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1

Imaging Upper Mantle Interfaces under the Pacific Plate  

NASA Astrophysics Data System (ADS)

The Pacific provides an ideal region for the study of upper mantle interfaces due to its broad extent and relatively homogeneous structure. Multi-taper correlation (MTC) methods for the estimation of teleseismic receiver fuctions (RF's) provide a natural way to study these interfaces due to their sensitivity to impedence contrasts and desirable statistical properties. Recent improvements to the MTC algorithm (Park and Levin, 2005 GJI, submitted) permit the reconstruction of Ps conversions from interfaces below 100km depth. Here we apply these new techniques to imaging interfaces in the upper mantle beneath four ocean islands in the Pacific (broadband stations RAR, PPT, POHA, and XMAS). In particular, we attempt to constrain the depth, sharpness, and topography of the 410 km and 660 km discontinuities, and examine evidence for a low velocity zone above the transition zone in this area.

Park, J.; Leahy, G. M.

2005-12-01

2

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

3

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

4

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

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

5

Episodic North America and Pacific Plate motions  

NASA Astrophysics Data System (ADS)

The North America plate motion for the period 20-0 m.y. is modeled by two absolute angular velocity vectors, with a change occurring at about 9 m.y. The model incorporates new geologic constraints based on (1) the recognition of a discontinuity in North America plate motion at 9 m.y., (2) a reexamination of the Iceland and Yellowstone hotspot traces, (3) improved delineation of the present North America - Pacific relative motion, and (4) a revised history of Pacific absolute motion. The two-stage model is consistent with several features of the late Cenozoic geologic history of North America, including geological observations relating to tectonism along a large portion of both the eastern and western boundaries of North America. This plate model, combined with a previously established Pacific plate model, makes specific predictions concerning the 15-0 m.y. history of the North America-Pacific plate boundary which compare favorably with the known history. These models together resolve most of the discrepancies previously encountered between absolute and relative motion models of the two plates. The implications of the North America plate model are the greatest for those events related to the 9 m.y. change in its motion. Among the geologic consequences of this change are rifting in the western United States, intense compressional deformation along the northern Caribbean plate boundary, a hiatus in Aleutian arc volcanic activity, and a change in the orientation of the Lesser Antilles arc. This picture reinforces the notion that the major plates behave rigidly and transmit stresses over great distances. The predictive power of the model may help in interpreting the history of the North America plate boundary in those areas where clear observations are lacking. An extra force needs to be applied to a plate to cause a change in plate motion. By treating the plate as a rigid spherical shell overlying a uniformly viscous fluid, we derive a simple class of forces sufficient to cause a given change in plate motion. Such force balance considerations indicate that an additional force applied in the northwest Pacific region, toward the northeast, would result in the observed change in North America plate motion. This force is surprisingly similar to that which apparently caused a large change in Pacific plate motion about 5 m.y. later. We propose that a common mantle process is responsible for both changes and is related to the ability of the northwest Pacific subducted lithosphere to enter into the lower mantle.

Pollitz, Fred F.

1988-08-01

6

Plate kinematics in the western Pacific derived from geodetic observations  

E-print Network

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

Tregoning, Paul

7

Focal Mechanisms and Plate Tectonics of the Southwest Pacific  

Microsoft Academic Search

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

Tracy Johnson; Peter Molnar

1972-01-01

8

Pacific trench motions controlled by the asymmetric plate configuration  

NASA Astrophysics Data System (ADS)

We present a novel explanation for absolute trench-normal motions of slabs surrounding the Pacific. Rapid subduction-zone retreat on the eastern side of the Pacific and slow advance in the west can result from the large-scale asymmetric plate configuration. We use simple fluid dynamics to explain the mechanical background of this hypothesis, and we use the results of a simple finite difference scheme to estimate the effect on trench motion velocities. The hypothesis is based on two key assumptions. First, we follow the concept of plate-scale horizontal counterflow in the asthenosphere driven by accretion of asthenosphere into lithosphere and by plate motion. Second, we assume that horizontally wide slabs without large slab windows drift passively in the mantle flow field and do not retreat as a result of flow around the slab. If the asthenosphere transfers flow-related horizontal shear stress into deeper levels of the mantle, an asymmetry in the plate configuration leads to different net pressure forces on the two slabs and thus affects the retreat behavior. In an ocean with an asymmetric ridge position, the slab of the smaller plate should retreat faster than the slab of the large plate, which may even advance. Also, the domain of a slower moving plate should collapse faster than the domain of the faster plate. Our model explains the counterintuitive negative correlation between slab age and retreat velocity observed in the Pacific. It also accords with the topographic asymmetry of the ridge flanks along the Pacific rise.

Nagel, Thorsten J.; Ryan, William B. F.; Malinverno, Alberto; Buck, W. Roger

2008-06-01

9

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

10

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

Microsoft Academic Search

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

Kristine M. Larson; Jeff Freymueller

1995-01-01

11

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

Microsoft Academic Search

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

Tanya Atwater; Joann Stock

1998-01-01

12

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

NASA Astrophysics Data System (ADS)

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.

Abe, N.; Fujiwara, T.

2013-12-01

13

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

NASA Technical Reports Server (NTRS)

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.

Ward, Steven N.

1990-01-01

14

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

15

Azimuthal anisotropy layering and plate motion in the Pacific Ocean  

NASA Astrophysics Data System (ADS)

We recently developed a three dimensional radially and azimuthally anisotropic model of the upper mantle in north America, using a combination of long-period 3-component surface and overtone waveforms, and SKS splitting measurements (Yuan and Romanowicz, 2010, Yuan et al., 2011). We showed that azimuthal anisotropy is a powerful tool to detect layering in the upper mantle, revealing two domains in the cratonic lithosphere, separated by a sharp laterally varying boundary in the depth range 100-150 km, which seems to coincide with the mid-lithospheric boundary (MLD) found in receiver function studies. Contrary to receiver functions, azimuthal anisotropy also detects the lithosphere-asthenosphere boundary (LAB) as manifested by a change in the fast axis direction, which becomes quasi-parallel to the absolute plate motion below ~250 km depth. A zone of stronger azimuthal anisotropy is found below the LAB both in the western US (peaking at depths of 100-150km) and in the craton (peaking at a depth of about 300 km). Here we show preliminary attempts at expanding our approach to the global scale, with a specific goal of determining whether such an anisotropic LAB can also be observed in the Pacific ocean. We started with our most recent global upper mantle radially anisotropic shear velocity model, determined using the Spectral Element Method (SEMum2; French et al., this meeting). We augment the corresponding global surface wave and overtone dataset (period range 60 to 400 s) with deep events and shorter period body waves, in order to ensure optimal deeper depth (>250km) anisotropy recovery due to the paucity of shear wave splitting measurements in the oceans. Our preliminary results, which do not yet incorporate SKS splitting measurements, look promising as they confirm the layering found previously in North America, using a different, global dataset and starting model. In the Pacific, our study confirms earlier azimuthal anisotropy results in the region (e.g. Smith et al. 2004; Maggi et al. 2006) that the shallow upper mantle beneath the ocean basin is strongly stratified. Our results further illustrate that 1) a shallow anisotropy domain (~100 km) is present, which is high in velocity and has in general a northward anisotropy direction where the plate is old (>80 Ma); and 2) there is a deeper domain (100-200 km) with stronger anisotropy, which correlates spatially with the low velocity zone and has a fast axis direction in good agreement with the absolute plate motion direction (HS3 NUVEL-1A). The boundary between the anisotropy domains clearly follows the age progressive deepening of the fast velocity in the shallow domain, suggesting an oceanic LAB that separates the Pacific lithosphere and the underlying asthenosphere.

Yuan, H.; Romanowicz, B. A.

2012-12-01

16

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

USGS Publications Warehouse

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

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

1980-01-01

17

Volcanic Structure of the Basaltic Shield Volcano of Socorro Island, Mathematician Ridge, Pacific Plate  

Microsoft Academic Search

Socorro Island is a pantellerite and perialkaline shield volcano built at the northern segment of the Mathematician ridge in the Pacific plate. Active spreading along the ridge terminated following major plate boundary re-organization and ridge jumping eastwards to the East Pacific Rise. Cessation of spreading and ridge jumping are recorded in the marine magnetic anomaly pattern that preserve a record

M. Escorza-Reyes; J. A. Pavon-Moreno; L. Perez-Cruz; J. U. Fucugauchi

2009-01-01

18

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

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

19

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

NASA Technical Reports Server (NTRS)

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

Larson, Kristine M.; Freymueller, Jeff

1995-01-01

20

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

Microsoft Academic Search

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

Mizuho Ishida

1992-01-01

21

Relative motion history of the Pacific-Nazca (Farallon) plates since 30 million years ago  

Microsoft Academic Search

Relative plate motion history since 30 Ma between the Pacific and the southern portion of the Nazca (Farallon) plates is examined. The history is constrained by available seafloor magnetic anomaly data and a two-minute grid of predicted bathymetry derived from satellite altimetry and shipboard sensors. These data are used to create a new plate motion reconstruction based on new magnetic

Douglas T Wilder

2003-01-01

22

Laser shockwave technique for characterization of nuclear fuel plate interfaces  

SciTech Connect

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.

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

23

Laser shockwave technique for characterization of nuclear fuel plate interfaces  

NASA Astrophysics Data System (ADS)

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.

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

2013-01-01

24

Fast P wave propagation in subducted Pacific lithosphere: Refraction from the plate  

NASA Astrophysics Data System (ADS)

P waves traveling from events in the Tonga-Kermadec seismic zone to stations in New Zealand are very fast with highly emergent, dispersed waveforms. Ray tracing has shown the waves to travel close to the subducted Pacific plate throughout their length, and synthetic seismogram calculations have shown the dispersion requires a very thin (8-12 km) fast layer. Previous work has been based on data from analog records and one digital, single-component short-period instrument; no polarization analysis was possible, and measurements of dispersion were limited by the bandwidth. From January 1991 to August 1992 we deployed nine broad band, three-component seismometers in good sites for observing these arrivals; the data are augmented by three-component, short-period digital records from new stations of the New Zealand National Network. In this study we analyze 1191 broad-band and 2076 short period seismograms from 71 events for polarization of the initial P wave. The polarization directions are found to be up to 30 deg off the great circle path and consistently steep (20 deg from vertical). They are too steep to be explained by standard ray paths or refraction from a fast horizontal layer. We invert the polarization directions for a tilted interface beneath the array and use arrival times to control the depth to the interface, which is found to lie close to the top of the subducted plate inferred from the seismicity. We conclude that these precursive, emergent P waves have traveled through a fast layer close to the top of the subducted plate and refract upward to the station. A second arrival, with lower dominant frequency near 1 Hz and normal travel time, is occasionally seen on both broad band and short-time stations. Its polarization direction is similarly steep but difficult to measure; the evidence suggests that it also travels within the plate with similar ray path to the precursor.

Smith, Gideon; Gubbins, David; Mao, Weijian

1994-12-01

25

A revised Latest Cretaceous and Early Cenozoic apparent polar wander path for the Pacific plate  

E-print Network

The apparent polar wander path (APWP) for the Pacific plate during the Late Cretaceous and Early Cenozoic has been constrained primarily by seamount magnetic anomaly inversions and seafloor magnetic anomaly skewness. The reliability of these data...

Beaman, Melissa A.

2007-09-17

26

Mapping the Miocene Farallon Ridge jump on the Pacific plate: a seismic line of weakness  

NASA Astrophysics Data System (ADS)

Bathymetric and magnetic data are used to obtain estimates, on the Pacific and Nazca plates, of the boundaries separating lithosphere generated at the old Farallon Ridge from the more recent one created at the present-day East Pacific Rise. An excellent correlation is found with the sites of known teleseismically recorded intraplate seismicity, suggesting that these boundaries, which are lines of age discontinuity in the plate, must be zones of weakness of the lithospheric plate. In particular, the so-called Region C, identified by Okal et al. as a major site of seismic release, sits on a small piece of Farallon plate, in the immediate vicinity of the northern extension of the fossil Roggeveen Rise, cut across by the East Pacific Rise during the ridge jump.

Okal, Emile A.; Bergeal, Jean-Marie

1983-04-01

27

Seamounts, knolls and petit spots on the NW Pacific Plate represent intra-plate volcanism from the Cretaceous to present  

NASA Astrophysics Data System (ADS)

Most of seamounts of the western Pacific formed before 70 Ma in the so-called West Pacific Seamount Province (WPSP) which is characterized by relatively short seamount chains maybe indicating a significant short-lived hotspot system (Koppers et al., 2003). As for the NW Pacific Plate offshore of Northeast Japan, the Joban and Japanese Seamount Trail are also composed of middle Cretaceous seamounts, which are erupted on the northern margin of WPSP. The 120 to 100 Ma seamounts in the Joban seamount chain do not show a middle Cretaceous hotspot track, whereas the Japanese seamount chain shows a well-established ENE to WSW trend in this age range. On the other hand, the unnamed knolls, which are well-circular and flat-topped in shape, are scattered on the NW Pacific Plate and are not aligned to any volcanic chains. These were correspond to eruptive ages of 70 Ma based on Ar-Ar ages of a second volcanic event in the NW Pacific. As the last stage, we should note that Hirano et al. (2006) reported the 0-1, 2, 4.2, 6.0 and 8.6 Ma volcanoes, called petit spots, in the Japan Trench on the outer-rise system. The petit spot volcanoes imply episodic eruptions of magma over a distance of 600 km of plate motion on the flexural Pacific Plate before its subduction but with low volumes of magma production. The volume of volcanic edifice of the petit spot volcanoes certainly is several orders of magnitude less than the Cretaceous seamounts and knolls. Therefore, we can interpret that the petit spot volcanoes are not related to any mantle plumes and hotspots. Evidence includes the geochemical data and the tectonic alignment of the volcanoes which show that the petit spot lavas escaped along fractures in the lithosphere and were sourced from small pockets of asthenospheric melts. The bathymetric map and sidescan sonar imagery of the ocean-ward slope in the Tonga Trench also shows a possible presence of young volcanoes. Such small volcanoes, therefore, may be ubiquitous on the ocean floor, where incipient melts in the asthenosphere can be squeezed out by tectonic forces associated with plate flexure of outer-rise.

Hirano, N.; Nakanishi, M.; Koppers, A. A.

2007-12-01

28

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

Microsoft Academic Search

The Australian-Pacific transform plate boundary fault zone along the Macquarie and McDougall segments of the Macquarie Ridge Complex (MRC), south of New Zealand, is characterized by dominantly normal faults and pull-apart basins, in apparent conflict with the regional transpressional tectonic setting. We propose that present-day curvature of the transform is inherited from a preexisting divergent plate boundary and that the

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

2003-01-01

29

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

Microsoft Academic Search

The Australian-Pacific transform plate boundary fault zone along the Macquarie and McDougall segments of the Macquarie Ridge Complex, south of New Zealand, is characterized by dominantly normal faults and pull-apart basins, in apparent conflict with the regional transpressional tectonic setting. We propose that present day curvature of the transform is inherited from a preexisting divergent plate boundary and that the

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

2002-01-01

30

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

Microsoft Academic Search

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

Joann Stock; Peter Molnar

1982-01-01

31

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

Microsoft Academic Search

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

E. I. Gordeev

2008-01-01

32

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

NASA Astrophysics Data System (ADS)

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).

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

2013-12-01

33

Inception of the eastern California shear zone and evolution of the PacificNorth American plate boundary: From kinematics  

E-print Network

] The San Andreas Fault (SAF) is the transform boundary between the Pacific and the North American plates American plates (Figure 1), the San Andreas Fault (SAF) proper accommodates 20%­75% of the relative plate proper, collectively referred to as the San Andreas Fault system [Wallace, 1990]. Furthermore, up to 25

Liu, Mian

34

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

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

35

Lithospheric evolution of the Pacific–North American Plate Boundary considered in three dimensions  

Microsoft Academic Search

Tomographic images developed using the combined seismic networks of California and Nevada provide a three-dimensional view into Neogene Pacific–North American plate boundary evolution. Images reveal structures similar in size and spatial distribution to the large-scale structures observed at the surface. A prominent linear anomaly in the mantle is imaged beneath the western foothills to a depth of 70–90 km. Called the

Glenn P. Biasi

2009-01-01

36

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

USGS Publications Warehouse

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.

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

2007-01-01

37

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

38

Tectonics and plate boundary processes along the Southeast Indian Ridge and the East Pacific Rise  

NASA Astrophysics Data System (ADS)

Classical plate tectonics describes crustal deformation in a simple kinematic way, with deformation occurring only at narrow boundaries of plates with rigid interiors. Many dynamic processes at these boundaries are not well understood. There are also apparent deviations from classical plate tectonics where significant intraplate deformation occurs. In this thesis, we analyze and model geophysical data from the Southeast Indian Ridge (SEIR) and the East Pacific Rise (EPR) to address some of these issues. Hotspots often affect the dynamics of nearby spreading centers. As shown by bathymetry, side-scan sonar, and magnetic anomaly data, the Amsterdam-St. Paul (ASP) hotspot has altered the spreading history and geometry of nearby SEIR spreading axes. The hotspot thickened the oceanic crust near the spreading center and reorganized the plate boundary through rift propagation and ridge jumps, creating the youngest known transform fault in the process. The region near the ASP plateau has been suggested as where a wide, diffuse, NW-SE trending oceanic plate boundary meets the SEIR. Using data from the SEIR, we perform a statistical analysis and examine predictions of the model to test its validity. The boundary is not confirmed on statistical grounds, but evidence suggests that it does exist. However, it does not extend south of the St. Paul Fracture Zone, narrowing the previously proposed boundary by 800 km where it meets the SEIR. We also test the hypothesis that deformation near the eastern end of the SEIR, including a large intraplate earthquake can be explained by an additional plate boundary. If the earthquake lies on a plate boundary, its sense of slip should be right-lateral rather than the observed left-lateral motion, ruling out the hypothesis. Asymmetric geophysical properties of the EPR near 17°S suggest more melt beneath the Pacific side than the Nazca side. Numerical modeling results indicate that the asymmetry may be produced by pressure-driven across-axis mantle flow from the Pacific superswell. Across-axis flow extends upwelling and melting to the west of the axis, but limits upwelling to the east, shutting off melting and accounting for the observed asymmetry.

Conder, James Andrew

39

Nazca absolute plate motion and Pacific basin inter-hotspot motion  

NASA Astrophysics Data System (ADS)

Historically, hotspots have been used to define a fixed reference frame for plate motions: however, since hotspots are rooted within a dynamically convecting mantle, it is hard to believe that the fixity is absolute and instead slow motion between hotspots are expected to be occurring. Thus "how slow" is the central issue that needs to be addressed. Harada and Hamano (2000) and Harada and Wessel (2003, in prep.) showed that the mean speed since 70Ma for inter-hotspot motion within the Pacific plate is less than 4 or 5 mm per year. Recently, Steinberger (2002) suggested a numerical model for westward motion of the Easter hotspot at several cm per year relative to the Hawaii and Louisville hotspots. To test his hypothesis we dredged more than 70 sites along the Nazca Ridge and Easter Seamount Chain during the Drift expedition, Leg 6, of the R/V Revelle and dated more than 20 samples using the Ar/Ar method to examine the motion of the Easter hotspot relative to the Pacific hotspots. To estimate the positions and ages of the Easter hotspot track on the Nazca plate, we needed a good model of the absolute motion of the Nazca plate (Nazca APM) and present location of the Easter hotspot. For the modeling of the Nazca APM, we combined several existing models of Pacific APM with Pacific-Nazca relative motions (Pac-Naz RPM) determined from magnetic anomalies, and investigated the differences of these Nazca APM models. To determine the present location of the Easter hotspot, we applied the hot-spotting technique (Wessel and Kroenke, 1997) using the Nazca APM models, and then examined the differences in the optimal CVA locations. Because the hot-spotting technique can predict the present position of a hotspot without using any age data, we could test the modeled ages of the theoretical hotspot track by comparing them with observed ages of the hotspot track. The present position of the Easter hotspot is found to be near Salas y Gomez Island, not Easter Island. Although there are some dispersion owing to the various Nazca APM models used, the result shows that the position and ages of the modeled hotspot track well explain the observed geometry and ages, and there appears to be no systematic difference with time or distance from the present position. The suggested speed for inter-hotspot motion between the Easter and the Pacific hotspots would therefore be less than 10 mm per year.

Harada, Y.; Wessel, P.; Naar, D.; Wilder, D.; Duncan, R. A.; Mahoney, J. J.; Johnson, K. T.; Pyle, D. G.; Ray, J. S.

2003-04-01

40

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

USGS Publications Warehouse

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.

Geist, E. L.

1996-01-01

41

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

USGS Publications Warehouse

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

Lahr, J. C.; Plafker, G.

1980-01-01

42

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

SciTech Connect

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.

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

1992-10-01

43

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

NASA Astrophysics Data System (ADS)

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.

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

2010-11-01

44

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

45

Rayleigh wave tomography of the Pacific-North American plate boundary in Southern California  

NASA Astrophysics Data System (ADS)

Southern California is the location of a unique transform plate boundary on land that divides the North American and the Pacific plate. This tectonic system was formed during the Miocene period with the subduction of the Farallon plate and the East Pacific Rise beneath California roughly 30 Ma years ago. However, the stresses surrounding this tectonic system are only partially understood due to lack of data availability offshore which makes up half of this plate boundary. Here we employ seismic tomography methods using land and offshore data to consider tectonic stresses, mantle flow dynamics, and earthquake hazard analysis in and surrounding southern California. We use Rayleigh waves recorded by an array of 34 ocean bottom seismometers (OBS) deployed as part of the ALBACORE project offshore southern California on 18-32 Ma seafloor. The OBS's recorded for a 12 month duration from August 2010 to 2011 and are combined with 82 land stations which recorded data simultaneously from the southern California Integrated Seismic Network. We analyze ~100 teleseismic events at distances ranging from 30° to 120° with good signal-to-noise ratios for magnitudes of 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 16 - 80 seconds. The inversion technique considers non-great circle path propagation by representing the arriving wave field as two interfering plane waves. Preliminary results indicate that phase velocities for periods above 20s are approximately 0.8 % lower than previous studies for the seafloor age bin 20-52 Ma that used oceanic raypaths recorded by land stations. The strength of anisotropy is consistent at 2.5 % for nearly all periods within error. The dominant direction of azimuthal anisotropy is not consistent with Pacific plate motion direction. The fast direction for periods below 33 s displays an E-W azimuth that agrees with shear wave splitting results previously reported from island stations. At longer periods, anisotropy indicates a counter clockwise rotation in fast direction with increasing depth and period. This rotation is consistent with a model where rotation is maximum at the surface where the E-W trending Transverse Ranges show 90° to 110° rotation and is minimum for mantle depths at 100-150 km, suggesting that the mantle is being rotated by drag from the surface.

