system seismic boundary: Topics by

  • Interstellar heliospheric probe/heliospheric boundary explorer mission—a mission to the outermost boundaries of the solar system

    NASA Astrophysics Data System (ADS)

    Wimmer-Schweingruber, Robert F.; McNutt, Ralph; Schwadron, Nathan A.; Frisch, Priscilla C.; Gruntman, Mike; Wurz, Peter; Valtonen, Eino


    The Sun, driving a supersonic solar wind, cuts out of the local interstellar medium a giant plasma bubble, the heliosphere. ESA, jointly with NASA, has had an important role in the development of our current understanding of the Suns immediate neighborhood. Ulysses is the only spacecraft exploring the third, out-of-ecliptic dimension, while SOHO has allowed us to better understand the influence of the Sun and to image the glow of interstellar matter in the heliosphere. Voyager 1 has recently encountered the innermost boundary of this plasma bubble, the termination shock, and is returning exciting yet puzzling data of this remote region. The next logical step is to leave the heliosphere and to thereby map out in unprecedented detail the structure of the outer heliosphere and its boundaries, the termination shock, the heliosheath, the heliopause, and, after leaving the heliosphere, to discover the true nature of the hydrogen wall, the bow shock, and the local interstellar medium beyond. This will greatly advance our understanding of the heliosphere that is the best-known example for astrospheres as found around other stars. Thus, IHP/HEX will allow us to discover, explore, and understand fundamental astrophysical processes in the largest accessible plasma laboratory, the heliosphere.

  • Boundary Layer

    NASA Technical Reports Server (NTRS)

    Loitsianskii. L. G.


    The fundamental, practically the most important branch of the modern mechanics of a viscous fluid or a gas, is that branch which concerns itself with the study of the boundary layer. The presence of a boundary layer accounts for the origin of the resistance and lift force, the breakdown of the smooth flow about bodies, and other phenomena that are associated with the motion of a body in a real fluid. The concept of boundary layer was clearly formulated by the founder of aerodynamics, N. E. Joukowsky, in his well-known work “On the Form of Ships” published as early as 1890. In his book “Theoretical Foundations of Air Navigation,” Joukowsky gave an account of the most important properties of the boundary layer and pointed out the part played by it in the production of the resistance of bodies to motion. The fundamental differential equations of the motion of a fluid in a laminar boundary layer were given by Prandtl in 1904; the first solutions of these equations date from 1907 to 1910. As regards the turbulent boundary layer, there does not exist even to this day any rigorous formulation of this problem because there is no closed system of equations for the turbulent motion of a fluid. Soviet scientists have done much toward developing a general theory of the boundary layer, and in that branch of the theory which is of greatest practical importance at the present time, namely the study of the boundary layer at large velocities of the body in a compressed gas, the efforts of the scientists of our country have borne fruit in the creation of a new theory which leaves far behind all that has been done previously in this direction. We shall herein enumerate the most important results by Soviet scientists in the development of the theory of the boundary layer.

  • The analysis of the Tectonics – SSS – Seismicity System in the 3D-model of the Rasvumchorr Mine – Central Open Pit Natural and Technical System (Khibiny)

    NASA Astrophysics Data System (ADS)

    Zhirov, Dmitry; Klimov, Sergey; Zhirova, Anzhela; Panteleev, Alexey; Rybin, Vadim


