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Sample records for 660-km seismic discontinuity

  1. The post-spinel transformation in Mg2SiO4 and its relation to the 660-km seismic discontinuity

    NASA Astrophysics Data System (ADS)

    Shim, Sang-Heon; Duffy, Thomas S.; Shen, Guoyin

    2001-05-01

    The 660-km seismic discontinuity in the Earth's mantle has long been identified with the transformation of (Mg,Fe)2SiO4 from γ-spinel (ringwoodite) to (Mg,Fe)SiO3-perovskite and (Mg,Fe)O-magnesiowüstite. This has been based on experimental studies of materials quenched from high pressure and temperature, which have shown that the transformation is consistent with the seismically observed sharpness and the depth of the discontinuity at expected mantle temperatures. But the first in situ examination of this phase transformation in Mg2SiO4 using a multi-anvil press indicated that the transformation occurs at a pressure about 2GPa lower than previously thought (equivalent to ~600km depth) and hence that it may not be associated with the 660-km discontinuity. Here we report the results of an in situ study of Mg2SiO4 at pressures of 20-36GPa using a combination of double-sided laser-heating and synchrotron X-ray diffraction in a diamond-anvil cell. The phase transformation from γ-Mg2SiO4 to MgSiO3-perovskite and MgO (periclase) is readily observed in both the forward and reverse directions. In contrast to the in situ multi-anvil-press study, we find that the pressure and temperature of the post-spinel transformation in Mg2SiO4 is consistent with seismic observations for the 660-km discontinuity.

  2. 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.

  3. 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

  4. 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

  5. Precise determination of phase relations in pyrolite across the 660 km seismic discontinuity by in situ X-ray diffraction and quench experiments

    NASA Astrophysics Data System (ADS)

    Nishiyama, Norimasa; Irifune, Tetsuo; Inoue, Toru; Ando, Jun-ichi; Funakoshi, Ken-ichi

    2004-06-01

    Mineral assemblage changes in a pyrolite composition with increasing pressure were observed by in situ X-ray diffraction and quench experiments at pressures near that of the 660 km seismic discontinuity and at a fixed temperature of 1600 °C. According to results obtained by in situ X-ray diffraction experiments, ringwoodite (Rw) was observed with majorite garnet and CaSiO 3-rich perovskite at pressures of about 20-22 GPa. Dissociation of ringwoodite to MgSiO 3-rich perovskite and magnesiowüstite (Mw) was completed at 22.0±0.2 GPa according to Matsui et al.'s periclase pressure scale, and at 21.7±0.1 GPa according to Shim et al.'s gold pressure scale. Majorite garnet persisted to about 24 GPa where pyrolite transformed to a lower mantle mineral assemblage, i.e. MgSiO 3-perovskite, CaSiO 3-rich perovskite, and magnesiowüstite. Thus, majorite garnet coexists with the lower mantle assemblage at pressures of about 22-24 GPa. In the quench experiments, an assemblage of MgSiO 3-perovskite, magnesiowüstite, CaSiO 3-rich perovskite, and majorite garnet was synthesized at 22.5 GPa and 1600 °C, in which Mg-perovskite contained 2.8 wt.% Al 2O 3, and was significantly poorer in Fe than coexisting magnesiowüstite. The Fe-Mg partition coefficient between Mg-perovskite and magnesiowüstite including ferric iron ( Kapp=0.27±0.06) is very close to that in the Al-free system, which suggests that these P- T conditions are in the vicinity of those of ringwoodite decomposition. Both the results of in situ X-ray diffraction and quench experiments in the present study yield a convergent result that ringwoodite decomposes into Mg-perovskite and magnesiowüstite before the garnet-to-perovskite transition at 1600 °C in pyrolite. The relation between the Al content in Mg-perovskite and Kapp in pyrolite is non-linear, which is consistent with the Fe-Mg partitioning between Mg-perovskite and magnesiowüstite previously reported for a simpler MgO-FeO-Al 2O 3-SiO 2 system.

  6. 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

  7. Bent Mantle Plumes and Channel Flow Under the 660 Km Discontinuity in Western Pacific

    NASA Astrophysics Data System (ADS)

    Yuen, D. A.; Tosi, N.

    2011-12-01

    Recent high-resolution seismic imaging by multiply-reflected S waves of the transition zone topography beneath the Hawaiian archipelago gives strong evidence for a 1000 to 2000 km wide hot thermal anomaly ponding beneath the 660 km boundary west of Hawaii islands (Cao et al., Science ,2011). This scenario suggests that Hawaiian volcanism may not be caused by a stationary narrow plume rising from the core-mantle boundary but by hot plume material first held back beneath the 660 km discontinuity and then entrained under the transition zone before coming up to the surface. Using a cylindrical convection model with multiple phase transitions, we investigate the particular dynamical conditions needed for obtaining this peculiar plume morphology. Focusing on the role exerted by pressure-dependent thermodynamic and transport parameters, we show that a strong reduction of the coefficient of thermal expansion in the lower mantle and a viscosity hill at a depth of around 1800 km are needed for plumes to have enough focused buoyancy to reach and pass through the 660 km phase boundary. The lateral spreading of plumes near the top of the lower mantle manifests itself as a channel flow whose length is controlled by the viscosity contrast due to temperature variations . For small amounts of viscosity contrast , broad and highly viscous plumes are generated which tend to pass through the transition zone relatively unscathed. For higher values , between 100 and 1000 ,we obtain horizontal channel flows beneath the 660 km boundary as long as 1500 km within a timescale that resembles that of Hawaiian hotspot history. This finding may account for the origin of the broad hot anomaly observed west of Hawaii. For a normal thermal anomaly of 450 K associated with a lower mantle plume, we obtain activation energies of about 400 kJ/mol and 600 kJ/mol for viscosity contrasts of 100 and 1000, respectively, in good agreement with values based on lower mantle mineral physics. If an increase of

  8. 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.

  9. Mapping of the 410- and 660-km discontinuities beneath the Japanese islands

    NASA Astrophysics Data System (ADS)

    Tono, Yoko; Kunugi, Takashi; Fukao, Yoshio; Tsuboi, Seiji; Kanjo, Kenji; Kasahara, Keiji

    2005-03-01

    A family of core-reflected shear waves generated by the 28 June 2002 Vladivostok deep earthquake, including near vertical reflections from the 410- and 660-km discontinuities, were recorded by ˜500 tiltmeters of the Hi-net and ˜60 broadband seismometers of the F-net in Japan. The observed upper mantle reflections were cross-correlated with synthetics calculated on the basis of the spectral element method for a fully three-dimensional Earth model using the Earth Simulator supercomputer to accurately determine the depths of the reflection points. The mapped upper mantle discontinuities were compared with a high-resolution P wave tomographic image. The 660-km discontinuity is depressed at a constant level of ˜15 km along the bottom of the horizontally extending aseismic slab under southwestern Japan. The transition from the normal to the depressed level occurs within a lateral distance of less than ˜200 km. Observations suggest that the reflections from the 410-km discontinuity interfere with those from slab-related structures on top of this discontinuity, leading to a spuriously large elevation of the 410-km discontinuity in and near the subducted slab. Records at stations relatively free from such interference effects, however, still imply elevation of this discontinuity within the slab.

  10. Tomographic structure of East Asia: II. Stagnant slab above 660 km discontinuity and its geodynamic implications

    NASA Astrophysics Data System (ADS)

    Chen, Yongshun John; Pei, Shunping

    2010-12-01

    P-wave arrival times of both regional and teleseismic earthquakes were inverted to obtain mantle structures of East Asia. No fast (slab) velocity anomalies was not find beneath the 660-km discontinuity through tomography besides a stagnant slab within the transition zone. Slow P-wave velocity anomalies are present at depths of 100-250 km below the active volcanic arc and East Asia. The western end of the flat stagnant slab is about 1 500 km west to active trench and may also be correlated with prominent surface topographic break in eastern China. We suggested that active mantle convection might be operating within this horizontally expanded "mantle wedge" above both the active subducting slabs and the stagnant flat slabs beneath much of the North China plain. Both the widespread Cenozoic volcanism and associated extensional basins in East Asia could be the manifestation of this vigorous upper mantle convection. Cold or thermal anomalies associated with the stagnant slabs above the 660-km discontinuity have not only caused a broad depression of the boundary due to its negative Clapeyron slope but also effectively shielded the asthenosphere and continental lithosphere above from any possible influence of mantle plumes in the lower mantle.

  11. 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

  12. Detection of the structure near the 410 km and 660 km discontinuities in Japan subduction zone from the waveform triplication

    NASA Astrophysics Data System (ADS)

    Cui, H.; Zhou, Y.

    2015-12-01

    Slab subduction plays an important role in the mantle material circulation [Stern, 2002], and can also affect the feature of the 410 km and 660 km seismic discontinuities (410 and 660) [Lebedev et al., 2002]. Japan subduction zone is a natural laboratory for studying the mantle composition and velocity structure associated with the deep subduction of the Pacific plate. In this study, triplicated waveforms of an intermediate-depth earthquake at the Hokkaido of Japan (2011/10/21, 08:02:37.62, 142.5315°E, 43.8729°N, Mb6.0, relocated depth: 188 km) are retrieved from the dense Chinese Digital Seismic Network (CDSN). P and S waveforms are filtered with the band of 0.05-1.0 Hz and 0.02-0.5 Hz, respectively, and then integrated into the displacement data. The relative traveltime and synthetic waveform fitting is applied to mapping the deep structure. The best fitting models are obtained through the trial and error tests. We find a 15 km uplift of the 410 and a 25 km depression of the 660, indicating the cold environment caused by the subduction slab; both the 410 and 660 show the sharp discontinuity, but a smaller velocity contrast than the IASP91 model [Kennett and Engdahl, 1991]. Atop the 410 and 660, there are high-velocity layers associated with the subduction (or stagnant) slab. We also find a low-velocity anomaly with the thickness of ~65 km below the 660, which may relate to the slab dehydration or the hot upwelling at the top of the lower mantle. The seismic velocity ratio (VP/VS) shows a lower zone at the depth of ~210-395 km, showing the consistency with the low Poisson's ratio signature of the oceanic plate; a higher zone at the depth of ~560-685 km, implying the hydrous mantle transition zone.

  13. 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

  14. Strength contrast between majorite and ringwoodite: Implication for the separation of crustal material from slab near 660 km depth

    NASA Astrophysics Data System (ADS)

    Nishihara, Y.; Kawazoe, T.; Nishi, M.; Ohuchi, T.; Higo, Y.; Funakoshi, K.; Irifune, T.

    2012-12-01

    Many seismic observations have shown that some of subducting lithospheres penetrates into deeper mantle across 660 km discontinuity. Former oceanic crust, which forms uppermost layer of the slab, consists mainly of majorite-rich garnet (hereafter majorite) near 660 km depth. Majorite is denser than surrounding mantle at shallower depth than 660 km where the ambient mantle consists mostly of ringwoodite, but is less dense at deeper part of the mantle where the Mg-perovskite is the dominant phase. Thus the crustal component may separate from the slab near 660 km depth. Karato (1997) discussed that the separation of crustal component can occur when the crustal component is significantly stronger than surrounding mantle based on dynamic calculation. However, it is unclear whether the separation of the crustal material occurs because plastic strength of related materials at the deep mantle conditions has not been known. In this study, we conducted deformation experiments at pressure and temperature conditions corresponding to the Earth's deep mantle in order to determine strength contrast between majorite and ringwoodite. Deformation experiments at pressure of ~17 GPa and temperature of 1473 and 1673 K were carried out using SPEED-MkII-D installed at BL04B1, SPring-8, Japan. Majorite (Mj) synthesized from a gel with chemistry of the majoritic garnet in oceanic crust and (Mg0.6Fe0.4)2SiO4 ringwoodite synthesized from olivine were placed vertically and deformed uniaxially under same temperature, pressure and stress conditions. Strain measurements were carried out during deformation based on X-ray radiography using synchrotron radiation. Strain rates were 0.7-2.4 x 10-5 s-1 for Mj and 1.2-14.5 x 10-5 s-1 for Rw. Relative strain rate of Rw and Mj (strain rate for Rw divided by that for Mj at same condition) determined at 7 different deformation conditions were 1.2-2.5 (Mj was always stronger in the present experimental conditions). However, an extrapolation of present

  15. 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

  16. Seismic imaging of mantle transition zone discontinuities beneath the northern Red Sea and adjacent areas

    NASA Astrophysics Data System (ADS)

    Mohamed, A. A.; Gao, S. S.; Elsheikh, A. A.; Liu, K. H.; Yu, Y.; Fat-Helbary, R. E.

    2014-11-01

    The dramatic asymmetry in terms of surface elevation, Cenozoic volcanisms and earthquake activity across the Red Sea is an enigmatic issue in global tectonics, partially due to the unavailability of broad-band seismic data on the African Plate adjacent to the Red Sea. Here, we report the first comprehensive image of the mantle transition zone (MTZ) discontinuities using data from the Egyptian National Seismic Network, and compare the resulting depths of the 410 and 660-km discontinuities with those observed on the Arabian side. Our results show that when a standard earth model is used for time-to-depth conversion, the resulting depth of the discontinuities increases systematically towards the axis of the Afro-Arabian Dome (AAD) from both the west and east. Relative to the westernmost area, the maximum depression of the 410-km discontinuity is about 30 km, and that of the 660-km discontinuity is about 45 km. The observed systematic variations can best be explained by a model involving a hydrated MTZ and an upper-mantle low-velocity zone beneath the AAD. Models invoking one or more mantle plumes originated from the MTZ or the lower-mantle beneath the study area are not consistent with the observations.

  17. Mantle Discontinuities under Iranian Plateau and Turan Shield from the Modeling of Seismic Triplications

    NASA Astrophysics Data System (ADS)

    Tseng, Tai-Lin; Chi, Hui-Ching; Huang, Bor-Shouh; Godoladze, Tea; Javakhishvili, Zurab; Karakhanyan, Arkadi

    2015-04-01

    Recent studies of seismic tomography show velocity anomalies in the mantle transition zone (TZ) under Zagros and Iranian Plateau, which are created by active collision between Africa and Eurasia. Remnants of Neo-Tethys slab that subducted before the collision might had experienced a break-off and likely be rested in the deep mantle. In this study, we utilize triplicate arrivals of high-resolution P waveforms to investigate the velocity structure of mantle beneath this continental collision zone and the surroundings. By combining several broadband arrays in eastern Turkey and Caucasus, we construct a fan of profiles, each about 800 km long, which consist of triplicate waveforms generated from the 410- and 660-km discontinuities. The method is particularly sensitive to the size of the velocity contrast for the sampled regions, including the central Iranian Plateau, Turan shield and part of South Caspian basin. Our results show that the lower TZ under the stable Turan shield is fast. The corresponding 660-km contrast is about 4.5% only, smaller than the value in global average model IASP91, but fairly close to that under the northern Indian shield in Precambrian age. For profiles sampling Iran, we observe azimuthal changes in the waveforms which require further data division or grouping. The preliminary analysis suggests that the velocity near the bottom of the TZ is comparable to model appropriate for Turan and probably has a slightly shallower 660-km discontinuity. We hope the comparisons between velocity structures under different terranes can improve our understandings to the lithosphere-mantle dynamics under the process of continental collision.

  18. 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.

  19. 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.

  20. 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.

  1. Seismic Discontinuities within the Crust and Mantle Beneath Indonesia as Inferred from P Receiver Functions

    NASA Astrophysics Data System (ADS)

    Woelbern, I.; Rumpker, G.

    2015-12-01

    Indonesia is situated at the southern margin of SE Asia, which comprises an assemblage of Gondwana-derived continental terranes, suture zones and volcanic arcs. The formation of SE Asia is believed to have started in Early Devonian. Its complex history involves the opening and closure of three distinct Tethys oceans, each accompanied by the rifting of continental fragments. We apply the receiver function technique to data of the temporary MERAMEX network operated in Central Java from May to October 2004 by the GeoForschungsZentrum Potsdam. The network consisted of 112 mobile stations with a spacing of about 10 km covering the full width of the island between the southern and northern coast lines. The tectonic history is reflected in a complex crustal structure of Central Java exhibiting strong topography of the Moho discontinuity related to different tectonic units. A discontinuity of negative impedance contrast is observed throughout the mid-crust interpreted as the top of a low-velocity layer which shows no depth correlation with the Moho interface. Converted phases generated at greater depth beneath Indonesia indicate the existence of multiple seismic discontinuities within the upper mantle and even below. The strongest signal originates from the base of the mantle transition zone, i.e. the 660 km discontinuity. The phase related to the 410 km discontinuity is less pronounced, but clearly identifiable as well. The derived thickness of the mantle-transition zone is in good agreement with the IASP91 velocity model. Additional phases are observed at roughly 33 s and 90 s relative to the P onset, corresponding to about 300 km and 920 km, respectively. A signal of reversed polarity indicates the top of a low velocity layer at about 370 km depth overlying the mantle transition zone.

  2. Effects of topography on upper mantle discontinuities for array detections of PP precursors

    NASA Astrophysics Data System (ADS)

    Thomas, C.; Lessing, S.; Rost, S.; Vanacore, E. A.; Schmerr, N. C.

    2014-12-01

    PP underside reflections off upper mantle discontinuities are frequently used to map discontinuity topography, impedance contrasts and to interpret these with respect to thermal and/or mineralogical variations. While the seismic discontinuities at 410 km and 660 km depth should be a global feature, several events show no detections or reduced amplitudes of the precursors. In this study, we investigate effects of topography on upper mantle discontinuities on array detections of PP precursors. Using the 2.5-D axisymmetric finite difference technique PSVaxi, we compute P-SV synthetic seismograms for two-dimensional model geometries with correct 3-D geometrical spreading. Retaining dominant periods of ~ 2 s, we investigate Gaussian-shaped upward or downward deflections of the 660 km discontinuity with varying lateral dimensions. Furthermore, we investigate effects of double discontinuities at ~660 km depth which are due to phase transformations in the non-olivine component of the mantle at subduction zone temperatures. Analyses of travel residuals indicate that topography of downward deflections of discontinuities is underestimated by 10 to 20 km while upward deflections are recovered within 10 km. Amplitude measurements show focussing and defocussing of PP precursor amplitudes by 60-70%. Reduced amplitudes of PP precursors are close or below the average noise level at seismic arrays and could result in non-detections. Double discontinuities at 660 km depth are recovered for lateral dimensions larger than 10° and if the two discontinuities are separated by at least 20 km. The observed effects in synthetic seismograms raise caution for interpretation of PP precursors in terms of impedance contrasts as well as thermal and mineralogical variations in the mantle.

  3. A fictitious domain method for fluid/solid interaction applied to the plate folding over the 660 Km depth boundary.

    NASA Astrophysics Data System (ADS)

    Cerpa, Nestor; Hassani, Riad; Gerbault, Muriel

    2014-05-01

    A large variety of geodynamical problems involve a mechanical system where a competent body is embedded in a more deformable medium, and hence they can be viewed as belonging to the field of solid/fluid interaction.The lithosphere/asthenosphere interaction in subduction zones is among those kind of problems which are generally difficult to tackle numerically since the immersed (solid) body can be geometrically complex and the surrounding (fluid) medium can thus undergo large deformation. Our work presents a new numerical approach for the study of subduction zones. The lithosphere is modeled as a Maxwell viscoelastic body sinking in the viscous asthenosphere. Both domains are discretized by the Finite Element Method (FEM) and we use a staggered coupling method. The interaction is provided by a non-matching interface method called the Fictitious Domain Method (FDM). We have validated this method with some 2-D benchmarks and examples. Through this numerical coupling method we aim at studying the effect of mantle viscosity on the cyclicity of slab folding on the 660 km depth discontinuity approximated as an impenetrable barrier. Depending on the kinematics condition imposed to the overriding and subducting plates, analog and numerical models have previously shown that cyclicity occurs. The viscosity of the asthenosphere (taken as an isoviscous or a double viscosity-layer fluid) impacts on folding cyclicity and consequently on the slab's dip as well as the stress regime of the overriding plate. In particular, applying far-field plate velocities corresponding to those of the South-American and Nazca plates at present, (4.3 cm/yr and 2.9 cm/yr respectively), we obtain periodic slab folding which is consistent with magmatism and sedimentalogical records. These data report cycles in orogenic growth of the order of 30-40 Myrs, a period that we reproduce when the mantle viscosity ranges in between 3 and 5 x 1020 Pa.s. Moreover, we reproduce episodic development of horizontal

  4. 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.

  5. 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.

  6. 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.

  7. Evidence for a ubiquitous seismic discontinuity at the base of the mantle

    PubMed

    Sidorin; Gurnis; Helmberger

    1999-11-12

    A sharp discontinuity at the base of Earth's mantle has been suggested from seismic waveform studies; the observed travel time and amplitude variations have been interpreted as changes in the depth of a spatially intermittent discontinuity. Most of the observed variations in travel times and the spatial intermittance of the seismic triplication can be reproduced by a ubiquitous first-order discontinuity superimposed on global seismic velocity structure derived from tomography. The observations can be modeled by a solid-solid phase transition that has a 200-kilometer elevation above the core-mantle boundary under adiabatic temperatures and a Clapeyron slope of about 6 megapascal per kelvin. PMID:10558981

  8. A Receiver Function Study of Mantle Transition Zone Discontinuities beneath Egypt and Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Liu, K. H.; Mohamed, A. A.; Gao, S. S.; Elsheikh, A. A.; Yu, Y.; Fat-Helbary, R. E.

    2014-12-01

    The dramatic asymmetry in terms of surface elevation, Cenozoic volcanisms, and earthquake activity across the Red Sea is an enigmatic issue in global tectonics, partially due to the unavailability of broadband seismic data on the African plate adjacent to the Red Sea. Here we report the first results from a receiver function study of the mantle transition zone (MTZ) discontinuities using data from the Egyptian National Seismic Network, and compare the resulting depths of the 410 and 660 km discontinuities (d410 and d660) with those observed on the Arabian side. Results using more than 6000 P-to-S receiver functions recorded at 49 broadband seismic stations in Egypt, Saudi Arabia and adjacent areas show that when the IASP91 Earth model is used for time-to-depth conversion, the resulting depth of the discontinuities increases systematically toward the axis of the Afro-Arabian Dome (AAD) from both the west and east. Relative to the westernmost area, the maximum depression of the 410-km discontinuity is about 30 km, and that of the 660-km discontinuity is about 45 km. Highly correlated d410 and d660 depths suggest that the observed apparent depth variations are mostly caused by lateral velocity anomalies in the upper mantle, while the 15 km additional depression of the d660 relative to the d410 requires either a colder-than-normal MTZ or the presence of water in the MTZ. We tested several models involving upper mantle and MTZ velocity anomalies and undulations of the MTZ discontinuities due to temperature anomalies and water content, and found that the observed systematic variations can best be explained by a model involving a hydrated MTZ and an upper-mantle low-velocity zone beneath the AAD (Mohamed et al., 2014, doi: 10.1093/gji/ggu284). Models invoking one or more mantle plumes originated from the MTZ or the lower-mantle beneath the study area are not consistent with the observations.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. Combination of the discontinuous Galerkin method with finite differences for simulation of seismic wave propagation

    NASA Astrophysics Data System (ADS)

    Lisitsa, Vadim; Tcheverda, Vladimir; Botter, Charlotte

    2016-04-01

    We present an algorithm for the numerical simulation of seismic wave propagation in models with a complex near surface part and free surface topography. The approach is based on the combination of finite differences with the discontinuous Galerkin method. The discontinuous Galerkin method can be used on polyhedral meshes; thus, it is easy to handle the complex surfaces in the models. However, this approach is computationally intense in comparison with finite differences. Finite differences are computationally efficient, but in general, they require rectangular grids, leading to the stair-step approximation of the interfaces, which causes strong diffraction of the wavefield. In this research we present a hybrid algorithm where the discontinuous Galerkin method is used in a relatively small upper part of the model and finite differences are applied to the main part of the model.

  17. Multiple transition zone seismic discontinuities and low velocity layers below western United States

    NASA Astrophysics Data System (ADS)

    Tauzin, B.; van der Hilst, R. D.; Wittlinger, G.; Ricard, Y.

    2013-05-01

    With P-to-S converted waves recorded at seismic stations of the U.S. Transportable Array, we image the fine structure of upper mantle and transition zone (TZ) beneath the western U.S. We map the topographies of seismic discontinuities by stacking data by common conversion points along profiles. Systematic depth and amplitude measurements are performed not only for the well-known "410" and "660" interfaces but also for minor seismic discontinuities identified around 350, 590, and 630 km depths. The amplitude of conversion suggests shear wave velocity (Vs) increase by 4% at the 410 and the 660. The observed 660 velocity contrast is smaller than expected from the 6% in IASP91 but consistent with a pyrolitic model of mantle composition. The Gorda plate, subducted under northern California, is tracked to the TZ where it seems to flatten and induce uplift of the 410 under northern Nevada. Maps of 410/660 amplitude/topography reveal that the TZ is anomalous beneath the geographical borders of Washington, Oregon, and Idaho, with (1) a thickened TZ, (2) a sharp change in depth of the 660, (3) a reduced 410 conversion amplitude in the North, and (4) a positive "630" discontinuity. Such anomalous structure might be inherited from the past history of plate subduction/accretion. A thinned TZ under the Yellowstone suggests higher-than-average temperatures, perhaps due to a deep thermal plume. Both the "350" and the "590" negative discontinuities extend over very large areas. They might be related either to an increased water content in the TZ, a significant amount of oceanic material accumulated through the past 100 Myr, or both.

  18. 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

  19. 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

  20. 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.

  1. Experimental constraints on coesite abundances in eclogite and implications for the X seismic discontinuity

    NASA Astrophysics Data System (ADS)

    Knapp, Nadia; Woodland, Alan B.; Klimm, Kevin

    2015-07-01

    We have experimentally tested the possibility that the coesite-stishovite transition in eclogite bodies is responsible for the X discontinuity, a locally observed, low-impedance jump in seismic wave velocities at 260-330 km depth. We determined phase relations and free SiO2 abundances in three natural-analog eclogite compositions that simulate different subduction scenarios in terms of pressure-temperature conditions and whether or not melt extraction occurred. Eclogitic compositions representing residues after either shallow or deep melting contain either no coesite or else too little (<4 wt %) to produce the observed impedance contrast for the X discontinuity. Only an unmodified mid-ocean ridge basalt (MORB) composition was found to contain just enough coesite (6-8 wt %) to be consistent with the expected impedance contrast when it transforms to stishovite. However, we assert that MORB cannot remain compositionally unmodified during subduction down to ~300 km. Fluid loss due to dehydration reactions during the transformation from basalt to eclogite lowers bulk SiO2 content. In addition, the MORB wet solidus intersects the coesite-stishovite boundary at ~290 km, implying that at greater depths a melt phase should be present before stishovite stability is reached. Our data indicate that melt generation is an efficient means of lowering the free SiO2 content in the mineral assemblage. This study also confirms previous work indicating that exsolution of SiO2 from the Ca-Eskola (Ca0.5AlSi2O6) component in clinopyroxene is not a feasible mechanism for producing significant stishovite upon reaching its stability field. We conclude that the coesite-stishovite transition in eclogite bodies is not a viable petrological explanation for the X discontinuity.

  2. 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.

  3. Seismic structure of the western U.S. mantle and the origin of the Yellowstone hotspot

    NASA Astrophysics Data System (ADS)

    Schmandt, B.; Dueker, K.; Humphreys, E.; Hansen, S. M.

    2012-12-01

    As a result of EarthScope's Transportable Array and prior seismic deployments the quality of mantle imaging beneath Yellowstone is unparalleled among hotspots. P-to-s receiver functions mapped to depth through P and S body-wave tomography models image continuous 410 and 660 km discontinuities beneath the area covered by the TA prior to the middle of the year 2011. Mean depths to the 410 and 660 km discontinuities of 410 and 656 km imply a mantle transition zone that is about 4 km thicker than the global average and hence has a slightly cooler mean temperature and/or enhanced water content. Compared to the mean 660 depth beneath this ~2000 km wide area, the 660 beneath the Yellowstone hotspot is deflected upward by 12-18 km over an area about 200 km wide. This is the most anomalous shallowing of the 660 imaged and its horizontal extent is similar to the area where P and S tomography image low-velocity mantle extending from the top of the transition zone to about 900 km depth. Together, these results indicate a high-temperature, plume-like upwelling extending across the 660. The depth of 410 km discontinuity beneath the Yellowstone region is within 5 km of the mean depth implying the plume is vertically heterogeneous and possibly discontinuous. Tomography images a similar vertically heterogeneous thermal plume. The irregular plume structure may be intrinsic to the dynamics of upwelling through the transition zone, or distortion may be caused by subduction-induced mantle flow. Topography of the 410 and 660 confirm that subducted slabs beneath the western U.S. are highly segmented, as inferred from recent tomography studies. We find no evidence of regionally pervasive velocity discontinuities between 750 and 1400 km depth. The plume's depth of origin within the lower mantle remains uncertain.