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

2013-12-01

46

Tears or thinning? Subduction structures in the Pacific plate beneath the Japanese Islands  

NASA Astrophysics Data System (ADS)

The nature of a subduction zone at depth is affected by the evolution of its tectonic system, and the geometry of the trench line can change over time due to slab roll-back or the arrival of a distinctive feature with the incoming oceanic lithosphere. The configuration of the plate has to accommodate such changes with buckling, thinning or the formation of tears depending on the rate of influx to the trench. Tomographic imaging is commonly used to recognise the presence of such tears through marked reductions in wavespeed anomalies in localised zones. A good example is provided by Pacific plate subduction beneath the Japanese Islands. A horizontal tear in the plate below 300 km depth can be recognised at the southern end of the Izu-Bonin arc associated with the change in slab morphology to the much steeper Mariana arc. Beneath southern Honshu a break in the fast wavespeeds associated with the Pacific plate has been described as a tear based on the evidence of converted phases from the edge of the zone and tensional focal mechanisms for seismic events in the tear zone. In the north, close to the Hokkaido bend in the subduction zone, the reduction in the shear wavespeed anomaly is just as dramatic, but here the characteristics of high frequency guided waves from deep earthquakes indicate continuity of slab material with thinning of the slab. The thinned slab has less wavespeed contrast within the affected cells and so appears in the tomographic images as a weakened anomaly. The various modes of slab deformation represent different ways in which the subducted material accommodates the strains imposed by the evolution of the geometry of the subduction scenario. Not all significant reductions in wavespeed anomalies represent tears and thus it is important that such interpretations be checked against the characteristics of wave propagation through the zone.

Kennett, B. L. N.; Furumura, T.

2010-05-01

47

Reconstruction of Pacific-Nazca Plates, Nazca Ridge, and Easter Seamount Chain  

NASA Astrophysics Data System (ADS)

Relative plate motion history since 30 Ma between the Pacific and Nazca (Farallon) plates has been constrained by available seafloor magnetic anomaly data and a two-minute grid of predicted bathymetry. These data are used to create a new plate reconstruction based on finite and stage poles of rotation and radiometric ages along the Easter-Salas y Gomez-Nazca Ridge volcanic lineament. An iterative process of anomaly identifications, pole calculations and anomaly rotations was used to test for self-consistency in the interpretation. The new identified magnetic isochrons (10y, 7y, 6c, 5d, 5b, 5aa, 5o, 4a, and 3a) and the predicted tectonic history provide an improved understanding between chrons 7y (24.73 Ma) and 3 (4.18 Ma). However, the finite poles for 6c and 5d are poorly constrained. Eleven stage poles were calculated using the nine finite poles and two published instantaneous Euler vectors for the 1o and 2a isochrons. The stage poles indicate full-spreading rates increased from about 175 mm/yr to about 205 mm/yr after the break-up of the Farallon plate, and then have slowed to about 145 mm/yr. The tectonic reconstruction indicates two major southward propagating events, the first starting by 28 Ma and terminating by 18 Ma. The second starting in association with breakup of the Farallon plate around 24 Ma and terminating by about 11 Ma. Lithosphere was transferred from Nazca to Pacific during the first event and in the opposite sense during the second. Development of the Mendoza microplate east of the second propagator occurred at about 20 Ma and this dual spreading process appears to have lasted until about 15 Ma. Radiometric ages, geochemical data, relative and absolute motion models presented at the Nice AGU meeting by Duncan et al., Ray et al., Wilder et al., and Harada et al. indicate that since 30 Ma: 1) a hotspot located near Salas y Gomez Island does not require significant motion of the hotspot with respect to the Hawaiian hotspot; 2) that this hotspot has generated similar proportions of OIB vs. MORB end-member compositions in most samples collected east of Salas y Gomez; and 3) that the change of plate motion velocity was primarily accommodated by the combination of propagating rifts and microplate formation, including a rapid clockwise rotation of spreading direction and rapid increase in spreading rate, followed by a subsequent decline until present.

Naar, D. F.; Wilder, D. T.; Duncan, R. A.; Wessel, P.; Harada, Y.; Mahoney, J. J.; Ray, J. S.; Johnson, K. T.

2003-12-01

48

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

NASA Astrophysics Data System (ADS)

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.

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

49

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

PubMed

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

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

2006-06-29

50

Influence of lateral acceleration on capillary interfaces between parallel plates  

Microsoft Academic Search

The paper considers limits for the refill of capillary liquid vanes of propellant management systems for low gravity applications\\u000a under the influence of residual acceleration. The limit of existence of a connected capillary liquid interfaces in the vanes\\u000a is analyzed. A mathematical approach to describe the characteristics of a liquid meniscus in the vane is derived under the\\u000a assumptions of

Armin de Lazzer; Michael Stange; Michael Dreyer; Hans J. Rath

2003-01-01

51

Slow earthquakes associated with fault healing on a serpentinized plate interface  

PubMed Central

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

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

2013-01-01

52

Kinematics of the northern Walker Lane: An incipient transform fault along the Pacific–North American plate boundary  

Microsoft Academic Search

In the western Great Basin of North America, a system of dextral faults accommodates 15%-25% of the Pacific-North American plate motion. The northern Walker Lane in northwest Nevada and northeast California occupies the northern terminus of this system. This young evolving part of the plate boundary offers insight into how strike-slip fault systems develop and may reflect the birth of

James E. Faulds; Christopher D. Henry; Nicholas H. Hinz

2005-01-01

53

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

NASA Technical Reports Server (NTRS)

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

Hwangbo, H.; Coyle, M. J.

1979-01-01

54

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)

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.

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

2013-04-01

55

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

PubMed

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

Mila-Schaaf, Karlo; Hudson, Maui

2009-02-01

56

North american--pacific relative plate motion in southern california from interferometry.  

PubMed

Very long baseline interferometry measurements of baselines crossing the San Andreas fault zone in southern California have provided observational constraints on rates of elastic tectonic strain accumulation. The single site located near this fault (the Jet Propulsion Laboratory site) moves in a direction concordant with the Pacific plate motion vector but at approximately half the net rate relative to North America. This motion agrees approximately in amount with geologically determined displacement rates on the San Andreas fault alone but not with the local strike of the fault. When considered together with complementary geodetic data, these results suggest a complex relation between the short-term accumulation of elastic strain and its permanent accommodation on existing faults. PMID:17756870

Lyzenga, G A; Golombek, M P

1986-09-12

57

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

58

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

USGS Publications Warehouse

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

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

2003-01-01

59

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

Microsoft Academic Search

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

M. R. Legg; A. Barberopoulou

2007-01-01

60

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

Microsoft Academic Search

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

Robert Hall

2002-01-01

61

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

NASA Astrophysics Data System (ADS)

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.

Gordeev, E. I.

2008-12-01

62

Volcanisms and Earthquakes Related to the Pacific Plate Subduction in Northeast Asia  

NASA Astrophysics Data System (ADS)

It is very known that an integrated plate system displays in Northeast Asia from the Pacific Plate subduction zone via arc islands and back-arc basin to the continental margin with rifting system. Based on this geological background many huge earthquakes and volcanic eruptions occurred in this area from the Mesozoic to the present such as Fujiyama Volcano in Japan, Cheju Volcano in South Korea, Changbaishan Volcano in China and M 7.3 deep focus earthquake in Wangqing, Northeast China of June 28,2002, M9 earthquake in Northeast Japan of March 11,2011 and so on. Now it is tectonic active phase in the Northeast Asia, even in the globe. The Changbaishan Volcano is huge volcanic group with some 12-103 km2 area and hundreds volcanic cones crossed the boundary between China and Korea covered 41° -42.5° latitude north and 127° -129° longitude east. It is among largest active and dangerous volcanoes on the Globe and composed of three main volcanoes (eruptive centers): Tianchi(2755 m a.s.l.), Wangtian'e (2438m a.s.l.) and South Paotaishan (2434m a.s.l.), which distribution assumes as tripod. These three eruptive centers have similar magma system and different ages. They were built from the Early Miocene to the Recent by basaltic flow as lava plateau, trachyte composing of volcanic cones and pyroclastic deposits covering the tops of the mountains and other places. Tianchi volcano is younger than others. According to historic documents the largest eruption of Tianchi volcano occurred in 1014-1019 AD., after that there were still several eruptions until 1903 AD. The frequencies of Changbaishan volcanic eruptions corresponded to those of the Pacific, especially Japan. There is systematic magma evolution from basic basalt, intermediate trachyte to acid pantellerite with 87Sr/86Sr 0.704771-0.710096, 143Nd/144Nd 0.512487-0.512602, which indicated that the magma derived from rich mantle. Geophysical data reveal a buried magmatic reservoir is lying below the volcanoes. Recently, the west Pacific fire ring is very active accompanied with frequent volcanic eruptions and earthquakes; the earthquake frequency and intensity and geochemical anomaly also obviously strengthen in the surrounding of Changbaishan volcanoes. It reveals that volcanic activity and possibility of re-eruption is going to strengthen. Therefore we must put attention to volcanic action.

Liu, J.; Chen, X.

2012-04-01

63

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

USGS Publications Warehouse

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

Gromme, S.; Vine, F. J.

1972-01-01

64

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

65

The northern edge of Pacific plate position near Kamchatka-Aleutian junction  

NASA Astrophysics Data System (ADS)

Two geochemical transects were carried out through Kamchatka: one previously studied SE-NW across the arc and one SW-NE trending along the Sredinny Range (SR) back arc zone. These data with Ar-Ar dating constrain magma source in space and time and allows us to relate these to tectonic position setting of the region at a given time. The cross arc transect from Gamchen volcano in Eastern Volcanic Front (EVF) through Central Kamchatka Depression (CKD) to Ichinsky volcano in SR based on Quaternary rocks showed continuous geochemical zonation from arc front to back arc of present subduction zone, including strong and gradual increase in LILE, LREE and HFSE in whole rocks. The transect along the SR from the Achtang lava field to Tekletunup volcano (the back arc zone) comprises two age groups of volcanic rocks each with uniform in geochemical features. Late Miocene-Pliocene rocks (3-6 Ma) represent voluminous plateau lavas of depleted basalts with low HFSE and HREE. Fluid-mobile elements are enriched and enrichment patterns are in fact similar to the typical arc front lavas. The younger group of Quaternary rocks (<1 Ma) is represented by monogenetic cones and stratovolcanoes that combine the typical LILE/HFSE-enrichment of a subduction setting with enrichment in all incompatible elements. In Eocene-Miocene times SR represented the active volcanic front of the Proto-Kamchatka subduction zone. In later times Kamchatka arc system has been modified by the accretion of the Kronotsky terranes. The time of accretion and the SE-outward 200 km shift of the subduction zone to the presently active EVF has been estimated from 40 to 2 Ma. Our data can help to better constrain the timing of this event by arguing that the systematic change in SR rock geochemistry with time is the result of this arc shift and has been facilitated by a massive slab roll-back event. In this scenario the SR plateau lavas represent the volcanic front until as recently as 3 Ma. The younger Quaternary rocks at SR are the present back arc lavas of the recent subduction zone. Both, the systematic geochemical zonation from contemporary arc front to back arc and the uniformity of geochemistry of young volcanic rocks along the SR show that the volcanism of the region is explained by the only one mechanism - subduction of the Pacific Plate below Kamchatka. A trend is documented from fluid-dominated melting in the EVF, through the upwelling of a strongly fluid-fluxed mantle below the CKD to melting of a fluid-enriched mantle aided by strong upwelling and decompression in the SR back arc zone. Magmatism has continued to be active in SR up to the Holocene even though seismic data today do not show a signal for a downgoing plate below this region. But the absence of the seismicity does not mean the absence of plate because at temperatures higher than 600-700°C seismicity is lost. We argue that the northern edge of the Pacific Plate is represented by a wide (150 km) boundary as a set of transform faults which can be projected on Kamchatka surface from the morphology of the downgoing oceanic plate. Also this edge is marked by the termination of Holocene volcanoes on surface along of SR. The absence of the young volcanism to the north of the on-land projection of the Alpha fault marks the plate boundary at depth.

Gordeychik, Boris; Churikova, Tatiana; Volynets, Anna; Wörner, Gerhard; Layer, Paul

2010-05-01

66

Interseismic locking of the plate interface in the northern Cascadia subduction zone, inferred from inversion of GPS data  

Microsoft Academic Search

We inverted GPS velocities from 20 continuous and 53 campaign sites in the northern Cascadia subduction zone using a Bayesian inverse method to estimate the locking state of the plate interface. The results are consistent with previous estimates based on thermal arguments and forward modeling. They suggest that the completely locked segment of the plate interface is offshore and that

Shoichi Yoshioka; Kelin Wang; Stephane Mazzotti

2005-01-01

67

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

68

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

Microsoft Academic Search

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,

Tsuyoshi Komiya; Shigenori Maruyama

2007-01-01

69

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

70

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

NASA Astrophysics Data System (ADS)

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 the region, but provide little help in long-term reconstruction. Plate boundaries shifted rapidly in the Cenozoic. During convergence of the major plates, there were numerous important episodes of extension, forming ocean basins and causing subsidence within continental regions, probably driven by subduction. Within eastern Indonesia, New Guinea and the Melanesian arcs, there are multiple Cenozoic sutures, with very short histories compared to most well-known older orogenic belts. They preserve a record of major changes in tectonics, including subduction polarity reversals, elimination of volcanic arcs, changing plate boundaries and extension within an overall contractional setting. Rapid tectonic changes have occurred within periods of less than 5 Ma. Many events would be overlooked or ignored in older orogenic belts, even when evidence is preserved, because high resolution dating is required to identify them, and the inference of almost simultaneous contraction and extension seems contradictory. There were three important periods in regional development: at about 45, 25 and 5 Ma. At these times, plate boundaries and motions changed, probably because of major collision events. The 45 Ma plate reorganisation may be related to India-Asia collision, although some important intra-Pacific events, such as voluminous Eocene boninite magmatism, seem to be older and require other causes. Indentation of Asia by India modified the Asian continent, but there is little indication that India has been the driving force of tectonics in most of SE Asia. The most important Cenozoic plate boundary reorganisation was at about 25 Ma. The New Guinea passive margin collided with the East Philippines-Halmahera-South Caroline Arc system. The Australian margin, in the Bird's Head region, also began to collide with the SE Asian margin in Sulawesi. The Ontong Java Plateau collided with the Melanesian Arc. These collisions caused a major change in the character of plate boundaries between about 25 and 20 Ma. Since 25 Ma, tectonic events east of Eurasia were driven by motion of the Pacific Plate. Further, west, the movement of Australia northwards caused rotations of blocks and accretion of microcontinental fragments to SE Asia. Plate motions and boundaries changed again at about 5 Ma, for uncertain reasons, possibly as a consequence of Pacific Plate motion changes, arc-continent collision in Taiwan, or other boundary changes at the Pacific margin, for example in the Philippines. Areas to the west and east of New Guinea, the Banda Sea and Woodlark Basin, illustrate the speed of change, the unexpected interplay of convergence and extension, and the importance of subduction as the engine of change. Subduction has been the principal driving mechanism for tectonic change, although its manifestations are varied. They include collision-related phenomena, partitioning of oblique convergence, and effects of hinge roll-back and pull forces of subducting slabs. Magmatism is not always associated with subduction, depending on the movement of subduction hinge, and there may be important extension of the upper plate both perpendicular and parallel to the length of subduction zones. Strike-slip faulting is observably very important within the Pacific-Australia-Eurasia convergent setting, yet appears in few tectonic models. Long-term strike-slip deformation can explain some of the complexities of areas such as New Guinea, including magmatism and its absence, and thermo-chronological data showing very young and rapid cooling of the mobile belt and fold belt. The inadequacies of the tectonic model reflect in part the difficulties of applying rigid plate tectonics, when there is clear evidence of changing

Hall, Robert

2002-04-01

71

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

72

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

E-print Network

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...

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

2012-01-01

73

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

USGS Publications Warehouse

Deep tremor under Shikoku, Japan, consists primarily, and perhaps entirely, of swarms of low-frequency earthquakes (LFEs) that occur as shear slip on the plate interface. Although tremor is observed at other plate boundaries, the lack of cataloged low-frequency earthquakes has precluded a similar conclusion about tremor in those locales. We use a network autocorrelation approach to detect and locate LFEs within tremor recorded at three subduction zones characterized by different thermal structures and levels of interplate seismicity: southwest Japan, northern Cascadia, and Costa Rica. In each case we find that LFEs are the primary constituent of tremor and that they locate on the deep continuation of the plate boundary. This suggests that tremor in these regions shares a common mechanism and that temperature is not the primary control on such activity. Copyright 2009 by the American Geophysical Union.

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

2009-01-01

74

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

Microsoft Academic Search

Young volcanoes are newly discovered on the cool, thick, and old Pacific Plate approximately 600 km ESE off the northern Japan Trench, during KR04-08 cruise using R\\/V Kairei (JAMSTEC) in 2004. The site was predicted lava eruption based on previous study for young alkali-basalt lavas (5.95 Ma) on the Japan Trench oceanward slope (the Kaiko knolls lava field). We named

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

2005-01-01

75

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

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

76

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

NASA Technical Reports Server (NTRS)

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.

Ward, Steven N.

1988-01-01

77

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

NASA Astrophysics Data System (ADS)

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.

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

2011-01-01

78

The magnetic properties of some DSDP basalts from the North Pacific and inferences for Pacific plate tectonics  

Microsoft Academic Search

One hundred seven basalt samples from seven DSDP sites in the North Pacific studied for magnetic properties were found to have a mean magnetization of 0.005 emu\\/cm3, a mean susceptibility of 0.001, and a mean Koenigsberger ratio of 10. The mean remanence coercivity as measured by the mean demagnetizing field is 90 Oc. The titanomagnetite in most of these old

Monte Marshall

1978-01-01

79

Inception of the eastern California shear zone and evolution of the Pacific-North American plate boundary: From kinematics to geodynamics  

Microsoft Academic Search

The San Andreas Fault (SAF) is the transform boundary between the Pacific and the North American plates, yet up to 25% of the relative plate motion is now accommodated by the eastern California shear zone (ECSZ). Here we investigate the inception of the ECSZ and its geodynamic interactions with the SAF using a 3-D viscoelastoplastic finite element model. For a

Mian Liu; Hui Wang; Qingsong Li

2010-01-01

80

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

81

Tectonics and plate boundary processes along the Southeast Indian Ridge and the East Pacific Rise  

Microsoft Academic Search

Classical plate tectonics describes crustal deformation in a simple kinematic way, with deformation occurring only at narrow boundaries of plates with rigid interiors. Many dynamic processes at these boundaries are not well understood. There are also apparent deviations from classical plate tectonics where significant intraplate deformation occurs. In this thesis, we analyze and model geophysical data from the Southeast Indian

James Andrew Conder

2001-01-01

82

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)

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.

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

2013-12-01

83

Uncertainties and implications of the Late Cretaceous and Tertiary position of North America relative to the Farallon, Kula, and Pacific Plates  

NASA Astrophysics Data System (ADS)

We present updated global plate reconstructions and calculated uncertainties of the Pacific, Kula, and Farallon/Vancouver plates relative to North America for selected times since 68 Ma. Improved magnetic data from the Indian Ocean decrease the uncertainties in. the global plate circuit approach; these uncertainties are now considerably smaller than those inherent in equivalent reconstructions based on the assumption of fixed hotspots. Major differences between these results and those of others are due to our use of more detailed Africa-North America reconstructions, separate Vancouver and Farallon plate reconstructions, and the assumption of a rigid Antarctica plate during Cenozoic time. The uncertainties in the relative positions of the Pacific and North America plates since the time of anomaly 7 (26 Ma) range up to ±100 km in position, or from 1 to 3 m.y. in time. If the Mendocino triple junction initiated at about 28.5 Ma, its position would have been at 31.3°N ± 130 km relative to fixed North America. Unacceptable overlap of oceanic crust of the Pacific plate with continental crust of western North America in the anomaly 10 (30 Ma) reconstruction is a minimum of 340±200 km along an azimuth of N60°E and may be accounted for by Basin and Range extension. Pacific-North America displacement in the past 20 Ma is found to be considerably less than that calculated by fixed hotspot reconstructions. Farallon (Vancouver)-North America convergence velocity decreased greatly between the times of anomalies 24 and 21 (56 to 50 Ma), prior to the 43 Ma age of the Hawaiian-Emperor bend and the often quoted 40 Ma "end" of the Laramide orogeny. A change in direction of Farallon-North America convergence occurred sometime between 50 and 42 Ma and also may not correlate with the time of the Hawaiian-Emperor bend. The lack of data from subducted parts of the Farallon and Kula plates permits many possibilities regarding the position of the Kula-Farallon ridge, the age of subducted crust, or the position of oceanic plateaus during the Laramide orogeny, leaving open the question of the relationship between plate tectonic scenarios and tectonic style during Laramide time. Displacements of points on the various oceanic plates along the west coast of an arbitrarily fixed North America during the interval between anomalies 30/31 and 18 (68 to 42 Ma) are found to be: Pacific plate, 1700±200 km northward; Farallon plate, 3200±400 km northeastward; Vancouver plate, 3000±400 km northeastward; Kula plate, if attached to the Pacific plate after A24 time, 2500±400 km northward.

Stock, Joann; Molnar, Peter

1988-12-01

84

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

85

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

USGS Publications Warehouse

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.

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

2009-01-01

86

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

USGS Publications Warehouse

A large, high quality P-wave data set comprising short-period and broadband signals sampling four separate regions in the lowermost mantle beneath the Cocos plate, Mexico, the central Pacific, and the north Pacific is analyzed using regional one-dimensional double-array stacking and modelling with reflectivity synthetics. A data-screening criterion retains only events with stable PcP energy in the final data stacks used for modelling and interpretation. This significantly improves the signal stacks relative to including unscreened observations, allows confident alignment on the PcP arrival and allows tight bounds to be placed on P-wave velocity structure above the core-mantle boundary (CMB). The PcP reflections under the Cocos plate are well modelled without any ultra-low velocity zone from 5 to 20??N. At latitudes from 15 to 20??N, we find evidence for two P-wave velocity discontinuities in the D??? region. The first is ???182 km above the CMB with a ??ln Vp of +1.5%, near the same depth as a weaker discontinuity (<+0.5%) observed from 5 to 15??N in prior work. The other reflector is ???454 km above the CMB, with a ??ln Vp of +0.4%; this appears to be a shallower continuation of the joint P- and S-wave discontinuity previously detected south of 15?? N, which is presumed to be the perovskite to post-perovskite phase transition. The data stacks for paths bottoming below Mexico have PcP images that are well matched with the simple IASP91 structure, contradicting previous inferences of ULVZ presence in this region. These particular data are not very sensitive to any D??? discontinuities, and simply bound them to be Pacific confirm the presence of a ???15-km thick ultra-low velocity zone (ULVZ) just above the CMB, with ??ln Vp and ??ln Vs of around -3 to -4% and -4 to -8%, respectively. The ULVZ models predict previous S-wave data stacks well. The data for this region indicate laterally varying Vp discontinuities in D???, with one subregion having a ??ln Vp of 0.5% 140 km above the CMB. Beneath the north Pacific, the PcP arrivals are compatible with only weak ULVZ (??ln Vp ??? 0 to -3%), and there is a weak D??? reflector with ??ln Vp = 0.5%, near 314 km above the CMB. These results indicate localized occurrence of detectable ULVZ structures rather than ubiquitous ULVZ structure and emphasize the distinctiveness between the large low shear velocity province under the central Pacific and circum-Pacific regions. ?? 2008 Elsevier B.V.

