Sample records for pacific plate interface

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    We image the subducted slab underneath a 450 km long transect of the Alaska subduction zone. Dense stations in southern Alaska are set up to investigate (1) the geometry and velocity structure of the downgoing plate and their relation to slab seismicity, and (2) the interplate coupled zone where the great 1964 (magnitude 9.3) had greatest rupture. The joint teleseismic migration of two array datasets (MOOS, Multidisciplinary Observations of Onshore Subduction, and BEAAR, Broadband Experiment Across the Alaska Range) based on teleseismic receiver functions (RFs) using the MOOS data reveal a shallow-dipping prominent low-velocity layer at ~25-30 km depth in southern Alaska. Modeling of these RF amplitudes shows a thin (3-6.5 km) low-velocity layer (shear wave velocity less than 3 km/s), which is ~20-30% slower than normal oceanic crustal velocities, between the subducted slab and the overriding North America plate. The observed low-velocity megathrust layer (with Vp/Vs ratio exceeding 2.0) may be due to a thick sediment input from the trench in combination of elevated pore fluid pressure in the channel. The subducted crust below the low-velocity channel has gabbroic velocities with a thickness of 11-15 km. Both velocities and thickness of the low-velocity channel abruptly increase as the slab bends in central Alaska, which agrees with previously published RF results. Our image also includes an unusually thick low-velocity crust subducting with a ~20 degree dip down to 130 km depth at approximately 200 km inland beneath central Alaska. The unusual nature of this subducted segment has been suggested to be due to the subduction of the Yakutat terrane. Subduction of this buoyant crust could explain the shallow dip of the thrust zone beneath southern Alaska. We also show a clear image of the Yakutat and Pacific plate subduction beneath the Kenai Peninsula, and the along-strike boundary between them at megathrust depths. Our imaged western edge of the Yakutat terrane, at ~30-42 km depth in the central Kenai along the megathrust, aligns with the western end of the geodetically locked patch with high slip deficit, and coincides with the boundary of aftershock events from the 1964 earthquake. It seems plausible that this sharp change in the nature of the downgoing plate controls the slip distribution of great earthquakes on this plate interface.

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    We image the subducted slab underneath a 450 km long transect of the Alaska subduction zone. Dense stations in southern Alaska are set up to investigate (1) the geometry and velocity structure of the downgoing plate and their relationship to slab seismicity, and (2) the interplate coupled zone where the great 1964 earthquake (magnitude 9.3) exhibited the largest amount of rupture. The joint teleseismic migration of two array datasets based on teleseismic receiver functions (RFs) reveals a prominent, shallow-dipping low-velocity layer at ~25-30 km depth in southern Alaska. Modeling of RF amplitudes suggests the existence of a thin (3-5 km) low-velocity layer (shear wave velocity of ~2.0-2.5 km/s) that is ~20-40% slower than underlying oceanic crustal velocities, and is sandwiched between the subducted slab and the overriding North America plate. The observed low-velocity megathrust layer (with P-to-S velocity ratio of 1.9-2.3) may be due to a thick sediment input from the trench in combination with elevated pore fluid pressure in the channel. The subducted crust below the low-velocity channel has gabbroic velocities with a thickness of ~15 km. Both velocities and thickness of the low-velocity channel abruptly increase downdip in central Alaska, which agrees with previously published results. Our image also includes an unusually thick low-velocity crust subducting with a ~20 degree dip down to 130 km depth at approximately 200 km inland beneath central Alaska. The unusual nature of this subducted segment has been suggested to be due to the subduction of the Yakutat terrane. We also show a clear image of the Yakutat and Pacific plate subduction beneath the Kenai Peninsula, and the along-strike boundary between them at megathrust depths. Our imaged western edge of the Yakutat terrane, at 25-30 km depth in the central Kenai along the megathrust, aligns with the western end of a geodetically locked patch with high slip deficit, and coincides with the boundary of aftershock events from the 1964 earthquake. It appears that this sharp change in the nature of the downgoing plate could control the slip distribution of great earthquakes on this plate interface.

  4. Alaska Megathrust 2: Imaging the megathrust zone and Yakutat/Pacific plate interface in the Alaska subduction zone

    NASA Astrophysics Data System (ADS)

    Kim, YoungHee; Abers, Geoffrey A.; Li, Jiyao; Christensen, Douglas; Calkins, Josh; Rondenay, Stéphane

    2014-03-01

    We image the slab underneath a 450 km long transect of the Alaska subduction zone to investigate (1) the geometry and velocity structure of the downgoing plate and their relationship to slab seismicity and (2) the interplate coupled zone where the great 1964 earthquake (Mw 9.2) exhibited the largest amount of rupture. The joint teleseismic migration of two array data sets based on receiver functions (RFs) reveals a prominent, shallow-dipping low-velocity layer at ~25-30 km depth in southern Alaska. Modeling of RF amplitudes suggests the existence of a thin layer (Vs of ~2.1-2.6 km/s) that is ~20-40% slower than underlying oceanic crustal velocities, and is sandwiched between the subducted slab and the overriding plate. The observed megathrust layer (with Vp/Vs of 1.9-2.3) may be due to a thick sediment input from the trench in combination with elevated pore fluid pressure in the channel. Our image also includes an unusually thick low-velocity crust subducting with a ~20° dip down to 130 km depth at ~200 km inland beneath central Alaska. The unusual nature of this subducted segment results from the subduction of the Yakutat terrane crust. Our imaged western edge of the Yakutat terrane aligns with the western end of a geodetically locked patch with high slip deficit, and coincides with the boundary of aftershock events from the 1964 earthquake. It appears that this sharp change in the nature of the downgoing plate could control the slip distribution of great earthquakes on this plate interface.

  5. Plate kinematics in the western Pacific derived from geodetic observations

    E-print Network

    Tregoning, Paul

    Tectonophysics: Plate motions­present and recent (3040), 3040 Marine Geology and Geophysics: Plate tectonics (8150, 8155, 8157, 8158); KEYWORDS: GPS, North Bismarck Plate, Australian Plate, Pacific Plate, tectonic spanning the Australian Plate and the western Pacific region to derive new tectonic models of the motions

  6. Focal Mechanisms and Plate Tectonics of the Southwest Pacific

    Microsoft Academic Search

    Tracy Johnson; Peter Molnar

    1972-01-01

    Ninety-six new focal mechanisms were determined for earthquakes on the belt of seismic activity separating the Pacific and Australian plates. The direction of convergence of these plates varies from Ntg-SW to E-W. The Australian plate underthrusts the Pacific plate to the ENE under the Solomon and New Hebrides islands and overthrusts the Pacific to the east along the Tonga-Kermadec arc

  7. Cenozoic plate tectonic reconstructions and plate boundary processes in the Southwest Pacific

    Microsoft Academic Search

    William R. Keller

    2005-01-01

    The Australia-Pacific-Antarctic plate circuit has long been a weak link in global plate reconstruction models for Cenozoic time. The time period spanning chron 20 to chron 7 (43-25 Ma) is particularly problematic for global plate models because seafloor spreading was occurring in two poorly constrained regions in the Southwest Pacific - the Macquarie Basin southwest of New Zealand, and the

  8. Pacific Rim and Pacific Plate Tectonism Associated With the Hawaiian Emperor Bend

    NASA Astrophysics Data System (ADS)

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

    2002-12-01

    Widespread Pacific Rim and Pacific plate tectonism both appear to be closely associated with a pronounced change in Pacific absolute plate motion (APM) that occurred about 43 Ma as revealed by the Hawaiian Emperor Bend. In the Western Pacific prior to the change, as the Pacific plate moved toward the north, Proto Izu -- Bonin -- Mariana (IBM) subduction was already occurring by 49 Ma, perhaps as early as 52 Ma near the northern end of the Proto IBM, evidenced by the emplacement of boninites in the forearc (Cosca et al., 1998). If the Philippine Basin -- Pacific plate circuit is traced though the Coral Sea basin after closing the Ayu and Sorel troughs, it is evident that the alignment of the Proto IBM (Kyushu -- Palau) subduction zone roughly paralleled the Pacific APM during the initiation of subduction. At ~ 43 Ma, Proto-IBM Trench subduction rapidly increased, possibly causing the major change in Pacific (and Australia) APM that produced the prominent bend in the Hawaiian-Emperor chain. This change also produced a the minor bend in the Louisville chain, as the Pacific plate began to move west-northwestward, as well as at least five more noticeable bends in other seamount chains across the Central Pacific. In the Northeastern Pacific, the expansive magmatic activity, which occurred during the early stage of Aleutian Arc growth between 55--50 Ma, began to wane between 45 and 40 Ma (Scholl et al., 1987). After the 43 Ma change in Pacific APM, the Aleutian subduction zone began to accommodate dextral slip at its western end, as well as continuing convergence at its eastern end. To the south, in the Eastern Pacific, Ridge propagation began about 43 Ma both north and south of the Murray FZ (extending southward to the Clarion FZ). Much farther to the south, changes are also apparent in the Pacific -- Antarctic spreading pattern at ~43 Ma. In the Central Pacific, following the 43 Ma change in Pacific plate motion, intraplate subduction began along the Manus -- North Solomon -- Vitiaz (Melanesian) Trench, which was aligned parallel to the post 43 Ma Pacific APM. Subduction was heralded by metamorphic events in the Solomon Islands' Florida Group and Eastern Belt Islands that occurred between ~44 and ~35 Ma (Neef and McDougal, 1976), after which the earliest Lemau Intrusives were emplaced between 38 and 32 Ma in New Ireland (Stewart and Sandy, 1988) near the western end of the Melanesian Arc. To the southwest, on the Australia Plate, the Louisiade Plateau also formed over the Lord Howe Hotspot about 43 Ma as a concomitant change in Australia APM also occurred.

  9. 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.

  10. Cenozoic plate tectonic reconstructions and plate boundary processes in the Southwest Pacific

    NASA Astrophysics Data System (ADS)

    Keller, William R.

    The Australia-Pacific-Antarctic plate circuit has long been a weak link in global plate reconstruction models for Cenozoic time. The time period spanning chron 20 to chron 7 (43-25 Ma) is particularly problematic for global plate models because seafloor spreading was occurring in two poorly constrained regions in the Southwest Pacific - the Macquarie Basin southwest of New Zealand, and the Adare Basin north of the Ross Sea, Antarctica. I present a new shipboard dataset collected aboard several recent geophysical cruises which places important constraints on the tectonic evolution of these two regions. Utilizing multibeam bathymetry, magnetic, gravity, and seismic data in the Macquarie Basin, I am able to locate tectonic features and magnetic anomalies with greater accuracy than was previously possible. These tectonic features and magnetic anomalies are then used to calculate relative motion between the Australia and Pacific Plates for chrons 18-11 (40-30 Ma). I use revised locations of the rifted margins along the boundary of the Macquarie Basin to determine a best-fit pre-rift reconstruction for this region. During this same time period, seafloor spreading between East and West Antarctica was occurring along the Adare Trough, an extinct spreading center located north of the Ross Sea. Motion along the Adare Trough accounts for roughly 180 km of previously unrecognized motion between East and West Antarctica. I present multibeam and seismic data in the Adare Basin that place constraints on the timing and character of motion along this plate boundary.

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

    Microsoft Academic Search

    Kristine M. Larson; Jeff Freymueller

    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

  12. Pacific-North America Plate Tectonics of the Neogene Southwestern United States: An Update

    Microsoft Academic Search

    Tanya Atwater; Joann Stock

    1998-01-01

    We use updated rotations within the Pacific-Antarctica-Africa-North America plate circuit to calculate Pacific-North America plate reconstructions for times since chron 13 (33 Ma). The direction of motion of the Pacific plate relative to stable North America was fairly steady between chrons 13 and 4, and then changed and moved in a more northerly direction from chron 4 to the present

  13. 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.

  14. 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.

  15. 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.

  16. 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.; Márquez-Azúa, 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 S09°W ± 38° and 1.9 ± 0.3 mm yr-1 towards S19°E ± 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.

  17. 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.

  18. Geometry and relative motion of the Philippine sea plate and Pacific plate beneath the Kanto-Tokai district, Japan

    Microsoft Academic Search

    Mizuho Ishida

    1992-01-01

    The recent acquisition of high-density and improved seismic data by the Kanto-Tokai (K-T) Observational Network of the National Research Institute of Earth Science and Disaster Prevention requires the revision of conventional plate configuration models for the K-T district. We propose a new interpretation of the configuration and relative motion of the Philippine Sea (PHS) plate. Pacific (PAC) plate, and Eurasian

  19. On the role of slab pull in the Cenozoic motion of the Pacific plate Claudio Faccenna,1,2

    E-print Network

    Demouchy, Sylvie

    ., 39, L03305, doi:10.1029/2011GL050155. 1. Introduction [2] The motion of tectonic plates is generally]. [4] Here, we revise the plate geometry and the tectonic event history in/around the Pacific plateOn the role of slab pull in the Cenozoic motion of the Pacific plate Claudio Faccenna,1,2 Thorsten

  20. 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.

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

    SciTech Connect

    Perton, M.; Levesque, D.; Monchalin, J.-P.; Lord, M. [National Research Council Canada, 75 de Mortagne Blvd, Boucherville, Quebec, J4B 6Y4 (Canada); Smith, J. A.; Rabin, B. H. [Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-6188 (United States)

    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.

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

    E-print Network

    Clouard, Valerie

    Break-up spots: Could the Pacific open as a consequence of plate kinematics? Valérie Clouard a plate due to intraplate stresses. Present-day intraplate volcanism would define break up spots to break up the lithosphere. This hypothesis was revisited by Sheth Available online at www

  3. 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.

  4. Upwelling in the Jurassic-Cretaceous Pacific Ocean: Biota Changes and Sedimentary Evidence for Paleoequatorial Crossings of the Pacific Plate

    NASA Astrophysics Data System (ADS)

    Erba, E.

    2007-12-01

    The migration of the Pacific Plate during the Jurassic and Cretaceous can be traced by deciphering the lithological and paleontological composition of sediments deposited under different paleoenvironmental conditions. Several sites drilled during DSDP and ODP legs recovered Cretaceous and, partly, Jurassic sedimentary successions that have been used to reconstruct paleoceanographic changes related to paleolatitudes. In the Pacific Ocean chert, radiolarite and porcellanite are the dominant pelagic lithologies in specific intervals of the Mesozoic, more commonly represented by limestone. The siliceous lithotypes are the expression of biogenic sedimentation in the equatorial fertility belt, whereas limestones result from production of calcareous plankton under stable, oligotrophic conditions. The widespread distribution of massive chert is easily detectable on seismic profiles, where constitutes a strong reflector trough the Northwestern Pacific. Nannofossil quantitative data and sedimentary changes are combined to define the paleoequatorial upwelling belt, characterized by physico-chemico-trophic conditions favoring opportunistic taxa. The results are consistent with previous reconstructions based on shallow-water successions from the tropical Pacific, recording atoll drowning at peri-equatorial locations. The pelagic and neritic carbonate crisis zone approximately between 10° S and 10 °N paleolatidudes may be used to constrain the motions of the Pacific Plate.

  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. Tectonics of the Hjort region of the Macquarie Ridge Complex, southernmost Australian-Pacific plate boundary, southwest Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Meckel, Timothy Ashworth

    The Hjort Ridge, Trench, and Plateau comprise the southernmost portion of the Macquarie Ridge Complex (MRC), the Australian-Pacific plate boundary south of New Zealand. The MRC is an ideal location to study deformation and structural development at an obliquely convergent plate boundary involving oceanic lithosphere. This dissertation documents structures and processes in the Hjort region associated with incipient subduction, an outstanding problem in plate tectonics. I investigated the evolution of the plate boundary from ˜33 Ma to the present day, concentrating on the active and recent structural development. Interpretations are based on analyses of recently collected geophysical data in the Hjort region, including swath bathymetry, reflectivity, seismic reflection, gravity, magnetics, and seismicity. The Australian plate is actively underthrusting the Pacific plate along the Hjort Trench, but self-sustaining subduction does not appear to have commenced. Transpression along the length of the plate boundary has been accommodated by lithospheric flexure, strike slip faulting, and geographically limited underthrusting. A consistent relationship exists between the convergence angle and the amount of dynamically supported topography; up to 50 km of convergence has been accommodated by flexure forming ridges and troughs. A continuous, strike slip fault accommodates oblique convergence along the length of the boundary. Where angles of convergence are highest (>20°), underthrusting is observed in addition. Gravity modeling and seismicity suggest ˜50 km of underthrusting in the southern Hjort Trench, but only define an eastwardly dipping Australian slab to about 20 km depth. Lithosphere underthrust in the southern trench is translated subparallel to the ˜N-trending boundary, limiting the eastward extent of underthrust slab. Reconstructions of the plate boundary since 33.3 Ma show that the Antarctic-Australian-Pacific triple junction migrated southward with respect to the Australian plate resulting in the present day curved plate boundary. Migration resulted in lengthening of the dextral transform fault connecting the Macquarie Ridge and Southeast Indian Ridge spreading centers and shortening of the easternmost ridge-segment of latter spreading center. The MRC in the Hjort region changed from a dextral transform into an obliquely convergent zone of incipient subduction.

  8. Uncertainties in the relative positions of the Australia, Antarctica, Lord Howe, and Pacific plates since the late cretaceous

    Microsoft Academic Search

    Joann Stock; Peter Molnar

    1982-01-01

    We determined parameters that describe finite rotations and their uncertainity regions for relative plate motion at the spreading centers between the Pacific and Antarctic plates, between Australia and Antarctica, and between the Lord Howe Rise and Australia. We combined these to yield a range of possible finite rotations describing the relative positions of the Pacific, Australia, Antarctica, and Lord Howe

  9. Into the subduction plate interface: insights from exhumed terranes (Invited)

    NASA Astrophysics Data System (ADS)

    Agard, P.; Angiboust, S.; Plunder, A.

    2013-12-01

    In order to place constraints on the still elusive lithological and physical nature of the subduction plate interface, we herein present critical petrological (and modelling) data from intermediate depths along the subduction interface. Their implications, ranging from long-term underplating and exhumation to short-lived seismic events, are confronted with the recent wealth of geophysical/chemical data from the literature. Emphasis is placed on findings from two major localities showing deeply subducted ophiolitic remnants (Zermatt-Saas, Monviso), which crop out in the classic, well-preserved fossil subduction setting of the Western Alps. Both ophiolite remnants in fact represent large, relatively continuous fragments of oceanic lithosphere (i.e., several km-thick tectonic slices across tens of km) exhumed from ~80 km depths and thereby provide important constraints on interplate coupling mechanisms. We show that pervasive hydrothermal processes and seafloor alteration promoting fluid incorporation in both mafic and associated ultramafic rocks was essential, together with the presence of km-thick serpentinite soles, to decrease the density of the tectonic slices and prevent them from an irreversible sinking into the mantle. The Monviso case sudy (particularly the Lago Superiore Unit) provides further insights on both seismicity and fluid flow along the subduction plate interface at ~80 km depths: (1) Eclogite breccias, reported here for the first time, mark the locus of an ancient fault zone associated with intraslab, intermediate-depth earthquakes at ~80 km depth. They correspond to m-sized blocks made of 1-10 cm large fragments of eclogite mylonite later embedded in serpentinite in a ~100m thick eclogite facies shear zone. We suggest that seismic brecciation (possibly at magnitudes Mw ~4) occurred in the middle part of the oceanic crust, accompanied by the input of externally-derived fluids. (2) Prominent fluid-rock interactions, as attested by ubiquitous metasomatic rinds, affected the fragments of mylonitic basaltic eclogites and calcschists dragged and dismembered within serpentinite during eclogite-facies deformation. Detailed petrological and geochemical investigations point to a massive, pulse-like, fluid-mediated element transfer essentially originating from serpentinite. Antigorite breakdown, occurring ca. 15 km deeper than the maximum depth reached by these eclogites, is regarded as the likely source of this highly focused fluid/rock interaction and element transfer. Such a pulse-like, subduction-parallel fluid migration pathway within the downgoing oceanic lithosphere may have been promoted by transient slip behaviour along the LSZ under eclogite-facies conditions. 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 indicate that the detachment of such large-scale oceanic tectonic slices is promoted by fluid circulation along the subduction interface (as well as by subducting a strong and originally discontinuous mafic crust).

  10. Overview on the Plate Boundaries Along the Western Mexican Pacific Margin

    NASA Astrophysics Data System (ADS)

    Mortera-Gutierrez, C. A.; Bandy, W. L.; Michaud, F.; Ortega Ramírez, J.

    2013-05-01

    The cinematic of the Pacific, Rivera and Cocos oceanic plates have a significant impact on the subduction process and seismic cycles occurring along the western Mexican Pacific margin of the North American and Caribbean plates. Sections of Pacific (PAC), Rivera (RIV), Cocos (COC), North American (NAM) and Caribbean (CAB) plate boundaries along the western margin of Mexico are not well constrained. From north to south: the transform-rift system at Gulf of California has been generally considered as part of PAC-NAM plate boundary. However results of the FAMEX cruise at 2002 evidenced that Tosco-Abreojos Fault System along the western margin of Baja California Peninsula is active. Should this tectonic structure be considered as a plate boundary? At the RIV plate northern corner (including Mazatlan Basin), the scatter seismicity recorded between Tamayo FZ and the Marias Islands restricts the characterization of the plate boundary between the RIV and NAM plates. Some authors have proposed that Tamayo FZ and Marias I. Escarpment are the RIV-NAM plate boundary. Recently other authors have called that RIV-NAM boundary is a geomorphology lineament that runs from a Rivera Rise transform at 23N to the northern end of Marias I. Escarpment. Even so this concept is not sustained with seismic activity. Further this thought would imply that the oceanic lithosphere of Mazatlan Basin would form part of NAM plate. Other thoughts are either that there is a diffuse RIV-NAM plate boundary to the north of the Maria Archipelago, or Middle America Subduction Zone is gradually extending northward of the Maria Is. While the plate boundary at SE corner of the RIV plate is neither well defined morphologically nor seismically constraint, offshore Colima Coast. Some authors have proposed that this zone is a diffuse plate boundary between RIV and COC plates, result of a NE-SW shear plate motion. Other authors have proposed that the RIV-COC boundary extends E-W from the El Gordo Graben (EGG) at the Middle American Trench (MAT) to northern tip of the East Pacific Rise (EPR). Results of recently multibeam and magnetic surveys indicate that this boundary is possible segmented as an echelon E-W structure, north of EGG. Clearly these hypotheses on the RIV-COC plate boundary show that its configuration is neither well seismic nor morphology constrained. To the south, the triple junction point of COC, NAM, and CAB plate boundaries is also another case where the boundaries are poorly constrained seismically and morphologically. Traditionally, the COC-NAM-CAB triple junction point has been positioned where the MAT trend bends by the Tehuantepec Ridge (TR) collision, but no offshore geophysical data sustain that NAM-CAB plate boundary extends to MAT-TR point. In the last decade, the Servicio Sismológico Nacional (SSN) has extended its seismic station network at the southern Mexican territory. From this data, the distribution of offshore earthquakes covers a broad marine zone in front the Chiapas and Guatemala coastline and does not show a defined earthquake concentration associated to the proposed offshore extension of the Polochic-Motogua Fault through Guatemala and Mapastepec Fault through Chiapas, Mexico.

  11. 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.

  12. 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.

  13. Incoming plate faulting in the Northern and Western Pacific and implications for subduction zone water budgets

    NASA Astrophysics Data System (ADS)

    Emry, Erica L.; Wiens, Douglas A.

    2015-03-01

    The greatest uncertainty in the amount of water input into the Earth at subduction zones results from poor constraints on the degree of mantle serpentinization in the incoming plate. Recent studies suggest that the depth of serpentinization within the incoming plate mantle is likely controlled by the depth of extensional faulting caused by lithospheric bending at the outer rise and trench. We explore the maximum depth of extension within the incoming plate at Northwestern Pacific subduction zones in order to estimate the depth limit of serpentinization and to identify any significant variation between subduction zone segments. We relocate trench earthquakes to identify which events occurred within the incoming plate and determine accurate depths for 63 incoming plate earthquakes occurring during 1988-2011 by inverting teleseismic broadband P and SH waveforms. We observe that the top 10-15 km of the incoming plate mantle experiences extensional faulting at all of the subduction zones with a reasonable sample of earthquakes; 60% of the total number of extensional earthquakes occur at crustal depths or within the top 5 km of the incoming plate mantle, 80% occur above 10 km within the mantle, and 95% occur above 15 km. There is evidence for variation throughout the different regions of study, for example extensional earthquakes occur down to 20 km below the crust in the western Aleutians and Izu-Bonin. We propose that the incoming plate mantle is most strongly hydrated in the upper 5 km, and that partial serpentinization exists regionally within the incoming plate mantle to ?15 km. Making reasonable assumptions about the degree of serpentinization and incorporating previous estimates of crustal water, we calculate that the total water carried into the Northern and Western Pacific subduction zones is generally higher than previous estimates, and is approximately 4- 6 ×108 Tg /Myr, or ? 45- 70 ×103 Tg /Myr per kilometer of subduction zone.

  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. 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.

  16. Block kinematics of the PacificNorth America plate boundary in the southwestern United States from inversion of GPS,

    E-print Network

    McCaffrey, Robert

    Block kinematics of the Pacific­­North America plate boundary in the southwestern United States­North America plate boundary in the southwestern United States from inversion of GPS, seismological of the southwestern United States (30°­41°N) is represented by a finite number of rotating, elastic-plastic spherical

  17. Cretaceous Pacific plate movement beneath SE China: Evidence from episodic volcanism and related intrusions

    NASA Astrophysics Data System (ADS)

    Liu, Lei; Xu, Xisheng; Xia, Yan

    2014-02-01

    Extensive Late Mesozoic igneous rocks in SE China have been widely considered to be generated under the paleo-Pacific tectonic regime, the plate subduction model, however, remains controversial. This study focuses on the Cretaceous volcanic rocks in northwestern Zhejiang Province. Zircon U-Pb age determination indicates that Cretaceous volcanism in northwestern Zhejiang took place at three episodes of 140-130, 130-127 and 123-118 Ma, in good agreement with the coeval lower volcanic series in southeastern Zhejiang, but lacking the episode at 110-88 Ma corresponding to the upper volcanic series. The Cretaceous volcanic rocks in Zhejiang therefore show an oceanward younging trend. In situ zircon Hf isotope analyses of three episodes of volcanics yield ?Hf(t) values of - 11.2 to - 8.7, -4.8 to - 2.4 and - 4.4 to + 2.2, respectively. The entire sequences display typical isotopic features of magma mixing, implying progressive involvement of juvenile component. Based on systematical researches on the Cretaceous volcanic rocks and a series of granitoid plutons in Zhejiang, it is also identified that the juvenile component involvement gradually occurred from the inland to the coast under an enhanced lithospheric extensional tectonic setting. All the observations in this study indicate the northwestward paleo-Pacific plate subduction with episodic slab rollback which triggered the arc system to retreat towards the Pacific Ocean, rather than the southwestward subduction related to the ridge subduction along the Lower Yangtze River belt.

  18. 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.

  19. Relationship between the present-day stress field and plate boundary forces in the Pacific Northwest

    USGS Publications Warehouse

    Geist, E.L.

    1996-01-01

    The relationship between plate boundary forces and the observed stress field in the Pacific Northwest is established using numerical models of continental deformation. Because the orientation of the greatest horizontal principal stress throughout the Pacific Northwest differs considerably from the direction of convergence between the Juan de Fuca and North American plates, the relationship between the stress field and forces acting along the subduction zone has been unclear. To address this relationship, a two-dimensional finite element model developed by Bird [1989] is used that incorporates critical aspects of continental deformation such as a stratified rheology and interaction between thermal and mechanical components of deformation. Boundary conditions are specified in terms of either velocity or shear traction, depending on whether the computed shear stress at the plate boundary is less than or exceeds, respectively, a prescribed limit. Shear-stress limits on the subduction and transform plate boundaries are independently varied to determine the relative effect of forces along these boundaries on intraplate deformation. Results from this study indicate that the shear stress limit of both subduction and transform boundaries is low, and that the intraplate stress field is attributed, in part, to the normal component of relative plate motion along the transform boundaries. However, the models also indicate that although the subduction zone fault is weak, a minimum shear strength ( ??? 10 MPa) for the fault is necessary to explain the observed stress field. The balance among forces along the tectonic boundaries of North America results in a surprising degree of variation in the present-day stress field.

  20. Transition conditions at the interface between floating plates Hyuck Chung

    E-print Network

    Fox, Colin

    ice thickness, mass density and Young's modulus to be constant. This model is often used to study-H to list them all here.) A similar technique is used in [3] to solve a plate-plate interaction with an open

  1. Finite element computation of the vibrations of a plate-fluid system with interface damping

    E-print Network

    Rodríguez, Rodolfo

    by finite element and modal reduction methods. A more detailed study of flexible porous damping materialsFinite element computation of the vibrations of a plate-fluid system with interface damping Alfredo excitation. The system consists of an acoustic fluid and a plate, with a thin layer of a noise damping

  2. Ridge subduction sparked reorganization of the Pacific plate-mantle system 60-50 million years ago

    NASA Astrophysics Data System (ADS)

    Seton, Maria; Flament, Nicolas; Whittaker, Joanne; Müller, R. Dietmar; Gurnis, Michael; Bower, Dan J.

    2015-03-01

    A reorganization centered on the Pacific plate occurred ~53-47 million years ago. A "top-down" plate tectonic mechanism, complete subduction of the Izanagi plate, as opposed to a "bottom-up" mantle flow mechanism, has been proposed as the main driver. Verification based on marine geophysical observations is impossible as most ocean crust recording this event has been subducted. Using a forward modeling approach, which assimilates surface plate velocities and shallow thermal structure of slabs into mantle flow models, we show that complete Izanagi plate subduction and margin-wide slab detachment induced a major change in sub-Pacific mantle flow, from dominantly southward before 60 Ma to north-northeastward after 50 Ma. Our results agree with onshore geology, mantle tomography, and the inferred motion of the Hawaiian hot spot and are consistent with a plate tectonic process driving the rapid plate-mantle reorganization in the Pacific hemisphere between 60 and 50 Ma. This reorganization is reflected in tectonic changes in the Pacific and surrounding ocean basins.

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

    SciTech Connect

    Iidaka, Takashi; Mizoue, Megumi; Suyehiro, Kiyoshi (Tokyo Univ. (Japan))

    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.

  4. Upper boundary of the Pacific plate subducting beneath Hokkaido, Japan, estimated from ScSp phase

    NASA Astrophysics Data System (ADS)

    Osada, Kinue; Yoshizawa, Kazunori; Yomogida, Kiyoshi; Suetsugu, Daisuke; Bina, Craig; Inoue, Toru; Wiens, Douglas; Jellinek, Mark

    2010-11-01

    Three-dimensional geometry of the upper boundary of the Pacific plate subducting beneath Hokkaido, Japan, was obtained using the ScSp phase: the phase converted from ScS (S wave reflected at the core-mantle boundary) to P wave at the plate boundary. Taking the advantage of a dense seismic network, "Hi-net", recently deployed across the Japanese islands, we applied several seismic array analyses to the recorded waveform data for a large nearby deep earthquake, in order to enhance very weak ScSp signals in the original records. At first, we set up five blocks for the region in plate dip directions. After aligning the travel times of ScS and stacking seismograms among stations in a given sub-block perpendicular to each dip direction, we searched for the optimal plate model (i.e., two-dimensional geometry of the upper boundary) for each block. The model was parameterized by seven depth grids, and seismograms were stacked based on the travel time of ScSp as a time lag of each sub-block, so that the optimal model would yield the maximum spectral energy of ScSp after stacking. This model parameter search was conducted, using ray tracings of ScSp with a reference velocity model and a non-linear inversion scheme (Neighbourhood Algorithm). The optimal model of each block was combined each other by cubic spline interpolation, in order to construct an overall three-dimensional geometry of the upper boundary of the plate. Next, we performed the frequency-wavenumber ( f- k) spectral analysis to refine the above result. Assuming each station as a reference point, we made beam output from records of its adjacent stations as a function of wavenumber vector ( kx, ky) and frequency. The peak of its power spectrum was considered to represent the wavenumber vector of ScSp, that is, azimuth of arrival and slowness, so that we can estimate the position and depth of the corresponding ScS- ScSp conversion. In the frequency range from 0.5 to 1.5 Hz, we could estimate the conversion points for 21 stations or hypothetical arrays, and revised the geometry of the upper boundary obtained by the non-linear stacking approach in the previous step. The final plate model was compared with the distribution of intraplate earthquakes in the Pacific plate. This comparison clearly reveals that the upper seismic zone merges with the lower from 150 to 200 km in depth, deviating systematically away from the upper boundary where the boundary is slightly bumped in a convex manner.

  5. 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.

  6. 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

  7. 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.

  8. 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 investigators)

    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.

  9. Interseismic GPS strain data inversion to estimate slip-deficit rates at plate interfaces: application to the Kanto region, central Japan

    NASA Astrophysics Data System (ADS)

    Noda, Akemi; Hashimoto, Chihiro; Fukahata, Yukitoshi; Matsu'ura, Mitsuhiro

    2013-04-01

    We developed an inversion method to estimate unbiased interseismic slip-deficit rates at plate interfaces from observed GPS velocity data with an elastic dislocation model. In this method, first, we subtract theoretical surface velocities due to known steady relative plate motion from the observed GPS data, and presume the residuals to be caused by slip deficit at plate interfaces. However, the observed GPS data always include rigid block translation and rotation, which cannot be explained by the elastic dislocation model. We treated the rigid block translation and rotation as systematic errors in the analysis, and removed them by transforming the velocity data into the average strain rates of triangle elements composed of adjacent GPS stations. By this transformation, original information about intrinsic deformation is preserved. Applying a unified Bayesian inversion formula to the GPS strain data, we can obtain unbiased slip-deficit rate distribution. We demonstrated the applicability of the method of GPS strain data inversion through the analysis of interseismic GPS velocity data (1996-2000) in the Kanto region, central Japan, where the North American (NAM), Pacific (PAC) and Philippine Sea (PHS) plates are interacting with each other in a complicated way. From this analysis we found a broad and high slip-deficit rate zone on the NAM-PHS plate interface, extending from southeast off the Boso peninsula to the Tokai region through the Izu-Mainland collision zone. Two high slip-deficit rate zones along the Sagami and Suruga troughs correspond to the source regions of the 1923 Kanto earthquake (M7.9) and a potential Tokai earthquake. On the PHS-PAC plate interface, though the estimation errors are large, we found a moderate slip-deficit rate zone far southeast off the Boso peninsula, where an M7.4 earthquake has occurred in 1953.

  10. Structural discontinuities inside the Pacific plate offshore of the Tohoku and Kanto regions revealed by seismic reflection imaging

    NASA Astrophysics Data System (ADS)

    Panayotopoulos, Y.; Kasahara, K.; Hirata, N.; Abe, S.; Katou, M.; Kato, A.; Obara, K.

    2012-12-01

    We have investigated the material properties and the tectonic processes that govern the Pacific plate just before it is subducted in the Japan Trench Subduction zone. We reprocessed the 500 km long data retrieved by the summer 1991 seismic survey offshore of the Boso peninsula and Tohoku regions and produced a high resolution image of the Pacific plate crust and Mantle lithosphere beneath it. We have conducted a CMP gather analysis combining 18828 traces and applied a first arrival mute at almost every 4 shots. Consecutively we applied NMO corrections after determining stacking velocity values every 30 CMP gathers, which is equivalent to every 800 m along the profile. The corrected traces enabled us to retrieve a high resolution image of the sediments deposited on the Pacific plate. The upper part of the plate is characterized by a thick sequence of sediments offshore of the Boso peninsula that becomes progressively thinner towards the north in the region offshore the Tohoku region. This could be due to the geometry of the profile, since the southern part is further away from the trench than the north. Offshore Tohoku the sediments are possibly eroded and redeposit inside the trench by down going currents. Our profile intersects with a seamount range that is currently subducting under the Japan Trench. The sedimentary sequence on the Pacific plate around this range is disturbed by a thick sequence of possibly volcanic origin sediments derived from the seamount range. The sedimentary units offshore Boso peninsula display an uplift of several hundred meters. In the southernmost part of our profile we were able to observe several long scale discontinuities inside the plate, that stretch down to the Moho. This area greatly coincides with the Kashima fault zone, previously observed only by the shift of the magnetic anomalies on the plate. The Pacific sea plate crust immediately to the north of this fault zone is significantly thicker than the average crustal thickness offsore the Tohoku part. This could imply that the subducting Pacific plate is coupled stronger beneath the Kanto region than it is under the Tohoku area.

  11. Complex Faulting in the Pacific-North America Transform Offshore Southern California And Implications on Plate Boundary Tectonics and Tsunamigenesis

    Microsoft Academic Search

    M. R. Legg; A. Barberopoulou

    2007-01-01

    Complexity in the tectonic model for Pacific-North America transform motion in the offshore southern California region is demonstrated by earthquakes near San Clemente Island and Fortymile Bank. Observed focal mechanisms show movements opposite to those predicted by the plate tectonic theory for right-slip on NW- trending transform faults and observed in other parts of the California Continental Borderland. Also, there

  12. Cenozoic geological and plate tectonic evolution of SE Asia and the SW Pacific: computer-based reconstructions, model and animations

    Microsoft Academic Search

    Robert Hall

    2002-01-01

    A plate tectonic model for the Cenozoic development of the region of SE Asia and the SW Pacific is presented and its implications are discussed. The model is accompanied by computer animations in a variety of formats, which can be viewed on most desktop computers. GPS measurements and present seismicity illustrate the high rates of motions and tectonic complexity of

  13. 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.

  14. Subduction of the Pacific Plate Beneath the Kamchatka: Volcanism and Tectonic Earthquakes

    NASA Astrophysics Data System (ADS)

    Gordeev, E. I.

    2008-12-01

    The results of studying subduction process of the Pacific plate beneath the Kamchatka and related processes are described. The focal mechanism solutions estimated from Centroid Moment Tensor (CMT) catalog and sequence of the largest earthquakes occurred in Kamchatka were used to asses velocity of subducted slab. The boundary of contact for subducted slab is determined at a depth of 30-70 km, and is considered as a plane at azimuth 217° and with a dip angle of 25°. The rate of subduction estimated from CMT mechanisms yields V=0.9 cm/yr for southern zone (south of Shipunsky Cape), and V=1.4 cm/yr for central zone (from Shipunsky Cape to Kronotsky Cape). The largest coupled consistent earthquakes recorded from 1737 were used for analysis. The results show, that for the southern area V=6.6 - 7.1 cm yr (two couples), and for the central part V=6.6 cm yr. The estimated value of velocity for the creep part of subducted slab is about 5 to 15 per cent of the bulk velocity. The Pacific plate subducts at a rate of 8 cm yr. Series of GPS observations conducted from 1997 up to 2007 were used to estimate the rate at which Kamchatka is deformed under the effect of the subducted slab (along-slab direction). The average values of rate and velocity variations versus the average rate were estimated response to permanent GPS station PETR. It was shown that the motion at BKI (Bering) regardless KlU (Klyuchi) is uneven: variations of velocity reach up to 30 per cent (at average running window of 1 year). There are about 28 active volcanoes in Kamchatka that provide intensive volcanic activity in this region. The volcanoes produce about 16-17% of magmatic rocks erupted by all volcanoes in the Earth. Over the past 5 years, eruptions of Sheveluch, Klyuchevskoy, Bezymianny, Karymsky, and Mutnovsky volcanoes have occurred. Although many of these volcanoes are in sparsely populated areas, they lie adjacent to the heavily North Pacific air routes between North America, Europe and Asia. The Institute of Volcanology and Seismology (IVS) of the Russian Academy of Sciences (RAS) and Kamchatka Branch of Geophysical Survey (KB GS) of RAS monitor and study Kamchatka's hazardous volcanoes, to forecast and record eruptive activity, and implement public safety measures. To meet its mission, the IVS and KB GS maintains a volcano monitoring network to detect signs of volcanic unrest; conducts basic geological, geophysical, and geochemical investigations of Kamchakan volcanoes; and provides accurate and timely warnings of imminent activity to local, state and federal agencies.