    Main hazardous factors during the operation of deposits represent tectonics (structural dislocation), strain and stress state (SSS), and seismicity. The cause and effect relationships in the Fault Tectonics – SSS – Seismicity system were analyzed using a 3D geological and structural Rasvumchorr Mine – Central Open Pit model. This natural and technical system (NTS) has resulted from the development of the world-class apatite-nepheline deposits the Apatite Circus and Rasvumchorr Plateau. The 3D model integrates various spatial data on the earth’s surface topography before and after mining, geometry of mines and dumps, SSS measurements and rock pressure, seismicity, fault tectonics and etc. The analysis of the 3D model has clearly demonstrated the localization of three main seismic emanation zones in the areas of maximum anthropogenic variation of the initial rock state, and namely: ore pass zone under the Southern edge of the Central open pit, collapse and joining zone of the Rasvumchorr Mine and NW edge of the open pit, and zone under the Apatite Circus plate – collapse console. And, on the contrary, in the area of a large dump under the underground mine, a perennial seismic minimum zone was identified. The relation of the seismicity and fault tectonics was revealed only in three local sectors near come certain echelon fissures of the Main Fault(MF). No confinement of increased seismicity areas to the MF and other numerous echelon fissures is observed. The same picture occurs towards manifestations of rock pressure. Only an insignificant part of echelon fissures (including low rank of hierarchy) controls hazardous manifestations of rock pressure (dumps, strong deformations of the mine contour, etc.). It is shown that the anthropogenic factor (explosive, geometry and arrangement of mined spaces and collapse console), as well as the time factor significantly change orientation and structure (contrast and heterogeneity) of the stress fields. Time series of natural

  • Attraction Basins as Gauges of Robustness against Boundary Conditions in Biological Complex Systems

    PubMed Central

    Demongeot, Jacques; Goles, Eric; Morvan, Michel; Noual, Mathilde; Sené, Sylvain


    One fundamental concept in the context of biological systems on which researches have flourished in the past decade is that of the apparent robustness of these systems, i.e., their ability to resist to perturbations or constraints induced by external or boundary elements such as electromagnetic fields acting on neural networks, micro-RNAs acting on genetic networks and even hormone flows acting both on neural and genetic networks. Recent studies have shown the importance of addressing the question of the environmental robustness of biological networks such as neural and genetic networks. In some cases, external regulatory elements can be given a relevant formal representation by assimilating them to or modeling them by boundary conditions. This article presents a generic mathematical approach to understand the influence of boundary elements on the dynamics of regulation networks, considering their attraction basins as gauges of their robustness. The application of this method on a real genetic regulation network will point out a mathematical explanation of a biological phenomenon which has only been observed experimentally until now, namely the necessity of the presence of gibberellin for the flower of the plant Arabidopsis thaliana to develop normally. PMID:20700525

  • Boundary-spanning actors in complex adaptive governance systems: The case of multisectoral nutrition.


    Pelletier, David; Gervais, Suzanne; Hafeez-Ur-Rehman, Hajra; Sanou, Dia; Tumwine, Jackson


    A growing literature highlights complexity of policy implementation and governance in global health and argues that the processes and outcomes of policies could be improved by explicitly taking this complexity into account. Yet there is a paucity of studies exploring how this can be achieved in everyday practice. This study documents the strategies, tactics, and challenges of boundary-spanning actors working in 4 Sub-Saharan Africa countries who supported the implementation of multisectoral nutrition as part of the African Nutrition Security Partnership in Burkina Faso, Mali, Ethiopia, and Uganda. Three action researchers were posted to these countries during the final 2 years of the project to help the government and its partners implement multisectoral nutrition and document the lessons. Prospective data were collected through participant observation, end-line semistructured interviews, and document analysis. All 4 countries made significant progress despite a wide range of challenges at the individual, organizational, and system levels. The boundary-spanning actors and their collaborators deployed a wide range of strategies but faced significant challenges in playing these unconventional roles. The study concludes that, under the right conditions, intentional boundary spanning can be a feasible and acceptable practice within a multisectoral, complex adaptive system in low- and middle-income countries. © 2017 The Authors. The International Journal of Health Planning and Management Published by John Wiley & Sons Ltd.

  • Stability analysis of spectral methods for hyperbolic initial-boundary value systems

    NASA Technical Reports Server (NTRS)

    Gottlieb, D.; Lustman, L.; Tadmor, E.


