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Sample records for accretionary prism sediments

  1. into the accretionary prism

    NASA Astrophysics Data System (ADS)

    Okamoto, Atsushi; Musya, Michimasa; Hashimoto, Yoshitaka; Tsuchiya, Noriyoshi

    2014-12-01

    Carbon dioxide and methane are major components in geofluids; however, there is little evidence showing how C-H-O fluids evolve in a subduction zone. We investigated fluid inclusions in quartz veins from the Eocene-Oligocene Shimanto belt (Murotohanto subbelt) on Muroto Peninsula, SW Japan using microthermometry and laser Raman spectroscopy. Quartz veins that cut the cleavage of the host rocks in the Murotohanto subbelt contain one-phase carbonic inclusions (CH4) and two-phase aqueous inclusions (CH4 ± CO2 vapor and H2O liquid). The vapor in the two-phase inclusions is essentially CH4 in the northern part of the belt and a CO2-CH4 mixture in the southern part; values of [InlineEquation not available: see fulltext.] (=CO2 / (CO2 + CH4)) vary from 0 to 0.9. Within a single CO2-bearing vein, [InlineEquation not available: see fulltext.] values decrease from the vein wall ([InlineEquation not available: see fulltext.] = 0.5 to 0.9) to the vein center ([InlineEquation not available: see fulltext.] = 0), and the homogenization temperature increases from approximately 180°C to 240°C-250°C, indicating a transition of the carbonic species from CO2-CH4 to CH4 during vein formation. CO2-dominant fluids are rare in most accretionary prisms formed under low-grade metamorphic conditions, and the generation of CO2 cannot be explained by diagenesis of organic matter in sediments under the P-T conditions of formation of the CO2-bearing veins (235°C to 245°C, 165 to 200 MPa). The CO2 fluids are distributed preferentially near an out-of-sequence thrust that brings the Murotohanto subbelt into contact with the late Oligocene-early Miocene Nabae subbelt and its many volcanic and intrusive rocks. We therefore suggest that the CO2 fluids were generated in association with near-trench magmatism during the middle Miocene and that the fluids were injected and mixed with the CH4 pore fluids of the sediments in the accretionary prism.

  2. Physical properties of the Nankai inner accretionary prism sediments at Site C0002, IODP Expedition 348.

    NASA Astrophysics Data System (ADS)

    Kitamura, M.; Kitajima, H.; Henry, P.; Valdez, R. D., II; Josh, M.; Tobin, H. J.; Saffer, D. M.; Hirose, T.; Toczko, S.; Maeda, L.

    2014-12-01

    Integrated Ocean Drilling Program (IODP) Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) Expedition 348 focused on deepening the existing riser hole at Site C0002 to ~3000 meters below seafloor (mbsf) to access the deep interior of the Miocene inner accretionary prism. This unique tectonic environment, which has never before been sampled in situ by ocean drilling, was characterized through riser drilling, logging while drilling (LWD), mud gas monitoring and sampling, and cuttings and core analysis. Shipboard physical properties measurements including moisture and density (MAD), electrical conductivity, P-wave, natural gamma ray, and magnetic susceptibility measurements were performed mainly on cuttings samples from 870.5 to 3058.5 mbsf, but also on core samples from 2163 and 2204 mbsf. MAD measurements were conducted on seawater-washed cuttings ("bulk cuttings") in two size fractions of >4 mm and 1-4 mm from 870.5 to 3058.5 mbsf, and hand-picked intact cuttings from the >4 mm size fractions within 1222.5-3058.5 mbsf interval. The bulk cuttings show grain density of ~2.7 g/cm3, bulk density of 1.9 g/cm3 to 2.2 g/cm3, and porosity of 50% to 32%. Compared to the values on bulk cuttings, the intact cuttings show almost the same grain density, but higher bulk density and lower porosity, respectively. Combined with the MAD measurements on hand-picked intact cuttings and discrete core samples from previous expeditions, porosity generally decreases from ~60% to ~20% from the seafloor to 3000 mbsf at Site C0002. Electrical conductivity and P-wave velocity on discrete samples, which were prepared from both cuttings and core samples in the depth interval of 1745.5-3058.5 mbsf, range 0.15-0.9 S/m and 1.7-4.5 km/s, respectively. The electrical resistivity on discrete samples is higher than the LWD resistivity data but the overall depth trends are similar. The electrical conductivity and P-wave velocity on discrete samples corrected for in-situ pressure and temperature

  3. Causes and consequences of the great strength variability among soft Nankai accretionary prism sediments from offshore SW-Japan

    NASA Astrophysics Data System (ADS)

    Stipp, Michael; Schumann, Kai; Leiss, Bernd; Ullemeyer, Klaus

    2014-05-01

    The Nankai Trough Seismogenic Zone Experiment of the International Ocean Discovery Program (IODP) is the very first attempt to drill into the seismogenic part of a subduction zone. Offshore SW-Japan the oceanic Philippine sea plate is subducted beneath the continental Eurasian plate causing earthquakes of magnitude 8.0 to 8.5 and related tsunamis with a recurrence rate of 80-100 years. For the tsunamigenic potential of the forearc slope and accreted sediments their mechanical strength, composition and fabrics have been investigated. 19 drill core samples of IODP Expeditions 315, 316 and 333 were experimentally deformed in a triaxial cell under consolidated and undrained conditions at confining pressures of 400-1000 kPa, room temperature, axial shortening rates of 0.01-9.0 mm/min, and up to an axial strain of ˜64% (Stipp et al., 2013). With respect to the mechanical behavior, two distinct sample groups could be distinguished. Weak samples from the upper and middle forearc slope of the accretionary prism show a deviatoric peak stress after only a few percent strain (< 10%) and a continuous stress decrease after a maximum combined with a continuous increase in pore pressure. Strong samples from the accretionary prism toe display a constant residual stress at maximum level or even a continuous stress increase together with a decrease in pore pressure towards high strain (Stipp et al., 2013). Synchrotron texture and composition analysis of the experimentally deformed and undeformed samples using the Rietveld refinement program MAUD indicates an increasing strength of the illite and kaolinite textures with increasing depth down to 523 m below sea floor corresponding to a preferred mineral alignment due to compaction. Experimentally deformed samples have generally stronger textures than related undeformed core samples and they show also increasing strength of the illite and kaolinite textures with increasing axial strain. Mechanically weak samples have a bulk clay plus

  4. Ultrasonic P-wave velocity measurements with variable effective pressure at the boundary between slope basin sediments and the accretionary prism: IODP Expedition 315 Site C0001

    NASA Astrophysics Data System (ADS)

    Hashimoto, Y.; Knuth, M. W.; Tobin, H. J.; 314/315/316 Scientist, I.

    2008-12-01

    IODP Expedition 315 Site C0001 is located on the hanging wall of the midslope megasplay fault in the Nankai subduction zone off Kii peninsula (SW Japan), and penetrated an unconformity between ~200 m thick slope basin sediments and the accretionary prism. While a down-section porosity increase was clearly observed at the boundary from ~50% to ~60%, logging velocity does not appear to decrease at the boundary, which suggests that different diagenetic processes might exist above and below the boundary. In this study, we conducted ultrasonic P-wave velocity measurements with pore pressure control. We also conducted observations of sediment and chemical analysis. We examined the relationships between the acoustic properties, sediment textures, logging data from IODP Expedition 314 Site C0001 and data from shipboard core analysis. The ultrasonic P-wave velocity measurements were conducted under constant pore pressure (500 kPa) and varying confining pressure to control effective pressure. The confining pressure ranges from 550 kPa to a maximum calculated from the density of overlying sediments (lithostatic pressure - hydrostatic pressure). 8 samples were analyzed, located from ~70 m to ~450 m below the sea floor. P-wave velocity ranges from ~1620 m/s to ~1990 m/s under the hydrostatic pressure condition. These velocities are in good agreement with the logging data. Porosity-velocity relationship in the analyzed data also coincide with that observed in the logging data. Samples shallower than ~300 m fall within previously-defined empirical relationships for normal- and high- consolidation. The deeper samples (at ~370 m and ~450 m below sea floor) show much higher velocity than that predicted by the empirical relationship, suggesting that significant cementation is present in those samples. The textural observations of sediments indicate a decrease in pore space with depth. Quartz and feldspar grains are surrounded by clay mineral matrices. Grain size seems to be almost

  5. Extreme efficiency of mud volcanism in dewatering accretionary prisms

    NASA Astrophysics Data System (ADS)

    Kopf, Achim; Klaeschen, Dirk; Mascle, Jean

    2001-07-01

    Drilling results from two mud volcanoes on the Mediterranean Ridge accretionary complex as well as bottom sampling and the wealth of geophysical data acquired recently have provided fundamental knowledge of the 3D geometry of mud extrusions. Mud volcanism is generally related to buoyancy (density inversion), and is triggered by the collision of the African and Eurasian blocks, forcing undercompacted clayey sediments to extrude along faults in the central and hinterlandward parts of the prism. Volumetric estimates of extruded mud in several well-studied areas were based on pre-stack depth-migrated seismic profiles across the entire, up to >150 km wide, prism. The resulting volumes of mud were combined with ages from mud dome drilling, so that rates of mud extrusion were obtained. Subtracting the solid rock mass from the bulk mud volume using physical property data, fluid flux as a function of mud volcanism alone has been quantified for the first time. The volume of fluid extruding with the mud is found to be variable, but reaches up to 15 km 3 fluid per km trench length and Ma along cross sections with abundant mud volcanoes. Such large fluid quantities in a region some 50-150 km behind the deformation front exceed estimates from those elsewhere (where undoubtedly the majority of the interstitial fluid is lost due to compaction). Such fluids near the backstop are likely to result predominantly from mineral dehydration and diagenetic reactions at depth, and consequently provide a window to understand deeper processes along the deep décollement. More importantly, the enormous rates with which such fluids and liquified mud escape along the out-of-sequence faults alter fluid budget calculations in subduction zones drastically.

  6. Accretionary prism-forearc interactions as reflected in the sedimentary fill of southern Thrace Basin (Lemnos Island, NE Greece)

    NASA Astrophysics Data System (ADS)

    Maravelis, A. G.; Pantopoulos, G.; Tserolas, P.; Zelilidis, A.

    2015-06-01

    Architecture of the well-exposed ancient forearc basin successions of northeast Aegean Sea, Greece, provides useful insights into the interplay between arc magmatism, accretionary prism exhumation, and sedimentary deposition in forearc basins. The upper Eocene-lower Oligocene basin fill of the southern Thrace forearc basin reflects the active influence of the uplifted accretionary prism. Deep-marine sediments predominate the basin fill that eventually shoals upwards into shallow-marine sediments. This trend is related to tectonically driven uplift and compression. Field, stratigraphic, sedimentological, petrographic, geochemical, and provenance data on the lower Oligocene shallow-marine deposits revealed the accretionary prism (i.e. Pindic Cordillera or Biga Peninsula) as the major contributor of sediments into the forearc region. Field investigations in these shallow-marine deposits revealed the occurrence of conglomerates with: (1) mafic and ultramafic igneous rock clasts, (2) low-grade metamorphic rock fragments, and (3) sedimentary rocks. The absence of felsic volcanic fragments rules out influence of a felsic source rock. Geochemical analysis indicates that the studied rocks were accumulated in an active tectonic setting with a sediment source of mainly mafic composition, and palaeodispersal analysis revealed a NE-NNE palaeocurrent trend, towards the Rhodopian magmatic arc. Thus, these combined provenance results make the accretionary prism the most suitable candidate for the detritus forming these shallow-marine deposits.

  7. GPS Velocities and Structure Across the Burma Accretionary Prism and Shillong Plateau in Bangladesh

    NASA Astrophysics Data System (ADS)

    Akhter, S. H.; Steckler, M. S.; Seeber, L.; Agostinetti, N. P.; Kogan, M. G.

    2010-12-01

    We have installed a suite of 18 GPS receiver across the Bengal Basin, covering the country of Bangladesh, near the junction of the Indian Shield, the Himayalan collision belt and the Burma Arc subduction zone. The crust of the Indian Shield thins eastward across the hinge zone of an Early Cretaceous continental margin. The thin continental and/or oceanic crust of the eastern Bengal Basin beyond the hinge zone is overlain by a thick sedimentary sequence of 16 km or more. This heavily-sedimented basin is being overridden from the north by the Shillong Massif, a 2-km high plateau exposing Indian Shield, and from the east by the accretionary prism of the Burma Arc subduction system. The soft collision of the Burma Arc with the Bengal Basin and Ganges-Brahmaputra Delta (GBD) has built a large accretionary prism that widens northwards to 250-300 km. The prism reaches as much as half way across the deep Bengal Basin and the thrust front is blind and buried by the rapid sedimentation of the GBD. Our GPS data cover the frontal region of this unusual subaerial accretionary prism. The convergence across this belt is oblique and partitioned. Our GPS array in Bangladesh shows similar velocity gradients across the accretionary prism corresponding to both E-W shortening and N-S dextral shear. The rates are consistent with the data further east in India. How this motion is partitioned into elastic earthquake-cycle loading and permanent inelastic deformation is unclear. The north-dipping Dauki thrust fault is responsible for the uplifted Shillong Plateau overriding the low-lying and rapidly subsiding Surma Basin. This crustal scale convergent boundary could represent the beginning of a forward jump of the Himalayan front. The surface expression of this boundary is a regional south-verging anticline folding Quaternary sediment into its forelimb at the deformation front south of the Plateau. This suggests that the Dauki Fault, too, is blind and extends well south of the topographic

  8. Types of convergent margins and structural and metamorphic patterns of accretionary prisms

    SciTech Connect

    Cloos, M.; Shreve, R.L.

    1985-01-01

    Theoretical modeling of the subduction channel (shear zone) at convergent plate margins quantifies the processes of sediment subduction, offscraping, underplating and formation of subduction melange by upwelling. Although bedding anisotropy and variations in lithology and pore-fluid pressure control the details of the deformation near the inlet to the subduction channel, the theory shows there are only five basic kinematic patterns which can result in the development of a distinctive type of margin (Types A-E). All incoming sediment is subducted and subduction erosion can occur at Type A margins. All sediment is subducted but a thick, narrow accretionary prism grows by underplating of subducted sediment at Type B margins. Offscraping leads to the development of a broad, tapering prism at Type C, D, and E margins. Incoming sediment is offscraped and subducted sediment is underplated at Type C margins. Melange upwells from depth and is offscraped and underplated at Type D and E margins. Incoming sediment is also offscraped at Type D margins. The structural and metamorphic histories of the fundamental tectonostratigraphic units within the accretionary prism are distinct during steady-state subduction. The bedded slope cover is not metamorphosed and not intensely tectonized upslope from the inlet. During final dewatering and accretion, offscraped materials undergo a subhorizontally-directed compression whereas underplated materials undergo a simple-shear-style of deformation. The metamorphic changes in subducted sediment or upwelled melange depend upon the depth of maximum burial and the thermal structure of the margin. Various episodic factors, such as seamount or ridge subduction, can modify the structural and metamorphic contrasts.

  9. Regional Variation of CH4 and N2 Production Processes in the Deep Aquifers of an Accretionary Prism

    PubMed Central

    Matsushita, Makoto; Ishikawa, Shugo; Nagai, Kazushige; Hirata, Yuichiro; Ozawa, Kunio; Mitsunobu, Satoshi; Kimura, Hiroyuki

    2016-01-01

    Accretionary prisms are mainly composed of ancient marine sediment scraped from the subducting oceanic plate at a convergent plate boundary. Large amounts of anaerobic groundwater and natural gas, mainly methane (CH4) and nitrogen gas (N2), are present in the deep aquifers associated with an accretionary prism; however, the origins of these gases are poorly understood. We herein revealed regional variations in CH4 and N2 production processes in deep aquifers in the accretionary prism in Southwest Japan, known as the Shimanto Belt. Stable carbon isotopic and microbiological analyses suggested that CH4 is produced through the non-biological thermal decomposition of organic matter in the deep aquifers in the coastal area near the convergent plate boundary, whereas a syntrophic consortium of hydrogen (H2)-producing fermentative bacteria and H2-utilizing methanogens contributes to the significant production of CH4 observed in deep aquifers in midland and mountainous areas associated with the accretionary prism. Our results also demonstrated that N2 production through the anaerobic oxidation of organic matter by denitrifying bacteria is particularly prevalent in deep aquifers in mountainous areas in which groundwater is affected by rainfall. PMID:27592518

  10. GPS Velocities and Structure Across the Burma Accretionary Prism and Shillong Anticline in Bangladesh

    NASA Astrophysics Data System (ADS)

    Steckler, M. S.; Akhter, S. H.; Seeber, L.; Bilham, R. G.; Kogan, M. G.; Masson, F.; Maurin, T.; Mondal, D.; Piana Agostinetti, N.; Rangin, C.; Saha, P.

    2012-12-01

    We installed a suite of 25 GPS receivers between 2003 and 2012 covering the deltaic country of Bangladesh, which lies near the junction of the Indian Shield, the Himayalan collision belt and the Indo-Burman Wedge. The crust of the Indian Shield thins southeastward in the Bengal Basin across the hinge zone of an Early Cretaceous continental margin. The thin continental and/or oceanic crust of the Bengal Basin beyond the hinge zone is overlain by the southward prograding Ganges-Brahmaputra Delta (GBD) creating a total sediment thickness of ≥16 km. This heavily-sedimented basin is being overthrust from the north by the Shillong Massif, a 2-km high basement-cored anticlinorium exposing Indian Shield, and from the east by the accretionary prism of the Indo-Burma Wedge. The soft, oblique collision of Burma with the Bengal Basin and Ganges-Brahmaputra Delta (GBD) has built a large accretionary prism that widens northwards to 250-300 km. The prism reaches as much as half way across the deep Bengal Basin. The outer folds and the thrust front are blind and buried by the rapid sedimentation of the GBD. The GPS data in Bangladesh cover the frontal region of this unusual subaerial accretionary prism, while observations from India and Myanmar provide velocities for more internal parts of the system. The convergence across this belt is oblique and partitioned. The velocity gradients across the accretionary prism indicate E-W shortening at ~13 mm/y and N-S dextral shear at ~25 mm/y. The shortening appears to be more concentrated farther west, towards the thrust front, while the shear is more distributed and does not extend to the frontal folds. How this motion is further partitioned into elastic earthquake-cycle loading and permanent inelastic deformation remains unclear. The north-dipping Dauki thrust fault raises the Shillong Massif lowers the rapidly subsiding Surma Basin foredeep. This crustal scale convergent boundary could represent the beginning of a forward jump of the

  11. Deformation processes in an accretionary prism: a study from the Torlesse terrane of New Zealand

    NASA Astrophysics Data System (ADS)

    George, Annette D.

    The style of deformation observed in rocks of the Torlesse (Pahau) terrane, exposed in the Aorangi Range of the North Island, records accretion of thick trench fill by offscraping at the toe of a growing accretionary prism during the early Cretaceous. The relatively coherent nature of the Aorangi Range rocks enables detailed study of the deformation processes produced by offscraping and subsequently within the prism, and many of the structures observed in these rocks are consistent with those described from both modern accreting margins and other ancient accretionary terranes. Overprinting relationships indicate three phases of folding and multiple faulting events. Early deformation involved large-scale sheath-like folding oblique to the overall trend of the margin, and development of an anastomosing axial-planar cleavage. Folding of the sediments promoted dewatering; the subsequent disruption of strata, by shearing parallel to bedding and low-angle to bedding faulting, records the transition to more brittle responses to the deformation. The most widespread folding phase ( D2) produced numerous upright, typically isoclinal folds, with local development of an axial-planar S2 cleavage in macroscopic and some mesascopic fold hinges. The variable plunge of the fold axes to the NNE and SSW within the axial surface indicates progressive rotation of the fold axes after formation. Mesozoic strike-slip faulting most likely produced the open E-W-trending folds and warps of the third folding phase ( D3), in bedding already rotated to moderate dips. Faults which overprint the Mesozoic deformation, were formed in response to renewed subduction along the eastern coast of the North Island during the Cenozoic.

  12. Fluid expulsion sites on the Cascadia accretionary prism: mapping diagenetic deposits with processed GLORIA imagery

    USGS Publications Warehouse

    Carson, Bobb; Seke, Erol; Paskevich, Valerie F.; Holmes, Mark L.

    1994-01-01

     Point-discharge fluid expulsion on accretionary prisms is commonly indicated by diagenetic deposition of calcium carbonate cements and gas hydrates in near-surface (<10 m below seafloor; mbsf) hemipelagic sediment. The contrasting clastic and diagenetic lithologies should be apparent in side scan images. However, sonar also responds to variations in bottom slope, so unprocessed images mix topographic and lithologic information. We have processed GLORIA imagery from the Oregon continental margin to remove topographic effects. A synthetic side scan image was created initially from Sea Beam bathymetric data and then was subtracted iteratively from the original GLORIA data until topographic features disappeared. The residual image contains high-amplitude backscattering that we attribute to diagenetic deposits associated with fluid discharge, based on submersible mapping, Ocean Drilling Program drilling, and collected samples. Diagenetic deposits are concentrated (1) near an out-of-sequence thrust fault on the second ridge landward of the base of the continental slope, (2) along zones characterized by deep-seated strikeslip faults that cut transversely across the margin, and (3) in undeformed Cascadia Basin deposits which overlie incipient thrust faults seaward of the toe of the prism. There is no evidence of diagenetic deposition associated with the frontal thrust that rises from the dècollement. If the dècollement is an important aquifer, apparently the fluids are passed either to the strike-slip faults which intersect the dècollement or to the incipient faults in Cascadia Basin for expulsion. Diagenetic deposits seaward of the prism toe probably consist dominantly of gas hydrates

  13. Deformation of the Nankai Trough inner accretionary prism: The role of inherited structures

    NASA Astrophysics Data System (ADS)

    Boston, Brian; Moore, Gregory F.; Jurado, María. José; Sone, Hiroki

    2016-02-01

    Accretionary prisms commonly grow seaward, with the strata of the inner prism consisting of older, previously accreted outer prism rocks overlain by thick fore-arc basin strata. We focus on the Nankai Trough inner accretionary prism using three-dimensional (3-D) seismic data and logging data from the Integrated Ocean Drilling Program (IODP). We update the 3-D seismic volume using well velocity data to better constrain deeper horizons. Interpretation of these horizons reveals multiple folds with axial surfaces that strike near parallel to modern outer prism thrust faults, and we interpret that these folds formed as a result of thrust faulting. Reactivation of one inner prism thrust fault continued until at least ˜0.44 Ma, after the modern fore-arc basin formed, indicating that the inner prism had continued deformation until that time. Structural restorations of these folded seismic horizons demonstrate that ˜580 m of slip occurred on this steeply dipping reactivated thrust after fore-arc basin formation. Structural interpretation and analysis of logging-while-drilling data, including borehole images, in the deep inner prism revealed intense deformation of a generally homogenous lithology characterized by bedding that dips steeply (60°-90°), intersected by faults and fractures that have a range of dips and densities. Our study of the deep Kumano Basin provides new insights into the structure of the inner prism and reveals that although the inner prism has partially preserved inherited outer prism structures, these older folds and faults are steeply rotated and cut by multiple fracture populations during subsequent deformation.

  14. Rates of fluid expulsion across the northern Cascadia accretionary prism: Constraints from new heat flow and multichannel seismic reflection data

    SciTech Connect

    Davis, E.E.; Hyndman, R.D. ); Villinger, H. )

    1990-06-10

    One hundred and ten closely spaced probe heat flwo measurements provide new constraints on the thermal regime of the northern Cascadia accretionary prism off Vancouver Island. Complementary heat flow values have been obtained from the depth of a bottom-simulating seismic reflector (BSR) that is interpreted to mark the thermally controlled base of a methane hydrate layer. The only local heat flow variations observed are associated with a sediment slump that is seen in SeaMARC II acoustic images and with the outcrop of several major thrust faults. Fluid expulsion resulting from the dewatering of the prism sediments appears to occur regionally in the 10-20-km-wide zone landward of the deformation front. In this area there is a significant disagreement between the probe and BSR heat flow estimates (roughly 30%) that can be explained by a regionally uniform vertical fluid flow at a rate of about 8 {times} 10{sup {minus}10} m/s. This is in good agreement with the estimated fluid expulsin rate required by the decrease in porosity landward of the deformation front, as estimated from the increase in seismic velocities derived from multichannel reflection data. The heat flow in Cascadia Basin seaward of the deformation front is in excellent agreement with that predicted by cooling plate models. Landward, there is a regional trend of decreasing heat flow across the accretionary prism, which is consistent with a model of simple tectonic thickening. Temperatures at the interface between the prism and the oceanic crust continue to increase landward, and reach 400-450 C beneath the middle to inner continental shelf. Initiation of megathrust earthquake failure along the main subduction thrust may be thus restricted by the high temperatures to the zone beneath the continental slope and outer shelf.

  15. Tectonic features of out-of-sequence-thrusts in central Nankai accretionary prism

    NASA Astrophysics Data System (ADS)

    Saito, S.; Kuramoto, S.; Ashi, J.; Kinoshita, M.; Ujiie, K.; Sagaguchi, A.; Lallemant, S.; Toki, T.; Kubo, Y.; Misawa, N.

    2002-12-01

    During NT02-02 and YK02-02 cruises, deep-tow camera, multi-beam bathymetry, and diving survey were conducted in central Nankai accretionary prism, off Kii Peninsula. A system of out-of-sequence thrusts (OOST) defines high ridges, roughly parallel to the deformation front. The surface manifestation of the OOST is characterized by right-stepped en-echelon arrangement of ridges, which suggests a dextral slip component along the OOST. A series of deep-tow camera and dive surveys were conducted on the sites of OOST. Observation of outcrops and rock-sampling documented that the ridges are composed dominantly of stratified shale, siltstone and partly of sandstone covered by present talus debris and clayey ooze. Exposures along the southern limb of the ridges indicate that the beddings of the sediments dip generally northwestward at an angle of about 20 to 30 degree. In contrast to the southern limb of the ridge, outcrops along the northern limb of the ridge show southward dipping bedding. Active cold seepages with Calyptogena colony, bacteria mat, and carbonate chimney were observed at several sites on the slope of OOST ridges. All the active cold seepages observed from the submersible are located on the gentle foot of the slope. High heat flow, low chlorinity of interstitial water chemistry, and high natural gamma radiation at the active colony suggests seepage from the inside of the basement.

  16. Seismic structure of the southern Cascadia subduction zone and accretionary prism north of the Mendocino triple junction

    USGS Publications Warehouse

    Gulick, S.P.S.; Meltzer, A.M.; Clarke, S.H.

    1998-01-01

    Four multichannel-seismic reflection profiles, collected as part of the Mendocino triple junction seismic experiment, image the toe of the southern Cascadia accretionary prism. Today, 250-600 m of sediment is subducting with the Gorda plate, and 1500-3200 m is accreting to the northern California margin. Faults imaged west and east of the deformation front show mixed structural vergence. A north-south trending, 20 km long portion of the central margin is landward vergent for the outer 6-8 km of the toe of the prism. This region of landward vergence exhibits no frontal thrust, is unusually steep and narrow, and is likely caused by a seaward-dipping backstop close to the deformation front. The lack of margin-wide preferred seaward vergence and wedge-taper analysis suggests the prism has low basal shear stress. The three southern lines image wedge-shaped fragments of oceanic crust 1.1-7.3 km in width and 250-700 m thick near the deformation front. These wedges suggest shortening and thickening of the upper oceanic crust. Discontinuities in the seafloor west of the prism provide evidence for mass wasting in the form of slump blocks and debris fans. The southernmost profile extends 75 km west of the prism imaging numerous faults that offset both the Gorda basin oceanic crust and overlying sediments. These high-angle faults, bounding basement highs, are interpreted as strike-slip faults reactivating structures originally formed at the spreading ridge. Northeast or northwest trending strike-slip faults within the basin are consistent with published focal mechanism solutions and are likely caused by north-south Gorda-Pacific plate convergence. Copyright 1998 by the American Geophysical Union.

  17. GPS Velocity Field in Bangladesh: Delta Subsidence, Seasonal Water Loading and Shortening Across the Burma Accretionary Prism and Shillong Massif

    NASA Astrophysics Data System (ADS)

    Steckler, M. S.; Mondal, D. R.; Nooner, S. L.; Akhter, S. H.; Seeber, L.; Bettadpur, S. V.; Sazedul Karim, C.; Howe, M.; Masson, F.; Maurin, T.; Rangin, C.

    2013-12-01

    We installed a suite of 25 GPS receivers between 2003 to 2012 covering the deltaic country of Bangladesh, which lies near the junction of the Indian Shield, the Himayalan collision belt and the Indo-Burman wedge. The crust of the Indian Shield thins southeastward in Bengal Basin across the hinge zone of an Early Cretaceous continental margin. The thin continental and/or oceanic crust of the Bengal Basin beyond the hinge zone is overlain by the southwest prograding Ganges-Brahmaputra Delta (GBD) creating a total sediment thickness of ≥16 km. The GBD is formed by the convergence of these great rivers which together supply >1GT/y of sediment. Their flow, the second largest on earth, is strongly seasonal and causes widespread flooding during the summer monsoon. The heavily-sedimented GBD is being overridden from the north by the Shillong Massif, a 2-km high basement-cored anticlinorium exposing Indian Shield, and from the east by the accretionary prism of the Indo-Burma wedge. The soft, oblique collision of the Burma platelet with the Bengal Basin and the GBD has built a large accretionary prism that widens northwards to 250-300 km. The prism extends westward up to half way across the GBD. The outer folds and thrust front are blind due to burial by the rapid sedimentation of the GBD. The GPS data in Bangladesh cover the frontal region of this unusual subaerial accretionary prism, while observations from India and Myanmar provide velocities for more internal parts of the system. The GPS velocities provide data on multiple processes taking place in the region. The vertical component shows both long-term and seasonal signals. The horizontal components quantify the shortening and lateral motion between the GBD and both the Indo-Burman wedge and Shillong Massif. The Indo-Burman convergence is oblique and partitioned into multiple strike-slip faults and a large number of thrust folds, presumably rooted into a basal megathrust.. The velocity gradients across the

  18. Deformation-induced dehydration structures in the Nankai accretionary prism

    NASA Astrophysics Data System (ADS)

    Famin, V.; Byrne, T.; Lewis, J. C.; Kanagawa, K.; Behrmann, J.; Iodp 314/315/316 Scientists, E.

    2008-12-01

    This study investigates the chemical changes caused by deformation in the hanging wall of a major, probably seismogenic thrust fault in the Kumano forearc basin, Nankai Trough. In cores from IODP Expedition 315 (site C0001), the clay sediments display numerous deformation structures including tilted beddings, decimeter scale faults and shear zones with normal or thrust offsets, and clusters of parallel curviplanar veins interpreted as earthquake-induced dewatering structures. Curviplanar veins are often observed to merge into small oblique shear zones with millimeter offsets, or to branch on larger shear zones with a ~30° angle. This suggests that some shear zones may form by the coalescence of veins. Curviplanar veins and shear zones appear darker than the surrounding clay at the macroscopic observation scale, and brighter and therefore denser under CT-scan imaging. At the micro-scale, clay has a preferred crystallographic orientation in the deformation structures and no preferred orientation outside. Electron probe micro-analysis reveals that the dark material has a higher sum of major elements (65-80 wt%), i.e. a lower volatile content (assumed to be mostly water) than the host sediment (50-60 wt%). All the major elements are equally enriched in proportion to the volatile depletion. Mass balance calculation indicates that a 20-30 wt% water loss is required to account for chemical change in the deformation microstructures. The water loss may be due to clay dehydration or to pore collapse. Shear zones are equally dehydrated as the curviplanar veins from the mass balance standpoint. In 1 m3 of sediment, a deformed volume of 1 % should produce about 6.2 L of water. Given the low permeability of the sediment, dehydration may increase the pore pressure and enhance further deformation. Deformation localization would be self-sustained by fluid overpressure, suggesting that dewatering veins may evolve into larger deformation structures after an earthquake.

  19. The 50 Ma granodiorite of the eastern Gulf of Alaska - Melting in an accretionary prism in the forearc

    NASA Astrophysics Data System (ADS)

    Barker, Fred; Farmer, G. L.; Ayuso, R. A.; Plafker, George; Lull, J. S.

    1992-05-01

    The paper addresses the generation of granitic rocks by the melting of flyschoid sediments in an accretionary prism as part of an investigation of 50-Ma silicic igneous rocks in the Gulf of Alaska, near Cordova, Alaska. Three intrusive bodies exhibiting a range of chemical and initial isotopic compositions were chosen: the McKinley Peak, Rude River, and Sheep Bay plutons. The present chemical data, modeling, and comparison with melting experiments of graywacke by Conrad et al. (1988) indicate that the granodiorite originated by large fractions (65-90 percent) of melting of the Orca Group graywacke and argillite. Plagioclase, pyroxene, and biotite were residual to melting at about 850-950 C and at low H2O activities. It is suggested that the distinct chemical and isotopic compositions of the McKinley Peak pluton result from variations in the character of the flysch at depth in the prism, rather than from mixing between melts of the flysch and mafic magmas injected into the prism itself.

  20. Approximate General Coulomb Model for Accretionary Prisms: An Integrated Study of the Kumano Transect, Nankai Subduction Zone, Southwest Japan

    NASA Astrophysics Data System (ADS)

    Skarbek, Rob; Ikari, Matt; Hüpers, Andre; Rempel, Alan; Wilson, Dean; Kitajima, Hiroko

    2014-05-01

    In accretionary wedges, the mechanical and hydrologic properties along splay faults and the plate boundary fault at the base of the wedge are intimately related to properties within the wedge itself, as well as to sedimentation and/or mass wasting at the wedge surface, and accretionary flux at the wedge toe; Coulomb wedge theories tie these processes together and have been successful in their application to convergent margins. Most such theories assume for the sake of simplicity that mechanical parameters (e.g. bulk density, compressibility, frictional strength) and pore pressure are constant throughout the overlying wedge. However, the values of these parameters must necessarily change with depth and distance from the trench. Here, we derive a model for a fully general Coulomb wedge, parameterized using data specific to the Kumano transect at Nankai, to better understand the location of the basal plate interface and the properties of material composing an actively accretionary prism. We use shear strength data collected for incoming sediments at Integrated Ocean Drilling Program Site C0011 of the NanTroSEIZE project to parameterize the wedge's coefficient of friction. Preliminary results of models where the friction coefficient of the wedge decreases with depth, with other parameters constant and zero cohesion, indicate that including depth dependent frictional strength in the wedge decreases the taper angle of the wedge, with the effect becoming more pronounced with distance from the trench. This model will be further refined by including seismically and numerically determined spatial variations in fluid pressure within the wedge, as well as detailed locations of the upper and basal wedge surfaces along the Kumano transect determined from 3-D seismic data.

  1. Accretionary prisms of the Sikhote-Alin Orogenic Belt: Composition, structure and significance for reconstruction of the geodynamic evolution of the eastern Asian margin

    NASA Astrophysics Data System (ADS)

    Kemkin, I. V.; Khanchuk, A. I.; Kemkina, R. A.

    2016-12-01

    We present overview for geological studies of the terranes of the Sikhote-Alin orogenic belt in the Russian Far East. The belt is formed by accretionary prisms with alternating tectonic packets of thrust-like slices which consist of complexly deformed marine (pelagic and hemipelagic deposits, as well as oceanic plateau and paleo-guyot fragments), marginal oceanic turbidites and chaotic (subduction mélange) formations. We reconstruct a stepwise history of accretion of paleo-oceanic crustal fragments of different ages, based on detailed lithological-biostratigraphic and structural analysis. We propose geodynamic model for evolution of the eastern margin of the paleo-Asian continent during the Mesozoic time by combining geological observations for the region with geological data for others terranes of the Sikhote-Alin Orogenic Belt. We recognize several principal Mesozoic geological processes that have led to formation of the continental crust at the eastern margin of Asia: (i) accretion of paleo-oceanic fragments to the continent margin during the subduction of the paleo-Pacific plate along the convergent margins, (ii) subsequent intense deformation of rocks of the accretionary prisms of the transform margin including folding and multiple thrusting which led to a multifold increase in thickness of sediments, (iii) formation of granitic-metamorphic complexes due to intrusion of the orogenic granites into the accretionary prisms.

  2. Microbial methane production in deep aquifer associated with the accretionary prism in Japan.

    PubMed

    Kimura, Hiroyuki; Nashimoto, Hiroaki; Shimizu, Mikio; Hattori, Shohei; Yamada, Keita; Koba, Keisuke; Yoshida, Naohiro; Kato, Kenji

    2010-04-01

    To identify the methanogenic pathways present in a deep aquifer associated with an accretionary prism in Southwest Japan, a series of geochemical and microbiological studies of natural gas and groundwater derived from a deep aquifer were performed. Stable carbon isotopic analysis of methane in the natural gas and dissolved inorganic carbon (mainly bicarbonate) in groundwater suggested that the methane was derived from both thermogenic and biogenic processes. Archaeal 16S rRNA gene analysis revealed the dominance of H(2)-using methanogens in the groundwater. Furthermore, the high potential of methane production by H(2)-using methanogens was shown in enrichments using groundwater amended with H(2) and CO(2). Bacterial 16S rRNA gene analysis showed that fermentative bacteria inhabited the deep aquifer. Anaerobic incubations using groundwater amended with organic substrates and bromoethanesulfonate (a methanogen inhibitor) suggested a high potential of H(2) and CO(2) generation by fermentative bacteria. To confirm whether or not methane is produced by a syntrophic consortium of H(2)-producing fermentative bacteria and H(2)-using methanogens, anaerobic incubations using the groundwater amended with organic substrates were performed. Consequently, H(2) accumulation and rapid methane production were observed in these enrichments incubated at 55 and 65 degrees C. Thus, our results suggested that past and ongoing syntrophic biodegradation of organic compounds by H(2)-producing fermentative bacteria and H(2)-using methanogens, as well as a thermogenic reaction, contributes to the significant methane reserves in the deep aquifer associated with the accretionary prism in Southwest Japan.

  3. Interstitial water chemistry of sediments of the Costa Rica Accretionary Complex off the Nicoya Peninsula

    NASA Astrophysics Data System (ADS)

    Zuleger, E.; Gieskes, J. M.; You, C.-F.

    Interstitial water analyses from numerous piston, gravity, and Alvin push cores show that fluid flow at the Costa Rica Accretionary Prism is spatially limited and can only be detected by visually directed cores in zones of biogenic activity. Most of the sites cored show evidence for normal diagenetic processes in rapidly deposited, organic carbon-rich sediments, with little evidence for fluid advection. However, in visually directed Alvin push cores, obtained from black sulfidic sediments characterized by the presence of Calyptogena clams or tubeworms, evidence for fluids advected upward from greater depth horizons is shown. These zones are associated with a large mudvolcano on the prism and with the zoes of Out Of Sequence Thrusts. As changes from sea water concentrations are still relatively small, substantial mixing with sea water must have occurred during this upward fluid movement.

  4. Origin and transport of pore fluids in the Nankai accretionary prism inferred from chemical and isotopic compositions of pore water at cold seep sites off Kumano

    NASA Astrophysics Data System (ADS)

    Toki, Tomohiro; Higa, Ryosaku; Ijiri, Akira; Tsunogai, Urumu; Ashi, Juichiro

    2014-12-01

    We used push corers during manned submersible dives to obtain sediment samples of up to 30 cm from the subseafloor at the Oomine Ridge. The concentrations of B in pore water extracted from the sediment samples from cold seep sites were higher than could be explained by organic matter decomposition, suggesting that the seepage fluid at the site was influenced by B derived from smectite-illite alteration, which occurs between 50°C and 160°C. Although the negative δ18OH2O and δDH2O values of the pore fluids cannot be explained by freshwater derived from clay mineral dehydration (CMD), we considered the contribution of pore fluids in the shallow sediments of the accretionary prism, which showed negative δ18OH2O and δDH2O values according to the results obtained during Integrated Ocean Drilling Program (IODP) Expeditions 315 and 316. We calculated the mixing ratios based on a four-end-member mixing model including freshwater derived from CMD, pore fluids in the shallow (SPF) accretionary prism sediment, seawater (SW), and freshwater derived from methane hydrate (MH) dissociation. However, the Oomine seep fluids were unable to be explained without four end members, suggesting that deep-sourced fluids in the accretionary prism influenced the seeping fluids from this area. This finding presents the first evidence of deep-sourced fluids at cold seep sites in the Oomine Ridge, indicating that a megasplay fault is a potential pathway for the deep-sourced fluids.

  5. Paleotemperature of the Nankai accretionary prism estimated by vitrinite reflectance of carbonaceous materials retrieved during the IODP Expedition 348

    NASA Astrophysics Data System (ADS)

    Fukuchi, R.; Yamaguchi, A.; Yamamoto, Y.; Ashi, J.

    2015-12-01

    Integrated Ocean Drilling Program (IODP) Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) Expedition 348 took place from 13 September 2013 to 29 January 2014. During the Exp. 348, cuttings, mud gas, and logging data were collected from Holes C0002N and C0002P down to 3058.5 mbsf. Cores were collected from 2163 to 2218 mbsf of Hole C0002P. Three lithologic units were identified at Site C0002 based on geological and geochemical characteristics of core and cuttings samples: Unit III (875.5-975.5 mbsf in Hole C0002N), Unit IV (975.5-1665.5 mbsf in Hole C0002N), and Unit V (1665.5-2325.5 mbsf in Hole C0002N, and 1965.5-3058.5 mbsf in Hole C0002P) (Tobin et al., 2015). To evaluate whole thermal structure of the Site C0002, we performed vitrinite reflectance analysis for cuttings samples collected every ~100 m, and for borehole core samples collected every ~10 m of Hole C0002N and C0002P. Vitrinite reflectance (Ro) is an indicator to estimate maximum paleotemperature, which has been widely applied to reveal tectonic evolution of on-land accretionary complex in Southwest Japan (e.g. Underwood et al., 1992; Ohomori et al., 1997) and thermal anomalies along fault slip zones reflecting frictional heating due to seismic slip (e.g. Sakaguchi et al., 2011). This is the first study that applied vitrinite analyses systematically to the deep portion of modern accretionary prisms. In this presentation, we report preliminary results of vitrinite reflectance analysis. Ro values are 0.15 to 0.20 in Unit III (forearc basin strata), 0.21 to 0.27 in Unit IV (accretionary prism strata), and 0.26 to 0.38 in Unit V (hemipelagic sediment), respectively. In general, Ro values tend to be gradually and continuously increasing with depth. Estimated paleotemperatures are ~67°C in Unit IV and ~77°C in Unit V. Estimated paleotemperatures are lower than estimated modern temperatures based on borehole temperature measurements and their downward extrapolations (Sugihara et al., 2014). Gaps on

  6. Earthquake faulting in subduction zones: insights from fault rocks in accretionary prisms

    NASA Astrophysics Data System (ADS)

    Ujiie, Kohtaro; Kimura, Gaku

    2014-12-01

    Subduction earthquakes on plate-boundary megathrusts accommodate most of the global seismic moment release, frequently resulting in devastating damage by ground shaking and tsunamis. As many earthquakes occur in deep-sea regions, the dynamics of earthquake faulting in subduction zones is poorly understood. However, the Integrated Ocean Drilling Program (IODP) Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) and fault rock studies in accretionary prisms exhumed from source depths of subduction earthquakes have greatly improved our understanding of earthquake faulting in subduction zones. Here, we review key advances that have been made over the last decade in the studies of fault rocks and in laboratory experiments using fault zone materials, with a particular focus on the Nankai Trough subduction zone and its on-land analog, the Shimanto accretionary complex in Japan. New insights into earthquake faulting in subduction zones are summarized in terms of the following: (1) the occurrence of seismic slip along velocity-strengthening materials both at shallow and deep depths; (2) dynamic weakening of faults by melt lubrication and fluidization, and possible factors controlling coseismic deformation mechanisms; (3) fluid-rock interactions and mineralogical and geochemical changes during earthquakes; and (4) geological and experimental aspects of slow earthquakes.

  7. A lithium isotopic study of sub-greenschist to greenschist facies metamorphism in an accretionary prism, New Zealand

    NASA Astrophysics Data System (ADS)

    Qiu, Lin; Rudnick, Roberta L.; Ague, Jay J.; McDonough, William F.

    2011-01-01

    fluids, 2) the slab-derived fluids will have heavy δ7Li of > + 10 after reacting with the prism sediments during their ascent, and 3) the [Li] of the slab-derived fluids is likely in the range of 0 < [Li] ≤ 41(μg/g). Thus, isotopically heavy slab-derived fluids that traverse sediments in accretionary prisms may leave little trace in the rocks and their surface compositional characteristics will reflect the net result of their interaction with the sediments of the prism.

  8. Understanding tectonic stress and rock strength in the Nankai Trough accretionary prism, offshore SW Japan

    NASA Astrophysics Data System (ADS)

    Huffman, Katelyn A.

    Understanding the orientation and magnitude of tectonic stress in active tectonic margins like subduction zones is important for understanding fault mechanics. In the Nankai Trough subduction zone, faults in the accretionary prism are thought to have historically slipped during or immediately following deep plate boundary earthquakes, often generating devastating tsunamis. I focus on quantifying stress at two locations of interest in the Nankai Trough accretionary prism, offshore Southwest Japan. I employ a method to constrain stress magnitude that combines observations of compressional borehole failure from logging-while-drilling resistivity-at-the-bit generated images (RAB) with estimates of rock strength and the relationship between tectonic stress and stress at the wall of a borehole. I use the method to constrain stress at Ocean Drilling Program (ODP) Site 808 and Integrated Ocean Drilling Program (IODP) Site C0002. At Site 808, I consider a range of parameters (assumed rock strength, friction coefficient, breakout width, and fluid pressure) in the method to constrain stress to explore uncertainty in stress magnitudes and discuss stress results in terms of the seismic cycle. I find a combination of increased fluid pressure and decreased friction along the frontal thrust or other weak faults could produce thrust-style failure, without the entire prism being at critical state failure, as other kinematic models of accretionary prism behavior during earthquakes imply. Rock strength is typically inferred using a failure criterion and unconfined compressive strength from empirical relations with P-wave velocity. I minimize uncertainty in rock strength by measuring rock strength in triaxial tests on Nankai core. I find strength of Nankai core is significantly less than empirical relations predict. I create a new empirical fit to our experiments and explore implications of this on stress magnitude estimates. I find using the new empirical fit can decrease stress

  9. In-situ stress and strength in the Nankai inner accretionary prism at Site C0002, IODP NanTroSEIZE

    NASA Astrophysics Data System (ADS)

    Kitajima, H.; Valdez, R. D.; Kitamura, M.; Sone, H.; Saffer, D. M.; Tobin, H. J.; Hirose, T.; Kuo, S. T.

    2015-12-01

    As a part of the International Ocean Discovery Program (IODP) Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE), a deep riser borehole has been drilled into the Kumano forearc basin and the underlying inner accretionary wedge at Site C0002, located ~35 km landward from the trench. One of the primary objectives of drilling the riser site was to characterize in-situ stress and pore pressure in the hanging wall above the locked plate boundary. Here, we: (1) investigate the mechanical strength and deformation behavior of prism sediment via laboratory experiments on core samples; and (2) quantify in-situ stress (Sv, Sh, and SH), and pore pressure (Pp) in the Kumano basin and the inner prism. We conducted triaxial compression experiments on core samples recovered from ~ 2200 meters below sea floor (mbsf) during IODP Expedition 348, at effective pressures (Pe) ranging from 8 and 36 MPa, and at temperatures of either 25°C or 60°C. Our preliminary results indicate that the prism (20 - 42% porosity) rocks deform brittlely at Pe < 22 MPa, but exhibit strain hardening at Pe = 36 MPa. This pressure-porosity condition for a brittle-ductile transition is consistent with previous work defining yield models for incoming sediments at the Nankai Trough (Kitajima and Saffer, 2012). Combining P-wave velocity logs and downhole measurements of leak-off pressure at Site C0002 with an empirical relationship between P-wave velocity, porosity, and effective stress, we show that the Kumano forearc basin is in a uniaxial-strain loading path, which defines a normal faulting stress regime (Sv>SH>=Sh), whereas the inner accretionary prism is in a triaxial-strain loading path that defines a strike-slip faulting regime (SH>Sv>Sh). We estimate excess pore pressure below ~2000 mbsf ranging from 0-12 MPa, corresponding to a pore pressure ratio λ* of 0 - 0.40.

  10. Drilling into the deep interior of the Nankai accretionary prism: Preliminary results of IODP NanTroSEIZE Expedition 348

    NASA Astrophysics Data System (ADS)

    Tobin, H. J.; Hirose, T.; Saffer, D. M.; Toczko, S.; Maeda, L.

    2014-12-01

    International Ocean Discovery Program (IODP) Expedition 348, the latest advance of the NanTroSEIZE project, started on 13 September 2013 and was completed on 29 January 2014. During Expedition 348, the drilling vessel Chikyu advanced the ultra-deep riser hole at Site C0002, located 80 km offshore of the Kii Peninsula, from a depth of 860 meters below sea floor (mbsf) to 3058.5 mbsf, the world record for the deepest scientific ocean drilling, and cased it for future deepening. The drilling operation successfully obtained data on formation physical properties from logging while drilling (LWD) tools, as well as from lithological analyses of cuttings and core from the interior of the active accretionary prism at the Nankai Trough. IODP Site C0002 is the currently only borehole to access the deep interior of an active convergent margin. Preliminary scientific results of Expedition 348 are as follows: (1) Fine-grained turbiditic mudstones with coarser silty and sandy interbeds, exhibiting steep dips (between ~60 and 90 degrees) are predominant in the prism down to ~3000 mbsf. The biostratigraphic age of the sediments in the lowermost part of the hole is thought to be 9-11 Ma, with an assumed age of accretion of 3-5 Ma. (2) Slickenlined surfaces, deformation bands and mineral veins are present throughout the drilled interval, while well-developed scaly clay fabrics are increasingly observed below ~2200 mbsf. A substantial fault zone with well-developed foliation was successfully cored from the deep interior of the prism at ~2205 mbsf. (3) Porosity generally decreases from ~60% to ~20% from the seafloor to 3000 mbsf. However, physical properties including grain density, electrical conductivity and P-wave velocity suggest fairly homogeneous properties in the interior of the prism between ~2000 and 3000 mbsf. (4) Mud gas analysis during the riser drilling indicates that a source of methane gas shifts from microbial origin to thermogenic at around 2325 mbsf. (5) The maximum

  11. Initiation and development of slickenlined surfaces in clay-rich material of the Nankai Trough accretionary prism

    NASA Astrophysics Data System (ADS)

    Crespo-Blanc, Ana; Schleicher, Anja

    2016-04-01

    During the International Ocean Discovery Program (IODP) Expedition 348, which is part of the Nankai Trough Seismogenic Zone Experiment (stage 3), the drilling vessel Chikyu advanced the deep riser hole at Site C0002, located 80 km offshore of the Kii Peninsula (Japan), from a depth of 860 meters below sea floor (mbsf) to 3058.5 mbsf. Underlying the Kumano Basin sediments, the Nankai accretionary prism appears, below 975.5 mbsf. It accreted during Upper Miocene to Pliocene times and is formed mainly by turbiditic silty claystone with rarely observed sandstone intercalations. Cuttings from both the 1-4 mm and >4 mm size fractions were investigated, showing slickenlined surfaces and deformation bands together with carbonate veins throughout the entire section from 1045.5 until 3058.5 mbsf. A scaly fabric is increasingly observed below approximately 2400 mbsf. Clay-rich cuttings were selected at different depth for specific SEM-EDS analysis, in order to investigate the initiation and development of the slickenlined surfaces, from both a structural and mineralogical point of view. Two end-members of the slickenlined surface types were observed: a) isolated smooth and uniform planes, between 20 and 50 μm long, formed by single grains of smectite with marked lineations and frequently jagged boundaries and b) microfaults (longer than 100 μm) with sharp boundaries to the undeformed rock, formed by aggregates of illite and smectite and with a well-developed lineation. In transition between these two end-member types, planes that are apparently unconnected draw a single plane and show subparallel lineations. Concerning the orientation of the slickenlines, it seems to be coherent with that observed in an array of conjugated faults, i.e. all the slickenlines belong to the same plane, in turn sub-perpendicular to the intersection of conjugated planes. These observations suggest that the slickenlined surfaces initiated along single grains of smectite and that with increasing

  12. Heat flow survey in the vicinity of the branches of the megasplay fault in the Nankai accretionary prism

    NASA Astrophysics Data System (ADS)

    Yamano, Makoto; Kawada, Yoshifumi; Hamamoto, Hideki

    2014-12-01

    Heat flow measurements were conducted at four sites in the Nankai accretionary prism southeast of the Kii Peninsula, around the area where the megasplay fault reaches the surface, in conjunction with long-term monitoring of bottom water temperature at nearby stations. Analysis of the obtained data showed that variations in bottom water temperature seriously affect surface heat flow measurements in the areas with water depths of less than about 2,800 m. This effect can reach up to 20% to 30% and may have significantly contributed to a large scatter in the heat flow values previously measured in the study area. The temperature records were also used to determine heat flows from sediment temperature profiles disturbed by bottom water temperature variations. Results of measurements at sites deeper than 2,800 m indicate that the regional heat flow, corrected for surface disturbances including the influence of bathymetric relief, is about 65 mW/m2, which is consistent with the value calculated using subduction thermal models. Local high heat flow values were obtained in the vicinity of the tips of the branches of the splay fault, suggesting advective heat transport by upward pore fluid flow along the faults.

  13. Seafloor distribution and last glacial to postglacial activity of mud volcanoes on the Calabrian accretionary prism, Ionian Sea

    NASA Astrophysics Data System (ADS)

    Ceramicola, Silvia; Praeg, Daniel; Cova, Andrea; Accettella, Daniela; Zecchin, Massimo

    2014-06-01

    Mud volcanoes (MVs) are abundant along the eastern Mediterranean subduction zones, recording mud breccia extrusion over long timescales (106 years), but to date relatively few have been recognised in the northern Ionian Sea on the Calabrian accretionary prism (CAP). In the present study, the seafloor distribution and recent activity of MVs is investigated across a 35,600 km2 sector of the CAP using a regional acoustic dataset (multibeam bathymetric and backscatter imagery, integrated with subbottom profiles) locally ground-truthed by sediment cores. A total of 54 MVs are identified across water depths of 150-2,750 m using up to four geophysical criteria: distinctive morphology, high backscatter, unstratified subbottom facies and, in one case, a hydroacoustic flare. Fourteen MVs are identified from 3-4 criteria, of which five have been previously proven by cores containing mud breccia beneath up to 1.6 m of hemipelagic sediments (Madonna dello Ionio MVs 1-3, Pythagoras MV and the newly named Sartori MV), while nine others are identified for the first time (Athena, Catanzaro, Cerere, Diana, Giunone, Minerva, `right foot', Venere 1 and 2). Forty other as yet unnamed MVs are inferred from 1-2 geophysical criteria (three from distinctive morphology alone). All but one possible MV lie on the inner plateau of the CAP, landwards of the Calabrian Escarpment in a zone up to 120 km wide that includes the inner pre-Messinian wedge and the fore-arc basins, where they are interpreted to record the ascent from depth of overpressured fluids that interacted with tectonic structures and with evaporitic or shale seals within the fore-arc basins. The rise of fluids may have been triggered by post-Messinian out-of-sequence tectonism that affected the entire pre-Messinian prism, but Plio-Quaternary sedimentation rates and depositional styles support the inference that significant mud volcanism has taken place only on the inner plateau. Sedimentation rates across the CAP applied to a 12

  14. Temporal variation of the Rayleigh admittance: Implication for S-wave velocity changes in the toe of the Nankai accretionary prism

    NASA Astrophysics Data System (ADS)

    Tonegawa, Takashi; Araki, Eiichiro; Kimura, Toshinori; Nakamura, Takeshi

    2016-04-01

    implies that S-wave velocity within the accretionary prism tended to be high. This change may indicate fluid emissions from marine sediments due to the horizontal compaction.

  15. Biogas production using anaerobic groundwater containing a subterranean microbial community associated with the accretionary prism

    PubMed Central

    Baito, Kyohei; Imai, Satomi; Matsushita, Makoto; Otani, Miku; Sato, Yu; Kimura, Hiroyuki

    2015-01-01

    In a deep aquifer associated with an accretionary prism, significant methane (CH4) is produced by a subterranean microbial community. Here, we developed bioreactors for producing CH4 and hydrogen (H2) using anaerobic groundwater collected from the deep aquifer. To generate CH4, the anaerobic groundwater amended with organic substrates was incubated in the bioreactor. At first, H2 was detected and accumulated in the gas phase of the bioreactor. After the H2 decreased, rapid CH4 production was observed. Phylogenetic analysis targeting 16S rRNA genes revealed that the H2-producing fermentative bacterium and hydrogenotrophic methanogen were predominant in the reactor. The results suggested that syntrophic biodegradation of organic substrates by the H2-producing fermentative bacterium and the hydrogenotrophic methanogen contributed to the CH4 production. For H2 production, the anaerobic groundwater, amended with organic substrates and an inhibitor of methanogens (2-bromoethanesulfonate), was incubated in a bioreactor. After incubation for 24 h, H2 was detected from the gas phase of the bioreactor and accumulated. Bacterial 16S rRNA gene analysis suggested the dominance of the H2-producing fermentative bacterium in the reactor. Our study demonstrated a simple and rapid CH4 and H2 production utilizing anaerobic groundwater containing an active subterranean microbial community. PMID:25267392

  16. Relating sulfate and methane dynamics to geology: Accretionary prism offshore SW Taiwan

    NASA Astrophysics Data System (ADS)

    Chuang, Pei-Chuan; Dale, Andrew W.; Wallmann, Klaus; Haeckel, Matthias; Yang, Tsanyao Frank; Chen, Nai-Chen; Chen, Hsiao-Chi; Chen, Hsuan-Wen; Lin, Saulwood; Sun, Chih-Hsien; You, Chen-Feng; Horng, Chorng-Shern; Wang, Yunshuen; Chung, San-Hsiung

    2013-07-01

    Geochemical data (CH4, SO42-, I-, Cl-, particulate organic carbon (POC), δ13C-CH4, and δ13C-CO2) are presented from the upper 30 m of marine sediment on a tectonic submarine accretionary wedge offshore southwest Taiwan. The sampling stations covered three ridges (Tai-Nan, Yung-An, and Good Weather), each characterized by bottom simulating reflectors, acoustic turbidity, and different types of faulting and anticlines. Sulfate and iodide concentrations varied little from seawater-like values in the upper 1-3 m of sediment at all stations; a feature that is consistent with irrigation of seawater by gas bubbles rising through the soft surface sediments. Below this depth, sulfate was rapidly consumed within 5-10 m by anaerobic oxidation of methane (AOM) at the sulfate-methane transition. Carbon isotopic data imply a mainly biogenic methane source. A numerical transport-reaction model was used to identify the supply pathways of methane and estimate depth-integrated turnover rates at the three ridges. Methane gas ascending from deep layers, facilitated by thrusts and faults, was by far the dominant term in the methane budget at all sites. Differences in the proximity of the sampling sites to the faults and anticlines mainly accounted for the variability in gas fluxes and depth-integrated AOM rates. By comparison, methane produced in situ by POC degradation within the modeled sediment column was unimportant. This study demonstrates that the geochemical trends in the continental margins offshore SW Taiwan are closely related to the different geological settings.

  17. Deformation and dewatering of the subducting plate and evolution of the decollement zone under the northern Barbados accretionary prism: Insights from three-dimensional seismic reflection data

    NASA Astrophysics Data System (ADS)

    Zhao, Zhiyong

    A 3-D seismic data set reveals a detailed structure and stratigraphy of the subducting plate and overlying sediment under the toe of the northern Barbados accretionary prism. The oceanic basement shows a preexisting horst and graben structure. The upper Cretaceous to lower Eocene sedimentary unit mostly fills in basement lows. The subducting middle to upper Eocene and Oligocene units overlie a smoothed sedimentary surface. Based on the landward thinning, we estimate that the upper two sedimentary units have lost 25% of their total initial void space within 3.5 km landward of the thrust front due to the load of the prism. This suggests that the current fluid expulsion rate under the 3.5-km prism toe is 1008 m3/yr per kilometer of strike length, much higher than previously published estimates. The fluid discharge is expected to increase to 1092 m3/yr per kilometer of strike length within 64,000 years as a thicker sedimentary section is subducted. Our results also suggest that the basement indirectly controls fluid movement in the underthrust Oligocene unit by creating secondary normal faults that act as major fluid conduits between the overlying decollement and the underlying more permeable middle to upper Eocene turbidite-bearing section. A constrained seismic inversion was conducted on the 3-D seismic data set to study the physical properties of the decollement/protodecollement zone (PDZ). The inversion results suggest that part of the PDZ is likely scrapped off by the prism. Fluid conduits along the decollement may originate from spatial variations of initial physical properties of the protodecollement and then be enhanced by shear-induced consolidation. There are significant differences in physical properties between the northern and southern PDZ covered by this study. The differences coincide with a change in the structure of the prism. A larger prism taper in the southern area may result from a stronger decollement. The larger prism taper coupled with less

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

    USGS Publications Warehouse

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

    1998-01-01

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

  19. Observations and Rock Analyses in a Kumano Mud Volcano in Nankai Accretionary Prism

    NASA Astrophysics Data System (ADS)

    Morita, S.; Aoike, K.; Sawada, T.; Ashi, J.; Gulick, S. P.; Flemings, P. B.; Kuramoto, S.; Saito, S.; Mikada, H.; Kinoshita, M.

    2002-12-01

    Kumano Basin is a forearc basin on the eastern Nankai Accretionary Prism off southwest Japan. Recent bathymetric survey showed existence of small knolls in the Kumano Basin. Submersible and ROV dives, sidescan sonar and deep-towed camera investigations revealed so far that at least five of the small knolls are mud volcanoes erupted on the Kumano Basin floor. In June and August, 2002, Dive 677 and 681 by submersible SHINKAI 6500 (YK02-02: R/V Yokosuka) and Dive 267 by ROV KAIKO (KR02-10: R/V Kairei) were performed in one of the mud volcanoes, Kumano Knoll No.4, which is 100 m high and 800 m in diameter at the foot of the knoll. The knoll has a plateau of about 300 m diameter on the top, which shows bumpy surface where there are waves, steps and craters of several meters in diameter. The craters imply active or dead cold seeps and are occasionally accompanied by Calyptogena colonies. The plateau is mostly covered with mud. Rock gravels and boulders were observed mainly on outer slope of the knoll. Sidescan sonar and subbottom profiler data by KAIKO system show marked contrasts in sonic reflectivity and penetration between the Kumano Knoll No.4 and the Kumano Basin floor. The high sonic reflectivity and the low penetration on the knoll indicate that main body of the knoll is composed of clastic ejecta as a mud volcano. On the Kumano Knoll No.4, the dives obtained semi-consolidated mudstone, mud breccia, and biotite arkose sandstone. Chronological analysis on nannofossil indicates the sedimentary rocks are in the late Early Miocene through the Middle Miocene. According to this age and geological information on land, it is likely that the sedimentary rocks on the knoll were originally deposited at the beginning of formation of the Kumano Basin. Porosity of these sedimentary rocks is very low (< 18 %). Some mud breccias contain calcite veins that cut the angular mud gravels. These features lead to finding processes until when the sedimentary rocks reached to the seafloor

  20. Tectonic stratification and seismicity of the accretionary prism of the Azerbaijani part of Greater Caucasus

    NASA Astrophysics Data System (ADS)

    Alizade, Akif; Kangarli, Talat; Aliyev, Fuad

    2013-04-01

    The Greater Caucasus has formed during last stage of the tectogenesis in a geodynamic condition of the lateral compression, peculiar to the zone pseudo-subduction interaction zone between Northern and Southern Caucasian continental microplates. Its present day structure formed as a result of horizontal movements of the different phases and sub-phases of Alpine tectogenesis (from late Cimmerian to Valakhian), and is generally regarded as zone where, along Zangi deformation, the insular arc formations of the Northern edge of South Caucasian microplate thrust under the Meso-Cenozoic substantial complex contained in the facials of marginal sea of Greater Caucasus. The last, in its turn, has been pushed beneath the North-Caucasus continental margin of the Scythian plate along Main Caucasus Thrust fault. Data collected from the territory of Azerbaijan and its' sector of the Caspian area stands for pseudo-subduction interaction of microplates which resulted in the tectonic stratification of the continental slope of Alpine formations, marginal sea and insular arc into different scale plates of south vergent combined into napping complexes. In the orogeny's present structure, tectonically stratified Alpine substantial complex of the marginal sea of Greater Caucasus bordered by Main Caucasus and Zangi thrusts, is represented by allochthonous south vergent accretionary prism in the front of first deformation with its' root buried under the southern border of Scythian plate. Allocated beneath mentioned prism, the autochthonous bedding is presented by Meso-Cenosoic complex of the Northern flank of the South-Caucasian miroplate, which is in its' turn crushed and lensed into southward shifted tectonic microplates gently overlapping the northern flank of Kura flexure along Ganykh-Ayrichay-Alyat thrust. Data of real-time GPS measurement of regional geodynamics indicates that pseudo-subduction of South Caucasian microplate under the North Caucasian microplate still continues during

  1. Sequence stratigraphy, structural style, and age of deformation of the Malaita accretionary prism (Solomon arc-Ontong Java Plateau convergent zone)

    NASA Astrophysics Data System (ADS)

    Phinney, Eric J.; Mann, Paul; Coffin, Millard F.; Shipley, Thomas H.

    2004-10-01

    Possibilities for the fate of oceanic plateaus at subduction zones range from complete subduction of the plateau beneath the arc to complete plateau-arc accretion and resulting collisional orogenesis. Deep penetration, multi-channel seismic reflection (MCS) data from the northern flank of the Solomon Islands reveal the sequence stratigraphy, structural style, and age of deformation of an accretionary prism formed during late Neogene (5-0 Ma) convergence between the ˜33-km-thick crust of the Ontong Java oceanic plateau and the ˜15-km-thick Solomon island arc. Correlation of MCS data with the satellite-derived, free-air gravity field defines the tectonic boundaries and internal structure of the 800-km-long, 140-km-wide accretionary prism. We name this prism the "Malaita accretionary prism" or "MAP" after Malaita, the largest and best-studied island exposure of the accretionary prism in the Solomon Islands. MCS data, gravity data, and stratigraphic correlations to islands and ODP sites on the Ontong Java Plateau (OJP) reveal that the offshore MAP is composed of folded and thrust faulted sedimentary rocks and upper crystalline crust offscraped from the Solomon the subducting Ontong Java Plateau (Pacific plate) and transferred to the Solomon arc. With the exception of an upper, sequence of Quaternary? island-derived terrigenous sediments, the deformed stratigraphy of the MAP is identical to that of the incoming Ontong Java Plateau in the North Solomon trench. We divide the MAP into four distinct, folded and thrust fault-bounded structural domains interpreted to have formed by diachronous, southeast-to-northwest, and highly oblique entry of the Ontong Java Plateau into a former trench now marked by the Kia-Kaipito-Korigole (KKK) left-lateral strike-slip fault zone along the suture between the Solomon arc and the MAP. The structural style within each of the four structural domains consists of a parallel series of three to four fault propagation folds formed by the

  2. Structure and deformation of the Southern Taiwan accretionary prism: The active submarine Fangliao Fault Zone offshore west Hengchun Peninsula

    NASA Astrophysics Data System (ADS)

    Deffontaines, Benoit; Liu, Char-Shine; Hsu, Ho-Han

    2016-12-01

    What is the structural geometry of the southern Taiwan transition zone from the Manila subduction offshore to the Taiwan onshore collision, specifically in the western flank of the Hengchun peninsula that corresponds to the summit of the Manila subduction accretionary prism? This paper aims to decipher the onshore/offshore structures and tectonic deformation that occur west of the Hengchun Ridge through both detailed topographic analyses and interpretation of numerous old and new seismic profiles. From a geomorphic point of view, both Fangliao and Hongchai submarine canyons have different structural and landslide implications. The Fangliao Canyon is guided by a N-S elongated mud diapir (the Fangliao Ridge), intruding an inferred N010°E trending, left lateral strike-slip fault zone. Conversely, the arcuate and concave shape of the Hongchai Canyon appear to follow the crown and the northern boundary of a newly recognized Hongchai submarine landslide situated on the steep western flank of the onshore asymmetric Hengchun Anticline. Our results highlight that both Fangliao and Hengchun Faults are linear, near-vertical left-lateral strike-slip faults. They converge onshore to the Chaochou Fault. This study demonstrates that neotectonics combine with morphostructural analysis of the submarine canyon drainages lead to a better comprehension of the present deformation in the northern part of the Manila accretionary prism.

  3. Influence of Stress History on Elastic and Frictional Properties of Core Material from IODP Expeditions 315 and 316, NanTroSEIZE Transect: Implications for the Nankai Trough Accretionary Prism

    NASA Astrophysics Data System (ADS)

    Knuth, M. W.; Tobin, H. J.; Marone, C.; Saffer, D. M.; Hashimoto, Y.

    2009-12-01

    We present results of ultrasonic P and S-wave velocity measurements on core material recovered during NanTroSEIZE Stage 1 Expeditions 315 and 316 to the Nankai Trough Accretionary Margin, focusing on how different stress paths during subduction and exhumation along regional thrust faults influence the elastic moduli and anisotropy of various components of the accretionary prism. The influence of changes in pore pressure and confining pressure on the elastic properties of prism material has important implications for its mechanical strength, and understanding how elastic properties change along various stress paths will help us use 3D seismic tomography to draw inferences about overpressurization and fluid flow within the accretionary prism. We compare the velocities measured during shipboard physical properties characterization and logging-while-drilling data from Expedition 314 with 3D seismic velocity data and the results of previous shore-based studies to establish in situ conditions for material at various locations within the prism. We test both intact core material and disaggregated gouge and unlithified sediments from the upper prism, subjecting both samples types to a progression of confining pressure, pore pressure, and axial loading conditions representing normal consolidation and overconsolidation stress paths due to compaction and dewatering during burial and subsequent uplift by thrust faulting. While making continuous ultrasonic velocity measurements to determine changes in dynamic and quasistatic elastic moduli during axial and isotropic loading, we also subject granular material to frictional shear in a biaxial double-direct shearing configuration to measure how its frictional properties vary as a function of stress history.

  4. Physical properties of the Nankai inner accretionary prism at Site C0002, IODP Expedition 348

    NASA Astrophysics Data System (ADS)

    Kitamura, Manami; Kitajima, Hiroko; Henry, Pierre; Valdez, Robert; Josh, Matthew

    2014-05-01

    Integrated Ocean Drilling Program (IODP) Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) Expedition 348 focused on deepening the existing riser hole at Site C0002 to ~3000 meters below seafloor (mbsf) to access the deep interior of the Miocene inner accretionary prism. This unique tectonic environment, which has never before been sampled in situ by ocean drilling, was characterized through riser drilling, logging while drilling (LWD), mud gas monitoring and sampling, and cuttings and core analysis. Shipboard physical properties measurements including moisture and density (MAD), electrical conductivity, P-wave, natural gamma ray, and magnetic susceptibility measurements were performed mainly on cuttings samples from 870.5 to 3058.5 mbsf, but also on core samples from 2163 and 2204 mbsf. MAD measurements were conducted on seawater-washed cuttings ("bulk cuttings") in two size fractions of >4 mm and 1-4 mm from 870.5 to 3058.5 mbsf, and hand-picked intact cuttings from the >4 mm size fractions within 1222.5-3058.5 mbsf interval. The bulk cuttings show grain density of 2.68 g/cm3 and 2.72 g/cm3, bulk density of 1.9 g/cm3 to 2.2 g/cm3, and porosity of 50% to 32%. Compared to the values on bulk cuttings, the intact cuttings show almost the same grain density (2.66-2.70 g/cm3), but higher bulk density (2.05-2.41 g/cm3) and lower porosity (37-18%), respectively. The grain density agreement suggests that the measurements on both bulk cuttings and intact cuttings are of good quality, and the differences in porosity and density are real, but the values from the bulk cuttings are affected strongly by artifacts of the drilling process. Thus, the bulk density and porosity data on handpicked cuttings are better representative of formation properties. Combined with the MAD measurements on hand-picked intact cuttings and discrete core samples from previous expeditions, porosity generally decreases from ~60% to ~20% from the seafloor to 3000 mbsf at Site C0002. Electrical

  5. New insights into the active deformation of accretionary prisms: examples from the Western Makran, Iran

    NASA Astrophysics Data System (ADS)

    Penney, Camilla; Copley, Alex; Oveisi, Benham

    2016-04-01

    The Makran subduction zone, along the southern coasts of Iran and Pakistan, hosts one of the largest exposed accretionary wedges in the world. The western Makran has been characterised by a lack of shallow and thrust seismicity in both the instrumental and historical periods. The Mw 6.1 2013 Minab earthquake thus provides a rare opportunity to study the deformation of the accretionary wedge in the transition region between continent-continent collision, in the Zagros, and oceanic subduction, in the Makran. We study the source parameters and slip distribution of this earthquake using seismology, geodesy and field observations. We observe left-lateral strike-slip motion on a fault striking ENE-WSW; approximately perpendicular to the faults of the Minab-Zendan-Palami fault zone, the main structure previously thought to accommodate the right-lateral shear between the Zagros and the Makran. The fault that ruptured in 2013 is one of a series of approximately E-W striking left-lateral faults visible in the geology and geomorphology. These accommodate a velocity field equivalent to right-lateral shear on N-S striking planes by clockwise rotations about vertical axes. The longitudinal range of shear in the western Makran is likely to be controlled by the distance over which the underthrusting Arabian lithosphere deepens in the transition from continent-continent collision to oceanic subduction. The lack of observed megathrust seismicity in the western Makran has led to assertions that the convergence in this region may be aseismic, in contrast to the eastern Makran, which experienced an Mw8.1 earthquake in 1945. The right-lateral Sistan Suture Zone, which runs ~N-S along the Iran-Afghanistan border to the north of the Makran, appears to separate these regimes. However, right-lateral faulting is not observed south of ~27°N, within the wedge. The Minab earthquake and the 2013 Balochistan earthquake show that the Makran accretionary wedge is dominated by strike-slip faulting

  6. Impact of sedimentation on evolution of accretionary wedges: Insights from high-resolution thermomechanical modeling

    NASA Astrophysics Data System (ADS)

    Mannu, Utsav; Ueda, Kosuke; Willett, Sean D.; Gerya, Taras V.; Strasser, Michael

    2016-12-01

    Syntectonic sedimentation history is a potential cause of differentiated accretionary wedge structures along the subduction margin. Recent efforts to model the role of sedimentation on wedge evolution have highlighted the importance of spatiotemporal history of sedimentation on the evolution of the wedge. Moreover, reconstruction of deformation history of the accretionary wedges using reflection seismic and borehole data has further substantiated the impact of sedimentation on wedge evolution. We conduct several numerical experiments using a high-resolution dynamic 2-D thermomechanical plate subduction model to systematically investigate and quantify different effects of sedimentation on accretionary wedge evolution. Models with sedimentation suggest migration of deformation to parts of the wedge lying outside the sedimentation zone leading to emergence/reactivation of out-of-sequence thrusts (OOSTs). Frequency and length of new thrust sheets are correlated with sedimentation in the trench. Models undergo a transition period of 1.5 Myr following the onset of sedimentation, after which they continue to grow under a new steady state. Stabilization of the wedge and increased load on the oceanic plate due to sedimentation create conditions in which smaller wedge-top basins combine to form a large and flat forearc basin. Last but not the least, emergence of OOST in models of accretionary wedges undergoing sedimentation provides important insights in to evolution of potentially tsunamigenic OOSTs like the Megasplay Fault seaward of the Kumano forearc basin.

