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Sample records for 660-km seismic discontinuity

  1. Seismic evidence against a mantle chemical discontinuity near 660 km depth beneath Izu-Bonin

    NASA Astrophysics Data System (ADS)

    Castle, John C.; Creager, Kenneth C.

    We analyze P-wave codas from 12 deep Izu-Bonin earthquakes recorded by hundreds of Western United States seismograph stations for evidence of small-amplitude phases caused by near-source mantle discontinuities. For nearly every event, the dominant phase in the coda is the result of an S-to-P conversion from a nearly horizontal discontinuity ranging in depth from 650 to 690 km. This is interpreted as a thermally depressed spinel to perovskite and magnesiowüstite phase transition. If the 660-km seismic discontinuity is also associated with a change in chemistry, it would be dynamically depressed by a subducting slab. We consistently see that there is no nearly horizontal discontinuity between 700 and 1000 km with shear wave velocity contrast exceeding 1%; this observation places constraints on the properties of a postulated chemical discontinuity separating the upper and lower mantles.

  2. Topography of the 660-km seismic discontinuity beneath Izu-Bonin: Implications for tectonic history and slab deformation

    NASA Astrophysics Data System (ADS)

    Castle, John C.; Creager, Kenneth C.

    1998-06-01

    We analyze the P wave codas of 65 paths from deep northwestern Pacific earthquakes recorded by arrays of stations in Germany, the western United States, India, and Turkmenistan. We identify a phase resulting from a near-source S-to-P conversion at a nearly horizontal discontinuity ranging in depth from 650 to 730 km, which we interpret as a thermally depressed spinel to perovskite and magnesiowüstite phase transition. We migrate these data along with 39 more from Wicks and Richards [1993], accounting for three-dimensional ray bending by the sloping discontinuity, to produce a high-resolution topography map of the 660-km discontinuity in the Izu-Bonin region. Assuming an equilibrium phase transition, we interpret the discontinuity depth in terms of local temperatures. The slab, if defined by a thermal anomaly greater than -400°K, is only about 100 km thick near 28°N suggesting the slab is penetrating into the lower mantle with little or no advective thickening. Farther to the north, however, cold material appears spread out over a wide region, consistent with the slab having been laid down flat on the 660-km discontinuity as the trench retreated 2000 km eastward. Both the narrow slab to the south and the flat-lying slab to the north are consistent with recent high-resolution tomographic images. The depression to 745 km along the arc is consistent with a maximum thermal anomaly of about 1100°K. Along the entire arc, the depression occurs directly beneath the deepest earthquakes, even where seismicity is dipping at 45° and stops at 450 km depth, suggesting that the slab steepens to a vertical dip at the deepest seismicity. This change to a vertical orientation suggests that the slab loses strength temporarily through a physical process which causes the seismicity to increase dramatically and then abruptly cease.

  3. Imaging Resolution of 410-km and 660-km Discontinuities

    NASA Astrophysics Data System (ADS)

    Deng, Kai; Zhou, Ying

    2014-05-01

    Seismic discontinuities in the mantle transition zone at depths of about 410 and 660 km are associated with olivine phase transformations. The depths of the discontinuities provide important constraints on the thermal structure of the mid mantle. Teleseismic receiver functions as well as PP and SS precursors have been widely used in imaging topographic variations of the 410 and 660 discontinuities. Ray-theory based migration and stacking methods are often used to enhance signals of the converted and reflected waves, assuming that the effects of 3-D structure in wavespeed can be averaged out. In this study, we investigate the resolution of traditional methods in imaging the 410-km and 660-km discontinuity topography based on wave propagation simulations using the Spectral Element Method (SEM). We calculate synthetic seismograms in laterally heterogeneous wavespeed models with lateral variations in the 410-km and 660-km discontinuity depths. The SEM synthetics are processed following standard migration and stacking techniques to image the discontinuities. We show that 3-D wave speed structure beneath seismic stations can introduce significant artifacts in transition zone discontinuity topography. We also investigate finite-frequency effects of P-to-S converted waves as well as PP and SS precursors in imaging the discontinuities by varying the length scale of depth variations in the 410-km and 660-km discontinuities in SEM simulations, and show that wave front healing effects depend on the length scale of the depth variation as well as epicentral distances. Finally we compare receiver function delay times with calculations based on finite frequency sensitivity and show that wave front healing effects can be properly accounted for.

  4. Imaging Resolution of the 410-km and 660-km Discontinuities

    NASA Astrophysics Data System (ADS)

    Deng, K.; Zhou, Y.

    2014-12-01

    Structure of seismic discontinuities at depths of about 410 km and 660 km provides important constraints on mantle convection as the associated phase transformations in the transition zone are sensitive to thermal perturbations. Teleseismic P-to-S receiver functions have been widely used to map the depths of the two discontinuities. In this study, we investigate the resolution of receiver functions in imaging topographic variations of the 410-km and 660-km discontinuities based on wave propagation simulations using the Spectral Element Method (SEM). We investigate finite-frequency effects of direct P waves as well as P-to-S converted waves by varying the length scale of discontinuity topography in the transition zone. We show that wavefront healing effects are significant in broadband receiver functions. For example, at a period of 10 to 20 seconds, the arrival anomaly in P-to-S converted waves is about 50% of what predicted by ray theory when the topography length scale is in the order of 400 km. The observed arrival anomaly further reduces to 10-20% when the topography length scale reduces to about 200 km. We calculate 2-D boundary sensitivity kernels for direct P waves as well as receiver functions based on surface wave mode summation and confirm that finite frequency-effects can be properly accounted for. Three-dimensional wavespeed structure beneath seismic stations can also introduce significant artifacts in transition zone discontinuity topography if time corrections are not applied, and, the effects are dependent on frequency.

  5. Effect of water in depleted mantle on post-spinel transition and implication for 660 km seismic discontinuity

    NASA Astrophysics Data System (ADS)

    Ghosh, Sujoy; Ohtani, Eiji; Litasov, Konstantin D.; Suzuki, Akio; Dobson, David; Funakoshi, Kenichi

    2013-06-01

    We have determined the post-spinel transition boundary in anhydrous and hydrous Mg2SiO4 in a temperature range from 1173 to 2023 K at 19.3-25.4 GPa using synchrotron in situ X-ray diffraction measurements. The phase boundary in Mg2SiO4 is located at 22 GPa and 1800 K and 22.1 GPa and 1500 K, which is slightly lower (~0.3-0.5 GPa) than that determined in the previous in situ measurements using the same pressure scale [e.g. Katsura et al., 2003, Post-spinel transition in Mg2SiO4 determined by high P-Tin situ X-ray diffractometry. Phys. Earth Planet. Inter. 136, 11-24]. The Clapeyron slope of Mg2SiO4 was found to be gentle i.e. between -0.4 and -0.7 MPa/K, which is also consistent with previous in situ measurements, but inconsistent with diamond anvil cell experiments and theoretical estimations. The phase boundary in Mg2SiO4+2 wt% H2O which is relevant to Fe free-depleted harzburgitic composition is located between 23.4 and 23.6 GPa and 1500 K, which shifts the hydrous boundary to the higher pressures relative to anhydrous Mg2SiO4 from 1.3 to 1.0 GPa. The result for hydrous Mg2SiO4 shows steeper Clapeyron slope between -3.2 and -3.1 MPa/K compared with anhydrous Mg2SiO4 and hydrous pyrolite system. The present data suggest that water has a strong influence on 660 km discontinuity and the depressions observed at this boundary in several regions, especially related to subduction zones, can be explained by the presence of water in depleted harzburgite component.

  6. Bridging the Gap Between Seismic Observations and Mineral Physics Interpretations: a Hypothesis for Hydrous Majorite Associated With a Stagnant Slab Near the 660 km Discontinuity

    NASA Astrophysics Data System (ADS)

    Tajima, F.; Katayama, I.; Nakagawa, T.

    2008-12-01

    Our broadband seismic body waveform analyses have determined a fairly broad region of high velocity anomaly (HVA) in the northwestern Pacific suggesting that the subducting plate is lying flat or piling up in the upper mantle transition zone (MTZ). That is in agreement with long- wavelength tomography studies although we found that a typical wavelength of HVA is shorter, and the total volume of the stagnant slab is considerably less than the tomographic image and much smaller than that of subducted plate during the known subduction history (Tajima and Grand, 1998). We also found variation of the discontinuity depth (~660 to 690 km) with HVA and a highly localized low velocity anomaly zone (LVAZ) near the 660 km discontinuity (Tajima and Nakagawa, 2006). We postulated a variable distribution of geochemical properties associated with a cold stagnant slab at the bottom of the MTZ where the contrast of a hydrous garnet-rich layer (subducted crust of MORB origin) versus bulk peridotite is involved. The estimated seismic properties in the MTZ, which are not unambiguous, can be checked for various conditions and validated through synthetic high pressure (P) and temperature (T) experiments. Two recent experimental studies under high P and T conditions provide supportive feedback for this hypothesis, i.e., a positive Clapeyron slope for hydrous garnet-perovskite phase transformation (Sano et al., 2006) and weaker hydrous garnet than peridotite in the MTZ (Katayama and Karato, 2008). On the other hand, seismic velocity measurements in laboratory experiments show that the garnetite with a MORB composition has significantly lower P- and S-wave velocities than wadsleyite and ringwoodite when these data are extrapolated to the conditions of the MTZ (Kono et al., 2007). However, the ultrasonic P- and S-wave velocity measurements of dry materials were performed at pressures up to 14.3 GPa at room temperature, and then the estimates of elastic properties for the MTZ condition are

  7. Depressed mantle discontinuities beneath Iceland: Evidence of a garnet controlled 660 km discontinuity?

    NASA Astrophysics Data System (ADS)

    Jenkins, J.; Cottaar, S.; White, R. S.; Deuss, A.

    2016-01-01

    The presence of a mantle plume beneath Iceland has long been hypothesised to explain its high volumes of crustal volcanism. Practical constraints in seismic tomography mean that thin, slow velocity anomalies representative of a mantle plume signature are difficult to image. However it is possible to infer the presence of temperature anomalies at depth from the effect they have on phase transitions in surrounding mantle material. Phase changes in the olivine component of mantle rocks are thought to be responsible for global mantle seismic discontinuities at 410 and 660 km depth, though exact depths are dependent on surrounding temperature conditions. This study uses P to S seismic wave conversions at mantle discontinuities to investigate variation in topography allowing inference of temperature anomalies within the transition zone. We employ a large data set from a wide range of seismic stations across the North Atlantic region and a dense network in Iceland, including over 100 stations run by the University of Cambridge. Data are used to create over 6000 receiver functions. These are converted from time to depth including 3D corrections for variations in crustal thickness and upper mantle velocity heterogeneities, and then stacked based on common conversion points. We find that both the 410 and 660 km discontinuities are depressed under Iceland compared to normal depths in the surrounding region. The depression of 30 km observed on the 410 km discontinuity could be artificially deepened by un-modelled slow anomalies in the correcting velocity model. Adding a slow velocity conduit of -1.44% reduces the depression to 18 km; in this scenario both the velocity reduction and discontinuity topography reflect a temperature anomaly of 210 K. We find that much larger velocity reductions would be required to remove all depression on the 660 km discontinuity, and therefore correlated discontinuity depressions appear to be a robust feature of the data. While it is not possible

  8. Role of the transition zone and 660 km discontinuity in mantle dynamics

    NASA Astrophysics Data System (ADS)

    Ringwood, A. E.

    1994-10-01

    Recent seismic evidence suggests that subducted slabs experience resistance to further descent when they encounter the 660 km seismic discontinuity. Several possible causes of this resistance are evaluated. It is concluded that the chemical composition of the lower mantle is similar to that of the upper mantle, and that compositional change is therefore unlikely to be the cause of resistance to slab penetration. The proposal that a large increase of viscosity at the 660 km discontinuity impedes descending slabs is also rejected. However, three other factors are identified, each of which is capable of causing substantial resistance to descending slabs: (1) the negative slope of the transformation of silicate spinel to Mg-perovskite+magnesiowuestite; (2) differentiation of oceanic lithosphere into basaltic and depleted peridotitic layers, causing the slab to be buoyant compared with surrounding mantle pyrolite between depths of 660-800 km; (3) the accumulation of former oceanic crust to produce a gravitationally stable layer of garnetite (about 50 km thick) on top of the 660 km discontinuity. The combined effects of these sources of resistance provide a filter for subducted slabs. Those slabs with seismic zones extending below 600 km may possess sufficient negative buoyancy and strength to overcome the barriers and penetrate into the lower mantle. However, the resistance causes strong buckling and plastic thickening of these slabs, which accumulate to form huge blobs or 'megaliths' underneath the 660 km discontinuity. In contrast, slabs with seismic zones extending no deeper than 300 km possess much smaller degrees of negative buoyancy and strength and hence are unable to penetrate the 660 km discontinuity. Slabs of this type are recycled within the transition zone and upper mantle. Mixing and petrological homogenization processes are less efficient in the transition zone than in the upper mantle (above 400 km). The transition zone is composed mainly of ancient slabs

  9. Multiplicity of the 660-km discontinuity beneath the Izu-Bonin area

    NASA Astrophysics Data System (ADS)

    Zhou, Yuan-Ze; Yu, Xiang-Wei; Yang, Hui; Zang, Shao-Xian

    2012-05-01

    The relatively simple subducting slab geometry in the Izu-Bonin region provides a valuable opportunity to study the multiplicity of the 660-km discontinuity and the related response of the subducting slab on the discontinuity. Vertical short-period recordings of deep events with simple direct P phases beneath the Izu-Bonin region were retrieved from two seismic networks in the western USA and were used to study the structure of the 660-km discontinuity. After careful selection and pre-processing, 23 events from the networks, forming 32 pairs of event-network records, were processed. Related vespagrams were produced using the N-th root slant stack method for detecting weak down-going SdP phases that were inverted to the related conversion points. From depth histograms and the spatial distribution of the conversion points, there were three clear interfaces at depths of 670, 710 and 730 km. These interfaces were depressed approximately 20-30 km in the northern region. In the southern region, only two layers were identified in the depth histograms, and no obvious layered structure could be observed from the distribution of the conversion points.

  10. Topography of the 410 and 660 km discontinuities beneath the Korean Peninsula and southwestern Japan using teleseismic receiver functions

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Hyun; Rhie, Junkee; Park, Yongcheol; Kim, Kwang-Hee

    2014-09-01

    Topography of the 410 and 660 km seismic upper mantle discontinuities beneath the Korean Peninsula and southwestern Japan were determined using teleseismic receiver functions. P receiver functions were migrated from delayed times to corresponding piercing (conversion) points of P-to-S converted phases, using one-dimensional (1-D) and three-dimensional (3-D) models. Receiver functions were then stacked using Common Conversion Point (CCP) techniques, to enhance signal-to-noise ratios and thereby reduce uncertainty (noise). The 410 and 660 km discontinuities were clearly imaged, as positively valued amplitude peaks of CCP stacked receiver functions in the study area. Topographic variations were roughly consistent with the low temperature of the subducting Pacific Plate. However, the complex structure of the subducting Pacific Plate produced distinct changes of upper mantle discontinuities, which cannot be explained by temperature variations alone. Depression of the 410 km discontinuity, observed in a wide region extending from the Korean Peninsula to Kyushu Island, may be related to trench rollback history. Furthermore, the topography of the 660 km discontinuity varies significantly with latitude. At latitudes higher than 38°N, its depth remains unchanged, despite the presence of the stagnant slab, while significant depression has been observed at latitudes below 36°N. This may have been caused by differences in the angles of subduction of the Japan slab and the Izu-Bonin slab. However, heterogeneity of the water content of slabs may also have contributed to this topographical difference.

  11. The kinetics of the reaction of majorite plus ferropericlase to ringwoodite: Implications for mantle upwellings crossing the 660 km discontinuity

    NASA Astrophysics Data System (ADS)

    Dobson, D. P.; Mariani, E.

    2014-12-01

    We have measured the kinetics of reaction between MgO and majoritic garnet at 20 GPa and 1773-2123 K as a proxy for the reaction between perovskite and ferropericlase during mantle upwelling across the 660 km seismic discontinuity. Ringwoodite forms a layer between MgO and garnet and, in the case of aluminous garnets the interface between ringwoodite and garnet develops a fingering instability resulting in a complex intergrowth at this interface. By contrast, the MgO-ringwoodite interface is always planar for an initial planar MgO-garnet interface. Two thicknesses are therefore defined; (1) a layer thickness, X1, which is the maximum thickness of ringwoodite which forms a plane-parallel bounded layer next to the MgO, and (2) an interface thickness, X2, which is the maximum extent of the intergrowth region away from the ringwoodite layer. The growth of both of these regions can be described by apparent rate constants, ki, which are Arrhenius with ln ⁡ (k10) = - 6.36 ± 0.25m2 /s and E1 = 456 ± 40 kJ /mol for the ringwoodite layer, and ln ⁡ (k20) = - 9.2 ± 3.3m2 /s and E2 = 371 ± 53 kJ /mol for the intergrowth region. The fingering instability is caused by the incompatibility of aluminium in ringwoodite and its low chemical diffusivity in garnet which results in an increase of surface area at the ringwoodite-garnet interface to minimise the aluminium concentration at the interface. The intergrowth region contains a fine-grained mixture of ringwoodite and garnet which coarsens very slowly with time. This might result in a transient weakening of upwelling regions of mantle just above the 660 km seismic discontinuity allowing some viscous decoupling between the upper and lower mantle.

  12. In situ X-ray diffraction study of post-spinel transformation in peridotite mantle: Implication to 660 km discontinuity

    NASA Astrophysics Data System (ADS)

    Litasov, K.; Ohtani, E.; Suzuki, A.; Funakoshi, K.

    2004-12-01

    The 660-km seismic discontinuity in the Earth's mantle is identified with the transformation of ringwoodite (spinel (Mg,Fe)2SiO4-phase) to (Mg,Fe)SiO3-perovskite and (Mg,Fe)O-ferropericlase. It was suggested using quench experiments that the transformation boundary has significant negative Clapeyron slope (-3 MPa/K, Ito and Takahashi, 1989) responsible for depressions and elevations of the 660-km discontinuity in subduction zones and hot spots of mantle plumes. Recent in situ x-ray diffraction studies in Mg2SiO4 system indicate that negative slope of the boundary is much gentler (-1.3 MPa/K) (Fei et al., 2004). Therefore there must be another factors resulting in significant depth variations of the 660-km discontinuity. In this study, we present the phase relations in anhydrous pyrolite by in situ X-ray diffraction measurements to examine the influence of additional components and Mg/Si-ratio on post-spinel phase transformation. Experiments were carried out using Speed-1500 multianvil apparatus installed at BL04B1 at synchrotron radiation facility `Spring-8' (Hyogo, Japan). Starting materials were synthetic glass representing SiO2-Al2O3-FeO-MgO-CaO-pyrolite. Graphite capsule were used as a sample container. Co-doped MgO was used as the pressure medium and a cylindrical LaCrO3 heater was used as the heating element. Temperature was measured with a WRe thermocouple. Different equation of states for Au and MgO was used for pressure calibration. The phase relations were determined at 20-25 GPa and temperature up to 2300 K. We observed easy nucleation of Mg-perovskite and ferropericlase from ringwoodite-bearing assembly in the temperature range of 1600-2200 K. The obtained post-spinel phase boundary can be expressed as P (GPa) = - 0.0004 T (K) + 22.26 using pressures calibrated by Au scale (Anderson et al., 1989). The choice of pressure scale does not have significant influence on the slope of phase transformation. Our experiments demonstrated that variations of

  13. The thermal influence of the subducting slab beneath South America from 410 and 660 km discontinuity observations

    NASA Astrophysics Data System (ADS)

    Collier, J. D.; Helffrich, G. R.

    2001-11-01

    Regional seismic network data from deep South American earthquakes to western United States and western European seismic arrays is slant stacked to detect weak near-source interactions with upper mantle discontinuities. These observations are complemented by an analysis of earlier work by Sacks & Snoke (1977) who observed S to P conversions from deep events to stations in South America, and similar observations from 1994-95 events using the BANJO and SEDA networks. Observations of the depth of the 410km discontinuity are made beneath central South America in the vicinity of the aseismic region of the subducting Nazca Plate. These results image the 410km discontinuity over a lateral extent of up to 850km perpendicular to the slab and over a distance of 2700km along the length of the slab. Away from the subducting slab the discontinuity is mainly seen near its global average depth, whilst inside the slab there is evidence for its elevation by up to around 60km but with significant scatter in the data. These results are consistent with the presence of a continuous slab through the aseismic region with a thermal anomaly of 900°C at 350km depth. This value is in good agreement with simple thermal models though our data are too sparse to accurately constrain them. Sparse observations of the 660km discontinuity agree with tomographic models suggesting penetration of the lower mantle by the slab in the north but stagnation at the base of the transition zone in the south. The geographical distribution of the data, however, does not allow us to rule out the possibility of slab stagnation at the base of the transition zone in the north. These observations, together with the presence of deep earthquakes, require more complicated thermal models than previously used to explain them, possibly including changes in slab dip and age with depth.

  14. Density Structures of Oceanic Slabs and Surrounding Mantle Around the 660 km Discontinuity: Implications for the Fate of Old and Young Slabs

    NASA Astrophysics Data System (ADS)

    Ganguly, J.; Saxena, S. K.; Freed, A. M.

    2007-05-01

    We calculated density variations as a function of temperature around the 660 km deep seismic discontinuity in the Earth's mantle in different types of compositional units associated with a subducting slab and the ambient mantle. The calculations are based on computational thermodynamic approach of minimization of Gibbs free energy at a specified P-T condition, subject to the bulk compositional constraints of the system, that simultaneously yield stable mineral assemblage, mineral compositions and modal abundances. These results are converted to density profiles using appropriate data for physical properties and equations of state that are applicable to high P-T conditions. In addition, we also calculated thermal structures of several slabs, with the extremes being given by Tonga (140 Myr at trench, vertical velocity: 14 cm/yr; average dip: 60 degrees) and Peru (41 Myr, 4.4 cm/yr, 35 degrees). A slab was assumed to be lithologically stratified with a top basaltic crust, followed downwards by residual harzburgite and slightly depleted pyrolite. The surrounding mantle is taken to be undepleted pyrolite. Integration of the results of thermal and density calculations show that that all components of the Tonga slab are heavier than both ambient and thermally perturbed adjacent mantle, which has been cooled due to contact with the slab. Thus, old slabs with thermal minimum below 750 C, as in Tonga, should easily penetrate into the lower mantle unless resisted by slab roll back and/or a viscosity jump at the top of the lower mantle. In contrast, the harzburgite layer in warmer slabs, such as Peru, Marianas and Izu-Bonin, is slightly lighter than ambient mantle, causing near neutral or marginally negative net buoyancy of the slab. In this case, other factors, such as rollback and slab dip angle, may explain why some slabs in the northwest Pacific appear to penetrate into the lower mantle while others do not. In Peru-type warm slabs, buoyancy of the harzburgite layer may

  15. Seismic Structure of the Mantle Discontinuities beneath Northeast Asia

    NASA Astrophysics Data System (ADS)

    Li, J.; WANG, X.; Guo, G.

    2015-12-01

    Seismic structure of the upper mantle discontinuities is important for understanding the thermal structure, composition of the mantle, and scales of mantle circulation as well. Northeast Asia is located at the front edge of the subducting Pacific slab, which is an ideal place to study the interaction between the upper mantle discontinuities and the subducting slab. Seismic tomography images have revealed different morphologies of slabs in the deep mantle. A prominent stagnant slab is trapped in the MTZ beneath Japan Sea and southern Kuril trench; while the slabs penetrate into the lower mantle directly beneath the northern Kuril and southern Izu-Bonin trench. Due to the sparse distribution of seismic stations in the sea, investigation of the deep mantle structure beneath the broad sea regions is very limited. In this study, we applied the multiple-ScS reverberations analysis to waveforms recorded by the Chinese Regional Seismic Network and F-net. We took advantage of the dense distribution of stations and spatial clusters of intermediate and deep earthquakes occurred beneath Okhotsk Sea, Russia and Northeast China, and conducted a common-reflection-point (CRP) stacking to the data, that allows us to map the topography of the 410-km and 660-km discontinuities beneath Japan Sea, Kuril, and adjacent regions in detail. We also compiled previous results obtained from the high frequency receiver function and S-to-P converted wave analyzes, and compared the results in the overlapping island or continental margin regions. The comparison shows that the array stacking technique to long-period signals is effective in extracting the robust features of the upper mantle discontinuities. It can be used not only as a complimentary method to short-period waveform analysis, but also as an independent way which can be applied to regions with limited station coverage. This is the first time to show systematically a complete view of the topography of the 410-km and 660-km

  16. Topography of upper mantle seismic discontinuities beneath the North Atlantic: The Azores, Canary and Cape Verde plumes

    NASA Astrophysics Data System (ADS)

    Saki, Morvarid; Thomas, Christine; Nippress, Stuart E. J.; Lessing, Stephan

    2015-01-01

    We are mapping the topography of upper mantle seismic discontinuities beneath the North Atlantic and surrounding regions by using precursor arrivals to PP and SS seismic waves that reflect off the seismic discontinuities. Numerous source-receiver combinations have been used in order to collect a large dataset of reflection points beneath our investigation area. We analysed over 1700 seismograms from MW > 5.8 events using array seismic methods to enhance the signal to noise ratio. The measured time lag between PP (SS) arrivals and their corresponding precursors on robust stacks are used to measure the depth of the transition zone boundaries. The reflectors' depths show a correlation between the location of known hotspots and a significantly depressed 410 km discontinuity indicating a temperature increase of 50-300 K compared to the surrounding mantle. For the 660 km discontinuity three distinct behaviours are visible: (i) normal depths beneath Greenland and at a distance of a few hundred kilometres away from known hotspots, (ii) shallower 660 km discontinuity compared with the global average value near hotspots closer to the Mid-Atlantic Ridge, and (iii) very few observations of a 660 km discontinuity at the hotspot locations. We interpret our observations as a large upwelling beneath the southern parts of our study region, possibly due to the South Atlantic convection cell. The thermal anomaly may be ponding beneath the endothermic 660 km phase transformation and likely does not extend through the top of the transition zone as a whole, except for those branches which appear as the thinner upwellings of Azores, Canaries and Cape Verde hotspots at the surface.

  17. Body-wave imaging of Earth's mantle discontinuities from ambient seismic noise.

    PubMed

    Poli, P; Campillo, M; Pedersen, H

    2012-11-23

    Ambient seismic noise correlations are widely used for high-resolution surface-wave imaging of Earth's lithosphere. Similar observations of the seismic body waves that propagate through the interior of Earth would provide a window into the deep Earth. We report the observation of the mantle transition zone through noise correlations of P waves as they are reflected by the discontinuities associated with the top [410 kliometers (km)] and the bottom (660 km) of this zone. Our data demonstrate that high-resolution mapping of the mantle transition zone is possible without using earthquake sources. PMID:23180858

  18. Body-wave imaging of Earth's mantle discontinuities from ambient seismic noise.

    PubMed

    Poli, P; Campillo, M; Pedersen, H

    2012-11-23

    Ambient seismic noise correlations are widely used for high-resolution surface-wave imaging of Earth's lithosphere. Similar observations of the seismic body waves that propagate through the interior of Earth would provide a window into the deep Earth. We report the observation of the mantle transition zone through noise correlations of P waves as they are reflected by the discontinuities associated with the top [410 kliometers (km)] and the bottom (660 km) of this zone. Our data demonstrate that high-resolution mapping of the mantle transition zone is possible without using earthquake sources.

  19. Topography of Upper Mantle Seismic Discontinuities Beneath the North Atlantic: The Azores, Canary and Cape Verde Plumes

    NASA Astrophysics Data System (ADS)

    Thomas, C.; Saki, M.; Nippress, S. E. J.; Lessing, S.

    2014-12-01

    We are mapping the topography of upper mantle seismic discontinuities beneath the North Atlantic and surrounding regions by using precursor arrivals to PP and SS seismic waves that reflect off the seismic discontinuities. Numerous source-receiver combinations have been used in order to collect a large dataset of reflection points beneath our investigation area. We analysed over 1700 seismograms from MW>5.8 events using array seismic methods to enhance the signal to noise ratio. The measured time lag between PP (SS) arrivals and their corresponding precursors on robust stacks are used to measure the depth of the transition zone boundaries. The reflectors' depths show a correlation between the location of known hotspots and a significantly depressed 410 km discontinuity indicating a temperature increase of 50-300 K compared to the surrounding mantle. For the 660 km discontinuity three distinct behaviours are visible: i) normal depths beneath Greenland and at a distance of a few hundred kilometres away from known hotspots, ii) shallower 660 km discontinuity compared with the global average value near hotspots closer to the Mid-Atlantic Ridge and iii) very few observations of a 660 km discontinuity at the hotspot locations. We interpret our observations as a large upwelling beneath the southern parts of our study region, possibly due to the South Atlantic convection cell. The thermal anomaly may be blocked by endothermic phase transformation and likely does not extend through the top of the transition zone except for those branches which appear as the Azores, Canaries and Cape Verde hotspots at the surface.

  20. Topography of upper mantle seismic discontinuities beneath the North Atlantic: the Azores, Canary and Cape Verde plumes

    NASA Astrophysics Data System (ADS)

    Saki, Morvarid; Thomas, Christine; Nippress, Stuart E. J.; Lessing, Stephan

    2015-04-01

    We are mapping the topography of upper mantle seismic discontinuities beneath the North Atlantic and surrounding regions by using precursor arrivals to PP and SS seismic waves that reflect off the seismic discontinuities. Many source-receiver combinations have been used in order to collect a large dataset of reflection points beneath our investigating area. We analyzed over 1700 seismograms from MW>5.8 events using array seismic methods to enhance the signal to noise ratio. The measured time lag between PP (SS) arrivals and their corresponding precursors on robust stacks are used to measure the depth of the transition zone boundaries. The reflectors' depths show a correlation between the location of hotspots and a significantly depressed 410 km discontinuity indicating a temperature increase of 200-300 K compared to the surrounding mantle. For the 660 km discontinuity three distinct behaviours are visible: i) normal depths beneath Greenland and at a distance of a few hundred kilometres away from the hotspots and ii) shallower 660 km discontinuity compared with the global average value near hotspots closer to the Mid-Atlantic Ridge and iii) very few observations of a 660 km discontinuity at the hotspot locations. We interpret our observations as a large upwelling beneath the southern parts of our study region, possibly due to the South Atlantic convection cell. The thermal anomaly may be blocked by endothermic phase transformation and likely does not extend through the top of the transition zone as whole except for those branches which appear as the Azores, Canaries and Cape Verde hotspots at the surface.

  1. Mapping Upper Mantle Seismic Discontinuities Using Singular Spectrum Analysis

    NASA Astrophysics Data System (ADS)

    Gu, Y. J.; Dokht, R.; Sacchi, M. D.

    2015-12-01

    Seismic discontinuities are fundamental to the understanding of mantle composition and dynamics. Their depth and impedance are generally determined using secondary seismic phases, most commonly SS precursors and P-to-S converted waves. However, the analysis and interpretation using these approaches often suffer from incomplete data coverage, high noise levels and interfering seismic phases, especially near tectonically complex regions such as subduction zones and continental margins. To overcome these pitfalls, we apply Singular Spectrum Analysis (SSA) to remove random noise, reconstruct missing traces and enhance the robustness of SS precursors and P-to-S conversions from seismic discontinuities. Our method takes advantage of the predictability of time series in frequency-space domain and performs a rank reduction using a singular value decomposition of the trajectory matrix. We apply SSA to synthetic record sections as well as observations of 1) SS precursors beneath the northwestern Pacific subduction zones, and 2) P-to-S converted waves from the Western Canada Sedimentary Basin (WCSB). In comparison with raw or interpolated data, the SSA enhanced reflectivity maps show a greater resolution and a stronger negative correlation between the depths of the 410 and 660 km discontinuities. These effects can be attributed to the suppression of incoherent noise, which tends to reduce the signal amplitude during normal averaging procedures, through rank reduction and the emphasis of principle singular values. Our new results suggest a more laterally coherent 520 km reflection in the western Pacific regions. Similar improvements in data imaging are achieved in western Canada, where strong lateral variations in discontinuity topography are observed in the craton-Cordillera boundary zone. Improvements from SSA relative to conventional approaches are most notable in under-sampled regions.

  2. Searching for the signal of the Iceland plume: Seismic observations of mantle discontinuities

    NASA Astrophysics Data System (ADS)

    Jenkins, J.; Cottaar, S.; White, R. S.; Deuss, A. F.

    2015-12-01

    The presence of a mantle plume beneath Iceland has long been hypothesised to explain its high volumes of crustal volcanism. Practical constraints in seismic tomography mean that thin slow velocity anomalies representative of a plume signature are difficult to image. However it is possible to infer the presence of temperature anomalies at depth from the effect they have on phase transitions in surrounding mantle material. Here, we use P to S seismic wave conversions at mantle discontinuities to search for the signal of a mantle plume beneath Iceland. We employ a large data set from a wide range of seismic stations across the North Atlantic region and a dense network in Iceland, including more than 100 University of Cambridge run stations. Data are used to create over 6000 receiver functions which are converted from time to depth including 3D corrections for variations in crustal thickness and upper mantle velocity heterogeneities. The global transition zone discontinuities at depths of 410 and 660km are thought to be caused by phase changes in the olivine component of mantle rocks. We find that both the 410 and 660 discontinuities are depressed under Iceland compared to normal depths in the surrounding region. The opposite signs of the Clapeyron slopes describing the olivine phase transitions predict anti-correlation of discontinuity topography, thus observations of correlated discontinuities are generally dismissed as an artefact due to under corrected upper mantle velocity variations. We suggest instead that the correlated topography we observe is caused by a garnet (as opposed to olivine) phase transition at 660 described by a positive Clapeyron slope, such that depression of the 660 is representative of a hot anomaly at depth. Observations of additional discontinuities in the upper mantle as well as observations of a deep ~1000km discontinuity also have the potential to shed light on the presence of a mantle plume at depth.

  3. Large-scale depressions on the 660 seismic discontinuity beneath Europe: signature of the role of akimotoite in subducting slabs

    NASA Astrophysics Data System (ADS)

    Cottaar, S.; Deuss, A. F.

    2015-12-01

    The upper and lower mantle are delineated by a seismic discontinuity around 660 km depth. This discontinuity is regularly associated with the dissociation of ringwoodite to bridgmanite and periclase, which has a negative Clapeyron slope, and appears to play a role in global mantle dynamics. Here we study the topography of this discontinuity and the one around 410 km, using receiver functions and investigate the effect of subducting and ponding slabs beneath Europe. We collected ~150,000 receiver functions across Europe over a time period from 2000 to 2014. After quality control, we use ~28,000 in a common conversion point stack. Corrections for lateral velocity variations are applied using the P- and S-velocity models in EU60 from Zhu et al. (2015). While northern Europe shows an average mantle transition zone, strong anomalous depressions of 30 km are seen in the topography of the 660 beneath central Europe and around the Mediterranean. There is no (anti-)correlated topographic anomaly on the 410 in these regions. The observed depressions beneath central Europe correlate with elevated seismic velocities above 660 km, and are therefore probably caused by cold subducted slab material. Temperature effects on the ringwoodite-bridgmanite transition alone cannot explain such a depression. Several wt% water deepens the 660 and increases the Clapeyron slope, but other geophysical observations, e.g. elevated Vp/Vs ratio, attenuation and electric conductivity, are not seen in these regions in various studies. Our preferred alternative hypothesis is the suggestion of Yu et al. (2011) that ringwoodite dissociates into akimotoite and periclase at temperatures beneath ~1400 K within the slab The subsequent transition of akimotoite to bridgmanite has a strong negative Clapeyron slope, which explains the deep discontinuity seen here in combination with cold temperatures, as well as providing a mechanism for slabs to pond in the mantle transition zone.

  4. Upper-mantle seismic discontinuities and the thermal structure of subduction zones

    USGS Publications Warehouse

    Vidale, J.E.; Benz, H.M.

    1992-01-01

    The precise depths at which seismic velocities change abruptly in the upper mantle are revealed by the analysis of data from hundreds of seismometers across the western United States. The boundary near 410 km depth is locally elevated, that near 660 km depressed. The depths of these boundaries, which mark phase transitions, provide an in situ thermometer in subduction zones: the observed temperature contrasts require at least moderate thickening of the subducting slab near 660 km depth. In addition, a reflector near 210 km depth may mark the bottom of the aesthenosphere.

  5. On the penetration of the 660 km phase change by mantle downflows

    NASA Technical Reports Server (NTRS)

    Bercovici, David; Schubert, Gerald; Tackley, Paul J.

    1993-01-01

    We present a simple analytic model of the interaction of cold convective downwelling currents with an endothermic phase change. The model describes the ponding and lateral spreading of downflows along the phase transition interface. A simple comparison of the vertical forces on the ponding material provides a necessary condition for a downflow to penetrate the phase boundary. This condition is fundamentally dependent on the geometry of the downflow. For planar downwellings, the model predicts a minimum ponding time before the structure can penetrate the phase boundary. For columnar (axisymmetric) downflows, there is no minimum time of spreading required before penetration can proceed. The model thus provides an explanation for the observation that in numerical models of three-dimensional convection with an endothermic phase change, cylindrical downflows penetrate the phase interface while planar ones do not. Since descending slabs in the Earth's mantle display a wide spectrum of geometries between planar and cylindrical (given various trench curvatures, as well as intersections of two or more subduction zones), this phenomenon may explain, in part, why some slabs appear to extend into the lower mantle while others are deflected at the 660 km discontinuity.

  6. A New Approach to Study the Upper-Mantle Seismic Discontinuities Based on Triplication Data: Application to the Kuril Subduction Zone Using Hi-net Array

    NASA Astrophysics Data System (ADS)

    Park, S.; Okeler, A.; Ishii, M.

    2015-12-01

    Constraining seismic properties of the 410- and 660-km discontinuities is crucial for understanding the mantle composition and dynamics. One approach to study the transition zone is to use the "triplicated" arrivals of seismic data. When a wavefield encounters an abrupt increase in wave speed with depth, three different phases, direct, reflected, and transmitted phases, result, and they can arrive at the same distance, producing the triplicated arrivals. Properties of the triplication pattern provide constraints on the depth and velocity jump of the discontinuities. One of the challenging aspects of using the triplication data, however, is to identify the three individual phases, since they arrive close in time and the waveforms often overlap. In order to separate the phases, we apply Radon transform to the data. Based on the transformed data, the caustics are identified, and the depth and the velocity jump of the discontinuities are obtained. This method is applied to study the Kuril subduction zone, beneath a region northeast of Japan. We take advantage of the High-Sensitivity Seismograph Network in Japan that consists of more than 700 stations, to capture the triplication pattern with dense sampling in distance. Given the distribution of the stations, deep and intermediate earthquakes in the Sea of Okhotsk region that are located within the triplication distance range are considered. We constrain the percentage velocity jump and depth of the 410- and 660-km discontinuities. The discontinuity depth estimates show significant deviations from the global average, but are, in general, comparable to the SS precursors and tomographic studies of the region.

  7. Mantle discontinuities and temperature under the North American continental keel

    NASA Astrophysics Data System (ADS)

    Li, Aibing; Fischer, Karen M.; Wysession, Michael E.; Clarke, Timothy J.

    1998-09-01

    A ubiquitous feature of upper-mantle seismic velocity models has been the presence of high-velocity `keels' beneath stable continental interiors. Uncertainty remains, however, regarding the maximum depth to which continental keels extend, the degree to which they have cooled the mantle that surrounds them and their role in mantle flow. Here we investigate thermal anomalies across the eastern margin of the North American continental keel by imaging the seismic discontinuities at depths of 410 and 660km with compressional-to-shear converted waves recorded by a 1,500-km-long seismometer deployment in the eastern United States. The thickness of the transition zone (the region nominally between depths of 410 and 660km) and the depth to the `410-km' discontinuity indicate that cold keel material and sub-keel downwellings must be largely confined to the upper mantle and may impinge on the transition zone only in localized regions and with thermal anomalies of less than ~150K. A 20-km depression of the `660-km' discontinuity to the south of the westernmost stations coincides with a region of fast velocity in the deep transition zone and may be associated with the remnants of the subducted Farallon plate,,.

  8. High resolution receiver function imaging of the seismic velocity discontinuities in the crust and upper mantle beneath eastern margin of Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Wu, J.; Wang, W.; Fang, L.; Ming, Y.

    2015-12-01

    The collision between Indian and Eurasian plates started about 50 Ma has resulted in intense deformation and crustal shortening in the Tibetan Plateau. Though studied with decades, the mechanism of deformation and southeastward expansion of the Tibetan Plateau remain controversial. As the tectonic transitional zone between the uplifting Tibetan Plateau and the Yangtze block, the eastern margin of the Tibetan Plateau is of particular interest. In past 10 years, several large scale dense seismic arrays were deployed in the eastern Tibetan Plateau with an average inter-station distance about 35km. We collected the seismic data of these densely deployed seismic arrays and the permanent seismic network in the eastern margin of the Tibetan Plateau, and obtained more than 300,000 high quality teleseismic Ps receiver functions. We have obtained high-resolution topographies of the Moho and upper mantle discontinuities beneath the eastern Tibetan Plateau by using receiver function common conversion points stacking technique. The results show a strong lateral variation of the crustal thickness, the depths of 410km and 660km seismic velocity discontinuities, and the thickness of upper mantle transitional zone in this region. Although the depth of the upper mantle discontinuities beneath Sichuan basin is similar to that of the average earth model, the thickness of the upper mantle transitional zone in the southeastern margin of the Tibetan Plateau is about 30km thicker. The lateral variation of the thickness of upper mantle transitional zone in the region may be related to the subduction process of the India plate. The spatial distribution of the velocity discontinuities has a good correlation with surface tectonic structure, indicating the upper mantle dynamic process has great inference on the crustal deformation and shortening in eastern margin of Tibetan Plateau.

  9. Upper mantle discontinuity structure from underside reflections

    NASA Astrophysics Data System (ADS)

    Schmerr, Nicholas C.

    This research investigates Earth structure in the mantle transition zone, a range of depths bounded by two major solid-state phase transformations of the mineral olivine: the conversion of olivine to wadsleyite near 410 km depth, and the dissociation of ringwoodite into Mg-silicate perovskite plus magnesiowuestite near 660 km depth. The phase transformations are dependent upon the thermal and chemical state of the mantle; lateral heterogeneity in mantle temperature and composition will change the transformation depth. The denser, more compact structures of olivine possess higher seismic wave speeds and densities, thus giving rise to seismic discontinuities at the phase transitions. The depth and sharpness of the 410 and 660 km discontinuities are mapped using seismic energy that reflects from the underside of these boundaries to investigate the thermal and chemical state of the mantle. Underside reflections of shear and compressional seismic waves arrive as precursory energy several hundred seconds before the seismic phases SS and PP, which form as underside reflections off the crust. Using broadband datasets of precursors to SS and PP, topographic variation maps of the 410 km and 660 km boundaries are produced for study regions beneath the Pacific Ocean and South American continent. Beneath most of the Pacific, the discontinuities are found close to the global average, suggesting that the mantle in this region is not significantly perturbed in temperature and chemistry. However, within 1000 km of several Pacific hotspots, including Hawaii, there is evidence for hot upwelling material rising through the transition zone that correlates with the edges of extremely hot (i.e., seismically low velocity) regions of the lowermost mantle, supporting whole mantle convection. Beneath the South American continent there is evidence for both thermal and chemical variation near the subducting Nazca plate, consistent with cold, and hydrated materials sinking into the mantle

  10. Unstructured discontinuous Galerkin for seismic inversion.

    SciTech Connect

    van Bloemen Waanders, Bart Gustaaf; Ober, Curtis Curry; Collis, Samuel Scott

    2010-04-01

    This abstract explores the potential advantages of discontinuous Galerkin (DG) methods for the time-domain inversion of media parameters within the earth's interior. In particular, DG methods enable local polynomial refinement to better capture localized geological features within an area of interest while also allowing the use of unstructured meshes that can accurately capture discontinuous material interfaces. This abstract describes our initial findings when using DG methods combined with Runge-Kutta time integration and adjoint-based optimization algorithms for full-waveform inversion. Our initial results suggest that DG methods allow great flexibility in matching the media characteristics (faults, ocean bottom and salt structures) while also providing higher fidelity representations in target regions. Time-domain inversion using discontinuous Galerkin on unstructured meshes and with local polynomial refinement is shown to better capture localized geological features and accurately capture discontinuous-material interfaces. These approaches provide the ability to surgically refine representations in order to improve predicted models for specific geological features. Our future work will entail automated extensions to directly incorporate local refinement and adaptive unstructured meshes within the inversion process.

  11. Seismic array constraints on the D″ discontinuity beneath Central America

    NASA Astrophysics Data System (ADS)

    Whittaker, Stefanie; Thorne, Michael S.; Schmerr, Nicholas C.; Miyagi, Lowell

    2016-01-01

    We analyzed 16,150 transverse component seismic recordings from 54 deep-focus earthquakes in the South American and Caribbean regions recorded at broadband stations in North America between 2005 and 2012. We treated subgroups of seismic stations within 3° radius geographical bins as seismic arrays and performed vespagram analysis. We focused on the S, ScS, and Scd arrivals and collected data in the epicentral distance range from 55° to 90°. In particular, we searched for D″ discontinuity presence in the vespagrams in a 25° by 35° (or 1520 by 2130 km) area beneath Central America. Analysis of these data showed 125 clear Scd observations, 180 Scd observations of lesser quality, and 343 nonobservations. We produced a new map of the discontinuity height beneath Central America. Our map shows an average discontinuity height of 286 ± 6 km (σ = 76 km). The region is punctuated by a large topographic high centered at approximately 10°N and 90°W with a maximum height of 380 km. Two smaller topographic highs are located at approximately 4°N and 81°W (discontinuity height of 320 km) and at 4°N and 70°W (height of 315 km). The observation of multiple Scd arrivals collocated with the strongest gradients in inferred topography provides evidence for topographic variation on the discontinuity rather than multiple discontinuities. The regions where the discontinuity has the greatest height can be explained by localized enrichment of mid-ocean ridge basalt from the subducted Farallon slab impinging on the core-mantle boundary.

  12. Seismic images of the mantle transition zone beneath Northeast China and the Sino-Korean craton from P-wave receiver functions

    NASA Astrophysics Data System (ADS)

    Zhang, Ruiqing; Gao, Zhanyong; Wu, Qingju; Xie, Zhenxing; Zhang, Guangcheng

    2016-04-01

    Seismic data from northeast (NE) China and the Sino-Korean craton were combined to image the upper mantle discontinuities at 410 and 660 km. Fine-scale topographic variations on these two discontinuities provide important clues for both delineating geometry of the subducting Pacific slab particularly at arc-arc junction and interpreting regional Cenozoic intraplate volcanism. We used over 90,000 receiver functions from 1916 teleseismic earthquakes recorded by 584 broadband seismic stations, primary those of temporary seismic arrays. We found the average depths of the two discontinuities to be 410 km and 672 km, respectively, beneath the study area. Results show that the 660-km discontinuity is strongly depressed by about 20-30 km in a narrow region beneath and around the Changbaishan volcano, consistent with the results of previous receiver function studies. In contrast, much of the Sino-Korean craton exhibits typical transition zone thickness (~ 260 km) and thus offers no evidence of a stagnated Pacific slab. Our results also reveal an elevated 660-km discontinuity and a thinner transition zone both to the west of the observed depression region and beneath the Kuril-Japan arc junction. This feature is most likely due to a tearing of the descending Pacific plate at both its leading and junction edges. An additional elevated 660-km discontinuity together with a thinner transition zone appears in the vicinity of the Dariganga lava field, supporting interpretations of a deep-rooted mantle plume. Our observations of an elevated 410-km discontinuity and a thicker transition zone correlate spatially with the diffuse distribution of volcanism around Hannuoba, Aershan and Wudalianchi. This correlation may suggest lithospheric removal as a mechanism for these magmatic activities.

  13. Large-scale mantle discontinuity topography beneath Europe: Signature of akimotoite in subducting slabs

    NASA Astrophysics Data System (ADS)

    Cottaar, Sanne; Deuss, Arwen

    2016-01-01

    The mantle transition zone is delineated by seismic discontinuities around 410 and 660 km, which are generally related to mineral phase transitions. Study of the topography of the discontinuities further constrains which phase transitions play a role and, combined with their Clapeyron slopes, what temperature variations occur. Here we use P to S converted seismic waves or receiver functions to study the topography of the mantle seismic discontinuities beneath Europe and the effect of subducting and ponding slabs beneath southern Europe on these features. We combine roughly 28,000 of the highest quality receiver functions into a common conversion point stack. In the topography of the discontinuity around 660 km, we find broadscale depressions of 30 km beneath central Europe and around the Mediterranean. These depressions do not correlate with any topography on the discontinuity around 410 km. Explaining these strong depressions by purely thermal effects on the dissociation of ringwoodite to bridgmanite and periclase requires unrealistically large temperature reductions. Presence of several wt % water in ringwoodite leads to a deeper phase transition, but complementary observations, such as elevated Vp/Vs ratio, attenuation, and electrical conductivity, are not observed beneath central Europe. Our preferred hypothesis is the dissociation of ringwoodite into akimotoite and periclase in cold downwelling slabs at the bottom of the transition zone. The strongly negative Clapeyron slope predicted for the subsequent transition of akimotoite to bridgmanite explains the depression with a temperature reduction of 200-300 K and provides a mechanism to pond slabs in the first place.

  14. Vertically Discontinuous Seismic Signatures From Continuous Thermochemical Plumes

    NASA Astrophysics Data System (ADS)

    Harris, A. C.; Kincaid, C.; Savage, B.

    2008-12-01

    , which appears slow for all compositions in a hot plume. Complex seismic signatures are predicted for mantle upwellings forming from source regions containing oceanic lithosphere, including strong variations in velocity with depth. Strong thermal signatures above 300km may be masked by compositional effects below 300km. Results predict that a vertically continuous upwelling will give a spatially discontinuous seismic result.

  15. Gray-level transformation and Canny edge detection for 3D seismic discontinuity enhancement

    NASA Astrophysics Data System (ADS)

    Di, Haibin; Gao, Dengliang

    2014-11-01

    In a 3D seismic survey, detecting seismic discontinuities is vital to robust structural and stratigraphic analysis in the subsurface. Previous methods have difficulty highlighting subtle discontinuities from seismic data in cases where the local amplitude variation is of non-zero mean. This study proposes implementing a gray-level transformation and the Canny edge detector for improved imaging of discontinuities. Specifically, the new process transforms seismic signals to be of zero mean and helps amplify subtle discontinuities, leading to an enhanced visualization for structural and stratigraphic details. Applications to various 3D seismic datasets demonstrate that the new algorithm helps better define channels, faults, and fractures than the traditional similarity, amplitude gradient, and semblance attributes.

  16. Global seismic data reveal little water in the mantle transition zone

    NASA Astrophysics Data System (ADS)

    Houser, C.

    2016-08-01

    Knowledge of the Earth's present water content is necessary to constrain the amount of water and other volatiles the Earth acquired during its formation and the amount that is cycled back into the interior from the surface. This study compares 410 and 660 km discontinuity depth with shear wave tomography within the mantle transition zone to identify regions with seismic signals consistent with water. The depth of the 410 and 660 km discontinuities is determined from a large updated dataset of SS-S410S and SS-S660S differential travel times, known as SS precursors. The discontinuity depths measured from binning and stacking the SS precursor data are then compared to the shear velocity model HMSL-S06 in the transition zone. Mapping all the possible combinations, very few locations match the predictions from mineral physics for the effects of water on discontinuity depth and shear velocity. The predictions, although not yet measured at actual transition zone temperatures and pressures, are a shallow 410 km discontinuity, a deep 660 km discontinuity, and a slow shear velocity. Only 8% of the bins with high-quality data are consistent with these predictions, and the calculated average water content within these bins is around 0.6 wt.%. A few isolated locations have patterns of velocity/topography that are consistent with water, while there are large regional-scale patterns consistent with cold/hot temperature anomalies. Combining this global analysis of long period seismic data and the current mineral physics predictions for water in transition zone minerals, I find that the mantle transition zone is generally dry, containing less than one Earth ocean of water. Although subduction zones could be locally hydrated, the combined discontinuity and velocity data show no evidence that wadsleyite or ringwoodite have been globally hydrated by subduction or initial Earth conditions.

  17. Seismic small-scale discontinuity sparsity-constraint inversion method using a penalty decomposition algorithm

    NASA Astrophysics Data System (ADS)

    Zhao, Jingtao; Peng, Suping; Du, Wenfeng

    2016-02-01

    We consider sparsity-constraint inversion method for detecting seismic small-scale discontinuities, such as edges, faults and cavities, which provide rich information about petroleum reservoirs. However, where there is karstification and interference caused by macro-scale fault systems, these seismic small-scale discontinuities are hard to identify when using currently available discontinuity-detection methods. In the subsurface, these small-scale discontinuities are separately and sparsely distributed and their seismic responses occupy a very small part of seismic image. Considering these sparsity and non-smooth features, we propose an effective L 2-L 0 norm model for improvement of their resolution. First, we apply a low-order plane-wave destruction method to eliminate macro-scale smooth events. Then, based the residual data, we use a nonlinear structure-enhancing filter to build a L 2-L 0 norm model. In searching for its solution, an efficient and fast convergent penalty decomposition method is employed. The proposed method can achieve a significant improvement in enhancing seismic small-scale discontinuities. Numerical experiment and field data application demonstrate the effectiveness and feasibility of the proposed method in studying the relevant geology of these reservoirs.

  18. Low-velocity zone atop the 410-km seismic discontinuity in the northwestern United States.

    PubMed

    Song, Teh-Ru Alex; Helmberger, Don V; Grand, Stephen P

    2004-02-01

    The seismic discontinuity at 410 km depth in the Earth's mantle is generally attributed to the phase transition of (Mg,Fe)2SiO4 (refs 1, 2) from the olivine to wadsleyite structure. Variation in the depth of this discontinuity is often taken as a proxy for mantle temperature owing to its response to thermal perturbations. For example, a cold anomaly would elevate the 410-km discontinuity, because of its positive Clapeyron slope, whereas a warm anomaly would depress the discontinuity. But trade-offs between seismic wave-speed heterogeneity and discontinuity topography often inhibit detailed analysis of these discontinuities, and structure often appears very complicated. Here we simultaneously model seismic refracted waves and scattered waves from the 410-km discontinuity in the western United States to constrain structure in the region. We find a low-velocity zone, with a shear-wave velocity drop of 5%, on top of the 410-km discontinuity beneath the northwestern United States, extending from southwestern Oregon to the northern Basin and Range province. This low-velocity zone has a thickness that varies from 20 to 90 km with rapid lateral variations. Its spatial extent coincides with both an anomalous composition of overlying volcanism and seismic 'receiver-function' observations observed above the region. We interpret the low-velocity zone as a compositional anomaly, possibly due to a dense partial-melt layer, which may be linked to prior subduction of the Farallon plate and back-arc extension. The existence of such a layer could be indicative of high water content in the Earth's transition zone.

  19. Seismic evidence for a tilted mantle plume and north-south mantle flow beneath Iceland

    USGS Publications Warehouse

    Shen, Y.; Solomon, S.C.; Bjarnason, I. Th; Nolet, G.; Morgan, W.J.; Allen, R.M.; Vogfjord, K.; Jakobsdottir, S.; Stefansson, R.; Julian, B.R.; Foulger, G.R.

    2002-01-01

    Shear waves converted from compressional waves at mantle discontinuities near 410- and 660-km depth recorded by two broadband seismic experiments in Iceland reveal that the center of an area of anomalously thin mantle transition zone lies at least 100 km south of the upper-mantle low-velocity anomaly imaged tomographically beneath the hotspot. This offset is evidence for a tilted plume conduit in the upper mantle, the result of either northward flow of the Icelandic asthenosphere or southward flow of the upper part of the lower mantle in a no-net-rotation reference frame. ?? 2002 Elsevier Science B.V. All rights reserved.

  20. The excitation of long period seismic waves by a source spanning a structural discontinuity

    NASA Astrophysics Data System (ADS)

    Woodhouse, J. H.

    Simple theoretical results are obtained for the excitation of seismic waves by an indigenous seismic source in the case that the source volume is intersected by a structural discontinuity. In the long wavelength approximation the seismic radiation is identical to that of a point source placed on one side of the discontinuity or of a different point source placed on the other side. The moment tensors of these two equivalent sources are related by a specific linear transformation and may differ appreciably both in magnitude and geometry. Either of these sources could be obtained by linear inversion of seismic data but the physical interpretation is more complicated than in the usual case. A source which involved no volume change would, for example, yield an isotropic component if, during inversion, it were assumed to lie on the wrong side of the discontinuity. The problem of determining the true moment tensor of the source is indeterminate unless further assumptions are made about the stress glut distribution; one way to resolve this indeterminancy is to assume proportionality between the integrated stress glut on each side of the discontinuity.

  1. Seismic Waves Reflected from Discontinuities within Earth's Upper Mantle.

    PubMed

    Engdahl, E R; Flinn, E A

    1969-01-10

    Precursors to normtial seismic waves of the PKPPKP type in the distance range of 55 degrees to 75 degrees are ascribed to reflection of this phase from within the earth's upper mantle. The new observations confirm the existence of a sharply defined transition zone, probably worldwide in extent, at a depth of approximately 650 kilometers. These data are shown to be a useful tool for the study of upper mantle structure on a global basis.

  2. Seismic evidence of the Hainan mantle plume by receiver function analysis in southern China

    NASA Astrophysics Data System (ADS)

    Wei, S. Shawn; Chen, Y. John

    2016-09-01

    The Lei-Qiong region is the largest igneous province in southern China and may be a surface expression of a mantle plume beneath the region (the Hainan mantle plume). To investigate the existence of the Hainan mantle plume, we used P-to-S receiver function to image the major seismic discontinuities beneath this region with a regional dense broadband array. We found that the Moho discontinuity beneath the Leizhou Peninsula, mostly covered by Cenozoic basaltic outcrops, is 10-15 km deeper compared to the adjacent region of Eurasian continental margin, showing a thickened local crust by upwelling mantle materials. Additionally, the imaged 410- and 660-km discontinuities suggest a thinner-than-normal mantle transition zone beneath the region, implying that hot materials penetrate through the transition zone from the lower mantle. Both seismic evidences support the existence of the mantle plume, which might be 170-200°C hotter than the surrounding mantle.

  3. Imaging Mantle Discontinuities Beneath North America Using ScS Reverberations

    NASA Astrophysics Data System (ADS)

    Griebel, K. A.; Schmerr, N. C.; Courtier, A. M.; Lekic, V.

    2015-12-01

    Seismic discontinuities are rapid changes in velocity and density over depth that arise from mechanisms such as changes in mineralogy, major element composition, melt content, volatile abundance, anisotropy, or a combination of the above. Seismic imaging of discontinuities complements information provided by seismic tomography and is important for understanding the dynamics and the structure of the mantle. For example, imaging variations in the depth and sharpness of discontinuities can trace underlying variations in temperature and composition in the mantle. We use ScSScS precursors and ScS postcursors (ScS reverberations) to map the depth and sharpness of upper- and mid- mantle discontinuities beneath North America. To observe the reverberations, we collected broadband data recordings of earthquakes with depth > 300 km, source moment magnitude ≥ 5.5, and location < 60 degrees of EarthScope USArray stations. Two primary source regions met our qualifications: earthquakes from the subduction of the Nazca plate beneath South America, and earthquakes from the subduction of the Pacific plate beneath the Sea of Okhotsk. Our dataset consists of ~15 deep focus earthquakes that have well defined ScS and ScSScS arrivals. We use array processing to generate vespagrams for detecting the ScS reverberations. Seismic energy falling at the appropriate slowness and travel time for reflections from upper- and mid- mantle discontinuities is migrated to depth. We use the resulting ScS reverberation derived reflectivity profiles to obtain estimates for discontinuity depth and impedance contrast in the regions falling between the source and array. We can use this information to image parts of the mantle under North America. Preliminary results indicate presence of multiple discontinuities in the upper mantle, including the 410 km discontinuity, a complex 660 km discontinuity, and intermittent mid-mantle discontinuities at 800-900 km depth.

  4. Sharpness of upper-mantle discontinuities determined from high-frequency reflections

    USGS Publications Warehouse

    Benz, H.M.; Vidale, J.E.

    1993-01-01

    AN understanding of the nature of seismic discontinuities in the Earth's upper mantle is important for understanding mantle processes: in particular, the amplitude and sharpness of these discontinuities are critical for assessing models of upper-mantle phase changes and chemical layering. So far, seismic studies aimed at determining the thickness and lateral variability of upper-mantle discontinuities have yielded equivocal results, particularly for the discontinuity at 410km depth1,2. Here we present short-period (0.8-2.0 s) recordings of upper-mantle precursors to the seismic phase P???P??? (PKPPKP) from two South American earthquakes recorded by the ???700-station short-period array in California. Our results show that the 410- and 660-km discontinuities beneath the Indian Ocean are locally simple and sharp, corresponding to transition zones of 4 km or less. These observations pose problems for mineral physics models3-5, which predict a transitional thickness greater than 6 km for the peridotite to ??-spinel phase transition. In contrast to the results of long-period studies6,7, we observe no short-period arrivals from near 520 km depth.

  5. Sharpness of upper-mantle discontinuities determined from high-frequency reflections

    USGS Publications Warehouse

    Benz, H.M.; Vidale, J.E.

    1993-01-01

    AN understanding of the nature of seismic discontinuities in the Earth's upper mantle is important for understanding mantle processes: in particular, the amplitude and sharpness of these discontinuities are critical for assessing models of upper-mantle phase changes and chemical layering. So far, seismic studies aimed at determining the thickness and lateral variability of upper-mantle discontinuities have yielded equivocal results, particularly for the discontinuity at 410km depth1,2. Here we present short-period (0.8-2.0 s) recordings of upper-mantle precursors to the seismic phase P???P??? (PKPPKP) from two South American earthquakes recorded by the ???700-station short-period array in California. Our results show that the 410- and 660-km discontinuities beneath the Indian Ocean are locally simple and sharp, corresponding to transi-tion zones of 4 km or less. These observations pose problems for mineral physics models3-5, which predict a transitional thickness greater than 6 km for the peridotite to ??-spinel phase transition. In contrast to the results of long-period studies6,7, we observe no short-period arrivals from near 520 km depth. ?? 1993 Nature Publishing Group.

  6. Seismic evidence for olivine phase changes at the 410- and 660-kilometer discontinuities.

    PubMed

    Lebedev, Sergei; Chevrot, Sébastien; van der Hilst, Rob D

    2002-05-17

    The view that the seismic discontinuities bounding the mantle transition zone at 410- and 660-kilometer depths are caused by isochemical phase transformations of the olivine structure is debated. Combining converted-wave measurements in East Asia and Australia with seismic velocities from regional tomography studies, we observe a correlation of the thickness of, and wavespeed variations within, the transition zone that is consistent with olivine structural transformations. Moreover, the seismologically inferred Clapeyron slopes are in agreement with the mineralogical Clapeyron slopes of the (Mg,Fe)2SiO4 spinel and postspinel transformations. PMID:12016311

  7. Seismic imaging of a mid-lithospheric discontinuity beneath Ontong Java Plateau

    NASA Astrophysics Data System (ADS)

    Tharimena, Saikiran; Rychert, Catherine A.; Harmon, Nicholas

    2016-09-01

    Ontong Java Plateau (OJP) is a huge, completely submerged volcanic edifice that is hypothesized to have formed during large plume melting events ∼90 and 120 My ago. It is currently resisting subduction into the North Solomon trench. The size and buoyancy of the plateau along with its history of plume melting and current interaction with a subduction zone are all similar to the characteristics and hypothesized mechanisms of continent formation. However, the plateau is remote, and enigmatic, and its proto-continent potential is debated. We use SS precursors to image seismic discontinuity structure beneath Ontong Java Plateau. We image a velocity increase with depth at 28 ± 4 km consistent with the Moho. In addition, we image velocity decreases at 80 ± 5 km and 282 ± 7 km depth. Discontinuities at 60-100 km depth are frequently observed both beneath the oceans and the continents. However, the discontinuity at 282 km is anomalous in comparison to surrounding oceanic regions; in the context of previous results it may suggest a thick viscous root beneath OJP. If such a root exists, then the discontinuity at 80 km bears some similarity to the mid-lithospheric discontinuities (MLDs) observed beneath continents. One possibility is that plume melting events, similar to that which formed OJP, may cause discontinuities in the MLD depth range. Plume-plate interaction could be a mechanism for MLD formation in some continents in the Archean prior to the onset of subduction.

  8. Synthetic Seismic Signature of Thermal Mantle plumes

    NASA Astrophysics Data System (ADS)

    Goes, S.; Hansen, U.

    2002-12-01

    With increasing resolution in global tomographic models and targeted regional experiments the first seismic images of mantle plumes have emerged. The low velocity anomalies interpreted as plumes are generally significantly more complex than the simple head-tail model of a mantle upwelling. Although some models show low velocities crossing the 660 km discontinuity, the significance of the lower mantle anomalies is still heavily debated. In order to obtain a better idea of the expected seismic signature of a mantle plume we perform a set of three-dimensional numerical experiments with parameters relevant to the Earth's mantle. The thermal plumes thus obtained are converted into P and S velocity structure taking into account the effect of temperature, pressure, an average mantle composition including phase transitions and anelasticity on the seismic velocities. Excess plume temperatures were constrained to be about 300oC below the lithosphere to be consistent with surface observations. Such plumes are 400-800 km wide. An abrupt lowering of the viscosity above 660 km causes additional narrowing in the upper mantle. VP (VS) anomalies range from -2.2 (-4) % above the transition zone to -0.5 (-1) % in the lower mantle. Due to the varying sensitivity of seismic velocities to temperature with depth and mineralogy, variations in amplitude and width of the seismic plume do not coincide with the variations in the thermal structure of the plume. Reduced sensitivity in the transition zone may hamper imaging continuous whole mantle plumes. Seismic anelasticity structure follows the thermal structure more closely and yields plume anomalies of up to 200% in dln(1/QS).

  9. Using Seismic Discontinuities to Image Melt and Dynamics in the Sub-Continental Upper Mantle

    NASA Astrophysics Data System (ADS)

    Schmerr, N. C.; Courtier, A. M.; Hier-Majumder, S.; Lekic, V.

    2014-12-01

    Continents are assembled from multiple Proterozoic and Archean terranes to form stable cratonic platforms with associated deformation typically localized to margins and/or rift zones. Successive episodes of subsequent extension, compression, magmatism, accretion, and rifting have left the sub-continental upper mantle with a complex signature of thermal and chemical heterogeneity. One key interest is the history of melt production, migration, and storage in sub-continental upper mantle as it provides a window into past and present dynamical processes, including the differentiation and formation of continental structure. Here we examine seismic discontinuities within the mantle that arise from a wide range of mechanisms, including changes in mineralogy, major element composition, melt content, volatile abundance, anisotropy, or a combination of the above. Using a dataset of broadband seismograms of underside reflected S-waves arriving as precursors to the seismic phase SS, we determine the depth and impedance contrast of discontinuities in the depth range of 80-410 km. Our observations are compared to predictions for the seismic moduli from a mineral physics database using the software MuMaP (Multiphase Material Properties). MuMaP modeling allows us to vary the average regional temperature, mantle composition and account for the effects of melt (if present). In our initial study of the western North American plate, we detect the presence of the 410 km discontinuity, a discontinuity at 300 km depth (X), and a G discontinuity at 60-80 km depth. The X is indicative of the coesite to stishovite phase transition in the upper mantle and suggests substantial mixing of subducted basalt with the mantle. The presence of the G may indicate partial melt in the asthenosphere, melt frozen into the lithosphere, and/or anisotropic fabrics preserved beneath the continent. These hypotheses are evaluated against MuMap predictions for melt content and anisotropic structure in the upper

  10. Partial melting as the Cause of the Aesthenosphere - Lithosphere Seismic Discontinuity

    NASA Astrophysics Data System (ADS)

    Weidner, D. J.; Li, L.