Hutko, A. R.; Lay, T.; Revenaugh, J.

2009-01-01

87

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

88

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

PubMed

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

Abo Sabah, Saddam Hussein; Kueh, Ahmad Beng Hong

2014-01-01

89

Episodic Mesozoic thickening and reworking of the North China Archean lower crust correlated to the fast-spreading Pacific plate  

NASA Astrophysics Data System (ADS)

A central target in Earth sciences is to understand the processes controlling the stabilization and destruction of Archean continents. The North China craton (NCC) has in part lost its dense crustal root after the Mesozoic, and thus it is a key region to test models of crust-mantle differentiation and subsequent evolution of the continental crust. However, the timing and mechanisms responsible for its crustal thickening and reworking have been long debated. Here we report the Early Cretaceous Yinan (eastern NCC) adakitic granites, for which major/trace elemental models demonstrate that they are complementary to the analogy of the documented eclogitic relicts within the NCC. Based on their Late Archean inherited zircons, depleted mantle Nd model ages of ˜2.8 Ga, large negative ?Nd(t) values (-36.7 to -25.3) and strongly radiogenic initial 87Sr/86Sr ratios (0.7178-0.7264), we suggest that the Yinan adakitic granites were potentially formed by the dehydration melting of a thickened Archean mica-bearing mafic lower crust during the Early Cretaceous (ca. 124 Ma), corresponding to a major period (117-132 Ma) of the NCC Mesozoic intrusive magmatism. Combined previous results, it is shown that the thickening and reworking of the North China Archean lower crust occurred largely as two short-lived episodes at 155-180 Ma and 117-132 Ma, rather than a gradual, secular event. These correlated temporally with the superfast-spreading Pacific plate during the Mesozoic. The synchroneity of these events suggests rapid plate motion of the Pacific plate driving the episodic NCC crustal thickening and reworking, resulting in dense eclogitic residues that became gravitationally unstable. The onset of lithospheric delamination occurred when upwelling asthenosphere heated the base of lower crust to form coeval felsic magmas with or without involvement of juvenile mantle material. Collectively, the circum-Pacific massive crustal production could be attributed to the unusually rapid motion of Pacific at 155-180 Ma and 117-132 Ma.

Zhang, Jun-Bo; Ling, Wen-Li; Liu, Yong-Sheng; Duan, Rui-Chun; Gao, Shan; Wu, Yuan-Bao; Yang, Hong-Mei; Qiu, Xiao-Fei; Zhang, Yong-Qing

2014-02-01

90

Plate convergence, transcurrent faults and internal deformation adjacent to Southeast Asia and the western Pacific  

NASA Technical Reports Server (NTRS)

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.

Fitch, T. J.

1971-01-01

91

Higher Harmonic Imaging of Tight Cracks in Glass Plates and Weld Interface with Mode-Converted Transverse Waves  

NASA Astrophysics Data System (ADS)

Higher harmonic imaging technique is applied for delineate the weld interface of thin metal plates and detecting tight cracks in glass plates. The technique of mode-converted shear wave is used for extracting higher harmonics and imaging the harmonic amplitudes. The backscattered higher harmonic wave is captured by a focused transducer in water immersion. High-pass filters of different cut-off frequencies are inserted in the reception circuit to extract higher harmonics and reduce the fundamental frequency component.

Kawashima, Koichiro; Sekino, Kouichi; Ichigo, Kazuyoshi

2008-06-01

92

Slab pull effects from a flexural analysis of the Tonga and Kermadec trenches (Pacific Plate)  

Microsoft Academic Search

Thin-plate flexure models have been frequently used to explain the mechanical behaviour of the lithosphere at oceanic trenches, but little attention has been paid to using them as a way to check the relative importance of different plate-driving mechanisms. A 2-D numerical algorithm accounting for the flexural deflection of the lithosphere controlled by multilayered elastic-plastic rheology (brittle-elastic-ductile) has been applied

Daniel Garcia-Castellanos; Montserrat Torne; Manel Fernàndez

2000-01-01

93

A reappraisal of seafloor spreading lineations in the Gulf of California: Implications for the transfer of Baja California to the Pacific plate and estimates of Pacific-North America motion  

Microsoft Academic Search

An analysis of seafloor spreading lineations in the southern Gulf of California demonstrates that divergence of the Baja peninsula from North America since 3.6 Ma has been significantly slower than Pacific-North America (PA-NA) motion estimated solely from closures of global plate circuits. This discrepancy remains unchanged or increases with modifications to the plate circuits and kinematic data used to predict

Charles DeMets

1995-01-01

94

True polar wander since 32 Ma B.P.: A paleomagnetic investigation of the skewness of magnetic anomaly 12r on the Pacific plate  

NASA Astrophysics Data System (ADS)

We test the fixed hot spot and fixed spin axis hypotheses through a paleomagnetic investigation of the skewness of crossings of magnetic anomaly 12r (32 Ma B.P.) between the Galapagos and Clarion fracture zones on the Pacific plate. We focus on this region for three reasons. First, numerical experiments show that these crossings, of all those available from the Pacific plate, should contain the most information about the location of the 32 Ma B.P. paleomagnetic pole for the Pacific plate. Second, many of the available crossings are from vector aeromagnetic profiles, which have superior signal-to-noise ratios. Third, the rate of seafloor spreading recorded in these crossings exceeds the threshold (half rate of 50 mm a-1) above which anomalous skewness is negligible. The new pole (83.5°N, 44.6°E) has compact 95% confidence limits (ellipse with major semiaxis length of 3.1° toward 84° clockwise from north and minor semiaxis length of 1.2°) and is not subject to the biases inherent in other methods for estimating Pacific plate paleomagnetic poles. The pole differs significantly by ?5° from the pole predicted if the Pacific hot spots have been fixed with respect to the spin axis, thus demonstrating, for the first time from paleomagnetic data, that Pacific hot spots have moved relative to the spin axis since the formation of the elbow in the Hawaiian-Emperor chain. The pole is consistent, however, with previously published paleomagnetic poles in a reference frame fixed relative to Indo-Atlantic hot spots. Thus, the new results require no motion between Pacific and Indo-Atlantic hot spots since 32 Ma B.P. Instead, superimposed on whatever motion occurs between hot spots, as expected for true polar wander.

Horner-Johnson, Benjamin C.; Gordon, Richard G.

2010-09-01

95

Late cretaceous pelagic sediments, volcanic ASH and biotas from near the Louisville hotspot, Pacific Plate, paleolatitude ???42??S  

USGS Publications Warehouse

Dredging on the deep inner slope of the Tonga Trench, immediately north of the intersection between the Louisville Ridge hotspot chain and the trench, recovered some Late Cretaceous (Maestrichtian) slightly tuffaceous pelagic sediments. They are inferred to have been scraped off a recently subducted Late Cretaceous guyot of the Louisville chain. In the vicinity of the Louisville hotspot (present location 50??26???S, 139??09???W; Late Cretaceous location ???42??S, longitude unknown) Late Cretaceous rich diatom, radiolarian, silicoflagellate, foraminiferal and coccolith biotas, accumulated on the flanks of the guyot and are described in this paper. Rich sponge faunas are not described. ?Inoceramus prisms are present. Volcanic ash is of within-plate alkalic character. Isotope ratios in bulk carbonate ??18O - 2.63 to + 0.85, ??13C + 2.98 to 3.83) are normal for Pacific Maestrichtian sediments. The local CCD may have been shallower than the regional CCD, because of high organic productivity. In some samples Late Cretaceous materials have been mixed with Neogene materials. Mixing may have taken place on the flanks of the guyot during transit across the western Pacific, or on the trench slope during or after subduction and offscraping about 0.5 Ma. ?? 1989.

Ballance, P. F.; Barron, J. A.; Blome, C. D.; Bukry, D.; Cawood, P. A.; Chaproniere, G. C. H.; Frisch, R.; Herzer, R. H.; Nelson, C. S.; Quinterno, P.; Ryan, H.; Scholl, D. W.; Stevenson, A. J.; Tappin, D. G.; Vallier, T. L.

1989-01-01

96

ELSEVIER Tectonophysics 293 (1998) 225238 Plate boundary deformation between the Pacific and North America in  

E-print Network

Fuca Ridge and the Cascadia subduction zone resulted in ridge fragmentation in the Explorer region to resolve these issues. Here, the interaction of the Juan de Fuca Ridge and the Cascadia subduction zone has of the consequences of plate tectonics is that a spreading ridge will eventually approach a subduction zone

97

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

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

98

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

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

99

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

100

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

NASA Astrophysics Data System (ADS)

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.

Villagomez, D.; Spikings, R.

2013-05-01

101

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

USGS Publications Warehouse

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.

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

2001-01-01

102

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)

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.

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

2010-12-01

103

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

Microsoft Academic Search

Pore fluid pressures in subduction zones are a primary control on fault strength and slip dynamics. Numerous studies document elevated pore pressures in the outer wedge along several margins. Seismic observations and the occurrence of non-volcanic tremor provide additional evidence for the presence of near-lithostatic pore pressures at the plate interface far down-dip from the trench (~35 km depth). Here

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

2010-01-01

104

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

105

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

USGS Publications Warehouse

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.

Parsons, T.; Thatcher, W.

2011-01-01

106

The Oligocene-Miocene Pacific-Australia plate boundary, south of New Zealand: Evolution from oceanic spreading to strike-slip faulting  

Microsoft Academic Search

Since the Eocene, the Pacific—Australia plate boundary south of New Zealand has evolved from a spreading system into a transform boundary. Swath data acquired in the Southeast Tasman oceanic crust, between the Macquarie Ridge complex and the Resolution Ridge system, show that the spreading fabric changes orientation southwards along the Puysegur Trench, striking successively N60°E, N85°E and N120°E. This reflects

Geoffroy Lamarche; Jean-Yves Collot; Ray A. Wood; Marc Sosson; Rupert Sutherland; Jean Delteil

1997-01-01

107

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)

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.

Argus, Donald F.; Gordon, Richard G.

1990-01-01

108

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

NASA Astrophysics Data System (ADS)

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

Brothers, Daniel Stephen

109

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.

2002-09-01

110

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

E-print Network

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,

Brothers, Daniel Stephen

2009-01-01

111

Along-strike Changes in Plate-bending Seismicity in the Mariana Islands: Implications for Strength of Interplate Coupling and Hydration of the Subducting Pacific Slab  

NASA Astrophysics Data System (ADS)

The occurrence of plate-bending earthquakes not only indicates the degree of coupling experienced along the shallow thrust of a subduction zone, but also the potential depth extent of slab hydration due to water circulation along faults prior to subduction. Using a combination of hypocentroidal decomposition relative relocation and teleseismic P & SH waveform inversion techniques, we refine the locations of earthquakes occurring seaward of the Marianas trench during 1976-2010 in order to determine the depth to which extension occurs in the subducting slab. A total of 205 CMT earthquakes in the Pacific plate or within a region 80 km west of the trench were located. Of those, 40 events ranging from Mw 4.9-7.4 were found to be intraplate trench and outer rise earthquakes. Six of these earthquakes were compressional and occurred only in the region south of Guam. The remainder of the events were extensional and are located throughout the entire length of the subduction zone. In the central part of the margin, east of the Celestial Serpentinite Seamount, extensional events occur directly beneath bathymetrically determined horst and graben structures in the incoming plate. The largest of these earthquakes was a Mw 7.4 event occurring during 1990 in a section of the trench where seamounts on the Pacific seafloor are being subducted. Preliminary results from inversion of teleseismic P waveforms for several of the plate bending events in this area give depths of 10-20 km. As expected, the weakly coupled Mariana subduction zone exhibits predominantly extensional earthquakes in the trench and outer rise along most of the margin. However, the southernmost section may be more strongly coupled, as evidenced by the 1993 Mw 7.7 Guam earthquake - thought by some to have occurred along the shallow thrust zone. Accurate depths obtained through waveform modeling will help us to determine whether the compressional earthquakes in the Pacific slab south of Guam are simply bending events located below the neutral plane or whether the entire incoming plate is under compression due to increased coupling within the southern part of the Marianas seismogenic zone. In addition, we observed a difference in the frequency of CMT earthquakes between the more seismic southern half and the generally quieter northern half of the subduction zone. Extensional faulting continues to a depth of at least 20 km in the subducting slab east of Celestial Serpentinite Seamount and provides a significant pathway for fluid circulation and hydration of the slab. Results from an upcoming ocean-bottom seismometer (OBS) experiment will allow us to better define the degree of hydration in the subducting slab and the depth range of plate-bending earthquakes.

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

2010-12-01

112

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

NASA Astrophysics Data System (ADS)

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.

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

113

Tectonic evolution of the Pacific margin of Antarctica 2. Structure of Late Cretaceous-early Tertiary plate boundaries in the Bellingshausen Sea from seismic reflection and gravity data  

NASA Astrophysics Data System (ADS)

Interpretations of multichannel seismic (MCS) reflection and potential field data suggest that some prominent gravity anomalies in the Bellingshausen Sea are associated with plate boundaries that were active during the Late Cretaceous and early Tertiary. Between 83° and 93°W, a belt of negative anomalies extends along the West Antarctic continental slope, which we term the continental slope gravity anomaly (CSGA). MCS profiles show that the CSGA coincides with an acoustically opaque structural high imaged beneath the lower slope. We interpret this structure as the upper part of an accretionary prism which formed during southward subduction of the Phoenix and Charcot plates, before Chatham Rise separated from West Antarctica. MCS profiles crossing the same margin to the northeast show no evidence of an extensive buried accretionary prism, but instead reveal an abrupt northeastward steepening of the continental slope near 78°W. We attribute this change in tectonic style, at least in part, to subduction erosion resulting from subduction of rough oceanic basement which formed at the Antarctic-Phoenix ridge after an abrupt decrease in spreading rate at chron 23r (52 Ma). Near 95°W, the Bellingshausen gravity anomaly (BGA) consists of a prominent low-high gravity couple which crosses the West Antarctic continental shelf, slope, and rise. The BGA corresponds to a buried asymmetric basement trough, where Cretaceous oceanic basement dips beneath more elevated basement to the east. The trough probably formed after subduction of Charcot plate ocean floor stalled at the nearby Antarctic Peninsula margin, near the end of the Cretaceous Normal Superchron. Ocean floor to the east of the BGA became attached to the Antarctic Peninsula, and the BGA trough subsequently accommodated a small amount of convergent motion between the Antarctic Peninsula and the ocean floor to the west (initially part of the Marie Byrd Land plate and later part of the Bellingshausen plate). Tectonism probably ceased at the BGA at chron 27 (61 Ma), as a result of a general plate reorganization in the South Pacific.

Cunningham, Alex P.; Larter, Robert D.; Barker, Peter F.; Gohl, Karsten; Nitsche, Frank O.

2002-12-01

114

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

USGS Publications Warehouse

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

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

2003-01-01

115

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

NASA Astrophysics Data System (ADS)

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

Li, J.-Y.

2006-03-01

116

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

E-print Network

) anomalies (slab suction [e.g., McKenzie, 1969; Turcotte and Oxburgh, 1967; Forsyth and Uyeda, 1975; Hager and O'Connell, 1981]), (3) propelled by potential energy variations over the oceanic plate (ridge push

Demouchy, Sylvie

117

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

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.

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

1996-01-01

118

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

PubMed

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

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

2009-01-30

119

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

120

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

SciTech Connect

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.

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

1993-04-01

121

Evidence for True Polar Wander since mid-Cenozoic time: A Paleomagnetic Investigation of the Skewness of Magnetic Anomaly 12r (32 Ma) Between the Galapagos and Clarion Fracture Zones on the Pacific Plate  

NASA Astrophysics Data System (ADS)

In recent years, some researchers have asserted that there has been no motion of the Pacific hotspots relative to the spin axis since the age (ca. 47 Ma) of the elbow in the Hawaiian-Emperor chain (e.g., Tarduno et al. 2003). In contrast, the apparent polar wander of the Indo-Atlantic hotspots shows distinct motion of the hotspots relative to the spin axis over the same time interval (e.g., Morgan 1981; Besse and Courtillot 2002). If this latter shift is due to true polar wander, one would expect to see a similar shift of Pacific hotspots relative to the spin axis. Here we present critical new data and analyses to test these distinctly different hypotheses. Specifically, we present results of an investigation of the skewness of magnetic anomaly crossings of anomaly 12r between the Galapagos and Clipperton and between the Clipperton and Clarion fracture zones on the Pacific plate. We chose to focus on these adjacent regions for three reasons. First, numerical experiments showed that these crossings, of all those available from the Pacific plate, should contain the most information about the location of the 32 Ma paleomagnetic pole for the Pacific plate. Second, many of the available crossings are from vector aeromagnetic profiles, which have superior signal to noise ratios (Horner-Johnson and Gordon, 2003). Third, the rate of seafloor spreading recorded in these crossings exceeds the threshold (half rate of 50 mm/yr) above which no anomalous skewness occurs. Moreover, for the first time, we combine uncertainties in plate- hotspot rotations (Andrews et al. 2005) with paleomagnetic uncertainties to obtain the total uncertainties of our new paleomagnetic pole reconstructed into the Pacific hotspot frame of reference. The results show significant and unambiguous motion of Pacific hotspots relative to the spin axis since 32 Ma. Moreover, when the 32 Ma Pacific plate paleomagnetic pole is reconstructed into the Pacific hotspot reference frame, it is consistent with the paleomagnetic pole of the Indo-Atlantic hotspots. We conclude that the global set of hotspots have mainly moved in unison relative to the spin axis since 32 Ma, which is most simply interpreted as true polar wander.

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

2007-12-01

122

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

USGS Publications Warehouse

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

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

2008-01-01

123

Reconstructing the Cenozoic evolution of the mantle: Implications for mantle plume dynamics under the Pacific and Indian plates  

NASA Astrophysics Data System (ADS)

The lack of knowledge of the initial thermal state of the mantle in the geological past is an outstanding problem in mantle convection. The resolution of this problem also requires the modelling of 3-D mantle evolution that yields maximum consistency with a wide suite of geophysical constraints. Quantifying the robustness of the reconstructed thermal evolution is another major concern. To solve and estimate the robustness of the time-reversed (inverse) problem of mantle convection, we analyse two different numerical techniques: the quasi-reversible (QRV) and the backward advection (BAD) methods. Our investigation extends over the 65 Myr interval encompassing the Cenozoic era using a pseudo-spectral solution for compressible-flow thermal convection in 3-D spherical geometry. We find that the two dominant issues for solving the inverse problem of mantle convection are the choice of horizontally-averaged temperature (i.e., geotherm) and mechanical surface boundary conditions. We find, in particular, that the inclusion of thermal boundary layers that yield Earth-like heat flux at the top and bottom of the mantle has a critical impact on the reconstruction of mantle evolution. We have developed a new regularisation scheme for the QRV method using a time-dependent regularisation function. This revised implementation of the QRV method delivers time-dependent reconstructions of mantle heterogeneity that reveal: (1) the stability of Pacific and African ‘large low shear velocity provinces’ (LLSVP) over the last 65 Myr; (2) strong upward deflections of the CMB topography at 65 Ma beneath: the North Atlantic, the south-central Pacific, the East Pacific Rise (EPR) and the eastern Antarctica; (3) an anchored deep-mantle plume ascending directly under the EPR (Easter and Pitcairn hotspots) throughout the Cenozoic era; and (4) the appearance of the transient Reunion plume head beneath the western edge of the Deccan Plateau at 65 Ma. Our reconstructions of Cenozoic mantle evolution thus suggest that mantle plumes play a key role in driving surface tectonic processes and large-scale volcanism.

Glišovi?, Petar; Forte, Alessandro M.

2014-03-01

124

INTERFACE  

E-print Network

Allows use of any input range Easy to drive with the ADA4941 No pipeline delay Single-supply 2.5 V operation with 1.8 V/2.5 V/3 V/5 V logic interface Serial interface SPI®-/QSPI™-/MICROWIRE™-/DSP-compatible Ability to daisy-chain multiple ADCs and busy indicator 10-lead package: MSOP (MSOP-8 size) and 3 mm × 3 mm QFN (LFCSP), SOT-23 size APPLICATIONS Battery-powered equipment Data acquisition systems Medical instruments Seismic data acquisition systems

Low Power Dissipation

125

Seismicity and volcanism in the Pacific Northwest: Evidence for the segmentation of the Juan De Fuca Plate  

NASA Astrophysics Data System (ADS)

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

Weaver, Craig S.; Michaelson, Caryl A.

126

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)

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.

Yang, Yong-Tai

2013-11-01

127

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  

Microsoft Academic Search

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

Beate Leitner

1999-01-01

128

INTERFACE  

E-print Network

INL: ±2.25 LSB maximum Dynamic range: 99.7 dB typical True differential analog input range: ±VREF 0 V to VREF with VREF between 2.9 V to 5.0 V Allows use of any input range Easy to drive with the ADA4941 No pipeline delay Single-supply 2.5 V operation with 1.8 V/2.5 V/3 V/5 V logic interface Serial interface SPI-/QSPI™-/MICROWIRE™-/DSP-compatible Ability to daisy-chain multiple ADCs and busy indicator 10-lead MSOP (MSOP-8 size) and 10-lead 3 mm × 3 mm QFN (LFCSP), SOT-23 size APPLICATIONS Battery-powered equipment Data acquisition systems Medical instruments Seismic data acquisition systems

Daisy Chain

129

Plate Motions  

NSDL National Science Digital Library

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.

Nunn, Jeffrey

130

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)

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.

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

131

Widespread remagnetizations associated with sedimentary greigite (Fe3S4): Implications for Neogene tectonic rotations within the Australia-Pacific plate boundary zone, New Zealand  

NASA Astrophysics Data System (ADS)

Greigite (Fe3S4) can grow at any time during diagenesis when dissolved iron and sulfide are available in sedimentary pore waters. Greigite can produce syn-depositional paleomagnetic signals that are useful for paleomagnetic studies, but it can also produce late remagnetizations that make paleomagnetic interpretations much more complicated. Determining the timing of remanence acquisition is therefore a key aspect of paleomagnetic studies of the spatially and stratigraphically widespread sedimentary sequences in which greigite is the dominant remanence carrier. We demonstrate from paleomagnetic results, which are constrained rigorously by field tests, that late diagenetic greigite growth has remagnetized up to 65% of sampled localities on the Hikurangi margin, East Coast, New Zealand. This means that the magnetizations that record large, clockwise vertical axis tectonic rotations (50-80°) of the Hikurangi margin are often considerably younger than the age of the host sediments, with remagnetizations clustered at 5-8 Ma. The remagnetizations require much greater rotation rates (8-14°/Ma) than were inferred before the remagnetizations were recognized and that are also much greater than the present geodetically observed rate (3-4°/Ma). This requires a change in tectonic regime, with slower rotation rates since development of the North Island shear belt at 1-2 Ma. Our results are consistent with long- and short-term deformation on the Hikurangi margin being driven by realignment of the subducting Pacific plate, with collision of the Hikurangi Plateau in the late Miocene potentially being key to both initiation of tectonic rotations and widespread remagnetization of Neogene sediments. The remagnetizations are inferred to have been caused by migration of gas hydrates through the sediments in association with collision of the Hikurangi Plateau.