  15. The Baja California Borderland and the Neogene Evolution of the Pacific-North American Plate Boundary

    NASA Astrophysics Data System (ADS)

    Fletcher, J. M.; Eakins, B. W.

    2001-12-01

    New observational data on Neogene faulting in the borderland of Baja California places important constraints on tectonic models for the evolution of the Pacific-North American (P-NA) plate boundary and rifting in the Gulf of California. Neogene faults in the borderland range from strike slip to normal slip and accommodate integrated transtension. Most have east-facing escarpments and likely reactivate the former east-dipping accretionary complex. Numerous lines of evidence indicate that Neogene faults are still active and accomplish a significant component ( ~1-5 mm/yr) of Pacific-North American shearing. Quaternary volcanoes are found offshore and along the Pacific coastal margin, Quaternary marine terraces are warped and uplifted as high as 200 masl. Many of the offshore faults have fresh escarpments and cut Holocene sediments. Extensive arrays of Quaternary fault scarps are found throughout the coastal region and in Bahia Magdalena they are clearly associated with major faults that bound recently uplifted islands. A prominent band of seismicity follows the coast and eight earthquakes (Ms>5.0) were teleseismically recorded between 1973 and 1998. This evidence for active shearing indicates that the Baja microplate has not yet been completely transferred to the Pacific plate. The best lithologic correlation that can be used to define the total Neogene slip across the borderland faults is the offset between the Magdalena submarine fan and its Baja source terrane. The distal facies of the fan drilled during DSDP leg 63 is dominated by mudstone and siltstone that contain reworked Paleogene cocoliths derived from strata correlative with the Tepetate formation found throughout the borderland and fine-grained sandstone derived from a source terrane of granitoid basement. The Middle Miocene La Calera formation of the Cabo trough is one of many granitoid-clast syn-rift alluvial deposits that could form the continental counterpart of the submarine fan near the mouth of the proto-gulf. However, regardless of the exact source, the Magdalena fan must have been transported beyond a major submarine canyon system south of Todos Santos by 13.5 Ma when sedimentation rates significantly diminished. This places a maximum of { ~}200 km total slip on the borderland faults since 13.5 Ma. Alternatively, all components of the Magdalena fan could have been derived from reworking Cenozoic strata within the borderland. The sandstone facies could be derived from the Oligocene El Cien Fm., which is a granitoid clast conglomerate that overlies the Tepetate Fm. and crops out ~100 km west of La Paz. If true, the total slip across borderland faults may be only a few tens of kilometers. Key structural relations along the submarine Tosco-Abreojos fault system support this lower slip estimate including: relatively short ({ ~}30 km width) pull-apart basins, correlative strata on either side of the fault, and a strong pattern of splaying, which indicates a lateral termination only { ~}50 km to the SE of the Magdalena fan. These new observations require significant modifications to existing tectonic models, which usually assign { ~}300 km of offset to the borderland. Lower finite slip estimates suggest that the borderland may not have formed the main P-NA plate boundary and long-term Neogene slip rates need not be significantly different from Quaternary slip rates. Lower finite slip estimates also allow stronger correlations between Farallon derived microplates and the patterns of Neogene faulting, volcanism, topographic variations, and surface heat flow in the overlying continental crust of Baja California.

  16. 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.

  17. Illuminating the plate interface structure beneath Cook Strait, New Zealand, with

    E-print Network

    Sheehan, Anne F.

    Illuminating the plate interface structure beneath Cook Strait, New Zealand, with receiver of the North Island of New Zealand, we image seismic impedance discontinuities in the upper mantle beneath Cook beneath Cook Strait, New Zealand, with receiver functions, J. Geophys. Res., 112, B06310, doi:10

  18. Biased geodetic inference on asperity distribution on a subducted plate interface: a quantitative study

    NASA Astrophysics Data System (ADS)

    Hirai, Takashi; Sagiya, Takeshi

    2013-04-01

    The asperity model was developed to explain plate boundary behavior such as interplate earthquakes. Asperity is defined as a strongly-coupled region on the plate interface. Since interplate earthquakes are considered to occur on asperities, it is important to know the asperity distribution, which can be inferred from interseismic crustal deformation through estimation of the slip deficit distribution. Slip deficit is the difference between the long-term plate convergence rate and the actual relative displacement rate of the plate interface. It is a kinematic description of plate interaction. The relation between the estimated slip deficit and the asperity is still not clearly understood. We have conducted a quantitative comparison between them by combining a forward simulation of crustal deformation, as a result of plate subduction, and a geodetic data inversion. We found that the seismic moment accumulation rate is likely to be overestimated in most cases. The degree of overestimation increases in the case of small asperity areas. Conversely, if no slip deficit is detected by geodetic data inversion, it is highly probable that no asperity exists. Such a misinference may lead to an incorrect estimation of strong ground motion in future earthquakes, and appropriate measures should be taken to allow for this.

  19. A very hydrous mantle under the western Pacific region: Implications for formation of marginal basins and style of Archean plate tectonics

    Microsoft Academic Search

    Tsuyoshi Komiya; Shigenori Maruyama

    2007-01-01

    The western Pacific region has been refrigerated by the subducting cold oceanic plates since 450 Ma. However, the region is also characterized by the presence of many oceanic microplates less than 1300 km across, as well as active magmatism; the Philippine Sea plate is representative. We have compiled and examined petrochemical characters of drilled basalts of DSDP from the Philippine Sea plate,

  20. Accelerated subduction of the Pacific Plate after mega-thrust earthquakes: evidence from GPS and GRACE

    NASA Astrophysics Data System (ADS)

    Heki, K.; Mitsui, Y.; Matsuo, K.; Tanaka, Y.

    2012-12-01

    Interplate thrust earthquakes are often followed by afterslips (Heki et al., 1997; Miyazaki et al., 2004; Ozawa et al., 2012). They let the fore-arc move slowly trenchward and accelerate plate convergence. Accelerated convergence of the oceanic side (including ocean floor and slab) has been suggested by changes of focal mechanisms of earthquakes within oceanic plates after mega-thrust events, i.e. change from trench-normal compression to tension in outer rise regions, and from down-dip tension to compression in intermediate depths (Lay et al., 1989). However, landward acceleration of the oceanic plate has never been observed geodetically due to the scarcity of appropriate islands on oceanic plates near trenches. The westward velocity of GPS stations in NE Japan show gradient decreasing from east to west reflecting the E-W compressional stress built up by the inter-plate coupling. We found that such coupling significantly enhanced after the 2003 Tokachi-Oki earthquake (Mw8.0), Hokkaido, in the segments adjacent to the ruptured fault. The coupling was further enhanced after the 2011 Tohoku-Oki earthquake (Mw9.0). Movement of the ocean floor benchmark after the 2011 event suggests that the current (i.e. 2011-2012) subduction of the Pacific Plate is about three times as fast as the geological average, e.g. NUVEL-1 (DeMets et al., 1990). Such a temporary acceleration of the subduction would be a response of the subducting slab to the sudden decrease of interplate coupling (decoupling); because slab-pull and ridge-push cannot change, viscous traction has to increase to recover the force balance. We will present a simple physical model assuming a thin low-viscosity layer on the slab surface that has enabled such a rapid adjustment. The accelerated subduction would account for high regional interplate seismicity after mega-thrust earthquakes, especially successive ruptures of remote segments, e.g. the 2003 Tokachi-Oki, 2006 Kuril, and 2011 Tohoku-Oki earthquakes. GRACE satellite gravimetry revealed coseismic gravity drops in the back-arc regions due to the dilatation of island arc lithosphere for the 2004 Sumatra-Andaman (Han et al., 2005), 2010 Maule (Heki and Matsuo, 2010), and 2011 Tohoku-oki (Matsuo and Heki, 2011) earthquakes. Postseismic slow gravity increase centered in the fore-arc region was first found for the 2004 Sumatra-Andaman earthquake (Ogawa and Heki, 2007). Here we show that similar postseismic gravity increases also followed the other two mega-thrust earthquakes. We assume that they also reflect accelerating subduction of oceanic plates, i.e. episodic convergence at the boundary propagates into oceanic plate interior by stress diffusion (Bott and Dean, 1973), and postseismic thickening of the coseismically thinned lithosphere causes the on-going gravity increases.

  1. Crustal structure and configuration of the subducting Philippine Sea plate beneath the Pacific coast industrial zone in Japan inferred from receiver function analysis

    NASA Astrophysics Data System (ADS)

    Igarashi, T.; Iidaka, T.; Sakai, S.; Hirata, N.

    2012-12-01

    We apply receiver function (RF) analyses to estimate the crustal structure and configuration of the subducting Philippine Sea (PHS) plate beneath the Pacific coast industrial zone stretching from Tokyo to Fukuoka in Japan. Destructive earthquakes often occurred at the plate interface of the PHS plate, and seismic activities increase after the 2011 Tohoku earthquake (Mw9.0) around the Tokyo metropolitan area. Investigation on the crustal structure is the key to understanding the stress concentration and strain accumulation process, and information on configuration of the subducting plate is important to mitigate future earthquake disasters. In this study, we searched for the best-correlated velocity structure model between an observed receiver function at each station and synthetic ones by using a grid search method. Synthetic RFs were calculated from many assumed one-dimensional velocity structures that consist of four layers with positive velocity steps. Observed receiver functions were stacked without considering back azimuth or epicentral distance. We further constructed the vertical cross-sections of depth-converted RF images transformed the lapse time of time series to depth by using the estimated structure models. Telemetric seismographic network data covered on the Japanese Islands including the Metropolitan Seismic Observation network, which constructed under the Special Project for Earthquake Disaster Mitigation in the Tokyo Metropolitan area and maintained by Special Project for Reducing Vulnerability for Urban Mega Earthquake Disasters, are used. We selected events with magnitudes greater or equal to 5.0 and epicentral distance between 30 and 90 degrees based on USGS catalogues. As a result, we clarify spatial distributions of the crustal S-wave velocities. Estimated average one-dimensional S-wave velocity structure is approximately equal to the JMA2011 structural model although the velocity from the ground surface to 5 km in depth is slow. In particular, the Kanto plain and Boso peninsula are covered in thick sediment layers. The velocity perturbations in the crust are consistent with existing tomography models. There are low-velocity zones in the upper crust to the crust-mantle boundary corresponding to volcanoes. In contrast, non-volcanic mountain foothills are relatively high-velocity zones. We also elucidated the configuration of PHS plate to a depth of about 60 km. The PHS plate subducts to the northwest and the direction coincides with plate motion. The northeastern margin of PHS plate is estimated from the plate thickness, which gradually decreases to the northeast after contact with the underlying Pacific plate beneath the Tokyo metropolitan area. Asperities of some large earthquakes seem to be corresponded to the high-velocity area in the PHS slab. On the other hand, non-volcanic low-frequency earthquakes located in the plate interface are characterized by relatively low-velocity areas. They may indicate the serpentinized mantle wedge which reflects dehydration of the subducting oceanic crust.

  2. GPS measurements of crustal deformation within the Pacific-Australia plate boundary zone in Irian Jaya, Indonesia

    NASA Astrophysics Data System (ADS)

    Puntodewo, S. S. O.; McCaffrey, R.; Calais, E.; Bock, Y.; Rais, J.; Subarya, C.; Poewariardi, R.; Stevens, C.; Genrich, J.; Fauzi; Zwick, P.; Wdowinski, S.

    1994-10-01

    Global Positioning System (GPS) measurements made in 1991, 1992 and 1993 provide preliminary estimates of slip distribution between the Australian and Pacific plates in Irian Jaya, Indonesia. We interpret the GPS results with constraints from earthquake mechanisms and slip vectors, recent marine surveys, and geology. Three GPS sites in southeastern Irian Jaya show motions that are within 10 mm/yr of the expected motion of Australia. A coast-to-coast N-S baseline along 140.5°E crosses all known onland regions of active deformation but reveals no more than 15 mm/yr of shortening and 20 mm/yr of left-lateral shear in the 27-month period. The remaining 40 mm/yr of expected convergence between the Pacific and Australian plates probably occurs at the New Guinea trough. GPS sites on the island of Biak, at 136°E, and at Sorong, near the western tip of Bird's Head (at 131°E), both move 90-100 mm/yr in a WSW direction relative to Irian Jaya, but less than 15 mm/yr relative to each other. These sites are on either side of the Sorong fault and demonstrate that it is not presently the major boundary between the Australian and Pacific plates. Instead the plate boundary is now south of the Sorong and Biak sites. Earthquakes suggest possible structures that accomodate motion between Bird's Head and Australia but the relative importance of them remains uncertain.

  3. Seismic structure of the North Pacific oceanic crust prior plate bending at the Alaska subduction zone

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Seismic reflection profiles across North Pacific oceanic Plate reveal the internal structure of a mature oceanic crust (42-56Ma) formed at fast (70mm/yr, half rate) to intermediate (28mm/yr, half rate) spreading rates. Data used in this study were collected with the R/V Langseth in summer 2011 as part of the ALEUT (Alaska Langseth Experiment to Understand the megathrust) program. MCS data were acquired with two 8-km streamers and a 6600 cu. in. air gun array. We collected a series of profiles across the subduction zone system but also across the preexisting structures of the oceanic crust before being affected by subduction zone processes. Additionally, two 400-km OBS refraction lines were shot coincident with MCS profiles. The multi-channel seismic (MCS) data across oceanic crust formed at fast spreading rates contain abundant bright reflectors mostly confined in the lower crust above the Moho discontinuity and dipping predominantly toward the paleo-ridge. Along these profiles, the Moho discontinuity is observed as a bright event with remarkable lateral continuity. The lengths of the dipping reflectors are on the order of 5-km, with apparent dips between 10 and 30°. These reflectors represent discrete events, with spacing between 0.3 to 5 km without any obvious regularity. These dipping events appear to sole out within the middle crust (1 to 1.5 s beneath basement) and most of them terminate at the Moho. The Moho is much weaker or absent on the northern profiles acquired across the North Pacific oceanic crust formed at intermediate spreading rates. Basement topography is rougher and no clear dipping events have been imaged suggesting that the spreading rate may be an important factor that controls the strength and abundance of such dipping reflectors and the lateral change in the Moho reflection characters. Lower crustal dipping reflections (LCDR) have been only imaged at very few places across the Pacific oceanic crust: (Eittreim et al., 1988, Reston et al. 1999, Ranero et al., 1997, Hallenborg et al., 2003). These LCDR have been interpreted as being either formed near the spreading center during accretion or off-axis post-accretion structures. Interpretations proposed included lithologic banding from passive accretion, shear structures from active mantle upwelling, off-axis magmatism, or enhanced reflectivity of latent structures by crustal aging (e.g., hydrothermal circulation, etc). Another alternative that we propose is that the dipping reflectors are shear zones that form in the lower crustal mush zone due to active upwelling that contain frozen melts segregated into the shear zones during deformation. Characteristics of the wide-angle reflection data are also different between the two lines. Lateral variations in the Moho reflections and crustal refractions are clearly observed and will be discussed with respect to the structures imaged on the coincident reflection images. The transition between fast to intermediate spreading rates occurs near a triple junction that separated the Pacific, Kula and Farallon plates that ceased spreading in the Late Eocene. MCS profiles across and around the fossil triple junction reveal deep reflections into the crust and below the Moho down to 15-km depth. These reflections could possibly be caused by gabbroic melts that froze in the mantle lithosphere when the triple junction was abandoned.

  4. Tidal triggering of earthquakes in the subducting Philippine Sea plate beneath the locked zone of the plate interface in the Tokai region, Japan

    Microsoft Academic Search

    Sachiko Tanaka; Haruo Sato; Shozo Matsumura; Masakazu Ohtake

    2006-01-01

    We found a characteristic space–time pattern of the tidal triggering effect on earthquake occurrence in the subducting Philippine Sea plate beneath the locked zone of the plate interface in the Tokai region, central Japan, where a large interplate earthquake may be impending. We measured the correlation between the Earth tide and earthquake occurrence using microearthquakes that took place in the

  5. 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.

  6. Rayleigh phase velocities in the upper mantle of the Pacific-North American plate boundary in southern California

    NASA Astrophysics Data System (ADS)

    Escobar, L.; Weeraratne, D. S.; Kohler, M. D.

    2013-05-01

    The Pacific-North America plate boundary, located in Southern California, presents an opportunity to study a unique tectonic process that has been shaping the plate tectonic setting of the western North American and Mexican Pacific margin since the Miocene. This is one of the few locations where the interaction between a migrating oceanic spreading center and a subduction zone can be studied. The rapid subduction of the Farallon plate outpaced the spreading rate of the East Pacific Rise rift system causing it to be subducted beneath southern California and northern Mexico 30 Ma years ago. The details of microplate capture, reorganization, and lithospheric deformation on both the Pacific and North American side of this boundary is not well understood, but may have important implications for fault activity, stresses, and earthquake hazard analysis both onshore and offshore. We use Rayleigh waves recorded by an array of 34 ocean bottom seismometers deployed offshore southern California for a 12 month duration from August 2010 to 2011. Our array recorded teleseismic earthquakes at distances ranging from 30° to 120° with good signal-to-noise ratios for magnitudes Mw ? 5.9. The events exhibit good azimuthal distribution and enable us to solve simultaneously for Rayleigh wave phase velocities and azimuthal anisotropy. Fewer events occur at NE back-azimuths due to the lack of seismicity in central North America. We consider seismic periods between 18 - 90 seconds. The inversion technique considers non-great circle path propagation by representing the arriving wave field as two interfering plane waves. This takes advantage of statistical averaging of a large number of paths that travel offshore southern California and northern Mexico allowing for improved resolution and parameterization of lateral seismic velocity variations at lithospheric and sublithospheric depths. We present phase velocity results for periods sampling mantle structure down to 150 km depth along the west coast margin. With this study, we seek to understand the strength and deformation of the Pacific oceanic lithosphere resulting from plate convergence and subduction beneath Southern California 30 Ma as well as translational stresses present today. We also test for predictions of several geodynamic models which describe the kinematic mantle flow that accompanies plate motion within this area including passive mantle drag due to Pacific plate motion and toroidal flow in the western U.S. region that may extend offshore.

  7. Metamorphic soles and flip flops: rheology of the plate interface during early subduction stages

    NASA Astrophysics Data System (ADS)

    Agard, Philippe

    2014-05-01

    Metamorphic soles underlie most extensive ophiolites worldwide (i.e., ~several 100 km long, non metamorphosed obducted pieces of oceanic lithosphere). These metamorphic soles (MS) are tectonic slices dragged along and welded to the ophiolite and generally comprise m to ~500 m thick (strongly deformed and thus partly thinned) high-T granulite to amphibolite facies mafic protoliths, together with subordinate metaradiolarites. There is wide recognition that these HT MS formed during subduction initiation (ie., < 1-2 My after inception) at the expense of the upper part of the oceanic crust, atop the incipiently underthrusting lower plate. This sole observation implies a spectacular yet unaccounted for jump of the lower contact of the ophiolite thrust during early subduction stages, from above to below the MS. Besides, the review of recent P-T determinations constraining the formation of high-T MS evidences a fairly narrow range between 1±0.2 GPa, 700-850°C. This is, consistently, significantly warmer than the later subduction regime, during which (a) lower T amphibolite to greenschist facies units from the top of the oceanic crust, yet with comparatively greater amounts of metasediments, become accreted below the high-T MS, (b) later, non metamorphosed and/or HP-LT units derived from uppermost crustal material are underthrust beneath the metamorphic sole s.l., as in W. Turkey or Oman. This contribution tentatively explains how metamorphic soles get attached to the upper plate ophiolite by a simple conceptual model of the plate interface rheology during early subduction stages. This model draws on the existence of a major flip, in terms of mechanical behaviour, as the plate interface progressively cools: (1) rheological data suggest that the mechanical resistance of the upper plate mantle is initially greater than that of the lower plate (variably hydrothermalized) oceanic crust; (2) as the system cools, and even more so once the upper plate mantle gets incipiently serpentinized (i.e., at ~700-750°C), the effective resistance of both lithologies/domains will progressively converge. I propose that this particular P-T window corresponds to the transient, optimal period during which similar effective rheology on both sides maximizes interplate mechanical coupling: deformation gets distributed over a larger band (on the 500 m to km scale), which allows the high-T MS to be transfered from the downgoing plate to the upper plate. (3) at decreasing, lower T, the lower plate oceanic crust becomes stronger than the upper plate mantle (this crust also gets efficiently eclogitized at depths and thus rarely returned with respect to subduction duration). The plate interface becomes highly localized again and later underthrusting and tectonic slicing at the toe of the upper plate detaches progressively shallower parts of the incoming material. Flip flops are firmly tied to the ophiolite by then... This interpretation of the plate interface rheology during progressive cooling is consistent with reports of low-temperature obduction-related deformation (i.e., 700-900°C) at the base of the ophiolite mantle itself. It may also provide constraints on the long-term mechanical properties of both basalt and peridotite.

  8. 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.

  9. Origin and evolution of marginal basins of the NW Pacific: Diffuse-plate tectonic reconstructions

    E-print Network

    Xu, Junyuan; Ben-Avraham, Zvi; Yu, Ho-Shing

    2012-01-01

    Formation of the gigantic linked dextral pull-apart basin system in the NW Pacific is due to NNE- to ENE-ward motion of east Eurasia. This mainly was a response to the Indo-Asia collision which started about 50 Ma ago. The displacement of east Eurasia can be estimated using three aspects: (1) the magnitude of pull-apart of the dextral pull-apart basin system, (2) paleomagnetic data from eastern Eurasia and the region around the Arctic, and (3) the shortening deficits in the Large Tibetan Plateau. All the three aspects indicate that there was a large amount (about 1200 km) of northward motion of the South China block and compatible movements of other blocks in eastern Eurasia during the rifting period of the basin system. Such large motion of the eastern Eurasia region contradicts any traditional rigid plate tectonic reconstruction, but agrees with the more recent concepts of non-rigidity of both continental and oceanic lithosphere over geological times. Based on these estimates, the method developed for resto...

  10. 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.

  11. 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.

  12. Dose Variation at Bone\\/Titanium Interfaces Using Titanium Hollow Screw Osseointegrating Reconstruction Plates

    Microsoft Academic Search

    Abdelkarim S Allal; Michel Richter; Mariateresa Russo; Michel Rouzaud; John M Kurtz

    1998-01-01

    Purpose: To evaluate dose variations at bone\\/titanium interfaces in an experimental model designed to simulate postoperative radiotherapy in patients with mandibular reconstructions using a titanium hollow-screw osseointegrating reconstruction plate (THORP) system.Materials and Methods: The model consisted of a 25 × 25 × 10 mm3 block of fresh bovine femoral diaphysis, to the surface of which a segment of THORP system

  13. Influence of cumulative convergence on lithospheric thrust fault development and topography along the Australian-Pacific plate boundary south of New Zealand

    Microsoft Academic Search

    T. A. Meckel; P. Mann; Sharon Mosher; Millard F. Coffin

    2005-01-01

    The development of faulting and topography resulting from initial convergence within oceanic lithosphere is largely unknown. We explore relationships among convergence, structural development, and topography along ~1500 km of the submarine Australian-Pacific plate boundary south of New Zealand, the Macquarie Ridge Complex (MRC). Due to the variable orientation of the boundary and close proximity of the Australian-Pacific poles of rotation,

  14. Influence of cumulative convergence on lithospheric thrust fault development and topography along the Australian-Pacific plate boundary south of New Zealand

    Microsoft Academic Search

    T. A. Meckel; P. Mann; Sharon Mosher; Millard F. Coffin

    2005-01-01

    The development of faulting and topography resulting from initial convergence within oceanic lithosphere is largely unknown. We explore relationships among convergence, structural development, and topography along ?1500 km of the submarine Australian-Pacific plate boundary south of New Zealand, the Macquarie Ridge Complex (MRC). Due to the variable orientation of the boundary and close proximity of the Australian-Pacific poles of rotation,

  15. Crustal motion studies in the southwest Pacific: Geodetic measurements of plate convergence in Tonga, Vanuatu and the Solomon Islands

    NASA Astrophysics Data System (ADS)

    Phillips, David A.

    The southwest Pacific is one of the most tectonically dynamic regions on Earth. This research focused on crustal motion studies in three regions of active Pacific-Australia plate convergence in the southwest Pacific: Tonga, the New Hebrides (Vanuatu) and the Solomons Islands. In Tonga, new and refined velocity estimates based on more than a decade of Global Positioning System (GPS) measurements and advanced analysis techniques are much more accurate than previously reported values. Convergence rates of 80 to 165 mm/yr at the Tonga trench represent the fastest plate motions observed on Earth. For the first time, rotation of the Fiji platform relative to the Australian plate is observed, and anomalous deformation of the Tonga ridge was also detected. In the New Hebrides, a combined GPS dataset with a total time series of more than ten years led to new and refined velocity estimates throughout the island arc. Impingement of large bathymetric features has led to arc fragmentation, and four distinct tectonic segments are identified. The central New Hebrides arc segment is being shoved eastward relative to the rest of the arc as convergence is partitioned between the forearc (Australian plate) and the backarc (North Fiji Basin) boundaries due to impingement of the d'Entrecasteaux Ridge and associated Bougainville seamount. The southern New Hebrides arc converges with the Australian plate more rapidly than predicted due to backarc extension. The first measurements of convergence in the northern and southernmost arc segments were also made. In the Solomon Islands, a four-year GPS time series was used to generate the first geodetic estimates of crustal velocity in the New Georgia Group, with 57--84 mm/yr of Australia-Solomon motion and 19--39 mm/yr of Pacific-Solomon motion being observed. These velocities are 20--40% lower than predicted Australia-Pacific velocities. Two-dimensional dislocation models suggest that most of this discrepancy can be attributed to locking of the San Cristobal trench and elastic strain accumulation in the forearc. Anomalous motion at Simbo island is also observed.

  16. 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.

  17. 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. [School of Metallurgy and Materials Engineering, University College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of)

    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.

  18. Changes in electrical resistivity track changes in plate coupling of the Hikurangi subduction interface, New Zealand (Invited)

    NASA Astrophysics Data System (ADS)

    Heise, W.; Caldwell, G.; Hill, G.; Bertrand, E. A.; Bennie, S.; Ogawa, Y.

    2013-12-01

    Inter-plate coupling on the Hikurangi subduction margin along the east coast of New Zealand's North Island changes from north to south from almost uncoupled to locked. Magnetotelluric (MT) data from the northern part of the Hikurangi margin show a dipping conductor is present above the subduction interface and is interpreted to mark a layer of fluid and/or clay rich sediments within the subduction interface shear zone. Results from a MT profile in the southern part of the Hikurangi subduction margin, where the plates are locked, show the conductivity structure is markedly different than in the north. Here, no conductor is observed along the plate interface. The difference in plate-coupling and resistivity structure between the northern and southern parts of the Hikurangi margin suggest that the presence of fluid and/or clay rich sediments plays an important role in controlling the frictional processes at the interface and thus the inter-seismic coupling.

  19. Load Sharing Mechanism Across Graft-Bone Interface in Static Cervical Locking Plate Fixation

    PubMed Central

    Han, In Ho; Kuh, Sung Uk; Chin, Dong Kyu; Jin, Byung Ho; Cho, Yong Eun

    2009-01-01

    Objective This study is a retrospective clinical study over more than 4 years of follow up to understand the mechanism of load sharing across the graft-bone interface in the static locking plate (SLP) fixation compared with non-locking plate (NLP). Methods Orion locking plates and Top non-locking plates were used for SLP fixation in 29 patients and NLP fixation in 24 patients, respectively. Successful interbody fusion was estimated by dynamic X-ray films. The checking parameters were as follows : screw angle (SA) between upper and lower screw, anterior and posterior height of fusion segment between upper and lower endplate (AH & PH), and upper and lower distance from vertebral endplate to the end of plate (UD & LD). Each follow-up value of AH and PH were compared to initial values. Contributions of upper and lower collapse to whole segment collapse were estimated. Results Successful intervertebral bone fusion rate was 100% in the SLP group and 92% in the NLP group. The follow-up mean value of SA in SLP group was not significantly changed compared with initial value, but follow-up mean value of SA in NLP group decreased more than those in SLP group (p=0.0067). Statistical analysis did not show a significant difference in the change in AH and PH between SLP and NLP groups (p>0.05). Follow-up AH of NLP group showed more collapse than PH of same group (p=0.04). The upper portion of the vertebral body collapsed more than the lower portion in the SLP fixation (p=0.00058). Conclusion The fused segments with SLP had successful bone fusion without change in initial screw angle, which was not observed in NLP fixation. It suggests that there was enough load sharing across bone-graft interface in SLP fixation. PMID:19444346

  20. 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.

  1. Preliminary Investigation to Resolve the Shear Velocity Structure of the Mantle Transition Zone beneath the Caroline Plate, Equatorial Western Pacific

    NASA Astrophysics Data System (ADS)

    Konishi, K.; Kawai, K.; Fuji, N.; Lee, S.; Geller, R. J.

    2013-12-01

    The Mantle Transition Zone (MTZ), which lies in the depth range from 410-660 km, is considered to be a region capable of carrying a large amount of water and other volatiles. A unique feature of the MTZ beneath the northwest Pacific rim is the stagnant slab which lies below much of the West Philippine Basin and extends laterally over a distance of thousands of kilometers beneath Korea and northeast China. In recent years, suggestions have been made that explain the seismicity and intra-plate volcanism in this region in terms of hydrous magmatic plumes rising from the MTZ. However, the exact mechanism remains under debate. An equally important, but less well-known, observation is that a stagnant slab appears to exist beneath much of the Caroline Plate in the equatorial western Pacific as well. If a stagnant slab does exist here, it is most likely a result of the long northward migration of the Australian Plate and subduction since its breakaway from the Antarctic. However, due to tectonic complexity and the lack of seismic stations, the structure and properties of the stagnant slab and the MTZ beneath the Caroline plate are not well understood. Also it is unclear if the large volcanic outflows around the Caroline Plate such as the Eurpik Rise can be explained by a hydrous magmatic plume stemming from the MTZ. To understand the shear-wave velocity structure of the MTZ beneath the Caroline Plate, we employ a body wave waveform inversion technique. Fuji et al. (PEPI, 2010) conducted body wave waveform inversion for the mantle transition zone beneath Japan. In this study we present preliminary results for an application of their methods to infer upper mantle and MTZ structure beneath the Caroline plate. We also estimate the resolving power of full-waveform inversion for a dataset obtained from the IRIS (Incorporated Research Institutions for Seismology) network for shear velocity structure in the upper mantle, especially for the mantle transition zone beneath the Caroline Plate using transverse component body wave data in order to examine whether it is possible to reliably infer the existence of a high velocity anomaly because the dataset is relatively small and there are not many seismic stations to the east of this region.

  2. Observation of prominent S-to-P converted phases from the deep-subducted Western Pacific slab interfaces and their mineralogical implications

    NASA Astrophysics Data System (ADS)

    He, X.; Hong, T.

    2013-12-01

    A prominent S-to-P converted phase is observed between the direct P and S waves in regional seismograms at South Korean stations for the deep-focus earthquakes in the western Pacific subducting slab. The focal depths of the events are ~ 577 km. The amplitudes of the phase reach to ~50 % of amplitude of direct P waves. These anomalous S-to-P converted waves appear to develop on the subducting slab interfaces at a depth of ~300 km beneath stations considering their traveltimes and phase polarization. Development of such large-amplitude slab-converted phase requires a strong seismic contrasts across the slab interface in the upper-mantle. Hydrous gabbro in the oceanic crust may produce a low-velocity layer at the top of slab, yielding high impedance contrasts across the slab interface. The observation suggests that the gabbro-to-eclogite reaction appears to occur along slab interface at the upper mantle. The water contents and slab geometry are constrained by comparing the synthetic seismograms for various cases with observed seismograms. We finally discuss the geodynamic implication for water distribution in the slab, which may be crucial for understanding the volcanic evolution and deep-subduction process in the northeastern Eurasian plate.

  3. Electromagnetic imaging the of the Pacific-North American plate boundary in central California, USA

    NASA Astrophysics Data System (ADS)

    Wheelock, B. D.; Constable, S.; Key, K. W.

    2010-12-01

    The continental margin of central California lies adjacent to a segment of the San Andreas fault (SAF) that exhibits a transition between locked behavior south of the town of Cholame, and freely slipping (creeping) behavior north of the town of Parkfield. Recent reports of non-volcanic tremor (NVT) near the town of Cholame represent the first observation of NVT in a strike-slip environment. Dense clusters of tremor episodes located at the northern limit of the locked section of the SAF were found to originate within the ductile lower crust at depths between 15 and 30~km, and have been interpreted as evidence of high pore fluid pressure. An excess of fluids in this region is likely given its history of subduction, which transports large quantities of water into the forearc crust and mantle. We present a study that uses deep electromagnetic imaging methods to estimate the abundance and distribution of pore fluids at depths associated with non-volcanic tremor. This study extends a previously collected terrestrial profile of magnetotelluric (MT) data (Becken et al. 2008, Geophysical Journal International) into the offshore environment. We deployed 21 seafloor instruments that collected controlled-source electromagnetic (CSEM) and MT data in a line extending from the coast near Morro Bay, across the continental shelf, and out onto the Pacific plate. The marine MT data results in apparent resistivity and phase estimates at periods between 1~s and 20,000~s, sufficient for probing the upper 100~km of regional conductivity. A significant coast effect, marked by asymptotic behavior in the TE mode of the MT responses, is observed at the deep water sites. This necessitates accurate bathymetry modeling when inverting. The CSEM transmitter was towed by all receivers broadcasting a compact broadband binary waveform with a 0.25~Hz fundamental frequency. The controlled-source signal is observed above the noisefloor at source-receiver offsets up to 6~km, which provides constraints on the conductivity structure of the upper 3~km of the crust. By extending the preceding line of terrestrial MT measurements to the west, we are able to constrain any differences in crust and mantle conductivity associated with the transition across the continental boundary. Furthermore, we address whether the deeply-sourced fluids migrating into the root of the SAF identified in Becken et al. (2008) are related to the fossil subduction zone. Inversion of this combined data set aims to detect the source region of these deep fluids, put constraints on their abundance, and further reveal any pathways by which they may reach the San Andreas fault.

  4. 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.

  5. Streaking in Cascadia ETS Events and Implications for the Subduction Plate Interface

    NASA Astrophysics Data System (ADS)

    Houston, H.; Ghosh, A.

    2011-12-01

    The manner in which episodic tremor and slow slip (ETS) propagates across the subduction plate interface provides constraints on its properties and the physical processes involved. We have been examining catalogs of tremor locations to study propagation patterns during ETS. Tremor in the large Cascadia ETS events propagates mainly via three modes: 1) the slow along-strike advance of ETS, 2) rapid tremor reversals (RTRs) that propagate back from the tremor front in an opposite direction to the along-strike advance, but at speeds 10-40 times faster (Houston et al., Nature Geoscience, 2011), and 3) streaks, even faster migrations of tremor parallel to the plate-convergence direction at speeds ~ 70 km/hr (Ghosh et al., G3, 2011). The UW Seismology group has recently deployed an EarthScope-funded seismic experiment, the Array of Arrays, to image tremor more precisely with eight subarrays. A 15-month catalog of high-resolution tremor locations has been generated based on the triangulation of back-projected beams from the subarrays. We detect tremor streaks in this catalog automatically and systematically determine streak propagation properties. Key issues for constraining streak-generation processes include systematic differences between up- and down-dip traveling streaks, how streak properties may depend on depth, and whether streaks accelerate or decelerate during propagation. Stacking automatically-detected streaks can address some of these issues. Two approaches to automatically detecting streaks have been developed and applied to the M6.8 2010 ETS. One method declares a streak when averaged epicenters continue to move in a roughly constant direction for more than 10 km. The second declares a streak if epicenters during a specified time interval, say 20 min, are sufficiently well-correlated with time. The two methods agree well and detect several streaks per day of 15-30 min duration with speeds consistent with those inferred for the 2008 ETS. Although the detection methods have no azimuthal bias, most of the detected streaks align with one direction; furthermore, that direction lies much closer to the plate convergence direction than directly down-dip (the down-dip and plate convergence directions differ significantly along most of Cascadia). Many more streaks are detected in the actual catalog than in randomized versions, in which the times within each hour are permuted. These results lend substantial credence to convergence-parallel streaks as real features of ETS. Streak propagation patterns suggest the plate interface is anisotropic along the slip direction. The ubiquity of streaking parallel to plate convergence implies control by corrugated or smeared structures on the plate interface. This could occur via such structures controlling the orientation of an advancing slip pulse, which could carry streaks along its peak (Rubin, G3, 2011), or more directly via heterogeneous physical properties (such as rheology or permeability) elongated in the convergence direction. In this connection, we note that daily tremor bands in Cascadia ETS are also often oriented parallel to the convergence direction whether the ETS is advancing north or south, even though the direction of ETS advance would be expected to affect the orientation of a slip pulse on a homogeneous interface.

  6. 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.

  7. Paleomagnetic constraints on Cenozoic deformation along the northwest margin of the Pacific-Australian plate boundary zone through New Zealand

    NASA Astrophysics Data System (ADS)

    Turner, Gillian M.; Michalk, Daniel M.; Little, Timothy A.

    2012-02-01

    New Zealand straddles the boundary between the Australian and Pacific plates, a zone of oblique continental convergence and transform motion. The actively deforming region offers a unique opportunity to study the dynamics of deformation, including vertical-axis rotation of rigid blocks within a transcurrent plate boundary zone. We present and interpret paleomagnetic data from three new and three previously published sites from the NW part of the South Island (NW Nelson region), where sedimentary strata dated between 36 and 10 Ma overlie the crystalline Paleozoic basement assemblages of the Gondwana margin. Compared with reference directions from the Australian apparent polar wander path, none of the results provide evidence of post-Eocene vertical-axis rotation. This suggests that for the past 36 Myr NW Nelson has remained a strong, coherent block that has moved as a contiguous part of the Australian plate. This is in marked contrast to the strongly rotated nature of more outboard accreted terranes to the east. For example, the Hikurangi Margin in the North Island (NW of the Alpine Fault) and the Marlborough region in the NE of the South Island (SE of the Alpine Fault), have both undergone diverse clockwise rotations of up to 140° since the early Paleogene. The NW tip of the South Island seems to have acted as a rigid backstop relative to these more complex oroclinal deformations. We infer that, because of its relatively stiff bulk rheology, it has not been drawn into the distributed plate boundary rotational deformation associated with the New Zealand Orocline.