    2012-12-01

    The classical view of how partial melts affects seismic velocity models the system as a mechanical aggregate of solid mineral phases with pockets of liquid with zero shear moduli. Such a system has a slow decrease in seismic velocity as the amount of partial melt increases, giving no opportunity for a seismic discontinuity. We assert that a much stronger effect of partial melting results from the dynamic interaction of a solid and liquid that are in thermodynamic equilibrium. Dynamic melting in response to the stress field of the seismic wave will dramatically soften the sound velocities. The salient properties are the volume change on melting, the productivity of melt with pressure, and the characteristic time of melting. In this context, the seismic wave perturbs the equilibrium between the solid and the liquid forcing the increase of one at the expense of the other. In this system, the velocity decrease is independent of the magnitude of the stress field of the seismic wave and the effect is much greater than that of the mechanical mixture of solid and melt. Here we present data on natural samples. KLB1, undergoing partial melting at LVZ conditions. Effective elastic moduli are derived from sinusoidal stress variations at seismic frequencies. The results support the dynamic melting model outline above. These data are successfully modeled by the thermodynamic program MELTS. With this program several scenarios are considered. We find that a mantle peridotite that has been partially melted to 1% and then the melt removed by compaction will display a velocity discontinuity, decreasing the velocity, as the solidus is crossed from solid to partial melt. The total amount of melt required for generating the low velocity zone may well be less than 1% in such a system.

  11. Stable discontinuous grid implementation for collocated-grid finite-difference seismic wave modelling

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenguo; Zhang, Wei; Li, Hong; Chen, Xiaofei

    2013-03-01

    Simulating seismic waves with uniform grid in heterogeneous high-velocity contrast media requires small-grid spacing determined by the global minimal velocity, which leads to huge number of grid points and small time step. To reduce the computational cost, discontinuous grids that use a finer grid at the shallow low-velocity region and a coarser grid at high-velocity regions are needed. In this paper, we present a discontinuous grid implementation for the collocated-grid finite-difference (FD) methods to increase the efficiency of seismic wave modelling. The grid spacing ratio n could be an arbitrary integer n ≥ 2. To downsample the wavefield from the finer grid to the coarser grid, our implementation can simply take the values on the finer grid without employing a downsampling filter for grid spacing ratio n = 2 to achieve stable results for long-time simulation. For grid spacing ratio n ≥ 3, the Gaussian filter should be used as the downsampling filter to get a stable simulation. To interpolate the wavefield from the coarse grid to the finer grid, the trilinear interpolation is used. Combining the efficiency of discontinuous grid with the flexibility of collocated-grid FD method on curvilinear grids, our method can simulate large-scale high-frequency strong ground motion of real earthquake with consideration of surface topography.

  12. Seismic imaging of transition zone discontinuities suggests hot mantle west of Hawaii.

    PubMed

    Cao, Q; van der Hilst, R D; de Hoop, M V; Shim, S-H

    2011-05-27

    The Hawaiian hotspot is often attributed to hot material rising from depth in the mantle, but efforts to detect a thermal plume seismically have been inconclusive. To investigate pertinent thermal anomalies, we imaged with inverse scattering of SS waves the depths to seismic discontinuities below the Central Pacific, which we explain with olivine and garnet transitions in a pyrolitic mantle. The presence of an 800- to 2000-kilometer-wide thermal anomaly (ΔT(max) ~300 to 400 kelvin) deep in the transition zone west of Hawaii suggests that hot material does not rise from the lower mantle through a narrow vertical plume but accumulates near the base of the transition zone before being entrained in flow toward Hawaii and, perhaps, other islands. This implies that geochemical trends in Hawaiian lavas cannot constrain lower mantle domains directly. PMID:21617072

  13. Changes in seismic anisotropy shed light on the nature of the Gutenberg discontinuity.

    PubMed

    Beghein, Caroline; Yuan, Kaiqing; Schmerr, Nicholas; Xing, Zheng

    2014-03-14

    The boundary between the lithosphere and asthenosphere is associated with a platewide high-seismic velocity "lid" overlying lowered velocities, consistent with thermal models. Seismic body waves also intermittently detect a sharp velocity reduction at similar depths, the Gutenberg (G) discontinuity, which cannot be explained by temperature alone. We compared an anisotropic tomography model with detections of the G to evaluate their context and relation to the lithosphere-asthenosphere boundary (LAB). We find that the G is primarily associated with vertical changes in azimuthal anisotropy and lies above a thermally controlled LAB, implying that the two are not equivalent interfaces. The origin of the G is a result of frozen-in lithospheric structures, regional compositional variations of the mantle, or dynamically perturbed LAB. PMID:24578529

  14. Seismic imaging of transition zone discontinuities suggests hot mantle west of Hawaii.

    PubMed

    Cao, Q; van der Hilst, R D; de Hoop, M V; Shim, S-H

    2011-05-27

    The Hawaiian hotspot is often attributed to hot material rising from depth in the mantle, but efforts to detect a thermal plume seismically have been inconclusive. To investigate pertinent thermal anomalies, we imaged with inverse scattering of SS waves the depths to seismic discontinuities below the Central Pacific, which we explain with olivine and garnet transitions in a pyrolitic mantle. The presence of an 800- to 2000-kilometer-wide thermal anomaly (ΔT(max) ~300 to 400 kelvin) deep in the transition zone west of Hawaii suggests that hot material does not rise from the lower mantle through a narrow vertical plume but accumulates near the base of the transition zone before being entrained in flow toward Hawaii and, perhaps, other islands. This implies that geochemical trends in Hawaiian lavas cannot constrain lower mantle domains directly.

  15. Changes in seismic anisotropy shed light on the nature of the Gutenberg discontinuity.

    PubMed

    Beghein, Caroline; Yuan, Kaiqing; Schmerr, Nicholas; Xing, Zheng

    2014-03-14

    The boundary between the lithosphere and asthenosphere is associated with a platewide high-seismic velocity "lid" overlying lowered velocities, consistent with thermal models. Seismic body waves also intermittently detect a sharp velocity reduction at similar depths, the Gutenberg (G) discontinuity, which cannot be explained by temperature alone. We compared an anisotropic tomography model with detections of the G to evaluate their context and relation to the lithosphere-asthenosphere boundary (LAB). We find that the G is primarily associated with vertical changes in azimuthal anisotropy and lies above a thermally controlled LAB, implying that the two are not equivalent interfaces. The origin of the G is a result of frozen-in lithospheric structures, regional compositional variations of the mantle, or dynamically perturbed LAB.

  16. Mantle transition zone discontinuities beneath the contiguous United States

    NASA Astrophysics Data System (ADS)

    Gao, Stephen S.; Liu, Kelly H.

    2014-08-01

    Using over 310,000 high-quality radial receiver functions recorded by the USArray and other seismic stations in the contiguous United States, the depths of the 410 km and 660 km discontinuities (d410 and d660) are mapped in over 1,000 consecutive overlapping circles with a radius of 1°. The average mantle transition zone (MTZ) thickness for both the western and central/eastern U.S. is within 3 km from the global average of 250 km, suggesting an overall normal MTZ temperature beneath both areas. The Pacific Coast Ranges and the southern Basin and Range Province are underlain by a depressed d410, indicating higher-than-normal temperature in the upper MTZ. The proposed Yellowstone and Raton hot spots are not associated with clear undulations of the MTZ discontinuities, but d410 beneath another proposed hot spot, Bermuda, is depressed significantly and d660 has a normal depth. Low-temperature regions are found in the upper MTZ associated with the subducted Juan de Fuca slab beneath the northern Rocky Mountains and in two circular areas beneath the northern Basin and Range Province and the southern Colorado Plateau. Part of the Great Plains is characterized by a depressed d660. This observation, when combined with results from seismic tomography, suggests the existence of a cold region in the lower MTZ, probably associated with subducted Farallon slab segments.

  17. Seismic discontinuities beneath the southwestern United States from S receiver functions

    NASA Astrophysics Data System (ADS)

    Akanbi, Olufemi; Li, Aibing

    2016-05-01

    S-receiver functions along the Colorado Plateau-Rio Grande Rift-Great Plains Transect known as LA RISTRA in the southwestern United States have been utilized to map seismic discontinuities beneath this tectonically active region. Individual receiver functions were stacked according to ray piercing points with moveout corrections in order to improve the signal-to-noise ratio of the converted S-to-P phases. A mantle discontinuity, which is interpreted as the lithosphere-asthenosphere boundary (LAB), is observed along the profile with depth ranging from 80 km beneath the Rio Grande Rift (RGR) to 100 km beneath the Great Plains (GP) and 120-180 km beneath the Colorado Plateau (CP). The shallow LAB beneath the Rio Grande Rift is indicative of lithosphere extension and asthenosphere upwarp. The LAB deepens sharply at the RGR-CP and RGR-GP boundaries, providing evidence for edge-driven, small-scale mantle convection beneath LA RISTRA. Two local discontinuities beneath the southeastern Colorado Plateau are imaged at ~ 250 km and ~ 300 km and could be the top and base of the eroded lithosphere, respectively. The S receiver function images suggest that edge-driven, small-scale convection is probably the mantle source for recent extension and uplift in the Rio Grande Rift and the Colorado Plateau.

  18. Experimental monitoring of the hydro-mechanical state of a discontinuity using controlled source seismic method

    NASA Astrophysics Data System (ADS)

    Place, Joachim; Blake, Oshaine; Rietbrock, Andreas; Faulkner, Dan

    2013-04-01

    Great earthquakes often occur in crystalline rocks, and basement rocks can host geothermal and hydrocarbon resources. In such rocks, the fluid storage and transfer properties depend mainly on the natural fault and fracture networks. Therefore, it is of primary importance to characterise the physical properties of the fault zones in order to better understand the seismogenic processes and how the resources can be exploited. Seismic waves are known to be sensitive to many parameters which evolve depending on the fault response to stresses and fluid type. Therefore seismic methods show a great potential to monitor the hydro-mechanical state of structures remotely, with no need for drilling through the structures. We developed a basic experimental approach at sample scale to monitor the mechanical coupling through a discontinuity between a granite sample in contact with a piece of steel, when the effective pressure (Peff) and the nature of the filling fluid vary. Piezoceramics utilised both as sources and sensors are located on the steel (in which the attenuation is assumed to be zero) and both generate and record the P and S wave fields reflected off the discontinuity at normal incidence. This permits the normal (Bn) and tangential (Bt) fracture compliances to be calculated after Schoenberg's linear slip theory from the measurement of P-P and S-S reflection coefficients. The roughness of the sample surface, as well as the effect of fluid type (air or water) and Peff were studied. Under dry conditions, it is observed that the poorer the contact area, the higher Bn and Bt, meaning that the seismic energy of P and S waves is less transmitted. Increasing the effective pressure decreases the compliances, which is interpreted as the effect of the closure of the voids at the interface; this permits more seismic energy to be transmitted through the interface. It is also observed that Bn is significantly higher than Bt at low Peff (<60 MPa). Under water saturated conditions

  19. Mantle Transition Zone Discontinuities Beneath Alaska

    NASA Astrophysics Data System (ADS)

    Dahm, H. H.; Gao, S. S.; Liu, K. H.; Yang, B.

    2015-12-01

    The 410 and 660 km discontinuities (d410 and d660) beneath Alaska and adjacent areas are imaged by stacking radial receiver functions recorded by about 400 broadband seismic stations with up to 30 years of recording period, using the 1D IASP91 earth model. Significant and spatially systematic variations in the apparent depths of the d410 and d660 are observed. The mean apparent depth of d410 and d660 for the entire study area is 416±1.87 km and 664±1.83 km, respectively. The variations of the apparent depths of d410 and d660 result in a complex mantle transition zone (MTZ) structure. Central and south-central Alaska are characterized by a normal MTZ thickness, suggesting that the subducting Pacific slab does not thermally affect the upper MTZ. Beneath the Yakutat microplate, a complex MTZ structure is observed with an overall thin MTZ thickness, coinciding with a low velocity zone and thin lithospheric thickness revealed by previous seismic tomography and receiver function studies. Two large regions with hot MTZ are mapped beneath NNW and NNE Alaska with abnormal temperature ranges between +360 and +390 °K. Despite of the complexity of the MTZ structure beneath Alaska, the mean MTZ thickness for the entire Alaskan orocline is 247 ±2.76 km, suggesting normal MTZ temperature on average. For the majority of the areas, our study shows that lateral upper mantle velocity variations contribute the bulk of the observed apparent undulations of the MTZ discontinuities.

  20. Seismic evidence for silicate melt atop the 410-km mantle discontinuity

    USGS Publications Warehouse

    Revenaugh, Justin; Sipkin, S.A.

    1994-01-01

    LABORATORY results demonstrating that basic to ultrabasic melts become denser than olivine-rich mantle at pressures above 6 GPa (refs 1-3) have important implications for basalt petrogenesis, mantle differentiation and the storage of volatiles deep in the Earth. A density cross-over between melt and solid in the extensively molten Archaean mantle has been inferred from komatiitic volcanism and major-element mass balances, but present-day evidence of dense melt below the seismic low-velocity zone is lacking. Here we present mantle shear-wave impedance profiles obtained from multiple-ScS reverberation mapping for corridors connecting western Pacific subduction zone earthquakes with digital seismograph stations in eastern China, imaging a ~5.8% impedance decrease roughly 330 km beneath the Sea of Japan, Yellow Sea and easternmost Asia. We propose that this represents the upper surface of a layer of negatively buoyant melt lying on top of the olivine ??? ??- phase transition (the 410-km seismic discontinuity). Volatile-rich fluids expelled from the partial melt zone as it freezes may migrate upwards, acting as metasomatic agents and perhaps as the deep 'proto-source' of kimberlites. The remaining, dense, crystalline fraction would then concentrate above 410 km, producing a garnet-rich layer that may flush into the transition zone.

  1. Upper Mantle Discontinuity Structure Beneath the Western Atlantic Ocean and Eastern North America from SS Precursors

    NASA Astrophysics Data System (ADS)

    Schmerr, N. C.; Beghein, C.; Kostic, D.; Baldridge, A. M.; West, J. D.; Nittler, L. R.; Bull, A. L.; Montesi, L.; Byrne, P. K.; Hummer, D. R.; Plescia, J. B.; Elkins-Tanton, L. T.; Lekic, V.; Schmidt, B. E.; Elkins, L. J.; Cooper, C. M.; ten Kate, I. L.; Van Hinsbergen, D. J. J.; Parai, R.; Glass, J. B.; Ni, J.; Fuji, N.; McCubbin, F. M.; Michalski, J. R.; Zhao, C.; Arevalo, R. D., Jr.; Koelemeijer, P.; Courtier, A. M.; Dalton, H.; Waszek, L.; Bahamonde, J.; Schmerr, B.; Gilpin, N.; Rosenshein, E.; Mach, K.; Ostrach, L. R.; Caracas, R.; Craddock, R. A.; Moore-Driskell, M. M.; Du Frane, W. L.; Kellogg, L. H.

    2015-12-01

    Seismic discontinuities within the mantle arise from a wide range of mechanisms, including changes in mineralogy, major element composition, melt content, volatile abundance, anisotropy, or a combination of the above. In particular, the depth and sharpness of upper mantle discontinuities at 410 and 660 km depth are attributed to solid-state phase changes sensitive to both mantle temperature and composition, where regions of thermal heterogeneity produce topography and chemical heterogeneity changes the impedance contrast across the discontinuity. Seismic mapping of this topography and sharpness thus provides constraint on the thermal and compositional state of the mantle. The EarthScope USArray is providing unprecedented access to a wide variety of new regions previously undersampled by the SS precursors. This includes the boundary between the oceanic plate in the western Atlantic Ocean and continental margin of eastern North America. Here we use a seismic array approach to image the depth, sharpness, and topography of the upper mantle discontinuities, as well as other possible upper mantle reflectors beneath this region. This array approach utilizes seismic waves that reflect off the underside of a mantle discontinuity and arrive several hundred seconds prior to the SS seismic phase as precursory energy. In this study, we collected high-quality broadband data SS precursors data from shallow focus (< 30 km deep), mid-Atlantic ridge earthquakes recorded by USArray seismometers in Alaska. We generated 4th root vespagrams to enhance the SS precursors and determine how they sample the mantle. Our data show detection of localized structure on the discontinuity boundaries as well as additional horizons, such as the X-discontinuity and a potential reflection from a discontinuity near the depth of the lithosphere-asthenosphere boundary. These structures are related to the transition from predominantly old ocean lithosphere to underlying continental lithosphere, as while

  2. 3D Discontinuous Galerkin elastic seismic wave modeling based upon a grid injection method

    NASA Astrophysics Data System (ADS)

    Monteiller, V.

    2015-12-01

    Full waveform inversion (FWI) is a seismic imaging method that estimates thesub-surface physical properties with a spatial resolution of the order of thewavelength. FWI is generally recast as the iterative optimization of anobjective function that measures the distance between modeled and recordeddata. In the framework of local descent methods, FWI requires to perform atleast two seismic modelings per source and per FWI iteration.Due to the resulting computational burden, applications of elastic FWI have been usuallyrestricted to 2D geometries. Despite the continuous growth of high-performancecomputing facilities, application of 3D elastic FWI to real-scale problemsremain computationally too expensive. To perform elastic seismic modeling with a reasonable amount of time, weconsider a reduced computational domain embedded in a larger background modelin which seismic sources are located. Our aim is to compute repeatedly thefull wavefield in the targeted domain after model alteration, once theincident wavefield has been computed once for all in the background model. Toachieve this goal, we use a grid injection method referred to as the Total-Field/Scattered-Field (TF/SF) technique in theelectromagnetic community. We implemented the Total-Field/Scattered-Field approach in theDiscontinuous Galerkin Finite Element method (DG-FEM) that is used to performmodeling in the local domain. We show how to interface the DG-FEM with any modeling engine (analytical solution, finite difference or finite elements methods) that is suitable for the background simulation. One advantage of the Total-Field/Scattered-Field approach is related to thefact that the scattered wavefield instead of the full wavefield enter thePMLs, hence making more efficient the absorption of the outgoing waves at theouter edges of the computational domain. The domain reduction in which theDG-FEM is applied allows us to use modest computational resources opening theway for high-resolution imaging by full

  3. Receiver Function Study of the Upper Mantle Discontinuities beneath Northeast China: Evidence for Local Mantle Upwelling Beneath the Songliao Basin

    NASA Astrophysics Data System (ADS)

    Tao, K.; Chen, Y. J.; Liu, H.; Niu, F.; Ning, J.; Grand, S. P.; Kawakatsu, H.; Tanaka, S.; Necessarray Project Team

    2011-12-01

    We employ receiver function technique and pseudo-station stacking method to study the crust and upper mantle discontinuities beneath Northeast China. Receiver functions are calculated from waveforms recorded by the NorthEast China Extended SeiSmic Array (NECESSArray). NECESSArray is a large deployment of 120 high quality broadband seismographs operated by a multi-national collaboration of China, United States and Japan. The operation of this array began in September 2009 and lasted for two years. This seismic experiment was designed to study the behavior of the Pacific subducting slab in the mantle transition zone, the cause of intraplate continental magmatism and tectonics in Northeast China, and the evolution of ancient Archean lithosphere. Preliminary results show strong velocity heterogeneity beneath the Songliao basin. In this region, there is a negative pulse before the Ps conversion of the Moho in most receiver functions and this may indicate the existence of a low velocity zone in the crust of the Songliao basin. There exists a negative pulse at about 37 s which might stand for the signature of a low velocity zone above the 410-km discontinuity. The most important finding is that both of the 410-km and the 660-km discontinuities are depressed. This observation suggests that a local mantle upwelling probably exists in the upper mantle above, including the upper part of, the transition zone, while the remnant subducted Pacific slab is remained in the lower part of the transition zone.

  4. On the 300km discontinuity with Conversion Phases SdP in the Tonga-Fiji Region

    NASA Astrophysics Data System (ADS)

    Zhou, Y.; Sui, Y.

    2011-12-01

    results from other researchers (c.f., Williams and Revenaugh, Geology, 2005), the conversion phases are at relatively high frequency, which means the 300 km discontinuity should be a first-order one as the 660 km discontinuity. Because of the limitation of focal depths which are useful for studying the 300 km discontinuity, we can't retrieve the information for the 520 or 660 km discontinuities. What's more, there is no obvious signal for the 410 km discontinuity, which may mean that the 300 km discontinuity is much stronger than the 410 km discontinuity or the topography of the 410 km discontinuity is larger than the 300 km discontinuity. Because of the small topography in the subduction zone of the Tonga-Fiji region, the 300 km discontinuity may be sensitive to pressure, but not temperature. And the discontinuity may be associated with either the coesite to stishovite transition or exsolution of stishovite from clinopyroxenes containing excess silica (William and Revenaugh, Geology, 2005; Zheng, et al., Science, 2007).

  5. Mantle Transition Zone Discontinuities beneath the Contiguous United States

    NASA Astrophysics Data System (ADS)

    Gao, S. S.; Liu, K. H.

    2014-12-01

    The depths of the 410 km (d410) and 660 km (d660) discontinuities are robust indicators of in-situ temperature in the upper and lower boundary, respectively, of the mantle transition zone (MTZ), and thus can provide critical constraints on the depth extent of major tectonic features. Using over 310,000 high-quality radial receiver functions recorded by the USArray and other seismic stations in the contiguous United States, the depths of the d410 and d660 are mapped in over 1000 consecutive overlapping circles with a radius of 1 degree. The average MTZ thickness for both the western and central/eastern US is within 3 km from the global average of 250 km, suggesting an overall normal MTZ temperature beneath both areas. The Pacific Coast Ranges and the southern Basin and Range Province are underlain by a depressed d410, indicating higher-than-normal temperature in the upper MTZ. The proposed Yellowstone and Raton hotspots are not associated with clear undulations of the MTZ discontinuities, but d410 beneath another proposed hotspot, Bermuda, is depressed significantly and d660 has a normal depth. Low-temperature regions are found in the upper MTZ associated with the subducted Juan de Fuca slab beneath the northern Rocky Mountains, and in two circular areas beneath the northern Basin and Range Province and the southern Colorado Plateau. Part of the Great Plains is characterized by a depressed d660. This observation, when combined with results from seismic tomography, suggests the existence of a cold region in the lower MTZ, probably associated with subducted Farallon slab segments.

  6. Seismic reflection mapping of discontinuous sandstone bodies. Part I: synthetic modeling studying

    SciTech Connect

    Dobecki, T.L.

    1980-06-01

    Utilizing depth models consistent with the size, velocity, and density of observed sandstone channels in the upper Cretaceous Mesa Verde and Tertiary Wasatch formations, the synthetic seismic response of such channel lenses has been computed. By varying the lens thickness, depth, number, and separation, it was possible to observe the net effect on the seismic response and, in turn, how these affects might influence interpretation of field data.

  7. A discussion on “The 410-km-depth discontinuity: A sharpness estimate from near-critical reflections” by Vidale et al.

    NASA Astrophysics Data System (ADS)

    Krishna, V. G.; Ramesh, D. S.

    Vidale et al. [1995] presented a convincing evidence of a fairly sharp ‘410-km’ seismic discontinuity uncjer the western United States by examining clear noise-free reflected arrivals from this discontinuity in the near-critical distance range of 11.5° to 14° (Fig. Ia). They reconstructed the P velocity-depth model from the arrival times of the 410-km reflection and initial P waves across the distance range 8°-14°. The prominent features of the upper mantle P velocity model given by them include; a low velocity layer (LVL) in the depth range of about 110-200 km with a broad transitional bottom, a fairly large velocity gradient (0.4 km/s velocity increase from 200 to 410 km depth) above the 410-km discontinuity which is sharp and associated with a 5.5% velocity increase.Seismic estimates of sharpness as well as velocity contrast at the ‘410-km’ and ‘660-km’ discontinuities in the mantle transition zone provide important constraints to plausible models of composition, temperature and convective processes in the deep earth. The rapid increases of seismic wave velocities inferred in the transition zone, at depths of 410-Km and 660-km, are classically associated [Ringwood, 1975] with the pressure-induced phase transitions in Olivine which is considered to be the predominant mineral in the upper mantle. Recent observations of high quality coherent seismic reflections from the transition zone [Benz and Vidale, 1993; Vidale et al., 1995] conclusively reveal that the 410-km discontinuity is fairly sharp. Contrastingly the experimental results from mineral physics [Akaogi et al., 1989; Bina and Wood, 1987; Katsura and Ito, 1989] predict a substantially larger transition width, on the order of 6-19 km for the olivine-beta spinel phase transition at pressures corresponding to 410-km-depth discontinuity. Similar inconsistencies in the magnitude of velocity contrast at the 410-km discontinuity are also found [Duffy et al., 1995; Jeanloz, 1995] by comparison of

  8. Correlation of the 410 km Discontinuity Low Velocity Layer with Tomographic Wavespeed Variations

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Dueker, K. G.

    2010-12-01

    The transition zone water-filter model predicts that a hydrous melt layer at the 410-km discontinuity is only actively produced in upwelling region, and does not exist in downwelling region (Bercovici and Karato, 2003). This prediction has been tested by stacking of P-S receiver functions using the RISTRA linear array which crosses west-Texas, New Mexico and Utah. The receiver functions are binned into the NW, SE, SW azimuthal quadrants and stacked to produce well-resolved images of the 410- and 660-km discontinuities. The three receiver function quadrant stack images find a correlation between the occurrence of negative polarity 410-km low velocity layer arrival and the teleseismic body wave velocity tomogram of Schmandt and Humphreys (2010); the 410 low velocity layer arrival is absent where the velocities about the 410 km discontinuity are relatively high and present where the velocities are low. Our finding is consistent with a simple interpretation of the transition zone water filter model which predicts the production of a hydrous melt layer where upflow of sufficiently hydrated transition zone mantle occurs and destruction of a hydrous melt layer where there is downflow. We test this prediction by analyzing the Colorado Rockies Experiment and Seismic Transects (CREST) seismic data which was collected in 2008-2009. This 15 month deployment of 59 CREST stations in tandem with 31 Transportable Array stations yields a total of 161 Mb>5.5 events at 30°-95° distances. The P-S receiver functions are calculated using a multi-channel deconvolution methodology and filtered with a 30-3 s post-deconvolution filter. The receiver function dataset contains about 1800 SV components after RMS, cross-correlation, and visual data quality culling. Common conversion point images are constructed using Pds timing correction from a 3-D upper mantle tomography model (McCarthy and Aster, pers. com.) to account for lateral P/S velocity heterogeneity.

  9. NEXD: A Software Package for High Order Simulation of Seismic Waves using the Nodal Discontinuous Galerkin Method

    NASA Astrophysics Data System (ADS)

    Schumacher, F.; Lambrecht, L.; Friederich, W.

    2015-12-01

    In geophysics numerical simulations are a key tool to understand the processes of earth. For example, global simulations of seismic waves excited by earthquakes are essential to infer the velocity structure within the earth. Furthermore, numerical investigations can be helpful on local scales in order to find and characterize oil and gas reservoirs. Moreover, simulations enable a better understanding of wave propagation in borehole and tunnel seismic applications. Even on microscopic scales, numerical simulations of elastic waves can help to increase knowledge about the behaviour of materials, e.g. to understand the mechanism of crack propagation in rocks. To deal with highly complex heterogeneous models, here the Nodal Discontinuous Galerkin Method (NDG) is used to calculate synthetic seismograms. The advantage of this method is that complex mesh geometries can be computed by using triangular or tetrahedral elements for domain discretization together with a high order spatial approximation of the wave field. The simulation tool NEXD is presented which has the capability of simulating elastic and anelastic wave fields for seismic experiments for one-, two- and three- dimensional settings. The implementation of poroelasticity and simulation of slip interfaces are currently in progress and are working for the one dimensional part. External models provided by e.g. Trelis/Cubit can be used for parallelized computations on triangular or tetrahedral meshes. For absorbing boundary conditions either a fluxes based approach or a Nearly Perfectly Matched Layer (NPML) can be used. Examples are presented to validate the method and to show the capability of the software for complex models such as the simulation of a tunnel seismic experiment.

  10. Toward a comprehensive understanding of transition zone seismic discontinuities: A new constraint near the stagnant slab region beneath China

    NASA Astrophysics Data System (ADS)

    Song, T. R. A.; Shen, X.; Stixrude, L. P.; Lithgow-Bertelloni, C. R.

    2015-12-01

    Plate tectonics and subduction operating over much of the Earth's history can induce mantle mixing, chemical heterogeneities and recycle volatiles into the mantle. Some slabs are penetrating into the deep lower mantle, but others are stagnated near the transition zone (TZ). Presumably, the thermochemical state of the TZ is a consequence of delicate balance and feedback between the short-term and long-term mixing. Near the stagnant slab, what's the thermochemical state of the TZ? what's the degree of hydration in the TZ? TZ seismic discontinuities hold the key to resolve the mystery of mass and heat transport in the Earth's mantle as well as the composition of the Earth's interior. But deciphering discontinuity properties are not trivial. Data were typically limited to either mantle triplications, converted waves (P-to-S or S-to-P) or mantle reflections (e.g. SS precursors, ScS reverberations). These observations place constraints on the velocity gradient near the discontinuity as well as discontinuity reflectivity, but hardly offer independent information on the density jump or/and density gradient. In few cases where multiple datasets are jointly analysed to resolve the density jump, the region of sensitivity (or the fresnel zone) of different dataset does not necessarily coincide. Finally, the use of short period (~1 Hz) data (e.g., P'P' precursors) or long period (~> 0.1 Hz) data (e.g., SS precursors) does not allow us to simultaneously address the transition width and the gradient near the discontinuity. We advocate a simple and effective strategy. Specifically, we involve broadband direct converted waves (e.g., P410s, P660s) and the topside reflections (the multiples, e.g., PpP410s, PpP660s) in the context of P wave receiver function technique. Such a tactic not only minimizes tradeoffs between velocity and density jumps, but allows self-consistent estimates of the shear velocity jump, the density jump, the transition width and the velocity/density gradient

  11. Evidence from three-dimensional seismic reflectivity images for enhanced melt supply beneath mid-ocean-ridge discontinuities

    PubMed

    Kent; Singh; Harding; Sinha; Orcutt; Barton; White; Bazin; Hobbs; Tong; Pye

    2000-08-10

    Quantifying the melt distribution and crustal structure across ridge-axis discontinuities is essential for understanding the relationship between magmatic, tectonic and petrologic segmentation of mid-ocean-ridge spreading centres. The geometry and continuity of magma bodies beneath features such as overlapping spreading centres can strongly influence the composition of erupted lavas and may give insight into the underlying pattern of mantle flow. Here we present three-dimensional images of seismic reflectivity beneath a mid-ocean ridge to investigate the nature of melt distribution across a ridge-axis discontinuity. Reflectivity slices through the 9 degrees 03' N overlapping spreading centre on East Pacific Rise suggest that it has a robust magma supply, with melt bodies underlying both limbs and ponding of melt beneath large areas of the overlap basin. The geometry of melt distribution beneath this offset is inconsistent with large-scale, crustal redistribution of melt away from centres of upwelling. The complex distribution of melt seems instead to be caused by a combination of vertical melt transport from the underlying mantle and subsequent focusing of melt beneath a magma freezing boundary in the mid-crust.

  12. Global Observations of Mantle Discontinuities Using SS and PP Precursors

    NASA Astrophysics Data System (ADS)

    Deuss, Arwen

    2009-10-01

    SS and PP precursors are currently the only body wave data types that have significant coverage in both oceanic and continental regions to study the existence and characteristics of mantle discontinuities on a global scale. Here, the techniques used by global seismologists to observe SS and PP precursors are reviewed. Seismograms, aligned on SS or PP, are stacked using normal move out (NMO) techniques to obtain common depth point gathers. Bootstrap methods are employed to determine 95% confidence levels of the stacks and robustness of the observations. With these relatively simple techniques, a range of discontinuities has been found in the mantle up to 1,200 km depth. The stacks are dominated by the transition zone discontinuities at 410, 520 and 660 km depth, but additional discontinuities at 220, 300-350, 800-900 and 1,100-1,200 km depth are also seen in certain regions. An overview is given of the most recent observational results with a discussion of their mineral physical interpretation and geodynamical significance. Both seismology and mineral physics agree on the level of complexity at the transition discontinuities: a simple 410, a more complicated 520 and a highly complicated 660-km discontinuity are consistently found in both disciplines.

  13. Seismic Discontinuities beneath the Southwestern United States from S Receiver Functions

    NASA Astrophysics Data System (ADS)

    Akanbi, O. E.; Li, A.

    2015-12-01

    S- Receiver functions along the Colorado Plateau-Rio Grande Rift-Great Plains Transect known as La RISTRA in the southwestern United States have been utilized to map the Moho and lithosphere-asthenosphere boundary (LAB) beneath this tectonically active region. The receiver functions were stacked according to ray piercing points with moveout corrections in order to improve the signal-to-noise ratio of converted S-to-P phases. The Moho appears at 30-40 km beneath the Rio Grande Rift (RGR) and deepens to 35-45 km beneath the Great Plains (GP) and the Colorado Plateau (CP). A sharp discontinuity is observed along the profile with the average depth of 80 km beneath the RGR, 100 km beneath the GP, and 160 km beneath the CP. This discontinuity is consistent with the top of a low velocity zone in a shear wave model beneath the array and is interpreted as the LAB. Strong phases imaged at ~90 km beneath the CP and GP could be a combination of side-lobes of the Moho conversions and primary Sp phases from a mid-lithosphere discontinuity (MLD). The relatively shallow Moho and LAB beneath the Rio Grande Rift is indicative of lithosphere extension and asthenosphere upwarp. In addition, the LAB shows depth-step depressions at the RGR-CP and RGR-GP boundaries, providing evidence for mantle downwelling. The variation of the lithospheric depth across the RISTRA array supports that edge-driven, small-scale mantle convection is largely responsible for the recent extension and uplift in the Rio Grande Rift and the Colorado Plateau.

  14. Mantle transition zone beneath a normal seafloor in the northwestern Pacific: Electrical conductivity, seismic discontinuity, and water content

    NASA Astrophysics Data System (ADS)

    Matsuno, Tetsuo; Suetsugu, Daisuke; Utada, Hisashi; Baba, Kiyoshi; Tada, Noriko; Shimizu, Hisayoshi; Shiobara, Hajime; Isse, Takehi; Sugioka, Hiroko; Ito, Aki

    2016-04-01

    We conducted a joint electromagnetic and seismic field experiment to probe water content reserved in the mantle transition zone (MTZ) beneath a normal seafloor around the Shatsky Rise in the northwestern Pacific. Specifically for the investigation of the MTZ structure, we developed new ocean bottom instruments for providing higher S/N ratio data and having higher mobility in field experiment than ever. We installed our state-of-the-art instruments in two arrays to the north and south of the Shatsky Rise for 5 years from 2010 to 2015. We first analyzed data obtained in our and previous studies to elucidate an electrical conductivity structure through the magnetotelluric and geomagnetic depth sounding methods and seismic discontinuity depths or thickness of the MTZ through the P-wave receiver function method. An electrical conductivity structure beneath two observational arrays is represented well by an average 1-D model beneath the northern Pacific. A MTZ thickness beneath the north array is thicker than a global average of MTZ thickness by 22 km, and that beneath the south array is similar to the average. For estimating water content in the MTZ, we implemented a series of forward modeling of the electromagnetic responses based on the average 1-D electrical conductivity model, temperature profiles of the MTZ involving temperature anomalies estimated from the MTZ thickness perturbations, and electrical conductivities of dry and hydrous MTZ materials (wadsleyite and ringwoodite). A result of the forward modeling indicates that the maximum water content in the MTZ beneath the north array is 0.5 wt.%.

  15. Imaging the seismic structure of the crust and upper mantle beneath the Great Plains, Rio Grande Rift, and Colorado Plateau using receiver functions

    NASA Astrophysics Data System (ADS)

    Wilson, David; Aster, Richard; Ni, James; Grand, Stephen; West, Michael; Gao, Wei; Baldridge, W. Scott; Semken, Steve

    2005-05-01

    The seismic structure of the crust and upper mantle of the southwestern United States is examined using receiver functions calculated from teleseismic arrivals recorded in the Colorado Plateau-Rio Grande Rift-Great Plains Seismic Transect (LA RISTRA) experiment. We apply receiver function estimation and filtering methods developed by Wilson and Aster (2005) to produce receiver functions with decreased sensitivity to noise and deconvolutional instability. Crustal thickness and Vp/Vs ratios are estimated using both direct and reverberated P-to-S receiver function modes. We apply regularized receiver function migration methods to produce a multiple-suppressed image of the velocity discontinuity structure of the subsurface. Our results show that crustal thickness averages 44.1 ± 2.3 km beneath the Great Plains (GP) and 45.6 ± 1.1 km beneath the Colorado Plateau (CP). Crustal thinning beneath the Rio Grande Rift (RGR) is broadly symmetric about the rift axis, with the thinnest crust (35 km) located directly beneath the rift axis, suggesting a pure shear stretched lithosphere beneath the RGR. We also observe a prominent northwest dipping discontinuity, ranging from 65 to 85 km deep beneath the CP, and possible subcrustal discontinuities beneath the GP. These discontinuities, along with recent xenolith data, are consistent with preserved ancient lithospheric structures such as relict suture zones associated with Proterozoic subduction. We observe an upper mantle discontinuity at 220-300 km depth that may correlate with similar discontinuities observed beneath eastern North America. We also observe relatively flat discontinuities at 410 and 660 km depth, indicating there is not a large-scale thermal anomaly beneath the RGR at these depths.

  16. Global Scale Exploration Seismics: Mapping Mantle Discontinuities with Inverse Scattering Methods and Millions of Seismograms

    NASA Astrophysics Data System (ADS)

    van der Hilst, R. D.; de Hoop, M. V.; Shim, S. H.; Shang, X.; Wang, P.; Cao, Q.

    2012-04-01

    Over the past three decades, tremendous progress has been made with the mapping of mantle heterogeneity and with the understanding of these structures in terms of, for instance, the evolution of Earth's crust, continental lithosphere, and thermo-chemical mantle convection. Converted wave imaging (e.g., receiver functions) and reflection seismology (e.g. SS stacks) have helped constrain interfaces in crust and mantle; surface wave dispersion (from earthquake or ambient noise signals) characterizes wavespeed variations in continental and oceanic lithosphere, and body wave and multi-mode surface wave data have been used to map trajectories of mantle convection and delineate mantle regions of anomalous elastic properties. Collectively, these studies have revealed substantial ocean-continent differences and suggest that convective flow is strongly influenced by but permitted to cross the upper mantle transition zone. Many questions have remained unanswered, however, and further advances in understanding require more accurate depictions of Earth's heterogeneity at a wider range of length scales. To meet this challenge we need new observations—more, better, and different types of data—and methods that help us extract and interpret more information from the rapidly growing volumes of broadband data. The huge data volumes and the desire to extract more signal from them means that we have to go beyond 'business as usual' (that is, simplified theory, manual inspection of seismograms, …). Indeed, it inspires the development of automated full wave methods, both for tomographic delineation of smooth wavespeed variations and the imaging (for instance through inverse scattering) of medium contrasts. Adjoint tomography and reverse time migration, which are closely related wave equation methods, have begun to revolutionize seismic inversion of global and regional waveform data. In this presentation we will illustrate this development - and its promise - drawing from our work

  17. Mid mantle seismic anisotropy around subduction zones

    NASA Astrophysics Data System (ADS)

    Faccenda, M.

    2014-02-01

    There is increasing evidence for mid mantle seismic anisotropy around subduction zones whose interpretation remains elusive. In this study I estimate the strain-induced mid mantle fabric and associated seismic anisotropy developing in 3D petrological-thermo-mechanical subduction models where the slab is either stagnating over the 660 km discontinuity or penetrating into the lower mantle. The modelling of synthetic lattice-preferred-orientation (LPO) development of wadsleyite and perovskite has been calibrated with results from deformational experiments and ab-initio atomic scale models, and the single crystal elastic tensor of the different mineral phases is scaled by local P-T conditions. The lower transition zone (ringwoodite + garnet) is assumed to be isotropic. Mid mantle fabric develops in proximity of the subducting slab where deformation and stresses are high, except at depths where upwelling or downwelling material undergoes phase transformations, yielding to LPO reset. The upper transition zone (wadsleyite + garnet) is characterized by weak transverse isotropy (2-3%) with symmetry axes oriented and fast S wave polarized dip-normal. A slightly stronger transverse isotropy develops in the lower mantle (perovskite + periclase), where the symmetry axes, the polarization of the fast S wave and the maximum Vp and dVs are parallel to the slab dip and subduction direction. For stagnating slab models this translates into negative and positive radial anisotropy in the upper transition zone and lower mantle back-arc, respectively, minimum delay times for vertically travelling shear waves and large shear wave splitting for waves propagating horizontally in the lower mantle. These results may help in reconciling the seismic anisotropy patterns observed in some subduction zones with subduction-induced deformation, such as those measured in the mid mantle between the Australian plate and the New Hebrides-Tonga-Kermadec trenches that I interpret as related to stagnating

  18. Structure of the Upper Mantle Beneath Northern Eurasia Derived from Russian Deep-Seismic PNE Profiles

    NASA Astrophysics Data System (ADS)

    Ryberg, Trond; Tittgemeyer, Marc; Wenzel, Friedemann

    From 1968 until 1990, Russian scientists carried out an intensive program of deep seismic sounding across the territory of the former Soviet Union, using Peaceful Nuclear Explosions (PNEs) as powerful sources for elastic waves. The explosions, both chemical and nuclear, were recorded by up to 400 shot-period (1-2 Hz) three-component, analog recording systems. The average station spacing of about 10 km along the profiles provided a data density not previously available for studies of the upper mantle and the transition zone. Observation distances of more than 3000 km allow the investigation of the velocity structure of the Earths crust and upper mantle to a depth of 700 km. The analog data have been digitized and used to constrain the fine structure of the upper mantle below Northern Eurasia. They reveal reflections and refractions from upper mantle discontinuities at 410, 520 and 660 km depth. Several properties of the recorded phases have been used to derive a regional P wave velocity model. Synthetic seismograms were calculated and compared with the observations to test these models. Characteristic for all the data in northern Eurasia is the absence of strong pre-critical reflections predicted by the global IASP91 model for the 660 km discontinuity. The appearance of two additional characteristic travel-time branches in the distance range of 2200 km was interpreted as being caused by the proposed and disputed upper mantle discontinuity at 520 km depth. Synthetic seismograms were calculated to constrain its properties. The recordings on the Quartz profile in Northern Eurasia have been used to constrain the nature of the globally observed high-frequency teleseismic P phase, which can be observed for shot-receiver distances of more than 3000 km. We suggest that this phase is caused by velocity fluctuations in the upper mantle acting as scatterers. This hypothesis was tested by extensive numerical simulations of the wave propagation using finite difference methods

  19. Seismic tomography reveals the upper-mantle structure beneath the Carpathian-Pannonian system

    NASA Astrophysics Data System (ADS)

    Dando, B. D.; Houseman, G.; Stuart, G. W.; Hegedus, E.; Kovacs, A.; Brueckl, E. P.; Hausmann, H.; Radovanovic, S.

    2009-12-01

    The Carpathian Basins Project (CBP) aims to understand the formation of the Miocene-age extensional basins contained within the convergent arc of the Alpine-Carpathian system. To test competing models for the recent geological evolution of the Carpathian-Pannonian lithosphere and upper mantle, we present a new tomographic determination of P-wave velocity structure to depths of 700 km beneath this region. This model is based on inversion of seismic travel-time residuals from 97 broadband seismic stations. We include CBP data from a 15-month deployment of a high resolution network of 46 stations deployed NW-SE across the Vienna and western Pannonian basins through Austria, Hungary and Serbia, together with 10 broadband stations spread across the Pannonian basin and a further 41 permanent broadband stations. We use P-wave arrival times from 232 teleseismic events. To avoid contamination of our inversion results from crustal velocity variations, deterministic corrections are applied to our travel-time residuals using crustal velocity models obtained from controlled source experiments and sediment thickness maps. Our 3-D velocity model images the fast velocity structure of the eastern Alps down to ~350 km. Beneath the Pannonian basin the velocity variation at 300 km depth is dominated by a fast region which extends eastward from the Alpine anomaly and reaches down into the mantle transition zone (MTZ). This fast structure is limited on the North side by slow material beneath the North Carpathians. At depths greater than 450 km, below the eastern Pannonian basin, a slow anomaly extends to the base of the model. Beneath the same region Hetenyi et al. (submitted to GRL), used receiver functions from the CBP dataset, to show a localised depression of the 660 km discontinuity of up to ~40 km. We aim to address how the depression of the 660 km discontinuity and its associated density and velocity variations affect our tomographic images. Our results will help to provide

  20. Control Effect of a Large Geological Discontinuity on the Seismic Response and Stability of Underground Rock Caverns: A Case Study of the Baihetan #1 Surge Chamber

    NASA Astrophysics Data System (ADS)

    Cui, Zhen; Sheng, Qian; Leng, Xianlun

    2016-06-01

    In this paper, the seismic stability of the #1 surge chamber of the Baihetan hydropower plant, which is influenced by a large dominating geological discontinuity [the interlayer shear weakness zone (ISWZ) C2)], is studied. An advanced, nonlinear, continuously yielding (CY) model was adopted to describe the complex mechanical properties of ISWZ C2. This model considers a power function type, normal stress dependent behavior and the progressive damage that occurred during shear tests. The applicability of the CY model is proved via a comparison with field test results and the theoretical solution. Verification work was conducted in 3DEC code to show that the 3DEC software is suitable for implementing this model. Three ground motion waveforms were utilized to conduct a seismic analysis of the #1 surge chamber after a special response spectrum matching process. The seismic analysis confirmed the control effect of ISWZ C2 on the seismic stability of the cavern. The majority of the cavern's seismic displacement consists of elastic body movement, while the plastic deformation is relatively limited. Further, most of the deformations were caused by the contact deformation of C2. For the contact deformation of C2, the magnitude of permanent shear deformation is larger than that of the normal deformation. The magnitude of permanent shear deformation is more notable along the strike direction of C2, and the permanent normal displacement n of C2 mainly occurs along the dip direction of C2. Finally, the seismic stability of the cavern is assessed via the overload method. The seismic safety factor of the cavern is approximately 2-3.

  1. Seismic structure and heterogeneity in the upper mantle

    NASA Astrophysics Data System (ADS)

    Kenntt, B. L. N.

    The earliest models of the seismic velocity structure of the upper mantle were smooth. But, since the introduction of strong gradients near 400 km depth by Jeffreys to explain the '20° discontinuity" in observed travel times, there has been a steady accumulation of detail in mantle structure. For a particular region, a smoothed and averaged representation of the seismic structure in the upper mantle can be derived from long-period body wave and higher mode surface wave observations. The vertical resolving power of such techniques is limited by the relatively long wavelengths. In contrast short-period observations offer potential resolution, but are susceptible to the influence of lateral heterogeneity. Fortunately the major features of the upper mantle can be discerned but important questions for structural processes such as the detailed nature ofthe transitions near 410 and 660 km are generally inaccessible. There is a natural tendency to overweight those observations on which particularly clear features are seen (as compared with the statistical anonymity of less spectacular data) which can lead to unwarranted generalizationsof specific results. To reconcile different views of mantle structure requires us to address the purpose for which the mantle structures are to be used. For example, fine detail in a velocity model which is insignificant for travel time studies can have a profound effect on amplitudes and short-period seismic waveforms. The variability in the patterns of body wave observations, especially atshort periods, provides strong evidence for 1-2 per cent heterogeneity on scales around 200 km in the upper mantle. Such features are superimposed on larger scale and larger amplitude lateral variations which can be mapped using surface wave studies. Much of the pattern of lateral variability in the upper mantle is likely to be due to thermal processes both directly by the influence of temperature and indirectly by compositional effects induced by flow

  2. The nature of the 660-kilometer discontinuity in Earth's mantle from global seismic observations of PP precursors.

    PubMed

    Deuss, Arwen; Redfern, Simon A T; Chambers, Kit; Woodhouse, John H

    2006-01-13

    The 660-kilometer discontinuity, which separates Earth's upper and lower mantle, has been detected routinely on a global scale in underside reflections of precursors to SS shear waves. Here, we report observations of this discontinuity in many different regions, using precursors to compressional PP waves. The apparent absence of such precursors in previous studies had posed major problems for models of mantle composition. We find a complicated structure, showing single and double reflections ranging in depth from 640 to 720 kilometers, that requires the existence of multiple phase transitions at the base of the transition zone. The results are consistent with a pyrolite mantle composition.

  3. Seismic Evidence of Localized Distribution of Fluids or Melts in the Mantle Transition Zone

    NASA Astrophysics Data System (ADS)

    Tajima, F.; Nakagawa, T.

    2009-04-01

    Seismic tomography models have shown flattened broad high velocity anomaly (HVA), i.e., the image of a subducted slab (stagnant slab) trapped in the upper mantle transition zone (MTZ) associated with the northwestern Pacific subduction zones. Our body waveform analysis in a relatively high frequency band (approximately 0.03 to 1 Hz) has determined a fairly broad region of HVA's where the structure can be delineated largely with layered models but the typical wavelength of HVA is shorter than that in tomography models. The HVA's are accompanied by a depression of the "660 km" discontinuity depth (model M3.11) or not (model M2.0), indicating a possible variation of geochemical properties at the bottom of the upper mantle. A hypothesis is proposed for this implication, i.e., that the structural variation may represent the contrast between a hydrous garnet-rich layer (subducted crust) and bulk peridotite associated with a stagnant slab. This hypothesis is supported by the results of recent laboratory experiments. The garnet-rich layer can flow and descend faster than bulk peridotite as hydrous garnet is weaker and denser than peridotite in the MTZ (Katayama and Karato, 2008). Given that the Clapeyron slope for hydrous garnet-perovskite is positive at about 660 km (Sano et al., 2006), two zones of HVA with, and without a depression in the discontinuity depth may exist next to each other at the bottom of the MTZ (Tajima et al., 2008). Here we report highly localized low velocity anomaly (LVA) zones which are located in the region of structural change of the "660 km" discontinuity depth. The LVA zones were found from anomalous broadened P waveforms observed for deep focus events, which propagated close to data modeled with a typical layered model for a stagnant slab but could not be synthesized with such layered models (Tajima and Grand, 1998; Tajima and Nakagawa, 2006). Here note that the source processes of the events are short and simple, and the corresponding SH

  4. Wet Fault or Dry Fault? A Laboratory Approach to Remotely Monitor the Hydro-Mechanical State of a Discontinuity Using Controlled-Source Seismics

    NASA Astrophysics Data System (ADS)

    Place, Joachim; Blake, Oshaine; Faulkner, Daniel; Rietbrock, Andreas

    2014-11-01

    Stress variation and fluid migration occur in deformation zones, which are expected to affect seismic waves reflected off or propagating across such structures. We developed a basic experimental approach to monitor the mechanical coupling with respect to seismic coupling across a single discontinuity between a granite sample in contact with a steel platen. Piezoceramics located on the platen were used to both generate and record the P and S wave fields reflected off the discontinuity at normal incidence. This way, normal ( B n) and tangential ( B t) compliances were calculated using Schoenberg's linear slip theory (Schoenberg, J Acoust Soc Am 68:1516-1521, 1980) when the roughness, the effective pressure ( P eff, up to 200 MPa), and the nature of the filling (gas or water) vary. We observe that increasing the effective pressure decreases B n and B t, which is interpreted as the effect of the closure of the voids at the interface, permitting more seismic energy to be transmitted across the interface. Values of B n are significantly higher than those of B t at low P eff (<60-80 MPa) in dry conditions, and significantly drop under water-saturated conditions. The water filling the voids therefore helps to transmit the seismic energy of compressional waves across the interface. These results show that the assumption B n ≈ B t commonly found in some theoretical approaches does not always stand. The ratio B n/ B t actually reflects the type of saturating fluids and the effective pressure, in agreement with other experimental studies. However, we illustrate that only the relative variations of this ratio seem to be relevant, not its absolute value as suggested in previous studies. Consequently, the use of B n against B t plots may allow effective pressure variation and the nature of the pore fluid to be inferred. In this respect, this experimental approach at sample scale helps to pave the way for remotely monitoring in the field the hydro-mechanical state of deformation

  5. Mid-mantle seismic anisotropy patterns around subduction zones predicted by numerical modelling

    NASA Astrophysics Data System (ADS)

    Faccenda, Manuele

    2014-05-01

    There is increasing evidence for mid mantle seismic anisotropy around subduction zones whose interpretation remains elusive. In this study I estimate the strain-induced mid mantle fabric and associated seismic anisotropy developing in 3D petrological-thermo-mechanical subduction models where the slab is either stagnating over the 660 km discontinuity or penetrating into the lower mantle. The modeling of synthetic lattice-preferred-orientation (LPO) development of wadsleyite and perovskite has been calibrated with results from deformational experiments and ab-initio atomic scale models, and the single crystal elastic tensor of the different mineral phases is scaled by local P-T conditions. The lower transition zone (ringwoodite + garnet) is assumed to be isotropic. Mid mantle fabric develops in proximity of the subducting slab where deformation and stresses are high, except at depths where upwelling or downwelling material undergoes phase transformations, yielding to LPO reset. The upper transition zone (wadsleyite + garnet) is characterized by weak transverse isotropy (2-3%) with symmetry axes oriented and fast S wave polarized dip-normal. A slightly stronger transverse isotropy develops in the lower mantle (perovskite + periclase), where the symmetry axes, the polarization of the fast S wave and the maximum Vp and dVs are parallel to the slab dip and subduction direction. For stagnating slab models this translates into negative and positive radial anisotropy in the upper transition zone and lower mantle back-arc, respectively, minimum delay times for vertically travelling shear waves and large shear wave splitting for waves propagating horizontally in the lower mantle. These results may help in reconciling the seismic anisotropy patterns observed in some subduction zones with subduction-induced deformation, such as those measured in the mid mantle between the Australian plate and the New Hebrides-Tonga-Kermadec trenches that I interpret as related to stagnating

  6. Mantle transition zone structure beneath the Changbai volcano: Insight into deep slab dehydration and hot upwelling near the 410 km discontinuity

    NASA Astrophysics Data System (ADS)

    Tian, You; Zhu, Hongxiang; Zhao, Dapeng; Liu, Cai; Feng, Xuan; Liu, Ting; Ma, Jincheng

    2016-08-01

    We study the detailed mantle transition zone structure beneath the active Changbai intraplate volcano in Northeast China by using a receiver-function method. A total of 3005 teleseismic receiver functions recorded by 70 broadband stations are obtained by using a common-conversion-point stacking method. For conducting the time-to-depth conversion, we use a three-dimensional velocity model of the study region so as to take into account the influence of structural heterogeneities. Our results reveal significant depth variations of the 410, 520, and 660 km discontinuities. A broad depression of the 410 km discontinuity and a low-velocity anomaly are revealed beneath the Changbai volcano, which may reflect a large-scale hot mantle upwelling around the 410 km discontinuity with a positive Clapeyron slope. The 520 km discontinuity is identified clearly, and its uplift occurs above the stagnant Pacific slab. We also find a prominent depression of the 660 km discontinuity, which is elongated along the trend of deep earthquake clusters in a range of 39°N-44°N latitude, and the depression area has a lateral extent of about 400 km. Because the 520 and 660 km discontinuities correspond to positive and negative Clapeyron slopes, respectively, we think that the 520 uplift and the 660 depression are caused by the cold subducting Pacific slab. A part of the Pacific slab may have penetrated into the lower mantle and so caused the large-scale 660 depression in front of the deep earthquake clusters. Our results also reveal a part of the upper boundary of the subducting Pacific slab in the mantle transition zone.

  7. Grain size evolution in the mantle and its effect on geodynamics, seismic velocities and attenuation

    NASA Astrophysics Data System (ADS)

    Dannberg, Juliane; Eilon, Zach; Gassmoeller, Rene; Moulik, Pritwiraj; Myhill, Robert; Faul, Ulrich; Asimow, Paul

    2015-04-01

    viscosities than their cores. Dynamic recrystallisation in subducting slabs results in lower seismic velocities and Q than would be predicted from purely thermal models. A change in physical parameters such as activation volume is required across the 660 km discontinuity to match the higher Q observed seismically in the lower mantle. The very slow grain growth in the lower mantle predicted by high pressure experiments produces unrealistically large travel time delays (>20 s) and t* values (>4 s) in our synthetic calculations with our current constitutive relationships for deriving Vs and Q. Benchmarking our dynamic models against seismic observations will involve further adjustments to the grain size evolution in the lower mantle as well as the tuning of these constitutive relationships.

  8. Seismic Constraints on the Japan Subduction Zone from Waveform Inversions of SS precursors

    NASA Astrophysics Data System (ADS)

    Dokht, R.; Gu, Y. J.; Sacchi, M. D.

    2014-12-01

    Arrival times of long-period secondary mantle reflections such as SS and PP precursors have made significant contributions to the understanding of the mantle structure and slab dynamics beneath the Pacific Northwest. Due to strong sensitivities to discontinuity depths, the timing information is often correlated with P/S velocity models from high-resolution seismic tomography while stacked reflection amplitudes provide a measure of impedance contrast. A potential pitfall in the interpretations of SS-precursor measurements is velocity-discontinuity depth ambiguity, as the timing of secondary reflections is mainly 'corrected' based on existing smoothed velocity estimates. In this study we quantitatively investigate the amplitude information of a dense SS precursor data set sampling the northwestern Pacific region. We model the full waveforms of SS precursors using the Genetic Algorithm (GA), an effective nonlinear inversion technique, and properly account for the tradeoff between shear wave velocity and discontinuity depth perturbation. The inverted shear velocities clearly show a consistent high-velocity, dipping structure along the Wadati-Benioff zone, likely in connection with the descending Japan slab. The slab appears to stagnate and horizontally deflect within the upper mantle transition zone beneath northeastern China. The integrity of the deflected slab appears to be compromised beneath the Changbai hotspot where a low velocity anomaly interrupts the flat lying high velocity structure and extends upward to, at least, mid MTZ depths. This anomaly does not appear to reach the Changbai hotspot, though its connection with observed low velocities in the lithosphere and asthenosphere may not be ruled out. Our nonlinear waveform inversion results also show a 600-km wide low velocity zone (up to -4% relative to the Preliminary Reference Earth Model (PREM)) atop the 660-km discontinuity on the oceanic side of the subducting Japan slab. The cause of this anomaly remains

  9. New high-order, semi-implicit Hybridized Discontinuous Galerkin - Spectral Element Method (HDG-SEM) for simulation of complex wave propagation involving coupling between seismic, hydro-acoustic and infrasonic waves: numerical analysis and case studies.

    NASA Astrophysics Data System (ADS)

    Terrana, S.; Vilotte, J. P.; Guillot, L.

    2015-12-01

    New seismological monitoring networks combine broadband seismic receivers, hydrophones and micro-barometers antenna, providing complementary observation of source-radiated waves. Exploiting these observations requires accurate and multi-media - elastic, hydro-acoustic, infrasound - wave simulation methods, in order to improve our physical understanding of energy exchanges at material interfaces.We present here a new development of a high-order Hybridized Discontinuous Galerkin (HDG) method, for the simulation of coupled seismic and acoustic wave propagation, within a unified framework ([1],[2]) allowing for continuous and discontinuous Spectral Element Methods (SEM) to be used in the same simulation, with conforming and non-conforming meshes. The HDG-SEM approximation leads to differential - algebraic equations, which can be solved implicitly using energy-preserving time-schemes.The proposed HDG-SEM is computationally attractive, when compared with classical Discontinuous Galerkin methods, involving only the approximation of the single-valued traces of the velocity field along the element interfaces as globally coupled unknowns. The formulation is based on a variational approximation of the physical fluxes, which are shown to be the explicit solution of an exact Riemann problem at each element boundaries. This leads to a highly parallel and efficient unstructured and high-order accurate method, which can be space-and-time adaptive.A numerical study of the accuracy and convergence of the HDG-SEM is performed through a number of case studies involving elastic-acoustic (infrasound) coupling with geometries of increasing complexity. Finally, the performance of the method is illustrated through realistic case studies involving ground wave propagation associated to topography effects.In conclusion, we outline some on-going extensions of the method.References:[1] Cockburn, B., Gopalakrishnan, J., Lazarov, R., Unified hybridization of discontinuous Galerkin, mixed and

  10. Plume's buoyancy and heat fluxes from the deep mantle estimated by an instantaneous mantle flow simulation based on the S40RTS global seismic tomography model

    NASA Astrophysics Data System (ADS)

    Yoshida, Masaki

    2012-11-01

    It is still an open question as to how much heat is transported from the deep mantle to the upper mantle by mantle upwelling plumes, which would impose a strong constraint on models of the thermal evolution of the earth. Here I perform numerical computations of instantaneous mantle flow based on a recent highly resolved global seismic tomography model (S40RTS), apply new simple fluid dynamics theories to the plume's radius and velocity, considering a Poiseuille flow assumption and a power-law relationship between the boundary layer thickness and Rayleigh number, and estimate the plume's buoyancy and heat fluxes from the deep lower mantle under varying plume viscosity. The results show that for some major mantle upwelling plumes with localized strong ascent velocity under the South Pacific and Africa, the buoyancy fluxes of each plume beneath the ringwoodite to perovskite + magnesiowüstite ("660-km") phase decomposition boundary are comparable to those inferred from observed hotspot swell volumes on the earth, i.e., on the order of 1 Mg s-1, when the plume viscosity is 1019-1020 Pa s. This result, together with previous numerical simulations of mantle convection and the gentle Clausius-Clapeyron slope for the 660-km phase decomposition derived from recent high-pressure measurements under dehydrated/hydrated conditions in the mantle transition zone, implies that mantle upwelling plumes in the lower mantle penetrate the 660-km phase decomposition boundary without significant loss in thermal buoyancy because of the weak thermal barrier at the 660-km boundary. The total plume heat flux under the South Pacific is estimated to be about 1 TW beneath the 660-km boundary, which is significantly smaller than the core-mantle boundary heat flux. Previously published scaling laws for the plume's radius and velocity based on a plume spacing theory, which explains well plume dynamics in three-dimensional time-dependent mantle convection, suggest that these plume fluxes depend

  11. Modelling the density contrast and depth of the Moho discontinuity by seismic and gravimetric-isostatic methods with an application to Africa

    NASA Astrophysics Data System (ADS)

    Bagherbandi, Mohammad; Sjöberg, Lars E.

    2012-06-01

    The crustal thickness (Moho depth) is of interest in several geosciences applications, such as geography, geophysics and geodesy. Usually the crustal depth and density variations are estimated by seismic survey data. As such data collection is very time-consuming and expensive an attractive option could be to use a gravimetric/isostatic model. In this case, realistic estimates for the crustal density and Moho density contrast (MDC) are important. In this study, we first use the seismic crustal thickness of CRUST2.0 model as a known parameter in combination with gravimetric data in estimating the crust-mantle density contrast by the isostatic model of Vening Meinesz-Moritz. We present different models to estimate the MDC and its impact on the modelling of the gravimetric-isostatic Moho depth. The theory is applied to estimate the Moho depth of the African continental crust by using different models for the MDC: (a) constant value (0.6 g/cm3), (b) Pratt-Hayford's model, (c) CRUST2.0 as input to three gravimetric/isostatic models based on Vening Meinesz-Moritz theory. The isostatic models agree by 5.8-7.1 km in the rms with the regional seismic model at a resolution of 2° × 2°, and the smallest rms difference at a resolution of 1° × 1° is of 7.2 km. For comparison, the rms differences of CRUST2.0 and the regional seismic model are 8.8 and 9.1 km at the resolutions of 2° (interpolated) and 1°, respectively. The result suggests that the gravimetric/isostatic Moho model can be used in densification of the CRUST2.0 Moho geometry, and to improve it in areas with poor data.

  12. Global overview of subduction seismicity

    NASA Astrophysics Data System (ADS)

    Funiciello, F.; Presti, D.; Heuret, A.; Piromallo, C.

    2013-12-01

    In the framework of the EURYI Project ';Convergent margins and seismogenesis: defining the risk of great earthquakes by using statistical data and modelling', we propose the first global overview of subduction seismicity. Previous studies have been focused on interplate seismicity, intraslab seismicity, upper plate deformation, or relation between interplate and intraslab seismicity, but the three components of subduction seismicity have been never approached in an systematic and exhaustive study. To allow such a study, nodal planes and seismic moments of worldwide subduction-related earthquakes heve been extracted by EHB hypocenter and CMT Harvard catalogues for the period 1976 - 2007. Data were collected for centroid depths between sea level and 700 km and for magnitude Mw 5.5. For each subduction zone, a set of trench-normal transects were constructed choosing a 120km width of the cross-section on each side of a vertical plane and a spacing of 1 degree along the trench. For each of the 505 resulting transects, the whole subduction seismogenic zone was mapped as focal mechanisms projected on to a vertical plane after their faulting type classification according to the Aki-Richards convention. Transect by transect, fist the seismicity that can be considered not related to the subduction process under investigation was removed, then was selected the upper plate seismicity (i.e. earthquakes generated within the upper plate as a result of the subduction process). After deletion from the so obtained event subset of the interplate seismicity as identified in the framework of this project by Heuret et al. (2011), we can be reasonably confident that the remaining seismicity can be related to the subducting plate. Among these earthquakes we then selected the shallow (0-70 km), intermediate (70-300 km) and deep (300-660 km) depth seismicity. Following Heuret et al. (2011), the 505 transects were merged into 62 larger segments that were ideally homogeneous in terms of their

  13. Surface wave attenuation in the shallow subsurface from multichannel-multishot seismic data: a new approach for detecting fractures and lithological discontinuities

    NASA Astrophysics Data System (ADS)

    Ikeda, Tatsunori; Tsuji, Takeshi

    2016-07-01

    Surface wave analysis generally neglects amplitude information, instead using phase information to delineate near-surface S-wave velocity structures. To effectively characterize subsurface heterogeneities from amplitude information, we propose a method of estimating lateral variation of attenuation coefficients of surface waves from multichannel-multishot (multifold) seismic data. We extend the concept of the common midpoint cross-correlation method, used for phase velocity estimation, to the analysis of attenuation coefficients. Our numerical experiments demonstrated that when used together, attenuation coefficients and phase velocities could characterize a lithological boundary as well as fracture zone. We applied the proposed method to multifold seismic reflection data acquired in Shikoku Island, Japan. We clearly observed abrupt changes in lateral variation of estimated attenuation coefficients around fault locations associated with a lithological boundary and with well-developed fractures, whereas phase velocity results could detect only the lithological boundary. Our study demonstrated that simultaneous interpretation of attenuation coefficients and phase velocities has the potential to distinguish localized fractures from lithological boundaries.

  14. What drives the Tibetan crust to the South East Asia? Role of upper mantle density discontinuities as inferred from the continental geoid anomalies

    NASA Astrophysics Data System (ADS)

    Rajesh, S.

    2012-04-01

    The Himalaya-Tibet orogen formed as a result of the northward convergence of India into the Asia over the past 55 Ma had caused the north south crustal shortening and Cenozoic upliftment of the Tibetan plateau, which significantly affected the tectonic and climatic framework of the Asia. Geodetic measurements have also shown eastward crustal extrusion of Tibet, especially along major east-southeast strike slip faults at a slip rate of 15-20 mm a-1 and around 40 mm a-1. Such continental scale deformations have been modeled as block rotation by fault boundary stresses developed due to the India-Eurasia collision. However, the Thin Sheet model explained the crustal deformation mechanism by considering varying gravitational potential energy arise out of varying crustal thickness of the viscous lithosphere. The Channel Flow model, which also suggests extrusion is a boundary fault guided flow along the shallow crustal brittle-ductile regime. Although many models have proposed, but no consensus in these models to explain the dynamics of measured surface geodetic deformation of the Tibetan plateau. But what remains conspicuous is the origin of driving forces that cause the observed Tibetan crustal flow towards the South East Asia. Is the crustal flow originated only because of the differential stresses that developed in the shallow crustal brittle-ductile regime? Or should the stress transfer to the shallow crustal layers as a result of gravitational potential energy gradient driven upper mantle flow also to be accounted. In this work, I examine the role of latter in the light of depth distribution of continental geoid anomalies beneath the Himalaya-Tibet across major upper mantle density discontinuities. These discontinuity surfaces in the upper mantle are susceptible to hold the plastic deformation that may occur as a result of the density gradient driven flow. The distribution of geoid anomalies across these density discontinuities at 220, 410 and 660 km depth in the

  15. Synthetic seismic signature of thermal mantle plumes

    NASA Astrophysics Data System (ADS)

    Goes, S.; Hansen, U.