  4. 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

  5. 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).

  6. Seismic Imaging of Mantle Plumes

    NASA Astrophysics Data System (ADS)

    Nataf, Henri-Claude

    The mantle plume hypothesis was proposed thirty years ago by Jason Morgan to explain hotspot volcanoes such as Hawaii. A thermal diapir (or plume) rises from the thermal boundary layer at the base of the mantle and produces a chain of volcanoes as a plate moves on top of it. The idea is very attractive, but direct evidence for actual plumes is weak, and many questions remain unanswered. With the great improvement of seismic imagery in the past ten years, new prospects have arisen. Mantle plumes are expected to be rather narrow, and their detection by seismic techniques requires specific developments as well as dedicated field experiments. Regional travel-time tomography has provided good evidence for plumes in the upper mantle beneath a few hotspots (Yellowstone, Massif Central, Iceland). Beneath Hawaii and Iceland, the plume can be detected in the transition zone because it deflects the seismic discontinuities at 410 and 660 km depths. In the lower mantle, plumes are very difficult to detect, so specific methods have been worked out for this purpose. There are hints of a plume beneath the weak Bowie hotspot, as well as intriguing observations for Hawaii. Beneath Iceland, high-resolution tomography has just revealed a wide and meandering plume-like structure extending from the core-mantle boundary up to the surface. Among the many phenomena that seem to take place in the lowermost mantle (or D''), there are also signs there of the presence of plumes. In this article I review the main results obtained so far from these studies and discuss their implications for plume dynamics. Seismic imaging of mantle plumes is still in its infancy but should soon become a turbulent teenager.

  7. Buoyancy, bending, and seismic visibility in deep slab stagnation

    NASA Astrophysics Data System (ADS)

    Bina, Craig R.; Kawakatsu, Hitoshi; Suetsugu, D.; Bina, C.; Inoue, T.; Wiens, D.; Jellinek, M.

    2010-11-01

    The petrological consequences of deep subhorizontal deflection ("stagnation") of subducting slabs should affect both apparent seismic velocity structures and slab morphology. We construct kinematic thermal models of stagnant slabs and perform thermodynamic modeling of the consequent perturbation of high-pressure phase transitions in mantle minerals, focusing upon Japan as our study area. We calculate associated thermo-petrological buoyancy forces and bending moments which (along with other factors such as viscosity variations and rollback dynamics) may contribute to slab deformation. We consider effects of variations in depth of stagnation, post-stagnation dip angle, phase transition sharpness, transition triplication due to multiple intersection of geotherms with phase boundaries, and potential persistence of metastable phases due to kinetic hindrance. We also estimate seismic velocity anomalies, as might be imaged by seismic tomography, and corresponding seismic velocity gradients, as might be imaged by receiver-function analysis. We find that buoyant bending moment gradients of petrological origin at the base of the transition zone may contribute to slab stagnation. Such buoyancy forces vary with the depth at which stagnation occurs, so that slabs may seek an equilibrium slab stagnation depth. Metastable phase bending moment gradients further enhance slab stagnation, but they thermally decay after ∱/4600•700 km of horizontal travel, potentially allowing stagnant slabs to descend into the lower mantle. Stagnant slabs superimpose zones of negative velocity gradient onto a depressed 660-km seismic discontinuity, affecting the seismological visibility of such features. Seismologically resolvable details should depend upon both stagnation depth and the nature of the imaging technique (travel-time tomography vs. boundary-interaction phases). While seismic tomography appears to yield images of stagnant slabs, discontinuity topography beneath Japan resolved by

  8. Simultaneous inversion for mantle shear velocity and the topography of transition zone discontinuities

    NASA Astrophysics Data System (ADS)

    Gu, Y. J.; Dziewonski, A. M.

    2001-05-01

    A method is presented for the simultaneous inversions of shear velocity in the mantle and the topography of transition zone discontinuities. Each travel time residual, corrected for crust and free surface topography, is modeled as resulting from contributions from three-dimensional shear velocity perturbations to a spherical Earth model and boundary undulations to the 410 and 660 km discontinuities. This approach minimizes tradeoffs between velocity and topography. We expand the lateral variations in velocity and the topography of each discontinuity using 362 spherical B-splines; we expand the radial variations using 14 cubic B-splines. To increase the reliability of the measurements, particularly in the undersampled southern hemisphere, we re-examine the topography of the 410- and 660 km discontinuities from more than 21,000 SH-component records. This new data set is significantly larger than those used earlier studies of SS precursors. The long-wavelength features of our new topography maps of the 410- and 660-km discontinuities are compatible with results of earlier studies: the large-scale patterns are dominated by low degree spherical harmonics, particularly at degrees 1 and 2. We also include an independent measurement of the global transition zone thickness for additional constraints on the structure in the transition zone. The best-fit model from the joint inversion reduces the variance of the absolute and differential travel times of S, SS and ScS by 40 to 70 %, and the differential travel times of SS precursors by up to 90%.

  9. 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.

  10. The Mohorovičić discontinuity beneath the continental crust: An overview of seismic constraints

    NASA Astrophysics Data System (ADS)

    Carbonell, Ramon; Levander, Alan; Kind, Rainer

    2013-12-01

    The seismic signature of the Moho from which geologic and tectonic evolution hypotheses are derived is to a large degree a result of the seismic methodology which has been used to obtain the image. Seismic data of different types, passive source (earthquake) broad-band recordings, and controlled source seismic refraction, densely recorded wide-angle deep seismic reflection, and normal incidence reflection (using VibroseisTM, explosives, or airguns), have contributed to the description of the Moho as a relatively complex transition zone. Of critical importance for the quality and resolution of the seismic image are the acquisition parameters, used in the imaging experiments. A variety of signatures have been obtained for the Moho at different scales generally dependent upon bandwidth of the seismic source. This variety prevents the development of a single universally applicable interpretation. In this way source frequency content, and source and sensor spacing determine the vertical and lateral resolution of the images, respectively. In most cases the different seismic probes provide complementary data that gives a fuller picture of the physical structure of the Moho, and its relationship to a petrologic crust-mantle transition. In regional seismic studies carried out using passive source recordings the Moho is a relatively well defined structure with marked lateral continuity. The characteristics of this boundary change depending on the geology and tectonic evolution of the targeted area. Refraction and wide-angle studies suggest the Moho to be often a relatively sharp velocity contrast, whereas the Moho in coincident high quality seismic reflection images is often seen as the abrupt downward decrease in seismic reflectivity. The origin of the Moho and its relation to the crust-mantle boundary is probably better constrained by careful analysis of its internal details, which can be complex and geographically varied. Unlike the oceanic Moho which is formed in a

  11. 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.

  12. Stable Collocated-grid Finite Difference Seismic Wave Modeling Using Discontinuous Grids with Locally Variable Time Steps

    NASA Astrophysics Data System (ADS)

    Li, H.; Zhang, Z.; Chen, X.

    2012-12-01

    It is widely accepted that they are oversampled in spatial grid spacing and temporal time step in the high speed medium if uniform grids are used for the numerical simulation. This oversampled grid spacing and time step will lower the efficiency of the calculation, especially high velocity contrast exists. Based on the collocated-grid finite-difference method (FDM), we present an algorithm of spatial discontinuous grid, with localized grid blocks and locally varying time steps, which will increase the efficiency of simulation of seismic wave propagation and earthquake strong ground motion. According to the velocity structure, we discretize the model into discontinuous grid blocks, and the time step of each block is determined according to the local stability. The key problem of the discontinuous grid method is the connection between grid blocks with different grid spacing. We use a transitional area overlapped by both of the finer and the coarser grids to deal with the problem. In the transitional area, the values of finer ghost points are obtained by interpolation from the coarser grid in space and time domain, while the values of coarser ghost points are obtained by downsampling from the finer grid. How to deal with coarser ghost points can influent the stability of long time simulation. After testing different downsampling methods and finally we choose the Gaussian filtering. Basically, 4th order Rung-Kutta scheme will be used for the time integral for our numerical method. For our discontinuous grid FDM, discontinuous time steps for the coarser and the finer grids will be used to increase the simulation efficiency. Numerical tests indicate that our method can provide a stable solution even for the long time simulation without any additional filtration for grid spacing ratio n=2. And for larger grid spacing ratio, Gaussian filtration could be used to preserve the stability. With the collocated-grid FDM, which is flexible and accurate in implementation of free

  13. 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

  14. Seismic velocity discontinuities in the crust and uppermost mantle beneath the Tokyo metropolitan area inferred from receiver function analysis

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    We apply receiver function (RF) analyses to estimate the seismic velocity structure and seismic velocity discontinuities in the crust and uppermost mantle beneath the Tokyo metropolitan area, central Japan. Destructive earthquakes often occurred at various places including the subducting Philippine Sea plate (PSP), the subducting Pacific plate (PAP), and inland earthquake in this area. Investigation on the crustal structure and configurations of the subducting plates is the key to understanding the stress and strain concentration process and important to mitigate future earthquake disasters. A RF analysis is widely used to estimate velocity discontinuities in the crust and mantle beneath each seismic station. However, crustal structure beneath the Kanto plain could not be analyzed for lack of applicable seismic stations. Recently, comprehensive surveys are conducted as the Special Project for Earthquake Disaster Mitigation in the Tokyo Metropolitan area from 2007. The Metropolitan Seismic Observation network (MeSO-net) is constructed under this project. In this study, we searched for the best correlated velocity structure model between an observed RF at each station and synthetic ones by using a grid search method. Synthetic RFs calculated from assumed many one-dimensional velocity structures which consisting of four layers. We further constructed the vertical cross-sections of depth converted RF images transformed the lapse time of time series to depth by using the estimated structure models. MeSO-net data and telemetric seismographic network data operated by NIED, JMA and ERI are used. We used events with magnitudes greater or equal to 5.0 and epicentral distances between 30 and 90 degrees based on USGS catalogues. As a result, we clarify spatial distributions of the crustal S-wave velocities. The Boso Peninsula and Kanto plain are covered in the thick low-velocity sediment layers. We image standard velocity distributions in the deep crust of the Boso Peninsula

  15. 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.

  16. Upper Mantle Seismic Velocity Structure Beneath Eastern Africa and the Origin of Cenozoic Extensional Tectonism (Invited)

    NASA Astrophysics Data System (ADS)

    Nyblade, A.; Julia, J.; Adams, A. N.; Mulibo, G. D.; Tugume, F. A.

    2009-12-01

    The seismic structure of the upper mantle beneath eastern Africa will be reviewed using results from body wave tomography, surface wave tomography, and images of the 410 and 660 km discontinuities. Most of the data used for obtaining these results come from temporary deployments of broadband seismic stations in Ethiopia, Kenya, Uganda and Tanzania over the past decade. The ensemble of seismic results point to a deep-seated low velocity zone beneath the East African rift system that extends from the uppermost mantle, through the upper mantle, and into the mantle transition zone. The low velocity anomaly may also extend through the mantle transition zone and link with the low velocity zone in the lower mantle under southern Africa, commonly referred to as the African Superplume. This is in contrast to southern Africa, were there is little evidence for a pronounced low velocity anomaly in the upper mantle. The existence of a seismic low velocity zone beneath eastern African that extends to depths of more than 500 km supports the possibility that there is a geodynamic connection between the African Superplume and the origin of Cenozoic extensional tectonism in eastern Africa.

  17. The Mohorovicic discontinuity in ocean basins: Some observations from seismic data

    NASA Astrophysics Data System (ADS)

    Mutter, J. C.; Carton, Hélène D.

    2013-12-01

    Since the late 1970s studies of the oceanic crust using airgun sources and towed hydrophone arrays have been conducted in a wide range of ocean basin settings including mid-ocean ridges and old oceanic crust. The very earliest studies were performed at the fast-spreading East Pacific Rise (EPR) and revealed a very distinct almost continuous vertical incidence reflection event at a depth corresponding to the crust-mantle transition as inferred from seismic refraction studies. This suggested that the transition was quite sharp in comparison to the source wavelength. That Moho was observed very close to or even exactly beneath the ridge crest implied that it was formed at essentially zero age. Since then, many experiments using progressively improving airgun arrays and streamer systems have expanded these observations. Here we review the literature presenting studies of “normal” oceanic crust produced at mid-ocean ridges with the objective of assessing the age of formation of Moho and the nature of variability of Moho signature in multi-channel seismic data. Moho is observed as a consistent feature for all spreading rates but appears quite variable, being very distinct in some areas, complex in form in others and absent in many regions (as much as 40%). Although fast-spread crust is associated with the strongest, simplest and most laterally continuous Moho images we see significant variability at almost all spreading rates and ages. Where Moho is absent from vertical incidence data this cannot be fully explained by the effect of scattering or attenuation in the crustal section above. Moho can be observed at zero age in only a small number of areas at or near Overlapping Spreading Centers on the EPR. After three decades of marine seismic studies many fundamental questions remain concerning the nature of the Moho that will require targeted experiments to solve.

  18. 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.%.

  19. 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

  20. Project WILAS: Seismic imaging of crustal and upper mantle structures beneath the western Iberian Peninsula by means of the receiver-function technique

    NASA Astrophysics Data System (ADS)

    Dündar, Süleyman; Dias, Nuno A.; Silveira, Graça; Vinnik, Lev; Haberland, Christian

    2013-04-01

    660 km beneath the area under investigation. While applying the common data processing steps (e.g., rotation, deconvolution and moveout-correction) to the selected data-set, we were able to create approximately 4.500 PRFs. The signals from the Moho, 410-km and 660-km discontinuities are clearly visible in many PRF stacks. The Moho depth range is from 26 to 34 km, with an average value of 29 km. No significant lateral variations in the depths of the "410-km" and "660-km" discontinuities have been identified so far. In the second phase of this project, the S-receiver-function technique will be applied in order to map the thickness of the underlying mantle lithosphere. Additionally, joint inversion of PRFs and waveforms of SKS will be used to investigate depth-localized azimuthal anisotropy and the related past and present mantle flows.

  1. Locating and quantifying the seismic discontinuities in a complex medium through the migration and AVA analysis of reflected and converted waves: an application to the Mt Vesuvius volcano

    NASA Astrophysics Data System (ADS)

    Auger, E.; Virieux, J.; Zollo, A.

    2003-02-01

    In this paper, we show how the migration of active seismic data can be used to identify and position a seismic discontinuity in a complex medium, and how the amplitude variations of the converted P to S waves can be interpreted to constrain the seismic velocities below the interface. For the application we turn our attention on Mt Vesuvius, an active volcano threatening a densely populated area. To better define its plumbing system, we investigate a mid-crust seismic discontinuity first identified by Zollo et al. (1996, Science,274, 592-594) and assumed to be the top of a layer containing low-velocity material. We deduce a reference velocity model from previous works on first arrival times, and use it to migrate PP reflected and PS converted waves. In the migration image, the interface extends at least 20000 m NE and 20000 m SW of the volcano, at the depth of 8000 m, and with a mean dip less than 3 per cent. The migration of finite-difference synthetics exclude the fact that the migrated phases interpreted as 8000 m deep reflections or conversions might be multiples in the shallow layers. The PS and first arrival amplitudes are compared at a fixed station and for all the shots to determine the variations of the P-to-S conversion coefficient with the angle of incidence. It appears to vary very slowly over the whole range of incidence angle at disposal (50∘-80∘). This implies a dramatic drop of S-wave velocity from approximately 3600 m s-1 above to less than 1000 m s-1 below the interface. The smoothness of the variations indicate that the P-wave velocity also diminishes across the interface. The very low S-wave velocity, other geophysical observations at Vesuvius and in other volcanic systems, lead to the conclusion that below the 8000 m discontinuity there is a very extended layer of hot, partially molten material.

  2. Mid-mantle deformation inferred from seismic anisotropy.

    PubMed

    Wookey, James; Kendall, J-Michael; Barruol, Guilhem

    2002-02-14

    With time, convective processes in the Earth's mantle will tend to align crystals, grains and inclusions. This mantle fabric is detectable seismologically, as it produces an anisotropy in material properties--in particular, a directional dependence in seismic-wave velocity. This alignment is enhanced at the boundaries of the mantle where there are rapid changes in the direction and magnitude of mantle flow, and therefore most observations of anisotropy are confined to the uppermost mantle or lithosphere and the lowermost-mantle analogue of the lithosphere, the D" region. Here we present evidence from shear-wave splitting measurements for mid-mantle anisotropy in the vicinity of the 660-km discontinuity, the boundary between the upper and lower mantle. Deep-focus earthquakes in the Tonga-Kermadec and New Hebrides subduction zones recorded at Australian seismograph stations record some of the largest values of shear-wave splitting hitherto reported. The results suggest that, at least locally, there may exist a mid-mantle boundary layer, which could indicate the impediment of flow between the upper and lower mantle in this region. PMID:11845205

  3. Passive Seismic Experiment "13 BB Star" in the Margin of the East European Craton, Northern Poland

    NASA Astrophysics Data System (ADS)

    Polkowski, M.; Grad, M.; Wilde-Piórko, M.; Suchcicki, J.; Arant, T.

    2014-12-01

    Passive experiment "13 BB star" is dedicated to study deep structure of the Earth's interior in the marginal zone of the East European Craton in northern Poland. The seismic network consists of 13 broadband stations on the area of c. 120 km in diameter. The network is located in the area well recognized from the point of view velocities of sedimentary cover and crustal structure. Good records obtained since summer 2013, and expected during next 1.5 years long recording campaign, should yield images of detailed structure of the lithosphere-asthenosphere boundary (LAB), „410", "?520", and „660" km discontinuities, as well as mantle-core boundary and inner core. The LAB is investigated recently very effectively, mostly using seismic methods because their deep penetration and relatively good resolution. The nature of LAB is still debated, particularly under "cold" Precambrian shields and platforms. We show examples of local and teleseismic records, array transfer function of "13 BB star" network and preliminary noise analysis. National Science Centre Poland provided financial support for this work by NCN grant DEC- 2011/02/A/ST10/00284.

  4. 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.

  5. 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

  6. Upper Mantle Seismic Structure Beneath Southern Africa: Constraints on the Buoyancy Supporting the African Superswell

    NASA Astrophysics Data System (ADS)

    Brandt, Martin B. C.; Grand, Stephen P.; Nyblade, Andrew A.; Dirks, Paul H. G. M.

    2012-04-01

    We present new one-dimensional SH-wave velocity models of the upper mantle beneath the Kalahari craton in southern Africa obtained from waveform inversion of regional seismograms from an Mw = 5.9 earthquake located near Lake Tanganyika recorded on broadband seismic stations deployed during the 1997-1999 Southern African Seismic Experiment. The velocity in the lithosphere beneath the Kalahari craton is similar to that of other shields, and there is little evidence for a significant low velocity zone beneath the lithosphere. The lower part of the lithosphere, from 110 to 220 km depth, is slightly slower than beneath other shields, possibly due to higher temperatures or a decrease in Mg number (Mg#). If the slower velocities are caused by a thermal anomaly, then slightly less than half of the unusually high elevation of the Kalahari craton can be explained by shallow buoyancy from a hot lithosphere. However, a decrease in the Mg# of the lower lithosphere would increase the density and counteract the buoyancy effect of the higher temperatures. We obtain a thickness of 250 ± 30 km for the mantle transition zone, which is similar to the global average, but the velocity gradient between the 410 and 660 km discontinuities is less steep than in global models, such as PREM and IASP91. We also obtain velocity jumps of between 0.16 ± 0.1 and 0.21 ± 0.1 km/s across the 410 km discontinuity. Our results suggest that there may be a thermal or chemical anomaly in the mantle transition zone, or alternatively that the shear wave velocity structure of the transition zone in global reference models needs to be refined. Overall, our seismic models provide little support for an upper mantle source of buoyancy for the unusually high elevation of the Kalahari craton, and hence the southern African portion of the African Superswell.

  7. 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

  8. Accelerating the discontinuous Galerkin method for seismic wave propagation simulations using the graphic processing unit (GPU)—single-GPU implementation

    NASA Astrophysics Data System (ADS)

    Mu, Dawei; Chen, Po; Wang, Liqiang

    2013-02-01

    We have successfully ported an arbitrary high-order discontinuous Galerkin (ADER-DG) method for solving the three-dimensional elastic seismic wave equation on unstructured tetrahedral meshes to an Nvidia Tesla C2075 GPU using the Nvidia CUDA programming model. On average our implementation obtained a speedup factor of about 24.3 for the single-precision version of our GPU code and a speedup factor of about 12.8 for the double-precision version of our GPU code when compared with the double precision serial CPU code running on one Intel Xeon W5880 core. When compared with the parallel CPU code running on two, four and eight cores, the speedup factor of our single-precision GPU code is around 12.9, 6.8 and 3.6, respectively. In this article, we give a brief summary of the ADER-DG method, a short introduction to the CUDA programming model and a description of our CUDA implementation and optimization of the ADER-DG method on the GPU. To our knowledge, this is the first study that explores the potential of accelerating the ADER-DG method for seismic wave-propagation simulations using a GPU.

  9. Toward a Comprehensive Understanding of Transition Zone Seismic Discontinuities: Part I. New Constraints from Receiver Function Forward and Backward Scattering Waves

    NASA Astrophysics Data System (ADS)

    Shen, X.; Song, T. R. A.; Yuan, X.

    2014-12-01

    Transition zone discontinuities, among all, hold the key to resolve the mystery of mass and heat transport in the Earth's mantle and the composition of the Earth's interior. In previous efforts, the data are limited to either upper mantle triplications, converted waves or mantle reflections (e.g. SS precursors, ScS reverberations). When multiple datasets are jointly analyzed, they are often restrained at relatively long period (~ 0.1 Hz). To complement previous efforts, we advocate a simple and effective strategy to tackle a number of seismic observables altogether. 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 also allows a superior resolution on the sharpness of the boundary and a detailed description of transition zone discontinuities. Here we summarize our first attempt in the region of stagnant slab beneath Chinese continent. We processed waveforms from 1000 stations of the Chinese seismic array using an automatic scheme to remove noisy waveforms and retained close to ~300,000 high quality receiver functions in the L-Q-T coordinate system. While avoiding interferences from other mantle waves, we perform slowness stacking of direct converted waves and the multiples, respectively, at several discrete frequency bands between 0.05 Hz and 1Hz and obtain amplitude estimates and uncertainties through the bootstrap method. To properly calibrate the amplitudes of receiver functions, we take into account the effect of incoherent stacking due to discontinuity topography and frequency-dependent attenuation. Our findings indicate that the 410 is a sharp boundary with a small density jump (<< 5 km, ΔVs=5-6%, Δρ=1.5-2%), but there is no significant gradient near the sharp transition. While the 660 is best described by a sharp boundary and

  10. Self-consistent Synthetic Mantle Discontinuities From Joint Modeling of Geodynamics and Mineral Physics and Their Effects on the 3D Global Wave Field

    NASA Astrophysics Data System (ADS)

    Schuberth, B.; Piazzoni, A.; Bunge, H.; Igel, H.; Steinle-Neumann, G.; Moder, C.; Oeser, J.

    2007-12-01

    Our current understanding of mantle structure and dynamics is to a large part based on inversion of seismic data resulting in tomographic images and on direct analysis of a wide range of seismic phases such as Pdiff, PcP, ScS SdS etc. For solving inverse problems, forward modeling is needed to obtain a synthetic dataset for a given set of model parameters. In this respect, great progress has been made over the last years in the developement of sophisticated numerical full waveform modeling tools. However, the main limitation in the application of this new class of techniques for the forward problem of seismology is the lack of accurate predictions of mantle heterogeneity that allow us to test hypotheses about Earth's mantle. Such predictive models should be based on geodynamic and mineralogical considerations and derived independently of seismological observations. Here, we demonstrate the feasibility of joining forward simulations from geodynamics, mineral physics and seismology to obtain earth-like seismograms. 3D global wave propagation is simulated for dynamically consistent thermal structures derived from 3D mantle circulation modeling (e.g. Bunge et al. 2002), for which the temperatures are converted to seismic velocities using a recently published, thermodynamically self-consistent mineral physics approach (Piazzoni et al. 2007). Assuming a certain, fixed mantle composition (e.g. pyrolite) our mineralogic modeling algorithm computes the stable phases at mantle pressures for a wide range of temperatures by system Gibbs free energy minimization. Through the same equations of state that model the Gibbs free energy, we compute elastic moduli and density for each stable phase assemblage at the same P-T conditions. One straightforward application of this approach is the study of the seismic signature of synthetic mantle discontinuities arising in such models, as the temperature dependent phase transformations occuring at around 410 Km and 660 Km depth are

  11. Accelerating the discontinuous Galerkin method for seismic wave propagation simulations using multiple GPUs with CUDA and MPI

    NASA Astrophysics Data System (ADS)

    Mu, Dawei; Chen, Po; Wang, Liqiang

    2013-12-01

    We have successfully ported an arbitrary high-order discontinuous Galerkin method for solving the three-dimensional isotropic elastic wave equation on unstructured tetrahedral meshes to multiple Graphic Processing Units (GPUs) using the Compute Unified Device Architecture (CUDA) of NVIDIA and Message Passing Interface (MPI) and obtained a speedup factor of about 28.3 for the single-precision version of our codes and a speedup factor of about 14.9 for the double-precision version. The GPU used in the comparisons is NVIDIA Tesla C2070 Fermi, and the CPU used is Intel Xeon W5660. To effectively overlap inter-process communication with computation, we separate the elements on each subdomain into inner and outer elements and complete the computation on outer elements and fill the MPI buffer first. While the MPI messages travel across the network, the GPU performs computation on inner elements, and all other calculations that do not use information of outer elements from neighboring subdomains. A significant portion of the speedup also comes from a customized matrix-matrix multiplication kernel, which is used extensively throughout our program. Preliminary performance analysis on our parallel GPU codes shows favorable strong and weak scalabilities.

  12. Toward a Comprehensive Understanding of Transition Zone Seismic Discontinuities: Part II. Inferences on the State of the Transition Zone with a Stagnant Slab

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Plate tectonic processes operating over much of the Earth's history induce long-term mantle mixing of chemical heterogeneities, recycling of volatiles and regulate basalt geochemistry. Through broadband analysis of P-wave receiver function conversions and topside reflections, we characterize the 410 and 660 seismic discontinuities beneath China (see Shen et al., DI013, this meeting) and simultaneously determine the shear velocity and density jumps, the sharpness of the boundary as well as the gradient immediately above/below the boundary. Within the thermodynamic framework, HeFESTo, we explore these observations with respect to seismic properties predicted in a volatile/melt free mantle, where harzburgite and basalt rock assemblages are either fully equilibrated or mechanically mixed. We find that observed shear velocity (5-6%) and density jumps (1.5-2%) across the 410 are both too low to be consistent with the olivine-wadsleyite phase transition in a pyrolitic mantle; the 410 is sharp (<< 5 km) and it requires Mg-rich harzburgite (Mg# >~ 0.93) in the mantle; the gradient near the 410 is very low, inconsistent with a dry pyrolitic mantle. The observed 660 not only consists of a sharp boundary (<< 5 km) with relatively small shear velocity (3.5-4%) and density jumps (4-4.5%), but it also involves a substantial velocity/density gradient near the boundary (> 0.003 km/s/km; > 0.003 g/cm3/km). These observations coincide very well with the post-spinel and post-garnet phase transitions in a mantle with about 75% harzburgite fully equilibrated with 25% basalt. Taking into account of previous mantle triplication analyses and electric conductivity profiles in the region, these results lead us to examine the following hypotheses: The harzburgite assemblage in the mantle transition zone beneath China is probably at least as depleted as Archean cratonic peridotites. Near the 410, the mantle is either relatively dry (e.g., the water content is well below the solubility of

  13. 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.

  14. A seismic discontinuity in the upper mantle between the Eastern Alps and the Western Carpathians: Constraints from wide angle reflections and geological implications

    NASA Astrophysics Data System (ADS)

    Oeberseder, T.; Behm, M.; Kovács, I.; Falus, G.