  8. Heat flow anomaly on the seaward side of the Japan Trench associated with deformation of the incoming Pacific plate

    NASA Astrophysics Data System (ADS)

    Yamano, Makoto; Hamamoto, Hideki; Kawada, Yoshifumi; Goto, Shusaku

    2014-12-01

    Extensive heat flow measurements were conducted on the seaward side of the Japan Trench for investigation of the extent and the origin of high heat flow previously found on the incoming Pacific plate. The obtained data combined with the existing data showed that high and variable heat flow values are pervasively distributed seawards of the northern half of the trench and within about 150 km of the trench axis. In this anomalous zone, the average heat flow is 60 to 70mW/m2, appreciably higher than the value typical for the seafloor age of about 135 m.y. The occurrence of the anomalous heat flow along the trench indicates that it results from processes closely related to deformation of the incoming plate. Heating by intra-plate "petit-spot" volcanism and/or fluid flow along normal faults developed on the trench slope may yield local heat flow peaks but cannot raise regional average heat flow. The most probable cause of the observed widespread anomalous heat flow is efficient vertical heat transport by hydrothermal circulation in a permeable layer in the oceanic crust, which is gradually developed by fracturing due to plate bending. Similar heat flow and temperature structure anomalies on the seaward side of the trench may exist in other subduction zones.

  9. 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.

  10. Relationship between tectonic evolution of North China craton and Pacific plate subduction slab evolution since ~47 Ma

    NASA Astrophysics Data System (ADS)

    An, M.

    2011-12-01

    The Pacific plate movement happened some obviously changes at ~47 Ma. If we only consider the Pacific plate subduction just since this time, we can find that the subduction slab can reach eastern North China after ~20My (at ~27 Ma), and the slab may be destructed completely when it reach this position (An et al., 2009, G-cubed, doi:10.1029/2009GC002562). In the 20-My-movement processes, the evolution of the cold slab can be divided into several stages with the slab is heated and destructed. In different evolution stages, the slab also can result in different effects on the overlying asthenosphere and lithosphere. The slab evolution showed some temporal consistence with the tectonic activities in the eastern North China, and also with the Japan Sea opening; Furthermore, the possible effects acted on the overlying lithosphere by the slab in different stages can interpret the tectonic events happened in eastern North China since the early Paleogene (An et al., 2011, Earth Science Frontiers, 18(3)(in Chinese with English abstract), http://www.earthsciencefrontiers.net.cn/CN/abstract/abstract4277.shtml). For example, regional lithosphere seems to be thickening, Tangshan-Xingtai faults became active but the activities of the Taihangshan Piedmont faults decreased.

  11. 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.

  12. Plate Coupling, Block Rotation and Crustal Deformation in the Pacific Northwest

    Microsoft Academic Search

    R. McCaffrey; A. I. Qamar; R. W. King; R. Wells

    2006-01-01

    GPS measurements in the northwestern US and adjacent parts of Canada describe the relative motions of crustal blocks, the interseismic friction on faults, and the permanent deformation associated with convergence between the Juan de Fuca and North American plates. To estimate angular velocities of the oceanic Juan de Fuca and Explorer plates and several continental crustal blocks, we invert the

  13. Upper Plate Deformation is Dominated by Varying Interface Coupling in the Chilean Subduction Context

    NASA Astrophysics Data System (ADS)

    Vigny, C.; Socquet, A.; Madariaga, R.; Ruegg, J.; Campos, J.; Barrientos, S.

    2008-12-01

    It has been almost two decades now that GPS has been used to measure plate tectonics and quantify plate deformation. In South America, the debate rapidly focused on the motion of the Nazca plate relative to the South America plate. Space geodesy allows to compare plate motions averaged over a few years to plate motion averaged over several million of years. Since the initial work of (Larson et al., 1997) which found similar rates, it is well known now (eg: Norabuena et al, 1998; Norabuena et al, 1999; Angermann et al., 1999; Altamimi et al., 2002; Kendrick et al, 2003; Vigny et al, 2008) that in fact the present day motion of the Nazca plate is around 15% slower than its Nuvel-1A estimate. This finding has the important consequence that along the South American margin, instead of nearing 8 cm/yr, today's subduction rate ranges from 5.5 cm/yr in Equator to 7 cm/yr in central Chile, before it decreases again to 6.5 cm/yr in southern Chile. Part of this convergence rate is taken up by permanent strain contributing to the building of the Andes, but most of it generates elastic deformation recovered during the seismic cycle with an average of one M=8 event every ten years and at least one M>8.7 per century in what corresponds to the Chilean portion of the Nazca subduction. Surface deformation is representative of these processes and GPS measurements made in the area aim at quantifying the different contributions and defining the style of deformation. Up to now, two different families of models have been presented: 2-plates model, involving homogeneous medium where the slab geometry varies with latitude and depth, (Klotz et al., 2001; Khazaradze et al., 2003); 3-plates model involving a rigid sliver between the 2 main plates (Kendrick et al., 2003; Brooks et al, 2003). Steady state velocities predicted by these models differ at the cm/yr level in places and GPS measurements should allow to discriminate easily between them. However, recent measurements we carried out on small scale dense networks in Chile in the vicinity of the trench (Concepion - 36° S, Coquimbo - 30° S, Antofagasta - 22° S) show that the deformation exhibits very different patterns in distinct areas and abrupt changes with latitude. We demonstrate that to model these patterns with a full coupling on the trench is not possible everywhere, and following others, we conclude that coupling must be varying on the subduction interface, both with depth and along strike, and can reach value as low as 40% regionally and even less locally. Moreover, these low-coupling areas could correspond to transient deformation associated to the seismic cycle. This signal completely dominates the deformation patterns we measured at the surface over the last decade, and renders extremely difficult to detect the permanent deformation not taken up by the recoverable elastic deformation or even to simply quantify the style of deformation.

  14. 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.

  15. 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.

  16. Rheology of the plate interface — Dissolution precipitation creep in high pressure metamorphic rocks

    NASA Astrophysics Data System (ADS)

    Wassmann, Sara; Stöckhert, Bernhard

    2013-11-01

    Subduction zone models invoke deformation to be concentrated along the plate interface, in a region of particularly low temperature. Geophysical observations do not provide constraints on temperature, stress and deformation patterns with desired resolution. In contrast, the record of high pressure metamorphic rocks exhumed from subduction zones provides details on P-T-history, deformation mechanisms, and stress state, albeit not readily correlated with the former dynamic situation on larger scale. Here we review available information on dissolution precipitation creep (DPC) in high pressure metamorphic rocks, which - if representative for subduction zones in general - can pose constraints on conditions, rheology, and flow patterns along the plate interface. The key observations and conclusions are that: (1) Deformation is typically highly inhomogeneous and localized into shear zones; (2) stresses are generally too low to drive crystal plastic deformation; (3) microfabrics suggest dissolution precipitation creep to be the predominant deformation mechanism; (4) an aqueous fluid at quasi-lithostatic pressure is available throughout, allowing for tensile fracturing and crack healing or sealing; (5) low stress combined with high strain rates required for localized deformation at typical subduction rates implies low viscosity; and (6) contribution of shear heating to the thermal budget of subduction zones should be moderate. The dominant deformation mechanism DPC is reviewed in some detail, including experimental and theoretical approaches. Various examples of DPC in high pressure metamorphic rocks are illustrated, emphasizing the role of interphase boundaries as sites of dissolution. Rheology governed by DPC is proposed to control interplate coupling and development of a subduction channel with return flow, being a likely candidate for rapid exhumation of high pressure metamorphic rocks.

  17. Earth's Decelerating Tectonic Plates

    Microsoft Academic Search

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

    2008-01-01

    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

  18. 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.

  19. 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

  20. 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

  1. Correlation of Physical Properties, Logging and Lithology Obtained by Drilling at the 45Ma Pacific Plate: ODP-Leg 200 H2Osite

    Microsoft Academic Search

    J. Kasahara; M. Nakamura; Y. Sun; S. Haraguchi; R. Stephene

    2002-01-01

    The ODP leg 200 drilled at H2O site, which is located at a 45 Ma oceanic crust in the eastern Pacific plate. The main objective of the H2O site was to drill a hole into the basaltic layer for a downhole seismometer installation. The hole required to install a reentry corn and to be cased and cemented for the casing.

  2. The Interface of Pacific and Other Knowledges in a Supplementary Education Site

    ERIC Educational Resources Information Center

    Fairbairn-Dunlop, Peggy

    2014-01-01

    Because identity (language and culture) are central to Pacific knowledge and knowledge construction processes, Pacific students' educational experiences should be viewed through a cultural lens that sees Pacific knowledge and practices as valid and valued. This study explores the relationship between culture and educational outcomes as seen…

  3. Evaluation of a new approach for modelling the screw-bone interface in a locking plate fixation: a corroboration study.

    PubMed

    Moazen, Mehran; Mak, Jonathan H; Jones, Alison C; Jin, Zhongmin; Wilcox, Ruth K; Tsiridis, Eleftherios

    2013-07-01

    Computational modelling of the screw-bone interface in fracture fixation constructs is challenging. While incorporating screw threads would be a more realistic representation of the physics, this approach can be computationally expensive. Several studies have instead suppressed the threads and modelled the screw shaft with fixed conditions assumed at the screw-bone interface. This study assessed the sensitivity of the computational results to modelling approaches at the screw-bone interface. A new approach for modelling this interface was proposed, and it was tested on two locking screw designs in a diaphyseal bridge plating configuration. Computational models of locked plating and far cortical locking constructs were generated and compared to in vitro models described in prior literature to corroborate the outcomes. The new approach led to closer agreement between the computational and the experimental stiffness data, while the fixed approach led to overestimation of the stiffness predictions. Using the new approach, the pattern of load distribution and the magnitude of the axial forces, experienced by each screw, were compared between the locked plating and far cortical locking constructs. The computational models suggested that under more severe loading conditions, far cortical locking screws might be under higher risk of screw pull-out than the locking screws. The proposed approach for modelling the screw-bone interface can be applied to any fixation involved application of screws. PMID:23636756

  4. Sub-crustal earthquakes within the Australia-Pacific plate boundary zone beneath the Southern Alps, New Zealand

    NASA Astrophysics Data System (ADS)

    Boese, C. M.; Stern, T. A.; Townend, J.; Bourguignon, S.; Sheehan, A.; Smith, E. G. C.

    2013-08-01

    Sub-crustal earthquakes have been observed sporadically for ?40 years in the central South Island of New Zealand. We report on 20 events recorded between December 2008 and February 2012 near the Alpine Fault in the continental collision zone between the Australian and Pacific plates. A subset of 18 events at depths of 47-74 km occurs south of Mt. Cook and together with recently reported tremor locations indicates along-strike variations in deformation behaviour along the plate boundary. The sub-crustal earthquakes south of Mt. Cook increase in depth, frequency and size southwards towards the Puysegur subduction zone. Focal mechanisms could be determined for 14 earthquakes and exhibit predominantly strike-slip and reverse faulting solutions. Stress inversion analysis of the focal mechanisms yields a stress field favouring oblique-reverse faulting. We interpret the geographic and vertical distributions of these sub-crustal events in relation to a previously proposed tectonic model of a remnant passive margin that formed south of New Zealand in the Eocene and was overridden when dextral strike-slip motion initiated on the Alpine Fault. We infer that sub-crustal earthquakes occur along the leading edge of this structure, which is attached to the continental Australian crust.

  5. Small repeating earthquakes and inter-plate aseismic slip in and around the Kanto district after the 2011 off the Pacific coast of Tohoku earthquake

    NASA Astrophysics Data System (ADS)

    Igarashi, T.; Iidaka, T.; Sakai, S.; Obara, K.; Hirata, N.

    2013-12-01

    The 2011 off the Pacific coast of Tohoku earthquake (Mw9.0) was the largest earthquake in recorded history in Japan. For the stress changes by this earthquake, the seismic activities around the Kanto district including Tokyo metropolitan area have changed significantly. We detect many small repeating earthquakes beneath this area. They may suggest induced interplate aseismic slips at the subducting Philippine Sea (PHS) plate and the subducting Pacific (PAC) plate. The upper boundary of the PAC plate contacts the PHS plate beneath this area, but the northeastern limit of the PHS plate remains poorly understood. In this study, we first estimate the configuration of the subducting PHS plate and PAC plate and the limit of PHS plate beneath the Kanto district by applying receiver function (RF) analysis. Thereafter, we investigate the space-time characteristics of the inter-plate aseismic slips from sequences of small repeating earthquakes beneath the Kanto district after the 2011 Tohoku earthquake. We made many vertical cross-sections of depth-converted RF images to investigate plate configurations. Telemetric seismographic network data covered on the Kanto district including the Metropolitan Seismic Observation network, which constructed under the Special Project for Earthquake Disaster Mitigation in the Tokyo Metropolitan area and maintained by Special Project for Reducing Vulnerability for Urban Mega Earthquake Disasters, are used. We selected events with a good S/N and epicentral distance between 30 and 90 degrees based on USGS catalogues. As a result, we elucidated the configuration of PHS plate and PAC plate beneath the Kanto district. The PHS plate subducts to the northwest and the direction coincides with plate motion. The northeastern limit of PHS plate is estimated from the change of plate thickness, which gradually decreases to the northeast after contact with the underlying PAC plate beneath the Tokyo metropolitan area. There is little seismic activity from the limit to the thickness of 5 km. Using these plate configurations, we classified small repeating earthquakes and estimated inter-plate aseismic slip at each plate. Although the resultant slip-rates before the 2011 main-shock correspond to the relative plate motion in these areas, they increased in both plates after the event. At the PAC plate, they occur around the coseismic slip area of the largest aftershock and cannot detect within it. Furthermore, the slip areas expanded to the deeper part beyond the northeastern limit of the PHS plate. The slip-rate peaked immediately after the 2011 main-shock and gradually decreases to the velocity of relative plate motion in the next one year or two. The rate of decrease was rapid at the trench-side of the largest aftershock. On the other hand, the slip-rate at the PHS plate increased significantly at relatively deeper part of the west of the largest aftershock. The location with fast slip-rates changes at different times. These slip-rates increases may be caused by localized stress changes with coseismic slips and/or post-seismic deformation.

  6. Plate Coupling, Block Rotation and Crustal Deformation in the Pacific Northwest

    NASA Astrophysics Data System (ADS)

    McCaffrey, R.; Qamar, A. I.; King, R. W.; Wells, R.

    2006-12-01

    GPS measurements in the northwestern US and adjacent parts of Canada describe the relative motions of crustal blocks, the interseismic friction on faults, and the permanent deformation associated with convergence between the Juan de Fuca and North American plates. To estimate angular velocities of the oceanic Juan de Fuca and Explorer plates and several continental crustal blocks, we invert the GPS velocities with seafloor spreading rates, earthquake slip vector azimuths, fault slip azimuths and rates. We also determine the distribution of frictional properties on the block-bounding faults. The Cascadia megathrust is locked offshore, except in southern Oregon, where significant locking extends inland. Most of Oregon and southwest Washington rotate clockwise relative to North America at rates of 0.4 to 1.0°/Myr. No shear or extension along the Cascades volcanic arc is occurring at the mm/yr level during the past decade. The agreement of spin rates derived from GPS velocities with those estimated from paleomagnetic declination anomalies suggests that the rotations have been steady for several millions of years. Rotations in the PNW do not result in net westward flux of crustal material. Rotation of Oregon and western Washington indicates that the rate of permanent shortening, the type that causes upper plate earthquakes, across the Puget Sound region is 4.4±0.3 mm/yr.

  7. Plate motion

    SciTech Connect

    Gordon, R.G. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

    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.

  8. 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.

  9. True Polar Wander and Hotspot Fixity: A Paleomagnetic Investigation of the Skewness of Magnetic Anomaly 12r (32 Ma B.P.) on the Pacific Plate

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    Prior studies have shown that Pacific hotspots and Indo-Atlantic hotspots have moved in approximate unison relative to the spin axis since 65 Ma B.P. [Morgan, 1981; Gordon and Cape, 1981; Gordon, 1982] and since 56 Ma B.P. [Petronotis et al., 1994], which is most simply interpreted as true polar wander. In contrast, Pacific hotspots and Indo-Atlantic hotspots give conflicting results for 72 Ma B.P. and for 81 Ma B.P., which may indicate motion between Pacific hotspots and Indo-Atlantic hotspots [Tarduno and Cottrell, 1997; Petronotis et al., 1999; Tarduno et al., 2003]. Thus it is important to estimate Pacific plate apparent polar wander (APW) for more time intervals. From such estimates the APW of Pacific hotspots can be inferred and compared with that of Indo-Atlantic hotspots [e.g., Besse and Courtillot 2002]. Here we present a study of the skewness of anomaly 12r between the Galapagos and Clipperton and between the Clipperton and Clarion fracture zones. We chose this region for several reasons: First, numerical experiments, like those conducted by Acton and Gordon [1991], indicate that magnetic profiles between the Galapagos and Clarion fracture zones should contain the most information about the Pacific plate paleomagnetic pole for chron C12r (32 Ma B.P.). Second, in these two spreading rate corridors, spreading half rates range from 72 to 86 mm/a and therefore have negligible anomalous skewness, given that they exceed ?50 mm/a [Roest et al., 1992; Dyment et al. 1994]. Third, vector aeromagnetic profiles are available for analysis. One of the challenges to interpreting magnetic anomalies in low latitudes where the anomalies strike nearly north-south is the very low amplitude of the signal relative to the noise, the latter of which can be especially intense near the present magnetic equator due to the amplification of diurnal variation by the equatorial electrojet. Previously we showed that vector aeromagnetic profiles record low-latitude Pacific plate magnetic anomalies due to seafloor spreading with much greater clarity than do shipboard profiles in the same region [Horner-Johnson and Gordon, 2003]. The pole that we obtain has compact 95% confidence limits. We reduce the profiles to this pole and show that the appearance of the reduced-to-the-pole profiles is sensitive to the assumed pole position. The new pole shows that Pacific hotspots have moved significantly relative to the spin axis during the formation of the Hawaiian island and seamount chain, and is consistent with Pacific hotspots having moved in approximate unison with Indo-Atlantic hotspots relative to the spin axis since 32 Ma B.P.

  10. 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.

  11. Estimate of Interplate Coupling along the Nankai Trough, Southwest Japan, Using a New Plate Interface Model

    Microsoft Academic Search

    T. Kobayashi; M. Hashimoto; T. Tabei

    2006-01-01

    Great thrust earthquakes such as Nankai and Tonankai earthquakes have occurred periodically at the Nankai Trough, southwest Japan, where the Philippine Sea Plate (PHS) subducts beneath the Eurasian Plate. Recent seismic surveys have revealed that a clear boundary lies at about 10 km shallower than the upper surface of the slab earthquakes distribution which had been regarded as the plate

  12. 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.

  13. 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.

  14. Stress Drops of Earthquakes on the Subducting Pacific Plate in the South-East off Hokkaido, Japan

    NASA Astrophysics Data System (ADS)

    Saito, Y.; Yamada, T.

    2013-12-01

    Large earthquakes have been occurring repeatedly in the South-East of Hokkaido, Japan, where the Pacific Plate subducts beneath the Okhotsk Plate in the north-west direction. For example, the 2003 Tokachi-oki earthquake (Mw8.3 determined by USGS) took place in the region on September 26, 2003. Yamanaka and Kikuchi (2003) analyzed the slip distribution of the earthquake and concluded that the 2003 earthquake had ruptured the deeper half of the fault plane of the 1952 Tokachi-oki earthquake. Miyazaki et al. (2004) reported that a notable afterslip was observed at adjacent areas to the coseismic rupture zone of the 2003 earthquake, which suggests that there would be significant heterogeneities of strength, stress and frictional properties on the surface of the Pacific Plate in the region. In addition, some previous studies suggest that the region with a large slip in large earthquakes permanently have large difference of strength and the dynamic frictional stress level and that it would be able to predict the spatial pattern of slip in the next large earthquake by analyzing the stress drop of small earthquakes (e.g. Allmann and Shearer, 2007 and Yamada et al., 2010). We estimated stress drops of 150 earthquakes (4.2 ? M ? 5.0), using S-coda waves, or the waveforms from 4.00 to 9.11 seconds after the S wave arrivals, of Hi-net data. The 150 earthquakes were the ones that occurred from June, 2002 to December, 2010 in south-east of Hokkaido, Japan, from 40.5N to 43.5N and from 141.0E to 146.5E. First we selected waveforms of the closest earthquakes with magnitudes between 3.0 and 3.2 to individual 150 earthquakes as empirical Green's functions. We then calculated source spectral ratios of the 150 pairs of interested earthquakes and EGFs by deconvolving the individual S-coda waves. We finally estimated corner frequencies of earthquakes from the spectral ratios by assuming the omega-squared model of Boatwright (1978) and calculated stress drops of the earthquakes by using the model of Madariaga (1976). The estimated values of stress drop range from 1 to 10 MPa with a little number of outliers(Fig.(a)). Fig.(b) shows the spatial distribution of stress drops in south-east off Hokkaido, Japan. We found that earthquakes occurred around 42N 145E had larger stress drops. We are going to analyze smaller earthquakes and investigate the spatial pattern of the stress drop in the future. Fig. (a) Estimated values of stress drop with respect to seismic moments of earthquakes. (b) Spatial distribution of stress drops.

  15. Plate Tectonics

    NSDL National Science Digital Library

    This data tip from Bridge, the Ocean Sciences Education Teacher Resource Center archive, includes a variety of educational sites to visit on plate tectonic theory. Learners can use underwater earthquake data to identify plate boundaries with links to the National Oceanic and Atmospheric Administration's Acoustic Monitoring Program Ocean Seismicity data. Data from the Northeast Pacific, eastern Equatorial Pacific, and North Atlantic are examined in more detail.

  16. 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.

  17. Constraints on Pacific Plate Paleo-equator from Detailed Skewness Analysis of Magnetic Isochrons 32-25 near the Molokai, Clarion and Clipperton Fracture Zones

    NASA Astrophysics Data System (ADS)

    Meng, L.; Stock, J.

    2008-12-01

    Plate tectonics study based on total field marine magnetic anomalies measured by proton precession magnetometers has always been challenging in the equatorial area due to the relatively smaller amplitude of the anomaly and larger diurnal variations of the magnetic field resulting from the varying current of the ionosphere including the effect of the electrojet. Previous investigation of the magnetic anomalies in the equatorial Pacific has been used to study the paleomagnetic pole of the Pacific plate. However, the skewness of the magnetic data was low in coherence and accuracy, and the anomaly pattern is unable to be determined between the Clipperton fracture zone and the modern equator. Here we corrected a set of shipboard magnetic profiles using Comprehensive Model : Phase 4 ( CM4 ) which is designed to estimate the Near- Earth magnetic field by sources in the Earth's core, ionosphere and magnetosphere. We use the CM4 model to remove the diurnal variation of the ionosphere magnetic field which reduces the long-wavelength component of noise in magnetic data. In this study we deskewed more than 40 ship magnetic data sets in the central Pacific, including the Nathaniel B Palmer cruise NBP0207, by comparing the data profile with zero- skewness synthetics. The magnetic profiles are then mapped on a satellite gravity map along with their skewness values. Theoretical models show that for a ridge trending 170 degrees from north, a sudden ~90 degree change in skewness occurs when the magnetized crust moves across the paleo-equator. On the map we were able to identify that the skewness generally decreases systematically as the latitude increases. Despite the noisy data, we located positions where the ridge crossed the paleo-equator at the time of creation of the individual magnetic isochrons. The track of the paleo-equator moves southward relative to the Pacific plate during chron 32-25 time. The track of the paleo-equatorial crossing also has implications for constraints on the paleomagnetic pole.

  18. New insights into North America-Pacific plate boundary deformation from Lake Tahoe, Salton Sea and Southern Baja California

    E-print Network

    Brothers, Daniel Stephen

    2009-01-01

    to the Pacifi c Plate: Tectonics, v. 8, p. 99-115. Stock,c North America plate tectonics of the Neogene southwesternplate motion partitioning and the transition to seafl oor spreading in the Gulf of California: Tectonics,

  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. Images for the base of the Pacific lithospheric plate beneath Wellington, New Zealand, from 500 kg dynamite shots recorded on a 100 km-long, 1000 seismometer array

    NASA Astrophysics Data System (ADS)

    Stern, T. A.; Henrys, S. A.; Sato, H.; Okaya, D. A.

    2012-12-01

    Seismic P and S-wave reflections are recorded from a west-dipping horizon at depth of 105 km beneath Wellington, New Zealand. From the depth and dip of this horizon we interpret this horizon to be the bottom of the subducting Pacific plate. In May 2011 the Seismic Array on Hikurangi margin Experiment (SAHKE) recorded reflections on a ~100 km-long high-resolution seismic line across the lower North Island of New Zealand. The main goal of this experiment was to provide a detailed image of the west dipping subducted Pacific plate beneath the Wellington city region. The seismic line had ~1000 seismographs spaced between 50-100 m apart and the 500 kg shots were in 50 m-deep, drill holes. An exceptionally high-resolution image for the top of the subducting Pacific Plate at a depth of 20-25 km beneath the Wellington region is seen. In addition, on most of the shots are a pair of 10-14 Hz reflections between 27 and 29 s two-way-travel-time (twtt) at zero offset. The quality of this reflection pair varies from shot to shot. When converted to depth and ray-traced the best solution for these deep events is a west-dipping ( ~ 15 degrees) horizon at a depth of about 105 km. This is consistent with the dip of the upper surface of the plate beneath Wellington, and therefore we argue that the deep (~105 km) reflector is the base of the Pacific plate. On two of the shots another pair 5-8 Hz reflections can also be seen between 47 and 52 s, and the move-out of these events is consistent with them being S-wave reflections from the same 105 km deep, west-dipping, boundary for a Vp/Vs ~ 1.74. Both the P-and S-wave reflections occur in pairs of twtt-thickness of 2 and 5 s, respectively and appear to define a ~ 6-8 km thick channel at the base of the plate if the Vp/Vs ratio~ 5/2 or 2.5. Such a high value of Vp/Vs is consistent with the channel containing fluids or partial melt of an unknown percent. Although we can't rule out the double reflections in both P and S as being multiples, this seems unlikely as multiples are not seen any where else in the shot gathers. Thus the lithosphere-asthenosphere boundary (LAB), at least in this setting, appears to be a sharp boundary, less than 10 km thick. As the top of the subduction zone is 20-25 km deep beneath our profile, the total thickness of the plate beneath Wellington is about 80 km. This is consistent with the thickness of old oceanic plates measured elsewhere with passive seismic methods.

  1. Interaction of interface delamination and plasticity in tensile steel members reinforced by CFRP plates

    Microsoft Academic Search

    Massimiliano Bocciarelli; Pierluigi Colombi; Giulia Fava; Carlo Poggi

    2007-01-01

    This paper presents experimental and numerical results related to double shear lap tests performed on steel specimens reinforced\\u000a using CFRP plates. These tests have been simulated taking into account the elastic–plastic behavior of the steel and the delamination\\u000a between steel and CFRP by means of a cohesive approach. The results obtained are discussed in terms of: (i) maximum load bearing

  2. 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.

  3. Earthquakes along the Ryukyu-Kyushu Arc: Strain segmentation, lateral compression, and the thermomechanical state of the plate interface

    NASA Astrophysics Data System (ADS)

    Kao, Honn; Chen, Wang-Ping

    1991-12-01

    We systematically determined the focal depths and mechanisms of 49 large to moderate-sized earthquakes (mb?5.4) that occurred along the Ryukyu-Kyushu arc since 1963 by inverting the waveforms and amplitudes of P and SH wave trains at teleseismic distances. The results are sufficiently precise to delineate seismogenic structures near the plate interface in detail, revealing features not predicted by plate kinematics. In contrast to previous studies of this arc and those along other subduction zones, shallow seismicity along the plate interface is systematic, showing two distinct layers of activities. The second layer of seismicity is delineated by a few earthquakes that occurred at depths between 50 and 65 km, some 10-20 km directly beneath the seismogenic portion of the interplate thrust zone. These earthquakes indicate lateral compressional strain within the subducted slab as their P axes are subparallel to the local strike of the arc, not perpendicular to the arc as one would expect from the direction of plate convergence. The occurrence of these events cannot be accounted for by membrane stress due to the geometry of the subducted slab. To our knowledge, similar earthquakes occurred only beneath the northern Indoburman ranges and along the Banda arc where subducted slabs, as part of the Indian plate, are being dragged northward with their northern edges bumping into east-west trending collision zones nearby. By drawing an analogy between the tectonic settings of these three regions, we interpret events beneath the plate interface along the Ryukyu-Kyushu arc as a consequence of ongoing collision between the Philippine Sea plate and Eurasia near Taiwan. The interplate thrust zone is largely aseismic down to a depth of approximately 30 km. A large number of earthquakes showing low-angle thrust faulting commence at this depth and are accompanied by two events that show antithetic thrust faulting at a slightly shallower depth of 20-25 km. These observations suggest that the strength of the plate interface increases significantly below the depth of proximately 25±5 km. Based upon available heat flow measurements between the trench axis and the volcanic arc, we estimated the temperature field and magnitude of shear traction along the interplate thrust zone, the deepest interplate earthquakes (˜40-50 km) correspond to temperatures of approximately 730-980°C, comparable to the limiting temperature of intraplate mantle earthquakes (˜800°C) and that of intermediate- and deep-focus earthquakes at Wadati-Benioff zones (potential temperature ˜900°K). Therefore, the cessation of seismicity in general is probably controlled by similar temperature conditions regardless of the tectonic settings of source regions. The magnitude of shear traction along the seismogenic portion (˜40-50 km depth) of the interplate thrust zone seems to be of the order of 100 MPa which, in turn, implies a low average coefficient of friction of only 0.10±0.05, considerably less than those observed for laboratory specimens. The inception of intermediate-focus earthquakes within the subducted slab is at a depth of about 100 km. Whereas shallow earthquakes show no apparent variations along the entire arc, intermediate-depth earthquakes indicate downdip extension along the northern end of the arc near Kyushu but abruptly change to downdip compression along the rest of the arc. All available evidence indicates that this is a spatial pattern unrelated to earthquake cycles. At the moment, tectonic interpretation of such a distinct strain segmentation along the arc is enigmatic. Without the presence of clear discontinuities in the age of the subducted slab, the sudden switch in the strain field of the slab is difficult to explain by the continuously varying rate of subduction along the arc. In any case, this pattern of strain segmentation requires the presence of a major accommodation structure, such as a tear fault, in the subducted slab near the Tokara channel. Appendix is available with entire article on microfiche. Order from American Geophysical Union,

  4. Nanoscale investigation of the interface situation of plated nickel and thermally formed nickel silicide for silicon solar cell metallization

    NASA Astrophysics Data System (ADS)

    Mondon, A.; Wang, D.; Zuschlag, A.; Bartsch, J.; Glatthaar, M.; Glunz, S. W.

    2014-12-01

    In the context of nickel silicide formation from plated nickel layers for solar cell metallization, there are several open questions regarding contact adhesion and electrical properties. Nanoscale characterization by transmission electron microscopy has been employed to support these investigations. Interfacial oxides and silicide phases were investigated on differently prepared samples by different analytical methods associated with transmission electron microscopy analysis. Processing variations included the pre-treatment of samples before nickel plating, the used plating solution and the thermal budget for the nickel-silicon solid-state reaction. It was shown that interface oxides of only few nm thickness on both silicon and nickel silicide are present on the samples, depending on the chosen process sequence, which have been shown to play an important role in adhesion of nickel on silicide in an earlier publication. From sample pretreatment variations, conclusions about the role of an interfacial oxide in silicide formation and its influence on phase formation were drawn. Such an oxide layer hinders silicide formation except for pinhole sites. This reduces the availability of Ni and causes a silicide with low Ni content to form. Without an interfacial oxide a continuous nickel silicide of greater depth, polycrystalline modification and expected phase according to thermal budget is formed. Information about the nature of silicide growth on typical solar cell surfaces could be obtained from silicide phase and geometric observations, which were supported by FIB tomography. The theory of isotropic NiSi growth and orientation dependent NiSi2 growth was derived. By this, a very well performing low-cost metallization for silicon solar cells has been brought an important step closer to industrial introduction.

  5. 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.

  6. Geochronology and origin of the Pratt-Welker Seamount Chain, Gulf of Alaska: A new pole of rotation for the Pacific Plate

    NASA Astrophysics Data System (ADS)

    Turner, D. L.; Jarrard, R. D.; Forbes, R. B.

    1980-11-01

    40K-40Ar and fission-track dating of four seamounts near the southeast end of the Pratt-Welker seamount chain in the Gulf of Alaska, in conjunction with previously published K-Ar and fission-track ages near the northwest end of the chain, documents the complex origin of this seamount chain. Transitional basalts from the adjacent guyots Hodgkins, Davidson, and Denson are dated as 14.3 to 18.2 m.y. These ages, only slightly younger than the ages of the underlying crust, indicate formation of these three seamounts at or very near a spreading center. In contrast, alkalic series lavas (alkali olivine basalts and trachytes) from Kodiak, Giacomini, Dickins, and Hodgkins fit a systematic linear age progression: 23.9±0.6 m.y., 20.9±0.4 m.y., 4.0±0.2 m.y., and 2.8±0.2 m.y., respectively. Hodgkins has apparently experienced two generically different episodes of volcanism, separated by about 12 m.y. The age progression among dated alkali basalts is consistent with the hot spot hypothesis and suggests that for the last 24 m.y. the Pacific plate has moved northwest at 4.4±0.4 cm/yr with respect to the Pratt-Welker hot spot. This volcanic propagation rate, together with the rates from other parallel Neogene Pacific chains, allows an improved estimate of the pole and rate of rotation of the Pacific plate relative to hot spots: 70°N, 95°W, and 0.88°±0.10°/m.y. We conclude that no significant motion of the Pratt-Welker hot spot with respect to other Pacific hot spots has yet been detected. However, the Pratt-Welker age data may alternatively be explained by either the longitudinal roll or propagating crack hypothesis. New K-Ar ages from Horton guyot, in the Cobb seamount chain, indicate alkalic volcanism 20.7± .0 m.y. ago, consistent with a predicted age of 20 m.y. based on the hot spot hypothesis. Guyot depths from Horton and the dated Pratt-Welker seamounts are consistent with the K-Ar ages and normal subsidence of oceanic crust.

  7. 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.

  8. Early Miocene transpression across the Pacific-North American plate margin, initiation of the San Andreas fault, and tectonic wedge activation

    SciTech Connect

    McLaughlin, R.J. (Geological Survey, Menlo Park, CA (United States)); Underwood, M.B. (Univ. of Missouri, Columbia, MO (United States))

    1993-04-01

    Magnetic stripes on the Pacific plate (PAC) indicate that subduction along the North American plate (NAM) margin ceased about 26--28 Ma south of the Mendocino fracture zone (MFZ), when the Pacific-Farallon (PAC-FAR) ridge encountered the NAM. In this area the PAC-FAR ridge apparently was segmented and abandoned as it encountered the margin, and was thrust beneath the western lip of the NAM, possibly due to residual FAR slab-pull. Between [approximately] 26 and 23.5 Ma, compressional tectonism in the distal NAM overlying the hot, buoyant ridge, produced ocean floor volcanism and a series of borderland structural basins that filled with continent-derived clastics. Initiation of the San Andreas transform, and capture of a large segment of the NAM by the PAC appears to have occurred between [approximately] 24 and [approximately] 14 Ma. Beginning at least as early as 18 Ma, northeast of the San Andreas fault, blind thrusts, folding and tilting developed in the roof of a northeastwardly-propagating wedge complex beneath the length of the Coast Ranges. The wedge complex probably was multistage and may have been initiated as early as 70--60 Ma. In the Cape Mendocino and Loma Prieta regions, Miocene or younger northeast-vergent members of the roof thrust system root into the San Andreas fault and characteristically displace deep water marine rocks northeastward over the shallower margin. Total shortening across the transform margin based on deep crustal models must exceed 200 km since 70 Ma and is [ge]50 km since 28 Ma.

  9. 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.

  10. Geophysical evidence of trench-breaching slip along megathrust plate interface in the Japan Trench

    NASA Astrophysics Data System (ADS)

    Kodaira, Shuichi; Nakamura, Yasuyuki; Miura, Seiichi; Fujiwara, Toshiya; Kanamatsu, Toshiya; Ikehara, Ken

    2014-05-01

    Repeated bathymetry and seismic surveys along a profile in the central part of the rupture of the 2011 Tohoku-oki earthquake show that a co-seismic fault reaches the trench axis, forming a deformed sediment mass seaward of the frontal prism above a graben, probably due to large trench-ward movement of the hanging wall block. If the seismic structures we observed in the trench axis represent a structural proxy showing trench-breaching slip, it can be possible by using seismic data, to map an area where co-seismic slip reaches the trench axis. In order to test this hypothesis, we have started a high-resolution seismic imaging project along the entire Japan Trench axis, and the survey has been completed from 38 N to 40 N by the summer of 2013. Based on preliminary results from the survey, we found along the trench axis continuation of key structures which consist of a small-scale fold-and-thrust zone at the trench axis and seismically transparent zone at the landward, except 39.5 N to 40 N where extremely thin incoming sediments are observed due to rough geometry of the top of the igneous crust. Those structures are interpreted to be formed by overprinting "basal friction-driven thrust fault" and "gravity-driven normal fault" that alternatively occurred during an earthquake cycle with slip to the trench. Although we believe that the high-resolution seismic data have a potential to define the spatial distribution of slips to the trench, those data do not yield any information about temporal variations of the slip. In order to examine the temporal variation of slip to the trench, we will therefore integrate the seismic images with geological studies, such as piston-coring. Furthermore, in order to know even longer records of earthquake slips and evidences of seismic fault motions (i.e., high velocity slip) along megathrust interface at the trench axis, we proposed a new ocean drilling project, called JTRACK, which consists of along-and-across trench axis drilling transect in the Japan Trench.

  11. 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

  12. 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.

  13. The Biggest Plates on Earth: Plate Tectonics

    NSDL National Science Digital Library

    In this lesson, students investigate the movement of Earth's tectonic plates, the results of these movements, and how magnetic anomalies present at spreading centers document the motion of the crust. As a result of this activity, students will be able to describe the motion of tectonic plates, differentiate between three types of plate boundaries, infer what type of boundary exists between two tectonic plates, and understand how magnetic anomalies provide a record of geologic history and crustal motion around spreading centers. As an example, they will also describe plate boundaries and tectonic activity in the vicinity of the Juan de Fuca plate adjacent to the Pacific Northwest coast of North America.

  14. 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.

  15. Late Triassic bimodal igneous rocks in eastern Heilongjiang Province, NE China: Implications for the initiation of subduction of the Paleo-Pacific Plate beneath Eurasia

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Xu, Wen-Liang; Xu, Yi-Gang; Gao, Fu-hong; Ge, Wen-chun

    2015-01-01

    This paper reports new zircon LA-ICP-MS and SIMS U-Pb ages and Hf isotope data, and whole-rock major and trace element data for Late Triassic igneous rocks of eastern Heilongjiang Province, NE China. These data provide new insights into the timing of the initiation of subduction of the Paleo-Pacific Plate beneath the Eurasian continent. The zircon U-Pb age data indicate that a suite of Late Triassic (228-202 Ma) igneous rocks is present within the Songnen-Zhangguangcai Range Massif and within the western margin of the Khanka Massif. The Late Triassic igneous rocks within the Songnen-Zhangguangcai Range Massif consist of basalts, basaltic andesites, gabbro-diabases, and rhyolites, whereas coeval igneous rocks in the western margin of the Khanka Massif consist of hornblende gabbros and syenogranitic porphyries. These Late Triassic rocks constitute a geochemically bimodal igneous rock association that contains mafic rocks enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), and depleted in heavy rare earth elements (HREE) and high field strength elements (HFSE) such as Nb, Ta, Zr, Hf, and Ti. Zircons from these mafic rocks have ?Hf (t) values and TDM1 ages of +2.8 to +9.8 and 477-733 Ma, respectively, suggesting that they formed from a primary magma generated by the partial melting of depleted lithospheric mantle material that had been previously modified by subduction-related fluids. The coeval felsic rocks are characterized by enrichments in LREEs and LILEs, and depletions in HREEs and HFSEs (including Nb, Ta, and Ti), and their zircons have ?Hf (t) values and TDM2 ages of +0.6 to +7.9 and 766 to 1461 Ma, respectively, implying that these rocks were generated during the partial melting of juvenile crustal material. The Late Triassic bimodal igneous rocks in eastern Heilongjiang Province, combined with the regional geologic information, therefore record a post-orogenic extensional environment related to the final late Permian-Early Triassic closure of the Paleo-Asian Ocean. In addition, the presence of Late Triassic bimodal igneous rocks within the eastern margin of the Eurasian continent suggests that the subduction of the Paleo-Pacific Plate beneath the Eurasian continent began after the Late Triassic.

