Science.gov

Sample records for convergent plate boundary

  1. Composite transform-convergent plate boundaries: description and discussion

    USGS Publications Warehouse

    Ryan, H.F.; Coleman, P.J.

    1992-01-01

    The leading edge of the overriding plate at an obliquely convergent boundary is commonly sliced by a system of strike-slip faults. This fault system is often structurally complex, and may show correspondingly uneven strain effects, with great vertical and translational shifts of the component blocks of the fault system. The stress pattern and strain effects vary along the length of the system and change through time. These margins are considered to be composite transform-convergent (CTC) plate boundaries. Examples are given of structures formed along three CTC boundaries: the Aleutian Ridge, the Solomon Islands, and the Philippines. The dynamism of the fault system along a CTC boundary can enhance vertical tectonism and basin formation. This concept provides a framework for the evaluation of petroleum resources related to basin formation, and mineral exploration related to igneous activity associated with transtensional processes. ?? 1992.

  2. The proximity of hotspots to convergent and divergent plate boundaries

    NASA Technical Reports Server (NTRS)

    Weinstein, Stuart A.; Olson, Peter L.

    1989-01-01

    An analysis of four different hotspot distributions, ranging from Morgan's (1972) original list of 19 to Vogt's (1981) list of 117 reveals that the hotspots are preferentially located near divergent plate boundaries. The probability of this proximity occurring by chance alone is quite remote, less than 0.01 for all four hotspot distributions. The same analysis also reveals that the hotspots are preferentially excluded from regions near convergent plate boundaries. The probability of this exclusion occurring by chance alone is 0.1 or less for three out of the four distributions examined. We interpret this behavior as being a consequence of the effects of large scale convective circulation on ascending mantle plumes. Mantle thermal plumes, the most probable source of hotspots, arise from instabilities in a basal thermal boundary layer. Plumes are suppressed from regions beneath convergent boundaries by descending flow and are entrained into the upwelling flow beneath spreading centers. Plate-scale convective circulation driven by subduction may also advect mantle thermal plumes toward spreading centers.

  3. Convergent Plate Boundary Processes in the Archean: Evidence from Greenland

    NASA Astrophysics Data System (ADS)

    Polat, A.

    2014-12-01

    The structural, magmatic and metamorphic characteristics of Archean greenstone belts and associated TTG (tonalite, trondhjemite and granodiorite) gneisses in southern West Greenland are comparable to those of Phanerozoic convergent plate margins, suggesting that Archean continents grew mainly at subduction zones. These greenstone belts are composed mainly of tectonically juxtaposed fragments of oceanic crust including mafic to ultramafic rocks, with minor sedimentary rocks. Volcanic rocks in the greenstone belts are characterized mainly by island arc tholeiitic basalts, picrites, and boninites. The style of deformation and geometry of folds in 10 cm to 5 m wide shear zones are comparable to those occur on 1 to 50 km scale in the greenstone belts and TTG gneisses, suggesting that compressional tectonic processes operating at convergent plate boundaries were the driving force of Archean crustal accretion and growth. Field observations and trace element data suggest that Archean continental crust grew through accretion of mainly island arcs and melting of metamorphosed mafic rocks (amphibolites) in thickened arcs during multiple tectonothermal events. Fold patterns on cm to km scale are consistent with at least three phases of deformation and multiple melting events generating TTG melts that intruded mainly along shear zones in accretionary prism and magmatic arcs. It is suggested that Archean TTGs were produced by three main processes: (1) melting of thickened oceanic island arcs; (2) melting of subducted oceanic crust; and (3) differentiation of basaltic melts originating from metasomatized sub-arc mantle wedge peridotites.

  4. Locking, mass flux and topographic response at convergent plate boundaries - the Chilean case

    NASA Astrophysics Data System (ADS)

    Oncken, Onno

    2016-04-01

    On the long term, convergent plate boundaries have been shown to be controlled by either accretion/underplating or by subduction erosion. Vertical surface motion is coupled to convergence rate - typically with an uplift rate of the coastal area ranging from 0 to +50% of convergence rate in accretive systems, and -20 to +30% in erosive systems. Vertical kinematics, however, are not necessarily linked to horizontal strain mode, i.e. upper plate shortening or extension, in a simple way. This range of kinematic behaviors - as well as their acceleration where forearcs collide with oceanic ridges/plateau - is well expressed along the Chilean plate margin. Towards the short end of the time scale, deformation appears to exhibit a close correlation with the frictional properties and geodetic locking at the plate interface. Corroborating analogue experiments of strain accumulation during multiple earthquake cycles, forearc deformation and uplift focus above the downdip and updip end of seismic coupling and slip and are each related to a particular stage of the seismic cycle, but with opposite trends for both domains. Similarly, barriers separating locked domains along strike appear to accumulate most upper plate faulting interseismically. Hence, locking patters are reflected in topography. From the long-term memory contained in the forearc topography the relief of the Chilean forearc seems to reflect long term stability of the observed heterogeneity of locking at the plate interface. This has fundamental implications for spatial and temporal distribution of seismic hazard. Finally, the nature of locking at the plate interface controlling the above kinematic behavior appears to be strongly controlled by the degree of fluid overpressuring at the plate interface suggesting that the hydraulic system at the interface takes a key role for the forearc response.

  5. Continental Collision and the STEP-wise Evolution of Convergent Plate Boundaries: The Mediterranean Region

    NASA Astrophysics Data System (ADS)

    Wortel, M. J.; Govers, R.; Spakman, W.

    2008-12-01

    This contribution focusses on terminal stage subduction, often triggered by continent-continent or arc- continent collision. The landlocked basin setting of the Mediterranean region provides unique opportunities to study terminal stage subduction and its consequences. We use seismic tomography results on lithosphere and upper mantle structure as a source of information on plate boundary structure, and concentrate on the lithospheric scale aspects. Combining this structural information with process-oriented numerical modelling studies and regional observations, we present a 3D model for convergent plate boundary evolution after collision, in which slab detachment and the formation of tear or STEP (Subduction-Transform-Edge-Propagator; see R. Govers and M.J.R. Wortel, EPSL, 236, 505- 523, 2005) faults are key elements. A STEP fault laterally decouples subducting lithosphere from non- subducting lithosphere in a scissor type of fashion. It enhances the ability of a slab to retreat through the mantle flow around the edge of the subducted slab. In this way collision and back-arc extension may occur in close proximity. In our study area this specifically pertains to collision along the north African margin, STEP formation in easterly direction, CCW rotation of the southern Apennines slab and the opening of the Tyrrhenian Sea. Vertical tearing of subducted lithosphere may play an important role as well, but is probably not crucial. Similar processes are likely to have occurred in the eastern Mediterranean. On the basis of the good agreement between the Mediterranean-based model and the evolution of the Tonga-Fiji region we expect that the model may shed light on other complex convergent plate boundary regions, as well. In summary: Upon continental (or arc-continent) collision, along-trench variations in lithospheric properties of the subducting lithosphere may lead to disruption and segmentation of the subduction system. Following slab detachment along limited segments of

  6. The role of near-trench extension at convergent plate boundaries

    NASA Astrophysics Data System (ADS)

    Vannucchi, P.

    2009-04-01

    Knowledge of how convergent plate boundary coupling in the seismogenic zone controls the nucleation of subduction zone earthquakes is fundamental to assess seismic risks. Increased data at convergent margins has revealed the complexity of the earthquake cycle through the detection of strain-release processes like episodic tremors and slip events, low frequency earthquakes, afterslip, slip heterogeneity along the fault plane. The processes controlling the earthquake cycle and their interactions are still far from being understood; improved understanding will require better characterization of the fault zone. Here we compare in-situ observations from two major subduction zones drilled by ODP and IODP (Costa Rica Trench and Nankai Trough) with a well-preserved fossil convergent plate boundary zone in the Northern Apennines of Italy. At all three sites, deformation in the region above and at the updip limit of the seismogenic zone is dominated by extension and normal faulting (i.e. maximum principal stress is oriented sub-vertically). Episodes of reverse shearing are also present, but occur with less intensity, alternating with extension. Ocean Drilling Program Legs 170 and 205 offshore Costa Rica provide structural observations of the frontal part of the upper plate and décollement at about 2 km from the trench. Analysis of drilled cores reveals the presence of normal faults cutting the frontal part of the upper plate. Normal faults are also seen from seismic reflection to develop along all the forearc (about 60 km from the trench). The décollement damage zone is a few tens of meters in width; it develops mainly within frontal prism material. A clear cm-thick fault core is observed 1.6 km from the trench. Both the upper plate and the décollement damage zone show the co-existence of two distinct fracturing processes in which extension fracturing is frequent in the upper part of the damage zone farthest from the fault core, while both extension and shear fracturing

  7. Plate convergence measured by GPS across the Sundaland/Philippine Sea Plate deformed boundary: the Philippines and eastern Indonesia

    NASA Astrophysics Data System (ADS)

    Rangin, C.; Le Pichon, X.; Mazzotti, S.; Pubellier, M.; Chamot-Rooke, N.; Aurelio, M.; Walpersdorf, Andrea; Quebral, R.

    1999-11-01

    The western boundary of the Philippine Sea (PH) Plate in the Philippines and eastern Indonesia corresponds to a wide deformation zone that includes the stretched continental margin of Sundaland, the Philippine Mobile Belt (PMB), extending from Luzon to the Molucca Sea, and a mosaic of continental blocks around the PH/Australia/Sunda triple junction. The GPS GEODYSSEA data are used to decipher the present kinematics of this complex area. In the Philippines, the overall scheme is quite simple: two opposing rotations on either side of the left-lateral Philippine Fault, clockwise to the southwest and counterclockwise to the northeast, transfer 55 per cent of the PH/Sundaland convergence from the Manila Trench to the northwest to the Philippine Trench to the southeast. Further south, 80 per cent of the PH/Sunda convergence is absorbed in the double subduction system of the Molucca Sea and less than 20 per cent along both continental margins of northern Borneo. Finally, within the triple junction area between the Sundaland, PH and Australia plates, from Sulawesi to Irian Jaya, preferential subduction of the Celebes Sea induces clockwise rotation of the Sulu block, which is escaping toward the diminishing Celebes Sea oceanic space from the eastward-advancing PH Plate. To the south, we identify an undeformed Banda block that rotates counterclockwise with respect to Australia and clockwise with respect to Sundaland. The kinematics of this block can be defined and enable us to compute the rates of southward subduction of the Banda block within the Flores Trench and of eastward convergence of the Makassar Straits with the Banda block. The analysis made in this paper confirms that this deformation is compatible with the eastward motion of Sundaland with respect to Eurasia determined by the GEODYSSEA programme but is not compatible with the assumption that Sundaland belongs to Eurasia, as was often assumed prior to this study.

  8. Seismicity at the convergent plate boundary offshore Crete, Greece, observed by an amphibian network

    NASA Astrophysics Data System (ADS)

    Becker, D.; Meier, T.; Bohnhoff, M.; Harjes, H.-P.

    2010-04-01

    We investigate microseismic activity at the convergent plate boundary of the Hellenic subduction zone on- and offshore south-eastern Crete with unprecedented precision using recordings from an amphibian seismic network. The network configuration consisted of up to eight ocean bottom seismometers as well as five temporary short-period and six permanent broadband stations on Crete and surrounding islands. More than 2,500 local and regional events with magnitudes up to M L = 4.5 were recorded during the time period July 2003-June 2004. The magnitude of completeness varies between 1.5 on Crete and adjacent areas and increases to 2.5 in the vicinity of the Strabo trench 100 km south of Crete. Tests with different localization schemes and velocity models showed that the best results were obtained from a probabilistic earthquake localization using a 1-D velocity model and corresponding station corrections obtained by simultaneous inversion. Most of the seismic activity is located offshore of central and eastern Crete and interpreted to be associated with the intracrustal graben system (Ptolemy and Pliny trenches). Furthermore, a significant portion of events represents interplate seismicity along the NNE-ward dipping plate interface. The concentration of seismicity along the Ptolemy and Pliny trenches extends from shallow depths down to the plate interface and indicates active movement. We propose that both trenches form transtensional structures within the Aegean plate. The Aegean continental crust between these two trenches is interpreted as a forearc sliver as it exhibits only low microseismic activity during the observation period and little or no internal deformation. Interplate seismicity between the Aegean and African plates forms a 100-km wide zone along dip from the Strabo trench in the south to the southern shore-line of Crete in the north. The seismicity at the plate contact is randomly distributed and no indications for locked zones were observed. The plate

  9. Holocene turbidites reveal earthquake supercycles at a slow convergence plate boundary (Northern Algeria)

    NASA Astrophysics Data System (ADS)

    Ratzov, Gueorgui; Cattaneo, Antonio; Babonneau, Nathalie; Yelles, Karim; Bracene, Rabah; Lateb, Tassadite; Déverchere, Jacques

    2014-05-01

    Ongoing evidence for earthquake clustering calls upon records over numerous earthquake cycles to improve seismic hazard assessments, especially at places where recurrence times overstep historical records. Here, we show that meaningful information of large earthquakes recurrence intervals over several seismic cycles may be obtained using turbidite record offshore the Algerian margin. The Africa-Eurasia plate boundary is slowly convergent (~3mm/yr), with deformation in the investigated margin segment accommodated mainly onland, along thrusts and strike-slip faults. Historically, two relatively large earthquakes stroke the area in 1954 (Orléansville M6.7) and 1980 (El Asnam M7.3). Holocene turbidites emplaced offshore are triggered by thirteen earthquakes. Most of them tune to paleoseismic record of the El Asnam fault onland, whereas two are slightly diachronous (<100 yrs), and likely result from bursts of activity on nearby faults. Turbidites depict a bimodal distribution over ~8 kyrs that support the concepts of earthquake supercycles and rupture synchronization between nearby faults. Thirteen coastal paleoquakes underpin clusters of 3 to 6 events with mean recurrence intervals of ~300-600 years, separated by two periods of quiescence of ~1.7 ka without major events on any fault. They imply alternation of broad phases of strain loading and shorter phases of strain release along the fault network. More generally, our results demonstrate that fault slip rates are time-dependent and that earthquake occurrence might be strain-predictable rather than time- or slip-predictable. Turbidite paleoseismology investigation is ongoing on an adjacent margin segment where the Boumerdes M6.9 earthquake occurred in 2003. Preliminary results retrieved the traces of historical earthquakes, and established Holocene time-series. They support a similar bimodal seismic distribution, suggesting that earthquake supercycling should be a major strain release process along the Africa

  10. The behavior of a convergent plate boundary - Crustal deformation in the South Kanto district, Japan

    NASA Technical Reports Server (NTRS)

    Scholz, C. H.; Kato, T.

    1978-01-01

    The northwesternmost part of the Sagami trough, a part of the Philippine Sea-Eurasian plate boundary, was ruptured during the great South Kanto earthquake in 1923. Very extensive and frequent geodetic measurements of crustal deformation have been made in the South Kanto district since the 1890's, and these constitute the most complete data set on crustal movements in the world. These data were reanalyzed and interpreted and according to our interpretation indicate the following sequence of events. The coseismic movements were due to oblique thrust and right lateral slip of about 8 m on a fault outcropping at the base of the Sagami trough. This was followed by postseismic deformation resulting from reversed afterslip of 20-60 cm that occurred at an exponentially decaying rate in time. The interseismic deformation is produced by steady subduction at a rate of about 1.8 cm/yr. During subduction the top 10-15 km of the plate boundary is apparently locked, while deeper parts slip aseismically at an irregular rate. No significant precursory deformation was observed. The recurrence time for 1923 type earthquakes is 200-300 years. The Boso and Miura peninsulas are broken into a series of fault-bound blocks that move semi-independently of the surrounding region. The subduction zone itself, where it is exposed on land, is shown to be a wide zone encompassing several faults that are active at different times.

  11. Focal Mechanisms at the convergent plate boundary in Southern Aegean, Greece.

    NASA Astrophysics Data System (ADS)

    Moshou, Alexandra; Papadimitriou, Eleftheria; Drakatos, George; Evangelidis, Christos; Karakostas, Vasilios; Vallianatos, Filippos; Makropoulos, Konstantinos

    2014-05-01

    Greece is characterized by high seismicity, mainly due to the collision between the European and the African lithospheric plates and the dextral strike slip motion along the North Anatolia Fault zone and North Aegean Trough. The subduction of the Eastern Mediterranean oceanic plate along the Hellenic Arc under the Aegean microplate along with the accompanied roll back of the descending slab is considered the main tectonic feature of the region (Papazachos and Comninakis 1971; Makropoulos and Burton 1984; Papazachos et al. 2000a, b). The divergent motion between the Aegean block and mainland Europe is indicated by an extension zone in the northern Aegean, with Crete and Aegean diverging from mainland Europe at a rate of about 3.5 cm yr-1 with Africa moving northward relative to Europe at a rate of about 1 cm yr-1 (Dewey et al., 1989; Papazachos et al., 1998; Mc-Clusky et al., 2000; Reilinger et al., 2006). In this tectonically complicated area diverge types of deformation are manifested, in addition to the dominant subduction processes. Aiming to shed more light in the seismotectonic properties and faulting seismological data from the Hellenic Unified Seismological Network (HUSN) were selected and analyzed for determining focal mechanisms using the method of moment tensor inversion, additional to the ones being available from the routine moment tensor solutions and several publications. Thus, 31 new fault plane solutions for events with magnitude M>4.0, are presented in this study, by using the software of Ammon (Randall et al., 1995). For this scope the data from at least 4 stations were used with an adequate azimuthal coverage and with an epicentral distance not more than 350 km. The preparation of the data includes the deconvolution of instruments response, then the velocity was integrated to displacement and finally the horizontal components were rotated to radial and transverse. Following, the signal was inverted using the reflectivity method of Kennett (1983

  12. Links between crustal melting, plate boundary forces, and syn-convergent exhumation in the Sierras Pampeanas, Argentina

    NASA Astrophysics Data System (ADS)

    Mulcahy, S. R.; Roeske, S.; McClelland, W.; Jourdan, F.; Renne, P. R.; Vervoort, J. D.; Vujovich, G. I.

    2011-12-01

    Transitions from convergence to extension during an orogenic cycle result from the dynamic interaction between plate bounding forces, the thermal and rheologic evolution of the lithosphere, and contrasts in gravitational potential energy within an orogen. The presence of melt in the middle and lower crust, in particular, exerts a profound effect on the rheology of orogenic belts and in facilitating a change from convergence to extension and orogenic collapse. Determining whether or not melting was as an effective driving mechanism of extension within a given orogen requires accurately constraining the timing and duration of melting in the crust with respect to plate convergence, crustal thickening, and lithospheric extension. The Sierras Pampeanas of northwest Argentina record the transition from a Cambrian convergent margin to an Ordovician collisional orogen with the accretion of the allochthonous Precordillera terrane. Regional convergence associated with Famatina arc magmatism initiated as a result of east dipping subduction by ˜515-495 Ma and the majority of arc magmatism occurred from ˜485 to 465 Ma. Initial collision of the Precordillera terrane with the Famatina arc margin began by ~470 Ma and the terrane had fully collided by the Late Ordovician (˜458-449 Ma). Syn-convergent extension within the Sierra de Pie de Palo initiated at middle to lower crustal depths at ~436 Ma and continued through ~417 Ma. We present new U-Pb zircon and sphene, Lu-Hf garnet, and 40Ar/39Ar amphibole and mica ages and thermobarometry from lower crustal granulite facies migmatites of the Loma de Las Charcas. These data, coupled with existing regional isotopic ages and one-dimensional thermal modeling, suggest that: 1) regional peak granulite facies metamorphism occurred at ~465 Ma with near isothermal temperatures of ~850° C from ~5-12 kb within the Famatina arc; 2) Ordovician melts remained at temperatures above their solidus for 20-30 million years following peak granulite

  13. The Role of Serpentinites at Convergent Plate Boundaries: Using New Discoveries to Facilitate the Learning of Major Earth Processes

    NASA Astrophysics Data System (ADS)

    Ryan, J. G.

    2010-12-01

    A benefit of integrating a vital educational enterprise into a cutting-edge funded research initiative is the ability to bring new scientific discoveries quickly into the classroom without being bound to the textbook publication cycle. A key objective the MARGINS Data in the Classroom project was to facilitate the discovery-to-the-classroom transition of knowledge through the development of Web-deliverable, modular MARGINS “Mini-Lessons”. Some 34 Mini-Lessons are available for classroom use at http://serc.carleton.edu/margins/collection.html, and the development of new Mini-Lessons is a listed Education/Outreach priority of the successor GeoPRISMS Program. An important discovery that arose from the MARGINS Subduction Factory Initiative was the recognition that serpentinites - metamorphically hydrated products of ultramafic rocks rich in serpentine group minerals - are significant constituents of both the mantle wedge and downgoing plate. Serpentines are interesting mineralogically because of their distinctive physical properties, habits and appearance; and for their close affinities with olivine and Mg-rich pyroxenes. Given that serpentines primarily form through the hydration of olivine or Mg-rich pyroxenes, serpentinites constitute a reservoir of subduction-related H2O and entrained trace species in modified mantle rocks of the wedge or slab. As well, serpentine group minerals are interesting rheologically because, as sheet silicates, they can behave in a plastic fashion in rocks that are undergoing deformation, and can thus flow along faults in response to deforming stresses, or be easily entrained in fault rock assemblages along a subduction thrust. Two different MARGINS Mini-Lessons address the issue of serpentinite in subduction zone settings, focusing primarily on the observed occurrences of serpentinite seamounts in the forearc regions of the Mariana subduction system, a MARGINS Subduction Factory Focus Site, and their geochemical and geodynamic

  14. Investigating the deformation of upper crustal faults at the N-Chilean convergent plate boundary at different scales using high-resolution topography datasets and creepmeter measurements

    NASA Astrophysics Data System (ADS)

    Ewiak, O.; Victor, P.; Ziegenhagen, T.; Oncken, O.

    2012-04-01

    The Chilean convergent plate boundary is one of the tectonically most active regions on earth and prone to large megathrust earthquakes as e. g. the 2010 Mw 8.8 Maule earthquake which ruptured a mature seismic gap in south-central Chile. In northern Chile historical data suggests the existence of a seismic gap between Arica and Mejillones Peninsula (MP), which has not ruptured since 1877. Further south, the 1995 Mw 8.0 Antofagasta earthquake ruptured the subduction interface between MP and Taltal. In this study we investigate the deformation at four active upper plate faults (dip-slip and strike-slip) located above the coupling zone of the subduction interface. The target faults (Mejillones Fault - MF, Salar del Carmen Fault - SCF, Cerro Fortuna Fault - CFF, Chomache Fault - CF) are situated in forearc segments, which are in different stages of the megathrust seismic cycle. The main question of this study is how strain is accumulated in the overriding plate, what is the response of the target faults to the megathrust seismic cycle and what are the mechanisms / processes involved. The hyper arid conditions of the Atacama desert and the extremely low erosion rates enable us to investigate geomorphic markers, e .g. fault scarps and knickpoints, which serve as a record for upper crustal deformation and fault activity about ten thousands years into the past. Fault scarp data has been acquired with Differential-GPS by measuring high-resolution topographic profiles perpendicular to the fault scarps and along incised gullies. The topographic data show clear variations between the target faults which possibly result from their position within the forearc. The surveyed faults, e. g. the SCF, exhibit clear along strike variations in the morphology of surface ruptures attributed to seismic events and can be subdivided into individual segments. The data allows us to distinguish single, composite and multiple fault scarps and thus to detect differences in fault growth initiated

  15. The seismotectonics of plate boundaries

    NASA Technical Reports Server (NTRS)

    Berger, J.; Brune, J. N.; Goodkind, J.; Wyatt, F.; Agnew, D. C.; Beaumont, C.

    1981-01-01

    Research on the seismotectonics of plate boundaries is summarized. Instrumental development and an observational program designed to study various aspects of the seismotectonics of southern California and the northern Gulf of California are described. A unique superconducting gravimeter was further developed and supported under this program for deployment and operation at several sites. Work on Earth tides is also discussed.

  16. Flat plate puncture test convergence study.

    SciTech Connect

    Snow, Spencer; Ammerman, Douglas James; Molitoris, David; Tso, Chi-Fung; Yaksh, Mike

    2010-10-01

    The ASME Task Group on Computational Mechanics for Explicit Dynamics is investigating the types of finite element models needed to accurately solve various problems that occur frequently in cask design. One type of problem is the 1-meter impact onto a puncture spike. The work described in this paper considers this impact for a relatively thin-walled shell, represented as a flat plate. The effects of mesh refinement, friction coefficient, material models, and finite element code will be discussed. The actual punch, as defined in the transport regulations, is 15 cm in diameter with a corner radius of no more than 6 mm. The punch used in the initial part of this study has the same diameter, but has a corner radius of 25 mm. This more rounded punch was used to allow convergence of the solution with a coarser mesh. A future task will be to investigate the effect of having a punch with a smaller corner radius. The 25-cm thick type 304 stainless steel plate that represents the cask wall is 1 meter in diameter and has added mass on the edge to represent the remainder of the cask. The amount of added mass to use was calculated using Nelm's equation, an empirically derived relationship between weight, wall thickness, and ultimate strength that prevents punch through. The outer edge of the plate is restrained so that it can only move in the direction parallel to the axis of the punch. Results that are compared include the deflection at the edge of the plate, the deflection at the center of the plate, the plastic strains at radius r=50 cm and r=100 cm , and qualitatively, the distribution of plastic strains. The strains of interest are those on the surface of the plate, not the integration point strains. Because cask designers are using analyses of this type to determine if shell will puncture, a failure theory, including the effect of the tri-axial nature of the stress state, is also discussed. The results of this study will help to determine what constitutes an adequate

  17. Numerical comparison of different convergent plate contacts: subduction channel and subduction fault

    NASA Astrophysics Data System (ADS)

    De Franco, Roberta; Govers, Rob; Wortel, Rinus

    2007-10-01

    At convergent plate boundaries, the properties of the actual plate contact are important for the overall dynamics. Convergent plate boundaries both mechanically decouple and link tectonic plates and accommodate large amounts of strain. We investigate two fundamental physical states of the subduction contact: one based on a fault and the other based on a subduction channel. Using a finite element method, we determine the specific signatures of both states of the subduction contact. We pay particular attention to the overriding plate. In a tectonic setting of converging plates, where the subducting plate is freely moving, the subduction channel reduces compression relative to the fault model. In a land-locked basin setting, where the relative motion between the far field of the plates is zero, the subduction channel model produces tensile stress regime in the overriding plate, even though the amount of slab roll-back is small. The fault model shows a stronger development of slab roll-back and a compressive stress regime in the upper plate. Based on a consistent comparison of fault and channel numerical models, we find that the nature of the plate contact is one of the controlling factors in developing or not of backarc extension. We conclude that, the type of plate contact plays a decisive role in controlling the backarc state of stress. To obtain backarc extension, roll-back is required as an underling geodynamic process, but it is not always a sufficient condition.

  18. The nature and location of the plate boundary between the Anatolian and African plates

    NASA Astrophysics Data System (ADS)

    deǧer Özbakır, Ali; Wortel, Rinus; Govers, Rob

    2010-05-01

    Overall convergence of the African, Arabian and Eurasian plates, and the westward escape of Anatolia has resulted in an evolving plate boundary zone since the Miocene. In the Eastern Mediterranean, the current location and nature of the plate boundary between the Anatolian and the African plates is difficult to trace due to the scattered crustal earthquakes, and the absence of deeper earthquakes. In this study we aim to better constrain the nature and the location of the plate boundary. GPS-derived velocity field and stresses from earthquake mechanism solutions comprise the datasets which short time scale (elastic) models can be compared to. We model the stresses and deformation on the overriding plate by incorporating convergence of Africa and Arabia towards stable Eurasia, and rollback of the Hellenic trench. Investigation of the plate boundary consists of constraining the directions of motions over the segments which make up the boundary. We assume various types and locations for the plate boundary within the observational limits. We use a spherical plane stress finite element model to test these possibilities. We find that stresses and displacements are sensitive to both the location and the nature of the plate boundary. We obtain the minimum misfit with the data in a model where we assume the following: (1) the segment between Hellenic and the Cyprus arcs have both down-dip and fault parallel motions, (2) the connection between the Cyprus arc and Arabia--Eurasia collision zone is pure strike-slip. In all our models, an extra pull force on Anatolia is required to explain the high velocities in southwest Anatolia. This force may be related to return flow around the lateral edge of the Aegean slab.

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

    NASA Technical Reports Server (NTRS)

    Stein, S.; Gordon, R. G.

    1984-01-01

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

  20. The Rivera-Cocos Plate Boundary Revisited

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

    The nature of the boundary between the Rivera and Cocos plates has long been controversial. Early studies (predominantly earthquake studies) suggested that it was a NE oriented left lateral transform boundary. With the collection of multi-beam bathymetric data during the SEAMAT cruise of the N/O Jean Charcot in 1987 it became clear that this early proposal was not entirely correct as no clear transform morphology was observed. Shortly after the SEAMAT campaign, three main proposals emerged to explain this lack of transform morphology. The first two proposals favored the results of earthquake studies over the new multibeam data. The first proposed that the boundary is indeed a left-lateral transform boundary, you just cannot see it. In other words, it was a diffuse boundary and the resolution of the multi-beam data was not sufficient to reveal the associated deformation. The second proposal was that it was an east-west oriented, dextral transform, the proposal being based on the results of an earthquake directivity analysis. The third proposal favored the morphologic data over the earthquake data and proposed that the plate boundary was not a transform boundary, but was instead a divergent boundary, at least near the Middle America Trench in what is now called the EL Gordo Graben. Implicit in this proposal was that the earthquake activity did not reflect plate motions but rather were the result of local stresses. Since 2002, several marine geophysical campaigns have been conducted in the area of the Rivera-Cocos plate boundary with the aim of resolving this debate. During the 2002 BART and FAMEX campaigns of the N/O L'ATALANTE, multibeam bathymetric and seafloor backscatter data were collected along the boundary. During the MARTIC04 and MARTIC05 campaigns of the B/O EL PUMA dense total field magnetic surveys were conducted covering the entire plate boundary. Lastly, the multibeam coverage obtained during the BART/FAMEX campaigns was extended northward during the

  1. BOLIVAR & GEODINOS: Investigations of the Southern Caribbean Plate Boundary

    NASA Astrophysics Data System (ADS)

    Levander, A.; Schmitz, M.; Working Groups, B.

    2006-12-01

    The southern Caribbean-South American plate boundary has many similarities to California's San Andreas system: 1) The CAR-SA system consists of a series of strands of active right lateral strike-slip faults extending >1000 km from the Antilles subduction zone. This system has several names and includes the El Pilar, Coche, San Sebastian, Moron, and Oca faults. 2) The CAR-SA relative velocity has been about 20 mm/yr of mostly right lateral motion since about 55 Ma, giving a total displacement on the CAR-SA plate boundary similar to that of the San Andreas system. 3) The plate boundary has about 10% convergence in western SA, with less as one moves eastward due to relative convergence between North and South America. 4) The CAR-SA system has fold and thrust belts best developed continentward of the strike-slip faults, similar to the San Andreas. 5) There is a big bend in the CAR plate boundary at approximately the same distance from the Antilles trench as the big bend in Southern California is from the Cascadia subduction zone. The tectonic origins of the CAR-SA plate boundary and the San Andreas are very different, however, despite the similarities between the systems. Rather than impingement of a ridge on a trench, the CAR-SA system is thought to have resulted from a continuous oblique collision of the southern end of a Cretaceous island arc system with the northern edge of South America. During this process the CAR island arc and the modern CAR plate overrode a proto-Caribbean plate and destroyed a Mesozoic passive margin on the northern edge of SA. BOLIVAR and GEODINOS are multi-disciplinary investigations of the lithosphere and deeper structures associated with the diffuse CAR-SA plate boundary zone. We review a number of observations regarding the plate boundary obtained or confirmed from these studies: 1) The Caribbean Large Igneous Province, being overridden by the Maracaibo block in western Venezuela, can be identified beneath Aruba and coastal Venezuela

  2. Seismotectonic constraints on the convergence rate between the Rivera and North American plates

    NASA Astrophysics Data System (ADS)

    Kostoglodov, Vladimir; Bandy, William

    1995-09-01

    There are two significantly different types of models for the convergence rate between the Rivera and North American plates. The first type, the high-rate model (Bandy, 1992), predicts convergence rates of approximately 5.0 cm/yr near the southern end of the Rivera-North America subduction zone and between 2.0 and 3.0 cm/yr at its northern end. In contrast, the second type, the low-rate model (e.g., DeMets and Stein, 1990), predicts convergence rates of between 2.0 and 3.3 cm/yr near the southern end of the Rivera-North America subduction zone and between 0.6 and 1.7 cm/yr at its northern end. Seismotectonic relationships, which relate seismic characteristics of subduction zones (maximum magnitudes, maximum seismic depths, etc.) to plate tectonic parameters (convergence rates, age of the oceanic lithosphere, etc.) provide a means of distinguishing between the two different models. Three such relationships suggest that the Rivera-North American and Cocos-North American convergence rates should be roughly equal across the Rivera-Cocos plate boundary, favoring the high-rate model. Employing the high-rate model, one can evaluate the magnitude and distribution of the strike-slip component of forearc motion, Vss, produced by oblique convergence between the Rivera and North American plates. The analysis indicates both a progressive increase and clockwise reorientation of Vss northwestward along the plate contact zone of the Rivera-North America subduction zone. Such a distribution in Vss should produce a northwestward movement of and NW-SE oriented extension within the interior of the Jalisco Block, consistent with previous proposals of Jalisco Block motions. Also, such a distribution in Vss should produce a slight clockwise rotation of the Jalisco Block in the vicinity of Bahia de Banderas, consistent with paleomagnetic data.

  3. Turbulent boundary layer over a convergent and divergent superhydrophobic surface

    NASA Astrophysics Data System (ADS)

    Nadeem, Muhammad; Hwang, Jinyul; Sung, Hyung Jin

    2015-11-01

    Direct numerical simulation (DNS) of spatially developing turbulent boundary layer (TBL) over a convergent and divergent superhydrophobic surface (SHS) was performed. The convergent and divergent SHS was aligned in the streamwise direction. The SHS was modeled as a pattern of slip and no-slip surfaces. For comparison, DNS of TBL over a straight SHS was also carried out. The momentum thickness Reynolds number was varied from 800 to 1400. The gas fraction of the convergent and divergent SHS was the same as that of the straight SHS, keeping the slip area constant. The slip velocity in the convergent SHS was higher than that of the straight SHS. An optimal streamwise length of the convergent and divergent SHS was obtained. The convergent and divergent SHS gave more drag reduction than the straight SHS. The convergent and divergent SHS led to the modification of near wall-turbulent structures, resembling the narrowing and widening streaky structures near the wall. The convergent and divergent SHS had a relatively larger damping effect on near-wall turbulence than the straight SHS. These observations will be further analyzed statistically to demonstrate the effect of the convergent and divergent SHS on the interaction of inner and outer regions of TBL.

  4. Shock wave convergence in water with parabolic wall boundaries

    SciTech Connect

    Yanuka, D.; Shafer, D.; Krasik, Ya.

    2015-04-28

    The convergence of shock waves in water, where the cross section of the boundaries between which the shock wave propagates is either straight or parabolic, was studied. The shock wave was generated by underwater electrical explosions of planar Cu wire arrays using a high-current generator with a peak output current of ∼45 kA and rise time of ∼80 ns. The boundaries of the walls between which the shock wave propagates were symmetric along the z axis, which is defined by the direction of the exploding wires. It was shown that with walls having a parabolic cross section, the shock waves converge faster and the pressure in the vicinity of the line of convergence, calculated by two-dimensional hydrodynamic simulations coupled with the equations of state of water and copper, is also larger.

  5. Plate boundary segmentation in the northeastern Caribbean from geodetic measurements and Neogene geological observations

    NASA Astrophysics Data System (ADS)

    Calais, Éric; Symithe, Steeve; Mercier de Lépinay, Bernard; Prépetit, Claude

    2016-01-01

    The Caribbean-North America plate boundary in the northeastern Caribbean shows a remarkable example of along-strike transition from plate boundary-normal subduction in the Lesser Antilles, oblique subduction with no strain partitioning in Puerto Rico, and oblique subduction/collision with strain partitioning further west in Hispaniola. We show that this segmentation is well marked in the interseismic strain, as measured using space geodetic data, and in the Neogene deformation regime, as derived from geological observations. Hence, interseismic segmentation, which reproduces the geological segmentation persistent over a long time interval, is inherited from the geological history and long-term properties of the plate boundary. This result is relevant to the assessment of seismic hazard at convergent plate boundaries, where geodetic measurements often show interseismic segmentation between fully-and partially-coupled plate interface regions.

  6. Lateral straining of turbulent boundary layers. Part 2. Streamline convergence

    NASA Astrophysics Data System (ADS)

    Panchapakesan, N. R.; Nickels, T. B.; Joubert, P. N.; Smits, A. J.

    1997-10-01

    Experimental measurements are presented showing the effects of streamline convergence on developing turbulent boundary layers. The longitudinal pressure-gradient in these experiments is nominally zero so the only extra rate-of-strain is the lateral convergence. Measurements have been made of mean flow and turbulence quantities at two different Reynolds numbers. The results show that convergence leads to a significant reduction in the skin-friction and an increase in the boundary layer thickness. There are also large changes in the Reynolds stresses with reductions occurring in the inner region and some increase in the outer flow. This is in contrast to the results of Saddoughi & Joubert (1991) for a diverging flow of the same included angle and zero pressure-gradient which show much smaller changes in the stresses and an approach to equilibrium. A new non-dimensional parameter, [beta]D, is proposed to characterize the local effect of the convergence and it is shown how this parameter is related to Clauser's pressure-gradient parameter, [beta]x. It is suggested that this is an equilibrium parameter for turbulent boundary layers with lateral straining. In the present flow case [beta]D increases rapidly with streamwise distance leading to a significant departure from equilibrium. Measurement of terms in the transport equations suggest that streamline convergence leads to a reduction in production and generation and large increases in mean advection. The recovery of the flow after the removal of convergence has been shown to be characterized by a significant increase in the turbulent transport of shear-stress and turbulent kinetic energy from the very near-wall region to the flow further out where the stresses have been depleted by convergence.

  7. The Arabia-India plate boundary unveiled

    NASA Astrophysics Data System (ADS)

    Fournier, M.; Chamot-Rooke, N. R.; Rodriguez, M.; Petit, C.; Huchon, P.; Beslier, M.; Hazard, B.

    2009-12-01

    Since the advent of Plate Tectonics, tectonic plate boundaries were explored on land as at sea for search of active faults where the destructive energy of earthquakes is released. Yet, some plate boundaries, less active or considered as less dangerous to humankind, escaped general attention and remained unknown to a large extent. Among them, the boundary between two major tectonic plates: Arabia and India. The Arabia-India motion is currently accommodated along the Owen Fracture Zone (OFZ) in the NW Indian Ocean, which connects the spreading centers of the Sheba and Carlsberg ridge system to the Makran subduction zone. We recently surveyed this fracture zone onboard the R/V Beautemps-Beaupré (Owen Cruise, March 2009) using a high-resolution deep-water multibeam echo-sounder. Bathymetric data reveal a spectacular submarine fault system running over a distance of 800 km between the Arabia-India-Somalia triple junction to the south and the Dalrymple Trough to the north. The morphology of the active faults is well preserved on the seafloor where fault scarps can be followed over hundreds of kilometres. The surficial trace of the faults is not obscured by the sediments of the aggrading deep-sea fan of the Indus River. The fault system is segmented in five main segments connected by pull apart basins. The length of the individual, apparently uninterrupted, segments is between 100 km and 220 km. The largest pull-apart basin at the latitude 20°N (20°N-Basin) corresponds to a right step-over of about 12 km between two fault segments. The 20°N-Basin is bounded by a normal fault scarp with a throw of 450-500 m. Numerous minor normal faults cutting the floor of the basin attest to recent activity. The 20°N-Basin is directly supplied in turbidity-current deposits by an active channel of the Indus fan. The preservation of tectonic features indicates that the dip-slip motion has exceeded the rate of burial by sediments. Some compressional structures are also deduced from

  8. A new plate boundary in the Ionian Sea

    NASA Astrophysics Data System (ADS)

    Polonia, Alina; Torelli, Luigi; Artoni, Andrea; Bortoluzzi, Giovanni; Faccenna, Claudio; Ferranti, Luigi; Gasperini, Luca; Govers, Rob; Monaco, Carmelo; Neri, Giancarlo; Orecchio, Barbara; Rinus Wortel, M. J.

    2014-05-01

    The Calabrian Arc (CA) is a narrow and arcuate subduction system resulting from Africa/Eurasia plate convergence and slab rollback in the Tyrrhenian region. The very slow present-day plate convergence suggests a decrease in subduction efficiency, but underplating may still be active in the central CA where GPS data suggests an outward motion of Calabria relative to Apulia. Shortening in the accretionary wedge is taken up along the outer deformation front and out-of-sequence thrust faults (splay faults). Transtensive deformation accounts for margin segmentation along transfer tectonics systems bounding different margin segments. Transfer faults represent the shallow expression of deeply rooted processes at the slab edge. One of these structures is the NNW-SSE trending transtensive STEP (Slab Transfer Edge Propagator) fault system located East of the Malta Escarpment from the Alfeo seamount to the Etna volcano. Margin segmentation occurs along a second NW-SE trending crustal discontinuity delimiting two distinct lobes of the subduction complex close to the Messina Straits region. The Western Lobe (WL) of the subduction complex, offshore Sicily, is a down-dropped and very low tapered (about 1.5° ) wedge detaching on the base of the Messinian evaporites. The Eastern Lobe (EL), in front of Central Calabria, shows a more elevated accretionary wedge, steeper topographic slopes, higher deformation rates and a deeper basal detachment. High resolution tomographic images suggest a strong interplay between structural development and slab dynamics: the WL corresponds to areas where the slab is detached, while beneath the EL the slab is continuous. Newly acquired geophysical data (Urania cruise, October 2013), reveal that the deformation zone between the two lobes of the accretionary wedge displays fresh seafloor scarps and mud volcanoes suggesting it represents an active tectonic boundary and a deep fluid/mud conduit. We propose that this discontinuity is a new plate boundary

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

    SciTech Connect

    Cronin, V.S. )

    1990-05-01

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

  10. Western Irian Jaya: The end-product of oblique plate convergence in the late tertiary

    NASA Astrophysics Data System (ADS)

    Dow, D. B.; Sukamto, R.

    1984-06-01

    The island of New Guinea is the surface expression of the deformed northern margin of the Australian continental block: to the south undeformed continental crust is overlain by flat-lying platform sediments that form a conformable sequence from late Palaeozoic to late Tertiary. Along the New Guinea Cordillera these platform sediments have been tightly folded and overthrust to the south as a result of crustal shortening caused by convergence between the Australian Plate and the Pacific Plate. The earth movements resulting from this convergence started at the end of the Miocene and continue to the present day. It is postulated that all the major structures of western Irian Jaya were caused by this orogeny and can be explained by the convergence directed southwest-northeast, between the Australian and Pacific plates. It is further postulated that the convergence has remained essentially constant since the start of the earth movements. This convergence is consistent with that postulated in the Circum-Pacific Plate Tectonic Map (AAPG, 1981) of 12.5 cm/yr directed about 15° south of west, only if the effects of the Sorong-Yapen fault system are taken into account. This complex, east-west-trending fault system forms the southern boundary of the Pacific Plate and has responded to the convergence by left-lateral strike-slip displacement of at least 370 km since the late Miocene. As a consequence, south of the Sorong-Yapen fault system the convergence has been directed more to the south i.e. at least 45° south of west. In this region south of the fault zones, the north-south component of the convergence has been accommodated in the east by folding and overthrusting over a wide zone of interaction called the New Guinea Mobile Belt (Dow, 1977). In the west on the other hand, the Australian continental crust has been a stable buttress (Kepala Burung, Fig. 2) which, following convergence, has protruded into the Pacific Plate. Its northeastern margin has therefore been exposed

  11. Origin of production gases from convergent plate margins

    SciTech Connect

    Jeffrey, A.W.A.; Poreda, R.J.; Gwilliam, W.J.; Kaplan, I.R.; Craig, H.

    1987-05-01

    Molecular and isotopic composition of hydrocarbon production gases from four convergent plate margins have been measured. New Zealand is represented by two gases from the Taranaki basin in the back arc of the active Tonga-Kermadec subduction system. Gases from Barbados and Taiwan are from forearc locations in the active Lesser Antilles system and relict northern Manila Trench system. Philippine gases from offshore Palawan are associated with the Palawan Trough. Gases from Taiwan, the Maiu field in New Zealand, and the Nido field in Palawan have very high /sup 3/He//sup 4/He ratios, indicating considerable mantle input of helium to the gas reservoirs. Variations in /sup 3/He//sup 4/He ratios in neighboring fields are quite striking and suggest localized sources for the mantle components. Possible sources include shallow igneous bodies and fractures or faults tapping a direct mantle source. Measurements of helium isotope ratios in hydrocarbon production gases have been compiled and show a striking association of mantle helium with gases from subduction zones in contrast to deep subsided or rifted sedimentary basins. The dynamics of the subduction process, involving the interaction of upper mantle and crustal rocks, is apparently responsible for the injection of volatile mantle components into reservoired gases. Current exploration techniques are based on maturation and gas migration theories developed from the study of subsiding sedimentary basins. At convergent margins, such technique may have to be amended to include the effects of subduction dynamics on the source, maturation, and migration of hydrocarbons.

  12. Plate tectonics beyond plate boundaries: the role of ancient structures in intraplate orogenesis

    NASA Astrophysics Data System (ADS)

    Heron, Philip; Pysklywec, Russell; Stephenson, Randell

    2015-04-01

    The development of orogens that occur at a distance from plate boundaries (i.e., `intraplate' deformation) cannot be adequately explained through conventional plate tectonic theory. Intraplate deformation infers a more complex argument for lithospheric and mantle interaction than plate tectonic theory allows. As a result, the origins of intraplate orogenesis are enigmatic. One hypothesis is the amalgamation of continental material (i.e., micro-plates) leaves inherent scars on the crust and mantle lithosphere. Previous studies into continent-continent collisions identify a number of scenarios from accretionary tectonics that affect the crust and mantle (namely, the development of a Rayleigh-Taylor instability, lithospheric underplating, lithospheric delamination, and lithospheric subduction). Any of these processes may weaken the lithosphere allowing episodic reactivation of faults within continental interiors. Hence, continental convergence (i.e., shortening) at a time after continental collision may cause the already weakened crust and mantle lithosphere to produce intraplate deformation. In order to better understand the processes involved in deformation away from plate boundaries, we present suites of continental shortening models (using the high-resolution thermal-mechanical modelling code SOPALE) to identify the preferred style of deformation. We model ancient structures by applying weak subduction scarring, changing the rheological conditions, and modifying the thermal structure within the lithosphere. To highlight the role of surface processes on plate and lithosphere deformation, the effect of climate-driven erosion and deposition on the tectonic structure of intraplate deformation is also addressed. We explore the relevance of the models to previously studied regions of intraplate orogenesis, including the Pyrenees in Europe, the Laramide orogen in North America, Tien Shan orogen in Central Asia, and Central Australia. The findings of the simulations with

  13. Crustal deformation and volcanism at active plate boundaries

    NASA Astrophysics Data System (ADS)

    Geirsson, Halldor

    Most of Earth's volcanoes are located near active tectonic plate boundaries, where the tectonic plates move relative to each other resulting in deformation. Likewise, subsurface magma movement and pressure changes in magmatic systems can cause measurable deformation of the Earth's surface. The study of the shape of Earth and therefore studies of surface deformation is called geodesy. Modern geodetic techniques allow precise measurements (˜1 mm accuracy) of deformation of tectonic and magmatic systems. Because of the spatial correlation between tectonic boundaries and volcanism, the tectonic and volcanic deformation signals can become intertwined. Thus it is often important to study both tectonic and volcanic deformation processes simultaneously, when one is trying to study one of the systems individually. In this thesis, I present research on crustal deformation and magmatic processes at active plate boundaries. The study areas cover divergent and transform plate boundaries in south Iceland and convergent and transform plate boundaries in Central America, specifically Nicaragua and El Salvador. The study is composed of four main chapters: two of the chapters focus on the magma plumbing system of Hekla volcano, Iceland and the plate boundary in south Iceland; one chapter focuses on shallow controls of explosive volcanism at Telica volcano, Nicaragua; and the fourth chapter focuses on co- and post-seismic deformation from a Mw = 7.3 earthquake which occurred offshore El Salvador in 2012. Hekla volcano is located at the intersection of a transform zone and a rift zone in Iceland and thus is affected by a combination of shear and extensional strains, in addition to co-seismic and co-rifting deformation. The inter-eruptive deformation signal from Hekla is subtle, as observed by a decade (2000-2010) of GPS data in south Iceland. A simultaneous inversion of this data for parameters describing the geometry and source characteristics of the magma chamber at Hekla, and

  14. The transpressive tectonics and large earthquake distribution along the plate boundary in North Africa

    NASA Astrophysics Data System (ADS)

    Meghraoui, Mustapha; Pondrelli, Silvia

    2010-05-01

    The Tell Atlas and Rif Mountains of northern Africa have been the site of several large and moderate seismic events in the last decades. However, the thrust and fold system of NW Algeria experienced the largest earthquakes in the last centuries along the Africa-Eurasia plate boundary. This shallow seismic activity was very often associated with surface faulting and deformation as for the Mw 7.3 El Asnam (10/10/1980) and the Mw 6.8 Zemmouri-Boumerdes (21/05/2003) earthquakes. We study the active tectonics along the plate boundary in North Africa from the seismicity database, individual large and moderate earthquakes, the seismic moment tensor summation, the geodetic measurements (GPS and InSAR) and the structural and kinematic of active faults. Neotectonic structures and significant seismicity (Mw>5) indicate that coeval east-west trending right-lateral faulting and NE-SW thrust-related folding result from the oblique convergence at the plate boundary. A simple modeling of block tectonics suggests that transpression and block rotation govern the mechanics of the Africa - Eurasia plate boundary in the Tell Atlas and Rif Mountains. The tectonic restraining bend of NW Algeria combined with the ~ 5 mm/yr convergence between Africa and Eurasia justify the large seismic activity on the thrust and fold system of the Tell Atlas and the relatively passive active deformation along the adjacent sections of the plate boundary.

  15. Prototypical Concepts and Misconceptions of Plate Tectonic Boundaries

    NASA Astrophysics Data System (ADS)

    Sibley, D. F.; Patino, L. C.

    2003-12-01

    Students of geology encounter many prototypical/exemplar concepts* that include representative, but not necessarily defining, features and characteristics. This study of students' prototypical representations of plate tectonic boundaries indicates that their representations are rich sources of information about their misconceptions about plate tectonics. After lectures in plate tectonics and mountain building, 353 students in a general education geology class were asked to draw a continent-continent convergent boundary. For this study, a correct answer is defined as having the major features in correct proportions as depicted in the plate boundary diagrams on the USGS web. Fifty-two percent of the drawings were either incorrect or incomplete such that they could not be interpreted. Only 48% were readily interpretable, and of these 22% drew the boundary correctly, showing a thickening of crust where two continents collide. Thirty-three percent drew the boundary showing concave slabs of continental crust as one might imagine two pieces of firm rubber pushed together on a rigid surface and 45% depicted mountains as one might imagine inverted ice cream cones on a rigid plank. Twenty-one senior class geology majors and graduate students were given the same assignment. Forty-eight percent rendered a correct drawing, whereas 38% drew the same ice cream cone on a plank type picture that 45% of the general education students drew. In a second class of 12 geology majors, only 1 student drew a cross section of a continent-ocean boundary similar to standard representation. Four of 12 drew mountains on the top of continental crust over a subduction zone but did not draw a compensating mass within the crust or lithosphere. Prototypical drawings provide more information about students' concepts than do most multiple-choice questions. For example, sixty-two percent of theses students who drew mountains similar to foam rubber pads pushed together on a desk or ice cream cones on a

  16. Models for rupture mechanics of plate boundaries and crustal deformation

    NASA Astrophysics Data System (ADS)

    Nur, A.

    1983-02-01

    The role of pull aparts and pushups in transcurrent systems, the rotation of faults and blocks within transcurrent fault systems, the role of accretion tectonics in plate boundary deformation, and power law creep behavior and the yielding at plate boundaries were investigated.

  17. Simulating faults and plate boundaries with a transversely isotropic plasticity model

    NASA Astrophysics Data System (ADS)

    Sharples, W.; Moresi, L. N.; Velic, M.; Jadamec, M. A.; May, D. A.

    2016-03-01

    In mantle convection simulations, dynamically evolving plate boundaries have, for the most part, been represented using an visco-plastic flow law. These systems develop fine-scale, localized, weak shear band structures which are reminiscent of faults but it is a significant challenge to resolve the large- and the emergent, small-scale-behavior. We address this issue of resolution by taking into account the observation that a rock element with embedded, planar, failure surfaces responds as a non-linear, transversely isotropic material with a weak orientation defined by the plane of the failure surface. This approach partly accounts for the large-scale behavior of fine-scale systems of shear bands which we are not in a position to resolve explicitly. We evaluate the capacity of this continuum approach to model plate boundaries, specifically in the context of subduction models where the plate boundary interface has often been represented as a planar discontinuity. We show that the inclusion of the transversely isotropic plasticity model for the plate boundary promotes asymmetric subduction from initiation. A realistic evolution of the plate boundary interface and associated stresses is crucial to understanding inter-plate coupling, convergent margin driven topography, and earthquakes.

  18. Dynamics of diffuse oceanic plate boundaries: insensitivity to rheology

    NASA Astrophysics Data System (ADS)

    Zatman, Stephen; Gordon, Richard G.; Mutnuri, Kartik

    2005-07-01

    Diffuse plate boundaries, which are zones of deformation hundreds to thousands of kilometres wide, occur in both continental and oceanic lithosphere. Here, we build on our prior work in which we described analytic approximations to simple dynamical models that assume that the vertically averaged viscous force resisting deformation in diffuse oceanic plate boundaries (DOPBs) is described by either a linear Newtonian viscous rheology or a yield-stress (high-exponent power-law) rheology. An important observation is that the poles of relative rotation of adjacent component plates tend to lie in the diffuse plate boundary that separates them. A key cause of this tendency is that a faster spin is needed to balance a component of torque through the middle of a diffuse plate boundary than to balance an equal component of torque lying 90° from the middle of the diffuse boundary. The strength of that tendency depends on rheology, however, with the tendency being stronger for a yield-stress rheology than for a Newtonian viscous rheology. For the special case of the pole of rotation lying outside of and along the strike of the boundary, these large differences can be simply explained in terms of the distribution of boundary-perpendicular normal forces acting across the boundary. In the Newtonian case, the distribution of forces has an along-strike gradient that can balance a component of torque about the middle of the boundary, while in the yield-stress case, the distribution of forces has zero along-strike gradient and cannot balance a component of torque about the middle of the diffuse plate boundary. To expand our analysis to intermediate power laws of geophysical interest (i.e. power-law exponents of 3 to 30), as well as to investigate more thoroughly the behaviour for a high-exponent power law, we numerically integrate the force distribution to obtain the torques. Results for intermediate power laws resemble the yield-stress rheology much more than they resemble the

  19. The Plate Boundary Observatory Borehole Seismic Network

    NASA Astrophysics Data System (ADS)

    Hasting, M.; Eakins, J.; Anderson, G.; Hodgkinson, K.; Johnson, W.; Mencin, D.; Smith, S.; Jackson, M.; Prescott, W.

    2006-12-01

    As part of the NSF-funded EarthScope Plate Boundary Observatory, UNAVCO will install and operate 103 borehole seismic stations throughout the western United States. These stations continuously record three- component seismic data at 100 samples per second, using Geo-Space HS-1-LT 2-HZ geophones in a sonde developed by SONDI and Consultants (Duke University). Each seismic package is connected to an uphole Quanterra Q330 data logger and Marmot external buffer, from which UNAVCO retrieves data in real time. UNAVCO uses the Antelope software suite from Boulder Real-Time Technologies (BRTT) for all data collection and transfer, metadata generation and distribution, and monitoring of the network. The first stations were installed in summer 2005, with 19 stations installed by September 2006, and a total of 28 stations expected by December 2006. In a prime example of cooperation between the PBO and USArray components of EarthScope, the USArray Array Network Facility (ANF), operated by UC San Diego, handled data flow and network monitoring for the PBO seismic stations in the initial stages of network operations. We thank the ANF staff for their gracious assistance over the last several months. Data flow in real time from the remote stations to the UNAVCO Boulder Network Operations Center, from which UNAVCO provides station command and control; verification and distribution of metadata; and basic quality control for all data. From Boulder, data flow in real time to the IRIS DMC for final quality checks, archiving, and distribution. Historic data are available from June 2005 to the present, and are updated in real time with typical latencies of less than ten seconds. As of 1 September 2006, the PBO seismic network had returned 60 GB of raw data. Please visit http://pboweb.unavco.org for additional information on the PBO seismic network.

  20. Study on plate silencer with general boundary conditions

    NASA Astrophysics Data System (ADS)

    Liu, Gongmin; Zhao, Xiaochen; Zhang, Wenping; Li, Shuaijun

    2014-09-01

    A plate silencer consists of an expansion chamber with two side-branch rigid cavities covered by plates. Previous studies showed that, in a duct, the introduction of simply supported or clamped plates into an air conveying system could achieve broadband quieting from low to medium frequencies. In this study, analytical formulation is extended to the plate silencer with general boundary conditions. A set of static beam functions, which are a combination of sine series and third-order polynomial, is employed as the trial functions of the plate vibration velocity. Greens function and Kirchhoff-Helmholtz integral are used to solve the sound radiation in the duct and the cavity, and then the vibration velocity of the plate is obtained. Having obtained the vibration velocity, the pressure perturbations induced by the plate oscillation and the transmission loss are found. Optimization is carried out in order to obtain the widest stopband. The transmission loss calculated by the analytical method agrees closely with the result of the finite element method simulation. Further studies with regard to the plate under several different classical boundary conditions based on the validated model show that a clamped-free plate silencer has the worst stopband. Attempts to release the boundary restriction of the plate are also made to study its effect on sound reflection. Results show that a softer end for a clamped-clamped plate silencer helps increase the optimal bandwidth, while the same treatment for simply supported plate silencer will result in performance degradation.

  1. Analysis of plate spin motion and its implications for strength of plate boundary

    NASA Astrophysics Data System (ADS)

    Matsuyama, Takeshi; Iwamori, Hikaru

    2016-02-01

    In this study, we investigate the driving forces of plate motion, especially those of plate spin motion, that are related to the toroidal components of the global plate velocity field. In previous works, numerical simulations of mantle convection have been used to examine the extent to which toroidal velocity components are naturally generated on the surface, by varying key parameters, notably the rheological properties of plates and plate boundaries. Here, we take the reverse approach and perform analyses of observed plate motions, which show an increase in the toroidal/poloidal ratio at high degrees of spherical harmonic expansion, as well as a rapid change in the plate spin rate and the estimated driving stress around a critical plate size of approximately 1000 km. This quantitative relationship constrains the strength at plate boundaries to 3-75 MPa, which is consistent with several seismological observations, including those from the NE Japan arc associated with the 2011 Tohoku earthquake.

  2. Seismotectonics of the eastern Himalayan and indo-burman plate boundary systems

    NASA Astrophysics Data System (ADS)

    Kumar, Ajay; Mitra, Supriyo; Suresh, G.

    2015-11-01

    The eastern Himalayan and Indo-Burman plate boundary systems are distinct from the rest of the India-Eurasia continental collision, due to oblique convergence across two orthogonal plate boundaries resulting in a zone of distributed deformation both within and away from the plate boundary. To understand the seismotectonics of this region, we model the source mechanism of 44 earthquakes using waveform inversion and combine them with source mechanism of 30 previously studied earthquakes. Depth distribution of these earthquakes reveal that the entire crust beneath northeast India is seismogenic. From spatial distribution and source mechanism it is evident that the N20°E convergence between India and Tibet is accommodated by N-S convergence and E-W subduction. The N-S convergence is accommodated through (a) shallow thrust earthquakes within the eastern Himalayan wedge, (b) lower crustal thrust earthquakes along the northern edge of Shillong Plateau, (c) lower crustal dextral strike-slip earthquakes in the Kopili fault zone, and (d) sinistral strike-slip earthquakes within the Bengal Basin crust. The E-W subduction results in shallow thrust earthquakes to intermediate depth strike-slip earthquakes and deep focus thrust earthquakes underneath the Indo-Burman convergence zone. Orientation of the fault plane and slip vectors point to downdip extension and along arc compression of the subducted Indian plate in response to slab pull forces and buckling at depth. Earthquake slip vectors are in good agreement with the GPS velocity vectors across northeast India and conforms to the clockwise rotating "microplates" model.

  3. Shells on a Sphere: Tectonic Plate Motion and Plate Boundary Deformation

    NASA Astrophysics Data System (ADS)

    Apel, Edwin Victor, III

    Plate motion models have matured from being based only on geology and seismicity to incorporating space-based geodetic methods like GPS. I use a block modeling approach to incorporate both rigid block rotation and near-boundary elastic strain accumulation effects in a formal inversion of GPS velocities. Independent Okhotsk and Amurian microplate motions are tested using GPS velocities that constrain the plate kinematics of northeast Asia. Modeling favors scenarios with independent OKH and AMU motion, based on the application of F-test statistics. The plate-motion parameters of the independent plates are consistent with the kinematics inferred from earthquake focal mechanism solutions along their boundaries. GPS-measured velocities (15 from continuously recording stations within the stable India plate interior) geodetically constrain India plate motion, intraplate strain, and plate boundary deformation around the India plate. Dense station coverage from previously published studies allows rigorous testing of boundary parameterizations. I develop robust India plate motion parameters and see good agreement between predicted plate directions from the preferred model and the seismological data. Available GPS data in and around the Aegean region is combined and used to evaluate plate motion models, elastic plate boundary deformation and its relationship to seismogenic coupling along the Hellenic subduction zone. The A.D. 365 M ˜8.4, the A.D. 1303 M˜8 Crete suggest that portions of the plate interface must be locked. The primary focus of this study is to examine potential upper plate deformation resulting from a locked subduction interface, active hanging-wall extension, or both. I consider multiple model scenarios in an attempt to interpret the both the horizontal and vertical geodetic signals in the region and its implications for earthquake hazard assessment.

  4. Shallow repeating slow-slip-events along the convergent block boundary in northern Hokkaido, Japan

    NASA Astrophysics Data System (ADS)

    Ikeda, S.; Heki, K.; Kimura, T.

    2015-12-01

    The Japanese Islands are divided into several crustal blocks [e.g. Loveless and Meade, 2010 JGR]. In the Northern Hokkaido, the boundary between the Amurian and the North American Plates run north-south between 44.0N and 45.4N. The east-west block convergence is considered to be as fast as ~1 cm/year there, but few large earthquakes are known to have occurred along this boundary. Recently, a slow slip event (SSE) is reported to have occurred in a segment at ~45.0N over a 4 months period from 2012 summer to the early 2013 [Ohzono et al., 2014 GJI]. The maximum surface movements was about 15 mm, and the moment magnitude of the SSE would not exceed 6.0 (fault slip is estimated as 10 cm). This suggests that plate convergence takes place as episodic SSEs in this block boundary. In this research, we looked for signatures of repeating SSEs along this block boundary using continuous GNSS data of the dense array GEONET in Japan. In order to detect faint signatures of SSEs in the coordinate time series, we adopted the method using AIC (Akaike's Information Criterion) similar to Nishimura et al. [2013 JGR] and Nishimura [2014 PEPS]. As a result, we were able to find numbers of SSE signals in various segments along the boundary. The detected SSEs are all fairly small, and surface movements did not exceed a few millimeters (except the 2012-2013 SSE reported in Ohzono et al. [2014]). We also searched earthquakes that may have triggered these SSEs. Although the 2012 SSE seems to have been triggered by a deep earthquake beneath Sakhalin on Aug. 14, 2012, no clear triggering earthquakes were identified for other SSEs. SSEs in subduction zones are known to recur fairly regularly, e.g. biannually repeating SSE in the SW part of the Ryukyu Arc [Heki and Kataoka, 2008 JGR]. However, shallow SSEs along the block boundary in the northern Hokkaido did not show such regular occurrences. We plan to confirm these SSE occurrences by comparing GNSS data with the Hi-Net tiltmeter records.

  5. Interplay of plate convergence and arc migration in the central Mediterranean (Sicily and Calabria)

    NASA Astrophysics Data System (ADS)

    Nijholt, Nicolai; Govers, Rob; Wortel, Rinus

    2016-04-01

    velocities in the Sicily-Calabria region. In these models, we combine far-field velocity boundary conditions, GPE-related body forces, and slab pull/trench suction at the subduction contacts. The location and nature of model faults are based on geological and seismicity observations, and as these faults do not fully enclose blocks our models require both fault slip and distributed strain. We vary fault friction in the models. Extrapolating the (short term) model results to geological time scales, we are able to make a first-order assessment of the regional strain and block rotations resulting from the interplay of arc migration and plate convergence during the evolution of this complex region.

  6. 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

  7. The North America - South America plate boundary zone: new elements for a geodynamic model

    NASA Astrophysics Data System (ADS)

    Roest, W. R.; Pichot, T.; Patriat, M.; Westbrook, G. K.; Gutscher, M.

    2011-12-01

    The location and functioning of the North America - South America plate boundary zone remain unknown, despite significant past efforts to decipher its precise position and the associated deformation. The Barracuda Ridge and the Tiburon Rise, two major oceanic basement ridges, are situated at the western end of this diffuse plate-boundary zone, where they enter the subduction zone beneath the Lesser Antilles island arc. The deformation of these features, and the intervening sedimentary basins and their stratigraphy record the history of NoAM-SoAM motion in this area. Kinematic studies based on reconstruction of past plate motions and GPS measurements predict small convergence during the Tertiary in the western part of this boundary zone, between the Marathon and Fifteen Twenty fracture zones. However, the differences between the different models remains too large to predict the NoAM-SoAM relative motions in this area confidently, as small changes in the postions of their rotation poles have major consequences for the expected distribution of deformation, because of their proximity to the area. Recent geophysical data acquired in this region has enabled us to locate the major structural features, and to propose an improved timing of the deformation. Seismic lines confirm the transpressional tectonic regime over a zone that is about 250 km wide, between the Barracuda Trough and the Tiburon Rise. The geodynamic situation is complicated by the fact that the deformation in the area of the Tiburon Rise and the Barracuda Ridge is clearly influenced by the flexural bulge of the active subduction zone, which uplifts the western ends of both ridges and provides a distinct western boundary to the Tiburon sedimentary basin, a trough situated between them. We have attempted to distinguish the influence of both the NoAM-SoAM convergence and the subduction process. In the North Atlantic west of Iberia, an apparently similar diffuse plate boundary zone between Europe and Africa

  8. Stress fields of the overriding plate at convergent margins and beneath active volcanic arcs.

    PubMed

    Apperson, K D

    1991-11-01

    Tectonic stress fields in the overriding plate at convergent plate margins are complex and vary on local to regional scales. Volcanic arcs are a common element of overriding plates. Stress fields in the volcanic arc region are related to deformation generated by subduction and to magma generation and ascent processes. Analysis of moment tensors of shallow and intermediate depth earthquakes in volcanic arcs indicates that the seismic strain field in the arc region of many convergent margins is subhorizontal extension oriented nearly perpendicular to the arc. A process capable of generating such a globally consistent strain field is induced asthenospheric corner flow below the arc region. PMID:17774792

  9. Convergence of intense aerial acoustic waves radiated by a rectangular transverse vibrating plate

    NASA Astrophysics Data System (ADS)

    Nakai, Tomoki; Asami, Takuya; Miura, Hikaru

    2016-07-01

    A stripe-mode rectangular transverse vibrating plate can be used as a sound source that emits intense ultrasonic waves in air by placing a jut driving point outside the vibrating plate. The aim of this research was to use this vibrating plate to focus sound waves in the direction perpendicular to the nodal lines of the vibrating plate, which differs from the conventional direction. In this study, we investigated new methods for focusing the emitted sound waves by arranging reflective plates around the vibrating plate, using a design equation for each node between nodes in the vibrating plate, and placing additional reflective plates at an outer position beyond the convergence point, and found that a powerful acoustic field can be formed at an arbitrary position.

  10. A diffuse plate boundary model for Indian Ocean tectonics

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Fitch, T. J.

    1971-01-01

    A model for oblique convergence between plates of lithosphere is proposed in which at least a fraction of slip parallel to the plate margin results in transcurrent movements on a nearly vertical fault which is located on the continental side of a zone of plate consumption. In an extreme case of complete decoupling only the component of slip normal to the plate margin can be inferred from underthrusting. Recent movements in the western Sunda region provide the most convincing evidence for decoupling of slip, which in this region is thought to be oblique to the plate margin. A speculative model for convergence along the margins of the Philippine Sea is constructed from an inferred direction of oblique slip in the Philippine region. This model requires that the triple point formed by the junction of the Japanese and Izu-Bonin trenches and the Nankai trough migrate along the Sagami trough.