    A constant coefficient hyperbolic system in one space variable, with zero initial data is discussed. Dissipative boundary conditions are imposed at the two points x = + or – 1. This problem is discretized by a spectral approximation in space. Sufficient conditions under which the spectral numerical solution is stable are demonstrated – moreover, these conditions have to be checked only for scalar equations. The stability theorems take the form of explicit bounds for the norm of the solution in terms of the boundary data. The dependence of these bounds on N, the number of points in the domain (or equivalently the degree of the polynomials involved), is investigated for a class of standard spectral methods, including Chebyshev and Legendre collocations.

  • GPS Imaging suggests links between climate, magmatism, seismicity, and tectonics in the Sierra Nevada-Long Valley Caldera-Walker Lane system, western United States

    NASA Astrophysics Data System (ADS)

    Hammond, W. C.; Blewitt, G.; Kreemer, C.; Smith, K.


    The Walker Lane is a region of complex active crustal transtension in the western Great Basin of the western United States, accommodating about 20% of the 50 mm/yr relative motion between the Pacific and North American plates. The Long Valley caldera lies in the central Walker Lane in eastern California, adjacent to the eastern boundary of the Sierra Nevada/Great Valley microplate, and experiences intermittent inflation, uplift, and volcanic unrest from the magma chamber that resides at middle crustal depths. Normal and transform faults accommodating regional tectonic transtension pass by and through the caldera, complicating the interpretation of the GPS-measured strain rate field, estimates of fault slip rates, and seismic hazard. Several dozen continuously recording GPS stations measure strain and uplift in the area with mm precision. They observe that the most recent episode of uplift at Long Valley began in mid-2011, continuing until late 2016, raising the surface by 100 mm in 6 years. The timing of the initiation of uplift coincides with the beginning of severe drought in California. Furthermore, the timing of a recent pause in uplift coincides with the very wet 2016-2017 winter, which saw approximately double normal snow pack. In prior studies, we showed that the timing of changes in geodetically measured uplift rate of the Sierra Nevada coincides with the timing of drought conditions in California, suggesting a link between hydrological loading and Sierra Nevada elevation. Here we take the analysis three steps further to show that changes in Sierra Nevada uplift rate coincide in time with 1) enhanced inflation at the Long Valley caldera, 2) shifts in the patterns and rates of horizontal tensor strain rate, and 3) seismicity patterns in the central Walker Lane. We use GPS solutions from the Nevada Geodetic Laboratory and the new GPS Imaging technique to produce robust animations of the time variable strain and uplift fields. The goals of this work are to

  • Recent advancements on the development of web-based applications for the implementation of seismic analysis and surveillance systems

    NASA Astrophysics Data System (ADS)

    Friberg, P. A.; Luis, R. S.; Quintiliani, M.; Lisowski, S.; Hunter, S.


    Recently, a novel set of modules has been included in the Open Source Earthworm seismic data processing system, supporting the use of web applications. These include the Mole sub-system, for storing relevant event data in a MySQL database (see M. Quintiliani and S. Pintore, SRL, 2013), and an embedded webserver, Moleserv, for serving such data to web clients in QuakeML format. These modules have enabled, for the first time using Earthworm, the use of web applications for seismic data processing. These can greatly simplify the operation and maintenance of seismic data processing centers by having one or more servers providing the relevant data as well as the data processing applications themselves to client machines running arbitrary operating systems.Web applications with secure online web access allow operators to work anywhere, without the often cumbersome and bandwidth hungry use of secure shell or virtual private networks. Furthermore, web applications can seamlessly access third party data repositories to acquire additional information, such as maps. Finally, the usage of HTML email brought the possibility of specialized web applications, to be used in email clients. This is the case of EWHTMLEmail, which produces event notification emails that are in fact simple web applications for plotting relevant seismic data.Providing web services as part of Earthworm has enabled a number of other tools as well. One is ISTI’s EZ Earthworm, a web based command and control system for an otherwise command line driven system; another is a waveform web service. The waveform web service serves Earthworm data to additional web clients for plotting, picking, and other web-based processing tools. The current Earthworm waveform web service hosts an advanced plotting capability for providing views of event-based waveforms from a Mole database served by Moleserve.The current trend towards the usage of cloud services supported by web applications is driving improvements in Java