  7. The effect of fault-bend folding on seismic velocity in the marginal ridge of accretionary prisms

    USGS Publications Warehouse

    Cai, Y.; Wang, Chun-Yong; Hwang, W.-t.; Cochrane, G.R.

    1995-01-01

    Fluid venting in accretionary prisms, which feeds chemosynthetic biological communities, occurs mostly on the marginal thrust ridge. New seismic data for the marginal ridge of the Cascadia prism show significantly lower velocity than that in the adjacent oceanic basin and place important constraints on the interpretations of why fluid venting occurs mostly on the marginal ridge. We employed a finite-element method to analyze a typical fault-bend folding model to explain the phenomenon. The fault in the model is simulated by contact elements. The elements are characterized not only by finite sliding along a slide line, but also by elastoplastic deformation. We present the results of a stress analysis which show that the marginal ridge is under subhorizontal extension and the frontal thrust is under compression. This state of stress favors the growth of tensile cracks in the marginal ridge, facilitates fluid flow and reduces seismic velocities therein; on the other hand, it may close fluid pathways along the frontal thrust and divert fluid flow to the marginal ridge. ?? 1995 Birkha??user Verlag.

  8. 3D Pre-stack depth imaging of the Nankai Trough accretionary prism off Shikoku Island, Japan

    NASA Astrophysics Data System (ADS)

    Costa Pisani, P.; Ike, T.; Moore, G.; Reshef, M.; Bangs, N.; Gulick, S.; Shipley, T.; Kuramoto, S.

    2003-12-01

    During 1999 we acquired an 8x90 km 3D seismic dataset across the toe of the Nankai Through accretionary prism south of Shikoku. Previous processing steps have focused on 3D pre-stack time migration of the entire survey and 2D pre-stack depth migration (PSDM) of two in-lines that cross the Leg 190/196 drill sites. In this study, we conducted 3D PSDM of the seaward half of the data set to improve structural images and to derive the velocity structure of the underthrust sedimentary section in order to better understand its 3D compaction and dewatering history. Velocities derived from pre-stack depth migration are considered to most accurately reflect actual in-situ formation velocities. Our processing procedure started with pre-stack time migration in the cross-line direction to image the data into 2D inlines, allowing us to use 2D migration velocity analysis (MVA) techniques to update the velocity field. 3D imaging of target volumes of data around the leg 190/196 drill holes using several distinctive reflections as depth marker horizons provided constraints for the migration input velocity model. We then 2D MVA on every 5th inline (total of 32 lines), using a top-down, layer stripping technique with Residual Move Out picking to iteratively update the velocity model and flatten the Common Reflection Point (CRP) gathers. We also compared CRP gathers with image gathers in order to detect dipping events and velocity anisotropy. We then used the resulting 3D velocity field as input to a full 3D PSDM of the entire data set. The depth image clarified the accretionary prism's structure, including the numerous thrust faults, the basal décollement, and the underthrusting Shikoku Basin sedimentary unit. The thickness of the underthrust section decreases landward because of compaction. The velocity model shows that the underthrust section's velocity increases about 20% over the first 15 km landward. Along strike variations in velocity are generally less than about 5-10%.

  9. In situ stress magnitudes at the toe of the Nankai Trough Accretionary Prism, offshore Shikoku Island, Japan

    NASA Astrophysics Data System (ADS)

    Huffman, K. A.; Saffer, D. M.

    2016-02-01

    Quantifying the orientation and magnitude of tectonic stresses is essential toward understanding deformation and faulting in subduction zones. However, constraints on in situ horizontal stress magnitudes (Shmin and SHmax) are rare. We estimate Shmin and SHmax at Ocean Drilling Program Site 808 at the toe of the Nankai accretionary prism offshore Japan, using coupled constraints from (1) the width of wellbore breakouts together with estimates of rock strength and a model describing stress redistribution at the borehole wall and (2) limits on regional differential stress defined by failure on preexisting faults. Our analysis extends from 175 to 915 m below seafloor (mbsf) and spans the active frontal thrust. For an upper bound on rock unconfined compressive strength (UCS) and assuming hydrostatic formation pore pressure, Shmin and SHmax (referenced to the seafloor) increase from 6.5 MPa at 175 mbsf to 17.4 MPa at 915 mbsf, with the stress state gradually transitioning from a thrust or strike-slip faulting regime above 800 mbsf to a normal faulting regime below. For cases with higher formation pore pressure, horizontal stresses are slightly lower but follow a similar pattern. We show that estimated Shmin and SHmax are strongly dependent on UCS, breakout width, and friction coefficient, all of which are characterized by uncertainty. Our results suggest that the prism is near thrust failure in the upper ~300 mbsf, but far from failure below. This may be reconciled with active thrusting if thrust faults are locally weaker than the surrounding rock or if SHmax fluctuates during the seismic cycle.

  10. The relationship between mud volcanoes, petroleum migration and accretionary prisms: Lessons from the Caucasus, the Australian margin and Venezuela

    SciTech Connect

    Ware, P.

    1996-08-01

    Mud volcanoes have been widely documented in areas of overpressure where explosive expansion of trapped methane has occurred during argillokinesis. In an area with high sedimentation rate, such as the Gulf of Mexico, there may be no time for fine-grained sediment to de-water before being covered by impermeable material. In an accretionary wedge this process is complicated by overthrusting of off-scraped material which increases the overburden pressure and provides many more avenues for the migration of fluids through the system. In some cases, such as is seen in the Caribbean, the fluids may escape directly to the surface (or seabottom) through high permeability beds. When this happens there may be no diapirism. In other cases, such as in Venezuela, the forearc may be the site of rapid, laterally-derived, sedimentation, and fluids from the overthrusted rocks may be forced to escape through several kilometers of recent deltaic sediments. Since these fluids may include petroleum, this has obvious exploration potential. If there are no suitable reservoir rocks, such as in Timor, there may be no commercial accumulations. However, many giant fields are associated, world-wide, with mud volcanoes, such as those in Azerbaijan.

  11. Fluid pressure, sediment compressibility, and secular and transient strain in subduction prisms: Results from ODP CORK borehole hydrologic observatories

    NASA Astrophysics Data System (ADS)

    Davis, E. E.; Becker, K.

    2005-12-01

    Instruments for long-term hydrogeological monitoring in Ocean Drilling Program boreholes have been installed in five subduction zone settings, including Cascadia, Barbados, Mariana, Costa Rica, and Nankai. Pressure records reveal a wide range of average formation states that are consistent with formation permeability and proximity to sources of formation fluid. For example, near-hydrostatic pressures (excess pore-pressure ratio λ* ~ 0) are observed in the silty parts of the Nankai accretionary prism and in the upper oceanic crust beneath the Costa Rica prism, where well-drained conditions are inferred to be present, and elevated pressures (λ* up to 0.5) have been recorded in finer-grained sedimentary sections near the toe of prisms (e.g., at the level of the decollement in the fine-grained part of the Barbados accretionary prism). In no instances have high pressures (approaching lithostatic, λ* = 1) been observed, although operational difficulties have thus far precluded installations in underthrust sediment sequences where the highest average pressures are expected to be maintained. Records often reveal non-steady behavior, with variations occurring over a broad frequency range. Tidal-frequency variations present in all records are the consequence of oceanographic loading at the seafloor. The amplitude of these signals provide constraints on formation compressibility. Estimated values vary with depth and consolidation state, and range from 5 x 10-9 to 3.5 x 10-10 Pa-1. Once these signals are removed, other transients can be observed, including ones correlated with both seismic and aseismic deformation. Secular strain has been seen in hydrologically isolated parts of the formations at several sites. At the Mariana forearc site, seismic-frequency pressure variations and persistent positive pressure changes were observed at the time of two large (Mb ~ 7.0) deep (~ 70 km) earthquakes located roughly 200 km away; these signals are inferred to reflect local formation

  12. Diversity and biogeochemical structuring of bacterial communities across the Porangahau ridge accretionary prism, New Zealand

    USGS Publications Warehouse

    Hamdan, L.J.; Gillevet, P.M.; Pohlman, J.W.; Sikaroodi, M.; Greinert, J.; Coffin, R.B.

    2011-01-01

    Sediments from the Porangahau ridge, located off the northeastern coast of New Zealand, were studied to describe bacterial community structure in conjunction with differing biogeochemical regimes across the ridge. Low diversity was observed in sediments from an eroded basin seaward of the ridge and the community was dominated by uncultured members of the Burkholderiales. Chloroflexi/GNS and Deltaproteobacteria were abundant in sediments from a methane seep located landward of the ridge. Gas-charged and organic-rich sediments further landward had the highest overall diversity. Surface sediments, with the exception of those from the basin, were dominated by Rhodobacterales sequences associated with organic matter deposition. Taxa related to the Desulfosarcina/Desulfococcus and the JS1 candidates were highly abundant at the sulfate-methane transition zone (SMTZ) at three sites. To determine how community structure was influenced by terrestrial, pelagic and in situ substrates, sequence data were statistically analyzed against geochemical data (e.g. sulfate, chloride, nitrogen, phosphorous, methane, bulk inorganic and organic carbon pools) using the Biota-Environmental matching procedure. Landward of the ridge, sulfate was among the most significant structuring factors. Seaward of the ridge, silica and ammonium were important structuring factors. Regardless of the transect location, methane was the principal structuring factor on SMTZ communities. FEMS Microbiology Ecology ?? 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. No claim to original US government works.

  13. Seismic slip propagation along a fault in the Shimanto accretionary prism detected by vitrinite reflectance studies

    NASA Astrophysics Data System (ADS)

    Kitamura, M.; Mukoyoshi, H.; Hirose, T.

    2011-12-01

    Quantitative assessment of heat generation along faults during fault movement is of primary importance in understanding the dynamics of earthquakes. Last several years localized heat anomaly in a fault zone due to rapid seismic sliding has been detected by various analyses of fault zone materials, such as ferromagnetic resonance signal (Fukuchi et al., 2005), trace elements and isotopes (e.g., Ishikawa et al., 2008) and mineralogical change of clay (e.g., Hirono et al., 2008) and vitrinite reflectance (O'Hara, 2004). Here we report a heat anomaly found in a fault zone in the Shimanto accretionary complex by vitrinite reflectance measurements. Mature faults in nature mostly experience multiple seismic events, resulting in integrated heat anomaly. Thus, in addition to vitrinite reflectance measurements across natural faults, we performed high-velocity friction experiments on a mixture of quartz and vitrinite grains to evaluate how multiple rapid-slip events affect vitrinite reflectance in a fault zone. A localized heat anomaly is found in one of fault zones which are developed within a mélange unit in the Cretaceous Shimanto belt, SW Japan. A principle slip zone with thickness of ~5 mm forms within cataclastic damage zone with thickness of ~3 m. The slip zone is mainly composed of well-foliated clay minerals. Host rocks are characterized by a block-in-matrix texture: aligned sandstone and chert blocks embedded in mudstone matrix. We measured vitrinite reflectance across the fault zone by the same method as reported in Sakaguchi et al., (2011). The measurement reveals that the principle slip zone underwent localized temperature of more than 220°C, while background temperature of both damage zone and host rocks is ~170°C. Since fault motion along most active faults occurs seismological, that inevitably generates frictional heat, the localized heat anomaly is possibly caused by the rapid seismic slip. In order to evaluate the change in vitrinite reflectance by

  14. The Variscan accretionary prism in the Kaczawa Mountains (W Sudetes, SW Poland): lithostratigraphic, sedimentological, volcanic, metamorphic and structural evidence

    NASA Astrophysics Data System (ADS)

    Kryza, Ryszard; Kostylew, Joanna; Zalasiewicz, Jan

    2013-04-01

    The Sudetes (SW Poland) at the NE edge of the Bohemian Massif (Central-European Variscides) are a structural mosaic comprising various basement units, some interpreted as fragments of a Variscan accretionary prism (Baranowski et al., 1990; Collins et al., 2000; Kryza & Zalasiewicz, 2008). The best example is the Kaczawa structural unit in the West Sudetes. Its accretionary nature is evident from: Lithostratigraphy, sedimentology and volcanism. Neighbouring tectonic units of the Kaczawa Mountains contain different fragments of Palaeozoic successions: (a) a Cambrian (and Neoproterozoic?) - Ordovician volcano-sedimentary sequence (with WP type bimodal volcanic and shallow-water sedimentary rocks), (b) Silurian - Devonian MORB-type metabasalts, shales and cherts (with graptolites and conodonts), and (c) Late Devonian - Early Carboniferous polygenetic mélange bodies that record overlapping dynamic sedimentary and tectonic processes. This suggests evolving palaeotectonic environments, from initial rift within continental crust, through mature basin likely underlined by oceanic-type lithosphere, to a subduction setting (mélanges; Baranowski et al., 1990; Collins et al., 2000; Kryza & Zalasiewicz, 2008, and refs. therein). Metamorphism. Diverse PT metamorphic paths detected in various tectonic units of the Kaczawa Mountains are strong evidence for the subduction/accretionary affinity. Relatively higher-grade metamorphic units bear evidence of blueschist-facies metamorphism, overprinted by a low-T greenschist facies event (pseudosection modelling yielded: ~270oC and 8.5 kb for the peak-P, and ~310oC and 6 kb for the peak-T stages). The estimated P/T gradient of ~10 oC/km is typical of a subduction setting (Kryza et al., 2011). Other tectonic units, including the mélange bodies, experienced lower-grade metamorphic parageneses (e.g. widespread pumpellyite) and white-mica structural data (Kostylew et al., 2013; and refs. therein). The diverse metamorphic PT paths indicate

  15. Interrelationship of fluid venting and structural evolution: Alvin observations from the frontal accretionary prism, Oregon

    SciTech Connect

    Moore, J.C.; Orange, D. ); Kulm, L.D. )

    1990-06-10

    Seismic reflection and Sea Beam bathymetric data plus submarine geological measurements define a ramp anticline at the deformatoin front of the central Oregon subduction zone. At its northern termination the ramp anticline is deeply incised by a large 500-m-deep submarine canyon and cut by a probable backthrust. To the south along the strike of the fold, a smaller submarine canyon shallowly erodes the anticline, and backthrusting is not apparent in the submersible observations. Two Alvin dives along a transect through the southern canyon show active fluid vents demarked by biological communities at the frontal thrust and at the breached crest of the anticline. Along a northern transect, encompassing the large submarine canyon, 10 Alvin dives indicated no venting on the formal thrust, limited venting in the canyon, but numerous biological communities along a scarp interpreted as the surface trace of the backthrust. These observations suggest a scenario of vent and structural-geomorphic development consisting of (1) frontal thrust faulting and associated venting, facilitated by high fluid pressure; (2) erosion of the oversteepened seaward flank of the ramp anticline assisted by seepage forces and leading to fluid flow out of stratigraphically controlled conduits in the limbs of the overthrust deposits; (3) locking of the frontal thrust due to dewatering or a local decrease in wedge taper associated with development of the large canyon, leading to failure along the backthrust; and (4) redirection of fluid flow by the backthrust. Thus, within {le}0.3 m.y., deformation of the relatively permeable sediments of the Oregon margin results in stratigraphically controlled flow being partially captured by faults.

  16. Preliminary results of three-dimensional stress orientation in the accretionary prism in Nankai Subduction Zone, Japan by anelastic strain recovery measurements of core samples retrieved from IODP NanTroSEIZE Site C0009

    NASA Astrophysics Data System (ADS)

    Lin, W.; Byrne, T. B.; Yamamoto, Y.

    2010-12-01

    During IODP Expedition 319, the first riser-drilling borehole in ocean was penetrated by D/V CHIKYU at Site C0009 in the Nankai convergent margin, Japan. From 0 mbsf (meters below seafloor) to 1285 mbsf, the borehole crossed the Kumano forearc basin and from 1285 mbsf to the bottom depth of 1604 mbsf, the Nankai accretionary prism. In a short depth range of 84.20 m from 1509.7 to 1593.9 mbsf, core samples were retrieved by rotary core barrel drilling. We collected 3 whole-round core samples for measurements of anelastic strain recovery (ASR) by the same methods of sample preparation and anelastic strain data acquisition conducted in the previous Stage-1 expeditions of the same NanTroSEIZE drilling program (Byrne et al., 2009; GRL, Vol.36, L23310). Anelastic normal strains, measured every ten minutes in nine directions, including six independent directions, were used to calculate the anelastic strain tensors. All three samples showed coherent strain recovery over a long period more than 1 month. The three samples were from C0009A (3R,1531 mbsf; 4R, 1540 mbsf and 8R, 1577 mbsf, respectively) in lithologic Unit IV interpreted as accretionary prism or deformed slope sediments. All samples are composed of silty clays or hemipelagic muds with relatively high porosities (30%~). The ASR measurement results in Kumano Forearc Basin obtained from C0002 (Byrne et al., 2009) showed the maximum stress orientation is nearly vertical and a normal stress regime. However, the ASR results in the accretionary prism from C0009 show that the maximum principal stress axes plunge gently or are nearly horizontal and the stress regimes appear to be strike-slip or thrust (reverse fault) types. The maximum horizontal principal stress orientaions obtained from the ASR tests also show very good consistency with the stress orientaions determined from borehole breakouts in the same borehole and the same depth range (Lin et al., 2010; GRL, Vol.37, L13303). These results suggest that three

  17. The Late Cambrian Takaka Terrane, NW Nelson, New Zealand: Accretionary-prism development and arc collision followed by extension and fan-delta deposition at the SE margin of Gondwana

    NASA Astrophysics Data System (ADS)

    Pound, K. S.

    2013-12-01

    Re-evaluation of field and lab data indicates that the Cambrian portion of the Takaka Terrane in the Cobb Valley area of NW Nelson, New Zealand preserves the remnants of an accretionary prism complex, across which the Lockett Conglomerate fan-delta was deposited as a consequence of extension. Previous work has recognized that the structurally disrupted lower Takaka Terrane rocks present an amalgam of sedimentary and igneous rocks generated prior to convergence (Junction Formation) or during convergence (Devil River Volcanics Group, Haupiri Group), including arc-related and MORB components. Portions of the sequence have in the past been loosely described as an accretionary prism. Reevaluation of the detailed mapping, sedimentological and provenance studies shows that remnants of a stratigraphic sequence (Junction Formation, Devil River Volcanics Group, Haupiri Group) can be traced through 10 fault-bounded slices, which include a mélange-dominated slice (Balloon Mélange). These slices are the remnants of the accretionary prism; the stratigraphy within each slice generally youngs to the east, and the overall pattern of aging (based on relative age from provenance studies, sparse fossils, stratigraphic relations, and limited isotopic data) indicates that the older rocks generally dominate fault slices to the east, and younger rocks dominate fault slices to the west, delineating imbricate slices within an eastward-dipping subduction zone, in which the faults record a complex history of multi-phase reactivation. The Lockett Conglomerate is a ~500-m thick fan-delta conglomerate that is the preserved within one of the fault slices, where it is stratigraphically and structurally highest unit in the lower Takaka Terrane; it is also present as blocks within the Balloon Melange. The Lockett Conglomerate is marine at its base and transitions upwards to fluvial facies. The Lockett Conglomerate has previously been interpreted to result from erosion consequent on continued

  18. Tectonic implications for the occurrence of ocean floor, hotspot, and island arc materials within accretionary prisms: Examples from the Mesozoic-Cenozoic NW Pacific Rim

    NASA Astrophysics Data System (ADS)

    Ogawa, Y.; Hirano, N.; Hirano, N.; Taniguchi, H.; Taniguchi, H.; Taniguchi, H.

    2001-12-01

    On-land Mesozoic-Cenozoic accretionary prisms exposed in Japan commonly have basaltic rocks incorporated as blocks into melanges or fault zones during a prolonged history of subduction and/or obduction. Chemical signatures of these basaltic rocks and their mode of occurrence with sedimentary covers and/or associated sedimentary rocks indicate that most of these isolated small basaltic blocks consistently display a WPB chemistry, whereas large slabs of basaltic rocks around the Izu Arc collision zone show MORB chemistry with rare examples of IAT, BABB, and/or WPB affinities. Comparing with the present uniformitarian examples of convergent plate boundaries in the western Pacific that we know through the DSDP and ODP projects and submersible and seismic surveys, we can interpret some of the basaltic material with WPB affinity in the Japanese accretionary prisms as relict edifices of seamounts with hotspot origin. These hotspot-related basaltic rocks are commonly associated with reefal limestones and were incorporated into continental margin melanges either by submarine sliding from the downgoing oceanic plate or by shallow-level offscraping along decollement surfaces during the subduction of oceanic plates. Older, uplifted parts of the fossil accretionary prisms on the continent side further inward from the trench where the deeper levels of accreted material are exposed include larger amounts of basaltic blocks. This observation suggests that significant amount of underplating might have occurred in the deeper levels of oceanic crust along decollement zones at structurally lower depths. The metamorphic belts (e.g.Sambagawa, Chichibu, Shimanto etc.) have commonly alkaline rocks or plateau-type E-MORB basalts without any trace of N-MORB rocks with rare special exceptions. Besides these ordinary accretionary prism examples formed by a simple plate subduction system, another type of accretion resulting from island arc or ridge collision is observed to have occurred in

  19. Prism

    NASA Astrophysics Data System (ADS)

    Kuno, Yoshitaka

    2000-11-01

    The PRISM project in Japan to consider a high-intensity low-energy muon source is discussed. PRISM would include solenoid pion capture and phase rotation to create a muon beam of 1012μ±/sec with high purity and small energy spread, if it is combined with the planned 50-GeV proton synchrotron in the KEK/JAERI Joint Project. The PRISM could be extended to a front end of a neutrino factory in the future.

  20. Detection of Seismic Anisotropy Using Ocean Bottom Seismometers: A Case Study from the Accretionary Prism Off Southwest Taiwan

    NASA Astrophysics Data System (ADS)

    Cheng, W. B.; Lin, J. Y.; Hsu, S. K.; Dong, J. J.

    2014-12-01

    A multicomponent ocean-bottom seismometer data set was collected by National Central University, Taiwan in the accreationary prism off southwestern Taiwan in 2013 and 2014, respectively. The OBS contains four component receivers, including a three component 4.5 Hz geophone unit containing three orthogonal components and a hydrophone. GI-gun shots located at 1 mile and 1.5 miles radius from the OBS, with spacing approximately 40 m along the sail line. The OBS recorded data at a sampling rate of 250 Hz and from a shot pattern that gave good azimuthal coverage around the OBS. Based on P and P-S converted waves recorded between the direct and multiple arrivals, this experiment targeted the top few hundred meters of sediment in the study area. Synthetic seismograms were calculated from a model representative of the sediment sequence at this site indicating that converted amplitudes are dominated by P to S mode-converted waves generated on reflection. After preliminary processing, including a static correction, the data were optimally rotated to radial (R) and transverse (T) components. The principal technique used to detect the anisotropy was azimuthal stacking of the radial and transverse horizontal geophone components. The R component shows azimuthal variation of traveltime indicating variation of velocity with azimuth; the corresponding T component shows azimuthal variation of amplitude and phase. From the radial component azimuthal gather and mode-converted wave amplitude variation for the first few layers and determined corresponding anisotropy parameter and VP/VS values. We attribute the observed azimuthal anisotropy to the presence of microcracks and grain boundary orientation due to stress since fracture at this depth is not likely to occur.

  1. Evaluation of Coseismic Fluid-Rock Interaction in Fault Zones on the Basis of Geochemistry of Fault Rocks in Accretionary Prisms

    NASA Astrophysics Data System (ADS)

    Ishikawa, T.; Hirono, T.; Honda, G.

    2011-12-01

    Recent studies revealed that concentration and isotopic composition of fluid-mobile trace elements such as Li, Rb, Cs and Sr in slip-zone rocks can change significantly during coseismic fluid-rock interaction at high temperatures (e.g., Ishikawa et al., 2008). In this study, we summarize the results obtained for fault-zone rocks recovered from various depths of the subduction zones. Analysis of a slip-zone sample recovered from shallow portion (0.27 km bsf) of the magasplay fault at Site C0004, IODP Exp. 316, Nankai Trough showed no clear fluid-induced geochemical signals, although a peak temperature over 300 deg. C is estimated on the basis of vitrinite reflectance data (Sakaguchi et al., 2011). In contrast, a major reverse fault in a fossil accretionary prism, the Emi Group (burial depth, 1-2 km) exhibited marked decreases of Li, Rb and Cs relative to adjacent host rocks, suggesting coseismic fluid-rock interactions at >350 deg. C. Geochemical signals observed in the Emi slip zone have a strong resemblance to those observed in the Taiwan chelungpu fault at comparable depths (1.1-1.2 km). Slip-zone samples collected from a fossil out-of-sequence thrust at greater depth (2.5-5.5 km) adjacent to the Kure Melange in the Shimanto accretionary prism showed unique geochemical characteristics, in which effects from disequilibrium flash melting to generate pseudotachylyte coexist with those from fluid-rock interactions at >350 deg. C. In the cases of Emi and Chelungpu, it is possible that the fluid-induced geochemical signatures, together with fluidization structures observed in these samples, resulted from thermal pressurization. On the other hand, the Kure data suggest a slip process in which high-temperature pore fluids were generated by frictional slip, but the thermally-enhanced pressure might not have reached a sufficient level to cause thermal pressurization, and the temperature continued to increase to attain melting. Kinetic estimation suggests that fluid

  2. Precambrian crustal contribution to the Variscan accretionary prism of the Kaczawa Mountains (Sudetes, SW Poland): evidence from SHRIMP dating of detrital zircons

    NASA Astrophysics Data System (ADS)

    Kryza, Ryszard; Zalasiewicz, Jan; Mazur, Stanisław; Aleksandrowski, Paweł; Sergeev, Sergey; Larionov, Alexander

    2007-11-01

    SHRIMP dating of detrital zircons from sandstones of the Gackowa Formation (Kaczawa Complex, Sudetes, SW Poland) indicates input from late (550-750 Ma) and early Proterozoic to Archaean sources (˜2.0-3.4 Ga, the latter being the oldest recorded age from the Sudetic region). These dates preclude within-terrane derivation from seemingly correlatory acid volcanic rocks of early Palaeozoic age. Rather, they indicate provenance from Cadomian and older rocks that currently form part of other, geographically distant terranes; the most likely source identified to date is the Lusatian Block in the Saxothuringian Zone. Hence, the Gackowa Formation may be late Proterozoic rather than early Palaeozoic in depositional age, possibly coeval with the late Proterozoic (pre-Cadomian) greywackes of Lusatia, being subsequently tectonically interleaved with early Palaeozoic volcanic rocks into the Kaczawa accretionary prism during the Variscan orogeny. However, correlation with the lithologically similar early Ordovician Dubrau Quartzite of Saxothuringia, and so assignation to the early Paleozoic (post-Cadomian) rift succession deposited at the northern margin of Gondwana, cannot yet be precluded.

  3. Lithologic Controls on Structure Highlight the Role of Fluids in Failure of a Franciscan Complex Accretionary Prism Thrust Fault

    NASA Astrophysics Data System (ADS)

    Bartram, H.; Tobin, H. J.; Goodwin, L. B.

    2015-12-01

    Plate-bounding subduction zone thrust systems are the source of major earthquakes and tsunamis, but their mechanics and internal structure remain poorly understood and relatively little-studied compared to faults in continental crust. Exposures in exhumed accretionary wedges present an opportunity to study seismogenic subduction thrusts in detail. In the Marin Headlands, a series of thrusts imbricates mechanically distinct lithologic units of the Mesozoic Franciscan Complex including pillow basalt, radiolarian chert, black mudstone, and turbidites. We examine variations in distribution and character of structure and vein occurrence in two exposures of the Rodeo Cove thrust, a fossil plate boundary exposed in the Marin Headlands. We observe a lithologic control on the degree and nature of fault localization. At Black Sand Beach, deformation is localized in broad fault cores of sheared black mudstone. Altered basalts, thrust over greywacke, mudstone, and chert, retain their coherence and pillow structures. Veins are only locally present. In contrast, mudstone is virtually absent from the exposure 2 km away at Rodeo Beach. At this location, deformation is concentrated in the altered basalts, which display evidence of extensive vein-rock interaction. Altered basalts exhibit a pervasive foliation, which is locally disrupted by both foliation-parallel and cross-cutting carbonate-filled veins and carbonate cemented breccia. Veins are voluminous (~50%) at this location. All the structures are cut by anastomosing brittle shear zones of foliated cataclasite or gouge. Analyses of vein chemistry will allow us to compare the sources of fluids that precipitated the common vein sets at Rodeo Beach to the locally developed veins at Black Sand Beach. These observations lead us to hypothesize that in the absence of a mechanically weak lithology, elevated pore fluid pressure is required for shear failure. If so, the vein-rich altered basalt at Rodeo Beach may record failure of an

  4. Accretionary processes along the Middle America Trench off Costa Rica

    SciTech Connect

    Shipley, T.H.; Stoffa, P.L. ); McIntosh, K.; Silver, E.A. )

    1990-06-01

    The geometry of large-scale structures within modern accretionary prisms is known entirely from seismic reflection studies using single or grids of two-dimensional profiles. Off Costa Rica the authors collected a three-dimensional reflection data set covering a 9 km wide {times} 22 km long {times} 6 km thick volume of the accretionary prism just arcward of the Middle America Trench. The three-dimensional processing and ability to examine the prism as a volume has provided the means to map structures from a few hundred meters to kilometers in size with confidence. Reflections from within the prism define the gross structural features and tectonic processes active along this particular portion of the Middle America Trench. So far in the analysis, these data illustrate the relationships between the basement, the prism shape, and overlying slope sedimentary deposits. For instance, the subducted basement relief (of several hundred meters amplitude) does seem to affect the larger scale through-going faults within the prism. Offscraping of the uppermost 45 m of sediments occurs within 4 km of the trench creating a small pile of sediments at the base of the trench. How this offscraped sediment is incorporated into the prism is still being investigated. Underplating of parts of the 400 m thick subducted section begin: at a very shallow structural level, 4 to 10 km arcward of the trench. Amplitude anomalies associated with some of the larger arcward dipping structures in the prism and surface mud volcanoes suggest that efficient fluid migration paths may extend from the top of the downgoing slab at the shelf edge out into the lower and middle slope region, a distance of 50 to 100 km.

  5. Metatranscriptomic analysis of diminutive Thiomargarita-like bacteria ("Candidatus Thiopilula" spp.) from abyssal cold seeps of the Barbados Accretionary Prism.

    PubMed

    Jones, Daniel S; Flood, Beverly E; Bailey, Jake V

    2015-05-01

    Large sulfur-oxidizing bacteria in the family Beggiatoaceae are important players in the global sulfur cycle. This group contains members of the well-known genera Beggiatoa, Thioploca, and Thiomargarita but also recently identified and relatively unknown candidate taxa, including "Candidatus Thiopilula" spp. and "Ca. Thiophysa" spp. We discovered a population of "Ca. Thiopilula" spp. colonizing cold seeps near Barbados at a ∼4.7-km water depth. The Barbados population consists of spherical cells that are morphologically similar to Thiomargarita spp., with elemental sulfur inclusions and a central vacuole, but have much smaller cell diameters (5 to 40 μm). Metatranscriptomic analysis revealed that when exposed to anoxic sulfidic conditions, Barbados "Ca. Thiopilula" organisms expressed genes for the oxidation of elemental sulfur and the reduction of nitrogenous compounds, consistent with their vacuolated morphology and intracellular sulfur storage capability. Metatranscriptomic analysis further revealed that anaerobic methane-oxidizing and sulfate-reducing organisms were active in the sediment, which likely provided reduced sulfur substrates for "Ca. Thiopilula" and other sulfur-oxidizing microorganisms in the community. The novel observations of "Ca. Thiopilula" and associated organisms reported here expand our knowledge of the globally distributed and ecologically successful Beggiatoaceae group and thus offer insight into the composition and ecology of deep cold seep microbial communities.

  6. Thermochronology of the Torlesse accretionary complex, Wellington region, New Zealand

    NASA Astrophysics Data System (ADS)

    Kamp, Peter J. J.

    2000-08-01

    The Torlesse Complex comprises several Mesozoic accretionary prism complexes together forming continental basement over large parts of New Zealand. This study focuses on the thermal history of relatively low grade graywacke rocks exposed in a transect in southern North Island that crosses the structural grain of the Torlesse Complex, including its older and younger parts. Zircon fission track (FT) ages for the Late Triassic Rakaia Terrane, which is the most inboard of the accretionary complexes, are partially annealed, some possibly reset, and may indicate early Cretaceous (134±10 Ma) cooling from maximum temperatures (Tmax), probably related to imbrication of younger complexes of the Pahau Terrane. Numerical modeling of the zircon FT ages and published 40ArA/39Ar muscovite and biotite ages for the Rakaia Terrane suggest Tmax values of 265-310°C and exhumation from depths of 10-12 km. The rocks underlying the Aorangi Range and involving the youngest accretionary complex have experienced much lower Tmax values of ≤210° and ≥110°C, bracketed by reset apatite FT ages and detrital zircon FT ages. The occurrence of a circa 100 Ma component of zircon FT ages in both the weakly and highly indurated rocks beneath the Aorangi Range, as well as in remnants of an overlying Albian accretionary slope basin (Whatarangi Formation), imply multistorey accretion and incorporation of sediment into the youngest prism. This circa 100 Ma zircon FT age component also places a maximum age on the termination of Mesozoic subduction beneath the New Zealand region. The occurrence of reset apatite FT ages across the whole of the Wellington transect indicates that at least 4 km of exhumation occurred during the late Miocene.

  7. Interaction between hydrocarbon seepage, chemosynthetic communities and bottom water redox at cold seeps of the Makran accretionary prism: insights from habitat-specific pore water sampling and modeling

    NASA Astrophysics Data System (ADS)

    Fischer, D.; Sahling, H.; Nöthen, K.; Bohrmann, G.; Zabel, M.; Kasten, S.

    2011-09-01

    The interaction between fluid seepage, bottom water redox, and chemosynthetic communities was studied at cold seeps across one of the world's largest oxygen minimum zones (OMZ) located at the Makran convergent continental margin. Push cores were obtained from seeps within and at the lower boundary of the core-OMZ with a remotely operated vehicle. Extracted pore water was analyzed for sulfide and sulfate contents. Depending on oxygen availability, seeps were either colonized by microbial mats or by mats and macrofauna. The latter, including ampharetid polychaetes and vesicomyid clams, occurred in distinct benthic habitats which were arranged in a concentric fashion around gas orifices. At most sites colonized by microbial mats, hydrogen sulfide was exported into the bottom water. Where macrofauna was widely abundant, hydrogen sulfide was consumed within the sediment. Numerical modeling of pore water profiles was performed in order to assess rates of fluid advection and bioirrigation. While the magnitude of upward fluid flow decreased from 11 cm yr-1 to <1 cm yr-1 and the sulfate/methane transition zone (SMTZ) deepened with increasing distance from the central gas orifice, the fluxes of sulfate into the SMTZ did not significantly differ (6.6-9.3 mol m-2 yr-1). Depth-integrated rates of bioirrigation increased from 162 cm yr-1 in central habitats characterized by microbial mats and sparse macrofauna to 348 cm yr-1 in habitats of large and small vesicomyid clams. These results reveal that chemosynthetic macrofauna inhabiting the outer seep habitats at the lower boundary of the OMZ efficiently bioirrigate and thus transport sulfate into the upper 10 to 15 cm of the sediment. In this way bioirrigation compensates for the lower upward flux of methane in outer habitats and stimulates rates of anaerobic oxidation of methane (AOM) with sulfate high enough to provide sulfide for chemosynthesis. Through bioirrigation macrofauna engineer their geochemical environment and fuel

  8. Triassic deformation of Permian Early Triassic arc-related sediments in the Beishan (NW China): Last pulse of the accretionary orogenesis in the southernmost Altaids

    NASA Astrophysics Data System (ADS)

    Tian, Zhonghua; Xiao, Wenjiao; Sun, Jimin; Windley, Brian F.; Glen, Richard; Han, Chunming; Zhang, Zhiyong; Zhang, Ji'en; Wan, Bo; Ao, Songjian; Song, Dongfang

    2015-11-01

    The Beishan orogenic collage (BOC) in the southernmost Altaids provides evidence of the final stage of evolution of the Paleo-Asian Ocean. However, the closure time of the Paleo-Asian Ocean in the BOC is controversial. From field mapping, and structural analysis of mesoscale, superposed folds in Early Triassic sediments in the Hongyanjing Basin in the central BOC, we define at least two phases of deformation, which we can bracket in age as end-Permian to Early-Late Triassic. The sandstones in the basin are poorly sorted with angular clasts, which indicates immaturity characteristic of proximal and rapid deposition. Geochemical data indicate that the Hongyanjing Basin probably developed in an arc-related setting near an active continental margin or mature island arc. Combined with published regional geological data, we interpret the Hongyanjing Basin as a Permian-Early Triassic inter-arc basin between the Carboniferous Mazongshan arc to the north and the Ordovician to Permian Huaniushan-Dundunshan arc to the south. In addition, the age distribution of our sediments shows that the active continental margin or continental arc on which the Hongyanjing arc-related basin sat was somehow independently distributed in the Paleo-Asian Ocean without any major contribution of provenance from the Tarim Craton and Dunhuang Block to the south and Southern Mongolia accretionary system to the north. Deformation of the superposed folds began in the end-Permian, continued in the Early Triassic, and ended before the middle Late Triassic (219 Ma). Therefore the accretionary orogenesis in the Beishan part of the southernmost Altaids was still ongoing in the early to middle Triassic, and it finished in the Late Triassic, which might have been the last pulse of the accretionary orogenesis in the southernmost Altaids. We correlate this terminal event with tectonic developments in the Kunlun and Qinling orogens in the Tethyan domain.

  9. Metatranscriptomic Analysis of Diminutive Thiomargarita-Like Bacteria (“Candidatus Thiopilula” spp.) from Abyssal Cold Seeps of the Barbados Accretionary Prism

    PubMed Central

    Flood, Beverly E.

    2015-01-01

    Large sulfur-oxidizing bacteria in the family Beggiatoaceae are important players in the global sulfur cycle. This group contains members of the well-known genera Beggiatoa, Thioploca, and Thiomargarita but also recently identified and relatively unknown candidate taxa, including “Candidatus Thiopilula” spp. and “Ca. Thiophysa” spp. We discovered a population of “Ca. Thiopilula” spp. colonizing cold seeps near Barbados at a ∼4.7-km water depth. The Barbados population consists of spherical cells that are morphologically similar to Thiomargarita spp., with elemental sulfur inclusions and a central vacuole, but have much smaller cell diameters (5 to 40 μm). Metatranscriptomic analysis revealed that when exposed to anoxic sulfidic conditions, Barbados “Ca. Thiopilula” organisms expressed genes for the oxidation of elemental sulfur and the reduction of nitrogenous compounds, consistent with their vacuolated morphology and intracellular sulfur storage capability. Metatranscriptomic analysis further revealed that anaerobic methane-oxidizing and sulfate-reducing organisms were active in the sediment, which likely provided reduced sulfur substrates for “Ca. Thiopilula” and other sulfur-oxidizing microorganisms in the community. The novel observations of “Ca. Thiopilula” and associated organisms reported here expand our knowledge of the globally distributed and ecologically successful Beggiatoaceae group and thus offer insight into the composition and ecology of deep cold seep microbial communities. PMID:25724961

  10. A stochastic prediction of in situ stress magnitudes from the distributions of rock strength and breakout width at IODP Hole C0002A in Nankai accretionary prism, SW Japan

    NASA Astrophysics Data System (ADS)

    Song, Insun; Chang, Chandong; Lee, Hikweon

    2015-04-01

    . The results from this new approach of stress estimation are comparable with previous other results (e.g., Chang et al., 2010, G3; Lee et al., 2013, MPG). This stochastic model is prominent because it gives not only both values of SHmax and Shmin simultaneously but also information about statistical reliability of the determined values quantified by sensitivity and uncertainty. Our result shows that the two stress magnitudes in Nankai accretionary prism are not completely independent in terms of sensitivity, suggesting that other independent measure of one of the two stresses might be definitely useful (e.g., from leak-off test).

  11. Three-Dimensional Modeling of Fluid and Heat Transport in an Accretionary Complex

    NASA Astrophysics Data System (ADS)

    Paula, C. A.; Ge, S.; Screaton, E. J.

    2001-12-01

    As sediments are scraped off of the subducting oceanic crust and accreted to the overriding plate, the rapid loading causes pore pressures in the underthrust sediments to increase. The change in pore pressure drives fluid flow and heat transport within the accretionary complex. Fluid is channeled along higher permeability faults and fractures and expelled at the seafloor. In this investigation, we examined the effects of sediment loading on fluid flow and thermal transport in the decollement at the Barbados Ridge subduction zone. Both the width and thickness of the Barbados Ridge accretionary complex increase from north to south. The presence of mud diapers south of the Tiburon Rise and an observed southward decrease in heat flow measurements indicate that the increased thickness of the southern Barbados accretionary prism affects the transport of chemicals and heat by fluids. The three-dimensional geometry and physical properties of the accretionary complex were utilized to construct a three-dimensional fluid flow/heat transport model. We calculated the pore pressure change due to a period of sediment loading and added this to steady-state pressure conditions to generate initial conditions for transient simulations. We then examined the diffusion of pore pressure and possible perturbation of the thermal regime over time due to loading of the underthrust sediments. The model results show that the sediment-loading event was sufficient to create small temperature fluctuations in the decollement zone. The magnitude of temperature fluctuation in the decollement was greatest at the deformation front but did not vary significantly from north to south of the Tiburon Rise.

  12. Speculations on the petroleum geology of the accretionary body: an example from the central Aleutians

    USGS Publications Warehouse

    McCarthy, J.; Stevenson, A.J.; Scholl, D. W.; Vallier, T.L.

    1984-01-01

    In the 300 km wide Adak-Amlia sector of the central Aleutian Trench ??? 36 000 km3 of offscraped trench fill makes up the wedge-shaped mass of the Aleutian accretionary body. Within this wedge, seismic reflection profiles reveal an abundance of potential hydrocarbon-trapping structures. These structures include antiforms, thrust and normal faults, and stratigraphic pinchouts. Maximum closure on these features is 2 km. In addition, the silt and possibly sand size sediment within the offscraped turbidite deposits, and the porous diatomaceous pelagic deposits interbedded with and at the base of the wedge, may define suitable reservoirs for the entrapment of hydrocarbons. Potential seals for these reservoirs include diagenetically-altered and -produced siliceous and carbonate sediment. The organic carbon input into the central Aleutian Trench, based on carbon analyses of DSDP Legs 18 and 19 core samples, suggests that the average organic carbon content within the accretionary body is approximately 0.3-0.6%. Heat flow across the Aleutian Terrace indicates that at present the oil generation window lies at a depth of 3-6.5 km. At depths of 8 km (which corresponds to the maximum depth the offscraped sediment has been seismically resolved beneath the lower trench slope), the probable high (170-180??C) temperatures prohibit all but gas generation. The dewatering of trench sediment and subducted oceanic crust should produce an abundance of fluids circulating within the accretionary body. These fluids and gases can conduct hydrocarbons to any of the abundant trapping geometries or be lost from the system through sea floor seepage. In the Aleutian accretionary body all the conditions necessary for the formation of oil and gas deposits exist. The size and ultimate preservation of these deposits, however, are dependent on the deformational history of the prism both during accretion and after the accretion process has been superceded by subsequent tectonic regimes. ?? 1984.

  13. Accretionary orogens: definition, character, significance

    NASA Astrophysics Data System (ADS)

    Cawood, P. A.; Kroener, A.; Windley, B. F.

    2003-04-01

    Classic models of orogens involve a Wilson cycle of ocean opening and closing with orogenesis related to continent-continent collision. Such models fail to explain the geological history of a significant number of orogenic belts throughout the world in which deformation, metamorphism and crustal growth took place in an environment of on-going plate convergence. These belts are termed accretionary orogens but have also been refereed to as non-collisional orogens, Pacific-type orogens, Turkic-type and exterior orogens. Accretionary orogens evolve in generally curvilinear belts comprising dominantly mafic to silicic igneous rocks and their sedimentary products and accumulated largely in marine settings. They are variably deformed and metamorphosed by tectono-thermal events aligned parallel to, and punctuating, facies trends. Accretionary orogens form at sites of subduction of oceanic lithosphere and consist of magmatic arcs systems along with material accreted from the downgoing plate and eroded from the upper plate. Deformational features include structures formed in extension and compressive environments during steady-state convergence (arc/backarc vs. accretionary prism) that are overprinted by short regional compressive orogenic events. Orogenesis takes place through coupling across the plate boundary with strain concentrated in zones of mechanical and thermal weakening such as the magmatic arc and back arc region. Potential driving mechanisms for coupling include accretion of buoyant lithosphere (terrane accretion), flat slab subduction, and rapid absolute upper plate motion over-riding the downgoing plate. The Circum-Pacific region provides outstanding examples of accretionary orogens. The Pacific formed during breakup of Rodinia in the Neoproterozoic and has never subsequently closed, resulting in a series of overall ocean-ward younging orogenic systems that have always faced an open ocean, yet have been the sites of repeated tectono-thermal events and

  14. Sediment flux and accretion history on the Cascadia and Sumatra margins

    NASA Astrophysics Data System (ADS)

    McNeill, L. C.; Geersen, J.; Springett, J.; Trehu, A. M.; Wilson, D. J.

    2013-12-01

    The growth of accretionary prisms and continental margins, and the properties of the prism interior and plate boundary are a function of input sediment through time and the history of accretion, erosion, and sediment subduction on the margin. Input sediment volumes are affected by changing sediment sources and pathways, climate, oceanic basement topography, and erosion and reworking of material from the forearc itself. Seismic reflection data have been compiled on the Cascadia margin, imaging the oceanic plate structure and stratigraphy, and forearc structure to analyse these processes at several locations along the margin, providing more detail than earlier compilations of sediment flux. These seismic data are integrated with ocean drilling data on the oceanic plate to establish the history of deposition on the oceanic plate and in the trench. Sediment flux into the subduction zone since the late Miocene can then be estimated and compared with the volume of the currently active prism. Several specific factors are considered, including: décollement position; compaction; reaccretion of sediment eroded from the prism into the trench; prism age; reduction in sediment flux prior to Pleistocene glaciation on the margin; mixing of older prism mélange with the modern prism on the Washington margin; potential changes in convergence rate and direction with time; margin-parallel motion of forearc material. In some cases, these parameters or their temporal change generate significant uncertainty. Initial results suggest that on the southern Washington margin, input sediment since late Miocene broadly balances with prism volume, supporting predominant accretion. On the central Oregon margin (where the prism may be younger), the prism volume is similar or slightly less than the sediment input, and on the southern Oregon margin, the prism volume is significantly less than the sediment input. This supports the hypothesis that basal and surface erosion of the prism and sediment

  15. Deformation characteristics and associated clay-mineral variation in 2-3 km buried Hota accretionary complex, central Japan

    NASA Astrophysics Data System (ADS)

    Yamamoto, Y.; Kameda, J.; Yamaguchi, H.

    2009-12-01

    Although deformation and physical/chemical properties variation in aseismic-seismic transition zone were essential to examine critical changes in environmental parameters that result in earthquake, they are poorly understood because the appropriate samples buried 2-4 km have not been collected yet (scientific drilling has never reached there and most of ancient examples experienced the deeper burial depth and suffered thermal and physical overprinting). The lower to middle Miocene Hota accretionary complex is a unique example of on land accretionary complex, representing deformation and its physical/chemical properties of sediments just prior to entering the seismogenic realm. The maximum paleotemperature was estimated approximately 55-70°C (based on vitrinite reflectance) indicative of a maximum burial depth about 2-3 km assuming a paleo-geothermal gradient as 25-35°C/km. Accretionary complex in this temperature/depth range corresponds with an intermediate range between the core samples collected from the modern accretionary prism (e.g. Nankai, Barbados, and so on) and rocks in the ancient accretionary complexes on land. This presentation will treat the detailed structural and chemical analyses of the Hota accretionary complex to construct deformation properties of décollement zone and accretionary complex in its 2-3 km depth range and to discuss the interrelation between the early diagenesis (hydrocarbon/cations generation and sediment dewatering, etc.) and transition of the deformation properties. The deformation in this accretionary complex is characterized by two deformation styles: one is a few centimeter-scale phacoidal deformation representing clay minerals preferred orientation in the outer rim, whereas random fabric in the core, quite similar texture to the rocks in the present-Nankai décollement. The other is S-C style deformation (similar deformation to the mélanges in ancient accretionary complex on land) exhibiting block-in-matrix texture and

  16. Accretionary orogens through Earth history

    USGS Publications Warehouse

    Cawood, Peter A.; Kroner, A.; Collins, W.J.; Kusky, T.M.; Mooney, W.D.; Windley, B.F.

    2009-01-01

    Accretionary orogens form at intraoceanic and continental margin convergent plate boundaries. They include the supra-subduction zone forearc, magmatic arc and back-arc components. Accretionary orogens can be grouped into retreating and advancing types, based on their kinematic framework and resulting geological character. Retreating orogens (e.g. modern western Pacific) are undergoing long-term extension in response to the site of subduction of the lower plate retreating with respect to the overriding plate and are characterized by back-arc basins. Advancing orogens (e.g. Andes) develop in an environment in which the overriding plate is advancing towards the downgoing plate, resulting in the development of foreland fold and thrust belts and crustal thickening. Cratonization of accretionary orogens occurs during continuing plate convergence and requires transient coupling across the plate boundary with strain concentrated in zones of mechanical and thermal weakening such as the magmatic arc and back-arc region. Potential driving mechanisms for coupling include accretion of buoyant lithosphere (terrane accretion), flat-slab subduction, and rapid absolute upper plate motion overriding the downgoing plate. Accretionary orogens have been active throughout Earth history, extending back until at least 3.2 Ga, and potentially earlier, and provide an important constraint on the initiation of horizontal motion of lithospheric plates on Earth. They have been responsible for major growth of the continental lithosphere through the addition of juvenile magmatic products but are also major sites of consumption and reworking of continental crust through time, through sediment subduction and subduction erosion. It is probable that the rates of crustal growth and destruction are roughly equal, implying that net growth since the Archaean is effectively zero. ?? The Geological Society of London 2009.

  17. The first actual record of deep open-ocean conditions in the Ediacaran: Fe speciation in pelagic deep-sea sediments in accretionary complexes in Wales, UK

    NASA Astrophysics Data System (ADS)

    Sato, T.; Asanuma, H.; Okada, Y.; Maruyama, S.; Shozugawa, K.; Matsuo, M.; Windley, B. F.

    2014-12-01

    The first oxidation of a deep ocean in Earth history is considered to have occurred in the Neoproterozoic, coincident with the metazoan diversification; however, the Neoproterozoic geological record has so far been limited to only continental shelves, slopes, or basins at the deepest. Here, we document Neoproterozoic pelagic deep-sea sediments in reconstructed oceanic plate stratigraphy (OPS) in accretionary complexes (ACs) in Anglesey and Lleyn, Wales, UK. The OPS mostly consists of mid-ocean ridge basalts, pelagic red-bedded cherts, hemipelagic siliceous mudstones and turbidite sandstones, in ascending order. Only at Porth Felen in Lleyn Peninsula does the OPS contain black mudstones (ca. 10 m-thick) instead of pelagic red-bedded cherts. Based on the tectonic reconstruction of these ACs, the OPS at Porth Felen has the oldest depositional age. Our new U-Pb date of detrital zircons separated from the turbidite sandstones at Porth Felen has the youngest age of 580±13 Ma. These results suggest that the black mudstones at Porth Felen were deposited no later than the early Ediacaran. We have analyzed these black mudstones by 57Fe Mössbauer spectroscopy, and found that about a quarter of their iron content is contained in pyrite, while the other components are paramagnetic Fe2+ or occasionally paramagnetic Fe3+ in clay minerals. The red cherts in the younger OPS contain hematite as the main iron mineral, paramagnetic Fe3+, and paramagnetic Fe2+. The occurrence of hematite in a deep-sea chert essentially indicates a primary oxidizing depositional condition, whereas pyrite is indicative of a reducing environment. The present data confirm that a reducing deep-sea existed in the early Ediacaran during the black mudstone deposition, and that an oxidizing deep-sea had been established by the late Ediacaran. In conclusion, our results provide the first direct evidence of an actual deep open-ocean in the Ediacaran to clarify the timing and extent of the Neoproterozoic

  18. Modeling consolidation and dewatering near the toe of the northern Barbados accretionary complex

    USGS Publications Warehouse

    Stauffer, P.; Bekins, B.A.

    2001-01-01

    At the toe of the northern Barbados accretionary complex, temperature and pore water chemistry data indicate that fluid flow is channeled along the de??collement and other shallow thrust faults. We examine mechanisms that may prevent consolidation and maintain high permeability over large sections of the de??collement. High-resolution bulk density data from five boreholes show that the de??collement is well consolidated at some sites while other sites remain underconsolidated. Underconsolidated de??collement behavior is associated with kilometer-scale negative-polarity seismic reflections from the de??collement plane that have been interpreted to be fluid conduits. We use a coupled fluid flow/consolidation model to simulate the loading response of a 10-km-long by 680-m-thick slice of sediment as it enters the accretionary complex. The simulations capture 185 ka (5 km) of subduction, with a load function representing the estimated effective stress of the overriding accretionary prism (3.8?? taper angle). Simulation results of bulk density in the de??collement 3.2 km arcward of the deformation front are compared with observations. The results show that persistent high pore pressures at the arcward edge of the simulation domain can explain underconsolidated behavior. The scenario is consistent with previous modeling results showing that high pore pressures can propagate intermittently along the de??collement from deeper in the complex. Simulated seaward fluxes in the de??collement (1-14 cm yr-1) lie between previous estimates from modeling studies of steady state (1 m yr-1) flow. Maximum simulated instantaneous fluid sources (2.5??10-13 s-1) are comparable to previous estimates. The simulations show minor swelling of incoming sediments (fluid sources ??? -3 ?? 1015 s-1) up to 3 km before subduction that may help to explain small-scale shearing and normal faulting proximal to the protode??collement. Copyright 2001 by the American Geophysical Union.

  19. Slope basins, headless canyons, and submarine palaeoseismology of the Cascadia accretionary complex

    USGS Publications Warehouse

    McAdoo, B.G.; Orange, D.L.; Screaton, E.; Lee, H.; Kayen, R.

    1997-01-01

    A combination of geomorphological, seismic reflection and geotechnical data constrains this study of sediment erosion and deposition at the toe of the Cascadia accretionary prism. We conducted a series of ALVIN dives in a region south of Astoria Canyon to examine the interrelationship of fluid flow and slope failure in a series of headless submarine canyons. Elevated head gradients at the inflection point of canyons have been inferred to assist in localized failures that feed sediment into a closed slope basin. Measured head gradients are an order of magnitude too low to cause seepage-induced slope failure alone; we therefore propose transient slope failure mechanisms. Intercanyon slopes are uniformly unscarred and smooth, although consolidation tests indicate that up to several metres of material may have been removed. A sheet-like failure would remove sediment uniformly, preserving the observed smooth intercanyon slope. Earthquake-induced liquefaction is a likely trigger for this type of sheet failure as the slope is too steep and short for sediment flow to organize itself into channels. Bathymetric and seismic reflection data suggest sediment in a trench slope basin between the second and third ridges from the prism's deformation is derived locally. A comparison of the amounts of material removed from the slopes and that in the basin shows that the amount of material removed from the slopes may slightly exceed the amount of material in the basin, implying that a small amount of sediment has escaped the basin, perhaps when the second ridge was too low to form a sufficient dam, or through a gap in the second ridge to the south. Regardless, almost 80% of the material shed off the slopes around the basin is deposited locally, whereas the remaining 20% is redeposited on the incoming section and will be re-accreted.

  20. Timing of deformational events in the Río San Juan complex: Implications for the tectonic controls on the exhumation of high-P rocks in the northern Caribbean subduction-accretionary prism

    NASA Astrophysics Data System (ADS)

    Escuder-Viruete, Javier; Valverde-Vaquero, Pablo; Rojas-Agramonte, Yamirka; Gabites, Janet; Castillo-Carrión, Mercedes; Pérez-Estaún, Andrés

    2013-09-01

    An integrated structural, petrological and geochronological study was undertaken to constrain the tectonic history and controls on the exhumation of the high-P rocks of the Río San Juan complex in the northern Caribbean subduction-accretionary wedge. In the main structural units of the complex, microtextural analyses were performed to identify the fabrics formed at peak of metamorphism in eclogite-facies conditions and during the main retrogressive event toward the low-P amphibolite or blueschist/greenschist-facies conditions. U-Pb SHRIMP dating on zircon rims (71.3 ± 0.7 Ma) coupled with 40Ar-39Ar analyses on phengite (~ 70-69 Ma) in felsic sills placed temporal constraints on the exhumation of the Jagua Clara serpentinite-matrix mélange during the blueschist-facies stage at the early Maastrichtian. In the Cuaba unit, U-Pb TIMS zircon ages of 89.7 ± 0.1 Ma and 90.1 ± 0.2 Ma obtained for the crystallization of tonalitic/trondhjemitic melts in the lower Guaconejo and upper Jobito subunits, respectively, are similar. These ages coupled with a U-Pb SHRIMP zircon age of 87 ± 1.8 Ma obtained in a garnet amphibolite and a group of older 40Ar-39Ar cooling ages on calcic amphibole constrain the exhumation of the Guaconejo subunit from the high-P stage to the low-P stage at the ~ 90-83 Ma time interval. Further, the age data collectively supports a genetic relationship between the distributed extensional ductile shearing, the related decompression and the local partial anatexis in the subunit, at least from the Turonian-Coniacian boundary to the early Campanian. A group of younger 40Ar-39Ar ages obtained in the mylonitized amphibolites of the basal Jobito detachment zone indicates late ductile deformation and exhumation/cooling in the late Campanian to Maastrichtian (~ 75-70 Ma). Therefore, structural and age data established deformation partitioning and reworking of retrograde fabrics during ~ 20 Ma in the Cuaba unit. The different exhumation rates obtained for the

  1. Sediment Accretion During Horst and Graben Subduction associated with the Tohoku Oki M9 Earthquake, Northern Japan

    NASA Astrophysics Data System (ADS)

    Moore, J. C.; Chester, F. M.

    2015-12-01

    The stratigraphic sequence within the frontal accretionary prism of the Japan Trench, the site of large slip during the Tohoku earthquake, is unique due to horst and graben subduction. Boreholes at IODP Site C0019, penetrating the toe of the Tohoku accretionary prism, document a younger over older intraprism thrust contact with a 9 Ma age gap across the basal plate boundary fault. The anomalously young (Quaternary to Pliocene), fault-bounded sediment package is 130 m thick, of a total of 820 m of sediment above the plate boundary fault. In contrast, typical accretionary prism structure consists of stacked sediment packages on imbricate faults above the basal decollement resulting in an overall increase in age downward. Site C0019 penetrates the prism directly above a horst of the subducting Pacific oceanic crust. Here the plate-boundary fault consists of a thin, weak smectitic pelagic clay that is probably the principal slip surface of ~50 m offset in the 2011 Tohoku earthquake. The fault continues seaward deepening off the seaward edge of the horst and beneath the sediment fill of the adjacent graben, dying out at the landward base of the next incoming horst. The plate boundary fault and its splays in the graben form a narrow-taper protoprism and a small sedimentary basin of trench fill marking the seaward edge of the upper plate. The modern fault and sediment distributions within the graben are used to motivate a viable model for the presence of anomalously young sediments directly above the plate boundary fault. In this model sediments in the trench are thrust over the incoming horst by propagation of the plate boundary thrust up the landward-dipping fault of the incoming horst and along the smectitic clay layer to emplace Quaternary and Pliocene trench deposits directly on top of the incoming horst. These young deposits are in turn overlain by sediments 9 Ma or older that have been transported out of the graben along imbricate faults associated with the

  2. Geomicrobiology and Methanogenesis in Accretionary Complexes

    NASA Astrophysics Data System (ADS)

    Colwell, F. S.; Delwiche, M.; Reed, D.; Boyd, S.; Nunoura, T.; Inagaki, F.; Takai, K.

    2003-12-01

    As elsewhere in subsurface environments, microbes are known to colonize the sediments of accretionary margins. In fact, much of the methane present in hydrates along continental margins originates from microbial activity. However, models to predict hydrate distribution or the amount of methane in the sediments lack reliable values for in situ microbial methane production rates. Our studies of hydrate-bearing sediments focus first on the molecular identification of the microbes present and then on estimating realistic methanogenic rates to be used in these models. 16S rDNA extracted from deep marine sediments, then sequenced, and compared to known sequences indicates the presence of diverse bacterial and archaeal lineages. In one example, the Nankai Trough, Archaea (both Crenarchaeota and Euryarchaeota) and Bacteria (e.g., Proteobacteria, Actinobacteria, green non-sulfur) were detected at various depths above, within, and below the hydrate stability zone. Often methanogens cannot be detected using molecular approaches in accretionary sediments, but at least one methanogen (Methanoculleus submarinus) has been isolated from deep sediments that contain hydrates. Although culture-based enrichments for methanogens often yield evidence of methanogenic activity methanogenic rates derived from these studies are likely several orders of magnitude higher than the rates that are possible under in situ conditions. By combining data on methanogen numbers at various depths and realistic methanogenesis rates obtained from starved methanogens we hope to determine the productivity of methanogens on a volumetric basis for the sediments. These data will be used in models that predict hydrate distribution and formation rates in marine sediments.

  3. Lithospheric cooling as a basin forming mechanism within accretionary crust.

    NASA Astrophysics Data System (ADS)

    Holt, P. J.; Allen, M.; van Hunen, J.; Björnseth, H. M.

    2009-04-01

    Widely accepted basin forming mechanisms are limited to flexure of the lithosphere, lithospheric stretching, lithospheric cooling following rifting and, possibly, dynamic topography. In this work forward models have been used to investigate lithospheric growth due to cooling beneath accretionary crust, as a new basin forming mechanism. Accretionary crust is formed from collision of island arcs, accretionary complexes and fragments of reworked older crust at subduction zones, and therefore has thin lithosphere due to melting and increased convection. This is modeled using a 1D infinite half space cooling model similar to lithospheric cooling models for the oceans. The crustal composition and structure used in the models has been varied around average values of accretionary crust to represent the heterogeneity of accretionary crust. The initial mantle lithosphere thickness used in the model was 20 km. The model then allows the lithosphere to thicken as it cools and calculates the subsidence isostatically. The model produces sediment loaded basins of 2-7 km for the various crustal structures over 250 Myrs. Water-loaded tectonic subsidence curves from the forward models were compared to tectonic subsidence curves produced from backstripping wells from the Kufrah and Ghadames basins, located on the accretionary crust of North Africa. A good match between the subsidence curves for the forward model and backstripping is produced when the best estimates for the crustal structure, composition and the present day thickness of the lithosphere for North Africa are used as inputs for the forward model. This shows that lithospheric cooling provides a good method for producing large basins with prolonged subsidence in accretionary crust without the need for initial extension.

  4. Fluid venting and seepage at accretionary ridges: the Four Way Closure Ridge offshore SW Taiwan

    NASA Astrophysics Data System (ADS)

    Klaucke, Ingo; Berndt, Christian; Crutchley, Gareth; Chi, Wu-Cheng; Lin, Saulwood; Muff, Sina

    2016-06-01

    Within the accretionary prism offshore SW Taiwan, widespread gas hydrate accumulations are postulated to occur based on the presence of a bottom simulating reflection. Methane seepage, however, is also widespread at accretionary ridges offshore SW Taiwan and may indicate a significant loss of methane bypassing the gas hydrate system. Four Way Closure Ridge, located in 1,500 m water depth, is an anticlinal ridge that would constitute an ideal trap for methane and consequently represents a site with good potential for gas hydrate accumulations. The analysis of high-resolution bathymetry, deep-towed sidescan sonar imagery, high-resolution seismic profiling and towed video observations of the seafloor shows that Four Way Closure Ridge is and has been a site of intensive methane seepage. Continuous seepage is mainly evidenced by large accumulations of authigenic carbonate precipitates, which appear to be controlled by the creation of fluid pathways through faulting. Consequently, Four Way Closure Ridge is not a closed system in terms of fluid migration and seepage. A conceptual model of the evolution of gas hydrates and seepage at accretionary ridges suggests that seepage is common and may be a standard feature during the geological development of ridges in accretionary prisms. The observation of seafloor seepage alone is therefore not a reliable indicator of exploitable gas hydrate accumulations at depth.

  5. Composite Spectrometer Prisms

    NASA Technical Reports Server (NTRS)

    Breckinridge, J. B.; Page, N. A.; Rodgers, J. M.

    1985-01-01

    Efficient linear dispersive element for spectrometer instruments achieved using several different glasses in multiple-element prism. Good results obtained in both two-and three-element prisms using variety of different glass materials.

  6. Observations at convergent margins concerning sediment subduction, subduction erosion, and the growth of continental crust

    USGS Publications Warehouse

    Von Huene, R.; Scholl, D. W.

    1991-01-01

    At ocean margins where two plates converge, the oceanic plate sinks or is subducted beneath an upper one topped by a layer of terrestrial crust. This crust is constructed of continental or island arc material. The subduction process either builds juvenile masses of terrestrial crust through arc volcanism or new areas of crust through the piling up of accretionary masses (prisms) of sedimentary deposits and fragments of thicker crustal bodies scraped off the subducting lower plate. At convergent margins, terrestrial material can also bypass the accretionary prism as a result of sediment subduction, and terrestrial matter can be removed from the upper plate by processes of subduction erosion. Sediment subduction occurs where sediment remains attached to the subducting oceanic plate and underthrusts the seaward position of the upper plate's resistive buttress (backstop) of consolidated sediment and rock. Sediment subduction occurs at two types of convergent margins: type 1 margins where accretionary prisms form and type 2 margins where little net accretion takes place. At type 2 margins (???19,000 km in global length), effectively all incoming sediment is subducted beneath the massif of basement or framework rocks forming the landward trench slope. At accreting or type 1 margins, sediment subduction begins at the seaward position of an active buttress of consolidated accretionary material that accumulated in front of a starting or core buttress of framework rocks. Where small-to-mediumsized prisms have formed (???16,300 km), approximately 20% of the incoming sediment is skimmed off a detachment surface or decollement and frontally accreted to the active buttress. The remaining 80% subducts beneath the buttress and may either underplate older parts of the frontal body or bypass the prism entirely and underthrust the leading edge of the margin's rock framework. At margins bordered by large prisms (???8,200 km), roughly 70% of the incoming trench floor section is

  7. Sedimentation in the central segment of the Aleutian Trench: Sources, transport, and depositional style

    SciTech Connect

    Stevenson, A.J.; Scholl, D.W.; Vallier, T.L. ); Underwood, M.B. )

    1990-05-01

    The central segment of the Aleutian Trench (162{degree}W to 175{degree}E) is an intraoceanic subduction zone that contains an anomalously thick sedimentary fill (4 km maximum). The fill is an arcward-thickening and slightly tilted wedge of sediment characterized acoustically by laterally continuous, closely spaced, parallel reflectors. These relations are indicative of turbidite deposition. The trench floor and reflection horizons are planar, showing no evidence of an axial channel or any transverse fan bodies. Cores of surface sediment recover turbidite layers, implying that sediment transport and deposition occur via diffuse, sheetlike, fine-grained turbidite flows that occupy the full width of the trench. The mineralogy of Holocene trench sediments document a mixture of island-arc (dominant) and continental source terranes. GLORIA side-scan sonar images reveal a westward-flowing axial trench channel that conducts sediment to the eastern margin of the central segment, where channelized flow cases. Much of the sediment transported in this channel is derived from glaciated drainages surrounding the Gulf of Alaska which empty into the eastern trench segment via deep-sea channel systems (Surveyor and others) and submarine canyons (Hinchinbrook and others). Insular sediment transport is more difficult to define. GLORIA images show the efficiency with which the actively growing accretionary wedge impounds sediment that manages to cross a broad fore-arc terrace. It is likely that island-arc sediment reaches the trench either directly via air fall, via recycling of the accretionary prism, or via overtopping of the accretionary ridges by the upper parts of thick turbidite flows.

  8. Cretaceous high-pressure metamorphic belts of the Central Pontides (northern Turkey): pre-collisional Pacific-type accretionary continental growth of Laurasian Margin

    NASA Astrophysics Data System (ADS)

    Aygul, Mesut; Okay, Aral I.; Oberhaensli, Roland; Sudo, Masafumi

    2014-05-01

    Cretaceous blueschist-facies metamorphic rocks crop out widely in the central part of the Pontides, an east-west trending mountain belt in northern Turkey. They comprise an accretionary wedge along to the southern Laurasian active continental margin and predate the opening of Black Sea basin. From North to South, the wedge consists of a low grade metaflysch unit with marble, Na-amphibole-bearing metabasite and serpentinite blocks. An extensional shear zone separates the accreted distal terrigenous sediments from HP/LT micaschists and metabasites of oceanic origin, known as Domuzdaǧ Complex. The shear zone reaches up to one km in thickness and consists of tectonic slices of serpentinite, metabasite, marble, phyllite and micaschist with top to the NW sense of shear. The Domuzdaǧ Complex predominantly consists of carbonaceous micaschist and metabasite with serpentinite, and minor metachert, marble and metagabbro. Metabasites consist mainly of epidote-blueschists sometimes with garnet. Fresh lawsonite-blueschists are found as blocks within the shear zone. Peak metamorphic assemblages in the micaschists are chloritoid-glaucophane and garnet-chloritoid-glaucophane-lawsonite in addition to phengite, paragonite, quartz, chlorite and rutile (P: 17 ± 1 Kbar, T: 390-450 °C). To the south, lithologies change slightly, with metabasite and thick, pale marble with few metachert and metapelitic horizons. The degree of metamorphism also changes. The metabasites range from high-pressure upper-greenschist facies with growth of sodic-amphibole to lower greenschist without any HP index mineral, suggesting a general decrease in pressure toward south within the prism. While Domuzdaǧ Complex represents deep-seated underplated oceanic sediments and basalts, the carbonate-rich southern parts can be interpreted as seamounts integrated into the accretionary prism. Ar/Ar dating on phengite separates both from terrigenous and oceanic metasediments give consistent plateau ages of 100 ± 2

  9. The role of subducting bathymetric highs on the oceanic crust to deformation of accretionary wedge and earthquake segmentation in the Java forearc

    NASA Astrophysics Data System (ADS)

    Singh, S. C.; Mukti, M.; Deighton, I.

    2014-12-01

    Stratigraphic and structural observations of newly acquired seismic reflection data along the offshore south Java reveal the structural style of deformation along the forearc and the role of subducting bathymetric highs to the morphology of the forearc region. The forearc region can be divided in to two major structural units: accretionary wedge and forearc and forearc basin where a backthrust marks the boundary between the accretionary wedge and the forearc basin sediments. The continuous compression in the subduction zone has induced younger landward-vergent folds and thrusts within the seaward margin of the forearc basin sediments, which together with the backthrust is referred as the Offshore South Java Fault Zone (OSJFZ), representing the growth of the accretionary wedge farther landward. Seaward-vergent imbricated thrusts have deformed the sediments in the accretionary wedge younging seaward, and have developed fold-thrust belts in the accretionary wedge toward trench. Together with the backthrusts, these seaward-vergent thrusts characterize the growth of accretionary wedge in South of Java trench. Based on these new results, we suggest that accretionary wedge mechanic is not the first order factor in shaping the morphology of the accretionary wedge complex. Instead the subducting bathymetric highs play the main role in shaping the forearc that are manifested in the uplift of the forearc high and intense deformation along the OSJFZ. These subducting highs also induce compression within the accretionary sediments, evident from landward deflection of the subduction front at the trench and inner part of accretionary wedge in the seaward margin of the forearc basin. Intense deformation is also observed on the seaward portion of the accretionary wedge area where the bathymetric highs subducted. We suggest that these subducted bathymetric features define the segment boundaries for megathrust earthquakes, and hence reducing the maximum size of the earthquakes in the

  10. Seismic reflection images of the accretionary wedge of Costa Rica

    SciTech Connect

    Shipley, T.H.; Stoffa, P.L. ); McIntosh, K.; Silver, E.A. )

    1990-05-01

    The large-scale structure of modern accretionary wedges is known almost entirely from seismic reflection investigations using single or grids of two-dimensional profiles. The authors will report on the first three-dimensional seismic reflection data volume collected of a wedge. This data set covers a 9-km-wide {times} 22-km-long {times} 6-km-thick volume of the accretionary wedge just arcward of the Middle America Trench off Costa Rica. The three-dimensional processing has improved the imaging ability of the multichannel data, and the data volume allows mapping of structures from a few hundred meters to kilometers in size. These data illustrate the relationships between the basement, the wedge shape, and overlying slope sedimentary deposits. Reflections from within the wedge define the gross structural features and tectonic processes active along this particular convergent margin. So far, the analysis shows that the subdued basement relief (horst and graben structures seldom have relief of more than a few hundred meters off Costa Rica) does affect the larger scale through going structural features within the wedge. The distribution of mud volcanoes and amplitude anomalies associated with the large-scale wedge structures suggests that efficient fluid migration paths may extend from the top of the downgoing slab at the shelf edge out into the lower and middle slope region at a distance of 50-100 km. Offscraping of the uppermost (about 45 m) sediment occurs within 4 km of the trench, creating a small pile of sediments near the trench lower slope. Underplating of parts of the 400-m-thick subducted sedimentary section begins at a very shallow structural level, 4-10 km arcward of the trench. Volumetrically, the most important accretionary process is underplating.

  11. Optical switch using Risley prisms

    DOEpatents

    Sweatt, William C.; Christenson, Todd R.

    2003-04-15

    An optical switch using Risley prisms and rotary microactuators to independently rotate the wedge prisms of each Risley prism pair is disclosed. The optical switch comprises an array of input Risley prism pairs that selectively redirect light beams from a plurality of input ports to an array of output Risley prism pairs that similarly direct the light beams to a plurality of output ports. Each wedge prism of each Risley prism pair can be independently rotated by a variable-reluctance stepping rotary microactuator that is fabricated by a multi-layer LIGA process. Each wedge prism can be formed integral to the annular rotor of the rotary microactuator by a DXRL process.

  12. Optical Switch Using Risley Prisms

    SciTech Connect

    Sweatt, William C.; Christenson, Todd R.

    2005-02-22

    An optical switch using Risley prisms and rotary microactuators to independently rotate the wedge prisms of each Risley prism pair is disclosed. The optical switch comprises an array of input Risley prism pairs that selectively redirect light beams from a plurality of input ports to an array of output Risley prism pairs that similarly direct the light beams to a plurality of output ports. Each wedge prism of each Risley prism pair can be independently rotated by a variable-reluctance stepping rotary microactuator that is fabricated by a multi-layer LIGA process. Each wedge prism can be formed integral to the annular rotor of the rotary microactuator by a DXRL process.

