection plates. Tectonics, 32, 1-19. doi:10.1002/tect.20045 Rea, D. K., & Dixon, J. M. (1983). Late Cretaceous and Paleogene tectonic evolution of the North Pacific Ocean. Earth and Planetary Science Letters, 65, 145-166. Shephard, G. E., Müller, R. D., & Seton, M. (2013). The tectonic evolution of the Arctic since Pangea breakup: Integrating constraints from surface geology and geophysics with mantle structure. Earth-Science Reviews, 124, 148-183. doi:10.1016/j.earscirev.2013.05.012 Mammerickx, J., & Sharman, G. F. (1988). Tectonic evolution of the North Pacific during the Cretaceous quiet period. Journal of Geophysical Research, 93(B4), 3009-3024. doi:10.1029/JB093iB04p03009

  2. Tracing the Farallon plate through seismic imaging with USArray

    NASA Astrophysics Data System (ADS)

    Porritt, Robert William

    The Farallon plate system has been subducting off the western United States since at least the middle Mesozoic. This plate has undergone virtually every subduction process during this time including a long episode of flat-slab subduction, generation of microplates, and formation of oceanic plateaus. The shallow remains of this plate are two small microplates, the Gorda and Juan de Fuca, in the Pacific Northwest. The anomalous nature of these two small plates and the missing deeper evidence of subduction has motivated this study. The USArray seismic experiment has provided unprecedented spatial sampling of the seismic wavefield in the continuous United States. Utilizing this dataset, new imaging methods have been implemented and older imaging methods have been revitalized. This study first uses ambient seismic noise in the Pacific Northwest to extract short period Rayleigh waves which are sensitive to lithospheric scale structure. Phase velocities from this model are then combined with teleseismic delay times of body waves and surface waves to image the structure of the continuous United States from the surface through the mantle transition zone. The resolving power of this model allows tracing of the Farallon plate from the trench to the lower mantle. The seismic velocity structure of the continuous United States is broadly composed of a slow western half and fast eastern half separated by the Rocky Mountain Front. The low velocity of the western U.S. contains several high velocity anomalies. While previous work has focused on individual anomalies and suggested they represent lithospheric instabilities, a larger regional view indicates that these are the western remnants of the Farallon plate. Below the thick cratonic lithosphere of the eastern U.S., the Farallon plate contains significant topography due to a subducted heterogeneity of the oceanic plate and a viscosity contrast through the mantle transition zone. The velocity models presented herein provide a cohesive picture of Farallon subduction for the past 150 Ma.

  3. 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.

  4. Deck view, west approach; former Western Pacific (now Union Pacific) ...

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

    Deck view, west approach; former Western Pacific (now Union Pacific) Railroad at left; wind turbine generators atop hill in background; view to northeast; 90mm lens - Carroll Overhead Bridge, Altamont Pass Road, Livermore, Alameda County, CA

  5. 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 Pacific Congress on Computational Mechanics, July 2010, iopscience.iop.org/1757-899X/10/1/012012. [4] G. Morra, P. Chatelain, P. Tackley and P. Koumoutzakos, 2007, Large scale three-dimensional boundary element simulation of subduction, in Proceeding International Conference on Computational Science - Part III, LNCS 4489, pp. 1122-1129. Interaction between two subducting slabs.

  6. Alignment between seafloor spreading directions and absolute plate motions through time

    NASA Astrophysics Data System (ADS)

    Williams, Simon E.; Flament, Nicolas; Müller, R. Dietmar

    2016-02-01

    The history of seafloor spreading in the ocean basins provides a detailed record of relative motions between Earth's tectonic plates since Pangea breakup. Determining how tectonic plates have moved relative to the Earth's deep interior is more challenging. Recent studies of contemporary plate motions have demonstrated links between relative plate motion and absolute plate motion (APM), and with seismic anisotropy in the upper mantle. Here we explore the link between spreading directions and APM since the Early Cretaceous. We find a significant alignment between APM and spreading directions at mid-ocean ridges; however, the degree of alignment is influenced by geodynamic setting, and is strongest for mid-Atlantic spreading ridges between plates that are not directly influenced by time-varying slab pull. In the Pacific, significant mismatches between spreading and APM direction may relate to a major plate-mantle reorganization. We conclude that spreading fabric can be used to improve models of APM.

  7. Computational valve plate design

    NASA Astrophysics Data System (ADS)

    Kalbfleisch, Paul

    Axial piston machines are widely used in many industries for their designs compactness, flexibility in power transfer, variable flow rate, and high efficiencies as compared to their manufacturing costs. One important component of all axial piston machines that is a very influential on the performance of the unit is the valve plate. The aim of this research is to develop a design methodology that is general enough to design all types of valve plates and the simple enough not to require advanced technical knowledge from the user. A new style of valve plate designs has been developed that comprehensively considers all previous design techniques and does not require significant changes to the manufacturing processes of valve plates. The design methodology utilizes a previously developed accurate computer model of the physical phenomenon. This allows the precise optimization of the valve plate design through the use of simulations rather than expensive trial and error processes. The design of the valve plate is clarified into the form of an optimization problem. This formulation into an optimization problem has motivated the selection of an optimization algorithm that satisfies the requirements of the design. The proposed design methodology was successfully tested in a case study in the shown to be very successful in improving required performance of the valve plate design.

  8. Earthquakes and plate tectonics.

    USGS Publications Warehouse

    Spall, H.

    1982-01-01

    Earthquakes occur at the following three kinds of plate boundary: ocean ridges where the plates are pulled apart, margins where the plates scrape past one another, and margins where one plate is thrust under the other. Thus, we can predict the general regions on the earth's surface where we can expect large earthquakes in the future. We know that each year about 140 earthquakes of magnitude 6 or greater will occur within this area which is 10% of the earth's surface. But on a worldwide basis we cannot say with much accuracy when these events will occur. The reason is that the processes in plate tectonics have been going on for millions of years. Averaged over this interval, plate motions amount to several mm per year. But at any instant in geologic time, for example the year 1982, we do not know, exactly where we are in the worldwide cycle of strain build-up and strain release. Only by monitoring the stress and strain in small areas, for instance, the San Andreas fault, in great detail can we hope to predict when renewed activity in that part of the plate tectonics arena is likely to take place. -from Author

  9. Eastern Pacific Ocean Conference

    NASA Astrophysics Data System (ADS)

    The promotion of interaction among investigators of all oceanographic disciplines studying the eastern Pacific Ocean was the goal of the 1990 Eastern Pacific Ocean Conference (EPOC), held October 17-19 on the snow-covered slopes of Mt. Hood, Oreg. Thirty oceanographers representing all disciplines attended.Dick Barber, Duke University Marine Lab, Beaufort, N.C., chaired a session on the eastern equatorial Pacific Ocean, emphasizing issues related to biological activity. Steve Ramp of the Naval Postgraduate School in Montery, Calif., chaired a session on recent results from northern and central California experiments. On October 19, following an early morning earthquake, a business meeting and discussions regarding a collaboration in future experiments were held.

  10. A great earthquake rupture across a rapidly evolving three-plate boundary.

    PubMed

    Furlong, Kevin P; Lay, Thorne; Ammon, Charles J

    2009-04-10

    On 1 April 2007 a great, tsunamigenic earthquake (moment magnitude 8.1) ruptured the Solomon Islands subduction zone at the triple junction where the Australia and Solomon Sea-Woodlark Basin plates simultaneously underthrust the Pacific plate with different slip directions. The associated abrupt change in slip direction during the great earthquake drove convergent anelastic deformation of the upper Pacific plate, which generated localized uplift in the forearc above the subducting Simbo fault, potentially amplifying local tsunami amplitude. Elastic deformation during the seismic cycle appears to be primarily accommodated by the overriding Pacific forearc. This earthquake demonstrates the seismogenic potential of extremely young subducting oceanic lithosphere, the ability of ruptures to traverse substantial geologic boundaries, and the consequences of complex coseismic slip for uplift and tsunamigenesis. PMID:19359581

  11. Pole of rotating analysis of present-day Juan de Fuca plate motion

    NASA Technical Reports Server (NTRS)

    Nishimura, C.; Wilson, D. S.; Hey, R. N.

    1984-01-01

    Convergence rates between the Juan de Fuca and North American plates are calculated by means of their relative, present-day pole of rotation. A method of calculating the propagation of errors in addition to the instantaneous poles of rotation is also formulated and applied to determine the Euler pole for Pacific-Juan de Fuca. This pole is vectorially added to previously published poles for North America-Pacific and 'hot spot'-Pacific to obtain North America-Juan de Fuca and 'hot spot'-Juan de Fuca, respectively. The errors associated with these resultant poles are determined by propagating the errors of the two summed angular velocity vectors. Under the assumption that hot spots are fixed with respect to a mantle reference frame, the average absolute velocity of the Juan de Puca plate is computed at approximately 15 mm/yr, thereby making it the slowest-moving of the oceanic plates.

  12. An estimate of tidal and non-tidal modulations of plate subduction speed in the transition zone in the Tokai district

    NASA Astrophysics Data System (ADS)

    Tanaka, Yoshiyuki; Yabe, Suguru; Ide, Satoshi

    2015-09-01

    Non-volcanic tremors and slow slip events in subduction zones have been found to be triggered by small external stress disturbances, as demonstrated by the synchronization of temporal variations in tremor rate with diurnal and semi-diurnal tides. Therefore, long-term variations in tremor rate might be predicted by amplitude modulations of diurnal and semi-diurnal tides at decadal time scales. Given that tremors and slow slips are shear slip on the plate boundary, their long-term variations must be associated with fluctuations in plate subduction speed below the seismogenic zone. In previous work, we showed a good correlation between long-term seismicity and empirically calculated tremor rate based on observed tidal levels in the Nankai region, western Japan. Here, we present an improved method of modeling long-term slip rate fluctuation based on the calculation of Coulomb stress due to ocean and solid earth tides on the plate interface. We also include the effects of non-tidal ocean variations, such as the Pacific Decadal Oscillation and the Kuroshio Current, employing an ocean model developed by the Japan Meteorological Agency. We apply the method to the Tokai district, where the effects of the Kuroshio Current are large, and demonstrate the importance of considering non-tidal effects. Our calculated slip rate fluctuations could amount to 1 mm/year in decadal scales, and periods with faster rates partly corresponded to variations in seismicity. Slow slip events in the study region weakly corresponded to times of higher stress.

  13. Fracture of composite plates containing periodic buffer strips

    NASA Technical Reports Server (NTRS)

    Erdogan, F.; Bakioglu, M.

    1974-01-01

    Fracture of a composite plate which consists of perfectly bonded parallel load carrying laminates and buffer strips is considered. Fatigue cracks appear and spread in main laminates or in buffer strips or in both perpendicular to the interfaces. The external load is applied to the plate parallel to the strips and away from the crack region. The problem is solved for fully imbedded cracks and for broken laminates or strips. Corresponding stress intensity factors are calculated.

  14. Off-axis crustal thickness across and along the east pacific rise within the MELT area

    PubMed

    Canales; Detrick; Bazin; Harding; Orcutt

    1998-05-22

    Wide-angle seismic data along the Mantle Electromagnetic and Tomography (MELT) arrays show that the thickness of 0.5- to 1. 5-million-year-old crust of the Nazca Plate is not resolvably different from that of the Pacific Plate, despite an asymmetry in depth and gravity across this portion of the East Pacific Rise. Crustal thickness on similarly aged crust on the Nazca plate near a magmatically robust part of the East Pacific Rise at 17 degrees15'S is slightly thinner (5.1 to 5.7 kilometers) than at the 15 degrees55'S overlapping spreading center (5.8 to 6.3 kilometers). This small north-south off-axis crustal thickness difference may reflect along-axis temporal variations in magma supply, whereas the across-axis asymmetry in depth and gravity must be caused by density variations in the underlying mantle. PMID:9596565

  15. Pacific Northwest report, abstracts

    NASA Astrophysics Data System (ADS)

    The Pacific Northwest Region of the American Geophysical Union held its 35th annual meeting September 28-30, 1988, at the Royal Roads Millitary College in Victoria, British Columbia; 113 scientists attended. The ten sessions covered hydrology, general geophysics, geomagnetism, marine geology, oceanography, seismology, volcanology, and tectonophysics in 61 oral and 5 poster papers. Abstracts of the papers follow this introduction. At the banquet, E. Irving of the Pacific Geoscience Center spoke on “The Fall of Fixism.” The 36th annual meeting will be held in fall 1989 in Portland, Ore.; Ansel Johnson of Portland State University is convenor.

  16. Plate removal following orthognathic surgery.

    PubMed

    Little, Mhairi; Langford, Richard Julian; Bhanji, Adam; Farr, David

    2015-11-01

    The objectives of this study are to determine the removal rates of orthognathic plates used during orthognathic surgery at James Cook University Hospital and describe the reasons for plate removal. 202 consecutive orthognathic cases were identified between July 2004 and July 2012. Demographics and procedure details were collected for these patients. Patients from this group who returned to theatre for plate removal between July 2004 and November 2012 were identified and their notes were analysed for data including reason for plate removal, age, smoking status, sex and time to plate removal. 3.2% of plates were removed with proportionally more plates removed from the mandible than the maxilla. 10.4% of patients required removal of one or more plate. Most plates were removed within the first post-operative year. The commonest reasons for plate removal were plate exposure and infection. The plate removal rates in our study are comparable to those seen in the literature. PMID:26325615

  17. Biomechanics of bone-fracture fixation by stiffness-graded plates in comparison with stainless-steel plates

    PubMed Central

    Ganesh, VK; Ramakrishna, K; Ghista, Dhanjoo N

    2005-01-01

    Background In the internal fixation of fractured bone by means of bone-plates fastened to the bone on its tensile surface, an on-going concern has been the excessive stress-shielding of the bone by the excessively-stiff stainless-steel plate. The compressive stress-shielding at the fracture-interface immediately after fracture-fixation delays callus formation and bone healing. Likewise, the tensile stress-shielding of the layer of the bone underneath the plate can cause osteoporosis and decrease in tensile strength of this layer. Method In order to address this problem, we propose to use stiffness-graded plates. Accordingly, we have computed (by finite-element analysis) the stress distribution in the fractured bone fixed by composite plates, whose stiffness is graded both longitudinally and transversely. Results It can be seen that the stiffness-graded composite-plates cause less stress-shielding (as an example: at 50% of the healing stage, stress at the fracture interface is compressive in nature i.e. 0.002 GPa for stainless steel plate whereas stiffness graded plates provides tensile stress of 0.002 GPa. This means that stiffness graded plate is allowing the 50% healed bone to participate in loadings). Stiffness-graded plates are more flexible, and hence permit more bending of the fractured bone. This results in higher compressive stresses induced at the fractured faces accelerate bone-healing. On the other hand, away from the fracture interface the reduced stiffness and elastic modulus of the plate causes the neutral axis of the composite structure to be lowered into the bone resulting in the higher tensile stress in the bone-layer underneath the plate, wherein is conducive to the bone preserving its tensile strength. Conclusion Stiffness graded plates (with in-built variable stiffness) are deemed to offer less stress-shielding to the bone, providing higher compressive stress at the fractured interface (to induce accelerated healing) as well as higher tensile stress in the intact portion of the bone (to prevent bone remodeling and osteoporosis). PMID:16045807

  18. Shear-wave splitting and implications for mantle flow beneath the MELT region of the east pacific rise

    PubMed

    Wolfe; Solomon

    1998-05-22

    Shear-wave splitting across the fast-spreading East Pacific Rise has been measured from records of SKS and SKKS phases on the ocean-bottom seismometers of the Mantle Electromagnetic and Tomography (MELT) Experiment. The direction of fast shear-wave polarization is aligned parallel to the spreading direction. Delay times between fast and slow shear waves are asymmetric across the rise, and off-axis values on the Pacific Plate are twice those on the Nazca Plate. Splitting on the Pacific Plate may reflect anisotropy associated with spreading-induced flow above a depth of about 100 km, as well as a deeper contribution from warm asthenospheric return flow from the Pacific Superswell region. PMID:9596569

  19. Teleseismic receiver function imaging of the Pacific Northwest, United States

    NASA Astrophysics Data System (ADS)

    Eager, Kevin Charles

    The origins of widespread Cenozoic tectonomagmatism in the Pacific Northwest, United States likely involve complex dynamics including subduction of the Juan de Fuca plate and mantle upwelling processes, all of which are reflected in the crust and upper mantle. To provide an improved understanding of these processes, I analyze P-to- S converted phases using the receiver function method to image topographic variations on regional seismic discontinuities in the upper mantle, which provides constraints on mantle thermal structure, and the crust-mantle interface, which provides constraints on crustal thickness and composition. My results confirm complexity in the Juan de Fuca slab structure as found by regional tomographic studies, including limited evidence of the slab penetrating the transition zone between the 410 and 660 km discontinuities. Evidence is inconclusive for a simple mantle plume beneath the central Oregon High Lava Plains, but indicates a regional increase in mantle temperatures stretching to the east. This result implies the inflow of warm material, either from around the southern edge of the Juan de Fuca plate as it descends into the mantle, or from a regional upwelling to the east related to the Yellowstone hotspot. Results for regional crustal structure reveal thin (˜31 km) crust beneath the High Lava Plains relative to surrounding regions that exhibit thicker (35+ km) crust. The thick (≥ 40 km) crust of the Owyhee Plateau has a sharp western boundary and normal Poisson's ratio, a measure of crustal composition. I find a slightly thickened crust and low Poisson's ratio between Steens Mountain and the Owyhee Plateau, consistent with residuum from source magma of the Steens flood basalts. Central and southern Oregon exhibit very high Poisson's ratios and low velocity zones within the crust, suggesting a degree of intracrustal partial melt not seen along the center of the age-progressive High Lava Plains magmatic track, perhaps due to crustal melt drainage facilitated by the Brothers Fault zone. To perform the data analysis for this work, I developed a new MATLAB-based toolbox for handling large receiver function datasets called FuncLab that will be distributed to the scientific community.