  12. Dynamic behaviour of thin composite plates for different boundary conditions

    SciTech Connect

    Sprintu, Iuliana E-mail: rotaruconstantin@yahoo.com; Rotaru, Constantin E-mail: rotaruconstantin@yahoo.com

    2014-12-10

    In the context of composite materials technology, which is increasingly present in industry, this article covers a topic of great interest and theoretical and practical importance. Given the complex design of fiber-reinforced materials and their heterogeneous nature, mathematical modeling of the mechanical response under different external stresses is very difficult to address in the absence of simplifying assumptions. In most structural applications, composite structures can be idealized as beams, plates, or shells. The analysis is reduced from a three-dimensional elasticity problem to a oneor two-dimensional problem, based on certain simplifying assumptions that can be made because the structure is thin. This paper aims to validate a mathematical model illustrating how thin rectangular orthotropic plates respond to the actual load. Thus, from the theory of thin plates, new analytical solutions are proposed corresponding to orthotropic rectangular plates having different boundary conditions. The proposed analytical solutions are considered both for solving equation orthotropic rectangular plates and for modal analysis.

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

    USGS Publications Warehouse

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

    1990-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    -type rocks dredged from the Tonga forearc. These geologic and kinematic data do not require a plate boundary between the LHR and Pacific from c. 84-55 Ma, in agreement with previous studies. A plate boundary may have existed before 55 Ma, however net convergence/divergence at this boundary would have been minor, with a possible strike-slip component. By combining geologic observations with a kinematic analysis, we propose that from 0-55 Ma an Antarctic plate circuit must be used in reconstructions, in which LHR-Pacific motion is unconstrained. From 55-74 Ma Antarctic or Australian circuits can be reconciled with regional geology when revised relative motion histories at the Australian-Antarctic ridge and in the WARS are adopted. A well-constrained Antarctic circuit predicts <50 km of strike-slip motion at a LHR-Pacific boundary. Alternatively, an Australian circuit assuming the LHR was part of the Pacific plate, predicts 100-150 km of extension in the WARS, that is orthogonal in the Ross Sea and oblique further east. Prior to 74 Ma neither plate circuit is preferable, as more data are needed to better constrain regional spreading histories.

  15. Slab dragging and the recent geodynamic evolution of the western Mediterranean plate boundary region

    NASA Astrophysics Data System (ADS)

    Spakman, Wim; Chertova, Maria V.; van den Berg, Arie P.; Thieulot, Cedric; van Hinsbergen, Douwe J. J.

    2016-04-01

    The Tortonian-Present geodynamic evolution of the plate boundary between North Africa and Iberia is characterized by first-order enigmas. This concerns, e.g., the diffuse tectonic activity of the plate boundary; the crustal thickening below the Rif; the closing of the northern Moroccan marine gateways prior to the Messinian Salinity Crisis; crustal extension of the central to eastern Betics; the origin and sense of motion of the large left-lateral Trans Alboran Shear Zone (TASZ) and Eastern Betic Shear Zone (EBSZ); and lithosphere delamination of the North African continental edge. Many explanations have been given for each of these seemingly disparate tectonic features, which invariably have been addressed in the plate tectonic context of the NW-SE relative plate convergence between the major plates since the Tortonian, mostly independently from each other. Usually there is no clear role for the subducted slab underlying the region, except for presumed rollback, either to SW or to the W, depending on the type of observations that require explanation. Here we integrate the dynamic role of the slab with the NW-SE relative plate convergence by 3-D numerical modelling of the slab evolution constrained by absolute plate motions (Chertova et al., JGR,2014 & Gcubed 2014). By combining observations and predictions from seismology, geology, and geodesy, with our numerical 3-D slab-mantle dynamics modelling, we developed a new and promising geodynamic framework that provides explanations of all noted tectonic enigmas in a coherent and connected way. From the Tortonian until today, we propose that mantle-resisted slab dragging combines with the NW-SE plate convergence across the (largely) unbroken plate boundary to drive the crustal deformation of the region. Slab dragging is the lateral transport, pushing or pulling, of slab through the mantle by the absolute motion of the subducting plate (Chertova et al., Gcubed, 2014). Because the slab is connected to both the Iberian

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

    PubMed

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

    2009-04-10

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

  17. Swath sonar mapping of Earth's submarine plate boundaries

    NASA Astrophysics Data System (ADS)

    Carbotte, S. M.; Ferrini, V. L.; Celnick, M.; Nitsche, F. O.; Ryan, W. B. F.

    2014-12-01

    The recent loss of Malaysia Airlines flight MH370 in an area of the Indian Ocean where less than 5% of the seafloor is mapped with depth sounding data (Smith and Marks, EOS 2014) highlights the striking lack of detailed knowledge of the topography of the seabed for much of the worlds' oceans. Advances in swath sonar mapping technology over the past 30 years have led to dramatic improvements in our capability to map the seabed. However, the oceans are vast and only an estimated 10% of the seafloor has been mapped with these systems. Furthermore, the available coverage is highly heterogeneous and focused within areas of national strategic priority and community scientific interest. The major plate boundaries that encircle the globe, most of which are located in the submarine environment, have been a significant focus of marine geoscience research since the advent of swath sonar mapping. While the location of these plate boundaries are well defined from satellite-derived bathymetry, significant regions remain unmapped at the high-resolutions provided by swath sonars and that are needed to study active volcanic and tectonic plate boundary processes. Within the plate interiors, some fossil plate boundary zones, major hotspot volcanoes, and other volcanic provinces have been the focus of dedicated research programs. Away from these major tectonic structures, swath mapping coverage is limited to sparse ocean transit lines which often reveal previously unknown deep-sea channels and other little studied sedimentary structures not resolvable in existing low-resolution global compilations, highlighting the value of these data even in the tectonically quiet plate interiors. Here, we give an overview of multibeam swath sonar mapping of the major plate boundaries of the globe as extracted from public archives. Significant quantities of swath sonar data acquired from deep-sea regions are in restricted-access international archives. Open access to more of these data sets would

  18. Fluid budgets at convergent plate margins: Implications for the extent and duration of fault-zone dilation

    USGS Publications Warehouse

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

    1999-01-01

    Faults at convergent plate boundaries are important conduits for fluid escape, and recent evidence suggests that fluid expulsion along them is both transient and heterogeneous. For the Nankai and Barbados convergent margins, we have used numerical models to investigate the long-term partitioning of expelled fluids between diffuse flow and flow along connected high-permeability fault conduits. For a simple case of spatial heterogeneity, we estimated the extent of high-permeability conduits necessary to maintain a balance between incoming and expelled fluids. For the case of transient expulsion, we constrained the duration of elevated permeability required to balance the fluid budgets. Comparison of modeled and observed geochemical profiles suggests that the initiation of connected flow conduits is delayed with respect to the time of accretion into each accretionary complex and may be related to burial below a critical depth, either where the overlying wedge is sufficiently thick to prevent fluid escape to the sea floor or where sediments behave brittlely.

  19. Repeating Earthquakes on the Queen Charlotte Plate Boundary

    NASA Astrophysics Data System (ADS)

    Hayward, T. W.; Bostock, M. G.

    2015-12-01

    The Queen Charlotte Fault (QCF) is a major plate boundary located off the northwest coast of North America that has produced large earthquakes in 1949 (M8.1) and more recently in October, 2012 (M7.8). The 2012 event was dominated by thrusting despite the fact that plate motions at the boundary are nearly transcurrent. It is now widely believed that the plate boundary comprises the QCF (i.e., a dextral strike-slip fault) as well as an element of subduction of the Pacific Plate beneath the North American Plate. Repeating earthquakes and seismic tremor have been observed in the vicinity of the QCF; providing insight into the spatial and temporal characteristics of repeating earthquakes is the goal of this research. Due to poor station coverage and data quality, traditional methods of locating earthquakes are not applicable to these events. Instead, we have implemented an algorithm to locate local (i.e., < 100 km distance to epicenter) earthquakes using a single, three-component seismogram. This algorithm relies on the P-wave polarization and, through comparison with larger local events in the Geological Survey of Canada catalogue, is shown to yield epicentral locations accurate to within 5-10 km. A total of 24 unique families of repeating earthquakes has been identified, and 4 of these families have been located with high confidence. Their epicenters locate directly on the trace of the QCF and their depths are shallow (i.e., 5-15 km), consistent with the proposed depth of the QCF. Analysis of temporal recurrence leading up to the 2012 M7.8 event reveals a non-random pattern, with an approximately 15 day periodicity. Further analysis is planned to study whether this behaviour persists after the 2012 event and to gain insight into the effects of the 2012 event on the stress field and frictional properties of the plate boundary.

  20. Bolivar: Crustal Structure of the Caribbean-South America plate boundary at 70W

    NASA Astrophysics Data System (ADS)

    Guedez, M. C.; Zelt, C. A.; Magnani, B. M.; Levander, A.

    2006-12-01

    The Caribbean-South America plate boundary is characterized by tectonic transpression with oblique convergence. The ~ 20 mm/yr eastward displacement of the Caribbean plate, with respect to a fixed South America causes the plate boundary to have a dominant right-lateral strike-slip component, accommodated by the San Sebastian-El Pilar fault system. To the west, relative plate motion is complicated by the northeastward tectonic escape of the Maracaibo block along the Bocono and Santa Marta strike-slip faults, and the shortening between North and South America. The convergence rate between the Maracaibo block and the Caribbean has been estimated to be ~ 2 mm/yr. The multidisciplinary BOLIVAR project seeks to understand the complex plate interaction of the Caribbean- South American diffuse plate boundary. We hypothesize that this may be a site of continental growth by island arc accretion of the Leeward Antilles onto South America. The active-seismic component of the project, completed in June 2004, concentrated along five main onshore-offshore profiles extending from the Caribbean basin to the front of the fold and thrust belts of Venezuela. Seismic refraction data were acquired as well as coincident multi-channel seismic (MCS) lines in the offshore sections. We present results from seismic reflection and wide-angle refraction data along a 450 km-long onshore- offshore north-south striking profile at 70 degrees west longitude. Refraction data were used to develop 2-D velocity models from independent and simultaneous traveltime inversion of first arrivals and PmP reflections from 40 Ocean Bottom Seismometers (OBS) and about ~ 80 land recorders. A coincident MCS profile was processed and interpreted independently. Offshore western Venezuela the Caribbean plate is anomalously thick ~ 15 km. The velocity model from wide-angle data is well correlated with the structures interpreted in the reflection data; in particular in the upper and middle crust of the Southern

  1. A dual reciprocity boundary element solution method for the free vibration analysis of fluid-coupled Kirchhoff plates

    NASA Astrophysics Data System (ADS)

    Uğurlu, B.

    2015-03-01

    A boundary element solution method is proposed for linear vibration analysis of fluid-coupled thin plates. The method is based on replacing the associated biharmonic operator with two successive harmonic operators, leading to a coupled system of boundary integral equations with simpler properties: the fundamental solution has an elementary form, and complicated singularity removal techniques can be avoided. The fluid flow due to the plate motion is taken as a potential field, and its effect on the plate dynamics is incorporated into the analysis by invoking another boundary integral solution, described over the fluid-plate interface. The body terms in the plate boundary integral equations are considered by the dual reciprocity boundary element formulation. Three different radial basis functions are employed as interpolation functions, alone and augmented with polynomial and sine expansions, to represent the body terms. The performance of the method is investigated from several perspectives by adopting plates with different shapes and/or boundary conditions; excellent approximations are obtained in general: the convergence behavior is consistent, both dry and wet frequency parameters are predicted accurately, and the mode shapes are captured even with rough models. In some of the studied problems, however, deviated results are obtained for specific modes. Furthermore, it is observed that the performance of the method depends on the implemented DRM functions, and combining radial basis functions with global expansions does not yield noticeable improvements.

  2. Tracking the India-Arabia Transform Plate Boundary during Paleogene Times.

    NASA Astrophysics Data System (ADS)

    Rodriguez, M.; Huchon, P.; Chamot-Rooke, N. R. A.; Fournier, M.; Delescluse, M.

    2014-12-01

    The Zagros and Himalaya mountain belts are the most prominent reliefs built by continental collision. They respectively result from Arabia and India collision with Eurasia. Convergence motions at mountain belts induced most of plate reorganization events in the Indian Ocean during the Cenozoic. Although critical for paleogeographic reconstructions, the way relative motion between Arabia and India was accommodated prior to the formation of the Sheba ridge in the Gulf of Aden remains poorly understood. The India-Arabia plate-boundary belongs to the category of long-lived (~90-Ma) oceanic transform faults, thus providing a good case study to investigate the role of major kinematic events over the structural evolution of a long-lived transform system. A seismic dataset crossing the Owen Fracture Zone, the Owen Basin, and the Oman Margin was acquired to track the past locations of the India-Arabia plate boundary. We highlight the composite age of the Owen Basin basement, made of Paleocene oceanic crust drilled on its eastern part, and composed of pre-Maastrichtian continental crust overlaid by Early Paleocene ophiolites on its western side. A major transform fault system crossing the Owen Basin juxtaposed these two slivers of lithosphere of different ages, and controlled the uplift of marginal ridges along the Oman Margin. This transform system deactivated ~40 Ma ago, coeval with the onset of ultra-slow spreading at the Carlsberg Ridge. The transform boundary then jumped to the edge of the present-day Owen Ridge during the Late Eocene-Oligocene period, before seafloor spreading began at the Sheba Ridge. This migration of the plate boundary involved the transfer of a part of the Indian oceanic lithosphere accreted at the Carlsberg Ridge to the Arabian plate. The episode of plate transfer at the India-Arabia plate boundary during the Late Eocene-Oligocene interval is synchronous with a global plate reorganization event corresponding to geological events at the Zagros and

  3. Modeling the Philippine Mobile Belt: Tectonic blocks in a deforming plate boundary zone

    NASA Astrophysics Data System (ADS)

    Galgana, G. A.; Hamburger, M. W.; McCaffrey, R.; Bacolcol, T. C.; Aurelio, M. A.

    2007-12-01

    The Philippine Mobile Belt, a seismically active, rapidly deforming plate boundary zone situated along the convergent Philippine Sea/Eurasian plate boundary, is examined using geodetic and seismological data. Oblique convergence between the Philippine Sea Plate and the Eurasian plate is accommodated by nearly orthogonal subduction along the Philippine Trench and the Manila Trench, as well as by strike-slip faulting along the Philippine Fault system. We develop a model of active plate boundary deformation in this region, using elastic block models constrained by known fault geometries, published GPS observations and focal mechanism solutions. We then present an estimate of block rotations, fault coupling, and intra-block deformation, based on the best-fit model that minimizes the misfit between observed and predicted geodetic vectors and earthquake slip vectors. Slip rates along the Philippine fault vary from ~22 - 36 mm/yr in the Central Visayas and about 10 to 40 mm/yr in Luzon, trending almost parallel to the fault trace. In northern Luzon, Philippine Fault splays accommodate transpressional strain. The Central Visayas block experiences convergence with the Sundaland block along the Negros Trench and the Mindoro-Palawan collision zone. On the eastern side of Central Visayas, sinistral strike-slip faulting occurs along the NNW-SSE-trending Philippine Fault. Mindanao Island in southern Philippines is dominated by east-verging subduction along the Cotabato Trench, and strain partitioning (strike- slip faulting with west-verging subduction) in eastern Mindanao along the southern Philippine Fault and Philippine Trench, respectively. Oblique active sinistral strike slip faults in Central and Eastern Mindanao that were hypothesized to be responsible for basin formation are obvious boundaries for tectonic blocks. Located south of Mindanao Island we define an adjoining oceanic block defined by the N-S trending complex dual subduction zone of Sangihe and Halmahera

  4. Carbon on Quartz Grain Boundaries: Continuous Films versus Isolated Plates

    NASA Astrophysics Data System (ADS)

    Price, J. D.; Watson, E. B.; Wark, D. A.

    2003-12-01

    Piston-cylinder experiments on quartzites containing a small amount of carbon were conducted at 1.0-1.4 GPa and 850-1500° C in order to assess the microstructure of graphite along grain boundaries in deep crustal materials. In one series of experiments, polished 3mm diameter single-crystal quartz discs were coated with ˜50 to 150 nm of evaporated carbon or 500 to 1000 nm of alcohol-based carbon paint. Stacks of these were subjected to high P-T conditions for durations ranging from 5 minutes to 10 days. Observations from our earlier experiments suggested that the coatings become discontinuous with time at high temperature. However, more recent observations show that coated disc boundaries contain a dark, interconnected material: those subjected to lower temperatures and shorter durations exhibited continuous films; those run at higher temperatures for longer durations contained thicker, yet still interconnected dendrite and plate structures. In contrast, relatively fine-grained synthetic quartzites produced at similar conditions typically do not contain continuous films. Quartz powder with an initial grain size between 75-150 μ m, coated with 30-50 nm of evaporated carbon, was subjected to 850-1300° C for durations ranging from 1 hour to 6 days. Only very short runs at low temperatures contained irregular boundaries still darkened by a connected film; longer duration and higher temperature quartzites exhibited texturally-equilibrated quartz grains accompanied by isolated small opaque carbon plates located along grain corners, edges, and grain boundaries. Identical features are seen in additional quartzite materials constructed in graphite cylinders using uncoated powdered silica glass or smaller quartz crystals (<22 μ m) taken to 1000° C and 1.4 GPa for 14 days. The results suggest that carbon may remain as a connected surface, at least metastably, on silicate mineral boundaries in the absence of grain boundary movement. With grain growth, carbon diffuses

  5. Sonic imaging reveals new plate boundary structures offshore New Zealand

    NASA Astrophysics Data System (ADS)

    Collot, J.-Y.; Delteil, J.; Herzer, R. H.; Wood, R.; Lewis, K.

    Recent bathymetry and sonar imagery studies of offshore portions of the plate boundary transecting New Zealand allow the first confident mapping of detailed tectonic and sedimentary patterns of the region. Working in late 1993 aboard the R/V L'Atalante of the Institut Francais de Recherche pour l' Exploitation de la Mer (IFREMER), we recorded soundings of a wide swath of seabed to elucidate major structural transitions along the plate boundary. Results of the study, part of the GEODYNZ-SUD program developed jointly by institutions in France and New Zealand, will be complemented by New Zealand cruises to the Puysegur and Hikurangi margins. The total data set will be processed and interpreted during the next two years.

  6. Radiation efficiency of plates subjected to turbulent boundary layer fluctuations.

    PubMed

    Kou, Yiwei; Liu, Bilong; Chang, Daoqing

    2016-05-01

    The modal averaged radiation efficiency of a rectangular plate subjected to turbulent boundary layer fluctuations is discussed in this letter. Numerical results demonstrate that below the hydrodynamic coincidence frequency, the modal averaged radiation efficiency will be larger with the increase of the convection velocity, and an increase of the structural damping will increase the modal averaged radiation efficiency at sub-critical frequencies. PMID:27250169

  7. Tectonics of the Nazca-Antarctic plate boundary

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  8. Finite element modeling of stress in the Nazca plate - Driving forces and plate boundary earthquakes

    NASA Technical Reports Server (NTRS)

    Richardson, R. M.

    1978-01-01

    The state of stress within the Nazca plate due to plate driving forces and large plate boundary earthquakes has been analyzed by applying a finite element method using the wave front solution technique to models of the intraplate stress field in a single plate using a refined grid. Although only static elastic models have been explicitly calculated, certain limiting cases of an elastic plate over a viscous asthenosphere were also treated. A state of nearly east-west compression inferred from the source mechanism of thrust earthquakes in the interior of the plate requires ridge pushing forces. The net pulling force on the oceanic plate by the subducted slab has a maximum value comparable to pushing forces. The estimated horizontal deviatoric stress in intraplate regions, based on potential forces associated with the ridge, is on the order of a few hundred bars. The intraplate stress field in the region of the 1960 earthquake may change by a few tens of bars at most once the asthenosphere has relaxed, with changes on the order of one bar occurring at greater distances into the plate. The changes in the intraplate stress field are probably not noticeable unless the lithosphere is near failure.

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

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

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

  10. Defects and boundary layers in non-Euclidean plates

    NASA Astrophysics Data System (ADS)

    Gemmer, J. A.; Venkataramani, S. C.

    2012-12-01

    We investigate the behaviour of non-Euclidean plates with constant negative Gaussian curvature using the Föppl-von Kármán reduced theory of elasticity. Motivated by recent experimental results, we focus on annuli with a periodic profile. We prove rigorous upper and lower bounds for the elastic energy that scales like the thickness squared. In particular we show that are only two types of global minimizers—deformations that remain flat and saddle shaped deformations with isolated regions of stretching near the edge of the annulus. We also show that there exist local minimizers with a periodic profile that have additional boundary layers near their lines of inflection. These additional boundary layers are a new phenomenon in thin elastic sheets and are necessary to regularize jump discontinuities in the azimuthal curvature across lines of inflection. We rigorously derive scaling laws for the width of these boundary layers as a function of the thickness of the sheet.

  11. Inherited segmentation of the Iberian-African margins and tectonic reconstruction of a diffuse plate boundary.

    NASA Astrophysics Data System (ADS)

    Fernàndez, Manel; Torne, Montserrat; Vergés, Jaume; Casciello, Emilio

    2016-04-01

    Diffuse plate-boundary regions are characterized by non-well defined contacts between tectonic plates thus making difficult their reconstruction through time. The Western Mediterranean is one of these regions, where the convergence between the African and Iberian plates since Late Cretaceous resulted in the Betic-Rif arcuate orogen, the Gulf of Cadiz imbricate wedge, and the Alboran back-arc basin. Whereas the Iberia-Africa plate boundary is well defined west to the Gorringe Bank and along the Gloria Fault, it becomes much more diffuse eastwards with seismicity spreading over both the south-Iberian and north-African margins. Gravity data, when filtered for short wavelengths, show conspicuous positive Bouguer anomalies associated with the Gorringe Bank, the Gulf of Cadiz High and the Ronda/Beni-Bousera peridotitic massifs reflecting an inherited Jurassic margin segmentation. The subsequent Alpine convergence between Africa and Iberia reactivated these domains, producing crustal-scale thrusting in the Atlantic segments and eventually subduction in the proto-Mediterranean segments. The Jurassic segmentation of the Iberia-Africa margins substantiates the double-polarity subduction model proposed for the region characterized by a change from SE-dipping polarity in the Gorringe, Gulf of Cadiz and Betic-Rif domains, to NW-dipping polarity in the proto-Algerian domain. Therefore, the Algerian and Tyrrhenian basins in the east and the Alboran basin in the west are the result of SSE-E and NW-W retreating slabs of oceanic and/or hyper-extended Tethyan domains, respectively.

  12. Initiation of deep convection along boundary layer convergence lines in a semitropical environment

    SciTech Connect

    Fankhauser, J.C.; Crook, N.A.; Tuttle, J.; Miller, L.J.; Wade, C.G.

    1995-02-01

    The initiation of deep convection through forcing along boundary layer convergence lines is examined using observations from the Convection and Precipitation/Electrification (CaPE) Experiment conducted in east-central Florida during the summer of 1991. The study is concerned with the evolution and interaction of two converging air masses that were initially separated by an intervening boundary layer characterized by neutral stability and horizontal convective rolls. As anticipated, major thunderstorms erupt when the east coast breeze eventually collides with thunderstorm outflows from the west, but unexpected convection takes place prior to their merger along a well-defined confluence zone associated with a persistent quasi-stationary roll vortex signature. In this study, complementary interactions between roll vortex convergence lines and the sea-breeze front are not sufficient to trigger deep convection. However, organized convergence along the eastward-spreading thunderstorm outflows did interact periodically with roll vortex convergence maxima to initiate a new series of new storms. Results from two-dimensional numerical model simulations replicate many of the observed boundary layer features. Surface heating produces circulations similar to sea-breeze frontal zones that appear near the coastlines and progress steadily toward each other as the interior boundary layer deepens. Vertical velocity maxima develop over the associated convergence zones, but weaker periodic maxima also occur within the interior air mass at intervals similar to the spacing of observed horizontal roll vortices.

  13. Lower plate deformation structures along the Costa Rica erosive plate boundary - results from IODP Expedition 344 (CRISP 2)

    NASA Astrophysics Data System (ADS)

    Brandstätter, Jennifer; Kurz, Walter; Micheuz, Peter; Krenn, Kurt

    2015-04-01

    The primary objective of Integrated Ocean Drilling Program (IODP) Expedition 344 offshore the Osa Peninsula in Costa Rica was to sample and quantify the material entering the seismogenic zone of the Costa Rican erosive subduction margin. Fundamental to this objective is an understanding of the nature of both the subducting Cocos plate crust and of the overriding Caribbean plate. The subducting Cocos plate is investigated trying to define its hydrologic system and thermal state. The forearc structures recorded by the sediment deposited on the forearc, instead, document periods of uplift and subsidence and provide important information about the process of tectonic erosion that characterizes the Costa Rica margin. Offshore the western margin of Costa Rica, the oceanic Cocos plate subducts under the Caribbean plate, forming the southern end of the Middle America Trench. Subduction parameters including the age, convergence rate, azimuth, obliquity, morphology, and slab dip all vary along strike. The age of the Cocos plate at the Middle America Trench decreases from 24 Ma offshore the Nicoya Peninsula to 15 Ma offshore the Osa Peninsula. Subduction rates vary from 70 mm/y offshore Guatemala to 90 mm/y offshore southern Costa Rica. Convergence obliquity across the trench varies from offshore Nicaragua, where it is as much as 25° oblique, to nearly orthogonal southeast of the Nicoya Peninsula. Passage of the Cocos plate over the Galapagos hotspot created the aseismic Cocos Ridge, an overthickened welt of oceanic crust. This ridge is ~25 km thick, greater than three times normal oceanic crustal thickness. During IODP Expedition 344, the incoming Cocos plate was drilled at sites U1381 and U1414. Site U1381 is located ~4.5 km seaward of the deformation front offshore the Osa Peninsula and Caño Island. It is located on a local basement high. Basement relief often focuses fluid flow, so data from this site are likely to document the vigor of fluid flow in this area. Site U

  14. Formation of plate boundaries: The role of mantle volatilization

    NASA Astrophysics Data System (ADS)

    Seno, Tetsuzo; Kirby, Stephen H.

    2014-02-01

    In the early Earth, convection occurred with the accumulation of thick crust over a weak boundary layer downwelling into the mantle (Davies, G.F., 1992. On the emergence of plate tectonics. Geology 20, 963-966.). This would have transitioned to stagnant-lid convection as the mantle cooled (Solomatov, V.S., Moresi, L.-N., 1997. Three regimes of mantle convection with non-Newtonian viscosity and stagnant lid convection on the terrestrial planets. Geophys. Res. Lett. 24, 1907-1910.) or back to a magma ocean as the mantle heated (Sleep, N., 2000. Evolution of the mode of convection within terrestrial planets. J. Geophys. Res. 105(E7): 17563-17578). Because plate tectonics began operating on the Earth, subduction must have been initiated, thus avoiding these shifts. Based on an analogy with the continental crust subducted beneath Hindu Kush and Burma, we propose that the lithosphere was hydrated and/or carbonated by H2O-CO2 vapors released from magmas generated in upwelling plumes and subsequently volatilized during underthrusting, resulting in lubrication of the thrust above, and subduction of the lithosphere along with the overlying thick crust. Once subduction had been initiated, serpentinized forearc mantle may have formed in a wedge-shaped body above a dehydrating slab. In relict arcs, suture zones, or rifted margins, any agent that warms and dehydrates the wedge would weaken the region surrounding it, and form various types of plate boundaries depending on the operating tectonic stress. Thus, once subduction is initiated, formation of plate boundaries might be facilitated by a major fundamental process: weakening due to the release of pressurized water from the warming serpentinized forearc mantle.

  15. Coupling, fluids and foreshocks - preparing megathrust ruptures at the Chilean plate boundary

    NASA Astrophysics Data System (ADS)

    Oncken, O.; Moreno, M.; Schurr, B.

    2014-12-01

    Recent studies have suggested that geodetic locking at convergent plate boundaries is closely related to slip distribution of subsequent megathrust earthquakes. The nature of locking and its evolution towards rupture, however, remains a matter of debate. The international initiative IPOC (Integrated Plate Boundary Observatory Chile; ipoc-network.org) addresses these goals at the Chilean margin. We explore geophysical and geodetic data collected in the decade before an event to identify the petrophysical state as well as change along the plate interface leading up to a megathrust event. Seismological data exhibit well defined changes of reflectivity and Vp/Vs ratio along the plate interface that released the M=8.8Maule earthquake of 2010. High Vp/Vs domains, interpreted as zones of elevated pore fluid pressure, spatially correlate with lower locking degree, and exhibit higher background seismicity as expected for partly creeping domains. In turn, unstable slip associated to a higher degree of locking is promoted in lower pore fluid pressure domains. We speculate that hydraulic loading during the terminal stage of a seismic cycle to close to lithostatic pore pressure with an equivalent reduction of effective strength may be as relevant for earthquake triggering as stress loading from long-term plate convergence. In contrast to the Maule earthquake, the Pisagua Mw=8.1 earthquake of 2014, while also rupturing a geodetically well-defined major asperity, was preceded by a protracted series of foreshocks. Since July 2013 three seismic clusters hit this part of the plate boundary with increasing magnitudes in a domain that was transitional between a fully locked and a creeping portion. Leading up to this earthquake the b-value of the foreshocks gradually dropped during the years prior to the earthquake, reversing its trend a few days before the Pisagua earthquake. We conclude that gradual weakening of the central part of the Northern Chile seismic gap accentuated by the

  16. What drives micro-plate motion and deformation in the northeastern Caribbean plate boundary region?

    NASA Astrophysics Data System (ADS)

    Govers, R. M. A.; Wortel, M. J. R.; van Benthem, S.

    2015-12-01

    The north Caribbean plate boundary zone is a broad deformation zone with several fault systems and tectonic blocks that move with different velocities. The indentation by the Bahamas Platform (the "Bahamas Collision") is generally invoked as a cause of this fragmentation. We propose that a second driver of deformation is the western edge of the south-dipping Puerto Rico slab moving sideways with the North America plate. This proposal derives from our recently imaged tomographic structure of the Lesser Antilles - Puerto Rico slab. The westward motion of the slab edge results in a push on the Caribbean plate further west. We refer to this second mechanism for deformation as "Slab Edge Push". The motion of the North America plate relative to the Caribbean plate causes both drivers to migrate from east to west. The Bahamas Collision and Slab Edge Push have been operating simultaneously since the Miocene. The question is the relative importance of the two mechanisms. We use mechanical finite element models that represent the two mechanisms from the Late Oligocene (30 Ma) to the Present. For the Present, both models successfully reproduce observed deformation, implying that both models are viable. Back in time the Slab Edge Push mechanism better reproduces observations. Neither mechanism successfully reproduces the observed Miocene counter-clockwise rotation of Puerto Rico. We use this rotation to tune a final model that includes fractional contributions of both mechanisms. Both mechanisms contribute equally to the motion of the Caribbean plate. We find that the Slab Edge Push was the dominant driver of deformation in the north Caribbean plate boundary zone since 30 Ma.

  17. Turbulent thermal boundary layer on a permeable flat plate

    SciTech Connect

    Vigdorovich, I. I.

    2007-06-15

    Scaling laws are established for the profiles of temperature, turbulent heat flux, rms temperature fluctuation, and wall heat transfer in the turbulent boundary layer on a flat plate with transpiration. In the case of blowing, the temperature distribution represented in scaling variables outside the viscous sublayer has a universal form known from experimental data for flows over impermeable flat plates. In the case of suction, the temperature distribution is described by a one-parameter family of curves. A universal law of heat transfer having the form of a generalized Reynolds analogy provides a basis for representation of the heat flux distributions corresponding to different Reynolds numbers and transpiration velocities in terms of a function of one variable. The results are obtained without invoking any special closure hypotheses.

  18. Stiffened plate bending analysis by the boundary element method

    NASA Astrophysics Data System (ADS)

    Fernandes, G. R.; Venturini, W. S.

    In this work, the plate bending formulation of the boundary element method (BEM) based on the Kirchhoff's hypothesis, is extended to the analysis of stiffened elements usually present in building floor structures. Particular integral representations are derived to take directly into account the interactions between the beams forming grid and surface elements. Equilibrium and compatibility conditions are automatically imposed by the integral equations, which treat this composite structure as a single body. Two possible procedures are shown for dealing with plate domain stiffened by beams. In the first, the beam element is considered as a stiffer region requiring therefore the discretization of two internal lines with two unknowns per node. In the second scheme, the number of degrees of freedom along the interface is reduced by two by assuming that the cross-section motion is defined by three independent components only.

  19. The Plate Boundary Observatory: Operational Status and Data Plans

    NASA Astrophysics Data System (ADS)

    Anderson, G.; Feaux, K.; Jackson, M.; Prescott, W.

    2004-05-01

    The Plate Boundary Observatory (PBO), part of the larger NSF-funded EarthScope project, is designed to study the three-dimensional strain field resulting from deformation across the active boundary zone between the Pacific and North American plates in the western United States. The science goals of PBO require that plate boundary deformation be adequately characterized over the wide range of spatial and temporal scales common to active continental tectonic processes. PBO will meet these needs using 875 continuous GPS sites, 175 borehole strainmeter stations, and five laser strainmeters, all installed over the next five years. In addition, 255 existing continuous GPS sites will be incorporated into PBO, and there will be a pool of 100 portable GPS receivers available for survey-mode observations. These stations will provide raw observations from which PBO Analysis Centers will create a wide range of derived data products, including time series of strain and GPS station position, GPS velocity vectors, and regional strain maps. All PBO data and data products will be made available to the community as rapidly and freely as possible through the EarthScope Data Portal. PBO began operations in September 2003 and the first five new PBO continuous GPS stations were installed in January 2004, with the first PBO borehole strainmeter installations anticipated by September 2004. The initial data from the first PBO sites are now available through the PBO archives at the UNAVCO Facility in Boulder and the Scripps Orbit and Permanent Array Center in San Diego. We will present an update on the current status of, and future plans for, PBO operations, data collection and analysis, and distribution of PBO data products.

  20. Measuring Transient Signals in Plate Boundary Faults Zones with Strainmeters

    NASA Astrophysics Data System (ADS)

    Hodgkinson, Kathleen; Mencin, Dave; Phillips, David; Henderson, Brent; Gottlieb, Mike; Gallaher, Warren; Johnson, Wade; Pyatt, Chad; Van Boskirk, Elizabeth; Fox, Otina; Mattioli, Glen; Meertens, Chuck

    2014-05-01

    One of the fundamental goals the U.S. National Science Foundation (NSF) funded Earthscope program was to provide a high-quality, continuous geodetic data set that would allow the scientific community to study the evolution of plate boundary zones. Of particular importance was enabling investigation of the role aseismic transient deformation plays in the release of accumulated stress. For example, to allow the comparison of the amount of strain released through Episodic Tremor and Slip (ETS) events to that released in subduction zone earthquakes or, provide the ability to geodetically illuminate the kinematics of fault creep in strike-slip fault zones. The ability to easily integrate these measurements with compatible geophysical data sets was also an essential objective. With goals such as these in mind NSF funded the Plate Boundary Observatory (PBO) to record the continuous deformation field across the western US Plate Boundary. PBO, built and operated by UNAVCO, now consists of over 1100 GPS stations, 76 co-located borehole strain and seismic sites, 6 long baseline strainmeters, Depending on the scientific questions being addressed sites may also have tiltmeter, meteorological, pore pressure and meteorological instrumentation. This presentation will focus on the transient deformation signals recorded by the PBO strainmeter network. PBO strainmeters, which excel in recording signals on the order of nanostrain over hours, have provided unprecedented temporal resolution of aseismic transients such as ETS events in the Cascadia subduction zone, creep signals along the central section of the San Andreas fault system and tsunami generated strain waves. UNAVCO is responsible not only for the ongoing operation of PBO but also the generation of data products associated with each instrument type. In this presentation we will highlight some of the transient signals these instruments have captured, outline the processing steps required to extract these signals data and

  1. Convergence of shock waves between conical and parabolic boundaries

    NASA Astrophysics Data System (ADS)

    Yanuka, D.; Zinowits, H. E.; Antonov, O.; Efimov, S.; Virozub, A.; Krasik, Ya. E.

    2016-07-01

    Convergence of shock waves, generated by underwater electrical explosions of cylindrical wire arrays, between either parabolic or conical bounding walls is investigated. A high-current pulse with a peak of ˜550 kA and rise time of ˜300 ns was applied for the wire array explosion. Strong self-emission from an optical fiber placed at the origin of the implosion was used for estimating the time of flight of the shock wave. 2D hydrodynamic simulations coupled with the equations of state of water and copper showed that the pressure obtained in the vicinity of the implosion is ˜7 times higher in the case of parabolic walls. However, comparison with a spherical wire array explosion showed that the pressure in the implosion vicinity in that case is higher than the pressure in the current experiment with parabolic bounding walls because of strong shock wave reflections from the walls. It is shown that this drawback of the bounding walls can be significantly minimized by optimization of the wire array geometry.

  2. Active faulting south of the Himalayan Front: Establishing a new plate boundary

    NASA Astrophysics Data System (ADS)

    Yeats, Robert S.; Thakur, V. C.

    2008-06-01

    New tectonic uplifts south of the Salt Range Thrust and Himalayan Front Thrust (HFT) represent an outward step of the plate boundary from the principal tectonic displacement zone into the Indo-Gangetic Plain. In Pakistan, the Lilla Anticline deforms fine-grained overbank deposits of the Jhelum River floodplain 15 km south of the Salt Range. The anticline is overpressured in Eocambrian non-marine strata. In northwest India south of Dehra Dun, the Piedmont Fault (PF) lies 15 km south of the HFT. Coalescing fans derived from the Himalaya form a piedmont (Old Piedmont Zone) 15-20 km wide east of the Yamuna River. This zone is uplifted as much as 15-20 m near the PF, and bedding is tilted 5-7° northeast. Holocene thermoluminescence-optically-stimulated luminescence dates for sediments in the Old Piedmont Zone suggest that the uplift rate might be as high as several mm/a. The Old Piedmont Zone is traced northwest 200 km and southeast another 200 km to the Nepal border. These structures, analogous to protothrusts in subduction zones, indicate that the Himalayan plate boundary is not a single structure but a series of structures across strike, including reactivated parts of the Main Boundary Thrust north of the range front, the HFT sensu stricto, and stepout structures on the Indo-Gangetic Plain. Displacement rates on all these structures must be added to determine the local India-Himalaya convergence rate.

  3. Analysis of grain boundary dislocations by large angle convergent beam electron diffraction.

    PubMed

    Morniroli, J P; Cherns, D

    1996-01-01

    Large angle convergent beam electron diffraction (LACBED) is used to analyse secondary dislocations in sigma3 and sigma9 grain boundaries in silicon. By selecting reflections from crystal planes common to the adjoining grains, LACBED images are insensitive to the boundaries except where dislocations are present. The dislocation images are closely similar to those for dislocations in single crystals and can be analysed by standard Cherns-Preston rules. It is shown that, for both boundaries, sufficient common reflections can be selected for a complete analysis, and that dislocations can be analysed assuming integer values of g x b, implying that the Burgers vectors are Displacement Shift Complete (DSC) lattice vectors. For both sigma3 and sigma9 boundaries, DSC dislocations are identified which are specific to these boundaries. The experimental conditions for the analysis of grain boundaries are explained, and the extension of the method to other coincidence boundaries is discussed. PMID:22666917

  4. Plate Tectonics: From Plate Boundary Zone Tectonics To Extensive Intraplate Tectonics

    NASA Astrophysics Data System (ADS)

    Ishikawa, M.

    2004-12-01

    Plates makes up earth's surface, and tectonic activity is generally concentrated on plate boundary zones. In restrict meaning, plate tectonics of the earth is regarded as mixture of plate boundary zone tectonics and extensive intraplate tectonics. For example, the Asian continent never behaves as rigid plate that was deformed extensively when the Indian continent collided with it. I infer that extensive intraplate tectonics reflects rheological weakening of wet mantle. To demonstrate effect of H2O component on plate strength, one-dimensional rheological profiles of 100 km depth were constructed by assuming 20km thick upper crust and 20km thick lower crust. Temperature-depth profiles were calculated based on one-dimensional steady-state static heat transfer at given surface heat flows. Power law creep and Byerlee_fs law were used to estimate strength in ductile regime and brittle regime respectively. Creep strength for upper crust, lower crust, dry mantle and wet mantle were calculated using creep parameters of granite, granulite, dry dunite and wet dunite. The minimum value between power law creep strength and Byerlee_fs law strength gives the strength of the lithosphere. Strength profile at surface heat flow of 55mW/m2 (continental average is 56.5mW/m2) and strain rate of 10-15/s (intraplate deformation is about 10-15/s - 10-16/s in Asia) shows a significant difference in strength for using dry mantle and wet mantle. In case of dry mantle, the uppermost mantle is quite strong. However, if wet peridotite represent the upper mantle, there is very little strength in the uppermost mantle. The cumulative lithospheric strength, i.e. integral strength from surface to 100km depth, and the cumulative mantle strength, i.e. integral strength from 40km to 100km depth were calculated with changing strain rate. For example, to deform continental lithosphere at strain rate of 10-15/s, wet mantle has a cumulative strength of about 2x1012N/m whereas the cumulative strength of dry

  5. Features on Venus generated by plate boundary processes

    NASA Technical Reports Server (NTRS)

    Mckenzie, Dan; Ford, Peter G.; Johnson, Catherine; Parsons, Barry; Sandwell, David; Saunders, Stephen; Solomon, Sean C.

    1992-01-01

    Various observations suggest that there are processes on Venus that produce features similar to those associated with plate boundaries on earth. Synthetic aperture radar images of Venus, taken with a radar whose wavelength is 12.6 cm, are compared with GLORIA images of active plate boundaries, obtained with a sound source whose wavelength is 23 cm. Features similar to transform faults and to abyssal hills on slow and fast spreading ridges can be recognized within the Artemis region of Venus but are not clearly visible elsewhere. The composition of the basalts measured by the Venera 13 and 14 and the Vega 2 spacecraft corresponds to that expected from adiabatic decompression, like that which occurs beneath spreading ridges on earth. Structures that resemble trenches are widespread on Venus and show the same curvature and asymmetry as they do on earth. These observations suggest that the same simple geophysical models that have been so successfully used to understand the tectonics of earth can also be applied to Venus.

  6. Stress accumulation and release at complex transform plate boundaries

    SciTech Connect

    Verdonck, D.; Furlong, K.P. )

    1992-10-01

    Finite element methods are used to model the dynamics of deformation along complex transform plate boundaries, specifically the San Andreas fault system, California. Effects of mantle rheology and fault geometry on the stress buildup and release are investigated. No prior knowledge of the earthquake cycle time or amount of fault slip is assumed that the results suggest that the San Andreas fault slips at low shear stress (about 15 MPa). Although the maximum stress on the fault is 15 MPa, models with an upper mantle shear zone deforming entirely by dislocation creep accumulate stresses that exceed 100 MPa, a stress level high enough to drive localized dynamic recrystallization and a shift in dominant deformation mechanism to diffusion creep. Models in which the mantle shear zone deform locally by diffusion creep reach a dynamic steady state where lithospheric shear stresses never exceed the specified fault stress anywhere in the model and indicate that the strength of the upper mantle is an important parameter in the dynamics of plate boundary deformation. 17 refs.

  7. How transpressive is the northern Caribbean plate boundary?

    NASA Astrophysics Data System (ADS)

    Corbeau, J.; Rolandone, F.; Leroy, S.; Meyer, B.; Mercier de Lépinay, B.; Ellouz-Zimmermann, N.; Momplaisir, R.

    2016-04-01

    Transpressive deformation at the northern Caribbean plate boundary is accommodated mostly by two major strike-slip faults, but the amount and location of accommodation of the compressional component of deformation are still debated. We collected marine geophysical data including multibeam bathymetry and multichannel seismic reflection profiles along this plate boundary around Hispaniola, in the Jamaica Passage, and in the Gulf of Gonâve. The data set allows us to image the offshore active strike-slip faults as well as the compressional structures. We confirm that the Enriquillo-Plantain-Garden Fault Zone (EPGFZ) in the Jamaica Passage has a primary strike-slip motion, as indicated by active left-lateral strike-slip-related structures, i.e., restraining bend, asymmetrical basin, en echelon pressures ridges, and horsetail splay. Based on topographic cross sections across the EPGFZ, we image a very limited compressional component, if any, for at least the western part of the Jamaica Passage. Toward the east of the Jamaica Passage, the fault trace becomes more complex, and we identify adjacent compressional structures. In the Gulf of Gonâve, distributed folding and thrust faulting of the most recent sediments indicate active pervasive compressional tectonics. Estimates of shortening in the Jamaica Passage and in the Gulf of Gonâve indicate an increase of the compressional component of deformation toward the east, which nonetheless remains very small compared to that inferred from block modeling based on GPS measurements.

  8. The Plate Boundary Observatory: Operational Status and Data Plans

    NASA Astrophysics Data System (ADS)

    Anderson, G.; Feaux, K.; Jackson, M.; Prescott, W.; Stolte, C.; Wright, J.

    2004-12-01

    The Plate Boundary Observatory (PBO), part of the NSF-funded EarthScope project, is designed to study the three-dimensional strain field resulting from deformation across the active boundary zone between the Pacific and North American plates in the western United States. The science goals of PBO require that plate boundary deformation be adequately characterized over the wide range of spatial and temporal scales common to active continental tectonic processes. PBO will meet these needs using 875 continuous GPS sites, 143 borehole strainmeter stations, and five laser strainmeters, all installed over the next five years. In addition, there will be a pool of 100 portable GPS receivers available for survey-mode observations, and in 2005, we anticipate incorporating 225 existing continuous GPS sites into PBO with funding under the PBO Nucleus proposal. These stations will provide raw observations from which PBO Analysis Centers will create a wide range of derived data products, including time series of strain and GPS station position, GPS velocity vectors, and strainmeter and GPS processing auxiliary information. All PBO data and data products will be made available to the community as rapidly and freely as possible through the PBO Archives and ultimately through the EarthScope Data Access System, part of the EarthScope Portal. PBO began operations in September 2003 and the first five new PBO continuous GPS (CGPS) stations were installed in January 2004. Currently, there are 39 stations installed and collecting data, of which 27 are returning data automatically to PBO Headquarters in Boulder on a daily basis. Data from 14 of these stations are available through the PBO GPS Archives at the UNAVCO Facility in Boulder and the Scripps Orbit and Permanent Array Center in San Diego. We anticipate having a total of 50 CGPS stations installed by the end of September 2004 and an additional 200 CGPS stations installed by the end of September 2005. The first PBO borehole

  9. New GPS constraints on active deformation along the Africa-Iberia plate boundary

    NASA Astrophysics Data System (ADS)

    Koulali, A.; Ouazar, D.; Tahayt, A.; King, R. W.; Vernant, P.; Reilinger, R. E.; McClusky, S.; Mourabit, T.; Davila, J. M.; Amraoui, N.

    2011-08-01

    We use velocities from 65 continuous stations and 31 survey-mode GPS sites as well as kinematic modeling to investigate present day deformation along the Africa-Iberia plate boundary zone in the western Mediterranean region. The GPS velocity field shows southwestward motion of the central part of the Rif Mountains in northern Morocco with respect to Africa varying between 3.5 and 4.0 mm/yr, consistent with prior published results. Stations in the southwestern part of the Betic Mountains of southern Spain move west-southwest with respect to Eurasia (˜ 2-3 mm/yr). The western component of Betics motion is consistent with partial transfer of Nubia-Eurasia plate motion into the southern Betics. The southward component of Betics motion with respect to Iberia is kinematically consistent with south to southwest motion of the Rif Mountains with respect to Africa. We use block modeling, constrained by mapped surface faults and seismicity to estimate the geometry and rates of strain accumulation on plate boundary structures. Our preferred plate boundary geometry includes one block between Iberia and Africa including the SW Betics, Alboran Sea, and central Rif. This geometry provides a good fit to the observed motions, suggesting a wide transpressive boundary in the westernmost Mediterranean, with deformation mainly accommodated by the Gloria-Azores fault system to the West and the Rif-Tell lineament to the East. Block boundaries encompass aspects of earlier interpretations suggesting three main deformation styles: (i) extension along the NE-SW trending Trans-Alboran shear zone, (ii) dextral strike-slip in the Betics corresponding to a well defined E-W seismic lineament, and (iii) right lateral strike-slip motion extending West to the Azores and right-lateral motion with compression extending East along the Algerian Tell. We interpret differential motion in the Rif-Alboran-Betic system to be driven both by surface processes related the Africa-Eurasia oblique convergence and

  10. Seismic and geodetic constraints on plate boundary deformation across the northern Macquarie Ridge and southern South Island of New Zealand

    NASA Astrophysics Data System (ADS)

    Moore, M. A.; Anderson, H. J.; Pearson, C.

    2000-12-01

    In the southern New Zealand region the boundary between the Australian and Pacific plates changes from oblique continental convergence in the central South Island of New Zealand to interoceanic transcurrent motion along the Macquarie Ridge. Source parameters of recent (post-1964) upper crustal events, Mw>=5.3, in the region 43-53°S, 155-175°E are determined using P- and SH-waveform analysis in order to investigate the nature of strain accommodated seismically throughout the region. Repeated occupation of three geodetic networks across the southern South Island provides estimates of contemporary crustal strain. Seismicity over the last 35 years shows uneven spatial and temporal distribution, with clusters of events occurring in regions along the plate boundary that exhibit structural variation. Focal mechanisms of individual earthquakes vary widely but are consistent with the accommodation of long-term estimates of the relative plate motion. Across the southern South Island, geodetically measured principal contraction directions are consistent with P-axis orientations. The mode of accommodation of the relative plate motion varies throughout the region, influenced by the change in crustal composition on either side of the plate boundary, the underlying structure as a relic of previous relative motions, and the variation of obliquity of the relative motion with respect to these structures.

  11. Physics-Based Predictive Simulation Models for Earthquake Generation at Plate Boundaries

    NASA Astrophysics Data System (ADS)

    Matsu'Ura, M.

    2002-12-01

    cycles in and around Japan. The total simulation system is divided into three components: a crust-mantle structure model, a tectonic loading model and a dynamic rupture model. For a San Andreas type of plate boundaries we have already developed a standard model. In the case of convergent plate boundaries, although the basic equations governing the earthquake generation cycle are essentially the same as those in the case of transcurrent plate boundaries, the practical modelling is much more difficult, because of complexity in geometry of plate interfaces. For the present we have developed a 3-D standard structure model of plate interfaces in and around Japan, the viscoelastic slip-response functions for this structure model, and the slip- and time-dependent fault constitutive law with an inherent strength-restoration mechanism. Combining all these elements, we can construct a quasi-static tectonic loading model. For the dynamic rupture process, we have developed a simulation algorithm for rupture propagation on a 3-D curved fault surface by applying BIEM. In the last stage of CAMP the quasi-static loading model and the dynamic rupture model are connected with each other through a simulation platform on the Earth Simulator. Outputs of the simulation system are the crustal deformation, internal stress change and seismic wave radiation associated with the progress of seismic and/or aseismic slip on the plate interfaces. From comparison of these computed data and observed data, we can extract useful information to estimate the past slip history and the present stress state on the plate interfaces by using a technique of inversion analysis.

  12. The Magmatic Component of the Plate Boundary Observatory.

    NASA Astrophysics Data System (ADS)

    Mencin, D.; Jackson, M.; Lisowski, M.; Feaux, K.; Andersen, G.; Bohnenstiehl, K.; Hodgkinson, K.; Coyle, B.; Friesen, B.; Pauk, B.; Walls, C.; Meertens, C.

    2007-12-01

    The Plate Boundary Observatory (PBO) component of the NSF-funded Earthscope program has a significant complement of instruments devoted to the study of magmatic systems. There are ten target areas: Akutan, Unimak, Augustine, Mt St Helens, Long Valley, Yellowstone, Lake Tahoe, Medicine Lake, Mt Lassen, and Mt Shasta that include 22 borehole strainmeters, 22 borehole seismometers, 26 borehole tiltmeters and 110 continuous GPS stations all returning data in near real-time. In conjunction with the existing instrumentation operated by the USGS Volcanic Hazards Programs Volcano Observatories, this represents a significant array of tools for exploring various volcanic processes. In the first four years of the project, PBO has captured two volcanic events (Mt St Helens and Augustine) far exceeding the anticipation of capturing one event in the first 15 years of the project. This presentation gives an overview and status of the program, the various targets, instrumentation and results.

  13. Viscoelastic Postseismic Rebound to Strike-Slip Earthquakes in Regions of Oblique Plate Convergence

    NASA Technical Reports Server (NTRS)

    Cohen, Steven C.

    1999-01-01

    According to the slip partitioning concept, the trench parallel component of relative plate motion in regions of oblique convergence is accommodated by strike-slip faulting in the overriding continental lithosphere. The pattern of postseismic surface deformation due to viscoelastic flow in the lower crust and asthenosphere following a major earthquake on such a fault is modified from that predicted from the conventual elastic layer over viscoelastic halfspace model by the presence of the subducting slab. The predicted effects, such as a partial suppression of the postseismic velocities by 1 cm/yr or more immediately following a moderate to great earthquake, are potentially detectable using contemporary geodetic techniques.

  14. The Development of the San Andreas Plate Boundary through Northern California: Insights from GPS, Crustal Structure, and Lithospheric Modeling

    NASA Astrophysics Data System (ADS)

    Furlong, K. P.; Williams, T.; Hayes, G. P.

    2007-12-01

    thinning that occurs approximately 200 km south of the MTJ (i.e. ca. 4-5 million years after MTJ passage), and (4) development of the precursor faults to the San Andreas plate boundary structures appear to be driven by the combination of MCC crustal deformation and the development of localized shear within the MTJ-formed slab window. Further structural complexities arise in developing these precursor faults in the upper crust with its pre- existing convergent margin structures, which are either overprinted or reactivated as a result of their orientation and segmentation. The addition of GPS observations to the existing catalog of geophysical and tectonic characteristics of the northern San Andreas system allow us to place the transition from a mature convergent margin to an active translational plate boundary into a physically constrained framework. The MCC model of plate boundary evolution is consistent with these kinematic and structural constraints and thus provides a useful framework model for unraveling the processes that drive the development of the San Andreas plate boundary after MTJ passage and the cessation/removal of subduction from the western margin of North America.

  15. Evolution of faulting and plate boundary deformation in the Southern Taranaki Basin, New Zealand

    NASA Astrophysics Data System (ADS)

    Reilly, Cathal; Nicol, Andrew; Walsh, John J.; Seebeck, Hannu

    2015-05-01

    Faulting and folding in the Southern Taranaki Basin constrain the evolution of the New Zealand plate boundary since ~ 80 Ma. Sedimentary rocks up to 8 km thick record multiple phases of deformation which have been examined using 2D and 3D seismic reflection data, resulting in fault displacement-time curves and basin-wide isopach maps with temporal resolutions of 5-10 Myr and 1-4 Myr pre- and post-~ 23 Ma respectively. Three main phases of tectonic activity have been recognised; Late Cretaceous and Palaeocene extension (~ 80-55 Ma), mainly Oligocene and younger contraction and Plio-Pleistocene (~ 3.7-0 Ma) extension. Most of the largest faults (e.g., Cape Egmont Fault) accrued displacement during the Late Cretaceous and were reactivated one or more times during subsequent episodes of deformation. The oldest phase of extension occurred during Gondwana break-up and was ubiquitous throughout the basin. Contraction along the eastern boundary of the basin, associated with the onset of Hikurangi Margin subduction, commenced as early as Late Eocene. The zone of contraction widened and migrated westward during the Miocene with reverse faults and folds in westernmost parts of the basin formed in the Late Miocene (~ 7-5 Ma). Initiation and episodic widening of this zone of contraction may have been partly triggered by changes in the rate of plate convergence. Contraction is now mainly confined to the northern South Island and has been succeeded to the north by Plio-Pleistocene extension. The present day transition zone between extension in the north and contraction in the south is defined by a WNW-trending line across the basin. The extension-contraction transition migrated southward during the Late Miocene and Pliocene consistent with steepening of the subducting plate and associated southward movement of the southern termination of the Hikurangi subduction system.

  16. Coseismic slip resolution along a plate boundary megathrust: the Nankai Trough, southwest Japan

    USGS Publications Warehouse

    Sagiya, Takeshi; Thatcher, Wayne

    1999-01-01

    Geodetic survey measurements are used to estimate the coseismic slip distribution in the 1944 Tonankai (Mw=8.1) and 1946 Nankaido (Mw=8.3) earthquakes and to assess quantitatively the degree to which this slip is resolved on the plate boundary megathrust. Data used include 798 angle changes from triangulation surveys, 328 leveling section differences, and 5 coseismic tidal gage offsets. Many of the nominally coseismic triangulation data span ∼50 years, nearly half the earthquake cycle, and correction for interseismic deformation using post-1950 observations is applied. Microseismicity is used to define the configuration of the plate boundary interface and approximate it with a continuous, multisegment fault model. Because the onshore geodetic data have very limited resolving power for offshore fault segments, offshore coseismic slip was constrained by Satctke's [1993] estimation based on tsunami data. The majority of the coseismic slip occurs between 15 and 25 km depth. Although resolution declines toward the trench axis, it is sufficiently good to define two distinct high-slip regions, one off southeastern Shikoku Island (11 m maximum) and the other offshore of Kii Peninsula (3 m maximum). The slip magnitude off southeastern Shikoku, coupled with the plate convergence rate, would imply an recurrence interval of about 270 years, much-longer than the average repeat time of ∼120 years for historical great earthquakes on the Nankai Trough. However, the maximum coseismic slip is sensitive to the assumed fault geometry, and slippage on trough-parallel splay faults could significantly decrease the maximum slip to about 6 m.

  17. Patterns of seismogenesis for giant plate-boundary earthquakes in island-arc-type subduction systems

    NASA Astrophysics Data System (ADS)

    Kirby, S. H.

    2006-12-01

    The global record of giant earthquake occurrence in subduction zones during the instrumental and historical eras is woefully short; only about 16 events with magnitudes above 8.4 are reasonably well documented since 1700. We find no examples of giant (M > 8.4) interplate thrust events and/or wide-ranging tsunamis sourced in the classic island arcs with fast backarc spreading (Bonin, Marianas, Tonga-Kermadec, Vanuatu, and South Scotia). The Sumatra-Andaman Earthquake of 2004 (SAE) ruptured a sector of the INDIA-BURMA subduction boundary and evidently had no known historical antecedents, suggesting that the return time may be many centuries to millennia and consistent with low convergence rates. Moreover, the persistence of rupture to the north in the weakly volcanic Nicobar/Andaman sector gives one pause to reflect on the assumption that island arcs, especially those with active back-arc spreading such as the Marianas, do not produce great interplate- thrust earthquakes. The Andaman/Nicobar subduction segment is an unusual island arc. Only two arc volcanoes occur between the convergent plate boundary west of the Andamans and the backarc ridge/transform system to the east. Backarc spreading in the Andaman/ Nicobar segment is unusual because the NNW spreading directions are nearly parallel to the trench/deformation-front as do the INDIA-BURMA plate motions across it. This geometry suggests that arc-normal extension, trench migration and associated slab normal motions may not mechanically decouple this subduction system. The Nicobar sector of the rupture for the 2004 event is roughly 200 km wide judging from the aftershock distribution; a distribution that persists to the east under the Nicobar Islands, suggesting that the plate-boundary dip is very shallow in that latitude range. If this is correct, then the down-dip limitation on seismogenic slip set by serpentinized forearc mantle (Hyndman et al., 2003) may not control rupture width as it apparently does for many

  18. Convergence

    NASA Astrophysics Data System (ADS)

    Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

    2005-09-01

    Call for Papers: Convergence The Journal of Optical Networking (JON) invites submissions to a special issue on Convergence. Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and

  19. Diurnal cycle in convergence patterns in the boundary layer east of the Andes and convection

    NASA Astrophysics Data System (ADS)

    Nicolini, Matilde; Skabar, Yanina García

    2011-06-01

    The South American Low-Level Jet Experiment (SALLJEX) provided a unique dataset to investigate the existence of a mesoscale low-level circulation and of a diurnal cycle in its related convergence pattern over the Southeastern South American region east of the Andes, as well as its relationship with deep convection during the warm season. The present paper builds upon high-resolution analyses produced, assimilating the data collected during the SALLJEX field campaign using BRAMS, and explores their capability to reproduce mesoscale circulations not resolved by the low density observational network available in this region. Results of the analyses show a diurnal oscillation signal in the mean boundary layer convergence pattern over the plains with a nocturnal (daytime) convergence (divergence) maximum. These results are coherent with previous findings of a nocturnal phase in the mature stage of organized deep convection and related precipitation in subtropical latitudes east of the Andes during the warm season. The diurnal cycle of convergence/divergence in the boundary layer is described over a 15-day period, during which different synoptic conditions occurred. During weakly forced environments a regime characterized by nocturnal eastward anomaly flow and convergence and daytime westward anomaly flow and divergence related to a mesoscale northwestern mountain-central plain flow regime dominates over the plains between the Andes Mountains, the Parana River Valley, and the southern Brazil mountain range. In contrast, during synoptic conditions dominated by the presence of a deep thermal low over northwestern Argentina and a related low-level jet, convergence at night is mainly accomplished by the predominantly meridional low-level jet, which exhibits an anomalous weak wind speed diurnal cycle with respect to its summer climatological mean. On the other hand daytime divergence is completely produced by the zonal wind component as in the previous synoptic situation

  20. Convergence

    NASA Astrophysics Data System (ADS)

    Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

    2005-09-01

    Call for Papers: Convergence The Journal of Optical Networking (JON) invites submissions to a special issue on Convergence. Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and

  1. Crustal Deformation at the Arabian Plate-Boundary observed by InSAR

    NASA Astrophysics Data System (ADS)

    Jonsson, S.; Cavalié, O.; Akoglu, A. M.; Wang, T.; Xu, W.; Feng, G.; Dutta, R.; Abdullin, A. K.

    2013-12-01

    The Arabian plate is bounded by a variety of active plate boundaries, with extension in the Red Sea and Gulf of Aden to the south, compression in Turkey and Iran to the north, and transform faults to the west and to the east. Internally, however, the Arabian plate has been shown to be tectonically rather stable, despite evidence of recent volcanism and earthquake faulting. We use InSAR observations to study recent tectonic and volcanic activity at several locations at the Arabian plate boundary as well within the plate itself. The region near the triple junction between the Arabian, Eurasian, and Anatolian plates has often been the focus of studies on continental deformation behavior and interseismic deformation. Here we use large-scale InSAR data processing to map the deformation near the triple junction and find the deformation to be focused on major faults with little intra-plate deformation. The eastern part of the East Anatolian Fault appears to have a very shallow locking depth with limited fault-normal deformation. Several major earthquakes that have occurred in recent years on the Arabian plate boundary, including the 2011 magnitude 7.1 Van earthquake in eastern Turkey. It occurred as a result of convergence of the Arabian plate towards Eurasia and caused significant surface deformation that we have analyzed with multiple coseismic InSAR, GPS, and coastal uplift observations. We use high-resolution Cosmo-Skymed and TerraSAR-X data to derive 3D coseismic displacements from offsets alone, as some of the interferograms are almost completely incoherent. By identifying point-like targets within the images, we were able to derive accurate pixel offsets between SAR sub-images containing such targets, which we used to estimate the 3D coseismic displacements. The derived 3D displacement field helped in constraining the causative northward dipping thrust-fault. The Qadimah fault is a recently discovered fault located on the Red Sea coast north of Jeddah and under the

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

    NASA Astrophysics Data System (ADS)

    Anderson, G.; Hodgkinson, K.; Jackson, M.; Wright, J.

    2005-12-01

    The Plate Boundary Observatory (PBO), part of the NSF-funded EarthScope project, is designed to study the three-dimensional strain field resulting from deformation across the active boundary zone between the Pacific and North American plates in the western United States. To meet these goals, PBO will install 891 continuous GPS stations, up to 174 borehole strainmeter stations, and five laser strainmeters, over the next five years. In addition, 209 previously existing continuous GPS stations will be incorporated into PBO through the PBO Nucleus project, and there will be a pool of 100 portable GPS receivers available for survey-mode observations. To date, 209 PBO GPS stations have been installed, of which 182 have returned data. In addition, PBO now handles data flow for 29 PBO Nucleus stations. Most of these stations return data to the PBO data center in Boulder on a daily basis. These data are then processed by the PBO GPS Analysis Centers, at Central Washington University and the University of California, Berkeley, and the PBO GPS Analysis Center Coordinator at MIT. These groups create a range of GPS products, including station position time series, GPS velocity vectors, and related information. At present, these centers are processing data on a daily basis from about 300 stations; typical position uncertainties are approximately 1.5 mm horizontally and 4 mm vertically, both of which will improve as more data are analyzed. All PBO GPS data products are archived at and available from the UNAVCO Facility, with a second archive under development at the IRIS Data Management Center. PBO now has six borehole strainmeters and one laser strainmeter installed, with data returned at least once per day, and PBO handles data flow for a previously installed laser strainmeter as well. These data are analyzed on a daily basis by the Borehole Strainmeter Data Analysis Center in Socorro, New Mexico, and the Laser Strainmeter Data Analysis Center at the University of California

  3. Accommodation of collisional shortening along the Alpine plate boundary : plate kinematics vs rheological controls

    NASA Astrophysics Data System (ADS)

    Rosenberg, Claudio; Bellahsen, Nicolas

    2016-04-01

    The style of collision in the Alps varies along strike, reflecting different amounts and different modes of accommodation of collisional shortening. These differences control the patterns of exhumation during collision. Whereas the western Alps largely consist of a metamorphic complex formed during subduction and largely exhumed before the initiation of collision, the subduction nappe-stack of the Central and the Eastern Alps is strongly overprinted by collisional shortening and by Barrovian metamorphism. Based on compiled and new data we estimate amounts of collisional shortening along the strike of the chain and set it in relationship to the geometry of the collisional prism. The western Alpine collisional structures form a very large (in map view), but moderately shortened wedge, terminating in front of a poorly developed Molasse basin. Shortening of this wedge was mainly localized along its external parts, resulting in accretion of basement and cover units thrusted towards the foreland. Back-folding and back-thrusting are barely developed and no shortening takes place in the upper, Adriatic plate. In the Central Alps, the amount of collisional shortening is larger and it is distributed both in the lower and in the upper plate. The collisional prism is bivergent and partitioning of the amount of shortening between the upper and lower plates varies along strike, being most probably controlled by rheological, heterogeneities. The thickened accreted lower plate is strongly affected by Barrovian metamorphism where shortening is largest and localized within a confined area. A deep Molasse basin developed in front of the prism. In the Eastern Alps collisional kinematics vary from east to west, with orogen-parallel displacements dominating in the east and orogen-perpendicular ones in the West, where they culminate in the structural and metamorphic dome of the Tauern Window. Nowhere else in the Alps collisional shortening is so strongly localized in one and the same

  4. Effect of Convergent and Divergent Boundaries on Flow Resistance through Porous Media

    NASA Astrophysics Data System (ADS)

    Bhanu Prakasham Reddy, N.; Krishnaiah, S.; Ramakrishna Reddy, M.

    2015-12-01

    An experimental investigation on the effect of convergent and divergent streamlines on the total energy loss in the porous medium and the effect on linear parameter, a, and non-linear parameter, b, for different ratios of radii of the test section was studied in a convergent and divergent permeameter. This paper presents the results of applying dimensional analysis to obtain a relationship between friction factor (fd) and Reynolds number (Rd) for flow in porous media with convergent and divergent boundaries, using pore size of the media (d) as characteristic length. Using friction factor (fd) and Reynolds number (Rd) relationship, theoretical curves, are developed and verified with the help of existing experimental data. In the present case, Mc Corquodale data of size 1.66 cm was used as media and water as fluid, to develop curves relating friction factor (fd) and Reynolds number (Rd) for different ratios of radii of the test section of convergent permeameter and divergent permeameter with the same convergent and divergent angle of 0.328 rad.