Rowan, C.; Roberts, A. P.

2011-12-01

132

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)

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.

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

133

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

NASA Astrophysics Data System (ADS)

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

Bormann, Jayne M.

134

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

135

Suloy, Pacific Ocean  

NASA Technical Reports Server (NTRS)

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

1992-01-01

136

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)

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

Peker, Mevlut Fatih

137

How Plates Move  

NSDL National Science Digital Library

This information on the two major types of plate interaction and the resulting features discusses the Mid Atlantic Ridge and the mid-ocean ridges in connection with divergence and ocean trenches and connects the Pacific Ring of Fire to the concept of subduction. Volcanic activity as a result of subduction is also covered. The site also features links to goals, objectives, and materials for a hands-on lesson on how plates move.

138

Spatial distribution of focal mechanisms for interplate and intraplate earthquakes associated with the subducting Pacific plate beneath the northeastern Japan arc: A triple-planed deep seismic zone  

Microsoft Academic Search

The northeastern Japan arc is located in one of the most seismically active subduction zones in the world. In this study, we relocated hypocenters and determined focal mechanisms of small earthquakes (M<=5) beneath the arc in order to investigate in detail the stress distribution in and around the descending oceanic plate. In the hypocenter relocation we adopted a ``source region

Toshihiro Igarashi; Toru Matsuzawa; Norihito Umino; Akira Hasegawa

2001-01-01

139

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

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.

Batiza, R.; Oestrike, R.; Futa, K.

1982-01-01

140

Evidence for crustal thickening and shortening of the overriding plate during incipient plate/plate subduction  

NASA Astrophysics Data System (ADS)

Evidence from a study of the Macquarie Ridge Complex and comparison with other plate boundaries displaying varying development of intraplate compressional structures, indicate that thickening and shorting of the overriding plate occur during incipient subduction. The Macquarie Ridge Complex has been produced by a tectonic history oblique compression between the Indian/Australian and Pacific plates at their common boundary south of New Zealand. In the central Macquarie Ridge Complex intraplate transpressive forces have resulted in the uplift of oceanic crust of the Indian/Australian plate to form the Macquarie Ridge and incipient subduction of the Pacific oceanic plate at the Macquarie Trench. The uplift has been effected by thickening and shortening of the oceanic crust of the overriding Indian/Australian plate accompanied by shallow seismicity at the ridge, whereas the Pacific plate at the trench has not been thickened. Post-1964 earthquakes of the Macquarie Ridge Complex form a single narrow band some tens of kilometres wide. In the central Macquarie Ridge Complex the band of seismicity is confined to the ridge and not the trench, suggesting that crustal thickening rather than subduction is the preferred style of tectonism for incipient subduction zones. Fault plane solutions indicate dextral motion that is consistent with anticlockwise rotation of the Pacific plate relative to the Australian plate, and with transpression and incipient subduction in the central segment of the Complex.

Williamson, P. E.; Jones, T. D.; McCue, K. F.

1989-04-01

141

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

142

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)

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

Andolina, Vincent L.

143

Channel plate for DNA sequencing  

DOEpatents

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.

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

1998-01-01

144

Channel plate for DNA sequencing  

DOEpatents

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.

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

1998-01-13

145

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)

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.

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

2013-12-01

146

Recent plate motions and crustal deformation  

SciTech Connect

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.

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

1991-01-01

147

The Nature of Tectonic Plates  

NSDL National Science Digital Library

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.

Rhinehart, Ken

148

Coseismic slip distribution of the 2011 off the Pacific Coast of Tohoku Earthquake (M9.0) refined by means of seafloor geodetic data  

NASA Astrophysics Data System (ADS)

On 11 March 2011, the devastating M9.0 Tohoku Earthquake occurred on the interface of the subducting Pacific plate, and was followed by a huge tsunami that killed about 20,000 people. Several geophysical studies have already suggested that the very shallow portion of the plate interface might have played an important role in producing such a large earthquake and tsunami. However, the sparsity of seafloor observations leads to insufficient spatial resolution of the fault slip on such a shallow plate interface. For this reason, the location and degree of the slip has not yet been estimated accurately enough to assess future seismic risks. Thus, we estimated the coseismic slip distribution based on terrestrial GPS observations and all available seafloor geodetic data that significantly improve the spatial resolution at the shallow portion of the plate interface. The results reveal that an extremely large (greater than 50 m) slip occurred in a small (about 40 km in width and 120 km in length) area near the Japan Trench and generated the huge tsunami. The estimated slip distribution and a comparison of it with the coupling coefficient distribution deduced from the analysis of the small repeating earthquakes suggest that the 2011 Tohoku Earthquake released strain energy that had accumulated over the past 1000 years, probably since the Jogan Earthquake in 869. The accurate assessments of seismic risks on very shallow plate interfaces in subduction zones throughout the world can be obtained by improving the quality and quantity of seafloor geodetic observations.

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

2012-07-01

149

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

ERIC Educational Resources Information Center

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

Hughes, Phillip; And Others

150

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.

151

Tectonics of the Easter plate  

NASA Technical Reports Server (NTRS)

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.

Engeln, J. F.; Stein, S.

1984-01-01

152

Cooling history of the Pacific lithosphere  

NASA Astrophysics Data System (ADS)

Plate tectonics is expressed most simply in oceanic plates where a thermal boundary layer or "lithosphere" forms and thickens as the plate cools during its journey away from mid-ocean ridges. Numerous studies based dominantly on surface observables have established that the oceanic lithosphere, particularly across the Pacific, does not cool continuously as it ages. Based on a seismic model of the Pacific upper mantle inferred from a new compilation of seismic surface wave dispersion measurements, we show that, on average, the Pacific lithosphere has experienced a punctuated cooling history, cooling diffusively at ages until ˜70 Ma and then reheating in the Central Pacific between ages of 70 and 100 Ma predominantly at depths between 70 and 150 km. At ages from 100 Ma to about 135 Ma, the processes of reheating are substantially weaker than in the Central Pacific. We show that thermal boundary layer instabilities (TBI) develop naturally as the plate cools and, with the right rheology, can explain the mean characteristics of the observed cooling history of the Pacific plate.

Ritzwoller, Michael H.; Shapiro, Nikolai M.; Zhong, Shi-Jie

2004-09-01

153

Plate Tectonics  

NSDL National Science Digital Library

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 ...

Rohlfing, Mrs.

2011-02-03

154

Kinematics to dynamics in the New Zealand plate-boundary zone  

NASA Astrophysics Data System (ADS)

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.

Lamb, Simon

2014-05-01

155

Tethyan closure, Andean orogeny, and westward drift of the Pacific Basin  

Microsoft Academic Search

The deep-sea trenches that circumscribe the Pacific basin are moving westward relative to the deep mantle by a few cm\\/yr, together with the Pacific seafloor. While the westward drift of the Pacific basin dominates the observed net westward rotation of Earth's tectonic plates relative to the deep mantle source of the Pacific hotspots, its cause remains uncertain. We demonstrate that

Laurent Husson; Clinton P. Conrad; Claudio Faccenna

2008-01-01

156

Plating on stainless steel alloys  

SciTech Connect

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

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

1981-09-11

157

A Western Pacific Hotspot?  

NASA Astrophysics Data System (ADS)

The petrology of volcanic rocks from the St. Andrew Strait and helium isotope ratios of backarc lavas from the Manus Basin have been used to propose the existence of an active hotspot beneath the eastern Bismarck Sea (Johnson et al., 1978; Macpherson et al., 1998). The past influence of this hotspot can be assessed by mapping its present location onto a plate tectonic reconstruction of the western Pacific (Macpherson and Hall, 2001). During the Middle Eocene the nascent Izu-Bonin-Mariana (IBM) arc lay above the hotspot. The volume of magma emplaced at the IBM arc at that time substantially exceeds the average magma production rate for mature island arcs. Furthermore, the ultramafic (boninitic) character of much of this magmatism requires elevated temperatures. The geochemistry of contemporaneous magmatism in the backarc resembles ocean island basalts and much of the backarc region experienced significant uplift at that time. All of these features can be explained by the influx of hot, buoyant, chemically distinct mantle beneath the IBM and its hinterland. The lithosphere lying above the hotspot during the later Eocene was subsequently subducted. During the Oligo-Miocene the hotspot was traversed by parts of the Caroline Plate where the Euripik Rise is found. This is an aseismic rise that possesses the geophysical characteristics of thickened oceanic crust formed by excess, basaltic magmatism and is the type of structure that would result from the passage of relatively young oceanic lithosphere over a mantle hotspot. Plate reconstruction for the western Pacific predicts a hotspot trail that is consistent with the Middle Eocene and Oligo-Miocene geology of the IBM and Caroline Plates, respectively (Macpherson and Hall, 2001). Parts of the trail have been disrupted by subsequent sea-floor spreading or lost through subduction but the remaining vestiges are consistent with the action of a thermal anomaly throughout much of the Cenozoic. More speculatively, buoyancy differences between the IBM, supported by hot mantle, and older, colder lithosphere of the adjacent Pacific Plate may have provided a mechanism to propagate widespread subduction at the nascent IBM arc. Johnson RW, Smith IEM, &Taylor SR, BMR J. Aus. Geol. Geophys. 3, 55-69, (1978). Macpherson CG, Hilton, DR, Sinton, JM, Poreda RJ &Craig H. Geology 26, 1007-1010, (1998). Macpherson CG &Hall R, Earth Planet. Sci. Lett. 186, 215-230, (2001).

MacPherson, C. G.; Hall, R.

2003-04-01

158

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.

159

Is the Pacific splitting in two? 26 January 2008  

E-print Network

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

Clouard, Valerie

160

Plate Tectonics  

NSDL National Science Digital Library

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 ...

Walls, Mrs.

2011-01-30

161

Plate Tectonics  

NSDL National Science Digital Library

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.

Smoothstone; Company, Houghton M.

162

Intermittent plate tectonics?  

PubMed

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

Silver, Paul G; Behn, Mark D

2008-01-01

163

Plate Tectonics  

NSDL National Science Digital Library

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.

National Science Teachers Association (NSTA)

2007-03-21

164

How Shifting Plates Caused the Earthquake and Tsunami in Japan  

NSDL National Science Digital Library

The sudden movement of the Pacific tectonic plate under the North American plate caused a massive earthquake and a tsunami in Japan in 2011. This resource provides interactive maps illustrating the shifting plates and rising water, the shaking magnitude and subsequent tsunami wave heights. Additional interactive maps reflecting aftershocks, infrastructure impact and radiation levels throughout the affected environment are available.

2011-03-13

165

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

Microsoft Academic Search

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

Charles Demets; Seth Stein

1990-01-01

166

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

Microsoft Academic Search

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

Martin Meschede; Wolfgang Frisch

1998-01-01

167

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

USGS Publications Warehouse

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.

Smoczyk, Gregory M.; Hayes, Gavin; Hamburger, Michael W.; Benz, Harley M.; Villasenor, Antonio; Furlong, Kevin P.

2013-01-01

168

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

NASA Technical Reports Server (NTRS)

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?

Demets, Charles; Stein, Seth

1990-01-01

169

Plate Tectonics  

NSDL National Science Digital Library

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.

2006-01-01

170

Overriding plate controls on subduction evolution  

NASA Astrophysics Data System (ADS)

Geologic and geophysical observations indicate that the thickness, density, and strength of the lithosphere vary on the Earth. However, the role of the overriding plate lithosphere properties on the evolution and morphology of subduction is not well understood. This paper presents time-dependent numerical models of subduction that vary the overriding plate thickness, strength, and density and allow for a plate interface that evolves with time via an anisotropic brittle failure rheology. We examine the effect of these parameters on subduction evolution, in particular, the emergence of (a) asymmetric versus symmetric subduction, (b) trench retreat versus advance, (c) subduction zone geometry, (d) slab stagnation versus penetration into the lower mantle, and (e) flat slab subduction. Almost all of the models presented result in sustained asymmetric subduction from initiation. Trench advance occurs in models with a thick and or strong overriding plate. Slab dip, measured at a depth below the plate boundary interface, has a negative correlation with an increase in overriding plate thickness. Overriding plate thickness exerts a first-order control over slab penetration into the lower mantle, with penetration most commonly occurring in models with a thick overriding plate. Periods of flat slab subduction occur with thick, strong overriding plates producing strong plate boundary interface coupling. The results provide insight into how the overriding plate plays a role in establishing advancing and retreating subduction as well as providing an explanation for the variation of slab geometry across subduction zones on Earth, where similar patterns of evolution are observed.

Sharples, W.; Jadamec, M. A.; Moresi, L. N.; Capitanio, F. A.

2014-08-01

171

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

Microsoft Academic Search

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

Tetsuzo Seno; Seth Stein; Alice E. Gripp

1993-01-01

172

Parallel Plate Antenna.  

National Technical Information Service (NTIS)

The invention as disclosed is a parallel plate antenna having a number of stacked horizontal plates and two vertical plates. Alternating ones of the horizontal plates are electrically coupled to one vertical plate such that the horizontal plates coupled t...

D. F. Rivera

2009-01-01

173

Organization of the tectonic plates in the last 200 Myr Gabriele Morra a,n  

E-print Network

Organization of the tectonic plates in the last 200 Myr Gabriele Morra a,n , Maria Seton b a c t The present tessellation of the Earth's surface into tectonic plates displays a remarkably in the past to explore the dynamics governing this timescale. The Pacific plate is the largest tectonic plate

Müller, Dietmar

174

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

Microsoft Academic Search

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

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

175

Short-wavelength geoid, bathymetry and the convective pattern beneath the Pacific Ocean  

Microsoft Academic Search

Geoid and topography over the Pacific Ocean are filtered to enhance small and intermediate wavelength. The filtered maps and rotations characterizing the absolute motion of the Pacific Plate are used to discuss the origin of lineaments coinciding with tracks issued from spots of known recent volcanism. It is concluded that the convective pattern beneath the plates consists of numerous rising

L. Fleitout; C. Moriceau

1992-01-01

176

Izanagi-Pacific Ridge Subduction and its Geodynamic Consequences  

NASA Astrophysics Data System (ADS)

As part of a global plate tectonic model for 140 Ma to the present we present a revised plate reconstruction for the western Pacific and investigate its geodynamic consequences. In our plate model, mid-ocean ridge subduction beneath southern Japan occurs at 60-55 Ma, 20 million years later than proposed for Kula-Pacific or Farallon- Izanagi ridge subduction. The difference arises because Izanagi-Pacific (I-P) spreading ceases in previous models after 110 Ma while our model incorporates continued spreading until the I-P ridge subducts beneath eastern Asia at 60-55 Ma. We regard cessation of spreading at the I-P ridge between 110 and 80 Ma as unlikely as the Izanagi plate was undergoing rapid motion, driven by net slab-pull force, from the north-northwest, immediately prior to the proposed spreading cessation. Metamorphism of the Ryoke Belt in southern Japan has previously been attributed to Kula-Pacific ridge subduction at 85 Ma, but the high-T/low-P Ryoke Belt cannot be uniquely linked to a ridge subduction event. We propose that sub-parallel subduction of the I-P mid-ocean ridge beneath Japan at 60-55 Ma resulted in nearly simultaneous slab break-off along the length of the Japanese trench (approximately 2700 km). Geological evidence for this model includes cessation of a major accretion phase in the late Cretaceous, emplacement of the Okitsu Melange due to subduction of hot, buoyant material at 55 Ma, and cross-cutting fault fabrics that indicate a counter-clockwise rotation in relative plate motions between Eurasia and the I-P plate, consistent with palaeothermal and palaeopressure data, some time between 55 and 34 Ma. Rapid subduction of the I-P ridge, over a vast distance, may have triggered a chain reaction of tectonic plate reorganizations. With complete subduction of the I-P ridge at 55 Ma, forces acting on the western edge of the Pacific Plate would have changed from ridge-push to slab pull, changing Pacific absolute plate motions from northwest to west. A combination of Australian and Pacific plate motion changes between 53 Ma and 50 Ma then initiated both the Tonga-Kermadec subduction system and the Izu-Bonin-Marianas subduction systems around 50Ma, likely due to convergence across a fracture zone caused by the Pacific plate motion change. We suggest that the observed slowdown of sub-Pacific mantle flow at 47 Ma was due to progressive impediment of lateral sub-Pacific mantle flow by the descending slabs of the Izu-Bonin-Marianas and Tonga-Kermadec subduction zones.

Müller, R. D.; Whittaker, J. M.; Sdrolias, M.

2007-12-01

177

A Cenozoic diffuse alkaline magmatic province (DAMP) in the southwest Pacific without rift or plume origin  

E-print Network

A Cenozoic diffuse alkaline magmatic province (DAMP) in the southwest Pacific without rift or plume of the Pacific Plate. A key to generating the Cenozoic magmatism is the combination of metasomatized lithosphere. The model may also provide a mechanism for warming south Pacific mantle and resulting Cenozoic alkaline

Müller, Dietmar

178

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

179

High-frequency seismic radiation during Maule earthquake (Chile, 27/02/2010, Mw 8.8) inferred by backprojection of P waves: evidence of activation of two distinct zones at the downdip part of the plate interface  

NASA Astrophysics Data System (ADS)

We back-project the seismic radiation released by Maule earthquake (Chile, 27/02/2010, Mw 8.8) in three frequency bands: 0.4-3 Hz, 1-4 Hz, 2-8 Hz. We measure the coherence of the seismic traces at 557 stations of US array by semblance. Travel times are estimated starting from a 1D global velocity model (ak135) corrected by two terms: a static correction and a dynamic correction. Static corrections are the mean time corrections to the 1D velocity model, and dynamic corrections are finer time shifts depending on the source-receiver path. Both terms are extracted from the time shifts between different receivers of P-phases of 23 high-magnitude calibration aftershocks, most of which have high precision locations based on the temporary deployment following the Maule earthquake (IMAD). The dynamic corrections are extended over a fine source grid by kriging interpolation. This procedure makes the backprojection results independent of the main shock catalog hypocentre and allows coherent imaging to higher frequencies. During the first 20 seconds of the rupture process, the source is stable nearby the nucleation point, which is close to epicentre proposed by Vigny et al (Science, 2011) based on high rate GPS motion. Afterwards, it moves bilaterally, with the northern front moving with an average velocity of ˜3 km/s. Most of the energy is emitted from the northern patch of the bi-lateral rupture (˜70%), with sporadic emissions from the southern patch. The maximum of stacked energy is located about 150 km north-eastwards from the epicenter and a relative maximum appears south of Arauco peninsula. In the dip direction, energy is mostly emitted from the down-dip edge of the co-seismic area, roughly matching the aftershock distribution. Specifically, we find that coherent radiation is emitted from two distinct belts nearly parallel to the trench. The position of these belts is in good agreement with the location of the aftershocks, which also are arranged in two disconnected zones of the subduction interface at different depths, the deeper of which is characterised by a large number of repeating event clusters (Rietbrock, Jenkins et al., this session). Thus, our backprojection analysis in combination with the aftershock distribution demonstrates the existence of a peculiar doubled downdip transition from seismogenic behaviour to stable sliding. We suspect fluids released from the downgoing plate to be the cause of the transitions in frictional behaviour because of (1) the co-location of high Vp/Vs ratios with the deep interface seismicity, (2) systematic decrease of depth of onset of deeper seismicity with younging incoming plate age, (3) patchy occurrence along-strike of deeper seismicity.

Palo, M.; Tilmann, F. J.; Krueger, F.; Ehlert, L.; Lange, D.; Rietbrock, A.; Jenkins, J.; Hicks, S. P.

2013-12-01

180

Plate TectonicsPlate Tectonics Plate TectonicsPlate Tectonics  

E-print Network

ridge systems #12;Concentration of earthquakes #12;Mid-ocean ridge systems #12;Deep Sea Drilling Project, transform boundaries ­ travel 1 to 11 cm/yr relative to one another #12;14 tectonic plates today #12;Mid-ocean

Siebel, Wolfgang

181

How Shifting Plates Caused the Earthquake and Tsunami in Japan  

NSDL National Science Digital Library

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.

Times, New Y.

182

Evolution of the Mariana Convergent Plate Margin System  

Microsoft Academic Search

The Mariana convergent plate margin system of the western Pacific provides opportunities for studying the tectonic and geochemical processes of intraoceanic plate subduction without the added complexities of continental geology. The system's relative geologic simplicity and the well-exposed sections of lithosphere in each of its tectonic provinces permit in situ examination of processes critical to understanding subduction tectonics. Its general

Patricia Fryer

1996-01-01

183

Evolution of the mariana convergent plate margin system  

Microsoft Academic Search

The Mariana convergent plate margin system of the western Pacific provides opportunities for studying the tectonic and geochemical processes of intraoceanic plate subduction without the added complexities of continental geology. The system's relative geologic simplicity and the well-exposed sections of lithosphere in each of its tectonic provinces permit in situ examination of processes critical to understanding subduction tectonics. Its general

Patricia Fryer

1996-01-01

184

Beyond Plate Tectonics: “Plate ” Dynamics  

E-print Network

Plate tectonics dogma has resulted in a variety of theories that frequently violate first principles. In this article it is suggested that ridges are in compression, not tension from convection cells, triple junctions cause hot spots (not vice versa), mantle plumes do not cause hot spot tracks, chord push creates pressures well in excess of lithostatic load, the arch effect demonstrates that rifts form both in compression and tension, surging (i.e. the sudden and rapid motion of the plates) occurs episodically, the presence of a basal shear zone a few meters thick during surging, the preferred initiation of subduction zones at the ridge, revision of the Wilson Cycle, the conformance of “old ” school geologists and plate tectonicians, earth-based non bolide impact mass extinctions, the loss of the earth’s magnetic field and its subsequent reappearance, additional application of the least work (or maximum

Richard Moody

185

Recent tectonic plate decelerations driven by mantle convection  

NASA Astrophysics Data System (ADS)

We explore recent changes in tectonic plate velocities using a model of mantle flow that is based on a new high-resolution global tomography model derived from simultaneous inversions of global seismic, geodynamic and mineral physical data sets. This plate-coupled mantle convection model incorporates a viscosity structure that reconciles both glacial isostatic adjustment and global convection-related data sets. The convection model successfully reproduces present-day plate velocities and global surface gravity and topography constraints. We predict time-dependent changes in mantle buoyancy that give rise to present-day decelerations of several major plates, in particular the fast-moving Pacific and Nazca plates. We verify the plausibility of these predicted plate decelerations using space geodetic and oceanic magnetic anomaly constraints on tectonic plate motions. These plate kinematic constraints are employed to determine a new global map of present-day plate decelerations that agree well with the mantle flow predictions.