  16. Plate Motions

    NSDL National Science Digital Library

    Jeffrey Nunn

    To prepare for this exercise students read the Chapter on plate tectonics in their text book. In class, they are given a color isochron map of the sea floor. They are given 4 tasks: Answer basic questions about the timing and rate of opening of the N. and S. Atlantic; Determine what has happened to the oceanic crust that is created on the eastern side of the East Pacific Rise; Determine what type of plate boundary existed on the western edge of the N. America plate before the San Andreas Fault and when this transition occurred; and Reconstruct the motion of the plates over the last 40 Ma assuming that the surface area of the Earth has not changed.

  17. Slow slip and aseismic deformation episodes associated with the subducting Pacific plate offshore Japan, revealed by changes in seismicity (Invited)

    NASA Astrophysics Data System (ADS)

    Marsan, D.; Reverso, T.; Helmstetter, A.; Enescu, B.

    2013-12-01

    Aseismic phenomena, including slow slip, can alter the surrounding seismicity. We here investigate how seismicity can be used in order to reveal episodes of aseismic deformation: transient anomalous increases of seismicity activity are searched for, as signatures of episodic aseismic deformation in a fault zone. An objective method is proposed, that accounts for both earthquake interactions and transient loading. Applying it to the 1990 - 2011 (pre-Tohoku) seismicity of the Japan subduction zone, we find several significant instances of aseismic transients. Small scale and short duration transients are favored updip of the subducting plate.Large scale transients are mostly observed off-shore Ibaraki prefecture, in a partly decoupled zone that extends downdip. The four most intense of such transients have occurred periodically every 5.9 years, and are likely due to slow slip episodes. Other aseismic phenomena, including possible fluid intrusion in the outer-rise, are also detected. Finally, the seismicity in January and February 2011, close to the epicenter of the mega-thrust Tohoku earthquake, is found to be due to aseismic loading, confirming previous studies, although this transient is only one among others, and is not the most intense nor the most significant for the 21 year-long period studied here.

  18. 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.

  19. 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.

  20. Average slip rate at the transition zone on the plate interface beneath the Kii Peninsula, Japan, estimated from deep low-frequency tremors

    NASA Astrophysics Data System (ADS)

    Ishida, Ryosuke; Hiramatsu, Yoshihiro; Matsuzawa, Takanori; Obara, Kazushige

    2013-09-01

    We investigated the average slip rate at the transition zone on the plate interface beneath the Kii Peninsula, Japan, using an empirical method based on a proportional relation of sizes between short-term slow slip events and nonvolcanic deep low-frequency tremors. The estimated average slip rates are 3.0±0.4 cm/yr, 2.6±0.4 cm/yr, and 2.4±0.4 cm/yr, in the northern, central, and southern Kii Peninsula, respectively. Values in the northern and the central areas compensate for the difference between the slip deficit rate at the transition zone and the convergence rate of the subducting Philippine Sea plate. The discrepancy among those rates is, however, large in the southern area, suggesting a lateral variation in the proportional relation or the existence of a steady, or quasi-steady, slip.

  1. Observations of seafloor fluid venting along the transform margin between the North American and Pacific plates in the Gulf of California

    NASA Astrophysics Data System (ADS)

    Lundsten, E. M.; Anderson, K.; Paull, C. K.; Caress, D. W.; Thomas, H.; Gwiazda, R.; Herguera, J.; McGann, M. L.; Edwards, B. D.; Hinojosa, A.; Mejia Mercado, B.; Sanchez, A.; Conlin, D.; Thompson, D.

    2012-12-01

    Detailed surveys of the seafloor morphology at nine representative sections of the North American - Pacific Plate boundary on the floor of the Gulf of California were conducted by the Monterey Bay Aquarium Research Institute (MBARI) during a two ship expedition in March and April 2012. One of the objectives of this program was to better understand the distribution and impact of seafloor fluid venting along an active transform fault. At issue is whether the fault itself forms an active fluid flow conduit. An autonomous underwater vehicle (AUV) provided detailed bathymetry of the seafloor, and a remotely operated vehicle (ROV) allowed ground-truth observations and sampling of the surveyed area. The AUV surveys provide high-resolution multibeam bathymetry with a vertical precision of 0.15 m, horizontal resolution of 1.0 and 2-10 kHz CHIRP seismic reflection profiles. The nine surveys captured the morphology of a highly active fault zone in unprecedented detail. Among the features highlighted by these surveys are areas of distinctive seafloor textures. This distinctive morphology commonly occurs on the surface of elevated features that are up to 10 m higher than the surrounding seafloor and is characterized by considerable fine scale surface topography observed in both the AUV and ROV surveys. The surface topography is made up of broken and irregular blocks of methane-derived carbonates, separated by seafloor craters and open cracks that are 1 to 2 m deep and up to 10 m across. Individual patches of this distinctive morphology which are commonly ~100 m across occur within two of the nine survey areas. The presence of active chemosynthetic biological communities in open karst-like cracks show many of these sites are areas of active fluid seepage. In some places methane bubble venting was observed. Seepage was only observed where truncated strata exposed permeable layers adjacent to the fault rather than directly along the fault trace.

  2. Structural and Tectonic Map Along the Pacific-North America Plate Boundary in Northern Gulf of California, Sonora Desert and Valle de Mexicali, Mexico, from Seismic Reflection Evidence

    NASA Astrophysics Data System (ADS)

    Gonzalez-Escobar, M.; Suarez-Vidal, F.; Mendoza-Borunda, R.; Martin Barajas, A.; Pacheco-Romero, M.; Arregui-Estrada, S.; Gallardo-Mata, C.; Sanchez-Garcia, C.; Chanes-Martinez, J.

    2012-12-01

    Between 1978 and 1983, Petróleos Mexicanos (PEMEX) carried on an intense exploration program in the northern Gulf of California, the Sonora Desert and the southern part of the Mexicali Valley. This program was supported by a seismic reflection field operation. The collected seismic data was 2D, with travel time of 6 s recording, in 48 channels, and the source energy was: dynamite, vibroseis and air guns. Since 2007 to present time, the existing seismic data has been re-processing and ire-interpreting as part of a collaboration project between the PEMEX's Subdirección de Exploración (PEMEX) and CICESE. The study area is located along a large portion of the Pacific-North America plate boundary in the northern Gulf of California and the Southern part of the Salton Trough tectonic province (Mexicali Valley). We present the result of the processes reflection seismic lines. Many of the previous reported known faults were identify along with the first time described located within the study region. We identified regions with different degree of tectonic activity. In structural map it can see the location of many of these known active faults and their associated seismic activity, as well as other structures with no associated seismicity. Where some faults are mist placed they were deleted or relocated based on new information. We included historical seismicity for the region. We present six reflection lines that cross the aftershocks zone of the El Mayor-Cucapah earthquake of April 4, 2010 (Mw7.2). The epicenter of this earthquake and most of the aftershocks are located in a region where pervious to this earthquake no major earthquakes are been reported. A major result of this study is to demonstrate that there are many buried faults that increase the seismic hazard.

  3. A variety of slip behaviors along plate interface and interplay among them before and after the 2011 Mw9.0 Tohoku-Oki earthquake (Invited)

    NASA Astrophysics Data System (ADS)

    Kato, A.; Obara, K.

    2013-12-01

    Prior to the 11 March 2011 Mw 9.0 Tohoku earthquake in Japan, two distinct sequences of foreshock migrations along the trench axis toward the mainshock epicenter were identified by an earthquake catalog created using a waveform correlation technique [Kato et al., 2012, Science]. In addition, the time history of quasi-static slip along the plate interface extracted from small repeating earthquakes shows that transient slip coincided with the two sequences of earthquake migrations. The transient slip first started to build up from mid- to late February. After the Mw 7.3 foreshock, the amount of transient slip increased abruptly to the north of the Mw 7.3 epicenter, though it slightly slowed down logarithmically with time, a phenomenon commonly observed in afterslip. In contrast, slip in the earthquake migration zone (to the south of the Mw 7.3 epicenter) increased almost linearly during the final phase. Geodetic measurements also detected transient deformation after the Mw 7.3 foreshock [Ohta et al., 2012, GRL]. These results provide strong evidence for the propagation of slow-slip events toward the Mw 9.0 epicenter. The slow-slip events may have caused stress loading onto the prospective hypocenter of the Mw 9.0 mainshock and prompted the initiation of unstable dynamic rupture. Similar stress loading by transient slip onto prospective hypocenter was identified by earthquake migrations prior to the 2008 Mw 6.8 interplate (Ibaraki-Oki) earthquake, and by geodetic measurement before the 2004 Mw 7.0 earthquake offshore of eastern Hokkaido [Murakami et al., 2006, GRL]. Stress loading by slow slip transients plays a crucial role to prompt initiation of dynamic rupture, provided that large-sized potential earthquake-nucleation patch is close to failure. After the Tohoku-Oki mainshock rupture, any subsequent seismicity along the plate interface in the foreshock area was abruptly terminated, and has remained very low ever since [Kato and Igarashi, 2012, GRL]. This observation indicates that the accumulated stress along the plate interface was almost entirely released from the foreshock area. On-fault aftershocks including small repeating earthquakes have been concentrated at edges of the large slip-zone. It is thus likely that the stress increase generated by abrupt mainshock slip termination triggered the post-seismic transient afterslip event. It is of crucial importance to advance our understanding of interplay between dynamic and quasi-static slip.

  4. Construction of a grazing incidence x-ray reflection system for liquid-vapor interfaces by use of an imaging plate

    NASA Astrophysics Data System (ADS)

    Yano, Yohko F.; Iijima, Takao

    2000-06-01

    We have constructed a grazing incidence x-ray reflection system for liquid-vapor interfaces by use of an imaging plate as an area detector. The reflectivity data were obtained with high resolution even by use of a conventional x-ray tube. The surface reflectivity measurements for pure water, ethanol and 2-butoxyethanol were performed and the values of the surface roughness were obtained as 4.1±0.1, 7.1±0.3 and 6.2±0.2 Å, respectively. For water, slight broadening of reflection peaks was observed. This was caused by the surface curvature due to the large surface tension. By fitting the reflection profiles, the radius of curvature was found to be nearly 100 m for water and ten times larger for ethanol and 2-butoxyethanol.

  5. 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 tribolog

  6. Plate boundary deformation of the Pacific plate. Two case studies. (1) Crustal structure of the northwestern Vizcaino block and Gorda escarpment, offshore northern California, and implications for postsubduction deformation of a paleoaccretionary margin. (2) A focused look at the Alpine fault, New Zealand: Seismicity, focal mechanisms and stress observations

    NASA Astrophysics Data System (ADS)

    Leitner, Beate

    Two examples of Pacific rim plate boundary deformation are presented. In the first part of the thesis crustal models are derived for the northwestern part of the Vizcaino block in California using marine seismic and gravity data collected by the Mendocino Triple Junction Seismic Experiment. A northwest-southeast trending kink in the Moho is imaged and interpreted to have formed under compression by reactivation of preexisting thrust faults in the paleoaccretionary prism at the seaward margin of the Vizcaino block. The study suggests that the deformation resulted from mainly north-south compression between the Pacific-Juan de Fuca plates across the Mendocino transform fault and predates late Pliocene Pacific-North America plate convergence. In the second part, 195 earthquakes recorded during the duration of the Southern Alps Passive Seismic Experiment (SAPSE) are analysed. Precise earthquake locations and focal mechanisms provide unprecedented detail of the seismotectonics in the central South Island. The short term (6 month) SAPSE seismicity is compared with long term (8 years) seismicity recorded by the New Zealand National Seismic network and the Lake Pukaki network. The seismicity rate of the Alpine fault is low, but comparable to locked sections of the San Andreas fault, with large earthquakes expected. Changes of the depth of the seismogenic zone, generally uniform at about 10--12 km, occur only localised over distances smaller than 30 km, suggesting that thermal perturbations must be of similar scale. This implies that the thermal effects of the uplift of the Southern Alps do not change the seismogenic depth significantly and are not in accordance with most of the present thermal models. Both the Hope and Porters Pass fault zones are seismically active and deformation is accommodated near the fault zones and in the adjacent crust. North of Mt Cook, a triangular shaped region along the Alpine fault is characterised by absence of earthquakes. We interpret this as the result of the plate boundary shift from the Alpine fault to the Hope and Porters Pass fault zones. The study region shows distributed deformation in a 60--100 km wide zone on NNE-SSW trending thrust faults and strikeslip mechanisms on transfer faults.

  7. University Center Plated Entrees

    E-print Network

    Lee, Herbie

    , artichokes and herbs served with Crushed Yukon Golds and lemon-caper buerre blanc Pacific Salmon Florentine en Croute $23.95 Salmon filet and lemon creamed spinach wrapped in flaky puff pastry served with lemon-pecan Basmati pilaf and sauce Béarnaise #12;University Center Plated Entrees Poultry Moroccan

  8. 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, R.; Oestrike, R.; Futa, K.

    1982-01-01

    We present petrographic, chemical and isotopic data for fresh lava samples dredged from three regions: (1) the fossil Galapagos Rise; (2) an elongate volcano near this extinct spreading center; and (3) the East Pacific Rise at 10??S. The samples from the Galapagos Rise are among the first samples from any fossil spreading center to be analyzed. Alkalic picrites from the elongate seamount and transitional basalts from the East Pacific Rise are both somewhat unusual rock types considering their respective tectonic environments. 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. ?? 1982.

  9. 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.

  10. Channel plate for DNA sequencing

    DOEpatents

    Douthart, Richard J. (Richland, WA); Crowell, Shannon L. (Eltopia, WA)

    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.

  11. Recent plate motions and crustal deformation

    SciTech Connect

    Lisowski, M. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

    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.

  12. Plate TectonicsPlate Tectonics Plate TectonicsPlate Tectonics

    E-print Network

    Siebel, Wolfgang

    Plate TectonicsPlate Tectonics #12;Plate TectonicsPlate Tectonics · Lithosphere ­ strong, rigid, transform boundaries ­ travel 1 to 11 cm/yr relative to one another #12;14 tectonic plates today #12;Mid asthenosphere that flows · 8 large lithospheric plates and 6 smaller ones ­ separated by divergent, convergent

  13. Earth science: The slippery base of a tectonic plate

    NASA Astrophysics Data System (ADS)

    Rychert, Catherine A.

    2015-02-01

    High-resolution imaging of the base of the Pacific plate as it descends beneath New Zealand discloses a 10-kilometre-thick channel that decouples the plate from underlying upper mantle. See Letter p.85

  14. 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.

  15. 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.

  16. 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 coupl

  17. The Nature of Tectonic Plates

    NSDL National Science Digital Library

    Ken Rhinehart

    This lesson provides an overview of the various types of interactions between tectonic plates. The discussion uses the analogy of a cracked egg to describe the tectonic plates composing Earth's crust. Other topics include the concentrated earthquake and volcanic activity associated with plate boundaries, types of interactions at the boundaries, and how plate motions are affecting the Atlantic and Pacific Oceans. The lesson includes an activity in which students will use online references to locate a hypothetical nuclear power plant in a geologically safe area, investigate the history of large earthquakes in South Carolina, provide a likely location for a hypothetical geothermal power plant, and others.

  18. HMK 1_Plate Boundaries: Present, future, & past

    NSDL National Science Digital Library

    Brian Hampton

    Prior to this homework assignment, students will have been exposed (for ~2-3 in class activities and lectures) to general concepts in plate tectonics, plate boundaries, hot spot volcanoes, use of earthquake/volcano trends at plate boundaries, as well as GPS as a modern use to document plate motion. Students receive this activity as a homework assignment to be completed outside of class. Their task is to use provided topographic/bathymetric data, earthquake and volcano distribution, GPS data, as well as ocean floor and hot spot age trends to characterize plate motion in modern, future, and ancient plate boundaries. This is a three-part exercise that involves a modern plate boundary study form the eastern margin of the Pacific plate, a potential future plate boundary in eastern Africa, and a identification of possible ancient plate boundaries in the Eurasian plate.

  19. Pacific Lamprey

    USGS Multimedia Gallery

    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

  20. 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.

  1. Movie of the Pacific/Antarctic Ridge

    NSDL National Science Digital Library

    This set of movie clips shows ten million years of seafloor spreading at the axis of the Pacific/Antarctic Ridge. The clips show bathymetry and magnetic anomalies from the present day, and from 9.9 million years ago to the present. There is also a flyby down the Pitman Fracture Zone, a remote portion of the Pacific/Antarctic plate boundary in the south Pacific Ocean. Quicktime versions formatted for Macintosh users are also provided.

  2. 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.

  3. Ultrasonic guided waves in composite plates: A study of interface bond condition and material properties determination with broadband focussed air coupled ultrasounds

    Microsoft Academic Search

    Sorin Vasile Teles

    2004-01-01

    This work is focused on two important aspects of the study of the composite materials: characterization of interface bonding in layered composites and evaluation of elastic material properties in air-coupled experiments. The characterization of interface condition in a layered composite is critical to understand the behavior of the material under various stress situations. A closed disbond, alternatively known as zero-volume

  4. Relationship between outer forearc subsidence and plate boundary kinematics along the Northeast Japan convergent margin

    NASA Astrophysics Data System (ADS)

    Regalla, Christine; Fisher, Donald M.; Kirby, Eric; Furlong, Kevin P.

    2013-12-01

    Tectonic erosion along convergent plate boundaries, whereby removal of upper plate material along the subduction zone interface drives kilometer-scale outer forearc subsidence, has been purported to explain the evolution of nearly half the world's subduction margins, including part of the history of northeast Japan. Here, we evaluate the role of plate boundary dynamics in driving forearc subsidence in northeastern Japan. A synthesis of newly updated analyses of outer forearc subsidence, the timing and kinematics of upper plate deformation, and the history of plate convergence along the Japan trench demonstrate that the onset of rapid fore-arc tectonic subsidence is contemporaneous with upper plate extension during the opening of the Sea of Japan and with an acceleration in convergence rate at the trench. In Plio-Quaternary time, relative uplift of the outer forearc is contemporaneous with contraction across the arc and a decrease in plate convergence rate. The coincidence of these changes across the forearc, arc, backarc system appears to require an explanation at the scale of the entire plate boundary. Similar observations along other western Pacific margins suggest that correlations between forearc subsidence and major changes in plate kinematics are the rule, rather than the exception. We suggest that a significant component of forearc subsidence at the northeast Japan margin is not the consequence of basal tectonic erosion, but instead reflects dynamic changes in plate boundary geometry driven by temporal variations in plate kinematics. If correct, this model requires a reconsideration of the mass balance and crustal recycling of continental crust at nonaccretionary margins.

  5. Kinematics to dynamics in the New Zealand plate-boundary zone

    NASA Astrophysics Data System (ADS)

    Lamb, Simon

    2014-05-01

    New Zealand straddles the boundary between the Australian and Pacific plate, with a transition from subduction of Pacific plate oceanic lithosphere in the North, beneath North Island to oblique continental collision in South Island. Cenozoic relative plate motion has resulted in a complex pattern of faulting and block rotation in a zone up to 250 km wide, with displacements on individual faults up to 100s of kilometres. Here, I use a compilation of seismic reflection/refraction studies and high quality receiver function analyses, together with simple Airy isostasy, to determine the regional crustal and mantle structure. The buoyancy stress in the deforming layer is calculated by integrating the vertical normal stress with depth. This, in combination with plate-boundary stresses, must drive deformation. Horizontal gradients of buoyancy stress can be compared with horizontal gradients of strain rate, using the method of England & Molnar (1997), in the context of a simple thin sheet model of lithospheric deformation. I derive a velocity field for the New Zealand plate-boundary zone, using the method of Lamb (2000). This is representative of deformation over tens of thousands of years, based on fault slip, strain rate azimuth and paleomagnetic data, in the context of the short term relative plate motions. Comparison of appropriate combinations of horizontal gradients of vorticity and dilatation with horizontal gradients of buoyancy stress shows that deformation has some of the features of a Newtonian fluid. In detail, the minima in buoyancy stress, calculated from the vertical density structure, are offset horizontally from that calculated from gradients of strain rate, suggesting strong lateral contrasts in viscosity if deformation is strongly coupled at all levels in the lithosphere, with viscosities in the range 1 - 10 x 10**21 Pa s. However, subduction of Pacific plate lithosphere along the Hikurangi margin, and evidence for underthrusting beneath the Southern Alps, implies decoupling of deformation at depths > 50 km in these regions. In this case, best-fit viscosities for the top 50 km are in the range 1 - 5 x 10**21 Pa s. Given the characteristic strain rates in the plate-boundary zone, all these viscosities imply plate-boundary deviatoric stresses generally < 20 MPa, and are consistent with previous low estimates of shear stresses on the subduction plate interface based on a simple force balance (Lamb 2006). Fluid-like behaviour of the New Zealand plate-boundary zone is consistent with both geodetic data and the observed pattern of shear wave splitting. References: England, P.C., and P. Molnar, Science, 278, 647-649, 1997. Lamb, S., JGR, 105, 25,627-25,653, 2000. Lamb, S., JGR, 111, B07401, doi:10.1029/2005JB003916, 2006.

  6. Plate Tectonics

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2007-03-21

    The Plate Tectonics SciPack explores the various materials that make up Earth and the processes they undergo to provide a framework for understanding how continents are created and change over time. The focus is on Standards and Benchmarks related to Earth's layers, oceanic and continental plates and the interactions between plates.In addition to comprehensive inquiry-based learning materials tied to Science Education Standards and Benchmarks, the SciPack includes the following additional components:? Pedagogical Implications section addressing common misconceptions, teaching resources and strand maps linking grade band appropriate content to standards. ? Access to one-on-one support via e-mail to content "Wizards".? Final Assessment which can be used to certify mastery of the concepts.Learning Outcomes:Plate Tectonics: Layered Earth? Identify that Earth has layers (not necessarily name them), and that the interior is hotter and more dense than the crust.? Identify the crust as mechanically strong, and the underlying mantle as deformable and convecting.Plate Tectonics: Plates? Identify that the outermost layer of Earth is made up of separate plates.? Choose the correct speed of the motion of plates.? Identify the ocean floor as plate, in addition to the continents (to combat the common idea that only continents are plates, floating around on the oceans).? Recognize that oceans and continents can coexist on the same plate.Plate Tectonics: Plate Interactions? Identify the different interactions between plates.? Discuss what happens as a result of those interactions.Plate Tectonics: Consequences of Plate Interactions? Explain why volcanoes and earthquakes occur along plate boundaries. ? Explain how new sea floor is created and destroyed.? Describe features that may be seen on the surface as a result of plate interactions.Plate Tectonics: Lines of Evidence? Use plate tectonics to explain changes in continents and their positions over geologic time.? Provide evidence for the idea of plates, including the location of earthquakes and volcanoes, continental drift, magnetic orientation of rocks in the ocean floor, etc.

  7. The Indosinian collision-extension event between the South China Block and the Palaeo-Pacific plate: Evidence from Indosinian alkaline granitic rocks in Dashuang, eastern Zhejiang, South China

    NASA Astrophysics Data System (ADS)

    Mao, Jianren; Ye, Haimin; Liu, Kai; Li, Zilong; Takahashi, Yutaka; Zhao, Xilin; Kee, Weon-Seo

    2013-07-01

    This study reports on the first comprehensive analysis of the geology, petrology and origin of the Dashuang pluton in Jinhua, eastern Zhejiang, South China, which is predominantly composed of quartz monzonite and subordinate quartz syenite that includes variable amounts of aegirine-augite. The quartz monzonite has a porphyritic texture defined by K-feldspar phenocrysts, whereas the quartz syenite shows considerable variation in grain size and is categorised into fine- and coarse-grained types. Zircons from the quartz monzonite and fine-grained quartz syenite yield LA-MC-ICP-MS (laser ablation-multi-collector-inductively coupled plasma-mass spectrometry) U-Pb ages of 231.60 ± 0.86 Ma and 231.7 ± 1.1 Ma, respectively, indicating crystallisation in the Middle Triassic. The chemistry of the quartz monzonite indicates a calc-alkaline to alkaline evolutionary trend, which may reflect partial melting of upper mantle contaminated by Proterozoic basement rocks, subjected to fractional crystallisation during ascent. Both the fine- and coarse-grained quartz syenites are alkaline and have high rare earth element (REE) concentrations, especially light rare earth elements (LREE), and are relatively enriched in large ion lithosphere elements (LILE). The Al2O3 and NaO2 contents of the quartz syenite increase proportionally with SiO2, owing to greater amounts of aegirine-augite and feldspar. The fine-grained quartz syenite has the lowest initial 87Sr/86Sr ratio and lowest Nd model age, and the highest ?Nd value compared with the quartz monzonite. The quartz syenite compositions are best explained by fractional crystallisation of an enriched mantle-derived alkaline magma. Slight chemical variations result from source heterogeneities, as well as the spatially variable degrees of melting, assimilation, and other factors. Our new age and geochemical data for the alkaline rocks in eastern Zhejiang, considered together with collisional granites from South Korea, support a history of collision and extension between the Palaeo-Pacific plate and the South China Block during the Indosinian. We use these data to refine the geodynamic model for Indosinian multi-plate convergence in South China.

  8. Plate Tectonics

    NSDL National Science Digital Library

    Mrs. Rohlfing

    2011-02-03

    Students will go over the main points of plate tectonics, including the theory of continental drift, different types of plate boundaries, seafloor spreading, and convection currents. We have been spending time learning about plate tectonics. We have discussed the theory of continental drift, we have talked about the different types of plate boundaries, we have also learned about seafloor spreading and convection currents. Plate Boundary Diagram Now is your chance ...

  9. Preface: 5th International Symposium on the Interface between Analytical Chemistry and Microbiology - April 19th to 21st, 2004: Hosted at Pacific Northwest National Laboratory

    SciTech Connect

    Allmaier, Guenter; Wunschel, David S.; Wahl, Karen L.

    2004-04-19

    This is an introduction to a special issue of the Journal of microbiological Methods based on a recent meeting held at PNNL: the 5th International Symposium on the Interface between Analytical Chemistry and Microbiology.

  10. High-resolution animated tectonic reconstruction of the South Pacific and West Antarctic Margin

    Microsoft Academic Search

    Graeme Eagles; Karsten Gohl; Robert D. Larter

    2004-01-01

    An animated reconstruction shows South Pacific plate kinematics between 90 and 45 Ma, using the satellite-derived gravity anomaly field, interpolated isochrons and plate rotation parameters from both published and new work on marine geophysical data. The Great South Basin and Bounty Trough, New Zealand, are shown as the earliest Pacific–Antarctic plate boundary that opened before 83 Ma. The earliest true

  11. High-resolution animated tectonic reconstruction of the South Pacific and West Antarctic Margin

    Microsoft Academic Search

    Graeme Eagles; Karsten Gohl; Robert D. Larter

    2004-01-01

    An animated reconstruction shows South Pacific plate kinematics between 90 and 45 Ma, using the satellite-derived gravity anomaly field, interpolated isochrons and plate rotation parameters from both published and new work on marine geophysical data. The Great South Basin and Bounty Trough, New Zealand, are shown as the earliest Pacific-Antarctic plate boundary that opened before 83 Ma. The earliest true

  12. The possible reflection of mantle discontinuities in Pacific geoid and bathymetry

    Microsoft Academic Search

    Pål Wessel; David Bercovici; Loren W. Kroenke

    1994-01-01

    Geoid anomalies over the Pacific plate show lineated undulations approximately oriented in the direction of absolute plate motion. Conventional spectral analyses have revealed a broad range of dominant wavelengths, but as filtering is direction-dependent, results are difficult to interpret. Here, we present a new approach designed to quantify the correlation between the geoid undulations and Pacific plate motion. We calculate

  13. The possible reflection of mantle discontinuities in Pacific Geoid and bathymetry

    Microsoft Academic Search

    Pal Wessel; David Bercovici; Loren W. Kroenke

    1994-01-01

    Geoid anomalies over the Pacific plate show lineated undulations approximately oriented in the direction of absolute plate motion. Conventional spectral analyses have revealed a broad range of dominant wavelengths, but as filtering is direction-dependent, results are difficult to interpret. Here, we present a new approach designed to quantify the correlation between the geoid undulations and Pacific plate motion. We calcualte

  14. Plate tectonic constraints on the cessation of subduction beneath the Baja California peninsula, Mexico

    Microsoft Academic Search

    J. M. Stock

    2007-01-01

    I review published models, existing global plate tectonic data and published marine geophysical observations west of Baja California to assess the timing and conditions under which subduction ceased along the W margin of Baja California. The relative motion of the Farallon microplate fragments can be reconstructed using Pacific- North America global plate motions (from the Pacific-Antarctica-Nubia-North America plate circuit) added

  15. Pacific Mountain System

    NSDL National Science Digital Library

    This web page guides the user through the Pacific Mountain System geologic province, one of the most geologically young and tectonically active in North America. The generally rugged, mountainous landscape of this province, which includes parts of Washington, Oregon, and California, provides evidence of ongoing mountain-building. One map shows the plate tectonic setting of the Pacific Mountain System which straddles the boundaries between several of Earth's moving plates. This province includes the active volcanoes of the Cascade Range and the young, steep mountains of the Pacific Border and the Sierra Nevada. The user can find out more with links to USGS Cascades Volcano Observatory, Seattle region earthquake hazards, or North Cascades National Park geology. Links are provided to a simple shaded relief map and to several other shaded relief maps including ones with National Park locations and with major and subprovince boundaries. Image gallery links are given to several national parks sites: Lassen Volcanic National Park, Yosemite National Park, and North Cascades National Park.

  16. Integrating plate coupling and transient slip events along the subduction zone interface in Nankai Trough, SW Japan using GEONET GPS time series

    Microsoft Academic Search

    Z. Liu; S. Owen; D. Dong; P. Lundgren; F. Webb; E. Fielding; M. Simons; E. A. Hetland

    2008-01-01

    Large earthquakes (M~=8) have occurred repeatedly along the Nankai trough, Southwest Japan, over the past 1000 years. Recently, time-varying slow earthquakes such as short-\\/long-term slow slip transients, non- volcanic tremor, low\\/very-low frequency earthquakes have been observed in the region. To understand the interseismic plate loading process and its relation to large earthquakes and slow transient events, we use recently reanalyzed

  17. Plate Tectonics

    NSDL National Science Digital Library

    Smoothstone

    This interactive Flash explores plate tectonics and provides an interactive map where users can identify plate boundaries with name and velocities as well as locations of earthquakes, volcanoes, and hotspots. The site also provides animations and supplementary information about plate movement and subduction. This resource is a helpful overview or review for introductory level high school or undergraduate physical geology or Earth science students.

  18. Plate Tectonics

    NSDL National Science Digital Library

    Mrs. Walls

    2011-01-30

    Create a poster all about Plate Tectonics! Directions: Make a poster about Plate Tectonics. (20 points) Include at least (1) large picture (15 points) on your poster complete with labels of every part (10 points). (15 points) Include at least three (3) facts about Plate Tectonics. (5 points ...

  19. 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

  20. Is the Pacific splitting in two? 26 January 2008

    E-print Network

    Clouard, Valerie

    to this feat. The world's biggest tectonic plate under the Pacific seems to be tearing apart, forming a new mid the middle of tectonic plates that don't need to be weakened first. Island chains like the Hawaiian://www.newscientist.com/article.ns?id=mg19626333.100 6 December 2007 The day tectonic plates come to rest http

  1. Tectonic Plates and Plate Boundaries

    NSDL National Science Digital Library

    2005-12-17

    This interactive activity adapted from NASA features world maps that identify different sections of the Earth's crust called tectonic plates. The locations of different types of plate boundaries are also identified, including convergent, divergent, and transform boundaries.

  2. A plate-tectonic model for the Mesozoic and Early Cenozoic history of the Caribbean plate

    Microsoft Academic Search

    Martin Meschede; Wolfgang Frisch

    1998-01-01

    We present a model in which the Caribbean plate is an intra-American feature formed along the Caribbean spreading center as opposed to the current model that considers the Caribbean plate as a far-travelled crustal segment that formed in the Pacific region. Paleomagnetic data, which cover an age range from Jurassic through Paleocene, indicate the ophiolite complexes in Costa Rica and

  3. Kinematics to dynamics in the New Zealand plate-boundary zone

    NASA Astrophysics Data System (ADS)

    Lamb, S. H.

    2013-12-01

    New Zealand straddles the boundary between the Australian and Pacific plate, with a transition from subduction of Pacific oceanic lithosphere beneath North Island, to oblique continental collision in South Island. Cenozoic relative plate motion has resulted in a complex pattern of faulting and block rotation in a zone up to 250 km wide, with displacements on individual faults up to 100s of kilometres. Active deformation must be driven by a combination of plate-boundary forces and internal buoyancy forces. I use a compilation of seismic reflection/refraction studies and high quality receiver function analyses, together with simple Airy isostasy, to determine regional crustal and mantle structure. Integration of the vertical normal stress to the base of the deforming layer yields the buoyancy stress. Horizontal gradients of this can be compared with horizontal gradients of strain rate, using the method of England & Molnar (1997), in the context of a simple thin sheet model of deformation. Thus, if deformation is that of a Newtonian fluid, then appropriate combinations of the horizontal gradients of vorticity and dilatation are related to gradients of buoyancy stress by the fluid viscosity. However, the short term geodetic deformation is strongly biased by elastic strain accumulation related to locking on the plate interface, and cannot be used to determine the plate-boundary velocity field averaged over many seismic cycles (see Lamb & Smith 2013). Therefore, I derive here a velocity field for the plate-boundary zone, which is representative of deformation over tens of thousands of years. This is based on an inversion of fault slip, strain rate azimuth and paleomagnetic data, in the context of the short term relative plate motions, solved in a network of triangles spanning the plate-boundary, using the method of Lamb (2000). A comparison of gradients of buoyancy stress with the appropriate combinations of gradients of vorticity and dilatation shows that deformation in the plate-boundary zone does have features that are fluid-like, characterized by a variable viscosity in the range 1 - 10 x 10^21 Pa s. Given the strain rates in the plate-boundary zone, viscosities imply plate-boundary deviatoric stresses < 20 MPa, and are consistent with previous low estimates of shear stresses in subduction zones based on a simple force balance (Lamb 2006). References: England, P.C., and P. Molnar, (1997), Science, 278, 647-649. Lamb, S. (2000), J. Geophys. Res., 105, 25,627-25,653. Lamb, S., (2006), J. Geophys. Res., 111, B07401, doi:10.1029/2005JB003916. Lamb, S., and E. Smith (2013), J. Geophys. Res. Solid Earth, 118, doi:10.1002/jgrb.50221.

  4. Seismicity of the Earth 1900-2012 Philippine Sea plate and vicinity

    USGS Publications Warehouse

    Smoczyk, Gregory M.; Hayes, Gavin; 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.

  5. Pacific Historic Parks

    NSDL National Science Digital Library

    Designed to support and fund educational materials and interpretive programs for four National Parks throughout the Pacific (including the Kalaupapa National Historical Park), the Pacific Historic Parks organization has a visually enticing website. On the homepage, visitors will find information about their work in four sections, including "Education" and "Locations". First-time visitors may want to start by looking over the "Locations" area. Here they will find information about each park, complete with a Google Map interface that will let them learn more about each site. In the "Education" area, visitors can download a copy of their educational brochure and also take a look at several of their booklets for educators. Moving on, the "Audio Tour" area contains a copy of the accompanying brochure for an audio tour narrated by actor Jamie Lee Curtis.

  6. 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?

  7. A model for the motion of the Philippine Sea plate consistent with NUVEL-1 and geological data

    Microsoft Academic Search

    Tetsuzo Seno; Seth Stein; Alice E. Gripp

    1993-01-01

    We investigate angular velocity vectors of the Philippine Sea (PH) plate relative to the adjacent major plates, Eurasia (EU) and Pacific (PA), and the smaller Caroline (CR) plate. Earthquake slip vector data along the Philippine Sea plate are inverted, subject to the constraint that EU-PA motion equals that predicted by the global relative plate model NUVEL-1. The resulting solution fails

  8. Pacific Fisheries Environmental Laboratory

    NSDL National Science Digital Library

    NOAA

    The Pacific Fisheries Environmental Laboratory (PFEL) examines the role of environmental variability on marine ecosystems and commercially important fish stocks. Research areas include comparative fisheries oceanography, physical oceanography, and climate and marine fisheries. This extensive site features both model-derived environmental index products as well as time series data, including sea surface temperature, salinity, isotherm depth, surface winds and pressure maps, and upwelling indices. A live access server also allows users to download and visualize data using a simple graphical user interface. PFEL is also the west coast regional site for the NOAA CoastWatch program, which provides dissemination of oceanographic satellite observation data.

  9. Plate Tectonics

    NSDL National Science Digital Library

    2006-01-01

    In this lesson, students are introduced to the theory of plate tectonics and explore how the theory was developed and supported by evidence. Through class discussion, videos, and activities, students seek connections between tectonic activity and geologic features and investigate how the theory of plate tectonics evolved.

  10. Plate Tectonics

    NSDL National Science Digital Library

    Timothy Heaton

    This site contains 25 questions on the topic of plate tectonics, which covers the development of the theory, crustal movements, geologic features associated with tectonics, and plate boundaries (convergent, divergent, transform). This is part of the Principles of Earth Science course at the University of South Dakota. Users submit their answers and are provided immediate verification.

  11. An expression of Philippine Sea plate rotation: the Parece Vela and Shikoku Basins

    Microsoft Academic Search

    Maria Sdrolias; Walter R. Roest; R. Dietmar Mqllera

    The Philippine Sea plate, located between the Pacific, Eurasian and Australian plates, is the world's largest marginal basin plate. The motion of the Philippine Sea plate through time is poorly understood as it is almost entirely surrounded by subduction zones and hence, previous studies have relied on palaeomagnetic analysis to constrain its rotation. We present a comprehensive analysis of geophysical

  12. Plate motions: fundamentals

    E-print Network

    Déverchère, Jacques

    lithospheric plates" · Plate tectonics = a kinematic theory ­ Rigid plates (no intraplate deformation") · Convergent = subductions ("trenches") · Strike-slip = transform faults · Plate tectonics describesPlate motions: fundamentals · Assume a pie-shaped wedge plate B, rotating around E (=rotation pole

  13. SAMI Automated Plug Plate Configuration

    E-print Network

    Lorente, Nuria P F; Goodwin, Michael

    2012-01-01

    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 x 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. 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.