  20. GEODVEL: Plate Motions From Space Geodesy

    NASA Astrophysics Data System (ADS)

    Argus, D. F.; Gordon, R. G.; Ma, C.; Eanes, R. J.; Heflin, M. B.; Owen, S. E.; Willis, P.

    2006-12-01

    We determine the relative angular velocities among eleven major plates using four space geodetic techniques. The data input consist of site motions estimated from 24 years of VLBI, 24 years of SLR, 14 years of GPS, and 12 years of DORIS data. We assign sites to plates on the basis of geology. We let sites move independently of plates if they are suspected of moving significantly due to isostatic adjustment to unloading of the late Pleistocene ice sheets. GEODVEL differs substantially from REVEL [Sella et al. 2002]. The 95% confidence limits in the GEODVEL angular velocities exclude REVEL for 19 of 21 plate pairs. The median angular velocity difference is 0.026 deg/Myr, which is 2.9 mm/yr. We will show that this difference is due partly to differences in the means by which the velocity of Earth's center is determined. (Sella et al. 2002 adopt ITRF19997; ITRF2000 differs from ITRF1997 by 2 mm/yr; we estimate the Earth center velocity to be near ITRF2000.) The relative angular velocities of seven plates are tightly constrained: North America, Eurasia, South America, Nubia, Pacific, Australia, and Antarctica. The three-dimensional standard error ellipsoids have principal semiaxes between 0.005 deg/Myr and 0.014 deg/Myr long; the one-dimensional 95% confidence limits are 0.6 to 1.8 mm/yr. We will compare GEODVEL against an updated set of angular velocities determined from seafloor spreading rates and transform azimuths.

  1. The surface and through crack problems in layered orthotropic plates

    NASA Technical Reports Server (NTRS)

    Erdogan, Fazil; Wu, Binghua

    1991-01-01

    An analytical method is developed for a relatively accurate calculation of Stress Intensity Factors in a laminated orthotropic plate containing a through or part-through crack. The laminated plate is assumed to be under bending or membrane loading and the mode 1 problem is considered. First three transverse shear deformation plate theories (Mindlin's displacement based first-order theory, Reissner's stress-based first-order theory, and a simple-higher order theory due to Reddy) are reviewed and examined for homogeneous, laminated and heterogeneous orthotropic plates. Based on a general linear laminated plate theory, a method by which the stress intensity factors can be obtained in orthotropic laminated and heterogeneous plates with a through crack is developed. Examples are given for both symmetrically and unsymmetrically laminated plates and the effects of various material properties on the stress intensity factors are studied. In order to implement the line-spring model which is used later to study the surface crack problem, the corresponding plane elasticity problem of a two-bonded orthotropic plated containing a crack perpendicular to the interface is also considered. Three different crack profiles: an internal crack, an edge crack, and a crack terminating at the interface are considered. The effect of the different material combinations, geometries, and material orthotropy on the stress intensity factors and on the power of stress singularity for a crack terminating at the interface is fully examined. The Line Spring model of Rice and Levy is used for the part-through crack problem. The surface crack is assumed to lie in one of the two-layered laminated orthotropic plates due to the limitation of the available plane strain results. All problems considered are of the mixed boundary value type and are reduced to Cauchy type of singular integral equations which are then solved numerically.

  2. Beyond plate tectonics

    NASA Astrophysics Data System (ADS)

    Cloud, P.

    1980-08-01

    The application of the approaches of terrestrial plate tectonics to other members of the solar system and to the history and future of the earth is discussed. The concepts of the plate tectonics of the earth are introduced, with attention given to sea floor spreading and differences between the current model of lithospheric plates and the classical concepts of continental drift, and the interdisciplinary nature of plate tectonics studies is emphasized. Relations between the origins of the earth and the solar system are considered, including the meteorites, sun, terrestrial planets, the moon and the terrestrial satellites. Problems connected with the early history of the earth and the related evolution of the biosphere, atmosphere, hydrosphere and crust are then discussed, with consideration given to the implications of lunar petrology and cosmochemistry and solar evolution. Finally, the paleoclimatological aspects of earth's future as the habitat of mankind is discussed, and earth science facilities and institutions desirable to promote further research are indicated.

  3. Growth Plate Fractures

    MedlinePlus

    ... then fixed into place with special implants like screws or wires, or by attaching metal plates to ... the knee joint. The fracture is fixed with screws. This restores normal joint alignment. In other cases, ...

  4. Flat plate solar oven

    SciTech Connect

    Parikh, M.

    1981-01-01

    The construction of an Indian Rs. 186 (US $20.33) flat-plate solar oven is described. Detailed drawings are provided and relevant information on cooking times and temperature for different foods is given.

  5. 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.

  6. 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)

  7. Plate tectonics: Metamorphic myth

    NASA Astrophysics Data System (ADS)

    Korenaga, Jun

    2016-01-01

    Clear evidence for subduction-induced metamorphism, and thus the operation of plate tectonics on the ancient Earth has been lacking. Theoretical calculations indicate that we may have been looking for something that cannot exist.

  8. Fiji in the South Pacific.

    ERIC Educational Resources Information Center

    Scott, Rosalind; Semaan, Leslie

    This text introduces Fiji and other island nations located in the Pacific, the world's largest ocean. Cut off from the world by vast expanses of water, these people developed a unique culture. Contents include: Teacher Overview, Geography of the South Pacific Islands, History of the South Pacific, Fiji, Traditional Village Life, Yaquna Ceremony,…

  9. Fiji in the South Pacific.

    ERIC Educational Resources Information Center

    Scott, Rosalind; Semaan, Leslie

    This text introduces Fiji and other island nations located in the Pacific, the world's largest ocean. Cut off from the world by vast expanses of water, these people developed a unique culture. Contents include: Teacher Overview, Geography of the South Pacific Islands, History of the South Pacific, Fiji, Traditional Village Life, Yaquna Ceremony,

  10. Positive battery plate

    NASA Technical Reports Server (NTRS)

    Rowlette, John R. (Inventor)

    1985-01-01

    The power characteristics of a lead acid battery are improved by incorporating a dispersion of 1 to 10% by weight of a thermodynamically stable conductivity additive, such as conductive tin oxide coated glass fibers (34) of filamentary glass wool (42) in the positive active layer (32) carried on the grid (30) of the positive plate (16). Positive plate potential must be kept high enough to prevent reduction of the tin oxide to tin by utilizing an oversized, precharged positive paste.

  11. Fractal multifiber microchannel plates

    NASA Technical Reports Server (NTRS)

    Cook, Lee M.; Feller, W. B.; Kenter, Almus T.; Chappell, Jon H.

    1992-01-01

    The construction and performance of microchannel plates (MCPs) made using fractal tiling mehtods are reviewed. MCPs with 40 mm active areas having near-perfect channel ordering were produced. These plates demonstrated electrical performance characteristics equivalent to conventionally constructed MCPs. These apparently are the first MCPs which have a sufficiently high degree of order to permit single channel addressability. Potential applications for these devices and the prospects for further development are discussed.

  12. Deep earthquakes in the southwest Pacific: A tectonic interpretation

    SciTech Connect

    Hamburger, M.W.; Isacks, B.L.

    1987-12-10

    This paper examines the spatial distribution deep earthquakes in the Tonga-Fiji-New Hebrides region of the southwest Pacific. Our interpretation emphasizes the complex Cenozoic tectonics of the Pacific/Indo-Australian plate boundary as a primary control on the distribution and deformation of subducted lithosphere. Most deep earthquakes in the interarc region are associated with the contorted Pacific plate lithosphere subducted at the Tonga Trench. However, anomalous groups of deep earthquakes located west of the Tonga zone are unrelated to the present plate configuration. Tectonic reconstructions of the region to 8 m.y. B.P. provide circumstantial evidence that (1) the anomalous events west of the Tonga zone occur in two pieces of detached lithosphere, subducted at the Vitiaz and proto-New Hebrides trenches during the late Miocene, (2) the flattening of the inclined seismic zone in northernmost Tonga is related to the rapid opening of the Lau Basin since 4 m.y. B.P., and (3) the sharp westward curvature of the Tonga seismic zone in this area coincides with a preexisting bend in the late Miocene Vitiaz arc. The sharpness of its present curvature appears to be secondary effect of shear flow in the lower mantle and compression between detached (Vitiaz) and attached (Tonga) lithosphere. Thus much of the contortion of the subducted lithosphere beneath Tonga-Fiji may be produced by local tectonic interactions, rather than collision of the slab with an impenetrable boundary in the midmantle. copyright American Geophysical Union 1987

  13. The Pacific Rim.

    ERIC Educational Resources Information Center

    Thomas, Paul F., Ed.

    1988-01-01

    The articles in this special edition were compiled to provide information to Canadian social studies teachers about Pacific Rim countries. Section 1, entitled "The Big Picture and Future Interests," contains: (1) "Social Studies for the 21st Century" (J. Tucker); (2) "Culture and Communication: A Perspective on Asian Studies for Tomorrow's…

  14. OCLC in Asia Pacific.

    ERIC Educational Resources Information Center

    Chang, Min-min

    1998-01-01

    Discusses the Online Computer Library Center (OCLC) and the changing Asia Pacific library scene under the broad headings of the three phases of technology innovation. Highlights include WorldCat and the OCLC shared cataloging system; resource sharing and interlibrary loan; enriching OCLC online catalog with Asian collections; and future outlooks.…

  15. Profile of Pacific Schools.

    ERIC Educational Resources Information Center

    Northwest Regional Educational Lab., Portland, OR.

    This profile contains tables and charts which provide baseline information on the Pacific Region school systems. The Region comprises the State of Hawaii, the Territories of American Samoa and Guam, the Commonwealth of the Northern Marianas, the Federated States of Micronesia, the Republic of Belau, and the Republic of the Marshall Islands.

  16. The dynamic response of inelastic, delaminated composite plates

    SciTech Connect

    Williams, T.O.; Addessio, F.L.

    1997-04-01

    The dynamic behavior of metal matrix composite (MMC) plates is considered. In particular, the influence of inelastic deformations and delamination at the interfaces of the lamina on the macroscopic and local response of Al{sub 2}O{sub 3}/Al plates are studied. The work is carried out using a recently developed plate theory which models both delamination and localized history-dependent effects such, as inelasticity. A linear debonding model for the interface is employed for the current work. The theory models both the initiation and growth of delaminations without imposing any restrictions on the location, size, or direction of growth of the delamination. In the current work the response of the individual lamina in the plate are modeled using the Method of Cells (MOC) micromechanical model. The inelastic behavior in the matrix is modeled using the unified viscoplastic theory of Bodner and Partom. The behavior of a Al{sub 2}O{sub 3}/Al plate under dynamic cylindrical bending subjected to a ramp and hold type of loading is examined. For simplicity, the plate is assumed to be composed of a cross-ply layup. It is shown that both inelastic deformations and delamination have a strong influence on dynamic plate behavior. The inelastic deformations have strong effect on the axial displacement while delamination has greater influence on the deflection.

  17. The cascading effects of absolute reference frames and geomagnetic polarity timescales on global plate motions

    NASA Astrophysics Data System (ADS)

    Zahirovic, S.; Seton, M.; Müller, R. D.; Torsvik, T. H.

    2011-12-01

    Global plate motion models use Africa and the Pacific as the base of plate rotation hierarchies, with many other plates moving relative to them. Relative plate motions in the Mesozoic are generally well resolved where seafloor spreading histories are preserved to the present-day. However, the choice of absolute reference frames, whether they are fixed-hotspot, moving-hotspot, true-polar wander-corrected or pure paleomagnetic, can have significant consequences for the absolute plate velocities of smaller plates that are at the mercy of the cascading effects of movement within a complex plate motion hierarchy. We use GPlates to sample plate velocities through time at equally spaced mesh nodes that are contained within continuously closing plate polygons. We calculate root-mean square plate velocities to isolate the effects of different absolute reference frames on absolute plate velocity trends. Apart from being a quality-control tool for the creation of global plate motion models, this approach allows us to track the source of plate velocity spikes, some of which may be indicative of plate reorganisation events. We use a similar approach to test whether alternative geomagnetic polarity time-scales introduce or help reduce anomalous plate velocity fluctuations in global plate motion models. The choice of timescales can affect the seafloor spreading rates partitioned across stage rotations and models of sea level change. Such a workflow may help test alternative timescales, in order to study the model-dependence and controversies that have recently surfaced regarding proposed plate reorganisation events and the mid-Cretaceous seafloor spreading pulse.

  18. Palaeotectonic implications of increased late Eocene-early Oligocene volcanism from South Pacific DSDP sites

    USGS Publications Warehouse

    Kennett, J.P.; Von Der Borch, C.; Baker, P.A.; Barton, C.E.; Boersma, A.; Cauler, J.P.; Dudley, W.C., Jr.; Gardner, J.V.; Jenkins, D.G.; Lohman, W.H.; Martini, E.; Merrill, R.B.; Morin, R.; Nelson, Campbell S.; Robert, C.; Srinivasan, M.S.; Stein, R.; Takeuchi, A.; Murphy, M.G.

    1985-01-01

    Late Eocene-early Oligocene (42-35 Myr) sediments cored at two DSDP sites in the south-west Pacific contain evidence of a pronounced increase in local volcanic activity, particularly in close association with the Eocene-Oligocene boundary. This pulse of volcanism is coeval with that in New Zealand and resulted from the development of an Indo- Australian / Pacific Plate boundary through the region during the late Eocene. The late Eocene / earliest Oligocene was marked by widespread volcanism and tectonism throughout the Pacific and elsewhere, and by one of the most important episodes of Cenozoic climatic cooling. ?? 1985 Nature Publishing Group.

  19. Plate convergence west of Patagonia and the Antarctic Peninsula since 61 Ma

    NASA Astrophysics Data System (ADS)

    Eagles, Graeme; Scott, Benjamin G. C.

    2014-12-01

    A new plate kinematic model portrays plate motions immediately west and south of Drake Passage in the southeast Pacific Ocean. Overall intermediate-to-slow rate spreading generated oceanic lithosphere as the Phoenix plate diverged from the Antarctic plate. The model shows a history of Phoenix plate motion that is interpretable as having been affected by a northeast-increasing gradient in the slab pull force since chron 18 (39 Ma), during which time newer, less dense lithosphere was subducting in the southwest than in the northeast. The model allows first calculations of Phoenix-Farallon (Nazca) plate motion parameters in the south Pacific plate circuit. Using these parameters, it is possible to show that the simplest assumptions about the ridge's segmentation, length and migration are consistent with existing suggestions of its location from consideration of slab window-related volcanism at sites in South America around 50 and 20 Ma. The parameters thus define ridge locations that can be used to define which plates were subducting beneath South America and the Magallanes and Antarctic plates, and when. We consider the relationships between the plate convergence rate, obliquity and the history of magmatism on the Antarctic Peninsula and at the North Patagonian batholith, showing that magmatic pulses can be related to accelerations in the plate convergence rate. Between these settings, Phoenix-South American plate motion was almost parallel to the Fuegian trench. Here, magmatism in Paleocene to early Miocene times must be related to the presence of a slab subducted beneath the region by the less oblique collision further north. Later magmatism can be related to migration of the Phoenix-Farallon ridge and Phoenix-Farallon-Antarctic triple junction into the area south of the Fuegian margin, which brought it into slow low-obliquity convergence with first Farallon and then Antarctic plate lithosphere.