  • Simulating Seismic Wave Propagation in Viscoelastic Media with an Irregular Free Surface

    NASA Astrophysics Data System (ADS)

    Liu, Xiaobo; Chen, Jingyi; Zhao, Zhencong; Lan, Haiqiang; Liu, Fuping


    In seismic numerical simulations of wave propagation, it is very important for us to consider surface topography and attenuation, which both have large effects (e.g., wave diffractions, conversion, amplitude/phase change) on seismic imaging and inversion. An irregular free surface provides significant information for interpreting the characteristics of seismic wave propagation in areas with rugged or rapidly varying topography, and viscoelastic media are a better representation of the earth’s properties than acoustic/elastic media. In this study, we develop an approach for seismic wavefield simulation in 2D viscoelastic isotropic media with an irregular free surface. Based on the boundary-conforming grid method, the 2D time-domain second-order viscoelastic isotropic equations and irregular free surface boundary conditions are transferred from a Cartesian coordinate system to a curvilinear coordinate system. Finite difference operators with second-order accuracy are applied to discretize the viscoelastic wave equations and the irregular free surface in the curvilinear coordinate system. In addition, we select the convolutional perfectly matched layer boundary condition in order to effectively suppress artificial reflections from the edges of the model. The snapshot and seismogram results from numerical tests show that our algorithm successfully simulates seismic wavefields (e.g., P-wave, Rayleigh wave and converted waves) in viscoelastic isotropic media with an irregular free surface.

  • Seismic Reflection Imaging of the Heat Source of an Ultramafic-Hosted Hydrothermal System (Rainbow, Mid-Atlantic Ridge 36° 10-17’N)

    NASA Astrophysics Data System (ADS)

    Canales, J. P.; Dunn, R. A.; Sohn, R. A.; Horning, G.; Arai, R.; Paulatto, M.


    Most of our understanding of hydrothermal systems and the nature of their heat sources comes from models and observations at fast and intermediate spreading ridges. In these settings, hydrothermal systems are mainly located within the axial zone of a spreading segment, hosted in basaltic rock, and primarily driven by heat extracted from crystallization of crustal melt sills. In contrast, hydrothermal systems at slow-spreading ridges like the Mid-Atlantic Ridge (MAR) show a great variety of venting styles and host-rock lithology, and are located in diverse tectonic settings like axial volcanic ridges, non-transform discontinuities (NTDs), the foot of ridge valley walls, and off-axis inside corner highs. Among MAR systems, the Rainbow hydrothermal field (RHF) stands out as an end-member of this diversity: an ultramafic-hosted system emitting H2 and CH4-rich fluids at high temperatures and high flow rates, which suggests a magmatic heat source despite the lack of evidence for recent volcanism and its location within an NTD with presumably low magma budget. We present 2D multichannel seismic reflection images across the Rainbow massif from the NSF-funded MARINER multidisciplinary geophysical study that reveal, for the first time, the magmatic system driving hydrothermal circulation in an ultramafic setting. Data were acquired in 2013 onboard the RV M. Langseth with an 8-km-long hydrophone streamer. The images have been obtained from pre-stack depth migrations using a regional 3D P-wave velocity model from a coincident controlled-source seismic tomography experiment using ocean bottom seismometers. Our images show a complex magmatic system centered beneath the RHF occupying an areal extent of ~3.7×6 km2, with partially molten sills ranging in depth between ~3.4 km and ~6.9 km below the seafloor. Our data also image high-amplitude dipping reflections within the massif coincident with strong lateral velocity gradients that may arise from detachment fault planes

  • Synthetic earthquake catalogs simulating seismic activity in the Corinth Gulf, Greece, fault system