  15. Plate-induced Miocene extension in southern California

    SciTech Connect

    Stuart, W.D. (Geological Survey, Pasadena, CA (United States) Univ. of California, Santa Barbara, CA (United States))

    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.

  16. Improved performance of railcar/rail truck interface components

    E-print Network

    Story, Brett Alan

    2009-05-15

    The objective of this research is to improve the railcar/rail truck interface by developing a low maintenance bearing interface with a favorable friction coefficient. Friction and wear at the center bowl/center plate bearing interface cause high...

  17. Average slip rate at the transition zone on the plate interface in the Nankai subduction zone, Japan, estimated from short-term SSE catalog

    NASA Astrophysics Data System (ADS)

    Itaba, S.; Kimura, T.

    2013-12-01

    Short-term slow slip events (S-SSEs) in the Nankai subduction zone, Japan, have been monitored by borehole strainmeters and borehole accelerometers (tiltmeters) mainly. The scale of the S-SSE in this region is small (Mw5-6), and therefore there were two problems in S-SSE identification and estimation of the fault model. (1) There were few observatories that can detect crustal deformation associated with S-SSEs. Therefore, reliability of the estimated fault model was low. (2) The signal associated with the S-SSE is relatively small. Therefore, it was difficult to detect the S-SSE only from strainmeter and tiltmeter. The former problem has become resolvable to some extent by integrating the data of borehole strainmeter, tiltmeter and groundwater (pore pressure) of the National Institute of Advanced Industrial Science and Technology, tiltmeter of the National Research Institute for Earthquake Science and Disaster Prevention and borehole strainmeter of the Japan Meteorological Agency. For the latter, by using horizontal redundant component of a multi-component strainmeter, which consists generally of four horizontal extensometers, it has become possible to extract tectonic deformation efficiently and detect a S-SSE using only strainmeter data. Using the integrated data and newly developed technique, we started to make a catalog of S-SSE in the Nankai subduction zone. For example, in central Mie Prefecture, we detect and estimate fault model of eight S-SSEs from January 2010 to September 2012. According to our estimates, the average slip rate of S-SSE is 2.7 cm/yr. Ishida et al. [2013] estimated the slip rate as 2.6-3.0 cm/yr from deep low-frequency tremors, and this value is consistent with our estimation. Furthermore, the slip deficit rate in this region evaluated by the analysis of GPS data from 2001 to 2004 is 1.0 - 2.6 cm/yr [Kobayashi et al., 2006], and the convergence rate of the Philippine Sea plate in this region is estimated as 5.0 - 7.0 cm/yr. The difference between the slip deficit rate and the convergence rate is 2.4-6.0 cm/yr, and it is comparable to the average slip rate of S-SSE. Consequently, slow earthquakes such as S-SSEs and tremor that we can detect, roughly cover 50-100 % of quasi-static slip in this region.

  18. Plate Tectonics, The Cause of Earthquakes

    NSDL National Science Digital Library

    John Louie

    This page provides an overview of the role of plate tectonics in the generation of earthquakes. It provides a map of plate locations and figures that illustrate fault types and tectonic environments (extensional, transform, and compressional). Examples of surface features in the Pacific Northwest, Nevada, Indonesia, the San Andreas Fault, the Red Sea, the Zagoros Mountains in Iran, and on the planet Venus are provided.

  19. Cooling history of the Pacific lithosphere Michael H. Ritzwoller*, Nikolai M. Shapiro, Shi-Jie Zhong

    E-print Network

    Ritzwolle, Mike

    Cooling history of the Pacific lithosphere Michael H. Ritzwoller*, Nikolai M. Shapiro, Shi or blithosphereQ forms and thickens as the plate cools during its journey away from mid-ocean ridges. Numerous, particularly across the Pacific, does not cool continuously as it ages. Based on a seismic model of the Pacific

  20. 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.

  1. Musical Plates

    NSDL National Science Digital Library

    2007-12-12

    This on-line project is part of the Center for Improved Engineering and Science Education (CIESE) program. As they complete this series of lessons, students will use real-time data to solve a problem, study the correlation between earthquakes and tectonic plates, and determine whether or not there is a relationship between volcanoes and plate boundaries. Musical Plates has four Core Activities that will teach students how to access and interpret real-time earthquake and volcano data and to how use the information to solve a real-world problem. Each of the core activities is designed to be used in a 45-minute class period. This unit also has three enrichment lessons and a final project lesson that can also be used for assessment.

  2. The Plate Boundary Observatory: Data Management Progress and Highlights

    Microsoft Academic Search

    G. Anderson; B. Blackman; J. Eakins; K. Hodgkinson; J. Matykiewicz; F. Boler; M. Beldyk; B. Henderson; B. Hoyt; E. Lee; E. Persson; J. Smith; D. Torrez; J. Wright; M. Jackson; C. Meertens

    2007-01-01

    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, UNAVCO will install 880 continuous GPS stations, 103 borehole strainmeter stations, 28 tiltmeters, and five laser

  3. How Shifting Plates Caused the Earthquake and Tsunami in Japan

    NSDL National Science Digital Library

    New York Times

    This page features USGS visualizations including a slide show of the sudden movement of the Pacific tectonic plate under the North American plate caused a massive earthquake and a tsunami. It also contains maps of the magnitude of shaking and predicted tsunami wave heights from the March 11, 2011 earthquake and tsunami in Japan.

  4. Kinematic evolution of the Northeast Japan convergent margin and implications for plate boundary dynamics

    NASA Astrophysics Data System (ADS)

    Regalla, C.; Fisher, D. M.; Furlong, K. P.; Kirby, E.

    2012-12-01

    Tectonic erosion along convergent plate boundaries, whereby removal of upper plate material along the subduction zone interface drives mass loss and subsidence of the outer forearc, has been invoked to explain the geologically recent evolution of nearly half the world's subduction margins. However, the mechanisms that initiate and sustain forearc subsidence are not well understood. We provide new analyses of the kinematic evolution of the northeast Japan margin, considered a type example of erosive margins, that demonstrate that vertical motions of the outer forearc are coincident with changes in upper plate kinematics and lower plate convergence rate. New constraints on the timing and kinematics of deformation along inner forearc faults indicate Plio-Quaternary inversion of Miocene extensional structures. The initiation of reverse slip along the inner forearc Futaba (5.6 to 3.9 Ma), Oritusme (5.9 to 4.8 Ma), and Noehij (Pliocene) faults are constrained by new U-Pb ages from tephras in growth strata. The initiation of an earlier phase of extension along the Oritusme and Futaba faults is identified from thick sequences of Miocene rift-related sediments in the hanging walls that are absent in the footwalls. Existing biostratigraphic and geochronolgic ages near the base of the syn-extensional sequences constrain the initiation of extension to 23.9-21.0 and ~20.8 Ma for the Futaba and Oritsume faults, and cross sections across these structures require nearly complete thrust inversion of Miocene extensional displacement. A regional synthesis of deformation demonstrates that the timing and kinematics of forearc deformation are contemporaneous with previously documented Miocene extension and Plio-Quaternary inversion in the backarc. Moreover, reconstructions of Pacific-Honshu convergence rates indicate that 1) the initiation of forearc subsidence and upper plate extension is coincident with a two to three fold increase in margin-perpendicular convergence, and 2) the onset of arc-normal shortening and increased frontal accretion occurred during a period of relatively constant convergence rate. The temporal correlation between deformation along upper plate faults, forearc subsidence, and lower plate convergence rates at the Northeast Japan margin suggests that the vertical motions of the forearc are likely governed by changes in lower plate kinematics. We hypothesize that an acceleration in plate convergence drives changes in slab geometry at shallow depths that allows for subsidence of the forearc, and suggest that a portion of the subsidence record previously interpreted as tectonic erosion instead reflects an upper plate response to plate boundary dynamics.

  5. High-resolution animated tectonic reconstruction of the South Pacific and West Antarctic Margin

    NASA Astrophysics Data System (ADS)

    Eagles, Graeme; Gohl, Karsten; Larter, Robert D.

    2004-07-01

    An animated reconstruction shows South Pacific plate kinematics between 90 and 45 Ma, using the satellite-derived gravity anomaly field, interpolated isochrons and plate rotation parameters from both published and new work on marine geophysical data. The Great South Basin and Bounty Trough, New Zealand, are shown as the earliest Pacific-Antarctic plate boundary that opened before 83 Ma. The earliest true Pacific-Antarctic seafloor formed within the eastern parts of this boundary, but later and farther west, seafloor formed within its Antarctic flank. After 80 Ma, the Bellingshausen plate converged with an oceanic part of the Antarctic plate to its east, while its motion simultaneously caused rifting in continental Antarctica to the south. The Pacific-Bellingshausen spreading center developed a set of long offset transform faults that the Pacific-Antarctic plate boundary inherited around chron C27 when the Bellingshausen plate ceased to move independently as part of a Pacific-wide plate tectonic reorganization event. Southwest of these transforms the Pacific-Antarctic Ridge saw an increase in transform-fault segmentation by ˜58 Ma. One of the long offset Pacific-Bellingshausen transforms, referred to as "V," was modified during the C27 reorganization event when a Pacific-Antarctic-Phoenix triple junction initiated on its southern edge. Eastern parts of "V" started to operate in the Pacific-Phoenix spreading system, lengthening it even more, while its western parts operated in the Pacific-Antarctic system. This complicated feature was by-passed and deactivated by ridge axis propagation to its northwest at ˜47 Ma. We interpret our animation to highlight possible connections between these events.

  6. A trapped Philippine Sea plate origin for MORB from the inner slope of the Izu^Bonin trench

    E-print Network

    Taylor, Brian

    A trapped Philippine Sea plate origin for MORB from the inner slope of the Izu^Bonin trench Susan M Pacific plate or a trapped remnant of Philippine Sea plate on which the Izu^Bonin arc was built. Although clearly support a Philippine Sea plate origin. The isotopic signature of the inner trench slope samples

  7. Creep of phyllosilicates at the onset of plate tectonics

    Microsoft Academic Search

    Elodie Amiguet; Bruno Reynard; Bertrand Van de Moortele; Nadege Hilairet; Yanbin Wang

    2012-01-01

    Plate tectonics is the unifying paradigm of geodynamics yet the mechanisms and causes of its initiation remain controversial. Some models suggest that plate tectonics initiates when the strength of lithosphere is lower than 20-200 MPa, below the frictional strength of lithospheric rocks (>700 MPa). At present-day, major plate boundaries such as the subduction interface, transform faults, and extensional faults at

  8. Tethyan closure, Andean orogeny, and westward drift of the Pacific Basin Laurent Husson a,

    E-print Network

    Husson, Laurent

    the westward drift of the Pacific basin dominates the observed net westward rotation of Earth's tectonic plates distribution of tectonic plates, and was triggered by the mid-Cenozoic closure of the Tethys Ocean, via reserved. 1. Introduction The tectonic plates that cover the surface of the Earth are, on average, drifting

  9. PACIFIC COAST SALMON pacific Coast Salmon

    E-print Network

    181 PACIFIC COAST SALMON UNIT 12 pacific Coast Salmon Unit 12 ROBERT G. KOPE NMFS Northwest Fisheries Science Center Seattle Washington INTRODUCTION Pacific salmon support important commercial and recreational fisheries in Washington, Oregon, and California. Salmon are a vital part of the cul- ture

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

    Microsoft Academic Search

    Charles S. McCreery

    1981-01-01

    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

  11. 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 a

  12. Tectonic Plates and Plate Boundaries

    NSDL National Science Digital Library

    Continents were once thought to be static, locked tight in their positions in Earth's crust. Similarities between distant coastlines, such as those on opposite sides of the Atlantic, were thought to be the work of a scientist's overactive imagination, or, if real, the result of erosion on a massive scale. This interactive feature shows 11 tectonic plates and their names, the continents that occupy them, and the types of boundaries between them.

  13. Southeast Pacific tectonic evolution from Early Oligocene to Present

    NASA Astrophysics Data System (ADS)

    Tebbens, S. F.; Cande, S. C.

    1997-06-01

    Plate tectonic reconstructions of the Nazca, Antarctic, and Pacific plates are presented from late Oligocene to Present. These reconstructions document major plate boundary reorganizations in the southeast Pacific at dirons 6C (24 Ma), 6(o) (20 Ma), and 5A (12 Ma) and a smaller reorganization at chron 3(o) (5 Ma). During the chron 6(o) reorganization it appears that a ridge propagated into crust north of the northernmost Pacific-Antarctic Ridge, between the Chiloe fracture zone (FZ) of the Chile ridge and Agassiz FZ of the Pacific-Nazca ridge, which resulted in a northward jump of the Pacific-Antarctic-Nazca (PAC-ANT-NAZ) mid-ocean triple junction. During the chron 5A reorganization the Chile ridge propagated northward from the Valdivia FZ system to the Challenger FZ, through lithosphere formed roughly 5 Myr earlier at the Pacific-Nazca ridge. During this reorganization a short-lived microplate (the Friday microplate) existed at the PAC-ANT-NAZ triple junction. The PAC-ANT-NAZ triple junction jumped northward 500 km as a result of this reorganization, from a location along the Valdivia FZ to a location along the Challenger FZ. The chron 5A reorganization also included a change in spreading direction of the Chile and Pacific-Antarctic ridges. The reorganization at chron 3(o) initiated the formation of the Juan Fernandez and Easter microplates along the East Pacific rise. The manner of plate boundary reorganization at chron 6(o) and chron 5A (and possibly today at the Juan Fernandez microplate) included a sequence of rift propagation, transfer of lithosphere from one plate to another, microplate formation, and microplate abandonment and resulted in northward migration of the PAC-ANT-NAZ triple junction. The associated microplate differs from previously studied microplates in that there is no failed ridge.

  14. 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.

  15. Measuring electrical resistivity to interpret tectonic plate coupling

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2013-12-01

    The coupling of tectonic plates—the degree to which the plates are locked together or free to move—is controlled by factors ranging from temperature and pressure to the shear stress between the plates as well as the shape of the interface between the plates. At subduction margins, GPS observations can be used to identify places where the subducting plates are locked or unlocked. At the Hikurangi margin, a subduction zone that runs north to south off New Zealand's eastern coast, a strong longitudinal gradient in plate coupling is present that is unexplained by any of the familiar factors.

  16. Plate Tectonics II: Plates, plate boundaries, and driving forces

    NSDL National Science Digital Library

    Anne Egger

    2003-03-18

    The distribution of earthquakes and volcanoes around the world confirmed the theory of plate tectonics first proposed by Wegener. These phenomena also help categorize plate boundaries into three different types: convergent, divergent, and transform.

  17. Tectonic Plates and Plate Boundaries (WMS)

    NSDL National Science Digital Library

    Eric Sokolowsky

    2004-06-14

    The earths crust is constantly in motion. Sections of the crust, called plates, push against each other due to forces from the molten interior of the earth. The areas where these plates collide often have increased volcanic and earthquake activity. These images show the locations of the plates and their boundaries in the earths crust. Convergent boundaries are areas where two plates are pushing against each other and one plate may be subducting under another. Divergent boundaries have two plates pulling away from each other and indicate regions where new land could be created. Transform boundaries are places where two plates are sliding against each other in opposite directions, and diffuse boundaries are places where two plates have the same relative motion. Numerous small microplates have been omitted from the plate image. These images have been derived from images made available by the United States Geological Surveys Earthquake Hazards Program.

  18. 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.

  19. A Forecaster's Overview of the Northwest Pacific

    NSDL National Science Digital Library

    2014-09-14

    This module provides an introduction to the northwest Pacific for weather forecasters. It touches on major aspects of the geography, oceanography, and climatology. Geography looks at plate tectonics, topography, and human population. Oceanography examines ocean currents, coastal tidal ranges, and sea ice distribution. Climatology briefly discusses jets streams, distribution of synoptic features, storm tracks of tropical and extratropical cyclones, the fronts, and sensible weather associated with the Northeast and Southwest Monsoons.

  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. 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.

  2. 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;4:23–8. PMID:25715873

  3. Caribbean plate tectonics

    NSDL National Science Digital Library

    Sting

    This illustration available at Wikimedia Commons shows the plate tectonic setting in the Caribbean. Plate boundaries are color-coded by margin type and plate motions are noted with direction and magnitude in mm/yr.

  4. PACIFIC COAST GROUNDFISH FISHERIES pacific Coast

    E-print Network

    ) Pacific hake (whiting). Many of the stocks included in the FMP have geographic ranges that extend beyond hake trawl fishery, there are vessels that deliver their catch to motherships as well as to shoreside components of Pa- cific Coast groundfish total ex-vessel value in 2006. Pacific hake 44% Sablefish 28

  5. Seattle Pacific University undergraduate

    E-print Network

    Nelson, Tim

    of Seattle Pacific University are these three preeminent goals: We seek to graduate people of competenceSeattle Pacific University 2010-2011 undergraduate catalog #12;1 2010-2011 Undergraduate Catalog This is the 2010-11 edition of the Seattle Pacific University Undergraduate Catalog. It includes academic policies

  6. Pacific biomarkers, inc.

    PubMed

    Ehlers, Mario R

    2008-06-01

    Pacific Biomarkers, Inc. is a recently incorporated, wholly owned subsidiary of Pacific Biometrics, Inc. (PBI), a specialty clinical trials laboratory. Pacific Biomarkers was created to provide biomarker testing services for clinical drug development, specifically in the areas of ligand-binding assays, multiplexing and immunogenicity testing, in a regulatory-compliant environment. PMID:20477411

  7. Revised tectonic boundaries in the Cocos Plate off Costa Rica: Implications for the segmentation of the convergent margin and for plate tectonic models

    Microsoft Academic Search

    Udo Barckhausen; Cesar R. Ranero; R. von Huene; Steven C. Cande; Hans A. Roeser

    2001-01-01

    The oceanic Cocos Plate subducting beneath Costa Rica has a complex plate tectonic history resulting in segmentation. New lines of magnetic data clearly define tectonic boundaries which separate lithosphere formed at the East Pacific Rise from lithosphere formed at the Cocos-Nazca spreading center. They also define two early phase Cocos-Nazca spreading regimes and a major propagator. In addition to these

  8. Tsunamis and Earthquakes (Local Tsunamis in the Pacific Northwest)

    NSDL National Science Digital Library

    On the Pacific Northwest an oceanic tectonic plate (Juan de Fuca) is being pulled and driven (subducted) beneath the North American continental plate. Earthquakes generated along that fault may produce local tsunamis. Local tsunamis are those generated by earthquakes near the coast. This site provides links to external webpages describing the physics behind a tsunami. Resources featured in the links include glossary of terms and photo galleries.

  9. Structural patterns and tectonic history of the Bauer microplate, Eastern Tropical Pacific

    Microsoft Academic Search

    Barry W. Eakins; Peter F. Lonsdale

    2003-01-01

    The Bauer microplate was an independent slab of oceanic lithosphere that from 17 Ma to 6 Ma grew from 1.4 × 105 km2 to 1.2 × 106 km2 between the rapidly diverging Pacific and Nazca plates. Growth was by accretion at the lengthening and overlapping axes of the (Bauer-Nazca) Galapagos Rise (GR) and the (Pacific-Bauer) East Pacific Rise (EPR). EPR and GR

  10. 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.

  11. High Reliability Robot Friendly ORU Interface

    NASA Technical Reports Server (NTRS)

    Voellmer, George M. (inventor)

    1991-01-01

    Presented here is 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 means of a triangular interface comprising 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 has to be placed accurately enough to fall into the cup member of the base plate assembly. The cup member 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 and base plates from deflecting. This accounts for precision in the placement of the article. The novelty is believed to reside in using deflecting plates in conjunction with kinematic mounts to provide distributed forces to the two members.

  12. Modeling the mechanisms for the 100 Ma plate reorganisation

    NASA Astrophysics Data System (ADS)

    McKeon, R. L.; Morra, G.; Müller, 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.

  13. 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.

  14. The photovoltaic-array\\/power-conditioning interface

    Microsoft Academic Search

    H. M. Branz; G. W. Hart; C. H. Cox III

    1982-01-01

    Two years' of effort to improve terrestrial flat-plate photovoltaic (PV) system efficiency through increased understanding of the array\\/power conditioner interface is reported. The flat-plate PV array is a highly variable source of dc electrical energy due to changing insolation and other factors. Computer simulation based on statistically typical weather data is used to analyze the terrestrial flat-plate PV source and

  15. 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.

  16. 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.

  17. Copper Map Plate Detail

    USGS Multimedia Gallery

    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...

  18. Plate Tectonics Animation

    NSDL National Science Digital Library

    2002-01-01

    Plate tectonics describes the behavior of Earth's outer shell, with pieces (plates) bumping and grinding and jostling each other about. Explore these maps and animations to get a jump start on understanding plate tectonic processes, history, and how motion of the plates affects our planet today.

  19. Planet Earth: Plate Tectonics

    E-print Network

    Watts, A. B. "Tony"

    , ice and sediment for long periods of geological time (>105 a). · Controlled and passive (e-plate system #12;Relative plate motions on a sphere A In a three-plate system, A, B and C, if AB and BC are known then CA can be found. See GG p23-24. Euler's theorem: motion of any spherical plate can

  20. Mapping Plate Tectonic Boundaries

    NSDL National Science Digital Library

    Michael Kerwin

    To prepare for this activity, students do background reading on Plate Tectonics from the course textbook. Students also participate in a lecture on the discovery and formulation of the unifying theory of plate tectonics, and the relationship between plate boundaries and geologic features such as volcanoes. Lastly, in lecture, students are introduced to a series of geologic hazards caused by certain plate tectonic interactions. The activity gives students practices at identifying plate boundaries and allows them to explore lesser known tectonically active regions.

  1. MACMA: a Virtual Lab for Plate Tectonics

    NASA Astrophysics Data System (ADS)

    Grigne, C.; Combes, M.; Tisseau, C.

    2013-12-01

    MACMA (Multi-Agent Convective MAntle) is a tool developed to simulate evolutive plate tectonics and mantle convection in a 2-D cylindrical geometry (Combes et al., 2012). The model relies mainly on a force balance to compute the velocity of each plate, and on empirical rules to determine how plate boundaries move and evolve. It includes first-order features of plate tectonics: (a) all plates on Earth do not have the same size, (b) subduction zones are asymmetric, (c) plates driven by subducting slabs and upper plates do not exhibit the same velocities, and (d) plate boundaries are mobile, can collide, merge and disappear, and new plate boundaries can be created. The MACMA interface was designed to be user-friendly and a simple use of the simulator can be achieved without any prerequisite knowledge in fluid dynamics, mantle rheology, nor in numerical methods. As a preliminary study, the simulator was used by a few students from bachelor's degree to master's degree levels. An initial configuration for plate tectonics has to be created before starting a simulation: the number and types of plate boundaries (ridge, subduction, passive margins) has to be defined and seafloor ages must be given. A simple but interesting exercise consists in letting students build such an initial configuration: they must analyze a map of tectonic plates, choose a 2-D section and examine carefully a map of seafloor ages. Students mentioned that the exercise made them realize that the 3-D spherical structure of plate tectonics does not translate directly in a simple 2-D section, as opposed to what is usually shown in books. Physical parameters: e.g. mantle viscosity, number of layers to consider in the mantle (upper and lower mantle, possible asthenosphere), initial time and mantle temperature, have to be chosen, and students can use this virtual lab to see how different scenarios emerge when parameters are varied. Very importantly, the direct visualization of the mobility of plate boundaries is a feature that clearly seems interesting to students. They are used to see dynamic representations of continental drift, but this does not include the dynamics of the oceanic lithosphere and the corresponding fluctuations in seafloor age distribution. The 2-D geometry of the simulator is a simplification that actually brings a clearer view of plate boundary creations, migrations, and collisions, together with global plate tectonics reorganization events.

  2. Plate Tectonics: The Hawaiian Archipelago

    NSDL National Science Digital Library

    Since the Hawaiian Islands were all created by volcanic activity, it is somewhat surprising that only the island of Hawaii now possesses any active volcanoes. Why did the volcanoes that built the other islands stop erupting and why are those on the big island still active? This video segment, adapted from a NOVA television broadcast, shows how plumes of hot material rise from the Earth's interior to create 'hot spots' in the crust which are the locations of volcanic activity. Movement of the Pacific Plate causes volcanic islands to continually form, migrate away from the hot spot, and become extinct, forming chains of islands like the Hawaiian Islands. The segment is four minutes thirty-seven seconds in length.

  3. Geomorphology and structural segmentation of the crest of the southern (Pacific-Antarctic) East Pacific Rise

    Microsoft Academic Search

    Peter Lonsdale

    1994-01-01

    Geomorphology of the boundary between Pacific and Antarctic plates was mapped with a Sea Beam multibeam echosounder and a SeaMARC II bathymetric side scan sonar, from the southern end of Juan Fernandez microplate at 35 deg S to Heezen transform at 56 deg S. There are six spreading center systems separated by two large, left-stepping nontransform offsets (at 36.5 deg

  4. 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.

  5. Global plate velocities from the Global Positioning System

    Microsoft Academic Search

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

    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

  6. An oceanic flood basalt province within the Caribbean plate

    Microsoft Academic Search

    C. W. Sinton; R. A. Duncan; M. Storey; J. Lewis; J. J. Estrada

    1998-01-01

    The thick oceanic crust of the Caribbean plate appears to be the tectonized remnant of an eastern Pacific oceanic plateau that has been inserted between North and South America. The emplacement of the plateau into its present position has resulted in the obduction and exposure of its margins, providing an opportunity to study the age relations, internal structure and compositional

  7. 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.

  8. Estimation of current plate motions in Papua New Guinea from Global Positioning System observations

    Microsoft Academic Search

    Paul Tregoning; Kurt Lambeck; Art Stolz; Peter Morgan; Simon C. McClusky; Peter van der Beek; Herbert McQueen; Russell J. Jackson; Rodney P. Little; Alex Laing; Brian Murphy

    1998-01-01

    Plate tectonic motions have been estimated in Papua New Guinea from a 20 station network of Global Positioning System sites that has been observed over five campaigns from 1990 to 1996. The present velocities of the sites are consistent with geological models in which the South Bismarck, Woodlark, and Solomon Sea Plates form the principal tectonic elements between the Pacific

  9. 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.

  10. 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.

  11. 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.

  12. The strength of large-scale plate boundaries: Constraints from the dynamics of the Philippine Sea plate since ~5 Ma

    NASA Astrophysics Data System (ADS)

    Iaffaldano, G.

    2012-12-01

    Friction controls most of the strength of tectonic plate boundaries, and thus the force mutually exchanged between plates. Estimates of the plate-boundary friction-coefficient are therefore of paramount importance to our understanding of the lithosphere torque balance. However, several lines of evidence indicate that the friction-coefficient of plate margins is significantly lower than is measured in laboratory experiments performed on fractured rocks. This poses a significant limit to extrapolation from the laboratory scale to the large-scale of Earth's lithosphere. The record of past and present-day plate motions represents an efficient probe into the torque balance of plate tectonics, because plate-motions readjust virtually instantaneously to temporal changes in driving and resisting forces. Here I derive inferences on the strength of large-scale plate boundaries by focusing on the convergence of the fast-moving Philippine Sea plate towards Eurasia, since subduction initiation ~5 Myr ago. Because at the present-day the Philippine slab reaches depths shallower than the 410-km transition zone in the upper mantle, its weight is unlikely to provide sufficient driving force to shear the trailing plate over the viscous mantle at the observed rates. Using global models of the coupled mantle/lithosphere system, I argue that frictional coupling with the Pacific and Eurasia plates is the main driver for the dynamics of the Philippine Sea plate. This allows me to infer that the friction-coefficient of large-scale plate boundaries is in range 0.01 to 0.07, and that the amount of sediments entering plate margins efficiently modulates the friction-coefficient, contributing significantly to its lateral variations. Importantly, I corroborate my conclusions by focusing on the present-day vertical deformation of the Philippine Sea/Eurasia margin, evident from observed trench-parallel gravity anomalies.

  13. The strength of large-scale plate boundaries: Constraints from the dynamics of the Philippine Sea plate since ˜5 Ma

    NASA Astrophysics Data System (ADS)

    Iaffaldano, Giampiero

    2012-12-01

    Friction controls most of the strength of tectonic plate boundaries, and thus the force mutually exchanged between plates. Estimates of the plate-boundary friction-coefficient are therefore of paramount importance to our understanding of the lithosphere torque balance. However, several lines of evidence indicate that the friction-coefficient of plate margins is significantly lower than is measured in laboratory experiments on fractured rocks. This poses a significant limit to extrapolation from the laboratory scale to the large-scale of Earth's lithosphere. The record of past and present-day plate motions represents an efficient probe into the torque balance of plate tectonics, because plate-motions readjust virtually instantaneously to temporal changes in driving and resisting forces. Here I derive inferences on the strength of large-scale plate boundaries by focusing on the convergence of the fast-moving Philippine Sea plate towards Eurasia, since subduction initiation ˜5 Myr ago. Because at the present-day the Philippine slab reaches depths shallower than the 410-km transition zone in the upper mantle, its weight is unlikely to provide sufficient driving force to shear the trailing plate over the viscous mantle at the observed rates. Using global models of the coupled mantle/lithosphere system, I argue that frictional coupling with the Pacific and Eurasia plates is the main driver for the dynamics of the Philippine Sea plate. This allows me to infer that the friction-coefficient of large-scale plate boundaries is in range 0.01-0.07, and that the amount of sediments entering plate margins efficiently modulates the friction-coefficient, contributing significantly to its lateral variations. Importantly, I corroborate my conclusions by looking at the present-day vertical deformation of the Philippine Sea/Eurasia margin, evident from observed trench-parallel gravity anomalies.

  14. Geologic maps of Pacific basin and rim

    SciTech Connect

    Craddock, C.

    1986-07-01

    A major component of the Circum-Pacific Map Project is to compile five regional geologic maps at a scale of 1:10 million and a final map of the Pacific Ocean basin at a scale of 1:17 million. The Geologic Map of the Northeast Quadrant was published in 1983, and the Geologic Map of the Southeast Quadrant in 1985. The Geologic Maps of the Northwest Quadrant, the Southwest Quadrant, and the Antarctic Region are expected to reach publication during 1986. The Geologic Map of the Pacific Basin, with energy and mineral resources, is scheduled for publication in 1989. Each geologic map is a synthesis of a large amount of information. The land areas portray rock types by patterns and ages by colors; major faults are shown if they form the boundaries for map units. The oceanic areas include bathymetric contours, 13 sea-floor sediment types, all Deep Sea Drilling Program (DSDP) sites, selected DSDP columns, and selected sites of pre-Quaternary bedrock or sediment recovery. A correlation diagram on each map shows stratigraphic columns for the five regional maps, map units, geologic ages, and a time scale. An inset map shows presently active tectonic plates. The principal information sources for each sheet are given in a reference list, and each map is accompanied by explanatory notes. This map series represents the first integrated set of geologic maps of the entire Pacific Ocean basin and rim, including the Antarctic continent- altogether more than half the surface area of planet Earth.

  15. Create Your Plate

    MedlinePLUS

    ... Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook with Heart-Healthy Foods Holiday Meal Planning ... Healthy Diet Create Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook with ...

  16. Plate Tectonics: Further Evidence

    NSDL National Science Digital Library

    The representation depicts the spreading of the sea floor along the mid-ocean ridges. The resource generally describes the theory of plate tectonics, including the movement of plates with regard to one another.

  17. External Resource: Plate Tectonics

    NSDL National Science Digital Library

    1900-01-01

    This Windows to the Universe interactive webpage connects students to the study and understanding of plate tectonics, the main force that shapes our planets surface. Topics: plate tectonics, lithosphere, subduction zones, faults, ridges.

  18. The PLATES Project

    NSDL National Science Digital Library

    This is the web page for PLATES, a program of research into plate tectonic and geologic reconstructions at the University of Texas at Austin Institute for Geophysics. The page contains links to a brief overview of plate tectonics and plate reconstructions using the PLATES Project's global plate reconstruction model, in addition to movies in the format of powerpoint animations which can be downloaded for later use. Models are shown on the evolution of the earth's oceans and the movement of the earth's tectonic plates from the Late Precambrian through the present day, reconstructing (i.e. "predicting") geological environments through geologic history. Maps of the following can be accessed: late Neo-Proterozoic, Silurian, early Jurassic, early Cretaceous, Cretaceous-Tertiary Boundary, and Oligocene. Movies are available on the following subjects: global plate motion, Jurassic to present day, opening of the Indian Ocean, and tectonic evolution of the Arctic region.

  19. Growth Plate Injuries

    MedlinePLUS

    ... may be negatively affected. How Are Growth Plate Fractures Diagnosed? A child who has persistent pain, or ... 1999. Used with the author’s permission. Type I: Fracture Through the Growth Plate The epiphysis is completely ...

  20. 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.

  1. Plate Tectonic Primer

    NSDL National Science Digital Library

    Lynn Fichter

    This site gives an in-depth look at the theory of plate tectonics and how it works. The structure of the Earth is discussed, with brief rock type descriptions. The structure of the lithosphere, plate boundaries, interplate relationships, and types of plates are all covered in detail.

  2. Earthquakes and Plate Tectonics

    NSDL National Science Digital Library

    This article describes the theory of plate tectonics and its relation to earthquakes and seismic zones. Materials include an overview of plate tectonics, a description of Earth's crustal plates and their motions, and descriptions of the four types of seismic zones.

  3. Rotatable shear plate interferometer

    DOEpatents

    Duffus, Richard C. (Livermore, CA)

    1988-01-01

    A rotatable shear plate interferometer comprises a transparent shear plate mounted obliquely in a tubular supporting member at 45.degree. with respect to its horizontal center axis. This tubular supporting member is supported rotatably around its center axis and a collimated laser beam is made incident on the shear plate along this center axis such that defocus in different directions can be easily measured.

  4. Earliest Eocene (53 Ma) convergence in the Southwest Pacific; evidence from pre-obduction dikes in the ophiolite of New Caledonia.

    E-print Network

    Boyer, Edmond

    plate tectonic reconstructions of subduction systems in that area. The chemistry and age of dikes to the reorientation of the Pacific plate motion that occurred at ca. 43 Ma and confirm new interpretations showing that changes in mantle flow, hotspot and plate motion may have occurred as soon as late Paleocene or early

  5. 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.

  6. 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.

  7. NSTX Upgrade Armor Plate Backing Plate

    E-print Network

    Princeton Plasma Physics Laboratory

    .1 Finite Element Software and OPERA Electromagnetic program. 3.) Opera electromagnetic program and results backing plate calculation 2.) Build and evaluate a Finite Element Model for The Armor Eddy Current

  8. Mantle Convection Moving Plates

    NSDL National Science Digital Library

    This demonstration models the manner in which the convection currents in the mantle of the Earth cause movement of the plates. Convection currents in the mantle were thought, for many years, to be solely responsible for plate tectonic movements, with the movement taking rocks down at destructive margins and new rocks forming when plates spread. It is now thought likely that there are three possible driving mechanisms for plate tectonics. In addition to movement of mantle convection currents as shown in this demonstration, scientists also consider the mass of the subducted plate (the sinking slab) at the subduction zone dragging the surface part of the plate across the surface and the new plate material sliding off the higher oceanic ridges at constructive margins.

  9. North Pacific Regional Summary North Pacific

    E-print Network

    is limited to a few vessels using troll gear and management of salmon fisheries is deferred to the Alaska to overfishing. The North Pacific Region has seven catch share programs (a type of market-based management), more.5 billion pounds) in 2008. Landings revenue was dominated by walleye pollock ($384 million), salmon ($368

  10. The Fate of Unsubducted Fragments of the Farallon Plate

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Forsyth, D.; Savage, B.

    2008-12-01

    The Monterrey, Guadalupe, and Magdalena microplates all ceased subducting before the Farallon-Pacific spreading centers disappeared beneath the North American continent, leaving behind plate fragments that became incorporated into the Pacific plate as spreading ceased. Spreading directions changed dramatically on the Monterrey and Magdalena spreading centers, suggesting that the Farallon slab detached from the microplate fragments before or during the cessation of spreading. Although the sinking Farallon plate must have detached from all three microplates, it is not known where the detachments occurred and how much of the young slab was left behind still attached to the unsubducted surface microplates. After the microplates were incorporated into the Pacific plate, the plates moved relative to North America on predominantly strike- slip faults, as much as 820 km in the case of the Monterrey microplate. Did the slab fragments move along with the fossil microplates and coastal crustal blocks? We address the fate of the unsubducted fragments by looking for associated seismic velocity anomalies using teleseismic Rayleigh wave tomography and the stations of the USArray, NARS-Baja and RESBAN arrays. There are high velocity anomalies landward of each of the fossil oceanic microplates, indicating that slab fragments translated along with the surface plates. At least in the case of the Guadalupe plate, high shear velocity anomalies continue to depths exceeding 100 km, suggesting that the leading edge of the microplate slab was shoved downward into the mantle or that thermally induced density contrasts induced downward convection. We estimate how much slab may have remained attached to the surface microplate by integrating the velocity anomaly over the volume of the anomalous region.

  11. 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.

  12. From Convergence to Subduction - Plate Boundary Formation through New Zealand

    NASA Astrophysics Data System (ADS)

    Furlong, K. P.; Kamp, P. J.; Hayes, G. P.

    2007-12-01

    In contrast to the normal 'Wilson cycle' sequence of subduction leading to continental collision and associated mountain building, the evolution of the New Zealand plate boundary in the Neogene reflects the converse - initially a period of continental convergence that is followed by the emplacement of subduction. Plate reconstructions allow us to place limits on the location and timing of the continental convergence and subduction zones and the migration of the transition between the two plate boundary regimes. Relative plate motions and reconstructions since the Early to Mid-Miocene require significant continental convergence in advance of the emplacement of the southward migrating Hikurangi subduction - a sequence of tectonism seen in the present plate boundary geography of Hikurangi subduction beneath North Island and convergence in the Southern Alps along the Alpine Fault. In contrast to the transition from subduction to continental convergence where the leading edge of the upper plate is relatively thin and deformable, the transition from a continental convergent regime, with its associated crustal and lithospheric thickening, to subduction of oceanic lithosphere requires substantial thinning (removal) of upper plate continental lithosphere to make room for the slab. The simple structure of the Wadati-Benioff zone seen in the present day geometry of the subducting Pacific plate beneath North Island indicates that this lithospheric adjustment occurs quickly. Associated with this rapid lithospheric thinning is the development of a series of ephemeral basins, younging to the south, that straddle the migrating slab edge. Based on this association between localized vertical tectonics and slab emplacement, we argue that the tectonic history of these basins record the effects of lithospheric delamination driven by the southward migrating leading edge of the subducting Pacific slab. Although the New Zealand plate boundary is often described as simply two subduction zones linked by the transpressive Alpine Fault, in actuality the present is merely a snapshot view of an ongoing and complex evolution from convergence to subduction.

  13. 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

  14. Pacific Journal of Mathematics

    NSDL National Science Digital Library

    The electronic October issue of the Pacific Journal of Mathematics is available as of October, 2000. Articles on Stekloff eigenvalues, Cantor systems, and Bertini Theorems are among those featured. Articles may be viewed in .pdf, hyperdvi, dvi, or .ps format.

  15. Hypervelocity plate acceleration

    SciTech Connect

    Marsh, S.P.; Tan, T.H.