  20. Caribbean plate interactions

    SciTech Connect

    Ball, M. )

    1993-02-01

    Vector analysis of plate motions, derived from studies of Atlantic magnetic lineations and fracture zone trends, indicates the following relative movements between the Caribbean, North American, and South American Plates. (1) During Early Jurassic to Early Cretaceous, the North American Plate moved 1900 km westward and 900 km northward relative to the South American Plate. A broad zone including the Caribbean region, i.e., the zone between the North and South America Plates, was a site of left-lateral shear and north-south extension. (2) During Early Cretaceous to Late Cretaceous, the North American Mate moved an additional 1200 km westward relative to South America across this zone. (3) During Late Cretaceous to the end of the Eocene, the North American Plate moved 200 km westward and 400 km northward relative to the South American Plate. (4) From the end of the Eocene to near the end of the Miocene, North America converged on South America some 200 km and moved 100 km eastward relative to it. Through the Mesozoic and earliest Tertiary history of the Caribbean, the region was a shear zone within which left-lateral displacement exceeded 3000 km and north-south extension exceeded 1300 km. In regard to time, 80% of the history of the Caribbean region is one of north-south extension and left-lateral shear. In terms of space, 97% of the shear is left-lateral and the ratio of divergence versus convergence is 7 to 1. Thus, characterizing the Caribbean region, and the Atlantic to its east, as a zone of north-south extension and left-lateral shear, is a fair generalization.

  1. Using Plate Mapping to Examine Portion Size and Plate Composition for Large and Small Divided Plates

    PubMed Central

    Sharp, David E.; Sobal, Jeffery; Wansink, Brian

    2015-01-01

    Does the size of a plate influence the serving of all items equally, or does it influence the serving of some foods – such as meat versus starch versus vegetables – very differently? To examine this, we utilize a promising new plate mapping method where people drew a meal on a paper plate to examine sensitivity to small versus large three-compartment divided plates in portion size and meal composition in a sample of 109 university students. The total drawn meal area was 37% bigger on large plates than small plates, that is, the portion of plate coverage did not differ by plate size. Men and women drew bigger vegetable portions and men drew bigger meat portions on large plates when compared to small plates. These results suggest that men and women are differentially sensitive to plate size for overall meal size and for meal composition. Implications for decreasing portion size and improving meal balance are discussed. PMID:25280373

  2. Interface standardization

    NASA Astrophysics Data System (ADS)

    Spencer, R.; Wong, V.

    1983-11-01

    Central-station applications create a large and attractive market for photovoltaics in the near future. However, some significant barriers lie between the industry of today and realization of that market. Manufacturing capacity and price are two principal impediments. The Utilities, which are the future system owners, are gaining experience with central-station PV power through the Sacramento Municipal Utility District, Hesperia and similar small central-station installations. SMUD has recognized that competition must be maintained to help reduce prices. So little standardization exists that the cost is driven upward to redefine mechanical and electrical interfaces for each vendor. New structues are required for each vendor and nonoptimum field geometries result from attempts to include more than one vendor in an array field. Standards at some hardware level are required.

  3. Interface standardization

    NASA Technical Reports Server (NTRS)

    Spencer, R.; Wong, V.

    1983-01-01

    Central-station applications create a large and attractive market for photovoltaics in the near future. However, some significant barriers lie between the industry of today and realization of that market. Manufacturing capacity and price are two principal impediments. The Utilities, which are the future system owners, are gaining experience with central-station PV power through the Sacramento Municipal Utility District, Hesperia and similar small central-station installations. SMUD has recognized that competition must be maintained to help reduce prices. So little standardization exists that the cost is driven upward to redefine mechanical and electrical interfaces for each vendor. New structues are required for each vendor and nonoptimum field geometries result from attempts to include more than one vendor in an array field. Standards at some hardware level are required.

  4. 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.

  5. Detailed Seismic Velocity Structure of the Plate Boundary, Cascadia Subduction Zone, from Prestack Waveform Inversion

    NASA Astrophysics Data System (ADS)

    Fortin, W.; Holbrook, W.; Tobin, H. J.; Keranen, K. M.; Everson, E.; Mallick, S.; Padhi, A.

    2013-12-01

    Understanding the geologic makeup of the Cascadia Subduction Zone (CSZ) has great importance for understanding seismic hazards in the coastal margin of the U.S. Pacific Northwest. The Cascadia margin is a potential earthquake and tsunami threat to the many millions who live in the area, yet details of its structure and mechanics remain poorly understood. In particular, the character of the subduction interface is elusive due to the CSZ's relatively aseismic behavior and low seismic reflectivity, making imaging difficult for passive and active source methods, respectively. In July 2012 seismic data were acquired as a part of the COAST project, spanning the important transition from the Cascadia basin, across the deformation front, and into the accretionary wedge. This modern data, coupled with sophisticated pre-stack full waveform seismic inversion methods, allows us to create highly detailed velocity models. While still computationally expensive, current computing clusters can perform these inversions with enough lateral density to yield highly detailed velocity information in both the vertical and horizontal. Here we present pre-stack full waveform inversions of a seismic line from the center of the COAST survey offshore Washington state as a cross section of the velocity structure of the CSZ. This detailed velocity model is a necessary initial step toward a detailed porosity cross section to be used to determine the role of fluids in the CSZ. Using these new data we investigate the lateral variability in reflectivity of the subducting plate boundary reflection in terms of its seismic velocity.

  6. The effects of emitter-tied field plates on lateral PNP ionizing radiation response

    SciTech Connect

    Barnaby, H.J.; Schrimpf, R.D.; Cirba, C.R.; Pease, R.L.; Fleetwood, D.M.; Kosier, S.L.

    1998-03-01

    Radiation response comparisons of lateral PNP bipolar technologies reveal that device hardening may be achieved by extending the emitter contact over the active base. The emitter-tied field plate suppresses recombination of carriers with interface traps.

  7. Elastocapillary coalescence of plates and pillars

    PubMed Central

    Wei, Z.; Schneider, T. M.; Kim, J.; Kim, H.-Y.; Aizenberg, J.; Mahadevan, L.

    2015-01-01

    When a fluid-immersed array of supported plates or pillars is dried, evaporation leads to the formation of menisci on the tips of the plates or pillars that bring them together to form complex patterns. Building on prior experimental observations, we use a combination of theory and computation to understand the nature of this instability and its evolution in both the two- and three-dimensional setting of the problem. For the case of plates, we explicitly derive the interaction torques based on the relevant physical parameters associated with pillar deformation, contact-line pinning/depinning and fluid volume changes. A Bloch-wave analysis for our periodic mechanical system captures the window of volumes where the two-plate eigenvalue characterizes the onset of the coalescence instability. We then study the evolution of these binary clusters and their eventual elastic arrest using numerical simulations that account for evaporative dynamics coupled to capillary coalescence. This explains both the formation of hierarchical clusters and the sensitive dependence of the final structures on initial perturbations, as seen in our experiments. We then generalize our analysis to treat the problem of pillar collapse in three dimensions, where the fluid domain is completely connected and the interface is a minimal surface with the uniform mean curvature. Our theory and simulations capture the salient features of experimental observations in a range of different situations and may thus be useful in controlling the ensuing patterns. PMID:25792949

  8. Miniature plasmonic wave plates.

    PubMed

    Drezet, Aurélien; Genet, Cyriaque; Ebbesen, Thomas W

    2008-07-25

    Linear birefringence, as implemented in wave plates, is a natural way to control the state of polarization of light. We report on a general method for designing miniature planar wave plates using surface plasmons. The resonant optical device considered here is a single circular aperture surrounded by an elliptical antenna grating. The difference between the short and long axis of each ellipsis introduces a phase shift on the surface plasmons which enables the realization of a quarter wave plate. Furthermore, the experimental results and the theoretical analysis show that the general procedure used does not influence the optical coherence of the polarization state and allows us to explore completely the surface of the unit Poincaré sphere by changing only the shape of the elliptical grating. PMID:18764329

  9. 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.

  10. Nitrided Metallic Bipolar Plates

    SciTech Connect

    Brady, Michael P; Tortorelli, Peter F; Pihl, Josh A; Toops, Todd J; More, Karren Leslie; Meyer III, Harry M; Vitek, John Michael; Wang, Heli; Turner, John; Wilson, Mahlon; Garzon, Fernando; Rockward, Tommy; Connors, Dan; Rakowski, Jim; Gervasio, Don

    2008-01-01

    The objectives are: (1) Develop and optimize stainless steel alloys amenable to formation of a protective Cr-nitride surface by gas nitridation, at a sufficiently low cost to meet DOE targets and with sufficient ductility to permit manufacture by stamping. (2) Demonstrate capability of nitridation to yield high-quality stainless steel bipolar plates from thin stamped alloy foils (no significant stamped foil warping or embrittlement). (3) Demonstrate single-cell fuel cell performance of stamped and nitrided alloy foils equivalent to that of machined graphite plates of the same flow-field design ({approx}750-1,000 h, cyclic conditions, to include quantification of metal ion contamination of the membrane electrode assembly [MEA] and contact resistance increase attributable to the bipolar plates). (4) Demonstrate potential for adoption in automotive fuel cell stacks. Thin stamped metallic bipolar plates offer the potential for (1) significantly lower cost than currently-used machined graphite bipolar plates, (2) reduced weight/volume, and (3) better performance and amenability to high volume manufacture than developmental polymer/carbon fiber and graphite composite bipolar plates. However, most metals exhibit inadequate corrosion resistance in proton exchange membrane fuel cell (PEMFC) environments. This behavior leads to high electrical resistance due to the formation of surface oxides and/or contamination of the MEA by metallic ions, both of which can significantly degrade fuel cell performance. Metal nitrides offer electrical conductivities up to an order of magnitude greater than that of graphite and are highly corrosion resistant. Unfortunately, most conventional coating methods (for metal nitrides) are too expensive for PEMFC stack commercialization or tend to leave pinhole defects, which result in accelerated local corrosion and unacceptable performance.

  11. Polyaxial Screws in Locked Plating of Tibial Pilon Fractures.

    PubMed

    Yenna, Zachary C; Bhadra, Arup K; Ojike, Nwakile I; Burden, Robert L; Voor, Michael J; Roberts, Craig S

    2015-08-01

    This study examined the axial and torsional stiffness of polyaxial locked plating techniques compared with fixed-angle locked plating techniques in a distal tibia pilon fracture model. The effect of using a polyaxial screw to cross the fracture site was examined to determine its ability to control relative fracture site motion. A laboratory experiment was performed to investigate the biomechanical stiffness of distal tibia fracture models repaired with 3.5-mm anterior polyaxial distal tibial plates and locking screws. Sawbones Fourth Generation Composite Tibia models (Pacific Research Laboratories, Inc, Vashon, Washington) were used to model an Orthopaedic Trauma Association 43-A1.3 distal tibia pilon fracture. The polyaxial plates were inserted with 2 central locking screws at a position perpendicular to the cortical surface of the tibia and tested for load as a function of axial displacement and torque as a function of angular displacement. The 2 screws were withdrawn and inserted at an angle 15° from perpendicular, allowing them to span the fracture and insert into the opposing fracture surface. Each tibia was tested again for axial and torsional stiffness. In medial and posterior loading, no statistically significant difference was found between tibiae plated with the polyaxial plate and the central screws placed in the neutral position compared with the central screws placed at a 15° position. In torsional loading, a statistically significant difference was noted, showing greater stiffness in tibiae plated with the polyaxial plate and the central screws placed at a 15° position compared with tibiae plated with the central screws placed at a 0° (or perpendicular) position. This study showed that variable angle constructs show similar stiffness properties between perpendicular and 15° angle insertions in axial loading. The 15° angle construct shows greater stiffness in torsional loading. PMID:26270750

  12. The San Andreas fault experiment. [gross tectonic plates relative velocity

    NASA Technical Reports Server (NTRS)

    Smith, D. E.; Vonbun, F. O.

    1973-01-01

    A plan was developed during 1971 to determine gross tectonic plate motions along the San Andreas Fault System in California. Knowledge of the gross motion along the total fault system is an essential component in the construction of realistic deformation models of fault regions. Such mathematical models will be used in the future for studies which will eventually lead to prediction of major earthquakes. The main purpose of the experiment described is the determination of the relative velocity of the North American and the Pacific Plates. This motion being so extremely small, cannot be measured directly but can be deduced from distance measurements between points on opposite sites of the plate boundary taken over a number of years.

  13. Northeast Pacific flatfish management

    NASA Astrophysics Data System (ADS)

    Trumble, Robert J.

    1998-03-01

    Exploitation of northeast Pacific flatfish effectively began in the late 1800s with the fishery for Pacific halibut. Harvest of other flatfish occurred on a limited, local basis until foreign fishing fleets came to the area in the late 1950s. When US and Canadian fishermen replaced the foreign fleets in the 1970s and 1980s, a conservation-based management system designed to control foreign fishing was applied to the domestic fleet. Flatfish stock assessment is based on scientific surveys, both trawl and longline, and on catch-age models. In Alaskan waters since 1989 and since 1996 in Canadian waters, mandatory observers collect data on species composition, discards of flatfish and other groundfish, and catch and discards of prohibited species. Fishermen pay observer costs. Most biomass and harvest occurs in the Bering Sea-Aleutian Islands area. Many northeast Pacific flatfish are near record-high abundance, an order of magnitude higher than 20 years ago. Exploitation rates based on F35% or F0.1 generate acceptable biological catch of more than 1 million mt, but annual harvest reaches only 300,000 mt. Total groundfish harvest is limited by an optimum yield limit of 2 million mt in the Bering Sea-Aleutian Islands, where the acceptable biological catch is 3 million mt, and by limits on amounts of Pacific halibut and other prohibited species bycatch. Most flatfish are relatively low-value species, and fishermen chose to fish for more valuable species. A large, powerful fleet which developed under open access in the US saw fishing time decline and economic problems increase as catching capacity grew, while Canada stabilized its fleet with limited entry and catch restrictions for individual vessels.

  14. Survey of ion plating sources. [conferences

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1979-01-01

    Based on the type of evaporation source, gaseous media and mode of transport, the following is 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 sustrate/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.

  15. Plate-mantle coupling from post-Pangea plate kinematics

    NASA Astrophysics Data System (ADS)

    Zahirovic, Sabin; Dietmar Müller, R.; Seton, Maria; Flament, Nicolas

    2015-04-01

    Convection in the Earth's mantle that involves plates at the surfaces gives rise to plate velocities that vary through time and depend on the balance of plate boundary forces, with the present-day providing a snapshot of this ongoing process. However, present-day plate velocities do not capture plate behaviour over geologically representative timeframes and thus cannot be used to evaluate factors limiting plate velocities. Previous studies investigated the effects of continental keels on plate speeds by either using the present-day snapshot or a limited number of reconstructed plate configurations, often leading to conflicting results. For example, an early assumption was that continental keels (especially cratons) were unlikely to impede fast plate motions because India's velocity approached ~20 cm/yr in the Eocene prior to the collision with Eurasia. We employ a modern plate reconstruction approach with evolving global topological plate boundaries for the post-Pangea timeframe (since 200 Ma) to evaluate factors controlling plate velocities. Plate boundary configurations and plate velocities are extracted from the open-source and cross-platform plate reconstruction package GPlates (www.gplates.org) at 1 Myr intervals. For each plate, at each timestep, the area of continental and cratonic lithosphere is calculated to evaluate the effect on plate velocities. Our results support that oceanic plates tend to be 2-3 times faster than plates with large portion of continental plate area, consistent with predictions of numerical models of mantle convection. The fastest plates (~8.5 cm/yr RMS) are dominated by oceanic plate area and high subducting portion of plate perimeter, while the slowest plates (~2.6-2.8 cm/yr RMS) are dominated by continental plate area and bounded by transforms and mid-oceanic ridge segments. Importantly, increasing cratonic fractions (both Proterozoic and Archean lithosphere) significantly impede plate velocities, suggesting that deep continental keels impinge on asthenospheric flow to increase shear traction, thus anchoring the plate in the more viscous mantle transition zone. However, plates with significant cratonic fragments exhibit short-lived (~10 Myr) accelerations, such as the rapid motion of the Indian plate that is correlated with plume head arrivals as recorded by large igneous province (LIPs) emplacement, highlighting the necessity to analyse plate velocities over long geological timeframes. By evaluating factors controlling plate velocities in the post-Pangea timeframe, simple principles can be applied to highlight potential plate velocity artefacts for Paleozoic and earlier times for which no hotspot tracks, nor in-situ seafloor spreading histories, are preserved. Based on the post-Pangea timeframe, a principle that can be applied to pre-Pangea times is that plates with less than ~50% continental area can reach RMS velocities of ~20 cm/yr, while plates with more than 50% continental fraction do not exceed RMS velocities of ~10 cm/yr. Similarly, plates with large portions of continental or cratonic area with RMS velocities exceeding ~15 cm/yr for more than ~10 Myr should be flagged as potential artefacts requiring further justification of plate driving forces in such scenarios.