    2011-05-01

    Seismic investigation of the lithosphere by means of active source experiments is mostly confined to the crust and the Moho. Structures in the upper mantle are more likely to be discovered by analyses of teleseismic data, although these methods are restricted in their resolution capabilities. The relatively rare evidence for upper mantle refractors or reflectors in active source data enables challenging and interesting studies of the lower and not so well known part of the lithosphere. We present such an example from the tectonically complex region between the Eastern Alps and the Western Carpathians. This area was covered by several extensive 3D wide-angle reflection/refraction experiments within the last decade, and their layout was designed to illuminate the crustal structure and in particular the Moho discontinuity. In some areas, reflections from below the Moho are also recorded. These reflections occur at recording offsets between 200 and 500 km, and they are particularly strong in cross line recordings. We derive a set of travel times from the data and perform a tomographic inversion for the depth and shape of the reflecting interface. The inversion makes use of an existing 3D crustal model which also includes the Moho topography. Since the upper mantle velocities are poorly constrained and the azimuthal distribution of the rays is biassed, several tests are applied to investigate the reliability of possible solutions. The results from the tomographic inversion indicate an overall horizontal and radially dipping reflector. The average depth of the reflector is 55 km, which is about 25 km below the crust-mantle transition, and amplitude modelling suggests that the reflecting interface represents a velocity increase. The investigated area is further characterised by deep sedimentary basins, high heat flow, high velocities in the lower crust, diffuse Moho signature and a strong positive Bouguer anomaly. Nearby xenolith outcrops exhibit a pronounced change in

  15. 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

  16. 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

  17. Discontinuous and smooth 3D structure of the upper mantle and crust across and along the Eurasia-Africa plate boundary

    NASA Astrophysics Data System (ADS)

    Marone, F.; van der Meijde, M.; van der Lee, S.; Giardini, D.

    2003-04-01

    body could be a fragment of African lithosphere that subducted in an early stage of NW subduction of oceanic lithosphere in the western Mediterranean. Not only convergence has been recorded in the upper mantle, but also extension has its own signature. This is particularly clear for the Algero-Proven{çal and Tyrrhenian basins, where a shallow low-velocity layer (asthenosphere) is observed. The lithosphere-asthenosphere system of the western Mediterranean clearly distinguishes itself from the structure of the older eastern Atlantic Ocean and from the structure below oceanic crust of comparable age as the western Mediterranean. We suggest that, rather than a young ocean, the western Mediterranean represents a strongly extended continent in the back arc region of a rapdily retreating subducting slab, and only partly affected by sea-floor spreading. Receiver function analysis shows a relatively sharp 660-km discontinuity throughout the region. The 410-km discontinuity, shows more complex behavior and the amplitudes ofP toS conversions at this discontinutiy appear to be frequency dependent. This frequency dependence is particularly clear in stacks of receiver functions for 9 of the 23 seismic stations analyzed. We attribute this behavior to finite thickness of the 410-km phase transiton interval of olivine to wadsleyite. We find this interval to be up to 30 km thick and attribute these large thicknesses to the presence of up to at least 700 ppm water at depths near 410 km.

  18. Seismicity of west Texas

    SciTech Connect

    Dumas, D.B.

    1981-01-01

    A four year seismic study has found the Basin and Range province of west Texas and the adjacent area of Mexico to be more seismically active then than heretofore known. A University of Texas five station seismic array around the Marfa Basin has located or detected approximately 800 local and regional earthquakes with S-P times of less than 30 sec. A crustal model for the Basin and Range is derived from natural and artificial sources and contains four layers having velocities of 3.60, 4.93, 6.11, and 6.60 km/sec, respectively, overlying a mantle of 8.37 km/sec. A moderate level of seismic activity has been detected near Van Horn, in the Marfa Basin, and along the Texas-Mexico border between latitudes 30 and 31/sup 0/N. Five earthquake sequences were recorded, two near the Texas-Mexico border and three in the Marfa Basin. Four of these sequences showed quiescent periods in foreshock activity preceding the main shock. On the eastern side of the Marfa Basin a diffuse linear seismic zone may represent an unmapped fault, striking N 50/sup 0/W that coincides with Muehlberger's proposed eastern boundary of Basin and Range faulting. A new epicenter for the Valentine, Texas earthquake of August 16, 1931 has been relocated instrumentally at the northern end of this diffuse zone. Regional and local teleseismic P-wave arrival time anomalies observed for the nearby Gnome underground nuclear explosion of 1961 are used to determine station corrections and thus to locate the new 1931 epicenter at 3.69/sup 0/N, 104.57/sup 0/W. Several estimates of magnitude (m/sub b/) based on intensity data range from 5.6 to 6.4. Fault-plane and composite fault-plane solutions support Muehlberger's hypothesis that the Basin and Range is undergoing extension in a SW-NE direction.

  19. 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

  20. The contribution of the seismic component of Topo-Iberia to the imaging of the deep structure of the Iberian Peninsula and North Morocco

    NASA Astrophysics Data System (ADS)

    Diaz, Jordi; Gallart, Josep; de Lis Mancilla, Flor; Villaseñor, Antonio; Bonatto, Luciana; Schimmel, Martin; Harnafi, Mimoun; El Moudnib, Lahcen

    2015-04-01

    Topo-Iberia has been a large-scale Spanish project running from 2007 to 2013 that integrated more than 150 researchers on Earth Sciences. One of its key assets was the management of an observatory platform, named IberArray, aimed to provide new geophysical datasets (seismic, GPS, MT) to constrain the structure of Iberia with unprecedented resolution. The IberArray seismic pool was composed by 70+ BB stations, covering the study area in 3 deployments with a site-density of 60km x 60km. The data base holds ~300 sites, including the permanent networks in the area. Hence it forms a unique seismic database in Europe that allows for multiple analyses to constrain the complex geodinamics of the Western Mediterranean. A summary of new results coming from different techniques is presented here. The SKS splitting analysis has provided a spectacular image of the rotation of the fast velocity direction along the Gibraltar Arc. In central and northern Iberia, the fast polarization directions are close to EW, consistently with global mantle flow models considering contributions of surface plate motion, density variations and net lithosphere rotation. Those results suggest an asthenospheric origin of the observed anisotropy related to present-day mantle flow. Receiver functions have revealed the crustal thickness variations beneath the Atlas, Rif and southern Iberia, evidencing a relevant crustal root beneath the Rif, in agreement with recent, high-density active seismic experiments. The Variscan Iberian massif shows a flat Moho discontinuity, while the areas reworked in the Alpine orogeny show a slightly thicker crust. Beneath N Iberia, the imbrication of the Iberian and Eurasian crusts results in complex receiver functions. Depths exceeding 45 km are observed along the Pyrenean range, while the crust thins to values of 26-28 km close to the Atlantic coasts. The geometry of the 410-km and 660-km discontinuities has been investigated using novel cross

  1. Seismic structure of the North American lithosphere and upper mantle imaged using Surface and S waveform tomography

    NASA Astrophysics Data System (ADS)

    Schaeffer, A. J.; Lebedev, S.

    2010-12-01

    The evolution, stability, and dynamics of continental lithosphere remain a central focus of Earth Science research. The continued deployment of the US Array is producing a massive new dataset that samples North America at scales from tectonic units to continent-wide domains and enables resolution of structure and deformation of the lithosphere previously possible only at regional scales. With this resolving power come new challenges relating to efficient management and processing of such large data volumes. In this study, we have assembled a dataset comprising over 3.5 million three-component broadband seismic waveforms from more than 3000 stations. We augment available US Array stations with ~600 additional North American stations of the GSN and affiliates, Canadian National Seismograph Network, regional arrays, past PASSCAL experiments, and other stations from Iceland, Greenland, Central and South America, the Caribbean, and several Mid-Atlantic Islands. We exploit the resolving power of this unprecedentedly large dataset using the Automated Multimode Inversion of surface- and S-wave forms. The waveforms are inverted for path-averaged linear constraints on elastic structure along the source-receiver paths. The linear equations are then simultaneously solved for a high-resolution 3D upper mantle shear velocity model of the continent. We present a model of the North American continent's and the surrounding Ocean's (Pacific, Atlantic, Gulf of Mexico) upper mantle structure down to the 660 km discontinuity. Clearly identifiable boundaries between different tectonic features such as basins and relic mountain ranges are readily observable. For example, a strong correlation between the Hudson Bay geoid anomaly can be identified with an underlying domain of particularily cold cratonic lithosphere. Our model also includes the 3D distribution of azimuthal anisotropy within these structures, which provides new insight into past and present dynamics of the lithosphere and

  2. Integrated seismic model of the crust and upper mantle of the Trans-European Suture zone between the Precambrian craton and Phanerozoic terranes in Central Europe

    NASA Astrophysics Data System (ADS)

    Wilde-Piórko, Monika; Świeczak, Marzena; Grad, Marek; Majdański, Mariusz

    2010-01-01

    The structure and evolution of the Trans-European Suture zone (TESZ), contact between Precambrian Europe to the northeast and Phanerozoic terranes to the southwest is one of the main tectonic questions in Europe. The knowledge of the crustal structure, lithosphere-asthenosphere boundary and mantle transition zone between two seismic discontinuities at depths "410" and "660" km, is one of the most important issues to understand the Earth's dynamics. To create a mantle model of the TESZ and surroundings we used different seismic data collected along the 950 km long POLONAISE'97 profile P4. Previous results of 2-D ray-tracing and P-wave travel time modelling and new results of P-wave travel time residuals methods and receiver function sections provide facts about the seismic structure from the surface down to 900 km depth. In the TESZ a large basin, about 125 km wide, is filled with sedimentary strata (Vp < 6.0 km s - 1 ) to about 20 km depth. This basin is asymmetric with its northeast margin being most abrupt. The crystalline crust under this basin is only about 20 km thick today indicating that the lithosphere of Baltica was either thinned drastically or terminated along the northeast margin of the basin. The East European craton (EEC) has a ~ 45 km thick three-layered crust. The crust of the accreted terranes to the southwest is relatively thin (~ 30 km) and similar to that found in other non-cratonal areas of Western Europe. The lower crust is relatively fast (Vp > 7.0 km s - 1 ) along most of the P4 profile. However, lower values to the southwest may indicate the termination of Baltica. High velocity (~ 8.35 km s - 1 ) uppermost mantle lies beneath the Avalonia/Variscan terranes, and may be due to rifting and/or subduction. The seismic lithosphere thickness for the EEC is about 200 km, while it is only 90 km in the Palaeozoic platform (PP). The mantle transition zone is shallower and about 30 km thicker under the EEC, which could be due to thermal conditions

  3. 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

  4. 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.

  5. 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

  6. 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.…

  7. The amount of water reserved in a "normal" oceanic mantle transition zone beneath the northwestern Pacific, inferred from data of coincident ocean bottom electromagnetic and seismic observations

    NASA Astrophysics Data System (ADS)

    Matsuno, T.; Suetsugu, D.; Utada, H.; Baba, K.; Tada, N.; Shimizu, H.; Shiobara, H.; Isse, T.; Sugioka, H.; Ito, A.

    2015-12-01

    "Is the mantle transition zone (MTZ) a major water reservoir of the Earth?" To answer this question, we have inferred the amount of water reserved in a "normal" oceanic MTZ beneath the northwestern Pacific from electrical and seismic structures. The field experiment was conducted with arrays of ocean bottom electromagnetometers and broadband ocean bottom seismometers in 2010-2014. Our innovative ocean bottom instruments, Earth's electric field observation system was used to measure time-variations of electric field with high S/N ratio at periods of >105s where the electromagnetic field is sensitive to the MTZ, and broadband ocean bottom seismometer of the next generation was used to record the earth motion with as low noise level as land stations. Electromagnetic data were first analyzed to derive MT and GDS response functions at periods of >105s. Then, model responses were numerically obtained from electrical conductivity models overlain by earth-surface land-ocean heterogeneity. Comparison between the observation and the prediction suggested that a MTZ electrical conductivity structure beneath the northwestern Pacific is similar to an averaged 1-D structure of the north Pacific [Shimizu et al., 2010]. Seismic data were analyzed through a P-wave receiver function method. Depths of 410 and 660 km discontinuities and thickness of the MTZ were variable by areas. The MTZ thickness beneath the southern part of Area A (northwest to the Shatsky Rise), 270 km, is larger a global average of 243 km [e.g., Flanagan & Shearer, 1989], while those beneath Area B (southeast to the Shatsky Rise), 241 and 248 km, are comparable to the average. The water content and a thermal structure in the MTZ beneath Area A were inferred from the data. First, a temperature perturbation was determined to -70~-150 K from the thickness perturbation of the MTZ. Then, a thermal structure for Area A is assumed to a structure [Katsura et al., 2010] with the temperature perturbation. Electrical

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. Lehmann discontinuity due to dehydration of phengite

    NASA Astrophysics Data System (ADS)

    Ono, S.

    2007-12-01

    It is known that the Lehmann discontinuity has several unique features. The depth of this seismic discontinuity is around 220 km depth. However, this discontinuity has not been detected everywhere at around 220 km depth. It is observed under continents more than as often as under oceans. An increase in the compressional or shear wave velocity and in seismic reflections has been reported. A regionally varying negative seismological Clapeyron slope has been estimated. A seismic transition from anisotropic to a more isotropic state occurs at depths corresponding to the Lehmann discontinuity. Although several models have been proposed to explain these features of this discontinuity, previous models failed to clear these unique features. Here, we propose a new model to explain the origin of the Lehmann discontinuity. We conducted experiments with hydrous sediment. The temperature was varied between 1073 and 1673 K, while a pressure of 6-15 GPa was applied using the multi-anvil press. The typical pelite composition was used as the sediment [1]. Garnet, clinopyroxene, and silica phases were present in all of the experiments. Three hydrous phases were observed at temperatures below 1573 K. The stable crystalline hydrous minerals consisted of phengite below 8 GPa, topaz-OH from 9-12 GPa, and phase egg above 12 GPa. The breakdown boundaries of topaz-OH and phase egg show a positive Clapeyron slope. In contrast, the breakdown reaction of phengite gave a negative slope at about 7 GPa corresponding to 220 km depth. The upper temperature limit for phengite is greater than 1473 K. This phase is thus likely to be stable within average adiabatic mantle conditions [1]. Above ~220 km depth the deformation mechanism of olivine is dislocation creep, which gives a preferred orientation to the crystals. The seismic anisotropies are likely to result from the preferred orientation of olivine. As pressure increases, the diffusion creep becomes dominant. If sediments migrate by the

  14. On discontinuing dialysis.

    PubMed

    Wight, J

    1993-06-01

    Ethical issues relating to the withdrawal of dialysis are discussed, comparing dialysis with other life-support systems, particularly artificial ventilation. It is argued that there is no ethical difference between discontinuing treatment in each case. One practical difference between the two is that patients with chronic renal failure are less likely to have reduced autonomy, and so can engage in discussions with their doctors regarding the situations in which their life-supporting treatment might be discontinued. It is argued that doctors caring for patients on dialysis have an ethical duty to discuss with these patients the circumstances in which they may wish to discontinue dialysis. PMID:8331641

  15. 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. PMID:10879532

  16. Discontinuing benzodiazepines: best practices.

    PubMed

    Guaiana, G; Barbui, C

    2016-06-01

    In July 2015, the Canadian Agency for Drugs and Technologies in Health (CADTH) released a Rapid Response report summary, with a critical appraisal, on discontinuation strategies for patients with long-term benzodiazepines (BDZ) use. The CADTH document is a review of the literature. It includes studies whose intervention is BDZ discontinuation. Also, clinical guidelines, systematic reviews and meta-analyses are included. What emerges from the CADTH guidelines is that the best strategy remains gradual tapering of BDZ with little evidence for the use of adjunctive medications. The results show that simple interventions such as discontinuation letters from clinicians, self-help information and support in general, added to gradual tapering may be associated with a two- to three-fold higher chance of successful withdrawal, compared with treatment as usual. We suggest possible implications for day-to-day clinical practice. PMID:26818890

  17. Explosive synchronization is discontinuous

    NASA Astrophysics Data System (ADS)

    Vlasov, Vladimir; Zou, Yong; Pereira, Tiago

    2015-07-01

    Spontaneous explosive is an abrupt transition to collective behavior taking place in heterogeneous networks when the frequencies of the nodes are positively correlated with the node degree. This explosive transition was conjectured to be discontinuous. Indeed, numerical investigations reveal a hysteresis behavior associated with the transition. Here, we analyze explosive synchronization in star graphs. We show that in the thermodynamic limit the transition to (and out of) collective behavior is indeed discontinuous. The discontinuous nature of the transition is related to the nonlinear behavior of the order parameter, which in the thermodynamic limit exhibits multiple fixed points. Moreover, we unravel the hysteresis behavior in terms of the graph parameters. Our numerical results show that finite-size graphs are well described by our predictions.

  18. 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…

  19. Lithospheric Discontinuities Beneath North America (Invited)

    NASA Astrophysics Data System (ADS)

    Fischer, K. M.; Abt, D. L.; Yuan, H.; Romanowicz, B. A.

    2009-12-01

    The goal of this study is to compare lithospheric discontinuities between the stable cratonic core of North America and surrounding regions that have experienced more recent tectonic activity. Are the properties of the cratonic lithosphere-asthenosphere boundary (LAB) fundamentally different from the LAB in regions with thinner lithosphere? Do significant discontinuities exist within the cratonic lithosphere? Sp and Ps converted seismic waves from 93 permanent seismic stations spanning North America, including stations of the EarthScope Reference Array, were used to image the discontinuity structure of the upper mantle. Receiver functions were calculated with frequency-domain deconvolution and migrated to depth with 1D models that account for variations in crustal structure and mantle velocities between stations. Prominent Sp phases from a negative velocity contrast were found at depths of 50-120 km. To interpret these Sp phases as either the LAB or a mid-lithospheric discontinuity (MLD), we compared their depth to the transition from the low-velocity asthenosphere to the high velocity lithospheric lid in the absolute shear velocity model from surface wave tomography that was used to migrate the receiver functions. In the tectonically active western U.S., the negative Sp phases were interpreted as the LAB at depths of 50-105 km. On average, the amplitudes of these Sp phases are the largest in North America. They are consistent with a large and rapid LAB velocity gradient and an anomalously hot and shallow asthenosphere that is very rich in water or contains partial melt. In the regions of the southern and eastern U.S where the Sp phases were interpreted as the LAB, the discontinuity lies at depths of 75-110 km and also implies the presence of water or melt in the asthenosphere. In contrast, no Sp phases were observed at depths comparable to the base of the thick high velocity lithosphere that lies beneath cratonic North America and portions of the Phanerozoic

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. Seismic Tomographic Images of the Cratonic Upper Mantle Beneath the Canadian Western Superior Province: a Remnant Archean Slab?

    NASA Astrophysics Data System (ADS)

    Sol, S.; Thomson, C. J.; Kendall, J.; White, D.; VanDecar, J. C.; Asudeh, I.

    2001-12-01

    \\def\\twist{\\raise 0.1em ~} Broadband digital data of the Lithoprobe TW{\\twist}ST experiment were tomographically inverted for upper--mantle P and S velocity structures beneath the Western Superior Province. The 17 portable broadband stations were arrayed in northern Ontario, Canada, so as to crosscut the strike of many subprovinces as well as the boundary with the Proterozoic Trans--Hudson Orogen to the north. The resulting tomographic images reveal three robust velocity anomalies: (i) a dipping tabular high--velocity anomaly; (ii) a relatively shallow low--velocity anomaly directly above the positive anomaly; and (iii) a deep low--velocity body. The first anomaly could be interpreted as a 30--50 km thick eclogite/dunite layer representing a remnant subducted oceanic lithosphere. The presence of this slab--shaped body within the cratonic root suggests its origin at around 2.7 Ga and its SE--NW strike is perceptibly oblique to the main E--W trend of the subprovince boundaries. Resolution tests suggest that this dipping high--velocity anomaly could extend to the vicinity of the 660 km seismic discontinuity. The low--velocity anomalies may be related to processes that occurred at the edges of the descending slab or may be expressions of later upwelling material. The presence of a thick cratonic root (≈300 km) may also be revealed by the tomographic images. Previous SKS--splitting large delay times (1.1 to 2.1s) are consistent with a thick root, and fast polarization trends, which are broadly subparallel to the lithotectonic boundaries, appear at the southern end of the array to be somewhat rotated as if influenced by the presence of an `oblique' structure. It may be wrong to assume the apparent slab structure is stationary in the upper mantle. Helmstaedt and Schulze's [1989] model of continental--root formation by imbrication of subducted Archean plates suggests another possibility, namely subsequent delamination and sinking of one or more plates due to changing

  5. 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

  6. [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.

  7. Ubiquitous Low-Velocity Layer Atop the 410-km Discontinuity in the Northern Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Jasbinsek, J. J.; Dueker, K. G.

    2006-12-01

    Receiver functions (RF) from three 30-station IRIS-PASSCAL small aperture arrays (2-15 km station spacing) operated for ten months each in the northern Rocky Mountains show a ubiquitous negative polarity P to S arrival (NPA) just preceding the 410-km discontinuity arrival. Data from the arrays was divided into NW, SE and SW backazimuths and stacked to form nine quadrant stacks (QS). Remarkably, the NPA is apparent in 8 of the 9 QS, with 7 of the 8 displaying a similar dipole shape (paired negative and positive swings). Each QS contains clear P to S arrivals from the 410- and 660-km discontinuities and display the correct moveout. To model the NPA, a "double gradient slab" model consisting of five parameters is used: top gradient thickness and shear wave velocity drop; a constant velocity layer; bottom gradient thickness and shear wave velocity increase. Model misfit is assessed via a grid search over the model space using a reflectivity code to calculate synthetic seismograms. Assessment of model likelihood is done by calculating 1- and 2-D marginal probability density functions (PDF). Model parameters for each QS are well resolved and uncorrelated, with the exception of the anti-correlation of the top and bottom gradients. To define an average model, the probability distributions of each QS for each parameter are multiplied to form summary 1-D marginal PDF from which 90% probability bounds are calculated. These probability bounds are: the top gradient is < 8 km with a velocity decrement of 0.3-0.5 km/s; the constant velocity layer thickness is < 5 km; and, the bottom gradient is 29-37 km with a velocity increase of 0.4-0.6 km/s. The effective width of the low velocity layer atop the 410 (herein called the 410-LVL) is characterized as the layer thickness plus half the two gradient widths. Thus, the 410-LVL is found to have a mean thickness of 26 km and a mean shear wave velocity decrement of 8.3%. These results contrast with 410-LVL widths of 25-90 km and shear

  8. 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.

  9. Unstable supercritical discontinuous percolation transitions

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Cheng, Xueqi; Zheng, Zhiming; Chung, Ning Ning; D'Souza, Raissa M.; Nagler, Jan

    2013-10-01

    The location and nature of the percolation transition in random networks is a subject of intense interest. Recently, a series of graph evolution processes have been introduced that lead to discontinuous percolation transitions where the addition of a single edge causes the size of the largest component to exhibit a significant macroscopic jump in the thermodynamic limit. These processes can have additional exotic behaviors, such as displaying a “Devil's staircase” of discrete jumps in the supercritical regime. Here we investigate whether the location of the largest jump coincides with the percolation threshold for a range of processes, such as Erdős-Rényipercolation, percolation via edge competition and via growth by overtaking. We find that the largest jump asymptotically occurs at the percolation transition for Erdős-Rényiand other processes exhibiting global continuity, including models exhibiting an “explosive” transition. However, for percolation processes exhibiting genuine discontinuities, the behavior is substantially richer. In percolation models where the order parameter exhibits a staircase, the largest discontinuity generically does not coincide with the percolation transition. For the generalized Bohman-Frieze-Wormald model, it depends on the model parameter. Distinct parameter regimes well in the supercritical regime feature unstable discontinuous transitions—a novel and unexpected phenomenon in percolation. We thus demonstrate that seemingly and genuinely discontinuous percolation transitions can involve a rich behavior in supercriticality, a regime that has been largely ignored in percolation.

  10. 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

  11. 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.

  12. 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. PMID:22442480

  13. The Eifel Plume-imaged with converted seismic waves

    NASA Astrophysics Data System (ADS)

    Budweg, Martin; Bock, Günter; Weber, Michael

    2006-08-01

    Receiver functions (RF) are used to investigate the upper mantle structure beneath the Eifel, the youngest volcanic area of Central Europe. Data from 96 teleseismic events recorded by 242 seismological stations from permanent and a temporary network has been analysed. The temporary network operated from 1997 November to 1998 June and covered an area of approximately 400 × 250 km2 centred on the Eifel volcanic fields. The average Moho depth in the Eifel is approximately 30 km, thinning to ca. 28 km under the Eifel volcanic fields. RF images suggest the existence of a low velocity zone at about 60-90 km depth under the West Eifel. This observation is supported by P- and S-wave tomographic results and absorption (but the array aperture limits the resolution of the tomographic methods to the upper 400 km). There are also indications for a zone of elevated velocities at around 200 km depth, again in agreement with S-wave and absorption tomographic results. This anomaly is not visible in P-wave tomography and could be due to S-wave anisotropy. The RF anomalies at the Moho, at 60-90 km, and near 200 km depth have a lateral extent of about 100 km. The 410 km discontinuity under the Eifel is depressed by 15-25 km, which could be explained by a maximum temperature increase of +200°C to +300°C. In the 3-D RF image of the Eifel Plume we also notice two additional currently unexplained conversions between 410 and 550 km depth. They could represent remnants of previous subduction or anomalies due to delayed phase changes. The lateral extent of these conversions and the depression of the 410 km discontinuity is about 200 km. The 660 km discontinuity does not show any depth deviation from its expected value. Our observations are consistent with interpretation in terms of an upper mantle plume but they do not rule out connections to processes at larger depth.

  14. 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.

  15. 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

  16. 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;…

  17. 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…

  18. 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.

  19. Thermal classification of lithospheric discontinuities beneath USArray

    NASA Astrophysics Data System (ADS)

    Hansen, Steven M.; Dueker, Ken; Schmandt, Brandon

    2015-12-01

    Broadband seismic data from the United States were processed into Ps and Sp receiver function image volumes for the purpose of constraining negative velocity gradients (NVG) at depths between the Moho and 200 km. Moho depth picks from the two independent datasets are in good agreement, however, large discrepancies in NVG picks occur and are attributed to free-surface multiples which obscure deep NVG arrivals in the Ps data. From the Sp data, shallow NVG are found west of the Rockies and in the central US while deep and sporadic NVG are observed beneath the Great Plains and northern Rockies. To aid the interpretation of the observed NVG arrivals, the mantle thermal field is estimated by mapping surface wave tomography velocities to temperature assuming an anelastic olivine model. The distribution of temperature versus NVG depth is bi-modal and displays two distinct thermal populations that are interpreted to represent both the lithosphere-asthenosphere boundary (LAB) and mid-lithosphere discontinuities (MLD). LAB arrivals occur in the western US at 60-85 km and 1200-1400 °C depth suggesting that they manifest partial melt near the base of the thermal plate. MLD arrivals primarily occur at 70-110 km depth and 700-900 °C and we hypothesize that these arrivals are caused by a low-velocity metasomatic layer containing phlogopite resulting from magma crystallization products that accumulate within long-lived thick lithosphere.

  20. 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

  1. 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

  2. The upper-mantle transition zone beneath the Chile-Argentina flat subduction zone

    NASA Astrophysics Data System (ADS)

    Bagdo, Paula; Bonatto, Luciana; Badi, Gabriela; Piromallo, Claudia

    2016-04-01

    The main objective of the present work is the study of the upper mantle structure of the western margin of South America (between 26°S and 36°S) within an area known as the Chile-Argentina flat subduction zone. For this purpose, we use teleseismic records from temporary broad band seismic stations that resulted from different seismic experiments carried out in South America. This area is characterized by on-going orogenic processes and complex subduction history that have profoundly affected the underlying mantle structure. The detection and characterization of the upper mantle seismic discontinuities are useful to understand subduction processes and the dynamics of mantle convection; this is due to the fact that they mark changes in mantle composition or phase changes in mantle minerals that respond differently to the disturbances caused by mantle convection. The discontinuities at a depth of 410 km and 660 km, generally associated to phase changes in olivine, vary in width and depth as a result of compositional and temperature anomalies. As a consequence, these discontinuities are an essential tool to study the thermal and compositional structure of the mantle. Here, we analyze the upper-mantle transition zone discontinuities at a depth of 410 km and 660 km as seen from Pds seismic phases beneath the Argentina-Chile flat subduction.