    1991-01-01

    Shock tubes have been used to accelerate 1.5-mm-thick stainless steel plates to high velocity while retaining their integrity. The fast shock tubes are 5.1-cm-diameter, 15.2-cm-long cylinders of PBX-9501 explosive containing a 1.1-cm-diameter cylindrical core of low-density polystyrene foam. The plates have been placed directly in contact with one face of the explosive system. Plane-wave detonation was initiated on the opposite face. A Mach disk was formed in the imploding styrofoam core, which provided the impulse required to accelerate the metal plate to high velocity. Parametric studies were made on this system to find the effect of varying plate metal, plate thickness, foam properties, and addition of a barrel. A maximum plate velocity of 9.0 km/s has been observed. 6 refs., 17 figs.

  16. Plates and FEM

    NASA Astrophysics Data System (ADS)

    Blaauwendraad, J.

    The word plate is a collective term for systems in which transfer of forces occurs in two directions; walls, deep beams, floors and bridge slabs are all plates. We distinguish two main categories, plates that are loaded in their plane, and plates loaded perpendicularly to their plane. For both categories we give an approach with differential equations, such that a basic understanding is provided and for certain characteristic cases an exact solution can be determined. We follow the displacement method, working with differential equations. In plates that are loaded in their plane, the plane stress state is called the membrane state. All stress components are parallel to the mid- plane of the plate. In special cases we can simply determine the stresses.

  17. 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.

  18. Understanding Plate Motions

    NSDL National Science Digital Library

    This interactive site uses illustrations and photographs along with text to explain the movement of tectonic plates and the result of this movement on the surface of the Earth. There is a detailed discussion of the movement at each of the four types of plate boundaries: divergent, convergent, transform, and plate boundary zones. Both lateral and vertical movements are depicted by maps and diagrams and resulting Earth structures are shown in photographs.

  19. Geology - Plate Tectonics

    NSDL National Science Digital Library

    Visitors to this site can learn about the theory of plate tectonics, the history of its development, and the mechanisms that drive the formation, movement, and destruction of continents and tectonic plates. A selection of animations depicts the movements of crustal plates and continents through time. Each animation is accompanied by an interactive time scale that provides links to descriptions of the geology and paleontology of the selected era or period.

  20. 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

  1. Surface preparation and plating

    SciTech Connect

    Dini, J.W.; Waldrop, F.B.; Reno, R.W.

    1982-10-06

    This chapter covers electroplating and electroless nickel plating since coatings of this type play an important role in diamond turning technology. Items to be discussed include preparation of substrates prior to coating, plating defects such as pits and nodules and their influence on optics, the influence of stress in coatings, plating details for copper, gold, silver, and electroless nickel, and the importance of additives and their influence on grain size and structure of deposits. Some comments are made on future challenges that could be presented to the plating community to further improve the quality of coatings applied for diamond turning purposes. 60 references, 8 figures, 9 tables.

  2. Plates on the Move

    NSDL National Science Digital Library

    This fun Web article is part of OLogy, where kids can collect virtual trading cards and create projects with them. Here, they learn about the Earth's outer shell and its constant movement. It begins with an overview that explains tectonic plates. There is an animation that shows recent earthquakes and their relationship to plate boundaries. Students can click to explore 12 individual volcanoes, mountains, hotspots, and earthquakes. For each of the geological formations or events, they will see a map that shows how the plates are moving, an animation about plate interaction, stats, and a story about that particular formation or event.

  3. Acceleration of metal plates

    NASA Astrophysics Data System (ADS)

    Marsh, S. P.; McQueen, R. G.; Tan, T. H.

    1989-08-01

    High-explosive charges were used to accelerate stainless steel plates to velocities of 6 to 7 km/s. A two-stage system was used in which the first stage is a plane-wave detonating system that accelerates the plate down a short barrel. The second stage consists of a hollow cylindrical charge through which the moving plate passes. After an adjustable delay this charge is detonated on the outer circumference of the entry side of the charge. Flash radiographs and witness plates show no breakup in the first stage but bowing and frequent breakup in the second stage.

  4. 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.

  5. Author's personal copy Plate tectonic reconstructions with continuously closing plates$

    E-print Network

    Bower, Dan J.

    Author's personal copy Plate tectonic reconstructions with continuously closing plates$ Michael May 2011 Keywords: Geodynamics Plate tectonics a b s t r a c t We present a new algorithm for modeling margins and plates, traditional global plate tectonic reconstructions have become inadequate

  6. 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

  7. A Great Earthquake Rupture Across a Rapidly Evolving Three-Plate Boundary

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    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.

  8. Mapping Plate Boundaries

    NSDL National Science Digital Library

    Rurik Johnson

    2009-11-12

    This in-class exercise, profiled on the Starting Point website, is intended to have the students discover plate boundaries based on the uneven geographic occurrence of geologic hazards. The website details the learning goals, teaching notes and materials, and context for this activity. It offers an extensive list of links to additional resources and materials for lecture on geologic hazards and plate tectonics.

  9. How Do Plates Move?

    NSDL National Science Digital Library

    The representation shows the circulation of convection cells in the mantle related to plate movement. A static cross-sectional diagram and accompanying text illustrates the how material heated by the core rises and then sinks when it eventually cools down and attributes this cycle of heating and cooling to tectonic plate movement.

  10. 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.

  11. The Moving Plates

    NSDL National Science Digital Library

    This lesson focuses on relative versus absolute velocity. Students can use a program (must be connected to the internet) to calculate the different types of velocities for different points along plate boundaries. A very brief description of the earth's plates is given, with links to additional information and images. Includes discussion questions.

  12. Review of plate tectonics

    Microsoft Academic Search

    Kevin Burke; A. M. C. Sengor

    1979-01-01

    This article reviews advances in plate tectonics in a variety of different plate environments. Mapping using multibeam echo sounding and deep-water photographic and geophysical packages and understanding of mid-oceanic ridges, the subsidence of sea floor as oceanic lithosphere cools with age, the nature and behavior of oceanic and continental transform faults, and advances in knowledge of subduction zones including the

  13. Fashion Plate Collection

    NSDL National Science Digital Library

    There are fashion plates, and then there are the exquisite fashion plates that constitute the University of Washington Libraries digitized collection. The plates were first collected by long-time home economics professor Blanche Payne, who taught at the University from 1927 to 1966. The plates come from leading French, American, and British fashion journals of the 19th and early 20th century and they document many stylistic periods, such as the Empire, Romantic, Victorian, and Edwardian. Visitors will want to start by reading an essay on the collection, and then they should feel welcome to browse the collection of over 400 plates at their leisure, or to browse the collection by subject. One fascinating aspect of the site is an extended excerpt from the 1913 book "Dame fashion" which comments on the history and transformation of various fashions during the 19th century.

  14. Thermophoresis of Graphene Plates

    NASA Astrophysics Data System (ADS)

    Bubenchikov, A. M.; Bubenchikov, M. A.; Potekaev, A. I.; Maslov, A. S.; Ovcharenko, V. V.; Usenko, O. V.

    2014-11-01

    Thermophoresis of graphene plates in an air medium is discussed within the framework of a molecular-kinetic approach. Its rate is found to be independent of the plate area and the aspect ratio of a rectangular graphene. It does depend on the plate orientation in space, which is controlled by the principle of least resistance. The dependence is expressed via a geometrical parameter ?, whose limiting values within the variation interval are found to be 0.46 and 0.65. A solution of the Euler problem on the Brownian rotation of a plate around its center of mass as a result of collisions of molecules in the temperature gradient field allowed us to obtain for the graphene plates a statistical average of ? =0.5. This value turned out to be the same as the one for spherical nanoparticles, for which rotations are irrelevant.

  15. 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.

  16. Plate Tectonics Prof. Thomas Herring

    E-print Network

    Herring, Thomas

    1 Plate Tectonics Prof. Thomas Herring MIT 05/14/02 Lexington HS Plate tectonics 2 Contact/14/02 Lexington HS Plate tectonics 3 Overview · Development of the Plate tectonic theory · Geological Data ­ Sea-floor spreading ­ Fault types from earthquakes ­ Transform faults ­ Today's measurements of plate tectonics 05

  17. 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

  18. 21 CFR 102.46 - Pacific whiting.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 2012-04-01 false Pacific whiting. 102.46 Section 102.46 Food and Drugs...Specific Nonstandardized Foods § 102.46 Pacific whiting. “Pacific whiting” or “North Pacific whiting” is the common...

  19. 21 CFR 102.46 - Pacific whiting.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 2010-04-01 false Pacific whiting. 102.46 Section 102.46 Food and Drugs...Specific Nonstandardized Foods § 102.46 Pacific whiting. “Pacific whiting” or “North Pacific whiting” is the common...

  20. 21 CFR 102.46 - Pacific whiting.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 2013-04-01 false Pacific whiting. 102.46 Section 102.46 Food and Drugs...Specific Nonstandardized Foods § 102.46 Pacific whiting. “Pacific whiting” or “North Pacific whiting” is the common...

  1. 21 CFR 102.46 - Pacific whiting.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 2011-04-01 false Pacific whiting. 102.46 Section 102.46 Food and Drugs...Specific Nonstandardized Foods § 102.46 Pacific whiting. “Pacific whiting” or “North Pacific whiting” is the common...

  2. 21 CFR 102.46 - Pacific whiting.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 2014-04-01 false Pacific whiting. 102.46 Section 102.46 Food and Drugs...Specific Nonstandardized Foods § 102.46 Pacific whiting. “Pacific whiting” or “North Pacific whiting” is the common...

  3. PLATE TECTONICS USING GIS Understanding plate tectonics using real

    E-print Network

    PLATE TECTONICS USING GIS Understanding plate tectonics using real global data sets pertaining OF THE UPSTATE, SC An afternoon field trip to observe the evidences for plate tectonic history, and to witness

  4. 19. 'Southern Pacific Company, Pacific Lines, Remodeling of Piers For ...

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

    19. 'Southern Pacific Company, Pacific Lines, Remodeling of Piers For Renewal of Br. 210-C Near Tehama, Sac. Division, Scale 1' = 40' & 1/4' = 1'-0', Sept. 1927, M.W.D., Drawing 5935, Sheet 2.' - Southern Pacific Railroad Shasta Route, Bridge No. 210.52, Milepost 210.52, Tehama, Tehama County, CA

  5. Pacific tectonics: Eastern-Pacific "stationarity" of EPR and causative association with Equator

    NASA Astrophysics Data System (ADS)

    Bostrom, R. C.

    2003-04-01

    The fundamentals of present-day Pacific tectonics are observed to be: its N/S mirror-symmetry about the Equator, displayed by the major transforms; its E/W asymmetry, represented by the western motion of the world's largest plate, originating in the eastern Equatorial Pacific; and correspondingly, development of the globally most voluminous subduction, at the western Pacific margin. The configuration seen at present is maintained at a fundamental level. The maximum in convective upwelling develops as coalescing plumes in the Galapagos region in the eastern Pacific. This has been found (Lonsdale 1988; McGuire and Hilde 2002; Chen and Lin 2002) to produce steady westward propagation of the Nazca/Cocos axis. Continually renewed, it determines the orientation and locus of a quasi-stationary EPR, centered on the Equator. Magnetic dating of boundaries in satellite gravity images records the Cenozoic history of the EPR, namely re-orientation in consequence of slow counter-clockwise re-orientation of the Equator. Relative to the present, during Maastrichtian times both Equator and plate motion were aligned WNW, recorded paleomagnetically and by features in the western, older part of the Pacific crust. Material subducted at that time accumulated principally beneath the SE Asia margin. Its slow heating is believed to play a role in the deep-seated activity and back-arc spreading associated with latter-day convergence in that region. The mechanism primarily responsible for the Pacific regime may be that mantle convection is not immune, as is generally tacitly supposed, to the minute westward tilt (c. 0.36°) under which it takes place. The latter, now astronomically quantifiable without tidal identification, represents the attraction component of water and solid-Earth masses which averaged over unit day lags the direction of purely geocentric g. Under gravity minutely E/W asymmetric, convection as always promoting the most efficient dissipative configuration, favors disproportionately large surface-west displacement, maximum at the contemporary Equator (=west limb of EPR upwelling). Some conclusions are a), that it is no longer adequate to model global convection assuming that angular momentum is conserved internally; in reality a considerable part is exported, here measured by expansion of the lunar orbit; and b), that the tectonics of an Earth simultaneously under vigorous convection and in asynchronous rotation relative to the mass center of Kuiper's Earth-Moon double planet, differs fundamentally from the regime developing within a fictitious isolated planet.

  6. Mapping The Pacific Coast

    NSDL National Science Digital Library

    Maps of the Pacific Coast from the earliest period of European exploration continue to interest cartographers, geographers, and antiquarians. The maps in the Quivira Collection date from 1540 to 1802 and include early depictions of California as an island, Russian cartographic interpretations of the Pacific Coast, and overland maps across the continent westward to the ocean. All told, this online collection includes forty-five maps, books, and illustrations organized into six thematic galleries. Visitors can start by listening to an audio introduction, and then look around through the thematic galleries, which include such intriguing headings as " In the Wake of Captain James Cook" and "Secret Russian Explorations in the Pacific". Of course, visitors must click their way into the "California as an Island" section, if not just for a taste of six examples of what is perhaps one of the best-known cartographic mistakes in the world.

  7. Asia-Pacific.com!

    NSDL National Science Digital Library

    Asia-Pacific.com!, an invaluable resource for users interested in business and economics in Asia and the Pacific Rim, offers an informative assortment of resources, news, and data. The site links to respected media sources throughout the region including Singapore Business Times, Jakarta Post, and The Australian, as well as in-depth journal articles, and book reviews, tables of contents, and purchasing information. Data analysis includes links to economic sources, company annual reports, and trade reports. Users are also invited to send their questions and queries to Asia-Pacific.com!'s panel of experts, who include George T. Haley, Associate Professor/ Director of Marketing and International Business Programs at the University of New Haven, Usha C.V. Haley, Associate Professor of Strategy and International Business at the New Jersey Institute of Technology, and Tan Chin Tiong, Professor and Provost of the new Singapore Management University.

  8. 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

  9. ANTHROPOLOGY 343 PACIFIC ISLANDS ARCHAEOLOGY

    E-print Network

    ANTHROPOLOGY 343 PACIFIC ISLANDS ARCHAEOLOGY 2014, Fall Term William S. Ayres Department Archaeology, Ayres, Fall 2014 1 Anthropology 343 Pacific Islands Archaeology University of Oregon Fall islands are revealed through archaeological evidence. A review of basic archaeological concepts provides

  10. PACIFIC EARTHQUAKE ENGINEERING RESEARCH CENTER

    E-print Network

    Adolphs, Ralph

    PACIFIC EARTHQUAKE ENGINEERING RESEARCH CENTER PEER Testbed Study on a Laboratory Building, Berkeley PEER Report 2005/12 Pacific Earthquake Engineering Research Center College of Engineering to "exercise" the PEER performance-based earthquake engineering methodology. All projects involved

  11. 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

  12. 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, C.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.

  13. Plate Tectonics Jigsaw

    NSDL National Science Digital Library

    Anne Egger

    This activity is a slight variation on an original activity, Discovering Plate Boundaries, developed by Dale Sawyer at Rice University. I made different maps, including more detail in all of the datasets, and used a different map projection, but otherwise the general progression of the activity is the same. More information about jigsaw activities in general can be found in the Jigsaws module. The activity occurs in several sections, which can be completed in one or multiple classes. In the first section, students are divided into "specialist" groups, and each group is given a global map with a single dataset: global seismicity, volcanoes, topography, age of the seafloor, and free-air gravity. Each student is also given a map of plate boundaries. Their task in the specialist group is to become familiar with their dataset and develop categories of plate boundaries based only on their dataset. Each group then presents their results to the class. In the second section, students reorganize into groups with 1-2 of each type of specialist per group. Each new group is given a plate, and they combine their different datasets on that one plate and look for patterns. Again, each plate group presents to the class. The common patterns and connections between the different datasets quickly become apparent, and the final section of the activity involves a short lecture from the instructor about types of plate boundaries and why the common features are generated at those plate boundaries. A follow-up section or class involves using a problem-solving approach to explain the areas that don't "fit" into the typical boundary types - intra-plate volcanism, earthquakes in the Eastern California Shear Zone, etc.

  14. Tsunami Strike! Pacific Edition

    NSDL National Science Digital Library

    2014-09-14

    Tsunami Strike! Pacific Edition is a scenario-based learning experience for kids from middle school through high school (approximate ages 13-17). The scenario tells the story of four main characters at different locations in the Pacific basin who are each impacted by a major tsunami that originates in Alaska’s Aleutian Islands. Over the course of the story, learners not only view the unfolding events and how each of the characters responds, but also observe how warning scientists analyze and communicate the tsunami threat. Fourteen short lessons provide interactive instruction focused on the science, safety, and history of tsunamis.

  15. 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.

  16. Mountains and Moving Plates

    NSDL National Science Digital Library

    These are the lecture notes for a class on plate tectonics and mountain building which is taught at the University of Wisconsin-Madison. The course describes the connections between the earth's tectonic plates, earthquakes, and its many mountain ranges. Topics include basic geography, the structure of the earth's interior, the relationships between the seismic cycle, volcanism, and plate movements, erosion of mountains, and mass wasting. Links are provided to additional resources, including aerial photos of geologic features, an interactive map of geology and topography of the United States, and a glossary.

  17. Plate Tectonics at Work

    NSDL National Science Digital Library

    This is a brief description of the results of plate movement according to the Theory of Plate Tectonics. It explains how divergence at the mid-ocean ridges accounts for the discoveries of Harry Hess. The site also refers to the invention of the magnetometer and the discovery of the young age of the ocean floor basalt. It concludes that these are the kinds of discoveries and thinking that ultimately led to the development of the theory of plate tectonics and that in just a few decades, have greatly changed our view of and notions about our planet and the sciences that attempt to explain its existence and development.

  18. PD characteristics in void in series with fissure-like interface

    Microsoft Academic Search

    Qinmin Liu; M. Asai; M. Nagao; M. Kosaki

    1997-01-01

    The partial discharge (PD) characteristics in void in series with fissure-like interface between insulation material were studied at room temperature. The interface between needle-plane electrodes was formed by two insulating plates of epoxy resin. The minute interfacial gap and the surface roughness of the plates were changed artificially. By the decrease of the interfacial gap from 400 pm to 0

  19. 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,…

  20. Oregon offers something for everyone who loves the outdoors --especially geologists. Oregon is a land filled with wonder and intrigue. Over the state's long history, plate tectonic and volcanic activity

    E-print Network

    Tullos, Desiree

    . Oregon is a land filled with wonder and intrigue. Over the state's long history, plate tectonic tectonic plate under- neath the Pacific Ocean produced the Coast Range over millions of years. Hot fluids coming off the diving plate, beginning about 35 million years ago, resulted in the volcanic eruptions

  1. Visualizing Earthquakes at Divergent Plate Margins

    NSDL National Science Digital Library

    Cara Harwood

    This screenshot from the visualization shows both continental rift zones, and ocean spreading centers, both types of divergent plate boundaries. The visualization shows how earthquakes at all types of divergent margins are shallow and have a low-magnitude. Click the image to enlarge or view the MP4 movie (MP4 Video 79.3MB Aug22 11).The purpose of this activity is to introduce students to the distribution and characteristics of earthquakes associated with divergent plate boundaries. Students will learn about how the magnitude and distribution of earthquakes at divergent boundaries are related to processes that occur at these boundaries and to the geometry and position of the two diverging plates. Because the depth of earthquakes can be difficult for students to visualize in 2D representations, this activity allows students to visualize the 3D distribution of earthquakes within Earth's surface, which is essential for understanding how different types of earthquakes occur in different tectonic settings. Locations featured in the visualization include the Mid-Atlantic Ridge, the East Pacific Rise, and the East African Rift Zone. Talking points and questions are included to facilitate using this visualization as part of an interactive lecture. In addition to playing back the visualization, instructors can also download the visualization software and data set and explore it themselves.

  2. Violin plate modes.

    PubMed

    Gough, Colin

    2015-01-01

    As the first step toward developing a generic model for the acoustically radiating vibrational modes of the violin and related instruments, the modes of both freely supported and edge-constrained top and back plates have been investigated as functions of shape, arching height, elastic anisotropy, the f-holes and associated island area, thickness graduations, and the additional boundary constraints of the ribs, soundpost, and bass-bar present in the assembled instrument. Comsol shell structure finite element software has been used as a quasi-experimental tool, with physical and geometric properties varied smoothly, often over several orders of magnitude, allowing the development of the plate modes to be followed continuously from those of an initially square plate to those of doubly-arched, guitar-shaped, orthotropic plates and their dependence on all the above factors. PMID:25618046

  3. Plate Tectonics Learning Module

    NSDL National Science Digital Library

    Rita Haberlin

    This plate tectonics unit was designed to be used with a college course in physical geography. Subject matter covered includes: the development of the theory including Wegener's Continental Drift Hypothesis and the existence of Pangaea, Harry Hess and his work on sea-floor spreading, and the final theory. It points out that global features such as deep oceanic trenches, mid-ocean ridges, volcanic activity, and the location of earthquake epicenters can now be related to the story of plate tectonics, since most geological activity occurs along plate boundaries. Divergent, convergent and transform plate boundaries are discussed in detail. This module contains a study guide and outline notes, study questions, and practice quizzes. One feature of the module is a web exploration section with links to twelve outside sites that augment the instruction.

  4. myPlate (image)

    MedlinePLUS

    ... food choices. The guide encourages you to eat less and avoid oversized portions. Half your plate should be filled with fruits and vegetables. At least half of your grains should be whole grains. You also should switch ...

  5. 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)

  6. elementsair ceramic plate

    E-print Network

    many current day applications. Anything that creates waste heat (e.g. engines, computers, electronicsearth elementsair L ceramic plate Thermoelectric Module Construction for Low Temperature Gradient related carbon dioxide emissions are the largest contributors to greenhouse gasses [1]. Thermoelectric

  7. Farallon Plate Remnants

    NSDL National Science Digital Library

    NASA/Goddard Space Flight Center Scientific Visualization Studio

    This image and short video from the NASA's Scientific Visualization Studio shows the remnants of the Farallon Plate based on seismic tomography studies. The studies were conducted by Hans-Peter Bunge at Princeton University in 2000.

  8. 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.

  9. 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.

  10. Growth Plate Fractures

    MedlinePLUS

    ... Harris system and is described here. Type I Fractures These fractures break through the bone at the ... and completely disrupting the growth plate. Type II Fractures These fractures break through part of the bone ...

  11. The Pacific is Viable

    Microsoft Academic Search

    Helen Hughes

    ll is quiet in the Pacific. The past year has seen no coups or new insurrections. Nauru voted out those who led it from riches to rags and now struggles to save something from the wreckage. But for the 30th successive year, there has been no growth. With aid running at more than $1.5 billion a year to soften the

  12. Plastic in the Pacific

    NSDL National Science Digital Library

    KQED

    2012-08-08

    Imagine every person on earth had 100 pounds of plastic. That's how much new plastic will be manufactured this year. In this video from QUEST produced by KQED, learn how much of that will end up in the ocean in a massive area dubbed the Pacific Garbage Patch.

  13. Is pacifism irrational?

    Microsoft Academic Search

    Kevin Klement

    1999-01-01

    When I tell others I disavow the use of violence in any and all its forms, I get different responses. My critics view my pacifism as essentially irrational. They can easily think of circumstances when the only rational action would be to initiate violence in self?defense or to defend others. Allowing oneself or others to be hurt by not acting,

  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. 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.

  16. Plate Tectonics: An Introduction

    NSDL National Science Digital Library

    In the early 1900s, most geologists thought that Earth's appearance, including the arrangement of the continents, had changed little since its formation. This video segment describes the impact the theory of plate tectonics has had on our understanding of Earth's geological history, and provides a brief overview of what is currently known about the Earth's tectonic plates and their motions. The segment is two minutes twenty-one seconds in length. A background essay and list of discussion questions are also provided.

  17. Tsunami source of the 2011 off the Pacific coast of Tohoku Earthquake

    NASA Astrophysics Data System (ADS)

    Fujii, Yushiro; Satake, Kenji; Sakai, Shin'ichi; Shinohara, Masanao; Kanazawa, Toshihiko

    2011-07-01

    Tsunami waveform inversion for the 11 March, 2011, off the Pacific coast of Tohoku Earthquake ( M 9.0) indicates that the source of the largest tsunami was located near the axis of the Japan trench. Ocean-bottom pressure, and GPS wave, gauges recorded two-step tsunami waveforms: a gradual increase of sea level (~2 m) followed by an impulsive tsunami wave (3 to 5 m). The slip distribution estimated from 33 coastal tide gauges, offshore GPS wave gauges and bottom-pressure gauges show that the large slip, more than 40 m, was located along the trench axis. This offshore slip, similar but much larger than the 1896 Sanriku "tsunami earthquake," is responsible for the recorded large impulsive peak. Large slip on the plate interface at southern Sanriku-oki (~30 m) and Miyagi-oki (~17 m) around the epicenter, a similar location with larger slip than the previously proposed fault model of the 869 Jogan earthquake, is responsible for the initial water-level rise and, presumably, the large tsunami inundation in Sendai plain. The interplate slip is ~10 m in Fukushima-oki, and less than 3 m in the Ibaraki-oki region. The total seismic moment is estimated as 3.8 × 1022 N m ( M w = 9.0).

  18. A computational model for predicting damage evolution in laminated composite plates

    E-print Network

    Phillips, Mark Lane

    1999-01-01

    The feasibility of producing a model capable of predicting the evolution of interface degradation, matrix cracking, and delimitation at multiple sites in laminated continuous fiber composite plates subjected to monotonic loading, while still being...

  19. Seismological evidence of mantle flow driving plate motions at a palaeo-spreading centre

    NASA Astrophysics Data System (ADS)

    Kodaira, Shuichi; Fujie, Gou; Yamashita, Mikiya; Sato, Takeshi; Takahashi, Tsutomu; Takahashi, Narumi

    2014-05-01

    A long-standing question about the dynamics of mid-ocean spreading centres is whether mantle upwelling is passive or active. During passive upwelling, the motion of the overlying plate would be expected to drive mantle flow. In contrast, during active upwelling, decompression melting of the mantle beneath the spreading axis would result in a low-density melt that creates local buoyancy, forcing mantle convection and driving plate motion. Seismic images of older parts of the Pacific Plate reveal dipping reflectors in the lower crust that could be shear zones created by active mantle flow, but there is little seismological evidence to indicate that mantle flow drags the plate. Here we use active-source seismic data to image the Pacific Plate that was created at a palaeo-spreading centre in the northwest Pacific Ocean. We identify very high P-wave velocities of 8.5-8.6 km s-1 and strong seismic anisotropy of 8.5-9.8% in the uppermost mantle, immediately below the lower-crustal dipping reflectors. We suggest that such strong seismic anisotropy, caused by the alignment of olivine crystals in response to mantle flow, could have been generated if mantle flow was much faster than plate motion. We conclude that both the lower-crustal dipping reflectors and the anisotropy were formed by a drag force at the Moho caused by rapid mantle flow, providing direct evidence for active mantle flow at a spreading centre.

  20. 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.

  1. Musical Plates: A Study of Plate Tectonics

    NSDL National Science Digital Library

    2007-01-01

    In this project, students use Real-Time earthquake and volcano data from the Internet to explore the relationship between earthquakes, plate tectonics, and volcanoes. There is a teachers guide that explains how to use real time data, and in the same section, there is a section for curriculum standards, Supplement and enrichment activities, and assessment suggestions. Included on this webpage are four core activities, and three enrichment activities, including an activity where the student writes a letter to the president. There is also a link to reference materials that might also interest you and your students.

  2. An Introduction to Plate Tectonics

    NSDL National Science Digital Library

    This page is a brief introduction to plate tectonics. It starts with a discussion of the evolution of the theory of plate tectonics and the arguments supporting it. It then discusses the processes associated with tectonics and the types of plate boundaries: divergent, convergent and transform boundaries. It concludes with a discussion of the current hypotheses of what causes plates to move.

  3. Caribbean plate interactions

    SciTech Connect

    Ball, M. (Geological Survey, Denver, CO (United States))

    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.

  4. Sediment subduction - A probable key for seismicity and tectonics at active plate boundaries

    Microsoft Academic Search

    Vladimir Kostoglodov

    1988-01-01

    A model involving extensive occurrence of sediment subduction and viscous interaction of lithospheric plates at convergent zones is applied to derive simple relations between extremal values of seismic and global tectonic parameters. The strength of mechanical coupling at the interface zone is defined as the maximum shear stress at the base of the over-thrusting plate. A test of these relations

  5. Asymptotic analysis of contact problems between an elastic material and thin-rigid plates

    Microsoft Academic Search

    Mustapha El Jarroudi

    2010-01-01

    We consider an elastic material in contact with a three-dimensional rigid plate of varying thickness. We suppose that a perfect adhesion occurs along thin zones disposed in a self-similar way on the interface between the two materials. We suppose that the elasticity coefficients in the plate depend on its thickness and tend to infinity as this thickness tends to zero.

  6. 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.

  7. Global strike-slip faults: Bounds from plate tectonics

    NASA Astrophysics Data System (ADS)

    Gordon, R. G.; Argus, D. F.

    2006-12-01

    According to the tenets of plate tectonics, a transform fault is a strike-slip fault along which neither convergence nor divergence occurs. Analysis of global plate motion data indicates that the only true transform faults are the strike-slip faults that offset segments of mid-ocean ridges. Thus, many of Earth's major strike-slip fault systems are not true transform faults as they accommodate large components of oblique convergence or oblique divergence. This is particularly true for several important ocean-continent systems such as the San Andreas, the strike-slip systems bounding the northern and southern Caribbean plate, the Alpine fault system of New Zealand, the Anatolian fault system, and the Azores-Gibraltar-Alboran sea system. These strike-slip systems are commonly sites of large scale mountain building and basin formation. Here we examine the far-field constraints on the motions of the plates bounding several of these strike-slip systems using both conventional plate motion circuits and results from global positioning system and other space geodetic data. We pay particular attention to the San Andreas fault system in central and northern California, where the San Andreas system is part of the boundary between the Sierran microplate and the Pacific plate. Most of the fault system accommodates obliquely convergent motion, giving rise to the California Coast Range, but in the northern San Francisco Bay Area it is obliquely divergent, producing San Pablo Bay and a gap in the Coast Range that permits the Sierran watershed to drain to the Pacific through the Golden Gate.

  8. 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.

  9. Cadmium plating replacements

    SciTech Connect

    Nelson, M.J.; Groshart, E.C.

    1995-03-01

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

  10. Limb lengthening over plate

    PubMed Central

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

    2012-01-01

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

  11. Tectonic Plates, Earthquakes, and Volcanoes

    NSDL National Science Digital Library

    According to theory of plate tectonics, Earth is an active planet -- its surface is composed of many individual plates that move and interact, constantly changing and reshaping Earth's outer layer. Volcanoes and earthquakes both result from the movement of tectonic plates. This interactive feature shows the relationship between earthquakes and volcanoes and the boundaries of tectonic plates. By clicking on a map, viewers can superimpose the locations of plate boundaries, volcanoes and earthquakes.

  12. Pacific Tsunami Museum

    NSDL National Science Digital Library

    The Pacific Tsunami Museum is dedicated to promoting public education about tsunamis for citizens of Hawaii and the Pacific Region, as well as preserving the social and cultural history of Hawaii. Materials available at the museum's site include a listing of exhibits, a link to a webcam overlooking Hilo Bay, and event announcements. There is also a listing of programs sponsored by the museum, including class visits, a tsunami observer program and evacuation notification team, and a walking tour of historical tsunami sites. The students' page features games and puzzles, a frequently-asked-questions feature, links to related websites, and an online collection of tsunami warning signs. Other materials include a collection of tsunami-related art, interviews with survivors, and an archive of photographs.

  13. Pacific Marine Environmental Laboratory

    NSDL National Science Digital Library

    Located in Seattle, Washington, PMEL carries out interdisciplinary scientific investigations in oceanography and atmospheric science. Current programs focus on open ocean observations in support of long-term monitoring and forecasting. A comprehensive site focusing on NOAA research in the Pacific Ocean. Site includes an abundant amount of information, data, publications, and links to additional resources. Features interactive data sets, maps, 3-D visualizations, and video.

  14. PACIFIC ISLANDS DIGITAL ELEVATION MODELS Coastal Models Supporting our Nation's Needs through Science and Technology

    E-print Network

    modeling work, done in collaboration with the National Tsunami Hazard Mitigation Program (NTHMP. Seismic activity at plate boundaries along the Pacific Ring of Fire, along with other tectonic stresses to effectively maintain marine ecosys- tems and coastal resources, coordinate planning and mitigation efforts

  15. Electrical Conductivity and Anisotropy in Pacific Lithosphere: CSEM Results from APPLE

    Microsoft Academic Search

    J. Behrens; S. Constable; M. Everett; L. MacGregor

    2003-01-01

    Strain associated with plate formation at mid-ocean ridge spreading centers may influence electrical conductivity at various depths in the lithosphere, and may leave an anisotropic fabric frozen in place. By measuring lithospheric electrical conductivity and anisotropy, insight may be gained regarding the formation and evolution of oceanic crust and mantle. Controlled-source electromagnetic (CSEM) sounding of 35 Ma Pacific lithosphere was

  16. CENOZOIC RECONSTRUCTIONS, LAND AND SEA 35 Cenozoic reconstructions of SE Asia and the SW Pacific

    E-print Network

    Royal Holloway, University of London

    : changing patterns of land and sea RobertHall SE Asia Research Group, Department of Geology, Royal Holloway with SEAsia enlarged the area of land connected to Eurasia. Later, the continuing collision with Australia led to connections between Australia, Eurasia, and the Pacific. Despite long-term convergence of the major plates

  17. Quaternary Science Reviews 21 (2002) 16931704 Interior hydrography and circulation of the glacial Pacific Ocean

    E-print Network

    Lynch-Stieglitz, Jean

    shorter than that for plate tectonics, the total surface carbon reservoir in the atmosphere Abstract The deep water of the Pacific Ocean is a key component of the global climate system on the time), suggesting that this is a global phenomenon during the glacial time. The upper water mass has a distinctly

  18. 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.

  19. Flat plate project

    NASA Astrophysics Data System (ADS)

    Wijbrans, Klaas C.; Korsten, Maarten J.

    1991-03-01

    The flat plate project is a pilot study for the creation of intelligent robotic systems. In these systems vision robotics and artificial intelligence aspects have to be combined. The final goal is to give a robot the capacity to learn to solve the problem represented by a toy for a two year old child. This toy is called the ''Holle Bol'' in Dutch. It consists of a plastic ball with differently shaped holes in it and a number of small blocks that must be put into the corresponding holes. To investigate the problems associated with this project first a simplification of the problem has been studied. In this case a flat plate with differently shaped holes is used. The paper describes the results of the flat plate pilot project.

  20. Miniature plasmonic wave plates

    E-print Network

    Drezet, Aurelien; Ebbesen, Thomas W

    2010-01-01

    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 in short and long axis of each ellipses 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 Poincare sphere by changing only the shape of the elliptical grating.

  1. 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

  2. A plate tectonic model of the Palaeozoic tectonic history of New South Wales

    Microsoft Academic Search

    Erwin Scheibner

    1973-01-01

    An updated* tectonic model for the Palaeozoic tectonic history of New South Wales, based on actualistic models of plate tectonics, has resulted from tectonic analyses and syntheses during the compilation of the Tectonic Map of New South Wales.Most emphasis is given to marginal seas, which characterize Pacific marginal mobile zones. Marginal seas form in the regime of lithospheric tension under

  3. Completion of the 16 station Plate Boundary Observatory (PBO) network on Mt. St. Helens, WA

    Microsoft Academic Search

    K. Austin; K. Hafner; K. Fengler; S. Doelger

    2006-01-01

    The Plate Boundary Observatory (PBO), part of the larger NSF-funded EarthScope project, is completing year 3 of the installation phase of 852 continuously operating GPS stations in the Western United States. Some of these GPS stations are focused specifically on centers of volcanic activity. Mt. St. Helens is one of these volcanic areas of interest in the Pacific Northwest (PNW)

  4. Neural interfacing

    Microsoft Academic Search

    A. Sarje; N. Thakor

    2004-01-01

    The problem of interfacing microsystems to neurons or brain has led to exciting developments in the fields of micro\\/nanotechnologies and integrated circuitry and systems. Neurons have been patterned using micro\\/nanotechnologies to form structural and functional networks. Micro-electrodes and integrated circuitry have been developed for large scale, multichannel measurements from brain tissue. Driving force for this technology comes from research and

  5. Nitrided Metallic Bipolar Plates

    SciTech Connect

    Brady, Michael P [ORNL; Tortorelli, Peter F [ORNL; Pihl, Josh A [ORNL; Toops, Todd J [ORNL; More, Karren Leslie [ORNL; Meyer III, Harry M [ORNL; Vitek, John Michael [ORNL; Wang, Heli [National Renewable Energy Laboratory (NREL); Turner, John [National Renewable Energy Laboratory (NREL); Wilson, Mahlon [Los Alamos National Laboratory (LANL); Garzon, Fernando [Los Alamos National Laboratory (LANL); Rockward, Tommy [Los Alamos National Laboratory (LANL); Connors, Dan [GenCell Corp; Rakowski, Jim [Allegheny Ludlum; Gervasio, Don [Arizona State University

    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.

  6. Tectonic Plate Motion

    NSDL National Science Digital Library

    The representation shows the direction of motion of the Earth's major plates as measured through NASA's satellite laser ranging (SLR) technology. A series of world maps, accompanying text, and the subsequent links explain this technology in great detail. One can click on the Index Map for Satellite Laser Ranging site Velocity and see the vectors (arrows) that indicate the direction and rate of movement of Earth's plates in much more detail. Accompanying text gives a more detailed explanation of what each sub map is showing.

  7. License plate detection algorithm

    NASA Astrophysics Data System (ADS)

    Broitman, Michael; Klopovsky, Yuri; Silinskis, Normunds

    2013-12-01

    A novel algorithm for vehicle license plates localization is proposed. The algorithm is based on pixel intensity transition gradient analysis. Near to 2500 natural-scene gray-level vehicle images of different backgrounds and ambient illumination was tested. The best set of algorithm's parameters produces detection rate up to 0.94. Taking into account abnormal camera location during our tests and therefore geometrical distortion and troubles from trees this result could be considered as passable. Correlation between source data, such as license Plate dimensions and texture, cameras location and others, and parameters of algorithm were also defined.

  8. 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.

  9. Plate Tectonics and Volcanism

    NSDL National Science Digital Library

    2012-08-03

    This is a lesson where learners explore plate movement and the relationship between plate tectonics and volcanoes. The lesson models scientific inquiry using the 5E instructional model and includes teacher notes, prerequisite concepts, common misconceptions, student journal and reading. This is lesson five in the Astro-Venture Geology Training Unit that was developed to increase students' awareness of and interest in astrobiology and the many career opportunities that utilize science, math and technology skills. The lessons are designed for educators to use with the Astro-Venture multimedia modules.

  10. Plating under reduced pressure

    SciTech Connect

    Dini, J.W.; Beat, T.G.; Cowden, W.C. (Lawrence Livermore National Lab., CA (United States)); Ryan, L.E.; Hewitt, W.B. (TRW, Inc., Redondo Beach, CA (United States))

    1992-06-01

    Plating under reduced pressure was evaluated for both electroless nickel and electrodeposited copper systems. The objective was to reduce pitting of these coatings thereby further enhancing their usage for diamond turning applications. Cursory experiments with electroless nickel showed reduced porosity when deposition was done at around 500 torr. Detailed experiments with electrodeposited copper at around 100 torr provided similar results. Scanning tunneling microscopy was effectively used to show the improvement in the copper deposits plated under reduced pressure. Benefits included reduced surface roughness and finer and denser grain structure.