  16. 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.

  17. 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.

  18. Is structural interface standardization beneficial?

    NASA Technical Reports Server (NTRS)

    Dombert, W. E.

    1983-01-01

    Factors applicable to fixed angle, large field and fixed angle, large building flat plate photovoltaic (PV) generator arrays are discussed in the context of standardization. It is concluded that structural interface standardization may be highly desirable in any one major project, but not at this time in the overall PV industry. Attempts to mandate such standardization will act as a deterrent to long-range improvements. In specific projects, structural standardization should be defined at the largest practical interface, leaving the maximum possible freedom to the module and array manufacturer. There is a corollary area, however, where detailed standards would benefit the industry; the matter of Standard Practices. Work being done towards definition of acceptable/desirable practices in materials, finishes, fastening and locking methods, grounding techniques, lightning protection, etc., and in handling the environmental ranges, should be continued.

  19. Overall contact conductance of a prototype Parallel Fin Thermal Interface

    NASA Technical Reports Server (NTRS)

    Stobb, C. A.; Limardo, Jose G.

    1992-01-01

    The Parallel Fin Thermal Interface has been developed and tested as an orbital replaceable interface. The interface consists of two identical plates with pairs of opposing parallel straight fins. Each pair of fins is sandwiched between two insert plates pressed against the fins with enough force for good heat transfer through the interface. Two prototype parallel fin interfaces were built (Model 140 and 380) with different fin and insert plate dimensions. Samples of the interfacing surfaces were found to have roughness values ranging from 22 to 35 microinches. Overall interface conductance (Hc) values of 46.7 to 74.2 Btu/hr sq ft-F were obtained for the 140 model in vacuum with an interface pressure from 18.8 to 37.5 psi, respectively. The Model 380 exhibited Hc values from 31.2 to 46.8 Btu/hr sq ft-F in vacuum, with respective interface pressures of 14.2 and 22.0 psi. Several correlations were found to agree with test data to within 20 percent.

  20. The Pacific RANET Project

    NASA Astrophysics Data System (ADS)

    Postawko, S.; Ah Poe, A.; Morrissey, M.

    2004-12-01

    There are few places in the world more vulnerable to the effects of climate variability and change than the island nations of the tropical Pacific Ocean. The region also faces great challenges in communicating the issues related to climate to the general population. Lack of communications infrastructure, multiple languages, and knowledgeable personnel to deliver information, are all challenges for these countries. However, a recently developed international consortium is taking the first steps to addressing these challenges. The RANET (RAdio and interNET communications) project was originally developed for the countries of Africa, with initial funding from NOAA, to make weather, climate, and other environmental information more accessible to remote and resource-poor communities. The program is now expanding into Asia and the Pacific. RANET works to build telecommunication bridges between scientific-based products and remote communities that could benefit from such information.?The RANET project in the Pacific is a consortium of partners from the Pacific Island nations, the U.S., New Zealand, Australia, and others. Coordination of the project is loosely overseen by a Steering Committee, made up of representatives from the various interested partners. For regions where the appropriate technology exists (which includes the capital cities of nearly all of the island states of the Pacific), information is downloaded via a digital satellite receiver. This can then be broadcast within a country by many means, including Community FM Radio stations. The information distributed includes technical information needed by meteorological and related services to improve their own products and services, as well as a second level of information designed to serve communities, including weather forecasts, bulletins, warnings, etc. The primary challenge at this time is developing content that is both relevant and understandable to these remote communities. While some information will be common to all countries, it will be necessary to have more location-specific information as well. In addition to education of the general population, it is hoped that making weather, climate, and environmental information more accessible will encourage students from the islands into the study of these areas in their tertiary education.

  1. INL HIP Plate Fabrication

    SciTech Connect

    B. H. Park; C. R. Clark; J. F. Jue

    2010-02-01

    This document outlines the process used to bond monolithic fuel plates by Hot Isostatic Pressing (HIP). This method was developed at Idaho National Laboratory (INL) for the Reduced Enrichment for Research and Test Reactors (RERTR) program. These foils have been used in a number of irradiation experiments in support of the United States Global Threat Reduction Initiative (GTRI) program.

  2. 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

  3. 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…

  4. 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).

  5. 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.

  6. Development of transtensional and transpressive plate boundaries due to noncircular (cycloid) relative plate motion

    SciTech Connect

    Cronin, V.S. )

    1990-05-01

    The trace of a transform fault commonly is assumed to be circular and concentric with the finite relative motion of the plates adjacent to the fault. These assumptions have led to controversy as the transform fault label has been applied to the San Andreas fault in California because the San Andreas fault is neither circular nor concentric with the motion of the Pacific plate relative to the North American plate. The assumption of circular relative plate motion over a finite time interval is not generally valid. When finite relative plate motion is not circular, the length and orientation of a transform fault must change through time. The length and orientation of ridge-ridge transform faults in oceanic crust evolve through the migration, propagation, and abandonment of ridge segments. Transform faults that bound continental crust evolve differently than do transform faults along mid-ocean ridges because continental transform faults typically do not have ridges at both ends and because of the rheological differences between oceanic and continental crust. Along continent-continent transform faults in which the initial displacement is entirely strike slip, later displacements will be progressively more divergent or convergent (i.e., transtensive or transpressive). Transtension can result in the development of deep basins with high heat flow. Transpression can result in folding, reverse faulting, and decoupling of the crust from its lower crustal or mantle lithosphere in the region adjacent to the transform fault. Regardless of whether the transform boundary becomes transtensional or transpressional, the boundary evolves from a discrete transform fault to a broader, structurally complex accommodation zone (sensu lato).

  7. Subduction zone plate bending earthquakes and implications for the hydration of the downgoing plate

    NASA Astrophysics Data System (ADS)

    Emry, E. L.; Wiens, D. A.

    2011-12-01

    The greatest uncertainty in the amount of water input into the Earth at subduction zones results from poor constraints on the degree and depth extent of mantle serpentinization in the downgoing slab. The maximum depth of serpentinization is thought to be partly controlled by the maximum depth of tensional earthquakes in the outer rise and trench and is expected to vary from subduction zone to subduction zone or even along-strike for a single subduction zone. We explore the maximum depth of extensional faulting on the incoming plate for various subduction zones in order to gain insight into the possible extent of slab serpentinization. We relocate trench events at island arc subduction zones using hypocentroidal decomposition to determine which earthquakes occurred within the incoming plate. For earthquakes with Mw ~5.5+, we determine accurate depths and refine the CMT focal mechanism by inverting teleseismic P and SH waveforms. Results from the Mariana outer rise indicate that extensional earthquakes occur in the Pacific plate at depths ranging from 10-20 km beneath the top of the crust, with the character of trench seismicity changing significantly between the northern and southern portions of the subduction zone. In comparision, results from the Aleutian subduction zone show extensional trench earthquakes occurring from 5-30 km below the surface of the subducting slab. Compressional incoming plate earthquakes occur only near the Alaskan Peninsula, possibly due to stronger coupling between the slab and overriding plate in this region. Further results from oceanic arc subduction zones will be presented and differences between subduction zones as well as along-strike differences in the character of trench seismicity will be highlighted. If the presence of extensional faulting indicates subducting lithosphere hydration, then we expect that as much as the top 30 km of the slab may be hydrated and that the degree of slab serpentinization may vary significantly between subduction zones, potentially affecting arc geochemistry, intermediate depth seismicity, and the subduction zone water budget.

  8. Plate Motions, Regional Deformation, and Time-Variation of Plate Motions

    NASA Technical Reports Server (NTRS)

    Gordon, R. G.

    1998-01-01

    The significant results obtained with support of this grant include the following: (1) Using VLBI data in combination with other geodetical, geophysical, and geological data to bound the present rotation of the Colorado Plateau, and to evaluate to its implications for the kinematics and seismogenic potential of the western half of the conterminous U.S. (2) Determining realistic estimates of uncertainties for VLBI data and then applying the data and uncertainties to obtain an upper bound on the integral of deformation within the "stable interior" of the North American and other plates and thus to place an upper bound on the seismogenic potential within these regions. (3) Combining VLBI data with other geodetic, geophysical, and geologic data to estimate the motion of coastal California in a frame of reference attached to the Sierra Nevada-Great Valley microplate. This analysis has provided new insights into the kinematic boundary conditions that may control or at least strongly influence the locations of asperities that rupture in great earthquakes along the San Andreas transform system. (4) Determining a global tectonic model from VLBI geodetic data that combines the estimation of plate angular velocities with individual site linear velocities where tectonically appropriate. and (5) Investigation of the some of the outstanding problems defined by the work leading to global plate motion model NUVEL-1. These problems, such as the motion between the Pacific and North American plates and between west Africa and east Africa, are focused on regions where the seismogenic potential may be greater than implied by published plate tectonic models.

  9. Tracking slabs beneath northwestern Pacific subduction zones

    NASA Astrophysics Data System (ADS)

    Gu, Yu Jeffrey; Okeler, Ahmet; Schultz, Ryan

    2012-05-01

    This study uses the amplitudes of bottom-side reflected shear waves to constrain the morphology and dynamics of subducted oceanic lithosphere beneath northwestern Pacific subduction zones. Across Honshu arc, the 410- and 660-km seismic discontinuities are detected at the respective depths of 395 5 and 685 5 km within the Wadati-Benioff zone. Their topographies are negatively correlated along slab dip, showing the dominant effect of temperature on the olivine phase changes within the upper mantle transition zone. The base of the upper mantle shows broad depressions as well as localized zones of shallow/average depths beneath Korea and northeast China. The 15 + km peak-to-peak topography west of the Wadati-Benioff zones suggests that the stagnant part of the subducted Pacific plate is not as flat as previously suggested. Eastward slab 'pile-up' is also possible at the base of the upper mantle. Across southern Kuril arc, the shear wave reflection coefficients of major olivine phase boundaries fall below 5% within the Wadati-Benioff zone. The apparent reflection gaps and the spatial connection between a strong reflector at ~ 900 km depth may imply 1) possible compositional variations at the top and bottom of the transition zone and 2) substantial mass/heat flux across the 660-km seismic discontinuity. We also identify strong reflectors within the subducted oceanic lithosphere at mid transition zone depths. The depths and strengths of these reflectors are highly variable between Honshu and southern Kuril islands.

  10. The 1990 Western Pacific Geophysics meeting

    NASA Astrophysics Data System (ADS)

    The 1990 Western Pacific Geophysics Meeting was held in Kanazawa, Japan from 15-21 Aug. 1990. This was the first meeting of a new series of meetings for the American Geophysical Union, and it proved to be very successful in terms of the scientific program and attendance, which included over 1,000 participants. The intent of this meeting was an effort on the part of the American Geophysical Union (AGU) and several Japanese geophysical societies to gather individual Earth and space scientists at a major scientific meeting to focus on geophysical problems being studied in the western Pacific rim. The meeting was organized along the lines of a typical AGU annual meeting with some invited talks, many contributed talks, poster sessions, and with emphasis on presentations and informal discussions. The program committee consisted of scientists from both the U.S. and Japan. This meeting provided ample opportunities for U.S. and Japanese scientists to get to know each other and their works on a one-to-one basis. It was also a valuable opportunity for students studying geophysics to get together and interact with each other and with scientists from both the U.S. and Japan. There were 939 abstracts submitted to the conference and a total of 102 sessions designed as a result of the abstracts received. The topics of interest are as follows: space geodetic and observatory measurements for earthquake and tectonic studies; gravity, sea level, and vertical motion; variations in earth rotation and earth dynamics; sedimentary magnetism; global processes and precipitation; subsurface contaminant transport; U.S. Western Pacific Rim initiatives in hydrology; shelf and coastal circulation; tectonics, magmatism, and hydrothermal processes; earthquake prediction and hazard assessment; seismic wave propagation in realistic media; and dynamics and structure of plate boundaries and of the Earth's deep interior.

  11. Energy resources of Pacific Coast of Colombia

    SciTech Connect

    Bueno Salazar, R.

    1986-07-01

    Despite failure of modest exploration efforts to yield commercial hydrocarbon production in the Choco-Pacific coastal basin of Colombia, recent geophysical, geochemical, and surface geologic investigations indicate a potential for petroleum accumulations, which could be related to fields located on the western basins of Ecuador that in fact constitute an extension of the Colombian Pacific geologic scheme. The Choco-Pacific coastal basin of Colombia covers an area of approximately 70,000 km/sup 2/, of which 14,000 km/sup 2/ lies offshore. The structural style of this area corresponds to a convergent plate basin created over folded oceanic sediments and adjacent to the subduction zone. Such a framework could be conducive to an attractive array of potential hydrocarbon-bearing traps. Geochemical knowledge of potential source rocks of Cretaceous and early Tertiary age confers an added attraction to the area. Most evaluations reveal kerogen-rich, gas-prone organic matter. Nevertheless, the existence of oil seeps from Cretaceous outcrops could indicate sufficient thermal maturity for oil generation. Adequate reservoirs could be found in sandy or calcareous rocks of late Eocene to Oligocene age, predominantly of marine origin with an estimated thickness exceeding 20,000 ft. Colombia has been one of the leading world producers of gold and platinum, mostly derived from the vast alluvial cover of the onshore area of the basin. In rocks cropping out in the Western Cordillera (eastern margin of the basin), deposits of potentially commercial value of porphyry copper and molybdenum, as well as massive sulfur, manganese, and bauxite, have been found.

  12. The 1990 Western Pacific Geophysics meeting

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The 1990 Western Pacific Geophysics Meeting was held in Kanazawa, Japan from 15-21 Aug. 1990. This was the first meeting of a new series of meetings for the American Geophysical Union, and it proved to be very successful in terms of the scientific program and attendance, which included over 1,000 participants. The intent of this meeting was an effort on the part of the American Geophysical Union (AGU) and several Japanese geophysical societies to gather individual Earth and space scientists at a major scientific meeting to focus on geophysical problems being studied in the western Pacific rim. The meeting was organized along the lines of a typical AGU annual meeting with some invited talks, many contributed talks, poster sessions, and with emphasis on presentations and informal discussions. The program committee consisted of scientists from both the U.S. and Japan. This meeting provided ample opportunities for U.S. and Japanese scientists to get to know each other and their works on a one-to-one basis. It was also a valuable opportunity for students studying geophysics to get together and interact with each other and with scientists from both the U.S. and Japan. There were 939 abstracts submitted to the conference and a total of 102 sessions designed as a result of the abstracts received. The topics of interest are as follows: space geodetic and observatory measurements for earthquake and tectonic studies; gravity, sea level, and vertical motion; variations in earth rotation and earth dynamics; sedimentary magnetism; global processes and precipitation; subsurface contaminant transport; U.S. Western Pacific Rim initiatives in hydrology; shelf and coastal circulation; tectonics, magmatism, and hydrothermal processes; earthquake prediction and hazard assessment; seismic wave propagation in realistic media; and dynamics and structure of plate boundaries and of the Earth's deep interior.

  13. Empowerment at Pacific Gas & Electric.

    ERIC Educational Resources Information Center

    Kaufman, Steven B.

    1991-01-01

    Pacific Gas and Electric's employee involvement program aggressively focuses on customer service, performance measurement tied to management bonuses, and commitment to change in the organizational culture. (SK)

  14. The Microstructure of Rolled Plates from Cast Billets of U-10Mo Alloys

    SciTech Connect

    Nyberg, Eric A.; Joshi, Vineet V.; Burkes, Douglas; Lavender, Curt A.