  5. Convergence

    NASA Astrophysics Data System (ADS)

    Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

    2005-08-01

    Call for Papers: Convergence The Journal of Optical Networking (JON) invites submissions to a special issue on Convergence. Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and

  6. Convergence

    NASA Astrophysics Data System (ADS)

    Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

    2005-06-01

    Call for Papers: Convergence The Journal of Optical Networking (JON) invites submissions to a special issue on Convergence. Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and

  7. Convergence

    NASA Astrophysics Data System (ADS)

    Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

    2005-05-01

    Call for Papers: Convergence The Journal of Optical Networking (JON) invites submissions to a special issue on Convergence. Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and

  8. Convergence

    NASA Astrophysics Data System (ADS)

    Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

    2005-04-01

    Call for Papers: Convergence The Journal of Optical Networking (JON) invites submissions to a special issue on Convergence. Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and

  9. Convergence

    NASA Astrophysics Data System (ADS)

    Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

    2005-01-01

    Call for Papers: Convergence

    Guest Editors: Thomas E. Darcie, University of Victoria Robert Doverspike, AT&T Martin Zirngibl, Lucent Technologies

    Coordinating Associate Editor: Steven K. Korotky, Lucent Technologies

    The Journal of Optical Networking (JON) invites submissions to a special issue on Convergence. Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly

  10. Convergence

    NASA Astrophysics Data System (ADS)

    Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

    2004-12-01

    Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and data, video and data, private-line and virtual private-line, fixed and mobile, and local and long-haul services. These

  11. Convergence

    NASA Astrophysics Data System (ADS)

    Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

    2004-12-01

    Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and data, video and data, private-line and virtual private-line, fixed and mobile, and local and long-haul services. These

  12. Convergence

    NASA Astrophysics Data System (ADS)

    Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

    2005-03-01

    Call for Papers: Convergence Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and data, video and data, private-line and virtual private-line, fixed and mobile, and local and

  13. Convergence

    NASA Astrophysics Data System (ADS)

    Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

    2005-02-01

    Call for Papers: Convergence Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and data, video and data, private-line and virtual private-line, fixed and mobile, and local and

  14. Characteristics of transition in a flat-plate boundary layer

    NASA Astrophysics Data System (ADS)

    Choi, Myung-Ryul; Choi, Haecheon; Kang, Shin-Hyoung

    1998-11-01

    A direct numerical simulation of the spatially evolving transition in a flat-plate boundary layer is performed in the region of ( 115000<= Re_x<= 340000 ) with ( 1537× 99× 128 ) grid points. Inflow disturbances, similar to the two dimensional T-S wave combined with three dimensional waves, are generated on the upstream wall through time-dependent localized blowing and suction. A ( Λ ) vortex, consisting of two legs, is identified at a downstream location of blowing and suction. Soon a hairpin vortex, consisting of a head and two legs, is formed from the ( Λ ) vortex through the self induction mechanism. At a later time new hairpin vortices are successively produced behind the first hairpin vortex. At the final stage six hairpin vortices are observed. As the vortices move downstream in time, the legs of the ( Λ ) vortex get stronger and become quasi-streamwise vortices, while the head of the hairpin vortex changes into an ( Ω ) shape. Near the end of the computational domain the hairpin vortices and quasi-streamwise vortices are entangled with each other and convect downstream together; these phenomena are compared with the characteristics of a turbulent spot. It is shown that the spikes and saw-tooth like jumps in the streamwise velocity signals, observed in experiments, are associated with the heads and legs of the hairpin vortices, respectively.

  15. Plate boundary re-organization in the western Mediterranean

    NASA Astrophysics Data System (ADS)

    Wortel, M. J.; Govers, R. M.; Baes, M.

    2010-12-01

    The TOPO-EUROPE ESF Collaborative Research Project TOPOMED addresses an intriguing process of plate boundary re-organization, considered to be active in the western Mediterranean region. The opening of the Algero-Provencal Basin (between Spain, Corsica-Sardinia and NW Africa) by roll-back of the African lithosphere, led to collision of the migrating arc-trench system with the NW African (Maghrebian) continental margin, in the M. Miocene. TOPOMED investigates the hypothesis that this event prompted the subsequent and probably still ongoing evolution of the Calabrian Arc in the east, and possibly that of the Gibraltar Arc in the west. In this contribution we focus on the role of STEP faults (Subduction-Transform-Edge-Propagators [Govers and Wortel, EPSL 2005]) in the evolution of the arcs. Furthermore, seismic activity along the margins of NW Africa and northern Sicily indicates the possibility that a new subduction zone is being formed, accommodating the continuing ~ N-S motion between Africa and Eurasia (Europe) after arc-continent collision. The postulated processes involved are subduction polarity reversal and subduction initiation along a STEP fault. The Mediterranean setting offers unique opportunities to study the arcs’ evolution and the subduction initiation process in a natural setting. We explore the differences between the margins’ settings on the basis of observations and report on numerical modeling results pertaining to the inferred processes of subduction initiation.

  16. Obliquely convergent plate motion and its relation with forearc sliver movement, El Salvador volcanic arc

    NASA Astrophysics Data System (ADS)

    Tikoff, B.; DeMets, C.; Garibaldi, N.; Hernandez, W.; Hernandez, D.

    2012-12-01

    The magmatic arc in El Salvador is interpreted to result from the subduction of the Cocos plate underneath the Caribbean plate along the Middle America trench. In addition, El Salvador contains a fore-arc sliver that moves 11 mm/yr westward relative to the back-arc. Well-defined strike-slip faults along the magmatic arc accommodate forearc sliver motion, but are offset at several locations by en echelon pull-apart step-overs with abundant normal faults. All basaltic-andesitic magmatic centers (San Miguel, San Vincente, San Salvador, Santa Ana) are located within these step-overs, while the two major rhyolitic calderas (Ilopango, Coatepeque) occur directly along the strike-slip faults. There are two puzzling aspects about the strike-slip tectonism. First, a silicic, shallow magma body that intrudes the San Miguel fault zone (part of the El Salvador fault system) was emplaced syn-tectonically (sigmoidal field and magnetic foliations, subhorizontally plunging magnetic lineations and dextral shear at the microscale). Within the dextrally sheared portion of the intrusion, an obsidian band with a 40Ar/39Ar age of 7.46 Ma indicates that dextral strike-slip tectonism in the Salvadoran arc has been an ongoing process for ~7.5 Ma. This casts significant doubt on whether Cocos ridge subduction (that started ~1 Ma ago) is the cause of the ongoing forearc movement. The potentially more significant problem is that the fore-arc sliver in El Salvador moves 11 mm/yr westward relative to the back-arc despite a nearly orthogonal angle of convergence (with a convergence rate of ~77 mm/yr) near El Salvador and absence of significant frictional coupling along the subduction interface. Further, GPS indicates that the Nicaraguan and Salvadoran forearcs define a semi-rigid sliver moving at nearly the same trench-parallel rates despite along-trench changes in the subduction angle. Consequently, it is tempting to attribute the movement of both forearc slivers to Cocos ridge subduction

  17. Average properties of compressible laminar boundary layer on flat plate with unsteady flight velocity

    NASA Technical Reports Server (NTRS)

    Moore, Franklin K; Ostrach, Simon

    1957-01-01

    The time-average characteristics of boundary layers over a flat plate in nearly quasi-steady flow are determined. The plate may be either insulated or isothermal. The time averages are found without specifying the plate velocity explicitly except that it is positive and has an average value.

  18. Free vibrations of thermally stressed orthotropic plates with various boundary conditions

    NASA Technical Reports Server (NTRS)

    Bailey, C. D.; Greetham, J. C.

    1973-01-01

    An analytical investigation of the vibrations of thermally stressed orthotropic plates in the prebuckled region is presented. The investigation covers the broad class of trapezoidal plates with two opposite sides parallel. Each edge of the plate may be subjected to different uniform boundary conditions. variable thickness and arbitrary temperature distributions (analytical or experimental) for any desired combination of boundary conditions may be prescribed. Results obtained using this analysis are compared to experimental results obtained for isotropic plates with thermal stress, and to results contained in the literature for orthotropic plates without thermal stress. Good agreement exists for both sets of comparisons.

  19. Convergence

    NASA Astrophysics Data System (ADS)

    Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

    2005-01-01

    Call for Papers: Convergence

    Guest Editors: Thomas E. Darcie, University of Victoria Robert Doverspike, AT&T Martin Zirngibl, Lucent Technologies

    Coordinating Associate Editor: Steven K. Korotky, Lucent Technologies

    The Journal of Optical Networking (JON) invites submissions to a special issue on Convergence. Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly

  20. The Stokes problem with various well-posed boundary conditions - Symmetric formulations that converge for all velocity/pressure spaces

    NASA Technical Reports Server (NTRS)

    Hughes, Thomas J. R.; Franca, Leopoldo P.

    1989-01-01

    Symmetric finite-element formulations are presented for the primitive-variables form of the Stokes equations. These formulations are convergent for any combination of pressure and velocity interpolations. Various boundary conditions, such as pressure, are accommodated.

  1. Subcrustal earthquakes in the plate boundary zone of New Zealand's South Island

    NASA Astrophysics Data System (ADS)

    Boese, C. M.; Stern, T. A.; Townend, J.; Sheehan, A. F.; Molnar, P. H.; Collins, J. A.; Karalliyadda, S.; Bourguignon, S.; Bannister, S. C.

    2012-12-01

    Sporadic, intermediate-depth earthquakes have been observed for ~40 years in the vicinity of the Alpine Fault, a 460 km-long transpressive fault forming the western boundary of the Southern Alps. The Alpine Fault represents the plate boundary between the Australian and Pacific Plates in New Zealand and links two subduction zones of opposite polarity in the North and South. Several earthquakes at depths of 59-85 km have been recorded by the Southern Alps Microearthquake Borehole Array (SAMBA) since its deployment in November 2008. Due to large numbers of impulsive phase arrivals, focal mechanisms were obtained for these events during routine processing. In 2009 and early 2010, several additional temporary seismometer networks were operating in the central Southern Alps (Alpine Fault Array ALFA, Deep Fault Drilling Project 2010 DFDP10) and the offshore region west of the South Island (Marine Observations of Anisotropy Near Aotearoa MOANA). To gain more insight about the cause and mechanism of these deep events, a comprehensive analysis has been performed incorporating data from all available instruments. Accurate hypocentres of 22 earthquakes (ML<4) and focal mechanisms of at least 14 events have been obtained. The focal mechanisms reveal that reverse faulting predominates at depth in the continental collision zone between the Pacific and Australian Plates. The intermediate-depth events occur below the Moho discontinuity, which has been mapped in detail using wide-angle reflection/refraction data obtained during the South Island Geophysical Transect (SIGHT) project in 1995/96. Although the cause for these subcrustal earthquakes is not yet clear, they have previously been interpreted to result from intra-continental subduction (Reyners 1987), high shear-strain gradients due to depressed geotherms and viscous deformation of mantle lithosphere (Kohler and Eberhart-Phillips 2003). On the basis of the locations and mechanisms obtained using SAMBA, we have argued that

  2. The fluid budget of a continental plate boundary fault: Quantification from the Alpine Fault, New Zealand

    NASA Astrophysics Data System (ADS)

    Menzies, Catriona D.; Teagle, Damon A. H.; Niedermann, Samuel; Cox, Simon C.; Craw, Dave; Zimmer, Martin; Cooper, Matthew J.; Erzinger, Jörg

    2016-07-01

    Fluids play a key role in modifying the chemical and physical properties of fault zones, which may prime them for repeated rupture by the generation of high pore fluid pressures and precipitation of commonly weak, secondary minerals. Fluid flow paths, sources and fluxes, and the permeability evolution of fault zones throughout their seismic cycles remain poorly constrained, despite their importance to understanding fault zone behaviour. Here we use geochemical tracers of fluid-rock exchange to determine budgets for meteoric, metamorphic and mantle fluids on a major compressional tectonic plate boundary. The Alpine Fault marks the transpressional Pacific-Australian plate boundary through South Island, New Zealand and appears to fail in regular (329 ± 68 yrs) large earthquakes (Mw ∼ 8) with the most recent event in 1717 AD. Significant convergent motion has formed the Southern Alps and elevated geothermal gradients in the hangingwall, which drive crustal fluid flow. Along the Alpine Fault the Alpine Schist of the Pacific Plate is thrust over radiogenic metasedimentary rocks on the Australian plate. The absence of highly radiogenic (87Sr/86Sr > 0.7200) strontium isotope ratios of hangingwall hot springs and hydrothermal minerals formed at a range of depths in the Alpine Fault damage zone indicates that the fluid flow is restricted to the hangingwall by a cross-fault fluid flow barrier throughout the seismogenic crust. Helium isotope ratios measured in hot springs near to the Alpine Fault (0.15-0.81 RA) indicate the fault is a crustal-scale feature that acts as a conduit for fluids from the mantle. Rock-exchanged oxygen, but meteoric water-like hydrogen isotope signatures of hydrothermal veins indicate that partially rock-exchanged meteoric fluids dominate down to the top of the brittle to ductile transition zone at ∼6 km. Geochemical tracer transport modelling suggests only ∼0.02 to 0.05% of total rainfall west of the Main Divide penetrates to depth, yet this

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

    NASA Astrophysics Data System (ADS)

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

    1994-10-01

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

  4. Crustal deformation evidences for viscous coupling and fragmented lithosphere at the Nubia-Iberia plate boundary (Western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Palano, Mimmo; González, Pablo J.; Fernández, José

    2016-04-01

    A spatially dense crustal velocity field, based on up to 15 years of GNSS observations at more than 380 sites and extensively covering the Iberian Peninsula and Northern Africa, allow us to provide new insights into two main tectonic processes currently occurring in this area. We detected a slow large-scale clockwise rotation of the Iberian Peninsula with respect to a local pole located closely to the northwestern sector of the Pyrenean mountain range (Palano et al., 2015). Although this crustal deformation pattern could suggest a rigid rotating lithosphere block, this model would predict significant shortening along the Western (off-shore Lisbon) and North Iberian margin which cannot totally ruled out but currently is not clearly observed. Conversely, we favour the interpretation that this pattern reflects the quasi-continuous straining of the ductile lithosphere in some sectors of South and Western Iberia in response to viscous coupling of the NW Nubia and Iberian plate boundary in the Gulf of Cádiz. Furthermore, the western Mediterranean basin appears fragmented into independent crustal tectonic blocks, which delimited by inherited lithospheric shear structures and trapped within the Nubia-Eurasia collision, are currently accommodating most of the plate convergence rate. Among these blocks, an (oceanic-like western) Algerian one is currently transferring a significant fraction of the Nubia-Eurasia convergence rate into the Eastern Betics (SE Iberia) and likely causing the eastward motion of the Baleares Promontory. Most of the observed crustal ground deformation can be attributed to processes driven by spatially variable lithospheric plate forces imposed along the Nubia-Eurasia convergence boundary. Nevertheless, the observed deformation field infers a very low convergence rates as observed also at the eastern side of the western Mediterranean, along the Calabro Peloritan Arc, by space geodesy (e.g. Palano, 2015). References Palano M. (2015). On the present

  5. Investigation of Perforated Convergent-divergent Diffusers with Initial Boundary Layer

    NASA Technical Reports Server (NTRS)

    Weinstein, Maynard I

    1950-01-01

    An experimental investigation was made at Mach number 1.90 of the performance of a series of perforated convergent-divergent supersonic diffusers operating with initial boundary layer, which was induced and controlled by lengths of cylindrical inlets affixed to the diffusers. Supercritical mass-flow and peak total-pressure recoveries were decreased slightly by use of the longest inlets (4 inlet diameters in length). Combinations of cylindrical inlets, perforated diffusers, and subsonic diffuser were evaluated as simulated wind tunnels having second throats. Comparisons with noncontracted configurations of similar scale indicated conservatively computed power reductions of 25 percent.

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

    USGS Publications Warehouse

    Spall, H.

    1978-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

    The cinematic of the Pacific, Rivera and Cocos oceanic plates have a significant impact on the subduction process and seismic cycles occurring along the western Mexican Pacific margin of the North American and Caribbean plates. Sections of Pacific (PAC), Rivera (RIV), Cocos (COC), North American (NAM) and Caribbean (CAB) plate boundaries along the western margin of Mexico are not well constrained. From north to south: the transform-rift system at Gulf of California has been generally considered as part of PAC-NAM plate boundary. However results of the FAMEX cruise at 2002 evidenced that Tosco-Abreojos Fault System along the western margin of Baja California Peninsula is active. Should this tectonic structure be considered as a plate boundary? At the RIV plate northern corner (including Mazatlan Basin), the scatter seismicity recorded between Tamayo FZ and the Marias Islands restricts the characterization of the plate boundary between the RIV and NAM plates. Some authors have proposed that Tamayo FZ and Marias I. Escarpment are the RIV-NAM plate boundary. Recently other authors have called that RIV-NAM boundary is a geomorphology lineament that runs from a Rivera Rise transform at 23N to the northern end of Marias I. Escarpment. Even so this concept is not sustained with seismic activity. Further this thought would imply that the oceanic lithosphere of Mazatlan Basin would form part of NAM plate. Other thoughts are either that there is a diffuse RIV-NAM plate boundary to the north of the Maria Archipelago, or Middle America Subduction Zone is gradually extending northward of the Maria Is. While the plate boundary at SE corner of the RIV plate is neither well defined morphologically nor seismically constraint, offshore Colima Coast. Some authors have proposed that this zone is a diffuse plate boundary between RIV and COC plates, result of a NE-SW shear plate motion. Other authors have proposed that the RIV-COC boundary extends E-W from the El Gordo Graben (EGG) at

  8. Convergent evolution of alternative splices at domain boundaries of the BK channel.

    PubMed

    Fodor, Anthony A; Aldrich, Richard W

    2009-01-01

    Alternative splicing is a widespread mechanism for generating transcript diversity in higher eukaryotic genomes. The alternative splices of the large-conductance calcium-activated potassium (BK) channel have been the subject of a good deal of experimental functional characterization in the Arthropoda, Chordata, and Nematoda phyla. In this review, we examine a list of splices of the BK channel by manual curation of Unigene clusters mapped to mouse, human, chicken, Drosophila, and Caenorhabditis elegans genomes. We find that BK alternative splices do not appear to be conserved across phyla. Despite this lack of conservation, splices occur in both vertebrates and invertebrates at identical regions of the channel at experimentally established domain boundaries. The fact that, across phyla, unique splices occur at experimentally established domain boundaries suggests a prominent role for the convergent evolution of alternative splices that produce functional changes via changes in interdomain communication. PMID:18694345

  9. Geodynamics of flat-slab subduction, sedimentary basin development, and hydrocarbon systems along the southern Alaska convergent plate margin

    NASA Astrophysics Data System (ADS)

    Finzel, Emily S.

    field that provides evidence that a wide zone of diffuse deformation defines the present-day boundaries between the North America, Pacific, and Bering plates in Alaska and western Canada. In southern Alaska, boundary forces related to flat-slab subduction of the Yakutat microplate are the dominant driver for lithospheric deformation, whereas in central and northern Alaska and inboard parts of western Canada, buoyancy forces and basal tractions may be the dominant contributors.

  10. Isla del Coco, on Cocos Plate, Converges with Isla de San Andrés, on the Caribbean Plate, at 78 mm/yr

    NASA Astrophysics Data System (ADS)

    Protti, M.; Gonzalez, V. M.; Freymueller, J. T.; Doelger, S.

    2013-05-01

    Isla del Coco is the only land mass of the Cocos Plate that emerges above sea level. This makes it the only place where Cocos Plate motion can be measured using Global Navigation Satellite System (GNSS) monitoring. Global Positioning System (GPS) observations have been carried out sporadically over more than two decades on Isla del Coco, allowing precise measurement of the motion of the Cocos Plate. Recently, in May 2011, a continuous GPS station was built and instrumented at Isla del Coco, in Wafer Bay, by OVSICORI UNA and UNAVCO, as part of the COCONet regional GNSS network. Position time series from this CGPS station (ISCO: Isla del Coco) show a steady motion of Isla del Coco at a speed of 90.9±1.5mm/yr in the N35oE direction in ITRF2008 and convergence with the Caribbean Plate at 78±1mm/yr. This result is consistent with the findings of the earliest GPS studies, and agrees within uncertainty with the estimated convergence rate of 76.4±2.6 mm/yr of the MORVEL plate motion model. MORVEL is based on an average over the last 780,000 years, and our result suggests that Cocos Caribbean plate motions have been constant over that time interval.

  11. BOLIVAR: the Caribbean-South America plate boundary between 60W and 71W as imaged by seismic reflection data

    NASA Astrophysics Data System (ADS)

    Magnani, M.; Mann, P.; Clark, S. A.; Escalona, A.; Zelt, C. A.; Christeson, G. L.; Levander, A.

    2007-12-01

    We present the results of ~6000km of marine multi-channel seismic (MCS) reflection data collected offshore Venezuela as part of the Broadband Ocean Land Investigation of Venezuela and the Antilles arc Region project (BOLIVAR). The imaged area spans almost 12 degrees of longitude and 5 degrees of latitude and encompasses the diffuse plate boundary between South America (SA) and the SE Caribbean plate (CAR). This plate boundary has been evolving for at least the past 55My when the volcanic island arc that borders the CAR plate started colliding obliquely with the SA continent: the collision front has migrated from west to east. BOLIVAR MCS data show that the crustal architecture of the present plate boundary is dominated by the eastward motion of the Caribbean plate with respect to SA and is characterized by a complex combination of convergent and strike-slip tectonics. To the north, the reflection data image the South Caribbean Deformed Belt (SCDB) and the structures related to the thrusting of the CAR plate under the Leeward Antilles volcanic arc region. The data show that the CAR underthrusting continues as far east as the southern edge of the Aves ridge and detailed stratigraphic dating of the Venezuela basin and trench deposits suggests that the collision began in the Paleogene. The amount of shortening along the SCDB decreases toward the east, in part due to the geometry of plate motion vectors and in part as a result of the NNE escape of the Maracaibo block in western Venezuela. South of the SCDB the MCS profiles cross the Leeward Antilles island arc and Cenozoic sedimentary basins, revealing a complex history of Paleogene-Neogene multiphase extension, compression, and tectonic inversion, as well as the influence of the tectonic activity along the right-lateral El Pilar - San Sebastian fault system. East of the Bonaire basin the MCS data image the southern end of the Aves Ridge abandoned volcanic island arc and the southwestern termination of the Grenada basin

  12. Finite Element Modeling of Crustal Deformation in the North American Caribbean Plate Boundary Zone

    NASA Technical Reports Server (NTRS)

    Lundgren, P.; Russo, R.

    1995-01-01

    We have developed 2-dimensional spherical shell finite element models of elastic displacement in the North American-Caribbean (NA-Ca) plate boundary zone (PBZ) in order to quantify crust and fault motions in the PBZ.

  13. Investigation of the Interaction of External Disturbances with Roughened Flat Plate Boundary Layer

    NASA Technical Reports Server (NTRS)

    Davis, Sanford S.; Dietz, A. J.

    1996-01-01

    The interaction of an external disturbance with a laminar boundary layer over a flat plate with distributed roughness is investigated using combined experimental and numerical methods. The experiment is modeled with an unsteady boundary layer code using second order backward differencing. The simulation includes the second order scattering from roughness elements at and near the first streamwise station of predicted boundary layer instability. A comparison of experimental measurements of the boundary layer perturbation due to the wake from a vibrating ribbon with the computed first order forced boundary layer perturbation showed excellent agreement. Second order roughness induced eigenfunctions from boundary layer theory are examined and compared with other forms of excitation

  14. From transtension to transpression along the northern Caribbean plate boundary off Cuba: implications for the Recent motion of the Caribbean plate

    NASA Astrophysics Data System (ADS)

    Calais, Eric; de Lepinay, Bernard Mercier

    1991-02-01

    Marine geophysical surveys using Seabeam, single-channel seismic reflection, gravimetric and magnetic measurements have been conducted along a segment of the northern Caribbean transcurrent plate boundary (SEACARIB II cruise). The data allow a better definition of the geometry and the tectonic regime of this major strike-slip area. They support the following results: (1) Along the southern Cuban margin, the Oriente fault displays a discontinuous trace, mainly composed of dextral offset, "en echelon" segments. Some pull-apart basins are located between fault segments (Cabo Cruz basin, Chivirico and Baitiquiri basins). In the Windward Passage area, the plate boundary enters into the Tortue Channel and is not connected with the subduction front off northern Hispaniola. (2) The eastern part of the Oriente Deep and the Santiago Promontory are characterised by active compressional tectonics. They form the Santiago Deformed Belt, described here for the first time. This deformed belt can be divided longitudinally into three main segments, each one characterised by a particular tectonic style. Its development is related to a transpressional mechanism along the left-lateral Oriente strike-slip fault. Our observations suggest that a tectonic and kinematic reorganisation occurred recently in this area, probably in the Late Pliocene, which may be compared with the recent geological events recorded on land in the northern Caribbean domain. The precise knowledge of both geometry and structures along the Oriente strike-slip fault south of Cuba provides new constraints for the recent kinematic evolution along the northern Caribbean transcurrent plate boundary: it leads us to infer the existence of a convergence component associated with the slip component along the Oriente transform fault.

  15. Recovering physical property information from subduction plate boundaries using 3D full-waveform seismic inversion

    NASA Astrophysics Data System (ADS)

    Bell, R. E.; Morgan, J. V.; Warner, M.

    2013-12-01

    Our understanding of subduction margin seismogenesis has been revolutionised in the last couple of decades with the discovery that the size of the seismogenic zone may not be controlled simply by temperature and a broad spectrum of seismic behaviour exists from stick-slip to stable sliding. Laboratory and numerical experiments suggest that physical properties, particularly fluid pressure may play an important role in controlling the seismic behaviour of subduction margins. Although drilling can provide information on physical properties along subduction thrust faults at point locations at relatively shallow depths, correlations between physical properties and seismic velocity using rock physics relationships are required to resolve physical properties along the margin and down-dip. Therefore, high resolution seismic velocity models are key to recovering physical property information at subduction plate boundaries away from drill sites. 3D Full waveform inversion (FWI) is a technique pioneered by the oil industry to obtain high-resolution high-fidelity models of physical properties in the sub-surface. 3D FWI involves the inversion of low-frequency (>2 to <7 Hz), early arriving (principally transmitted) seismic data, to recover the macro (intermediate to long-wavelength) velocity structure. Although 2D FWI has been used to improve velocity models of subduction plate boundaries before, 3D FWI has not yet been attempted. 3D inversions have superior convergence and accuracy, as they sample the subsurface with multi-azimuth multiply-crossing wavefields. In this contribution we perform a suite of synthetic tests to investigate if 3D FWI could be used to better resolve physical property information along subduction margin plate boundaries using conventionally collected 3D seismic data. We base our analysis on the Muroto Basin area of the Nankai margin and investigate if the acquisition parameters and geometry of the subduction margin render 3D seismic data collected across

  16. Evolving deformation along a transform plate boundary: Example from the Dead Sea Fault in northern Israel

    NASA Astrophysics Data System (ADS)

    Weinberger, Ram; Gross, Michael R.; Sneh, Amihai

    2009-10-01

    We analyzed geologic structures adjacent to the Dead Sea Fault (DSF) along the margins of the Sinai and Arabian plates in northern Israel in order to investigate the style and sequence of deformation associated with a transform plate boundary. The field area, located between the Hula basin in northern Israel and the Lebanese restraining bend in southern Lebanon, is divided into distinct structural blocks by a series of distributed faults that comprise this approximately N-S trending section of the DSF. Cretaceous and Tertiary rocks within and adjacent to the structural blocks are folded into broad anticlines and synclines, with more intense localized shortening manifested by tight folds and thrust duplexes. Kinematic analyses of folds, faults, and veins provide evidence for two directions of regional shortening: (1) NW-SE shortening responsible for the formation of NE-SW trending fold axes and left-lateral strike-slip motion along N-S trending faults and (2) E-W shortening as indicated by N-S trending fold axes, N-S striking thrust faults, and extensional calcite-filled veins that strike E-W. Crosscutting relations and U-Th ages of the vein material suggest that the E-W phase of transform-normal shortening represents the most recent and presently active phase of deformation. The structural analysis provides evidence for the transition from an early (Miocene-lower Pliocene) phase of pure strike-slip motion to a late (Pleistocene to Recent) phase of convergent strike slip. The latter phase is characterized by strain partitioning, which is manifested by discrete left-lateral strike-slip motion across weak N-S faults and the development of a fold-thrust belt in response to transform-normal shortening. Analogous to the strain partitioning observed in southern California, we suggest that blind thrust faults adjacent to the DSF in the study area may pose a seismic risk to populations in northern Israel and southern Lebanon.

  17. Skin friction and Reynolds stress measurements for a turbulent boundary layer following manipulation using flat plates

    NASA Technical Reports Server (NTRS)

    Westphal, R. V.

    1986-01-01

    Research has been undertaken to experimentally study the alterations in turbulent boundary-layer properties due to turbulence manipulation using thin flat plates. Plate geometry and placement within the boundary layer were selected to coincide with recent studies. Direct, local measurements of skin friction and Reynolds stresses were made within the boundary layer downstream of the manipulator devices for cases with an approach momentum thickness Reynolds number of 3700. A strong tendency for recovery of the Reynolds stresses was observed, accompanied by local skin-friction reductions of up to 15 percent. The mean velocity profile in the manipulated flow displayed the same similarity shape in the logarithmic region as a natural boundary layer, but had an enhanced wake component. The results indicate that the plate wake plays an important role in the boundary layer response to this sort of manipulation.

  18. Structural acoustic control of plates with variable boundary conditions: design methodology.

    PubMed

    Sprofera, Joseph D; Cabell, Randolph H; Gibbs, Gary P; Clark, Robert L

    2007-07-01

    A method for optimizing a structural acoustic control system subject to variations in plate boundary conditions is provided. The assumed modes method is used to build a plate model with varying levels of rotational boundary stiffness to simulate the dynamics of a plate with uncertain edge conditions. A transducer placement scoring process, involving Hankel singular values, is combined with a genetic optimization routine to find spatial locations robust to boundary condition variation. Predicted frequency response characteristics are examined, and theoretically optimized results are discussed in relation to the range of boundary conditions investigated. Modeled results indicate that it is possible to minimize the impact of uncertain boundary conditions in active structural acoustic control by optimizing the placement of transducers with respect to those uncertainties. PMID:17614487

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

    USGS Publications Warehouse

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

    1995-01-01

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

  20. Inter- and intra-plate deformation at North American plate boundaries

    NASA Technical Reports Server (NTRS)

    Beavan, John; Gilbert, Lewis E.; Scholz, Chris

    1992-01-01

    A geodetic network which spans the region between San Francisco and Lake Tahoe has been measured 5 times completely with triangulation in 1880, 1922, 1929, 1943, 1963. A resurvey with the Global Positioning System (GPS) in 1991 allows the formation of 1 coseismic and 4 interseismic epochs. The data from this network provide a unique opportunity to examine the temporal and spatial evolution of the strain field associated with the 1906 San Francisco earthquake in particular and with the Pacific-North American plate boundary in general. Calculations of strain rate from the network data lead to the following conclusions. (1) There is no resolvable (greater than 0.05 microradians/yr) strain in between Sutter Buttes and the Sierra Nevada. (2) Throughout the time since the 1906 earthquake, a region extending at least as far east as the westernmost Great Valley has been undergoing deformation related to Pac:Nam interaction and the associated earthquake cycle. (3) In the time and space of overlap, our results agree with those from the United States Geological Survey (USGS) trilateration data. Both data sets indicate that strain must be accumulating to the east of Vaca. (4) The San Andreas discrepancy cannot be accommodated in the Great Valley at the 1 sigma level of our results. It is possible to absorb it in that region at the 2 sigma level. (5) Strain rate is elevated in the years following the earthquake and decays slowly with time. It is possible that the rate in the Coast Ranges increases until around 1950 and then decays. With the exception of one epoch, strain rate in the Coast Ranges is consistently fault parallel, shows no sign changes, and is consistent with monotonic strain accumulation.

  1. Water Release from Cold Serpentinized Forearc Mantle During Subduction Associated with Changes in Incoming Oceanic Plate Thermal Structure and Plate Boundary Kinematics: New Insights into Serpentinite Belts and Plate-Boundary Rheology

    NASA Astrophysics Data System (ADS)

    Kirby, Stephen

    2016-04-01

    Kirby, Wang, and Brocher (Earth Planets and Space, 2014) recently showed how the change in kinematics of the California margin from subduction motion to continental transform motion with the birth and growth of the San Andreas Fault System (SAFS) beginning at about 33 Ma BP likely led to a warming of the former forearc mantle and the release of water from serpentinized mantle by dehydration and a likely increase in fluid pressures along the SAFS. Such a mantle source of pressurized water gives insights into both the low sliding resistance for the SAFS and the mobilization and ascent of some serpentinized mantle peridotites through the crust. Thermal modeling by others has also shown that changes in the incoming plate age and subduction rate can also lead to warming of the forearc mantle during subduction. This development gives insights into the Mesozoic and Paleogene ages of emplacement of some, but not all, California serpentinites. Recent mineralogical and geochemical observations of serpentinite blocks in serpentinize mélange bodies in the San Francisco Bay Area (Uno and Kirby, 2014 AGU Meeting and Lewis and Kirby, 2015 AGU Meeting) suggest that these rocks sustained multiple stages of serpentinization that are broadly consistent with the model of Kirby et al. (2014). A new development comes from interpretation of investigations in the literature of localized late-stage silica-carbonate-water alteration of serpentinite bodies in California that this alteration occurred largely in Neogene time when the highest rates of water release from the former forearc mantle probably occurred. This presentation also suggests that the occurrence of serpentinite belts emplaced in Cenozoic time during changing plate-boundary kinematics, such as the Cenozoic closing of the Tethys Ocean bordering Eurasia by subduction and collision and arc reversal and decreasing convergence rates under the Greater Antilles and Colombia and New Guinea, may give insights into the serpentinite

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

    NASA Astrophysics Data System (ADS)

    Beardsley, Amanda Gail

    2007-12-01

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

  3. Convergence to equilibrium for the Cahn-Hilliard equation with dynamic boundary conditions

    NASA Astrophysics Data System (ADS)

    Wu, Hao; Zheng, Songmu

    This paper is concerned with the asymptotic behavior of solution to the Cahn-Hilliard equation {∂u}/{∂t}= Δμ, μ=- Δu-u+u 3, (x,t)∈Ω×R +subject to the following dynamic boundary conditions: σ sΔ||u-∂ νu+h s-g su= {1}/{Γ s} u t, t>0, x∈Γ, ∂ νμ=0, t>0, x∈Γ and the initial condition u| t=0=u 0(x), x∈Ω, where Ω is a bounded domain in R n (n⩽3) with smooth boundary Γ , and Γs>0, σs>0, gs>0, hs are given constants; Δ || is the tangential Laplacian operator, and ν is the outward normal direction to the boundary. This problem has been considered in the recent paper by Racke and Zheng (Adv. Differential Equations 8 (1) (2003) 83) where the global existence and uniqueness were proved. In a very recent manuscript by Prüss, Racke and Zheng (Konstanzer Schrift. Math. Inform. 189 (2003)) the results on existence of global attractor and maximal regularity of solution have been obtained. In this paper, convergence of solution of this problem to an equilibrium, as time goes to infinity, is proved.

  4. Integrating seismological and tectonic studies to constrain lithospheric evolution at complex plate boundaries

    NASA Astrophysics Data System (ADS)

    Hayes, Gavin Peter

    The relative motion of tectonic plates across their boundaries generates deformation in the surrounding lithosphere. How this deformation is expressed reflects both present-day plate configurations and how plate boundaries evolve. To understand the behavior of plate boundaries, we must study how they have developed. The advances made in seismology over the past fifty years---both in observation and application---provide tools ideal for such analysis. Here, I use these tools to investigate the tectonic evolution of complex plate boundaries. I focus on two areas that have experienced geologically recent plate tectonic variations---the Mendocino triple junction in northern California, and the Australia:Pacific plate boundary south of New Zealand. In northern California, the northward migration of the Mendocino triple junction over the past ˜10Ma has driven a synchronous pattern of thickening and thinning of North American crust. In studying this deformation I find major thinning is localized to a narrow region of crust in the Redwood Valley area. This thinning is accompanied by a steeply dipping Moho (>15°), and by high Poisson's Ratio's in the lower crust, characteristic of layers of melt. These melts may link to shallow (˜10km) dike injections that drive a migrating sequence of seismicity in the shallow crust near Lake Pillsbury. The limited data sets available led me to develop new tools in receiver function and crustal velocity ratio analyses that significantly improve our ability to resolve spatial changes in crustal properties. The application of these techniques forms a second major aspect of this thesis. Finally, I analyze the deformation of Australian lithosphere adjacent to the plate boundary south of New Zealand. I perform earthquake relocations on the distribution of intra- and inter-plate seismicity, and combined with plate reconstructions since the late Oligocene show that deformation occurs over a ˜150km wide area west of the current plate boundary

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

    NASA Astrophysics Data System (ADS)

    Lamb, S. H.

    2013-12-01

    New Zealand straddles the boundary between the Australian and Pacific plate, with a transition from subduction of Pacific oceanic lithosphere beneath North Island, to oblique continental collision in South Island. Cenozoic relative plate motion has resulted in a complex pattern of faulting and block rotation in a zone up to 250 km wide, with displacements on individual faults up to 100s of kilometres. Active deformation must be driven by a combination of plate-boundary forces and internal buoyancy forces. I use a compilation of seismic reflection/refraction studies and high quality receiver function analyses, together with simple Airy isostasy, to determine regional crustal and mantle structure. Integration of the vertical normal stress to the base of the deforming layer yields the buoyancy stress. Horizontal gradients of this can be compared with horizontal gradients of strain rate, using the method of England & Molnar (1997), in the context of a simple thin sheet model of deformation. Thus, if deformation is that of a Newtonian fluid, then appropriate combinations of the horizontal gradients of vorticity and dilatation are related to gradients of buoyancy stress by the fluid viscosity. However, the short term geodetic deformation is strongly biased by elastic strain accumulation related to locking on the plate interface, and cannot be used to determine the plate-boundary velocity field averaged over many seismic cycles (see Lamb & Smith 2013). Therefore, I derive here a velocity field for the plate-boundary zone, which is representative of deformation over tens of thousands of years. This is based on an inversion of fault slip, strain rate azimuth and paleomagnetic data, in the context of the short term relative plate motions, solved in a network of triangles spanning the plate-boundary, using the method of Lamb (2000). A comparison of gradients of buoyancy stress with the appropriate combinations of gradients of vorticity and dilatation shows that deformation in

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

    NASA Astrophysics Data System (ADS)

    Stock, J. M.

    2011-12-01

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

  7. Analytical solutions to the fundamental frequency of arbitrary laminated plates under various boundary conditions

    NASA Astrophysics Data System (ADS)

    Luo, Yingqin; Hong, Ming; Liu, Yuan

    2015-03-01

    In recent years, as the composite laminated plates are widely used in engineering practice such as aerospace, marine and building engineering, the vibration problem of the composite laminated plates is becoming more and more important. Frequency, especially the fundamental frequency, has been considered as an important factor in vibration problem. In this paper, a calculation method of the fundamental frequency of arbitrary laminated plates under various boundary conditions is proposed. The vibration differential equation of the laminated plates is established at the beginning of this paper and the frequency formulae of specialty orthotropic laminated plates under various boundary conditions and antisymmetric angle-ply laminated plates with simply-supported edges are investigated. They are proved to be correct. Simple algorithm of the fundamental frequency for multilayer antisymmetric and arbitrary laminated plates under various boundary conditions is studied by a series of typical examples. From the perspective of coupling, when the number of laminated plates layers N > 8-10, some coupling influence on the fundamental frequency can be neglected. It is reasonable to use specialty orthotropic laminated plates with the same thickness but less layers to calculate the corresponding fundamental frequency of laminated plates. Several examples are conducted to prove correctness of this conclusion. At the end of this paper, the influence of the selected number of layers of specialty orthotropic laminates on the fundamental frequency is investigated. The accuracy and complexity are determined by the number of layers. It is necessary to use proper number of layers of special orthotropic laminates with the same thickness to simulate the fundamental frequency in different boundary conditions.

  8. The International Plate Boundary Observatory Chile (IPOC) in the northern Chile seismic gap

    NASA Astrophysics Data System (ADS)

    Schurr, B.; Asch, A.; Sodoudi, F.; Manzanares, A.; Ritter, O.; Klotz, J.; Chong-Diaz, G.; Barrientos, S.; Villotte, J.-P.; Oncken, O.

    2009-04-01

    Fast convergence between the oceanic Nazca and the continental South American plate is accommodated by recurrent rupture of large segments of the two plates' interface. The resulting earthquakes are among the largest and, for their sizes, most frequent on Earth. Along the Chilean and southern Peruvian margin, all segments have ruptured at least once in the past 150 years for which there exist historic and/or instrumental records. The one segment that is most mature for re-rupture stretches for more than 500 km along the northernmost Chilean coast between roughly -23° and -18° latitude. It last broke in 1877 in a magnitude ~8.8 earthquake, triggering a major Tsunami. From the historical record, it has been known to have a recurrence cycle of approximately 110 years. The adjoining segments to the north and south broke rather recently in 1995 and 2001 in M>8 earthquakes and an M 7.7 earthquake encroached the southern part of the gap in 2007. The IPOC project intends to investigate this segment of the Nazca-South American plate boundary, on which a strong to devastating earthquake is expected to occur within the next years, by monitoring at a variety of time-scales deformation, seismicity, and magnetotelluric fields in the subduction zone at the closing stages of the interseismic cycle before and possibly during occurrence of a big earthquake. For that purpose, installation of long-term observatories in Northern Chile started in 2006 in a close cooperation of the Universidad de Chile (Santiago, Chile), the Universidad Catolica del Norte (Antofagasta, Chile), the Institut de Physique du Globe de Paris (Paris, France), and the German Research Centre for Geosciences (GFZ, Potsdam, Germany). Currently we are operating 14 modern seismological stations equipped with STS-2 broadband seismometers and accelerometers (EPI sensor). At least two more stations will be installed in the near future. To cope with the high resolution and dynamic of the sensors and data acquisition

  9. Accelerated plate tectonics.

    PubMed

    Anderson, D L

    1975-03-21

    The concept of a stressed elastic lithospheric plate riding on a viscous asthenosphere is used to calculate the recurrence interval of great earthquakes at convergent plate boundaries, the separation of decoupling and lithospheric earthquakes, and the migration pattern of large earthquakes along an arc. It is proposed that plate motions accelerate after great decoupling earthquakes and that most of the observed plate motions occur during short periods of time, separated by periods of relative quiescence. PMID:17799689

  10. Anisotropy from SKS splitting across the Pacific-North America plate boundary offshore southern California

    NASA Astrophysics Data System (ADS)

    Ramsay, Joseph; Kohler, Monica D.; Davis, Paul M.; Wang, Xinguo; Holt, William; Weeraratne, Dayanthie S.

    2016-07-01

    SKS arrivals from ocean bottom seismometer (OBS) data from an offshore southern California deployment are analyzed for shear-wave splitting. The project involved 34 OBSs deployed for 12 months in a region extending up to 500 kilometers west of the coastline into the oceanic Pacific plate. The measurement process consisted of removing the effects of anisotropy using a range of values for splitting fast directions and delay times to minimize energy along the transverse seismometer axis. Computed splitting parameters are unexpectedly similar to onland parameters, exhibiting WSW-ENE fast polarization directions and delays between 0.8 and 1.8 s, even for oceanic plate sites. This is the first SKS splitting study to extend across the entire boundary between the North America and Pacific plates, into the oceanic part of the Pacific plate. The splitting results show that the fast direction of anisotropy on the Pacific plate does not align with absolute plate motion (APM), and they extend the trend of anisotropy in southern California an additional 500 km west, well onto the oceanic Pacific plate. We model the finite strain and anisotropy within the asthenosphere associated with density-buoyancy driven mantle flow and the effects of APM. In the absence of plate motion effects, such buoyancy driven mantle flow would be NE-directed beneath the Pacific plate observations. The best-fit patterns of mantle flow are inferred from the tomography-based models that show primary influences from foundering higher-density zones associated with the history of subduction beneath North America. The new offshore SKS measurements, when combined with measurements onshore within the plate boundary zone, indicate that dramatic lateral variations in density-driven upper mantle flow are required from offshore California into the plate boundary zone in California and western Basin and Range.

  11. Converging shear rheometer

    NASA Astrophysics Data System (ADS)

    Baek, Hyung M.; Mix, Adam W.; Giacomin, A. Jeffrey

    2014-05-01

    For highly viscous fluids that slip in parallel sliding plate rheometers, we want to use a slightly converging flow to suppress this wall slip. In this work, we first attack the steady shear flow of a highly viscous Newtonian fluid between two gently converging plates with no slip boundaries using the equation of motion in cylindrical coordinates, which yields no analytical solution. Then we treat the same problem using the lubrication approximation in Cartesian coordinates to yield exact, explicit solutions for dimensionless velocity, pressure and shear stress. This work deepens our understanding of a drag flow through a gently converging slit of arbitrary convergence angle. We also employ the corotational Maxwell model to explore the role of viscoelasticity in this converging shear flow. We then compare these analytical solutions to finite element calculations for both Newtonian and corotational Maxwell cases. A worked example for determining the Newtonian viscosity using a converging shear rheometer is also included. With this work, we provide the framework for exploring other constitutive equations or other boundary conditions in future work. Our results can also be used to design the linear bearings used for the parallel sliding plate rheometer (SPR). This work can also be used to evaluate the error in the shear stress that is caused by bearing misalignment and specify the parallelism tolerance for the linear bearings incorporated into a SPR.

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

    NASA Astrophysics Data System (ADS)

    Lamb, Simon

    2014-05-01

    New Zealand straddles the boundary between the Australian and Pacific plate, with a transition from subduction of Pacific plate oceanic lithosphere in the North, beneath North Island to oblique continental collision in South Island. Cenozoic relative plate motion has resulted in a complex pattern of faulting and block rotation in a zone up to 250 km wide, with displacements on individual faults up to 100s of kilometres. Here, I use a compilation of seismic reflection/refraction studies and high quality receiver function analyses, together with simple Airy isostasy, to determine the regional crustal and mantle structure. The buoyancy stress in the deforming layer is calculated by integrating the vertical normal stress with depth. This, in combination with plate-boundary stresses, must drive deformation. Horizontal gradients of buoyancy stress can be compared with horizontal gradients of strain rate, using the method of England & Molnar (1997), in the context of a simple thin sheet model of lithospheric deformation. I derive a velocity field for the New Zealand plate-boundary zone, using the method of Lamb (2000). This is representative of deformation over tens of thousands of years, based on fault slip, strain rate azimuth and paleomagnetic data, in the context of the short term relative plate motions. Comparison of appropriate combinations of horizontal gradients of vorticity and dilatation with horizontal gradients of buoyancy stress shows that deformation has some of the features of a Newtonian fluid. In detail, the minima in buoyancy stress, calculated from the vertical density structure, are offset horizontally from that calculated from gradients of strain rate, suggesting strong lateral contrasts in viscosity if deformation is strongly coupled at all levels in the lithosphere, with viscosities in the range 1 - 10 x 10**21 Pa s. However, subduction of Pacific plate lithosphere along the Hikurangi margin, and evidence for underthrusting beneath the Southern Alps

  13. Ancient plate kinematics derived from the deformation pattern of continental crust: Paleo- and Neo-Tethys opening coeval with prolonged Gondwana-Laurussia convergence

    NASA Astrophysics Data System (ADS)

    Kroner, Uwe; Roscher, Marco; Romer, Rolf L.

    2016-06-01

    Province and the opening of Neo-Tethys at ca. 300 Ma. The Euler pole for the final closure of the Rheic Ocean is positioned near Oslo (Laurussia). Thus, the concomitant formation of convergent and divergent plate boundaries during the assembly of Pangea is due to the relocation of the particular rotational axis. From a geodynamic point of view, coupled collisional (western Pangea) and extensional tectonics (eastern Pangea) due to plate tectonic reorganization is fully explained by slab pull and ridge push forces.

  14. Weak incident shock interactions with Mach 8 laminar boundary layers. [of flat plate

    NASA Technical Reports Server (NTRS)

    Kaufman, L. G., II; Johnson, C. B.

    1974-01-01

    Weak shock-wave interactions with boundary layers on a flat plate were investigated experimentally in Mach 8 variable-density tunnel for plate-length Reynolds numbers. The undisturbed boundary layers were laminar over the entire plate length. Pressure and heat-transfer distributions were obtained for wedge-generated incident shock waves that resulted in pressure rises ranging from 1.36 to 4.46 (both nonseparated and separated boundary-layer flows). The resulting heat-transfer amplifications ranged from 1.45 to 14. The distributions followed established trends for nonseparated flows, for incipient separation, and for laminar free-interaction pressure rises. The experimental results corroborated established trends for the extent of the pressure rise and for certain peak heat-transfer correlations.

  15. Global isostatic geoid anomalies for plate and boundary layer models of the lithosphere

    NASA Technical Reports Server (NTRS)

    Hager, B. H.

    1981-01-01

    Commonly used one dimensional geoid models predict that the isostatic geoid anomaly over old ocean basins for the boundary layer thermal model of the lithosphere is a factor of two greater than that for the plate model. Calculations presented, using the spherical analogues of the plate and boundary layer thermal models, show that for the actual global distribution of plate ages, one dimensional models are not accurate and a spherical, fully three dimensional treatment is necessary. The maximum difference in geoid heights predicted for the two models is only about two meters. The thermal structure of old lithosphere is unlikely to be resolvable using global geoid anomalies. Stripping the effects of plate aging and a hypothetical uniform, 35 km, isostatically-compensated continental crust from the observed geoid emphasizes that the largest-amplitude geoid anomaly is the geoid low of almost 120 m over West Antarctica, a factor of two greater than the low of 60 m over Ceylon.

  16. Exploring the Pacific-Australian transform plate-boundary in central South Island, New Zealand

    NASA Astrophysics Data System (ADS)

    Stern, T.; Okaya, D.; Davey, F.; Henrys, S.; Little, T.

    2006-12-01

    Lithospheric structure beneath and adjacent to the continental transform of central South Island, New Zealand (the Alpine Fault) has been investigated with both geophysical and geological methods. Principal features that have been seismically imaged include a spectacular example of a lower crustal detachment that separates the obducting greywacke-schist rocks from lower crust and mantle below. This detachment can be seen as a zone of strong reflectivity that is sub-horizontal at 35 km depth beneath the Southern Alps. The detachment then forms a SE-dipping ramp that gets progressively steeper until at a depth of ~15 km it dips at 60 degrees. If the reflectivity that defines the detachment is projected upwards it would intersect with the surface trace of the Alpine Fault. In the hanging wall of the Alpine Fault low P-wave seismic wave speeds and high electrical conductivity are mapped. These properties are interpreted to mean inter-connected fluid, high fluid pressures and reduced effective normal stresses. Consistent with such high fluid pressures are extensive quartz veining and geological evidence for deep crustal embrittlement along vertical shear planes. Mantle deformation adjacent to the Alpine Fault is detected with SKS splitting results and Pn wave speeds from mutually perpendicular, offshore, seismic lines. P-wave anisotropy of up to 13% is seen in the mantle lid within 20 km of the fault. Moreover, combining SKS and Pn observations suggest that the lateral extent of mantle deformation may be as much as 200 km from the Alpine Fault, and that all the anisotropy can be assigned to finite deformation of the lithospheric mantle. Flexural modeling shows the effective elastic thickness (Te) to be vanishingly small beneath the Southern Alps. Beyond the coastlines values of Te are greater than 20 km. We propose that the weakness and the wide zone of deformation are phenomena of plate boundaries where both strike-slip and convergence have persisted for several

  17. Receptivity of Flat-Plate Boundary Layer in a Non-Uniform Free Stream (Vorticity Normal to the Plate)

    NASA Technical Reports Server (NTRS)

    Kogan, M. N.; Ustinov, M. V.

    1997-01-01

    Work is devoted to study of free-stream vorticity normal to leading edge interaction with boundary layer over plate and resulting flow distortion influence on laminar-turbulent transition. In experiments made the wake behind the vertically stretched wire was used as a source of vortical disturbances and its effect on the boundary layer over the horizontally mounted plate with various leading edge shapes was investigated. The purpose of experiments was to check the predictions of theoretical works of M.E. Goldstein, et. al. This theory shows that small free-stream inhomogeneity interacting with leading edge produces considerable distortion of boundary layer flow. In general, results obtained confirms predictions of Goldstein's theory, i.e., the amplification of steady vortical disturbances in boundary layer caused by vortex lines stretching was observed. Experimental results fully coincide with predictions of theory for large Reynolds number, relatively sharp leading edge and small disturbances. For large enough disturbances the flow distortion caused by symmetric wake unexpectedly becomes antisymmetric in spanwise direction. If the leading edge is too blunt the maximal distortion takes place immediately at the nose and no further amplification was observed. All these conditions and results are beyond the scope of Goldstein's theory.

  18. Measurement of transitional boundary layer on a flat plate using a computational Preston tube method

    NASA Astrophysics Data System (ADS)

    Jeon, W. P.; Kang, S. H.

    1995-11-01

    The development of the transitional boundary layers on a flat plate in uniform and non-uniform incoming flows was experimentally investigated. The mean velocity profiles and the wall shear stresses on a flat plate were measured in the wakes which were generated by circular cylinders and a flat plate ahead of the test plate. A computational Preston tube method (CPM) originally proposed by Nitsche et al. (1983) was adopted and refined to measure the skin friction coefficients in the transitional boundary layer. The CPM was verified as a useful tool to measure the skin-friction over the transitional boundary layer with reasonable accuracy. As the turbulence level in the wakes increased, the starting and ending points of the transition moved progressively upstream. For the same turbulence intensities, the transition was delayed with increase of the length scale. The skin-friction coefficients at the downstream stations in the wake flow were considerably and consistently smaller than the values in the equilibrium turbulent boundary layer of the uniform flow. The transition length for the cases of the plate-wake were shorter than those for the cases of the cylinder-wake as well as the uniform flow.

  19. Boundary-layer transition on a plate subjected to simultaneous spanwise and chordwise pressure gradients

    NASA Technical Reports Server (NTRS)

    Boldman, D. R.; Brinich, P. F.

    1974-01-01

    The boundary-layer transition on a short plate was studied by means of the china-clay visual technique. The plate model was mounted in a wind tunnel so that it was subjected to small simultaneous spanwise and chordwise pressure gradients. Results of the experimental study, which was performed at three subsonic velocities, indicated that the transition pattern was appreciably curved in the spanwise direction but quite smooth and well behaved. Reasonable comparisons between predictions of transition and experiment were obtained from two finite-difference two-dimensional boundary-layer calculation methods which incorporated transition models based on the concept of a transition intermittency factor.

  20. What drives microplate motion and deformation in the northeastern Caribbean plate boundary region?

    NASA Astrophysics Data System (ADS)

    Wortel, M. J.; Govers, R. M.; van Benthem, S.

    2013-12-01

    The north Caribbean plate boundary zone is a broad deformation zone with several fault systems and tectonic blocks that move with different velocities. The indentation by the Bahamas Platform (the "Bahamas collision") is generally invoked as a cause of this fragmentation. On the basis of upper mantle structure we propose that a second driver of deformation may be the western edge of the south-dipping slab along the northern Caribbean plate boundary; the westward motion of this slab edge results in a push on the Caribbean plate further west. We refer to this second mechanism for deformation as "Slab Edge Push". The motion of the North America plate relative to the Caribbean plate causes both drivers to migrate from east to west. Bahamas collision and Slab Edge Push have been operating simultaneously since the Miocene. The question is: What is the relative importance of the two mechanisms? We use mechanical finite element models that represent the two mechanisms from the Late Oligocene (30 Ma) to the Present. For the Present, both models successfully reproduce observed deformation, implying that both models are viable. Back in time the Slab Edge Push mechanism better reproduces observations. Neither mechanism successfully reproduces the observed Miocene counter-clockwise rotation of Puerto Rico. We use this rotation to tune a final model that includes fractional contributions of both mechanisms. We find that the Slab Edge Push was the dominant driver of deformation in the north Caribbean plate boundary zone since 30 Ma.

  1. Evidence of left-lateral active motion at the North America-Caribbean plate boundary

    NASA Astrophysics Data System (ADS)

    Leroy, S. D.; Ellouz, N.; Corbeau, J.; Rolandone, F.; Mercier De Lepinay, B. F.; Meyer, B.; Momplaisir, R.; Granja, J. L.; Battani, A.; Burov, E. B.; Clouard, V.; Deschamps, R.; Gorini, C.; Hamon, Y.; LE Pourhiet, L.; Loget, N.; Lucazeau, F.; Pillot, D.; Poort, J.; Tankoo, K.; Cuevas, J. L.; Alcaide, J.; Poix, C. J.; Mitton, S.; Rodriguez, Y.; Schmitz, J.; Munoz Martin, A.

    2014-12-01

    The North America-Caribbean plate boundary is one of the least-known among large plate boundaries. Although it was identified early on as an example of a strike-slip fault in the north of Hispaniola, its structure and rate of motion remains poorly constrained. We present the first direct evidence for active sinistral strike-slip motion along this fault, based on swath seafloor mapping of the northern Haiti area. There is evidence for ~16.5 km of apparent strike-slip motion along the mapped segment of the Septentrional fault zone off Cap Haitien town which is terminated to the east onland Dominican republic and in the west to southern Cuban margin. By evaluating these new constraints within the context of geodetic models of global plate motions, we estimate an activity of the fault since 2 Ma with an angular velocity for the Caribbean plate relative to the North America predicted 6-12 mmyr-1 sinistral motion along the Septentrional fault zone. This transform fault was initiated around 20 million years ago in its western segment and since 2 Ma in its eastern segment in response to a regional reorganization of plate velocities and directions, which induced a change in configuration of plate boundaries.

  2. Irregular plate boundary controls on Foreland Basin sedimentation (Miocene, Kahramanmaraş Foreland Basin, SE Turkey)

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    The northern movement of the Arabian Plate led to the development of a compressional regime in the south-eastern part of Turkey after the Late Cretaceous. The collision of the Arabian Plate with the Anatolide-Taurides Platform and subsequent development of the Kahramanmaraş Foreland Basin at the beginning of the Miocene evolved as a result of this movement. An irregular plate geometry or promontory of the Arabian Plate caused partitioning of the plate margin (precollision-collision-postcollision). This irregular plate boundary was delimited by western and northern boundary faults and an interior basin fault. The NW-oriented small wedge top basins on the overlying Anatolide-Taurides Platform obliquely cut through the foredeep basin. The region (across the wedge top basin) on the irregular promontory of the underlying Arabian Plate contains different sedimentation depocentres. Small fining-upward submarine fan deposits (including pebbly channel deposits and coarsening-upward lobe sequences) are located at the centre of the irregular part of the plate (in the Tanır region) and overlie planktic foraminifera-bearing claystones. These submarine fan sediments pass outboard into distal interbedded turbidite claystones and siltstones in a downdip direction (S-SE). The boundary fault intersection of the promontory led to the development of a submarine slope environment with irregular sea-floor topography in the Fırnız area (4-5 km south-east of the Tanır region). The slump deposits, sandy debrites, and fine-grained thin-bedded turbidites filled this region. Structural alignments and seismicity associated with the plate margin were the main controlling factors on the geometry of the depocentre, sediment quantity, sediment input, sedimentary facies, local sea level changes, and post-sedimentary deformation in the Kahramanmaraş Foreland Basin.

  3. Plate boundary evolution in the western-central Mediterranean: From the past to the present.

    NASA Astrophysics Data System (ADS)

    Wortel, Rinus; Faccenna, Claudio; Govers, Rob; Polonia, Alina; Baes, Marzieh

    2013-04-01

    The evolution of the Calabrian and Gibraltar arcs and that of the margins of northern Africa and Sicily are part of the final phase of opening of the western Mediterranean basins. Jointly, they are the central topic of the TopoMed project concerning the plate boundary reorganization of the western-central Mediterranean, one of the projects of the TOPO-EUROPE programme (EUROCORES/ESF). The structure and evolution of the Gibraltar arc region are discussed in a separate presentation. This final stage of opening shows intriguing lateral variations from the Calabrian Arc, via the northern margin of Sicily to the North-African (Algerian) margin. In concert, they provide an excellent opportunity to study the evolution of an expanding oceanic realm that may be at the verge of entering a new phase of closure. Our studies encompass detailed analyses of deep penetration seismic data, multibeam bathymetry and field observations, and numerical model experiments addressing lithospheric scale process-oriented aspects. Special attention is given to the aspect that the region is embedded in a context of ongoing Africa-Eurasia plate convergence and to the role of structures, inherited from earlier stages of basin opening, in controlling the recent and ongoing evolution. For the Calabrian accretionary wedge the focus is on assessing the present state of deformation, including seismic activity, and other accompanying processes. We show that the Calabrian wedge is segmented (in direction along the arc) in two different lobes, the western and eastern lobe corresponding with detached and still continuous parts of the subducting slab, respectively. For the Northern Sicily margin we propose that its earlier history involving STEP faulting has preconditioned the lithosphere structure to the extent that it promotes initiation of a new southward-dipping subduction zone. The northern African margin is in a very special transitional situation in which the retreating northward subduction has

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Continental collision occurs at strike-slip plate boundaries where transform motion and oblique convergence create processes of surficial mountain building and deformation within the deeper crust and lithospheric mantle. The Pacific/Australian transform plate boundary in South Island, New Zealand, is characterized by active oblique continent-continent collision with an associated Southern Alps orogen that exhibits both high exhumation rates and rapid strike-slip movement. Beginning in the 1990s, this system was the focus of a decade-long collaborative USA-New Zealand multi-disciplinary study to understand lithospheric structure and processes involved in this transpression. Funded primarily by the NSF Continental Dynamics program and the New Zealand Science Foundation, this project known as SIGHT (South Island Geophysical Transect) with its companion SAPSE (Southern Alps Passive Seismic Experiment) included the following disciplines that involved substantial field observation experiments: seismic reflection, explosion refraction, onshore-offshore wide-angle reflection/refraction, regional and teleseismic passive seismology, magnetotellurics, laboratory petrophysics, gravity, regional geological investigations, and rheological analyses. More than fifty scientists and students from both nations participated in the combined set of studies that have led to over forty-five journal publications, an AGU Monograph, and a dozen graduate theses. Primary results of the project indicate the Pacific-Australian strike-slip plate boundary (Alpine fault) is not vertical but is eastward dipping and rheologically weak based on diverse geophysical data. Most deformation is within the Pacific plate that hosts the Southern Alps orogen. High mantle seismic velocities vertically disposed beneath the orogen suggest Pacific and perhaps Australian mantle lithosphere contribute to a zone of plate-boundary-parallel distributed mantle shortening. The crustal root of the overlying Southern Alps

  5. Tsunamis from Tectonic Sources along Caribbean Plate Boundaries

    NASA Astrophysics Data System (ADS)

    Lopez, A. M.; Chacon, S.; Zamora, N.; Audemard, F. A.; Dondin, F. J. Y.; Clouard, V.; Løvholt, F.; Harbitz, C. B.; Vanacore, E. A.; Huerfano Moreno, V. A.

    2015-12-01

    The Working Group 2 (WG2) of the Intergovernmental Coordination Group for the Tsunami and Other Coastal Hazards Warning System for the Caribbean and Adjacent Regions (ICG/CARIBE-EWS) in charge of Tsunami Hazards Assessment, has generated a list of tsunami sources for the Caribbean region. Simulating these worst-case, most credible scenarios would provide an estimate of the resulting effects on coastal areas within the Caribbean. In the past few years, several publications have addressed this issue resulting in a collection of potential tsunami sources and scenarios. These publications come from a wide variety of sources; from government agencies to academic institutions. Although these provide the scientific community with a list of sources and scenarios, it was the interest of the WG2 to evaluate what has been proposed and develop a comprehensive list of sources, therefore leaving aside proposed scenarios. The seismo-tectonics experts of the Caribbean within the WG2 members were tasked to evaluate comprehensively which published sources are credible, worst-cases, and consider other sources that have been omitted from available reports. Among these published sources are the GEM Faulted Earth Subduction Characterization Project, and the LANTEX/Caribe Wave annual exercise publications (2009-2015). Caribbean tectonic features capable of generating tsunamis from seismic dislocation are located along the Northeastern Caribbean, the Lesser Antilles Trench, and the Panamá and Southern Caribbean Deformed Belts. The proposed sources have been evaluated based on historical and instrumental seismicity as well as geological and geophysical studies. This paper presents the sources and their justification as most-probable tsunami sources based on the context of crustal deformation due to Caribbean plate interacting with neighboring North and South America plates. Simulations of these sources is part of a subsequent phase in which effects of these tectonically induced tsunamis

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

    NASA Technical Reports Server (NTRS)

    Bischke, R. E.

    1974-01-01

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

  7. Deformation of plate boundaries associated with subduction of continental margins: insights from 3D thermo-mechanical laboratory experiments (Invited)

    NASA Astrophysics Data System (ADS)

    Boutelier, D. A.; Cruden, A. R.

    2013-12-01

    -dimensional. Three-dimensional, non-cylindrical thermomechanical laboratory experiments of arc-continent collision investigate the impact of the flexural strength of the orogen and along-strike coupling of the neighboring segments of the plate boundary in the cases of diachronous collisions because of obliquity of the subducting passive margin or obliquity of the convergence in the subduction zone. The experiments reveal that deformation is continuous along-strike, but also fundamentally three-dimensional. Progressive along-strike structural variations arise because coupling between neighboring segments induces either advanced or delayed failure of the arc lithosphere and passive margin. The modeling results suggest that orogenic belts should experience deeper subduction of continental crust and hence higher-pressure metamorphism where the two plates first collided than elsewhere along the plate boundary where collision subsequently propagated. Furthermore, during the initial stage of collision the accretionary wedge is partially subducted, which leads to lubrication of the interplate zone and a reduction of shear traction. Therefore, a large convergence obliquity angle does not produce a migrating fore-arc sliver. Rather, the pressure force generated by subduction of the buoyant continental crust causes fore-arc motion. It follows that convergence obliquity during collision does not yield trench-parallel deformation of the fore arc and its influence on the collision process is limited.

  8. Tectonics of the Scotia-Antarctica plate boundary constrained from seismic and seismological data

    NASA Astrophysics Data System (ADS)

    Civile, D.; Lodolo, E.; Vuan, A.; Loreto, M. F.

    2012-07-01

    The plate boundary between the Scotia and Antarctic plates runs along the broadly E-W trending South Scotia Ridge. It is a mainly transcurrent margin that juxtaposes thinned continental and transitional crust elements with restricted oceanic basins and deep troughs. Seismic profiles and regional-scale seismological constraints are used to define the peculiarities of the crustal structures in and around the southern Scotia Sea, and focal solutions from recent earthquakes help to understand the present-day geodynamic setting. The northern edge of the western South Scotia Ridge is marked by a sub-vertical, left-lateral master fault. Locally, a narrow wedge of accreted sediments is present at the base of the slope. This segment represents the boundary between the Scotia plate and the independent South Shetland continental block. Along the northern margin of the South Orkney microcontinent, the largest fragment of the South Scotia Ridge, an accretionary prism is present at the base of the slope, which was possibly created by the eastward drift of the South Orkney microcontinent and the consequent subduction of the transitional crust present to the north. East of the South Orkney microcontinent, the physiography and structure of the plate boundary are less constrained. Here the tectonic regime exhibits mainly strike-slip behavior with some grade of extensional component, and the plate boundary is segmented by a series of NNW-SSE trending release zones which favored the fragmentation and dispersion of the crustal blocks. Seismic data have also identified, along the north-western edge of the South Scotia Ridge, an elevated region - the Ona Platform - which can be considered, along with the Terror Rise, as the conjugate margin of the Tierra del Fuego, before the Drake Passage opening. We propose here an evolutionary sketch for the plate boundary (from the Late Oligocene to the present) encompassing the segment from the Elephant Island platform to the Herdman Bank.

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

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  11. The Northwestern (Maghreb) boundary of the Nubia (Africa) Plate

    NASA Astrophysics Data System (ADS)

    Mauffret, Alain

    2007-01-01

    A study of the present compressional deformation of the Northwestern (Maghreb) Nubia (Africa) margin is derived from the analysis of more than 20,000 km of seismic profiles. In the western part the compression is distributed in a large zone with on-land compression in Algeria, mainly strike-slip deformation on the Algerian margin and folds and strike-slip faulting in Eastern Spain. In the middle of the Algerian margin, around Algiers, the evidences of compression become more obvious. In this area a ridge trending N-S that is interpreted as a middle to late Miocene spreading center interacted with the transpressional margin that trends E-W. North of the location of the Boumerdes-Zemmouri earthquake the oceanic crust is deformed by blind thrusts up to 60 km from the coast. These thrusts are south dipping and with the northward dipping thrusts located onshore form a wedge that maybe a positive flower structure at a crustal scale related to the right-lateral transpression of the margin. In the eastern part of the Northwestern (Maghreb) Nubia (Africa) Deformed Belt, off eastern Algeria and Tunisia, the deformation is more intense but limited to the north by the continental slope. Large late Miocene Tortonian folds are cut by the Messinian erosional surface but the present deformation is also evident. It is suggested that the deformation with a double vergence may be followed up to the north of Sicily. After the docking (18 Ma) of the Kabylies to the Africa Plate, the crust has been thinned and the Algerian Basin opened during the middle-late Miocene with an E-W direction. From the late Miocene to the Present the margin has been rethickened by transpression and uplifted.

  12. Overriding plate structure of the Nicaragua convergent margin: Constraints on the limits of the seismogenic zone and the 1992 tsunami earthquake

    NASA Astrophysics Data System (ADS)

    Sallarès, V.; Meléndez, A.; Prada, M.; Ranero, C. R.; McIntosh, K.; Grevemeyer, I.