    NASA Astrophysics Data System (ADS)

    Console, Rodolfo; Carluccio, Roberto; Papadimitriou, Eleftheria; Karakostas, Vassilis


    The characteristic earthquake hypothesis is the basis of time-dependent modeling of earthquake recurrence on major faults. However, the characteristic earthquake hypothesis is not strongly supported by observational data. Few fault segments have long historical or paleoseismic records of individually dated ruptures, and when data and parameter uncertainties are allowed for, the form of the recurrence distribution is difficult to establish. This is the case, for instance, of the Corinth Gulf Fault System (CGFS), for which documents about strong earthquakes exist for at least 2000 years, although they can be considered complete for M ≥ 6.0 only for the latest 300 years, during which only few characteristic earthquakes are reported for individual fault segments. The use of a physics-based earthquake simulator has allowed the production of catalogs lasting 100,000 years and containing more than 500,000 events of magnitudes ≥ 4.0. The main features of our simulation algorithm are (1) an average slip rate released by earthquakes for every single segment in the investigated fault system, (2) heuristic procedures for rupture growth and stop, leading to a self-organized earthquake magnitude distribution, (3) the interaction between earthquake sources, and (4) the effect of minor earthquakes in redistributing stress. The application of our simulation algorithm to the CGFS has shown realistic features in time, space, and magnitude behavior of the seismicity. These features include long-term periodicity of strong earthquakes, short-term clustering of both strong and smaller events, and a realistic earthquake magnitude distribution departing from the Gutenberg-Richter distribution in the higher-magnitude range.

  • Seismic imaging of Late Cretaceous magmatic system in the northern margin of South China Sea

    NASA Astrophysics Data System (ADS)

    Xia, S.; Xu, H.; Sun, J.; Zhao, F.; Fan, C.


    The origin and evolution of magmatism in the rifting margins are the fundamentally geological subjects, and remain the focus of intense study. Different from the classical volcanic or nonvolcanic rifting margins, the northern margin of South China Sea (SCS) experienced uniquely regional tectonic processes, and formed plentiful intraplate seamounts mainly at the postrift period. There is considerable controversy over what caused the intensively postrift intraplate volcanism. Here we combine a new crustal structure with previously systematic petrologic and seismic tomographic results to first provide importantly new insights into a mantle plume origin and complex multilevel plumbing system of intraplate seamounts in the northern margin of SCS. Large amounts of active melts from the lower mantle migrated upward and reached the base of the lithosphere. The volatile-rich and overheated magmas continued ascending along the weak zone through the lithosphere and intruded into the lower crust. The intrusion magmas then ascended forward along the faults formed during the rifting, and supplied the magma source for the formation of intraplate seamounts in the northern margin of SCS. It supplies an important implication for the volume and range of late Cenozoic basaltic magmatism deriving from the Hainan mantle plume. Keywords: South China Sea; Late Cretaceous; Magmatic System; Hainan Plume AcknowledgementsThe field work of this study was assisted by the captain and crew of the R/V Shiyan 2. Prof. Xuelin Qiu supplied great helps for the successful implementation of the cruise. This work was partially supported by grants from the National Natural Science Foundation of China (Grant Nos. 91328206 and 41576041).

  • 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

  • Seismic imaging of the southern California plate-boundary around the South-Central Transverse Ranges using double-difference tomography

    NASA Astrophysics Data System (ADS)

    Share, P. E.; Ben-Zion, Y.; Thurber, C. H.; Zhang, H.; Guo, H.