    2015-03-01

    This report covers the examination of 13 samples of rolled plates from three separate castings of uranium, alloyed with 10 wt% molybdenum (U-10Mo) which were sent from the Y-12 National Security Complex (Y12) to the Pacific Northwest National Laboratory (PNNL).

  15. Fractures, not Plumes, Have Controlled Major Seamount Volcanism in the Pacific over 170 Million Years

    NASA Astrophysics Data System (ADS)

    Natland, J. H.; Winterer, E. L.

    2003-12-01

    The distribution of guyots and atolls and large volcanic islands on the Pacific plate can be used to outline the likely connection between stresses acting on the plate and the gradual development of large, linear volcanic chains over the past 170 Ma. We construe three general periods with different stress regimes in the history of the Pacific plate. 1) During the Jurassic and Early Cretaceous, the Pacific plate was surrounded by ridge segments and there were no major stress alignments within it. Within-plate volcanism thus assumed the scattered arrangement for the condition of no tectonic stress (1), and the large Magellan and Wake seamount clusters formed. Near the eastern boundaries of the plate, complex and shifting patterns of ridge reorganization dictated formation of very long, splayed, near-axis ridges such as Horizon Guyot and Necker Ridge. 2) At about 90 Ma, the growing middle-aged Pacific plate achieved its first persistent stress regime with the formation of subduction boundaries along its western or northwestern margin. The plate was no longer static but began to move over the asthenosphere and into the mantle. Subduction boundaries and the overall direction of subduction are uncertain, but this imparted a general yet not fully stable component of tension across the plate, producing the NNW Gilbert-Marshall, Line and Emperor Seamount ridges, generally orthogonal to the overall direction of least principal stress. The Line Island seamount chain, being near ridge axes, sustained a variable stress regime. It thus has no age progression of rocks dated between 70-90 Ma (2), great width, and a dual orientations of ridges. 3) By 47 Ma, nearly half of the boundaries of the Pacific plate now were trenches spanning from the Aleutians to New Zealand. In addition, northward migration of the Indian plate and Australia caught a major portion of the westerly moving Pacific plate between the northeast corner of the Tonga Trench and the Aleutians. The plate could not shift laterally in response to whatever was occurring along its eastern spreading boundaries. A very consistent and strong stress regime therefore developed across the Pacific plate with a NNE direction of least principal stress. The change in stress orientation may have taken up to 10 million years, during an interval marked by little or no volcanic productivity at the western end of the Hawaiian chain. Since that time, the predominant alignment of both linear island chains and Puka Puka-type ridges, from the Kodiak-Bowie chain in the Gulf of Alaska to the Louisville Ridge south of the Antarctic convergence, has been orthogonal to this direction. Development of large-volume persistent chains and shorter small-volume chains indicates patterns of differential stress in the plate, variable fertility and geochemistry of the asthenosphere and/or shallow convective overturn of the asthenosphere rather than the action of mantle plumes of different sizes and depths of origin. Tapping of enriched mantle by widespread volcano clusters during the Mesozoic suggests the presence of a shallow asthenospheric source layer rather than multiple narrow conduits. (1) Hieronymus, C.F., and Bercovici, D. 2000. Earth Planet. Sci. Lett. 181, 539-554. (2) Davis, A.S., Gray, L.B., Clague, D.A., and Hein, J.R., 2002 Geochem. Geophys. Geosyst. 3: 10.1029/2001GC0000190, 1-28.

  16. Transition on the Geometry of the Cocos Plate in Central-Southern Mexico.

    NASA Astrophysics Data System (ADS)

    Rodríguez-Domínguez, M. Á.; Perez-Campos, X.; Valencia-Cabrera, D.; Clayton, R. W.; Cordoba-Montiel, F.; Valdes-Gonzales, C. M.; Brudzinski, M. R.; Cabral-Cano, E.; Arciniega-Ceballos, A.

    2014-12-01

    The tectonic setting, produced by the interaction between the Cocos and North American plates, follows complex geometries along the Pacific coast. Previous studies in central Mexico showed that the slab dips nearly horizontally before steeply subducting into the continental mantle; in contrast, in southern Mexico, the slabs dips under the continental plate at a constant angle. Receiver functions from four seismic networks: GECO (Geometry of Cocos), SSN (Servicio Sismológico Nacional), OxNet (Oaxaca Network) and UV (Universidad Veracruzana) are used to study the crustal structure underneath the stations, and image the subducting Cocos plate in order to define the geometry and the transition angle in central-southern Mexico.

  17. Simulation of high-resolution x-ray zone plates.

    PubMed

    Kurokhtin, Alexei N; Popov, Alexei V

    2002-02-01

    A full-wave approach to quantitative characterization of x-ray zone plate lenses is proposed. Distributed focusing efficiency eta(z) of a multifocus optical element is defined as the energy flux through the Airy disk of a reference perfect lens with variable focal length z. Maxima of this function characterize diffraction efficiencies and spatial resolution of the zone plate foci. The parabolic wave equation is used to take into account diffraction effects inside the optical element. Rough and fuzzy interface models are introduced to describe realistic zone profiles. Numerical simulation reveals the limited capability of zone width reduction to improve the zone plate imaging performance. The possibilities of second-order focus enhancement by optimization of the zone plate thickness, line-to-space ratio, and zone tilt are studied numerically. PMID:11822594

  18. Franciscan complex calera limestones: Accreted remnants of farallon plate oceanic plateaus

    USGS Publications Warehouse

    Tarduno, J.A.; McWilliams, M.; Debiche, M.G.; Sliter, W.V.; Blake, M.C.

    1985-01-01

    The Calera Limestone, part of the Franciscan Complex of northern California, may have formed in a palaeoenvironment similar to Hess and Shatsky Rises of the present north-west Pacific1. We report here new palaeomagnetic results, palaeontological data and recent plate-motion models that reinforce this assertion. The Calera Limestone may have formed on Farallon Plate plateaus, north of the Pacific-Farallon spreading centre as a counterpart to Hess or Shatsky Rises. In one model2, the plateaus were formed by hotspots close to the Farallon_Pacific ridge axis. On accretion to North America, plateau dissection in the late Cretaceous to Eocene (50-70 Myr) could explain the occurrence of large volumes of pillow basalt and exotic blocks of limestone in the Franciscan Complex. Partial subduction of the plateaus could have contributed to Laramide (70-40 Myr) compressional events3. ?? 1985 Nature Publishing Group.

  19. North Pacific Acoustic Laboratory.

    PubMed

    Worcester, Peter F; Spindel, Robert C

    2005-03-01

    A series of long-range acoustic propagation experiments have been conducted in the North Pacific Ocean during the last 15 years using various combinations of low-frequency, wide-bandwidth transmitters and horizontal and vertical line array receivers, including a 2-dimensional array with a maximum vertical aperture of 1400 m and a horizontal aperture of 3600 m. These measurements were undertaken to further our understanding of the physics of low-frequency, broadband propagation and the effects of environmental variability on signal stability and coherence. In this volume some of the results are presented. In the present paper the central issues these experiments have addressed are briefly summarized. PMID:15810685

  20. Pacific rim lures explorationists

    SciTech Connect

    Nation, L.

    1991-09-01

    The Pacific Rim has been far and away the most attractive hunting ground for explorationists in the past year. Observers point to political initiatives coupled with a growing demand as igniting the region's numerous hydrocarbon possibilities. This paper describes some of the new incentives and the resultant exploration results and developments in China, Thailand, Malaysia, Indonesia, and Vietnam. A major sign of the region's political maturity is the willingness for the countries involved to solve the longstanding disputes over the claims in hydrocarbon-prone South China Sea.

  1. Obesity and Native Hawaiians/Pacific Islanders

    MedlinePlus

    ... Population Profiles > Native Hawaiian/Other Pacific Islander > Obesity Obesity and Native Hawaiians/Pacific Islanders Native Hawaiians/Pacific ... data available at this time. HEALTH IMPACT OF OBESITY More than 80 percent of people with type ...

  2. Renewable liquid reflecting zone plate

    DOEpatents

    Toor, Arthur; Ryutov, Dmitri D.

    2003-12-09

    A renewable liquid reflecting zone plate. Electrodes are operatively connected to a dielectric liquid in a circular or other arrangement to produce a reflecting zone plate. A system for renewing the liquid uses a penetrable substrate.

  3. What Are Growth Plate Injuries?

    MedlinePlus

    ... Find a Clinical Trial Journal Articles Growth Plate Injuries PDF Version Size: 123 KB Audio Version Time: ... 6 MB November 2014 What Are Growth Plate Injuries? Fast Facts: An Easy-to-Read Series of ...

  4. Microchannel plate streak camera

    DOEpatents

    Wang, C.L.

    1984-09-28

    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.

  5. Microchannel plate streak camera

    DOEpatents

    Wang, C.L.

    1989-03-21

    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 is disclosed. 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 1,000 KeV x-rays. 3 figs.

  6. 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.

  7. 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.

  8. North American plate dynamics

    NASA Technical Reports Server (NTRS)

    Richardson, Randall M.; Reding, Lynn M.

    1991-01-01

    Deformation within the North American plate in response to various tectonic processes is modeled using an elastic finite element analysis. The tectonic processes considered in the modeling include ridge forces associated with the normal thermal evolution of oceanic lithosphere, shear and normal stresses transmitted across transforms, normal stresses transmitted across convergent boundaries, stresses due to horizontal density contrasts within the continent, and shear tractions applied along the base of the plate. Model stresses are calculated with respect to a lithostatic reference stress state. Shear stresses transmitted across transform boundaries along the San Andreas and Caribbean are small, of the order of 5-10 MPa. Also, compressive stresses of the order of 5-10 MPa transmitted across the major transforms improve the fit to the data. Compressive stresses across convergent margins along the Aleutians and the Middle America trench are important.

  9. Evolution of the Pacific-Juan de Fuca-North America Slab Window System: A Trench- Ridge-Fault Example From the Pacific Rim

    NASA Astrophysics Data System (ADS)

    McCrory, P. A.; Wilson, D. S.; Stanley, R. G.

    2006-12-01

    The subduction margins that rim the Pacific Ocean contain a complex record of Cenozoic slab-window interactions. The formation, growth, and healing of slab windows is generally a transient process marked by a migrating pulse of forearc volcanism derived from asthenospheric upwelling behind the trailing edges of the subducted slabs. Variations in slab-window processes result from differing plate kinematic configurations around the Pacific Rim, and can yield a series of overprinted tectonic episodes. The sequence of slab windows that formed beneath western US and Mexico starting ca. 28.5 Ma are somewhat atypical in that they mark the cessation of microplate subduction rather than continued ridge subduction. The initial `Pioneer' slab window produced an episode of forearc volcanism ca. 27-25 Ma which thermally weakened the overlying western Transverse Ranges and California Borderlands region. A second window, the `Monterey' slab window, opened beneath the same region ca. 19-15 Ma, following capture of the Monterey plate fragment by the Pacific plate. This episode is roughly coeval with initiation of western Transverse Ranges rotation, suggesting the combination of additional thermal weakening from a second slab window and the northwestward motion of a partially subducted plate fragment in concert with the Pacific plate initiated the pulling apart and clockwise pivoting of the adjacent continental crust. The similar capture of the Magdalena plate fragment by the Pacific plate and formation of the `Magdalena' slab window ca. 12.5 Ma are coeval with Baja California pulling away from the Mexican continental margin. Here, the landward break formed along the already thermally weakened volcanic arc. In California, cessation of subduction correlated with a major reconfiguration of the plate boundary. An initial period of forearc volcanism, distributed crustal extension and basin subsidence ca. 19-12.5 Ma continued until the slab window and overlying continental crust cooled and strengthened. As the locus of weakest crust shifted eastward with the active slab window, transform motion coalesced along a through-going system of strike-slip faults, including the modern San Andreas transform. We suggest similar processes occur in a range of slab-window settings as demonstrated by the crustal rotation, extension, and transform faulting documented along slab-window transients in western Canada ca. 52 and 39 Ma (Madsen et al., 2005, Geosphere) and in southern Alaska ca. 52 Ma (Cole et al., 2006, GSA Bulletin).

  10. Plate motion and deformation

    SciTech Connect

    Minster, B.; Prescott, W.; Royden, L.

    1991-02-01

    Our goal is to understand the motions of the plates, the deformation along their boundaries and within their interiors, and the processes that control these tectonic phenomena. In the broadest terms, we must strive to understand the relationships of regional and local deformation to flow in the upper mantle and the rheological, thermal and density structure of the lithosphere. The essential data sets which we require to reach our goal consist of maps of current strain rates at the earth's surface and the distribution of integrated deformation through time as recorded in the geologic record. Our success will depend on the effective synthesis of crustal kinematics with a variety of other geological and geophysical data, within a quantitative theoretical framework describing processes in the earth's interior. Only in this way can we relate the snapshot of current motions and earth structure provided by geodetic and geophysical data with long-term processes operating on the time scales relevant to most geological processes. The wide-spread use of space-based techniques, coupled with traditional geological and geophysical data, promises a revolution in our understanding of the kinematics and dynamics of plate motions over a broad range of spatial and temporal scales and in a variety of geologic settings. The space-based techniques that best address problems in plate motion and deformation are precise space-geodetic positioning -- on land and on the seafloor -- and satellite acquisition of detailed altimetric and remote sensing data in oceanic and continental areas. The overall science objectives for the NASA Solid Earth Science plan for the 1990's, are to Understand the motion and deformation of the lithosphere within and across plate boundaries'', and to understand the dynamics of the mantle, the structure and evolution of the lithosphere, and the landforms that result from local and regional deformation. 57 refs., 7 figs., 2 tabs.

  11. 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.

  12. 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.

  13. Plates with Incompatible Prestrain

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Kaushik; Lewicka, Marta; Schäffner, Mathias

    2016-01-01

    We study effective elastic behavior of the incompatibly prestrained thin plates, where the prestrain is independent of thickness and uniform through the plate's thickness h. We model such plates as three-dimensional elastic bodies with a prescribed pointwise stress-free state characterized by a Riemannian metric G, and seek the limiting behavior as {h to 0} . We first establish that when the energy per volume scales as the second power of h, the resulting {Γ} -limit is a Kirchhoff-type bending theory. We then show the somewhat surprising result that there exist non-immersible metrics G for whom the infimum energy (per volume) scales smaller than h 2. This implies that the minimizing sequence of deformations carries nontrivial residual three-dimensional energy but it has zero bending energy as seen from the limit Kirchhoff theory perspective. Another implication is that other asymptotic scenarios are valid in appropriate smaller scaling regimes of energy. We characterize the metrics G with the above property, showing that the zero bending energy in the Kirchhoff limit occurs if and only if the Riemann curvatures R 1213, R 1223 and R 1212 of G vanish identically. We illustrate our findings with examples; of particular interest is an example where {G_{2 × 2}} , the two-dimensional restriction of G, is flat but the plate still exhibits the energy scaling of the Föppl-von Kármán type. Finally, we apply these results to a model of nematic glass, including a characterization of the condition when the metric is immersible, for {G = Id3 + γ n ⊗ n} given in terms of the inhomogeneous unit director field distribution { n in R^3}.

  14. Dynamics of convergent plate boundaries: Insights from subduction-related serpentinite melanges from the northern edge of the Caribbean plate

    NASA Astrophysics Data System (ADS)

    García-Casco, A.