  13. Project PRISM: PRISM's Annotated Resource List.

    ERIC Educational Resources Information Center

    Cunnion, Maryellen; And Others

    The final of three volumes on Project PRISM, a program to help middle school teachers meet the needs of gifted and talented children in their classes without removing them from the mainstream, lists resources on the education of gifted and talented children. Materials are organized according to four basic types: books, periodicals, curriculum aids…

  14. Long-distance multistep sediment transfer at convergent plate margins (Barbados, Lesser Antilles)

    NASA Astrophysics Data System (ADS)

    Limonta, Mara; Garzanti, Eduardo; Resentini, Alberto; Andò, Sergio; Boni, Maria; Bechstädt, Thilo

    2015-04-01

    We present a regional provenance study of the compositional variability and long distance multicyclic transport of terrigenous sediments along the convergent and transform plate boundaries of Central America, from the northern termination of the Andes to the Lesser Antilles arc-trench system. We focus on high-resolution bulk-petrography and heavy-mineral analyses of modern beach and fluvial sediments and Cenozoic sandstones of Barbados island, one of the places in the world where an active accretionary prism is subaerially exposed (Speed et al., 2012). The main source of siliciclastic sediment in the Barbados accretionary prism is off-scraped quartzose to feldspatho-litho-quartzose metasedimentaclastic turbidites, ultimately supplied from South America chiefly via the Orinoco fluvio-deltaic system. Modern sand on Barbados island is either quartzose with depleted heavy-mineral suites recycled from Cenozoic turbidites and including epidote, zircon, tourmaline, andalusite, garnet, staurolite and chloritoid, or calcareous and derived from Pleistocene coral reefs. The ubiquitous occurrence of clinopyroxene and hypersthene, associated with green-brown kaersutitic hornblende in the north or olivine in the south, points to reworking of ash-fall tephra erupted from andesitic (St. Lucia) and basaltic (St. Vincent) volcanic centers in the Lesser Antilles arc transported by the prevailing anti-trade winds in the upper troposphere. Modern sediments on Barbados island and those shed by other accretionary prisms such as the Indo- Burman Ranges and Andaman-Nicobar Ridge (Garzanti et al., 2013) define the distinctive mineralogical signature of Subduction Complex Provenance, which is invariably composite. Detritus recycled dominantly from accreted turbidites and oceanic mudrocks is mixed in various proportions with detritus from the adjacent volcanic arc or carbonate reefs widely developed at tropical latitudes. Ophiolitic detritus may be locally prominent. Quantitative provenance

  15. Prism users guide.

    SciTech Connect

    Weirs, V. Gregory

    2012-03-01

    Prism is a ParaView plugin that simultaneously displays simulation data and material model data. This document describes its capabilities and how to use them. A demonstration of Prism is given in the first section. The second section contains more detailed notes on less obvious behavior. The third and fourth sections are specifically for Alegra and CTH users. They tell how to generate the simulation data and SESAME files and how to handle aspects of Prism use particular to each of these codes.

  16. Detection of low-chloride fluids beneath a cold seep field on the Nankai accretionary wedge off Kumano, south of Japan

    NASA Astrophysics Data System (ADS)

    Toki, T.; Tsunogai, U.; Gamo, T.; Kuramoto, S.; Ashi, J.

    2004-11-01

    Chemical and isotopic characteristics were determined for interstitial waters extracted from surface sediments in and around dense biological communities on the seafloor of the Nankai accretionary prism off Kumano, south of Japan. We found the following unique features when compared with usual interstitial water samples of normal seafloor in those of samples from bacterial mats on the Oomine Ridge, one of the outer ridge in the Nankai accretionary prism: (1) significant depletion of chloride concentration (maximum 10% depletion from bottom seawater), (2) high concentrations of CH4 and ΣCO2 (more than 660 μmol/kg and 60 mmol/kg, respectively), (3) sulfate depletion (more than 90% depletion compared to bottom seawater), and (4) δDH2O and δ18OH2O depletion [more than 4‰ and 0.7‰ depletion, respectively, compared to standard mean ocean water (SMOW)]. The highest CH4 value among these samples was comparable to the highest value so far reported at one of the most active seep areas in the Nankai Trough, suggesting that these sites should also be regarded as one of the most active seep sites in the Nankai Trough. The chemical compositions of the samples taken from the Oomine Ridge strongly suggest that the fluid originates not from normal sediment-seawater interaction at the sediment surface of hemipelagic environments, but from active seepage of fluids that are rich in CH4 and ΣCO2, depleted in Cl- and SO42-, and low in δDH2O and δ18OH2O compared to normal seawater. Values for the carbon isotopic composition (δ13CCH4) of the dissolved methane in the interstitial fluid [less than -70‰ PeeDee Belemnite (PDB)] and for the C2H6/CH4 ratio (less than 10-3) suggest that the methane originates from microbial production in a relatively shallow layer of sediment, not from the deep sedimentary layer of higher temperature than 60 °C at the depth of more than 300 m below the seafloor. The Cl-=0 mmol/kg extrapolated end-member δDH2O and δ18OH2O values of low

  17. Prism adaptation by mental practice.

    PubMed

    Michel, Carine; Gaveau, Jérémie; Pozzo, Thierry; Papaxanthis, Charalambos

    2013-09-01

    The prediction of our actions and their interaction with the external environment is critical for sensorimotor adaptation. For instance, during prism exposure, which deviates laterally our visual field, we progressively correct movement errors by combining sensory feedback with forward model sensory predictions. However, very often we project our actions to the external environment without physically interacting with it (e.g., mental actions). An intriguing question is whether adaptation will occur if we imagine, instead of executing, an arm movement while wearing prisms. Here, we investigated prism adaptation during mental actions. In the first experiment, participants (n = 54) performed arm pointing movements before and after exposure to the optical device. They were equally divided into six groups according to prism exposure: Prisms-Active, Prisms-Imagery, Prisms-Stationary, Prisms-Stationary-Attention, No Conflict-Prisms-Imagery, No Prisms-Imagery. Adaptation, measured by the difference in pointing errors between pre-test and post-test, occurred only in Prisms-Active and Prisms-Imagery conditions. The second experiment confirmed the results of the first experiment and further showed that sensorimotor adaptation was mainly due to proprioceptive realignment in both Prisms-Active (n = 10) and Prisms-Imagery (n = 10) groups. In both experiments adaptation was greater following actual than imagined pointing movements. The present results are the first demonstration of prism adaptation by mental practice under prism exposure and they are discussed in terms of internal forward models and sensorimotor plasticity.

  18. Slow and delayed deformation and uplift of the outermost subduction prism following ETS and seismogenic slip events beneath Nicoya Peninsula, Costa Rica

    NASA Astrophysics Data System (ADS)

    Davis, Earl E.; Villinger, Heinrich; Sun, Tianhaozhe

    2015-01-01

    Two ODP CORK (Ocean Drilling Program circulation obviation retrofit kit) borehole hydrologic observatory sites deployed in 2002 at the toe of the subduction prism off Nicoya Peninsula, Costa Rica were visited in December 2013. The five years of seafloor and formation fluid pressure data collected since the previous visit include clear signals associated with an episodic tremor and slip (ETS) event off the coast of Nicoya Peninsula in 2009, and a Mw 7.6 subduction thrust earthquake beneath the Peninsula in 2012. Formation pressure anomalies associated with the ETS event are similar to ones observed following ETS events observed previously here, as well as ones following very low frequency earthquake swarms within the Nankai accretionary prism off southwestern Japan. Positive and negative impulsive transients in the hanging wall and foot wall of the subduction thrust, respectively, suggest contractional and dilatational strain generated by local slip propagating up the thrust fault beneath the outermost prism. In the case of the 2009 event, the transients occurred roughly two weeks after the initiation of slip observed at GPS sites along the adjacent coast. At the same time, a decrease in seafloor pressure at the prism site relative to the subducting plate was observed, indicating concurrent uplift of the prism of 1.2 cm. Other events at the prism toe following ETS events closer to the coast are seen in 2006, 2007, 2008, 2010, and 2011. The time between the initiation of ETS slip constrained by GPS and the onset of the prism toe transients suggest up-dip “rupture” propagation along the seaward part of the subduction thrust at rates of a few km/day. In the case of the 2009 event, the slip at the prism toe (c. 11 cm), estimated from the 1.2 cm uplift and the local dip on the decollement (6°), is roughly a factor of 5 greater than the slip further landward estimated from GPS data by Dixon et al. (in press). In other cases, slip at the toe is less or unresolvable

  19. PRISM Spectrograph Optical Design

    NASA Technical Reports Server (NTRS)

    Chipman, Russell A.

    1995-01-01

    The objective of this contract is to explore optical design concepts for the PRISM spectrograph and produce a preliminary optical design. An exciting optical configuration has been developed which will allow both wavelength bands to be imaged onto the same detector array. At present the optical design is only partially complete because PRISM will require a fairly elaborate optical system to meet its specification for throughput (area*solid angle). The most complex part of the design, the spectrograph camera, is complete, providing proof of principle that a feasible design is attainable. This camera requires 3 aspheric mirrors to fit inside the 20x60 cm cross-section package. A complete design with reduced throughput (1/9th) has been prepared. The design documents the optical configuration concept. A suitable dispersing prism material, CdTe, has been identified for the prism spectrograph, after a comparison of many materials.

  20. An evaluation of factors influencing pore pressure in accretionary complexes: Implications for taper angle and wedge mechanics

    USGS Publications Warehouse

    Saffer, D.M.; Bekins, B.A.

    2006-01-01

    At many subduction zones, accretionary complexes form as sediment is off-scraped from the subducting plate. Mechanical models that treat accretionary complexes as critically tapered wedges of sediment demonstrate that pore pressure controls their taper angle by modifying basal and internal shear strength. Here, we combine a numerical model of groundwater flow with critical taper theory to quantify the effects of sediment and de??collement permeability, sediment thickness, sediment partitioning between accretion and underthrusting, and plate convergence rate on steady state pore pressure. Our results show that pore pressure in accretionary wedges can be viewed as a dynamically maintained response to factors which drive pore pressure (source terms) and those that limit flow (permeability and drainage path length). We find that sediment permeability and incoming sediment thickness are the most important factors, whereas fault permeability and the partitioning of sediment have a small effect. For our base case model scenario, as sediment permeability is increased, pore pressure decreases from near-lithostatic to hydrostatic values and allows stable taper angles to increase from ??? 2.5?? to 8??-12.5??. With increased sediment thickness in our models (from 100 to 8000 m), increased pore pressure drives a decrease in stable taper angle from 8.4??-12.5?? to 15?? to <4??) with increased sediment thickness (from <1 to 7 km). One key implication is that hydrologic properties may strongly influence the strength of the crust in a wide range of geologic settings. Copyright 2006 by the American Geophysical Union.

  1. Origin and evolution of fluids from mud volcanoes in the Barbados accretionary complex

    NASA Astrophysics Data System (ADS)

    Godon, Arnaud; Jendrzejewski, Nathalie; Castrec-Rouelle, Maryse; Dia, Aline; Pineau, Françoise; Boulègue, Jacques; Javoy, Marc

    2004-05-01

    A large collection of fluids (54 interstitial fluids and four expelled fluids) were sampled at the Manon site, at the outer edge of the Barbados accretionary complex. These warm fluids (up to 20°C) are expelled by sub-marine (5000 mbsl) mud volcanoes consisting of diapirs (unchanneled flow) and diatremes (channeled). Chlorine stable isotope ratios of these fluids were measured by IRMS with a reproducibility of ± 0.05‰ (1σ) versus SMOC (Standard Mean Ocean Chloride). A large range of δ 37Cl between -5.3‰ and +0.1‰ is observed. Data from each volcanic structure describe a mixing between seawater and a low-δ 37Cl fluid. The whole set of data is interpreted as the result of a mixing between two deep components and seawater. The two deep fluids are chemically distinct (e.g., in Ca, Mg, K, Li, Sr and Br contents and Br/Cl ratio). They display low and significantly different 87Sr/ 86Sr ratios (0.707790 and 0.707892, respectively) and δ 37Cl values (-4.51 and -5.24‰, respectively). Physicochemical processes such as mineralogical transformation, diffusion, compaction or ion filtration are known to fractionate chlorine stable isotopes and can produce fluids with negative δ 37Cl values. Ion filtration due to sediment compaction appears to be the more likely process to explain the negative δ 37Cl values observed at the Manon site. A model for the generation of these signatures is proposed where a residual negative δ 37Cl fluid reservoir is created at the bottom of the prism or the sediment pile. Further compaction/fracturing and/or dewatering of the slab may flush out these fluids and focus them towards the décollement zone. Mixing between the fluids and ultimately with seawater and water released during gas hydrate destabilizations may explain the data set within the individual cores and between the different structures.

  2. Neogene Sediment Transport, Deposition, and Exhumation from the Southern Alaska Syntaxis to the Eastern Aleutian Subduction Zone

    NASA Astrophysics Data System (ADS)

    Ridgway, K. D.; Witmer, J. W.; Enkelmann, E.; Plafker, G.; Brennan, P. R.

    2011-12-01

    Over 5 km of Neogene sedimentary strata are well exposed in the Chugach-St. Elias Ranges within the southern Alaska syntaxis. This syntaxis forms where the Pacific-North America plate boundary changes from the northwest-trending Queen Charlotte-Fairweather transform system to the southwest-trending Alaska-Aleutian subduction zone. Active collision and subduction of the buoyant Yakutat microplate in the syntaxis results in a wide collisional zone defined by active mountain belts, extensive glaciation, and thick packages of synorogenic strata. New stratigraphic and U-Th/He thermochronologic data from Neogene synorogenic strata, named the Yakataga and Redwood Formations, provide insights on collisional tectonics, glacial erosion, and sediment transport, deposition, burial, and exhumation from the onshore Chugach and St. Elias Ranges to the exposed accretionary prism of the Aleutian trench. Stratigraphic analyses show that along the southeastern part of the syntaxis, Neogene strata are characterized by deposition in braid delta, shallow marine, and glaciomarine slope apron depositional systems that resulted in construction of a broad continental shelf. In the central part of the syntaxis, marine shelf and upper slope environments deposited thick-bedded sandstone and mudstone in a thrust belt/foreland basin system. Along the southwestern part of the syntaxis, Neogene strata were deposited in a regional submarine fan system that filled the easternmost part of the Aleutian trench. Geologic mapping of the contact between the Yakataga Formation and underlying strata along the syntaxis document an angular unconformity with maximum stratigraphic separation (> 5 km) in the central part of the syntaxis. Along strike, this unconformity becomes conformable along both the southwestern and southeastern parts of the syntaxis. The regional angular unconformity and facies transitions both point to the importance of the central part of the syntaxis in the generation and distribution of

  3. Insights on frictional processes in sheared clastic marine sediments using ultrasonic nondestructive testing

    NASA Astrophysics Data System (ADS)

    Knuth, M. W.; Tobin, H. J.; Marone, C.; Ikari, M.

    2010-12-01

    We investigate changes in the elastic properties of deforming core materials recovered from the Nankai Trough Accretionary Prism along the IODP NanTroSEIZE transect. We shear clastic marine sediments while simultaneously making ultrasonic velocity measurements across the deforming layers. Examining the resulting changes in elastic moduli at the laboratory scale allows us to identify characteristic “fingerprints” of deformation style during direct-shear experiments, which may then be compared with measurements conducted at the field scale to infer how deformation is localized within the accretionary prism. Identifying relationships between hold time and attenuation may also shed light on fault healing mechanisms taking place immediately following a rupture. Together the effects of sliding rate and hold time on elastic moduli provide us with new ways of constraining the mechanical behavior of large plat-boundary settings throughout the seismic cycle. We tested intact core material, remolded layers, and disaggregated granular powders derived from a range of depths from IODP sites C0007 and C0004 penetrating the frontal thrust and a large out-of-sequence thrust in the outer prism, respectively. Samples were deformed in a double-direct shear configuration, varying first the strain rate and then subjecting the gouge layer to a series of slides and holds of increasing duration. Elastic wave propagation depends on micromechanical interactions and gouge layer strength, so as the shear zone evolves changes in elastic wavespeed provide a means to interrogate strain materials non-destructively, providing insight into frictional processes and mechanics as that deformation is taking place. Our results suggest that there are characteristic changes in P and S-wave velocity and attenuation for marine clastic to hemipelagic sediments as a function of sliding rate and hold time. Ultimately, examining variation in elastic moduli during a simulated seismic cycle may provide insight

  4. In situ stress magnitude and rock strength in the Nankai accretionary complex: a novel approach using paired constraints from downhole data in two wells

    NASA Astrophysics Data System (ADS)

    Huffman, K. A.; Saffer, D. M.; Dugan, B.

    2016-07-01

    We present a method to simultaneously constrain both far-field horizontal stress magnitudes ( S hmin and S Hmax) and in situ rock unconfined compressive strength (UCS), using geophysical logging data from two boreholes located 70 m apart that access the uppermost accretionary prism of the Nankai subduction zone . The boreholes sample the same sediments and are affected by the same tectonic stress field, but were drilled with different annular pressures, thus providing a unique opportunity to refine estimates of both in situ stress magnitudes and rock strength. We develop a forward model to predict the angular width of compressional wellbore failures (borehole breakouts), and identify combinations of S Hmax and UCS that best match breakout widths observed in resistivity images from the two boreholes. The method requires knowledge of S hmin, which is defined by leak-off tests conducted during drilling. Our results define a normal to strike-slip stress regime from 900 to 1386 m below seafloor, consistent with observations from seismic and core data. Our analysis also suggests that in situ values of UCS are generally slightly lower that commonly assumed on the basis of published empirical relations between UCS and P-wave velocity.

  5. PRISM project optical instrument

    NASA Technical Reports Server (NTRS)

    Taylor, Charles R.

    1994-01-01

    The scientific goal of the Passively-cooled Reconnaissance of the InterStellar Medium (PRISM) project is to map the emission of molecular hydrogen at 17.035 micrometers and 28.221 micrometers. Since the atmosphere is opaque at these infrared wavelengths, an orbiting telescope is being studied. The availability of infrared focal plane arrays enables infrared imaging spectroscopy at the molecular hydrogen wavelengths. The array proposed for PRISM is 128 pixels square, with a pixel size of 75 micrometers. In order to map the sky in a period of six months, and to resolve the nearer molecular clouds, each pixel must cover 0.5 arcminutes. This sets the focal length at 51.6 cm. In order for the pixel size to be half the diameter of the central diffraction peak at 28 micrometers would require a telescope aperture of 24 cm; an aperture of 60 cm has been selected for the PRISM study for greater light gathering power.

  6. Stress states at site C0002, Nankai accretionary wedge, down to 2000 m below seafloor

    NASA Astrophysics Data System (ADS)

    Chang, Chandong; Song, Insun; Lee, Hikweon

    2015-04-01

    The boreholes drilled at site C0002 under the Nankai Trough Seismogenic Zone Experiment project, southwest Japan were used to estimate in situ stress states that prevail in the plate interface region between Philippine Sea plate and the Eurasian plate. The depth covered in this study is from seafloor down to ~2000 meter below seafloor (mbsf), somewhat shallow compared to the depths of the megasplay fault (~5000 mbsf) and the plate interface (~6800 mbsf). However, the shallow stress may reflect some tectonic processes prevailing in this region and may give some insight into tectonic settings. Multiple techniques of borehole observations and borehole tests were used to estimate the magnitudes and the orientations of the stresses. The borehole breakouts in the vertical boreholes indicate a consistent orientation (margin-parallel) of the maximum horizontal principal stress (SHmax) throughout the depths. The analysis on the geometry (or azimuthal span) of borehole breakouts and rock strengths (from log-based estimations) suggests that the stress states in the upper forearc basin sediments above the unconformity (~980 mbsf) are constrained to be in favor of normal faulting (vertical stress (Sv) > SHmax > least horizontal stress (Shmin)). The stress states in the old accretionary prism below the unconformity down to ~1400 mbsf are possibly varying with depth between normal, strike-slip and reverse faulting favored stress regimes. At depths below 1400 mbsf, occurrences of borehole stress indicators (breakouts and drilling-induced tensile fractures (DITFs)) are limited due to optimally controlled mud pressures. Two sets of breakouts (1616 and 1862 mbsf) and DITFs (1648 and 1884 mbsf) were jointly used to constrain stress states there, which yielded that Shmin is 79-85% of Sv and SHmax is nearly equal to Sv, suggesting a mixed stress regime for normal and strike-slip faulting (Sv ~ SHmax > Shmin). The range of constrained Shmin is consistent with the results from leak

  7. Contrasts in Faulting and Veining Across the Aseismic to Seismic Transition, Kodiak Accretionary Complex, Alaska

    NASA Astrophysics Data System (ADS)

    Rowe, C. D.; Thompson, E.; Moore, J. C.

    2002-12-01

    Structure and Character of Veined Zones in Kodiak Accretionary Prism Subduction thrust systems produce the world's largest earthquakes. The transition from aseismic to seismogenic faulting occurs at approximately 4 km depth. The chemical and physical controls on this transition are not well understood, but previous research indicates that phase transformations, fluid pressure changes, and formation of authigenic minerals and cements may produce changes in cohesion and coefficient of friction which control fault behavior. We have described and sampled areas of paleo faulting and fluid flow in an ancient subduction thrust system, Kodiak Archipelago, Alaska. We are comparing two formations: the upper Paleocene Ghost Rocks Fm., which previous work has shown to have been exposed to ~ 250° C and 12 km depth (well within the seismogenic zone) and the Eocene Sitkalidak Fm., which has been exposed to 100-125° C at 2.4-3.9 km depth, (accreted before it crossed the aseismic-seismogenic boundary.) Field observations confirmed earlier work and supported project hypotheses. The Ghost Rocks Fm. is characterized by discrete heavily veined zones meters to tens of meters thick. Individual veins in these zones commonly reach thickness of up to several centimeters and are primarily composed of clean calcite and quartz. In contrast, the Sitkalidak Fm. is characterized by a small volume of web-like networks of very fine veins rarely exceeding a few mm in thickness. These veins are composed of laumontite and "dirty" calcite. In the Sitkalidak Fm., stratal disruption is characterized by conjugate shear fracturing, leaving lustrous black residues on shear surfaces, followed by extensional fractures with veining, indicating rising fluid pressures. In the Ghost Rocks Fm., there is little evidence for conjugate shear fracturing. Stratal disruption is accomplished by extensive extensional fracturing and veining as well as ductile deformation and rotation of sediments under non-coaxial strain

  8. Oceanic, island arc, and back-arc remnants into eastern Kamchatka accretionary complexes

    SciTech Connect

    Fedorchuk, A.V.; Vishnevskaya, V.S.; Izvekov, I.N. )

    1990-06-01

    The Kamchatsky Mts. accretionary complex in the Eastern Kamchatka orogenic belt was studied for identification of the oceanic and suprasubduction components into accretionary wedges. That complex is divided into two tectonic units. The Lower unit is formed sedimentary and tectonic melanges containing arc-related components (Late Senonian volcaniclastics and boninitic gabbro) and oceanic fragments (Fe-Ti-tholeiites, ocean island basalts, and pelagic sediments of Valanginian to Turonian age). The Upper unit consists of ductile deformed oceanic cumulates from troctolites to Fe-Ti-gabbro, 151 to 172 Ma, which are intruded MORB-like diabases with suprasubduction characteristics, 122 to 141 Ma, and are overlain by basalts similar to latter. The Lower and Upper units are separated by a SW-dipping thrust, which is related by an ophiolitoclastic olistostrome of Late Campanian to Early Maestrichtian age. Both units are covered by Paleocene authoclastic deposits. They are all thrusted over the early Neogene island arc complex, 16 to 20 Ma. The Lower unit of the Kamchatsky Mys accretionary complex was originated in a shear zone between a Late Cretaceous island arc and an Early Cretaceous oceanic plate. The Upper unit represents a Jurassic oceanic remnant that formed a basement of Early Cretaceous back-arc or fore-arc basin. Both units were superposed in the latest Cretaceous. The Kamchatsky Mys accretionary complex was emplaced into the Eastern Kamchatka orogenic belt during late Neogene by collision of the early Neogene island arc.

  9. Generalization of Prism Adaptation

    ERIC Educational Resources Information Center

    Redding, Gordon M.; Wallace, Benjamin

    2006-01-01

    Prism exposure produces 2 kinds of adaptive response. Recalibration is ordinary strategic remapping of spatially coded movement commands to rapidly reduce performance error. Realignment is the extraordinary process of transforming spatial maps to bring the origins of coordinate systems into correspondence. Realignment occurs when spatial…

  10. Prism Adaptation in Schizophrenia

    ERIC Educational Resources Information Center

    Bigelow, Nirav O.; Turner, Beth M.; Andreasen, Nancy C.; Paulsen, Jane S.; O'Leary, Daniel S.; Ho, Beng-Choon

    2006-01-01

    The prism adaptation test examines procedural learning (PL) in which performance facilitation occurs with practice on tasks without the need for conscious awareness. Dynamic interactions between frontostriatal cortices, basal ganglia, and the cerebellum have been shown to play key roles in PL. Disruptions within these neural networks have also…

  11. Acoustic dispersive prism

    NASA Astrophysics Data System (ADS)

    Esfahlani, Hussein; Karkar, Sami; Lissek, Herve; Mosig, Juan R.

    2016-01-01

    The optical dispersive prism is a well-studied element, which allows separating white light into its constituent spectral colors, and stands in nature as water droplets. In analogy to this definition, the acoustic dispersive prism should be an acoustic device with capability of splitting a broadband acoustic wave into its constituent Fourier components. However, due to the acoustical nature of materials as well as the design and fabrication difficulties, there is neither any natural acoustic counterpart of the optical prism, nor any artificial design reported so far exhibiting an equivalent acoustic behaviour. Here, based on exotic properties of the acoustic transmission-line metamaterials and exploiting unique physical behaviour of acoustic leaky-wave radiation, we report the first acoustic dispersive prism, effective within the audible frequency range 800 Hz–1300 Hz. The dispersive nature, and consequently the frequency-dependent refractive index of the metamaterial are exploited to split the sound waves towards different and frequency-dependent directions. Meanwhile, the leaky-wave nature of the structure facilitates the sound wave radiation into the ambient medium.

  12. Acoustic dispersive prism.

    PubMed

    Esfahlani, Hussein; Karkar, Sami; Lissek, Herve; Mosig, Juan R

    2016-01-07

    The optical dispersive prism is a well-studied element, which allows separating white light into its constituent spectral colors, and stands in nature as water droplets. In analogy to this definition, the acoustic dispersive prism should be an acoustic device with capability of splitting a broadband acoustic wave into its constituent Fourier components. However, due to the acoustical nature of materials as well as the design and fabrication difficulties, there is neither any natural acoustic counterpart of the optical prism, nor any artificial design reported so far exhibiting an equivalent acoustic behaviour. Here, based on exotic properties of the acoustic transmission-line metamaterials and exploiting unique physical behaviour of acoustic leaky-wave radiation, we report the first acoustic dispersive prism, effective within the audible frequency range 800 Hz-1300 Hz. The dispersive nature, and consequently the frequency-dependent refractive index of the metamaterial are exploited to split the sound waves towards different and frequency-dependent directions. Meanwhile, the leaky-wave nature of the structure facilitates the sound wave radiation into the ambient medium.

  13. Dove prism heterodyne refractometer

    NASA Astrophysics Data System (ADS)

    Hsu, Cheng-Chih; Lee, Chia-Yun; Chu, Kuan-Ho; Wu, Tsai-Chen

    2015-10-01

    In this study, we proposed an alternative method, integrating a Dove prism and precision circular heterodyne interferometry, for measuring the refractive index and concentration of sodium chloride and hydrogen peroxide solutions with low phase error. Due to the optical properties of the Dove prism, the test light undergoes total internal reflection (TIR) at the interface between the test sample and the prism. The light beam travels in and out of the Dove prism while maintaining the same direction. Therefore, only slight alignment is required, leading to only small errors in the phase and refractive index. In this study, the phase error, refractive index error, and resolution of the concentration are approximated to be 0.003°, 2×10-5, and 1×10-3 M, respectively. The proposed method has the advantages of a simple optical configuration, ease of operation, little alignment required, and high stability, and it allows for high-precision measurement of the refractive index and concentration of the liquid sample.

  14. Project PRISM: Project Manual.

    ERIC Educational Resources Information Center

    Cunnion, Maryellen; And Others

    The first of three volumes of Project PRISM, a program designed to help classroom teachers (grades 6 through 8) provide for the needs of their gifted and talented students without removing those students from the mainstream of education, outlines the project's background and achievements. Sections review the following project aspects (sample…

  15. Project PRISM: Parent Information.

    ERIC Educational Resources Information Center

    Cunnion, Maryellen; And Others

    The second of three documents on Project PRISM, a program designed to help middle school classroom teachers provide for the needs of gifted and talented students without removing them from the mainstream, notes guidelines for parents. The following topics are addressed (sample subtopics in parentheses): characteristics of the gifted (common myths…

  16. Reflection by Porro Prisms

    NASA Astrophysics Data System (ADS)

    Greenslade, Thomas B.

    2010-04-01

    Students all know that reflection from a plane mirror produces an image that is reversed right to left and so cannot be read by anyone but Leonardo da Vinci, who kept his notes in mirror writing. A useful counter-example is the Porro prism, which produces an image that is not reversed.

  17. Acoustic dispersive prism

    PubMed Central

    Esfahlani, Hussein; Karkar, Sami; Lissek, Herve; Mosig, Juan R.

    2016-01-01

    The optical dispersive prism is a well-studied element, which allows separating white light into its constituent spectral colors, and stands in nature as water droplets. In analogy to this definition, the acoustic dispersive prism should be an acoustic device with capability of splitting a broadband acoustic wave into its constituent Fourier components. However, due to the acoustical nature of materials as well as the design and fabrication difficulties, there is neither any natural acoustic counterpart of the optical prism, nor any artificial design reported so far exhibiting an equivalent acoustic behaviour. Here, based on exotic properties of the acoustic transmission-line metamaterials and exploiting unique physical behaviour of acoustic leaky-wave radiation, we report the first acoustic dispersive prism, effective within the audible frequency range 800 Hz–1300 Hz. The dispersive nature, and consequently the frequency-dependent refractive index of the metamaterial are exploited to split the sound waves towards different and frequency-dependent directions. Meanwhile, the leaky-wave nature of the structure facilitates the sound wave radiation into the ambient medium. PMID:26739504

  18. Less-expensive Rochon prisms

    NASA Technical Reports Server (NTRS)

    Ammann, E. O.; Massey, G. A.

    1970-01-01

    Inexpensive Rochon prisms can be produced by substituting easily polished glass for one-half of the calcite. Reciprocal polarizing properties of a conventional Rochon prism are retained, and angular separation between ordinary and extraordinary rays is the same as in all-calcite prism.

  19. Paleozoic accretionary orogenesis in the eastern Beishan orogen: constraints from zircon U-Pb and 40Ar/39Ar geochronology

    NASA Astrophysics Data System (ADS)

    Ao, Songjian; Xiao, Wenjiao; Windley, Brian; Mao, Qigui

    2016-04-01

    The continental growth mechanism of the Altaids in Central Asia is still in controversy between models of continuous subduction-accretion versus punctuated accretion by closure of multiple oceanic basins. The Beishan orogenic belt, located in the southern Altaids, is a natural laboratory to address this controversy. Key questions that are heavily debated are: the closure time and subduction polarity of former oceans, the emplacement time of ophiolites, and the styles of accretion and collision. This paper reports new structural data, zircon ages and Ar-Ar dates from the eastern Beishan Orogen that provide information on the accretion process and tectonic affiliation of various terranes. Our geochronological and structural results show that the younging direction of accretion was northwards and the subduction zone dipped southwards under the northern margin of the Shuangyingshan micro-continent. This long-lived and continuous accretion process formed the Hanshan accretionary prism. Our field investigations show that the emplacement of the Xiaohuangshan ophiolite was controlled by oceanic crust subduction beneath the forearc accretionary prism of the Shuangyingshan-Mazongshan composite arc to the south. Moreover, we address the age and terrane affiliation of lithologies in the eastern Beishan orogen through detrital zircon geochronology of meta-sedimentary rocks. We provide new information on the ages, subduction polarities, and affiliation of constituent structural units, as well as a new model of tectonic evolution of the eastern Beishan orogen. The accretionary processes and crustal growth of Central Asia were the result of multiple sequences of accretion and collision of manifold terranes. Reference: Ao, S.J., Xiao, W., Windley, B.F., Mao, Q., Han, C., Zhang, J.e., Yang, L., Geng, J., Paleozoic accretionary orogenesis in the eastern Beishan orogen: Constraints from zircon U-Pb and 40Ar/39Ar geochronology. Gondwana Research, doi: http://dx.doi.org/10.1016/j

  20. Permissive tracts for sediment-hosted lead-zinc-silver deposits in Mauritania (phase V, deliverable 72): Chapter J1 in Second projet de renforcement institutionnel du secteur minier de la République Islamique de Mauritanie (PRISM-II)

    USGS Publications Warehouse

    Mauk, Jeffrey L.; Horton, John D.

    2012-01-01

    This report contains the USGS results of the PRISM-II Mauritania Minerals Project and is presented in cooperation with the Ministry of Petroleum, Energy, and Mines of the Islamic Republic of Mauritania. The Report is composed of separate chapters consisting of multidisciplinary interpretive reports with accompanying plates on the geology, structure, geochronology, geophysics, hydrogeology, geochemistry, remote sensing (Landsat TM and ASTER), and SRTM and ASTER digital elevation models of Mauritania. The syntheses of these multidisciplinary data formed the basis for additional chapters containing interpretive reports on 12 different commodities and deposit types known to occur in Mauritania, accompanied by countrywide mineral resource potential maps of each commodity/deposit type. The commodities and deposit types represented include: (1) Ni, Cu, PGE, and Cr deposits hosted in ultramafic rocks; (2) orogenic, Carlin-like, and epithermal gold deposits; (3) polymetallic Pb-Zn-Cu vein deposits; (4) sediment-hosted Pb-Zn-Ag deposits of the SEDEX and Mississippi Valley-type; (5) sediment-hosted copper deposits; ( 6) volcanogenic massive sulfide deposits; (7) iron oxide copper-gold deposits; (8) uranium deposits; (9) Algoma-, Superior-, and oolitic-type iron deposits; (10) shoreline Ti-Zr placer deposits; (11) incompatible element deposits hosted in pegmatites, alkaline rocks, and carbonatites, and; (12) industrial mineral deposits. Additional chapters include the Mauritanian National Mineral Deposits Database are accompanied by an explanatory text and the Mauritania Minerals Project GIS that contains all of the interpretive layers created by USGS scientists. Raw data not in the public domain may be obtained from the Ministry of Petroleum, Energy, and Mines in Nouakchott, Mauritania.

  1. Refraction, including prisms.

    PubMed

    Hiatt, R L

    1991-02-01

    The literature in the past year on refraction is replete with several isolated but very important topics that have been of interest to strabismologists and refractionists for many decades. The refractive changes in scleral buckling procedures include an increase in axial length as well as an increase in myopia, as would be expected. Tinted lenses in dyslexia show little positive effect in the nonasthmatic patients in one study. The use of spectacles or bifocals as a way to control increase in myopia is refuted in another report. It has been shown that in accommodative esotropia not all patients will be able to escape the use of bifocals in the teenage years, even though surgery might be performed. The hope that disposable contact lenses would cut down on the instance of giant papillary conjunctivitis and keratitis has been given some credence, and the conventional theory that sclerosis alone is the cause of presbyopia is attacked. Also, gas permeable bifocal contact lenses are reviewed and the difficulties of correcting presbyopia by this method outlined. The practice of giving an aphakic less bifocal addition instead of a nonaphakic, based on the presumption of increased effective power, is challenged. In the review of prisms, the majority of articles concern prism adaption. The most significant report is that of the Prism Adaptation Study Research Group (Arch Ophthalmol 1990, 108:1248-1256), showing that acquired esotropia in particular has an increased incidence of stable and full corrections surgically in the prism adaptation group versus the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

  2. Tectonic wedging in the forearc basin - Accretionary prism transition, Lesser Antilles forearc

    NASA Technical Reports Server (NTRS)

    Torrini, Rudolph, Jr.; Speed, Robert C.

    1989-01-01

    This paper describes regional structure of the inner forearc of the southern Lesser Antilles, which contains an extensive 50-70 km wide inner forearc deformation belt (IFDB) developed above crystalline basement of the undeformed forearc basin (FAB), close to and perhaps above its probable subduction trace with Atlantic lithosphere. The IFDB is analyzed, with emphasis placed on five transects across the belt, using mainly migrated seismic sections and balanced model cross sections. The IFDB features and its evolution are discussed, with special attention given to the major structures divided by early and late stages of development, paleobathymetric history, event timing, displacement and strain, and alternative tectonic explanations.

  3. Evolution of antivergent folds on a Paleozoic accretionary prism, Arkansas: An alternative view

    NASA Astrophysics Data System (ADS)

    Babaei, Abdolali

    1990-10-01

    Rocks around the western plunge of the Benton uplift in the Ouachita Mountains of western Arkansas show multiple periods of deformation during the Ouachita orogeny. Seismic-reflection interpretations and surface geology are consistent with a thick section of highly deformed Paleozoic rocks that are separated as thrust sheets by north-vergent regional-scale thrust faults. North-vergent folds develop in such a setting; however, south-vergent folds with the axial planes dipping opposite to the direction of underthrusting are also observed on the Benton uplift. Development of such folds has been explained by models such as mechanical decoupling along zones of low shear strength in trenches, backthrusting, and backfolding, but none explains the south-vergent folds of the Benton uplift, mostly because of lack of adequate field data. Geometrical analyses show that reactivation of thrust faults during a secondary phase of deformation tightened and reoriented open folds of an initial phase and, as a result, developed the macroscopic and mesoscopic antivergent folds in the Benton uplift. Curvilinear map traces of the thrust faults and broad open folds that refold earlier structures indicate that there was continuous deformation after the development of antivergent folds.

  4. Evolution of antivergent folds on a Paleozoic accretionary prism, Arkansas: An alternative view

    SciTech Connect

    Babaei, A. )

    1990-10-01

    Rocks around the western plunge of the Benton uplift in the Ouachita Mountains of western Arkansas show multiple periods of deformation during the Ouachita orogeny. Seismic-reflection interpretations and surface geology are consistent with a thick section of highly deformed Paleozoic rocks that are separated as thrust sheets by north-vergent regional-scale thrust faults. North-vergent folds develop is such a setting; however, south-vergent folds with the axial planes dipping opposite to the direction of underthrusting are also observed on the Benton uplift. Development of such folds has been explained by models such as mechanical decoupling along zones of low shear strength in trenches, backthrusting, and backfolding, but none explains the south-vergent folds of the Benton uplift, mostly because of lack of adequate field data. Geometrical analyses show the reactivation of thrust faults during a secondary phase of deformation tightened and reoriented open folds of an initial phase and, as a result, developed the macroscopic and mesoscopic antivergent folds in the Benton uplift. Curvilinear map traces of the thrust faults and broad open folds that refold earlier structures indicate that there was continuous deformation after the development of antivergent folds.

  5. High precision prism scanning system

    NASA Astrophysics Data System (ADS)

    García-Torales, G.; Flores, J. L.; Muñoz, Roberto X.

    2007-03-01

    Risley prisms are commonly used in continuous scanning manner. Each prism is capable of rotating separately about a common axis at different speeds. Scanning patterns are determined by the ratios of the wedge angles, the speed and direction of rotation of both prisms. The use of this system is conceptually simple. However, mechanical action in most applications becomes a challenge often solved by the design of complex control algorithms. We propose an electronic servomotor system that controls incremental and continuous rotations of the prisms wedges by means of an auto-tuning PID control using a Adaline Neural Network Algorithm, NNA.

  6. Acoustic Velocity Of The Sediments Offshore Southwestern Taiwan

    NASA Astrophysics Data System (ADS)

    Tsai, C.; Liu, C.; Huang, P.

    2004-12-01

    Along the Manila Trench south of 21øXN, deep-sea sediments are being underthrusted beneath the Taiwan accretionary prism which is composed of the Kaoping Slope and Hengchun Ridge. Offshore southwestern Taiwan, foreland sediments and Late Miocene strata of the Tainan Basin are being accreted onto the fold-and thrust belt of the syn-collision accretionary wedge of the Kaoping Slope. The Kaoping Slope consists of thick Neogene to Recent siliciclastics deformed by fold-and-thrust structures and mud diapers. These Pliocene-Quaternary sediments deposited in the Kaoping Shelf and upper slope area are considered to be paleo-channel deposits confined by NNE-SSW trend mud diapiric structure. Seismic P-wave velocities of the sediment deposited in the Kaoping Shelf and Kaoping Slope area are derived from mutichannel seismic reflection data and wide-angle reflection and refraction profiles collected by sonobuoys. Sediment velocity structures constrained from mutichannel seismic reflection data using velocity spectrum analysis method and that derived from sonobuoy data using tau-sum inversion method are compared, and they both provide consistent velocity structures. Seismic velocities were analyzed along the seismic profile from the surface to maximum depths of about 2.0 km below the seafloor. Our model features a sediment layer1 with 400 ms in thickness and a sediment layer2 with 600 ms in thickness. For the shelf sediments, we observe a linear interval velocity trend of V=1.53+1.91T in layer1, and V=1.86+0.87T in layer2, where T is the one way travel time within the layer. For the slop sediment, the trend of V=1.47+1.93T in layer1, and V=1.70+1.55T in layer2. The layer1¡¦s velocities gradients are similar between the shelf (1.91 km/sec2) and the slope(1.93 km/sec2). It means layer1 distributes over the slope and shelf widely. The result of the sediment velocity gradients in this area are in good agreement with that reported for the south Atlantic continental margins.

  7. Compound prism design principles, II: triplet and Janssen prisms.

    PubMed

    Hagen, Nathan; Tkaczyk, Tomasz S

    2011-09-01

    Continuing the work of the first paper in this series [Appl. Opt. 50, 4998-5011 (2011)], we extend our design methods to compound prisms composed of three independent elements. The increased degrees of freedom of these asymmetric prisms allow designers to achieve greatly improved dispersion linearity. They also, however, require a more careful tailoring of the merit function to achieve design targets, and so we present several new operands for manipulating the compound prisms' design algorithm. We show that with asymmetric triplet prisms, one can linearize the angular dispersion such that the spectral sampling rate varies by no more than 4% across the entire visible spectral range. Doing this, however, requires large prisms and causes beam compression. By adding a beam compression penalty to the merit function, we show that one can compromise between dispersion linearity and beam compression in order to produce practical systems. For prisms that do not deviate the beam, we show that Janssen prisms provide a form that maintains the degrees of freedom of the triplet and that are capable of up to 32° of dispersion across the visible spectral range. Finally, in order to showcase some of the design flexibility of three-element prisms, we also show how to design for higher-order spectral dispersion to create a two-dimensional spectrum.

  8. Anatexis of accretionary wedge, Pacific-type magmatism, and formation of vertically stratified continental crust in the Altai Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Jiang, Y. D.; Schulmann, K.; Sun, M.; Å típská, P.; Guy, A.; Janoušek, V.; Lexa, O.; Yuan, C.

    2016-12-01

    Granitoid magmatism and its role in differentiation and stabilization of the Paleozoic accretionary wedge in the Chinese Altai are evaluated in this study. Voluminous Silurian-Devonian granitoids intruded a greywacke-dominated Ordovician sedimentary succession (the Habahe Group) of the accretionary wedge. The close temporal and spatial relationship between the regional anatexis and the formation of granitoids, as well as their geochemical similarities including rather unevolved Nd isotopic signatures and the strong enrichment of large-ion lithophile elements relative to many of the high field strength elements, may indicate that the granitoids are product of partial melting of the accretionary wedge rocks. Whole-rock geochemistry and pseudosection modeling show that regional anatexis of fertile sediments could have produced a large amount of melts compositionally similar to the granitoids. Such process could have left a high-density garnet- and/or garnet-pyroxene granulite residue in the deep crust, which can be the major reason for the gravity high over the Chinese Altai. Our results show that melting and crustal differentiation can transform accretionary wedge sediments into vertically stratified and stable continental crust. This may be a key mechanism contributing to the peripheral continental growth worldwide.

  9. Through a prism darkly: re-evaluating prisms and neglect.

    PubMed

    Striemer, Christopher L; Danckert, James A

    2010-07-01

    Many studies have demonstrated that prism adaptation can reduce several symptoms of visual neglect: a disorder in which patients fail to respond to information in contralesional space. The dominant framework to explain these effects proposes that prisms influence higher order visuospatial processes by acting on brain circuits that control spatial attention and perception. However, studies that have directly examined the influence of prisms on perceptual biases inherent to neglect have revealed very few beneficial effects. We propose an alternative explanation whereby many of the beneficial effects of prisms arise via the influence of adaptation on circuits in the dorsal visual stream controlling attention and visuomotor behaviors. We further argue that prisms have little influence on the pervasive perceptual biases that characterize neglect.

  10. An unusual occurrence of mafic accretionary lapilli in deep-marine volcaniclastics on 'Eua, Tonga: Palaeoenvironment and process

    NASA Astrophysics Data System (ADS)

    Cunningham, J. K.; Beard, A. D.

    2014-03-01

    Reports of occurrences of accretionary lapilli on Earth, whether in historic time or in the geological record, are restricted to subaerial environments or to shallow marine environments when faunal evidence exists to determine palaeodepths. The proximity of the deep ocean to subduction zones/island arcs (where moist explosive volcanism conducive to ash aggregate formation is common) makes this surprising. In this paper, accretionary lapilli are reported within Middle Miocene mafic glass-rich volcaniclastics on 'Eua, the island closest to the Tonga Trench, a persistent high in the frontal arc basin. The glass in the accretionary lapilli has been subjected to advanced palagonitisation, but concentric layers marked by micro-aggregates containing shard-shaped particles survive to determine one group of occurrences as layered accretionary lapilli. The palaeoenvironment, as established by pelagic microfauna, is clearly deep marine, not less than 1600 m. The host rocks, typically gravel/sand in grain size, contain sedimentary structures (normal grading to inverse and normal-to-inverse grading, lack of grading, large-scale cross-bedding, slump bedding and sedimentary dykes) suggesting that the full spectrum of sediment gravity flow types, including less ordered debris flows, has been active. In an island arc environment, a range of sediment gravity flow types can be initiated, some by pyroclastic flows entering the sea. However, the thin beds of accretionary lapilli do not exhibit features of sediment gravity flow deposits or those of submarine pyroclastic flows. Possible transport processes must account for the matrix between the ash aggregates, which is either coarse-grained or absent. Modelling of particle descent times to 1600 m through a sea water column provides one explanation for the features displayed.

  11. Multibeam collimator uses prism stack

    NASA Technical Reports Server (NTRS)

    Minott, P. O.

    1981-01-01

    Optical instrument creates many divergent light beams for surveying and machine element alignment applications. Angles and refractive indices of stack of prisms are selected to divert incoming laser beam by small increments, different for each prism. Angles of emerging beams thus differ by small, precisely-controlled amounts. Instrument is nearly immune to vibration, changes in gravitational force, temperature variations, and mechanical distortion.

  12. Fate of mass-transport deposits in convergent margins: Super- or sub-critical state in accretionary- or non-accretionary slope toes

    NASA Astrophysics Data System (ADS)

    Ogawa, Y.; Kawamura, K.; Anma, R.

    2011-12-01

    Co-seismic mass-transportation is evidenced by voluminous bathymetric change during subduction type earthquakes of magnitude 8 or 9 class, exemplified by the March 11 2011 Tohoku earthquake in the Japan trench, where 50 m horizontal dislocation with 10 m vertical uplift was detected for the large tsunami(Kawamura et al., this session). On account of such successive mass transportation in the trench slope toe being slid into the grabens at the trench axis of the Pacific plate side lead the continuous migration of the trench slope toward the Honshu arc since the middle Miocene, playing the efficient role for the tectonic erosion (Hilde, 1983 Tectonophysics; von Huene & Lallemand, 1990 GSAB). Previously accreted materials of the former prism are largely exposed in the inner slope along the Japan trench, and the present slope is composed of brecciated, calcareous cemented mudstone and sandstone of middle Miocene age according to the submersible observation and sampling (Ogawa, 2011 Springer Book). Due to this trench migration landward, the island volcanic arc front vastly retreated to the west since the middle Miocene for more than 100 km. Such mass transportation occurred compensating the slope instability due to super-critical state of the slope angle. However, the tectonic erosion process is apt not to be preserved in ancient prisms (or "terranes") because they are entirely lost from the surface by erosion and subduction. On the other hand, many examples of such gravitational mass transportation deposits, slid-slumped deposits, liquefied and injected bodies, which are totally classified as mélanges or chaotic deposits, or olistostromes are preserved in ancient on-land prisms such as in the Shimanto and Miura-Boso accretionary complexes(Yamamoto et al., 2009 Island Arc), because they are preserved by offscraping process during plate subduction. Similar processes are known from the present Nankai prism surface and were observed by submersible and bathymetric survey

  13. Neoproterozoic and Paleozoic accretionary orogens exposed at different crustal levels

    NASA Astrophysics Data System (ADS)

    Kroener, A.

    2002-12-01

    Accretionary orogens in the upper crust are dominated by trench and forearc deposits, obducted ophiolite fragments, exotic terranes and well defined structural boundaries such as major shear zones. The Neoproterozoic Arabian-Nubian shield (ANS) of western Arabia and NE Africa, the huge terrain of the Neoproterozoic to Palaeozoic Central Asian mobile belt (CAMB) and the present Indonesian Archipelago are prime examples of such orogens. In the ANS and CAMB, field relationships, rock associations, differences in structural style and metamorphic grade, and geochronology have led to the recognition of terrane assemblages that are related to processes of lateral accretion as now observed in the southwest Pacific and lasting for several hundred my. In the ANS, ocean crust and arc formation began about 900 Ma ago, and terrane accretion was completed by ~600 Ma, whereas in the CAMB the oldest oceanic crust formed some 1000 Ma ago, and terrane accretion continued into the late Palaeozoic. Typical rock associations are trench and forearc sediments, island-arc volcanics, calc-alkaline granitoids, dismembered ophiolite suites and gneissic rocks (microcontinents?) constituting exotic terranes and mostly of distinctly older age and more complex tectono-metamorphic history than the surrounding lower grade rocks. Shear zones frequently separate the terranes and in the ANS also constitue seismic discontinuities extending to the lower crust. The middle to lower crustal high grade assemblages of the Neoproterozoic Mozambique belt (MB) of East Africa, Madagascar, southernmost India, Sri Lanka and East Antarctica are considered to be a deep crustal analogue to the upper crustal accretionary belts described above. Typical characteristics are (1) voluminous calc-alkaline granitoid suites, now layered gneisses, and interpreted as root zones of arc terranes, (2) tectonic interdigitation of Archaean to Palaeoproterozoic gneisses with Neoproterozoic rocks, probably brought about during

  14. Thrust fault growth within accretionary wedges: New Insights from 3D seismic reflection data

    NASA Astrophysics Data System (ADS)

    Orme, H.; Bell, R. E.; Jackson, C. A. L.

    2015-12-01

    The shallow parts of subduction megathrust faults are typically thought to be aseismic and incapable of propagating seismic rupture. The 2011 Tohoku-Oki earthquake, however, ruptured all the way to the trench, proving that in some locations rupture can propagate through the accretionary wedge. An improved understanding of the structural character and physical properties of accretionary wedges is therefore crucial to begin to assess why such anomalously shallow seismic rupture occurs. Despite its importance, we know surprisingly little regarding the 3D geometry and kinematics of thrust network development in accretionary prisms, largely due to a lack of 3D seismic reflection data providing high-resolution, 3D images of entire networks. Thus our current understanding is largely underpinned by observations from analogue and numerical modelling, with limited observational data from natural examples. In this contribution we use PSDM, 3D seismic reflection data from the Nankai margin (3D Muroto dataset, available from the UTIG Academic Seismic Portal, Marine Geoscience Data System) to examine how imbricate thrust fault networks evolve during accretionary wedge growth. Previous studies have reported en-echelon thrust fault geometries from the NW part of the dataset, and have related this complex structure to seamount subduction. We unravel the evolution of faults within the protothrust and imbricate thrust zones by interpreting multiple horizons across faults and measuring fault displacement and fold amplitude along-strike; by doing this, we are able to investigate the three dimensional accrual of strain. We document a number of local displacement minima along-strike of faults, suggesting that, the protothrust and imbricate thrusts developed from the linkage of smaller, previously isolated fault segments. We also demonstrate that the majority of faults grew upward from the décollement, although there is some evidence for downward fault propagation. Our observations

  15. Thrust fault segmentation and downward fault propagation in accretionary wedges: New Insights from 3D seismic reflection data

    NASA Astrophysics Data System (ADS)

    Orme, Haydn; Bell, Rebecca; Jackson, Christopher

    2016-04-01

    The shallow parts of subduction megathrust faults are typically thought to be aseismic and incapable of propagating seismic rupture. The 2011 Tohoku-Oki earthquake, however, ruptured all the way to the trench, proving that in some locations rupture can propagate through the accretionary wedge. An improved understanding of the structural character and physical properties of accretionary wedges is therefore crucial to begin to assess why such anomalously shallow seismic rupture occurs. Despite its importance, we know surprisingly little regarding the 3D geometry and kinematics of thrust network development in accretionary prisms, largely due to a lack of 3D seismic reflection data providing high-resolution, 3D images of entire networks. Thus our current understanding is largely underpinned by observations from analogue and numerical modelling, with limited observational data from natural examples. In this contribution we use PSDM, 3D seismic reflection data from the Nankai margin (3D Muroto dataset, available from the UTIG Academic Seismic Portal, Marine Geoscience Data System) to examine how imbricate thrust fault networks evolve during accretionary wedge growth. We unravel the evolution of faults within the protothrust and imbricate thrust zones by interpreting multiple horizons across faults and measuring fault displacement and fold amplitude along-strike; by doing this, we are able to investigate the three dimensional accrual of strain. We document a number of local displacement minima along-strike of faults, suggesting that, the protothrust and imbricate thrusts developed from the linkage of smaller, previously isolated fault segments. Although we often assume imbricate faults are likely to have propagated upwards from the décollement we show strong evidence for fault nucleation at shallow depths and downward propagation to intersect the décollement. The complex fault interactions documented here have implications for hydraulic compartmentalisation and pore

  16. Compound prism design principles, I

    PubMed Central

    Hagen, Nathan; Tkaczyk, Tomasz S.

    2011-01-01

    Prisms have been needlessly neglected as components used in modern optical design. In optical throughput, stray light, flexibility, and in their ability to be used in direct-view geometry, they excel over gratings. Here we show that even their well-known weak dispersion relative to gratings has been overrated by designing doublet and double Amici direct-vision compound prisms that have 14° and 23° of dispersion across the visible spectrum, equivalent to 800 and 1300 lines/mm gratings. By taking advantage of the multiple degrees of freedom available in a compound prism design, we also show prisms whose angular dispersion shows improved linearity in wavelength. In order to achieve these designs, we exploit the well-behaved nature of prism design space to write customized algorithms that optimize directly in the nonlinear design space. Using these algorithms, we showcase a number of prism designs that illustrate a performance and flexibility that goes beyond what has often been considered possible with prisms. PMID:22423145

  17. 21 CFR 886.1660 - Gonioscopic prism.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Gonioscopic prism. 886.1660 Section 886.1660 Food... DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1660 Gonioscopic prism. (a) Identification. A gonioscopic prism is a device that is a prism intended to be placed on the eye to study the anterior...

  18. 21 CFR 886.1660 - Gonioscopic prism.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Gonioscopic prism. 886.1660 Section 886.1660 Food... DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1660 Gonioscopic prism. (a) Identification. A gonioscopic prism is a device that is a prism intended to be placed on the eye to study the anterior...

  19. 21 CFR 886.1660 - Gonioscopic prism.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Gonioscopic prism. 886.1660 Section 886.1660 Food... DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1660 Gonioscopic prism. (a) Identification. A gonioscopic prism is a device that is a prism intended to be placed on the eye to study the anterior...

  20. 21 CFR 886.1660 - Gonioscopic prism.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Gonioscopic prism. 886.1660 Section 886.1660 Food... DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1660 Gonioscopic prism. (a) Identification. A gonioscopic prism is a device that is a prism intended to be placed on the eye to study the anterior...

  1. 21 CFR 886.1660 - Gonioscopic prism.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Gonioscopic prism. 886.1660 Section 886.1660 Food... DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1660 Gonioscopic prism. (a) Identification. A gonioscopic prism is a device that is a prism intended to be placed on the eye to study the anterior...

  2. Prism Window for Optical Alignment

    NASA Technical Reports Server (NTRS)

    Tang, Hong

    2008-01-01

    A prism window has been devised for use, with an autocollimator, in aligning optical components that are (1) required to be oriented parallel to each other and/or at a specified angle of incidence with respect to a common optical path and (2) mounted at different positions along the common optical path. The prism window can also be used to align a single optical component at a specified angle of incidence. Prism windows could be generally useful for orienting optical components in manufacture of optical instruments. "Prism window" denotes an application-specific unit comprising two beam-splitter windows that are bonded together at an angle chosen to obtain the specified angle of incidence.

  3. Prism beamswitch for radio telescopes.

    PubMed

    Payne, J M; Ulich, B L

    1978-12-01

    A dielectric prism and switching mechanism have been constructed for beamswitching a Cassegrain radio telescope. Spatially extended radio sources may be mapped without significant confusion utilizing the sensitivity and stability inherent in the conventional Dicke radiometer.

  4. Confined deep water system development on the accretionary wedge (Miocene, Kahramanmaraş Foreland Basin, S turkey)

    NASA Astrophysics Data System (ADS)

    Gül, Murat; Cronin, Bryan T.; Gürbüz, Kemal

    2012-09-01

    According to theoretical studies, the foreland basin consists of: accretionary wedge (including wedge top or piggyback basin), foredeep, forebulge and backbulge depozones. All of them are parallel to the orogenic belts of the overlying and underlying plates. The closure of the southern branch of the Neotethys during the Late Cretaceous led to an oblique collision of the Arabian Plate and the Anatolide-Taurides Platform, leading to the development of the Miocene Kahramanmaraş Foreland Basin (KFB). Thus, the promontory shape of the Arabian Plate prevented the development of an accretionary wedge parallel to the orogenic belt. The accretionary wedge of the KFB includes blocks of various sizes and age (mainly Mesozoic limestone) scattered within an Early Tertiary matrix (mass wasting deposits and shallow to deep marine sediments). At the beginning of the Miocene, transtensional tectonism led to the development of half-graben basins on top of the accretionary wedge. These basins (namely; the Tekir and Çukurhisar) also cut the foredeep of the KFB obliquely (in contrast with the theoretical study). This paper focuses on the evolution and fillings of those basins. Initially, claystone and basin margin reef deposits filled the half-graben basins as a consequence of the Lower Miocene sea invasion. Then, long and narrow conglomeratic channels starting from the northern edge of the basins (fan-delta) progressed southwards, passing into sandy lobes, then into claystones. An activation of the boundary faults of the wedge top basin stopped the progression of the Lower-Middle Miocene sediments and led to their deformation. Then, the sedimentation of the KFB shifted towards the basin centre during the Middle Miocene.

  5. The Saint-Daniel Melange: Evolution of an accretionary complex in the Dunnage Terrane of the Quebec Appalachians

    NASA Astrophysics Data System (ADS)

    Cousineau, Pierre A.; St-Julien, Pierre

    1992-08-01

    The Saint-Daniel Mélange is part of a series of mélanges located along the Baie Verte-Brompton line in the Northern Appalachians. This line marks the suture between rocks of oceanic affinities and those of the ancient passive margin of North America with which they collided during the Taconian (Middle to Late Ordovician) orogeny. The Saint-Daniel Mélange contains a wide variety of lithologies including well-bedded to dismembered sedimentary sequences, pebbly mudstone, olistostromes, and slivers of igneous and metamorphic rocks. Black shales with interbeds of green shale, calcareous siltstone, or sandstone are the dominant units. They exhibit various stages of mélange formation such as those present in shallow parts of an accretionary complex. Units of oceanic origin include sediments derived from the forearc basin and slivers of an ophiolite and of a magmatic arc. Units derived from sediments of the passive margin of North America are also present. The ratio between these various lithologies changes greatly within the mélange on a kilometric scale along strike. The Saint-Daniel Mélange is a structural complex in which the various units were assigned a sequential order mimicking a stratigraphic order. The Saint-Daniel Mélange is interpreted as the relict of an accretionary complex because of its actual structural position within the Northern Appalachians and because all its lithologies and their structural fabric can be found in modern accretionary complexes.

  6. Progressive deformation of the Chugach accretionary complex, Alaska, during a paleogene ridge-trench encounter

    USGS Publications Warehouse

    Kusky, Timothy M.

    1997-01-01

    west and 50 Ma in the east. Exhumation of deeper levels of the southern Alaska accretionary wedge and formation of this late fault array is interpreted as a critical taper adjustment to subduction of progressively younger oceanic lithosphere yielding a shallower basal de´collement dip as the Kula-Farallon ridge approached the accretionary prism. The late structures also record different kinematic regimes associated with subduction of different oceanic plates, before and after ridge subduction. Prior to triple junction passage, subduction of the Farallon plate occurred at nearly right angles to the trench axis, whereas after triple junction migration, subduction of the Kula plate involved a significant component of dextral transpression and northward translation of the Chugach terrane. The changes in kinematics are apparent in the sequence of late structures from: (1) thrusting; (2) near-trench plutonism associated with normal + strike-slip faulting; (3) very late gouge-filled dextral faults.

  7. Laser system with partitioned prism

    SciTech Connect

    Nettleton, J. E.; Barr, D. N.

    1985-03-26

    An array of optical frequency-sensitive elements such as diffraction gratings or interference filters are arranged in a row, and the optical path of the laser cavity can be directed to include one of these elements. A partitioned optical prism consisting of a triangular portion and one or more paralleogramatic portions are used to direct the path. Between the portions are piezoelectric elements which, when energized, expand to provide an air gap between the portions and to allow total reflection of an optical ray at the surface of the prism next to the gap.

  8. Episodic fluid flow in the Nankai accretionary complex: Timescale, geochemistry, flow rates, and fluid budget

    USGS Publications Warehouse

    Saffer, D.M.; Bekins, B.A.

    1998-01-01

    Down-hole geochemical anomalies encountered in active accretionary systems can be used to constrain the timing, rates, and localization of fluid flow. Here we combine a coupled flow and solute transport model with a kinetic model for smectite dehydration to better understand and quantify fluid flow in the Nankai accretionary complex offshore of Japan. Compaction of sediments and clay dehydration provide fluid sources which drive the model flow system. We explicitly include the consolidation rate of underthrust sediments in our calculations to evaluate the impact that variations in this unknown quantity have on pressure and chloride distribution. Sensitivity analysis of steady state pressure solutions constrains bulk and flow conduit permeabilities. Steady state simulations with 30% smectite in the incoming sedimentary sequence result in minimum chloride concentrations at site 808 of 550 mM, but measured chlorinity is as low as 447 mM. We simulate the transient effects of hydrofracture or a strain event by assuming an instantaneous permeability increase of 3-4 orders of magnitude along a flow conduit (in this case the de??collement), using steady state results as initial conditions. Transient results with an increase in de??collement permeability from 10-16 m2 to 10-13 m2 and 20% smectite reproduce the observed chloride profile at site 808 after 80-160 kyr. Modeled chloride concentrations are highly sensitive to the consolidation rate of underthrust sediments, such that rapid compaction of underthrust material leads to increased freshening. Pressures within the de??collement during transient simulations rise rapidly to a significant fraction of lithostatic and remain high for at least 160 kyr, providing a mechanism for maintaining high permeability. Flow rates at the deformation front for transient simulations are in good agreement with direct measurements, but steady state flow rates are 2-3 orders of magnitude smaller than observed. Fluid budget calculations

  9. Preserving with Prisms: Producing Nets

    ERIC Educational Resources Information Center

    Prummer, Kathy E.; Amador, Julie M.; Wallin, Abraham J.

    2016-01-01

    Two mathematics teachers in a small rural school decided to create a task that would engage seventh graders. The goal of the real-world activity was to help students develop geometric and spatial reasoning and to support their understanding of volume of rectangular prisms. The impetus for the task came from the teachers' desire to engage students…

  10. Rotatable prism for pan and tilt

    NASA Technical Reports Server (NTRS)

    Ball, W. B.

    1980-01-01

    Compact, inexpensive, motor-driven prisms change field of view of TV camera. Camera and prism rotate about lens axis to produce pan effect. Rotating prism around axis parallel to lens produces tilt. Size of drive unit and required clearance are little more than size of camera.

  11. Ferromanganese nodules from MANOP Sites H, S, and R-Control of mineralogical and chemical composition by multiple accretionary processes

    USGS Publications Warehouse

    Dymond, J.; Lyle, M.; Finney, B.; Piper, D.Z.; Murphy, K.; Conard, R.; Pisias, N.

    1984-01-01

    The chemical composition of ferromanganese nodules from the three nodule-bearing MANOP sites in the Pacific can be accounted for in a qualitative way by variable contributions of distinct accretionary processes. These accretionary modes are: 1. (1) hydrogenous, i.e., direct precipitation or accumulation of colloidal metal oxides in seawater, 2. (2) oxic diagenesis which refers to a variety of ferromanganese accretion processes occurring in oxic sediments; and 3. (3) suboxic diagenesis which results from reduction of Mn+4 by oxidation of organic matter in the sediments. Geochemical evidence suggests processes (1) and (2) occur at all three MANOP nodule-bearing sites, and process (3) occurs only at the hemipelagic site, H, which underlies the relatively productive waters of the eastern tropical Pacific. A normative model quantitatively accounts for the variability observed in nearly all elements. Zn and Na, however, are not well explained by the three end-member model, and we suggest that an additional accretionary process results in greater variability in the abundances of these elements. Variable contributions from the three accretionary processes result in distinct top-bottom compositional differences at the three sites. Nodule tops from H are enriched in Ni, Cu, and Zn, instead of the more typical enrichments of these elements in nodule bottoms. In addition, elemental correlations typical of most pelagic nodules are reversed at site H. The three accretionary processes result in distinct mineralogies. Hydrogenous precipitation produces ??MnO2. Oxic diagenesis, however, produces Cu-Ni-rich todorokite, and suboxic diagenesis results in an unstable todorokite which transforms to a 7 A?? phase ("birnessite") upon dehydration. The presence of Cu and Ni as charge-balancing cations influence the stability of the todorokite structure. In the bottoms of H nodules, which accrete dominantly by suboxic diagenesis, Na+ and possibly Mn+2 provide much of the charge balance for

  12. Long Term Observations of Subsurface Pore Pressure in the Kumano Basin and Upper Accretionary Wedge along the NanTroSIEZE Transect, offshore Japan: Signals from the 2011 Tohoku Earthquake

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Saffer, D. M.

    2013-12-01

    Subsurface pore pressure as a sensitive measure of strain and formation properties has provided insights into the wide range of fault slip behaviors, contributing to the understanding of fault and earthquake mechanics. Pore pressures from off shore borehole observatory are especially important, as 1) they are the only detectable signals of small and slow events; 2) they provide our only access to the outer forearc, where the tsunami hazards are triggered by the fault slip. As part of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) a suite of borehole sensors were installed as part of a long-term borehole observatory at IODP Site C0002, during IODP Expedition # 332 in December of 2010. The observatory includes a broadband seismometer, short period geophones, a volumetric strainmeter, temperature sensors, an accelerometer, and formation pore pressure monitoring at two depths: one in the mudstones of the Kumano Basin in an interval spanning 757-780 meters below seafloor (mbsf), and a second in the uppermost accretionary wedge in an interval from 937 - 980 mbsf. Here, we report on pore pressure records acquired at a sampling frequency of 1/60 Hz, spanning the period from December 2010 to January 2013, which were recovered in early 2013. We observe a clear hydraulic signal from March 11, 2011 Tohoku earthquake and aftershocks, including both dynamic pore pressure changes during passage of surface waves and shifts in formation pressure following the event. Pressure exhibit an increase of ~3 kPa in the upper sediment screened interval following the earthquake, and decrease by ~5 kPa in the accretionary prism interval. Both of the offset changes persist through the end of the data recording. These pore pressure changes may reflect static stress changes from the earthquake, or local site effects related to shaking. We also observe a clear increase in formation pore pressures associated with drilling operations at nearby holes in November and December 2012. These

  13. Accretionary Lapilli (Carbonate Spherules) at the Cretaceous-Paleogene ('KT') Boundary in Belize (Central America)

    NASA Astrophysics Data System (ADS)

    King, D. T.; Petruny, L. W.

    2013-08-01

    The Chicxulub impact event produced accretionary lapilli (or carbonate spherules) that fell across a wide area. This paper compares Chicxulub ('KT') accretionary lapilli from two sites in Belize: Albion Island and Armenia.

  14. Diffractively corrected counter-rotating Risley prisms.

    PubMed

    Nie, Xin; Yang, Hongfang; Xue, Changxi

    2015-12-10

    Using the vector refraction equation and the vector diffraction equation, we obtain the expressions of the direction cosines of the refractive rays for the two wedge prisms, and the direction cosines of the diffractive rays for two wedge grisms, in which diffractive gratings were etched into the prism faces to correct the chromatic aberrations. A mathematical model between the two vector equations is proposed to compare the difference angle chromatic aberrations when the Risley prisms/grisms are rotating at different angles. We conclude that the use of diffractively corrected prisms offers a new method to correct chromatic aberrations in Risley prisms.

  15. A Liquid Prism for Refractive Index Studies

    NASA Astrophysics Data System (ADS)

    Edmiston, Michael D.

    2001-11-01

    A hollow glass prism filled with liquid becomes a "liquid prism". A simple method for constructing hollow glass prisms is presented. A method is given for a demonstration that uses the liquid prism with a laser or laser pointer so the audience can observe differences in refractive index for various liquids. The demonstration provides a quick and easy determination of the sugar content of soft drinks and juices. The prism makes it easy to determine a numerical value for the refractive index of a liquid.

  16. Geology of the Idonnappu Belt, central Hokkaido, Japan: Evolution of a Cretaceous Accretionary Complex

    NASA Astrophysics Data System (ADS)

    Kiyokawa, Shoichi

    1992-12-01

    The Cretaceous Idonnappu Belt, located along the western Hidaka Mountains of central Hokkaido Island in Japan, records evidence of west to northwest directed underthrusting of oceanic crust. The Idonnappu fault divides the Idonnappu Belt into two subbelts; the western Oku-niikappu (ON) subbelt and the eastern Koiboku (KO) subbelt. The ON subbelt is dominated by a melange facies. It includes various thicknesses of pillow basalts, bedded radiolarian cherts, limestones, and greenish siliceous shales, all of which are intermixed with a highly sheared shaley matrix that displays a scaly cleavage. The KO subbelt is dominated by a thick flysch sequence and alternations of sandstone and shale with thin tectonic melange. The stratigraphic sequences within these belts usually young toward the west and display westward vergent structures. Outcrop- to microscopic-scale structures in the melange zone of the Idonnappu Belt, however, suggest eastward vergence. Detailed biostratigraphic studies show that structural packages young toward the east ranging in age from Lower to Upper Cretaceous. These observations are consistent with an accretionary prism model in which oceanic crust is underthrust toward the west or north west. In the middle Miocene, a change to westward vergence was caused by uplift of the Hidaka Mountains.

  17. New access to the deep interior of the Nankai accretionary complex and comprehensive characterization of subduction inputs and recent mega splay fault activity (IODP-NanTroSEIZE Expedition 338)

    NASA Astrophysics Data System (ADS)

    Strasser, Michael; Moore, Gregory F.; Kanagawa, Kyuichi; Dugan, Brandon; Fabbri, Olivier; Toczko, Sean; Maeda, Lena

    2013-04-01

    The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is a coordinated, multi-expedition Integrated Ocean Drilling Program (IODP) drilling project designed to investigate fault mechanics and seismogenesis along subduction megathrusts through direct sampling, in situ measurements, and long-term monitoring in conjunction with allied laboratory and numerical modeling studies. IODP Expedition 338 (1 October 2012 - 13 January 2013), extended riser Hole C0002F from 856 meters below the sea floor (mbsf) to 2005 mbsf. Site C0002 is the centerpiece of the NanTroSEIZE project, and is planned to be deepened to eventually reach the seismogenic fault zone during upcoming drilling expeditions. The original Exp. 338 operational plan to case the hole to 3600 mbsf had to be revised as sudden changes in sea conditions resulted in damage to parts of the riser system, thus the hole was suspended at 2005 mbsf but left for future re-entry. The revised operation plan included additional riserless logging and coring of key targets not sampled during previous NanTroSEIZE expeditions, but relevant to comprehensively characterize the alteration stage of the oceanic basement input to the subduction zone, the early stage of Kumano Basin evolution and the recent activity of the shallow mega splay fault zone system and submarine landslides. Here we present preliminary results from IODP Exp. 338: Logging While Drilling (LWD), mud gas monitoring and analysis on cuttings from the deep riser hole characterize two lithological units within the internal accretionary prism, separated by a prominent fault zone at ~1640 mbsf. Internal style of deformation, downhole increase of thermogenically formed formation gas and evidence for mechanical compaction and cementation document a complex structural evolution and provide unprecedented insights into the mechanical state and behavior of the wedge at depth. Additionally, multiple samples of the unconformity between the Kumano Basin and accretionary prism

  18. Mechanics of Slip-to-the-Trench and Frontal Prism Deformation for the 2011 Tohoku-oki Earthquake

    NASA Astrophysics Data System (ADS)

    Chester, F. M.

    2014-12-01

    The slip magnitude of the 2011 Mw 9.0 Tohoku-oki earthquake rupture was as much as ~50 m below the ~20-km-wide frontal prism of accreted sediments at the trench. Mechanical explanations for prism deformation and shallow slip consider the rate-dependence and dynamic weakening of friction along the basal thrust, dynamic unloading of the thrust from wave propagation into a compliant wedge with a free upper surface, and large magnitude stress release at depth that propagates slip to shallow depths. Borehole data and core samples from IODP expedition 343/343T are used to understand frontal prism behavior over the seismic cycle. Wedge taper, experimental determination of Coulomb failure strength of the prism, and measurements of pore pressure and sediment density are used to determine apparent friction of the basal thrust and stress in the prism for compressively critical and extensionally critical conditions assuming an elastic - perfectly Coulomb plastic wedge. Model results are compared to independent measures of in situ stress in the prism from borehole deformation, sliding friction of basal thrust material at quasi-static and seismic slip-rates in experiments, and the average coseismic shear strength of the thrust from borehole temperature-profiles. These data define the pre-seismic, co-seismic, and post-seismic stress states and suggest the prism remains in a stable, elastic state over the seismic cycle with a dynamic stress drop of approximately 1 MPa in the vicinity of the borehole. Results likely describe the state of the frontal prism ~15-20 km landward from the borehole. Trenchward, however, the prism has a much smaller taper and undergoes coseismic shortening under a compressively critical state and diminishing basal slip. Variations in shallow slip magnitude along the trench could partly reflect changes in prism geometry associated with roughness of the subducting slab and sediment input, and variations in frictional properties of the basal thrust.

  19. PRISM Polarimetry of Massive Stars

    NASA Astrophysics Data System (ADS)

    Kerkstra, Brennan; Lomax, Jamie R.; Bjorkman, Karen S.; Bjorkman, Jon Eric; Skiff, Brian; Covey, Kevin R.; Wisniewski, John P.