    We derive P and S seismic velocities within and around the South-Central Transverse Ranges section of the San Andreas Fault (SAF), using a new double-difference tomography algorithm incorporating both event-pair and station-pair differential times. The event-pair data can determine high-resolution relative earthquake locations and resolve fine-scale structure in seismogenic zones, whereas station-pair data allow for better absolute locations and higher resolution of structure near the surface where stations are most dense. The tomographic results are based on arrival times of P and S waves generated by 17,753 M>1 local events from 1/1/2010 to 6/30/2015 recorded by 259 stations within a 222 km x 164 km region. The resulting P and S velocity models include low velocities along major fault segments and across-fault velocity contrasts. For example, at depths 50 km parallel to the SAF around Coachella Valley but offset to the NE by 13 km. This is interpreted to mark a dipping section of the SAF that separates granites at depth in the SW from gneisses and schists in the NE. Analysis of fault zone head waves propagating along these sections of the SAF and SJFZ show that major bimaterial interfaces are associated with the observed velocity contrasts. Additional features within the models include elongated low velocity anomalies extending from the SJFZ trifurcation area, which itself has associated low velocity at great depth

  • Quantitative Estimation of Seismic Velocity Changes Using Time-Lapse Seismic Data and Elastic-Wave Sensitivity Approach

    NASA Astrophysics Data System (ADS)

    Denli, H.; Huang, L.


    Quantitative monitoring of reservoir property changes is essential for safe geologic carbon sequestration. Time-lapse seismic surveys have the potential to effectively monitor fluid migration in the reservoir that causes geophysical property changes such as density, and P- and S-wave velocities. We introduce a novel method for quantitative estimation of seismic velocity changes using time-lapse seismic data. The method employs elastic sensitivity wavefields, which are the derivatives of elastic wavefield with respect to density, P- and S-wave velocities of a target region. We derive the elastic sensitivity equations from analytical differentiations of the elastic-wave equations with respect to seismic-wave velocities. The sensitivity equations are coupled with the wave equations in a way that elastic waves arriving in a target reservoir behave as a secondary source to sensitivity fields. We use a staggered-grid finite-difference scheme with perfectly-matched layers absorbing boundary conditions to simultaneously solve the elastic-wave equations and the elastic sensitivity equations. By elastic-wave sensitivities, a linear relationship between relative seismic velocity changes in the reservoir and time-lapse seismic data at receiver locations can be derived, which leads to an over-determined system of equations. We solve this system of equations using a least- square method for each receiver to obtain P- and S-wave velocity changes. We validate the method using both surface and VSP synthetic time-lapse seismic data for a multi-layered model and the elastic Marmousi model. Then we apply it to the time-lapse field VSP data acquired at the Aneth oil field in Utah. A total of 10.5K tons of CO2 was injected into the oil reservoir between the two VSP surveys for enhanced oil recovery. The synthetic and field data studies show that our new method can quantitatively estimate changes in seismic velocities within a reservoir due to CO2 injection/migration.

  • Vertical-Axis Rotations Within Columbia River Basalt Flows Define a Sharp Eastern Boundary of the Coast Range Block with Potentially Increased Seismic Risk for Portland, Oregon

    NASA Astrophysics Data System (ADS)

    Hagstrum, J. T.; Wells, R. E.; Evarts, R. C.; Blakely, R. J.; Beeson, M. H.


    Paleomagnetic analysis of the Miocene Columbia River Basalt Group (CRBG) in the northern Willamette Valley of Oregon was undertaken as part of a larger mapping and hydrogeologic investigation of the CRBG’s internal stratigraphy and structure. Differences in paleomagnetic directions between flows due to geomagnetic reversals and paleosecular variation, in combination with geochemical data, provide the most reliable means of flow identification. In addition, vertical-axis rotations between CRBG sites in the Portland area and sampling localities within the same flow units on the relatively stable Columbia Plateau were calculated. Clockwise rotations for sites within the northern Willamette Valley are remarkably consistent and have a weighted mean of 29°±3° (N=94). Available paleomagnetic data from CRBG sites along the Oregon coast at Cape Lookout (19°±22°, N=4) and Cape Foulweather (29°±18°, N=4) show similar results. East of the Portland Hills fault zone along the Columbia River Gorge, however, clockwise rotations are much less averaging 12°±3° (N=15). North of Portland, the CRBG rotational values drop abruptly from ~29° to 6°±17° (N=3) across an unnamed fault near Woodland, WA, identified using aeromagnetic data; to the south, the values drop from ~29° to 18°±3° (N=6) across the Mt. Angel-Gales Creek fault zone east of Salem, OR. The eastern boundary of the Oregon Coast Range block is thus defined by three offset NW-trending fault segments, with the offsets corresponding to the Portland and Willamette pull-apart basins. North of the Coast Range block’s northern boundary, which is roughly coincident with the Columbia River, CRBG rotations also are about half that (15°±3°, N=15) found within the block. Northward movement and clockwise rotation of the Oregon Coast Range block have previously been modeled as decreasing continuously eastward to the Columbia Plateau. Our new paleomagnetic data indicate an abrupt step down of rotational values by