    2012-04-01

    Subduction-related rock complexes, many of them tectonic melanges, occur in the Central America-Caribbean-Andean belt. I review the lithology and P-T-t paths of HP rocks and offer interpretations and generalizations on the thermal estate of the subducting plate(s), the melange forming events, and the exhumation history of rock complexes formed in the northern branch of the Caribbean subduction zone (Cuba and nearby Guatemala and Dominican Republic; ca. 3000 km apart). These complexes contain high pressure rocks formed and exhumed at the convergent (Pacific-Atlantic) leading edge of the Caribbean plate during ca. 100 Ma (early Cretaceous-Oligocene), attesting for long lasting oceanic -followed by continental- subduction/accretion in the region. Lithologic data indicate a complex melange-forming process. In most cases, the HP rocks represent subducted MOR-related lithologies occurring as tectonic blocks within serpentinite-matrix melanges interpreted as exhumed fragments of the subduction channel(s). Most of these melanges, however, contain fragments of arc/forearc-related non metamorphic and metamorphic (low-P and high-P) sedimentary and igneous rocks. While the HP blocks of arc/forearc material indicate subduction erosion at depth, the interpretation of the LP and non-metamorphic blocks is not straight forward. Indeed, tectonic blocks of HP metamafic rocks are surrounded by antigorite-serpentinite which, in turn, is surrounded by a low-P, low-T (chrysotile-lizardite) serpentinite that makes much of the mélange. These relations indicate that the melanges represent, in fact, tectonic stacks of shallow low-T forearc serpentinite that incorporate tectonic blocks/slices of the subduction-channel (high-P, high-T serpentinite and HP metamafic blocks) and of the arc/forearc crust (low-P and non-metamorphic blocks). This picture is similar to that of HP continental margin-derived tectonic stacks containing exotic slices of antigoritite-serpentine melanges (with blocks of MORB-derived eclogite) incorporated late in the convergent history when oceanic subduction was completed. Hence, incorporation of tectonic slices of the subduction channel into the shallow (low-P, low-T) melanges and subducted/accreted continental margins occur when collision-related dynamics imposed by subduction of buoyant continental or oceanic lithosphere affected the plate margin. Aqueous fluid, sourced from both subducted sediment and metamafic/ultramafic material, was available in large quantity in the subduction environment, as indicated by massive antigoritite, rinds of metasomatic rocks around included HP metamafic rocks, retrogressed eclogite, jadeitite and hydrothermal veins within antigoritite. Such a vigorous hydrology (fluid-flow) deep in the subduction environment point to the development of wide subduction channels and explain the abundance of accreted blocks. It can also explain the scarcity of large scale (>km) slices of the subducted oceanic lithosphere in the belt, for these are likely the result of focalized distribution of deformation occurring when forearc peridotite is barely hydrated (Agard et al., Long-term coupling along the subduction plate interface: Insights from exhumed rocks and models. This session, EGU 2012). Alternatively, these large tectonic slices may have been formed by the collision dynamics caused by late-stage subduction/accretion of the continental margin (or buoyant -thick- oceanic crust). Except maturation (cooling) of the subduction zone with time at orogenic belt-scale, no other simple generalization can be reached on the thermal state of the subducting plate and the exhumation process of the subduction channel. P-T-t paths of HP rocks indicate that slab fragments ranging from cold to hot coexisted during relatively short time intervals (ca. 10 Myr), and some fragments of the subduction channel were exhumed shortly after formation while others lasted several tens of Myr to arrive to the near-surface forearc/accretionary environment. A rather variable thermal state and dynamic history of the subduction environment(s) in space and time suggests that along strike (local/occasional) geodynamic complexities (e.g., age of lithosphere, angle of subduction, convergence rate,... more than one subduction zone) characterized the plate margin and controlled its evolution.

  15. Pacific Northwest: paradise lost

    SciTech Connect

    Thomas, W.V.

    1980-04-18

    An influx of new residents to the Pacific Northwest is changing social patterns and is endangering the region's valued wilderness and resources. A growing population and a feeling that the national govenment is more exploitive than conserving of its resources combines with a political tension between progressive populism and conservative Mormon influences to make residents wary of either newcomers or new prosperity. The abundant hydro power is threatened as power demand increases and utilities, industries, and the state and local governments compete for their fair share. A plan to restructure the Bonneville Power Administration (BPA) has been introduced in Congress to give it a single appointed administrator with the authority to decide how power will be distributed and which new power sources to develop. Concern about the two national nuclear waste repositories at Hanford and Idaho Falls led to a six-month moratorium at Hanford to warn the government that the site was not intended to be a permanent solution. A legislative proposal to set up regional nuclear parks will not relieve the Pacific Northwest's problems for some time. Leaders blame the policymakers for looking on the area as too remote and underpopulated to worry about. 18 references (DCK)

  16. About the REL Pacific Region

    ERIC Educational Resources Information Center

    Regional Educational Laboratory Pacific, 2014

    2014-01-01

    REL Pacific is one of ten Regional Educational Laboratories established and funded by the U.S. Department of Education's Institute of Education Sciences. Their region encompasses approximately 4.9 million square miles and serves seven Pacific island entities, including American Samoa; the Commonwealth of the Northern Mariana Islands; the Federated…

  17. The East Asian Sea: A vanished Cenozoic ocean between the Pacific and Indian oceans revealed by subducted slab constraints

    NASA Astrophysics Data System (ADS)

    Wu, Jonny; Lu, Renqi; Suppe, John; Kanda, Ravi V. S.

    2014-05-01

    We have mapped an extensive 2500 km by 7500 km swath of sub-horizontal slabs at 600 to 1200 km depths that we call the 'East Asian Sea'. The northern margin of the East Asian Sea slabs begin at Taiwan and Japan, and extend south to SE Australia near New Zealand, underlying the Philippine Sea, the Caroline Sea, New Guinea, and northern to eastern Australia. When restored with other mapped slabs under Asia-Oceania, the mapped slabs reveal a vanished ocean that existed between the Pacific and Indian oceans in the Cenozoic. The subduction of the Asian Sea fills a crucial gap in plate tectonic reconstructions of East Asia by accounting for a significant proportion of fast Pacific and Indo-Australian convergence towards Eurasia since 43 Ma, during which time the Pacific moved ~3000 km WNW and Australia moved ~2500 km northward in a near-orthogonal direction relative to a mantle reference. In addition, the Australian plate expanded up to 2000 km at its northern and eastern margins. Slabs were primarily mapped from the MITP08 global P-wave mantle tomographic model (Li et al., 2008) and compared to other global P- and S-wave global tomography. Reconstructed slab lengths were assessed by quantitative flexural slip unfolding of mid-slab surfaces to a spherical Earth surface model. Seismic tomographic volumes were also calculated for selected serial cross-sections. We present a plate tectonic reconstruction with the slab constraints, with the implication that the East Asian Sea was progressively overrun and subducted beneath the Philippine Sea, the Caroline Sea and the expanding Melanesian arcs. Reconstructions to earlier periods indicate the East Asian Sea was originally Pacific or proto-Pacific mantle lithosphere, and was fragmented from the Pacific plate during the major ~45 Ma Eocene motion change. This implies that the East Asian Sea was initially the upper plate of the Mariana and Tonga-Kermadec Western Pacific subduction zones.

  18. Gravity and Flexure Modelling of Subducting Plates

    NASA Astrophysics Data System (ADS)

    Hunter, J. A.; Watts, A. B.; SO 215 Shipboard Scientific Party

    2012-04-01

    The long-term strength of the lithosphere is determined by its flexural rigidity, which is commonly expressed through the effective elastic thickness, Te. Flexure studies have revealed a dependence of Te on thermal age. In the oceans, loads formed on young (70 Ma) seafloor. In the continents, loads on young (1000 Ma) lithosphere. Recent studies have questioned the relationship of Te with age, especially at subduction zones, where oceanic and continental lithosphere are flexed downwards by up to ~6 km over horizontal distances of up to ~350 km. We have therefore used free-air gravity anomaly and topography profile data, combined with forward and inverse modelling techniques, to re-assess Te in these settings. Preliminary inverse modelling results from the Tonga-Kermadec Trench - Outer Rise system, where the Pacific plate is subducting beneath the Indo-Australian plate, show large spatial variations in Te that are unrelated to age. In contrast to the southern end of the system, where Te is determined by the depth to the 600° C and 900° C isotherms, the northern end of the system shows a reduction in strength. Results also suggest a reduction in Te trenchward of the outer rise that is coincident with a region of pervasive extensional faulting visible in swath bathymetry data. In a continental setting, the Ganges foreland basin has formed by flexure of the Indo-Australian plate in front of the migrating loads of the Himalaya. Preliminary forward modelling results, using the Himalaya as a known surface topographic load, suggest that Te is high - consistent with the great age of Indian cratonic lithosphere. However, results from inverse modelling that solves for unknown loads (vertical shear force and bending moment) show significant scatter and display trade-offs between Te and these driving loads.

  19. Plate tectonics and crustal deformation around the Japanese Islands

    NASA Technical Reports Server (NTRS)

    Hashimoto, Manabu; Jackson, David D.

    1993-01-01

    We analyze over a century of geodetic data to study crustal deformation and plate motion around the Japanese Islands, using the block-fault model for crustal deformation developed by Matsu'ura et al. (1986). We model the area including the Japanese Islands with 19 crustal blocks and 104 faults based on the distribution of active faults and seismicity. Geodetic data are used to obtain block motions and average slip rates of faults. This geodetic model predicts that the Pacific plate moves N deg 69 +/- 2 deg W at about 80 +/- 3 mm/yr relative to the Eurasian plate which is much lower than that predicted in geologic models. Substantial aseismic slip occurs on the subduction boundaries. The block containing the Izu Peninsula may be separated from the rigid part of the Philippine Sea plate. The faults on the coast of Japan Sea and the western part of the Median Tectonic Line have slip rates exceeding 4 mm/yr, while the Fossa Magna does not play an important role in the tectonics of the central Japan. The geodetic model requires the division of northeastern Japan, contrary to the hypothesis that northeastern Japan is a part of the North American plate. Owing to rapid convergence, the seismic risk in the Nankai trough may be larger than that of the Tokai gap.

  20. 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.

  1. Plate fixation of clavicle fractures: a comparative study between Reconstruction Plate and Dynamic Compression Plate.

    PubMed

    Shahid, Rizwan; Mushtaq, Abid; Maqsood, Mohammad

    2007-04-01

    This study aimed at comparing the results of clavicular fracture fixation with AO Reconstruction (Recon) plate and Dynamic Compression Plate (DCP). The case notes of 39 patients with 40 acute and chronic clavicular fractures were retrospectively reviewed. The indications for fixation for acute cases comprised open fractures, the presence of sufficient skin tenting to risk skin integrity, neurovascular compromise and severe lateral displacement or comminution. Cases of symptomatic atrophic non-union after at least 12 months conservative management or previous failed 1/3 tubular plate fixation were also included in the study. In total 24 fractures were fixed with Recon Plate and 16 with DCP. Mean time to union was 4.2 months for the Recon plate group and 5.4 months for the DCP group. Eight of the DCP group complained of plate prominence requiring plate removal. Recon plates should be used in preference to DCP whenever clavicular fracture fixation is indicated. PMID:17515226

  2. A lithosphere-dynamics constraint on mantle flow: Analysis of the Eurasian plate

    NASA Astrophysics Data System (ADS)

    Warners-Ruckstuhl, K. N.; Meijer, P. Th.; Govers, R.; Wortel, M. J. R.

    2010-09-01

    We present a method to estimate the poorly understood mechanical coupling between lithosphere and underlying mantle, and apply it to the Eurasian plate. Mechanical equilibrium of tectonic plates requires the torque from mantle tractions ($\\overline{TM) to be balanced by the torques from edge forces ($\\overline{TE) and lithospheric body forces ($\\overline{TB). The direction of $\\overline{TE proves tightly constrained by plate boundary nature but $\\overline{TB is affected uncertainties in the density structure of continents. We consistently find that the non-zero torque required from mantle tractions does not agree with the orientation of any published absolute motion model. We conclude that mechanical balance of the Eurasian plate requires an actively convecting mantle, which should result in a torque on the Eurasian plate located in the southwest Pacific.

  3. Transformation characteristics of α1 Plates in Cu-Zn-Al Alloys

    NASA Astrophysics Data System (ADS)

    Wu, M. H.; Hamada, Y.; Wayman, C. M.

    1994-12-01

    The formation of α1 plates during isothermal aging of a Cu-26.7 wt pct Zn-4.0 wt pct Al alloy at 150 °C to 350 °C follows thermally activated incubation kinetics. Early stage α1 plates possess an ordered 18R or 9R long-period stacking order (LPSO) crystal structure, with antiphase domain boundaries running continuously across the interface. The plates also exhibit invariant plane strain (IPS) crystallography consistent with calculations of the phenomenological theory of martensite crystallography (PTMC). The ordered LPSO structure and IPS crystallography are gradually annealed out only after extended aging as the structure changes to the equilibrium disordered face-centered cubic (fcc) one. High-resolution transmission electron microscopy (TEM) analyses reveal that early stage α1 plates have straight coherent interfaces. Prolonged aging induces misfit dislocations at the interface and causes the interface to protrude into the parent phase. Although microanalytical analyses indicate that a composition difference exists between the α1 plates and the parent matrix, solute depletion was observed at neighboring defects. These observations support the proposed transformation mechanism that the α1 plates nucleate at solute depleted defects through a shear mechanism and that subsequent plate growth is then controlled by a diffusional process.

  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. Tomography and Dynamics of Western-Pacific Subduction Zones

    NASA Astrophysics Data System (ADS)

    Zhao, D.

    2012-01-01

    We review the significant recent results of multiscale seismic tomography of the Western-Pacific subduction zones and discuss their implications for seismotectonics, magmatism, and subduction dynamics, with an emphasis on the Japan Islands. Many important new findings are obtained due to technical advances in tomography, such as the handling of complex-shaped velocity discontinuities, the use of various later phases, the joint inversion of local and teleseismic data, tomographic imaging outside a seismic network, and P-wave anisotropy tomography. Prominent low-velocity (low-V) and high-attenuation (low-Q) zones are revealed in the crust and uppermost mantle beneath active arc and back-arc volcanoes and they extend to the deeper portion of the mantle wedge, indicating that the low-V/low-Q zones form the sources of arc magmatism and volcanism, and the arc magmatic system is related to deep processes such as convective circulation in the mantle wedge and dehydration reactions in the subducting slab. Seismic anisotropy seems to exist in all portions of the Northeast Japan subduction zone, including the upper and lower crust, the mantle wedge and the subducting Pacific slab. Multilayer anisotropies with different orientations may have caused the apparently weak shear-wave splitting observed so far, whereas recent results show a greater effect of crustal anisotropy than previously thought. Deep subduction of the Philippine Sea slab and deep dehydration of the Pacific slab are revealed beneath Southwest Japan. Significant structural heterogeneities are imaged in the source areas of large earthquakes in the crust, subducting slab and interplate megathrust zone, which may reflect fluids and/or magma originating from slab dehydration that affected the rupture nucleation of large earthquakes. These results suggest that large earthquakes do not strike anywhere, but in only anomalous areas that may be detected with geophysical methods. The occurrence of deep earthquakes under the Japan Sea and the East Asia margin may be related to a metastable olivine wedge in the subducting Pacific slab. The Pacific slab becomes stagnant in the mantle transition zone under East Asia, and a big mantle wedge (BMW) has formed above the stagnant slab. Convective circulations and fluid and magmatic processes in the BMW may have caused intraplate volcanism (e.g., Changbai and Wudalianchi), reactivation of the North China craton, large earthquakes, and other active tectonics in East Asia. Deep subduction and dehydration of continental plates (such as the Eurasian plate, Indian plate and Burma microplate) are also found, which have caused intraplate magmatism (e.g., Tengchong) and geothermal anomalies above the subducted continental plates. Under Kamchatka, the subducting Pacific slab shortens toward the north and terminates near the Aleutian-Kamchatka junction. The slab loss was induced by friction with the surrounding asthenosphere, as the Pacific plate rotated clockwise 30 Ma ago, and then it was enlarged by the slab-edge pinch-off by the asthenospheric flow. The stagnant slab finally collapses down to the bottom of the mantle, which may trigger upwelling of hot mantle materials from the lower mantle to the shallow mantle. Suggestions are also made for future directions of the seismological research of subduction zones.

  6. A kinematic model for the evolution of the Gorda Plate

    NASA Technical Reports Server (NTRS)

    Stoddard, Paul R.

    1987-01-01

    The magnetic lineation pattern produced by the Gorda Rise reflects a complex tectonic history marked by propagating ridges and nonrigid deformation of the Gorda plate. The Pacific-side lineation pattern is matched using a kinematic model which incorporates northward and southward propagating ridge segments and ridge rotation. By superimposing flexural-slip style deformation on the resulting Gorda-side lineations, and allowing convergent motion at the Mendocino Fracture Zone, the Gorda magnetic pattern is also successfully predicted. A similar model, but one which does not allow convergence at the Mendocino Fracture Zone, fails to produce the observed lineation pattern. Model predictions of the amount of material that would be 'obducted' at the Mendocino due to convergence between the Gorda and Pacific agree with bathymetric and density estimates of the amount of material located along the Mendocino Ridge.

  7. 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.

  8. 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.