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

2009-12-01

186

Volcanism in response to plate flexure.  

PubMed

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

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

2006-09-01

187

Plating on some difficult-to-plate metals and alloys  

SciTech Connect

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

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

1980-02-01

188

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

E-print Network

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

Husson, Laurent

189

New kinematic models for Pacific-North America motion from 3 Ma to present, I: Evidence for steady motion and biases in the NUVEL-1A model  

Microsoft Academic Search

We use velocities derived from 2-4.5 years of continuous GPS observations at 21 sites on the Pacific and North American plates along with a subset of the NUVEL-1A data to examine the steadiness of Pacific-North America motion since 3.16 Ma, the transfer of Baja California to the Pacific plate, and the magnitude of biases in the NUVEL-1A estimate of Pacific-North

Charles DeMets; Timothy H. Dixon

1999-01-01

190

Creation of the Cocos and Nazca plates by fission of the Farallon plate  

NASA Astrophysics Data System (ADS)

Throughout the Early Tertiary the area of the Farallon oceanic plate was episodically diminished by detachment of large and small northern regions, which became independently moving plates and microplates. The nature and history of Farallon plate fragmentation has been inferred mainly from structural patterns on the western, Pacific-plate flank of the East Pacific Rise, because the fragmented eastern flank has been subducted. The final episode of plate fragmentation occurred at the beginning of the Miocene, when the Cocos plate was split off, leaving the much reduced Farallon plate to be renamed the Nazca plate, and initiating Cocos-Nazca spreading. Some Oligocene Farallon plate with rifted margins that are a direct record of this plate-splitting event has survived in the eastern tropical Pacific, most extensively off northern Peru and Ecuador. Small remnants of the conjugate northern rifted margin are exposed off Costa Rica, and perhaps south of Panama. Marine geophysical profiles (bathymetric, magnetic and seismic reflection) and multibeam sonar swaths across these rifted oceanic margins, combined with surveys of 30-20 Ma crust on the western rise-flank, indicate that (i) Localized lithospheric rupture to create a new plate boundary was preceded by plate stretching and fracturing in a belt several hundred km wide. Fissural volcanism along some of these fractures built volcanic ridges (e.g., Alvarado and Sarmiento Ridges) that are 1-2 km high and parallel to "absolute" Farallon plate motion; they closely resemble fissural ridges described from the young western flank of the present Pacific-Nazca rise. (ii) For 1-2 m.y. prior to final rupture of the Farallon plate, perhaps coinciding with the period of lithospheric stretching, the entire plate changed direction to a more easterly ("Nazca-like") course; after the split the northern (Cocos) part reverted to a northeasterly absolute motion. (iii) The plate-splitting fracture that became the site of initial Cocos-Nazca spreading was a linear feature that, at least through the 680 km of ruptured Oligocene lithosphere known to have avoided subduction, did not follow any pre-existing feature on the Farallon plate, e.g., a "fracture zone" trail of a transform fault. (iv) The margins of surviving parts of the plate-splitting fracture have narrow shoulders raised by uplift of unloaded footwalls, and partially buried by fissural volcanism. (v) Cocos-Nazca spreading began at 23 Ma; reports of older Cocos-Nazca crust in the eastern Panama Basin were based on misidentified magnetic anomalies. There is increased evidence that the driving force for the 23 Ma fission of the Farallon plate was the divergence of slab-pull stresses at the Middle America and South America subduction zones. The timing and location of the split may have been influenced by (i) the increasingly divergent northeast slab pull at the Middle America subduction zone, which lengthened and reoriented because of motion between the North America and Caribbean plates; (ii) the slightly earlier detachment of a northern part of the plate that had been entering the California subduction zone, contributing a less divergent plate-driving stress; and (iii) weakening of older parts of the plate by the Galapagos hotspot, which had come to underlie the equatorial region, midway between the risecrest and the two subduction zones, by the Late Oligocene.

Lonsdale, Peter

2005-08-01

191

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

USGS Publications Warehouse

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

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

2002-01-01

192

A Forecaster's Overview of the Northwest Pacific  

NSDL National Science Digital Library

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.

Comet

2010-08-31

193

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

NSDL National Science Digital Library

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.

Egger, Anne

2003-03-18

194

Preliminary determination of Pacific-North America relative motion in the southern Gulf of California using the Global Positioning System  

NASA Technical Reports Server (NTRS)

GPS data from experiments conducted in 1985 and 1989 in the southern Gulf of California, Mexico, allow a determination of relative motion between the Pacific and North American plates. The data indicate motion by Cabo San Lucas on the Pacific plate relative to North America at a rate of 47 + or - 7 mm/yr and azimuth of 57 + or - 6 deg west of north, equivalent within uncertainties to the NUVEL-1 global plate motion model.

Dixon, T. H.; Gonzalez, G.; Lichten, S. M.; Tralli, D. M.; Ness, G. E.

1991-01-01

195

Pacific subduction and Mesozoic mineralization in eastern China  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

196

Seismic Hazard of American Samoa and Neighboring South Pacific Islands: Data, Methods, Parameters, and Results.  

National Technical Information Service (NTIS)

American Samoa and the neighboring islands of the South Pacific lie near active tectonic-plate boundaries that host many large earthquakes which can result in strong earthquake shaking and tsunamis. To mitigate earthquake risks from future ground shaking,...

C. S. Mueller, D. E. McNamara, K. S. Rukstales, M. Walling, M. D. Petersen, N. Luco, S. C. Harmsen

2012-01-01

197

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

SciTech Connect

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.

Cabre, R.

1983-01-01

198

A Subduction Scissor and Development of the Intervening Plate Collision at South Island, New Zealand  

Microsoft Academic Search

The continental plate collision across South Island, New Zealand is bounded to the north by west-dipping Hikurangi subduction of the Pacific plate and to the south by east-dipping Fiordland-Puysegur subduction of the Australian plate. As such, South Island is in the midst of a type of 'subduction scissor'. The tectonic behaviour of the deep plate portion of South Island (viz.,

R. N. Pysklywec; S. Ellis; A. R. Gorman

2007-01-01

199

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.

200

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

SciTech Connect

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.

McCreery, C.S.

1981-05-01

201

Seismic anisotropy of the Pacific slab and mantle wedge beneath the Japanese islands  

Microsoft Academic Search

The mantle beneath the Japanese islands is complex because of subduction of the Pacific and Philippine Sea plates and the deformation associated with it. Detection of seismic anisotropy should be useful for understanding the processes occurring in such mantle. Here we resolve seismic anisotropy of the mantle wedge from that of the underlying subducted Pacific slab using a large number

Yoko Tono; Yoshio Fukao; Takashi Kunugi; Seiji Tsuboi

2009-01-01

202

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

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.

Wells, R. E.

1989-01-01

203

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

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

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

2001-01-01

204

DECEMBER 2000 U. S. Pacific  

E-print Network

. . . . 103 KILLER WHALE (Orcinus orca): Eastern North Pacific Transient Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 KILLER WHALE (Orcinus orca): Eastern North Pacific Offshore Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 KILLER WHALE (Orcinus orca): Eastern North Pacific Southern Resident Stock

205

Plate Tectonics Animation  

NSDL National Science Digital Library

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.

2002-01-01

206

Seattle Pacific University undergraduate  

E-print Network

Sciences School of Psychology, Family, and Community School of Theology APPENDIXES Faculty Board of publication. The University reserves the right, however, to make changes of any nature in programs, calendar. #12;2 About Seattle Pacific University "Seattle Pacific University seeks to be a premier Christian

Nelson, Tim

207

PACIFIC NORTHWEST CYBER SUMMIT  

SciTech Connect

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.

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

2013-08-07

208

The 5 September 2012 Nicoya, Costa Rica Mw 7.6 earthquake rupture process from joint inversion of high-rate GPS, strong-motion, and teleseismic P wave data and its relationship to adjacent plate boundary interface properties  

NASA Astrophysics Data System (ADS)

On 5 September 2012, a large thrust earthquake (Mw 7.6) ruptured a densely instrumented seismic gap on the shallow-dipping plate boundary beneath the Nicoya Peninsula, Costa Rica. Ground motion recordings directly above the rupture zone provide a unique opportunity to study the detailed source process of a large shallow megathrust earthquake using very nearby land observations. Hypocenter relocation using local seismic network data indicates that the event initiated with small emergent seismic waves from a hypocenter ~10 km offshore, 13 km deep on the megathrust. A joint finite-fault inversion using high-rate GPS, strong-motion ground velocity recordings, GPS static offsets, and teleseismic P waves reveals that the primary slip zone (slip > 1 m) is located beneath the peninsula. The rupture propagated downdip from the hypocenter with a rupture velocity of ~3.0 km/s. The primary slip zone extends ~70 km along strike and ~30 km along dip, with an average slip of ~2 m. The associated static stress drop is ~3 MPa. The seismic moment is 3.5 × 1020 Nm, giving Mw = 7.6. The coseismic large-slip patch directly overlaps an onshore interseismic locked region indicated by geodetic observations and extends downdip to the intersection with the upper plate Moho. At deeper depths, below the upper plate Moho, seismic tremor and low-frequency earthquakes have been observed. Most tremor locates in adjacent areas of the megathrust that have little coseismic slip; a region of prior slow slip deformation to the southeast also has no significant coseismic slip or aftershocks. An offshore locked patch indicated by geodetic observations does not appear to have experienced coseismic slip, and aftershocks do not overlap this region, allowing the potential for a comparable size rupture offshore in the future.

Yue, Han; Lay, Thorne; Schwartz, Susan Y.; Rivera, Luis; Protti, Marino; Dixon, Timothy H.; Owen, Susan; Newman, Andrew V.

2013-10-01

209

Mapping Plate Tectonic Boundaries  

NSDL National Science Digital Library

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.

Kerwin, Michael

210

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

211

Interface automata  

Microsoft Academic Search

Conventional type systems specify interfaces in terms of values and domains. We present a light-weight formalism that captures the environment that can make them work together. According to the alternating approach, one interface refines another if it has weaker input assumptions, and stronger output guarantees. We show that these notions have game-theoretic foundations that lead to efficient algorithms for checking

Luca de Alfaro; Thomas A. Henzinger

2001-01-01

212

Global plate velocities from the Global Positioning System  

Microsoft Academic Search

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

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

1997-01-01

213

Seismicity and plate tectonics in south central Alaska  

NASA Technical Reports Server (NTRS)

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.

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

1974-01-01

214

SeattlePacificUniversity SeattlePacific  

E-print Network

to be a premier Christian University fully committed to engaging the culture and changing the world by graduating and distinguished history in Christian higher education, Seattle Pacific University entered the new century, will be some of the Christian university's most important contributions in this century. Guiding the work

Nelson, Tim

215

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

ERIC Educational Resources Information Center

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

Mamak, Alexander; Luce, Pat

216

Plate tectonics and the Gulf of California region  

SciTech Connect

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.

Schmidt, N.

1990-11-01

217

Warping and cracking of the Pacific plate by thermal contraction  

E-print Network

such as the Hawaiian-Emperor seamounts are well explained by the mantle plume model [Morgan, 1971; Sleep, 1992]. (2]; extension of the lithosphere or boudinage [Dunbar and Sandwell, 1988]; and thermal bending stress caused material [Janney et al., 2000]. The small-scale convection model predicts extension and volcanism

Fialko, Yuri

218

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

Microsoft Academic Search

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

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

219

Stop motion microphotography of laser driven plates  

SciTech Connect

Laser driven plates have been used for several years for high velocity shock wave and impact studies. Recent questions about the integrity and ablation rates of these plates coupled with an improved capability for microscopic stop motion photography led to this study. For these experiments, the plates were aluminum, coated on the ends of optical fibers. A high power laser pulse in the fiber ionizes the aluminum at the fiber/coating interface. The plasma thus created accelerates the remaining aluminum to high velocities, several kilometers per second. We defined {open_quotes}thick{close_quotes} or {open_quotes}thin{close_quotes} coatings as those where a flying plate (flyer) was launched vs. the material being completely ionized. Here we were specifically interested in the thick/thin boundary to develop data for the numerical models attempting to predict flyer behavior.

Frank, A.M. [Lawrence Livermore National Lab., CA (United States); Trott, W.M. [Sandia National Labs., Albuquerque, NM (United States)

1994-09-01

220

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

221

SKITTER/implement mechanical interface  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

222

Partitioning of Oblique Plate Convergence at the Sumatran Plate Boundary  

NASA Astrophysics Data System (ADS)

At the Sumatran plate boundary, the Indo-Australian plate subducts beneath the Sunda block at a rate of ~5-6 cm/yr, in a direction of ~10° oblique to the trench-normal. Such oblique plate convergence is partitioned into subduction along the Sumatran subduction interface and strike-slip motion along the Sumatran fault. The Sumatran GPS Array (SuGAr), first established in 2002 with 6 stations, now has 50 stations. Using the decade-long time series, we have estimated long-term background rates for the SuGAr stations, with simultaneous estimation of a large number of earthquake parameters. By projecting the long-term rates into trench-normal and trench-parallel directions, we are able to separate deformation related to subduction and transform motion, respectively, to first order. For subduction-related trench-normal velocities, we find stations on the Mentawai islands -- where a great earthquake has been forecast for the coming decades -- have almost double the velocity of stations on the Batu islands where low coupling has been proposed. This observation strongly supports the idea that an earthquake on the Mentawai seismic gap is overdue, and the Batu section is likely a weakly coupled barrier between strongly coupled regions to the north and south. For transform-related trench-parallel velocities, we find rates progressively decrease from ~25 mm/yr on islands offshore Sumatra to ~15 mm/yr at the Sumatran west coast, and close to zero in the backarc. We will explore plausible models for the heterogeneous coupling on the Mentawai subduction interface and forearc sliver translation.

Feng, L.; Hill, E. M.; Qiu, Q.; Banerjee, P.; Lubis, A.; Sieh, K. E.

2012-12-01

223

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.

224

External Resource: Plate Tectonics  

NSDL National Science Digital Library

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.

1900-01-01

225

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.

226

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.

227

Observe animations of processes that occur along plate boundaries  

NSDL National Science Digital Library

Here are three animations that reveal how tectonic plates move relative to each other at three types of plate boundaries--transform, convergent, and divergent boundaries. Key features such as the asthenosphere are labeled in the animations. In addition, each animation is equipped with movie control buttons that allow students to play, pause, and move forward and backward through each clip. The animation of a transform boundary shows the North American and Pacific plates sliding past one another, while an oceanic plate subducts under a continental plate producing volcanic activity in the convergent boundary animation. Two coordinated movie clips are used to demonstrate what occurs at a divergent boundary from different viewpoints. Copyright 2005 Eisenhower National Clearinghouse

Education, Terc. C.; Littell, Mcdougal

2003-01-01

228

Plate Tectonic Primer  

NSDL National Science Digital Library

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.

Fichter, Lynn

229

Optimal truss plates  

Microsoft Academic Search

Sandwich plates comprised of truss cores faced with either planar trusses or solid sheets are optimally designed for minimum weight subject to prescribed combinations of bending and transverse shear loads. Motivated by recent advances in manufacturing possibilities, attention is focussed on plates with truss elements and faces made from a single material. The optimized plates are compared with similarly optimized

Nathan Wicks; John W Hutchinson

2001-01-01

230

Angular shear plate  

Microsoft Academic Search

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

Mitchell C. Ruda; Alan W. Greynolds; Tilman W. Stuhlinger

2009-01-01

231

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.

232

Metallic glass as a temperature sensor during ion plating  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

233

Metallic glass as a temperature sensor during ion plating  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

234

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

NASA Astrophysics Data System (ADS)

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.

Iaffaldano, G.

2012-12-01

235

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

NASA Astrophysics Data System (ADS)

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.

Iaffaldano, Giampiero

2012-12-01

236

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

Microsoft Academic Search

The interseismic deformation associated with plate coupling at a subduction zone is commonly simulated by the steady-slip model in which a reverse dip-slip is imposed on the down-dip extension of the locked plate interface, or by the backslip model in which a normal slip is imposed on the locked plate interface. It is found that these two models, although totally

Shaorong Zhao; Shuzo Takemoto

2000-01-01

237

Slow slip events and seismic tremor at circum-Pacific subduction zones  

NASA Astrophysics Data System (ADS)

It has been known for a long time that slip accompanying earthquakes accounts for only a fraction of plate tectonic displacements. However, only recently has a fuller spectrum of strain release processes, including normal, slow, and silent earthquakes (or slow slip events) and continuous and episodic slip, been observed and generated by numerical simulations of the earthquake cycle. Despite a profusion of observations and modeling studies the physical mechanism of slow slip events remains elusive. The concurrence of seismic tremor with slow slip episodes in Cascadia and southwestern Japan provides insight into the process of slow slip. A perceived similarity between subduction zone and volcanic tremor has led to suggestions that slow slip involves fluid migration on or near the plate interface. Alternatively, evidence is accumulating to support the notion that tremor results from shear failure during slow slip. Global observations of the location, spatial extent, magnitude, duration, slip rate, and periodicity of these aseismic slip transients indicate significant variation that may be exploited to better understand their generation. Most slow slip events occur just downdip of the seismogenic zone, consistent with rate- and state-dependent frictional modeling that requires unstable to stable transitional properties for slow slip generation. At a few convergent margins the occurrence of slow slip events within the seismogenic zone makes it highly likely that transitions in frictional properties exist there and are the loci of slow slip nucleation. Slow slip events perturb the surrounding stress field and may either increase or relieve stress on a fault, bringing it closer to or farther from earthquake failure, respectively. This paper presents a review of slow slip events and related seismic tremor observed at plate boundaries worldwide, with a focus on circum-Pacific subduction zones. Trends in global observations of slow slip events suggest that (1) slow slip is a common phenomena observed at almost all subduction zones with instrumentation capable of recording it, (2) different frictional properties likely control fast versus slow slip, (3) the depth range of slow slip may be related to the thermal properties of the plate interface, and (4) the equivalent seismic moment of slow slip events is proportional to their duration (Mo??), different from the Mo??3 scaling observed for earthquakes.

Schwartz, Susan Y.; Rokosky, Juliana M.

2007-09-01

238

An improved plating process  

NASA Technical Reports Server (NTRS)

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.

Askew, John C.

1994-01-01

239

Discovering Plate Boundaries  

NSDL National Science Digital Library

Students are initially assigned to one of four maps of the world: Seismology, Volcanology, Geochronology or Topography. They are also given a map of the world's plate boundaries and are asked to classify the boundaries based upon the data from their assigned map. Students are then assigned to a tectonic plate, such that each plate group contains at least one "expert" on each map. As a group, they must classify their plate's boundaries using data from all four maps. Recent volcanic and seismic events are discussed in the plate tectonic context. Has minimal/no quantitative component Uses geophysics to solve problems in other fields

Henning, Alison

240

Paper microzone plates.  

PubMed

This paper describes 96- and 384-microzone plates fabricated in paper as alternatives to conventional multiwell plates fabricated in molded polymers. Paper-based plates are functionally related to plastic well plates, but they offer new capabilities. For example, paper-microzone plates are thin (approximately 180 microm), require small volumes of sample (5 microL per zone), and can be manufactured from inexpensive materials ($0.05 per plate). The paper-based plates are fabricated by patterning sheets of paper, using photolithography, into hydrophilic zones surrounded by hydrophobic polymeric barriers. This photolithography used an inexpensive formulation photoresist that allows rapid (approximately 15 min) prototyping of paper-based plates. These plates are compatible with conventional microplate readers for quantitative absorbance and fluorescence measurements. The limit of detection per zone loaded for fluorescence was 125 fmol for fluorescein isothiocyanate-labeled bovine serum albumin, and this level corresponds to 0.02 the quantity of analyte per well used to achieve comparable signal-to-noise in a 96-well plastic plate (using a solution of 25 nM labeled protein). The limits of detection for absorbance on paper was approximately 50 pmol per zone for both Coomassie Brilliant Blue and Amaranth dyes; these values were 0.4 that required for the plastic plate. Demonstration of quantitative colorimetric correlations using a scanner or camera to image the zones and to measure the intensity of color, makes it possible to conduct assays without a microplate reader. PMID:19572563

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

2009-08-01

241

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.

242

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

NASA Technical Reports Server (NTRS)

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

Argus, Donald F.; Heflin, Michael B.

1995-01-01

243

Beyond Interface  

NSDL National Science Digital Library

Beyond Interface is an exhibition of digital art, created in conjunction with the Museums and the Web 1998 conference held in April. The conference and the Website are coordinated by Archives & Museums Informatics. Beyond Interface is curated by Steve Dietz, who explains, "This online exhibition presents a simple proposition. There is art that is created to 'be' on the Net. After that, it gets more complex very quickly. Beyond Interface explores some of the complicating issues but does not attempt a comprehensive investigation." Users can follow links to the works of 24 net artists, writings on the philosophies of net art, and the complete conference proceedings of Museums and the Web 1998, which include the Best of the Web Award for 1998.

244

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

245

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

246

Tsunami Strike! Pacific Edition  

NSDL National Science Digital Library

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 Alaskaâs 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.

Comet

2011-08-23

247

Hypervelocity plate acceleration  

SciTech Connect

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.

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

1991-01-01

248

PACIFIC EARTHQUAKE ENGINEERING RESEARCH CENTER  

E-print Network

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

Adolphs, Ralph

249

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.

250

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.

251

Plate Motion Calculator  

NSDL National Science Digital Library

This program calculates tectonic plate motion at any location on Earth using one or more plate motion models. The possible plate motion models are GSRM v1.2 (2004), CGPS (2004), HS3-NUVEL1A, REVEL 2000, APKIM2000.0, HS2-NUVEL1A, NUVEL 1A, NUVEL 1, and two models for ITRF2000. Plates or frames are selected from dropdown lists or can be entered by the user. Position coordinates can be entered in geographic coordinates (decimal degrees, or degrees/minutes/seconds) or in WGS84 cartesian XYZ, as either a single point or multiple points.

Estey, Lou

252

Introduction to Plate Tectonics  

NSDL National Science Digital Library

In this lab students interpret bathymetric, topography, sea floor ages, and earthquake distributions to reinforce concepts about the different types of plate boundaries. Each student must interpret several sets of data to determine the location and type of plate boundary. To develop a set of basic analytical skills, the students draw several diagrams and graphs to reinforce the data presented in figures. Students are also asked to think critically about plate rates and what happens to the crust at the different plate boundaries. This activity uses online and/or real-time data and has minimal/no quantitative component.

Cochran, Elizabeth

253

Fiji in the South Pacific.  

ERIC Educational Resources Information Center

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,…

Scott, Rosalind; Semaan, Leslie

254

Pacific Southwest Research Station  

E-print Network

Pacific Southwest Research Station General Technical Report PSW-GTR-245 (English) August 2013 United States Department of Agriculture Forest Service Proceedings of the Fourth International Symposium for employment on the bases of race, color, national origin, age, disability, sex, gender identity, religion

Standiford, Richard B.

255

Australia in the Pacific.  