  • Experimental and Analytical Seismic Studies of a Four-Span Bridge System with Innovative Materials

    NASA Astrophysics Data System (ADS)

    Cruz Noguez, Carlos Alonso

    As part of a multi-university project utilizing the NSF Network for Earthquake Engineering Simulation (NEES), a quarter-scale model of a four-span bridge incorporating plastic hinges with different advanced materials was tested to failure on the three shake table system at the University of Nevada, Reno (UNR). The bridge was the second test model in a series of three 4-span bridges, with the first model being a conventional reinforced-concrete (RC) structure. The purpose of incorporating advanced materials was to improve the seismic performance of the bridge with respect to two damage indicators: (1) column damage and (2) permanent deformations. The goals of the study presented in this document were to (1) evaluate the seismic performance of a 4-span bridge system incorporating SMA/ECC and built-in rubber pad plastic hinges as well as post-tensioned piers, (2) quantify the relative merit of these advanced materials and details compared to each other and to conventional reinforced concrete plastic hinges, (3) determine the influence of abutment-superstructure interaction on the response, (4) examine the ability of available elaborate analytical modeling techniques to model the performance of advanced materials and details, and (5) conduct an extensive parametric study of different variations of the bridge model to study several important issues in bridge earthquake engineering. The bridge model included six columns, each pair of which utilized a different advanced detail at bottom plastic hinges: shape memory alloys (SMA), special engineered cementitious composites (ECC), elastomeric pads embedded into columns, and post-tensioning tendons. The design of the columns, location of the bents, and selection of the loading protocol were based on pre-test analyses conducted using computer program OpenSees. The bridge model was subjected to two-horizontal components of simulated earthquake records of the 1994 Northridge earthquake. Over 340 channels of data were collected

  • Characterization of Carbonate Hydrostratigraphy Using Ambient Seismic Noise: A Pilot Study in the Floridan Aquifer System, Ocala, FL, USA

    NASA Astrophysics Data System (ADS)

    James, S.; Screaton, E.; Russo, R. M.; Panning, M. P.; Bremner, P. M.; Stanciu, A. C.; Torpey, M. E.; Hongsresawat, S.; Farrell, M. E.


    Defining zones of high and low hydraulic conductivity within aquifers is vital to hydrogeologic research and groundwater management. Carbonate aquifers are particularly difficult to characterize due to dissolution and dolomitization. We investigated a new imaging technique for aquifer characterization that uses cross-correlation of ambient seismic noise to determine seismic velocity structure. Differences in densities between confining units and high permeability flow zones can produce distinct seismic velocities in the correlated signals. We deployed an array of 9 short period geophones from 11/2013 to 3/2014 in Indian Lake State Forest, Florida, to determine if the high frequency diffusive seismic wavefield can be used for imaging hydrostratigraphy. Here, a thin surficial layer of siliciclastic deposits overlie a ~ 0.6 km sequence of Cenozoic limestone and dolomite units that comprise the Floridan Aquifer System (FAS). A low permeability dolomite unit vertically divides the FAS throughout most of Florida. Deep boreholes surrounding the site constrain hydrostratigraphy, however the horizontal continuity of the middle dolomite unit as well as its effectiveness as a confining unit in the study area are not well known. The stations were spaced at distances ranging from 0.18 to 2.6 km, and yielded 72 cross-correlation Green’s functions for Rayleigh wave propagation at frequencies between 0.2 and 40 Hz, with dominant peaks around 0.8 Hz, 3 Hz and 13 Hz. Local vehicle traffic did interfere to a degree with the correlation of the diffuse waves, but was minimized by using only nighttime data. At the lowest frequencies (greatest depths) investigated, velocities increase with depth; however, correlations become less coherent at higher frequencies, perhaps due to shallow complex scattering. Comparison of cross-correlations for all station pairs also indicates spatial variations in velocity. Thus, the method shows promise for characterization of the heterogeneity of the