  9. Seismic slip on an upper-plate normal fault during a large subduction megathrust rupture

    NASA Astrophysics Data System (ADS)

    Hicks, Stephen P.; Rietbrock, Andreas

    2015-12-01

    Quantification of stress accumulation and release during subduction zone seismic cycles requires an understanding of the distribution of fault slip during earthquakes. Reconstructions of slip are typically constrained to a single, known fault plane. Yet, slip has been shown to occur on multiple faults within the subducting plate owing to stress triggering, resulting in phenomena such as earthquake doublets. However, rapid stress triggering from the plate interface to faults in the overriding plate has not been documented. Here we analyse seismic data from the magnitude 7.1 Araucania earthquake that occurred in the Chilean subduction zone in 2011. We find that the earthquake, which was reported as a single event in global moment tensor solutions, was instead composed of two ruptures on two separate faults. Within 12 s a thrust earthquake on the plate interface triggered a second large rupture on a normal fault 30 km away in the overriding plate. This configuration of partitioned rupture is consistent with normal-faulting mechanisms in the ensuing aftershock sequence. We conclude that plate interface rupture can trigger almost instantaneous slip in the overriding plate of a subduction zone. This shallow upper-plate rupture may be masked from teleseismic data, posing a challenge for real-time tsunami warning systems.

  10. EarthScope Plate Boundary Observatory Data in the College Classroom (Invited)

    NASA Astrophysics Data System (ADS)

    Eriksson, S. C.; Olds, S. E.

    2009-12-01

    The Plate Boundary Observatory (PBO) is the geodetic component of the EarthScope project, designed to study the 3-D strain field across the active boundary zone between the Pacific and North American tectonics plates in the western United States. All PBO data are freely available to scientific and educational communities and have been incorporated into a variety of activities for college and university classrooms. UNAVCO Education and Outreach program staff have worked closely with faculty users, scientific researchers, and facility staff to create materials that are scientifically and technically accurate as well as useful to the classroom user. Availability of processed GPS data is not new to the geoscience community. However, PBO data staff have worked with education staff to deliver data that are readily accessible to educators. The UNAVCO Data for Educators webpage, incorporating an embedded Google Map with PBO GPS locations and providing current GPS time series plots and downloadable data, extends and updates the datasets available to our community. Google Earth allows the visualization GPS data with other types of datasets, e.g. LiDAR, while maintaining the self-contained and easy-to-use interface of UNAVCO’s Jules Verne Voyager map tools, which have multiple sets of geological and geophysical data. Curricular materials provide scaffolds for using EarthScope data in a variety of forms for different learning goals. Simple visualization of earthquake epicenters and locations of volcanoes can be used with velocity vectors to make simple deductions of plate boundary behaviors. Readily available time series plots provide opportunities for additional science skills, and there are web and paper-based support materials for downloading data, manipulating tables, and using plotting programs for processed GPS data. Scientists have provided contextual materials to explore the importance of these data in interpreting the structure and dynamics of the Earth. These data and their scientific context are now incorporated into the Active Earth Display developed by IRIS. Formal and informal evaluations during the past five years have provided useful data for revision and on-line implementation.

  11. Boundary element method for 3-D cracks in a plate

    NASA Technical Reports Server (NTRS)

    Fares, N.; Li, V. C.

    1988-01-01

    Fundamental solutions which automatically satisfy boundary conditions at the interfaces of an elastic plate perfectly bonded to two elastic halfspaces are implemented in a three-dimensional BEM for crack problems. The BEM features a new integration scheme for highly singular kernels. The capability is achieved through a part analytic and part numerical integration procedure, such that the analytic part of the integration is similar for all slip/opening variations. Part-through elliptic cracks in an elastic plate with traction-free surfaces are analyzed and the SIF values along the crack front are found to compare favorably with the numerical SIF results of Raju and Newman (1979).

  12. Advances in sputtered and ion plated solid film lubrication

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1985-01-01

    The glow discharge or ion assisted vacuum deposition techniques, primarily sputtering and ion plating, have rapidly emerged and offer great potential to deposit solid lubricants. The increased energizing of these deposition processes lead to improved adherence and coherence, favorable morphological growth, higher density, and reduced residual stresses in the film. These techniques are of invaluable importance where high precision machines tribo-components require very thin, uniform lubricating films (0.2 m), which do not interface with component tolerances. The performance of sputtered MoS2 films and ion plated Au and Pb films are described in terms of film thickness, coefficient of friction, and wear lives.

  13. 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.

  14. 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.

  15. A new seismically constrained subduction interface model for Central America

    NASA Astrophysics Data System (ADS)

    Kyriakopoulos, C.; Newman, A. V.; Thomas, A. M.; Moore-Driskell, M.; Farmer, G. T.

    2015-08-01

    We provide a detailed, seismically defined three-dimensional model for the subducting plate interface along the Middle America Trench between northern Nicaragua and southern Costa Rica. The model uses data from a weighted catalog of about 30,000 earthquake hypocenters compiled from nine catalogs to constrain the interface through a process we term the "maximum seismicity method." The method determines the average position of the largest cluster of microseismicity beneath an a priori functional surface above the interface. This technique is applied to all seismicity above 40 km depth, the approximate intersection of the hanging wall Mohorovičić discontinuity, where seismicity likely lies along the plate interface. Below this depth, an envelope above 90% of seismicity approximates the slab surface. Because of station proximity to the interface, this model provides highest precision along the interface beneath the Nicoya Peninsula of Costa Rica, an area where marked geometric changes coincide with crustal transitions and topography observed seaward of the trench. The new interface is useful for a number of geophysical studies that aim to understand subduction zone earthquake behavior and geodynamic and tectonic development of convergent plate boundaries.

  16. Friction and stress coupling on the subduction interfaces

    NASA Astrophysics Data System (ADS)

    Tan, E.; Lavier, L.; van Avendonk, H.

    2011-12-01

    At a subduction zone, the down-going oceanic plate slides underneath the overriding plate. The frictional resistance to the relative motion between the plates generates great earthquakes along the subduction interface, which can cause tremendous damage in the civil life and property. There is a strong incentive to understand the frictional strength of the subduction interface. One fundamental question of mechanics of subuction is the degree of coupling between the plates, which is linked to the size of earthquakes. It has been noted that the trench-parallel (along-strike) gravity variation correlates positively with the trench-parallel topography anomaly and negatively with the activity of great earthquake (Song and Simons, 2003). Regions with a negative trench-parallel gravity anomaly are more likely to have great earthquakes. The interpretation of such correlation is that strong coupling along subduction interface will drag down the for-arc region of the overriding plate, which generates the gravity and topography anomalies, and could store more strain energy to be released during a great earthquake. We developed a 2D numerical thermo-mechanical code for modeling subduction. The numerical method is based on an explicit finite element method similar to the Fast Lagrangian Analysis of Continua (FLAC) technique. The constitutive law is visco-elasti-plastic with strain weakening. The cohesion and friction angle are reduced with increasing plastic strain after yielding. To track different petrologic phases, Lagrangian particles are distributed in the domain. Basalt-eclogite, sediment-schist and peridotite-serpentinite phase changes are included in the model. Our numerical models show that the degree of coupling negatively correlates with the coefficient of friction. In the low friction case, the subduction interface has very shallow dipping angle, which helps to elastically couple the downing plate with the overriding plate. The topography and gravity anomalies of the low friction case also indicate strong coupling between plates.

  17. Palaeotsunamis in the Pacific Islands

    USGS Publications Warehouse

    Goff, J.; Chague-Goff, C.; Dominey-Howes, D.; McAdoo, B.; Cronin, S.; Bonte-Grapetin, Michael, M.; Nichol, S.; Horrocks, M.; Cisternas, M.; Lamarche, G.; Pelletier, B.; Jaffe, B.; Dudley, W.

    2011-01-01

    The recent 29 September 2009 South Pacific and 27 February 2010 Chilean events are a graphic reminder that the tsunami hazard and risk for the Pacific Ocean region should not be forgotten. Pacific Islands Countries (PICs) generally have short (<150 years) historic records, which means that to understand their tsunami hazard and risk researchers must study evidence for prehistoric events. However, our current state of knowledge of palaeotsunamis in PICs as opposed to their circum-Pacific counterparts is minimal at best. We briefly outline the limited extent of our current knowledge and propose an innovative methodology for future research in the Pacific. Each PIC represents a point source of information in the Pacific Ocean and this would allow their palaeotsunami records to be treated akin to palaeo-DART?? (Deep-ocean Assessment and Reporting of Tsunamis) buoys. Contemporaneous palaeotsunamis from local, regional and distant sources could be identified by using the spatial distribution of island records throughout the Pacific Ocean in conjunction with robust event chronologies. This would be highly innovative and, more importantly, would help provide the building blocks necessary to achieve more meaningful disaster risk reduction for PICs. ?? 2010 Elsevier B.V.

  18. New Kinematic Block Model for the Caribbean Plate

    NASA Astrophysics Data System (ADS)

    Symithe, S. J.; Calais, E.; Freed, A. M.

    2013-12-01

    The quasi-frontal subduction of the north and south American plates under the Lesser Antilles and the left- and right-lateral strike slip along the northern and southern margins of the Caribbean plate offer the opportunity to study the transition from subduction to strike-slip faulting along major plate boundaries. In addition, the segmentation and degree of interplate coupling along the Lesser Antilles subduction is key to our understanding of the earthquake potential of a subduction zone whose length is similar to the rupture area of the Mw9.0, 2011, Tohoku earthquake in Japan. Previous studies used GPS data and a block modeling approach to infer coupling at the plate interface and strain partitioning at the transition with strike-slip fault in the northeastern Caribbean (Manaker et al., 2008; Benford et al., 2013), with three main findings: (1) a correlation between strong interplate coupling and strain partitioning, (2) low coupling of the Lesser Antilles and Puerto Rico subduction, and, (3) internal deformation within the upper plate in Hispaniola. These studies were however based on a sparse and inhomogeneous GPS data set. Here we use a much updated geodetic GPS data set (~300 stations, 50% continuous) and earthquake slip vectors to expand these previous studies to the entire Caribbean region (excluding Central America, except to define the stable Caribbean plate). We use the block modeling approach described in McCaffrey et al. (2002) to test the optimal block geometry for the northern, eastern and southern boundaries of the Caribbean plate. We solve for variations in interplate coupling along the subduction plate boundaries, estimate angular velocities for each block/plate, and determine strain accumulation rates for all major faults in the region.

  19. Vibration characteristics of rectangular plate in compressible inviscid fluid

    NASA Astrophysics Data System (ADS)

    Liao, Chan-Yi; Ma, Chien-Ching

    2016-02-01

    This paper presents a mathematical derivation of the vibration characteristics of an elastic thin plate placed at the bottom of a three dimensional rectangular container filled with compressible inviscid fluid. A set of beam functions is used as the admissible functions of the plate in a fluid-plate system, and the motion of the fluid induced by the deformation of the plate is obtained from a three-dimensional acoustic equation. Pressure from the fluid over the fluid-plate interface is integrated to form a virtual mass matrix. The frequency equation of the fluid-plate system is derived by combining mass, stiffness, and the virtual mass matrix. Solving the frequency equation makes it possible to obtain the dynamic characteristic of the fluid-plate system, such as resonant frequencies, corresponding mode shapes, and velocity of the fluid. Numerical calculations were performed for plates coupled with fluids with various degrees of compressibility to illustrate the difference between compressible and incompressible fluids in a fluid-plate system. The proposed method could be used to predict resonant frequencies and mode shapes with accuracy compared to that of incompressible fluid theory (IFT). The proposed method can be used to analyze cases involving high value of sound velocity, such as incompressible fluids. When the sound velocity approaches infinity, the results obtained for compressible fluids are similar to those of incompressible fluids. We also examined the influence of fluid compressibility on vibration characteristics in which a decrease in sound velocity was shown to correspond to a decrease in resonant frequency. Additional modes, not observed in incompressible fluids, were obtained in cases of low sound velocity, particularly at higher resonant frequencies. Fluid velocity plots clearly reveal that the additional resonant modes can be attributed to the compressible behavior of the fluid.

  20. Reconstructing past plate motions with abyssal hill topography

    NASA Astrophysics Data System (ADS)

    Dahn, M. R.; Pockalny, R. A.; King, C.

    2013-12-01

    The seafloor spreading history of oceanic plates is primarily reconstructed by using a combination of dated seafloor magnetic anomalies and fracture zone trends to locate Euler poles and determine rotation rates. In some regions, these conventional measures of determining spreading history do not exist and alternative methods are required. Abyssal hills are elongate, topographic highs that are created at and form parallel to the ridge axis of spreading centers. Once formed, the abyssal hills are transported onto the ridge flank and provide a record of ridge axis orientation. We propose using the orientation of abyssal hill topography to supplement existing plate motion reconstruction methods and to serve as a stand-alone method for regions where conventional methods will not apply. Our new method uses high-resolution bathymetry grids created with multibeam data with grid-node spacing of 100-200 m, determined by regional water depths. The bathymetric grids are detrended to remove depth-age relationships and spatially filtered to remove anomalous regions where seafloor age is unknown. The detrended grids are then clipped to remove anomalously deep (e.g., fracture zones) or anomalously shallow topography (e.g., seamounts). Abyssal hill orientations are determined by calculating the modal frequencies of slope azimuth for pre-defined sub-regions (e.g., 50 km x 50 km) of these modified grids. The Euler Pole is then found by an iterative least-squares method from a grid of potential Euler Poles; first a coarse grid and then a fine grid are utilized to avoid local minima. At each potential Euler Pole, the sum of the differences between predicted and observed abyssal hill trends is squared and the minimum value identifies the location of the best-fit Euler Pole. Our method was applied to the well-mapped Cocos-Pacific plate boundary along the northern East Pacific Rise for the past 3 Ma and the poorly constrained Mid-Cretaceous seafloor (84 - 120 Ma) in the southwest Pacific Ocean. The results for the northern East Pacific Rise are very encouraging and our calculated Euler Poles are within 4 degrees of the NUVEL 1a and 2 degrees of the MORVEL global relative motion models. We also applied our method to the EMAG2 magnetic anomaly intensity grids with similar encouraging results; 17 degrees NUVEL 1a & 11 degrees MORVEL. The results for the southwest Pacific are still preliminary, but the method effectively identifies regions with similar abyssal hill trends and may be useful for more detailed tectonic reconstructions of the enigmatic region.

  1. Locking plate technology: current concepts.

    PubMed

    Greiwe, R Michael; Archdeacon, Michael T

    2007-01-01

    The management of fractures with traditional plating techniques has undergone a paradigm shift over the past 20 years. For many fractures, anatomic reduction using a dynamic compression plate has been the gold standard. However, minimally invasive approaches combined with biologically friendly internal fixation have become accepted methods of complex fracture treatment. The orthopedic literature has demonstrated advantages when comparing locking plate techniques with traditional compression plating techniques, particularly in fractures about the knee. The advantages of locking plates apply most directly to cases of highly comminuted fractures, unstable metadiaphyseal segments, and osteoporotic fractures. The biomechanical properties of locking plates have distinguished and defined their clinical use compared to traditional plates. A thorough understanding of these properties will assist the orthopedic surgeon in choosing the appropriate construct when faced with a difficult fracture. Compression plating requires absolute stability for bone healing. In contrast, locking plates function as "internal fixators" with multiple anchor points. This type of fixed-angle device converts axial loads across the bone to compressive forces across fracture sites, minimizing gap length and strain. The strain theory demonstrates that anatomic reduction is not required for bone healing, and that tolerable strain (2%-10%) can promote secondary bone healing. Callus formation is further promoted when biologically friendly surgical approaches are combined with locking plate "internal fixators". In contrast, conventional plates function by creating an environment where primary bone healing occurs. This plate provides "absolute rigidity" and requires anatomic reduction fixed in compression. Primary bone healing occurs in this manner. In highly comminuted, segmentally deficient, or porotic bone, bone quality is poor and "absolute rigidity" does not exist. Furthermore, soft-tissue stripping adds a biologic insult to the poor bone quality. These disadvantages may lead to poor outcomes such as nonunion, implant failure, malunion, or even infection. These disadvantages remain theoretical, as no prospective studies clearly demonstrate a difference between plating methods in difficult metadiaphyseal or osteoporotic fractures. However, the overwhelming biomechanical evidence has led to a more biologically friendly approach to these fractures. The indications for use of locking plates are evolving. The literature demonstrates low rates of nonunion and overall complication rates with locking plates in difficult metaphyseal and diaphyseal fractures. Anatomic reduction of the articular surface remains paramount. Hybrid techniques that combine the benefits of compression plate fixation with the biological and biomechanical advantages of locking plates are the most likely end result of current locking plate applications. PMID:17288090

  2. Writing and Visualization for Teaching Plate Tectonics

    NASA Astrophysics Data System (ADS)

    Thomas, S. F.