ERIC Educational Resources Information Center

Discusses Australia's growth since European settlement and its development into a major world trader in industrial and high technology raw materials. Examines the country's expanding relations with New Zealand and other Pacific states which is the outgrowth of the realization that all will gain from greater international cooperation. (GEA)

Kennedy, Kerry; Welch, Ian

1988-01-01

256

Plastic in the Pacific  

NSDL National Science Digital Library

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.

Kqed

2012-08-08

257

Identifying slab fragments in the lower mantle by comparing seismic and plate reconstruction models  

NASA Astrophysics Data System (ADS)

We combine results from seismic tomography and plate motion history to investigate structure and evolution of slabs of subducted lithosphere in the lower mantle beneath western Pacific. We selected earthquakes and stations along a wide corridor from the Aleutians to Australia. We measured P and S differential travel times by waveform multi-channel phase cross-correlation (MCPCC). MCPCC enables to measure differential travel times without selecting a reference trace. We use phase cross-correlation rather than standard cross-correlation as it is better suited to measure differential travel times on the first onset even if the first onset is not the most energetic peak. Direct P and S wave measurements were complemented by PP-P, PcP-P, SS-S and ScS-S differential travel time measurements. Both P and S datasets were then inverted simultaneously to obtain high resolution P and S wave velocity models. Synthetic test were performed to assess the models quality and results are only interpreted in the well resolved areas. Paleomagnetic data were used to reconstruct the plate motion of western Pacific from 130 My ago to present. 130 My ago, the Panthalassa Ocean was made of 4 plates. The Pacific plate was initially separated by ridges to the Izanagi plate to the North-East, the Farallon plate to the East and the Phoenix plate to the South. The Izanagi plate subducted beneath Eurasia until 60 My ago and disappeared in the mantle when the ridge between Izanagi and Pacific plates subducted. In the South West Pacific, the Phoenix plate subducted beneath the Gondwana until 120My ago. Between 120-45 My ago a left-lateral transform fault took place between the Lord Howe Rise plate and the remaining portions of the Phoenix plate. During this period, a rift opened between the Australian plate and Lord Howe Rise plate. From 45 My to now, subduction took place between Pacific and Lord Howe Rise plate. Meanwhile, Australia and India plate have moved toward the North since 70 My and the collision between India and Asia occurred about 30 My ago. This northward motion induced the East-West opening of the West Philippine Basin and its rotation clock-wise between 50 and 40 My ago. This basin was then called the Philippine plate. The Philippine plate moved toward north from 30 My ago 10 My following the northward motion of Australia. 20 My ago, Philippine also rotated clockwise due to both the opening of the Shikoku and Parece Vela Basins and to the split of the Izu-Bonin Arc into two parts. The Philippine plate has been surrounded by subductions, the Ryuku and Philippine trenches to the west and the Izu-Bonin and Mariana trenches to the east since 10 My. Errors on the plate reconstruction models are due to the hypothesis of fixed hotspots and to the difficulty of determining precisely oceanic plate boundaries and plate relative motions. Therefore, we compare these models with tomographic images to obtain independent constraints on plate motion history. We identify the different slab fragments in the lower mantle and we are able to unravel subduction history over the last 120 My.

Duval, S.; Stutzmann, E.; Besse, J.; van der Hilst, R. D.

2010-12-01

258

Soft Interfaces  

NASA Astrophysics Data System (ADS)

Paul Adrien Maurice Dirac, one of the greatest physicists of the twentieth century, died in 1984. Dirac's college, St. John's of Cambridge, generously endowed annual lectures to be held at Cambridge University in his memory. This volume contains a much expanded version of the 1994 Dirac Lecture by Nobel Laureate Pierre Gilles de Gennes. The book presents an impressionistic tour of the physics of soft interfaces. Full of insight and interesting asides, it not only provides an accessible introduction to this topic, but also lays down many markers and signposts that will be of interest to researchers in physics or chemistry. Features discussions of wetting and dewetting, the dynamics of different types of interface and adhesion and polymer/polymer welding.

Gilles de Gennes, Pierre; Edwards, Introduction By Sam

1997-04-01

259

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.

260

Accurate license plate localization  

Microsoft Academic Search

Vehicle license plate identification system is an image- processing technology used to identify vehicles by their license plates. This technology is used in various security and traffic applications. This data is also used for enforcement, data collection, and can be used to keep a time record on the entry or exit of vehicles for automatic payment calculations. The significant advantage

S. Mohamed Mansoor Roomi; M. Anitha; R. Bhargavi

2011-01-01

261

Mapping Plate Boundaries  

NSDL National Science Digital Library

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.

Johnson, Rurik

2009-11-12

262

Intro to Plate Tectonic Theory  

NSDL National Science Digital Library

This website from PBS provides information about the plate tectonics, the theory that the Earth's outer layer is made up of plates, which have moved throughout time. The four types of plate boundaries are described and illustrated with animations. The first page of plate tectonics also provides a plate tectonics activity and information about related people and discoveries.

2008-05-28

263

Plate Tectonics Prof. Thomas Herring  

E-print Network

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

Herring, Thomas

264

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

265

Making Room for the Pacific: Southward Migration of Pacific Subduction Beneath New Zealand and Tectonic Consequences of Delaminating the Australian Lithosphere  

Microsoft Academic Search

Over the past 20 Ma, as a consequence of the substantial obliquity to plate motions, the southwestern edge of the subducting Pacific slab has migrated southward sweeping beneath the North Island of New Zealand to its present position beneath the northern South Island. In many locations where a well-defined slab edge migrates, such as northern California where the Gorda slab

P. J. Kamp; K. P. Furlong

2003-01-01

266

The surface and through crack problems in layered orthotropic plates  

NASA Technical Reports Server (NTRS)

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

Erdogan, Fazil; Wu, Binghua

1991-01-01

267

Physical characteristics of subduction interface type seismogenic zones revisited  

Microsoft Academic Search

Based on global earthquake catalogs, the hypocenters, nodal planes, and seismic moments of worldwide subduction plate interface earthquakes were extracted for the period between 1900 and 2007. Assuming that the seismogenic zone coincides with the distribution of 5.5 ? M < 7 earthquakes, the subduction interface seismogenic zones were mapped for 80% of the trench systems and characterized with geometrical

Arnauld Heuret; Serge Lallemand; Francesca Funiciello; Claudia Piromallo; Claudio Faccenna

2011-01-01

268

Late mesozoic-quaternary plate tectonics and the Geysers-Clear Lake geothermal anomaly, Northern Coast Ranges, California (Abstract)  

Microsoft Academic Search

The development of structures related to the Geysers-Clear Lake geothermal anomaly can be explained in terms of relative motions of the North American and Pacific plates. Hypothetically, plate convergence during Late Jurassic to mid-Tertiary time produced a west-stepping subduction zone that thrust successively younger plates of sediments and volcanic rocks of the Franciscan assemblage eastward beneath oceanic crust and depositionally

1977-01-01

269

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

E-print Network

Author's personal copy Plate tectonic reconstructions with continuously closing plates$ Michael are downwellings controlled by the history of subduction, that these mantle down- wellings push hot mantle

Bower, Dan J.

270

Trench migration and upper plate strain over a convecting mantle  

NASA Astrophysics Data System (ADS)

Trench motion and upper plate deformation ultimately respond to mantle flow. Herein I build upon the mantle flow model results of Conrad and Behn (2010) and compute the drag forces underneath all plates, and show that they control the dynamics of plates and plate boundaries. The small misfit angle between between the traction azimuths of mantle traction and absolute plate motion corroborates the idea that convective mantle drag is a prominent driver of plate tectonics. Less intuitive is the fact that the interplay between the drag forces from the upper and lower plates, that amounts to -5 to 8.5 × 1012 N m-1 (per unit trench length), dictates both trench migration rates and upper plate deformation. At odds with the classic view that assigns the prime role to the idiosyncrasies of subduction zones (slab age, interplate friction, water content etc), I find that the intrinsic properties of subduction zones in fact only modulate this behavior. More specifically, the mean value of the integrated trenchward mantle drag force from the lower and upper plates (from -2 to 6.5 × 1012 N m-1) controls upper plate deformation. Conversely, it is the difference between the lower and upper plates mantle drag forces (from -3 to 10 × 1012 N m-1) that controls trench migration rates. In addition, I find that a minimum trenchward force of ˜2.5 × 1012 N m-1 must be supplied by mantle drag before trenches can actually advance, and before upper plates undergo compression. This force results from the default tendency of slabs to rollback when solely excited by their own buoyancy, and is thus the effective tensional force that slab pull exerts on the plate interface.

Husson, Laurent

2012-12-01

271

Trench migration and upper plate strain over a convecting mantle  

NASA Astrophysics Data System (ADS)

Trench motion and upper plate deformation ultimately respond to mantle flow. Herein I build upon the mantle flow model results of Conrad and Behn (2010) and compute the drag forces underneath all plates, and show that they control the dynamics of plates and plate boundaries. The small misfit angle between between the traction azimuths of mantle traction and absolute plate motion corroborates the idea that convective mantle drag is a prominent driver of plate tectonics. Less intuitive is the fact that the interplay between the drag forces from the upper and lower plates, that amounts to -5 to 8.5 TN/m (per unit trench length), dictates both trench migration rates and upper plate deformation. At odds with the classic view that assigns the prime role to the idiosyncrasies of subduction zones (slab age, interplate friction, water content etc), I find that the intrinsic properties of subduction zones in fact only modulate this behavior. More specifically, the mean value of the integrated trenchward mantle drag force from the lower and upper plates (from -2 to 6.5 TN/m) controls upper plate deformation. Conversely, it is the difference between the lower and upper plates mantle drag forces (from -3 to 10 TN/m) that controls trench migration rates. In addition, I find that a minimum trenchward force of ~2.5 TN/m must be supplied by mantle drag before trenches can actually advance, and before upper plates undergo compression. This force results from the default tendency of slabs to rollback when solely excited by their own buoyancy, and is thus the effective tensional force that slab pull exerts on the plate interface.

Husson, Laurent

2013-04-01

272

Plate Tectonics Jigsaw  

NSDL National Science Digital Library

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.

Egger, Anne

273

Influence of skin\\/core debonding on free vibration behavior of foam and honeycomb cored sandwich plates  

Microsoft Academic Search

The dynamic behavior of partially delaminated at the skin\\/core interface sandwich plates with flexible cores is studied. The commercial finite element code ABAQUS is used to calculate natural frequencies and mode shapes of the sandwich plates containing a debonding zone. The influence of the debonding size, debonding location and types of debonding on the modal parameters of damaged sandwich plates

Vyacheslav N. Burlayenko; Tomasz Sadowski

2010-01-01

274

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.

275

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.

276

The Pacific RANET Project  

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

277

Growth Plate Injuries  

MedlinePLUS

... knee or ankle. Prognosis is poor, since premature stunting of growth is almost inevitable. A newer classification, ... and growth. Will the Affected Limb of a Child With a Growth Plate Injury Still Grow? Most ...

278

Half Wave Plate Program  

NSDL National Science Digital Library

The Half Wave Plate program displays the effect of a half wave plate on an incident electromagnetic wave. The default electromagnetic wave is plane polarized but this polarization can be changed by specifying the components of the waveâs Jones vector using the input fields. The slider can be used to rotate the half wave plate to change its orientation. Half Wave Plate is an Open Source Physics program written for the teaching of optics. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the optics_halfwave.jar file will run the program if Java is installed. Other optics programs are also available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Optics.

Simov, Kiril; Christian, Wolfgang

2008-05-20

279

Quarter Wave Plate Program  

NSDL National Science Digital Library

The Quarter Wave Plate program displays the effect of a quarter wave plate on an incident electromagnetic wave. The default electromagnetic wave is plane polarized but this polarization can be changed by specifying the components of the waveâs Jones vector using the input fields. The slider can be used to rotate the quarter wave plate to change its orientation. Quarter Wave Plate is an Open Source Physics program written for the teaching of optics. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the optics_quarterwave.jar file will run the program if Java is installed. Other optics programs are also available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Optics.

Simov, Kiril; Christian, Wolfgang

2008-05-20

280

Visualizing Earthquakes at Divergent Plate Margins  

NSDL National Science Digital Library

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.

Harwood, Cara

281

76 FR 38370 - Western Pacific Fisheries; Approval of a Marine Conservation Plan for Pacific Insular Areas...  

Federal Register 2010, 2011, 2012, 2013

...Pacific Insular Areas; Western Pacific Sustainable Fisheries Fund AGENCY: National Marine...INFORMATION CONTACT: Jarad Makaiau, Sustainable Fisheries, NMFS Pacific Islands Regional...be deposited into the Western Pacific Sustainable Fisheries Fund (Fund) for use by...

2011-06-30

282

78 FR 48861 - Western Pacific Fisheries; Approval of a Marine Conservation Plan for Pacific Insular Areas...  

Federal Register 2010, 2011, 2012, 2013

...Pacific Insular Areas; Western Pacific Sustainable Fisheries Fund AGENCY: National Marine...INFORMATION CONTACT: Jarad Makaiau, Sustainable Fisheries, NMFS Pacific Islands Regional...be deposited into the Western Pacific Sustainable Fisheries Fund (Fund) for use by...

2013-08-12

283

Positive battery plate  

NASA Technical Reports Server (NTRS)

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.

Rowlette, John R. (Inventor)

1985-01-01

284

A new estimate for present-day Cocos-Caribbean plate motion: Implications for slip along the Central American volcanic arc  

Microsoft Academic Search

Velocities from 153 continuously-operating GPS sites on the Caribbean, North American, and Pacific plates are combined with 61 newly estimated Pacific-Cocos seafloor spreading rates and additional marine geophysical data to derive a new estimate of present-day Cocos-Caribbean plate motion. A comparison of the predicted Cocos-Caribbean direction to slip directions of numerous shallow-thrust subduction earthquakes from the Middle America trench between

Charles DeMets

2001-01-01

285

A computational model for predicting damage evolution in laminated composite plates  

E-print Network

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...

Phillips, Mark Lane

2012-06-07

286

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

. 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

Tullos, Desiree

287

The 1990 Western Pacific Geophysics meeting  

NASA Technical Reports Server (NTRS)

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.

1990-01-01

288

Musical Plates: A Study of Plate Tectonics  

NSDL National Science Digital Library

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.

2007-01-01

289

Caribbean plate interactions  

SciTech Connect

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.

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

1993-02-01

290

Pacific Northwest election results  

NASA Astrophysics Data System (ADS)

Six AGU members have been elected members of the Regional Committee of the AGU Pacific Northwest Region. Their terms are July 1, 1986, to June 30, 1988. The Regional Committee, which directs the activities of the branch, is composed of a representative of each of the AGU sections taking part in branch activities.Those elected are Robert M. Ellis, Tectonophysics Section; Stephen L. Gillett, Geomagnetism and Paleomagnetism Section; Tark S. Hamilton, Volcanology, Geochemistry, and Petrology Section; Renner B. Hofmann, Seismology Section; Charles W. Slaughter, Hydrology Section; and Richard E. Thomson, Ocean Sciences Section.

Qamar, Anthony

291

Pacific rim lures explorationists  

SciTech Connect

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.

Nation, L.

1991-09-01

292

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."

293

PacificSouthwestResearchStationPrograms Pacific Southwest Research Station  

E-print Network

PacificSouthwestResearchStationPrograms Pacific Southwest Research Station Publications List Air Pollution and Global Change Impacts on Western Forest Ecosystems Center for Urban Forest Research Chemical and Fire Effects Research Natural Areas Sierra Nevada Research Center Sudden Oak Death Research Timber

Standiford, Richard B.

294

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

295

Segmentation of the Pacific-Nazca spreading center, 1°N-20°S  

Microsoft Academic Search

A continuous Sea Beam swath along 2500 km of the crest of the fast-spreading East Pacific Rise (EPR) defines the location and morphology of seven systems of spreading centers. They are bounded by six transform fault systems, where reconnaissance swaths mapped additional short axes of plate accretion. The spreading center systems are subdivided by nontransform offsets, most of which step

Peter Lonsdale

1989-01-01

296

Relative motions of hotspots in the Pacific, Atlantic and Indian Oceans since late Cretaceous time  

Microsoft Academic Search

The history of the motion of the Pacific plate over the Hawaiian hotspot defined by the ages of volcanic rocks along the Hawaiian-Emperor chain is used here to calculate relative positions of hotspots (presumed to be fixed) beneath Iceland, Tristan de Cunha, Reunion, Kerguelen, and St. Paul's Island. The positions are found to lie from several hundred to more than

Peter Molnar; Joann Stock

1987-01-01

297

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.

298

India Plate Motion, Intraplate deformation and Plate Boundary Processes (Invited)  

NASA Astrophysics Data System (ADS)

We use GPS-measured velocities to geodetically constrain India plate motion, intraplate strain, and examine plate boundary deformation and plate interactions around the India plate. Our solution includes 15 GPS velocities from continuously recording stations from within the stable India plate interior that are used to estimate angular velocity of the India plate with respect to its neighbors. We test a two-plate India system divided along the topographically prominent Narmada Son Lineament and find this scenario to be significant only to 89%. Dense station coverage along the Himalayan range front allows us to rigorously test boundary parameterizations and develop a preferred plate boundary model. In our preferred model the Himalayan Range Front accumulates ~50% of the India-Eurasia convergence with as much as 18 mm/yr of slip accumulation along some segments. We compare earthquake slip vector orientations with predicted divergence directions from our preferred model along the India-Somalia plate boundary. We see good agreement between predicted plate directions from our preferred model and the seismological data. Deviations between our model and the slip vectors highlight areas of diffuse oceanic deformation along the plate boundary. We estimate convergence vectors for the relative plate pairs along the Sumatra subduction zone. We test for the transition between Australian plate convergence and India plate convergence along the Sumatra subduction zone and refine the estimated motion of the Burman sliver plate.

Apel, E. V.; Burgmann, R.; Banerjee, P.

2010-12-01

299

49 CFR 71.10 - Pacific zone.  

Code of Federal Regulations, 2012 CFR

...Secretary of Transportation STANDARD TIME ZONE BOUNDARIES § 71.10 Pacific...fifth zone, the Pacific standard time zone, includes that part of the continental...the mountain and Pacific standard time zones described in § 71.9, but...

2012-10-01

300

49 CFR 71.10 - Pacific zone.  

Code of Federal Regulations, 2013 CFR

...Secretary of Transportation STANDARD TIME ZONE BOUNDARIES § 71.10 Pacific...fifth zone, the Pacific standard time zone, includes that part of the continental...the mountain and Pacific standard time zones described in § 71.9, but...

2013-10-01

301

49 CFR 71.10 - Pacific zone.  

Code of Federal Regulations, 2010 CFR

...Secretary of Transportation STANDARD TIME ZONE BOUNDARIES § 71.10 Pacific...fifth zone, the Pacific standard time zone, includes that part of the continental...the mountain and Pacific standard time zones described in § 71.9, but...

2010-10-01

302

49 CFR 71.10 - Pacific zone.  

Code of Federal Regulations, 2011 CFR

...Secretary of Transportation STANDARD TIME ZONE BOUNDARIES § 71.10 Pacific...fifth zone, the Pacific standard time zone, includes that part of the continental...the mountain and Pacific standard time zones described in § 71.9, but...

2011-10-01

303

Engineering surface waves in flat phononic plates  

NASA Astrophysics Data System (ADS)

Surface acoustic-wave phenomena span a wide range of length scales going from the devastation of earthquakes down to image reconstruction of buried nanostructures. In solid-fluid systems, the so-called Scholte-Stoneley waves (SSWs) dominate the scene at the interface with their evanescent fields decaying away into both media. Understanding and manipulating these waves in patterned surfaces would enable new applications of sound to be devised for imaging and acoustic signal processing, although this task has so far remained elusive. Here, we report SSW modes displaying directional gaps and band folding in fluid-loaded solid phononic plates. The plates are inhomogeneously patterned with in-plane periodic modulations of the elastic constants, but present flat surfaces free of corrugations. We experimentally demonstrate control of SSWs, which opens a promising route toward acoustic fluid sensing, microscopy, and signal processing.

Estrada, Héctor; Candelas, Pilar; Belmar, Francisco; Uris, Antonio; García de Abajo, F. Javier; Meseguer, Francisco

2012-05-01

304

Cadmium plating replacements  

SciTech Connect

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.

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

1995-03-01

305

Cadmium plating replacements  

NASA Technical Reports Server (NTRS)

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.

Nelson, Mary J.; Groshart, Earl C.

1995-01-01

306

PACIFIC EARTHQUAKE ENGINEERING RESEARCH CENTER  

E-print Network

of the intensity measures is also shown to be useful for characterizing the effect of near-fault ground motionsPACIFIC EARTHQUAKE ENGINEERING RESEARCH CENTER Vector-Valued Ground Motion Intensity Measures University PEER Report 2006/08 Pacific Earthquake Engineering Research Center College of Engineering

Baker, Jack W.

307

Aid Has Failed the Pacific  

Microsoft Academic Search

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

Helen Hughes

2003-01-01

308

Bipolar battery plate  

NASA Technical Reports Server (NTRS)

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.

Rowlette, John J. (Inventor)

1987-01-01

309

Nitrided Metallic Bipolar Plates  

SciTech Connect

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.

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

310

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.

311

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.

312

Plate Tectonics and Volcanism  

NSDL National Science Digital Library

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.

313

The East Pacific Rise: An Active Not Passive Spreading System  

NASA Astrophysics Data System (ADS)

Traditional plate tectonic interpretations of mid-oceanic ridges regard spreading as an entirely passive phenomenon. From this one would assume that the oceanic ridges will move over the mantle in response to the geodynamics of the diverging plates, and do not remain fixed spatially over any protracted period of time. An analysis of the kinematics of ridge motions in the Indo-Atlantic hotspot frame of reference since 83 Ma generally supports this view, with the notable exception of the East Pacific Rise (EPR). The Pacific-Nazca/Farallon segment of the EPR north of Easter Island (27°S) is oriented essentially N-S, and has produced more than 9500km of E-W spreading in the past 80 Ma, making it the dominant ridge in the world's plate system over this interval of time. Yet despite the large amount of E-W divergence, the spreading center has maintained its longitudinal position to within <±250 km of the current ridge axis. Global mantle convective flow modeling indicates that the EPR, unlike any other extensive segment of the mid-oceanic ridge system, is underlain by an active upwelling system extending from the core-mantle boundary to the surface. We suggest that the lack of E-W motion of the EPR apparent from the kinematics is a consequence of these mantle dynamics; this ridge is thus not behaving as a passive plate boundary, but is actively and directly linked to, and controlled by, whole mantle upwelling. This observation overturns the notion that ridges are always entirely passive features of the plate system. Subduction of the northern EPR beneath western North America has thus resulted in the overriding of an active upwelling system that has contributed significantly to the evolution of Basin and Range kinematics and superimposed dynamics, including significant contributions from dynamic topography.

Rowley, D. B.; Rowan, C. J.; Forte, A. M.; Moucha, R.; Grand, S. P.; Simmons, N. A.