  3. 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...

  4. Bursts in discontinuous Aeolian saltation.

    PubMed

    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

  5. Discontinuities in Jovian sulphur plasma

    NASA Technical Reports Server (NTRS)

    Mekler, Y.; Eviatar, A.; Siscoe, G. L.

    1979-01-01

    The radial distribution of the Jovian sulfur plasma is discussed. Spectra of the ionized sulfur in the Jovian magnetosphere indicate a sharp discontinuity in visible sulfur emission at a radial distance of six Jupiter radii (Io orbit), outside of which emission is greatly reduced and the plasma is observed not to be in corotation with the planet. Possible explanations of this phenomenon include an effect of Io on the electron temperature outside its orbit, leading to the suppression of S II emission by second ionization, and a current system in Jupiter's ionosphere which prevents plasma from diffusing outward and decouples it from the corotation field. This discontinuity also requires reconciliation with Pioneer observations of the radial and pitch-angle diffusion of energetic charged particles.

  6. 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

  7. Upper mantle shear and compressional velocity structures beneath southern Africa

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Wen, L.; Weidner, D.

    2005-12-01

    The velocity structures in the upper mantle play an important role in understanding mantle composition and temperature. In this study, we constrain the fine seismic shear and compressional velocity structures in the upper mantle beneath southern Africa by waveform modeling the seismic data recorded in the Kaapvaal array at the distance range of 9°-28° for an event occurring near Lake Tanganyika in east Africa. We then explore mineralogical models that would explain the inferred seismic structures. The seismic data recorded at this distance range provide excellent sampling of both the SH and P velocity structures in the top 800 km of the mantle. The first direct arrivals in both the P and SH data become weak at an epicentral distance of about 20°, indicating presence of a low velocity zone beneath southern Africa at a depth of about 150 km. In the SH data, the observed travel times of the reflected and triplicated phases off the 410-km discontinuity require a large shear velocity reduction in the low velocity zone and a small shear velocity jump across the 410-km discontinuity; the observed triplications at the 660-km discontinuity require a large shear velocity jump across the 660-km discontinuity. In the P wave data, the observed travel times of the triplication at the 410-km discontinuity suggest a small P wave velocity reduction in the low velocity zone, a large velocity jump across the 410-km discontinuity and a high Vp/Vs ratio in the transition zone; the triplication at the 660-km discontinuity is indiscernible, suggesting a small P wave velocity jump across the 660-km discontinuity. Overall, the seismic data can be explained by a 150-km thick high-velocity lid overlying a low velocity zone between 150 km and 405 km depths with a P wave velocity reduction of -1.5% and an SH wave velocity reduction of -9%, followed by a small shear velocity jump of 3% and a large P velocity jump of 10% across the 410-km discontinuity, a transition zone with a high Vp

  8. 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.

  9. Discontinuous gas exchange in insects.

    PubMed

    Quinlan, Michael C; Gibbs, Allen G

    2006-11-01

    Insect respiratory physiology has been studied for many years, and interest in this area of insect biology has become revitalized recently for a number of reasons. Technical advances have greatly improved the precision, accuracy and ease with which gas exchange can be measured in insects. This has made it possible to go beyond classic models such as lepidopteran pupae and examine a far greater diversity of species. One striking result of recent work is the realization that insect gas exchange patterns are much more diverse than formerly recognized. Current work has also benefited from the inclusion of comparative methods that rigorously incorporate phylogenetic, ecological and life history information. We discuss these advances in the context of the classic respiratory pattern of insects, discontinuous gas exchange. This mode of gas exchange was exhaustively described in moth pupae in the 1950s and 1960s. Early workers concluded that discontinuous gas exchange was an adaptation to reduce respiratory water loss. This idea is no longer universally accepted, and several competing hypotheses have been proposed. We discuss the genesis of these alternative hypotheses, and we identify some of the predictions that might be used to test them. We are pleased to report that what was once a mature discipline, in which the broad parameters and adaptive significance of discontinuous gas exchange were thought to be well understood, is now a thriving and vigorous field of research. PMID:16870512

  10. 77 FR 33314 - POSTNET Barcode Discontinuation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-06

    ... 111 POSTNET Barcode Discontinuation AGENCY: Postal Service. TM ACTION: Final rule; correction. SUMMARY..., Domestic Mail Manual (DMM ) which discontinued price eligibility based on the use of POSTNET TM barcodes on... Postal Service published a final rule in the Federal Register (77 FR 26185-26191) to discontinue...

  11. Discontinuous Mixed Covolume Methods for Parabolic Problems

    PubMed Central

    Zhu, Ailing

    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 L2. PMID:24983008

  12. 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... Discontinued studies. The fact that a study has been discontinued before the planned termination must be reported to EPA, with the reason for termination, if submission of information concerning the study is,...

  13. 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... Discontinued studies. The fact that a study has been discontinued before the planned termination must be reported to EPA, with the reason for termination, if submission of information concerning the study is,...

  14. 38 CFR 21.9635 - Discontinuance dates.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... individual is enrolled in an institution of higher learning on the date of expiration of his or her period of... Discontinuance dates. The effective date of a reduction or discontinuance of educational assistance will be as... payment, the discontinuance date of educational assistance for the purpose of that lump sum payment...

  15. 38 CFR 21.9635 - Discontinuance dates.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... individual is enrolled in an institution of higher learning on the date of expiration of his or her period of... Discontinuance dates. The effective date of a reduction or discontinuance of educational assistance will be as... payment, the discontinuance date of educational assistance for the purpose of that lump sum payment...

  16. 38 CFR 21.9635 - Discontinuance dates.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... individual is enrolled in an institution of higher learning on the date of expiration of his or her period of... Discontinuance dates. The effective date of a reduction or discontinuance of educational assistance will be as... payment, the discontinuance date of educational assistance for the purpose of that lump sum payment...

  17. A synthesis on lower mantle reflectors/scatterers and discontinuities beneath the western Pacific subduction zones

    NASA Astrophysics Data System (ADS)

    Vanacore, E.; Niu, F.; Kawakatsu, H.

    2004-12-01

    Strong seismic reflectors/scatterers and discontinuities have been observed in the lower mantle at various depths beneath western Pacific subduction zones. The lateral extension of these anomalous structures, however, is not well constrained. The information may hold the key to the understanding of the nature of these seismic structures as well as the related mantle processes. For example, are these seismic anomalies primordial chemical reservoirs, or pieces of subducted oceanic crusts or even parts of a highly heterogeneous global compositional boundary? In this study, we used teleseismic S to P and P to S converted waves to determine the locations and depths of lower reflectors/scatterers and discontinuities in the western Pacific. Our data are collected from several seismic arrays (J-array and Hinet in Japan, the Kaapvaal broadband seismic array, and short-period arrays in the western US) from recent deep earthquakes occurred in the study regions. The spread of conversion points among various arrays allow us to better constrain the lateral extension of the anomalous structure. For example, the mid-mantle discontinuity observed by Niu and Kawakatsu [1997] at the 110° E, 5° S appears to extend to further south and west by at least 100 km once the Kaapvaal data is combined. For the islands in the study region where seismic arrays are available, for example Japan and Indonesia, we also conduct receiver-function imaging to improve geographic coverage. By combining different types of seismic data, we expect to achieve a synthesized view of anomalous structures at middle to lower mantle depths.

  18. Mechanisms and geologic significance of the mid-lithosphere discontinuity in the continents

    NASA Astrophysics Data System (ADS)

    Karato, Shun-Ichiro; Olugboji, Tolulope; Park, Jeffrey

    2015-07-01

    The stable continents have a puzzling structure. Recent seismological studies have revealed a marked drop in seismic velocity at middle-lithosphere depths, but a generally small velocity drop at the lithosphere-asthenosphere boundary. The mid-lithosphere discontinuity has previously been attributed to changes in composition and/or crystal alignment (anisotropy) caused by metasomatic alteration, as well as to partial melting and/or accretion of intruded materials that occurred after the formation of the continents. We show that these models cannot easily explain the global presence of a large seismic velocity drop in the middle lithosphere and a small velocity change at the lithosphere-asthenosphere boundary. These models are also difficult to reconcile with long-term continental stability and, in particular, observations of nearly depth-invariant ages of rocks in the continental lithosphere that do not support the notion of late alteration events. Instead, we propose an elastically accommodated grain-boundary sliding model that predicts a substantial velocity drop at the mid-lithosphere discontinuity and a weak seismic signal at the lithosphere-asthenosphere boundary, as observed, without invoking late-stage modifications to the lithosphere. In this model, the mid-lithosphere discontinuity is a general feature of the stable continents, the precise depth of which depends primarily on temperature and water content. Consequently, the depth of the mid-lithosphere discontinuity may provide clues to the evolution of continents.

  19. Upper mantle structure beneath the Japan Islands using single-scattering analysis

    NASA Astrophysics Data System (ADS)

    Tonegawa, T.; Hirahara, K.; Shibutani, T.; Shiomi, K.

    2006-12-01

    In the Japan subduction zone where the Pacific plate is subducting, we can investigate the dynamics of the upper mantle beneath the subduction zone, such as the structure of the descending slab, the undulation of the seismic discontinuities and its relation, by imaging the detailed structure beneath the Japan Islands. The high sensitivity accelerometer (hereafter tiltmeter) network has recently been deployed with high-density spacing (700 stations in Japan) by NIED, and these tiltmeters can be used as long-period seismometer. In this study, we used these recordings to image upper mantle discontinuities, including the subducting Pacific slab from the Japan trench and the 410 and 660 km discontinuities, beneath the Japanese Islands by calculating receiver functions with teleseismic waves. For deconvolution, since tiltmeter seismograms have just horizontal component, we obtained source-time function by stacking all of vertical components observed at F-net broadband stations, that is, we consider these stacked waveforms as source-time functions. We applied a low- pass filter of 0.16 Hz. Assuming all later phases of P-coda in receiver function are the P-to-S scattered phases, we migrated time-domain receiver functions to depth section using 1-D JMA velocity model. As a result, the seismic discontinuities correspoding to the oceanic Moho and lower boundary of the descending slab can be imaged down to 400 km and 500 km depth, respectively. The 410 km and 660 km discontinuities are clearly imaged, and our result also shows a depression of the 660 km discontinuity affected by the stagnant slab.

  20. Multiscale seismic attributes: source-corrected wavelet response and application to high-resolution seismic data

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

    A wavelet-based method was presented in a previous work to introduce multiscale seismic attributes for high-resolution seismic data. Because of the limited frequency bandwidth of the seismic source, we observed distortions in the seismic attributes based on the wavelet response of the subsurface discontinuities (Le Gonidec et al.). In this paper, we go further in the seismic source-correction by considering Lévy alpha-stable distributions introduced in the formalism of the continuous wavelet transform (CWT). The wavelets are Gaussian derivative functions (GDF), characterized by a derivative order. We show that a high-resolution seismic source, after a classical signature processing, can be taken into account with a GDF. We demonstrate that in the framework of the Born approximation, 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. We apply the method for the SYSIF seismic device (Marsset et al.; Ker et al.) and show that the source-corrections allow to define seismic attributes for layer thicknesses in the range [24; 115 cm]. We present the analysis for two seismic reflectors identified on a SYSIF profile, and we show that the source-corrected multiscale analysis quantifies their complex geometries.

  1. Premature discontinuation of contraception in Australia.

    PubMed

    Bracher, M; Santow, G

    1992-01-01

    Life-history data from a nationally representative survey of Australian women were used to examine discontinuation of contraceptive methods because of accidental pregnancy, side effects or dissatisfaction. The pill was the most successfully used method, with a first-year discontinuation rate of 10% for all three reasons. Side effects dominated the reasons for the premature discontinuation of both the pill and the IUD, while the reasons for discontinuing the condom stemmed equally from pregnancy and dissatisfaction with the method. Discontinuation of the diaphragm resulted largely from accidental pregnancy. Hazards models were used to identify the correlates of discontinuation of each method. Predictors of premature discontinuation reflect the availability of methods, physiological reactions to them and the social characteristics of their users. Discontinuation of the pill because of side effects or dissatisfaction was more likely among poorly educated women, non-Protestants and recent users, and less likely among teenagers. Discontinuation of the IUD was related entirely to physiological factors: Nulliparous women and users of unmedicated devices were at a greater risk than other women of accidental pregnancy, and nulliparous women were at greater risk of discontinuation associated with side effects. Nulliparous women were also more likely to discontinue the condom because of pregnancy, as were non-Protestants and the Australian-born. PMID:1612144

  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. Flame front as hydrodynamic discontinuity

    NASA Astrophysics Data System (ADS)

    Fukumoto, Yasuhide; Abarzhi, Snezhana

    2012-11-01

    We applied generalized Rankine-Hugoniot conditions to study the dynamics of unsteady and curved fronts as a hydrodynamic discontinuity. It is shown that the front is unstable and Landau-Darrieus instability develops only if three conditions are satisfied (1) large-scale vorticity is generated in the fluid bulk; (2) energy flux across the front is imbalanced; (3) the energy imbalance is large. The structure of the solution is studied in details. Flows with and without gravity and thermal diffusion are analyzed. Stabilization mechanisms are identified. NSF 1004330.

  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. Seismicity on the area of the Waste Isolation Pilot Plant (WIPP)

    SciTech Connect

    Sanford, A.; Sanford, S.; Wallace, T.; Barrows, L.; Sheldon, J.; Ward, R.; Johansen, S.; Merritt, L.

    1980-05-01

    Since April 1974, New Mexico Institute of Mining and Technology (NMIMT) has operated a short-period vertical-component seismograph 7 km from the center of the WIPP site. Peak magnifications ranged from 405 K to 1400 K. In the time period from April 1974 to February 1979, approximately 500 earthquakes were recorded by the instrument to distances as great as 660 km. With the aid of readings from stations operated by other organizations, epicenters and magnitudes for 159 earthquakes within about 300 km of the WIPP site were obtained. The greatest concentration of seismic activity is centered on the Central Basin Platform. This zone of activity, approximately 120 km in a NS direction and 100 km in an EW direction, approaches to within 60 km of the site. Other significant clusters of earthquakes occur near Synder, Big Springs and Valentine, Texas. Comparable levels of earthquake activity are observed within 100, 200, and 300 km of the site. Most reported Quaternary faulting lies to the west of 104.3/sup 0/W longitude. Comparable levels of activity were observed to the east and west of this longitude indicating the observed distribution of earthquake activity is probably not representative of the long-term (500,000 years) seismicity of the region. Several lines of evidence suggest that most earthquakes from the Delaware Basin eastward are induced by the production of hydrocarbons, but absolutely convincing proof is lacking. If due to natural tectonic forces, an extrapolation of the observed earthquake-frequency relation indicates an earthquake of magnitude 5 1/2 is possible somewhere within 300 km of the site each 100 years.

  6. A ubiquitous low-velocity layer at the base of the mantle transition zone

    NASA Astrophysics Data System (ADS)

    Shen, Xuzhang; Yuan, Xiaohui; Li, Xueqing

    2014-02-01

    Global stacks of receiver functions clearly exhibit the upper mantle stratification. Besides the most prominent seismic discontinuities, such as the Moho and the 410 and 660 km discontinuities, a negative discontinuity is detected at a depth of ~600 km, indicating a low-velocity layer at the base of the mantle transition zone. The slant-slack technique helps to identify the primary conversions from the multiple reverberations. Presence of the negative 600 km discontinuity underneath both continent and ocean island stations, where the crustal thickness significantly differs, also precludes the possible cause of crustal reverberations. We conclude that the negative 600 km discontinuity could be a global feature, possibly resulted from accumulation of ancient subducted oceanic crust. The X-discontinuity at ~300 km depth is also observed in our global stacks, which can be explained by the coesite-stishovite phase transformation.

  7. Receiver function images of the mantle transition zone beneath NE China: New constraints on intraplate volcanism, deep subduction and their potential link

    NASA Astrophysics Data System (ADS)

    Liu, Zheng; Niu, Fenglin; Chen, Yongshun John; Grand, Steve; Kawakatsu, Hitoshi; Ning, Jieyuan; Tanaka, Satoru; Obayashi, Masayuki; Ni, James

    2015-02-01

    In order to better understand the deep subduction geometry of the Pacific plate and genesis of intraplate volcanism in northeast China (NE China), we computed a total of 45,505 receiver functions from 788 teleseismic events recorded by 255 stations (NECESSArray temporal and permanent stations) in NE China. We used a common-conversion-point stacking (CCP) method to generate a 3D reflectivity volume beneath the study area. To position the P-to-S conversions to the correct depths, we employed 3D crustal and mantle models as references to make time to depth conversion. The 3D reflectivity volume was generated in an area between 115°-135°E and 40°-49°N, in the depth range of 300 to 800 km. We found significant topographic relief on the 660-km discontinuity across the study area. In particular, in a westward Pacific plate subduction section between 40°N and ∼45.5°N, the 660-km discontinuity is depressed by as much as ∼30-40 km along the western extension of the deep seismicity. The depression is elongated along the strike of the deep seismicity and is confined to a 200-300 km region in the E-W direction of subduction. To the west of this depression the 660-km discontinuity is uplifted by 5-10 km in a rectangular area of ∼100 km by 200 km centered at about 125°E and 43°N. In the north, the 660-km discontinuity is moderately depressed (∼20 km) in a broad area that extends further west. The high and low regions in the 660-km topographic map correlate, respectively, with low- and high-velocity anomalies in the P- and S-wave tomographic velocity images at the same depth. Our results suggest that slab stagnation might not be occurring in the southern part of the NE China, where the Changbaishan volcanic complex is located, thus the magmatism is unlikely caused by dehydration of the flat-lying Pacific slab in the transition zone. The low velocity mantle upwelling arising from a gap of stagnant slabs is a likely source that feeds the volcanic complex in NE China.

  8. 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.

  9. 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.

  10. 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.

  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. 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

  13. 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

  14. 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

  15. Student Discontinuations: Is the System Failing?

    ERIC Educational Resources Information Center

    McSherry, Wilfred; Marland, Glenn R.

    1999-01-01

    Discusses factors associated with fairness and equity in relation to student discontinuation in nursing education. Shows how discontinuation is an integral part of higher education quality reviews. Promotes pre-exit counseling, monitoring of attrition, and review of academic and professional standards. (SK)

  16. 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…

  17. Discontinuous Galerkin Methods: Theory, Computation and Applications

    SciTech Connect

    Cockburn, B.; Karniadakis, G. E.; Shu, C-W

    2000-12-31

    This volume contains a survey article for Discontinuous Galerkin Methods (DGM) by the editors as well as 16 papers by invited speakers and 32 papers by contributed speakers of the First International Symposium on Discontinuous Galerkin Methods. It covers theory, applications, and implementation aspects of DGM.

  18. 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...

  19. 38 CFR 21.7135 - Discontinuance dates.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) 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...

  20. 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...

  1. 27 CFR 11.38 - Discontinued products.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Discontinued products. 11.38 Section 11.38 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU... products. When a producer or importer discontinues the production or importation of a product, a...

  2. Evidence for coronavirus discontinuous transcription.

    PubMed Central

    Jeong, Y S; Makino, S

    1994-01-01

    Coronavirus subgenomic mRNA possesses a 5'-end leader sequence which is derived from the 5' end of genomic RNA and is linked to the mRNA body sequence. This study examined whether coronavirus transcription involves a discontinuous transcription step; the possibility that a leader sequence from mouse hepatitis virus (MHV) genomic RNA could be used for MHV subgenomic defective interfering (DI) RNA transcription was examined. This was tested by using helper viruses and DI RNAs that were easily distinguishable. MHV JHM variant JHM(2), which synthesizes a subgenomic mRNA encoding the HE gene, and variant JHM(3-9), which does not synthesize this mRNA, were used. An MHV DI RNA, DI(J3-9), was constructed to contain a JHM(3-9)-derived leader sequence and an inserted intergenic region derived from the region preceding the MHV JHM HE gene. DI(J3-9) replicated efficiently in JHM(2)- or JHM(3-9)-infected cells, whereas synthesis of subgenomic DI RNAs was observed only in JHM(2)-infected cells. Sequence analyses demonstrated that the 5' regions of both helper virus genomic RNAs and genomic DI RNAs maintained their original sequences in DI RNA-replicating cells, indicating that the genomic leader sequences derived from JHM(2) functioned for subgenomic DI RNA transcription. Replication and transcription of DI(J3-9) were observed in cells infected with an MHV A59 strain whose leader sequence was similar to that of JHM(2), except for one nucleotide substitution within the leader sequence. The 5' region of the helper virus genomic RNA and that of the DI RNA were the same as their original structures in virus-infected cells, and the leader sequence of DI(J3-9) subgenomic DI RNA contained the MHV A59-derived leader sequence. The leader sequence of subgenomic DI RNA was derived from that of helper virus; therefore, the genomic leader sequence had a trans-acting property indicative of a discontinuous step in coronavirus transcription. Images PMID:8139040

  3. Mantle transition zone structure beneath India and Western China from migration of PP and SS precursors

    NASA Astrophysics Data System (ADS)

    Lessing, Stephan; Thomas, Christine; Rost, Sebastian; Cobden, Laura; Dobson, David P.

    2014-04-01

    We investigate the seismic structure of the upper-mantle and mantle transition zone beneath India and Western China using PP and SS underside reflections off seismic discontinuities, which arrive as precursors to the PP and SS arrival. We use high-resolution array seismic techniques to identify precursory energy and to map lateral variations of discontinuity depths. We find deep reflections off the 410 km discontinuity (P410P and S410S) beneath Tibet, Western China and India at depths of 410-440 km and elevated underside reflections of the 410 km discontinuity at 370-390 km depth beneath the Tien Shan region and Eastern Himalayas. These reflections likely correspond to the olivine to wadsleyite phase transition. The 410 km discontinuity appears to deepen in Central and Northern Tibet. We also find reflections off the 660 km discontinuity beneath Northern China at depths between 660 and 700 km (P660P and S660S) which could be attributed to the mineral transformation of ringwoodite to magnesiowuestite and perovskite. These observations could be consistent with the presence of cold material in the middle and lower part of the mantle transition zone in this region. We also find a deeper reflector between 700 and 740 km depth beneath Tibet which cannot be explained by a depressed 660 km discontinuity. This structure could, however, be explained by the segregation of oceanic crust and the formation of a neutrally buoyant garnet-rich layer beneath the mantle transition zone, due to subduction of oceanic crust of the Tethys Ocean. For several combinations of sources and receivers we do not detect arrivals of P660P and S660S although similar combinations of sources and receivers give well-developed P660P and S660S arrivals. Our thermodynamic modelling of seismic structure for a range of compositions and mantle geotherms shows that non-observations of P660P and S660S arrivals could be caused by the dependence of underside reflection coefficients on the incidence angle of the

  4. 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.

  5. 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.

  6. 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)

  7. 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

  8. [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

  9. Signal integrity analysis on discontinuous microstrip line

    NASA Astrophysics Data System (ADS)

    Qiao, Qingyang; Dai, Yawen; Chen, Zipeng

    2013-03-01

    In high speed PCB design, microstirp lines were used to control the impedance, however, the discontinuous microstrip line can cause signal integrity problems. In this paper, we use the transmission line theory to study the characteristics of microstrip lines. Research results indicate that the discontinuity such as truncation, gap and size change result in the problems such as radiation, reflection, delay and ground bounce. We change the discontinuities to distributed parameter circuits, analysed the steady-state response and transient response and the phase delay. The transient response cause radiation and voltage jump.

  10. 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.

  11. 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

  12. Receiver Function Diffractional Tomography of Mantle Transition Zone Structure

    NASA Astrophysics Data System (ADS)

    Zhou, Ying

    2015-04-01

    Teleseismic P waves generate secondary converted S waves at major seismic discontinuities. The converted S waves arrive in the P -wave coda and provide important constraints on the depths of the discontinuities. Receiver Functions are based on spectral ratios between horizontal and vertical component P-wave coda seismograms and have been widely used to study the structure of seismic discontinuities. Traditional Receiver Function studies are based on ray theory, which is a high-frequency approximation and breaks down when the length scale of discontinuity depth perturbations becomes comparable to or smaller than the size of the Fresnel zone. To account for wave diffraction effects in Receiver Function imaging, we calculate finite-frequency sensitivity of Receiver Functions to depth perturbations of the 410-km and 660-km discontinuities. The boundary sensitivity kernels are formulated in the framework of traveling-wave mode summation to account for complete wave interactions within the measurement window. The sensitivity kernels allow us to image high-resolution topographic structure of the mantle transition zone discontinuities beneath the continental United States using Receiver Functions at USArray TA stations. The 2-D tomographic problems are solved in regularized least-square inversions. The 410-km and 660-km discontinuities in our model show ~10-20 km of downward deflection in regions associated with fast seismic (slab) anomalies, and the geometry of the discontinuity anomalies suggests a NW/SE orientation of the subducting slab. The perturbations in transition zone thickness in general agree with a thermal origin but show significant small-scale variations with thinning of the transition zone along a NE channel where the slab breaks apart. The amount of thinning (~10 km) of the transition zone is similar to that beneath the Yellowstone hotspot.

  13. Lithospheric discontinuities beneath Australia: interaction of large-scale and fine scale structure

    NASA Astrophysics Data System (ADS)

    Kennett, Brian L. N.; Yoshizawa, Kazunori

    2016-04-01

    Understanding the complex heterogeneity of the continental lithosphere involves a wide variety of spatial scales and the synthesis of multiple classes of information. Seismic surface waves and multiply reflected body waves provide the main information on broad-scale structure, and bounds on the extent of the lithosphere-asthenosphere transition (LAT) can be found from the vertical gradients of S wavespeed. Information on finer scale structures comes though body wave studies, including detailed seismic tomography and P wave reflectivity extracted from stacked autocorrelograms of continuous component records. With the inclusion of deterministic large-scale structure and realistic medium-scale stochastic features there is not a need for strong fine-scale variations. The resulting multi-scale heterogeneity model for the Australian region gives a good representation of the character of observed seismograms and their geographic variations and matches the observations of P wave reflectivity. The presence of reflections in the 0.5-3.0 Hz band in the uppermost mantle suggests variations on vertical scales of a few hundred metres with amplitudes of the order of 1%. There are some indications of a change of reflection character in the lower part of the lithosphere in the transition to the asthenosphere. In some parts of central Australia there is a reasonable tie between a change in reflectivity and other information on mid-lithospheric discontinuities. Individual seismic probes illuminate different aspects of the heterogeneity, but the full spectrum has to be taken into account to understand the properties of apparent discontinuities and their geodynamic implications. Once fine-scale structure is taken into consideration it becomes apparent that wave interference plays a very important role in determining the nature of apparent discontinuities seen with lower frequency probes such as S wave receiver functions. Changes in the character of fine-scale heterogeneity can

  14. Refined seismic stratigraphy in prograding carbonates

    SciTech Connect

    Pomar, L. )

    1991-03-01

    Complete exposure of the upper Miocene Reef Complex in the sea cliffs of Mallorca (Spain) allows for a more refined interpretation of seismic lines with similar progradational patterns. A 6 km long high-resolution cross section in the direction of reef progradation displays four hierarchical orders of accretional units. Although all these units are of higher order, they all exhibit similar characteristics as a third order depositional sequence and can likewise be interpreted as the result of high order sea-level cycles. The accretional units are composed of lagoonal horizontal beds, reefal sigmoids and gently dipping slope deposits. They are bounded by erosion surfaces at the top and basinwards by their correlative conformities. These architectural patterns are similar to progradational sequences seen on seismic lines. On seismic lines, the progradational pattern often shows the following geometrical details: (1) discontinuous climbing high-energy reflectors, (2) truncation of clinoforms by these high-energy reflectors with seaward dips, (3) transparent areas intercalated between clinoforms. Based on facies distribution in the outcrops of Mallorca the high-energy reflectors are interpreted as sectors where the erosion surfaces truncated the reef wall and are overlain by lagoonal sediments deposited during the following sealevel rise. The more transparent zones seem to correspond with areas of superposition of undifferentiated lagoonal beds. Offlapping geometries can also be detected in highest quality seismic lines. The comparison between seismic and outcrop data provides a more accurate prediction of lithologies, facies distribution, and reservoir properties on seismic profiles.