    2003-04-01

    With increasing resolution in global tomographic models and targeted regional experiments the first seismic images of mantle plumes have emerged. In order to obtain a better idea of the expected seismic signature of a purely thermal mantle plume we perform a set of three-dimensional numerical experiments with parameters relevant to the Earth's mantle. The thermal plumes thus obtained are converted into P- and S-velocity structure taking into account the effect of temperature, pressure, an average mantle composition including phase transitions and anelasticity on the seismic velocities. Excess plume temperatures were constrained to be about 300oC below the lithosphere to be consistent with surface observations. Models with depth-dependent expansivity and conductivity and temperature and depth-dependent viscosity predict plumes that are 500-800 km wide in the lower mantle. An abrupt lowering of the viscosity above 660 km of at least a factor 30 can narrow upper mantle plumes to 100-200 km. Due to the varying sensitivity of seismic velocities to temperature with depth and mineralogy, variations in amplitude and width of the seismic plume do not coincide with the variations in the thermal structure of the plume. Anomalies of 2-4% are expected in the uppermost mantle. Reduced sensitivity in the transition zone as well as complexities due to phase boundary topography may hamper imaging continuous whole mantle plumes. Lower mantle plumes that are consistent with temperature constrasts of 100-300oC below the lithosphere will have seismic amplitudes of only 0.5-1%. Seismic anelasticity structure follows the thermal structure more closely and yields plume anomalies of 100-200% in dln(1/QS).

  16. Cultural Discontinuities and Schooling.

    ERIC Educational Resources Information Center

    Ogbu, John U.

    1982-01-01

    Attempts to define the cultural discontinuity (between schools and students) hypothesis by distinguishing between universal, primary, and secondary discontinuities. Suggests that each of these is associated with a distinct type of school problem, and that secondary cultural discontinuities commonly affect minority students in the United States.…

  17. Mantle discontinuities under southern Africa from precursors to P′ P′df

    USGS Publications Warehouse

    Xu, Fei; Vidale, John E.; Earle, Paul; Benz, Harley M.

    1998-01-01

    We investigate the reflection properties of upper-mantle discontinuities beneath southern Africa using precursors to the df branch of PKPPKP (P′ P′). The P′ P′df branch is weaker than the ab and bc branches, but it does not have the complication of a caustic and appears across a wider distance range. Stacks from hundreds of short-period seismograms recorded in California from the March 9, 1994 Tonga earthquake (Mw = 7.6) show an ∼5% reflection (at 3.5 s dominate period) from 660-km depth indicating a sharp “660” under southern Africa. A 3.5 s period reflection from 410-km depth is also visible in these stacks, but only ∼2% the strength of P′ P′df. This result contrasts with the observation of the “410” and the “660” reflecting comparable amounts of high-frequency energy under the Indian Ocean [Benz and Vidale, 1993a], indicating either a diffuse “410” boundary under southern Africa or global variations in the impedance change across the “410”. A 1.5 s period reflection may indicate the existence of fine-scale heterogeneity near 320-km depth. Reflectivity synthetic seismograms also show that a previously claimed reflection from 785-km depth has the more likely explanation as PcPPKP.

  18. Mantle discontinuities under southern Africa from precursors to P‧ P‧df

    NASA Astrophysics Data System (ADS)

    Xu, Fei; Vidale, John E.; Earle, Paul S.; Benz, Harley M.

    We investigate the reflection properties of upper-mantle discontinuities beneath southern Africa using precursors to the df branch of PKPPKP (P‧ P‧). The P‧ P‧ df branch is weaker than the ab and bc branches, but it does not have the complication of a caustic and appears across a wider distance range. Stacks from hundreds of short-period seismograms recorded in California from the March 9, 1994 Tonga earthquake (Mw = 7.6) show an ∼5% reflection (at 3.5 s dominate period) from 660-km depth indicating a sharp “660” under southern Africa. A 3.5 s period reflection from 410-km depth is also visible in these stacks, but only ∼2% the strength of P‧ P‧df. This result contrasts with the observation of the “410” and the “660” reflecting comparable amounts of high-frequency energy under the Indian Ocean [Benz and Vidale, 1993a], indicating either a diffuse “410” boundary under southern Africa or global variations in the impedance change across the “410”. A 1.5 s period reflection may indicate the existence of fine-scale heterogeneity near 320-km depth. Reflectivity synthetic seismograms also show that a previously claimed reflection from 785-km depth has the more likely explanation as PcPPKP.

  19. Origins of the 520-km discontinuity

    NASA Astrophysics Data System (ADS)

    Vinnik, Lev

    2016-04-01

    The 520-km discontinuity is often explained by the phase transition from wadsleyite to ringwoodite, although the theoretical impedance of this transition is so small that the related converted and reflected seismic phases could hardly be seen in the seismograms. At the same time there are numerous reports on observations of a large discontinuity at this depth, especially in the data on SS precursors and P-wave wide-angle reflections. Revenaugh and Jordan (1991) argued that this discontinuity is related to the garnet/post-garnet transformation. Gu et al. (1998) preferred very deep continental roots extending into the transition zone. Deuss and Woodhouse proposed splitting of the 520-km discontinuity into two discontinuities, whilst Bock (1994) denied evidence of the 520-km discontinuity in the SS precursors. Our approach to this problem is based on the analysis of S and P receiver functions. Most of our data are related to hot-spots in and around the Atlantic where the appropriate converted phases are often comparable in amplitude with P410s and S410p. Both S and P receiver functions provide strong evidence of a low S velocity in a depth range from 450 km to 510 km at some locations. The 520-km discontinuity appears to be the base of this low-velocity layer. Our observations of the low S velocity in the upper transition zone are very consistent with the indications of a drop in the solidus temperature of carbonated peridotite in the same pressure range (Keshav et al. 2011), and this phenomenon provides a viable alternative to the other explanations of the 520-km discontinuity.

  20. Variations of Hales Discontinuity beneath South India

    NASA Astrophysics Data System (ADS)

    Goyal, Ayush; Kosre, Goukaran Kumar; Borah, Kajaljyoti

    2016-04-01

    Thermodynamic studies show the spinel-garnet transition in fertile and hot mantle should be relatively narrow and should show up in the seismological studies as a discontinuity. The evidence for a shallow lithospheric mantle discontinuity was first proposed by Hales (1969) based on seismological travel time measurement from the Early Rise experiment in the Central United States, where a ~4% increase in the S-wave velocity at a depth of 75 km was observed. The recent studies show, in cratonic blocks with colder geotherms, that it appears at greater depths and over broader intervals, that is, from the Moho to 150 km depth. Different studies interpreted that Hales discontinuity may be due to seismic anisotropy or pervasive partial melts or cation ordering in mantle olivine. In the present study an attempt is made to model the Hales discontinuity in the South Indian shield, by jointly inverting group velocity dispersion and receiver functions, calculated from teleseismic earthquakes recorded at 20 broadband seismograph locations in the study region. South Indian shield is an amalgamation of several crustal blocks, namely, Eastern Dharwar Craton (EDC), Western Dharwar Craton (WDC), Southern Granulite Terrain (SGT) etc. Inversion modeling results show deeper Hales discontinuity (~104-110 km depth) in the south of WDC and SGT, while in the north of Western Dharwar Craton and Eastern Dharwar Craton it varies from ~70-80 km. It is also observed that the Hales Discontinuity is present at greater depth in the western part of Dharwar Craton, compared to the eastern part. Details of the depth, thickness, and the cause of the Hales discontinuity are also investigated. Keywords: Hales Discontinuity, South Indian Shield, Receiver Function, Craton, Inversion modeling.

  1. Complex geometry of the subducted Pacific slab inferred from receiver function

    NASA Astrophysics Data System (ADS)

    Zhang, Ruiqing; Wu, Qingju; Zhang, Guangcheng

    2014-05-01

    In recent years, slab tear has received considerable attention and been reported in many arc-arc junctures in Pacific plate subdution zones. From 2009 to 2011, we deployed two portable experiments equipped with CMG-3ESPC seismometers and the recorders of REFTEK-130B in NE China. The two linear seismic arrays were designed nearly parallel, and each of them containing about 60 seismic stations extended about 1200 km from west to east spanning all surface geological terrains of NE China. The south one was firstly set up and continually operated over two year, while the north deployment worked only about one year. By using the teleseismic data collected by these two arrays, we calculate the P receiver functions to map topographic variation of the upper mantle discontinuities. Our sampled region is located where the juncture between the subducting Kuril and Japan slabs reaches the 660-km discontinuity. Distinct variation of the 660-km discontinuity is mapped beneath the regions. A deeper-than-normal 660 km discontinuity is observed locally in the southeastern part of our sampled region. The depression of the 660 km discontinuity may be resulted from an oceanic lithospheric slab deflected in the mantle transition zone, in good agreement with the result of earlier tomographic and other seismic studies in this region. The northeastern portion of our sampled region, however, does not show clearly the deflection of the slab. The variation of the tomography of the 660-km discontinuity in our sampled regions may indicate a complex geometry of the subducted Pacific slab.

  2. Seismically imaging the Afar plume

    NASA Astrophysics Data System (ADS)

    Hammond, J. O.; Kendall, J. M.; Bastow, I. D.; Stuart, G. W.; Keir, D.; Ayele, A.; Ogubazghi, G.; Ebinger, C. J.; Belachew, M.

    2011-12-01

    Plume related flood basalt volcanism in Ethiopia has long been cited to have instigated continental breakup in northeast Africa. However, to date seismic images of the mantle beneath the region have not produced conclusive evidence of a plume-like structure. As a result the nature and even existence of a plume in the region and its role in rift initiation and continental rupture are debated. Previous seismic studies using regional deployments of sensors in East-Africa show that low seismic velocities underlie northeast Africa, but their resolution is limited to the top 200-300km of the Earth. Thus, the connection between the low velocities in the uppermost mantle and those imaged in global studies in the lower mantle is unclear. We have combined new data from Afar, Ethiopia with 6 other regional experiments and global network stations across Ethiopia, Eritrea, Djibouti and Yemen, to produce high-resolution models of upper mantle P- and S- wave velocities to the base of the transition zone. Relative travel time tomographic inversions show that the top 100km is dominated by focussed low velocity zones, likely associated with melt in the lithosphere/uppermost asthenosphere. Below these depths a broad SW-NE oriented sheet like upwelling extends down to the top of the transition zone. Within the transition zone two focussed sharp-sided low velocity regions exist: one beneath the Western Ethiopian plateau outside the rift valley, and the other beneath the Afar depression. The nature of the transition zone anomalies suggests that small upwellings may rise from a broader low velocity plume-like feature in the lower mantle. This interpretation is supported by numerical and analogue experiments that suggest the 660km phase change and viscosity jump may impede flow from the lower to upper mantle creating a thermal boundary layer at the base of the transition zone. This allows smaller, secondary upwellings to initiate and rise to the surface. Our images of secondary upwellings

  3. Seismic evidence for water deep in Earth's upper mantle.

    PubMed

    van der Meijde, Mark; Marone, Federica; Giardini, Domenico; van der Lee, Suzan

    2003-06-01

    Water in the deep upper mantle can influence the properties of seismic discontinuities in the mantle transition zone. Observations of converted seismic waves provide evidence of a 20- to 35-kilometer-thick discontinuity near a depth of 410 kilometers, most likely explained by as much as 700 parts per million of water by weight.

  4. Mapping the Hawaiian plume conduit with converted seismic waves

    PubMed

    Li; Kind; Priestley; Sobolev; Tilmann; Yuan; Weber

    2000-06-22

    The volcanic edifice of the Hawaiian islands and seamounts, as well as the surrounding area of shallow sea floor known as the Hawaiian swell, are believed to result from the passage of the oceanic lithosphere over a mantle hotspot. Although geochemical and gravity observations indicate the existence of a mantle thermal plume beneath Hawaii, no direct seismic evidence for such a plume in the upper mantle has yet been found. Here we present an analysis of compressional-to-shear (P-to-S) converted seismic phases, recorded on seismograph stations on the Hawaiian islands, that indicate a zone of very low shear-wave velocity (< 4 km s(-1)) starting at 130-140 km depth beneath the central part of the island of Hawaii and extending deeper into the upper mantle. We also find that the upper-mantle transition zone (410-660 km depth) appears to be thinned by up to 40-50 km to the south-southwest of the island of Hawaii. We interpret these observations as localized effects of the Hawaiian plume conduit in the asthenosphere and mantle transition zone with excess temperature of approximately 300 degrees C. Large variations in the transition-zone thickness suggest a lower-mantle origin of the Hawaiian plume similar to the Iceland plume, but our results indicate a 100 degrees C higher temperature for the Hawaiian plume.

  5. Modern Regression Discontinuity Analysis

    ERIC Educational Resources Information Center

    Bloom, Howard S.

    2012-01-01

    This article provides a detailed discussion of the theory and practice of modern regression discontinuity (RD) analysis for estimating the effects of interventions or treatments. Part 1 briefly chronicles the history of RD analysis and summarizes its past applications. Part 2 explains how in theory an RD analysis can identify an average effect of…

  6. Wave field features of shallow vertical discontinuity and their application in non-destructive detection

    USGS Publications Warehouse

    Liu, J.; Xia, J.; Luo, Y.; Chen, C.; Li, X.; Huang, Y.

    2007-01-01

    The geotechnical integrity of critical infrastructure can be seriously compromised by the presence of fractures or crevices. Non-destructive techniques to accurately detect fractures in critical infrastructure such as dams and highways could be of significant benefit to the geotechnical industry. This paper investigates the application of shallow seismic and georadar methods to the detection of a vertical discontinuity using numerical simulations. The objective is to address the kinematical analysis of a vertical discontinuity, determine the resulting wave field characteristics, and provide the basis for determining the existence of vertical discontinuities based on the recorded signals. Simulation results demonstrate that: (1) A reflection from a vertical discontinuity produces a hyperbolic feature on a seismic or georadar profile; (2) In order for a reflection from a vertical discontinuity to be produced, a reflecting horizon below the discontinuity must exist, the offset between source and receiver (x0) must be non-zero, on the same side of the vertical discontinuity; (3) The range of distances from the vertical discontinuity where a reflection event is observed is proportional to its length and to x0; (4) Should the vertical crevice (or fracture) pass through a reflecting horizon, dual hyperbolic features can be observed on the records, and this can be used as a determining factor that the vertical crevice passes through the interface; and (5) diffractions from the edges of the discontinuity can be recorded with relatively smaller amplitude than reflections and their ranges are not constrained by the length of discontinuity. If the length of discontinuity is short enough, diffractions are the dominant feature. Real-world examples show that the shallow seismic reflection method and the georadar method are capable of recording the hyperbolic feature, which can be interpreted as vertical discontinuity. Thus, these methods show some promise as effective non

  7. Seismological detection of "730-km" discontinuity beneath Japan subduction zone

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Park, J. J.; Karato, S. I.

    2015-12-01

    Because the mantle transition zone likely contains a large amount of water (Karato, 2011; Pearson et al., 2014), vertical material transport across the transition would cause partial melting that may produce seismic signals above and/or below the transition zone. Schmandt et al. (2014) observed a seismic low-velocity zone (LVZ) at the top of the lower mantle (~730 km) beneath the southwestern US, arguing for dehydration melting due to downward flow across the 670-km discontinuity (670) from the transition zone. These authors further proposed a correlation between seismic velocity reductions and the direction of water transport, in which LVZ at ~730 km indicates materials moving downward from the transition zone, while the lack of LVZ at this depth would suggest an upward flow of mantle materials. Other regions also need to be investigated to confirm the correlation between this seismic feature and mantle water transport. We test their model by detecting "730-km" discontinuity beneath the Japan subduction zone using frequency-dependent receiver functions. In addition, water transport above the 410-km discontinuity (410) also plays an important role in global water circulation (Bercovici and Karato, 2003). Seismological studies (e.g. Courtier and Revenaugh, 2007; Schaeffer and Bostock, 2010) have observed LVZs above the 410, which might be caused by dehydration melting due to the upwelling of hydrated materials across the 410-km discontinuity from the transition zone. In this study, we also detect potential LVZs above 410 to establish a correlation between seismic velocity drop and flow direction. Around the Japan subduction zone, our preliminary results show evidence of low velocity zones below 670 in regions where stagnant slab is present for a substantial amount of time but not in other regions suggesting a variety of vertical mass transport in this region. Key words: transition zone, water transport, subduction zone, melting, receiver functions

  8. Britannia rules the seismic waves

    SciTech Connect

    Green, P.

    1984-04-01

    When a longwall mining operation penetrates an unforeseen discontinuity in the coal seam, all hell breaks loose. Productivity plummets while the shearer cuts through rock, and the high proportion of reject material overwhelms the preparation plant. And, if the discontinuity is large enough, the face may have to be abandoned. To avert such catastrophies, a technique developed in Britain for mapping the presence of discontinuities has been applied in the Meigs No. 1 mine of the Southern Ohio Coal Co. in Athens, Ohio. The technology, called in-seam seismic surveying, is similar to seismic exploration in the oil and gas industry. The principle of the in-seam survey is simple: A shock wave is sent through the coal seam. If there is a sandstone channel or a displacement fault in the seam, the sound waves will be reflected back and can be picked up by geophones. Conversely, geophones installed on the opposite side of a channel or fault will not pick up the sound waves (see box). Seismic surveys have been made for four years by Britain's National Coal Board (NCB), and were developed because practically all its production is from longwall mining, and knowing what lies ahead is critical. And with about 500 ft between longwall entries there's a large amount of unpenetrated seam to contain hidden discontinuities. Hence the interest in in-seam seismic surveys.

  9. Mingus Discontinuous Multiphysics

    2014-05-13

    Mingus provides hybrid coupled local/non-local mechanics analysis capabilities that extend several traditional methods to applications with inherent discontinuities. Its primary features include adaptations of solid mechanics, fluid dynamics and digital image correlation that naturally accommodate dijointed data or irregular solution fields by assimilating a variety of discretizations (such as control volume finite elements, peridynamics and meshless control point clouds). The goal of this software is to provide an analysis framework form multiphysics engineering problems withmore » an integrated image correlation capability that can be used for experimental validation and model« less

  10. Discontinuous ephemeral streams

    NASA Astrophysics Data System (ADS)

    Bull, William B.

    1997-07-01

    Many ephemeral streams in western North America flowed over smooth valley floors before transformation from shallow discontinuous channels into deep arroyos. These inherently unstable streams of semiarid regions are sensitive to short-term climatic changes, and to human impacts, because hillslopes supply abundant sediment to infrequent large streamflow events. Discontinuous ephemeral streams appear to be constantly changing as they alternate between two primary modes of operation; either aggradation or degradation may become dominant. Attainment of equilibrium conditions is brief. Disequilibrium is promoted by channel entrenchment that causes the fall of local base level, and by deposition of channel fans that causes the rise of local base level. These opposing base-level processes in adjacent reaches are maintained by self-enhancing feedback mechanisms. The threshold between erosion and deposition is crossed when aggradational or degradational reaches shift upstream or downstream. Extension of entrenched reaches into channel fans tends to create continuous arroyos. Upvalley migration of fan apexes tends to create depositional valley floors with few stream channels. Less than 100 years is required for arroyo cutting, but more than 500 years is required for complete aggradation of entrenched stream channels and valley floors. Discontinuous ephemeral streams have a repetitive sequence of streamflow characteristics that is as distinctive as sequences of meander bends or braided gravel bars in perennial rivers. The sequence changes from degradation to aggradation — headcuts concentrate sheetflow, a single trunk channel conveys flow to the apex of a channel fan, braided distributary channels end in an area of diverging sheetflow, and converging sheetflow drains to headcuts. The sequence is repeated at intervals ranging from 15 m for small streams to more than 10 km for large streams. Lithologic controls on the response of discontinuous ephemeral streams include: (1

  11. Mingus Discontinuous Multiphysics

    SciTech Connect

    Pat Notz, Dan Turner

    2014-05-13

    Mingus provides hybrid coupled local/non-local mechanics analysis capabilities that extend several traditional methods to applications with inherent discontinuities. Its primary features include adaptations of solid mechanics, fluid dynamics and digital image correlation that naturally accommodate dijointed data or irregular solution fields by assimilating a variety of discretizations (such as control volume finite elements, peridynamics and meshless control point clouds). The goal of this software is to provide an analysis framework form multiphysics engineering problems with an integrated image correlation capability that can be used for experimental validation and model

  12. Kinematics of Strong Discontinuities

    NASA Technical Reports Server (NTRS)

    Peterson, K.; Nguyen, G.; Sulsky, D.

    2006-01-01

    Synthetic Aperture Radar (SAR) provides a detailed view of the Arctic ice cover. When processed with the RADARSAT Geophysical Processor System (RGPS), it provides estimates of sea ice motion and deformation over large regions of the Arctic for extended periods of time. The deformation is dominated by the appearance of linear kinematic features that have been associated with the presence of leads. The RGPS deformation products are based on the assumption that the displacement and velocity are smooth functions of the spatial coordinates. However, if the dominant deformation of multiyear ice results from the opening, closing and shearing of leads, then the displacement and velocity can be discontinuous. This presentation discusses the kinematics associated with strong discontinuities that describe possible jumps in displacement or velocity. Ice motion from SAR data are analyzed using this framework. It is assumed that RGPS cells deform due to the presence of a lead. The lead orientation is calculated to optimally account for the observed deformation. It is shown that almost all observed deformation can be represented by lead opening and shearing. The procedure used to reprocess motion data to account for leads will be described and applied to regions of the Beaufort Sea. The procedure not only provides a new view of ice deformation, it can be used to obtain information about the presence of leads for initialization and/or validation of numerical simulations.

  13. LAB and other lithospheric discontinuities below Cratons

    NASA Astrophysics Data System (ADS)

    Sodoudi, Forough

    2013-04-01

    Cratons are extremely stable continental areas of the Earth's crust, which have been formed and remained largely unchanged since Precambrian. However, their formation and how they survived destruction over billions of years remains a subject of debate. Seismic properties of the cratonic lithosphere reflect its composition and physical state and obtain basic constraints on processes of the formation and evolution of continents. Insight on these issues may be gained by determining the depth and the nature of the Lithosphere-Asthenosphere Boundary (LAB), which is a necessary element of the plate tectonic theory. However, It has proved quite "elusive" beneath the oldest continental areas. What is missing to date is a consensus on the feature that would correspond to the LAB and whether such a feature exists everywhere beneath cratons. The relatively recently developed S receiver function technique employing S-to-P conversions appears promising for detecting the LAB with a sufficiently high resolution and density. A growing number of regional observations obtained from S receiver function studies has detected discontinuities characterized by a significant negative velocity contrast in the upper mantle. However, challenges still remain in detecting the S-to-P conversions from the LAB beneath the Precambrian cratons. Some recent SRF studies observed a deep (> 160 km) negative velocity contrast beneath cratons and interpreted it as the LAB. For example, a deep LAB at about 250 km was reported beneath the Kalahari craton by different authors. Similar results were also obtained beneath some parts of the Canadian shield, East European Craton, Australia, the Arabian Shield and Tanzania craton. In contrast, other SRF studies found no evidence for negative discontinuities at these depths in the North American craton, in Kalahari craton or in Australia. Instead they revealed a very sharp negative velocity gradient at much shallower depth (60-150 km), leading some authors to infer

  14. Moho depth and two discontinuities variation in Taiwan from radial teleseismic receiver functions

    NASA Astrophysics Data System (ADS)

    Ton, C.; Chen, C. H.

    2005-12-01

    In this study, we use data recorded by the stations of Broadband Array in Taiwan for Seismology (BATS) to investigate the depths of major discontinuities of the crust in Taiwan. From the differential times between direct P wave and converted Ps phase and several multiple phases on radial teleseismic receiver function, we determine the Moho depth and the Vp/Vs ratios at these stations. More importantly, we develop a method which can let us use more seismic phases to examine other discontinuities in the crust. Using the arrival times of some specific phases on radial teleseismic receiver function, except for Moho discontinuity, we found that there are two discontinuities ( denoted by discontinuity 1 and discontinuity 2 ) existing in the crust that beneath some of stations. The Moho depth in Taiwan varies from 22 to 39 km and Vp/Vs ratios varies from 1.64~1.87. The deepest Moho depth in Taiwan locates at the Central Mountain Range (CMR) and consistent with the result obtained from gravity survey. The discontinuity 1 and the discontinuity 2 exist clearly in the CMR, in the southern region and the northeastern region of Taiwan. These two discontinuities both become unapparent in the northern region (volcano region) and in the southeastern region (plate convergent area) of Taiwan. The depth of the discontinuity 1 varies from 4.5 to 11 km and while the depth of the discontinuity 2 varies from 12 to 22 km in our estimation. Based on these results, we imply that the discontinuity 1 and 2 are basement and the Conrad discontinuity respectively.

  15. [Comment on “Seismology in the days of old” by Inge Lehmann] The Lehmann discontinuity

    NASA Astrophysics Data System (ADS)

    Anderson, D. L.; Bolt, B. A.; Morse, S. A.

    Recent reflections by Inge Lehmann on her discovery of the inner core (Eos, January 20, 1987, p. 33; see also Bolt [1987, 1982]) remind us that this outstanding Earth scientist is now in her 100th year. The inner core boundary (ICB) is one of the three great seismic-compositional discontinuities that divide Earth into crust, mantle, core, and inner core. The other two discontinuities are well known by names honoring their discoverers, Andrija Mohorovicic and Beno Gutenberg. In this tradition, it is fitting that the ICB be called the Lehmann Discontinuity in honor of its discoverer.

  16. Spectral methods for discontinuous problems

    NASA Technical Reports Server (NTRS)

    Abarbanel, S.; Gottlieb, D.; Tadmor, E.

    1985-01-01

    Spectral methods yield high-order accuracy even when applied to problems with discontinuities, though not in the sense of pointwise accuracy. Two different procedures are presented which recover pointwise accurate approximations from the spectral calculations.

  17. Regression Discontinuity Designs in Epidemiology

    PubMed Central

    Moscoe, Ellen; Mutevedzi, Portia; Newell, Marie-Louise; Bärnighausen, Till

    2014-01-01

    When patients receive an intervention based on whether they score below or above some threshold value on a continuously measured random variable, the intervention will be randomly assigned for patients close to the threshold. The regression discontinuity design exploits this fact to estimate causal treatment effects. In spite of its recent proliferation in economics, the regression discontinuity design has not been widely adopted in epidemiology. We describe regression discontinuity, its implementation, and the assumptions required for causal inference. We show that regression discontinuity is generalizable to the survival and nonlinear models that are mainstays of epidemiologic analysis. We then present an application of regression discontinuity to the much-debated epidemiologic question of when to start HIV patients on antiretroviral therapy. Using data from a large South African cohort (2007–2011), we estimate the causal effect of early versus deferred treatment eligibility on mortality. Patients whose first CD4 count was just below the 200 cells/μL CD4 count threshold had a 35% lower hazard of death (hazard ratio = 0.65 [95% confidence interval = 0.45–0.94]) than patients presenting with CD4 counts just above the threshold. We close by discussing the strengths and limitations of regression discontinuity designs for epidemiology. PMID:25061922

  18. Observations in variations in the amplitude and depths of the 410 and 520 km discontinuities from PdP and SdS bounce point studies.

    NASA Astrophysics Data System (ADS)

    Darensburg, A.; Ainiwaer, A.; Gurrola, H.

    2015-12-01

    To gain a better understanding of the upper mantle transition zone, we beamform EarthScope Transportable array data of events from the western Pacific ring of fire to produce relatively high frequency (0.75 Hz) PdP functions (underside P reflections from a depth d) of the mantle beneath the central Pacific from the society Islands across the Aleutian trench. Like most PdP studies, we fail to image the 660 km discontinuity so we focus on the 410, and 520. It is believed that the 410 and 520 km discontinuities are the result of exothermic phase changes in the Olivine mineral system at pressure and temperatures consistent with the indicated depths. Because these boundaries are hypothesized to be exothermic, we expect them to be deeper in hot regions and shallow in cool. Modeling of these boundaries by mineral physicists suggest the 410 occurs over a 10 km interval and the 520 over about 30 km. Our observed amplitudes of P410P as a function of frequency compared to waveform modeling indicate that the 410 phase change must occur over less 6 km. Our observations of a strong 520 km discontinuity at 0.75 Hz also suggests that this velocity contrast occurs over less than 10 km rather than the hypothesized 30 km. We found that the average depth to the 410 km discontinuity across our study area to be 420 km to 425km. The 520 km discontinuity appears to be strongest around Hawaii and north of the Aleutian trench. The depths of the P410P and P520P phases appear to be correlated in most areas where they occur together; deepest the north of the Aleutian trench and southwestern Alaska; and shallowest south of the westernmost Aleutian trench. One of the more surprising observations was that the P520P phase appears to be the smallest or not observable in regions with the strongest P410P phase. SdS observations will be added to this study for the AGU meeting.

  19. Martian seismicity

    NASA Technical Reports Server (NTRS)

    Phillips, Roger J.; Grimm, Robert E.

    1991-01-01

    The design and ultimate success of network seismology experiments on Mars depends on the present level of Martian seismicity. Volcanic and tectonic landforms observed from imaging experiments show that Mars must have been a seismically active planet in the past and there is no reason to discount the notion that Mars is seismically active today but at a lower level of activity. Models are explored for present day Mars seismicity. Depending on the sensitivity and geometry of a seismic network and the attenuation and scattering properties of the interior, it appears that a reasonable number of Martian seismic events would be detected over the period of a decade. The thermoelastic cooling mechanism as estimated is surely a lower bound, and a more refined estimate would take into account specifically the regional cooling of Tharsis and lead to a higher frequency of seismic events.

  20. Mixing of discontinuously deforming media

    NASA Astrophysics Data System (ADS)

    Smith, L. D.; Rudman, M.; Lester, D. R.; Metcalfe, G.

    2016-02-01

    Mixing of materials is fundamental to many natural phenomena and engineering applications. The presence of discontinuous deformations—such as shear banding or wall slip—creates new mechanisms for mixing and transport beyond those predicted by classical dynamical systems theory. Here, we show how a novel mixing mechanism combining stretching with cutting and shuffling yields exponential mixing rates, quantified by a positive Lyapunov exponent, an impossibility for systems with cutting and shuffling alone or bounded systems with stretching alone, and demonstrate it in a fluid flow. While dynamical systems theory provides a framework for understanding mixing in smoothly deforming media, a theory of discontinuous mixing is yet to be fully developed. New methods are needed to systematize, explain, and extrapolate measurements on systems with discontinuous deformations. Here, we investigate "webs" of Lagrangian discontinuities and show that they provide a template for the overall transport dynamics. Considering slip deformations as the asymptotic limit of increasingly localised smooth shear, we also demonstrate exactly how some of the new structures introduced by discontinuous deformations are analogous to structures in smoothly deforming systems.

  1. Mixing of discontinuously deforming media.

    PubMed

    Smith, L D; Rudman, M; Lester, D R; Metcalfe, G

    2016-02-01

    Mixing of materials is fundamental to many natural phenomena and engineering applications. The presence of discontinuous deformations-such as shear banding or wall slip-creates new mechanisms for mixing and transport beyond those predicted by classical dynamical systems theory. Here, we show how a novel mixing mechanism combining stretching with cutting and shuffling yields exponential mixing rates, quantified by a positive Lyapunov exponent, an impossibility for systems with cutting and shuffling alone or bounded systems with stretching alone, and demonstrate it in a fluid flow. While dynamical systems theory provides a framework for understanding mixing in smoothly deforming media, a theory of discontinuous mixing is yet to be fully developed. New methods are needed to systematize, explain, and extrapolate measurements on systems with discontinuous deformations. Here, we investigate "webs" of Lagrangian discontinuities and show that they provide a template for the overall transport dynamics. Considering slip deformations as the asymptotic limit of increasingly localised smooth shear, we also demonstrate exactly how some of the new structures introduced by discontinuous deformations are analogous to structures in smoothly deforming systems. PMID:26931594

  2. The Gutenberg discontinuity: melt at the lithosphere-asthenosphere boundary.

    PubMed

    Schmerr, Nicholas

    2012-03-23

    The lithosphere-asthenosphere boundary (LAB) beneath ocean basins separates the upper thermal boundary layer of rigid, conductively cooling plates from the underlying ductile, convecting mantle. The origin of a seismic discontinuity associated with this interface, known as the Gutenberg discontinuity (G), remains enigmatic. High-frequency SS precursors sampling below the Pacific plate intermittently detect the G as a sharp, negative velocity contrast at 40- to 75-kilometer depth. These observations lie near the depth of the LAB in regions associated with recent surface volcanism and mantle melt production and are consistent with an intermittent layer of asthenospheric partial melt residing at the lithospheric base. I propose that the G reflectivity is regionally enhanced by dynamical processes that produce melt, including hot mantle upwellings, small-scale convection, and fluid release during subduction.

  3. Phase unwrapping using discontinuity optimization

    SciTech Connect

    Flynn, T.J.

    1998-03-01

    In SAR interferometry, the periodicity of the phase must be removed using two-dimensional phase unwrapping. The goal of the procedure is to find a smooth surface in which large spatial phase differences, called discontinuities, are restricted to places where their presence is reasonable. The pioneering work of Goldstein et al. identified points of local unwrap inconsistency called residues, which must be connected by discontinuities. This paper presents an overview of recent work that treats phase unwrapping as a discrete optimization problem with the constraint that residues must be connected. Several algorithms use heuristic methods to reduce the total number of discontinuities. Constantini has introduced the weighted sum of discontinuity magnitudes as a criterion of unwrap error and shown how algorithms from optimization theory are used to minimize it. Pixels of low quality are given low weight to guide discontinuities away from smooth, high-quality regions. This method is generally robust, but if noise is severe it underestimates the steepness of slopes and the heights of peaks. This problem is mitigated by subtracting (modulo 2{pi}) a smooth estimate of the unwrapped phase from the data, then unwrapping the resulting residual phase. The unwrapped residual is added to the smooth estimate to produce the final unwrapped phase. The estimate can be computed by lowpass filtering of an existing unwrapped phase; this makes possible an iterative algorithm in which the result of each iteration provides the estimate for the next. An example illustrates the results of optimal discontinuity placement and the improvement from unwrapping of the residual phase.

  4. Seismic volumetric flattening and segmentation

    NASA Astrophysics Data System (ADS)

    Lomask, Jesse

    Two novel algorithms provide seismic interpretation solutions that use the full dimensionality of the data. The first is volumetric flattening and the second is image segmentation for tracking salt boundaries. Volumetric flattening is an efficient full-volume automatic dense-picking method applied to seismic data. First local dips (step-outs) are calculated over the entire seismic volume. The dips are then resolved into time shifts (or depth shifts) in a least-squares sense. To handle faults (discontinuous reflections), I apply a weighted inversion scheme. Additional information is incorporated in this flattening algorithm as geological constraints. The method is tested successfully on both synthetic and field data sets of varying degrees of complexity including salt piercements, angular unconformities, and laterally limited faults. The second full-volume interpretation method uses normalized cuts image segmentation to track salt interfaces. I apply a modified version of the normalized cuts image segmentation (NCIS) method to partition seismic images along salt interfaces. The method is capable of tracking interfaces that are not continuous, where conventional horizon tracking algorithms may fail. This method partitions the seismic image into two groups. One group is inside the salt body and the other is outside. Where the two groups meet is the salt boundary. By imposing bounds and by distributing the algorithm on a parallel cluster, I significantly increase efficiency and robustness. This method is demonstrated to be effective on both 2D and 3D seismic data sets.

  5. Multichannel seismic-reflection profiling on the R/V Maurice Ewing during the Los Angeles Region Seismic Experiment (LARSE), California

    USGS Publications Warehouse

    Brocher, Thomas M.; Clayton, Robert W.; Klitgord, Kim D.; Bohannon, Robert G.; Sliter, Ray; McRaney, John K.; Gardner, James V.; Keene, J.B.

    1995-01-01

    This report describes the acquisition of deep-crustal multichannel seismic-reflection data in the Inner California Borderland aboard the R/V Maurice Ewing, conducted in October 1994 as part of the Los Angeles Regional Seismic Experiment (LARSE). LARSE is a cooperative study of the crustal structure of southern California involving earth scientists from the U.S. Geological Survey, Caltech, the University of Southern California, the University of California Los Angeles, and the Southern California Earthquake Center (SCEC). During LARSE, the R/V Ewing's 20- element air gun array, totaling 137.7 liters (8470 cu. in.), was used as the primary seismic source for wide-angle recording along three main onshore-offshore lines centered on the Los Angeles basin and the epicenters of the 1933 Long Beach and 1994 Northridge earthquakes. The LARSE onshore-offshore lines were each 200-250 km long, with the offshore portions being between 90 and 150 km long. The nearly 24,000 air gun signals generated by the Ewing were recorded by an array of 170 PASSCAL REFTEK recorders deployed at 2 km intervals along all three of the onshore lines and 9 ocean bottom seismometers (OBSs) deployed along two of the lines. Separate passes over the OBS-deployment lines were performed with a long air gun repetition rate (60 and 90 seconds) to minimize acoustic-wave interference from previous shots in the OBS data. The Ewing's 4.2-km, 160-channel, digital streamer was also used to record approximately 1250 km of 40-fold multichannel seismic-reflection data. To enhance the fold of the wide-angle data recorded onshore, mitigating against cultural and wind noise in the Los Angeles basin, the entire ship track was repeated at least once resulting in fewer than about 660 km of unique trackline coverage in the Inner Borderland. Portions of the seismic-reflection lines were repeated up to 6 times. A variety of other geophysical data were also continuously recorded, including 3.5 kHz bathymetry, multi

  6. Seismic Ecology

    NASA Astrophysics Data System (ADS)

    Seleznev, V. S.; Soloviev, V. M.; Emanov, A. F.

    The paper is devoted to researches of influence of seismic actions for industrial and civil buildings and people. The seismic actions bring influence directly on the people (vibration actions, force shocks at earthquakes) or indirectly through various build- ings and the constructions and can be strong (be felt by people) and weak (be fixed by sensing devices). The great number of work is devoted to influence of violent seismic actions (first of all of earthquakes) on people and various constructions. This work is devoted to study weak, but long seismic actions on various buildings and people. There is a need to take into account seismic oscillations, acting on the territory, at construction of various buildings on urbanized territories. Essential influence, except for violent earthquakes, man-caused seismic actions: the explosions, seismic noise, emitted by plant facilities and moving transport, radiation from high-rise buildings and constructions under action of a wind, etc. can exert. Materials on increase of man- caused seismicity in a number of regions in Russia, which earlier were not seismic, are presented in the paper. Along with maps of seismic microzoning maps to be built indicating a variation of amplitude spectra of seismic noise within day, months, years. The presence of an information about amplitudes and frequencies of oscillations from possible earthquakes and man-caused oscillations in concrete regions allows carry- ing out soundly designing and construction of industrial and civil housing projects. The construction of buildings even in not seismically dangerous regions, which have one from resonance frequencies coincident on magnitude to frequency of oscillations, emitted in this place by man-caused objects, can end in failure of these buildings and heaviest consequences for the people. The practical examples of detail of engineering- seismological investigation of large industrial and civil housing projects of Siberia territory (hydro power

  7. Technological Discontinuities and Organizational Environments.

    ERIC Educational Resources Information Center

    Tushman, Michael L.; Anderson, Philip

    1986-01-01

    Technological effects on environmental conditions are analyzed using longitudinal data from the minicomputer, cement, and airline industries. Technology evolves through periods of incremental change punctuated by breakthroughs that enhance or destroy the competence of firms. Competence-destroying discontinuities increase environmental turbulence;…

  8. The Morphosyntax of Discontinuous Exponence

    ERIC Educational Resources Information Center

    Campbell, Amy Melissa

    2012-01-01

    This thesis offers a systematic treatment of discontinuous exponence, a pattern of inflection in which a single feature or a set of features bundled in syntax is expressed by multiple, distinct morphemes. This pattern is interesting and theoretically relevant because it represents a deviation from the expected one-to-one relationship between…

  9. Characterization and Petrological Constraints of the Midlithospheric Discontinuity

    NASA Astrophysics Data System (ADS)

    Rader, Erika; Emry, Erica; Schmerr, Nicholas; Frost, Daniel; Cheng, Cheng; Menard, Julie; Yu, Chun-Quan; Geist, Dennis

    2015-10-01

    Within continental lithosphere, widespread seismic evidence suggests a sharp discontinuous downward decrease in seismic velocity at 60-160 km depth. This midlithospheric discontinuity (MLD) may be due to anisotropy, melt, hydration, and/or mantle metasomatism. We survey global seismologic observations of the MLD, including observed depths, velocity contrasts, gradients, and locales across multiple seismic techniques. The MLD is primarily found in regions of thick continental lithosphere and is a decrease in seismic shear velocity (2-7% over 10-20 km) at 60-160 km depth, the majority of observations clustering at 80-100 km. Of xenoliths in online databases, 25% of amphibole-bearing xenoliths, 90% of phlogopite-bearing xenoliths, and none of carbonate-bearing xenoliths were formed at pressures associated with these depth (2-5 GPa). We used Perple_X modeling to evaluate the elastic moduli and densities of multiple petrologies to test if the MLD is a layer of crystallized melt. The fractional addition of 5-10% phlogopite, 10-15% carbonate, or 45-100% pyroxenite produce a 2-7% velocity decrease. We postulate this layer of crystallized melt would originate at active margins of continents and crystallize in place as the lithosphere cools. The concentration of mildly incompatible elements (Y, Ho, Er, Yb, and Lu) in xenoliths near the MLD is consistent with higher degrees of melting. Thus, we postulate that the MLD is the seismological signature of a chemical interface related to the paleointersection of a volatile-rich solidus and progressively cooling lithosphere. Furthermore, the MLD may represent a remnant chemical tracer of the lithosphere-asthenosphere boundary (LAB) from when the lithosphere was active and young.

  10. Physico-chemical constraints on cratonic lithosphere discontinuities

    NASA Astrophysics Data System (ADS)

    Aulbach, Sonja; Rondenay, Stéphane; Huismans, Ritske

    2014-05-01

    The origins of the mid-lithospheric discontinuity (MLD) and lithosphere-asthenosphere boundary (LAB) have received much attention over the recent years. Peculiarities of cratonic lithosphere construction - compositional and rheological stratification due to thickening in collisional settings or by plume subcretion, multiple metasomatic overprints due to longevity - offer a variety of possibilities for the generation of discontinuities. Interconnected small degrees of conductive partial melt (carbonate-rich melts, such as carbonatites and kimberlites, or highly alkaline melts) at the cratonic LAB, which produce seismic discontinuities, may be generated in the presence of volatiles. These depress the peridotite solidus sufficiently to intersect the mantle adiabat at depths near the cratonic LAB at ~160-220 km, i.e. above the depth of metal saturation where carbonatite becomes unstable. The absence of agreement between the different seismic and magnetotelluric estimates for the depth of the LAB beneath Kaapvaal may be due to impingement of a plume, leading to a pervasively, but heterogeneously metasomatised ('asthenospherised') hot and deep root. Such a root and hot sublithosphere may yield conflicting seismic-thermal-geochemical depths for the LAB. The question arises whether the chemical boundary layer should be defined as above or below the asthenospherised part of the SCLM, which has preserved isotopic, compositional (non-primitive olivine forsterite content) and physical evidence (e.g. from teleseismic tomography and receiver functions) for a cratonic heritage and which therefore is still distinguishable from the asthenospheric mantle. If cratonic lithosphere overlies anomalously hot mantle for extended periods of time, the LAB may be significantly thinned, aided by penetration of relatively high-degree Fe-rich partial melts, as has occurred beneath the Tanzanian craton. Xenoliths from the deep Slave craton show little evidence for 'asthenospherisation'. Its root

  11. 38 CFR 21.7635 - Discontinuance dates.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ....S.C. 3680(e)) (b) Course discontinued—course interrupted—course terminated—course not satisfactorily...) (e) Discontinued by VA. If VA discontinues payment to a reservist following the procedures stated...

  12. Bursts in discontinuous Aeolian saltation

    PubMed Central

    Carneiro, M. V.; Rasmussen, K. R.; Herrmann, H. J.

    2015-01-01

    Close to the onset of Aeolian particle transport through saltation we find in wind tunnel experiments a regime of discontinuous flux characterized by bursts of activity. Scaling laws are observed in the time delay between each burst and in the measurements of the wind fluctuations at the fluid threshold Shields number θc. The time delay between each burst decreases on average with the increase of the Shields number until sand flux becomes continuous. A numerical model for saltation including the wind-entrainment from the turbulent fluctuations can reproduce these observations and gives insight about their origin. We present here also for the first time measurements showing that with feeding it becomes possible to sustain discontinuous flux even below the fluid threshold. PMID:26073305

  13. Discontinuities in recurrent neural networks.

    PubMed

    Gavaldá, R; Siegelmann, H T

    1999-04-01

    This article studies the computational power of various discontinuous real computational models that are based on the classical analog recurrent neural network (ARNN). This ARNN consists of finite number of neurons; each neuron computes a polynomial net function and a sigmoid-like continuous activation function. We introduce arithmetic networks as ARNN augmented with a few simple discontinuous (e.g., threshold or zero test) neurons. We argue that even with weights restricted to polynomial time computable reals, arithmetic networks are able to compute arbitrarily complex recursive functions. We identify many types of neural networks that are at least as powerful as arithmetic nets, some of which are not in fact discontinuous, but they boost other arithmetic operations in the net function (e.g., neurons that can use divisions and polynomial net functions inside sigmoid-like continuous activation functions). These arithmetic networks are equivalent to the Blum-Shub-Smale model, when the latter is restricted to a bounded number of registers. With respect to implementation on digital computers, we show that arithmetic networks with rational weights can be simulated with exponential precision, but even with polynomial-time computable real weights, arithmetic networks are not subject to any fixed precision bounds. This is in contrast with the ARNN that are known to demand precision that is linear in the computation time. When nontrivial periodic functions (e.g., fractional part, sine, tangent) are added to arithmetic networks, the resulting networks are computationally equivalent to a massively parallel machine. Thus, these highly discontinuous networks can solve the presumably intractable class of PSPACE-complete problems in polynomial time.

  14. Reinforced ceramics employing discontinuous phases

    SciTech Connect

    Becher, P.F.

    1990-01-01

    The fracture toughness of ceramics can be improved by the incorporation of a variety of discontinuous reinforcing phases and microstructures. Observations of crack paths in these systems indicate that these reinforcing phases bridge the crack tip wake region. Recent developments in micromechanics toughening models applicable to such systems are discussed and compared with experimental observations. Because material parameters and microstructural characteristics are considered, the crack bridging models provide a means to optimize the toughening effects. 18 refs., 2 figs.

  15. 40 CFR 159.167 - Discontinued studies.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 25 2013-07-01 2013-07-01 false Discontinued studies. 159.167 Section 159.167 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS... Discontinued studies. The fact that a study has been discontinued before the planned termination must...

  16. 40 CFR 159.167 - Discontinued studies.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Discontinued studies. 159.167 Section 159.167 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS... Discontinued studies. The fact that a study has been discontinued before the planned termination must...

  17. 40 CFR 159.167 - Discontinued studies.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 24 2014-07-01 2014-07-01 false Discontinued studies. 159.167 Section 159.167 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS... Discontinued studies. The fact that a study has been discontinued before the planned termination must...

  18. 40 CFR 159.167 - Discontinued studies.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 24 2011-07-01 2011-07-01 false Discontinued studies. 159.167 Section 159.167 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS... Discontinued studies. The fact that a study has been discontinued before the planned termination must...

  19. 40 CFR 159.167 - Discontinued studies.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 25 2012-07-01 2012-07-01 false Discontinued studies. 159.167 Section 159.167 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS... Discontinued studies. The fact that a study has been discontinued before the planned termination must...

  20. Discontinuous mixed covolume methods for parabolic problems.

    PubMed

    Zhu, Ailing; Jiang, Ziwen

    2014-01-01

    We present the semidiscrete and the backward Euler fully discrete discontinuous mixed covolume schemes for parabolic problems on triangular meshes. We give the error analysis of the discontinuous mixed covolume schemes and obtain optimal order error estimates in discontinuous H(div) and first-order error estimate in L(2).

  1. The Hales discontinuity and upper mantle anisotropy beneath cratons

    NASA Astrophysics Data System (ADS)

    Musacchio, G.; White, D. J.; Thomson, C. J.

    2003-04-01

    Seismic velocity discontinuities are commonly found within the upper 100 km of the mantle lithosphere, with great variability in their depth, lateral extent, and the polarity of velocity jump. Among the more commonly observed is the Hales discontinuity, identified in a variety of tectonic environments, and commonly associated with a high-velocity, highly reflective and sometimes anisotropic layer. In the Archean Western Superior Province of the Canadian Shield, long range R/WAR profiling gives a high-resolution estimate of the mantle V_P in the shallow upper mantle, providing a more certain determination of the nature of the Hales dicontinuity. Ray-based travel-time inversion of the data, have shown that Vp in the uppermost mantle is 8.0-8.3 km/s. A 15-20 km thick layer (layer-H) with >6% seismic anisotropy (N-S V_P of 8.3 km/s and E-W V_P of 8.8 km/s) dips northward at ˜10^o from a minimum depth of 48-50 km. The attitude of layer-H is consistent with the general tectonic strike; its depth range (50-75 km) falls within that of the Hales discontinuity. If a link between the Hales discontinuity and layer-H can be drawn, observations strengthen the objection that the estimated velocity contrast (0.2 to 0.4 km/s depending on the direction of wave propagation) is relatively high if layer-H represents a phase transition, and thus (re)opens the debate on the nature of shallow upper-mantle boundaries beneath continents. The high V_P and intermediate anisotropy of upper-mantle layer-H requires a harzburgite peridotitic composition with the a-axis of olivine aligned E-W. Layer-H might have emplaced during accretion (2.7 Ga Kenoran orogeny) of the North American proto-craton and be relic oceanic lithosphere. The Hales discontinuity might be an expression of continents accretion and map relic slabs in the shallow upper mantle.

  2. Constraining density and velocity jumps across the 410 km discontinuity

    NASA Astrophysics Data System (ADS)

    Saki, Morvarid; Thomas, Christine; Cobden, Laura; Abreu, Rafael

    2016-04-01

    We investigate the velocity and density structure of the olivine-to-wadsleyite transition using polarities of precursor arrivals to PP seismic waves that reflect off the 410 km discontinuity beneath the Northern Atlantic. Numerous source-receiver combinations have been used in order to collect a dataset of reflection points beneath our investigation area. We analyzed over 1700 seismograms from Mw > 5.8 using array seismology methods to enhance the signal to noise ratio. For each event the polarity of the PP phase is compared to polarity of the precursor signal and we find several events where the polarity of the precursors are opposite to that of PP. There does not seem to be any dependency of the observed polarities on the propagation direction of the seismic waves but interestingly there seems to be a dependency on the distance between source and receiver. The events with epicentral distances greater than 119 degrees mostly show opposite polarities, while for those with smaller epicentral distances the same polarity of the main phase and precursor signal is dominant. Using Zeoppritz equations, we analyzed more than 64 million combinations of density, compressional and shear wave velocities for both layers, above and below the 410 km discontinuity in order to find the best combination of those parameters that can explain the observations. The results are indicating combinations of density, P and S wave velocity exhibiting a smaller contrast compared to those from the pyrolite model (the density jump, however is still positive to provide physically meaningful results). The calculated reductions in both compressional and shear wave velocities go up to 13% but mostly fall within the range of less than 7- 8%. We interpret this reduction in elastic properties and seismic velocity of minerals as the effect of a higher than normal content of water of wadsleyite in this region, while we can exclude a reduction in iron.

  3. Seismic seiches

    USGS Publications Warehouse

    McGarr, Arthur; Gupta, Harsh K.

    2011-01-01

    Seismic seiche is a term first used by Kvale (1955) to discuss oscillations of lake levels in Norway and England caused by the Assam earthquake of August 15, 1950. This definition has since been generalized to apply to standing waves set up in closed, or partially closed, bodies of water including rivers, shipping channels, lakes, swimming pools and tanks due to the passage of seismic waves from an earthquake.

  4. Discontinuous dynamics with grazing points

    NASA Astrophysics Data System (ADS)

    Akhmet, M. U.; Kıvılcım, A.

    2016-09-01

    Discontinuous dynamical systems with grazing solutions are discussed. The group property, continuation of solutions, continuity and smoothness of solutions are thoroughly analyzed. A variational system around a grazing solution which depends on near solutions is constructed. Orbital stability of grazing cycles is examined by linearization. Small parameter method is extended for analysis of grazing orbits, and bifurcation of cycles is observed in an example. Linearization around an equilibrium grazing point is discussed. The results can be extended on functional differential equations, partial differential equations and others. Appropriate illustrations are depicted to support the theoretical results.

  5. Directional complex-valued coherence attributes for discontinuous edge detection

    NASA Astrophysics Data System (ADS)

    Wang, Shangxu; Yuan, Sanyi; Yan, Binpeng; He, Yanxiao; Sun, Wenju

    2016-06-01

    We propose directional complex-valued coherence attributes through a simple calculation of the cross-correlation between neighboring complex seismic traces normalized by their corresponding envelope within a local time window along a certain spatial direction. For 3D seismic data with varying directional geological edges, the complex-valued coherence attributes along different spatial directions are distinct, and the coherence along a certain direction can highlight discontinuities at (or near) the perpendicular direction. These separate directional coherence attributes can assist in interpreting the dominant direction(s) of fault development, which is vital in determining sweet spots and locating hydrocarbon wells, and can facilitate the detection of weak or hidden geological edges. In addition, we obtain the minimum complex-valued coherence attribute by comparing all directional coherence volumes to describe the entire lineament and spatial extension direction of geological abnormalities (e.g., channels). In essence, the minimum coherence attribute can be regarded as the result of implementing multi-trace complex-valued coherence calculation along the direction perpendicular to the structural trend. An example of 3D synthetic data with a fault system and channel complex is employed to demonstrate the effectiveness of the directional and minimum complex-valued coherence attributes. The application on a real 3D seismic data of tight sandstone reservoir with faults, flexures and fractures, illustrates that the directional and minimum complex-valued coherence attributes can highlight subtle structures and the directional details of geological abnormalities, which are favorably consistent with the manually interpreted results.

  6. Seismic bearing

    NASA Astrophysics Data System (ADS)

    Power, Dennis

    2009-05-01

    Textron Systems (Textron) has been using geophones for target detection for many years. This sensing capability was utilized for detection and classification purposes only. Recently Textron has been evaluating multiaxis geophones to calculate bearings and track targets more specifically personnel. This capability will not only aid the system in locating personnel in bearing space or cartesian space but also enhance detection and reduce false alarms. Textron has been involved in the testing and evaluation of several sensors at multiple sites. One of the challenges of calculating seismic bearing is an adequate signal to noise ratio. The sensor signal to noise ratio is a function of sensor coupling to the ground, seismic propagation and range to target. The goals of testing at multiple sites are to gain a good understanding of the maximum and minimum ranges for bearing and detection and to exploit that information to tailor sensor system emplacement to achieve desired performance. Test sites include 10A Site Devens, MA, McKenna Airfield Ft. Benning, GA and Yuma Proving Ground Yuma, AZ. Geophone sensors evaluated include a 28 Hz triax spike, a 15 Hz triax spike and a hybrid triax spike consisting of a 10 Hz vertical geophone and two 28 Hz horizontal geophones. The algorithm uses raw seismic data to calculate the bearings. All evaluated sensors have triaxial geophone configuration mounted to a spike housing/fixture. The suite of sensors also compares various types of geophones to evaluate benefits in lower bandwidth. The data products of these tests include raw geophone signals, seismic features, seismic bearings, seismic detection and GPS position truth data. The analyses produce Probability of Detection vs range, bearing accuracy vs range, and seismic feature level vs range. These analysis products are compared across test sites and sensor types.

  7. Seismic interferometry of the mantle transition zone beneath the western United States

    NASA Astrophysics Data System (ADS)

    Anderson, H. R.; Thorne, M. S.; Schmerr, N. C.; Brown, S. P.

    2011-12-01

    Determination of mantle structure is critical in understanding the ongoing dynamic processes in the Earth's interior and determining how the deep interior is connected to volcanic and tectonic features at the surface. Discontinuities within the mantle originating from solid-to-solid mineralogical phase transitions of olivine are important indicators of mantle temperature and composition, and provide key clues for interpreting velocity heterogeneity imaged by seismic tomography. Here we develop a new cross-correlation interferometry technique, to image the detailed topography of discontinuity surfaces and associated phase transitions within the mantle transition zone. Our interferometric technique is applied to 185 events originating along the South American subduction zone, recorded as transverse component broadband seismograms at dense seismic arrays in North America, including EarthScope's Transportable Array, and at the Japanese F-net seismic network. To retrieve upper mantle discontinuity structure, we study underside reflections of S-wave energy from the upper mantle discontinuities, arriving as precursory energy to the seismic phase SS. Our interferometric analysis consists of migrating the direct S-wave energy transmitted through the transition zone discontinuities recorded at North American seismic arrays with SS precursor energy reflecting off the underside of the discontinuities recorded at the F-net seismic array. This approach removes uncertainties in earthquake location and seismic velocity structure on the source side of the underside reflection point, providing enhanced vertical resolution of discontinuity topography over past studies. We present newly detailed images of the mantle discontinuity structure beneath the western United States, and compare our results with tomographic imaging. Initial results indicate large variations in mantle temperature and composition across the western United States associated with the subducting Juan de Fuca slab

  8. Factors Affecting Seismic Velocity in Alluvium

    NASA Astrophysics Data System (ADS)

    Huckins-Gang, H.; Mercadante, J.; Prothro, L.

    2015-12-01

    Yucca Flat at the Nevada National Security Site has been selected as the Source Physics Experiment (SPE) Dry Alluvium Geology Phase II site. The alluvium in this part of Yucca Flat is typical of desert basin fill, with discontinuous beds that are highly variable in clast size and provenance. Detailed understanding of the subsurface geology will be needed for interpretation of the SPE seismic data. A 3D seismic velocity model, created for Yucca Flat using interval seismic velocity data, shows variations in velocity within alluvium near the SPE Phase II site beyond the usual gradual increase of density with depth due to compaction. In this study we examined borehole lithologic logs, geophysical logs, downhole videos, and laboratory analyses of sidewall core samples to understand which characteristics of the alluvium are related to these variations in seismic velocity. Seismic velocity of alluvium is generally related to its density, which can be affected by sediment provenance, clast size, gravel percentage, and matrix properties, in addition to compaction. This study presents a preliminary subdivision of the alluvial strata in the SPE Phase II area into mappable units expected to be significant to seismic modeling. Further refinements of the alluvial units may be possible when seismic data are obtained from SPE Phase II tests. This work was done by National Security Technologies, LLC, under Contract No. DE-AC52-06NA25946 with the U.S. Department of Energy.

  9. Seismic Studies

    SciTech Connect

    R. Quittmeyer

    2006-09-25

    This technical work plan (TWP) describes the efforts to develop and confirm seismic ground motion inputs used for preclosure design and probabilistic safety 'analyses and to assess the postclosure performance of a repository at Yucca Mountain, Nevada. As part of the effort to develop seismic inputs, the TWP covers testing and analyses that provide the technical basis for inputs to the seismic ground-motion site-response model. The TWP also addresses preparation of a seismic methodology report for submission to the U.S. Nuclear Regulatory Commission (NRC). The activities discussed in this TWP are planned for fiscal years (FY) 2006 through 2008. Some of the work enhances the technical basis for previously developed seismic inputs and reduces uncertainties and conservatism used in previous analyses and modeling. These activities support the defense of a license application. Other activities provide new results that will support development of the preclosure, safety case; these results directly support and will be included in the license application. Table 1 indicates which activities support the license application and which support licensing defense. The activities are listed in Section 1.2; the methods and approaches used to implement them are discussed in more detail in Section 2.2. Technical and performance objectives of this work scope are: (1) For annual ground motion exceedance probabilities appropriate for preclosure design analyses, provide site-specific seismic design acceleration response spectra for a range of damping values; strain-compatible soil properties; peak motions, strains, and curvatures as a function of depth; and time histories (acceleration, velocity, and displacement). Provide seismic design inputs for the waste emplacement level and for surface sites. Results should be consistent with the probabilistic seismic hazard analysis (PSHA) for Yucca Mountain and reflect, as appropriate, available knowledge on the limits to extreme ground motion at

  10. An analysis of a seismic reflection from the base of a gas hydrate zone, offshore Peru

    USGS Publications Warehouse

    Miller, J.J.; Lee, M.W.; Von Huene, R.

    1991-01-01

    Seismic reflection data recorded near ODP Site 688, offshore Peru, exhibit a persistent bottom-simulating reflector (BSR) from a depth corresponding to the theoretical base of the gas hdyrate stability field. To carry out a quantitative analysis of the BSR, the seismic data were reprocessed using signature deconvolution and true amplitude recovery techniques. Results indicate the BSR is discontinuous laterally. -from Authors

  11. High Resolution Seismic Study of the Holocene Infill of the Elkhorn Slough, Central California

    EPA Science Inventory

    The seismic analysis of the sedimentary infill of the Elkhorn Slough, central California, reveals a succession of three main seismic units: U1, U2, U3, with their correspondent discontinuities d2, d3. These units are deposited over a paleorelief representing the channel location ...

  12. Upper mantle discontinuity beneath the SW-Iberia peninsula: A multidisciplinary view.

    NASA Astrophysics Data System (ADS)

    Palomeras, Imma; de Lis Mancilla, Flor; Ayarza, Puy; Afonso, Juan Carlos; Diaz, Jordi; Morales, Jose; Carbonell, Ramon; Topoiberia Working Group

    2010-05-01

    Evidence for an upper mantle discontinuity located between 60 and 70 km depth have been provided by different seismic data sets acquired in the Southern Iberian peninsula. First indications of such a discontinuity were obtained by the very long offsets seismic refraction shot gathers acquired within the DSS ILIHA project in the early 90's. Clear seismic events recoded by the dense wide-angle seismic reflection shot gathers of the IBERSEIS experiment (2003) provided further constraints on the depth of the discontinuity and first-order estimates of its physical properties beneath the Ossa Morena Zone. Furthermore, the normal incidence Vibroseis deep seismic reflection images of the ALCUDIA transect (2007) extends this structure to the northeast beneath the Central Iberian Zone. This transect images deep laterally discontinuous reflections at upper mantle travel times (19 s) that roughly correspond to depths within the range of 60-70 km. Receiver function studies of the passive seismic recordings acquired by the IBERARRAY (TOPOIBERIA projects) provides additional support for the existence of this upper mantle structure and suggests that this is a relatively large scale regional feature. Two major scenarios need to be addressed when discussing the origin and nature of this deep structure. One is the tectonic scenario in which the structure maybe be related to a major tectonic event such as an old subduction process and therefore represent an ancient slab. A second hypothesis, would relate this feature to a phase change in the mantle. This latter assumption requires this feature ought to be a broader scale boundary which could be identified by different seismic techniques. Reflectivity modeling carried out over the IBERSEIS wide angle reflection data concludes that the observed phase is consistent with an heterogeneous gradient zone located at, approximately, 61-72 km depth. A layered structure with alternating velocities within ranges 8.1 to 8.3 km/s is necessary in

  13. Seismic Tomography.

    ERIC Educational Resources Information Center

    Anderson, Don L.; Dziewonski, Adam M.

    1984-01-01

    Describes how seismic tomography is used to analyze the waves produced by earthquakes. The information obtained from the procedure can then be used to map the earth's mantle in three dimensions. The resulting maps are then studied to determine such information as the convective flow that propels the crustal plates. (JN)

  14. Seismic Symphonies

    NASA Astrophysics Data System (ADS)

    Strinna, Elisa; Ferrari, Graziano

    2015-04-01

    The project started in 2008 as a sound installation, a collaboration between an artist, a barrel organ builder and a seismologist. The work differs from other attempts of sound transposition of seismic records. In this case seismic frequencies are not converted automatically into the "sound of the earthquake." However, it has been studied a musical translation system that, based on the organ tonal scale, generates a totally unexpected sequence of sounds which is intended to evoke the emotions aroused by the earthquake. The symphonies proposed in the project have somewhat peculiar origins: they in fact come to life from the translation of graphic tracks into a sound track. The graphic tracks in question are made up by copies of seismograms recorded during some earthquakes that have taken place around the world. Seismograms are translated into music by a sculpture-instrument, half a seismograph and half a barrel organ. The organ plays through holes practiced on paper. Adapting the documents to the instrument score, holes have been drilled on the waves' peaks. The organ covers about three tonal scales, starting from heavy and deep sounds it reaches up to high and jarring notes. The translation of the seismic records is based on a criterion that does match the highest sounds to larger amplitudes with lower ones to minors. Translating the seismogram in the organ score, the larger the amplitude of recorded waves, the more the seismogram covers the full tonal scale played by the barrel organ and the notes arouse an intense emotional response in the listener. Elisa Strinna's Seismic Symphonies installation becomes an unprecedented tool for emotional involvement, through which can be revived the memory of the greatest disasters of over a century of seismic history of the Earth. A bridge between art and science. Seismic Symphonies is also a symbolic inversion: the instrument of the organ is most commonly used in churches, and its sounds are derived from the heavens and

  15. A Practical Guide to Regression Discontinuity

    ERIC Educational Resources Information Center

    Jacob, Robin; Zhu, Pei; Somers, Marie-Andrée; Bloom, Howard

    2012-01-01

    Regression discontinuity (RD) analysis is a rigorous nonexperimental approach that can be used to estimate program impacts in situations in which candidates are selected for treatment based on whether their value for a numeric rating exceeds a designated threshold or cut-point. Over the last two decades, the regression discontinuity approach has…

  16. 38 CFR 21.7135 - Discontinuance dates.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) Eligibility expires. If the veteran is pursuing a course on the date of expiration of eligibility as... Bill-Active Duty) Payments-Educational Assistance § 21.7135 Discontinuance dates. The effective date of... dependent. If more than one type of reduction or discontinuance is involved, the earliest date will...

  17. 38 CFR 21.7135 - Discontinuance dates.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) Eligibility expires. If the veteran is pursuing a course on the date of expiration of eligibility as... Bill-Active Duty) Payments-Educational Assistance § 21.7135 Discontinuance dates. The effective date of... dependent. If more than one type of reduction or discontinuance is involved, the earliest date will...

  18. Discontinued drugs in 2008: cardiovascular drugs.

    PubMed

    Zhang, Xu-Song; Xiang, Bing-Ren

    2009-07-01

    This perspective is part of an annual series of papers discussing drugs dropped from clinical development in the previous year. Specifically, this paper focuses on the 16 cardiovascular drugs discontinued in 2008. Information for this perspective was derived from a search of the Pharmaprojects database for drugs discontinued after reaching Phase I-III clinical trials. PMID:19548849

  19. Discontinuity detection in multivariate space for stochastic simulations

    SciTech Connect

    Archibald, Rick Gelb, Anne Saxena, Rishu Xiu Dongbin

    2009-04-20

    Edge detection has traditionally been associated with detecting physical space jump discontinuities in one dimension, e.g. seismic signals, and two dimensions, e.g. digital images. Hence most of the research on edge detection algorithms is restricted to these contexts. High dimension edge detection can be of significant importance, however. For instance, stochastic variants of classical differential equations not only have variables in space/time dimensions, but additional dimensions are often introduced to the problem by the nature of the random inputs. The stochastic solutions to such problems sometimes contain discontinuities in the corresponding random space and a prior knowledge of jump locations can be very helpful in increasing the accuracy of the final solution. Traditional edge detection methods typically require uniform grid point distribution. They also often involve the computation of gradients and/or Laplacians, which can become very complicated to compute as the number of dimensions increases. The polynomial annihilation edge detection method, on the other hand, is more flexible in terms of its geometric specifications and is furthermore relatively easy to apply. This paper discusses the numerical implementation of the polynomial annihilation edge detection method to high dimensional functions that arise when solving stochastic partial differential equations.