    2016-01-01

    We present the early results from our long-term, multi-epoch filter polarization survey of massive stars in and around young Galactic clusters. These BVRI polarization data were obtained using the PRISM instrument mounted on the 1.8m Perkins Telescope at Lowell Observatory. We first detail the creation of our new semi-automated polarization data reduction pipeline that we developed to process these data. Next, we present our analysis of the instrumental polarization properties of the PRISM instrument, via observations of polarized and unpolarized standard stars. Finally, we present early results on the total and intrinsic polarization behavior of several isolated, previously suggested classical Be stars, and discuss these results in the context of the larger project.BK acknowledges support from a NSF/REU at the University of Oklahoma. This program was also supported by NSF-AST 11411563, 1412110, and 1412135.

  20. Prism. Volume 4, Number 1

    DTIC Science & Technology

    2012-01-01

    Any copy- righted portions of this journal may not be reproduced or extracted without permission of the copyright proprietors. PRISM should be...building process in this setting is the diminution of the newly integrated fighting forces’ quality . ■■ the Cold War is a key background in all of...is to clar- ify what signifies a “national emergency,” for instance, was demonstrated by the Salvadoran example. according to the 1992 Chapúltepec

  1. Three timescales in prism adaptation.

    PubMed

    Inoue, Masato; Uchimura, Motoaki; Karibe, Ayaka; O'Shea, Jacinta; Rossetti, Yves; Kitazawa, Shigeru

    2015-01-01

    It has been proposed that motor adaptation depends on at least two learning systems, one that learns fast but with poor retention and another that learns slowly but with better retention (Smith MA, Ghazizadeh A, Shadmehr R. PLoS Biol 4: e179, 2006). This two-state model has been shown to account for a range of behavior in the force field adaptation task. In the present study, we examined whether such a two-state model could also account for behavior arising from adaptation to a prismatic displacement of the visual field. We first confirmed that an "adaptation rebound," a critical prediction of the two-state model, occurred when visual feedback was deprived after an adaptation-extinction episode. We then examined the speed of decay of the prism aftereffect (without any visual feedback) after repetitions of 30, 150, and 500 trials of prism exposure. The speed of decay decreased with the number of exposure trials, a phenomenon that was best explained by assuming an "ultraslow" system, in addition to the fast and slow systems. Finally, we compared retention of aftereffects 24 h after 150 or 500 trials of exposure: retention was significantly greater after 500 than 150 trials. This difference in retention could not be explained by the two-state model but was well explained by the three-state model as arising from the difference in the amount of adaptation of the "ultraslow process." These results suggest that there are not only fast and slow systems but also an ultraslow learning system in prism adaptation that is activated by prolonged prism exposure of 150-500 trials.

  2. Mineral potential for sediment-hosted copper deposits in the Islamic Republic of Mauritania (phase V, deliverable 75): Chapter K in Second projet de renforcement institutionnel du secteur minier de la République Islamique de Mauritanie (PRISM-II)

    USGS Publications Warehouse

    Taylor, Cliff D.; Giles, Stuart A.

    2015-01-01

    Although mineral occurrence data and descriptive geological information are adequate to delineate areas favorable for sediment-hosted copper deposits, this review indicates that potential for this type of deposit in Mauritania is low.

  3. Mass-transport deposit and mélange formation in the Ligurian accretionary complex (NW-Italy) via mutual interactions of tectonic, sedimentary and diapiric processes

    NASA Astrophysics Data System (ADS)

    Festa, A.; Codegone, G.; Dilek, Y.; Ogata, K.; Pini, G.

    2011-12-01

    Slope instability and material removal from the overriding plate are common in frontal wedges of subduction-accretionary complexes, form mass-transport deposits (MTDs), and play an important role in controlling the internal dynamics of a critical taper Coulomb wedge and its slope instability. We present different examples of ancient MTDs emplaced during the late Cretaceous-Miocene evolution of the External Ligurian accretionary wedge and the related wedge-top basins (Epiligurian Units Auct.) in the NW-Apennines, Italy. These MTDs consist of sedimentary mélanges or olistostromes and display heterogeneous deformation controlled by the degree of sediment consolidation and the velocity of gravitational processes (Festa et al., 2010 IGR; Pini et al., 2011 Springer Book). Decimeter- to meter-thick shear zones associated with localized visco-plastic deformation and highly disturbed rounded and/or subangular blocks randomly distributed in a brecciated matrix form the two end-members of structures. Crosscutting relationships between MTDs and coherent successions, tectonic mélanges - broken formation and injection bodies (shaly-dykes and/or diapirs) allow us to document their time-progressive development, the correlation with tectonic and diapiric processes, and the material redistribution forming polygenic mélanges in the frontal part of the External Ligurian accretionary wedge. Out-of-sequence "megathrust" and strike-slip faulting, fluid overpressure, presence of low-permeable layers and methane-rich fluid circulation in the sedimentary column were the main factors that controlled the emplacement of various MTDs. In all the examples described, mass-transport was closely associated and had mutual interactions with tectonic and diapiric processes (Festa, 2011 GSA Sp Publ). Tectonics played the most prominent role (directly and indirectly), whereas fluid flow and overpressure strongly controlled the mechanical behavior of sediments and facilitated the emplacement of

  4. Inverse solutions for tilting orthogonal double prisms.

    PubMed

    Li, Anhu; Ding, Ye; Bian, Yongming; Liu, Liren

    2014-06-10

    An analytical reverse solution and actual examples are given to show how to direct a laser beam from a pair of orthogonal prisms to given targets in free space. Considering the influences of double-prism structural parameters, a lookup table method to seek the numerical reverse solution of each prism's tilting angle is also proposed for steering the double-prism orientation to track a target position located in the near field. Some case studies, as well as a specified elliptical target trajectory scanned by the cam-based driving double prisms, exhibit the significant application values of the theoretical derivation. The analytic reverse and numerical solutions can be generalized to investigate the synthesis of scanning patterns and the controlling strategy of double-prism tilting motion, the potentials of which can be explored to perform the orientation and position tracking functions in applications of precision engineering fields.

  5. Sediment flow routing during formation of forearc basins: Constraints from integrated analysis of detrital pyroxenes and stratigraphy in the Kumano Basin, Japan

    NASA Astrophysics Data System (ADS)

    Buchs, David M.; Cukur, Deniz; Masago, Hideki; Garbe-Schönberg, Dieter

    2015-03-01

    The evolution of sediment flow routing during complete evolution of the Kumano forearc basin is determined through integration of stratigraphic and sediment provenance analyses in the upper Nankai forearc. A new approach uses the compositional variability of detrital clinopyroxenes and orthopyroxenes collected at eight major rivers in Japan and three drill sites in the basin and nearby slope environment, including the first drill cuttings retrieved by the Integrated Ocean Drilling Program (IODP). Joint interpretation of these datasets reveals that the sedimentation history of the basin is characterised by three main phases separated by newly-recognised time-transgressive boundaries. We show that the Kumano Basin initiated as a trench-slope basin in the early Quaternary (∼1.93 Ma) and that it progressively evolved towards an upper slope environment with increased turbidite confinement and influence from climatic forcing. Basin initiation was broadly synchronous with development of the Nankai megasplay fault, suggesting a causal relationship with construction of the Nankai accretionary prism. Unlike preceding studies documenting long-distance longitudinal transport of clastic material along the lower Nankai forearc, only limited longitudinal transport is documented by detrital pyroxenes in the upper forearc. These results suggest that transverse canyons are a major control on the sediment flow routing during maturation of forearc basins and that long-distance longitudinal flows along convergent margins are principally restricted to near-trench environments, even in the presence of large forearc basins.

  6. Error and adjustment of reflecting prisms

    NASA Astrophysics Data System (ADS)

    Mao, Wenwei

    1997-12-01

    A manufacturing error in the orientation of the working planes of a reflecting prism, such as an angle error or an edge error, will cause the optical axis to deviate and the image to lean. So does an adjustment (position error) of a reflecting prism. A universal method to be used to calculate the optical axis deviation and the image lean caused by the manufacturing error of a reflecting prism is presented. It is suited to all types of reflecting prisms. A means to offset the position error against the manufacturing error of a reflecting prism and the changes of image orientation is discussed. For the calculation to be feasible, a surface named the 'separating surface' is introduced just in front of the real exit face of a real prism. It is the image of the entrance face formed by all reflecting surfaces of the real prism. It can be used to separate the image orientation change caused by the error of the prism's reflecting surfaces from the image orientation change caused by the error of the prism's refracting surface. Based on ray tracing, a set of simple and explicit formulas of the optical axis deviation and the image lean for a general optical wedge is derived.

  7. P and S wave velocity measurements on sediments from the hanging-wall of megasplay fault, NantroSEIZE Stage 1

    NASA Astrophysics Data System (ADS)

    Hashimoto, Y.; Tobin, H. J.; Knuth, M. W.

    2010-12-01

    The evolution of elastic moduli in an accretionary prism setting provides insight into diagenetic and strengthening processes related to mechanical porosity decrease, cementation, strain history, and fluid release. Variability within the accretionary complex and along the decollement may have implications for wedge geometry, fluid migration, and seismogenesis. In this study, we describe the results of laboratory measurements of P-wave and S-wave velocities through sediments obtained from Sites C0001, C0002 and C0004. All sites are located in the hanging wall of the Mega-splay fault in the Nankai accretionary prism. We also made textural observations to examine the relationship between acoustic properties and textures, both within core samples and in the context of core-log-seismic integration. Our measurement procedure is as follows: Pore fluid pressure of 500kPa was applied and confining pressure was changed to control the effective pressure. The maximum effective pressure was estimated for each sample from the accumulation of the bulk density of sediments and hydrostatic pore fluid pressure at the depth of recovery. 1MHz Lead Zirconate Titanate (PZT) shear wave transducers are used in a source-receiver pair to measure wavespeed. PZT in a shear orientation generates a weak compressional mode in addition to its primary shear mode. This allowed us to identify P and S-wave arrivals in each test. The error can be as large as ~2 µs (about 5% error). Porosities are corrected to remove smectite effects from the on-board measured porosity. Porosity ranges ~0.6 - ~0.45, ~0.37 - ~0.27, and ~0.47 - ~0.39 for Site C0001, C0002, and C0004, respectively. P-wave velocity covered ~1630 km/s - 1990 km/s, ~2010 km/s - ~2370 km/s, and ~1700 km/s - ~2200 km/s for Site C0001, C0002 and Site C0004, respectively. S-wave velocity ranges from ~720 - ~950 m/s for Site C0002 samples and from ~650 - ~940 m/s for Site C0004. The Vp/Vs ratio ranged from ~2.4 - ~2.7 for Site C0002 and from ~2

  8. Computational economy improvements in PRISM

    SciTech Connect

    Tonse, Shaheen R.; Brown, Nancy J.

    2003-01-29

    The PRISM piecewise solution mapping procedure, in which the solution of the chemical kinetic ODE system is parameterized with quadratic polynomials, is applied to CFD simulations of H{sub 2}+air combustion. Initial cost of polynomial construction is expensive, but it is recouped as the polynomial is reused. We present two methods that help us to parameterize only in places that will ultimately have high reuse. We also implement non-orthogonal Gosset factorial designs, that reduce polynomial construction costs by a factor of two over previously used orthogonal factorial designs.

  9. Accretionary lapilli: what’s holding them together?

    USGS Publications Warehouse

    Adams, Paul M.; Lynch, David K.; Buesch, David C.

    2016-01-01

    Accretionary lapilli from Tagus cone, Isla Isabela, Galápagos were analyzed using scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) techniques. Our main findings are (1) the lapilli formed and hardened in a few minutes while still aloft in the dispersing eruption column. (2) Palagonite rinds developed first on the basaltic glass clasts, and subsequently crystallized (3) The crystallization products contain submicron lamellar crystals of a clay (probably smectite) on the surfaces of basaltic glass clasts and (4) The interlocking of these lamellar clays from adjacent clasts binds and cements them together to form the accretionary lapillus. We argue that palagonite and possibly clay formation occur primarily in the presence of hot water vapor.

  10. The PRISM/PRIME Project

    NASA Astrophysics Data System (ADS)

    Barlow, R. J.

    2011-09-01

    Lepton Flavour violation is predicted by many theories beyond the standard model. In the muon sector such a violation entails not only direct μ→eγ decay but also the conversion process μ→e. To measure this to high precision requires a large number of muons of very similar energy, and this is difficult to achieve from a muon target with conventional beam optics. PRISM is an FFAG system designed to accept large numbers of muons ( 10/sec) with a wide range of energies, and render them monochromatic by accelerating the less energetic muons and decelerating the more energetic ones. To preserve Liouville's theorem, this is accompanied by a broadening in the timing of the muons, hence the name 'Phase Rotated Intense Slow Muon source.' The principles of this device have been demonstrated and components prototyped. PRIME is a detector (PRISM Muon Electron Conversion) which has been designed to stop 20 MeV bunches of muons in a thin foil, giving a very clean signal and reaching a background sensitivity of 10, four orders of magnitude better than today's limits and probing the interesting region for BSM theories.

  11. U and Sr Isotopic Distributions in Riverine Waters Collected From Taiwan Accretionary Prism: Tectonic or Climatic Control

    NASA Astrophysics Data System (ADS)

    You, C.; Nakamura, E.; Wong, R.; Lee, S.; Chiu, H.; Chung, S.

    2006-12-01

    Riverine U and Sr isotopic compositions are sensitive tracers for quantifying physical erosion and chemical weathering in small catchments, as well as the characteristic of lithological or hydrological source regions. More than 60 river waters collected from four major rivers and their tributaries, Danshui, Choshui, Erhjen and Kao-ping, surrounding the Taiwan orogenic belt were analyzed for Sr and U isotopes, as well as major ions and trace elements. There are large U-234/U-238 activity variations among river catchments in Taiwan. For instance, the Danshui river and the Kaoping river show similar U-234/U-238 activity ranges of 1.17-5.35 and 1.14-5.71 respectively, in contrast to much smaller variations observed in the Choshui and the Erhjen river, 1.22-2.95 and 1.22-2.48 respectively. The Sr isotopic ratio in river waters vary largely, Sr-87/Sr-86=0.709192- 0.715006, systematically become more radiogenic toward upper stream station in all catchments, except for samples affected by hot springs, mud volcano fluids and seawater mixing in estuary. Major ion ratios in river waters change dramatically in all drainage catchments, varying more than 50 and 200 times for Na/Cl and Ca/Na, respectively. Samples collected from wet and dry season display distinct variations in chemical and isotopic compositions, emphasizing shifted in weathering source regimes. It is interesting to note that the upper stream stations are characterized with large degree of U disequilibrium, as well as more radiogenic Sr isotopic signature, high Na/Cl and low Ca/Na ratios. These results were combined with available lithological, tectonic, climatic and hydrological information to decipher possible controls on chemical weathering and reaction mechanism in an active mountain building region.

  12. PRISM Canada. Priorities in School Mathematics.

    ERIC Educational Resources Information Center

    Alberta Univ., Edmonton. Faculty of Education.

    The Priorities in School Mathematics (PRISM) Canada Project was initiated in September 1977 as a companion study to the National Council of Teachers of Mathematics (NCTM) PRISM Project. These twin projects were designed to help provide guidelines and suggestions for curriculum changes during the 1980's. Two instruments were used, a Preferences…

  13. Arc-parallel extension and fluid flow in an ancient accretionary wedge: The San Juan Islands, Washington

    USGS Publications Warehouse

    Schermer, E.R.; Gillaspy, J.R.; Lamb, R.

    2007-01-01

    Structural analysis of the Lopez Structural Complex, a major Late Cretaceous terrane-bounding fault zone in the San Juan thrust system, reveals a sequence of events that provides insight into accretionary wedge mechanics and regional tectonics. After formation of regional ductile flattening and shear-related fabrics, the area was crosscut by brittle structures including: (1) southwest-vergent thrusts, (2) extension veins and normal faults related to northwest-southeast extension, and (3) conjugate strike-slip structures that record northwest-southeast extension and northeast-southwest shortening. Aragonite-bearing veins are associated with thrust and normal faults, but only rarely with strike-slip faults. High-pressure, low-temperature (HP-LT) minerals constrain the conditions for brittle deformation to ???20 km and <250 ??C. The presence of similar structures elsewhere indicates that the brittle structural sequence is typical of the San Juan nappes. Sustained HP-LT conditions are possible only if structures formed in an accretionary prism during active subduction, which suggests that these brittle structures record internal wedge deformation at depth and early during uplift of the San Juan nappes. The structures are consistent with orogen-normal shortening and vertical thickening followed by vertical thinning and along-strike extension. The kinematic evolution may be related initially to changes in wedge strength, followed by response to overthickening of the wedge in an unbuttressed, obliquely convergent setting. The change in vein mineralogy indicates that exhumation occurred prior to the strike-slip event. The pressure and temperature conditions and spatial and temporal extent of small faults associated with fluid flow suggest a link between these structures and the silent earthquake process. ?? 2007 Geological Society of America.

  14. Formation of the Yakuno ophiolite; accretionary subduction under medium-pressure-type metamorphic conditions

    NASA Astrophysics Data System (ADS)

    Osozawa, Soichi; Takeuchi, Hiroshi; Koitabashi, Toru

    2004-11-01

    The notion that the Yakuno ophiolite and overlying Maizuru Group represents an accretionary prism formed during the Permian evolution of Japan on the Yakuno eruptive sequence, association of hemipelagic mudstone with silicic tuff, exotic fossiliferous limestones derived from previously accreted sea-mounts, upward coarsening of sequences terrigenous sandstone and conglomerate, and mildly deformed Permian and Triassic forearc basin formations. The most important indicator, however, is the seaward imbrication and repetition observed in both the Maizuru Group and the ophiolite itself. D1 deformation structures include axial-planar foliations (pressure-solution cleavage for the Maizuru Group and granulite-amphibolite metamorphic layering in the ophiolite), flattening type strain, symmetric pressure shadows and fringes, and isoclinal folds showing axial-planar foliations and thrust faulting at their overturned limb. The exceptional asymmetry observed indicates seaward-directed shearing near the thrust, while D1 structures in the Maizuru zone are explained by off-scraping, above the basal decollement. The later Jurassic D2 kink fold structure includes a first-order asymmetric kink with a brittle thrust at its overturned limb, more-or-less coeval with M2 retrograde metamorphism. Medium-pressure M1 prograde metamorphism in the Yakuno ophiolite produced layering of granulite and amphibolite, and in the Maizuru Group, formation of illite along pressure-solution cleavage of mudstones. The metamorphic grade is controlled by the stratigraphic relationships and appears typical of that in ocean floor regions. However, there was only one episode of M1 prograde metamorphism which occurred contemporaneously with D1 off-scraping. Given that subduction zones are normally characterized by high P/ T metamorphic regimes, the observed P/ T history appears to reflect relatively unusual conditions. Such high thermal gradients may plausibly reflect the approach of a young, hot oceanic plate

  15. Deformation processes at the down-dip limit of the seismogenic zone: The example of Shimanto accretionary complex

    NASA Astrophysics Data System (ADS)

    Palazzin, G.; Raimbourg, H.; Famin, V.; Jolivet, L.; Kusaba, Y.; Yamaguchi, A.

    2016-09-01

    In order to constrain deformation processes close to the brittle-ductile transition in seismogenic zone, we have carried out a microstructural study in the Shimanto accretionary complex (Japan), the fossil equivalent of modern Nankai accretionary prisms. The Hyuga Tectonic Mélange was sheared along the plate interface at mean temperatures of 245 °C ± 30 °C, as estimated by Raman spectroscopy of carbonaceous material (RSCM). It contains strongly elongated quartz ribbons, characterized by very high fluid inclusions density, as well as micro-veins of quartz. Both fluid inclusion planes and micro-veins are preferentially developed orthogonal to the stretching direction. Furthermore, crystallographic preferred orientation (CPO) of quartz c-axes in the ribbons has maxima parallel to the stretching direction. Recrystallization to a small grain size is restricted to rare deformation bands cutting across the ribbons. In such recrystallized quartz domains, CPO of quartz c-axes are orthogonal to foliation plane. The evolution of deformation micro-processes with increasing temperature can be further analyzed using the Foliated Morotsuka, a slightly higher-grade metamorphic unit (342 ± 30 °C by RSCM) from the Shimanto accretionary complex. In this unit, in contrast to Hyuga Tectonic Mélange, recrystallization of quartz veins is penetrative. CPO of quartz c-axes is concentrated perpendicularly to foliation plane. These variations in microstructures and quartz crystallographic fabric reflect a change in the dominant deformation mechanism with increasing temperatures: above 300 °C, dislocation creep is dominant and results in intense quartz dynamic recrystallization. In contrast, below 300 °C, quartz plasticity is not totally activated and pressure solution is the major deformation process responsible for quartz ribbons growth. In addition, the geometry of the quartz ribbons with respect to the phyllosilicate-rich shear zones shows that bulk rheology is controlled by

  16. Provenance of Marine Sediment in the Gulf of Alaska, IODP Expedition 341: Links Between Sediment Derivation, Glacial Systems, and Exhumation of the Coastal Mountain Belts

    NASA Astrophysics Data System (ADS)

    Allen, W. K.; Dunn, C. A.; Enkelmann, E.; Ridgway, K.; Colliver, L.

    2015-12-01

    Provenance analysis of Neogene sand and diamict beds from marine boreholes drilled by the IODP Expedition 341 provides a marine sedimentary record of the interactions between tectonics, climate and sediment deposition along a glaciated convergent margin. The 341 boreholes represent a cross-margin transect that sampled the continental shelf, slope, and deep sea Surveyor Fan of the Gulf of Alaska. Our dataset currently consists of ~ 650 detrital zircons selected for double dating method utilizing both detrital zircon fission track (FT) and U-Pb analysis from sand and diamict beds, as well as zircon U-Pb geochronology and apatite FT from igneous and gneissic clasts. Detrital zircon U-Pb geochronology of sand records dominant peak ages of 53, 62, 70, and 98 Ma with minor populations of 117, 154, and 170 Ma. Most of these ages can be correlated to primary igneous sources in the Coast Plutonic Complex, the Chugach Metamorphic Complex, the plutonic rocks of Wrangellia, and the Sanak-Baranoff plutonic belt. All samples analyzed to date, covering a 10 Myr range, share nearly identical detrital zircon populations suggesting similar primary sediment sources and reworking of sediment in thrust belts and accretionary prisms along this convergent margin. Plutonic and gneissic clasts collected from the boreholes on the shelf have already been double dated. These clasts have general U-Pb zircon crystallization ages of 52-54 Ma and apatite fission track cooling ages of 10-12 Ma. These results, along with previous published studies, indicate that these clasts were derived from the Chugach Metamorphic Complex and were eroded and transported by the Bagley Ice Field and Bering Glacier. Future results using this approach should allow us to pinpoint which parts of the exhumed onshore ranges and which glacial systems provided sediment to marine environments in the Gulf of Alaska.

  17. Detrital zircon geochronology and provenance analysis applied to the onshore Makran accretionary wedge, SE Iran

    NASA Astrophysics Data System (ADS)

    Mohammadi, A.; Burg, J.; Winkler, W.; Ruh, J. B.; Von Quadt, A.

    2013-12-01

    The Makran is one of the largest accretionary wedges in the world, located in Southeast Iran. The Makran Basin is composed of turbidity sediments ranging in age from late Cretaceous to Holocene. The analysis of detrital zircons is important to interpret the provenance of the sediments and to clarify the geological history of the sedimentary basins and their surrounding source regions. We present about 2777 new U-Pb ages (ICP laser ablation mass spectrometry) from individual detrital zircons of 18 sandstone samples collected throughout the onshore Makran. 101 detrital zircon ages from a late Cretaceous fine grained sandstone ranges from 180-160 Ma (Mid-Jurassic). 478 detrital zircon ages obtained from the mid to late Eocene sandstone reveals different sources for the NE and NW parts of the Makran Basin. Zircon grains in the NE basin belong to two populations peaked at Mid-Jurassic and Mid-Eocene, with the noticeable absence of Cretaceous grains. In the NW basin, detrital zircons are Mid-Cretaceous to Mid-Eocene. 587 detrital zircon grains from fine to medium grained Oligocene sandstones collected in different parts of the basin range from Mid-Cretaceous to Mid-Eocene. 1611 detrital zircon age from Early Miocene sandstones collected in the eastern and western parts of the basin show distinctly different detrital zircon ages. They range from Mid-Cretaceous to Mid-Eocene in the eastern basin, from Late Cretaceous to Mid-Eocene in the west. Detrital zircon ages from Mid and Late Miocene sandstones rang from Late Cretaceous to Mid-Eocene. These new detrital zircon U-Pb age data show that the eastern and western parts of the Makran Basin received sediments from different source areas during Eocene and Early Miocene times. Mid and Late Miocene sediment are recycled (cannibalism) from the Oligocene units of the basin.

  18. Accretionary origin for the late Archean Ashuanipi Complex of Canada

    NASA Technical Reports Server (NTRS)

    Percival, J. A.

    1988-01-01

    The Ashuanipi complex is one of the largest massif granulite terrains of the Canadian Shield. It makes up the eastern end of the 2000 km long, lower-grade, east-west belts of the Archean Superior Province, permitting lithological, age and tectonic correlation. Numerous lithological, geochemical and metamorphic similarities to south Indian granulites suggest common processes and invite comparison of tectonic evolution. The Ashuanipi granulite terrain of the Cannadian Superior Province was studied in detail, and an origin through self-melting of a 55 km thick accretionary wedge seems possible.

  19. 21 CFR 886.1650 - Ophthalmic bar prism.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ophthalmic bar prism. 886.1650 Section 886.1650...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1650 Ophthalmic bar prism. (a) Identification. An ophthalmic bar prism is a device that is a bar composed of fused prisms of gradually...

  20. 21 CFR 886.1650 - Ophthalmic bar prism.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Ophthalmic bar prism. 886.1650 Section 886.1650...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1650 Ophthalmic bar prism. (a) Identification. An ophthalmic bar prism is a device that is a bar composed of fused prisms of gradually...

  1. 21 CFR 886.1650 - Ophthalmic bar prism.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Ophthalmic bar prism. 886.1650 Section 886.1650...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1650 Ophthalmic bar prism. (a) Identification. An ophthalmic bar prism is a device that is a bar composed of fused prisms of gradually...

  2. An Easily Constructed Trigonal Prism Model.

    ERIC Educational Resources Information Center

    Yamana, Shukichi

    1984-01-01

    A model of a trigonal prism which is useful for teaching stereochemistry (especially of the neodymium enneahydrate ion), can be made easily by using a sealed, empty envelope. The steps necessary to accomplish this task are presented. (JN)

  3. Evaluation of Deconvolution Methods for PRISM Images

    NASA Astrophysics Data System (ADS)

    Schwind, Peter; Palubinskas, Gintautas; Storch, Tobias; Muller, Rupert

    2008-11-01

    Within the scope of a project by the European Space Agency (ESA), the German Aerospace Center (DLR) is responsible for the establishment of prototype processors for ALOS/AVNIR-2 and ALOS/PRISM data. This processing chain not only includes radiometric and geometric correction for ALOS/AVNIR-2 and ALOS/PRISM but also atmospheric correction for ALOS/AVNIR-2. In addition to that an optional deconvolution step for the ALOS/PRISM data is offered to improve the image quality. This paper gives a short introduction into the processing chain as a whole and a more in-depth look into the deconvolution strategies taken into consideration for ALOS/PRISM images.

  4. Structural controls on the development of submarine channel/fan systems since the Pleistocene in the accretionary wedge off SW Taiwan

    NASA Astrophysics Data System (ADS)

    Shen, Kang-Nien; Tien-Shun Lin, Andrew; Lin, Che-Chuan; Liu, Char-Shine; Wang, Yunshuen

    2016-04-01

    The accretionary wedge off SW Taiwan is the result of incipient arc-continent collision between the Luzon volcanic arc and the northern rifted margin of the South China Sea (SCS). Dynamic interactions of thrusting, folding and a rigorous sediment supply from the Taiwan mountain belts have resulted in two arrays of canyons/channels and slope-fan systems in the accretionary wedge. The Penghu canyon/fan system lies in the lower wedge and near the northern rifted margin of the SCS. The Penghu canyon is a river-fed canyon and receives sediments from southern Taiwan and SE China during eustatic lowstands. It becomes detached from river inputs during eustatic highstands as it is in the present-day. The Gaoping canyon/fan system in the south traverses both the upper slope and lower slope domains of the accretionary wedge. This system is a river-fed system during a full eustatic cycle and it drains sediments from the onshore Gaoping River. We interpreted multiple grids of multichannel seismic reflection data of MCS994, MCS1000-6, MCS1014, MCS1046 collected onboard Ocean Research I during 2012 April to 2013 August to map out thrust/fold structures and channel/fan systems in the study area. Seismic facies analyses were performed on seismic sections and key stratal surfaces of base of Pliocene and base of Pleistocene are correlated from boreholes drilled in the shelf of the northern SCS margin. Our results show that the upper Gaoping Canyon has been confined by structural ridges with limited switching of canyon courses, whereas the lower Gaoping canyon/fan system has been developed on lower slope with channel/levee deposition in multiple slope fans since early Pleistocene. Pleistocene lateral aggrading channel-and-levee systems are especially evident near the modern canyon course in the lower slope. The Penghu can/fan system in the lower accretionary wedge is also evident by seismic facies showing channel cut-and-fill, channel abandonment and channel-and-levee systems. This

  5. Ray picture for prism-film coupling

    NASA Astrophysics Data System (ADS)

    Hoekstra, H. J. W. M.; van't Spijker, J. C.; Koerkamp, H. M. M. Klein

    1993-10-01

    Tien and Ulrich introduced a description of the prism-film coupler, with use of the ray picture. The model given is discussed, and it is argued that the effect of the Goss-Hanchen shift cannot be neglected in general. Relatively simple expressions are given for the computation of the coupling efficiency of a prism-loaded planar structure as a function of the angle of incidence of the incoming beam. Computational results are presented and compared with those of other methods.

  6. OPERA: Objective Prism Enhanced Reduction Algorithms

    NASA Astrophysics Data System (ADS)

    Universidad Complutense de Madrid Astrophysics Research Group

    2015-09-01

    OPERA (Objective Prism Enhanced Reduction Algorithms) automatically analyzes astronomical images using the objective-prism (OP) technique to register thousands of low resolution spectra in large areas. It detects objects in an image, extracts one-dimensional spectra, and identifies the emission line feature. The main advantages of this method are: 1) to avoid subjectivity inherent to visual inspection used in past studies; and 2) the ability to obtain physical parameters without follow-up spectroscopy.

  7. Neutron energy analysis by silicon prisms

    NASA Astrophysics Data System (ADS)

    Schulz, J.; Ott, F.; Hülsen, Ch.; Krist, Th.

    2013-11-01

    Neutron energy analysing by refraction with prisms allows to measure different wavelengths at the same time thus avoiding losses due to monochromatization. We built and tested a refractive energy analysing device made from small prisms, where losses only occur due to the attenuation in the material. We measured the refraction and the transmission of MgF2 and Si prisms at the V14 reflectometer in Berlin at 4.9 Å to check their applicability. The experimentally determined linear attenuation coefficients are 0.055 cm-1 for the MgF2 and 0.03 cm-1 for the Si prisms. An energy analyser consisting of silicon prism layers was measured at the EROS reflectometer at the LLB in a white neutron beam. The useful wavelength band was 2.4-7.6 Å. At 6.7 Å a wavelength resolution of 5% and a transmission of 53% were achieved. The surface roughness of the prisms could be determined to be (0.011±0.006)deg.

  8. Liquid Temperature Measurements Using Two Different Tunable Hollow Prisms

    PubMed Central

    Calixto, Sergio; Rosete-Aguilar, Martha; Torres-Gomez, Ismael

    2017-01-01

    This paper describes the design, fabrication, and testing of two hollow prisms. One is a prism with a grating glued to its hypotenuse. This ensemble, prism + grating, is called a grism. It can be applied as an on-axis tunable spectrometer. The other hollow prism is a constant deviation one called a Pellin-Broca. It can be used as a tunable dispersive element in a spectrometer with no moving parts. The application of prisms as temperature sensors is shown. PMID:28146068

  9. Liquid Temperature Measurements Using Two Different Tunable Hollow Prisms.

    PubMed

    Calixto, Sergio; Rosete-Aguilar, Martha; Torres-Gomez, Ismael

    2017-01-29

    This paper describes the design, fabrication, and testing of two hollow prisms. One is a prism with a grating glued to its hypotenuse. This ensemble, prism + grating, is called a grism. It can be applied as an on-axis tunable spectrometer. The other hollow prism is a constant deviation one called a Pellin-Broca. It can be used as a tunable dispersive element in a spectrometer with no moving parts. The application of prisms as temperature sensors is shown.

  10. Formation of forearc basins by collision between seamounts and accretionary wedges: an example from the New Hebrides subduction zone

    USGS Publications Warehouse

    Collot, J.-Y.; Fisher, M.A.

    1989-01-01

    Seabeam data reveal two deep subcircular reentrants in the lower arc slope of the New Hebrides island arc that may illustrate two stages in the development of a novel type of forearc basin. The Malekula reentrant lies just south of the partly subducted Bougainville seamount. This proximity, as well as the similarity in morphology between the reentrant and an indentation in the lower arc slope off Japan, suggests that the Malekula reentrant formed by the collision of a seamount with the arc. An arcuate fold-thrust belt has formed across the mouth of the reentrant, forming the toe of a new accretionary wedge. The Efate reentrant may show the next stage in basin development. This reentrant lies landward of a lower-slope ridge that may have begun to form as an arcuate fold-thrust belt across the mouth of a reentrant. This belt may have grown by continued accretion at the toe of the wedge, by underplating beneath the reentrant, and by trapping of sediment shed from the island arc. These processes could result in a roughly circular forearc basin. Basins that may have formed by seamount collision lie within the accretionary wedge adjacent to the Aleutian trenches. -Authors

  11. Subsea Gas Emissions from the Barbados Accretionary Complex

    NASA Astrophysics Data System (ADS)

    Barnard, A.; Sager, W. W.; Snow, J. E.; Max, M. D.

    2015-12-01

    We study newly identified gas plumes in the water column from the Barbados Accretionary Complex using multibeam echo soundings from cruise AT21-02. The multibeam data were used to define a region with several ~600 - 900 m tall gas plumes in the water column directly above cratered hummocky regions of the sea floor that have relatively high backscatter, at a water depth of ~1500 m. The natural gas hydrate stability zone reaches a minimum depth of ~600 m in the water column, similar to that of the tallest imaged bubble plumes, implying hydrate shells on the gas bubbles. Maximum tilt of the plume shows current shear in a direction from northwest to southeast (~128°), similar to the transport direction of North Atlantic Deep Water. The source of hydrocarbons, determined from existing geochemical data, suggests the gas source was subjacent marine Cretaceous source rocks. North-south trending faults, craters and mud volcanoes associated with the gas plumes point to the presence of a deep plumbing system and indicate that gas is a driver of mud volcanism. The widespread occurrence of seafloor morphology related to venting indicates that subsea emissions from the Barbados Accretionary Complex are substantial.

  12. Décollement processes at the Nankai accretionary margin, southeast Japan: Propagation, deformation, and dewatering

    NASA Astrophysics Data System (ADS)

    Morgan, Julia K.; Karig, Daniel E.

    1995-08-01

    The décollement zone, expressed on seismic profiles and observed in drill cores from the Nankai accretionary margin off the southeast coast of Japan, reveals several unique characteristics which appear to distinguish it from thrust faults identified in the same setting. Physical manifestations of these include evidence for the asymmetric distribution of deformation structures about the décollement, the extension of this fault zone well in front of the tectonic deformation front, and the absence of features indicative of precursory shear, for example, folded sediments, shear bands, and penetrative mineral fabrics. These characteristics suggest that the mode of formation and evolution of this décollement zone may be unique from that of most thrust faults. We propose that the décollement zone propagates not as a shear fracture controlled by tectonic stress conditions but rather as a subhorizontal tension fracture propagating under high pore pressures. To test this possibility, physical property measurements and clay mineral fabrics were obtained for several samples from the Nankai décollement zone using computed tomography and X ray texture methods. Our findings suggest that deformation within the décollement zone is partitioned into a volumetric component, preserved as reduced porosities within coherent fragments, and a localized shear component, evidenced by mineral preferred orientations along discrete slip surfaces. We suggest that the reduced porosities result from the destruction of "cementation" in the sediments during the early stages of deformation and may arise from cyclic fatiguing of the sediment induced by fluctuating pore pressures. The nonpenetrative shear fabrics probably develop as the tectonic deformation front migrates seaward, and the weakened protodécollement subsequently accommodates shear displacements along discrete fractures.

  13. Morphology, seismic characteristics and development of the sediment dispersal system along the Taiwan-Luzon convergent margin

    NASA Astrophysics Data System (ADS)

    Hsiung, Kan-Hsi; Su, Chih-Chieh; Yu, Ho-Shing; Chang, Jih-Hsin

    2015-12-01

    The sediment dispersal system along the convergent margin between Taiwan and Luzon links the terrestrial and shallow marine sediments from the source areas nearby Taiwan orogen to the ultimate sink in the northern Manila Trench. Using seismic reflection profiles and bathymetry mapping we determine three distinct morpho-tectonic features of the Penghu Submarine Canyon, deep-sea Penghu Channel and oceanic Manila Trench which are linearly interconnected to form a longitudinal sediment route. Seismic profiles show characteristic features of truncated strata along canyon walls and cut-and-fills in canyon bottom. Deformed and uplifted bathymetric ridges and troughs and volcanic intrusions with unstratified and chaotic seismic facies are associated with the Penghu Channel. The seismic facies of the trench wedge are characterized by sub-horizontal and conformable layers of sediment stacking upwards to the trench floor. The sediment wedge adjacent to the inner lower slope is deformed to blind folds and thrust faults as precursors of the accretionary prism. The most prominent seismic characteristics is wide-spread undulating reflectors on the seafloor along the west edge of the sediment dispersal system and the toe of the South China Sea Basin floor, suggesting a large sediment wave field with a turbidity currents origin. The location, orientation and geometry of this sediment routing system are mainly controlled by underlying tectonics in progressive changes from arc-continental collision in transition to subduction. The deep-sea Penghu Channel is formed by compression in transitional zone of the North Luzon Ridge region, neither subduction nor channel erosion. The sediments in northern Manila Trench are mainly transported by turbidity currents via the upslope deep-sea Penghu Channel and Penghu Canyon and trench axis is filled up to a flat-floor trench wedge without sediment ponding. A four-stage development of sediment dispersal system in Taiwan-Luzon convergent margin

  14. Accretionary Complexes: Recorders of Plate Tectonism and Environmental Conditions Through Time on Earth and Possibly Those Early Noachian (Hadean-equivalent) in Age on Mars

    NASA Astrophysics Data System (ADS)

    Dohm, J. M.; Maruyama, S.; Miyamoto, H.; Viviano-Beck, C. E.; Anderson, R. C.

    2014-12-01

    On Earth, highlighted in Japan, North America, Europe, and Greenland, accretionary complexes comprehensively record information compiled while the oceanic crust is en route from the mid-oceanic ridge to the subduction zone, spanning hundreds of millions of years. At the zone, oceanic crustal materials are stacked along thrust faults and/or subducted to be eventually recycled into the mantle. The surviving accretionary-complex materials include Ocean Plate Stratigraphy (OPS). The ideal succession of the OPS (from oldest to youngest) is mid-ocean ridge basalt, pelagic sediment including radiolarian chert, hemipelagic sediment including siliceous shale, and trench turbidite deposits. Therefore, accretionary complexes often record diverse environmental conditions from deep- to shallow-marine environments, including those perturbed by magmatic, impact, and possibly extrasolar events. Stratigraphic, impact-crater, paleotectonic, and magnetic-anomaly information point to Early Noachian (Hadean-equivalent) Martian geologic terrains; they are extremely ancient environmental records compared to those destroyed on Earth due to differences in planetary mass and evolutional states. Such record a dynamic phase of the evolution of Mars, including interacting ocean, landmass, and atmosphere, as well as possible plate tectonism during an operating dynamo. A candidate accretionary complex and nearby outcrops of steeply dipping beds comprising olistostrome-like blocks, nearby and in the Claritas rise, respectively, may be key evidence of major crustal shortening related to plate tectonism, in addition to being extremely ancient environmental records. Claritas rise is a rugged promontory about 250 km across, which forms the northwest part of an extremely ancient and large mountain range, Thaumasia highlands, with a length nearing 2,400 km, or approximating that of the Himalayas. Future investigation of the ancient Martian basement, which includes geochemical analyses for possible OPS

  15. Controls on accretion of flysch and melange belts at convergent margins: evidence from the Chugach Bay thrust and Iceworm melange, Chugach accretionary wedge, Alaska

    USGS Publications Warehouse

    Kusky, Timothy M.; Bradley, Dwight C.; Haeussler, Peter J.; Karl, Susan M.

    1997-01-01

    Controls on accretion of flysch and melange terranes at convergent margins are poorly understood. Southern Alaska's Chugach terrane forms the outboard accretionary margin of the Wrangellia composite terrane, and consists of two major lithotectonic units, including Triassic-Cretaceous melange of the McHugh Complex and Late Cretaceous flysch of the Valdez Group. The contact between the McHugh Complex and the Valdez Group on the Kenai Peninsula is a tectonic boundary between chaotically deformed melange of argillite, chert, greenstone, and graywacke of the McHugh Complex and a less chaotically deformed melange of argillite and graywacke of the Valdez Group. We assign the latter to a new, informal unit of formational rank, the Iceworm melange, and interpret it as a contractional fault zone (Chugach Bay thrust) along which the Valdez Group was emplaced beneath the McHugh Complex. The McHugh Complex had already been deformed and metamorphosed to prehnite-pumpellyite facies prior to formation of the Iceworm melange. The Chugach Bay thrust formed between 75 and 55 Ma, as shown by Campanian-Maastrichtian depositional ages of the Valdez Group, and fault-related fabrics in the Iceworm melange that are cut by Paleocene dikes. Motion along the Chugach Bay thrust thus followed Middle to Late Cretaceous collision (circa 90-100 Ma) of the Wrangellia composite terrane with North America. Collision related uplift and erosion of mountains in British Columbia formed a submarine fan on the Farallon plate, and we suggest that attempted subduction of this fan dramatically changed the subduction/accretion style within the Chugach accretionary wedge. We propose a model in which subduction of thinly sedimented plates concentrates shear strains in a narrow zone, generating melanges like the McHugh in accretionary complexes. Subduction of thickly sedimented plates allows wider distribution of shear strains to accommodate plate convergence, generating a more coherent accretionary style

  16. The PRISM3D paleoenvironmental reconstruction

    USGS Publications Warehouse

    Dowsett, H.; Robinson, M.; Haywood, A.M.; Salzmann, U.; Hill, Daniel; Sohl, L.E.; Chandler, M.; Williams, Mark; Foley, K.; Stoll, D.K.

    2010-01-01

    The Pliocene Research, Interpretation and Synoptic Mapping (PRISM) paleoenvironmental reconstruction is an internally consistent and comprehensive global synthesis of a past interval of relatively warm and stable climate. It is regularly used in model studies that aim to better understand Pliocene climate, to improve model performance in future climate scenarios, and to distinguish model-dependent climate effects. The PRISM reconstruction is constantly evolving in order to incorporate additional geographic sites and environmental parameters, and is continuously refined by independent research findings. The new PRISM three dimensional (3D) reconstruction differs from previous PRISM reconstructions in that it includes a subsurface ocean temperature reconstruction, integrates geochemical sea surface temperature proxies to supplement the faunal-based temperature estimates, and uses numerical models for the first time to augment fossil data. Here we describe the components of PRISM3D and describe new findings specific to the new reconstruction. Highlights of the new PRISM3D reconstruction include removal of Hudson Bay and the Great Lakes and creation of open waterways in locations where the current bedrock elevation is less than 25m above modern sea level, due to the removal of the West Antarctic Ice Sheet and the reduction of the East Antarctic Ice Sheet. The mid-Piacenzian oceans were characterized by a reduced east-west temperature gradient in the equatorial Pacific, but PRISM3D data do not imply permanent El Niño conditions. The reduced equator-to-pole temperature gradient that characterized previous PRISM reconstructions is supported by significant displacement of vegetation belts toward the poles, is extended into the Arctic Ocean, and is confirmed by multiple proxies in PRISM3D. Arctic warmth coupled with increased dryness suggests the formation of warm and salty paleo North Atlantic Deep Water (NADW) and a more vigorous thermohaline circulation system that may

  17. Seep carbonates and chemosynthetic coral communities in the Early Paleocene alpine accretionary wedge: evidences from the Bocco Shale (Internal Liguride ophiolitic sequence, Northern Apennine, Italy)

    NASA Astrophysics Data System (ADS)

    Pandolfi, Luca; Boschi, Chiara; Luvisi, Edoardo; Alessandro, Ellero; Marroni, Michele; Meneghini, Francesca

    2014-05-01

    In Northern Apennines, the Internal Liguride units are characterized by an ophiolite sequence that represents the stratigraphic base of a Late Jurassic-Early Paleocene sedimentary cover. The Bocco Shale represents the youngest deposit recognized in the sedimentary cover of the ophiolite sequence, sedimented just before the inception of subduction-related deformation history. The Bocco Shale has been interpreted as a fossil example of deposits related to the frontal tectonic erosion of the alpine accretionary wedge slope. The frontal tectonic erosion resulted in a large removal of material from the accretionary wedge front reworked as debris flows and slide deposits sedimented on the lower plate above the trench deposits. These trench-slope deposits may have been successively deformed and metamorphosed during the following accretion processes. The frontal tectonic erosion can be envisaged as a common process during the convergence-related evolution of the Ligure-Piemontese oceanic basin in the Late Cretaceous-Early Tertiary time span. In the uppermost Internal Liguride tectonic unit (Portello Unit of Pandolfi and Marroni. 1997), that crops-out in Trebbia Valley, several isolated blocks of authigenic carbonates, unidentificated corals and intrabasinal carbonatic arenites have been recognized inside the fine-grained sediments that dominate the Early Paleocene Lavagnola Fm. (cfr. Bocco Shale Auctt.). The preliminary data on stable isotopes from blocks of authigenic carbonates (up to 1 m thick and 3 m across) and associated corals archive a methane signatures in their depleted carbon isotope pattern (up to δ13C -30‰ PDB) and suggest the presence of chemosynthetic paleocommunities. The seep-carbonates recognized at the top of Internal Liguride succession (cfr. Bocco Shale Auctt.) occur predominantly as blocks in very thick mudstone-dominated deposits and probably developed in an environment dominated by the expulsion of large volume of cold methane-bearing fluids

  18. Amagmatic Accretionary Segments, Ultraslow Spreading and Non-Volcanic Rifted Margins (Invited)

    NASA Astrophysics Data System (ADS)

    Dick, H. J.; Snow, J. E.

    2009-12-01

    The evolution of non-volcanic rifted margins is key to understanding continental breakup and the early evolution of some of the world’s most productive hydrocarbon basins. However, the early stages of such rifting are constrained by limited observations on ancient heavily sedimented margins such as Newfoundland and Iberia. Ultraslow spreading ridges, however, provide a modern analogue for early continental rifting. Ultraslow spreading ridges (<20 mm/yr) comprise ~30% of the global ridge system (e.g. Gakkel, Southwest Indian, Terceira, and Knipovitch Ridges). They have unique tectonics with widely spaced volcanic segments and amagmatic accretionary ridge segments. The volcanic segments, though far from hot spots, include some of the largest axial volcanoes on the global ridge system, and have, unusual magma chemistry, often showing local isotopic and incompatible element enrichment unrelated to mantle hot spots. The transition from slow to ultraslow tectonics and spreading is not uniquely defined by spreading rate, and may also be moderated by magma supply and mantle temperature. Amagmatic accretionary segments are the 4th class of plate boundary structure, and, we believe, the defining tectonic feature of early continental breakup. They form at effective spreading rates <12 mm/yr, assume any orientation to spreading, and replace transform faults and magmatic segments. At amagmatic segments the earth splits apart with the mantle emplaced directly to the seafloor, and great slabs of peridotite are uplifted to form the rift mountains. A thick conductive lid suppresses mantle melting, and magmatic segments form only at widely spaced intervals, with only scattered volcanics in between. Amagmatic segments link with the magmatic segments forming curvilinear plate boundaries, rather than the step-like morphology found at faster spreading ridges. These are all key features of non-volcanic rifted margins; explaining, for example, the presence of mantle peridotites emplaced

  19. Accretionary margin of north-western Hispaniola: morphology, structure and development of part of the northern Caribbean plate boundary

    USGS Publications Warehouse

    Dillon, William P.; Austin, James A.; Scanlon, K.M.; Terence, Edgar N.; Parson, L.M.

    1992-01-01

    Broad-range side-scan sonar (GLORIA) images and single- and multi-channel seismic reflection profiles demonstrate that the margin of north-western Hispaniola has experienced compression as a consequence of oblique North American-Caribbean plate convergence. Two principal morphological or structural types of accretionary wedges are observed along this margin. The first type is characterized by a gently sloping (???4??) sea floor and generally margin-parallel linear sets of sea-floor ridges that gradually deepen towards the flat Hispaniola Basin floor to the north. The ridges are caused by an internal structure consisting of broad anticlines bounded by thrust faults that dip southwards beneath Hispaniola. Anticlines form at the base of the slope and are eventually sheared and underthrust beneath the slope. In contrast, the second type of accretionary wedge exhibits a steeper (???6-16??) sea-floor slope characterized by local slumping and a more abrupt morphological transition to the adjacent basin. The internal structure appears chaotic on seismic reflection profiles and probably consists of tight folds and closely spaced faults. We suggest that changes in sea-floor declivity and internal structure may result from variations in the dip or frictional resistance of the de??collement, or possibly from changes in the cohesive strength of the wedge sediments. The observed pattern of thickening of Hispaniola Basin turbidites towards the insular margin suggests differential southwards tilting of the Hispaniola Basin strata, probably in response to North America-Caribbean plate interactions since the Early Tertiary. Based upon indirect age control from adjacent parts of the northern caribbean plate boundary, we infer a Late Eocene to Early Miocene episode of transcurrent motion (i.e. little or no tilting), an Early Miocene to Late Pliocene period of oblique convergence (i.e. increased tilt) during which the accretionary wedge began to be constructed, and a Late Pliocene to

  20. Coulomb theory applied to accretionary and nonaccretionary wedges: Possible causes for tectonic erosion and/or frontal accretion

    NASA Astrophysics Data System (ADS)

    Lallemand, Serge E.; Schnürle, Philippe; Malavieille, Jacques

    1994-06-01

    Based on observations from both modem convergent margins and sandbox modeling, we examine the possible conditions favoring frontal accretion and/or frontal and basal tectonic erosion. Mean characteristic parameters (μ, μ*b and λ) are used to discuss the mechanical stability of 28 transects across the frontal part of convergent margins where the Coulomb theory is applicable. Natural observations reveal that "typical accretionary wedges" are characterized by low tapers with smooth surface slope and subducting plate, low convergence rates and thick trench sediment, while "nonaccretionary wedges" display large tapers with irregular surface slopes and rough subducting plate, high convergence rates and almost no trench fill. Sandbox experiments were performed to illustrate the effects of seamounts/ridges in the subduction zone on the deformation of an accretionary wedge. These experiments show that a wedge of sand is first trapped and pushed in front of the seamount which acts as a moving bulldozer. This is followed by a tunnelling effect of the subducting seamount through the frontal wedge material, which results in considerable sand reworking. At an advanced subduction stage, the décollement jumps back from a high level in the wedge to its former basal position. We conclude that a high trench sedimentation rate relative to the convergence rate leads to frontal accretion. In contrast, several conditions may favor tectonic erosion of the upper plate. First, oceanic features, such as grabens, seamounts or ridges, may trap upper plate material during their subduction process. Second, destabilization of the upper plate material by internal fluid overpressuring causing hydrofracturing is probably another important mechanism.

  1. Eocene extension in Idaho generated massive sediment floods into Franciscan trench and into Tyee, Great Valley, and Green River basins

    USGS Publications Warehouse

    Dumitru, Trevor A.; Ernst, W.G.; Wright, James E.; Wooden, Joseph L.; Wells, Ray E.; Farmer, Lucia P.; Kent, Adam J.R.; Graham, Stephan A.

    2013-01-01

    The Franciscan Complex accretionary prism was assembled during an ∼165-m.y.-long period of subduction of Pacific Ocean plates beneath the western margin of the North American plate. In such fossil subduction complexes, it is generally difficult to reconstruct details of the accretion of continent-derived sediments and to evaluate the factors that controlled accretion. New detrital zircon U-Pb ages indicate that much of the major Coastal belt subunit of the Franciscan Complex represents a massive, relatively brief, surge of near-trench deposition and accretion during Eocene time (ca. 53–49 Ma). Sediments were sourced mainly from the distant Idaho Batholith region rather than the nearby Sierra Nevada. Idaho detritus also fed the Great Valley forearc basin of California (ca. 53–37 Ma), the Tyee forearc basin of coastal Oregon (49 to ca. 36 Ma), and the greater Green River lake basin of Wyoming (50–47 Ma). Plutonism in the Idaho Batholith spanned 98–53 Ma in a contractional setting; it was abruptly superseded by major extension in the Bitterroot, Anaconda, Clearwater, and Priest River metamorphic core complexes (53–40 Ma) and by major volcanism in the Challis volcanic field (51–43 Ma). This extensional tectonism apparently deformed and uplifted a broad region, shedding voluminous sediments toward depocenters to the west and southeast. In the Franciscan Coastal belt, the major increase in sediment input apparently triggered a pulse of massive accretion, a pulse ultimately controlled by continental tectonism far within the interior of the North American plate, rather than by some tectonic event along the plate boundary itself.

  2. Ultradispersive adaptive prism based on a coherently prepared atomic medium

    SciTech Connect

    Sautenkov, Vladimir A.; Li Hebin; Rostovtsev, Yuri V.; Scully, Marlan O.

    2010-06-15

    We have experimentally demonstrated an ultra-dispersive optical prism made from a coherently driven Rb atomic vapor. The prism possesses spectral angular dispersion that is 6 orders of magnitude higher than that of a prism made of optical glass; such angular dispersion allows one to spatially resolve light beams with different frequencies separated by a few kilohertz. The prism operates near the resonant frequency of atomic vapor and its dispersion is optically controlled by a coherent driving field.

  3. Comparing Volumes of Prisms and Pyramids

    ERIC Educational Resources Information Center

    Vinogradova, Natalya

    2012-01-01

    Students' experience in using formulas for volumes is often limited to substituting numbers into given formulas. An activity presented in this article may help students make connections between the formulas for volumes of prisms and volumes of pyramids. In addition, some interesting facts from number theory arise, demonstrating strong connections…

  4. Prisms Throw Light on Developmental Disorders

    ERIC Educational Resources Information Center

    Brookes, Rebecca L.; Nicolson, Roderick I.; Fawcett, Angela J.

    2007-01-01

    Prism adaptation, in which the participant adapts to prismatic glasses that deflect vision laterally, is a specific test of cerebellar function. Fourteen dyslexic children (mean age 13.5 years); 14 children with developmental coordination disorder (DCD): 6 of whom had comorbid dyslexia; and 12 control children matched for age and IQ underwent…

  5. Dual-prism interferometer for collimation testing

    SciTech Connect

    Hii, King Ung; Kwek, Kuan Hiang

    2009-01-10

    An air-wedge lateral-shear interferometer using two prisms is presented. With a variable shear, the interferometer is suitable for testing collimation of a wide range of beam sizes down to a few millimeters in diameter. No antireflection coatings are necessary. Collimation for a light source with short coherent length is also demonstrated.

  6. Comparing the Volumes of Rectangular Prisms

    ERIC Educational Resources Information Center

    Assuah, Charles K.; Wiest, Lynda R.

    2010-01-01

    Can middle-grades students determine which of two rectangular prisms has a larger volume? Can they do so without using a formula? Geometry, and particularly the concept of volume, is important in many subjects, such as physics and chemistry. Students greatly enhance their mathematics knowledge when they make generalizations and construct arguments…

  7. Reflecting Schmidt/Littrow Prism Imaging Spectrometer

    NASA Technical Reports Server (NTRS)

    Breckinridge, J. B.; Page, N. A.; Shack, R. V.; Shannon, R. R.

    1985-01-01

    High resolution achieved with wide field of view. Imaging Spectrometer features off-axis reflecting optics, including reflecting "slit" that also serves as field flattener. Only refracting element is prism. By scanning slit across object or scene and timing out signal, both spectral and spatial information in scene are obtained.

  8. PRISM3 Pliocene Sea surface Temperature Reconstruction

    NASA Astrophysics Data System (ADS)

    Dowsett, H.; Robinson, M.; Foley, K.; Caballero, R.

    2008-12-01

    The Pliocene Research, Interpretation and Synoptic Mapping (PRISM) Project provides a conceptual model and synoptic view of the earth during a considerably warmer than modern (2-3°C warmer global mean annual temperature) interval (mid-Piacenzian Age, Pliocene Epoch; ~3.3 to 3.0 Ma) through reconstruction of sea-surface temperature (SST) and other paleoenvironmental parameters. The PRISM3 SST fields include new equatorial Pacific and subpolar - polar North Atlantic components based upon multiproxy (faunal, alkenone and Mg/Ca) temperature analyses from new sites. These data are presented in 12 interpolated global fields with 2° spatial resolution representing monthly SST estimates. Results show a reduced longitudinal temperature gradient across the equatorial Pacific and extension of warm North Atlantic surface conditions into the eastern regions of the Arctic Ocean near Spitzbergen. These data are part of the PRISM3 paleoenvironmental reconstruction designed in part to provide climate modeling groups with new SST and alternative land cover reconstructions, 3-dimensional deep ocean temperature, topography and sea level. The PRISM3 reconstruction is the primary data source for the new Pliocene Climate Model Intercomparison Project (PlioMIP).

  9. Precise Global DEM Generation by ALOS PRISM

    NASA Astrophysics Data System (ADS)

    Tadono, T.; Ishida, H.; Oda, F.; Naito, S.; Minakawa, K.; Iwamoto, H.

    2014-04-01

    The Japan Aerospace Exploration Agency (JAXA) generated the global digital elevation/surface model (DEM/DSM) and orthorectified image (ORI) using the archived data of the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) onboard the Advanced Land Observing Satellite (ALOS, nicknamed "Daichi"), which was operated from 2006 to 2011. PRISM consisted of three panchromatic radiometers that acquired along-track stereo images. It had a spatial resolution of 2.5 m in the nadir-looking radiometer and achieved global coverage, making it a suitable potential candidate for precise global DSM and ORI generation. In the past 10 years or so, JAXA has conducted the calibration of the system corrected standard products of PRISM in order to improve absolute accuracies as well as to validate the high-level products such as DSM and ORI. In this paper, we introduce an overview of the global DEM/DSM dataset generation project, including a summary of ALOS and PRISM, in addition to the global data archive status. It is also necessary to consider data processing strategies, since the processing capabilities of the level 1 standard product and the high-level products must be developed in terms of both hardware and software to achieve the project aims. The automatic DSM/ORI processing software and its test processing results are also described.

  10. Behavioral Consultant Application. PRISM Project Technical Report.

    ERIC Educational Resources Information Center

    Smith, Jesse

    This brief paper describes the Peer Coaching Rural In-Service Model (PRISM) Behavioral Consultant (PBC) program, an online tool for teachers that provides advice on handling simple classroom behavior problems. PBC's advice is based on a series of rules and expressions used by the computer program to make inferences and eliminate inappropriate…

  11. 21 CFR 886.1665 - Ophthalmic rotary prism.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ophthalmic rotary prism. 886.1665 Section 886.1665...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1665 Ophthalmic rotary prism. (a) Identification. An ophthalmic rotary prism is a device with various prismatic powers intended to be handheld...

  12. 21 CFR 886.1655 - Ophthalmic Fresnel prism.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Ophthalmic Fresnel prism. 886.1655 Section 886...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1655 Ophthalmic Fresnel prism. (a) Identification. An ophthalmic Fresnel prism is a device that is a thin plastic sheet with embossed rulings...

  13. 21 CFR 886.1665 - Ophthalmic rotary prism.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Ophthalmic rotary prism. 886.1665 Section 886.1665...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1665 Ophthalmic rotary prism. (a) Identification. An ophthalmic rotary prism is a device with various prismatic powers intended to be handheld...

  14. 21 CFR 886.1655 - Ophthalmic Fresnel prism.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Ophthalmic Fresnel prism. 886.1655 Section 886...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1655 Ophthalmic Fresnel prism. (a) Identification. An ophthalmic Fresnel prism is a device that is a thin plastic sheet with embossed rulings...

  15. 21 CFR 886.1665 - Ophthalmic rotary prism.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Ophthalmic rotary prism. 886.1665 Section 886.1665...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1665 Ophthalmic rotary prism. (a) Identification. An ophthalmic rotary prism is a device with various prismatic powers intended to be handheld...

  16. 21 CFR 886.1665 - Ophthalmic rotary prism.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Ophthalmic rotary prism. 886.1665 Section 886.1665...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1665 Ophthalmic rotary prism. (a) Identification. An ophthalmic rotary prism is a device with various prismatic powers intended to be handheld...

  17. Symmetry Breaking Analysis of Prism Adaptation's Latent Aftereffect

    ERIC Educational Resources Information Center

    Frank, Till D.; Blau, Julia J. C.; Turvey, Michael T.

    2012-01-01

    The effect of prism adaptation on movement is typically reduced when the movement at test (prisms off) differs on some dimension from the movement at training (prisms on). Some adaptation is latent, however, and only revealed through further testing in which the movement at training is fully reinstated. Applying a nonlinear attractor dynamic model…

  18. 21 CFR 886.5810 - Ophthalmic prism reader.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Ophthalmic prism reader. 886.5810 Section 886.5810...) MEDICAL DEVICES OPHTHALMIC DEVICES Therapeutic Devices § 886.5810 Ophthalmic prism reader. (a) Identification. An ophthalmic prism reader is a device intended for use by a patient who is in a supine...

  19. 21 CFR 886.1655 - Ophthalmic Fresnel prism.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ophthalmic Fresnel prism. 886.1655 Section 886...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1655 Ophthalmic Fresnel prism. (a) Identification. An ophthalmic Fresnel prism is a device that is a thin plastic sheet with embossed rulings...

  20. 21 CFR 886.5810 - Ophthalmic prism reader.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ophthalmic prism reader. 886.5810 Section 886.5810...) MEDICAL DEVICES OPHTHALMIC DEVICES Therapeutic Devices § 886.5810 Ophthalmic prism reader. (a) Identification. An ophthalmic prism reader is a device intended for use by a patient who is in a supine...

  1. 21 CFR 886.1665 - Ophthalmic rotary prism.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Ophthalmic rotary prism. 886.1665 Section 886.1665...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1665 Ophthalmic rotary prism. (a) Identification. An ophthalmic rotary prism is a device with various prismatic powers intended to be handheld...

  2. 21 CFR 886.5810 - Ophthalmic prism reader.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Ophthalmic prism reader. 886.5810 Section 886.5810...) MEDICAL DEVICES OPHTHALMIC DEVICES Therapeutic Devices § 886.5810 Ophthalmic prism reader. (a) Identification. An ophthalmic prism reader is a device intended for use by a patient who is in a supine...

  3. 21 CFR 886.5810 - Ophthalmic prism reader.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Ophthalmic prism reader. 886.5810 Section 886.5810...) MEDICAL DEVICES OPHTHALMIC DEVICES Therapeutic Devices § 886.5810 Ophthalmic prism reader. (a) Identification. An ophthalmic prism reader is a device intended for use by a patient who is in a supine...

  4. 21 CFR 886.5810 - Ophthalmic prism reader.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Ophthalmic prism reader. 886.5810 Section 886.5810...) MEDICAL DEVICES OPHTHALMIC DEVICES Therapeutic Devices § 886.5810 Ophthalmic prism reader. (a) Identification. An ophthalmic prism reader is a device intended for use by a patient who is in a supine...

  5. Magnetic prism alignment system for measuring large-angle strabismus.

    PubMed

    Bishop, John Edward

    2014-02-01

    Prismatic measurement of large-angle strabismus requires the simultaneous use of two or more prisms for neutralization. To facilitate the clinical measurement of large-angle strabismus a new prism system was designed utilizing a flat plate and a ferrous metal surface coupled with prisms containing rare earth magnets implanted in their base and bottom surfaces.

  6. Boolean Operations with Prism Algebraic Patches

    PubMed Central

    Bajaj, Chandrajit; Paoluzzi, Alberto; Portuesi, Simone; Lei, Na; Zhao, Wenqi

    2009-01-01

    In this paper we discuss a symbolic-numeric algorithm for Boolean operations, closed in the algebra of curved polyhedra whose boundary is triangulated with algebraic patches (A-patches). This approach uses a linear polyhedron as a first approximation of both the arguments and the result. On each triangle of a boundary representation of such linear approximation, a piecewise cubic algebraic interpolant is built, using a C1-continuous prism algebraic patch (prism A-patch) that interpolates the three triangle vertices, with given normal vectors. The boundary representation only stores the vertices of the initial triangulation and their external vertex normals. In order to represent also flat and/or sharp local features, the corresponding normal-per-face and/or normal-per-edge may be also given, respectively. The topology is described by storing, for each curved triangle, the two triples of pointers to incident vertices and to adjacent triangles. For each triangle, a scaffolding prism is built, produced by its extreme vertices and normals, which provides a containment volume for the curved interpolating A-patch. When looking for the result of a regularized Boolean operation, the 0-set of a tri-variate polynomial within each such prism is generated, and intersected with the analogous 0-sets of the other curved polyhedron, when two prisms have non-empty intersection. The intersection curves of the boundaries are traced and used to decompose each boundary into the 3 standard classes of subpatches, denoted in, out and on. While tracing the intersection curves, the locally refined triangulation of intersecting patches is produced, and added to the boundary representation. PMID:21516262

  7. High-Power Prismatic Devices for Oblique Peripheral Prisms

    PubMed Central

    Peli, Eli; Bowers, Alex R.; Keeney, Karen; Jung, Jae-Hyun

    2016-01-01

    ABSTRACT Purpose Horizontal peripheral prisms for hemianopia provide field expansion above and below the horizontal meridian; however, there is a vertical gap leaving the central area (important for driving) without expansion. In the oblique design, tilting the bases of both prism segments toward the horizontal meridian moves the field expansion area vertically and centrally (closing the central gap) while the prisms remain in the peripheral location. However, tilting the prisms results also in a reduction of the lateral field expansion. Higher prism powers are needed to counter this effect. Methods We developed, implemented, and tested a series of designs aimed at increasing the prism power to reduce the central gap while maintaining wide lateral expansion. The designs included inserting the peripheral prisms into carrier lenses that included yoked prism in the opposite direction, combination of two Fresnel segments attached at the base and angled to each other (bi-part prisms), and creating Fresnel prism–like segments from nonparallel periscopic mirror pairs (reflective prisms). Results A modest increase in lateral power was achieved with yoked-prism carriers. Bi-part combination of 36Δ Fresnel segments provided high power with some reduction in image quality. Fresnel reflective prism segments have potential for high power with superior optical quality but may be limited in field extent or by interruptions of the expanded field. Extended apical scotomas, even with unilateral fitting, may limit the utility of very high power prisms. The high-power bi-part and reflective prisms enable a wider effective eye scanning range (more than 15 degrees) into the blind hemifield. Conclusions Conventional prisms of powers higher than the available 57Δ are limited by the binocular impact of a wider apical scotoma and a reduced effective eye scanning range to the blind side. The various designs that we developed may overcome these limitations and find use in various other

  8. Fresnel prisms and their effects on visual acuity and binocularity.

    PubMed Central

    Véronneau-Troutman, S

    1978-01-01

    1. The visual acuity with the Fresnel membrane prism is significantly less than that with the conventional prism of the same power for all prism powers from 12 delta through 30 delata at distance and from 15 delta through 30 delta at near. 2. The difference in the visual acuity between base up and base down, and between base in and base out, is not significantly different for either the Fresnel membrane prism or for the conventional prism. 3. For both Fresnel membrane prism and the conventional prism, the visual acuity when looking straight ahead. 4. Using Fresnel membrane prisms of the same power from different lots, the visual acuity varied significantly. The 30 delta prism caused the widest range in visual acuity. 5. When normal subjects are fitted with the higher powers of the Fresnel membrane prism, fusion and stereopsis are disrupted to such an extent that the use of this device to restore or to improve binocular vision in cases with large-angle deviations is seriously questioned. 6. Moreover, the disruption of fusion and stereopsis is abrupt and severe and does not parallel the decrease in visual acuity. The severely reduced ability to maintain fusion may be related to the optical aberrations, which, in turn, may be due to the molding process and the polyvinyl chloride molding material. 7. Through the flexibility of the membrane prism is a definite advantage, because of its proclivity to reduce visual acuity and increase aberrations its prescription for adults often must be limited to only one eye. 8. For the same reasons in the young child with binocular vision problems, the membrane prism presently available should be prescribed over both eyes only in powers less than 20 delta. When the membrane prism is to be used as a partial occluder (over one eye only), any power can be used. 9. The new Fresnel "hard" prism reduces visual acuity minimally and rarely disrupts binocularity, thus increasing the potential for prismotherapy to establish binocularity. This

  9. Self-referenced prism deflection measurement schemes with microradian precision

    SciTech Connect

    Olson, Rebecca; Paul, Justin; Bergeson, Scott; Durfee, Dallin S

    2005-08-01

    We have demonstrated several inexpensive methods that can be used to measure the deflection angles of prisms with microradian precision. The methods are self-referenced, where various reversals are used to achieve absolute measurements without the need of a reference prism or any expensive precision components other than the prisms under test. These techniques are based on laser interferometry and have been used in our laboratory to characterize parallel-plate beam splitters, penta prisms, right-angle prisms, and corner cube reflectors using only components typically available in an optics laboratory.

  10. Linking magmatism with collision in an accretionary orogen

    PubMed Central

    Li, Shan; Chung, Sun-Lin; Wilde, Simon A.; Wang, Tao; Xiao, Wen-Jiao; Guo, Qian-Qian

    2016-01-01

    A compilation of U-Pb age, geochemical and isotopic data for granitoid plutons in the southern Central Asian Orogenic Belt (CAOB), enables evaluation of the interaction between magmatism and orogenesis in the context of Paleo-Asian oceanic closure and continental amalgamation. These constraints, in conjunction with other geological evidence, indicate that following consumption of the ocean, collision-related calc-alkaline granitoid and mafic magmatism occurred from 255 ± 2 Ma to 251 ± 2 Ma along the Solonker-Xar Moron suture zone. The linear or belt distribution of end-Permian magmatism is interpreted to have taken place in a setting of final orogenic contraction and weak crustal thickening, probably as a result of slab break-off. Crustal anatexis slightly post-dated the early phase of collision, producing adakite-like granitoids with some S-type granites during the Early-Middle Triassic (ca. 251–245 Ma). Between 235 and 220 Ma, the local tectonic regime switched from compression to extension, most likely caused by regional lithospheric extension and orogenic collapse. Collision-related magmatism from the southern CAOB is thus a prime example of the minor, yet tell-tale linking of magmatism with orogenic contraction and collision in an archipelago-type accretionary orogen. PMID:27167207

  11. Unraveling the New England orocline, east Gondwana accretionary margin

    NASA Astrophysics Data System (ADS)

    Cawood, P. A.; Pisarevsky, S. A.; Leitch, E. C.

    2011-10-01

    The New England orocline lies within the Eastern Australian segment of the Terra Australis accretionary orogen and developed during the late Paleozoic to early Mesozoic Gondwanide Orogeny (310-230 Ma) that extended along the Pacific margin of the Gondwana supercontinent. The orocline deformed a pre-Permian arc assemblage consisting of a western magmatic arc, an adjoining forearc basin and an eastern subduction complex. The orocline is doubly vergent with the southern and northern segments displaying counter-clockwise and clockwise rotation, respectively, and this has led to contrasting models of formation. We resolve these conflicting models with one that involves buckling of the arc system about a vertical axis during progressive northward translation of the southern segment of the arc system against the northern segment, which is pinned relative to cratonic Gondwana. Paleomagnetic data are consistent with this model and show that an alternative model involving southward motion of the northern segment relative to the southern segment and cratonic Gondwana is not permissible. The timing of the final stage of orocline formation (˜270-265 Ma) overlaps with a major gap in magmatic activity along this segment of the Gondwana margin, suggesting that northward motion and orocline formation were driven by a change from orthogonal to oblique convergence and coupling between the Gondwana and Pacific plates.

  12. Linking magmatism with collision in an accretionary orogen.

    PubMed

    Li, Shan; Chung, Sun-Lin; Wilde, Simon A; Wang, Tao; Xiao, Wen-Jiao; Guo, Qian-Qian

    2016-05-11

    A compilation of U-Pb age, geochemical and isotopic data for granitoid plutons in the southern Central Asian Orogenic Belt (CAOB), enables evaluation of the interaction between magmatism and orogenesis in the context of Paleo-Asian oceanic closure and continental amalgamation. These constraints, in conjunction with other geological evidence, indicate that following consumption of the ocean, collision-related calc-alkaline granitoid and mafic magmatism occurred from 255 ± 2 Ma to 251 ± 2 Ma along the Solonker-Xar Moron suture zone. The linear or belt distribution of end-Permian magmatism is interpreted to have taken place in a setting of final orogenic contraction and weak crustal thickening, probably as a result of slab break-off. Crustal anatexis slightly post-dated the early phase of collision, producing adakite-like granitoids with some S-type granites during the Early-Middle Triassic (ca. 251-245 Ma). Between 235 and 220 Ma, the local tectonic regime switched from compression to extension, most likely caused by regional lithospheric extension and orogenic collapse. Collision-related magmatism from the southern CAOB is thus a prime example of the minor, yet tell-tale linking of magmatism with orogenic contraction and collision in an archipelago-type accretionary orogen.

  13. Present-day stress states underneath the Kumano basin to 2 km below seafloor based on borehole wall failures at IODP site C0002, Nankai accretionary wedge

    NASA Astrophysics Data System (ADS)

    Chang, Chandong; Song, Insun

    2016-11-01

    We constrain the state of stress to 2 km below seafloor in the Nankai accretionary prism at the Integrated Ocean Drilling Program (IODP) site C0002F, southwest Japan, based on borehole wall failures and rock strengths. The logging-while-drilling resistivity images from 872.5 to 2005.5 m below seafloor show that drilling-mud control in riser drilling worked properly to minimize borehole wall failures. Available breakouts indicate a consistent maximum compression orientation subparallel to the subducting plate margin. Breakout analysis with drill logs suggests that breakouts occurred only when borehole pressure was slightly lowered and time lag between hole cutting and image logging was several hours. This indicates that the observed breakouts are not immediate stress-induced failure but brought up into shape gradually with time due to other mechanisms. Laboratory investigations on deformation and failure of the cores suggest that the time-delayed breakout might be a result of progressive rock spall-out in borehole wall damage zones that occur at a stress level close to failure condition. We constrain stress magnitudes assuming that the stress state is sufficient to bring about the damage zones at the borehole wall. An integrated method utilizing breakouts, drilling-induced tensile fractures, and a leak-off test suggests that the stress states are on the boundary between strike-slip faulting and normal faulting stress regimes, and somewhat variable depending on depth. The stress magnitudes in the accretionary wedge appear to be controlled by frictional strength of the rock, such that the differential stresses are constrained by the laboratory determined frictional coefficients.