  15. Discontinuation of Statins: What Are the Risks?

    PubMed

    Marrs, Joel C; Kostoff, Matthew D

    2016-07-01

    The key benefits of statin therapy have been well established in both primary and secondary prevention cardiovascular patients. Many studies have shown a significant statin discontinuation rate within the first year of initiation whether for primary or secondary prevention. National guidelines for the management of dyslipidemia highlight the lack of benefit seen with statin therapy in patients with chronic kidney disease receiving dialysis, heart failure with reduced ejection fraction, and patients greater than 75 years of age without atherosclerotic cardiovascular disease. Available data outside of these patient populations do not support discontinuation of statin therapy. Recent studies support an association with statin discontinuation and increased risk of myocardial infarction and cardiovascular death. Based on the available data, discontinuation of statin therapy should be carefully considered. PMID:27221503

  16. 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.

  17. 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

  18. Discontinuity Detection for Analysis of Telerobot Trajectories

    NASA Technical Reports Server (NTRS)

    Yeom, Kiwon; Ellis, Stephen R.; Adelstein, Bernard D.

    2013-01-01

    To identify spatial and temporal discontinuities in telerobot movement in order to describe the shift in operators control and error correction strategies from continuous control to move-and-wait strategies. This shift was studied under conditions of simulated increasingly time-delayed teleoperation. The ultimate goal is to determine if the time delay associated with the shift is invariant with independently imposed control difficulty. We expect this shift to manifest itself as changes in the number of discontinuity of movement path. We proposed an approach to spatial and temporal discontinuity detection algorithm for analysis of teleoperated trajectory in three dimensional space. The algorithm provides a simple and potentially objective method for detecting the discontinuity during telerobot operation and evaluating the difficulty of rotational coordinate condition in teleoperation.

  19. Reducing discontinuation in family planning programs.

    PubMed

    Roberts, D; Panitchpakdi, P; Loevinsohn, B

    1993-01-01

    Management strategies for reducing discontinuation in family planning programs are summarized; the strategies are practical and show how to analyze data for women who stop using contraception. Common factors that are associated with high levels of discontinuation are identified. Recommendations are made for how program managers can change service delivery in order to improve client continuation. Understanding the size and nature of discontinuation is an important precursor to a solution. Data collection on discontinuation could be combined with a system for tracking and follow-up of individual clients. The reasons that women stop using contraception are identified as those which clinics can or cannot control. A clinic discontinues is one who is a "no show" within a reasonable period of time. Decisions need to be made about the type of discontinues to be tracked, e.g. all new acceptors or pill users only. How to identify no shows, how to use the daily register tracking system, and how to calculate discontinuation rates are described. A special daily record tracking system can be used to track clients over years and does not replace the client medical and reproductive history record. The advantages are that client forms to not have to be redesigned and staff training is simple. The disadvantages apply to large clinics and the need for ample filing areas and proper management. An example is given of a working solution in Kenya for a community-based distribution program. Discontinuation rates may be calculated in various ways; a more exact measure tends to be the most useful. Recalculating discontinuation rates at regular intervals can provide an effective way to check standards of care. A tally sheet can be used to track characteristics of discontinues; a sample is given and analyzed to show interpretations which point the way to program changes. Comparisons may be made by age, method type, length of use. An example is given of the Rwanda service delivery system and

  20. 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.

  1. 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

  2. Co-Seismic Deformations Impact on Geodetic Time Series and Reference Frame Determination

    NASA Astrophysics Data System (ADS)

    Metivier, L.; Collilieux, X.; Lercier, D.; Altamimi, Z.; Beauducel, F.

    2014-12-01

    One of the major sources of error in reference frame determination comes from the undetected discontinuities in station position time series, particularly in GNSS data. Until now, discontinuities in station position time series due to large earthquakes were usually detected visually. Based on a geophysical modeling, we develop a method to predict the effect of co-seismic deformations on position series. Investigating a global network of GPS stations, we demonstrate that a systematic global modeling of co-seismic deformations helps greatly to detect discontinuities in GPS coordinate time series. We show that numerous discontinuities induced by earthquakes are too small to be visually detected because of seasonal variations and GPS noise that disturb their identification. However, not taking these discontinuities into account has a large impact on the station velocity estimation, considering today's precision requirements. Beyond time series discontinuities, we also investigate GPS station displacements induced by two decades of accumulated seismicity. We show here that the accumulation of very small co-seismic deformations may explain non-linear behaviors of GPS station position. It raises the unexpected question of the treatment of such station non-linear motions in reference frame elaboration.

  3. 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

  4. 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...

  5. 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...

  6. 27 CFR 478.57 - 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... 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. 27 CFR 478.127 - Discontinuance of business.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 3 2011-04-01 2010-04-01 true 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...

  12. 27 CFR 555.128 - Discontinuance of business.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 3 2011-04-01 2010-04-01 true 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...

  13. 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...

  14. 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...

  15. 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...

  16. Identifying the Factors Underlying Discontinuation of Triptans

    PubMed Central

    Wells, Rebecca E.; Markowitz, Shira Y.; Baron, Eric P.; Hentz, Joseph G.; Kalidas, Kavita; Mathew, Paul G.; Halker, Rashmi; Dodick, David W.; Schwedt, Todd J.

    2014-01-01

    Objective To identify factors associated with triptan discontinuation among migraine patients. Background It is unclear why many migraine patients who are prescribed triptans discontinue this treatment. This study investigated correlates of triptan discontinuation with a focus on potentially modifiable factors to improve compliance. Methods This multi-center cross-sectional survey (n=276) was performed at U.S. tertiary care headache clinics. Headache fellows who were members of the American Headache Society Headache Fellows Research Consortium recruited episodic and chronic migraine patients who were current triptan users (use within prior 3 months and for ≥ 1 year) or past triptan users (no use within 6 months; prior use within 2 years). Univariate analyses were first completed to compare current triptan users to past users for: migraine characteristics, other migraine treatments, triptan education, triptan efficacy, triptan side effects, type of prescribing provider, Migraine Disability Assessment (MIDAS) scores and Beck Depression Inventory (BDI) scores. Then, a multivariable logistic regression model was selected from all possible combinations of predictor variables to determine the factors that best correlated with triptan discontinuation. Results Compared to those still using triptans (n=207), those who had discontinued use (n=69) had higher rates of medication overuse (30 vs. 18%, p=0.04), were more likely to have ever used opioids for migraine treatment (57 vs. 38%, p=0.006) as well as higher MIDAS (mean 63 vs. 37, p=0.001) and BDI scores (mean 10.4 vs. 7.4, p=0.009). Compared to discontinued users, current triptan users were more likely to have had their triptan prescribed by a specialist (neurologist, headache specialist, or pain specialist) (74 vs. 54%, p=0.002) and were more likely to report headache resolution (53 vs. 14%, p<0.001) or a reduction in pain intensity (71 vs. 28%, p<0.001) most of the time from their triptan. On a 1-5 scale (1=disagree

  17. 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.

  18. 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

  19. Selective serotonin reuptake inhibitor discontinuation during pregnancy

    PubMed Central

    Ejaz, Resham; Leibson, Tom; Koren, Gideon

    2014-01-01

    Abstract Question I have a patient who discontinued her selective serotonin reuptake inhibitor in pregnancy against my advice owing to fears it might affect the baby. She eventually attempted suicide. How can we deal effectively with this situation? Answer The “cold turkey” discontinuation of needed antidepressants is a serious public health issue strengthened by fears and misinformation. It is very important for physicians to ensure that evidence-based information is given to women in a way that is easy to understand. The risks of untreated moderate to severe depression far outweigh the theoretical risks of taking selective serotonin reuptake inhibitors. PMID:25642484

  20. 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.

  1. 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.

  2. 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.

  3. Seismic refraction exploration

    SciTech Connect

    Ruehle, W.H.

    1980-12-30

    In seismic exploration, refracted seismic energy is detected by seismic receivers to produce seismograms of subsurface formations. The seismograms are produced by directing seismic energy from an array of sources at an angle to be refracted by the subsurface formations and detected by the receivers. The directivity of the array is obtained by delaying the seismic pulses produced by each source in the source array.

  4. 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

  5. High resolution upper mantle discontinuity images across the Pacific Ocean from SS precursors using local slant stack filters

    NASA Astrophysics Data System (ADS)

    Zheng, Zhao; Ventosa, Sergi; Romanowicz, Barbara

    2015-07-01

    SS precursor observations are a powerful tool to study the topography and character of transition zone discontinuities, especially in regions such as ocean basins where few seismic stations exist, precluding other high resolution approaches. Still, the available coverage is limited by the distribution of sources and stations, but also by the level of noise and by the fact that, in some distance ranges, interfering seismic phases mask the weak signal from the SS precursors. We introduce an array data processing tool, the local slant-stack filter, to address these challenges and clean up the otherwise noisy SS precursor record sections. We show that these filters are a powerful tool for extracting the weak yet coherent SS precursor signals while removing interfering seismic phases as well as random noise, yielding robust precursor traveltime measurements with spatial resolution higher than what can be achieved by the conventional common midpoint stacking method. The effectiveness of the filters are demonstrated by application to synthetic and real data. We systematically apply this filtering method to an SS precursor data set recorded by the U.S. Transportable Array that samples a vast region of the Pacific Ocean and its northwest margin, and present maps of 410 and 660 discontinuity topography. We discuss correlations observed between our discontinuity images and several fine-scale heterogeneities revealed by mantle shear wave tomography in the vicinity of Hawaii and the Pacific Superswell.

  6. 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.

  7. 38 CFR 21.4135 - Discontinuance dates.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ....4135, see the List of CFR Sections Affected, which appears in the Finding Aids section of the printed...) VOCATIONAL REHABILITATION AND EDUCATION Administration of Educational Assistance Programs Payments... veteran or eligible person dies while pursuing a program of education, the discontinuance date...

  8. 38 CFR 21.7635 - Discontinuance dates.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) VOCATIONAL REHABILITATION AND EDUCATION Educational Assistance for Members of the Selected Reserve Payments...) In all other cases if the reservist dies while pursuing a program of education, the discontinuance...) (k) Incarceration in prison or penal institution for conviction of a felony. (1) The provisions...

  9. 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.

  10. 38 CFR 21.9635 - Discontinuance dates.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) VOCATIONAL REHABILITATION AND EDUCATION Post-9/11 GI Bill Payments-Educational Assistance § 21.9635... individual dies while pursuing a program of education, the discontinuance date of educational assistance will... effective the last date of attendance; and (ii) Independent study or distance learning effective on...

  11. 38 CFR 21.9635 - Discontinuance dates.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) VOCATIONAL REHABILITATION AND EDUCATION Post-9/11 GI Bill Payments-Educational Assistance § 21.9635... individual dies while pursuing a program of education, the discontinuance date of educational assistance will... effective the last date of attendance; and (ii) Independent study or distance learning effective on...

  12. 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.

  13. Life and Literature: Continuities and Discontinuities

    ERIC Educational Resources Information Center

    Freeman, Mark

    2007-01-01

    This essay calls attention, first, to some of the significant discontinuities between life and literature, living and telling. Perhaps foremost among them is the fact that while living takes place now, in the present moment, telling must await the passage of time. This element of delay, it is argued, underscores the potential importance of…

  14. General practitioners' decisions about discontinuation of medication: an explorative study.

    PubMed

    Nixon, Michael Simon; Vendelø, Morten Thanning

    2016-06-20

    Purpose - The purpose of this paper is to investigate how general practitioners' (GPs) decisions about discontinuation of medication are influenced by their institutional context. Design/methodology/approach - In total, 24 GPs were interviewed, three practices were observed and documents were collected. The Gioia methodology was used to analyse data, drawing on a theoretical framework that integrate the sensemaking perspective and institutional theory. Findings - Most GPs, who actively consider discontinuation, are reluctant to discontinue medication, because the safest course of action for GPs is to continue prescriptions, rather than discontinue them. The authors conclude that this is in part due to the ambiguity about the appropriateness of discontinuing medication, experienced by the GPs, and in part because the clinical guidelines do not encourage discontinuation of medication, as they offer GPs a weak frame for discontinuation. Three reasons for this are identified: the guidelines provide dominating triggers for prescribing, they provide weak priming for discontinuation as an option, and they underscore a cognitive constraint against discontinuation. Originality/value - The analysis offers new insights about decision making when discontinuing medication. It also offers one of the first examinations of how the institutional context embedding GPs influences their decisions about discontinuation. For policymakers interested in the discontinuation of medication, the findings suggest that de-stigmatising discontinuation on an institutional level may be beneficial, allowing GPs to better justify discontinuation in light of the ambiguity they experience. PMID:27296879

  15. 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.

  16. 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.

  17. Seismic wave propagation through an in-situ stressed rock mass

    NASA Astrophysics Data System (ADS)

    Fan, L. F.; Sun, H. Y.

    2015-10-01

    This paper presents an analytical study of seismic wave propagation through an in-situ stressed rock mass. The joint deformation is assumed to satisfy the nonlinear Bandis-Barton (B-B) deformational model. The displacement discontinuity method (DDM) is introduced to take account of the effect of in-situ stress. The amplitude- and frequency-dependence of seismic wave propagation through an in-situ stressed rock mass are analyzed. The effects of in-situ stress on seismic attenuation, energy transmission and effective seismic velocity are discussed. The results show that seismic attenuation, energy transmission and effective seismic velocity are influenced by seismic wave amplitude and frequency, and in-situ stress. Moreover, the amplitude- and frequency-dependence of a seismic wave obtained by conventional DDM are special cases when in-situ stress is not considered. The effect of in-situ stress on seismic attenuation, energy transmission and effective seismic velocity can be neglected when either the amplitude or the frequency is sufficiently large. When the frequency is sufficiently small, the effect of in-situ stress on seismic attenuation and energy transmission can also be neglected, but its effect on the effective seismic velocity cannot be ignored.

  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. 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.

  20. 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

  1. Receiver Function Images of Crust and Upper Mantle: Evidence For Depp-seated Differences Between Precambrian and Paleozoic Provinces In Northern Europe

    NASA Astrophysics Data System (ADS)

    Alinaghi, A.; Bock, G.; Kind, R.; Tor Working Group; Svekalapko Working Group

    The crust-mantle boundary and upper mantle discontinuities underneath the North German Basin, the Tornquist Zone and the Baltic Shield have been detected and inves- tigated by receiver functions. Teleseismic earthquakes recorded by the TOR seismic profile and the SVEKALAPKO seismic network have been used to calculate distance and source equalized receiver functions. To enhance converted P-to-S amplitudes and to enable a consistent mapping of discontinuities, receiver functions were stacked and the arrival times of Ps were measured and plotted over the study area. The resulting delay time map of Moho is accompanied by crustal thickness measurement made us- ing Zhu &Kanamori Method so that both maps show considerable thickening of crust across the TESZ from 30 km in the German Basin to over 50 km in the Scandinavian Shield. In the Blatic Shield across SVEKALAPKO seismic network Moho takes on a complex shape in sharp contrast to the flat surface topography. Moho depths ranging from 40 to 60 km are observed under the SVEKALAPKO stations . The two major 410 km and 660 km upper mantle discontinuities are clearly observed both under the TOR profile and underneath the SVEKALAPKO network. Maps depicting the arrival times of Ps phases stemming from each of those discontinuities are presented along with a Map of the time difference between the arrival times of the aforementioned phases. While the arrival times of Ps from 410 km and 660 km discontinuities un- dergo changes across the TESZ, the difference between the arrival times of P410s and P660s phases, being a measure of the thickness of the transition zone, grows larger . This is an indication of cooler upper mantle underneath the Baltic Shield( Precam- brian) than that of the North German Basin(Paleozoic). Across the SVEKALAPKO profile the thickness of the transition zone shows signs of increase in the eastern part while traces of some local anomalies can be found in the central parts.

  2. 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.

  3. Seismic resolution of lowermost mantle structure

    NASA Astrophysics Data System (ADS)

    Hempel, Stefanie; Thomas, Christine; Nissen-Meyer, Tarje

    2015-04-01

    We use the axisymmetric, spherical Earth spectral elements code AxiSEM to model seismic compressional waves which sample laterally varying lowermost mantle structures. Synthetic seismograms with dominant periods between 1 and 16 seconds are computed for approximately 1500 models of D'' heterogeneities varying in thickness, lateral wavelength, topographic behaviour and elastic properties. We use high-resolution array seismological stacking techniques to process the synthetic data. Our study shows, that the position of the reflector inferred from 1D backprojecting techniques as used in previous studies is overestimated with increasing inclination of the slope of the structure, whereas undulating reflectors are underestimated in height. For models with D'' topography we find D'' discontinuity reflections in only a small subset of stacks, but an apparent topography of the CMB. Various factors such as very thick or very thin D'' layers, strong topography, convex curvature of the reflector towards the seismic source lead to invisibility of the D'' reflector in most cases. Our study also reveals, that amplitude studies lead to highly ambiguous information due to the multiple dependencies of the amplitude. The thickness of seismic velocity gradients was previously underestimated, leaving wider gradients possible to be delected. Our observations in synthetic seismograms explain the intermittence of D'' observations, as well as enable us to discuss accuracy of array seismological observations. Thus, seismic observations can more reliably be used to support or exclude possible mineralphysical or geodynamical interpretations.

  4. New Madrid seismic zone recurrence intervals

    SciTech Connect

    Schweig, E.S. Center for Earthquake Research and Information, Memphis, TN ); Ellis, M.A. )

    1993-03-01

    Frequency-magnitude relations in the New Madrid seismic zone suggest that great earthquakes should occur every 700--1,200 yrs, implying relatively high strain rates. These estimates are supported by some geological and GPS results. Recurrence intervals of this order should have produced about 50 km of strike-slip offset since Miocene time. No subsurface evidence for such large displacements is known within the seismic zone. Moreover, the irregular fault pattern forming a compressive step that one sees today is not compatible with large displacements. There are at least three possible interpretations of the observations of short recurrence intervals and high strain rates, but apparently youthful fault geometry and lack of major post-Miocene deformation. One is that the seismological and geodetic evidence are misleading. A second possibility is that activity in the region is cyclic. That is, the geological and geodetic observations that suggest relatively short recurrence intervals reflect a time of high, but geologically temporary, pore-fluid pressure. Zoback and Zoback have suggested such a model for intraplate seismicity in general. Alternatively, the New Madrid seismic zone is geologically young feature that has been active for only the last few tens of thousands of years. In support of this, observe an irregular fault geometry associated with a unstable compressive step, a series of en echelon and discontinuous lineaments that may define the position of a youthful linking fault, and the general absence of significant post-Eocene faulting or topography.

  5. Parallel Implementation of the Discontinuous Galerkin Method

    NASA Technical Reports Server (NTRS)

    Baggag, Abdalkader; Atkins, Harold; Keyes, David

    1999-01-01

    This paper describes a parallel implementation of the discontinuous Galerkin method. Discontinuous Galerkin is a spatially compact method that retains its accuracy and robustness on non-smooth unstructured grids and is well suited for time dependent simulations. Several parallelization approaches are studied and evaluated. The most natural and symmetric of the approaches has been implemented in all object-oriented code used to simulate aeroacoustic scattering. The parallel implementation is MPI-based and has been tested on various parallel platforms such as the SGI Origin, IBM SP2, and clusters of SGI and Sun workstations. The scalability results presented for the SGI Origin show slightly superlinear speedup on a fixed-size problem due to cache effects.

  6. 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.

  7. Archetypal oscillator for smooth and discontinuous dynamics.

    PubMed

    Cao, Qingjie; Wiercigroch, Marian; Pavlovskaia, Ekaterina E; Grebogi, Celso; Thompson, J Michael T

    2006-10-01

    We propose an archetypal system to investigate transitions from smooth to discontinuous dynamics. In the smooth regime, the system bears significant similarities to the Duffing oscillator, exhibiting the standard dynamics governed by the hyperbolic structure associated with the stationary state of the double well. At the discontinuous limit, however, there is a substantial departure in the dynamics from the standard one. In particular, the velocity flow suffers a jump in crossing from one well to another, caused by the loss of local hyperbolicity due to the collapse of the stable and unstable manifolds of the stationary state. In the presence of damping and external excitation, the system has coexisting attractors and also a chaotic saddle which becomes a chaotic attractor when a smoothness parameter drops to zero. This attractor can bifurcate to a high-period periodic attractor or a chaotic sea with islands of quasiperiodic attractors depending on the strength of damping. PMID:17155164

  8. Archetypal oscillator for smooth and discontinuous dynamics

    NASA Astrophysics Data System (ADS)

    Cao, Qingjie; Wiercigroch, Marian; Pavlovskaia, Ekaterina E.; Grebogi, Celso; T. Thompson, J. Michael

    2006-10-01

    We propose an archetypal system to investigate transitions from smooth to discontinuous dynamics. In the smooth regime, the system bears significant similarities to the Duffing oscillator, exhibiting the standard dynamics governed by the hyperbolic structure associated with the stationary state of the double well. At the discontinuous limit, however, there is a substantial departure in the dynamics from the standard one. In particular, the velocity flow suffers a jump in crossing from one well to another, caused by the loss of local hyperbolicity due to the collapse of the stable and unstable manifolds of the stationary state. In the presence of damping and external excitation, the system has coexisting attractors and also a chaotic saddle which becomes a chaotic attractor when a smoothness parameter drops to zero. This attractor can bifurcate to a high-period periodic attractor or a chaotic sea with islands of quasiperiodic attractors depending on the strength of damping.

  9. Bounded extremum seeking with discontinuous dithers

    DOE PAGESBeta

    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

  10. Discontinuous Growth of Onion Structure under Shear

    NASA Astrophysics Data System (ADS)

    Fujii, Shuji

    Discontinuous growth process of the Multilamellar vesicle (so called Onion) driven by shear quench was investigated by viscometry and microscopy in detail. Discontinuous Onion growth was observed when the final shear rate corresponded to the intermediate shear rate domain where the shear-thickening and shear-thinning viscosity appeared. In this process, large Onion transformed back into the lamellae and then formed large Onion. Small Onion to lamellae degradation process might be achieved by two modes, first the disruption of the configurational order of densely packed Onions followed by the rupture of Onion as second process. The second process would be characterized by the shear-banding flow pattern composed of the Onion-Lα coexisting state. We suggest that the appearance of the shear-band structure and the Onion reformation developed from the shear-band might be scaled by considering the mechanical energy balance with the bending elastic energy of bilayers.

  11. Panic anxiety after abrupt discontinuation of mianserin.

    PubMed

    Kuniyoshi, M; Arikawa, K; Miura, C; Inanaga, K

    1989-06-01

    We observed a case of withdrawal after abrupt discontinuation of mianserin. A 41-year-old woman was treated according to a diagnosis of depression, which was her 6th episode. Mianserin 30 mg/day, etizolam 1 mg/day and flunitrazepam 1 mg/day were administered. When the patient discontinued taking the drugs by herself because of subsiding of these symptoms, severe panic anxiety appeared. This panic anxiety was not relieved by taking etizolam and flunitrazepam again, but subsided rapidly by the re-administration of mianserin 30 mg/day, and because of that the depressive symptom also disappeared. From these experiences panic anxiety seemed to be a withdrawal symptom, and involvement of the noradrenergic system in panic anxiety as well as serotonergic system was suggested. PMID:2796025

  12. 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. PMID:23758356

  13. 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.

  14. 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.

  15. Discontinuation of Antidepressants During Attempts to Conceive

    PubMed Central

    Psaros, Christina; Freeman, Marlene; Safren, Steven A.; Barsky, Maria; Cohen, Lee S.

    2016-01-01

    Background Many women discontinue antidepressants (ADs) when trying to conceive, although risk of depressive relapse is high. We examined the feasibility and potential clinical effect of cognitive behavioral therapy for the prevention of recurrence (CBT-PR) for women with a history of recurrent major depressive disorder (MDD) who planned to discontinue maintenance AD treatment for pregnancy. Methods This was an open preliminary study of CBT-PR in women (N = 12) planning or early in pregnancy with remitted MDD on maintenance ADs with a plan to discontinue ADs for pregnancy. Participants received 12 sessions of CBT-PR during the acute phase and optional monthly booster sessions during follow-up. Participants were assessed monthly during the acute phase and then twice additionally during follow-up by an independent rater using mood scales (depression module of the Mini-International Neuropsychiatric Interview and Montgomery-Åsberg Depression Rating Scale); pregnancy status was also assessed. Results Over the 24 weeks of the trial, 75% (n = 9) of participants did not restart ADs and did not relapse to depression. Of the 3 who reintroduced AD, 2 experienced a depressive relapse, whereas one did not meet full criteria for MDD. Adherence to the intervention was very good with all participants completing all therapy sessions and assessments. Conclusions Cognitive behavioral therapy for the prevention of recurrence seems feasible and may provide protection for women with recurrent depression on ADs who discontinue their medication while trying to conceive. The extent to which euthymia is sustainable with CBT-PR requires further study; the results of which may broaden treatment choices for women in anticipation of and during pregnancy. PMID:24911438

  16. Extrapolation discontinuous Galerkin method for ultraparabolic equations

    NASA Astrophysics Data System (ADS)

    Marcozzi, Michael D.

    2009-02-01

    Ultraparabolic equations arise from the characterization of the performance index of stochastic optimal control relative to ultradiffusion processes; they evidence multiple temporal variables and may be regarded as parabolic along characteristic directions. We consider theoretical and approximation aspects of a temporally order and step size adaptive extrapolation discontinuous Galerkin method coupled with a spatial Lagrange second-order finite element approximation for a prototype ultraparabolic problem. As an application, we value a so-called Asian option from mathematical finance.

  17. 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.

  18. 3D seismic image processing for interpretation

    NASA Astrophysics Data System (ADS)

    Wu, Xinming

    Extracting fault, unconformity, and horizon surfaces from a seismic image is useful for interpretation of geologic structures and stratigraphic features. Although interpretation of these surfaces has been automated to some extent by others, significant manual effort is still required for extracting each type of these geologic surfaces. I propose methods to automatically extract all the fault, unconformity, and horizon surfaces from a 3D seismic image. To a large degree, these methods just involve image processing or array processing which is achieved by efficiently solving partial differential equations. For fault interpretation, I propose a linked data structure, which is simpler than triangle or quad meshes, to represent a fault surface. In this simple data structure, each sample of a fault corresponds to exactly one image sample. Using this linked data structure, I extract complete and intersecting fault surfaces without holes from 3D seismic images. I use the same structure in subsequent processing to estimate fault slip vectors. I further propose two methods, using precomputed fault surfaces and slips, to undo faulting in seismic images by simultaneously moving fault blocks and faults themselves. For unconformity interpretation, I first propose a new method to compute a unconformity likelihood image that highlights both the termination areas and the corresponding parallel unconformities and correlative conformities. I then extract unconformity surfaces from the likelihood image and use these surfaces as constraints to more accurately estimate seismic normal vectors that are discontinuous near the unconformities. Finally, I use the estimated normal vectors and use the unconformities as constraints to compute a flattened image, in which seismic reflectors are all flat and vertical gaps correspond to the unconformities. Horizon extraction is straightforward after computing a map of image flattening; we can first extract horizontal slices in the flattened space

  19. 14 CFR 221.300 - Discontinuation of electronic tariff system.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 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...

  20. 14 CFR 221.300 - Discontinuation of electronic tariff system.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 4 2013-01-01 2013-01-01 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...

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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...

  6. 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 241.3 Postal Service UNITED STATES POSTAL SERVICE ORGANIZATION AND ADMINISTRATION ESTABLISHMENT CLASSIFICATION, AND DISCONTINUANCE § 241.3 Discontinuance of post offices. (a) Introduction—(1) Coverage. This section establishes the rules governing...

  7. 39 CFR 241.3 - Discontinuance of post offices.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 39 Postal Service 1 2011-07-01 2011-07-01 false Discontinuance of post offices. 241.3 Section 241.3 Postal Service UNITED STATES POSTAL SERVICE ORGANIZATION AND ADMINISTRATION ESTABLISHMENT CLASSIFICATION, AND DISCONTINUANCE § 241.3 Discontinuance of post offices. (a) Introduction—(1) Coverage. This section establishes the rules governing...

  8. 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…

  9. 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 THAN BROADCAST) Applications and Licenses § 5.81 Discontinuance of station operation. In case of permanent discontinuance of operation of a fixed...

  10. 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.

  11. 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

  12. Contraceptive discontinuation among married women in the United States.

    PubMed

    Grady, W R; Hayward, M D; Florey, F A

    1988-01-01

    Using data from the 1982 National Survey of Family Growth (NSFG), this analysis reports differentials in contraceptive discontinuation among married women aged 15-44 years in the United States. The total discontinuation rate is broken down into change to no method (termination) or to a different method (a method switch), and rates are obtained for specific methods. In addition, sociodemographic differences in risks associated with each type of discontinuation are shown. Discontinuation rates are compared to use-failure rates to provide a more comprehensive understanding of the implications of discontinuation for contraceptive efficacy. PMID:3176095

  13. 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.