  20. Discontinuity Detection in Multivariate Space for Stochastic Simulations

    SciTech Connect

    Archibald, Richard K; Gelb, Anne; Saxena, Rishu; Xiu, Dongbin

    2009-01-01

    Edge detection has traditionally been associated with detecting physical space jump discontinuities in one dimension, e.g. seismic signals, and two dimensions, e.g. digital images. Hence most of the research on edge detection algorithms is restricted to these contexts. High dimension edge detection can be of significant importance, however. For instance, stochastic variants of classical differential equations not only have variables in space/time dimensions, but additional dimensions are often introduced to the problem by the nature of the random inputs. The stochastic solutions to such problems sometimes contain discontinuities in the corresponding random space and a prior knowledge of jump locations can be very helpful in increasing the accuracy of the final solution. Traditional edge detection methods typically require uniform grid point distribution. They also often involve the computation of gradients and/or Laplacians, which can become very complicated to compute as the number of dimensions increases. The polynomial annihilation edge detection method, on the other hand, is more flexible in terms of its geometric specifications and is furthermore relatively easy to apply. This paper discusses the numerical implementation of the polynomial annihilation edge detection method to high dimensional functions that arise when solving stochastic partial differential equations.

  1. Mantle transition zone beneath northeast China from P-receiver function

    NASA Astrophysics Data System (ADS)

    Zhang, R.; Wu, Q.

    2015-12-01

    We used receiver functions to examine lateral topographical variations on the 410- and 660-km beneath northeast China and particularly the Kuril-Japan arc junctions. Compared to other receiver functions studies, our analysis was based on greater station coverage of higher density by combining all recent seismic arrays so far deployed in northeast China. Our image shows that the 410-km is featured by a ~10-20 km uplift extending in the NNE direction beneath some areas of the Quaternary basaltic rocks distributed at Abaga and at Wudalianchi. The Clapeyron slope of the olivine phase transiton at 410-km suggests that the uplift is compatible with a negative thermal anomaly. We also confirm a significant depression of the 660 from the Changbai volcanism in the north to Korea in the south along the NW-SE direction. The depression is also accompanied by an uplift of the 660 to the west. The shallow 660-km discontinuity is also particularly detected beneath the Kuril-Japan arc junctions, while it was not detected before. The thermal anomaly at 410 km depth is most likely a remnant of a detached mantle lithosphere that recently sank to depth, thus providing robust evidence for the source and evolution of these basalts. The depression of the 660-km discontinuity may support that the subducting Pacific slab bends sharply and becomes stagnant when it meets strong resistance at a depth of about 670 km. After accumulation to a great extent the stagnant slab finally penetrates into the lower mantle. Combined with the previous triplicated studies, the shallow 660-km may suggest that descending Pacific slab at its leading and junction edges might be accommodated by a tearing near a depth of 660 km. Acknowledgements. Two liner seismic arrays were deployed by the Institute of Geophysics, China Earthquake Administration. The data of the permanent stations were provided by the Data Management Centre of China, National Seismic Network at the Institute of Geophysics, China Earthquake

  2. Slab interaction with the PPV transition causes complex seismic structure near the CMB.

    NASA Astrophysics Data System (ADS)

    van den Berg, A.; Yuen, D. A.; Christiansen, M. D.

    2006-12-01

    The recently discovered lower mantle phase transition from perovskite to the denser postperovskite (PPV) polymorph is thought to be the cause of detailed seismic structure in the D" layer which is currently the target of intensified seismological investigations. Recently the PPV phase boundary has been relocated in P,T space (Hirose and Sinmyo, 2006). In particular the newly determined Clapeyron slope of 11.5 MPa/K is related to strong lateral topography of the phase boundary which in turn is reflected in lateral variations of the seismic wave velocities. The temperature intercept at the core mantle boundary (CMB) of the PPV Clapeyron curve is estimated at 3500 K from the new mineral physics data. This relative positioning of this temperature intercept with respect to the temperature at the CMB is very important . This may imply that the PPV phase only exists in low temperature regions near the CMB especially around the cold downwellings. The latter implication is related to the thickness of the thermal boundary layer at the bottom of the mantle which depends strongly on the local thermal conductivity. We have used 2-D numerical models to study the interaction of cold highly viscous slabs interacting with the exothermic PPV phase boundary to investigate the potential of the PPV transion as a source of small-scale seismic heterogeneities near the CMB. We apply an Extended Boussinesq (EBA) formulation and include both the spinel to perovskite transition near 660 km depth and the PPV boundary next to the CMB. The model includes both latent heat effects and lateral variations of phase boundaries associated with PPV, controlled by the local temperature. A 2-D cylindrical (90 degree) model domain is applied, using finite element models with the element grid-size down to 5 km near CMB, which is sufficient for delineating the phase transition to well below the seismic resolution. Model runs are started from a cold slab-like temperature distribution in the upper mantle

  3. Local variability in the 410-km mantle discontinuity under a hotspot

    NASA Astrophysics Data System (ADS)

    Leahy, G. M.

    2009-10-01

    Observations of the natural variability in the structure of seismic discontinuities in the Earth's mantle can be used to infer spatial variations in temperature and composition. Here I present a high-resolution analysis of converted seismic waves from the olivine-wadsleyite phase transition beneath Rarotonga, Cook Islands. New advances in seismic signal processing permit the determination of local variations in phase transition thickness in addition to variations in absolute depth. I find that the depth and thickness of the phase transition vary systematically underneath the island, and further that temperature alone is insufficient to explain these observations. A chemical anomaly is required, consistent with the presence of a plume in the mantle.

  4. Medical factors associated with early IVF discontinuation.

    PubMed

    Troude, Pénélope; Guibert, Juliette; Bouyer, Jean; de La Rochebrochard, Elise

    2014-03-01

    Even when IVF is reimbursed by the social insurance system, as in France, high discontinuation rates have been reported and some patients drop out as soon as the first failed IVF cycle. This study aims to investigate medical factors associated with treatment discontinuation in an IVF centre after the first unsuccessful cycle. The study included 5135 couples recruited in eight French IVF centres and who had had an unsuccessful first IVF cycle in these centres in 2000-2002 (i.e. no live birth). Of these couples with a first failed IVF, 1337 did not have a second IVF in the centre (26%, 'early discontinuation group') and 3798 continued treatment with a second IVF in the centre. The characteristics of couples who discontinued IVF treatment were compared with those who continued using logistic regressions. Older women, women with duration of infertility >5years, with female factor or unexplained infertility, with 0 or 1 oocyte retrieved and no embryo transfer during the first IVF were more likely to discontinue treatment early. Risk of early discontinuation was associated with medical factors that are also well known to be associated with impaired chance of successful IVF. Even when IVF is reimbursed by the social insurance system, as in France, high discontinuation rates have been reported and some patients drop out as soon as the first failed IVF cycle. This study aims to investigate medical factors associated with treatment discontinuation in an IVF centre after the first unsuccessful cycle. The study included 5135 couples recruited in eight French IVF centres who had had an unsuccessful first IVF cycle in these centres in 2000-2002 (i.e. who remained childless after a first cycle). Of these couples with a first failed IVF, 1337 did not have a second IVF in the centre and 3798 continued treatment with a second IVF in the centre. The characteristics of couples who discontinued IVF treatment were compared with those who continued. After a first failed IVF cycle, more

  5. [Prospective evaluation of antidepressant discontinuation].

    PubMed

    Mourad, I; Lejoyeux, M; Adès, J

    1998-01-01

    The authors prospectively assessed symptoms induced by the interruption of antidepressants in 16 patients (11 women and 5 men), aged from 33 to 85 years (mean = 52.4 +/- 16.4), treated with antidepressants since at least two weeks. All patients were free of alcohol abuse or dependence disorder and of other dependence to psychoactive substances. None of them presented medical illness. Diagnosis were made by separate evaluations by two authors and confirmed with a semistructered assessment instrument: the Schedule for Affective Disorders and Schizophrenia (Lifetime Version). All patients were submitted to a brutal discontinuation of their antidepressant agent. Patients were assessed twice, before the interruption of the antidepressant, and 72 hours later. Effects of antidepressant interruption were assessed by several means. Modification of anxiety and depression were evaluated using the Montgomery Asberg Depression Rating Scale (MADRS) and the Hamilton Anxiety Scale. Symptoms of withdrawal were assessed with Cassano and al.'s scale SESSH including an evaluation of anxiety, agitation, irritability, anergy, difficulty on concentrating, depersonalization, sleep and appetite disorders, muscle pains, nausea, tremor, sweating, altered taste, hyperosmia, paresthesias, photophobia, motor incoordination, dizziness, hyperacousia pain, delirium. Fourteen of the 16 patients (87.5%) presented modifications of their somatic or psychic state 3 days after the interruption of the antidepressant treatment. Most frequent symptoms were: increase in anxiety (31%), increase in irritability (25%), sleep disorders (19%), decrease of anergia and fatigue (19%). Mean scores of anxiety and depression were not significantly modified by the withdrawal. Following TCAs interruption (7 patients) most frequent symptoms were sleep disorders; increase in anxiety, nausea. Among patients withdrawn from SSRIs (6 patients), most frequent symptoms were increase in anxiety, increase in irritability

  6. Does the Sharpness of the Gutenberg Discontinuity Require Melt?

    NASA Astrophysics Data System (ADS)

    Bagley, B.; Revenaugh, J.

    2008-12-01

    A low-velocity zone (LVZ) underlying the fast seismic lid has been recognized since Gutenberg (1959). While, strictly speaking, the asthenosphere and the LVZ are defined by different properties, their upper boundaries are functionally equivalent in the oceanic setting. The Gutenberg (G) discontinuity marks the seismically sharp upper boundary of the lid-low-velocity transition beneath oceans and is characterized by an abrupt shear wave impedance decrease of roughly 9%. Explanations for the low seismic velocities include a contrast in volatile content, structurally bound water, and the effects of temperature and grain size. Partial melt, which once enjoyed the status of an obvious cause, has fallen from favor, primarily because of the difficulty of retaining a connecting fluid phase in the LVZ. But recent results demonstrate large velocity decrements for very small grain boundary melt fractions that could remain unconnected and trapped in the LVZ (Faul and Jackson, 2007). In order to provide better constraints on the structure of the low-velocity zone, we have examined the G discontinuity beneath a large portion of the central and western Pacific. Our focus is on the sharpness of the G reflector and the impedance decrease across it. Using multiple ScS reverberations we sampled the G discontinuity along a series of oceanic paths. We obtain impedance decreases between 4.7 and 14.2%, averaging 9.1%, assuming a first-order discontinuity. Our data do not, however, require the change in impedance to be sharp and can easily tolerate an extended transition of 10 to 15 km with little change in the estimated impedance contrast. However, extending the transition further requires a greater net impedance decrease across the interval. This provides an important constraint on the thickness of the transition interval. Preliminary results that consider acceptable net impedance contrasts (obtained from surface wave and turning wave constraints on LVZ severity) impose a conservative

  7. Solving ordinary differential equations with discontinuities

    SciTech Connect

    Gear, C.W.; Osterby, O.

    1981-09-01

    An algorithm is described that can detect and locate some discontinuities and provide information about their size, order and position. However, the success of the algorithm is strongly dependent on the location of the discontinuity with respect to the steps that straddle it. The major advantage of the scheme appears to be that a more reliable error estimate can be used when a discontinuity is present so that codes will be more robust. In some cases significant savings may accrue but it appears that a better restarting procedure than the one used will be necessary to realize most of those benefits.

  8. On the origin of the D'' discontinuity: Combining seismological observations with mineral physics

    NASA Astrophysics Data System (ADS)

    Cobden, L. J.; Thomas, C.

    2013-12-01

    The D'' region is one of the most seismologically complex and intriguing parts of the Earth. Many independent studies have observed reflections of both P and/or S waves from structures located c. 100-400 km above the CMB. These structures are often assumed to demarcate the top of the D'' layer and loosely referred to as 'the D'' discontinuity'. Unlike the major discontinuities of the upper mantle, which appear readily in global seismic inversions of 1-D structure but may be absent in regional seismic datasets, the D'' discontinuity is typically absent from 1-D reference models yet readily observed in regional seismic datasets. Furthermore, significant lateral variations are seen in the amplitude, polarity and timing of P and S wave reflections, both within and between different studies, and in some regions no reflections are detected. It is thus not clear if D'' reflections represent a globally ubiquitous discontinuity, or arise from local to regional scale heterogeneity. Most recently, a popular hypothesis is that the D'' discontinuity represents the phase change from perovskite to post-perovskite. This hypothesis is based on a consistency between the seismic properties of D'' reflections in the Caribbean region (where typically strong S-wave reflections are accompanied by weaker P-wave reflections) and the experimentally-inferred transformation pressure and velocity contrast of the phase change. However, it becomes more difficult to explain D'' reflections in terms of the pv-ppv transformation in regions such as Siberia, where strong reflections are seen in both P and S waves. Accordingly, we consider the possibility that D'' reflections may be generated by a range of alternative thermochemical phenomena. We compile observations of D'' reflections from several locations around the globe, and quantitatively assess how well different thermochemical models fit the seismic properties of the reflections at each location. Our compilation includes both published seismic

  9. Discontinuous spirals of stable periodic oscillations.

    PubMed

    Sack, Achim; Freire, Joana G; Lindberg, Erik; Pöschel, Thorsten; Gallas, Jason A C

    2013-01-01

    We report the experimental discovery of a remarkable organization of the set of self-generated periodic oscillations in the parameter space of a nonlinear electronic circuit. When control parameters are suitably tuned, the wave pattern complexity of the periodic oscillations is found to increase orderly without bound. Such complex patterns emerge forming self-similar discontinuous phases that combine in an artful way to produce large discontinuous spirals of stability. This unanticipated discrete accumulation of stability phases was detected experimentally and numerically in a Duffing-like proxy specially designed to bypass noisy spectra conspicuously present in driven oscillators. Discontinuous spirals organize the dynamics over extended parameter intervals around a focal point. They are useful to optimize locking into desired oscillatory modes and to control complex systems. The organization of oscillations into discontinuous spirals is expected to be generic for a class of nonlinear oscillators. PMID:24284508

  10. Discontinuous Spirals of Stable Periodic Oscillations

    PubMed Central

    Sack, Achim; Freire, Joana G.; Lindberg, Erik; Pöschel, Thorsten; Gallas, Jason A. C.

    2013-01-01

    We report the experimental discovery of a remarkable organization of the set of self-generated periodic oscillations in the parameter space of a nonlinear electronic circuit. When control parameters are suitably tuned, the wave pattern complexity of the periodic oscillations is found to increase orderly without bound. Such complex patterns emerge forming self-similar discontinuous phases that combine in an artful way to produce large discontinuous spirals of stability. This unanticipated discrete accumulation of stability phases was detected experimentally and numerically in a Duffing-like proxy specially designed to bypass noisy spectra conspicuously present in driven oscillators. Discontinuous spirals organize the dynamics over extended parameter intervals around a focal point. They are useful to optimize locking into desired oscillatory modes and to control complex systems. The organization of oscillations into discontinuous spirals is expected to be generic for a class of nonlinear oscillators. PMID:24284508

  11. Discontinuity stresses in metallic pressure vessels

    NASA Technical Reports Server (NTRS)

    1971-01-01

    The state of the art, criteria, and recommended practices for the theoretical and experimental analyses of discontinuity stresses and their distribution in metallic pressure vessels for space vehicles are outlined. The applicable types of pressure vessels include propellant tanks ranging from main load-carrying integral tank structure to small auxiliary tanks, storage tanks, solid propellant motor cases, high pressure gas bottles, and pressurized cabins. The major sources of discontinuity stresses are discussed, including deviations in geometry, material properties, loads, and temperature. The advantages, limitations, and disadvantages of various theoretical and experimental discontinuity analysis methods are summarized. Guides are presented for evaluating discontinuity stresses so that pressure vessel performance will not fall below acceptable levels.

  12. Discontinuous structure transition in a Debye cluster

    SciTech Connect

    Sheridan, T. E.

    2012-05-15

    We consider the structural phases of a cluster of identical particles confined in a two-dimensional biharmonic well and interacting through a screened Coulomb (Yukawa) potential (e.g., dusty plasma). For n = 6 particles, we show that there are one discontinuous and three continuous structure transitions, giving five structure phases. Two of these phases, the straight line and zigzag configurations, have previously been studied experimentally. We experimentally verify the discontinuous transition and observe the remaining three phases.

  13. Discontinuities of multi-Regge amplitudes

    NASA Astrophysics Data System (ADS)

    Fadin, V. S.

    2015-04-01

    In the BFKL approach, discontinuities of multiple production amplitudes in invariant masses of produced particles are discussed. It turns out that they are in evident contradiction with the BDS ansatz for n-gluon amplitudes in the planar N = 4 SYM at n ≥ 6. An explicit expression for the NLO discontinuity of the two-to-four amplitude in the invariant mass of two produced gluons is is presented.

  14. Historical seismicity

    USGS Publications Warehouse

    Dengler, L.

    1992-01-01

    The North Coast region of California in the vicinity of Cape Mendocino is one of the state's most seismically active areas, accounting for 25 percent of seismic energy release in California during the last 50 years. the region is located in a geologically dynamic are surrounding the Mendocino triple junction where three of the Earth's tectonic plates join together ( see preceding article by Sam Clarke). In the historic past the North Coast has been affected by earthquakes occurring on the San Andreas fault system to the south, the Mendocino fault to the southwest, and intraplate earthquakes within both the Gorda and North American plates. More than sixty of these earthquakes have caused damage since the mid-1800's. Recent studies indicate that California's North Coast is also at risk with respect to very large earthquakes (magnitude >8) originating along the Cascadia subduction zone. Although the subduction zone has not generated great earthquakes in historic time, paleoseismic evidence suggests that such earthquakes have been generated by the subduction zone in the recent prehistoric past. 

  15. Comparing the Gibraltar and Calabrian subduction zones (central western Mediterranean) based on seismic tomography

    NASA Astrophysics Data System (ADS)

    Argnani, Andrea; Battista Cimini, Giovanni; Frugoni, Francesco; Monna, Stephen; Montuori, Caterina

    2016-04-01

    The Central Western Mediterranean (CWM) was shaped by a complex tectonic and geodynamic evolution. Deep seismicity and tomographic studies point to the existence, under the Alboran and Tyrrhenian Seas, of lithospheric slabs extending down to the bottom of the mantle transition zone, at 660 km depth. Two narrow arcs correspond to the two slabs, the Gibraltar and Calabrian Arcs (e.g., Monna et al., 2013; Montuori et al., 2007). Similarities in the tectonic and mantle structure of the two areas have been explained by a common subduction and roll-back mechanism for the opening of the CWM, in which the two arcs are symmetrical end products. In spite of this unifying model, a wide amount of literature from different disciplines shows that many aspects of the two areas are still controversial. We present a new 3-D tomographic model at mantle scale for the Calabrian Arc and compare it with a recently published 3-D tomographic model for the Gibraltar Arc by Monna et al (2013). The two models are based on non-linear inversion of teleseismic phase arrivals, and have scale and parametrization that allow for a direct comparison. Unlike previous studies the tomographic models here presented include Ocean Bottom Seismometer broadband data, which improved the resolution of the mantle structures in the marine areas surrounding the arcs. We focus on key features of the two models that constrain reconstructions of the geodynamic evolution of the CWM (e.g., Monna et al., 2015). At Tortonian time the opening of the Tyrrhenian basin was in its initial stage, and the Calabrian arc formed subsequently; on the contrary, the Gibraltar arc was almost completely defined. We hypothesize that the complexity of the continental margin approaching the subduction zone played a key role during the final stages of the arc formation. References Monna, S., G. B. Cimini, C. Montuori, L. Matias, W. H. Geissler, and P. Favali (2013), New insights from seismic tomography on the complex geodynamic evolution

  16. Seismic sources

    DOEpatents

    Green, M.A.; Cook, N.G.W.; McEvilly, T.V.; Majer, E.L.; Witherspoon, P.A.

    1987-04-20

    Apparatus is described for placement in a borehole in the earth, which enables the generation of closely controlled seismic waves from the borehole. Pure torsional shear waves are generated by an apparatus which includes a stator element fixed to the borehole walls and a rotor element which is electrically driven to rapidly oscillate on the stator element to cause reaction forces transmitted through the borehole walls to the surrounding earth. Longitudinal shear waves are generated by an armature that is driven to rapidly oscillate along the axis of the borehole, to cause reaction forces transmitted to the surrounding earth. Pressure waves are generated by electrically driving pistons that press against opposite ends of a hydraulic reservoir that fills the borehole. High power is generated by energizing the elements for more than about one minute. 9 figs.

  17. 27 CFR 555.128 - Discontinuance of business.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 3 2010-04-01 2010-04-01 false Discontinuance of business... Discontinuance of business. Where an explosive materials business or operations is discontinued and succeeded by... such facts and shall be delivered to the successor. Where discontinuance of the business or...

  18. 27 CFR 478.127 - Discontinuance of business.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 3 2010-04-01 2010-04-01 false Discontinuance of business... Records § 478.127 Discontinuance of business. Where a licensed business is discontinued and succeeded by a... be delivered to the successor. Where discontinuance of the business is absolute, the records shall...

  19. 27 CFR 478.57 - Discontinuance of business.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 3 2010-04-01 2010-04-01 false Discontinuance of business... Licenses § 478.57 Discontinuance of business. (a) Where a firearm or ammunition business is either discontinued or succeeded by a new owner, the owner of the business discontinued or succeeded shall within...

  20. 27 CFR 478.127 - Discontinuance of business.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 3 2014-04-01 2014-04-01 false Discontinuance of business... Records § 478.127 Discontinuance of business. Where a licensed business is discontinued and succeeded by a... be delivered to the successor. Where discontinuance of the business is absolute, the records shall...

  1. 27 CFR 478.57 - Discontinuance of business.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 3 2014-04-01 2014-04-01 false Discontinuance of business... Licenses § 478.57 Discontinuance of business. (a) Where a firearm or ammunition business is either discontinued or succeeded by a new owner, the owner of the business discontinued or succeeded shall within...

  2. 27 CFR 478.127 - Discontinuance of business.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 3 2013-04-01 2013-04-01 false Discontinuance of business... Records § 478.127 Discontinuance of business. Where a licensed business is discontinued and succeeded by a... be delivered to the successor. Where discontinuance of the business is absolute, the records shall...

  3. 27 CFR 555.128 - Discontinuance of business.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 3 2014-04-01 2014-04-01 false Discontinuance of business... Discontinuance of business. Where an explosive materials business or operations is discontinued and succeeded by... such facts and shall be delivered to the successor. Where discontinuance of the business or...

  4. 27 CFR 555.128 - Discontinuance of business.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 3 2013-04-01 2013-04-01 false Discontinuance of business... Discontinuance of business. Where an explosive materials business or operations is discontinued and succeeded by... such facts and shall be delivered to the successor. Where discontinuance of the business or...

  5. 27 CFR 17.187 - Discontinuance of business.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Discontinuance of business... PRODUCTS Miscellaneous Provisions § 17.187 Discontinuance of business. The manufacturer shall notify TTB when business is to be discontinued. Upon discontinuance of business, a manufacturer's entire stock...

  6. 27 CFR 478.57 - Discontinuance of business.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... Licenses § 478.57 Discontinuance of business. (a) Where a firearm or ammunition business is either discontinued or succeeded by a new owner, the owner of the business discontinued or succeeded shall within 30... 27 Alcohol, Tobacco Products and Firearms 3 2013-04-01 2013-04-01 false Discontinuance of...

  7. Using Cross-Correlation to Detect Upper Mantle Phases beneath Spain and Morocco

    NASA Astrophysics Data System (ADS)

    Bonatto, L.; Schimmel, M.; Gallart, J.; Morales, J.

    2012-04-01

    A novel technique is implemented to search for weak amplitude upper mantle phases that arrive in the P-wave coda. Cross-correlation and stacking techniques are applied in order to detect waveform similarity and eliminate the source influence from the vertical and radial component of records from single stations. A pilot wave is selected from the vertical component, this wavelet contains the P-wave and part of its coda. Phase cross-correlation (PCC) and geometrically normalized cross-correlation (CCGN) are performed between this pilot and the vertical, and the radial component of each event. It is expected that this procedure detects P to s conversions, and reflections at different mantle discontinuities (such as 410-km and 660-km depth discontinuities). Stacking is used to enhance signals which arrive consistently (near receiver conversions and reflections) and attenuate isolated depth phases and also spurious arrivals. Besides the source equalization, PCC and CCGN provide relative travel times with respect to the P phase through their correlation maxima. The data set used in the real data example is obtained from more than 40 stations selected from the first phase of the IberArray seismic network deployment (TopoIberia project) in south Spain and north Morocco. P-wave reflections and P to s conversions at 410-km and 660-km upper mantle discontinuities were detected beneath the studied region. Both discontinuities are on average within the expected depth range from global studies.

  8. Method for simulating discontinuous physical systems

    DOEpatents

    Baty, Roy S.; Vaughn, Mark R.

    2001-01-01

    The mathematical foundations of conventional numerical simulation of physical systems provide no consistent description of the behavior of such systems when subjected to discontinuous physical influences. As a result, the numerical simulation of such problems requires ad hoc encoding of specific experimental results in order to address the behavior of such discontinuous physical systems. In the present invention, these foundations are replaced by a new combination of generalized function theory and nonstandard analysis. The result is a class of new approaches to the numerical simulation of physical systems which allows the accurate and well-behaved simulation of discontinuous and other difficult physical systems, as well as simpler physical systems. Applications of this new class of numerical simulation techniques to process control, robotics, and apparatus design are outlined.

  9. Observations of oceanic crust and mantle structures at a deep ocean seismic array in the Eastern Mid Atlantic

    NASA Astrophysics Data System (ADS)

    Hannemann, Katrin; Krüger, Frank; Dahm, Torsten

    2016-04-01

    In 2011, twelve ocean bottom stations (OBS) were installed approximately 100 km North of the Gloria Fault during the DOCTAR project (Deep OCean Test ARray). This fault marks the plate boundary between the Eurasian and African plate in the North Eastern Mid Atlantic. The experiment took place in water depth of 4-6 km, 800 km West of the Portuguese coast. The stations were equipped with broad band seismometers which recorded for ten months. We employ P and S receiver functions (RF) to have a closer look at the structure of crust and mantle. The ocean is a quite noisy environment, therefore the number of usable events is low (around 20) compared to RF studies on land. We use several quality criteria (e.g. signal to noise ratio, relative spike position) to select proper processing parameters for the calculation of the RF and carefully reviewed all later on used RF. Despite the low number of events, the usage of an array of OBS with an aperture of 75 km allows us to investigate deeper discontinuities (e.g. in 410 and 660 km depth) compared to single station approaches which are usually employed for OBS. Furthermore, we increase the number of usable events by applying array methods. We use move out corrected and stacked RF to have a closer look at the mantle transition zone, and estimate average depth values for the Moho, the lithosphere asthenosphere boundary (LAB) and the base of the asthenosphere. The Moho lies at depth of 7 km, the LAB at approximately 50 km and the asthenosphere has an approximated thickness of 110 km. We observe a slight increase in the time difference of the mantle discontinuity conversion times compared to PREM. RF give just information regarding the impedance contrast at a discontinuity instead of velocities. We additionally use P wave polarization of teleseismic events to estimate absolute S velocities beneath the single stations. All in all, we use the information gained by the RF analysis, and the analysis of the P wave polarization to

  10. Rockburst Generation in Discontinuous Rock Masses

    NASA Astrophysics Data System (ADS)

    He, Ben-Guo; Zelig, Ravit; Hatzor, Yossef H.; Feng, Xia-Ting

    2016-10-01

    We study rockburst generation in discontinuous rock masses using theoretical and numerical approaches. We begin by developing an analytical solution for the energy change due to tunneling in a continuous rock mass using linear elasticity. We show that the affected zone where most of the increase in elastic strain energy takes place is restricted to an annulus that extends to a distance of three diameters from the tunnel center, regardless of initial tunnel diameter, magnitude of in situ stress, and in situ stress ratio. By considering local elastic strain concentrations, we further delineate the Rockbursting Prone Zone found to be concentrated in an annulus that extends to one diameter from the tunnel center, regardless of original stress ratio, magnitude, and the stiffness of the rock mass. We proceed by arguing that in initially discontinuous rock masses shear stress amplification due to tunneling will inevitably trigger block displacements along preexisting discontinuities much before shear failure of intact rock elements will ensue, because of the lower shear strength of discontinuities with respect to intact rock elements, provided of course that the blocks are removable. We employ the numerical discrete element DDA method to obtain, quantitatively, the kinetic energy, the elastic strain energy, and the dissipated energy in the affected zone in a discontinuous rock due to tunneling. We show that the kinetic energy of ejected blocks due to strain relaxation increases with increasing initial stress and with decreasing frictional resistance of preexisting discontinuities. Finally, we demonstrate how controlled strain energy release by means of top heading and bench excavation methodology can assist in mitigating rockburst hazards due to stain relaxation.

  11. Mid-lithospheric Discontinuity Beneath the Malawi Rift, Deduced from Gravity Studies and its Relation to the Rifting Process.

    NASA Astrophysics Data System (ADS)

    Njinju, E. A.; Atekwana, E. A.; Mickus, K. L.; Abdelsalam, M. G.; Atekwana, E. A.; Laó-Dávila, D. A.

    2015-12-01

    The World Gravity Map satellite gravity data were used to investigate the lithospheric structure beneath the Cenozoic-age Malawi Rift which forms the southern extension of the Western Branch of the East African Rift System. An analysis of the data using two-dimensional (2D) power spectrum methods indicates the two distinctive discontinuities at depths of 31‒44 km and 64‒124 km as defined by the two steepest slopes of the power spectrum curves. The shallower discontinuity corresponds to the crust-mantle boundary (Moho) and compares well with Moho depth determined from passive seismic studies. To understand the source of the deeper discontinuity, we applied the 2D power spectrum analysis to other rift segments of the Western Branch as well as regions with stable continental lithospheres where the lithospheric structure is well constrained through passive seismic studies. We found that the deeper discontinuity corresponds to a mid-lithospheric discontinuity (MLD), which is known to exist globally at depths between 60‒150 km and as determined by passive seismic studies. Our results show that beneath the Malawi Rift, there is no pattern of N-S elongated crustal thinning following the surface expression of the Malawi Rift. With the exception of a north-central region of crustal thinning (< 35 km), most of the southern part of the rift is underlain by thick crust (~40‒44 km). Different from the Moho, the MLD is shallower beneath the axis of the Malawi Rift forming a N-S trending zone with depths of 64‒80 km, showing a broad and gentle topography. We interpret the MLD as representing a sharp density contrast resulting from metasomatized lithosphere due to lateral migration along mobile belts of hot mantle melt or fluids from a distant plume and not from an ascending asthenosphere. These fluids weaken the lithosphere enhancing rift nucleation. The availability of satellite gravity worldwide makes gravity a promising technique for determining the MLD globally.

  12. Ray theory of gas dynamic discontinuities

    NASA Astrophysics Data System (ADS)

    Kentzer, Czeslaw P.

    1987-12-01

    A geometric theory of the motion of surfaces of discontinuity is based on the quasi-linear algebraic system of generalized Rankine-Hugoniot jump conditions for an ideal gas. Vanishing of a characteristic determinant is necessary for the existence of a nontrivial jump. Geometrical, dynamical, and persistence conditions are applied to the discontinuity of an arbitrary strength, resulting in a set of Hamiltonian equations for the position coordinates and for the space-time normal to the surface. The rays are defined as the integral curves of the Hamiltonian system and generate the singular surface that satisfies the imposed jump conditions.

  13. Cathodic protection of pipelines in discontinuous permafrost

    SciTech Connect

    Mitchell, C.J.; Wright, M.D.; Waslen, D.W.

    1997-08-01

    This paper discusses the challenges in providing cathodic protection for a pipeline located in an area with discontinuous permafrost. Specific challenges included: unknown time for the permafrost to melt out, unpredictable current distribution characteristics and wet, inaccessible terrain. Based on preliminary pipe-to-soil data, it appears that cathodic protection coverage was achieved in discontinuous permafrost regions without the need of local anodes. Future work is required to verify whether this conclusion can be extended over the course of an annual freeze-thaw cycle.

  14. Current discontinuities on superconducting cosmic strings

    SciTech Connect

    Troyan, E. Vlasov, Yu. V.

    2011-07-15

    The propagation of current perturbations on superconducting cosmic strings is considered. The conditions for the existence of discontinuities similar to shock waves have been found. The formulas relating the string parameters and the discontinuity propagation speed are derived. The current growth law in a shock wave is deduced. The propagation speeds of shock waves with arbitrary amplitudes are calculated. The reason why there are no shock waves in the case of time-like currents (in the 'electric' regime) is explained; this is attributable to the shock wave instability with respect to perturbations of the string world sheet.

  15. Seismic facies analysis of lacustrine system: Paleocene upper Fort Union Formation, Wind River basin, Wyoming

    SciTech Connect

    Liro, L.M.; Pardus, Y.C.

    1989-03-01

    The authors interpreted seismic reflection data, supported by well control, to reconstruct the stratigraphic development of Paleocene Lake Waltman in the Wind River basin of Wyoming. After dividing the upper Fort Union into eight seismic sequences, the authors mapped seismic attributes (amplitude, continuity, and frequency) within each sequence. Interpretation of the variation in seismic attributes allowed them to detail delta development and encroachment into Lake Waltman during deposition of the upper Fort Union Formation. These deltas are interpreted as high-energy, well-differentiated lobate forms with distinct clinoform morphology on seismic data. Prograding delta-front facies are easily identified on seismic data as higher amplitude, continuous events within the clinoforms. Seismic data clearly demonstrate the time-Transgressive nature of this facies. Downdip of these clinoforms, homogeneous shales, as evidenced by low-amplitude, generally continuous seismic events, accumulated in an interpreted quiet, areally extensive lacustrine setting. Seismic definition of the lateral extent of this lacustrine facies is excellent, allowing them to effectively delineate changes in the lake morphology during deposition of the upper Fort Union Formation. Encasing the upper Fort Union lacustrine deposits are fluvial-alluvial deposits, interpreted from discontinuous, variable-amplitude seismic facies. The authors highlight the correlation of seismic facies data and interpretation to well log data in the Frenchie Draw field to emphasize the accuracy of depositional environment prediction from seismic data.

  16. Lithospheric Convergence Preceded Extension in the Pannonian-Carpathian System

    NASA Astrophysics Data System (ADS)

    Houseman, Gregory; Stuart, Graham; Dando, Ben; Hetenyi, Gyorgy; Lorinczi, Piroska; Hegedus, Endre; Brueckl, Ewald

    2010-05-01

    The continuing collision of the Adriatic block with European continental lithosphere has its clearest expression now in the Alpine collision zone. Recent tomographic images of the upper mantle beneath the eastern Alps and western Pannonian Basin support the interpretation that in the Early Miocene the collision zone extended further east: a steeply dipping seismically fast structure stretches downward beneath the Eastern Alps reaching to the base of the transition zone, consistent with the long history of convergence in this region. This high velocity structure also extends eastward beneath the extensional Pannonian Basin. The high velocity anomaly beneath the Basin is strongly developed in transition zone depths (410 to 660 km) but the anomaly weakens upward. High velocities beneath the center of the extensional basin are unexpected because there is substantive evidence that the onset of extension in the Pannonian domain at around 17 Ma produced rapid extension of the lithosphere and replacement of the lower part of the lithosphere by hot asthenosphere. These deeper structures, however, must be explained by the long history of convergence that preceded the extension of the basin. Further evidence of a history of sustained convergence in the present Pannonian region is found in the depression of the 660 km seismic discontinuity beneath the Alps (Lombardi et al., EPSL, 2009) and also beneath the Pannonian Basin (Hetenyi et al., GRL, 2009). The 660 km discontinuity in both places is depressed by as much as 40 km, whereas the 410 km discontinuity is at approximately nominal depths. Evidently in both regions relatively dense material derived from the mid-Miocene collision sits stagnant on top of the 660 km discontinuity, where further descent is obstructed by the negative Clapeyron slope of the spinel-to-perovskite phase transition and/or the high viscosity of the lower mantle. The rapid extension of the Intra-Carpathian Basins in the Mid-Miocene (between about 17 and

  17. Elastic wave finite-difference simulation using discontinuous curvilinear grid with non-uniform time step: two-dimensional case

    NASA Astrophysics Data System (ADS)

    Li, Hong; Zhang, Wei; Zhang, Zhenguo; Chen, Xiaofei

    2015-07-01

    A discontinuous grid finite-difference (FD) method with non-uniform time step Runge-Kutta scheme on curvilinear collocated-grid is developed for seismic wave simulation. We introduce two transition zones: a spatial transition zone and a temporal transition zone, to exchange wavefield across the spatial and temporal discontinuous interfaces. A Gaussian filter is applied to suppress artificial numerical noise caused by down-sampling the wavefield from the finer grid to the coarser grid. We adapt the non-uniform time step Runge-Kutta scheme to a discontinuous grid FD method for further increasing the computational efficiency without losing the accuracy of time marching through the whole simulation region. When the topography is included in the modelling, we carry out the discontinuous grid method on a curvilinear collocated-grid to obtain a sufficiently accurate free-surface boundary condition implementation. Numerical tests show that the proposed method can sufficiently accurately simulate the seismic wave propagation on such grids and significantly reduce the computational resources consumption with respect to regular grids.

  18. Seismic sources

    DOEpatents

    Green, Michael A.; Cook, Neville G. W.; McEvilly, Thomas V.; Majer, Ernest L.; Witherspoon, Paul A.

    1992-01-01

    Apparatus is described for placement in a borehole in the earth, which enables the generation of closely controlled seismic waves from the borehole. Pure torsional shear waves are generated by an apparatus which includes a stator element fixed to the borehole walls and a rotor element which is electrically driven to rapidly oscillate on the stator element to cause reaction forces transmitted through the borehole walls to the surrounding earth. Logitudinal shear waves are generated by an armature that is driven to rapidly oscillate along the axis of the borehole relative to a stator that is clamped to the borehole, to cause reaction forces transmitted to the surrounding earth. Pressure waves are generated by electrically driving pistons that press against opposite ends of a hydraulic reservoir that fills the borehole. High power is generated by energizing the elements at a power level that causes heating to over 150.degree. C. within one minute of operation, but energizing the elements for no more than about one minute.

  19. Long-range Receiver Function Profile of Crustal and Mantle Discontinuities From the Aleutian Arc to Tierra del Fuego

    NASA Astrophysics Data System (ADS)

    Spieker, Kathrin; Rondenay, Stéphane; Sawade, Lucas

    2016-04-01

    The Circum-Pacific belt, also called the Pacific Ring of Fire, is the most seismically active region on Earth. Multiple plate boundaries form a zone characterized by frequent volcanic eruptions and seismicity. While convergent plate boundaries such as the Peru-Chile trench dominate the Circum-Pacific belt, divergent and transform boundaries are present as well. The eastern section of the Circum-Pacific belt extends from the Aleutian arc, through the Cascadia subduction zone, San Andreas Fault, middle America trench and the Andean margin down to Tierra del Fuego. Due to the significant hazards posed by this tectonic activity, the region has been densely instrumented by thousands of seismic stations deployed across fifteen countries, over a distance of more than 15000 km. Various seismological studies, including receiver function analyses, have been carried out to investigate the crustal and mantle structure beneath local segments of the eastern Circum-Pacific belt (i.e., at ~100-500 km scale). However, to the best of our knowledge, no study to date has ever attempted to combine all available seismic data from the eastern Circum-Pacific belt to generate a continuous profile of seismic discontinuities extending from the Aleutians to Tierra del Fuego. Here, we use results from the "Global Imaging using Earthquake Records" (GLImER) P-wave receiver function database to create a long-range profile of crustal and upper mantle discontinuities across the entire eastern portion of the Circum-Pacific belt. We image intermittent crustal and mantle discontinuities along the profile, and examine them with regard to their behaviour and properties across transitions between different tectonic regimes.

  20. Stability of Conservation Laws with Discontinuous Coefficients

    NASA Astrophysics Data System (ADS)

    Klausen, Runhild Aae; Risebro, Nils Henrik

    1999-09-01

    We prove L1 contractivity of weak solutions to a conservation law with a flux function that may depend discontinuously on the space variable. Furthermore, we show that the L1 difference between solutions to conservation laws with different flux functions is bounded by the total variation with respect to the space variable, of the difference between the flux functions.

  1. Cathodic protection of pipelines in discontinuous permafrost

    SciTech Connect

    Mitchell, C.J.; Wright, M.D.; Waslen, D.W.

    1997-10-01

    There are many unknowns and challenges in providing cathodic protection (CP) for a pipeline located in discontinuous permafrost areas. Preliminary pipe-to-soil data indicates that CP coverage was achieved in these regions without needing local anodes. Work is required to verify whether this conclusion can be extended over the course of an annual freeze-thaw cycle.

  2. Characterization of Asymmetric Coplanar Waveguide Discontinuities

    NASA Technical Reports Server (NTRS)

    Dib, Nihad I.; Katehi, Linda P. B.; Gupta, Minoo; Ponchak, George E.

    1993-01-01

    A general technique to characterize asymmetric coplanar waveguide (CPW) discontinuities with air bridges where both the fundamental coplanar and slotline modes may be excited together is presented. First, the CPW discontinuity without air bridges is analyzed using the space-domain integral equation (SDIE) approach. Second, the parameters (phase, amplitude, and wavelength) of the coplanar and slotline modes are extracted from an amplitude modulated-like standing wave existing in the CPW feeding lines. Then a 2n x 2n generalized scattering matrix of the n-port discontinuity without air bridges is derived which includes the occurring mode conversion. Finally, this generalized scattering matrix is reduced to an n x n matrix by enforcing suitable conditions at the ports which correspond to the excited slotline mode. For the purpose of illustration, the method is applied to a shielded asymmetric short-end CPW shunt stub, the scattering parameters of which are compared with those of a symmetric one. Experiments are performed on both discontinuities and the results are in good agreement with theoretical data. The advantages of using air bridges in CPW circuits as opposed to bond wires are also discussed.

  3. 27 CFR 18.38 - Permanent discontinuance.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Permanent discontinuance. 18.38 Section 18.38 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS PRODUCTION OF VOLATILE FRUIT-FLAVOR CONCENTRATE Qualification...

  4. 27 CFR 18.38 - Permanent discontinuance.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Permanent discontinuance. 18.38 Section 18.38 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS PRODUCTION OF VOLATILE FRUIT-FLAVOR CONCENTRATE Qualification...

  5. 77 FR 33314 - POSTNET Barcode Discontinuation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-06

    ... Postal Service published a final rule in the Federal Register (77 FR 26185-26191) to discontinue price... Periodicals automation letters and flats) that were inadvertently omitted in the original final rule, but does... and allow only Intelligent Mail barcodes (IMbs) for automation price eligibility purposes,...

  6. Nonrenewable resource extraction under discontinuous price policy

    SciTech Connect

    Kalt, J.P.; Otten, A.L.

    1985-01-01

    Temporal discontinuities in public policy with respect to nonrenewable resource pricing can have significant impacts on the time patterns of resource extraction. These impacts arise from the effect of price discontinuities on the relative values of Hotelling rents across time periods. Whether faced with intertemporal price continuity or price discontinuity, the planning task of the wealth-maximizing producer is to equate the present value of each period's marginal contribution to the stream of net revenues from production across time. This rule for extraction provides the key to understanding the response to a price jump such as occurs upon the removal of price controls. The rational producer holds back at least some output until the price jump occurs. At the moment, the producer pushes output up sharply, raising marginal extraction cost by the absolute amount of the price jump and, thereby, maintaining the value of the Hotelling rent given by the gap between price and marginal extraction cost. US natural gas policy options, as well as plausible alternatives, are simulated to illustrate the effects of discontinuous regulatory regimes. 15 references, 1 table.

  7. Discontinued drugs in 2010: cardiovascular drugs.

    PubMed

    Zhao, Hong-ping; Zhang, Xu-song; Xiang, Bing-ren

    2011-10-01

    This perspective is a paper discussing drugs dropped from clinical development in the previous years. Specifically, this paper focuses on 16 cardiovascular drugs discontinued in 2010 after reaching Phase I - III clinical trials. Information for this perspective is mainly derived from a search of Pharmaprojects. PMID:21870899

  8. Active seismic experiment

    NASA Technical Reports Server (NTRS)

    Kovach, R. L.; Watkins, J. S.; Talwani, P.

    1972-01-01

    The Apollo 16 active seismic experiment (ASE) was designed to generate and monitor seismic waves for the study of the lunar near-surface structure. Several seismic energy sources are used: an astronaut-activated thumper device, a mortar package that contains rocket-launched grenades, and the impulse produced by the lunar module ascent. Analysis of some seismic signals recorded by the ASE has provided data concerning the near-surface structure at the Descartes landing site. Two compressional seismic velocities have so far been recognized in the seismic data. The deployment of the ASE is described, and the significant results obtained are discussed.

  9. In-process discontinuity detection during friction stir welding

    NASA Astrophysics Data System (ADS)

    Shrivastava, Amber

    The objective of this work is to develop a method for detecting the creation of discontinuities (e.g., voids) during friction stir welding. Friction stir welding is inherently cost-effective, however, the need for significant weld inspection can make the process cost-prohibitive. A new approach to weld inspection is required -- where an in-situ characterization of weld quality can be obtained, reducing the need for post-process inspection. Friction stir welds with discontinuity and without discontinuity were created. In this work, discontinuities are generated by reducing the friction stir tool rotation frequency and increasing the tool traverse speed in order to create "colder" welds. During the welds, forces are measured. Discontinuity sizes for welds are measured by computerized tomography. The relationship between the force transients and the discontinuity sizes indicate that the force measurement during friction stir welding can be effectively used for detecting discontinuities in friction stir welds. The normalized force transient data and normalized discontinuity size are correlated to develop a criterion for discontinuity detection. Additional welds are performed to validate the discontinuity detection method. The discontinuity sizes estimated by the force measurement based method are in good agreement with the discontinuity sizes measured by computerized tomography. These results show that the force measurement based discontinuity detection model method can be effectively used to detect discontinuities during friction stir welding.

  10. Plumes and Drips Beneath Northeast China and the Western United States (Invited)

    NASA Astrophysics Data System (ADS)

    Grand, S. P.; Tang, Y.; Niu, F.; Obayashi, M.; Chen, Y. J.; Kawakatsu, H.; Ning, J.; Ni, J.

    2013-12-01

    Northeast China and the western United States share common features in their tectonic history. Both regions experienced compressional tectonics and mountain building due to stresses induced by subduction processes on their boundaries. In Northeast China these events occurred in the Mesozoic and in the western United States a little later, up to the early Cenozoic. Subsequently, both regions experienced extension and widespread intraplate magmatism as the boundary conditions changed. We review the results from several seismic investigations for both regions and compare results. The NECESS project was a multi-national collaboration that consisted of the deployment of 140 broadband seismic stations across Northeast China. P and S wave tomography, receiver function analysis, and surface wave dispersion inversions were conducted to image the seismic structure of the upper mantle beneath the region. Fast seismic velocities from 500 to 660 km depth and a depressed 660 km discontinuity were found below the eastern edge of Northeast China. These observations are likely showing the subducting Pacific plate. At 420 latitude a gap in the deep transition zone fast velocities is observed coincident with an uplifted 660 km discontinuity. The shear wave tomography image shows a roughly 200 km diameter slow anomaly that can be traced from just below the gap in high velocities at 660 km depth to the shallow mantle beneath the Changbaishan volcanic field. We propose the gap in the deep slabs is a pathway for return flow upwelling that results in surface volcanism. Such deep upwelling at edges or gaps in deep slabs may be a common feature in subduction environments. In the shallow mantle strong lateral variations in velocity are seen across Northeast China that are associated with Cenozoic volcanic zones. Beneath a portion of the Xing'an mountains at 1160 longitude, a shallow slow anomaly associated with Pleistocene volcanism is adjacent to a high velocity anomaly at depths below 200

  11. Seismic characteristics of central Brazil crust and upper mantle: A deep seismic refraction study

    USGS Publications Warehouse

    Soares, J.E.; Berrocal, J.; Fuck, R.A.; Mooney, W.D.; Ventura, D.B.R.

    2006-01-01

    A two-dimensional model of the Brazilian central crust and upper mantle was obtained from the traveltime interpretation of deep seismic refraction data from the Porangatu and Cavalcante lines, each approximately 300 km long. When the lines were deployed, they overlapped by 50 km, forming an E-W transect approximately 530 km long across the Tocantins Province and western Sa??o Francisco Craton. The Tocantins Province formed during the Neoproterozoic when the Sa??o Francisco, the Paranapanema, and the Amazon cratons collided, following the subduction of the former Goia??s ocean basin. Average crustal VP and VP/VS ratios, Moho topography, and lateral discontinuities within crustal layers suggest that the crust beneath central Brazil can be associated with major geological domains recognized at the surface. The Moho is an irregular interface, between 36 and 44 km deep, that shows evidences of first-order tectonic structures. The 8.05 and 8.23 km s-1 P wave velocities identify the upper mantle beneath the Porangatu and Cavalcante lines, respectively. The observed seismic features allow for the identification of (1) the crust has largely felsic composition in the studied region, (2) the absence of the mafic-ultramafic root beneath the Goia??s magmatic arc, and (3) block tectonics in the foreland fold-and-thrust belt of the northern Brasi??lia Belt during the Neoproterozoic. Seismic data also suggested that the Bouguer gravimetric discontinuities are mainly compensated by differences in mass distribution within the lithospheric mantle. Finally, the Goia??s-Tocantins seismic belt can be interpreted as a natural seismic alignment related to the Neoproterozoic mantle domain. Copyright 2006 by the American Geophysical Union.

  12. Crust and mantle discontinuities, shear wave velocity structure, and azimuthal anisotropy beneath North America

    NASA Astrophysics Data System (ADS)

    Li, Aibing

    This thesis contains four chapters which investigate seismic discontinuity structure and shear wave velocity structure in the crust and upper mantle beneath the eastern and western edges of the North American craton. In chapters one and two, we imaged the Moho and discontinuities in the upper mantle and transition zone by stacking P to S converted phases on receiver functions recorded at the MOMA array in the eastern United States. The most interesting result is the relatively flat "410" discontinuity, which suggests that the North American lithospheric keel and any associated cold downwelling is largely confined in the upper mantle. A ˜20 km depression on the "660" discontinuity to southwest of the array may pinpoint the location of the subducted Farallon plate in the deep transition zone. Moho depth varies from 30 km to 49 km across the array, and a discontinuity observed at depths of 280 km to 320 km is most plausibly explained as the base of a low velocity zone. In chapters three and four, we applied a surface wave inversion technique to the northeastern United States and to the Colorado Rocky Mountain region. Azimuthally anisotropic phase velocities were obtained and then inverted for shear wave velocity structure. The North American lithospheric keel is imaged with high velocity anomalies in both study areas. Keel morphology is complex at its eastern edge, possibly reflecting erosion by a mantle plume. Strong velocity variations in the crust and shallow upper mantle across the Rocky Mountain region indicate that the mountains are supported by both crustal and mantle buoyancy. The strength of anisotropy increases with period beneath the keel in the east and beneath the central Rockies in the west, suggesting a highly anisotropic asthenosphere and mechanical decoupling between the lithosphere and deeper mantle.

  13. Stress channelling and partitioning of seismicity in the Charlevoix seismic zone, Québec, Canada

    NASA Astrophysics Data System (ADS)

    Baird, Alan F.; McKinnon, Stephen D.; Godin, Laurent

    2009-10-01

    The Charlevoix seismic zone (CSZ) in the St Lawrence valley of Québec is historically the most active in eastern Canada. The structurally complex region comprises rift faults formed during the opening of the Iapetus Ocean, superimposed by a 350 Ma meteorite impact structure, resulting in a circular highly fractured zone. Although seismicity is localized along two steeply dipping planar rift-parallel zones, previous work indicates that most of the large-scale rift faults bound the low magnitude background seismicity rather than generate earthquakes themselves. In order to gain insight into the mechanics of the partitioning of this seismicity, a 2-D model of the CSZ was built using the stress analysis code FLAC. The rift faults are represented by frictional discontinuities. The heavily fractured impact structure is represented by an elastic continuum of reduced modulus. Boundary displacements are used to generate a regional stress field with the major horizontal component in the direction of tectonic loading. Given a high strength, the rift faults have little effect on the stress patterns. Stress trajectories naturally flow around the crater of reduced elastic modulus, leaving the fractured area with lower stresses than the background level. However, when the rift faults have low strength, they are unable to support stress trajectories inclined to them, due to the resolved shear stress exceeding their strength. This prevents trajectories from flowing out of the rift, effectively channelling higher magnitude stresses into the region of the impact structure between the faults. Low-strength bounding faults can thus explain the localization of seismicity into linear bands, rather than distributed seismicity throughout the impact structure. It also explains how the rift faults act as boundaries to regions of low magnitude seismicity. These results indicate that the interplay between faults of varying strength and zones of differing elastic modulus can give rise to

  14. Global study of great (M>= 7) deep focus seismic events having regard to the May 24, 2013 Mw 8.3 earthquake the Sea of Okhotsk, Russia

    NASA Astrophysics Data System (ADS)

    Varga, Peter; Rogozhin, Evgeny; Süle, Bálint; Andreeva, Nadezda

    2014-05-01

    Distribution of great seismic events M >= 7.0 and consequently the released seismic energy along the Earth radius is of bimodal character. 90% of the great seismic events, which are responsible for the most of energy released, occur relatively close to the Earth's surface, at an average depth of 50 km. The vast majority of remaining 10% is associated with seismic events that occur very deep, an average of 580-590 km, above the border between transition zone and lower mantle (660 km). These very deep earthquakes (depth >= 500 km) differ significantly from the shallow events. For the study of the distribution of M >= 7.0 earthquakes and their radiated energy a catalogue was completed for the time-interval between 1900 and 2013. Examination of the source zones in which both shallow and deep M >= 7.0 earthquakes occur shows that linear distribution of deep earthquakes is considerably shorter than that found for the shallow earthquakes, which determine the length of the zone. The position of very deep (≥ 500 km) earthquakes foci show where the down going lithosperic plates conflict with the upper boundary of lower mantle, and where they probably cross it. This passage generates compression - elongation inside the slab. A comparison of temporal distribution of shallow and deep seismic events of a given source zone suggests that there is no direct relationship in the distribution of these two different earthquake activities. The largest of these great deep earthquakes, the May 24, 2013 Mw 8.3 earthquake the Sea of Okhotsk, was preceded by an earthquake swarm, which consists 58 M >= 5 events and occurred between May 15 and 24, 2013 in the higher part of the sinking slab east of Kamchatka. The aftershock activity after the Okhotsk Sea earthquake was moderate: twelve events with magnitudes above M 4 were observed till June 27. These events determine a fault area (2.64x104 km2) similar to the case of a shallow M 8.3 event. The effect of Okhotsk Sea was felt throughout

  15. Seismic intrusion detector system

    DOEpatents

    Hawk, Hervey L.; Hawley, James G.; Portlock, John M.; Scheibner, James E.

    1976-01-01

    A system for monitoring man-associated seismic movements within a control area including a geophone for generating an electrical signal in response to seismic movement, a bandpass amplifier and threshold detector for eliminating unwanted signals, pulse counting system for counting and storing the number of seismic movements within the area, and a monitoring system operable on command having a variable frequency oscillator generating an audio frequency signal proportional to the number of said seismic movements.

  16. An adaptive pseudospectral method for discontinuous problems

    NASA Technical Reports Server (NTRS)

    Augenbaum, Jeffrey M.

    1988-01-01

    The accuracy of adaptively chosen, mapped polynomial approximations is studied for functions with steep gradients or discontinuities. It is shown that, for steep gradient functions, one can obtain spectral accuracy in the original coordinate system by using polynomial approximations in a transformed coordinate system with substantially fewer collocation points than are necessary using polynomial expansion directly in the original, physical, coordinate system. It is also shown that one can avoid the usual Gibbs oscillation associated with steep gradient solutions of hyperbolic pde's by approximation in suitably chosen coordinate systems. Continuous, high gradient solutions are computed with spectral accuracy (as measured in the physical coordinate system). Discontinuous solutions associated with nonlinear hyperbolic equations can be accurately computed by using an artificial viscosity chosen to smooth out the solution in the mapped, computational domain. Thus, shocks can be effectively resolved on a scale that is subgrid to the resolution available with collocation only in the physical domain. Examples with Fourier and Chebyshev collocation are given.

  17. Discontinuous percolation transitions in real physical systems

    NASA Astrophysics Data System (ADS)

    Cho, Y. S.; Kahng, B.

    2011-11-01

    We study discontinuous percolation transitions (PTs) in the diffusion-limited cluster aggregation model of the sol-gel transition as an example of real physical systems, in which the number of aggregation events is regarded as the number of bonds occupied in the system. When particles are Brownian, in which cluster velocity depends on cluster size as vs˜sη with η=-0.5, a larger cluster has less probability to collide with other clusters because of its smaller mobility. Thus, the cluster is effectively more suppressed in growth of its size. Then the giant cluster size increases drastically by merging those suppressed clusters near the percolation threshold, exhibiting a discontinuous PT. We also study the tricritical behavior by controlling the parameter η, and the tricritical point is determined by introducing an asymmetric Smoluchowski equation.

  18. Discontinuous envelope function in semiconductor heterostructures

    NASA Astrophysics Data System (ADS)

    Drouhin, Henri-Jean; Bottegoni, Federico; Nguyen, T. L. Hoai; Wegrowe, Jean-Eric; Fishman, Guy

    2013-09-01

    Based on a proper definition of the current operators for non-quadratic Hamiltonians, we derive the expression for the transport current which involves the derivative of the imaginary part of the free-electron current, highlighting peculiarities of the extra terms. The expression of the probability current, when Spin-Orbit Interaction (SOI) is taken into account, requires a reformulation of the boudary conditions. This is especially important for tunnel heterojunctions made of non-centrosymmetric semiconductors. Therefore, we consider a model case: tunneling of conduction electrons through a [110]-oriented GaAs barrier. The new boundary conditions are reduced to two set of equations: the first one expresses the discontinuity of the envelope function at the interface while the other one expresses the discontinuity of the derivative of the envelope function.

  19. Bounded extremum seeking with discontinuous dithers

    DOE PAGES

    Scheinker, Alexander; Scheinker, David

    2016-03-21

    The analysis of discontinuous extremum seeking (ES) controllers, e.g. those applicable to digital systems, has historically been more complicated than that of continuous controllers. We establish a simple and general extension of a recently developed bounded form of ES to a general class of oscillatory functions, including functions discontinuous with respect to time, such as triangle or square waves with dead time. We establish our main results by combining a novel idea for oscillatory control with an extension of functional analytic techniques originally utilized by Kurzweil, Jarnik, Sussmann, and Liu in the late 80s and early 90s and recently studiedmore » by Durr et al. Lastly, we demonstrate the value of the result with an application to inverter switching control.« less

  20. Constant-force approach to discontinuous potentials.

    PubMed

    Orea, Pedro; Odriozola, Gerardo

    2013-06-01

    Aiming to approach the thermodynamical properties of hard-core systems by standard molecular dynamics simulation, we propose setting a repulsive constant-force for overlapping particles. That is, the discontinuity of the pair potential is replaced by a linear function with a large negative slope. Hence, the core-core repulsion, usually modeled with a power function of distance, yields a large force as soon as the cores slightly overlap. This leads to a quasi-hardcore behavior. The idea is tested for a triangle potential of short range. The results obtained by replica exchange molecular dynamics for several repulsive forces are contrasted with the ones obtained for the discontinuous potential and by means of replica exchange Monte Carlo. We found remarkable agreements for the vapor-liquid coexistence densities as well as for the surface tension.

  1. Global Seismic Imaging of the Lithosphere Asthenosphere Boundary

    NASA Astrophysics Data System (ADS)

    Tharimena, S.; Rychert, C.; Harmon, N.

    2015-12-01

    The lithosphere asthenosphere boundary (LAB) beneath oceans separates rigid, conductively cooling plates from the underlying warm ductile convecting mantle, characterized by low seismic wave velocities and high attenuation. The depth and nature of the lithosphere asthenosphere boundary is fundamental to our understanding of plate tectonics and mantle convection. Although conductive cooling models establish that oceanic lithosphere cools, thickens and subsides as it ages, this simple realization of the tectonic plates is not well understood. The depth, sharpness, composition and defining mechanism of the LAB remains elusive. Although oceanic lithosphere constitutes the bulk of the tectonic plates, precisely imaging the LAB has proved challenging. Here we use SS precursors from 25 years of seismic data to image and globally map the depth of the LAB across the Pacific, Atlantic and Indian Oceans. The result represents a vast improvement in lateral coverage of discontinuities in comparison to previous results. The depth of the discontinuity varies from 25 to 130 km within an error of ±5 km. We observe a general trend of increasing discontinuity depth with plate age, although some old oceanic lithosphere has shallower discontinuities. Overall, the results are suggestive of two distinct mantle layers.

  2. Elastic wave propagation in variable media using a discontinuous Galerkin method.

    SciTech Connect

    Ober, Curtis Curry; Smith, Thomas Michael; Collis, Samuel Scott; Overfelt, James Robert; Schwaiger, Hans

    2010-04-01

    Motivated by the needs of seismic inversion and building on our prior experience for fluid-dynamics systems, we present a high-order discontinuous Galerkin (DG) Runge-Kutta method applied to isotropic, linearized elasto-dynamics. Unlike other DG methods recently presented in the literature, our method allows for inhomogeneous material variations within each element that enables representation of realistic earth models - a feature critical for future use in seismic inversion. Likewise, our method supports curved elements and hybrid meshes that include both simplicial and nonsimplicial elements. We demonstrate the capabilities of this method through a series of numerical experiments including hybrid mesh discretizations of the Marmousi2 model as well as a modified Marmousi2 model with a oscillatory ocean bottom that is exactly captured by our discretization. A discontinuous Galerkin method for solving the equations of linear isotropic elasticity has been presented. The formulation is designed to accommodate variation of media parameters within elements, curved elements and unstructured heterogeneous meshes. We have demonstrated that each of these important features of the formulation can produce results that are significantly different from formulations that do not possess these capabilities suggesting that each of these capabilities may be important for effective full waveform inversion of elastic medium.

  3. Accelerated Transonic Flow past a curvature discontinuity

    NASA Astrophysics Data System (ADS)

    de Cointet, Thomas; Ruban, Anatoly

    2014-11-01

    The aim of this talk is to investigate High Reynolds number Transonic flow past a discontinuity in body curvature. Starting with the inviscid flow outside the boundary layer, our analysis will focus on the flow in a vicinity of the point of discontinuity, where a solution of the Euler equations will be sought in self-similar form. This reduces the Euler equations to an ordinary differential equation. The analysis of this equation shows that the pressure gradient on the airfoil surface develops a strong singularity, which is proportional to (x0 - x) - 1 / 3 as the discontinuity point x0 is approached. We then study the response of the boundary layer to this extremely favourable pressure gradient. We show that the boundary layer splits into two parts, the main body of the boundary layer that becomes inviscid on approach to the singularity, and a thin viscous sublayer situated near the wall. The analysis of the behaviour of the solution in the viscous sublayer shows that Prandtl's hierarchical concept breaks down in a small region surrounding the singular point, where the viscous-inviscid interaction model should be used. In the final part of this talk we present a full formulation of the viscous-inviscid interaction problem and discuss numerical results.

  4. Evidence for back scattering of near-podal seismic P'P' waves from the 150-220 km zone in Earth's upper mantle

    SciTech Connect

    Tkalcic, H; Flanagan, M P; Cormier, V F

    2005-07-15

    The deepest and most inaccessible parts of Earth's interior--the core and core-mantle boundary regions can be studied from compressional waves that turn in the core and are routinely observed following large earthquakes at epicentral distances between 145{sup o} and 180{sup o} (also called P', PKIKP or PKP waves). P'P' (PKPPKP) are P' waves that travel from a hypocenter through the Earth's core, reflect from the free surface and travel back through the core to a recording station on the surface. P'P' waves are sometimes accompanied by precursors, which were reported first in the 1960s as small-amplitude arrivals on seismograms at epicentral distances of about 50{sup o}-70{sup o}. Most prominent of these observed precursors were explained by P'P' waves generated by earthquakes or explosions that did not reach the Earth's surface but were reflected from the underside of first order velocity discontinuities at 410 and 660 km in the upper mantle mantle. Here we report the discovery of hitherto unobserved near-podal P'P' waves (at epicentral distance less than 10{sup o}) and very prominent precursors preceding the main energy by as much as 55 seconds. We interpret these precursors as a back scattered energy from undocumented structure in the upper mantle, in a zone between 150 and 220 km depth beneath Earth's surface. From these observations, we identify a frequency dependence of Q (attenuation quality factor) in the lithosphere that can be modeled by a flat relaxation spectrum below about 0.05-0.1 Hz and increasing with as the first power of frequency above this value, confirming pioneering work by B. Gutenberg.

  5. 14 CFR 221.300 - Discontinuation of electronic tariff system.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 4 2011-01-01 2011-01-01 false Discontinuation of electronic tariff system... of electronic tariff system. In the event that the electronic tariff system is discontinued, or the source of the data is changed, or a filer discontinues its business, all electronic data records prior...

  6. 14 CFR 221.300 - Discontinuation of electronic tariff system.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Discontinuation of electronic tariff system... of electronic tariff system. In the event that the electronic tariff system is discontinued, or the source of the data is changed, or a filer discontinues its business, all electronic data records prior...

  7. 27 CFR 46.138 - Discontinuance of business.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 2 2012-04-01 2011-04-01 true Discontinuance of business. 46.138 Section 46.138 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU....138 Discontinuance of business. A dealer who for any reason discontinues business is not entitled to...

  8. 27 CFR 46.138 - Discontinuance of business.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 2 2014-04-01 2014-04-01 false Discontinuance of business. 46.138 Section 46.138 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU....138 Discontinuance of business. A dealer who for any reason discontinues business is not entitled to...

  9. 27 CFR 31.162 - Discontinuance of business.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Discontinuance of business... and Reports § 31.162 Discontinuance of business. When a wholesale dealer in liquors who is required, under § 31.160, to file a monthly summary report discontinues business, a monthly summary report...

  10. Program Discontinuance: A Faculty Perspective Revisited. Adopted Fall 2012

    ERIC Educational Resources Information Center

    Academic Senate for California Community Colleges, 2012

    2012-01-01

    The 1998 Academic Senate for California Community Colleges paper Program Discontinuance: A Faculty Perspective presented issues of program discontinuance and addressed principles and key factors for effective faculty participation in the development of fair and equitable program discontinuance processes. In 2009, an Academic Senate resolution…

  11. 39 CFR 241.3 - Discontinuance of post offices.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 39 Postal Service 1 2010-07-01 2010-07-01 false Discontinuance of post offices. 241.3 Section 241... CLASSIFICATION, AND DISCONTINUANCE § 241.3 Discontinuance of post offices. (a) Introduction—(1) Coverage. This section establishes the rules governing the Postal Service's consideration of whether an existing...

  12. 27 CFR 555.61 - Discontinuance of business or operations.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... Permits § 555.61 Discontinuance of business or operations. Where an explosive materials business or operations is either discontinued or succeeded by a new owner, the owner of the business or operations... 27 Alcohol, Tobacco Products and Firearms 3 2013-04-01 2013-04-01 false Discontinuance of...

  13. 27 CFR 555.61 - Discontinuance of business or operations.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Permits § 555.61 Discontinuance of business or operations. Where an explosive materials business or operations is either discontinued or succeeded by a new owner, the owner of the business or operations... 27 Alcohol, Tobacco Products and Firearms 3 2014-04-01 2014-04-01 false Discontinuance of...

  14. Mohorovicic discontinuity depth analysis beneath North Patagonian Massif

    NASA Astrophysics Data System (ADS)

    Gómez Dacal, M. L.; Tocho, C.; Aragón, E.