    2012-04-01

    We present 2D P-wave velocity models of the Nicaragua convergent margin along two perpendicular wide-angle seismic profiles acquired in the rupture area of the 1992 tsunami earthquake. The models focus on the structure of the overriding plate and the geometry of the inter-plate boundary. In the trench-perpendicular profile, the basement shows increasing velocity reflecting a progressive decrease in the degree of rock fracturing of the igneous basement. Upper mantle-like velocities are obtained at a depth of ~10 km beneath the fore-arc Sandino basin, indicating that the mantle wedge is shallow and located close to the trench. A mismatch between the inter-plate reflector in the velocity models and along coincident multi-channel seismic profiles is best explained by a ~15% velocity anisotropy, suggesting locally-enhanced rock fracturing which is related with the presence of a prominent subducted seamount. The frontal part of the overriding plate is probably too fractured to store elastic energy, unless the presence of local asperities such as the subducted seamount makes it conditionally stable by locally increasing the normal stress. The downdip limit of the seismogenic zone occurs near the tip of the mantle wedge, indicating that it is probably controlled by the presence of a weak, serpentinized mantle wedge beneath the Sandino basin. The hypocenter of the 1992 main shock is not particularly shallow (20-22 km), but seismological data indicate that it triggered sub-events near the trench, the main of which coincides with the subducted seamount. We show that the slow propagation velocity and long duration of the 1992 earthquake could be explained by rupture propagating within the fractured basement rocks and not into the sediments.

  13. Seismotectonics of plate boundaries. Final report, 1 November 1973-30 June 1981

    SciTech Connect

    Berger, J.; Brune, J.N.; Goodkind, J.; Wyatt, F.; Agnew, D.C.; Beaumont, C.

    1981-06-01

    Research on the seismotectonics of plate boundaries is summarized. Instrumental development and an observational program designed to study various aspects of the seismotectonics of southern California and the northern Gulf of California are described. A unique superconducting gravimeter was further developed and supported under this program for deployment and operation at several sites. Work on Earth tides is also discussed.

  14. Fundamental and subharmonic transition to turbulence in zero-pressure-gradient flat-plate boundary layers

    NASA Astrophysics Data System (ADS)

    Sayadi, Taraneh; Hamman, Curtis W.; Moin, Parviz

    2012-09-01

    In this fluid dynamics video, recent simulations of transition to turbulence in compressible (M = 0.2), zero-pressure-gradient flat-plate boundary layers triggered by fundamental (Klebanoff K-type) and subharmonic (Herbert H-type) secondary instabilities of Tollmien-Schlichting waves are highlighted.

  15. An investigation of the turbulence scale tensor in a flat-plate boundary layer

    NASA Technical Reports Server (NTRS)

    Sullivan, R. D.; Donaldson, C. D.; Sandri, G.

    1979-01-01

    A differential equation for the scale tensor in turbulent flow is developed from basic considerations and applied to the flow of a constant-density fluid in the boundary layer on a flat plate. Results from preliminary runs of a computer implementation are discussed.

  16. What drives microplate motion and deformation in the northeastern Caribbean plate boundary region?

    NASA Astrophysics Data System (ADS)

    Benthem, Steven; Govers, Rob; Wortel, Rinus

    2014-05-01

    The north Caribbean plate boundary zone is a broad deformation zone with several fault systems and tectonic blocks that move with different velocities. The indentation by the Bahamas Platform (the "Bahamas Collision") is generally invoked as a cause of this fragmentation. We propose that a second driver of deformation is the western edge of the south dipping Puerto Rico slab moving sideways with the North America plate. The westward motion of the slab edge results in a push on the Caribbean plate farther west. We refer to this second mechanism for deformation as "Slab Edge Push." The motion of the North America plate relative to the Caribbean plate causes both drivers to migrate from east to west. The Bahamas Collision and Slab Edge Push have been operating simultaneously since the Miocene. The question is the relative importance of the two mechanisms. We use mechanical finite element models that represent the two mechanisms from the late Oligocene (30 Ma) to the present. For the present, both models successfully reproduce observed deformation, implying that both models are viable. Back in time the Slab Edge Push mechanism better reproduces observations. Neither mechanism successfully reproduces the observed Miocene counterclockwise rotation of Puerto Rico. We use this rotation to tune a final model that includes fractional contributions of both mechanisms. We find that the Slab Edge Push was the dominant driver of deformation in the north Caribbean plate boundary zone since 30 Ma.

  17. Discovering plate boundaries: Laboratory and classroom exercises using geodetic data to develop students' understanding of plate motion

    NASA Astrophysics Data System (ADS)

    Olds, S. E.

    2010-12-01

    To introduce the concept of plate boundaries, typical introductory geology exercises include students observing and plotting the location of earthquakes and volcanoes on a map to visually demarcate plate boundaries. Accompanying these exercises, students are often exposed to animations depicting the movement of Earth’s tectonic plates over time. Both of these teaching techniques are very useful for describing where the tectonics plates have been in the past, their shapes, and where the plates are now. With the integration of data from current geodetic techniques such as GPS, InSAR, LiDAR, students can learn that not only have the tectonic plates moved in the past, but they are moving, deforming, and changing shape right now. Additionally, GPS data can be visualized using time scales of days to weeks and on the scale of millimeters to centimeters per year. The familiar temporal and spatial scales of GPS data also help students understand that plate tectonics is a process that is happening in the present and can ease the transition to thinking about processes that are typically described using deep time, a very difficult concept for students to grasp. To provide a more robust learning environment, UNAVCO has been incorporating high-precision GPS data into free, place-based, data-rich learning modules for educators and students in introductory Earth science courses at secondary and undergraduate levels. These modules integrate new scientific discoveries related to crustal deformation and explore applications of GPS, LiDAR, and InSAR techniques to research. They also provide students with case studies highlighting the process of scientific discovery, providing context and meaning. Concurrent to these efforts, tools to visualize the inter-relationships of geophysical and geologic processes, structures, and measurements including high-precision GPS velocity data are an essential part of the learning materials. Among the suite of visualization tools that UNAVCO has made

  18. Numerical modeling of the transitional boundary layer over a flat plate

    NASA Astrophysics Data System (ADS)

    Ivanov, Dimitry; Chorny, Andrei

    2015-11-01

    Our example is connected with fundamental research on understanding how an initially laminar boundary layer becomes turbulent. We have chosen the flow over a flat plate as a prototype for boundary-layer flows around bodies. Special attention was paid to the near-wall region in order to capture all levels of the boundary layer. In this study, the numerical software package OpenFOAM has been used in order to solve the flow field. The results were used in a comparative study with data obtained from Large Eddy Simulation (LES). The composite SGS-wall model is presently incorporated into a computer code suitable for the LES of developing flat-plate boundary layers. Presently this model is extended to the LES of the zero-pressure gradient, flat-plate turbulent boundary layer. In current study the time discretization is based on a second order Crank-Nicolson/Adams-Bashforth method. LES solver using Smagorinsky and the one-equation LES turbulence models. The transition models significantly improve the prediction of the onset location compared to the fully turbulent models.LES methods appear to be the most promising new tool for the design and analysis of flow devices including transition regions of the turbulent flow.

  19. Measurements of strain at plate boundaries using space based geodetic techniques

    NASA Technical Reports Server (NTRS)

    Robaudo, Stefano; Harrison, Christopher G. A.

    1993-01-01

    We have used the space based geodetic techniques of Satellite Laser Ranging (SLR) and VLBI to study strain along subduction and transform plate boundaries and have interpreted the results using a simple elastic dislocation model. Six stations located behind island arcs were analyzed as representative of subduction zones while 13 sites located on either side of the San Andreas fault were used for the transcurrent zones. The length deformation scale was then calculated for both tectonic margins by fitting the relative strain to an exponentially decreasing function of distance from the plate boundary. Results show that space-based data for the transcurrent boundary along the San Andreas fault help to define better the deformation length scale in the area while fitting nicely the elastic half-space earth model. For subduction type bonndaries the analysis indicates that there is no single scale length which uniquely describes the deformation. This is mainly due to the difference in subduction characteristics for the different areas.

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

    PubMed

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

    2009-04-24

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

  1. 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., Jr.; 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

  2. Late Miocene to recent plate tectonic history of the southern Central America convergent margin

    NASA Astrophysics Data System (ADS)

    Morell, Kristin D.

    2015-10-01

    New plate reconstructions constrain the tectonic evolution of the subducting Cocos and Nazca plates across the southern Central American subduction zone from late Miocene to recent. Because of the strong relationships between lower and upper (Caribbean) plate dynamics along this margin, these constraints have wide-ranging implications for the timing and growth of upper plate deformation and volcanism in southern Central America. The reconstructions outline three important events in the Neogene history of this margin: (1) the coeval development of the Panama Triple Junction with the initiation of oblique subduction of the Nazca plate at ˜8.5 Ma; (2) the initiation of seamount and rough crust subduction beginning at ˜3-4 Ma; and (3) Cocos Ridge subduction from ˜2 to 3 Ma. A comparison of these events with independent geologic, geomorphic, volcanic, and stratigraphic data sets reveals that the timing, rates, and origin of subducting crust directly impacted the Neogene growth of upper plate deformation and volcanism in southern Central America. These analyses constrain the timing, geometry, and causes of a number of significant tectonic and volcanic processes, including rapid Plio-Quaternary arc-fore arc contraction due to Cocos Ridge subduction, the detachment of the Panama microplate at ˜1-3 Ma, and the late Miocene cessation of mantle-wedge-derived volcanism across ˜300 km of the subduction zone.

  3. Receptivity of flat-plate boundary layer in a non-uniform free stream (vorticity normal to the plate)

    NASA Technical Reports Server (NTRS)

    Kogan, M. N.

    1994-01-01

    Recent progress in both the linear and nonlinear aspects of stability theory has highlighted the importance of the receptivity problem. One of the most unclear aspects of receptivity study is the receptivity of boundary-layer flow normal to vortical disturbances. Some experimental and theoretical results permit the proposition that quasi-steady outer-flow vortical disturbances may trigger by-pass transition. In present work such interaction is investigated for vorticity normal to a leading edge. The interest in these types of vortical disturbances arise from theoretical work, where it was shown that small sinusoidal variations of upstream velocity along the spanwise direction can produce significant variations in the boundary-layer profile. In the experimental part of this work, such non-uniform flow was created and the laminar-turbulent transition in this flow was investigated. The experiment was carried out in a low-turbulence direct-flow wind tunnel T-361 at the Central Aerohydrodynamic Institute (TsAGI). The non-uniform flow was produced by laminar or turbulent wakes behind a wire placed normal to the plate upstream of the leading edge. The theoretical part of the work is devoted to studying the unstable disturbance evolution in a boundary layer with strongly non-uniform velocity profiles similar to that produced by outer-flow vorticity. Specifically, the Tollmien-Schlichting wave development in the boundary layer flow with spanwise variations of velocity is investigated.

  4. Discovering Plate Boundaries Update: Builds Content Knowledge and Models Inquiry-based Learning

    NASA Astrophysics Data System (ADS)

    Sawyer, D. S.; Pringle, M. S.; Henning, A. T.

    2009-12-01

    Discovering Plate Boundaries (DPB) is a jigsaw-structured classroom exercise in which students explore the fundamental datasets from which plate boundary processes were discovered. The exercise has been widely used in the past ten years as a classroom activity for students in fifth grade through high school, and for Earth Science major and general education courses in college. Perhaps more importantly, the exercise has been used extensively for professional development of in-service and pre-service K-12 science teachers, where it simultaneously builds content knowledge in plate boundary processes (including natural hazards), models an effective data-rich, inquiry-based pedagogy, and provides a set of lesson plans and materials which teachers can port directly into their own classroom (see Pringle, et al, this session for a specific example). DPB is based on 4 “specialty” data maps, 1) earthquake locations, 2) modern volcanic activity, 3) seafloor age, and 4) topography and bathymetry, plus a fifth map of (undifferentiated) plate boundary locations. The jigsaw is structured so that students are first split into one of the four “specialties,” then re-arranged into groups with each of the four specialties to describe the boundaries of a particular plate. We have taken the original DPB materials, used the latest digital data sets to update all the basic maps, and expanded the opportunities for further student and teacher learning. The earthquake maps now cover the recent period including the deadly Banda Aceh event. The topography/bathymetry map now has global coverage and uses ice-free elevations, which can, for example, extend to further inquiry about mantle viscosity and loading processes (why are significant portions of the bedrock surface of Greenland and Antarctica below sea level?). The volcanic activity map now differentiates volcano type and primary volcanic lithology, allowing a more elaborate understanding of volcanism at different plate boundaries

  5. Using Global Plate Velocity Boundary Conditions for Embedded Regional Geodynamic Models

    NASA Astrophysics Data System (ADS)

    Taramon Gomez, Jorge; Morgan, Jason; Perez-Gussinye, Marta

    2015-04-01

    The treatment of far-field boundary conditions is one of the most poorly resolved issues for regional modeling of geodynamic processes. In viscous flow, the choice of far-field boundary conditions often strongly shapes the large-scale structure of a geosimulation. The mantle velocity field along the sidewalls and base of a modeling region is typically much more poorly known than the geometry of past global motions of the surface plates as constrained by global plate motion reconstructions. For regional rifting models it has become routine to apply highly simplified 'plate spreading' or 'uniform rifting' boundary conditions to a 3-D model that limits its ability to simulate the geodynamic evolution of a specific rifted margin. One way researchers are exploring the sensitivity of regional models to uncertain boundary conditions is to use a nested modeling approach in which a global model is used to determine a large-scale flow pattern that is imposed as a constraint along the boundaries of the region to be modeled. Here we explore the utility of a different approach that takes advantage of the ability of finite element models to use unstructured meshes than can embed much higher resolution sub-regions within a spherical global mesh. In our initial project to validate this approach, we create a global spherical mesh in which a higher resolution sub-region is created around the nascent South Atlantic Rifting Margin. Global Plate motion BCs and plate boundaries are applied for the time of the onset of rifting, continuing through several 10s of Ma of rifting. Thermal, compositional, and melt-related buoyancy forces are only non-zero within the high-resolution subregion, elsewhere, motions are constrained by surface plate-motion constraints. The total number of unknowns needed to solve an embedded regional model with this approach is less than 1/3 larger than that needed for a structured-mesh solution on a Cartesian or spherical cap sub-regional mesh. Here we illustrate

  6. Target Plate Conditions During Stochastic Boundary Operation on DIII-D

    SciTech Connect

    Watkins, J; Evans, T; Moyer, R; Lasnier, C; Rudakov, D

    2006-05-15

    A major concern for large tokamaks like ITER is the presence of edge localized modes (ELMs) that repeatedly send large bursts of particles and heat into the divertor plates. Operation with resonant magnetic perturbations (RMP) at the boundary of DIII=D has suppressed ELMs for values of q95 {approx} 3.7. At the target plate, the conditions during ELM suppressed operation for both high and low collisionality are observed by a set of radially distributed Langmuir probes. At high collisionality (n*{approx}1), the target plate particle flux and temperature drops by > 30% during ELM suppression. At low collisionality (n*{approx}0.1), the core density, target plate density, and target plate particle flux drop but the plate electron temperature increases after the ELMs are suppressed. The ELM-suppressed target plate heat flux is nearly the same as the heat flux between ELMs but the (5X higher) transient heat flux peaks due to ELMs are eliminated.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    The late Cretaceous to mid Eocene history of the southwest and southernmost Pacific has been subject to starkly contrasting interpretations, ranging from relative tectonic quiescence with the Lord Howe Rise (LHR) being part of the Pacific plate to a dynamic subduction setting. In the first scenario the Tasman Sea would have formed as a consequence of divergence between the Pacific and Australian plates, whereas in the second scenario it would have formed as a marginal basin associated with subduction. The first scenario is supported by a number of arguments, including a lack of evidence for deformation and tectonic activity in New Zealand during this period and a geodynamic modelling inference, namely that the bend in the Hawaiian-Emperor chain can be better reproduced if the LHR is part of the Pacific plate. The second scenario is supported by regional plate kinematic models reconciling a variety of observations including back-arc basin formation and destruction through time and the history of arc-continent collisions. The primary problem with the first scenario is the use of a plate circuit that leaves relative motion between East and West Antarctica unconstrained, leading to an improbable history of periodic compression and extension. The main problem with the alternative scenario is a lack of sampled late Cretaceous volcanic arc rocks east of the LHR. We analysed available geological and geophysical data to constrain the locations of and movements along the plate boundaries in the southwest and southern Pacific from the late Cretaceous to mid Eocene, and assessed how Pacific plate motion is best quantified during this period. Geological and geophysical evidence suggests that a plate boundary separated the Pacific plate from the LHR. The distribution of lower mantle slab material that is imaged by seismic tomography beneath New Zealand is best explained if subduction occurred to the east of the LHR during the entire late Cretaceous to mid Eocene period. Rocks

  8. Characterization of the Absolute Crystal Polarity across Twin Boundaries in Gallium Phosphide Using Convergent-Beam Electron Diffraction.

    PubMed

    Cohen; McKernan; Carter

    1999-05-01

    : The measurement of absolute crystal polarity is crucial to understanding the structural properties of many planar defects in compound semiconductors. Grain boundaries, including twin boundaries, in the sphalerite lattice are uniquely characterized by the crystallographic misorientation of individual grains and the direction of the crystal polarity in domains adjoining the grain boundary. To evaluate crystal polarity in gallium phosphide (GaP), asymmetrical interference contrast in convergent-beam electron-diffraction (CBED) patterns was used to ascertain the nature and direction of polar bonds. The direction of the asymmetry in the electron diffraction reflections was correlated with the crystal polarity of a sample with known polarity. The CBED technique was applied to determine the polar orientation of grains adjoining Sigma = 3 coherent and lateral twin boundaries in polycrystalline GaP. PMID:10383990

  9. Boundary layer analysis of the ridge singularity in a thin plate

    NASA Astrophysics Data System (ADS)

    Lobkovsky, Alexander E.

    1996-04-01

    Large deformations of thin elastic plates and shells present a formidable problem in continuum mechanics that is generally intractable except by numerical methods. Conventional approaches break down in the limit of small plate thickness due to the appearance of discontinuities in the solution that require a boundary layer treatment. We examine a simple case of a plate bent by forces exerted along its boundary so as to create a sharp crease in the limit of infinitely small thickness. We find a separable boundary layer solution of the von Kármán plate equations that is valid along the ridge line. We confirm a scaling argument [T. A. Witten and Hao Li, Europhys. Lett. 23, 51 (1993)] that the ridge possesses a characteristic radius of curvature R given by the thickness of the sheet h and the length of the ridge X, viz., R~h1/3X2/3. The elastic energy of the ridge scales as E~κ(X/h)1/3, where κ is the bending modulus of the sheet. We determine the dependence of these quantities on the dihedral angle of the ridge π-2α. For all angles R~α-4/3 and E~α7/3. The framework developed in this paper is suitable for the determination of other properties of ridges such as their interaction or behavior under various types of loading. We expect these results to have broad importance in describing forced crumpling of thin sheets.

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

    PubMed

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

    2006-06-29

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

  11. In-Flight Boundary-Layer Transition of a Large Flat Plate at Supersonic Speeds

    NASA Technical Reports Server (NTRS)

    Banks, D. W.; Frederick, M. A.; Tracy, R. R.; Matisheck, J. R.; Vanecek, N. D.

    2012-01-01

    A flight experiment was conducted to investigate the pressure distribution, local-flow conditions, and boundary-layer transition characteristics on a large flat plate in flight at supersonic speeds up to Mach 2.00. The tests used a NASA testbed aircraft with a bottom centerline mounted test fixture. The primary objective of the test was to characterize the local flow field in preparation for future tests of a high Reynolds number natural laminar flow test article. A second objective was to determine the boundary-layer transition characteristics on the flat plate and the effectiveness of using a simplified surface coating. Boundary-layer transition was captured in both analog and digital formats using an onboard infrared imaging system. Surface pressures were measured on the surface of the flat plate. Flow field measurements near the leading edge of the test fixture revealed the local flow characteristics including downwash, sidewash, and local Mach number. Results also indicated that the simplified surface coating did not provide sufficient insulation from the metallic structure, which likely had a substantial effect on boundary-layer transition compared with that of an adiabatic surface. Cold wall conditions were predominant during the acceleration to maximum Mach number, and warm wall conditions were evident during the subsequent deceleration.

  12. Plate-Tectonic Analysis of Shallow Seismicity: Apparent Boundary Width, beta-Value, Corner Magnitude, Coupled Lithosphere Thickness, and Coupling in 7 Tectonic Settings

    NASA Astrophysics Data System (ADS)

    Bird, P.; Kagan, Y. Y.

    2003-12-01

    A new plate model [Bird, 2003, G3, 10.1029/2001GC000252] is used to analyze the mean seismicities of 7 types of plate boundary (CRB continental rift boundary, CTF continental transform fault, CCB continental convergent boundary, OSR oceanic spreading ridge, OTF oceanic transform fault, OCB oceanic convergent boundary, SUB subduction zone). We compare the plate-like (non-orogen) regions of model PB2002 with the CMT catalog to select apparent boundary half-widths, and then assign 95% of shallow earthquakes to one of these settings. A tapered Gutenberg-Richter model of the frequency/moment relation is fit to the subcatalog for each setting by maximum-likelihood. Best-fitting β values range from 0.53 to 0.92, but all 95%-confidence ranges are consistent with a common value of 0.61-0.66. To better determine some corner magnitudes we expand the subcatalogs by: (1) inclusion of orogens; and (2) inclusion of years 1900-1975 from the catalog of Pacheco and Sykes [1992]. Combining both earthquake statistics and the plate-tectonic constraint on moment rate, corner magnitudes include: CRB 7.64-.26+.76, CTF 8.01-.21+.45, CCB 8.46-.39+.21, OCB 8.04-.22+.52, and SUB 9.58-.46+.48. Coupled lithosphere thicknesses are found to be: CRB 3.0-1.4+7.0 km; CTF 8.6-4.1+11 km; CCB 18-11+? km; OSR 0.13-0.09+.13 km for normal-faulting and 0.40-.21+? km for strike-slip; OTF 12-7.1+?, 1.6-0.5+1.4, and 1.5-0.6+1.2 km at low, medium, and high velocities; OCB 3.8-2.3+13.7 km, and SUB 18.0-10.8+? km. Generally high coupling of subduction and continental plate boundaries suggests that here all seismic gaps are dangerous unless proven to be creeping. Generally low coupling within oceanic lithosphere suggests a different model of isolated seismic asperities surrounded by large seismic gaps which may be permanent.

  13. Numerical models of the dynamics of lithospheric deformation at complex plate boundaries

    NASA Astrophysics Data System (ADS)

    Malservisi, Rocco

    Plate boundaries are the sites where deformation induced by the relative motion of lithospheric blocks occurs. Observation of surface deformation, relative velocity of regions of the crust, and seismicity, all provide information on this process. In this thesis, I study lithospheric deformation at several complex plate boundaries. Lithospheric rheology and the earthquake cycle can have large effects on the observed surface velocity field. The Eastern California Shear Zone, an area likely characterized by a contrast in viscosity in the lower crust/upper mantle, provides a plate boundary segment to analyze those effects. I find that the contrast in the rheology of the lower layers (lower crust/upper mantle) can induce an asymmetric strain accumulation. This opens up the possibility of asymmetric coseismic displacement during an earthquake. Strike-slip creeping faults and their interaction with the surrounding lithosphere affect the patterns of strain accumulation and earthquake potential. In particular, I analyze the effect of fault geometry and of locked patches of the fault on the surface creep rate, and the possibility to apply observed patterns of micro-seismicity as a further constraint to map the distribution of fault creep. This allows me to further assess the seismic risk on the Hayward Fault. I find that the transition creates regions of higher stress that may generate the micro-seismicity. Comparing the results of my model with the micro-seismicity, the non-recurrent earthquakes mainly cluster in the transition zones while the repeating earthquakes occur principally in the fully creeping areas. Another aspect of plate boundary deformation analyzed in this thesis is the accommodation of the transpressional regime in the region of Fiordland, South Island, New Zealand. I find that the bending of the Australian plate, which is subducting beneath Fiordland, can provide that needed support. Furthermore, I find that in order to provide the correct dynamic support

  14. An analytical method of free vibration for laminated plates including various boundary conditions

    NASA Astrophysics Data System (ADS)

    Xia, Chuanyou; Wen, Lizhou

    1991-10-01

    It is shown that, by introducing the displacement function Phi(x, y, t), the system of original differential equations developed by Whitney and Pagano (1970) for the first-order shear deformation theory of symmetric cross-ply laminated plates can be transformed into a single differential equation of the displacement function. On the basis of this differential equation an exact solution is given to the problem of free vibration of symmetric cross-ply laminated plates including various boundary conditions. It is shown that the natural frequencies obtained by the present analytical method are lower than those of results obtained using approximate methods.

  15. Plate boundary forces in the vicinity of Trinidad-the-transition from transpression to transtension in the Southern Caribbean plate boundary zones

    SciTech Connect

    Algar, S.T.; Pindell, J.L. )

    1993-02-01

    Deformation in the southern Caribbean plate boundary zones as recorded in the Northern Range of Trinidad initiated in the Oligocene with northward vergent gravity sliding of Northern Range sediments due to uplift and oversteepening of the previously passive margin by the eastward migration of the Caribbean flexural forebulge. Progressive east-southeast transvergence of the Caribbean Plate with respect to South America overthrust incorporated the Northern Range sediments into the Caribbean accretionary prism, thrusting them south-southeast to produce a Middle Miocene transpressive foreland fold and thrust belt in southern Trinidad. Late Miocene deformation within Trinidad was increasingly dominated by right-lateral strike-slop (RLSS) faulting, at the expense of transpressive compressional features. Right-stepping of RLSS motion initiated the Gulf of Paria and Caroni pull-apart basins, Since Early Pliocene these basins and other areas to the north of Trinidad have undergone north-south extension in addition to east-west trending RLSS. Such extension caused the northward withdrawal of Caribbean terranes from atop of the Northern Range, Resulting in rapid isostatically induced uplift (approximately 0.5 mmyr[sup -1]). This change in deformation style may relate to a hitherto unrecognized shift in the relative motion of the eastern Caribbean Plate with respect to South America: from east-southeast-directed transpression to east-northeast-directed transtension.

  16. Crustal Structure of the Caribbean-South American Diffuse Plate Boundary: Subduction Zone Migration and Polarity Reversal Along BOLIVAR Profile 64W

    NASA Astrophysics Data System (ADS)

    Clark, S. A.; Levander, A.; Magnani, M.; Zelt, C. A.; Sawyer, D. S.; Ave Lallemant, H. G.

    2005-12-01

    The BOLIVAR (Broadband Ocean-Land Investigation of Venezuela and the Antilles arc Region) project is an NSF funded, collaborative seismic experiment in the southeast Caribbean region. The purpose of the project is to understand the diffuse plate boundary created by the oblique collision between the Caribbean and South American plates. Profile 64W of the BOLIVAR experiment, a 450 km-long, N-S transect onshore and offshore Venezuela located at ~64°W longitude, images the deep crustal structures formed by this collision. The active source components of profile 64W include 300 km of MCS reflection data, 33 coincident OBSs, and 344 land seismic stations which recorded 7500 offshore airgun shots and 2 explosive land shots. Results from the reflection and refraction seismic data along 64W show complex crustal structure across the entire span of the diffuse plate boundary. The onshore portion of 64W crosses the fold and thrust belt of the Serrania del Interior, which formed at ~16 Ma by collision of the Caribbean forearc with the northern South American passive margin. Underlying the Serrania del Interior is a south-vergent, remnant Lesser Antillean subduction zone. As this Lesser Antilles subduction impinged on continental crust, it caused a polarity reversal and jump offshore to the north. Convergence was initially localized in the closure and inversion of the Grenada Basin. However, subduction could not develop because of the ~20-km-thick crust of the Aves Ridge; instead, north-vergent subduction initiated further to the north, where ~12-km-thick Caribbean oceanic crust of the Venezuela Basin began to subduct beneath the Aves Ridge in the Pliocene (~4 Ma) and appears to continue subducting today. Between the remnant subduction zone and the modern one, the El Pilar and Coche dextral strike-slip faults accommodate most of the transform motion of the plate boundary. From the Serrania del Interior to the Aves Ridge, ~260 km of accreted orogenic float comprises the diffuse

  17. A preliminary investigation of boundary-layer transition along a flat plate with adverse pressure gradient

    NASA Technical Reports Server (NTRS)

    Von Doenhoff, Albert E

    1938-01-01

    Boundary-layer surveys were made throughout the transition region along a smooth flat plate placed in an airstream of practically zero turbulence and with an adverse pressure gradient. The boundary-layer Reynolds number at the laminar separation point was varied from 1,800 to 2,600. The test data, when considered in the light of certain theoretical deductions, indicated that transition probably began with separation of the laminar boundary layer. The extent of the transition region, defined as the distance from a calculated laminar separation point to the position of the first fully developed turbulent boundary-layer profile, could be expressed as a constant Reynolds number run of approximately 70,000. Some speculations are presented concerning the application of the foregoing concepts, after certain assumptions have been made, to the problem of the connection between transition on the upper surface of an airfoil at high angles of attack and the maximum lift.

  18. Vertical crustal motion of active plate convergence in Taiwan derived from tide gauge, altimetry, and GPS data

    NASA Astrophysics Data System (ADS)

    Chang, Emmy T. Y.; Chao, Benjamin F.; Chiang, Chieh-Chung; Hwang, Cheinway

    2012-11-01

    Located at the converging junction between the Eurasian and Philippine Sea plates, the island of Taiwan is subject to an active lithospheric deformation as well as seismicity. Taking the difference between the satellite altimetry data (ALT) that give the absolute sea level variation and the tide gauge data (TG) that record the relative sea level variation, we obtain the absolute vertical crustal motion of the tide gauge sites. We use 20 TG stations along the west and east coasts of Taiwan along with the ALT measurements from the TOPEX/Poseidon-Jason satellites in the nearby waters. The ALT-TG results are compared with vertical GPS measurements in discussing vertical motion. We find a general subsidence of the entire Taiwan coast during the past two decades. The west coast sees no prominent vertical motion but with a severe local subsidence due to the over-withdrawal of groundwater. On the east coast, the ALT-TG results in the northern section demonstrate a northward dipping motion. The elastic thickness of the neighboring oceanic lithosphere modeled as an elastic plate with the flexure of the subducting plate shows that the adjacent Philippine Sea plate should be an old, thick oceanic plate, which could drag the slab into the mantle as manifested in a gentle northward subsidence in the northeast Taiwan. In the southern section of the east coast, the ALT-TG results reveal a segmented or undulating pattern in the vertical-motion rates. Judging from the different behaviors between the co-seismic and interseismic vertical motions marked by the major earthquakes during the studied period, we postulate a temporal saw-tooth scenario for the deformation in phases. It demonstrates the opposite motions under different mechanisms in the frontal sections of the subduction zone, which can be understood with lateral collision and slab dragging subject to varied temporal and spatial dependences.

  19. MHD free convective boundary layer flow of a nanofluid past a flat vertical plate with Newtonian heating boundary condition.

    PubMed

    Uddin, Mohammed J; Khan, Waqar A; Ismail, Ahmed I

    2012-01-01

    Steady two dimensional MHD laminar free convective boundary layer flows of an electrically conducting Newtonian nanofluid over a solid stationary vertical plate in a quiescent fluid taking into account the Newtonian heating boundary condition is investigated numerically. A magnetic field can be used to control the motion of an electrically conducting fluid in micro/nano scale systems used for transportation of fluid. The transport equations along with the boundary conditions are first converted into dimensionless form and then using linear group of transformations, the similarity governing equations are developed. The transformed equations are solved numerically using the Runge-Kutta-Fehlberg fourth-fifth order method with shooting technique. The effects of different controlling parameters, namely, Lewis number, Prandtl number, buoyancy ratio, thermophoresis, Brownian motion, magnetic field and Newtonian heating on the flow and heat transfer are investigated. The numerical results for the dimensionless axial velocity, temperature and nanoparticle volume fraction as well as the reduced Nusselt and Sherwood number have been presented graphically and discussed. It is found that the rate of heat and mass transfer increase as Newtonian heating parameter increases. The dimensionless velocity and temperature distributions increase with the increase of Newtonian heating parameter. The results of the reduced heat transfer rate is compared for convective heating boundary condition and found an excellent agreement. PMID:23166688

  20. MHD Free Convective Boundary Layer Flow of a Nanofluid past a Flat Vertical Plate with Newtonian Heating Boundary Condition

    PubMed Central

    Uddin, Mohammed J.; Khan, Waqar A.; Ismail, Ahmed I.

    2012-01-01

    Steady two dimensional MHD laminar free convective boundary layer flows of an electrically conducting Newtonian nanofluid over a solid stationary vertical plate in a quiescent fluid taking into account the Newtonian heating boundary condition is investigated numerically. A magnetic field can be used to control the motion of an electrically conducting fluid in micro/nano scale systems used for transportation of fluid. The transport equations along with the boundary conditions are first converted into dimensionless form and then using linear group of transformations, the similarity governing equations are developed. The transformed equations are solved numerically using the Runge-Kutta-Fehlberg fourth-fifth order method with shooting technique. The effects of different controlling parameters, namely, Lewis number, Prandtl number, buoyancy ratio, thermophoresis, Brownian motion, magnetic field and Newtonian heating on the flow and heat transfer are investigated. The numerical results for the dimensionless axial velocity, temperature and nanoparticle volume fraction as well as the reduced Nusselt and Sherwood number have been presented graphically and discussed. It is found that the rate of heat and mass transfer increase as Newtonian heating parameter increases. The dimensionless velocity and temperature distributions increase with the increase of Newtonian heating parameter. The results of the reduced heat transfer rate is compared for convective heating boundary condition and found an excellent agreement. PMID:23166688

  1. Partitioning of oblique convergence in the Northern Andes subduction zone: Migration history and the present-day boundary of the North Andean Sliver in Ecuador

    NASA Astrophysics Data System (ADS)

    Alvarado, A.; Audin, L.; Nocquet, J. M.; Jaillard, E.; Mothes, P.; Jarrín, P.; Segovia, M.; Rolandone, F.; Cisneros, D.

    2016-05-01

    Along the Ecuadorian margin, oblique subduction induces deformation of the overriding continental plate. For the last 15 Ma, both exhumation and tectonic history of Ecuador suggest that the northeastward motion of the North Andean Sliver (NAS) was accompanied by an eastward migration of its eastern boundary and successive progressively narrowing restraining bends. Here we present geologic data, earthquake epicenters, focal mechanisms, GPS results, and a revised active fault map consistent with this new kinematic model. All data sets concur to demonstrate that active continental deformation is presently localized along a single major fault system, connecting fault segments from the Gulf of Guayaquil to the eastern Andean Cordillera. Although secondary faults are recognized within the Cordillera, they accommodate a negligible fraction of relative motion compared to the main fault system. The eastern limit is then concentrated rather than distributed as first proposed, marking a sharp boundary between the NAS, the Inca sliver, and the Subandean domain overthrusting the South American craton. The NAS limit follows a northeast striking right-lateral transpressional strike-slip system from the Gulf of Guayaquil (Isla Puná) to the Andean Cordillera and with the north-south striking transpressive faults along the eastern Andes. Eastward migration of the restraining belt since the Pliocene, abandonment of the sutures and reactivation of north-south striking ancient fault zones lead to the final development of a major tectonic boundary south and east of the NAS, favoring its extrusion as a continental sliver, accommodating the oblique convergence of the Nazca oceanic plate toward South America.

  2. Dynamic Stability Optimization of Laminated Composite Plates under Combined Boundary Loading

    NASA Astrophysics Data System (ADS)

    Shafei, Erfan; Kabir, Mohammad Zaman

    2011-12-01

    Dynamic stability and design optimization of laminated simply supported plates under planar conservative boundary loads are investigated in current study. Examples can be found in internal connecting elements of spacecraft and aerospace structures subjected to edge axial and shear loads. Designation of such elements is function of layup configuration, plate aspect ratio, loading combinations, and layup thickness. An optimum design aims maximum stability load satisfying a predefined stable vibration frequency. The interaction between compound loading and layup angle parameter affects the order of merging vibration modes and may stabilize the dynamic response. Laminated plates are assumed to be angle-plies symmetric to mid-plane surface. Dynamic equilibrium PDE has been solved using kernel integral transformation for modal frequency values and eigenvalue-based orthogonal functions for critical stability loads. The dictating dynamic stability mode is shown to be controlled by geometric stiffness distributions of composite plates. Solution of presented design optimization problem has been done using analytical approach combined with interior penalty multiplier algorithm. The results are verified by FEA approach and stability zones of original and optimized plates are stated as final data. Presented method can help designers to stabilize the dynamic response of composite plates by selecting an optimized layup orientation and thickness for prescribed design circumstances.

  3. Late Neogene geohistory analysis of the Humboldt Basin and its relationship to convergence of the Juan de Fuca Plate

    NASA Astrophysics Data System (ADS)

    McCrory, Patricia A.

    1989-03-01

    Geohistory analysis of Neogene Humboldt basin strata provides important constraints for hypotheses of the tectonic evolution of the southern Cascadia subduction margin, leading up to the arrival of the Mendocino triple junction. This analysis suggests that the tectonic evolution of the Humboldt basin area was dominated by coupling between the downgoing Juan de Fuca plate and the continental margin. This coupling is reflected in the timing of major hiatuses within the basin sedimentary sequence and margin uplift and subsidence which occur during periods of tectonic plate adjustment. Stratigraphic evidence indicates that Humboldt basin originated at the base of the continental slope in early Miocene time. Syndepositional uplift of basin strata began in the late Pliocene and was both thermal isostatic and tectonic in origin. Isostatic uplift was a function of an increasingly more buoyant slab being subducted, whereas tectonic uplift was due to imbricated thrusting of the accretionary complex and underplating of offscraped sediment during subduction. A component of margin uplift is postulated to have been caused by a change in the rate of convergence between the Juan de Fuca and North American plates. Coeval with late Pliocene uplift documented onshore was a sharp decrease in covergence rate ˜3 Ma. A reduction in rate of tectonic uplift, observed in the Eel River section, in early Pleistocene time was coeval with a marked increase in relative motion parallel to the continental margin. This localized subsidence may have been caused by syndepositional folding.

  4. Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake.

    PubMed

    Schurr, Bernd; Asch, Günter; Hainzl, Sebastian; Bedford, Jonathan; Hoechner, Andreas; Palo, Mauro; Wang, Rongjiang; Moreno, Marcos; Bartsch, Mitja; Zhang, Yong; Oncken, Onno; Tilmann, Frederik; Dahm, Torsten; Victor, Pia; Barrientos, Sergio; Vilotte, Jean-Pierre

    2014-08-21

    On 1 April 2014, Northern Chile was struck by a magnitude 8.1 earthquake following a protracted series of foreshocks. The Integrated Plate Boundary Observatory Chile monitored the entire sequence of events, providing unprecedented resolution of the build-up to the main event and its rupture evolution. Here we show that the Iquique earthquake broke a central fraction of the so-called northern Chile seismic gap, the last major segment of the South American plate boundary that had not ruptured in the past century. Since July 2013 three seismic clusters, each lasting a few weeks, hit this part of the plate boundary with earthquakes of increasing peak magnitudes. Starting with the second cluster, geodetic observations show surface displacements that can be associated with slip on the plate interface. These seismic clusters and their slip transients occupied a part of the plate interface that was transitional between a fully locked and a creeping portion. Leading up to this earthquake, the b value of the foreshocks gradually decreased during the years before the earthquake, reversing its trend a few days before the Iquique earthquake. The mainshock finally nucleated at the northern end of the foreshock area, which skirted a locked patch, and ruptured mainly downdip towards higher locking. Peak slip was attained immediately downdip of the foreshock region and at the margin of the locked patch. We conclude that gradual weakening of the central part of the seismic gap accentuated by the foreshock activity in a zone of intermediate seismic coupling was instrumental in causing final failure, distinguishing the Iquique earthquake from most great earthquakes. Finally, only one-third of the gap was broken and the remaining locked segments now pose a significant, increased seismic hazard with the potential to host an earthquake with a magnitude of >8.5. PMID:25119049

  5. Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake

    NASA Astrophysics Data System (ADS)

    Schurr, Bernd; Asch, Günter; Hainzl, Sebastian; Bedford, Jonathan; Hoechner, Andreas; Palo, Mauro; Wang, Rongjiang; Moreno, Marcos; Bartsch, Mitja; Zhang, Yong; Oncken, Onno; Tilmann, Frederik; Dahm, Torsten; Victor, Pia; Barrientos, Sergio; Vilotte, Jean-Pierre

    2014-08-01

    On 1 April 2014, Northern Chile was struck by a magnitude 8.1 earthquake following a protracted series of foreshocks. The Integrated Plate Boundary Observatory Chile monitored the entire sequence of events, providing unprecedented resolution of the build-up to the main event and its rupture evolution. Here we show that the Iquique earthquake broke a central fraction of the so-called northern Chile seismic gap, the last major segment of the South American plate boundary that had not ruptured in the past century. Since July 2013 three seismic clusters, each lasting a few weeks, hit this part of the plate boundary with earthquakes of increasing peak magnitudes. Starting with the second cluster, geodetic observations show surface displacements that can be associated with slip on the plate interface. These seismic clusters and their slip transients occupied a part of the plate interface that was transitional between a fully locked and a creeping portion. Leading up to this earthquake, the b value of the foreshocks gradually decreased during the years before the earthquake, reversing its trend a few days before the Iquique earthquake. The mainshock finally nucleated at the northern end of the foreshock area, which skirted a locked patch, and ruptured mainly downdip towards higher locking. Peak slip was attained immediately downdip of the foreshock region and at the margin of the locked patch. We conclude that gradual weakening of the central part of the seismic gap accentuated by the foreshock activity in a zone of intermediate seismic coupling was instrumental in causing final failure, distinguishing the Iquique earthquake from most great earthquakes. Finally, only one-third of the gap was broken and the remaining locked segments now pose a significant, increased seismic hazard with the potential to host an earthquake with a magnitude of >8.5.

  6. Control of boundary layer transition location and plate vibration in the presence of an external acoustic field

    NASA Technical Reports Server (NTRS)

    Maestrello, L.; Grosveld, F. W.

    1991-01-01

    The experiment is aimed at controlling the boundary layer transition location and the plate vibration when excited by a flow and an upstream sound source. Sound has been found to affect the flow at the leading edge and the response of a flexible plate in a boundary layer. Because the sound induces early transition, the panel vibration is acoustically coupled to the turbulent boundary layer by the upstream radiation. Localized surface heating at the leading edge delays the transition location downstream of the flexible plate. The response of the plate excited by a turbulent boundary layer (without sound) shows that the plate is forced to vibrate at different frequencies and with different amplitudes as the flow velocity changes indicating that the plate is driven by the convective waves of the boundary layer. The acoustic disturbances induced by the upstream sound dominate the response of the plate when the boundary layer is either turbulent or laminar. Active vibration control was used to reduce the sound induced displacement amplitude of the plate.

  7. Stress in the lithosphere from non-tectonic loads with implications for plate boundary processes

    NASA Astrophysics Data System (ADS)

    Luttrell, Karen Marie

    Stress in the lithosphere from non-tectonic loads is calculated, making use of semi-analytic Fourier models. Sources of non-tectonic stress include coastal lithospheric bending in response to the rise in eustatic sea level since the Last Glacial Maximum, lithospheric rebound and pore pressure changes in response to the intermittent load of Ancient Lake Cahuilla in the Salton trough, stress sustained through the formation and long-term support of local short-wavelength topography, and topography created by the ejecta debris from impact craters on the surface of the icy Galilean satellites. Stresses from time varying surface water loads are calculated along major plate boundaries globally to determine to what extent, if any, these loads influence the major tectonic processes at work in plate boundary regions, such as the earthquake cycle on major faults. It is determined that the stress perturbations from these loads are generally an order of magnitude smaller than the tectonic stress accumulation rate. Their ability to noticeably affect the seismic cycle is therefore restricted to specific circumstances including when the tectonic loading rate is particularly low, such as along secondary plate boundary fault structures, when the nontectonic loading rate is particularly high, such as in the case of catastrophic flooding events, or when the fault in question is already critically stressed to a near-failure level. Stresses from local topography are calculated along the global mid-ocean ridge and along the Chilean subduction megathrust. The predicted orientations of these stresses are compared to a presumed ridge-normal and transform-strike-slip faulting regime or the focal mechanism of a single large earthquake, respectively. Quantitative constraints for the coincident tectonic stresses are subsequently established with implications for the strength of the plate boundary faults and the necessity of particular topographic and bathymetric features.

  8. Unsteady Boundary-Layer Flow over Jerked Plate Moving in a Free Stream of Viscoelastic Fluid

    PubMed Central

    Mehmood, Ahmer; Ali, Asif; Saleem, Najma

    2014-01-01

    This study aims to investigate the unsteady boundary-layer flow of a viscoelastic non-Newtonian fluid over a flat surface. The plate is suddenly jerked to move with uniform velocity in a uniform stream of non-Newtonian fluid. Purely analytic solution to governing nonlinear equation is obtained. The solution is highly accurate and valid for all values of the dimensionless time 0 ≤ τ < ∞. Flow properties of the viscoelastic fluid are discussed through graphs. PMID:24892060

  9. Plane Wave Diffraction by a Finite Plate with Impedance Boundary Conditions

    PubMed Central

    Nawaz, Rab; Ayub, Muhammad; Javaid, Akmal

    2014-01-01

    In this study we have examined a plane wave diffraction problem by a finite plate having different impedance boundaries. The Fourier transforms were used to reduce the governing problem into simultaneous Wiener-Hopf equations which are then solved using the standard Wiener-Hopf procedure. Afterwards the separated and interacted fields were developed asymptotically by using inverse Fourier transform and the modified stationary phase method. Detailed graphical analysis was also made for various physical parameters we were interested in. PMID:24755624

  10. A formal derivation for the Blasius similarity solution for flat-plate boundary layer

    NASA Astrophysics Data System (ADS)

    Lin, Hao

    2015-11-01

    The Blasius solution is a classical solution for a laminar boundary layer attached to a semi-infinite flat plate. The key of the solution strategy is to reduce the boundary layer equations, which are PDEs, to a set of ODEs, using a similarity variable transform. Conceptually, the similarity suggests that the velocity profile in each transverse cross-section appears ``self-similar''. In many classical text books and typical classroom lectures on fluid mechanics, the existence of the similarity solution is argued heuristically. The similarity variable is defined a priori so as to collapse the PDEs. It appears somewhat mystical that the PDEs can be perfectly reduced via such an approach. Here we present a rigorous derivation for the existence of a similarity solution, which naturally arises from the fact that there is no apparent streamwise length scale for a semi-infinite plate. Conversely, a similarity solution cannot exist if the plate size is finite. This derivation can be useful in fluids education, in topics including similarity, scaling arguments, and boundary layer theory.

  11. Critical exponents from parallel plate geometries subject to periodic and antiperiodic boundary conditions

    NASA Astrophysics Data System (ADS)

    da Silva, José B.; Leite, Marcelo M.

    2012-04-01

    We introduce a renormalized one-particle irreducible, 1PI, vertex part scalar field theory setting in momentum space to computing the critical exponents ν and η, at least at two-loop order, for a layered parallel plate geometry separated by a distance L, with periodic as well as antiperiodic boundary conditions on the plates. We utilize massive and massless fields in order to extract the exponents in independent ultraviolet and infrared scaling analysis, respectively, which are required in a complete description of the scaling regions for finite size systems. We prove that fixed points and other critical amounts either in the ultraviolet or in the infrared regime dependent on the plates boundary condition are a general feature of normalization conditions. We introduce a new description of typical crossover regimes occurring in finite size systems. Avoiding these crossovers, the three regions of finite size scaling present for each of these boundary conditions are shown to be indistinguishable in the results of the exponents in periodic and antiperiodic conditions, which coincide with those from the (bulk) infinite system.

  12. Raman scattering measurements within a flat plate boundary layer in an inductively coupled plasma wind tunnel

    SciTech Connect

    Studer, Damien; Vervisch, Pierre

    2007-08-01

    High temperature air chemistry is a crucial issue concerning next reusable space vehicle thermal protection system. The aim of this paper is to measure N{sub 2} and O{sub 2} densities and characteristic temperatures thanks to spontaneous Raman scattering within the boundary layer of a stainless steel flat plate cooled down at 300 K. This shear-flow test configuration is considered as a nonequilibrium air plasma test case. Vibrational and rotational temperatures are determined by comparing experimental spectra with computed ones. The density calculation is performed using the ratio of first vibrational transition intensities for both cases with and without plasma at 38 hPa. Several sections were investigated between 15 and 40 mm from the leading edge. All these sections exhibit a classical boundary layer pattern. The rotational temperature is completely in equilibrium with the plate and reaches 2500 K at the outer edge of the boundary layer. On the contrary, the vibrational temperature drops to 1500 K near of the plate and is about 5000 K in the freestream. Molecular densities are smaller than expected at equilibrium, about 60% of the equilibrium value in the freestream for N{sub 2}.

  13. Paleocurrents beside an obliquely convergent plate boundary (Sulaiman foldbelt, southwestern Himalayas, west-central Pakistan)

    SciTech Connect

    Waheed, A.; Wells, N.A.; Ahmad, N.

    1988-01-01

    Cretaceous to Holocene paleocurrents at the north and south ends of the Sulaiman Range show flow trending westward, then variably eastward, southward, and finally eastward. Pre-orogenic Cretaceous shelf sandstones show dispersal to the southwest, north-northwest, and west-southwest off the craton. However, Paleocene marine sandstones in the south spread east-southeast, and early Eocene deltaic sandstones in the north spread southeast and north. These sandstones indicate slope reversal of the Cretaceous shelf. Post-Oligocene fluvial molasse shows mostly southward drainage. The 3.852 in northern molasse section comprises a lower 2,378 m of claystones and upwardly fining sandstones that are thought to represent meandering rivers, and an upper 1,474 m dominated by conglomerates, representing gravelly braided rivers. Lower paleocurrents were to the southeast, but variable, whereas upper paleocurrents were more uniform and gradually shifted from southeast to east The 3,146-m southern section comprised (1) a basal 1,160 m claystone and sandstone sequence (meandering streams with very diverse flow directions, overall to the southwest), (2) a middle 1,703 m sequence dominated by pebbly sandstone with very large bedforms (big sandy braided rivers with less diverse flow to the southwest), and (3) an upper 283 m conglomeratic sequence (gravelly braided streams that still flow uniformly westsouthwest). Early flow obliquely toward the Sulaiman Range suggests no uplift of the range until the onset of modern eastward drainage and the influx of conglomerates, which occurred 700 m lower in the north. The northern and southern sections otherwise show similar histories of fluvial sedimentation.

  14. In-Flight Boundary-Layer Transition on a Large Flat Plate at Supersonic Speeds

    NASA Technical Reports Server (NTRS)

    Banks, Daniel W.; Fredericks, Michael Alan; Tracy, Richard R.; Matisheck, Jason R.; Vanecek, Neal D.

    2012-01-01

    A flight experiment was conducted to investigate the pressure distribution, local flow conditions, and boundary-layer transition characteristics on a large flat plate in flight at supersonic speeds up to Mach 2.0. The primary objective of the test was to characterize the local flow field in preparation for future tests of a high Reynolds number natural laminar flow test article. The tests used a F-15B testbed aircraft with a bottom centerline mounted test fixture. A second objective was to determine the boundary-layer transition characteristics on the flat plate and the effectiveness of using a simplified surface coating for future laminar flow flight tests employing infrared thermography. Boundary-layer transition was captured using an onboard infrared imaging system. The infrared imagery was captured in both analog and digital formats. Surface pressures were measured with electronically scanned pressure modules connected to 60 surface-mounted pressure orifices. The local flow field was measured with five 5-hole conical probes mounted near the leading edge of the test fixture. Flow field measurements revealed the local flow characteristics including downwash, sidewash, and local Mach number. Results also indicated that the simplified surface coating did not provide sufficient insulation from the metallic structure, which likely had a substantial effect on boundary-layer transition compared with that of an adiabatic surface. Cold wall conditions were predominant during the acceleration to maximum Mach number, and warm wall conditions were evident during the subsequent deceleration. The infrared imaging system was able to capture shock wave impingement on the surface of the flat plate in addition to indicating laminar-to-turbulent boundary-layer transition.

  15. Effect of plate permeability on nonlinear stability of the asymptotic suction boundary layer

    NASA Astrophysics Data System (ADS)

    Wedin, Hâkan; Cherubini, Stefania; Bottaro, Alessandro

    2015-07-01

    The nonlinear stability of the asymptotic suction boundary layer is studied numerically, searching for finite-amplitude solutions that bifurcate from the laminar flow state. By changing the boundary conditions for disturbances at the plate from the classical no-slip condition to more physically sound ones, the stability characteristics of the flow may change radically, both for the linearized as well as the nonlinear problem. The wall boundary condition takes into account the permeability K ̂ of the plate; for very low permeability, it is acceptable to impose the classical boundary condition (K ̂=0 ). This leads to a Reynolds number of approximately Rec=54 400 for the onset of linearly unstable waves, and close to Reg=3200 for the emergence of nonlinear solutions [F. A. Milinazzo and P. G. Saffman, J. Fluid Mech. 160, 281 (1985), 10.1017/S0022112085003482; J. H. M. Fransson, Ph.D. thesis, Royal Institute of Technology, KTH, Sweden, 2003]. However, for larger values of the plate's permeability, the lower limit for the existence of linear and nonlinear solutions shifts to significantly lower Reynolds numbers. For the largest permeability studied here, the limit values of the Reynolds numbers reduce down to Rec=796 and Reg=294 . For all cases studied, the solutions bifurcate subcritically toward lower Re, and this leads to the conjecture that they may be involved in the very first stages of a transition scenario similar to the classical route of the Blasius boundary layer initiated by Tollmien-Schlichting (TS) waves. The stability of these nonlinear solutions is also investigated, showing a low-frequency main unstable mode whose growth rate decreases with increasing permeability and with the Reynolds number, following a power law Re-ρ, where the value of ρ depends on the permeability coefficient K ̂. The nonlinear dynamics of the flow in the vicinity of the computed finite-amplitude solutions is finally investigated by direct numerical simulations, providing a

  16. Long-offset and multi-fold ocean bottom seismographic survey for imaging lithospheric scale structures in plate convergent margins

    NASA Astrophysics Data System (ADS)

    Kodaira, S.; Takahashi, N.; Nakanishi, A.; Fujie, G.; Ito, A.; Miura, S.; Sato, T.; Tsuru, T.; Park, J.; Kaneda, Y.

    2005-05-01

    Recent availability of a large number of ocean bottom seismographs (OBSs), a large volume of air-gun array and a long streamer cable for academics provide several new findings of lithospheric scale structures in plate convergent margins. Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has acquired long-offset seismic data using a super-densely deploy OBS (i.e. 1 - 5 km spacing OBSs along 100 - 500 km long profiles) since 1999. Long-offset multichannel seismic (MCS) data by a two-ship experiment, as well as conventional 2D MCS data, have been also acquired at a part of the profiles. Some of those profiles have been designed as combined onshore - offshore profiles for imaging a land-ocean transition zone. In a plate convergent margin, an oceanic plate subducts deep into a lithosphere and an island arc crust grows due to an accretion of melts welling up from subducted materials. Our obtained long-offset and multi-fold seismic data successfully provide fine images of subducting and overriding plates, which had not been imaged by conventional type of wide-angle seismic survey, in those complicated tectonic setting. One of the most striking findings is an image of several scales of subducted seamounts/ridges in the Nankai trough seismogenic zone, the SW Japan. We detected the subducted seamount/ridges, which are 50 - 100 km wide, distributing from near trough axis to ~ 40 km deep beneath the Japanese island. An important aspect, from a point of view of a geodynamic process, those structures are strongly correlated with slip zones of magnitude 8-class earthquakes, i.e.; subducted seamounts/ridge control the rupture propagations. We have also acquired very long offset seismic data (more than 500 km long) along and across the Izu-Bonin-Mariana (IBM) subduction zone in which ongoing crustal accretion process is proposed. Although the data is still processing, we expect, from our data, new and important information for the crustal accretion process at the IBM

  17. Tectonics of the Easter plate

    NASA Technical Reports Server (NTRS)

    Engeln, J. F.; Stein, S.

    1984-01-01

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

  18. The Diffuse Plate boundary of Nubia and Iberia in the Western Mediterranean: Crustal deformation evidence for viscous coupling and fragmented lithosphere

    NASA Astrophysics Data System (ADS)

    Palano, Mimmo; González, Pablo J.; Fernández, José

    2015-11-01

    A spatially dense GNSS-based crustal velocity field for the Iberian Peninsula and Northern Africa allows us to provide new insights into two main tectonic processes currently occurring in this area. In particular, we provide, for the first time, clear evidence for a large-scale clockwise rotation of the Iberian Peninsula with respect to stable Eurasia (Euler pole component: N42.612°, W1.833°, clockwise rotation rate of 0.07 deg/Myr). We favor the interpretation that this pattern reflects the quasi-continuous straining of the ductile lithosphere in some sectors of South and Western Iberia in response to viscous coupling of the NW Nubia and Iberian plate boundary in the Gulf of Cádiz. We furnish evidence for a fragmentation of the western Mediterranean basin into independent crustal tectonic blocks, which are delimited by inherited lithospheric shear structures. Among these blocks, an (oceanic-like western) Algerian one is currently transferring a significant fraction of the Nubia-Eurasia convergence rate into the Eastern Betics (SE Iberia) and likely causing the eastward motion of the Baleares Promontory. These processes can be mainly explained by spatially variable lithospheric plate forces imposed along the Nubia-Eurasia convergence boundary.

  19. The October 28, 2012 Mw 7.8 Haida Gwaii underthrusting earthquake and tsunami: Slip partitioning along the Queen Charlotte Fault transpressional plate boundary

    NASA Astrophysics Data System (ADS)

    Lay, Thorne; Ye, Lingling; Kanamori, Hiroo; Yamazaki, Yoshiki; Cheung, Kwok Fai; Kwong, Kevin; Koper, Keith D.

    2013-08-01

    The Pacific/North American plate boundary is undergoing predominantly right-lateral strike-slip motion along the Queen Charlotte and Fairweather transform faults. The Queen Charlotte Fault (QCF) hosted the largest historical earthquake in Canada, the 1949 MS 8.1 strike-slip earthquake, which ruptured from offshore northern Haida Gwaii several hundred kilometers northwestward. On January 5, 2013 an Mw 7.5 strike-slip faulting event occurred near the northern end of the 1949 rupture zone. Along central and southern Haida Gwaii the relative plate motion has ∼20% oblique convergence across the left-stepping plate boundary. There had been uncertainty in how the compressional component of plate motion is accommodated. The October 28, 2012 Mw 7.8 Haida Gwaii earthquake involved slightly (∼20°) oblique thrust faulting on a shallow (∼18.5°) northeast-dipping fault plane with strike (∼320°) parallel to the QCF, consistent with prior inferences of Pacific Plate underthrusting beneath Haida Gwaii. The rupture extended to shallow depth offshore of Moresby Island beneath a 25-30 km wide terrace of sediments that has accumulated in a wedge seaward of the QCF. The shallow thrusting caused seafloor uplift that generated substantial localized tsunami run-up and a modest far-field tsunami that spread across the northern Pacific, prompting a tsunami warning, beach closure, and coastal evacuation in Hawaii, although ultimately tide gauges showed less than 0.8 m of water level increase. The mainshock rupture appears to have spread with a ∼2.3 km/s rupture velocity over a length of ∼150 km, with slip averaging 3.3 m concentrated beneath the sedimentary wedge. The event was followed by a substantial aftershock sequence, in which almost all of the larger events involve distributed intraplate normal faulting extending ∼50 km oceanward from the QCF. The highly oblique slip partitioning in southern Haida Gwaii is distinctive in that the local plate boundary-parallel motion on

  20. Boundary layer flow of air over water on a flat plate

    NASA Technical Reports Server (NTRS)

    Nelson, John; Alving, Amy E.; Joseph, Daniel D.

    1993-01-01

    A non-similar boundary layer theory for air blowing over a water layer on a flat plate is formulated and studied as a two-fluid problem in which the position of the interface is unknown. The problem is considered at large Reynolds number (based on x), away from the leading edge. A simple non-similar analytic solution of the problem is derived for which the interface height is proportional to x(sub 1/4) and the water and air flow satisfy the Blasius boundary layer equations, with a linear profile in the water and a Blasius profile in the air. Numerical studies of the initial value problem suggests that this asymptotic, non-similar air-water boundary layer solution is a global attractor for all initial conditions.

  1. Experiments on the stability of the flat-plate boundary layer with suction

    NASA Technical Reports Server (NTRS)

    Reynolds, G. A.; Saric, W. S.

    1982-01-01

    Experiments have been conducted in the VPI and SU Stability Wind Tunnel on a flat-plate wind-tunnel model equipped with porous suction panels. Detailed hot-wire measurements were conducted in the laminar boundary layer to investigate the stabilizing effects of suction on growing Tollmien-Schlichting waves, which were introduced into the boundary layer using a vibrating ribbon. Special care was taken to minimize external disturbances and to avoid extraneous experimental bias. The measurements, which included mean-flow and disturbance-amplitude profiles across the boundary layer, showed that suction applied through discrete porous strips can be as effective as suction applied continuously over a much longer streamwise length. The measurements also showed that suction is more effective when placed forward, nearer to the region of neutral stability, than when placed in the region of maximum growth rate. These results also provided meaningful comparison with recent theory.

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

    SciTech Connect

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

    1991-03-01

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

  3. Effect of time-evolving age and convergence rate of the subducting plate on the Cenozoic adakites and boninites

    NASA Astrophysics Data System (ADS)

    Kim, Yoon-Mi; Lee, Changyeol

    2014-12-01

    Partial melting of subducting oceanic crust expressed as high-Mg volcanic rocks such as adakites and boninites has been actively studied for decades, and Lee and King (2010) reported that time-evolving subduction parameters such as the age and the subduction rate of the converging oceanic plate play important roles in transient partial melting of the subducting oceanic crust (e.g., Aleutians). However, few subduction model experiments have considered time-evolving subduction parameters, posing problems for studies of transient partial melting of subducting oceanic crust in many subduction zones. Therefore, we constructed two-dimensional kinematic-dynamic subduction models for the Izu-Bonin, Mariana, Northeast Japan, Kuril, Tonga, Java-Sunda, and Aleutian subduction zones that account for the last 50 Myr of their evolution. The models include the time-evolving age and convergence rate of the incoming oceanic plate, so the effect of time-evolving subduction parameters on transient partial melting of oceanic crust can be evaluated. Our model calculations revealed that adakites and boninites in the Izu-Bonin and Aleutian subduction zones resulted from transient partial melting of oceanic crust. However, the steady-state subduction model using current subduction parameters did not produce any partial melting of oceanic crust in the aforementioned subduction zones, indicating that time-evolving subduction parameters are crucial for modeling transient eruption of adakites and boninites. Our model calculations confirm that other geological processes such as forearc extension, back-arc opening, mantle plumes and ridge subduction are required for partial melting of the oceanic crust in the Mariana, Northeast Japan, Tonga, and southeastern Java-Sunda subduction zones.

  4. Polynomial decay rate of a thermoelastic Mindlin-Timoshenko plate model with Dirichlet boundary conditions

    NASA Astrophysics Data System (ADS)

    Grobbelaar-Van Dalsen, Marié

    2015-02-01

    In this article, we are concerned with the polynomial stabilization of a two-dimensional thermoelastic Mindlin-Timoshenko plate model with no mechanical damping. The model is subject to Dirichlet boundary conditions on the elastic as well as the thermal variables. The work complements our earlier work in Grobbelaar-Van Dalsen (Z Angew Math Phys 64:1305-1325, 2013) on the polynomial stabilization of a Mindlin-Timoshenko model in a radially symmetric domain under Dirichlet boundary conditions on the displacement and thermal variables and free boundary conditions on the shear angle variables. In particular, our aim is to investigate the effect of the Dirichlet boundary conditions on all the variables on the polynomial decay rate of the model. By once more applying a frequency domain method in which we make critical use of an inequality for the trace of Sobolev functions on the boundary of a bounded, open connected set we show that the decay is slower than in the model considered in the cited work. A comparison of our result with our polynomial decay result for a magnetoelastic Mindlin-Timoshenko model subject to Dirichlet boundary conditions on the elastic variables in Grobbelaar-Van Dalsen (Z Angew Math Phys 63:1047-1065, 2012) also indicates a correlation between the robustness of the coupling between parabolic and hyperbolic dynamics and the polynomial decay rate in the two models.

  5. Plate boundary deformation at the latitude of the Salton Trough - northern Gulf of California (Invited)

    NASA Astrophysics Data System (ADS)

    Stock, J. M.

    2013-12-01

    Along the Pacific-North America plate boundary zone, the segment including the southern San Andreas fault to Salton Trough and northern Gulf of California basins has been transtensional throughout its evolution, based on Pacific-North America displacement vectors calculated from the global plate circuit (900 × 20 km at N54°W since 20 Ma; 460 × 20 km at N48°W since 11 Ma). Nevertheless, active seismicity and focal mechanisms show a broad zone of plate boundary deformation within which the inferred stress regime varies locally (Yang & Hauksson 2013 GJI), and fault patterns in some regions suggest ongoing tectonic rotation. Similar behavior is inferred to have occurred in this zone over most of its history. Crustal structure in this region is constrained by surface geology, geophysical experiments (e.g., the 2011 Salton Seismic Imaging Project (SSIP), USGS Imperial Valley 1979, PACE), and interdisciplinary marine and onland studies in Mexico (e.g., NARS-Baja, Cortes, and surveys by PEMEX). Magnetic data (e.g., EMAG-2) aids in the recognition of large-scale crustal provinces and fault boundaries in regions lacking detailed geophysical surveys. Consideration of existing constraints on crustal thickness and architecture, and fault and basin evolution suggests that to reconcile geological deformation with plate motion history, the following additional factors need to be taken into account. 1) Plate boundary displacement via interacting systems of rotating blocks, coeval with slip on steep strike slip faults, and possibly related to slip on low angle extensional faults (e.g, Axen & Fletcher 1998 IGR) may be typical prior to the onset of seafloor spreading. This fault style may have accommodated up to 150 km of plate motion in the Mexican Continental Borderland and north of the Vizcaino Peninsula, likely between 12 and 15 Ma, as well as explaining younger rotations adjacent to the Gulf of California and current deformation southwest of the Salton Sea. 2) Geophysical

  6. GEM Plate Boundary Simulations for the Plate Boundary Observatory: A Program for Understanding the Physics of Earthquakes on Complex Fault Networks via Observations, Theory and Numerical Simulation

    NASA Astrophysics Data System (ADS)

    Rundle, J. B.; Rundle, P. B.; Klein, W.; de sa Martins, J.; Tiampo, K. F.; Donnellan, A.; Kellogg, L. H.

    The last five years have seen unprecedented growth in the amount and quality of geodetic data collected to characterize crustal deformation in earthquake-prone areas such as California and Japan. The installation of the Southern California Integrated Geodetic Network (SCIGN) and the Bay Area Regional Deformation (BARD) network are two examples. As part of the recently proposed Earthscope NSF/GEO/EAR/MRE initiative, the Plate Boundary Observatory (PBO) plans to place more than a thousand GPS, strainmeters, and deformation sensors along the active plate boundary of the western coast of the United States, Mexico and Canada (http://www.earthscope.org/pbo.com.html). The scientific goals of PBO include understanding how tectonic plates interact, together with an emphasis on understanding the physics of earthquakes. However, the problem of understanding the physics of earthquakes on complex fault networks through observations alone is complicated by our inability to study the problem in a manner familiar to laboratory scientists, by means of controlled, fully reproducible experiments. We have therefore been motivated to construct a numerical simulation technology that will allow us to study earthquake physics via numerical experiments. To be considered successful, the simulations must not only produce observables that are maximally similar to those seen by the PBO and other observing programs, but in addition the simulations must provide dynamical predictions that can be falsified by means of observations on the real fault networks. In general, the dynamical behavior of earthquakes on complex fault networks is a result of the interplay between the geometric structure of the fault network and the physics of the frictional sliding process. In constructing numerical simulations of a complex fault network, we will need to solve a variety of problems, including the development of analysis techniques (also called data mining), data assimilation, space-time pattern definition

  7. Evolution of the boundary between the Philippine Sea Plate and Australia: palaeomagnetic evidence from eastern Indonesia

    NASA Astrophysics Data System (ADS)

    Ali, Jason R.; Hall, Robert

    1995-12-01

    The boundary between the Philippine Sea and Australian plates is the left-lateral Sorong Fault system of eastern Indonesia. Until recently, modelling this boundary for the period before about 5 Ma was difficult; the Tertiary motion of the Philippine Sea Plate was uncertain and palaeomagnetic data from areas adjacent to the fault were lacking. Recent geological and palaeomagnetic studies of the area north of the Sorong Fault have elucidated the Tertiary motion history of the Philippine Sea Plate, providing a reference for examining movements within the fault system. We report new palaeomagnetic data from within the Sorong Fault Zone, from the islands of Taliabu and Obi. Taliabu is part of the Sula Platform and is considered to be derived from Australia. Pelagic limestones from the Upper Cretaceous Tanamu Formation of Taliabu yielded a direction of D = 329.1°, I = -34.9° implying counter-clockwise rotation and a formation latitude of 19 ± 5°S. Sula and Misool are postulated to be part of a single microcontinent which had a different Late Cretaceous-mid-Tertiary movement history from Australia. The Sula Platform was transported to its present position by movement along the Sorong Fault system in the Late Miocene. Obi includes rocks of Philippine Sea and Australian origin; all the new sites are in rocks of Philippine Sea Plate origin. Since the Early Neogene the Philippine Sea Plate, which includes all islands north of the Sorong Fault, has rotated 40° clockwise and moved 10-15° northwards. Philippine Sea Plate rocks within the Sorong Fault Zone record similar latitude shifts, but different rotations. In north Obi, the Upper Oligocene Anggai River Formation and the Middle Miocene Woi Formation record ˜ 60° and ˜ 30° counter-clockwise rotations, respectively. The sense of rotation is consistent with motion within a left-lateral fault system, with the Philippine Sea and Australian plates providing the shear couple. In contrast, the Woi Formation in southeast

  8. Late Cenozoic tectonics of the Middle Atlas Mountains, Morocco: Continental deformation in the diffuse western Mediterranean plate boundary

    NASA Astrophysics Data System (ADS)

    Gomez, Francisco Gustavo

    -Eurasian plate convergence since the Early Miocene. The diffuse plate boundary comprises large, relatively rigid crustal blocks (Moroccan Meseta, High Plateau, and Saharan Platform) bounded by narrow deformable zones (the Atlas). In this context, the Middle Atlas can be interpreted as an accommodation zone resulting from differential movements between two large crustal blocks impinging on stable Africa. The Atlas Mountains exemplify the possible structural influence of inherited crustal weaknesses in a diffuse plate boundary such as the western Mediterranean region.