  14. 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

  15. Continuous-Discontinuous Model for Ductile Fracture

    SciTech Connect

    Seabra, Mariana R. R.; Cesar de Sa, Jose M. A.

    2010-06-15

    In this contribution, a continuum-dicontinuum model for ductile failure is presented. The degradation of material properties trough deformation is described by Continuum Damage Mechanics in a non-local integral formulation to avoid mesh dependence. In the final stage of failure, the damaged zone is replaced by a cohesive macro crack and subsequent traction-free macro crack for a more realistic representation of the phenomenon. The inclusion of the discontinuity surfaces is performed by the XFEM and Level Set Method and avoids the spurious damage growth typical of this class of models.

  16. Receiver function probing of the crust and the upper mantle underneath north German basin, Scandinavia and the Baltic shield: evidence of ancient collision zones

    NASA Astrophysics Data System (ADS)

    Alinaghi, A.; Kind, R.; Bock, G.

    2002-05-01

    Teleseismic earthquakes (distance: 30-90 degrees)recorded by TOR (passive-source seismic experiment, north Germany and Scandinavia, 1996-1997), GRSN (German Regional Seismic Network, 1992-1999), and SVEKALAPKO (seismic experiment, Finland, 1998-1999) have been used for calculating receiver functions. Source and epicentral distance equalized receiver functions were utilized to probe into the crust and upper mantle beneath the recording stations. Detailed images of the crust-mantle boundary across the studied regions show a pronounced increase of the crustal thickness at the junction between northern Europe Paleozoic and Precambrian provinces known as TESZ( TransEuropean Suture Zone). This is accompanied by some north dipping intracrustal structures which run deep into the lower crust and are believed to be remnants of an ancient subduction zone. Another significance of the TESZ is its effect on the two major upper mantle discontinuities and thereby on the upper mantle transition zone. The deepening of the moho is associated with early arrival of 410 km discontinuity compared to predicted time by IASP91 velocity model, while the 660 km discontinuity has been affected to a lesser degree. The crust, underneath the Baltic shield, is thicker (on average 45-50 km) than beneath the north German Basin( 30-35 km on average ), and the moho shows a complex topography in sharp contrast to rather flat surface topography. Beneath SVEKALAPKO, both in stacked time domain and migrated receiver function sections the 410 km and 660 km upper mantle discontinuities arrive earlier than predicted by IASP91 velocity model. This is an indication of higher shear velocity of upper mantle in the Baltic shield compared to that of the Paleozoic northern Europe. We found no sign of the lithosphere-asthenosphere in our study which might be explained by the masking effect of the moho multiples and/or lack of strong Ps conversions due to gradual lithosphere-asthenosphere boundary

  17. 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.

  18. 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

  19. Dynamic origins of seismic wavespeed variation in D″

    NASA Astrophysics Data System (ADS)

    Bower, Dan J.; Gurnis, Michael; Sun, Daoyuan

    2013-01-01

    The D″ discontinuity is defined by a seismic velocity increase of 1-3% about 250 km above the core-mantle boundary (CMB), and is mainly detected beneath locations of inferred paleosubduction. A phase change origin for the interface can explain a triplicated arrival observed in seismic waveform data and is supported by the recent discovery of a post-perovskite phase transition. We investigate the interaction of slabs, plumes, and the phase change within D″ in 2-D compressible convection calculations, and predict waveform complexity in synthetic seismic data. The dynamic models produce significant thermal and phase heterogeneity in D″ over small distances and reveal a variety of behaviors including: (1) distinct pPv blocks separated by upwellings, (2) notches at the top of a pPv layer caused by plume heads, (3) regions of Pv embedded within a pPv layer due to upwellings. Advected isotherms produce complicated thermal structure that enable multiple crossings of the phase boundary. Perturbations to S, SdS, and ScS arrivals (distances <84 degrees) are linked to the evolutionary stage of slabs and plumes, and can be used to determine phase boundary height and velocity increase, volumetric wavespeed anomaly beneath the discontinuity, and possibly the lengthscale of slab folding near the CMB. Resolving fine-scale structure beneath the interface requires additional seismic phases (e.g., Sd, SKS) and larger distances (>80 degrees).

  20. 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.

  1. Discontinuous precipitation in cobalt-tungsten alloys

    SciTech Connect

    Zieba, P.; Cliff, G.; Lorimer, G.W.

    1997-05-01

    Discontinuous precipitation in a Co32 wt% W alloy aged in the temperature range from 875 K to 1025 K has been investigated. Philips EM 430 STEM has been used to characterize the microstructure and to measure the composition profiles across individual lamellae of {epsilon}{sub Co} and Co{sub 3} W phases in partially transformed specimens. Two kinds of cellular precipitates have been found in the alloy. The initial transformation product, identified as primary lamellae with spacing of a few nanometers is replaced during prolonged ageing by secondary lamellae with a much larger interlamellar spacing, typically a few tens of nm. Line scans across cell boundaries of the primary lamellae revealed that, just behind the advancing cell boundary, the solute content is far from the equilibrium state. This solute excess within the cells is quickly removed at the ageing temperature. Calculations show that the diffusion process was too rapid to be identified as ordinary volume diffusion. Investigation of the kinetics showed that discontinuous precipitation is controlled by diffusion processes at the advancing cell boundary. This proposal has been confirmed by STEM analysis of tungsten profiles in the depleted {epsilon}{sub Co} lamellae.

  2. Subcell resolution in simplex stochastic collocation for spatial discontinuities

    NASA Astrophysics Data System (ADS)

    Witteveen, Jeroen A. S.; Iaccarino, Gianluca

    2013-10-01

    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.

  3. 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.

  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. 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

  6. 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

  7. 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

  8. 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

  9. [Discontinuation of depression treatment from the perspective of suicide prevention].

    PubMed

    Cho, Yoshinori

    2012-01-01

    It is assumed that discontinuation of treatment for depression may increase the risk of suicide. A population-based register study in Denmark did not find a lower risk among people over age 50 who followed treatment in comparison with those who discontinued treatment with antidepressants at an early stage. This result, however, does not allow us to think superficially that early discontinuation of treatment does not increase the risk of suicide. It is because the study has limitations without information of such as psychiatric diagnoses, severity of the depressed state, and reasons of discontinuation. It is safe for clinicians to aim at preventing discontinuation of treatment. Particularly, in Japan and South Korea where there is a sociocultural climate of tolerability for suicide, suicide can occur in milder depressed state and discontinuation of treatment should be taken more seriously than in Western countries. PMID:22897025

  10. Precursors to the shear failure of rock discontinuities

    NASA Astrophysics Data System (ADS)

    Hedayat, Ahmadreza; Pyrak-Nolte, Laura J.; Bobet, Antonio

    2014-08-01

    Active geophysical monitoring of potential failure along mechanical discontinuities in rock requires identification of precursory signatures to failure in geophysical signals. Active ultrasonic monitoring of shear failure along frictional discontinuities was performed to determine the signatures of potential failure. An instrumented direct shear apparatus was used to apply a constant shearing rate to a discontinuity that was held under a constant normal stress. Transmitted and reflected compressional and shear waves were recorded during the shearing process. Ultrasonic precursors were identified as distinct maxima in the amplitude of transmitted shear waves as well as minima in the amplitude of reflected shear waves that occurred well before the peak shear strength of a frictional discontinuity. The precursors are linked to changes in the local shear specific stiffness along the discontinuity, while the discontinuity's macroscopic shear strength continues to increase prior to failure.

  11. Seismic signal of avalanches

    NASA Astrophysics Data System (ADS)

    Pesaresi, Damiano; Ravanat, Xavier; Thibert, Emmanuel

    2010-05-01

    The characterization of avalanches with seismic signals is an important task. For risk mitigation, estimating remotely avalanche activity by means of seismic signals is a good alternative to direct observations that are often limited by visual conditions and observer's availability. In seismology, the main challenge is to discriminate avalanche signals within the natural earth seismic activity and background noise. Some anthropogenic low frequency (infra-sound) sources like helicopters also generate seismic signals. In order to characterize an avalanche seismic signal, a 3-axis broad band seismometer (Guralp 3T) has been set-up on a real scale avalanche test site in Lautaret (France). The sensor is located in proximity of 2 avalanche paths where avalanches can be artificially released. Preliminary results of seismic records are presented, correlated with avalanche physical parameters (volume released, velocity, energy).

  12. The harang discontinuity in auroral belt ionospheric currents

    NASA Technical Reports Server (NTRS)

    Herpner, J. P.

    1971-01-01

    Observations are compared to the Harang discontinuity to illustrate the reality and form of the discontinuity near midnight. High latitude magnetic disturbances and auroral displays were not found to be completely identical on any two days. The typical diurnal behavior during the night hours between 60 and 70 deg magnetic latitude was illustrated, using two patterns. Convection, time variablity, and current continuity of the Harang discontinuity are considered.

  13. Mapping Europe's Seismic Hazard

    NASA Astrophysics Data System (ADS)

    Giardini, Domenico; Wössner, Jochen; Danciu, Laurentiu

    2014-07-01

    From the rift that cuts through the heart of Iceland to the complex tectonic convergence that causes frequent and often deadly earthquakes in Italy, Greece, and Turkey to the volcanic tremors that rattle the Mediterranean, seismic activity is a prevalent and often life-threatening reality across Europe. Any attempt to mitigate the seismic risk faced by society requires an accurate estimate of the seismic hazard.

  14. 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.

  15. 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.

  16. 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}.

  17. 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.

  18. Statistical strength models for composites with discontinuities

    SciTech Connect

    Cheng, Ming-Chih.

    1991-01-01

    This thesis investigates the microfracture process in laminated composites based on a problematic approach. Two probabilistic fracture models, a statistical model and a stochastic model, were developed for predicting the failure stress in composites containing geometric discontinuities such as holes and cracks. A two-parameter Weibull distribution of fiber strength and the elastic properties of matrix materials are used in the analysis. The results show that the fracture stress is related to notch size by a power law similar to that proposed by Mar and Lin. Experiments were conducted to verify the probabilistic fracture models developed. The strength reduction factors for boron/epoxy (0/-45/0/45)s laminates were obtained and the fiber damage near the hole edge was studied. The experimental data agree well with the predictions from the probabilistic fracture models.

  19. Volcano seismicity in Alaska

    NASA Astrophysics Data System (ADS)

    Buurman, Helena

    I examine the many facets of volcano seismicity in Alaska: from the short-lived eruption seismicity that is limited to only the few weeks during which a volcano is active, to the seismicity that occurs in the months following an eruption, and finally to the long-term volcano seismicity that occurs in the years in which volcanoes are dormant. I use the rich seismic dataset that was recorded during the 2009 eruption of Redoubt Volcano to examine eruptive volcano seismicity. I show that the progression of magma through the conduit system at Redoubt could be readily tracked by the seismicity. Many of my interpretations benefited greatly from the numerous other datasets collected during the eruption. Rarely was there volcanic activity that did not manifest itself in some way seismically, however, resulting in a remarkably complete chronology within the seismic record of the 2009 eruption. I also use the Redoubt seismic dataset to study post-eruptive seismicity. During the year following the eruption there were a number of unexplained bursts of shallow seismicity that did not culminate in eruptive activity despite closely mirroring seismic signals that had preceded explosions less than a year prior. I show that these episodes of shallow seismicity were in fact related to volcanic processes much deeper in the volcanic edifice by demonstrating that earthquakes that were related to magmatic activity during the eruption were also present during the renewed shallow unrest. These results show that magmatic processes can continue for many months after eruptions end, suggesting that volcanoes can stay active for much longer than previously thought. In the final chapter I characterize volcanic earthquakes on a much broader scale by analyzing a decade of continuous seismic data across 46 volcanoes in the Aleutian arc to search for regional-scale trends in volcano seismicity. I find that volcanic earthquakes below 20 km depth are much more common in the central region of the arc

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. Bayesian methods for discontinuity detection in climate model predictions.

    SciTech Connect

    Safta, Cosmin; Debusschere, Bert J.; Najm, Habib N.; Sargsyan, Khachik

    2010-06-01

    Discontinuity detection is an important component in many fields: Image recognition, Digital signal processing, and Climate change research. Current methods shortcomings are: Restricted to one- or two-dimensional setting, Require uniformly spaced and/or dense input data, and Give deterministic answers without quantifying the uncertainty. Spectral methods for Uncertainty Quantification with global, smooth bases are challenged by discontinuities in model simulation results. Domain decomposition reduces the impact of nonlinearities and discontinuities. However, while gaining more smoothness in each subdomain, the current domain refinement methods require prohibitively many simulations. Therefore, detecting discontinuities up front and refining accordingly provides huge improvement to the current methodologies.

  5. Experiencing antipsychotic discontinuation: results from a survey of Australian consumers.

    PubMed

    Salomon, C; Hamilton, B; Elsom, S

    2014-12-01

    Despite high reported rates of antipsychotic non-adherence, little is known about consumer experiences during discontinuation. This study was designed to increase understanding of antipsychotic discontinuation from consumer perspectives. In 2011-2012, 98 Australian consumers involved with participating organizations completed an anonymous survey detailing past antipsychotic discontinuation attempts. Of the 88 participants who reported at least one discontinuation attempt, over half (n = 47, 54.7%) reported stopping without clinician knowledge or support. This group was 35% (confidence interval 15.4-54.6%) more likely to stop abruptly than those (n = 41, 45.3%) stopping with clinician support (P = 0.002). Only 10 participants (23.3%) recalled being given information about discontinuation symptoms other than relapse; however, 68 participants (78.2%) reported experiencing a range of discontinuation symptoms including physical, cognitive, emotional, psychotic or sleep-related disturbances. Findings cannot be readily generalized because of sampling constraints. However, the significant number of participants who reported discontinuation symptoms, in addition to psychosis, is consistent with previous research. This study provides new insight into consumer motivations for discontinuation and possible problems in clinical communication that may contribute to frequent non-collaborative discontinuation attempts. Mental health nurses, who play a pivotal role in medication communication events, may benefit from increased awareness of consumer perspectives on this topic. PMID:25298092

  6. 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

  7. Using P-wave Triplications to Constrain the Mantle Transition Zone beneath Central Iranian Plateau and Surrounding Area

    NASA Astrophysics Data System (ADS)

    Chi, H. C.; Tseng, T. L.

    2014-12-01

    The Iranian Plateau is a tectonically complex region resulting from the continental collision between the African and Eurasian plates. The convergence of the two continents created the Zagros Mountains, the high topography southwest of Iran, and active seismicity along the Zagros-Bitlis suture. Tomographic studies in Iran reveal low seismic speeds and high attenuation of Sn wave in the uppermost mantle beneath the Iranian Plateau relative to adjacent regions. The deeper structure, however, remains curiously inconclusive. By contrast, a prominent fast seismic anomaly is found under central Tibet near depth of 600 km in the mantle transition zone (TZ), and it is speculated to be the remnant of lithosphere detached during the continental collision. We conduct a comparative study that utilizes triplicate arrivals of high-resolution P waveforms to investigate the velocity structure of mantle beneath the central Iranian Plateau and surroundings. Due to the abrupt increase in seismic wave speeds and density across the 410- and 660-km discontinuities, seismic waves at epicentral distances of 15-30 degrees would form multiple arrivals and the relative times and amplitudes between them are most sensitive to the variations in seismic speeds near the TZ. We combine several broadband arrays to construct 8 seismic profiles, each about 800 km long, that mainly sample the TZ under central Iranian Plateau, Turan shield and part of South Caspian basin. Move-outs between arrivals are clear in the profiles. Relative timings suggest a slightly smaller 660-km contrast under stable Turan shield. In the next stage, it is necessary to model waveforms after the source effect being removed properly. Our preliminary tests show that the F-K method can efficiently calculate the synthetic seismograms. We will determine the 1D velocity model for each sampled sector by minimizing the overall misfits between observed and predicted waveforms. The lateral variations may be further explored by

  8. 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

  9. 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

  10. Discontinuation of Buprenorphine Maintenance Therapy: Perspectives and Outcomes

    PubMed Central

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

    2015-01-01

    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. PMID:25601365

  11. 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

  12. 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.

  13. Discontinuous deformation analysis of particulate media

    NASA Astrophysics Data System (ADS)

    Thomas, Patricia Ann

    Many geotechnical engineering problems involve the localization of deformations along distinct shear planes, such as the response of a layer of soil to displacement along an underlying bedrock fault. Understanding the process of deformation localization and the propagation of shear zones to the surface would aid in the siting of structures near faults, and in developing mitigation techniques. Discrete numerical methods are especially suited to this type of problem, because the discontinuous nature of soil and the kinematics of soil deformation are modeled directly. This research involves the development and validation of Discontinuous Deformation Analysis (DDA), a type of discrete numerical method, as a tool capable of modeling realistic soil behavior, thus providing the foundation for its application to complex soil mechanics problems, such as earthquake fault rupture propagation. First, a review of the two primary types of discrete numerical modeling, the Distinct Element Method (DEM) and DDA is presented along with a discussion of the key aspects of modeling particulate materials with these methods. Next, several extensions to the numerical program Discontinuous Deformation Analysis for Disks (DDAD), implemented during the process of developing DDAD as a tool for modeling particulate materials, were implemented. A flexible, stress-controlled boundary was incorporated, allows simulation of geotechnical biaxial shear tests that are commonly performed on specimens of granular soils. Using this boundary, the stress-strain and volumetric responses of simulated assemblies of particles were investigated. A new type of particle, the disk cluster, was developed and implemented. A disk cluster is a group of circular disks permanently attached to form a single particle. Disk clusters more accurately represent the nonspherical shape of particulate materials, minimize the problem of excessive rotation that occurs with perfectly circular elements, and retain the simplicity of

  14. 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...

  15. 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...

  16. 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...

  17. 27 CFR 21.3 - Stocks of discontinued formulas.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 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...

  18. 27 CFR 31.162 - Discontinuance of business.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Discontinuance of business. 31.162 Section 31.162 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY ALCOHOL ALCOHOL BEVERAGE DEALERS Records and Reports Wholesale Dealers' Records and Reports § 31.162 Discontinuance...

  19. 20 CFR 658.501 - Basis for discontinuation of services.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 20 Employees' Benefits 4 2014-04-01 2014-04-01 false Basis for discontinuation of services. 658.501 Section 658.501 Employees' Benefits EMPLOYMENT AND TRAINING ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) ADMINISTRATIVE PROVISIONS GOVERNING THE JOB SERVICE SYSTEM Discontinuation of Services...

  20. 47 CFR 90.157 - Discontinuance of station operation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Discontinuance of station operation. 90.157 Section 90.157 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Applications and Authorizations § 90.157 Discontinuance...

  1. 47 CFR 90.157 - Discontinuance of station operation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Discontinuance of station operation. 90.157 Section 90.157 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Applications and Authorizations § 90.157 Discontinuance...

  2. 47 CFR 90.157 - Discontinuance of station operation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Discontinuance of station operation. 90.157 Section 90.157 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Applications and Authorizations § 90.157 Discontinuance...

  3. 47 CFR 90.157 - Discontinuance of station operation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Discontinuance of station operation. 90.157 Section 90.157 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Applications and Authorizations § 90.157 Discontinuance...

  4. 47 CFR 90.157 - Discontinuance of station operation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Discontinuance of station operation. 90.157 Section 90.157 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Applications and Authorizations § 90.157 Discontinuance...

  5. Discontinuities in Early Development of the Understanding of Physical Causality

    ERIC Educational Resources Information Center

    Aschersleben, Gisa; Henning, Anne; Daum, Moritz M.

    2013-01-01

    Research on early physical reasoning has shown surprising discontinuities in developmental trajectories. Infants possess some skills that seem to disappear and then re-emerge in childhood. It has been suggested that prediction skills required in search tasks might cause these discontinuities (Keen, 2003). We tested 3.5- to 5-year-olds'…

  6. 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.

  7. 38 CFR 8.17 - Discontinuance of premium waiver.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2014-07-01 2014-07-01 false Discontinuance of premium... 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...

  8. 38 CFR 8.17 - Discontinuance of premium waiver.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2011-07-01 2011-07-01 false Discontinuance of premium... 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...

  9. 38 CFR 8.17 - Discontinuance of premium waiver.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Discontinuance of premium... 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...

  10. 24 CFR 203.288 - Discontinuance of adjusted premium charge.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 24 Housing and Urban Development 2 2014-04-01 2014-04-01 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...

  11. 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...

  12. 24 CFR 203.288 - Discontinuance of adjusted premium charge.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 24 Housing and Urban Development 2 2011-04-01 2011-04-01 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...

  13. 24 CFR 203.288 - Discontinuance of adjusted premium charge.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 24 Housing and Urban Development 2 2012-04-01 2012-04-01 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...

  14. 38 CFR 8.17 - Discontinuance of premium waiver.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2012-07-01 2012-07-01 false Discontinuance of premium... 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...

  15. 38 CFR 8.17 - Discontinuance of premium waiver.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2013-07-01 2013-07-01 false Discontinuance of premium... 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...

  16. 24 CFR 203.288 - Discontinuance of adjusted premium charge.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 24 Housing and Urban Development 2 2013-04-01 2013-04-01 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...

  17. 27 CFR 19.211 - 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. 19.211 Section 19.211 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS DISTILLED SPIRITS PLANTS Qualification of Distilled Spirits Plants Permanent Discontinuance...

  18. 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...

  19. 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...

  20. 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...

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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....

  6. An analysis of the personal reasons for discontinuing IUD use.

    PubMed

    Petta, C A; Amatya, R; Farr, G; Chi, I

    1994-10-01

    The objective of this study was to evaluate possible factors associated with discontinuing use of TCu 380A IUDs due to personal reasons among 2748 users. Overall, a total of 88 subjects discontinued using the TCu 380A IUD within 12 months postinsertion for personal reasons. The most common reasons were planned pregnancy (32%) and husband or family opinion against IUD use (26%). The gross cumulative 12-month life table discontinuation rate for all personal reasons was 4.0 per 100 women. Having no education and/or living in a rural area were the sociodemographic characteristics associated with an increased risk of discontinuation for personal reasons. Effective and regular counseling about IUD use, especially among illiterate women, may help prevent IUD discontinuations related to personal reasons. PMID:7813222

  7. 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.

  8. High-resolution seismic array imaging using teleseismic scattered waves

    NASA Astrophysics Data System (ADS)

    Tong, P.; Liu, Q.; Chen, C.; Basini, P.; Komatitsch, D.

    2013-12-01

    The advent of dense seismic networks, new modeling and imaging techniques, and increased HPC capacity makes it feasible to resolve subsurface interfaces and structural anomalies beneath seismic arrays at unprecedented details based on teleseismic scattered records. To accurately and efficiently simulate the full propagation of teleseismic waves beneath receiver arrays at the frequencies relevant to scattering imaging, we develop a hybrid method that interfaces a frequency-wavenumber (FK) calculation, which provides semi-analytical solutions to one-dimensional layered background models, with a 2D/3D spectral-element (SEM) numerical solver to calculate synthetic responses of local media to plane-wave incidence. This hybrid method accurately deals with local heterogeneities and discontinuity undulations, and represents an efficient tool for the forward modelling of teleseismic coda (including converted and scattered) waves. Meanwhile, adjoint tomography is a powerful tool for high-resolution imaging in heterogeneous media, which can resolve large velocity contrasts through the use of 2D/3D initial models and full numerical simulations for forward wavefields and sensitivity kernels. In the framework of adjont tomography and hybrid method, we compute sensitivity kernels for teleseismic coda waves, which provide the basis for mapping variations in subsurface discontinuities, density and velocity structures through nonlinear conjugate-gradient methods. Various 2D synthetic imaging examples show that inversion of teleseismic coda phases based on the 2D SEM-FK hybrid method and adjoint techniques is a promising tool for structural imaging beneath dense seismic arrays. 3D synthetic experiments will be performed to test the feasibility of seismic array imaging using adjoint method and 3D SEM-FK hybrid method. We will also apply this hybrid imaging techniques to realistic seismic data, such as the recorded SsPmP phases in central Tibet, to explore high-resolution subsurface

  9. 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

  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. 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.

  12. 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.

  13. 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.

  14. Active metasurface terahertz deflector with phase discontinuities.

    PubMed

    Su, Xiaoqiang; Ouyang, Chunmei; Xu, Ningning; Cao, Wei; Wei, Xin; Song, Guofeng; Gu, Jianqiang; Tian, Zhen; O'Hara, John F; Han, Jiaguang; Zhang, Weili

    2015-10-19

    Metasurfaces provide great flexibility in tailoring light beams and reveal unprecedented prospects on novel functional components. However, techniques to dynamically control and manipulate the properties of metasurfaces are lagging behind. Here, for the first time to our knowledge, we present an active wave deflector made from a metasurface with phase discontinuities. The active metasurface is capable of delivering efficient real-time control and amplitude manipulation of broadband anomalous diffraction in the terahertz regime. The device consists of complementary C-shape split-ring resonator elements fabricated on a doped semiconductor substrate. Due to the Schottky diode effect formed by the hybrid metal-semiconductor, the real-time conductivity of the doped semiconductor substrate is modified by applying an external voltage bias, thereby effectively manipulating the intensity of the anomalous deflected terahertz wave. A modulation depth of up to 46% was achieved, while the characteristics of broadband frequency responses and constant deflected angles were well maintained during the modulation process. The modulation speed of diffraction amplitude reaches several kilohertz, limited by the capacitance and resistance of the depletion region. The scheme proposed here opens up a novel approach to develop tunable metasurfaces. PMID:26480376

  15. Initiator RNA in Discontinuous Polyoma DNA Synthesis*

    PubMed Central

    Reichard, Peter; Eliasson, Rolf; Söderman, Gunilla

    1974-01-01

    During replication of polyoma DNA in isolated nuclei, RNA was found attached to the 5′ ends of growing progeny strands. This RNA starts with either ATP or GTP and can be labeled at its 5′ end with 32P from β-labeled nucleotides. Digestion of progeny strands with pancreatic DNase released 32P-labeled RNA that, on gel electrophoresis, gave a distinct peak in the position expected for a decanucleotide. We believe that this short RNA is involved in the initiation of the discontinuous synthesis of DNA and propose the name “initiator RNA” for it. The covalent linkage of initiator RNA to 5′ ends of growing DNA chains was substantiated by the finding that 32P was transferred to ribonucleotides by alkaline hydrolysis of purified initiator RNA obtained by DNase digestion of polyoma progeny strands synthesized from [α-32P]dTTP. While initiator RNA was quite homogeneous in size, it had no unique base sequence since digestion with pancreatic RNase of initiator RNA labeled at its 5′ end with 32P released a variety of different [32P]oligonucleotides. The switch from RNA to DNA synthesis during strand elongation may thus depend on the size of initiator RNA rather than on a specific base sequence. PMID:4373733

  16. Proceedings of seismic engineering 1991

    SciTech Connect

    Ware, A.G. )

    1991-01-01

    This book contains proceedings of the Seismic Engineering Technical Subcommittee of the ASME Pressure Vessels and Piping Division. Topics covered include: seismic damping and energy absorption, advanced seismic analysis methods, new analysis techniques and applications of advanced methods, seismic supports and test results, margins inherent in the current design methods, and risk assessment, and component and equipment qualification.

  17. The Propagation of Seismic Waves in the Presence of Strong Elastic Property Contrasts

    NASA Astrophysics Data System (ADS)

    Saleh, R.; Jeyaraj, R.; Milkereit, B.; Liu, Q.; Valley, B.