    2013-05-01

    The North Patagonian Massif is a 100000 km2, sub-rectangular plateau that stands out 500 to 700 m higher in altitude than the surrounding topography. The creation of this plateau took place during the Oligocene through a sudden uplift without noticeable internal deformation. This quite different mechanical response between the massif and the surrounding back arc, the short time in which this process took place and a regional negative Bouguer anomaly in the massif area, raise the question about the isostatic compensation state of the previously mentioned massif. In the present work, a comparison between different results about the depth of the Mohorovicic discontinuity beneath the North Patagonian Massif and a later analysis is made. It has the objective to analyze the crustal thickness in the area to contribute in the determination of the isostatic balance and the better understanding of the Cenozoic evolution of the mentioned area. The comparison is made between four models; two of these were created with seismic information (Feng et al., 2006 and Bassin et al., 2000), another model with gravity information (Barzaghi et al., 2011) and the last one with a combination of both techniques (Tassara y Etchaurren, 2011). The latter was the result of the adaptation to the work area of a three-dimensional density model made with some additional information, mainly seismic, that constrain the surfaces. The work of restriction and adaptation of this model, the later analysis and comparison with the other three models and the combination of both seismic models to cover the lack of resolution in some areas, is presented here. According the different models, the crustal thickness of the study zone would be between 36 and 45 Km. and thicker than the surrounding areas. These results talk us about a crust thicker than normal and that could behave as a rigid and independent block. Moreover, it can be observed that there are noticeable differences between gravimetric and seismic

  15. Visualization, Extraction and Quantification of Discontinuities in Compressible Flows

    NASA Technical Reports Server (NTRS)

    Samtaney, Ravi; Morris, R. D.; Cheeseman, P.; Sunelyansky, V.; Maluf, D.; Wolf, D.

    2000-01-01

    Scientific visualizations of two-dimensional compressible flow of a gas with discontinuities are presented. The numerical analogue to experimental techniques such as schlieren imaging, shadowgraphs, and interferograms are discussed. Edge detection techniques are utilized to identify the discontinuities. In particular, the zero crossing of the Laplacian of a field (usually density) is recommended for extracting the discontinuities. An algorithm to extract and quantify the discontinuities is presented. To illustrate the methods developed in the report, the example chosen is that of an unsteady interaction of a shock wave with a contact discontinuity.

  16. Seismic Migration Imaging of the Lithosphere beneath the Afar Rift System, East Africa

    NASA Astrophysics Data System (ADS)

    Lee, T. T. Y.; Chen, C. W.; Rychert, C.; Harmon, N.

    2015-12-01

    The Afar Rift system in east Africa is an ideal natural laboratory for investigating the incipient continental rifting, an essential component of plate tectonics. The Afar Rift is situated at the triple junction of three rifts, namely the southern Red Sea Rift, Gulf of Aden Rift and Main Ethiopian Rift (MER). The ongoing continental rifting at Afar transitions to seafloor spreading toward the southern Red Sea. The tectonic evolution of Afar is thought to be influenced by a mantle plume, but how the plume affects and interacts with the Afar lithosphere remains elusive. In this study, we use array seismic data to produce high-resolution migration images of the Afar lithosphere from scattered teleseismic wavefields to shed light on the lithospheric structure and associated tectonic processes. Our preliminary results indicate the presence of lithospheric seismic discontinuities with depth variation across the Afar region. Beneath the MER axis, we detect a pronounced discontinuity at 55 km depth, characterized by downward fast-to-slow velocity contrast, which appears to abruptly deepen to 75 km depth to the northern flank of MER. This discontinuity may be interpreted as the lithosphere-asthenosphere boundary. Beneath the Ethiopian Plateau, on the other hand, a dipping structure with velocity increase is identified at 70-90 km depth. Further synthesis of observations from seismic tomography, receiver functions, and seismic anisotropy in the Afar region will offer better understanding of tectonic significance of the lithospheric discontinuities.

  17. Angola Seismicity MAP

    NASA Astrophysics Data System (ADS)

    Neto, F. A. P.; Franca, G.

    2014-12-01

    The purpose of this job was to study and document the Angola natural seismicity, establishment of the first database seismic data to facilitate consultation and search for information on seismic activity in the country. The study was conducted based on query reports produced by National Institute of Meteorology and Geophysics (INAMET) 1968 to 2014 with emphasis to the work presented by Moreira (1968), that defined six seismogenic zones from macro seismic data, with highlighting is Zone of Sá da Bandeira (Lubango)-Chibemba-Oncócua-Iona. This is the most important of Angola seismic zone, covering the epicentral Quihita and Iona regions, geologically characterized by transcontinental structure tectono-magmatic activation of the Mesozoic with the installation of a wide variety of intrusive rocks of ultrabasic-alkaline composition, basic and alkaline, kimberlites and carbonatites, strongly marked by intense tectonism, presenting with several faults and fractures (locally called corredor de Lucapa). The earthquake of May 9, 1948 reached intensity VI on the Mercalli-Sieberg scale (MCS) in the locality of Quihita, and seismic active of Iona January 15, 1964, the main shock hit the grade VI-VII. Although not having significant seismicity rate can not be neglected, the other five zone are: Cassongue-Ganda-Massano de Amorim; Lola-Quilengues-Caluquembe; Gago Coutinho-zone; Cuima-Cachingues-Cambândua; The Upper Zambezi zone. We also analyzed technical reports on the seismicity of the middle Kwanza produced by Hidroproekt (GAMEK) region as well as international seismic bulletins of the International Seismological Centre (ISC), United States Geological Survey (USGS), and these data served for instrumental location of the epicenters. All compiled information made possible the creation of the First datbase of seismic data for Angola, preparing the map of seismicity with the reconfirmation of the main seismic zones defined by Moreira (1968) and the identification of a new seismic

  18. General spline filters for discontinuous Galerkin solutions

    PubMed Central

    Peters, Jörg

    2015-01-01

    The discontinuous Galerkin (dG) method outputs a sequence of polynomial pieces. Post-processing the sequence by Smoothness-Increasing Accuracy-Conserving (SIAC) convolution not only increases the smoothness of the sequence but can also improve its accuracy and yield superconvergence. SIAC convolution is considered optimal if the SIAC kernels, in the form of a linear combination of B-splines of degree d, reproduce polynomials of degree 2d. This paper derives simple formulas for computing the optimal SIAC spline coefficients for the general case including non-uniform knots. PMID:26594090

  19. Discontinuous Galerkin methods for extended hydrodynamics

    NASA Astrophysics Data System (ADS)

    Suzuki, Yoshifumi

    This dissertation presents a step towards high-order methods for continuum-transition flows. In order to achieve maximum accuracy and efficiency for numerical methods on a distorted mesh, it is desirable that both governing equations and corresponding numerical methods are in some sense compact. We argue our preference for a physical model described solely by first-order partial differential equations called hyperbolic-relaxation equations, and, among various numerical methods, for the discontinuous Galerkin method. Hyperbolic-relaxation equations can be generated as moments of the Boltzmann equation and can describe continuum-transition flows. Two challenging properties of hyperbolic-relaxation equations are the presence of a stiff source term, which drives the system towards equilibrium, and the accompanying change of eigenstructure. The first issue can be solved by an implicit treatment of the source term. To cope with the second difficulty, we develop a space-time discontinuous Galerkin method, based on Huynh's "upwind moment scheme." It is called the DG(1)--Hancock method. The DG(1)--Hancock method for one- and two-dimensional meshes is described, and Fourier analyses for both linear advection and linear hyperbolic-relaxation equations are conducted. The analyses show that the DG(1)--Hancock method is not only accurate but efficient in terms of turnaround time in comparison to other semi- and fully discrete finite-volume and discontinuous Galerkin methods. Numerical tests confirm the analyses, and also show the properties are preserved for nonlinear equations; the efficiency is superior by an order of magnitude. Subsequently, discontinuous Galerkin and finite-volume spatial discretizations are applied to more practical equations, in particular, to the set of 10-moment equations, which are gas dynamics equations that include a full pressure/temperature tensor among the flow variables. Results for flow around a micro-airfoil are compared to experimental data and

  20. Dynamic Rupture Modeling in Three Dimensions on Unstructured Meshes Using a Discontinuous Galerkin Method

    NASA Astrophysics Data System (ADS)

    Pelties, C.; Käser, M.

    2010-12-01

    We will present recent developments concerning the extensions of the ADER-DG method to solve three dimensional dynamic rupture problems on unstructured tetrahedral meshes. The simulation of earthquake rupture dynamics and seismic wave propagation using a discontinuous Galerkin (DG) method in 2D was recently presented by J. de la Puente et al. (2009). A considerable feature of this study regarding spontaneous rupture problems was the combination of the DG scheme and a time integration method using Arbitrarily high-order DERivatives (ADER) to provide high accuracy in space and time with the discretization on unstructured meshes. In the resulting discrete velocity-stress formulation of the elastic wave equations variables are naturally discontinuous at the interfaces between elements. The so-called Riemann problem can then be solved to obtain well defined values of the variables at the discontinuity itself. This is in particular valid for the fault at which a certain friction law has to be evaluated. Hence, the fault’s geometry is honored by the computational mesh. This way, complex fault planes can be modeled adequately with small elements while fast mesh coarsening is possible with increasing distance from the fault. Due to the strict locality of the scheme using only direct neighbor communication, excellent parallel behavior can be observed. A further advantage of the scheme is that it avoids spurious high-frequency contributions in the slip rate spectra and therefore does not require artificial Kelvin-Voigt damping or filtering of synthetic seismograms. In order to test the accuracy of the ADER-DG method the Southern California Earthquake Center (SCEC) benchmark for spontaneous rupture simulations was employed. Reference: J. de la Puente, J.-P. Ampuero, and M. Käser (2009), Dynamic rupture modeling on unstructured meshes using a discontinuous Galerkin method, JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 114, B10302, doi:10.1029/2008JB006271

  1. Crustal Deformation Styles Along the Reprocessed Deep Seismic Reflection Transect of the Central Iberian Zone (Iberian Peninsula)

    NASA Astrophysics Data System (ADS)

    Ehsan, Siddique Akhtar; Carbonell, Ramon; Ayarza, Puy; Marti, David; Martinez-Poyatos, David; Simancas, Jose Fernando; Azor, Antonio; Marzan, Ignacio; Mansilla, Luis; Perez-Estaun, Andres

    2014-05-01

    The multichannel normal incidence deep seismic reflection profile ALCUDIA was acquired in summer 2007 and is 230 km long. This transect samples an intracontinental Variscan orogenic crust going across, from north to south, the major crustal domain (the Central Iberian Zone) and a suture zone with the Ossa-Morena Zone (the Central Unit) that build up the southwestern part of the Iberian Peninsula basement. The multichannel deep seismic high resolution (60-90 fold) profile images 20 s (TWTT), about 70 km depth. The reassessment of this data aims to provide better structural constraints on the shallow and deep structures. The ALCUDIA seismic image shows an upper crust c. 13 km thick decoupled from the comparatively reflective lower crust. The shallow reflectivity of the upper crust can be correlated with surface geological features mapped in the field whereas the deep reflectivity suggests imbricate thrust systems and listric extensional faults. The reflectivity of the mid-lower crust is relatively continuous, revealing high amplitude, and horizontal to arcuate reflection events delineating boudinage shaped geometries. A transpressional flower structure can be interpreted from the seismic image which involves a subcrustal mantle wedge. The ALCUDIA seismic image reveals a laminated c. 1.5 km thick, subhorizontal to flat Moho indicating an average crustal thickness of 31-33 km. The seismic signature of the Moho varies along the transect being highly reflective beneath the Central Iberian Zone (CIZ) and discontinuous and diffuse below the Ossa-Morena Zone (OMZ). The gravity response across the ALCUDIA transect suggests relatively high density bodies in the mid-lower crust of the southern half of the transect. The seismic results suggest two major horizontal limits/discontinuities, a horizontal discontinuity at c. 13-15 km (the Conrad discontinuity) and the Moho discontinuity located at a depth of c. 31 km.

  2. Gran Canaria temporary broadband seismic network: an study of the seismicity and Earth structure

    NASA Astrophysics Data System (ADS)

    Almendros, Javier; de Lis Mancilla, Flor; Martinez-Arevalo, Carmen; Carmona, Enrique; Sanchez, Nieves; Heit, Benjamin; Garcia, Alicia; Martin-Leon, Rosa; Buontempo, Luisa; Yuan, Xiahoui

    2010-05-01

    The present project is a joint effort between different institutions to deploy a dense seismic network at Gran Canaria island (Canary Islands, Spain). The interstation distance is around 20 km. The broadband seismic network is composed of one permanent (Guralp CMG-3T 120 s) and five temporary stations (Guralp CMG-3ESP 60 s). The permanent station is a 120 s Guralp CMG-3T and belongs to the Canary Island Seismic Network, run by the Instituto Geográfico Nacional (IGN) of Spain. The temporary stations are 60 s Guralp CMG-3ESP, provided by the GFZ seismic pool. The deployment was carried out in December 2009. The stations will be recording during two years. The improvement of the seismic network allow us to tackle the following issues: the detection and analysis of any local seismicity of tectonic and/or volcanic origin at Gran Canaria island; to contribute to the understanding of the regional seismicity with special interest in the oceanic channel between Tenerife and Gran Canaria Island in collaboration with a project running a dense temporary seismic network in Tenerife; to study the crustal and upper mantle structure, under Gran Canaria to constrain the crustal structure, the source of the volcanism, and better sample the mantle discontinuities and anisotropy. To study the Earth structure, we use receiver function analysis, ambient seismic noise and SKS anisotropy techniques, This project is part of a long-term research of the crustal and the mantle structure of the Canary Islands, which has started with Gran Canaria and Tenerife Islands and will eventually continue with the rest of the archipelago. The origin of the Canary Islands is generally attributed to a broad mantle upwelling under a slow moving plate, resulting in spatially and temporally distributed volcanic activity and a large number of seamounts and islands. A controversial discussion has been going on about the factors that control the evolution of the volcanic edifices, the type of the melting

  3. Seismic response of rock slopes: Numerical investigations on the role of internal structure

    NASA Astrophysics Data System (ADS)

    Arnold, L.; Applegate, K.; Gibson, M.; Wartman, J.; Adams, S.; Maclaughlin, M.; Smith, S.; Keefer, D. K.

    2013-12-01

    The stability of rock slopes is significantly influenced and often controlled by the internal structure of the slope created by such discontinuities as joints, shear zones, and faults. Under seismic conditions, these discontinuities influence both the resistance of a slope to failure and its response to dynamic loading. The dynamic response, which can be characterized by the slope's natural frequency and amplification of ground motion, governs the loading experienced by the slope in a seismic event and, therefore, influences the slope's stability. In support of the Network for Earthquake Engineering Simulation (NEES) project Seismically-Induced Rock Slope Failure: Mechanisms and Prediction (NEESROCK), we conducted a 2D numerical investigation using the discrete element method (DEM) coupled with simple discrete fracture networks (DFNs). The intact rock mass is simulated with a bonded assembly of discrete particles, commonly referred to as the bonded-particle model (BPM) for rock. Discontinuities in the BPM are formed by the insertion of smooth, unbonded contacts along specified planes. The influence of discontinuity spacing, orientation, and stiffness on slope natural frequency and amplification was investigated with the commercially available Particle Flow Code (PFC2D). Numerical results indicate that increased discontinuity spacing has a non-linear effect in decreasing the amplification and increasing the natural frequency of the slope. As discontinuity dip changes from sub-horizontal to sub-vertical, the slope's level of amplification increases while the natural frequency of the slope decreases. Increased joint stiffness decreases amplification and increases natural frequency. The results reveal that internal structure has a strong influence on rock slope dynamics that can significantly change the system's dynamic response and stability during seismic loading. Financial support for this research was provided by the United States National Science Foundation (NSF

  4. Deep earthquakes beneath the Fiji Basin, SW Pacific: Earth's most intense deep seismicity in stagnant slabs

    USGS Publications Warehouse

    Okal, E.A.; Kirby, S.H.

    1998-01-01

    Previous work has suggested that many of the deep earthquakes beneath the Fiji Basin occur in slab material that has been detached and foundered to the bottom of the transition zone or has been laid down by trench migration in a similar recumbent position. Since nowhere else in the Earth do so many earthquakes occur in slabs stagnated in the transition zone, these earthquakes merit closer study. Accordingly, we have assembled from historical and modern data a comprehensive catalogue of the relocated hypocenters and focal mechanisms of well-located deep events in the geographic area between the bottoms of the main Vanuatu and Tonga Wadati-Benioff zones. Two regions of deep seismogenesis are recognized there: (i) 163 deep shocks have occurred north of 15??S in the Vityaz Group from 1949 to 1996. These seismological observations and the absence of other features characteristic of active subduction suggest that the Vityaz group represents deep failure in a detached slab that has foundered to a horizontal orientation near the bottom of the transition zone. (ii) Another group of nearly 50 'outboard' deep shocks occur between about 450 and 660 km depth, west of the complexly buckled and offset western edge of the Tonga Wadati-Benioff zone. Their geometry is in the form of two or possibly three small-circle arcs that roughly parallel the inferred motion of Tonga trench migration. Earthquakes in the southernmost of these arcs occur in a recumbent high-seismic-wavespeed slab anomaly that connects both to the main inclined Tonga anomaly to the east and a lower mantle anomaly to the west [Van der Hilst, R., 1995. Complex morphology of subducted lithosphere in the mantle beneath the Tonga trench. Nature, Vol. 374, pp. 154-157.]. Both groups show complexity in their focal mechanisms. The major question raised by these observations is the cause of this apparent temporary arrest in the descent of the Tonga slab into the lower mantle. We approach these questions by considering the

  5. Formation of magnetic discontinuities through viscous relaxation

    SciTech Connect

    Kumar, Sanjay; Bhattacharyya, R.; Smolarkiewicz, P. K.

    2014-05-15

    According to Parker's magnetostatic theorem, tangential discontinuities in magnetic field, or current sheets (CSs), are generally unavoidable in an equilibrium magnetofluid with infinite electrical conductivity and complex magnetic topology. These CSs are due to a failure of a magnetic field in achieving force-balance everywhere and preserving its topology while remaining in a spatially continuous state. A recent work [Kumar, Bhattacharyya, and Smolarkiewicz, Phys. Plasmas 20, 112903 (2013)] demonstrated this CS formation utilizing numerical simulations in terms of the vector magnetic field. The magnetohydrodynamic simulations presented here complement the above work by demonstrating CS formation by employing a novel approach of describing the magnetofluid evolution in terms of magnetic flux surfaces instead of the vector magnetic field. The magnetic flux surfaces being the possible sites on which CSs develop, this approach provides a direct visualization of the CS formation, helpful in understanding the governing dynamics. The simulations confirm development of tangential discontinuities through a favorable contortion of magnetic flux surfaces, as the magnetofluid undergoes a topology-preserving viscous relaxation from an initial non-equilibrium state with twisted magnetic field. A crucial finding of this work is in its demonstration of CS formation at spatial locations away from the magnetic nulls.

  6. Scaling behaviors at discontinuous quantum transitions

    NASA Astrophysics Data System (ADS)

    Nespolo, Jacopo; Campostrini, Massimo; Pelissetto, Andrea; Vicari, Ettore

    First-order (or discontinuous) quantum phase transitions (FOQTs) are characterized by a vanishing energy gap and jumps in the values of some observables across the critical point in the thermodynamic limit. Unlike what happens at continuous transitions, the correlation lengths remain finite at FOQTs. Nevertheless, finite systems at FOQTs exhibit finite-size effects, in the form of a rounding and smoothing of the discontinuities. We show that a scaling theory, similar to the usual finite-size scaling, can be formulated at FOQTs, and that the relevant scaling variable is extremely sensitive to the choice of boundary conditions. We further consider the scaling effects due to the presence of spatial inhomogeneities, in analogy with trap-size scaling at continuous transitions. Our results are supported by numerical simulations on the ferromagnetic quantum Ising chain and on the q-state quantum Potts chain with q > 4 . We provide FSS predictions for the energy gap and the magnetization of finite quantum chains, which can be relevant for quantum computation applications.

  7. Shock and Discontinuities Analysis Tool (SDAT)

    NASA Astrophysics Data System (ADS)

    Viñas, A. F.; Holland, M. P.

    2005-05-01

    We have developed an analysis/visualization tool to study shocks and other discontinuities from satellite observations of plasma and magnetic field data. The tool uses an extension of the Viñas-Scudder analysis method based on the Rankine-Hugoniot conservation equations and published in JGR (1985). SDAT provides shock parameters such as the normal components n, shock speed Us, angle between the normal and the upstream magnetic field ΘBn, Alfvén and magnetosonic Mach numbers, deHoffman-Teller velocity and many other important shock parameters to describe the shock . SDAT was developed fully in IDL. As currently configured, SDAT reads ASCII data from any space mission for the analysis. All data displays and graphics generated by SDAT are written in Postcript and a summary of the analysis is generated as an ASCII file. The input plasma (ρ, V, Tp and Te) and magnetic field (B) data is read from different files at their own native resolution. The tool allows for data zooming in time and the input data can be in any coordinate system. Examples of real satellite data are included to facilitate the learning process in the usage of the tool. This tool is available to the space physics community. As configured, the tool is basically complete for shock analysis; however, work continues to generalize SDAT for the analysis of other types of discontinuities.

  8. Seismic system and method

    SciTech Connect

    Rietsch, E.F.

    1988-10-11

    This patent describes aeismic apparatus for providing an enhanced seismic signal comprising: a plurality of seismic detector means for detecting vibrations of the earth surface and providing a corresponding plurality of seismic signals representative of the detected vibrations, multiplexing means for multiplexing the seismic signals from the seismic detector means to provide a multiplexed signal, memory means receiving the multiplexed signals for separating and storing portions of the multiplexed signal according to the detector means of origin so that each stored portion is in effect a sample of a seismic signal from a detector means, means for deriving from the stored samples a statistical reference for the seismic signals from the plurality of detector means, means for discarding outlying samples from the stored samples in accordance with the statistical reference, means for combining the remaining samples in a predetermined manner to provide an enhanced seismic signal, and means connected to the discarding means for determining whether or not a statistical significant deviation exists between the rejection rates of the seismic detector means.

  9. Seismic Imaging and Monitoring

    SciTech Connect

    Huang, Lianjie

    2012-07-09

    I give an overview of LANL's capability in seismic imaging and monitoring. I present some seismic imaging and monitoring results, including imaging of complex structures, subsalt imaging of Gulf of Mexico, fault/fracture zone imaging for geothermal exploration at the Jemez pueblo, time-lapse imaging of a walkway vertical seismic profiling data for monitoring CO{sub 2} inject at SACROC, and microseismic event locations for monitoring CO{sub 2} injection at Aneth. These examples demonstrate LANL's high-resolution and high-fidelity seismic imaging and monitoring capabilities.

  10. Seismic Waveguide of Metamaterials

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Hoon; Das, Mukunda P.

    We developed a new method of an earthquake-resistant design to support conventional aseismic system using acoustic metamaterials. The device is an attenuator of a seismic wave that reduces the amplitude of the wave exponentially. Constructing a cylindrical shell-type waveguide composed of many Helmholtz resonators that creates a stop-band for the seismic frequency range, we convert the seismic wave into an attenuated one without touching the building that we want to protect. It is a mechanical way to convert the seismic energy into sound and heat.

  11. Subcell resolution in simplex stochastic collocation for spatial discontinuities

    SciTech Connect

    Witteveen, Jeroen A.S.; Iaccarino, Gianluca

    2013-10-15

    Subcell resolution has been used in the Finite Volume Method (FVM) to obtain accurate approximations of discontinuities in the physical space. Stochastic methods are usually based on local adaptivity for resolving discontinuities in the stochastic dimensions. However, the adaptive refinement in the probability space is ineffective in the non-intrusive uncertainty quantification framework, if the stochastic discontinuity is caused by a discontinuity in the physical space with a random location. The dependence of the discontinuity location in the probability space on the spatial coordinates then results in a staircase approximation of the statistics, which leads to first-order error convergence and an underprediction of the maximum standard deviation. To avoid these problems, we introduce subcell resolution into the Simplex Stochastic Collocation (SSC) method for obtaining a truly discontinuous representation of random spatial discontinuities in the interior of the cells discretizing the probability space. The presented SSC–SR method is based on resolving the discontinuity location in the probability space explicitly as function of the spatial coordinates and extending the stochastic response surface approximations up to the predicted discontinuity location. The applications to a linear advection problem, the inviscid Burgers’ equation, a shock tube problem, and the transonic flow over the RAE 2822 airfoil show that SSC–SR resolves random spatial discontinuities with multiple stochastic and spatial dimensions accurately using a minimal number of samples.

  12. Swept Impact Seismic Technique (SIST)

    USGS Publications Warehouse

    Park, C.B.; Miller, R.D.; Steeples, D.W.; Black, R.A.

    1996-01-01

    A coded seismic technique is developed that can result in a higher signal-to-noise ratio than a conventional single-pulse method does. The technique is cost-effective and time-efficient and therefore well suited for shallow-reflection surveys where high resolution and cost-effectiveness are critical. A low-power impact source transmits a few to several hundred high-frequency broad-band seismic pulses during several seconds of recording time according to a deterministic coding scheme. The coding scheme consists of a time-encoded impact sequence in which the rate of impact (cycles/s) changes linearly with time providing a broad range of impact rates. Impact times used during the decoding process are recorded on one channel of the seismograph. The coding concept combines the vibroseis swept-frequency and the Mini-Sosie random impact concepts. The swept-frequency concept greatly improves the suppression of correlation noise with much fewer impacts than normally used in the Mini-Sosie technique. The impact concept makes the technique simple and efficient in generating high-resolution seismic data especially in the presence of noise. The transfer function of the impact sequence simulates a low-cut filter with the cutoff frequency the same as the lowest impact rate. This property can be used to attenuate low-frequency ground-roll noise without using an analog low-cut filter or a spatial source (or receiver) array as is necessary with a conventional single-pulse method. Because of the discontinuous coding scheme, the decoding process is accomplished by a "shift-and-stacking" method that is much simpler and quicker than cross-correlation. The simplicity of the coding allows the mechanical design of the source to remain simple. Several different types of mechanical systems could be adapted to generate a linear impact sweep. In addition, the simplicity of the coding also allows the technique to be used with conventional acquisition systems, with only minor modifications.

  13. 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

  14. 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.

  15. Seismic Catalogue and Seismic Network in Haiti

    NASA Astrophysics Data System (ADS)

    Belizaire, D.; Benito, B.; Carreño, E.; Meneses, C.; Huerfano, V.; Polanco, E.; McCormack, D.

    2013-05-01

    The destructive earthquake occurred on January 10, 2010 in Haiti, highlighted the lack of preparedness of the country to address seismic phenomena. At the moment of the earthquake, there was no seismic network operating in the country, and only a partial control of the past seismicity was possible, due to the absence of a national catalogue. After the 2010 earthquake, some advances began towards the installation of a national network and the elaboration of a seismic catalogue providing the necessary input for seismic Hazard Studies. This paper presents the state of the works carried out covering both aspects. First, a seismic catalogue has been built, compiling data of historical and instrumental events occurred in the Hispaniola Island and surroundings, in the frame of the SISMO-HAITI project, supported by the Technical University of Madrid (UPM) and Developed in cooperation with the Observatoire National de l'Environnement et de la Vulnérabilité of Haiti (ONEV). Data from different agencies all over the world were gathered, being relevant the role of the Dominican Republic and Puerto Rico seismological services which provides local data of their national networks. Almost 30000 events recorded in the area from 1551 till 2011 were compiled in a first catalogue, among them 7700 events with Mw ranges between 4.0 and 8.3. Since different magnitude scale were given by the different agencies (Ms, mb, MD, ML), this first catalogue was affected by important heterogeneity in the size parameter. Then it was homogenized to moment magnitude Mw using the empirical equations developed by Bonzoni et al (2011) for the eastern Caribbean. At present, this is the most exhaustive catalogue of the country, although it is difficult to assess its degree of completeness. Regarding the seismic network, 3 stations were installed just after the 2010 earthquake by the Canadian Government. The data were sent by telemetry thought the Canadian System CARINA. In 2012, the Spanish IGN together

  16. Shallow Moho with aseismic upper crust and deep Moho with seismic lower crust beneath the Japanese Islands obtained by seismic tomography using data from dense seismic network

    NASA Astrophysics Data System (ADS)

    Matsubara, Makoto; Obara, Kazushige

    2015-04-01

    P-wave seismic velocity is well known to be up to 7.0 km/s and over 7.5 km/s in the lower crust and in the mantle, respectively. A large velocity gradient is the definition of the Moho discontinuity between the crust and mantle. In this paper, we investigates the configuration of Moho discontinuity defined as an isovelocity plane with large velocity gradient derived from our fine-scale three-dimensional seismic velocity structure beneath Japanese Islands using data obtained by dense seismic network with the tomographic method (Matsubara and Obara, 2011). Japanese Islands are mainly on the Eurasian and North American plates. The Philippine Sea and Pacific plates are subducting beneath these continental plates. We focus on the Moho discontinuity at the continental side. We calculate the P-wave velocity gradients between the vertical grid nodes since the grid inversion as our tomographic method does not produce velocity discontinuity. The largest velocity gradient is 0.078 (km/s)/km at velocities of 7.2 and 7.3 km/s. We define the iso-velocity plane of 7.2 km/s as the Moho discontinuity. We discuss the Moho discontinuity above the upper boundary of the subducting oceanic plates with consideration of configuration of plate boundaries of prior studies (Shiomi et al., 2008; Kita et al., 2010; Hirata et al, 2012) since the Moho depth derived from the iso-velocity plane denotes the oceanic Moho at the contact zones of the overriding continental plates and the subducting oceanic plates. The Moho discontinuity shallower than 30 km depth is distributed within the tension region like northern Kyushu and coastal line of the Pacific Ocean in the northeastern Japan and the tension region at the Cretaceous as the northeastern Kanto district. These regions have low seismicity within the upper crust. Positive Bouguer anomaly beneath the northeastern Kanto district indicates the ductile material with large density in lower crust at the shallower portion and the aseismic upper crust

  17. Augmented proper orthogonal decompositional for problems with moving discontinuities

    SciTech Connect

    Brenner, T.; Fontenot, R.; Cizmas, P.; O'Brien, T.; Breault, R.

    2010-01-01

    A method is proposed to augment the proper orthogonaldecomposition basis functionswith discontinuitymodes to better capture moving discontinuities in reduced-order models. Moving discontinuities can be shocks in unsteady gas flows or bubbles in multiphase flow. The method is shown to work for a simple test problem using the first-order wave equation. A method for detecting discontinuities numerically is developed using mathematical morphology. This method is shown to properly identify the edges of bubbles in multiphase flow.

  18. A General approach for calculating coupling impedances of small discontinuities

    NASA Astrophysics Data System (ADS)

    Kurennoy, Sergei S.; Gluckstern, Robert L.; Stupakov, Gennady V.

    A general theory of the beam interaction with small discontinuities of the vacuum chamber is developed taking into account the reaction of radiated waves back on the discontinuity. The reactive impedance calculated earlier is reproduced as the first order, and the resistive one as the second order of a perturbation theory based on this general approach. The theory also gives, in a very natural way, the results for the trapped modes due to small discontinuities obtained earlier by a different method.

  19. Scanning Seismic Intrusion Detector

    NASA Technical Reports Server (NTRS)

    Lee, R. D.

    1982-01-01

    Scanning seismic intrusion detector employs array of automatically or manually scanned sensors to determine approximate location of intruder. Automatic-scanning feature enables one operator to tend system of many sensors. Typical sensors used with new system are moving-coil seismic pickups. Detector finds uses in industrial security systems.

  20. Borehole seismic unit

    NASA Astrophysics Data System (ADS)

    Seavey, R. W.

    1982-05-01

    Fracture orientation can be measured by using a triaxial geophone package located at the fracture interval within the wellbore. Seismic signals produced by the fracture can be recorded and measured to determine the direction of the fracture. A description of a borehole seismic unit and procedures to accomplish this task are reported.

  1. Seismic Computerized Alert Network

    USGS Publications Warehouse

    1986-01-01

    In 1985 the USGS devised a model for a Seismic Computerized Alert Network (SCAN) that would use continuous monitoring of seismic data from existing types of instruments to provide automatic, highly-reliable early warnings of earthquake shaking. In a large earthquake, substantial damaging ground motions may occur at great distances from the earthquake's epicenter.

  2. Universal quantum computation by discontinuous quantum walk

    SciTech Connect

    Underwood, Michael S.; Feder, David L.

    2010-10-15

    Quantum walks are the quantum-mechanical analog of random walks, in which a quantum ''walker'' evolves between initial and final states by traversing the edges of a graph, either in discrete steps from node to node or via continuous evolution under the Hamiltonian furnished by the adjacency matrix of the graph. We present a hybrid scheme for universal quantum computation in which a quantum walker takes discrete steps of continuous evolution. This ''discontinuous'' quantum walk employs perfect quantum-state transfer between two nodes of specific subgraphs chosen to implement a universal gate set, thereby ensuring unitary evolution without requiring the introduction of an ancillary coin space. The run time is linear in the number of simulated qubits and gates. The scheme allows multiple runs of the algorithm to be executed almost simultaneously by starting walkers one time step apart.

  3. Discontinuous Galerkin Methods for Turbulence Simulation

    NASA Technical Reports Server (NTRS)

    Collis, S. Scott

    2002-01-01

    A discontinuous Galerkin (DG) method is formulated, implemented, and tested for simulation of compressible turbulent flows. The method is applied to turbulent channel flow at low Reynolds number, where it is found to successfully predict low-order statistics with fewer degrees of freedom than traditional numerical methods. This reduction is achieved by utilizing local hp-refinement such that the computational grid is refined simultaneously in all three spatial coordinates with decreasing distance from the wall. Another advantage of DG is that Dirichlet boundary conditions can be enforced weakly through integrals of the numerical fluxes. Both for a model advection-diffusion problem and for turbulent channel flow, weak enforcement of wall boundaries is found to improve results at low resolution. Such weak boundary conditions may play a pivotal role in wall modeling for large-eddy simulation.

  4. Weld stresses beyond elastic limit: Materials discontinuity

    NASA Technical Reports Server (NTRS)

    Verderaime, V.

    1989-01-01

    When welded structures depend on properties beyond the elastic limit to qualify their ultimate safety factor, and weld-parent materials abruptly change at the interface, then stress discontinuity is inevitable. The stress concentration is mildly sensitive to material relative strain hardening and acutely sensitive to applied stress fields. Peak stresses occur on the weld surface, at the interface, and dissipate within a 0.01-inch band. When the stress is intense, the weld will always fracture at the interface. The analysis incorporates a classical mechanics model to more sharply define stress spikes within the bandwidth, and suggests a relative material index and Poisson's ratio related to strain hardening. Implications are discussed which are applicable to industries of high performance structures.

  5. Capillary breakup of discontinuously rate thickening suspensions.

    PubMed

    Zimoch, Pawel J; McKinley, Gareth H; Hosoi, A E

    2013-07-19

    Using discontinuously rate thickening suspensions (DRTS) as a model system, we show that beads-on-a-string morphologies can arise as a result of external viscous drag acting during capillary-driven breakup of a non-Newtonian fluid. To minimize the perturbative effect of gravity, we developed a new experimental test platform in which the filament is supported in a horizontal position at the surface of an immiscible oil bath. We show that the evolution of thin DRTS filaments during the capillary thinning process is well described by a set of one-dimensional slender filament equations. The strongly rate-dependent rheology of the test fluid and the aspect ratio of the filament couple to control the thinning dynamics and lead to a simple criterion describing the localized arrest of the capillary thinning process and the subsequent formation of complex, high aspect ratio beads-on-a-string structures. PMID:23909338

  6. Evolution equation for infinitesimal rotational discontinuities

    NASA Technical Reports Server (NTRS)

    Sonnerup, B. U. O.; Qian, S.; Wang, D.-J.

    1990-01-01

    An evolution equation in the form of a modified Korteweg-de Vries equation is developed which describes the small-amplitude version of the infinitesimal rotational discontinuity (RD) studied by Wang and Sonnerup (1984). It is shown that the small-amplitude version of the equilibrium pulse solution obtained by Wang and Sonnerup is metastable and thus unlikely to arise spontaneously. When the initial pulse amplitude is smaller than and/or the initial pulse width is greater than the equilibrium value, the pulse decays. When the reverse is the case, the pulse is converted to an infinitesimal intermediate-mode solitary wave having greater pulse amplitude and speed. A simulation experiment is performed in which one of the equilibrium intermediate-mode solitary waves overtakes another, less rapidly moving version of the same wave. The existence of multipeaked intermediate-mode solitary pulses is demonstrated.

  7. From weak discontinuities to nondissipative shock waves

    SciTech Connect

    Garifullin, R. N. Suleimanov, B. I.

    2010-01-15

    An analysis is presented of the effect of weak dispersion on transitions from weak to strong discontinuities in inviscid fluid dynamics. In the neighborhoods of transition points, this effect is described by simultaneous solutions to the Korteweg-de Vries equation u{sub t}'+ uu{sub x}' + u{sub xxx}' = 0 and fifth-order nonautonomous ordinary differential equations. As x{sup 2} + t{sup 2} {yields}{infinity}, the asymptotic behavior of these simultaneous solutions in the zone of undamped oscillations is given by quasi-simple wave solutions to Whitham equations of the form r{sub i}(t, x) = tl{sub i} x/t{sup 2}.

  8. DISCONTINUED OR LITTLE USED LARGE GATE VALVE AND VALVE ASSEMBLY ...

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

    DISCONTINUED OR LITTLE USED LARGE GATE VALVE AND VALVE ASSEMBLY PATTERNS, PATTERN STORAGE BUILDING. - Stockham Pipe & Fittings Company, Pattern Storage, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

  9. Analysis of Waveguide Junction Discontinuities Using Finite Element Method

    NASA Technical Reports Server (NTRS)

    Deshpande, Manohar D.

    1997-01-01

    A Finite Element Method (FEM) is presented to determine reflection and transmission coefficients of rectangular waveguide junction discontinuities. An H-plane discontinuity, an E-plane ridge discontinuity, and a step discontinuity in a concentric rectangular waveguide junction are analyzed using the FEM procedure. Also, reflection and transmission coefficients due to presence of a gap between two sections of a rectangular waveguide are determined using the FEM. The numerical results obtained by the present method are in excellent agreement with the earlier published results. The numerical results obtained by the FEM are compared with the numerical results obtained using the Mode Matching Method (MMM) and also with the measured data.

  10. MHD discontinuities in solar flares: Continuous transitions and plasma heating

    NASA Astrophysics Data System (ADS)

    Ledentsov, L. S.; Somov, B. V.

    2015-12-01

    The boundary conditions for the ideal MHD equations on a plane discontinuity surface are investigated. It is shown that, for a given mass flux through a discontinuity, its type depends only on the relation between inclination angles of a magnetic field. Moreover, the conservation laws on a surface of discontinuity allow changing a discontinuity type with gradual (continuous) changes in the conditions of plasma flow. Then there are the so-called transition solutions that satisfy simultaneously two types of discontinuities. We obtain all transition solutions on the basis of the complete system of boundary conditions for the MHD equations. We also found the expression describing a jump of internal energy of the plasma flowing through the discontinuity. Firstly, this allows constructing a generalized scheme of possible continuous transitions between MHD discontinuities. Secondly, it enables the examination of the dependence of plasma heating by plasma density and configuration of the magnetic field near the discontinuity surface, i.e., by the type of the MHD discontinuity. It is shown that the best conditions for heating are carried out in the vicinity of a reconnecting current layer near the areas of reverse currents. The result can be helpful in explaining the temperature distributions inside the active regions in the solar corona during flares observed by modern space observatories in soft and hard X-rays.

  11. Discontinuities detection using transmission electrical resistivity imaging

    NASA Astrophysics Data System (ADS)

    Lesparre, Nolwenn; Cabrera, Justo; Boyle, Alistair; Grychtol, Bartłomiej; Adler, Andy

    2015-04-01

    In the context of nuclear waste storage, low permeability clays are investigated as potential geological barrier. Discontinuities in such formations might facilitate the radionuclide transport to the environment. The underground platform of Tournemire (Aveyron, France) presents the opportunity to perform in-situ experiments to evaluate the potential of geophysical methods to detect and characterize the presence of discontinuities in the sub-surface. In this work, we apply transmission electrical resistivity tomography to image the medium surrounding a regional fault. A specific array of electrodes were set up, adapted for the characterization of the fault. Electrodes were placed along the tunnel as well as at the surface above the tunnel on both sides of the fault. The objective of a such geometry is to acquire data in transmission across the massif in addition to classical protocol such as Schlumberger or dipole-dipole in order to better cover the sounded medium. 3D models considering the gallery geometry, the topography and the injection of current in transmission through the massif were developed for the analysis of such particular data sets. For the reconstruction of the medium electrical resistivity, the parametrization of the inverse problem was adapted to the geometry of the experience in a scope to reduce the inversion under-determination. The resulting image obtained with classical protocols and transmission current injection is compared to an image obtained using only classical protocols to better highlight the interest of a transmission experiment in terms of resolution and penetration depth. The addition of protocols in transmission allows a better coverage of the sounded medium so the resulting image presents a better resolution at higher depths than the image resulting from a single profile of electrodes. The proposed configuration of electrical resistivity measurements in transmission is then promising for hydrogeophysical studies, in particular for

  12. A new seismically constrained subduction interface model for Central America

    NASA Astrophysics Data System (ADS)

    Kyriakopoulos, C.; Newman, A. V.; Thomas, A. M.; Moore-Driskell, M.; Farmer, G. T.

    2015-08-01

    We provide a detailed, seismically defined three-dimensional model for the subducting plate interface along the Middle America Trench between northern Nicaragua and southern Costa Rica. The model uses data from a weighted catalog of about 30,000 earthquake hypocenters compiled from nine catalogs to constrain the interface through a process we term the "maximum seismicity method." The method determines the average position of the largest cluster of microseismicity beneath an a priori functional surface above the interface. This technique is applied to all seismicity above 40 km depth, the approximate intersection of the hanging wall Mohorovičić discontinuity, where seismicity likely lies along the plate interface. Below this depth, an envelope above 90% of seismicity approximates the slab surface. Because of station proximity to the interface, this model provides highest precision along the interface beneath the Nicoya Peninsula of Costa Rica, an area where marked geometric changes coincide with crustal transitions and topography observed seaward of the trench. The new interface is useful for a number of geophysical studies that aim to understand subduction zone earthquake behavior and geodynamic and tectonic development of convergent plate boundaries.

  13. Discontinuation of buprenorphine maintenance therapy: perspectives and outcomes.

    PubMed

    Bentzley, Brandon S; Barth, Kelly S; Back, Sudie E; Book, Sarah W

    2015-05-01

    Buprenorphine maintenance therapy (BMT) is increasingly the preferred opioid maintenance agent due to its reduced toxicity and availability in an office-based setting in the United States. Although BMT has been shown to be highly efficacious, it is often discontinued soon after initiation. No current systematic review has yet investigated providers' or patients' reasons for BMT discontinuation or the outcomes that follow. Hence, provider and patient perspectives associated with BMT discontinuation after a period of stable buprenorphine maintenance and the resultant outcomes were systematically reviewed with specific emphasis on pre-buprenorphine-taper parameters predictive of relapse following BMT discontinuation. Few identified studies address provider or patient perspectives associated with buprenorphine discontinuation. Within the studies reviewed providers with residency training in BMT were more likely to favor long term BMT instead of detoxification, and providers were likely to consider BMT discontinuation in the face of medication misuse. Patients often desired to remain on BMT because of fear of relapse to illicit opioid use if they were to discontinue BMT. The majority of patients who discontinued BMT did so involuntarily, often due to failure to follow strict program requirements, and 1 month following discontinuation, rates of relapse to illicit opioid use exceeded 50% in every study reviewed. Only lower buprenorphine maintenance dose, which may be a marker for attenuated addiction severity, predicted better outcomes across studies. Relaxed BMT program requirements and frequent counsel on the high probability of relapse if BMT is discontinued may improve retention in treatment and prevent the relapse to illicit opioid use that is likely to follow BMT discontinuation.

  14. Shallow Moho with aseismic upper crust and deep Moho with seismic lower crust beneath the Japanese Islands obtained by seismic tomography using data from dense seismic network

    NASA Astrophysics Data System (ADS)

    Matsubara, Makoto; Obara, Kazushige

    2015-04-01

    P-wave seismic velocity is well known to be up to 7.0 km/s and over 7.5 km/s in the lower crust and in the mantle, respectively. A large velocity gradient is the definition of the Moho discontinuity between the crust and mantle. In this paper, we investigates the configuration of Moho discontinuity defined as an isovelocity plane with large velocity gradient derived from our fine-scale three-dimensional seismic velocity structure beneath Japanese Islands using data obtained by dense seismic network with the tomographic method (Matsubara and Obara, 2011). Japanese Islands are mainly on the Eurasian and North American plates. The Philippine Sea and Pacific plates are subducting beneath these continental plates. We focus on the Moho discontinuity at the continental side. We calculate the P-wave velocity gradients between the vertical grid nodes since the grid inversion as our tomographic method does not produce velocity discontinuity. The largest velocity gradient is 0.078 (km/s)/km at velocities of 7.2 and 7.3 km/s. We define the iso-velocity plane of 7.2 km/s as the Moho discontinuity. We discuss the Moho discontinuity above the upper boundary of the subducting oceanic plates with consideration of configuration of plate boundaries of prior studies (Shiomi et al., 2008; Kita et al., 2010; Hirata et al, 2012) since the Moho depth derived from the iso-velocity plane denotes the oceanic Moho at the contact zones of the overriding continental plates and the subducting oceanic plates. The Moho discontinuity shallower than 30 km depth is distributed within the tension region like northern Kyushu and coastal line of the Pacific Ocean in the northeastern Japan and the tension region at the Cretaceous as the northeastern Kanto district. These regions have low seismicity within the upper crust. Positive Bouguer anomaly beneath the northeastern Kanto district indicates the ductile material with large density in lower crust at the shallower portion and the aseismic upper crust

  15. Mantle Discontinuities and the Origins of the U.S. Cratonic Lithosphere

    NASA Astrophysics Data System (ADS)

    Fischer, K. M.; Hopper, E.

    2014-12-01

    The goals of this work are to probe how mantle lithosphere discontinuity structure varies beneath the cratonic terranes of the northern U.S. and to relate this structure to the processes that created and modified the cratonic mantle. Our region samples the Archean Wyoming, Medicine Hat and Superior cratons, and the Proterozoic terranes that lie between them. We imaged the mantle using Sp phases recorded by permanent and temporary seismic networks, including EarthScope's Transportable Array. Sp receiver functions for individual waveforms were obtained by extended time multi-taper deconvolution, and migrated into a 3D volume using common conversion point stacking, a spline representation of phase Fresnel zones, and 3D models for crust and mantle structure. The stack was bootstrapped. In the cratonic mantle, we observe multiple mid-lithospheric discontinuities (MLDs) that are characterized by three types of structures: a relatively continuous negative discontinuity (velocity decrease with depth) that lies in the 65-100 km depth range; deeper negative MLDs (80-145 km) that are more discontinuous and intermittent; and occasional positive MLDs at the greatest depths (>125 km). In contrast to the tectonically active western U.S., beneath cratonic regions we typically do not observe a strong negative discontinuty at the base of the tomographically-defined lithosphere, indicating that the transition to asthenospheric properties is gradual. The MLDs indicate strong layering in the cratonic mantle lithosphere. In multiple cases, one negative discontinuity dips below another, consistent with a slab of lithosphere imbricated beneath pre-existing cratonic mantle. One of the clearest examples is a north-dipping phase at depths of 80-130 km beneath the Cheyenne Belt, the suture between the Wyoming Craton and the accreted Proterozoic terranes to its south. In Sept. 2013, an unusual earthquake occurred within the high velocity mantle of the Wyoming craton at ~76 km, a depth that

  16. Crustal Seismicity and Recent Faults in Southern Peru

    NASA Astrophysics Data System (ADS)

    David, C.; Comte, D.; Tavera, H.; Audin, L.; Herail, G.

    2004-12-01

    time seems seismically active and could be associated with sinestral strike-slips. The Purgatorio fault which has been identified by a pronounced discontinuity of the topography and the presence of terraces of accumulation could be associated with pure component movements. The correlation between seismological data and geomorpho-tectonic observations on field gives new insight in the southern Peru forearc deformation.

  17. 25 CFR 175.21 - Discontinuance of service.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Discontinuance of service. 175.21 Section 175.21 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER INDIAN ELECTRIC POWER UTILITIES Utility Service Administration § 175.21 Discontinuance of service. Failure of customer(s) to comply...

  18. 25 CFR 175.21 - Discontinuance of service.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 25 Indians 1 2014-04-01 2014-04-01 false Discontinuance of service. 175.21 Section 175.21 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER INDIAN ELECTRIC POWER UTILITIES Utility Service Administration § 175.21 Discontinuance of service. Failure of customer(s) to comply...

  19. 25 CFR 175.21 - Discontinuance of service.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 25 Indians 1 2011-04-01 2011-04-01 false Discontinuance of service. 175.21 Section 175.21 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER INDIAN ELECTRIC POWER UTILITIES Utility Service Administration § 175.21 Discontinuance of service. Failure of customer(s) to comply...

  20. 25 CFR 175.21 - Discontinuance of service.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 25 Indians 1 2012-04-01 2011-04-01 true Discontinuance of service. 175.21 Section 175.21 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER INDIAN ELECTRIC POWER UTILITIES Utility Service Administration § 175.21 Discontinuance of service. Failure of customer(s) to comply...

  1. 25 CFR 175.21 - Discontinuance of service.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 25 Indians 1 2013-04-01 2013-04-01 false Discontinuance of service. 175.21 Section 175.21 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER INDIAN ELECTRIC POWER UTILITIES Utility Service Administration § 175.21 Discontinuance of service. Failure of customer(s) to comply...

  2. 27 CFR 19.19 - Discontinuance of storage facilities.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false Discontinuance of storage... Provisions § 19.19 Discontinuance of storage facilities. If TTB determines that a proprietor's bonded storage... spirits stored in the facility to another storage facility. The transfer will take place at such time...

  3. 27 CFR 19.79 - Discontinuance of storage facilities.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Discontinuance of storage... Provisions Activities Not Subject to This Part § 19.79 Discontinuance of storage facilities. When the appropriate TTB officer finds that any facilities for the storage of spirits on bonded premises are unsafe...

  4. 27 CFR 19.19 - Discontinuance of storage facilities.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Discontinuance of storage... Provisions § 19.19 Discontinuance of storage facilities. If TTB determines that a proprietor's bonded storage... spirits stored in the facility to another storage facility. The transfer will take place at such time...

  5. 7 CFR 247.17 - Notification of discontinuance of participant.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 4 2012-01-01 2012-01-01 false Notification of discontinuance of participant. 247.17 Section 247.17 Agriculture Regulations of the Department of Agriculture (Continued) FOOD AND NUTRITION SERVICE, DEPARTMENT OF AGRICULTURE CHILD NUTRITION PROGRAMS COMMODITY SUPPLEMENTAL FOOD PROGRAM § 247.17 Notification of discontinuance...

  6. 7 CFR 247.17 - Notification of discontinuance of participant.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 4 2011-01-01 2011-01-01 false Notification of discontinuance of participant. 247.17 Section 247.17 Agriculture Regulations of the Department of Agriculture (Continued) FOOD AND NUTRITION SERVICE, DEPARTMENT OF AGRICULTURE CHILD NUTRITION PROGRAMS COMMODITY SUPPLEMENTAL FOOD PROGRAM § 247.17 Notification of discontinuance...

  7. 7 CFR 247.17 - Notification of discontinuance of participant.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 4 2010-01-01 2010-01-01 false Notification of discontinuance of participant. 247.17 Section 247.17 Agriculture Regulations of the Department of Agriculture (Continued) FOOD AND NUTRITION SERVICE, DEPARTMENT OF AGRICULTURE CHILD NUTRITION PROGRAMS COMMODITY SUPPLEMENTAL FOOD PROGRAM § 247.17 Notification of discontinuance...

  8. 27 CFR 25.85 - Notice of permanent discontinuance.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Notice of permanent discontinuance. 25.85 Section 25.85 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY ALCOHOL BEER Qualification of a Brewery Discontinuance of...

  9. 27 CFR 25.85 - Notice of permanent discontinuance.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Notice of permanent discontinuance. 25.85 Section 25.85 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS BEER Qualification of a Brewery Discontinuance of...

  10. 27 CFR 25.85 - Notice of permanent discontinuance.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Notice of permanent discontinuance. 25.85 Section 25.85 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS BEER Qualification of a Brewery Discontinuance of...

  11. 27 CFR 25.85 - Notice of permanent discontinuance.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false Notice of permanent discontinuance. 25.85 Section 25.85 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY ALCOHOL BEER Qualification of a Brewery Discontinuance of...

  12. 27 CFR 25.85 - Notice of permanent discontinuance.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Notice of permanent discontinuance. 25.85 Section 25.85 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS BEER Qualification of a Brewery Discontinuance of...

  13. 27 CFR 31.138 - Discontinuance of business.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Discontinuance of business. 31.138 Section 31.138 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU... § 31.138 Discontinuance of business. A dealer going out of business must register that event within...

  14. 27 CFR 72.37 - Discontinuance of administrative proceedings.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 2 2010-04-01 2010-04-01 false Discontinuance of administrative proceedings. 72.37 Section 72.37 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX... to effect such sale or retention will be discontinued....

  15. EVALUATING DISCONTINUITIES IN COMPLEX SYSTEMS: TOWARD QUANTITATIVE MEASURE OF RESILIENCE

    EPA Science Inventory

    The textural discontinuity hypothesis (TDH) is based on the observation that animal body mass distributions exhibit discontinuities that may reflect the texture of the landscape available for exploitation. This idea has been extended to other complex systems, hinting that the ide...

  16. Transition density of one-dimensional diffusion with discontinuous drift

    NASA Technical Reports Server (NTRS)

    Zhang, Weijian

    1990-01-01

    The transition density of a one-dimensional diffusion process with a discontinuous drift coefficient is studied. A probabilistic representation of the transition density is given, illustrating the close connections between discontinuities of the drift and Brownian local times. In addition, some explicit results are obtained based on the trivariate density of Brownian motion, its occupation, and local times.

  17. Auditory discontinuities interact with categorization: Implications for speech perception

    NASA Astrophysics Data System (ADS)

    Holt, Lori L.; Lotto, Andrew J.; Diehl, Randy L.

    2004-09-01

    Behavioral experiments with infants, adults, and nonhuman animals converge with neurophysiological findings to suggest that there is a discontinuity in auditory processing of stimulus components differing in onset time by about 20 ms. This discontinuity has been implicated as a basis for boundaries between speech categories distinguished by voice onset time (VOT). Here, it is investigated how this discontinuity interacts with the learning of novel perceptual categories. Adult listeners were trained to categorize nonspeech stimuli that mimicked certain temporal properties of VOT stimuli. One group of listeners learned categories with a boundary coincident with the perceptual discontinuity. Another group learned categories defined such that the perceptual discontinuity fell within a category. Listeners in the latter group required significantly more experience to reach criterion categorization performance. Evidence of interactions between the perceptual discontinuity and the learned categories extended to generalization tests as well. It has been hypothesized that languages make use of perceptual discontinuities to promote distinctiveness among sounds within a language inventory. The present data suggest that discontinuities interact with category learning. As such, ``learnability'' may play a predictive role in selection of language sound inventories.

  18. 24 CFR 203.288 - Discontinuance of adjusted premium charge.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 24 Housing and Urban Development 2 2010-04-01 2010-04-01 false Discontinuance of adjusted premium... Premium § 203.288 Discontinuance of adjusted premium charge. Notwithstanding any provision in the mortgage instrument, there shall be no adjusted mortgage insurance premium due the Commissioner on account of...

  19. 27 CFR 21.3 - Stocks of discontinued formulas.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Stocks of discontinued..., DEPARTMENT OF THE TREASURY LIQUORS FORMULAS FOR DENATURED ALCOHOL AND RUM General Provisions § 21.3 Stocks of discontinued formulas. Denaturers, or specially denatured spirits dealers or users, having on hand stocks...

  20. Probabilistic Seismic Hazard Analysis

    SciTech Connect

    Not Available

    1988-01-01

    The purpose of Probabilistic Seismic Hazard Analysis (PSHA) is to evaluate the hazard of seismic ground motion at a site by considering all possible earthquakes in the area, estimating the associated shaking at the site, and calculating the probabilities of these occurrences. The Panel on Seismic Hazard Analysis is charged with assessment of the capabilities, limitations, and future trends of PSHA in the context of alternatives. The report identifies and discusses key issues of PSHA and is addressed to decision makers with a modest scientific and technical background and to the scientific and technical community. 37 refs., 19 figs.

  1. The Seismic Wavefield

    NASA Astrophysics Data System (ADS)

    Kennett, B. L. N.

    2002-12-01

    The two volumes of The Seismic Wavefield are a comprehensive guide to the understanding of seismograms in terms of physical propagation processes within the Earth. The focus is on the observation of earthquakes and man-made sources on all scales, for both body waves and surface waves. Volume I provides a general introduction and a development of the theoretical background for seismic waves. Volume II looks at the way in which observed seismograms relate to the propagation processes. Volume II also discusses local and regional seismic events, global wave propagation, and the three-dimensional Earth.

  2. Southern Africa seismic structure and source studies

    NASA Astrophysics Data System (ADS)

    Zhao, Ming

    1998-09-01

    The upper mantle seismic velocity structure beneath southern Africa is investigated using travel time and waveform data. Waveform and travel time data used in this study come mainly from a large mine tremor in South Africa (msb{b} 5.6) recorded on stations of the southern Africa and the Tanzania Broadband Seismic Experiment. Auxiliary data along similar profiles are obtained from other moderate events within eastern and southern Africa. The waveform data from the large tremor show upper mantle triplications for both the 400 and 670-km discontinuities between 18sp° and 27sp° distance. The most notable feature of the data is a large, late P phase that propagates to at least 27sp°. This phase is striking because of its late arrival time (as much as 15 seconds after direct P at 27sp°) and high amplitude relative to the first arrival. Travel times from all available stations are used to invert for the P wave velocity structure down to 800 km depth and S wave velocity structure down to 200 km using the Wiechert-Herglotz (W-H) inversion technique. The P wave velocities from the uppermost mantle down to 300 km are as much as 3% higher than the global average and are slightly slower than the global average between 300 and 400 km depths. The velocity gradient between 300 and 400 km is 0.0015 1/s. The S wave travel time data yield fast velocities above 200-km depth. The S wave velocity structure appears inconsistent with the P wave structure model indicating varying Poisson's ratio in the upper mantle. Little evidence is found for a pronounced upper mantle low velocity zone. Both sharp and gradual-change 400-km discontinuities are favored by the waveform data. The 670-km discontinuity appears as a gradual-change zone. The source mechanism of the mb 5.6 mining tremor itself is important for seismic discrimination and insight into mining tremor sources. Source parameters for this event as well as some other large mining tremors from the South African gold mines are studied

  3. Impact of solar wind tangential discontinuities on the Earth's magnetosphere

    NASA Astrophysics Data System (ADS)

    Grib, S. A.

    2012-12-01

    The collision of a solar wind tangential discontinuity with the bow shock and magnetopause is considered in the scope of an MHD approximation. Using MHD methods of trial calculations and generalized shock polars, it has been indicated that a fast shock refracted into the magnetosheath originates when density increases across a tangential discontinuity and a fast rarefaction wave is generated when density decreases at this discontinuity. It has been indicated that a shock front shift under the action of collisions with a tangential discontinuity is experimentally observed and a fast bow shock can be transformed into a slow shock. Using a specific event as an example, it has been demonstrated that solar wind tangential discontinuity affects the geomagnetic field behavior.

  4. Plasma field characteristics of directional discontinuities in the interplanetary medium

    NASA Technical Reports Server (NTRS)

    Solodyna, C. V.; Belcher, J. W.; Sari, J. W.

    1977-01-01

    The paper examines plasma and magnetic-field changes occurring across 1359 directional discontinuities taken from interplanetary data spanning almost four solar rotations. The plasma field characteristics of these events exhibit a distinct variation with large-scale solar-wind velocity. At low velocities, tangential discontinuities appear to predominate. At higher velocities, a substantial and increasing fraction of directional discontinuities exhibits the plasma field properties expected of outwardly propagating rotational discontinuities. The results of Sari (1972, 1975) and of the present study suggest that in the calculation of propagation diffusion coefficients for low-energy cosmic rays, the effects of directional discontinuities should be subtracted from the magnetic fluctuation spectrum during relatively quiet wind conditions. It is not clear that such subtraction is necessary during more disturbed periods.

  5. Method of migrating seismic records

    DOEpatents

    Ober, Curtis C.; Romero, Louis A.; Ghiglia, Dennis C.

    2000-01-01

    The present invention provides a method of migrating seismic records that retains the information in the seismic records and allows migration with significant reductions in computing cost. The present invention comprises phase encoding seismic records and combining the encoded seismic records before migration. Phase encoding can minimize the effect of unwanted cross terms while still allowing significant reductions in the cost to migrate a number of seismic records.

  6. A weighted Runge-Kutta discontinuous Galerkin method for wavefield modelling

    NASA Astrophysics Data System (ADS)

    He, Xijun; Yang, Dinghui; Wu, Hao

    2015-03-01

    In this paper, we propose a weighted Runge-Kutta (RK) discontinuous Galerkin (WRKDG) method for wavefield modelling. For this method, we first transform the seismic wave equations in 2-D heterogeneous anisotropic media into a first-order hyperbolic system, and then combine the discontinuous Galerkin method (DGM) with a weighted RK time discretization. The time discretization is based on an implicit diagonal RK method and an explicit technique, which changes the implicit RK method into an explicit one. In addition, we introduce a weighting factor in the process. Linear and quadratic polynomials for spatial basis functions are typically employed. We investigate the properties of the method in great detail, including the stability criteria and numerical dispersion relations for solving the 2-D acoustic equations. Our analysis indicates that the stability condition for the WRKDG method is more relaxed compared with the classic total variation diminishing (TVD) RK discontinuous Galerkin (RKDG) method, resulting in a 1.7 times superiority for P1 element and is about as efficient as TVD RKDG method for P2 element in computational efficiency. We also demonstrate that the WRKDG method can suppress numerical dispersion more efficiently than the staggered-grid (SG) method on the same grid. The WRKDG method is applied to simulate the wavefields in a large velocity contrast model, a 2-D homogeneous transversely isotropic (TI) model, a fluid-filled fracture model, and a 2-D SEG/EAGE salt dome model. Regular rectangular and irregular triangular elements are used. The numerical results show that the WRKDG method can effectively suppress numerical dispersion and provide accurate information on the wavefield on a coarse mesh. Therefore, the method evidently reduces the scale of the problem and increases computational efficiency. In addition, promising numerical tests show that the WRKDG method combines well with split perfectly matched layer boundary conditions.

  7. Seismic sequences in the Sombrero Seismic Zone

    NASA Astrophysics Data System (ADS)

    Pulliam, J.; Huerfano, V. A.; ten Brink, U.; von Hillebrandt, C.

    2007-05-01

    The northeastern Caribbean, in the vicinity of Puerto Rico and the Virgin Islands, has a long and well-documented history of devastating earthquakes and tsunamis, including major events in 1670, 1787, 1867, 1916, 1918, and 1943. Recently, seismicity has been concentrated to the north and west of the British Virgin Islands, in the region referred to as the Sombrero Seismic Zone by the Puerto Rico Seismic Network (PRSN). In the combined seismicity catalog maintained by the PRSN, several hundred small to moderate magnitude events can be found in this region prior to 2006. However, beginning in 2006 and continuing to the present, the rate of seismicity in the Sombrero suddenly increased, and a new locus of activity developed to the east of the previous location. Accurate estimates of seismic hazard, and the tsunamigenic potential of seismic events, depend on an accurate and comprehensive understanding of how strain is being accommodated in this corner region. Are faults locked and accumulating strain for release in a major event? Or is strain being released via slip over a diffuse system of faults? A careful analysis of seismicity patterns in the Sombrero region has the potential to both identify faults and modes of failure, provided the aggregation scheme is tuned to properly identify related events. To this end, we experimented with a scheme to identify seismic sequences based on physical and temporal proximity, under the assumptions that (a) events occur on related fault systems as stress is refocused by immediately previous events and (b) such 'stress waves' die out with time, so that two events that occur on the same system within a relatively short time window can be said to have a similar 'trigger' in ways that two nearby events that occurred years apart cannot. Patterns that emerge from the identification, temporal sequence, and refined locations of such sequences of events carry information about stress accommodation that is obscured by large clouds of

  8. Stability of Dynamical Systems with Discontinuous Motions:

    NASA Astrophysics Data System (ADS)

    Michel, Anthony N.; Hou, Ling

    In this paper we present a stability theory for discontinuous dynamical systems (DDS): continuous-time systems whose motions are not necessarily continuous with respect to time. We show that this theory is not only applicable in the analysis of DDS, but also in the analysis of continuous dynamical systems (continuous-time systems whose motions are continuous with respect to time), discrete-time dynamical systems (systems whose motions are defined at discrete points in time) and hybrid dynamical systems (HDS) (systems whose descriptions involve simultaneously continuous-time and discrete-time). We show that the stability results for DDS are in general less conservative than the corresponding well-known classical Lyapunov results for continuous dynamical systems and discrete-time dynamical systems. Although the DDS stability results are applicable to general dynamical systems defined on metric spaces (divorced from any kind of description by differential equations, or any other kinds of equations), we confine ourselves to finite-dimensional dynamical systems defined by ordinary differential equations and difference equations, to make this paper as widely accessible as possible. We present only sample results, namely, results for uniform asymptotic stability in the large.

  9. Capillary surface discontinuities above reentrant corners

    NASA Technical Reports Server (NTRS)

    Korevaar, H. J.

    1982-01-01

    A particular configuration of a vertical capillary tube for which S is the equilibrium interface between two fluids in the presence of a downward pointing gravitational field was investigated. S is the graph a function u whose domain is the (horizontal) cross section gamma of the tube. The mean curvature of S is proportional to its height above a fixed reference plane and lambda is a prescribed constant and may be taken between zero and pi/2. Domains gamma for which us is a bounded function but does not extend continuously to d gamma are sought. Simple domains are found and the behavior of u in those domains is studied. An important comparison principle that has been used in the literature to derive many of the results in capillarity is reviewed. It allows one to deduce the approximate shape of a capillary surface by constructing comparison surfaces with mean curvature and contact angle close to those of the (unknown) solution surface. In the context of nonparametric problems the comparison principle leads to height estimates above and below for the function u. An example from the literature where these height estimates have been used successfully is described. The promised domains for which the bounded u does not extend continuously to the boundary are constructed. The point on the boundary at which u has a jump discontinuity will be the vertext of a re-entrant corner having any interior angle theta pi. Using the comparison principle the behavior of u near this point is studied.

  10. Discontinuous Galerkin Methods for Neutrino Radiation Transport

    NASA Astrophysics Data System (ADS)

    Endeve, Eirik; Hauck, Cory; Xing, Yulong; Mezzacappa, Anthony

    2015-04-01

    We are developing new computational methods for simulation of neutrino transport in core-collapse supernovae, which is challenging since neutrinos evolve from being diffusive in the proto-neutron star to nearly free streaming in the critical neutrino heating region. To this end, we consider conservative formulations of the Boltzmann equation, and aim to develop robust, high-order accurate methods. Runge-Kutta discontinuous Galerkin (DG) methods, offer several attractive properties, including (i) high-order accuracy on a compact stencil and (ii) correct asymptotic behavior in the diffusion limit. We have recently developed a new DG method for the advection part for the transport solve, which is high-order accurate and strictly preserves the physical bounds of the distribution function; i.e., f ∈ [ 0 , 1 ] . We summarize the main ingredients of our bound-preserving DG method and discuss ongoing work to include neutrino-matter interactions in the scheme. Research sponsored in part by Oak Ridge National Laboratory, managed by UT-Battelle, LLC for the U. S. Department of Energy

  11. Discontinuous jamming transition in driven foam

    NASA Astrophysics Data System (ADS)

    Dennin, Michael

    2007-03-01

    Aqueous foam (gas bubbles with liquid walls) is a surprising substance. Every molecule in foam is in a fluid state, either liquid or gas. Yet, the entire foam holds its shape as a solid would. In fact, when subjected to an applied strain at a slow enough strain rate, the initial response of the foam is the same as an elastic solid. On the other hand, under sufficiently large stress or strain, the foam can flow in a fashion similar to a fluid. This is similar to plastic flow that occurs in many ``molecular'' solids. In this talk, we will focus on experimental studies of the transition from solid behavior to flowing behavior, with an emphasis on to what degree this ``jamming'' transition is analogous to a ``real'' phase transition. We will focus on recent results using a model, two-dimensional foam: bubble rafts. Bubble rafts are a single layer of bubbles on the surface of water. By focusing on a two-dimensional system, it is relatively easy to track individual bubbles and gain insight into the connection between bubble dynamics (the mesoscopic scale) and the response of the entire foam (macroscopic scale). We will focus on recent measurements of a discontinuous transition from solid to fluid like behavior in the bubble raft.