  14. Enamel prism morphology in molar teeth of small eutherian mammals.

    PubMed

    Dumont, E R

    1996-01-01

    Data summarizing enamel prism shape, size and spacing are reported for the molar enamel of 55 species of small eutherian mammals including primates, bats, tree shrews, flying lemurs, insectivorans and representatives of a variety of fossil families. Confocal photomicrographs reveal that the subsurface enamel of most species is characterized by arc-shaped prisms. The lack of a clear distinction between pattern 2 and pattern 3 prism configurations within single specimens suggests that the broad category "arc-shaped prisms" is the most appropriate descriptive grouping for these species. Of the total sample, three species exhibit only circular prisms while no evidence of prismatic enamel was found in two bats. Prism shape is not an informative phylogenetic character at the ordinal level for these morphologically primitive and relatively thin-enameled taxa. Significant differences between species in several prism size and spacing variables (central distance between prisms, prism diameter, prism area and the ratio of prism area to estimated ameloblast area) suggest the potential for further analyses of quantitative variation to document evolutionary relationships within or among family-level groups.

  15. Plutons and accretionary episodes of the Klamath Mountains, California and Oregon

    USGS Publications Warehouse

    Irwin, William P.; Wooden, Joseph L.

    1999-01-01

    The Klamath Mountains consist of various accreted terranes and include many plutons that range in composition from gabbro to granodiorite. Some of the plutons (preaccretionary plutons) were parts of terranes before the terranes accreted; others (accretionary plutons) intruded during or after the accretion of their host terrane(s). This report attempts to (1) graphically illustrate how the Klamath Mountains grew by the accretion of allochthonous oceanic terranes during early Paleozoic to Cretaceous times, (2) identify the plutons as either preaccretionary or accretionary, and (3) genetically relate the plutonic intrusions to specific accretionary episodes. The eight accretionary episodes portrayed in this report are similar to those shown by Irwin and Mankinen (1998) who briefly described the basis for the timing of the episodes and who illustrated the ~110 degrees of clockwise rotation of the Klamath Mountains since Early Devonian time. Each episode is named for the accreting terrane. In all episodes (Figs. 1-8), the heavy black line represents a fault that separates the accreting oceanic rocks on the left from earlier accreted terranes on the right. The preaccretionary plutons are shown within the accreting oceanic crustal rocks to the left of the heavy black line, and the accretionary plutons in most instances are shown intruding previously accreted terranes to the right. Episodes earlier than the Central Metamorphic episode (Fig. 1), and that may have been important in the formation of the early Paleozoic nucleous of the province (the Eastern Klamath terrane), are not known. The 'Present Time' distribution of the accreted terranes and plutons is shown at a large scale in Figure 9. The schematic vertical section (Fig. 10) depicts the terranes as a stack of horizontal slabs that include or are intruded by vertical plutons. Note that at their base the ~170 Ma preaccretionary plutons of the Western Hayfork subterrane are truncated by the ~164 Ma Salt Creek

  16. [Integration design and diffraction characteristics analysis of prism-grating-prism].

    PubMed

    He, Tian-Bo; Bayanheshig; Li, Wen-Hao; Kong, Peng; Tang, Yu-Guo

    2014-01-01

    Prism-grating-prism (PGP) module is the important dispersing component in the hyper spectral imager. In order to effectively predict the distribution of diffraction efficiency of the whole PGP component and its diffraction characteristics before fabrication, a method of the PGP integration design is proposed. From the point of view of the volume phase holographic grating (VPHG) design, combined with the restrictive correlation between the various parameters of prisms and grating, we compiled the analysis software for calculating the whole PGP's diffraction efficiency. Furthermore, the effects of the structure parameters of prisms and grating on the PGP's diffraction characteristics were researched in detail. In particular we discussed the Bragg wavelength shift behaviour of the grating and a broadband PGP spectral component with high diffraction efficiency was designed for the imaging spectrometers. The result of simulation indicated that the spectral bandwidth of the PGP becomes narrower with the dispersion coefficient of prism 1 material decreasing; Bragg wavelength shift characteristics broaden the bandwidth of VPHG both spectrally and angularly, higher angular selectivity is desirable for selection requirements of the prism 1 material, and it can be easily tuned to achieve spectral bandwidth suitable for imaging PGP spectrograph; the vertex angle of prism 1, the film thickness and relative permittivity modulation of the grating have a significant impact on the distribution of PGP's diffraction efficiency, so precision control is necessary when fabrication. The diffraction efficiency of the whole PGP component designed by this method is no less than 50% in the wavelength range from 400 to 1000 nm, the specific design parameters have been given in this paper that have a certain reference value for PGP fabrication.

  17. Effects of Prism Eyeglasses on Objective and Subjective Fixation Disparity.

    PubMed

    Schroth, Volkhard; Joos, Roland; Jaschinski, Wolfgang

    2015-01-01

    In optometry of binocular vision, the question may arise whether prisms should be included in eyeglasses to compensate an oculomotor and/or sensory imbalance between the two eyes. The corresponding measures of objective and subjective fixation disparity may be reduced by the prisms, or the adaptability of the binocular vergence system may diminish effects of the prisms over time. This study investigates effects of wearing prisms constantly for about 5 weeks in daily life. Two groups of 12 participants received eyeglasses with prisms having either a base-in direction or a base-out direction with an amount up to 8 prism diopters. Prisms were prescribed based on clinical fixation disparity test plates at 6 m. Two dependent variables were used: (1) subjective fixation disparity was indicated by a perceived offset of dichoptic nonius lines that were superimposed on the fusion stimuli and (2) objective fixation disparity was measured with a video based eye tracker relative to monocular calibration. Stimuli were presented at 6 m and included either central or more peripheral fusion stimuli. Repeated measurements were made without the prisms and with the prisms after about 5 weeks of wearing these prisms. Objective and subjective fixation disparity were correlated, but the type of fusion stimulus and the direction of the required prism may play a role. The prisms did not reduce the fixation disparity to zero, but induced significant changes in fixation disparity with large effect sizes. Participants receiving base-out prisms showed hypothesized effects, which were concurrent in both types of fixation disparity. In participants receiving base-in prisms, the individual effects of subjective and objective effects were negatively correlated: the larger the subjective (sensory) effect, the smaller the objective (motor) effect. This response pattern was related to the vergence adaptability, i.e. the individual fusional vergence reserves.

  18. Total internal reflection photonic crystal prism.

    PubMed

    Schonbrun, Ethan; Abashin, Maxim; Blair, John; Wu, Qi; Park, Wounjhang; Fainman, Yeshaiahu; Summers, Christopher J

    2007-06-25

    An integrated total internal reflection prism is demonstrated that generates a transversely localized evanescent wave along the boundary between a photonic crystal and an etched out trench. The reflection can be described by either the odd symmetry of the Bloch wave or a tangential momentum matching condition. In addition, the Bloch wave propagates through the photonic crystal in a negative refraction regime, which manages diffraction within the prism. A device with three input channels has been fabricated and tested that illuminates different regions of the reflection interface. The reflected wave is then sampled by a photonic wire array, where the individual channels are resolved. Heterodyne near field scanning optical microscopy is used to characterize the spatial phase variation of the evanescent wave and its decay constant.

  19. Opera: Objective-Prism Reduction Package

    NASA Astrophysics Data System (ADS)

    García Dabó, C. E.; Gallego, J.

    1998-06-01

    Surveys of star-forming galaxies are of vital importance to constrain galactic evolution theories. One of the most successful searching methods is the objective-prism (OP) technique, which can register thousands of low resolution spectra in large areas. The UCM-CIDA (Universidad Complutense de Madrid-Centro de Investigación F. J. Duarte) project expects to cover 150 square degrees and detect ˜ 2000 Hα emission line galaxies.

  20. Evaluations of 1990 PRISM design revisions

    SciTech Connect

    Van Tuyle, G.J.; Slovik, G.C.; Chan, B.C.; Aronson, A.L.; Kennett, R.J.

    1992-03-01

    Analyses of the 1990 version of the PRISM Advanced Liquid Metal Reactor (ALMR) design are presented and discussed. Most of the calculations were performed using BNL computer codes, particularly SSC and MINET. In many cases, independent BNL calculations were compared against analyses presented by General Electric when they submitted the PRISM design revisions for evaluation by the Nuclear Regulatory Commission (NRC). The current PRISM design utilizes the metallic fuel developed by Argonne National Laboratory (ANL) which facilitates the passive/``inherent`` shutdown mechanism that acts to shut down reactor power production whenever the system overheats. There are a few vulnerabilities in the passive shutdown, with the most worrisome being the positive feedback from sodium density decreases or sodium voiding. Various postulated unscrammed events were examined by GE and/or BNL, and much of the analysis discussed in this report is focused on this category of events. For the most part, the BNL evaluations confirm the information submitted by General Electric. The principal areas of concern are related to the performance of the ternary metal fuel, and may be resolved as ANL continues with its fuel development and testing program.

  1. Risley prism universal pointing system (RPUPS)

    NASA Astrophysics Data System (ADS)

    Dixon, John; Engel, James R.; Vaillancourt, Robert; Schwarze, Craig; Potter, Kevin

    2015-09-01

    OPTRA is currently developing a Risley Prism Universal Pointing System (RPUPS): a highly customizable cued beamsteering system. The RPUPS consists of a visible or infrared cueing imager co-aligned with an optical beam steering system's pointing-field-of-regard. The cueing imager is used to identify a region-of-interest within its wide field-of-view, via a wireless tablet device. The tablet user can choose to manually or automatically, identify and track regions-of-interest. The optical beam steering system uses a matched pair of Risley Prisms to direct an interrogating optical system's instantaneous-field-of-view onto the identified region-of-interest. The tablet updates the user with real time information from both the cueing imager and the interrogating optical system. Risley prism material and geometry choices provide operating wavelength, aperture size, and field-of-regard flexibility for this front-end pointing component. Back-end components may be receive-only, transmit-only, or transmit/receive combinations. The flexibility of the RPUPS allows for mission specific customization where applications include but are not limited to: synthetic foveated imaging, spectroscopic probes and laser (LIDAR) ranging and tracking. This paper will focus on the design and anticipated applications of the RPUPS.

  2. Prisms to Shift Pain Away: Pathophysiological and Therapeutic Exploration of CRPS with Prism Adaptation.

    PubMed

    Christophe, Laure; Chabanat, Eric; Delporte, Ludovic; Revol, Patrice; Volckmann, Pierre; Jacquin-Courtois, Sophie; Rossetti, Yves

    Complex Regional Pain Syndrome (CRPS) is an invalidating chronic condition subsequent to peripheral lesions. There is growing consensus for a central contribution to CRPS. However, the nature of this central body representation disorder is increasingly debated. Although it has been repeatedly argued that CRPS results in motor neglect of the affected side, visual egocentric reference frame was found to be deviated toward the pain, that is, neglect of the healthy side. Accordingly, prism adaptation has been successfully used to normalize this deviation. This study aimed at clarifying whether 7 CRPS patients exhibited neglect as well as exploring the pathophysiological mechanisms of this manifestation and of the therapeutic effects of prism adaptation. Pain and quality of life, egocentric reference frames (visual and proprioceptive straight-ahead), and neglect tests (line bisection, kinematic analyses of motor neglect and motor extinction) were repeatedly assessed prior to, during, and following a one-week intense prism adaptation intervention. First, our results provide no support for visual and motor neglect in CRPS. Second, reference frames for body representations were not systematically deviated. Third, intensive prism adaptation intervention durably ameliorated pain and quality of life. As for spatial neglect, understanding the therapeutic effects of prism adaptation deserves further investigations.

  3. Prisms to Shift Pain Away: Pathophysiological and Therapeutic Exploration of CRPS with Prism Adaptation

    PubMed Central

    Volckmann, Pierre; Jacquin-Courtois, Sophie

    2016-01-01

    Complex Regional Pain Syndrome (CRPS) is an invalidating chronic condition subsequent to peripheral lesions. There is growing consensus for a central contribution to CRPS. However, the nature of this central body representation disorder is increasingly debated. Although it has been repeatedly argued that CRPS results in motor neglect of the affected side, visual egocentric reference frame was found to be deviated toward the pain, that is, neglect of the healthy side. Accordingly, prism adaptation has been successfully used to normalize this deviation. This study aimed at clarifying whether 7 CRPS patients exhibited neglect as well as exploring the pathophysiological mechanisms of this manifestation and of the therapeutic effects of prism adaptation. Pain and quality of life, egocentric reference frames (visual and proprioceptive straight-ahead), and neglect tests (line bisection, kinematic analyses of motor neglect and motor extinction) were repeatedly assessed prior to, during, and following a one-week intense prism adaptation intervention. First, our results provide no support for visual and motor neglect in CRPS. Second, reference frames for body representations were not systematically deviated. Third, intensive prism adaptation intervention durably ameliorated pain and quality of life. As for spatial neglect, understanding the therapeutic effects of prism adaptation deserves further investigations. PMID:27668094

  4. Structural development of the western Makran Accretionary Complex, Offshore Iran

    NASA Astrophysics Data System (ADS)

    Burberry, C. M.; Jackson, C. A.

    2013-12-01

    The Makran Accretionary Complex (MAC), which straddles the southern offshore regions of Iran and Pakistan, is a fold-thrust system bound by the Murray Ridge and Ornach Nal Fault to the east, and the Minab Fault System (MFS) to the west. It is c. 1000 km wide and the frontal c. 125 km of the system is submerged beneath the Gulf of Oman. Relatively little is known about this system, despite the fact that constitutes a large portion of the Central Tethyan Orogen and is one of the largest accretionary complexes in the world. We use offshore 2D seismic reflection data to investigate the structural style and evolution of the Iranian segment of the MAC. The MAC is divided into two morphologically distinct domains: (i) a northern domain (Domain 1), which is located landward of a prominant break-in-slope on the seabed and is characterised by a series of normal fault-bound sub-basins that are approximately 50 km wide, and which contain numerous, unconformity-bound seismic units; and (ii) a southern domain (Domain 2), which is located basinward of the prominent seabed slope break, and is characterised by alternating ridges and troughs. Seismic data indicate that these structures are laterally continuous (over 100 km long) north-dipping thrust faults, which are overlain by south-verging, non-cylindrical, fault-propagation folds. Towards the western end of the study area, immediately offshore of the prominent onshore trace of the MFS, there is no single structure that can be reliably interpreted as the offshore extension of the MFS. Instead, a series of oblique-slip faults with thrust and strike-slip components are identified, spanning a zone that is c. 40 km wide. In the north and close to the coastline, the faults are dominantly strike-slip, whereas further south, closer to the deformation front, the thrust-sense component is more important. Irrespective of their slip sense, faults in this zone have a similar N-S strike to the onshore trace of the MFS. In addition, the basin

  5. Propagation tectonics and multiple accretionary processes of the Qinling Orogen

    NASA Astrophysics Data System (ADS)

    Dong, Yunpeng; Zhang, Xiaoning; Liu, Xiaoming; Li, Wei; Chen, Qing; Zhang, Guowei; Zhang, Hongfu; Yang, Zhao; Sun, Shengsi; Zhang, Feifei

    2015-05-01

    The Qinling Orogen was built through collision between the North China and South China Blocks. Previous detailed geological, geochemical and geochronological investigations revealed that the mountain range can be divided into four tectonic units with distinct tectono-lithostratigraphy, which are, from north to south, the southern sector of the North China Block, North Qinling Belt, South Qinling Belt and northern sector of the South China Block, separated by the Kuanping, Shangdan and Mianlue sutures. According to the petrology, geochemistry and geochronology of ophiolitic mélanges and related magmatic rocks, as well as the features of sedimentary units, we think that the North China Block, the North Qinling Belt and the South China Block were originally independent continental units while the South Qinling Belt had been the northern part of the South China Block. These units experienced three episodes of accretionary tectonic processes and amalgamation from south to north. The Neoproterozoic accretion took place along the Luonan-Luanchuan Fault and Kuanping ophiolitic mélange belt as a result of southward subduction and subsequent collision between the North Qinling and North China Blocks during ca. 1.0-0.8 Ga related to the formation of the supercontinent of Rodinia. The Paleozoic accretion occurred along the Shangdan suture resulted from northward subduction of oceanic lithosphere in the Early Paleozoic and subsequent continental subduction in the Late Paleozoic. Late Triassic accretion took place along the Mianlue suture between the South Qinling and South China Blocks due to northward subduction of the Mianlue oceanic lithosphere during the Permian-Early Triassic and subsequent collision in the Late Triassic. After the Late Triassic collision along the Mianlue suture the whole Qinling Mountain range entered the phase of intense intracontinental deformation.

  6. Mud volcano venting induced gas hydrate formation at the upper slope accretionary wedge, offshore SW Taiwan

    NASA Astrophysics Data System (ADS)

    Lin, Saulwood; Tseng, Yi-Ting; Cheng, Wan-Yen; Chou, Cheng-Tien; Chen, NeiChen; Hsieh, I.-Chih

    2016-04-01

    TsanYao Mud Volcano (TYMV) is the largest mud volcano cone in the Hengchun Mud Volcano Group (HCMVG), located at the upper slope of the accrretionary wedge, southwest of Taiwan. The region is under active tectonic activity with the Philippine Plate, moving northwestward at a rate of ~8 cm/year. This region also receives huge quantity of suspended particle load of ~100 mT/year at present time from adjacent small rivers of the Island of Taiwan. Large loads of suspended sediments influx become a major source of organic carbon and later gas and other hydrocarbon. Gas and fluid in the mud volcano are actively venting from deep to the sea floor on the upper slope of the accretionary wedge. In order to understand venting on the HCMVG, echo sounder, towcam and coring were carried out. Pore water sulfate, chloride, potassium, calcium, stable isotope O-18, gas compositions, dissolved sulfide were analysed. The HCMVG consists of 12 volcano cones of different sizes. Large quantity of gas and fluid are venting directly from deep to the TYMV structure high, as well as 50+ other vents as appeared as flares on the echo sounder. Some flares are reaching to the atmosphere and likely a source of green house gases to the atmosphere. Venting fluids include gas bubbles, suspended particle, mud, and breccia. Breccia size could reach more than 12 cm in diameter. Circular bands in different color appeared around the cone may represent stages of vent eruptions. Compositions of vent gas include methane, ethane and propane. High proportions of ethane and propane in the vent gas demonstrated that source of gas are thermogenic in origin. Patchy authigenic carbonate, bacterial mats, bivalves, tube worms and other chemosynthesis organisms were supported by venting gas AOM process near the sea floor. Pore water chloride concentrations show distinct variation pattern from center cone to the side of the volcano, with low in the center and high away from the cone. Pore water with higher than seawater

  7. Strengthening of synthetic quartz-rich sediments during time-dependent compaction due to pressure solution-precipitation compaction creep

    NASA Astrophysics Data System (ADS)

    Noda, H.; Okazaki, K.; Katayama, I.

    2013-12-01

    During diagenesis, incohesive sediments are compacted and gain strength against shear deformation for a geologically long time scale. The evolution of shear strength as well as the change in the mechanical and hydraulic characteristics under shear deformation is of significant importance in considering deformation at shallow part of the subduction zones and in accretionary prisms. Sediments after induration due to time-dependent diagenesis process probably deform with increases in porosity and permeability much more significantly than normally compacted incohesive sediments. An active fault in a shallow incohesive medium may favor thermal pressurization of pore fluid when slid rapidly, while the lack of time-dependent healing effect may cause stable (e.g., rate-strengthening) frictional property there. On the other hand, indurated sediments may deform with significant post-failure weakening, and thus exhibit localization of deformation or unstable behavior. In order to investigate how the time-dependent compaction and induration affect the mechanical and hydraulic characteristics of sediments under deformation, we have conducted a series of compaction experiments under hydrothermal conditions (at temperatures from R.T. to 500 °C, 200 MPa confining pressure, 100 MPa pore water pressure, and for various time), and following triaxial deformation experiments for the compacted samples, with monitoring permeability and storage capacity with pore pressure oscillation method [Fischer and Paterson, 1992]. Previous work [e.g., Niemeijer et at., 2003] reported that under the adopted conditions, quartz aggregate deforms by pressure solution-precipitation creep. The initial synthetic sediments have been prepared by depositing commercially available crushed quartzite the grain size of which is about 6 μm on average. 4 cm long samples have been extracted from the middle of 10 cm long deposited columns. The experiments have been performed with a gas-medium apparatus in Hiroshima

  8. Linking megathrust earthquakes to brittle deformation in a fossil accretionary complex

    PubMed Central

    Dielforder, Armin; Vollstaedt, Hauke; Vennemann, Torsten; Berger, Alfons; Herwegh, Marco

    2015-01-01

    Seismological data from recent subduction earthquakes suggest that megathrust earthquakes induce transient stress changes in the upper plate that shift accretionary wedges into an unstable state. These stress changes have, however, never been linked to geological structures preserved in fossil accretionary complexes. The importance of coseismically induced wedge failure has therefore remained largely elusive. Here we show that brittle faulting and vein formation in the palaeo-accretionary complex of the European Alps record stress changes generated by subduction-related earthquakes. Early veins formed at shallow levels by bedding-parallel shear during coseismic compression of the outer wedge. In contrast, subsequent vein formation occurred by normal faulting and extensional fracturing at deeper levels in response to coseismic extension of the inner wedge. Our study demonstrates how mineral veins can be used to reveal the dynamics of outer and inner wedges, which respond in opposite ways to megathrust earthquakes by compressional and extensional faulting, respectively. PMID:26105966

  9. Linking megathrust earthquakes to brittle deformation in a fossil accretionary complex.

    PubMed

    Dielforder, Armin; Vollstaedt, Hauke; Vennemann, Torsten; Berger, Alfons; Herwegh, Marco

    2015-06-24

    Seismological data from recent subduction earthquakes suggest that megathrust earthquakes induce transient stress changes in the upper plate that shift accretionary wedges into an unstable state. These stress changes have, however, never been linked to geological structures preserved in fossil accretionary complexes. The importance of coseismically induced wedge failure has therefore remained largely elusive. Here we show that brittle faulting and vein formation in the palaeo-accretionary complex of the European Alps record stress changes generated by subduction-related earthquakes. Early veins formed at shallow levels by bedding-parallel shear during coseismic compression of the outer wedge. In contrast, subsequent vein formation occurred by normal faulting and extensional fracturing at deeper levels in response to coseismic extension of the inner wedge. Our study demonstrates how mineral veins can be used to reveal the dynamics of outer and inner wedges, which respond in opposite ways to megathrust earthquakes by compressional and extensional faulting, respectively.

  10. Forward Versus Back Thrusts in Accretionary Wedges: Effects of Rheology and Thickness of the Décollement Layer

    NASA Astrophysics Data System (ADS)

    Ito, Garrett; Olive, Jean-Arthur; Moore, Gregory; Gutscher, Marc-Andre; Weiss, Jonathan

    2016-04-01

    The mechanical processes that control whether major thrusts in accretionary wedges verge forward toward the foreland, versus backward toward the hinterland has long been a topic of debate. Whereas forethrusts are the most common major thrusts, the importance of the globally rare back thrusts has recently been highlighted given their prominence along the Cascadia margin off of the NW coast of North America as well as along the Andaman-Sumatra subduction zone, in the rupture area of the great 2004 earthquake. We address this problem using 2-D numerical models that use a finite-difference, particle-in-cell method with a viscoelastic-plastic rheology for simulating thrusting in accretionary wedges. Simulations of a weak frictional décollement confirm prior numerical and analogue modeling studies in that they predict lower wedge tapers and repeated sequences of doubly verging conjugate thrusts. A forward dipping backstop was shown in prior laboratory experiments to promote backthrusting, and our results confirm that backthrusting occurs near the backstop but as the wedge widens away from the backstop forethrusts become dominant. Other laboratory experimental studies have found that a non-brittle, viscously deforming décollement can promote backthrusting. Our numerical models show that if the viscosity of the décollement layer η is too high, such that the stress scale, ηU/H (where U is the convergence rate and H is the décollement layer thickness), is comparable to the frictional strength at the base, then forethrusts dominate. For ηU/H less than the basal frictional strength, doubly verging faults are prominent over a wide range of décollement layer thicknesses. Only for cases with relatively low ηU/H and décollement layer thicknesses H that are 25-33% of the thickness of the whole, incoming sediment layer do backthrusts dominate. Thus backthrusting appears to require unusual rheological properties of the deepest sediments, which is consistent with the rarity

  11. Accretionary complex structure and kinematics during Paleozoic arc continent collision in the southern Urals

    NASA Astrophysics Data System (ADS)

    Alvarez-Marron, J.; Brown, D.; Perez-Estaun, A.; Puchkov, V.; Gorozhanina, Y.

    2000-10-01

    The southern Urals contain a well-preserved accretionary complex that has overthrust the continental margin during arc-continent collision between the East European Craton (EEC) and the Magnitogorsk island arc in the Late Devonian. Within the accretionary complex, we study three tectonic units that differ in deformation style, and each provides a unique geodynamic implication. The Zilair Nappe, the largest and best exposed unit, consists of 5-6 km of syncollisional, arc-derived Upper Devonian to Lower Carboniferous polymictic and graywacke turbidites that were deposited across the continental margin and incorporated by frontal accretion into the accretionary complex. The Zilair Nappe is a bivergent thrust imbricate where the west-vergent thrusts dominate and have associated kilometer-scale ramp anticlines with well developed east-dipping axial planar cleavage. Along its eastern contact, however, the cleavage fans until it dips moderately westward and the folds are east-vergent. Following its emplacement, west-vergent, basement-involved thrusting that breached the whole accretionary complex imbricated the Zilair Nappe. The Timirovo Duplex is structurally beneath the Zilair Nappe, and outcrops for several tens of kilometers along its northwestern margin. The duplex forms a west-vergent thrust stack composed of a highly deformed and sheared Lower and Middle Devonian reef carbonates of the former EEC margin platform. These rocks were shallowly underplated at the base of the accretionary complex during emplacement over the margin. The Suvanyak Complex outcrops along the eastern contact of the Zilair Nappe, and consists of polydeformed greenschist facies metasediments of the former EEC slope that were offscraped, underplated and incorporated at the rear of the accretionary complex.

  12. The Eurekan Orogeny: convergent intraplate deformation through accretionary tectonics?

    NASA Astrophysics Data System (ADS)

    Heron, Philip; Pysklywec, Russell; Stephenson, Randell

    2015-04-01

    The Eurekan Orogeny, which created much of the high topography (~1-2km) of Ellesmere Island and adjacent Greenland, exhibits a crustal architecture linked to intraplate orogenesis in the Cenozoic. These features occurred as a result of mountain-building processes the dynamics of which are not well understood. It is generally considered that the rotation of Greenland in the Eocene (related to sedimentary basin formation in Baffin Bay) produced compressional tectonics between Greenland and Ellesmere Island. As part of this process, the Eurekan Orogeny formed away from a traditional convergent ocean-closure plate boundary, and may represent a style of intraplate deformation. One hypothesis is the amalgamation of continental material (i.e., micro-plates) leave deformational `scars' in the crust and mantle lithosphere (specifically in the Ellesmere Island case through accretionary orogenesis in the Palaeozoic). This weakening of the lithosphere may produce episodic reactivation of faults within continental interiors. For example, lithospheric shortening at a time after continental collision could cause the previously deformed crust and mantle lithosphere to produce intraplate deformation. In this work, the geodynamic evolution of the Eurekan Orogeny and its relationship to the tectonics of the Canadian polar margin and northern Baffin Basin is explored using high-resolution thermal-mechanical numerical experiments with the modelling code SOPALE. The modelling of the High Arctic is constrained by the first-order crustal structure of the region (deduced by local gravity field and passive seismological data). Presented are suites of numerical experiments that investigate how the pre-existing lithospheric structures (both crustal and sub-crustal) control the evolution of the resulting intraplate orogen. The influence of other primary modelling parameters, such as crustal thickness and assumed rheology, is also explored. To highlight the role of surface processes on plate

  13. Wollaston prism phase-stepping point diffraction interferometer and method

    DOEpatents

    Rushford, Michael C.

    2004-10-12

    A Wollaston prism phase-stepping point diffraction interferometer for testing a test optic. The Wollaston prism shears light into reference and signal beams, and provides phase stepping at increased accuracy by translating the Wollaston prism in a lateral direction with respect to the optical path. The reference beam produced by the Wollaston prism is directed through a pinhole of a diaphragm to produce a perfect spherical reference wave. The spherical reference wave is recombined with the signal beam to produce an interference fringe pattern of greater accuracy.

  14. Characterization of Metabolically Active Bacterial Populations in Subseafloor Nankai Trough Sediments above, within, and below the Sulfate–Methane Transition Zone

    PubMed Central

    Mills, Heath J.; Reese, Brandi Kiel; Shepard, Alicia K.; Riedinger, Natascha; Dowd, Scot E.; Morono, Yuki; Inagaki, Fumio

    2012-01-01

    A remarkable number of microbial cells have been enumerated within subseafloor sediments, suggesting a biological impact on geochemical processes in the subseafloor habitat. However, the metabolically active fraction of these populations is largely uncharacterized. In this study, an RNA-based molecular approach was used to determine the diversity and community structure of metabolically active bacterial populations in the upper sedimentary formation of the Nankai Trough seismogenic zone. Samples used in this study were collected from the slope apron sediment overlying the accretionary prism at Site C0004 during the Integrated Ocean Drilling Program Expedition 316. The sediments represented microbial habitats above, within, and below the sulfate–methane transition zone (SMTZ), which was observed approximately 20 m below the seafloor (mbsf). Small subunit ribosomal RNA were extracted, quantified, amplified, and sequenced using high-throughput 454 pyrosequencing, indicating the occurrence of metabolically active bacterial populations to a depth of 57 mbsf. Transcript abundance and bacterial diversity decreased with increasing depth. The two communities below the SMTZ were similar at the phylum level, however only a 24% overlap was observed at the genus level. Active bacterial community composition was not confined to geochemically predicted redox stratification despite the deepest sample being more than 50 m below the oxic/anoxic interface. Genus-level classification suggested that the metabolically active subseafloor bacterial populations had similarities to previously cultured organisms. This allowed predictions of physiological potential, expanding understanding of the subseafloor microbial ecosystem. Unique community structures suggest very diverse active populations compared to previous DNA-based diversity estimates, providing more support for enhancing community characterizations using more advanced sequencing techniques. PMID:22485111

  15. Infrared hyperspectral imaging polarimeter using birefringent prisms.

    PubMed

    Craven-Jones, Julia; Kudenov, Michael W; Stapelbroek, Maryn G; Dereniak, Eustace L

    2011-03-10

    A compact short-wavelength and middle-wavelength infrared hyperspectral imaging polarimeter (IHIP) is introduced. The sensor includes a pair of sapphire Wollaston prisms and several high-order retarders to form an imaging Fourier transform spectropolarimeter. The Wollaston prisms serve as a birefringent interferometer with reduced sensitivity to vibration versus an unequal path interferometer, such as a Michelson. Polarimetric data are acquired through the use of channeled spectropolarimetry to modulate the spectrum with the Stokes parameter information. The collected interferogram is Fourier filtered and reconstructed to recover the spatially and spectrally varying Stokes vector data across the image. The IHIP operates over a ±5° field of view and implements a dual-scan false signature reduction technique to suppress polarimetric aliasing artifacts. In this paper, the optical layout and operation of the IHIP sensor are presented in addition to the radiometric, spectral, and polarimetric calibration techniques used with the system. Spectral and spectropolarimetric results from the laboratory and outdoor tests with the instrument are also presented.

  16. New Light on a Prism: The Concert for All Reasons

    ERIC Educational Resources Information Center

    Linaberry, Robin

    2004-01-01

    The prism concert concept was introduced in this country at the Eastman School of Music in 1975. The development of Eastman's inaugural prism concert is commonly attributed to Donald Hunsberger and Gustav Meier, conductors of the wind ensemble and orchestra, respectively. The basic idea is that different styles of music performed by different…

  17. Portable Remote Imaging Spectrometer (PRISM): Laboratory and Field Calibration Results

    NASA Astrophysics Data System (ADS)

    Mccubbin, I. B.; Green, R. O.; Mouroulis, P.; Van Gorp, B.; Dierssen, H. M.

    2012-12-01

    The Portable Remote Imaging Spectrometer (PRISM) is an airborne sensor tailored specifically for the challenges of coastal ocean research. PRISM has high throughput, high-uniformity and low polarization sensitivity. PRISM is an airborne imaging spectrometer sensor that has been developed by the Jet Propulsion Laboratory (JPL) with funding from NASA's Earth Science and Technology Office, Airborne Science Office, and Ocean Biology and Biogeochemistry Office. Development of PRISM started in August 2009. Laboratory measurements of the sensor characteristics as well as measurements over land and water calibration sites will be reported. The objective of the PRISM program is to provide a facility instrument for the community of coastal ocean scientists in order to address specific science questions that have been identified by NASA as critical to the understanding of terrestrial processes. PRISM is a push-broom sensor, and utilizes a Dyson spectrometer, which has 3-nm spectral resolution from 350-1000 nm. The objective of the PRISM 2012 airborne campaign was to a) provide instrument calibration data by overflying specific well-characterized ground targets, and b) perform an investigation into the health of specific seagrass types as indicative of coastal habitat health in the Elkhorn Slough region of Monterey Bay, CA. In May and July of 2012 PRISM flew engineering test flights and an initial science campaign. The initial results from the May and July 2012 flight campaigns will be presented.

  18. Priorities in School Mathematics: Executive Summary of the PRISM Project.

    ERIC Educational Resources Information Center

    National Council of Teachers of Mathematics, Inc., Reston, VA.

    The Priorities in School Mathematics Project (PRISM) was designed by the National Council of Teachers of Mathematics to collect information on current beliefs and reactions to possible mathematics curriculum changes during the 1980's. The first component of PRISM was a survey of preferences for alternative content topics, instructional goals,…

  19. 21 CFR 886.1655 - Ophthalmic Fresnel prism.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Ophthalmic Fresnel prism. 886.1655 Section 886.1655 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... provides the optical effect of a prism. The device is intended to be applied to spectacle lenses to give...

  20. 21 CFR 886.1655 - Ophthalmic Fresnel prism.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Ophthalmic Fresnel prism. 886.1655 Section 886.1655 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... provides the optical effect of a prism. The device is intended to be applied to spectacle lenses to give...

  1. Controls on accretion of flysch and mélange belts at convergent margins: Evidence from the Chugach Bay thrust and Iceworm mélange, Chugach accretionary wedge, Alaska

    NASA Astrophysics Data System (ADS)

    Kusky, Timothy M.; Bradley, Dwight C.; Haeussler, Peter J.; Karl, Sue

    1997-12-01

    Controls on accretion of flysch and mélange terranes at convergent margins are poorly understood. Southern Alaska's Chugach terrane forms the outboard accretionary margin of the Wrangellia composite terrane, and consists of two major lithotectonic units, including Triassic-Cretaceous mélange of the McHugh Complex and Late Cretaceous flysch of the Valdez Group. The contact between the McHugh Complex and the Valdez Group on the Kenai Peninsula is a tectonic boundary between chaotically deformed melange of argillite, chert, greenstone, and graywacke of the McHugh Complex and a less chaotically deformed mélange of argillite and graywacke of the Valdez Group. We assign the latter to a new, informal unit of formational rank, the Iceworm mélange, and interpret it as a contractional fault zone (Chugach Bay thrust) along which the Valdez Group was emplaced beneath the McHugh Complex. The McHugh Complex had already been deformed and metamorphosed to prehnite-pumpellyite facies prior to formation of the Iceworm mélange. The Chugach Bay thrust formed between 75 and 55 Ma, as shown by Campanian-Maastrichtian depositional ages of the Valdez Group, and fault-related fabrics in the Iceworm mélange that are cut by Paleocene dikes. Motion along the Chugach Bay thrust thus followed Middle to Late Cretaceous collision (circa 90-100 Ma) of the Wrangellia composite terrane with North America. Collision related uplift and erosion of mountains in British Columbia formed a submarine fan on the Farallon plate, and we suggest that attempted subduction of this fan dramatically changed the subduction/accretion style within the Chugach accretionary wedge. We propose a model in which subduction of thinly sedimented plates concentrates shear strains in a narrow zone, generating mélanges like the McHugh in accretionary complexes. Subduction of thickly sedimented plates allows wider distribution of shear strains to accommodate plate convergence, generating a more coherent accretionary style

  2. Large-aperture Dove prism for a rotational shearing interferometer

    NASA Astrophysics Data System (ADS)

    Moreno, Ivan; Paez, Gonzalo; Garcia-Marquez, Jorge; Strojnik, Marija

    2002-12-01

    An analytical expression is derived for the tilt introduced into a wave front by a Dove prism with manufacturing errors: error in the base angles and in the pyramidal angle. We found that the tilt decreases when the base angles are increased above the values of traditional design. The increase in the length-aperture ratio of a prism is detrimental to its performance. However, a Dove prism with a widened aperture increases throughput and keeps prism weight manageable for implementation in the rotational shearing interferometer. Thus, we propose a Dove prism designed with a widened aperture to increase throughput in the rotational shearing interferometer and with larger base angles to minimize the wave-front tilt introduced due to manufacturing errors.

  3. Neutral density filters with Risley prisms: analysis and design.

    PubMed

    Duma, Virgil-Florin; Nicolov, Mirela

    2009-05-10

    We achieve the analysis and design of optical attenuators with double-prism neutral density filters. A comparative study is performed on three possible device configurations; only two are presented in the literature but without their design calculus. The characteristic parameters of this optical attenuator with Risley translating prisms for each of the three setups are defined and their analytical expressions are derived: adjustment scale (attenuation range) and interval, minimum transmission coefficient and sensitivity. The setups are compared to select the optimal device, and, from this study, the best solution for double-prism neutral density filters, both from a mechanical and an optical point of view, is determined with two identical, symmetrically movable, no mechanical contact prisms. The design calculus of this optimal device is developed in essential steps. The parameters of the prisms, particularly their angles, are studied to improve the design, and we demonstrate the maximum attenuation range that this type of attenuator can provide.

  4. Modified formula of Malus’ law for Glan Taylor polarizing prisms

    NASA Astrophysics Data System (ADS)

    Zhu, Huafeng; Song, Lianke; Chen, Jianwen; Gao, Hongyi; Li, Ruxin; Xu, Zhizhan

    2005-01-01

    A simple three-axis model has been developed, which has been successfully applied to the analysis of the light transmittance in spatial incident angle and the simulation of modified formula of Malus' law for Glan-Taylor prisms. Our results indicate that the fluctuations on the cosine squared curve are due to specific misalignments between the axis of the optical system, the optical axis of the prism and the mechanical axis (rotation axis) of prism, which results in the fact that different initial relative location of the to-be-measured-prism in the testing system corresponds to different shape of Malus' law curve. Methods to get absolutely smooth curve are proposed. This analysis is available for other kinds of Glan-type prisms.

  5. Effect of lateral stress on the consolidation state of sediment from the Nankai Trough

    NASA Astrophysics Data System (ADS)

    Valdez, R. D., II; Kitajima, H.; Saffer, D. M.

    2015-12-01

    In order to better understand the mechanics of seismogenesis and stress state along subduction plate boundaries, the Integrated Ocean Drilling Program (IODP) Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) program has focused on drilling a transect of boreholes across the subduction zone offshore SW Japan to collect core samples and geophysical logs. One primary target of the drilling effort is a major splay fault (the "megasplay") that branches from the décollement ~55 km landward of the trench and reaches the seafloor ~30 km from the trench. Three drillsites near the tip of the megasplay sampled the same 1.24-1.65 Ma slope apron sediment section at a reference location 0.75 km seaward of the megasplay fault tip (Site C0008), at the fault tip (Site C0022), and 0.30 km landward (Site C0004) where the section is overridden by accretionary prism sediment. We report on a suite of laboratory experiments conducted on coeval core samples from the three sites, to test the hypothesis that increasing horizontal stress with proximity to the megasplay fault leads to overconsolidation. We conducted uniaxial constant rate of strain (CRS) and triaxial consolidation experiments to define consolidation state and yield behavior of the sediment, and to estimate in situ effective stress magnitudes. The consolidation state is described in terms of the over-consolidation ratio (OCR), which is the ratio of stress at yield in the experiments to the in situ vertical stress expected for normal consolidation. Values of OCR increase with proximity to the fault, with values ranging from 0.5-1 at the reference Site C0008, to 1.4-1.5 at Site C0022 at the tip of the fault, to 1.7-2.1 in the footwall of the fault at Site C0004, defining a trend of progressively increasing overconsolidation. We attribute this pattern to increasing horizontal stress as the megasplay fault is approached. Assuming that the sediment is at a critical state (i.e. on the verge of shear failure) at the tip of the

  6. Oblique subduction modelling indicates along-trench tectonic transport of sediments.

    PubMed

    Malatesta, Cristina; Gerya, Taras; Crispini, Laura; Federico, Laura; Capponi, Giovanni

    2013-01-01

    Convergent plate margins are currently distinguished as 'accretional' or 'erosional', depending on the tendency to accumulate sediments, or not, at the trench. Accretion and erosion can coexist along the same margin and we have noticed that this mostly occurs where subduction is oblique. Here we show that at oblique subduction zones, sediments that enter the trench are first buried, and later migrate laterally parallel to the trench and at various depths. Lateral migration of sediments continues until they reach a physical barrier where they begin to accumulate. The accretionary wedge size decreases along the trench moving away from the barrier. We therefore suggest that the gradual variation of the accretionary wedge size and sediment amount at the trench along one single subduction zone, as observed in many active plate margins worldwide, can be explained by the lateral tectonic migration of sediments driven by obliquity of subduction as well.

  7. Deformation and veining processes on the subduction zone; example from the Cretaceous Shimanto accretionary complex in Japan

    NASA Astrophysics Data System (ADS)

    Tokiwa, T.; Kageyama, N.; Yoshida, H.

    2015-12-01

    In this study, the authors discuss the relationship between deformation and veining stages in the accretionary complex in order to understand the deformation and fluid flow process during the subduction. This study deals with the Miyama Formation in the Cretaceous Shimanto accretionary complex located in the Kii Peninsula of Japan. The deformation can be divided three types with four types of vein. Based on the differences, the process can be divided four stage by their cutting relationship as follow. Stage 1; the deformation (D1) in this stage is characterized by the aspect ratio of the deformed clasts with range from 0.1 to 0.4, and pinch-and-swell structure and budinaged structures of the sandstone are developed. The veins (V1) are recognized only within the sandstone, and the veins are cut by muddy matrix. Stage 2; the deformation (D2) is characterized by the aspect ratio is more than 0.4, and is distributed along the unit boundary. The clasts such as sandstone and chert are strongly sheared, and random fabric is often recognized. The vein (V2) in this stage cut the D1, and the V2 and D2 are cut by each other. Stage 3; outcrop-scale faults (D3) cutting D1 and D2 has been progressed in this stage. The vein (V3) is recognized along D3. Stage 4; the vein (V4) cutting D1 to D3 is developed in this stage. From the above-mentioned occurrence and data shown by previous studies of the Miyama Formation, process of each Stage interpreted as follows; Stage 1 developed underthrusting, Stages 2 and 3 correspond to underplating of subducted sediments. In addition, it is considered that Stage 4 is in later stage of underplating. The main components of the V1 to V3 veins are calcite and/or quartz. On the other hand, the V4 vein consists mainly of siderite and ankerite, and contain an abundance of Fe than the other veins. Morphological feature of V1 and V3 veins also show blocky texture suggesting higher rate growth than fracture opening, and V2 vein indicate syn-taxial growth

  8. Motion control of the wedge prisms in Risley-prism-based beam steering system for precise target tracking.

    PubMed

    Zhou, Yuan; Lu, Yafei; Hei, Mo; Liu, Guangcan; Fan, Dapeng

    2013-04-20

    Two exact inverse solutions of Risley prisms have been given by previous authors, based on which we calculate the gradients of the scan field that open a way to investigate the nonlinear relationship between the slewing rate of the beam and the required angular velocities of the two wedge prisms in the Risley-prism-based beam steering system for target tracking. The limited regions and singularity point at the center and the edge of the field of regard are discussed. It is found that the maximum required rotational velocities of the two prisms for target tracking are nearly the same and are dependent on the altitude angle. The central limited region is almost independent of the prism parameters. The control singularity at the crossing center path can be avoided by switching the two solutions.

  9. Prism adaptation in spinocerebellar ataxia type 2.

    PubMed

    Fernandez-Ruiz, Juan; Velásquez-Perez, Luis; Díaz, Rosalinda; Drucker-Colín, René; Pérez-González, Ruth; Canales, Nalia; Sánchez-Cruz, Gilberto; Martínez-Góngora, Edilberto; Medrano, Yaquelín; Almaguer-Mederos, Luis; Seifried, Carola; Auburger, Georg

    2007-09-20

    Patients with spinocerebellar ataxia type 2 (SCA2), develop severe pontine nuclei, inferior olives, and Purkinje cell degeneration. This form of autosomal dominant cerebellar ataxia is accompanied by progressive ataxia and dysarthria. Although the motor dysfunction is well characterized in these patients, nothing is known about their motor learning capabilities. Here we tested 43 SCA2 patients and their matched controls in prism adaptation, a kind of visuomotor learning task. Our results show that their pattern of brain damage does not entirely disrupt motor learning. Rather, patients had impaired adaptation decrement, but surprisingly a normal aftereffect. Moreover, the mutation degree could discriminate the degree of adaptation. This pattern could reflect the net contribution of two adaptive mechanisms: strategic control and spatial realignment. Accordingly, SCA2 patients show an impaired strategic control that affects the adaptation rate, but a normal spatial realignment measured through the aftereffect. Our results suggest that the neural areas subserving spatial realignment are spared in this form of spinocerebellar ataxia.

  10. Prisms and neglect: what have we learned?

    PubMed

    Newport, Roger; Schenk, Thomas

    2012-05-01

    Since Rossetti et al. (1998) reported that prism adaptation (PA) can lead to a substantial reduction of neglect symptoms PA has become a hot topic in neglect-research. More than 280 articles have been published in this area. Not all of those studies investigated the therapeutic potential of this technique, many studies examined the responsiveness to PA as a way to subdivide neglect into separate subsyndromes, other studies focussed on the process of PA itself in an effort to illuminate its underlying neurobiological mechanisms. In this article we will review research in all of these three areas to determine whether and to what extent research on PA in neglect patients has fulfilled its promise as a new way to improve the treatment of neglect, enhance our understanding of this complex syndrome and provide new insights into the neurobiology of sensorimotor learning.

  11. Formation of ophiolite-bearing tectono-sedimentary mélanges in accretionary wedges by gravity driven submarine erosion: Insights from analogue models and case studies

    NASA Astrophysics Data System (ADS)

    Malavieille, Jacques; Molli, Giancarlo; Genti, Manon; Dominguez, Stephane; Beyssac, Olivier; Taboada, Alfredo; Vitale-Brovarone, Alberto; Lu, Chia-Yu; Chen, Chih-Tung

    2016-10-01

    Orogenic wedges locally present chaotic tectonostratigraphic units that contain exotic blocks of various size, origin, age and lithology, embedded in a sedimentary matrix. The occurrence of ophiolitic blocks, sometimes huge, in such "mélanges" raises questions on (i) the mechanisms responsible for the incorporation of oceanic basement rocks into an accretionary wedge and (ii) the mechanisms allowing exhumation and redeposition of these exotic elements in "mélanges" during wedge growth. To address these questions, we present the results of a series of analogue experiments performed to characterize the processes and parameters responsible for accretion, exhumation and tectonosedimentary reworking of oceanic basement lithospheric fragments in an accretionary wedge. The experimental setup is designed to simulate the interaction between tectonics, erosion and sedimentation. Different configurations are applied to study the impact of various parameters, such as irregular oceanic floor due to structural inheritance, or the presence of layers with contrasted rheology that can affect deformation partitioning in the wedge (frontal accretion vs basal accretion) influencing its growth. Image correlation technique allows extracting instantaneous velocity field, and tracking of passive particles. By retrieving the particle paths determined from models, the pressure-temperature path of mélange units or elementary blocks can be discussed. The experimental results are then compared with observations from ophiolite-bearing mélanges in Taiwan (Lichi and Kenting mélanges) and Raman spectroscopy of carbonaceous material (RSCM) Thermometry data on rocks from the northern Apennines (Casanova mélange). A geological scenario is proposed following basic observations. The tectonic evolution of the retroside of doubly vergent accretionary wedges is mainly controlled by backthrusting and backfolding. The retro wedge is characterized by steep slopes that are prone to gravitational

  12. Structural Features and Gas Hydrate Distribution Across the Boundary of the Submarine Taiwan Accretionary Wedge and Passive China Continental Margin Offshore Southwestern Taiwan

    NASA Astrophysics Data System (ADS)

    Han, W.; Liu, C.; Lin, C.; Hsu, H.; Ko, C.; Chen, S.; Chung, S.; Wang, Y.

    2012-12-01

    This study analyzes a 3D seismic data volume in the upper reach of the Penghu Submarine Canyon for gas hydrate investigation. This 3D seismic data set runs across the deformation front which separates the passive China continental slope from the Taiwan accretionary wedge. Bottom-simulating reflectors (BSRs) are widely distributed in the study area which suggests that gas hydrates are present in both the extensional and compressive structure domains. We use 3D seismic images to map the spatial distribution of BSRs, and to identify structural and sedimentary features across the deformation front. Seismic attribute analysis of the 3D seismic volume has been performed which helps to reveal structure details and physical properties of the substrata. Our study identifies detailed structural variations across the deformation front: In the passive continental slope domain, besides normal faults, buried submarine canyons and paleo-topography of the continental slope before the arc-continent collision are recognized, while in the accretionay wedge domain, the fold and thrust structures dominate. BSR distribution in the 3D box correlates well with the seafloor topography, buried channels and fluid migration paths, we suggest that there may be different gas hydrate systems for the passive continental slope and for the accretionary wedge domains. As the Penghu Submarine Canyon is an important conduit offshore southwestern Taiwan for transporting terrestrial and shallow marine sediments, we suggest that the buried channels that filled with coarse-grain sediments could be good reservoirs for gas hydrates and free gases. Accurate substrata velocity models derived from a large-offset 2D seismic profile data in the study area will help us to better estimate the gas hydrate concentration in those reservoirs.

  13. Large beam deflection using cascaded prism array

    NASA Astrophysics Data System (ADS)

    Wang, Wei-Chih; Tsui, Chi-Leung

    2012-04-01

    Endoscopes have been utilize in the medical field to observe the internals of the human body to assist the diagnosis of diseases, such as breathing disorders, internal bleeding, stomach ulcers, and urinary tract infections. Endoscopy is also utilized in the procedure of biopsy for the diagnosis of cancer. Conventional endoscopes suffer from the compromise between overall size and image quality due to the required size of the sensor for acceptable image quality. To overcome the size constraint while maintaining the capture image quality, we propose an electro-optic beam steering device based on thermal-plastic polymer, which has a small foot-print (~5mmx5mm), and can be easily fabricated using conventional hot-embossing and micro-fabrication techniques. The proposed device can be implemented as an imaging device inside endoscopes to allow reduction in the overall system size. In our previous work, a single prism design has been used to amplify the deflection generated by the index change of the thermal-plastic polymer when a voltage is applied; it yields a result of 5.6° deflection. To further amplify the deflection, a new design utilizing a cascading three-prism array has been implemented and a deflection angle to 29.2° is observed. The new design amplifies the beam deflection, while keeping the advantage of simple fabrication made possible by thermal-plastic polymer. Also, a photo-resist based collimator lens array has been added to reduce and provide collimation of the beam for high quality imaging purposes. The collimator is able to collimate the exiting beam at 4 μm diameter for up to 25mm, which potentially allows high resolution image capturing.

  14. Mechanisms underlying neglect recovery after prism adaptation.

    PubMed

    Serino, Andrea; Angeli, Valentina; Frassinetti, Francesca; Làdavas, Elisabetta

    2006-01-01

    Prism adaptation (PA) has been demonstrated to be effective in improving hemispatial neglect. However not all patients seem to benefit from this procedure. Thus, the objective of the present work is to provide behavioural and neuroanatomical predictors of recovery by exploring the reorganization of low-order visuo-motor behaviour and high-order visuo-spatial representation induced by PA. To this end, 16 neglect patients (experimental group) were submitted to a PA treatment for 10 daily sessions. Neglect and oculo-motor responses were assessed before the treatment, 1 week, 1 and 3 months after the treatment. Eight control patients, who received general cognitive stimulation, were submitted to the same tests at the same time interval. The results showed that experimental patients obtained, as a consequence of PA, a long lasting neglect recovery, a reorganization of low-order visuo-motor behaviour during and after prism exposure (error reduction and after-effect, respectively) and a leftward deviation of oculo-motor responses. Importantly, the level of error reduction obtained in the first week of treatment was predictive of neglect recovery and the amelioration of oculo-motor responses, and the degree of eye movement deviation was positively related to neglect amelioration. Finally, the study of patients' neuroanatomical data showed that severe occipital lesions were associated with a lack of error reduction, poor neglect recovery and reduced oculo-motor system amelioration. In conclusion, the present results suggest that low-order visuo-motor reorganization induced by PA promotes a resetting of the oculo-motor system leading to an improvement in high-order visuo-spatial representation able to ameliorate neglect.

  15. Different sources of suspended sediment according to particle size determined by natural radionuclides

    NASA Astrophysics Data System (ADS)

    Mizugaki, S.; Ohtsuka, J.; Maruyama, M.; Hamamoto, S.; Murakami, Y.

    2012-12-01

    Extensive human activity and climate change have given great impacts on the sediment balance and connectivity between fluvial and coastal systems, causing sediment-related problems such as sedimentation in reservoir, coastal erosion and water pollution by prolonged turbid water. The dynamics of suspended sediment is one of the most important issues in watershed and coastal management. Suspended sediment load transported to ocean by a river commonly represents a mixture of sediments delivered from different locations and source types within the contributing catchment. In our previous study, we have found that the three natural radionuclides are available to discriminate the source areas of suspended sediment represented by six different bed rock type (sedimentary rock, accretionary sedimentary rock, accretionary basalt block, accretionary volcanic rock, plutonic rock and metamorphic rock), and that the contribution of each source areas to suspended sediment can be estimated (Mizugaki et al., 2012). To elucidate the sources of suspended sediment from mountain to coastal area, the fingerprinting was conducted using natural radionuclide tracers across a couple of adjacent watersheds, the Saru River and Mu River watersheds in central Hokkaido, northern Japan. We collected suspended sediments at outlets of the 13 sub-catchments (0.7-27.2 km2) and 12 stream channels with mid- to large-scaled watershed areas (17-1,333 km2), deposited sediments across a dam reservoir and coastal sediments, in total 389 samples. For collected sediment samples, grain size distributions were measured by laser-diffraction particle size analyzer. The specific surface areas of the samples were estimated using their grain size distribution and the spherical approximation of the particles in each class. For fingerprint the source of suspended sediment, three natural radionuclide activities, 212Pb, 228Ac and 40K, were measured by gamma-ray spectrometry. Specific surface area of the sediment showed

  16. Pure rotation of a prism on a ramp

    PubMed Central

    Zhao, Zhen; Liu, Caishan; Ma, Daolin

    2014-01-01

    In this work, we study a prism with a cross section in polygon rolling on a ramp inclined at a small angle. The prism under gravity rolls purely around each individual edge, intermittently interrupted by a sequence of face collisions between the side face of the prism and the ramp. By limiting the prism in a planar motion, we propose a mathematical model to deal with the events of the impacts. With a pair of laser-Doppler vibrometers, experiments are also conducted to measure the motions of various prisms made of different materials and with different edge number. Not only are good agreements achieved between our numerical and experimental results, but also an intriguing physical phenomenon is discovered: the purely rolling motion is nearly independent of the prism's materials, yet it is closely related to the prism's geometry. Imagine that an ideal circular section can be approximately equivalent to a polygon with a large enough edge number N, the finding presented in this paper may help discover the physical mechanism of rolling friction. PMID:25197242

  17. Goldmann Tonometer Prism with an Optimized Error Correcting Applanation Surface

    PubMed Central

    McCafferty, Sean; Lim, Garrett; Duncan, William; Enikov, Eniko; Schwiegerling, Jim

    2016-01-01

    Purpose We evaluate solutions for an applanating surface modification to the Goldmann tonometer prism, which substantially negates the errors due to patient variability in biomechanics. Methods A modified Goldmann or correcting applanation tonometry surface (CATS) prism is presented which was optimized to minimize the intraocular pressure (IOP) error due to corneal thickness, stiffness, curvature, and tear film. Mathematical modeling with finite element analysis (FEA) and manometric IOP referenced cadaver eyes were used to optimize and validate the design. Results Mathematical modeling of the optimized CATS prism indicates an approximate 50% reduction in each of the corneal biomechanical and tear film errors. Manometric IOP referenced pressure in cadaveric eyes demonstrates substantial equivalence to GAT in nominal eyes with the CATS prism as predicted by modeling theory. Conclusion A CATS modified Goldmann prism is theoretically able to significantly improve the accuracy of IOP measurement without changing Goldmann measurement technique or interpretation. Clinical validation is needed but the analysis indicates a reduction in CCT error alone to less than ±2 mm Hg using the CATS prism in 100% of a standard population compared to only 54% less than ±2 mm Hg error with the present Goldmann prism. Translational Relevance This article presents an easily adopted novel approach and critical design parameters to improve the accuracy of a Goldmann applanating tonometer. PMID:27642540

  18. Performance characterization of scanning beam steered by tilting double prisms.

    PubMed

    Li, Anhu; Yi, Wanli; Zuo, Qiyou; Sun, Wansong

    2016-10-03

    A pair of orthogonal tilting double prisms with a tracking precision better than submicroradian order exhibits a good application potential in laser tracking fields. In the paper, the beam scanning performance determined by both the structure parameters and the tilting motions of two prisms is overall investigated. The functional relation between the structure parameters and the exact beam scanning range is established, the capability of high-accuracy beam steering is validated together with the investigation of the scanning error sources and the nonlinear control laws, and the beam shape distortion degree under multi-parameter combinations is demonstrated. These studies can provide important references for the development of tilting double prisms.

  19. Error compensation in a pointing system based on Risley prisms.

    PubMed

    Bravo-Medina, Beethoven; Strojnik, Marija; Garcia-Torales, Guillermo; Torres-Ortega, Hector; Estrada-Marmolejo, Ruben; Beltrán-González, Anuar; Flores, Jorge L

    2017-03-10

    Risley prisms are widely used for beam pointing in several optical systems. The exact solution for the inverse problem does not exist, except using numerical methods. However, the errors introduced by misalignment are usually greater than the approximation errors. We present a novel method to compensate alignment errors in pointing systems based on Risley prisms. The prism model that we used is based on paraxial approximation with an additional vector to compensate typical alignment errors. Simulation and experimental results show that the improvement in pointing accuracy is achievable even in comparison with exact ray tracing methods.

  20. Appraisal of gas hydrate resources based on a P- and S-impedance reflectivity template: case study from the deep sea sediments in Iran

    NASA Astrophysics Data System (ADS)

    Shoar, Behnam Hosseini; Javaherian, Abdolrahim; Keshavarz Farajkhah, Nasser; Seddigh Arabani, Mojtaba

    2013-12-01

    The occurrence of a bottom simulating reflector (BSR) in the 2D seismic data from Makran's accretionary prism reveals the presence of gas hydrate and free gas several hundred meters below the seafloor of Iran's deep sea. According to the global distribution of marine hydrates, they are widely present in deep sea sediments, where high operational costs and hazards cause a lack of well log information. Therefore, developing a method to quantify the hydrate resources with seismic data is an ultimate goal for unexplored regions. In this study, the so-called reflectivity templates (RTs) are introduced for quantification of the hydrate and free gas near the BSR. These RTs are intuitive crossplots of P-impedance and S-impedance contrasts across the BSR. They are calculated theoretically based on the effective medium theory for different hydrate distribution modes with some assumptions on porosity and mineralogical composition of unconsolidated sediments. This technique suggests the possibility of using the amplitude variation versus offset (AVO) analysis of the BSR for a quantitative interpretation when well log data are not available. By superimposing the AVO-derived P-impedance and S-impedance contrasts across the BSR on these RTs, the saturations of the hydrate and free gas near the BSR could be estimated. Validation of this approach by synthetic data showed that a reliable quantification could be achieved if the model parameters were rearranged to a form in which the AVO inversion was independent of the S-wave to P-wave velocity-ratio assumption. Based on this approach applied on the 2D marine pre-stack time migrated seismic line in offshore Iran, 4% to 28% of the gas hydrate and 1% to 2% of the free gas are expected to be accumulated near the thrusted-ridge and thrusted-footwall types of BSRs.

  1. Why Is White Light Dispersed by a Prism?

    ERIC Educational Resources Information Center

    Crawford, Frank S.

    1979-01-01

    Presents the answer to a question, which is intended for high school students, about the dispersion of white light by a glass prism. Why the high frequency waves travel slower than the lower frequencies in glass is also presented. (HM)

  2. 3. ELEVATION. FROM SOUTH WITH CANAL PRISM. Canal Road ...

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

    3. ELEVATION. FROM SOUTH WITH CANAL PRISM. - Canal Road Bridge, Canal Road spanning Delaware Canal Diversion, Locks 22 & 23 in Delaware Canal State Park in Williams Township, Raubsville, Northampton County, PA

  3. NORTHERLY STRETCH OF MILLBURY PORTION; GENERAL VIEW ACROSS CANAL PRISM ...

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

    NORTHERLY STRETCH OF MILLBURY PORTION; GENERAL VIEW ACROSS CANAL PRISM TO TOWPATH BERM (LATER FILL ENCROACHING LEFT) NEAR CENTER OF THIS STRETCH; VIEW TO SOUTHWEST - Blackstone Canal Worcester-Millbury Segment, Eastern bank of Blackstone River, Millbury, Worcester County, MA

  4. 5. VIEW NORTHWEST SHOWING AQUEDUCT PRISM. NOTE INTERIOR STONE WORK ...

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

    5. VIEW NORTHWEST SHOWING AQUEDUCT PRISM. NOTE INTERIOR STONE WORK OF THE PARAPET WALL AND REMAINS OF 1920 TIMBER AND CONCRETE FLOORING SYSTEM. - Chesapeake & Ohio Canal, Conococheague Creek Aqueduct, Milepost 99.80, Williamsport, Washington County, MD

  5. Development of an unbonded capping system for clay masonry prisms

    SciTech Connect

    Crouch, L.K.; Henderson, R.C.; Sneed, W.A. Jr.

    1999-07-01

    To ascertain if an unbonded capping system was feasible for clay masonry prisms, the compressive strengths of thirty clay masonry prisms capped with an unbonded capping system modeled after ASTM C 1231 were compared with those of thirty masonry prisms capped with ASTM C 67 approved high-strength gypsum cement at the ages of 7 and 28 days. All prisms were constructed by a professional mason using Grade SW, Type FBS cored face brick from the same lot and ASTM C 270 Type S PC-lime mortar. There was no significant difference in mean compressive strength for the two capping methods at either age. In addition, capping with the unbonded capping system was faster and easier. Further, 28-day results obtained using the unbonded capping system had a lower coefficient of variation and higher mean compressive strength than those obtained with high-strength gypsum.

  6. MEGARA Optics: stain removal in PBM2Y prisms

    NASA Astrophysics Data System (ADS)

    Aguirre-Aguirre, D.; Izazaga-Pérez, R.; Villalobos-Mendoza, B.; Carrasco, E.; Gil de Paz, A.; Gallego, J.; Iglesias, J.

    2017-01-01

    MEGARA is the new integral-field and multi-object optical spectrograph for the GTC. For medium and high resolution, the dispersive elements are volume phase holographic gratings, sandwiched between two flat windows and two prisms of high optical precision. The prisms are made of Ohara PBM2Y optical glass. After the prisms polishing process, some stains appeared on the surfaces. For this, in this work is shown the comparative study of five different products (muriatic acid, paint remover, sodium hydroxide, aqua regia and rare earth liquid polish) used for trying to eliminate the stains of the HR MEGARA prisms. It was found that by polishing with the hands the affected area, and using a towel like a kind of pad, and polish during five minutes using rare earth, the stains disappear completely affecting only a 5% the rms of the surface quality. Not so the use of the other products that did not show any apparent result.

  7. Strongly-Refractive One-Dimensional Photonic Crystal Prisms

    NASA Technical Reports Server (NTRS)

    Ting, David Z. (Inventor)

    2004-01-01

    One-dimensional (1D) photonic crystal prisms can separate a beam of polychromatic electromagnetic waves into constituent wavelength components and can utilize unconventional refraction properties for wavelength dispersion over significant portions of an entire photonic band rather than just near the band edges outside the photonic band gaps. Using a ID photonic crystal simplifies the design and fabrication process and allows the use of larger feature sizes. The prism geometry broadens the useful wavelength range, enables better optical transmission, and exhibits angular dependence on wavelength with reduced non-linearity. The properties of the 1 D photonic crystal prism can be tuned by varying design parameters such as incidence angle, exit surface angle, and layer widths. The ID photonic crystal prism can be fabricated in a planar process, and can be used as optical integrated circuit elements.

  8. Prisms with total internal reflection as solar reflectors

    DOEpatents

    Rabl, Arnulf; Rabl, Veronika

    1978-01-01

    An improved reflective wall for radiant energy collection and concentration devices is provided. The wall is comprised of a plurality of prisms whose frontal faces are adjacent and which reflect the desired radiation by total internal reflection.

  9. PRISM: Shedding Light on NCTM's Recommendations for the 1980s.

    ERIC Educational Resources Information Center

    Suydam, Marilyn N; Higgins, Jon L.

    1980-01-01

    Information from the Priorities in School Mathematics (PRISM) project, designed as a systematic attempt to assess preferences and priorities for mathematics curriculum change, are presented in relation to eight NCTM recommendations. (MP)

  10. Origin of accretionary lapilli from the Pompeii and Avellino deposits of Vesuvius

    SciTech Connect

    Sheridan, M.F.; Wohletz, K.H.

    1983-01-01

    Accretionary lapilli from the Pompeii and Avellino Plinian ash deposits of Vesuvius consist of centimeter-sized spheroids composed of glass, crystal, and lithic fragments of submillimeter size. The typical structure of the lapilli consists of a central massive core surrounded by concentric layers of fine ash with concentrations of larger clasts and vesicles and a thin outer layer of dust. Clasts within the lapilli larger than 125 ..mu..m are extremely rare. The median grain-size of the fine ash is about 50 ..mu..m and the size-distribution is well sorted. Most constituent particles of accretionary lapilli display blocky shapes characteristic of grains produced by phreatomagmatic hydroexplosions. We have used the scanning electron microscope (SEM) in conjunction with energy dispersive spectral analysis (EDS) to investigate the textural and chemical variation along traverses from the core to the rim of lapilli from Vesuvius.

  11. Stereoscopic Display on Computer Monitor Using a Single Wedge Prism

    NASA Astrophysics Data System (ADS)

    Park, Tae-Soo; Park, Chan-Young; Lee, Han-Bae; Park, Seung-Han

    2002-02-01

    We propose a novel stereoscopic display technique which uses only a single wedge prism. It can provide good depth perception from a stereoscopic pair image displayed on a computer monitor. One element of the stereoscopic pair image is inversely distorted to correct the deformation induced by the wedge prism. The computer simulation and experimental demonstration show that this technique can be successfully applied to the Internet environment.

  12. Measurement of thin film parameters with a prism coupler.

    PubMed

    Ulrich, R; Torge, R

    1973-12-01

    The prism coupler, known from experiments on integrated optics, can be used to determine the refractive index and the thickness of a light-guiding thin film. Both parameters are obtained simultaneously and with good accuracy by measuring the coupling angles at the prism and fitting them by a theoretical dispersion curve. The fundamentals and limitations. of this method are discussed, its practical use, and mathematical procedures for the evaluation.

  13. Wedge Prism for Direction Resolved Speckle Correlation Interferometry

    SciTech Connect

    Pechersky, M.J.

    1999-01-20

    The role of a wedge prism for strain sign determination and enhancing the sensitivity for sub-fringe changes is emphasized. The design and incorporation aspects for in-plane sensitive interferometers have been described in detail. Some experimental results dealing with stress determination by laser annealing and speckle corelation interferometry are presented. The prism can also be applied to produce standardized carrier fringes in spatial phase shifting interferometry.

  14. Prism coupling into clad uniform optical waveguides

    SciTech Connect

    Revelli, J.F.; Sarid, D.

    1980-07-01

    The theory of prism coupling into multilayered dielectric slab waveguides is presented. In addition to including the possibility of high index cladding, the present theory also extends the region of validity of previously reported work to cover the regime of ''strong coupling''. The limiting conditions for validity of the present theory are that both ..cap alpha../sub m//k and ..cap alpha../sub m/ +- p/k be much smaller than either unity or vertical-bar..beta../sub m/-..beta../sub m/ +- pvertical-bar, where m is the mode under consideration, ..cap alpha../sub m/ is the leakage of that mode, and vertical-bar..beta../sub m/-..beta../sub m/ +- pvertical-bar is the separation of the effective indices of adjacent modes. A numerical example is presented in which the coupling efficiency into a uniform or slab waveguide with ..delta..n=0.002 is calculated for various cladding thicknesses with a cladding index of 2.5. The introduction of cladding is found to reduce coupling efficiency in this example due to increased phase mismatch between the incident and ''ideal'' beams.

  15. APEX - the Hyperspectral ESA Airborne Prism Experiment

    PubMed Central

    Itten, Klaus I.; Dell'Endice, Francesco; Hueni, Andreas; Kneubühler, Mathias; Schläpfer, Daniel; Odermatt, Daniel; Seidel, Felix; Huber, Silvia; Schopfer, Jürg; Kellenberger, Tobias; Bühler, Yves; D'Odorico, Petra; Nieke, Jens; Alberti, Edoardo; Meuleman, Koen

    2008-01-01

    The airborne ESA-APEX (Airborne Prism Experiment) hyperspectral mission simulator is described with its distinct specifications to provide high quality remote sensing data. The concept of an automatic calibration, performed in the Calibration Home Base (CHB) by using the Control Test Master (CTM), the In-Flight Calibration facility (IFC), quality flagging (QF) and specific processing in a dedicated Processing and Archiving Facility (PAF), and vicarious calibration experiments are presented. A preview on major applications and the corresponding development efforts to provide scientific data products up to level 2/3 to the user is presented for limnology, vegetation, aerosols, general classification routines and rapid mapping tasks. BRDF (Bidirectional Reflectance Distribution Function) issues are discussed and the spectral database SPECCHIO (Spectral Input/Output) introduced. The optical performance as well as the dedicated software utilities make APEX a state-of-the-art hyperspectral sensor, capable of (a) satisfying the needs of several research communities and (b) helping the understanding of the Earth's complex mechanisms. PMID:27873868

  16. Rotational and accretionary evolution of the Klamath Mountains, California and Oregon, from Devonian to present time

    USGS Publications Warehouse

    Irwin, William P.; Mankinen, Edward A.

    1998-01-01

    The purpose of this report is to show graphically how the Klamath Mountains grew from a relatively small nucleus in Early Devonian time to its present size while rotating clockwise approximately 110°. This growth occurred by the addition of large tectonic slices of oceanic lithosphere, volcanic arcs, and melange during a sequence of accretionary episodes. The Klamath Mountains province consists of eight lithotectonoic units called terranes, some of which are divided into subterranes. The Eastern Klamath terrane, which was the early Paleozoic nucleus of the province, is divided into the Yreka, Trinity, and Redding subterranes. Through tectonic plate motion, usually involving subduction, the other terranes joined the early Paleozoic nucleus during seven accretionary episodes ranging in age from Early Devonian to Late Jurassic. The active terrane suture is shown for each episode by a bold black line. Much of the western boundary of the Klamath Mountains is marked by the South Fork and correlative faults along which the Klamath terranes overrode the Coast Range rocks during an eighth accretionary episode, forming the South Fork Mountain Schist in Early Cretaceous time.

  17. Petrology of blueschist from the Western Himalaya (Ladakh, NW India): Exploring the complex behavior of a lawsonite-bearing system in a paleo-accretionary setting

    NASA Astrophysics Data System (ADS)

    Groppo, Chiara; Rolfo, Franco; Sachan, Himanshu K.; Rai, Santosh K.

    2016-05-01

    Although the Himalaya is the archetype of collisional orogens, formed as a consequence of the closure of the Neo-Tethyan ocean separating India from Asia, high-pressure metamorphic rocks are rare. Beside few eclogites, corresponding to the metamorphosed continental Indian crust dragged below Asia or underthrusted beneath southern Tibet, blueschists occur seldom along the Yarlung-Tsangpo Suture zone, i.e. the suture marking the India-Asia collision. These blueschists, mostly interpreted as related to paleo-accretionary prisms formed in response to the subduction of the Neo-Tethyan ocean below the Asian plate, are crucial for constraining the evolution of the India-Asia convergence zone during the closure of the Neo-Tethyan Ocean. In the Western Himalaya, the best occurrence of blueschist is that of the Sapi-Shergol Ophiolitic Mélange in Ladakh. This unit is dominated by volcanoclastic sequences rich in mafic material with subordinate interbedding of metasediments, characterized by very fresh lawsonite blueschist-facies assemblages. In this paper, the lawsonite blueschist-facies metasediments have been petrologically investigated with the aims of (i) constraining the P-T evolution of the Sapi-Shergol Ophiolitic Mélange, (ii) evaluating the influence of Fe2O3 and of H2O on the stability of the high-pressure mineral assemblages, (iii) understanding the processes controlling lawsonite formation and preservation, and (iv) interpreting the P-T evolution of the Sapi-Shergol blueschists in the framework of India-Asia collision. Our results indicate that (i) the Sapi-Shergol blueschists experienced a cold subduction history along a low thermal gradient, up to peak conditions of ca. 470 °C, 19 kbar; furthermore, in order to preserve lawsonite in the studied lithologies, exhumation must have been coupled with significant cooling, i.e. the resulting P-T path is characterized by a clockwise hairpin loop along low thermal gradients (< 8-9 °C/km); (ii) the presence of ferric

  18. 40Ar/39Ar geochronology of Andaman Ophiolite: Evidence for a Pleistocene mega thrusting event within the Andaman-Nicobar Accretionary Wedge

    NASA Astrophysics Data System (ADS)

    Pande, K.; Ray, J. S.