  9. Upper Plate Tectonics and Fluid Flow Along the Middle America Convergent Margin

    NASA Astrophysics Data System (ADS)

    Huguen, C.; Ranero, C. R.; Weinrebe, W.; Sahling, H.; Borhmann, G.; Klaucke, I.

    2002-12-01

    We present new multibeam bathymetry, side scan sonar, sub-bottom profiling, deep towed video camera images and sampling from active structures related to tectonics and fluid flow at the overriding plate of the Middle America subduction zone. Data were collected during SONNE 163-1 cruise at key locations based on full bathymetric coverage of the margin with a ~ 100 m grid. We surveyed normal faults along the middle-upper continental slope and associated mounds. Also, the locus of seamount subduction was investigated. The new bathymetry has been gridded at ~ 25 m. Deep towed side scan sonar data have a resolution of ~ 1 m. Subbottom high resolution profiling images the upper ~ 100 m of slope sediment. Deep towed camera observations and sampling were used to ground truth the geophysical data. The canyon system present in the upper slope terminates abruptly at the ~ mid slope where normal faulting develops. Roughly coincident with the faulting development, groups of small mounds (few 100s m to 1 km long and < 100 m to 150 m high) occur along the upper-middle slope. These mounds, previously interpreted as mud volcanoes, do not show evidence of mud flows in the side scan data. Deep towed camera and dredging at numerous locations indicate that the surface of the mounds is made of chemoherm carbonates that yield a characteristic high reflectivity in back scatter images. The mounds seem to be areas of fluid discharge and chemosynthetic fauna was observed locally in all of the structures investigated. The mounds are spatially coincident and may be associated to the development of the faults. Their fate may also be related to the faulting: mounds disappear downslope as the fault throw increases. Data from the areas of active seamount subduction show clear evidence for recent/ongoing tectonism at the uplifted overriding plate. The largest deformation occurs at the summit of the uplift and at the trail of the seamount where sliding and slumping are active. Areas of the summit

  10. The boundary between the Indian and Asian tectonic plates below Tibet

    PubMed Central

    Zhao, Junmeng; Yuan, Xiaohui; Liu, Hongbing; Kumar, Prakash; Pei, Shunping; Kind, Rainer; Zhang, Zhongjie; Teng, Jiwen; Ding, Lin; Gao, Xing; Xu, Qiang; Wang, Wei

    2010-01-01

    The fate of the colliding Indian and Asian tectonic plates below the Tibetan high plateau may be visualized by, in addition to seismic tomography, mapping the deep seismic discontinuities, like the crust-mantle boundary (Moho), the lithosphere-asthenosphere boundary (LAB), or the discontinuities at 410 and 660 km depth. We herein present observations of seismic discontinuities with the P and S receiver function techniques beneath central and western Tibet along two new profiles and discuss the results in connection with results from earlier profiles, which did observe the LAB. The LAB of the Indian and Asian plates is well-imaged by several profiles and suggests a changing mode of India-Asia collision in the east-west direction. From eastern Himalayan syntaxis to the western edge of the Tarim Basin, the Indian lithosphere is underthrusting Tibet at an increasingly shallower angle and reaching progressively further to the north. A particular lithospheric region was formed in northern and eastern Tibet as a crush zone between the two colliding plates, the existence of which is marked by high temperature, low mantle seismic wavespeed (correlating with late arriving signals from the 410 discontinuity), poor Sn propagation, east and southeast oriented global positioning system displacements, and strikingly larger seismic (SKS) anisotropy. PMID:20534567

  11. First epoch geodetic measurements with the Global Positioning System across the northern Caribbean plate boundary zone

    NASA Technical Reports Server (NTRS)

    Dixon, T. H.; Gonzalez, G.; Lichten, S. M.; Katsigris, E.

    1991-01-01

    The first geodetic survey across the northern Caribbean plate boundary zone with GPS was conducted in June 1986. Baseline vectors defined by the six-station regional GPS network ranged from 170 to 1260 km in length. Repeatability of independent daily baseline estimates was better than 8 mm plus 1.3 parts in 10 to the 8th of baseline length for horizontal components. The wet tropospheric path delay during the experiment was both high, sometimes exceeding 30 cm at zenith, and variable, sometimes exceeding 5 cm variation over several hours. Successful carrier phase cycle ambiguity resolution (bias fixing) could not be achieved prior to construction of a regional troposphere model. With optimum troposphere treatment and single-day orbital arcs, most biases on baselines were resolved up to about 550 km in length. With multiday orbital arcs most biases in the network were resolved regardless of baseline length. The results suggest that constraints on plate-boundary zone deformation in the Greater Antilles, and on the North America-Caribbean relative plate motion vector, can be obtained with a series of GPS experiments spanning less than 10 and 15 years, respectively.

  12. The boundary between the Indian and Asian tectonic plates below Tibet.

    PubMed

    Zhao, Junmeng; Yuan, Xiaohui; Liu, Hongbing; Kumar, Prakash; Pei, Shunping; Kind, Rainer; Zhang, Zhongjie; Teng, Jiwen; Ding, Lin; Gao, Xing; Xu, Qiang; Wang, Wei

    2010-06-22

    The fate of the colliding Indian and Asian tectonic plates below the Tibetan high plateau may be visualized by, in addition to seismic tomography, mapping the deep seismic discontinuities, like the crust-mantle boundary (Moho), the lithosphere-asthenosphere boundary (LAB), or the discontinuities at 410 and 660 km depth. We herein present observations of seismic discontinuities with the P and S receiver function techniques beneath central and western Tibet along two new profiles and discuss the results in connection with results from earlier profiles, which did observe the LAB. The LAB of the Indian and Asian plates is well-imaged by several profiles and suggests a changing mode of India-Asia collision in the east-west direction. From eastern Himalayan syntaxis to the western edge of the Tarim Basin, the Indian lithosphere is underthrusting Tibet at an increasingly shallower angle and reaching progressively further to the north. A particular lithospheric region was formed in northern and eastern Tibet as a crush zone between the two colliding plates, the existence of which is marked by high temperature, low mantle seismic wavespeed (correlating with late arriving signals from the 410 discontinuity), poor Sn propagation, east and southeast oriented global positioning system displacements, and strikingly larger seismic (SKS) anisotropy. PMID:20534567

  13. Quasi-simultaneous interaction method for solving 2D boundary layer flows over plates and airfoils

    NASA Astrophysics Data System (ADS)

    Bijleveld, H. A.; Veldman, A. E. P.

    2012-11-01

    This paper studies unsteady 2D boundary layer flows over dented plates and a NACA 0012 airfoil. An inviscid flow is assumed to exist outside the boundary layer and is solved iteratively with the boundary layer flow together with the interaction method until a matching solution is achieved. Hereto a quasi-simultaneous interaction method is applied, in which the integral boundary layer equations are solved together with an interaction-law equation. The interaction-law equation is an approximation of the external flow and based on thin-airfoil theory. It is an algebraic relation between the velocity and displacement thickness. The interaction-law equation ensures that the eigenvalues of the system of equations do not have a sign change and that no singularities occur. Three numerical schemes are used to solve the boundary layer flow with the interaction method. These are: a standard scheme, a splitting method and a characteristics solver. All schemes use a finite difference discretization. The three schemes yield comparable results for the simulations carried out. The standard scheme is deviating most from the splitting and characteristics solvers. The results show that the eigenvalues remain positive, even in separation. As expected, the addition of the interaction-law equation prevents a sign change of the eigenvalues. The quasi-simultaneous interaction scheme is applicable to the three numerical schemes tested.

  14. Laminar-Boundary-Layer Oscillations and Transition on a Flat Plate

    NASA Technical Reports Server (NTRS)

    Schubauer, G B; Skramstad, H K

    1948-01-01

    This is an account of an investigation in which oscillations were discovered in the laminar boundary layer along a flat plate. These oscillations were found during the course of an experiment in which transition from laminar to turbulent flow was being studied on the plate as the turbulence in the wind stream was being reduced to unusually low values by means of damping screens. The first part of the paper deals with experimental methods and apparatus, measurements of turbulence and sound, and studies of transition. A description is then given of the manner in which oscillations were discovered and how they were found to be related to transition, and then how controlled oscillations were produced and studied in detail.

  15. Prehistoric earthquakes on the Caribbean-South American plate boundary, central Range Fault, Trinidad

    USGS Publications Warehouse

    Prentice, Carol S.; Crosby, Christopher J.; Weber, John C.; Ragona, Daniel

    2010-01-01

    Recent geodetic studies suggest that the Central Range fault is the principal plate-boundary structure accommodating strike-slip motion between the Caribbean and South American plates. Our study shows that the fault forms a topographically prominent lineament in central Trinidad. Results from a paleoseismic investigation at a site where Holocene sediments have been deposited across the Central Range fault indicate that it ruptured the ground surface most recently between 2710 and 550 yr B.P. If the geodetic slip rate of 9–15 mm/yr is representative of Holocene slip rates, our paleoseismic data suggest that at least 4.9 m of potential slip may have accumulated on the fault and could be released during a future large earthquake (M > 7).

  16. Prehistoric earthquakes on the Caribbean-South American plate boundary, central range fault, Trinidad

    USGS Publications Warehouse

    Prentice, C.S.; Weber, J.C.; Crosby, C.J.; Ragona, D.

    2010-01-01

    Recent geodetic studies suggest that the Central Range fault is the principal plate-boundary structure accommodating strike-slip motion between the Caribbean and South American plates. Our study shows that the fault forms a topographically prominent lineament in central Trinidad. Results from a paleoseismic investigation at a site where Holocene sediments have been deposited across the Central Range fault indicate that it ruptured the ground surface most recently between 2710 and 550 yr B.P. If the geodetic slip rate of 9-15 mm/yr is representative of Holocene slip rates, our paleoseismic data suggest that at least 4.9 m of potential slip may have accumulated on the fault and could be released during a future large earthquake (M > 7). ?? 2010 Geological Society of America.

  17. Plate boundary deformation and man-made subsidence around geothermal fields on the Reykjanes Peninsula, Iceland

    NASA Astrophysics Data System (ADS)

    Keiding, M.; Árnadóttir, T.; Jónsson, S.; Decriem, J.; Hooper, A.

    2010-07-01

    We present Interferometric Synthetic Aperture Radar (InSAR) data from 1992-1999 and 2003-2008 as well as GPS data from 2000-2009 for the active plate boundary on the Reykjanes Peninsula, southwest Iceland. The geodetic data reveal deformation mainly due to plate spreading, anthropogenic subsidence caused by geothermal fluid extraction and, possibly, increasing pressure in a geothermal system. Subsidence of around 10 cm is observed during the first 2 years of production at the Reykjanes geothermal power plant, which started operating in May 2006. We model the surface subsidence around the new power plant using point and ellipsoidal pressure sources in an elastic halfspace. Short-lived swarms of micro-earthquakes as well as aseismic fault movement are observed near the geothermal field following the start of production, possibly triggered by the stresses induced by geothermal fluid extraction.

  18. The Northern Caribbean Plate Boundary Offshore Hispaniola: Strike-slip and Compressive Tectonic Processes

    NASA Astrophysics Data System (ADS)

    Corbeau, J.; Rolandone, F.; Leroy, S. D.; Mercier De Lepinay, B. F.; Meyer, B.; Ellouz, N.

    2014-12-01

    The boundary between the Caribbean plate and the North American plate is transpressive due to the oblique collision between these two plates. The transpressive movement is partitioned and accommodated in the Hispaniola region along two left-lateral strike-slip structures surrounding a fold-and-thrust belt. New multibeam bathymetry data and multichannel seismic reflection profiles have been recently collected during the Haiti-SIS and Haiti-SIS 2 cruises, along part of the northern Caribbean plate boundary between Cuba, Jamaica and Hispaniola. From the north to the south, three types of deformations are observed. In the Windward Passage, the analysis of the data set reveals that the movement on the Oriente fault between Cuba and Hispaniola is purely left-lateral strike-slip according to the GPS measurements. In the Gonave basin, west of Hispaniola, the deformation is compressive. A series of folds is identified and moves toward the southwest. The Enriquillo-Plantain-Garden Fault (EPGF) is localized in the Jamaica Passage, between Jamaica and Hispaniola. The analysis of the data set reveals that the left-lateral EPGF recently intersects inherited basins from the eastern Cayman Trough margin. The study of the actual EPGF active trace shows that this fault moves with a pure strike-slip component, at least in its western part: the presence of a little push-up structure and a set of three en echelon folds is highlighting in the western part of the Jamaica Passage. The shortening rate in the inherited basins crossed by the EPGF increases from west to east (5.8% to 8.5%), indicating that a thrusting component is also accommodated around the EPGF.

  19. Relaxation of the accelerating-gas boundary layer to the test-gas boundary layer on a flat plate in an expansion tube

    NASA Technical Reports Server (NTRS)

    Gupta, R. N.; Trimpi, R. L.

    1973-01-01

    An analytic investigation of the relaxation of the accelerating-gas boundary layer to the test-gas boundary layer over a flat plate mounted in an expansion tube has been conducted. In this treatment, nitrogen has been considered as the test gas and helium as the accelerating gas. The problem is analyzed in two conically similar limits: (1) when the time lag between the arrival of the shock and the interface at the leading edge of the plate is very large, and (2) when this time lag is negligible. The transient laminar boundary-layer equations of a perfect binary-gas mixture are taken as the flow governing equations. These coupled equations have been solved numerically by Gauss-Seidel line-relaxation method. The results predict the transient behavior as well as the time required for an all-helium accelerating-gas boundary layer to relax to an all-nitrogen boundary layer.

  20. Model representation of boundary-layer convergence triggering deep convection over complex terrain: A case study from COPS

    NASA Astrophysics Data System (ADS)

    Barthlott, Christian; Schipper, Janus Willem; Kalthoff, Norbert; Adler, Bianca; Kottmeier, Christoph; Blyth, Alan; Mobbs, Stephen

    2010-02-01

    An isolated thunderstorm from the Convective and Orographically-induced Precipitation Study in southwest Germany and east France in 2007 is analyzed. On July 15, deep convection developed east of the Black Forest crest, although convective available potential energy (CAPE) was only moderate and convective inhibition (CIN) was high. Data analysis revealed that convection was triggered by updrafts penetrating the capping inversion of the planetary boundary layer as a result of low-level convergence. Although the numerical weather prediction model COSMO-DE of the German Weather Service (2.8 km grid resolution) simulated a convergence line and the evolution of a line of low clouds in good agreement with radar and satellite observations, no precipitating deep convection developed from this line of clouds. For an improved representation of orographic effects, simulations with a finer grid resolution of 1 km were performed. Despite almost optimal conditions, i.e. moderate amount of CAPE and almost vanishing CIN, the updrafts required to overcome CIN were not reached in both model configurations. Although both simulations did not initiate deep convection, the results suggest that in an air mass convection situation without mid-tropospheric forcing, the simulated location and timing of convergence lines with coexistent large values of CAPE and low values of CIN can be used as diagnostic parameters for deep convection nowcasting.

  1. Architectural Blueprint for Plate Boundary Observatories based on interoperable Data Management Platforms

    NASA Astrophysics Data System (ADS)

    Kerschke, D. I.; Häner, R.; Schurr, B.; Oncken, O.; Wächter, J.

    2014-12-01

    Interoperable data management platforms play an increasing role in the advancement of knowledge and technology in many scientific disciplines. Through high quality services they support the establishment of efficient and innovative research environments. Well-designed research environments can facilitate the sustainable utilization, exchange, and re-use of scientific data and functionality by using standardized community models. Together with innovative 3D/4D visualization, these concepts provide added value in improving scientific knowledge-gain, even across the boundaries of disciplines. A project benefiting from the added value is the Integrated Plate boundary Observatory in Chile (IPOC). IPOC is a European-South American network to study earthquakes and deformation at the Chilean continental margin and to monitor the plate boundary system for capturing an anticipated great earthquake in a seismic gap. In contrast to conventional observatories that monitor individual signals only, IPOC captures a large range of different processes through various observation methods (e.g., seismographs, GPS, magneto-telluric sensors, creep-meter, accelerometer, InSAR). For IPOC a conceptual design has been devised that comprises an architectural blueprint for a data management platform based on common and standardized data models, protocols, and encodings as well as on an exclusive use of Free and Open Source Software (FOSS) including visualization components. Following the principles of event-driven service-oriented architectures, the design enables novel processes by sharing and re-using functionality and information on the basis of innovative data mining and data fusion technologies. This platform can help to improve the understanding of the physical processes underlying plate deformations as well as the natural hazards induced by them. Through the use of standards, this blueprint can not only be facilitated for other plate observing systems (e.g., the European Plate

  2. Evolution of southern Caribbean plate boundary, vicinity of Trinidad and Tobago

    NASA Technical Reports Server (NTRS)

    Robertson, Paul; Burke, Kevin

    1989-01-01

    The tectonic evolution of the southeastern corner of the Caribbean is examined, using field data from the El Pilar fault zone of Trinidad and offshore seismic data. It is found that the dominant process in the region's tectonic evolution is strike-slip motion on at least five major fault systems in a 250-km wide east-west-trending plate-boundary zone extending from Grenada in the north to the Orinoco River in the south. The geological effects of this evolution over the past 30 m y are described.

  3. Conditional ɛ-uniform boundedness of Galerkin projectors and convergence of an adaptive mesh method as applied to singularly perturbed boundary value problems

    NASA Astrophysics Data System (ADS)

    Blatov, I. A.; Dobrobog, N. V.; Kitaeva, E. V.

    2016-07-01

    The Galerkin finite element method is applied to nonself-adjoint singularly perturbed boundary value problems on Shishkin meshes. The Galerkin projection method is used to obtain conditionally ɛ-uniform a priori error estimates and to prove the convergence of a sequence of meshes in the case of an unknown boundary layer edge.

  4. Crustal strain rate patterns of the western North America Plate boundary

    NASA Astrophysics Data System (ADS)

    Hackl, M.; Malservisi, R.; Furlong, K.; Kirby, E.

    2009-04-01

    The knowledge of the crustal strain rate tensor provides a description of geodynamic processes such as fault strain accumulation. We use interpolation of GPS geodetic measurements to derive the regional strain rate field for selected regions within the western North America plate boundary. We applied the interpolation scheme to data from the Eastern California Shear Zone, the Mendocino triple junction region, and the transition from the Sierra block to the Pacific North West. Our results allow us to define regions of localization of the strain rate at the northern end of the San Andrea Fault system and within the boundary between the Sierra Nevada and Basin and Range. These results help to understand the way in which strain is accommodated in the Sierra/Pacific North West transition. The results will be compared with geologic and tectonic observation of the region.

  5. Calculation of oblique-shock-wave laminar-boundary-layer interaction on a flat plate

    NASA Technical Reports Server (NTRS)

    Goldberg, U.; Reshotko, E.

    1980-01-01

    A finite difference solution to the problem of the interaction between an impinging oblique shock wave and the laminar boundary layer on a flat plate is presented. The boundary layer equations coupled with the Prandtl-Meyer relation for the external flow are used to calculate the flow field. A method for the calculation of the separated flow region is presented and discussed. Comparisons between this theory and the experimental results of other investigators show fairly good agreement. Results are presented for the case of a cooled wall with an oncoming flow at Mach number 2.0 without and with suction. The results show that a small amount of suction greatly reduces the extent of the separated region in the vicinity of the shock impingement location.

  6. Experimental study of boundary layer transition on a heated flat plate

    NASA Technical Reports Server (NTRS)

    Sohn, K. H.; Reshotko, E.; Zaman, K. B. M. Q.

    1991-01-01

    A detailed investigation to the document momentum and thermal development of boundary layers undergoing natural transition on a heated flat plate was performed. Experimental results of both overall and conditionally sampled characteristics of laminar, transitional, and low Reynolds number turbulent boundary layers are presented. Measurements were done in a low-speed, closed-loop wind tunnel with a freestream velocity of 100 ft/s and zero pressure gradient over a range of freestream turbulence intensities from 0.4 to 6 percent. The distributions of skin friction, heat transfer rate, and Reynolds shear stress were all consistent with previously published data. Reynolds analogy factors for momentum thickness Reynolds number, Re(sub theta) less than 2300 were found to be well predicted by laminar and turbulent correlations which accounted for an unheated starting length and uniform heat flux. A small dependence of turbulence results on the freestream turbulence intensity was observed.

  7. Interaction of a synthetic jet with a flat plate boundary layer

    NASA Astrophysics Data System (ADS)

    Rampunggoon, Prakit

    The interaction of a 2-dimensional modeled synthetic jet with a flat plate boundary layer is investigated numerically using an incompressible Navier-Stokes solver. A simple, two-dimensional synthetic jet configuration along with a flat plate, laminar Blasius boundary layer was used in the current study. The oscillating diaphragm of the actuator is modeled in a realistic manner as a moving boundary in an effort to accurately compute the flow inside the jet cavity. The primary focus of the current study is on describing the dynamics of the synthetic jet in the presence of external crossflow. However, in addition, simulations of the jet with quiescent external flow have also been performed. A systematic framework was put forth for characterizing the jet that consists of computing the various moments of the velocity profile along with an integral measure of the profile skewness. A comprehensive parametric study has been carried out where the diaphragm amplitude, external flow Reynolds number, boundary layer thickness, and slot dimensions are varied; and the scaling of the jet characteristics with parameters is examined. The simulations also allow us to extract some interesting flow physics associated with the vortex dynamics of the jet and to elucidate the effect of external cross flow on jet development. In addition, a low-dimensional model for jet velocity profile is proposed and tested. Finally, the so-called "virtual aero-shaping" effect of synthetic jets is examined and the current simulations indicate a simple scaling of this effect with the dynamical characteristics of the jet and external crossflow.

  8. Effect of plate permeability on nonlinear stability of the asymptotic suction boundary layer.

    PubMed

    Wedin, Håkan; Cherubini, Stefania; Bottaro, Alessandro

    2015-07-01

    The nonlinear stability of the asymptotic suction boundary layer is studied numerically, searching for finite-amplitude solutions that bifurcate from the laminar flow state. By changing the boundary conditions for disturbances at the plate from the classical no-slip condition to more physically sound ones, the stability characteristics of the flow may change radically, both for the linearized as well as the nonlinear problem. The wall boundary condition takes into account the permeability K̂ of the plate; for very low permeability, it is acceptable to impose the classical boundary condition (K̂=0). This leads to a Reynolds number of approximately Re(c)=54400 for the onset of linearly unstable waves, and close to Re(g)=3200 for the emergence of nonlinear solutions [F. A. Milinazzo and P. G. Saffman, J. Fluid Mech. 160, 281 (1985); J. H. M. Fransson, Ph.D. thesis, Royal Institute of Technology, KTH, Sweden, 2003]. However, for larger values of the plate's permeability, the lower limit for the existence of linear and nonlinear solutions shifts to significantly lower Reynolds numbers. For the largest permeability studied here, the limit values of the Reynolds numbers reduce down to Re(c)=796 and Re(g)=294. For all cases studied, the solutions bifurcate subcritically toward lower Re, and this leads to the conjecture that they may be involved in the very first stages of a transition scenario similar to the classical route of the Blasius boundary layer initiated by Tollmien-Schlichting (TS) waves. The stability of these nonlinear solutions is also investigated, showing a low-frequency main unstable mode whose growth rate decreases with increasing permeability and with the Reynolds number, following a power law Re(-ρ), where the value of ρ depends on the permeability coefficient K̂. The nonlinear dynamics of the flow in the vicinity of the computed finite-amplitude solutions is finally investigated by direct numerical simulations, providing a viable scenario for

  9. Empirical Tsunami Hazard Assessment of Near-Field Plate-Boundary and Crustal Fault Sources Demonstrated for the Pacific Coast of Canada

    NASA Astrophysics Data System (ADS)

    Leonard, L. J.; Rogers, G. C.

    2015-12-01

    We demonstrate an empirical method for preliminary tsunami hazard assessment of near-field fault sources that lack long historic records, paleoseismic/paleotsunami data and/or adequate tsunami modelling studies. Along the Pacific coast of Canada, the North America plate boundary is characterized by varying degrees of convergence with adjacent oceanic plates and microplates. The 1700 M~9 Cascadia earthquake ruptured at least the full extent of Juan de Fuca plate subduction as far north as central Vancouver Island; paleoseismic data show that similar events have occurred approximately every 500 years throughout the Holocene, accompanied by large tsunamis. Further north along the margin, the paleoseismic and paleotsunami histories of the Explorer, Winona, and Haida Gwaii segments of the margin are unknown. The Explorer plate is subducting beneath Vancouver Island at about half the rate of the Juan de Fuca plate; this locked segment may rupture independently or it may slip concurrently with the rest of the Cascadia subduction zone system to the south. The tsunamigenic potential of the Winona segment off northern Vancouver Island is poorly understood. The occurrence of the 2012 M7.8 thrust earthquake off southern Haida Gwaii confirmed the tsunamigenic nature of partitioned convergent slip on this dominantly transform margin segment. Parts of the coastline face additional tsunami hazard from submarine crustal faults. For potentially tsunamigenic faults with unknown history, we use (1) geophysical data to constrain fault rupture area, (2) empirical relations to estimate earthquake magnitude from the rupture area, (3) plate motion models and geodetic data to constrain convergence and thrust earthquake recurrence rates, and (4) empirical relations to estimate near-field tsunami runup at coastal sites, given distance from the rupture. The success of this approach is demonstrated by general agreement between expected and observed earthquake magnitude and near-field tsunami

  10. Direct simulation of flat-plate boundary layer with mild free-stream turbulence

    NASA Astrophysics Data System (ADS)

    Wu, Xiaohua; Moin, Parviz

    2014-11-01

    Spatially evolving direct numerical simulation of the flat-plate boundary layer has been performed. The momentum thickness Reynolds number develops from 80 to 3000 with a free-stream turbulence intensity decaying from 3 percent to 0.8 percent. Predicted skin-friction is in agreement with the Blasius solution prior to breakdown, follows the well-known T3A bypass transition data during transition, and agrees with the Erm and Joubert Melbourne wind-tunnel data after the completion of transition. We introduce the concept of bypass transition in the narrow sense. Streaks, although present, do not appear to be dynamically important during the present bypass transition as they occur downstream of infant turbulent spots. For the turbulent boundary layer, viscous scaling collapses the rate of dissipation profiles in the logarithmic region at different Reynolds numbers. The ratio of Taylor microscale and the Kolmogorov length scale is nearly constant over a large portion of the outer layer. The ratio of large-eddy characteristic length and the boundary layer thickness scales very well with Reynolds number. The turbulent boundary layer is also statistically analyzed using frequency spectra, conditional-sampling, and two-point correlations. Near momentum thickness Reynolds number of 2900, three layers of coherent vortices are observed: the upper and lower layers are distinct hairpin forests of large and small sizes respectively; the middle layer consists of mostly fragmented hairpin elements.

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

    USGS Publications Warehouse

    Schouten, Hans; Klitgord, Kim D.

    1982-01-01

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

  12. Flowfield measurements in a separated and reattached flat plate turbulent boundary layer

    NASA Technical Reports Server (NTRS)

    Patrick, William P.

    1987-01-01

    The separation and reattachment of a large-scale, two-dimensional turbulent boundary layer at low subsonic speed on a flat plate has been studied experimentally. The separation bubble was 55 cm long and had a maximum bubble thickness, measured to the height of the mean dividing streamline, of 17 cm, which was twice the thickness of the inlet boundary layer. A combination of laser velocimetry, hot-wire anemometry, pneumatic probing techniques, and flow visualization were used as diagnostics. Principal findings were that an outer inviscid rotational flow was defined which essentially convected over the blockage associated with the inner, viscously dominated bubble recirculation region. A strong backflow region in which the flow moved upstream 100 percent of the time was measured near the test surface over the central 35 percent of the bubble. A laminar backflow boundary layer having pseudo-turbulent characteristics including a log-linear velocity profile was generated under the highly turbulent backflow. Velocity profile shapes in the reversed flow region matched a previously developed universal backflow profile at the upstream edge of the separation region but not in the steady backflow region downstream. A smoke flow visualization movie and hot-film measurements revealed low frequency nonperiodic flapping at reattachment. However, forward flow fraction data at reattachment and mean velocity profiles in the redeveloping boundary layer downstream of reattachment correlated with backward-facing step data when the axial dimension was scaled by the distance from the maximum bubble thickness to reattachment.

  13. Young tectonics of a complex plate boundary zone: Indentation, rotation, and escape in Alaska

    NASA Astrophysics Data System (ADS)

    Wallace, W. K.; Ruppert, N. A.

    2012-12-01

    Convergence of thick crust of the Yakutat block with the southern margin of Alaska is widely recognized as a dominant influence on the tectonics of Alaska since at least late Miocene time. It is less clear how this convergence relates to the distribution, type, and orientation of geologic structures, and to the boundaries between the tectonic provinces that they define. We propose that convergence of Yakutat block includes two distinct components that influence deformation and topography in different ways: 1) The crust of the exposed, southern Yakutat block is too thick to subduct, which has caused the collisional St. Elias orogen. Detachment of the upper part of the mafic basement allows delamination and sinking of the remaining mafic crust and lithospheric mantle. The collisional orogen drives rigid counterclockwise rotation of the southern Alaska block south of the arcuate, right-lateral Denali fault. The western boundary of this block is a zone of distributed contraction in the western Alaska Range and Cook Inlet. 2) The northern part of the Yakutat block is thin enough to subduct but thick and buoyant enough to cause localized flat-slab subduction orthogonal to rotation of the southern Alaska block. Consequences include the gently antiformal Talkeetna Mountains that span the forearc basin, a gap in the magmatic arc, and a basement-involved fold-and-thrust belt in the northern Alaska Range. An arcuate oroclinal hinge from southern Alaska to the northeastern Brooks Range reflects indentation since at least Paleocene time. Traction above the subducted Yakutat block along the southern part of this hinge drives current indentation. North of the subducted Yakutat block, indentation is reflected by left-lateral block rotation that accommodates shortening between the Denali and Tintina faults and by contraction farther north along the northern edge of the arcuate northeastern Brooks Range. Western Alaska accommodates both northward indentation and westward convergence

  14. Low Intensity Characteristic of Plate-Boundary S-S Reflections Within a Region of Strong Plate-Boundary P-P Reflections and low Seismicity Along the Japan Trench Subduction Zone

    NASA Astrophysics Data System (ADS)

    Mochizuki, K.; Kasahara, J.; Hino, R.; Nishino, M.; Yamada, T.; Shinohara, M.; Kanazawa, T.

    2003-12-01

    It has been pointed out that the epicenters of the microearthquakes along the forearc slope of the Japan Trench are not uniformly distributed but clustered in seismically active zones that are oriented perpendicular to the trench axis. One of the clear seismic-aseismic boundaries of such seismic clusters can be identified in latitude 39° N. A seismic survey was conducted in 1996 with one profile running across the boundary and parallel to the trench axis, and a P-wave velocity structure model was obtained by travel-time inversion (Fujie, 1999). A strong anti-correlation between the seismicity and the intensity of the plate-boundary P-P reflected waves was found: strong plate-boundary P-P reflected waves were observed in a region where seismicity is quite low, and vice versa (Fujie et al., 2002). They discussed that a thin layer of low P-wave velocities (3~4 km/s) with its thickness up to a few hundred meters along the plate boundary could explain the intensity of the reflections. Results of finite-difference waveform calculations support this estimation (Moghaddam, 2002). Another seismic survey was carried out in 2001 with 7 trench-parallel profiles in the same region as the 1996 survey in order to map and verify the strong anti-correlation. The strong anti-correlation was observed over the seismic-aseismic boundary region, and it was inferred that a thin layer with low P-wave velocities along the plate boundary exists beneath the aseismic zone in the region. Understanding the characteristics of plate-boundary S-S reflections in addition to those of P-P reflections would greatly help put better constraints on the physical properties along the plate boundary. Substantial P-to-S conversion at the base of the sedimentary layers was observed. S-wave velocities, especially those of the sedimentary layers, should be precisely determined in order to have good estimates of the arrival times of the plate-boundary S-S reflected waves. The S-wave velocities of the

  15. Chemical and isotopic evidence of gas-influenced flow at a transform plate boundary: Monterey Bay, California

    USGS Publications Warehouse

    Martin, J.B.; Orange, D.L.; Lorenson, T.D.; Kvenvolden, K.A.

    1997-01-01

    Chemical and isotopic compositions of pore fluids document upward flow through communities of vesicomyid clams in Monterey Bay, California. Within the clam communities, the sulfate reduction zone is only 10 cm thick, and Ca and Mg concentrations decrease to values as low as 2.2 mM and 34.5 mM, respectively, at depths less than 30 cm below the sediment-water interface. Less than 5 m outside the communities, the base of the sulfate reduction zone is deeper than the greatest penetration of the cores (-30 cm), and Ca and Mg exhibit only minor changes from seawater values. The sediment exhibits no significant variation in grain size, mineralogy, organic carbon, nitrogen, or carbonate content throughout the region. The composition of pore fluid within clam communities results from upward flow of altered fluid rather than different diagenetic reactions within and outside the communities. Isotopically light dissolved inorganic carbon (DIC), with ??13C values ranging from -3.2 to -54.1???, could reflect carbon sources from either oxidized thermogenic methane and/or a mixture of oxidized microbial methane and solid organic carbon. The C1/(C2+C3) ratios (ranging from 34 to 1142) and the hydrogen and carbon isotopic compositions of methane (??D values of -109 to -156???; ??13C values of -30.6 to -86.6???) suggest that methane is primarily microbial but that a minor component could be thermally generated. Any thermogenic methane would have migrated from great depths, possibly >2 km. The presence of methane is likely to contribute to fluid flow by reducing the density of the fluids. Past fluid migration and venting are reflected by widespread carbonate mineralization at the sediment-water interface. This mineralization and the geographic distribution and proportions of microbial and thermogenic methane suggest that vent sites migrate when permeability is reduced during carbonate cementation. These results demonstrate that along with convergent and divergent plate boundaries

  16. Relaminarization of the boundary layer over a flat plate in shock tube experiments

    NASA Astrophysics Data System (ADS)

    Hinckel, J. N.; Nagamatsu, H. T.

    1986-06-01

    The relaminarization of the boundary layer over a flat plate in the shock tube was investigated by using the partially reflected shock wave technique. The flow Mach number was approximately 0.14, which corresponds to the inleft flow Mach number for the first row of vanes in a gas turbine. The thin film platinum heat gauges were used to measure the heat transfer rate and the Stanton number was calculated from the oscilloscope voltage traces. The Reynolds number was varied by changing the operation pressure of the shock tube and the values varied from 2.3 x 10 to the 4th to 5.3 x 10 to the 5th. For a Reynolds number range of 7 x 10 to the 4th to 3.5 x 10 to the 5th, the relaminarization of the boundary layer was observed. This phenomenon is due to the decay of the turbulence level in the flow as the reflected shock wave moves upstream from the flat plate. As the Reynolds number increased, the relaminarization was delayed and the delay was related to the turbulence generated by the reflected shock wave.

  17. Divergent plate boundaries and crustal spreading on Venus: Evidence from Aphrodite Terra

    NASA Technical Reports Server (NTRS)

    Crumpler, L. S.; Head, James W.

    1989-01-01

    The modes of lithospheric heat transfer and the tectonic styles may differ between Earth and Venus, depending on how the high surface temperature (700 K = 430 C), dense and opaque atmosphere (approx. 10 MPa = 100 bars), lack of water oceans, and the other known ways in which Venus differs from Earth, influence basic lithospheric processes, thermal gradient, upper mantle temperature, thermal and chemical evolution, and convection. A fundamental question is whether the lithosphere of Venus is horizontally stable, like the other terrestrial planets, or is mobile like that on Earth. The variety of characteristics, their integrated relationships, and their predictable behavior throughout Western Aphrodite Terra are similar to those features known to occur in association with the terrestrial seafloor at spreading centers and divergent plate boundaries. It is concluded that Western Aphrodite Terra represents the site of crustal spreading centers and divergent plate boundaries. The extent of similar characteristics and processes elsewhere on Venus outside of the 13,000 km long Western and Eastern Aphrodite Terra rise is unknown at the present, but their presence in other areas of the equatorial highlands, suggested from recent analysis, may be tested with forthcoming Magellan data.

  18. Preliminary Heat Flow Measurements from Plate Boundary Observatory Boreholes along the San Andreas Fault System

    NASA Astrophysics Data System (ADS)

    McDonald, K. J.; Harris, R. N.; Williams, C.; Grubb, F. V.; Fulton, P. M.; Chapman, D. S.

    2009-12-01

    Knowledge of the subsurface thermal regime is critical for understanding lithospheric rheology, fault mechanics and geodynamic processes. We report new heat flow values from boreholes drilled during the installation of borehole strain meters as part of the Plate Boundary Observatory (PBO) help constrain the role of temperature in determining the spatial and temporal pattern of deformation within along strike-slip faults in California. The new boreholes sites along this plate boundary system are clustered in the San Francisco Bay Area (n=5), San Juan Batista (n=5), Parkfield (n=7), and Anza (n=5). The boreholes vary in depth from 97 to 245 m. Temperature profiles were measured in each borehole and more than 899 thermal conductivity measurements were determined from drill cuttings and core samples. Heat production measurements are currently in progress. Temperature gradients have been corrected for the perturbing effects of terrain and combined with thermal conductivity to form thermal resistance plots and calculate heat flow. In general these plots indicate constant heat flow in the lower parts of the holes consistent with conductive heat transfer. Overall heat flow values are consistent with elevated heat flow that characterizes much of the California Coast Ranges. This study will help constrain the role of temperature in determining the spatial and temporal pattern of deformation within and along strike-slip faults in California.

  19. Seismic imaging of a plate boundary in the eastern margin of the Japan Sea

    NASA Astrophysics Data System (ADS)

    No, T.; Sato, T.; Takahashi, N.; Kodaira, S.; Kaneda, Y.

    2011-12-01

    Large earthquakes have frequently occurred in the eastern margin of the Japan Sea (e.g., the 1964 Niigata earthquake (MJMA 7.5), 1983 Nihonkai-Chubu earthquake (MJMA 7.7), 1993 Hokkaido-Nansei-Oki earthquake (MJMA 7.8)), and these earthquakes have caused very strong vibrations, large tsunamis, and serious damage on the coast of the Japan Sea. Nakamura (1983) and Kobayashi (1983) suggested that the eastern margin of the Japan Sea is located along the boundary between the Eurasian Plate and the North America plate. However, since this area has not been identified as one of the priority areas to be investigated, the observation didn't obtain exact evidence of a plate boundary in the eastern margin of Japan Sea. Therefore, we have performed seismic surveys at the eastern margin of the Japan Sea since 2009. Objectives of this study are to reveal structural characteristics around a plate boundary of the Japan Sea with the large earthquakes and understand the tectonics as the geologic background. In 2009-2011, we conducted a multi-channel seismic (MCS) survey and ocean bottom seismometer (OBS) survey around the Yamato basin and the eastern margin of the southern Japan Sea using the R/V KAIREI, JAMSTEC (Japan Agency for Marine-Earth Science and Technology). Survey lines were crooked to avoid the many fishing operations and equipment in the survey area. We shot a tuned airgun array with a spacing of 50 m. This array has a total capacity of 7,800 cubic inches (about 130 liters). The standard air pressure was 2,000 psi (about 14 MPa). During the shooting, we towed a 444-channel hydrophone streamer cable with a 5600-m maximum offset, and the group interval was 12.5 m. The towing depth of the streamer cable was maintained at 12 m below the sea surface using depth controllers. The sampling rate was 2 ms, and the recording length was 15 s. We deployed OBSs, and a refraction survey using an airgun array with a spacing of 200 m. An airgun array in OBS survey used the same

  20. Temperature, lithosphere-asthenosphere boundary, and heat flux beneath the Antarctic Plate inferred from seismic velocities

    NASA Astrophysics Data System (ADS)

    An, Meijian; Wiens, Douglas A.; Zhao, Yue; Feng, Mei; Nyblade, Andrew; Kanao, Masaki; Li, Yuansheng; Maggi, Alessia; Lévêque, Jean-Jacques

    2015-12-01

    We estimate the upper mantle temperature of the Antarctic Plate based on the thermoelastic properties of mantle minerals and S velocities using a new 3-D shear velocity model, AN1-S. Crustal temperatures and surface heat fluxes are then calculated from the upper mantle temperature assuming steady state thermal conduction. The temperature at the top of the asthenosphere beneath the oceanic region and West Antarctica is higher than the dry mantle solidus, indicating the presence of melt. From the temperature values, we generate depth maps of the lithosphere-asthenosphere boundary and the Curie temperature isotherm. The maps show that East Antarctica has a thick lithosphere similar to that of other stable cratons, with the thickest lithosphere (~250 km) between Domes A and C. The thin crust and lithosphere beneath West Antarctica are similar to those of modern subduction-related rift systems in East Asia. A cold region beneath the Antarctic Peninsula is similar in spatial extent to that of a flat-subducted slab beneath the southern Andes, indicating a possible remnant of the Phoenix Plate, which was subducted prior to 10 Ma. The oceanic lithosphere generally thickens with increasing age, and the age-thickness correlation depends on the spreading rate of the ridge that formed the lithosphere. Significant flattening of the age-thickness curves is not observed for the mature oceanic lithosphere of the Antarctic Plate.

  1. Experimental study of boundary layer transition with elevated freestream turbulence on a heated flat plate

    NASA Technical Reports Server (NTRS)

    Sohn, Ki-Hyeon; Reshotko, Eli

    1991-01-01

    A detailed investigation to document momentum and thermal development of boundary layers undergoing natural transition on a heated flat plate was performed. Experimental results of both overall and conditionally sampled characteristics of laminar, transitional, and low Reynolds number turbulent boundary layers are presented. Measurements were acquired in a low-speed, closed-loop wind tunnel with a freestream velocity of 100 ft/s and zero pressure gradient over a range of freestream turbulence intensities (TI) from 0.4 to 6 percent. The distributions of skin friction, heat transfer rate and Reynolds shear stress were all consistent with previously published data. Reynolds analogy factors for R(sub theta) is less than 2300 were found to be well predicted by laminar and turbulent correlations which accounted for an unheated starting length. The measured laminar value of Reynolds analogy factor was as much as 53 percent higher than the Pr(sup -2/3). A small dependence of turbulent results on TI was observed. Conditional sampling performed in the transitional boundary layer indicated the existence of a near-wall drop in intermittency, pronounced at certain low intermittencies, which is consistent with the cross-sectional shape of turbulent spots observed by others. Non-turbulent intervals were observed to possess large magnitudes of near-wall unsteadiness and turbulent intervals had peak values as much as 50 percent higher than were measured at fully turbulent stations. Non-turbulent and turbulent profiles in transitional boundary layers cannot be simply treated as Blasius and fully turbulent profiles, respectively. The boundary layer spectra indicate predicted selective amplification of T-S waves for TI is approximately 0.4 percent. However, for TI is approximately 0.8 and 1.1 percent, T-S waves are localized very near the wall and do not play a dominant role in transition process.

  2. Predicting Earthquake Occurrence at Subduction-Zone Plate Boundaries Through Advanced Computer Simulation

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

    In general, predicting the occurrence of earthquakes is very difficult, because of the complexity of actual faults and nonlinear interaction between them. From the standpoint of earthquake prediction, however, our target is limited to the large events that completely break down a seismogenic zone. To such large events we may apply the concept of the earthquake cycle. The entire process of earthquake generation cycles generally consists of tectonic loading due to relative plate motion, quasi-static rupture nucleation, dynamic rupture propagation and stop, and restoration of fault strength. This process can be completely described by a coupled nonlinear system, which consists of an elastic/viscoelastic slip-response function that relates fault slip to shear stress change and a fault constitutive law that prescribes change in shear strength with fault slip and contact time. The shear stress and the shear strength are related with each other through boundary conditions on the fault. The driving force of this system is observed relative plate motion. The system to describe the earthquake generation cycle is conceptually quite simple. The complexity in practical modeling mainly comes from complexity in structure of the real earth. Recently, we have developed a physics-based, predictive simulation system for earthquake generation at plate boundaries in and around Japan, where the four plates of Pacific, North American, Philippine Sea and Eurasian are interacting with each other. The simulation system consists of a crust-mantle structure model, a quasi-static tectonic loading model, and a dynamic rupture propagation model. First, we constructed a realistic 3D model of plate interfaces in and around Japan by applying an inversion technique to ISC hypocenter data, and computed viscoelastic slip-response functions for this structure model. Second, we introduced the slip- and time-dependent fault constitutive law with an inherent strength-restoration mechanism as a basic

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

    USGS Publications Warehouse

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

    2010-01-01

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

  4. Development of an Auto-Convergent Free-Boundary Axisymmetric Equilibrium Solver

    SciTech Connect

    Huang, J.; Menard, J.

    2006-01-01

    The calculation of the magnetic flux given an assumed value for the current profile in axisymmetric toroidal plasmas is essential in studying the effects of various magnetohydrodynamic (MHD) instabilities upon controlled fusion. To this end, an iterative, modular algorithm coupled with a fast, direct elliptic solver for the Grad-Shafranov equation has been used to reconstruct the desired free-boundary equilibrium solution. This free-boundary Grad-Shafranov (FBGS) equilibrium algorithm is modified with the application of the von Hagenow method for determining the flux on the computational boundary, greatly reducing the time cost from O(N3) to O(N2 ln N) machine operations as compared to current Green’s function methods. The inherent variance in implementing the von Hagenow method gives a mean error bound of 0.1 percent with respect to the normal Green’s method. The improvements will allow the grid resolution to be increased efficiently and automatically to reduce the maximum Grad-Shafranov error to values needed for accurate stability calculations on a more effective time scale.

  5. Large-eddy simulation of separation-reattachment of a flat-plate turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Cheng, Wan; Pullin, Dale; Samtaney, Ravi

    2014-11-01

    We describe large-eddy simulations (LES) of turbulent boundary-layer flow over a flat plate at high Reynolds number in the presence of three-dimensional flow separation. The stretched-vortex subgrid-scale model is used in the bulk of the flow domain combined with a wall-model that is a two-dimensional extension of that described by Chung and Pullin [J. Fluid Mech. 631, 281 (2009)]. Wall-normal averaging of the wall-parallel, stream-wise momentum equations combined with local inner scaling for the resolved-scale velocity gives an ordinary differential equation describing the wall shear-stress vector at each wall point. Together with a specification of a slip velocity at a raised, wall-parallel plane, this provides a boundary condition for the outer LES that allows local backflow. The present LES is motivated by experiments on flows exhibiting separation induced by the response of a turbulent boundary layer to an adverse-favorable pressure-gradient profile. Detailed discussion of detachment and reattachment of the separation bubble will be presented.

  6. The roof plate boundary is a bi-directional organiser of dorsal neural tube and choroid plexus development.

    PubMed

    Broom, Emma R; Gilthorpe, Jonathan D; Butts, Thomas; Campo-Paysaa, Florent; Wingate, Richard J T

    2012-11-01

    The roof plate is a signalling centre positioned at the dorsal midline of the central nervous system and generates dorsalising morphogenic signals along the length of the neuraxis. Within cranial ventricles, the roof plate gives rise to choroid plexus, which regulates the internal environment of the developing and adult brain and spinal cord via the secretion of cerebrospinal fluid. Using the fourth ventricle as our model, we show that the organiser properties of the roof plate are determined by its boundaries with the adjacent neuroepithelium. Through a combination of in ovo transplantation, co-culture and electroporation techniques in chick embryos between embryonic days 3 and 6, we demonstrate that organiser properties are maintained by interactions between the non-neural roof plate and the neural rhombic lip. At the molecular level, this interaction is mediated by Delta-Notch signalling and upregulation of the chick homologue of Hes1: chairy2. Gain- and loss-of-function approaches reveal that cdelta1 is both necessary and sufficient for organiser function. Our results also demonstrate that while chairy2 is specifically required for the maintenance of the organiser, its ectopic expression is not sufficient to recapitulate organiser properties. Expression of atonal1 in the rhombic lip adjacent at the roof plate boundary is acutely dependent on both boundary cell interactions and Delta-Notch signalling. Correspondingly, the roof plate boundary organiser also signals to the roof plate itself to specify the expression of early choroid plexus markers. Thus, the roof plate boundary organiser signals bi-directionally to acutely coordinate the development of adjacent neural and non-neural tissues. PMID:23052907

  7. Abbot Ice Shelf, structure of the Amundsen Sea continental margin and the southern boundary of the Bellingshausen Plate seaward of West Antarctica

    PubMed Central

    Cochran, James R; Tinto, Kirsty J; Bell, Robin E

    2015-01-01

    Inversion of NASA Operation IceBridge airborne gravity over the Abbot Ice Shelf in West Antarctica for subice bathymetry defines an extensional terrain made up of east-west trending rift basins formed during the early stages of Antarctica/Zealandia rifting. Extension is minor, as rifting jumped north of Thurston Island early in the rifting process. The Amundsen Sea Embayment continental shelf west of the rifted terrain is underlain by a deeper, more extensive sedimentary basin also formed during rifting between Antarctica and Zealandia. A well-defined boundary zone separates the mildly extended Abbot extensional terrain from the deeper Amundsen Embayment shelf basin. The shelf basin has an extension factor, β, of 1.5–1.7 with 80–100 km of extension occurring across an area now 250 km wide. Following this extension, rifting centered north of the present shelf edge and proceeded to continental rupture. Since then, the Amundsen Embayment continental shelf appears to have been tectonically quiescent and shaped by subsidence, sedimentation, and the advance and retreat of the West Antarctic Ice Sheet. The Bellingshausen Plate was located seaward of the Amundsen Sea margin prior to incorporation into the Antarctic Plate at about 62 Ma. During the latter part of its independent existence, Bellingshausen plate motion had a clockwise rotational component relative to Antarctica producing convergence across the north-south trending Bellingshausen Gravity Anomaly structure at 94°W and compressive deformation on the continental slope between 94°W and 102°W. Farther west, the relative motion was extensional along an east-west trending zone occupied by the Marie Byrd Seamounts. Key Points: Abbot Ice Shelf is underlain by E-W rift basins created at ∼90 Ma Amundsen shelf shaped by subsidence, sedimentation, and passage of the ice sheet Bellingshausen plate boundary is located near the base of continental slope and rise PMID:26709352

  8. EarthScope Plate Boundary Observatory Data in the College Classroom (Invited)

    NASA Astrophysics Data System (ADS)

    Eriksson, S. C.; Olds, S. E.

    2009-12-01

    The Plate Boundary Observatory (PBO) is the geodetic component of the EarthScope project, designed to study the 3-D strain field across the active boundary zone between the Pacific and North American tectonics plates in the western United States. All PBO data are freely available to scientific and educational communities and have been incorporated into a variety of activities for college and university classrooms. UNAVCO Education and Outreach program staff have worked closely with faculty users, scientific researchers, and facility staff to create materials that are scientifically and technically accurate as well as useful to the classroom user. Availability of processed GPS data is not new to the geoscience community. However, PBO data staff have worked with education staff to deliver data that are readily accessible to educators. The UNAVCO Data for Educators webpage, incorporating an embedded Google Map with PBO GPS locations and providing current GPS time series plots and downloadable data, extends and updates the datasets available to our community. Google Earth allows the visualization GPS data with other types of datasets, e.g. LiDAR, while maintaining the self-contained and easy-to-use interface of UNAVCO’s Jules Verne Voyager map tools, which have multiple sets of geological and geophysical data. Curricular materials provide scaffolds for using EarthScope data in a variety of forms for different learning goals. Simple visualization of earthquake epicenters and locations of volcanoes can be used with velocity vectors to make simple deductions of plate boundary behaviors. Readily available time series plots provide opportunities for additional science skills, and there are web and paper-based support materials for downloading data, manipulating tables, and using plotting programs for processed GPS data. Scientists have provided contextual materials to explore the importance of these data in interpreting the structure and dynamics of the Earth. These data

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

    NASA Technical Reports Server (NTRS)

    Baltuck, M.; Dixon, T. H.

    1984-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  11. Summary of the stratigraphy and structural elements related to plate convergence of the Quetta-Muslim Bagh-Sibi region, Balochistan, west-central Pakistan

    USGS Publications Warehouse

    Maldonado, Florian; Mengal, Jan M.; Khan, Shahid H.; Warwick, Peter D.

    2011-01-01

    The four major faults that bound the structural terrane are the Frontal (F), Ghazaband-Zhob (GZ), Gwal-Bagh (GB), and Chaman (C) faults. Four major periods of deformation are recognized: (1) emplacement of ophiolitic rocks onto the continental margin of the India plate; (2) convergence of the India-Eurasia plates; (3) deposition of Tertiary-Quaternary molasse units followed by major folding and thrusting, and formation of strike-slip faults; and (4) deposition of Pleistocene molasse units with subsequent folding, thrusting, and strike-slip motion that continues to the present.

  12. Seismicity and Seismic Hazard along the Western part of the Eurasia-Nubia plate boundary

    NASA Astrophysics Data System (ADS)

    Bezzeghoud, Mourad; Fontiela, João; Ferrão, Celia; Borges, José Fernando; Caldeira, Bento; Dib, Assia; Ousadou, Farida

    2016-04-01

    The seismic phenomenon is the most damaging natural hazard known in the Mediterranean area. The western part of the Eurasia-Nubia plate boundary extends from the Azores to the Mediterranean region. The oceanic part of the plate boundary is well delimited from the Azores Islands, along the Azores-Gibraltar fault to approximately 12°W (west of the Strait of Gibraltar). From 12°W to 3.5°E, including the Iberia-Nubia region and extending to the western part of Algeria, the boundary is more diffuse and forms a wider area of deformation. The boundary between the Iberia and Nubia plates is the most complex part of the margin. This region corresponds to the transition from an oceanic boundary to a continental boundary, where Iberia and Nubia collide. Although most earthquakes along this plate boundary are shallow and generally have magnitudes less than 5.5, there have been several high-magnitude events. Many devastating earthquakes, some of them tsunami-triggering, inflicted heavy loss and considerable economic damage to the region. From 1920 to present, three earthquakes with magnitudes of about 8.0 (Mw 8.2, 25 November 1941; Ms 8.0, 25 February 1969; and Mw 7.9, 26 May 1975) occurred in the oceanic region, and four earthquakes with magnitudes of about 7.0 (Mw 7.1, 8 May 1939, Santa Maria Island and Mw 7.1, January 1980, Terceira and Graciosa Islands, both in the Azores; Ms 7.1, 20 May 1931, Azores-Gibraltar fracture zone; and Mw 7.3, 10 October 1980, El Asnam, Algeria) occurred along the western part of the Eurasia-Nubia plate boundary. In general, large earthquakes (M ≥7) occur within the oceanic region, with the exception of the El Asnam (Algeria) earthquakes. Some of these events caused extensive damage. The 1755 Lisbon earthquake (˜Mw 9) on the Portugal Atlantic margin, about 200 km W-SW of Cape St. Vincent, was followed by a tsunami and fires that caused the near-total destruction of Lisbon and adjacent areas. Estimates of the death toll in Lisbon alone (~70

  13. Plate tectonics and offshore boundary delimitation: Tunisia-Libya case at the International Court of Justice

    NASA Astrophysics Data System (ADS)

    Stanley, Daniel Jean

    1982-03-01

    The first major offshore boundary dispute where plate tectonics constituted a significant argument was recently brought before the International Court of Justice by Libya and Tunisia concerning the delimitation of their continental shelves. Libya placed emphasis on this concept to determine natural prolongation of its land territory under the sea. Tunisia contested use of the entire African continental landmass as a reference unit and views geography, geomorphology and bathymetry as relevant as geology. The Court pronounced that “It is the outcome, not the evolution in the long-distant past, which is of importance.” Moreover, it is the present-day configuration of coasts and seabed that are the main factors, not geology.

  14. Tonalite sill emplacement at an oblique plate boundary: northeastern margin of the Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Parry, Matthew; Sˇtípská, Pavla; Schulmann, Karel; Hrouda, Frantisˇek; Jezˇek, Josef; Kröner, Alfred

    1997-10-01

    A tonalitic sill has been examined at the Variscan transpressive boundary of the Lugian and Silesian plates at the NE margin of the Bohemian Massif. A structural, petrological and geochronological study reveals that it was emplaced syn-tectonically with major ductile shearing in lower crustal rocks. Magmatic and pre-rheological critical melt percentage (RCMP) fabrics are concordant with the hanging wall structures but discordant with those of the footwall. The AMS study shows the predominance of flattening strain at the margins and plane strain fabrics in the core. Numerical modelling of AMS fabrics is in good agreement with the hypothesis of magma flow and deformation in oblique transpression. A tectonic model was developed explaining emplacement and syn-tectonic deformation of progressively cooled tonalitic intrusion.

  15. Multibeam investigation of the active North Atlantic plate boundary reorganization tip

    NASA Astrophysics Data System (ADS)

    Hey, Richard; Martinez, Fernando; Höskuldsson, Ármann; Eason, Deborah E.; Sleeper, Jonathan; Thordarson, Sigvaldi; Benediktsdóttir, Ásdís; Merkuryev, Sergey

    2016-02-01

    The previous orthogonal ridge/transform staircase geometry south of Iceland is being progressively changed to the present continuous oblique Reykjanes Ridge spreading geometry as North America-Eurasia transform faults are successively eliminated from north to south. This reorganization is commonly interpreted as a thermal phenomenon, caused by warmer Iceland plume mantle progressively interacting with the ridge, although other diachronous seafloor spreading reorganizations are thought to result from tectonic rift propagation. New marine geophysical data covering our reinterpretation of the reorganization tip near 57°N show successive transform eliminations at a propagation velocity of ∼110 km/Myr, ten times the spreading half rate, followed by abrupt reorganization slowing at the Modred transform as it was converted to a migrating non-transform offset. Neither the simple thermal model nor the simple propagating rift model appears adequate to explain the complicated plate boundary reorganization process.

  16. XFEM simulation of a quenched cracked glass plate with moving convective boundaries

    NASA Astrophysics Data System (ADS)

    Ghaffari, Diyako; Rash Ahmadi, Samrand; Shabani, Farzin

    2016-02-01

    A moving quenched soda-lime glass plate with an initial edge crack is modeled, applying the eXtended finite-element method (XFEM) in order to investigate the stress field components and Von Mises stress around the crack. The convective heat with moving boundaries is considered in thermal formulation. The Crank-Nicolson time integration scheme is reformed and adjusted with a view to accurately solving the system of transient heat conduction matrix equations. In order to simulate the whole stages of the problem formulation, MATLAB XFEM (MXFEM) codes are written and employed. The stress distribution contours are plotted in detail and the stress fields around the crack tip are compared quantitatively. The variations of stress intensity factors (SIFs) during crack propagation are obtained through the calculation of the domain form of the interaction integral. In order to verify the procedure and display the ability of the developed formulation, the results are compared with experimental outputs from the literature.

  17. Controlling Bragg gaps induced by electric boundary conditions in phononic piezoelectric plates

    NASA Astrophysics Data System (ADS)

    Kherraz, N.; Haumesser, L.; Levassort, F.; Benard, P.; Morvan, B.

    2016-02-01

    A Phononic Crystal (PC), constituted of a homogeneous piezoelectric plate covered by a 1D periodic arrangement of thin metallic electrodes on both surfaces, is studied. The application of Electric Boundary Conditions (EBCs) on the electrodes enables the propagation control of the ultrasonic guided waves in the PC. The band structure is investigated for different EBCs: the electrodes are either at a floating potential or they are alternately short-circuited and at a floating potential. In the latter case, a Bragg gap appears for the fundamental S0 guided Lamb mode. These results are verified experimentally and compared to finite element calculations. A physical interpretation is also given, relying on the symmetry of the electric potential fields associated with these guided modes.

  18. Recording Plate Boundary Deformation Processes Around The San Jacinto Fault, California

    NASA Astrophysics Data System (ADS)

    Hodgkinson, K.; Mencin, D.; Borsa, A.; Fox, O.; Walls, C.; Van Boskirk, E.

    2012-04-01

    The San Jacinto Fault is one of the major faults which form the San Andreas Fault System in southern California. The fault, which lies to the west of the San Andreas, is one of the most active in the region. While strain rates are higher along the San Andreas, 23-37 mm/yr compared to 12-22 mm/yr along the San Jacinto, there have been 11 earthquakes of M6 and greater along the San Jacinto in the past 150 years while there have been none of this magnitude on the San Andreas in this region. UNAVCO has installed an array of geodetic and seismic instruments along the San Jacinto as part of the Plate Boundary Observatory (PBO). The network includes 25 GPS stations within 20 km of the surface trace with a concentration of borehole instrumentation in the Anza region where there are nine boreholes sites. Most of the borehole sites contain a GTSM21 4-component strainmeter, a Sonde-2 seismometer, a MEMS accelerometer and a pore pressure sensor. Thus, the array has the capability to capture plate boundary deformation processes with periods of milliseconds (seismic) to decades (GPS). On July 7th 2010 a M5.4 earthquake occurred on the Coyote Creek segment of the fault. The event was preceded by a M4.9 earthquake in the same area four weeks earlier and four earthquakes of M5 and greater within a 20 km radius of the epicenter in the past 50 years. In this study we will present the signals recorded by the different instrument types for the July 7th 2010 event and will compare the coseismic displacements recorded by the GPS and strainmeters with the displacement field predicted by Okada [1992]. All data recorded as part of the PBO observatory are publically available from the UNAVCO, the IRIS Data Management Center and the Northern California Earthquake Data Center.

  19. Tectonic activity evolution of the Scotia-Antarctic Plate boundary from mass transport deposit analysis

    NASA Astrophysics Data System (ADS)

    Pérez, Lara F.; Bohoyo, Fernando; Hernández-Molina, F. Javier; Casas, David; Galindo-Zaldívar, Jesús; Ruano, Patricia; Maldonado, Andrés.

    2016-04-01

    The spatial distribution and temporal occurrence of mass transport deposits (MTDs) in the sedimentary infill of basins and submerged banks near the Scotia-Antarctic plate boundary allowed us to decode the evolution of the tectonic activity of the relevant structures in the region from the Oligocene to present day. The 1020 MTDs identified in the available data set of multichannel seismic reflection profiles in the region are subdivided according to the geographic and chronological distributions of these features. Their spatial distribution reveals a preferential location along the eastern margins of the eastern basins. This reflects local deformation due to the evolution of the Scotia-Antarctic transcurrent plate boundary and the impact of oceanic spreading along the East Scotia Ridge (ESR). The vertical distribution of the MTDs in the sedimentary record evidences intensified regional tectonic deformation from the middle Miocene to Quaternary. Intensified deformation started at about 15 Ma, when the ESR progressively replaces the West Scotia Ridge (WSR) as the main oceanic spreading center in the Scotia Sea. Coevally with the WSR demise at about 6.5 Ma, increased spreading rates of the ESR and numerous MTDs were formed. The high frequency of MTDs during the Pliocene, mainly along the western basins, is also related to greater tectonic activity due to uplift of the Shackleton Fracture Zone by tectonic inversion and extinction of the Antarctic-Phoenix Ridge and involved changes at late Pliocene. The presence of MTDs in the southern Scotia Sea basins is a relevant indicator of the interplay between sedimentary instability and regional tectonics.

  20. Logistical Support for the Installation of the Plate Boundary Observatory GPS and Borehole Strainmeter Networks

    NASA Astrophysics Data System (ADS)

    Kurnik, C.; Austin, K.; Coyle, B.; Dittmann, T.; Feaux, K.; Friesen, B.; Johnson, W.; Mencin, D.; Pauk, B.; Walls, C.

    2007-12-01

    The Plate Boundary Observatory (PBO), part of the NSF-funded EarthScope project, is designed to study the three- dimensional strain field resulting from deformation across the active boundary zone between the Pacific and North American plates in the western United States. To meet these goals, UNAVCO will install 880 continuous GPS stations, 103 borehole strainmeter stations, 28 tiltmeters, and five laser strainmeters by October 2008. Such a broad network presents significant logisitical challenges, including moving supplies, equipment, and personnel around 6 million square kilometers, and this requires accurate tracking and careful planning. The PBO logistics chain includes the PBO headquarters at UNAVCO in Boulder, Colorado and five regional offices in the continental United States and Alaska, served by dozens of suppliers spread across the globe. These offices are responsible for building and maintaining sites in their region. Most equipment and supplies first arrive in Boulder, where they are tagged and entered into a UNAVCO-wide equipment database, assembled and quality checked as necessary, and sent on to the appropriate regional office. Larger items which are costly to store and ship from Boulder, such as batteries or long sections of stainless steel pipe and bar required for monuments, are shipped directly from the supplier to each region as needed. These supplies and equipment are also tracked through the ordering, delivery, installation, and maintenance cycle via Earned Value Management techniques which allow us to meet NSF and other Federal procurement rules. Early prototypes and assembly configurations aid the development of material and supply budgets. A thorough understanding of Federal procurement rules at project start up is critical as the project moves forward.

  1. Irregular earthquake recurrence patterns and slip variability on a plate-boundary Fault

    NASA Astrophysics Data System (ADS)

    Wechsler, N.; Rockwell, T. K.; Klinger, Y.

    2015-12-01

    The Dead Sea fault in the Levant represents a simple, segmented plate boundary from the Gulf of Aqaba northward to the Sea of Galilee, where it changes its character into a complex plate boundary with multiple sub-parallel faults in northern Israel, Lebanon and Syria. The studied Jordan Gorge (JG) segment is the northernmost part of the simple section, before the fault becomes more complex. Seven fault-crossing buried paleo-channels, offset by the Dead Sea fault, were investigated using paleoseismic and geophysical methods. The mapped offsets capture the long-term rupture history and slip-rate behavior on the JG fault segment for the past 4000 years. The ~20 km long JG segment appears to be more active (in term of number of earthquakes) than its neighboring segments to the south and north. The rate of movement on this segment varies considerably over the studied period: the long-term slip-rate for the entire 4000 years is similar to previously observed rates (~4 mm/yr), yet over shorter time periods the rate varies from 3-8 mm/yr. Paleoseismic data on both timing and displacement indicate a high COV >1 (clustered) with displacement per event varying by nearly an order of magnitude. The rate of earthquake production does not produce a time predictable pattern over a period of 2 kyr. We postulate that the seismic behavior of the JG fault is influenced by stress interactions with its neighboring faults to the north and south. Coulomb stress modelling demonstrates that an earthquake on any neighboring fault will increase the Coulomb stress on the JG fault and thus promote rupture. We conclude that deriving on-fault slip-rates and earthquake recurrence patterns from a single site and/or over a short time period can produce misleading results. The definition of an adequately long time period to resolve slip-rate is a question that needs to be addressed and requires further work.

  2. Numerical model for the generation of the ensemble of lithospheric plates and their penetration through the 660-km boundary

    NASA Astrophysics Data System (ADS)

    Trubitsyn, V. P.; Trubitsyn, A. P.