    2012-12-01

    In an active underground mine there are many seismic activities taking place, such as seismic noises, blasts, tremors and microseismic events. In between the activities, the microseismic events are mainly used for monitoring purposes. The frequency content of microseismic events can be up to few KHz, which can result in wavelengths on the order of a few meters in hard rock environment. In an underground mine, considering the presence of both small wavelength and strong elastic contrasts, the simulation of seismic wave propagation is a challenge. With the recent availability of detailed 3D rock property models of mines, in addition to the development of efficient numerical techniques (such as Spectral Element Method (SEM)), and parallel computation facilities, a solution for such a problem is achievable. Most seismic wave scattering studies focus on large scales (>1 km) and weak elastic contrasts (velocity perturbations less than 10%). However, scattering in the presence of small-scale heterogeneities and large elastic contrasts is an area of ongoing research. In a mine environment, the presence of strong contrast discontinuities such as massive ore bodies, tunnels and infrastructure lead to discontinuities of displacement and/or stress tensor components, and have significant impact on the propagation of seismic waves. In order to obtain an accurate image of wave propagation in such a complex media, it is necessary to consider the presence of these discontinuities in numerical models. In this study, the effects of such a contrast are illustrated with 2D/3D modeling and compared with real broadband 3-component seismic data. The real broadband 3-component seismic data will be obtained in one of the Canadian underground mines in Ontario. One of the possible scenarios investigated in this study that may explain the observed complexity in seismic wavefield pattern in hard rock environments is the effect of near field displacements rather than far field. Considering the

  18. 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.

  19. 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. PMID:22680875

  20. Thermodynamical and Hydrological Discontinuities in Polythermal Glaciers

    NASA Astrophysics Data System (ADS)

    Aschwanden, A.; Kirner, P.; Rappaz, J.; Blatter, H.

    2006-12-01

    Polythermal glaciers exhibit various thermodynamical and hydrological discontinuities. In this work, two discontinuities are investigated in more detail: the cold-temperate transition surface (CTS), which separates cold ice from temperate ice, and (2) the basal thermal transition (BTT) from sliding in the temperate ice to non- sliding in the cold ice. Ice is defined as temperate if a change in heat content leads to a change in water content alone, and is considered cold if a change in heat content leads to a temperature change alone. The dynamics of the CTS are mainly controlled by the flow field of the glacier and the amount of liquid water in the temperate ice. The two most significant sources contributing to the content of liquid water at the CTS are water entrapped in the firn of the accumulation area and englacial melting due to strain heating. {Pettersson2004a} measured an absolute liquid water of about 7 grams of water per kilogram ice in the upper part of the CTS. Less than 10% of this water can be explained by englacial melting due to strain heating {AschwandenBlatter2005}. The difference can thus be attributed to water entrapment, which is an important boundary condition for the modeling of the dynamics of the CTS. The modeling is performed using a finite element software. To obtain better energy conservation in the scheme, the enthalpy equation (instead of the Fourier equation) is solved together with the constitutive equations for enthalpy in temperate ice (ice water mixture). The mathematical singularity is avoided by a novel regularization scheme applying a brine pocket scheme with a ternary mixture of ice, water and salt. The salt content is assumed to be large enough to regularize the scheme but small enough to influence the results negligibly. This opens the possibility to predict the reaction of the CTS to changes in the amount of trapped water and changes in the flow field due to a changing climate. For a precise modeling of the dynamics of the

  1. Stress relaxation in discontinuously reinforced composites

    SciTech Connect

    Shi, N.; Arsenault, R.J.

    1995-05-01

    It has been observed that in discontinuously-reinforced Al{sub 2}0{sub 3}/NiAl composites that as the reinforcement size increases the average density of dislocations generated from the relaxation of the thermal stresses increases, and the corresponding thermal residual stresses slightly decrease. Similar changes result when the reinforcement morphology changes from spheres to short fibers to continuous filaments. The changes of dislocation density and thermal residual stresses with respect to particle size are in contrast to those observed in the SiC/Al counterpart A previously developed simple model used to explain the SiC/Al data, which was based on prismatic dislocation punching, suggested that the density of the misfit dislocations decreases when the reinforcement size increases. In this investigation, a simple model is proposed to explain the anomaly in the development of thermal residual stresses and the generation of misfit dislocations as a function of the particle size and shape in Al{sub 2}0{sub 3}/NiAl composites. As a result of a lack of sufficient independent-slip-systems in low symmetry materials such as NiAl, plastic relaxation of the thermal stresses is severely constrained as compared to fcc Al. As such, plastic relaxation requires collaborative slips in an aggregate of grains. This only occurs when the length scale of the varying misfit thermal stress field is much larger than the average grain size. That is, the mechanism of plastic relaxation becomes operative when the reinforcement size increases.

  2. 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

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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

  9. 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

  10. Dissipation mechanisms in a pair of solar-wind discontinuities.

    NASA Technical Reports Server (NTRS)

    Unti, T. W. J.; Neugebauer, M.; Atkinson, G.; Wu, C.-S.

    1972-01-01

    A pair of sharp closely spaced discontinuities in the solar wind was recorded by the high time resolution instruments aboard Ogo 5 on Mar. 14, 1968. There is plasma turbulence within the double structure, and there appear to be small-amplitude hydromagnetic waves radiating from the discontinuities. The generation of the plasma turbulence is discussed in terms of magnetic drift waves. Although it seems probable that the surfaces are tangential discontinuities, arguments are also advanced that the double structure may represent the Petschek mechanism in which rapid field-line merging occurs between standing waves.

  11. 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.

  12. Seismicity, 1980-86

    SciTech Connect

    Hill, D.P.; Eaton, J.P.; Jones, L.M.

    1990-01-01

    Tens of thousands of small earthquakes occur in California each year, reflecting brittle deformation of the margins of the Pacific and North American plates as they grind inexorably past one another along the San Andreas fault system. The deformational patterns revealed by this ongoing earthquake activity provide a wealth of information on the tectonic processes along this major transform boundary that, every few hundred years, culminate in rupture of the San Andreas fault in a great (M {approx} 8) earthquake. This chapter describes the regional seismicity and the San Andreas transform boundary; seismicity along the San Andreas Fault system; and focal mechanisms and transform-boundary kinematics. Seismicity patterns and the earthquake cycle and distributed seismicity and deformation of the plate margins are discussed.

  13. Seismic attenuation in Florida

    SciTech Connect

    Bellini, J.J.; Bartolini, T.J.; Lord, K.M.; Smith, D.L. . Dept. of Geology)

    1993-03-01

    Seismic signals recorded by the expanded distribution of earthquake seismograph stations throughout Florida and data from a comprehensive review of record archives from stations GAI contribute to an initial seismic attenuation model for the Florida Plateau. Based on calculations of surface particle velocity, a pattern of attenuation exists that appears to deviate from that established for the remainder of the southeastern US. Most values suggest greater seismic attenuation within the Florida Plateau. However, a separate pattern may exist for those signals arising from the Gulf of Mexico. These results have important implications for seismic hazard assessments in Florida and may be indicative of the unique lithospheric identity of the Florida basement as an exotic terrane.

  14. Seismic Ray Theory

    NASA Astrophysics Data System (ADS)

    Cerveny, V.

    2001-07-01

    The seismic ray method plays an important role in seismology, seismic exploration, and in the interpretation of seismic measurements. Seismic Ray Theory presents the most comprehensive treatment of the method available. Many new concepts that extend the possibilities and increase the method's efficiency are included. The book has a tutorial character: derivations start with a relatively simple problem, in which the main ideas are easier to explain, and then advance to more complex problems. Most of the derived equations are expressed in algorithmic form and may be used directly for computer programming. This book will prove to be an invaluable advanced text and reference in all academic institutions in which seismology is taught or researched.

  15. Passive seismic experiment

    NASA Technical Reports Server (NTRS)

    Latham, G. V.; Ewing, M.; Press, F.; Sutton, G.; Dorman, J.; Nakamura, Y.; Toksoz, N.; Lammlein, D.; Duennebier, F.

    1972-01-01

    The establishment of a network of seismic stations on the lunar surface as a result of equipment installed by Apollo 12, 14, and 15 flights is described. Four major discoveries obtained by analyzing seismic data from the network are discussed. The use of the system to detect vibrations of the lunar surface and the use of the data to determine the internal structure, physical state, and tectonic activity of the moon are examined.

  16. AUTOMATING SHALLOW SEISMIC IMAGING

    SciTech Connect

    Steeples, Don W.

    2003-09-14

    The current project is a continuation of an effort to develop ultrashallow seismic imaging as a cost-effective method potentially applicable to DOE facilities. The objective of the present research is to develop and demonstrate the use of a cost-effective, automated method of conducting shallow seismic surveys, an approach that represents a significant departure from conventional seismic-survey field procedures. Initial testing of a mechanical geophone-planting device suggests that large numbers of geophones can be placed both quickly and automatically. The development of such a device could make the application of SSR considerably more efficient and less expensive. The imaging results obtained using automated seismic methods will be compared with results obtained using classical seismic techniques. Although this research falls primarily into the field of seismology, for comparison and quality-control purposes, some GPR data will be collected as well. In the final year of th e research, demonstration surveys at one or more DOE facilities will be performed. An automated geophone-planting device of the type under development would not necessarily be limited to the use of shallow seismic reflection methods; it also would be capable of collecting data for seismic-refraction and possibly for surface-wave studies. Another element of our research plan involves monitoring the cone of depression of a pumping well that is being used as a proxy site for fluid-flow at a contaminated site. Our next data set will be collected at a well site where drawdown equilibrium has been reached. Noninvasive, in-situ methods such as placing geophones automatically and using near-surface seismic methods to identify and characterize the hydrologic flow regimes at contaminated sites support the prospect of developing effective, cost-conscious cleanup strategies for DOE and others.

  17. 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.

  18. Response of mantle transition zone thickness to plume buoyancy flux

    NASA Astrophysics Data System (ADS)

    Das Sharma, S.; Ramesh, D. S.; Li, X.; Yuan, X.; Sreenivas, B.; Kind, R.

    2010-01-01

    The debate concerning thermal plumes in the Earth's mantle, their geophysical detection and depth characterization remains contentious. Available geophysical, petrological and geochemical evidence is at variance regarding the very existence of mantle plumes. Utilizing P-to-S converted seismic waves (P receiver functions) from the 410 and 660 km discontinuities, we investigate disposition of these boundaries beneath a number of prominent hotspot regions. The thickness of the mantle transition zone (MTZ), measured as P660s-P410s differential times (tMTZ), is determined. Our analyses suggest that the MTZ thickness beneath some hotspots correlates with the plume strength. The relationship between tMTZ, in response to the thermal perturbation, and the strength of plumes, as buoyancy flux B, follows a power law. This B-tMTZ behavior provides unprecedented insights into the relation of buoyancy flux and excess temperature at 410-660 km depth below hotspots. We find that the strongest hotspots, which are located in the Pacific, are indeed plumes originating at the MTZ or deeper. According to the detected power law, even the strongest plumes may not shrink the transition zone by significantly more than ~40 km (corresponding to a maximum of 300-400° excess temperature).

  19. 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.

  20. 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

  1. 48 CFR 49.302 - Discontinuance of vouchers.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... proposal for fee to the TCO within 1 year from the effective date of termination, unless the period is extended by the TCO. When the use of vouchers is discontinued, the contractor shall submit all...

  2. 48 CFR 49.302 - Discontinuance of vouchers.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... proposal for fee to the TCO within 1 year from the effective date of termination, unless the period is extended by the TCO. When the use of vouchers is discontinued, the contractor shall submit all...

  3. Entropy-bounded discontinuous Galerkin scheme for Euler equations

    NASA Astrophysics Data System (ADS)

    Lv, Yu; Ihme, Matthias

    2015-08-01

    An entropy-bounded Discontinuous Galerkin (EBDG) scheme is proposed in which the solution is regularized by constraining the entropy. The resulting scheme is able to stabilize the solution in the vicinity of discontinuities and retains the optimal accuracy for smooth solutions. The properties of the limiting operator according to the entropy-minimum principle are proofed, and an optimal CFL-criterion is derived. We provide a rigorous description for locally imposing entropy constraints to capture multiple discontinuities. Significant advantages of the EBDG-scheme are the general applicability to arbitrary high-order elements and its simple implementation for multi-dimensional configurations. Numerical tests confirm the properties of the scheme, and particular focus is attributed to the robustness in treating discontinuities on arbitrary meshes.

  4. 27 CFR 40.525 - Discontinuance of operations.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS... to discontinue operations and close a factory must dispose of all processed tobacco on hand, make...

  5. 27 CFR 40.525 - Discontinuance of operations.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS... to discontinue operations and close a factory must dispose of all processed tobacco on hand, make...

  6. 27 CFR 40.525 - Discontinuance of operations.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS... to discontinue operations and close a factory must dispose of all processed tobacco on hand, make...

  7. 27 CFR 40.525 - Discontinuance of operations.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS... to discontinue operations and close a factory must dispose of all processed tobacco on hand, make...

  8. 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.

  9. 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... (AVIATION PROCEEDINGS) ECONOMIC REGULATIONS UNIFORM SYSTEM OF ACCOUNTS AND REPORTS FOR LARGE CERTIFICATED AIR CARRIERS Profit and Loss Classification Section 16 Objective...

  10. 38 CFR 21.5835 - Specific discontinuance dates.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... due to physical or mental incapacity, VA will discontinue the dependent child's award of educational... his or her dependent child is not incapable of self support due to physical or mental incapacity,...

  11. 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.

  12. 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.

  13. 38 CFR 21.4278 - Reentrance after discontinuance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... (CONTINUED) VOCATIONAL REHABILITATION AND EDUCATION Administration of Educational Assistance Programs Assessment and Pursuit of Courses § 21.4278 Reentrance after discontinuance. (a) Conditions permitting... institution in the same program of education and the educational institution has— (i) Approved the...

  14. Seismic geometric attribute analysis for fracture characterization: New methodologies and applications

    NASA Astrophysics Data System (ADS)

    Di, Haibin

    In 3D subsurface exploration, detection of faults and fractures from 3D seismic data is vital to robust structural and stratigraphic analysis in the subsurface, and great efforts have been made in the development and application of various seismic attributes (e.g. coherence, semblance, curvature, and flexure). However, the existing algorithms and workflows are not accurate and efficient enough for robust fracture detection, especially in naturally fractured reservoirs with complicated structural geometry and fracture network. My Ph.D. research is proposing the following scopes of work to enhance our capability and to help improve the resolution on fracture characterization and prediction. For discontinuity attribute, previous methods have difficulty highlighting subtle discontinuities from seismic data in cases where the local amplitude variation is 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 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 is superior to previous discontinuity-detection methods. Integrating both discontinuity magnitude and discontinuity azimuth helps better define channels, faults and fractures, than the traditional similarity, amplitude gradient and semblance attributes. For flexure attribute, the existing algorithm is computationally intensive and limited by the lateral resolution for steeply-dipping formations. This study proposes a new and robust volume-based algorithm that evaluate flexure attribute more accurately and effectively. The algorithms first volumetrically fit a cubic surface by using a diamond 13-node grid cell to seismic data, and then compute flexure using the spatial derivatives of the built surface. To avoid

  15. Mohorovičić Discontinuity at the Contact of the Adriatic Microplate and Pannonian Segment

    NASA Astrophysics Data System (ADS)

    Sumanovac, F.; Oreskovic, J.

    2009-12-01

    , Transition zone and Dinaridic crust) can be easily followed on all other profiles. Transition zone is very wide and covers the major part of the SW part of the Pannonian basin. It can be concluded that it corresponds with the ophiolite zones in more recent tectonic maps. The Tisia block can be compared with the Pannonian crust, whereas the Dinaridic crust would relate to the structural units of the Dinarides. However, the NE boundary of the Transition zone is located much further north than the boundary of the Tisia block in published tectonic maps. Due to a marked 2-D structure, the obtained results enabled the development of a 3-D structural map of the Mohorovičić discontinuity. The main fault in the upper mantle, which was defined on the basis of geometrical relations and a 3-D presentation of the interface, indicates a subduction of the Adriatic microplate beneath the Pannonian segment in the NE wing of the Dinarides. Brückl, E., et al., 2003. ALP 2002 Seismic Experiment. Studia Geophysica et Geodaetica, 47, 671-679. Šumanovac, F., et al., 2009. Crustal structure at the contact of the Dinarides and Pannonian basin based on 2-D seismic and gravity interpretation of the Alp07 profile in the ALP2002 experiment, Geophys. J. Int., 179, doi:10.1111/j.l365-246X.2009.04288.x.

  16. 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

  17. 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...

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Severe spontaneous vertebral fractures after denosumab discontinuation: three case reports.

    PubMed

    Aubry-Rozier, B; Gonzalez-Rodriguez, E; Stoll, D; Lamy, O

    2016-05-01

    Osteoporosis treatments are usually given for a limited period of time in order to balance benefits and risks. We report three cases of postmenopausal women without any previous fragility fracture who presented severe spontaneous vertebral fractures after denosumab discontinuation. We think that the occurrence of these fractures could be explained by the severe rebound effect observed after denosumab discontinuation and that a consensus regarding the end of treatment with denosumab has to be defined. PMID:26510845

  4. Factors Associated with Successful Discontinuation of Hormone Therapy

    PubMed Central

    Reed, Susan D.; Nekhyludov, Larissa; Grothaus, Louis C.; Ludman, Evette J.; Ehrlich, Kelly; LaCroix, Andrea Z.

    2014-01-01

    Abstract Background: Careful management of symptoms, particularly sleep and mood disturbances, may assist women in discontinuing hormone therapy (HT). We sought to describe characteristics associated with successful HT cessation in women who attempted to discontinue estrogen pills/patches with or without progestin. Methods: We invited 2,328 women, aged 45–70, enrolled January 1, 2005, to May 31, 2006, at Group Health in Washington State and Harvard Vanguard Medical Associates in Massachusetts, to participate in a telephone survey about HT practices. For the sample, we selected 2,090 women with estrogen dispensings (pharmacy data) during the study period, 200 women without HT dispensing after January 2005, and 240 women with no estrogen dispensings; 1,358 (58.3%) completed the survey. These analyses are based on survey responses. Results: Among 802 women who attempted HT discontinuation, the mean age was 50 years, 93% were postmenopausal, 90% were white, 30% had had a hysterectomy, and 75% experienced hot flashes after discontinuation. Those who did not succeed had greater trouble sleeping (74% vs. 57%) and mood disturbances (51% vs. 34%) than those who succeeded. In multivariable analyses, factors associated with successful discontinuation included doctor advice (odds ratio [OR] 2.62, 95% confidence interval [CI] 1.68–4.08), lack of symptom improvement (OR 4.21, CI 1.50–12.17), vaginal bleeding (OR 5.96, CI 1.44–24.6), and learning to cope with symptoms (OR 3.36, CI 2.21–5.11). Factors associated with unsuccessful HT discontinuation included trouble sleeping (OR 0.40, CI 0.26–0.61) and mood swings or depression (OR 0.63, CI 0.42–0.92). Conclusions: Doctor advice is strongly associated with successful HT discontinuation. Symptom management, particularly sleep and mood disturbances, may help women discontinue HT. PMID:24443881

  5. Seismic Response of In-filled Fractures

    NASA Astrophysics Data System (ADS)

    Acosta-Colon, A. A.; Pyrak-Nolte, L. J.; Olander, M.

    2008-12-01

    Current and ancient karsts environments contain mechanical discontinuities, such as fractures, pipes and caves that range in size from a few millimeters to several meters. These discontinuities are either unfilled, partially-filled or completely in-filled with sediments that range in size from a few microns (clays) to meters (boulders). Sediment within a fracture creates a sub-porosity that quite clearly affects fracture porosity, permeability and storativity. This study investigates the affect of a sub-porosity on the seismic response of in-filled fractures and consequently our ability to probe changes in the subsurface caused by the deposition or erosion of a sub-porosity. Experiments were performed to study the seismic response of a water-saturated fracture filled with sediments (acrylic spheres). The experimental setup consisted of a synthetic fracture created by the separation of two acrylic (Lucite) cylinders. The separation of the fracture was controlled by using computer-controlled linear actuators that incremented the aperture of the fracture in 50 μm steps over a distance of 20 mm. The fracture was water-saturated and filled with acrylic spheres (grains). The spheres ranged in size from 250 microns to 7.79 mm. Several different grain packings were used to infill the fracture. The packings included single layer and multiple layers with a single grain size, and layers composed of multiple grain sizes. Compressional and shear waves were propagated across the fracture using contact piezoelectric transducers (central frequency of 1 MHz) to send and receive the signal. A water-saturated fracture with no grains was used as a standard. The infill material affected the phase, spectral content and velocity of the transmitted compressional wave because of acoustic scattering and wave interference within the infill layer. To study these differences, a time-frequency analysis was performed to determine velocity dispersion and the spectral content of the waves. The

  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. 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

  9. Simulation of Seismic Scattering from Rock Fractures

    NASA Astrophysics Data System (ADS)

    Petrovitch, C.; Teasdale, N.; Pyrak-Nolte, L. J.; de Hoop, M. V.

    2010-12-01

    Accurate predictions of the hydraulic and mechanical properties of fractured subsurface reservoirs are hampered because the coupled processes among fluid properties, mechanical behavior, and seismic scattering are not well understood. A goal of laboratory experiments is to illuminate fundamental physical behavior that can be used on the laboratory scale and translated to the field scale. Our approach to understanding the interrelationship between the hydraulic and seismic properties of fractures is based on determining the relevant geometric length scales that define a fracture and affect fluid flow, as well as the length scales associated with seismic measurements that quantify physical changes in fractures. To achieve this goal, we use a combination of numerical simulation and laboratory measurements to obtain the necessary range of relevant scales. We performed computational seismic scattering simulations from rough fluid-filled (either gas or water-saturated) fractures and compared the simulations to laboratory measurements. Plane-wave compressional-mode source and receiver transducers (water-coupled, 1 MHz central frequency, piezoelectric) were used to measure wave propagation across a single rough fracture. The fracture sample was an acrylic replica of an induced fracture from a carbonate rock (Austin Chalk). An acrylic sample was used to visualize the fluid-saturation of the sample. Reflection and transmission full-waveform measurements were made in 1 mm increments over a 60 mm by 60 mm region of the fracture. The roughness of the fracture surfaces was measured using laser profilometry. The surface roughness data were used to create the computational domain, and the measured arrival times, peak-to-peak amplitudes and frequency content are compared to the simulation results. Many fracture scattering simulations are done by assuming the fracture lies in a 2Dl plane and employ the displacement-discontinuity boundary conditions at the fracture’s surface

  10. 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.

  11. 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

  12. 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.

  13. Upper mantle structure beneath the Japan Islands imaged by receiver function -With Hi-net tiltmeter data-

    NASA Astrophysics Data System (ADS)

    Tonegawa, T.; Hirahara, K.; Shibutani, T.; Shiomi, K.

    2005-12-01

    In the Japan subduction zone where the Pacific plate is subducting, we can investigate the dynamics of the upper mantle beneath the subduction zone by imaging the detailed structure beneath the Japan Islands. Recently, the undulation of the seismic discontinuities in the upper mantle beneath the Japan Islands has been well detected by receiver function (RF) analysis based on the broadband seismograms (e.g. Tonegawa et al., 2005). However, the density of broadband stations expanding throughout the Japan Islands is still insufficient (130 stations in Japan) to investigate the relation between the slab and 410 or 660 km discontinuities. The high sensitivity accelerometer (hereafter tiltmeter) network has recently been deployed with high-density spacing (700 stations in Japan) by NIED, and these tiltmeters can be used as long-period seismometer. If we can use the recordings obtained by the tiltmeter to disclose the structure of the upper mantle, it is possible to dramatically improve our knowledge on the dynamics of the upper mantle. In this study, we examine whether these recordings are available to demonstrate the seismic discontinuities in the upper mantle by calculating the RF from tiltmeter recordings. We select a tiltmeter station and a F-net (broadband network expanding in the Japan Islands) station, whose distance is approximately 4 km, and compare the recordings with velocity seismogram by changing the frequency band. Those RFs would be similar when applying the low-pass filter of longer than 6 sec. Based on this trial, we decide to set the low-pass filter of 6 and 10 sec, when producing the RFs from the tiltmeter recordings. Since tiltmeter seismograms have only the horizontal recordings, we need to obtain the vertical component or sourcetime function. Therefore, we make the sourcetime function by stacking all of vertical components obtained by F-net broadband stations, that is, we consider these stacked waveforms as sourcetime functions. For making the

  14. 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

  15. Seismic source parameters

    SciTech Connect

    Johnson, L.R.

    1994-06-01

    The use of information contained on seismograms to infer the properties of an explosion source presents an interesting challenge because the seismic waves recorded on the seismograms represent only small indirect, effects of the explosion. The essential physics of the problem includes the process by which these elastic waves are generated by the explosion and also the process involved in propagating the seismic waves from the source region to the sites where the seismic data are collected. Interpretation of the seismic data in terms of source properties requires that the effects of these generation and propagation processes be taken into account. The propagation process involves linear mechanics and a variety of standard seismological methods have been developed for handling this part of the problem. The generation process presents a more difficult problem, as it involves non-linear mechanics, but semi-empirical methods have been developed for handling this part of the problem which appear to yield reasonable results. These basic properties of the seismic method are illustrated with some of the results from the NPE.

  16. 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.

  17. 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

  18. SMARTer Discontinuation Trial Designs for Developing an Adaptive Treatment Strategy

    PubMed Central

    Compton, Scott N.; Rynn, Moira A.; Walkup, John T.; Murphy, Susan A.

    2012-01-01

    Abstract Objective Developing evidenced-based practices for the management of childhood psychiatric disorders requires research studies that address how to treat children during both the acute phase of the disorder and beyond. Given the selection of a medication for acute treatment, discontinuation trials are used to evaluate the effects of treatment duration (e.g., time on medication) and/or maintenance strategies following successful acute-phase treatment. Recently, sequential multiple assignment randomized trials (SMART) have been proposed for use in informing sequences of critical clinical decisions such as those mentioned. The objective of this article is to illustrate how a SMART study is related to the standard discontinuation trial design, while addressing additional clinically important questions with similar trial resources. Method The recently completed Child/Adolescent Anxiety Multimodal Study (CAMS), a randomized trial that examined the relative efficacy of three acute-phase treatments for pediatric anxiety disorders, along with a next logical step, a standard discontinuation trial design, is used to clarify the ideas. This example is used to compare the discontinuation trial design relative to the SMART design. Results We find that the standard discontinuation trial can be modified slightly using a SMART design to yield high-quality data that can be used to address a wider variety of questions in addition to the impact of treatment duration. We discuss how this innovative trial design is ultimately more efficient and less costly than the standard discontinuation trial, and may result in more representative comparisons between treatments. Conclusions Mental health researchers who are interested in addressing questions concerning the effects of continued treatment (for different durations) following successful acute-phase treatment should consider SMART designs in place of discontinuation trial designs in their research. SMART designs can be used to

  19. An active seismic experiment proposal onboard the NASA 2009 MSL

    NASA Astrophysics Data System (ADS)

    Lognonné, P.; Experiment Team

    NASA will launch in 2009 a 900 kg class rover to Mars. This rover will land with a new descent system, called the ``sky-crane''. After releasing the rover on the ground, the sky-crane will have a final flight until a hard landing about 2 km away from the rover. The science objectives of the 2009 MSL mission, among others, are to characterize the geology of the landing region at all appropriate spatial scales, to interpret the processes that have formed and modified rocks and regolith and to determine present state, distribution, and cycling of water. We propose to perform with the sky-crane an active seismic experiment for subsurface characterization. This experiment will be conducted after the rover deployment. The proposed idea is to deploy a seismic receiver line by ejecting about 10 seismic nodes from the sky-crane and then to record then the reflected signals from the impact of the sky-crane. Preliminary modeling and tests indicate that a penetration depth of several hundred meters will be reached. The experiment will be used to determine a 2D geological profile of the landing site subsurface, to determine the depth and shape of the dry regolith/icy regolith discontinuity and to identify possible layering structures in the subsurface. In addition, information on the structure of the regolith (mean size of building blocs) and on the presence of liquid water will be obtained by an analysis of the seismic coda and attenuation. The seismic high frequency noise will also be monitored, especially during windy periods, and will be used to get additional information on the subsurface. The proposed experiment is based on a consortium between academics laboratories and seismic industry and will be a first example of a resource oriented experiment on another planet than Earth. The complete mass of the experiment will be 2.5 kg. Seismic nodes will have their own acquisition/power and telemetry system and will be based on high sensitive geophones developed for seismic

  20. 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.

  1. 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.

  2. 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.

  3. Downhole seismic array system

    SciTech Connect

    Petermann, S.G.

    1992-03-03

    This patent describes an apparatus of receiving seismic signals from an earth formation at least at one or more points in a wellbore penetrating the formation. It comprises a sonde including extensible and retractable support means thereon for supporting seismic signal receiver means, hydraulic actuator means for extending and reacting the support means, body means for supporting the actuator means and the support means and signal transmitting means for transmitting electrical signals related to seismic signals received by the receiver means; tubing means connected to the sonde for deploying the sonde in the wellbore, the tubing means including electrical conductor means disposed therein for conducting electrical signals between means on the surface of the formation and the sonde and the tubing means comprising means for conducting hydraulic fluid to the sonde for operation of the actuator means; and means for supplying hydraulic fluid from the surface of the formation through the tubing means to the sonde for operating the actuator means.