2011-12-01

314

Slip partitioning along major convergent plate boundaries  

NASA Astrophysics Data System (ADS)

Along plate boundaries characterized by oblique convergence, earthquake slip vectors are commonly rotated toward the normal of the trench with respect to predicted plate motion vectors. Consequently, relative plate motion along such convergent margins must be partitioned between displacements along the thrust plate interface and deformation within the forearc and back-arc regions. The deformation behind the trench may take the form of strike-slip motion, back-arc extension, or some combination of both. We observe from our analysis of the Harvard Moment Tensor Catalog that convergent arcs characterized by back-arc spreading, specifically the Marianas and New Hebrides, are characterized by a large degree of slip partitioning. However, the observed rates, directions, and location of back-arc spreading are not sufficient to account for degree of partitioning observed along the respective arcs, implying that the oblique component of subduction is also accommodated in part by shearing of the overriding plate. In the case of the Sumatran arc, where partitioning is accommodated by strike-slip faulting in the overriding plate, the degree of partitioning is similar to that observed along the Marianas, but the result is viewed with caution because it is based on a predicted plate motion vector that is based on locally derived earthquake slip vectors. In the case of the Alaskan-Aleutian arc, where back-arc spreading is also absent, the degree of partitioning is less and rotation of slip vectors toward the trench normal appears to increase linearly as a function of the obliquity of convergence. If partitioning in the Alaskan-Aleutian arc is accommodated by strike-slip faulting within the upper plate, the positive relationship between obliquity of convergence and the rotation of earthquake slip vectors to the trench normal may reflect that either (1) the ratio of the depth extent of strike-slip faults behind the trench Z s to the subduction thrust Z t increases westward along the arc, (2) the dip of the subduction thrust increases westward along the arc, or (3) the strength of the subduction thrust decreases westward along the arc.

Yu, Guang; Wesnousky, Steven G.; Ekström, Göran

1993-06-01

315

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

Microsoft Academic Search

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

Peter Lonsdale

1977-01-01

316

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

Microsoft Academic Search

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)

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

2006-01-01

317

An outline of the interdisciplinary survey on a new type intra-plate volcanism -  

Microsoft Academic Search

Several very young volcanoes (< 1 Ma) were discovered on the Early Cretaceous (~135 Ma) NW Pacific Plate. They are very small knolls on the abyssal plane (~ 6000 m water depth) and erupted strong to moderate alkaline basalt, generally including deep-seated xenoliths. This volcanic field is far from any trenches and also spreading centers, therefore these are classified as

N. Abe; N. Hirano; T. Fujiwara; S. Machida; E. Araki; K. Baba; M. Ichiki; M. Nakanishi; Y. Ogawa; H. Sugioka; K. Suyehiro; T. Ishii; T. Suzuki; A. Takahashi; E. Takahashi; J. Yamamoto

2005-01-01

318

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

Microsoft Academic Search

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

Erwin Scheibner

1973-01-01

319

On the competing roles of fault reactivation and brittle failure in generating plate tectonics from mantle convection  

NASA Astrophysics Data System (ADS)

Fault reactivation plays a fundamental role in the generation of plate tectonics from mantle convection. Converging and transform plate margins are mechanically weak due to both preexisting faults and preserved shear zones within the crust and lithosphere, on the one hand, and continuous brittle failure of lithosphere, on the other hand. Transform margins are the site for nucleating new converging margins. Lithospheric earthquakes demonstrate that oceanic lithosphere within a trench can deform as fast as the upper mantle. Models demonstrate that faulted converging plate margins contribute to producing plate tectonic-like motion. Preexisting faults and a power law plastic rheology dynamically interact and together give rise to plate-like motion. Faults have an important influence over outer rise and trench topography and by comparing models with observations, interplate stress is about 10-30 MPa. Subduction can initiate on preexisting faults when interplate coupling is as high as 10-30 MPa if the oceanic plate already has slabs attached to it — as was the case for the Pacific plate when the Marianas nucleated. Modeled plates only change velocity slowly in response to the initiation of new subduction zones; the initiation of subduction in the Western Pacific at ? 45 Ma was likely the result of a change in Pacific plate motion as opposed to causing the change in the direction of plate motion. The locations of the greatest amount of present day brittle failure within oceanic lithosphere are not located at arbitrary positions on oceanic plates, rather brittle failure occurs in close proximity t o long lived zones of preexisting weakness. Old weak structures are reused by the convecting system because it takes less energy t o reactivate a preexisting structure than it does t o create an entirely new plate margin from pristine, intact lithosphere.

Gurnis, Michael; Zhong, Shijie; Toth, John

320

78 FR 32624 - Western Pacific Fishery Management Council; Public Meetings  

Federal Register 2010, 2011, 2012, 2013

...fishery management issues in the Western Pacific Region. DATES: The...4. Report from the Pacific Islands Fisheries Science Center...Bottomfish: Hawaii and the Western Pacific 2. Assessments a...Overfishing of North Pacific Western and Central Pacific...

2013-05-31

321

Roving the Pacific: Pacific Manuscripts Bureau Microfilming in the Pacific Islands.  

ERIC Educational Resources Information Center

Provides an overview of microfilming by the Pacific Manuscripts Bureau (PMB), a non-profit organization established in 1968 to identify and preserve archives, manuscripts, and rare printed documents relating to the South Pacific Islands. Describes a 1997 PMB microfilming expedition to Papua New Guinea and the Solomon Islands. (PEN)

Maidment, Ewan

1998-01-01

322

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

323

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

NASA Technical Reports Server (NTRS)

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.

Gordon, R. G.

1998-01-01

324

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

SciTech Connect

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

Cronin, V.S. (Univ. of Wisconsin, Milwaukee (USA))

1990-05-01

325

The effect of austenitic interface layer on microstructure of AISI 420 martensitic stainless steel joined by keyhole PTA welding process  

Microsoft Academic Search

In this study, a martensitic stainless steel plate of 10mm thick was welded by keyhole plasma transfer arc (PTA) welding technique both itself and using austenitic stainless steel plate of 2mm thick in interface. So, penetration depth, microstructure, mechanical behavior and interface layer effects of keyhole plasma welding were investigated. After keyhole plasma welding, microstructural analysis including metallographic examination, and

Bulent Kurt; Nuri Orhan; Ilyas Somunkiran; Mehmet Kaya

2009-01-01

326

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.

327

Plate Tectonic Movement Visualizations  

NSDL National Science Digital Library

This collection provides a wide array of visual resources and supporting material about plate tectonic movements. Visualizations include simple animations, GIS-based animated maps, paleogeographic maps and globes, and numerous illustrations and photos. This collection is not exhaustive but does represent some of the best sources for teaching. Resources can be incorporated into lectures, labs, or other activities.

2007-04-15

328

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.

329

elementsair ceramic plate  

E-print Network

and earth to generate electrical power [7, 8]. Temperature differences of about -0.35° to 0.7°C werearth elementsair L ceramic plate Thermoelectric Module Construction for Low Temperature Gradient Power Generation Y. Meydbray, R. Singh, Ali Shakouri University of California at Santa Cruz, Electrical

330

Canadian Pacific Railway Collection  

NSDL National Science Digital Library

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.

2005-01-01

331

Plates with incompatible prestrain  

E-print Network

We study the effective elastic behavior of incompatibly prestrained plates, where the prestrain is independent of thickness as well as uniform through the thickness. We model such plates as three-dimensional elastic bodies with a prescribed pointwise stress-free state characterized by a Riemannian metric $G$ with the above properties, and seek the limiting behavior as the thickness goes to zero. Our results extand the prior analysis in M. Lewicka, M. R. Pakzad ESAIM Control Optim. Calc. Var. 17 (2011), no. 4. We first establish that the $\\Gamma$-limit is a Kirchhoff type bending. Further, we show that the minimum energy configuration contains non-trivial Kirchhoff type bending -- i.e., the scaling of the three-dimensional energy is of the order of the cube of the plate thickness -- if and only if the Riemann curvatures $R^3_{112}, R^3_{221}$ and $ R_{1212}$ of $G$ do not identically vanish. We demonstrate through examples, the existence of a new regime where the three above curvatures of $G$ vanish (while the mid-plane of the plate may or may not be flat), but the limiting configuration still has energy that is of the order of F\\"oppl - von K\\'arm\\'an plates. Finally, we apply these results to a model of nematic glass, including a characterization of the condition when the metric is immersible, for $G=\\mbox{Id}_3 +\\gamma\\vec n\\otimes \\vec n$ given in terms of the inhomogeneous unit director field distribution $\\vec n\\in\\mathbb{R}^3$.

Kaushik Bhattacharya; Marta Lewicka; Mathias Schäffner

2014-01-08

332

Palaeotsunamis in the Pacific Islands  

USGS Publications Warehouse

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.

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

333

Relation between subduction megathrust earthquakes, sediment thickness at trench, and plate coupling  

NASA Astrophysics Data System (ADS)

Extreme seismic events (Mw 8.5 and higher) are uniformly characterized by trench-parallel rupture lengths longer than about 250 km, whereas downdip rupture width ranges from less than 70 km (e.g., Central Aleutians) to more than 200 km (e.g., Andaman-Sumatra). The ability of rupture to propagate in the trench-parallel direction thus appears to play a fundamental role in determining the potential magnitude that an earthquake can achieve for a given subduction zone. The rupture length may be influenced by the nature of the plate interface and the normal stresses applied to the plate interface (plate coupling). The nature of the plate interface is potentially modified by sediment subduction. Subduction of a thick section of trench sediment constructs a laterally homogenous layer between upper and lower plates that smoothes subducted sea-floor relief and strength-coupling asperities (Ruff, 1989). Such a homogeneous interface running parallel to the subduction zone tends to favor long trench-parallel propagation of rupture, and thus large earthquake magnitudes. Compressive normal stresses applied along the plate interface may also tune the earthquake magnitude potential (Ruff & Kanamori, 1980). This plate coupling across the subducting interface can be indirectly estimated by Upper Plate Strain analysis, by using the back-arc as a strain sensor from which we can infer the back-arc stress state. Compressive back-arcs indicate that large stresses are transmitted across the plate interface whereas extensional settings indicate weak plate coupling. Here we present the results of a study funded by the European Science Foundation - EURYI project titled "Convergent margin and seismogenesis". Maximal earthquake magnitude, sediment thickness at the trench and Upper Plate Strain are characterized for worldwide subduction zones in order to test how plate coupling and sediment thickness combine to explain the occurrence of mega-events at the subduction interface. Subduction zones are described through an initial set of 505 transects, systematically extracted each 1° of trench, and merged into 62 subduction segments of homogeneous seismogenetic conditions. Maximal earthquake magnitude has been estimated by combining instrumental and historical seismicity. Trench sediment thickness has been constrained for 48 subduction segments; based on a compilation of 165 different seismic-reflection lines (33% of the initial set of transects).

Heuret, A.; Conrad, C. P.; Funiciello, F.; Lallemand, S.

2011-12-01

334

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.

335

Geodynamical Analysis of Plate Reconstructions based on Subduction History Models  

NASA Astrophysics Data System (ADS)

We present a novel method to produce global subduction history models from plate reconstructions and use their predicted geodynamic behaviour as a quality metric for the physical consistency of absolute motions. We show that modelled slabs constructed by advecting material into the mantle according to absolute and relative plate motions given by a particular reconstruction are better correlated with the present day slab dips observed in mantle tomography than instantaneous kinematic quantities like present convergence rate. A complete simulation incorporating lithospheric thickness derived from oceanic age and a rheological model of the lithosphere was run using the Boundary Element Method-based software BEMEarth to infer the global pattern of mantle flow. The predicted plate motion orientations in the form of Euler pole location for the present day and mid-Cretaceous (125 Ma) were compared with the kinematic model for a set of rheologies and mantle structures, and found to be a robust and efficient indicator of the physical consistency of kinematic reconstructions based on their effect on the balance of plate driving forces. As an application example, during the Early Cretaceous, the predicted motion of the Farallon plate was found to be more consistent with the regional geology of the Western North American Cordillera system than the instantaneous motion suggested by a reconstruction at 125 Ma based on sparse hotspot track data on the Pacific Plate. This suggests that a methodology based on forward geodynamic modellling could be used to predict absolute plate motions in reconstructions for times that are ill-constrained by observations constraining absolute plate motions.

Quevedo, L. E.; Butterworth, N. P.; Matthews, K. J.; Morra, G.; Müller, R. D.

2011-12-01

336

The Fight Over Pacific Salmon  

NSDL National Science Digital Library

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.

Payne, Laura X.

1998-01-01

337

Plate Puzzle Page 1 of 20 Plate Puzzle 1  

E-print Network

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

Benitez-Nelson, Claudia

338

ANU College of Asia & the Pacific  

E-print Network

Pacific public policy 20 Water win 21 Dealing with disasters 22 Asia Pacific culture, history & language ancient Pacific settlements lost to climate change, to advising on oceania's social policies. our people, a pioneer in the building of an Asia Pacific economic and policy community; AL Basham, author of what

Chen, Ying

339

Tertiary Achievement in Pacific Ako (TAPA) Awards TERTIARY ACHIEVEMENT IN PACIFIC AKO (TAPA) AWARDS 2012  

E-print Network

Tertiary Achievement in Pacific Ako (TAPA) Awards 1 TERTIARY ACHIEVEMENT IN PACIFIC AKO (TAPA) AWARDS 2012 BACKGROUND The TAPA Awards have been established to encourage Pacific students to pursue Achievement in Pacific Ako (or TAPA) Awards. 2. The Awards are available for domestic-status Pacific students

Waikato, University of

340

Current plate motions relative to the hotspots consistent with the MORVEL global set of plate relative angular velocities  

NASA Astrophysics Data System (ADS)

Estimates of plate motions relative to the hotspots are useful in investigations of plate driving forces, motion between hotspots, and in estimating the net-rotation of the lithosphere. HS3B-MORVEL is a new set of angular velocities of the plates relative to the hotspots. In HS3B-MORVEL, relative plate angular velocities are constrained to be consistent with those of MORVEL, which is a new closure-enforced global set of angular velocities. MORVEL describes the geologically current motions of 25 plates, 18 of which are determined solely from marine geophysical data, which typically average motion over hundreds of thousands to millions of years [DeMets, Gordon, and Argus 2010]. Seven other plates are tied in partly or entirely through geodetic data. The HS3B data set builds on the HS3 data set, which includes two volcanic propagation rates and eleven segment trends and is determined from the age and location of volcanoes from four plates [Gripp and Gordon, 2002]. In HS3B we adjust the volcanic propagation rates from HS3 for a 10% bias in K/Ar age dates. In HS3B-MORVEL, the angular velocity relative to the hotspots of eight plates—Eurasia, Nubia, Somalia, Lwandle, Antarctica, Sundaland, Amur, and Yangtze—all differ insignificantly from zero. The motion of the other 17 plates differ significantly from zero (p<0.05). The net rotation of the lithosphere is ?0.1°/Myr lower than found for HS3-NUVEL1A. We construct two further sets of absolute plate angular velocities. The first set of angular velocities, T57-MORVEL, is determined from the data set of Morgan and Phipps Morgan [2006], which consists of 57 trends of widely distributed hotspot tracks. All angular velocities in T57-MORVEL lie outside the 95% confidence limits of the corresponding HS3B-MORVEL angular velocity. We consider two hypotheses to explain this discrepancy: (1) Pacific hotspots move relative to non-Pacfic hotspots at ?5-15 mm/yr, or (2) anachronism—some T57 trends may average plate motion over tens of millions of years, while the HS3B data average over only the past ?6 Myr. The second set of angular velocities, SKS-MORVEL, uses the shear-wave splitting data set of Kreemer [2009] to constrain the direction of plate motion. All angular velocities in SKS-MORVEL lie within the 95% confidence limits of the corresponding HS3B-MORVEL angular velocity. Thus, the alternative "absolute" frames of reference from the orientation of shear-wave splitting and from hotspot tracks are mutually consistent.

Zheng, Lin; Gordon, Richard G.; Kreemer, Corné; Demets, Charles; Argus, Donald F.

2010-05-01

341

Modeling Reality Based Interfaces  

Microsoft Academic Search

The last decade has seen a wave of HCI research aimed at integrating the physical and digital worlds. This work has led to the development of a range of interaction styles such as tangible user interfaces (6), mixed reality interfaces and sensing interfaces (1). Common to these interfaces is that they change the interaction with computers from a segregated specialized

Orit Shaer

342

Plate tectonics and crustal deformation around the Japanese Islands  

NASA Technical Reports Server (NTRS)

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.

Hashimoto, Manabu; Jackson, David D.

1993-01-01

343

North American plate dynamics  

NASA Technical Reports Server (NTRS)

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.

Richardson, Randall M.; Reding, Lynn M.

1991-01-01

344

Microchannel plate streak camera  

DOEpatents

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.

Wang, C.L.

1984-09-28

345

Microchannel plate streak camera  

DOEpatents

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.

Wang, Ching L. (Livermore, CA)

1989-01-01

346

Microchannel plate streak camera  

DOEpatents

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.

Wang, C.L.

1989-03-21

347

Bipolar battery plate  

NASA Technical Reports Server (NTRS)

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.

Rowlette, John J. (Inventor)

1985-01-01

348

PNSN - Pacific Northwest Seismic Network  

NSDL National Science Digital Library

The PNSN operates seismograph stations and locates earthquakes in Washington and Oregon. The web site provides information on Pacific Northwest earthquake activity and hazards. PNSN is based at the University of Washington in the Department of Earth and Space Sciences.

PNSN is operated jointly by the University of Washington, the University of Oregon, and Oregon State University

349

The Pacific Northwest Hydrological Observatory (PNW HO): Hypothesis and model testing power through diversity  

Microsoft Academic Search

The Pacific Northwest Hydrological Observatory (PNW HO) is a proposed national facility for the examination of the linkages between hydrologic and biogeochemical cycles, sustainability of water resources in the face of increasing human demands and climate change, hydrologic and ecosystem interactions, and hydrologic extremes. The PNW HO infrastructure will support research that examines forcings, feedbacks and couplings across hydro-eco-climatic interfaces,

J. J. McDonnell; G. Grant; D. Hulse

2004-01-01

350

Friction and stress coupling on the subduction interfaces  

NASA Astrophysics Data System (ADS)

At a subduction zone, the down-going oceanic plate slides underneath the overriding plate. The frictional resistance to the relative motion between the plates generates great earthquakes along the subduction interface, which can cause tremendous damage in the civil life and property. There is a strong incentive to understand the frictional strength of the subduction interface. One fundamental question of mechanics of subuction is the degree of coupling between the plates, which is linked to the size of earthquakes. It has been noted that the trench-parallel (along-strike) gravity variation correlates positively with the trench-parallel topography anomaly and negatively with the activity of great earthquake (Song and Simons, 2003). Regions with a negative trench-parallel gravity anomaly are more likely to have great earthquakes. The interpretation of such correlation is that strong coupling along subduction interface will drag down the for-arc region of the overriding plate, which generates the gravity and topography anomalies, and could store more strain energy to be released during a great earthquake. We developed a 2D numerical thermo-mechanical code for modeling subduction. The numerical method is based on an explicit finite element method similar to the Fast Lagrangian Analysis of Continua (FLAC) technique. The constitutive law is visco-elasti-plastic with strain weakening. The cohesion and friction angle are reduced with increasing plastic strain after yielding. To track different petrologic phases, Lagrangian particles are distributed in the domain. Basalt-eclogite, sediment-schist and peridotite-serpentinite phase changes are included in the model. Our numerical models show that the degree of coupling negatively correlates with the coefficient of friction. In the low friction case, the subduction interface has very shallow dipping angle, which helps to elastically couple the downing plate with the overriding plate. The topography and gravity anomalies of the low friction case also indicate strong coupling between plates.

Tan, E.; Lavier, L.; van Avendonk, H.

2011-12-01

351

Flutter of a rectangular plate?  

Microsoft Academic Search

We address theoretically the linear stability of a variable aspect ratio, rectangular plate in an uniform and incompressible axial flow. The flutter modes are assumed to be two-dimensional but the potential flow is calculated in three dimensions. For dierent values of aspect ratio, two boundary conditions are studied: a clamped- free plate and a pinned-free plate. We assume that the

Christophe Eloy; Claire Souilliez; Lionel Schouveiler

2006-01-01

352

Warm Working of Armor Plate.  

National Technical Information Service (NTIS)

Taking advantage of warm working to improve the toughness of armor plate requires that the plates be able to be rolled on present day mills. Calculations indicated that a 50 inch wide steel plate with hardnesses in excess of 400 BHN could not be rolled th...

E. J. Ripling, N. N. Breyer, R. P. O'Shea

1967-01-01

353

Vibration analysis of folded plates  

Microsoft Academic Search

The finite element-transfer matrix method (FETMM) is used to study the natural frequencies of folded plate structures. The FETMM used is based on combining the stiffness and mass matrices of each flat plate element in one strip to establish the transfer matrix relation between the left side and right side of a folded strip. The cantilever folded plate or supported

W. H. Liu; C. C. Huang

1992-01-01

354

Lesson 3. Plate Tectonics Overview  

E-print Network

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

Chen, Po

355

The Pacific Northwest GPS Velocity Field (Invited)  

NASA Astrophysics Data System (ADS)

Surface velocities derived from GPS observations have allowed high resolution views of the active deformation and rotation of the Cascadia forearc and backarc as well as elastic strain accumulation arising from subduction fault locking. We present an update of the Pacific Northwest GPS velocity field presented earlier by McCaffrey et al. (Geophys. Jour. Int., 2007) and Payne et al. (Geology, 2008). The new velocity field includes more recent survey-mode and continuous observations as well as an expanded area, extending from the Oregon and Washington coasts on the west to Yellowstone on the east. It combines new Scripps Orbit and Permanent Array Center (SOPAC) daily solutions for 1994-2010 for the Basin and Range Geodetic (BARGN), Eastern Basin and Range - Yellowstone (EBRY), Pacific Northwest Geodetic Array (PANGA), Plate Boundary Observatory (PBO), and Western Canada Deformation Array (WCDA) networks (http://sopac.ucsd.edu/processing/gamit) with our solutions using data from surveys conducted by Idaho National Laboratory, Massachusetts Institute of Technology, National Geodetic Survey, Geologic Survey of Canada, Rensselaer Polytechnic Institute, US Geological Survey, University of Washington, and others, 1991-2010. The new field reveals that the large-scale clockwise rotation seen in western Washington and Oregon also extends southward into southern Idaho and the Snake River Plain as well as into the northern Basin and Range of Nevada. The axes of rotation generally fall near the Oregon-Washington-Idaho border and the Idaho Batholith. Continued densification of the network around the Snake River Plain is permitting a better view of its relationship to nearby Basin and Range extension. We will present interpretations of the active tectonics of the region based on this new field.

McCaffrey, R.; King, R. W.; Payne, S. J.