  11. Volcanoes, Plates, and Chains

    NSDL National Science Digital Library

    In this lesson students will discover how seamounts in the Axial-Cobb-Eikelberg-Patton chain were formed. They will learn about the processes that form seamounts, describe the movement of tectonic plates in the Gulf of Alaska region and explain the types of volcanic activity that might be associated with these movements, and describe how a combination of hotspot activity and tectonic plate movement could produce the arrangement of seamounts observed in this chain. This hands-on activity uses online data resources and includes: focus questions, learning objectives, teaching time, audio/visual materials needed, background information, learning procedures, evaluations, extensions, as well as resources and student handouts.

  12. Discovering Plate Boundaries

    NSDL National Science Digital Library

    Rice University's Earth Science Department offers the Discovering Plate Boundaries educational activity. The exercise is described as a "data rich exercise to help students discover the processes that occur at plate tectonic boundaries" and has been used successfully with 5th graders to undergraduates. The site provides the necessary downloads of maps; earthquake, volcanic, seafloor, topographic, and bathymetric data; and teacher guides and complete instructions. Because the activity can be geared towards such a large range of students, is well designed, and is easily accessible, educators will definitely appreciate the site.

  13. 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.

  14. 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.

  15. 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.

  16. Characterizing Plate Boundaries

    NSDL National Science Digital Library

    Bill Hirt

    To prepare for this exercise students read about the processes that operate at plate boundaries and how they are related to the distinct patterns of seismicity, volcanism, surface elevations (e.g., ridges versus trenches), and seafloor ages characteristic of different boundary types. During the week the assignment is available online, students have access to: (1) an index map that locates three boundaries they are to study; and (2) four maps from Sawyer's Discovering Plate Boundaries website that provide the data mentioned above. Student tasks are to: (1) document patterns in each type of data along the three targeted boundaries; and (2) use these observations in conjunction with their understandings of the processes that operate along different types of boundaries to decide whether each of the targeted sites is most likely to be a divergent, convergent, or shear boundary. This activity gives students practice in map reading, interpreting the likely tectonic setting of a boundary by pulling together constraints from several types of data, and collaborating with their classmates in an online environment. The activity also provides a foundation for understanding a wide range of phenomena that are discussed later in the semester in the context of plate tectonic processes. Teaching Tips Adaptations that allow this activity to be successful in an online environment Sawyer's Discovering Plate Boundaries is a jigsaw exercise in which students collaboratively develop an empirical classification of plate boundaries by first studying an individual data set (e.g., seismicity) and then working as part of a multidisciplinary team to develop a composite classification for the boundaries of a single plate using several types of data. In order for the classification to be truly empirical, students are not introduced to the "traditional" classification of plate boundaries till the end of the exercise. In adapting this assignment to the online environment I have: (1) asked students to prepare by becoming familiar with the standard classification of plate boundaries and the processes that operate at them; (2) limited their work to three targeted boundaries of different types; and (3) provided guidance about which features to look for in the each data set. I have found that these modifications help online students, who often work alone "on their own schedules", to avoid getting "lost" and frustrated with the assignment and to compensate for the lack of collaborative input they would receive in a classroom setting. Elements of this activity that are most effective The success of this exercise is really seems to depend on how well a student follows the directions. If a student learns about the geologic differences among plate boundaries, makes careful observations, and thoughtfully compares his or her observations to the expected patterns he or she typically does quite well based on answers to the follow-up questions. If, on the other hand, a student simply looks up the types of the targeted boundaries on a map and then attempts to "back out" the observations that he or she thinks should fit, the result is often inconsistency and a poor score on the questions. (I can often tell which approach a student is taking based on the queries they post to the discussion board, but rarely seem to be able to get those who are trying to work backwards through the assignment to change direction.) Recommendations for other faculty adapting this activity to their own course: To date my experience developing an engaging online exercise to help students learn the principles of plate tectonics has only been partly successful. I think that having such an exercise is critical, however, because this topic provides the framework for so much of what we learn in the geosciences. Based on my efforts to adapt elements of Discovering Plate Boundaries to an online environment I would offer three recommendations. (1) Provide examples. Confronted with an unfamiliar map students are sometimes confused when asked to decide if seafloor age, for example, is uniform or variable

  17. 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.

  18. Mesozoic Plate Tectonic Evolution of the Northern Margin of Pangea

    NASA Astrophysics Data System (ADS)

    Miller, E. L.

    2011-12-01

    Asia joined Laurentia and Baltica during the formation of the Urals in the Early Permian. Subsequently, the northern margin of Pangea shared a paleo-Pacific facing margin. Analysis of events along this (mostly active) margin provides insight into the plate tectonic setting and evolution of the Arctic basins and their temporal links to Pacific margin events. A 3-phase tectonic evolution characterizes the northern margin of Pangea during the Mesozoic: 1. Permo-Triassic rifting (Siberian Trap magmatism)was linked to rifting in a series of back-arc basins developed along the northern margin of Pangea. Triassic-Jurasic deep-water sedimentary seqences deposited in these basins were subsequently deformed during phase 2 events. 2. Lithospheric shortening/convergence across this margin deformed these basinal sediments and shed syn-orogenic deposits cratonward in the Jura-Cretaceous. Syn-orogenic basinal successions are widespread from the Verkoyansk margin of Siberia to the Brooks Range fold and thrust belt. Their sources are well-characterized by U-Pb ages of detrital zircon suites and include Pennsylvanian-Permian, Triassic and Jurassic magmatic belts, implying convergence and emplacement of a long-lived arc system onto the continental margin. 3. Structures related to phase 2 are cut and overprinted by voluminous, syn-extensional, slab-related magmatism that developed during southward or Pacific-ward migration of a N-dipping subducting slab. It is inferred that the earliest part of the Amerasia Basin likely opened during part of this magmatic event, 135 to 90 Ma. The final culmination of this magmatic event is the Ohotsk-Chukotsk volcanic belt, ~90-75 Ma;after this, magmatism continues to migrate Pacific-ward in a series of steps. Utilizing plate models of the Arctic by Lawver et al.(2002) it can be shown that some of the differences in the timing and style of Mesozoic orogenesis along the northern paleo-Pacific margin of Pangea (and especially the differences between the Canadian margin and the Arctic-Siberian margin) might be explained by along-strike differences in the nature of motion of the overriding (continental) plate with respect to paleo-Pacific subduction zones (towards vs. away).

  19. 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).

  20. Gravity models of two-level collision of lithospheric plates in northeastern Asia

    NASA Astrophysics Data System (ADS)

    Petrishchevsky, A. M.

    2013-11-01

    Structural forms of emplacement of crustal and mantle rigid sheets in collision zones of lithospheric plates in northeastern Asia are analyzed using formalized gravity models reflecting the rheological properties of geological media. Splitting of the lithosphere of moving plates into crustal and mantle constituents is the main feature of collision zones, which is repeated in the structural units irrespective of their location, rank, and age. Formal signs of crustal sheet thrusting over convergent plate boundaries and subduction of the lithospheric mantle beneath these boundaries have been revealed. The deep boundaries and thickness of lithospheric plates and asthenospheric lenses have been traced. A similarity in the deep structure of collision zones of second-order marginal-sea buffer plates differing in age is displayed at the boundaries with the Eurasian, North American, and Pacific plates of the first order. Collision of oceanic crustal segments with the Mesozoic continental margin in the Sikhote-Alin is characterized, as well as collision of the oceanic lithosphere with the Kamchatka composite island arc. A spatiotemporal series of deep-seated Middle Mesozoic, Late Mesosoic, and Cenozoic collision tectonic units having similar structure is displayed in the transitional zone from the Asian continent to the Pacific plate.

  1. DECEMBER 2000 U. S. Pacific

    E-print Network

    , P. Scott Hill, Pierre Kleiber, Robert Read, Scott Spitz, and Tim Gerrodette NOAA . . . . . . . . . . . . . . . . . . . . . . . . 68 PACIFIC WHITE-SIDED DOLPHIN (Lagenorhynchus obliquidens): California

  2. 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)

  3. 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.

  4. 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…

  5. 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).

  6. Earthquakes and Plates

    NSDL National Science Digital Library

    The representation depicts global distribution of earthquakes. A world map shows the location of large earthquakes that occurred from 1975-1995. A slider at the bottom left of the map allows the user to change the map to reveal the location of major plates or to select both views layered on top of one another.

  7. Plate Tectonics Quiz

    NSDL National Science Digital Library

    This quiz for younger students asks them 10 questions about plate motions, rock types in continental and oceanic crust, crustal formation and mountain building, the supercontinent Pangea, and the theory of continental drift. A link to a page on continental drift provides information to answer the questions.

  8. Martian plate tectonics

    Microsoft Academic Search

    N. H. Sleep

    1994-01-01

    The northern lowlands of Mars have been produced by plate tectonics. Preexisting old thick highland crust was subducted, while seafloor spreading produced thin lowland crust during late Noachian and Early Hesperian time. In the preferred reconstruction, a breakup margin extended north of Cimmeria Terra between Daedalia Planum and Isidis Planitia where the highland-lowland transition is relatively simple. South dipping subduction

  9. Plate Tectonics: Lines of Evidence

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2006-11-01

    This Science Object is the fifth of five Science Objects in the Plate Tectonics SciPack. It explores the physical, geographical, and geological evidence for the theory of continental drift and plate tectonics. Plate tectonics provide a unifying framework for understanding Earth processes and history, and is supported by many lines of evidence. Over geologic time, plates move across the globe creating different continents (and positions of continents). Learning Outcomes:? Use plate tectonics to explain changes in continents and their positions over geologic time.? Provide evidence for the idea of plates, including the location of earthquakes and volcanoes, continental drift, magnetic orientation of rocks in the ocean floor, etc.

  10. Earth: Plates on the Move

    NSDL National Science Digital Library

    In this activity, students explore how the movement of tectonic plates forms mountains, volcanoes, oceans, and earthquakes. It first describes the plates and the various types of interaction at plate boundaries. An interactive map of the world shows the relationship between plate boundaries and earthquakes, allowing the student to click on selected place to explore a volcano, mountain, hotspot or earthquake. They then zoom in the see how the plates are moving, play an animation about the plate interaction, and read a story about the event. In addition, a set of links lead to more detailed information.

  11. Structural geomorphology of a fast-spreading rise crest: The East Pacific Rise near 3°25?S

    Microsoft Academic Search

    Peter Lonsdale

    1977-01-01

    A deeply-towed instrument package was used in a detailed survey of the crest of the East Pacific Rise (EPR) near 3°25'S, where the Pacific and Nazca plates are separating at 152 mm\\/yr. A single 90 km-long traverse of the rise crest extends near-bottom observations onto the rise flanks. A ridge at the spreading axis is defined by its steep regional

  12. Interface Structure

    NASA Astrophysics Data System (ADS)

    Percus, J. K.

    Phase-separated fluids are analyzed from several viewpoints: local thermodynamic, in which all density correlations are ignored; mean field, which correctly treats those at medium range; and a modified Kac-Siegert form which only coarse-grains those at short range. The last form appears as an ensemble average over tail potential fields, and is treated variationally with a Gaussian ansatz. Application to a planar interface shows the anticipated surface softening as any confining field is removed, and in statistically homogeneous condensation, a form of the familiar level set description assumes relevance. Suggestions are made as to removing the Gaussian assumption.

  13. PACIFIC HIGHLY MIGR ATORY PEL AGIC FISHERIES pacific highly migratory

    E-print Network

    (mahi mahi), large pelagic sharks, and others. Many are valuable and highly prized by both commercial Harvest rate Stock status Tropical tunas Bigeye tuna Overfishing Not overfished Eastern Pacific2 109 Not overfished Subtotal, billfish 65,292 89,292 89,292 Oceanic sharks Bigeye thresher (North Pacific) 4 Unknown

  14. Plate Puzzle Page 1 of 20 Plate Puzzle 1

    E-print Network

    Benitez-Nelson, Claudia

    plotting activities. Good follow-up activities are: plate tectonics flip book, epicenter plotting using tectonics. The map is an attractive display of plate tectonic features such earthquake epicenters boundaries so that one can examine the relationship of the tectonic features to the plate boundaries. The map

  15. Is structural interface standardization beneficial?

    NASA Astrophysics Data System (ADS)

    Dombert, W. E.

    1983-11-01

    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.

  16. 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.

  17. Embodied User Interfaces: Towards Invisible User Interfaces

    Microsoft Academic Search

    Kenneth P. Fishkin; Thomas P. Moran; Beverly L. Harrison

    1998-01-01

    There have been several recent examples of user interface techniques in which the user uses a computational device by physically manipulating the device. This paper proposes that these form an interesting new paradigm for user interface design, Embodied User Interfaces. This paper presents and defines this paradigm, and places it in the evolution of user interface paradigms leading towards the

  18. A three-plate kinematic model for Lau Basin opening

    NASA Astrophysics Data System (ADS)

    Zellmer, Kirsten E.; Taylor, Brian

    2001-05-01

    We present revised compilations of bathymetry, magnetization, acoustic imagery, and seismicity data for the Lau Basin and surrounds. We interpret these data to more precisely locate the plate boundaries in the region and to derive a three-plate kinematic model for the opening of the Lau Basin during the Brunhes Chron. Our tectonic model includes the Niuafo'ou microplate, which is separated from the Australian Plate along the Peggy Ridge-Lau Extensional Transform Zone-Central Lau Spreading Center and from the Tongan Plate along the newly discovered Fonualei Rift and Spreading Center. Our model shows that Australia-Tonga plate motion between 15.5°S and 19°S is partitioned across the microplate, and it resolves the former apparent conflict between geodetic versus seafloor spreading velocities. Regionally, this implies that the angular rate of opening of the Lau Basin has been faster than that of the Havre Trough to the south and that the rapid current rates of Pacific subduction at the Tonga Trench (˜240 mm/yr at 16°S) have been sustained for at least 0.78 m.y.

  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. Pacific Northwest National Laboratory

    NSDL National Science Digital Library

    The Pacific Northwest National Laboratory, one of nine US Department of Energy multi-program national laboratories, conducts research concerning environmental science and technology. This huge site holds information on research in atmospheric science and climate change, analytic and physical chemistry, computational science and engineering, environmental remediation, statistics, thermal and energy systems, and so much more. Many of the individual research pages contain downloadable publications. Section headings for the site include Energy, Environment, Health and Safety, Information Technology, National Security, and Nuclear Technology, among others. Also included here is the Environmental Molecular Sciences Laboratory, a facility that conducts "fundamental research on the physical, chemical, and biological processes that underpin critical environmental issues."

  1. 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.

  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. Plate Tectonics: Lake Mead, Nevada

    NSDL National Science Digital Library

    2005-10-21

    Using animations to illustrate the theory of plate tectonics, this video segment adapted from Discovering Women takes you to Lake Mead, Nevada, to see visual evidence of how plate movement has been stretching the North American continent.

  4. Tectonic Plates, Earthquakes, and Volcanoes

    NSDL National Science Digital Library

    The representation shows earthquake and volcanic activity corresponds to plate boundaries. This interactive topographical map with the ocean water removed shows the boundaries of major plates and the locations of major volcanic eruptions and earthquakes worldwide.

  5. What Are Growth Plate Injuries?

    MedlinePLUS

    ... for growth plate injuries are: ? Falling down ? Competitive sports (like football) ? Recreational activities. Other reasons for growth plate injuries are: ? Child abuse ? Injury from extreme cold (for example, frostbite) ? Radiation ( ...

  6. What Are Growth Plate Injuries?

    MedlinePLUS

    ... for growth plate injuries are: Falling down Competitive sports (like football) Recreational activities. Other reasons for growth plate injuries are: Child abuse Injury from extreme cold (for example, frostbite) Radiation ( ...

  7. Radiation efficiency of damped plates.

    PubMed

    Kou, Yiwei; Liu, Bilong; Tian, Jing

    2015-02-01

    The radiation efficiency of damped plates is discussed in this letter. Below the critical frequency of a plate, numerical results show that the radiation efficiency is much influenced by damping. Some modifications of the classical formulas given by Cremer for an infinite plate and Leppington for a finite rectangular plate are proposed to include the influence of the damping on the radiation efficiency. PMID:25698034

  8. 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.

  9. Aid Has Failed the Pacific

    Microsoft Academic Search

    Helen Hughes

    2003-01-01

    er capita income has grown at less than 1% a year in the Pacific during the past 30 years. In some islands it has declined. Population has grown at more than 3% a year. The discrepancy between population and income growth lies at the core of the Pacific's problems. The little income growth that has taken place has gone to

  10. Pacific Educational Research Journal, 1996.

    ERIC Educational Resources Information Center

    Berg, Kathleen F., Ed.; Lai, Morris K., Ed.

    1996-01-01

    This first issue of the new "Pacific Educational Research Journal" offers articles covering diverse subjects and using diverse research methods. The new journal represents a rejuvenation of a previous publication to address educational issues specific to the Pacific region. Ethnic groups specifically addressed include Hawaiians, second-generation…

  11. Upper plate stressing and seismicity in the subduction earthquake cycle

    NASA Astrophysics Data System (ADS)

    Taylor, M. A. J.; Dmowska, R.; Rice, J. R.

    1998-10-01

    We investigate upper plate stressing during the earthquake cycle in a subduction segment, using three-dimensional (3-D) elastic models to address the effects of strongly heterogeneous coupling along strike of the interplate interface. We show how heterogeneity controls the locations and mechanisms of seismicity in the upper plate. Oblique subduction segments, two from the Aleutians (Andreanof Islands 1986 and Rat Islands 1965) and one from Indonesia (Biak 1996) are studied. All examples of upper plate seismicity from the Aleutians represent events occurring toward the beginning of a new cycle, while in Biak, Indonesia, the examined events occur both toward the end of one cycle and the beginning of the next. In the majority of cases studied, the location and mode of the upper plate seismicity are consistent with space- and time-dependent stressing as predicted by modeling. This confirms earlier observations that seismicity in the vicinity of large/great subduction earthquakes (toward the outer rise, at intermediate depth, and now in the upper plate) depends, in an interpretable manner, on the stage in the earthquake cycle as well as on distribution of coupling along the interplate interface.

  12. THE PARALLEL PLATE PLASMA PROBLEM

    Microsoft Academic Search

    Hall

    1962-01-01

    The parallel plate plasma problem is considered under the assumption of ; uniform density and a specular reflection boundary condition at the plates. The ; impedance of the device is derived for several different models of the plasma ; medium. The impedance of a hydromagnetic medium exhibits resonances whenever the ; plate separation is an odd multiple of a half

  13. Lesson 3. Plate Tectonics Overview

    E-print Network

    Chen, Po

    Lesson 3. Plate Tectonics #12;Overview · Prior to the 1970s that with the development of the theory of plate tectonics. · Knowledge of the ocean floors of the Earth #12;Overview · Plate tectonics explains the formaBon of the Earth's two

  14. Glacial isostasy and plate motion

    Microsoft Academic Search

    Volker Klemann; Zdenek Martinec; Erik R. Ivins

    2008-01-01

    The influence of glacial-isostatic adjustment (GIA) on the motion of tectonic plates is usually neglected. Employing a recently developed numerical approach, we examine the effect of glacial loading on the motion of the Earth’s tectonic plates where we consider an elastic lithosphere of laterally variable strength and the plates losely connected by low viscous zones. The aim of this paper

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Microchannel plate streak camera

    DOEpatents

    Wang, Ching L. (Livermore, CA)

    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.

  20. 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.

  1. 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.

  2. 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.

  3. Volcanism and vertical tectonics in the Pacific Basin related to global Cretaceous transgressions

    NASA Astrophysics Data System (ADS)

    Schlanger, Seymour O.; Jenkyns, Hugh C.; Premoli-Silva, Isabella

    1981-02-01

    The dominance of volcanic processes and the importance of vertical tectonics in the geological evolution of the Pacific Basin has been recognised since the time of Charles Darwin. Data gathered on several legs of the Deep Sea Drilling Project (DSDP) and numerous marine expeditions in the past decade have confirmed Menard's postulate that the Pacific Basin was the scene of volcanism on an enormous scale in Mesozoic time. Widespread mid-plate volcanism between ˜110 and 70 m.y. B.P. characterised the area bounded by the Line Islands, the Mid-Pacific Mountains and the Nauru Basin-Marshall Islands. Heating of the Pacific lithospheric plate during this period of volcanism resulted in regional uplift and the bathymetric evolution of the area diverged significantly from a "normal" Parsons-Sclater subsidence curve. The Farallon plate, now almost entirely subducted, was also the scene of mid-plate volcanism that produced such features as the Nicoya Plateau now found as an allochthonous ophiolitic terrain landward of the middle America trench. Large, benthonic, reef-associated foraminifera comprising a pseudorbitoid fauna, hitherto considered to be largely restricted to Central America, have now been additionally recorded from DSDP Sites 165, 315 and 316 in the Line Islands, Site 462 in the Nauru Basin, and in New Guinea. The distribution of this fauna, of Campanian/Maastrichtian age, is interpreted as indicating "stepping stone" connections (aseismic ridges, plateaus and seamounts) between the Caribbean, Farallon, and Pacific plates 70-80 m.y. B.P. Similarities between the geology of the Nauru Basin and the Caribbean Ocean crust reinforce the interpretation of the latter as a former part of the Farallon plate. Estimates of the sea-level and continental freeboard change caused by the thermally induced uplift of the Pacific and Farallon plates, as well as substantial areas in the Atlantic and Indian Ocean Basins, indicate that such shallowing of the sea floor could have been the major factor in causing global Cretaceous transgressions.

  4. [The biological plate osteosynthesis].

    PubMed

    Gautier, E; Ganz, R

    1994-01-01

    The continually evolving understanding of bone biology and the analysis of clinical complications have led to a modified approach in internal fixation using plates. Anatomical reduction of the fragments in comminuted diaphyseal and metaphyseal fractures itself is no longer a goal. Important reduction aims are the correct length of the bone, and axial and torsional alignment. The preservation of the viability of the bone fragments is the key to unimpaired fracture healing. The primary stability of an osteosynthesis seems to be of minor importance for bone healing. More important is the rapid integration of unreduced but vital fragments into the fracture callus which buttresses the fracture area opposite the plate reducing the risk for overload and fatigue failure of the implant. Additional primary bone grafting leeds to local vascular disturbance of the bone and is rarely indicated. Indirect reduction technique with the aid of the fracture table or the distractor and a minimal but optimal use of implant material is the new concept to achieve undisturbed fracture repair in metaphyseal and diaphyseal fractures. In articular fractures the anatomic restoration of the articular surface can be obtained by the combination of indirect reduction technique (ligamentotaxis, soft tissue taxis) and accurate direct reduction of certain strategic fragments. Modifications of the plate design (limited contact, point contact) which minimize additional vascular damage to the bone help to accomplish this new concept. PMID:7975946

  5. Discovering Plate Boundaries

    NSDL National Science Digital Library

    Dale Sawyer

    1997-09-15

    Discovering Plate Boundaries is based on 5 world maps containing earthquake, volcano, topography, satellite gravity, and seafloor age data. The novel aspect of the exercise is the "jigsaw" manner in which student groups access the maps and use them to discover, classify, and describe plate boundary types. The exercise is based only on observation and description, which makes it useful at a wide variety of levels; it has been used successfully in 5th grade classes, as well as in non-major earth science classes. The exercise is based on a set of wall maps that are not consumed during the exercise. Other inexpensive materials required include two 11x17 black and white copies per student and colored pencils. Because the exercise is not based on student access to the web, it is not dependent on classroom technology equipment. The exercise takes three 50-minute class periods to complete, and involves the students in making presentations to one another in small groups as well as to the whole class. The students come away from the exercise with knowledge of the key features of each type of plate boundary and a sense of why each looks and acts the way it does.

  6. Azimuthal anisotropy layering in the Pacific upper mantle

    NASA Astrophysics Data System (ADS)

    Yuan, H.; French, S. W.; Romanowicz, B. A.

    2013-12-01

    As the mechanically strong outer layer of the Earth, the lithosphere is a fundamental component in plate tectonics. Resolving the internal structure of the lithosphere and underlying asthenosphere, as well as the coupling between the two, is critical for our understanding of the formation, stabilization and subsequent deformation of continents and oceans. One key aspect of the problem, identified as one of the Grand Challenges of modern seismology, is the thickness of lithosphere, or the depth of the lithosphere-asthenosphere-boundary (LAB). Seismic detection of the LAB, however, remains 'elusive', possibly due to the smooth character of the seismic velocity gradient across the boundary. In continents recent surface wave studies have proven azimuthal anisotropy a powerful tool in revealing the internal structure of the continental lithosphere and its boundary with the asthenosphere (e.g. Yuan and Romanowicz, 2010). Here we expand our regional waveform inversion to the much greater size Pacific region, focusing on the 3D anisotropic structure of the oceanic upper mantle. Specifically, we look for the anisotropy stratification signal beneath the ocean basins, and correlate it with simultaneously inverted isotropic shear velocities to infer the structure of the Pacific oceanic lithosphere and asthenosphere, and the LAB topography throughout the region. Our results show a strong age progressive pattern in isotropic shear velocity, radial anisotropy and azimuthal anisotropy. Two domains of azimuthal anisotropy are observed in the upper 250 km, each possessing a distinct fast axis direction of anisotropy. An anisotropic LAB is drawn in the Pacific, which maps the rapid depth variation of fast axis directions toward the current absolute plate direction. At slightly shallower depth, an isotropic shear velocity horizon is robustly defined throughout the ocean basin, based on maximum negative velocity gradients with respect to depth. We argue that the offset between the two horizons reflects differences in the thermal and chemical properties of the Pacific oceanic lithosphere.

  7. 78 FR 12015 - Western Pacific Fisheries; Fishing in the Marianas Trench, Pacific Remote Islands, and Rose Atoll...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-21

    ...0648-BA98 Western Pacific Fisheries; Fishing in the Marianas Trench, Pacific Remote...proposes to establish requirements for fishing in the Marianas Trench, Pacific Remote...and western Pacific pelagic fisheries. Fishing regulations for the western Pacific...

  8. 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.

  9. 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).

  10. 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.

  11. 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.

  12. The Theory of Plate Tectonics

    NSDL National Science Digital Library

    This is a brief overview of the Theory of Plate Tectonics. According to the theory, the Earth's surface layer, or lithosphere, consists of seven large and 18 smaller plates that move and interact in various ways. Along their boundaries, they converge, diverge, and slip past one another, creating the Earth's seismic and volcanic activities. These plates lie atop a layer of partly molten rock called the asthenosphere. The plates can carry both continents and oceans, or exclusively one or the other. The site also explains interaction at the plate boundaries, which causes earthquakes, volcanoes and other forms of mountain building.

  13. 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.

  14. Using plate mapping to examine portion size and plate composition for large and small divided plates.

    PubMed

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

    2014-12-01

    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 vegetables - differently? To examine this question, we used the new method of plate mapping, 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, which showed that 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 that plate size may influence portion size and change the proportions of foods served. PMID:25280373

  15. Fuel cell end plate structure

    DOEpatents

    Guthrie, Robin J. (East Hartford, CT); Katz, Murray (Newington, CT); Schroll, Craig R. (Glastonbury, CT)

    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.

  16. 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.

  17. Canadian Pacific Railway Collection

    NSDL National Science Digital Library

    2005-01-01

    The Canadian Pacific Railway collection provides access to over 1500 images documenting the company's activities all around British Columbia from the 1880s to the 1950s. The pictures portray railway stations both urban and rural, along with images of workers, buildings, hotels, ships, and yards that were part of the railroad's vast empire. Visitors can click on the Collection area to get started and the search function is another good way to focus in on items of interest. Within the History tab is an elegant and well-developed essay on the company, complete with illustrative images while the Photographers section provides great insight into who exactly took these pictures. And, of course, casual users may just wish to click on the Gallery to get a sampling of the works that make up this archive.

  18. Decoupling of Pacific subduction zone guided waves beneath central Japan: Evidence for thin slab

    NASA Astrophysics Data System (ADS)

    Padhy, Simanchal; Furumura, Takashi; Maeda, Takuto

    2014-11-01

    The fine-scale seismic structure of the northeast Japan subduction zone is studied based on waveform analyses of moderate-sized (M4.5-6), deep-focus earthquakes (h >350 km) and the finite difference method (FDM) simulation of high-frequency (up to 8 Hz) wave propagation. Strong regional S wave attenuation anomalies for specific source-receiver paths connecting the cluster of events occurring in central part of the Sea of Japan recorded at fore arc stations in northern and central Japanese Islands (Honshu) are used to model the deeper structure of the subducting Pacific Plate, where recent teleseismic tomography has shown evidence for a possible slab tear westward beneath the Sea of Japan. The character of the observed anomalous S wave attenuation and the following high-frequency coda can be captured with the two-dimensional (2-D) FDM simulation of seismic waves in heterogeneous plate model, incorporating the thinning of the plate at depth, which is also compared with other possible causes of dramatic attenuation of high-frequency S wave due to low-Q or much weaker heterogeneities in the slab. The results of simulation clearly demonstrate that the dramatic loss of high-frequency S wavefield from the plate into the surrounding mantle occurred due to the variation in the plate geometry (i.e., thinning of the plate) at depth near the source rather than due to variation in physical properties, such as due to the lowered-Q and weaker heterogeneities in the plate. The presence of such a thin zone defocuses the high-frequency slab-guided S wave energy from the subducting plate into the surrounding mantle and acts as a geometric antiwaveguide. Based on the sequence of simulation results obtained, we propose thinning of Pacific Plate at depth subducting beneath northeastern Japan, localized to central part of Honshu, in agreement with the observations.

  19. Introduction The Pacific hake (Merluccius produc-

    E-print Network

    69(1­ 4) 1 Introduction The Pacific hake (Merluccius produc- tus Ayres 1855, also known as Pacific at 2.5 mil- lion metric tons (t) (Helser and Martell, Pacific Hake, Merluccius productus, Autecology and Oceans Canada. ABSTRACT--Pacific hake, Merluccius productus, the most abundant groundfish

  20. Maori and Pacific Master's Scholarships Are you a Maori or Pacific student looking to

    E-print Network

    Auckland, University of

    the impact of health issues on Maori and Pacific peoples, from a Maori/Pacific perspective interest you? YesMaori and Pacific Master's Scholarships Are you a Maori or Pacific student looking to undertake of scholarships for Maori and Pacific students for work on various smoking-related projects next year. We

  1. Analysis on interfacial reactions between Sn–Zn solders and the Au\\/Ni electrolytic-plated Cu pad

    Microsoft Academic Search

    Kyung-Seob Kim; Jun-Mo Yang; Chong-Hee Yu; In-Ok Jung; Heon-Hee Kim

    2004-01-01

    Interface reactions between Sn–Zn lead-free solders and the Au\\/Ni electrolytic-plated Cu pad after isothermal aging were investigated. The intermetallic compounds at the interface between solder and the Au\\/Ni electrolytic-plated Cu pad were examined by field-emission scanning electron microscopy and transmission electron microscopy. During the reflow, Zn firstly reacted with Au and then was transformed to the ?-AuZn (cubic phase, JCPDS

  2. IPRC: International Pacific Research Center

    NSDL National Science Digital Library

    The International Pacific Research Center's (IPRC) website addresses "climate variation and predictability in the Asia-Pacific region, including regional aspects of global environmental change." The site offers the goals and objectives of the research activities in IPRC's four main themes: Indo-Pacific Ocean Climate, Regional Ocean Influences, Asian-Australian Monsoon System, and Impacts of Global Environmental Change. Visitors can find information on the people involved with IPRC, its international meetings and workshops, the latest news, and potential employment opportunities. The website offers downloads of IPRC's annual reports, its semiannual newsletter, _Climate_, and workshop publications.

  3. The Fight Over Pacific Salmon

    NSDL National Science Digital Library

    Payne, Laura X.

    1998-01-01

    This week's In The News focuses on the recently heightened, ongoing US-Canada controversy over fishing rights. Since the expiration of the Pacific Salmon Treaty in 1994, the United States and Canada have been unable to agree on salmon catch quotas in the north Pacific. With the opening of the fishing season on July 1, 1998, newspapers reported tension at the docks and rumors of protests in British Colombia. The twelve resources listed offer background information on Pacific Salmon and the salmon fisheries controversy, and include several US and Canadian perspectives.

  4. Effect of interlayer thickness on shear deformation behavior of AA5083 aluminum alloy\\/SS41 steel plates manufactured by explosive welding

    Microsoft Academic Search

    Jun Hyun Han; Jae Pyoung Ahn; Myung Chul Shin

    2003-01-01

    An AA5083 aluminum alloy plate and an SS41 steel plate were cladded by an explosive welding method using an AA1050 aluminum alloy interlayer plate. The effects of the interlayer thickness on the interface morphology and the shear deformation behavior of the cladded plates were studied. The interfacial zone was composed of an intermetallic compound, FeAl3, formed by the AA1050 interlayer.

  5. Phanerozoic tectonic evolution of the Circum-North Pacific

    USGS Publications Warehouse

    Nokleberg, Warren J.; Parfenov, Leonid M.; Monger, James W.H.; Norton, Ian O.; Khanchuk, Alexander I.; Stone, David B.; Scotese, Christopher R.; Scholl, David W.; Fujita, Kazuya

    2000-01-01

    The Phanerozoic tectonic evolution of the Circum-North Pacific is recorded mainly in the orogenic collages of the Circum-North Pacific mountain belts that separate the North Pacific from the eastern part of the North Asian Craton and the western part of the North American Craton. These collages consist of tectonostratigraphic terranes that are composed of fragments of igneous arcs, accretionary-wedge and subduction-zone complexes, passive continental margins, and cratons; they are overlapped by continental-margin-arc and sedimentary-basin assemblages. The geologic history of the terranes and overlap assemblages is highly complex because of postaccretionary dismemberment and translation during strike-slip faulting that occurred subparallel to continental margins.We analyze the complex tectonics of this region by the following steps. (1) We assign tectonic environments for the orogenic collages from regional compilation and synthesis of stratigraphic and faunal data. The types of tectonic environments include cratonal, passive continental margin, metamorphosed continental margin, continental-margin arc, island arc, oceanic crust, seamount, ophiolite, accretionary wedge, subduction zone, turbidite basin, and metamorphic. (2) We make correlations between terranes. (3) We group coeval terranes into a single tectonic origin, for example, a single island arc or subduction zone. (4) We group igneous-arc and subduction- zone terranes, which are interpreted as being tectonically linked, into coeval, curvilinear arc/subduction-zone complexes. (5) We interpret the original positions of terranes, using geologic, faunal, and paleomagnetic data. (6) We construct the paths of tectonic migration. Six processes overlapping in time were responsible for most of the complexities of the collage of terranes and overlap assemblages around the Circum-North Pacific, as follows. (1) During the Late Proterozoic, Late Devonian, and Early Carboniferous, major periods of rifting occurred along the ancestral margins of present-day Northeast Asia and northwestern North America. The rifting resulted in the fragmentation of each continent and the formation of cratonal and passive continental-margin terranes that eventually migrated and accreted to other sites along the evolving margins of the original or adjacent continents. (2) From about the Late Triassic through the mid-Cretaceous, a succession of island arcs and tectonically paired subduction zones formed near the continental margins. (3) From about mainly the mid-Cretaceous through the present, a succession of igneous arcs and tectonically paired subduction zones formed along the continental margins. (4) From about the Jurassic to the present, oblique convergence and rotations caused orogenparallel sinistral and then dextral displacements within the upper-plate margins of cratons that have become Northeast Asia and North America. The oblique convergences and rotations resulted in the fragmentation, displacement, and duplication of formerly more nearly continuous arcs, subduction zones, and passive continental margins. These fragments were subsequently accreted along the expanding continental margins. (5) From the Early Jurassic through Tertiary, movement of the upper continental plates toward subduction zones resulted in strong plate coupling and accretion of the former island arcs and subduction zones to the continental margins. Accretions were accompanied and followed by crustal thickening, anatexis, metamorphism, and uplift. The accretions resulted in substantial growth of the North Asian and North American Continents. (6) During the middle and late Cenozoic, oblique to orthogonal convergence of the Pacifi c plate with present-day Alaska and Northeast Asia resulted in formation of the modern-day ring of volcanoes around the Circum-North Pacific. Oblique convergence between the Pacific plate and Alaska also resulted in major dextral-slip faulting in interior and southern Alaska and along the western p

  6. Plates on the Move

    NSDL National Science Digital Library

    In this activity, students create a model of sea floor spreading using two sheets of white paper and a metric ruler. The paper strips are pulled through a slit representing a mid-ocean ridge and divergent plate boundary. The model mimics how molten material rises to the surface and then spreads out in both directions. The resource is part of the teacher's guide accompanying the video, NASA SCI Files: The Case of the Shaky Quake. Lesson objectives supported by the video, additional resources, teaching tips and an answer sheet are included in the teacher's guide.

  7. Tethered Triangular Plate

    NSDL National Science Digital Library

    Zhang, Zhenli

    2005-01-31

    Simulation Software: Glotzer Group Code Simulation Method: Brownian Dynamics BD simulation of polymer tethered triangular plates. A system of building blocks of composition P10bT18b at a concentration of 0.20, was run starting at an effectively infinite temperature then instantaneously quenched to a temperature of 0.83. The system was then run for 12,000,000 time steps forming a hexagonally packing twisted columnar phase.The solve was favorable for the tethers. Simulation Model: United Atom Bead Spring with Lennard-Jones and FENE

  8. Dynamics of Tectonic Plates

    E-print Network

    Pechersky, E; Sadowski, G; Yambartsev, A

    2014-01-01

    We suggest a model that describes a mutual dynamic of tectonic plates. The dynamic is a sort of stick-slip one which is modeled by a Markov random process. The process defines a microlevel of the dynamic. A macrolevel is obtained by a scaling limit which leads to a system of integro-differential equations which determines a kind of mean field systems. Conditions when Gutenberg-Richter empirical law are presented on the mean field level. These conditions are rather universal and do not depend on features of resistant forces.

  9. Flat plate solar collectors

    NASA Astrophysics Data System (ADS)

    Hussmann, E.

    1982-08-01

    Flat plate collectors of conventional design with high efficiency were developed. A special metal sheet fastened to the absorber led to a construction which is gas tight and tolerates no flow conditions. Such collectors have a long service life. The influence of the cover system on efficiency was investigated by computer simulation. The type of panel, the number and selective coatings on the panel or on the absorber were varied. Loads from the environment and operating loads e.g., pressure rise related to temperature rise and thermal stresses were analyzed, especially for cover systems and the bonding of the panels, to the absorber. Prototypes were built and tested.

  10. Plate Tectonics: Further Evidence

    NSDL National Science Digital Library

    Early evidence showing striking similarities between regions on opposite sides of vast oceans suggested that in Earth's distant past what are now separate continents may once have been connected. However, this evidence said nothing about how the continents could have moved to their present positions. This video shows how seafloor spreading creates new oceanic crust and how the crust is destroyed by subduction into Earth's mantle, providing the mechanism and forces that propel tectonic plates across Earth's surface. The segment is two minutes nine seconds in length.