    2014-11-01

    In the kinematic theory of lithospheric plate tectonics, the position and parameters of the plates are predetermined in the initial and boundary conditions. However, in the self-consistent dynamical theory, the properties of the oceanic plates (just as the structure of the mantle convection) should automatically result from the solution of differential equations for energy, mass, and momentum transfer in viscous fluid. Here, the viscosity of the mantle material as a function of temperature, pressure, shear stress, and chemical composition should be taken from the data of laboratory experiments. The aim of this study is to reproduce the generation of the ensemble of the lithospheric plates and to trace their behavior inside the mantle by numerically solving the convection equations with minimum a priori data. The models demonstrate how the rigid lithosphere can break up into the separate plates that dive into the mantle, how the sizes and the number of the plates change during the evolution of the convection, and how the ridges and subduction zones may migrate in this case. The models also demonstrate how the plates may bend and break up when passing the depth boundary of 660 km and how the plates and plumes may affect the structure of the convection. In contrast to the models of convection without lithospheric plates or regional models, the structure of the mantle flows is for the first time calculated in the entire mantle with quite a few plates. This model shows that the mantle material is transported to the mid-oceanic ridges by asthenospheric flows induced by the subducting plates rather than by the main vertical ascending flows rising from the lower mantle.

  3. Late Cretaceous to Present evolution of the NW Africa peri-cratonic in the Africa-Eurasia plate convergence context

    NASA Astrophysics Data System (ADS)

    Ghorbal, B.; Bertotti, G.; Andriessen, P. A. M.

    2009-04-01

    Africa-Eurasia plate convergence is the main mechanism to explain topographic evolution and patterns of Tertiary vertical motions recorded around the entire Mediterranean and even further east. However, most of the studies are concentrated on the Eurasian side of the Mediterranean Realm. Along the NW Africa pericratonic zone (western Mediterranean side) extending longitudinally from the Anti-Atlas to the Rif Mountains, the highest topography is observed in the High Atlas intracontinental belt and in the Pan-African Anti-Atlas belt, and not in the youngest belt, the Rif. The combination of AFT and (U-Th)/He low-thermal dating, performed on pre-Cenozoic basement rocks along the Moroccan pericratonic transect (500km) yield ages ranging respectively between 90-9Ma and 65-7Ma, documenting vertical motions of subsidence and exhumation in between Late Cretaceous and Present. Time-Temperature models show that vertical movements are spatially zoned through Morocco, with the highest amplitude of vertical movements in the High Atlas (>4-5km) and more modest amounts in the Anti-Atlas and the Western Meseta (<2.5km) from Late Cretaceous onward. Precious information provided by the AFT and AHe ages indicates that the entire NW African peri-cratonic zone including the Western Meseta and the Anti-Atlas in addition to the Atlas and the Rif systems experienced Tertiary deformation. Two stages of folding are distinguished on the basis of low-thermal dating results along the pericratonic transect. The first is a lithospherical folding of ~500km in the Late Cretaceous (confirming that this process is a primary response to recently induced compressional stress fields) and the second is a crustal folding of ~100-150km wavelength in the Late Eocene that occurred independently to the mantle, requiring therefore the existence of a decoupling in between the base of the crust and the high mantle.

  4. The giant coastal landslides of Northern Chile: Tectonic and climate interactions on a classic convergent plate margin

    NASA Astrophysics Data System (ADS)

    Mather, Anne E.; Hartley, Adrian J.; Griffiths, James S.

    2014-02-01

    Documented for the first time are an extensive suite of late Neogene giant terrestrial coastal landslides along the classic convergent margin of western South America (18° to 24° south). These are remarkable in terms of their unusual abundance and atypical setting, such failures previously being linked with oceanic volcanic edifices or over-steepened glaciated coastlines. Located within the hyper-arid Coastal Cordillera of the Atacama Desert of Northern Chile we report the presence of more than 60 individual large-scale landslides with individual volumes up to 9 km3 developed over a horizontal coastline distance of some 650 km. These landslides were emplaced as a combination of rock avalanches and multiple rotational failures. The majority terminated directly into the Pacific - likely generating significant tsunami hazard to the Chilean and south Peruvian coastline in a region which is today considered to be part of a notorious seismic gap. The proliferation and scale of these Late Neogene giant landslides in this actively uplifting, hyperarid terrain suggests they are the main geomorphic agent for relief reduction, probably triggered by megathrust earthquakes and potentially providing a unique palaeoseismic archive. The temporal and spatial distribution of these giant landslides corresponds with a period of surface steepening of the forearc wedge in the Central Andes and south to north differential uplift associated with factors such as aseismic ridge subduction. The resulting surface gradient increases, combined with the persistent climatic aridity of the region, have served to limit effective relief-reducing geomorphic processes in this oversteepened terrain to large-scale landsliding. The phenomena documented here geospatially link previously recognised large-scale slope failures from the off-shore environment and higher altitude areas of the Andean forearc, suggesting that large-scale landsliding is capable of transferring sediment on a regional scale to the

  5. Tsunami effects at Korean Nuclear Power Plant Sites by Plate Boundary Earthquakes

    NASA Astrophysics Data System (ADS)

    Jin, Sobeom; Hyun, Seung Gyu; Bae, Jae Seok; Kim, Gun Hyeong; Yoon, Sung Bum

    2015-04-01

    Great earthquakes have occurred at the Nankai Trough due to the subduction of the Philippine Sea plate beneath Honshu, Japan. The 1707 Hoei tsunami associated with the Mw 8.7 earthquake, in particular, was the largest event generated in this area. The Nankai Trough is one of the most earthquake-prone area near Japan. And the tsunami affected to Korea according to a Korean historic literature. In this study, new hypothetical plate boundary earthquakes (Mw 9.6) ruptured simultaneously from the Nankai Trough to the Ryukyu Trench (NTRT) are proposed and applied to evaluate the tsunami effects at the Nuclear Power Plant Sites in Korea. In order to make reasonable tsunami sources the asperity model is adapted. The numerical model using the modified leap-frog finite difference scheme is employed to simulate the propagation of tsunami generated at NTRT. This numerical model considering the dispersion effect and inundation of tsunami is then employed to estimate the maximum tsunami heights. Predicted results will be used to make the measures against unexpected tsunami attacks.

  6. Extinct mid-ocean ridges and insights on the influence of hotspots at divergent plate boundaries

    NASA Astrophysics Data System (ADS)

    MacLeod, Sarah; Dietmar Müller, R.; Williams, Simon; Matthews, Kara

    2016-04-01

    We review all global examples of confirmed or suspected extinct mid-ocean ridges that are preserved in present-day ocean basins. Data on their spreading rate prior to extinction, time of cessation, length of activity, bathymetric and gravity signature are analysed. This analysis identifies some differences between subgroups of extinct ridges, including microplate spreading ridges, back-arc basin ridges and large-scale mid-ocean ridges. Crustal structure of extinct ridges is evaluated using gravity inversion to seek to resolve a long-standing debate on whether the final stages of spreading leads to development of thinned or thickened crust. Most of the ridges we assess have thinner crust at their axes than their flanks, yet a small number are found to have a single segment that is overprinted by an anomalous feature such as a seamount or volcanic ridge. A more complex cessation mechanism is necessary in these cases. The location of spreading centres at their time of cessation relative to hotspots was also evaluated using a global plate reconstruction. This review provides strong evidence for the long-term interaction of spreading centres with hotspots and plate boundaries have been frequently modified within the radius of a hotspot zone of influence.

  7. Prediction and measurement of heat transfer rates for the shock-induced unsteady laminar boundary layer on a flat plate

    NASA Technical Reports Server (NTRS)

    Cook, W. J.

    1972-01-01

    The unsteady laminar boundary layer induced by the flow-initiating shock wave passing over a flat plate mounted in a shock tube was theoretically and experimentally studied in terms of heat transfer rates to the plate for shock speeds ranging from 1.695 to 7.34 km/sec. The theory presented by Cook and Chapman for the shock-induced unsteady boundary layer on a plate is reviewed with emphasis on unsteady heat transfer. A method of measuring time-dependent heat-transfer rates using thin-film heat-flux gages and an associated data reduction technique are outlined in detail. Particular consideration is given to heat-flux measurement in short-duration ionized shocktube flows. Experimental unsteady plate heat transfer rates obtained in both air and nitrogen using thin-film heat-flux gages generally agree well with theoretical predictions. The experimental results indicate that the theory continues to predict the unsteady boundary layer behavior after the shock wave leaves the trailing edge of the plate even though the theory is strictly applicable only for the time interval in which the shock remains on the plate.

  8. The Formation of the Betic-Alboran System in the Iberia-Africa Plate Boundary: a New Kinematic Evolution Model

    NASA Astrophysics Data System (ADS)

    Fernandez, M.; Verges, J.

    2013-12-01

    Several geodynamic models have been proposed so far to explain the origin and evolution of the Betic-Rif arcuate orogeny and the inner Alboran back-arc basin. Many of these models propose that the Alboran domain underwent a large westward drifting (> 600 km) driven by a subduction rollback, eventually resulting in a symmetric configuration in both the S-Iberia and N-African margins. Alternative models with a more autochthonous component assume that the Oligocene subduction trench extended continuously along the whole Iberian Mediterranean margin from the present Gibraltar arc to the Alps. Common assumptions to all these models are: i) the initial time is about 35 Ma (Eocene-Oligocene), ii) the plate boundary is continuous and non-segmented, iii) the initial subduction polarity is NW-dipping, and iv) the slab must underwent a twisted roll-back to explain the present position of the HP-LT metamorphic rocks involving slab rupture, detachment and tearing. Recent geophysical models based on seismic data, tomography and potential fields draw an arcuate mantle slab restricted below the Betic-Rif orogen, dipping towards the E below the Gibraltar Strait and turning to the SE and S beneath the Betics. In addition, the crust beneath the northern Moroccan margin shows a smooth thinning toward the Alboran basin whereas the southern Iberian margin presents a much sharper thinning. These findings put severe limitations to some of the proposed models and open room for new kinematic proposals. One of the most recent models is based on the following considerations: i) the reconstruction starts in Late Cretaceous times at the onset of northern Africa convergence, ii) displacements and initial configuration are based on plate reconstructions of the Atlantic-Ligurian-Tethys region, and iii) the model assumes that subduction polarity changes laterally from NW-dipping in the Algerian segment to SE-dipping in the Betic-Rif segment. Apart from its simplicity, this model requires a moderate

  9. Active faulting in northern Chile: ramp stacking and lateral decoupling along a subduction plate boundary?

    NASA Astrophysics Data System (ADS)

    Armijo, Rolando; Thiele, Ricardo

    1990-04-01

    Two large features parallel to the coastline of northern Chile have long been suspected to be the sites of young or active deformation: (1) The 700-km long Coastal Scarp, with average height (above sea level) of about 1000 m; (2) The Atacama Fault zone, that stretches linearly for about 1100 km at an average distance of 30-50 km from the coastline. New field observations combined with extensive analysis of aerial photographs demonstrate that both the Coastal Scarp and the Atacama Fault are zones of Quaternary and current fault activity. Little-degraded surface breaks observed in the field indicate that these fault zones have recently generated large earthquakes ( M = 7-8). Normal fault offsets observed in marine terraces in the Coastal Scarp (at Mejillones Peninsula) require tectonic extension roughly orthogonal to the compressional plate boundary. Strike-slip offsets of drainage observed along the Salar del Carmen and Cerro Moreno faults (Atacama Fault system) imply left-lateral displacements nearly parallel to the plate boundary. The left-lateral movement observed along the Atacama Fault zone may be a local consequence of E-W extension along the Coastal Scarp. But if also found everywhere along strike, left-lateral decoupling along the Atacama Fault zone would be in contradiction with the right lateral component of Nazca-South America motion predicted by models of present plate kinematics. Clockwise rotation with left-lateral slicing of the Andean orogen south of the Arica bend is one way to resolve this contradiction. The Coastal Scarp and the Atacama Fault zone are the most prominent features with clear traces of activity within the leading edge of continental South America. The great length and parallelism of these features with the subduction zone suggest that they may interact with the subduction interface at depth. We interpret the Coastal Scarp to be a west-dipping normal fault or flexure and propose that it is located over an east-dipping ramp stack at

  10. Strain modeling of attachment zones developed between brittle and ductile crust at wrenching plate boundaries

    NASA Astrophysics Data System (ADS)

    Teyssier, C.; Tikoff, B.; Weber, J.

    2001-12-01

    Using strain modeling we analyze the ductile deformation beneath rigid upper crustal blocks that rotate and translate in wrench zones. We define the zone of deformation as an "attachment zone" and assume strain continuity between the wrench shearing in the ductile crust and the horizontal shearing induced by the rotation/translation of rigid blocks. For reasonable amounts of rotation/translation of rigid blocks and reasonable thicknesses of attachment zones, the orientation and shape of the finite strain ellipsoids within attachment zones are calculated, and the orientation of planar and linear fabrics are predicted. Attachment zones beneath rotating blocks should display radiating foliation and concentric lineations; if rotation of rigid blocks is driven from below, deformation in the attachment zone is dominated by the wrench component, altering significantly the radiating and concentric patterns of foliation and lineation. Attachment zones beneath translating blocks display a wide range of foliation orientations, with steep foliations below the central part of rigid blocks, and gently dipping foliations toward the margins. Below the upper crustal strike-slip faults, foliation is shallowly dipping, strain intensity is maximum, and there is an abrupt reversal of sense of shear across a presumed discontinuity. The linear belt of greenschist-grade metamorphic rocks in Trinidad's Northern Ranges and eastern Venezuela's Paria Peninsula is a candidate for an exhumed attachment zone developed beneath translating upper crustal blocks during Neogene highly oblique convergence between the Caribbean and South America plates.

  11. 3D Simulation of the Entire Process of Earthquake Generation at Subduction-Zone Plate Boundaries

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

    In general, the entire process of earthquake generation consists of tectonic loading due to relative plate motion, quasi-static rupture nucleation, dynamic rupture propagation and stop, and restoration of fault strength. This process can be completely described by a coupled nonlinear system, which consists of an elastic/viscoelastic slip-response function that relates fault slip to shear stress change and a fault constitutive law that prescribes change in shear strength with fault slip and contact time. The shear stress and the shear strength are related with each other through boundary conditions on the fault. The driving force of this system is observed relative plate motion. The system to describe the earthquake generation cycle is conceptually quite simple. The complexity in practical modelling mainly comes from complexity in structure of the real earth. As a product of Crustal Activity Modelling Program (CAMP), which is one of the three main programs composing the Solid Earth Simulator project (1998-2003) promoted by MEXT, we have completed a physics-based predictive simulation model for the entire process of earthquake generation cycles in and around Japan, where the four plates of Pacific, North American, Philippine Sea and Eurasian are interacting with each other in a very complicated way. The total simulation system consists of a crust-mantle structure model, a tectonic loading model and a dynamic rupture model. First, we constructed a realistic 3D standard model of plate interfaces in and around Japan by applying an inversion technique to ISC hypocenter distribution data, and computed viscoelastic slip-response functions for this structure model. Second, we introduced the slip- and time-dependent fault constitutive law with an inherent strength-restoration mechanism as a basic equation governing the entire process of earthquake generation. Third, combining all these elements, we developed a simulation model for quasi-static stress accumulation due to

  12. Lost in Iceland? Fracture Zone Complications Along the Mid-Atlantic Plate Boundary

    NASA Astrophysics Data System (ADS)

    Brandsdóttir, B.; Einarsson, P.; Detrick, R. S.; Mayer, L.; Calder, B.; Driscoll, N.; Richter, B.

    2003-12-01

    The mid-Atlantic plate boundary breaks up into a series of segments across Iceland. Two transform zones, the South Iceland Seismic Zone (SISZ) and the Tjörnes Fracture Zone (TFZ) separate the on land rift zones from the Reykjanes Ridge (RR), and the Kolbeinsey Ridge (KR), offshore N-Iceland. Both are markedly different from fracture zones elsewhere along the plate boundary. The 80 km E-W and 10--15 km N-S SISZ is made up of more than 20 N-S aligned, right-lateral, strike-slip faults whereas the TFZ consists of a broad zone of deformation, roughly 150 km E-W and 75 km N-S. The over-all left-lateral transform motion within the SISZ is accommodated by bookshelf faulting whereas the right-lateral transform motion within the TFZ is incorporated within two WNW-trending seismic zones, spaced ˜40 km apart, the Grímsey Seismic Zone (GSZ) and the Húsavík-Flatey fault (HFF). Recently collected EM300 and RESON8101 multibeam bathymetric data along with CHIRP subbottom data has unveiled some tectonic details within the TFZ. The GSZ runs along the offshore extension of the Northern Volcanic Rift Zone (NVRZ) and is made up of four left-stepping, en-echelon, NS-striking rift segments akin to those on land. Large GSZ earthquakes seem to be associated with lateral strike-slip faulting along ESE-striking fault planes. Fissure swarms transecting the offshore volcanic systems have also been subjected to right-lateral transformation along the spreading direction. As the Reykjanes Peninsula, the on land extension of the RR, the GSZ bears the characteristics of an oblique rift zone. The plate boundary segments connecting to the RR and KR are thus symmetrical with respect to the plate separation vector (105° ) and orientation of individual volcanic systems. The HFF has an overall strike of N65° W and can be traced continuously along its 75--80 km length, between the Theistareykir volcanic system within the NVRZ, across the central TFZ-graben, the Skjálfandi bay, and into the largest

  13. Crustal and upper mantle investigations of the Caribbean-South American plate boundary

    NASA Astrophysics Data System (ADS)

    Bezada, Maximiliano J.

    The evolution of the Caribbean --- South America plate boundary has been a matter of vigorous debate for decades and many questions remain unresolved. In this work, and in the framework of the BOLIVAR project, we shed light on some aspects of the present state and the tectonic history of the margin by using different types of geophysical data sets and techniques. An analysis of controlled-source traveltime data collected along a boundary-normal profile at ˜65°W was used to build a 2D P-wave velocity model. The model shows that the Caribbean Large Igenous Province is present offshore eastern Venezuela and confirms the uniformity of the velocity structure along the Leeward Antilles volcanic belt. In contrast with neighboring profiles, at this longitude we see no change in velocity structure or crustal thickness across the San Sebastian - El Pilar fault system. A 2D gravity modeling methodology that uses seismically derived initial density models was developed as part of this research. The application of this new method to four of the BOLIVAR boundary-normal profiles suggests that the uppermost mantle is denser under the South American continental crust and the island arc terranes than under the Caribbean oceanic crust. Crustal rocks of the island arc and extended island arc terranes of the Leeward Antilles have a relatively low density, given their P-wave velocity. This may be caused by low iron content, relative to average magmatic arc rocks. Finally, an analysis of teleseismic traveltimes with frequency-dependent kernels produced a 3D P-wave velocity perturbation model. The model shows the structure of the mantle lithosphere under the study area and clearly images the subduction of the Atlantic slab and associated partial removal of the lower lithosphere under northern South America. We also image the subduction of a section of the Caribbean plate under South America with an east-southeast direction. Both the Atlantic and Caribbean subducting slabs penetrate the

  14. Production of three-dimensional, spatially stimulated disturbance waves by periodic blowing and suction in a plate boundary layer flow

    NASA Astrophysics Data System (ADS)

    Konzelmann, U.; Rist, U.; Fasel, H.

    An attempt has been made to study disturbance waves by numerically simulating temporally periodic blowing and suction through a hole in a plate. Modified mixed spectral and difference methods were used, and the resulting vortex strength components are shown. With a few modifications, the procedure can be used for realistic simulation of active boundary layer influences.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  17. Coexisting shortening and extension along the "Africa-Eurasia" plate boundary in southern Italy

    NASA Astrophysics Data System (ADS)

    Cuffaro, M.; Riguzzi, F.; Scrocca, D.; Doglioni, C.

    2009-04-01

    We performed geodetic strain rate field analyses along the "Africa (Sicily microplate)"-"Eurasia (Tyrrhenian microplate)" plate boundary in Sicily (southern Italy), using new GPS velocities from a data set spanning maximum ten years (1998-2007). Data from GPS permanent stations maintained from different institutions and the recent RING network, settled in Italy in the last five years by the Istituto Nazionale di Geofisica e Vulcanologia, were included into the analysis. Two dimensional strain and rotation rate fields were estimated by the distance weighted approach on a regularly spaced grid (30*30km), estimating the strain using all stations, but data from each station are weighted by their distance from the grid node by a constant a=70km that specifies how the effect of a station decays with distance from the node grid interpolation. Results show that most of the shortening of the Africa-Eurasia relative motion is distributed in the northwestern side offshore Sicily, whereas the extension becomes comparable with shortening on the western border of the Capo d'Orlando basin, and grater in the northeastern side, offshore Sicily, as directly provided by GPS velocities which show a larger E-ward component of sites located in Calabria with respect to those located either in northern Sicily or in the Ustica-Aeolian islands. Moreover, where shortening and extension have mostly a similar order of magnitude, two rotation rate fields can be detected, CCW in the northwestern side of Sicily, and CW in the northeastern one respectively. Also, 2-D dilatation field records a similar pattern, with negative values (shortening) in the northwestern area of Sicily close to the Ustica island, and positive values (extension) in the northeastern and southeastern ones, respectively. Principal shortening and extension rate axes are consistent with long-term geological features: seismic reflection profiles acquired in the southern Tyrrhenian seismogenic belt show active extensional faults

  18. Lithospheric structure beneath the Caribbean- South American plate boundary from S receiver functions

    NASA Astrophysics Data System (ADS)

    Masy, J.; Levander, A.; Niu, F.

    2010-12-01

    We have analyzed teleseismic S-wave data recorded by the permanent national seismic network of Venezuela and the BOLIVAR broadband array (Broadband Onshore-offshore Lithospheric Investigation of Venezuela and the Antilles arc Region) deployed from 2003 to 2005. A total of 28 events with Mw > 5.7 occurring at epicentral distances from 55° to 85° were used. We made Sp receiver functions to estimate the rapid variations of lithospheric structure in the southern Caribbean plate boundary region to try to better understand the complicated tectonic history of the region. Estimated Moho depth ranges from ~20 km beneath the Caribbean Large Igneous Provinces to ~50 km beneath the Mérida Andes in western Venezuela and the Sierra del Interior in northeastern Venezuela. These results are consistent with previous receiver functions studies (Niu et al., 2007) and active source profiles (Schmitz et al., 2001; Bezada et al., 2007; Clark et al., 2008; Guedez, 2008; Magnani et al., 2009). Beneath the Maracaibo Block we observe a signal at a depth of 100 km dipping ~24° towards the continent, which we interpret as the top of the oceanic Caribbean slab that is subducting beneath South America from the west. The deeper part of the slab was previously imaged using P-wave tomography (Bezada et al, 2010), and the upper part inferred from intermediate depth seismicity (Malavé and Suarez, 1995). These studies indicate flat slab subduction beneath northern Colombia and northwestern Venezuela with the slab dipping between 20° - 30° beneath Lake Maracaibo. Like others we attribute the flat slab subduction to the uplift of the Mérida Andes (for example Kellogg and Bonini, 1982). In eastern Venezuela beneath the Sierra del Interior we also observe a deep signal that we interpret as deep South American lithosphere that is detaching from the overriding plate as the Atlantic subducts and tears away from SA (Bezada et al., 2010; Clark et al, 2008). The lithosphere-asthenosphere boundary (LAB

  19. Receiver Functions Imaging of the Moho and LAB in the Southern Caribbean plate boundary and Venezuela

    NASA Astrophysics Data System (ADS)

    Masy, J.; Levander, A.; Niu, F.

    2011-12-01

    We have made teleseismic Ps and Sp receiver functions from data recorded from 2003 to 2009 by the permanent national seismic network of Venezuela, the BOLIVAR (Broadband Onshore-offshore Lithospheric Investigation of Venezuela and the Antilles arc Region) and WAVE (Western Array for Venezuela) experiments. The receiver functions show rapid variations in Moho and lithosphere-asthenosphere boundary (LAB) depths both across and along the southern Caribbean plate boundary region. We used a total of 69 events with Mw > 6 occurring at epicentral distances from 30° to 90° for the Ps receiver functions, and 43 events with Mw > 5.7 from 55° to 85° to make Sp receiver functions. For CCP stacking we constructed a 3D velocity model from numerous active source profiles (Schmitz et al., 2001; Bezada et al., 2007; Clark et al., 2008; Guedez, 2008; Magnani et al., 2009), from finite-frequency P wave upper mantle tomography model of Bezada et al., (2010) and the Rayleigh wave tomography model of Miller et al., (2009). The Moho ranges in depth from ~25 km beneath the Caribbean Large Igneous Provinces to ~55 km beneath the Mérida Andes in western Venezuela. These results are consistent with previous receiver functions studies (Niu et al., 2007) and the available active source profiles. Beneath the Maracaibo Block in northwestern Venezuela, we observe a strong positive signal at 40 to 60 km depth dipping ~6° towards the continent. We interpret this as the Moho of the Caribbean slab subducting beneath northernmost South America from the west. Beneath northern Colombia and northwestern Venezuela the top of this slab has been previously inferred from intermediate depth seismicity (Malavé and Suarez, 1995), which indicates a slab dipping between 20° - 30° beneath Lake Maracaibo. Our results could indicate that the slab is tearing beneath Lake Maracaibo as suggested previously by Masy et al. (2011). The deeper (> 100 km depth) part of the slab has been imaged using P

  20. UNAVCO Plate Boundary Observatory 2007 Student Field Assistant Program in the Alaska Region

    NASA Astrophysics Data System (ADS)

    Marzulla, A.; Gasparich, S.; Pauk, B.; Feaux, K.; Jackson, M.

    2007-12-01

    The UNAVCO, Inc. Plate Boundary Observatory (PBO) Student Field Assistant Program strives to engage students in further study and careers in the Earth Sciences. Student Field Assistants from a variety of educational backgrounds ranging from high school graduates to master's level students spend a three to five month field season working in tandem with UNAVCO regional Field Engineers. The students work closely with senior staff to reconnaissance, install, and maintain a network of 875 permanent Global Positioning System (GPS) stations in one of the five PBO regions covering the western United States, including Alaska. Practical skills, such as power tool use, drilling, welding, firearms training, and proper field safety procedures, are taught and expected of the students. Installation and maintenance of new and existing GPS stations composes the bulk of the student's responsibilities and duties. When not in the field, students prepare gear and arrange logistics for site installations and maintenance as well as enter metadata and complete installation reports from recently constructed sites. An understanding of the operations of the GPS receivers and the scientific benefit of the network allows for an appreciation and great attention to detail during installation of the sites. Student assistance in the Alaska region during 2007 PBO AK field season was critical to the successful installation of 36 new GPS stations throughout Alaska. Significant benchmarks of the field season included installing six logistically difficult stations in Prince William Sounds, completing the Denali Fault GPS network, four new tiltmeters on Akutan Volcano, completing all installs on the Seward Peninsula as well as several new GPS stations throughout the western interior of the state. Alaska is a prominent area for much movement and deformation as the Pacific Plate subducts beneath the North American Plate resulting in an area of high volcanic activity and heightened crustal deformation. The

  1. Surface constraints on the temporal and spatial evolution of the Farallon-Pacific-North America plate boundary

    NASA Astrophysics Data System (ADS)

    McQuarrie, N.; Oskin, M.

    2009-05-01

    Extension and volcanism are two surface derived data sets used to infer mantle processes back in time. We integrate two new large GIS-based datasets to create palinspastic restorations of extension and volcanism allowing us to readdress the relationship between plate-boundary deformation, intra-plate extension and magmatism in western North America. Using ArcGIS and custom software, we retrodeformed the NAVDat (North American Volcanic Database, navdat.geongrid.org) using the western North America reconstruction of McQuarrie and Wernicke (2005). We compare this data to strain rates calculated over a 50 km-grid forward- deformed from 36 Ma to present. With the deformed grid and palinspastically restored volcanic dataset we quantitatively compare rates of magmatism and deformation and evaluate the age, location, and migration of Cenozoic volcanic arcs. A first order conclusion from this study is that magmatism, throughout the Basin and Range, is primarily driven by plate boundary effects. The plate boundary effects include subduction and rollback of the Farallon plate, creation and expansion of slab windows as the Pacific plate intercepts the North American plate and re-establishment of the ancestral Cascade arc along the eastern margin of the Sierra Nevada at ˜ 15 Ma. Notable exceptions include the Yellowstone hotspot system along the northern boarder of our study area and late-stage (<8 Ma) passive, extension related asthenospheric upwelling that accompanied a thinning lithosphere along the eastern and western margins of the Basin and Range. The palinspastic reconstructions presented here highlight that the classic, high-angle, Basin and Range faulting that comprises most of the physiographic Basin and Range province commenced during a remarkably amagmatic period. These observations largely contradicts the active rifting model where magmatism triggers Basin and Range extension

  2. Watching structural and geodynamic features of a plate boundary: Peceneaga-Camena Fault

    NASA Astrophysics Data System (ADS)

    Besutiu, L.; Zlagnean, L.

    2009-04-01

    The Peceneaga - Camena Fault represents one of the major lithosphere contacts on the Romanian territory. Its nature and dynamics have been subject to many geological and geophysical researches since the beginning of the 20th century. Based on geophysical evidence some authors consider PCF as a plate boundary, the strike-slip contact between the Moesian Micro-Plate (MoP) and East European Plate (EEP). Deep seismic soundings along the international line II had revealed its trans-crustal nature, with a 10 km step at both Conrad and Moho discontinuities. It is likely that the geodynamic evolution of this major tectonic accident is tightly connected to the opening of the W Black Sea basin. Seismic tomography studies have outlined strong fingerprints of the W Black Sea opening within its NW inland. In depth extension of PCF may be clearly seen within the tomography images down to more than 150 km. It seems that lithosphere expelled by the rifting split MoP into several compartments by creating or reactivating a NW trending major fault system to which the PCF belongs. After the W Black Sea rifting ended its evolution, the geodynamic engine in the area seems to be the active rifting in the SW Arabian Plate (red Sea and Aden Bay) pushing northward the Arabian Plate by about 48 mm/yr, and further on, pushing a MoP segment towards the Carpathians. Under this pushing, the above-mentioned MoP compartments move towards the Carpathians, staying together by friction. However, when tectonic forces overcome the friction, the slivers may relatively slip each other, thus generating earthquakes along their wedges. The presence of some scarce seismicity along PCF seems to confirm the idea. To check up the above mentioned geodynamic scenario, a geodetic experiment has been imagined to monitor PCF flanks displacement. Two Leica TC 1201 total stations were installed on the southern flank of PCF (belonging to MoP) in order to measure the distance to a laser reflector installed on the

  3. Plate tectonics and offshore boundary delimitation: Tunisia-Libya case at the International Court of Justice

    SciTech Connect

    Stanley, D.J.

    1983-03-01

    Advances in the technology for exploiting resources of the oceans, particularly recovery of hydrocarbons and minerals in deep water, is benefiting a growing number of nations. At the same time, however, economic and political pressures have induced concern and there is now a much increased emphasis on jurisdiction to divide the offshore areas between the 132 coastal nations. Negotiations affect research operations at sea and, in consequence, marine scientists have been made aware of offshore problems as highlighted by the Law of the Sea Treaty (UNCLOS III) and complications arising from the legal versus scientific definitions of continental shelves and margins. The first major offshore boundary case of international scope where plate tectonics has constituted a significant argument is the one recently brought before the International Court of Justice by Libya and Tunisia concerning the delimitation of their continental shelves. Of the two parties, Libya placed the greatest emphasis on this concept as a means to determine natural prolongation of its land territory into and under the sea. Tunisia contested Libya's use of the whole of the African continental landmass as a reference unit; in Tunisia's view, considerations of geography, geomorphology, and bathymetry are at least as relevant as are those of geology. In its landmark judgment (February 1982) - which almost certainly will have far-reaching consequences in future such boundary delimitation cases - the court pronounced that It is the outcome, not the evolution in the long-distant past, which is of importance, and that it is the present-day configuration of the coasts and sea bed which are the main factors to be considered, not geology.

  4. Effect of viscous dissipation on natural convection flow between vertical parallel plates with time-periodic boundary conditions

    NASA Astrophysics Data System (ADS)

    Jha, Basant K.; Ajibade, Abiodun O.

    2012-04-01

    This article investigates the natural convection flow of viscous incompressible fluid in a channel formed by two infinite vertical parallel plates. Fully developed laminar flow is considered in a vertical channel with steady-periodic temperature regime on the boundaries. The effect of internal heating by viscous dissipation is taken into consideration. Separating the velocity and temperature fields into steady and periodic parts, the resulting second order ordinary differential equations are solved to obtain the expressions for velocity, and temperature. The amplitudes and phases of temperature and velocity are also obtained as well as the rate of heat transfer and the skin-friction on the plates. In presence of viscous dissipation, fluids of relatively small Prandtl number has higher temperature than the channel plates and as such, heat is being transferred from the fluid to the plate.

  5. Effect of viscous dissipation on natural convection flow between vertical parallel plates with time-periodic boundary conditions

    NASA Astrophysics Data System (ADS)

    Jha, B. K.; Ajibade, A. O.

    2011-12-01

    This article investigates the natural convection flow of viscous incompressible fluid in a channel formed by two infinite vertical parallel plates. Fully developed laminar flow is considered in a vertical channel with steady-periodic temperature regime on the boundaries. The effect of internal heating by viscous dissipation is taken into consideration. Separating the velocity and temperature fields into steady and periodic parts, the resulting second order ordinary differential equations are solved to obtain the expressions for velocity, and temperature. The amplitudes and phases of temperature and velocity are also obtained as well as the rate of heat transfer and the skin friction on the plates. In presence of viscous dissipation, fluids of relatively small Prandtl number has higher temperature than the channel plates and as such, heat is being transferred from the fluid to the plate.

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

    NASA Technical Reports Server (NTRS)

    Solomon, Sean C.

    1987-01-01

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

  7. Chlorine isotope geochemistry of Icelandic thermal fluids: Implications for geothermal system behavior at divergent plate boundaries

    NASA Astrophysics Data System (ADS)

    Stefánsson, Andri; Barnes, Jaime D.

    2016-09-01

    The chlorine isotope composition of thermal fluids from Iceland were measured in order to evaluate the source of chlorine and possible chlorine isotope fractionation in geothermal systems at divergent plate boundaries. The geothermal systems studied have a wide range of reservoir temperatures from 40 to 437 °C and in-situ pH of 6.15 to 7.15. Chlorine concentrations range from 5.2 to 171 ppm and δ37 Cl values are -0.3 to + 2.1 ‰ (n = 38). The δ37 Cl values of the thermal fluids are interpreted to reflect the source of the chlorine in the fluids. Geothermal processes such as secondary mineral formation, aqueous and vapor speciation and boiling were found to have minimal effects on the δ37 Cl values. However, further work is needed on incorporation of Cl into secondary minerals and its effect on Cl isotope fractionation. Results of isotope geochemical modeling demonstrate that the range of δ37 Cl values documented in the natural thermal fluids can be explained by leaching of the basaltic rocks by meteoric source water under geothermal conditions. Magmatic gas partitioning may also contribute to the source of Cl in some cases. The range of δ37 Cl values of the fluids result mainly from the large range of δ37 Cl values observed for Icelandic basalts, which range from -0.6 to + 1.2 ‰.

  8. Is the Teisseyre-Tornquist Zone an ancient plate boundary of Baltica?

    NASA Astrophysics Data System (ADS)

    Mazur, Stanislaw; Mikolajczak, Mateusz; Krzywiec, Piotr; Malinowski, Michal; Buffenmyer, Vinton; Lewandowski, Marek

    2015-12-01

    The Teisseyre-Tornquist Zone (TTZ) is generally regarded as a fossil plate boundary in Europe that extends 2000 km from the Baltic Sea to the Black Sea. We used an integrated approach merging potential fields and seismic data to explore crustal architecture across the TTZ in central Poland. The aim of the study was to test whether the TTZ coincides with an early Paleozoic (Caledonian) suture formed through the closure of the Tornquist Ocean along the SW Baltica margin. The suture is presumed to separate the East European Craton (EEC) from the Paleozoic terranes of Western Europe. Two seismic reflection lines from the PolandSPAN™ experiment were used to image the deep structure at the SW margin of the EEC. Lines PL-5300 and PL-5400 run NE-SW in central and northern Poland, respectively. The seismic interpretation down to top of basement was integrated with 2-D gravity and magnetic modeling to highlight the structure of the deep crust. Both the gravity and magnetic models show a suture that welds together two blocks at the base of crust. However, top of basement above the suture dips uniformly to the SW and is overlain by undisturbed lower Paleozoic and younger sediments. By implication, the suture must have developed in the Precambrian and both crustal blocks amalgamated belong to the EEC. Consequently, the Caledonian suture, formed by the closure of the Tornquist Ocean between Avalonia and Baltica, must be located farther southwest beneath thick upper Paleozoic and Mesozoic sediments.

  9. Tidal calibration of Plate Boundary Observatory borehole strainmeters: Roles of vertical and shear coupling

    USGS Publications Warehouse

    Roeloffs, Evelyn

    2010-01-01

    A multicomponent borehole strainmeter directly measures changes in the diameter of its cylindrical housing at several azimuths. To transform these measurements to formation strains requires a calibration matrix, which must be estimated by analyzing the installed strainmeter's response to known strains. Typically, theoretical calculations of Earth tidal strains serve as the known strains. This paper carries out such an analysis for 12 Plate Boundary Observatory (PBO) borehole strainmeters, postulating that each of the strainmeters' four gauges responds ("couples") to all three horizontal components of the formation strain tensor, as well as to vertical strain. Orientation corrections are also estimated. The fourth extensometer in each PBO strainmeter provides redundant information used to reduce the chance that coupling coefficients could be misleadingly fit to inappropriate theoretical tides. Satisfactory fits between observed and theoretically calculated tides were obtained for three PBO strainmeters in California, where the calculated tides are corroborated by other instrumentation, as well as for six strainmeters in Oregon and Washington, where no other instruments have ever recorded Earth tidal strain. Several strainmeters have unexpectedly large coupling coefficients for vertical strain, which increases the strainmeter's response to atmospheric pressure. Vertical coupling diminishes, or even changes the sign of, the apparent response to areal strain caused by Earth tides or deep Earth processes because near the free surface, vertical strains are opposite in sign to areal strain. Vertical coupling does not impair the shear strain response, however. PBO borehole strainmeters can provide calibrated shear strain time series of transient strain associated with tectonic or magmatic processes.

  10. Joint Inversion for Bulk Sound and Shear Wave Velocity Heterogeneity Beneath the Mediterranean Plate Boundary Region

    NASA Astrophysics Data System (ADS)

    Schmid, C.; van der Lee, S.; Giardini, D.

    2005-12-01

    We present new 3-D models for shear wave and compressional wave velocity anomalies for the mantle beneath the Mediterranean plate boundary region down to a depth of ~1500 km. These new models are based on a combined set of P and S body-wave arrival time data, which was measured by interstation cross-correlation. Stations used were from the MIDSEA deployment and permanent networks in the region. We invert these data jointly for bulk sound and shear wave velocity heterogeneity. The resulting models of P and S velocity heterogeneity are similar to each other. P wave velocity heterogeneity appears to be dominated by variations in shear modulus. We do not find evidence for large scale anti-correlation between bulk sound and shear wave velocity heterogeneity. We further constrain the mantle's S-velocity with regional S and surface waves and Moho detections. The Mediterranean region is substantially slower than the global average at shallow mantle depths and faster than average at transition zone depths. Our models show high velocities related to present and recent subduction northwards beneath the Hellenic trench, northwestwards beneath the Calabrian Arc, and a much shorter slab dipping southwestwards beneath the Apennines. Our models show somewhat surprising evidence of past subduction in the transition zone beneath the western Mediterranean and in the lower mantle beneath northeastern Africa. The only significantly slower region at transition zone depths is found beneath the Ionian Sea.

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

    NASA Astrophysics Data System (ADS)

    Rangin, Claude

    2016-01-01

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

  12. Propagation of rifting along the Arabia-Somalia Plate Boundary: The Gulfs of Aden and Tadjoura

    NASA Astrophysics Data System (ADS)

    Manighetti, Isabelle; Tapponnier, Paul; Courtillot, Vincent; Gruszow, Sylvie; Gillot, Pierre-Yves

    1997-02-01

    The localization and propagation of rifting between Arabia and Somalia are investigated by assessing the deformation geometry and kinematics at different scales between the eastern Gulf of Aden and the Gulf of Tadjoura, using bathymetric, magnetic, seismological, and structural evidence. Large-scale, southwestward propagation of the Aden ridge, markedly oblique to the Arabia-Somalia relative motion vector, began about 30 Myr ago between the Error and Sharbithat ridges. It was an episodic process, with stages of rapid propagation, mostly at rates >10 cm/yr, interrupted by million year pauses on transverse discontinuities coinciding with rheological boundaries between different crustal provinces of the Arabia-Somalia plate. The longest pause was at the Shukra-El Sheik discontinuity (≈45°E), where the ridge tip stalled for ≈13 Myr, between ≈17 and ≈4 Ma. West of that discontinuity, rifting and spreading took place at an azimuth (≈N25°±10°E) and rate (1.2±0.3 cm/yr) different from those of the global Arabia-Somalia motion vector (≈N39°, ≈1.73 cm/yr), implying an additional component of movement (N65°±10°E, 0.7±0.2 cm/yr) due to rotation of the Danakil microplate. At Shukra-El Sheik, the typical oceanic ridge gives way to a narrow, WSW trending axial trough, resembling a large fissure across a shallow shelf. This trough is composed of about eight rift segments, which result from normal faulting and fissuring along N110°-N130°E trends. All the segments step to the left southwestward, mostly through oblique transfer zones with en échelon normal faults. Only two segments show clear, significant overlap. There is one clear transform, the Maskali fault, between the Obock and Tadjoura segments. The latter segment, which encroaches onland, is composed of two parallel subrifts (Iboli, Ambabbo) that propagated northwestward and formed in succession. The most recent, southwestern subrift (Ambabbo) represents the current tip of the Aden ridge. We propose

  13. Contrasting styles of (U)HP rock exhumation along the Cenozoic Adria-Europe plate boundary (Western Alps, Calabria, Corsica)

    NASA Astrophysics Data System (ADS)

    Malusà, Marco G.; Faccenna, Claudio; Baldwin, Suzanne L.; Fitzgerald, Paul G.; Rossetti, Federico; Balestrieri, Maria Laura; Danišík, Martin; Ellero, Alessandro; Ottria, Giuseppe; Piromallo, Claudia

    2015-06-01

    Since the first discovery of ultrahigh pressure (UHP) rocks 30 years ago in the Western Alps, the mechanisms for exhumation of (U)HP terranes worldwide are still debated. In the western Mediterranean, the presently accepted model of synconvergent exhumation (e.g., the channel-flow model) is in conflict with parts of the geologic record. We synthesize regional geologic data and present alternative exhumation mechanisms that consider the role of divergence within subduction zones. These mechanisms, i.e., (i) the motion of the upper plate away from the trench and (ii) the rollback of the lower plate, are discussed in detail with particular reference to the Cenozoic Adria-Europe plate boundary, and along three different transects (Western Alps, Calabria-Sardinia, and Corsica-Northern Apennines). In the Western Alps, (U)HP rocks were exhumed from the greatest depth at the rear of the accretionary wedge during motion of the upper plate away from the trench. Exhumation was extremely fast, and associated with very low geothermal gradients. In Calabria, HP rocks were exhumed from shallower depths and at lower rates during rollback of the Adriatic plate, with repeated exhumation pulses progressively younging toward the foreland. Both mechanisms were active to create boundary divergence along the Corsica-Northern Apennines transect, where European southeastward subduction was progressively replaced along strike by Adriatic northwestward subduction. The tectonic scenario depicted for the Western Alps trench during Eocene exhumation of (U)HP rocks correlates well with present-day eastern Papua New Guinea, which is presented as a modern analog of the Paleogene Adria-Europe plate boundary.

  14. Mélange as a Plate Boundary Rock and its Seismogenic Roof Thrust - An Example From the Shimanto Belt, Japan

    NASA Astrophysics Data System (ADS)

    Kitamura, Y.; Sato, K.; Ikesawa, E.; Kimura, G.; Kondo, H.; Ujiie, K.; Onishi, C. T.; Kawabata, K.; Hashimoto, Y.; Mukoyoshi, H.; Masago, H.

    2003-12-01

    A tectonic mélange of the ancient accretionary prism of the Shimanto Belt, Japan is investigated to understand a plate boundary process, especially of seismogenic zone in subduction zone. We analyzed deformation fabric, magnetic fabrics, deformation mechanisms and their thermal condition by using vitrinite reflectance. The investigated Mugi mélange is located in western Shikoku. In the Mugi mélange, systematic fabrics such as Y-P-R fabric formed by micro shear and pressure solution mechanisms are penetrated throughout the mélange pile. Magnetic ellipsoids obtained from the anisotropy of magnetic susceptibility (AMS) are highly oblate. Maximum and minimum axes of the ellipsoids are in accordance with shear orientation of mélange and mean pole of foliation, respectively. These facts suggest that the Mugi mélange was formed as a result of underthrusting of trench filling sediments. Vitrinite reflectance ranges from 2.52% to 3.08%, which correlates to the maximum paleo-temperature of ca. 240 §C to 260 §C. Pseudotachylite of the most reliable seismogenic rock was found from the upper boundary roof fault of the Mugi mélange. The fault is composed of about 1 m thick cataclastic zone injected by many veins. The overlying Hiwasa formation is sandstone-dominated and folded coherent piles. The finding of the pseudotachylite in this study area is another example from the ancient accretionary complex after the first one from the Okitsu mélange in western Shikoku Island. The setting of the pseudotachylite from the boundary fault between tectonic mélange and overlying folded coherent pile is quite similar to that of the first one. There is no thermal gap between the mélange and coherent piles but temperature obtained from vitrinite reflectance gradually rises in descending from the coherent piles to the mélange beyond the boundary fault. Such setting suggests that paleo-isotherm was parallel to the orientation of the boundary fault. The isotherm in the seismogenic

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

    NASA Technical Reports Server (NTRS)

    Solomon, Sean C.

    1987-01-01

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

  16. Kinematics of the New Zealand plate boundary: Relative motion by GPS across networks of 1000 km and 50 km spacing

    NASA Technical Reports Server (NTRS)

    Meertens, Charles M.; Rocken, Christian; Perin, Barbara; Walcott, Richard

    1993-01-01

    The NASA/DOSE 'Kinematics of the New Zealand Plate Boundary' experiment is a four-year cooperative Global Positioning System (GPS) experiment involving 6 universities and institutions in New Zealand and the United States. The investigation covers two scales, the first on the scale of plates (approximately 1000 km) and the second is on the scale of the plate boundary zone (approximately 50 km). In the first portion of the experiment, phase A, the objective is to make direct measurements of tectonic plate motion between the Australian and Pacific plates using GPS in order to determine the Euler vector of this plate pair. The phase A portion of this experiment was initiated in December 1992 with the first-epoch baseline measurements on the large scale network. The network will be resurveyed two years later to obtain velocities. The stations which were observed for phase A are shown and listed. Additional regional stations which will be used for this study are listed and are part of either CIGNET or other global tracking networks. The phase A portion of the experiment is primarily the responsibility of the UNAVCO investigators. Therefore, this report concentrates on phase A. The first year of NASA funding for phase A included only support for the field work. Processing and analysis will take place with the second year of funding. The second part of the experiemnt measured relative motion between the Australian and Pacific plates across the pate boundary zone between Hokitika and Christchurch on the South Island of New Zealand. The extent and rate of deformation will be determined by comparisons with historical, conventional surveys and by repeated GPS measurements to be made in two years. This activity was the emphasis of the LDGO portion of the study. An ancillary experiment, phase C, concentrated on plate boundary deformation in the vicinity of Wellington and was done as part of training during the early portion of the field campaign. Details of the objectives of the

  17. North American plate dynamics

    NASA Technical Reports Server (NTRS)

    Richardson, Randall M.; Reding, Lynn M.

    1991-01-01

    Deformation within the North American plate in response to various tectonic processes is modeled using an elastic finite element analysis. The tectonic processes considered in the modeling include ridge forces associated with the normal thermal evolution of oceanic lithosphere, shear and normal stresses transmitted across transforms, normal stresses transmitted across convergent boundaries, stresses due to horizontal density contrasts within the continent, and shear tractions applied along the base of the plate. Model stresses are calculated with respect to a lithostatic reference stress state. Shear stresses transmitted across transform boundaries along the San Andreas and Caribbean are small, of the order of 5-10 MPa. Also, compressive stresses of the order of 5-10 MPa transmitted across the major transforms improve the fit to the data. Compressive stresses across convergent margins along the Aleutians and the Middle America trench are important.

  18. Wide-angle velocity modeling and receiver functions imaging a lithospheric shear tear in the southeast Caribbean-South America plate boundary

    NASA Astrophysics Data System (ADS)

    Clark, S. A.; Levander, A.; Zelt, C. A.; Niu, F.; Sobiesiak, M.

    2007-05-01

    Two models for slab detachment have been proposed for the lithospheric structure of the northern South America plate boundary with the southeast Caribbean, where westward subduction of oceanic South America transitions to east-west transform between continental South America and the Caribbean plate. In the tensile tear model, oblique convergence causes northwest-dipping subduction, and tension on the subducting slab results in detachment orthogonal to the motion vectors. Conversely, the shear tear model predicts detachment parallel to the motion vectors along a vertical plane, with shear stress focused on the edge of the propagating transform boundary. We present new active-source onshore-offshore wide-angle tomography, integrated with new passive-source receiver function analysis, from profile 64W of the BOLIVAR (Broadband Ocean-Land Investigation of Venezuela and the Antilles arc Region) project. Profile 64W is a 460 km-long, north-south, onshore-offshore reflection/refraction/teleseismic transect located approximately at 64 deg W longitude that extends from the southeastern Caribbean across the Serrania del Interior and into the Maturin basin. The various datasets image deep crustal and upper mantle structure across the entire diffuse plate boundary zone. The active-source components of profile 64W include 33 OBSs and 344 land seismic stations which recorded 7500 offshore airgun shots and 2 chemical explosive land shots. Receiver functions along 64W were picked from hundreds of events at 18 temporary and permanent broadband stations. Close agreement exists between the wide-angle inversion of first arrivals, PmP, and Pn, and receiver function analysis for the Moho conversion, indicating that the Moho deepens northward from 35 km beneath the Guiana shield craton (from receiver functions only) to 45 km beneath the Serrania del Interior; to the north, Moho abruptly shoals to a depth of 25 km. We interpret this step change in Moho depth to be the lower crustal plate

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  20. The EarthScope Plate Boundary Observatory (PBO) Facility: Innovations, Transformations, and Impact

    NASA Astrophysics Data System (ADS)

    Jackson, M. E.; Mencin, D.; Feaux, K.

    2013-12-01

    The word 'transformation' is not used lightly in science. However, the transformative nature of the EarthScope Plate Boundary Observatory facility on the science community is large and measurable. The impact of the creation, execution and delivery of the PBO resulted in radical changes in the way the geodesy community views permanent, continuously operating (and often) real-time GPS and strain networks, open data policies, and the ability for consortium based facilities, such as UNAVCO, to manage and deliver on large National Science Foundation investments. Our presentation will explore these innovations and transformations from the community, facility, and science perspectives. In the genesis of the EarthScope proposal there was a distinct shift away from the PBO being managed and constructed by prominent PI's within the community to a vesting of the responsibility and authority in UNAVCO to execute on behalf of the entire community. This tipping away from individual PI concerns towards a communal behavior allowed the construction of a facility based on broad input from, and equal access for, any member of the geodesy community. The open and transparent nature of EarthScope, including the open data policy for both facility and PI derived data was truly transformative. One of the key tenants of the PBO was strict adherence to not redesigning unless absolutely necessary. For example PBO monumentation and data processing practices were adopted wholesale from the SCIGN project, while the station selection, project management, permitting practices, data downloading, metadata, and, data communications were refactored for optimum use for the broader geodesy community and to scale with the large geography that confronted PBO. The PBO strainmeter network, one of the largest in the world, started by looking at the procedures of 30 years of heterogeneous installations around the word then crafted, created, and amalgamated new drilling, grouting, installation, and data

  1. High-Resolution LiDAR Topography of the Plate-Boundary Faults in Northern California

    NASA Astrophysics Data System (ADS)

    Prentice, C. S.; Phillips, D. A.; Furlong, K. P.; Brown, A.; Crosby, C. J.; Bevis, M.; Shrestha, R.; Sartori, M.; Brocher, T. M.; Brown, J.

    2007-12-01

    GeoEarthScope acquired more than 1500 square km of airborne LiDAR data in northern California, providing high-resolution topographic data of most of the major strike-slip faults in the region. The coverage includes the San Andreas Fault from its northern end near Shelter Cove to near Parkfield, as well as the Rodgers Creek, Maacama, Calaveras, Green Valley, Paicines, and San Gregorio Faults. The Hayward fault was added with funding provided by the US Geological Survey, the City of Berkeley, and the San Francisco Public Utilities Commission. Data coverage is typically one kilometer in width, centered on the fault. In areas of particular fault complexity the swath width was increased to two kilometers, and in selected areas swath width is as wide as five kilometers. A five-km-wide swath was flown perpendicular to the plate boundary immediately south of Cape Mendocino to capture previously unidentified faults and to understand off-fault deformation associated with the transition zone between the transform margin and the Cascadia subduction zone. The data were collected in conjunction with an intensive GPS campaign designed to improve absolute data accuracy and provide quality control. Data processing to classify the LiDAR point data by return type allows users to filter out vegetation and produce high-resolution DEMs of the ground surface beneath forested regions, revealing geomorphic features along and adjacent to the faults. These data will allow more accurate mapping of fault traces in regions where the vegetation canopy has hampered this effort in the past. In addition, the data provide the opportunity to locate potential sites for detailed paleoseismic studies aimed at providing slip rates and event chronologies. The GeoEarthScope LiDAR data will be made available via an interactive data distribution and processing workflow currently under development.

  2. A new approach to study rotational deformation near plate boundaries by combining paleomagnetism and geodetic observations

    NASA Astrophysics Data System (ADS)

    Ginsburg, N.; Granot, R.; Hamiel, Y.

    2014-12-01

    Vertical axis rotations are a significant component of crustal deformation and provide important constraints on the tectonic history of plate boundaries. Geodetic measurements can be used to calculate present-day rotations whereas paleomagnetic measurements can be used for calculating finite long-term (millions of years) rotations. Here we present a new approach for integrating both datasets through mechanical modeling that links these time scales. We test this approach in northern Israel, a region where a tectonic triple junction lies at the intersection between two deformation zones: (1) The Dead Sea Fault, and (2) The Carmel-Gilboa Fault System. We examined the distribution of crustal deformation and rotation rates near these two major fault zones. First, rotation rates were calculated from current interseismic global positioning system (GPS) measurements that were recorded during 12 years. We analyzed the GPS velocities using a 3D dislocation slip model that takes into account motion on major active faults in the study area. This model was then modified to account for the total deformation of the crust during several seismic cycles. Rotations from the mechanical modeling were compared against finite rotations determined based on primary magnetic remanence directions from 30 Neogenic basaltic sites. Paleomagnetic results indicate significant (>20º) rotations near the edges of fault segments. These results disagree with interseismic rotations calculated from the GPS measurements; however they are in general agreement with the vertical axis rotations obtained from the mechanical model. The comparison to the modified model suggests that the tectonic setting of the Carmel-Gilboa Fault system was fairly stable during the last ~10 Myr. Furthermore, the new suggested method for comparing interseismic recent deformation with long-term deformation provides important new insights on the timing, magnitude and style of deformation near major faults.

  3. EarthScope Plate Boundary Observatory, Southwest Region - Communications, Challenges, and Cooperation

    NASA Astrophysics Data System (ADS)

    Turner, R. C.; Mann, D.; Walls, C. P.; Basset, A.; Lawrence, S.; Berglund, H. T.

    2015-12-01

    The Southwest Region of the EarthScope Plate Boundary Observatory is engaged in efforts to expand capabilities and renovate the network. These efforts include GNSS hardware modernization (in cooperation with state and local agencies), communications upgrades that improve data throughput and decrease recurring costs, co-location of prototype instruments for use in earthquake early warning, and working to ensure consistent high-quality data in the face of radio spectrum encroachment.The Global Positioning System (GPS) is but one of a growing number of global navigation satellite systems (GNSS) with the potential to improve geodetic observations. In addition to strategic deployment of GNSS-capable hardware, the Southwest region is currently developing an agreement with Caltrans to augment the network with GNSS systems at about a dozen stations. The upgrades will consist of a number of Caltrans-provided GLONASS-ready receivers and project is scheduled for completion by early 2016.The Southwest Region has continued to upgrade and build new radio networks to improve dependability, monitoring, and data download rates (including transfers of high-rate data). Here, we highlight one such network near Hollister, CA, which eliminated several cellular modems and improved reliability.UNAVCO and Scripps have been working in collaboration to augment a subset of GPS stations with low-cost strong-motion sensors for use in Earthquake Early Warning systems. To date, 21 PBO stations have been upgraded with MEMS accelerometers along the San Andreas and San Jacinto Faults in Northern and Southern California, 15 of which stream data to UNAVCO in real time.As the use of the radio frequency spectrum increases, PBO faces more radio frequency interference (RFI) in our data communications networks; in addition, RFI issues are beginning to impact GNSS data collection. Here we report on a PBO site suspected of suffering from RFI and discuss briefly mitigation efforts to minimize these effects.

  4. The EarthScope Plate Boundary Observatory Akutan Alaskan Volcano Tiltmeter Installation

    NASA Astrophysics Data System (ADS)

    Pauk, B. A.; Gallaher, W.; Dittmann, T.; Smith, S.

    2007-12-01

    During August of 2007, the Plate Boundary Observatory (PBO) successfully installed four Applied Geomechanics Lily Self Leveling Borehole Tiltmeters on Akutan Volcano, in the central Aleutian islands of Alaska. All four stations were collocated with existing PBO Global Positioning Systems (GPS) stations installed on the volcano in 2005. The tiltmeters will aid researchers in detecting and measuring flank deformation associated with future magmatic intrusions of the volcano. All four of the tiltmeters were installed by PBO field crews with helicopter support provided by JL Aviation and logistical support from the Trident Seafood Corporation, the City of Akutan, and the Akutan Corporation. Lack of roads and drivable trails on the remote volcanic island required that all drilling equipment be transported to each site from the village of Akutan by slinging gear beneath the helicopter and with internal loads. Each tiltmeter hole was drilled to a depth of approximately 30 feet with a portable hydraulic/pneumatic drill rig. The hole was then cased with splined 2.75 inch PVC. The PVC casing was cemented in place with grout and the tiltmeters were installed and packed with fine grain sand to stabilize the tiltmeters inside the casing. The existing PBO NetRS GPS receivers were configured to collect the tiltmeter data through a spare receiver serial port at one sample per minute and 1 hour files. Data from the GPS receivers and tiltmeters is telemetered directly or through a repeater radio to a base station located in the village of Akutan that transmits the data using satellite based communications to connect to the internet and to the UNAVCO Facility data archive where it is made freely available to the public.

  5. Fault and graben growth along active magmatic divergent plate boundaries in Iceland and Ethiopia

    NASA Astrophysics Data System (ADS)

    Trippanera, D.; Acocella, V.; Ruch, J.; Abebe, B.

    2015-11-01

    Recent studies highlight the importance of annual-scale dike-induced rifting episodes in developing normal faults and graben along the active axis of magmatic divergent plate boundaries (MDPB). However, the longer-term (102-105 years) role of diking on the cumulative surface deformation and evolution of MDPB is not yet well understood. To better understand the longer-term normal faults and graben along the axis of MDPB, we analyze fissure swarms in Iceland and Ethiopia. We first focus on the simplest case of immature fissure swarms, with single dike-fed eruptive fissures; these consist of a <1 km wide graben bordered by normal faults with displacement up to a few meters, consistent with theoretical models and geodetic data. A similar structural pattern is found, with asymmetric and multiple graben, within wider mature fissure swarms, formed by several dike-fed eruptive fissures. We then consider the lateral termination of normal faults along these grabens to detect their upward or downward propagation. Most faults terminate as open fractures on flat surface, suggesting downward fault propagation; this is consistent with recent experiments showing dike-induced normal faults propagating downward from the surface. However, some normal faults also terminate as open fractures on monoclines, which resemble fault propagation folds; this suggests upward propagation of reactivated buried faults, promoted by diking. These results suggest that fault growth and graben development, as well as the longer-term evolution of the axis of MDPB, may be explained only through dike emplacement and that any amagmatic faulting is not necessary.

  6. The Future of the Plate Boundary Observatory in the GAGE Facility and beyond 2018

    NASA Astrophysics Data System (ADS)

    Mattioli, G. S.; Bendick, R. O.; Foster, J. H.; Freymueller, J. T.; La Femina, P. C.; Miller, M. M.; Rowan, L.

    2014-12-01

    The Geodesy Advancing Geosciences and Earthscope (GAGE) Facility, which operates the Plate Boundary Observatory (PBO), builds on UNAVCO's strong record of facilitating research and education in the geosciences and geodesy-related engineering fields. Precise positions and velocities for the PBO's ~1100 continuous GPS stations and other PBO data products are used to address a wide range of scientific and technical issues across North America. A large US and international community of scientists, surveyors, and civil engineers access PBO data streams, software, and other on-line resources daily. In a global society that is increasingly technology-dependent, consistently risk-averse, and often natural resource-limited, communities require geodetic research, education, and infrastructure to make informed decisions about living on a dynamic planet. The western U.S. and Alaska, where over 95% of the PBO sensor assets are located, have recorded significant geophysical events like earthquakes, volcanic eruptions, and tsunami. UNAVCO community science provides first-order constraints on geophysical processes to support hazards mapping and zoning, and form the basis for earthquake and tsunami early warning applications currently under development. The future of PBO was discussed at a NSF-sponsored three-day workshop held in September 2014 in Breckenridge, CO. Over 40 invited participants and community members, including representatives from interested stakeholder groups, UNAVCO staff, and members of the PBO Working Group and Geodetic Infrastructure Advisory Committee participated in workshop, which included retrospective and prospective plenary presentations and breakout sessions focusing on specific scientific themes. We will present some of the findings of that workshop in order to continue a dialogue about policies and resources for long-term earth observing networks. How PBO fits into the recently released U.S. National Plan for Civil Earth Observations will also be

  7. Abbot Ice Shelf, structure of the Amundsen Sea continental margin and the southern boundary of the Bellingshausen Plate seaward of West Antarctica

    NASA Astrophysics Data System (ADS)

    Cochran, James R.; Tinto, Kirsty J.; Bell, Robin E.

    2015-05-01

    Inversion of NASA Operation IceBridge airborne gravity over the Abbot Ice Shelf in West Antarctica for subice bathymetry defines an extensional terrain made up of east-west trending rift basins formed during the early stages of Antarctica/Zealandia rifting. Extension is minor, as rifting jumped north of Thurston Island early in the rifting process. The Amundsen Sea Embayment continental shelf west of the rifted terrain is underlain by a deeper, more extensive sedimentary basin also formed during rifting between Antarctica and Zealandia. A well-defined boundary zone separates the mildly extended Abbot extensional terrain from the deeper Amundsen Embayment shelf basin. The shelf basin has an extension factor, β, of 1.5-1.7 with 80-100 km of extension occurring across an area now 250 km wide. Following this extension, rifting centered north of the present shelf edge and proceeded to continental rupture. Since then, the Amundsen Embayment continental shelf appears to have been tectonically quiescent and shaped by subsidence, sedimentation, and the advance and retreat of the West Antarctic Ice Sheet. The Bellingshausen Plate was located seaward of the Amundsen Sea margin prior to incorporation into the Antarctic Plate at about 62 Ma. During the latter part of its independent existence, Bellingshausen plate motion had a clockwise rotational component relative to Antarctica producing convergence across the north-south trending Bellingshausen Gravity Anomaly structure at 94°W and compressive deformation on the continental slope between 94°W and 102°W. Farther west, the relative motion was extensional along an east-west trending zone occupied by the Marie Byrd Seamounts. The copyright line for this article was changed on 5 JUN 2015 after original online publication.

  8. Monitoring the northern Chile megathrust with the Integrated Plate boundary Observatory Chile (IPOC)

    NASA Astrophysics Data System (ADS)

    Schurr, Bernd; Asch, Günter; Cailleau, Beatrice; Diaz, Guillermo Chong; Barrientos, Sergio; Vilotte, Jean-Pierre; Oncken, Onno

    2010-05-01

    thousand aftershocks during the following week using waveform cross-correlation and the double-difference algorithm. Aftershocks reveal that rupture during this earthquake was confined to the deeper part (35 - 55 km depth) of the seismogenic coupling zone, except near the Mejillones peninsula that marks rupture termination in the south. Here earthquake activity reaches to depths of 20 km and even shallower, possibly indicating upper plate activation. The sequence also features an M 6.8 earthquake that broke the oceanic slab on an almost vertical plane at the down-dip end of the megathrust rupture. Confrontation with the aftershock distribution of the 1995 M 8.0 Antofagasta earthquake on the adjoining southern segment reveals an intriguing mirror symmetry with an axis crossing the Mejillones peninsula, emphasizing the penisula's significance as a segment boundary. Since then activity inside the remaining seismic gap to the north picked up with three earthquakes exceeding magnitude 6, maybe heralding the next great rupture.

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

    PubMed

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

    2013-12-01

    The mechanics of great subduction earthquakes are influenced by the frictional properties, structure, and composition of the plate-boundary fault. We present observations of the structure and composition of the shallow source fault of the 2011 Tohoku-Oki earthquake and tsunami from boreholes drilled by the Integrated Ocean Drilling Program Expedition 343 and 343T. Logging-while-drilling and core-sample observations show a single major plate-boundary fault accommodated the large slip of the Tohoku-Oki earthquake rupture, as well as nearly all the cumulative interplate motion at the drill site. The localization of deformation onto a limited thickness (less than 5 meters) of pelagic clay is the defining characteristic of the shallow earthquake fault, suggesting that the pelagic clay may be a regionally important control on tsunamigenic earthquakes. PMID:24311682

  10. Stress triggering of the great Indian Ocean strike-slip earthquakes in a diffuse plate boundary zone

    NASA Astrophysics Data System (ADS)

    Wiseman, Kelly; Bürgmann, Roland

    2012-11-01

    On April 11, 2012, two great magnitude 8+ earthquakes occurred within a two-hour period off the west coast of northern Sumatra, Indonesia, in the broadly distributed India-Australia plate boundary zone. The magnitude 8.6 mainshock holds the distinction of being both the largest instrumentally recorded strike-slip earthquake and the largest earthquake away from a recognized plate boundary fault. The mainshock involved sequential ruptures of multiple fault planes oriented nearly perpendicular to each other. The adjacent 2004 megathrust earthquake statically loaded the northern Wharton Basin oceanic lithosphere on both of the 2012 mainshock fault plane orientations, and greatly enhanced the rate of earthquake activity in the region for a year. Viscoelastic relaxation of the asthenosphere following the 2004 and 2005 megathrust earthquakes continued to positively stress the offshore region, correlating with the locations of later strike-slip earthquakes, including two magnitude 7+ and the 2012 magnitude 8+ earthquakes.

  11. Receptivity of Flat-Plate Boundary Layer in a Non-Uniform Free Stream (Vorticity Normal to the Plate)

    NASA Technical Reports Server (NTRS)

    Kogan, M. N.; Shumilkin, V. G.; Ustinov, M. V.; Zhigulev, S. V.

    1999-01-01

    Experimental and theoretical studies of low speed leading edge boundary layer receptivity to free-stream vorticity produced by upstream wires normal to the leading edge are discussed. Data include parametric variations in leading edge configuration and details of the incident disturbance field including single and multiple wakes. The induced disturbance amplitude increases with increases in the leading edge diameter and wake interactions. Measurements agree with the theory of M. E. Goldstein.

  12. Cascadia slow slip events and earthquake initiation theories: Hazards research with Plate Boundary Observatory geodetic data (Invited)

    NASA Astrophysics Data System (ADS)

    Roeloffs, E. A.; Beeler, N. M.

    2013-12-01

    The relationship of transient slow slip events (SSEs) to great earthquakes is a global focus of intense and critical hazards research. Plate Boundary Observatory (PBO) GPS and borehole strainmeter (BSM) networks in the Cascadia forearc provide detailed data that can be compared with simulations predicting how SSEs might evolve as a great earthquake approaches. Cascadia SSEs represent aseismic slip of a few cm in the direction of plate convergence over a period of days or weeks, in a depth range down-dip from the locked zone expected to generate the next great Cascadia subduction earthquake. During an SSE, shear stress borne in the SSE depth range is transferred up-dip at an above-background loading rate. If shear stress on the locked zone is continually accumulating, the daily probability of reaching a threshold failure stress is elevated during an SSE . Alternatively, if dynamic instability is due to rate-weakening fault strength, then SSEs still promote earthquake initiation, but that initiation may be delayed until after the SSE ends, and short-duration SSEs may have negligible effect. In some numerical simulations, great earthquakes could nucleate in the SSE depth range, where effective pressure is assumed to be low. Certain models predict that successive SSEs will slip to increasingly shallower depths, eventually encountering higher effective stress where shear heating can destabilize slip and lead to dynamic rupture. PBO GPS stations have recorded surface deformation from SSEs since inception in 2003; borehole strainmeters (BSMs) have recorded SSE strain signals since 2007. GPS and seismic tremor data show that SSEs reoccur all along the Cascadia subduction zone. An SSE is in progress somewhere in Cascadia much of the time, so the short-term probability increase warranted by a typical SSE is presumably low. We could, however, detect differences among successive SSEs and use criteria informed by the models described above to judge whether a distinctive SSE

  13. Unsteady heat-flux measurements of second-mode instability waves in a hypersonic flat-plate boundary layer

    NASA Astrophysics Data System (ADS)

    Kegerise, Michael A.; Rufer, Shann J.