    2015-12-01

    A geochronological study the Andaman ophiolite was performed along a ~120 km corridor on the eastern margin of the Andaman Islands, which forms part of the Andaman-Nicobar accretionary wedge. This Cretaceous ophiolite sequence occurs as imbricate thrust wedges overlying the Paleogene flysch and Neogene pelagic sediments. Incremental heating 40Ar/39Ar dating of three pillow basalts and a peridotite samples reveals that the ophiolite has a composite thermal history. Apparent age spectra of all the samples suggest a clear two stage evolution, with the high temperature steps (1000 to 1400oC) and the lower temperature steps (400-950oC) showing a staircase pattern and a plateau-like pattern, respectively. The apparent ages of the highest temperature steps vary from 135 Ma to 97 Ma, which appear to suggest multiple crystallization ages. Interestingly, the plateau-like spectra for the lower temperature steps yield indistinguishable ages, although with very high errors (as high as 67% at 1s), across all the samples. The isochron ages too overlap with the plateau-like ages. Thus the weighted average of the plateau-like ages of 0.9±0.3 (2s) Ma most likely represents the timing of the latest thermal resetting. Based on the above information we conclude that while different units of the Andaman ophiolite may have been formed at different times, all had seen a major thermal resetting. Considering the position of these rocks vis-à-vis the structural configuration of the Andaman-Nicobar accretionary wedge we infer that there was a mega thrusting event in the region at ~0.9 Ma which was possibly responsible for exhumation of the current outcrops of the ophiolite sequence along the east coast of the Andman Islands.

  19. Control of structural inheritance on thrust initiation and material transfer in accretionary wedges

    NASA Astrophysics Data System (ADS)

    Leever, Karen; Geersen, Jacob; Ritter, Malte; Lieser, Kathrin; Behrmann, Jan

    2016-04-01

    Faults in the incoming sediment layer are commonly observed in subduction zone settings and well developed in the incoming plate off Sumatra. To investigate how they affect the structural development of the accretionary wedge, we conducted a series of 2D analogue tectonic experiments in which a 2 cm thick quartz sand layer on top of a thin detachment layer of glass beads was pulled against a rigid backstop by a basal conveyor belt in a 20cm wide box with glass walls. A gap at the base of the back wall avoids entrainment of the glass beads. At regular spacing of either 2.3, 5.5 or 7.8 cm (fractions of the thrust sheet length in the reference model), conjugate pairs of weakness zones dipping 60deg were created by cutting the sand layer with a thin (1 mm) metal blade. Both the undisturbed sand and the pre-cuts have an angle of internal friction of ~29o, but their cohesion is different by 50 Pa (110 Pa for the undisturbed material, 60 Pa along the pre-cuts). Friction of the glass beads is ~24deg. The experiments are monitored with high resolution digital cameras; displacement fields derived from digital image correlation are used to constrain fault activity. In all experiments, a critically tapered wedge developed with a surface slope of 7.5deg. In the reference model (no weakness zones in the input section), the position of new thrust faults is controlled by the frontal slope break. The average length of the thrust sheets is 11 cm and the individual thrusts accommodate on average 8 cm displacement each. The presence of weakness zones causes thrust initiation at a position different from the reference case, and affects their dip. For a fault spacing of 7.8 cm (or 75% of the reference thrust sheet length), every single incoming weakness zone causes the formation of a new thrust, thus resulting in thrust sheets shorter than the equilibrium case. In addition, less displacement is accommodated on each thrust. As a consequence, the frontal taper is smaller than expected

  20. Numerical modeling of porosity waves in the Nankai accretionary wedge décollement, Japan: implications for aseismic slip

    NASA Astrophysics Data System (ADS)

    Joshi, Ajit; Appold, Martin S.

    2016-10-01

    Seismic and hydrologic observations of the Nankai accretionary wedge décollement, Japan, show that overpressures at depths greater than ˜2 km beneath the seafloor could have increased to near lithostatic values due to sediment compaction and diagenesis, clay dehydration, and shearing. The resultant high overpressures are hypothesized then to have migrated in rapid surges or pulses called `porosity waves' up the dip of the décollement. Such high velocities—much higher than expected Darcy fluxes—are possible for porosity waves if the porous media through which the waves travel are deformable enough for porosity and permeability to increase strongly with increasing fluid pressure. The present study aimed to test the hypothesis that porosity waves can travel at rates (kilometers per day) fast enough to cause aseismic slip in the Nankai décollement. The hypothesis was tested using a one-dimensional numerical solution to the fluid mass conservation equation for elastic porous media. Results show that porosity waves generated at depths of ˜2 km from overpressures in excess of lithostatic pressure can propagate at rates sufficient to account for aseismic slip along the décollement over a wide range of hydrogeological conditions. Sensitivity analysis showed porosity wave velocity to be strongly dependent on specific storage, fluid viscosity, and the permeability-depth gradient. Overpressure slightly less than lithostatic pressure could also produce porosity waves capable of traveling at velocities sufficient to cause aseismic slip, provided that hydrogeologic properties of the décollement are near the limits of their geologically reasonable ranges.

  1. PRISM3 Global Paleoclimate Reconstruction: A Global Warming Data Set

    NASA Astrophysics Data System (ADS)

    Dowsett, H. J.; Chandler, M. A.; Cronin, T. M.; Dwyer, G. S.; Haywood, A. M.; Hill, D. J.; Robinson, M. M.; Salzmann, U.; Williams, M.

    2007-12-01

    The Pliocene Research, Interpretation and Synoptic Mapping (PRISM) Project provides a conceptual model and synoptic view of the earth during the last interval considerably warmer than modern (3.3 to 3.0 Ma) through reconstruction of sea-surface temperature (SST) and other paleoenvironmental parameters. The first PRISM reconstruction, with its foundation in a global network of paleontological analyses, was completed in the early 1990s. Since then, several significant revisions have been released culminating in the PRISM2 data set. The primary goal of PRISM remains a better understanding of the Earth's climate system during the mid-Pliocene, and to that end, includes the development of digital data sets for use with climate models. The new PRISM3 reconstruction, slated to be released early in 2008, has revised SST fields based upon integration of previous and new faunal and floral analyses with new geochemical proxies and biomarkers, a revised vegetation/land cover data set utilizing the BIOME 4 vegetation classification scheme, 3-dimensional land ice distribution based upon ice-sheet model experiments, new sea level estimates based upon stable isotopes and bottom water temperatures, and revised sea-ice distribution. A deep ocean temperature reconstruction, PRISM3D, adds a 3- dimensional component, which can be used for initiating coupled ocean-atmosphere GCM simulations. PRISM3 is a collaborative effort between the U.S. Geological Survey (USGS), National Science Foundation (NSF), National Aeronautics and Space Administration (NASA), British Antarctic Survey (BAS), and several national and international academic institutions (Columbia University, Duke University, George Mason University, University of Leeds and University of Leicester).

  2. Early Cretaceous wedge extrusion in the Indo-Burma Range accretionary complex: implications for the Mesozoic subduction of Neotethys in SE Asia

    NASA Astrophysics Data System (ADS)

    Zhang, Ji'en; Xiao, Wenjiao; Windley, Brian F.; Cai, Fulong; Sein, Kyaing; Naing, Soe

    2017-03-01

    The Indo-Burma Range (IBR) of Myanmar, the eastern extension of the Yarlung-Tsangpo Neotethyan belt of Tibet in China, contains mélanges with serpentinite, greenschist facies basalt, chert, sericite schist, silty slate and unmetamorphosed Triassic sandstone, mudstone and siltstone interbedded with chert in the east, and farther north high-pressure blueschist and eclogite blocks in the Naga Hills mélange. Our detailed mapping of the Mindat and Magwe sections in the middle IBR revealed a major 18 km antiformal isocline in a mélange in which greenschist facies rocks in the core decrease in grade eastwards and westwards symmetrically `outwards' to lower grade sericite schist and silty slate, and at the margins to unmetamorphosed sediments, and these metamorphic rocks are structurally repeated in small-scale imbricated thrust stacks. In the Mindat section the lower western boundary of the isoclinal mélange is a thrust on which the metamorphic rocks have been transported over unmetamorphosed sediments of the Triassic Pane Chaung Group, and the upper eastern boundary is a normal fault. These relations demonstrate that the IBR metamorphic rocks were exhumed by wedge extrusion in a subduction-generated accretionary complex. Along strike to the north in the Naga Hills is a comparable isoclinal mélange in which central eclogite lenses are succeeded `outwards' by layers of glaucophane schist and glaucophanite, and to lower grade greenschist facies sericite schist and slate towards the margins. In the Natchaung area (from west to east) unmetamorphosed Triassic sediments overlie quartzites, sericite schists, actinolite schists and meta-volcanic amphibolites derived from MORB-type basalt, which are in fault contact with peridotite. Olivine in the peridotite has undulatory extinction suggesting deformation at 600-700 °C, similar to the peak temperature of the amphibolite; these relations suggest generation in a metamorphic sole. The amphibolites have U/Pb zircon ages of 119

  3. Cerebellar lesions and prism adaptation in macaque monkeys.

    PubMed

    Baizer, J S; Kralj-Hans, I; Glickstein, M

    1999-04-01

    If a laterally displacing prism is placed in front of one eye of a person or monkey with the other eye occluded, they initially will point to one side of a target that is located directly in front of them. Normally, people and monkeys adapt easily to the displaced vision and correct their aim after a few trials. If the prism then is removed, there is a postadaptation shift in which the subject misses the target and points in the opposite direction for a few trials. We tested five Macaque monkeys for their ability to adapt to a laterally displacing prism and to show the expected postadaptation shift. When tested as normals, all five animals showed the typical pattern of adaptation and postadaptation shift. Like human subjects, the monkeys also showed complete interocular transfer of the adaptation but no transfer of the adaptation between the two arms. When preoperative training and testing was complete, we made lesions of various target areas on the cerebellar cortex. A cerebellar lesion that included the dorsal paraflocculus and uvula abolished completely the normal prism adaptation for the arm ipsilateral to the lesion in one of the five monkeys. The other four animals retained the ability to prism-adapt normally and showed the expected postadaptation shift. In the one case in which the lesion abolished prism adaptation, the damage included Crus I and II, paramedian lobule and the dorsal paraflocculus of the cerebellar hemispheres as well as lobule IX, of the vermis. Thus in this case, the lesion included virtually all the cerebellar cortex that receives mossy-fiber visual information relayed via the pontine nuclei from the cerebral cortex. The other four animals had damage to lobule V, the classical anterior lobe arm area and/or vermian lobules VI/VII, the oculomotor region. When tested postoperatively, some of these animals showed a degree of ataxia equivalent to that of the case in which prism adaptation was affected, but prism adaptation and the

  4. Adaptation to Leftward Shifting Prisms Alters Motor Interhemispheric Inhibition.

    PubMed

    Martín-Arévalo, Elisa; Schintu, Selene; Farnè, Alessandro; Pisella, Laure; Reilly, Karen T

    2016-12-18

    Adaptation to rightward shifting prisms (rightward prism adaptation, RPA) ameliorates neglect symptoms in patients while adaptation to leftward shifting prisms (leftward prism adaptation, LPA) induces neglect-like behaviors in healthy subjects. It has been hypothesized that prism adaptation (PA) modulates interhemispheric balance between the parietal cortices by inhibiting the posterior parietal cortex (PPC) contralateral to the prismatic deviation, but PA's effects on interhemispheric inhibition (IHI) have not been directly investigated. Since there are hyper-excitable connections between the PPC and primary motor cortex (M1) in the left hemisphere of neglect patients, we reasoned that LPA might mimic right hemisphere lesions by reducing parietal IHI, hyper-exciting the left PPC and PPC-M1 connections, and in turn altering IHI at the motor level. Namely, we hypothesized that LPA would increase IHI from the left to the right M1. We examined changes in left-to-right and right-to-left IHI between the 2 M1s using the ipsilateral silent period (iSP) (Meyer et al. 1995) before and after either LPA or RPA. The iSP was significantly longer after LPA but only from left-to-right and it did not change at all after RPA. This is the first physiological demonstration that LPA alters IHI in the healthy brain.

  5. Research on beam splitting prism in laser heterodyne interferometer

    NASA Astrophysics Data System (ADS)

    Fu, Xiu-hua; Xiong, Shi-fu; Kou, Yang; Pan, Yong-gang; Chen, Heng; Li, Zeng-yu; Zhang, Chuan-xin

    2014-08-01

    With the rapid development of optical testing technology, laser heterodyne interferometer has been used more and more widely. As the testing precision requirements continue to increase, the technical prism is an important component of heterodyne interference. The research utilizing thin film technology to improve optical performance of interferometer has been a new focus. In the article, based on the use requirements of interferometer beam splitting prism, select Ta2O5 and SiO2 as high and low refractive index materials respectively, deposit on substrate K9. With the help of TFCalc design software and Needle method, adopting electron gun evaporation and ion assisted deposition, the beam splitting prism is prepared successfully and the ratio of transmittance and reflectance for this beam splitting prism in 500~850 nm band, incident angle 45 degree is 8:2. After repeated tests, solved the difference problem of film deposition process parameters ,controlled thickness monitoring precision effectively and finally prepared the ideal beam splitting prism which is high adhesion and stable optics properties. The film the laser induced damage threshold and it meet the requirements of heterodyne interferometer for use.

  6. Genomes to natural products PRediction Informatics for Secondary Metabolomes (PRISM).

    PubMed

    Skinnider, Michael A; Dejong, Chris A; Rees, Philip N; Johnston, Chad W; Li, Haoxin; Webster, Andrew L H; Wyatt, Morgan A; Magarvey, Nathan A

    2015-11-16

    Microbial natural products are an invaluable source of evolved bioactive small molecules and pharmaceutical agents. Next-generation and metagenomic sequencing indicates untapped genomic potential, yet high rediscovery rates of known metabolites increasingly frustrate conventional natural product screening programs. New methods to connect biosynthetic gene clusters to novel chemical scaffolds are therefore critical to enable the targeted discovery of genetically encoded natural products. Here, we present PRISM, a computational resource for the identification of biosynthetic gene clusters, prediction of genetically encoded nonribosomal peptides and type I and II polyketides, and bio- and cheminformatic dereplication of known natural products. PRISM implements novel algorithms which render it uniquely capable of predicting type II polyketides, deoxygenated sugars, and starter units, making it a comprehensive genome-guided chemical structure prediction engine. A library of 57 tailoring reactions is leveraged for combinatorial scaffold library generation when multiple potential substrates are consistent with biosynthetic logic. We compare the accuracy of PRISM to existing genomic analysis platforms. PRISM is an open-source, user-friendly web application available at http://magarveylab.ca/prism/.

  7. Prism-based single-camera system for stereo display

    NASA Astrophysics Data System (ADS)

    Zhao, Yue; Cui, Xiaoyu; Wang, Zhiguo; Chen, Hongsheng; Fan, Heyu; Wu, Teresa

    2016-06-01

    This paper combines the prism and single camera and puts forward a method of stereo imaging with low cost. First of all, according to the principle of geometrical optics, we can deduce the relationship between the prism single-camera system and dual-camera system, and according to the principle of binocular vision we can deduce the relationship between binoculars and dual camera. Thus we can establish the relationship between the prism single-camera system and binoculars and get the positional relation of prism, camera, and object with the best effect of stereo display. Finally, using the active shutter stereo glasses of NVIDIA Company, we can realize the three-dimensional (3-D) display of the object. The experimental results show that the proposed approach can make use of the prism single-camera system to simulate the various observation manners of eyes. The stereo imaging system, which is designed by the method proposed by this paper, can restore the 3-D shape of the object being photographed factually.

  8. Study of dose calculation on breast brachytherapy using prism TPS

    NASA Astrophysics Data System (ADS)

    Fendriani, Yoza; Haryanto, Freddy

    2015-09-01

    PRISM is one of non-commercial Treatment Planning System (TPS) and is developed at the University of Washington. In Indonesia, many cancer hospitals use expensive commercial TPS. This study aims to investigate Prism TPS which been applied to the dose distribution of brachytherapy by taking into account the effect of source position and inhomogeneities. The results will be applicable for clinical Treatment Planning System. Dose calculation has been implemented for water phantom and CT scan images of breast cancer using point source and line source. This study used point source and line source and divided into two cases. On the first case, Ir-192 seed source is located at the center of treatment volume. On the second case, the source position is gradually changed. The dose calculation of every case performed on a homogeneous and inhomogeneous phantom with dimension 20 × 20 × 20 cm3. The inhomogeneous phantom has inhomogeneities volume 2 × 2 × 2 cm3. The results of dose calculations using PRISM TPS were compared to literature data. From the calculation of PRISM TPS, dose rates show good agreement with Plato TPS and other study as published by Ramdhani. No deviations greater than ±4% for all case. Dose calculation in inhomogeneous and homogenous cases show similar result. This results indicate that Prism TPS is good in dose calculation of brachytherapy but not sensitive for inhomogeneities. Thus, the dose calculation parameters developed in this study were found to be applicable for clinical treatment planning of brachytherapy.

  9. The Program for Regional and International Shorebird Monitoring (PRISM)

    USGS Publications Warehouse

    Bart, J.; Andres, B.; Brown, S.; Donaldson, G.; Harrington, B.; Johnston, V.; Jones, S.; Morrison, R.I.G.; Skagen, S.K.

    2005-01-01

    This report describes the a??Program for Regional and International Shorebird Monitoringa?? (PRISM). PRISM is being implemented by a Canada-United States Shorebird Monitoring and Assessment Committee formed in 2001 by the Canadian Shorebird Working Group and the U.S. Shorebird Council. PRISM provides a single blueprint for implementing the shorebird conservation plans recently completed in Canada and the United States. The goals of PRISM are to (1) estimate the size of breeding population of 74 shorebird taxa in North America; (2) describe the distribution, abundance, and habitat relationships for each of these taxa; (3) monitor trends in shorebird population size; (4) monitor shorebird numbers at stopover locations, and; (5) assist local managers in meeting their shorebird conservation goals. PRISM has four main components: arctic and boreal breeding surveys, temperate breeding surveys, temperate non-breeding surveys, and neotropical surveys. Progress on, and action items for, each major component are described. The more important major tasks for immediate action are carrying out the northern surveys, conducting regional analyses to design the program of migration counts, and evaluating aerial photographic surveys for migration and winter counts.

  10. Prism sodium-cooled reactor design and performance

    SciTech Connect

    Kwant, W.; Magee, P.M.; Patel, M.R. )

    1989-01-01

    The Power Reactor Inherently Safe Module (PRISM) program is being conducted at General Electric (GE) under U.S. Department of Energy sponsorship to develop a conceptual design for an advanced sodium-cooled liquid-metal reactor plant. The PRISM design emphasizes inherent safety, modular construction, and factory fabrication. A PRISM power plant includes a number of reactor modules, which will be fabricated in a factory and shipped by whatever combination of barge, rail, and road transport that is most economical for a particular site. The target commercial PRISM plant utilizes nine reactor modules arranged in three identical 465-MW(electric) power blocks for an overall plant net electrical rating of 1395 MW(electric). Each power block has three identical reactor modules, each with its own steam generator, that jointly supply saturated steam to a single turbine generator. The PRISM's features of fewer and simpler safety systems, seismic isolation, passive decay heat removal, inherent reactivity control, and generous margins from structural and fuel damage limits during potential accident situations will result in significant gains in public safety and protection of the owner's investment. The use of standardized modular construction and extensive factory fabrication is resulting in a plant design that is economically competitive against projected coal plants and other nuclear design approaches.

  11. Genomes to natural products PRediction Informatics for Secondary Metabolomes (PRISM)

    PubMed Central

    Skinnider, Michael A.; Dejong, Chris A.; Rees, Philip N.; Johnston, Chad W.; Li, Haoxin; Webster, Andrew L. H.; Wyatt, Morgan A.; Magarvey, Nathan A.

    2015-01-01

    Microbial natural products are an invaluable source of evolved bioactive small molecules and pharmaceutical agents. Next-generation and metagenomic sequencing indicates untapped genomic potential, yet high rediscovery rates of known metabolites increasingly frustrate conventional natural product screening programs. New methods to connect biosynthetic gene clusters to novel chemical scaffolds are therefore critical to enable the targeted discovery of genetically encoded natural products. Here, we present PRISM, a computational resource for the identification of biosynthetic gene clusters, prediction of genetically encoded nonribosomal peptides and type I and II polyketides, and bio- and cheminformatic dereplication of known natural products. PRISM implements novel algorithms which render it uniquely capable of predicting type II polyketides, deoxygenated sugars, and starter units, making it a comprehensive genome-guided chemical structure prediction engine. A library of 57 tailoring reactions is leveraged for combinatorial scaffold library generation when multiple potential substrates are consistent with biosynthetic logic. We compare the accuracy of PRISM to existing genomic analysis platforms. PRISM is an open-source, user-friendly web application available at http://magarveylab.ca/prism/. PMID:26442528

  12. Stress effects in prism coupling measurements of thin polymer films

    NASA Astrophysics Data System (ADS)

    Agan, S.; Ay, F.; Kocabas, A.; Aydinli, A.

    2005-02-01

    Due to the increasingly important role of some polymers in optical waveguide technologies, precise measurement of their optical properties has become important. Typically, prism coupling to slab waveguides made of materials of interest is used to measure the relevant optical parameters. However, such measurements are often complicated by the softness of the polymer films when stress is applied to the prism to couple light into the waveguides. In this work, we have investigated the optical properties of three different polymers, polystyrene (PS), polymethyl-methacrylate (PMMA), and benzocyclobutane (BCB). For the first time, the dependence of the refractive index, film thickness, and birefringence on applied stress in these thin polymer films was determined by means of the prism coupling technique. Both symmetric trapezoid shaped and right-angle prisms were used to couple the light into the waveguides. It was found that trapezoid shaped prism coupling gives better results in these thin polymer films. The refractive index of PMMA was found to be in the range of 1.4869 up to 1.4876 for both TE and TM polarizations under the applied force, which causes a small decrease in the film thickness of up to 0.06 μm. PMMA waveguide films were found not to be birefringent. In contrast, both BCB and PS films exhibit birefringence albeit of opposing signs.

  13. PRISM: A Practical Mealtime Imaging Stereo Matcher

    NASA Astrophysics Data System (ADS)

    Nishihara, H. K.

    1984-02-01

    A fast stereo-matching algorithm designed to operate in the presence of noise is described. The algorithm has its roots in the zero-crossing theory of Marr and Poggio but does not explicitly match zero-crossing contours. While these contours are for the most part stably tied to fixed surface locations, some fraction is always perturbed significantly by system noise. Zero-crossing contour based matching algorithms tend to I- very sensitive to these local distortions and ar, prevented from operating well on signals with moderate noise levels even though a substantial amount of information may still be present. The dual representation ¬â€?regions of constant sign in the V2G convolution persist much further into the noise than does the local geometry of the zero-crossing contours that delimit them. The PRISM system was designed to test this approach. The initial design task of the implementation has been to rapidly detect obstacles in a robotics work space and determine their rough extents and heights. In this case speed and reliability are important but precision is less critical. The system uses a pair of inexpensive vidicon cameras mounted above the workspace of a PUMA robot manipulator. The digitized video signals are fed to a high speed digital convolver that applies a 322 VG operator to the images at a 106 pixel per second rate. Matching is accomplished in software on a lisp machine with individual near/far tests taking less than i3luth of a second. A 36 by 26 matrix of absolute height measurements - in mm - over a 100 pixel disparity range is produced in 30 seconds from image acquisition to final output. Three scales of resolution are used in a coarse guides fine search. Acknowledgment: This report describes research done at the Artificial Intelligence Laboratory of the Massachusetts Institute of 'Technology Support for the laboratory's artificial intelligence research is provided in part by the Advanced Research Projects Agency of the Department of Defense

  14. The PRISM4 (mid-Piacenzian) Palaeoenvironmental Reconstruction

    NASA Technical Reports Server (NTRS)

    Dowsett, Harry; Dolan, Aisling; Rowley, David; Moucha, Robert; Forte, Alessandro M.; Mitrovica, Jerry X.; Pound, Matthew; Salzmann, Ulrich; Robinson, Marci; Chandler, Mark; Foley, Kevin; Haywood, Alan

    2016-01-01

    The mid-Piacenzian is known as a period of relative warmth when compared to the present day. A comprehensive understanding of conditions during the Piacenzian serves as both a conceptual model and a source for boundary conditions as well as means of verification of global climate model experiments. In this paper we present the PRISM4 reconstruction, a paleoenvironmental reconstruction of the mid-Piacenzian (approximately 3 Ma) containing data for paleogeography, land and sea ice, sea-surface temperature, vegetation, soils, and lakes. Our retrodicted paleogeography takes into account glacial isostatic adjustments and changes in dynamic topography. Soils and lakes, both significant as land surface features, are introduced to the PRISM reconstruction for the first time. Sea-surface temperature and vegetation reconstructions are unchanged but now have confidence assessments. The PRISM4 reconstruction is being used as boundary condition data for the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) experiments.

  15. Density functional theory and simulations of colloidal triangular prisms.

    PubMed

    Marechal, Matthieu; Dussi, Simone; Dijkstra, Marjolein

    2017-03-28

    Nanopolyhedra form a versatile toolbox to investigate the effect of particle shape on self-assembly. Here we consider rod-like triangular prisms to gauge the effect of the cross section of the rods on liquid crystal phase behavior. We also take this opportunity to implement and test a previously proposed version of fundamental measure density functional theory (0D-FMT). Additionally, we perform Monte Carlocomputer simulations and we employ a simpler Onsager theory with a Parsons-Lee correction. Surprisingly and disappointingly, 0D-FMT does not perform better than the Tarazona and Rosenfeld's version of fundamental measure theory (TR-FMT). Both versions of FMT perform somewhat better than the Parsons-Lee theory. In addition, we find that the stability regime of the smectic phase is larger for triangular prisms than for spherocylinders and square prisms.

  16. Enhanced scanning agility using a double pair of Risley prisms.

    PubMed

    Roy, Gilles; Cao, Xiaoying; Bernier, Robert; Roy, Simon

    2015-12-01

    Scanners with one pair of Risley prisms are robust and precise and they can be operated continuously. In this paper, we present a new scanner based on the use of two pairs of Risley prisms. The concept was driven by the need to add flexibility to Risley prism scanners used for lidar 3D mapping applications, while maintaining compactness and robustness. The first pair covers a FOV narrower than the second pair. The second pair is used to position the first Risley pair scan pattern anywhere within its own, larger, FOV. Doing so, it becomes possible, without additional scanner components, to increase the sampling point density at a specific location, to increase the sampling uniformity of the scanned area, and, while in motion, to maintain the sampling of a specific area of interest.

  17. The PRISM4 (mid-Piacenzian) paleoenvironmental reconstruction

    USGS Publications Warehouse

    Dowsett, Harry J.; Dolan, Aisling M.; Rowley, David; Moucha, Robert; Forte, Alessandro; Mitrovica, Jerry X.; Pound, Matthew; Salzmann, Ulrich; Robinson, Marci M.; Chandler, Mark; Foley, Kevin M.; Haywood, Alan M.

    2016-01-01

    The mid-Piacenzian is known as a period of relative warmth when compared to the present day. A comprehensive understanding of conditions during the Piacenzian serves as both a conceptual model and a source for boundary conditions as well as means of verification of global climate model experiments. In this paper we present the PRISM4 reconstruction, a paleoenvironmental reconstruction of the mid-Piacenzian ( ∼ 3 Ma) containing data for paleogeography, land and sea ice, sea-surface temperature, vegetation, soils, and lakes. Our retrodicted paleogeography takes into account glacial isostatic adjustments and changes in dynamic topography. Soils and lakes, both significant as land surface features, are introduced to the PRISM reconstruction for the first time. Sea-surface temperature and vegetation reconstructions are unchanged but now have confidence assessments. The PRISM4 reconstruction is being used as boundary condition data for the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) experiments.

  18. The PRISM4 (mid-Piacenzian) paleoenvironmental reconstruction

    NASA Astrophysics Data System (ADS)

    Dowsett, Harry; Dolan, Aisling; Rowley, David; Moucha, Robert; Forte, Alessandro M.; Mitrovica, Jerry X.; Pound, Matthew; Salzmann, Ulrich; Robinson, Marci; Chandler, Mark; Foley, Kevin; Haywood, Alan

    2016-07-01

    The mid-Piacenzian is known as a period of relative warmth when compared to the present day. A comprehensive understanding of conditions during the Piacenzian serves as both a conceptual model and a source for boundary conditions as well as means of verification of global climate model experiments. In this paper we present the PRISM4 reconstruction, a paleoenvironmental reconstruction of the mid-Piacenzian ( ˜ 3 Ma) containing data for paleogeography, land and sea ice, sea-surface temperature, vegetation, soils, and lakes. Our retrodicted paleogeography takes into account glacial isostatic adjustments and changes in dynamic topography. Soils and lakes, both significant as land surface features, are introduced to the PRISM reconstruction for the first time. Sea-surface temperature and vegetation reconstructions are unchanged but now have confidence assessments. The PRISM4 reconstruction is being used as boundary condition data for the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) experiments.

  19. Metamorphic complexes in accretionary orogens: Insights from the Beishan collage, southern Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Song, Dongfang; Xiao, Wenjiao; Windley, Brian F.; Han, Chunming; Yang, Lei

    2016-10-01

    The sources of ancient zircons and the tectonic attributions and origins of metamorphic complexes in Phanerozoic accretionary orogens have long been difficult issues. Situated between the Tianshan and Inner Mongolia orogens, the Beishan orogenic collage (BOC) plays a pivotal role in understanding the accretionary processes of the southern Central Asian Orogenic Belt (CAOB), particularly the extensive metamorphic and high-strained complexes on the southern margin. Despite their importance in understanding the basic architecture of the southern CAOB, little consensus has been reached on their ages and origins. Our new structural, LA-ICP-MS zircon U-Pb and Hf isotopic data from the Baidunzi, Shibandun, Qiaowan and Wutongjing metamorphic complexes resolve current controversial relations. The metamorphic complexes have varied lithologies and structures. Detrital zircons from five para-metamorphic rocks yield predominantly Phanerozoic ages with single major peaks at ca. 276 Ma, 286 Ma, 427 Ma, 428 Ma and 461 Ma. Two orthogneisses have weighted mean ages of 294 ± 2 Ma and 304 ± 2 Ma with no Precambrian inherited zircons. Most Phanerozoic zircons show positive εHf(t) values indicating significant crustal growth in the Ordovician, Silurian and Permian. The imbricated fold-thrust deformation style combined with diagnostic zircon U-Pb-Hf isotopic data demonstrate that the metamorphic rocks developed in a subduction-accretion setting on an arc or active continental margin. This setting and conclusion are supported by the nearby occurrence of Ordovician-Silurian adakites, Nb-rich basalts, Carboniferous-Permian ophiolitic mélanges, and trench-type turbidites. Current data do not support the presence of a widespread Precambrian basement in the evolution of the BOC; the accretionary processes may have continued to the early Permian in this part of the CAOB. These relationships have meaningful implications for the interpretation of the tectonic attributions and origins of other

  20. Origin and Migration of Methane in Gas Hydrate-bearing Sediments Relevant to Their Subsurface Occurrences in The Nankai Trough

    NASA Astrophysics Data System (ADS)

    Uchida, T.; Waseda, A.

    2003-04-01

    Although gas hydrates are known to occur in the Arctic in association with permafrost regimes and in the deep offshore at the continental margins, the geologic and geophysical issues controlling their occurrences and distributions are still remained. The Nankai Trough runs along the Japanese Island, where forearc basins and accretionary prisms developed extensively and BSRs (bottom simulating reflector) have been recognized widely. High resolution seismic surveys in 1997, 2001 and 2002 and drilling the Nankai Trough wells conducted by the METI (Ministry of Economy, Trade and Industry) have revealed the subsurface gas hydrate widely distributed at the depth interval from 200 to 270 mbsf. All the core samples containing gas hydrates were subjected to X-ray CT imagery so as to observe sedimentary textures and occurrences inside of cores without disturbances before provided to various analyses. Subsurface occurrences of natural gas hydrate can be classified into six types; 1) pore-space hydrate, 2) platy hydrate, 3) layered/massive hydrate, 4) disseminated hydrate, 5) nodule hydrate and 6) vein/dyke hydrate. The anomalies of chloride contents in pore water, core temperature depression, core observation as well as visible gas hydrates confirmed well-interconnected and highly saturated pore-space hydrates as intergranular pore filling within sand layers within the methane hydrate stability zone. Hydrate saturations are higher than 60 % throughout most hydrate-dominant sand layers and in some parts close to 100% pore saturation. Muddy sediments such as silts and clays were free of hydrate or contained low concentrations. Carbon and hydrogen isotope compositions of CH4 and hydrocarbon compositions contained in gas hydrate indicate that methane is generated by microbial reduction of CO2. Both carbon isotope compositions of CH4 and CO2 in the sediments become heavier gradually with depths shallower than 100 mbsf. In deeper depths, the origins of hydrocarbon change from

  1. Petrogenesis and tectonic implications of Early Jurassic volcanic rocks of the Raohe accretionary complex, NE China

    NASA Astrophysics Data System (ADS)

    Wang, Zhi-Hui; Ge, Wen-Chun; Yang, Hao; Bi, Jun-Hui; Ji, Zheng; Dong, Yu; Xu, Wen-Liang

    2017-02-01

    The Raohe accretionary complex, located at the border between the Russian Far East and Northeastern China, is a significant part of the western Pacific Oceanic tectonic regime. Due to lack of precise age and geochemical constraints, the tectonic setting and petrogenesis of the magmatic rocks in this area remain undefined, resulting in debate about crustal growth mechanisms and subduction-related accretionary processes in Northeastern China. Here, we report whole-rock major and trace element and Sr-Nd isotope data, together with zircon U-Pb ages and in situ zircon Hf isotope data for calc-alkaline andesites, dacites, rhyolites, rhyolitic crystal tuffs, Nb-enriched andesites and basaltic andesites, and high-Mg andesites of the Raohe accretionary complex in NE China. Samples were collected from Late Triassic to Early Jurassic strata. However, geochronological results in this study indicated that the studied magmatism occurred in the Early Jurassic (187-174 Ma). The calc-alkaline volcanic rocks possess geochemical characteristics typical of arc magmas that form at active continental margins, such as moderate enrichments in large ion lithophile elements (LILEs) and light rare earth elements (LREEs), and depletions in high field strength elements (HFSEs). They have positive εHf(t) values of +3.4 to +10.6 and relatively high (87Sr/86Sr)i values of 0.7047-0.7102. While the Nb-enriched andesites and basaltic andesites have higher TiO2, Hf, Nb, and Zr contents and higher Nb/Ta (24.0-87.6), Nb/U (11.9-75.9), (Nb/Th)PM (0.67-2.70), and (Nb/La)PM (1.95-5.00) ratios than typical arc basalts. They have negative εNd(t) values (-5.5 to -6.0) and relatively variable (87Sr/86Sr)i values of 0.7047-0.7114, suggesting an origin via the partial melting of mantle wedge peridotite that had been metasomatized by slab-derived melt. The high-Mg volcanic rocks, characterized by high MgO and Mg#, TiO2, Al2O3, Cr, Ni, (La/Yb)N and (La/Sm)N, but low Ba/Th ratios, are geochemically similar to

  2. Late Cretaceous to early Tertiary transtension and strain partitioning in the Chugach Accretionary Complex, SE Alaska

    USGS Publications Warehouse

    Davis, J.S.; Roeske, S.M.; Karl, S.M.

    1998-01-01

    Shear zones in the Late Cretaceous Sitka Graywacke of the Chugach accretionary complex in southeast Alaska record constrictional finite strains, with maximum principal s tretches plunging shallowly subparallel to strike of the shear zones. Macrostructural analysis indicates the finite strain formed during one deformation event. Microstructural analysis of the shear zones shows that this deformation is ductile, promoted mostly through deformation of low-strength lithic clasts and pressure solution. Kinematic indicators from some of the shear zones indicate dominantly dextral motion. Although multiple scenarios can explain constrictional finite strains in a shear zone, these dextral strike-slip shear zones must have experienced a component of extension across them in order to generate constrictional finite strains. Therefore, the shear zones are dextral transtensional shear zones, an uncommon tectinic regime in an accretionary complex. The transtensional shear zones reflect strike-slip motion related to partitioning of Late Cretaceous to Early Tertiary right-oblique convergence between North America and the Farallon plate. The extensional component that was superposed on the strike-slip shear zones to generate transtension resulted from contemporaneous collapse of the forearc following thickening related to underplating.Shear zones in the Late Cretaceous Sitka Graywacke of the Chugach accretionary complex in southeast Alaska record constrictional finite strains, with maximum principal stretches plunging shallowy sub-parallel to strike of the shear zones. Macrostructural analysis indicates the finite strain formed during one deformation event. Microstructural analysis of the shear zones shows that this deformation is ductile, promoted mostly through deformation of low-strength lithic clasts and pressure solution. Kinematic indicators from some of the shear zones indicate dominantly dextral motion. Although multiple scenarios can explain constrictional finite strains

  3. Polymeric waveguide prism-based electro-optic beam deflector

    NASA Astrophysics Data System (ADS)

    Sun, Lin; Kim, Jin-ha; Jang, Chiou-Hung; An, Dechang; Lu, Xuejun; Zhou, Qingjun; Taboada, John M.; Chen, Ray T.; Maki, Jeffery J.; Tang, Suning; Zhang, Hua; Steier, William H.; Zhang, Cheng H.; Dalton, Larry R.

    2001-07-01

    Beam steering devices without moving parts are highly desirable for their potential application in emerging optical technologies such as holographic optical storage systems, all optical networks, and optical switches. We demonstrate a thin-film waveguide beam deflector device that consists of an electro-optic prism array within a polymer waveguide. An electrode structure defines the prism array within the planar waveguide. The deflection efficiency of 28 mrad/kV and the maximum deflection angle of +/- 8.4 mrad at +/- 300 V are obtained for this demonstration device. Further optimization of electrode-field poling and processing is likely to improve these results by at least an order of magnitude.

  4. Beam distortion of rotation double prisms with an arbitrary incident angle.

    PubMed

    Li, Anhu; Zuo, Qiyou; Sun, Wansong; Yi, Wanli

    2016-07-01

    The distortion of beam shape in rotation Risley prisms is discussed in this paper. Using the ray-tracing method based on vector refraction theorem, a rigorous theoretical model of beam distortion with an arbitrary incident angle is established to explore the influencing factors. For a specified double-prism pair, the emergent beam is squeezed in one direction while stretched in the mutual perpendicular direction, the distortion of which is determined by the relative rotation angle. Moreover, the distortion of beam shape is greatly influenced by the wedge angles and the refractive indices of the prisms, as well as different double-prism configurations, while uncorrelated to the prism thickness and the distance between two prisms. This paper demonstrates the regular change of the beam shape with multiparameter variations in rotation double prisms, which can be applied to the design of rotation double-prism systems.

  5. Late Cretaceous to Early Tertiary transtension and strain partitioning in the Chugach accretionary complex, SE Alaska

    NASA Astrophysics Data System (ADS)

    Davis, J. Steven; Roeske, Sarah M.; Karl, Sue M.

    1998-05-01

    Shear zones in the Late Cretaceous Sitka Graywacke of the Chugach accretionary complex in southeast Alaska record constrictional finite strains, with maximum principal stretches plunging shallowly subparallel to strike of the shear zones. Macrostructural analysis indicates the finite strain formed during one deformation event. Microstructural analysis of the shear zones shows that this deformation is ductile, promoted mostly through deformation of low-strength lithic clasts and pressure solution. Kinematic indicators from some of the shear zones indicate dominantly dextral motion. Although multiple scenarios can explain constrictional finite strains in a shear zone, these dextral strike-slip shear zones must have experienced a component of extension across them in order to generate constrictional finite strains. Therefore, the shear zones are dextral transtensional shear zones, an uncommon tectonic regime in an accretionary complex. The transtensional shear zones reflect strike-slip motion related to partitioning of Late Cretaceous to Early Tertiary right-oblique convergence between North America and the Farallon plate. The extensional component that was superposed on the strike-slip shear zones to generate transtension resulted from contemporaneous collapse of the forearc following thickening related to underplating.

  6. 4. VIEW SOUTH SHOWING AQUEDUCT PRISM. NOTE 1920 TIMBER AND ...

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

    4. VIEW SOUTH SHOWING AQUEDUCT PRISM. NOTE 1920 TIMBER AND CONCRETE FLOORING SYSTEM, POCKETS FOR VERTICAL POSTS AND BRIDGING, STEEL BRACES ADDED BY THE NATIONAL PARK SERVICE CIRCA 1962. - Chesapeake & Ohio Canal, Conococheague Creek Aqueduct, Milepost 99.80, Williamsport, Washington County, MD

  7. 3. GENERAL VIEW ACROSS CANAL PRISM TO TOWPATH BERM NORTH ...

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

    3. GENERAL VIEW ACROSS CANAL PRISM TO TOWPATH BERM NORTH OF THE SPILLWAY; VIEW TO WEST FROM ROUTE 146 EMBANKMENT. - Blackstone Canal Millbury Segment, Beginning northwest of State Route 146 & McCracken Road, running along west side of Route 146, Millbury, Worcester County, MA

  8. 1. GENERAL VIEW, TOWPATH BERM (CENTER) AND CANAL PRISM (LEFT) ...

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

    1. GENERAL VIEW, TOWPATH BERM (CENTER) AND CANAL PRISM (LEFT) SOUTH OF THE SPILLWAY; VIEW TO SOUTH. - Blackstone Canal Millbury Segment, Beginning northwest of State Route 146 & McCracken Road, running along west side of Route 146, Millbury, Worcester County, MA

  9. 2. GENERAL VIEW ACROSS CANAL PRISM TO TOWPATH BERM SOUTH ...

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

    2. GENERAL VIEW ACROSS CANAL PRISM TO TOWPATH BERM SOUTH OF THE SPILLWAY; VIEW TO SOUTHWEST FROM ROUTE 146 EMBANKMENT. - Blackstone Canal Millbury Segment, Beginning northwest of State Route 146 & McCracken Road, running along west side of Route 146, Millbury, Worcester County, MA

  10. 3. VIEW SOUTH SHOWING AQUEDUCT PRISM. NOTE 1920 TIMBER AND ...

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

    3. VIEW SOUTH SHOWING AQUEDUCT PRISM. NOTE 1920 TIMBER AND CONCRETE FLOORING SYSTEM, CUT STONE FACE OF PARAPET WALL, AND WROUGHT IRON BOLTS USED TO SECURE THE RUBBING RAIL. - Chesapeake & Ohio Canal, Conococheague Creek Aqueduct, Milepost 99.80, Williamsport, Washington County, MD

  11. The Portable Remote Imaging Spectrometer (PRISM) Coastal Ocean Sensor

    NASA Technical Reports Server (NTRS)

    Mouroulis, Pantazis; VanGorp, Byron E.; Green, Robert O.; Eastwppd, Michael; Wilson, Daniel W.; Richardson, Brandon; Dierssen, Heidi

    2012-01-01

    PRISM is an airborne pushbroom imaging spectrometer intended to address the needs of airborne coastal ocean science research. Its critical characteristics are high throughput and signal-to-noise ratio, high uniformity of response to reduce spectral artifacts, and low polarization sensitivity. We give a brief overview of the instrument and results from laboratory calibration measurements regarding the spatial, spectral, radiometric and polarization characteristics.

  12. Compact prisms for polarisation splitting of fibre laser beams

    SciTech Connect

    Davydov, B L; Yagodkin, D I

    2005-11-30

    Simple compact monoprisms for spatial splitting of polarised laser beams with relatively small diameters (no more than 1 mm) are considered. Prisms can be made of optically inactive CaCO{sub 3}, {alpha}-BaB{sub 2}O{sub 4} ({alpha}-BBO), LiIO{sub 3}, LiNbO{sub 3}, YVO{sub 4}, and TiO{sub 2} crystals known in polarisation optics. The exact solution of the Snell equation for the extraordinary wave reflected from a surface arbitrarily tilted to its wave vector is obtained. The analysis of variants of the solution allows the fabrication of prisms with any deviation angles of the extraordinary wave by preserving the propagation direction of the ordinary wave. Three variants of prisms are considered: with minimised dimensions, with the Brewster output of the extraordinary beam, and with the deviation of the extraordinary wave by 90{sup 0}. Calcite prisms with the deviation angles for the extraordinary beam {approx}19{sup 0} and 90{sup 0} are tested experimentally. (control of laser radiation parameters)

  13. Synthesis and photocatalytic activity of porous bismuth oxychloride hexagonal prisms.

    PubMed

    Ding, Liyong; Chen, Huan; Wang, Qingqian; Zhou, Tengfei; Jiang, Qingqing; Yuan, Yuhong; Li, Jinlin; Hu, Juncheng

    2016-01-18

    Porous BiOCl hexagonal prisms have been successfully prepared through a simple solvothermal route. These novel BiOCl HPs with porous structures are assembled from nanoparticles and exhibit high activity and selectivity toward the photocatalytic aerobic oxidation of benzyl alcohol to benzaldehyde and degradation of methyl orange.

  14. Portable Remote Imaging Spectrometer (PRISM): Laboratory and Field Calibration

    NASA Technical Reports Server (NTRS)

    Mouroulis, Pantazis; Van Gorp, Byron; Green, Robert O.; Eastwood, Michael; Boardman, Joseph; Richardson, Brandon S.; Rodriguez, Jose I.; Urquiza, Eugenio; Franklin, Brian D.; Gao, Bo-Cai

    2012-01-01

    We report the characteristics of the Portable Remote Imaging Spectrometer, an airborne sensor specifically designed for the challenges of coastal ocean research. PRISM has high signal to noise ratio and uniformity, as well as low polarization sensitivity. Acquisition of high quality data has been demonstrated with the first engineering flight.

  15. Drum dispersion equation for Littrow-type prism spectrometers.

    PubMed

    Sidran, M; Stalzer, H J; Hauptman, M H

    1966-07-01

    A simple analytic procedure has been developed for calibrating the wavelength drum of a Littrow-type prism spectrometer. Only three measured drum readings are required to specify the drum calibration over a broad wavelength range (uv to ir) with an accuracy of the order of the instrumental accuracy. This procedure can be applied to different prism materials for which measurements of refractive index have been performed. It is based on an approximate expression, derived from geometrical optics, relating the drum reading D(lambda) to the calculated refractive index n(lambda): D= A - B(a(2) - n(2))((1/2)). The index n(lambda) is calculated from the appropriate parametric equation. The temperature for the n(lambda) values need not be exactly that of the prism temperature during measurements. This expression was investigated for wavelengths in the range 0.3 micro to 2.25 micro using a sodium chloride prism. Computed drum positions D agreed with measured drum positions to within experimental error. Unknown wavelengths were computed from their measured drum positions to within the accuracy of the measurements.

  16. The Pacific Oaks College's Prism Principles Professional Development Approach

    ERIC Educational Resources Information Center

    Beyer, Kalani

    2012-01-01

    In a struggling atmosphere for education, one college is optimistic about the future by offering school districts its PRISM Principles professional development as a means to ensure that "no child is left behind." Pacific Oaks College & Children's School is known for its premiere programs in early childhood education, human…

  17. Payloads with Resource-Efficient Integration for Science Missions (PRISM)

    NASA Astrophysics Data System (ADS)

    Emam, O.; FitzGeorge, T.; Whittaker, A.; Wishart, A.; Fowell, S.; Prochazka, M.; Bentley, R.; Cole, R.; Brown, P.; Carr, C.; Cupido, E.; Oddy, T.

    2009-05-01

    PRISM is a collaborative industry and academia project to demonstrate the practicality of a highly integrated payload processing architecture, in order to exploit improvements in spacecraft computer performance to reduce multi-instrument payload mass and power requirements. Integrated architectures also provide opportunities for a greater degree of autonomy and advanced target selection (e.g. inter-instrument triggering). The PRISM architecture has potential advantages for missions such as EJSM (Europa Jupiter System Mission) or Solar Orbiter. The key technology objectives of PRISM are application partitioning on a qualifiable operating system, supported by the software required for fault-tolerant centralised processing, and the development of an application development environment for writing and testing instrument control applications. A working demonstrator has been implemented on a LEON3 platform, with representative payload applications from an in-situ magnetometer and a remote sensing extreme ultra-violet imager, both proposed for Solar Orbiter. PRISM is supported by the UK Science and Technology Facilities Council (STFC).

  18. Generalized prism-array lenses for hard X-rays.

    PubMed

    Cederström, Björn; Ribbing, Carolina; Lundqvist, Mats

    2005-05-01

    A Fresnel-like X-ray lens can be constructed by a triangular array of identical prisms whose base corresponds to the 2pi-shift length. Each column of prisms is progressively shifted from the optical axis by an arbitrary fraction of the prism height. Similarly to the multi-prism lens, quasi-parabolic profiles are formed by a superposition of straight-line segments. The resulting projected lens profile is approximately linear with a Fresnel-lens pattern superimposed on it to provide the focusing. This geometry exhibits a significantly larger effective aperture than conventional parabolic refractive lenses. Prototype lenses were fabricated by deep reactive ion etching of silicon. These one-dimensionally focusing lenses were tested at a synchrotron beamline and provided focal line-widths down to 1.4 microm FWHM and an intensity gain of 39 at a photon energy of 13.4 keV. Fabrication imperfections gave rise to unwanted interference effects resulting in several intensity maxima in the focal plane. The presented design allows the focal length to be shortened without decreasing the feature size of the lens. Furthermore, this feature size does not limit the resolution as for real Fresnel optics.

  19. A new processing technology and detection method for isosceles prism

    NASA Astrophysics Data System (ADS)

    Guo, Rui; Su, Ying; Chen, Chaoping; Zhang, Yunlong; Li, Wenting; Zhang, Feng; Xu, Zengqi; Liu, Xuanmin

    2016-10-01

    The optical parallelism is an important indicators of isosceles prism. However, it cannot be directly measured in the processing process, and it is measured when the small surface is coated with silver film, which results in low processing rate. By analyzing the principles of the first optical parallelism and the second optical parallelism, this paper provides a new processing and detection method for isosceles prism. The good verticality between the three working face for isosceles prism and a side face can ensure the second optical parallelism. The small difference of 67.5°can ensure the first optical parallelism. By changing the position of the incident light when testing, the number of reflections can be reduced from seven to three. The reflection principle deduces the formula: θII(7)=2.4θII(3) which to improve the machining accuracy and avoid the surface imperfections in detection. By using this process, precision and productivity can be effectively improved, the complexity of the process is reduced, and the qualification of isosceles prism has been improved.

  20. Budding Architects: Exploring the Designs of Pyramids and Prisms

    ERIC Educational Resources Information Center

    Leavy, Aisling; Hourigan, Mairéad

    2015-01-01

    The context of students as architects is used to examine the similarities and differences between prisms and pyramids. Leavy and Hourigan use the Van Hiele Model as a tool to support teachers to develop expectations for differentiating geometry in the classroom using practical examples.

  1. 49 CFR 390.203 - PRISM State registration/biennial updates.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 5 2013-10-01 2013-10-01 false PRISM State registration/biennial updates. 390.203... FEDERAL MOTOR CARRIER SAFETY REGULATIONS; GENERAL Unified Registration System § 390.203 PRISM State... the Performance and Registration Information Systems Management (PRISM) program (authorized...

  2. 49 CFR 390.203 - PRISM State registration/biennial updates.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 5 2014-10-01 2014-10-01 false PRISM State registration/biennial updates. 390.203... FEDERAL MOTOR CARRIER SAFETY REGULATIONS; GENERAL Unified Registration System § 390.203 PRISM State... the Performance and Registration Information Systems Management (PRISM) program (authorized...

  3. Superconducting magnetic Wollaston prism for neutron spin encoding

    SciTech Connect

    Li, F. Parnell, S. R.; Wang, T.; Baxter, D. V.; Hamilton, W. A.; Maranville, B. B.; Semerad, R.; Cremer, J. T.; Pynn, R.

    2014-05-15

    A magnetic Wollaston prism can spatially split a polarized neutron beam into two beams with different neutron spin states, in a manner analogous to an optical Wollaston prism. Such a Wollaston prism can be used to encode the trajectory of neutrons into the Larmor phase associated with their spin degree of freedom. This encoding can be used for neutron phase-contrast radiography and in spin echo scattering angle measurement (SESAME). In this paper, we show that magnetic Wollaston prisms with highly uniform magnetic fields and low Larmor phase aberration can be constructed to preserve neutron polarization using high temperature superconducting (HTS) materials. The Meissner effect of HTS films is used to confine magnetic fields produced electromagnetically by current-carrying HTS tape wound on suitably shaped soft iron pole pieces. The device is cooled to ∼30 K by a closed cycle refrigerator, eliminating the need to replenish liquid cryogens and greatly simplifying operation and maintenance. A HTS film ensures that the magnetic field transition within the prism is sharp, well-defined, and planar due to the Meissner effect. The spin transport efficiency across the device was measured to be ∼98.5% independent of neutron wavelength and energizing current. The position-dependent Larmor phase of neutron spins was measured at the NIST Center for Neutron Research facility and found to agree well with detailed simulations. The phase varies linearly with horizontal position, as required, and the neutron beam shows little depolarization. Consequently, the device has advantages over existing devices with similar functionality and provides the capability for a large neutron beam (20 mm × 30 mm) and an increase in length scales accessible to SESAME to beyond 10 μm. With further improvements of the external coupling guide field in the prototype device, a larger neutron beam could be employed.

  4. Study of dose calculation on breast brachytherapy using prism TPS

    SciTech Connect

    Fendriani, Yoza; Haryanto, Freddy

    2015-09-30

    PRISM is one of non-commercial Treatment Planning System (TPS) and is developed at the University of Washington. In Indonesia, many cancer hospitals use expensive commercial TPS. This study aims to investigate Prism TPS which been applied to the dose distribution of brachytherapy by taking into account the effect of source position and inhomogeneities. The results will be applicable for clinical Treatment Planning System. Dose calculation has been implemented for water phantom and CT scan images of breast cancer using point source and line source. This study used point source and line source and divided into two cases. On the first case, Ir-192 seed source is located at the center of treatment volume. On the second case, the source position is gradually changed. The dose calculation of every case performed on a homogeneous and inhomogeneous phantom with dimension 20 × 20 × 20 cm{sup 3}. The inhomogeneous phantom has inhomogeneities volume 2 × 2 × 2 cm{sup 3}. The results of dose calculations using PRISM TPS were compared to literature data. From the calculation of PRISM TPS, dose rates show good agreement with Plato TPS and other study as published by Ramdhani. No deviations greater than ±4% for all case. Dose calculation in inhomogeneous and homogenous cases show similar result. This results indicate that Prism TPS is good in dose calculation of brachytherapy but not sensitive for inhomogeneities. Thus, the dose calculation parameters developed in this study were found to be applicable for clinical treatment planning of brachytherapy.

  5. Superconducting magnetic Wollaston prism for neutron spin encoding.

    PubMed

    Li, F; Parnell, S R; Hamilton, W A; Maranville, B B; Wang, T; Semerad, R; Baxter, D V; Cremer, J T; Pynn, R

    2014-05-01

    A magnetic Wollaston prism can spatially split a polarized neutron beam into two beams with different neutron spin states, in a manner analogous to an optical Wollaston prism. Such a Wollaston prism can be used to encode the trajectory of neutrons into the Larmor phase associated with their spin degree of freedom. This encoding can be used for neutron phase-contrast radiography and in spin echo scattering angle measurement (SESAME). In this paper, we show that magnetic Wollaston prisms with highly uniform magnetic fields and low Larmor phase aberration can be constructed to preserve neutron polarization using high temperature superconducting (HTS) materials. The Meissner effect of HTS films is used to confine magnetic fields produced electromagnetically by current-carrying HTS tape wound on suitably shaped soft iron pole pieces. The device is cooled to ~30 K by a closed cycle refrigerator, eliminating the need to replenish liquid cryogens and greatly simplifying operation and maintenance. A HTS film ensures that the magnetic field transition within the prism is sharp, well-defined, and planar due to the Meissner effect. The spin transport efficiency across the device was measured to be ~98.5% independent of neutron wavelength and energizing current. The position-dependent Larmor phase of neutron spins was measured at the NIST Center for Neutron Research facility and found to agree well with detailed simulations. The phase varies linearly with horizontal position, as required, and the neutron beam shows little depolarization. Consequently, the device has advantages over existing devices with similar functionality and provides the capability for a large neutron beam (20 mm × 30 mm) and an increase in length scales accessible to SESAME to beyond 10 μm. With further improvements of the external coupling guide field in the prototype device, a larger neutron beam could be employed.

  6. Superconducting magnetic Wollaston prism for neutron spin encoding

    NASA Astrophysics Data System (ADS)

    Li, F.; Parnell, S. R.; Hamilton, W. A.; Maranville, B. B.; Wang, T.; Semerad, R.; Baxter, D. V.; Cremer, J. T.; Pynn, R.

    2014-05-01

    A magnetic Wollaston prism can spatially split a polarized neutron beam into two beams with different neutron spin states, in a manner analogous to an optical Wollaston prism. Such a Wollaston prism can be used to encode the trajectory of neutrons into the Larmor phase associated with their spin degree of freedom. This encoding can be used for neutron phase-contrast radiography and in spin echo scattering angle measurement (SESAME). In this paper, we show that magnetic Wollaston prisms with highly uniform magnetic fields and low Larmor phase aberration can be constructed to preserve neutron polarization using high temperature superconducting (HTS) materials. The Meissner effect of HTS films is used to confine magnetic fields produced electromagnetically by current-carrying HTS tape wound on suitably shaped soft iron pole pieces. The device is cooled to ˜30 K by a closed cycle refrigerator, eliminating the need to replenish liquid cryogens and greatly simplifying operation and maintenance. A HTS film ensures that the magnetic field transition within the prism is sharp, well-defined, and planar due to the Meissner effect. The spin transport efficiency across the device was measured to be ˜98.5% independent of neutron wavelength and energizing current. The position-dependent Larmor phase of neutron spins was measured at the NIST Center for Neutron Research facility and found to agree well with detailed simulations. The phase varies linearly with horizontal position, as required, and the neutron beam shows little depolarization. Consequently, the device has advantages over existing devices with similar functionality and provides the capability for a large neutron beam (20 mm × 30 mm) and an increase in length scales accessible to SESAME to beyond 10 μm. With further improvements of the external coupling guide field in the prototype device, a larger neutron beam could be employed.

  7. Seismic velocity structure of the sediment seaward of Cascadia Subduction Zone deformation front

    NASA Astrophysics Data System (ADS)

    Han, S.; Gibson, J. C.; Carbotte, S. M.; Canales, J. P.; Nedimovic, M. R.; Carton, H. D.

    2015-12-01

    We present seismic velocity structure of the sediment section seaward of the Cascadia Subduction Zone deformation front (DF), derived from multichannel seismic data acquired during the 2012 Juan de Fuca Ridge to Trench experiment. Detailed velocity analyses are conducted on every 100th prestack-time-migrated common reflection point gather (625 m spacing) within 45 km seaward of the DF along two ridge-to-trench transects offshore Oregon at 44.6˚N and Washington at 47.4˚N respectively, and on every 200th common mid-point gather (1250 m spacing) along a ~400 km-long trench-parallel transect ~15 km from the DF. We observe a landward increase of sediment velocity starting from ~15-20 km from the DF on both Oregon and Washington transects, which may result from increased horizontal compressive tectonic stress within the accretionary wedge and thermally induced dehydration processes in the sediment column. Although the velocity of near-basement sediments at 30 km from the DF is similar (~3.1 km/s) on both transects, the velocity increases are larger on the Washington transect, to ~4.0 km/s beneath the DF (sediment thickness ~3.2 km), than on the Oregon transect, to ~3.6 km/s beneath the DF (sediment thickness ~3.5 km). The long-wavelength sediment velocity structure on the trench-parallel transect confirms this regional difference in deep sediment velocity and also highlights variations related to a group of WNW-trending strike-slip faults along the margin. Offshore Washington, where higher sediment velocity seaward of the DF is observed, the accretionary wedge is wide with a decollement located close to the basement and landward-verging thrust faults. By contrast, offshore Oregon, the lower sediment velocity seaward of the DF is associated with a narrow accretionary wedge, a shallow decollement ~1 km above the basement, and seaward-verging thrust faults. The regional differences in deep sediment velocity may be related to the along-strike variation in sediment

  8. Accretion process of sediments below Kumano basin by analyzing cuttings from IODP Exp.319, the first riser drilling

    NASA Astrophysics Data System (ADS)

    Kawabata, K.; Sakaguchi, A.; Kitamura, Y.; Saito, S.

    2012-12-01

    The structure, stress condition and rock properties of accreted sediments in the Nankai Trough have been studied by reflection seismology and deep sea drillings. Accretion processes have been suggested by onland geological studies that the sediments are circulated with undergoing lithification and deformation along thrusts in shallow subduction zone driven by the plate motion. However the process in the modern Nankai Trough has yet to be elucidated. We discuss the accretion process of the shallow Nankai Trough accretionary prism below Kumano basin by clarifying thermal structure and materials by vitrinite measurement and whole rock chemical analyses, respectively, using cuttings samples from IODP The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) the first scientific riser drilling Expedition 319 at Site C0009. Cuttings were collected with an interval of every 5 m from 703.9 to 1604 m and cores were recovered from 1509.7 m to 1593.9 m below sea floor (mbsf). Due to poor consolidation of drilled sediments, cuttings samples typically consist of sand and silt floating in a matrix of mixed sedimentary and drilling muds, and solid rock chips were not retrieved above 802.7 mbsf. Visual description based on macro- and micro-scopic observation, XRD and XRF analysis, rocks properties and the age of washed cuttings (i.e. grains without mud) were made throughout the hole, which allowed to establish some indexes to estimate lithology. Four lithologic units (Unit I - IV) were defined at Site C0009 based on compositional and textural variations of cuttings samples, which are believed to closely reflect lithologic changes of drilled sequences, and show good consistency with logging data. Unit IV is believed to be accreted sediment by mainly age and the textural change of sediments. Dissoluble component ratios (TiO2/P2O5) and clay content ratios in the samples analyzed by XRF and XRD are different from that in basin sediment, which might support Unit IV are accreted

  9. Middle Jurassic oceanic island igneous rocks of the Raohe accretionary complex, northeastern China: Petrogenesis and tectonic implications

    NASA Astrophysics Data System (ADS)

    Wang, Zhi-Hui; Ge, Wen-Chun; Yang, Hao; Zhang, Yan-Long; Bi, Jun-Hui; Tian, De-Xin; Xu, Wen-Liang

    2015-11-01

    Whole-rock major and trace element, and Sr, Nd, and Hf isotopic data, together with zircon U-Pb ages and in situ zircon Hf isotopes, are reported for Middle Jurassic igneous rocks of the Raohe accretionary complex, northeastern China, to investigate their petrogenesis and tectonic implications. The igneous rocks consist of pillow basalt, pyroxenite, gabbro, plagioclasite, and plagiogranite. The zircons from one plagioclasite and one plagiogranite are euhedral-subhedral and display fine-scale oscillatory growth zoning, indicating a magmatic origin. Zircon U-Pb dating gives an emplacement age of 169-167 Ma. The basalts are associated with late Paleozoic to middle Mesozoic sediments typical of ocean plate stratigraphy; i.e., limestone, bedded chert, and siliceous shale. The basalts, which show geochemical features similar to those of oceanic island basalts (OIBs), are enriched in TiO2, light rare earth elements (LREEs) (average: La/Smn = 2.12), and Nb (average: Zr/Nb = 12.24), and are characterized by positive Nb anomalies (averages: Nb/Thpm = 1.46, Nb/Lapm = 1.31). The rocks are depleted in heavy rare earth elements (HREEs) (average: Gd/Ybn = 2.03) and exhibit high εNd(t) (+8.2 to +8.3) and εHf(t) (+9.0 to +9.1) values. The geochemical features indicate the Jurassic OIB-like basalts were derived by a low degree of partial melting (<5%) of peridotite in the garnet stability field. The intermediate-mafic intrusive rocks show typical OIB affinities and are geochemically similar to the basalts. Most of the intermediate-mafic intrusive rocks are enriched in LREEs and Nb, depleted in HREEs, and show low Zr/Nb ratios and high εNd(t) (+7.2 to +8.2) and εHf(t) (+8.8 to +10.3) values, indicating they were derived from a common source and are the products of fractional crystallization of the OIB-like basalts. All of the igneous rocks are likely fragments of oceanic islands/seamounts. The identification of OIB-like basalts and associated intermediate-mafic intrusive rocks

  10. Experimental static aerodynamics of a regular hexagonal prism in a low density hypervelocity flow

    NASA Technical Reports Server (NTRS)

    Guy, R. W.; Mueller, J. N.; Lee, L. P.

    1972-01-01

    A regular hexagonal prism, having a fineness ratio of 1.67, has been tested in a wind tunnel to determine its static aerodynamic characteristics in a low-density hypervelocity flow. The prism tested was a 1/4-scale model of the graphite heat shield which houses the radioactive fuel for the Viking spacecraft auxiliary power supply. The basic hexagonal prism was also modified to simulate a prism on which ablation of one of the six side flats had occurred. This modified hexagonal prism was tested to determine the effects on the aerodynamic characteristics of a shape change caused by ablation during a possible side-on stable reentry.

  11. Experimental volcanic ash aggregation: Internal structuring of accretionary lapilli and the role of liquid bonding

    NASA Astrophysics Data System (ADS)

    Mueller, Sebastian B.; Kueppers, Ulrich; Ayris, Paul M.; Jacob, Michael; Dingwell, Donald B.

    2016-01-01

    Explosive volcanic eruptions can release vast quantities of pyroclastic material into Earth's atmosphere, including volcanic ash, particles with diameters less than two millimeters. Ash particles can cluster together to form aggregates, in some cases reaching up to several centimeters in size. Aggregation alters ash transport and settling behavior compared to un-aggregated particles, influencing ash distribution and deposit stratigraphy. Accretionary lapilli, the most commonly preserved type of aggregates within the geologic record, can exhibit complex internal stratigraphy. The processes involved in the formation and preservation of these aggregates remain poorly constrained quantitatively. In this study, we simulate the variable gas-particle flow conditions which may be encountered within eruption plumes and pyroclastic density currents via laboratory experiments using the ProCell Lab System® of Glatt Ingenieurtechnik GmbH. In this apparatus, solid particles are set into motion in a fluidized bed over a range of well-controlled boundary conditions (particle concentration, air flow rate, gas temperature, humidity, liquid composition). Experiments were conducted with soda-lime glass beads and natural volcanic ash particles under a range of experimental conditions. Both glass beads and volcanic ash exhibited the capacity for aggregation, but stable aggregates could only be produced when materials were coated with high but volcanically-relevant concentrations of NaCl. The growth and structure of aggregates was dependent on the initial granulometry, while the rate of aggregate formation increased exponentially with increasing relative humidity (12-45% RH), before overwetting promoted mud droplet formation. Notably, by use of a broad granulometry, we generated spherical, internally structured aggregates similar to some accretionary pellets found in volcanic deposits. Adaptation of a powder-technology model offers an explanation for the origin of natural accretionary

  12. Accretionary lapilli, tektites, or concretions: the ubiquitous spherules of Meridiani Planum

    NASA Astrophysics Data System (ADS)

    DiGregorio, Barry E.

    2004-11-01

    One of the most enigmatic discoveries made by the NASA Mars Exploration Rover Opportunity (MER-B) at the Meridiani Planum landing site are the ubiquitous spherules referred to as "blueberries" by the science team. They cover the entire landing area and can be seen in every direction within view of the rover cameras. Subsequent analysis of a small grouping of the spherules laying on top of a rock outcrop by Mossbauer spectroscopy showed an intense hematite signature not found on the rock or in the surrounding basaltic soils. Spherules were also found attached to and embedded within sedimentary sulfate rock outcrops found at the landing area that have been determined by the MER science team as having been formed in an acidic liquid water environment. The appearance of most of the Meridiani spherules is strikingly similar to the morphology and size of terrestrial accretionary lapilli and show similarities to terrestrial tektites. Accretionary lapilli are spherical balls and fragments with a concentric layered structure that are formed by a variety of mechanisms including hydrovolcanic eruptions, geysers and large meteorite impacts in water. Tektites are glassy impact spherules that form as a result of large meteorite impacts and also seem apparent in some of the rover images. Tektites can be perfectly spherical or have teardrop and dumbbell shapes. A lack of a visible volcanic source capable of producing high volumes of accretionary lapilli as seen in the MER-B images, in combination with the strong spectral signature of hematite, that some of the spherules display, led the MER science team to favor a concretion hypothesis thus far. All of these types of spherules involve interaction of with surface water or ice to form. Problems exist in explaining how the Martian "concretions", if that is indeed what they are, are of such uniform size and have such a wide distribution. Evidence from Martian orbit and on the surface indicate that the Meridiani Planum landing ellipse

  13. Physical properties of southern Alaska margin sediments in the context of global convergent margins

    NASA Astrophysics Data System (ADS)

    Daigle, H.; Piña, O.; Screaton, E.; James, S.

    2014-12-01

    At convergent margins, the deformation response due to external forcing by sedimentation, tectonic stress, and volume changes during chemical reactions is closely interrelated with the ability of excess pore pressure to dissipate. These excess pore pressures in turn can affect plate boundary fault location and strength, rates of sediment accretion or subduction, the taper angle of material on the overriding plate, and may also play a role in the generation of earthquakes and propagation of seismic slip. Offshore southern Alaska, rapid sedimentation and glacial loading are interpreted to have influenced the location of thrust faulting by rapid transport of sediment offshore, where previously active faults were deactivated by increased normal stresses as a result of sediment loading. The response of the wedge to external forcing is linked to permeability of the wedge sediments, as well as those in the underriding plate. We determined permeability of sediments from the glacial sediment dominated accretionary wedge, sampled at Sites U1420 and U1421 on the Yakutat Block, and sediments from the Surveyor Fan that overlies the Pacific Plate and are inputs to the Aleutian Trench, sampled at Sites U1417 and U1418. We found that the Surveyor Fan sediments have porosity-permeability relationships that are comparable to sediments from other reference sites worldwide. However, the sediments in the wedge have somewhat higher permeability, much larger grain sizes, and are much less compressible compared with other wedge sediments. This suggests that the physical properties that control overpressure generation and dissipation in the input sediments to the Aleutian Trench are comparable to other subduction zones, but that the accretionary wedge on the Yakutat Block is uniquely strong and well-drained due to the predominance of glacigenic sediments.

  14. A ~9.4 Ma Ash Record from the Andaman Accretionary Wedge: Petrochemical Implications for Arc Evolution

    NASA Astrophysics Data System (ADS)

    Cawthern, T. R.; Johnson, J. E.; Bryce, J. G.; Blichert-Toft, J.; Flores, J. A.

    2010-12-01

    Coupled chemical and isotopic signatures in arc lavas are critical for resolving temporal variations in the magnitude, source, and composition of subduction inputs to the slab-mantle interface. Dewatering of the subducting plate within this zone can potentially affect tectonic and igneous processes. In 2006, the National Gas Hydrate program of India drilled a ~700 meter long (~9.4 Ma) marine sediment core (Site 17) in a relatively undeformed portion of the Andaman accretionary wedge. This record contains abundant and well-preserved volcanic ash layers and provides the ideal opportunity to study the temporal variation in bulk ash chemistry during the past ~9.4 Ma. Petrographic examination of ashes at Site 17 reveals mineralogically distinct mafic ashes in the deeper half of the core and felsic ashes near the top of the core. Volcanic ashes are absent from the middle of the core (~6.3-1.5 Ma), synchronous with the beginning of active backarc spreading (4-0 Ma) in the Andaman Sea [1]. Mafic ashes consist predominantly of feldspar, hornblende, pyroxene, and dark colored glass with microlitic feldspar. Felsic, more silica-rich ashes contain mostly thin-walled colorless volcanic glass shards, biotite, and feldspar. This transition from mafic to felsic ashes most likely reflects: 1) the bimodal behavior of a single steady-state and flare-up volcanic system linked with crustal assimilation and changes in the relative proportions of the input of mantle-derived melts or 2) a fundamental change in the amount or type of sediment input to the Sunda subduction zone. It is also possible that the ash record reflects contributions from multiple volcanic centers to this site. The apparent monotonic compositional shift, however, suggests that the record is from a relatively small arc segment. Trends in ɛHf vs age at Site 17, coupled with the disparate ash silica contents, provide concrete evidence for arc evolution during the past ~9.4 Ma. The older, more mafic ashes have ɛHf >7

  15. Stratal disruption and development of mélange, Western Newfoundland: effect of high fluid pressure in an accretionary terrain during ophiolite emplacement

    NASA Astrophysics Data System (ADS)

    Waldron, J. W. F.; Turner, D.; Stevens, K. M.

    The Bay of Islands Ophiolite was emplaced onto the continental margin of North America during the mid-Ordovician Taconic orogeny, when tectonic slices of continental margin sediments were accreted to the moving allochthon. Tectonic slices grade into and are surrounded by mélange. Early fracture in sandstones formed without grain breakage and allowed penetration of liquid petroleum along fracture planes. Other fractures involved cataclastic flow and were sometimes re-activated during formation of later pressure solution cleavage. Shear-fracture and extension-fracture boudinage affect competent strata; extensional veins cut cement in limestone beds and are filled by shale, quartz, calcite and bitumen. Folds also formed, at a time when siltstone and sandstone were at least partially lithified. Mélange matrix shows abundant shear and extension fractures in a variety of orientations. Coaxial extension responsible for disruption of bedding can be explained by a brittle accretionary wedge model in which high fluid pressures resulted from tectonic dewatering of shales. Surface slope decreased as fluid pressure rose beneath the ophiolite, causing horizontal extension of the wedge. After escape of excess water the surface slope steepened again as renewed stacking occurred.

  16. Forward and inverse solutions for three-element Risley prism beam scanners.

    PubMed

    Li, Anhu; Liu, Xingsheng; Sun, Wansong

    2017-04-03

    Scan blind zone and control singularity are two adverse issues for the beam scanning performance in double-prism Risley systems. In this paper, a theoretical model which introduces a third prism is developed. The critical condition for a fully eliminated scan blind zone is determined through a geometric derivation, providing several useful formulae for three-Risley-prism system design. Moreover, inverse solutions for a three-prism system are established, based on the damped least-squares iterative refinement by a forward ray tracing method. It is shown that the efficiency of this iterative calculation of the inverse solutions can be greatly enhanced by a numerical differentiation method. In order to overcome the control singularity problem, the motion law of any one prism in a three-prism system needs to be conditioned, resulting in continuous and steady motion profiles for the other two prisms.

  17. The effect of compliant prisms on subduction zone earthquakes and tsunamis

    NASA Astrophysics Data System (ADS)

    Lotto, Gabriel C.; Dunham, Eric M.; Jeppson, Tamara N.; Tobin, Harold J.

    2017-01-01

    Earthquakes generate tsunamis by coseismically deforming the seafloor, and that deformation is largely controlled by the shallow rupture process. Therefore, in order to better understand how earthquakes generate tsunamis, one must consider the material structure and frictional properties of the shallowest part of the subduction zone, where ruptures often encounter compliant sedimentary prisms. Compliant prisms have been associated with enhanced shallow slip, seafloor deformation, and tsunami heights, particularly in the context of tsunami earthquakes. To rigorously quantify the role compliant prisms play in generating tsunamis, we perform a series of numerical simulations that directly couple dynamic rupture on a dipping thrust fault to the elastodynamic response of the Earth and the acoustic response of the ocean. Gravity is included in our simulations in the context of a linearized Eulerian description of the ocean, which allows us to model tsunami generation and propagation, including dispersion and related nonhydrostatic effects. Our simulations span a three-dimensional parameter space of prism size, prism compliance, and sub-prism friction - specifically, the rate-and-state parameter b - a that determines velocity-weakening or velocity-strengthening behavior. We find that compliant prisms generally slow rupture velocity and, for larger prisms, generate tsunamis more efficiently than subduction zones without prisms. In most but not all cases, larger, more compliant prisms cause greater amounts of shallow slip and larger tsunamis. Furthermore, shallow friction is also quite important in determining overall slip; increasing sub-prism b - a enhances slip everywhere along the fault. Counterintuitively, we find that in simulations with large prisms and velocity-strengthening friction at the base of the prism, increasing prism compliance reduces rather than enhances shallow slip and tsunami wave height.