  • Local Technical Resources for Development of Seismic Monitoring in Caucasus and Central Asia – GMSys2009 Data Acquisition System

    NASA Astrophysics Data System (ADS)

    Chkhaidze, D.; Basilaia, G.; Elashvili, M.; Shishlov, D.; Bidzinashvili, G.


    Caucasus and Central Asia represents regions of high seismic activity, composing a significant part of Alpine-Himalayan continental collision zone. Natural catastrophic events cause significant damage to the infrastructure worldwide, among these approximately ninety percent of the annual loss is due to earthquakes. Monitoring of Seismic Activity in these regions and adequate assessment of Seismic Hazards represents indispensible condition for safe and stable development. Existence of critical engineering constructions in the Caucasus and Central Asia such as oil and gas pipelines, high dams and nuclear power plants dramatically raises risks associated with natural hazards and eliminates necessity of proper monitoring systems. Our initial efforts were focused on areas that we are most familiar; the geophysical community in the greater Caucuses and Central Asia experiencing many of the same problems with the monitoring equipment. As a result, during the past years GMSys2009 was develop at the Institute of Earth Sciences of Ilia State University. Equipment represents a cost-effective, multifunctional Geophysical Data Acquisition System (DAS) to monitor seismic waves propagating in the earth and related geophysical parameters. Equipment best fits local requirements concerning power management, environmental protection and functionality, the same time competing commercial units available on the market. During past several years more than 30 units were assembled and what is most important installed in Georgia, Armenia, Azerbaijan and Tajikistan. GMSys2009 utilizes standard MiniSEED data format and data transmission protocols, making it possible online waveform data sharing between the neighboring Countries in the region and international community. All the mentioned installations were technically supported by the group of engineers from the Institute of Earth Sciences, on site trainings for local personnel in Armenia, Azerbaijan and Tajikistan was provided creating a

  • Blended Wing Body (BWB) Boundary Layer Ingestion (BLI) Inlet Configuration and System Studies

    NASA Technical Reports Server (NTRS)

    Kawai, Ronald T.; Friedman, Douglas M.; Serrano, Leonel


    A study was conducted to determine the potential reduction in fuel burned for BLI (boundary layer ingestion) inlets on a BWB (blended wing body) airplane employing AFC (active flow control). The BWB is a revolutionary type airplane configuration with engines on the aft upper surface where thick boundary layer offers the greatest opportunity for ram drag reduction. AFC is an emerging technology for boundary layer control. Several BLI inlet configurations were analyzed in the NASA-developed RANS Overflow CFD code. The study determined that, while large reductions in ram drag result from BLI, lower inlet pressure recovery produces engine performance penalties that largely offset this ram drag reduction. AFC could, however, enable a short BLI inlet that allows surface mounting of the engine which, when coupled with a short diffuser, would significantly reduce drag and weight for a potential 10% reduction in fuel burned. Continuing studies are therefore recommended to achieve this reduction in fuel burned considering the use of more modest amounts of BLI coupled with both AFC and PFC (Passive Flow Control) to produce a fail-operational system.

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