  4. 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.

  5. Canadian Seismic Agreement

    SciTech Connect

    Wetmiller, R.J.; Lyons, J.A.; Shannon, W.E.; Munro, P.S.; Thomas, J.T.; Andrew, M.D.; Lapointe, S.P.; Lamontagne, M.; Wong, C.; Anglin, F.M.; Adams, J.; Cajka, M.G.; McNeil, W.; Drysdale, J.A. )

    1992-05-01

    This is a progress report of work carried out under the terms of a research agreement entitled the Canadian Seismic Agreement'' between the US Nuclear Regulatory Commission (USNRC), the Canadian Commercial Corporation and the Geophysics Division of the Geological Survey of Canada (GD/GSC) during the period from July 01, 1989 to June 30, 1990. The Canadian Seismic Agreement'' supports generally the operation of various seismograph stations in eastern Canada and the collection and analysis of earthquake data for the purpose of mitigating seismic hazards in eastern Canada and the northeastern US. The specific activities carried out in this one-year period are summarized below under four headings; Eastern Canada Telemetred Network and local network developments, Datalab developments, strong-motion network developments and earthquake activity. During this period the first surface fault unequivocably determined to have accompanied a historic earthquake in eastern North America, occurred in northern Quebec.

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. 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

  11. 3D dynamic rupture with anelastic wave propagation using an hp-adaptive Discontinuous Galerkin method

    NASA Astrophysics Data System (ADS)

    Tago, J.; Cruz-Atienza, V. M.; Etienne, V.; Virieux, J.; Benjemaa, M.; Sanchez-Sesma, F. J.

    2010-12-01

    Simulating any realistic seismic scenario requires incorporating physical basis into the model. Considering both the dynamics of the rupture process and the anelastic attenuation of seismic waves is essential to this purpose and, therefore, we choose to extend the hp-adaptive Discontinuous Galerkin finite-element method to integrate these physical aspects. The 3D elastodynamic equations in an unstructured tetrahedral mesh are solved with a second-order time marching approach in a high-performance computing environment. The first extension incorporates the viscoelastic rheology so that the intrinsic attenuation of the medium is considered in terms of frequency dependent quality factors (Q). On the other hand, the extension related to dynamic rupture is integrated through explicit boundary conditions over the crack surface. For this visco-elastodynamic formulation, we introduce an original discrete scheme that preserves the optimal code performance of the elastodynamic equations. A set of relaxation mechanisms describes the behavior of a generalized Maxwell body. We approximate almost constant Q in a wide frequency range by selecting both suitable relaxation frequencies and anelastic coefficients characterizing these mechanisms. In order to do so, we solve an optimization problem which is critical to minimize the amount of relaxation mechanisms. Two strategies are explored: 1) a least squares method and 2) a genetic algorithm (GA). We found that the improvement provided by the heuristic GA method is negligible. Both optimization strategies yield Q values within the 5% of the target constant Q mechanism. Anelastic functions (i.e. memory variables) are introduced to efficiently evaluate the time convolution terms involved in the constitutive equations and thus to minimize the computational cost. The incorporation of anelastic functions implies new terms with ordinary differential equations in the mathematical formulation. We solve these equations using the same order

  12. 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. PMID:16710418

  13. 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.

  14. Solving the cardiac bidomain equations for discontinuous conductivities.

    PubMed

    Austin, Travis M; Trew, Mark L; Pullan, Andrew J

    2006-07-01

    Fast simulations of cardiac electrical phenomena demand fast matrix solvers for both the elliptic and parabolic parts of the bidomain equations. It is well known that fast matrix solvers for the elliptic part must address multiple physical scales in order to show robust behavior. Recent research on finding the proper solution method for the bidomain equations has addressed this issue whereby multigrid preconditioned conjugate gradients has been used as a solver. In this paper, a more robust multigrid method, called Black Box Multigrid, is presented as an alternative to conventional geometric multigrid, and the effect of discontinuities on solver performance for the elliptic and parabolic part is investigated. Test problems with discontinuities arising from inserted plunge electrodes and naturally occurring myocardial discontinuities are considered. For these problems, we explore the advantages to using a more advanced multigrid method like Black Box Multigrid over conventional geometric multigrid. Results will indicate that for certain discontinuous bidomain problems Black Box Multigrid provides 60% faster simulations than using conventional geometric multigrid. Also, for the problems examined, it will be shown that a direct usage of conventional multigrid leads to faster simulations than an indirect usage of conventional multigrid as a preconditioner unless there are sharp discontinuities. PMID:16830931

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. Discontinuous automorphisms of the proper Galilei and Euclidean groups

    SciTech Connect

    Adeleke, S.A. )

    1989-04-01

    The author shows that there are numerous discontinuous automorphisms of the three-dimensional Euclidean group and thus of the Galilei group, as numerous as the subsets of the real numbers, 2{sup aleph-null}, to be exact. These automorphisms arise from the derivations of the field of real numbers. Tits gave an example of a discontinuous automorphism for the semidirect product of the general linear group GL{sub n}(K) in n dimensions with the additive group of n {times} n matrices. He observes that if one uses the quaternion representation of the rotations and the form of Tits example, one obtains discontinuous automorphisms of the Euclidean group in three dimensions. He shows that all automorphisms of the Euclidean group in higher dimensions are continuous.

  1. 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.

  2. 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.

  3. 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.

  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. Efficient Displacement Discontinuity Method Using Fast Multipole Techniques

    SciTech Connect

    Morris, J.P.; Blair, S.C.

    2000-02-18

    The Displacement Discontinuity method has been widely used in geomechanics because it accurately captures the behavior of fractures within a rock mass by explicitly accounting for discontinuities. Unfortunately, boundary element techniques require the interactions between all pairs of elements to be evaluated and traditional approaches to the Displacement Discontinuity method are computationally expensive for large problem sizes. Approximate summation techniques, such as the Fast Multipole Method (FMM), calculate the interactions between N entities in time proportional to N. We have implemented a modified Fast Multipole approach which performs the necessary calculations in optimal time and with reduced memory usage. Furthermore, the FMM introduces parameters which can be selected to give the desired trade-off between efficiency and accuracy. The FMM approach permits much larger problems to be solved using desktop computers, opening up a range of applications. We present results demonstrating the speed of the code and several test cases involving rock fracture in compression.

  6. 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.

  7. Nonstructural seismic restraint guidelines

    SciTech Connect

    Butler, D.M.; Czapinski, R.H.; Firneno, M.J.; Feemster, H.C.; Fornaciari, N.R.; Hillaire, R.G.; Kinzel, R.L.; Kirk, D.; McMahon, T.T.

    1993-08-01

    The Nonstructural Seismic Restraint Guidelines provide general information about how to secure or restrain items (such as material, equipment, furniture, and tools) in order to prevent injury and property, environmental, or programmatic damage during or following an earthquake. All SNL sites may experience earthquakes of magnitude 6.0 or higher on the Richter scale. Therefore, these guidelines are written for all SNL sites.

  8. 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.

  9. Geothermal induced seismicity program plan

    SciTech Connect

    Not Available

    1981-03-01

    A plan for a National Geothermal Induced Seismicity Program has been prepared in consultation with a panel of experts from industry, academia, and government. The program calls for baseline seismic monitoring in regions of known future geothermal development, continued seismic monitoring and characterization of earthquakes in zones of geothermal fluid production and injection, modeling of the earthquake-inducing mechanism, and in situ measurement of stresses in the geothermal development. The Geothermal Induced Seismicity Program (GISP) will have as its objectives the evaluation of the seismic hazard, if any, associated with geothermal resource exploitation and the devising of a technology which, when properly utilized, will control or mitigate such hazards.

  10. 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

  11. Factors affecting medication discontinuation in patients with overactive bladder symptoms

    PubMed Central

    Shim, Eun-Jung; Kim, Young-Mi; Kim, Donguk

    2015-01-01

    Objective To find out the factors affecting medication discontinuation in patients with overactive bladder (OAB) symptoms. Methods The clinical data of 125 patients with OAB symptoms who had taken antimuscarinics and behavioral therapy were retrospectively reviewed. Antimuscarinics related outcomes were evaluated by an independent observer with telephone interview. All patients were asked about duration of medication and reason of continuation or discontinuation of antimuscarinics. To determine pre-treatment factors predicting self-report discontinuation of antimuscarinics, variables of only those with P-values <0.25 on the univariate analysis were included in the Cox proportional hazard modeling. Results Mean follow-up was 39.6 months and the proportion of discontinuation of antimuscarinics was 60.0% (75/125). The mean duration of medication was 21.2 months in the continuation group and 3.3 months in the discontinuation group. The reasons of discontinuation of antimuscarinics were improved OAB symptoms (46.7%), tolerable OAB symptoms (33.3%), no change of OAB symptoms (1.3%), side-effects (8.0%) and no desire to take long-term medication (10.7%). The variables affecting remaining cumulative probability of antimuscarinics were age, history of anti-incontinence surgery or vaginal surgery, and having stress predominant urinary incontinence on urodynamic study. Conclusion The lower rate of cumulative continuation of antimuscarinics encourages us to give a more detailed counseling and education to the patients with OAB symptoms before prescription. And explorations about newer agent and non-pharmacologic treatment with good efficacy and lower side-effects are needed. PMID:26623416

  12. Development of a New Experimental Apparatus for the Study of the Mechanical Behaviour of a Rock Discontinuity Under Monotonic and Cyclic Loads

    NASA Astrophysics Data System (ADS)

    Ferrero, A. M.; Migliazza, M.; Tebaldi, G.

    2010-11-01

    The shear behaviour of rock discontinuities in seismic condition is still not fully understood although earthquakes can be an important triggering cause of instability phenomena of rock blocks. For this purpose, a special apparatus was designed and developed at the University of Parma (Italy), which is to be placed inside the MTS press available in the Laboratory of Materials Testing. The press allows the application of monotonic and cyclic loads, in load or in deformation control. Quantitative evaluation of the rock-joint damage is realized by a photogrammetric survey of the discontinuity before and after the tests. The surface comparison enables the identification of the damaged areas. Finally, theoretical and experimental results are interpreted in the light of the damage model developed by Belem et al. (Rock Mech Rock Eng 33(4):217-242, 2001) for a quantitative evaluation of joint roughness and resistance.

  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. Midnight velocity shear zone and the concept of Harang discontinuity

    SciTech Connect

    Koskinen, H.E.J.; Pulkkinen, T.I.

    1995-06-01

    The authors address the question of the origin and meaning of the Harang discontinuity. They consider mappings of the ionosphere, auroral zones, and magnetosphere. They argue for a relation between the velocity shear zone in the auroral ionosphere and the Harang discontinuity. However because of the upward directed field-aligned currents it is very hard to trace field lines well enough to show mappings of these zones. They argue however for the behavior of auroral arcs in relation to the appearance of substorm events to provide strong support for this relationship.

  15. Exploring the Use of Discontinuous Galerkin Methods for Numerical Relativity

    NASA Astrophysics Data System (ADS)

    Hebert, Francois; Kidder, Lawrence; Teukolsky, Saul; SXS Collaboration

    2015-04-01

    The limited accuracy of relativistic hydrodynamic simulations constrains our insight into several important research problems, including among others our ability to generate accurate template waveforms for black hole-neutron star mergers, or our understanding of supernova explosion mechanisms. In many codes the algorithms used to evolve the matter, based on the finite volume method, struggle to reach the desired accuracy. We aim to show improved accuracy by using a discontinuous Galerkin method. This method's attractiveness comes from its combination of spectral convergence properties for smooth solutions and robust stability properties for shocks. We present the status of our work implementing a testbed GR-hydro code using discontinuous Galerkin.

  16. Limiters for high-order discontinuous Galerkin methods

    NASA Astrophysics Data System (ADS)

    Krivodonova, Lilia

    2007-09-01

    We describe a limiter for the discontinuous Galerkin method that retains as high an order as possible, and does not automatically reduce to first order. The limiter is a generalization of the limiter introduced in [R. Biswas, K. Devine, J.E. Flaherty, Parallel adaptive finite element methods for conservation laws, Applied Numerical Mathematics 14 (1994) 255-284]. We present the one-dimensional case and extend it to two-dimensional problems on tensor-product meshes. Computational results for examples with both smooth and discontinuous solutions are shown.

  17. 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.

  18. 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

  19. Imaging the LAB and other major lithospheric discontinuities beneath South Africa

    NASA Astrophysics Data System (ADS)

    Sodoudi, Forough; Kind, Rainer; Kaestle, Emanuel

    2013-04-01

    sharper boundary at 150-220 km depth can be identified across the whole region. This boundary may show an intralithospheric discontinuity beneath cratons and may reveal the LAB beneath the younger belts. In addition, a 100 km LVZ can be also observed, which may confirm the so-called "8 degree discontinuity" seen in dense, long-range seismic profiles.

  20. 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

  1. Seismic Rotations Observed with Inertial Seismic Sensors

    NASA Astrophysics Data System (ADS)

    Jean, V.

    2006-12-01

    Recent interest of the seismological community has arisen for possible rotation effects of the Earth on signals recorded by inertial seismometers. Wiechert and Schluter (1903) and more recently Pancha et al. (2000), Igel et al. (2005, 2006) show that, in the teleseismic range, rotations may be neglected and account for less than 0.1% of the translation waves generated by earthquakes. On the contrary, we may see effects of rotation on seismic traces recorded in the near field of an earthquake. As instruments will deliver unsaturated signals in this near field, rotation detection will be more and more frequent. We may observe rotation effects as well in the noise signal at long period. - In the near field, the three components integrated signal of the accelerograms (i.e; velocity signal) diverge and this drift is the effect of an nearly invisible little jump in acceleration signal. The second integrated step diverges and the co-seismic displacement could not be estimated. - By studying the long period noise, we have found that the two horizontal components of some of GEOSCOPE stations with STS-1 seismometer from Streckeisen, present the same noise both in amplitude and in phase with a coherency greater than 95%. This similarity could occur at some stations and not at others and during some time periods. Therefore, the noise has a quite stable horizontal polarisation at N045 during these periods. We may argue that these two separate effects comes from ground rotations and the way they are recorded by seismic instruments. For example, GEOSCOPE stations equipped by STS-2 which have a quite different mechanical structure do not exhibit the polarisation effect. Mechanical pendulums as vertical LaCoste sensor and horizontal 'garden-gate' sensor present effects of rotations on the different translation motions of the mass. Therefore, for the long period noise, a quite probable explanation is that a rotation around the vertical axis acts similarly on the two horizontal

  2. 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.

  3. Comment on '3-D frequency-domain seismic wave modelling in heterogeneous, anisotropic media using a Gaussian quadrature grid approach' by Bing Zhou and S. A. Greenhalgh

    NASA Astrophysics Data System (ADS)

    de Basabe, Jonás D.

    2011-08-01

    Zhou & Greenhalgh have recently presented an application of the Gaussian quadrature grid to seismic modelling in which the authors propose a meshing scheme that partitions the domain independently of the discontinuities in the media parameters. This comment aims to clarify the implications that this strategy has on the accuracy.

  4. Intermediate depth seismicity - a reflection seismic approach

    NASA Astrophysics Data System (ADS)

    Haberland, C.; Rietbrock, A.

    2004-12-01

    During subduction the descending oceanic lithosphere is subject to metamorphic reactions, some of them associated with the release of fluids. It is now widely accepted, that these reactions and associated dehydration processes are directly related with the generation of intermediate depth earthquakes (dehydration embrittlement). However, the structure of the layered oceanic plate at depth and the location of the earthquakes relative to structural units of the subducting plate (sources within the oceanic crust and/or in the upper oceanic mantle lithosphere?) are still not resolved yet. This is in mainly due to the fact that the observational resolution needed to address these topics (in the range of only a few kilometers) is hardly achieved in field experiments and related studies. Here we study the wavefields of intermediate depth earthquakes typically observed by temporary networks in order to assess their high-resolution potential in resolving structure of the down going slab and locus of seismicity. In particular we study whether the subducted oceanic Moho can be detected by the analysis of secondary phases of local earthquakes (near vertical reflection). Due to the irregular geometry of sources and receivers we apply an imaging technique similar to diffraction stack migration. The method is tested using synthetic data both based on 2-D finite difference simulations and 3-D kinematic ray tracing. The accuracy of the hypocenter location and onset times crucial for the successful application of stacking techniques (coherency) was achieved by the use of relatively relocated intermediate depth seismicity. Additionally, we simulate the propagation of the wavefields at larger distance (wide angle) indicating the development of guided waves traveling in the low-velocity waveguide associated with the modeled oceanic crust. We also present application on local earthquake data from the South American subduction zone.

  5. 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.

  6. Seismic Study of the Southernmost Andes. The Contact Between Scotia and South American Plates

    NASA Astrophysics Data System (ADS)

    Tassone, A.; Cominguez, A. H.; Yagupsky, D.; Alvarado, P.; Lodolo, E.; Menichetti, M.

    2003-12-01

    The relationships between the sinistral Magallanes-Fagnano continental transform fault (MFS), a major segment of the boundary between Scotia-South American plates, and the northern flank of the western Scotia Sea, characterized mostly by compressional structures, have not been yet clearly identified. From data processing, depth seismic-migration modeling and interpretation of 800 km of seismic reflection profiles, this study presents one morpho-structural analysis of these two main tectonic elements. In the offshore part of the Malvinas fold-and-thrust belt, five main seismic units have been recognized. Steeply dipping (mainly to the south) reverse faults cut through the folds. Some of these faults represent old extensional faults of the Middle-Mesozoic Rocas Verdes marginal basin rifting, which have been subsequently inverted by compressional stress fields. A noticeable fault system is recognized in the seismic profile, which involves both the sedimentary cover and the acoustic basement. This fault is interpreted as the result of shear stresses produced along the transcurrent South American-Scotia plate boundary. In the SW border of Malvinas Basin, four major discontinuities were recognized. Each discontinuity represents important changes in the regional geodynamic evolution: Early-Late Jurassic rift; Thermal subsidence (Late Jurassic-Late Cretaceous); Transitional stage, to Foreland basin (Late Cretaceous-Eocene) and Foreland (since Eocene).

  7. 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

  8. 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.

  9. Discontinuous behavior near excavations in a bedded salt formation

    SciTech Connect

    Stormont, J.C.

    1990-10-01

    Discontinuous behavior is being observed and measured in the vicinity of excavations constructed in a bedded salt formation 650 m below ground surface for the Waste Isolation Pilot Plant (WIPP) Facility. The 2 m thick salt layer in the immediate roof acts as a beam, shearing along a thin overlying anhydrite/clay seam. The floor of the excavations is comprised of a 1 m thick salt layer underlain by a 1 m thick predominately anhydrite layer (referred to as MB139). In the ribs, there is limited fracturing within the first meter of most larger excavations. Vertical fractures develop in pillars at most intersections. The discontinuous behavior is qualitatively consistent with analyses of the formation behaving as a layered medium (elastic beam analysis) and limited tensile and compressive failure of the rock salt. The significance of the discontinuous behavior is that can dominate the effective fluid transport properties of the formation near the excavation, and therefore requires considerations in the design of repository seals. Furthermore, the discontinuous behavior must be monitored and is a very important consideration in the maintenance program designed to assume a safe underground environment. 22 refs., 17 figs.

  10. 27 CFR 21.3 - Stocks of discontinued formulas.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... formulas. 21.3 Section 21.3 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, 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...

  11. 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. PMID:25172113

  12. 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. PMID:23430991

  13. 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…

  14. 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

  15. 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.

  16. 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…

  17. 20 CFR 658.503 - Discontinuation of services.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 20 Employees' Benefits 4 2014-04-01 2014-04-01 false Discontinuation of services. 658.503 Section 658.503 Employees' Benefits EMPLOYMENT AND TRAINING ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED... response in accordance with § 658.502, within 20 working days, or has not requested a hearing, the...

  18. 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...

  19. 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…

  20. 14 CFR 16 - Objective Classification-Discontinued Operations

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 false Objective Classification-Discontinued Operations Section 16 Section Section 16 Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) ECONOMIC REGULATIONS UNIFORM SYSTEM OF ACCOUNTS AND REPORTS FOR...

  1. 27 CFR 40.461 - Discontinuance of operations.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... discontinue operations and close out a factory shall dispose of all cigarette papers and tubes on hand, in... BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes Operations by...

  2. 27 CFR 40.461 - Discontinuance of operations.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... discontinue operations and close out a factory shall dispose of all cigarette papers and tubes on hand, in... BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes Operations by...

  3. 27 CFR 40.461 - Discontinuance of operations.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... discontinue operations and close out a factory shall dispose of all cigarette papers and tubes on hand, in... BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes Operations by...

  4. 27 CFR 40.525 - Discontinuance of operations.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 2 2011-04-01 2011-04-01 false Discontinuance of operations. 40.525 Section 40.525 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO...

  5. 27 CFR 40.461 - Discontinuance of operations.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 2 2011-04-01 2011-04-01 false Discontinuance of operations. 40.461 Section 40.461 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO...

  6. 27 CFR 40.461 - Discontinuance of operations.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... discontinue operations and close out a factory shall dispose of all cigarette papers and tubes on hand, in... BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes Operations by...

  7. Effects of discontinuous magnetic permeability on magnetodynamic problems

    NASA Astrophysics Data System (ADS)

    Guermond, J.-L.; Léorat, J.; Luddens, F.; Nore, C.; Ribeiro, A.

    2011-07-01

    A novel approximation technique using Lagrange finite elements is proposed to solve magneto-dynamics problems involving discontinuous magnetic permeability and non-smooth interfaces. The algorithm is validated on benchmark problems and is used for kinematic studies of the Cadarache von Kármán Sodium 2 (VKS2) experimental fluid dynamo.

  8. 47 CFR 87.111 - Suspension or discontinuance of operation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Suspension or discontinuance of operation. 87.111 Section 87.111 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Operating Requirements and Procedures Operating Procedures §...

  9. 47 CFR 87.111 - Suspension or discontinuance of operation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Suspension or discontinuance of operation. 87.111 Section 87.111 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Operating Requirements and Procedures Operating Procedures §...

  10. 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,…

  11. 78 FR 64065 - Discontinuance of Annual Financial Assessments

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-25

    ... AFFAIRS Discontinuance of Annual Financial Assessments AGENCY: Department of Veterans Affairs. ACTION... requesting that veterans submit an annual financial assessment following initial enrollment. FOR FURTHER... requires a veteran to submit a financial assessment (38 CFR 17.36(d)(3)(iv)) using the Application...

  12. 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

  13. 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…

  14. Where Words Collide: Social Class, Schools and Linguistic Discontinuity

    ERIC Educational Resources Information Center

    Ruairc, Gerry Mac

    2011-01-01

    The prestige accorded to standard language varieties, particularly within the field of education, together with language management role of schools with respect to the variety and the extent to which linguistic differences construct discontinuous relationships between the school and specific social groups provide the rationale for this paper. This…

  15. 27 CFR 478.57 - Discontinuance of business.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... transfer or possess a semiautomatic assault weapon, except as provided in the law, any licensed manufacturer, licensed importer, or licensed dealer intending to discontinue business shall, prior to going out of business, transfer in compliance with the provisions of this part any semiautomatic assault...

  16. 27 CFR 478.57 - Discontinuance of business.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... transfer or possess a semiautomatic assault weapon, except as provided in the law, any licensed manufacturer, licensed importer, or licensed dealer intending to discontinue business shall, prior to going out of business, transfer in compliance with the provisions of this part any semiautomatic assault...

  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 Payments-Educational Assistance § 21.9630 Suspension...

  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. 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...

  2. Grades, Gender, and Encouragement: A Regression Discontinuity Analysis

    ERIC Educational Resources Information Center

    Owen, Ann L.

    2010-01-01

    The author employs a regression discontinuity design to provide direct evidence on the effects of grades earned in economics principles classes on the decision to major in economics and finds a differential effect for male and female students. Specifically, for female students, receiving an A for a final grade in the first economics class is…

  3. 27 CFR 19.695 - Notice of permanent discontinuance.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... BUREAU, DEPARTMENT OF THE TREASURY ALCOHOL DISTILLED SPIRITS PLANTS Distilled Spirits for Fuel Use... a proprietor permanently discontinues operations as an alcohol fuel plant, the proprietor must file... of the alcohol fuel plant permit and the proprietor's request that the permit be cancelled; (b)...

  4. 27 CFR 19.695 - Notice of permanent discontinuance.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... a proprietor permanently discontinues operations as an alcohol fuel plant, the proprietor must file... of the alcohol fuel plant permit and the proprietor's request that the permit be cancelled; (b) A written statement disclosing whether or not all spirits, including fuel alcohol, have been...

  5. 27 CFR 19.695 - Notice of permanent discontinuance.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... BUREAU, DEPARTMENT OF THE TREASURY ALCOHOL DISTILLED SPIRITS PLANTS Distilled Spirits for Fuel Use... a proprietor permanently discontinues operations as an alcohol fuel plant, the proprietor must file... of the alcohol fuel plant permit and the proprietor's request that the permit be cancelled; (b)...

  6. 27 CFR 19.945 - Notice of permanent discontinuance.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... permanently discontinues operations as an alcohol fuel plant shall, after completion of the operations, file a letterhead notice with the appropriate TTB officer. The notice shall be accompanied— (a) By the alcohol fuel... disclosing, as applicable, whether (1) all spirits (including fuel alcohol) have been lawfully disposed...

  7. 27 CFR 19.695 - Notice of permanent discontinuance.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... a proprietor permanently discontinues operations as an alcohol fuel plant, the proprietor must file... of the alcohol fuel plant permit and the proprietor's request that the permit be cancelled; (b) A written statement disclosing whether or not all spirits, including fuel alcohol, have been...

  8. 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.

  9. 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.

  10. 27 CFR 44.161 - Discontinuance of operations.

    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 operations. 44.161 Section 44.161 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO EXPORTATION OF TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES, WITHOUT PAYMENT OF TAX, OR...

  11. How Can Comparison Groups Strengthen Regression Discontinuity Designs?

    ERIC Educational Resources Information Center

    Wing, Coady; Cook, Thomas D.

    2011-01-01

    In this paper, the authors examine some of the ways that different types of non-equivalent comparison groups can be used to strengthen causal inferences based on regression discontinuity design (RDD). First, they consider a design that incorporates pre-test data on assignment scores and outcomes that were collected either before the treatment…

  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. 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. Pseudo-discontinuities in the isomer shift near magnetic transitions

    NASA Astrophysics Data System (ADS)

    Kolk, B.; Hall, D. B.; Zheng, Y.; Lumetta, J. T.

    1983-12-01

    It is shown that a relatively small non-linear behavior of the velocity drive system used in Mössbauer effect studies yields pseudo-discontinuities in the isomer shift near the critical temperature T c of a magnetic-paramagnetic transition. The anomaly of the57Fe isomer shift in iron is attributed to this effect.

  17. Real Time Seismic Prediction while Drilling

    NASA Astrophysics Data System (ADS)

    Schilling, F. R.; Bohlen, T.; Edelmann, T.; Kassel, A.; Heim, A.; Gehring, M.; Lüth, S.; Giese, R.; Jaksch, K.; Rechlin, A.; Kopf, M.; Stahlmann, J.; Gattermann, J.; Bruns, B.

    2009-12-01

    operation. First experiments indicate that parts of the ISIS system can be used for smaller diameters e.g. in vertical drilling. In unconsolidated rocks S-waves are strongly attenuated. For the Sonic Softground Probing (SSP) system P-waves are used. A vibration-seismic correlation positioning system was developed. One transmitter and several receiver are placed within the cutting wheel. During drilling, a specially coded transmitter signal is sent directly from the cutterhead via the face support medium in the direction of tunneling. With this geometry, boulders can be detected 50 m ahead of the working face. Fracture zones and other discontinuities can be localized, and the physical properties of the upcoming rocks can be partly determined nearly in real time, while using sound velocity and attenuation as indicators. All evaluation is based on real time 3D velocity models which are determined during the drilling operation. Different technologies allow a seismic prediction while drilling in various rock types and geologies. Seismic prediction during vertical drilling will significantly profit from the lesson learned from state of the art tunneling systems.

  18. '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.

  19. 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.

  20. 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.