    2016-08-01

    In this paper, we report on the application of the atomic layer thermopile (ALTP) heat-flux sensor to the measurement of laminar-to-turbulent transition in a hypersonic flat-plate boundary layer. The centerline of the flat-plate model was instrumented with a streamwise array of ALTP sensors, and the flat-plate model was exposed to a Mach 6 freestream over a range of unit Reynolds numbers. Here, we observed an unstable band of frequencies that are associated with second-mode instability waves in the laminar boundary layer that forms on the flat-plate surface. The measured frequencies, group velocities, phase speeds, and wavelengths of these instability waves are consistent with data previously reported in the literature. Heat flux time series, and the Morlet wavelet transforms of them, revealed the wave-packet nature of the second-mode instability waves. In addition, a laser-based radiative heating system was used to measure the frequency response functions (FRF) of the ALTP sensors used in the wind tunnel test. These measurements were used to assess the stability of the sensor FRFs over time and to correct spectral estimates for any attenuation caused by the finite sensor bandwidth.

  14. Breaking into the Plate: Seismic and Hydroacoustic Analysis of a 7.6 Mw Oceanic Fracture Zone Earthquake Adjacent to the Central Indian Ridge Plate Boundary

    NASA Astrophysics Data System (ADS)

    Bohnenstiehl, D. R.; Tolstoy, M.; Chapp, E.

    2003-12-01

    Where oceanic spreading segments are offset laterally from one another, the differential motion of the plates is accommodated by strike-slip motion along ridge-perpendicular transform faults. Off-axis from the ridge-transform intersection, no differential motion is require, and the fracture zone trace is thought to be inactive except where reactivated by intra-plate stresses. On 15 July 2003, an earthquake with a magnitude of 7.6 Mw occurred near the northern Central Indian Ridge (CIR), the divergent boundary separating the Somalian plate from the Indian and Australian plates. The size of this event places it within the 99th quantile of magnitude for shallow (< 40 km depth) strike-slip events (null axis plunge >45 deg) within the global Harvard CMT catalog. The earthquake's epicenter is near 2.5 deg S, 68.33 deg E, where the CIR is marked by a series of short (<100 km long) right-stepping transforms that offset the northwest trending spreading segments (20 mm/yr). Seismic signals associated with the mainshock and its largest aftershocks were recorded well by land-based seismic networks. Regional seismic phases (Pn, Sn), as well oceanic T-waves, where also recorded at an IMS hydroacoustic station to the north of the Diego Garcia atoll. T-wave signals recorded at Diego Garcia were cross correlated to determine accurate travel time differences. These traveltime differences were used in a plane wave fitting inversion to determine the horizontal slowness components and estimate the back azimuth to the epicenter. Aftershock locations are derived using the azimuthal information and Pn-T traveltime differences. Together, the seismically- and hydroacoustically-derived epicenters show a linear band of aftershocks extending more than 200 km along the off-axis trace of a right stepping transform. We interpret these aftershock events as delineating the length of the mainshock rupture. As the well-constrain hypocenter of the mainshock lies near the western edge of this

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

    NASA Technical Reports Server (NTRS)

    Solomon, Sean C.

    1991-01-01

    During our participation in the NASA Crustal Dynamics Project under NASA contract NAS-27339 and grant NAG5-814 for the period 1982-1991, we published or submitted for publication 30 research papers and 52 abstracts of presentations at scientific meetings. In addition, five M.I.T. Ph.D. students (Eric Bergman, Steven Bratt, Dan Davis, Jeanne Sauber, Anne Sheehan) were supported wholly or in part by this project during their thesis research. Highlights of our research progress during this period include the following: application of geodetic data to determine rates of strain in the Mojave block and in central California and to clarify the relation of such strain to the San Andreas fault and Pacific-North American plate motions; application of geodetic data to infer post seismic deformation associated with large earthquakes in the Imperial Valley, Hebgen Lake, Argentina, and Chile; determination of the state of stress in oceanic lithosphere from a systematic study of the centroid depths and source mechanisms of oceanic intraplate earthquakes; development of models for the state of stress in young oceanic regions arising from the differential cooling of the lithosphere; determination of the depth extent and rupture characteristics of oceanic transform earthquakes; improved determination of earthquake slip vectors in the Gulf of California, an important data set for the estimation of Pacific-North American plate motions; development of models for the state of stress and mechanics of fold-and-thrust belts and accretionary wedges; development of procedures to invert geoid height, residual bathymetry, and differential body wave travel time residuals for lateral variations in the characteristic temperature and bulk composition of the oceanic upper mantle; and initial GPS measurements of crustal deformation associated with the Imperial-Cerro Prieto fault system in southern California and northern Mexico. Full descriptions of the research conducted on these topics may be

  16. MHD forced convective laminar boundary layer flow from a convectively heated moving vertical plate with radiation and transpiration effect.

    PubMed

    Uddin, Md Jashim; Khan, Waqar A; Ismail, A I Md

    2013-01-01

    A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to x(m) whilst the magnetic field and mass transfer velocity are taken to be proportional to x((m-1)/2) where x is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory. PMID:23741295

  17. MHD Forced Convective Laminar Boundary Layer Flow from a Convectively Heated Moving Vertical Plate with Radiation and Transpiration Effect

    PubMed Central

    Uddin, Md. Jashim; Khan, Waqar A.; Ismail, A. I. Md.

    2013-01-01

    A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to whilst the magnetic field and mass transfer velocity are taken to be proportional to where is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory. PMID:23741295

  18. Unsteady Boundary Layer Flow and Heat Transfer of a Casson Fluid past an Oscillating Vertical Plate with Newtonian Heating

    PubMed Central

    Hussanan, Abid; Zuki Salleh, Mohd; Tahar, Razman Mat; Khan, Ilyas

    2014-01-01

    In this paper, the heat transfer effect on the unsteady boundary layer flow of a Casson fluid past an infinite oscillating vertical plate with Newtonian heating is investigated. The governing equations are transformed to a systems of linear partial differential equations using appropriate non-dimensional variables. The resulting equations are solved analytically by using the Laplace transform method and the expressions for velocity and temperature are obtained. They satisfy all imposed initial and boundary conditions and reduce to some well-known solutions for Newtonian fluids. Numerical results for velocity, temperature, skin friction and Nusselt number are shown in various graphs and discussed for embedded flow parameters. It is found that velocity decreases as Casson parameters increases and thermal boundary layer thickness increases with increasing Newtonian heating parameter. PMID:25302782

  19. The turbulent boundary layer on a porous plate: An experimental study of the heat transfer behavior with adverse pressure gradients

    NASA Technical Reports Server (NTRS)

    Blackwell, B. F.; Kays, W. M.; Moffat, R. J.

    1972-01-01

    An experimental investigation of the heat transfer behavior of the near equilibrium transpired turbulent boundary layer with adverse pressure gradient has been carried out. Stanton numbers were measured by an energy balance on electrically heated plates that form the bottom wall of the wind tunnel. Two adverse pressure gradients were studied. Two types of transpiration boundary conditions were investigated. The concept of an equilibrium thermal boundary layer was introduced. It was found that Stanton number as a function of enthalpy thickness Reynolds number is essentially unaffected by adverse pressure gradient with no transpiration. Shear stress, heat flux, and turbulent Prandtl number profiles were computed from mean temperature and velocity profiles. It was concluded that the turbulent Prandtl number is greater than unity in near the wall and decreases continuously to approximately 0.5 at the free stream.

  20. Seismo-electromagnetic phenomena in the western part of the Eurasia-Nubia plate boundary

    NASA Astrophysics Data System (ADS)

    Gonçalves da Silva, Hugo; Bezzeghoud, Mourad; Biagi, Pier; Namorado Rosa, Rui; Salgueiro da Silva, Manuel; Caldeira, Bento; Heitor Reis, Artur; Borges, José Fernando; Tlemçani, Mouhaydine; Manso, Marco

    2010-05-01

    This paper presents a future research plan that aims to monitor Seismo-electromagnetic (SEM) phenomena in the western part of the Eurasia-Nubia plate boundary (WENP). This region has a significant tectonic activity [1] combined with relatively low electromagnetic noise levels and for that reason presents the possibility to perform high quality SEM measurements. Further, it is known that low-frequency [ultra (ULF), very (VLF), and low-frequencies (LF)] electromagnetic (EM) waves produce more convincing earthquake precursors (compared to higher frequencies) because of less contamination, large skin depth, and low attenuation [2]. Thus, two SEM effects will be considered: ULF electromagnetic field emissions [3], and VLF/LF radio broadcastings [4]. With respect to the ULF measurements, as a start, three ULF sensors are planned to be installed in the South of Iberian Peninsula supported by the existing networks of seismic research stations. Subsequent development of this initial plan could result in the implementation of a lager ULF monitoring network not only in the Iberian Peninsula, but also in the rest of Europe. Possible integration in the SEGMA array is now under consideration. Another perspective is to use a portable station to track seismic events. Regarding the VLF/LF radio broadcastings, a receiver is planned to be mounted in University of Évora. Radio signals from up to 10 transmitters (in these bands) of interest to study the seismic activity in the WENP region will be monitored. Actually, the radio path from the transmitter to the receiver should cross the epicentral area, therefore two possible transmitters are the ones installed in Monaco (France) and Sicily (Italy). Furthermore, the system will integrate the INFREP network and in this context it will not be restricted to WENP region. With the development of these research plans we aim to collect novel SEM data emerging from the seismic activity in the WENP region. We expect to address the time

  1. The EarthScope Plate Boundary Observatory Response to the 2006 Augustine Alaskan Volcanic Eruption

    NASA Astrophysics Data System (ADS)

    Pauk, B.; Feaux, K.; Jackson, M.; Friesen, B.; Enders, M.; Baldwin, A.; Fournier, K.; Marzulla, A.

    2006-12-01

    During September of 2006, UNAVCO installed five permanent Plate Boundary Observatory (PBO) GPS stations on Augustine Volcano, in the lower Cook Inlet of Alaska. The installations were done at the request of the PBO Magmatic Systems committee in response to the January 11, 2006 eruption of Augustine Volcano. Prior to the eruption, PBO installed five permanent GPS stations on Augustine in 2004. The five existing stations on the volcano were instrumental in detecting precursory deformation of the volcano's flanks prior to and during the eruption. During the course of the first explosive phase of the eruption, two existing PBO stations, AV03 and AV05 were subsequently destroyed by separate pyroclastic flows. The existing station AV04 was heavily damaged by a separate pyroclastic flow during the continuous phase of the eruption and was repaired during September as well. Existing stations AV01 and AV02 were not affected or damaged by the eruption and remained operating during the entire eruptive phase and subsequent debris flows. All five new stations, and maintenance on the three remaining existing stations, were completed by PBO field crews with helicopter support provided by Maritime Helicopters. Lack of roads and drivable trails on the remote volcanic island required that all equipment be transported to each site from an established base camp by slinging gear beneath the helicopter and internal loads. Each new and existing station installed on the volcano consists of a standard short braced GPS monument, two solar panels mounted to an inclined structure, and a six foot high Plaschem enclosure with two solar panels mounted to one of the inclined sides. Each Plaschem houses 24 12 volt batteries that power a Trimble NetRS GPS receiver and one or two Intuicom radios and are recharged by the solar panels. Data from each GPS receiver is telemetered directly or through a repeater radio to a base station located in the town of Homer that transmits the data over the internet

  2. The Plate Boundary Observatory Borehole Strainmeter Program: Overview of Data Analysis and Products

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

    The PBO borehole strainmeter network is now the largest in the US with 19 strainmeters installed along the Western US Plate Boundary: 14 in the Pacific North West and 5 in Anza, Southern California. With five drilling crews operating though October 2006 the network should grow to 28 strainmeters by December 2006. The areas include Parkfield and Mt St. Helens, PBO's first strainmeter installation in a volcanic region. PBO strainmeter sites are multi-instrumented. Seismic, pore pressure, atmospheric pressure, rainfall and temperature data are measured at almost all sites. Tiltmeters will also be installed at some sites. The strainmeters record at 20-sps, 1-sps and 10-minute interval and are downloaded hourly. The 1-sps data are sent to the NCEDC and IRIS DMC within a few minutes of being retrieved from the strainmeter. The data are archived in SEED format and can be viewed and analyzed with any SEED handling software. PBO's Borehole Strainmeter Analysis Center (BSMAC) in Socorro, NM, produces processed strain data every 10 to 14 days. The data are stored in XML format giving the user the option to use PBO edits or to work with unedited data. The XML file contains time series corrections for the atmospheric pressure, the Earth tides and borehole effects. Every 3 months the data are reviewed and the borehole trends and tidal signal are re- estimated to form the best possible processed data set. PBO reviewed the quality of the data collected by the first 8 strainmeters in a workshop in January 2006. The group discussed coring, examined the borehole trends, tidal signal, and a PSD analysis of data from each strainmeter. A second workshop, focusing on data analysis and in-situ calibration, will take place in October 2006. The UNAVCO strainmeter web page (http://pboweb.unavco.org) provides links to the raw and processed data and is a source for information on data formats, links to software and instrument documentation. An XML log file for each strainmeter provides a

  3. Neogene north American-Caribbean plate boundary across Northern Central America: Offset along the polochic fault

    NASA Astrophysics Data System (ADS)

    Burkart, Burke

    1983-12-01

    The Polochic fault was a segment of the North American-Caribbean plate boundary across Central America in the Neogene. Its 130 km of left slip was previously determined by matching structures and stratigraphie outcrop patterns of northwest and central Guatemala across the fault. Additional support for the model and the youthfulness of the recorded offset comes from an essentially perfect match of major geomorphic features across the fault. A reconstruction process which eliminates 123 km of left slip brings together rivers and drainage divides that existed before the Polochic became active. With the reconstruction carried across the isthmus on an east-west fault the regional structural geology assumes the coherent pattern of a continuous orogenic belt whose geometry is compatible with the model of collisional tectonics centered on the Motagua "suture zone". Confined within this belt, narrowed to some 60 km by the reconstruction, lie the major Laramide thrusts, folds and tectonically emplaced serpentinites of Guatemala. Crystalline rocks of Guatemala re-join the Chiapas Massif and Paleozoic sedimentary rocks, exposed in the core of an almost-continuous anticlinorium, extend from southern Chiapas to Lake Izabal. The Polochic does not bend in eastern Guatemala but continues eastward to the Motagua fault where it dies. Westward drift of the northern block resulted in rifting which extended from eastern Guatemala into the Caribbean along the Cayman trough. The Honduras depression may represent an element of a triple junction along with the Polochic and Izabal-Cayman rift. The Polochic continues westward into the Pacific Ocean and offsets the Middle America trench. The Polochic has offset the Miocene volcanic belt of northern Central America, confirming the previous estimate of a Neogene time of movement. About 300 km of relative east-west Neogene displacement has been recorded on the Mid-Cayman rise, only 130 km of which can be accounted for across the Polochic. It is

  4. The EarthScope Plate Boundary Observatory (PBO) High-rate Real-time Cascadia network

    NASA Astrophysics Data System (ADS)

    Austin, K. E.; Borsa, A. A.; Feaux, K.; Jackson, M. E.; Williams, T. B.

    2010-12-01

    As part of the 2009 American Recovery and Reinvestment Act (ARRA), NSF is investing in onshore-offshore instrumentation to support studies of the Cascadia margin. EarthScope's Plate Boundary Observatory (PBO) is upgrading 232 of its GPS stations in the Pacific Northwest to high-rate sampling and real-time telemetry and providing streaming data from this network to the public for scientific research, education, and hazard monitoring. This effort expands UNAVCO’s real-time GPS operations beyond its original pilot project of 100 stations to include a comprehensive regional network that spans the states of Washington and Oregon, and extends south into California to the Mendocino triple junction. By blanketing the Pacific Northwest with real-time GPS coverage, the NSF is hoping to create a natural laboratory in an area of great scientific interest and high geophysical hazard in order to spur new volcano and earthquake research opportunities. Streaming high-rate data in real-time will enable researchers to routinely analyze for strong ground motion monitoring and earthquake hazards mitigation. At stations with collocated meteorological instruments, met data is being streamed as well, opening the possibility for combined GPS/met processing in real time by the atmospheric community. Funding for field upgrades provide for the installation of 3G capable modems or high speed data radios, as well as for updating the power at each location. Finally, the new funding also expands opportunities for research using high-rate GPS data from a large-aperture network, since 1 Hz streams will be permanently archived and freely available via FTP. PBO deployed new data distribution software in June 2010, to which stations being added soon after field upgrades have been completed. PBO is currently providing 1Hz-streaming data in BINEX, RTCM2.3 and RTCM 3.0 formats via the NTrip protocol, from servers located at UNAVCO headquarters in Boulder, CO. Data latency varies according to the

  5. 2011 Operations and Maintenance Activities in the East Region of UNAVCO's Plate Boundary Observatory

    NASA Astrophysics Data System (ADS)

    Dittmann, T.; Feaux, K.; Kasmer, D.; Jenkins, F.; Mencin, D.

    2011-12-01

    2011 marked Year 3 of Operations and Maintenance of the Plate Boundary Observatory (PBO). In the East Region of PBO, it was a year characterized by several major projects as well as scheduled ongoing maintenance activities. The most significant major project was a USGS/ARRA funded communications upgrade in Yellowstone National Park. This upgrade consisted of bringing 8 existing PBO stations within the Yellowstone volcanic region to near real-time communications. This work will be completed on time and in collaboration with the National Park Service. The upgrade promises to provide much faster latency for invaluable data being recorded for one of the most geodetically critical regions of the current PBO network. Another significant ongoing project in the East Region has been supporting the community that continues to use PBO data. In particular, support of Kristine Larson (Univ of CO) both in installing webcams at PBO sites for monitoring snow depth as well as supporting vegetative surveys at current PBO sites. Similarly, the East Region responded promptly to the community with requests for data quality issues that are station hardware related, including replacing GPS antennae and receivers. With regards to ongoing operations and maintenance projects, reasons for site visits in 2011 were dominated by two significant situations: battery replacement and CDMA modem swaps. 83 site visits were required as part of the Operations and Maintenance strategic battery plan of 5 year battery replacements. This proved to be a considerable challenge due to the scale and geography of the scheduled replacements- the sites were spread throughout the entire network, east to west and north to south. 20 station visits were required due to a Verizon upgrade of the older Alltel network purchased by Verizon. These stations are predominantly in the Rocky Mountain region, but often times had limited access to due weather. Overall, despite record snowfalls throughout the west, state of health

  6. The EarthScope Plate Boundary Observatory Alaska Region: Highlights from the 2012 Summer Field Season

    NASA Astrophysics Data System (ADS)

    Enders, M.; Bierma, R. M.; Boyce, E. S.; Willoughby, H.; Fend, M.; Feaux, K.

    2012-12-01

    UNAVCO has now completed its fourth year of operation and maintenance of the 138 continuous GPS stations, 12 tiltmeters and 31 data communications relays that comprise the Alaska region of the EarthScope Plate Boundary Observatory (PBO). The successful operation of the autonomous GPS and tiltmeter network in Alaska continues to be a challenge, because of logistics, weather, and other difficulties related to working in Alaska. PBO engineers continue to work on network enhancements to make the stations more robust, while improving overall data quality and station uptime to better serve the EarthScope science community. In the summer of 2012, PBO engineers completed maintenance activities in Alaska, which resulted in a 95% operational status for the Alaska network within PBO. PBO engineers completed a total of 87 maintenance visits in the summer of FY2012, including 62 routine maintenance and 25 unscheduled maintenance visits to GPS and data communications stations. We present a number of highlights and accomplishments from the PBO 2012 summer field season in Alaska, for example the deployment of a newly designed methanol fuel cell at AV35, a critical station that serves as the main repeater for the real time network on Unimak Island. In addition, PBO engineers also completed the installation of three Inmarsat BGAN terminals for data telemetry following successful testing at AC60 Shemya. Lastly, PBO engineers completed scheduled battery replacements at most of the PBO stations on Unimak Island, in collaboration with the USGS/Alaska Volcano Observatory. In addition to routine maintenance and planned station improvements to sites in Alaska, numerous critical repairs were made at stations on Unimak Island and elsewhere to ensure that the PBO network continues to function well and continues to meet the requirements stipulated by the NSF. We also present some of the station failures unique to Alaska, which we encountered during the course of the 2012 field season, as well

  7. The Earthscope Plate Boundary Observatory Alaska Region an Overview of Network Operation, Maintenance and Improvement

    NASA Astrophysics Data System (ADS)

    Enders, M.; Boyce, E. S.; Bierma, R.; Walker, K.; Feaux, K.

    2011-12-01

    UNAVCO has now completed its third year of operation of the 138 continuous GPS stations, 12 tiltmeters and 31 communications relays that comprise the Alaska Region of the Earthscope Plate Boundary Observatory. Working in Alaska has been challenging due to the extreme environmental conditions encountered and logistics difficulties. Despite these challenges we have been able to complete each summer field season with network operation at 95% or better. Throughout the last three years we have analyzed both our successes and failures to improve the quality of our network and better serve the scientific community. Additionally, we continue to evaluate and deploy new technologies to improve station reliability and add to the data set available from our stations. 2011 was a busy year for the Alaska engineering team and some highlights from last year's maintenance season include the following. This spring we completed testing and deployment of the first Inmarsat BGAN satellite terminal for data telemetry at AC60 Shemya Island. Shemya Island is at the far western end of the Aleutian Islands and is one of the most remote and difficult to access stations in the PBO AK network. Until the installation of the BGAN, this station was offline with no data telemetry for almost one year. Since the installation of the BGAN in early April 2011 dataflow has been uninterrupted. This year we also completed the first deployments of Stardot NetCamSC webcams in the PBO Network. Currently, these are installed and operational at six GPS stations in Alaska, with plans to install several more next season in Alaska. Images from these cameras can be found at the station homepages linked to from the UNAVCO website. In addition to the hard work put in by PBO engineers this year, it is important that we recognize the contributions of our partners. In particular the Alaska Volcano Observatory, the Alaska Earthquake Information Center and others who have provided us with valuable engineering assistance

  8. Update on Plate Boundary Observatory (PBO) Activities in the PNW Region

    NASA Astrophysics Data System (ADS)

    Hafner, K.

    2005-12-01

    As of September 2005 The Plate Boundary Observatory (PBO), part of the larger NSF-funded EarthScope project, is completing year 2 in the installation phase of 875 continuously operating GPS instruments in the Western United States. The Pacific Northwest (PNW) region will install 149 continuous GPS stations by the end of 2008. These sites are distributed along the fore and back-arc of the Cascadia Subduction Zone and at Mt. St. Helens. At the end of year 2, the PNW Region of PBO reached its year two installation goal of 41 GPS stations. The scientific emphasis priority during year 2 was to capture Episodic Tremor And Slip (ETS) on the Cascadia Subduction Zone by installing GPS sites stations in southern Oregon, on the Olympic peninsula (where four strainmeters were also installed) and on Mt. St. Helens. Work on Mt. St. Helens volcano included the installation of five stations in October 2004. Data analyses showed that one of the PBO sites located high on the SE flank of the volcano moved 4 cm SE between mid-November 2004 and January 2005. This was most likely due to growth of the new lava dome against the SE crater wall. As a result of this activity, the PBO obtained two additional permits from the USFS, and these sites were installed at the beginning of February, 2005. PBO has continued to work with the USFS to complete the permitting process for nine more GPS locations on the flanks of the volcano. Due to required cultural and botanical surveys, these permits are not expected to be approved until at least June of 2006. The pace of installations will increase during year three of the project where scientific priortity will shift to installing stations in southern Oregon and the backarc/Basin and Range transition zone. For the PNW region, this translates into approximately 4 new GPS installations per month. In addition to continued construction, activities will focus on completing reconnaissance and permit submittal activities for all sites proposed to be located on

  9. Plate Boundary Observatory Southwest Region Network Operations, Expansion and Communications Hardening

    NASA Astrophysics Data System (ADS)

    Mann, D.; Walls, C. P.; Basset, A.; Turner, R.; Lawrence, S.; Feaux, K.; Mattioli, G. S.

    2014-12-01

    The Southwest Region of the Plate Boundary Observatory manages 480 continuously operating GPS stations located principally along the transform system of the San Andreas fault, Eastern California Shear Zone and the northern Baja peninsula. In the past year, network uptime averaged 98% with greater than 99% data acquisition. In an effort to modernize the network, we have started to replace Trimble NETRS receivers with GNSS capable NETR9 receivers. Currently, we have 431 NetRS receivers deployed in the region, and 48 NetR9 receivers. In addition, 82 stations (17%) stream 1 Hz data over the VRS3Net typically with <0.5 second latency and an average completeness of >92%. Based on their typical data download rates, approximately 252 (53%) of all stations are capable of streaming 1 Hz, but have not yet been added to the real time network because of lack of resources. In the immediate aftermath of the M8.2 Chile earthquake in April 2014, high rate data downloads from the entire SW network had a success rate of 95% and 71% for 1 Hz and 5 Hz data downloads respectively. We have continued to upgrade critical radio networks, including the San Francisco Bay Area, Anza Borrego, and Santa Barbara networks. These efforts are ongoing, but they have already significantly improved data download rates and dependability. We are also converting cell modem to radio communications whenever possible for increased reliability and cost savings. In December 2013 the 13-station Edison network expansion was completed through cost recovery contracts. These stations span coastal southern California in Orange, San Diego and Los Angeles counties including a hybrid site on the Elly oil platform. The primary purpose of the stations is to aid in the seismic source characterization of the San Onofre Nuclear Generating Station and assess the strain field associated with the Oceanside Blind Thrust and Newport Inglewood fault. The new stations fill a gap between SCIGN and PBO. Three sites have WXT520

  10. The Plate Boundary Observatory: Current status and plans for the next five years

    NASA Astrophysics Data System (ADS)

    Mattioli, G. S.; Feaux, K.; Meertens, C. M.; Mencin, D.; Miller, M.

    2013-12-01

    UNAVCO currently operates and maintains the NSF-funded Plate Boundary Observatory (PBO), which is the geodetic facility of EarthScope. PBO was designed and built from 2003 to 2008 with $100M investment from the NSF Major Research Equipment and Facilities Construction (MREFC) Program. UNAVCO operated and maintained PBO under a Cooperative Agreement (CA) with NSF from 2008 to 2013 and will continue PBO O&M for the next five years as part of the new Geodesy Advancing Geosciences and EarthScope (GAGE) Facility. PBO is largest continuous GPS and borehole geophysical network in the Americas, with 1100 continuous Global Positioning System (cGPS) sites, including several with multiple monuments, 79 boreholes, with 75 tensor strainmeters, 78 short-period, 3-component seismometers, and pore pressure sensors at 23 sites. PBO also includes 26 tiltmeters deployed at volcanoes in Alaska, Mt St Helens, and Yellowstone caldera and 6 long-baseline laser strainmeters. Surface meteorological sensors are collocated at 154 GPS sites. UNAVCO provides high-rate (1 Hz), low-latency (<1 s) GPS data streams (RT-GPS) from 382 stations in PBO. UNAVCO has delivered over 62 Tb of geodetic data to the EarthScope community since its PBO's inception in 2004. Over the past year, data return for the cGPS component of PBO is 98%, well above the data return metric of 85% set by the NSF, a result of efforts to upgrade power systems and communications infrastructure. In addition, PBO has set the standard for the design, construction, and operation of other multi-hazard networks across the Americas, including COCONet in the Caribbean region and TLALOCNet in Mexico. Funding to support ongoing PBO O&M has declined from FY2012 CA levels under the new GAGE Facility. The implications for data return and data quality metrics as well as replacement of aging PBO GPS instruments with GNSS-compatible systems are as yet unknown. A process to assess the cost of specific PBO components, data rates, enhanced

  11. Active Pacific North America Plate boundary tectonics as evidenced by seismicity in the oceanic lithosphere offshore Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Hauksson, Egill; Kanamori, Hiroo; Stock, Joann; Cormier, Marie-Helene; Legg, Mark

    2014-03-01

    Pacific Ocean crust west of southwest North America was formed by Cenozoic seafloor spreading between the large Pacific Plate and smaller microplates. The eastern limit of this seafloor, the continent-ocean boundary, is the fossil trench along which the microplates subducted and were mostly destroyed in Miocene time. The Pacific-North America Plate boundary motion today is concentrated on continental fault systems well to the east, and this region of oceanic crust is generally thought to be within the rigid Pacific Plate. Yet, the 2012 December 14 Mw 6.3 earthquake that occurred about 275 km west of Ensenada, Baja California, Mexico, is evidence for continued tectonism in this oceanic part of the Pacific Plate. The preferred main shock centroid depth of 20 km was located close to the bottom of the seismogenic thickness of the young oceanic lithosphere. The focal mechanism, derived from both teleseismic P-wave inversion and W-phase analysis of the main shock waveforms, and the 12 aftershocks of M ˜3-4 are consistent with normal faulting on northeast striking nodal planes, which align with surface mapped extensional tectonic trends such as volcanic features in the region. Previous Global Positioning System (GPS) measurements on offshore islands in the California Continental Borderland had detected some distributed Pacific and North America relative plate motion strain that could extend into the epicentral region. The release of this lithospheric strain along existing zones of weakness is a more likely cause of this seismicity than current thermal contraction of the oceanic lithosphere or volcanism. The main shock caused weak to moderate ground shaking in the coastal zones of southern California, USA, and Baja California, Mexico, but the tsunami was negligible.

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

    NASA Technical Reports Server (NTRS)

    Ward, Steven N.

    1988-01-01

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

  13. Free Vibration Analysis of Patch Repaired Plates with a Through Crack by p-Convergent Layerwise Element

    PubMed Central

    Ahn, Jae S.; Yang, Seung H.; Woo, Kwang S.

    2014-01-01

    The high-order layerwise element models have been used for damaged plates and shells in the presence of singularities such as crack, cutout, and delamination. In this study, the extension of a proposed finite element model has been tested for free vibration analysis of composite laminated systems. For the elements, three-dimensional displacement fields can be captured by layer-by-layer representation. For the elements, higher-order shape functions are derived by combination of one- and two-dimensional shape functions based on higher-order Lobatto shape functions, not using pure higher-order three-dimensional shape functions. The present model can relieve difficulty of aspect ratios in modeling very thin thickness of bonding layer. For verification of the model, natural frequencies and corresponding mode shapes are calculated and then compared with reference values for uncracked and cracked plates. Also, the vibration characteristics of one-sided patch repaired plates with a through internal crack are investigated with respect to variation of crack length, size and thickness of patch, and shear modulus of adhesive, respectively. PMID:25215321

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  15. Consideration of SH-wave fundamental modes in piezoelectromagnetic plate: electrically open and magnetically open boundary conditions

    NASA Astrophysics Data System (ADS)

    Zakharenko, A. A.

    2013-11-01

    This report studies the dispersive wave propagation in the transversely isotropic (6 mm) piezoelectromagnetic (PEM) plate when the mechanical, electrical, and magnetic boundary conditions for both the upper and lower free surfaces of the plate are as follows: the mechanically free, electrically open, and magnetically open surfaces. This study follows some original results obtained in book. The fundamental modes' dispersion relations are graphically shown for the following well-known PEM composite materials: BaTiO3-CoFe2O4 and PZT-5H-Terfenol-D. It is natural that for large values of the nondimensional parameter kd (k is the wave number and d is the plate half-thickness), the velocities of both the fundamental modes approach the surface shear-horizontal wave called the piezomagnetic exchange surface Melkumyan wave. It is well known that plate waves are usually utilized in the nondestructive testing and evaluation, for instance, in the airspace industry. Also, PEM materials are used as smart ones in various technical devices such as dispersive wave delay lines, (biochemi)sensors, lab-on-a-chip, etc.

  16. Effects of thermal radiation and viscous dissipation on boundary layer flow of nanofluids over a permeable moving flat plate

    NASA Astrophysics Data System (ADS)

    Motsumi, T. G.; Makinde, O. D.

    2012-10-01

    The effects of suction, viscous dissipation, thermal radiation and thermal diffusion are numerically studied on a boundary layer flow of nanofluids over a moving flat plate. The partial differential equations governing the motion are transformed into ordinary differential equations using similarity solutions, and are solved using the Runge-Kutta-Fehlberg method with the shooting technique. The effects of nanoparticle volume fraction, the type of nanoparticles, the radiation parameter, the Brinkman number, the suction/injection parameter and the relative motion of the plate on the nanofluids velocity, temperature, skin friction and heat transfer characteristics are graphically presented and then discussed quantitatively. A comparative study between the previously published and the present results in a limiting sense reveals excellent agreement between them.

  17. Boundary layer flow and heat transfer on a moving plate in a copper-water nanofluid using Buongiorno model

    NASA Astrophysics Data System (ADS)

    Bakar, Nor Ashikin Abu; Bachok, Norfifah; Arifin, Norihan Md.

    2016-06-01

    The study of the steady two dimensional boundary layer flow of a copper (Cu)-water nanofluid on a moving plate is investigated. The assumption is the plate moves in the same or opposite direction to the free stream. The nonlinear partial differential equations are transformed into nonlinear ordinary differential equations using a similarity variables,then a shooting technique is used to solved it numerically. The numerical results for skin friction coefficient, the local Nusselt number, the local Sherwood number as well as the velocity, temperature and concentration profiles are obtained. The effect of nanoparticle volume fraction, Brownian motion and thermophoresis parameters on heat transfer are examined. The results show that the local Nusselt number and the local Sherwood number increase with increasing in the Brownian motion parameter Nb and thermophoresis parameter Nt.

  18. What can we Learn From Small Non-Recoverable Strains at Plate Boundaries?

    NASA Astrophysics Data System (ADS)

    Lewis, J. C.; Pluhar, C. J.

    2003-12-01

    Background seismicity carries often overlooked information about how the crust responds to plate motions. Integrating focal mechanisms for background seismicity with (1) geologic observations, and (2) geodetic constraints, is critical to establishing a better understanding of both the rock record and contemporary deformation. Treating the crust as a micropolar continuum it is possible to constrain not only the orientations and relative magnitudes of the principal strains but also the vorticity of crustal blocks with respect to the large-scale continuum. We show the utility of this approach with examples from the Cascadia margin and the Coso Range (within the Eastern California shear zone). In the upper crust of the Cascadia margin, seismogenic strain appears to be dominated by accommodation of motion of the Oregon forearc block. This suggests that the shallow crust is responding to long-term motion of the Oregon forearc rather than the interseismic locking of the subduction megathrust. In the area west of Mt. Rainier, this response is marked by non-zero relative vorticity in a regime of N-S shortening and crustal thickening. To date, geologic studies necessary to evaluate the significance of this vorticity have not been completed. In contrast within the Coso Range of California, seismogenic strain at Wild Horse Mesa indicates a component of relative vorticity that is broadly consistent with paleomagnetically constrained finite rotations of the ca. 3 Ma lava flows that compose the mesa. This area is centered at a right-releasing step in the Eastern California shear zone and thus is experiencing active transtension. Stratigraphic constraints have been used to suggest that significant dextral shearing in this region initiated ca. 3.5-2 Ma. The seismogenic response to transtension is depth-dependent plane strain with crustal thinning above 5 km and horizontal dextral shearing from 5-8 km. Both structural levels indicate subhorizontal E-W maximum stretching. Relative

  19. Crustal structure of a transform plate boundary: San Francisco Bay and the central California continental margin

    USGS Publications Warehouse

    Holbrook, W.S.; Brocher, T.M.; ten Brink, U.S.; Hole, J.A.

    1996-01-01

    lower-crustal velocity of Pacific oceanic crust suggest that it was underplated by magmatism associated with the nearby Pioneer seamount. The Salinian Block consists of a 15-km-thick layer of velocity 6.0-6.2 km/s overlying a 5-km-thick, high-velocity (7.0 km/s) lower crust that may be oceanic crust, Cretaceous arc-derived lower crust, or a magmatically underplated layer. The strong structural variability across the margin attests to the activity of strike-slip faulting prior to and during development of the transcurrent Pacific/North American plate boundary around 29 Ma. Copyright 1996 by the American Geophysical Union.

  20. EarthScope's Plate Boundary Observatory as the Mother of Invention (Invited)

    NASA Astrophysics Data System (ADS)

    Blewitt, G.; Hammond, W. C.; Kreemer, C.

    2013-12-01

    The Plate Boundary Observatory (PBO) component of EarthScope includes a network of over 1,100 permanent, continuously operating GPS stations. After 5 years of site selection, permitting, and construction, the network was completed in 2008. Having such an unprecedented number of high quality stations in western North America has enabled us to image geology in action, as it happens, such as contemporary uplift of the Sierra Nevada, and block rotation in the Walker Lane. Yet, when PBO was in its planning stages, questions were raised as to whether GPS analysis could keep up with the flood of data, while producing results with the highest achievable accuracy. The general consensus was that the challenge would be met by a combination of innovative data processing methods together with the inevitable progress in computer speed and capacity. Various innovations made by the geodetic community over the last decade have enabled massive operational processing of GPS data with high accuracy. For example, now in 2013, the Nevada Geodetic Laboratory operationally produces position time series and quality assurance data from all ~7,000 GPS geodetic stations in the world that make data publicly available. Of these stations, 4,000 have daily time series updated the next day, and 2,000 have 5-minute time series updated within 1-2 hours of real time. The RMS precision of daily positions for well-sited stations are at the level of 1-2 mm horizontal, and 3-6 mm vertical in the International Terrestrial Reference Frame (ITRF). For 5-minute positions, the precision is at the level of 6-12 mm horizontal, and 15-30 mm vertical. Here we review some of the innovations that have made all of this possible, which were in part driven by challenges presented by EarthScope. First of all, at the data processing level, much creative effort went into making computer processing time scale linearly with the number of GPS stations. The Precise Point Positioning (PPP) technique invented in 1997 has been

  1. Crustal structure of a transform plate boundary: San Francisco Bay and the central California continental margin

    NASA Astrophysics Data System (ADS)

    Holbrook, W. Steven; Brocher, Thomas M.; ten Brink, Uri S.; Hole, John A.

    1996-10-01

    lower-crustal velocity of Pacific oceanic crust suggest that it was underplated by magmatism associated with the nearby Pioneer seamount. The Salinian Block consists of a 15-km-thick layer of velocity 6.0-6.2 km/s overlying a 5-km-thick, high-velocity (7.0 km/s) lower crust that may be oceanic crust, Cretaceous arc-derived lower crust, or a magmatically underplated layer. The strong structural variability across the margin attests to the activity of strike-slip faulting prior to and during development of the transcurrent Pacific/North American plate boundary around 29 Ma.

  2. EarthScope: Cyberinfrastructure to access Plate Boundary Observatory data products and services

    NASA Astrophysics Data System (ADS)

    Meertens, C. M.; Mattioli, G. S.; Miller, M.; Boler, F. M.; Crosby, C. J.; Mencin, D.; Phillips, D. A.; Snett, L.

    2013-12-01

    The wealth of data from geodetic observing systems, especially the Plate Boundary Observatory (PBO), presents major data management challenges. The challenges are driven by ingenious new uses of Global Positioning System (GPS) data, demands for higher-rate, lower latency data, the need for continued access and long term preservation of archival data, the expansion of data users into other science, engineering and commercial arenas, and the growth of enhanced products that expand the utility of the data. To meet these challenges, UNAVCO has established a comprehensive suite of data services encompassing sensor network data operations, data product generation (through the activities of partners at Massachusetts Institute of Technology, Central Washington University, New Mexico Institute of Mining and Technology, and the University of California, San Diego - UCSD), data management, access and archiving, and advanced cyberinfrastructure. PBO sensor systems include 1,100 continuously operating GPS stations, 79 borehole geophysical sites (with a combination of strainmeters, tiltmeters, seismometers, pore pressure gauges, and meteorological sensors), and 6 long baseline strainmeters. Imaging data acquired for EarthScope include large volumes of satellite synthetic aperture radar (SAR) and airborne LiDAR data. Core data products such as daily GPS position time series and derived crustal motion velocities have been augmented with real-time data streams and positions calculated every second from 367 PBO stations. Higher rate (5 Hz) data files are available for applications such as GPS seismology. Efforts are underway with UCSD to integrate GPS and accelerometers at a subset of PBO sites to increase the reliability and capability of the observations. These observations have utility for research and hazards mitigation. Ingenious methods of GPS data analysis, developed by the University of Colorado and the University Corporation for Atmospheric Research, measure snow depth

  3. The Dauki Thrust Fault and the Shillong Anticline: An incipient plate boundary in NE India?

    NASA Astrophysics Data System (ADS)

    Ferguson, E. K.; Seeber, L.; Steckler, M. S.; Akhter, S. H.; Mondal, D.; Lenhart, A.

    2012-12-01

    The Shillong Massif is a regional contractional structure developing across the Assam sliver of the Indian plate near the Eastern Syntaxis between the Himalaya and Burma arcs. Faulting associated with the Shillong Massif is a major source of earthquake hazard. The massif is a composite basement-cored asymmetric anticline and is 100km wide, >350km long and 1.8km high. The high relief southern limb preserves a Cretaceous-Paleocene passive margin sequence despite extreme rainfall while the gentler northern limb is devoid of sedimentary cover. This asymmetry suggests southward growth of the structure. The Dauki fault along the south limb builds this relief. From the south-verging structure, we infer a regional deeply-rooted north-dipping blind thrust fault. It strikes E-W and obliquely intersects the NE-SW margin of India, thus displaying three segments: Western, within continental India; Central, along the former passive margin; and Eastern, overridden by the west-verging Burma accretion system. We present findings from recent geologic fieldwork on the western and central segments. The broadly warped erosional surface of the massif defines a single anticline in the central segment, east of the intersection with the hinge zone of the continental margin buried by the Ganges-Brahmaputra Delta. The south limb of the anticline forms a steep topographic front, but is even steeper structurally as defined by the Cretaceous-Eocene cover. Below it, Sylhet Trap Basalts intrude and cover Precambrian basement. Dikes, presumably parallel to the rifted margin, are also parallel to the front, suggesting thrust reactivation of rift-related faults. Less competent Neogene clastics are preserved only near the base of the mountain front. Drag folds in these rocks suggest north-vergence and a roof thrust above a blind thrust wedge floored by the Dauki thrust fault. West of the hinge zone, the contractional structure penetrates the Indian continent and bifurcates. After branching into the

  4. The EarthScope Plate Boundary Observatory Distributed Data Management System

    NASA Astrophysics Data System (ADS)

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

    2007-05-01

    EarthScope is an ambitious multi-year project funded by the United States National Science Foundation to explore the structure and dynamics of the North American continent using a wide range of geophysical methods. The Plate Boundary Observatory (PBO), being built by UNAVCO, is the geodetic component of EarthScope, and will comprise 880 continuous GPS stations, 103 borehole strainmeter stations, 28 tiltmeters, and five laser strainmeters; in addition, PBO will manage data for 209 existing GPS stations and 11 GPS stations installed by the USArray segment of EarthScope. As of February 2007, 561 of these stations have been installed. PBO data flow is managed from the PBO Boulder Network Operations Center (NOC), located at UNAVCO Headquarters. Automated systems at the NOC retrieve data from our stations at least daily, monitor the status of the network and alert operators to problems, and pass data on for analysis, archiving, and distribution. Real-time network status can be found at http:pboweb.unavco.org/soh_map. PBO's analysis centers generate high-quality derived data products from PBO raw data. Two centers, at Central Washington University and the New Mexico Institute of Mining and Technology, process raw GPS data to produce initial PBO GPS products including network solutions and station position time series, andthese products are combined by the Analysis Center Coordinator at MIT to produce the official PBO GPS products. Two analysis centers, at UNAVCO's Socorro office and the University of California, San Diego, process data from the PBO borehole and laser strainmeter networks and produce cleaned time series of shear, areal, and linear strain, Earth tides, pore fluid pressure, and other parameters. The UNAVCO Facility archives and distributes all PBO GPS data products and runs a secondary archive offsite; to date, these centers hold more than 2.5 TB of PBO products. The IRIS Data Management Center and Northern California Earthquake Data Center archive and

  5. Rhyolitic components of the Michipicoten greenstone belt, Ontario: Evidence for late Archaen intracontinental rifts or convergent plate margins in the Canadian Shield?

    NASA Technical Reports Server (NTRS)

    Sylvester, P. J.; Attoh, K.; Schulz, K. J.

    1986-01-01

    Rhyolitic rocks often are the dominant felsic end member of the biomodal volcanic suites that characterize many late Archean greenstone belts of the Canadian Shield. The rhyolites primarily are pyroclastic flows (ash flow tuffs) emplaced following plinian eruptions, although deposits formed by laval flows and phreatomagmatic eruptions also are presented. Based both on measured tectono-stratigraphic sections and provenance studies of greenstone belt sedimentary sequences, the rhyolites are believed to have been equal in abundance to associated basaltic rocks. In many recent discussions of the tectonic setting of late Archean Canadian greenstone belts, rhyolites have been interpreted as products of intracontinental rifting . A study of the tectono-stratigraphic relationships, rock associations and chemical characteristics of the particularly ell-exposed late Archean rhyolites of the Michipicoten greenstone belt, suggests that convergent plate margin models are more appropriate.

  6. The Caribbean-South American plate boundary at 65°W: Results from wide-angle seismic data

    NASA Astrophysics Data System (ADS)

    Bezada, M. J.; Magnani, M. B.; Zelt, C. A.; Schmitz, M.; Levander, A.

    2010-08-01

    We present the results of the analysis of new wide-angle seismic data across the Caribbean-South American plate boundary in eastern Venezuela at about 65°W. The ˜500 km long profile crosses the boundary in one of the few regions dominated by extensional structures, as most of the southeastern Caribbean margin is characterized by the presence of fold and thrust belts. A combination of first-arrival traveltime inversion and simultaneous inversion of PmP and Pn arrivals was used to develop a P wave velocity model of the crust and the uppermost mantle. At the main strike-slip fault system, we image the Cariaco Trough, a major pull-apart basin along the plate boundary. The crust under the Southern Caribbean Deformed Belt exhibits a thickness of ˜15 km, suggesting that the Caribbean Large Igneous Province extends to this part of the Caribbean plate. The velocity structures of basement highs and offshore sedimentary basins imaged by the profile are comparable to those of features found in other parts of the margin, suggesting similarities in their tectonic history. We do not image an abrupt change in Moho depth or velocity structure across the main strike-slip system, as has been observed elsewhere along the margin. It is possible that a terrane of Caribbean island arc origin was accreted to South America at this site and was subsequently bisected by the strike-slip fault system. The crust under the continental portion of the profile is thinner than observed elsewhere along the margin, possibly as a result of thinning during Jurassic rifting.

  7. Estimating Fault Slip Rates and Deformation at Complex Strike-Slip Plate Boundaries

    NASA Astrophysics Data System (ADS)

    Thatcher, Wayne; Murray-Moraleda, Jessica

    2010-05-01

    initiation date of offset of geomorphic markers by faulting can introduce uncertainties much larger than quoted random errors. Second: Are rate estimates obtained by more than one geodetic or geologic method? For example, agreement between GPS and InSAR slip rate estimates on the Altyn Tagh and Haiyuan faults of Tibet make the geodetic estimates more reliable. Similarly, dating of multiple offset markers of differing age across these faults supports the consistency of the geologic rate estimates. Third: Is proposed rate change mechanism consistent with examples of changes in style and rate of deformation preserved in the geologic record? For example, temporal evolution of the multi-stranded San Andreas system during the past 5-10 Ma (Powell & Weldon 1992; Graymer et al. 2002) indicates activation and deactivation of different faults within the system accompanied by consequent changes in fault slip rate and/or creation of new crustal blocks. Fourth: Is there a quantitative analysis of mechanism proposed to explain rate change? Candidate mechanisms meriting quantitative analysis include (1) changes in frictional resistance of faults and creation of new fractures due to progressive rotation of irregularly shaped blocks, (2) episodic subduction of buoyant lithosphere, and (3) changes in the plate geometry (and so the forces acting) at major continent/ocean plate boundaries (e.g. Late Cenozoic migration of Mendocino triple junction off California). In most parts of southern California—for example, north of the San Andreas Big Bend and SE of Los Angeles--our block geometry closely resembles that assumed in previous studies (McCaffrey 2005 JGR; Meade & Hager 2005 JGR; Becker et al. 2005 GJI). In these regions GPS slip rates can be reliably estimated and values for individual faults generally agree from one study to another and are also consistent with geologic estimates. However, there is no consensus on block geometry in the Transverse Ranges, Los Angeles Basin and Central

  8. Upper Plate Deformation in Response to Aseismic Ridge Subduction along a Convergent Margin - the Piano Player Model: Osa Peninsula, Costa Rica

    NASA Astrophysics Data System (ADS)

    Gardner, T. W.; Fisher, D. M.; Morell, K. D.; Cupper, M. L.

    2008-12-01

    The Osa Peninsula, an outer forearc high ~20 km inboard of the Middle America Trench, is deforming in response to short wavelength variations in the bathymetry on the subducting aseismic Cocos Ridge, an elongate region of thickened crust ( up to 40% thicker) created by motion of the Cocos plate across the Galapagos Hotspot. Plate convergence is nearly orthogonal to the trench at ~90 mm/yr and the plate interface occurs at a depth ~5 km under the peninsula. Relief on the Cocos Ridge locally exceeds 1 km with the dominant topography expressed as two nearly parallel, but locally offset ridges separated by an axial graben. The strike of these features is sub-parallel to the convergence vector. Modern topography of the Osa Peninsula, elevation of the basement rocks (Early to Middle Tertiary Osa Mélange), elevations of late Quaternary marine deposits, and distribution of late Quaternary deformation rates directly mirror the bathymetry on the Cocos Ridge just outboard of the MAT. New geologic mapping, radiometric dating and fission track analysis constrain distribution and rates of deformation on the Osa Peninsula. The Osa Peninsula is fragmented into a complex set of blocks that vary in size from several kms on a side to <10 kms on a side. These blocks, which closely match the size, distribution and shape of bathymetric features on the incoming Cocos Ridge, are bounded by trench parallel and trench perpendicular, high angle, normal and reverse faults that extend to the plate interface, allowing for grossly different deformation histories over short distances. Fission track analyses of 4 sandstone samples from the Osa Mélange suggest that the basement rocks reached maximum burial temperatures of 60-80 ° C indicating burial depths of ~3-4 kms assuming a reasonable geothermal gradient of ~20 °/km. This suggests a very thin margin wedge prior to late Neogene unroofing. Rates of late Quaternary deformation are constrained by over 30 radiocarbon and 5 Optically Stimulated

  9. Experimental study of skin friction drag reduction on superhydrophobic flat plates in high Reynolds number boundary layer flow

    NASA Astrophysics Data System (ADS)

    Aljallis, Elias; Sarshar, Mohammad Amin; Datla, Raju; Sikka, Vinod; Jones, Andrew; Choi, Chang-Hwan

    2013-02-01

    In this paper, we report the measurement of skin friction drag on superhydrophobic-coated flat plates in high Reynolds (Re) number boundary layer flows, using a high-speed towing tank system. Aluminum flat plates with a large area (4 feet × 2 feet, 3/8 in. thick) and sharpened leading/trailing edges (1 in. long) were prepared as a boundary layer flow model. Spray coating of hydrophobic nanoparticles was applied to make two different types of superhydrophobic coatings: one with low contact angle and high contact angle hysteresis, and the other with high contact angle and low contact angle hysteresis. Skin friction drag of the superhydrophobic plates was measured in the flow speed up to 30 ft/s to cover transition and turbulent flow regimes (105 < ReL < 107), and was compared to that of an uncoated bare aluminum plate. A significant drag reduction was observed on the superhydrophobic plate with high contact angle and low contact angle hysteresis up to ˜30% in transition regime (105 < ReL < 106), which is attributed to the shear-reducing air layer entrapped on the superhydrophobic surface. However, in fully turbulence regime (106 < ReL < 107), an increase of drag was observed, which is ascribed to the morphology of the surface air layer and its depletion by high shear flow. The texture of superhydrophobic coatings led to form a rugged morphology of the entrapped air layer, which would behave like microscale roughness to the liquid flow and offset the drag-reducing effects in the turbulent flow. Moreover, when the superhydrophobic coating became wet due to the removal of air by high shear at the boundary, it would amplify the surface roughness of solid wall and increase the drag in the turbulent flow. The results illustrate that drag reduction is not solely dependent on the superhydrophobicity of a surface (e.g., contact angle and air fraction), but the morphology and stability of the surface air layer are also critical for the effective drag reduction using

  10. 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, G.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.

  11. Coupled effects of director orientations and boundary conditions on light induced bending of monodomain nematic liquid crystalline polymer plates

    NASA Astrophysics Data System (ADS)

    You, Yue; Xu, Changwei; Ding, Shurong; Huo, Yongzhong

    2012-12-01

    A photo-chromic liquid crystal polymers (LCPs) is a smart material for large light-activated variation or bending to transfer luminous energy into mechanical energy. We study the light induced behavior by modeling planar and homeotropic nematic network polymer plates. We effectively illustrate some reported experimental outcomes and theoretically predict some possible bending patterns. This paper constructs an understanding between the bending behaviors and interactions among the alignments, aspect ratios and boundary conditions, etc. Our work provides information on optimizing light induced bending in the process of micro-opto-mechanical system (MOMS) design.

  12. Structure of the tsunamigenic plate boundary and low-frequency earthquakes in the southern Ryukyu Trench

    PubMed Central

    Arai, Ryuta; Takahashi, Tsutomu; Kodaira, Shuichi; Kaiho, Yuka; Nakanishi, Ayako; Fujie, Gou; Nakamura, Yasuyuki; Yamamoto, Yojiro; Ishihara, Yasushi; Miura, Seiichi; Kaneda, Yoshiyuki

    2016-01-01

    It has been recognized that even weakly coupled subduction zones may cause large interplate earthquakes leading to destructive tsunamis. The Ryukyu Trench is one of the best fields to study this phenomenon, since various slow earthquakes and tsunamis have occurred; yet the fault structure and seismic activity there are poorly constrained. Here we present seismological evidence from marine observation for megathrust faults and low-frequency earthquakes (LFEs). On the basis of passive observation we find LFEs occur at 15–18 km depths along the plate interface and their distribution seems to bridge the gap between the shallow tsunamigenic zone and the deep slow slip region. This suggests that the southern Ryukyu Trench is dominated by slow earthquakes at any depths and lacks a typical locked zone. The plate interface is overlaid by a low-velocity wedge and is accompanied by polarity reversals of seismic reflections, indicating fluids exist at various depths along the plate interface. PMID:27447546

  13. Structure of the tsunamigenic plate boundary and low-frequency earthquakes in the southern Ryukyu Trench.

    PubMed

    Arai, Ryuta; Takahashi, Tsutomu; Kodaira, Shuichi; Kaiho, Yuka; Nakanishi, Ayako; Fujie, Gou; Nakamura, Yasuyuki; Yamamoto, Yojiro; Ishihara, Yasushi; Miura, Seiichi; Kaneda, Yoshiyuki

    2016-01-01

    It has been recognized that even weakly coupled subduction zones may cause large interplate earthquakes leading to destructive tsunamis. The Ryukyu Trench is one of the best fields to study this phenomenon, since various slow earthquakes and tsunamis have occurred; yet the fault structure and seismic activity there are poorly constrained. Here we present seismological evidence from marine observation for megathrust faults and low-frequency earthquakes (LFEs). On the basis of passive observation we find LFEs occur at 15-18 km depths along the plate interface and their distribution seems to bridge the gap between the shallow tsunamigenic zone and the deep slow slip region. This suggests that the southern Ryukyu Trench is dominated by slow earthquakes at any depths and lacks a typical locked zone. The plate interface is overlaid by a low-velocity wedge and is accompanied by polarity reversals of seismic reflections, indicating fluids exist at various depths along the plate interface. PMID:27447546

  14. Structure of the tsunamigenic plate boundary and low-frequency earthquakes in the southern Ryukyu Trench

    NASA Astrophysics Data System (ADS)

    Arai, Ryuta; Takahashi, Tsutomu; Kodaira, Shuichi; Kaiho, Yuka; Nakanishi, Ayako; Fujie, Gou; Nakamura, Yasuyuki; Yamamoto, Yojiro; Ishihara, Yasushi; Miura, Seiichi; Kaneda, Yoshiyuki

    2016-07-01

    It has been recognized that even weakly coupled subduction zones may cause large interplate earthquakes leading to destructive tsunamis. The Ryukyu Trench is one of the best fields to study this phenomenon, since various slow earthquakes and tsunamis have occurred; yet the fault structure and seismic activity there are poorly constrained. Here we present seismological evidence from marine observation for megathrust faults and low-frequency earthquakes (LFEs). On the basis of passive observation we find LFEs occur at 15-18 km depths along the plate interface and their distribution seems to bridge the gap between the shallow tsunamigenic zone and the deep slow slip region. This suggests that the southern Ryukyu Trench is dominated by slow earthquakes at any depths and lacks a typical locked zone. The plate interface is overlaid by a low-velocity wedge and is accompanied by polarity reversals of seismic reflections, indicating fluids exist at various depths along the plate interface.

  15. Turbulent combined-convection boundary layer with aiding flows along a heated vertical flat plate at higher freestream velocity

    NASA Astrophysics Data System (ADS)

    Abedina, Mohammad Zoynal; Islam, Mohammed Moinul; Hanif, Md. Abu; Alam, Md. Jahangir

    2016-07-01

    A numerical investigation is performed in the turbulent combined-convection boundary layer with aiding flows in air along a heated vertical flat plate at a higher freestream velocity (Reδ0 = 600) by time-developing direct numerical simulation (DNS). At higher freestream velocity, the transition from laminar to turbulent delays for aiding flows and relatively a lower and higher heat transfer rates are observed, respectively, in the laminar and turbulent region compared to that of lower freestream velocity. The wall shear stresses are higher in the laminar region compared to that in the turbulent region, and at higher freestream velocity, the wall shear stress in the transition region shows a higher peak value. The intensity of velocity and temperature fluctuations for aiding flows with higher freestream velocity become appreciably lower than that for lower freestream velocity due to the laminarization of the boundary layer.

  16. Scalings for unsteady natural convection boundary layers on an evenly heated plate with time-dependent heating flux

    NASA Astrophysics Data System (ADS)

    Lin, Wenxian; Armfield, S. W.

    2013-12-01

    It is of fundamental significance, especially with regard to application, to fully understand the flow behavior of unsteady natural convection boundary layers on a vertical plate heated by a time-dependent heat flux. Such an understanding is currently scarce. In this paper, the scaling analysis by Lin et al. [Phys. Rev. E 79, 066313 (2009), 10.1103/PhysRevE.79.066313] using a simple three-region structure for the unsteady natural convection boundary layer of a homogeneous Newtonian fluid with Pr >1 under isothermal heating was substantially extended for the case when the heating is due to a time-varying sinusoidal heat flux. A series of scalings was developed for the thermal boundary thickness, the plate temperature, the viscous boundary thicknesses, and the maximum vertical velocity within the boundary layer, which are the major parameters representing the flow behavior, in terms of the governing parameters of the flow, i.e., the Rayleigh number Ra, the Prandtl number Pr, and the dimensionless natural frequency fn of the time-varying sinusoidal heat flux, at the start-up stage, at the transition time scale which represents the ending of the start-up stage and the beginning of the transitional stage of the boundary-layer development, and at the quasi-steady stage. These scalings were validated by comparison to 10 full numerical solutions of the governing equations with Ra, Pr, and fn in the ranges 106≤Ra≤109, 3≤Pr≤100, and 0.01≤fn≤0.1 and were shown in general to provide an accurate description of the flow at different development stages, except for high-Pr runs in which a further, although weak, Pr dependence is present, which cannot be accurately predicted by the current scaling analysis using the simple three-region structure, attributed to the non-boundary-layer nature of the velocity field with high-Pr fluids. Some scalings at the transition time scale and at the quasi-steady stage also produce noticeable deviations from the numerical results when

  17. Kinematics to dynamics in the New Zealand Plate boundary zone: implications for the strength of the lithosphere

    NASA Astrophysics Data System (ADS)

    Lamb, Simon

    2015-05-01

    New Zealand straddles the boundary between the Australian and Pacific Plate. Cenozoic relative plate motion has resulted in a complex pattern of faulting and block rotation in a zone of continental lithosphere up to 250 km wide. I investigate the implications of the short-term kinematics for the strength of the deforming lithosphere. I use a compilation of seismic reflection/refraction studies and high quality receiver function analyses to determine both the regional structure of the crust, which ranges from 20 to 50 km thick, and fields of buoyancy stress (or GPE per unit volume). Deformation over thousands of years is quantified in terms of velocity and strain rate fields, based on an inversion of neotectonic fault slip and palaeomagnetic data, in the context of the short-term relative plate motions. Forces on the subduction megathrust, as well as deviatoric stresses in the behind subduction region, are calculated from simple 2-D force balances across the Hikurangi Margin, given negligible deviatoric stresses at the along-strike transition between backarc extension and compression. Average megathrust shear stresses are in the range 6-15 MPa, and average lithospheric stresses <20 MPa in the overriding plate. The regional lithospheric strength of the plate boundary zone, assuming a viscous rheology (Newtonian or power law), is determined from an inversion of the field of gradients of buoyancy stress (averaged over either the top 25 km of the crust, or 100-km-thick lithosphere) and strain rate, using the thin sheet stress balance equations, calibrated with the subduction force balance analysis. Effective viscosities for the deforming lithosphere and/or crust are in the range 0.1-5 × 1021 Pa s, with marked weakening in zones of high strain rate, and an abrupt transition to viscosities >1022 Pa s at the margins of the rigid plates. If lateral variations in effective viscosity are only due to non-Newtonian behaviour, these data indicate a bulk power law rheology, with

  18. Neotectonic map of Syria and some aspects of Late Cenozoic evolution of the northwestern boundary zone of the Arabian plate

    NASA Astrophysics Data System (ADS)

    Rukieh, M.; Trifonov, V. G.; Dodonov, A. E.; Minini, H.; Ammar, O.; Ivanova, T. P.; Zaza, T.; Yusef, A.; Al-Shara, M.; Jobaili, Y.

    2005-09-01

    The neotectonic map of Syria, 1:500,000, was compiled by the authors in 2003-2004. The map shows tectonic features formed or continued to develop during the Neogene and Quaternary in Syria and adjacent territories, including the Mediterranean realm. The neotectonic structure of the region was formed as a result of three phases of deformation. During the Early Miocene first phase, the Arabian plate moved along the Dead Sea-Jordan segments of the Levant (Dead Sea) transform fault zone, Roum fault and its continuation in the continental slope of the Mediterranean. The chain of the coastal anticlines in the "Arabian" side of the transform zone and the Lattaqie oblique (sinistral-thrust) boundary fault zone in the north were formed under the NNW-trending compression. The Lattaqie zone continued by the Cyprus arc in the west and by the Taurus (Bitlis) thrust in the east and further by the Main Thrust of the Zagros. After "quiet" (for Syria) epoch of the Middle Miocene when the Arabian plate moved to the NE, during the Late Miocene second phase of deformation, the Arabian plate moved again to the NNW along the same transform boundary. But a part of the Late Miocene plate motion (up to 20 km) resulted by shortening in the Anti-Leban-Palmyride fold-thrust belt that separated the Aleppo block from the main part of the Arabian plate. During the Pliocene-Quaternary third phase of deformation, the recent structural pattern of the Levant zone was formed in Lebanon and the northwestern Syria. At the same time, the Serghaya and smaller sinistral faults branched out the Levant zone and the system of the W-E-trending convex to the south dextral faults ruptured the Palmyrides and the stable part of the Arabian plate. The total Pliocene-Quaternary sinistral offset on the young Levant zone segments and the associated faults has reached 35-40 km, like on the Dead Sea-Jordan segments of the Levant fault zone. The faults, demonstrating the Pliocene-Quaternary activity are still active now

  19. Soret and Dufour effects on the flow of an Erying-Powell fluid over a flat plate with convective boundary condition

    NASA Astrophysics Data System (ADS)

    Qasim, M.

    2014-02-01

    This article addresses the heat and mass transfer effects in the boundary layer flow over a plate. Mathematical modelling is based upon the constitutive equations of the Erying-Powell fluid. The problem formulation takes into account the Soret and Dufour effects and convective boundary conditions. A numerical solution to the nonlinear flow problem is presented. The impact of the emerging parameters is analyzed.

  20. Anatomy of a Plate Boundary at Shallow Crustal Levels: a Composite Section from the Alpine Fault, New Zealand

    NASA Astrophysics Data System (ADS)

    Barth, N. C.; Toy, V. G.; Boulton, C. J.; Carpenter, B. M.

    2010-12-01

    New Zealand's Alpine Fault is mostly a moderately SE-dipping dextral reverse plate boundary structure, but at its southern end, strike-slip-normal motion is indicated by offset of recent surfaces, juxtaposition of sediments, and both brittle and ductile shear sense indicators. At the location of uplift polarity reversal fault rocks exhumed from both the hangingwall Pacific and footwall Australian Plates are juxtaposed, offering a remarkably complete cross section of the plate boundary at shallow crustal levels. We describe Alpine Fault damage zone and fault core structures overprinted on Pacific and Australian plate mylonites of a variety of compositions, in a fault-strike perpendicular composite section spanning the reversal in dip-slip polarity. The damage zone is asymmetric; on the Australian Plate 160m of quartzose paragneiss-derived mylonites are overprinted by brittle faults and fractures that increase in density towards the principal slip surface (PSS). This damage zone fabric consists of 1-10m-spaced, moderately to steeply-dipping, 1-20cm-thick gouge-filled faults, overprinted on and sub-parallel to a mylonitic foliation sub-parallel to the PSS. On the Pacific Plate, only 40m of the 330m section of volcaniclastic-derived mylonites have brittle damage in the form of unhealed fractures and faults, as well as a pervasive greenschist facies hydrothermal alteration absent in the footwall. These damage-related structures comprise a network of small-offset faults and fractures with increasing density and intensity towards the PSS. The active Pacific Plate fault core is composed of ~1m of cataclasite grading into folded protocataclasite that is less folded and fractured with increasing distance from the PSS. The active Australian Plate fault core is <1.5m wide and consists of 3 distinct foliated clay gouges, as well as a 4cm thick brittle ultracataclasite immediately adjacent to the active PSS. The Australian Plate foliated clay gouge contains stringers of quartz

  1. Stress Transfer Processes during Great Plate Boundary Thrusting Events: A Study from the Andaman and Nicobar Segments

    NASA Astrophysics Data System (ADS)

    Andrade, V.; Rajendran, K.

    2010-12-01

    The response of subduction zones to large earthquakes varies along their strike, both during the interseismic and post-seismic periods. The December 26, 2004 earthquake nucleated at 3° N latitude and its rupture propagated northward, along the Andaman-Sumatra subduction zone, terminating at 15°N. Rupture speed was estimated at about 2.0 km per second in the northern part under the Andaman region and 2.5 - 2.7 km per second under southern Nicobar and North Sumatra. We have examined the pre and post-2004 seismicity to understand the stress transfer processes within the subducting plate, in the Andaman (10° - 15° N ) and Nicobar (5° - 10° N) segments. The seismicity pattern in these segments shows distinctive characteristics associated with the outer rise, accretionary prism and the spreading ridge, all of which are relatively better developed in the Andaman segment. The Ninety East ridge and the Sumatra Fault System are significant tectonic features in the Nicobar segment. The pre-2004 seismicity in both these segments conform to the steady-state conditions wherein large earthquakes are fewer and compressive stresses dominate along the plate interface. Among the pre-2004 great earthquakes are the 1881 Nicobar and 1941 Andaman events. The former is considered to be a shallow thrust event that generated a small tsunami. Studies in other subduction zones suggest that large outer-rise tensional events follow great plate boundary breaking earthquakes due to the the up-dip transfer of stresses within the subducting plate. The seismicity of the Andaman segment (1977-2004) concurs with the steady-state stress conditions where earthquakes occur dominantly by thrust faulting. The post-2004 seismicity shows up-dip migration along the plate interface, with dominance of shallow normal faulting, including a few outer rise events and some deeper (> 100 km) strike-slip faulting events within the subducting plate. The September 13, 2002, Mw 6.5 thrust faulting earthquake at

  2. Late Mesozoic- Cenozoic plate boundaries in the North Atlantic – Arctic: Quantitative reconstructions using Hellinger criterion in GPlates

    NASA Astrophysics Data System (ADS)

    Gaina, Carmen; Watson, Robin; Cirbus, Juraj

    2015-04-01

    uncertainties are combined with a regional model and used to infer the plate boundaries during the formation of Labrador Sea and Baffin Bay. Challenges for establishing the continuation of these plate boundaries the Arctic domain are also discussed. References Chang, T. (1988), Estimating the relative rotation of two tectonic plates from boundary crossings, J. Am. Stat. Assoc., 83, 1178-1183. Hellinger, S. J. (1981), The uncertainties of finite rotations in plate tectonics, J Geophys Res, 86, 9312-9318. Hanna, M.S and T. Chang (1990), On graphically representing the confidence region for an unknown rotation in three dimensions. Computers & Geosciences 16 (2), 163-194. Royer, J. Y., and T. Chang (1991), Evidence for Relative Motions between the Indian and Australian Plates during the Last 20 My from Plate Tectonic Reconstructions - Implications for the Deformation of the Indo-Australian Plate, J Geophys Res, 96(B7), 11779-11802.