  12. Airborne electromagnetic imaging of discontinuous permafrost

    USGS Publications Warehouse

    Minsley, B.J.; Abraham, J.D.; Smith, B.D.; Cannia, J.C.; Voss, C.I.; Jorgenson, M.T.; Walvoord, M.A.; Wylie, B.K.; Anderson, L.; Ball, L.B.; Deszcz-Pan, M.; Wellman, T.P.; Ager, T.A.

    2012-01-01

    The evolution of permafrost in cold regions is inextricably connected to hydrogeologic processes, climate, and ecosystems. Permafrost thawing has been linked to changes in wetland and lake areas, alteration of the groundwater contribution to streamflow, carbon release, and increased fire frequency. But detailed knowledge about the dynamic state of permafrost in relation to surface and groundwater systems remains an enigma. Here, we present the results of a pioneering ???1,800 line-kilometer airborne electromagnetic survey that shows sediments deposited over the past ???4 million years and the configuration of permafrost to depths of ???100 meters in the Yukon Flats area near Fort Yukon, Alaska. The Yukon Flats is near the boundary between continuous permafrost to the north and discontinuous permafrost to the south, making it an important location for examining permafrost dynamics. Our results not only provide a detailed snapshot of the present-day configuration of permafrost, but they also expose previously unseen details about potential surface-groundwater connections and the thermal legacy of surface water features that has been recorded in the permafrost over the past ???1,000 years. This work will be a critical baseline for future permafrost studies aimed at exploring the connections between hydrogeologic, climatic, and ecological processes, and has significant implications for the stewardship of Arctic environments. ?? 2012 by the American Geophysical Union.

  13. Polar constellations design for discontinuous coverage

    NASA Astrophysics Data System (ADS)

    Sarno, Salvatore; Graziano, Maria Daniela; D'Errico, Marco

    2016-10-01

    A novel constellation design method is developed for discontinuous coverage of the globe and polar caps. It integrates and extends the applicability of the coverage regions and mitigates the limitations of the existing techniques based on streets-of-coverage (SOC) theory. In particular, the visibility conditions of the targets are mapped in the (Ω, u)-domain to identify the number of satellites per plane and the distance between successive orbits, whereas the planes are arranged around the equator exploiting satellites both in ascending and descending phase. The proposed approach is applied to design potential space segments in polar LEO supporting the existing maritime surveillance services over the globe and on the future polar routes. Results show they require a smaller total number of satellites with respect to the SOC-based configurations for revisit times less than one hour and wide range of swaths. In details, it is observed a reduction between 6% and 22% for global coverage and between 24% and 33% for the coverage of polar caps.

  14. The seismic design handbook

    SciTech Connect

    Naeim, F. )

    1989-01-01

    This book contains papers on the planning, analysis, and design of earthquake resistant building structures. Theories and concepts of earthquake resistant design and their implementation in seismic design practice are presented.

  15. BUILDING 341 Seismic Evaluation

    SciTech Connect

    Halle, J.

    2015-06-15

    The Seismic Evaluation of Building 341 located at Lawrence Livermore National Laboratory in Livermore, California has been completed. The subject building consists of a main building, Increment 1, and two smaller additions; Increments 2 and 3.

  16. Mantle transition zone thickness in the Central South-American Subduction Zone

    NASA Astrophysics Data System (ADS)

    Braunmiller, Jochen; van der Lee, Suzan; Doermann, Lindsey

    We used receiver functions to determine lateral variations in mantle transition zone thickness and sharpness of the 410- and 660-km discontinuities in the presence of subducting lithosphere. The mantle beneath the central Andes of South America provides an ideal study site owing to its long-lived subduction history and the availability of broadband seismic data from the dense BANJO/SEDA temporary networks and the permanent station LPAZ. For LPAZ, we analyzed 26 earthquakes between 1993-2003 and stacked the depth-migrated receiver functions. For temporary stations operating for only about one year (1994-1995), station stacks were not robust. We thus stacked receiver functions for close-by stations forming five groups that span the subduction zone from west to east, each containing 12 to 25 events. We found signal significant at the 2σ level for several station groups from P to S conversions that originate near 520- and 850-900 km depth, but most prominently from the 410- and 660-km discontinuities. For the latter, the P to S converted signal is clear in stacks for western groups and LPAZ, lack of coherent signal for two eastern groups is possibly due to incoherent stacking and does not necessitate the absence of converted energy. The thickness of the mantle transition zone increases progressively from a near-normal 255 km at the Pacific coast to about 295 km beneath station LPAZ in the Eastern Cordillera. Beneath LPAZ, the 410-km discontinuity appears elevated by nearly 40 km, thus thickening the transition zone. We compared signal amplitudes from receiver function stacks calculated at different low-pass frequencies to study frequency dependence and possibly associated discontinuity sharpness of the P to S converted signals. We found that both the 410- and 660-km discontinuities exhibit amplitude increase with decreasing frequency. Synthetic receiver function calculations for discontinuity topography mimicking observed topography show that the observed steep

  17. Geophysical and mineralogical constraints on the post-spinel transformation for the Tonga slab

    NASA Astrophysics Data System (ADS)

    Kaneshima, Satoshi; Kubo, Tomoaki; Yoshioka, Shoichi

    2012-04-01

    The depth of the post-spinel transformation is investigated for the Tonga slab, by using data from short period seismic networks at western United States and Japan for about 100 deep and intermediate-depth earthquakes within a small (˜200 km by 200 km) area near 20°S. Later phases in a time window ˜3 to 20 s after direct P waves are analyzed to search for S-to-P converted waves at the 660 km discontinuity, which represents the post-spinel transformation. We find that immediately beneath the foci of the deepest earthquakes the discontinuity is depressed down to the depths of 685 ± 5 km on average, and that it dips towards WNW by 10 ± 3 km within 70 km laterally. We constrain the thermal structure near the S to P conversion points based on a plausible assumption that the deepest earthquakes occur around the coldest core of the Tonga slab. The distribution of the hypocenters relocated in this study as well as previously published tomographic images of the same region suggest that the Tonga slab bends upward when approaching the 660 km discontinuity and transiently stagnates around the discontinuity. With these observations as the constraints, we numerically model the thermal structure of the Tonga slab, and estimate the temperature around the conversion points as 1200 ± 100 °C, which is 300 ± 100 K colder than the surrounding mantle. As the average depression of the discontinuity (down to 685 ± 5 km) corresponds to an pressure excess over the global average (660 km) by 1.0 ± 0.2 GPa, the assumption of equilibrium post-spinel transformation results in an estimate of the Clapeyron slope (C1) of -3.3-2.7+1.3 MPa/K. We also obtain an independent estimate of the Clapeyron slope (C2) of -2.0 ± 1.0 MPa/K, based on the observation of the dip of the discontinuity and the computed temperature variation (by about 200 K). The discrepancy between C1 and C2 is marginally significant and can be diminished by considering that the slab materials at the conversion points are

  18. Seismic evaluation of the Devonian Ohio Shale in the Big Ugly area, southwestern West Virginia

    SciTech Connect

    Zheng Li; Wilson, T. )

    1991-08-01

    The Devonian Ohio Shale was studied in the Big Ugly area of southwestern West Virginia by reprocessing and interpreting existing seismic and geologic data. These data suggest the presence of detached structures above three decollement zones and cross-strike discontinuities associated with the Alleghanian deformation west of Mann Mountain anticline. A basement growth structure, the Griffithsville basement high, localized detached structures along its southeast flank. High producing trends of gas from the Devonian Ohio Shale occur either near northwest-trending cross-strike structural discontinuities or in the northeast-trending detached structures where fracture density should be increased.

  19. Seismic Consequence Abstraction

    SciTech Connect

    M. Gross

    2004-10-25

    The primary purpose of this model report is to develop abstractions for the response of engineered barrier system (EBS) components to seismic hazards at a geologic repository at Yucca Mountain, Nevada, and to define the methodology for using these abstractions in a seismic scenario class for the Total System Performance Assessment - License Application (TSPA-LA). A secondary purpose of this model report is to provide information for criticality studies related to seismic hazards. The seismic hazards addressed herein are vibratory ground motion, fault displacement, and rockfall due to ground motion. The EBS components are the drip shield, the waste package, and the fuel cladding. The requirements for development of the abstractions and the associated algorithms for the seismic scenario class are defined in ''Technical Work Plan For: Regulatory Integration Modeling of Drift Degradation, Waste Package and Drip Shield Vibratory Motion and Seismic Consequences'' (BSC 2004 [DIRS 171520]). The development of these abstractions will provide a more complete representation of flow into and transport from the EBS under disruptive events. The results from this development will also address portions of integrated subissue ENG2, Mechanical Disruption of Engineered Barriers, including the acceptance criteria for this subissue defined in Section 2.2.1.3.2.3 of the ''Yucca Mountain Review Plan, Final Report'' (NRC 2003 [DIRS 163274]).

  20. Seismic offset balancing

    SciTech Connect

    Ross, C.P.; Beale, P.L.

    1994-01-01

    The ability to successfully predict lithology and fluid content from reflection seismic records using AVO techniques is contingent upon accurate pre-analysis conditioning of the seismic data. However, all too often, residual amplitude effects remain after the many offset-dependent processing steps are completed. Residual amplitude effects often represent a significant error when compared to the amplitude variation with offset (AVO) response that the authors are attempting to quantify. They propose a model-based, offset-dependent amplitude balancing method that attempts to correct for these residuals and other errors due to sub-optimal processing. Seismic offset balancing attempts to quantify the relationship between the offset response of back-ground seismic reflections and corresponding theoretical predictions for average lithologic interfaces thought to cause these background reflections. It is assumed that any deviation from the theoretical response is a result of residual processing phenomenon and/or suboptimal processing, and a simple offset-dependent scaling function is designed to correct for these differences. This function can then be applied to seismic data over both prospective and nonprospective zones within an area where the theoretical values are appropriate and the seismic characteristics are consistent. A conservative application of the above procedure results in an AVO response over both gas sands and wet sands that is much closer to theoretically expected values. A case history from the Gulf of Mexico Flexure Trend is presented as an example to demonstrate the offset balancing technique.

  1. Deformation and seismicity of Taiwan.

    PubMed

    Vita-Finzi, C

    2000-10-10

    14C-dated Holocene coastal uplift, conventional and satellite geodetic measurements, and coseismic and aseismic fault slip reveal the pattern of distributed deformation at Taiwan resulting from convergence between the Philippine Sea plate and Eurasia; as in other subduction orogenic settings, the locus of strain release and accumulation is strongly influenced by changes in fault geometry across strike. Uplift evidence from the islands of Lutao and Lanhsu is consistent with progressive oblique collision between the Luzon arc and the Chinese continental margin. In the Coastal Range, geodetic and seismic records show that shortening is taken up serially by discontinuous slip on imbricate faults. The geodetic data point to net extension across the Central Range, but deformed Holocene shorelines in the Hengchun Peninsula at its southern extremity suggest that the extension is a superficial effect partly caused by blind reverse faulting. The fastest shortening rates indicated by geodesy are recorded on the Longitudinal Valley fault and across the Chukou fault within the fold-and-thrust belt. In the former, the strain is dissipated mainly as aseismic reverse and strike-slip displacement. In contrast, the fold-and-thrust belt has witnessed five earthquakes with magnitudes of 6.5 or above in the 20th century, including the 1999.9.21 Chi-Chi earthquake (magnitude approximately 7.6) on a branch of the Chukou fault. The neotectonic and geodetic data for Taiwan as a whole suggest that the fold-and-thrust belt will continue to host the majority of great earthquakes on the island.

  2. Perceptual discontinuities and categorization: Implications for speech perception

    NASA Astrophysics Data System (ADS)

    Holt, Lori L.; Lotto, Andrew J.; Diehl, Randy L.

    2003-04-01

    Behavioral experiments with infants, adults and nonhuman animals converge with neurophysiological findings to suggest that there is a discontinuity in auditory processing of stimulus components differing in onset time by about 20 ms. This discontinuity has been implicated as a basis for boundaries between speech categories distinguished by VOT. Here, we investigate how this discontinuity interacts with the learning of novel perceptual categories. Adult listeners were trained to categorize a nonspeech acoustic cue that mimics the temporal distinction of VOT. One group of listeners learned categories with a boundary coincident with the perceptual discontinuity. Another group learned categories defined such that the perceptual discontinuity fell within a category. Listeners in the latter group required significantly more experience to reach criterion categorization performance. The evidence of interactions between the perceptual discontinuity and the learned categories extended to generalization tests as well. It has been hypothesized that languages make use of perceptual discontinuities to promote perceptual distinctiveness among sounds within a language inventory. The present data suggest that these influences interact with category learning. As such, learnability may play a predictive role in selection of language sound inventories. Moreover, it may be possible to observe predictable learning effects in infant speech perception.

  3. Magnetic discontinuities in magnetohydrodynamic turbulence and in the solar wind.

    PubMed

    Zhdankin, Vladimir; Boldyrev, Stanislav; Mason, Joanne; Perez, Jean Carlos

    2012-04-27

    Recent measurements of solar wind turbulence report the presence of intermittent, exponentially distributed angular discontinuities in the magnetic field. In this Letter, we study whether such discontinuities can be produced by magnetohydrodynamic (MHD) turbulence. We detect the discontinuities by measuring the fluctuations of the magnetic field direction, Δθ, across fixed spatial increments Δx in direct numerical simulations of MHD turbulence with an imposed uniform guide field B(0). A large region of the probability density function (pdf) for Δθ is found to follow an exponential decay, proportional to exp(-Δθ/θ(*)), with characteristic angle θ(*)≈(14°)(b(rms)/B(0))(0.65) for a broad range of guide-field strengths. We find that discontinuities observed in the solar wind can be reproduced by MHD turbulence with reasonable ratios of b(rms)/B(0). We also observe an excess of small angular discontinuities when Δx becomes small, possibly indicating an increasing statistical significance of dissipation-scale structures. The structure of the pdf in this case closely resembles the two-population pdf seen in the solar wind. We thus propose that strong discontinuities are associated with inertial-range MHD turbulence, while weak discontinuities emerge from dissipation-range turbulence. In addition, we find that the structure functions of the magnetic field direction exhibit anomalous scaling exponents, which indicates the existence of intermittent structures.

  4. Outcomes of patients with chronic lymphocytic leukemia after discontinuing ibrutinib

    PubMed Central

    Jain, Preetesh; Keating, Michael; Wierda, William; Estrov, Zeev; Ferrajoli, Alessandra; Jain, Nitin; George, Binsah; James, Danelle; Kantarjian, Hagop; Burger, Jan

    2015-01-01

    Ibrutinib is a Bruton tyrosine kinase inhibitor approved for the treatment of patients with relapsed refractory chronic lymphocytic leukemia (RR-CLL). We describe the characteristics, causes of discontinuation, and outcomes in patients who discontinued treatment with ibrutinib. One hundred twenty-seven patients were enrolled in various clinical trials of ibrutinib, with or without rituximab, at our center. Thirty-three (26%) patients have discontinued ibrutinib to date. The majority of those patients had high-risk features: 94% with unmutated immunoglobulin heavy chain variable gene rearrangement, 58% with del(17p) by fluorescence in situ hybridization, and 54% with a complex karyotype. Causes of discontinuation were disease transformation (7), progressive CLL (7), stem cell transplantation (3), adverse events (11), serious adverse events/deaths (3), and miscellaneous reasons (2). Twenty five patients (76%) died after discontinuing ibrutinib; the median overall survival was 3.1 months after discontinuation. Most patients with RR-CLL who discontinued ibrutinib early were difficult to treat and had poor outcomes. PMID:25573991

  5. Discontinuity of cortical gradients reflects sensory impairment

    PubMed Central

    Saadon-Grosman, Noam; Tal, Zohar; Itshayek, Eyal; Amedi, Amir; Arzy, Shahar

    2015-01-01

    Topographic maps and their continuity constitute a fundamental principle of brain organization. In the somatosensory system, whole-body sensory impairment may be reflected either in cortical signal reduction or disorganization of the somatotopic map, such as disturbed continuity. Here we investigated the role of continuity in pathological states. We studied whole-body cortical representations in response to continuous sensory stimulation under functional MRI (fMRI) in two unique patient populations—patients with cervical sensory Brown-Séquard syndrome (injury to one side of the spinal cord) and patients before and after surgical repair of cervical disk protrusion—enabling us to compare whole-body representations in the same study subjects. We quantified the spatial gradient of cortical activation and evaluated the divergence from a continuous pattern. Gradient continuity was found to be disturbed at the primary somatosensory cortex (S1) and the supplementary motor area (SMA), in both patient populations: contralateral to the disturbed body side in the Brown-Séquard group and before repair in the surgical group, which was further improved after intervention. Results corresponding to the nondisturbed body side and after surgical repair were comparable with control subjects. No difference was found in the fMRI signal power between the different conditions in the two groups, as well as with respect to control subjects. These results suggest that decreased sensation in our patients is related to gradient discontinuity rather than signal reduction. Gradient continuity may be crucial for somatotopic and other topographical organization, and its disruption may characterize pathological processing. PMID:26655739

  6. Discontinuity of cortical gradients reflects sensory impairment.

    PubMed

    Saadon-Grosman, Noam; Tal, Zohar; Itshayek, Eyal; Amedi, Amir; Arzy, Shahar

    2015-12-29

    Topographic maps and their continuity constitute a fundamental principle of brain organization. In the somatosensory system, whole-body sensory impairment may be reflected either in cortical signal reduction or disorganization of the somatotopic map, such as disturbed continuity. Here we investigated the role of continuity in pathological states. We studied whole-body cortical representations in response to continuous sensory stimulation under functional MRI (fMRI) in two unique patient populations-patients with cervical sensory Brown-Séquard syndrome (injury to one side of the spinal cord) and patients before and after surgical repair of cervical disk protrusion-enabling us to compare whole-body representations in the same study subjects. We quantified the spatial gradient of cortical activation and evaluated the divergence from a continuous pattern. Gradient continuity was found to be disturbed at the primary somatosensory cortex (S1) and the supplementary motor area (SMA), in both patient populations: contralateral to the disturbed body side in the Brown-Séquard group and before repair in the surgical group, which was further improved after intervention. Results corresponding to the nondisturbed body side and after surgical repair were comparable with control subjects. No difference was found in the fMRI signal power between the different conditions in the two groups, as well as with respect to control subjects. These results suggest that decreased sensation in our patients is related to gradient discontinuity rather than signal reduction. Gradient continuity may be crucial for somatotopic and other topographical organization, and its disruption may characterize pathological processing. PMID:26655739

  7. Seismicity in Northern Germany

    NASA Astrophysics Data System (ADS)

    Bischoff, Monika; Gestermann, Nicolai; Plenefisch, Thomas; Bönnemann, Christian

    2013-04-01

    Northern Germany is a region of low tectonic activity, where only few and low-magnitude earthquakes occur. The driving tectonic processes are not well-understood up to now. In addition, seismic events during the last decade concentrated at the borders of the natural gas fields. The source depths of these events are shallow and in the depth range of the gas reservoirs. Based on these observations a causal relationship between seismicity near gas fields and the gas production is likely. The strongest of these earthquake had a magnitude of 4.5 and occurred near Rotenburg in 2004. Also smaller seismic events were considerably felt by the public and stimulated the discussion on the underlying processes. The latest seismic event occurred near Langwedel on 22nd November 2012 and had a magnitude of 2.8. Understanding the causes of the seismicity in Northern Germany is crucial for a thorough evaluation. Therefore the Seismological Service of Lower Saxony (NED) was established at the State Office for Mining, Energy and Geology (LBEG) of Lower Saxony in January 2013. Its main task is the monitoring and evaluation of the seismicity in Lower Saxony and adjacent areas. Scientific and technical questions are addressed in close cooperation with the Seismological Central Observatory (SZO) at the Federal Institute for Geosciences and Natural Resources (BGR). The seismological situation of Northern Germany will be presented. Possible causes of seismicity are introduced. Rare seismic events at greater depths are distributed over the whole region and probably are purely tectonic whereas events in the vicinity of natural gas fields are probably related to gas production. Improving the detection threshold of seismic events in Northern Germany is necessary for providing a better statistical basis for further analyses answering these questions. As a first step the existing seismic network will be densified over the next few years. The first borehole station was installed near Rethem by BGR

  8. Intensity Based Seismic Hazard Map of Republic of Macedonia

    NASA Astrophysics Data System (ADS)

    Dojcinovski, Dragi; Dimiskovska, Biserka; Stojmanovska, Marta

    2016-04-01

    The territory of the Republic of Macedonia and the border terrains are among the most seismically active parts of the Balkan Peninsula belonging to the Mediterranean-Trans-Asian seismic belt. The seismological data on the R. Macedonia from the past 16 centuries point to occurrence of very strong catastrophic earthquakes. The hypocenters of the occurred earthquakes are located above the Mohorovicic discontinuity, most frequently, at a depth of 10-20 km. Accurate short -term prognosis of earthquake occurrence, i.e., simultaneous prognosis of time, place and intensity of their occurrence is still not possible. The present methods of seismic zoning have advanced to such an extent that it is with a great probability that they enable efficient protection against earthquake effects. The seismic hazard maps of the Republic of Macedonia are the result of analysis and synthesis of data from seismological, seismotectonic and other corresponding investigations necessary for definition of the expected level of seismic hazard for certain time periods. These should be amended, from time to time, with new data and scientific knowledge. The elaboration of this map does not completely solve all issues related to earthquakes, but it provides basic empirical data necessary for updating the existing regulations for construction of engineering structures in seismically active areas regulated by legal regulations and technical norms whose constituent part is the seismic hazard map. The map has been elaborated based on complex seismological and geophysical investigations of the considered area and synthesis of the results from these investigations. There were two phases of elaboration of the map. In the first phase, the map of focal zones characterized by maximum magnitudes of possible earthquakes has been elaborated. In the second phase, the intensities of expected earthquakes have been computed according to the MCS scale. The map is prognostic, i.e., it provides assessment of the

  9. Seismic evidence for an inner core transition zone

    PubMed

    Song; Helmberger

    1998-10-30

    Seismic waves that traverse Earth's inner core along north-south paths produce unusually broad pulse shapes at long periods (compared with waves along east-west paths) and reflections from below the inner core boundary at short periods. The observations provide compelling evidence for a seismic velocity discontinuity along north-south paths about 200 kilometers below the inner core boundary separating an isotropic upper inner core from an anisotropic lower inner core. The triplication associated with such a structure might be responsible for reported waveform complexity of short-period inner core arrivals along north-south paths and, if the depth of the boundary is laterally variable, their large travel-time variation.

  10. Seismic Safety Study

    SciTech Connect

    Tokarz, F J; Coats, D W

    2006-05-16

    During the past three decades, the Laboratory has been proactive in providing a seismically safe working environment for its employees and the general public. Completed seismic upgrades during this period have exceeded $30M with over 24 buildings structurally upgraded. Nevertheless, seismic questions still frequently arise regarding the safety of existing buildings. To address these issues, a comprehensive study was undertaken to develop an improved understanding of the seismic integrity of the Laboratory's entire building inventory at the Livermore Main Site and Site 300. The completed study of February 2005 extended the results from the 1998 seismic safety study per Presidential Executive Order 12941, which required each federal agency to develop an inventory of its buildings and to estimate the cost of mitigating unacceptable seismic risks. Degenkolb Engineers, who performed the first study, was recontracted to perform structural evaluations, rank order the buildings based on their level of seismic deficiencies, and to develop conceptual rehabilitation schemes for the most seriously deficient buildings. Their evaluation is based on screening procedures and guidelines as established by the Interagency Committee on Seismic Safety in Construction (ICSSC). Currently, there is an inventory of 635 buildings in the Laboratory's Facility Information Management System's (FIMS's) database, out of which 58 buildings were identified by Degenkolb Engineers that require seismic rehabilitation. The remaining 577 buildings were judged to be adequate from a seismic safety viewpoint. The basis for these evaluations followed the seismic safety performance objectives of DOE standard (DOE STD 1020) Performance Category 1 (PC1). The 58 buildings were ranked according to three risk-based priority classifications (A, B, and C) as shown in Figure 1-1 (all 58 buildings have structural deficiencies). Table 1-1 provides a brief description of their expected performance and damage state

  11. Discontinuous Spectral Difference Method for Conservation Laws on Unstructured Grids

    NASA Technical Reports Server (NTRS)

    Liu, Yen; Vinokur, Marcel; Wang, Z. J.

    2004-01-01

    A new, high-order, conservative, and efficient method for conservation laws on unstructured grids is developed. The concept of discontinuous and high-order local representations to achieve conservation and high accuracy is utilized in a manner similar to the Discontinuous Galerkin (DG) and the Spectral Volume (SV) methods, but while these methods are based on the integrated forms of the equations, the new method is based on the differential form to attain a simpler formulation and higher efficiency. A discussion on the Discontinuous Spectral Difference (SD) Method, locations of the unknowns and flux points and numerical results are also presented.

  12. Discontinuous Galerkin computation of the Maxwell eigenvalues on simplicial meshes

    NASA Astrophysics Data System (ADS)

    Buffa, Annalisa; Houston, Paul; Perugia, Ilaria

    2007-07-01

    This paper is concerned with the discontinuous Galerkin approximation of the Maxwell eigenproblem. After reviewing the theory developed in [A. Buffa, I. Perugia, Discontinuous Galerkin approximation of the Maxwell eigenproblem, Technical Report 24-PV, IMATI-CNR, Pavia, Italy, 2005 ], we present a set of numerical experiments which both validate the theory, and provide further insight regarding the practical performance of discontinuous Galerkin methods, particularly in the case when non-conforming meshes, characterized by the presence of hanging nodes, are employed.

  13. Risk of discontinuation of Advanced Therapy Medicinal Products clinical trials

    PubMed Central

    Hanna, Eve; Rémuzat, Cecile; Auquier, Pascal; Toumi, Mondher

    2016-01-01

    Objective Advanced therapy medicinal products (ATMPs) constitute a class of innovative products that encompasses gene therapy, somatic cell therapy, and tissue-engineered products (TEP). There is an increased investment of commercial and non-commercial sponsors in this field and a growing number of ATMPs randomized clinical trials (RCT) and patients enrolled in such trials. RCT generate data to prove the efficacy of a new therapy, but the discontinuation of RCTs wastes scarce resources. Our objective is to identify the number and characteristics of discontinued ATMPs trials in order to evaluate the rate of discontinuation. Methods We searched for ATMPs trials conducted between 1999 to June 2015 using three databases, which are Clinicaltrials.gov, the International Clinical Trials Registry Platform (ICTRP), and the EU Drug Regulating Authorities Clinical Trials (EudraCT). We selected the ATMPs trials after elimination of the duplicates. We identified the disease areas and the sponsors as commercial or non-commercial organizations. We classified ATMPs by type and trial status, that is, ongoing, completed, terminated, discontinued, and prematurely ended. Then, we calculated the rate of discontinuation. Results Between 1999 and June 2015, 143 withdrawn, terminated, or prematurely ended ATMPs clinical trials were identified. Between 1999 and June 2013, 474 ongoing and completed clinical trials were identified. Therefore, the rate of discontinuation of ATMPs trials is 23.18%, similar to that for non-ATMPs drugs in development. The probability of discontinuation is, respectively, 27.35, 16.28, and 16.34% for cell therapies, gene therapies, and TEP. The highest discontinuation rate is for oncology (43%), followed by cardiology (19.2%). It is almost the same for commercial and non-commercial sponsors; therefore, the discontinuation reason may not be financially driven. Conclusion No failure risk rate per development phase is available for ATMPs. The discontinuation rate may

  14. Accountability Accentuates Interindividual-Intergroup Discontinuity by Enforcing Parochialism

    PubMed Central

    Wildschut, Tim; van Horen, Femke; Hart, Claire

    2015-01-01

    Interindividual-intergroup discontinuity is the tendency for relations between groups to be more competitive than relations between individuals. We examined whether the discontinuity effect arises in part because group members experience normative pressure to favor the ingroup (parochialism). Building on the notion that accountability enhances normative pressure, we hypothesized that the discontinuity effect would be larger when accountability is present (compared to absent). A prisoner’s dilemma game experiment supported this prediction. Specifically, intergroup (compared to interindividual) interaction activated an injunctive ingroup-favoring norm, and accountability enhanced the influence of this norm on competitive behavior. PMID:26635691

  15. Coupling impedances of small discontinuities: A general approach

    NASA Astrophysics Data System (ADS)

    Kurennoy, Sergey S.; Gluckstern, Robert L.; Stupakov, Gennady V.

    1995-10-01

    A general theory of the beam interaction with small discontinuities of the vacuum chamber of an accelerator is developed taking into account the reaction of radiated waves back on the discontinuity. The reactive impedance calculated earlier is reproduced as the first order and the resistive one as the second order of a perturbation theory based on this general approach. The theory also gives, in an easy and natural way, the analytical results for the frequencies and coupling impedances of the trapped modes due to small discontinuities on the vacuum chamber of a general cross section. Formulas for two important particular cases-a circular and a rectangular chamber-are presented.

  16. Neotectonics and seismicity of the Clearlake region in northern California

    SciTech Connect

    Burns, K.L.

    1996-04-01

    Geological, topographic, and seismic methods were used to locate faults in the vicinity of Clearlake in northern California. The geological method, which seeks faults as discontinuities in the lithotope, found faults in the Tertiary-Cretaceous rocks east of Burns Valley. The topographic method, which is used to produce Fault Evaluation Reports, found a very active fault zone, the Konocti Bay fault zone, south of Highlands arm. It also found some active faults north of Highlands arm, in the eastern part of Burns Valley and on the lakeshore near Oak Park. The seismic method is the most enduring of the three methods but is limited by location accuracy; the results improve as monitoring continues because of increases in the density of events and improvements in the crustal velocity model. The seismic method identified faulting along the valley at Borax Lake and possibly also on a line running northeast from the city of Clearlake. The latter may be associated with the Burns Valley fault or with the line of scoria domes which runs parallel to it. Seismic observations over longer periods at higher resolution will be required in order to determine the location of active faults near the city. 47 refs., 13 figs.

  17. 100 years of seismic research on the Moho

    NASA Astrophysics Data System (ADS)

    Prodehl, Claus; Kennett, Brian; Artemieva, Irina M.; Thybo, Hans

    2013-12-01

    The detection of a seismic boundary, the “Moho”, between the outermost shell of the Earth, the Earth's crust, and the Earth's mantle by A. Mohorovičić was the consequence of increased insight into the propagation of seismic waves caused by earthquakes. This short history of seismic research on the Moho is primarily based on the comprehensive overview of the worldwide history of seismological studies of the Earth's crust using controlled sources from 1850 to 2005, by Prodehl and Mooney (2012). Though the art of applying explosions, so-called “artificial events”, as energy sources for studies of the uppermost crustal layers began in the early 1900s, its effective use for studying the entire crust only began at the end of World War II. From 1945 onwards, controlled-source seismology has been the major approach to study details of the crust and underlying crust-mantle boundary, the Moho. The subsequent description of history of controlled-source crustal seismology and its seminal results is subdivided into separate chapters for each decade, highlighting the major advances achieved during that decade in terms of data acquisition, processing technology, and interpretation methods. Since the late 1980s, passive seismology using distant earthquakes has played an increasingly important role in studies of crustal structure. The receiver function technique exploiting conversions between P and SV waves at discontinuities in seismic wavespeed below a seismic station has been extensively applied to the increasing numbers of permanent and portable broad-band seismic stations across the globe. Receiver function studies supplement controlled source work with improved geographic coverage and now make a significant contribution to knowledge of the nature of the crust and the depth to Moho.

  18. Landslide seismic magnitude

    NASA Astrophysics Data System (ADS)

    Lin, C. H.; Jan, J. C.; Pu, H. C.; Tu, Y.; Chen, C. C.; Wu, Y. M.

    2015-11-01

    Landslides have become one of the most deadly natural disasters on earth, not only due to a significant increase in extreme climate change caused by global warming, but also rapid economic development in topographic relief areas. How to detect landslides using a real-time system has become an important question for reducing possible landslide impacts on human society. However, traditional detection of landslides, either through direct surveys in the field or remote sensing images obtained via aircraft or satellites, is highly time consuming. Here we analyze very long period seismic signals (20-50 s) generated by large landslides such as Typhoon Morakot, which passed though Taiwan in August 2009. In addition to successfully locating 109 large landslides, we define landslide seismic magnitude based on an empirical formula: Lm = log ⁡ (A) + 0.55 log ⁡ (Δ) + 2.44, where A is the maximum displacement (μm) recorded at one seismic station and Δ is its distance (km) from the landslide. We conclude that both the location and seismic magnitude of large landslides can be rapidly estimated from broadband seismic networks for both academic and applied purposes, similar to earthquake monitoring. We suggest a real-time algorithm be set up for routine monitoring of landslides in places where they pose a frequent threat.

  19. HANFORD DOUBLE SHELL TANK (DST) THERMAL & SEISMIC PROJECT SEISMIC ANALYSIS OF HANFORD DOUBLE SHELL TANKS

    SciTech Connect

    MACKEY, T.C.

    2006-03-17

    M&D Professional Services, Inc. (M&D) is under subcontract to Pacific Northwest National Laboratory (PNNL) to perform seismic analysis of the Hanford Site double-shell tanks (DSTs) in support of a project entitled ''Double-Shell Tank (DSV Integrity Project--DST Thermal and Seismic Analyses)''. The overall scope of the project is to complete an up-to-date comprehensive analysis of record of the DST system at Hanford in support of Tri-Party Agreement Milestone M-48-14, The work described herein was performed in support of the seismic analysis of the DSTs. The thermal and operating loads analysis of the DSTs is documented in Rinker et al. (2004). The work statement provided to M&D (PNNL 2003) required that the seismic analysis of the DSTs assess the impacts of potentially non-conservative assumptions in previous analyses and account for the additional soil mass due to the as-found soil density increase, the effects of material degradation, additional thermal profiles applied to the full structure including the soil-structure response with the footings, the non-rigid (low frequency) response of the tank roof, the asymmetric seismic-induced soil loading, the structural discontinuity between the concrete tank wall and the support footing and the sloshing of the tank waste. The seismic analysis considers the interaction of the tank with the surrounding soil and the effects of the primary tank contents. The DSTs and the surrounding soil are modeled as a system of finite elements. The depth and width of the soil incorporated into the analysis model are sufficient to obtain appropriately accurate analytical results. The analyses required to support the work statement differ from previous analysis of the DSTs in that the soil-structure interaction (SSI) model includes several (nonlinear) contact surfaces in the tank structure, and the contained waste must be modeled explicitly in order to capture the fluid-structure interaction behavior between the primary tank and contained

  20. On cell entropy inequality for discontinuous Galerkin methods

    NASA Technical Reports Server (NTRS)

    Jiang, Guangshan; Shu, Chi-Wang

    1993-01-01

    We prove a cell entropy inequality for a class of high order discontinuous Galerkin finite element methods approximating conservation laws, which implies convergence for the one dimensional scalar convex case.

  1. PML-IRIS during Fingolimod Diagnosed after Natalizumab Discontinuation

    PubMed Central

    Killestein, J.; Vennegoor, A.; van Golde, A. E. L.; Bourez, R. L. J. H.; Wijlens, M. L. B.; Wattjes, M. P.

    2014-01-01

    Background. Natalizumab treatment is frequently discontinued and replaced by alternative medication in multiple sclerosis (MS) patients having a high risk of progressive multifocal leukoencephalopathy (PML). Case Presentation. We report a PML case that was missed on magnetic resonance imaging (MRI) at the time Natalizumab treatment was discontinued. The patient subsequently developed a PML-immune reconstitution inflammatory syndrome after the initiation of Fingolimod treatment, suggesting that immune reconstitution may occur even during Fingolimod induced lymphopenia. Conclusion. This report highlights the need for strict drug surveillance using MRI of Natalizumab-associated MS patients at the time of drug discontinuation and beyond. This is important with respect to pharmacovigilance purposes not only for Natalizumab, but also for alternative drugs used after Natalizumab discontinuation. PMID:25506447

  2. Robust state estimation for neural networks with discontinuous activations.

    PubMed

    Liu, Xiaoyang; Cao, Jinde

    2010-12-01

    Discontinuous dynamical systems, particularly neural networks with discontinuous activation functions, arise in a number of applications and have received considerable research attention in recent years. In this paper, the robust state estimation problem is investigated for uncertain neural networks with discontinuous activations and time-varying delays, where the neuron-dependent nonlinear disturbance on the network outputs are only assumed to satisfy the local Lipschitz condition. Based on the theory of differential inclusions and nonsmooth analysis, several criteria are presented to guarantee the existence of the desired robust state estimator for the discontinuous neural networks. It is shown that the design of the state estimator for such networks can be achieved by solving some linear matrix inequalities, which are dependent on the size of the time derivative of the time-varying delays. Finally, numerical examples are given to illustrate the theoretical results.

  3. Propagating plasma discontinuity in a tube immersed in distilled water

    NASA Astrophysics Data System (ADS)

    Song, Jian; Tang, Jingfeng; Wei, Liqiu; Zhang, Nan; Wang, Youyin; Yu, Daren

    2016-04-01

    In a dielectric tube partially surrounded by distilled water, a propagating discontinuity is observed in a cold argon plasma jet at atmospheric pressure in both the laminar and turbulent flow regimes. Through electrical and optical diagnostics, the mechanism of formation for this phenomenon is investigated. Results show that the strong polarization of the distilled water, the constraint from the electric field (or a sufficiently high electric field), and the transport of the active species are in combination responsible for the propagating plasma discontinuity. Indeed, smaller surface areas of the tube surrounded by distilled water, shorter distances between the distilled water and the ground electrodes, as well as larger gas flow rates can together make the discontinuous discharge channel appear more readily. In particular, when the flow switches from laminar to turbulent, the plasma behavior of the discontinuity no longer depends on the gas flow rate. This is mostly attributed to the extreme instability of turbulence which further suppresses the transport of active species.

  4. Discontinuation of Antidepressant Medication Among Latinos in the US

    PubMed Central

    Hodgkin, Dominic; Volpe-Vartanian, Joanna; Alegría, Margarita

    2009-01-01

    Despite recent growth in the variety of antidepressant medications available, many patients discontinue medication prematurely, for reasons such as nonresponse, side effects, stigma and miscommunication. Some analysts have suggested that Latinos may have higher antidepressant discontinuation rates than other US residents. This paper examines Latino antidepressant discontinuation, using data from a national probability survey of Latinos in the US. In this sample, 8% of Latinos had taken an antidepressant in the preceding 12 months. Among those users, 33.3% had discontinued taking antidepressants at the time of interview, and 18.9% had done so without prior input from their physician. Even controlling for clinical and other variables, patients who reported good or excellent English proficiency were less likely to stop at all. Patients were also less likely to stop if they were older, married, had public or private insurance, or had made eight or more visits to a nonmedical therapist. PMID:17570068

  5. 47 CFR 5.81 - Discontinuance of station operation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 1 2012-10-01 2012-10-01 false Discontinuance of station operation. 5.81 Section 5.81 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL EXPERIMENTAL RADIO SERVICE (OTHER... Commission's Office of Engineering and Technology for cancellation....

  6. Discontinuities, cross-scale patterns, and the organization of ecosystems

    USGS Publications Warehouse

    Nash, Kirsty L.; Allen, Craig R.; Angeler, David G.; Barichievy, Chris; Eason, Tarsha; Garmestani, Ahjond S.; Graham, Nicholas A.J.; Granholm, Dean; Knutson, Melinda; Nelson, R. John; Nystrom, Magnus; Stow, Craig A.; Sandstrom, Shana M.

    2014-01-01

    Ecological structures and processes occur at specific spatiotemporal scales, and interactions that occur across multiple scales mediate scale-specific (e.g., individual, community, local, or regional) responses to disturbance. Despite the importance of scale, explicitly incorporating a multi-scale perspective into research and management actions remains a challenge. The discontinuity hypothesis provides a fertile avenue for addressing this problem by linking measureable proxies to inherent scales of structure within ecosystems. Here we outline the conceptual framework underlying discontinuities and review the evidence supporting the discontinuity hypothesis in ecological systems. Next we explore the utility of this approach for understanding cross-scale patterns and the organization of ecosystems by describing recent advances for examining nonlinear responses to disturbance and phenomena such as extinctions, invasions, and resilience. To stimulate new research, we present methods for performing discontinuity analysis, detail outstanding knowledge gaps, and discuss potential approaches for addressing these gaps.

  7. 7 CFR 160.55 - Voluntary discontinuance of licensed inspection.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... licensed inspectors for making official inspections, gradings, and certifications of naval stores, shall give not less than 30 days notice in writing to the Administrator of the intention to discontinue...

  8. Calculation of Accurate Hexagonal Discontinuity Factors for PARCS

    SciTech Connect

    Pounders. J., Bandini, B. R. , Xu, Y, and Downar, T. J.

    2007-11-01

    In this study we derive a methodology for calculating discontinuity factors consistent with the Triangle-based Polynomial Expansion Nodal (TPEN) method implemented in PARCS for hexagonal reactor geometries. The accuracy of coarse-mesh nodal methods is greatly enhanced by permitting flux discontinuities at node boundaries, but the practice of calculating discontinuity factors from infinite-medium (zero-current) single bundle calculations may not be sufficiently accurate for more challenging problems in which there is a large amount of internodal neutron streaming. The authors therefore derive a TPEN-based method for calculating discontinuity factors that are exact with respect to generalized equivalence theory. The method is validated by reproducing the reference solution for a small hexagonal core.

  9. Method and device for detection of surface discontinuities or defects

    NASA Technical Reports Server (NTRS)

    Leger, L. J. (Inventor)

    1974-01-01

    Surface discontinuities of defects such as cracks and orifices are detected by applying a penetrating fluid, preferably a liquid, to a test surface so as to cause the liquid to penetrate any minute cracks or opening in the surface, removing the excess liquid from the surface, and leaving a residual in the discontinuities, cavities, or in the subsurface materials. A sheet of porous material impregnated with a sensitizing medium which will react with vapors of the residual liquid to form a visible pattern is applied to the test surface. The residual liquid trapped in the discontinuities, cavities, or subsurface material is vaporized, and, as the vapors contact the sensitizing medium on the sheet, a pattern corresponding to the discontinuity is formed on the sheet material and the penetrant completely removed from the sample.

  10. The utility of petroleum seismic exploration data in delineating structural features within salt anticlines

    USGS Publications Warehouse

    Stockton, S.L.; Balch, Alfred H.

    1978-01-01

    The Salt Valley anticline, in the Paradox Basin of southeastern Utah, is under investigation for use as a location for storage of solid nuclear waste. Delineation of thin, nonsalt interbeds within the upper reaches of the salt body is extremely important because the nature and character of any such fluid- or gas-saturated horizons would be critical to the mode of emplacement of wastes into the structure. Analysis of 50 km of conventional seismic-reflection data, in the vicinity of the anticline, indicates that mapping of thin beds at shallow depths may well be possible using a specially designed adaptation of state-of-the-art seismic oil-exploration procedures. Computer ray-trace modeling of thin beds in salt reveals that the frequency and spatial resolution required to map the details of interbeds at shallow depths (less than 750 m) may be on the order of 500 Hz, with surface-spread lengths of less than 350 m. Consideration should be given to the burial of sources and receivers in order to attenuate surface noise and to record the desired high frequencies. Correlation of the seismic-reflection data with available well data and surface geology reveals the complex, structurally initiated diapir, whose upward flow was maintained by rapid contemporaneous deposition of continental clastic sediments on its flanks. Severe collapse faulting near the crests of these structures has distorted the seismic response. Evidence exists, however, that intrasalt thin beds of anhydrite, dolomite, and black shale are mappable on seismic record sections either as short, discontinuous reflected events or as amplitude anomalies that result from focusing of the reflected seismic energy by the thin beds; computer modeling of the folded interbeds confirms both of these as possible causes of seismic response from within the salt diapir. Prediction of the seismic signatures of the interbeds can be made from computer-model studies. Petroleum seismic-reflection data are unsatisfactory for

  11. 41 CFR 109-39.105 - Discontinuance or curtailment of service.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... AVIATION, TRANSPORTATION, AND MOTOR VEHICLES 39-INTERAGENCY FLEET MANAGEMENT SYSTEMS 39.1-Establishment, Modification, and Discontinuance of Interagency Fleet Management Systems § 109-39.105 Discontinuance...

  12. Heat exchanger containing a component capable of discontinuous movement

    DOEpatents

    Wilson, D.G.

    1993-11-09

    Regenerative heat exchangers are described for transferring heat between hot and cold fluids. The heat exchangers have seal-leakage rates significantly less than those of conventional regenerative heat exchangers because the matrix is discontinuously moved and is releasably sealed while in a stationary position. Both rotary and modular heat exchangers are described. Also described are methods for transferring heat between a hot and cold fluid using the discontinuous movement of matrices. 11 figures.

  13. Determining the Locations and Discontinuities in the Derivatives of Functions

    SciTech Connect

    Archibald, Richard K; Gelb, Anne; Yoon, Jungho

    2007-01-01

    We introduce a method for detecting discontinuities in piecewise smooth functions and in their derivatives. The method is constructed from a local stencil of grid point values and is based on a polynomial annihilation technique. By varying the order of the method and the arrangement of the corresponding stencils, the jump discontinuities of a function and its derivatives can be identified with high order accuracy. The method is efficient and robust and can be applied to non-uniform distributions in one dimension.

  14. Shallow Mantle Discontinuities Beneath the North Anatolian Fault

    NASA Astrophysics Data System (ADS)

    Friedman, D. P.; Fischer, K. M.; Hopper, E.

    2015-12-01

    The goal of this study is to better understand deformation in the mantle lithosphere beneath continental strike-slip plate boundaries through Sp receiver function analysis of mantle discontinuities beneath the North Anatolian Fault (NAF). This fault zone marks the boundary between the Anatolian and Eurasian plates. Sp receiver functions were calculated using waveforms filtered with a variety of bandpasses, and 33 s to 4 s was found to produce coherent images while reducing interference between phases from the Moho and shallow mantle discontinuities. Using common conversion point stacking, we calculated 3D images of scattering beneath the region for two different cases: migration with the S-wave and P-wave velocities from the waveform tomography model of Fichtner et al. (2013) and with the AK135 velocity model. In both cases, a clear Moho is observed and Moho depth does not systematically vary between sides of the NAF. In contrast, shallow mantle discontinuities show pronounced changes in depth that correlate with strong lateral variations in mantle velocity observed in the Fichtner et al. tomography model, and some of these discontinuity depth variations occur within 50 km horizontally of the surface expression of the NAF. Where the tomography contains a clear high velocity lithospheric mantle layer, the Sp stack contains a negative velocity gradient at depths comparable to the base of the high velocity layer that can be interpreted as the seismological LAB. Where the tomography shows low mantle velocities that persist to the crust, a feature that may represent either anomalously low velocity lithosphere or upwelling asthenosphere beneath thin lithosphere, mantle discontinuities differ significantly from surrounding regions. Mantle discontinuity depth variations beneath the NAF also occur when the data are migrated with the AK135 model. Hence, the presence of the discontinuity depth variations is not an artifact of the assumed velocity model, although depths differ

  15. Heat exchanger containing a component capable of discontinuous movement

    DOEpatents

    Wilson, David G.

    1993-01-01

    Regenerative heat exchangers are described for transferring heat between hot and cold fluids. The heat exchangers have seal-leakage rates significantly less than those of conventional regenerative heat exchangers because the matrix is discontinuously moved and is releasably sealed while in a stationary position. Both rotary and modular heat exchangers are described. Also described are methods for transferring heat between a hot and cold fluid using the discontinuous movement of matrices.

  16. Heat exchanger containing a component capable of discontinuous movement

    DOEpatents

    Wilson, David Gordon

    2001-04-17

    Regenerative heat exchangers are described for transferring heat between hot and cold fluids. The heat exchangers have seal-leakage rates significantly less than those of conventional regenerative heat exchangers because the matrix is discontinuously moved and is releasably sealed while in a stationary position. Both rotary and modular heat exchangers are described. Also described are methods for transferring heat between a hot and cold fluid using the discontinuous movement of matrices.

  17. Heat exchanger containing a component capable of discontinuous movement

    DOEpatents

    Wilson, David Gordon

    2002-01-01

    Regenerative heat exchangers are described for transferring heat between hot and cold fluids. The heat exchangers have seal-leakage rates significantly less than those of conventional regenerative heat exchangers because the matrix is discontinuously moved and is releasably sealed while in a stationary position. Both rotary and modular heat exchangers are described. Also described are methods for transferring heat between a hot and cold fluid using the discontinuous movement of matrices.

  18. Implications of bevacizumab discontinuation in adults with recurrent glioblastoma

    PubMed Central

    Anderson, Mark D.; Hamza, Mohamed A.; Hess, Kenneth R.; Puduvalli, Vinay K.

    2014-01-01

    Background Patients with recurrent glioblastoma benefiting from bevacizumab are often treated indefinitely due to concerns regarding rebound tumor recurrence upon discontinuation. However, treatment is discontinued for reasons other than disease progression in a subset of these patients, the characteristics and outcomes of which are poorly defined. Methods Of 342 adults with recurrent glioblastoma in our database treated with bevacizumab, 82 received treatment for ≥6 months; of these, bevacizumab was discontinued for reasons other than tumor progression in 18 patients (Bev-D) and for disease progression in the remainder (Bev-S). The impact of discontinuation on outcome was assessed with discontinuation as a time-dependent covariate in a Cox hazards model for progression-free survival. Results There was no difference in hazard rates for progression between Bev-D and Bev-S groups; the adjusted hazard ratio for progression using discontinuation as a time-dependent covariate was 0.91 (95% CI:0.47, 1.78). The median PFS after bevacizumab-discontinuation was 27 weeks (95% CI:15-NR). At progression, a higher proportion of Bev-D patients had local progression compared with the Bev-S patients. Salvage therapy in Bev-D patients yielded a PFS-26 weeks of 47% (95% CI:23%–94%) with a median PFS of 23 weeks (95% CI:12-NR), vs. 5% (95% CI: 1%–21%) and 9 weeks (95% CI: 6–11) in Bev-S patients (HR:0.3;CI, 0.1–0.6) (P = .0007). Conclusions Bevacizumab discontinuation unrelated to disease progression does not appear to cause rebound recurrence or worsen PFS in patients who benefit from bevacizumab. Additionally, Bev-D patients had an improved response to salvage therapy, findings which provide a strong basis for a prospective study. PMID:24596117

  19. Magnitude correlations in global seismicity

    SciTech Connect

    Sarlis, N. V.

    2011-08-15

    By employing natural time analysis, we analyze the worldwide seismicity and study the existence of correlations between earthquake magnitudes. We find that global seismicity exhibits nontrivial magnitude correlations for earthquake magnitudes greater than M{sub w}6.5.

  20. Induced seismicity. Final report

    SciTech Connect

    Segall, P.

    1997-09-18

    The objective of this project has been to develop a fundamental understanding of seismicity associated with energy production. Earthquakes are known to be associated with oil, gas, and geothermal energy production. The intent is to develop physical models that predict when seismicity is likely to occur, and to determine to what extent these earthquakes can be used to infer conditions within energy reservoirs. Early work focused on earthquakes induced by oil and gas extraction. Just completed research has addressed earthquakes within geothermal fields, such as The Geysers in northern California, as well as the interactions of dilatancy, friction, and shear heating, on the generation of earthquakes. The former has involved modeling thermo- and poro-elastic effects of geothermal production and water injection. Global Positioning System (GPS) receivers are used to measure deformation associated with geothermal activity, and these measurements along with seismic data are used to test and constrain thermo-mechanical models.

  1. Controllable seismic source

    SciTech Connect

    Gomez, Antonio; DeRego, Paul Jeffrey; Ferrell, Patrick Andrew; Thom, Robert Anthony; Trujillo, Joshua J.; Herridge, Brian

    2015-09-29

    An apparatus for generating seismic waves includes a housing, a strike surface within the housing, and a hammer movably disposed within the housing. An actuator induces a striking motion in the hammer such that the hammer impacts the strike surface as part of the striking motion. The actuator is selectively adjustable to change characteristics of the striking motion and characteristics of seismic waves generated by the impact. The hammer may be modified to change the physical characteristics of the hammer, thereby changing characteristics of seismic waves generated by the hammer. The hammer may be disposed within a removable shock cavity, and the apparatus may include two hammers and two shock cavities positioned symmetrically about a center of the apparatus.

  2. Controllable seismic source

    SciTech Connect

    Gomez, Antonio; DeRego, Paul Jeffrey; Ferrel, Patrick Andrew; Thom, Robert Anthony; Trujillo, Joshua J.; Herridge, Brian

    2014-08-19

    An apparatus for generating seismic waves includes a housing, a strike surface within the housing, and a hammer movably disposed within the housing. An actuator induces a striking motion in the hammer such that the hammer impacts the strike surface as part of the striking motion. The actuator is selectively adjustable to change characteristics of the striking motion and characteristics of seismic waves generated by the impact. The hammer may be modified to change the physical characteristics of the hammer, thereby changing characteristics of seismic waves generated by the hammer. The hammer may be disposed within a removable shock cavity, and the apparatus may include two hammers and two shock cavities positioned symmetrically about a center of the apparatus.

  3. Seismic ruggedness of relays

    SciTech Connect

    Merz, K.L. )

    1991-08-01

    This report complements EPRI report NP-5223 Revision 1, February 1991, and presents additional information and analyses concerning generic seismic ruggedness of power plant relays. Existing and new test data have been used to construct Generic Equipment Ruggedness Spectra (GERS) which can be used in identifying rugged relays during seismic re-evaluation of nuclear power plants. This document is an EPRI tier 1 report. The results of relay fragility tests for both old and new relays are included in an EPRI tier 2 report with the same title. In addition to the presentation of relay GERS, the tier 2 report addresses the applicability of GERS to relays of older vintage, discusses the important identifying nomenclature for each relay type, and examines relay adjustment effects on seismic ruggedness. 9 refs., 3 figs, 1 tab.

  4. 3-D Seismic Interpretation

    NASA Astrophysics Data System (ADS)

    Moore, Gregory F.

    2009-05-01

    This volume is a brief introduction aimed at those who wish to gain a basic and relatively quick understanding of the interpretation of three-dimensional (3-D) seismic reflection data. The book is well written, clearly illustrated, and easy to follow. Enough elementary mathematics are presented for a basic understanding of seismic methods, but more complex mathematical derivations are avoided. References are listed for readers interested in more advanced explanations. After a brief introduction, the book logically begins with a succinct chapter on modern 3-D seismic data acquisition and processing. Standard 3-D acquisition methods are presented, and an appendix expands on more recent acquisition techniques, such as multiple-azimuth and wide-azimuth acquisition. Although this chapter covers the basics of standard time processing quite well, there is only a single sentence about prestack depth imaging, and anisotropic processing is not mentioned at all, even though both techniques are now becoming standard.

  5. Unplanned discontinuation of tyrosine kinase inhibitors in chronic myeloid leukemia

    PubMed Central

    TSUTSUMI, YUTAKA; ITO, SHINICHI; OHIGASHI, HIROYUKI; SHIRATORI, SOUICHI; TESHIMA, TAKANORI

    2016-01-01

    This study was conducted to investigate the outcomes of patients with chronic myeloid leukemia (CML) who discontinued tyrosine kinase inhibitor (TKI) treatment. A single-center retrospective analysis was performed, including 46 chronic-phase (CP) CML patients who achieved complete molecular response (CMR) with TKIs. TKI treatment was discontinued in 13 patients based on their requests. The BCR-ABL transcript levels were monitored in the peripheral blood by quantitative polymerase chain reaction analysis following treatment discontinuation. Of the 13 patients who discontinued TKI treatment, 7 remained in CMR, with a median follow-up of 26 months (range, 10–60 months). The remaining 6 patients lost CMR following TKI discontinuation; 2 of these patients achieved a second CMR following re-administration of TKIs, 2 patients spontaneously achieved CMR and 2 remained in complete hematological response (CHR) without TKI treatment with a median follow-up of 29.5 months (range, 10–52 months). In conclusion, the survival of patients who lost CMR following TKI discontinuation may not be affected, even without re-administration of TKIs. Vigilant observation is recommended for such patients. The limitations of this study included the small patient sample, retrospective design and patient heterogeneity. Therefore, the results must be interpreted with caution. PMID:26870364

  6. Minimizers with discontinuous velocities for the electromagnetic variational method

    SciTech Connect

    De Luca, Jayme

    2010-08-15

    The electromagnetic two-body problem has neutral differential delay equations of motion that, for generic boundary data, can have solutions with discontinuous derivatives. If one wants to use these neutral differential delay equations with arbitrary boundary data, solutions with discontinuous derivatives must be expected and allowed. Surprisingly, Wheeler-Feynman electrodynamics has a boundary value variational method for which minimizer trajectories with discontinuous derivatives are also expected, as we show here. The variational method defines continuous trajectories with piecewise defined velocities and accelerations, and electromagnetic fields defined by the Euler-Lagrange equations on trajectory points. Here we use the piecewise defined minimizers with the Lienard-Wierchert formulas to define generalized electromagnetic fields almost everywhere (but on sets of points of zero measure where the advanced/retarded velocities and/or accelerations are discontinuous). Along with this generalization we formulate the generalized absorber hypothesis that the far fields vanish asymptotically almost everywhere and show that localized orbits with far fields vanishing almost everywhere must have discontinuous velocities on sewing chains of breaking points. We give the general solution for localized orbits with vanishing far fields by solving a (linear) neutral differential delay equation for these far fields. We discuss the physics of orbits with discontinuous derivatives stressing the differences to the variational methods of classical mechanics and the existence of a spinorial four-current associated with the generalized variational electrodynamics.

  7. Bifurcation and chaotic threshold of Duffing system with jump discontinuities

    NASA Astrophysics Data System (ADS)

    Tian, Ruilan; Zhou, Yufeng; Wang, Qiubao; Zhang, Lili

    2016-01-01

    Like for the smooth system, it is important to determine a criteria for bifurcation of the non-smooth system with jump discontinuities. Previously, the criteria have been constructed in some non-smooth systems with jump discontinuities which are the endpoints of interval. The research on bifurcation for non-smooth system with jump discontinuities, which are the interior points of interval, seems to be a new area. We construct the Duffing system with jump discontinuities in open interval. Bifurcation diagram of the unperturbed system is detected and Hamilton phase diagrams are simulated using Matlab. The jump discontinuities for the non-smooth Homoclinic orbit lead to a barrier for conventional nonlinear techniques to obtain the criteria for chaotic motion. Traditionally, these non-smooth factors were considered term by term. We will give a reasonable compromise based on all of characteristics of the non-smooth homoclinic orbits with the jump discontinuities. The extended Melnikov function is explicitly detected to judge the stable and unstable manifolds whether intersect transversally at any position of trajectory under the perturbation of damping and external forcing. It is worthwhile noting that the result reveals the effects of the non-smooth restoring force on the behaviors of nonlinear dynamical systems. The efficiency of the theoretical results is verified by the phase portraits, Poincaré surface of section, Largest Lyapnnov exponents diagram and bifurcation diagram.

  8. Hyperspherical Sparse Approximation Techniques for High-Dimensional Discontinuity Detection

    DOE PAGES

    Zhang, Guannan; Webster, Clayton G.; Gunzburger, Max; Burkardt, John

    2016-08-04

    This work proposes a hyperspherical sparse approximation framework for detecting jump discontinuities in functions in high-dimensional spaces. The need for a novel approach results from the theoretical and computational inefficiencies of well-known approaches, such as adaptive sparse grids, for discontinuity detection. Our approach constructs the hyperspherical coordinate representation of the discontinuity surface of a function. Then sparse approximations of the transformed function are built in the hyperspherical coordinate system, with values at each point estimated by solving a one-dimensional discontinuity detection problem. Due to the smoothness of the hypersurface, the new technique can identify jump discontinuities with significantly reduced computationalmore » cost, compared to existing methods. Several approaches are used to approximate the transformed discontinuity surface in the hyperspherical system, including adaptive sparse grid and radial basis function interpolation, discrete least squares projection, and compressed sensing approximation. Moreover, hierarchical acceleration techniques are also incorporated to further reduce the overall complexity. In conclusion, rigorous complexity analyses of the new methods are provided, as are several numerical examples that illustrate the effectiveness of our approach.« less

  9. The analysis of plane discontinuities in offset cylindrical waveguides.

    PubMed

    Homentcovschi, Dorel; Miles, Ronald N

    2015-06-01

    This paper applies the re-expansion method for analyzing the effects on the sound field due to planar discontinuities at the junction of two offset circular acoustic waveguides. The normal modes in the two waveguides are expanded at the junction plane into a system of functions accounting for velocity singularities at the corner points. As the new expansion has a high convergence order, only a few terms have to be considered for obtaining the solution of most practical problems. This paper gives the equivalent impedance accounting for nonplanar waves into a plane-wave analysis. The last section of the paper applies the re-expansion technique to the case of two offset pipes (step discontinuity) and to that of an offset aperture in a cylindrical pipe (diaphragm-type discontinuity). The plots of the discontinuity inductance, characterized by Karal's factor, are quite similar but the values in the second case are 1.5-2 times larger, showing that the diaphragm-type discontinuity excites much more nonplanar evanescent modes than the step discontinuity.

  10. Trapped modes in waveguides with many small discontinuities

    NASA Astrophysics Data System (ADS)

    Kurennoy, Sergey S.

    1995-03-01

    It has been demonstrated recently [G. V. Stupakov and S. S. Kurennoy, Phys. Rev. E 49, 794 (1994)] that a single small discontinuity (such as an enlargement or a hole) on a smooth waveguide can result in the appearance of trapped electromagnetic modes with frequencies slightly below the waveguide cutoff frequencies. The present paper studies a similar phenomenon for a waveguide with many small discontinuities, which is a good model for the vacuum chamber of large accelerators. Frequencies of trapped modes and their contributions to the coupling impedance are calculated. The frequencies for the cases of a few discontinuities or a periodic structure coincide well with those from numerical simulations. The trapped modes produce sharp resonance peaks of the coupling impedance near the cutoff frequencies. The magnitude of these peaks, as well as the existence itself of a trapped mode, strongly depends on the distribution of discontinuities, or on the distance between them if a regular array is considered. The impedance in the extreme case can be as large as N3 times that for a single discontinuity, where N is the number of discontinuities.

  11. Intra-oceanic crustal seismic reflecting zone below the dipping reflectors on Lofoten margin

    SciTech Connect

    Sellevoll, M.A.; Mokhtari, M.

    1988-07-01

    Multichannel seismic reflection measurements off Lofoten, Northern Norway, show an uneven, discontinuous reflector within the crystalline oceanic crust at a depth of 7-8 s (two-way travel time). This intra-oceanic crustal reflector is observed seaward as well as beneath sub-basement dipping reflectors, which are of disputed (oceanic or continental) origin. These observations indicate that the dipping reflectors are an integrated part of the oceanic crust.

  12. Induced Seismicity Monitoring System

    NASA Astrophysics Data System (ADS)

    Taylor, S. R.; Jarpe, S.; Harben, P.

    2014-12-01

    There are many seismological aspects associated with monitoring of permanent storage of carbon dioxide (CO2) in geologic formations. Many of these include monitoring underground gas migration through detailed tomographic studies of rock properties, integrity of the cap rock and micro seismicity with time. These types of studies require expensive deployments of surface and borehole sensors in the vicinity of the CO2 injection wells. Another problem that may exist in CO2 sequestration fields is the potential for damaging induced seismicity associated with fluid injection into the geologic reservoir. Seismic hazard monitoring in CO2 sequestration fields requires a seismic network over a spatially larger region possibly having stations in remote settings. Expensive observatory-grade seismic systems are not necessary for seismic hazard deployments or small-scale tomographic studies. Hazard monitoring requires accurate location of induced seismicity to magnitude levels only slightly less than that which can be felt at the surface (e.g. magnitude 1), and the frequencies of interest for tomographic analysis are ~1 Hz and greater. We have developed a seismo/acoustic smart sensor system that can achieve the goals necessary for induced seismicity monitoring in CO2 sequestration fields. The unit is inexpensive, lightweight, easy to deploy, can operate remotely under harsh conditions and features 9 channels of recording (currently 3C 4.5 Hz geophone, MEMS accelerometer and microphone). An on-board processor allows for satellite transmission of parameter data to a processing center. Continuous or event-detected data is kept on two removable flash SD cards of up to 64+ Gbytes each. If available, data can be transmitted via cell phone modem or picked up via site visits. Low-power consumption allows for autonomous operation using only a 10 watt solar panel and a gel-cell battery. The system has been successfully tested for long-term (> 6 months) remote operations over a wide range

  13. Multiscale seismic characterization of marine sediments by using a wavelet-based approach

    NASA Astrophysics Data System (ADS)

    Ker, Stephan; Le Gonidec, Yves; Gibert, Dominique

    2015-04-01

    We propose a wavelet-based method to characterize acoustic impedance discontinuities from a multiscale analysis of reflected seismic waves. This method is developed in the framework of the wavelet response (WR) where dilated wavelets are used to sound a complex seismic reflector defined by a multiscale impedance structure. In the context of seismic imaging, we use the WR as a multiscale seismic attributes, in particular ridge functions which contain most of the information that quantifies the complex geometry of the reflector. We extend this approach by considering its application to analyse seismic data acquired with broadband but frequency limited source signals. The band-pass filter related to such actual sources distort the WR: in order to remove these effects, we develop an original processing based on fractional derivatives of Lévy alpha-stable distributions in the formalism of the continuous wavelet transform (CWT). We demonstrate that the CWT of a seismic trace involving such a finite frequency bandwidth can be made equivalent to the CWT of the impulse response of the subsurface and is defined for a reduced range of dilations, controlled by the seismic source signal. In this dilation range, the multiscale seismic attributes are corrected from distortions and we can thus merge multiresolution seismic sources to increase the frequency range of the mutliscale analysis. As a first demonstration, we perform the source-correction with the high and very high resolution seismic sources of the SYSIF deep-towed seismic device and we show that both can now be perfectly merged into an equivalent seismic source with an improved frequency bandwidth (220-2200 Hz). Such multiresolution seismic data fusion allows reconstructing the acoustic impedance of the subseabed based on the inverse wavelet transform properties extended to the source-corrected WR. We illustrate the potential of this approach with deep-water seismic data acquired during the ERIG3D cruise and we compare

  14. A Discontinuous Galerkin Chimera Overset Solver

    NASA Astrophysics Data System (ADS)

    Galbraith, Marshall Christopher

    This work summarizes the development of an accurate, efficient, and flexible Computational Fluid Dynamics computer code that is an improvement relative to the state of the art. The improved accuracy and efficiency is obtained by using a high-order discontinuous Galerkin (DG) discretization scheme. In order to maximize the computational efficiency, quadrature-free integration and numerical integration optimized as matrix-vector multiplications is employed and implemented through a pre-processor (PyDG). Using the PyDG pre-processor, a C++ polynomial library has been developed that uses overloaded operators to design an efficient Domain Specific Language (DSL) that allows expressions involving polynomials to be written as if they are scalars. The DSL, which makes the syntax of computer code legible and intuitive, promotes maintainability of the software and simplifies the development of additional capabilities. The flexibility of the code is achieved by combining the DG scheme with the Chimera overset method. The Chimera overset method produces solutions on a set of overlapping grids that communicate through an exchange of data on grid boundaries (known as artificial boundaries). Finite volume and finite difference discretizations use fringe points, which are layers of points on the artificial boundaries, to maintain the interior stencil on artificial boundaries. The fringe points receive solution values interpolated from overset grids. Proper interpolation requires fringe points to be contained in overset grids. Insufficient overlap must be corrected by modifying the grid system. The Chimera scheme can also exclude regions of grids that lie outside the computational domain; a process commonly known as hole cutting. The Chimera overset method has traditionally enabled the use of high-order finite difference and finite volume approaches such as WENO and compact differencing schemes, which require structured meshes, for modeling fluid flow associated with complex

  15. [Discontinuation-Emergent Signs and Symptoms Inventory--Polish translation of the discontinuation signs and symptoms checklist].