  18. Considering Apical Scotomas, Confusion, and Diplopia When Prescribing Prisms for Homonymous Hemianopia

    PubMed Central

    Apfelbaum, Henry L.; Ross, Nicole C.; Bowers, Alex R.; Peli, Eli

    2013-01-01

    Purpose: While prisms are commonly prescribed for homonymous hemianopia to extend or expand the visual field, they cause potentially troubling visual side effects, including nonveridical location of perceived images, diplopia, and visual confusion. In addition, the field behind a prism at its apex is lost to an apical scotoma equal in magnitude to the amount of prism shift. The perceptual consequences of apical scotomas and the other effects of various designs were examined to consider parameters and designs that can mitigate the impact of these effects. Methods: Various configurations of sector and peripheral prisms were analyzed, in various directions of gaze, and their visual effects were illustrated using simulated perimetry. A novel “percept” diagram was developed that yielded insights into the patient's view through the prisms. The predictions were verified perimetrically with patients. Results: The diagrams distinguish between potentially beneficial field expansion via visual confusion and the pericentrally disturbing and useless effect of diplopia, and their relationship to prism power and gaze direction. They also illustrate the nonexpanding substitution of field segments of some popular prism designs. Conclusions: Yoked sector prisms have no effect at primary gaze or when gaze is directed toward the seeing hemifield, and they introduce pericentral field loss when gaze is shifted into them. When fitted unilaterally, sector prisms also have an effect only when the gaze is directed into the prism and may cause a pericentral scotoma and/or central diplopia. Peripheral prisms are effective at essentially all gaze angles. Since gaze is not directed into them, they avoid problematic pericentral effects. We derive useful recommendations for prism power and position parameters, including novel ways of fitting prisms asymmetrically. Translational Relevance: Clinicians will find these novel diagrams, diagramming techniques, and analyses valuable when prescribing

  19. Mechanics of fold-and-thrust belts and accretionary wedges Cohesive Coulomb theory

    NASA Technical Reports Server (NTRS)

    Dahlen, F. A.; Suppe, J.; Davis, D.

    1984-01-01

    A self-consistent theory for the mechanics of thin-skinned accretionary Coulomb wedges is developed and applied to the active fold-and-thrust belt of western Taiwan. The state of stress everywhere within a critical wedge is determined by solving the static equilibrium equations subject to the appropriate boundary conditions. The influence of wedge cohesion, which gives rise to a concave curvature of the critical topographic surface and affects the orientation of the principal stresses and Coulomb fracture within the wedge, is considered. The shape of the topographic surface and the angles at which thrust faults step up from the basal decollement in the Taiwanese belt is analyzed taking into account the extensive structural and fluid-pressure data available there. It is concluded that the gross geometry and structure of the Taiwan wedge are consistent with normal laboratory frictional and fracture strengths of sedimentary rocks.

  20. Early Jurassic Volcanic Rocks from the Raohe Accretionary Complex of NE China: Petrogenesis and Tectonic Implications

    NASA Astrophysics Data System (ADS)

    Wang, Zhihui; Ge, Wenchun

    2016-04-01

    The Raohe accretionary complex is located at the boundary between the Russian Far East and Northeast China, and is an important part of the Western Pacific Ocean tectonic regime. However, owing to the lack of precise age and geochemical constraints, the tectonic setting and petrogenesis of magmatic rocks in this area have been controversial, which has led to the debate on crustal growth mechanisms and subduction accretionary processes in the Northeast China. Herein, we report newly-defined calc-alkaline andesites, dacites, rhyolites, Nb-enriched basaltic-andesites and andesites, and N-MORB type basalts and basaltic-andesites from the Raohe accretionary complex, NE China. All these volcanic rocks are collected from rocks mapped previously as the Late Triassic to Early Jurassic stratums. LA-ICP-MS zircon U-Pb dating for one andesite, one dacites and three rhyolites indicate the occurrence of magmatic events in the Early Jurassic (186-174 Ma). They have positive ɛHf(t) values of +3.4 to +10.6 and relatively high (87Sr/86Sr)i values of 0.704711 to 0.710235. The calc-alkaline andesites, dacites and rhyolites are typical arc magmas, with moderately enriched LILEs and LREEs, distinctly negative HFSEs, consistent with the chemistry of volcanic rocks from an active continental margin setting. The Nb-enriched basaltic-andesites and andesites have higher TiO2, Nb, and Zr contents, higher Nb/Ta (24.03-87.60), Nb/U (11.89-75.94), (Nb/Th)PM (0.67-2.70), and (Nb/La)PM (1.95-5.00) ratios than typical arc basalts. They are relatively enriched in Nb, Zr, Hf and Ti. They have negative ɛNd(t) values of -5.47 to -6.04 and relatively variable (87Sr/86Sr)i values of 0.704648 to 0.711430, suggesting that they were possibly generated by a partial melting of mantle wedge peridotites metasomatized by slab-derived adakitic melts and minor fluids. The N-MORB type basalts and basaltic-andesites have comparatively low TiO2 concentrations (1.18-1.42 wt.%), show almost flat REE patterns with

  1. Structural geology of cuttings and cores recovered from below the Kumano forearc basin, Nankai accretionary margin of Japan: Expedition 319 of the Integrated Ocean Drilling Program (IODP)

    NASA Astrophysics Data System (ADS)

    Hayman, N. W.; Byrne, T. B.; Huftile, G.; McNeill, L. C.; Kanamatsu, T.; Saffer, D.; Araki, E.; Eguchi, N. O.; Toczko, S.; Takahashi, K.; Scientists, E.

    2009-12-01

    faults are in many cases slickensided, exhibit a range of kinematic indicators (thrust, strike-slip, and normal), and have a bimodal dip distribution, ~20° and ~60°. The younger structures may have developed during forearc development of, or beneath the Kumano basin whereas the shear zones likely formed within the frontal region of the late Miocene accretionary prism or possibly along the faulted slope apron.

  2. Planar prism spectrometer based on adiabatically connected waveguiding slabs

    NASA Astrophysics Data System (ADS)

    Civitci, F.; Hammer, M.; Hoekstra, H. J. W. M.

    2016-04-01

    The device principle of a prism-based on-chip spectrometer for TE polarization is introduced. The spectrometer exploits the modal dispersion in planar waveguides in a layout with slab regions having two different thicknesses of the guiding layer. The set-up uses parabolic mirrors, for the collimation of light of the input waveguide and focusing of the light to the receiver waveguides, which relies on total internal reflection at the interface between two such regions. These regions are connected adiabatically to prevent unwanted mode conversion and loss at the edges of the prism. The structure can be fabricated with two wet etching steps. The paper presents basic theory and a general approach for device optimization. The latter is illustrated with a numerical example assuming SiON technology.

  3. PRISM: Recovery of the primordial spectrum from Planck data

    NASA Astrophysics Data System (ADS)

    Lanusse, F.; Paykari, P.; Starck, J.-L.; Sureau, F.; Bobin, J.; Rassat, A.

    2014-11-01

    Aims: The primordial power spectrum describes the initial perturbations that seeded the large-scale structure we observe today. It provides an indirect probe of inflation or other structure-formation mechanisms. In this Letter, we recover the primordial power spectrum from the Planck PR1 dataset, using our recently published algorithm PRISM. Methods: PRISM is a sparsity-based inversion method that aims at recovering features in the primordial power spectrum from the empirical power spectrum of the cosmic microwave background (CMB). This ill-posed inverse problem is regularised using a sparsity prior on features in the primordial power spectrum in a wavelet dictionary. Although this non-parametric method does not assume a strong prior on the shape of the primordial power spectrum, it is able to recover both its general shape and localised features. As a results, this approach presents a reliable way of detecting deviations from the currently favoured scale-invariant spectrum. Results: We applied PRISM to 100 simulated Planck data to investigate its performance on Planck-like data. We then applied PRISM to the Planck PR1 power spectrum to recover the primordial power spectrum. We also tested the algorithm's ability to recover a small localised feature at k ~ 0.125 Mpc-1, which caused a large dip at ℓ ~ 1800 in the angular power spectrum. Conclusions: We find no significant departures from the fiducial Planck PR1 near scale-invariant primordial power spectrum with As = 2.215 × 10-9 and ns = 0.9624.

  4. Prism-coupled light emission from tunnel junctions

    NASA Technical Reports Server (NTRS)

    Ushioda, S.; Rutledge, J. E.; Pierce, R. M.

    1985-01-01

    Completely p-polarized light emission has been observed from smooth Al-AlO(x)-Au tunnel junctions placed on a prism coupler. The angle and polarization dependence demonstrate unambiguously that the emitted light is radiated by the fast-mode surface plasmon polariton. The emission spectra suggest that the dominant process for the excitation of the fast mode is through conversion of the slow mode to the fast mode mediated by residual roughness on the junction surface.

  5. An Assessment of the Crossed Porro Prism Resonator

    DTIC Science & Technology

    1980-08-01

    utilise Nd:YAIG lasers. Weapons Systems Research Laboratory is studying laser designation systems and Advanced Engineering Laboratory has recently...performed a feasibility study of a laser rangefinder for the RAAF(ref.l). This report has been prepared in response to the requirements of the above...the laser, but rather to study the change of energy with respect to the mis-slignment of the porro prisms. The relative pulse energy was monitored by

  6. Stereovision Imaging in Smart Mobile Phone Using Add on Prisms

    NASA Astrophysics Data System (ADS)

    Bar-Magen Numhauser, Jonathan; Zalevsky, Zeev

    2014-03-01

    In this work we present the use of a prism-based add on component installed on top of a smart phone to achieve stereovision capabilities using iPhone mobile operating system. Through these components and the combination of the appropriate application programming interface and mathematical algorithms the obtained results will permit the analysis of possible enhancements for new uses to such system, in a variety of areas including medicine and communications.

  7. Geochronological and Geochemical evidence of amphibolite from the Hualong Group, northwest China: Implication for the early Paleozoic accretionary tectonics of the Central Qilian belt

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Wang, Zongqi; Yan, Zhen; Ma, Zhenhui; He, Shengfei; Fu, Changlei; Wang, Dongsheng

    2016-04-01

    The Hualong Group, located in the Central Qilian belt, northwest China, consists mainly of schist, amphibolite, quartzite, and marble, ranging from greenschist to amphibolite facies metamorphism. On the basis of the medium-grade metamorphism, the group has been considered to comprise Proterozoic basement rocks. In this study, geochemical, Sr-Nd isotopic, and zircon U-Pb geochronological analyses were performed on lentoid amphibolites from the Hualong Group, to characterize their age, petrogensis, and tectonic setting. Uranium-lead zircon dating of amphibolite revealed a formation age of 456 ± 2 Ma and a metamorphic age of 440 ± 1 Ma. Major, trace, and rare earth element data indicate that the amphibolites are predominantly basaltic-andesitic to andesitic rocks, with island arc affinities. The trace element patterns show enrichment in large-ion lithophile elements and depletion in high field strength elements relative to the N-MORB which confirm their island arc signatures. Obviously enriched light REEs ((La/Yb)N = 2.5-16.9) to chondrite normalized REE patterns further support this interpretation. The εNd(t) values for the amphibolites range from 4.6 to + 2.1, indicating subducted sediments as a larger endmember in the source. Geochemical data for these rocks suggest an island arc setting, and the rocks were derived from the depleted mantle that was enriched by melts of subducted sediments in an active continental margin setting at ca. 456 Ma. Together with regional evidence it suggests that the Hualong Group is an accretionary complex that was incorporated into the Central Qilian belt during the 440-400 Ma orogenic event.

  8. Porosity, Pore Size, and Permeability of Sediments from Site C0002, IODP Expedition 338

    NASA Astrophysics Data System (ADS)

    Dugan, B.; Huepers, A.; Song, I.; Kitajima, H.; Esteban, L.

    2013-12-01

    Mercury injection capillary pressure (MICP) measurements were made on cuttings and core samples from Integrated Ocean Drilling Program (IODP) Site C0002 to evaluate porosity, pore throat size, and permeability of mud(stone) at the centerpiece drill site of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE). Core samples from 221-464 meters below sea floor (mbsf) in the Kumano forearc basin have MICP-determined porosities from 40-56%, median pore radii from 0.077-0.205 microns, and permeability from 3.3x10-10 - 2.0x10-9 m2. The porosity of these core samples is similar to shipboard porosity determined from moisture and density (MAD) analyses. During IODP Expedition 338 cuttings samples were recovered from ~865-2005 mbsf during riser drilling at Site C0002F. MICP analyses of cuttings samples, greater than 4 mm size fraction, from 928-1980 mbsf in the inner wedge of the accretionary prism constrain porosities from 21-44%, median pore radii from 0.021-0.032 microns, and permeability from 1.2x10-11 - 1.6x10-10 m2. The porosity of these cuttings samples is consistently lower than the MAD-determined porosity on cuttings from the >4mm size fraction, however the values are consistent with core-based, MAD-derived porosity from Hole C0002B above 1057 mbsf and with cuttings-based, MAD-derived porosity on select samples from 1700-2000 mbsf that were determined to be intact formation and not influenced by drilling disturbance. These results suggest that select formation cuttings or MICP-analyses can help define in situ porosity. Additional post-expedition research will be used to better understand the ability of MICP data to define mudstone permeability and to constrain permeability-porosity and permeability-grain size-pore throat relations for sediments at Site C0002. A detailed model of permeability and porosity behavior will inform modeling studies of pore pressure generation and fluid and heat transport.

  9. SSC analysis of the GEMs for reactivity control in PRISM

    SciTech Connect

    Slovik, G.C.; Rodnizki, J.

    1992-01-01

    The performance of three Gas Expansion Modules (GEMS) utilized the Advanced Liquid Metal Reactor (ALMR) concept, PRISM, was analyzed using the computer code, SSC. GE has submitted the PRISM design for a Preapplication Safety Evaluation Report (PSER). The draft PSER indicated a potential weakness in the Unscrammed Loss of Flow (ULOF) event, and GE modified the design by adding three GEMs. The PRISM design was analyzed by SSC for two cases. First, the design's original response to a ULOF where one Electro Magnetic (EM) pump fails to produce a coastdown was analyzed. Then the revised design with the GEMs included was analyzed. The original design had little or no safety margin for this case. The peak fuel temperature in the hot channel was predicted to be 1358K, which is above the solidus temperature of the fuel. However, after the GEMs were added, the loss of one EM pump coastdown became a benign event. The GEM feedback was predicted by SSC to dominate the other reactivity feedbacks and the GEMS, essentially, responded like passive control rods. The fuel temperature quickly dropped below operating temperatures, while the margin to sodium boiling was predicted to be greater than 350K.

  10. SSC analysis of the GEMs for reactivity control in PRISM

    SciTech Connect

    Slovik, G.C.; Rodnizki, J.

    1992-12-31

    The performance of three Gas Expansion Modules (GEMS) utilized the Advanced Liquid Metal Reactor (ALMR) concept, PRISM, was analyzed using the computer code, SSC. GE has submitted the PRISM design for a Preapplication Safety Evaluation Report (PSER). The draft PSER indicated a potential weakness in the Unscrammed Loss of Flow (ULOF) event, and GE modified the design by adding three GEMs. The PRISM design was analyzed by SSC for two cases. First, the design`s original response to a ULOF where one Electro Magnetic (EM) pump fails to produce a coastdown was analyzed. Then the revised design with the GEMs included was analyzed. The original design had little or no safety margin for this case. The peak fuel temperature in the hot channel was predicted to be 1358K, which is above the solidus temperature of the fuel. However, after the GEMs were added, the loss of one EM pump coastdown became a benign event. The GEM feedback was predicted by SSC to dominate the other reactivity feedbacks and the GEMS, essentially, responded like passive control rods. The fuel temperature quickly dropped below operating temperatures, while the margin to sodium boiling was predicted to be greater than 350K.

  11. Controllable Sonar Lenses and Prisms Based on ERFs

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph; Sherrit, Stewart; Chang, Zensheu; Bao, Xiaoqi; Paustian, Iris; Lopes, Joseph; Folds, Donald

    2004-01-01

    Sonar-beam-steering devices of the proposed type would contain no moving parts and would be considerably smaller and less power-hungry, relative to conventional multiple-beam sonar arrays. The proposed devices are under consideration for installation on future small autonomous underwater vehicles because the sizes and power demands of conventional multiple-beam arrays are excessive, and motors used in single-beam mechanically scanned systems are also not reliable. The proposed devices would include a variety of electrically controllable acoustic prisms, lenses, and prism/lens combinations both simple and compound. These devices would contain electrorheological fluids (ERFs) between electrodes. An ERF typically consists of dielectric particles floating in a dielectric fluid. When an electric field is applied to the fluid, the particles become grouped into fibrils aligned in rows, with a consequent increase in the viscosity of the fluid and a corresponding increase in the speed of sound in the fluid. The change in the speed of sound increases with an increase in the applied electric field. By thus varying the speed of sound, one varies the acoustic index of refraction, analogously to varying the index of refraction of an optical lens or prism. In the proposed acoustic devices, this effect would be exploited to control the angles of refraction of acoustic beams, thereby steering the beams and, in the case of lenses, controlling focal lengths.

  12. Spatial Compression Impairs Prism Adaptation in Healthy Individuals

    PubMed Central

    Scriven, Rachel J.; Newport, Roger

    2013-01-01

    Neglect patients typically present with gross inattention to one side of space following damage to the contralateral hemisphere. While prism-adaptation (PA) is effective in ameliorating some neglect behaviors, the mechanisms involved and their relationship to neglect remain unclear. Recent studies have shown that conscious strategic control (SC) processes in PA may be impaired in neglect patients, who are also reported to show extraordinarily long aftereffects compared to healthy participants. Determining the underlying cause of these effects may be the key to understanding therapeutic benefits. Alternative accounts suggest that reduced SC might result from a failure to detect prism-induced reaching errors properly either because (a) the size of the error is underestimated in compressed visual space or (b) pathologically increased error-detection thresholds reduce the requirement for error correction. The purpose of this study was to model these two alternatives in healthy participants and to examine whether SC and subsequent aftereffects were abnormal compared to standard PA. Each participant completed three PA procedures within a MIRAGE mediated reality environment with direction errors recorded before, during and after adaptation. During PA, visual feedback of the reach could be compressed, perturbed by noise, or represented veridically. Compressed visual space significantly reduced SC and aftereffects compared to control and noise conditions. These results support recent observations in neglect patients, suggesting that a distortion of spatial representation may successfully model neglect and explain neglect performance while adapting to prisms. PMID:23675332

  13. PRISM Triplet and Stereopairs to Build Digital Surface Models

    NASA Astrophysics Data System (ADS)

    Baiocchi, Valerio; Milone, Maria Vittoria; Mormile, Martina

    2012-04-01

    In the present paper the phases of extraction of a DSM from Prism stereopairs and triplets are illustrated. PRISM was a panchromatic radiometer carried onboard the Japanese remote sensing satellite ALOS (Advanced Land Observing Satellite); this work has mainly a methodological value cause on May 12, 2011, a command was sent to stop the onboard transmitter and now the sensor is no more operative. The sensor had three optical systems for forward, nadir and backward views with 2.5 meter nominal spatial resolution. Multiple Linear Array CCD chips were located on the focal plane of each camera, along one across-track line. Images here studied represent a coastal area that spans from the city of Pescara to the city of Ortona (both in Abruzzo region, Italy). The availability of PRISM stereopairs and triplets is not widely studied and in this paper accuracy of produced DEMs is compared with heights from terrestrial Lidar survey on the area of the city of Pescara (Abruzzo region, Italy). Extraction was executed with Geomatica 2012 using rigorous model, with GCPs.

  14. Large-deviation achromatic Risley prisms pointing systems

    NASA Astrophysics Data System (ADS)

    Lacoursiere, Jean; Doucet, Michel; Curatu, Eugene O.; Savard, Maxime; Verreault, Sonia; Thibault, Simon; Chevrette, Paul C.; Ricard, Benoit

    2002-06-01

    As part of the Infrared Eye project, this article describes the design of large-deviation, achromatic Risley prisms scanning systems operating in the 0.5 - 0.92 and 8 - 9.5 μm spectral regions. Designing these systems is challenging due to the large deviation required (zero - 25 degrees), the large spectral bandwidth and the mechanical constraints imposed by the need to rotate the prisms to any position in 1/30 second. A design approach making extensive use of the versatility of optical design softwares is described. Designs consisting of different pairs of optical materials are shown in order to illustrate the trade-off between chromatic aberration, mass and vignetting. Control of chromatic aberration and reasonable prism shape is obtained over 8 - 9.5 μm with zinc sulfide and germanium. The design is more difficult for the 0.5 - 0.92 μm band. Trade-offs consist in using sapphire with Cleartran« over a reduced bandwidth (0.75 - 0.9 μm ) or acrylic singlets with the Infrared Eye in active mode (0.85 - 0.86 μm). Non-sequential ray-tracing is used to study the effects of fresnelizing one element of the achromat to reduce its mass, and to evaluate detector narcissus in the 8 - 9.5 μm region.

  15. Sedimentary Record of Paleodeformation of the Saint Martin Anticline Reveals the Interaction Between Tectonics, Sedimentation Processes and Relative Sea-level Changes: Ganges-Brahmaputra Delta Burma Arc Collision, SE Bangladesh

    NASA Astrophysics Data System (ADS)

    Bastas-Hernandez, A.; McHugh, C. M.; Mondal, D. R.; Seeber, L.; Steckler, M. S.; Gurung, D.; Mustaque, S.; Marsh, J.; Akhter, S. H.

    2014-12-01

    Along the Ganges-Brahmaputra Delta Burma Arc collision zone, the Indian plate is converging obliquely with the Burma arc with a shortening GPS rate of 14 mm/yr. In this region tectonics, huge sediment supply from the erosion of the Himalayas (>1 GT/yr) and relative sea level changes interact. The extremely thick sediments of the Ganges-Brahmaputra Delta and Fan (~20 km) are being gradually accreted into a very wide thrust-fold belt along this subduction/collision zone. This interaction has led to the formation of a fold-and-thrust belt and wide accretionary prism that is exposed on land and on the shelf of the Burma forearc. Sedimentary sequence and structure document the seismo-tectonic and sedimentary evolution of St Martin's Island, which is an expression of an anticline in the outer part of the accretion forearc. During late Pleistocene sea-level low stands, the anticline and most of the rest of the shelf were exposed. The anticline ridge could then grow, receiving little erosion by local drainages. At some point during sea level rise, the coast advanced over the ridge and bevelled it. Then sea-level continued to rise and new sediment deposited forming an angular unconformity. A low-relief unconformity, in fact, separates the folded strata below from overlying strata of Holocene age. Where now exposed on the island above sea level, the unconformity is ~8000 y old. At that time, sea level was 30 m below the current level and thus rapid tectonic uplift is necessary to account for its current elevation. Dead coral heads of the species Porities that populate the coast were dated with U-Th (Mondal et al., 2013). They document a megathurst rupture and ~ 2m uplift that occurred during the Great Arakan earthquake in 1762 and further earthquakes are likely at ~ 1100 and 800 AD. Studies of the 1762 rupture suggest that the anticline rises during megathrust earthquakes (~2m) and subsides in the interseismic period (a few mm/yr; Steckler and Mondal 2014). Radiocarbon ages

  16. Stabilization of a self-referenced, prism-based, Cr:forsterite laser frequency comb using an intracavity prism

    SciTech Connect

    Tillman, Karl A.; Thapa, Rajesh; Knabe, Kevin; Wu Shun; Lim, Jinkang; Washburn, Brian R.; Corwin, Kristan L.

    2009-12-20

    The frequency comb from a prism-based Cr:forsterite laser has been frequency stabilized using intracavity prism insertion and pump power modulation. Absolute frequency measurements of a CW fiber laser stabilized to the P(13) transition of acetylene demonstrate a fractional instability of {approx}2x10{sup -11} at a 1 s gate time, limited by a commercial Global Positioning System (GPS)-disciplined rubidium oscillator. Additionally, absolute frequency measurements made simultaneously using a second frequency comb indicate relative instabilities of 3x10{sup -12} for both combs for a 1 s gate time. Estimations of the carrier-envelope offset frequency linewidth based on relative intensity noise and the response dynamics of the carrier-envelope offset to pump power changes confirm the observed linewidths.

  17. Slipstream: an early Holocene slump and turbidite record from the frontal ridge of the Cascadia accretionary wedge off western Canada and paleoseismic implications

    USGS Publications Warehouse

    Hamilton, T. S.; Enkin, Randolph J.; Riedel, Michael; Rogers, Gary C.; Pohlman, John W.; Benway, Heather M.

    2015-01-01

    Slipstream Slump, a well-preserved 3 km wide sedimentary failure from the frontal ridge of the Cascadia accretionary wedge 85 km off Vancouver Island, Canada, was sampled during Canadian Coast Guard Ship (CCGS) John P. Tully cruise 2008007PGC along a transect of five piston cores. Shipboard sediment analysis and physical property logging revealed 12 turbidites interbedded with thick hemipelagic sediments overlying the slumped glacial diamict. Despite the different sedimentary setting, atop the abyssal plain fan, this record is similar in number and age to the sequence of turbidites sampled farther to the south from channel systems along the Cascadia Subduction Zone, with no extra turbidites present in this local record. Given the regional physiographic and tectonic setting, megathrust earthquake shaking is the most likely trigger for both the initial slumping and subsequent turbidity currents, with sediments sourced exclusively from the exposed slump face of the frontal ridge. Planktonic foraminifera picked from the resedimented diamict of the underlying main slump have a disordered cluster of 14C ages between 12.8 and 14.5 ka BP. For the post-slump stratigraphy, an event-free depth scale is defined by removing the turbidite sediment intervals and using the hemipelagic sediments. Nine14C dates from the most foraminifera-rich intervals define a nearly constant hemipelagic sedimentation rate of 0.021 cm/year. The combined age model is defined using only planktonic foraminiferal dates and Bayesian analysis with a Poisson-process sedimentation model. The age model of ongoing hemipelagic sedimentation is strengthened by physical property correlations from Slipstream events to the turbidites for the Barkley Canyon site 40 km south. Additional modelling addressed the possibilities of seabed erosion or loss and basal erosion beneath turbidites. Neither of these approaches achieves a modern seabed age when applying the commonly used regional marine 14C reservoir age of

  18. Ganges-Brahmaputra Delta: Balance of Subsidence, Sea level and Sedimentation in a Tectonically-Active Delta (Invited)

    NASA Astrophysics Data System (ADS)

    Steckler, M. S.; Goodbred, S. L.; Akhter, S. H.; Seeber, L.; Reitz, M. D.; Paola, C.; Nooner, S. L.; DeWolf, S.; Ferguson, E. K.; Gale, J.; Hossain, S.; Howe, M.; Kim, W.; McHugh, C. M.; Mondal, D. R.; Petter, A. L.; Pickering, J.; Sincavage, R.; Williams, L. A.; Wilson, C.; Zumberge, M. A.

    2013-12-01

    Bangladesh is vulnerable to a host of short and long-term natural hazards - widespread seasonal flooding, river erosion and channel avulsions, permanent land loss from sea level rise, natural groundwater arsenic, recurrent cyclones, landslides and huge earthquakes. These hazards derive from active fluvial processes related to the growth of the delta and the tectonics at the India-Burma-Tibet plate junctions. The Ganges and Brahmaputra rivers drain 3/4 of the Himalayas and carry ~1 GT/y of sediment, 6-8% of the total world flux. In Bangladesh, these two great rivers combine with the Meghna River to form the Ganges-Brahmaputra-Meghna Delta (GBMD). The seasonality of the rivers' water and sediment discharge is a major influence causing widespread flooding during the summer monsoon. The mass of the water is so great that it causes 5-6 cm of seasonal elastic deformation of the delta discerned by our GPS data. Over the longer-term, the rivers are also dynamic. Two centuries ago, the Brahmaputra River avulsed westward up to 100 km and has since captured other rivers. The primary mouth of the Ganges has shifted 100s of km eastward from the Hooghly River over the last 400y, finally joining the Brahmaputra in the 19th century. These avulsions are influenced by the tectonics of the delta. On the east side of Bangladesh, the >16 km thick GBMD is being overridden by the Burma Arc where the attempted subduction of such a thick sediment pile has created a huge accretionary prism. The foldbelt is up to 250-km wide and its front is buried beneath the delta. The main Himalayan thrust front is <100 km north, but adjacent to the GBMD is the Shillong Massif, a 300-km long, 2-km high block of uplifted Indian basement that is overthrusting and depressing GBMD sediments to the south. The overthrusting Shillong Massif may represent a forward jump of the Himalayan front to a new plate boundary. This area ruptured in a ~M8 1897 earthquake. Subsidence from the tectonics and differential

  19. Precambrian accretionary history and phanerozoic structures-A unified explanation for the tectonic architecture of the nebraska region, USA

    USGS Publications Warehouse

    Carlson, M.P.

    2007-01-01

    The Phanerozoic history in Nebraska and adjacent regions contains many patterns of structure and stratigraphy that can be directly related to the history of the Precambrian basement rocks of the area. A process is proposed that explains the southward growth of North America during the period 1.8-1.6 Ga. A series of families of accretionary events during the Proterozoic emplaced sutures that remained as fundamental basement weak zones. These zones were rejuvenated in response to a variety of continental stress events that occurred during the Phanerozoic. By combining the knowledge of basement history with the history of rejuvenation during the Phanerozoic, both the details of Proterozoic accretionary growth and an explanation for the patterns of Phanerozoic structure and stratigraphy is provided. ?? 2007 The Geological Society of America. All rights reserved.

  20. Asymmetric transmission in prisms using structures and materials with isotropic-type dispersion.

    PubMed

    Gundogdu, Funda Tamara; Serebryannikov, Andriy E; Cakmak, A Ozgur; Ozbay, Ekmel

    2015-09-21

    It is demonstrated that strong asymmetry in transmission can be obtained at the Gaussian beam illumination for a single prism based on a photonic crystal (PhC) with isotropic-type dispersion, as well as for its analog made of a homogeneous material. Asymmetric transmission can be realized with the aid of refraction at a proper orientation of the interfaces and wedges of the prism, whereas neither contribution of higher diffraction orders nor anisotropic-type dispersion is required. Furthermore, incidence toward a prism wedge can be used for one of two opposite directions in order to obtain asymmetry. Thus, asymmetric transmission is a general property of the prism configurations, which can be obtained by using simple geometries and quite conventional materials. The obtained results show that strong asymmetry can be achieved in PhC prisms with (nearly) circular shape of equifrequency dispersion contours, in both cases associated with the index of refraction 01. For the comparison purposes, results are also presented for solid uniform non-magnetic prisms made of a material with the same value of n. It is shown in zero-loss approximation that the PhC prism and the ultralow-index material prism (0prism and the solid dielectric prism can show the same scenario at n>1. Possible contributions of scattering on the individual rods and diffraction on the wedge to the resulting mechanism are discussed. Analogs of unidirectional splitting and unidirectional deflection regimes, which are known from the studies of PhC gratings, are obtained in PhC prisms and solid uniform prisms, i.e. without higher diffraction orders.

  1. Metamorphism within the Chugach accretionary complex on southern Baranof Island, southeastern Alaska

    USGS Publications Warehouse

    Zumsteg, Cathy L.; Himmelberg, Glen R.; Karl, Susan M.; Haeussler, Peter J.

    2003-01-01

    On Baranof Island, southeastern Alaska, we identify four metamorphic events that affect rocks associated with the Chugach accretionary complex. This study focuses on the M1 and M4 metamorphic events. Mesozoic schists, gneisses, and migmatitic gneisses exposed near the Kasnyku pluton on central Baranof Island represent the M1 metamorphic rocks. These rocks underwent amphibolite facies metamorphism. Calculated temperatures and pressures range from about 620 to 780 ºC and 5.5 to 6.6 kbar and are compatible with the observed metamorphic mineral assemblages.The M4 metamorphism affected rocks of the Sitka Graywacke on southern Baranof Island, producing extensive biotite and garnet zones as well as andalusite and sillimanite zones at the contacts of the Crawfish Inlet and Redfish Bay plutons. Calculated M4 temperatures and pressures from the andalusite and sillimanite zones range from 575 to 755 ºC and 3.4 to 6.9 kbar. These results fall within the sillimanite stability field, at pressures higher than andalusite stability. These results may indicate the M4 metamorphic event occurred along a P-T path along which the equilibration of aluminosilicate-garnet-plagioclase-quartz did not occur or was not maintained. This interpretation is supported by the occurrence of andalusite and sillimanite within the same sample. We propose the data reflect a clockwise P-T path with peak M4 metamorphism of the sillimanite-bearing samples adjacent to the intrusions at an approximate depth of 15 to 20 km, followed by rapid uplift without reequilibration of garnet-plagioclase-aluminosilicate-quartz.The large extent of the biotite zone, and possibly the garnet zone, suggests that an additional heat source must have existed to regionally metamorphose these rocks during the M4 event. We suggest the M4 regional thermal metamorphism and intrusion of the Crawfish Inlet and Redfish Bay plutons were synchronous and the result of heat flux from a slab window beneath the accretionary complex at that

  2. Linking collisional and accretionary orogens during Rodinia assembly and breakup: Implications for models of supercontinent cycles

    NASA Astrophysics Data System (ADS)

    Cawood, Peter A.; Strachan, Robin A.; Pisarevsky, Sergei A.; Gladkochub, Dmitry P.; Murphy, J. Brendan

    2016-09-01

    Periodic assembly and dispersal of continental fragments has been a characteristic of the solid Earth for much of its history. Geodynamic drivers of this cyclic activity are inferred to be either top-down processes related to near surface lithospheric stresses at plate boundaries or bottom-up processes related to mantle convection and, in particular, mantle plumes, or some combination of the two. Analysis of the geological history of Rodinian crustal blocks suggests that internal rifting and breakup of the supercontinent were linked to the initiation of subduction and development of accretionary orogens around its periphery. Thus, breakup was a top-down instigated process. The locus of convergence was initially around north-eastern and northern Laurentia in the early Neoproterozoic before extending to outboard of Amazonia and Africa, including Avalonia-Cadomia, and arcs outboard of Siberia and eastern to northern Baltica in the mid-Neoproterozoic (∼760 Ma). The duration of subduction around the periphery of Rodinia coincides with the interval of lithospheric extension within the supercontinent, including the opening of the proto-Pacific at ca. 760 Ma and the commencement of rifting in east Laurentia. Final development of passive margin successions around Laurentia, Baltica and Siberia was not completed until the late Neoproterozoic to early Paleozoic (ca. 570-530 Ma), which corresponds with the termination of convergent plate interactions that gave rise to Gondwana and the consequent relocation of subduction zones to the periphery of this supercontinent. The temporal link between external subduction and internal extension suggests that breakup was initiated by a top-down process driven by accretionary tectonics along the periphery of the supercontinent. Plume-related magmatism may be present at specific times and in specific places during breakup but is not the prime driving force. Comparison of the Rodinia record of continental assembly and dispersal with that

  3. Studying the neural bases of prism adaptation using fMRI: A technical and design challenge.

    PubMed

    Bultitude, Janet H; Farnè, Alessandro; Salemme, Romeo; Ibarrola, Danielle; Urquizar, Christian; O'Shea, Jacinta; Luauté, Jacques

    2016-12-30

    Prism adaptation induces rapid recalibration of visuomotor coordination. The neural mechanisms of prism adaptation have come under scrutiny since the observations that the technique can alleviate hemispatial neglect following stroke, and can alter spatial cognition in healthy controls. Relative to non-imaging behavioral studies, fMRI investigations of prism adaptation face several challenges arising from the confined physical environment of the scanner and the supine position of the participants. Any researcher who wishes to administer prism adaptation in an fMRI environment must adjust their procedures enough to enable the experiment to be performed, but not so much that the behavioral task departs too much from true prism adaptation. Furthermore, the specific temporal dynamics of behavioral components of prism adaptation present additional challenges for measuring their neural correlates. We developed a system for measuring the key features of prism adaptation behavior within an fMRI environment. To validate our configuration, we present behavioral (pointing) and head movement data from 11 right-hemisphere lesioned patients and 17 older controls who underwent sham and real prism adaptation in an MRI scanner. Most participants could adapt to prismatic displacement with minimal head movements, and the procedure was well tolerated. We propose recommendations for fMRI studies of prism adaptation based on the design-specific constraints and our results.

  4. Randomized crossover clinical trial of real and sham peripheral prism glasses for hemianopia

    PubMed Central

    Bowers, Alex R.; Keeney, Karen; Peli, Eli

    2013-01-01

    Objective To evaluate the efficacy of real relative to sham peripheral prism glasses for patients with complete homonymous hemianopia and without visual neglect. Methods Patients recruited at 13 clinics were allocated by minimization into a double-masked, crossover trial with two groups. One group received real (57Δ) oblique and sham (≤ 5Δ) horizontal prisms; the other received real horizontal and sham oblique, in counterbalanced order. A masked data collector at each clinic administered questionnaires after each 4-week crossover period. Main outcome measure The primary outcome was the overall difference, across the two periods of the crossover, between the proportion of participants who wanted to continue with (said “yes” to) real prisms and the proportion who said yes to sham prisms. The secondary outcome was the difference in perceived mobility improvement between real and sham prisms. Results Of 73 patients randomized, 61 completed the crossover. A significantly higher proportion said yes to real than sham prisms (64% vs. 36%; odds ratio 5.3, 95% CI 1.8 to 21.0). Participants who continued wear after 6 months reported greater improvement in mobility with real than sham prisms at crossover end (p=0.002); participants who discontinued wear reported no difference. Conclusion Real peripheral prism glasses were more helpful for obstacle avoidance when walking than sham glasses, with no differences between the horizontal and oblique designs. Applications to clinical practice Peripheral prism glasses provide a simple and inexpensive mobility rehabilitation intervention for hemianopia. PMID:24201760

  5. Community-Based Trial of Peripheral Prism Visual Field Expansion Device for Hemianopia

    PubMed Central

    Bowers, Alex R.; Keeney, Karen; Peli, Eli

    2007-01-01

    Background Peripheral prism glasses, a novel visual field expansion device for hemianopia, showed promise in early, small-sample evaluations. Objective To determine functionality of the glasses for general mobility in a larger-scale, community-based, multi-center study with longer-term follow up. Methods Forty-three participants with homonymous hemianopia were fitted with temporary press-on™ Fresnel (40 prism diopter) peripheral prism segments. Follow up questionnaires, evaluating functional benefits for mobility, were administered in-office at week 6. Participants who continued wearing the prisms were interviewed again by telephone after 12 months (median). Primary outcome measures included: clinical success (a clinical decision to continue wear) and 5-point ratings of prism-helpfulness for obstacle avoidance when walking. Results Thirty-two participants (74%) continued prism-wear at week 6, and 20 (47%) were still wearing prisms after 12 months (8 hours per day ) rating the prism glasses as “very helpful” for obstacle avoidance and reporting significant benefits for obstacle avoidance in a variety of mobility situations. Success rates varied among clinic groups (27% to 81%), with higher rates at the clinics that fitted more patients. Conclusions Our results demonstrate the functional utility of peripheral prism glasses as a general mobility aid for hemianopic patients. PMID:18474776

  6. Separation of multiple images via directional guidance using structured prism and pyramid arrays.

    PubMed

    Lee, Hyemin; Seo, Hyein; Kang, Sunghwan; Yoon, Hyunsik

    2016-09-05

    We propose a new concept of separating images through a directional guide of multi-visuals by using structured prism or pyramid arrays. By placing prism arrays onto two different image arrays, the two collective images below the facets are guided to different directions. Using optical calculations, we identify a condition for successful image separation. Transparent pyramid arrays are used to separate four images into four directions. The direction of refracted rays can be controlled by the refractive index of prisms and liquid filled into the voids. In addition, the images can be switched by stretching and releasing an elastomeric prism array.

  7. Overland Tidal Power Generation Using Modular Tidal Prism

    SciTech Connect

    Khangaonkar, Tarang; Yang, Zhaoqing; Geerlofs, Simon H.; Copping, Andrea

    2010-03-01

    Naturally occurring sites with sufficient kinetic energy suitable for tidal power generation with sustained currents > 1 to 2 m/s are relatively rare. Yet sites with greater than 3 to 4 m of tidal range are relatively common around the U.S. coastline. Tidal potential does exist along the shoreline but is mostly distributed, and requires an approach which allows trapping and collection to also be conducted in a distributed manner. In this paper we examine the feasibility of generating sustainable tidal power using multiple nearshore tidal energy collection units and present the Modular Tidal Prism (MTP) basin concept. The proposed approach utilizes available tidal potential by conversion into tidal kinetic energy through cyclic expansion and drainage from shallow modular manufactured overland tidal prisms. A preliminary design and configuration of the modular tidal prism basin including inlet channel configuration and basin dimensions was developed. The unique design was shown to sustain momentum in the penstocks during flooding as well as ebbing tidal cycles. The unstructured-grid finite volume coastal ocean model (FVCOM) was used to subject the proposed design to a number of sensitivity tests and to optimize the size, shape and configuration of MTP basin for peak power generation capacity. The results show that an artificial modular basin with a reasonable footprint (≈ 300 acres) has the potential to generate 10 to 20 kw average energy through the operation of a small turbine located near the basin outlet. The potential of generating a total of 500 kw to 1 MW of power through a 20 to 40 MTP basin tidal power farms distributed along the coastline of Puget Sound, Washington, is explored.

  8. Analytic PRISM theory of structurally asymmetric polymer blends and copolymers

    SciTech Connect

    Schweizer, K.S. )

    1993-10-25

    Analytic PRISM theory with the new molecular closures is applied to determine the effective chi-parameters and spinodal instability curves for structurally asymmetric polymer alloys. Compressibility effects are found to be very important, and the use of a literal incompressible RPA-like approximation is shown to incur qualitative errors in most cases. A rich and nonadditive dependence of phase transition temperatures and apparent SANS chi-parameters on backbone stiffness asymmetry, attractive interaction potential asymmetry, and thermodynamic variables is found for binary homopolymer blends. A novel strategy for designing miscible mixtures based on a cancellation, or compensation, of the relevant asymmetries is identified. The influence of chain stiffness asymmetry in blends characterized by specific interactions is also studied. Generalization of the analytic PRISM theory to mixtures of random copolymers and periodic block copolymer melts is presented. All the rich behavior predicted for phase-separating homopolymer mixtures is again found for these systems, plus additional non mean field effects associated with random copolymer composition and block architecture. The theory is applied semiquantitatively to interpret recent experiments on polyolefin blends, diblock copolymers, and random copolymer alloys. Theoretical predictions are made which qualitatively account for recent experimental observations of a strong influence of stiffness asymmetry on phase separation temperatures, and the breakdown of the mean field random copolymer approach. Anomalous behavior is also predicted for deuterated mixtures due to an interference between the consequences of stiffness asymmetry and enthalipic interactions. The physical mechanism for the many non-Flory-Huggins effects predicted by the compressible PRISM theory is local, scalar density correlations, which appears to be different than the nematic fluctuation mechanism suggested by recent field theoretic work.

  9. EUCLID: design of the prism DMD NIR spectrograph

    NASA Astrophysics Data System (ADS)

    Content, Robert; Sharples, Ray M.; Blake, Simon; Talbot, R. Gordon

    2010-07-01

    EUCLID, the ESA Dark Energy Mission, contains a NIR and a visible imagers (NIP & VIS), and an NIR spectrograph (NIS). Different designs of the NIS have been studied especially a slitless design, a Digital Micromirror Device (DMD) design using grisms and another using prisms, and more recently a combination of the NIP and NIS into one instrument. We present the design of the prism DMD NIS. This design has the advantage over the slitless design of having a DMD mask which reduces the background by a factor of more than 100 and all the advantages over the grism DMD NIS that a prism gives over a grism as a higher and more uniform transmission, the absence of parasite orders, and a choice of the slope of the spectral resolution with wavelength. The field per spectrograph was made sufficiently large to reduce the number of spectrographs to two. The design was made so that the mapping of the sky of the NIS is easily compatible with the mapping strategy of the NIP and VIS. Two designs were made. In one, the field is larger but the surface shapes of the optics are complex which makes manufacturing more challenging. In the other, the design was made to be fully compatible with the manufacturing criteria of SESO after extensive discussions to carefully understand the manufacturing limitations especially the formula for highly aspheric surface shapes as biconics. This was done by directly integrating the criteria into the optimization process of ZEMAX. A calibration system that uses the DMD with the micromirrors in their OFF positions was also developed.

  10. Sealed One Piece Battery Having A Prism Shape Container

    DOEpatents

    Verhoog, Roelof; Barbotin, Jean-Loup

    2000-03-28

    A sealed one-piece battery having a prism-shaped container including: a tank consisting of a single plastic material, a member fixed and sealed to the tank and to partitions on the side of the tank opposite the transverse wall to seal the tank, two flanges fixed and sealed to longitudinal walls defining flow compartments for a heat-conducting fluid, and two tubes on the transverse wall of the tank forming an inlet and an outlet for fluid common to the compartments.

  11. Fano resonances in prism-coupled multimode square micropillar resonators

    NASA Astrophysics Data System (ADS)

    Lee, Ho-Tong; Zhou, Linjie; Poon, Andrew W.

    2005-06-01

    We report Fano resonances in a multimode square glass micropillar resonator; the resonances were obtained by using angle-resolved prism coupling. Our experiments reveal characteristically asymmetric line shapes of high-Q resonances and of detuned low-Q resonances in multimode reflection spectra. The asymmetric resonance line shapes evolve for an approximately pi phase within a 0.5° range of reflection angles. We model our observed asymmetric multimode resonances by the far-field interference between a light wave that is evanescently coupled with a high-Q mode orbit and a coherent light wave that is refractively coupled with a detuned low-Q mode orbit.

  12. Description of the PRISM system architecture and user interface

    NASA Astrophysics Data System (ADS)

    Constanza, P.; Larsson, C.; Thiemann, H.; Wedi, N.

    2003-04-01

    The PRISM system architecture enables the user to perform numerical experiments, allowing to couple interchangeable model components, e.g. atmosphere, ocean, biosphere, chemistry, via standardised interfaces. The coupler is based on standard interfaces implemented in the different model components. The exchange of data between the components will occur either in a direct way between components or through the coupler. The general architecture provides the infrastructure to configure, submit, monitor and subsequently post process, archive and diagnose the results of these coupled model experiments. There is an emphasis on choosing an architectural design that allows these activities to be done remotely, e.g. without the user physically being in the same place where the numerical computations take place. The PRISM general architecture gives the choice to the user either to work locally or to work through a central PRISM site where the user will be registered. Locally or via the Internet, the user will be able to use the same graphical user interface. The choice will depend of the local availability of the required resources. In addition a supervisor monitor program (SMS) gives full control over model simulations during run-time. The technology that realises the proposed architecture is known as "Web services". This includes the use of web servers, application servers, resource directories, discovery mechanisms and messages services. Currently there is no client software that can be used with browsers that does not build on Java technology. Java supports all the mechanisms needed for implementing web services using available standards. From a system maintenance point of view using one technology, Java, is the preferred way as this simplifies the task of adhering to multiple standards. The issue of standardisation of interfaces is important for complex and configurable systems such as PRISM. For example the extensible Markup Language (XML) allows for standardisation of

  13. Polarization manipulation in single refractive prism based holography lithography

    NASA Astrophysics Data System (ADS)

    Xiong, Wenjie; Xu, Yi; Xiao, Yujian; Lv, Xiaoxu; Wu, Lijun

    2015-01-01

    We propose theoretically and demonstrate experimentally a simple but effective strategy for polarization manipulation in single refractive prism based holographic lithography. By tuning the polarization of a single laser beam, we can obtain the pill shape interference pattern with a high-contrast where a complex optical setup and multiple polarizers are needed in the conventional holography lithography. Fabrication of pill shape two-dimensional polymer photonic crystals using one beam and one shoot holography lithography is shown as an example to support our theoretical results. This integrated polarization manipulation technique can release the crucial stability restrictions imposed on the multiple beams holography lithography.

  14. The PRISM palaeoclimate reconstruction and Pliocene sea-surface temperature

    USGS Publications Warehouse

    Dowsett, H.J.; ,

    2007-01-01

    In this paper, I present a summary of the Pliocene Research, Interpretation and Synoptic Mapping (PRISM) palaeoenvironmental reconstruction, with emphasis on its historical development and range of boundary condition datasets. Sea-surface temperature (SST), sea level, sea ice, land cover (vegetation and ice) and topography are discussed as well as many of the assumptions required to create an integrated global-scale reconstruction. New multiproxy research shows good general agreement on the magnitude of mid-Pliocene SST warming. Future directions, including maximum and minimum SST analyses and deep ocean temperature estimates aimed at a full three-dimensional reconstruction, are presented. ?? The Micropalaeontological Society 2007.

  15. Rock varnish in New York: An accelerated snapshot of accretionary processes

    NASA Astrophysics Data System (ADS)

    Krinsley, David H.; Dorn, Ronald I.; DiGregorio, Barry E.; Langworthy, Kurt A.; Ditto, Jeffrey

    2012-02-01

    Samples of manganiferous rock varnish collected from fluvial, bedrock outcrop and Erie Barge Canal settings in New York state host a variety of diatom, fungal and bacterial microbial forms that are enhanced in manganese and iron. Use of a Dual-Beam Focused Ion Beam Scanning Electron Microscope to manipulate the varnish in situ reveals microbial forms that would not have otherwise been identified. The relative abundance of Mn-Fe-enriched biotic forms in New York samples is far greater than varnishes collected from warm deserts. Moisture availability has long been noted as a possible control on varnish growth rates, a hypothesis consistent with the greater abundance of Mn-enhancing bioforms. Sub-micron images of incipient varnish formation reveal that varnishing in New York probably starts with the mortality of microorganisms that enhanced Mn on bare mineral surfaces; microbial death results in the adsorption of the Mn-rich sheath onto the rock in the form of filamentous networks. Clay minerals are then cemented by remobilization of the Mn-rich material. Thus, the previously unanswered question of what comes first - clay mineral deposition or enhancement of Mn - can be answered in New York because of the faster rate of varnish growth. In contrast, very slow rates of varnishing seen in warm deserts, of microns per thousand years, make it less likely that collected samples will reveal varnish accretionary processes than samples collected from fast-accreting moist settings.

  16. Coastal sedimentation

    NASA Technical Reports Server (NTRS)

    Schubel, J. R.

    1980-01-01

    Several important coastal sedimentation problems are identified. Application of existing or anticipated remote sensing techniques to examine these problems is considered. Specifically, coastal fine particle sediment systems, floods and hy hurricanes and sedimentation f of coastal systems, routes and rates of sediment transport on continental shelves, and dredging and dredged material disposal are discussed.

  17. A Pilot Study of Perceptual-Motor Training for Peripheral Prisms

    PubMed Central

    Houston, Kevin E.; Bowers, Alex R.; Fu, Xianping; Liu, Rui; Goldstein, Robert B.; Churchill, Jeff; Wiegand, Jean-Paul; Soo, Tim; Tang, Qu; Peli, Eli

    2016-01-01

    Purpose Peripheral prisms (p-prisms) shift peripheral portions of the visual field of one eye, providing visual field expansion for patients with hemianopia. However, patients rarely show adaption to the shift, incorrectly localizing objects viewed within the p-prisms. A pilot evaluation of a novel computerized perceptual-motor training program aiming to promote p-prism adaption was conducted. Methods Thirteen patients with hemianopia fitted with 57Δ oblique p-prisms completed the training protocol. They attended six 1-hour visits reaching and touching peripheral checkerboard stimuli presented over videos of driving scenes while fixating a central target. Performance was measured at each visit and after 3 months. Results There was a significant reduction in touch error (P = 0.01) for p-prism zone stimuli from pretraining median of 16.6° (IQR 12.1°–19.6°) to 2.7° ( IQR 1.0°–8.5°) at the end of training. P-prism zone reaction times did not change significantly with training (P > 0.05). P-prism zone detection improved significantly (P = 0.01) from a pretraining median 70% (IQR 50%–88%) to 95% at the end of training (IQR 73%–98%). Three months after training improvements had regressed but performance was still better than pretraining. Conclusions Improved pointing accuracy for stimuli detected in prism-expanded vision of patients with hemianopia wearing 57Δ oblique p-prisms is possible and training appears to further improve detection. Translational Relevance This is the first use of this novel software to train adaptation of visual direction in patients with hemianopia wearing peripheral prisms. PMID:26933522

  18. Kinematic markers dissociate error correction from sensorimotor realignment during prism adaptation.

    PubMed

    O'Shea, Jacinta; Gaveau, Valérie; Kandel, Matthieu; Koga, Kazuo; Susami, Kenji; Prablanc, Claude; Rossetti, Yves

    2014-03-01

    This study investigated the motor control mechanisms that enable healthy individuals to adapt their pointing movements during prism exposure to a rightward optical shift. In the prism adaptation literature, two processes are typically distinguished. Strategic motor adjustments are thought to drive the pattern of rapid endpoint error correction typically observed during the early stage of prism exposure. This is distinguished from so-called 'true sensorimotor realignment', normally measured with a different pointing task, at the end of prism exposure, which reveals a compensatory leftward 'prism after-effect'. Here, we tested whether each mode of motor compensation - strategic adjustments versus 'true sensorimotor realignment' - could be distinguished, by analyzing patterns of kinematic change during prism exposure. We hypothesized that fast feedforward versus slower feedback error corrective processes would map onto two distinct phases of the reach trajectory. Specifically, we predicted that feedforward adjustments would drive rapid compensation of the initial (acceleration) phase of the reach, resulting in the rapid reduction of endpoint errors typically observed early during prism exposure. By contrast, we expected visual-proprioceptive realignment to unfold more slowly and to reflect feedback influences during the terminal (deceleration) phase of the reach. The results confirmed these hypotheses. Rapid error reduction during the early stage of prism exposure was achieved by trial-by-trial adjustments of the motor plan, which were proportional to the endpoint error feedback from the previous trial. By contrast, compensation of the terminal reach phase unfolded slowly across the duration of prism exposure. Even after 100 trials of pointing through prisms, adaptation was incomplete, with participants continuing to exhibit a small rightward shift in both the reach endpoints and in the terminal phase of reach trajectories. Individual differences in the degree of

  19. Generation of High Resolution Global DSM from ALOS PRISM

    NASA Astrophysics Data System (ADS)

    Takaku, J.; Tadono, T.; Tsutsui, K.

    2014-04-01

    Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM), one of onboard sensors carried on the Advanced Land Observing Satellite (ALOS), was designed to generate worldwide topographic data with its optical stereoscopic observation. The sensor consists of three independent panchromatic radiometers for viewing forward, nadir, and backward in 2.5 m ground resolution producing a triplet stereoscopic image along its track. The sensor had observed huge amount of stereo images all over the world during the mission life of the satellite from 2006 through 2011. We have semi-automatically processed Digital Surface Model (DSM) data with the image archives in some limited areas. The height accuracy of the dataset was estimated at less than 5 m (rms) from the evaluation with ground control points (GCPs) or reference DSMs derived from the Light Detection and Ranging (LiDAR). Then, we decided to process the global DSM datasets from all available archives of PRISM stereo images by the end of March 2016. This paper briefly reports on the latest processing algorithms for the global DSM datasets as well as their preliminary results on some test sites. The accuracies and error characteristics of datasets are analyzed and discussed on various fields by the comparison with existing global datasets such as Ice, Cloud, and land Elevation Satellite (ICESat) data and Shuttle Radar Topography Mission (SRTM) data, as well as the GCPs and the reference airborne LiDAR/DSM.

  20. The PRISM (Pliocene Palaeoclimate) reconstruction: Time for a paradigm shift

    USGS Publications Warehouse

    Dowsett, Harry J.; Robinson, Marci M.; Stoll, Danielle K.; Foley, Kevin M.; Johnson, Andrew L. A.; Williams, Mark; Riesselman, Christina

    2013-01-01

    Global palaeoclimate reconstructions have been invaluable to our understanding of the causes and effects of climate change, but single-temperature representations of the oceanic mixed layer for data–model comparisons are outdated, and the time for a paradigm shift in marine palaeoclimate reconstruction is overdue. The new paradigm in marine palaeoclimate reconstruction stems the loss of valuable climate information and instead presents a holistic and nuanced interpretation of multi-dimensional oceanographic processes and responses. A wealth of environmental information is hidden within the US Geological Survey's Pliocene Research,Interpretation and Synoptic Mapping (PRISM) marine palaeoclimate reconstruction, and we introduce here a plan to incorporate all valuable climate data into the next generation of PRISM products. Beyond the global approach and focus, we plan to incorporate regional climate dynamics with emphasis on processes, integrating multiple environmental proxies wherever available in order to better characterize the mixed layer, and developing a finer time slice within the Mid-Piacenzian Age of the Pliocene, complemented by underused proxies that offer snapshots into environmental conditions. The result will be a proxy-rich, temporally nested, process-oriented approach in a digital format - a relational database with geographic information system capabilities comprising a three-dimensional grid representing the surface layer, with a plethora of data in each cell.

  1. Composite Yb:YAG/SiC-prism thin disk laser.

    PubMed

    Newburgh, G A; Michael, A; Dubinskii, M

    2010-08-02

    We report the first demonstration of a Yb:YAG thin disk laser wherein the gain medium is intracavity face-cooled through bonding to an optical quality SiC prism. Due to the particular design of the composite bonded Yb:YAG/SiC-prism gain element, the laser beam impinges on all refractive index interfaces inside the laser cavity at Brewster's angles. The laser beam undergoes total internal reflection (TIR) at the bottom of the Yb(10%):YAG thin disk layer in a V-bounce cavity configuration. Through the use of TIR and Brewster's angles, no optical coatings, either anti-reflective (AR) or highly reflective (HR), are required inside the laser cavity. In this first demonstration, the 936.5-nm diode pumped laser performed with approximately 38% slope efficiency at 12 W of quasi-CW (Q-CW) output power at 1030 nm with a beam quality measured at M(2) = 1.5. This demonstration opens up a viable path toward novel thin disk laser designs with efficient double-sided room-temperature heatsinking via materials with the thermal conductivity of copper on both sides of the disk.

  2. The effect of diagenesis and fluid migration on rare earth element distribution in pore fluids of the northern Cascadia accretionary margin

    USGS Publications Warehouse

    Kim, Ji-Hoon; Torres, Marta E.; Haley, Brian A.; Kastner, Miriam; Pohlman, John W.; Riedel, Michael; Lee, Young-Joo

    2012-01-01

    Analytical challenges in obtaining high quality measurements of rare earth elements (REEs) from small pore fluid volumes have limited the application of REEs as deep fluid geochemical tracers. Using a recently developed analytical technique, we analyzed REEs from pore fluids collected from Sites U1325 and U1329, drilled on the northern Cascadia margin during the Integrated Ocean Drilling Program (IODP) Expedition 311, to investigate the REE behavior during diagenesis and their utility as tracers of deep fluid migration. These sites were selected because they represent contrasting settings on an accretionary margin: a ponded basin at the toe of the margin, and the landward Tofino Basin near the shelf's edge. REE concentrations of pore fluid in the methanogenic zone at Sites U1325 and U1329 correlate positively with concentrations of dissolved organic carbon (DOC) and alkalinity. Fractionations across the REE series are driven by preferential complexation of the heavy REEs. Simultaneous enrichment of diagenetic indicators (DOC and alkalinity) and of REEs (in particular the heavy elements Ho to Lu), suggests that the heavy REEs are released during particulate organic carbon (POC) degradation and are subsequently chelated by DOC. REE concentrations are greater at Site U1325, a site where shorter residence times of POC in sulfate-bearing redox zones may enhance REE burial efficiency within sulfidic and methanogenic sediment zones where REE release ensues. Cross-plots of La concentrations versus Cl, Li and Sr delineate a distinct field for the deep fluids (z > 75 mbsf) at Site U1329, and indicate the presence of a fluid not observed at the other sites drilled on the Cascadia margin. Changes in REE patterns, the presence of a positive Eu anomaly, and other available geochemical data for this site suggest a complex hydrology and possible interaction with the igneous Crescent Terrane, located east of the drilled transect.

  3. Patterns of sediment accumulation in the tidal marshes of Maine

    USGS Publications Warehouse

    Wood, M.E.; Kelley, J.T.; Belknap, D.F.

    1989-01-01

    One year's measurements of surficial sedimentation rates (1986-1987) for 26 Maine marsh sites were made over marker horizons of brick dust. Observed sediment accumulation rates, from 0 to 13 mm yr-1, were compared with marsh morphology, local relative sea-level rise rate, mean tidal range, and ice rafting activity. Marshes with four different morphologies (back-barrier, fluvial, bluff-toe, and transitional) showed distinctly different sediment accumulation rates. In general, back-barrier marshes had the highest accumulation rates and blufftoe marshes had the lowest rates, with intermediate values for transitional and fluvial marshes. No causal relationship between modern marsh sediment accumulation rate and relative sea-level rise rate (from tide gauge records) was observed. Marsh accretionary balance (sediment accumulation rate minus relative sea-level rise rate) did not correlate with mean tidal range for this meso- to macro-tidal area. Estimates of ice-rafted debris on marsh sites ranged from 0% to >100% of measured surficial sedimentation rates, indicating that ice transport of sediment may make a significant contribution to surficial sedimentation on Maine salt marshes. ?? 1989 Estuarine Research Federation.

  4. Prism Foil from an LCD Monitor as a Tool for Teaching Introductory Optics

    ERIC Educational Resources Information Center

    Planinsic, Gorazd; Gojkosek, Mihael

    2011-01-01

    Transparent prism foil is part of a backlight system in LCD monitors that are widely used today. This paper describes the optical properties of the prism foil and several pedagogical applications suitable for undergraduate introductory physics level. Examples include experiments that employ refraction, total internal reflection, diffraction and…

  5. Investigating First Year Elementary Mathematics Teacher Education Students' Knowledge of Prism

    ERIC Educational Resources Information Center

    Bozkurt, Ali; Koc, Yusuf

    2012-01-01

    The purpose of this study was to investigate first year elementary mathematics teacher education students' knowledge of prism. For this goal, the participants were asked to define the geometric concept of prism. The participants were 158 first year elementary mathematics teacher education students from a public university in Southern Turkey. The…

  6. Electron sharing and anion-π recognition in molecular triangular prisms.

    PubMed

    Schneebeli, Severin T; Frasconi, Marco; Liu, Zhichang; Wu, Yilei; Gardner, Daniel M; Strutt, Nathan L; Cheng, Chuyang; Carmieli, Raanan; Wasielewski, Michael R; Stoddart, J Fraser

    2013-12-02

    Stacking on a full belly: Triangular molecular prisms display electron sharing among their triangularly arranged naphthalenediimide (NDI) redox centers. Their electron-deficient cavities encapsulate linear triiodide anions, leading to the formation of supramolecular helices in the solid state. Chirality transfer is observed from the six chiral centers of the filled prisms to the single-handed helices.

  7. Hierarchically triangular prism structured Co3O4: Self-supported fabrication and photocatalytic property

    EPA Science Inventory

    The formation of ammonium cobalt (II) phosphate was utilized to synthesize unprecedented 3D structures of Co3O4, triangular prisms and trunk-like structures, via a self-supported and organics-free method. The length of a triangular side of the prepared 3D triangular prisms is ~1...

  8. Standardization of motion sickness induced by left-right and up-down reversing prisms

    NASA Technical Reports Server (NTRS)

    Reschke, M. F.; Vanderploeg, J. M.; Brumley, E. A.; Kolafa, J. J.; Wood, S. J.

    1990-01-01

    Reversing prisms are known to produce symptoms of motion sickness, and have been used to provide a chronic stimulus for training subjects on symptom recognition and regulation. However, testing procedures with reversing prisms have not been standardized. A set of procedures were evaluated which could be standardized using prisms for provocation and to compare the results between Right/Left Reversing Prisms (R/L-RP) and Up/Down Reversing Prisms (U/D-RP). Fifteen subjects were tested with both types of prisms using a self paced walking course throughout the laboratory with work stations established at specified intervals. The work stations provided tasks requiring eye-hand-foot coordination and various head movements. Comparisons were also made between these prism tests and two other standardized susceptibility tests, the KC-135 parabolic static chair test and the Staircase Velocity Motion Test (SVMT). Two different types of subjective symptom reports were compared. The R/L-RP were significantly more provocative than the U/D-RP. The incidence of motion sickness symptoms for the R/L-RP was similar to the KC-135 parabolic static chair test. Poor correlations were found between the prism tests and the other standardized susceptibility tests, which might indicate that different mechanisms are involved in provoking motion sickness for these different tests.

  9. Partners in Portraiture: An Account of the Collaborative Work of Projects PRISM and Co-Arts.

    ERIC Educational Resources Information Center

    Kaiser, Jon E.; And Others

    The evolution and implementation of a collaborative effort between an elementary school bilingual science education project (Process in Science Methods, or PRISM) of The Network, Inc., and a study of the educational effectiveness of community arts centers (Project Co-Arts) are described. With PRISM's focus on science and Co-Arts' concentration on…

  10. Impact of high power and angle of incidence on prism corrections for visual field loss

    NASA Astrophysics Data System (ADS)

    Jung, Jae-Hyun; Peli, Eli

    2014-06-01

    Prism distortions and spurious reflections are not usually considered when prescribing prisms to compensate for visual field loss due to homonymous hemianopia. Distortions and reflections in the high-power Fresnel prisms used in peripheral prism placement can be considerable, and the simplifying assumption that prism deflection power is independent of angle of incidence into the prisms results in substantial errors. We analyze the effects of high prism power and incidence angle on the field expansion, size of the apical scotomas, and image compression/expansion. We analyze and illustrate the effects of reflections within the Fresnel prisms, primarily due to reflections at the bases, and secondarily due to surface reflections. The strength and location of these effects differs materially depending on whether the serrated prismatic surface is placed toward or away from the eye, and this affects the contribution of the reflections to visual confusion, diplopia, false alarms, and loss of contrast. We conclude with suggestions for controlling and mitigating these effects in clinical practice.

  11. The use of prisms for vision rehabilitation after macular function loss: an evidence-based review.

    PubMed

    Markowitz, Samuel N; Reyes, Sophia V; Sheng, Li

    2013-05-01

    To determine the efficacy of prisms used for redirection of incoming images towards the peripheral retina in cases with macular function loss. Meta-analysis of published work reporting outcomes from interventions using prisms was performed. The primary outcome measure selected for analysis was visual acuity (VA) used for viewing distance targets. Pooled data from 449 cases where prisms were prescribed for wearing in distance glasses were analysed. Visual acuity was better after using prisms (1.05 versus 0.89 logMAR units, p < 0.044). Mean effect size for improving VA was 79 bigger than the effect size calculated for the control group (0.158 versus 0.002). Most patients (76%) reported compliance with the therapy and also reported other benefits directly derived from the realized VA improvement. Published studies collectively offer positive evidence in support of using prisms for low vision rehabilitation after macular function loss. Further research is required to reach definitive binding conclusions.

  12. Controlling Orientational Order in 1-D Assemblies of Multivalent Triangular Prisms.

    PubMed

    Kohlstedt, Kevin L; Olvera de la Cruz, Monica; Schatz, George C

    2013-01-03

    Multivalent nanostructures are becoming an increasingly important player in the self-assembly of supramolecular lattices. Understanding the role that shape plays in the coordination of the assemblies is crucial for the functional response of the material. We develop a simple design rule for the assembly of multivalent Au triangular nanoprisms into 1-D ordered arrays based on both the length of the valent DNA and the aspect ratio of the prism. Using MD simulations, we describe an order parameter that captures the short-range order of the assembly controlled by the design parameters. The order parameter shows that even short chains (N = 4) of prisms have a high degree of orientational order that transitions to no orientational order when the DNA length is similar to the prism length. Unlike isotropic polyvalent assemblies, we find that the highly oriented chains of prisms lose orientational order in discrete steps during melting as the prisms in the arrays dissociate.

  13. ePRISM: A case study in multiple proxy and mixed temporal resolution integration

    USGS Publications Warehouse

    Robinson, Marci M.; Dowsett, Harry J.

    2010-01-01

    As part of the Pliocene Research, Interpretation and Synoptic Mapping (PRISM) Project, we present the ePRISM experiment designed I) to provide climate modelers with a reconstruction of an early Pliocene warm period that was warmer than the PRISM interval (similar to 3.3 to 3.0 Ma), yet still similar in many ways to modern conditions and 2) to provide an example of how best to integrate multiple-proxy sea surface temperature (SST) data from time series with varying degrees of temporal resolution and age control as we begin to build the next generation of PRISM, the PRISM4 reconstruction, spanning a constricted time interval. While it is possible to tie individual SST estimates to a single light (warm) oxygen isotope event, we find that the warm peak average of SST estimates over a narrowed time interval is preferential for paleoclimate reconstruction as it allows for the inclusion of more records of multiple paleotemperature proxies.

  14. A unit structure Rochon prism based on the extraordinary refraction of uniaxial birefringent crystals.

    PubMed

    Wu, Wendi; Wu, Fuquan; Shi, Meng; Su, Fufang; Han, Peigao; Ma, Lili

    2013-06-03

    Based on the Fermat's principle, the universal theory of refraction and reflection of extraordinary rays (e-rays) in the uniaxial crystal is formulated. Using this theory, a new unit structure prism is designed, and its properties are studied. Based on the theoretical results, such a prism is achieved experimentally by using the Iceland crystal. In both theoretical and experimental studies, this new prism shows excellent polarization splitting performances such as big and adjustable splitting angle, comparing to the conventional Rochon prism. For the sample prism with the optical axis angle of 45°, the splitting angle reaches 19.8°in the normal incidence, and the maximum splitting angle reaches 28.44° while the incidence angle is -4°.

  15. The effect of décollement dip on geometry and kinematics of model accretionary wedges

    NASA Astrophysics Data System (ADS)

    Koyi, Hemin A.; Vendeville, Bruno C.

    2003-09-01

    We conducted a series of sand-box models shortened asymmetrically above a frictional-plastic décollement to study the influence of amount and sense of the décollement dip on the geometry and kinematics of accretionary wedges. Model results illustrate that the amount and direction of décollement dip strongly influence the geometry and mode of deformation of the resulting wedge. In general, for models having similar décollement frictional parameters, the resulting wedge is steeper, grows higher and is shorter when shortened above a décollement that dips toward the hinterland. At 42% bulk shortening, the length/height ratio of wedges formed above a 5°-dipping décollement was equal to 2.4 whereas this ratio was equal to 3 for wedges shortened above a horizontal décollement. Moreover, models with a hinterland dipping décollement undergo larger amounts of layer parallel compaction (LPC) and area loss than models shortened above a non-dipping décollement. The effect of décollement dip on wedge deformation is most pronounced when basal friction is relatively high (μ b=0.55), whereas its effect is less significant in models where the basal décollement has a lower friction (μ b=0.37). Model results also show that increasing basal slope has a similar effect to that of increasing basal friction; the wedge grows taller and its critical taper steepens.

  16. Headless submarine canyons and fluid flow on the toe of the Cascadia accretionary complex

    USGS Publications Warehouse

    Orange, D.L.; McAdoo, B.G.; Moore, J.C.; Tobin, H.; Screaton, E.; Chezar, H.; Lee, H.; Reid, M.; Vail, R.

    1997-01-01

    Headless submarine canyons with steep headwalls and shallowly sloping floors occur on both the second and third landward vergent anticlines on the toe of the Cascadia accretionary complex off central Oregon (45 ??N, 125?? 30??W). In September 1993, we carried out a series of nine deep tow camera sled runs and nine ALVIN dives to examine the relationship between fluid venting, structure and canyon formation. We studied four canyons on the second and third landward vergent anticlines, as well as the apparently unfailed intercanyon regions along strike. All evidence of fluid expulsion is associated with the canyons; we found no evidence of fluid flow between canyons. Even though all fluid seeps are related to canyons, we did not find seeps in all canyons, and the location of the seeps within the canyons differed. On the landward facing limb of the second landward vergent anticline a robust cold seep community occurs at the canyon's inflection point. This seep is characterized by chemosynthetic vent clams, tube worms and extensive authigenic carbonate. Fluids for this seep may utilize high-permeability flow paths either parallel to bedding within the second thrust ridge or along the underlying thrust fault before leaking into the overriding section. Two seaward facing canyons on the third anticlinal ridge have vent clam communities near the canyon mouths at approximately the intersection between the anticlinal ridge and the adjacent forearc basin. No seeps were found along strike at the intersection of the slope basin and anticlinal ridge. We infer that the lack of seepage along strike and the presence of seeps in canyons may be related to fluid flow below the forearc basin/slope unconformity (overpressured by the impinging thrust fault to the west?) directed toward canyons at the surface.

  17. Contributions of Arctic PRISM to monitoring western hemispheric shorebirds

    USGS Publications Warehouse

    Skagen, Susan K.; Smith, Paul A.; Andres, Brad A.; Donaldson, Garry; Brown, Stephen

    2012-01-01

    for assessing its vulnerability and subsequent listing under the U.S. Endangered Species Act and the Canadian Species at Risk Act. To meet the need for information on population size and trends, shorebird biologists from Canada and the United States proposed a shared blueprint for shorebird monitoring across the Western Hemisphere in the late 1990s; this effort was undertaken in concert with the development of the Canadian and U.S. Shorebird Conservation Plans (Donaldson et al. 2000, Brown et aL 2001). Soon thereafter, partners in the monitoring effort adopted the name "Program for Regional and International Shorebird Monitoring" (PRISM). Among the primary objectives of PRISM were to estimate the population sizes and trends of breeding North American shorebirds and describe their distributions (Bart et al. 2002). PRISM members evaluated ongoing and potential monitoring approaches to address 74 taxa (including subspecies) and proposed a combination of arctic andboreal breeding surveys, temperate breeding and non-breeding surveys, and neotropical surveys.

  18. Foreword: contributions of Arctic PRISM to monitoring western hemispheric shorebirds

    USGS Publications Warehouse

    Skagen, Susan K.; Smith, Paul A.; Andres, Brad A.; Donaldson, Garry; Brown, Stephen

    2012-01-01

    listing under the U.S. Endangered Species Act and the Canadian Species at Risk Act. To meet the need for information on population size and trends, shorebird biologists from Canada and the United States proposed a shared blueprint for shorebird monitoring across the Western Hemisphere in the late 1990s; this effort was undertaken in concert with the development of the Canadian and the U.S. Shorebird Conservation Plans. Soon thereafter, partners in the monitoring effort adopted the name "Program for Regional and International Shorebird Monitoring" (PRISM). Among the primary objectives of PRISM were to estimate the population sizes and trends of breeding North American shorebirds and describe their distributions. PRISM members evaluated ongoing and potential monitoring approached to address 74 taxa (including subspecies) and proposed a combination of arctic and boreal breeding surveys, temperate breeding and non-breeding surveys, and neotropical surveys.

  19. Optical device with conical input and output prism faces

    DOEpatents

    Brunsden, Barry S.