    2004-12-01

    The Theory of Plate Tectonics is probably the most important paradigm for understanding the workings of our planet. As such it is an integral part in any Introductory Geology course. Whereas geology majors usually easily embrace the Theory of Plate Tectonics, the enthusiasm for the coherence and elegance of this theory appears to be much more subdued among the majority of non-science majors. While visual and electronic media certainly support the teaching of the theory, pretty pictures and animations are not sufficient for many non-science majors to grasp the concepts of interacting lithospheric plates. It is well known that students do better in learning scientific concepts if they create their own understanding through research and inquiry-based learning, by working in the field, manipulating real earth-science data, and through writing. Writing assignments give instructors the opportunity to assess their students' learning and to clarify misconceptions yet they also have to be willing to teach students how to craft a science paper. Most electronic media and textbook-added CD-ROMs are not useful for making the structure of a science paper transparent. I found many of the necessary ingredients for effectively teaching plate tectonics in the interactive CD-ROM, "Our Dynamic Planet", developed by Wm. Prothero together with G. Kelly (University of California at Santa Barbara). It allows students to select and manipulate real earth-science data of plate-tectonically active regions, and provides an electronic interface that lets students create graphical representations of their collected data. A downloadable Teacher's Manual provides suggestions on teaching students to write a scientific argument, rooted in sound pedagogy. Originally designed for a large oceanography class, the material was modified for use in a small introductory geology class for non-science majors. Various assignments were given to instruct students in writing a scientific argument based on their own collected data and observations. The main goals are for students o To see the relationship between data and the development of a scientific theory o To understand the elements of scientific discourse o To learn how to derive conclusions from interpretations and observations o To back interpretations with observations o To be able to write a scientific argument o To understand the Theory of Plate Tectonics, and o To gain a better understanding about how science works The results of several surveys will be presented that confirm that most of the expected outcomes continue to be met.

  3. Media independent interface. Interface control document

    NASA Technical Reports Server (NTRS)

    1987-01-01

    A Media Independent Interface (MII) is specified, using current standards in the industry. The MII is described in hierarchical fashion. At the base are IEEE/International Standards Organization (ISO) documents (standards) which describe the functionality of the software modules or layers and their interconnection. These documents describe primitives which are to transcent the MII. The intent of the MII is to provide a universal interface to one or more Media Access Contols (MACs) for the Logical Link Controller and Station Manager. This interface includes both a standardized electrical and mechanical interface and a standardized functional specification which defines the services expected from the MAC.

  4. Plumes do not Exist: Plate Circulation is Confined to Upper Mantle

    NASA Astrophysics Data System (ADS)

    Hamilton, W. B.

    2002-12-01

    Plumes from deep mantle are widely conjectured to define an absolute reference frame, inaugurate rifting, drive plates, and profoundly modify oceans and continents. Mantle properties and composition are assumed to be whatever enables plumes. Nevertheless, purported critical evidence for plume speculation is false, and all data are better interpreted without plumes. Plume fantasies are made ever more complex and ad hoc to evade contradictory data, and have no predictive value because plumes do not exist. All plume conjecture derives from Hawaii and the guess that the Emperor-Hawaii inflection records a 60-degree change in Pacific plate direction at 45 Ma. Paleomagnetic latitudes and smooth Pacific spreading patterns disprove any such change. Rationales for other fixed plumes collapse when tested, and hypotheses of jumping, splitting, and gyrating plumes are specious. Thermal and physical properties of Hawaiian lithosphere falsify plume predictions. Purported tomographic support elsewhere represents artifacts and misleading presentations. Asthenosphere is everywhere near solidus temperature, so melt needs a tensional setting for egress but not local heat. Gradational and inconsistent contrasts between MORB and OIB are as required by depth-varying melt generation and behavior in contrasted settings and do not indicate systematically unlike sources. MORB melts rise, with minimal reaction, through hot asthenosphere, whereas OIB melts react with cool lithosphere, and lose mass, by crystallizing refractories and retaining and assimilating fusibles. The unfractionated lower mantle of plume conjecture is contrary to cosmologic and thermodynamic data, for mantle below 660 km is more refractory than that above. Subduction, due to density inversion by top-down cooling that forms oceanic lithosphere, drives plate tectonics and upper-mantle circulation. It organizes plate motions and lithosphere stress, which controls plate boundaries and volcanic chains. Hinge rollback is the key to kinematics. Arcs advance and collide, fast-spreading Pacific shrinks, etc. A fore-arc basin atop an overriding plate shows that hinge and non-shortening plate front there track together: velocities of rollback and advance are equal. Convergence velocity commonly also equals rollback velocity but often is greater. Slabs sinking broadside push upper mantle back under incoming plates and force rapid Pacific spreading, whereas overriding plates flow forward with retreating hinges. Backarc basins open behind island arcs migrating with hinges. Slabs settle on uncrossable 660-km discontinuity. (Contrary tomographic claims reflect sampling and smearing artifacts, notably due to along-slab raypaths.) Plates advance over sunken slabs and mantle displaced rearward by them, and ridges spread where advancing plates pull away. Ridges migrate over asthenosphere, producing geophysical and bathymetric asymmetry, and tap fresh asthenosphere into which slab material is recycled upward. Sluggish deep-mantle circulation is decoupled from rapid upper-mantle circulation, so plate motions can be referenced to semistable lower mantle. Global plate motions make kinematic sense if Antarctica, almost ringed by departing ridges and varying little in Cenozoic paleomagnetic position, is stationary: hinges roll back, ridges migrate, and directions and velocities of plate rotations accord with subduction, including sliding and crowding of oceanic lithosphere toward free edges, as the dominant drive. (The invalid hotspot and no-net-rotation frames minimize motions of hinges and ridges, and their plate motions lack kinematic sense.) Northern Eurasia also is almost stationary, Africa rotates very slowly counterclockwise toward Aegean and Zagros, Pacific plate races toward surface-exit subduction systems, etc.

  5. Free vibration analysis of arbitrarily shaped polygonal plates with simply supported edges using a sub-domain method

    NASA Astrophysics Data System (ADS)

    Kang, Sang Wook; Atluri, S. N.

    2009-11-01

    As an extension of the NDIF method developed by the authors, a practical analytical method for the free vibration analysis of a simply supported polygonal plate with arbitrary shape is proposed. Especially, the method is more effective for plates highly concave shapes because it employs a sub-domain method dividing the plate of interest with two sub-plates. The approximate solution of each sub-plate is assumed by linearly superposing plane waves propagated from edges of the sub-plate. Sub-system matrix equations for the two sub-plates are extracted by applying the simply supported boundary condition to the edges of each sub-plate (excepting the common interface of the two sub-plates). Finally, the sub-system matrix equations is merged into a single system matrix equation for the entire plate by considering the compatibility condition that the two sub-plates have the same displacement and slope at the common interface. The eigenvalues and mode shapes of the single plate are obtained from the determinant of a system matrix extracted from the entire system matrix equation. It is shown by several case studies that the proposed method has a good convergence characteristics and yields accurate eigenvalues and mode shapes, compared with another analytical method (NDIF method) and FEM (NASTRAN).

  6. Helium isotope ratios in circum-Pacific volcanic arcs

    NASA Astrophysics Data System (ADS)

    Poreda, R.; Craig, H.

    1989-04-01

    Volcanoes in the 'Ring of Fire' surrounding the Pacific Ocean are sited on tectonic arc segments marking the great subduction zones where oceanic crust returns to the mantle. Helium isotope ratios in volcanic gases along these arcs are close to those found in midocean-ridge basalts, revealing the presence of primordial He-3 released from the wedge of mantle material above the sinking plate. These results show that although the subduction of oceanic crust drives the arc volcanism, the subducted crust itself does not contribute a major fraction of the upwelling magma.

  7. Energized seal for orifice plate

    SciTech Connect

    Foster, J.H.; Beson, J.

    1991-08-27

    This patent describes an orifice fitting of the type having a body with a flow passage for connecting into a pipeline, an orifice seat located in the flow passage, a plate carrier which carries an orifice plate having a hole therethrough for the passage of gas, and gear means in the body for moving the plate carrier from an inactive position out of the flow passage to an active position in engagement with the seat and with the orifice plate in the flow passage, an improved means for sealing the plate carrier against the seat: an annular seal mounted to the plate carrier for sealing engagement with the seat; energizing means in the plate carrier actuable after the plate carrier is adjacent the seat for urging the seal against the seat; and wherein the orifice fitting has a slide valve carrier means which moves between open and closed positions transverse to the movement of the plate carrier for retaining the plate carrier in the active position, and wherein the energizing means is actuated by the movement of the slide valve carrier means to the closed position.

  8. Plating on difficult-to-plate metals: what's new

    SciTech Connect

    Wiesner, H.J.

    1980-07-30

    Some of the changes since 1970 in procedures for plating on such materials as titanium, molybdenum, silicon, aluminum, and gallium arsenide are summarized. While basic procedures for plating some of these materials were developed as many as 30 to 40 years ago, changes in the end uses of the plated products have necessitated new plating processes. In some cases, vacuum techniques - such as ion bombardment, ion implantation, and vacuum metallization - have been introduced to improve the adhesion of electrodeposits. In other cases, these techniques have been used to deposit materials upon which electrodeposits are required.

  9. Spot brazing of aluminum to copper with a cover plate

    NASA Astrophysics Data System (ADS)

    Hayashi, Junya; Miyazawa, Yasuyuki

    2014-08-01

    It is difficult to join dissimilar metals when an intermetallic compound is formed at the joining interface. Spot brazing can be accomplished in a short time by resistance heating. Therefore, it is said that the formation of a intermetallic compound can be prevented. In this study, aluminum and copper were joined by spot brazing with a cover plate. The cover plate was used to supply heat to base metals and prevent heat dissipation from the base metals. The ability to braze Al and Cu was investigated by observation and analysis. Pure aluminum (A1050) plate and oxygen-free copper (C1020) plate were used as base metals. Cu-Ni-Sn-P brazing filler was used as the brazing filler metal. SPCC was employed as cover plate. Brazing was done with a micro spot welder under an argon gas atmosphere. Brazing ability was estimated by tensile shear strength and cross sectional microstructure observation. Al and Cu can be joined by spot brazing with Cu-Ni-Sn-P brazing filler and cover plate.

  10. Hydration of the incoming plate in the Kuril subduction zone

    NASA Astrophysics Data System (ADS)

    Fujie, G.; Kodaira, S.; Yamashita, M.; Sato, T.; Takahashi, T.; Takahashi, N.; Noguchi, N.

    2010-12-01

    Water supplied from the subducting oceanic plate by dehydration is inferred to cause seismicity and magmatism in subduction zones. It is important, therefore, to reveal the distribution of water within the incoming plate for understanding seismic and volcanic activities in subduction zones. In 2009 and 2010, to reveal the detailed seismic structure and hydration process within the incoming plate, we conducted a wide-angle seismic survey in the Kuril subduction zone, where the old Pacific plate formed in the eastern Pacific ridge is subducting from south to north beneath the island arc of Japan. We designed a north-south 500km-long seismic experimental line to be perpendicular to the Kuril trench. The northern end of our line is located at about 30km south of the trench axis and well-developed horst and graben structure is observed around the northern end. We deployed 80 Ocean Bottom Seismometers (OBSs) at intervals of 6km and shot a large tuned airgun array towed by R/V Kairei. In addition, we obtained MCS reflection data using a 444-channel hydrophone streamer (6km long) along the same line. We modelled both P-wave and S-wave velocity structures by the traveltime inversion using refraction, reflection and PS-conversion traveltimes. Our results show that P-wave velocity beneath the well-developed horst and graben structure is about 5% lower than that in the south of outer rise. This is consistent with a previous structure study in the Chili subduction zone that shows the P-wave velocity in the vicinity of the trench axis is lower than that of normal oceanic plate. More notable feature of our results is the regional variations of Vp/Vs. The S-wave velocity, as well as P-wave velocity, gradually decreases toward the trench axis. However Vp/Vs is not uniform; Vp/Vs immediately beneath the sediments is remarkably high beneath the well-developed horst and graben structure, and Vp/Vs decreases with depth (high Vp/Vs is confined to the top of the oceanic plate). Since the high Vp/Vs implies the high degree of crustal hydration, one plausible explanation for our Vp/Vs model is that normal faults related to the well-developed horst and graben structure provide pathways for water percolation from sediments to oceanic crust, and lead to crustal hydration of the incoming plate.

  11. The Asia-Pacific Region.

    ERIC Educational Resources Information Center

    Braddock, Richard

    2002-01-01

    Examines research management within higher education institutions in the Asia-Pacific region including research and current trends in knowledge production, institutional aspects, research funding, and good practice in research management. (EV)

  12. Deformation of island-arc lithosphere due to steady plate subduction

    NASA Astrophysics Data System (ADS)

    Fukahata, Yukitoshi; Matsu'ura, Mitsuhiro

    2016-02-01

    Steady plate subduction elastically brings about permanent lithospheric deformation in island arcs, though this effect has been neglected in most studies based on elastic dislocation theory. We investigate the characteristics of the permanent lithospheric deformation using a kinematic model, in which steady slip motion is given along a plate interface in the elastic lithosphere overlying the viscoelastic asthenosphere under gravity. As a rule of thumb, long-term lithospheric deformation can be understood as a bending of an elastic plate floating on non-viscous fluid, because the asthenosphere behaves like water on the long term. The steady slip below the lithosphere-asthenosphere boundary does not contribute to long-term lithospheric deformation. Hence, the key parameters that control the lithospheric deformation are only the thickness of the lithosphere and the geometry of the plate interface. Slip on a plate interface generally causes substantial vertical displacement, and gravity always tries to retrieve the original gravitational equilibrium. For a curved plate interface gravity causes convex upward bending of the island-arc lithosphere, while for a planar plate interface gravity causes convex downward bending. Larger curvature and thicker lithosphere generally results in larger deformation. When the curvature changes along the plate interface, internal deformation is also involved intrinsically, which modifies the deformation field due to gravity. Because the plate interface generally has some curvature, at least near the trench, convex upward bending of the island-arc lithosphere, which involves uplift of island-arc and subsidence around the trench, is always realized. On the other hand, the deformation field of the island-arc lithosphere sensitively depends on lithospheric thickness and plate interface geometry. These characteristics obtained by the numerical simulation are consistent with observed topography and free-air gravity anomalies in subduction zones: a pair of topography and gravity anomalies, high in the arc and low around the trench, is observed without exceptions all over the world, while there are large variety in the amplitude and horizontal scale of the topography and gravity anomalies.

  13. Tectonostratigraphic terranes of the frontier circum-Pacific region

    SciTech Connect

    Howell, D.G.; Jones, D.L.; Schermer, E.R.

    1983-03-01

    Many major exploration frontiers around the Pacific are in regions where complex geologic relations reflect plate-tectonic processes, crustal mobility, and accretion of exotic terranes. The destruction of the proto-Pacific ocean (Panthalassa) involved accretion of terranes to cratonal regions such as Gondwana and Laurasia. Terranes in southwestern New Zealand and eastern Antarctica were also probably accreted during the Paleozoic. The southern margin of Siberia, extending into China, underwent a protracted period of accretion from the late Precambrian through the early Mesozoic. Mid-Paleozoic accretion is reflected in the Innuitian foldbelt of the Arctic Ocean, the Black Clastic unit of the northern Rocky Mountains, and the Antler orogeny of the western US cordillera. The Mesozoic breakup of Pangaea and the acceleration of subduction aided in the rifting and dispersal of terranes from equatorial paleolatitudes. Fragments of these terranes now compose much of the continental margins of the Pacific basin, including New Zealand, Indochina, southern China, southeast Siberia, the North American cordillera, and South America. Some terranes are presently being further fragmented by post-accretionary dispersion processes such as strike-slip faulting in western North America and Japan. Although the character and distribution of terranes in the western US are fairly well documented, details are needed for other terranes around the Pacific basin. Interpretation of structure and stratigraphy at depth will be aided by more data on the timing of accretion and the nature of deformation associated with accretion and dispersion. Such data are needed for further define specific exploration targets in the circum-Pacific region.

  14. 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.

  15. 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.

  16. Ion plating for the future

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1981-01-01