    PubMed

    Cubała, Wiesław Jerzy; Landowski, Jerzy; Springer, Janusz

    2013-01-01

    A number of preclinical and clinical studies are focused on mechanisms of SSRI discontinuation syndrome as well as the patient populations and agents that are most affected by this phenomenon. Characteristics of onset, duration, and severity of any discontinuation symptoms and spontaneous reports of taper/poststudy-emergent adverse events should be compared with those of the active comparator in these studies. Besides, common clinical practice supplies a number of problems associated with SSRI discontinuation syndrome as related to treatment planning and management. The recommended instrument for evaluating SSRI discontinuation syndrome symptoms is the Discontinuation-Emergent Signs and Symptoms (DESS) inventory. DESS is a 43-item checklist that can be administered in a clinician-rated form, a self-rated form, or an interactive voice-response form. The paper presents the Polish version of DESS inventory along with its application and interpretation instructions. DESS inventory is of substantial advance in common psychiatric practice as it enables effective SSRI discontinuation management on drug tapering and in case of the non-compliance with the treatment. Its use in the systematic studies facilitates conclusive outcome results and is of prime importance as being comparable with literature outcomes. PMID:24946477

  16. Seismic detection of folded, subducted lithosphere at the core-mantle boundary.

    PubMed

    Hutko, Alexander R; Lay, Thorne; Garnero, Edward J; Revenaugh, Justin

    2006-05-18

    Seismic tomography has been used to infer that some descending slabs of oceanic lithosphere plunge deep into the Earth's lower mantle. The fate of these slabs has remained unresolved, but it has been postulated that their ultimate destination is the lowermost few hundred kilometres of the mantle, known as the D'' region. Relatively cold slab material may account for high seismic velocities imaged in D'' beneath areas of long-lived plate subduction, and for reflections from a seismic velocity discontinuity just above the anomalously high wave speed regions. The D'' discontinuity itself is probably the result of a phase change in relatively low-temperature magnesium silicate perovskite. Here, we present images of the D'' region beneath the Cocos plate using Kirchhoff migration of horizontally polarized shear waves, and find a 100-km vertical step occurring over less than 100 km laterally in an otherwise flat D'' shear velocity discontinuity. Folding and piling of a cold slab that has reached the core-mantle boundary, as observed in numerical and experimental models, can account for the step by a 100-km elevation of the post-perovskite phase boundary due to a 700 degrees C lateral temperature reduction in the folded slab. We detect localized low velocities at the edge of the slab material, which may result from upwellings caused by the slab laterally displacing a thin hot thermal boundary layer.

  17. The seismic analyzer: interpreting and illustrating 2D seismic data.

    PubMed

    Patel, Daniel; Giertsen, Christopher; Thurmond, John; Gjelberg, John; Gröller, M Eduard

    2008-01-01

    We present a toolbox for quickly interpreting and illustrating 2D slices of seismic volumetric reflection data. Searching for oil and gas involves creating a structural overview of seismic reflection data to identify hydrocarbon reservoirs. We improve the search of seismic structures by precalculating the horizon structures of the seismic data prior to interpretation. We improve the annotation of seismic structures by applying novel illustrative rendering algorithms tailored to seismic data, such as deformed texturing and line and texture transfer functions. The illustrative rendering results in multi-attribute and scale invariant visualizations where features are represented clearly in both highly zoomed in and zoomed out views. Thumbnail views in combination with interactive appearance control allows for a quick overview of the data before detailed interpretation takes place. These techniques help reduce the work of seismic illustrators and interpreters.

  18. Seismic signature of crustal magma and fluid from deep seismic sounding data across Tengchong volcanic area

    NASA Astrophysics Data System (ADS)

    Bai, Z. M.; Zhang, Z. Z.; Wang, C. Y.; Klemperer, S. L.

    2012-04-01

    . There are typical tectonic and deep origin mechanisms for the moderate-strong earthquakes nearby SP Tuantian, and precaution should be added on this area in case of the potential earthquake. Our fusion image also clearly revealed that there exist two remarkable positions on the Moho discontinuity through which the heat from the upper mantle was transmitted upward, and this is attributed to the widely distributed hot material within the crust and upper mantle. We acknowledge the financial support of the Ministry of Land and Resources of China (SinoProbe-02-02), and the National Nature Science Foundation of China (No. 41074033 and No. 40830315). Key Words: Seismic Signature, Magma, Tengchong Volcanic Area, Deep Seismic Sounding, Seismic Attribute Fusion Li, Chang, van der Hilst, D., Meltzer, A.S., Engdahl, E.R., 2008. Subduction of the Indian lithosphere beneath the Tibetan Plateau and Burma. Earth Planet. Sci. Lett. 274. doi:10.1016/j.epsl.2008.07.016. Lebedev, S., van der Hilst, R.D., 2008. Global upper-mantle tomography with the automated multi-mode surface and S waveforms. Geophys. J. Int. 173 (2), 505-518. Wang C.Y. and Huangfu G.. 2004. Crustal structure in Tengchong Volcano-Geothermal Area, western Yunnan, China. Tectonophysics, 380: 69-87.

  19. Selective serotonin reuptake inhibitor discontinuation syndrome: proposed diagnostic criteria.

    PubMed Central

    Black, K; Shea, C; Dursun, S; Kutcher, S

    2000-01-01

    OBJECTIVE: To establish specific criteria by which selective serotonin reuptake inhibitor (SSRI) discontinuation syndrome may be identified. DATA SOURCES: MEDLINE and PSYCHLIT databases were searched for case reports published from 1986 to 1997 inclusive, and references of relevant articles were also searched. STUDY SELECTION: Forty-six case reports of symptoms following the discontinuation of fluoxetine, fluvoxamine, paroxetine or sertraline were selected. Three studies of SSRI discontinuation were also reviewed. DATA EXTRACTION: Demographic and treatment information, as well as the timing, duration, number, nature and frequency of dicontinuation symptoms. DATA SYNTHESIS: Paroxetine was most frequently implicated. The drug had been tapered in half of the cases. In some cases, symptom onset began during taper, whereas, in most cases, symptoms began within 1 to 3 days of drug discontinuation. Fifty-three different symptoms were reported, with dizziness being the most common. Other common symptoms were nausea or emesis, fatigue, headache, gait instability and insomnia. Shock-like sensations, paresthesia and visual disturbances were the most rare. Without intervention, symptoms persisted for more than a week in half of the cases. In cases in which the SSRI was restarted, symptoms resolved within 72 hours. In some cases, withdrawal symptoms recurred when the same SSRI was again discontinued. CONCLUSIONS: Findings were used to construct diagnostic criteria for the SSRI discontinuation syndrome. These criteria are 2 or more of the following symptoms developing within 1 to 7 days of discontinuation or reduction in dosage of an SSRI after at least 1 month's use, when these symptoms cause clinically significant distress or impairment and are not due to a general medical condition or recurrence of a mental disorder: dizziness, light-headedness, vertigo or feeling faint; shock-like sensations or paresthesia; anxiety; diarrhea; fatigue; gait instability; headache; insomnia

  20. Seismic Inversion Methods

    NASA Astrophysics Data System (ADS)

    Jackiewicz, Jason

    2009-09-01

    With the rapid advances in sophisticated solar modeling and the abundance of high-quality solar pulsation data, efficient and robust inversion techniques are crucial for seismic studies. We present some aspects of an efficient Fourier Optimally Localized Averaging (OLA) inversion method with an example applied to time-distance helioseismology.

  1. Seismic Inversion Methods

    SciTech Connect

    Jackiewicz, Jason

    2009-09-16

    With the rapid advances in sophisticated solar modeling and the abundance of high-quality solar pulsation data, efficient and robust inversion techniques are crucial for seismic studies. We present some aspects of an efficient Fourier Optimally Localized Averaging (OLA) inversion method with an example applied to time-distance helioseismology.

  2. Mobile seismic exploration

    NASA Astrophysics Data System (ADS)

    Dräbenstedt, A.; Cao, X.; Polom, U.; Pätzold, F.; Zeller, T.; Hecker, P.; Seyfried, V.; Rembe, C.

    2016-06-01

    Laser-Doppler-Vibrometry (LDV) is an established technique to measure vibrations in technical systems with picometer vibration-amplitude resolution. Especially good sensitivity and resolution can be achieved at an infrared wavelength of 1550 nm. High-resolution vibration measurements are possible over more than 100 m distance. This advancement of the LDV technique enables new applications. The detection of seismic waves is an application which has not been investigated so far because seismic waves outside laboratory scales are usually analyzed at low frequencies between approximately 1 Hz and 250 Hz and require velocity resolutions in the range below 1 nm/s/√Hz. Thermal displacements and air turbulence have critical influences to LDV measurements at this low-frequency range leading to noise levels of several 100 nm/√Hz. Commonly seismic waves are measured with highly sensitive inertial sensors (geophones or Micro Electro-Mechanical Sensors (MEMS)). Approaching a laser geophone based on LDV technique is the topic of this paper. We have assembled an actively vibration-isolated optical table in a minivan which provides a hole in its underbody. The laser-beam of an infrared LDV assembled on the optical table impinges the ground below the car through the hole. A reference geophone has detected remaining vibrations on the table. We present the results from the first successful experimental demonstration of contactless detection of seismic waves from a movable vehicle with a LDV as laser geophone.

  3. The viking seismic experiment.

    PubMed

    Anderson, D L; Duennebier, F K; Latham, G V; Toksöz, M F; Kovach, R L; Knight, T C; Lazarewicz, A R; Miller, W F; Nakamura, Y; Sutton, G

    1976-12-11

    A three-axis short-period seismometer is now operating on Mars in the Utopia Planitia region. The noise background correlates well with wind gusts. Although no quakes have been detected in the first 60 days of observation, it is premature to draw any conclusions about the seismicity of Mars. The instrument is expected to return data for at least 2 years.

  4. Hanford Seismic Network

    SciTech Connect

    Reidel, S.P.; Hartshorn, D.C.

    1997-05-01

    This report describes the Hanford Seismic Network. The network consists of two instrument arrays: seismometers and strong motion accelerometers. The seismometers determine the location and magnitude of earthquakes, and the strong motion accelerometers determine ground motion. Together these instruments arrays comply with the intent of DOE Order 5480.20, Natural Phenomena Hazards Mitigation.

  5. High Voltage Seismic Generator

    NASA Astrophysics Data System (ADS)

    Bogacz, Adrian; Pala, Damian; Knafel, Marcin

    2015-04-01

    This contribution describes the preliminary result of annual cooperation of three student research groups from AGH UST in Krakow, Poland. The aim of this cooperation was to develop and construct a high voltage seismic wave generator. Constructed device uses a high-energy electrical discharge to generate seismic wave in ground. This type of device can be applied in several different methods of seismic measurement, but because of its limited power it is mainly dedicated for engineering geophysics. The source operates on a basic physical principles. The energy is stored in capacitor bank, which is charged by two stage low to high voltage converter. Stored energy is then released in very short time through high voltage thyristor in spark gap. The whole appliance is powered from li-ion battery and controlled by ATmega microcontroller. It is possible to construct larger and more powerful device. In this contribution the structure of device with technical specifications is resented. As a part of the investigation the prototype was built and series of experiments conducted. System parameter was measured, on this basis specification of elements for the final device were chosen. First stage of the project was successful. It was possible to efficiently generate seismic waves with constructed device. Then the field test was conducted. Spark gap wasplaced in shallowborehole(0.5 m) filled with salt water. Geophones were placed on the ground in straight line. The comparison of signal registered with hammer source and sparker source was made. The results of the test measurements are presented and discussed. Analysis of the collected data shows that characteristic of generated seismic signal is very promising, thus confirms possibility of practical application of the new high voltage generator. The biggest advantage of presented device after signal characteristics is its size which is 0.5 x 0.25 x 0.2 m and weight approximately 7 kg. This features with small li-ion battery makes

  6. High-order Hybridized Discontinuous Galerkin (HDG) method for wave propagation simulation in complex geophysical media (elastic, acoustic and hydro-acoustic); an unifying framework to couple continuous Spectral Element and Discontinuous Galerkin Methods

    NASA Astrophysics Data System (ADS)

    Terrana, Sebastien; Vilotte, Jean-Pierre; Guillot, Laurent; Mariotti, Christian

    2015-04-01

    Today seismological observation systems combine broadband seismic receivers, hydrophones and micro-barometers antenna that provide complementary observations of source-radiated waves in heterogeneous and complex geophysical media. Exploiting these observations requires accurate and multi-physics - elastic, hydro-acoustic, infrasonic - wave simulation methods. A popular approach is the Spectral Element Method (SEM) (Chaljub et al, 2006) which is high-order accurate (low dispersion error), very flexible to parallelization and computationally attractive due to efficient sum factorization technique and diagonal mass matrix. However SEMs suffer from lack of flexibility in handling complex geometry and multi-physics wave propagation. High-order Discontinuous Galerkin Methods (DGMs), i.e. Dumbser et al (2006), Etienne et al. (2010), Wilcox et al (2010), are recent alternatives that can handle complex geometry, space-and-time adaptativity, and allow efficient multi-physics wave coupling at interfaces. However, DGMs are more memory demanding and less computationally attractive than SEMs, especially when explicit time stepping is used. We propose a new class of higher-order Hybridized Discontinuous Galerkin Spectral Elements (HDGSEM) methods for spatial discretization of wave equations, following the unifying framework for hybridization of Cockburn et al (2009) and Nguyen et al (2011), which allows for a single implementation of conforming and non-conforming SEMs. When used with energy conserving explicit time integration schemes, HDGSEM is flexible to handle complex geometry, computationally attractive and has significantly less degrees of freedom than classical DGMs, i.e., the only coupled unknowns are the single-valued numerical traces of the velocity field on the element's faces. The formulation can be extended to model fractional energy loss at interfaces between elastic, acoustic and hydro-acoustic media. Accuracy and performance of the HDGSEM are illustrated and

  7. Seismic Structure of the Mantle Beneath the Pacific Hemisphere

    NASA Astrophysics Data System (ADS)

    Bagley, Brian C.

    Aside from xenoliths, the Earth's mantle is a region that is inaccessible directly, leaving us with limited tools to investigate its characteristics indirectly. Seismology is a tool well-suited for this purpose, and has provided valuable insight regarding many fundamental processes occurring within the mantle. It is fortuitous that the mantle is layered, and that these layers are often punctuated by distinct changes in density and/or velocity that are seismically detectable. By investigating the seismic structure of the mantle we are able to infer properties such as composition, temperature, anisotropy, and water content. Seismic tomography has informed our understanding of subduction and the fate of slabs, and we are beginning to realize that the lower mantle might also be rich with heterogeneity. Our picture of the Earth's mantle is becoming clearer, however, there is much that we do not understand. Receiver function studies of the oceans are fewer and suffer the common malady of looking beneath oceanic islands, not generic oceanic crust. Most of the detailed information regarding the seismic discontinuity structure of open ocean mantle comes from bottom-side reflections that are precursors to SS phases (a shear wave that has traveled from source to receiver with one bottom-side surface bounce in between). SS and PP (a compressional wave with a path analogous to SS) precursors offer extensive geographic coverage and good sensitivity to small velocity contrasts and reasonable localization. They do not perform well for shallow reflectors, or reflectors near the larger transition zone discontinuities. In our studies we use multiple ScS reverberations to gain better resolution of these features. The primary goals of this research are to study mantle discontinuities, and fill in some of the missing detail regarding mantle heterogeneity. We do this by examining the Pacific ocean, beginning with the open ocean mantle, then moving to the subduction zones in the west

  8. The effect of mechanical discontinuities on the growth of faults

    NASA Astrophysics Data System (ADS)

    Bonini, Lorenzo; Basili, Roberto; Bonanno, Emanuele; Toscani, Giovanni; Burrato, Pierfrancesco; Seno, Silvio; Valensise, Gianluca

    2016-04-01

    The growth of natural faults is controlled by several factors, including the nature of host rocks, the strain rate, the temperature, and the presence of fluids. In this work we focus on the mechanical characteristics of host rocks, and in particular on the role played by thin mechanical discontinuities on the upward propagation of faults and on associated secondary effects such as folding and fracturing. Our approach uses scaled, analogue models where natural rocks are simulated by wet clay (kaolin). A clay cake is placed above two rigid blocks in a hanging wall/footwall configuration on either side of a planar fault. Fault activity is simulated by motor-controlled movements of the hanging wall. We reproduce three types of faults: a 45°-dipping normal fault, a 45°-dipping reverse fault and a 30°-dipping reverse fault. These angles are selected as representative of most natural dip-slip faults. The analogues of the mechanical discontinuities are obtained by precutting the wet clay cake before starting the hanging wall movement. We monitor the experiments with high-resolution cameras and then obtain most of the data through the Digital Image Correlation method (D.I.C.). This technique accurately tracks the trajectories of the particles of the analogue material during the deformation process: this allows us to extract displacement field vectors plus the strain and shear rate distributions on the lateral side of the clay block, where the growth of new faults is best seen. Initially we run a series of isotropic experiments, i.e. experiments without discontinuities, to generate a reference model: then we introduce the discontinuities. For the extensional models they are cut at different dip angles, from horizontal to 45°-dipping, both synthetic and antithetic with respect to the master fault, whereas only horizontal discontinuities are introduced in the contractional models. Our experiments show that such discontinuities control: 1) the propagation rate of faults

  9. Discontinuous dual-primal mixed finite elements for elliptic problems

    NASA Technical Reports Server (NTRS)

    Bottasso, Carlo L.; Micheletti, Stefano; Sacco, Riccardo

    2000-01-01

    We propose a novel discontinuous mixed finite element formulation for the solution of second-order elliptic problems. Fully discontinuous piecewise polynomial finite element spaces are used for the trial and test functions. The discontinuous nature of the test functions at the element interfaces allows to introduce new boundary unknowns that, on the one hand enforce the weak continuity of the trial functions, and on the other avoid the need to define a priori algorithmic fluxes as in standard discontinuous Galerkin methods. Static condensation is performed at the element level, leading to a solution procedure based on the sole interface unknowns. The resulting family of discontinuous dual-primal mixed finite element methods is presented in the one and two-dimensional cases. In the one-dimensional case, we show the equivalence of the method with implicit Runge-Kutta schemes of the collocation type exhibiting optimal behavior. Numerical experiments in one and two dimensions demonstrate the order accuracy of the new method, confirming the results of the analysis.

  10. Midcrustal discontinuities and the assembly of the Himalayan midcrust

    NASA Astrophysics Data System (ADS)

    Larson, Kyle P.; Cottle, John M.

    2014-05-01

    Detailed quartz lattice preferred orientation (LPO) data define two structural discontinuities in the exhumed high-grade metamorphic core of the Himalaya exposed in the upper Tama Kosi region of east central Nepal. The structures are marked by abrupt breaks in a general trend of up structural section increasing quartz LPO-defined deformation temperatures. Deformation associated with the upper structural discontinuity, which occurs within sillimanite grade rocks, is postpeak metamorphism in both the hanging wall and the footwall. New geochronologic data constrain the timing of metamorphism in the hanging wall of the upper discontinuity to between 24 and 16 Ma, indistinguishable from previously published ages for the footwall. Movement across this structure represents Early Miocene strain localization and thickening in the Himalayan midcrust. Movement across the lower discontinuity, which occurs between staurolite and kyanite grade rocks, appears to be synmetamorphic with material in its footwall at approximately 10 Ma, but postpeak metamorphism for material in its hanging wall. This movement is interpreted to reflect the underplating and incorporation of material into the metamorphic core. The recognition of two thrust-sense discontinuities in the exhumed Himalayan core in the Tama Kosi region is consistent with other similar structures recognized along the Himalaya. The widespread nature of these structures reinforces that they are important to our understanding of the evolution of the kinematics of large, hot orogens.

  11. Solutions of the Wheeler-Feynman equations with discontinuous velocities.

    PubMed

    de Souza, Daniel Câmara; De Luca, Jayme

    2015-01-01

    We generalize Wheeler-Feynman electrodynamics with a variational boundary value problem for continuous boundary segments that might include velocity discontinuity points. Critical-point orbits must satisfy the Euler-Lagrange equations of the action functional at most points, which are neutral differential delay equations (the Wheeler-Feynman equations of motion). At velocity discontinuity points, critical-point orbits must satisfy the Weierstrass-Erdmann continuity conditions for the partial momenta and the partial energies. We study a special setup having the shortest time-separation between the (infinite-dimensional) boundary segments, for which case the critical-point orbit can be found using a two-point boundary problem for an ordinary differential equation. For this simplest setup, we prove that orbits can have discontinuous velocities. We construct a numerical method to solve the Wheeler-Feynman equations together with the Weierstrass-Erdmann conditions and calculate some numerical orbits with discontinuous velocities. We also prove that the variational boundary value problem has a unique solution depending continuously on boundary data, if the continuous boundary segments have velocity discontinuities along a reduced local space.

  12. Solutions of the Wheeler-Feynman equations with discontinuous velocities.

    PubMed

    de Souza, Daniel Câmara; De Luca, Jayme

    2015-01-01

    We generalize Wheeler-Feynman electrodynamics with a variational boundary value problem for continuous boundary segments that might include velocity discontinuity points. Critical-point orbits must satisfy the Euler-Lagrange equations of the action functional at most points, which are neutral differential delay equations (the Wheeler-Feynman equations of motion). At velocity discontinuity points, critical-point orbits must satisfy the Weierstrass-Erdmann continuity conditions for the partial momenta and the partial energies. We study a special setup having the shortest time-separation between the (infinite-dimensional) boundary segments, for which case the critical-point orbit can be found using a two-point boundary problem for an ordinary differential equation. For this simplest setup, we prove that orbits can have discontinuous velocities. We construct a numerical method to solve the Wheeler-Feynman equations together with the Weierstrass-Erdmann conditions and calculate some numerical orbits with discontinuous velocities. We also prove that the variational boundary value problem has a unique solution depending continuously on boundary data, if the continuous boundary segments have velocity discontinuities along a reduced local space. PMID:25637913

  13. The Residue of Lithospheric Convergence in the Alpine-Pannonian-Carpathian system

    NASA Astrophysics Data System (ADS)

    Houseman, G. A.; Stuart, G. W.; Hetenyi, G.; Lorinczi, P.; Dando, B. D.

    2009-12-01

    The continuing collision of the Adriatic block with European continental lithosphere has its clearest expression now in the Alpine collision zone. In the Early Miocene the collision zone extended further east and included probably all of the regions within the Carpathian Mountain Range. In the Mid-Miocene between about 17 and 12 Ma, however, the Pannonian lithosphere extended rapidly and subsequently subsided, while convergence persisted in the Alps and the Carpathian arc. The change from convergence to extension in the Pannonian domain is associated with either rapid subduction roll-back or gravitational instability in which the lower part of the lithosphere was removed and replaced by hot asthenosphere. Throughout this time however, convergence has continued in the Alpine orogeny further west. It is surprising therefore to see similarities in the mantle transition zone beneath these two neighbouring regions whose lithospheres have, in the last 17 Myr at least, evolved in such different modes. New seismic images from beneath the Pannonian Basin (Hetenyi et al., GRL, in press) and from beneath the Alps (Lombardi et al., EPSL, 2009) show that both regions have a depressed 660 km discontinuity beneath a relatively normal-depth 410 km discontinuity. An important factor in both regions evidently is that relatively dense material derived from the mid-Miocene collision sits stagnant on top of the 660 km discontinuity, where further descent is obstructed by the negative Clapeyron slope of the spinel-to-perovskite phase transition and the high viscosity of the lower mantle. While the depression of the 660 km discontinuity beneath the Alps is directly associated with ongoing convergence, that beneath the Pannonian appears to be decoupled from the upper mantle circulation that accompanied the Miocene Pannonian extension. If the cold material at the base of the Pannonian upper mantle is the residue of lithospheric subduction, delamination, or gravitational instability, the

  14. EGLACOM project: seismic and oceanographic data integration

    NASA Astrophysics Data System (ADS)

    Petronio, L.; Lipizer, M.; Rebesco, M.; Deponte, D.; Ursella, L.; Fragiacomo, C.

    2009-04-01

    studies show that the AW inflow is variable in nature, both in terms of heat content and of transport intensity, therefore a detailed study of its structure is of particular importance. In order to study the thermohaline structure and the spatial extension of the AW inflow with a seismic oceanography approach, about 1000 Km of multichannel seismic reflection lines were acquired simultaneously with several types of oceanographic data. Seismic data interpretation is supported by 60 XBT (Expandable Bathy-Thermograph) profiles obtained concurrently during the seismic acquisition, 6 additional CTD (Conductivity-Temperature-Depth) casts carried out within 10 days from the XBT launches and sea-surface temperature and salinity measured continuously by a thermosalinograph installed on the vessel prow. In addition, Vessel-Mounted Acoustic Doppler Current Profiler (VM-ADCP) data were acquired during navigation to continuously monitor the velocity distribution in the upper water column. The velocity field, together with the sea-surface temperature data from the NOAA-18 satellite were used to obtain information on the dynamic in the area. The seismic data processing is still in progress as well as the elaboration of oceanographic data. The first results obtained display a good correlation between seismic reflectors and discontinuities in vertical temperature and salinity gradients. XBT sections and CTD profiles allow to recognise the spatial extension of the water masses of Atlantic and Arctic origin present in the area, and show the progressive cooling and shallowing of the warm and salty AW proceeding northwards. References: Holbrook W. S., P. Páramo, S. Pearse, and W. Schmitt, 2003, Thermohaline fine structure in an oceanographic front from seismic reflection profiling: Science, 301, 821-824. Jones S. M., R. J. J. Hardy, R. W. Hobbs, and D. Hardy, 2008, The new synergy between seismic reflection imaging and oceanography: First Break, 26, 51-57. Nakamura Y., T. Noguchi, T. Tsuji, S

  15. A high-order discontinuous Galerkin method for wave propagation through coupled elastic-acoustic media

    NASA Astrophysics Data System (ADS)

    Wilcox, Lucas C.; Stadler, Georg; Burstedde, Carsten; Ghattas, Omar

    2010-12-01

    We introduce a high-order discontinuous Galerkin (dG) scheme for the numerical solution of three-dimensional (3D) wave propagation problems in coupled elastic-acoustic media. A velocity-strain formulation is used, which allows for the solution of the acoustic and elastic wave equations within the same unified framework. Careful attention is directed at the derivation of a numerical flux that preserves high-order accuracy in the presence of material discontinuities, including elastic-acoustic interfaces. Explicit expressions for the 3D upwind numerical flux, derived as an exact solution for the relevant Riemann problem, are provided. The method supports h-non-conforming meshes, which are particularly effective at allowing local adaptation of the mesh size to resolve strong contrasts in the local wavelength, as well as dynamic adaptivity to track solution features. The use of high-order elements controls numerical dispersion, enabling propagation over many wave periods. We prove consistency and stability of the proposed dG scheme. To study the numerical accuracy and convergence of the proposed method, we compare against analytical solutions for wave propagation problems with interfaces, including Rayleigh, Lamb, Scholte, and Stoneley waves as well as plane waves impinging on an elastic-acoustic interface. Spectral rates of convergence are demonstrated for these problems, which include a non-conforming mesh case. Finally, we present scalability results for a parallel implementation of the proposed high-order dG scheme for large-scale seismic wave propagation in a simplified earth model, demonstrating high parallel efficiency for strong scaling to the full size of the Jaguar Cray XT5 supercomputer.

  16. A high-order discontinuous Galerkin method for wave propagation through coupled elastic-acoustic media

    SciTech Connect

    Wilcox, Lucas C.; Stadler, Georg; Burstedde, Carsten; Ghattas, Omar

    2010-12-10

    We introduce a high-order discontinuous Galerkin (dG) scheme for the numerical solution of three-dimensional (3D) wave propagation problems in coupled elastic-acoustic media. A velocity-strain formulation is used, which allows for the solution of the acoustic and elastic wave equations within the same unified framework. Careful attention is directed at the derivation of a numerical flux that preserves high-order accuracy in the presence of material discontinuities, including elastic-acoustic interfaces. Explicit expressions for the 3D upwind numerical flux, derived as an exact solution for the relevant Riemann problem, are provided. The method supports h-non-conforming meshes, which are particularly effective at allowing local adaptation of the mesh size to resolve strong contrasts in the local wavelength, as well as dynamic adaptivity to track solution features. The use of high-order elements controls numerical dispersion, enabling propagation over many wave periods. We prove consistency and stability of the proposed dG scheme. To study the numerical accuracy and convergence of the proposed method, we compare against analytical solutions for wave propagation problems with interfaces, including Rayleigh, Lamb, Scholte, and Stoneley waves as well as plane waves impinging on an elastic-acoustic interface. Spectral rates of convergence are demonstrated for these problems, which include a non-conforming mesh case. Finally, we present scalability results for a parallel implementation of the proposed high-order dG scheme for large-scale seismic wave propagation in a simplified earth model, demonstrating high parallel efficiency for strong scaling to the full size of the Jaguar Cray XT5 supercomputer.

  17. Mantle transition zone thinning beneath eastern Africa: Evidence for a whole-mantle superplume structure

    NASA Astrophysics Data System (ADS)

    Mulibo, Gabriel D.; Nyblade, Andrew A.

    2013-07-01

    to S conversions from the 410 and 660 km discontinuities observed in receiver function stacks reveal a mantle transition zone that is ~30-40 km thinner than the global average in a region ~200-400 km wide extending in a SW-NE direction from central Zambia, across Tanzania and into Kenya. The thinning of the transition zone indicates a ~190-300 K thermal anomaly in the same location where seismic tomography models suggest that the lower mantle African superplume structure connects to thermally perturbed upper mantle beneath eastern Africa. This finding provides compelling evidence for the existence of a continuous thermal structure extending from the core-mantle boundary to the surface associated with the African superplume.

  18. Seismic imaging a carbonate reservoir: The Paris Basin Dogger

    SciTech Connect

    Mougenot, D.

    1995-08-01

    Within the Dogger project, seven partners joined forces (CGG, DHYCA, EAP, ESSO-REP, IFP, TOTAL, TRITON France) to develop an appropriate seismic acquisition, processing and interpretation methodology in order to improve the description of the main oil reservoir (30 m) lying at the top of the Dogger carbonates in the Paris Basin, at a depth of 1900 m. High-resolution 2D Vibroseismic is used to record high frequencies (up to 100 Hz) at the level of the target, and provides sufficiently adequate vertical resolution for the reflections at the top and at the base of the reservoir not to interfere. The upper frequency content of the 3D seismic (70 Hz) is more difficult to enhance. Yet the essential contribution made by the 3D is to evidence, via horizon attributes, sub-meridian lineaments corresponding to faults with throw of several meters which is too weak to be detected on vertical sections. The distribution of these faults, via which water tends to invade the reservoir, and the organization of the amplitudes at the top reservoir reflector, which seems to suggest lateral variations in porosity, are a valuable guide for setting up wells. Three-component seismic (2D-3c) and S-wave emissions did not produce any reflections beyond 30 Hz at the level of the target which is a poor reflector (PS & SS). Only borehole seismic (VSP, offset VSP), where high frequencies are much less attenuated than with surface seismic, provides detailed imaging of the reservoir in converted mode (up to 110 Hz in PP and in PS). The combination of a continuous spatial sampling, such as that obtained in 3D, and of a Vibroseis emission adapted to frequency attenuation, such as that used in 2D, can supply useful information about the thin and discontinuous Dogger reservoir which cannot he provided by mere correlation of the borehole data.

  19. Teaching Reflection Seismic Processing

    NASA Astrophysics Data System (ADS)

    Forel, D.; Benz, T.; Pennington, W. D.

    2004-12-01

    Without pictures, it is difficult to give students a feeling for wave propagation, transmission, and reflection. Even with pictures, wave propagation is still static to many. However, when students use and modify scripts that generate wavefronts and rays through a geologic model that they have modified themselves, we find that students gain a real feeling for wave propagation. To facilitate teaching 2-D seismic reflection data processing (from acquisition through migration) to our undergraduate and graduate Reflection Seismology students, we use Seismic Un*x (SU) software. SU is maintained and distributed by Colorado School of Mines, and it is freely available (at www.cwp.mines.edu/cwpcodes). Our approach includes use of synthetic and real seismic data, processing scripts, and detailed explanation of the scripts. Our real data were provided by Gregory F. Moore of the University of Hawaii. This approach can be used by any school at virtually no expense for either software or data, and can provide students with a sound introduction to techniques used in processing of reflection seismic data. The same software can be used for other purposes, such as research, with no additional expense. Students who have completed a course using SU are well equipped to begin using it for research, as well. Scripts for each processing step are supplied and explained to the students. Our detailed description of the scripts means students do not have to know anything about SU to start. Experience with the Unix operating system is preferable but not necessary -- our notes include Computer Hints to help the beginner work with the Unix operating system. We include several examples of synthetic model building, acquiring shot gathers through synthetic models, sorting shot gathers to CMP gathers, gain, 1-D frequency filtering, f-k filtering, deconvolution, semblance displays and velocity analysis, flattening data (NMO), stacking the CMPs, and migration. We use two real (marine) data sets. One

  20. Final Technical Report ''Double discontinuities in space plasma''

    SciTech Connect

    Yun Chow Whang

    2004-05-13

    This research used high-resolution magnetic field data to examine the interior structures of MHD shocks in interplanetary space and in the magnetotail; we discovered that a slow-mode shock is often followed by an adjoining rotational discontinuity layer on the postshock side. The thickness of each layer is of the order of a few ion inertial lengths. Such a compound structure is known as a double discontinuity. When the magnetic field rotates by several degrees per ion inertial length inside a thin layer, the Hall current term becomes important in the generalized Ohm's law. Steady state solutions based on the Hall-MHD theory have been obtained to show the merging of a rotational layer and a slow shock layer to form a compound structure like the observed double discontinuities.

  1. Resolution properties of the Fourier method for discontinuous waves

    NASA Technical Reports Server (NTRS)

    Gottlieb, David; Shu, Chi-Wang

    1992-01-01

    In this paper we discuss the wave-resolution properties of the Fourier approximations of a wave function with discontinuities. It is well known that a minimum of two points per wave is needed to resolve a periodic wave function using Fourier expansions. For Chebyshev approximations of a wave function, a minimum of pi points per wave is needed. Here we obtain an estimate for the minimum number of points per wave to resolve a discontinuous wave based on its Fourier coefficients. In our recent work on overcoming the Gibbs phenomenon, we have shown that the Fourier coefficients of a discontinuous function contain enough information to reconstruct with exponential accuracy the coefficient of a rapidly converging Gegenbauer expansion. We therefore study the resolution properties of a Gegenbauer expansion where both the number of terms and the order increase.

  2. The effect of acute discontinuation of total parenteral nutrition.

    PubMed Central

    Wagman, L D; Newsome, H H; Miller, K B; Thomas, R B; Weir, G C

    1986-01-01

    The present study was undertaken to assess the impact of acute discontinuation (AD) of total parenteral nutrition (TPN) on serum glucose, insulin, and glucagon levels and on the generation of symptomatic hypoglycemia. Fifty studies were performed in 48 patients. In none of the 30 studies of 1 hour duration nor in the 20 studies of 8 hours duration was there a single episode of symptomatic hypoglycemia. One patient had a glucose below normal (60 mg/dl) during the first hour after AD. Glucose and insulin concentrations were elevated at the start of TPN discontinuation but returned to normal values within 60 minutes and remained there during the successive 7 hours of study. Although glucagon levels were slightly elevated at zero time, no significant decrease occurred. There was no evidence for counter-regulation based on the patterns of glucose and hormone levels. With some restrictions, acute discontinuation is a safe, rapid method of ending a prolonged TPN infusion. PMID:3094465

  3. Discontinuous phase transition in a dimer lattice gas

    NASA Astrophysics Data System (ADS)

    Dickman, Ronald

    2012-05-01

    I study a dimer model on the square lattice with nearest neighbor exclusion as the only interaction. Detailed simulations using tomographic entropic sampling show that as the chemical potential is varied, there is a strongly discontinuous phase transition, at which the particle density jumps by about 18% of its maximum value, 1/4. The transition is accompanied by the onset of orientational order, to an arrangement corresponding to the {1/2, 0, 1/2} structure identified by Phares et al. [Physica B 409, 1096 (2011)] in a dimer model with finite repulsion at fixed density. Using finite-size scaling and Binder's cumulant, the expected scaling behavior at a discontinuous transition is verified in detail. The discontinuous transition can be understood qualitatively given that the model possesses eight equivalent maximum-density configurations, so that its coarse-grained description corresponds to that of the q = 8 Potts model.

  4. Discontinuities of BFKL amplitudes and the BDS ansatz

    NASA Astrophysics Data System (ADS)

    Fadin, V. S.; Fiore, R.

    2015-12-01

    We perform an examination of discontinuities of multiple production amplitudes, which are required for further development of the BFKL approach. It turns out that the discontinuities of 2 → 2 + n amplitudes obtained in the BFKL approach contradict to the BDS ansatz for amplitudes with maximal helicity violation in N = 4 supersymmetric Yang-Mills theory with large number of colors starting with n = 2. Explicit expressions for the discontinuities of the 2 → 3 and 2 → 4 amplitudes in the invariant mass of pairs of produced gluons are obtained in the planar N = 4 SYM in the next-to-leading logarithmic approximation. These expressions can be used for checking the conjectured duality between the light-like Wilson loops and the MHV amplitudes.

  5. On the structure of contact binaries. I - The contact discontinuity

    NASA Technical Reports Server (NTRS)

    Shu, F. H.; Lubow, S. H.; Anderson, L.

    1976-01-01

    The problem of the interior structure of contact binaries is reviewed, and a simple resolution of the difficulties which plague the theory is suggested. It is proposed that contact binaries contain a contact discontinuity between the lower surface of the common envelope and the Roche lobe of the cooler star. This discontinuity is maintained against thermal diffusion by fluid flow, and the transition layer is thin to the extent that the dynamical time scale is short in comparison with the thermal time scale. The idealization that the transition layer has infinitesimal thickness allows a simple formulation of the structure equations which are closed by appropriate jump conditions across the discontinuity. The further imposition of the standard boundary conditions suffices to define a unique model for the system once the chemical composition, the masses of the two stars, and the orbital separation are specified.

  6. A tessellated continuum approach to thermal analysis: discontinuity networks

    NASA Astrophysics Data System (ADS)

    Jiang, C.; Davey, K.; Prosser, R.

    2016-08-01

    Tessellated continuum mechanics is an approach for the representation of thermo-mechanical behaviour of porous media on tessellated continua. It involves the application of iteration function schemes using affine contraction and expansion maps, respectively, for the creation of porous fractal materials and associated tessellated continua. Highly complex geometries can be produced using a modest number of contraction mappings. The associated tessellations form the mesh in a numerical procedure. This paper tests the hypothesis that thermal analysis of porous structures can be achieved using a discontinuous Galerkin finite element method on a tessellation. Discontinuous behaviour is identified at a discontinuity network in a tessellation; its use is shown to provide a good representation of the physics relating to cellular heat exchanger designs. Results for different cellular designs (with corresponding tessellations) are contrasted against those obtained from direct analysis and very high accuracy is observed.

  7. Fertility and contraceptive adoption and discontinuation in rural Kenya.

    PubMed

    Ferguson, A G

    1992-01-01

    After a long period of slow progress, the recent uptake of contraceptive use in Kenya has been dramatic. This report describes adoption of a method and method switching and discontinuation among a cohort of married women aged 25-34 in two contrasting rural areas. A retrospective "fertility diary" completed by each woman provided information on spousal separation, reproductive status, and contraceptive use over a period of 46-48 months. Contraceptive prevalence rose rapidly over the period in both areas, with significant net adoption of injectables in both areas and of IUDs in one only. Method discontinuation was concentrated among users of pills, barrier methods, and "natural" methods, and only one-third of all discontinuations were voluntary. The wide differences between the two rural areas in contraceptive prevalence were not totally reflected in recent fertility levels, and the contribution of other proximate determinants of fertility, particularly postpartum amenorrhea and spousal separation, are discussed.

  8. Monitoring Seasonal Changes in Permafrost Using Seismic Interferometry

    NASA Astrophysics Data System (ADS)

    James, S. R.; Knox, H. A.; Abbott, R. E.

    2015-12-01

    The effects of climate change in polar regions and their incorporation in global climate models has recently become an area of great interest. Permafrost holds entrapped greenhouse gases, e.g. CO2 and CH4, which are released to the atmosphere upon thawing, creating a positive feedback mechanism. Knowledge of seasonal changes in active layer thickness as well as long term degradation of permafrost is critical to the management of high latitude infrastructures, hazard mitigation, and increasing the accuracy of climate predictions. Methods for effectively imaging the spatial extent, depth, thickness, and discontinuous nature of permafrost over large areas are needed. Furthermore, continuous monitoring of permafrost over annual time scales would provide valuable insight into permafrost degradation. Seismic interferometry using ambient seismic noise has proven effective for recording velocity changes within the subsurface for a variety of applications, but has yet to be applied to permafrost studies. To this end, we deployed 7 Nanometrics Trillium posthole broadband seismometers within Poker Flat Research Range, located 30 miles north of Fairbanks, Alaska in a zone of discontinuous permafrost. Approximately 2 years worth of nearly continuous ambient noise data was collected. Using the python package MSNoise, relative changes in velocity were calculated. Results show high amounts of variability throughout the study period. General trends of negative relative velocity shifts can be seen between August and October followed by a positive relative velocity shift between November and February. Differences in relative velocity changes with both frequency and spatial location are also observed, suggesting this technique is sensitive to permafrost variation with depth and extent. Overall, short and long term changes in shallow subsurface velocity can be recovered using this method proposing seismic interferometry is a promising new technique for permafrost monitoring. Sandia

  9. Disparities in Discontinuing Rosiglitazone Following the 2007 FDA Safety Alert

    PubMed Central

    Qato, Danya M.; Trivedi, Amal N.; Mor, Vincent; Dore, David D.

    2016-01-01

    Background Responsiveness to the Food and Drug Administration (FDA) rosiglitazone safety alert, issued on May 21, 2007, has not been examined among vulnerable subpopulations of the elderly. Objective To compare time to discontinuation of rosiglitazone after the safety alert between black and white elderly persons, and across sociodemographic and economic subgroups. Research Design A cohort study. Subjects Medicare fee-for-service enrollees in 2007 who were established users of rosiglitazone identified from a 20% national sample of pharmacy claims. Measures Outcome of interest was time to discontinuation of rosiglitazone after the May alert. We modeled the number of days following the warning to the end of the days’ supply for the last rosiglitazone claim during the study period (May 21, 2007–December 31, 2007) using multivariable proportional hazards models. Results More than 67% of enrollees discontinued rosiglitazone within six months of the advisory. In adjusted analysis, white enrollees (hazard ratio = 0.90; 95% confidence interval, 0.86–0.94) discontinued rosiglitazone later than the comparison group of black enrollees. Enrollees with a history of low personal income also discontinued later than their comparison group (hazard ratio = 0.84; 95% confidence interval, 0.81–0.87). There were no observed differences across quintiles of area-level socioeconomic status. Conclusions White race and a history of low personal income modestly predicted later discontinuation of rosiglitazone after the FDA’s safety advisory in 2007. The impact of FDA advisories can vary among sociodemographic groups. Policymakers should continue to monitor whether risk management policies reach their intended populations. PMID:26978569

  10. Comparison of seismic sources for shallow seismic: sledgehammer and pyrotechnics

    NASA Astrophysics Data System (ADS)

    Brom, Aleksander; Stan-Kłeczek, Iwona

    2015-10-01

    The pyrotechnic materials are one of the types of the explosives materials which produce thermal, luminous or sound effects, gas, smoke and their combination as a result of a self-sustaining chemical reaction. Therefore, pyrotechnics can be used as a seismic source that is designed to release accumulated energy in a form of seismic wave recorded by tremor sensors (geophones) after its passage through the rock mass. The aim of this paper was to determine the utility of pyrotechnics for shallow seismic engineering. The work presented comparing the conventional method of seismic wave excitation for seismic refraction method like plate and hammer and activating of firecrackers on the surface. The energy released by various sources and frequency spectra was compared for the two types of sources. The obtained results did not determine which sources gave the better results but showed very interesting aspects of using pyrotechnics in seismic measurements for example the use of pyrotechnic materials in MASW.

  11. 'Fracking', Induced Seismicity and the Critical Earth

    NASA Astrophysics Data System (ADS)

    Leary, P.; Malin, P. E.

    2012-12-01

    and ore body distributions can be managed by operating in a context which affords many small failures for a few large successes. In reverse view, 'fracking' and induced seismicity could be rationally managed in a context in which many small successes can afford a few large failures. However, just as there is every incentive to acquire information leading to higher rates of productive well drilling and ore body exploration, there are equal incentives for acquiring information leading to lower rates of 'fracking'-induced seismicity. Current industry practice of using an effective medium approach to reservoir rock creates an uncritical sense that property distributions in rock are essentially uniform. Well-log data show that the reverse is true: the larger the length scale the greater the deviation from uniformity. Applying the effective medium approach to large-scale rock formations thus appears to be unnecessarily hazardous. It promotes the notion that large scale fluid pressurization acts against weakly cohesive but essentially uniform rock to produce large-scale quasi-uniform tensile discontinuities. Indiscriminate hydrofacturing appears to be vastly more problematic in reality than as pictured by the effective medium hypothesis. The spatial complexity of rock, especially at large scales, provides ample reason to find more controlled pressurization strategies for enhancing in situ flow.

  12. Continuous seismic reflection profiling of hydrogeologic features beneath New River, Camp Lejeune, North Carolina

    USGS Publications Warehouse

    Cardinell, A.P.; Harned, D.A.; Berg, S.A.

    1990-01-01

    A medium-power, wide-frequency seismic system was used to collect more than 100 miles of continuous seismic reflection profiling data over a 4- day period along a 24-mile segment of the New River estuary and Intracoastal Waterway. The seismic reflection data were evaluated to determine the continuity of aquifer sediments and correlation with existing borehole geophysical well-log data at the Base. Results indicate that the Castle Hayne aquifer, the major source of freshwater for the military base and surrounding area, and deeper aquifers are continuous beds that gently dip to the southeast. However, immediately above the Castle Hayne aquifer, the survey showed that sediment beds are thin and discontinuous. This not only allows rainfall to more easily percolate and recharge the aquifer, but also makes the Castle Hayne more vulnerable to contamination.

  13. A comparative study between shielded and open coplanar waveguide discontinuities

    NASA Technical Reports Server (NTRS)

    Dib, Nihad I.; Harokopus, W. P., Jr.; Ponchak, G. E.; Katehi, L. P. B.

    1993-01-01

    A comparative study between open and shielded coplanar waveguide (CPW) discontinuities is presented. The space domain integral equation method is used to characterize several discontinuities such as the open-end CPW and CPW series stubs. Two different geometries of CPW series stubs (straight and bent stubs) are compared with respect to resonant frequency and radiation loss. In addition, the encountered radiation loss due to different CPW shunt stubs is evaluated experimentally. The notion of forced radiation simulation is presented, and the results of such a simulation are compared to the actual radiation loss obtained rigorously. It is shown that such a simulation cannot give reliable results concerning radiation loss from printed circuits.

  14. Discontinuous Galerkin finite element methods for gradient plasticity.

    SciTech Connect

    Garikipati, Krishna.; Ostien, Jakob T.

    2010-10-01

    In this report we apply discontinuous Galerkin finite element methods to the equations of an incompatibility based formulation of gradient plasticity. The presentation is motivated with a brief overview of the description of dislocations within a crystal lattice. A tensor representing a measure of the incompatibility with the lattice is used in the formulation of a gradient plasticity model. This model is cast in a variational formulation, and discontinuous Galerkin machinery is employed to implement the formulation into a finite element code. Finally numerical examples of the model are shown.

  15. Trapped electromagnetic modes in a waveguide with a small discontinuity

    NASA Astrophysics Data System (ADS)

    Stupakov, G. V.; Kurennoy, S. S.

    1994-01-01

    We demonstrate that a small discontinuity (such as an enlargement or a hole) on a smooth waveguide can result in the appearance of trapped modes localized in the vicinity of the discontinuity. The frequencies of these modes lie slightly below the cutoff frequencies of the corresponding propagating modes in the waveguide. We find the distribution of the electromagnetic field in the modes and calculate their damping rate due to a finite conductivity of the walls. The contribution of the trapped modes to the longitudinal impedance is calculated.

  16. Calculating California Seismicity Rates

    USGS Publications Warehouse

    Felzer, Karen R.

    2008-01-01

    Empirically the rate of earthquakes = magnitude M is well fit by the Gutenberg-Richter relationship, logN=a-bM (1) where N is the number of earthquakes = M over a given time period, a is the number of M = 0 earthquakes over the same period, and b is a parameter that determines the ratio of larger to smaller earthquakes (Ishimoto and Iida 1939; Gutenberg and Richter 1944). Thus to characterize the seismicity rate, N, and risk in a given region we need to solve for the values of a and b. Here we are concerned with solving for the long term average values of these parameters for the state of California. My primary data source is a catalog of 1850-2006 M = 4.0 seismicity compiled with Tianqing Cao (Appendix H). Because earthquakes outside of the state can influence California I consider both earthquakes within the state and within 100 km of the state border (Figure 1).

  17. Seismic detection of tornadoes

    USGS Publications Warehouse

    Tatom, F. B.

    1993-01-01

    Tornadoes represent the most violent of all forms of atmospheric storms, each year resulting in hundreds of millions of dollars in property damage and approximately one hundred fatalities. In recent years, considerable success has been achieved in detecting tornadic storms by means of Doppler radar. However, radar systems cannot determine when a tornado is actually in contact with the ground, expect possibly at extremely close range. At the present time, human observation is the only truly reliable way of knowing that a tornado is actually on the ground. However, considerable evidence exists indicating that a tornado in contact with the ground produces a significant seismic signal. If such signals are generated, the seismic detection and warning of an imminent tornado can become a distinct possibility. 

  18. Albuquerque Basin seismic network

    USGS Publications Warehouse

    Jaksha, Lawrence H.; Locke, Jerry; Thompson, J.B.; Garcia, Alvin

    1977-01-01

    The U.S. Geological Survey has recently completed the installation of a seismic network around the Albuquerque Basin in New Mexico. The network consists of two seismometer arrays, a thirteen-station array monitoring an area of approximately 28,000 km 2 and an eight-element array monitoring the area immediately adjacent to the Albuquerque Seismological Laboratory. This report describes the instrumentation deployed in the network.

  19. Precise measurements of enthalpy of postspinel transition in Mg2SiO4 and application to the phase boundary calculation

    NASA Astrophysics Data System (ADS)

    Kojitani, Hiroshi; Inoue, Toru; Akaogi, Masaki

    2016-02-01

    Drop solution enthalpies (ΔH°d-s) of Mg2SiO4 ringwoodite, Mg2SiO4 forsterite, perovskite-type MgSiO3 (bridgmanite), and MgSiO3 enstatite were measured using a single batch of 2PbO · B2O3 solvent at 978 K. From the obtained ΔH°d-s values of Mg2SiO4 ringwoodite, MgSiO3 bridgmanite, and MgO, an enthalpy of the postspinel phase transition, Mg2SiO4 ringwoodite = MgSiO3 bridgmanite + MgO, was determined to be 78.54 ± 2.28 kJ/mol. Thermodynamic calculations using the obtained phase transition enthalpy and available thermochemical and thermoelastic data provided the phase transition pressure of 23.1 ± 1.4 GPa at 298 K. This value is comparable to those at about 2000 K determined by previous experimental and theoretical studies, implying a considerably gentle Clapeyron slope. Thermodynamic calculations of the postspinel boundary at high temperatures in the anhydrous condition by changing thermochemical and thermoelastic parameters within the uncertainties suggested that the postspinel transition pressure of Mg2SiO4 at high temperature is lower than the pressure corresponding to the global average depth of the "660 km" seismic discontinuity in the Earth's mantle (~23.5 GPa) estimated from one-dimensional reference Earth models and that a most likely Clapeyron slope is about -1 MPa/K. The postspinel transition in the hydrous condition with about 2 wt % H2O, which shows higher transition pressure and steeper Clapeyron slope than those in the anhydrous condition, gives a plausible explanation for seismic observations on the 660 km discontinuity, and therefore, hydrous mantle transition zone would be required.

  20. Establishing seismic design criteria to achieve an acceptable seismic margin

    SciTech Connect

    Kennedy, R.P.

    1997-01-01

    In order to develop a risk based seismic design criteria the following four issues must be addressed: (1) What target annual probability of seismic induced unacceptable performance is acceptable? (2). What minimum seismic margin is acceptable? (3) Given the decisions made under Issues 1 and 2, at what annual frequency of exceedance should the Safe Shutdown Earthquake ground motion be defined? (4) What seismic design criteria should be established to reasonably achieve the seismic margin defined under Issue 2? The first issue is purely a policy decision and is not addressed in this paper. Each of the other three issues are addressed. Issues 2 and 3 are integrally tied together so that a very large number of possible combinations of responses to these two issues can be used to achieve the target goal defined under Issue 1. Section 2 lays out a combined approach to these two issues and presents three potentially attractive combined resolutions of these two issues which reasonably achieves the target goal. The remainder of the paper discusses an approach which can be used to develop seismic design criteria aimed at achieving the desired seismic margin defined in resolution of Issue 2. Suggestions for revising existing seismic design criteria to more consistently achieve the desired seismic margin are presented.

  1. Seismicity in South Carolina

    USGS Publications Warehouse

    Shedlock, K.M.

    1988-01-01

    The largest historical earthquake in South Carolina, and in the southeastern US, occurred in the Coastal Plain province, probably northwest of Charleston, in 1886. Locations for aftershocks associated with this earthquake, estimated using intensities based on newspaper accounts, defined a northwest trending zone about 250 km long that was at least 100 km wide in the Coastal Plain but widened to a northeast trending zone in the Piedmont. The subsequent historical and instrumentally recorded seismicity in South Carolina images the 1886 aftershock zone. Instrumentally recorded seismicity in the Coastal Plain province occurs in 3 seismic zones or clusters: Middleton Place-Summervile (MPSSZ), Adams Run (ARC), and Bowman (BSZ). Approximately 68% of the Coastal Plain earthquakes occur in the MPSSZ, a north trending zone about 22 km long and 12 km wide, lying about 20 km northwest of Charleston. The hypocenters of MPSSZ earthquakes range in depth from near the surface to almost 12 km. Thrust, strike-slip, and some normal faulting are indicated by the fault plane solutions for Coastal Plain earthquakes. The maximum horizontal compressive stress, inferred from the P-axes of the fault plane solutions, is oriented NE-SW in the shallow crust (<9 km deep) but appears to be diffusely E-W between 9 to 12 km deep. -from Author

  2. Seismic basement in Poland

    NASA Astrophysics Data System (ADS)

    Grad, Marek; Polkowski, Marcin

    2016-06-01

    The area of contact between Precambrian and Phanerozoic Europe in Poland has complicated structure of sedimentary cover and basement. The thinnest sedimentary cover in the Mazury-Belarus anteclize is only 0.3-1 km thick, increases to 7-8 km along the East European Craton margin, and 9-12 km in the Trans-European Suture Zone (TESZ). The Variscan domain is characterized by a 1- to 2-km-thick sedimentary cover, while the Carpathians are characterized by very thick sediments, up to c. 20 km. The map of the basement depth is created by combining data from geological boreholes with a set of regional seismic refraction profiles. These maps do not provide data about the basement depth in the central part of the TESZ and in the Carpathians. Therefore, the data set is supplemented by 32 models from deep seismic sounding profiles and a map of a high-resistivity (low-conductivity) layer from magnetotelluric soundings, identified as a basement. All of these data provide knowledge about the basement depth and of P-wave seismic velocities of the crystalline and consolidated type of basement for the whole area of Poland. Finally, the differentiation of the basement depth and velocity is discussed with respect to geophysical fields and the tectonic division of the area.

  3. Testing How Depletion, Dehydration and Melt Affect Seismic Expressions of the Asthenosphere

    NASA Astrophysics Data System (ADS)

    Armitage, J. J.; Goes, S. D. B.; Hammond, J. O. S.

    2015-12-01

    Seismic images of the upper mantle beneath mid-ocean ridges and rift zones typically show discontinuities in wave speed that are often attributed to the presence of partial melt. To understand how lithosphere and asthenosphere differ in temperature, composition and melt content, it is necessary to test plausible dynamic scenarios against a wide range of observables. Here we take a first step at comparing seismic constraints with the seismic structure predicted for (1) a simple oceanic lithosphere-asthenosphere system, formed by melt extraction and dehydration at the ridge and half-space cooling as the lithosphere away from it and (2) continental break-up where there is significant partial melting. We have developed a relatively simple 2-D geodynamic model of decompression melting during extension that incorporates melt retention and dehydration. This model can explain the seismic structure below the East Pacific Rise as imaged by surface and body waves, including a double low velocity zone, with triangular anomaly above 50-60 km depth due to dry melting and low velocity layer between 60 and ~200km depth mainly resulting from solid-state anelasticity in hydrated mantle. We only require a minor contribution below the ridge of deep hydrous melt. Below Afar, in the East African Rift, S receiver functions have found a discontinuity in shear wave speeds at ~75km depth, consistent with the depth of the onset of dry melting. Yet, from the same forward model, no aspect of the melt zone leads to sufficiently sharp impedance contrast in isotropic velocity to explain the receiver-function signals. This suggests that something else is required to explain the seismic observations. We speculate that this may be a change in seismic anisotropy caused by a change in melt segregation characteristics.

  4. Mapping bedrock beneath glacial till using CDP seismic reflection methods

    SciTech Connect

    Keiswetter, D.; Black, R.; Steeples, D.

    1994-03-01

    This paper is a case history demonstrating the applicability of the common depth point (CDP) seismic reflection method to image bedrock beneath glacial till in northwestern Iowa. Reflections from the base of the 40-m thick glacial till are clearly observable on field files at around 45 to 50 ms two-way traveltime and possess a dominant frequency of around 100 Hz. The bedrock reflection is confirmed by drill data. The seismic data are of sufficient quality to detect local bedrock topographic changes and to interpret discontinuities along the till-bedrock interface. Finite-difference synthetic seismograms substantiate the interpreted reflections and the diffraction signatures from faults observed on the field files. At some locations along the seismic line, intra-till reflections are apparent on the field files. These intra-till features are on the order of tens of meters in length along the line traverse and reflections from them are not enhanced by common depth point processing. Intra-till reflections could be indicative of gravels or other alluvial materials that may serve as local aquifers.

  5. Seismic facies interpretation of Mesozoic sequences, Shiwandashan basin, China

    SciTech Connect

    Leu, Leikuang; Armentrout, J.M.; Faz, J.J. )

    1991-03-01

    Integration of outcrop and subsurface geologic data with seismic facies analysis identified three exploration plays in Shiwandashan basin, southeastern China: Triassic Submarine Fan: Elongate-mounded packages of variable amplitude, discontinuous, nonparallel reflections occur basinward of the slope and are downlapped by prograding slope clinoforms. This facies is undrilled. Basin modeling suggests the mounded seismic facies correlates with outcrops of Triassic marine siliclastic turbidites which grade laterally into basinal mudstone/limestone couplets. Triassic Shelf Carbonates: Localized, high amplitude parallel reflections occur in a retrograde succession at the top of the Triassic prograding clinoform. These high amplitude seismic facies are calibrated with drilled carbonate facies and are correlated with outcrops of upper Triassic shelf and shelf-edge reefs that contain two generations of migrated hydrocarbons. Jurassic Fan Deltas: Thick northeast-southwest bidirectional downlapping hummocks of variable amplitude reflections and intersecting northwest downlapping clinoforms form large mounds and grade laterally to moderately continuous parallel reflections. The hummocky-clinoform mound facies is calibrated by drilled, poorly sorted conglomerates and correlates with outcrops of a Jurassic synrift basin-fill succession. These Jurassic rocks are interpreted as fan-deltas grading laterally to sandy fluvial and shaley lacustrine facies. The geochemical data suggest a potential gas-prone play for the Triassic submarine fans and potential oil-prone play for the stratigraphically shallower Triassic shelf and shelf-edge reefs. The Jurassic fan delta play drilled tight with no hydrocarbons.

  6. Seismic upgrades of healthcare facilities.

    PubMed

    Yusuf, A

    1997-06-01

    Before 1989 seismic upgrading of hospital structures was not a primary consideration among hospital owners. However, after extensive earthquake damage to hospital buildings at Loma Prieta in Northern California in 1989 and then at Northridge in Southern California in 1994, hospital owners, legislators, and design teams become concerned about the need for seismic upgrading of existing facilities. Because the damage hospital structures sustained in the earthquakes was so severe and far-reaching, California has enacted laws that mandate seismic upgrading for existing facilities. Now hospital owners will have to upgrade buildings that do not conform to statewide seismic adequacy laws. By 2030, California expects all of its hospital structures to be sufficiently seismic-resistant. Slowly, regions in the Midwest and on the East Coast are following their example. This article outlines reasons and ways for seismic upgrading of existing facilities.

  7. Crust and upper mantle structures beneath Northeast China from receiver function studies

    NASA Astrophysics Data System (ADS)

    Guo, Zhen; Cao, Yuliang; Wang, Xianguang; John Chen, Y.; Ning, Jieyuan; He, Weiguang; Tang, Youcai; Feng, Yongge

    2014-06-01

    P-wave and S-wave receiver function analyses have been performed along a profile consisted of 27 broadband seismic stations to image the crustal and upper mantle discontinuities across Northeast China. The results show that the average Moho depth varies from about 37 km beneath the Daxing'anling orogenic belt in the west to about 33 km beneath the Songliao Basin, and to about 35 km beneath the Changbai mountain region in the east. Our results reveal that the Moho is generally flat beneath the Daxing'anling region and a remarkable Moho offset (about 4 km) exists beneath the basin-mountain boundary, the Daxing'anling-Taihang Gravity Line. Beneath the Tanlu faults zone, which seperates the Songliao Basin and Changbai region, the Moho is uplift and the crustal thickness changes rapidly. We interpret this feature as that the Tanlu faults might deeply penetrate into the upper mantle, and facilitate the mantle upwelling along the faults during the Cenozoic era. The average depth of the lithosphere-asthenosphere boundary (LAB) is ~80 km along the profile which is thinner than an average thickness of a continental lithosphere. The LAB shows an arc-like shape in the basin, with the shallowest part approximately beneath the center of the basin. The uplift LAB beneath the basin might be related to the extensive lithospheric stretching in the Mesozoic. In the mantle transition zone, a structurally complicated 660 km discontinuity with a maximum 35 km depression beneath the Changbai region is observed. The 35 km depression is roughly coincident with the location of the stagnant western pacific slab on top of the 660 km discontinuity revealed by the recent P wave tomography.

  8. Seismic Imager Space Telescope

    NASA Technical Reports Server (NTRS)

    Sidick, Erkin; Coste, Keith; Cunningham, J.; Sievers,Michael W.; Agnes, Gregory S.; Polanco, Otto R.; Green, Joseph J.; Cameron, Bruce A.; Redding, David C.; Avouac, Jean Philippe; Ampuero, Jean Paul; Leprince, Sebastien; Michel, Remi

    2012-01-01

    A concept has been developed for a geostationary seismic imager (GSI), a space telescope in geostationary orbit above the Pacific coast of the Americas that would provide movies of many large earthquakes occurring in the area from Southern Chile to Southern Alaska. The GSI movies would cover a field of view as long as 300 km, at a spatial resolution of 3 to 15 m and a temporal resolution of 1 to 2 Hz, which is sufficient for accurate measurement of surface displacements and photometric changes induced by seismic waves. Computer processing of the movie images would exploit these dynamic changes to accurately measure the rapidly evolving surface waves and surface ruptures as they happen. These measurements would provide key information to advance the understanding of the mechanisms governing earthquake ruptures, and the propagation and arrest of damaging seismic waves. GSI operational strategy is to react to earthquakes detected by ground seismometers, slewing the satellite to point at the epicenters of earthquakes above a certain magnitude. Some of these earthquakes will be foreshocks of larger earthquakes; these will be observed, as the spacecraft would have been pointed in the right direction. This strategy was tested against the historical record for the Pacific coast of the Americas, from 1973 until the present. Based on the seismicity recorded during this time period, a GSI mission with a lifetime of 10 years could have been in position to observe at least 13 (22 on average) earthquakes of magnitude larger than 6, and at least one (2 on average) earthquake of magnitude larger than 7. A GSI would provide data unprecedented in its extent and temporal and spatial resolution. It would provide this data for some of the world's most seismically active regions, and do so better and at a lower cost than could be done with ground-based instrumentation. A GSI would revolutionize the understanding of earthquake dynamics, perhaps leading ultimately to effective warning

  9. 48 CFR 49.303 - Procedure after discontinuing vouchers.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Procedure after discontinuing vouchers. 49.303 Section 49.303 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION CONTRACT MANAGEMENT TERMINATION OF CONTRACTS Additional Principles for...

  10. 48 CFR 49.302 - Discontinuance of vouchers.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Discontinuance of vouchers. 49.302 Section 49.302 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION CONTRACT MANAGEMENT TERMINATION OF CONTRACTS Additional Principles for Cost-Reimbursement Contracts Terminated...

  11. Derivative discontinuity with localized Hartree-Fock potential

    NASA Astrophysics Data System (ADS)

    Nazarov, V. U.; Vignale, G.

    2015-08-01

    The localized Hartree-Fock potential has proven to be a computationally efficient alternative to the optimized effective potential, preserving the numerical accuracy of the latter and respecting the exact properties of being self-interaction free and having the correct -1/r asymptotics. In this paper we extend the localized Hartree-Fock potential to fractional particle numbers and observe that it yields derivative discontinuities in the energy as required by the exact theory. The discontinuities are numerically close to those of the computationally more demanding Hartree-Fock method. Our potential enjoys a "direct-energy" property, whereby the energy of the system is given by the sum of the single-particle eigenvalues multiplied by the corresponding occupation numbers. The discontinuities c↑ and c↓ of the spin-components of the potential at integer particle numbers N↑ and N↓ satisfy the condition c↑N↑ + c↓N↓ = 0. Thus, joining the family of effective potentials which support a derivative discontinuity, but being considerably easier to implement, the localized Hartree-Fock potential becomes a powerful tool in the broad area of applications in which the fundamental gap is an issue.

  12. 14 CFR 170.25 - LORAN-C discontinuance criteria.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 3 2014-01-01 2014-01-01 false LORAN-C discontinuance criteria. 170.25 Section 170.25 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... costs (PVCM) of the LORAN-C approach exceed the present value of its remaining life-cycle benefits...

  13. 14 CFR 170.15 - ATCT discontinuance criteria.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 3 2014-01-01 2014-01-01 false ATCT discontinuance criteria. 170.15 Section 170.15 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... termination costs (CMPV) of the ATCT exceed the present value of its remaining life-cycle benefits (BPV):...

  14. The Age of Discontinuity; Guidelines to Our Changing Society.

    ERIC Educational Resources Information Center

    Drucker, Peter F.

    Concentrating on the social dimension of human experience and existence, this book probes certain profound changes occurring in contemporary technology, economy, society, politics, and education. The author discusses four major discontinuities: (1) the impact of the new technology on the industrial structure; (2) the shift from an "international…

  15. Kinetic theory and turbulent discontinuities. [shock tube flow

    NASA Technical Reports Server (NTRS)

    Johnson, J. A., III; I, L.; Li, Y.; Ramaian, R.; Santigo, J. P.

    1981-01-01

    Shock tube discontinuities were used to test and extend a kinetic theory of turbulence. In shock wave and contact surface fluctuations, coherent phenomena were found which provide new support for the microscopic nonempirical approach to turbulent systems, especially those with boundary layer-like instabilities.

  16. 38 CFR 21.9630 - Suspension or discontinuance of payments.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 2 2014-07-01 2014-07-01 false Suspension or discontinuance of payments. 21.9630 Section 21.9630 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS (CONTINUED) VOCATIONAL REHABILITATION AND EDUCATION Post-9/11 GI Bill...