  11. Earthquakes and Plate Tectonics

    NSDL National Science Digital Library

    2007-10-04

    This activity, from the Real World Learning Objects Resource Library, allows students to use first-hand data analysis to "determine if there is any pattern to earthquake events and speculate on the causes of earthquakes." Intended to be an introductory activity for a unit of study on earthquakes, this 60-minute activity is complete with learning goals, step-by-step classroom procedures, materials, assessment activities, and resources for further information. The "Content Materials" section contains directions for students and graphics to help students understand earthquakes and plate tectonics. This is an excellent resource for geology and earth science instructors that is ready to use for the classroom.

  12. Relationship between depth and age in the North Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Hillier, J. K.; Watts, A. B.

    2005-02-01

    The North Pacific contains active mid-oceanic ridges and the oldest, Jurassic (166.8 ± 4 Ma), drilled oceanic crust. Its bathymetry is therefore critical to studies of the applicability of thermal contraction models (e.g., the infinite half-space and cooling plate) to the subsidence of seafloor with crustal age. The bathymetry, however, contains seamounts and oceanic islands (e.g., Mid-Pacific Mountains), oceanic plateaus (e.g., Hess, Magellan, and Shatsky), and midplate topographic swells (e.g., Hawaii), which are unrelated to the current plate-scale thermal state of the oceanic lithosphere. We use here a regional-residual separation algorithm called MiMIC to remove these features and to isolate the depths associated with the subsidence of North Pacific oceanic crust. These depths, z (m), increase with time, t (Ma), as z = 3010 + 307? until 85 Ma. For greater ages the depths "flatten" and asymptotically approach ˜6.1 km and are well described by z = 6120 - 3010 exp(-0.026t). The flattening is not "abrupt" as recently described in z-t curves produced using the mean, median, and mode. As a result, the depths of both young and old seafloor are fit well (mean difference between and observed and calculated depths of 75 ± 54 m 1?) by a single cooling plate model. Using a thermal conductivity, k, of 3.138 mW m-2 as previous studies, however, gives a plate of similar thickness (i.e., thermal thickness, L, of ˜115 km) but one which is unreasonably hot (i.e., temperature at the base of the plate, Tb, of 1522 °C) and inexpansive (i.e., coefficient of thermal expansion, ?, of 2.57×10-5 °C-1). More reasonable values (i.e., Tb = 1363°C, k = 3.371 W m-1 °C-1, ? = 2.77×10-5 °C-1, and L = 120 km) are obtained if the crustal thickness is used to constrain Tb and a certain amount of the surface heat flow is allowed to be radiogenically generated within the oceanic lithosphere.

  13. Variations in oceanic plate bending along the Mariana trench

    NASA Astrophysics Data System (ADS)

    Zhang, Fan; Lin, Jian; Zhan, Wenhuan

    2014-09-01

    We quantify along-trench variations in plate flexural bending along the Mariana trench in the western Pacific Ocean. A 3-D interpreted flexural deformation surface of the subducting Pacific Plate was obtained by removing from the observed bathymetry the effects of sediment loading, isostatically-compensated topography based on gravity modeling, age-related lithospheric thermal subsidence, and residual short-wavelength features. We analyzed flexural bending of 75 across-trench profile sections and calculated five best-fitting tectonic and plate parameters that control the flexural bending. Results of analysis revealed significant along-trench variations: the trench relief varies from 0.9 to 5.7 km, trench-axis vertical loading (-V0) from -0.73×1012 to 3.17×1012 N/m, and axial bending moment (-M0) from 0.1×1017 to 2.7×1017 N. The effective elastic plate thickness seaward of the outer-rise region (TeM) ranges from 45 to 52 km, while that trench-ward of the outer-rise (Tem) ranges from 19 to 40 km. This corresponds to a reduction in Te of 21-61%. The transition from TeM to Tem occurs at a breaking distance of 60-125 km from the trench axis, which is near the outer-rise and corresponds to the onset of observed pervasive normal faults. The Challenger Deep area is associated with the greatest trench relief and axial vertical loading, while areas with seamounts at the trench axis are often associated with more subtle trench relief, smaller axial vertical loading, and greater topographic bulge at the outer-rise.

  14. Anomalous deepening of a belt of intraslab earthquakes in the Pacific slab crust under Kanto, central Japan: Possible anomalous thermal shielding, dehydration reactions, and seismicity caused by shallower cold slab material

    USGS Publications Warehouse

    Hasegawa, A.; Nakajima, J.; Kita, S.; Okada, T.; Matsuzawa, T.; Kirby, S.H.

    2007-01-01

    A belt of intraslab seismicity in the Pacific slab crust parallel to iso-depth contours of the plate interface has been found beneath Hokkaido and Tohoku. Hypocenter relocations have shown that this seismic belt does not run parallel to but obliquely to the iso-depth contours beneath Kanto, deepening toward the north from ???100 km to ???140 km depth. The depth limit of the contact zone with the overlying Philippine Sea slab is located close to and parallel to this obliquely oriented seismic belt, suggesting that the deepening of the seismic belt there is caused by the contact with the overlying slab. The contact with this cold slab hinders the heating of the Pacific slab crust by hot mantle wedge, which would cause delay of eclogite-forming phase transformations and hence deepening of the seismic belt there. The depth limit of the subducting low-velocity crust also deepens toward the north, supporting this idea. Copyright 2007 by the American Geophysical Union.

  15. 20. 'Portals and Gusset Plates for 3 180'61/2' c. ...

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

    20. 'Portals and Gusset Plates for 3 - 180'-6-1/2' c. to c. End Pins Single Track Through Spans, 10th, 11th, & 13th Crossings of Sacramento River, Southern Pacific Co. Sacramento Division, The Phoenix Bridge Co., C.O's. 839, 840 & 841, Drawing #12, Engineer C. Scheidl, Draftsman B. Heald, Scale 1-1/2' = 1'0', April 16th, 1901.' - Southern Pacific Railroad Shasta Route, Bridge No. 310.58, Milepost 310.58, Sims, Shasta County, CA

  16. 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.

  17. PACIFIC SOUTHWEST Forest and Range

    E-print Network

    Standiford, Richard B.

    PACIFIC SOUTHWEST Forest and Range Experiment Station FOREST SERVICE. U. S. DEPARTMENT;"Rest-Rotation Grazing at Harvey Valley...range, health, cattle gains, costs," by Raymond D, Ratliff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Trends in Range Health and Condition . . . . . . . . . . . . . . . . . . . . . . . . . 5

  18. Spreading behaviour of the Pacific-Farallon ridge system since 83 Ma

    NASA Astrophysics Data System (ADS)

    Rowan, Christopher J.; Rowley, David B.

    2014-06-01

    We present improved rotations, complete with uncertainties, for the Pacific-Farallon Ridge (PFR) between geomagnetic chrons 34y (83 Ma) and 10y (28.28 Ma). Despite substantial shortening since ˜55 Ma, this ridge system and its remnants (e.g. the East Pacific Rise) have produced as much as 45 per cent of all oceanic lithosphere created since the Late Cretaceous, but reconstructions face the twin challenges of extensive subduction of Farallon crust-which precludes reconstruction by fitting conjugate magnetic anomaly and fracture zone (FZ) traces-and asymmetric spreading behaviour for at least the past 51 Myr. We have calculated best-fit `half'-angle stage rotations between nine geomagnetic chron boundaries (34y, 33y, 29o, 24.3o, 20o, 18.2o, 17.1y, 13y and 10y) using combined anomaly and FZ data from both the northern and southern Pacific Plate. For rotations younger than chron 24.3o, estimates for spreading asymmetry, derived using anomaly picks from yet-to-be subducted Farallon/Nazca crust in the south Pacific, allow full stage rotations to be calculated. Between 50 and 83 Ma, where no direct constraints on spreading asymmetry are possible, a `best-fit' full stage rotation was calculated based on the net Nazca:Pacific spreading asymmetry (Pacific spreading fraction fPAC = 0.44) over the past 50 Myr, with conservative lower and upper bounds, based on variability in the degree of spreading asymmetry over periods of <15 Myr, assuming fPACs of 0.5 and 0.36, respectively. Synthetic flowlines generated from our new stage rotation produce a better match to Pacific FZ trends than previously published rotations. With the exception of the chron 18o-20o rotation, the six stage poles for rotations between chrons 33y and 13y (74-33 Ma) all cluster tightly at 60-75°E, 60-68°N, consistent with the relatively constant trend of the major Pacific FZs. This stability spans at least one episode of Farallon Plate fragmentation caused by subduction of PFR segments beneath the Americas, at 55-48 Ma, which appears to have greatly accelerated divergence on the surviving ridge without significantly affecting the location of the instantaneous rotation pole. Together with quasi-periodic 15-20 Myr variations in the degree of spreading asymmetry that also appear to correlate with changes in spreading rate, this indicates that forces other than slab pull may be a factor in determining Pacific-Farallon Plate motions.

  19. The science behind Plate Tectonics

    NSDL National Science Digital Library

    John Weber

    Plate tectonics is a quantitative, robust and testable, geologic model describing the surface motions of Earth's outer skin. It is based on real data and assumptions, and built using the scientific method. New space geodesy data provide important quantitative (and independent) tests of this model. In general, these new data show a close match to model predictions, and suggest that plate motion is steady and uniform over millions of years. Active research continues to refine the model and to better our understanding of plate motion and tectonics. The exercise presented here aims to help students experience the process of doing science and to understand the science underlying the plate tectonic theory. Key words: plate tectonics, global plate motion models, assumptions, geologic data (spreading rates, transform fault azimuths, earthquake slip vectors), space geodesy tests.

  20. Laser-based characterization of nuclear fuel plates

    NASA Astrophysics Data System (ADS)

    Smith, James A.; Cottle, Dave L.; Rabin, Barry H.

    2014-02-01

    Ensuring the integrity of fuel-clad and clad-clad bonding in nuclear fuels is important for safe reactor operation and assessment of fuel performance, yet the measurement of bond strengths in actual fuels has proved challenging. The laser shockwave technique (LST) originally developed to characterize structural adhesion in composites is being employed to characterize interface strength in a new type of plate fuel being developed at Idaho National Laboratory (INL). LST is a non-contact method that uses lasers for the generation and detection of large-amplitude acoustic waves and is well suited for application to both fresh and irradiated nuclear-fuel plates. This paper will report on initial characterization results obtained from fresh fuel plates manufactured by different processes, including hot isostatic pressing, friction stir welding, and hot rolling.

  1. Laser-based characterization of nuclear fuel plates

    SciTech Connect

    Smith, James A.; Cottle, Dave L.; Rabin, Barry H. [Idaho National Laboratory, Fuel Performance and Design, P.O. Box 1625, Idaho Falls, Idaho, 83415-6188 (United States)

    2014-02-18

    Ensuring the integrity of fuel-clad and clad-clad bonding in nuclear fuels is important for safe reactor operation and assessment of fuel performance, yet the measurement of bond strengths in actual fuels has proved challenging. The laser shockwave technique (LST) originally developed to characterize structural adhesion in composites is being employed to characterize interface strength in a new type of plate fuel being developed at Idaho National Laboratory (INL). LST is a non-contact method that uses lasers for the generation and detection of large-amplitude acoustic waves and is well suited for application to both fresh and irradiated nuclear-fuel plates. This paper will report on initial characterization results obtained from fresh fuel plates manufactured by different processes, including hot isostatic pressing, friction stir welding, and hot rolling.

  2. Laser-Based Characterization of Nuclear Fuel Plates

    SciTech Connect

    James A. Smith; David L. Cottle; Barry H. Rabin

    2013-07-01

    Ensuring the integrity of fuel-clad and clad-clad bonding in nuclear fuels is important for safe reactor operation and assessment of fuel performance, yet the measurement of bond strengths in actual fuels has proved challenging. The laser shockwave technique (LST) originally developed to characterize structural adhesion in composites is being employed to characterize interface strength in a new type of plate fuel being developed at Idaho National Laboratory (INL). LST is a non-contact method that uses lasers for the generation and detection of large-amplitude acoustic waves and is well suited for application to both fresh and irradiated nuclear-fuel plates. This paper will report on initial characterization results obtained from fresh fuel plates manufactured by different processes, including hot isostatic pressing, friction stir welding, and hot rolling.

  3. Effect of Decoupling of Lithospheric Plates on the Observed Geoid

    NASA Astrophysics Data System (ADS)

    Kaban, Mikhail K.; Petrunin, Alexey G.; Schmeling, Harro; Shahraki, Meysam

    2014-11-01

    A joint effect of weak zones, dividing lithospheric plates, and lateral viscosity variations (LVV) in the whole mantle on the observed geoid is investigated by a new numerical approach. This technique is based on the substantially revised method introduced by Zhang and Christensen (Geophys J Int 114:531-547, 1993) for solving the Navier-Stokes-Poisson equations in the spectral domain with strong LVV. Weak plate boundaries (WPB) are introduced based on an integrated global model of plate boundary deformations GSRM (Kreemer et al. in Geophys J Int 154:8-34, 2003). The effect of WPB on the geoid is significant and reaches -40 to 70 m with RMS ~20 m. The peaks are observed over large subduction zones in South America and the southwestern Pacific in agreement with previous studies. The positive geoid anomaly in South America could be explained largely by a dynamic effect of decoupling of the Nazca and South American plates. The negative changes of the geoid mostly relate to mid-oceanic ridges. The amplitude of the effect depends on the viscosity contrasts at WPB compared with the plate viscosity until its value reaches the limit of 2.5-3 orders of magnitude. This value might be considered as a level at which the plates are effectively decoupled. The effect of WPB exceeds the effect of LVV in the whole mantle and generally does not correlate with it. However, inclusion of LVV reduces the geoid perturbations due to WPB by about 10 m. Therefore, it is important to consider all factors together. The geoid changes mainly result from changes of the dynamic topography, which are about -300 to +500 m. The obtained results show that including WPB may significantly improve the reliability of instantaneous global dynamic models.

  4. Sharp Lithosphere-asthenosphere Boundaries of Oceanic Plates

    NASA Astrophysics Data System (ADS)

    Kawakatsu, H.; Kumar, P.; Shinohara, M.; Kanazawa, T.; Araki, E.; Suyehiro, K.

    2008-12-01

    P- and S-receiver function (RF) analysis of borehole broadband ocean bottom seismic data (Kumar et al., 2008, this meeting) and the high-resolution RF image of the subducting Pacific plate beneath the northeast Japan (Kawakatsu, 2008, this meeting) both show the presence of sharp lithosphere-asthenosphere boundaries (LABs) of oceanic plates which appear to show dependence on the plate age. The apparent plate-age dependence of the thickness of the oceanic plate is consistent with a thermally controlled origin for the oceanic LAB, but the fact it is observed in short period (~3s) indicates a sharp boundary (the transition thickness of less than 10-15km), thus a chemical or fabric origin. The observed amplitude of the LAB signals, on the other hand, requires a rather large S-wave speed reduction of ~7%, similar to the observation beneath the eastern North America (Rychert et al., 2007, JGR). One possibility to explain these features is the presence of partial melting in the asthenosphere. The depth of partial melting of the model of Mierdel et al. (2007, Science) estimated using a thermal model incorporating pressure and thermal effect on the thermal diffusivity (Honda&Yuen, 2001, GRL) reproduces the basic trend in the data. For a texturally equilibrated partially molten region, however, a 7% S-wave speed reduction translates into ~3.5% of melting (Takei, 2002, JGR) which may be unrealistically large. The presence of the rather strong LAB signal of oceanic plates reported here may be partly attributed to other mechanisms such as the presence of shear zone of partially-molten region in the asthenosphere (e.g., Holtzman et al., 2003, Science).

  5. Wave energy: a Pacific perspective.

    PubMed

    Paasch, Robert; Ruehl, Kelley; Hovland, Justin; Meicke, Stephen

    2012-01-28

    This paper illustrates the status of wave energy development in Pacific rim countries by characterizing the available resource and introducing the region's current and potential future leaders in wave energy converter development. It also describes the existing licensing and permitting process as well as potential environmental concerns. Capabilities of Pacific Ocean testing facilities are described in addition to the region's vision of the future of wave energy. PMID:22184673

  6. Rehabilitation services for the Pacific.

    PubMed Central

    Fitzgerald, M H; Barker, J C

    1993-01-01

    The Pacific Basin Rehabilitation Research and Training Center was created to help meet the challenges of rehabilitating people in rural remote communities in the United States-associated Pacific. We describe the center, the special region it serves, some of its many programs, and some of the ways it is helping communities in this region provide services that are appropriate and sensitive to the culture, the environment, and the disability. PMID:8351905

  7. Plate T-11: Appalachian Mountains

    NSDL National Science Digital Library

    Appalachian Mountain landforms clearly demonstrate the relation of plate tectonics and structure to geomorphology. The folded rocks record the convergence of two continental plates in Pennsylvanian/Permian time. This page uses text, maps, and remotely sensed imagery to explain the relationship between plate tectonics, geologic structures, and the resulting landforms. It is part of an out-of-print NASA publication entitled 'Geomorphology from Space'. Links to the rest of the book are provided.

  8. Global Topography and Tectonic Plates

    NSDL National Science Digital Library

    David Greene

    The goal of this activity is to investigate global topographic and tectonic features, especially the tectonic plates and their boundaries. Using a double-page size digital topographic map of the Earth that includes both land and sea floor topography, students are asked to draw plate boundaries, deduce plate motions and interactions, and explore the connections between topography and tectonic processes at the global scale.

  9. Tectonic Plate Movements and Hotspots

    NSDL National Science Digital Library

    Ken Rhinehart

    This lesson introduces the idea that rates and directions of plate movements can be measured. The discussion centers on the use of mantle 'hotspots' to determine plate motions. Examples include the Hawaiian Islands, the Galapagos Islands, and the Yellowstone hotspot. The lesson includes an activity in which students use online resources to answer questions about the Galapagos Islands and measure plate movement rates using online data for the Hawaiian Islands hotspot.

  10. Ion plating for the future

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1981-01-01

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

  11. Seismic evidence for sharp lithosphere-asthenosphere boundaries of oceanic plates.

    PubMed

    Kawakatsu, Hitoshi; Kumar, Prakash; Takei, Yasuko; Shinohara, Masanao; Kanazawa, Toshihiko; Araki, Eiichiro; Suyehiro, Kiyoshi

    2009-04-24

    The mobility of the lithosphere over a weaker asthenosphere constitutes the essential element of plate tectonics, and thus the understanding of the processes at the lithosphere-asthenosphere boundary (LAB) is fundamental to understand how our planet works. It is especially so for oceanic plates because their relatively simple creation and evolution should enable easy elucidation of the LAB. Data from borehole broadband ocean bottom seismometers show that the LAB beneath the Pacific and Philippine Sea plates is sharp and age-dependent. The observed large shear wave velocity reduction at the LAB requires a partially molten asthenosphere consisting of horizontal melt-rich layers embedded in meltless mantle, which accounts for the large viscosity contrast at the LAB that facilitates horizontal plate motions. PMID:19390042

  12. Carbon-assisted flyer plates

    DOEpatents

    Stahl, David B. (Los Alamos, NM); Paisley, Dennis L. (Santa Fe, NM)

    1994-01-01

    A laser driven flyer plate utilizing an optical fiber connected to a laser. The end of the optical fiber has a layer of carbon and a metal layer deposited onto it. The carbon layer provides the laser induced plasma which is superior to the plasma produced from most metals. The carbon layer plasma is capable of providing a flatter flyer plate, converting more of the laser energy to driving plasma, promoting a higher flyer plate acceleration, and providing a more uniform pulse behind the plate. In another embodiment, the laser is in optical communication with a substrate onto which a layer of carbon and a layer of metal have been deposited.

  13. Statistical tests of additional plate boundaries from plate motion inversions

    Microsoft Academic Search

    Seth Stein; R. G. Gordon

    1984-01-01

    The application of the F-ratio test, a standard statistical technique, to the results of relative plate motion inversions has been investigated. The method tests whether the improvement in fit of the model to the data resulting from the addition of another plate to the model is greater than that expected purely by chance. This approach appears to be useful in

  14. Isabella Anomaly: Lithospheric drip, delamination or fragment of the Farallon plate?

    NASA Astrophysics Data System (ADS)

    Forsyth, D. W.; Rau, C. J.

    2009-12-01

    The Isabella Anomaly or Central Valley Anomaly in California is perhaps the best known example of a high seismic velocity anomaly that has been interpreted as a lithospheric instability. High P and S velocities extend to a depth of at least 150 km and perhaps to several hundred km in a nearly cylindrical region 100-150 km across. The amplitude of the anomaly in the upper 200 km is similar to that of the subducted Gorda plate. This anomaly has been variously interpreted as a convective drip or as a remnant of the lithosphere delaminated from beneath the eastern Sierra Nevada. We suggest instead that the Isabella anomaly may represent a fragment of the subducted Farallon plate that is still attached to the Pacific lithosphere. Directly seaward of the anomaly is the fossil Monterrey microplate, which is a remnant of the Farallon plate that was left when subduction ceased before the spreading center itself subducted. The microplate was then incorporated into the Pacific plate, but it is not clear how much of the subducting slab remained attached to the surface microplate. New Rayleigh wave tomographic images of Baja California show that there are still fragments of the Farallon plate remaining attached to the unsubducted Guadelupe and Magdelena microplate remnants, with anomalies extending down to at least 150 km. The geometry of these anomalies in relationship to the microplates is very similar to that of the Isabella anomaly. A major question with this interpretation is whether a bit of oceanic lithosphere extending down into the asthenosphere could be dragged along with the surface microplate/Pacific plate for 20 Ma since subduction ceased. Another anomaly similar to the Isabella anomaly begins in the shallow mantle beneath the northern end of San Francisco bay and dips to the west - another candidate for a lithospheric drip or convective instability?

  15. Plate Tectonics: Layered Earth

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2006-11-01

    This Science Object is the first of five Science Objects in the Plate Tectonics SciPack. It explores the characteristics of the various layers of the Earth, using the way waves travel through the different layers to illustrate the differences in each layer. The interior of the earth is hot, under high pressure from gravitational pull, and more dense than its rocky outer crust. The earth is layered with a relatively thin crust; hot, deformable mantle; liquid outer core; and solid, metallic, and dense inner core. Learning Outcomes:? Identify that Earth has layers (not necessarily name them), and that the interior is hotter and more dense than the crust.? Identify the crust as mechanically strong, and the underlying mantle as deformable and convecting.

  16. Mine roof support plate

    SciTech Connect

    White, C.C.

    1981-02-10

    A support plate is disclosed for a mine roof including a substantially flat body engageable with the mine roof, the body having an enlarged central opening through which are passed one end of a roof bolt on which is threaded an expansion shell which is inserted into a mine roof opening. Ribs extend longitudinally of the flat body on both sides of the central opening for additional strength. The ribs are spaced a predetermined distance apart on opposite sides of the central opening. Centering members are provided on the body portion intermediate the ribs on opposite sides of the central opening, the centering members and ribs serving to center the washer and bolt portion of the bolt assembly.

  17. Plate Tectonics: Earthquake Epicenter

    NSDL National Science Digital Library

    John Pratte

    This lesson provides an overview of destructive earthquakes and their connection to tectonic movements of the Earth's crust. It includes a discussion of some especially destructive historic earthquakes, and a brief introduction to contintental drift and the theory of plate tectonics. There is also discussion of basic seismology (types of waves) and measures of the magnitude of an earthquake (the Richter Scale). The lesson inlcudes an activity in which students use an online simulator to locate the epicenter of an earthquake using readings from three different seismograph stations. After they have completed the simulation, they attempt to locate the epicenter of a real earthquake using data from the United States Geological Survey (USGS) earthquake website.

  18. Precise hypocenter distribution and earthquake generating and stress in and around the upper-plane seismic belt in the subducting Pacific slab beneath NE Japan

    NASA Astrophysics Data System (ADS)

    Kita, S.; Okada, T.; Nakajima, J.; Matsuzawa, T.; Uchida, N.; Hasegawa, A.

    2007-12-01

    1. Introduction We found an intraslab seismic belt (upper-plane seismic belt) in the upper plane of the double seismic zone within the Pacific slab, running interface at depths of 70-100km beneath the forearc area. The location of the deeper limits of this belt appears to correspond to one of the facies boundaries (from jadeite lawsonite blueschist to lawsonite amphibole eclogite) in the oceanic crust [Kita et al., 2006, GRL]. In this study, we precisely relocated intraslab earthquakes by using travel time differences calculated by the waveform cross-spectrum analysis to obtain more detailed distribution of the upper plane-seismic belt within the Pacific slab beneath NE Japan. We also discuss the stress field in the slab by examining focal mechanisms of the earthquakes. 2. Data and Method We relocated events at depths of 50-00 km for the period from March 2003 to November 2006 from the JMA earthquake catalog. We applied the double-difference hypocenter location method (DDLM) by Waldhauser and Ellsworth (2000) to the arrival time data of the events. We use relative earthquake arrival times determined both by the waveform cross-spectrum analysis and by the catalog-picking data. We also determine focal mechanisms using the P wave polarity. 3. Spatial distribution of relocated hypocenters In the upper portion of the slab crust, seismicity is very active and distributed relatively homogeneously at depths of about 70-100km parallel to the volcanic front, where the upper-plane seismic belt has been found. In the lower portion of slab crust and/or the uppermost portion of the slab mantle, seismicity is spatially very limited to some small areas (each size is about 20 x 20km) at depths around 65km. Two of them correspond to the aftershock area of the 2003 Miyagi (M7.1) intraslab earthquake and that of the 1987 Iwaizumi (M6.6) intraslab earthquake, respectively. Based on the dehydration embrittelment hypothesis, the difference of the spatial distribution of the seismicity in the slab should correspond to the difference of the spatial distribution of the hydrated minerals and their dehydration reactions. In the upper slab crust, the upper-plane seismic belt is found because the hydrated minerals could be distributed homogeneously and the dehydration reaction (from jadeite lawsonite blueschist to lawsonite amphibole eclogite [Hacker et al., 2003b]) occurs perhaps largely at depth of 70-100km. Our result also suggests that in the lower portion of the slab crust and/or the uppermost portion of the slab mantle, the hydrated minerals could be inhomogeneously distributed and the seismicity occurs at depths around 65km, where another dehydration reaction may exist. 4. Characteristics of the focal mechanisms We examined the stress distribution within the slab by using focal mechanisms of the upper plane, interplane and lower plane events. From the plate interface to about 20 km below it, downdip-compressional (DC) type events are dominant. Below 20km from the plate interface, downdip-tensional (DT) type events are dominant. Many of interplane events have DC type focal mechanisms because of their locations in the uppermost portions of the slab mantle. These results indicate that the stress neutral plane from the DC type to DT type could be located at depth of about 20km from the plate interface.

  19. Plate tectonics, damage and inheritance.

    PubMed

    Bercovici, David; Ricard, Yanick

    2014-04-24

    The initiation of plate tectonics on Earth is a critical event in our planet's history. The time lag between the first proto-subduction (about 4?billion years ago) and global tectonics (approximately 3?billion years ago) suggests that plates and plate boundaries became widespread over a period of 1?billion years. The reason for this time lag is unknown but fundamental to understanding the origin of plate tectonics. Here we suggest that when sufficient lithospheric damage (which promotes shear localization and long-lived weak zones) combines with transient mantle flow and migrating proto-subduction, it leads to the accumulation of weak plate boundaries and eventually to fully formed tectonic plates driven by subduction alone. We simulate this process using a grain evolution and damage mechanism with a composite rheology (which is compatible with field and laboratory observations of polycrystalline rocks), coupled to an idealized model of pressure-driven lithospheric flow in which a low-pressure zone is equivalent to the suction of convective downwellings. In the simplest case, for Earth-like conditions, a few successive rotations of the driving pressure field yield relic damaged weak zones that are inherited by the lithospheric flow to form a nearly perfect plate, with passive spreading and strike-slip margins that persist and localize further, even though flow is driven only by subduction. But for hotter surface conditions, such as those on Venus, accumulation and inheritance of damage is negligible; hence only subduction zones survive and plate tectonics does not spread, which corresponds to observations. After plates have developed, continued changes in driving forces, combined with inherited damage and weak zones, promote increased tectonic complexity, such as oblique subduction, strike-slip boundaries that are subparallel to plate motion, and spalling of minor plates. PMID:24717430

  20. Plate tectonics, damage and inheritance

    NASA Astrophysics Data System (ADS)

    Bercovici, David; Ricard, Yanick

    2014-04-01

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

  1. Stability of active mantle upwelling revealed by net characteristics of plate tectonics.

    PubMed

    Conrad, Clinton P; Steinberger, Bernhard; Torsvik, Trond H

    2013-06-27

    Viscous convection within the mantle is linked to tectonic plate motions and deforms Earth's surface across wide areas. Such close links between surface geology and deep mantle dynamics presumably operated throughout Earth's history, but are difficult to investigate for past times because the history of mantle flow is poorly known. Here we show that the time dependence of global-scale mantle flow can be deduced from the net behaviour of surface plate motions. In particular, we tracked the geographic locations of net convergence and divergence for harmonic degrees 1 and 2 by computing the dipole and quadrupole moments of plate motions from tectonic reconstructions extended back to the early Mesozoic era. For present-day plate motions, we find dipole convergence in eastern Asia and quadrupole divergence in both central Africa and the central Pacific. These orientations are nearly identical to the dipole and quadrupole orientations of underlying mantle flow, which indicates that these 'net characteristics' of plate motions reveal deeper flow patterns. The positions of quadrupole divergence have not moved significantly during the past 250 million years, which suggests long-term stability of mantle upwelling beneath Africa and the Pacific Ocean. These upwelling locations are positioned above two compositionally and seismologically distinct regions of the lowermost mantle, which may organize global mantle flow as they remain stationary over geologic time. PMID:23803848

  2. Tribological characteristics of gold films deposited on metals by ion plating and vapor deposition

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    The graded interface between an ion-plated film and a substrate is discussed as well as the friction and wear properties of ion-plated gold. X-ray photoelectron spectroscopy (XPS) depth profiling and microhardness depth profiling were used to investigate the interface. The friction and wear properties of ion-plated and vapor-deposited gold films were studied both in an ultra high vacuum system to maximize adhesion and in oil to minimize adhesion. The results indicate that the solubility of gold on the substrate material controls the depth of the graded interface. Thermal diffusion and chemical diffusion mechanisms are thought to be involved in the formation of the gold-nickel interface. In iron-gold graded interfaces the gold was primarily dispersed in the iron and thus formed a physically bonded interface. The hardness of the gold film was influenced by its depth and was also related to the composition gradient between the gold and the substrate. The graded nickel-gold interface exhibited the highest hardness because of an alloy hardening effect. The effects of film thickness on adhesion and friction were established.

  3. Metal vapor arc ion plating

    DOEpatents

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

    1986-09-09

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

  4. The STAR Resistive Plate Chambers

    E-print Network

    Llope, William J.

    Plate Chamber Note 1: internal glass plates electrically floating - take and keep correct voltage, Clermont-Ferrand 2 Float Glass: Bakelite: Has a stable resistivity (hopping conductivity) =10.V. Pick-up electrode Mylar Carbon layer glass glass glass glass glass glass Mylar Carbon layer Pick

  5. Plate Tectonics: Recycling the Seafloor

    NSDL National Science Digital Library

    Lisa Ayers Lawrence

    2012-12-27

    In this activity, learners work in teams to predict and outline the location of plate boundaries using the National Oceanic and Atmospheric Administration's Acoustic Monitoring Program's underwater earthquake data. Then, learners compare their estimates to the USGS's map of the plates and discuss.

  6. Flexural waves on narrow plates.

    PubMed

    Norris, Andrew N

    2003-05-01

    Flexural wave speeds on beams or plates depend upon the bending stiffnesses which differ by the well-known factor (1 - nu2). A quantitative analysis of a plate of finite lateral width displays the plate-to-beam transition, and permits asymptotic analysis that shows the leading order dependence on the width. Orthotropic plates are analyzed using both the Kirchhoff and Kirchhoff-Rayleigh theories, and isotropic plates are considered for Mindlin's theory with and without rotational inertia. A frequency-dependent Young's modulus for beams or strips of finite width is suggested, although the form of the correction to the modulus is not unique and depends on the theory used. The sign of the correction for the Kirchhoff theory is opposite to that for the Mindlin theory. These results indicate that the different plate and beam theories can produce quite distinct behavior. This divergence in predictions is further illustrated by comparison of the speeds for antisymmetric flexural, or torsional, modes on narrow plates. The four classical theories predict limiting wave speeds as the plate width vanishes, but the values are different in each case. The deviations can be understood in terms of torsional waves and how each theory succeeds, or fails, in approximating the effect of torsion. Dispersion equations are also derived, some for the first time, for the flexural edge wave in each of the four "engineering" theories. PMID:12765383

  7. Plate Motions from Space Geodesy

    Microsoft Academic Search

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

    2001-01-01

    We determine GEODVEL (GEODesy VELocity model), a model of the angular velocities among 9 major plates, using observations from the global positioning system (GPS), very long baseline interferometry (VLBI), and satellite laser ranging (SLR). We assign sites to plates on the basis of geological observations: the distribution of major faults, the locations of large and historical earthquakes, other seismicity, and

  8. Plate Borders and Mountain Building

    NSDL National Science Digital Library

    Schlumberger Excellence in Educational Development, Inc.

    This page features animations of four different types of plate boundaries, including one animation of the collision of two pieces of continental crust, forming steep mountain ranges. The animations are all presented in flash, and the plate convergence offers a useful, generic view of orogeny.

  9. Solar panel flat plate collector

    Microsoft Academic Search

    1978-01-01

    A system is disclosed for collecting heat energy from solar radiation to heat a liquid medium. The system includes a solar radiation collector plate which has its rear face adapted to cause a liquid medium to be in direct thermal contact with the rear face of the plate while flowing over and covering essentially all of the rear face. According

  10. Present-day plate motions

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

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

  11. How Mantle Slabs Drive Plate Tectonics

    Microsoft Academic Search

    Clinton P. Conrad; Carolina Lithgow-Bertelloni

    2002-01-01

    The gravitational pull of subducted slabs is thought to drive the motions of Earth's tectonic plates, but the coupling between slabs and plates is not well established. If a slab is mechanically attached to a subducting plate, it can exert a direct pull on the plate. Alternatively, a detached slab may drive a plate by exciting flow in the mantle

  12. Plate tectonics, damage and inheritance

    NASA Astrophysics Data System (ADS)

    Bercovici, D. A.; Ricard, Y. R.

    2013-12-01

    The initiation of plate tectonics on Earth is a critical event in our planet's history. The time lag between the first proto subduction about 4Ga, evident in geochemical analysis from ancient cratons, to global tectonics by 3-2.7Ga, suggests that plates and plate boundaries spread globally over a 1Gyr period. We hypothesize that when sufficient lithospheric damage, which promotes shear-localization and long-lived weak zones, combines with transient mantle flow and migrating proto-subduction, it leads to the accumulation of plate boundaries and eventually fully formed tectonic plates driven by subduction alone. We demonstrate this process with an idealized model of pressure-driven flow (wherein a low pressure zone is equivalent to downwelling suction or slab pull) in a lithosphere that self-weakens according to a mylonitic-type polycrystalline grain-damage mechanism (Bercovici and Ricard, Phys. Earth Planet. Int. v.202-203, pp27-55, 2012). In the simplest case, for Earth-like conditions, four successive orthogonal rotations of the driving pressure field yield relic damage zones that are inherited to form a nearly perfect plate, with passive spreading and strike-slip margins that persist and localize further, even as flow is only driven by subduction. For Venus' hotter surface conditions, accumulation and inheritance of damage is negligible; hence only subduction zones survive and plate tectonics does not spread, which is compatible with observations. After plates are developed, continued changes in driving forces combined with inherited damage and weak zones, promote increased tectonic complexity, such as oblique subduction, strike-slip boundaries that are subparallel to plate motion, and spalling of minor and micro plates.

  13. 76 FR 9001 - Pacific Fishery Management Council (Pacific Council); March 4-10, 2011 Pacific Council Meetings

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-16

    ...Management 1. Report on the International Pacific Halibut Commission Meeting 2. Incidental Catch Regulations in the Salmon Troll and Fixed Gear Sablefish Fisheries 3. Preliminary Alternatives for Incidental Catch Retention of Pacific Halibut in the...

  14. Statistical tests of additional plate boundaries from plate motion inversions

    NASA Technical Reports Server (NTRS)

    Stein, S.; Gordon, R. G.

    1984-01-01

    The application of the F-ratio test, a standard statistical technique, to the results of relative plate motion inversions has been investigated. The method tests whether the improvement in fit of the model to the data resulting from the addition of another plate to the model is greater than that expected purely by chance. This approach appears to be useful in determining whether additional plate boundaries are justified. Previous results have been confirmed favoring separate North American and South American plates with a boundary located beween 30 N and the equator. Using Chase's global relative motion data, it is shown that in addition to separate West African and Somalian plates, separate West Indian and Australian plates, with a best-fitting boundary between 70 E and 90 E, can be resolved. These results are generally consistent with the observation that the Indian plate's internal deformation extends somewhat westward of the Ninetyeast Ridge. The relative motion pole is similar to Minster and Jordan's and predicts the NW-SE compression observed in earthquake mechanisms near the Ninetyeast Ridge.

  15. Latest Developments in the Installation Planning for Stage 1, NEPTUNE Regional Cabled Observatory, Northeast Pacific

    Microsoft Academic Search

    C. R. Barnes

    2004-01-01

    NEPTUNE is a proposed innovative network of over 30 sub-sea observatories linked by over 3300 km of powered, fiber-optic cables covering the Juan de Fuca Plate (200,000 sq km), Northeast Pacific. Each observatory will host and power many scientific instruments on the surrounding seafloor, in boreholes in the seafloor, and buoyed up into the water column. Remotely operated and autonomous

  16. Circum-pacific late cenozoic structural rejuvenation: implications for sea floor spreading.

    PubMed

    Dott, R H

    1969-11-14

    The hypothesis of sea floor spreading and lithosphere plates seems to unify the origins of both oceanic ridges and volcanic arc-trench systems; therefore knowledge of well-known land areas should shed light upon sea floor tectonics. Impressive evidence of a major mid-Cenozoic discontinuity in the tectonic history of circum-Pacific land areas suggests a roughly synchronous change in sea floor development, more evidence for which may be anticipated in the future. PMID:17815749

  17. Sulfide deposits from the east Pacific rise near 21°N

    Microsoft Academic Search

    R. Hekinian; M. Fevrier; J. L. Bischoff; P. Picot; W. C. Shanks

    1980-01-01

    Massive sulfide deposits were discovered from the diving saucer Cyana on the accreting plate boundary region of the East Pacific Rise near 21°N. The deposits form conical and tubular structures lying on a basaltic basement. Mineralogical and geochemical analyses showed two main types of intimately associated products: a polymetallic sulfide-rich material composed of pyrite and marcasite in association, zinc-rich phases,

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

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

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

  19. 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.

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

    PubMed

    Zhong, S; Gurnis, M

    1995-02-10

    A finite-element formulation of faults has been incorporated into time-dependent models of mantle convection with realistic rheology, continents, and phase changes. Realistic tectonic plates naturally form with self-consistent coupling between plate and mantle dynamics. After the initiation of subduction, trenches rapidly roll back with subducted slabs temporarily laid out along the base of the transition zone. After the slabs have penetrated into the lower mantle, the velocity of trench migration decreases markedly. The inhibition of slab penetration into the lower mantle by the 670-kilometer phase change is greatly reduced in these models as compared to models without tectonic plates. PMID:17813909