2010-12-01

356

Phanerozoic tectonic evolution of the Circum-North Pacific  

USGS Publications Warehouse

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

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

357

Proceedings: Graphics interface '86/Vision interface '86  

SciTech Connect

This book contains papers presented at the Graphics interface conference. The Graphics interface conference is a major forum for the presentation of research in computer graphics and human-computer interaction. Sponsored by the Canadian Man-Computer Communications Society, the conferene draws an international audience with papers presented from France, Great Britain, the United States and Canada. The 1986 meeting was held jointly with Vision Interface '86, sponsored by the Canadian Image Processing and Pattern Recognition Society.

Not Available

1986-01-01

358

Characterizing Plate Boundaries  

NSDL National Science Digital Library

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 along the length of a boundary. Showing them what you mean using snapshots from a map can often clear questions like this up quickly. Similarly, for written work a single example that gives them a clear sense of "what you're looking for" and can often head off a lot of questions. (2) Choose the boundaries you ask students to study carefully. The scarcity of documented volcanism along a mid-ocean ridge or the burial of seafloor age belts by sediment along a trench can result in student observations that are correct, but problematic for correctly assessing the nature of a boundary. (3) Stay on top of student questions and comments, and be prepared to make well-publicized "mid-course corrections" if something you thought was clear turns out to be misunderstood. These minor corrections happen naturally in face-to-face classes but can require real diligence to catch and correct in the online environment.

Hirt, Bill

359

Media independent interface. Interface control document  

NASA Technical Reports Server (NTRS)

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.

1987-01-01

360

2009Asia-Pacific International Chemical Industry Exhibition PACIFIC INTERNATIONAL EXHIBITION (BEIJING) CO., LTD.  

E-print Network

, chemicals potential market is huge because the integrated environment and its development trend inside2009Asia-Pacific International Chemical Industry Exhibition PACIFIC INTERNATIONAL EXHIBITION organizations Gift for 60th national anniversary 2009 Asia-Pacific International Chemical Engineering Exhibition

Jayaram, Bhyravabotla

361

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.

362

What can seafloor fabric tell us about the nature of the 50 Ma plate-mantle event?  

NASA Astrophysics Data System (ADS)

Several different mechanisms have been proposed to account for the 50 Ma plate-mantle event, including India-Eurasia collision, the time dependence of the Reunion plume-push force, the subduction of the Izanagi-Pacific mid-ocean ridge, and transient ridge capture of the Hawaiian plume. We use a recent digital global seafloor tectonic fabric map derived from vertical gravity gradients together with magnetic anomaly identifications to analyse the geometry and timing of Late Cretaceous-Early Cenozoic fracture zone (FZ) bends. Two sets of closely spaced FZ bends in the North Atlantic, Weddell Sea and at the Southwest Indian Ridge between Antarctica and Africa produce an S-shape in the seafloor fabric. The older spreading ridge reorganisation initiated close to 70 Ma, and was completed around 55 Ma. The younger FZ bends are sharper, were initiated approximately 55-49 Ma and completed around 40-42 Ma, after which time spreading returned to its pre-S-bend azimuth. Additionally there is a distinct increase in seafloor roughness at the mid-Atlantic ridge at about 70 Ma reflecting a decrease in spreading rate. Seafloor fabric indicators of plate motion change produced at around 70 Ma coincide with emplacement of the Reunion plume and are restricted to parts of the Atlantic-Indian realm. The Pacific domain appears unaffected by the mechanism that drove plate motion changes in the Atlantic and Indian Oceans at this time. Yet, from ~55-40 Ma Pacific FZ bends and other oceanic and plate margin events are widespread. Along with formation of the younger part of the Atlantic-Indian S-bends, FZ bends and changes in FZ morphology in the northeast Pacific signify a reorientation of the Pacific-Farallon spreading ridge, a northward propagation of the Pacific-Antarctic ridge, increases in spreading rates at the Australia-Pacific ridge and a change in the direction of plate motion, with spreading terminating in the Tasman Sea. And initiation of Izu-Bonin-Mariana subduction. This clustering of observations in the Pacific suggests that the driving mechanism of the Eocene reorganisation is situated in this region. For the plume-push forces associated with the arrival of the Reunion plume head at 67 Ma to have driven Eocene plate motion changes, we would expect to see tectonic events in the Pacific beginning at round this time to coincide with initial plume emplacement. Additionally, for the emplacement and waning of the Reunion plume to have driven all the changes we see from ~70-40 Ma it might be expected that sharp FZ bends would form at 70 Ma in the Atlantic-Indian realm and would be succeeded by gradual FZ bends, but we observe the opposite. We favour subduction of the Pacific-Izanagi ridge as the driver of Eocene plate motion changes, and consider the Reunion plume to have perhaps only had a strong influence on plate motions at around the time of its initial eruption and only in parts of the Atlantic-Indian realm. Slab pull is a major driver of plate tectonics and therefore intersection of a young buoyant sub-parallel ridge at the northwest Pacific subduction zone is expected to significantly affect motion of the Pacific and neighbouring plates, and have a more subdued effect on distal regions.

Müller, R. D.; Matthews, K. J.

2011-12-01

363

Quasi-Love Surface Wave Observations on USArray: Evidence for Upper Mantle Anisotropy Along the North American Plate Boundary  

Microsoft Academic Search

Strong evidence for mantle anisotropy exists along the North American and Pacific plate boundary, likely a result of deformation of upper-mantle rocks from the applied stress of tectonic motion. We have observed anisotropy-sensitive Love-to-Rayleigh scattered waves, also known as Quasi-Love waves, on the USArray component of EarthScope, on propagation paths that cross the North American plate boundary. These observed Quasi-Love

D. M. Rieger

2008-01-01

364

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

Microsoft Academic Search

THE Cascadia subduction zone, a region of converging tectonic plates along the Pacific coast of North America, has a geological history of very large plate-boundary earthquakes1,2, but no such earthquakes have struck this region since Euro-American settlement about 150 years ago. Geophysical estimates of the moment magnitudes (Mw) of the largest such earthquakes range from 8 (ref. 3) to 9

Alan R. Nelson; Brian F. Atwater; Peter T. Bobrowsky; Lee-Ann Bradley; John J. Clague; Gary A. Carver; Mark E. Darienzo; Wendy C. Grant; Harold W. Krueger; Rodger Sparks; Thomas W. Stafford; Minze Stuiver

1995-01-01

365

Photovoltaic array: Power conditioner interface characteristics  

NASA Technical Reports Server (NTRS)

The electrical output (power, current, and voltage) of flat plate solar arrays changes constantly, due primarily to changes in cell temperature and irradiance level. As a result, array loads such as dc-to-ac power conditioners must be capable of accommodating widely varying input levels while maintaining operation at or near the maximum power point of the array. The array operating characteristics and extreme output limits necessary for the systematic design of array load interfaces under a wide variety of climatic conditions are studied. A number of interface parameters are examined, including optimum operating voltage, voltage energy, maximum power and current limits, and maximum open circuit voltage. The effect of array degradation and I-V curve fill factor or the array power conditioner interface is also discussed. Results are presented as normalized ratios of power conditioner parameters to array parameters, making the results universally applicable to a wide variety of system sizes, sites, and operating modes.

Gonzalez, C. C.; Hill, G. M.; Ross, R. G., Jr.

1982-01-01

366

Writing and Visualization for Teaching Plate Tectonics  

NASA Astrophysics Data System (ADS)

The Theory of Plate Tectonics is probably the most important paradigm for understanding the workings of our planet. As such it is an integral part in any Introductory Geology course. Whereas geology majors usually easily embrace the Theory of Plate Tectonics, the enthusiasm for the coherence and elegance of this theory appears to be much more subdued among the majority of non-science majors. While visual and electronic media certainly support the teaching of the theory, pretty pictures and animations are not sufficient for many non-science majors to grasp the concepts of interacting lithospheric plates. It is well known that students do better in learning scientific concepts if they create their own understanding through research and inquiry-based learning, by working in the field, manipulating real earth-science data, and through writing. Writing assignments give instructors the opportunity to assess their students' learning and to clarify misconceptions yet they also have to be willing to teach students how to craft a science paper. Most electronic media and textbook-added CD-ROMs are not useful for making the structure of a science paper transparent. I found many of the necessary ingredients for effectively teaching plate tectonics in the interactive CD-ROM, "Our Dynamic Planet", developed by Wm. Prothero together with G. Kelly (University of California at Santa Barbara). It allows students to select and manipulate real earth-science data of plate-tectonically active regions, and provides an electronic interface that lets students create graphical representations of their collected data. A downloadable Teacher's Manual provides suggestions on teaching students to write a scientific argument, rooted in sound pedagogy. Originally designed for a large oceanography class, the material was modified for use in a small introductory geology class for non-science majors. Various assignments were given to instruct students in writing a scientific argument based on their own collected data and observations. The main goals are for students o To see the relationship between data and the development of a scientific theory o To understand the elements of scientific discourse o To learn how to derive conclusions from interpretations and observations o To back interpretations with observations o To be able to write a scientific argument o To understand the Theory of Plate Tectonics, and o To gain a better understanding about how science works The results of several surveys will be presented that confirm that most of the expected outcomes continue to be met.

Thomas, S. F.

2004-12-01

367

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

NASA Astrophysics Data System (ADS)

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.

Rowan, Christopher J.; Rowley, David B.

2014-06-01

368

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

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.

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

2007-01-01

369

Dynamics of Tectonic Plates  

E-print Network

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.

Pechersky, E; Sadowski, G; Yambartsev, A

2014-01-01

370

Ultrafast microchannel plate photomultipliers.  

PubMed

Performance characteristics of several new types of photomultiplier tubes (PMT) with microchannel plates (MCP) are presented in this paper. They are the MCP-PMT with 6-microm diam channels, MCP-PMT with an S-l photocathode, and MCP-PMT with multi (discrete) anode and gatable MCP-PMT. Important requirements of an optical detector for picosecond lasers, fluorescence measurements, and material analysis are low light detectability, ultrafast time response, and versatile operation including modulation. The basic configuration, characteristics, and practical results of these detectors are described. PMID:20531532

Kume, H; Koyama, K; Nakatsugawa, K; Suzuki, S; Fatlowitz, D

1988-03-15

371

Earthquakes and Plate Tectonics  

NSDL National Science Digital Library

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.

2007-10-04

372

Plated wire memory subsystem  

NASA Technical Reports Server (NTRS)

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

Carpenter, K. H.

1974-01-01

373

Shuttle plate braiding machine  

NASA Technical Reports Server (NTRS)

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

Huey, Jr., Cecil O. (Inventor)

1994-01-01

374

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.

375

Automatic number plate detection for Korean vehicles  

Microsoft Academic Search

We consider the task of detection of Korean vehicle number plates (also named license plates or registration plates in other countries). A system for number plate detection must cope with wide variations in the appearance of the plates. Few yeas ago, Korea government permits the new types of license plates with wide width as same as foreign country. It occurred

Ho-Sub Yoon; Hong-Chang Lee; Jae-Yeon Lee

2009-01-01

376

Spot brazing of aluminum to copper with a cover plate  

NASA Astrophysics Data System (ADS)

It is difficult to join dissimilar metals when an intermetallic compound is formed at the joining interface. Spot brazing can be accomplished in a short time by resistance heating. Therefore, it is said that the formation of a intermetallic compound can be prevented. In this study, aluminum and copper were joined by spot brazing with a cover plate. The cover plate was used to supply heat to base metals and prevent heat dissipation from the base metals. The ability to braze Al and Cu was investigated by observation and analysis. Pure aluminum (A1050) plate and oxygen-free copper (C1020) plate were used as base metals. Cu-Ni-Sn-P brazing filler was used as the brazing filler metal. SPCC was employed as cover plate. Brazing was done with a micro spot welder under an argon gas atmosphere. Brazing ability was estimated by tensile shear strength and cross sectional microstructure observation. Al and Cu can be joined by spot brazing with Cu-Ni-Sn-P brazing filler and cover plate.

Hayashi, Junya; Miyazawa, Yasuyuki

2014-08-01

377

Heterogeneity of frontal structure of overriding plate controls co-seismic megathrust slip distribution in trench axial zone, Japan Trench and other subduction zones  

NASA Astrophysics Data System (ADS)

The 2011 off the Pacific coast of Tohoku earthquake induced a giant tsunami by a dynamic slip with the overshoot of the frontal part of the overriding plate near the Japan Trench axis. The maximum slip during the earthquake was detected beneath the deformed zone in the trench axial region of the Miyagi-oki region. The variation in coseismic slip rate would be controlled by a crustal structural variation in the plate interface, which results in a variation of a frictional nature. We estimated the P-wave velocity (Vp) structure to investigate the structural variation spatially correlating to the coseismic slip distribution during the 2011 earthquake by performing an airgun-ocean bottom seismometer experiment on the along-trench profile on the deformed zone in the Japan Trench axial region. We detected that the high Vp body in the hanging wall of the plate interface corresponding to the Cretaceous layer, which is more rigid than the sediment in the deformed zone, sticks out towards the trench axis in the Miyagi-oki segment. In the Miyagi-oki segment, the distance from the trench axis to the forefront of the rigid Cretaceous layer is shorter by ~40 km than in the Sanriku-oki. This means that the width of the less rigid sedimentary prism layer is smaller in the Miyagi-oki than that in the Sanriku-oki. We suggest that this along-arc variation of the hanging wall side structure would cause the difference in propagation of the dynamic slip toward the trench axis between the Miyagi-oki and the Sanriku-oki; the slip reached the trench axis in the Miyagi-oki but not in the Sanriku-oki during the 2011 earthquake. In addition, we found that the similar relationship between the hanging wall structure and the slip distribution of megathrust earthquake observed in Tohoku can recognized in the rupture zones of several major megathrust events, the 1952 Kamchatka, the 1964 Alaska, 1960 and 2010 Chile earthquakes. For example, the 1960 Chile earthquake exhibits the largest coseismic slip at the segment where the sticks out and sedimentary prism is the smallest. We suggest that surveying distribution of a backstop interface would supply important information to assess the passible location of peak slip during any future megathrust events.

Azuma, R.; Hino, R.; Ito, Y.; Mochizuki, K.; Uehira, K.; Murai, Y.; Sato, T.; Takanami, T.; Shinohara, M.; Kanazawa, T.

2013-12-01

378

Nonlinear analysis of the dynamics in the Mexican Pacific seismic region by using visual recurrence plots.  

NASA Astrophysics Data System (ADS)

The subduction in the Mexican South Pacific coast might be approximated as a subhorizontal slab bounded at the edge by the steep subduction geometry of the Cocos plate beneath the Caribbean plate to the east and of the Rivera plate beneath North America to the west. It has been reported a study that takes into account the geometry of the subducted Rivera and Cocos plates beneath the North American lithosphere defining, according their geometry, four regions: Jalisco, Michoacán, Guerrero and Oaxaca. By means of the visual recurrence analysis (VRA), in this work we study some dynamical features of the seismicity occurred for each region, Our analysis shows interesting differences among the recurrence plots of each region indicating a possible correlation between the subduction geometry and the nonlinear dynamical properties of each region.

Ramírez-Rojas, Alejandro; Moreno-Torres, Lucía; Flores-Márquez, Elsa

2013-04-01

379

Plating on difficult-to-plate metals: what's new  

SciTech Connect

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.

Wiesner, H.J.

1980-07-30

380

Spatial variations in effective elastic thickness in the Western Pacific Ocean and their implications for Mesozoic volcanism  

Microsoft Academic Search

We have used free-air gravity anomaly and bathymetric data, together with a moving window admittance technique, to determine the spatial variation in oceanic elastic thickness, Te, in the Western Pacific ocean. Synthetic tests using representative seamounts show that Te can be recovered to an accuracy of ± 5 km for plates up to 30 km thick, with increased accuracy of

L. M. Kalnins; A. B. Watts

2009-01-01

381

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

382

Selecting and Applying Interfacings  

E-print Network

interfacing correctly is an important component of clothing construction. Interfacing gives stability, shape and reinforcement to details such as collars, cuffs, waistbands, pockets, lapels and buttonholes. Interfacing prevents stretching and sagging..., such as metal- lic, beaded, raised designs and open work, are not suitable for use with fusibles. The key is always to test a sample of garment fabric with the interfacing for compatible heat, moisture, time and pressure requirements. (Always follow...

2006-05-01

383

Removal of the subchondral plate in acetabular preparation  

Microsoft Academic Search

Retention of the subchondral plate during acetabular preparation in total hip replacement is believed to be an important part\\u000a of modern cementing techniques. We have constructed a two-dimensional finite element analysis to assess the effect of retention\\u000a and removal of this relatively stiff structure. The finite element analysis demonstrates increased stiffness and stress concentrations\\u000a at the bone-cement interface that may

A. G. Sutherland; S. D’Arcy; D. Smart; G. P. Ashcroft

2000-01-01

384

The science behind Plate Tectonics  

NSDL National Science Digital Library

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.

Weber, John

385

Plate Tectonics: Lines of Evidence  

NSDL National Science Digital Library

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.

National Science Teachers Association (NSTA)

2006-11-01

386

Ion plated gold films: Properties, tribological behavior and performance  

NASA Technical Reports Server (NTRS)

The glow discharge energizing favorably modifies and controls the coating/substrate adherence and the nucleation and growth sequence of ion plated gold films. As a result the adherence, coherence, internal stresses, and morphology of the films are significantly improved. Gold ion plated films because of their graded coating/substrate interface and fine uniform densely packed microstructure not only improve the tribological properties but also induce a surface strengthening effect which improves the mechanical properties such as yield, tensile, and fatigue strength. Consequently significant improvements in the tribological performance of ion plated gold films as compared to vapor deposited gold films are shown in terms of decreased friction/wear and prolonged endurance life.

Spalvins, Talivaldis

1987-01-01

387

Laser-based characterization of nuclear fuel plates  

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

388

Tectonic Plate Movements and Hotspots  

NSDL National Science Digital Library

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.

Rhinehart, Ken

389

Effect of Decoupling of Lithospheric Plates on the Observed Geoid  

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

390

Pacific Northwest National Laboratory Sustainable PNNL  

E-print Network

Pacific Northwest National Laboratory Sustainable PNNL Sustainability at Pacific Northwest National of sustainability throughout our research and operations: environmental stewardship ­ minimizing use of water with the core principles of sustainability. Our success at incorporating sustainability into our work

391

Obesity and Native Hawaiians/Pacific Islanders  

MedlinePLUS

Obesity and Native Hawaiians/Pacific Islanders Native Hawaiians/Pacific Islanders were almost four times more likely to ... data available at this time. HEALTH IMPACT OF OBESITY More than 80 percent of people with type ...

392

Cancer and Asians/Pacific Islanders  

MedlinePLUS

... but they are twice as likely to have stomach cancer. Although Asian/Pacific Islander women are 30% less ... are almost three times as likely to have stomach cancer. Both Asian/Pacific Islander men and women have ...

393

Native Hawaiian & Other Pacific Islander Populations  

MedlinePLUS

... Other Pacific Islander individuals in the United States. States with the largest Native Hawaiian or Other Pacific Islander populations in 2011 were Hawaii (359,000) and California (329,000) . The Native ...

394

Diabetes in Asian and Pacific Islander Americans  

MedlinePLUS

... Islander Americans Diabetes in Asian and Pacific Islander Americans 4 Steps to Manage Your Diabetes for Life ... the disease. PDF Version (1,036 KB) * Asian Americans/Pacific Islanders and Diabetes (from the Office on ...

395

Indian Ocean warming modulates Pacific climate change  

PubMed Central

It has been widely believed that the tropical Pacific trade winds weakened in the last century and would further decrease under a warmer climate in the 21st century. Recent high-quality observations, however, suggest that the tropical Pacific winds have actually strengthened in the past two decades. Precise causes of the recent Pacific climate shift are uncertain. Here we explore how the enhanced tropical Indian Ocean warming in recent decades favors stronger trade winds in the western Pacific via the atmosphere and hence is likely to have contributed to the La Niña-like state (with enhanced east–west Walker circulation) through the Pacific ocean–atmosphere interactions. Further analysis, based on 163 climate model simulations with centennial historical and projected external radiative forcing, suggests that the Indian Ocean warming relative to the Pacific’s could play an important role in modulating the Pacific climate changes in the 20th and 21st centuries. PMID:23112174

Luo, Jing-Jia; Sasaki, Wataru; Masumoto, Yukio

2012-01-01

396

Pacific Islands The National Bycatch Report: Pacific Islands Region  

E-print Network

Reduction Success Stories Annual incidental take limits for two species of sea turtles (leatherback loggerhead and leatherback sea turtle bycatch. Circle hooks are also used by many participants in the Hawaii turtles) bycatch estimates were available for 2 fisheries and 23 species/groups in 2005. Pacific Islands

397

Seattle Pacific "Seattle Pacific University seeks to be a premier  

E-print Network

to be a premier Christian university fully committed to engaging the culture and changing the world by graduating and distinguished history in Christian higher education, Seattle Pacific University entered the new century, will be some of the Christian university's most important contributions in this century. Guiding the work

Nelson, Tim

398

Carbon-assisted flyer plates  

DOEpatents

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.

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

1994-01-01

399

License Plates of the World  

NSDL National Science Digital Library

Whether you're interested in collecting license plates, or are just moving to Andorra and wonder what your car will be wearing when it gets there, this site provided by collector Michael Kustermann can be a handy reference. A winner in the "labor of love" website category, this frames-based directory contains pictures of and descriptive information about a dizzying range of automobile license plates, arranged geographically. Special issue and commemorative plates are also covered, as well as links to collector's clubs and a bibliography about the art and science of license plate hunting and gathering. You'll never look at bumpers quite the same way.

400

Evolution of the western segment of Juan Fernández Ridge (Nazca Plate): plume vs. plate tectonic processes  

NASA Astrophysics Data System (ADS)

The Juan Fernandez Ridge (Eastern Pacific, Nazca Plate) is thought to be a classic hot spot trail because of the apparent age progression observed in 40Ar-39Ar data. However, geological evidence and some thermochronological data suggest a more complex pattern with a rejuvenation stage in Robinson Crusoe Island, the most eroded of the Juan Fernandez Archipelago. In fact, a postshield stage at 900-700 ka separates the underlying shield-related pile from the post-erosional alkaline succession (Ba/Yb=38.15; La/Yb=15.66; Ba/Y=20.27; Ba/Zr=2.31). Shield volcanoes grew at high effusion rate at ca. 5-4 Ma erupting mostly tholeiitic to transitional magmas (Ba/Yb=18.07-8.32; La/Yb=4.59-9.84; Ba/Y=4.24-8.18; Ba/Zr=0.73-1.09). Taken together, shield volcanoes form a continuous plateau with a base at ca. 3900 mbsl. However, a more complex structural pattern can be inferred from geophysical data, which suggest some intracrustal magma storage and a more extended area of magma ascent. A role for the Challenger Fracture Zone is hypothesized fueling the controversy between pristine plume origin and the effect of plate tectonic processes in the origin of intraplate volcanism. This research is supported by FONDECYT Project 1110966.

Lara, Luis E.; Rodrigo, Cristián; Reyes, Javier; Orozco, Gabriel

2014-05-01