  3. Discovering Plate Boundaries in Data-Integrated Environments: Preservice Teachers' Conceptualization and Implementation of Scientific Practices

    ERIC Educational Resources Information Center

    Sezen-Barrie, Asli; Moore, Joel; Roig, Cara E.

    2015-01-01

    Drawn from the norms and rules of their fields, scientists use variety of practices, such as asking questions and arguing based on evidence, to engage in research that will contribute to our understanding of Earth and beyond. In this study, we explore how preservice teachers' learn to teach scientific practices while teaching plate tectonic…

  4. Continental Subduction and Subduction Initiation Leading to Extensional Exhumation of Ultra-High Pressure Rocks During Ongoing Plate Convergence in Papua New Guinea

    NASA Astrophysics Data System (ADS)

    Buck, W. R.; Petersen, K. D.

    2014-12-01

    Subduction of continental rocks is necessary to produce ultra-high pressure (UHP) rocks but the mechanism bringing them to the surface is disputed. A major question is whether this involves fairly small diapirs of crust that move up through the mantle or it involves an entire subducted plate that undergoes coherent 'reverse subduction' (sometimes called 'eduction'). Both mechanisms have been invoked to explain the only known region of on-going exhumation of UHP rocks, on the D'Entrecasteaux Islands of Papua New Guinea. Ductile flow fabrics in the island rocks have been used to argue for a diapiric model while constraints on the plate kinematics of the region require relatively large (>100 km) amounts of recent (>6 Myr) extension, supporting eduction as a primary mechanism. A self-consistent thermo-mechanical model of continental subduction shows that eduction can be accompanied by some ductile flow within the crust. Also we show, that subduction and stacking of continental crust can cause a subduction zone to lock up and lead to subduction initiation elsewhere. When this happens the region of earlier continental subduction can reverse direction causing exhumation of rocks from depth of ~100 km followed by localized extension and plate spreading. This can occur even if a region is in overall convergence. Applied to New Guinea our results are consistent with earlier suggestions that extension of the Woodlark Basin was caused by the initiation of the New Britain Trench, as indicated on the attached figure. We suggest that this subduction initiation event triggered eduction that led to exposure of the D'Entrcasteaux Islands and exhumation of the UHP rocks there. Our numerical results are broadly consistent with the recently refined seismic structure of the region around the islands. The model implies that the present-day basement of the ~70 km wide Goodenough Bay, south of the islands, was subducted then exhumed. This can be tested by drilling.

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

    NASA Astrophysics Data System (ADS)

    Austin, K. E.; Blume, F.; Berglund, H. T.; Feaux, K.; Gallaher, W. W.; Hodgkinson, K. M.; Mattioli, G. S.; Mencin, D.

    2014-12-01

    The EarthScope Plate Boundary Observatory (PBO), through a NSF-ARRA supplement, has enhanced the geophysical infrastructure in in the Pacific Northwest by upgrading a total of 282 Plate Boundary Observatory GPS stations to allow the collection and distribution of high-rate (1 Hz), low-latency (<1 s) data streams (RT-GPS). These upgraded stations supplemented the original 100 RT-GPS stations in the PBO GPS network. The addition of the new RT-GPS sites in Cascadia should spur new volcano and earthquake research opportunities in an area of great scientific interest and high geophysical hazard. Streaming RT-GPS data will enable researchers to detect and investigate strong ground motion during large geophysical events, including a possible plate-interface earthquake, which has implications for earthquake hazard mitigation. A Mw 6.9 earthquake occurred on March 10, 2014, off the coast of northern California. As a response, UNAVCO downloaded high-rate GPS data from Plate Boundary Observatory stations within 500 km of the epicenter of the event, providing a good test of network performance.In addition to the 282 stations upgraded to real-time, 22 new meteorological instruments were added to existing PBO stations. Extensive testing of BGAN satellite communications systems has been conducted to support the Cascadia RT-GPS upgrades and the installation of three BGAN satellite fail over systems along the Cascadia margin will allow for the continuation of data flow in the event of a loss of primary communications during in a large geophysical event or other interruptions in commercial cellular networks. In summary, with these additional upgrades in the Cascadia region, the PBO RT-GPS network will increase to 420 stations. Upgrades to the UNAVCO data infrastructure included evaluation and purchase of the Trimble Pivot Platform, servers, and additional hardware for archiving the high rate data, as well as testing and implementation of GLONASS and Trimble RTX positioning on the

  6. Hydromagnetic natural convection flow between vertical parallel plates with time-periodic boundary conditions

    NASA Astrophysics Data System (ADS)

    Adesanya, S. O.; Oluwadare, E. O.; Falade, J. A.; Makinde, O. D.

    2015-12-01

    In this paper, the free convective flow of magnetohydrodynamic fluid through a channel with time periodic boundary condition is investigated by taking the effects of Joule dissipation into consideration. Based on simplifying assumptions, the coupled governing equations are reduced to a set of nonlinear boundary valued problem. Approximate solutions are obtained by using semi-analytical Adomian decomposition method. The effect of pertinent parameters on the fluid velocity, temperature distribution, Nusselt number and skin friction are presented graphically and discussed. The result of the computation shows that an increase in the magnetic field intensity has significant influence on the fluid flow.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  8. Experiments of dike-induced deformation: Insights on the long-term evolution of divergent plate boundaries

    NASA Astrophysics Data System (ADS)

    Trippanera, D.; Ruch, J.; Acocella, V.; Rivalta, E.

    2015-10-01

    The shallow transport of magma occurs through dikes causing surface deformation. Our understanding of the effects of diking at the surface is limited, especially on the long term, for repeated intrusive episodes. We use analogue models to study the upper crustal deformation induced by dikes. We insert metal plates within cohesive sand with three setups: in setup A, the intrusion rises upward with constant thickness and in setups B and C, the intrusion thickens at a fixed depth, with final rectangular (setup B) or triangular (setup C) shape in section. Setup A creates a doming delimited by reverse faults, with secondary apical graben, without close correspondence in nature. In setups B and C, a depression flanked by two uplifted areas is bordered by inward dipping normal faults propagating downward and, for deeper intrusions in setup B, also by inner faults, reverse at the surface; this deformation is similar to what is observed in nature, suggesting a consistent physical behavior. Dikes in nature initially propagate developing a mode I fracture at the tip, subsequently thickened by magma intrusion, without any host rock translation in the propagation direction (as in setup A). The deformation pattern in setups B and C depends on the intrusion depth and thickness, consistently to what is observed along divergent plate boundaries. The early deformation in setups B and C is similar to that from a single rifting episode (i.e., Lakagigar, Iceland, and Dabbahu, Afar), whereas the late stages resemble the structure of mature rifts (i.e., Krafla, Iceland), confirming diking as a major process in shaping divergent plate boundaries.

  9. A review of structural patterns and melting processes in the Archean craton of West Greenland: Evidence for crustal growth at convergent plate margins as opposed to non-uniformitarian models

    NASA Astrophysics Data System (ADS)

    Polat, Ali; Wang, Lu; Appel, Peter W. U.

    2015-11-01

    The Archean craton of West Greenland consists of many fault-bounded Eoarchean to Neoarchean tectonic terranes (crustal blocks). These tectonic terranes are composed mainly of tonalite-trondhjemite-granodiorite (TTG) gneisses, granitic gneisses, metavolcanic-dominated supracrustal belts, layered anorthositic complexes, and late- to post-tectonic granites. Rock assemblages and geochemical signatures in these terranes suggest that they represent fragments of dismembered oceanic island arcs, consisting mainly of TTG plutons, tholeiitic to calc-alkaline basalts, boninites, picrites, and cumulate layers of ultramafic rocks, gabbros, leucogabbros and anorthosites, with minor sedimentary rocks. The structural characteristics of the terrane boundaries are consistent with the assembly of these island arcs through modern style of horizontal tectonics, suggesting that the Archean craton of West Greenland grew at convergent plate margins. Several supracrustal belts that occur at or near the terrane boundaries are interpreted as relict accretionary prisms. The terranes display fold and thrust structures and contain numerous 10 cm to 20 m wide bifurcating, ductile shear zones that are characterized by a variety of structures including transposed and redistributed isoclinal folds. Geometrically these structures are similar to those occurring on regional scales, suggesting that the Archean craton of West Greenland can be interpreted as a continental scale accretionary complex, such as the Paleozoic Altaids. Melting of metavolcanic rocks during tectonic thickening in the arcs played an important role in the generation of TTGs. Non-uniformitarian models proposed for the origin of Archean terranes have no analogs in the geologic record and are inconsistent with structural, lithological, petrological and geochemical data collected from Archean terranes over the last four decades. The style of deformation and generation of felsic rocks on outcrop scales in the Archean craton of West

  10. Shear flow beneath oceanic plates - Local nonsimilarity boundary layers for olivine rheology

    NASA Technical Reports Server (NTRS)

    Yuen, D. A.; Tovish, A.; Schubert, G.

    1978-01-01

    The principle of local similarity, which has been used to model the two-dimensional boundary layers in the oceanic upper mantle, permits calculation of the temperature, velocity, and stress fields with essentially analytic techniques. Finite difference numerical methods are hard pressed to resolve the detail required by the large variation of viscosity between the lithosphere and the asthenosphere. In this paper the local similarity approximation has been justified by quantitatively evaluating the effect of nonsimilarity due to viscous heating, nonlinear temperature- and pressure-dependent rheology, buoyancy, adiabatic cooling, etc. Nonsimilar effects produce only small modifications of the locally similar boundary layers; important geophysical observables such as surface heat flux and ocean floor topography are given to better than 10 percent by the locally similar solution. A posteriori evaluations of the terms neglected in the boundary layer simplification of the complete equations have been conducted on the locally similar temperature and velocity profiles close to the spreading ridge. The boundary layer models are valid to depths of 100 km at 3 m.y. and 10 km at 0.3 m.y.

  11. "Discovering Plate Boundaries in Data-Rich Environments": Supporting Pre-service Teachers involvement in Unique Practices of Geosciences

    NASA Astrophysics Data System (ADS)

    Barrie, A. S.; Moore, J.

    2012-12-01

    plate tectonics using key scientific practices. As a result of the educational activities developed in this project, we will try help teachers to overcome their challenges and develop the pedagogical skills that novice teachers need to use to teach plate tectonics by focusing on key scientific practices with the help of previously-developed educational resources. Learning about the processes that occur at plate boundaries will help future teachers (and their students) understand natural disasters such as earthquakes and volcanoes. Furthermore, the study will have a significant, and broader, impact by 'teaching the teachers' and empowering novice teachers to overcome the challenges of reading maps and using argumentation in science classrooms.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  13. Turbulent Friction in the Boundary Layer of a Flat Plate in a Two-Dimensional Compressible Flow at High Speeds

    NASA Technical Reports Server (NTRS)

    Frankl, F.; Voishel, V.

    1943-01-01

    In the present report an investigation is made on a flat plate in a two-dimensional compressible flow of the effect of compressibility and heating on the turbulent frictional drag coefficient in the boundary layer of an airfoil or wing radiator. The analysis is based on the Prandtl-Karman theory of the turbulent boundary later and the Stodola-Crocco, theorem on the linear relation between the total energy of the flow and its velocity. Formulas are obtained for the velocity distribution and the frictional drag law in a turbulent boundary later with the compressibility effect and heat transfer taken into account. It is found that with increase of compressibility and temperature at full retardation of the flow (the temperature when the velocity of the flow at a given point is reduced to zero in case of an adiabatic process in the gas) at a constant R (sub x), the frictional drag coefficient C (sub f) decreased, both of these factors acting in the same sense.

  14. Discontinuous and smooth 3D structure of the upper mantle and crust across and along the Eurasia-Africa plate boundary

    NASA Astrophysics Data System (ADS)

    Marone, F.; van der Meijde, M.; van der Lee, S.; Giardini, D.

    2003-04-01

    We have acquired and analyzed new seismological data to investigate and map seismic discontinuities and to image smooth 3DS-velocity structure of the upper mantle and crust of the Africa-Eurasia suture zone. The results of this effort have a resolution that is complementary to that of existing studies. The new data have been recorded at 25 broadband seismic stations (MIDSEA project), temporarily deployed across and along the plate boundary region. We used additional seismic data from permanent networks in the region. We jointly inverted linear constraints on Moho depth and upper mantleS-velocity structure obtained by waveform modeling (ofS- and surface wave trains) and from point estimates of crustal thickness (from receiver function, gravity and active-source seismic studies). This joint inversion has yielded a Moho map and a 3D upper mantleS-velocity model. The Moho map shows strong lateral variations, which confirm the complex evolution of this plate boundary region. The Moho appears to be deeper than 45 km beneath mountain ranges (e.g. Alps), while in locations dominated by extension it is found shallower than 15 km (e.g. Algero-Provençal Basin). Beneath the eastern Atlantic Ocean, the crust may be up to 5 km thicker than standard oceanic crust (6 km). Serpentinization of the sub-Moho mantle at the Mid-Atlantic ridge could be a process contributing to the imaging of an anomalously deep apparent Moho in this region. Depsite the high level of heterogeneity, the region appears to be very close to isostatic equilibrium. The 3D upper mantleS-velocity structure shows strong correlation between the imaged heterogeneities and the tectonics along the plate boundary. The Eurasia-Africa suture zone manifests itself in the upper mantle mainly as a belt of fast material representing subducted oceanic lithosphere. A new, striking and resolved feature of our model is a high velocity anomaly imaged beneath eastern Spain between 250 and 500 km depth. We suggest that this fast

  15. Hypersonic Laminar Boundary Layer Velocimetry with Discrete Roughness on a Flat Plate

    NASA Technical Reports Server (NTRS)

    Bathel, Brett; Danehy, Paul M.; Inman, Jennifer A.; Watkins, A. Neal; Jones, Stephen B.; Lipford, William E.; Goodman, Kyle Z.; Ivey, Christopher B.; Goyne, Christopher P.

    2010-01-01

    Laminar boundary layer velocity measurements are made on a 10-degree half-angle wedge in a Mach 10 flow. Two types of discrete boundary layer trips were used to perturb the boundary layer gas. The first was a 2-mm tall, 4-mm diameter cylindrical trip. The second was a scaled version of the Orbiter Boundary Layer Transition (BLT) Detailed Test Objective (DTO) trip. Both 1-mm and 2.5-mm tall BLT DTO trips were tested. Additionally, side-view and plan-view axial boundary layer velocity measurements were made in the absence of these tripping devices. The free-stream unit Reynolds numbers tested for the cylindrical trips were 1.7x10(exp 6)/m and 3.3x10(exp 6)/m. The free-stream unit Reynolds number tested for the BLT DTO trips was 1.7x10(exp 6)/m. The angle of attack was kept at approximately 5-degrees for most of the tests resulting in a Mach number of approximately 8.3. These combinations of unit Reynolds numbers and angle of attack resulted in laminar flowfields. To study the precision of the measurement technique, the angle of attack was varied during one run. Nitric-oxide (NO) molecular tagging velocimetry (MTV) was used to obtain averaged axial velocity values and associated uncertainties. These uncertainties are as low as 20 m/s. An interline, progressive scan CCD camera was used to obtain separate images of the initial reference and shifted NO molecules that had been tagged by the laser. The CCD configuration allowed for sub-microsecond sequential acquisition of both images. The maximum planar spatial resolution achieved for the side-view velocity measurements was 0.07-mm in the wall-normal direction by 1.45-mm in the streamwise direction with a spatial depth of 0.5-mm. For the plan-view measurements, the maximum planar spatial resolution in the spanwise and streamwise directions was 0.69-mm by 1.28-mm, respectively, with a spatial depth of 0.5-mm. Temperature sensitive paint (TSP) measurements are provided to compliment the velocity data and to provide further

  16. Crustal movements at a divergent plate boundary: interplay between volcano deformation, geothermal processes, and plate spreading in the Northern Volcanic Zone, Iceland since 2008.

    NASA Astrophysics Data System (ADS)

    Drouin, Vincent; Sigmundsson, Freysteinn; Hreinsdóttir, Sigrún; Ofeigsson, Benedikt G.; Sturkell, Erik; Islam, Tariqul

    2014-05-01

    Iceland is a subaerial part of the Mid-Atlantic Ridge, where the divergent plate boundary between the North-American and Eurasian Plates can be studied. The Northern Volcanic Zone (NVZ) of Iceland, comprised of several volcanic systems, is particularly well suited to study interplay between volcanoes, geothermal areas and plate spreading, as the zone is relatively simple and accommodates the full spreading of the plates (18.6 mm/yr in a direction of 105 degrees according to NUVEL-1A predictions). The most recent volcanic activity in the area was the Krafla rifting episode (1975-1984). In 2007-2008 two intrusive events were detected: one in Upptypingar and the other in Þeistareykir. Extensive crustal deformation studies have been carried out in the NVZ; we report the results of recent GPS and Interferometric Synthetic Aperture Radar (InSAR) studies focusing on Krafla, Þeistareykir and Askja volcanic systems in the NVZ. An extensive GPS survey was undertaken in 2013, with over 135 stations occupied. This data was evaluated in conjunction with data acquired since 2008, to generate a velocity field spanning this entire time period. In addition to an existing continuous GPS (cGPS) station, three cGPS stations were installed in the area in 2011-2012. The 2008-2013 GPS velocities were compared to earlier GPS results, and complementary analysis of InSAR images was undertaken. Earlier studies have shown that the Krafla caldera underwent uplift during 1984-1989, followed by subsidence. Since 1995, the maximum subsidence in Krafla has shifted from directly above the shallow magma chamber towards an array of boreholes (geothermal exploitation) in Leirbotnar. Similar subsidence has been observed around another array of boreholes in Bjarnaflag, 7 km further south. The most significant signal on the velocities calculated from campaign GPS data over the 5 year period, is plate spreading with an E-W velocity of about 12 mm/yr over a 30 km wide area. However it also shows an

  17. Paleoseismic and Geomorphic Evidence for Quaternary Fault Slip on the Central Range Fault, South American-Caribbean Plate Boundary, Trinidad

    NASA Astrophysics Data System (ADS)

    Prentice, C. S.; Weber, J.; Crosby, C. J.

    2001-12-01

    The island of Trinidad is located along the transform plate boundary between the South American and Caribbean plates. GPS measurements show that relative motion along this boundary is nearly E-W right-lateral shear (Weber et al., 2001). Analysis and comparison of historic triangulation and GPS data suggest that a significant fraction (14+/-3 mm/yr) of the total plate-boundary motion (about 20 mm/yr) is being accommodated across the Central Range Fault in central Trinidad. Our new paleoseismic studies demonstrate that Quaternary surface rupture has occurred on this previously unrecognized, historically aseismic, active fault. Geomorphic evidence of Quaternary faulting along the Central Range Fault includes linear drainages, aligned topographic saddles and troughs, offset ridges, right-laterally deflected streams, and linear scarps. We mapped these features using 1:20,000 scale aerial photographs and field reconnaissance along a 25-km-long section between Pointe-a-Pierre on the west coast and Navet Dam. Geomorphic features near Manzanilla Bay on the east coast suggest that the Central Range Fault continues across the island as a Quaternary feature for another 25 km to the northeast. Marine geophysical surveys suggest this fault continues offshore to the west (Warm Springs fault), and steps to the north across the Gulf of Paria pull-apart basin to the El Pilar Fault. The extent of the fault offshore to the east is unknown. We exposed a 6-m-wide shear zone within Pliocene(?) material in a trench cut into a fluvial terrace, south of Samlalsingh Road near Bonne Aventure. The overlying Quaternary fluvial gravel is faulted and folded across the shear zone, and Quaternary fluvial deposits are faulted against the shear zone on the north side. A second excavation across a prominent scarp near Tabaquite, 12 km northeast of Samlalsingh Road, exposed a colluvial wedge and overlying unfaulted sediments. We interpret the colluvial wedge to represent deposits shed off the scarp in

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    This is the Final Technical Report on research conducted between 1 June 1997 and 14 September 2001 entitled "Transients in Pacific/North American plate boundary deformation: Synthesis and modeling of GPS and borehole strain observations." As the project title implies, our effort involved a geodetic study of strain transients, i.e., temporal variations in deformation rates, that occur within plate boundary zones and their relationship to earthquakes and plate motions. Important transients occur during and following large earthquakes, and there are also strain transients not apparently associated with earthquakes. A particularly intriguing class of transients, for which there is a modest but growing list of examples, are preseismic anomalies. Such earthquake precursors, if further documented and understood, would have obvious importance for earthquake hazard mitigation. Because the timescales for these diverse transients range over at least 6 orders of magnitude (minutes to years), no single geodetic technique is optimum. We therefore undertook a systematic synthesis of Global Positioning Satellite (GPS) and borehole strainmeter data in three areas in California where there are adequate numbers of both types of instruments (or their equivalent): the San Francisco Bay region (within the Bay Area Regional Deformation network), southern California (within the Southern California Integrated GPS Network), and Parkfield (where a two-color laser system provides a proxy for continuous GPS measurements). An integral component of our study was the elucidation of the physical mechanisms by which such transients occur and propagate. We therefore initiated the development of multiple forward models, using two independent approaches. In the first, we explored the response to specified earthquake slip in viscoelastic models that incorporated failure criteria and the geometry of major faults in California. In the second approach, we examined the dynamical response of a complex

  19. Convergence of shock waves generated by underwater electrical explosion of cylindrical wire arrays between different boundary geometries

    SciTech Connect

    Yanuka, D.; Zinowits, H. E.; Krasik, Ya. E.; Kozlov, M.

    2015-10-15

    The results of experiments and numerical simulations of a shock wave propagating between either conical or parabolic bounding walls are presented. The shock wave was generated by a microsecond timescale underwater electrical explosion of a cylindrical wire array supplied by a current pulse having an amplitude of ∼230 kA and a rise time of ∼1 μs. It is shown that with the same energy density deposition into the exploding wire array, the shock wave converges faster between parabolic walls, and as a result, the pressure in the vicinity of convergence is ∼2.3 times higher than in the case of conical walls. The results obtained are compared to those of earlier experiments [Antonov et al., Appl. Phys. Lett. 102, 124104 (2013)] with explosions of spherical wire arrays. It is shown that at a distance of ∼400 μm from the implosion origin the pressure obtained in the current experiments is higher than for the case of spherical wire arrays.

  20. Convergence of shock waves generated by underwater electrical explosion of cylindrical wire arrays between different boundary geometries

    NASA Astrophysics Data System (ADS)

    Yanuka, D.; Kozlov, M.; Zinowits, H. E.; Krasik, Ya. E.

    2015-10-01

    The results of experiments and numerical simulations of a shock wave propagating between either conical or parabolic bounding walls are presented. The shock wave was generated by a microsecond timescale underwater electrical explosion of a cylindrical wire array supplied by a current pulse having an amplitude of ˜230 kA and a rise time of ˜1 μs. It is shown that with the same energy density deposition into the exploding wire array, the shock wave converges faster between parabolic walls, and as a result, the pressure in the vicinity of convergence is ˜2.3 times higher than in the case of conical walls. The results obtained are compared to those of earlier experiments [Antonov et al., Appl. Phys. Lett. 102, 124104 (2013)] with explosions of spherical wire arrays. It is shown that at a distance of ˜400 μm from the implosion origin the pressure obtained in the current experiments is higher than for the case of spherical wire arrays.

  1. Deformation record of 4-d accommodation of strain in the transition from transform to oblique convergent plate margin, southern Alaska (Invited)

    NASA Astrophysics Data System (ADS)

    Roeske, S.; Benowitz, J.; Enkelmann, E.; Pavlis, T. L.

    2013-12-01

    Crustal deformation at the transition from a dextral transform to subduction in the northern Cordillera is complicated by both the bend of the margin and the presence of low-angle subduction of an oceanic plateau, the Yakutat microplate, into the 'corner'. The dextral Denali Fault system located ~400 km inboard of the plate margin shows a similar transition from a dominantly strike-slip to transpressional regime as it curves to the west. Thermochronologic and structural studies in both areas indicate crustal response through the transition region is highly varied along and across strike. Previous thermochronology along the Fairweather fault SE of the St. Elias bend shows the most rapid exhumation occurs in close proximity to the fault, decreasing rapidly away from it. Enkelmann et al. (2010) and more recent detrital zircon FT (Falkowski et al., 2013 AGU abstract) show rapid and deep exhumation concentrated in the syntaxis, but over a fairly broad area continuing north beyond the Fairweather fault. Although the region is dominantly under ice, borders of the rapidly exhuming region appear to be previously identified major high-angle faults. This suggests that structures controlling the extreme exhumation may have significant oblique slip component, or, if flower structure, are reverse faults, and the region may be exhuming by transpression, with a significant component of pure shear. Southwest of the syntaxis, where convergence dominates over strike-slip, thin-skinned fold-and-thrust belts in the Yakutat microplate strata account for the shortening. The long-term record of convergence in this area is more cryptic due to sediment recycling through deep underplating and/or limited exhumation by upper crustal shortening, but a wide range of thermochronologic studies suggests that initial exhumation in the region began ~ 30 Ma and most rapid exhumation in the syntaxis began ~ 5 Ma. In the eastern Alaska Range a significant component of strike-slip, in addition to

  2. The propagation of in-plane P-SV waves in a layered elastic plate with periodic interface cracks: exact versus spring boundary conditions

    NASA Astrophysics Data System (ADS)

    Kvasha, Oleg V.; Boström, Anders; Glushkova, Natalia V.; Glushkov, Evgeny V.

    2011-08-01

    The propagation of in-plane (P-SV) waves in a symmetrically three-layered thick plate with a periodic array of interface cracks is investigated. The exact dispersion relation is derived based on an integral equation approach and Floquet's theorem. The interface cracks can be a model for interface damage, but a much simpler model is a recently developed spring boundary condition. This boundary condition is used for the thick plate and also in the derivation of plate equations with the help of power series expansions in the thickness coordinate. For low frequencies (cracks small compared to the wavelength) the three approaches give more or less coinciding dispersion curves, and this is a confirmation that the spring boundary condition is a reasonable approximation at low frequencies.

  3. Wide-angle seismic constraints on the evolution of the deep San Andreas plate boundary by Mendocino triple junction migration

    USGS Publications Warehouse

    Hole, J.A.; Beaudoin, B.C.; Henstock, T.J.

    1998-01-01

    Recent wide-angle seismic observations that constrain the existence and structure of a mafic layer in the lower crust place strong constraints on the evolution of the San Andreas plate boundary system in northern and central California. Northward migration of the Mendocino Triple Junction and the subducted Juan de Fuca lithospheric slab creates a gap under the continent in the new strike-slip system. This gap must be filled by either asthenospheric upwelling or a northward migrating slab attached to the Pacific plate. Both processes emplace a mafic layer, either magmatic underplating or oceanic crust, beneath the California Coast Ranges. A slab of oceanic lithosphere attached to the Pacific plate is inconsistent with the seismic observation that the strike-slip faults cut through the mafic layer to the mantle, detaching the layer from the Pacific plate. The layer could only be attached to the Pacific plate if large vertical offsets and other complex structures observed beneath several strike-slip faults are original oceanic structures that are not caused by the faults. Otherwise, if oceanic slabs exist beneath California, they do not migrate north to fill the growing slab gap. The extreme heat pulse created by asthenospheric upwelling is inconsistent with several constraints from the seismic data, including a shallower depth to the slab gap than is predicted by heat flow models, seismic velocity and structure that are inconsistent with melting or metamorphism of the overlying silicic crust, and a high seismic velocity in the upper mantle. Yet either the Pacific slab model or the asthenospheric upwelling model must be correct. While the mafic material in the lower crust could have been emplaced prior to triple junction migration, the deeper slab gap must still be filled. A preexisting mafic layer does not reduce the inconsistencies of the Pacific slab model. Such material could, however, compensate for the decrease in mafic magma that would be produced if

  4. Mixed Convection Boundary Layer Flow over a Moving Vertical Flat Plate in an External Fluid Flow with Viscous Dissipation Effect

    PubMed Central

    Bachok, Norfifah; Ishak, Anuar; Pop, Ioan

    2013-01-01

    The steady boundary layer flow of a viscous and incompressible fluid over a moving vertical flat plate in an external moving fluid with viscous dissipation is theoretically investigated. Using appropriate similarity variables, the governing system of partial differential equations is transformed into a system of ordinary (similarity) differential equations, which is then solved numerically using a Maple software. Results for the skin friction or shear stress coefficient, local Nusselt number, velocity and temperature profiles are presented for different values of the governing parameters. It is found that the set of the similarity equations has unique solutions, dual solutions or no solutions, depending on the values of the mixed convection parameter, the velocity ratio parameter and the Eckert number. The Eckert number significantly affects the surface shear stress as well as the heat transfer rate at the surface. PMID:23577156

  5. Fluctuating pressures measured beneath a high-temperature, turbulent boundary layer on a flat plate at Mach number of 5

    NASA Technical Reports Server (NTRS)

    Parrott, Tony L.; Jones, Michael G.; Albertson, Cindy W.

    1989-01-01

    Fluctuating pressures were measured beneath a Mach 5, turbulent boundary layer on a flat plate with an array of piezoresistive sensors. The data were obtained with a digital signal acquisition system during a test run of 4 seconds. Data sampling rate was such that frequency analysis up to 62.5 kHz could be performed. To assess in situ frequency response of the sensors, a specially designed waveguide calibration system was employed to measure transfer functions of all sensors and related instrumentation. Pressure time histories were approximated well by a Gaussian prohibiting distribution. Pressure spectra were very repeatable over the array span of 76 mm. Total rms pressures ranged from 0.0017 to 0.0046 of the freestream dynamic pressure. Streamwise, space-time correlations exhibited expected decaying behavior of a turbulence generated pressure field. Average convection speed was 0.87 of freestream velocity. The trendless behavior with sensor separation indicated possible systematic errors.

  6. Double Diffusive Magnetohydrodynamic (MHD) Mixed Convective Slip Flow along a Radiating Moving Vertical Flat Plate with Convective Boundary Condition

    PubMed Central

    Rashidi, Mohammad M.; Kavyani, Neda; Abelman, Shirley; Uddin, Mohammed J.; Freidoonimehr, Navid

    2014-01-01

    In this study combined heat and mass transfer by mixed convective flow along a moving vertical flat plate with hydrodynamic slip and thermal convective boundary condition is investigated. Using similarity variables, the governing nonlinear partial differential equations are converted into a system of coupled nonlinear ordinary differential equations. The transformed equations are then solved using a semi-numerical/analytical method called the differential transform method and results are compared with numerical results. Close agreement is found between the present method and the numerical method. Effects of the controlling parameters, including convective heat transfer, magnetic field, buoyancy ratio, hydrodynamic slip, mixed convective, Prandtl number and Schmidt number are investigated on the dimensionless velocity, temperature and concentration profiles. In addition effects of different parameters on the skin friction factor, , local Nusselt number, , and local Sherwood number are shown and explained through tables. PMID:25343360

  7. Heat exchange in boundary layer on permeable plate at injection and combustion

    NASA Astrophysics Data System (ADS)

    Lukashov, V. V.; Terekhov, V. V.; Hanjalič, K.

    2014-12-01

    The peculiarities of the heat and mass exchange in a laminar boundary layer with combustion at the injection of the fuel mixture H2/N2 through the permeable surface are considered. It is shown that at a certain value of the injection parameter, the value of the heat flux into the wall averaged over the length has a maximum. An analytic estimate is proposed for determining the maximum heat flux at the combustion depending on the injection intensity. The obtained relations agree with the results of experimental studies and numerical modelling.

  8. Heat exchange in boundary layer on permeable plate at injection and combustion

    NASA Astrophysics Data System (ADS)

    Lukashov, V. V.; Terekhov, V. V.; Hanjalič, K.

    2013-12-01

    The peculiarities of the heat and mass exchange in a laminar boundary layer with combustion at the injection of the fuel mixture H2/N2 through the permeable surface are considered. It is shown that at a certain value of the injection parameter, the value of the heat flux into the wall averaged over the length has a maximum. An analytic estimate is proposed for determining the maximum heat flux at the combustion depending on the injection intensity. The obtained relations agree with the results of experimental studies and numerical modelling.

  9. Setting appropriate boundaries: Fate, patterning and competence at the neural plate border

    PubMed Central

    Groves, Andrew K.; LaBonne, Carole

    2014-01-01

    The neural crest and craniofacial placodes are two distinct progenitor populations that arise at the border of the vertebrate neural plate. This border region develops through a series of inductive interactions that begin before gastrulation and progressively divide embryonic ectoderm into neural and non-neural regions, followed by the emergence of neural crest and placodal progenitors. In this review, we describe how a limited repertoire of inductive signals – principally FGFs, Wnts and BMPs – set up domains of transcription factors in the border region which establish these progenitor territories by both cross-inhibitory and cross-autoregulatory interactions. The gradual assembly of different cohorts of transcription factors that results from these interactions is one mechanism to provide the competence to respond to inductive signals in different ways, ultimately generating the neural crest and cranial placodes. PMID:24321819

  10. Discovering Plate Boundaries in Data-integrated Environments: Preservice Teachers' Conceptualization and Implementation of Scientific Practices

    NASA Astrophysics Data System (ADS)

    Sezen-Barrie, Asli; Moore, Joel; Roig, Cara E.

    2015-08-01

    Drawn from the norms and rules of their fields, scientists use variety of practices, such as asking questions and arguing based on evidence, to engage in research that will contribute to our understanding of Earth and beyond. In this study, we explore how preservice teachers' learn to teach scientific practices while teaching plate tectonic theory. In particular, our aim is to observe which scientific practices preservice teachers use while teaching an earth science unit, how do they integrate these practices into their lessons, and what challenges do they face during their first time teaching of an earth science content area integrated with scientific practices. The study is designed as a qualitative, exploratory case study of seven preservice teachers while they were learning to teach plate tectonic theory to a group of middle school students. The data were driven from the video records and artifacts of the preservice teachers' learning and teaching processes as well as written reflections on the teaching. Intertextual discourse analysis was used to understand what scientific practices preservice teachers choose to integrate into their teaching experience. Our results showed that preservice teachers chose to focus on four aspects of scientific practices: (1) employing historical understanding of how the theory emerged, (2) encouraging the use of evidence to build up a theory, (3) observation and interpretation of data maps, and (4) collaborative practices in making up the theory. For each of these practices, we also looked at the common challenges faced by preservice teachers by using constant comparative analysis. We observed the practices that preservice teachers decided to use and the challenges they faced, which were determined by what might have come as in their personal history as learners. Therefore, in order to strengthen preservice teachers' background, college courses should be arranged to teach important scientific ideas through scientific practices

  11. On the convergence of a fourth-order method for a class of singular boundary value problems

    NASA Astrophysics Data System (ADS)

    Pandey, R. K.; Singh, Arvind K.

    2009-02-01

    In the present paper we extend the fourth order method developed by Chawla et al. [M.M. Chawla, R. Subramanian, H.L. Sathi, A fourth order method for a singular two-point boundary value problem, BIT 28 (1988) 88-97] to a class of singular boundary value problems where p(x)=xb0q(x), b0>=0 is a non-negative function. The order of accuracy of the method is established under quite general conditions on f(x,y) and is also verified by one example. The oxygen diffusion problem in a spherical cell and a nonlinear heat conduction model of a human head are presented as illustrative examples. For these examples, the results are in good agreement with existing ones.

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

    USGS Publications Warehouse

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

    2001-01-01

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

  13. Low heat flow inferred from >4Gyr zircons suggests Hadean plate boundary interactions

    NASA Astrophysics Data System (ADS)

    Hopkins, Michelle; Harrison, T. Mark; Manning, Craig E.

    2008-11-01

    The first ~600 million years of Earth history (the `Hadean' eon) remain poorly understood, largely because there is no rock record dating from that era. Detrital Hadean igneous zircons from the Jack Hills, Western Australia, however, can potentially provide insights into the conditions extant on our planet at that time. Results of geochemical investigations using these ancient grains have been interpreted to suggest the presence of a hydrosphere and continental crust before 4Gyr. An underexploited characteristic of the >4Gyr zircons is their diverse assemblage of mineral inclusions. Here we present an examination of over 400 Hadean zircons from Jack Hills, which shows that some inclusion assemblages are conducive to thermobarometry. Our thermobarometric analyses of 4.02-4.19-Gyr-old inclusion-bearing zircons constrain their magmatic formation conditions to about 700°C and 7kbar. This result implies a near-surface heat flow of ~75mWm-2, about three to five times lower than estimates of Hadean global heat flow. As the only site of magmatism on modern Earth that is characterized by heat flow of about one-quarter of the global average is above subduction zones, we suggest that the magmas from which the Jack Hills Hadean zircons crystallized were formed largely in an underthrust environment, perhaps similar to modern convergent margins.

  14. Low heat flow inferred from >4 Gyr zircons suggests Hadean plate boundary interactions.

    PubMed

    Hopkins, Michelle; Harrison, T Mark; Manning, Craig E

    2008-11-27

    The first approximately 600 million years of Earth history (the 'Hadean' eon) remain poorly understood, largely because there is no rock record dating from that era. Detrital Hadean igneous zircons from the Jack Hills, Western Australia, however, can potentially provide insights into the conditions extant on our planet at that time. Results of geochemical investigations using these ancient grains have been interpreted to suggest the presence of a hydrosphere and continental crust before 4 Gyr. An underexploited characteristic of the >4 Gyr zircons is their diverse assemblage of mineral inclusions. Here we present an examination of over 400 Hadean zircons from Jack Hills, which shows that some inclusion assemblages are conducive to thermobarometry. Our thermobarometric analyses of 4.02-4.19-Gyr-old inclusion-bearing zircons constrain their magmatic formation conditions to about 700 degrees C and 7 kbar. This result implies a near-surface heat flow of approximately 75 mW m(-2), about three to five times lower than estimates of Hadean global heat flow. As the only site of magmatism on modern Earth that is characterized by heat flow of about one-quarter of the global average is above subduction zones, we suggest that the magmas from which the Jack Hills Hadean zircons crystallized were formed largely in an underthrust environment, perhaps similar to modern convergent margins. PMID:19037314

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

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

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

  16. A 2006 earthquakes series at the Colima rift and its relationship to the Rivera-Cocos plate boundary

    NASA Astrophysics Data System (ADS)

    Yamamoto, J.; Jimenez, Z.

    2013-12-01

    From July 31 through 13 August 2006 a series of fourteen earthquakes (M 3.9 to 6.1) occurred in the western end of the Central Mexican Volcanic Belt (CMVB) in twenty five days period. The most prominent earthquake (Mw 6.1) occurred on 11 August 2006 at 14:30 UTC (9:30 local time) approximately at 18.37° N, 101.25° W and 81 km depth. The epicenter was less than 40 km from Huetamo, Michoacan a 41,250-inhabitant city and 60 km from the El Infiernillo dam embayment the third largest hydroelectric plant in Mexico. This earthquake was widely felt through out the region with minor to moderate reported damage. In Mexico City 250 km away from the epicenter the earthquake, produced alarm among the population and several buildings evacuated. The earthquake series developed into two activity clusters one centered in the coast and separated about 300 km from a second inland cluster. The initial coastal cluster consisted of a nearly linear activity distribution which includes two shallow-depth earthquakes and reverse faulting mechanism with a slight left lateral strike-slip component and a possible fault planes trending roughly east-west. Two normal faulting earthquakes located at the extremes of the graben system, and fault planes oriented in a nearly north-south direction followed. The earthquakes are located approximately between the trench and the coast along the El Gordo-Colima graben system, which has been proposed as the continuation of the diffuse boundary between the Rivera and Cocos plates. The reverse faulting earthquakes are congruent either, with the expected subduction of the Rivera or Cocos plate under the North America plate and the normal faulting earthquake that can be associated to motions in the graben.

  17. Plate motion

    SciTech Connect

    Gordon, R.G. )

    1991-01-01

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

  18. Volcanism in response to plate flexure.

    PubMed

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

    2006-09-01

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

  19. Transverse free vibrations of right triangular thin plates with combinations of clamped and simply supported boundary conditions: a highly accurate simplified solution

    NASA Astrophysics Data System (ADS)

    Saliba, H. T.

    1995-06-01

    The practical engineering problem of right angled triangular plates with combinations of clamped and simply supported boundary conditions is dealt with in this paper. A highly accurate, economical and practical solution is used for the transverse free vibration analysis of these plates. The solution is based on a modified superposition method. The accuracy of the solution is discussed. Numerical results are compared with previously published reliable data. The advantages of the solution used in the paper over previously published solutions are discussed. Eigenvalues, mode shapes and contour plots are provided for a large number of plates.

  20. Magmatism at the Eurasian–North American modern plate boundary: Constraints from alkaline volcanism in the Chersky Belt (Yakutia)

    PubMed Central

    Tschegg, Cornelius; Bizimis, Michael; Schneider, David; Akinin, Vyacheslav V.; Ntaflos, Theodoros

    2011-01-01

    The Chersky seismic belt (NE-Russia) forms the modern plate boundary of the Eurasian−North American continental plate. The geodynamic evolution of this continent−continent setting is highly complex and remains a matter of debate, as the extent and influence of the Mid-Arctic Ocean spreading center on the North Asian continent since the Eocene remains unclear. The progression from a tensional stress regime to a modern day transpressional one in the Chersky seismic belt, makes the understanding even more complicated. The alkaline volcanism that has erupted along the Chersky range from Eocene through to the Recent can provide constraints on the geodynamic evolution of this continental boundary, however, the source and petrogenetic evolution of these volcanic rocks and their initiating mechanisms are poorly understood. We studied basanites of the central Chersky belt, which are thought to represent the first alkaline volcanic activity in the area, after initial opening of the Arctic Ocean basin. We present mineral and bulk rock geochemical data as well as Sr–Nd–Pb–Hf isotopes of the alkaline suite of rocks combined with new precise K–Ar and 40Ar/39Ar dating, and discuss an integrated tectono-magmatic model for the Chersky belt. Our findings show that the basanites were generated from a homogeneous asthenospheric mantle reservoir with an EM-1 isotopic flavor, under relatively ‘dry’ conditions at segregation depths around 110 km and temperatures of ~ 1500 °C. Trace element and isotope systematics combined with mantle potential temperature estimates offer no confirmation of magmatism related to subduction or plume activity. Mineral geochemical and petrographical observations together with bulk geochemical evidence indicate a rapid ascent of melts and high cooling rates after emplacement in the continental crust. Our preferred model is that volcanism was triggered by extension and thinning of the lithosphere combined with adiabatic upwelling of the

  1. Plate Boundary Observatory Strainmeter Recordings of The M6.0 August 24, 2014 South Napa Earthquake

    NASA Astrophysics Data System (ADS)

    Hodgkinson, Kathleen; Mencin, David; Phillips, David; Mattioli, Glen; Meertens, Charles

    2015-04-01

    The 2014 Mw6.0 South Napa earthquake nucleated at 11 km depth near the West Napa fault, one of a complex system of sub-parallel major right lateral faults north of San Francisco that together accommodate much of the relative motion between the Pacific and North American tectonic plates. The South Napa event was the largest to have shaken the San Francisco Bay Area (SFBA) in almost 25 years. A major goal of the NSF-funded EarthScope Plate Boundary Observatory (PBO), installed and maintained by UNAVCO, was to enable researchers to study the interaction between the faults that form a plate boundary zone, and in particular, to investigate the role that aseismic transients contribute to strain accumulation and release. To realize this goal, PBO includes borehole tensor strainmeters (BSMs) installed in several targeted regions, including on to the north and east of San Francisco. Two PBO BSMs have been operating in the SFBA since 2008: B057, north of San Francisco and 30 km from the epicenter, and B054, 3 km from the Hayward Fault and 40 km from the epicenter. We find the coseismic strains recorded by B057 are close to those predicted using elastic half-space dislocation theory and the seismically determined focal mechanism, while a more complicated variable slip model may be required for observations from B054. Months after the event, B057 continued to record a significant postseismic signal. In this presentation we document the coseismic signals recorded by the PBO BSMs and characterize the temporal behavior of the postseismic signal at B057. The PBO network includes over 1100 GPS, 75 BSMs, 79 seismometers and arrays of tiltmeters, pore pressure sensors and meteorological instrumentation. UNAVCO generates an Earthscope Level 2 processed strain time-series combined into areal and shear strains for the PBO BSM network; the raw data are available from the IRIS DMC in mSEED format. For events of interest, such as the South Napa earthquake, UNAVCO generates a 1-sps

  2. Interaction between central volcanoes and fissure swarms along divergent plate boundaries: an example from Askja Volcano, Northern Iceland.

    NASA Astrophysics Data System (ADS)

    Trippanera, Daniele; Ruch, Joel; Acocella, Valerio; Urbani, Stefano; Thordarson, Thor

    2016-04-01

    Central volcanoes located along divergent plate boundaries are typically part of a larger volcanic system that consists of a central edifice and a fissure swarm through which magma propagates and spreads plates apart. Regional normal faults and graben structures develop within the volcanic system, also dissecting portions of the central volcano with ring-faults faults and eruptive fissures related to the caldera structure. Both the fissure swarm and the caldera structure influence the pathway of the ascending magma, however, the influences of the structures on magma propagation and vice versa are not well defined and understood. Here we aim to understand the relationship between the activity of the central volcano structures (e.g. caldera ring faults, radial dykes and cone sheets) and those of the fissure swarm (e.g. regional normal faults, regional dikes). We focus on Askja volcano, located in the Northern Volcanic Zone of Iceland. It is comprised of three nested calderas, largely filled in with subaerial basaltic lava flows and surrounded by a massive hyaloclastite mountain on the Eastern side. Formation of the youngest, the Öskjuvatn caldera, was initiated during the 1874-1876 rifting episode on the Askja system. This major event was followed by several localized radial and circumferential magmatic intrusions taking place along the new-formed caldera ring fault, as well as intruding in the fissure swarm related to the regional tectonics. In order to characterize the influence of the caldera structure on the regional tectonics, we analysed the structural framework of the caldera and direct surroundings using remote sensing (optical imagery and high resolution DEM from TanDEM-X data). Then we made detailed field measurements (500 data) by analysing azimuth, dip, and opening of eruptive fissures, dikes, faults and extension fractures. Both remote sensing and field measurements have been then integrated producing a detailed structural map of Askja. Our results show

  3. A sharp cadherin-6 gene expression boundary in the developing mouse cortical plate demarcates the future functional areal border.

    PubMed

    Terakawa, Youhei W; Inoue, Yukiko U; Asami, Junko; Hoshino, Mikio; Inoue, Takayoshi

    2013-10-01

    The mammalian cerebral cortex can be tangentially subdivided into tens of functional areas with distinct cyto-architectures and neural circuitries; however, it remains elusive how these areal borders are genetically elaborated during development. Here we establish original bacterial artificial chromosome transgenic mouse lines that specifically recapitulate cadherin-6 (Cdh6) mRNA expression profiles in the layer IV of the somatosensory cortex and by detailing their cortical development, we show that a sharp Cdh6 gene expression boundary is formed at a mediolateral coordinate along the cortical layer IV as early as the postnatal day 5 (P5). By further applying mouse genetics that allows rigid cell fate tracing with CreERT2 expression, it is demonstrated that the Cdh6 gene expression boundary set at around P4 eventually demarcates the areal border between the somatosensory barrel and limb field at P20. In the P6 cortical cell pellet culture system, neurons with Cdh6 expression preferentially form aggregates in a manner dependent on Ca(2+) and electroporation-based Cdh6 overexpression limited to the postnatal stages perturbs area-specific cell organization in the barrel field. These results suggest that Cdh6 expression in the nascent cortical plate may serve solidification of the protomap for cortical functional areas. PMID:22875867

  4. Development of second-mode instability in a Mach 6 flat plate boundary layer with two-dimensional roughness

    NASA Astrophysics Data System (ADS)

    Tang, Qing; Zhu, Yiding; Chen, Xi; Lee, Cunbiao

    2015-06-01

    Particle image velocimetry, PCB pressure sensors, and planar Rayleigh scattering are combined to study the development of second-mode instability in a Mach 6 flow over a flat plate with two-dimensional roughness. To the best of the authors' knowledge, this is the first time that the instantaneous velocity fields and flow structures of the second-mode instability waves passing through the roughness are shown experimentally. A two-dimensional transverse wall blowing is used to generate second-mode instability in the boundary layer and seeding tracer particles. The two-dimensional roughness is located upstream of the synchronization point between mode S and mode F. The experimental results showed that the amplitude of the second-mode instability will be greatly increased upstream of the roughness. Then it damps and recovers quickly in the vicinity downstream of the roughness. Further downstream, it acts as no-roughness case, which confirms Fong's numerical results [K. D. Fong, X. W. Wang, and X. L. Zhong, "Numerical simulation of roughness effect on the stability of a hypersonic boundary layer," Comput. Fluids 96, 350 (2014)]. It also has been observed that the strength of the amplification and damping effect depends on the height of the roughness.

  5. Numerical Study of Three-dimensional Spatial Instability of a Supersonic Flat Plate Boundary Layer

    NASA Technical Reports Server (NTRS)

    Maestrello, Lucio; Bayliss, A.; Krishnan, R.

    1989-01-01

    The behavior of spatially growing three-dimensional waves in a supersonic boundary layer was studied numerically by solving the complete Navier-Stokes equations. Satisfactory comparison with linear parallel and non-parallel stability theories, and experiment are obtained when a small amplitude inflow disturbance is used. The three-dimensional unsteady Navier-Stokes equations are solved by a finite difference method which is fourth-order and second-order accurate in the convection and viscous terms respectively, and second-order accurate in time. Spanwise periodicity is assumed. The inflow disturbance is composed of eigenfunctions from linear stability theory. By increasing the amplitude of the inflow disturbance, nonlinear effects in the form of a relaxation type oscillation of the time signal of rho(u) are observed.

  6. Tectonic Emplacement of the Ophiolitic Mélange in the West Junggar, NW China: Comment on the Plate Boundary Significance of Ophiolitic Mélange Belt

    NASA Astrophysics Data System (ADS)

    Wang, G.; Xu, Y.; Xiao, L.; Chen, C.

    2014-12-01

    Many ophiolitic mélanges distribute in the West Junggar, NW China. They are fault-contacted with Carboniferous turbidites with mostly NE trend and some NS trend with ages mostly Ordovician-Silurian and some Late Devonian. The boundary faults and the foliation inside the mélanges are of high-angle or nearly vertical. The NE trend ophiolitic mélange belts were structurally emplaced into the Carboniferous strata mainly by dextral transpressive deformation, but the NS trend ophiolitic mélange belts mainly by lateral extrusion deformation or pure shearing, suggesting a uniform stress field of nearly EW compression controlled the emplacements. The tectonic relationship between the ophiolitic mélanges and the Carboniferous turbidites imply that the ophiolitic mélanges are the main components of the basement of the Carboniferous strata. The geophysical data also reveal that high gravity, high magnetic and medium resistivity exist under the Carboniferous strata, matching well to the distribution of the ophiolitic mélanges on the surface. The neodymium model ages (TDM) of widely distributed Late Carboniferous-Permian granites are mostly between 0.352-0.923Ga and concentrate in 0.45-0.6Ga with positive eNd(t) mostly between 5~10, suggesting the Early Paleozoic rocks as the main magma source, consistent with the age of the ophiolitic mélanges, also coinciding with the conclusion of the ophiolitic mélanges as the basement of the Carboniferous strata. The Carboniferous turbidites primarily formed in residual basin. Early Permian terrestrial coarse molasses deposits unconformitily cover on the Carboniferous turbidites, suggesting the residual basin closed in Late Carboniferous. The accretionary complex or residual oceanic crust emplaced into the overlying Carboniferous turbidites through the dextral transpression or lateral extrusion due to EW convergent when the residual basin closed. The tectonic juxtaposition relationship between the ophiolitic mélanges and the

  7. Effects of Periodic Unsteady Wake Flow and Pressure Gradient on Boundary Layer Transition Along the Concave Surface of a Curved Plate. Part 3

    NASA Technical Reports Server (NTRS)

    Schobeiri, M. T.; Radke, R. E.

    1996-01-01

    Boundary layer transition and development on a turbomachinery blade is subjected to highly periodic unsteady turbulent flow, pressure gradient in longitudinal as well as lateral direction, and surface curvature. To study the effects of periodic unsteady wakes on the concave surface of a turbine blade, a curved plate was utilized. On the concave surface of this plate, detailed experimental investigations were carried out under zero and negative pressure gradient. The measurements were performed in an unsteady flow research facility using a rotating cascade of rods positioned upstream of the curved plate. Boundary layer measurements using a hot-wire probe were analyzed by the ensemble-averaging technique. The results presented in the temporal-spatial domain display the transition and further development of the boundary layer, specifically the ensemble-averaged velocity and turbulence intensity. As the results show, the turbulent patches generated by the wakes have different leading and trailing edge velocities and merge with the boundary layer resulting in a strong deformation and generation of a high turbulence intensity core. After the turbulent patch has totally penetrated into the boundary layer, pronounced becalmed regions were formed behind the turbulent patch and were extended far beyond the point they would occur in the corresponding undisturbed steady boundary layer.

  8. Rheologic effects of crystal preferred orientation in upper mantle flow near plate boundaries

    NASA Astrophysics Data System (ADS)

    Blackman, Donna; Castelnau, Olivier; Dawson, Paul; Boyce, Donald

    2016-04-01

    Observations of anisotropy provide insight into upper mantle processes. Flow-induced mineral alignment provides a link between mantle deformation patterns and seismic anisotropy. Our study focuses on the rheologic effects of crystal preferred orientation (CPO), which develops during mantle flow, in order to assess whether corresponding anisotropic viscosity could significantly impact the pattern of flow. We employ a coupled nonlinear numerical method to link CPO and the flow model via a local viscosity tensor field that quantifies the stress/strain-rate response of a textured mineral aggregate. For a given flow field, the CPO is computed along streamlines using a self-consistent texture model and is then used to update the viscosity tensor field. The new viscosity tensor field defines the local properties for the next flow computation. This iteration produces a coupled nonlinear model for which seismic signatures can be predicted. Results thus far confirm that CPO can impact flow pattern by altering rheology in directionally-dependent ways, particularly in regions of high flow gradient. Multiple iterations run for an initial, linear stress/strain-rate case (power law exponent n=1) converge to a flow field and CPO distribution that are modestly different from the reference, scalar viscosity case. Upwelling rates directly below the spreading axis are slightly reduced and flow is focused somewhat toward the axis. Predicted seismic anisotropy differences are modest. P-wave anisotropy is a few percent greater in the flow 'corner', near the spreading axis, below the lithosphere and extending 40-100 km off axis. Predicted S-wave splitting differences would be below seafloor measurement limits. Calculations with non-linear stress/strain-rate relation, which is more realistic for olivine, indicate that effects are stronger than for the linear case. For n=2-3, the distribution and strength of CPO for the first iteration are greater than for n=1, although the fast seismic

  9. Direct Numerical Simulations of Boundary Layer Transition on a Flat Plate

    NASA Technical Reports Server (NTRS)

    Rai, Man Mohan

    1997-01-01

    In recent years the techniques of computational fluid dynamics (CFD) have been used to compute flows associated with geometrically complex configurations. However, success in terms of accuracy and reliability has been limited to cases where the effects of turbulence and transition could be modeled in a straightforward manner. Even in simple flows, the accurate computation of skin friction and heat transfer using existing turbulence models has proved to be a difficult task, one that has required extensive fine-tuning of the turbulence models used. In more complex flows (for example, in turbomachinery flows in which vortices and wakes impinge on airfoil surfaces causing periodic transitions from laminar to turbulent flow) the development of a model that accounts for all scales of turbulence and predicts the onset of transition is an extremely difficult task. Fortunately, current trends in computing suggest that it may be possible to perform direct simulations of turbulence and transition at moderate Reynolds numbers in some complex cases in the near future. This presentation will focus on direct simulations of transition and turbulence using high-order accurate finite-difference methods. The advantage of the finite-difference approach over spectral methods is that complex geometries can be treated in a straightforward manner. Additionally, finite-difference techniques are the prevailing methods in existing application codes. An application of accurate finite-difference methods to direct simulations of transition and turbulence in a spatially evolving boundary layer subjected to high levels of freestream turbulence will be presented.

  10. Direct Numerical Simulations of Boundary Layer Transition on a Flat Plate

    NASA Technical Reports Server (NTRS)

    Rai, Man Mohan

    1998-01-01

    In recent years the techniques of computational fluid dynamics (CFD) have been used to compute flows associated with geometrically complex configurations. However, success in terms of accuracy and reliability has been limited to cases where the effects of turbulence and transition could be modeled in a straightforward manner. Even in simple flows, the accurate computation of skin friction and heat transfer using existing turbulence models has proved to be a difficult task, one that has required extensive fine-tuning of the turbulence models used. In more complex flows (for example, in turbomachinery flows in which vortices and wakes impinge on airfoil surfaces causing periodic transitions from laminar to turbulent flow) the development of a model that accounts for all scales of turbulence and predicts the onset of transition is an extremely difficult task. Fortunately, current trends in computing suggest that it may be possible to perform direct simulations of turbulence and transition at moderate Reynolds numbers in some complex cases in the near future. This presentation will focus on direct simulations of transition and turbulence using high-order accurate finite-difference methods. The advantage of the finite-difference approach over spectral methods is that complex geometries can be treated in a straightforward manner. Additionally, finite-difference techniques are the prevailing methods in existing application codes. An application of high-order-accurate finite-difference methods to direct simulations of transition and turbulence in a spatially evolving boundary layer subjected to high levels of freestream turbulence will be presented.

  11. Evolution of the Walker Lane: An Incipient Transform Fault and Future Pacific-North America Plate Boundary

    NASA Astrophysics Data System (ADS)

    Faulds, J. E.; Henry, C. D.

    2009-12-01

    -ward migration of the Mendocino triple junction (MTJ). The northern WL is the least developed part of the WL-ECSZ, with right slip decreasing from ~25 km to zero to the NW. Here, en echelon left-stepping dextral faults are analogous to Riedel shears developed above a through-going shear zone at depth. Coeval extension and dextral shear have induced slight counterclockwise rotations, which may ultimately rotate Riedel shears toward the main shear zone at depth, facilitate hard linkage between Riedel shears, and produce a through-going strike-slip fault. The WL-ECSZ now terminates near the south end of the Cascade arc near the latitude of the MTJ, suggesting that the SAF and WL-ECSZ are migrating N-ward at similar rates. With continued N-ward migration, the MTJ will collide with the NW-propagating WL off southern Oregon in ~8 Ma. The plate boundary will then likely jump inland to the WL-ECSZ. The current setting is one stage in the progressive dismembering of an Andean type margin through lateral growth and inland stepping of a transform fault. This process is fragmenting the continental margin and transferring slices of North America to the Pacific plate. Evolving transform faults may therefore be important in generating far-traveled exotic terranes.

  12. The northern Caribbean plate boundary in the Jamaica Passage: Structure and seismic stratigraphy

    NASA Astrophysics Data System (ADS)

    Corbeau, J.; Rolandone, F.; Leroy, S.; Mercier de Lépinay, B.; Meyer, B.; Ellouz-Zimmermann, N.; Momplaisir, R.

    2016-04-01

    Multibeam bathymetry data and multichannel seismic reflection profiles have been collected at the end of 2012 along the Enriquillo-Plantain-Garden Fault Zone (EPGFZ) in the Jamaica Passage, between Jamaica and Hispaniola. Analysis of the data set reveals the tectonic evolution and the stratigraphic complexity of the northern Caribbean boundary. Stratigraphic correlations with previous marine and on land studies are proposed to place the identified seismic sequences in their regional tectonic history. Two distinct crustal domains are interpreted. Typical stratigraphic sequences for the rifted blocks of the Eastern Cayman Trough margin are identified in five basins of the Jamaica Passage, highlighting the eastward limit of the Cayman Trough margin. These inherited basins are deformed and folded during a first phase of compression that could correspond to the regional tectonic rearrangement recorded in the early Miocene (about 20 Ma). A distinct crustal domain that we propose to relate to the Carib Beds (Caribbean typical reflectors A″, B″ and V) is identified in the southern part of the Jamaica Passage, indicating that the Caribbean Large Igneous Province could extend up to the extreme northeast part of the Lower Nicaragua Rise. The left-lateral EPGFZ currently cuts across two pre-existing basins, the Morant and Matley basins. During the activity of the EPGFZ, these basins are deformed and folded indicating a second phase of compression. In contrast, the Navassa basin, located in the middle of the Jamaica Passage, results from the strike-slip motion of the EPGFZ and is interpreted as an asymmetrical basin bordered by the EPGFZ only on its northern side.

  13. Structural Evolution of the India-Arabia Plate Boundary from Miocene to Present-Day (NW Indian Ocean) and Comparison with the Dead Sea Fault (Eastern Mediterranean Sea).

    NASA Astrophysics Data System (ADS)

    Rodriguez, M.; Huchon, P.; Chamot Rooke, N.; Fournier, M.; Delescluse, M.; Ben Avraham, Z.; Ten Brink, U. S.

    2014-12-01

    Arabia is bounded by the Dead Sea Transform (DST) to the west and by the Owen Fracture Zone (OFZ) to the east. These present-day major strike-slip fault systems activated during the Plio-Pleistocene, which contrasts with the age of inception of strike-slip motion, assumed to begin around 13-18 Ma for the DST and around 20 Ma at the edge of the Owen-Murray Ridge (OMR) for the India-Arabia plate boundary. This discrepancy between the age of the active strike-slip systems and the age of inception of strike-slip motion raises the question of the kinematic driver for the transition between successive generations of strike-slip faults. Using a recent mutibeam and seismic dataset crossing the OFZ and the OMR, we provide a new geodynamic framework for the Miocene to present-day structural evolution of the India-Arabia plate boundary, and highlight some similarities with the structural evolution of the DST. We first document a Late Miocene episode of uplift of the OMR uplift along the Miocene India-Arabia plate boundary. The onset of this uplift is coeval with a plate reorganization event marked by the onset of intra-plate deformation in the Central Indian Ocean. The OFZ emplaced around 3 Ma, with major pull-apart basins opening (20°N Basin, Dalrymple Trough) dated at 2.4 Ma by far-field correlation with ODP Sites. The opening of pull-apart basins is coeval with the last structural reorganization of the Makran accretionnary wedge, marked by the regional M-unconformity, and with a major intensification of the Indian monsoon. A Late Miocene episode of folding is also recognized at the Lebanon ranges prior to the onset of the present-day DST, which occurred in the Late Pliocene-Early Pleistocene. The similarities between the geological history of the India-Arabia plate boundary and the DST in the Late Miocene and the Late Pliocene-Early Pleistocene suggest that both plate boundaries recorded the same kinematic changes. Late Miocene (i.e. Tortonian) deformation is widely

  14. Integration of the Plate Boundary Observatory and Existing GPS Networks in Southern California: A Multi Use Geodetic Network

    NASA Astrophysics Data System (ADS)

    Walls, C.; Blume, F.; Meertens, C.; Arnitz, E.; Lawrence, S.; Miller, S.; Bradley, W.; Jackson, M.; Feaux, K.

    2007-12-01

    The ultra-stable GPS monument design developed by Southern California Geodetic Network (SCIGN) in the late 1990s demonstrates sub-millimeter errors on long time series where there are a high percentage of observations and low multipath. Following SCIGN, other networks such as PANGA and BARGEN have adopted the monument design for both deep drilled braced monuments (DDBM = 5 legs grouted 10.7 meters into bedrock/stratigraphy) and short drilled braced monuments (SDBM = 4 legs epoxied 2 meters into bedrock). A Plate Boundary Observatory (PBO) GPS station consists of a "SCIGN" style monument and state of the art NetRS receiver and IP based communications. Between the years 2003-2008 875 permanent PBO GPS stations are being built throughout the United States. Concomitant with construction of the PBO the majority of pre-existing GPS stations that meet stability specifications are being upgraded with Trimble NetRS and IP based communications to PBO standards under the EarthScope PBO Nucleus project. In 2008, with completed construction of the Plate Boundary Observatory, more than 1100 GPS stations will share common design specifications and have identical receivers with common communications making it the most homogenous geodetic network in the World. Of the 875 total Plate Boundary Observatory GPS stations, 211 proposed sites are distributed throughout the Southern California region. As of August 2007 the production status is: 174 stations built (81 short braced monuments, 93 deep drilled braced monuments), 181 permits signed, 211 permits submitted and 211 station reconnaissance reports. The balance of 37 stations (19 SDBM and 18 DDBM) will be built over the next year from Long Valley to the Mexico border in order of priority as recommended by the PBO Transform, Extension and Magmatic working groups. Fifteen second data is archived for each station and 1 Hz as well as 5 Hz data is buffered to be triggered for download in the event of an earthquake. Communications

  15. Plio-Quaternary paleostresses in the Atlantic passive margin of the Moroccan Meseta: Influence of the Central Rif escape tectonics related to Eurasian-African plate convergence

    NASA Astrophysics Data System (ADS)

    Chabli, Ahmed; Chalouan, Ahmed; Akil, Mostapha; Galindo-Zaldívar, Jesús; Ruano, Patricia; Sanz de Galdeano, Carlos; López-Garrido, Angel Carlos; Marín-Lechado, Carlos; Pedrera, Antonio

    2014-07-01

    The Atlantic Moroccan Meseta margin is affected by far field recent tectonic stresses. The basement belongs to the variscan orogen and was deformed by hercynian folding and metamorphism followed by a post-Permian erosional stage, producing the flat paleorelief of the region. Tabular Mesozoic and Mio-Plio-Quaternary deposits locally cover the Meseta, which has undergone recent uplift, while north of Rabat the subsidence continues in the Gharb basin, constituting the foreland basin of the Rif Cordillera. The Plio-Quaternary sedimentary cover of the Moroccan Meseta, mainly formed by aeolian and marine terraces deposits, is affected by brittle deformations (joints and small-scale faults) that evidence that this region - considered up to date as stable - is affected by the far field stresses. Striated faults are recognized in the oldest Plio-Quaternary deposits and show strike-slip and normal kinematics, while joints affect up to the most recent sediments. Paleostress may be sorted into extensional, only affecting Rabat sector, and three main compressive groups deforming whole the region: (1) ENE-WSW to ESE-WNW compression; (2) NNW-SSE to NE-SW compression and (3) NNE-SSW compression. These stresses can be attributed mainly to the NW-SE oriented Eurasian-African plate convergence in the western Mediterranean and the escape toward the SW of the Rif Cordillera. Local paleostress deviations may be related to basement fault reactivation. These new results reveal the tectonic instability during Plio-Quaternary of the Moroccan Meseta margin in contrast to the standard passive margins, generally considered stable.

  16. Cratonic platform and foredeep response to plate margin convergence: Devonian through Mississippian subsidence history in western Montana and east-central Idaho

    SciTech Connect

    Dorobek, S.L.; Reid, S.K. ); Elrich, M. ); Bond, G.C. ); Kominz, M.A. )

    1990-05-01

    Devonian and Mississippian sedimentary rocks of western Montana and east-central Idaho were deposited on a cratonic platform that faced a northern extension of the Antler foredeep. Subsidence analyses of this sequence and isopach maps illustrate regional patterns of subsidence related to convergence along the western North American plate margin. Tectonic stresses affected deposition on platform areas which were hundreds of kilometers inboard from the ancient continental margin. Wavelengths of paleostructural elements, tectonic inversion of these structures (i.e., transition of a paleohigh into a depocenter), and time scales involved in the inversion process cannot be attributed solely to flexure or to vertical displacements by in-plane stresses but suggest reactivation of Precambrian structural trends. Late Devonian (Frasnian) platform sedimentation began during a brief interval of increased subsidence across western Montana. This interval of increased platform subsidence is greater than a Late Devonian eustatic sea level rise (determined from subsidence analyses of Devonian strata from stable cratonic areas) and suggests some tectonic event must have influenced subsidence in Montana. Thin uppermost Devonian Strata contain numerous unconformities that may be related to flexure of the platform plus eustatic sea level fluctuations. Rapid subsidence across Montana during the Early Mississippian (Kinderhookian) resulted in a condensed platform sequence, which is overlain by deep water shaly carbonates. Rapid subsidence continued into the Osagean then slowed, allowing progradation of carbonate platform facies across Montana. A regional karst surface on top of the Meramecian platform coincides with conglomerate deposition and increased subsidence rates in the foredeep; unconformity durations on the platform also increase to the east.

  17. Effects of Mach Number, Leading-Edge Bluntness, and Sweep on Boundary-Layer Transition on a Flat Plate

    N