    1981-01-01

    A device for radially translating radiation in which a right circular cylinder is provided at each end thereof with conical prism faces. The faces are oppositely extending and the device may be severed in the middle and separated to allow access to the central part of the beam. Radiation entering the input end of the device is radially translated such that radiation entering the input end at the perimeter is concentrated toward the output central axis and radiation at the input central axis is dispersed toward the output perimeter. Devices are disclosed for compressing beam energy to enhance drilling techniques, for beam manipulation of optical spatial frequencies in the Fourier plane and for simplification of dark field and color contrast microscopy. Both refracting and reflecting devices are disclosed.

  20. Russia through the prism of the world biopharmaceutical market.

    PubMed

    Bairamashvili, Dmitrij I; Rabinovich, Mikhail L

    2007-07-01

    Trends in the Russian pharmaceutical biotechnology and related fields representing the major sector of domestic biotech are reviewed through the prism of the world biopharmaceuticals market. A special emphasis is placed on biogenerics and follow-on biologics. The revival of national pharmbiotech is seen in close cooperation between private companies and the state, academia and industry. One of the first positive steps toward promoting development of domestic biopharmaceuticals is the Federal Program of subsidized supply of expensive pharmaceuticals (Dopolnitel'- noe Lekarstvennoe Obespechenie). The program allows the Russian government to purchases expensive drugs to be provided free of cost to certain preferential categories of individuals. As an example, production of recombinant human insulin by the largest Russian fundamental biotechnological institute, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry under the trademark Insuran (Insulin produced by the Russian Academy of Science) is reviewed. Some prospects and problems of Russian biotech research related to medical area are briefly discussed.

  1. Dove prism based rotating dual beam bidirectional Doppler OCT

    PubMed Central

    Blatter, Cedric; Coquoz, Séverine; Grajciar, Branislav; Singh, Amardeep S. G.; Bonesi, Marco; Werkmeister, René M.; Schmetterer, Leopold; Leitgeb, Rainer A.

    2013-01-01

    Traditional Doppler OCT is highly sensitive to motion artifacts due to the dependence on the Doppler angle. This limits its accuracy in clinical practice. To overcome this limitation, we use a bidirectional dual beam technique equipped with a novel rotating scanning scheme employing a Dove prism. The volume is probed from two distinct illumination directions with variable controlled incidence plane, allowing for reconstruction of the true flow velocity at arbitrary vessel orientations. The principle is implemented with Swept Source OCT at 1060nm with 100,000 A-Scans/s. We apply the system to resolve pulsatile retinal absolute blood velocity by performing segment scans around the optic nerve head and circumpapillary scan time series. PMID:23847742

  2. Hybrid-integrated prism array optoelectronic targeting system

    NASA Astrophysics Data System (ADS)

    Chang, C. C.; Chang, H. C.; Tang, L. C.; Young, W. K.; Wang, J. C.; Huang, K. L.

    2005-11-01

    This investigation proposes a cost-effective, compact, and robust optoelectronic targeting system for measuring ballistic impact velocity and the distribution of projectile motion. The major elements of this system are four photo-gates hybridized by compound one-dimensional prism array and analog/digital electronic components. The number of light sources and photodetectors used in a photo-gate was reduced to one pair of light source and photodetector. The average velocity and location of the projectile are determined according to the measured time intervals ( ˜10 -8 s) passing each pair. The system can accurately measure the velocity of a bullet as it leaves a gun barrel, as well as the velocity at specific points along the trajectory outside the firearm. Additionally, the system uses a widespread low-powered laser pointer as a light source. Compared with other optoelectronic targeting systems that use high-powered lasers, the proposed system is both economical and safe.

  3. The PRISM project: Infrastructure and algorithms for parallel eigensolvers

    SciTech Connect

    Bischof, C.; Sun, X.; Huss-Lederman, S.; Tsao, A.

    1993-12-31

    The goal of the PRISM project is the development of infrastructure and algorithms for the parallel solution of eigenvalue problems. We are currently investigating a complete eigensolver based on the Invariant Subspace Decomposition Algorithm for dense symmetric matrices (SYISDA). After briefly reviewing the SYISDA approach, we discuss the algorithmic highlights of a distributed-memory implementation of an eigensolver based on this approach. These include a fast matrix-matrix multiplication algorithm, a new approach to parallel band reduction and tridiagonalization, and a harness for coordinating the divide-and-conquer parallelism in the problem. We also present performance results of these kernels as well as the overall SYISDA implementation on the Intel Touchstone Delta prototype and the IBM SP/1.

  4. Characterization of deflagrating munitions by rotating prism high speed photography

    NASA Astrophysics Data System (ADS)

    Kinsey, Trevor J.; Bussell, Tim J.; Chick, Michael C.

    1992-08-01

    We report on the use of a rotating prism high speed camera for determining the characteristics of a munition undergoing rapid deflagration in field experiments. The technique has been applied to study the controlled deflagration of Composition B filled 105 mm shell and 81 mm mortar bombs as representative thick and thin cased munitions respectively; however the report is mostly illustrated with results from the study on 105 mm shell. The deflagration event has been characterized in terms of case expansion rate, initial fragment velocity, time to case burst, time to reaction from the nose end and the deflagration rate of the filling. Products escaping from the fracturing case eventually obscured the image which limited the extent of the measurement.

  5. Rotational Dove prism scanning dual angle Doppler OCT

    NASA Astrophysics Data System (ADS)

    Blatter, Cedric; Coquoz, Séverine; Grajciar, Branislav; Singh, Amardeep S. G.; Werkmeister, René M.; Schmetterer, Leopold; Leitgeb, Rainer A.

    2013-03-01

    Traditional Doppler OCT is highly sensitive to motion artifacts due to the dependence on the Doppler angle. This limits its reproducibility in clinical practice. To overcome this limitation, we use a bidirectional technique with a novel rotating scanning scheme. The volume is probed simultaneously from two distinct illumination directions with variable controlled orientations, allowing reconstruction of the true flow velocity, independently of the vessel orientation. A Dove prism in the sample arm permits a rotation of the illumination directions that can be synchronized with the standard beam steering device. The principle is implemented with Swept Source OCT at 1060nm with 100,000 A-Scans/s. We apply the system to human retinal absolute blood velocity measurement by performing segment and circumpapillary time series scans around the optic nerve head. We also demonstrate microvasculature imaging by calculation of squared intensity differences between successive tomograms.

  6. Larmor labeling of neutron spin using superconducting Wollaston prisms

    NASA Astrophysics Data System (ADS)

    Li, Fankang

    Neutron spin Larmor labeling using magnetic Wollaston prisms (WP) provides a way to overcome some of the limitations arising from the nature of neutron beams: low flux and divergence. Using superconducting films and tapes, a series of strong, well-defined shaped magnetic fields can be produced due to both the zero-resistance and Meissner effect in superconductors. Using finite element simulations, the criterion to build a superconducting magnetic Wollaston prism with high encoding efficiency and low Larmor phase aberrations are presented. To achieve a high magnetic field and simplify the maintenance, we optimize the design using careful thermal analysis. The measured neutron spin flipping efficiency is measured to be independent of both the neutron wavelength and energizing current, which is a significant improvement over other devices with similar functions. A highly linear variation of the Larmor phase is measured across the device, which ensures a highly uniform encoding of scattering angles into the neutron spin Larmor phase. Using two WPs, the correlation function for a colloidal silica sample was measured by spin echo modulated small angle neutron scattering (SEMSANS) and agrees well with other techniques. Using Monte Carlo code (McStas), we further investigated the SEMSANS setup and showed the requirements to improve its performance. We have proposed a new technique to implement neutron spin echo on a triple axis neutron spectrometer to achieve high resolution measurements of the lifetime of dispersive phonon excitations. The spin echo is tuned by appropriate choice of magnetic fields instead of physically tilting the coils used in traditional methods. This new approach allows a higher energy resolution and a larger effective tilting angle and hence larger group velocity to be measured.

  7. Contaminated Sediment

    EPA Pesticide Factsheets

    Contaminated sediments are a significant problem in the Great Lakes basin. Persistent high concentrations of contaminants in the bottom sediments of rivers and harbors pose risks to aquatic organisms, wildlife, and humans.

  8. Aquatic Sediments.

    ERIC Educational Resources Information Center

    Sanville, W. D.; And Others

    1978-01-01

    Presents a literature review of aquatic sediments and its effect upon water quality, covering publications of 1976-77. This review includes: (1) sediment water interchange; (2) chemical and physical characterization; and (3) heavy water in sediments. A list of 129 references is also presented. (HM)

  9. Left-Deviating Prism Adaptation in Left Neglect Patient: Reflexions on a Negative Result

    PubMed Central

    Luauté, Jacques; Jacquin-Courtois, Sophie; O'Shea, Jacinta; Christophe, Laure; Rode, Gilles; Boisson, Dominique; Rossetti, Yves

    2012-01-01

    Adaptation to right-deviating prisms is a promising intervention for the rehabilitation of patients with left spatial neglect. In order to test the lateral specificity of prism adaptation on left neglect, the present study evaluated the effect of left-deviating prism on straight-ahead pointing movements and on several classical neuropsychological tests in a group of five right brain-damaged patients with left spatial neglect. A group of healthy subjects was also included for comparison purposes. After a single session of exposing simple manual pointing to left-deviating prisms, contrary to healthy controls, none of the patients showed a reliable change of the straight-ahead pointing movement in the dark. No significant modification of attentional paper-and-pencil tasks was either observed immediately or 2 hours after prism adaptation. These results suggest that the therapeutic effect of prism adaptation on left spatial neglect relies on a specific lateralized mechanism. Evidence for a directional effect for prism adaptation both in terms of the side of the visuomanual adaptation and therefore possibly in terms of the side of brain affected by the stimulation is discussed. PMID:23050168

  10. [Improving laser center wavelength detection accuracy based on multi-level combination prisms].

    PubMed

    Liu, Xiao-Dong; Zhang, Zhi-Jie

    2011-08-01

    In order to improve the spectral resolution of birefringence prism under the conditions of ensuring the quality of interference fringes image, the system used multi-level combination prisms and designed the method of interferometer fringes splice. According to calculation of the interferometer fringes intensity of multi-level combination prisms, the optical path difference function and the spectrum resolution, the present paper analyzed that the least spectrum resolution is 2.875 cm(-1) in multi-level combination prisms of four prisms structure. The method of interferometer fringes splice was designed to splice the section interferometer fringes, and in experiment the size of multi-level combination prisms is 30 mm x 28 mm x 10 mm. The standard 635 nm laser for getting the interferometer fringes was dealed with. Experimental data show that the detection spectrum distribution of the 635.0 nm laser was distorted by the direct splicing of the interference fringes, while the detection spectrum distribution of the 635.0 nm laser was consistent with the standard spectrum by the method of interferometer fringes splice. So the method can effectively avoid spectrum distortion by interferometer fringes splice in multi-level combination prisms.

  11. Beam steering uncertainty analysis for Risley prisms based on Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Yuan, Yan; Su, Lijuan; Huang, Fengzhen

    2017-01-01

    The Risley-prism system is applied in imaging LADAR to achieve precision directing of laser beams. The image quality of LADAR is affected deeply by the laser beam steering quality of Risley prisms. The ray-tracing method was used to predict the pointing error. The beam steering uncertainty of Risley prisms was investigated through Monte Carlo simulation under the effects of rotation axis jitter and prism rotation error. Case examples were given to elucidate the probability distribution of pointing error. Furthermore, the effect of scan pattern on the beam steering uncertainty was also studied. It is found that the demand for the bearing rotational accuracy of the second prism is much more stringent than that of the first prism. Under the effect of rotation axis jitter, the pointing uncertainty in the field of regard is related to the altitude angle of the emerging beam, but it has no relationship with the azimuth angle. The beam steering uncertainty will be affected by the original phase if the scan pattern is a circle. The proposed method can be used to estimate the beam steering uncertainty of Risley prisms, and the conclusions will be helpful in the design and manufacture of this system.

  12. Exploring the effects of ecological activities during exposure to optical prisms in healthy individuals.

    PubMed

    Fortis, Paola; Ronchi, Roberta; Calzolari, Elena; Gallucci, Marcello; Vallar, Giuseppe

    2013-01-01

    Prism adaptation improves a wide range of manifestations of left spatial neglect in right-brain-damaged patients. The typical paradigm consists in repeated pointing movements to visual targets, while patients wear prism goggles that displace the visual scene rightwards. Recently, we demonstrated the efficacy of a novel adaptation procedure, involving a variety of every-day visuo-motor activities. This "ecological" procedure proved to be as effective as the repetitive pointing adaptation task in ameliorating symptoms of spatial neglect, and was better tolerated by patients. However, the absence of adaptation and aftereffects measures for the ecological treatment did not allow for a full comparison of the two procedures. This is important in the light of recent findings showing that the magnitude of prism-induced aftereffects may predict recovery from spatial neglect. Here, we investigated prism-induced adaptation and aftereffects after ecological and pointing adaptation procedures. Forty-eight neurologically healthy participants (young and aged groups) were exposed to rightward shifting prisms while they performed the ecological or the pointing procedures, in separate days. Before and after prism exposure, participants performed proprioceptive, visual, and visual-proprioceptive tasks to assess prism-induced aftereffects. Participants adapted to the prisms during both procedures. Importantly, the ecological procedure induced greater aftereffects in the proprioceptive task (for both the young and the aged groups) and in the visual-proprioceptive task (young group). A similar trend was found for the visual task in both groups. Finally, participants rated the ecological procedure as more pleasant, less monotonous, and more sustainable than the pointing procedure. These results qualify ecological visuo-motor activities as an effective prism-adaptation procedure, suitable for the rehabilitation of spatial neglect.

  13. Adaptation to leftward-shifting prisms enhances local processing in healthy individuals.

    PubMed

    Reed, Scott A; Dassonville, Paul

    2014-04-01

    In healthy individuals, adaptation to left-shifting prisms has been shown to simulate the symptoms of hemispatial neglect, including a reduction in global processing that approximates the local bias observed in neglect patients. The current study tested whether leftward prism adaptation can more specifically enhance local processing abilities. In three experiments, the impact of local and global processing was assessed through tasks that measure susceptibility to illusions that are known to be driven by local or global contextual effects. Susceptibility to the rod-and-frame illusion - an illusion disproportionately driven by both local and global effects depending on frame size - was measured before and after adaptation to left- and right-shifting prisms. A significant increase in rod-and-frame susceptibility was found for the left-shifting prism group, suggesting that adaptation caused an increase in local processing effects. The results of a second experiment confirmed that leftward prism adaptation enhances local processing, as assessed with susceptibility to the simultaneous-tilt illusion. A final experiment employed a more specific measure of the global effect typically associated with the rod-and-frame illusion, and found that although the global effect was somewhat diminished after leftward prism adaptation, the trend failed to reach significance (p=.078). Rightward prism adaptation had no significant effects on performance in any of the experiments. Combined, these findings indicate that leftward prism adaptation in healthy individuals can simulate the local processing bias of neglect patients primarily through an increased sensitivity to local visual cues, and confirm that prism adaptation not only modulates lateral shifts of attention, but also prompts shifts from one level of processing to another.

  14. Measurement of the optical characteristics of electrowetting prism array for three-dimensional display

    NASA Astrophysics Data System (ADS)

    Kim, Yunhee; Choi, Yoon-Sun; Choi, Kyuwhan; Kwon, Yongjoo; Bae, Jungmok; Morozov, Alexander; Lee, Hong-Seok

    2013-03-01

    Recently liquid-based optical devices are emerging as attractive components in three-dimensional (3D) display for its compact structure and fast response time. Among them an electrowetting prism array is one of the promising 3D devices. It steers a beam, which enables to provide corresponding perspectives to observer. For high quality autostereoscopic 3D displays the important factors are the beam steering angle and the beam profile, the optical characteristics. In this paper, we propose a method to measure the optical characteristics of the liquid prism and show experimental results on our prototype electrowetting prism array, which consists of prisms with 200um by 200um size. A modified 4-f system is adopted for the proposed method. It provides two kinds of information of the optical characteristics of the liquid prism at the image plane and at the Fourier plane. First, the proposed measurement setup magnifies the image of the liquid micro prism array so that we can observe the status of the each prism array directly with bare eye and align a mask easily for selecting a prism to be examined at the image plane. Secondly, the steering angle can be calculated by measuring the displacement of the beam at the Fourier plane, where the angular profiles that have important information on the oilwater interface is observed precisely. The principle of the proposed method will be explained, and the measured optical characteristics from experimental results on the liquid prism we fabricated will be provided, which proves the validity of the measurement method.

  15. Adaptation to Leftward-shifting Prisms Enhances Local Processing in Healthy Individuals

    PubMed Central

    Reed, Scott A.; Dassonville, Paul

    2014-01-01

    In healthy individuals, adaptation to left-shifting prisms has been shown to simulate the symptoms of hemispatial neglect, including a reduction in global processing that approximates the local bias observed in neglect patients. The current study tested whether leftward prism adaptation can more specifically enhance local processing abilities. In three experiments, the impact of local and global processing was assessed through tasks that measure susceptibility to illusions that are known to be driven by local or global contextual effects. Susceptibility to the rod-and-frame illusion – an illusion disproportionately driven by both local and global effects depending on frame size – was measured before and after adaptation to left- and right-shifting prisms. A significant increase in rod-and-frame susceptibility was found for the left-shifting prism group, suggesting that adaptation caused an increase in local processing effects. The results of a second experiment confirmed that leftward prism adaptation enhances local processing, as assessed with susceptibility to the simultaneous-tilt illusion. A final experiment employed a more specific measure of the global effect typically associated with the rod-andframe illusion, and found that although the global effect was somewhat diminished after leftward prism adaptation, the trend failed to reach significance (p = .078). Rightward prism adaptation had no significant effects on performance in any of the experiments. Combined, these findings indicate that leftward prism adaptation in healthy individuals can simulate the local processing bias of neglect patients primarily through an increased sensitivity to local visual cues, and confirm that prism adaptation not only modulates lateral shifts of attention, but also prompts shifts from one level of processing to another. PMID:24560913

  16. The Calm Before the Storm: Exploring the Post Accretionary Doldrums Prior to the Late Heavy Bombardment

    NASA Astrophysics Data System (ADS)

    Bottke, W. F., Jr.

    2015-12-01

    The early bombardment of the inner solar system played a critical role in planetary evolution, but there is still considerable uncertainty about what happened when. Dynamical models suggest two major bombardment phases may have taken place: (i) a post-accretionary period where newly-formed worlds were struck by leftover planetesimals, and (ii) a late heavy bombardment period, possibly produced by conditions related to a violent reshuffling of the planets ~4.1-4.2 Gyr ago (Ga). If valid, a relative impact lull took place between the two bombardment phases. We explore the evidence for such doldrums in this talk. Consider: a) Mars. Geochemical and meteorite evidence indicates the giant 10,600 × 8,500 km Borealis basin formed > 4.5 Ga. Many postulated basins forming afterwards, however, can be ruled out by the surprisingly pristine nature of the Borealis boundary in topography and gravity. Three of the four largest remaining basins, Hellas, Isidis, and Argyre, have superposed craters counts indicating they are < 4.1 Ga. b) Asteroids. The oldest and most extensive sets of 39Ar-40Ar shock degassing ages, found within meteorites that were heavily shocked, shock-melted, or otherwise showed some evidence for having been part of a large collision, show age clusters between ~3.5-4.1 Ga and ~4.4-4.54 Ga. Using dynamical/impact heating models, it can be argued that relatively few projectiles were on planet-crossing orbits between ~4.1-4.4 Ga. c) Moon. The Moon is probably 4.47 Ga, yet most sample evidence for basin-sized impacts may be < 4.2 Ga. The age gap is curious unless many basins were created close in time to the solidification of the lunar crust. Using collisional/dynamical models, it can be shown that many early basins and craters formed > 4.4 Ga. Here the early impactors may be surviving debris from the Moon-forming giant impact event; note that ejecta initially escaping the Earth-Moon system can come back over many tens of Myr. This would leave doldrums between ~4

  17. Imaging accretionary structures in the crust and mantle of the southeastern U.S.A.

    NASA Astrophysics Data System (ADS)

    Hopper, E.; Fischer, K. M.; Wagner, L. S.; Hawman, R. B.; Rondenay, S.

    2014-12-01

    How is continental accretion accommodated in the crust and mantle lithosphere? We investigate this question in the southeastern U.S., where Mesozoic rifting left the exotic Suwannee Terrane behind on the Laurentian margin, and the accretionary structures of the Laurentia-Gondwana collision have been at least partially preserved. We analyze Sp phases recorded by SESAME (Southeastern Suture of the Appalachian Margin Experiment), nearby Transportable Array and permanent stations. Sp receiver functions for individual waveforms were obtained by extended time multi-taper deconvolution, and migrated into a 3D volume using common conversion point stacking, a spline function representation of phase Fresnel zones, and 3D crust and mantle velocities. Within the crust, we observe a pair of prominent phases (positive and negative, corresponding to a velocity increase and decrease with depth respectively). The lower, negative phase is continuous over more than 500 km of N-S distance. It is subhorizontal beneath the Blue Ridge and Inner Piedmont terranes, and south-dipping across the suture. The positive phase also dips south at the suture, then flattens in the lower crust. We observe such phases in both eastern and western Georgia, indicating along-strike continuity over at least ~170 km. Beneath SESAME stations in western Georgia, the negative phase is subhorizontal in the midcrust (~17 km depth) from 35.6°N, near the Blue Ridge Thrust, to 32.7°N. From 32.7°N to ~31°N, overlapping the suture zone inferred from COCORP reflection data, it dips south at a minimum angle of 8°. Further south, interference with the Moho may bias apparent phase depth. In the mantle, we observe a N-S transition in discontinuity structure across the suture. Ongoing work with wavefield migration (Bostock et al., 2001) should better resolve discontinuity dips and depths. The crustal phase pair likely represents the top of the Laurentian plate, overthrust by allochthonous Appalachian terranes and the

  18. The tectonic evolution of Southeast Asia through accretionary and extensional episodes since the Cretaceous

    NASA Astrophysics Data System (ADS)

    Seton, M.; Zahirovic, S.; Müller, R.

    2012-12-01

    Although a number of tectonic reconstructions exist that document the development of the present-day complex assemblage of exotic terranes in Southeast Asia, very few describe the continuously evolving plate boundaries and the geodynamic driving forces in the region. We propose a plate motion model that attempts to reconcile evidence from both surface geology and the subsurface mantle structure, and implement continuously closing plate polygons using our open-source plate reconstruction software, GPlates, for the eastern Asian margin and eastern Tethyan domain since the Cretaceous. We link the change from a compressional to an extensional regime along eastern Asia in the Late Cretaceous as the likely opening of the Proto South China Sea in a back-arc setting to account for obducted ophiolite sections on Palawan that are Cretaceous in age, with a likely Miocene emplacement resulting from subduction of the Proto South China Sea crust. Such an interpretation is also consistent with the timing of accretionary episodes along northern Borneo and the upper mantle slab visible in P-wave seismic tomography models. The development of Sundaland is also intricately linked to the opening of the Proto South China Sea and the accretion of Gondwana-derived micro-continental blocks, including East Java and West Sulawesi, in the Cretaceous. Whether Sundaland behaved as a rigid cohesive block, or whether Borneo rotated and moved relative to Sundaland has been a matter of debate due to inconsistencies between paleomagnetic and structural data. Paleomagnetic results indicate significant rotations of Borneo that are accommodated by oroclinal bending without the need for bounding transform faults, which are not obvious in both seismic and potential field data. In the absence of preserved seafloor, we use geological evidence such as ophiolite emplacements, magmatic episodes, paleomagnetic constraints, structural reactivation and deformation as proxies to build a self-consistent plate

  19. CLESSIDRA: Focusing Hard X-Rays Efficiently with Arrays Composed of Small Prisms

    SciTech Connect

    Jark, Werner; Perennes, Frederic; Matteucci, Marco; Mancini, Lucia; Menk, Ralf H.; Rigon, Luigi

    2007-01-19

    Small prisms arranged such that the number of prisms to traverse by an x-ray beam is linearly increasing with distance from the symmetry axis of the device will direct an incident wave to a common cross over point. This structure can be understood as a special form of the Fresnel version of a concave refractive x-ray lens. Indeed it is obtained by removing blocks of optically passive material of equal height from the concave lens shape. It will be shown that the structure has a high refraction efficiency and that the losses are produced by problems in the fabrication of sufficiently sharp tips for the prisms.

  20. Post-self-assembly covalent chemistry of discrete multicomponent metallosupramolecular hexagonal prisms.

    PubMed

    Wang, Ming; Lan, Wen-Jie; Zheng, Yao-Rong; Cook, Timothy R; White, Henry S; Stang, Peter J

    2011-07-20

    The multicomponent coordination-driven self-assembly of hexakis[4-(4-pyridyl)phenyl]benzene, cis-(PEt(3))(2)Pt(II)(OTf)(2), and amine- or maleimide-functionalized isophthalate forms discrete hexagonal prisms as single reaction products. The amino or maleimide groups decorating the isophthalate pillars of the prisms provide reactive sites for post-self-asssembly modifications. In this communication, we demonstrate that the hexagonal prisms can be functionalized without disrupting the prismatic cores, enabling the incorporation of new functionalities under mild conditions.

  1. Properties of YMnO{sub 3} self-assembled nanocrystalline prisms on GaN

    SciTech Connect

    Keenan, Cameron; Chandril, Sandeep; Myers, Thomas H.; Lederman, David; Ramos-Moore, E.; Cabrera, A. L.

    2008-01-07

    Growth of YMnO{sub 3} on GaN (0001) using molecular beam epitaxy at temperatures greater than 850 deg. C resulted in the spontaneous formation of crystalline prisms, ranging from 20 to 60 nm in height and 50 to 500 nm in lateral size, surrounded by a 6 nm thick continuous YMnO{sub 3} film. The local dielectric properties were measured using scanning surface probe microscopy. The prisms were ferroelectric at room temperature and their ferroelectric properties were enhanced for taller prisms. This is consistent with these structures being less constrained than the continuous layer, which is clamped by the surrounding unpolarized film.

  2. A bi-prism interferometer for hard x-ray photons

    SciTech Connect

    Isakovic, A.F.; Siddons, D.; Stein, A.; Warren, J.B.; Sandy, A.R.; Narayanan, M.S.; Ablett, J.M.; Metzler, M. and Evans-Lutterodt, K.

    2010-04-06

    Micro-fabricated bi-prisms have been used to create an interference pattern from an incident hard X-ray beam, and the intensity of the pattern probed with fluorescence from a 30 nm-thick metal film. Maximum fringe visibility exceeded 0.9 owing to the nano-sized probe and the choice of single-crystal prism material. A full near-field analysis is necessary to describe the fringe field intensities, and the transverse coherence lengths were extracted at APS beamline 8-ID-I. It is also shown that the maximum number of fringes is dependent only on the complex refractive index of the prism material.

  3. Energy related studies utilizing microcline thermochronology: Progress report, May 1, 1987-April 30, 1988

    SciTech Connect

    Not Available

    1988-04-30

    Rock samples from the Salton Sea Geothermal Field (sandstone, tuff, granite) and from accretionary prism sediments along the convergent margins in southeast Alaska and southwest Japan have been dated by the /sup 40/Ar/sup 39/Ar method. Paleotemperatures have been calculated. (ACR

  4. Two-beam prism interferometer for noise-free fringe generation.

    PubMed

    Ichikawa, H

    1994-01-01

    A triangular prism instead of a beam splitter was used in a Twyman-Green interferometer to improve fringe quality by removing multiple reflection. The basic principle and its performance are discussed.

  5. C&O Canal prism, with towpath (left) and fill under WM ...

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

    C&O Canal prism, with towpath (left) and fill under WM roadbed (right), milepost 142 vicinity, looking southwest. - Western Maryland Railway, Cumberland Extension, Pearre to North Branch, from WM milepost 125 to 160, Pearre, Washington County, MD

  6. Formation of CoS2 Nanobubble Hollow Prisms for Highly Reversible Lithium Storage.

    PubMed

    Yu, Le; Yang, Jing Fan; Lou, Xiong Wen David

    2016-10-17

    Metal-organic frameworks (MOFs) have been intensively used as the templates/precursors to synthesize complex hollow structures for various energy-related applications. Herein we report a facile two-step diffusion-controlled strategy to generate novel MOFs derived hierarchical hollow prisms composed of Nanosized CoS2 bubble-like subunits. Uniform zeolitic imidazolate framework-67 (ZIF-67) hollow prisms assembled by interconnected nanopolyhedra are first synthesized via a transformation process. Afterwards, these ZIF-67 building blocks are converted into CoS2 bubble-like hollow particles to form the complex hollow prisms through a sulfidation reaction with an additional annealing treatment. When evaluated as an electrode material for lithium-ion batteries, the as-obtained CoS2 nanobubble hollow prisms show remarkable electrochemical performance with good rate capability and long cycle life.

  7. Measurement of two-dimensional small angle deviation with a prism interferometer

    SciTech Connect

    Chatterjee, Sanjib; Kumar, Y. Pavan

    2008-09-20

    A new technique for the measurement of two-dimensional small angular deviation is presented. A compound prism, which effectively produces a combination of two right-angled prisms in orthogonal directions, and plane reference surfaces have been utilized for the measurement of the orthogonal components of the angular tilt of an incident plane wavefront. Each orthogonal component of the angular tilt is separately measured from the angular rotation of the resultant wedge fringes between two plane wavefronts generated due to splitting of the incident plane wavefront by the corresponding set of right-angled prism and plane reference surface. The technique is shown to have high sensitivity for the measurement of small angle deviation. A monolithic prism interferometer, which is practically insensitive to vibration, is also proposed. Results obtained for the measurement of a known tilt angle are presented.

  8. CONTROL OF LASER RADIATION PARAMETERS: Compact prisms for polarisation splitting of fibre laser beams

    NASA Astrophysics Data System (ADS)

    Davydov, B. L.; Yagodkin, D. I.

    2005-11-01

    Simple compact monoprisms for spatial splitting of polarised laser beams with relatively small diameters (no more than 1 mm) are considered. Prisms can be made of optically inactive CaCO3, α-BaB2O4 (α-BBO), LiIO3, LiNbO3, YVO4, and TiO2 crystals known in polarisation optics. The exact solution of the Snell equation for the extraordinary wave reflected from a surface arbitrarily tilted to its wave vector is obtained. The analysis of variants of the solution allows the fabrication of prisms with any deviation angles of the extraordinary wave by preserving the propagation direction of the ordinary wave. Three variants of prisms are considered: with minimised dimensions, with the Brewster output of the extraordinary beam, and with the deviation of the extraordinary wave by 90°. Calcite prisms with the deviation angles for the extraordinary beam ~19° and 90° are tested experimentally.

  9. Study on precision processing of L-form ZnSe deflect prism

    NASA Astrophysics Data System (ADS)

    Ye, Sizhe; Hui, Changshun; Zhang, Hao; Lu, Yongbin

    2016-10-01

    As the core component of optical system of Roll-Pitch seekers, the L-form ZnSe deflect prism is directly affecting the imaging quality of optical. For L-form defect prism's complex polyhedron plane structure and the feature of CVD ZnSe polycrystalline material, this paper propose one processing of single point diamond fly-cutting, analyze the transformation calculation method of each plane's coordinate. A kind of special clamp which ensure that all working surface of prism could be cut by once clamping is designed. Base on parameters of turning for CVD ZnSe , the deflect prisms are been processed, the measure result of angle error is below 12", the surface error (rms) reach 0.022λ, which satisfies the demand of manufacturing accuracy. It provide effective processing methods for optical parts with complex space.

  10. Evidence of light depolarization in grazing incidence germanium attenuated total reflection prisms.

    PubMed

    Rochat, Névine; Klymko, Nancy; Licitra, Christophe; Gambacorti, Narciso

    2011-09-01

    Attenuated total reflection (ATR) infrared absorption spectroscopy is a well-known vibrational spectroscopy technique for many different applications. In recent years this technique has been used to detect thin layer(s) lying on a solid substrate. Such a sample needs high pressure to ensure good optical contact between sample and prism and a p-polarization to enhance the signal to be detected. Such conditions have not been detailed in the literature regarding the effect of high pressure on the ATR measurement. This study shows the detrimental effect of high pressure on the ATR spectra. This effect is related to light depolarization induced by the germanium prism under high pressure. Moreover, the importance of polarizer position in the optical bench is highlighted. Indeed, due to the pressure-induced depolarization of the prism, the polarizer has to be placed before the prism to limit undesirable effects on the ATR spectrum baseline.

  11. Cavity Enhanced Absorption Spectroscopy Using a Broadband Prism Cavity and a Supercontinuum Source

    NASA Astrophysics Data System (ADS)

    Johnston, Paul S.; Lehmann, Kevin K.

    2009-06-01

    The multiplex advantage of current cavity enhanced spectrometers is limited by the high reflectivity bandwidth of the mirrors used to construct the high finesse cavity. Previously, we reported the design and construction of a new spectrometer that circumvents this limitation by utilizing Brewster^{,}s angle prism retroreflectors. The prisms, made from fused silica and combined with a supercontinuum source generated by pumping a highly nonlinear photonic crystal fiber, yields a spectral window ranging from 500 nm to 1750 nm. Recent progress in the instruments development will be discussed, including work on modeling the prism cavity losses, alternative prism material for use in the UV and mid-IR spectral regions, and a new high power supercontinuum source based on mode-locked picosecond laser.

  12. Does prism width from the shell prismatic layer have a random distribution?

    NASA Astrophysics Data System (ADS)

    Vancolen, Séverine; Verrecchia, Eric

    2008-10-01

    A study of the distribution of the prism width inside the prismatic layer of Unio tumidus (Philipsson 1788, Diss Hist-Nat, Berling, Lundæ) from Lake Neuchâtel, Switzerland, has been conducted in order to determine whether or not this distribution is random. Measurements of 954 to 1,343 prism widths (depending on shell sample) have been made using a scanning electron microscope in backscattered electron mode. A white noise test has been applied to the distribution of prism sizes (i.e. width). It shows that there is no temporal cycle that could potentially influence their formation and growth. These results suggest that prism widths are randomly distributed, and related neither to external rings nor to environmental constraints.

  13. Optics system design applying a micro-prism array of a single lens stereo image pair.

    PubMed

    Chen, Chien-Yue; Yang, Ting-Ting; Sun, Wen-Shing

    2008-09-29

    In this study we apply a micro-prism array technique to enable a single lens CCD to capture a stereo image for the simulation of double lens vision. A micro-prism array plate serves as the basis for design, which also improves the lightweight and portability of the overall system in addition to lowering the mass-production costs. Most important of all, this design possesses the characteristics of integration compatibility between general-purpose and video camera.

  14. Scale-model experiments of applying a Fresnel prism to greenhouse covering

    SciTech Connect

    Kurata, Kenji )

    1991-01-01

    Effects of applying a Fresnel prism to a south roof of an EW-oriented single-span greenhouse were studied using scale models and artificial light as well as under a natural light condition. The experiments confirmed the theoretical predictions that the application of a Fresnel prism increases the light transmissivity in winter and decreases it in summer. The experiments also revealed, however, large spatial variations of the light transmissivity in the greenhouse.

  15. The effect of a compliant accretionary wedge on earthquake rupture and tsunamigenesis

    NASA Astrophysics Data System (ADS)

    Lotto, Gabriel; Jeppson, Tamara; Dunham, Eric; Tobin, Harold

    2016-04-01

    The 11 March 2011 Tohoku megathrust earthquake ruptured through the shallowest part of the subduction zone boundary, resulting in tens of meters of displacement at the seafloor. This extreme shallow slip generated a devastating tsunami. The elastic properties of off-fault materials have an important role in determining slip along a fault. Laboratory ultrasonic velocity measurements performed on samples of rock obtained from the area surrounding the Tohoku earthquake principal fault zone during the Japan Trench Fast Drilling Project (JFAST) have shown that shallow off-fault materials are extremely compliant - P-wave velocities of 2.0-2.4 km/s, S-wave velocities of 0.7-1.0 km/s, and shear moduli ranging from 1.0-2.2 GPa. Seismic imaging around the JFAST drill site corroborates the presence of a compliant, low-velocity frontal prism at the toe of the hanging wall. This compliant wedge is likely a fairly robust feature across the horizontal extent of the Japan Trench and may have contributed to the large amount of displacement recorded. In order to investigate the impact of compliant off fault materials on earthquake rupture and tsunamigenesis, we employ a 2-D finite difference method that models the full seismic and tsunami wavefield associated with dynamic rupture on a dipping fault in a heterogeneous medium. Our numerical method rigorously couples the elastodynamic response of the solid Earth to that of a compressible ocean in the presence of gravity. Idealized models of subduction zone earthquakes show that the presence of a compliant wedge leads to increased slip, greater seafloor displacement, and a larger tsunami. However, preliminary results for a representative Tohoku geometry were not so simple; the compliant wedge enhanced slip and seafloor deformation but only in a localized zone, and tsunami height was not significantly affected. This surprising result indicates that the details of geometry and material structure we observe in real subduction zones are

  16. PrismTech Data Distribution Service Java API Evaluation

    NASA Technical Reports Server (NTRS)

    Riggs, Cortney

    2008-01-01

    My internship duties with Launch Control Systems required me to start performance testing of an Object Management Group's (OMG) Data Distribution Service (DDS) specification implementation by PrismTech Limited through the Java programming language application programming interface (API). DDS is a networking middleware for Real-Time Data Distribution. The performance testing involves latency, redundant publishers, extended duration, redundant failover, and read performance. Time constraints allowed only for a data throughput test. I have designed the testing applications to perform all performance tests when time is allowed. Performance evaluation data such as megabits per second and central processing unit (CPU) time consumption were not easily attainable through the Java programming language; they required new methods and classes created in the test applications. Evaluation of this product showed the rate that data can be sent across the network. Performance rates are better on Linux platforms than AIX and Sun platforms. Compared to previous C++ programming language API, the performance evaluation also shows the language differences for the implementation. The Java API of the DDS has a lower throughput performance than the C++ API.

  17. A prism based magnifying hyperlens with broad-band imaging

    NASA Astrophysics Data System (ADS)

    Habib, Md. Samiul; Stefani, Alessio; Atakaramians, Shaghik; Fleming, Simon C.; Argyros, Alexander; Kuhlmey, Boris T.

    2017-03-01

    Magnification in metamaterial hyperlenses has been demonstrated using curved geometries or tapered devices, at frequencies ranging from the microwave to the ultraviolet spectrum. One of the main issues of such hyperlenses is the difficulty in manufacturing. In this letter, we numerically and experimentally study a wire medium prism as an imaging device at THz frequencies. We characterize the transmission of the image of two sub-wavelength apertures, observing that our device is capable of resolving the apertures and producing a two-fold magnified image at the output. The hyperlens shows strong frequency dependent artefacts, a priori limiting the use of the device for broad-band imaging. We identify the main source of image aberration as the reflections supported by the wire medium and also show that even the weaker reflections severely affect the imaging quality. In order to correct for the reflections, we devise a filtering technique equivalent to spatially variable time gating so that ultra-broad band imaging is achieved.

  18. PRISM: A DATA-DRIVEN PLATFORM FOR MONITORING MENTAL HEALTH.

    PubMed

    Kamdar, Maulik R; Wu, Michelle J

    2016-01-01

    Neuropsychiatric disorders are the leading cause of disability worldwide and there is no gold standard currently available for the measurement of mental health. This issue is exacerbated by the fact that the information physicians use to diagnose these disorders is episodic and often subjective. Current methods to monitor mental health involve the use of subjective DSM-5 guidelines, and advances in EEG and video monitoring technologies have not been widely adopted due to invasiveness and inconvenience. Wearable technologies have surfaced as a ubiquitous and unobtrusive method for providing continuous, quantitative data about a patient. Here, we introduce PRISM-Passive, Real-time Information for Sensing Mental Health. This platform integrates motion, light and heart rate data from a smart watch application with user interactions and text entries from a web application. We have demonstrated a proof of concept by collecting preliminary data through a pilot study of 13 subjects. We have engineered appropriate features and applied both unsupervised and supervised learning to develop models that are predictive of user-reported ratings of their emotional state, demonstrating that the data has the potential to be useful for evaluating mental health. This platform could allow patients and clinicians to leverage continuous streams of passive data for early and accurate diagnosis as well as constant monitoring of patients suffering from mental disorders.

  19. How well proportioned are lens and prism spaces?

    NASA Astrophysics Data System (ADS)

    Aurich, R.; Lustig, S.

    2012-09-01

    The cosmic microwave background (CMB) anisotropies in spherical 3-spaces with a non-trivial topology are analysed with a focus on lens- and prism-shaped fundamental cells. The conjecture is tested that well-proportioned spaces lead to a suppression of large-scale anisotropies according to the observed CMB. The focus is put on lens spaces L(p, q) which are supposed to be oddly proportioned. However, there are inhomogeneous lens spaces whose shape of the Voronoi domain depends on the position of the observer within the manifold. Such manifolds possess no fixed measure of the well-proportioned property and allow a predestined test of the well-proportioned conjecture. Topologies having the same Voronoi domain are shown to possess distinct CMB statistics which thus provide a counter-example to the well-proportioned conjecture. The CMB properties are analysed in terms of cyclic subgroups Zp, and a new point of view for the superior behaviour of the Poincaré dodecahedron is found.

  20. Neural network interpretation of LWD data (ODP Leg 170) confirms complete sediment subduction at the Costa Rica convergent margin

    NASA Astrophysics Data System (ADS)

    Moritz, Erik; Bornholdt, Stefan; Westphal, Hildegard; Meschede, Martin

    2000-01-01

    The internal structure of a convergent plate boundary was the focus of ODP Leg 170 in 1996 at the subduction zone off Costa Rica. Although the structure of the subduction zone is rather well known from seismic surveys, prior to drilling of ODP Leg 170 it was a matter of discussion whether it is accretionary or non-accretionary. With a neural network approach, we confirm the evidence gained during drilling of Leg 170, that at least presently no lower-plate sediments are transferred to the upper plate by accretion. To supplement lithological information, Logging-While-Drilling geophysical data have been included in this study and were interpreted in terms of lithology using a genetically trained artificial neural network.

  1. Modelling the differential effects of prisms on perception and action in neglect.

    PubMed

    Leigh, Steven; Danckert, James; Eliasmith, Chris

    2015-03-01

    Damage to the right parietal cortex often leads to a syndrome known as unilateral neglect in which the patient fails to attend or respond to stimuli in left space. Recent work attempting to rehabilitate the disorder has made use of rightward-shifting prisms that displace visual input further rightward. After a brief period of adaptation to prisms, many of the symptoms of neglect show improvements that can last for hours or longer, depending on the adaptation procedure. Recent work has shown, however, that differential effects of prisms can be observed on actions (which are typically improved) and perceptual biases (which often remain unchanged). Here, we present a computational model capable of explaining some basic symptoms of neglect (line bisection behaviour), the effects of prism adaptation in both healthy controls and neglect patients and the observed dissociation between action and perception following prisms. The results of our simulations support recent contentions that prisms primarily influence behaviours normally thought to be controlled by the dorsal stream.

  2. Rhomboid prism pair for rotating the plane of parallel light beams

    NASA Technical Reports Server (NTRS)

    Orloff, K. L. (Inventor); Yanagita, H.

    1982-01-01

    An optical system is described for rotating the plane defined by a pair of parallel light beams. In one embodiment a single pair of rhomboid prisms have their respective input faces disposed to receive the respective input beams. Each prism is rotated about an axis of revolution coaxial with each of the respective input beams by means of a suitable motor and gear arrangement to cause the plane of the parallel output beams to be rotated relative to the plane of the input beams. In a second embodiment, two pairs of rhomboid prisms are provided. In a first angular orientation of the output beams, the prisms merely decrease the lateral displacement of the output beams in order to keep in the same plane as the input beams. In a second angular orientation of the prisms, the input faces of the second pair of prisms are brought into coincidence with the input beams for rotating the plane of the output beams by a substantial angle such as 90 deg.

  3. Application of derivative matrices of skew rays to design of compound dispersion prisms.

    PubMed

    Lin, Psang Dain

    2016-09-01

    Numerous optimization methods have been developed in recent decades for optical system design. However, these methods rely heavily on ray tracing and finite difference techniques to estimate the derivative matrices of the rays. Consequently, the accuracy of the results obtained from these methods is critically dependent on the incremental step size used in the tuning stage. To overcome this limitation, the present study proposes a comprehensive methodology for the design of compound dispersion prisms based on the first- and second-order derivative matrices of skew rays. The proposed method facilitates the analysis and design of prisms with respect to arbitrary system variables and provides an ideal basis for automatic prism design applications. Four illustrative examples are given. It is shown that the optical quantities required to evaluate the prism performance can be extracted directly from the proposed derivative matrices. In addition, it is shown in this study that the single-element 3D prism can have the same deviation angle and spectral dispersion as the 2D compound prism.

  4. Patients with homonymous hemianopia become visually qualified to drive using novel monocular sector prisms.

    PubMed

    Moss, Adam M; Harrison, Andrew R; Lee, Michael S

    2014-03-01

    Patients with homonymous hemianopia (HH) often fail to meet visual field (VF) requirements for a driver's license. We describe 2 patients with complete HH, who met the minimum VF requirements for driving using a novel, high-power, monocular sector prism system. Baseline VFs were assessed using automated and kinetic perimetry. Patients were fitted with glasses and press-on 57-PD peripheral monocular sector prisms placed on the lens ipsilateral to the VF defect above and below the visual axis with prisms oriented obliquely. Kinetic perimetry was reassessed both monocularly and binocularly, with and without prisms. The 2 patients had 95° and 82° angle of continuous, horizontal, binocular VF. With the use of the prism system, the binocular VF increased to 115° and 112° angles. Both patients reported improvement in quality of life and each holds a valid driver's license and has successfully operated a motor vehicle without any restrictions or accidents. These findings suggest that the addition of oblique 57-PD prisms to the ipsilateral spectacle lens above and below the visual axis for patients with complete HH can significantly increase horizontal VF, which may help an individual become visually qualified to obtain a driver's license.

  5. The effect of prism adaptation on the response AC/A ratio.

    PubMed

    Rainey, B B

    2000-05-01

    Vergence adaptation, also known as prism adaptation, is a phenomenon in which a patient's heterophoria changes after prolonged viewing through prism. The effect of prism adaptation on the accommodation-convergence relationship, quantified by the AC/A ratio, is not known. Previous studies of AC/A ratio stability and alterability have used only stimulus AC/A ratio calculations, or have measured accommodative responses to only one or two stimuli. The ideal study of AC/A ratio stability and alterability would measure accommodative responses to several accommodative stimuli, and use these along with vergence responses to calculate response AC/A ratios, rather than stimulus AC/A ratios. In addition, the gradient method should be used to avoid any effect of proximal vergence resulting from changes in target distance. This paper describes a project which investigated the effect of vergence (prism) adaptation on the gradient response AC/A ratio, using accommodative responses measured for five different accommodative stimuli. The response AC/A ratio did not significantly change following a period of adaptation to base-in prism for six of the eight subjects in this study. In addition, the response AC/A ratio did not significantly change following a period of adaptation to base-out prism for six of the eight subjects.

  6. Prism adaptation reverses the local processing bias in patients with right temporo-parietal junction lesions

    PubMed Central

    Rafal, Robert D.; List, Alexandra

    2009-01-01

    Lesions to the right temporo-parietal cortex commonly result in hemispatial neglect. Lesions to the same area are also associated with hyperattention to local details of a scene and difficulty perceiving the global structure. This local processing bias is an important factor contributing to neglect and may contribute to the higher prevalence of the disorder following right compared with left hemisphere strokes. In recent years, visuomotor adaptation to rightward-shifting prisms has been introduced as a promising treatment for hemispatial neglect. Explanations for these improvements have generally described a leftward realignment of attention, however, the present investigation provides evidence that prism adaptation reduces the local processing bias. Five patients with right temporal-parietal junction lesions were asked to identify the global or local levels of hierarchical figures before and after visuomotor adaptation to rightward-shifting prisms. Prior to prism adaptation the patients had difficulty ignoring the local elements when identifying the global component. Following prism adaptation, however, this pattern was reversed, with greater global interference during local level identification. The results suggest that prism adaptation may improve non-spatially lateralized deficits that contribute to the neglect syndrome. PMID:19416951

  7. Using Satellite Gravity to Map and Model Forearc Basins and Thickness of Trench Sediment Worldwide: Implications for Great Earthquakes

    NASA Astrophysics Data System (ADS)

    Blakely, R. J.; Scholl, D. W.; Wells, R. E.; von Huene, R.; Barckhausen, U.

    2006-12-01

    There is growing evidence that historic great earthquakes (M>8) favor segments of subduction zones that exhibit key geologic factors, such as high sediment influx into the trench (e.g., Ruff, 1989), the presence of young accretionary prisms (von Huene and Scholl, 1991), the presence of trench-slope forearc basins (Wells et al., 2003; Song and Simons, 2003), and the mineralogical structure of the upper plate. The USGS Tsunami Sources Working Group (http://walrus.wr.usgs.gov/tsunami/workshop/index.html) recently described and quantified these factors for all eastern Pacific subduction margins. Although the level of knowledge of subduction zones world-wide is highly uneven, free-air gravity anomalies observed at satellite altitudes provide a consistent measure of some of these geologic factors. Satellite gravity demonstrates, for example, that regions of greatest slip during past megathrust earthquakes around the circum-Pacific spatially correlate with forearc basins and their associated deep-sea terrace gravity lows, with amplitudes typically >20 mGal. Basins may evolve because interseismic subsidence, possibly linked to basal erosion of the forearc by the subducting plate, does not fully recover after earthquakes. By inference, therefore, forearc basin gravity lows should be predictors of the location of large moment release during future great earthquakes. Moreover, great earthquakes have a statistical propensity to occur at trenches with excess sediments, in contrast to trenches dominated by horst-and-graben bathymetry. After removing the effects of bathymetric depth, low densities associated with trench fill are evident in satellite gravity anomalies and thus permit identification of trench segments with high sediment influx. Additional studies using satellite gravity anomalies may lead to new avenues in understanding the geologic processes that accompany great megathrust earthquakes, but we must confirm the ability of satellite gravity data to serve as a

  8. Asymmetrical effects of adaptation to left- and right-shifting prisms depends on pre-existing attentional biases.

    PubMed

    Goedert, Kelly M; Leblanc, Andrew; Tsai, Sen-Wei; Barrett, Anna M

    2010-09-01

    Proposals that adaptation with left-shifting prisms induces neglect-like symptoms in normal individuals rely on a dissociation between the postadaptation performance of individuals trained with left- versus right-shifting prisms (e.g., Colent, Pisella, & Rossetti, 2000). A potential problem with this evidence is that normal young adults have an a priori leftward bias (e.g., Jewell & McCourt, 2000). In Experiment 1, we compared the line bisection performance of young adults to that of aged adults, who as a group may lack a leftward bias in line bisection. Participants trained with both left- and right-shifting prisms. Consistent with our hypothesis, while young adults demonstrated aftereffects for left, but not right prisms, aged adults demonstrated reliable aftereffects for both prisms. In Experiment 2, we recruited a larger sample of young adults, some of whom were right-biased at baseline. We observed an interaction between baseline bias and prism-shift, consistent with the results of Experiment 1: Left-biased individuals showed a reduced aftereffect when training with right-shifting prisms and right-biased individuals showed a reduced aftereffect when training with left-shifting prisms. These results suggest that previous failures to find generalizable aftereffects with right-shifting prisms may be driven by participants' baseline biases rather than specific effects of the prism itself.

  9. Plate Tectonics at 3.8-3.7 Ga: Field Evidence from the Isua Accretionary Complex, Southern West Greenland.

    PubMed

    Komiya; Maruyama; Masuda; Nohda; Hayashi; Okamoto

    1999-09-01

    A 1&rcolon;5000 scale mapping was performed in the Isukasia area of the ca. 3.8-Ga Isua supracrustal belt, southern West Greenland. The mapped area is divided into three units bounded by low-angle thrusts: the Northern, Middle, and Southern Units. The Southern Unit, the best exposed, is composed of 14 subunits (horses) with similar lithostratigraphy, bound by layer-parallel thrusts. Duplex structures are widespread in the Isua belt and vary in scale from a few meters to kilometers. Duplexing proceeded from south to north and is well documented in the relationship between link- and roof-thrusts. The reconstructed lithostratigraphy of each horse reveals a simple pattern, in ascending order, of greenstone with low-K tholeiitic composition with or without pillow lava structures, chert/banded iron-formation, and turbidites. The cherts and underlying low-K tholeiites do not contain continent- or arc-derived material. The lithostratigraphy is quite similar to Phanerozoic "oceanic plate stratigraphy," except for the abundance of mafic material in the turbidites. The evidence of duplex structures and oceanic plate stratigraphy indicates that the Isua supracrustal belt is the oldest accretionary complex in the world. The dominantly mafic turbidite composition suggests that the accretionary complex was formed in an intraoceanic environment comparable to the present-day western Pacific Ocean. The duplex polarity suggests that an older accretionary complex should occur to the south of the Isua complex. Moreover, the presence of seawater (documented by a thick, pillow, lava unit at the bottom of oceanic plate stratigraphy) indicates that the surface temperature was less than ca. 100 degrees C in the Early Archean. The oceanic geotherm for the Early Archean lithosphere as a function of age was calculated based on a model of transient half-space cooling at given parameters of surface and mantle temperatures of 100 degrees and 1450 degrees C, respectively, suggesting that the

  10. Preferential accumulation of gas hydrate in the Andaman accretionary wedge and relationship to anomalous porosity preservation

    NASA Astrophysics Data System (ADS)

    Rose, K.; Torres, M. E.; Johnson, J. E.; Hong, W.; Giosan, L.; Solomon, E. A.; Kastner, M.; Cawthern, T.; Long, P.; Schaef, T.

    2015-12-01

    In the marine environment, sediments in the gas hydrate stability zone often correspond to slope and basin settings. These settings are dominantly composed of fine-grained silt and clay lithofacies with typically low vertical permeability, and pore fluids frequently under-saturated with respect to methane. As a result, the pressure-temperature conditions requisite for a GHSZ to be present occur widely worldwide across marine settings, however, the distribution of gas hydrate in these settings is neither ubiquitous nor uniform. This study uses sediment core and borehole related data recovered by drilling at Site 17 in the Andaman Sea during the Indian National Gas Hydrate Program Expedition 1 in 2006, to investigate reservoir-scale controls on gas hydrate distribution. In particular, this study finds that conditions beyond reservoir pressure, temperature, salinity, and gas concentration, appear to influence the concentration of gas hydrate in host sediments. Using field-generated datasets along with newly acquired sedimentology, physical property, imaging and geochemical data with mineral saturation and ion activity products of key mineral phases such as amorphous silica and calcite, we document the presence and nature of secondary precipitates that contributed to anomalous porosity preservation at Site 17 in the Andaman Sea. This study demonstrates the importance of grain-scale subsurface heterogeneities in controlling the occurrence and distribution of concentrated gas hydrate accumulations in marine sediments, and document the importance that increased permeability and enhanced porosity play in supporting gas concentrations sufficient to support gas hydrate formation. This illustrates the complex balance and lithology-driven controls on hydrate accumulations of higher concentrations and offers insights into what may control the occurrence and distribution of gas hydrate in other sedimentary settings.

  11. Effect of prism adaptation on left dichotic listening deficit in neglect patients: glasses to hear better?

    PubMed

    Jacquin-Courtois, S; Rode, G; Pavani, F; O'Shea, J; Giard, M H; Boisson, D; Rossetti, Y

    2010-03-01

    Unilateral neglect is a disabling syndrome frequently observed following right hemisphere brain damage. Symptoms range from visuo-motor impairments through to deficient visuo-spatial imagery, but impairment can also affect the auditory modality. A short period of adaptation to a rightward prismatic shift of the visual field is known to improve a wide range of hemispatial neglect symptoms, including visuo-manual tasks, mental imagery, postural imbalance, visuo-verbal measures and number bisection. The aim of the present study was to assess whether the beneficial effects of prism adaptation may generalize to auditory manifestations of neglect. Auditory extinction, whose clinical manifestations are independent of the sensory modalities engaged in visuo-manual adaptation, was examined in neglect patients before and after prism adaptation. Two separate groups of neglect patients (all of whom exhibited left auditory extinction) underwent prism adaptation: one group (n = 6) received a classical prism treatment ('Prism' group), the other group (n = 6) was submitted to the same procedure, but wore neutral glasses creating no optical shift (placebo 'Control' group). Auditory extinction was assessed by means of a dichotic listening task performed three times: prior to prism exposure (pre-test), upon prism removal (0 h post-test) and 2 h later (2 h post-test). The total number of correct responses, the lateralization index (detection asymmetry between the two ears) and the number of left-right fusion errors were analysed. Our results demonstrate that prism adaptation can improve left auditory extinction, thus revealing transfer of benefit to a sensory modality that is orthogonal to the visual, proprioceptive and motor modalities directly implicated in the visuo-motor adaptive process. The observed benefit was specific to the detection asymmetry between the two ears and did not affect the total number of responses. This indicates a specific effect of prism adaptation on

  12. Northern Papua New Guinea: Structure and sedimentation in a modern arc-continent collision

    SciTech Connect

    Abbott, L.; Silver, E. )

    1990-05-01

    Northern Papua New Guinea and the Solomon Sea are the site of a modern oblique, arc-continent collision, which is progressing from northwest to southeast. By combining offshore seismic data from the Solomon Sea with geologic mapping in the Markham Valley area of northern Papua New Guinea the authors are predicting the outcome of this collision. The Huon Gulf is the present site of initial collision. Seismic profiles show this area is dominated by thin thrust sheets. Onshore, the bulk of the uplifted accretionary wedge is a melange with exotic blocks of a variety of lithologies. Structurally below the melange lies the Leron Formation composed of thick channelized sandstone and conglomerate. It dips north at approximately 40{degree} and is cut by several thrust fault with associated folds. Limestone blocks within the melange are reported to be 2 Ma, and Beryllium 10 anomalies from Bismarck arc volcanoes suggest that initial collision of the Finisterre block (375 km northwest of the present collision point) began no earlier than 3 Ma. This implies the collision is propagating laterally at about 125 km/m.y.. Large outcrops of basalt and gabbro within the melange suggest that segments of oceanic crust were incorporated into the accretionary wedge. Modern sedimentation within the collision zone grades from fluvial sediments in the Markham Valley to deep-water turbidites ponded behind a structural ridge near the point of incipient collision. The Markham submarine canyon occupies the collision front here, and efficiently erodes the accretionary wedge. This setting may serve as a modem analog for deposition of much of the Leron Formation which exhibits tremendous sediment reworking.

  13. Mechanisms for tectonic erosion of an accretionary complex in the d'Entrecasteaux Zone-New Hebrides Island arc collision zone

    SciTech Connect

    Collot, J.Y. ); Fisher, M.A. )

    1990-06-01

    In the southwest Pacific Ocean the d'Entrecasteaux Zone (DEZ) is an arcuate submarine mountain chain that collides with the central part of the New Hebrides island arc. The collision zone moves slowly (2.5 cm/yr) northward along the trench, owing to the small oblique angle between the DEZ and the azimuth of convergence. Extensive Seabeam bathymetry as well as single- and multichannel seismic reflection data were collected over both the collision zone and the accretionary wedge that lies south of this zone. These data indicate that the accretionary complex underwent considerable tectonic erosion in response to oblique subduction of the DEZ during the past 8 Ma. Simplified calculation indicates that the mean erosional rate of this complex is 800-900 km{sup 3}/Ma. The main mechanisms for tectonic erosion of the accretionary complex involve mass wasting and extensional tectonics. First, mobilization and mass wasting of accreted rocks result in overlapping slump masses that blanket the arc slope. Second, block sliding along an extensional detachment within accreted rocks strips off the upper (about 1 km) part of the accretionary complex. Third, as the DEZ moves northward, the accreted rocks in the wake of the DEZ lose support and collapse along large normal faults that trend oblique to the arc slope. An additional errosive mechanism involves the formation of a deep subcircular reentrant into the accretionary complex; the reentrant is believed to be a scar caused by the collision and subduction of a seamount. The reentrant cuts downward through the accreted rocks almost to the depth of the abyssal oceanic plain.

  14. Extended-Range Ultrarefractive 1D Photonic Crystal Prisms

    NASA Technical Reports Server (NTRS)

    Ting, David Z.

    2007-01-01

    by use of conventional prisms and diffraction gratings and is highly nonlinear.

  15. Highly Sideophile Element Abundance Constraints on the Nature of the Late Accretionary Histories of Earth, Moon and Mars

    NASA Technical Reports Server (NTRS)

    Walker, R. J.; Puchtel, I. S.; Brandon, A. D.; Horan, M. F.; James, O. B.

    2007-01-01

    The highly siderophile elements (HSE) include Re, Os, Ir, Ru, Pt and Pd. These elements are initially nearly-quantitatively stripped from planetary silicate mantles during core segregation. They then may be re-enriched in mantles via continued accretion sans continued core segregation. This suite of elements and its included long-lived radiogenic isotopes systems (Re-187 (right arrow) Os-187; Pt-190 (right arrow) Os-186) can potentially be used to fingerprint the characteristics of late accreted materials. The fingerprints may ultimately be useful to constrain the prior nebular history of the dominant late accreted materials, and to compare the proportion and genesis of late accretionary materials added to the inner planets. The past ten years have seen considerable accumulation of isotopic and compositional data for HSE present in the Earth's mantle, lunar mantle and impact melt breccias, and Martian meteorites. Here we review some of these data and consider the broader implications of the compiled data.

  16. Late Proterozoic evolution of the northern part of the Hamisana zone, northeast Sudan - Constraints on Pan-African accretionary tectonics

    NASA Technical Reports Server (NTRS)

    Miller, M. M.; Dixon, T. H.

    1992-01-01

    This paper describes deformation fabrics developed in the northern part of the Hamisana zone in northeast Sudan. New structural data are presented which establish a structural chronology that characterizes distinct events of accretion, folding, and thrust faulting and reactivation of accretion-related faults. The structural data point to an intraplate compressional origin for the Hamisana zone. A review of available isotopic age data is carried out, and it is concluded that Pan-African accretionary processes may have been analogous to Phanerozoic ophiolite and island arc accretion in the western North American Cordillera, where penetrative deformation occurred in response to periodic intraplate shortening events, rather than an ultimate collision of unrelated crustal fragments.

  17. Planar scanning method for detecting refraction characteristics of two-dimensional photonic quasi-crystal wedge-shaped prisms.

    PubMed

    Liu, Jianjun; Tan, Wei; Liu, Exian; Hu, Haili; Fan, Zhigang; Zhang, Tianhua; Zhang, Xiong

    2016-05-01

    In this study, a planar scanning method is proposed. This novel method adapts two monitors moving along double planar tracks that can be used to detect refraction characteristics of two-dimensional (2D) photonic quasi-crystal (PQC) wedge-shaped prisms. Refraction of a decagonal Penrose-type PQC prism is analyzed for a given incident beam and two polarization modes at different incident positions in the prism using this method. Refraction from the prism is irregular, indicating that nonuniformity in the arrangement of scatterers in the prism causes Bragg-like scattering irregularities. Numerical results show that this method can be used for guiding the design of a 2D PQC prism and for the analysis of its refraction characteristics.

  18. Field evidence for fault controlled intrusion of blue-schist-bearing melange into an accretionary wedge, Island Mountain, California

    SciTech Connect

    Lamons, R.

    1985-01-01

    Two lithologic units of the Franciscan are well exposed along a loop of the Eel River at Island Mountain. They are 1) zeolite or lower grade lithic graywackes, and 2) a 0.5 km wide band of black shaly melange containing blueschist, chert, greenstone, metagraywacke, and a graywacke-hosted copper deposit. Sedimentary features were not observed in the melange. The graywacke was subdivided on the basis of presence or absence of sodium-cobaltonitrate stained K-spar. Field relationships suggest that the blueschist-bearing melange was emplaced along steep NW-dipping faults in an accretionary wedge. Mapping of S. Jewett Rock and SW Lake Mountain quadrangles show narrow anastomosing bands of the melange following NW-trending faults. East of this band, graywackes without K-spar are folded along NW/SE axes. No folds were found to the west. Other Melange bands pinch out into faults which juxtapose graywackes of different facies. The sheared melange bands are not folded and shale beds in the graywacke show little shear so the melange bands are unlikely to be sheared olistostromes. The areal extent of graywacke is about ten times that of melange shales. Assuming this pattern continues laterally and at depth, the amount of ductile material in the melange is far less than that assumed by Cloos (1982) in his flow model for melange. The ductile melange may have been forced upward by metamorphically produced volatiles, or as a result of relative plate motion. It originated at depth, moved up along the top of a subducting slab, plucking clasts, then splayed upward into pre-existing faults in the accretionary wedge.

  19. Mud volcano field seaward of the Barbados Accretionary Complex: A deep-towed side scan sonar survey

    NASA Astrophysics Data System (ADS)

    Henry, Pierre; Le Pichon, Xavier; Lallemant, Siegfried; Foucher, Jean-Paul; Westbrook, Graham; Hobart, Michael

    1990-06-01

    A 30 km2 diapiric field has been identified near 13°50'N up to 12 km seaward of the deformation front of the Barbados accretionary complex. Using a deep-towed side scan sonar with a 3.5-kHz profiler, we identified 31 different diapiric structures. Based on seismic stratigraphy, we show that this field has been active for 200,000 years and that it is a transient feature triggered by the seaward propagation of the high pore fluid pressure associated with the décollement beneath the accretionary complex. Both basement and décollement in this area are anomalously shallow due to the presence of a N110° basement ridge. The height of the diapirs above seafloor does not exceed 40-50 m and can be related to the pressure head of the mud below the décollement. Two types of structures are identified: mud volcanoes and massively emplaced diapirs and ridges on the one hand, enigmatic circular very flat mud pies and conical mounds on the other hand. The second type of structures has steeper slopes and appears to be associated with very active venting, as confirmed by a submersible exploration reported in a companion paper (Le Pichon et al., this issue (b)). The venting results in the formation of a stiff carbonate crust and of large subsiding basins around the mud pies. Continuous active fluid expulsion through these structures indicates that an efficient piping system still connects them to the zone of anomalously high pore pressure below the protodécollement.

  20. Early Paleozoic accretionary orogenesis along northern margin of Gondwana constrained by high-Mg metaigneous rocks, SW Yunnan

    NASA Astrophysics Data System (ADS)

    Xing, Xiaowan; Wang, Yuejun; Cawood, Peter A.; Zhang, Yuzhi

    2015-12-01

    SW Yunnan of China constituted part of the northern margin of Gondwana facing the proto-Tethys ocean in the early Paleozoic. However, the evolution of the region and its relationship with the accretionary orogenism have been poorly established. This paper reports a set of new zircon U-Pb age data and whole-rock major oxides, elemental and Sr-Nd isotopic data for early Paleozoic metavolcanic rocks from the previously defined Lancang Group and reveals the development of an Ordovician suprasubduction zone in SW Yunnan. Zircon U-Pb ages of 462 ± 6 and 454 ± 27 Ma for two representative samples indicate eruption of the volcanic rocks in the Late Ordovician. Geochemical data for the metavolcanic rocks together with other available data indicate a calc-alkaline affinity with high Al2O3 (13.04-18.77 wt%) and low TiO2 (0.64-1.00 wt%). They have Mg-numbers ranging from 62 to 50 with SiO2 of 53.57-69.10 wt%, compositionally corresponding to the high-Mg andesitic rocks. They display enrichments in LREEs and LILEs with significant Eu negative anomalies (δEu = 0.20-0.33), and depletions in HFSEs, similar to arc volcanic rocks. Their initial 87Sr/86Sr ratios range from 0.721356 to 0.722521 and ɛNd(t) values from -7.63 to -7.62 with Nd model ages of 2.06-2.10 Ga. Integration of ages and geochemical data with available geological observations, we propose the presence of Ordovician magmatism related to proto-Tethyan evolution in SW Yunnan and the metaigneous rocks formed in an island-arc setting. They were part of a regional accretionary orogen that extended along the northern margin of Gondwana during Neoproterozoic to early Paleozoic period.

  1. Origin of Mineral Springs on the East Coast, North Island, NZ

    SciTech Connect

    Hunt, T.M.; Glover, R.B.

    1995-01-01

    Strongly mineralized waters emerge as warm and cold springs from parts of a Cenozoic accretionary prism which extends along the East Coast of the North Island. The chemistry of these waters is consistent with them having been derived from connate sea water in deeply-buried marine sediments and is distinct from springs in other parts of the prism and elsewhere in New Zealand. Most of these mineral springs are associated with three, long-wavelength, magnetic anomalies which modeling suggests are caused by deeply-buried ophiolite bodies within the prism or by seamounts on the top of the subducted Pacific Plate underlying the prism. It is postulated that these deep-seated bodies have facilitated the dewatering of marine sediments from deep within the prism or from the subducted plate. This ''devolved sea water'' has then risen, been modified by contact with overlying sediments and mixed with near-surface meteoric waters, before emerging at the mineral springs.

  2. XeCl excimer laser with new prism resonator configurations and its performance characteristics

    SciTech Connect

    Benerji, N. S. E-mail: bsingh@rrcat.gov.in; Singh, A.; Varshnay, N.; Singh, Bijendra E-mail: bsingh@rrcat.gov.in

    2015-07-15

    New resonator cavity configurations, namely, the prism resonator and unstable prism resonator, are demonstrated for the first time in an excimer (XeCl) laser with interesting and novel results. High misalignment tolerance ∼50 mrad is achieved with considerably reduced beam divergence of less than ∼1 mrad without reduction in output power capabilities of the laser. The misalignment tolerance of ∼50 mrad is a dramatic improvement of ∼25 times compared to ∼2 mrad normally observed in standard excimer laser with plane-plane cavity. Increase in depth of focus from 3 mm to 5.5 mm was also achieved in case of prism resonator configuration with an improvement of about 60%. Unstable prism resonator configuration is demonstrated here in this paper with further reduction in beam divergence to about 0.5 mrad using plano-convex lens as output coupler. The misalignment tolerance in case of unstable prism resonator was retained at about 30 mrad which is a high value compared to standard unstable resonators. The output beam spot was completely filled with flat-top profile with prism resonator configurations, which is desired for various material processing applications. Focusing properties and beam divergence in case of prism resonator have been investigated using SEM (scanning electron microscope) images. SEM images of the focused spot size (∼20 μm holes) on metal sheet indicate beam divergence of about 0.05 mrad which is about 1.5 times diffraction limit. Energy contained in this angle is thus sufficient for micro-machining applications. Clean and sharp edges of the micro-holes show high pointing stability with multiple shot exposures. Such characteristics of the excimer laser system will be extremely useful in micro-machining and other field applications.

  3. Adaptation to leftward-shifting prisms reduces the global processing bias of healthy individuals.

    PubMed

    Bultitude, Janet H; Woods, Jill M

    2010-05-01

    When healthy individuals are presented with peripheral figures in which small letters are arranged to form a large letter, they are faster to identify the global- than the local-level information, and have difficulty ignoring global information when identifying the local level. The global reaction time (RT) advantage and global interference effect imply preferential processing of global-level information in the normal brain. This contrasts with the local processing bias demonstrated following lesions to the right temporo-parietal junction (TPJ), such as those that lead to hemispatial neglect (neglect). Recent research from our lab demonstrated that visuo-motor adaptation to rightward-shifting prisms, which ameliorates many leftward performance deficits of neglect patients, improved the local processing bias of patients with right TPJ lesions (Bultitude, Rafal, & List, 2009). Here we demonstrate that adaptation to leftward-shifting prisms, which can induce neglect-like performance in neurologically healthy individuals, also reduces the normal global processing bias. Forty-eight healthy participants were asked to identify the global or local forms of hierarchical figures before and after adaptation to leftward- or rightward-shifting prisms. Prior to prism adaptation, both groups had greater difficulty ignoring irrelevant global information when identifying the local level (global interference) compared to their ability to ignore irrelevant local-level information when identifying the global level (local interference). Participants who adapted to leftward-shifting prisms showed a significant reduction in global interference, but there was no change in the performance of the rightward-shifting Prism Group. These results show, for the first time, that in addition to previously demonstrated effects on lateralised attention, prism adaptation can influence non-lateralised spatial attention in healthy individuals.

  4. PRISM: a web server and repository for prediction of protein–protein interactions and modeling their 3D complexes

    PubMed Central

    Baspinar, Alper; Cukuroglu, Engin; Nussinov, Ruth; Keskin, Ozlem; Gursoy, Attila

    2014-01-01

    The PRISM web server enables fast and accurate prediction of protein–protein interactions (PPIs). The prediction algorithm is knowledge-based. It combines structural similarity and accounts for evolutionary conservation in the template interfaces. The predicted models are stored in its repository. Given two protein structures, PRISM will provide a structural model of their complex if a matching template interface is available. Users can download the complex structure, retrieve the interface residues and visualize the complex model. The PRISM web server is user friendly, free and open to all users at http://cosbi.ku.edu.tr/prism. PMID:24829450

  5. Analytical models for the groundwater tidal prism and associated benthic water flux

    USGS Publications Warehouse

    King, Jeffrey N.; Mehta, Ashish J.; Dean, Robert G.

    2010-01-01

    The groundwater tidal prism is defined as the volume of water that inundates a porous medium, forced by one tidal oscillation in surface water. The pressure gradient that generates the prism acts on the subterranean estuary. Analytical models for the groundwater tidal prism and associated benthic flux are presented. The prism and flux are shown to be directly proportional to porosity, tidal amplitude, and the length of the groundwater wave; flux is inversely proportional to tidal period. The duration of discharge flux exceeds the duration of recharge flux over one tidal period; and discharge flux continues for some time following low tide. Models compare favorably with laboratory observations and are applied to a South Atlantic Bight study area, where tide generates an 11-m3 groundwater tidal prism per m of shoreline, and drives 81 m3 s −1 to the study area, which describes 23% of an observational estimate. In a marine water body, the discharge component of any oscillatory benthic water flux is submarine groundwater discharge. Benthic flux transports constituents between groundwater and surface water, and is a process by which pollutant loading and saltwater intrusion may occur in coastal areas.

  6. Digital Beam Steering Device Based on Decoupled Birefringent Prism Deflector and Polarization Rotator

    NASA Technical Reports Server (NTRS)

    Pishnyak, Oleg; Kreminska, Lyubov; Laventovich, Oleg D.; Pouch, John J.; Miranda, Felix A.; Winker, Bruce K.

    2004-01-01

    We describe digital beam deflectors (DBDs) based on liquid crystals. Each stage of the device comprises a polarization rotator and a birefringent prism deflector. The birefringent prism deflects the beam by an angle that depends on polarization of the incident beam. The prism can be made of the uniaxial smectic A (SmA) liquid crystal (LC) or a solid crystal such as yttrium orthovanadate (YVO4). SmA prisms have high birefringence and can be constructed in a variety of shapes, including single prisms and prismatic blazed gratings of different angles and profiles. We address the challenges of uniform alignment of SmA, such as elimination of focal conic domains. Rotation of linear polarization is achieved by an electrically switched twisted nematic (TN) cell. A DBD composed of N rotator-deflector pairs steers the beam into 2(sup N) directions. As an example, we describe a four-stage DBD deflecting normally incident laser beam within the range of +/- 56 mrad with 8 mrad steps. Redirection of the beam is achieved by switching the TN cells.

  7. Sufficient conditions for the avoidance of spectral dispersion in optical prisms.

    PubMed

    Lin, Ps