  17. 38 CFR 21.9630 - Suspension or discontinuance of payments.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 2 2010-07-01 2010-07-01 false Suspension or discontinuance of payments. 21.9630 Section 21.9630 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS (CONTINUED) VOCATIONAL REHABILITATION AND EDUCATION Post-9/11 GI Bill...

  18. 38 CFR 21.9630 - Suspension or discontinuance of payments.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 2 2011-07-01 2011-07-01 false Suspension or discontinuance of payments. 21.9630 Section 21.9630 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS (CONTINUED) VOCATIONAL REHABILITATION AND EDUCATION Post-9/11 GI Bill...

  19. 38 CFR 21.9630 - Suspension or discontinuance of payments.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 2 2012-07-01 2012-07-01 false Suspension or discontinuance of payments. 21.9630 Section 21.9630 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS (CONTINUED) VOCATIONAL REHABILITATION AND EDUCATION Post-9/11 GI Bill...

  20. 38 CFR 21.9630 - Suspension or discontinuance of payments.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 2 2013-07-01 2013-07-01 false Suspension or discontinuance of payments. 21.9630 Section 21.9630 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS (CONTINUED) VOCATIONAL REHABILITATION AND EDUCATION Post-9/11 GI Bill...

  1. Boston Naming Test Discontinuation Rule: "Rigorous" versus "Lenient" Interpretations.

    ERIC Educational Resources Information Center

    Ferman, Tanis J.; Ivnik, Robert J.; Lucas, John A.

    1998-01-01

    Two interpretations of the Boston Naming Test (BNT) (E. Kaplan, H. Goodglass, and S. Weintraub, 1983) discontinuation rule of six consecutive failures were found in BNT use with 655 normal older adults and 140 people with Alzheimer's disease. Differences between lenient and rigorous interpretations of responses could have impact on…

  2. Effect of motion discontinuities on discrimination of periodic trajectories.

    PubMed

    Wilson, Hugh R; Fung, Jeffrey

    2016-01-01

    Many biologically important motions are described by periodic trajectories. Radial frequency (RF) trajectories are one example, in which the motion of a difference of Gaussians (DOG) target moves along a path described by a sinusoidal deviation of the radius from a perfect circle (Or, Thabet, Wilkinson, & Wilson, 2011). Here we explore the hypothesis that visual processing of RF trajectories involves global spatio-temporal processes that are disrupted by motion discontinuity. To test this hypothesis, RF trajectories were used that interspersed smooth, continuous motion with three or four discontinuous jumps to other portions of the trajectory. These jumps were arranged so that the entire trajectory was traversed in the same amount of time as in the continuous motion control condition. The motion discontinuities increased thresholds by a factor of approximately 2.1 relative to continuous motion. This result provides support for global spatio-temporal processing of RF motion trajectories. Comparison with previous results suggests that motion discontinuities erase memory for earlier parts of the trajectory, thereby causing thresholds to be based on only the final segment viewed. Finally, it is shown that RF trajectories obey the 1/3 power law characteristic of biological motion.

  3. Fracture criteria for discontinuously reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Rack, H. J.; Goree, J. G.; Albritton, J.; Ratnarparkhi, P.

    1988-01-01

    The effect of sample configuration on the details of initial crack propagation in discontinuously whisker reinforced aluminum metal matrix composites was investigated. Care was taken to allow direct comparison of fracture toughness values utilizing differing sample configurations and orientations, holding all materials variables constant, e.g., extrusion ration, heat treatment, and chemistry.

  4. 77 FR 20988 - Discontinuance of Form CO in Registration Practices

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-09

    ... From the Federal Register Online via the Government Publishing Office LIBRARY OF CONGRESS Copyright Office 37 CFR Parts 201 and 202 Discontinuance of Form CO in Registration Practices Correction In rule document 2012-7429 appearing on pages 18705-18707 in the issue of March 28, 2012, make...

  5. Remedial Education and Student Achievement: A Regression-Discontinuity Analysis.

    ERIC Educational Resources Information Center

    Jacob, Brian A.; Lefgren, Lars

    This study used a regression discontinuity design to examine the causal effect of summer school and grade retention on student achievement. In 1996, the Chicago Public Schools instituted an accountability policy that tied summer school attendance and promotional decisions to performance on standardized tests, which created a highly non-linear…

  6. 38 CFR 8.17 - Discontinuance of premium waiver.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... SERVICE LIFE INSURANCE Premium Waivers and Total Disability § 8.17 Discontinuance of premium waiver. (a... premiums shall cease as of the date of such finding, and the insurance may be continued by payment of..., and if such premium was not paid within 31 days after the due date, the insurance lapsed. (c) If...

  7. Regression Discontinuity Designs with Multiple Rating-Score Variables

    ERIC Educational Resources Information Center

    Reardon, Sean F.; Robinson, Joseph P.

    2012-01-01

    In the absence of a randomized control trial, regression discontinuity (RD) designs can produce plausible estimates of the treatment effect on an outcome for individuals near a cutoff score. In the standard RD design, individuals with rating scores higher than some exogenously determined cutoff score are assigned to one treatment condition; those…

  8. Reversible brain inactivation induces discontinuous gas exchange in cockroaches.

    PubMed

    Matthews, Philip G D; White, Craig R

    2013-06-01

    Many insects at rest breathe discontinuously, alternating between brief bouts of gas exchange and extended periods of breath-holding. The association between discontinuous gas exchange cycles (DGCs) and inactivity has long been recognised, leading to speculation that DGCs lie at one end of a continuum of gas exchange patterns, from continuous to discontinuous, linked to metabolic rate (MR). However, the neural hypothesis posits that it is the downregulation of brain activity and a change in the neural control of gas exchange, rather than low MR per se, which is responsible for the emergence of DGCs during inactivity. To test this, Nauphoeta cinerea cockroaches had their brains inactivated by applying a Peltier-chilled cold probe to the head. Once brain temperature fell to 8°C, cockroaches switched from a continuous to a discontinuous breathing pattern. Re-warming the brain abolished the DGC and re-established a continuous breathing pattern. Chilling the brain did not significantly reduce the cockroaches' MR and there was no association between the gas exchange pattern displayed by the insect and its MR. This demonstrates that DGCs can arise due to a decrease in brain activity and a change in the underlying regulation of gas exchange, and are not necessarily a simple consequence of low respiratory demand.

  9. Fracture criteria for discontinuously reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Rack, H. J.; Goree, J. G.; Albritton, J.; Ratnaparkhi, P.

    1988-01-01

    Summarized is the progress achieved during the period September 16, 1987 to August 15, l988 on NASA Grant NAG1-724, Fracture Criteria for Discontinuously Reinforced Metal Matrix Composites. Appended are copies of three manuscripts prepared under NASA funding during the performance period.

  10. Dialogic Reverberations: Police, Domestic Abuse, and the Discontinuance of Cases

    ERIC Educational Resources Information Center

    Lea, Susan J.; Lynn, Nick

    2012-01-01

    This study investigated the social construction of domestic abuse by police officers, specifically in the context of arguments presented to the prosecutor for a decision on whether to proceed with or discontinue the case. Nineteen police files were examined with a particular focus on the MG3, the "Report to Crown Prosecutors for Charging…

  11. Regression Discontinuity Design in Gifted and Talented Education Research

    ERIC Educational Resources Information Center

    Matthews, Michael S.; Peters, Scott J.; Housand, Angela M.

    2012-01-01

    This Methodological Brief introduces the reader to the regression discontinuity design (RDD), which is a method that when used correctly can yield estimates of research treatment effects that are equivalent to those obtained through randomized control trials and can therefore be used to infer causality. However, RDD does not require the random…

  12. A Bayesian Nonparametric Causal Model for Regression Discontinuity Designs

    ERIC Educational Resources Information Center

    Karabatsos, George; Walker, Stephen G.

    2013-01-01

    The regression discontinuity (RD) design (Thistlewaite & Campbell, 1960; Cook, 2008) provides a framework to identify and estimate causal effects from a non-randomized design. Each subject of a RD design is assigned to the treatment (versus assignment to a non-treatment) whenever her/his observed value of the assignment variable equals or…

  13. Can eculizumab be discontinued in aHUS?

    PubMed Central

    Sahutoglu, Tuncay; Basturk, Taner; Sakaci, Tamer; Koc, Yener; Ahbap, Elbis; Sevinc, Mustafa; Kara, Ekrem; Akgol, Cuneyt; Caglayan, Feyza Bayraktar; Unsal, Abdulkadir; Daha, Mohamed R.

    2016-01-01

    Abstract Background: The management of atypical hemolytic uremic syndrome (aHUS) has evolved into better control of thrombotic microangiopathy (TMA) and recovery of renal functions since the recent introduction of the terminal complement cascade blocker, eculizumab, into clinical use. Better characterization of genotype–phenotype relations has become possible with genetic and clinical studies. However, these advances brought up some important issues, such as the possibility and timing of discontinuation of eculizumab and strategy of follow-up that need to be enlightened. Case Summary: One of our aHUS cases with a novel complement factor H mutation, who developed unusual laboratory findings (thrombocytopenia and mild creatinine elevation without other features of TMA) following discontinuation of eculizumab was presented. Literature and case reports relevant to discontinuation of eculizumab in aHUS patients were reviewed. Conclusion: Limited experience suggests that the risk of recurrence of TMA following discontinuation of eculizumab is relatively low for patients with MCP mutations, homozygous CFHR3/R1 deletions, anti-CFH antibodies, CFI mutations, and no identifiable mutations, whereas there is a major risk for patients with CFH mutations. Early detection of TMA recurrence and prompt retreatment with eculizumab seem to be efficient in controlling of TMA and restoration of kidney functions. PMID:27495036

  14. Derivative discontinuity with localized Hartree-Fock potential.

    PubMed

    Nazarov, V U; Vignale, G

    2015-08-14

    The localized Hartree-Fock potential has proven to be a computationally efficient alternative to the optimized effective potential, preserving the numerical accuracy of the latter and respecting the exact properties of being self-interaction free and having the correct -1/r asymptotics. In this paper we extend the localized Hartree-Fock potential to fractional particle numbers and observe that it yields derivative discontinuities in the energy as required by the exact theory. The discontinuities are numerically close to those of the computationally more demanding Hartree-Fock method. Our potential enjoys a "direct-energy" property, whereby the energy of the system is given by the sum of the single-particle eigenvalues multiplied by the corresponding occupation numbers. The discontinuities c↑ and c↓ of the spin-components of the potential at integer particle numbers N↑ and N↓ satisfy the condition c↑N↑ + c↓N↓ = 0. Thus, joining the family of effective potentials which support a derivative discontinuity, but being considerably easier to implement, the localized Hartree-Fock potential becomes a powerful tool in the broad area of applications in which the fundamental gap is an issue. PMID:26277131

  15. Sound propagation in a refracting atmosphere above an impedance discontinuity

    NASA Astrophysics Data System (ADS)

    Taherzadeh, Shahram; Harrop, Nick

    2002-11-01

    de Jongs formulation of sound propagation above a ground with a single impedance change has been extended to include effects of a refracting atmosphere and atmospheric turbulence. The theory is compared with a numerical algorithm based on a hybrid Boundary Integral Equation/Fast Field Program developed for predicting the propagation of sound in a refracting atmosphere above an uneven, discontinuous terrain. By using the analogy of sound diffraction over curved surfaces to atmospheric refraction over flat ground surfaces, the effect of temperature and wind velocity gradients in the presence of flat ground surfaces can be studied. Measurements of the excess attenuation of sound from a point source over a mixed impedance curved surface are carried out in an anechoic chamber as well as outdoor measurements over a tarmac-grass discontinuity. These measurements are compared with predictions based on the extended de Jong theory and the hybrid BIE/FFP algorithm in the nonturbulent case. Results show that where there is a single discontinuity between acoustically hard and finite impedance surfaces both models are found to give satisfactory agreement with measured data except when the discontinuity is midway between the source and the detector.

  16. Reciprocity principle for scattered fields from discontinuities in waveguides.

    PubMed

    Pau, Annamaria; Capecchi, Danilo; Vestroni, Fabrizio

    2015-01-01

    This study investigates the scattering of guided waves from a discontinuity exploiting the principle of reciprocity in elastodynamics, written in a form that applies to waveguides. The coefficients of reflection and transmission for an arbitrary mode can be derived as long as the principle of reciprocity is satisfied at the discontinuity. Two elastodynamic states are related by the reciprocity. One is the response of the waveguide in the presence of the discontinuity, with the scattered fields expressed as a superposition of wave modes. The other state is the response of the waveguide in the absence of the discontinuity oscillating according to an arbitrary mode. The semi-analytical finite element method is applied to derive the needed dispersion relation and wave mode shapes. An application to a solid cylinder with a symmetric double change of cross-section is presented. This model is assumed to be representative of a damaged rod. The coefficients of reflection and transmission of longitudinal waves are investigated for selected values of notch length and varying depth.

  17. Derivative discontinuity with localized Hartree-Fock potential

    SciTech Connect

    Nazarov, V. U.; Vignale, G.

    2015-08-14

    The localized Hartree-Fock potential has proven to be a computationally efficient alternative to the optimized effective potential, preserving the numerical accuracy of the latter and respecting the exact properties of being self-interaction free and having the correct −1/r asymptotics. In this paper we extend the localized Hartree-Fock potential to fractional particle numbers and observe that it yields derivative discontinuities in the energy as required by the exact theory. The discontinuities are numerically close to those of the computationally more demanding Hartree-Fock method. Our potential enjoys a “direct-energy” property, whereby the energy of the system is given by the sum of the single-particle eigenvalues multiplied by the corresponding occupation numbers. The discontinuities c{sub ↑} and c{sub ↓} of the spin-components of the potential at integer particle numbers N{sub ↑} and N{sub ↓} satisfy the condition c{sub ↑}N{sub ↑} + c{sub ↓}N{sub ↓} = 0. Thus, joining the family of effective potentials which support a derivative discontinuity, but being considerably easier to implement, the localized Hartree-Fock potential becomes a powerful tool in the broad area of applications in which the fundamental gap is an issue.

  18. The Nature and Determinants of Intranet Discontinuance after Mandatory Adoption

    ERIC Educational Resources Information Center

    Cho, Inho

    2008-01-01

    This research examines post-adoption behavior (discontinuance versus continuance) with the context of Intranet use. Multiple theories are used as theoretical frameworks to extend information communication technology research to the case of post-adoption behavior. Three research questions and six sets of hypotheses are formulated to distinguish…

  19. Effect of motion discontinuities on discrimination of periodic trajectories.

    PubMed

    Wilson, Hugh R; Fung, Jeffrey

    2016-01-01

    Many biologically important motions are described by periodic trajectories. Radial frequency (RF) trajectories are one example, in which the motion of a difference of Gaussians (DOG) target moves along a path described by a sinusoidal deviation of the radius from a perfect circle (Or, Thabet, Wilkinson, & Wilson, 2011). Here we explore the hypothesis that visual processing of RF trajectories involves global spatio-temporal processes that are disrupted by motion discontinuity. To test this hypothesis, RF trajectories were used that interspersed smooth, continuous motion with three or four discontinuous jumps to other portions of the trajectory. These jumps were arranged so that the entire trajectory was traversed in the same amount of time as in the continuous motion control condition. The motion discontinuities increased thresholds by a factor of approximately 2.1 relative to continuous motion. This result provides support for global spatio-temporal processing of RF motion trajectories. Comparison with previous results suggests that motion discontinuities erase memory for earlier parts of the trajectory, thereby causing thresholds to be based on only the final segment viewed. Finally, it is shown that RF trajectories obey the 1/3 power law characteristic of biological motion. PMID:26891831

  20. Bilateral filter regularized accelerated Demons for improved discontinuity preserving registration.

    PubMed

    Demirović, D; Šerifović-Trbalić, A; Prljača, N; Cattin, Ph C

    2015-03-01

    The classical accelerated Demons algorithm uses Gaussian smoothing to penalize oscillatory motion in the displacement fields during registration. This well known method uses the L2 norm for regularization. Whereas the L2 norm is known for producing well behaving smooth deformation fields it cannot properly deal with discontinuities often seen in the deformation field as the regularizer cannot differentiate between discontinuities and smooth part of motion field. In this paper we propose replacement the Gaussian filter of the accelerated Demons with a bilateral filter. In contrast the bilateral filter not only uses information from displacement field but also from the image intensities. In this way we can smooth the motion field depending on image content as opposed to the classical Gaussian filtering. By proper adjustment of two tunable parameters one can obtain more realistic deformations in a case of discontinuity. The proposed approach was tested on 2D and 3D datasets and showed significant improvements in the Target Registration Error (TRE) for the well known POPI dataset. Despite the increased computational complexity, the improved registration result is justified in particular abdominal data sets where discontinuities often appear due to sliding organ motion. PMID:25541494

  1. Premature Discontinuation in Adult Psychotherapy: A Meta-Analysis

    ERIC Educational Resources Information Center

    Swift, Joshua K.; Greenberg, Roger P.

    2012-01-01

    Objective: Premature discontinuation from therapy is a widespread problem that impedes the delivery of otherwise effective psychological interventions. The most recent comprehensive review found an average dropout rate of 47% across 125 studies (Wierzbicki & Pekarik, 1993); however, given a number of changes in the field over the past 2 decades,…

  2. Continuities and Discontinuities in Psychopathology between Childhood and Adult Life

    ERIC Educational Resources Information Center

    Rutter, Michael; Kim-Cohen, Julia; Maughan, Barbara

    2006-01-01

    The possible mechanisms involved in continuities and discontinuities in psychopathology between childhood and adult life are considered in relation to the findings from systematic, prospective, long-term longitudinal studies. Findings on schizophrenia, neurodevelopmental disorders, emotional disturbances, antisocial behaviour and substance abuse…

  3. 14 CFR Section 16 - Objective Classification-Discontinued Operations

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Objective Classification-Discontinued Operations Section 16 Section 16 Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION... AIR CARRIERS Profit and Loss Classification Section 16 Objective...

  4. MEDICATION USE FOLLOWING BARIATRIC SURGERY: FACTORS ASSOCIATED WITH EARLY DISCONTINUATION

    PubMed Central

    Kennedy, Amy L.; Nelson, Tracy; Pettine, Stefan; Miller, Benjamin F.; Hamilton, Karyn L.

    2013-01-01

    Background Medication discontinuation is a common result of bariatric surgery. The influence of individual patient characteristics and surgical outcomes on overall and specific medication discontinuation is not well understood. The purpose of the current study was to assess changes in medication use and identify individual characteristics and surgical outcomes associated with medication discontinuation among bariatric patients. Methods The patients included in the current study received bariatric surgery from the Northern Colorado Surgical Associates of Fort Collins, Colorado between October 2007 and September 2010. Demographic, weight, health, and medication data from 400 patients with at least one 6 or 12 month post-operative appointment were extracted from the Bariatric Outcome Longitudinal Database (BOLD). Multivariate regression analyses were used to investigate how patient factors affect total medication use over time, use of medications grouped by co-morbidity postoperatively, and use of specific medication classes post-operatively. Results Baseline co-morbidities, particularly type 2 diabetes (T2DM), male sex, and Roux-en-Y gastric bypass surgery were significantly associated with decreased total medication use following surgery. Weight loss, systemic disease, sex, baseline co-morbidities, surgical complications, and race were significantly associated with continued use of specific medications following surgery. Conclusions Bariatric surgery can help patients with certain characteristics discontinue medications, but is not effective for all patients. Baseline health, sex, race, bariatric procedure, surgical complications, and post-operative weight loss may affect how bariatric patients’ medication use changes pre-operatively to post-operatively. PMID:24234778

  5. Geologic Applications of Seismic Scattering

    NASA Astrophysics Data System (ADS)

    Revenaugh, Justin

    Once disregarded as noise, scattered seismic waves are finding increasing application in subsurface imaging. This sea change is driven by the increasing density and quality of seismic recordings and advances in waveform modeling which, together, are allowing seismologists to exploit their unique properties. In addition to extensive application in the energy exploration industry, seismic scattering is now used to characterize heterogeneity in the lower continental crust and subcrustal lithosphere, to examine the relationship between crustal structure and seismogenesis, and to probe the plumbing of active volcanoes. In each application, the study of seismic scattering brings wavelength-scale structure into sharper focus and characterizes the short scale-length fabric of geology.

  6. SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

    SciTech Connect

    Joel Walls; M.T. Taner; Naum Derzhi; Gary Mavko; Jack Dvorkin

    2003-04-01

    In this report we will show results of seismic and well log derived attenuation attributes from a deep water Gulf of Mexico data set. This data was contributed by Burlington Resources and Seitel Inc. The data consists of ten square kilometers of 3D seismic data and three well penetrations. We have computed anomalous seismic absorption attributes on the seismic data and have computed Q from the well log curves. The results show a good correlation between the anomalous absorption (attenuation) attributes and the presence of gas as indicated by well logs.

  7. Stability of discontinuity structures described by a generalized KdV-Burgers equation

    NASA Astrophysics Data System (ADS)

    Chugainova, A. P.; Shargatov, V. A.

    2016-02-01

    The stability of discontinuities representing solutions of a model generalized KdV-Burgers equation with a nonmonotone potential of the form φ( u) = u 4- u 2 is analyzed. Among these solutions, there are ones corresponding to special discontinuities. A discontinuity is called special if its structure represents a heteroclinic phase curve joining two saddle-type special points (of which one is the state ahead of the discontinuity and the other is the state behind the discontinuity).The spectral (linear) stability of the structure of special discontinuities was previously studied. It was shown that only a special discontinuity with a monotone structure is stable, whereas special discontinuities with a nonmonotone structure are unstable. In this paper, the spectral stability of nonspecial discontinuities is investigated. The structure of a nonspecial discontinuity represents a phase curve joining two special points: a saddle (the state ahead of the discontinuity) and a focus or node (the state behind the discontinuity). The set of nonspecial discontinuities is examined depending on the dispersion and dissipation parameters. A set of stable nonspecial discontinuities is found.

  8. Olivine anisotropy suggests Gutenberg discontinuity is not the base of the lithosphere.

    PubMed

    Hansen, Lars N; Qi, Chao; Warren, Jessica M

    2016-09-20

    Tectonic plates are a key feature of Earth's structure, and their behavior and dynamics are fundamental drivers in a wide range of large-scale processes. The operation of plate tectonics, in general, depends intimately on the manner in which lithospheric plates couple to the convecting interior. Current debate centers on whether the transition from rigid lithosphere to flowing asthenosphere relates to increases in temperature or to changes in composition such as the presence of a small amount of melt or an increase in water content below a specified depth. Thus, the manner in which the rigid lithosphere couples to the flowing asthenosphere is currently unclear. Here we present results from laboratory-based torsion experiments on olivine aggregates with and without melt, yielding an improved database describing the crystallographic alignment of olivine grains. We combine this database with a flow model for oceanic upper mantle to predict the structure of the seismic anisotropy beneath ocean basins. Agreement between our model and seismological observations supports the view that the base of the lithosphere is thermally controlled. This model additionally supports the idea that discontinuities in velocity and anisotropy, often assumed to be the base of the lithosphere, are, instead, intralithospheric features reflecting a compositional boundary established at midocean ridges, not a rheological boundary.

  9. Validation of an Adaptive Triangular Discontinuous Galerkin Shallow Water Model for the 2011 Tohoku Tsunami

    NASA Astrophysics Data System (ADS)

    Vater, Stefan; Behrens, Jörn

    2016-04-01

    We apply a tsunami simulation framework, which is based on depth-integrated hydrodynamic model equations, to the 2011 Tohoku tsunami event. While this model has been previously validated for analytic test cases and laboratory experiments, here it is applied to earthquake sources which are based on seismic inversion. Simulated wave heights and runup at the coast are compared to actual measurements. The discretization is based on a second-order Runge-Kutta discontinuous Galerkin (RKDG) scheme on triangular grids and features a robust wetting and drying scheme for the simulation of inundation events at the coast. Adaptive mesh refinement enables the efficient computation of large domains, while at the same time it allows for high local resolution and geometric accuracy. This work is part of the ASCETE (Advanced Simulation of Coupled Earthquake and Tsunami Events) project, which aims at an improved understanding of the coupling between the earthquake and the generated tsunami event. In this course, a coupled simulation framework has been developed which couples physics-based rupture generation with the presented hydrodynamic tsunami propagation and inundation model.

  10. A nodal discontinuous Galerkin method for reverse-time migration on GPU clusters

    NASA Astrophysics Data System (ADS)

    Modave, A.; St-Cyr, A.; Mulder, W. A.; Warburton, T.

    2015-11-01

    Improving both accuracy and computational performance of numerical tools is a major challenge for seismic imaging and generally requires specialized implementations to make full use of modern parallel architectures. We present a computational strategy for reverse-time migration (RTM) with accelerator-aided clusters. A new imaging condition computed from the pressure and velocity fields is introduced. The model solver is based on a high-order discontinuous Galerkin time-domain (DGTD) method for the pressure-velocity system with unstructured meshes and multirate local time stepping. We adopted the MPI+X approach for distributed programming where X is a threaded programming model. In this work we chose OCCA, a unified framework that makes use of major multithreading languages (e.g. CUDA and OpenCL) and offers the flexibility to run on several hardware architectures. DGTD schemes are suitable for efficient computations with accelerators thanks to localized element-to-element coupling and the dense algebraic operations required for each element. Moreover, compared to high-order finite-difference schemes, the thin halo inherent to DGTD method reduces the amount of data to be exchanged between MPI processes and storage requirements for RTM procedures. The amount of data to be recorded during simulation is reduced by storing only boundary values in memory rather than on disk and recreating the forward wavefields. Computational results are presented that indicate that these methods are strong scalable up to at least 32 GPUs for a three-dimensional RTM case.

  11. Olivine anisotropy suggests Gutenberg discontinuity is not the base of the lithosphere.

    PubMed

    Hansen, Lars N; Qi, Chao; Warren, Jessica M

    2016-09-20

    Tectonic plates are a key feature of Earth's structure, and their behavior and dynamics are fundamental drivers in a wide range of large-scale processes. The operation of plate tectonics, in general, depends intimately on the manner in which lithospheric plates couple to the convecting interior. Current debate centers on whether the transition from rigid lithosphere to flowing asthenosphere relates to increases in temperature or to changes in composition such as the presence of a small amount of melt or an increase in water content below a specified depth. Thus, the manner in which the rigid lithosphere couples to the flowing asthenosphere is currently unclear. Here we present results from laboratory-based torsion experiments on olivine aggregates with and without melt, yielding an improved database describing the crystallographic alignment of olivine grains. We combine this database with a flow model for oceanic upper mantle to predict the structure of the seismic anisotropy beneath ocean basins. Agreement between our model and seismological observations supports the view that the base of the lithosphere is thermally controlled. This model additionally supports the idea that discontinuities in velocity and anisotropy, often assumed to be the base of the lithosphere, are, instead, intralithospheric features reflecting a compositional boundary established at midocean ridges, not a rheological boundary. PMID:27606485

  12. Olivine anisotropy suggests Gutenberg discontinuity is not the base of the lithosphere

    NASA Astrophysics Data System (ADS)

    Hansen, Lars N.; Qi, Chao; Warren, Jessica M.

    2016-09-01

    Tectonic plates are a key feature of Earth’s structure, and their behavior and dynamics are fundamental drivers in a wide range of large-scale processes. The operation of plate tectonics, in general, depends intimately on the manner in which lithospheric plates couple to the convecting interior. Current debate centers on whether the transition from rigid lithosphere to flowing asthenosphere relates to increases in temperature or to changes in composition such as the presence of a small amount of melt or an increase in water content below a specified depth. Thus, the manner in which the rigid lithosphere couples to the flowing asthenosphere is currently unclear. Here we present results from laboratory-based torsion experiments on olivine aggregates with and without melt, yielding an improved database describing the crystallographic alignment of olivine grains. We combine this database with a flow model for oceanic upper mantle to predict the structure of the seismic anisotropy beneath ocean basins. Agreement between our model and seismological observations supports the view that the base of the lithosphere is thermally controlled. This model additionally supports the idea that discontinuities in velocity and anisotropy, often assumed to be the base of the lithosphere, are, instead, intralithospheric features reflecting a compositional boundary established at midocean ridges, not a rheological boundary.

  13. Olivine anisotropy suggests Gutenberg discontinuity is not the base of the lithosphere

    PubMed Central

    Qi, Chao; Warren, Jessica M.

    2016-01-01

    Tectonic plates are a key feature of Earth’s structure, and their behavior and dynamics are fundamental drivers in a wide range of large-scale processes. The operation of plate tectonics, in general, depends intimately on the manner in which lithospheric plates couple to the convecting interior. Current debate centers on whether the transition from rigid lithosphere to flowing asthenosphere relates to increases in temperature or to changes in composition such as the presence of a small amount of melt or an increase in water content below a specified depth. Thus, the manner in which the rigid lithosphere couples to the flowing asthenosphere is currently unclear. Here we present results from laboratory-based torsion experiments on olivine aggregates with and without melt, yielding an improved database describing the crystallographic alignment of olivine grains. We combine this database with a flow model for oceanic upper mantle to predict the structure of the seismic anisotropy beneath ocean basins. Agreement between our model and seismological observations supports the view that the base of the lithosphere is thermally controlled. This model additionally supports the idea that discontinuities in velocity and anisotropy, often assumed to be the base of the lithosphere, are, instead, intralithospheric features reflecting a compositional boundary established at midocean ridges, not a rheological boundary. PMID:27606485

  14. A review of the management of antidepressant discontinuation symptoms

    PubMed Central

    Wilson, Emma; Lader, Malcolm

    2015-01-01

    Strong evidence supports the existence of a discontinuation syndrome following the withdrawal of antidepressant medication, particularly second-generation antidepressants. The syndrome is a common phenomenon and guidance as to best avoid the symptoms is essential for both practitioners and patients. The current study reviewed the available literature on the best methods of discontinuation for antidepressants in order to avoid or prevent the occurrence of any unpleasant side effects associated with antidepressant withdrawal. Accordingly, an electronic search of the PubMed/MedLine database and Google Scholar was conducted to find relevant literature published within the last 10 years. From this, 18 related articles were identified; five clinical studies, one case series, one consensus panel’s recommendations and 11 literature reviews. Of the articles reviewed there is a general consensus as to tapering the drug slowly over a period of weeks or months. Also, in those patients who experience severe symptoms the drug should be reinstated and discontinued more gradually. The discontinuation syndrome does not occur as frequently or severely with longer-acting agents such as fluoxetine and therefore it is recommended that switching to this drug prior to withdrawal may be advisable. The articles reviewed also emphasize the need for patient education and reassurance throughout the discontinuation process. One in particular adds that cognitive behavioural therapy may be a useful tool in easing the patients’ distress. However, this review highlights the lack of controlled data to support the available guidelines. Furthermore, the guidance which is available is somewhat conflicting. Research approaches should address this issue as well as develop appropriate methods of withdrawal for specific drugs. PMID:26834969

  15. Analysis of factors associated with maintenance discontinuation in implant patients.

    PubMed

    Arai, K; Takeda, Y; Mori, Y; Terauchi, R; Furumori, T; Tanaka, S; Miyake, T; Baba, S; Kawazoe, T

    2015-01-01

    Maintenance following implant treatment is essential to ensure long-term stability. Accordingly, the objective of this study was to investigate the factors leading patients to discontinue maintenance following implant treatment. Among the 729 patients that underwent implantation at the Department of Oral Implantology, Osaka Dental University Hospital from January 2008 to December 2012, 41 patients were excluded from the study. Exclusion criteria comprised patients without a superstructure attachment, those who only underwent maxillary sinus floor augmentation procedures and those who discontinued visiting the hospital prior to superstructure attachment. Treatment was discontinued in 181 patients. The rate of discontinuation was 26.6 %. The odds ratio (OR) in the adjustment model was 1.552 (95 % CI 1.078-2.236) in males when compared with females. When compared with those who were 30-64 years old, the OR was 5.818 (95 % CI 3.017-11.220) in those 29 years old or younger and 1.561 (95 % CI 1.021-2.386) in those 65 years old or older. Moreover, when compared with those with a O'Leary's Plaque Control Record of all teeth and superstructures (PCR) level of 20 % or less following superstructure attachment, the OR was 2.113 (95 % CI 1.471-3.035) in those with a PCR level of 20 % or more following superstructure attachment. It is highly important to decrease maintenance discontinuation, especially in patients aged 29 years old or younger with a PCR level of 20 % or more following superstructure attachment. Moreover, a support system must be developed to enable patients with difficulties visiting the hospital to continue their maintenance program.

  16. Error Analysis for Discontinuous Galerkin Method for Parabolic Problems

    NASA Technical Reports Server (NTRS)

    Kaneko, Hideaki

    2004-01-01

    In the proposal, the following three objectives are stated: (1) A p-version of the discontinuous Galerkin method for a one dimensional parabolic problem will be established. It should be recalled that the h-version in space was used for the discontinuous Galerkin method. An a priori error estimate as well as a posteriori estimate of this p-finite element discontinuous Galerkin method will be given. (2) The parameter alpha that describes the behavior double vertical line u(sub t)(t) double vertical line 2 was computed exactly. This was made feasible because of the explicitly specified initial condition. For practical heat transfer problems, the initial condition may have to be approximated. Also, if the parabolic problem is proposed on a multi-dimensional region, the parameter alpha, for most cases, would be difficult to compute exactly even in the case that the initial condition is known exactly. The second objective of this proposed research is to establish a method to estimate this parameter. This will be done by computing two discontinuous Galerkin approximate solutions at two different time steps starting from the initial time and use them to derive alpha. (3) The third objective is to consider the heat transfer problem over a two dimensional thin plate. The technique developed by Vogelius and Babuska will be used to establish a discontinuous Galerkin method in which the p-element will be used for through thickness approximation. This h-p finite element approach, that results in a dimensional reduction method, was used for elliptic problems, but the application appears new for the parabolic problem. The dimension reduction method will be discussed together with the time discretization method.

  17. Imaging the Effects of Subducting Slabs on the Mantle Transition Zone with Pds Receiver Functions Beneath Southern Europe

    NASA Astrophysics Data System (ADS)

    Cottaar, S.; Deuss, A. F.

    2014-12-01

    The mantle is delineated by seismic discontinuities between 300 and 800 km depth. Variations in topography, width and occurrence of the discontinuities indicate lateral variations in temperature, composition and water content, as these variations influence the mantle phase transitions. Seismic studies of the conversions of pressure to shear waves (Pds phases) are an important tool to observe lateral variations in these discontinuities. Here we collect a Pds data set across all European seismic stations since 2000 that are available through ORFEUS or IRIS; resulting in ~500,000 event-station pairs. We deconvolve the radial component by the vertical component - assumed to represent the source component- using the iterative deconvolution method to obtain receiver functions. We assess the quality of a receiver function by the signal-to-noise ratio and by evaluating how well the radial component is reproduced when reconvolving the receiver function with the vertical component. This results in ~36,000 high quality receiver functions across Europe. Our receiver functions show little lateral variation in the depth of the transition zone discontinuities across the East European Craton, and we use this region as a reference to the more tectonically unstable regions. Around the Mediterranean, we look for signature of slabs ponding or penetrating at the discontinuity around 660 km. The Hellenic slab, which in tomographic models extends into the lower mantle, causes a signature of a disappearing '410' and a deeper, broader '660'. There are also potential signatures of '300' and '520' discontinuities in the slab region. To explain our observations we compute synthetic Ps receiver functions for mantle transition zone models of various temperatures for various compositional models. The synthetic seismic velocity models are computed using Perple_X (Connolly, 2005) with the mineral parameter database of Stixrude and Lithgow-Bertolloni (2011). The synthetics are computed with the

  18. Validating induced seismicity forecast models—Induced Seismicity Test Bench

    NASA Astrophysics Data System (ADS)

    Király-Proag, Eszter; Zechar, J. Douglas; Gischig, Valentin; Wiemer, Stefan; Karvounis, Dimitrios; Doetsch, Joseph

    2016-08-01

    Induced earthquakes often accompany fluid injection, and the seismic hazard they pose threatens various underground engineering projects. Models to monitor and control induced seismic hazard with traffic light systems should be probabilistic, forward-looking, and updated as new data arrive. In this study, we propose an Induced Seismicity Test Bench to test and rank such models; this test bench can be used for model development, model selection, and ensemble model building. We apply the test bench to data from the Basel 2006 and Soultz-sous-Forêts 2004 geothermal stimulation projects, and we assess forecasts from two models: Shapiro and Smoothed Seismicity (SaSS) and Hydraulics and Seismics (HySei). These models incorporate a different mix of physics-based elements and stochastic representation of the induced sequences. Our results show that neither model is fully superior to the other. Generally, HySei forecasts the seismicity rate better after shut-in but is only mediocre at forecasting the spatial distribution. On the other hand, SaSS forecasts the spatial distribution better and gives better seismicity rate estimates before shut-in. The shut-in phase is a difficult moment for both models in both reservoirs: the models tend to underpredict the seismicity rate around, and shortly after, shut-in.

  19. Is the X-discontinuity really related to the presence of eclogite bodies in the mantle?

    NASA Astrophysics Data System (ADS)

    Woodland, Alan; Knapp, Nadia; Klimm, Kevin

    2013-04-01

    A local seismic feature observed at ~300 km depth is referred to as the X-discontinuity (X-disc, e.g. Revenaugh & Jordan 1991). Several petrological explanations have been proposed for this discontinuity, but Pushcharovsky & Pushcharovsky (2012) attribute it to the formation of stishovite in eclogitic bodies, based upon the suggestion of Williams & Revenaugh (2005). If this link between the X-disc and the presence of eclogite is valid, it could have important geodynamic implications. In their model, stishovite appears in the eclogitic assemblage either through the transformation of previously existing free coesite or by exsolution of "excess" SiO2 from Ca-Eskola-bearing clinopyroxene (Ca0.50.5Si2O6). Essential to this model is if the amount of free SiO2 is enough to produce the observed seismic impedance contrast or not. To test whether exsolution of stishovite from Ca-Eskola-bearing clinopyroxene is a feasible mechanism, we have undertaken high-pressure experiments to determine the maximum Ca-Eskola component that can be incorporated in clinopyroxene over a range of P-T conditions, both shallower and deeper than that corresponding to the position of the X-disc. One series of experiments were performed in the simplified CaO-MgO-Al2O3-SiO2±Na2O system and one with 3 "natural" analog eclogite compositions (K2O-Na2O-CaO-MgO-FeO-Al2O3-SiO2). For the CMAS-experiments, all samples have the typical eclogitic assemblage of clinopyroxene + garnet ± SiO2 ± kyanite. With increasing pressure, the amount of garnet increases at the expense of clinopyroxene. Maximizing the Ca-Eskola content of clinopyroxene requires coexistence with a free SiO2 phase and an elevated Al2O3 content, but not necessarily the presence of kyanite. Ca-Eskola contents of ~20 mol % are obtained at 4 GPa, but decrease steadily with increasing pressure so that ˜ 4 mol % is present at pressures corresponding to the depth of the X-disc. Experiments in natural analog eclogite compositions produced even

  20. Deep seismic exploration into the Arctic Lithosphere: Arctic-2012 Russian wide-angle seismic experiment

    NASA Astrophysics Data System (ADS)

    Kashubin, S.

    2013-12-01

    Integrated geological and geophysical studies of the Earth's crust and upper mantle (the Russian project 'Arctic-2012') were carried out in 2012 in the Mendeleev Rise, central Arctic. The set of studies included wide-angle seismic observations along the line crossing the Mendeleev Rise in its southern part. The DSS seismic survey was aimed at the determination of the Mendeleev Rise crust type. A high-power air gun (120 liters or 7320 cu.in) and ocean stations with multi-component recording (X, Y, Z geophone components and a hydrophone) were used for the DSS. The line was studied using a dense system of observation: bottom station spacing was from 10 to 20 km, excitation point spacing (seismic traces interval) was 315 m. Observation data were obtained in 27 location points of bottom stations, the distance between the first and the last stations was 480 km, the length of the excitation line was 740 km. In DSS wave fields, in the first and later arrivals, there are refracted and reflected waves associated with boundaries in the sedimentary cover, with the top of the basement, and with boundaries in the consolidated crust, including its bottom (Moho discontinuity). The waves could be traced for offsets up to 170-240 km. The DSS line coincides with the near-vertical CMP line worked out with the use of a 4500-m-long seismic streamer and with a 50 m shot point interval that allowed essential detalization of the upper part of the section and taking it into account in the construction of a deep crust model. The deep velocity model was constructed using ray-trace modeling of compressional, shear, and converted waves with the use of the SeisWide program. Estimates were obtained for Vp/Vs velocity ratios, which played an important role in determining the type of crust. The results of the interpretation show that the Mendeleev Rise section corresponds to sections of a thin continental crust of shelf seas and a thinned continental crust of submarine ridges and rises.

  1. Seismic monitoring of geomorphic processes

    NASA Astrophysics Data System (ADS)

    Burtin, A.; Hovius, N.; Turowski, J. M.

    2014-12-01

    In seismology, the signal is usually analysed for earthquake data, but these represent less than 1% of continuous recording. The remaining data are considered as seismic noise and were for a long time ignored. Over the past decades, the analysis of seismic noise has constantly increased in popularity, and this has led to develop new approaches and applications in geophysics. The study of continuous seismic records is now open to other disciplines, like geomorphology. The motion of mass at the Earth's surface generates seismic waves that are recorded by nearby seismometers and can be used to monitor its transfer through the landscape. Surface processes vary in nature, mechanism, magnitude and space and time, and this variability can be observed in the seismic signals. This contribution aims to give an overview of the development and current opportunities for the seismic monitoring of geomorphic processes. We first describe the common principles of seismic signal monitoring and introduce time-frequency analysis for the purpose of identification and differentiation of surface processes. Second, we present techniques to detect, locate and quantify geomorphic events. Third, we review the diverse layout of seismic arrays and highlight their advantages and limitations for specific processes, like slope or channel activity. Finally, we illustrate all these characteristics with the analysis of seismic data acquired in a small debris-flow catchment where geomorphic events show interactions and feedbacks. Further developments must aim to fully understand the richness of the continuous seismic signals, to better quantify the geomorphic activity and improve the performance of warning systems. Seismic monitoring may ultimately allow the continuous survey of erosion and transfer of sediments in the landscape on the scales of external forcing.

  2. Seismic reflection constraints on the glacial dynamics of Johnsons Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

    Benjumea, Beatriz; Teixidó, Teresa

    2001-01-01

    During two Antarctic summers (1996-1997 and 1997-1998), five seismic refraction and two reflection profiles were acquired on the Johnsons Glacier (Livingston Island, Antarctica) in order to obtain information about the structure of the ice, characteristics of the ice-bed contact and basement topography. An innovative technique has been used for the acquisition of reflection data to optimise the field survey schedule. Different shallow seismic sources were used during each field season: Seismic Impulse Source System (SISSY) for the first field survey and low-energy explosives (pyrotechnic noisemakers) during the second one. A comparison between these two shallow seismic sources has been performed, showing that the use of the explosives is a better seismic source in this ice environment. This is one of the first studies where this type of source has been used. The analysis of seismic data corresponding to one of the reflection profiles (L3) allows us to delineate sectors with different glacier structure (accumulation and ablation zones) without using glaciological data. Moreover, vertical discontinuities were detected by the presence of back-scattered energy and the abrupt change in frequency content of first arrivals shown in shot records. After the raw data analysis, standard processing led us to a clear seismic image of the underlying bed topography, which can be correlated with the ice flow velocity anomalies. The information obtained from seismic data on the internal structure of the glacier, location of fracture zones and the topography of the ice-bed interface constrains the glacial dynamics of Johnsons Glacier.

  3. The impacts of mantle phase transitions and the iron spin crossover in ferropericlase on convective mixing—is the evidence for compositional convection definitive? New results from a Yin-Yang overset grid-based control volume model

    NASA Astrophysics Data System (ADS)

    Shahnas, M. H.; Peltier, W. R.

    2015-08-01

    High-resolution seismic tomographic images from several subduction zones provide evidence for the inhibition of the downwelling of subducting slabs at the level of the 660 km depth seismic discontinuity. Furthermore, the inference of old (~140 Myr) sinking slabs below fossil subduction zones in the lower mantle has yet to be explained. We employ a control volume methodology to develop a new anelastically compressible model of three-dimensional thermal convection in the "mantle" of a terrestrial planet that fully incorporates the influence of large variations in material properties. The model also incorporates the influence of (1) multiple solid-solid pressure-induced phase transitions, (2) transformational superplasticity at 660 km depth, and (3) the high spin-low spin iron spin transition in ferropericlase at midmantle pressures. The message passing interface-parallelized code is successfully tested against previously published benchmark results. The high-resolution control volume models exhibit the same degree of radial layering as previously shown to be characteristic of otherwise identical 2-D axisymmetric spherical models. The layering is enhanced by the presence of moderate transformational superplasticity, and in the presence of the spin crossover in ferropericlase, stagnation of cold downwellings occurs in the range of spin crossover depths (~1700 km). Although this electronic spin transition has been suggested to be invisible seismically, recent high-pressure ab initio calculations suggest it to have a clear signature in body wave velocities which could provide an isochemical explanation of a seismological signature involving the onset of decorrelation between Vp and Vs that has come to be interpreted as requiring compositional layering.

  4. Automating Shallow Seismic Imaging

    SciTech Connect

    Steeples, Don W.

    2004-12-09

    This seven-year, shallow-seismic reflection research project had the aim of improving geophysical imaging of possible contaminant flow paths. Thousands of chemically contaminated sites exist in the United States, including at least 3,700 at Department of Energy (DOE) facilities. Imaging technologies such as shallow seismic reflection (SSR) and ground-penetrating radar (GPR) sometimes are capable of identifying geologic conditions that might indicate preferential contaminant-flow paths. Historically, SSR has been used very little at depths shallower than 30 m, and even more rarely at depths of 10 m or less. Conversely, GPR is rarely useful at depths greater than 10 m, especially in areas where clay or other electrically conductive materials are present near the surface. Efforts to image the cone of depression around a pumping well using seismic methods were only partially successful (for complete references of all research results, see the full Final Technical Report, DOE/ER/14826-F), but peripheral results included development of SSR methods for depths shallower than one meter, a depth range that had not been achieved before. Imaging at such shallow depths, however, requires geophone intervals of the order of 10 cm or less, which makes such surveys very expensive in terms of human time and effort. We also showed that SSR and GPR could be used in a complementary fashion to image the same volume of earth at very shallow depths. The primary research focus of the second three-year period of funding was to develop and demonstrate an automated method of conducting two-dimensional (2D) shallow-seismic surveys with the goal of saving time, effort, and money. Tests involving the second generation of the hydraulic geophone-planting device dubbed the ''Autojuggie'' showed that large numbers of geophones can be placed quickly and automatically and can acquire high-quality data, although not under rough topographic conditions. In some easy-access environments, this device could

  5. Reflected and mode-converted seismic waves within the shallow aleutian subduction zone, southern Kenai Peninsula, Alaska

    USGS Publications Warehouse

    Stephens, C.D.; Page, R.A.; Lahr, J.C.

    1990-01-01

    Pronounced secondary phases observed in local recordings of quarry shots and earthquakes on the southern Kenai Peninsula are identified as reflected P and S and converted S-to-P phases originating within four depth ranges: in the upper few kilometers of the Cook Inlet Tertiary basin, at midcrustal depths within the overthrust North American plate, at about 35 km depth near the top of the Wadati-Benioff seismic zone in proximity to the inferred interplate megathrust, and at about 5-10 km below the megathrust in the subducted Pacific plate. The positions and origins of the mid-upper plate (MUP) discontinuity and similar reflectors are discussed. It appears the the MUP discontinuity is seismically inactive and does not represent a brittle-ductile transition zone within the upper plate. The two converted S-to-P phases generated near the top of the subducted plate could indicate a low velocity zone associated with subducted oceanic crust. -after Authors

  6. Elastic-Wavefield Seismic Stratigraphy: A New Seismic Imaging Technology

    SciTech Connect

    Bob A. Hardage; Milo M. Backus; Michael V. DeAngelo; Sergey Fomel; Khaled Fouad; Robert J. Graebner; Paul E. Murray; Randy Remington; Diana Sava

    2006-07-31

    The purpose of our research has been to develop and demonstrate a seismic technology that will provide the oil and gas industry a better methodology for understanding reservoir and seal architectures and for improving interpretations of hydrocarbon systems. Our research goal was to expand the valuable science of seismic stratigraphy beyond the constraints of compressional (P-P) seismic data by using all modes (P-P, P-SV, SH-SH, SV-SV, SV-P) of a seismic elastic wavefield to define depositional sequences and facies. Our objective was to demonstrate that one or more modes of an elastic wavefield may image stratal surfaces across some stratigraphic intervals that are not seen by companion wave modes and thus provide different, but equally valid, information regarding depositional sequences and sedimentary facies within that interval. We use the term elastic wavefield stratigraphy to describe the methodology we use to integrate seismic sequences and seismic facies from all modes of an elastic wavefield into a seismic interpretation. We interpreted both onshore and marine multicomponent seismic surveys to select the data examples that we use to document the principles of elastic wavefield stratigraphy. We have also used examples from published papers that illustrate some concepts better than did the multicomponent seismic data that were available for our analysis. In each interpretation study, we used rock physics modeling to explain how and why certain geological conditions caused differences in P and S reflectivities that resulted in P-wave seismic sequences and facies being different from depth-equivalent S-wave sequences and facies across the targets we studied.

  7. Seismic risk perception test

    NASA Astrophysics Data System (ADS)

    Crescimbene, Massimo; La Longa, Federica; Camassi, Romano; Pino, Nicola Alessandro

    2013-04-01

    The perception of risks involves the process of collecting, selecting and interpreting signals about uncertain impacts of events, activities or technologies. In the natural sciences the term risk seems to be clearly defined, it means the probability distribution of adverse effects, but the everyday use of risk has different connotations (Renn, 2008). The two terms, hazards and risks, are often used interchangeably by the public. Knowledge, experience, values, attitudes and feelings all influence the thinking and judgement of people about the seriousness and acceptability of risks. Within the social sciences however the terminology of 'risk perception' has become the conventional standard (Slovic, 1987). The mental models and other psychological mechanisms which people use to judge risks (such as cognitive heuristics and risk images) are internalized through social and cultural learning and constantly moderated (reinforced, modified, amplified or attenuated) by media reports, peer influences and other communication processes (Morgan et al., 2001). Yet, a theory of risk perception that offers an integrative, as well as empirically valid, approach to understanding and explaining risk perception is still missing". To understand the perception of risk is necessary to consider several areas: social, psychological, cultural, and their interactions. Among the various research in an international context on the perception of natural hazards, it seemed promising the approach with the method of semantic differential (Osgood, C.E., Suci, G., & Tannenbaum, P. 1957, The measurement of meaning. Urbana, IL: University of Illinois Press). The test on seismic risk perception has been constructed by the method of the semantic differential. To compare opposite adjectives or terms has been used a Likert's scale to seven point. The test consists of an informative part and six sections respectively dedicated to: hazard; vulnerability (home and workplace); exposed value (with reference to

  8. An integrated exploration model for Council Run field analogs: Regional geology and seismic stratigraphy of Devonian 6th Elk sandstones

    SciTech Connect

    Kelleher, G.; Johnson, R. )

    1991-08-01

    A geologic study of the Devonian Lock Haven 6th Elk formation along the structural front of Pennsylvania and Maryland suggest that present-day structures were active at the time of deposition. These structures barred deposition to the west and helped to localize sands in a northeast-southwest fairway. The 6th Elk sandstones occur in two major depositional lobes (located in Centre and Somerset counties in Pennsylvania, and Garret County, Maryland) and were deposited on a shallow-marine shelf by turbidity currents and later modified by storm-generated currents. Deposition of 6th Elk sands may also have been influenced by cross-strike discontinuities. A seismic study of the Council Run field aids in subsurface identification of the 6th Elk. A high-amplitude seismic anomaly across the Council Run field is correlated with increasing san thickness. Two dimensional modeling suggests that the seismic response is extremely sensitive to specific acquisition and processing techniques including filter and phase variability. Additional attribute analysis integrates the seismic data with the forward models. This results in a predictive method for potentially identifying 6th Elk sandstone development from seismic data. Applying the results of the seismic modeling at Council Run field to a seismic grid across the previously defined 6th Elk depositional fairway has identified many exploratory prospects in Lycoming and Bradford counties, Pennsylvania. This area coincides with the site of a third, previously documented, Upper Devonian depositional lobe.

  9. Passive seismic experiment and receiver functions analysis to determine crustal structure at the contact of the northern Dinarides and southwestern Pannonian Basin

    NASA Astrophysics Data System (ADS)

    Šumanovac, Franjo; Hegedűs, Endre; Orešković, Jasna; Kolar, Saša; Kovács, Attila C.; Dudjak, Darko; Kovács, István J.

    2016-06-01

    Passive seismic experiment was carried out at the SW contact of the Dinarides and Pannonian basin to determine the crustal structure and velocity discontinuities. The aim of the experiment was to define the relationship between the Adriatic microplate and the Pannonian segment as a part of the European plate. Most of the temporary seismic stations were deployed in Croatia along the Alp07 profile-a part of the active-source ALP 2002 project. About 300-km-long profile stretches from Istra peninsula to the Drava river, in a WSW-ESE direction. Teleseismic events recorded on 13 temporary seismic stations along the profile were analysed by P-receiver function method. Two types of characteristic receiver functions (RF) have been identified, belonging to Dinaridic and Pannonian crusts as defined on the Alp07 profile, while in transitional zone there are both types. Three major crustal discontinuities can be identified for the Dinaridic type: sedimentary basement, intracrustal discontinuity and Mohorovičić discontinuity, whereas the Pannonian type revealed only two discontinuities. The intracrustal discontinuity was not observed in the Pannonian type, thus pointing to a single-layered crust in the Pannonian basin. Two interpretation methods were applied: forward modelling of the receiver functions and H-κ stacking method, and the results were compared with the active-source seismic data at deep refraction profile Alp07. The receiver function modelling has given reliable results of the Moho depths that are in accordance with the seismic refraction results at the end of the Alp07 profile, that is in the area of Pannonian crust characterized by simple crustal structure and low seismic velocities (Vp between 5.9 and 6.2 km s-1). In the Dinarides and its peripheral parts, receiver function modelling regularly gives greater Moho depths, up to +15 per cent, due to more complex crustal structure. The depths of the Moho calculated by the H-κ stacking method vary within wide

  10. Times to Discontinue Antidepressants Over 6 Months in Patients with Major Depressive Disorder

    PubMed Central

    Jung, Woo-Young; Jang, Sae-Heon; Jae, Young-Myo; Kong, Bo-Geum; Kim, Ho-Chan; Choe, Byeong-Moo; Kim, Jeong-Gee; Kim, Choong-Rak

    2016-01-01

    Objective The aim of the present study was to investigate differences in discontinuation time among antidepressants and total antidepressant discontinuation rate of patients with depression over a 6 month period in a naturalistic treatment setting. Methods We reviewed the medical records of 900 patients with major depressive disorder who were initially prescribed only one kind of antidepressant. The prescribed antidepressants and the reasons for discontinuation were surveyed at baseline and every 4 weeks during the 24 week study. We investigated the discontinuation rate and the mean time to discontinuation among six antidepressants groups. Results Mean and median overall discontinuation times were 13.8 and 12 weeks, respectively. Sertraline and escitalopram had longer discontinuation times than that of fluoxetine, and patients who used sertraline discontinued use significantly later than those taking mirtazapine. No differences in discontinuation rate were observed after 24 weeks among these antidepressants. About 73% of patients discontinued antidepressant treatment after 24 weeks. Conclusion Sertraline and escitalopram tended to have longer mean times to discontinuation, although no difference in discontinuation rate was detected between antidepressants after 24 weeks. About three-quarters of patients discontinued antidepressant maintenance therapy after 24 weeks. PMID:27482246

  11. Procedures for computing site seismicity

    NASA Astrophysics Data System (ADS)

    Ferritto, John

    1994-02-01

    This report was prepared as part of the Navy's Seismic Hazard Mitigation Program. The Navy has numerous bases located in seismically active regions throughout the world. Safe effective design of waterfront structures requires determining expected earthquake ground motion. The Navy's problem is further complicated by the presence of soft saturated marginal soils that can significantly amplify the levels of seismic shaking as evidenced in the 1989 Loma Prieta earthquake. The Naval Facilities Engineering Command's seismic design manual, NAVFAC P355.l, requires a probabilistic assessment of ground motion for design of essential structures. This report presents the basis for the Navy's Seismic Hazard Analysis procedure that was developed and is intended to be used with the Seismic Hazard Analysis computer program and user's manual. This report also presents data on geology and seismology to establish the background for the seismic hazard model developed. The procedure uses the historical epicenter data base and available geologic data, together with source models, recurrence models, and attenuation relationships to compute the probability distribution of site acceleration and an appropriate spectra. This report discusses the developed stochastic model for seismic hazard evaluation and the associated research.

  12. Weak localization of seismic waves.

    PubMed

    Larose, E; Margerin, L; Van Tiggelen, B A; Campillo, M

    2004-07-23

    We report the observation of weak localization of seismic waves in a natural environment. It emerges as a doubling of the seismic energy around the source within a spot of the width of a wavelength, which is several tens of meters in our case. The characteristic time for its onset is the scattering mean-free time that quantifies the internal heterogeneity.

  13. Seismic Data Gathering and Validation

    SciTech Connect

    Coleman, Justin

    2015-02-01

    Three recent earthquakes in the last seven years have exceeded their design basis earthquake values (so it is implied that damage to SSC’s should have occurred). These seismic events were recorded at North Anna (August 2011, detailed information provided in [Virginia Electric and Power Company Memo]), Fukushima Daichii and Daini (March 2011 [TEPCO 1]), and Kaswazaki-Kariwa (2007, [TEPCO 2]). However, seismic walk downs at some of these plants indicate that very little damage occurred to safety class systems and components due to the seismic motion. This report presents seismic data gathered for two of the three events mentioned above and recommends a path for using that data for two purposes. One purpose is to determine what margins exist in current industry standard seismic soil-structure interaction (SSI) tools. The second purpose is the use the data to validated seismic site response tools and SSI tools. The gathered data represents free field soil and in-structure acceleration time histories data. Gathered data also includes elastic and dynamic soil properties and structural drawings. Gathering data and comparing with existing models has potential to identify areas of uncertainty that should be removed from current seismic analysis and SPRA approaches. Removing uncertainty (to the extent possible) from SPRA’s will allow NPP owners to make decisions on where to reduce risk. Once a realistic understanding of seismic response is established for a nuclear power plant (NPP) then decisions on needed protective measures, such as SI, can be made.

  14. Unintentional Discontinuation of Chronic Medications for Seniors in Nursing Homes

    PubMed Central

    Stall, Nathan M.; Fischer, Hadas D.; Wu, C. Fangyun; Bierman, Arlene S.; Brener, Stacey; Bronskill, Susan; Etchells, Edward; Fernandes, Olavo; Lau, Davina; Mamdani, Muhammad M.; Rochon, Paula; Urbach, David R.; Bell, Chaim M.

    2015-01-01

    Abstract Transitions of care leave patients vulnerable to the unintentional discontinuation of medications with proven efficacy for treating chronic diseases. Older adults residing in nursing homes may be especially susceptible to this preventable adverse event. The effect of large-scale policy changes on improving this practice is unknown. The objective of this study was to analyze the effect of a national medication reconciliation accreditation requirement for nursing homes on rates of unintentional medication discontinuation after hospital discharge. It was a population-based retrospective cohort study that used linked administrative records between 2003 and 2012 of all hospitalizations in Ontario, Canada. We identified nursing home residents aged ≥66 years who had continuous use of ≥1 of the 3 selected medications for chronic disease: levothyroxine, HMG-CoA reductase inhibitors (statins), and proton pump inhibitors (PPIs). In 2008 medication reconciliation became a required practice for accreditation of Canadian nursing homes. The main outcome measures included the proportion of patients who restarted the medication of interest after hospital discharge at 7 days. We also performed a time series analysis to examine the impact of the accreditation requirement on rates of unintentional medication discontinuation. The study included 113,088 adults aged ≥66 years who were nursing home residents, had an acute hospitalization, and were discharged alive to the same nursing home. Overall rates of discontinuation at 7-days after hospital discharge were highest in 2003–2004 for all nursing homes: 23.9% for thyroxine, 26.4% for statins, and 23.9% for PPIs. In most of the cases, these overall rates decreased annually and were lowest in 2011–2012: 4.0% for thyroxine, 10.6% for statins, and 8.3% for PPIs. The time series analysis found that nursing home accreditation did not significantly lower medication discontinuation rates for any of the 3 drug groups. From 2003

  15. The Mantle Seismic Heterogeneities Inferred by USArray Data

    NASA Astrophysics Data System (ADS)

    Ko, J. Y. T.; Zhan, Z.; Hung, S. H.; Li, D.; Helmberger, D. V.

    2015-12-01

    The detailed images of mantle seismic heterogeneities is establishing the link between modern mantle dynamics and past surface geological evolutions. The recent deployment of the USArray network of seismometers rolling from the west coast to the east coast of United States during 2004 to 2015 afford an extraordinary data set to investigate such mantle seismic heterogeneities. Here we first explored the D" structure beneath Caribbean region and found an east-to-west asymmetrical undulation of the D" discontinuity with a V-shaped depression of ~80-150 km over a lateral distance of 600 km, coinciding with a similar trend of shear wave velocity showing the most profound reduction of ~5% at the bottom of the thinnest D" layer. The strong correlation between the D" topography and velocity variations indicates lateral fluctuation in the D" temperature modulated by the reheated slab material has perturbed the phase transition boundary significantly and may reflect a transitional period of the proposed mega-plume scenario. Secondly, these emerging data not only shed light on the lowermost mantle structures but provide new constraints on the mid and upper mantle seismic velocity heterogeneities beneath the United States. We found that frequency-dependent traveltime residuals and amplitudes of S waves from South America events display considerable scatter patterns recorded by USArray stations which can be attributed to upper mantle heterogeneities beneath the U.S. and mid or lower mantle seismic anomalies along the raypaths. The analysis of waveform complexity is utilized in this work and gives complementary constraints on the location and geometry of these mantle heterogeneities such as possible slab remnants below Central and Eastern United States. We further exploited the newly developed 2D finite-difference method with various mantle heterogeneity models to better understand the possible geophysical features producing these anomalies.

  16. SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

    SciTech Connect

    Joel Walls; M.T. Taner; Naum Derzhi; Gary Mavko; Jack Dvorkin

    2002-10-01

    RSI has access to two synthetic seismic programs: Osiris seismic modeling system provided by Odegaard (Osiris) and synthetic seismic program, developed by SRB, implementing the Kennett method for normal incidence. Achieving virtually identical synthetic seismic traces from these different programs serves as cross-validation for both. The subsequent experiments have been performed with the Kennett normal incidence code because: We have access to the source code, which allowed us to easily control computational parameters and integrate the synthetics computations with our graphical and I/O systems. This code allows to perform computations and displays on a PC in MatLab or Octave environment, which is faster and more convenient. The normal incidence model allows us to exclude from the synthetic traces some of the physical effects that take place in 3-D models (like inhomogeneous waves) but have no relevance to the topic of our investigation, which is attenuation effects on seismic reflection and transmission.

  17. Seismic moulin tremor

    NASA Astrophysics Data System (ADS)

    Roeoesli, Claudia; Walter, Fabian; Ampuero, Jean-Paul; Kissling, Edi

    2016-08-01

    Through glacial moulins, meltwater is routed from the glacier surface to its base. Moulins are a main feature feeding subglacial drainage systems and thus influencing basal motion and ice dynamics, but their geometry remains poorly known. Here we show that analysis of the seismic wavefield generated by water falling into a moulin can help constrain its geometry. We present modeling results of hour-long seimic tremors emitted from a vertical moulin shaft, observed with a seismometer array installed at the surface of the Greenland Ice Sheet. The tremor was triggered when the moulin water level exceeded a certain height, which we associate with the threshold for the waterfall to hit directly the surface of the moulin water column. The amplitude of the tremor signal changed over each tremor episode, in close relation to the amount of inflowing water. The tremor spectrum features multiple prominent peaks, whose characteristic frequencies are distributed like the resonant modes of a semiopen organ pipe and were found to depend on the moulin water level, consistent with a source composed of resonant tube waves (water pressure waves coupled to elastic deformation of the moulin walls) along the water-filled moulin pipe. Analysis of surface particle motions lends further support to this interpretation. The seismic wavefield was modeled as a superposition of sustained wave radiation by pressure sources on the side walls and at the bottom of the moulin. The former was found to dominate the wave field at close distance and the latter at large distance to the moulin.

  18. Seismic event classification system

    DOEpatents

    Dowla, Farid U.; Jarpe, Stephen P.; Maurer, William

    1994-01-01

    In the computer interpretation of seismic data, the critical first step is to identify the general class of an unknown event. For example, the classification might be: teleseismic, regional, local, vehicular, or noise. Self-organizing neural networks (SONNs) can be used for classifying such events. Both Kohonen and Adaptive Resonance Theory (ART) SONNs are useful for this purpose. Given the detection of a seismic event and the corresponding signal, computation is made of: the time-frequency distribution, its binary representation, and finally a shift-invariant representation, which is the magnitude of the two-dimensional Fourier transform (2-D FFT) of the binary time-frequency distribution. This pre-processed input is fed into the SONNs. These neural networks are able to group events that look similar. The ART SONN has an advantage in classifying the event because the types of cluster groups do not need to be pre-defined. The results from the SONNs together with an expert seismologist's classification are then used to derive event classification probabilities.

  19. Seismic event classification system

    DOEpatents

    Dowla, F.U.; Jarpe, S.P.; Maurer, W.

    1994-12-13

    In the computer interpretation of seismic data, the critical first step is to identify the general class of an unknown event. For example, the classification might be: teleseismic, regional, local, vehicular, or noise. Self-organizing neural networks (SONNs) can be used for classifying such events. Both Kohonen and Adaptive Resonance Theory (ART) SONNs are useful for this purpose. Given the detection of a seismic event and the corresponding signal, computation is made of: the time-frequency distribution, its binary representation, and finally a shift-invariant representation, which is the magnitude of the two-dimensional Fourier transform (2-D FFT) of the binary time-frequency distribution. This pre-processed input is fed into the SONNs. These neural networks are able to group events that look similar. The ART SONN has an advantage in classifying the event because the types of cluster groups do not need to be pre-defined. The results from the SONNs together with an expert seismologist's classification are then used to derive event classification probabilities. 21 figures.

  20. 3D seismic attribute-assisted analysis of microseismic events in the Marcellus Shale

    NASA Astrophysics Data System (ADS)

    Hart, Ariel Kelton

    Microseismic monitoring is often used during the process of oil and gas exploitation to monitor seismicity that may be triggered by hydraulic fracturing, a common practice in the Appalachian Basin. Anthropogenically-induced minor upward fracture growth is not uncommon in the Marcellus shale; however, in the area of study, significant microseismic activity was registered above the target zone. In order to ascertain whether out-of-zone growth might have been predictable and identify which areas are more likely to experience brittle failure first, 3D seismic and microseismic data were analyzed with a focus on better understanding variations in the acoustic properties associated with unconventional naturally fractured reservoirs. Ant Tracking was used to identify areas of increased local seismic discontinuity, as these areas are generally more intensely deformed and may represent zones of increased fracture intensity. Ant Tracking results reveal discontinuities in the Marcellus are oriented approximately at N52E and N41W; discontinuities do not coincide with N25E trending folds apparent in the 3D seismic, but tend to follow deeper structural trends instead. These discontinuity orientations are interpreted to be a result of continued movement on deeper faults throughout the Paleozoic; these faults possibly acted as seed points for fractures further upsection and potentially led to the precipitation of the large N25E trending imbricate backthrusts seen in the 3D seismic. The reservoir's response to hydraulic fracturing also provided insights into local stress anisotropy and into optimal well and stage spacing needed to maximize drainage area and locate additional wells during the field development phase. Microseismic, well, and pump data used to gauge the reservoir's response to a hydraulic fracture treatment indicated that the number of stages, lateral length, total proppant volume, and fracture energy heavily influence how a well produces. SHmax in the area is oriented